Issue 4 Michaelmas 2005 www.bluesci.org
• Artificial Intelligence • Obesity •• Women In Science • Genetic Counselling •
New Parts For OldThe future of organ transplants
Risk & RationalityWhen to trust your instincts
The Sound of ScienceNew perspectives on music
in association withCambridge’s Science Magazine produced by
Editorial ..............................................................................................................................Cambridge News .............................................................................................................Focus ...................................................................................................................................On the Cover ...................................................................................................................A Day in the Life of... ......................................................................................................Away from the Bench .....................................................................................................Initiatives ............................................................................................................................History ...............................................................................................................................Arts and Reviews .............................................................................................................Dr Hypothesis ..................................................................................................................
Don’t Believe Your EyesJamie Horder finds out why looks can be deceiving.........................................................................
Man vs MachineAnand Kulkarni and Swanand Gore puzzle out computer chess..................................................
Lies, Damned Lies and StatisticsTom Walters puts risk and rationality under the spotlight................................................................
The Transcendance of TessellationsSwanand Gore on a whole mosaic of disciplines..............................................................................
Fat Of The LandHelen Stimpson weighs up the evidence for the ‘obesity epidemic’ ...........................................
Features
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The front cover shows a droplet of YBCO superconducting ‘ink’ viewed with an optical microscope.The droplethas cracked during the drying process to produce the striking black fissures visible in the photograph.Turn to page 20 for more details.
Photograph CompetitionWe want our readers to be able to see the sci-
ence that’s going on in Cambridge. If you have an
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seen throughout Cambridge. Send your images by
5pm on 14th November.
Article SubmissionsOur contributors make BlueSci what it is.
Whether you’re a novice or an accom-
plished writer why not try your hand at an
article for BlueSci?
Submissions for our Lent Term issue must
be received by 5pm on 14th November
2005.
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Next Issue:
January 2006
From The Managing Editor
Happy First Birthday, BlueSci! It’s hard tobelieve how quickly things have evolved— not only have we set up a magazine andall its infrastructure, but we have also creat-ed a website with events listings and newsarticles not available in the print edition(www.bluesci.org). There is also a subscrip-tions service ([email protected]) toget your own hard copies delivered eachterm. We have just begun a campaign toforge links with local schools to promoteenthusiasm for science and offer localschool students a chance to see their sci-ence writing published here in the future([email protected]).
It’s our shared vision to continue toreport science in Cambridge in the com-ing academic year as well as to facilitate
interactions between scientists.To this endwe are holding a first birthday celebrationin association with CUSP at The OldKitchen, Trinity College on Tuesday18 October from 6.30pm. We’re hopingthat as many people involved or interestedin science communication withinCambridge will attend this event to meetother like-minded individuals over birth-day cake and champagne. If you have notyet received an invitation and would like toattend, please email me at the addressbelow.
Thanks again for your support — keepthe feedback coming,
Louise [email protected]
Issue 4: Michaelmas 2005
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New term, new BlueSci! Welcome to thelatest edition of Cambridge’s popular sci-ence magazine.
Among the articles awaiting you in thisissue is the FOCUS section, where we takean in-depth look at a particular scientificdebate. This time, experts discuss thefuture of organ transplants, a thriving areaof medical research encompassing topicsas diverse as ethics and bioengineering.On page 26, however, the focus is on thepast, with a look at the history of theCavendish, one of Cambridge’s mostfamous labs. As always, DR HYPOTHESISanswers your scientific queries on theinside back page: this issue’s topics rangefrom life expectancy to life on otherplanets. If, like me, you’re a finalist begin-ning to wonder about a career afterCambridge, then turn to our regular fea-ture DAY IN THE LIFE. This issue, NerissaHannink talks to a genetic counsellor.
In CRACKING CONDUCTORS on page22,Tarek Mouganie talks about his workwith superconductors and how he tookthe fantastic photo that adorns this term’sBlueSci.We are now accepting entries for
next issue’s cover image: photographsfrom all areas of science are welcome.Send your picture and a brief explanationto [email protected] by 14November.
Ever been tricked by an optical illu-sion? In DON’T BELIEVE YOUR EYES,Jamie Horder explains how these appar-ently simple pictures manage to fool oureyes and brain. Find out about a ground-breaking interdisciplinary collaborationbased here in Cambridge in THE SOUNDOF SCIENCE. If you’ve been confused byconflicting reports about the so-called‘obesity epidemic’ affecting the UK andUS, discover the science behind theheadlines with our article, FAT OF THELAND. It’ll make you think twice aboutthat second helping of chocolate cake…
Finally, an invitation: for your news,events and article submissions. See ourwebsite (www.bluesci.org) for more details.Submissions from our readers makeBlueSci what it is, so get writing!
Emily [email protected]
BlueSci is published by Varsity Publications Ltd and printed byCambridge Printing Park. All copyright is the exclusive property ofVarsity Publications Ltd. No part of this publication may be repro-duced, stored in a retrieval system or transmitted in any form or
by any means, without the prior permission of the publisher.
From The Editor
Art meets science in a collaborationbetween Professor Roberto Cipolla andDr Carlos Hernandez-Esteban from theDepartment of Engineering, andAntony Gormley, the sculptor famousfor creating the ‘Angel of the North’ inGateshead.
Viewing sculptures in 2-D images isnever the same as seeing them for real, soCipolla and Hernandez-Esteban came upwith a way of using a series of photo-graphs of an object taken with a standardcamera to create accurate 3-D computer
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A group of Cambridge archaeologistshave begun a novel collaboration withresearchers from the Czech Republic tostudy how hunter-gatherers lived28,000 years ago. Professor MartinJones and a group of archaeological sci-entists from the McDonald Instituteand the Department of Archaeology areworking with colleagues from theAcademy of Sciences of the CzechRepublic at the site of Dolní Vestonicein the Czech Republic.The area, whichis approximately the size of centralCambridge, has been the focus ofresearch since the 1920s and is an“amazing site” to study, according to DrTamsin O’Connell, one of the project’sresearchers.
The group have made important dis-coveries about life in this era; finding forexample that the hearth of the house wasa focus of craft activities such as claymodelling and weaving as well as cookingand eating. Interestingly, many of thedwellings excavated in this area are con-
Professor Harry Coles and Dr MikhailPivnenko of the Centre of MolecularMaterials for Photonics and Electronicsin the Department of Engineering haveannounced the discovery of a class of‘blue-phase’ liquid crystals that remainstable over a wide range of temperatures.Liquid crystals are substances with prop-erties between those of a conventionalliquid and a solid crystal; the liquid crys-tal may flow like a liquid but the mole-cules may have a highly organised struc-ture, like in a solid crystal.The most com-mon applications of liquid crystals are inliquid crystal displays, but they are alsoimportant in the manufacture of super-strength polymers such as Kevlar.
The blue phase of a liquid crystal refersto the thermodynamically stable state ofthe crystal and — despite the name —can be almost any colour. Blue-phase liq-uid crystals have a number of potentialapplications in photonics (the technologyof generating and harnessing light) suchas electrically switchable colour displays,
but until now their sensitivity to temper-ature had hindered their widespread use.
The Cambridge researchers have dis-covered a solution to this instability.They made 30 different mixtures ofbimesogens (molecules that exhibit aliquid crystal phase) that show bluephases over a temperature range of40–50°C. It is the unusual structure ofthese bimesogens that give the bluephase its stability. They consist of tworod-like components linked by a flexiblechain, unlike normal blue phases inwhich liquid crystal molecules arearranged in a helix.The molecules are ofthe correct dimensions to reflect visiblelight, and by adjusting the twist of themolecule, red, green and blue reflectionshave been demonstrated.The researchersbelieve these materials will lead to a newgeneration of low-power-consumptionliquid crystal displays. Another applica-tion is for tuneable optical filters, whichcould be used to sort through signalstravelling at many different wavelengthsdown a single optical fibre in a fibreoptic cable. FM
Further information can be found in H. J.Coles, M. N. Pivnenko, Nature, 436:
997–1000 (2005)http://www-g.eng.cam.ac.uk/CMMPE
Crystal Clear
An Extra Dimension
28,000 Years Ago structed from mammoth bones, believedby archaeologists to be the best buildingmaterial available at the time due to harshweather conditions and a lack of nearbytrees.
What makes the contribution of theCambridge group to this collaborationso groundbreaking is that they are usingscientific techniques that have neverbeen applied to a site this old.The teamwill be using the latest biological andchemical methods to discover moreabout people’s diet and life in the coldand hostile Paleolithic environment.These include soil micromorphology,which allows investigation of soil struc-ture, and phytolith analysis, which givesresearchers information on vegetationcover and plant use by humans. In addi-tion, isotopic analysis of excavatedbones will show what kind of diets peo-ple might have had.The team intend toreturn to the area for at least the nexttwo years to unearth more informationabout the life of our species 28,000years ago. FM
www.arch.cam.ac.ukDr Tamsin O’Connell at work
Photomicrograph of a wide temperatureblue phase
models that can be viewed from anyangle. The Digital Pygmalion projectrelies on a computer program whichdetects the important features of theobject and its silhouette from multiplepictures, and then uses this information tocalibrate the position of the camera. Analgorithm creates an underlying ‘mathe-matical mesh’ which forms the basis ofthe 3-D reconstruction; next, the textureof the original sculpture can be laid ontop and additional lighting effects can beadded. Specially designed software allowsviewing of the finished product.
Among other applications, this tech-nique will revolutionize the digitalarchiving of museum collections andcan be used to create low-resolution 3-D models to help shoppers chooseproducts sold online.
Gormley plans to use the high-reso-lution 3-D representation of one of hisown sculptures produced by this tech-nique to help him scale up the life-sizeoriginal into a version more than 25metres tall. LB
www.eng.cam.ac.ukwww.antonygormley.com
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The circadian clock that governs key bio-chemical activities within plant cellsenables plants to optimize their rates ofphotosynthesis and metabolism, accord-ing to research from the Department ofPlant Sciences.
Plants possess an internal molecularclock which ensures that various physio-logical processes, such as stomatal open-ing, are cyclic, with a period of approxi-mately one day-night cycle.This particu-lar length of cycle was expected to hold aselective advantage on the basis that itwould be optimal for plant metabolism.
Researchers from the Department ofGenetics have won a prestigious grantfrom the Bill and Melinda GatesFoundation to investigate ways to reducethe incidence of malaria by targeting theinsect which carries and transmits theparasite. Professor Michael Ashburner andDr Steve Russell will share the £5 mil-lion award with colleagues at ImperialCollege London, the University ofWashington and the Fred HutchinsonCancer Research Centre in Seattle as partof the Gates Foundation project ‘GrandChallenges in Global Health’.
Dr Russell describes the statistics on
A new hi-tech laboratory is to be builtin Antarctica for the Cambridge-basedBritish Antarctic Survey (BAS).Construction of Halley VI is due to starton the Brunt Ice Shelf in January 2007.The laboratory is ingeniously designedto survive the hostile Antarctic condi-tions, including temperatures as low as-40°C, 80-mph winds, annual snowfallof 1.5 metres and days of near total dark-ness. The building’s unique feature isthat it will stand upon a set of collapsi-
Tick Tock: Plant Clocks
Lab on Skis
Fighting Malaria
Artist’s impression of the Halley VI laboratory: construction is due to start on the Brunt Ice Shelf in 2007
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Researchers at the University ofCambridge decided to directly test thisconcept using plants with mutations ingenes controlling periodicity. By growingwild-type, ‘long-period’ and ‘short-peri-od’ mutants of the cress Arabidopsisthaliana under light-dark cycles of varyinglength, they measured the impact of peri-odicity on plant fitness. Fitness wasassessed using indicators such as chloro-phyll concentration, photosynthetic rateand degree of biomass accumulation.
It was found that plants thrived bestwhen the intrinsic biological rhythm ofthe plant matched that of the externallight-dark cycle, a condition known as
malaria as “frightening”: it is the secondlargest killer in the world, with 3 milliondeaths annually and 40% of the world’spopulation at risk.The most deadly formof the malarial parasite, Plasmodium falci-parum, is transmitted in the bite of thefemale Anopheles gambiae mosquito.There is no vaccine to protect against theparasite, and control efforts have beenhampered by rapid increases in resistanceof the parasite to anti-malarial drugs andof the mosquitoes to insecticides.Researchers are now turning to geneticstrategies to reduce the Anopheles mos-quito population.
“Most of the methods that have beentried to control the insect population
ble ski-footed legs, permitting it to bemoved around by bulldozer.This mobil-ity will protect the base from beingswept out to sea on an iceberg.The newinstallation, which will be continuouslyinhabited by a dedicated team of scien-tists and engineers, will enable thegroundbreaking research performed bythe BAS to continue at this invaluablesite.The hole in the ozone layer was dis-covered due to observations and meas-urements taken on the Brunt Ice Shelf.Future work at Halley VI will includeexperiments to predict the weather in
space — important for preventing dam-age to satellite communications andpower systems — and investigations intothe interactions between snow, air andsunlight and their resultant effects on thelower atmosphere. The director of theBAS, Professor Chris Rapley CBE said,“Our current research programme isattempting to answer big questionsabout the Earth’s climate system — sothis remote and challenging place isvitally important for understanding ourworld.” WD
www.antarctica.ac.uk
have been spectacularly unsuccessful”,says Dr Russell. He and his team are,however, “very excited with this awardand are hopeful that working with ourcolleagues in London and Seattle willyield significant results”. Over the nextfive years, the international team hopeto develop a new technique which willdisrupt genes essential for female repro-duction, leading to female infertilityand a population decline. Anotherapproach under investigation is geneticmanipulation of the mosquitoes so thatthey can no longer transmit the para-site. CD
www.gen.cam.ac.ukwww.grandchallengesgh.org
circadian resonance. The fitness benefitsof circadian resonance were also evidentin competition experiments, in which‘long-period’ mutants out-competed‘short-period’ mutants under long light-dark cycles and vice versa.
The molecular pathways throughwhich the circadian clock controls theprocesses in question have yet to be elu-cidated. Further research in this area islikely to provide insights into ways ofmaximising crop yield and of increasingproductivity in situations where light-dark cycles may vary. WD
Further information can be found in Doddet al., Science, 309: 630–633 (2005)
The ethics of donation: amatter of trust and consent?Organ transplantation from deceaseddonors is a successful therapeuticapproach that can extend life expectan-cy and improve quality of life. Its suc-cess is, however, limited by the lowavailability of organs. Each year in theUK approximately 700 deceased indi-viduals become major organ donors,while over 6,000 people wait fororgans. In part, the shortfall in dona-tions reflects an increase in the numberof individuals who could benefit from atransplant, with the demand for organsand tissues set to escalate yet further inthe near future. For instance, the UKkidney transplant waiting list rose by26% between 1994 and 2003, and thisfigure is expected to increase to 33% by2011. Some researchers have stated thatthe current organ shortage is not mere-ly a problem of inadequate numbers ofpotential donors, but sub-optimal use ofthe available donor organ pool, exacer-bated by the failure of health profes-sionals to initiate the donation process.
Relatives of potential organ donorsremain the most important link in main-taining organ supply, as they must expresstheir lack of an objection before donationcan take place. Across the UK, relatives’refusal rates are around 40%, rising to 70%in non-white groups.These figures are sig-nificant, particularly as Asian and blackpopulations have higher rates of renal fail-ure than whites (mainly due to suscepti-bility to diabetes mellitus and hyperten-sion), making up 52% of kidney transplant
waiting lists in some areas. The reasons forrefusal are poorly understood: althoughreligious scholars in all major faiths per-ceive organ donation as a laudable practiceand ultimately a matter of personal choice,views persist among some congregationsand their leaders that organ donation isculturally and religiously inappropriate.
Undoubtedly, there is a need to rebuildthe trust the public is prepared to invest inhealth professionals responsible for thecare of the dying and the bereaved, as twomajor health scandals and new legislationhave highlighted. First, in the wake of theHarold Shipman affair, anecdotal reportsare springing up throughout the UKabout the restraint some doctors are exer-cising in prescribing analgesic medicationto the dying. Such practice may have pro-
found effects, by affecting the sufferingsustained by the dying and the consequentexperience of those who care for them,potentially influencing their decisionsabout post-death organ donation.
Secondly, the lack of consent for theretention of organs following post-mortem within a number of NHS Trustscame to public attention in 1999, whenover 50,000 body parts or pre-term babieswere discovered to be held by pathologyservices throughout the UK, sparkingnationwide concern and prompting some30,000 families to contact hospitals forinformation about their deceased relatives.Subsequent inquires indicated that organs,particularly hearts,were routinely removedpost-mortem and retained for use inresearch and teaching, without explicitconsent of the next-of-kin.These investi-
gations demonstrated weaknesses in theprotocols for post-mortem consent, andthat services for supporting bereaved fam-ilies were fragmented and inadequate.Good post-mortem practices, whichrespect the views of family members andinclude properly obtained consent, areessential to improve the donation process.
New legislation,The Human Tissue Act(2004), arose out of concern about organretention and evidence that the law gov-erning the post-mortem use of organs wasnot as comprehensive, clear or consistentas it might be.While the Act is to be wel-comed with its guiding principles ofinformed consent and communication, itdoes raise certain challenges for healthprofessionals and bereaved individuals, aswell as the need to work increasingly in
partnership. For instance, the Act has pro-vided that in the case of an adult “appro-priate consent” rests with “a person whostood in a qualifying relationship to himimmediately before he died”.There are anumber of criteria listed defining qualify-ing relationships, which could raise diffi-culties for bereaved individuals and theresponsibility they feel they have for deci-sions made on behalf of the deceased.
If organ transplantation is to remain aviable therapy, efforts must be made tofacilitate donation. This involves helpingrelatives to make decisions which canimpact upon their bereavement: it isimportant they do not regret these choic-es later. Western societies preserve theethos of organ donation as a ‘gift of life’, astand sensitive to relatives’ post-mortemdistress that preserves the notion that thebody is not property to be owned. Thus,although financial rewards or an offer topay for funeral expenses of a donor couldpotentially help increase organ supply, thenotion of organ trade is generally per-ceived as immoral. In addition,more couldbe done to highlight the benefits of dona-tion to society. Not making relatives awareof the option of donation limits their post-mortem choices and may deprive them offulfilling the wish of the decedent.
Dr Magi Sque is a Senior Lecturer at theSchool of Nursing and Midwifery, University
of Southampton
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Across the UK, relativesÕ refusal rates are around40%, rising to 70% in non-white groups“
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Views persist among some congregations andtheir leaders that organ donation is culturally and
religiously inappropriate“
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In 1954 a Boston doctor called JosephMurray carried out the first successfulorgan transplant. The patient, a 23-year-old man who received a kidneyfrom his identical twin, was able toenjoy another eight years of life. Hisdonor brother is still alive today. Thesuccess rates of kidney, heart, lung,cornea and liver transplants haveimproved steeply since this pioneering
surgical intervention, yet hundreds ofpeople die every year in the UK wait-ing for organs.We tend to feel uncom-fortable thinking of our own death,and so few people register as organdonors. Moreover, medical advancesand a decrease in the death rate ofhealthy individuals in road accidentsmean that only a very small number ofpeople become suitable donors.
New Parts for Old: the Future of Organ Transplants
Challenges and advances inxenotransplantationThe shortage of organs and tissues fordonation has made xenotransplanta-tion a realistic approach for the treat-ment of organ failure and disease. Inthe context of human xenotransplan-tation, it is envisaged that in thefuture, whole organs (heart, kidney) ortissue (pancreatic, islet cells or neuraltissue) from pigs may be transplantedinto human recipients.The comparablesize of pig organs to their humanequivalents and ease of breedingmakes this animal the optimal donorfor xenotransplants.These features alsofacilitate research into the immunolo-gy of xenograft rejection, and have ledto the development of a number ofgenetically engineered pig lines.
Transplantation of tissue from onespecies to another carries two majorproblems, which are the focus of thatresearch of numerous laboratories. Thefirst is immunological rejection and thesecond is the risk of zoonotic infection(diseases communicable from animals tohumans). Rejection of transplanted tissuehas proven to be a major obstacle in allexperimental studies to date. Porcine tis-sue expresses a number of specific epi-topes (proteins and carbohydrates on thesurface of cells) which trigger a very briskhuman immune response. In the case ofwhole organ transplants, the rejectionprocess mounted by the host is hyper-acute and takes place in a matter of sec-onds or minutes. The main mediators ofthis rejection process are pre-formedhuman antibodies, which react with theepitopes on the transplanted organ, lead-ing to rapid and irreversible damage ofthe blood vessels, ischaemia (inadequateoxygen delivery) and death of the trans-planted organ. In order to overcome thisrejection process, powerful immunosup-pressive drugs, similar to those used forallografting (human-to-human trans-plants), would be necessary.Immunosuppressive treatments for xeno-transplants would need to be much moreaggressive than those currently adoptedprior to allografts, which already putpatients in a susceptible position when
fighting opportunistic infections.Strategies aiming to modify the trans-
planted porcine tissue so it becomes lessimmunogenic are increasingly successful.They involve genetically engineering theporcine tissue, either to express factorsthat suppress the host immune responseor to remove the epitopes that driveimmune rejection. In the first case, thishas been achieved by generating porcinetissue capable of expressing inhibitors ofthe human complement cascade, a series
of proteins whose activation in adverseimmune reactions leads to rapid loss oftissue.This work was pioneered by DavidWhite and colleagues at Imutran, a com-pany originally based here in Cambridge.The second strategy, mainly undertakenby David Cooper and David Sachs atMassachusetts General Hospital inBoston, has involved removing the majorimmunogenic epitope in pig tissue, calledalpha 1,3-galactosyltransferase. Using thisapproach, the survival of transplanted
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In this edition of BlueSci, we explorein detail some of the questions associ-ated with human organ donation andtransplantation.
Magi Sque looks at the possible rea-sons behind the severe shortage oforgan donors in Britain and the issuesrelated to obtaining consent from therelatives of deceased potential donors.The scarcity of donated organs has
driven several areas of scientificresearch to develop alternative treat-ments for organ failure. A century aftera pig kidney and a goat liver wereunsuccessfully transplanted to two dif-ferent women in France, Roger Barkerinvestigates the challenges facing thepromising and extremely controversialarea of xenotransplantation, the graft-ing of tissue from one species into
another. Finally, Ben Hanson describesthe development of an artificial devicedesigned to assist cardiac functionwhich is being developed in Leeds.Along with stem cell technology, xeno-transplantation and ar tificial organspromise to open avenues previouslyconsidered purely fictional, but whichmay hold great benefits for humanhealth.
: the Future of Organ Transplants
organs has been extended in experimen-tal studies but is by no means longlasting.To date, successful transplants usingbaboons have only prolonged the life ofpig organs for months rather than years,but this does not exclude the very realpossibility that modified animal organsmay be one day used in the clinic.
The second major issue concerningxenotransplantation is the spread of infec-tion, which at its simplest level can be inthe form of bacteria and viruses com-monly found in farm-bred animals. Thisis a particular problem for transplantrecipients, whose immune systems arealready weakened by the stress of invasivesurgery and the drugs used to preventrejection of the donor organ.The risk ofsuch infections can be dramaticallyreduced if the animals are raised in specialquarantine conditions. A more seriousconcern, however, relates to viruses thatcould spread from the pig and cause dis-ease in humans. In particular, a class ofviruses known as porcine endogenousretroviruses (PERVs) do not cause diseasein pigs but could spread into the humanrecipient. Such infection could theoreti-cally trigger a hitherto unknown diseasein much the same way as has been postu-lated for the spread of AIDS from non-human primates, but based on tests onmore than 160 patients who have beenexposed to living porcine tissue, there isno evidence to support such risk. Datareported in 1999 by Khazal Paradis andcolleagues at Imutran clearly demonstrat-ed that, despite the presence of survivingpig cells years after transplantation, therewas no evidence of infection or disease inhuman recipients. In contrast, subsequentstudies, notably by Luc van der Laan and
colleagues in California, have includedtransplantation of pig tissue into severecombined immunodeficient (SCID) miceto show that the PERVs can spreadthroughout the host's body. In these micethere are no overt signs of disease, butclearly the fact that PERVs can escapeand spread under such circumstances is acause for concern. Still, it should be notedthat immunosuppression in organ recipi-ents is much less powerful than that seenwith SCID mice.
A further uncertainty is whether pigorgans and tissues have the capacity toperform the functions of their humanequivalent with comparable efficiency.Research suggests that this may dependon the specific organs.Xenotransplantation of liver, for example,could be problematic because of the largenumber of essential and often species-specific proteins produced, whereas thereis no reason to believe that pig dopamineneurons could not be used in patientswith Parkinson’s disease, as the graftedcells should be able to produce the miss-ing dopamine in sufficient concentrationsto mediate a positive effect. Moreover, in
terms of neurodegenerative disorders,rejection following transplantation of pigtissue into the brain has been shown to bemuch slower than with whole organs.This process relies less on antibodies and
the complement cascade and more on theother effector of the immune system,namely the T cells. While these cells docontribute to the chronic rejection oforgan transplants in xenotransplantation,it seems possible that the engineering ofneural tissue coupled to a strongimmunosuppressive therapy wouldenable neural tissue to be grafted success-fully into the adult brain of patients withneurological disorders.
The recent development of transgenicpig lines has enabled the field of xeno-transplantation to advance yet closer tothe clinic. As our understanding of thecomplex immune reactions induced byxenografts improve, so do strategies toovercome rejection. In the field of neuraltransplantation, emerging data suggeststhat cells transplanted from one speciesinto another may have a primary advan-tage over their allografted equivalent. Forexample, xenografted pig cells appear tohave a greater capacity to grow processesand migrate within the adult rodent brainthan rodent cells of the same type. If thisproves to be the case, then xenograftedtissue would have great potential toreplace cells lost in neurological condi-tions, as well as to recreate circuitsthrough long-distance neuronal connec-tions. It is, therefore, an exciting time forxenotransplantation and its potentialapplications in the treatment of clinicaland neurological disorders.
Dr Roger Barker is a University Lecturer inNeurology and Honorary Consultant
Neurologist at the Cambridge Centre forBrain Repair
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Transplantation of tissue from one species toanother carries two major problems: immunologi-
cal rejection and the risk of zoonotic infection“
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It seems possible that neural tissue could be grafted successfully into the adult brain of patients
with neurological disorders“
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Further Reading
For information on becoming an organ donor, go to www.uktransplant.org.uk orwww.bbc.co.uk/health/donation
For information on blood or bone marrow donations, go to www.blood.co.uk
A discussion of the ethics involved in organ donation can be found at:www.studentbmj.com/issues/03/07/education/232.php
For the University of Southampton’s study on organ donation and care ofbereaved relatives, go to www.nursingandmidwifery.soton.ac.uk/familybereavement
To explore the issues surrounding xenotransplantation further, read NatureBiotechnology 18: IT53–IT55 (2000).
To find out more about the work on cardiac assist devices at the University ofLeeds, go to www.mech-eng.leeds.ac.uk/cardiacassist/home.htm
Since 1 April 2005...
1,084 people in the UK
have received transplants
377 people have donated organs
6,331people are still
waiting for transplants
Figures from www.uktransplant.org;correct at time of going to press.
Artificial organs: direct cardiac compression heartassist deviceReplacement of diseased organs byartificial devices is an exciting chal-lenge facing researchers with a diversi-ty of scientific backgrounds. Forinstance, at the BiomedicalEngineering Research Group in Leeds,mechanical and electrical engineers,material and computer scientists,physicists and biologists are joiningforces to create joint replacements,synthetic tissues and devices to aidcardiovascular anomalies and disease.
Heart attacks or viral diseases canweaken the heart muscle, reducing itspumping power. When this happens, theheart often still has sufficient power tosustain life, but is unable to increase out-put to cope with greater pumpingdemands during exercise. Where a heartmuscle is weakened or failing, the treat-ment options available are limited andtransplantable hearts are rarely available.Recently, efforts are increasingly beingdirected towards providing mechanicalassistance to a weakened heart.
One strategy to increase pumpingpower is to implant a motorised pumpinto the bloodstream within the chestcavity. These pumps use a rapidly spin-ning impeller (similar to a propeller) toincrease the flow of blood and have beenfound to work in the few cases of humanimplantation so far. There are, however,some problems with this approach, whichare currently being tackled. The rapidlyspinning impeller can damage the fragileblood cells and potentially instigate bloodclots. Additionally, the immune systemmust be repressed with drugs in order toprevent rejection of the device. Thesecomplications are the result of bloodflowing through an artificial chamber,which may be recognised as foreign andattacked by the recipient's immune sys-tem. Alternatively, to avoid contactbetween the implant and the blood, theheart can be assisted with direct cardiaccompression (DCC), providing a com-pressive pressure to the heart's outer sur-face. One method of achieving this isthrough a surgical procedure known as acardiomyoplasty, which involves detach-ing the patient's own latissimus dorsimuscle (a sheet-like muscle across the
shoulder blade), and wrapping thisaround the heart. This muscle wrap isthen electrically stimulated so that it con-tracts in sync with the heartbeat. Thistechnique was shown to be successful inthat the heart can be briefly assisted.
Stimulation must, however, be carefullycontrolled since skeletal muscle — unlikehealthy heart muscle — fatigues overtime.
The difficulties associated with usinghuman muscle have driven attempts tocreate a mechanical ‘artificial muscle’assist device. Pneumatic pressure has beenapplied to hearts in different ways: byplacing the heart within a pressure vessel,surrounding the heart with an inflatablecuff, or applying inflatable patches. Thepneumatic actuators (cuffs, patches) havethe benefit of high power to weight andpower to volume ratios but the air hosessuch a device requires pass through theskin and so are a potential source ofinfection, while attachment to a pneu-matic pressure supply limits mobility.Several new ‘artificial muscle’ technolo-gies are being developed, but these newtechnologies are at early stages of devel-opment and are not yet suitable for animplantable cardiac compression device.
At the University of Leeds, we aredeveloping a DCC device consisting of aseries of bands to be placed circumferen-tially around the heart. These bands cancontract in the same way a belt may betightened around one’s waist. This con-traction is powered by miniature motors,one per band, which are individuallycontrolled.We can provide contraction inthe form of a wave in order to squeezeblood up and out of the ventricles, andcan apply varying levels of assistance to
different areas of the heart. Power for thedevice is provided by battery packs.
Control of the assistance force is cru-cial. If appropriate assistance is provided,allowing the heart muscle to rest, studieshave shown that the heart muscle canstart to regenerate. Assistance must begentle to avoid damage to the coronaryarteries that lie on the surface of the heartand supply blood to the heart muscle.After contracting to pump blood out ofthe heart, the device must relax quicklyand not restrict the refilling of the heart.The time between heart-beats varies, and
we are using a pacemaker as part of thesystem to sense when the heart beats andto synchronise the assist contraction.
The bands are inelastic in their circum-ference, but flexible. If these were direct-ly on the surface of the heart, the tissue
and blood vessels could be at risk ofabrasion, so we have used a structurewhich separates the contracting bandsfrom the heart's surface, provides a pro-tective cushion, and maintains the shapeof the device. To minimise interferencewith the heart during surgery, the deviceis constructed as a ‘sock’, slipped onto theventricles in one motion, and secured inplace. The motors are sheathed from thebody with a bio-compatible sheet.
We have created a novel testing simula-tor that uses a computerised model of theheart and circulatory system, which iscombined with a physical simulator rep-resenting a beating heart. This allowsphyscial testing of the mechanical per-formance of the assist device under real-istic conditions. With the computermodel we are also able to visualize howthe assistance will affect the blood pres-sure and flow throughout the body; thiscan be repeated for many different statesof heart failure and patient type.
We are developing new motor tech-nologies that will hopefully be used tocreate a flexible sheet of ‘artificial muscle’to replace the motorized belts currentlyused. The way the body reacts to assis-tance in the long term is yet to be deter-mined, although avoiding direct contactwith the bloodstream should greatlyreduce the likelihood of immune systemrejection.
Dr Ben Hanson is a Lecturer at the Schoolof Mechanical Engineering, University
College London, and a former ResearchFellow at the University of Leeds
Focu
s
luesci 09www.bluesci.org
The difficulties associated with using human muscle have driven attempts to create a mechanical ‘artificial muscle’ assist device
“”
Where a heart muscle is weakened or failing, thetreatment options available are fairly limited and
transplantable hearts are very rarely available“
”
Ben
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The ancient Greeks knew that if theywanted a stone column to appearstraight when viewed from a dis-tance, they had to construct it with aslight bulge in the middle.What theydidn’t know was how our eyes weretricked in this way. Today psycholo-gists describe these effects as an opti-cal or visual illusion and experimen-tal psychology and neuroscience haverevealed some of the brain processesbehind them. Although many illu-sions are still as mysterious as ever,some of the simpler ones are wellunderstood.
What happens when you look at avisual illusion? Light reflected from theillusion is focused by the lens in the eyeto form an image on the retina. Theretina consists of several layers of cells atthe back of the eye, including cellsknown as photoreceptors — the famousrods and cones. These photoreceptorsdetect light and convert it into an elec-trical voltage that the nervous systemcan interpret. The magnitude of this
voltage is proportional to the intensityof light emitted from a particular pointin the illusion. Brighter points generatelarger signals than darker points.
Photoreceptors communicate thesesignals to a layer of neurons on theouter surface of the retina, known asretinal ganglion cells. The properties ofthese ganglion cells are critical to thefunctioning of vision and are alsobelieved to be responsible for a numberof common optical illusions. A singleganglion cell receives inputs from mul-tiple photoreceptors via junctions calledchemical synapses. A ganglion cell is‘excited’ by light falling on photorecep-tors in a small, circular area of the reti-na, but is ‘inhibited’ by light strikingphotoreceptors in a ring-shaped areasurrounding this — a phenomenonknown as lateral inhibition.The greaterthe net excitement of a ganglion cell,the brighter a particular point appears.
Lateral inhibition is crucial inexplaining the Koffka Ring (Figure 1).The ganglion cells are excited by pho-toreceptors responding to the two greysemicircles, but are laterally inhibited byphotoreceptors responding to the sur-rounding pale or black region.The palearea causes a greater level of lateral inhi-bition than the black area because itreflects more light into the retina. Thesemicircle surrounded by the pale areatherefore seems darker as the ganglioncells are excited less. Although the lightfalling on the retina is of the sameintensity for both semicircles, the brainperceives the shades as being differentbecause of lateral inhibition.
Lateral inhibition is also important fordetecting edges and lines. A uniformlevel of light will lead to equal amountsof excitatory and inhibitory signalstransmitted by the photoreceptors toeach ganglion cell, which will cancelout the signal. Only a difference in lightover a small area of the retina, such as aline, can be detected. A specializedregion of the brain, called the visual
cortex, is responsible for line detection.The optic nerves carry signals from theeyes, through various areas of the brain,to the visual cortex, located in theoccipital lobes at the back of the head.
The visual cortex contains ‘simplecells’. Don’t let their name fool you, assimple cells are actually very clever.Each simple cell is activated by a light ordark line in a particular area of the visu-al field. For example, one simple cellmight respond to a vertical line at a spe-cific place in the top left of your vision,while another might respond to a tiltedline at a specific place in the bottomright of your vision. This happensbecause each simple cell receives inputfrom a group of ganglion cells arrangedin a line. If you’re thinking that theremust be many simple cells to detectevery possible line at any angle any-where you look… you’d be right! Thevisual cortex also contains ‘complexcells’.These respond to lines of a partic-ular orientation and other sophisticatedpatterns of stimulation, irrespective oftheir location in the visual field.
Lateral inhibition of simple and com-plex cells underlies Orbison’s Illusion(Figure 2) and the Ehrenstein Illusion(Figure 3). Simple and complex cells are
luesci10 Michaelmas 2005
Don’tBelieveYour Eyes
Jamie Horder finds out why looks can be decieving
Figure 1. Koffka Ring The two semicircles are an identical shadeof grey. The one which is seen on a palegrey background appears to be darkerthan the other, which is imposed on adark grey background.
Figure 2. OrbisonÕs Illusion This is a square and a number of diagonallines within a rectangle. Both shapesappear distorted — the square appearsto be ‘squashed’ into a kite shape, whilethe rectangle looks wedge-shaped.
Jon
Her
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arranged into ‘orientation hyper-columns’, or strips of tissue containingcells that respond to a particular orien-tation of a line. Adjacent columns havesimilar preferred orientations. Thesecolumns show lateral inhibition, in thesame way as the retinal ganglion cells. Ifyou simultaneously look at two lines ofdifferent orientation, lateral inhibitionwill cause them to appear at the wrongangles. It’s the same principle as in theKoffka Ring, but applied to directionrather than brightness.
Another feature of the orientationhypercolumns is the ‘tilt after-effect’.Each orientation-selective cell inhibitsboth its neighbours and itself. However,there is a delay built into this self-inhibi-tion. The activity of particular cells ishighest when you first look at an imageand gradually declines as the cells adapt.If you allow the cells long enough toadapt — typically one or two minutes— and then look at something else,strange things happen. For example, thecells responsible for detecting a 30-degree tilt to the right have adapted andare active at a lower than normal level.The brain interprets this as meaning thatvertical lines are tilted to the left!
Many other visual features, such asmotion and rotation, exhibit similarafter-effects. With this in mind, it’s pos-sible to decipher the basis of theMcCollough Effect (Figure 4). Afterstaring at the green- and purple-striped
squares for up to five minutes, switchingbetween them every 15 seconds or so,the white stripes appear purple in thecase of the vertical stripes and green forthe horizontal ones.
Somewhere in the visual cortex thereare red-vertical and green-horizontaledge-detecting cells. These cells canadapt: the mechanism of adaptation inthis case must be different because theeffect can last for days or weeks — butthe underlying principle is the same.
Optical illusions can be fun, but theycan also reveal information about thebrain.These examples show that illusionsare not random failures of our visual sys-tem, but, rather, necessary products ofthe way our brain processes the informa-tion it receives from our eyes. Maybe wecan’t believe everything we see?
Jamie Horder is a third year Natural Scientistspecializing in Experimental Psychology.
Figure 3. The Ehrenstein Illusion The square in this illusion, superimposedon a number of concentric circles,appears almost like a four-pointed star.
Figure 4. The McCollough Effect
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Britain’s highest ever ranked chessplayer, Michael Adams, recently suf-fered an overwhelming defeat byHydra, the world’s most powerful com-puter. With this the most recent in astring of computerized triumphs, thechess world is gradually accepting thatmachines have essentially ‘solved’ thegame. Until now, tasks like playingchess required human intelligence, anattribute that has taken millennia toemerge through countless cycles ofevolution. In stark contrast, machinesdesigned by us reached their currentstate within just two human life spans.Does the triumph of machine overman on the chessboard imply thatmachine intelligence has surpassed
human intelligence? Could the suc-cessful replication of human intelli-gence in machines jeopardize our exis-tence on Earth?
Since the emergence of artificial intelli-gence (AI) in the 1950s, researchers haveoften used chess as an experimental model.In the early days of computer chess,ClaudeShannon, the computer science pioneer,proposed two strategies for designing chessprograms.The first is called the ‘brute force’strategy. In computer science language,
brute force refers to trying every possiblesolution until the best one is found. It doesnot rely on human-like intelligence butexploits the computer’s ability to examineevery possible outcome. A second andmuch more complicated strategy tries tomimic the learning process of human chessgrandmasters using sophisticated program-ming languages. To date, computer pro-grammers have adopted a brute forceapproach to play to the strengths (calculat-ing) rather than the shortcomings (learn-ing) of the machine. Today’s computers,Hydra included, lack any real capacity tolearn; it is the team of programmers thatlearns from Hydra’s bad experiences andfine-tunes the chess programs so as to over-come the computer’s weaknesses. In the
early days, the brute force approach was oflimited value, since the marginal processingpower of contemporary computers madeinvestigating every possible solutionimpractical. More recently, however, themany-fold increase in computing powerhas allowed the brute force search tobecome a viable strategy. As a result, the1980s saw machines taking on the bestplayers and sometimes sharing the hon-ours. In 1997, the computer Deep Bluemade history by beating Garry Kasparov,
the most successful player in chess history.Although human players fought on brave-ly, managing a few drawn encounters withmachines such as Deep Blue and DeepFritz, it was clear that the computer’s bruteforce was dominating over human intelli-gence; a fact which Hydra finally demon-strated by crushing Adams whilst runningat only half of its design capacity.
What sort of black magic drives thesecomputers? Major reasons for their tri-umph are both computational and techno-logical. Computer chess programs view achess game as a tree,with board positions asnodes and moves as branches.The root ofthe game tree is the starting position andthe game tree branches out into nodes,eachof which corresponds to a possible move.Atthe start of the game, the tree can branchout in 20 ways because white can play herfirst move in 20 different ways (four knightmoves and 16 pawn moves).Black can thenmake a counter-move in 20 ways, leadingto a massive 400 combinations for the firstround alone. It is easy to imagine the expo-nential explosion of possibilities as the gameproceeds: within 10 moves the number ofpossible outcomes surpasses the number ofatoms in the universe. It is quixotic to takea brute force approach to search the entiregame tree for the next best move.
This is where theoretical analysis pavesthe way by cutting down on search space.The basic idea is to avoid unpromisingpaths in the tree, a process for which searchalgorithms are critical. Experts have devisedsome approximate ways to assess the relativemerits of moves quantitatively. A simpleheuristic is to assign points to pieces, forexample, 1 to pawn, 3 to knight, 3 to bish-
luesci12 Michaelmas 2005
“
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Intelligence is much more than justcalculating power and should not
be confused with computing speed
Machine
Anand Kulkarni and Swanand Gore puzzle out computer chess
Man versusJo
nH
eras
op, 5 to rook, 9 to queen and 200 to king.One can also give a greater weight to cen-tralized pieces, the pawn structure or thephase of the game. The ‘Minimax’ searchalgorithm makes use of such heuristics andworks on the assumption that each contest-ant plays so as to minimise the possibledamage caused by the opponent’s followingmove.This approach is depicted in Figure 1.
Over a span of more than 40 years, vari-ous improved algorithms have beendevised. These have allowed computerswith the same basic speed to play signifi-cantly better chess.One such algorithm, the‘Alpha-beta pruning’ technique reduces thenumber of terminal evaluations by pruningout parts of the search tree that are so goodfor one player that the opponent will neverallow them to be reached.
Along with sophisticated search algo-rithms and heuristics, hardware develop-ment has also had a major role in theremarkable performance of chess-playingcomputers. Moore’s law states that thenumber of transistors on an integrated cir-cuit (a rough measure of computer process-ing power) doubles every 18 months. Asprocessors get cheaper and faster with everygeneration, it has become possible to har-ness many of them together to vastlyimprove overall performance.Chess is also aproblem that is easily parallelized. Thismeans that we can give each of severalcomputers a branch of the game tree toevaluate and then check which processorhas found the best solution.Versions of theAlpha-beta pruning algorithm for parallelsystems were developed throughout the1980s and by the end of the decade the useof multiple processors within a single pro-gram was commonplace.
Another consequence of the decliningcost of hardware is the ability to developdedicated chess hardware. In 1980,Carnegie Mellon University in the USbegan developing specialized chips forimplementing the Minimax algorithmexclusively for chess moves. Based on thisspecial hardware, their 1988 chess machineHiTech was able to analyse up to one mil-lion board positions per second. The ver-sion of Deep Blue that defeated GaryKasparov in 1997 had 256 special purposechess processors working in parallel,analysing 200 million board positions persecond.This hardware,Application SpecificIntegrated Circuit (ASIC), accelerates spe-cific calculations needed for the Minimaxalgorithm using dedicated circuits to carryout a particular set of tasks. ASIC canimplement a specific algorithm at least 100times faster than programming the samealgorithm in conventional software on ageneral-purpose computer.ASIC machinesare efficient both in performance andpower consumption, but lack flexibility intheir dedicated hardware circuits, and soperform at a slower rate when the searchalgorithm is altered or when new chessknowledge is added.
Recently, an alternative to ASIC thatavoids these problems has emerged.Reconfigurable computing allows hard-ware circuits to be configured to suit the
particular tasks at hand.Reconfigurable sys-tems make use of Field Programmable GateArrays (FPGA), semiconductor devices thatprocess digital information and can be re-programmed after manufacture withoutslowing performance.
This latest hardware technology formsHydra’s basic building block. Hydra is acluster of 32 processors assisted by the samenumber of FPGA chess cards. It has a pro-cessing power of 100 billion calculations —or 200 million chess moves — per secondwith this configuration and can project thegame up to 40 moves ahead.
What are the implications of this signifi-cant chess achievement for other areas ofAI? The public is often intrigued by theidea that intelligent machines could super-sede us as the dominant life form on Earth.The triumph of machines over humans onthe chessboard tends to be misconstrued asa step towards this idea becoming a reality.Despite the popular impression that Hydraand Deep Blue are masterpieces of AI, theyare in fact no more capable of thought thana toaster. Intelligence is much more thanjust calculating power and should not beconfused with computing speed. Hydraand Deep Blue are examples of ‘expert sys-tems’, computers with large and powerfuldatabases that enable them to perform nar-rowly defined tasks extremely well. Theinsights gained from designing suchmachines might tell us how to solvetedious problems quickly with the latesthardware technology, but hardly addresslarge-scale issues in robotics and AI.Thesechallenging problems include replicating awide spectrum of human intelligence in amachine: knowledge, cognition and learn-ing from experience.
Learning is an essential component ofintelligence. Many AI researchers have been
trying to make chess machines intelligent byincluding human-like learning processes intheir programs, but there has been no greatsuccess to date.At present,the way we devel-op a computer chess machine is by trying toduplicate the knowledge and inferencemethods of human grandmasters. We havelittle idea of how to devise a system capableof learning in this way and also of inventingcompletely new games and negotiatingtheir rules.This is because humanity has yetto unravel the mysteries of the brain. It ishoped that within the next 30 years,we willhave a better understanding of how thehuman brain works, which will give us‘templates of intelligence’ for developingstronger AI. Herbert Simon and JohnMcCarthy, who are among the co-foundersof AI, have both referred to chess as theDrosophila of AI: it is a simple model, a test-bed.Hence, it may seem rash to expect fullyintelligent machines within a few decades,when computers have barely matched theaptitude of an insect in a half-century ofdevelopment. Instead, many long-time AIresearchers suggest that a few centuries maybe a more believable period.We have wait-ed millions of years for the evolution of nat-ural intelligence; we may have to wait cen-turies for its artificial equivalent. Until thenat least, human intelligence rules.
http://chess.about.com/od/computerchesswww.hydrachess.com
http://world.honda.com/ASIMO
Anand Kulkarni is a PhD student in theInstitute for Manufacturing.
Swanand Gore is a PhD student in theDepartment of Biochemistry
13luesciwww.bluesci.org
Figure 1. The approach used by the Minimax algorithm to pick the best next move.The nodesare board positions; oval nodes show positions where it is the computer’s move (marked A)and square nodes show those where the opponent is to move (marked C).The numbers showthe computer’s score at each board position. Let us assume that the computer thinks only twomoves ahead. According to the Minimax approach, the computer’s best action is A1 becausethe least gain with A1 is 15 and that with A2 is five, i.e. the worst score with A1 is better thanthe worst possible with other moves.This is a highly simplified scenario, in which just four ter-minal positions are evaluated; generally the computer searches many more moves ahead andthe average number of legal moves in any position is 35.
The London bombings of 7 July 2005and the attempted attacks two weekslater caused many people to abandontravelling by bus and tube. Those whochose to stay away from the tube net-work did so because they perceived therisk of travelling on public transport astoo great. But what governs our per-ception of risk and how easy is it to bemisled by the statistics we hear?
Analysis of the risks that surround us issomething that we have to do every day.Cognitive psychologists suggest thatthere are two mechanisms by whichhumans can judge risk: the ‘experimentalsystem’ and the ‘analytic system’.The for-mer gives rise to our intuitive under-standing of risk and relies on images andassociations formed in our minds. Thisprocess occurs with little conscious con-trol and it is the system which gives us a‘gut feeling’ that something is wrong —that we shouldn’t eat some strange-smelling food, or walk down a dark alley.By contrast, the analytic system requiresmuch more conscious thought. This isthe system by which we logically analyseevidence and statistics in order to reachreasoned conclusions.
We rely on our intuition in almost allsituations in daily life; if you walk into acrowded pub and feel threatened forsome reason, it’s not because you’ve per-formed an analysis of all the possibledangers and mitigating factors. If you hadstopped to calculate the exact probabili-ty that the bunch of guys with lots ofempty pint glasses and a certain team’sfootball shirt on were just up for a quietnight, and weren’t in fact going to takeoffence at your choice of wardrobetoday, it might well have been too late.
We need to be able to inform ourintuition by understanding and inter-preting data on the dangers that face us,data that may come in many different
forms. One factor in judging risks usingour intuition is the availability of mentalimages related to an event about whichwe are concerned. Images which are par-ticularly dramatic or disturbing, or whichwe are exposed to frequently, will berecalled more easily than other imagesand may make an event seem much morelikely than it really is. The shockingnature and extensive media coverage ofthe London bombings made the imagesof them much more accessible in peo-ple’s minds, and thus made it seem morelikely to them that the events would hap-pen again. Conversely, hazards which arehard to visualise are often perceived asbeing less dangerous.
Control is also another key factor inthe perception of risk. If a hazard seemsto be outside of your control it canappear more serious. Psychologists havesuggested that qualitative aspects of risksuch as these can be roughly split intotwo categories: ‘dread’ and ‘unknown’.Dread is typically associated with riskswhich appear uncontrollable or whichhave the potential for large-scale destruc-tion, even though they may be far in thefuture. Hazards like nuclear power, radia-tion and climate change are seen as beinghigh in both dread and unknown,whereas smoking and driving too fast areranked much lower in both categories.This may explain why people are muchmore likely to voluntarily expose them-selves to risks of the latter type.
The channels through which informa-tion about risks passes can also increaseor reduce their perceived severity. Trustin the source of information about a riskis crucial. Information from a trustedsource will be taken much more serious-ly than information from an unknown oruntrustworthy source, which can in somecases actually cause the recipient to takethe opposing view.
While the experimental system is asimple and robust method for assessingrisk, there is the danger that some riskscan be perceived as different from whatthey actually are — sometimes wildly so.The analytic system can be seen as akind of ‘reality check’ for our intuition.If some real data are available againstwhich we can check our ideas, then itwould be a good idea to use them. Hardfacts are useful, but again, there are dan-gers in assessing the statistics with whichwe are presented.
A lot of the confusion that is encoun-tered when assessing statistics occurssimply because they are presented in aform that makes them difficult to com-prehend. Percentages generally tell usvery little. If there is a 10% rise in mug-gings per year, what does that mean; onemore, making the total 11, or 1000more, bringing the total to 11,000?Furthermore, what is the overall popula-tion in which these muggings are occur-ring: is it your street? An entire city? Thecountry?
One story which made front-pagenews in June 2005 was a four-year studythat suggested that taking ibuprofenincreases your risk of heart attack. Thefigure that many newspapers reportedwas that taking ibuprofen increases yourrisk of a heart attack by 24%. Pretty scarystuff by the sound of it. Statistics, espe-cially on health-related stories, tend toget reported in this vague fashion. But isthere a better way? Humans like dealingwith real-life examples using numbers ina way which are easily comprehensible.Natural frequencies, which use actualnumbers rather than percentages, are agood way of expressing risks becausethey allow us to put the information in arealistic context.The actual data from thestudy stated that there would be oneextra heart attack per 1,000 or so peopleon ibuprofen.All of a sudden the statisticisn’t quite so shocking.
Legal evidence is another area wherethere are numerous statistical pitfalls.Although juries do not assess risk per se,they do have to deal with a great deal ofevidence, some of it backed up by statis-tics or probabilities and some not. In thecourse of assessing probabilities it can beeasy to fall for logical traps.
luesci14 Michaelmas 2005
Hazards which are hard to visualise are often perceived as
being less dangerous
“”
Lies,Damned Liesand StatisticsTom Walters puts risk and rationality under the spotlight
Jon
Her
as
The recent notorious case of RoyMeadow, the paediatrician called as anexpert witness in several cases wheremothers were accused of killing theirbabies, is a prime example. In each case,the defendant claimed that the childrenhad fallen victim to cot death or SuddenInfant Death Syndrome (SIDS).The tes-timony of Meadow as an expert witnesswas instrumental in the conviction ofthree mothers. However, this testimonywas later called into question. Meadowwas found to have misled the jury, caus-ing him to be discredited as an expertwitness, investigated by the GeneralMedical Council and eventually struckoff the medical register.
In the case of Sally Clark, the mother’stwo children had both died in similarcircumstances. Meadow claimed that theprobability that the defendant was inno-cent in this case was about 1 in 73 mil-lion. It appears that he reasoned thatsince the incidence of SIDS is around 1in 8,500, the probability of two casesoccurring in the same family was thatvalue squared, leading to the value of 1 in
73 million. He then inferred this to bethe probability that the defendant wasinnocent — damning testimony from anexpert witness.
There were, however, two errors inMeadow’s reasoning. The first was theassumption that the two deaths were
independent; that the fact that one deathhad already occurred had no bearing onthe probability of another death occur-ring. The probability that the seconddeath occurred due to natural causesshould be calculated as the probability ofa case of SIDS occurring given that acase has already occurred in the samefamily. Due to the possibility of either agenetic predisposition to SIDS or sharedenvironmental factors, it is reasonable tobelieve that the probability of this wouldbe considerably greater than 1 in 8,500.The Royal Statistical Society later criti-cized Meadow’s claim of 73 million to 1,saying that it had “no statistical basis”.
The second error of reasoning thathelped the jury to reach a guilty verdictin this case is more subtle, but has misledjuries in many cases. Many errors of rea-soning (fallacies) such as this are so com-mon that they have their own name. Itseems that the trap that Meadow, unwit-tingly or not, led the jury into was the‘prosecutor’s fallacy’: mixing up his con-ditional probabilities. (See ‘TheProsecutor’s Fallacy’, below.)
The figure that the prosecution quot-ed was the probability of a double cotdeath occurring given that the defendantwas innocent: very small indeed. Thequantity that we are actually interestedin, however, is the probability that thedefendant is innocent, given that a dou-
ble cot death has occurred. These twoquantities are not the same.That isn’t, ofcourse, to say that the defendant was def-initely innocent, but the crucial thing toremember when assessing statistics is thatit must be done in context. In the case ofa legal proceeding, that means evaluatingthe statistical and the non-statistical evi-dence simultaneously, quantifying whatyou can, and then leaving the jury tocome to a reasoned conclusion.
So, the moral of the story seems to be:trust your intuition, but don’t forget togive yourself a reality check every sooften. And, when dealing with statistics,remember to look beyond the numbersto check that the fancy figures meanwhat you think they do.
For more information, see BlueSci Online.
Tom Walters is a PhD student in the Centrefor the Neural Basis of Hearing
15luesciwww.bluesci.org
Try to spot the flaw in the standardexample of the prosecutor’s fallacy, asillustrated in the following hypothet-ical scenario:Some cellular material belonging to theoffender is found at a crime scene.Thishas been DNA profiled. A suspect hasbeen arrested and DNA profiled, andthe profiles match.The question for thejury is, did the suspect leave the sampleat the crime?
The first assumption is that if twoDNA samples were taken from a singleperson, they would give the same DNAprofile.This is reasonable, as it is almostcertain that two samples from the sameperson would give the same DNA pro-file.The second assumption is that it isvery unlikely that two people wouldhave the same DNA profile. So if thesuspect had left the sample at thecrime, it is almost certain that the pro-files would match whereas if someother, unknown, person had left thecrime sample there is a very smallchance that they would match. So theexpert witness says to the courtroom,
“the probability of a match if the sam-ple left at the crime scene had comefrom someone else is one in a million”.The jury then takes this to mean thatthere is a one in a million probabilitythat the crime sample did come fromsomeone else, and thus that there isonly a one in a million chance that thesuspect is innocent.
Can’t spot the flaw? Here’s a simplerexample of the same fallacy.
An animal with four legs is on trial,accused of being an elephant. Anexpert on elephants is brought in andsays, “if an animal is an elephant, thereis a very high probability that it hasfour legs”.“Aha!” says the prosecution,“if an animal has four legs, there is avery high probability that it is an ele-phant, therefore there is a very high
probability that this animal, which hasfour legs, is an elephant”.
This is an example of what statisti-cians call ‘transposing the conditional’.Conditional probability is the probabil-ity that an event, A, occurs, if someother event, B, has occurred.Mathematically, this is written P(A | B)where the ‘|’ means ‘given that’. SoP(four legs | elephant) (the probabilitythat the animal has four legs, given thatit is an elephant) may be 0.99, butP(elephant | four legs) is not. In factthere is a way of converting betweenthe two. This is called Bayes’ theoremand is written as follows:P(A|B)=P(B|A)P(A)/P(B). P(A) is theprior probability, in our case, the prob-ability that the randomly selected ani-mal we have in the stand is an elephantbefore we know anything about thenumber of legs it has. In the case of theDNA evidence, it is our prior knowl-edge of whether the suspect is likely tobe innocent or guilty, and this can onlybe found by assessing the other evi-dence in the case.
The Prosecutor’sFallacy
Hard facts are useful, but there aredangers in assessing the statistcs with
which we are presented
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Science often seems like a maze ofvery specialized disciplines, but thereare some universal ideas that tran-scend its boundaries. Tessellation isone such idea, in the league of otherall-pervasive themes like potentials,graphs, memes and entropy.Tessellation is the division of spacewithout gaps or overlaps betweenthe resulting regions. Flexible orgrowing entities compete for space; agas expands to fill its vessel and cellsgrow in a petri dish until space ornutrients run out. This competitionfrequently results in tessellation, forexample, beehives have hexagonalchambers because each bee grows itschamber in all directions until thehive is filled. A source of inspirationto scientists and mathematicians forcenturies, tessellation offers both away of describing the world and aneffective tool.Tessellations have beenrediscovered in different fields andrechristened; Thiessen polygons ingeography, Blum’s transforms inbiology and the domain of action incrystallography. This ubiquitydemonstrates tessellation’s utility aswell as its place as a fundamental,unifying principle.
Although they are often highly com-plicated, any tessellation can bedescribed solely in terms of a ‘genera-tor’, a ‘definition of distance’ and an‘assignment rule’. A generator is a geo-metric entity competing for its share ofspace and an assignment rule assigns
every point in space to a generatorusing the definition of distance to quan-tify the proximity of a point to a gener-ator. Figure 2 shows the territoriesformed by mouth-breeder fish, a clearexample of tessellation in nature. Themale mouth-breeder removes sand fromthe sand bed and spits it out towards theneighbouring diggers, creating breedingpits surrounded by sand walls. Here, afish is a generator competing for space,and the assignment rule is that pointsenclosed by its sand walls are assigned tothe nearest fish.The distance measure isstraight line Euclidean geometry. Thepits formed belong to the fish in themand are called the ‘dominance zones’ ofthe generators.A dominance zone is theset of points for which a particular gen-erator is closer than all others.The set ofdominance zone edges is called a ‘medi-al axis’ or ‘Voronoi skeleton’. Figure 3depicts an abstract tessellation pattern:the generators are points, the distance isline-of-sight distance and the assign-ment rule is least distance.
In other cases, we can generalize thegenerators to lines, curves or circles,which for example can be used tomodel the contribution of differentroads to pollution in a particular area.
The distance definition can also bechanged to account for, say, the direc-tion-dependent cost of travel, whetheruphill or downhill. The distance meas-ure changes when space is curved or ifobstacles obstruct the line of sight; youmight need to drive a long way to reach
a supermarket visible from your house,for example.
Town planning is one field in whichtessellation is a particularly importanttool. A town planner aims to maximizethe availability of urban infrastructure,because quality of life is influenced byhow much daily travel people mustundertake. Generators are hospitals, air-ports, schools or leisure centres, withtheir dominance zones roughly repre-senting their catchment areas. If a tes-sellation of hospitals results in verylarge dominance zones, then the num-ber of hospitals needs to be increased; ifone of the zones is too big, hospitalsneed to be relocated. If the nearestambulance is busy when you need it,then the next nearest must be calledinto service. The worst-case scenariocan be examined using ‘farthest point’tessellations, where the farthest, ratherthan the nearest, generator owns a par-ticular point. If the maximum distancebetween a generator and its dominancezone is not too great in such a tessella-tion, it means that the farthest ambu-lance is not too far away and the townis well accommodated. Complicationsarise when one accounts for roads tra-
luesci16 Michaelmas 2005
Tessellation offers both a way of describing theworld and an effective tool“
”
The Transcendence of TessellationsSwanand Gore on a whole mosaic of disciplines
Figure 2. Territories of male mouthbreederfish Tilapia mossambica. Reproduced fromBarlow, G. W. 1974. Hexagonal territories.Anim. Behav. 22:876–878
Figure 3. For a set of points (generators) in a plane, a simple tessellation can be defined by considering perpendicular bisectors of every pairof points (left).This results in one convex polygon (Voronoi region) per generator (middle).The corresponding Delaunnay tessellation is formedby joining the generators from adjacent regions (right). ÔDelaunnay triangulationÕ, a network of generators sharing dominance zone boundaries,is used for modelling the surfaces of solids. Reproduced from Poupon, A., ‘Voronoi and Voronoi-related tessellations in studies of protein structure andinteraction’, Curr. Op. in Str. Biol., 14:233–241 (2004).
versing the town. Typical networks aregenerally somewhere between the twoextreme cases — grid (Manhattan orMilton Keynes) and radial (London orKarlsruhe). The design of road net-works has inspired network-based tes-sellations, or ‘city Voronoi diagrams’,where distances are measured onlyalong the road network. Tessellationchanges dramatically when transport isrestricted to roads and this influencesdecisions on the location of facilities.
Tessellation-based techniques canalso be applied in biology. For instance,‘medial axis inference’ is useful forcharacterizing changes in the shapes ofbody organs. These changes can beincredibly subtle, yet can be importantindicators of disease: for example, theshapes of the amygdala and hippocam-pus, regions of the brain which areimportant for memory, learning andemotions, differ in shape considerablybetween those with and without schiz-ophrenia. A tessellation-based quantita-tive morphogenic assessment can,therefore, assist in the diagnosis of dis-orders. Similarly, differences betweentwins give clues about growth anddevelopment.
At the molecular level, a variant oftessellation called ‘alpha-shapes’ candetect cavities in macromolecules suchas proteins and DNA. Macromoleculesare the cogs of cellular machinery andcavities on their surface can indicateimportant areas where they interact,identifying potential targets for drugdesign. Since the chemical properties ofa molecule’s various constituent atomsdiffer, the distance definition must beadjusted using a weighted assignmentrule to take these chemical differencesand the interactions between the atomsinto account.
The nineteenth-century Germanmathematician Dirichlet used his ideasabout tessellation to study the distribu-tion of galaxies in the cosmos andastronomers today still use tessellationsfor studying the large-scale structure ofthe universe. Mass is not randomly dis-tributed in space, but occupies wallsand filaments. The density of matter isleast in the voids, greater in walls, stillgreater in filaments and greatest at ver-
tices, where the galaxies are. Three-dimensional tessellation models, withthe voids as boundaries of dominancezones, have yielded insights into thelarge-scale structure of our universe,just as they have for other dynamic
phenomena like the propagation ofcracks in crystalline materials, thespread of bark beetles, epidemics andeven forest fires.
In information theory, clustering andcompression are two increasinglyimportant applications of tessellation.Information theory, a cornerstone ofthe computer revolution, describes asignal being transmitted or encodedover a noisy communication channel.By compressing the data, one is able totransmit it more rapidly over a channelof a given bandwidth (those of youreading online are probably benefitingfrom this). Clustering is critical to anyprocess for classifying objects with sim-ilar properties. For example, before theyare packed up, eggs must be sorted into
large, medium and small sizes, eventhough the size of eggs is naturally scat-tered. From the point of view of tessel-lation, clustered objects have crowdedgenerators with smaller dominancezones.This is exploited by some pattern
recognition and data clustering algo-rithms. Delaunnay triangulation (seefigure 3) detects clusters by identifyingneighbours and the distances betweenthem.Automatic document analysis usestessellation to identify word boundariesand word flow: the document is firstscanned for characters and a tessellationcomputed, allowing adjacent characters,i.e. words, to be detected.
The human mind likes elegant,ordered constructs. It seems that naturedoes too.
www.voronoi.comwww.voronoigame.com
Swanand Gore is a PhD student in theDepartment of Biochemistry
luesci 17www.bluesci.org
Astronomers use tessellation for studying thelarge-scale structure of the universe“
”
Figure 1. Detail of Escher’s ‘Regular Division of the Plane Drawing #69’, 1948. ©2005 The M.C. Escher Company, the Netherlands. All rights reserved. Used by permission. www.mcescher.com
Figure 5. Voronoi diagrams with generatorsconsisting of points, straight lines and curves.Reproduced with permission from K. Hoff et al., 1999.Fast Computation of Generalized Voronoi DiagramsUsing Graphics Hardware Proc. ACM SIGGRAPH
We are a nation obsessed by ourweight: Celebrity Fat Club and DrGillian McKeith’s You Are What You Eatare television staples and gossip maga-zines are full of reports documentingPop Idol Michelle McManus’s weightloss. Obesity is now regarded as amajor public health issue and talk of an‘epidemic’ is everywhere. So, what arethe facts? How heavy are we and why?
Obesity is traditionally determined bycalculating the Body Mass Index (BMI),which relates height to weight. To workout your BMI,divide your weight in kilo-grams by your height in metres multipliedby itself.A BMI greater than 25 officiallymakes you overweight, while more than30 classes you as obese. Using this meas-urement, the incidence of obesity inBritain is estimated to have tripled in thelast 25 years, with over half of women andtwo-thirds of men now classed as over-weight or obese. The World HealthOrganization estimates that over a billionpeople worldwide are overweight andaround 300 million are clinically obese.
Obesity is associated with numeroushealth problems including diabetes, car-diovascular disease, high blood pressure,stroke, respiratory complications, andosteoarthritis.With around £2 billion peryear of an already overstretched NHSbudget being spent on obesity-related ill-nesses, it’s not surprising that publichealth officials are beginning to focus onreducing the population’s weight.
A simple principle governs body-weight: if we take in more energy than we
expend,we gain
w e i g h t .The most
basic advicefor losing
weight is to exer-cise more and eat less.
However, in reality body-weightis the result of the complicated
interplay between our genes and ourenvironment — but which is the moreimportant?
It is certainly true that our weight isdetermined by what we eat, but ourdesire for and response to eating hasrepeatedly been shown by scientists tohave a genetic component. Eating toomuch causes us all to gain weight, butunfortunately for some it happens morequickly than for others!
Molecular studies have identified someof the genetic factors involved in ourresponse to food. In 1994 work on miceled to the discovery of leptin, a hormoneproduced by fat cells. Leptin is detectedby the hypothalamus, a region of thebrain that controls appetite. In responseto leptin, the hypothalamus sends out
appetite-suppressing signals.Mutations in leptin genes and the pro-
tein in the brain which detects it (theleptin receptor) were found to cause obe-sity in mice.This was heralded as a break-through in our understanding of appetiteand weight gain. Despite the initial furoresurrounding this finding and the subse-quent identification of other genesdirectly involved in appetite control, ithas become evident that very few indi-
viduals are obese or overweightbecause of such clear-cut mutations.Rather, for most of us our genes spec-
ify a tendency to be larger or smaller.Drug companies have poured mil-
lions of pounds into the study of obesi-ty and the development of anti-obesity
drugs.The result is just a handful of med-icines that influence weight loss.Medicines currently available fall intotwo categories. The most common areappetite suppressants, which modulate
the activity of neurotransmitters thataffect mood and appetite, such ascatecholamine and serotonin. Thesecond type perturbs the action ofthe intestinal enzyme lipase.Whenlipase is disrupted, only about 70%of ingested fat is absorbed into the
bloodstream, leading to an immediatereduction in calorie intake and, theo-
retically, to weight loss. Scientists are alsoinvestigating the possibility of using aclass of anti-cancer drugs to treat obesity.These chemicals — known as angiogen-esis inhibitors — limit the growth ofblood vessels that feed tumours. Liketumours, fat cells need a blood supplyand, in 2003, it was demonstrated thatsome of the angiogenesis inhibitors couldsuppress weight gain in mice.
To date, no miracle cure has beenfound. Current drugs are only prescribedin extreme cases and are not recom-mended for long-term use. The mainproblem with the drugs is that they donot alter behaviour and so do not targetthe root cause of weight gain.
In the end, rising rates of obesity can betraced to features of our modern lifestyle.Food in the western world is now abun-dant and cheap, and we are increasinglyinactive.With a metabolism evolutionari-ly designed to store energy for times offood scarcity, we can’t help but gainweight.These environmental factors mustplay a major role in the global rise inbody-weight: our genetic make-up sim-ply hasn’t changed enough in the last 25years to account for the weight gain ofthe population.
Why though, are some of us more sus-ceptible to weight gain than others? Whatcontrols our willpower, our sensation oftaste, our tendency for depression, ourmoods, and our levels of anxiety? Allthese influence how and what we eat, butto what extent are they genetically pre-determined?
In the modern world, we don’t just eatfor sustenance and thus behaviour playsan enormous role in weight gain.Research so far has centred on the mech-anisms that physically control hunger, butthe importance of behavioural studies isbecoming increasingly apparent. Until wereally understand human behaviour andcombine this with our physiologicalknowledge, it is unlikely that we’ll trulyknow why we’re getting heavier.
Helen Stimpson is a postdoc in the MRCLaboratory of Molecular Biology
HelenStimpsonweighs up the factsbehind the ‘obesity epidemic’
luesci18 Michaelmas 2005
Fat of the Land
Over half of womenand two-thirds of menin Britain are classed as
obese
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Knowing nothing more about supercon-ductors than the dictionary definition(materials with zero electrical resistivityat temperatures close to absolute zero),it was with some trepidation that Iapproached the Department of MaterialsScience and Metallurgy to meet TarekMouganie, the scientist behind our coverimage. Thankfully Mouganie, a thirdyear PhD student in the department’sApplied Superconductivity andCryoscience Group, was not at all fazedby this and set about explaining to mewhat superconductors are, why he’sinterested in them, and of course howhis research came to produce the stun-ning image you see on the cover.
Superconductivity was discovered in1911 by the Dutch physicist HeikeKamerlingh Onnes. He observed thatwhen mercury was cooled to the temper-ature at which helium is liquid — 4.2 K(-269ºC) — its electrical resistance sud-denly disappeared. This lack of resistancemeans energy is not lost as it passesthrough a superconductor and so once setin motion, electrical current will flow for-ever in a closed loop of superconductingmaterial. In addition, superconductorshave interesting magnetic properties: themovement of a magnet over any conduc-tor induces a current in the conductorbut, in a superconductor, the induced cur-rent exactly mirrors the field that wouldotherwise have penetrated the material,causing the magnet to be repelled. Thiseffect is so strong that a magnet can actu-ally be made to levitate over a supercon-ductor.
Probably the most well-known applica-tion of superconductors is Magnetic
Resonance Imaging (MRI). By exposingthe body to a strong superconductor-derived magnetic field and then applyinga pulse of radio frequency (RF) radiation,hydrogen atoms in the body absorb ener-gy. The release of this energy uponremoval of the RF radiation is detectedand displayed graphically, providing doc-tors with a non-invasive method of look-ing inside the body. Other applications ofsuperconductors include their use in‘floating’ low-friction trains, high-energyparticle colliders and in the developmentof ultra-fast computers.
Despite the extraordinary properties ofsuperconductors, they are not as widelyused as one might expect. This is due tothe important fact that superconductorsonly exist below a certain critical temper-ature (Tc). Above the Tc superconductorsbehave like normal materials — a phe-nomenon which researchers are not yetable to fully explain. Commercially avail-able metallic superconductors operate atTcs in the region of 10 K (about -260ºC).These incredibly low temperatures areexpensive to achieve and are a majorlogistical problem in the development ofsuperconductor applications.
Understandably, the discovery of a ‘hightemperature’ superconductor in 1986caused great excitement. Swiss researchersMüller and Berdnorz created a ceramiccompound composed of lanthanum, bari-um,copper and oxygen that superconduct-ed at the highest temperature then known:30 K (-243ºC). This discovery — whichwas surprising because ceramics are nor-mally insulators — sparked a surge of activ-ity as scientists began creating ceramics ofevery imaginable combination in the huntfor higher and higher Tcs. In 1987, scientistssubstituted yttrium for lanthanum in theMüller and Berdnorz molecule to produceYBa2Cu3O7-5 (YBCO), a ceramic super-conductor with an impressive 92 K (-181ºC) Tc. Mouganie explained why peo-ple were so enthused by the quest for highTcs,“The inter-metallic, ‘low temperature’superconductors must be cooled using liq-uid helium in order to reach the incrediblylow temperatures needed; liquid helium iscomparable in price to the perfumeChanel No. 5. In contrast, ‘high tempera-ture’ ceramic conductors like YBCO canbe cooled using liquid nitrogen, whichcosts less than half the price of milk.”
Mouganie’s research involves the devel-opment of YBCO superconductors forcommercial application. He described achallenge he faced when beginning thisproject, “Unlike metallic superconductors,which can be bent easily to form supercon-ducting coils, the brittle nature of ceramicsmakes the formation of 3-D structures and2-D patterns much more difficult.”Mouganie approached this issue by devel-
oping an YBCO ‘ink’. The ink is a ‘sol-gel’;it is initially a solution but on heating con-verts to a gel. Using a specially built inkjetprinter, Mouganie has been able to print athin layer of YBCO onto a strip of metallictape which can then be manipulated toform a ceramic superconducting coil.
The eye-catching cover image and thepicture below left were taken duringdevelopment of the YBCO ink. The for-mer shows a segment of one droplet ofYBCO ink viewed under an opticalmicroscope.“In this case, the ink dried toorapidly, causing the surface of the dropletto crack.” The cover image is a close-upview of one of these cracks. The pictureon this page highlights another problem:“During the heating step, the componentsof the ink have coagulated and precipitat-ed to form large complexes.”
Mouganie has successfully created a 5-centimetre-long YBCO superconductingtape and the group are now collaboratingwith a German company to scale up theprocess.They plan to produce YBCO tapekilometres in length, which can be woundup to form coils. Although clearly pleasedat the success of the project, Mouganiedoes have one small regret:“Unfortunately,when dried correctly the YBCO ink pro-duces nothing more exciting than a trans-parent blue film, so it has put an end to theinteresting photographs!”
www.msm.cam.ac.uk/ascg www.superconductors.org
Tamzin Gristwood is a PhD student in theDepartment of Biochemistry
On
the
Cove
r
luesci20 Michaelmas 2005
Cracking ConductorsTarek Mouganie, the scientist behind our cover image, talks to Tamzin Gristwood
Once set in motion,electrical current will
flow forever in aclosed loop of super-conducting material
The brittle nature ofceramics makes theformation of 3-D
structures and 2-Dpatterns difficult
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The range of genetic tests availabletoday mean we can learn more thanever about the medical conditions we,and our children, may develop. But forevery test, patients need support andaccurate interpretation of results, arole often fulfilled by a genetic coun-sellor. With the sequencing of thehuman genome, and the new informa-tion we may gain from it about ourhealth, their role will be increasinglyimportant. Ann Kershaw works as acounsellor in the Genetics departmentat Addenbrooke’s NHS FoundationTrust hospital, Cambridge.
How would you describe your role?I work in the Department of Genetics,
which comprises 13 medically traineddoctors, six genetic counsellors and themolecular and cytogenetics laboratories.Together, we provide the regional genet-ic service for about 2.5 million people inEast Anglia.We also get a lot of referralsfrom outside the region as we hold sev-eral specialist clinics.
How did you become a genetic counseller?I trained as a nurse and then worked as
a health visitor in Cambridge.Addenbrooke’s was looking for a newcounsellor and I thought the role wouldenable me to spend more time withpatients and develop new skills.As genet-ics evolves rapidly there isn’t an opportu-nity to get bored.You have to work hardto keep up with new developments in thefield. We hold weekly meetings, journalclubs and seminars, and attend universitylectures, study days and conferences.
Historically, genetic counsellors werenurses, midwives and health visitors wholearnt ‘on the job’. Now there are alsograduates coming with a science back-ground and a Masters in GeneticCounselling. Both groups have some-thing to offer, and have had differentemphases during training, and it’s good tohave a mix.
Are you the first person the patient sees? Patients are allocated to the most appro-
priate member of staff. Patients needing adiagnosis will always see a doctor.A coun-sellor will usually see families with a knowndiagnosis.We see patients with single gene
disorders (such as cystic fibrosis),chromoso-mal anomalies (for example Down’s syn-drome) or a family history of cancer.
Our patients are referred to us by GPs,consultants and other health professionalsfor a whole range of reasons. Someonemay ask about breast cancer risk, and if wefeel they do not fulfill our high-risk crite-ria we may write to him or her or see thepatient only once. Or we may see some-one with a family history of somethinglike muscular dystrophy before a pre-nataltest; support them during and after thetest, and during future pregnancies.
What happens during a consultation on atypical day?
Normally I would see six families in aday with up to an hour per session.Duringa recent clinic I saw people with familyhistories of colon and breast cancer, cysticfibrosis and Huntington’s disease.The con-sultant will make a list of patients for me tosee and then it’s up to me to prepare forthat clinic, do the appropriate literaturesearches and organise any available testing.I advise people whether a test is available,and its pros and cons. We provide non-directive counselling enabling the family toarrive at the decision that is best for them.
Do you spend time on your own research?Primarily we have a clinical role and a
busy case load, so any research tends to bedone over and above the job, but we doencourage it. For example, I work with aneurologist researching Huntington’s dis-ease.There is a lot of psychological researchinvolved, such as how Huntington’s affectssleep and metabolism, which is the kind ofstudy we could publish. As counsellors weare particularly interested in the psychoso-cial aspects of inherited disease.
With so much information available on theInternet, is it hard to clarify for people whatis important and accurate?
The Internet has had a huge impact onour work. We now have a well-informedand educated client base. Because many ofthe conditions we see are rare, the first thingpeople do is to go on the Internet. It’schanged completely from when I first start-ed nursing. People now come in knowingabout the condition, so you have to be twosteps ahead and not be defensive. I think
that is empowering for patients. So my jobis to help them sift through information,and direct them towards good quality sites.
Considering the decisions that might followyour discussions, is your work stressful?
The workload is big and that is a factor,but the intensity of the consultation cansometimes be draining. People maybecome upset if they don’t agree withwhat you’re saying, for example if theybelieve a test is available and it isn’t. Somefamilies’ stories are very sad, so you have todeal with issues such as grief, bereavementand loss. Because we’re quite skilled indealing with people, we can usually man-age most challenging situations.
You develop coping strategies, and I havevery supportive colleagues, which is veryhelpful. Counsellors have formal psycho-logical supervision with an external super-visor.You can’t go home and discuss cases,as they are confidential so it took me awhile to learn to ‘switch off ’ at home.
What skills are needed for the job? A basic understanding of science, and the
way the health system works. Geneticcounselling is all about communication, sothe skill is to get the message across in termsof the genetics and the person’s risk. Youhave to be interested in people and be ableto put them at their ease quickly becauseyou have a short time to establish a relation-ship, and obtain all the information youneed in a consultation.
What are the benefits and downsides of yourjob?
It’s varied and diverse, I meet and workwith nice people, and I cover all sorts ofconditions and almost every aspect ofmedicine.Working with families is inter-esting and you can work with people fora long time and get to know them.Although we’re busy, we build up rela-tionships. I have worked with some ofmy Huntington’s families for 16 years.Patients with chronic conditions needsupport and continuity of care.
For more information about the work of agenetic counsellor visit www.agnc.co.uk
Nerissa Hannink is a postdoc in theDepartment of Plant Sciences
AD
ayin
the
Lifeof…
luesci 21www.bluesci.org Michaelmas 2005
A GeneticCounsellor Nerissa Hannink talks toAnn Kershaw about herwork as a genetic counsellor
Jon
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Located on the Western AntarcticPeninsula, surrounded by high moun-tains and glaciers, Rothera is the largestBritish Antarctic Survey base on thiscontinent. For eight weeks, this outpostof a hundred or so people was to be myhome, and the deep blue sea litteredwith giant icebergs, my office.
Scientists at Rothera study the processof sedimentation, where single-celledalgae called diatoms take up the ‘green-house gas’ carbon dioxide from the atmos-phere during photosynthesis, transportingit to the deep ocean as they sink.
I was working on a project to take sam-ples from three places: algae living near theocean surface, dead algae falling to the
depths and accumulated algae on theocean floor.Three times a week, three orfour of us took a small boat to the sam-pling site, a few kilometres off shore. Attimes the sea was covered in broken ice,making progress slow. Wearing enormousdry suits, we collected seawater using sili-cone tubing and a pump running off a carbattery.
The project was very much a teameffort, with people collecting samples foreach other and sharing the limited labora-tory space. For example, sometimes wehelped other scientists with a CTD cast, aninstrument that measures the conductivity,temperature and density of water by depth.This information is used by oceanogra-phers to calculate the water’s physical prop-erties and direction of movement.
There was a real cross-section of societyon base with scientists, pilots, mechanics,cooks, domestic staff, doctors, electricians,divers and many more getting to knoweach other. Living on base was comfort-able but basic and, thanks to the chefs, thefood was fantastic considering it arriveddried, tinned or frozen. For those who hadspent weeks in more remote parts of thecontinent, living in tents on dried food
and without a shower, Rothera was theheight of luxury!
This project taught me a great deal aboutthe work done of other BAS scientists andabout the importance of Antarctic science.Antarctica is not just a natural wildernessbut also a crucial part of our planet’s cli-mate system.The removal of carbon diox-ide by diatoms from the atmosphere couldalleviate the problems of climate change, asit is thought to have been an importantfactor in the cooling of the earth duringpast ice ages. Identifying the factors thatlimit diatom growth is therefore an impor-tant task, and a controversial one.Some sci-entists believe that it is the availability ofnutrients, such as iron, that is important,although calculations to determine thishave provided contradictory results. Muchwork is still urgently required in this rela-tively new field.
For more information about the BritishAntarctic Survey, see www.bas.ac.uk.To find
out about diatoms and sedimentation, seewww.indiana.edu/~diatom/diatom.html
Samia Mantoura is a PhD student in theDepartment of Earth Sciences
When asked if I would like to spendthree weeks on a field trip in theAzores, I didn’t have any hesitation insaying, “Yes please!”
This trip was part of an internationalproject known as the InternationalTransport of Ozone and its Precursors(ITOP) which has been set up to investi-gate the transport of pollutants such asnitric oxide and carbon monoxide fromNorth America to Europe.These pollutantscome from forest fires and the burning ofbiomass and fossil fuels.Though pollutionis often seen as a local problem, gases pro-duced in this way can be transported vastdistances by weather systems: pollutantsoriginating in North America can bedeposited in Europe three to five days later.In the presence of sunlight, these chemical-ly active gases react with other chemical
compounds to produce ozone, which con-tributes to the high concentration of ozoneobserved over many parts of Europe.
The ITOP campaign involved groupsfrom several UK universities, including theUniversities of Cambridge,Leeds,Leicesterand York.
Our team was based in Horta on theAtlantic island of Faial, the second largestof the nine islands that make up theAzores. Faial is one of the most beautifulplaces I have been fortunate enough tovisit, with a varied mixture of lush greenlandscape and hills, volcanic craters, dra-matic coastlines and, of course, the brightblue sea.
Most of our experiments were carriedout via a suite of instruments on a BAe-146 aircraft. I was involved in operatingthe on-board Tuneable Diode LaserAbsorption Spectrometer, which measuresthe concentrations of carbon dioxide andmethane. Flights, usually lasting betweenfive and seven hours, took place over theAzores, Portugal and beyond. Even on thedays we did not fly, there was work to bedone: either in the hot and stuffy tempo-rary labs that had been set up at the air-port, or on the aircraft itself.
The results of the ITOP study will con-tribute to furthering our understanding ofthe environmental impact of both local andglobal pollution. Despite the long hours,hard work, gruelling heat, constant sweat-ing and all the itching from mosquito andother insect bites, we did enjoy one or twofree days when we were able to go hikingand whale-watching.All in all it was a greatexperience and definitely one I would gothrough again!
http://badc.nerc.ac.uk/data/itop
Will Flynn is a PhD student at the Centre forAtmospheric Science, Department of Chemistry
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luesci Michaelmas 2005
Out Of The Frying Pan...Will Flynn investigates global pollution on holiday in the Azores
22
…And Into The FreezerSamia Mantoura gets cold in the name of science
Faial is one of themost beautiful placesI have been fortunate
enough to visit
“
” Mount Pico on Faial
Samia in the snow
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Initiatives
luesci [email protected]
Did you think gender inequality inthe sciences was a thing of the past?These statistics may make you thinkagain. Women still make up less than20% of lecturing staff in science,engineering and technology (SET) atthe University of Cambridge.Although females account forapproximately 50% of undergraduatesstudying biological sciences, this fig-ure is much lower when one consid-ers the physical sciences. The propor-tion of women involved in SET disci-plines is lower at the graduate level,and declines yet further at more sen-ior levels. These figures are not con-fined to the University of Cambridge;nationally, less than 10% of those
elected to Fellowships of the RoyalSociety are female.
Several factors have been suggestedfor this inequality, for example, thestereotypical scientist is a man – not awoman – in a white coat, and as thereare relatively few prominent seniorfemale scientists there are a lack of rolemodels for girls considering a career inSET. There is concern that schools areoften ill equipped to overcome theseissues when offering careers advice togirls interested in SET. As in other pro-fessions, women often take career-breaks to start a family but the rapidtechnological advances in SET make itespecially difficult for women to returnto the workplace, thus reducing the
number of women progressing to sen-ior positions.
So what is being done to address theseproblems? Following the publication ofa report entitled ‘The Rising Tide’ byHMSO in 1994, in which this under-representation of women in SET wasdocumented, a number of groups thatsupport women in SET have been setup. Nationally, these include theAssociation for Women in Science andEngineering (AWiSE), which is aregional network run by volunteers, andthe Women in Science, Engineering andTechnology Initiative (WiSETI), whichis a Cambridge University-funded ini-tiative. Both of which are currentlyactive in Cambridge.
A Woman’s Work?Cambridge scientists discuss networks for women in science, engineering and technology
AWiSE
AWiSE is a national organisation withbranches, meeting and eventsthroughout Britain. Its objectives areto promote SET for girls and women,form a collective voice for women inSET, provide a network for mutualsupport, act as a centre of informationand resources and act as a forum fordiscussion. In addition it is a valuableresource for keeping women in SETinformed about topical and ongoingissues that affect them. CambridgeAWiSE achieves these aims by:• Organising local events and meet-ings on topics such as “Attitudes toPar t Time and Flexible Working”which include short talks but alsoplenty of opportunity to discuss theissues and to meet women from otherfields within SET.• Setting up MentorSET which pro-vides professional women in SET withindependent mentors who can offerguidance, support and encouragementto help women further their careers.The organisation’s strong networkinginitiative has provided members withmany international opportunities andlinks with overseas. Today they net-work with US AWI, WISENET inAustralia, NZ AWISE, SAWISE inSouth Africa, Femmes et Sciences inFrance, CES in Germany and with theWomen in Science section of theEuropean Commission.
For information about AWiSE inCambridge including details of forth-coming meetings visit their website:www.awise.org/?q=CambridgeBranch oremail [email protected] more information on MentorSETgo to www.mentorset.org.uk.
WiSETI
WiSETI is a University organisationwith a remit to increase the numbersof women studying SET at Cambridge,to improve the recruitment, retentionand promotion rates of women in SETappointments and to raise the profileand enhance the self-confidence ofwomen in SET through a range of ini-tiatives.These include:• A recruitment programme aimed atencouraging women to apply for jobsin academic science and ensuring thatthey receive appropriate informationabout positions that may interestthem.• A Code of Practice and best prac-tice guides for the SET workplace.• Careers talks for undergraduatewomen, sponsored by Citigroup, inwhich a distinguished panel of guestsspeak about their careers.• An annual WiSETI lecture, spon-sored by Schlumberger, which waspresented in May 2005 by ProfessorKathy Sykes from the University ofBristol.• MentorNet, an international e-men-toring programme which offers stu-dents in SET the opportunity to bepaired with a mentor from industry oracademia, and exchange regular e-mails about careers, courses, profes-sional bodies etc.• Springboard Personal DevelopmentProgramme for undergraduates, whichencourages personal and professionaldevelopment through workshops, theSpringboard workbook and opportu-nities for networking.
To find out more, visit the website:www.admin.cam.ac.uk/offices/person-nel/equality/wiseti.
Dr Nancy J. Lane is Director of WiSETI atthe University of Cambridge; Dr Alison
Maguire is Recruitment Office for WiSETI;Dr Jenny Koenig is Chair of Cambridge
AWiSE and a Fellow of Lucy CavendishCollege; Dr Bojana Popovic is a postdoc in
the Department of Biochemistry.
Kat
herin
eB
orth
wick
Imagine a university that taught sci-ence degrees but did not have any lab-oratories. Imagine studying for adegree in science that did not involveany practical work whatsoever.Welcome to Cambridge in the mid-nineteenth century.
Unlike today, research was not consid-ered part and parcel of being a universi-ty professor, and practical training wasnot a standard part of the curriculum.Some favoured students were permittedto assist a professor in experiments butmost graduated with no hands-on expe-rience at all. The theories they weretaught in lectures had mostly been eluci-dated by gentlemen amateurs like JamesJoule, who had a laboratory at home, orby academic men of science like IsaacNewton, who experimented in his col-lege rooms. Private laboratories, ratherthan ones connected to institutions likeuniversities, were the norm. Those labsthat did exist in universities were smalloffshoots of lecture theatres wheredemonstrations were prepared, ratherthan spaces for research or teaching.
During the nineteenth century, howev-er, institutional laboratories of the kindmodern students and scientists mightrecognise did become increasingly com-mon: first in Germany and France andthen later in Britain and the UnitedStates. Accompanying this trend was a
growing emphasis on precision measure-ment, partly driven by recognition of itsrole in industrial progress. Physicists inBritain made the link between Germany’sexcellency in physics and its newfoundindustrial prosperity, using this to arguefor better facilities and increased funding.
In the 1860s the University Senaterecognised the growing clamour for newlaboratories in Britain by setting up acommittee to investigate the possibility ofestablishing one in Cambridge.This inves-tigation came out firmly in favour of cre-
ating a space for practical teaching andexperimentation, fitted out with the latestapparatus and supervised by a new profes-sor and his demonstrators. Several yearslater, the Cavendish Laboratory on FreeSchool Lane opened amidst a great deal of
interest… and not a little controversy.The Cavendish Laboratory was named
after the University Chancellor who hadprovided most of the funding, theUniversity itself being in a spot of finan-cial bother at the time. James ClerkMaxwell, now renowned for his work onelectricity and magnetism, was appointedthe first Cavendish Professor and helpedoversee the design and construction of thenew laboratory. It was modelled on thepioneering teaching laboratories of theGerman universities, which emphasisedthe importance of systematic practicaltraining and the use of elaborate instru-ments.As well as space for research it alsocontained lecture halls and a workshop forthe construction and repair of equipment.
Strange as it may sound to us now, con-cerns over whether or not practical workwas an appropriate part of a scientificeducation plagued the Cavendish’s earlyyears. It was a time when the manipula-tion of instruments carried undesirableassociations with factory work and man-ual labour, occupations considered entire-ly unsuitable for a student of theUniversity of Cambridge.Experimentation was considered bymany to be an intellectual step-downfrom the more cerebral activities of calcu-lating and theorizing. As Maxwell wor-ried,“If we succeed too well, and corruptthe minds of youth till they observevibrations and deflections and becomeSenior Ops. instead of Wranglers, we maybring the whole University and all theparents about our ears.” (A ‘Wrangler’ wassomeone who achieved a First in theMathematical Tripos, whilst ‘Senior Ops.’refers to a manual worker.)
All in all, the bill for the originalCavendish came to £8,450. An extrava-gant sum at the time, this amount repre-sents but a fraction of what laboratoriescost to build and equip now. In part, thisreflects changes in the technology ofphysics research since the nineteenth cen-tury: then, an item of apparatus usuallyfitted on the workbench and was oftenpieced together from relatively basic andeasily available materials. The twentiethcentury saw an incredible leap in the scaleof experimental physics, both in cost andsize. For example, the forthcoming exten-sion of the Cavendish is likely to costmore than £137 million, while somemodern physics instruments (such as theLarge Hadron Collider in Geneva) are soexpensive that they require financial sup-port from several nations.
Research in the new laboratory wasinitially carried out by college fellows,mainly new graduates of theMathematical Tripos which dominatedCambridge teaching in this era. It wasseveral years before undergraduates came
His
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luesci24 Michaelmas 2005
A Trip Down Free School LaneEmily Tweed and Victoria Leung investigate the history of the Cavendish Laboratory
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Concerns overwhether or not
practical work wasan appropriate
part of a scientificeducation plaguedthe Cavendish’s
early years
One of the earliest photographs of the practical class in the Cavendish, taken in 1933
Cav
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than 28 Nobel Prize recipients among itsresearchers past and present.
The laboratory was founded during acritical period in the history of physics. Itwas a time when science as a professionwas gaining increasing recognition: theterm ‘scientist’ was beginning to be wide-ly used, and the people it described weregrowing in number. Both the modernuniversity and modern physics as weknow them were taking shape.Cambridge was offering a greater rangeof courses, including the Natural SciencesTripos and research degrees, and its facil-ities were expanding accordingly.Physicists began to undertake systematicpractical training and form organizedgroups of researchers, reporting theirfindings in specialist journals and at insti-tutional seminars.
The new Cavendish Laboratoryoffered students a chance to movebeyond purely theoretical study for thefirst time, giving them the skills to pur-sue a career in research — an optionwhich, only a couple of decades before,would have been open to very few.Looking at the sprawling complex inWest Cambridge that the Cavendish nowoccupies, it seems a million miles awayfrom the tiny laboratory on Free SchoolLane that cost only a few thousandpounds and which was almost not builtfor fear that practical work would “cor-rupt the minds of youth”.
Emily Tweed is a third year Natural Scientistspecializing in Pathology;
Victoria Leung is a third year NaturalScientist specializing in Physics
to use the new facility, and several morebefore organised lab training and practicalexams were incorporated into under-graduate degree courses. The latter wasbrought about by the second CavendishProfessor, Lord Rayleigh,who introduced
the now familiar system where studentsmove between a series of experiments,writing reports and aided by demonstra-tors. In examinations, students might beasked to measure the resistance of alength of wire or the focal length of alens, or otherwise identify a piece ofapparatus and take a measurement withit. One answer from this era has becomeinfamous: one hapless student describedin 100 Years and More of Cambridge Physics“recognised in a thermometer a machinefor determining the specific gravity ofwater”!
Despite the odd undergraduate slip-up,the Cavendish soon gathered renown —particularly for the quality of its research.The lab became particularly famous for
Histo
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luesci 25www.bluesci.org
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The CavendishLaboratory was
founded during acritical period inthe history of
physics
Further Reading100 Years and More of Cambridge Physics, booklet available from Cavendish Laboratory.When Physics Became King, Iwan Rhys Morus, University of Chicago Press, 2005
the technical expertise of its workers:ironic considering the initial objectionsmade to its foundation.This experimen-tal focus contrasted with the Cavendish’scounterparts on the Continent, whichexcelled at theoretical physics, and wouldserve as the foundation for the illustriousyears ahead.
As in other laboratories, there was anoverriding emphasis on precision meas-urement and quantification, particularlywhen it came to physical constants andstandard units. As well as the demandsfrom industry, this ethos of exactitudegrew from a consensus among the physi-cists of the time that all the interesting,fundamental problems of their disciplinehad been solved and that their job wastherefore to fine-tune these theories byworking out the details and measuringthe necessary constants with ever greateraccuracy. One example of this was LordRayleigh’s work on the definition ofstandard electrical units such as the Ohmand Ampère.
Notoriously cramped and overcrowd-ed, the Cavendish was extended throughthe 1880s and 1890s as the community ofresearchers grew. Its prestige attractedresearchers from other universities andlater from abroad, including the youngErnest Rutherford, famous for hisresearch into atomic structure. Itremained at the forefront of experimentalphysics throughout the twentieth centuryand the Cavendish can count no fewer
The Cavendish Laboratory:The Early Years1846William Thompson, a Cambridge graduate, sets up BritainÕs first university physics laboratory in Glasgow.
1869Senate committee reports in favour of founding a physics laboratory in Cambridge.
1871Construction of the Cavendish Laboratory begins on Free School Lane. James Clerk Maxwell appointed first CavendishProfessor (after Thompson turns down the post).
1873Maxwell publishes A Treatise on Electricity and Magnetism, a groundbreaking work which proved the fundamental connec-tion between light and electro-magnetism and yielded a set of classic equations, which Einstein later acknowledged as theorigins of special relativity.
1874The Cavendish Laboratory officially opens, although it had been in informal use for several months already.
1877First undergraduate lectures on basic practical topics introduced.
1879Lord Rayleigh succeeds the late Maxwell as Cavendish Professor: he is later awarded a Nobel Prize for his work at theCavendish.
1882Women allowed to study at the Cavendish Lab for the first time: Maxwell had famously forbidden women studentsexcept at times when he was on holiday.
1884J.J.Thomson appointed Cavendish Professor: he later wins a Nobel Prize for his discovery of the electron following hisfamous Ôcathode rayÕ experiments.
1895 Ernest Rutherford joins the Cavendish as a research student; after work in Canada and Manchester he rejoins the lab asCavendish Professor in 1919.
Music. Emotional, ineffable, an enig-matic and ethereal art form. Suchdescriptions are commonplace, andwhilst there have been some attemptsin the past to uncover the scientificbasis of music, these have been limitedand in some cases led only to exasper-ation and resignation. Take, for exam-ple, Claude Lévi-Strauss, who tried todescribe the influence of music onhuman nature, including how we per-ceive musical time and its effects onthe internal organs. Eventually he gavein, concluding that “music will remainthe supreme mystery of human sci-ences”. But the mystery is slowlybeing unravelled as science meetsmusic head on.
In a quest that leads from decodingthe ways in which we process music tofundamental questions about its originsand purpose, the field of science andmusic draws on aspects of both disci-plines, including music analysis, experi-mental psychology and neuroscience.One of the few centres specialising inthis amalgamation is the Centre forMusic and Science (CMS), directed byDr Ian Cross, here in Cambridge.
Humans have the ability to perceiveeffortlessly the patterns of acoustic ener-gy that we know as sound. After travel-ling through the outer and middle ear,sounds arrive at the inner ear (thecochlea) where they are sorted into theirconstituent elementary frequencies.Thisinformation is then transmitted from thecochlea as a string of neural dischargesalong individual fibres of the auditorynerve, finally arriving at the auditorycortex in the temporal lobe of the brain.But this is only half the story. When itcomes to listening to music, not only donumerous regions of the brain becomeinvolved in processing its various per-ceptual elements (such as melody,rhythm and harmony), but the very con-struction of the ear has an importantinfluence on the details of this proce-dure.
Researchers in the field of psychoa-coustics, for example, have demonstrat-ed that the physiology of the ear has a
direct effect on our perception ofsounds as either pleasant or unpleasant(consonant or dissonant). Situated in thecochlea of the inner ear is the basilarmembrane. This membrane has groupsof sensory receptors, composed of haircells running along its length, thatbecome activated in response to soundsof specific frequencies. If the positionsof excitation on the basilar membraneare too close, interference occurs, result-ing in an unpleasant sensation for thelistener.
When it comes to deciphering therole of the brain, our understanding hasrecently begun to flourish with the useof brain-imaging techniques such aspositron emission tomography (PET)and functional magnetic resonanceimaging (fMRI). Blood flow increases tothose regions of the brain activated byparticular cognitive tasks, and PET andfMRI techniques are able to pinpointthese activated regions by measuringcertain properties of the blood.
Imaging studies of healthy individuals,together with evidence taken frompatients with brain damage, have shownthat there is no specialized ‘music centre’in the brain. Instead, many areas distrib-uted throughout the brain contribute tothe processing of music, including thosefunctioning in other kinds of cognition.Scientists are gradually mapping theseareas in greater detail. For example, theright temporal lobe of the auditory cor-tex is involved in perceiving aspects ofmelody, harmony and timbre. Differentregions within the auditory cortex alsoprocess various features of rhythm.
A more precise understanding of cer-tain brain structures has also beenattained. Recent work at the JohnHopkins University in Baltimore,Maryland, has revealed the existence ofpitch-sensitive neurons. The pitch of asound depends on its fundamental fre-quency, even when this frequency isphysically missing from a complex
sound. Individual cells have been foundin the auditory cortex of marmosetmonkeys that consistently responded ina similar way to various sounds that,although having no common frequency,shared the same fundamental frequency.For example, a neuron that responds to200 hertz also responds to the mixtureof 800, 1000 and 1,200 hertz because allhave the same fundamental frequency.The location of these pitch-sensitivecells is consistent with the location ofpitch-selective areas identified in humanbrain scans.
The response of the brain, however, isvariable and depends on factors such aspersonal experience or musical training.Studies have shown, for example, thatthe volume of the auditory cortex inmusicians is 130 percent larger than thatin non-musicians.
Music is, of course, more than a cata-logue of auditory aspects.The emotionalresponse that music evokes is key to thelistening experience, and the areas of thebrain responsible are partially segregatedfrom those that deal with the auditoryprocessing of music. Though researchinto this area is still in its infancy, PETimaging studies carried out on volun-teers listening to consonant or dissonantpatterns of notes have revealed that atleast two systems, each dealing with aseparate type of emotion, are involved.Furthermore, it has been shown that
Arts
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luesci26 Michaelmas 2005
The Sound of ScienceOwain Vaughan and Neta Spiro explore the biological and cultural phenomenon that is music
When music induceda pleasurable
response,it activated the samebrain structures asthose stirred by
food, sex, and drugs
Studies have shownthat the volume ofthe auditory cortex
in musicians is 130 percent larger
than that in non-musicians
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Tom
Wal
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when music induced a pleasurableresponse it activated the same brainstructures as those stirred by food, sex,and drugs.
A comprehensive explanation of ourmusical experiences cannot, however, beachieved through studies of the ear andbrain alone. To venture towards a morecomplete understanding, the science ofsound is being placed in a broader con-text, both theoretically and experimental-ly. Research by Dr Ian Cross and othermembers of the Cambridge CMSemphasizes music as a biological and cul-tural phenomenon, studying such issuesas the origins of music, the abilities thatpredispose humans to music, and the veryreasons for its existence.
Consider, for example, the followingthree aspects of music, hitherto largely
neglected. The first is that music is anembodied action, inextricably bound tothe movement of our bodies. Thenotion of sitting in a concert hall andsimply listening to music is unique toWestern classical music: most musicinvolves some kind of movement ordance. Indeed many cultures do not dis-tinguish between music and movementand have the same word for both. TheIgbo of Nigeria, for example, use theword nkwa to denote “singing, playinginstruments and dancing”. Secondly, thefact that music is embodied may providethe basis and explanation for music’scapacity for entrainment, the processthat allows us to act together in time.This is reflected in our ability, rare inthe animal kingdom, to tap along to abeat.Thirdly, that music is embedded insocial actions, playing an integral part inoccasions like weddings, funerals, andparties.This provides yet another way inwhich music can be imbued withmeaning, although the meaning mayvary from person to person. Combinedwith the idea of entrainment, this socialaspect of music allows it to create feel-ings of togetherness and of shared expe-
rience that most forms of language areunable to achieve.
These ideas contribute to the intrigu-ing suggestion that music - with thecapabilities it requires, the positive effectsit has on social cohesion, and the power itholds over our emotions - may haveplayed a key role in the evolution of thehuman mind.
These fresh angles, and the questionsthat they evoke, are thus encouraging newways to investigate the subject. Music andscience started out using physics, psy-chophysics, psychology, artificial intelli-gence, and neuroscience. But things movequickly. Recognition of the wide-rangingimpact of music, and our experience of ithas led to additional fields such as biology,archaeology and sociology entering thescore.The overture has ended; the opera isabout to begin.
Owain Vaughan is a PhD student in theDepartment of Chemistry; Neta Spiro is a
PhD student at the Institute for Logic,Language and Computation, University ofAmsterdam and the Centre for Music and
Science, Faculty of Music, University ofCambridge.
Arts
&Review
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Music may haveplayed a key role in
the evolution of the human mind
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Dear Dr Hypothesis,I have just returned from my summerholiday in the Caribbean which, as youcan imagine, was much warmer thanCambridge! Normally I’m addicted tothe wonders of my college buttery butwhile I was away I was much less hun-gry. It wasn’t just that I lay on thebeach all day, and simply needed lessenergy, as I was an active sightseer.Could there be a biological explanationas to why my appetite should bereduced in hot weather?
Ravenous Rita
DR HYPOTHESIS SAYS:Rita, the explanation for this phenome-non is considered controversial by somebut I will give you my favourite.This statesthat appetite is regulated not just by ourneed to consume food for energy, as manypeople think, but also by our need to con-trol the amount of heat generated whenfood is broken down, so as to maintain aconstant internal temperature. It followsfrom this that, on a cold day, you wouldneed to eat quite a bit to keep your bodytemperature steady relative to the muchcooler surroundings, whereas on a hot dayyou would be driven to eat less to reducethe energy generated and hence the heatproduced.Therefore buttery food seems alot less appealing in the heat of theCaribbean!
http:/books.nap.edu/open-book/0309048400/html/189.
Dear Dr Hypothesis,I was brushing my teeth the other nightand unfortunately forgot to follow theadvice of switching the tap off while Ibrushed. I noticed that, as the water felltowards the sink, the stream of waterappeared to become narrower. It lookedas if the amount of water was decreas-ing! Surely the water was not just evap-orating into thin air so, while I wouldnot wish you to waste further watertesting this phenomenon, I was wonder-ing whether you could explain it to me?
Observant Oscar
DR HYPOTHESIS SAYS:It is actually quite simple for me to answerthis query, Oscar.The effect is known as avena contracta — literally, a contractedvein. Inside the pipe, the water is underpressure from the column of water aboveit, with forces from the walls stopping itfrom leaking out sideways.The water jet isunder less pressure from the air once out-side the tap than it is from the pipe wallswhen it’s inside, which makes the waterspeed up as it is released. As you say, thewater can’t just vanish (a consequence of itbeing incompressible at subsonic speeds),so the jet has to reduce its cross-sectionalarea to compensate for its greater velocity.
Dr Hypothesis is most grateful to ProfessorMark Warner of the Cavendish Laboratory for
useful discussions.
Dear Dr Hypothesis,I am to retire next year and am look-ing forward to having enough free timein which to do many of the things thatI have always dreamed of, such as tak-ing a road trip across the States.Nevertheless, I am concerned about myfinancial situation and would like tostretch it as far as possible without run-ning into problems in my last few years.To this end, could you tell me howpopulation scientists calculate lifeexpectancies and what mine is likely tobe?
Thrifty Trevor
DR HYPOTHESIS SAYS:Life expectancy is usually defined as theaverage age until which a group of peopleof the same age and gender are likely tosurvive.This value is found from so-called‘life tables’, compiled by statisticians usingthe death rate at each age.They use thesefigures to calculate the probability ofmembers of a group surviving from onebirthday to the next, from which lifeexpectancy can be extrapolated. Forexample, figures released by the UK gov-ernment estimate that boys born in
England in 1980 could expect to live tothe age of 70.8,while girls could anticipatereaching 76.8 years old.You should alwaysbe careful when applying these figures toyourself as there can be a lot of variancearound these averages, depending onlifestyle. So maybe by refusing fish andchips and going for a run instead we canall lift the average life expectancy of ourgroups!
www.statistics.gov.ukmathworld.wolfram.com/LifeExpectancy.html
“If you accept that the universe is infinite,then there is an infinite amount of chancesfor anything to happen.Therefore, eventu-ally, everything will happen regardless ofthe likelihood. It follows from this that lifemust exist elsewhere in the universe butalso life must exist in very similar forms tothat which has evolved on this planet.”
“The answer to your question could befound using the famous Drake equation,which calculates the number of extrater-restrial civilizations (N) in our galaxy withwhich we can expect to make contact:
Where R* is the rate at which stars areformed; fp is the fraction of those starswhich have planets; ne is the average num-ber of planets which could support life perstar that has planets; fl is the fraction ofthese planets which actually do supportintelligent civilizations; fc is the fraction ofthese which are then willing and able tocommunicate with us; and L is the expect-ed lifetime of such a civilization. Currentvalues for N range from 0.05 to 5000:obviously some of these values are moreeasily quantified than others, and the resultobtained depends on the optimism of yourestimate!”
Dr
Hyp
othe
sis
luesci28 Michaelmas 2005
Dr Hypothesis
In the last issue Dr Hypothesis askedyou, the reader:
Is there life ‘out there’?
Read some of the answers below…
Dr Hypothesis needsyour problems!If you have any worries (of a purelyscientific nature, obviously) that youwould like Dr Hypothesis to answer,please contact him by email at [email protected] will award the author of the mostintriguing question a £10 book vouch-er. Unfortunately, Dr Hypothesis can-not promise to answer every ques-tion, but he will do his best to see thatthe most fascinating are discussed inthe next edition of BlueSci.
Dr Hypothesis needsyour problems!He challenges you with this puzzle:
When I hold a copy of BlueSci up to amirror the writing appears back-to-front.But, given that the mirror doesn’t seem tohave a preferred direction, why doesn’tthe writing also appear upside down?
Please email him with answers, thebest of which will be printed in thenext edition.
