一项有争议的意大利干细胞疗法——科学家称其未得到验证——将进行第一次科学试验。5月22日，意大利参议院投票通过一项众议院已批准的新法案——向都灵st amin a基金会的临床治疗试验拨款300万欧元。同时，该基金会将继续治疗在布雷西亚一家医院接受有争议疗法的12位病人。”这可能是议会第一次允许进行临床试验。”米兰大学un iStem干细胞中心主任ElenaCattaneo称。在意大利．St amina的疗法长期以来存在争议。该基金会称其已找到改变病人间充质意大利开展争议性干细胞治疗临床试验干细胞的方法．将来自骨髓的间充质干细胞转化为新神经细胞，再利用这些细胞治疗神经退行性疾病。不过很多干细胞科学家并不理会其声明；国际干细胞研究学会最近表示．并没有“临床试验可以提供令人信服的证据，表明这些细胞有益于患神经疾病的病人”。今年3月．当时的卫生部部长RenatoBaIduzzi——承受着来自病人的巨大压力——表示他对该疗法的支持并提出法案解决争端。如今．意大利参议院对经过修订的法案绿灯放行，允许St ami na继续为病人注射，对这些病人的治疗早已在布雷西亚开始：然而，该基Researchers0utl i neConcernsAAn international group of leading stem cell researchers has issued a statement that specifies concerns about the development and use of unproven stem cell therapies．The commentary is published online today inTheEMBOJournaI ahead of a debate in the ltalian parliament on whether to change a recent，law that allows certain untested stem celI therapies to be used by the public health system．T h e a ut h o r s of t h e commentary argue that rigorous clinical testing and regulation of stem cell therapies are essential to introduce safe and e仟ective medica|interventions for patients．Stem ceI|s m aY offe r unprecedented opportunities to develop treatments for many diseases with unmet medical needs．This wilI take time．However, onlY rigo rous scien ce a nd responsible regulation can ensure the safe and effective translation of science into effective therapies,” remarkedPaoloBianco,Pathologist,StemCellBiologist，Professor of金会不能继续接收新的病人。另外．药品管理局(AIFA)、国家健康研究所和国家移植中心将领导一项耗资300万欧元的临床治疗试验。该法案并没有具体规定这项研究的安排及目标疾病，但要求建立一个科学委员会来设计试验。在投票的一周前．乌迪内大学心理学家、Stami n a基金会主席DavideVannoi表示．他的治疗方法对各种神经退行性疾病都有效．其方法是基于发表在中国科学期刊上的体外和临床前研究．然而他并没有提供这些论文的复印件。进行遗传疾病研究的非营利基金会Telethon的总经理FrancescaP a si n eI|i称，这并没有说服力。“国际科学界的语言是英语。”她说。她还补充称．即使中国研究人员想获得国际认可．也需要使用英语。 boutUnprovenStemCellTherapiesPathology at theUnive rsity ofRoma”LaSapienza。1 and one of the13 authors of the commentary who come fromItaly,Germany,theUnitedKingdom，TheNetherlands and theUnitedStates．The concerns of the scientific community have been heightened by pending legislative action that may allow routine administration of unproven stem cell therapies to patients inItaly．Despite a lack of rigorous cIinicaI triaIs to test safety o r efficacy,a ban of the treatment by health authorities，and a lack of peer review by the scientific community,the privately fundedStaminaFoundation has been using cultured mesenchymaI stem cells that have been exposed to putative conditions that favour neuronal differentiation to treat difierent diseases in severely or terminally ill patients．TheItalianChamber decides shortly whether they wilI proceed with controversiaI legislation passed in theSenate on21March that al|ows the unproven stem celI treatment developed by theStaminaFoundation to be used for severely or terminally…new patients fo r18 months．”The adoption of this law may set a dangerous precedent for patients looking to be treated with other unproven stem cell therapies inEu rope and othe r count ries，“ remarkedHansClevers．Professor ofMoIecula rGenetjcs andPresident of theRoyalNetherlandsAcademy ofArts andSciences．”l rrational and unverified stem ce||treatments based on methods that are not validated or scientifically documented should not reach patients．Preventing this from happening is a specific responsibility of health authorities and gove rnments wo rldwide to make sure that the hope and trust of patients are not misused．” remarkedElenaCattaneo,Director of theCent re fo rStemCeI|Research at theUniversity ofMilan，Italy,and one of the scientists who contributed to the commentary．”Patients can be harmed and killed by medicines that have not been proven to be safe and effective via rigorously controlled clinical trials．The use of medicines that have not been manufactured to the highest possible standards is irresponsible．”Preclinical and clinicaI tests have been used successfullv in theDast fO r the introduction of theraPies fo r bone ma rrow t ra n sPl a nt ati o n a n d t h e regeneration of skin and cornea in patients．The authors of the commenta rv emPhasize that cell therapies must be approved bv inte rnational and nationaI regulatory agencies and remain under the strict vigilance of health authorities．Regulations already in place in theEuropeanUnion insist that stem cell therapies follow the same safety and efficacy rules as pharmaceuticals．They need to be prepared and manufactured in highly controlled environments with precise protocols，traceability and accountability．“It is diSCOnce rting that theItaIianSenate has passed amendments that permit the use of unproven stem cell therapies without proper vigilance or proper experiment．reclassifying them as transplants，“commentedBianco．ililll《ill翳淄t。；。，。、。。；。。。l s。；。。；；fic and可j。h。。l。。。。。i x。format；。。美重振制造业出新牌巨资成立三所创新研究机构美国奥巴马政府于本周宣布．计划斥资2亿美元创建3个新的先进制造业创新研究机构，其主要关注点集中在数字化制造、轻质复合材料生产以及下一代能源研发等领域。这些新研究所是奥巴马试图通过建立”制造业创新全国网络”，以重新启动美国制造业部门这一计划的又一步。奥巴马政府提交的2014财年财政预算案要求一次性投入10亿美元资助建立全国网络．该网络将由另外15个机构组成。这些机构将促进工业、大学和社区学院配合联邦政府机构．设计和实现制造业上的创新．而资金将来源于国防、能源和商业部门，以及宇航局和国家科学基金会。另外，企业合作伙伴和地方政府部门也将提供对等资金。去年，俄亥俄州扬斯顿启动了一个创新试点项目，该项目主要致力于辅助制造研究——也就是通常所说的3D打印技术。”这是伟大的又一步。这些创新机构已经激发了大量的热情。”加利福尼亚大学伯克利分校机械工程师DavidDornfeld提到。数字化制造研究所将开发用于帮助推动制造业从设计和样品研发到生产和检验阶段的软件。轻质复合材料制造研究所将尝试降低诸如医疗器械、交通工具等产品的制造和能源成本。新能源研究所将采用半导体技术．开发紧凑、高效能源。”新能源研究所主要针对能源部．但是另外两个则主要指向总统提议的方向。”Do rnfeId在参考了2012年先进制造业合作指导委员会提交给总统．并得到总统科学技术咨询委员会同意的一份报告后这样表示。然而．一些行业观察家尽管总体上支持制造业创新计划．但他们担心这些创新可能不够强健。佐治亚理工学院公共政策分析家Phi l ipShapi ra表示，它将支持美国制造业格局在某种程度上与德国、英国、日本和中国台湾的体系相差无几。“但是，154"中心可能太少了。”Shapi ra说。相比之下，德国拥有60个致力于技术和制造业创新的弗劳恩霍夫研究所。专家则同意．即使奥巴马从国会获}LI：IO,fZ美元，一旦脱离长期公共资金的补充，这些研究机构也无法独立支撑。奥巴马一直在试图振兴美国制造业，2月在国情咨文演讲中．奥巴马将制造业放在核心地位．指出首要任务是使美国成为新的就业和制造业的磁极，并宣布多成立3个制造业研究机构，同时要求国会帮助成立另外15个制造业研究机构．保障美国制造业的新一代革命。2012年8月16日，奥巴马政府就宣布在扬斯顿成立一家联邦政府和私营部门共同资助的制造业创新研究所——国家快速成型制造创新研究所。这是美国政府为促进制造业振兴推出的一大举措。Obama administration announces manufacturing institutesThe admini st ration ofUSP residentBa rack0bama announced thi s week that it is cornmitting usS200 mi|Iion to c reate th ree adva n ced— m an ufactu ring in novation institutes，focusing on digitaI manufactu ring，Iightweight composites and next_generatiOn power sources-The new institutes a re another step inObama’s plan to rebootAmerica’s manufacturing sector with aNationalNetwork forManufacturingInnovation．Obama’s fiscaI2014 budget requested a one—timeS1一billion investment to fund the network， which would consist of15 more institutes around the country．The institutes w．II mesh i ndu st rY，u nive rsities a nd community colleges with federal agencies to design and implement innovations in manufactu ring．Funding wiII come from the defence，energy and commerce departments,as well asNASA and theNationaIScienceFoundation．Indust ry pa rtne rs andIocaI governments will provide matching funds．A pilot programme for the initiative launched last yea r inYoungstown，Ohio，focusing on additive manufactu ring，often referred to as3D printing．“This is a great next step，’’saysDavidDornfeId，a mechanical engineer at theUniversity ofCaIifornia．Berkeley．。，AIot of enthusiasm has already been generated for these institutes_，'The digital manufacturing institute will develop softwa re to helP push manufactu ring from design and prototyping to production and testing stages．The institute for lightweight metals manufacturing will attempt to spur reductions in manufacturing and energy costs for products such as medicaI devices and vehicles．The next--generation power--sources institute will employ semiconductor technology to develop compact， high—efficiency power sources．”The bandgap semiconductor institute is fairly specific to theDepartment ofEne rgy，but the othe r two are right on target for where we advised the president to go"’saysDornfeld，referring to a report submitted to the president last year by theAdvancedManufacturingPartnership steering committee and endorsed by thePresident’sCouncil ofAdvisors onScience andTechnology．Whereas industry observers a re mostly positive about the manufactu ring initiative as a whole，some are concerned that the initiative may not be robust enough．PhilipShapira，a public— policy analyst at theGeorgiaInstitute ofTechnology inAtlanta， says that it would begin to support theUS manufacturing landscape in a way comparable to systems inGermany,theUnitedKingdom，Japan andTaiwan．“However,15 centres is probably the absolute mi nlmumj7Shapira adds．Germany, by comparison．has60FraunhOf；er institutes focusing on innovation in technology and manufacturing．Also,experts agree that even ifObama receivesS1 billion fromCongress，the institutes will not become self-sustaining without additionaIIong—te rm oubIlc financing．英国研究人员最新一项研究表明，人脑在经过短时间的微电流刺激TniJll练后．其计算能力可以得到明显提高，且效果可维持长达半年。这一研究成果发表在《当代生物学》期刊上。在英国牛津大学和伦敦大学学院研究人员所进行的这项研究中．51名志愿者被分成测试组和对照组两个组别．进行同样的数学能力培训。在为期5天的培训中．研究人员使用一种称为经颅随机噪声刺激(TRNS)的技术对25名测试脑部微电击可提高大脑运算能力组成员脑部被认为与运算能力有关的区域进行轻微的电击。研究人员测试发现，脑部经过轻微电击的测试组成员，数学运算能力明显高于对照组成员。而令他们惊讶的是，这一能力提高的效果至少可以持续半年时间。在实验过程中．研究人员通过近红外光谱技术(NlRS．一种光学脑成像技术)，对志愿者颅内血流量和氧气含量水平的变化情况进行监测。结果发现，对测试组成员脑部施加轻微电击后．其大脑神经元间的血液流动明显增强。研究人员据此认为．这是导致这些测试者运算能力得到提高的主要原因。研究论文作者之一、牛津大学的罗伊科恩卡多什博士表示．将神经科学与教育学相结合，可以更好地帮助人们提高认知能力，这对于那些神经退行性疾病患者、中风患者以及其他有学习障碍的人来说十分重要。“数学运算是人脑具有的一种高度复杂的认知能力，如果我们能够强化人的数学运算能力．那么就很有机会强化其他的相对较简单的认知能力。”作为该项研究手段的TRNs技术，是近几年才出现的一种新技术．这种非侵入式的刺激手段成本低廉．且不会给人体带来任何痛苦。研究人员认为，虽然目前TRNs对大脑神经元的影响还不十分清楚，但在经颅电刺激(TES)技术已被证明对许多认知功能具有很好效果的前提下，作为TES技术的一个分支，安全且无痛的TRN s技术具有很好的发展前景。Electrical shock can improve brain brain micro-computing powerIfVou are one ofthe20％of healthy adults who struggle with basic arithmetic，simple tasks like splitting the dinner bill can be excruciating．Now,a new study suggests that a gentle，painless electrical current applied to the brain can boost math performance fbr uD to6 months．Researchers don’t fuIIY understand how it works，however,and there could be side effects．The idea of using electrical cu rrent to alte r b rain activity is nothing new--electroshock therapy,which induces seizures fo‘ therapeutic effect,is probably the best known and most dramatic example．In recent years,howeveC a slew of studies has shown that much milder electricaI stimulation applied to targeted regions of the brain can dramatically accelerate learning in a wide range of tasks， from ma rksmanship to speech rehabili切tion after stroke．I n2010，c o g n i t i v e neuroscientistRoiCohenKadosh of theUniversity ofOxford in theUnitedKingdom showed that， when combined with training， electrical brain stimulation can make people better at very basic numerical tasks，such as judging which of two quantities is larger．However,it wasn‘t cIea r how those basic numericaI skills would translate to real-world math ability．To answe r that question，CohenKadosh rec ruited25 volunteers to practice math while receiving either reaI or”sham。。 brain stimulation．Two sponge— covered electrodes，fixed to either side ofthe forehead with a stretchy athletic band，targeted an area of3 the prefrontaI cortex considered key to arithmetic processing，saysJacquelineThompson，aPh．D． student inCohenKadoshls lab and a co—author on the study．The electricaI current slowly ramped uD to about1 milliamp--a tinyr fraction of the voltage of anAA batterv— then randomly fluctuated between high and low values．For the sham group，the researchers simulated the initial sensation of the increase by releasing a small amount of current,then turned it off．For roughly20 minutes per day over5 days，the pa rticipants memorized arbitrary mathematical“facts，”such as4#10=23，then performed a more sophisticated task requi ring muItipie steps of a rithmetic，also based on memorized symbols．A squiggle， for example，might mean”add2，” or”subtract1．”This is the nrst time that brain stimulation has been applied to improving such complex math skiIls，says neu roethicistPeterReiner of theUniversity ofBritishColumbia，Vancouver,inCanada．who wasn’t lnvolved in the research．The resea rchers also used a brain imaging technique called nea r—infra red spectroscopy to measu re how efficientIY the participants’brains were working as they performed the tasks．Although the two groups performed at the same level on the nrSt day,over the next4 days people receiving brain stimulation along with training learned to do the tasks two to five times faster than people receiving a sham treatment，the authors repo rt online today inCurrentBiology．Six months later,the researchers called the participants back and found that people who had received brain stimulation were still roughly30％faster at the same types of mathematicaI challenges．The targeted brain region also showed more efficient activity,ThompsonSavs．The fact that only participants who received electrical stimulation and practiced math showed lasting physiological changes in thei r brains suggests that experience is required to seal in the effects of stimulation，saysMichaelWeisend， a neu roscientist at theMindResearchNetwork inAlbuquerque，NewMexico，who wasn’t involved with the study．That。s valuable informat-on for people who hope to get benefits from stimulation alone，he says．。‘It's not going to be a magic bullet．”黧‘17二t-“”譬Intm nat[011ajScienti“c ondTechncflogical bffol i"ation“人造复眼”可媲美果蝇之眼能以每秒150帧的速度运转据物理学家组织网近日报道．在瑞士联邦理工大学(EPFL)工作的欧洲研究团队，建了一个可与果蝇等昆虫的复眼相媲美的人工眼。该研究成果发表在最新一期美国《国家科学院学报》上。在论文中，该研究小组描述了这项技术如何利用堆叠层微电子来解决准确地校准一个曲面上的光感受器和其他光学元件的难题。人的视觉是通过两个单透镜的眼睛获得的，可行之有效地精细区别对象。然而，大多数动物王国的其他成员依靠复合眼睛，即每只眼睛有多重透镜来看世界。其视力的清晰程度不如单镜头眼睛，但却提供了一个更大的视野．并能对运动作出更快速的响应。科学家一直在尝试研发人造复眼，希望能够复制几乎与果蝇一样的即时响应时间．以及其他昆虫能够在不必转动头部的情况下看到周围世界的能力。虽然在此领域中已经有许多研究者取得了一定的进展，但仍然存在两个症结：建立大小合适的眼睛和一个准确的包裹设计。而这支科学家团队已经努力在这两个方面取得了重大的突破。昆虫的眼睛表面是由非常小的被统称为小眼的光学单元构成。为了创建一个微小的人造复眼．研究人员开始复制了果蝇和其他节肢动物物种的小眼。其版本包括三层：外层透镜、中间光传感器层和通过层叠削减设计可灵活使用的内层电路板。该团队称其为ReSearCherS build curved insect-sized aA te am ofE u roPe a n resea rche rs wo rking atEcoIePoIytech nique f4d∈raIe deLausanne(EPFL)inSwitzerland has created an a rtificiaI compound eye that is comparable to those in insects such as the fruit fly．1n their paper published in theProceedings of theNationaIAcademv ofSciences，the team describes how they overcame the problem of accu rately aligning photoreceptors and other optical components on a curved surface by using stacked layers of microelectronics．Vision in humans is achieved by two single—lens eyes and works we||fo r fine discrimination of objects．Most other members of the animal kinIgdom，however,rely on compound eyes--where each eye has multiple lenses．Such eyes don。t provide the degree of clarity of single—lens eyes，but they do offer a larger feld of view and quick response times to movement．Scientists looking to replicate the nearly instant response times of flies and other insects as welI as thei r abiIity to see most of the wo rld a round them(without having to turn their heads)have been trying to create a rtificial compound eyes．While there has been much p rogress made by many researchers in this area，there have remained two sticking points： creating the eyes of the right size and with an accu rate wrapping design．In this new effort，theSwiss team appears to have made significant progress in both areas．In insects．the eye surface is made up of a mosaic of very sinail optical units known collectively as the ommatidia．To create a tiny artificiaI compound eye，the researchers set out to duplicate the ommatidia of fruit flies and other arthropod species．Their version consists of three layers：an outer layer ofIenses．a middle layer of light sensors，and an inner layer circuit board made flexible by using a stacked cut design．The result， which the team calls theCun垆CE． is an artificial compound eye with aA圈CurvACE，这是一个拥有180度视场的人工复眼，小得足够“坐在”一枚5分镍币上。不论是在高光还是低光环境中，该人工复眼可以每秒150帧运转。研究人员下一步将在微小的飞行机器人上嵌入这种眼(可能为一对)。该团队指出，这项新技术可能也会有其他的应用。例如“智能衣服”，当一个人移动时，可能会改变形状以提高舒适性。另一个潜在的应用是可作为安全传感器，甚至可通过该技术为人造皮肤提供纹理识别。 ficial compound eye180 degree field of view and that is small enough to sit on a nickel．TheCurvACE operates at150 frames per second and is able to operate in either high—or low-light environments．The next step for researchers wilI be embedding the eye(1ikely as a pair)in tiny flying robots．The team notes that their new technology may have other applications as well．They suggest“smart clothes”as one example． which could change shape as a person moves to improve comfoll：．Anothe r potential application would be as secu rity sensors or even as a means for providing texture recognition for artificial skin．AbstractIn most animaI species， vision is mediated by compound eyes．which offer lower resolution than vertebrate single—lens eyes， but significantly larger fields of view with negligible distortion and spherical aberration，as well as high temporal resolution in a tinv package．Compound eyes are ideally suited for fast panoramic motion perception．Engineering a miniature a rtificial compound eye is challenging because it requi res aCCU rate aIignment of photoreceptive and optical components on a curved surface．Here,we describe a unique design method for biomimetic compound eyes featu ring a pano ramic， undistorted field of view in a very thin package．The design consists of three planar layers of separatelyP roduced a r rays，nameIY，a microlens array,a neuromorphic photodetector array,and a flexible printed ci rcuit boa rd that a re stacked，cut，and curved to produce a mechanically flexible imager．Following this method，we have prototyped and characterized an artificial compound eye bearing a hemisphericaI field of view with embedded and programmable low-power signal processing，high temporal resolution，and local adaptation to iIlumination．美研发未来火箭燃料：离子液体更高效更环保从上个世纪70年代进行火箭发射到本世纪初最先进的好奇号火星车任务都在使用较为“原始”的动力，肼依然是目前火箭发射的燃料．该化学物质也被称为联氨。虽然肼可以释放出大量的能量，但是该物质是剧毒的，无论是吸入还是与皮肤接触都会造成损伤，可损害人体肝脏、眼睛．而且运输过程也较为困难，目前主要使用氮气进行密封存储运输。来自美国空军的研究所经过多年探索．科学家已经找到了替代肼的火箭燃料．不仅比肼燃料更加安全．也很环保．燃料释放能量也很高。这种新型推进剂是一种离子液体．分子具有一个正电荷或者一个负电荷，并以液体的形式存在。离子液体的特性使得该物质非常安全，有利于运输和存储，但是在此前的实验中，离子液体没有很强的释放能量特点，这意味着当它们燃烧时不会产生推动火箭所需的能量。来自美国空军火箭推进研究小组科学家汤姆霍金斯认为离子液体将是潜在的火箭燃料来源。当前的离子液体火箭推进剂的专业名称为AF—M315E．以液态的形式呈现，如果用低压处理，就会慢慢蒸发，这意味着离子液体火箭推进剂更加稳定，易燃性低于肼．也很容易处理使用。在毒性方面，AF-M315E仅释放出无毒的气体．比如水蒸气、氢气和二氧化碳等。离子液体火箭推进剂AF-M315EII,'tJ主要成分为羟基硝酸铵．而硝酸铵正是1995年俄克拉何马城爆炸案中炸弹的主要成分，科学家通过添加羟基分子将该物质的熔点降低了100摄氏度左右．这也是离子液体的临界参数。因此．如果要点燃AF-M315E绿色推进剂就显得有些困难，这似乎有悖常理，事实上这个特性意味着AF-M315E燃料在使用上更加安全。当该燃料被点燃时．可以释放出更大的能量，更高的温度会造成目前美国宇航局飞船发动机损坏，对此科学家认为我们应该需要更好的材料．以“抵抗”离子燃料产生的高温。使用这型绿色推进剂的火箭将在2015进行首次测试飞行，如果测试成功，那么将开启一个全新的载人航天时代。NASA。s new rocket fueI hel ps space agency’go green’_，一一一一From the rocketIaunches of the1970s uD toCuriosityMarsRover last year,spacecraft have used a fueI caIled hyd razine to propel them through space．In te rm s of rawPowe r， hydrazine is highly flammable and throws off an enormous amount of heat．But‘1hydrazine is also highly toxic,both when inhaled and when it makes contact with human skin． and its flammability makes it very d而cult to transport and handle．Afte r yea rs of resea rch， scientists from theAirForceOffice ofScientificResearch have found a replacement fueI that is not only safer than hydrazine，but also environmentally friendly and more efficient as well．What。s the sec ret?The new propellant is what。s called an energetic ionic liquid，orEIL．Ionic liquids are salt compounds in a liquid form whose molecules have either a positive or negative charge， which bonds them together more tightly and makes the liquid more stable．【Look，NASA，NoHands!AstronautsFly onBrainpowerAlone]This makes ionic liquids very safe and easy to handle．But before一5一 now,known ionic liquids weren。t very”energetic，”meaning they didn。t produce a high amount of energy when combusted．ButTomHawkins of theAirForce。sRocketPropulsionDivision thought there was potential in ionic liquids as a fuel source．And now a career of research into energetic ionic liquids that began atLehighUniversity in the1980s has finally yielded concrete results．The propellant，whose most recent iteration。s technicaI name isAF—M315E，has all the desirable properties of anEIL：It's a liquid，and because it has a low vapor pressure(meaning it evaporates slowly)it's more stable and far less flammable than fuels like hydrazine．It。s also easy to handle——Hawkins saysM315E isIess toxic to humans than cafieine．It。s also”green”because when combusted，M315E only throws off nontoxic gasses like water vapor,hydrogen and carbon dioxide．The main ing redient inM315E is hyd roxyl ammonjum nitrate．The latte r pa rt of that compound may sound fami|iar— ammonium nitrate is commonly used as a fertilizer in theUnitedStates．It’s aI so potentiaIly explosive：ammOnium nitrate was the main ingredient in the bombTimothyMcVeigh used in the1995OklahomaCity bombing,and was also probably responsible for the deadly accident at the fertilizer plant inWest，Texas onApril17，2013．[See also：WhyWas theTexasFertilizerPlantExplosionSoDeadly?]But ammonium nit rate is not the same substance as hydroxyl ammonium nitrate．By adding the hydroxyl group to the molecule，Hawkins explained，the compound’s melting point drops by more than100 degreesCelsius， which puts it in the realm of ionic liquids．This means that the green propellant is actually very difficult to ignite．nternatiol、a1Sciei艟ific andTechnologicalInfon]1ation美开发厚度为单原子直径的半导体薄膜有望将半导体技术带入原子量级美国北卡州立大学研究人员今天表示，他们开发出制造高质量原子量级半导体薄膜(薄膜厚度仅为单原子直径)的新技术。材料科学和工程助理教授曹林友(音译)说，新技术能将现有半导体技术的规模缩小到原子量级，包括激光器、发光二极管和计算机芯片等。研究人员研究的材料是硫化钼，它是一种价格低廉的半导体材料．电子和光学特性与目前半导体工业界所用的材料相似。然而，硫化钼又与其他半导体材料有所不同，因为A new era of a scientists have demonstrated the semiconductor molybdenum sulphide can be grown in layers onlY one atom thick without compromisingIts propertiesResearchers atNorthCarolinaStateUniversity have developed a new technique for creating high— quality semiconductor thin nIms on the atomic scale where the films are only one atom thick．The technique can be used to create these thin^Ims on aIarge scale,su仟icient to coat wafers that are two inches wide，or larger．“This couId be used to scale cu rrent semiconductor technologies down to the atomic scale,lasers，LEDs,computer chips， anythingj“saysLinyouCao．an assistant professor of materials science and engineering atNCState and senior author of a paper on the work．“People have been talking about this conce-pt for a long time， but it wasn’t possible．With this discovery,l think it's possible：'The researchers worked with molybdenum sulphide(MoS2)， an inexpensive semiconductor material with electronic and cIpticaI properties similar to materials already used in the semiconductor它能以单原子分层生长形成单层薄膜，同时薄膜不会失去原有的材料特性。在新技术中．研究人员将硫粉和氯化钼粉放置于炉内，并将温度逐步升高到850摄氏度，此时两种粉末出现蒸发(汽化)并发生化学反应形成硫化钼。继续保持高温，硫化钼能沉积到基片上．形成薄薄的硫化钼膜。曹林友表示，他们成功的关键是寻找到了新的硫化钼生长机理．即自限制生长．通过控制高温炉中分压和蒸汽压来精确地控制硫化钼层的厚度。分压代表悬浮在空气中的原子或分子聚集成固体沉淀到基片上的趋势：蒸汽压代表基片上的固体原子或分子汽化进入空气的趋势。为在基片上获得单层硫化钼，分压必须高于蒸汽压；分压越高．沉积到底部的硫化钼层就越多。如果分压高于在基片上形成单层薄膜的蒸汽压．但又低于形成双层薄膜的蒸汽压．那么在分压和蒸汽压之间的这种平衡能确保在单层硫化钼薄膜形成后薄膜生长自动停止，不再向多层发展。这就是”薄膜的自限制 mic．scale semiconductor devices industry．However,MoS2 is difierent from othe r semiconducto r mate riaIs becau se it can be grown in layers only one atom thick without compromising its properties．In the new techniq ue， resea rchers place sulphu r and molybdenum chloride powders in a furnace and gradually raise the temPe ratu re to8500C， which vaporises the powde r．The two substances react at high temperatures to formMoS2．While stilI under high temperatures，the vapour is then deposited in a thin layer onto the substrate．“The key to ou r success is the development of a new growth mechanism，a self-limiting growth；’Cao says．The researchers can precisely control the thickness of theMoS2 layer by controlling the pa rtial pressure and vapour pressure in the fumace．Pa rti aIP ressu re is the tendency of atoms or molecules suspended in the air to condense into a so|id and settle onto the substrate．9apou r p ressu re is the tendency of solid atoms or molecules on the substrate to vaporise and rise into the air,To create a single layer ofMoS2 on the substrate．the partial pressure must be higher than the vapour pressure．The higher the partial pressure，the more layers ofMoS2 will settIe to the bottom．If the pa rtiaI pressu re is higher than the vapour pressure of a single layer of atoms on the substrate，but not higher than the vapou r pressu re of twoIayers， the balance between the partial pressure and the vapour pressure can ensure that thin—f¨m growth automaticaIly stops once the monolayer is formed．Cao calls this。'self-limiting”growth．PartiaI pressure is controlled by adjusting the amount of molybdenum chIoride in the furnace．the more molybdenum is in the furnace，the higher the partial pressure．生长”。分压通过调节高温炉内氯化钼的量来控制．炉内钼的量越多．分压则越高。曹林友表示，利用该技术，他们每次都获得了晶片大小、原子直径厚的硫化钼单层薄膜。同时还可以通过改变分压获得2—4个原子直径厚的硫化钼薄膜。研究人员目前在试图寻找其他的方式．以制造类似的但每个原子层由不同材料组成的薄膜。同时，他们也在利用新技术制作场效应晶体管和发光二极管。“Using this technique，we can create ware卜scaIeMoS2 monolayer thin f¨ms．one atom thick，every time,'’Cao explains．“We can also produce layers that are two,three or four atoms thick：'Cao’s team is now trying to find ways to create similar thin nIms in which each atomic layer is made of a different material．cao js also working to create field—effect transistors andLEDs using the technique．Cao has filed a patent on the new technique．More details of this work iS detailed in the paper,“ControlledScalableSynthesis ofUniform．High—QualityMonolayer andFew- layerMoS2F¨ms?，byY．feiYu et aI published online onMay21st inScientificReports，a journaI of theNaturePublishingGroup．DOI：10．1038／srep01866The research was funded by theU．S．AmlvResearch0币ce．

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