国际科技信息

国际科技信息

The blackest substance on Earth: Nasa creates material that absorbs almost all light

Scientists already planning range of space applications, from light suppression to heat and weight reduction

Nasa engineers have come up with a material that absorbs more than 99 per cent of all light that strikes it.

Absorbent material usually pulls in ultraviolet and visible light - but this new material also captures infrared and far infrared light.

The development has even taken fellow Nasa scientists by surprise, and it promises to open new frontiers in space technology.

The team of engineers at Nasa's Goddard Space Flight Center in Greenbelt, Maryland, reported the findings recently at the SPIE Optics and Photonics conference.

John Hagopian, leading the team, said reflectance tests were extremely positive, showing that the material has 50 times more absorbtion qualities than its rivals.

He said: 'Though other researchers are reporting nearperfect absorption levels, mainly in the ultraviolet and visible, our material is darn near perfect across multiple wavelength bands - from the ultraviolet to the far infrared.

'No one else has achieved this milestone yet.'

The material is a thin coating of carbon nanotubes - hollow and multi-walled tubes about 10,000 times thinner than a strand of human hair.

They stand at 90 degrees from the surface they coat, which Nasa scientists have referred to as looking like shag-pile carpet.

It can be applied to a variety of surfaces, including silicon, silicon nitride, titanium, and stainless steel -the materials most commonly used in space science instruments.

Nasa is already thinking about practical applications for the material - the most obvious being as light-suppression on sensitive equipment.

The tiny gaps between the tubes collect and trap background light to prevent it from refl ecting off surfaces and interfering with the light that scientists actually want to measure.

Because only a small fraction of light refl ects off the coating, the human eye and sensitive detectors see the material as black.

The material could dramatically slash light refl ected off deep space equipment that is already straining to detect the faintest and farthest light sources.

Less obvious, however, is the fact that the material could also be used as a coolant.

The blacker the material, the more heat it radiates away, so the coating could be used on devices that remove heat from instruments and radiate it away to deep space.

Finally, it is a lot lighter than other materials that off less absorbtion - and weight is a critical factor in any payload being sent into space.

Goddard engineer Manuel Quijada, who co-authored the SPIE paper and carried out the refl ectance tests, said: 'We are a litile surprised by the results'.

He added: 'We knew it was absorbent. We just didn't think it would be this absorbent from the ultraviolet to the far infrared.'

Goddard scientist Ed Wollack summed it up by saying: 'This is a very promising material. It's robust, lightweight, and extremely black. It is betier than black paint by a long shot.'

美科学家研制出一种新超黑材料

美国科学家研制出一种新的超黑材料，能吸收几乎所有照射在其上的光，吸收率超过99%，在从紫外线到远红外线多个波段都获得了几近完美的吸光效果。科学家们表示，这种材料可广泛应用于从光抑制到为太空设备降温和“瘦身”等领域，有望开启太空技术研究的新时代。

新材料是由中空且多壁的碳纳米管组成的一层纤薄涂层，纳米管之间细小的孔隙能收集和捕获背景光以防止其从表面反射出去对要测量的光造成干扰，由于只有很少一部分光反射离开，人眼和灵敏的探测器看到该材料为黑色。该材料可用在太空科学仪器中主要使用的硅、氮化硅、钛、不锈钢等不同表面上。

科学家们表示，这种材料能显著减少用于探测宇宙中最微弱和最遥远的光的深空设备的发射光数量，因此，其最有可能用做太空传感装置的光抑制剂。另外，因为材料越黑，其辐射的热量就越多，所以，这种涂层也可作为冷却剂，用在一些为太空装置移除热量并将热量辐射回深空的设备中。在宇宙探索中，这些太空装置必须在超冷环境下工作，以收集宇宙深处物体发出的非常微弱的远红外信号。如果这些装置的冷度不够，其产生的热会淹没微弱信号。而且，这种涂层比其他吸光材料更轻，而对任何发往太空的装置来说，重量都是一个非常关键的因素。

领导该研究的美国航空航天局（NASA）戈达德太空飞行中心的科学家约翰·哈格比安表示：“反射测试的结果表明，该材料的吸收能力是目前吸收能力最强材料的50多倍，其在从紫外线到远红外线多个波段都获得了几近完美的吸收效果，这是前所未有的创新。”

该研究论文的合作者、戈达德研究中心的工程师曼纽尔·基哈达表示：“我们都对实验结果感到震惊，我们知道其吸光能力很强，但并没有想到其能将从紫外线到远红外线的光线一网打尽。”

戈达德的科学家爱德·沃莱克补充道：“这是一种非常有潜力的材料。它柔韧、轻便且非常黑，它比现在广泛使用的吸光材料黑漆不止好一点。”

Malaria Vaccine Candidate RTS,S Reduces the Risk of Malaria by Half in African Children, Study Finds

First results from a large-scale Phase III trial of RTS,S, published online in the New England Journal of Medicine (NEJM), show the malaria vaccine candidate to provide young African children with significant protection against clinical and severe malaria with an acceptable safety and tolerability profile. The results were announced at the Malaria Forum hosted by the Bill & Melinda Gates Foundation in Seattle, Washington.

Half the world's population is at risk of malaria. The disease is responsible for close to 800,000 deaths each year, most of whom are children under five in sub-Saharan Africa.

5 to 17 month-old children

The trial, conducted at 11 trial sites in seven countries across sub-Saharan Africa, including a UNC-led site in Lilongwe, Malawi, showed that three doses of RTS,S reduced the risk of children experiencing clinical malaria and severe malaria by 56 percent and 47 percent, respectively. This analysis was performed on data from the first 6,000 children aged 5 to 17 months, over a 12-month period following vaccination. Clinical malaria results in high fevers and chills. It can rapidly develop into severe malaria, typified by serious effects on the blood, brain, or kidneys that can prove fatal. These first Phase III results are in line with those from previous Phase II studies.

The widespread coverage of insecticidetreated bed nets (75 percent) in this study indicated that RTS,S can provide protection in addition to that already offered by existing malaria control interventions.

6 to 12 week-old infants

The trial is ongoing and efficacy and safety results in 6 to 12 week-old infants are expected by the end of 2012. These data will provide an understanding of the efficacy profile of the RTS,S malaria vaccine candidate in this age group, for both clinical and severe malaria.

Combined data in 6 to 12 week-old infants and 5 to 17 month-old children

An analysis of severe malaria episodes so far reported in all 15,460 infants and children enrolled in the trial at 6 weeks to 17 months of age has been performed. This analysis showed 35 percent efficacy over a follow-up period ranging between 0 and 22 months (average 11.5 months).

"The publication of the first results in children aged 5 to 17 months marks an important milestone in the development of RTS,S," said Irving Hoffman, PA, MPH, co-principal investigator at the Lilongwe site. "These results confirm findings from previous Phase II studies and support ongoing efforts to advance the development of this malaria vaccine candidate," said Hoffman, who is also associate professor of medicine in the UNC School of Medicine.

Long-term efficacy

The RTS,S malaria vaccine candidate is still under development. Further information about the longer-term protective effects of the vaccine, 30 months after the third dose, should be available by the end of 2014. This will provide evidence for national public health and regulatory authorities, as well as international public health organizations, to evaluate the benefits and risks of RTS,S.

Safety

The overall incidence of serious adverse events (SAEs) in this trial was comparable between the RTS,S candidate vaccine (18 percent) recipients and those receiving a control vaccine (22 percent)

Differences in rates of SAEs were observed between the vaccines groups for specific events, such as seizures and meningitis, and were higher in the malaria vaccine group. Seizures were considered to be related to fever and meningitis was considered unlikely to be vaccine-related. These events will continue to be monitored and additional information about the safety profile of the RTS,S malaria vaccine candidate will become available over the next three years.

"Making progress against this disease has been extremely difficult, and sadly, many have resigned themselves to malaria being a fact of life in Africa. This need not be the case," said Francis Martinson, MPH, PhD, co-principal investigator in Lilongwe and country director of UNC Project-Malawi. "Renewed interest in malaria by the international community, and scientific evidence such as that we are reporting today, should bring new hope that malaria can be controlled."

The vaccine is being developed in partnership by GSK and the PATH Malaria Vaccine Initiative (MVI), together with prominent African research centers. The partners are all represented on the Clinical Trials Partnership Committee, which is responsible for the conduct of the trial. Major funding for clinical development comes from a grant by the Bill & Melinda Gates Foundation to MVI.

疟疾疫苗研究现突破

英国制药企业葛兰素史克公司一款疟疾疫苗的临床测试结果显示，它可使非洲5个月至17个月年龄段婴儿患疟疾的风险降低大约一半。

显效果

这款疫苗名为“RTS，S”或Mosquirix，由葛兰素史克公司和非营利机构“疟疾疫苗倡议”合作研发。

这款疫苗1987年在葛兰素史克公司位于比利时的生物学实验室首度“现身”，1992年起以欧洲和美国健康成年人为对象展开测试，1998年起以赞比亚为起点，开始在非洲测试。

“RTS，S”疫苗现已进入最后一个临床试验阶段，以非洲布基纳法索、加蓬、加纳、肯尼亚、马拉维、莫桑比克和坦桑尼亚的15460名婴幼儿为对象，测定这一疫苗对这一疟疾易感染群体的效用。

与6000名5个月至17个月幼儿相关的测试结果已经得出，刊登于最新一期《新英格兰医学杂志》周刊，由比尔和梅琳达·盖茨基金会主持的“疟疾论坛”同步公开。

法新社18日援引测试结果报道，5个月至17个月幼儿注射3剂“RTS，S”疫苗后，患临床诊断性疟疾的风险降低56%。在疟疾的这一发病阶段，患者一般会出现高烧、发冷等症状。

另外，“RTS，S”可使这一年龄段幼儿患恶性疟疾的风险降低47%。恶性疟疾有可能导致血液、脑部和肾脏并发症，有致命威胁。

针对6周至12周婴儿的测试结果定于明年发布。

是突破

疟疾由疟原虫引发，经由疟蚊传播，婴幼儿是易感染群体。依据世界卫生组织公布的数据，全球78.1万人在2009年因疟疾失去生命，其中90%身处非洲，92%为5岁以下儿童。

一般而言，人体遭受疟蚊叮咬后，疟原虫进入人体血液，借助血液循环到达肝脏后发育成熟、繁殖，随后返回血液循环，影响血红细胞，引起发烧、身体疼痛甚至一些恶性并发症并导致死亡。

“RTS，S”的特别之处在于，它以寄生虫而非病毒、细菌为打击目标，免疫机理是在疟原虫进入人体血液后触发人体免疫应答，阻止这些寄生虫进入肝脏发育、繁殖。这款疫苗的副作用包括发烧和接种点红肿，属于儿童疫苗的常见反应。

葛兰素史克公司首席执行官安德鲁·威蒂说，这款疫苗取得前所未有的突破，但只能控制疟疾，难言根除。

比尔和梅琳达·盖茨基金会联合主席、美国微软公司创始人比尔·盖茨说，这款疫苗具“里程碑”意义，根除疟疾不再是不切实际的幻想。

存疑问

对抗疟疾的曙光显现，但疑问尚存。全球疫苗和免疫联盟首席执行官塞思·伯克利告诉法新社记者，若要把“RTS，S”推向市场，有效期和价格是需要解决的主要难题。

他说，疟疾“是最穷苦民众面临的巨大难题，疫苗研究耗时长久，因此，成功至关重要，即便是不完美的成功”。

英国国际开发大臣安德鲁·米切尔说：“有效、长效和划算的疫苗将对控制疟疾作出巨大贡献。”

葛兰素史克公司首席执行官威蒂说，这家企业已投入3亿美元研发“RTS，S”疫苗，力求低价生产，不求利润，当前尚难以确定价格。

“我们希望，可以在2015年前给非洲儿童送去这款疫苗，”威蒂说。

Germany: A fi rst as hydrogen-hybrid power station commissioned

Described as “a world premiere”, the Prime Minister of the State of Brandenburg, Matihias Platzeck, put into operation a hydrogen-hybrid power station in Prenzlau located north of Berlin (Germany) at the end of October.

Enertrag AG, Total Deutschland GmbH, Vattenfall and Deutsche Bahn have all been involved in this groundbreaking project, which aims to demonstrate the feasibility of a safe and sustainable supply and storage of energy by using a mix of purely renewable energy sources in practical testing. This technology is also important for the energy sector, because it enables the storage of wind energy and the smooth feed-in of power from wind farms into the grid.

As shown in the diagram, the hydrogen-hybrid power station unites for the first time wind, hydrogen and biogas to one compound. The electricity generated by three wind turbines is proportionately used to manufacture carbon dioxide-free hydrogen. This green hydrogen is stored and used to produce electricity and heat by means of a combined hydrogen-biogas power plant at times of high demand and simultaneously low supply of wind energy. Moreover, this hydrogen is also used in the pumps at Total hydrogen filling stations in Berlin and Hamburg. In this way, green hydrogen from the district where the plant is located guarantees carbon dioxide-free mobility in Berlin.

The total sum of investments for this hybrid power station adds up to €21 million. This pioneering project is being sponsored by the State of Brandenburg and the Federal Ministry of Transport.

At the event held to celebrate the offi cial opening, Prime Minister Matthias Platzeck said: “The hydrogen-hybrid power station is providing a real boost! This project is an innovative, practicable and efficient contribution to be more climate-friendly. This plant, unique in the world, makes it possible to transform the fluctuating wind energy into a reliable factor that can then be deployed in the long-term as a predictable source of energy for electricity, heat and mobility. We are assisting a quantum leap in modern storage technology today."

Werner Diwald, executive board member of Enertrag also said: “The goal of providing sufficient energy to cover all our electricity, heating and mobility needs solely from renewable sources is a central facet of the energy revolution and of a sustainable, economically viable and secure energy supply. The storage of renewable energy will play a significant role here. Hydrogen is unanimously considered to represent the primary medium for this job, as it is easily able to transport and store energy in large quantities at the required speed. For this reason, ENERTRAG has chosen to focus on hydrogen and, together with industrial partners, is developing solutions that will enable the supply of energy generated using domestic resources in Germany in accordance with society’s political goals.”

世界上第一座风力-氢混合发电站在德国投入运营

在德国勃兰登堡州的普伦茨劳，世界上第一座风力-氢气混合发电站投入运营。混合发电站可以把太阳能、风能等可再生能源和氢气、生物沼气、地热能等能源形式结合起来，用来解决可再生能源并网电量不稳定的问题。德国的这座电站可把风力发电产生的多余电量用来电解制取氢气，氢气可以直接用于电动汽车的氢燃料电池或者在用电高峰期和天然气混合用来重新发电。现阶段该电站的规模还比较小，由三台两兆瓦的风力发电机组成。下一阶段将会继续建设三座电站，建设更大的示范设备并将制备的氢气并网到天然气输送管道中去。

德国的能源企业Vattenfall、德意志铁路和石油企业Total都参与了该项目。目前可再生能源发电的大容量存储有现实的需求，但是由于在制取氢气过程中存在高达百分之六十的能量损失，该存储方案的经济型还有待验证。目前对于可再生能源的大容量长时间存储的技术方案还很有限，无论如何，该电站的实际运营都被认为是一个重要的开始。

Galaxy DNA-analysis software is now available 'in the cloud'

Galaxy -- an open-source, web-based platform for dataintensive biomedical and genetic research -- is now available as a "cloud computing" resource. A team of researchers including Anton Nekrutenko, an associate professor of biochemistry and molecular biology at Penn State University; Kateryna Makova, an associate professor of biology at Penn State; and James Taylor from Emory University, developed the new technology, which will help scientists and biomedical researchers to harness such tools as DNA-sequencing and analysis sotiware, as well as storage capacity for large quantities of scientific data. Details of the development will be published as a letier in the journal Nature Biotechnology.

Earlier papers by Nekrutenko and co-authors describing the technology and its uses are published in the journals Genome Research and Genome Biology.

Nekrutenko said that he and his team first developed the Galaxy computing system (http:// galaxyproject.org) in 2005 because "biology is in a state of shock. Biochemistry and biology labs generate mountains of data, and then scientists wonder, 'What do we do now? How do we analyze all these data?'" Galaxy, which was developed at Penn State and continues to use the University's servers for its computing power, solves many of the problems that researchers encounter by pulling together a variety of tools that allow for easy retrieval and analysis of large amounts of data, simplifying the process of genomic analysis. As described in one of the team's early papers in the journal Genome Research, Galaxy "combines the power of existing genome-annotation databases with a simple Web portal to enable users to search remote resources, combine data from independent queries, and visualize the results." Galaxy also allows other researchers to be able to review the steps that have been taken, for example, in the analysis of a string of genetic code. "Galaxy off ers scientifi c transparency -- the option of creating a public report of analyses. So, after a paper has been published, scientists in other labs can do studies in order to reproduce the results described," Nekrutenko said.

Now, Nekrutenko's team has taken Galaxy to the next level by developing an "in the cloud" option using, for example, the popular Amazon Web Services cloud. "A cloud is basically a network of powerful computers that can be accessed remotely without the need to worry about heating, cooling, and system administration. Such a system allows users, no matter where they are in the world, to shift the workload of software storage, data storage, and hardware infrastructure to this remote location of networked computers," Nekrutenko explained. "Rather than run Galaxy on one's own computer or use Penn State's servers to access Galaxy, now a researcher can harness the power of the cloud, which allows almost unlimited computing power." As a case study, the authors report on recent research published in Genome Biology in which scientists, with the help of Ian Paul, a professor of pediatrics at Penn State's Hershey Medical Center, analyzed DNA from nine individuals across three families using Galaxy Cloud. Thanks to the enormous computing power of the platiorm, the researchers were able to identify four heteroplasmic sites --variations in mitochondria, the part of the genome passed exclusively from mother to child.

"Galaxy Cloud offers many advantages other than the obvious ones, such as computing power for large amounts of data and the ability for a scientist without much computer training to use DNA-analysis tools that might not otherwise be accessible," Nekrutenko said. "For example, researchers need not invest in expensive computer infrastructure to be able to perform dataintensive, sophisticated scientific analyses."

Yet another advantage of Galaxy Cloud is its data-storage capacity. Using the Amazon Web Services cloud, researchers have the option of storing vast amounts of data in a secure location. "There are emerging technologies that will produce 100 times more data than existing 'next-generation' DNA sequencing, which already has reached the point where even more storage becomes an issue, not to mention analysis," Nekrutenko said.

新银河系统利用“云”分析DNA

美国宾夕法尼亚州立大学和埃默里大学的研究人员开发的新银河（Galaxy）系统，能利用“云”实现科学家对于与DNA（脱氧核糖核酸）测序和分析等相关软件工具的“驾驭”，并存储大量科学数据。相关研究进展将发表在《自然·生物技术》杂志上。

生物化学和生物学实验经常会产生如山的数据，如何分析这些数据令科学家十分头疼。Galaxy计算系统是为数据密集的生物医药和基因研究而设的、基于网络的开源平台。其能通过聚集多个具备快速检索功能和海量数据分析功用的工具，简化基因组分析的工程，从而解决科研人员面临的难题。

“云”是强大计算机的基础网络，可以远程使用，无需担心过热、过冷和系统管理。这种系统允许用户无论身处何方，都能转换软件存储的工作量和硬件的基础架构，以配合远程的网络计算机，同时近乎支持无限的计算能力。科研人员无需在自己的电脑上运行Galaxy，或者使用大学的服务器进入Galaxy，却仍能成为“云”的驾驭者。系统综合了现有基因组数据库和简易网络的力量，可令用户搜索远程的资源，整合单独的查询数据，并令结果可视化。同时，其他实验室的科研人员也可以查看Galaxy的工作进程，例如查看对于遗传密码的分析，赋予科学极大的透明性。

研究小组在之前发表的论文里，描述了如何利用Galaxy云服务为9个人分析DNA。基于这个平台的超强计算能力，科研人员能够识别出4个单细胞内含有两种或两种以上的细胞质的区域，即线粒体内的变异，基因组的这个部分会由母亲遗传给孩子。

此外，Galaxy云服务的一大优势就是它的数据存储和计算能力。科研人员表示，新兴技术将产生比现有的下一代DNA测序多100余倍的数据，但目前这些数据的存储已经成了问题，更不必说对其进行分析。而使用网络云服务，研究人员可以选择在安全的地方存储大量数据。

Galaxy的云服务还具有其他优点，例如可让对于计算机了解不多的科学家也能使用不易接触的DNA分析工具，因此不需要在计算机的基础建设方面过多投资，也能保证数据密集、复杂的科学分析得以执行。

Zinc oxide microwires improve the performance of light-emitting diodes压电—光电效应可将LED效能

Researchers have used zinc oxide microwires to signifi cantly improve the efficiency at which gallium nitride light-emitting diodes (LED) convert electricity to ultraviolet light. The devices are believed to be the first LEDs whose performance has been enhanced by the creation of an electrical charge in a piezoelectric material using the piezo-phototronic eff ect.

By applying mechanical strain to the microwires, researchers at the Georgia Institute of Technology created a piezoelectric potential in the wires, and that potential was used to tune the charge transport and enhance carrier injection in the LEDs. This control of an optoelectronic device with piezoelectric potential, known as piezo-phototronics, represents another example of how materials that have both piezoelectric and semiconducting properties can be controlled mechanically.

"By utilizing this effect, we can enhance the external effi ciency of these devices by a factor of more than four times, up to eight percent," said Zhong Lin Wang, a Regents professor in the Georgia Tech School of Materials Science and Engineering. "From a practical standpoint, this new effect could have many impacts for electrooptical processes – including improvements in the energy effi ciency of lighting devices."

Details of the research were reported in the Sept. 14 issue of the journal Nano Letters. The research was sponsored by the Defense Advanced Research Projects Agency (DARPA) and the U.S. Department of Energy (DOE). In addition to Wang, the research team mainly included Qing Yang, a visiting scientist at Georgia Tech from the Department of Optical Engineering at Zhejiang University in China.

Because of the polarization of ions in the crystals of piezoelectric materials such as zinc oxide, mechanically compressing or otherwise straining structures made from the materials creates a piezoelectric potential – an electrical charge. In the gallium nitride LEDs, the researchers used the local piezoelectric potential to tune the charge transport at the p-n junction.

The effect was to increase the rate at which electrons and holes recombined to generate photons, enhancing the external efficiency of the device through improved light emission and higher injection current. "The eff ect of the piezopotential on the transport behavior of charge carriers is signifi cant due to its modifi cation of the band structure at the junction," Wang explained.

提升4倍

美国佐治亚理工学院的研究人员利用氧化锌纳米线大幅提升了氮化镓发光二极管（LED）将电流转化为紫外线的效能。这个装置被认为是首个通过压电—光电效应在压电材料中产生电荷，从而使自身性能大幅提升的LED。相关研究报告发表在近期出版的《纳米快报》杂志上。

通过在纳米线上施加机械应变，佐治亚理工学院的研究人员在其中制造了压电电势。该电势被用于调整电荷的传输，并加强LED的载子注入。这种压电电势对于光电设备的控制被称为压电—光电效应。这一效应可增加电子和空穴重新结合以产生光子的速率，并通过提升发光强度和增加注入电流，加强设备的外部效能，使其提升4倍之多。

该校材料科学和工程系董事教授王中林表示，从实际情况来看，这个新效应可对光电过程产生诸多影响，包括提升照明装置的能源效率等。传统的LED一般使用量子阱等结构囚禁电子和空穴，这需要两者长时间保持足够靠近以进行重组。电子和空穴靠近的时间越长，LED装置的效率就越高。虽然一般LED的内部量子效率能达到80%，但传统的单p-n结点薄膜LED的外部效率却只有3%。

新装置内的氧化锌纳米线构成了p-n结的n，氮化镓薄膜则可作为其中的p。自由载子将被囚禁在这个界面区域内。压电—光电效应可在对设备施加0.093%压应力的情况下，使发光强度提升17倍，令结点电流增强4倍，从而使光电转化率提高约4.25倍。而在合适外应力的作用下，新装置的外部效率可达到7.82%，大大超过了传统LED的外量子效率。

研究小组制成的LED能发出波长约为390纳米的紫外线，但王中林教授认为未来可延伸至可见光范围，适用于各类光电设备。目前，高效的紫外线发射器在化学、生物、航空航天、军事和医疗技术领域都有需要。

王中林教授还表示，此次研究开辟了利用压电—光电效应调整光电设备的新领域。大幅提升LED照明设备的效率有望带来可观的能源节约，这对于在绿色和可再生能源技术领域的应用而言十分重要，此外，这一发现还能应用于其他由电场控制的光学器件上。

New generation of superlattice cameras add more 'color' to night vision

Recent breakthroughs have enabled scientists from the Northwestern University's Center for Quantum Devices to build cameras that can see more than one optical waveband or "color" in the dark. The semiconducting material used in the cameras –called type-II superlatices – can be tuned to absorb a wide range of infrared wavelengths, and now, a number of distinct infrared bands at the same time

The idea of capturing light simultaneously at different wavelengths isn't new. Digital cameras in the visible spectrum are commonly equipped with detectors that sense red, green, and blue light to replicate a vast majority of colors perceived by the human eye. Multi-color detection in the infrared spectrum, however, off ers unique functionalities beyond color representation. The resonant frequencies of compounds can often be found in this spectral range, which means that chemical spectroscopy can be relayed in images real-time.

"When coupled with imageprocessing algorithms performed on multiple wavebands, the amount of information rendered in a particular scene is tremendous," said Manijeh Razeghi, Walter P. Murphy Professor in Electrical Engineering and Computer Science at the McCormick School of Engineering and director of the Center for Quantum Devices.

Razeghi's group engineered the detection energies on the cameras to be extremely narrow, close to one-tenth of an electron volt, in what is known as the longwave infrared window. Creating the cameras was diffi cult, however, because the light-absorbing layers are prone to parasitic effects. Furthermore, the detectors were designed to be stacked one on top of another, which provided spatially coincident pixel registration but added significantly to the growth and fabrication challenges. Nevertheless, a dual-band longwave infrared 320-by-256 sized type-II superlattice camera was demonstrated for the first time in the world, the results of which were published in the July 2011 issue of Optics Letiers.

Such infrared photon cameras based on another material called HgCdTe were used in disaster relief in March 2011 when a catastrophic tsunami damaged Japans' nuclear reactors. These cameras provided accurate temperature information about the reactors from unmanned aerial vehicles, providing officials the information they needed to orchestrate cooling efforts and prevent nuclear meltdown.

HgCdTe, however, is considered to be an expensive technology in the long-wave infrared due to its poor spectral uniformity and therefore yield –areas in which type-II superlatices may prove more effi cient.

"Type-II superlattices can be grown uniformly even at very long-wavelengths because its energy gap is determined by the alternating InAs and GaSb quantum well thicknesses, rather than its composition as is the case with HgCdTe," Razeghi said. The high-resolution multi-band type-II superlatice camera also off ered very impressive performances, requiring only 0.5 milliseconds to capture a frame with temperature sensitivities as good as 0.015°C. "The high-performance, multifunctionality, and low cost off ered by type-II superlatices truly make it an atiractive infrared technology," she added.

新型超晶格摄像机问世

美国西北大学量子设备中心最近开发出一种功能强大的Ⅱ型超晶格摄像机，能通过调节吸收更宽波段的红外光，让人们能在黑夜中看到更加丰富多彩的景色。他们的研究发表在最近出版的《光学通讯》上。

可见光波段的数字摄像机配备的探测器通常只能感测红、绿、蓝那些能被裸眼看到的颜色，而红外波段多色彩探测提供了一种独特的功能，不仅仅是表现色彩。人们在这一光谱范围发现了多种相应频率的化学物质，因此能在图像中实时表现化学光谱。

新一代摄像机是世界上第一个双波段长波红外超晶格摄像机。他们为摄像机设计的探测能量极为狭窄，接近1/10电子伏特，也就是长波红外窗口的波长。探测器被设计成堆叠式，一个加在另一个上面，以使记录的像素保持空间一致。

麦克科密工程学院电力工程于计算机科学教授、量子设备中心主管曼尼亚·雷茨表示，将该摄像机和多波段图形处理算法结合，拍下的照片能携带大量信息。其高分辨率多带宽的性能，只需0.5毫秒就能捕获一帧清晰的画面，且温度敏感性达到0.015摄氏度。

这种红外光子摄像机是在另一种红外光探测材料碲镉汞（HgCdTe）的基础上造出来的。今年3月份，他们曾用HgCdTe探测摄像机拍摄日本被海啸损坏的核反应堆，为官方提供了精确的温度信息，协助制定冷却策略，预防核反应堆的融化。

然而在长红外波领域，HgCdTe是一种昂贵的技术，它们的光谱狭窄单一，所以新的摄像机有更多的利益。雷茨说：“即使在超长波段，Type-Ⅱ超晶格也能被均匀地生长出来，因为它的能带间隙（energy gap）是由砷化铟（InAs）和锑化镓（GaSb）交替决定，而不像HgCdTe那样由其成分确定。”

Brain circuits connected with memory discovered

A new study published last week in Science reveals the discovery of a brain pathway that helps us link events that happen close together and play a role in memories.

The research, led by Dr. Junghyup Suh from the Massachusetts Institute of Technology found the connection between the hippocampus and the entorhinal cortex. The entorhinal cortex receives the information from areas around the brain and then passes the information to the hippocampus.

To test this pathway, the researchers used specifically bred mice. These mice had a mutant strain which allowed the cells in the entorhinal cortex to be disabled by removing doxycycline from the food the mice were fed.

When mice are presented with a sound and then within 20 seconds given a shock, they quickly learn to associate this sound with the coming shock and freeze in their tracks when the sound is heard. This experiment was conducted on the mice with the disabled entorhinal cortex and researchers discovered that the mutant mice were less likely to react to the sound.

However, when the researchers administered the shock at the same time as the sound, both mice behaved the same. This shows that there is a connection between the connection of time and the entorhinal cortex.

Another experiment used a water maze and a small platform where the mice could fi nd to stop swimming and rest. They were allowed to find the platform and then 30 seconds later placed in the water maze. The mutant mice were less likely to be able to find the platform even though they had just found it 30 seconds prior. The linking of memories to what was currently happening appeared diffi cult for these mice.

When it comes to Alzheimer’s disease, patients have difficulty with memory. In Alzheimer’s, the entorhinal cortex is one of the fi rst areas of the brain that is damaged.

科学家发现与记忆相连脑路线

美国麻省理工学院大脑与认知科学院经实验研究，发现了在记忆过程中起关键作用的神经路径，能帮人们把相继发生的紧密事件联系在一起。相关论文发表在上周出版的《科学》杂志上。

要想形成情景记忆和工作记忆，必须能将各种不连续的短暂因素串在一起，而这要依靠大脑中的海马回—内嗅皮质网络，内嗅皮质接收来自周边脑区的信息，再把信息传递给海马回。但是哪些神经线路促成了这些因素互相连接还是个谜。在新研究中，麻省理工学院徐情浃（音译）博士领导的研究小组认为，是内嗅皮质到海马回的第三层输入端促成了这一过程的实现。

为了对这一路径进行检测，研究小组设计了一系列实验。他们先给小鼠一个声音，随后20秒内给它们制造一次震动，这些小鼠很快就学会了把声音和即将到来的震动联系在一起。再次听到声音时，它们会立即僵住，停止所有动作。他们还专门养了一种特殊的转基因鼠，这种鼠从内嗅皮质到海马回的第三层输入端被抑制，用这种转基因鼠来实验时，研究人员发现它们对声音的反应更少。而在声音和震动同时出现的情况下，两种小鼠行为相同。这表明在时间联想记忆和内嗅皮质之间存在一定的联系。

另外一项实验是利用水迷宫和一个小平台进行，小鼠发现这个平台就可以不必游泳而上来休息，在平台上呆30秒后它们将被放回水迷宫。而转基因鼠找到小平台的机会更少，即使它们30秒前刚刚在平台上呆过。研究人员发现，它们很难在记忆和最近所发生事件之间建立联系。

研究人员解释说，转基因鼠在执行空间工作记忆任务和追溯恐惧制约的编码阶段，显出了很大缺陷。而老年痴呆症患者在记忆方面也存在很大困难，病人的内嗅皮质区是最早受到伤害的脑区之一。这些结果表明，从内嗅皮质到海马回之间的第三层输入端，在短期联想记忆中起着关键作用。