首個光學(xué)拓?fù)浣^緣體研制成功 可有效減少光在傳輸過程中的散射

近日，以色列和德國科學(xué)家攜手合作，成功研制出首個光學(xué)拓?fù)浣^緣體，這種新設(shè)備通過一種獨(dú)特的“波導(dǎo)”網(wǎng)格，為光的傳輸護(hù)航，可減少傳輸過程中的散射?？茖W(xué)家們表示，最新研究對光學(xué)工業(yè)的發(fā)展大有裨益。研究發(fā)表在最新一期的《自然》雜志上。

隨著計(jì)算機(jī)的運(yùn)行速度不斷加快以及芯片變得越來越緊密，人們對操縱光的設(shè)備變得越來越小的渴求與日俱增。但當(dāng)這些設(shè)備變小時，制造過程中就會產(chǎn)生瑕疵，使光的移動變得毫無規(guī)律且無法預(yù)料。人們迫切需要新技術(shù)來阻止在光傳輸中各類瑕疵造成的散射。

以色列理工大學(xué)的莫迪凱·塞格弗教授領(lǐng)導(dǎo)的團(tuán)隊(duì)和德國耶拿大學(xué)的阿歷克斯 薩扎米特教授的團(tuán)隊(duì)攜手，解決了這個問題。在實(shí)驗(yàn)中，他們使用了一列螺旋狀、采用“蜂窩”網(wǎng)格結(jié)構(gòu)排列的“波導(dǎo)”（像電線引導(dǎo)電一樣引導(dǎo)光），在實(shí)驗(yàn)室展示了一種全新的“光學(xué)拓?fù)浣^緣體”。

在“蜂窩”網(wǎng)格結(jié)構(gòu)中，每個波導(dǎo)的厚度僅為頭發(fā)絲的十分之一，光在其中受到了拓?fù)浔Ｗo(hù)——即使存在瑕疵，光也會不間斷地流動。塞格弗表示：“拓?fù)浔Ｗo(hù)意味著，光不會注意瑕疵的存在，會在瑕疵周圍流動?！?/p>

拓?fù)浔Ｗo(hù)這一理念最初并非為了光而生，而是為了在固體物質(zhì)中流動的電子。然而，以色列理工大學(xué)的米克爾

瑞切特斯曼和約納坦 帕勞特尼克通過使用一列相互作用的波導(dǎo)，并讓波導(dǎo)變成螺旋狀而非直線形，從而將拓?fù)浔Ｗo(hù)引入光子學(xué)。瑞切特斯曼說：“波導(dǎo)的螺旋天性打破了對稱，因此，在前進(jìn)的方向上，波導(dǎo)會順時針旋轉(zhuǎn)，而在后退方向上，波導(dǎo)會逆時針旋轉(zhuǎn)。在我們的實(shí)驗(yàn)中，為了防止光傳輸出現(xiàn)不需要的散射，這一點(diǎn)是必須的?！?/p>

瑞切特斯曼接著說：“光子拓?fù)浣^緣體有望為我們探究和理解拓?fù)浔Ｗo(hù)提供一個全新的平臺。例如，很難或無法在固體物質(zhì)內(nèi)進(jìn)行的所有實(shí)驗(yàn)現(xiàn)在使用光能夠進(jìn)行了?！迸羷谔啬峥搜a(bǔ)充道：“最新理念有望成為光子通訊工業(yè)和光的超導(dǎo)體領(lǐng)域的重要部分。這一發(fā)現(xiàn)也意味著科學(xué)家們朝著光子計(jì)算和量子計(jì)算又前進(jìn)了一步。”

光學(xué)工業(yè)是現(xiàn)代計(jì)算和通訊的心臟，光學(xué)使大量數(shù)據(jù)可以通過光纖快速傳輸。建立在光的流動和對光進(jìn)行控制基礎(chǔ)上的技術(shù)是計(jì)算機(jī)芯片制造和太陽能電池的核心技術(shù)。

Team develops first photonic topological insulators to protect transport of light

Researchers at the Technion-Israel Institute of Technology have developed and successfully demonstrated a photonic Floquet topological insulator, a new device used to protect the transport of light through a unique, lattice of'waveguides.' The advancement may play a key role in the photonics industry. A description is published in the current issue of Nature.

The photonics industry is at the heart of modern computing and communication. It has allowed vast amounts of data to be transmitted extremely quickly over fiber optic lines that cross the oceans. Photonic technology(i.e., technology that is based on the flow and control of light) is at the heart of DVDs, fabrication of computer chips, and solar cells.

As computers get faster and computer chips get denser, there is a need for smaller and smaller devices that manipulate light.But when devices get smaller,imperfections in the fabrication processes can play a large role,making light move irregularly and unpredictably. In other words, there's a need for a new methodology to prevent unwanted scattering from any kind of defect.

Researchers in the group of Prof. Mordechai (Moti) Segev at the Technion, in collaboration with the group of Prof. Alex Szameit at the Friedrich-Schiller University in Jena, Germany, have done exactly that. Using a lattice-work of 'waveguides' (which are like wires that guide light instead of electricity), the researchers have experimentally demonstrated a'photonic topological insulator.' The researchers used an array of helical'waveguides' (shaped like curly hairs) arranged in a 'honeycomb'lattice structure, similar to the pattern observed in beehives.In such a structure, where each waveguide is thinner than a tenth of a human hair, light is 'topologically protected,' which means it flows uninterrupted despite the presence of defects.

According to Segev,"topological protection means that light simply flows around imperfections essentially without noticing them."

Topological protection was first conceived not for light, but for electrons flowing in a solid material. However, Dr. Mikael Rechtsman and Mr. Yonatan Plotnik from the Technion, figured out how to bring topological protection into photonics, using an array of waveguides that interact with one another. The additional step needed to achieve topological protection was to make the waveguides helical (in the shape of a helix), rather than straight. "The helical nature of the waveguides breaks the symmetry,so that in the forward direction the waveguides are spinning clockwise,and in the backward direction,counterclockwise" said Rechtsman."In our procedure, this is an essential ingredient in preventing unwanted scattering."

"Photonic topological insulators have the potential to provide an entirely new platform for probing and understanding topological protection," explained Rechtsman. "For example, all sorts of experiments that would be difficult or impossible to carry out in solid-state materials can now be accessed using light."

"Such new ideas might one day be an important part of the optical communication industry,being robust to scattering and disturbances: a super conductor of light," added Plotnik.

"This discovery is another step in the progress towards optical and quantum computing," said Julia Zeuner, a graduate student at Friedrich-Schiller University in Jena, who fabricated the sophisticated photonic structure and did part of the experiments.Her contributions, and those of her PhD advisor (Szameit), were absolutely crucial, and manifested a long standing Israeli-German collaboration between the teams."We have discovered a completely novel phenomena," concluded Segev, "and new phenomenon are destined to find applications in directions that we can't even imagine."

“垃圾DNA”在腦發(fā)育中起重要作用

最近，美國加利福尼亞大學(xué)舊金山分?？茖W(xué)家利用小鼠模型研究發(fā)現(xiàn)，過去認(rèn)為是垃圾的長非編碼RNA（lncRNAs）在大腦發(fā)育中扮演重要角色，和多種破壞性神經(jīng)疾病有關(guān)，如亨廷頓舞蹈病、老年癡呆癥等。

研究人員指出，這一發(fā)現(xiàn)把lncRNAs和神經(jīng)細(xì)胞類型、發(fā)展過程及人類疾病狀態(tài)聯(lián)系在一起，會促進(jìn)人們進(jìn)一步研究染色體中那些被忽視的DNA片段，確定它們的作用。

相關(guān)論文在線發(fā)表于近日出版的《細(xì)胞干細(xì)胞》雜志上。

UCSF研究人員指出，以往的基因組研究項(xiàng)目主要探索能給蛋白質(zhì)編碼的基因，在編碼基因末端含有大量的非編碼基因，被當(dāng)做垃圾擱置一邊。

他們集中研究了長非編碼RNA分子，這種分子就像信使RNA一樣，也是從DNA轉(zhuǎn)錄而來，由獨(dú)一無二的核苷酸序列構(gòu)成；不同的是，它們雖能指導(dǎo)蛋白質(zhì)的合成，但本身并不攜帶蛋白質(zhì)模板信息。

過去，人們一直以為它們不能影響細(xì)胞的命運(yùn)或活動。有證據(jù)表明，lncRNAs可以把結(jié)構(gòu)蛋白和含有DNA的染色體結(jié)合在一起，直接影響基因活動和細(xì)胞生理功能無需改變基因編碼。

也就是說在細(xì)胞內(nèi)，lncRNA分子的作用是“外在”的，超越于基因，不會因DNA的變化而改變。

研究小組結(jié)合了幾種互補(bǔ)的先進(jìn)測序技術(shù)，分析了成熟小鼠腦部室下區(qū)（在亨廷頓舞蹈病中這里的神經(jīng)元被破壞）神經(jīng)干細(xì)胞系lncRNAs的表達(dá)，識別出約2000個這種分子，其中有一組含有88個非編碼RNA的片段和亨廷頓舞蹈?。ㄒ环N致命的神經(jīng)退行性紊亂）之間有關(guān)聯(lián)，另一組特殊的長非編碼RNA與老年癡呆癥、痙攣性癲癇、大部分抑郁障礙和多種癌癥之間都有弱關(guān)聯(lián)。研究人員認(rèn)為，哺乳動物體內(nèi)（包括小鼠和人類）約有9000個lncRNAs分子。

“這些神秘的RNA分子在大腦中有什么功能，人們還只是剛開始研究?！闭撐母呒壸髡?、該校伊萊和伊迪特·布羅德中心再生醫(yī)學(xué)與干細(xì)胞研究中心神經(jīng)外科副教授丹尼爾·里姆說。實(shí)驗(yàn)中生成了大量的數(shù)據(jù)需要進(jìn)一步探索，他們建了一個網(wǎng)站讓其他科學(xué)家也能共享這些數(shù)據(jù)，共同研究lncRNAs在發(fā)育與疾病中的作用。

Brain Development Is Guided by Junk DNA that Isn’t Really Junk

Specific DNA once dismissed as junk plays an important role in brain development and might be involved in several devastating neurological diseases, UC San Francisco scientists have found.

Their discovery in mice is likely to further fuel a recent scramble by researchers to identify roles for long-neglected bits of DNA within the genomes of mice and humans alike.

While researchers have been busy exploring the roles of proteins encoded by the genes identified in various genome projects, most DNA is not in genes. This so-called junk DNA has largely been pushed aside and neglected in the wake of genomic gene discoveries, the UCSF scientists said.

In their own research, the UCSF team studies molecules called long noncoding RNA (lncRNA, often pronounced as “l(fā)ink” RNA), which are made from DNA templates in the same way as RNA from genes.

“The function of these mysterious RNA molecules in the brain is only beginning to be discovered,” said Daniel Lim,MD, PhD, assistant professor of neurological surgery, a member of the Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research at UCSF, and the senior author of the study,published online April 11 in the journal Cell Stem Cell.

Alexander Ramos, a student enrolled in the MD/PhD program at UCSF and first author of the study, conducted extensive computational analysis to establish guilt by association, linking lncRNAs within cells to the activation of genes.

Ramos looked specifically at patterns associated with particular developmental pathways or with the progression of certain diseases.He found an association between a set of 88 long noncoding RNAs and Huntington’s disease, a deadly neurodegenerative disorder. He also found weaker associations between specific groups of long noncoding RNAs and Alzheimer’s disease, convulsive seizures, major depressive disorder and various cancers.

“Alex was the team member who developed this new research direction, did most of the experiments, and connected results to the lab’s ongoing work,”Lim said. The study was mostly funded through Lim’s grant - a National Institutes of Health (NIH)Director’s New Innovator Award, a competitive award for innovative projects that have the potential for unusually high impact.

LncRNA versus Messenger RNA

Unlike messenger RNA, which is transcribed from the DNA in genes and guides the production of proteins, lncRNA molecules do not carry the blueprints for proteins.Because of this fact, they were long thought to not influence a cell’s fate or actions.

Nonetheless, lncRNAs also are transcribed from DNA in the same way as messenger RNA,and they, too, consist of unique sequences of nucleic acid building blocks.

Evidence indicates that lncRNAs can tether structural proteins to the DNA-containing chromosomes, and in so doing indirectly affect gene activation and cellular physiology without altering the genetic code. In other words,within the cell, lncRNA molecules act “epigenetically” — beyond genes — not through changes in DNA.

The brain cells that the scientists focused on the most give rise to various cell types of the central nervous system. They are found in a region of the brain called the subventricular zone, which directly overlies the striatum. This is the part of the brain where neurons are destroyed in Huntington’s disease, a condition triggered by a single genetic defect.

繼本月初丁肇中團(tuán)隊(duì)公布阿爾法磁譜儀項(xiàng)目首批研究暗物質(zhì)成果后，美國明尼蘇達(dá)州的地下暗物質(zhì)實(shí)驗(yàn)——超級低溫暗物質(zhì)搜尋計(jì)劃（Super-CDMS）日前報告了3個疑似暗物質(zhì)事例，計(jì)算結(jié)果表明其是大質(zhì)量弱相互作用粒子(WIMP)的可能性為99.81%，不足5西格瑪水平，并不會作為暗物質(zhì)證據(jù)進(jìn)行發(fā)布。

暗物質(zhì)粒子被認(rèn)為是大質(zhì)量弱相互作用粒子，非常難以被探測到。目前人們想要尋獲暗物質(zhì)有兩個辦法：將儀器送上太空，或者放在地下深處。阿爾法磁譜儀項(xiàng)目是前者，超級低溫暗物質(zhì)搜尋計(jì)劃則是后者。CDMS第一組實(shí)驗(yàn)CDMS-Ⅰ設(shè)置于史丹佛大學(xué)校園地下的隧道運(yùn)作，而目前進(jìn)行的CDMS-Ⅱ，位于明尼蘇達(dá)州素丹地礦國家公園的地底深處，該處在2010年曾報告了兩個潛在的暗物質(zhì)蹤跡，遺憾的是后來那些信號被證明來自于儀器本身。

美國地下暗物質(zhì)實(shí)驗(yàn)發(fā)現(xiàn)暗物質(zhì)初步線索

在日前舉行的美國物理學(xué)會會議上，科學(xué)家新公布了來自Super-CDMS實(shí)驗(yàn)的3個“有前途”的暗物質(zhì)線索，并將實(shí)驗(yàn)結(jié)果發(fā)表在公開論文網(wǎng)站Arxiv上。他們在Super-CDMS設(shè)施中布置了8個硅探測器，冷卻到零下459.67華氏度以讓其在接近深空的溫度下運(yùn)轉(zhuǎn)。通過捕獲暗物質(zhì)粒子碰撞探測器內(nèi)的原子核發(fā)生的稀有相互作用，得到了3個疑似的暗物質(zhì)事例——值得尋味的是，如果這真是WIMP，那么推測其質(zhì)量為8.6千兆電子伏，遠(yuǎn)比之前人們認(rèn)為的要輕，違背了其他研究結(jié)果。

計(jì)算結(jié)果表明，新探測到的“可疑分子”是大質(zhì)量弱相互作用粒子的可能性為99.81%。但在粒子物理學(xué)領(lǐng)域，現(xiàn)已采納更為嚴(yán)格的“5西格瑪”作為標(biāo)準(zhǔn)，即擁有5西格瑪水平的確定性（統(tǒng)計(jì)學(xué)上為“真”的比率是99.999%）才能算一項(xiàng)真正意義上的物理發(fā)現(xiàn)，3西格瑪只是科學(xué)家會承認(rèn)實(shí)驗(yàn)結(jié)果的一個水平。而研究小組也強(qiáng)調(diào)了本次結(jié)果的“初步”性質(zhì)，表示并不會作為暗物質(zhì)證據(jù)進(jìn)行發(fā)布，仍需進(jìn)一步數(shù)據(jù)來完善結(jié)論。

無獨(dú)有偶，在本月初，物理學(xué)家丁肇中及其團(tuán)隊(duì)公布了由其主持了18年的阿爾法磁譜儀項(xiàng)目首批研究成果，并表示現(xiàn)已收集到40萬個正電子，數(shù)據(jù)誤差僅1%，且觀察到宇宙射線流中正電子存在的比率符合暗物質(zhì)存在的理論預(yù)測。

而據(jù)BBC新聞網(wǎng)稱，近期3個關(guān)于暗物質(zhì)的早期提示——丁肇中團(tuán)隊(duì)在太空獲得證據(jù)、此次明尼蘇達(dá)地下實(shí)驗(yàn)室的線索與大型強(qiáng)子對撞機(jī)具備的揭曉暗物質(zhì)面紗的能力，已引起美國物理學(xué)會會議上科學(xué)家的轟動。

Super-CDMS researchers report possible evidence of WIMPs

Researchers working at the Super Cryogenic Dark Matter Search (CDMS) facility, located underground in Minnesota's Soudan Mine, are reporting in a paper uploaded to the preprint server arXiv that they've found three events that lie in the signal range of Weakly Interacting Massive Particles (WIMPs). The group also gave a talk detailing their results to an audience at this year's American Physical Society meeting—as part of that discussion, they made it clear the noted events do not rise to the level of discovery, nor do they imply the team has found evidence of the existence of dark matter.

Researchers in several facilities around the world (and aboard the International Space Station) are looking for evidence of WIMPs, because theory suggests that they constitute dark matter,the invisible material believed to make up approximately 85 percent of all matter that exists in the universe. Because WIMPs can't be seen directly, researchers look to events that might prove they exist,such as collisions between WIMPs and atomic nuclei. In order to find such evidence, researchers set up detectors they hope will catch such collisions that occur due to gravitational pull on WIMPs—they are believed to interact only rarely with normal matter through other means.

Researchers at the Super-CDMS facility have set up eight silicon detectors (cooled to -459.67 degrees Fahrenheit) in the hope of detecting the slight amount of heat given off by a collision between a WIMP and an atom's nucleus. The researchers report detection of three events that might have been the result of such collisions, though they are quick to add that the events might also have been due to something else, such as statistical errors. However, calculations indicate the events are 99.81 percent more likely to be WIMPs than background fluctuations,which translates to approximately a three-sigma level of confidence.

Interestingly, if the detected events do turn out to be the result of WIMP/nucleus collisions,it will mean that WIMPs are much lighter than scientists have been expecting—the detected collisions detected to just 8.6 gigaelectronvolts. The researchers note this finding is in line with results from other research efforts, though they also acknowledge that it contradicts the findings of other researchers.

Regardless, research at the Super-CDMS facility and elsewhere will continue until WIMP collisions are proven to exist, or not.

黑納米粒子可為光催化制氫反應(yīng)提速

美國科學(xué)家研發(fā)出一種原子尺度的“混亂工程”技術(shù)，可以將光催化反應(yīng)中低效的“白色”二氧化鈦納米粒子變成高效的“黑色”納米粒子?？茖W(xué)家們表示，最新技術(shù)有望成為氫清潔能源技術(shù)的關(guān)鍵。

加州大學(xué)伯克利分校以及伯克利勞倫斯國家實(shí)驗(yàn)室環(huán)境能源技術(shù)中心的科學(xué)家塞繆爾 毛領(lǐng)導(dǎo)的研究團(tuán)隊(duì)研發(fā)出的這項(xiàng)技術(shù)，通過工程方法，將“混亂工程”引入了半導(dǎo)體二氧化鈦納米晶體的結(jié)構(gòu)中，使白色的晶體變?yōu)楹谏?，新晶體不僅能吸收紅外線還可以吸收可見光和紫外線。塞繆爾·毛在美國化學(xué)會于新奧爾良舉辦的年度大會上指出：“我們已經(jīng)證明，黑色的二氧化鈦納米粒子能通過太陽光驅(qū)動的光催化反應(yīng)產(chǎn)生氫氣，而且，效率創(chuàng)下了新高。”

塞繆爾·毛解釋道：“在實(shí)驗(yàn)中，我們讓白色的二氧化鈦納米粒子承受高壓的氫氣，打亂了二氧化鈦納米粒子的結(jié)構(gòu)，合成出的黑色二氧化鈦納米粒子成為一種耐用且高效的光催化劑，而且也擁有了全新的潛能?！?/p>

氫氣可廣泛應(yīng)用于清潔電池或燃料中，并不會加速全球變暖，但是，使用氫氣面臨的最大挑戰(zhàn)是：如何高效且低成本地大規(guī)模制造出氫氣。盡管氫氣是宇宙中儲量最豐富的元素，但純氫在地球上少之又少，因?yàn)闅鋾魏纹渌愋偷脑咏Y(jié)合。用太陽光將水分子分解成氫氣和氧氣是理想的制造純氫的方式，但這一過程需要一種高效且不被水腐蝕的光催化劑，二氧化鈦能對抗水的腐蝕，但無法吸收紫外線，紫外線占據(jù)了太陽光10%的能量。

塞繆爾·毛的最新研究改變了這種現(xiàn)狀，最新技術(shù)不僅為制氫過程提供了一種極富前景的新的光催化劑，而且也消解了一些根深蒂固的科學(xué)觀念。塞繆爾 毛說：“我們的測試表明，一種好的半導(dǎo)體光催化劑不必是瑕疵最小且能態(tài)僅僅在導(dǎo)帶之下的單晶體。”

另外，伯克利實(shí)驗(yàn)室先進(jìn)光源中心進(jìn)行的特性研究測量結(jié)果表明，在100個小時的太陽光驅(qū)動制氫過程中，有40毫克氫氣源于光催化反應(yīng)，僅僅0.05毫克氫被黑色的二氧化鈦吸收。

Good cats wear black: Black nanoparticles could play key role in clean energy photocatalysis

A unique atomic-scale engineering technique for turning low-efficiency photocatalytic"white" nanoparticles of titanium dioxide into high-efficiency "black"nanoparticles could be the key to clean energy technologies based on hydrogen.

Samuel Mao, a scientist who holds joint appointments with Berkeley Lab's Environmental Energy Technologies Division and the University of California at Berkeley, leads the development of a technique for engineering disorder into the nanocrystalline structure of the semiconductor titanium dioxide. This turns the naturally white crystals black in color, a sign that the crystals are now able to absorb infrared as well as visible and ultraviolet light. The expanded absorption spectrum substantially improves the efficiency with which black titanium dioxide can use sunlight to split water molecules for the production of hydrogen.

"We have demonstrated that black titanium dioxide nanoparticles are capable of generating hydrogen through solardriven photocatalytic reactions with a record-high efficiency,"Mao said in a talk at the American Chemical Society (ACS)'s national meeting in New Orleans.

"The synthesis of black titanium dioxide nanoparticles was based on a hydrogenation process in which white titanium dioxide nanocrystals were subjected to high pressure hydrogen gas," said Mao."The unique disordered structure creates a photocatalyst that is both durable and efficient, and gives titanium dioxide, one of the moststudied of all oxide materials, a renewed potential."

The promise of hydrogen in batteries or fuels is a clean and renewable source of energy that does not exacerbate global climate change. The challenge is cost-effectively mass-producing it.Despite being the most abundant element in the universe, pure hydrogen is scarce on Earth because hydrogen combines with just about any other type of atom.Using solar energy to split the water molecule into hydrogen and oxygen is the ideal way to produce pure hydrogen. This, however,requires an efficient photocatalyst that water won't corrode. Titanium dioxide can stand up to water but until the work of Mao and his group was only able to absorb ultraviolet light, which accounts for barely ten percent of the energy in sunlight.

In his ACS talk, titled "Disorder Engineering: Turning Titanium Dioxide Nanoparticles Black," Mao described how he developed the concept of "disorder engineering,"and how the introduction of hydrogenated disorders creates mid-band gap energy states above the valence band maximum to enhance hydrogen mobility. His studies have not only yielded a promising new photocatalyst for generating hydrogen, but have also helped dispel some widely held scientific beliefs.

"Our tests have shown that a good semiconductor photocatalyst does not have to be a single crystal with minimal defects and energy levels just beneath the bottom of conduction band," Mao said.

歐核中心開發(fā)出廉價質(zhì)子束癌癥療法

即便在物理學(xué)家眼里，歐核中心那些“上帝粒子”的研究人員也都是高高在上，但現(xiàn)在，由該研究小組開發(fā)出的一項(xiàng)新成果被稱為“終于和普通人生活有了關(guān)系”。據(jù)英國《每日郵報》在線版日前報道，致力于“上帝粒子”項(xiàng)目的科學(xué)家們，正在研究利用高能帶電粒子束治療癌癥患者，以代替一直廣泛使用、有強(qiáng)烈副作用的放射療法，而該方法的廉價與高效有望每年福澤數(shù)以萬計(jì)的癌癥患者。

在位于日內(nèi)瓦邊境的歐洲核子研究中心內(nèi)，“上帝粒子”研究小組已開始與一家名為“先進(jìn)腫瘤治療”的英國公司合作，力求降低新型替代技術(shù)的成本。這種癌癥治療新技術(shù)，是使用該小組科學(xué)家們已經(jīng)“駕輕就熟”的帶正電的高能粒子束精確作用于腫瘤。其與傳統(tǒng)放射療法相比，不僅效果更明顯，且對于健康組織的傷害也遠(yuǎn)遠(yuǎn)小于前者?？茖W(xué)家們希望能夠用3年時間在英國建立起一家采用此療法的醫(yī)療中心，以幫助廣受癌癥折磨的患者。

“質(zhì)子束療法較之于放射療法，是一次巨大的進(jìn)步，但過高的成本一直阻礙它的普及。我們與歐核中心合作開發(fā)的新器械，將打破這種瓶頸，因?yàn)樗某杀局挥鞋F(xiàn)有同類產(chǎn)品的三分之一。”研究小組的合作者、“先進(jìn)腫瘤治療”公司的老板邁克·辛克萊爾博士說。

據(jù)《每日郵報》的數(shù)據(jù)，目前僅在英國每年就有大約有32萬人被確診罹患癌癥，而其中一半人會被安排接受放射療法?？茖W(xué)家們希望借助新型的質(zhì)子束療法，能令這些接受放射療法中的4萬名患者受益。

當(dāng)前，人們可以在瑞士和美國接受新方法的治療，不過所需費(fèi)用也相當(dāng)高昂。即使是在實(shí)行國家國民健康保險制度的英國，每人9萬鎊的費(fèi)用也非福利體制能夠承受。雖然兩家位于倫敦和曼徹斯特的治療中心將在2017年建成投入使用，但是每年1500人的接待能力，依然無法改變新技術(shù)只能服務(wù)于一小部分人的狀況。

針對這一點(diǎn)，研究小組提出了一個振奮人心的目標(biāo)：2016年在英國建成第一個使用廉價質(zhì)子束療法的醫(yī)療中心，每年為超過12000名患者提供服務(wù)。邁克 辛克萊爾表示，這是一項(xiàng)堪稱力挽狂瀾的創(chuàng)舉，將使先進(jìn)的醫(yī)療技術(shù)更廣泛地服務(wù)于社會大眾。

歐核中心2012年7月對希格斯玻色子（“上帝粒子”）的研究取得重大進(jìn)展，新粒子的發(fā)現(xiàn)也被作為“理解自然的一個里程碑”，不過大多數(shù)普通人認(rèn)為這和自己的生活關(guān)系不大，一覺醒來的世界并沒有因?yàn)橘|(zhì)量之源被找到而出現(xiàn)任何改變，但如今這些研究人員將要做的事，卻可能徹底改變每年數(shù)萬名癌癥患者的治療方式。

LHC proton beam technology to help battle cancer

Thousands of cancer patients could benefit from ambitious plans to bring atom-smashing technology to hospitals across the UK.

A British medical company is working with scientists at Cern,the European Centre for Nuclear Research, to develop affordable proton beam therapy (PBT), based on the same technology which drives the Large Hadron Collider(LHC), the world's biggest particle accelerator.

Unlike conventional radiotherapy that relies on high intensity X-rays, the treatment blasts tumours with protons, and it is said to be much more effective at targeting and destroying cancer and less destructive to surrounding tissue.

Two proton therapy facilities are already due to be launched at specialist NHS centres in London and Manchester in 2017, but they will only be able to take 1,500 patients a year and will focus on highly complex and difficult-to-treat cases.

The new proposal led by London company Advanced Oncotherapy PLC with the help of Cern scientists would see cheaper and more accessible PBT units established in 10 hospitals and clinics across the UK over five years and Dr Michael Sinclair,chief executive of Advanced Oncotherapy, hopes to open his first centre in 2016.

"Our intention is to make the treatment available both to the private sector and the NHS,” he says. "There are currently 320,000 new cancer patients diagnosed in Britain each year, and up to 15 per cent of those could benefit from this treatment.

"When the NHS facilities are opened, they will only be able to treat a small proportion of these cases. Our aim is to make this therapy available to the masses,which would be a massive step forward."

With each proton accelerator able to support three treatment rooms, the target is to help some 12,000 cancer patients a year and at around ￡26m each, the new Cern machines will be a third of the price of currently available equipment, said Dr Sinclair.

He adds: "This is a gamechanger. PBT offers a significant improvement for patients with cancer over conventional radiotherapy. Everybody recognises the advantages of the technique,but so far the big problem has always been cost."

Experts estimate that a quarter of UK cancer patients who receive radiation treatment- around 40,000 per year - could benefit from PBT, which is especially useful for targeting tumours in vulnerable parts of the body such as the eye or the brain.

As well as assisting Dr Sinclair,scientists at Cern are engaged in a long-term project to improve proton beam treatment with cutting edge technology.

科學(xué)家繪制出完整藥用小分子空間“地圖”

美國杜克大學(xué)化學(xué)家最近開發(fā)出一種新的計(jì)算機(jī)算法，能模擬出所有的含碳小分子，經(jīng)過分類編目后形成一份特殊的小分子空間“地圖”，幫助化學(xué)家在實(shí)驗(yàn)室里將這些分子真正制造出來。這一成果有望成為藥物開發(fā)人員的得力工具，以尋找更有效的藥物和新材料。相關(guān)論文在線發(fā)表于4月的《美國化學(xué)協(xié)會會刊》上。

小分子空間（SMU）是所有分子量在500道爾頓及以下、具有合成可能性的有機(jī)分子。這類分子約有1060種。目前的資料庫只描述了小分子空間中約10億種分子，迄今合成出來的化合物約有1億種。而且這些分子在結(jié)構(gòu)上很相似，很多來自空間中的同一區(qū)域。在那些未曾探索過的區(qū)域里，更可能存在著最棘手難題的分子答案。

為探索化學(xué)空間里的新區(qū)域，研究人員設(shè)計(jì)了一種新的計(jì)算機(jī)算法來繪制整個小分子空間。杜克大學(xué)博士后亞倫·威夏普編寫了新算法，讓小的隨機(jī)化學(xué)反應(yīng)變成苯環(huán)結(jié)構(gòu)，然后按照與之相符的小分子空間位置，給生成的新分子分類編目。

其中最大的困難是，找出哪種分子才是能在實(shí)驗(yàn)室合成的化合物。威夏普把他早期構(gòu)建出來的新分子繪成草圖，送到一些合成化學(xué)家那里，讓他們標(biāo)注這些分子中哪些合成出來不穩(wěn)定，或根本就不能合成。然后把這些意見加入算法規(guī)則，按照新的算法規(guī)則，這類化合物就不會再構(gòu)造出來。

經(jīng)過10次這樣的反復(fù)，他構(gòu)建出一個含有900萬個分子的虛擬數(shù)據(jù)庫，其中的化合物能代表小分子空間內(nèi)的每個區(qū)域，并繪制出新的“地圖”，顯示化學(xué)空間中尚未合成出其中任何化合物的空白區(qū)域。

“有了這份‘地圖’，化學(xué)家們只要能合成出這個區(qū)域內(nèi)的一種新分子，就造出了一種新型化合物?！蓖钠照f，“只要是在小分子‘地圖’上的空白區(qū)域里，就保證造出的東西還沒有人申請過專利?！?/p>

目前，研究小組已經(jīng)在線發(fā)布了該算法的源代碼，并希望科學(xué)家能立刻著手挖掘小分子空間中尚無人探索的區(qū)域，發(fā)現(xiàn)新的化合物。

Scientists Map All Possible Drug Compounds in ‘Small Molecule Universe

Researchers at Duke University have developed a digital library of all the small carboncontaining molecule structures that can possibly be developed as drugs— even ones that don't exist yet. The results provide "a nearinfinite source of diverse novel compounds" that could allow chemists to identify promising structures for new drugs.

Using a new computerized mathematical model they called the Algorithm for Chemical Space Exploration with Stochastic Search(ACSESS), researchers led by chemist David Beratan mapped all the possible organic structures in the "small molecule universe,"which is estimated to contain over 1 novemdecillion chemical compounds— that's 10^60, or 1 with 60 zeroes after it.

"The small-molecule universe is astronomical in size," Beratan told Duke Today, the university newsletter. "When we search it for new molecular solutions, we are lost. We don't know which way to look."

The molecular map created with ACSESS can help scientists navigate the vast field of possible compounds in order to see which chemical structures have already been developed, and how they might build the shapes in the unexplored "white space."

The researchers describe their algorithm and accompanying small molecule universe representative map (SMU-RUL) in a paper published this month in the Journal of the American Chemical Society.

Beratan told Duke Today that molecular solutions for many global issues can be found in the unexplored chemical space,"whether it's a cure for disease or a new material to capture sunlight."Developing all the compounds in that space would be prohibitively expensive and time-consuming,but the ACSESS model makes it easier to identify structures with useful properties.

Digital molecular libraries have already yielded advances in chemistry research.

The "GDB13" database, for example, which maps almost 1 billion possible organic compounds with 13 or fewer atoms, has led to several successful new drugs since it was released in 2009. Other methods expand on existing drug structures to model potential new ones.

The ACSESS library, however,dramatically expands the diversity of potential chemical compounds,and maps entirely new regions of the small molecule universe.

Postdoctoral associate Aaron Virshup programmed the algorithm to create a digital library of almost 9 million structures that represented different regions of the small molecule universe, then make random "chemical mutations" that can change the structure of each compound.

The algorithm also accounts for whether a chemical structure is unstable, to limit the library to compounds that can realistically be created.

"The idea was to start with a simple molecule and make random changes, so you add a carbon,change a double bond to a single bond, add a nitrogen," Virshup explained to Duke Today. With enough repetitions of the process,researchers can use ACSESS to get to any possible molecule.

The Duke team then created a self-organizing map of the structures revealed by the ACSESS model, which they compared to all the chemical compounds that exist in the PubChem database.

The resulting map revealed enormous swaths of unexplored chemical space, ripe for mining by scientists.

"With the map, we can tell chemists, if you can synthesize a new molecule in this region of space, you have made a new type of compound," Virshup told Duke Today. "If you're in the blank spaces on our small molecule map, you're guaranteed to make something that isn't patented yet."

胚胎干細(xì)胞移植成功恢復(fù)老鼠記憶能力

美國科學(xué)家首次將人類胚胎干細(xì)胞移植進(jìn)大腦受損的老鼠的神經(jīng)細(xì)胞內(nèi)，成功地幫助老鼠恢復(fù)了學(xué)習(xí)和記憶能力。研究人員表示，發(fā)表在最新一期《自然 生物技術(shù)》上的新研究將為神經(jīng)疾病的藥物篩查和新藥發(fā)現(xiàn)創(chuàng)建研究模型。威斯康辛大學(xué)麥迪遜分校神經(jīng)科學(xué)和神經(jīng)病學(xué)教授張?zhí)K?。ㄒ糇g）領(lǐng)導(dǎo)的科研團(tuán)隊(duì)通過化學(xué)方法，引導(dǎo)人類胚胎干細(xì)胞分化成神經(jīng)細(xì)胞，再將得到的中間細(xì)胞注射進(jìn)老鼠體內(nèi)，隨后，這些細(xì)胞形成了兩類常見且重要的神經(jīng)元：γ-氨基丁酸（GABA）和乙酰膽堿。該研究的主要作者、神經(jīng)科學(xué)和神經(jīng)病學(xué)教授張?zhí)K俊表示：“這兩類神經(jīng)元與人類的行為、情感、學(xué)習(xí)、記憶、上癮和某些精神問題都有關(guān)聯(lián)?！?/p>

實(shí)驗(yàn)初始，研究人員破壞了老鼠大腦內(nèi)的內(nèi)側(cè)隔核，該地區(qū)通過GABA和類膽堿神經(jīng)元與海馬體（大腦中被認(rèn)為是感情和記憶中心的部分）連接在一起。張?zhí)K俊說：“這一環(huán)路是學(xué)習(xí)和記憶能力的基礎(chǔ)。”

移植細(xì)胞則被放置在位于這些記憶環(huán)路另一端的海馬體內(nèi)，當(dāng)細(xì)胞移植進(jìn)去后，為了對大腦發(fā)出的化學(xué)指令做出反應(yīng)，它們開始變得專門化并同海馬體內(nèi)合適的細(xì)胞連接在一起。結(jié)果發(fā)現(xiàn)，移植后，老鼠在學(xué)習(xí)和記憶能力測試方面的得分高了很多。例如，它們在水迷宮測試中表現(xiàn)得更好，這一測試需要老鼠能記住游泳池內(nèi)一個隱藏平臺的位置。

張?zhí)K俊指出，確保幾乎所有被移植的細(xì)胞都變成神經(jīng)細(xì)胞非常關(guān)鍵，這意味著我們能預(yù)測最終會得到什么細(xì)胞以及在治療中如何使用它們，減少了注射形成腫瘤干細(xì)胞的機(jī)會?！霸诤芏嘁浦矊?shí)驗(yàn)中，注射初始原細(xì)胞經(jīng)常會產(chǎn)生大量腫瘤細(xì)胞，而我們的實(shí)驗(yàn)卻沒有出現(xiàn)這種情況，因?yàn)楸灰浦驳募?xì)胞是純凈的，而且命運(yùn)已被注定，這就使得它們不會‘節(jié)外生枝’，我們需要確保沒有注射進(jìn)癌癥的種子?！?/p>

張?zhí)K俊表示：“新得到的這兩種細(xì)胞都對大腦的功能至關(guān)重要。類膽堿神經(jīng)元與老年癡呆癥和唐氏綜合征有關(guān)；而GABA神經(jīng)元同精神分裂癥、癲癇、抑郁和上癮等精神疾病有關(guān)。很多精神方面的疾病，人們并不知道大腦的哪個部分出了錯，新研究有望為神經(jīng)疾病的藥物篩查和新藥發(fā)現(xiàn)創(chuàng)建模型。”

Stem cell transplant restores memory, learning in mice

For the first time, human embryonic stem cells have been transformed into nerve cells that helped mice regain the ability to learn and remember.

A study at UW-Madison is the first to show that human stem cells can successfully implant themselves in the brain and then heal neurological deficits, says senior author Su-Chun Zhang, a professor of neuroscience and neurology.

Once inside the mouse brain, the implanted stem cells formed two common, vital types of neurons, which communicate with the chemicals GABA or acetylcholine. "These two neuron types are involved in many kinds of human behavior, emotions,learning, memory, addiction and many other psychiatric issues," says Zhang.

The human embryonic stem cells were cultured in the lab,using chemicals that are known to promote development into nerve cells — a field that Zhang has helped pioneer for 15 years. The mice were a special strain that do not reject transplants from other species.

After the transplant, the mice scored significantly better on common tests of learning and memory in mice. For example,they were more adept in the water maze test, which challenged them to remember the location of a hidden platform in a pool.

The study began with deliberate damage to a part of the brain that is involved in learning and memory.

Three measures were critical to success, says Zhang: location,timing and purity. "Developing brain cells get their signals from the tissue that they reside in, and the location in the brain we chose directed these cells to form both GABA and cholinergic neurons."

The initial destruction was in an area called the medial septum, which connects to the hippocampus by GABA and cholinergic neurons. "This circuitry is fundamental to our ability to learn and remember," says Zhang.

The transplanted cells,however, were placed in the hippocampus — a vital memory center — at the other end of those memory circuits. After the transferred cells were implanted,in response to chemical directions from the brain, they started to specialize and connect to the appropriate cells in the hippocampus.

The process is akin to removing a section of telephone cable, Zhang says. If you can find the correct route, you could wire the replacement from either end.

For the study, published in the current issue of Nature Biotechnology, Zhang and first author Yan Liu, a postdoctoral associate at the Waisman Center on campus, chemically directed the human embryonic stem cells to begin differentiation into neural cells, and then injected those intermediate cells. Ushering the cells through partial specialization prevented the formation of unwanted cell types in the mice.

Ensuring that nearly all of the transplanted cells became neural cells was critical, Zhang says. "That means you are able to predict what the progeny will be, and for any future use in therapy, you reduce the chance of injecting stem cells that could form tumors. In many other transplant experiments,injecting early progenitor cells resulted in masses of cells —tumors. This didn't happen in our case because the transplanted cells are pure and committed to a particular fate so that they do not generate anything else. We need to be sure we do not inject the seeds of cancer."

Brain repair through cell replacement is a Holy Grail of stem cell transplant, and the two cell types are both critical to brain function, Zhang says. "Cholinergic neurons are involved in Alzheimer's and Down syndrome, but GABA neurons are involved in many additional disorders, including schizophrenia, epilepsy, depression and addiction."