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In a paper published in the April 25 early online edition of the Proceedings of the National Academy of Sciences, researchers at the University of California, San Diego School of Medicine, the Gladstone Institutes in San Francisco and colleagues report a game-changing advance in stem cell science: the creation of long-term, self-renewing, primitive neural precursor cells from human embryonic stem cells (hESCs) that can be directed to become many types of neuron without increased risk of tumor formation. “It’s a big step forward,” said Kang Zhang, MD, PhD, professor of ophthalmology and human genetics at Shiley Eye Center and director of the Institute for Genomic Medicine, both at UC San Diego. “It means we can generate stable, renewable neural stem cells or downstream products quickly, in great quantities and in a clinical grade – millions in less than a week – that can be used for clinical trials and, eventually, for clinical treatments. Until now, that has not been possible.”Human embryonic stem cells hold great promise in regenerative medicine due to their ability to become any kind of cell needed to repair and restore damaged tissues. But the potential of hESCs has been constrained（差遣，逼迫） by a number of practical problems, not least among them the difficulty of growing sufficient quantities of stable, usable cells and the risk that some of these cells might form tumors.To produce the neural stem cells, Zhang, with co-senior author Sheng Ding, PhD, a former professor of chemistry at The Scripps Research Institute and now at the Gladstone Institutes, and colleagues added small molecules in a chemically defined culture condition that induces hESCs to become primitive neural precursor cells, but then halts the further differentiation process.”And because it doesn’t use any gene transfer technologies or exogenous（外因的） cell products, there’s minimal risk of introducing mutations or outside contamination,” Zhang said. Assays of these neural precursor cells found no evidence of tumor formation when introduced into laboratory mice.By adding other chemicals, the scientists are able to then direct the precursor cells to differentiate into different types of mature neurons, “which means you can explore potential clinical applications for a wide range of neurodegenerative（神经变性的） diseases,” said Zhang. “You can generate neurons for specific conditions like amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease), Parkinson’s disease or, in the case of my particular research area, eye-specific neurons that are lost in macular degeneration, retinitis pigmentosa（色生性视网膜炎） or glaucoma（青光眼） .”The new process promises to have broad applications in stem cell research. The same method can be used to push induce pluripotent stem cells (stem cells artificially derived from adult, differentiated mature cells) to become neural stem cells, Zhang said. “And in principle, by altering the combination of small molecules, you may be able to create other types of stem cells capable of becoming heart, pancreas, or muscle cells, to name a few.”The next step, according to Zhang, is to use these stem cells to treat different types of neurodegenerative diseases, such as macular degeneration or glaucoma in animal models.

Latest insights into immunity to HIV could help to develop a vaccine to build antibodies’ defences against the disease, a University of Melbourne, Australia study has found. By investigating the action of the human antibodies called ADCC, in people with HIV, researchers were able to identify that the virus evolves to evade or ‘escape’ the antibodies.Professor Stephen Kent of the University of Melbourne and one of the senior authors on the paper said ADCC antibodies have been strongly implicated in protection from HIV in several vaccine trials but their action was poorly understood.”These results show what a slippery customer the HIV virus is, but also shows that these ADCC antibodies are really forcing the virus into changing, in ways that cause it to be weaker,” he said.”It also implies that if good ADCC antibodies were available prior to infection, via a vaccine, we might be able to stop the virus taking hold. This is the holy grail.”The group at the University of Melbourne’s Department of Microbiology and Immunology analysed blood samples of people with HIV and found their virus had evolved to evade or ‘escape’ the ADCC antibodies against HIV they are making to try to control their virus.The team led by Dr Ivan Stratov and Professor Kent employed a novel technology developed in their laboratory to find where ADCC antibodies were attacking the virus. They then looked at how the sequence of the virus had mutated over time to avoid the immune response.”There is an urgent need to identify effective immunity to HIV and our studies suggest ADCC responses supply significant immune pressure on the virus,” Dr Ivan Stratov, a clinician and researcher said.The group is now working on designing HIV vaccines to induce ADCC antibodies that make it more difficult for the virus to escape.The work was published in the prestigious international journal PNAS（美国科学院院报）.

A new study from University of Miami (UM) Rosenstiel School of Marine & Atmospheric Science scientists Chris Langdon, Remy Okazaki and Nancy Muehllehner and colleagues from the Australian Institute of Marine Science and the Max-Planck Institute for Marine Microbiology in Germany concludes that ocean acidification（酸化） , along with increased ocean temperatures, will likely severely reduce the diversity and resilience of coral reef ecosystems within this century. The research team studied three natural volcanic CO2 seeps in（渗进） Papua New Guinea to better understand how ocean acidification will impact coral reefs ecosystem diversity. The study details the effects of long-term exposure to high levels of carbon dioxide and low pH on Indo-Pacific coral reefs, a condition that is projected to occur by the end of the century as increased man-made CO2 emissions alter the current pH level of seawater, turning the oceans acidic.”These ‘champagne reefs’ are natural analogs of how coral reefs may look in 100 years if ocean acidification conditions continue to get worse,” said Langdon, UM Rosenstiel School professor and co-principal investigator of the study.The study shows shifts in the composition of coral species and reductions in biodiversity and recruitment on the reef as pH declined from 8.1 to 7.8. The team also reports that reef development would cease at a pH below 7.7. The IPCC 4th Assessment Report estimates that by the end of the century, ocean pH will decline from the current level of 8.1 to 7.8, due to rising atmospheric CO2 concentrations.”The seeps are probably the closest we can come to simulating the effect of man-made CO2 emissions on a coral reef,” said Langdon. “They allow us to see the end result of the complex interactions between species under acidic ocean conditions.”The reefs detailed in this study have healthy reefs nearby to supply larvae（幼虫） to replenish（弥补） the reefs. If pH was low throughout the region — as projected for year 2100 — then there would not be any healthy reefs to reseed damaged ones, according to Langdon.

As China’s economy continues to soar, its energy use and greenhouse gas emissions will keep on soaring as well— or so goes the conventional wisdom. A new analysis by researchers at Lawrence Berkeley National Laboratory (Berkeley Lab) now is challenging that notion, one widely held in both the United States and China. Well before mid-century, according to a new study by Berkeley Lab’s China Energy Group, that nation’s energy use will level off, even as its population edges past 1.4 billion. “I think this is very good news,” says Mark Levine, co-author of the report, “China’s Energy and Carbon Emissions Outlook to 2050″ and director of the group. “There’s been a perception（知觉，感受） that China’s rising prosperity means runaway growth in energy consumption. Our study shows this won’t be the case.”Along with China’s rise as a world economic power have come a rapid climb in energy use and a related boost in man-made carbon dioxide emissions. In fact, China overtook the United States in 2007 as the world’s leading emitter of greenhouse gases.Yet according to this new forecast, the steeply rising curve of energy demand in China will begin to moderate between 2030 and 2035 and flatten thereafter. There will come a time— within the next two decades— when the number of people in China acquiring cars, larger homes, and other accouterments of industrialized societies will peak. It’s a phenomenon known as saturation（饱和） . “Once nearly every household owns a refrigerator, a washing machine, air conditioners and other appliances, and once housing area per capita has stabilized, per household electricity growth will slow,” Levine explains.Similarly, China will reach saturation in road and rail construction before the 2030-2035 time frame, resulting in very large decreases in iron and steel demand. Additionally, other energy-intensive industries will see demand for their products flatten.The Berkeley Lab report also anticipates the widespread use of electric cars, a significant drop in reliance on coal for electricity generation, and a big expansion in the use of nuclear power— all helping to drive down China’s CO2 emissions. Although China has temporarily suspended approvals of new nuclear power plant construction in the wake of the disaster at Japan’s Fukushima Daiichi Nuclear Power Station, the long-range forecast remains unchanged.Key to the new findings is a deeper look at patterns of energy demand in China: a “bottom-up” modeling system that develops projections of energy use in far greater detail than standard methods and which is much more time- and labor-intensive to undertake. Work on the project has been ongoing for the last four years. “Other studies don’t have this kind of detail,” says Levine. “There’s no model outside of China that even comes close to having this kind of information, such as our data on housing stock and appliances.”Not only does the report examine demand for appliances such as refrigerators and fans, it also makes predictions about adoption of improvements in the energy efficiency of such equipment – just as Americans are now buying more efficient washing machines, cars with better gas-mileage, and less power-hungry light bulbs.Berkeley Lab researchers Nan Zhou, David Fridley, Michael McNeil, Nina Zheng, and Jing Ke co-authored the report with Levine. Their study is a “scenario analysis” that forecasts two possible energy futures for China, one an “accelerated improvement scenario” that assumes success for a very aggressive effort to improve energy efficiency, the other a more conservative（保守的） “continued improvement scenario” that meets less ambitious targets. Yet both of these scenarios, at a different pace, show similar moderation effects and a flattening of energy consumption well before 2050.

Want to convince someone to do something? A new University of Michigan study has some intriguing（有趣的） insights drawn from how we speak. The study, presented May 14 at the annual meeting of the American Association for Public Opinion Research, examines how various speech characteristics influence people’s decisions to participate in telephone surveys. But its findings have implications for many other situations, from closing sales to swaying（使摆荡） voters and getting stubborn spouses to see things your way.”Interviewers who spoke moderately fast, at a rate of about 3.5 words per second, were much more successful at getting people to agree than either interviewers who talked very fast or very slowly,” said Jose Benki, a research investigator at the U-M Institute for Social Research (ISR).For the study, Benki and colleagues used recordings of 1,380 introductory calls made by 100 male and female telephone interviewers at the U-M ISR. They analyzed the interviewers’ speech rates, fluency, and pitch, and correlated those variables with their success in convincing people to participate in the survey.Since people who talk really fast are seen as, well, fast-talkers out to pull the wool over our eyes, and people who talk really slow are seen as not too bright or overly pedantic（陈腐的） , the finding about speech rates makes sense. But another finding from the study, which was funded by the National Science Foundation, was counterintuitive.”We assumed that interviewers who sounded animated and lively, with a lot of variation in the pitch of their voices, would be more successful,” said Benki, a speech scientist with a special interest in psycholinguistics, the psychology of language.”But in fact we found only a marginal effect of variation in pitch by interviewers on success rates. It could be that variation in pitch could be helpful for some interviewers but for others, too much pitch variation sounds artificial, like people are trying too hard. So it backfires and puts people off.”Pitch, the highness or lowness of a voice, is a highly gendered quality of speech, influenced largely by body size and the corresponding size of the larynx, or voice box, Benki says. Typically, males have low-pitched voices and females high-pitched voices. Stereotypically, think James Earl Jones and Julia Child.Benki and colleagues Jessica Broome, Frederick Conrad, Robert Groves and Frauke Kreuter also examined whether pitch influenced survey participation decisions differently for male compared to female interviewers.They found that males with higher-pitched voices had worse success than their deep-voiced colleagues. But they did not find any clear-cut evidence that pitch mattered for female interviewers.The last speech characteristic the researchers examined for the study was the use of pauses. Here they found that interviewers who engaged in frequent short pauses were more successful than those who were perfectly fluent.”When people are speaking, they naturally pause about 4 or 5 times a minute,” Benki said. “These pauses might be silent, or filled, but that rate seems to sound the most natural in this context. If interviewers made no pauses at all, they had the lowest success rates getting people to agree to do the survey. We think that’s because they sound too scripted.”People who pause too much are seen as disfluent. But it was interesting that even the most disfluent interviewers had higher success rates than those who were perfectly fluent.”Benki and colleagues plan to continue their analyses, comparing the speech of the most and least successful interviewers to see how the content of conversations, as well as measures of speech quality, is related to their success rates.

A common reading of the recent subprime mortgage crisis（次贷危机） pins the blame on bankers and loan brokers who extended mortgages to those who could not afford them, thereby inflating a housing bubble that was destined to burst. While technically correct, that reading ignores the “politics of creditworthiness” that undergirded the rise of subprime mortgages, as explained in a new article in the June issue of the American Sociological Review by Simone Polillo, an assistant professor of sociology in the University of Virginia’s College of Arts & Sciences.Defining creditworthiness criteria is an exercise of moral authority, Polillo argues, and political contesting of those criteria is a fundamental aspect of financial innovation. The innovation of subprime mortgages（次级房贷） was made possible only after accepted “sound banking” criteria of creditworthiness had come to exclude a growing portion of Americans, Polillo writes in his article, “Money, Moral Authority, and the Politics of Creditworthiness.”After World War II, one typically qualified for a home loan with a substantial down payment and a record of employment and the prospect of future stable employment. By the late 1970s, it was clear that such criteria, in practice, often excluded or marginalized racial minorities, people from poor neighborhoods, individuals with poor credit histories and a growing portion of Americans affected by the breakdown of manufacturing and ever-withering employment benefits and stability.”Wildcat” financial innovators stepped into this opening with new, looser credit criteria, based not on employment, but solely on the collateral value of the real estate to be purchased. “Wildcat” is Polillo’s term for those who disobey “sound banking traditions” and thus create more inclusive, but more unstable credit systems.Outflanked by these new offerings, more conservative local banks, to varying degrees, gradually followed the wildcats’ lead, bolstered by claims from financial elites that the risks of such loans were parceled out by strategically bundling them into mortgage-backed securities.As was learned in the financial crisis of 2007-08, the whole enterprise was founded on a flawed assumption, based on historical trends, that home prices would continue to rise steadily for the foreseeable（可预知的） future, Polillo said.This was the latest example, among several in American history, of wildcat financial innovators spotting an underserved credit market, offering new financial products and creditworthiness standards to serve the underserved, and parlaying the innovations to financial elites and a wider market, he said.A similar process played out when Michael Milken led the junk bond revolution of the 1980s. Junk bonds provided credit to companies that, Milken thought, had been systematically undervalued by rating agencies. Milken was particularly interested in bonds that, from a position of high credit rating, had fallen to “below investment grade,” bonds he called “fallen angels.”"The fact that Milken became an emblem（意味） of reckless risk-taking and corruption,” Polillo said, “should not distract us from the process that made his success possible: the recasting of previously excluded actors as worthy of credit (fallen angels) and the creation of new products to serve them.”Milken’s case illustrates two pressures on prudent bankers who draw the line that establishes creditworthiness, Polillo said. First, those who are excluded may challenge how creditworthiness is defined and assessed. Second, new ideas may emerge within the banking system itself about how credit should be allocated.Creditworthiness criteria are constantly being contested by bankers, financial innovators, the state and local communities, Polillo argues. Significant disagreement between those groups about the boundaries of creditworthiness can destabilize the financial system, as happened in Milken’s junk bond revolution; in the subprime mortgage crisis; and in the post-Civil War clashes between “Greenbackers” and those who favored a gold standard.In such clashes, both sides often lay claim to “laws” of the market, but the issue really boils down to ideas about how we decide where to draw boundaries between outsiders and insiders, Polillo said.In the wake of such disruptions, the public grows skeptical of the competency of traditional monetary authorities like the Treasury, the Federal Reserve and Congress, and even banking elites, opening the door to debates on the proper role of the government and banks in the financial system, Polillo said.Such concerns underlie our current debates on the national budget deficit, the debt ceiling and government bailouts, he said. As these debates play out observers should be mindful of how the politics of creditworthiness are being contested once again.

For many movie stars, their age is a well-kept secret. In space, the same is true of the actual stars. Like our Sun, most stars look almost the same for most of their lives. So how can we tell if a star is one billion or 10 billion years old? Astronomers may have found a solution – measuring the star’s spin. “A star’s rotation slows down steadily with time, like a top spinning on a table, and can be used as a clock to determine its age,” says astronomer Soren Meibom of the Harvard-Smithsonian Center for Astrophysics（天体物理学） .Meibom presented his findings today in a press conference at the 218th meeting of the American Astronomical Society.Knowing a star’s age is important for many astronomical studies and in particular for planet hunters. With the bountiful（丰富的） harvest from NASA’s Kepler spacecraft (launched in 2009) adding to previous discoveries, astronomers have found nearly 2,000 planets orbiting distant stars. Now, they want to use this new zoo of planets to understand how planetary systems form and evolve and why they are so different from each other.”Ultimately, we need to know the ages of the stars and their planets to assess whether alien life might have evolved on these distant worlds,” says Meibom. “The older the planet, the more time life has had to get started. Since stars and planets form together at the same time, if we know a star’s age, we know the age of its planets too.”Learning a star’s age is relatively easy when it’s in a cluster of hundreds of stars that all formed at the same time. Astronomers have known for decades that if they plot the colors and brightnesses of the stars in a cluster, the pattern they see can be used to tell the cluster’s age. But this technique only works on clusters. For stars not in clusters (including all stars known to have planets), determining the age is much more difficult.Using the unique capabilities of the Kepler space telescope, Meibom and his collaborators measured the rotation rates for stars in a 1-billion-year-old cluster called NGC 6811. This new work nearly doubles the age covered by previous studies of younger clusters. It also significantly adds to our knowledge of how a star’s spin rate and age are related.

As the World Health Organisation suggests the E. coli outbreak in Germany is a strain never before seen in an outbreak – O104:H4 – laboratory science conducted at the University of Southampton indicates a role for copper in preventing the spread of such infections. Professor Bill Keevil, Head of the Microbiology Group and Director of the Environmental Healthcare Unit at the University of Southampton, explains: “A study looking at copper’s efficacy against new strains of E. coli has just been completed. Although it did not specifically look at O104, all the strains investigated have died rapidly on copper.”On a dry copper surface, the study shows 10 million E. coli bacteria are eliminated within 10 minutes. On a wet copper surface, one could expect a total kill within around 45 minutes. This antimicrobial（抗菌剂） property is inherent（固有的，内涵的） to the metal, and shared with alloys such as brass and bronze.In the wake of this outbreak, hand washing and careful food preparation have been highlighted as key concerns, as has cross-contamination. Any raw food placed on a work surface can contaminate（污染） other food, or have bacteria transferred onto it from previous items resting there. Deployed as a touch surface in food preparation areas, copper will continuously kill any pathogens that settle on it, reducing the risk of cross-contamination, and helping to prevent the spread of infection.

Paleontologists（古生物学家） have discovered that a group of remarkable ancient sea creatures existed for much longer and grew to much larger sizes than previously thought, thanks to extraordinarily well-preserved fossils discovered in Morocco. The creatures, known as anomalocaridids, were already thought to be the largest animals of the Cambrian period, known for the “Cambrian Explosion” that saw the sudden appearance of all the major animal groups and the establishment of complex ecosystems about 540 to 500 million years ago. Fossils from this period suggested these marine predators grew to be about two feet long. Until now, scientists also thought these strange invertebrates（无脊椎动物） — which had long spiny head limbs presumably used to snag worms and other prey, and a circlet of plates around the mouth— died out at the end of the Cambrian.Now a team led by former Yale researcher Peter Van Roy (now at Ghent University in Belgium) and Derek Briggs, director of the Yale Peabody Museum of Natural History, has discovered a giant fossilized anomalocaridid that measures one meter (more than three feet) in length. The anomalocaridid fossils reveal a series of blade like filaments（花丝，细丝） in each segment across the animal’s back, which scientists think might have functioned as gills.In addition, the creature dates back to the Ordovician period, a time of intense biodiversification that followed the Cambrian, meaning these animals existed for 30 million years longer than previously realized.”The anomalocaridids are one of the most iconic groups of Cambrian animals,” Briggs said. “These giant invertebrate predators and scavengers have come to symbolize the unfamiliar morphologies displayed by organisms that branched off early from lineages leading to modern marine animals, and then went extinct. Now we know that they died out much more recently than we thought.”The specimens are just part of a new trove of fossils from Morocco that includes thousands of examples of soft-bodied marine fauna dating back to the early Ordovician period, 488 to 472 million years ago. Because hard shells fossilize and are preserved more readily than soft tissue, scientists had an incomplete and biased view of the marine life that existed during the Ordovician period before the recent discoveries in Morocco. The animals found in Morocco inhabited a muddy sea floor in fairly deep water, and were trapped by sediment clouds that buried them and preserved their soft bodies.”The new discoveries in Morocco indicate that animals characteristic of the Cambrian, such as the anomalocaridids, continued to have a considerable impact on the biodiversity and ecology of marine communities many millions of years later,” Van Roy said.The paper appears in the May 26 issue of the journal Nature.