Science

In the recent U.S. Supreme Court hearing on A. Fisher v. the University of Texas about university admission policies regarding minority students, Chief Justice John Roberts asked, “What unique perspective does a minority student bring to a physics class?” As an African-American physicist researching string theory, and a teacher of university students since 1972, I have a response. Author: S. J. Gates

In science news around the world, SeaWorld announces that it will no longer breed orcas, China releases its first set of guidelines for the treatment of laboratory animals, a German mortician contracts Lassa fever in the first clear case of the disease's transmission outside of Africa, philanthropist Paul G. Allen launches a new bioscience research initiative, the U.S. National Science Foundation announces that it has indefinitely suspended a program to support museum biological collections, and more. Also corporate executive and leukemia survivor Greg Simon has been tapped to head Vice President Joe Biden's $1 billion "moonshot" to cure cancer. And Egypt's antiquities minister confirms that high-resolution radar scans of the walls of King Tutankhamun's tomb, taken last fall, have identified two hidden chambers.

This month, in a cavernous laboratory 1.4 kilometers beneath Italy's Apennine Mountains, physicists will begin filling a cylindrical tank with frigid liquid xenon. The tank is the heart of XENON 1 Ton (XENON1T), the biggest detector so far to hunt for weakly interacting massive particles (WIMPs): hypothetical particles that may make up dark matter. But even as XENON1T gears up to begin taking data, researchers are starting to have doubts about the concept of WIMPs. A few years ago, when the biggest WIMP detector weighed a few kilograms, most thought a 1-ton experiment would either find WIMPs or stick a dagger in the idea. But generations of ever bigger detectors have come up empty, and physicists are rethinking the argument for WIMPs and what it might take to find them. They have bigger detectors in the works and are laying plans for the ultimate WIMP detector. But even avid dark matter hunters aren't sure that giant detector is worth pursuing. Author: Adrian Cho

Since the Zika virus began racing through the Americas, scientists have been trying to figure out when and where it entered Brazil, where it was first detected in March 2015. Speculation has focused on the influx of fans for the World Cup in June and July 2014, or for a championship canoe race in September 2014. But a new genome analysis suggests the virus had likely been spreading there long before either event, having arrived sometime between May and December 2013. It could have arrived during the Confederations Cup soccer tournament in late June 2013, the authors say. That event brought the Tahitian national team to a stadium in Recife, near the epicenter of the Brazilian epidemic. But that was several months before cases of Zika were reported in Tahiti, and the authors think it's more fruitful to look at broader travel patterns rather than discrete events. They point out that during 2013, air travel from Zika-endemic areas to Brazil increased by almost 50%, from roughly 3500 passengers arriving per month to nearly 5000. Author: Gretchen Vogel

Several unprecedented videos of gelatinous sea creatures called comb jellies, or ctenophores, now threaten to upend the standard view of the evolution of the so-called through-gut. Comb jellies, jellyfish, sea sponges, and a few other creatures all were thought to lack an anus, which meant they had to eat and defecate through a single hole. These are descendants of some of the first animals to arise, so it has been thought that the through-gut and anus were an innovation that came after those lineages emerged—and perhaps something that drove the diversity of new animal forms. But on 15 March, at the Ctenopolooza meeting in St. Augustine, Florida, evolutionary biologist William Browne of the University of Miami in Florida debuted films of comb jellies pooping—and it wasn't through their mouths. Browne's videos elicited gasps from the audience, who is now rethinking when the through-gut first evolved—and whether it may have emerged more than once. Author: Amy Maxmen

When it comes to genome size, a rare Japanese flower, called Paris japonica, is the current heavyweight champ, with 50 times more DNA than humans. At the other end of the scale, there's now a new lightweight record-holder growing in petri dishes in southern California. This week in Science, researchers led by genome sequencing pioneer Craig Venter report engineering a bacterium to have the smallest genome—and the fewest genes—of any freely living organism, smaller than the flower's by a factor of 282,000. Known as Syn 3.0, the new organism has a genome whittled down to the bare essentials needed to survive and reproduce, just 473 genes. The microbe's streamlined genetic structure excites evolutionary biologists and biotechnologists, who anticipate adding genes back to it one by one to study their effects. "It's a tour de force," says George Church, a synthetic biologist at Harvard University. Author: Robert F. Service

After Kurdish separatists set off a car bomb Turkey's capital last week, killing 37 people, Turkish President Recep Tayyip Erdoğan announced that the definition of "terrorism" should be expanded to include all who provide support in the form of "propaganda" and specifically called out academics. Within hours of the president's speech, police arrived at the homes of four Turkish researchers who had signed a petition calling for peace. Three are now imprisoned; Turkish academics fear that many more arrests will follow. Science has interviewed one who eluded arrest: Meral Camcı, a literary scholar who had gone to France on vacation. Author: John Bohannon

China's economic slowdown could bring a windfall for basic science. Cosmic evolution, the structure of matter, the origins of life, and understanding how the brain works all deserve strengthened support, according to China's latest 5-year development plan, which could triple funding for basic research by 2020. An outline of the plan, which covers 2016 through 2020, received pro forma approval by the National People's Congress on 16 March at its closing session. Though details are still scarce, one expectation is that funding for basic research will rise to 10% of total R&D spending by 2020, up from less than 5% now. If the 10% goal is achieved, investment in basic research could hit 225 billion yuan, or about $34.5 billion, in 2020, compared with last year's $10 billion. Author: Hao Xin

About 3200 years ago, two armies clashed at a river crossing near the Baltic Sea. The confrontation can't be found in any history books—the written word didn't become common in these parts for another 2000 years—but this was no skirmish between local clans. Thousands of warriors came together in a brutal struggle, likely fought on a single day, using weapons crafted from wood, flint, and bronze, a metal then the height of military technology. Now, after a series of excavations between 2009 and 2015, researchers have begun to understand the battle and its startling implications for Bronze Age society. They have unearthed wooden clubs, bronze spearheads, and flint and bronze arrowheads, as well as the remains of more than 100 men. The scale of the carnage in Germany's Tollense Valley suggests more organization—and more violence—than archaeologists had expected, especially in what was long considered a Bronze Age backwater. The well-preserved bones and artifacts add detail to this picture, pointing to the existence of a trained warrior class and suggesting that people from across Europe joined the bloody fray. Author: Andrew Curry

Look at a protein-coding gene in the genome of any eukaryote—be it animal, plant, fungus, or protist—and you will likely find the coding region fragmented by intervening sequences known as introns. When the gene is transcribed, these introns have to be removed from the pre-messenger RNA (pre-mRNA) before a protein can be made. How these introns are removed has been studied intensively for decades without the aid of a three-dimensional map of the highly dynamic machine at the heart of the process: the spliceosome. On page 1416 of this issue, Agafonov et al. report the first molecular-resolution reconstruction of a central assembly of the human spliceosome, the U4/U6.U5 triple small nuclear ribonucleoprotein (tri-snRNP) complex, using cryo-electron microscopy (cryo-EM) (1). Together with high-resolution cryo-EM reconstructions of spliceosome assemblies from fungi (2-5) and the x-ray crystal structure of the U1 snRNP (6), these structural models of the splicing machinery launch a new era in understanding eukaryotic gene regulation. Author: Jamie H. D. Cate

Early Victorian naturalists marveled at the profusion of diversity they encountered as they traveled from temperate to tropical latitudes. The inverse relationship between latitude and species richness that these naturalists first observed is now referred to as the latitudinal diversity gradient. Various ecological and evolutionary explanations have been proposed for the latitudinal diversity gradient. Of these, perhaps none are more relevant to contemporary conservation issues than Janzen's hypothesis of latitudinal differences in species' climatic tolerances and thermal selectivity (1). On page 1437 of this issue, Chan et al. (2) advance Janzen's early theories by elucidating some of the potential selective pressures imposed by climate and climate variability. Authors: Timothy M. Perez, James T. Stroud, Kenneth J. Feeley

Density functional theory (DFT) stands out from all first-principles quantum mechanical methods for the simulation of materials, as it enables very good approximations for the complicated components of electronic motion called exchange and correlation. DFT is the method of choice for many materials simulations because of the availability of general-purpose programs that can perform calculations on any material. Results obtained with one DFT program need to be reproducible by any of the other DFT programs, and this has not been straightforward up to now. On page 10.1126/science.aad3000 of this issue, Lejaeghere et al. (1) describe an extensive effort by developers of the major solid-state DFT codes to provide a unified and reproducible benchmark of precision for their calculations based on a reliable criterion, the so-called Δ gauge. Using the Δ gauge, the authors found that the level of precision that can be achieved today in DFT calculations of elemental crystalline solids is comparable to the precision of the most advanced techniques for experimental measurement of the properties of materials. The work leads to the conclusion that the DFT simulation of elemental crystalline solids is a (computationally) solved problem, but also poses the question of whether we can achieve the same levels of validation and reproducibility for more complex simulations of materials involving several elements and/or several methods. Author: Chris-Kriton Skylaris

The remarkable electronic properties of graphene and related two-dimensional (2D) materials result from the confinement of electrons within the material. Similarly, the interstitial space between 2D materials can enable the 2D confinement of ions and electrolytes and alter their transport. Many different 2D sheets can be obtained by exfoliation of natural layered materials (1), and an exfoliation-reconstruction strategy can convert powders of layered materials into continuous, robust bulk forms in which lamellar nanochannels occupy a substantial volume fraction (up to several tens of percent). Nanofluidics, which enables the manipulation of confined ions and electrolytes, has applications in electrochemical energy conversion and storage, biosensing, and water purification. Authors: Andrew R. Koltonow, Jiaxing Huang

Clouds are an essential source of fresh water to continents and all ecosystems (1) and a major cooling factor in the climate budget (2). Yet, predicting their formation remains a challenge (2). In the atmosphere, cloud droplets form not from water vapor alone but through condensation of water on aerosol particles called cloud condensation nuclei (CCN) (3). On page 1447 of this issue, Ruehl et al. (4) show experimentally that surface effects play a central role in cloud droplet formation from CCN. Author: Barbara Noziere

Far from a random tangle, cellular DNA is packed into the nucleus with astounding precision. Indeed, there is growing appreciation for how the three-dimensional (3D) organization of the genome contributes to controlling gene expression. For instance, loops of DNA called insulated neighborhoods can protect small groups of genes from silencing or activation (1). If cancer can result from dysregulation of gene expression (2), then an enticing hypothesis is that disrupting insulated neighborhoods may lead to increased transcription of cancer genes. On page 1454 of this issue, Hnisz et al. (3) use tumor-derived sequencing data and targeted deletions in cells to show that disruption of insulated neighborhoods leads to activation of proto-oncogenes—genes with the potential to cause cancer. These findings strongly support disruption of chromatin structure as causally linked to tumorigenesis, and suggest that such disruptions may be the hidden culprit driving many tumors. Authors: Jeremiah Wala, Rameen Beroukhim

Historically, research ethics committees (RECs) have been guided by ethical principles regarding human experimentation intended to protect participants from physical harms and to provide assurance as to their interests and welfare. But research that analyzes large aggregate data sets, possibly including detailed clinical and genomic information of individuals, may require different assessment. At the same time, growth in international data-sharing collaborations adds stress to a system already under fire for subjecting multisite research to replicate ethics reviews, which can inhibit research without improving the quality of human subjects' protections (1, 2). “Top-down” national regulatory approaches exist for ethics review across multiple sites in domestic research projects [e.g., United States (3, 4), Canada (5), United Kingdom, (6), Australia (7)], but their applicability for data-intensive international research has not been considered. Stakeholders around the world have thus been developing “bottom-up” solutions. We scrutinize five such ef orts involving multiple countries around the world, including resource-poor settings (table S1), to identify models that could inform a framework for mutual recognition of international ethics review (i.e., the acceptance by RECs of the outcome of each other's review). Authors: Edward S. Dove, David Townend, Eric M. Meslin, Martin Bobrow, Katherine Littler, Dianne Nicol, Jantina de Vries, Anne Junker, Chiara Garattini, Jasper Bovenberg, Mahsa Shabani, Emmanuelle Lévesque, Bartha M. Knoppers

In any solar cell that begins to approach the theoretical limits of performance, an intense internal luminescence photon gas must be present (see the figure) (1). On page 1430 of this is sue, Pazos-Outón et al. (2) provide evidence for such an internal photon gas in lead halide photovoltaic cells. These materials thus have properties similar to those of GaAs and have the potential to be among the top-performing solar cell materials. This is scientifically remarkable, because these compounds are the first high-quality halide semiconductors. The materials show promise for photovoltaics, light-emitting diodes (LEDs), laser refrigeration, thermophotonics, and a host of other major optoelectronic applications. Author: Eli Yablonovitch

Genetic research has moved rapidly since the publication of Richard Dawkins's The Selfish Gene 40 years ago. In the intervening years, we have come to realize that many of the most interesting and important phenomena in human biology are not caused by any single gene. Citing a wealth of recent research that explores the ways genes work together to produce complex biological processes, Itai Yanai and Martin Lercher argue that it is time to embrace a new, more holistic, metaphor in their book, The Society of Genes. Author: Joseph Swift

In his 1962 review of Thomas Kuhn's The Structure of Scientific Revolutions, historian Charles Gillispie proclaimed it "a very bold venture, this essay." In hindsight, it seems not just bold but a pivotal point in our understanding of science. The book under review features essays contributed by historians, social scientists, and philosophers that reflect on the development, content, and impact of Kuhn's revolutionary book. Author: Sandra D. Mitchell

Authors: Francis S. Collins, James M. Anderson, Christopher P. Austin, James F. Battey, Linda S. Birnbaum, Josephine P. Briggs, Janine A. Clayton, Bruce Cuthbert, Robert W. Eisinger, Anthony S. Fauci, John I. Gallin, Gary H. Gibbons, Roger I. Glass, Michael M. Gottesman, Patricia A. Gray, Eric D. Green, Franziska B. Greider, Richard Hodes, Kathy L. Hudson, Betsy Humphreys, Stephen I. Katz, George F. Koob, Walter J. Koroshetz, Michael S. Lauer, Jon R. Lorsch, Douglas R. Lowy, John J. McGowan, David M. Murray, Richard Nakamura, Andrea Norris, Eliseo J. Perez-Stable, Roderic I. Pettigrew, William T. Riley, Griffin P. Rodgers, Paul A. Sieving, Martha J. Somerman, Catherine Y. Spong, Lawrence A. Tabak, Nora D. Volkow, Elizabeth L. Wilder