bluuebunny/crossref_metadata_2025 huggingface dataset:
Research Spotlight: Using satellite data to estimate the North Atlantic Ocean circulation
Authors: Tretkoff Ernie
Published: April 2011

By redistributing heat and freshwater around the planet, ocean currents play a crucial role in regulating Earth's climate. Accurate knowledge of the subtle regional variations in Earth's gravity field is fundamental to the measurement of ocean currents, but the challenge of mapping Earth's gravity in sufficient detail has previously limited scientists' ability to reliably determine the ocean's time‐mean circulation. To address this problem, in October 2009 the European Space Agency launched the Gravity field and steady‐state Ocean Circulation Explorer (GOCE) satellite with the aim of mapping Earth's gravity field with unprecedented spatial resolution. Bingham et al. present an initial assessment of the performance of GOCE by using the first data from the satellite to estimate the time‐mean circulation of the North Atlantic Ocean. This basin is particularly interesting because it contains the Gulf Stream, the world's strongest current and a key component of the global overturning circulation, which carries heat from the equator to high northerly latitudes. The scientists show that with just 2 months of observations, the GOCE estimate of the North Atlantic circulation is superior to that obtained from 8 years of data from the Gravity Recovery and Climate Experiment (GRACE) satellite. In many places, the current speeds estimated from the GOCE data compare well with those obtained from in situ observations, providing strong validation of the GOCE mission design. Accumulation of data as the mission progresses could lead to a more accurate and detailed map of the ocean's currents. (Geophysical Research Letters, doi:10.1029/2010GL045633, 2011)
Research Spotlight: Two eyes are better than one for measuring rain from space
Authors: Schultz Colin
Published: April 2011

One predicted consequence of climate change is a global redistribution of precipitation and the resultant shifts in regional rainfall volumes. To forecast the details of Earth's changing climate, researchers rely on the accurate detection and measurement of rainfall volumes. One type of rain, the light, warm drizzle often found in coastal regions or during a spring shower, is especially difficult to measure using satellite observations. The two most promising techniques for measuring warm rain—passive microwave (PMW), which sees through clouds and measures the microwave radiation emitted by rain, and visible/near‐infrared (VNIR) detection, which measures reflected sunlight at wavelengths up to near‐infrared absorption bands of water—both have shortcomings. In their new study, Bennartz et al. try to marry the two techniques, using the strengths of each to improve the accuracy of warm rain detection. The researchers assessed the viability of using combined VNIR and PMW data with a simplified cloud model before testing their technique with satellite observations and independently observed precipitation data for a region along the western coast of South Africa. (Journal of Geophysical Research‐Atmospheres, doi:10.1029/2009JD013679, 2010)
Research Spotlight: New method could improve hurricane surge forecasting
Authors: Tretkoff Ernie
Published: April 2011

In recent years, hurricanes in the Gulf of Mexico, including Katrina and Ike, caused some of the highest surges on record and significant flooding, highlighting the need for good surge forecasts that can be used for early warning and evacuation. However, current approaches for surge forecasting use models that take too much computational time or have spatial resolution too low to provide adequate forecast accuracy. Irish et al. propose a new method for determining probabilistic maximum hurricane surge forecasts. Their approach is based on calculations of surge response functions, which are derived from numerical simulations, along with analysis of meteorological forecasts. They applied the method to data from Hurricane Ike and found that they could accurately compute surge forecast probabilities within seconds, given publicly available meteorological forecast data. The method can provide a forecast of how surge would vary along the coast and identify areas most vulnerable to high surges. (Geophysical Research Letters, doi:10.1029/2010GL046347, 2011)
Research Spotlight: The rain that drowned Pakistan could have been predicted
Authors: Schultz Colin
Published: April 2011

In the middle of the week, during the heart of summer, at the onset of the 2010 monsoon season, the northern end of Pakistan was pounded by torrential rain. Some areas of the country were drowned in 300 millimeters (11.8 inches) of rain over 4 days—10 times the seasonal average. The extreme rainfall caused widespread flooding, killing 2000 people and causing more than $40 billion in damage by the time it let up and the water withdrew. A new analysis by Webster et al. suggests that some of this damage might have been prevented, because the heavy rains that triggered the flooding could have been predicted. (Geophysical Research Letters, doi:10.1029/2010GL046346, 2011)
Research Spotlight: Lost in a fog on Mars
Authors: Schultz Colin
Published: April 2011

A pair of cameras mounted on the back of the Phoenix Mars Lander were used to capture how laser light, emitted by the lander's light detection and ranging (lidar) system, was scattered by water ice in the red planet's thin atmosphere.Moores et al. used the unique technique during four nights in 2008 to give the first detailed profile of the ice water content in the Martian near‐surface atmosphere. The authors found that the icy fog is thickest around 50 meters above the surface, with a maximum concentration of 1.7 milligrams per cubic meter. They also found that the fog is not uniform but tends to decrease in thickness toward the surface. As the Martian night wears on, the surface of the planet cools below the frost point and water vapor in the atmosphere gets deposited on the ground. As the atmosphere is mixed by turbulence, more water is brought to lower altitudes, adding to the growing frost layer. Ice crystals also form in the air and precipitate to the ground from successively higher altitudes. The researchers estimate that by the time the Sun starts to rise in the morning, 2.5 micrometers of snow and frost have coated the surface of Mars in the northerly region around the Phoenix Lander. (Geophysical Research Letters, doi:10.1029/2010GL046315, 2011)
Research Spotlight: The varying life expectancies of American reservoirs
Authors: Schultz Colin
Published: April 2011

Tasked with controlling floods, coping through droughts, generating electricity, maintaining the flow of drinking water, preserving species' habitats, and managing the local environment, the United States' large‐scale freshwater management system is important. Unfortunately, as sediment is washed from river basins to reservoirs, the persistent addition of material eats away at a reservoir's capacity and, consequently, its useful life expectancy. Understanding the integrity of the reservoir system is particularly important, with climate projections anticipating warmer, drier conditions for some parts of the country. Using a database of sedimentation surveys conducted between 1775 and 1993, Graf et al. calculate the life expectancies of many of the nation's reservoirs. They find that although most of the country's large reservoirs were built between 1950 and 1960, they have a wide range of expiration dates. They find that most large reservoirs, those with capacities greater than 1.2 cubic kilometers (0.29 cubic mile), have useful life expectancies ranging from 200 to more than 1000 years, with the lowest average life expectancy in the interior West. (Water Resources Research, doi:10.1029/2009WR008836, 2010)
Record Summer Melt in Greenland in 2010
Authors: Tedesco M. , Fettweis X. , van den Broeke M. R. , van de Wal R. S. W. , Smeets C. J. P. P. , van de Berg W. J. , Serreze M. C. , Box J. E.
Published: April 2011

As Arctic temperatures increase, there is growing concern about the melting of the Greenland ice sheet, which reached a new record during the summer of 2010. Understanding the changing surface mass balance of the Greenland ice sheet requires appreciation of the close links among changes in surface air temperature, surface melting, albedo, and snow accumulation. Increased melting accelerates surface snow grain growth, leading to a decrease in surface albedo, which then fosters further melt. In turn, winter accumulation contributes to determining how much snow is required before a dark (e.g., lower albedo), bare ice surface is exposed in spring (Figure 1).
Specific Turns of Phrase Inspire Natural Skepticism: Comment on “Climate Science in a Postmodern World”
Authors: Richards Jeremy P.
Published: April 2011

Kenneth Verosub's Forum (Eos, 91(33), 291, doi:10.1029/2010EO330003, 2010) illustrates rather well how the discussions about climate change have become more about beliefs and rhetoric than anything that might usefully move humanity forward on a more sustainable path. Surprisingly, Verosub repeatedly decries skepticism as though it were some kind of social ill. But I was taught as a scientist to be exactly that: skeptical. Healthy skepticism should be what drives us to test hypotheses and seek better ones.
Finding a Way out of a Corner: Reply to Comments on “Climate Science in a Postmodern World”
Authors: Verosub Kenneth L.
Published: April 2011

It was never my intention to claim that postmodernism wasthe explanation for the climate change debate. Rather, I was trying to provide a somewhat different perspective on this controversial topic in hopes of broadening the discussion and lowering the volume. I am well aware of the scenario that Hapke lays out; in fact, one could describe similar scenarios for other issues where science intersects with public policy and where people hold strong opinions, such as evolution and creationism, the development of new energy resources, and the safety of genetically modified organisms. The key statement in Hapke's comment is that “similar messages are being heard daily by millions of people, and…[apparently] many believe them.” What we as scientists have not done but need to do is gain a better understanding of why so many people believe these messages. Only then will we be able to figure out an effective response to them. My observation about the pervasiveness of postmodernism in modern society was meant to be a small contribution toward gaining that understanding.
Water vapor trends over Boulder, Colorado
Authors: Tretkoff Ernie
Published: April 2011

Water vapor in the atmosphere is responsible for a significant portion of the greenhouse effect, and even small changes in the upper troposphere or lower stratosphere can have a large effect on climate. A new analysis of water vapor measurements by balloon‐borne frost point hygrometers over Boulder, Colo., shows that stratospheric water vapor has increased over the past 30 years. Hurst et al. broke the long measurement record into four discrete time periods and determined the water vapor trends in each period for five 2‐kilometer‐thick stratospheric layers (16–26 kilometers in altitude). The scientists found that, on average, stratospheric water vapor increased by about 1 part per million by volume (27%) over the past 30 years, though there were many shorter‐term variations in the record. Water vapor levels increased during 1980–1989 and 1990–2000, decreased from 2001 to 2005, and then increased again after 2005. The authors found that, at most, 30% of the observed water vapor increases can be attributed to greater amounts of methane oxidation in the stratosphere. The 2001–2005 decrease in midlatitude water vapor has been linked to observations of anomalously low tropopause temperatures in the tropics, but, to date, no connection between the observed water vapor increases and tropical tropopause temperatures has been found despite ongoing efforts. (Journal of Geophysical Research‐Atmospheres, doi:10.1029/2010JD015065, 2011)
IL‐6 promotes acute and chronic inflammatory disease in the absence of SOCS3
Authors: Croker Ben A , Kiu Hiu , Pellegrini Marc , Toe Jesse , Preston Simon , Metcalf Donald , O'Donnell Joanne A , Cengia Louise H , McArthur Kate , Nicola Nicos A , Alexander Warren S , Roberts Andrew W
Published: April 2011

The lack of expression of the suppressor of cytokine signalling‐3 (SOCS3) or inactivation of the negative regulatory capacity of SOCS3 has been well documented in rheumatoid arthritis, viral hepatitis and cancer. The specific qualitative and quantitative consequences of SOCS3 deficiency on interleukin‐6 (IL‐6)‐mediated pro‐ and anti‐inflammatory responses remain controversial in vitro and unknown in vivo. Mice with a conditional deletion of SOCS3 in hematopoietic cells develop lethal inflammatory disease during adult life and develop gross histopathological changes during experimental arthritis, typified by elevated IL‐6 levels. To clarify the nature of the IL‐6 responses in vivo, we generated mice deficient in SOCS3 (SOCS3−/Δvav) or both SOCS3 and IL‐6 (IL‐6−/−/SOCS3−/Δvav), and examined responses in models of acute and chronic inflammation. Acute responses to IL‐1β were lethal to SOCS3−/Δvav mice but not IL‐6−/−/SOCS3−/Δvav mice, indicating that IL‐6 was required for the lethal inflammation induced by IL‐1β. Administration of IL‐1β to SOCS3−/Δvav mice induced systemic apoptosis of lymphocytes in the thymus, spleen and lymph nodes that was dependent on the presence of IL‐6. IL‐6 deficiency prolonged survival of SOCS3−/Δvav mice and ameliorated spontaneous inflammatory disease developing during adult life. Infection of SOCS3−/Δvav mice with LCMV induced a lethal inflammatory response that was dependent on IL‐6, despite SOCS3−/Δvav mice controlling viral replication. We conclude that SOCS3 is required for survival during inflammatory responses and is a critical regulator of IL‐6 in vivo.
CoPt magnetic nanocrystals in the A1/L1 transformation
Authors: Demortière Arnaud , Petit Christophe
Published: April 2011

CoPt magnetic nanocrystals have been synthesized in a range of size from 2 to 4 nm using a colloidal chemical synthetic method. As-synthesized nanocrystals exhibit an equiatomic composition and a crystalline phase of type alloy CoPt A1 disordered. The morphology and the magnetic properties were investigated for different crystal size. In order to reach the crystalline transition toward the L10 ordered phase, a thermal annealing has been carried out on CoPt nanocrystals of 4 nm. We showed that the use of HOPG substrate both limits the coalescence effects and promotes the structural ordering. The modification of the crystalline structure selected area electron diffraction (SAED) and the magnetic properties (superconducting quantum interference device) has been studied for different heat-treatment conditions. Ferromagnetic properties at room temperature were achieved for nanocrystals of 16 nm in average size with a coercivity of 4 kOe.
Dispersion equation and eigenvalues for quantum wells using spectral parameter power series
Authors: Castillo-Pérez Raúl , Kravchenko Vladislav V. , Oviedo-Galdeano Héctor , Rabinovich Vladimir S.
Published: April 2011

We derive a dispersion equation for determining eigenvalues of inhomogeneous quantum wells in terms of spectral parameter power series and apply it for the numerical treatment of eigenvalue problems. The method is algorithmically simple and can be easily implemented using available routines of such environments for scientific computing as MATLAB.
Voltage bias induced modification of the transport property of all oxide Pr0.5Ca0.5MnO3/SrTi0.95Nb0.05O3 junctions
Authors: Ghosh Barnali , Das K. , Raychaudhuri A. K.
Published: April 2011

In this paper we report what happens to a virgin oxide junction Pr0.5Ca0.5MnO3/SrTi0.95Nb0.05O3 (PCMO/Nb:STO), when it is subjected to cycling of voltage bias of moderate value (±4 V). It is found that the initial cycling leads to formation of a permanent state of lower resistance where the lower resistance arises predominantly due to the development of a shunt across the device film (PCMO). On successive voltage cycling with increasing magnitude, this state transforms into states of successive lower resistance that can be transformed back to the initial stable state on cycling to below a certain bias. A simple model based on p-n junction with shunt has been used to obtain information on the change of the junction on voltage cycling. It has been shown that the observation can be explained if the voltage cycling leads to lowering of the barrier at the interface and also reduction in series resistance. It is suggested that this lowering can be related to the migration of oxygen ions, which causes the vacancies at the junction region. Cross-sectional imaging of the junction shows formation of permanent filamentary bridges across the thickness of the PCMO after the virgin p-n junction is first taken through a voltage cycle, which would explain the appearance of a finite shunt across the p-n junction.
Localized surface plasmon resonance properties of two-layered gold nanowire: Effects of geometry, incidence angle, and polarization
Authors: Wu Dajian , Liu Xiaojun , Li Bo
Published: April 2011

The extinction spectra of two-layered gold nanowires (TGNWs) have been calculated by using the vector wave function method. When the polarization direction of incident light is perpendicular to the incidence plane, it is found with increasing the incidence angle that the dipole resonance wavelength of TGNW shows a decrease, whereas the full-width at half-maximum (FWHM) for the dipole resonance peak decreases. With decreasing the shell thickness or increasing the dielectric constant of the inner core, the localized surface plasmon resonance (LSPR) of TGNW shows a distinct redshift, whereas the FWHM of the dipole peak increases. When the polarization direction of incident light is parallel to the incident plane, the LSPR in TGNW gradually appears with decreasing incidence angle and can be modulated by the geometry. We have ascribed the variations of the LSPR in TGNW to the competition between the variations of phase retardation and oscillation electrons.
The World Cup and the National Thing on Commercial Drive, Vancouver
Authors: Kingsbury Paul
Published: April 2011

Nationalism is central to global sports events such as the Olympics and the men's football World Cup. Recognizing the unique capacity of these multibillion dollar ‘mega-events’ to stage captivating spectacles and generate intense enjoyment for vast numbers of people, researchers usually examine sport-induced nationalism in terms of the socioeconomic staging of national identities, meanings, and ideologies. And yet, few theoretical and empirical studies ask the following questions: Why are nationalist sports spectacles so emotive for so many people? How do sports fans enjoy these televised global events in concrete local settings of, for example, cafés, streets, and sports bars? This paper attempts to provide answers by drawing on Slavoj Žižek's Lacanian concept of the “national Thing” and one month of research on the 2006 FIFA World Cup on Commercial Drive in Vancouver, British Columbia, Canada. I explore how the national Thing—a specific incarnation of social enjoyment—takes place in people's consumption of the World Cup in terms of community, belief, and anxiety.
Fossil evidence for serpentinization fluids fueling chemosynthetic assemblages
Authors: Lartaud Franck , Little Crispin T. S. , de Rafelis Marc , Bayon Germain , Dyment Jerome , Ildefonse Benoit , Gressier Vincent , Fouquet Yves , Gaill Françoise , Le Bris Nadine
Published: April 2011

Among the deep-sea hydrothermal vent sites discovered in the past 30 years, Lost City on the Mid-Atlantic Ridge (MAR) is remarkable both for its alkaline fluids derived from mantle rock serpentinization and the spectacular seafloor carbonate chimneys precipitated from these fluids. Despite high concentrations of reduced chemicals in the fluids, this unique example of a serpentinite-hosted hydrothermal system currently lacks chemosynthetic assemblages dominated by large animals typical of high-temperature vent sites. Here we report abundant specimens of chemosymbiotic mussels, associated with gastropods and chemosymbiotic clams, in approximately 100 kyr old Lost City-like carbonates from the MAR close to the Rainbow site (36 °N). Our finding shows that serpentinization-related fluids, unaffected by high-temperature hydrothermal circulation, can occur on-axis and are able to sustain high-biomass communities. The widespread occurrence of seafloor ultramafic rocks linked to likely long-range dispersion of vent species therefore offers considerably more ecospace for chemosynthetic fauna in the oceans than previously supposed.
Cardiolipin-based respiratory complex activation in bacteria
Authors: Arias-Cartin Rodrigo , Grimaldi Stéphane , Pommier Janine , Lanciano Pascal , Schaefer Cédric , Arnoux Pascal , Giordano Gérard , Guigliarelli Bruno , Magalon Axel
Published: April 2011

Anionic lipids play a variety of key roles in membrane function, including functional and structural effects on respiratory complexes. However, little is known about the molecular basis of these lipid–protein interactions. In this study, NarGHI, an anaerobic respiratory complex of
Escherichia coli
, has been used to investigate the relations in between membrane-bound proteins with phospholipids. Activity of the NarGHI complex is enhanced by anionic phospholipids both in vivo and in vitro. The anionic cardiolipin tightly associates with the NarGHI complex and is the most effective phospholipid to restore functionality of a nearly inactive detergent-solubilized enzyme complex. A specific cardiolipin-binding site is identified on the basis of the available X-ray diffraction data and of site-directed mutagenesis experiment. One acyl chain of cardiolipin is in close proximity to the heme
b
D
center and is responsible for structural adjustments of
b
D
and of the adjacent quinol substrate binding site. Finally, cardiolipin binding tunes the interaction with the quinol substrate. Together, our results provide a molecular basis for the activation of a bacterial respiratory complex by cardiolipin.
Characterization of Eyjafjallajökull volcanic ash particles and a protocol for rapid risk assessment
Authors: Gislason S. R. , Hassenkam T. , Nedel S. , Bovet N. , Eiriksdottir E. S. , Alfredsson H. A. , Hem C. P. , Balogh Z. I. , Dideriksen K. , Oskarsson N. , Sigfusson B. , Larsen G. , Stipp S. L. S.
Published: April 2011

On April 14, 2010, when meltwaters from the Eyjafjallajökull glacier mixed with hot magma, an explosive eruption sent unusually fine-grained ash into the jet stream. It quickly dispersed over Europe. Previous airplane encounters with ash resulted in sandblasted windows and particles melted inside jet engines, causing them to fail. Therefore, air traffic was grounded for several days. Concerns also arose about health risks from fallout, because ash can transport acids as well as toxic compounds, such as fluoride, aluminum, and arsenic. Studies on ash are usually made on material collected far from the source, where it could have mixed with other atmospheric particles, or after exposure to water as rain or fog, which would alter surface composition. For this study, a unique set of dry ash samples was collected immediately after the explosive event and compared with fresh ash from a later, more typical eruption. Using nanotechniques, custom-designed for studying natural materials, we explored the physical and chemical nature of the ash to determine if fears about health and safety were justified and we developed a protocol that will serve for assessing risks during a future event. On single particles, we identified the composition of nanometer scale salt coatings and measured the mass of adsorbed salts with picogram resolution. The particles of explosive ash that reached Europe in the jet stream were especially sharp and abrasive over their entire size range, from submillimeter to tens of nanometers. Edges remained sharp even after a couple of weeks of abrasion in stirred water suspensions.
Drivers of bacterial β-diversity depend on spatial scale
Authors: Martiny Jennifer B. H. , Eisen Jonathan A. , Penn Kevin , Allison Steven D. , Horner-Devine M. Claire
Published: April 2011

The factors driving β-diversity (variation in community composition) yield insights into the maintenance of biodiversity on the planet. Here we tested whether the mechanisms that underlie bacterial β-diversity vary over centimeters to continental spatial scales by comparing the composition of ammonia-oxidizing bacteria communities in salt marsh sediments. As observed in studies of macroorganisms, the drivers of salt marsh bacterial β-diversity depend on spatial scale. In contrast to macroorganism studies, however, we found no evidence of evolutionary diversification of ammonia-oxidizing bacteria taxa at the continental scale, despite an overall relationship between geographic distance and community similarity. Our data are consistent with the idea that dispersal limitation at local scales can contribute to β-diversity, even though the 16S rRNA genes of the relatively common taxa are globally distributed. These results highlight the importance of considering multiple spatial scales for understanding microbial biogeography.
Fire ants self-assemble into waterproof rafts to survive floods
Authors: Mlot Nathan J. , Tovey Craig A. , Hu David L.
Published: April 2011

Why does a single fire ant
Solenopsis invicta
struggle in water, whereas a group can float effortlessly for days? We use time-lapse photography to investigate how fire ants
S. invicta
link their bodies together to build waterproof rafts. Although water repellency in nature has been previously viewed as a static material property of plant leaves and insect cuticles, we here demonstrate a self-assembled hydrophobic surface. We find that ants can considerably enhance their water repellency by linking their bodies together, a process analogous to the weaving of a waterproof fabric. We present a model for the rate of raft construction based on observations of ant trajectories atop the raft. Central to the construction process is the trapping of ants at the raft edge by their neighbors, suggesting that some “cooperative” behaviors may rely upon coercion.
Secreted dengue virus nonstructural protein NS1 is an atypical barrel-shaped high-density lipoprotein
Authors: Gutsche Irina , Coulibaly Fasséli , Voss James E. , Salmon Jérôme , d'Alayer Jacques , Ermonval Myriam , Larquet Eric , Charneau Pierre , Krey Thomas , Mégret Françoise , Guittet Eric , Rey Félix A. , Flamand Marie
Published: April 2011

Dengue virus (DENV) causes the major arboviral disease of the tropics, characterized in its severe forms by signs of hemorrhage and plasma leakage. DENV encodes a nonstructural glycoprotein, NS1, that associates with intracellular membranes and the cell surface. NS1 is eventually secreted as a soluble hexamer from DENV-infected cells and circulates in the bloodstream of infected patients. Extracellular NS1 has been shown to modulate the complement system and to enhance DENV infection, yet its structure and function remain essentially unknown. By combining cryoelectron microscopy analysis with a characterization of NS1 amphipathic properties, we show that the secreted NS1 hexamer forms a lipoprotein particle with an open-barrel protein shell and a prominent central channel rich in lipids. Biochemical and NMR analyses of the NS1 lipid cargo reveal the presence of triglycerides, bound at an equimolar ratio to the NS1 protomer, as well as cholesteryl esters and phospholipids, a composition evocative of the plasma lipoproteins involved in vascular homeostasis. This study suggests that DENV NS1, by mimicking or hijacking lipid metabolic pathways, contributes to endothelium dysfunction, a key feature of severe dengue disease.
Microbial growth at hyperaccelerations up to 403,627 ×
g
Authors: Deguchi Shigeru , Shimoshige Hirokazu , Tsudome Mikiko , Mukai Sada-atsu , Corkery Robert W. , Ito Susumu , Horikoshi Koki
Published: April 2011

It is well known that prokaryotic life can withstand extremes of temperature, pH, pressure, and radiation. Little is known about the proliferation of prokaryotic life under conditions of hyperacceleration attributable to extreme gravity, however. We found that living organisms can be surprisingly proliferative during hyperacceleration. In tests reported here, a variety of microorganisms, including Gram-negative
Escherichia coli
,
Paracoccus denitrificans
, and
Shewanella amazonensis;
Gram-positive
Lactobacillus delbrueckii
; and eukaryotic
Saccharomyces cerevisiae
, were cultured while being subjected to hyperaccelerative conditions. We observed and quantified robust cellular growth in these cultures across a wide range of hyperacceleration values. Most notably, the organisms
P. denitrificans
and
E. coli
were able to proliferate even at 403,627 ×
g
. Analysis shows that the small size of prokaryotic cells is essential for their proliferation under conditions of hyperacceleration. Our results indicate that microorganisms cannot only survive during hyperacceleration but can display such robust proliferative behavior that the habitability of extraterrestrial environments must not be limited by gravity.
Fiber-connected, indefinite Morse 2-functions on connected
n
-manifolds
Authors: Gay David T. , Kirby Robion C.
Published: April 2011

We discuss generic smooth maps from smooth manifolds to smooth surfaces, which we call “Morse 2-functions,” and homotopies between such maps. The two central issues are to keep the fibers connected, in which case the Morse 2-function is “fiber-connected,” and to avoid local extrema over one-dimensional submanifolds of the range, in which case the Morse 2-function is “indefinite.” This is foundational work for the long-range goal of defining smooth invariants from Morse 2-functions using tools analogous to classical Morse homology and Cerf theory.
Higher-order intersections in low-dimensional topology
Authors: Conant Jim , Schneiderman Rob , Teichner Peter
Published: April 2011

We show how to measure the failure of the Whitney move in dimension 4 by constructing higher-order intersection invariants of
Whitney towers
built from iterated Whitney disks on immersed surfaces in 4-manifolds. For Whitney towers on immersed disks in the 4-ball, we identify some of these new invariants with previously known link invariants such as Milnor, Sato–Levine, and Arf invariants. We also define higher-order Sato–Levine and Arf invariants and show that these invariants detect the obstructions to framing a
twisted
Whitney tower. Together with Milnor invariants, these higher-order invariants are shown to classify the existence of (twisted) Whitney towers of increasing order in the 4-ball. A conjecture regarding the nontriviality of the higher-order Arf invariants is formulated, and related implications for filtrations of string links and 3-dimensional homology cylinders are described.
Role of test motivation in intelligence testing
Authors: Duckworth Angela Lee , Quinn Patrick D. , Lynam Donald R. , Loeber Rolf , Stouthamer-Loeber Magda
Published: April 2011

Intelligence tests are widely assumed to measure maximal intellectual performance, and predictive associations between intelligence quotient (IQ) scores and later-life outcomes are typically interpreted as unbiased estimates of the effect of intellectual ability on academic, professional, and social life outcomes. The current investigation critically examines these assumptions and finds evidence against both. First, we examined whether motivation is less than maximal on intelligence tests administered in the context of low-stakes research situations. Specifically, we completed a meta-analysis of random-assignment experiments testing the effects of material incentives on intelligence-test performance on a collective 2,008 participants. Incentives increased IQ scores by an average of 0.64 SD, with larger effects for individuals with lower baseline IQ scores. Second, we tested whether individual differences in motivation during IQ testing can spuriously inflate the predictive validity of intelligence for life outcomes. Trained observers rated test motivation among 251 adolescent boys completing intelligence tests using a 15-min “thin-slice” video sample. IQ score predicted life outcomes, including academic performance in adolescence and criminal convictions, employment, and years of education in early adulthood. After adjusting for the influence of test motivation, however, the predictive validity of intelligence for life outcomes was significantly diminished, particularly for nonacademic outcomes. Collectively, our findings suggest that, under low-stakes research conditions, some individuals try harder than others, and, in this context, test motivation can act as a third-variable confound that inflates estimates of the predictive validity of intelligence for life outcomes.
Symplectic homology product via Legendrian surgery
Authors: Bourgeois Frédéric , Ekholm Tobias , Eliashberg Yakov
Published: April 2011

This research announcement continues the study of the symplectic homology of Weinstein manifolds undertaken by the authors [Bourgeois F, Ekholm T, Eliashberg Y (2009) arXiv:0911.0026] where the symplectic homology, as a vector space, was expressed in terms of the Legendrian homology algebra of the attaching spheres of critical handles. Here, we express the product and Batalin–Vilkovisky operator of symplectic homology in that context.
Silicon carbonate phase formed from carbon dioxide and silica under pressure
Authors: Santoro Mario , Gorelli Federico , Haines Julien , Cambon Olivier , Levelut Claire , Garbarino Gaston
Published: April 2011

The discovery of nonmolecular carbon dioxide under high-pressure conditions shows that there are remarkable analogies between this important substance and other group IV oxides. A natural and long-standing question is whether compounds between CO
2
and SiO
2
are possible. Under ambient conditions, CO
2
and SiO
2
are thermodynamically stable and do not react with each other. We show that reactions occur at high pressures indicating that silica can behave in a manner similar to ionic metal oxides that form carbonates at room pressure. A silicon carbonate phase was synthesized by reacting silicalite, a microporous SiO
2
zeolite, and molecular CO
2
that fills the pores, in diamond anvil cells at 18–26 GPa and 600–980 K; the compound was then temperature quenched. The material was characterized by Raman and IR spectroscopy, and synchrotron X-ray diffraction. The experiments reveal unique oxide chemistry at high pressures and the potential for synthesis of a class of previously uncharacterized materials. There are also potential implications for CO
2
segregation in planetary interiors and for CO
2
storage.
Estimating the reproductive numbers for the 2008–2009 cholera outbreaks in Zimbabwe
Authors: Mukandavire Zindoga , Liao Shu , Wang Jin , Gaff Holly , Smith David L. , Morris J. Glenn
Published: April 2011

Cholera remains an important global cause of morbidity and mortality, capable of causing periodic epidemic disease. Beginning in August 2008, a major cholera epidemic occurred in Zimbabwe, with 98,585 reported cases and 4,287 deaths. The dynamics of such outbreaks, particularly in nonestuarine regions, are not well understood. We explored the utility of mathematical models in understanding transmission dynamics of cholera and in assessing the magnitude of interventions necessary to control epidemic disease. Weekly data on reported cholera cases were obtained from the Zimbabwe Ministry of Health and Child Welfare (MoHCW) for the period from November 13, 2008 to July 31, 2009. A mathematical model was formulated and fitted to cumulative cholera cases to estimate the basic reproductive numbersR0and the partial reproductive numbers from all 10 provinces for the 2008–2009 Zimbabwe cholera epidemic. Estimated basic reproductive numbers were highly heterogeneous, ranging from a low value of just above unity to 2.72. Partial reproductive numbers were also highly heterogeneous, suggesting that the transmission routes varied by province; human-to-human transmission accounted for 41–95% of all transmission. Our models suggest that the underlying patterns of cholera transmission varied widely from province to province, with a corresponding variation in the amenability of outbreaks in different provinces to control measures such as immunization. These data underscore the heterogeneity of cholera transmission dynamics, potentially linked to differences in environment, socio-economic conditions, and cultural practices. The lack of traditional estuarine reservoirs combined with these estimates ofR0suggest that mass vaccination against cholera deployed strategically in Zimbabwe and surrounding regions could prevent future cholera epidemics and eventually eliminate cholera from the region.
Regeneration of axons in injured spinal cord by activation of bone morphogenetic protein/Smad1 signaling pathway in adult neurons
Authors: Parikh Pranav , Hao Yuhan , Hosseinkhani Mohsen , Patil Shekhar B. , Huntley George W. , Tessier-Lavigne Marc , Zou Hongyan
Published: April 2011

Axon growth potential is highest in young neurons but diminishes with age, thus becoming a significant obstacle to axonal regeneration after injury in maturity. The mechanism for the decline is incompletely understood, and no effective clinical treatment is available to rekindle innate growth capability. Here, we show that Smad1-dependent bone morphogenetic protein (BMP) signaling is developmentally regulated and governs axonal growth in dorsal root ganglion (DRG) neurons. Down-regulation of the pathway contributes to the age-related decline of the axon growth potential. Reactivating Smad1 selectively in adult DRG neurons results in sensory axon regeneration in a mouse model of spinal cord injury (SCI). Smad1 signaling can be effectively manipulated by an adeno-associated virus (AAV) vector encoding BMP4 delivered by a clinically applicable and minimally invasive technique, an approach devoid of unwanted abnormalities in mechanosensation or pain perception. Importantly, transected axons are able to regenerate even when the AAV treatment is delivered after SCI, thus mimicking a clinically relevant scenario. Together, our results identify a therapeutic target to promote axonal regeneration after SCI.
IFN-λ determines the intestinal epithelial antiviral host defense
Authors: Pott Johanna , Mahlakõiv Tanel , Mordstein Markus , Duerr Claudia U. , Michiels Thomas , Stockinger Silvia , Staeheli Peter , Hornef Mathias W.
Published: April 2011

Type I and type III IFNs bind to different cell-surface receptors but induce identical signal transduction pathways, leading to the expression of antiviral host effector molecules. Despite the fact that type III IFN (IFN-λ) has been shown to predominantly act on mucosal organs, in vivo infection studies have failed to attribute a specific, nonredundant function. Instead, a predominant role of type I IFN was observed, which was explained by the ubiquitous expression of the type I IFN receptor. Here we comparatively analyzed the role of functional IFN-λ and type I IFN receptor signaling in the innate immune response to intestinal rotavirus infection in vivo, and determined viral replication and antiviral gene expression on the cellular level. We observed that both suckling and adult mice lacking functional receptors for IFN-λ were impaired in the control of oral rotavirus infection, whereas animals lacking functional receptors for type I IFN were similar to wild-type mice. Using Mx1 protein accumulation as marker for IFN responsiveness of individual cells, we demonstrate that intestinal epithelial cells, which are the prime target cells of rotavirus, strongly responded to IFN-λ but only marginally to type I IFN in vivo. Systemic treatment of suckling mice with IFN-λ repressed rotavirus replication in the gut, whereas treatment with type I IFN was not effective. These results are unique in identifying a critical role of IFN-λ in the epithelial antiviral host defense.
High density amorphous ice at room temperature
Authors: Chen Jing-Yin , Yoo Choong-Shik
Published: April 2011

The phase diagram of water is both unusual and complex, exhibiting a wide range of polymorphs including proton-ordered or disordered forms. In addition, a variety of stable and metastable forms are observed. The richness of H
2
O phases attests the versatility of hydrogen-bonded network structures that include kinetically stable amorphous ices. Information of the amorphous solids, however, is rarely available especially for the stability field and transformation dynamics—but all reported to exist below the crystallization temperature of approximately 150–170 K below 4–5 GPa. Here, we present the evidence of high density amorphous (HDA) ice formed well above the crystallization temperature at 1 GPa—well inside the so-called “no-man’s land.” It is formed from metastable ice VII in the stability field of ice VI under rapid compression using dynamic-diamond anvil cell (
d
-DAC) and results from structural similarities between HDA and ice VII. The formation follows an interfacial growth mechanism unlike the melting process. Nevertheless, the occurrence of HDA along the extrapolated melt line of ice VII resembles the ice Ih-to-HDA transition, indicating that structural instabilities of parent ice VII and Ih drive the pressure-induced amorphization.
Trichome-derived
O
-acyl sugars are a first meal for caterpillars that tags them for predation
Authors: Weinhold Alexander , Baldwin Ian Thomas
Published: April 2011

Plant glandular trichomes exude secondary metabolites with defensive functions, but these epidermal protuberances are surprisingly the first meal of Lepidopteran herbivores on
Nicotiana attenuata
.
O
-acyl sugars, the most abundant metabolite of glandular trichomes, impart a distinct volatile profile to the body and frass of larvae that feed on them. The headspace composition of
Manduca sexta
larvae is dominated by the branched chain aliphatic acids hydrolyzed from ingested
O
-acyl sugars, which waxes and wanes rapidly with trichome ingestion. In native habitats a ground-hunting predator, the omnivorous ant
Pogonomyrmex rugosus
, but not the big-eyed bug
Geocoris
spp., use these volatile aliphatic acids to locate their prey.
Expression of chemokine receptor CXCR3 on T cells affects the balance between effector and memory CD8 T-cell generation
Authors: Hu Joyce K. , Kagari Takashi , Clingan Jonathan M. , Matloubian Mehrdad
Published: April 2011

Generation of a robust immunological memory response is essential for protection on subsequent encounters with the same pathogen. The magnitude and quality of the memory CD8 T-cell population are shaped and influenced by the strength and duration of the initial antigenic stimulus as well as by inflammatory cytokines. Although chemokine receptors have been established to play a role in recruitment of effector CD8 T cells to sites of inflammation, their contribution to determination of T-cell fate and shaping of the long-lived memory T-cell population is not fully understood. Here, we investigated whether reduced access to antigen and inflammation through alterations in expression of inflammatory and homeostatic chemokine receptors has an impact on generation of effector and memory CD8 T cells. We found that in mice infected with lymphocytic choriomeningitis virus, colocalization of virus-specific CD8 T cells with antigen in spleen is dependent on expression of the inflammatory chemokine receptor, CXCR3. In addition, absence of CXCR3 expression on CD8 T cells leads to formation of fewer short-lived effector cells and more memory precursor cells. Furthermore, the memory CD8 T-cell population derived from CXCR3-deficient cells has fewer cells of the effector memory phenotype and exhibits a recall response of greater magnitude than that of WT cells. These data demonstrate that CD8 T-cell positioning relative to antigen and inflammatory cytokines in secondary lymphoid organs affects the balance of effector and memory T-cell formation and has both a quantitative and qualitative impact on the long-lived memory CD8 T-cell population.
Changes in cortical interneuron migration contribute to the evolution of the neocortex
Authors: Tanaka Daisuke H. , Oiwa Ryo , Sasaki Erika , Nakajima Kazunori
Published: April 2011

The establishment of the mammalian neocortex is often explained phylogenetically by an evolutionary change in the pallial neuronal progenitors of excitatory projection neurons. It remains unclear, however, whether and how the evolutionary change in inhibitory interneurons, which originate outside the neocortex, has been involved in the establishment of the neocortex. In this study, we transplanted chicken, turtle, mouse, and marmoset medial ganglionic eminence (MGE) cells into the embryonic mouse MGE in utero and compared their migratory behaviors. We found that the MGE cells from all of the species were able to migrate through the mouse neocortical subventricular zone and that both the mouse and marmoset cells subsequently invaded the neocortical cortical plate (CP). However, regardless of their birthdates and interneuron subtypes, most of the chicken and turtle cells ignored the neocortical CP and passed beneath it, although they were able to invade the archicortex and paleocortex, suggesting that the proper responsiveness of MGE cells to guidance cues to enter the neocortical CP is unique to mammals. When chicken MGE cells were transplanted directly into the neocortical CP, they were able to survive and mature, suggesting that the neocortical CP itself is essentially permissive for postmigratory development of chicken MGE cells. These results suggest that an evolutionary change in the migratory ability of inhibitory interneurons, which originate outside the neocortex, was involved in the establishment of the neocortex by supplying inhibitory components to the network.
Stem cell antigen-1 enhances tumorigenicity by disruption of growth differentiation factor-10 (GDF10)–dependent TGF-β signaling
Authors: Upadhyay Geeta , Yin Yuzhi , Yuan Hongyan , Li Xin , Derynck Rik , Glazer Robert I.
Published: April 2011

Stem cell antigen (Sca)-1/Ly6A, a glycerophosphatidylinositol-linked surface protein, was found to be associated with murine stem cell– and progenitor cell–enriched populations, and also has been linked to the capacity of tumor-initiating cells. Despite these interesting associations, this protein's functional role in these processes remains largely unknown. To identify the mechanism underlying the protein's possible role in mammary tumorigenesis, Sca-1 expression was examined in Sca-1
+/EGFP
mice during carcinogenesis. Mammary tumor cells derived from these mice readily engrafted in syngeneic mice, and tumor growth was markedly inhibited on down-regulation of Sca-1 expression. The latter effect was associated with significantly elevated expression of the TGF-β ligand growth differentiation factor-10 (GDF10), which was found to selectively activate TGF-β receptor (TβRI/II)-dependent Smad3 phosphorylation. Overexpression of GDF10 attenuated tumor formation; conversely, silencing of GDF10 expression reversed these effects. Sca-1 attenuated GDF10-dependent TGF-β signaling by disrupting the heterodimerization of TβRI and TβRII receptors. These findings suggest a new functional role for Sca-1 in maintaining tumorigenicity, in part by acting as a potent suppressor of TGF-β signaling.