Wireless solar water splitting using silicon-based semiconductors and earth-abundant catalysts     

Reece SY  Hamel JA  Sung K  Jarvi TD  Esswein AJ  Pijpers JJ  Nocera DG 《Science (New York, N.Y.)》2011,334(6056):645-648

We describe the development of solar water-splitting cells comprising earth-abundant elements that operate in near-neutral pH conditions, both with and without connecting wires. The cells consist of a triple junction, amorphous silicon photovoltaic interfaced to hydrogen- and oxygen-evolving catalysts made from an alloy of earth-abundant metals and a cobalt|borate catalyst, respectively. The devices described here carry out the solar-driven water-splitting reaction at efficiencies of 4.7% for a wired configuration and 2.5% for a wireless configuration when illuminated with 1 sun (100 milliwatts per square centimeter) of air mass 1.5 simulated sunlight. Fuel-forming catalysts interfaced with light-harvesting semiconductors afford a pathway to direct solar-to-fuels conversion that captures many of the basic functional elements of a leaf.  相似文献   

The coming paradigm shift in forensic identification science     

Saks MJ  Koehler JJ 《Science (New York, N.Y.)》2005,309(5736):892-895

Converging legal and scientific forces are pushing the traditional forensic identification sciences toward fundamental change. The assumption of discernible uniqueness that resides at the core of these fields is weakened by evidence of errors in proficiency testing and in actual cases. Changes in the law pertaining to the admissibility of expert evidence in court, together with the emergence of DNA typing as a model for a scientifically defensible approach to questions of shared identity, are driving the older forensic sciences toward a new scientific paradigm.  相似文献   

Neodymium-142 evidence for Hadean mafic crust     

O'Neil J  Carlson RW  Francis D  Stevenson RK 《Science (New York, N.Y.)》2008,321(5897):1828-1831

Neodymium-142 data for rocks from the Nuvvuagittuq greenstone belt in northern Quebec, Canada, show that some rock types have lower 142Nd/144Nd ratios than the terrestrial standard (epsilon142Nd = -0.07 to -0.15). Within a mafic amphibolite unit, 142Nd/144Nd ratios correlate positively with Sm/Nd ratios and produce a 146Sm-142Nd isochron with an age of 4280(-81)(+53) million years. These rocks thus sample incompatible-element-enriched material formed shortly after Earth formation and may represent the oldest preserved crustal section on Earth.  相似文献   

Inactivation of TNF signaling by rationally designed dominant-negative TNF variants     

Steed PM  Tansey MG  Zalevsky J  Zhukovsky EA  Desjarlais JR  Szymkowski DE  Abbott C  Carmichael D  Chan C  Cherry L  Cheung P  Chirino AJ  Chung HH  Doberstein SK  Eivazi A  Filikov AV  Gao SX  Hubert RS  Hwang M  Hyun L  Kashi S  Kim A  Kim E  Kung J  Martinez SP  Muchhal US  Nguyen DH  O'Brien C  O'Keefe D  Singer K  Vafa O  Vielmetter J  Yoder SC  Dahiyat BI 《Science (New York, N.Y.)》2003,301(5641):1895-1898

Tumor necrosis factor (TNF) is a key regulator of inflammatory responses and has been implicated in many pathological conditions. We used structure-based design to engineer variant TNF proteins that rapidly form heterotrimers with native TNF to give complexes that neither bind to nor stimulate signaling through TNF receptors. Thus, TNF is inactivated by sequestration. Dominant-negative TNFs represent a possible approach to anti-inflammatory biotherapeutics, and experiments in animal models show that the strategy can attenuate TNF-mediated pathology. Similar rational design could be used to engineer inhibitors of additional TNF superfamily cytokines as well as other multimeric ligands.  相似文献   

Molecular hydrogen as an energy source for Helicobacter pylori     

Olson JW  Maier RJ 《Science (New York, N.Y.)》2002,298(5599):1788-1790

The gastric pathogen Helicobacter pylori is known to be able to use molecular hydrogen as a respiratory substrate when grown in the laboratory. We found that hydrogen is available in the gastric mucosa of mice and that its use greatly increased the stomach colonization by H. pylori. Hydrogenase activity in H. pylori is constitutive but increased fivefold upon incubation with hydrogen. Hydrogen concentrations measured in the stomachs of live mice were found to be 10 to 50 times as high as the H. pylori affinity for hydrogen. A hydrogenase mutant strain is much less efficient in its colonization of mice. Therefore, hydrogen present in animals as a consequence of normal colonic flora is an energy-yielding substrate that can facilitate the maintenance of a pathogenic bacterium.  相似文献   

High-accuracy ab initio rotation-vibration transitions for water     

Polyansky OL  Császár AG  Shirin SV  Zobov NF  Barletta P  Tennyson J  Schwenke DW  Knowles PJ 《Science (New York, N.Y.)》2003,299(5606):539-542

The spectrum of water vapor is of fundamental importance for a variety of processes, including the absorption and retention of sunlight in Earth's atmosphere. Therefore, there has long been an urgent need for a robust and accurate predictive model for this spectrum. In our work on the high-resolution spectrum of water, we report first-principles calculations that approach experimental accuracy. To achieve this, we performed exceptionally large electronic structure calculations and considered a variety of effects, including quantum electrodynamics, which have routinely been neglected in studies of small many-electron molecules. The high accuracy of the resulting ab initio procedure is demonstrated for the main isotopomers of water.  相似文献   

Grasping primate origins     

Bloch JI  Boyer DM 《Science (New York, N.Y.)》2002,298(5598):1606-1610

The evolutionary history that led to Eocene-and-later primates of modern aspect (Euprimates) has been uncertain. We describe a skeleton of Paleocene plesiadapiform Carpolestes simpsoni that includes most of the skull and many postcranial bones. Phylogenetic analyses indicate that Carpolestidae are closely related to Euprimates. C. simpsoni had long fingers and an opposable hallux with a nail. It lacked orbital convergence and an ankle specialized for leaping. We infer that the ancestor of Euprimates was primitively an arboreal grasper adapted for terminal branch feeding rather than a specialized leaper or visually directed predator.  相似文献   

Increase in the Asian southwest monsoon during the past four centuries     

Anderson DM  Overpeck JT  Gupta AK 《Science (New York, N.Y.)》2002,297(5581):596-599

Climate reconstructions reveal unprecedented warming in the past century; however, little is known about trends in aspects such as the monsoon. We reconstructed the monsoon winds for the past 1000 years using fossil Globigerina bulloides abundance in box cores from the Arabian Sea and found that monsoon wind strength increased during the past four centuries as the Northern Hemisphere warmed. We infer that the observed link between Eurasian snow cover and the southwest monsoon persists on a centennial scale. Alternatively, the forcing implicated in the warming trend (volcanic aerosols, solar output, and greenhouse gases) may directly affect the monsoon. Either interpretation is consistent with the hypothesis that the southwest monsoon strength will increase during the coming century as greenhouse gas concentrations continue to rise and northern latitudes continue to warm.  相似文献   

White fat progenitor cells reside in the adipose vasculature   总被引：1，自引：0，他引：1  

Tang W  Zeve D  Suh JM  Bosnakovski D  Kyba M  Hammer RE  Tallquist MD  Graff JM 《Science (New York, N.Y.)》2008,322(5901):583-586

White adipose (fat) tissues regulate metabolism, reproduction, and life span. Adipocytes form throughout life, with the most marked expansion of the lineage occurring during the postnatal period. Adipocytes develop in coordination with the vasculature, but the identity and location of white adipocyte progenitor cells in vivo are unknown. We used genetically marked mice to isolate proliferating and renewing adipogenic progenitors. We found that most adipocytes descend from a pool of these proliferating progenitors that are already committed, either prenatally or early in postnatal life. These progenitors reside in the mural cell compartment of the adipose vasculature, but not in the vasculature of other tissues. Thus, the adipose vasculature appears to function as a progenitor niche and may provide signals for adipocyte development.  相似文献   

Physics. Searching for gravity's hidden strength     

Feng JL 《Science (New York, N.Y.)》2003,302(5646):795-797

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