Small interfering RNA-induced transcriptional gene silencing in human cells   总被引：1，自引：0，他引：1  

Morris KV  Chan SW  Jacobsen SE  Looney DJ 《Science (New York, N.Y.)》2004,305(5688):1289-1292

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Polar science. Race to plumb the frigid depths     

Krajick K 《Science (New York, N.Y.)》2007,315(5818):1525-1528

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Nutritional status and diet composition affect the value of diatoms as copepod prey     

Jones RH  Flynn KJ 《Science (New York, N.Y.)》2005,307(5714):1457-1459

The role of diatoms as key food for copepods at the base of pelagic food chains has been questioned recently on the grounds of toxicity. We show, using unialgal versus mixed algal diets of different nutritional status (i.e., nitrogen:carbon ratio) fed to Acartia tonsa, that diatoms per se are not toxic but that single-diatom diets are inadequate. Additionally, the nutritional state of the phytoplankton has a profound effect on copepod growth and growth efficiency. The ecological significance of laboratory demonstrations of diatom toxicity needs to be reconsidered.  相似文献   

Profiling the thermoelectric power of semiconductor junctions with nanometer resolution     

Lyeo HK  Khajetoorians AA  Shi L  Pipe KP  Ram RJ  Shakouri A  Shih CK 《Science (New York, N.Y.)》2004,303(5659):816-818

We have probed the local thermoelectric power of semiconductor nanostructures with the use of ultrahigh-vacuum scanning thermoelectric microscopy. When applied to a p-n junction, this method reveals that the thermoelectric power changes its sign abruptly within 2 nanometers across the junction. Because thermoelectric power correlates with electronic structure, we can profile with nanometer spatial resolution the thermoelectric power, band structures, and carrier concentrations of semiconductor junctions that constitute the building blocks of thermoelectric, electronic, and optoelectronic devices.  相似文献   

Linked reactivity at mineral-water interfaces through bulk crystal conduction     

Yanina SV  Rosso KM 《Science (New York, N.Y.)》2008,320(5873):218-222

The semiconducting properties of a wide range of minerals are often ignored in the study of their interfacial geochemical behavior. We show that surface-specific charge density accumulation reactions combined with bulk charge carrier diffusivity create conditions under which interfacial electron transfer reactions at one surface couple with those at another via current flow through the crystal bulk. Specifically, we observed that a chemically induced surface potential gradient across hematite (alpha-Fe2O3) crystals is sufficiently high and the bulk electrical resistivity sufficiently low that dissolution of edge surfaces is linked to simultaneous growth of the crystallographically distinct (001) basal plane. The apparent importance of bulk crystal conduction is likely to be generalizable to a host of naturally abundant semiconducting minerals playing varied key roles in soils, sediments, and the atmosphere.  相似文献   

Muscular thin films for building actuators and powering devices     

Feinberg AW  Feigel A  Shevkoplyas SS  Sheehy S  Whitesides GM  Parker KK 《Science (New York, N.Y.)》2007,317(5843):1366-1370

We demonstrate the assembly of biohybrid materials from engineered tissues and synthetic polymer thin films. The constructs were built by culturing neonatal rat ventricular cardiomyocytes on polydimethylsiloxane thin films micropatterned with extracellular matrix proteins to promote spatially ordered, two-dimensional myogenesis. The constructs, termed muscular thin films, adopted functional, three-dimensional conformations when released from a thermally sensitive polymer substrate and were designed to perform biomimetic tasks by varying tissue architecture, thin-film shape, and electrical-pacing protocol. These centimeter-scale constructs perform functions as diverse as gripping, pumping, walking, and swimming with fine spatial and temporal control and generating specific forces as high as 4 millinewtons per square millimeter.  相似文献   

Middle Paleolithic assemblages from the Indian subcontinent before and after the Toba super-eruption     

Petraglia M  Korisettar R  Boivin N  Clarkson C  Ditchfield P  Jones S  Koshy J  Lahr MM  Oppenheimer C  Pyle D  Roberts R  Schwenninger JL  Arnold L  White K 《Science (New York, N.Y.)》2007,317(5834):114-116

The Youngest Toba Tuff (YTT) eruption, which occurred in Indonesia 74,000 years ago, is one of Earth's largest known volcanic events. The effect of the YTT eruption on existing populations of humans, and accordingly on the course of human evolution, is debated. Here we associate the YTT with archaeological assemblages at Jwalapuram, in the Jurreru River valley of southern India. Broad continuity of Middle Paleolithic technology across the YTT event suggests that hominins persisted regionally across this major eruptive event.  相似文献   

A single IGF1 allele is a major determinant of small size in dogs   总被引：3，自引：0，他引：3  

Sutter NB  Bustamante CD  Chase K  Gray MM  Zhao K  Zhu L  Padhukasahasram B  Karlins E  Davis S  Jones PG  Quignon P  Johnson GS  Parker HG  Fretwell N  Mosher DS  Lawler DF  Satyaraj E  Nordborg M  Lark KG  Wayne RK  Ostrander EA 《Science (New York, N.Y.)》2007,316(5821):112-115

The domestic dog exhibits greater diversity in body size than any other terrestrial vertebrate. We used a strategy that exploits the breed structure of dogs to investigate the genetic basis of size. First, through a genome-wide scan, we identified a major quantitative trait locus (QTL) on chromosome 15 influencing size variation within a single breed. Second, we examined genetic variation in the 15-megabase interval surrounding the QTL in small and giant breeds and found marked evidence for a selective sweep spanning a single gene (IGF1), encoding insulin-like growth factor 1. A single IGF1 single-nucleotide polymorphism haplotype is common to all small breeds and nearly absent from giant breeds, suggesting that the same causal sequence variant is a major contributor to body size in all small dogs.  相似文献   

A gene expression map for the euchromatic genome of Drosophila melanogaster     

Stolc V  Gauhar Z  Mason C  Halasz G  van Batenburg MF  Rifkin SA  Hua S  Herreman T  Tongprasit W  Barbano PE  Bussemaker HJ  White KP 《Science (New York, N.Y.)》2004,306(5696):655-660

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A perovskite oxide optimized for oxygen evolution catalysis from molecular orbital principles     

Suntivich J  May KJ  Gasteiger HA  Goodenough JB  Shao-Horn Y 《Science (New York, N.Y.)》2011,334(6061):1383-1385

The efficiency of many energy storage technologies, such as rechargeable metal-air batteries and hydrogen production from water splitting, is limited by the slow kinetics of the oxygen evolution reaction (OER). We found that Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) (BSCF) catalyzes the OER with intrinsic activity that is at least an order of magnitude higher than that of the state-of-the-art iridium oxide catalyst in alkaline media. The high activity of BSCF was predicted from a design principle established by systematic examination of more than 10 transition metal oxides, which showed that the intrinsic OER activity exhibits a volcano-shaped dependence on the occupancy of the 3d electron with an e(g) symmetry of surface transition metal cations in an oxide. The peak OER activity was predicted to be at an e(g) occupancy close to unity, with high covalency of transition metal-oxygen bonds.  相似文献