HIV/AIDS. Malawi: a suitable case for treatment     

Cohen J 《Science (New York, N.Y.)》2002,297(5583):927-929

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HIV and heroin: a deadly international affair: Vietnam     

Cohen J 《Science (New York, N.Y.)》2003,301(5640):1657-1658

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Quantum communication with zero-capacity channels     

Smith G  Yard J 《Science (New York, N.Y.)》2008,321(5897):1812-1815

Communication over a noisy quantum channel introduces errors in the transmission that must be corrected. A fundamental bound on quantum error correction is the quantum capacity, which quantifies the amount of quantum data that can be protected. We show theoretically that two quantum channels, each with a transmission capacity of zero, can have a nonzero capacity when used together. This unveils a rich structure in the theory of quantum communications, implying that the quantum capacity does not completely specify a channel's ability to transmit quantum information.  相似文献   

Comment on "Wandering minds: the default network and stimulus-independent thought"     

Gilbert SJ  Dumontheil I  Simons JS  Frith CD  Burgess PW 《Science (New York, N.Y.)》2007,317(5834):43; author reply 43

Mason et al. (Reports, 19 January 2007, p. 393) attributed activity in certain regions of the "resting" brain to the occurrence of mind-wandering. However, previous research has demonstrated the difficulty of distinguishing this type of stimulus-independent thought from stimulus-oriented thought (e.g., watchfulness). Consideration of both possibilities is required to resolve this ambiguity.  相似文献   

Maximum benefit of a precise nitrogen application system for wheat   总被引：1，自引：0，他引：1  

Jon T. Biermacher  Francis M. Epplin  B. Wade Brorsen  John B. Solie  William R. Raun 《Precision Agriculture》2006,7(3):193-204

Research is ongoing to develop sensor-based systems to determine crop nitrogen needs. To be economic and to achieve wide adoption, a sensor-based site-specific application system must be sufficiently efficient to overcome both the cost disadvantage of dry and liquid sources of nitrogen relative to applications before planting of anhydrous ammonia and possible losses if weather prevents applications during the growing season. The objective of this study is to determine the expected maximum benefit of a precision N application system for winter wheat that senses and applies N to the growing crop in the spring relative to a uniform system that applies N before planting. An estimate of the maximum benefit would be useful to provide researchers with an upper bound on the cost of delivering an economically viable precision technology. Sixty five site-years of data from two dryland winter wheat nitrogen fertility experiments at experimental stations in the Southern Plains of the U.S.A. were used to estimate the expected returns from both a conventional uniform rate anhydrous ammonia (NH₃) application system before planting and a precise topdressing system to determine the value of the latter. For prices of $0.55 and $0.33 kg⁻¹ N for urea-ammonium nitrate (UAN) and NH₃, respectively, the maximum net value of a system of precise sensor-based nitrogen application for winter wheat was about $22–$31 ha⁻¹ depending upon location and assumptions regarding the existence of a plateau. However, for prices of $1.10 and $0.66 kg⁻¹ N for UAN and NH₃, respectively, the value was approximately $33 ha⁻¹. The benefit of precise N application is sensitive to both the absolute and relative prices of UAN and NH₃.This is journal paper AEJ-260 of the Oklahoma Agricultural Experiment Station, project H-2574.  相似文献   

Quantitative analysis of culture using millions of digitized books   总被引：1，自引：0，他引：1  

Michel JB  Shen YK  Aiden AP  Veres A  Gray MK;Google Books Team  Pickett JP  Hoiberg D  Clancy D  Norvig P  Orwant J  Pinker S  Nowak MA  Aiden EL 《Science (New York, N.Y.)》2011,331(6014):176-182

We constructed a corpus of digitized texts containing about 4% of all books ever printed. Analysis of this corpus enables us to investigate cultural trends quantitatively. We survey the vast terrain of 'culturomics,' focusing on linguistic and cultural phenomena that were reflected in the English language between 1800 and 2000. We show how this approach can provide insights about fields as diverse as lexicography, the evolution of grammar, collective memory, the adoption of technology, the pursuit of fame, censorship, and historical epidemiology. Culturomics extends the boundaries of rigorous quantitative inquiry to a wide array of new phenomena spanning the social sciences and the humanities.  相似文献   

Activating mutations of NOTCH1 in human T cell acute lymphoblastic leukemia   总被引：1，自引：0，他引：1  

Weng AP  Ferrando AA  Lee W  Morris JP  Silverman LB  Sanchez-Irizarry C  Blacklow SC  Look AT  Aster JC 《Science (New York, N.Y.)》2004,306(5694):269-271

Very rare cases of human T cell acute lymphoblastic leukemia (T-ALL) harbor chromosomal translocations that involve NOTCH1, a gene encoding a transmembrane receptor that regulates normal T cell development. Here, we report that more than 50% of human T-ALLs, including tumors from all major molecular oncogenic subtypes, have activating mutations that involve the extracellular heterodimerization domain and/or the C-terminal PEST domain of NOTCH1. These findings greatly expand the role of activated NOTCH1 in the molecular pathogenesis of human T-ALL and provide a strong rationale for targeted therapies that interfere with NOTCH signaling.  相似文献   

Snapshots of DsbA in action: detection of proteins in the process of oxidative folding     

Kadokura H  Tian H  Zander T  Bardwell JC  Beckwith J 《Science (New York, N.Y.)》2004,303(5657):534-537

DsbA, a thioredoxin superfamily member, introduces disulfide bonds into newly translocated proteins. This process is thought to occur via formation of mixed disulfide complexes between DsbA and its substrates. However, these complexes are difficult to detect, probably because of their short-lived nature. Here we show that it is possible to detect such covalent intermediates in vivo by a mutation in DsbA that alters cis proline-151. Further, this mutant allowed us to identify substrates of DsbA. Alteration of the cis proline, highly conserved among thioredoxin superfamily members, may be useful for the detection of substrates and intermediate complexes in other systems.  相似文献   

Paleoindian seafaring, maritime technologies, and coastal foraging on California's Channel Islands     

Erlandson JM  Rick TC  Braje TJ  Casperson M  Culleton B  Fulfrost B  Garcia T  Guthrie DA  Jew N  Kennett DJ  Moss ML  Reeder L  Skinner C  Watts J  Willis L 《Science (New York, N.Y.)》2011,331(6021):1181-1185

Three archaeological sites on California's Channel Islands show that Paleoindians relied heavily on marine resources. The Paleocoastal sites, dated between ~12,200 and 11,200 years ago, contain numerous stemmed projectile points and crescents associated with a variety of marine and aquatic faunal remains. At site CA-SRI-512 on Santa Rosa Island, Paleocoastal peoples used such tools to capture geese, cormorants, and other birds, along with marine mammals and finfish. At Cardwell Bluffs on San Miguel Island, Paleocoastal peoples collected local chert cobbles, worked them into bifaces and projectile points, and discarded thousands of marine shells. With bifacial technologies similar to those seen in Western Pluvial Lakes Tradition assemblages of western North America, the sites provide evidence for seafaring and island colonization by Paleoindians with a diversified maritime economy.  相似文献   

AIDS research. Microbicide fails to protect against HIV     

Cohen J 《Science (New York, N.Y.)》2008,319(5866):1026-1027

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