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991.
992.
Nepalese porters routinely carry head-supported loads equal to 100 to 200% of their body weight (Mb) for many days up and down steep mountain footpaths at high altitudes. Previous studies have shown that African women carry head-supported loads of up to 60% of their Mb far more economically than army recruits carrying equivalent loads in backpacks. Here we show that Nepalese porters carry heavier loads even more economically than African women. Female Nepalese porters, for example, carry on average loads that are 10% of their Mb heavier than the maximum loads carried by the African women, yet do so at a 25% smaller metabolic cost. 相似文献
993.
The main tasks for climate controllers in potato bulk stores are to keep the storage climate in an appropriate condition for quality conservation. To avoid extra energy costs by using cooling systems the internal climate of potato bulk stores is controlled with outdoor air. A conventionally designed controller is difficult to adapt for an optimal climate control to reduce quality loss. However, a controller designed with fuzzy logic is found as advantageous for adapting control parameters to improve the control process. A test stand is built to ventilate and to control two samples of potato bulks simultaneously with the same outdoor weather conditions for comparisons. Several experiments were carried out to compare climate controllers with different control algorithms, i.e. conventional to a different conventional and conventional to fuzzy. 相似文献
994.
Changelian PS Flanagan ME Ball DJ Kent CR Magnuson KS Martin WH Rizzuti BJ Sawyer PS Perry BD Brissette WH McCurdy SP Kudlacz EM Conklyn MJ Elliott EA Koslov ER Fisher MB Strelevitz TJ Yoon K Whipple DA Sun J Munchhof MJ Doty JL Casavant JM Blumenkopf TA Hines M Brown MF Lillie BM Subramanyam C Shang-Poa C Milici AJ Beckius GE Moyer JD Su C Woodworth TG Gaweco AS Beals CR Littman BH Fisher DA Smith JF Zagouras P Magna HA Saltarelli MJ Johnson KS Nelms LF Des Etages SG Hayes LS Kawabata TT 《Science (New York, N.Y.)》2003,302(5646):875-878
Because of its requirement for signaling by multiple cytokines, Janus kinase 3 (JAK3) is an excellent target for clinical immunosuppression. We report the development of a specific, orally active inhibitor of JAK3, CP-690,550, that significantly prolonged survival in a murine model of heart transplantation and in cynomolgus monkeys receiving kidney transplants. CP-690,550 treatment was not associated with hypertension, hyperlipidemia, or lymphoproliferative disease. On the basis of these preclinical results, we believe JAK3 blockade by CP-690,550 has potential for therapeutically desirable immunosuppression in human organ transplantation and in other clinical settings. 相似文献
995.
Blom T Franzén A Heinegård D Holmdahl R 《Science (New York, N.Y.)》2003,299(5614):1845; author reply 1845
996.
Dillehay TD Ramírez C Pino M Collins MB Rossen J Pino-Navarro JD 《Science (New York, N.Y.)》2008,320(5877):784-786
The identification of human artifacts at the early archaeological site of Monte Verde in southern Chile has raised questions of when and how people reached the tip of South America without leaving much other evidence in the New World. Remains of nine species of marine algae were recovered from hearths and other features at Monte Verde II, an upper occupational layer, and were directly dated between 14,220 and 13,980 calendar years before the present ( approximately 12,310 and 12,290 carbon-14 years ago). These findings support the archaeological interpretation of the site and indicate that the site's inhabitants used seaweed from distant beaches and estuarine environments for food and medicine. These data are consistent with the ideas that an early settlement of South America was along the Pacific coast and that seaweeds were important to the diet and health of early humans in the Americas. 相似文献
997.
Papke RT Koenig JE Rodríguez-Valera F Doolittle WF 《Science (New York, N.Y.)》2004,306(5703):1928-1929
Sex and recombination are driving forces in the evolution of eukaryotes. Homologous recombination is known to be the dominant process in the divergence of many bacterial species. For Archaea, the only direct evidence bearing on the importance or natural occurrence of homologous recombination is anecdotal reports of mosaicism from comparative genomic studies. Genetic studies, however, reveal that recombination may play a significant role in generating diversity among members of at least one archaeal group, the haloarchaea. We used multi-locus sequence typing to demonstrate that haloarchaea exchange genetic information promiscuously, exhibiting a degree of linkage equilibrium approaching that of a sexual population. 相似文献
998.
We report the observation of unusually strong and systematic changes in the electron transport in metallic single-walled carbon nanotubes that are undergoing collisions with inert gas atoms or small molecules. At fixed gas temperature and pressure, changes in the resistance and thermopower of thin films are observed that scale as roughly M(1/3), where M is the mass of the colliding gas species (He, Ar, Ne, Kr, Xe, CH4, and N2). Results of molecular dynamics simulations are also presented that show that the maximum deformation of the tube wall upon collision and the total energy transfer between the colliding atom and the nanotube also exhibit a roughly M(1/3) dependence. It appears that the transient deformation (or dent) in the tube wall may provide a previously unknown scattering mechanism needed to explain the atom collision-induced changes in the electrical transport. 相似文献
999.
Sun B Griffin BM Ayala-del-Río HL Hashsham SA Tiedje JM 《Science (New York, N.Y.)》2002,298(5595):1023-1025
1,1,1-Trichloroethane (TCA) is a ubiquitous environmental pollutant because of its widespread use as an industrial solvent, its improper disposal, and its substantial emission to the atmosphere. We report the isolation of an anaerobic bacterium, strain TCA1, that reductively dechlorinates TCA to 1,1-dichloroethane and chloroethane. Strain TCA1 required H2 as an electron donor and TCA as an electron acceptor for growth, indicating that dechlorination is a respiratory process. Phylogenetic analysis indicated that strain TCA1 is related to gram-positive bacteria with low DNA G+C content and that its closest relative is Dehalobacter restrictus, an obligate H2-oxidizing, chloroethene-respiring bacterium. 相似文献
1000.
McEwen AS Hansen CJ Delamere WA Eliason EM Herkenhoff KE Keszthelyi L Gulick VC Kirk RL Mellon MT Grant JA Thomas N Weitz CM Squyres SW Bridges NT Murchie SL Seelos F Seelos K Okubo CH Milazzo MP Tornabene LL Jaeger WL Byrne S Russell PS Griffes JL Martínez-Alonso S Davatzes A Chuang FC Thomson BJ Fishbaugh KE Dundas CM Kolb KJ Banks ME Wray JJ 《Science (New York, N.Y.)》2007,317(5845):1706-1709
Water has supposedly marked the surface of Mars and produced characteristic landforms. To understand the history of water on Mars, we take a close look at key locations with the High-Resolution Imaging Science Experiment on board the Mars Reconnaissance Orbiter, reaching fine spatial scales of 25 to 32 centimeters per pixel. Boulders ranging up to approximately 2 meters in diameter are ubiquitous in the middle to high latitudes, which include deposits previously interpreted as finegrained ocean sediments or dusty snow. Bright gully deposits identify six locations with very recent activity, but these lie on steep (20 degrees to 35 degrees) slopes where dry mass wasting could occur. Thus, we cannot confirm the reality of ancient oceans or water in active gullies but do see evidence of fluvial modification of geologically recent mid-latitude gullies and equatorial impact craters. 相似文献