Emergence of anoxia in the California current large marine ecosystem     

Chan F  Barth JA  Lubchenco J  Kirincich A  Weeks H  Peterson WT  Menge BA 《Science (New York, N.Y.)》2008,319(5865):920

Eastern boundary current systems are among the world's most productive large marine ecosystems. Because upwelling currents transport nutrient-rich but oxygen-depleted water onto shallow seas, large expanses of productive continental shelves can be vulnerable to the risk of extreme low-oxygen events. Here, we report the novel rise of water-column shelf anoxia in the northern California Current system, a large marine ecosystem with no previous record of such extreme oxygen deficits. The expansion of anoxia highlights the potential for rapid and discontinuous ecosystem change in productive coastal systems that sustain a major portion of the world's fisheries.  相似文献   

不同氮素水平下生菜累积硝酸盐能力的品种差异分析     

侯迷红  王春枝  王婵  郭世乾  李瑛 《勤云标准版测试》2005,(5)

利用盆栽试验研究了生菜3个不同品种(苦苣、大速生、油麦)在不同氮素供应水平(0、0.2、0.4、0.6gN/kg土)下硝酸盐累积能力的差异。研究结果表明:同一氮肥水平下不同品种生菜硝酸盐含量和硝酸还原酶活性均存在显著性差异;在不同氮肥水平下,生菜各个品种硝酸盐含量具有显著差异性,且随氮肥水平的升高,其硝酸盐含量、硝酸还原酶活性呈递增趋势。因此,实际生产中选择降低硝酸盐措施时应将降低氮肥施用量及筛选低硝酸盐含量品种同时加以考虑。  相似文献   

Prevention of organ allograft rejection by a specific Janus kinase 3 inhibitor     

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   

Single crystal metals encapsulated in carbon nanoparticles     

Ruoff RS  Lorents DC  Chan B  Malhotra R  Subramoney S 《Science (New York, N.Y.)》1993,259(5093):346-348

Single-domain microcrystals of LaC(2) encapsulated within nanoscale polyhedral carbon particles have been synthesized in a carbon arc. Typical particle sizes are on the order of 20 to 40 nanometers. The stoichiometry and phase of the La-containing crystals have been assigned from characteristic lattice spacings observed by high-resolution transmission electron microscopy and energy dispersive spectroscopy (EDS). EDS spectra show that La and C are the only elements present. Characteristic interatomic distances of 3.39 and 2.78 angstroms identify the compound inside the nanoparticle cavities as alpha-LaC(2), the phase of LaC(2) that is stable at room temperature. Bulk alpha-LaC(2) is metallic and hydrolytic. Observation of crystals of pure encapsulated alpha-LaC(2) that were exposed to air for several days before analysis indicates that the LaC(2) is protected from degradation bythe carbon polyhedral shells of the nanoparticles. A high percentage of the carbon nanoparticles have encapsulated LaC(2) single crystals. These carbon-coated metal crystals form a new class of materials that can be protected in their pure or carbide forms and may have interesting and useful properties.  相似文献   

Observation of superflow in solid helium     

Kim E  Chan MH 《Science (New York, N.Y.)》2004,305(5692):1941-1944

We report on the observation of nonclassical rotational inertia in solid helium-4 confined to an annular channel in a sample cell under torsional motion, demonstrating superfluid behavior. The effect shows up as a drop in the resonant oscillation period as the sample cell is cooled below 230 millikelvin. Measurement of 17 solid samples allows us to map out the boundary of this superfluid-like solid or supersolid phase from the melting line up to 66 bars. This experiment indicates that superfluid behavior is found in all three phases of matter.  相似文献   

RNA silencing genes control de novo DNA methylation   总被引：1，自引：0，他引：1  

Chan SW  Zilberman D  Xie Z  Johansen LK  Carrington JC  Jacobsen SE 《Science (New York, N.Y.)》2004,303(5662):1336

  相似文献   

Error Sources on Yield-Based Fertilizer Variable Rate Application Maps     

Chan  C. W.  Schueller  J. K.  Miller  W. M.  Whitney  J. D.  Wheaton  T. A.  Cornell  J. A. 《Precision Agriculture》2002,3(1):81-94

Spatially-variable application of inputs to agricultural fields is dependent upon accuracy of the input variables. The effects of boundary determination, interpolation method, and GPS location errors were studied for determining a variable rate nitrogen application map based upon yield maps of a 3.6 ha Florida citrus block. A general linear model for the mean absolute error approximated the error effects.  相似文献   

A domain in TNF receptors that mediates ligand-independent receptor assembly and signaling     

Chan FK  Chun HJ  Zheng L  Siegel RM  Bui KL  Lenardo MJ 《Science (New York, N.Y.)》2000,288(5475):2351-2354

A conserved domain in the extracellular region of the 60- and 80-kilodalton tumor necrosis factor receptors (TNFRs) was identified that mediates specific ligand-independent assembly of receptor trimers. This pre-ligand-binding assembly domain (PLAD) is physically distinct from the domain that forms the major contacts with ligand, but is necessary and sufficient for the assembly of TNFR complexes that bind TNF-alpha and mediate signaling. Other members of the TNFR superfamily, including TRAIL receptor 1 and CD40, show similar homotypic association. Thus, TNFRs and related receptors appear to function as preformed complexes rather than as individual receptor subunits that oligomerize after ligand binding.  相似文献   

Synthetic clonal reproduction through seeds     

Marimuthu MP  Jolivet S  Ravi M  Pereira L  Davda JN  Cromer L  Wang L  Nogué F  Chan SW  Siddiqi I  Mercier R 《Science (New York, N.Y.)》2011,331(6019):876

Cloning through seeds has potential revolutionary applications in agriculture, because it would allow vigorous hybrids to be propagated indefinitely. However, asexual seed formation or apomixis, avoiding meiosis and fertilization, is not found in the major food crops. To develop de novo synthesis of apomixis, we crossed Arabidopsis MiMe and dyad mutants that produce diploid clonal gametes to a strain whose chromosomes are engineered to be eliminated after fertilization. Up to 34% of the progeny were clones of their parent, demonstrating the conversion of clonal female or male gametes into seeds. We also show that first-generation cloned plants can be cloned again. Clonal reproduction through seeds can therefore be achieved in a sexual plant by manipulating two to four conserved genes.  相似文献   

Inquiry learning. Integrating content detail and critical reasoning by peer review     

Iyengar R  Diverse-Pierluissi MA  Jenkins SL  Chan AM  Devi LA  Sobie EA  Ting AT  Weinstein DC 《Science (New York, N.Y.)》2008,319(5867):1189-1190

  相似文献