芝麻同源四倍体特征特性研究   总被引：1，自引：1，他引：1  

卫双玲  张海洋  卫文星  张体德  路凤银  焦宏廷 《河南农业科学》2002,(2):10-11

对芝麻同源四倍体特征特性观察结果表明 ,同源四倍体较相应的二倍体植株增高 ,花器变大 ,千粒重提高 ( 4 .0 6g) ,结实率下降。同源四倍体的生长速度现蕾前较慢 ,以后速度加快  相似文献   

Magnetism from the atom to the bulk in iron, cobalt, and nickel clusters     

Billas IM  Châtelain A  de Heer WA 《Science (New York, N.Y.)》1994,265(5179):1682-1684

Molecular beam deflection measurements of small iron, cobalt, and nickel clusters show how magnetism develops as the cluster size is increased from several tens to several hundreds of atoms for temperatures between 80 and 1000 K. Ferromagnetism occurs even for the smallest sizes: for clusters with fewer than about 30 atoms the magnetic moments are atomlike; as the size is increased up to 700 atoms, the magnetic moments approach the bulk limit, with oscillations probably caused by surface-induced spin-density waves. The trends are explained in a magnetic shell model. A crystallographic phase transition from high moment to low moment in iron clusters has also been identified.  相似文献   

Moisture Stress as a Requirement for Flowering of Coffee     

Alvim Pde T 《Science (New York, N.Y.)》1960,132(3423):354

When coffee plants are watered at relatively short intervals, so as to maintain the water content of the soil at close to field capacity, the flower buds remain dormant and no fruits are formed. Irrigation or rain induces flowering only when preceded by a period of water shortage. Water stress is apparently essential to break the dormancy of coffee flower buds.  相似文献   

Revisiting the taxonomic impediment     

de Carvalho MR  Bockmann FA  Amorim DS  de Vivo M  de Toledo-Piza M  Menezes NA  de Figueiredo JL  Castro RM  Gill AC  McEachran JD  Compagno LJ  Schelly RC  Britz R  Lundberg JG  Vari RP  Nelson G 《Science (New York, N.Y.)》2005,307(5708):353

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Endocannabinoid hydrolysis generates brain prostaglandins that promote neuroinflammation   总被引：2，自引：0，他引：2  

Nomura DK  Morrison BE  Blankman JL  Long JZ  Kinsey SG  Marcondes MC  Ward AM  Hahn YK  Lichtman AH  Conti B  Cravatt BF 《Science (New York, N.Y.)》2011,334(6057):809-813

Phospholipase A(2)(PLA(2)) enzymes are considered the primary source of arachidonic acid for cyclooxygenase (COX)-mediated biosynthesis of prostaglandins. Here, we show that a distinct pathway exists in brain, where monoacylglycerol lipase (MAGL) hydrolyzes the endocannabinoid 2-arachidonoylglycerol to generate a major arachidonate precursor pool for neuroinflammatory prostaglandins. MAGL-disrupted animals show neuroprotection in a parkinsonian mouse model. These animals are spared the hemorrhaging caused by COX inhibitors in the gut, where prostaglandins are instead regulated by cytosolic PLA(2). These findings identify MAGL as a distinct metabolic node that couples endocannabinoid to prostaglandin signaling networks in the nervous system and suggest that inhibition of this enzyme may be a new and potentially safer way to suppress the proinflammatory cascades that underlie neurodegenerative disorders.  相似文献   

Impact of undergraduate science course innovations on learning     

Ruiz-Primo MA  Briggs D  Iverson H  Talbot R  Shepard LA 《Science (New York, N.Y.)》2011,331(6022):1269-1270

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Reciprocal control of T helper cell and dendritic cell differentiation     

Rissoan MC  Soumelis V  Kadowaki N  Grouard G  Briere F  de Waal Malefyt R  Liu YJ 《Science (New York, N.Y.)》1999,283(5405):1183-1186

It is not known whether subsets of dendritic cells provide different cytokine microenvironments that determine the differentiation of either type-1 T helper (TH1) or TH2 cells. Human monocyte (pDC1)-derived dendritic cells (DC1) were found to induce TH1 differentiation, whereas dendritic cells (DC2) derived from CD4+CD3-CD11c- plasmacytoid cells (pDC2) induced TH2 differentiation by use of a mechanism unaffected by interleukin-4 (IL-4) or IL-12. The TH2 cytokine IL-4 enhanced DC1 maturation and killed pDC2, an effect potentiated by IL-10 but blocked by CD40 ligand and interferon-gamma. Thus, a negative feedback loop from the mature T helper cells may selectively inhibit prolonged TH1 or TH2 responses by regulating survival of the appropriate dendritic cell subset.  相似文献   

Oxygen isotopes and emerald trade routes since antiquity     

Giuliani G  Chaussidon M  Schubnel HJ  Piat DH  Rollion-Bard C  France-Lanord C  Giard D  de Narvaez D  Rondeau B 《Science (New York, N.Y.)》2000,287(5453):631-633

Oxygen isotopic compositions of historical emerald artifacts from the Gallo-Roman period to the 18th century indicate that during historical times, artisans worked emeralds originating from deposits supposedly discovered in the 20th century. In antiquity, Pakistani and Egyptian emeralds were traded by way of the Silk Route. Together with Austrian stones, they were the only source of gem-quality emeralds. Immediately after the discovery of the Colombian mines by Spaniards in the 16th century, a new trade route was established, first via Spain to Europe and India and then directly via the Philippines to India. Since then, Colombian emeralds have dominated the emerald trade, and most of the high-quality emeralds cut in the 18th century in India originated from Colombia.  相似文献   

Design automation for integrated circuits     

Newell SB  de Geus AJ  Rohrer RA 《Science (New York, N.Y.)》1983,220(4596):465-471

With the ever-increasing complexity of integrated circuits, manual design methods have become intolerably slow and error-prone. The use of computers to automate some or all of the design process is necessary to minimize both design time and error incidence. In this article are discussed the design and fabrication of integrated circuits, selected techniques of design automation, and the problems associated with such automation.  相似文献   

Design of bioelectronic interfaces by exploiting hinge-bending motions in proteins     

Benson DE  Conrad DW  de Lorimier RM  Trammell SA  Hellinga HW 《Science (New York, N.Y.)》2001,293(5535):1641-1644

We report a flexible strategy for transducing ligand-binding events into electrochemical responses for a wide variety of proteins. The method exploits ligand-mediated hinge-bending motions, intrinsic to the bacterial periplasmic binding protein superfamily, to establish allosterically controlled interactions between electrode surfaces and redox-active, Ru(II)-labeled proteins. This approach allows the development of protein-based bioelectronic interfaces that respond to a diverse set of analytes. Families of these interfaces can be generated either by exploiting natural binding diversity within the superfamily or by reengineering the specificity of individual proteins. These proteins may have numerous medical, environmental, and defense applications.  相似文献