Bacteriophage and the toxigenicity of Clostridium botulinum type C

Nontoxigenic and bacteriophage-sensitive bacterial cultures have been isolated from toxigenic Clostridium botulinum type C, strain 468C, after treatment with either ultraviolet light or acridine orange. Two bacteriophages, designated CEbeta and CE(gamma), were isolated from toxigenic strain 468C. Both of these bacteriophages were capable of infecting the nontoxigenic type C cultures, but only bacteriophage CEbeta was involved in the change from nontoxigenicity to toxigenicity.     

GONG Observations of Solar Surface Flows

Doppler velocity observations obtained by the Global Oscillation Network Group (GONG) instruments directly measure the nearly steady flows in the solar photosphere. The sun's differential rotation is accurately determined from single observations. The rotation profile with respect to latitude agrees well with previous measures, but it also shows a slight north-south asymmetry. Rotation profiles averaged over 27-day rotations of the sun reveal the torsional oscillation signal-weak, jetlike features, with amplitudes of 5 meters per second, that are associated with the sunspot latitude activity belts. A meridional circulation with a poleward flow of about 20 meters per second is also evident. Several characteristics of the surface flows suggest the presence of large convection cells.     

美国谷物生产成本分析

美国是世界上谷物生产和贸易大国，２００１年，美国谷物收获面积达１．２３亿hm２，其中玉米、大豆和小麦等主要谷物的产量分别占世界产量的３９．６％、４４．５４％和９．１４％。同时，美国又是玉米、大豆和小麦的主要出口国家，根据美国农业部的统计（USDA—ERS，２００２），２００１年，美国玉米、大豆和小麦的出口额分别达到４５．０２亿、５４．０３亿和３３．７０亿美元，占世界出口总额的５３．６２％、４１．１８％和７３．４５％，均排在世界第一位。巨大的产量规模和贸易份额使美国谷物的供给价格成为国际谷物市场价格波动…     

Large On-Off Ratios and Negative Differential Resistance in a Molecular Electronic Device

A molecule containing a nitroamine redox center (2'-amino-4-ethynylphenyl-4'-ethynylphenyl-5'-nitro-1-benzenethiol) was used in the active self-assembled monolayer in an electronic device. Current-voltage measurements of the device exhibited negative differential resistance and an on-off peak-to-valley ratio in excess of 1000:1.     

Crystallographic evidence for a free silylium ion

Evidence for a three-coordinate silyl cation is provided by the crystal structure of [(Mes)3Si][H-CB11Me5Br6].C6H6 (where Mes is 2,4,6-trimethylphenyl). Free (Mes)3Si+ cations are well separated from the carborane anions and benzene solvate molecules. Ortho-methyl groups of the mesityl substituents shield the silicon atom from the close approach of nucleophiles, while remaining innocent as significant ligands themselves. The silicon center is three-coordinate and planar. The downfield 29Si nuclear magnetic resonance chemical shift in the solid state (226.7 parts per million) is almost identical to that in benzene solution and in "gas phase" calculations, indicating that three-coordination can be preserved in all phases.