Implications for mantle dynamics from the high melting temperature of perovskite     

van Keken PE  Yuen DA  van den Berg AP 《Science (New York, N.Y.)》1994,264(5164):1437-1439

Recent studies have implied that (Mg, Fe)SiO(3)-perovskite, a likely dominant mineral phase in the lower mantle, may have a high melting temperature. The implications of these findings for the dynamics of the lower mantle were investigated with the use of numerical convection models. The results showed that low homologous temperatures (0.3 to 0.5) would prevail in the modeled lower mantle, regardless of the effective Rayleigh number and internal heating rates. High-temperature ductile creep is possible under relatively cold conditions. In models with low rates of internal heating, local maxima of viscosity developed in the mid-lower mantle that were similar to those obtained from inversion of geoid, topography, and plate velocities.  相似文献   

A Microanalyzer for Very Small Gas Samples (0.4-1 mm.3)     

Berg WE 《Science (New York, N.Y.)》1946,104(2711):575-576

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Radiation Carcinogenesis     

Berg JW 《Science (New York, N.Y.)》1960,131(3403):796-866

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Atom collision-induced resistivity of carbon nanotubes     

Romero HE  Bolton K  Rosén A  Eklund PC 《Science (New York, N.Y.)》2005,307(5706):89-93

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   

A methylaspartate cycle in haloarchaea   总被引：1，自引：0，他引：1  

Khomyakova M  Bükmez Ö  Thomas LK  Erb TJ  Berg IA 《Science (New York, N.Y.)》2011,331(6015):334-337

Access to novel ecological niches often requires adaptation of metabolic pathways to cope with new environments. For conversion to cellular building blocks, many substrates enter central carbon metabolism via acetyl-coenzyme A (acetyl-CoA). Until now, only two such pathways have been identified: the glyoxylate cycle and the ethylmalonyl-CoA pathway. Prokaryotes in the haloarchaea use a third pathway by which acetyl-CoA is oxidized to glyoxylate via the key intermediate methylaspartate. Glyoxylate condensation with another acetyl-CoA molecule yields malate, the final assimilation product. This cycle combines reactions that originally belonged to different metabolic processes in different groups of prokaryotes, which suggests lateral gene transfer and evolutionary tinkering of acetate assimilation. Moreover, it requires elevated intracellular glutamate concentrations, as well as coupling carbon assimilation with nitrogen metabolism.  相似文献   

A physical map of the 1-gigabase bread wheat chromosome 3B   总被引：2，自引：0，他引：2  

Paux E  Sourdille P  Salse J  Saintenac C  Choulet F  Leroy P  Korol A  Michalak M  Kianian S  Spielmeyer W  Lagudah E  Somers D  Kilian A  Alaux M  Vautrin S  Bergès H  Eversole K  Appels R  Safar J  Simkova H  Dolezel J  Bernard M  Feuillet C 《Science (New York, N.Y.)》2008,322(5898):101-104

As the staple food for 35% of the world's population, wheat is one of the most important crop species. To date, sequence-based tools to accelerate wheat improvement are lacking. As part of the international effort to sequence the 17-billion-base-pair hexaploid bread wheat genome (2n = 6x = 42 chromosomes), we constructed a bacterial artificial chromosome (BAC)-based integrated physical map of the largest chromosome, 3B, that alone is 995 megabases. A chromosome-specific BAC library was used to assemble 82% of the chromosome into 1036 contigs that were anchored with 1443 molecular markers, providing a major resource for genetic and genomic studies. This physical map establishes a template for the remaining wheat chromosomes and demonstrates the feasibility of constructing physical maps in large, complex, polyploid genomes with a chromosome-based approach.  相似文献   

Assessment and selection of fungal antagonists against Rhizoctonia solani          下载免费PDF全文

Grosch R　 Faltin F　 Lottmann J　 Kofoet A　 Berg G 《浙江大学学报(农业与生命科学版)》2004,30(4):393-393

The soil-borne pathogen Rhizoctonia solani Kühn (teleomorph, Thanatephorus cucumeris [A.B. Frank] Donk) is worldwide responsible for serious damage of many economically important agricultural and horticultural crops. Control of Rhizoctonia diseases is difficult because this pathogen survives for many years as sclerotia in soil or as mycelium in organic matter under numerous environmental conditions. Furthermore, the pathogen has an extremely wide host range. To date, no effective con…  相似文献   

Metabolism of [(14)C]flusilazole in the goat     

Anderson JJ  Shalaby LM  Berg DS 《Journal of agricultural and food chemistry》1999,47(6):2439-2446

[Phenyl(U)-(14)C] and [triazole(3)-(14)C]flusilazole ([(bis 4-fluorophenyl)]methyl(1H-1,2,4-triazole-1-ylmethyl)silane; I) were extensively metabolized when fed to lactating goats (Capra hircus). The primary metabolites identified in goat tissues and milk were bis(4-fluorophenyl)(methyl)silanol (II) and 1H-1,2,4-triazole (III). Concentrations of total radiolabeled residues in the milk ranged from 0.09 to 0.74 microg/mL. Concentrations of radiolabeled residues found in tissues when the [(14)C] label was in the phenyl or triazole position, respectively, were 13.5 and 3.54 microg/g (liver), 8.74 and 0.75 microg/g (kidney), 0.41 and 0.52 microg/g (leg muscle), and 4.07 and 0.94 microg/g (back fat). Urine contained an additional major metabolite identified as [bis(4-fluorophenyl)](methyl)silylmethanol (IV) and its glucuronic acid conjugate (V). With either labeled form of flusilazole, the majority of the recovered radiolabel was excreted in urine or feces.  相似文献   

Ovine metabolism of lithogenic sapogenins. Synthesis of [2,2,4,4-(2)h(4)]sarsasapogenone, [2,2,4,4-(2)h(4)]sarsasapogenin,and [2,2,4,4-(2)h(4)]episarsasapogenin and evaluation of deuterium retention in a sheep-dosing trial     

Loader JI  Wilkins AL  Flåøyen A  Ryste E  Hove K 《Journal of agricultural and food chemistry》2003,51(9):2641-2645

The suitability of [2,2,4,4-(2)H(4)]sarsasapogenone (1b), [2,2,4,4-(2)H(4)]sarsasapogenin (2b), and [2,2,4,4-(2)H(4)]episarsasapogenin (3b) as isotopically labeled dosing substrates to determine the levels of free and conjugated sapogenins present in feces from sheep grazing saponin-containing plants implicated in the development of ovine heptagenous photosentization diseases was investigated. A 1:4 mixture of [2,2,4,4-(2)H(4)]sarsasapogenin (2b) and [2,2,4,4-(2)H(4)]episarsasapogenin (3b), obtained by reduction of [2,2,4,4-(2)H(4)]sarsasapogenone (1b), was found to retain 94% of incorporated deuterium, when dosed to one sheep. The recovery of the dosed mixture of genins 2b and 3b was calculated to be 85%. Considerable loss of deuterium and a lower recovery of genin material were observed when [2,2,4,4-(2)H(4)]sarsasapogenone (1b) was dosed.  相似文献   

Partitioning behavior of Alkan-1-ols between milkfat and aqueous phases as influenced by temperature     

Berg DP  Rankin SA 《Journal of agricultural and food chemistry》2005,53(7):2646-2651

Partitioning of volatile compounds between lipid and aqueous phases may influence flavor perception and availability to participate in flavor-generating reactions. The objective of this research was to characterize the partitioning of short-chain alkan-1-ols between milkfat and aqueous phases, as influenced by temperature, as compared to an octan-1-ol/water biphasic system (Log P). Temperature has a positive, but nonlinear, influence on Log P values for alkan-1-ols. There is an approximately 1 log decrease in Log P values of milkfat/water as compared to octan-1-ol/water systems; similar trends were observed across chain length. Temperature has a greater effect on alkan-1-ol partitioning in milkfat/water systems than octan-1-ol/water. The latter observation is primarily attributed to the solidification of milkfat at temperatures below 40 degrees C and the resulting reduction in liquid lipid solvent volume.  相似文献