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61.
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S Chakraborty R Knoche H Schulze DC Rubie D Dobson NL Ross RJ Angel 《Science (New York, N.Y.)》1999,283(5400):362-365
Rates of cation diffusion (magnesium, iron, and nickel) have been determined in olivine and its high-pressure polymorph, wadsleyite, at 9 to 15 gigapascals and 1100 degrees to 1400 degreesC for compositions that are relevant to Earth's mantle. Diffusion in olivine becomes strongly dependent on composition at high pressure. In wadsleyite, diffusion is one to two orders of magnitude faster than in olivine, depending on temperature. Homogenization of mantle heterogeneities (chemical mixing) and mineral transformations involving a magnesium-iron exchange will therefore occur considerably faster in the transition zone than at depths of less than 410 kilometers. 相似文献
63.
P. J. Dias M. Bland A. M. Shanks A. Beaumont S. B. Piertney I. M. Davies M. Snow 《Aquaculture International》2009,17(5):437-448
Mussel (Mytilus spp.) production is one of the most economically important aspects of global aquaculture and, in Scotland, production has
increased from 262 t in 1986 to 4,219 t in 2006. Until recently, mussel production in Scotland was considered to be based
exclusively on the blue mussel Mytilus edulis, the native species. In Europe, production is known to consist of M. edulis and M. galloprovincialis, while a third less profitable species M. trossulus occurs in the Baltic Sea, where it is unexploited. In Scotland, the sympatric occurrence of M. edulis, M. trossulus, M. galloprovincialis and their hybrids in cultivation in Loch Etive has recently been reported, with significant losses in production attributed
to the presence of M. trossulus. Samples of mussels were taken at three depths from 10 rope-farm sites in Loch Etive. The distribution of the Mytilus species and their hybrids in Loch Etive was investigated using the Me 15/16 nuclear DNA locus for species and hybrid identification.
All three species and their hybrids were detected and the data were in agreement with the Hardy–Weinberg model suggesting
panmixia. Frequencies of M. galloprovincialis and its hybrids were very low. Overall, M. trossulus (37%) was found to be more common than M. edulis (30%) and 23% of the sampled mussels were M. trossulus × M. edulis hybrids. Species distribution did not correlate with year of settlement nor with salinities taken at the time of sampling.
There were significant differences in species distribution due to site location and depth, with M. edulis being more frequent at 8 m depth and M. trossulus more common at shallower depths. These differences might be exploitable in management strategies for continuing production,
for example to decrease the prevalence of M. trossulus at shellfish farms in favour of the more desirable M. edulis. 相似文献
64.
Summary A field study was undertaken to examine the effect of fertiliser type and weed control system on grain yield, yield components and weed population in durum wheat ( Triticum turgidum. var. durum) grown in a 4-year rotation [bare fallow–barley ( Hordeum vulgare )–vetch ( Vicia sativa )–wheat]. Fertilisation treatments were: no fertilisation, organic fertilisation with 2500 kg ha−1 of compost (sheep manure and cereal straw) and chemical fertilisation with 100–60–60 kg ha−1 of NPK. Weed-control treatments were: no control, herbicide, harrowing with long-flex spring tines and strip sowing with inter-row hoeing. Chemical fertilisation increased grain yield with respect to the other treatments, amongst which no significant differences were noted. Weed-control systems afforded no improvement in yield compared with controls; indeed, yields obtained using inter-row hoeing were lower. The weed population consisted of a large variety of species, of which the most important were Convolvulus arvensis and Polygonum aviculare . Application of weed-control systems reduced weed density. Herbicide was the most effective, reducing weed biomass by 80%, whilst harrowing and hoeing reduced weed biomass by 40% and 52% respectively. Inter-row hoeing does not appear to be a viable alternative to herbicides, when used as the sole weed control method in a non-diverse cropping system in Mediterranean climates. The lack of response to compost suggests a need for further long-term research. 相似文献
65.
“Lissapol” NX and “Lubrol” L, used to improve the uptake of paraquat into plants were found in earlier work to reduce its movement. Several series of surfactants with widely varying solubilities in water were partitioned between cabbage wax and water. A marked correlation was found between the effect of surfactants on the movement of paraquat and the amount of surfactant partitioning into the wax. It is concluded that although surfactants increase the uptake of paraquat into leaves, this increase is offset by reduced movement following penetration of surfactants into leaf tissue. Surfactant partition into wax reduces the degree of penetration, but there is no evidence how surfactants in leaf tissue reduce movement. 相似文献
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67.
Detection of Clostridium botulinum types C and D toxin by ELISA 总被引:3,自引:0,他引:3
RJ THOMAS 《Australian veterinary journal》1991,68(3):111-113
An ELISA to detect Clostridium botulinum type D toxin was developed using polyclonal antibodies to a semi-purified toxic complex of the neurotoxin. Sensitivity of the ELISA for detecting type C and type D toxin compared with mouse inoculation was 70% and specificity 96% on samples from animals with botulism diagnosed on clinical signs and herd history. However, both mouse inoculation and the ELISA failed to detect toxin in many animals with a presumptive diagnosis of botulism. Some cross-reaction was seen with Clostridium novyi type A, but not with other clostridial species. While the ELISA described here cannot replace mouse inoculation for the diagnosis of botulism, it is a useful additional test. 相似文献
68.
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70.
Finlay BJ 《Science (New York, N.Y.)》2002,296(5570):1061-1063
The abundance of individuals in microbial species is so large that dispersal is rarely (if ever) restricted by geographical barriers. This "ubiquitous" dispersal requires an alternative view of the scale and dynamics of biodiversity at the microbial level, wherein global species number is relatively low and local species richness is always sufficient to drive ecosystem functions. 相似文献