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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 180 (1957), S. 1432-1433 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] For a long time the most popular explanation was that the season of drought was passed in the egg stage, the eggs lying dormant in the dried mud or sand of the water-course. In order to test this point, Edwards2 collected samples of sand and silt from the bods of rivers which five months earlier ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 178 (1956), S. 1297-1299 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Since these, observations were made, very little additional information on Simulium damnosum has appeared; but several illuminating observations have been made on species of Simulium in other countries which reveal a wide range of ovipositing behaviour both with regard to method and time. For ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 172 (1953), S. 352-353 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the course of routine dissections of wild-caught Anopheles gambice in Dar-es-Salaam, Tanganyika, during 1947-48, it was noted that while A. gambice had a high rate of infection with malaria parasites and with filaria larvae, it was very rarely that one and the same mosquito was infected with ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 221 (1969), S. 858-859 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] With a period of exposure of 1 h at 20 C, and at larvicide concentrations up to 10 p.p.m. (100 times greater than the normal field dose), egg masses were unaffected by DDT, Baytex, Methoxychlor, Abate and Dursban. With an exposure of 24 h and a concentration of 1 p.p.m., eggs were still unaffected ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 32 (1984), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Zero-offset-source VSP surveys provide information about the subsurface only within the Fresnel zone centered at the well. Offsetting the source location moves the reflection zones away from the well thus providing lateral cover.Conventional processing of this type of data gives rise to a distorted image of the subsurface. Using a simple ray-tracing scheme, this image may be reconstructed into the more familiar coordinate system of the surface seismic section. This simple data-independent mapping is based on the assumption of horizontal layering and requires a vertical velocity profile.The technique of placing the source away from the borehole was first applied to the single-offset-source VSP survey. However, data from any survey geometry (such as deviated well with rig source, walkaway VSP, etc.) can be mapped to the coordinate system defined by the appropriate seismic section.To obtain the best results from this type of survey the target area must be defined and simple modeling techniques used to optimize the source location(s). These pre-survey modeling methods may also be used to anticipate—and hence avoid a number of problem areas which experience has highlighted.The data from any VSP survey is the result of a realizable experiment and as such obeys the wave equation. This implies that the wave equation may be used to migrate the data to its true subsurface location. Theoretically, such a process is more secure than ray-tracing techniques, although its practice presents many difficulties.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 163 (1949), S. 109-110 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] DESPITE the great developments in residual insecticides in the last few years, there is still difficulty in assessing and comparing their value in controlling anopheles-under African conditions at least. The dramatic fall in the day-catch of mosquitoes * in houses treated with D.D.T. is now known ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 365 (1993), S. 133-135 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The radio emission from the jet of 3C273 has been mapped from the ground at resolutions down to 0.22 arcsec (ref. 2), and on milli-arcsec scales3'4 in the nucleus using very-long-baseline interferometry. The resolution of ground-based optical data, on the other hand, is limited to typically 1 ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 7 (1978), S. 129-137 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Laboratory techniques are described for evaluating the lethal and behavioral impact of pesticides on a range of stream macroinvertebrates under continuous through-flow and simulated stream conditions. The same basic test unit has been used, with slight modifications, to study the reactions of bothSimulium larvae and non-target stream invertebrates. On the basis of a standard 1-hr exposure period to different concentrations followed by a 24-hr holding period in a continuous flow of clean water, different test organisms showed wide and consistent differences in tolerance to each of the two insecticides tested. The widest difference between two organisms occurred in the case of the Amphipod,Gammarus pulex (LC90-95, 〉〉 1 ppm) which was found to be about 5000 x more tolerant to temephos than are nymphs of the mayfly,Baetis rhodani. (LC 90–95, 0.001– 0.002 ppm) The widest difference in the reactions of any one species is shown on the part ofGammarus which is about 100 times more susceptible to chlorpyrifos (LC 90–95, 0.05–0.1 ppm) than to temephos. The susceptibility levels of other indicator species such asAgrion,Hydropsyche, Brachycentras, Ephemera, etc. are discussed in relation to susceptibility levels ofSimulium larvae under the same test conditions, and also in relation to current field dosages of the two insecticides in practical and experimentalSimulium control.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 7 (1978), S. 139-147 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The behavioral reactions of a range of stream macroinvertebrates to short exposures to the organophosphorus insecticides temephos and chlorpyrifos methyl in running water have been studied in a laboratory experimental channel or simulated stream. The tests showed widely different types of response not only in accordance with susceptibility levels previously established, but also with regard to activation responses leading to detachment and downstream drift. The amphipodGammarus pulex was the most readily activated by both insecticides, even at sub-lethal levels. Nymphs of the mayflyBaetis rhodani were also readily activated, but to a less extent than would be expected in view of their established high susceptibility to both compounds. In the case ofSimulium larvae, detachment leading to drift during the 30-min exposure period was negligible with late instars exposed to each of the two insecticides, even at lethal levels. Both types of caddis larvae tested, the web-spinningHydropsyche pellucidula and the mobile case-bearingBrachycentrus subnubilis, showed little sign of activation to either insecticide, even at concentrations which subsequently produced high mortalities. Observations extended for up to 24 hr after the initial 30-min exposure, showed continued complete absence of activation and detachment, the majority of exposed larvae dyingin situ. These differences in reaction are discussed in relation to the interpretation of downstream drift following field application of these chemicals in practical and experimentalSimulium control.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 29 (1994), S. 6079-6084 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The precipitation of cementite under the influence of an externally applied stress, during the tempering of martensite in steels, is investigated using transmission electron microscopy. The stress appears to favour the development of particular crystallographic variants of cementite in any given plate of martensite. Hence, a Widmanstätten array of cementite particles in a normally tempered sample changes to an array consisting of just one variant in stress-tempered samples. The results are discussed in the context of the mechanism of carbide precipitation during the lower bainite reaction.
    Type of Medium: Electronic Resource
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