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  • 1
    Electronic Resource
    Electronic Resource
    Structure of the detergent phase and protein-detergent interactions in crystals of the wild-type (strain Y) Rhodobacter sphaeroides photochemical reaction center (1991)
    s.l. : American Chemical Society
    Biochemistry 30 (1991), S. 9403-9413 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00103a003
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  • 2
    Electronic Resource
    Electronic Resource
    TCRB-V gene usage in monozygotic twins discordant for multiple sclerosis (1994)
    Springer
    Immunogenetics 39 (1994), S. 281-285 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188792
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of compost and lime on population structure and element concentrations of forest soil invertebrates (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 165-173 
    Details
    ISSN: 1432-0789
    Keywords: Organic fertilization ; Lime ; Element concentrations ; Compost ; Microarthropods ; Lumbricidae ; Lumbricus rubellus ; Acari ; Collembola ; Soil acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We tested the effects of two organic fertilizers (composts) and lime on the soil fauna of a spruce stand. One compost was obtained from chopped wood and the other from household garbage. At the time of distribution the pH of the control plots averaged 3.2, the garbage compost had a pH of 7.5, and the wood compost of 6.2. During the experimental period the pH of the compost layers decreased. The pH of the former litter layer beneath the composts showed a steep increase after 5 months, but beneath the treatment with wood compost this effect did no persist. Liming increased the pH only slightly in the litter layer. The two types of compost, the litter layer, and lumbricids (Lumbricus rubellus) were analyzed for concentrations of essential and potentially toxic elements. The element burden was highest in the garbage compost with 7- to 11-fold concentrations of Zn, Cd, Pb, Mg, and Cu compared to the needle litter. K, Ba, and Ca were 4 times more concentrated. L. rubellus showed an increased Cu concentration after extraction from the highly contaminated sites of garbage compost. Despite the differences in Pb contamination in the needle litter and in the two compost types, all investigated individuals of L. rubellus contained similar concentrations of Pb. In contrast to Pb, Cd accumulated in this lumbricid. Seasonal fluctuations of microarthropods, their total abundance, and differences in the colonization of the compost layers were observed. Collembola abundance was significantly increased in the garbage compost plots in July 91. There were generally more Prostigmata in the control and limed plots than in the compost plots. Oribatid numbers fell under all treatments compared to the controls. Mesostigmata were identified to species level and 33 species were found in the experimental areas. Certain species, such as Arctoseius cetratus and Uropoda minima, were only found in the treated sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00361606
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  • 4
    Electronic Resource
    Electronic Resource
    Single Scattering Theory Versus Numerical Modelling In 2-D Random Media (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 112 (1993), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The scattering of acoustic waves in random media is investigated numerically by a finite difference method and is compared with the predictions of single scattering theory. the random media are characterized by autocorrelation functions which allow the construction of spatially anisotropic random structures with different correlation lengths a and b perpendicular and parallel to the propagation direction. If a equals b, the attenuation of the transmitted wave can be successfully explained by single scattering theory. the attenuation maximum occurs at kb≈ 1-2, where k is the wavenumber. For media with a 〉 b we observe a stronger attenuation than expected from single scattering theory for kb greater than 6. the attenuation peak is shifted to smaller kb values when the spatial anisotropy of the random fluctuations is increased. the investigation of the seismic coda shows that the single scattering theory cannot explain the time dependence of the coda. Coda Q, as determined from the coda decay rate under the single scattering assumption, does not describe the scattering attenuation. In 1-D random media the decay rate of the coda observed in transmission decreases with increasing standard deviation of the impedance fluctuations. In the 2-D case the decay rate increases slightly with the standard deviation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1993.tb01442.x
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  • 5
    Electronic Resource
    Electronic Resource
    Velocity shift in random media (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 115 (1993), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Seismic waves in a random medium (with standard deviation ε and correlation distance a of the relative slowness fluctuations) prefer fast paths, and therefore the apparent velocity of wave propagation is larger than the velocity which corresponds to the volume average of slowness. This velocity shift can be determined by ray perturbation theory (Snieder & Sambridge 1992), by the Huygens method (Podvin & Lecomte 1991) and by wave theory (Müller, Roth & Korn 1992). We apply all three methods to plane-wave propagation through a 2-D acoustic medium with Gaussian or exponential autocorrelation function of the slowness fluctuations. Ray perturbation theory gives numerical and analytical results, but has path-length (L) limitations. The Huygens method, which also gives the ray-theoretical velocity shift, can be used for L/a ratios of seismological interest. Wave theory shows that the velocity shift also depends on the wavelength λ and that for λ/a less than about 0.1 the velocity shift agrees with the result of the Huygens method. For λ/a= 1 the wave-theoretical (i.e. true) shift is lower than the Huygens-method shift by a factor of 0.25 to 0.5. Simple formulae for the ε dependence of the Huygens-method shift at long path lengths (L/a≤ 80) are given, and a correction factor is derived which approximately transforms plane-wave 2-D into spherical-wave 3-D velocity shifts; the latter correspond to 3-D two-point ray tracing.For short-period seismic waves, propagating to teleseismic distances, mantle heterogeneity with ε= 1 per cent and a= 100 km produces a velocity shift of about 0.2 per cent. Shifts of this order can explain the difference in earth models, derived from free oscillations on the one hand and from short-period body waves on the other. A velocity shift (or velocity dispersion) due to anelasticity would be additional.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1993.tb01206.x
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  • 6
    Electronic Resource
    Electronic Resource
    Seismic-wave traveltimes in random media (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 110 (1992), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A ray-theoretical relation is established between the autocorrelation function of the slowness fluctuations of a random medium and the autocorrelation function of the traveltime fluctuations on a profile perpendicular to the general propagation direction of an originally plane wave. Although this relation can be inverted exactly, it is preferable for applications to use the results of a forward calculation for a modified exponential autocorrelation function which represents slowness fluctuations with zero mean. The essential parameters of this autocorrelation function, standard deviation ε and correlation distance a, follow by simple relations from the maximum and the zero crossing of the corresponding autocorrelation function of the traveltime fluctuations. The traveltime analysis of 2-D finite-difference seismograms shows that ε and a can be reconstructed successfully, if the wavelength-to-correlation-distance ratio is 0.5 or less. Otherwise, ε is underestimated and a overestimated; however, both effects can be compensated for.The average traveltime, as determined from the finite-difference seismograms, is slightly, but systematically shorter than the traveltime according to the average slowness, i.e. the wave prefers fast paths through the medium. This is in agreement with results of Wielandt (1987) for a spherical low-velocity inclusion in a full-space and with results of Soviet authors, summarized by Petersen (1990). The velocity shift is proportional to ε2, it has dispersion similar to the dispersion related to anelasticity, and it increases with the pathlength of the wave.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1992.tb00710.x
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  • 7
    Electronic Resource
    Electronic Resource
    Current practices in the chemotherapeutic control of sea lice infestations in aquaculture: a review (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish diseases 16 (1993), S. 0 
    Details
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Abstract. This review surveys the available literature on the efficacy and ecotoxicology of chemotherapeutic agents for the control of sea lice (Copepoda: Caligidae) infestations in marine aquaculture. To date, treatment for the disease has relied almost exclusively on the use of the organophosphorus pesticides, trichlorfon and dichlorvos. While use of dichlorvos and trichlorfon appears to have little, if any, environmental impact, protracted use in some areas has led to reduced efficacy. Compounds proposed for sea lice control currently under field evaluation include azamethiphos (organophosphate), ivermectin (avermectin), pyrethrum (pyrethrin) and hydrogen peroxide. Although all of these compounds are effi cacious, at present published information on marine environmental toxicology is scarce and is limited to in vitro toxicity testing. Other compounds that have been considered for sea lice control include formalin, malathion (organophosphate), carbaryl (carbamate), diflubenzuron (insect growth regulator) and natural remedies (i.e. onions and garlic). In general, formaldehyde (aldehyde), malathion and natural compounds show either poor efficacy or unsuitable therapeutic margins. Although carbaryl and diflubenzuron are both efficacious and exhibit suitable therapeutic margins, available data suggests that the compounds, due to undesirable environmental toxicological characteristics, would be unsuitable for sea lice control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2761.1993.tb00844.x
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  • 8
    Electronic Resource
    Electronic Resource
    Domain inversion in KTiOPO4 crystal near the Curie point (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4823-4826 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A microscopic mechanism of the outdiffusion-induced domain inversion in KTiOPO4 crystals near the Curie point without applying an external electric field is developed. It is described in terms of a built-in electric field, for reasons of a gradient of donorlike centers. The predicted dominant role of the n-type charges is proved by experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357255
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  • 9
    Electronic Resource
    Electronic Resource
    Low-temperature thermoluminescence of cuprate high-temperature superconductors (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2712-2714 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermoluminescence (TL) of three different high-temperature superconducting materials, namely ErBaCuO, YbBaCuO, and (Bi,Pb)SrCaCuO, has been measured after x irradiation at 20 K. This comparative low-temperature TL investigation has revealed a close similarity in the structure of the glow curves for all three compounds in the 20–300 K temperature range. Strongest glow peaks are shown to appear below the superconducting transition temperature. The origin of the various glow peaks is discussed in terms of radiative recombination of thermally released holes with trapped electron centers. The model is supported by further TL measurements of the ErBaCuO compound, thermally treated, in reducing and oxidizing atmospheres. It is demonstrated that the TL intensity is closely related to the oxygen stoichiometry of the material, namely, the oxygen vacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356202
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  • 10
    Electronic Resource
    Electronic Resource
    Size dependence of the orientational disorder and melting transitions of finite N2 islands deposited on graphite (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3744-3748 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The orientational order–disorder and melting transition temperatures for quasi two-dimensional islands of N2 molecules deposited on graphite are calculated for sizes 1≤N≤256 molecules, using a Monte Carlo procedure with free surface boundary conditions. These transition temperatures are strong functions of N, and the values for 256 molecules are close to those measured experimentally for fractional macroscopic monolayers. Calculated results show that the two sublattice herringbone orientational structure persists up to the orientational transition temperature, above which hindered planar rotation occurs. The registered (square root of)3×(square root of)3 mass center structure exists until melting, where the islands disassociate. These features are consistent with experiment. Below melting, the root mean square fluctuations of the mass centers away from their (square root of)3×(square root of)3 equilibrium values are substantially larger than for bulk N2 or for small three-dimensional rare gas clusters. The fluctuations are also substantially larger for edge molecules than for those in the center.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462955
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