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  • 1
    Electronic Resource
    Electronic Resource
    Toxicity Measurements and Their Use in Treatment Strategies (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Water and environment journal 8 (1994), S. 0 
    Details
    ISSN: 1747-6593
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: The use of measured toxicity for evaluating the effects of a chemical or effluent on the environment, or monitoring the performance of an effluent treatment plant, is becoming increasingly important to complement the analytical techniques which are conventionally used. Although many consents on effluent discharges refer to specific chemical components, regulatory authorities are increasingly realizing the value of toxicity measurements to evaluate a combined effluent effect, particularly in the case of complex effluent streams.This paper (a) describes the basic principles of conventional methods of measuring toxicity, (b) highlights the benefits and shortcomings of these methods, and (c) outlines some promising methodologies which are being developed. The use of these measurements is then discussed in evaluating treatment alternatives, modifying existing treatment plants and conducting treatment evaluations. Several case studies are outlined to illustrate the use of toxicological measurements in assessing industrial wastewater treatment processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1747-6593.1994.tb00907.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Phospholipase C from Bacillus cereus on the Release of Membrane-Bound Choline-O-Acetyltransferase from Rat Hippocampal Tissue (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Some of the enzyme choline-O-acetyltransferase (ChAT) associated with central cholinergic nerve terminals appears to be nonionically associated with membranes. In the present study, we tested the possibility that some membrane-bound ChAT might be anchored to membranes by a phosphatidylinositol linkage by incubating rat hippocampal tissue with phospholipase C (PLC) from Bacillus cereus. The PLC selectively augmented the release of ChAT; also, the glycosylphosphatidylinositol-PLC inhibitor, zinc, blocked this increase in release. When control and PLC-treated hippocampal tissues were subjected to Triton X-114 phase separation, a procedure that separates amphiphilic from hydrophilic proteins, the detergent-soluble, membrane-bound fraction of tissue ChAT appeared to be the source of the ChAT released by PLC into the incubation medium. Zinc also blocked the temperature-dependent release of ChAT, but not lactic dehydrogenase, from hippocampal tissue. Extracellular membrane-bound ChAT appeared to be the source of the ChAT released by a low exogenous concentration of PLC, as well as that released by a temperature-dependent process during tissue incubation. Phosphatidylinositol-specific PLC from Bacillus thuringiensis released ChAT, but not lactic dehydrogenase, from a crude synaptosomal fraction prepared from rat hippocampal tissue. These results suggest that some of the membrane-bound ChAT in rat hippocampal tissue may be extracellular and anchored to the membrane by phosphatidylinositol, and also that an endogenous factor in hippocampal tissue may function to remove this extracellular ChAT from the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb02356.x
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  • 3
    Electronic Resource
    Electronic Resource
    On the Yakhot–Orszag renormalization group method for deriving turbulence statistics and models (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 364-390 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The purpose of this paper is to provide an independent, comprehensive, critical review of the "renormalization group'' theory of turbulence developed by Yakhot and Orszag [J. Sci. Comput. 1, 3 (1986)]. The first part of the paper is a confirmation of their basic theory for the Navier–Stokes equations, followed by a discussion of approximations in the scale removal procedure. The main part of the paper examines the YO derivations of the velocity-derivative skewness and the transport equation for the energy dissipation rate E. An algebraic error in the derivation of the skewness is corrected. Several problems are identified in the derivation of the E equation which suggest that the derivation should be reformulated. The present paper has become the basis for such a reformulation, to be published separately by Yakhot and Smith.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858310
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  • 4
    Electronic Resource
    Electronic Resource
    The dissipation-range spectrum and the velocity-derivative skewness in turbulent flows (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 992-994 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to determine the best representation of the turbulence spectrum in the dissipation range, the dynamical equation for the rate of energy dissipation E is used, together with a model spectrum of the form E[k] = CKE2/3k−5/3 exp[ − σkm], to obtain a prediction for the velocity derivative skewness S¯ at high Reynolds number: S¯ = S¯[CK,m]. The skewness data suggest that m=2 is the best model for laboratory-scale flows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857979
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  • 5
    Electronic Resource
    Electronic Resource
    Low-voltage, high-saturation, optically bistable self-electro-optic effect devices using extremely shallow quantum wells (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1049-1051 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Symmetric self-electro-optic effect devices (S-SEEDs) using extremely shallow GaAs/Al0.04Ga0.96As multiple quantum wells are demonstrated. By exploiting mainly exciton ionization, rather than the usual quantum-confined Stark shift, room-temperature optical bistability is obtained with no applied bias. The extremely shallow symmetric-SEED (symmetric E-SEED) exhibits contrast ratios (CRs)(approximately-equal-to)3.5, with biasses〈5 V, demonstrating system applicability and compatability with electronics. Large system tolerances Δλ(approximately-equal-to)6 nm and maximum bistability loop width (approximately-equal-to)70% are also obtained. Moreover, due to fast carrier escape times, the symmetric E-SEED exhibits useful CRs(approximately-greater-than)2 even at continuous-wave intensities (approximately-greater-than)70 μW/μm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106341
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  • 6
    Electronic Resource
    Electronic Resource
    Ambipolar lifetimes in GaAs/AlGaAs self-electro-optic-effect devices (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 687-689 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used an electrical technique to determine the ambipolar lifetime in p-i-n GaAs/AlGaAs self-electro-optic-effect devices in which the i region consists of a multiple quantum well structure (MQW). From an analysis of the voltage drop in the i region obtained from the forward current-voltage characteristics, values for the ambipolar lifetimes are derived for diodes with different MQW. A value of 80–90 ps is determined for the ambipolar lifetime which is found not to change significantly when the AlxGa1−xAs barrier thickness or composition is reduced from 65 to 35 A(ring) or x∼0.3 to 0.2, respectively, in the MQW. Since these changes in the barrier have previously been shown to improve photoresponse efficiency of the p-i-n diode, it is inferred that the carrier escape and collection times are smaller than 80–90 ps in devices with thin (35 A(ring)) or low (x∼0.2) AlxGa1−xAs barrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107822
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  • 7
    Electronic Resource
    Electronic Resource
    Diode-clamped symmetric self-electro-optic effect devices with subpicojoule switching energies (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1809-1811 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe symmetric self-electro-optic effect devices (S-SEEDs) with clamping diodes connected to the center node of the devices to ensure both diodes of the S-SEEDs have an electric field across them at all times. These diode-clamped S-SEEDs operate over a greater wavelength range, with greater powers before saturating, and have lower optical switching energies compared to conventional S-SEEDs. An 8×8 array of diode-clamped S-SEEDs has been built and tested. We have demonstrated bistable operation with voltage swings of only 2 V over a wavelength range of 15 nm. Required optical switching energies of 340–580 fJ were measured at input powers from 500 nW to 100 μW for devices with 10×10 μm mesas. This is the lowest reported switching energy for any SEED with acceptable bistable characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107171
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  • 8
    Electronic Resource
    Electronic Resource
    Radiative recombination in surface-free n+/n−/n+GaAs homostructures (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1572-1574 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that the radiative efficiencies and lifetimes of photoexcited carriers in epitaxial GaAs may both be enhanced by three to four orders of magnitude by the preparation of thin n+, doped layers at the surface and substrate interfaces. Samples were prepared by organometallic vapor phase epitaxy with n− region (∼1015 cm−3) thicknesses of 3–10 μm and n+ regions Si doped to concentrations of 5×1018 cm−3. Time-resolved luminescence in such structures (25–300 K), under both surface and bulk (near-band- edge) excitation conditions, reveals band-to-band-dominated recombination spectra, with carrier lifetimes ranging from a minimum of 150 ns at 50 K to 800 ns at room temperature. This is in sharp contrast to the subnanosecond lifetimes and poor raditive efficiencies typical in conventionally prepared, bulk or epitaxial GaAs, but is comparable to the best reported for high-purity LPE GaAs/AlxGa1−xAs double heterostructures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103357
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  • 9
    Electronic Resource
    Electronic Resource
    The Echinoderm Immune System (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 712 (1994), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1994.tb33575.x
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  • 10
    Electronic Resource
    Electronic Resource
    High-speed DNA sequencing by capillary gel electrophoresis (1991)
    [s.l.] : Nature Publishing Group
    Nature 349 (1991), S. 812-813 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE tremendous demands of the Human Genome Initiative for improved DNA sequencing methodologies has spurred a multitude of innovative new approaches to high-speed DNA sequence analysis. One of the most promising of these new techniques is capillary gel electrophoresis (CGE). This method is a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/349812a0
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