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  • 1
    Electronic Resource
    Electronic Resource
    Effects of ambient ammonia levels on blood ammonia, ammonia excretion and heart and scaphognathite rates of Nephrops norvegicus (1997)
    Springer
    Marine biology 127 (1997), S. 411-418 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During commercial handling of Nephropsnorvegicus (L.) there are a number of situations when the prawns may be exposed to very high ambient ammonia levels. These experiments evaluated the effects of increased levels of ambient total ammonia (TA = NH3 + NH4 +) on␣blood ammonia, ammonia efflux rates and on the cardio-ventilatory performance of N. norvegicus. When prawns were taken from 〈1 to 2000 μmol TA l−1 medium, blood TA concentrations increased rapidly for the first 2 h but tended to drop thereafter. Original blood TA levels were restored 6 h after the prawns were transferred back from seawater containing 2000 to 〈1 μmol TA l−1. Sudden exposure to 500, 1000, 2000 or 4000 μmol TA l−1 medium induced blood TA concentrations to increase respectively to 50, 30, 33 and 36% of external concentrations (normally, internal TA values are much higher than external levels). Immediately after transfer back to seawater with low ammonia concentration ( 〈1 μmol TA l−1), excretion rates were higher than those of control prawns, and the absolute amounts of TA excreted were considerably higher than those calculated to have accumulated in the haemolymph. Heart rate (HR) and scaphognathite rate (SR) were not altered when prawns were subjected to sudden alterations in ambient ammonia ( 〈1 to 2000 to 〈1 μmol TA l−1). When water ammonia concentrations were altered more gradually, both rates increased, but only at 4000 μmol TA l−1. These results show that N. norvegicus is able to remove ammonia from the haemolymph and/or transform ammonia into some other substance when subjected to increased levels of ambient ammonia. Possible mechanisms involved (e.g. active transport across the gills; storage in some other tissue; glutamate synthe sis) are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050028
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  • 2
    Electronic Resource
    Electronic Resource
    Haemolymph constituent levels and ammonia efflux rates of Nephrops norvegicus during emersion (1997)
    Springer
    Marine biology 127 (1997), S. 403-410 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nephropsnorvegicus (L.) were subjected to 8 h of emersion, either between layers of seawater-soaked hessian with periodical (20 min) flushes of seawater (high humidity, HH) or to unprotected emersion (low humidity, LH). Blood ammonia levels rose during emersion in both groups but reached higher levels under LH conditions. Ammonia efflux rates after re-immersion were higher than those of control prawns, and amounts of ammonia excreted at such times were considerably higher than those calculated to have accumulated in the blood during emersion. Possible explanations for such differences are discussed. C aO2 and C vO2 decreased rapidly to ca. 10% normoxia values within 2 h of HH and LH emersion and remained low throughout the remaining emersion time. Emersion-induced tissue hypoxia increased blood concentrations of glucose and lactate. Lactate accumulation was higher during LH emersion, compared with HH emersion. Blood pH dropped ca. 0.40 units but increased again after 2 h of re-immersion. Acidosis was probably related more to respiratory difficulties (CO2 accumulation) than to lactate accumulation, as blood lactate values remained high after 2 h of re-immersion. The ability of N. norvegicus to cope with emersion appears to be little influenced by high humidity conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050027
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  • 3
    Electronic Resource
    Electronic Resource
    Ammonia-N efflux rate and nutritional state of juvenile pink shrimp, Penaeus paulensis (Perez-Farfante), in relation to food type (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 29 (1998), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of squid flesh, two pelleted diets containing 41% and 53% protein, and starvation on the ammonia-N efflux rate and the biochemical composition of pink shrimp, Penaeus paulensis (Perez-Farfante), were investigated. A transient increase in the ammonia-N efflux rates of shrimp subjected to starvation was observed. Ammonia-N efflux rates of shrimp fed the diet with 41% protein were lower than in those fed the diet with 53% protein or squid flesh. Ammonia-N efflux rates were inversely related to body weight, except during starvation, which affected mainly small individuals. Increased ammonia-N excretion rates increased immediately after the ingestion of high-protein diets. Such rates were also found to be higher during light periods (cf. dark periods), possibly reflecting differences in activity levels. Dietary-related alterations in the blood, muscle and midgut gland constituents were also detected. In general terms, starvation tended to reduce the levels of such constituents, whilst pelleted diets promoted increases in lipid and carbohydrate concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1998.00232.x
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  • 4
    Electronic Resource
    Electronic Resource
    Measurements of laser-imprinted perturbations and Rayleigh–Taylor growth with the Nike KrF laser : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1969-1977 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nike is a 56 beam Krypton Fluoride (KrF) laser system using Induced Spatial Incoherence (ISI) beam smoothing with a measured focal nonuniformity 〈ΔI/I〉 of 1% rms in a single beam [S. Obenschain et al., Phys. Plasmas 3, 1996 (2098)]. When 37 of these beams are overlapped on the target, we estimate that the beam nonuniformity is reduced by 37, to (ΔI/I)≅0.15% (excluding short-wavelength beam-to-beam interference). The extraordinary uniformity of the laser drive, along with a newly developed x-ray framing diagnostic, has provided a unique facility for the accurate measurements of Rayleigh–Taylor amplified laser-imprinted mass perturbations under conditions relevant to direct-drive laser fusion. Data from targets with smooth surfaces as well as those with impressed sine wave perturbations agree with our two-dimensional (2-D) radiation hydrodynamics code that includes the time-dependent ISI beam modulations. A 2-D simulation of a target with a 100 Å rms randomly rough surface finish driven by a completely uniform beam gives final perturbation amplitudes similar to the experimental data for the smoothest laser profile. These results are promising for direct-drive laser fusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872560
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  • 5
    Electronic Resource
    Electronic Resource
    X-ray emission from plasmas created by smoothed KrF laser irradiation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3438-3447 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The x-ray emission from plasmas created by the Naval Research Laboratory Nike KrF laser [Phys. Plasmas 3, 2098 (1996) ] was characterized using imaging and spectroscopic instruments. The laser wavelength was 1/4 μm, and the beams were smoothed by induced spatial incoherence (ISI). The targets were thin foils of CH, aluminum, titanium, and cobalt and were irradiated by laser energies in the range 100–1500 J. A multilayer mirror microscope operating at an energy of 95 eV recorded images of the plasma with a spatial resolution of 2 μm. The variation of the 95 eV emission across the 800 μm focal spot was 1.3% rms. Using a curved crystal imager operating in the 1–2 keV x-ray region, the density, temperature, and opacity of aluminum plasmas were determined with a spatial resolution of 10 μm perpendicular to the target surface. The spectral line ratios indicated that the aluminum plasmas were relatively dense, cool, and optically thick near the target surface. The absolute radiation flux was determined at 95 eV and in x-ray bandpasses covering the 1–8 keV region. The electron temperature inferred from the slope of the x-ray flux versus energy data in the 5–8 keV region was 900 eV for an incident laser energy of 200 J and an intensity of ≈1013 W/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871496
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  • 6
    Electronic Resource
    Electronic Resource
    The Nike KrF laser facility: Performance and initial target experiments (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2098-2107 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Krypton-fluoride (KrF) lasers are of interest to laser fusion because they have both the large bandwidth capability ((approximately-greater-than)THz) desired for rapid beam smoothing and the short laser wavelength (1/4 μm) needed for good laser–target coupling. Nike is a recently completed 56-beam KrF laser and target facility at the Naval Research Laboratory. Because of its bandwidth of 1 THz FWHM (full width at half-maximum), Nike produces more uniform focal distributions than any other high-energy ultraviolet laser. Nike was designed to study the hydrodynamic instability of ablatively accelerated planar targets. First results show that Nike has spatially uniform ablation pressures (Δp/p〈2%). Targets have been accelerated for distances sufficient to study hydrodynamic instability while maintaining good planarity. In this review we present the performance of the Nike laser in producing uniform illumination, and its performance in correspondingly uniform acceleration of targets. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871661
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  • 7
    Electronic Resource
    Electronic Resource
    Observation of Rayleigh–Taylor growth to short wavelengths on Nike (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 565-570 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The uniform and smooth focal profile of the Nike KrF laser [S. Obenschain et al., Phys. Plasmas 3, 2098 (1996)] was used to ablatively accelerate 40 μm thick polystyrene planar targets with pulse shaping to minimize shock heating of the compressed material. The foils had imposed small-amplitude sinusoidal wave perturbations of 60, 30, 20, and 12.5 μm wavelength. The shortest wavelength is near the ablative stabilization cutoff for Rayleigh–Taylor growth. Modification of the saturated wave structure due to random laser imprint was observed. Excellent agreement was found between the two-dimensional simulations and experimental data for most cases where the laser imprint was not dominant. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873201
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  • 8
    Electronic Resource
    Electronic Resource
    A transputer-based measuring system for decentralized signal processing, applied to two-phase flow (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 5045-5049 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An innovative concept for decentralized processing of the signals of multiple sensors is presented. The basic idea is to connect every sensor via an analog-to-digital converter with a high-performance microprocessor, a transputer, that exclusively collects and processes its signal. The transputers are linked to a powerful network. Exemplarily, a measuring system based on this concept was used for the determination of local parameters of liquid–gas two-phase flows (e.g., local void fraction and bubble frequency). Up to six fiber-optical probes were utilized simultaneously to demonstrate the efficiency of the system. The signal processing under that special application may include on-line evaluation of flow parameters and on-line correction of errors of measurement due to sensor-induced effects. The concept of the new system, however, is basically independent of the number and type of sensors, as well as of the method of signal processing. The transputer-based measuring system thus provides a flexible, efficient tool for applications in which great amounts of data have to be evaluated or manipulated quickly. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146128
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  • 9
    Electronic Resource
    Electronic Resource
    Dynamic scaling concepts applied to numerical solutions of Smoluchowski's rate equation (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 7657-7667 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Smoluchowski's equation is widely applied to describe the time evolution of the cluster-size distribution during aggregation processes. Analytical solutions for this equation, however, are known only for a very limited number of kernels. Therefore, numerical methods have to be used for describing the time evolution of the cluster-size distribution. In this work, we present a novel self-consistent method for solving Smoluchowski's equation for any homogeneous kernel. The method considers dynamic scaling to be valid but does not need to assume a given form for the scaling distribution Φ(x). Moreover, the scaling distribution Φ(x) is obtained as a natural result of the algorithm. Due to the implementation of dynamic scaling concepts, the algorithm converges almost immediately with a minimal calculation effort. Comparing calculated size distributions with the corresponding analytical solutions shows the validity of the method. The method is then used to fit experimental data for diffusion limited aggregation. For this purpose, a fitting procedure is developed which allows us to fit the corresponding parameters for any given homogeneous kernel. As an application, a full comparison between the experimental data and the numerically obtained cluster-size distributions for the constant and the Brownian kernel was carried out. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480092
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  • 10
    Electronic Resource
    Electronic Resource
    Recent developments in and applications of resonance ionization mass spectrometry (1999)
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 471-477 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Resonance Ionization Mass Spectrometry (RIMS) has nowadays reached the status of a routine method for sensitive and selective ultratrace determination of long-lived radioactive isotopes in environmental, biomedical and technical samples. It provides high isobaric suppression, high to ultra-high isotopic selectivity and good overall efficiency. Experimental detection limits are as low as 106 atoms per sample and permit the fast and sensitive determination of ultratrace amounts of radiotoxic contaminations. Experimental arrangements for the detection of different radiotoxic isotopes, e.g. 236–244Pu, 89,90Sr and 99Tc in environmental samples are described, and the application of RIMS to the ultrarare long-lived radioisotope 41Ca for cosmochemical, radiodating and medical purposes are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051370
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