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  • Articles  (142)
  • 1995-1999  (110)
  • 1990-1994  (32)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 4137-4152 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-pressure planar microwave plasmas exhibit a pronounced spatial structure. If the discharge vessels are wide enough, they have a thin, plane homogeneous excitation region adjacent to a microwave coupling window, and they strongly decay in the direction normal to the window. The decay length of plasma parameters and activated neutrals differ by about one order of magnitude. This suggests a two-region approach for modeling of neutral particle kinetics assuming spatial homogeneity inside these two regions. The gaseous reactor volume is subdivided by a virtual interface on which mass exchange by directed gas flow, local microconvective mixing or diffusion, and exchange of enthalpy between the two different regions can be balanced. The main differences between the two regions are that electron-induced generation of activated neutrals is restricted to the excitation region (1) and that basic loss processes for activated neutrals due to the substrate surface and volume reactions are considered to occur in the second, chemical reaction region (2). Processes of loss of active neutral atoms by recombination at inert surfaces of the vessel are considered in both regions. Effectively, the model represents a system of two-coupled continuous flow stirred tank reactors given by a set of differential equations including unsteady-state Bernoulli equations. For the case of an example process concerning an oxygen plasma surface treatment, numerical solutions for initial values at the startup of the reactor are computed. The results for the dynamical behavior and the steady states of the concentrations, the temperatures, and the mass loss are in qualitative agreement with the experimental behavior of a real reactor arrangement. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 2060-2061 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Empirical economics 21 (1996), S. 617-632 
    ISSN: 1435-8921
    Keywords: C91 ; D81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract We test whether violations of expected utility theory in an Allais-paradox environment are sensitive to monetary incentives. Like Harrison (1994), we find that violations are significantly reduced when lotteries are real rather than hypothetical.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Rheologica acta 29 (1990), S. 261-280 
    ISSN: 1435-1528
    Keywords: Relaxation ; first normalstress difference ; Gaussianerror function ; stress test ; cone and platerheometer ; mirror relation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract By means of a cone and plate rheometer the relaxation of the shear stress and the first normal stress difference in polymer liquids upon cessation of a constant shear rate were examined. The experiments were conducted mostly in a high shear rate region of relevance for the processing of these materials. The relaxation behavior at these shear rates can only be measured accurately under extremely precise specifications of the rheometer. To determine under which conditions the integral normal thrust is a convenient measure for the relaxing local first normal stress difference the radial distribution of the pressure in the shear gap was measured. The shape of relaxation of both the shear stress and the first normal stress difference could be closely approximated for the entire measured shear rate and time range by a two parameter statistical function. In the range of measured shear rates, one of the parameters, the standard deviationS, is equal for the shear and the normal stress, and is independent of the shear rate within the limit of experimental error. The second parameter, the mean relaxation timet′ 50,τ of the shear stress andt′ 50,σ of the first normal stress difference, can be calculated approximately from the viscosity function and only a single relaxation experiment.
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  • 5
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We present the results of a complete tree-level calculation of the processes $pp(\bar{p}) \to Wb\bar{b}$ and $Wb\bar{b}+$ jet that includes the single-top signal and all irreducible backgrounds simultaneously. In order to probe the structure of the Wtb coupling with the highest possible accuracy and to look for possible deviations from standard model predictions, we identify sensitive observables and propose an optimal set of cuts which minimizes the background, as compared to the signal. At the Large Hadron Collider (LHC), the single-top and the single-antitop rates are different, and the corresponding asymmetry yields additional information. The analysis shows that the sensitivity for anomalous couplings will be improved at the LHC by a factor of 2–3, as compared to the expectations for the first measurements at the upgraded Tevatron. Still, the bounds on anomalous couplings obtained at hadron colliders will remain 2–8 times larger than those from high-energy $\gamma e$ colliders; however, these will not be available for some time. All basic calculations have been carried out using the computer package CompHEP. The known next-to-leading-order corrections to the single-top rate have been taken into account.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 181 (1997), S. 685-696 
    ISSN: 1432-1351
    Keywords: Key words Auditory cortex ; Dynamic receptive fields ; Spectro-temporal receptive fields ; Learning plasticity ; Time-course
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Learning-induced changes of the spectro-temporal characteristics of primary auditory cortex (AI) units were studied by response plane analysis of recordings from the AI in unanaesthetized Mongolian gerbils. Using response planes obtained prior to and after auditory discrimination training bins of significant change were identified and their spectro-temporal distribution was studied. Bins of significant changes were generally found to be distributed over the entire spectro-temporal receptive field but occurred most frequently within the first 100 ms of response in the spectral neighbourhood (1.5 octaves) of the frequency of the reinforced conditioned stimulus. Training-induced response decreases occurred early after 10 ms for reinforced conditioned tones and tones in the frequency neighbourhood. Response increases occurred so early only for non-reinforced tones in the neighbourhood of the reinforced frequency and occurred later (after 40 ms) for the reinforced tones. The results are discussed in the light of dynamic disinhibition.
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  • 7
    ISSN: 1432-1351
    Keywords: Key words Auditory cortex ; Specialized fields ; Temporal processing ; Frequency modulation ; Attention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Responses of multi-units in the auditory cortex (AC) of unanaesthetized Mongolian gerbils to pure tones and to linearly frequency modulated (FM) sounds were analysed. Three types of responses to pure tones could be clearly distinguished on the basis of spectral tuning properties, response latencies and overall temporal response pattern. In response to FM sweeps these three types discharged in a temporal pattern similar to tone responses. However, for all type-1 units the latencies of some phasic response components shifted systematically as a function of range and/or speed of modulation. Measurements of response latencies to FMs revealed that such responses were evoked whenever the modulation reached a particular instantaneous frequency (Fi). Effective Fi was: (1) independent of modulation range and speed, (2) always reached before the modulation arrived at a local maximum of the frequency response function (FRF) and consequently differed for downward and upward sweeps, and (3) was correlated with the steepest slope of that FRF maximum. The three different types of units were found in discrete and separate fields or regions of the AC. It is concluded that gross temporal response properties are one of the key features distinguishing auditory cortical regions in the Mongolian gerbil.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 55 (1999), S. 639-643 
    ISSN: 1432-1041
    Keywords: Key words Nicotine ; Cotinine ; Nasal administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Background and objectives: Arterial (A) and venous (V) plasma nicotine and cotinine concentrations were measured after nasal nicotine spray in tobacco smokers of both genders. The hypothesis for this research was that a greater A/V difference in plasma nicotine would be present in males than females because males have greater skeletal muscle mass to bind nicotine. Subjects and methods: Nine male and nine female healthy adult smokers were studied. They all abstained from use of tobacco overnight for 10 h or more prior to the study. Nicotine nasal spray was given in doses of 1–2.5 mg total, with half in each nostril while the subject was supine. Both A and V blood samples were obtained prior to and 3, 6, 10, 15, 20, and 30 min post-nasal nicotine spray. Results and conclusions: Nasal nicotine administration produced greater A than V plasma levels. There were no gender differences in A/V nicotine concentrations, disproving the above hypothesis, suggesting that other physiochemical factors besides skeletal muscle mass must be involved. Heart rate increases correlated well with arterial plasma nicotine levels (r=0.77). Males had less variance than females in the expected increase in arterial plasma nicotine concentrations with increased number of nasal sprays. Although there was considerable overlap, mean A cotinine concentrations were consistently slightly larger than V concentrations.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 264 (1991), S. 283-291 
    ISSN: 1432-0878
    Keywords: Actin fibrils ; Contractility ; Phalloidin staining ; Morphometry ; Physarum polycephalum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Fragments excised from front regions of thinspread Physarum plasmodia were used to examine a possible correlation between the periodical dynamic activity of such specimens and the spatial organization of actin fibrils. Under isotonic conditions, symmetrical contractions and relaxations of the entire fragment alternate with a period of 1–4 min, whereas under isometric conditions local contractions and relaxations occur simultaneously in different regions of the same specimen. Rapid fixation and phalloidin-staining at distinct stages of the contraction-relaxation cycle demonstrates the permanent existence of cytoplasmic actin fibrils under both isometric and isotonic conditions. During the transition from relaxation to contraction the fibrils shorten in length from 25.5 μm to 21.0 μm and increase in density from 1.2 fibrils/1000 μm2 to 2.3 fibrils/1000 μm2. The present results demonstrate that actin fibrils in Physarum plasmodia are not completely decomposed and reformed every contraction-relaxation cycle.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 50 (1991), S. 75-84 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We describe how to apply the unitary approximation to high energy scattering processes which involve the radiation of arbitrarily many photons. We compare our results to calculations of inclusive quantities using leading log resummation techniques well known from QCD. In contrast to the latter method the unitary approximation is also appropriate for differential cross sections. The Monte Carlo implementation of the method is discussed and detailed results are given for the case of radiative Bhabha scattering.
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