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  • Springer  (60)
  • Wiley  (10)
  • 1
    Electronic Resource
    Electronic Resource
    The role of the nuclear spin in optical pumping withD 2-light (1972)
    Springer
    The European physical journal 255 (1972), S. 14-24 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Optical pumping withD 2-light provides an excellent means for studying collisional relaxation in the excited2 P 3/2-state of alkali atoms. Collisional relaxation of orientations in that state very sensitively affects the spin orientation in the ground state. All these orientations may be easily created by absorption of σ+- or σ{−{-light. At a certain strength of the relaxation realized by a certain buffer gas pressure, the spin orientation in the ground state even vanishes, providedD 2-light is used for excitation. The condition for this situation is derived from the set of rate equations which governs the evolution of all the orientations involved. These conditions very markedly depend on the nuclear spin valueI. The validity of this dependence has been checked by magnetic decoupling of the nuclear spin and observing the associated shift of the pressure for vanishing spin orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01391668
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  • 2
    Electronic Resource
    Electronic Resource
    Multi-species detection in spray flames with tunable excimer lasers (1993)
    Springer
    Applied physics 56 (1993), S. 165-176 
    Details
    ISSN: 1432-0649
    Keywords: 33.20.Fb ; 35.80 ; 82.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Planar imaging with tunable excimer-laser sheet illumination is used to determine spatial distributions of different species in liquid-fuelled spray flames of commercial oil burning furnaces. Two burner configurations, which differ only in the fuel/air mixing devices, are investigated to understand why one configuration yields 30% less NOx emission. Iso-octane and n-heptane fuels are used. To understand the origin for NOx reduction spatial distributions of reactants (fuel, O2), the reaction intermediate OH and the pollutant NO are recorded. OH and O2 are measured by LIPF, NO by LIF. Fuel distributions are determined by another broad-band emission, whose origin is not yet identified. Both single shot and averaged distributions are recorded. The averaged distributions are extremely reproducible and depend sensitively on details of the burner geometry and the fuel/air mixing device. They can clearly be used to distinguish fine details in different injection systems. The spatial distribution of different species relative to each other yield considerable insight in the differences between the two combustion processes. On the basis of purely qualitative visualization it is possible to understand the origin for NOx reduction: it results from faster injection of air in the one fuel/air mixing device.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332196
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  • 3
    Electronic Resource
    Electronic Resource
    Planar imaging of a laboratory flame and of internal combustion in an automobile engine using UV rayleigh and fluorescence light (1993)
    Springer
    Applied physics 56 (1993), S. 177-184 
    Details
    ISSN: 1432-0649
    Keywords: 82.40.Py ; 33.20.Fb ; 33.20.Lg ; 35.80.+s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Rayleigh scattering of tunable excimer laser light (193 nm and 248 nm) is used to obtain 2-D images of the distribution of total densities in a laboratory flame and in a cylinder of an automobile engine. Because the UV light is very strongly scattered, there is ample signal and there is excellent contrast of Rayleigh light against surface scattered light, even in the small volume of the engine cylinder. The laboratory flame data are converted to an image of the temperature field. The Rayleigh images are compared with those from planar laser induced predissociative fluorescence, which yield state-specific densities of selected molecules. The experimental arrangement is the same except for the selection of laser wavelength and the filtering of the radiated light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332197
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  • 4
    Electronic Resource
    Electronic Resource
    On depth-dependence of photospheric oscillations (1979)
    Springer
    Solar physics 64 (1979), S. 13-25 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on results from photographic observations of photospheric oscillations as a function of depth. Using rms-values and power-spectra from shifts of entire line-profiles, we find qualitatively an increase of the velocity-amplitude with increasing height. We get more quantitative informations by comparing measured asymmetries of line-profiles with calculated ones derived from Voigt-functions containing a depth dependent velocity-field. We find the scale-height H 0 of photospheric velocity oscillations to be 930±100 km. This result is to be compared with H 0 = 1100±200 km obtained by Canfield (1976), who used velocity weighting functions of the line centres. Further, we show that a general observed line asymmetry of medium strong lines (c-shape) does not depend on the phase of oscillations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151112
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  • 5
    Electronic Resource
    Electronic Resource
    On diurnal variations of the solar rotation rate as derived from sunspot tracings (1981)
    Springer
    Solar physics 71 (1981), S. 395-399 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The heliographic positions of more than 100 sunspots were accurately measured several times a day from 1974 until 1979 by means of the computer-controlled tracing method described by Schröter and Wöhl (1975). A striking degree of constancy of the solar rotation rate (about 0.15% or 3 m s−1) is found, when east-west proper motion components of each individual stable sunspot is considered. However, large differences of the rotation rate are observed (up to 7% or 130 m s−1) when comparing different sunspots. We found no significant correlation of these fluctuations with characteristics of the sunspots (age, evolution, etc.).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167561
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  • 6
    Electronic Resource
    Electronic Resource
    Metastable equilibrium with random local fluctuations: Simulations of dynamic receptor pattern generation in a fluid mosaic membrane (1982)
    Springer
    Biological cybernetics 44 (1982), S. 121-128 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The generation of receptors in the animal cell's membrane was simulated by a model consisting of units in four possible states within a hexagonal area (playboard) ofn units of a triangular network. The state of each unit was determined by the previous state or itself and of its six nearest neighbours, as regulated by a set of transition rules, which kept the mean relative frequency (m.r.f.) of each state constant. The transition rules were applied to the system exactlyn times, regardedless whether this involved selection of a unit on 0, 1, 2 or more occasions (programme “random selection with repeat”; RS-R). Comparison to previous results obtained by other ways of application of the rules has shown that the RS-R programme accounted for the highest m.r.f. of quiet (Q) units and Q clusters (sub-patterns), and also for the longest survival of Q configurations through several generations. Functioning of the model under the RS-R programme simulates an integrated system in metastable equilibrium with random local fluctuations, such as the cytoplasmic membrane is imagined to be in standardized environmental conditions. The formation-persistence-disintegration cycle of the sub-patterns is believed to simulate the dynamic generation of transitory receptor configurations in the cell membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317971
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  • 7
    Electronic Resource
    Electronic Resource
    A simple model of dynamic receptor pattern generation (1979)
    Springer
    Biological cybernetics 32 (1979), S. 125-138 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A dynamic pattern generating automaton has been constructed. The rules controlling its function furnish the non-random generation of sub-patterns in consecutive cycles, within a large plane area, covered by four different classes of units of constant mean frequency in each class (standard system). The stabilization of certain specific sub-patterns over 100 subsequent cycles of pattern generation (modified systems) resulted in the modification of the frequency and frequency distribution of the sub-patterns relative to the standard system. Some new types of sub-patterns, not encountered in the standard system, also made appearance in the modified systems. The functioning of the standard and modified systems was analyzed and compared by the methods of mathematical statistics. The automaton was used to model certain features of the cytoplasmic membrane. The latter was regarded as a device by which the cell collects information about its environment. The dynamic generation of sub-patterns was taken as the cell's manner of asking questions, and the complementary chemical structures present in the environment were treated as possible answers to these. The irreversible question-answer interactions were regarded as signals and were modelled by the stabilization of specific sub-patterns. It was found that in a dynamic system like the model presented, it is not necessary to code each possible sub-pattern individually. Precise coding of the relative frequency of units per class and of their possible interactions is sufficient to furnish statistically constant mean frequencies for a given range of sub-patterns. In a dynamic system, the actual range of sub-patterns arisen in a population of identical individuals depends only on the size of the population. If the latter is appropriately large, all possible sub-patterns may be simultaneously present at any time at the average frequencies characteristic of each. Stabilized sub-patterns (signals) seem to modify specifically the frequencies of the other sub-patterns generated by the normal automaton. Some sub-patterns may disappear permanently, while others (new ones) may turn up and persist at given frequencies. Missense signals may definitively put the automaton out of order, i.e. result in the cell's complete misorientation in respect of its relations to the normal tissue structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337389
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  • 8
    Electronic Resource
    Electronic Resource
    An advanced version of the dynamic receptor pattern generation model: The flux model (1981)
    Springer
    Biological cybernetics 39 (1981), S. 105-109 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract In the recently described simple model of dynamic receptor pattern generation we used a two-dimensional hexagonal area of a regular triangular network, formed by a statistically constant distribution of unit electrostatic charges in a dynamic equilibrium. A set of 16 transition rules was applied to all units simultaneously; the next state of each unit depended only on the previous state of its six nearest neighbours, and the transition of the total pattern into the new one occurred in a single jump. Hence we designated the initial simple model as “jump model”. In this paper we describe an advanced version of the model, in which simplified rules are applied to one unit after the other in a sequential order, from left to right, starting with the top row of units. In the advanced version the state of a unit depends not only on that of its six nearest neighbours, but also on the state of all units preceding in sequence the one actually considered. This results in flux-like transitions. We therefore designated the advanced version as the “flux model”. It is shown that the flux model represents a closer approximation of physical and biological realities than the original jump model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336736
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  • 9
    Electronic Resource
    Electronic Resource
    Etude du Comportement Thermique de la Cellulose par Spectroscopie Infra Rouge II. Analyse in situ des évolutions spectrales entre 25 et 450°C (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 765-772 
    Details
    ISSN: 1572-8943
    Keywords: cellulose ; infrared spectroscopy ; in situ analysis ; thermal behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The part I of this work discusses the potentialities and limits of the in situ spectroscopic analysis of cellulose by Diffuse Reflectance Infrared Fourier Transform in an environment device. In this paper, we describe: the in situ evolutions of cellulose from 25 to 270°C under N2 or air; the evolution of a partially thermolyzed cellulose residue during thermal treatment from 25 to 450°C and finally the oxidation in air of a cellulose char at 300°C. We observe a limited evolution of the cellulose below 270°C. Only some carbonyle groups issued from rearrangement of cellulose chains are formed. The thermal treatment of the thermolyzed residue leads to a progressive aromatization of the solid between 270 and 450°C. The oxidation in air induces the formation of oxygenated groups (carbonyles, carboxylic acids, lactones) and proceeds by reaction on both aliphatic and aromatic sites. Some dehydration of carboxylic groups to anhydrides are observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010113329022
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  • 10
    Electronic Resource
    Electronic Resource
    The Influence of Structure and Lipophilicity of Hydantoin Derivatives on Anticonvulsant Activity (1999)
    Springer
    Structural chemistry 10 (1999), S. 355-366 
    Details
    ISSN: 1572-9001
    Keywords: Log P ; hydantoins ; anticonvulsant activity ; RP-HPLC ; pharmacophor model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The lipophilicity of a representative number of hydantoin derivatives was experimentally determined by RP-HPLC. The stationary phase of RP-HPLC proved a good model to simulate effects of membrane transport. These experimental values were correlated to theoretically estimated lipophilicity values on the basis of global minima structures of the compounds studied. Both these lipophilicity and structure similarities within a proposed pharmacological model for binding the hydantoin derivatives along the sodium channel were classified with respect to their biological activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022091411018
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