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  • 1
    Electronic Resource
    Electronic Resource
    Self-consistent approach for the two-dimensional Ising model with random bonds (1992)
    Springer
    The European physical journal 89 (1992), S. 361-368 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A system of random fermions withN colors is investigated. This model corresponds forN=4 to the two-dimensional Ising model with random bonds. The limitN→∞ can be treated exactly and leads to a self-consistent description which has a disordered phase between the high-and low-temperature phase of the pure system. We find that higher order moments of the random bond distribution, which appear in the 1/N-expansion, do not affect the qualitative picture of the self-consistentN→∞-limit. Moreover, we compare the specific heat for finite size systems with recent Monte Carlo results of Wang et al., and find excellent agreement. A comparison with the Monte Carlo data enables us to fix the renormalization of the disorder parameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01318169
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  • 2
    Electronic Resource
    Electronic Resource
    Lack of autoreceptor mediated regulation of the spontaneous dopamine turnover in the isolated neurointermediate lobe of the rat pituitary gland in vitro (1990)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 341 (1990), S. 182-185 
    Details
    ISSN: 1432-1912
    Keywords: Dopamine synthesis ; Dopamine autoreceptor ; Neurointermediate lobe ; Apomorphine ; Sulpiride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Isolated neurointermediate lobes of the rat pituitary gland were incubated in Krebs-HEPES solution and the spontaneous outflow of endogenous dopamine and its metabolites (DOPAC, HVA and MOPET) was determined by HPLC with electrochemical detection. The spontaneous outflow of dopamine metabolites (about 1500 fmol/10 min) largely exceeded that of dopamine (about 60 fmol/10 min). Apomorphine concentration-dependently (IC50, 205 nmol/l) reduced the spontaneous out-flow of the dopamine metabolites. The effect of apomorphine developed slowly and was progressive over an observation period of 70 min. After 1 h of exposure to a maximall effective concentration of apomorphine (10 gmol/l), the out-flow of metabolites was inhibited by 43%. The effect of apomorphine was not affected by the dopamine D2 receptor antagonist (−)-sulpiride nor by the dopamine D1 receptor antagonist SCH 23390. Neither quinpirole nor fenoldopam significantly affected the spontaneous outflow of dopamine metabolites. It was previously shown that the high rate of spontaneous outflow of dopamine metabolites from the dopaminergic nerves in the neurointermediate lobe reflects largely the immediate catabolism of newly synthesized dopamine. This high rate of spontaneous dopamine synthesis in the neurointermediate lobe is not controled by dopamine autoreceptors. Apomorphine appears to inhibit the spontaneous dopamine turnover by an inhibition not mediated by dopamine receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169728
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  • 3
    Electronic Resource
    Electronic Resource
    Relationship between electroultrafiltration (EUF) extractable nitrogen, grain yield, and optimum nitrogen fertilizer rates for winter wheat (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 37-43 
    Details
    ISSN: 1573-0867
    Keywords: nitrogen fertilizer rate ; electroultrafiltration ; wheat ; soil test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of the investigation was to examine whether there exist relationships between the optimum nitrogen fertilizer rate for winter wheat and soil nitrogen fractions extracted by electroultrafiltration (EUF) from autumn samples of the upper soil layer (0–30 cm). Optimum nitrogen fertilizer rates were derived from grain yield curves of field trials carried out with increasing nitrogen fertilizer rates on 19 different sites in 1985/86 and 1986/87. Most soils were luvisols derived from loess, two soils were brown earths and one a pararendzina. Total Nitrogen fertilizer rates were 0, 40, 80, and 120 kg N/ha applied twice before ear emergence. The final nitrogen rate at ear emergence was the same for all treatments, namely 60 kg N/ha. Optimum nitrogen fertilizer rates were derived from the grain yield curve fitted to a modified Mitscherlich equation. The optimum nitrogen fertilizer rates were correlated with the nitrogen fractions extracted by EUF. The regression equation thus obtained showed that NO 3 - , the organic N fraction (EUF Norg), and the EUF Norg-quotient each had a highly significant impact on the optimum nitrogen fertilizer rate. The higher the amounts of EUF-N extracted the lower the optimum nitrogen rate. Substituting the EUF Norg-fraction for total nitrogen concentration in the upper soil layer gave a poorer relationship between the optimum nitrogen fertilizer rate and the soil data. In absolute terms the EUF Norg-fraction had by far the greatest impact on calculating the optimum nitrogen fertilizer rate. The investigation shows that the EUF method is a suitable technique for the determination of available soil nitrogen from which optimum nitrogen fertilizer rates can be derived for winter wheat cultivated under soil and climatic conditions typical for cereal growing areas in central Europe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01054392
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  • 4
    Electronic Resource
    Electronic Resource
    Preoperative staging of gastrointestinal tumors by endosonography (1990)
    Springer
    Surgical endoscopy and other interventional techniques 4 (1990), S. 154-160 
    Details
    ISSN: 1432-2218
    Keywords: Preoperative staging ; Gastrointestinal tumors ; Endosonography ; Esophagus ; Stomach ; Rectum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intracavitary application of ultrasound was first performed for diagnostic purposes in 1967; since that time, it has been more and more widely used. As far as the gastrointestinal tract is concerned, endoscopically controlled ultrasonic probes provide visualization of the various layers of the intestinal wall. It is therefore possible to describe lesions of the esophagus, stomach, and the rectum with regard to their nature and depth of infiltration. Furthermore, periesophageal and perigastric organs can be visualized. It has become evident that endosonography is particularly important for pretherapeutic staging of tumors of the esophagus, stomach, and rectum. Here prospective comparative studies confirm the superiority of this new diagnostic procedure when compared to the methods available to date.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02336595
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  • 5
    Electronic Resource
    Electronic Resource
    Clonal derivatives of a human B-lymphoblastoid cell line producing prolactin—A cytogenetic characterization (1990)
    Springer
    Cytotechnology 3 (1990), S. 43-50 
    Details
    ISSN: 1573-0778
    Keywords: hPRL ; B-lymphoblastoid cell line ; karyotype
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The IM-9-P cell line is a variant of the human B-lymphoblastoid cell line IM-9 which ectopically secretes prolactin (hPRL). The heterogeneous line IM-9-P and three sublines of clonal origin, two of them positive and one negative for PRL gene expression, were subjected to cytogenetic analysis and compared with the reference line IM-9 which showed a normal female diploid karyotype. G-banding revealed several rearrangements in the chromosomes. Nine altered chromosomes including one stable marker chromosome were common to all analysed karyotypes of IM-9-P cells and their clones. A second marker chromosome ‘mar2’ occurred only in the karyotypes of the hPRL producing clones, but not in the non-producing clone. None of the visible alterations involve chromosome 6 which carries the PRL gene in humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365265
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamics of flux lines: thermal fluctuations (1991)
    Springer
    The European physical journal 82 (1991), S. 163-169 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A relaxational dynamics for ad-dimensional model of flux lines is investigated. The flux lines are subject to thermal fluctuations such that they form a “flux liquid” rather than a flux lattice. We find that the density-density auto correlation function decays as (logt/t 2)2 for large timest∼∞. In contrast, this correlation function decays for point-like vortices ast −2. At the transition to an empty lattice (Abrikosov-Meissner transition), the auto correlation function decays as a power law with dimension-dependent exponentsd+2 for flux lines andd for point-like vortices. Therefore, the fluctuations and the interactions of long flux lines have an accelerating effect on the relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01324321
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of anisotropy in the Abrikosov phase of copper oxide superconductors (1991)
    Springer
    The European physical journal 82 (1991), S. 335-338 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A “flux liquid” serves as a model for the Abrikosov phase of a type II superconductor with short coherence length and strong fluctuations. Here we discuss the effect of anisotropy due to the planes in the material and disorder due to impurities in terms of the density-density correlation function. We find that both effects change the qualitative behavior of the correlation lengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01357175
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  • 8
    Electronic Resource
    Electronic Resource
    Symmetries and broken symmetries in a model of disordered polyacetylene (1990)
    Springer
    The European physical journal 78 (1990), S. 281-288 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A random model on a chain is considered as a description of doped polyacetylene. Its Hamiltonian is invariant under a discrete chiral transformation. The density of states at the center of the band gap serves as an order parameter for symmetry breaking. We find that the randomness breaks the symmetry spontaneously. This result is in opposition to previous calculations in the continuum limit, where the symmetry is preserved. A consequence of the non-vanishing density of states is a non-vanishing conductance for the half-filled band due to thermal activated hopping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01307847
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  • 9
    Electronic Resource
    Electronic Resource
    Diffusion of flux lines in a random potential (1991)
    Springer
    The European physical journal 84 (1991), S. 17-30 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A liquid of flux lines in a random superconductor is considered. We find spontaneous breaking of a continous internal symmetry from averaging over the random potential. A corresponding Goldstone mode describes diffusion of the flux lines. The diffusion coefficient vanishes if we exceed a critical strength of randomness. This is accompanied by a divergent correlation length. An interpretation of the behavior is a “freezing” transition of the flux liquid into a glass-like state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01453754
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  • 10
    Electronic Resource
    Electronic Resource
    Quasiparticle states in disordered superfluids (1992)
    Springer
    The European physical journal 86 (1992), S. 33-38 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A model for disordered superfluids and superconductors is considered in terms of the Bogoliubov-de Gennes equation with a random order parameter field. Two characteristic cases are distinguished: model I with a real order parameter (time reversal invariant system) and model II with a complex order parameter (broken time reversal invariance). The fluctuations of the order parameter close the gap in both models, and we investigate the states at the center of the filled gap. The two models have distinctive properties in terms of the quasiparticle states due to different symmetries. Model II exhibits only localized quasiparticle states at the band center. In contrast, the fluctuations of the real order parameter of model I can be described by a nonlinear sigma model which leads to a transition from localized to extended states for dimensionsd〉2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323544
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