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  • 1
    Digitale Medien
    Digitale Medien
    Chaos in one-dimensional lattices under intense laser fields (2000)
    Springer
    The European physical journal 14 (2000), S. 329-335 
    Details
    ISSN: 1434-6036
    Schlagwort(e): PACS. 78.90.+t Other topics in optical properties, condensed matter spectroscopy and other interactions of particles and radiation with condensed matter - 05.45.-a Nonlinear dynamics and nonlinear dynamical systems
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract: A model is investigated where a monochromatic, spatially homogeneous laser field interacts with an electron in a one-dimensional periodic lattice. The classical Hamiltonian is presented and the technique of stroboscopic maps is used to study the dynamical behavior of the model. The electron motion is found to be completely regular only for small field amplitudes, developing a larger chaotic region as the amplitude increases. The quantum counterpart of the classical Hamiltonian is derived. Exact numerical diagonalizations show the existence of universal, random-matrix fluctuations in the electronic energy bands dressed by the laser field. A detailed analysis of the classical phase space is compatible with the statistical spectral analysis of the quantum model. The application of this model to describe transport and optical absorption in semiconductor superlattices submitted to intense infrared laser radiation is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s100510050137
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  • 2
    Digitale Medien
    Digitale Medien
    Molecular Dynamics Simulations on the Complexes of Glucoamylase II (471) from Aspergillus awamori var. X100 with 1-Deoxynojirimycin and Lentiginosine (1997)
    Springer
    Journal of molecular modeling 3 (1997), S. 249-260 
    Details
    ISSN: 0948-5023
    Schlagwort(e): Keywords: Glycosidase inhibitors ; protein-substrate adduct ; enzyme cavity ; azasugar ; polyhydroxylated indolizidines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Molecular dynamics (MD) simulations on the complexes of glucoamylase II (471) from Aspergillus awamori var. X100 with two powerful inhibitors, 1-deoxynojirimycin and (+)-lentiginosine, have been performed, in order to build a model for these complexes in solution and to clarify the structure-activity relationship. MD calculations were carried out for 105 ps, over a 15 Å sphere centered on the inhibitors. A 8 Å residue-based cut-off was used, and the calculations were performed with explicit inclusion of solvent molecules. The MD structure of the complex 1-deoxynojirimycin-glucoamylase shows only minor deviations from the available X-ray structure. The MD structure of the complex of (+)-lentiginosine-glucoamylase, obtained by docking the inhibitor into the active site, suggests us a suitable orientation for the molecule into the enzyme cavity, which can rationalize the high inhibition activity found for (+)-lentiginosine towards amyloglucosidase from A. niger.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s008940050037
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  • 3
    Digitale Medien
    Digitale Medien
    Measurement of the phase anisotropy of very high reflectivity interferential mirrors (1997)
    Springer
    Applied physics 65 (1997), S. 351-355 
    Details
    ISSN: 1432-0649
    Schlagwort(e): PACS: 42.70; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: -7  rad to 2×10-6 rad.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003400050283
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  • 4
    Digitale Medien
    Digitale Medien
    Existence theorems concerning simple integrals of the calculus of variations for discontinuous solutions (1987)
    Springer
    Archive for rational mechanics and analysis 98 (1987), S. 307-328 
    Details
    ISSN: 1432-0673
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00276912
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  • 5
    Digitale Medien
    Digitale Medien
    Salmon calcitonin and cGMP production by human kidney: Studies in vivo and in vitro (1983)
    Springer
    Calcified tissue international 35 (1983), S. 273-278 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Calcitonin ; Cyclic GMP ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary In order to evaluate whether or not the action of salmon calcitonin (sCT) at the kidney level could be mediated through specific receptors for the hormone, we have studied the effects of sCT infusions on urinary excretion of cyclic nucleotides in humans. Parallel in vitro studies have been conducted by evaluating the effects of sCT on cyclic nucleotide levels in primary cultures of cortical and medullary human kidney cells. In vivo experiments showed that sCT induced an increase in cGMP in human urine, which was rapid and short-lasting, being superimposable on the increase of urinary excretion of calcium and magnesium. The increase of inorganic phosphate urinary excretion was delayed and appeared to parallel that of urinary cAMP. On the other hand, our in vitro experiments showed that sCT stimulated the guanylate cyclase—cGMP system of human kidney cortical cells at nanomolar concentrations, while higher concentrations of the hormone were required to activate the adenylate cyclase—cAMP system. In addition, sCT was not able to significantly modify the cellular levels of either nucleotide in human kidney medullary cells. Present data demonstrated a direct effect of sCT on human kidney cortical cGMP production, while the efficacy of sCT on the kidney cortex adenylate cyclase—cAMP system appears to be delayed and/or reduced.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02405045
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  • 6
    Digitale Medien
    Digitale Medien
    Bone endothelial cells as estrogen targets (1993)
    Springer
    Calcified tissue international 53 (1993), S. 312-317 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Bone endothelium ; Estrogen receptors ; Parathyroid hormone response ; Angiogenesis ; Bone remodeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary In the present study, we investigated the effects of estrogens on bone endothelial cell metabolism and the presence of estrogen binding sites in the same cells. For these studies, we have used a continuous cell line of clonal bovine bone endothelial cells for evidence of a direct response to estrogensin vitro. Receptor analysis to intact viable cells was steroid specific and saturable, with an apparent dissociation constant of 17.2 nM and a Bmax of 3.2 × 104 sites/cell. Northern blot analysis revealed a 6.5-kilobase mRNA that hybridized with a cDNA to human estrogen receptor. The 6.5-kilobase size is in close agreement with the reported size of the human estrogen receptor mRNA.In vitro estrogen responses of bone endothelial cells included a stimulation of cell proliferation as well as an inhibition of parathyroid hormone responsiveness. These findings clearly demonstrate the presence of functional estrogen receptors in bone endothelial cellsin vitro, suggesting a role of estrogens in bone angiogenesis and in the entire process of bone remodeling.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01351835
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  • 7
    Digitale Medien
    Digitale Medien
    Adhesion, growth, and matrix production by osteoblasts on collagen substrata (1992)
    Springer
    Calcified tissue international 51 (1992), S. 202-212 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Osteoblasts ; Collagen type I ; “On gel” cultures ; Collagen sponges ; Osteocalcin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary A number of studies have demonstrated the pivotal role of collagen molecules in modulating cell growth and differentiation. In order to analyze the direct effects of collagen type I on the osteoblastic phenotype, we have devised an in vitro culture system for studying the interactions between bovine collagen type I and Saos-2 cells, a human osteoblastic cell line. Saos-2 cells were cultured both on top of collagen-coated culture dishes as well as inside a three-dimensional collagen network. Plating on dishes treated with collagen induced maximal adhesion of Saos-2 cells after 24-hour incubation. Cells cultured on collagen gel matrix expressed about 2.5-fold more alkaline phosphatase when compared with untreated plastic dishes. On collagen-coated dishes the responsiveness of Saos-2 cells to parathyroid hormone was decreased, whereas no modifications were observed in the effect of vasoactive intestinal peptide on these cells. Using a microfluorimetric measurement of DNA, an increase of proliferation was observed in Saos-2 cells cultured on collagen gel Saos-2 cells were also able to colonize collagen sponges and in this three-dimensional network they were able to synthesize osteocalcin, as assessed both by immunocytochemistry and radioimmunoassay. In this study we have demonstrated that bovine collagen type I exhibits favorable effects on attachment and functional and growth activities of a human osteoblastic cell line, encouraging its use as a bone graft material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00334548
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  • 8
    Digitale Medien
    Digitale Medien
    Effects of Ipriflavone on Perialveolar Bone Formation (1998)
    Springer
    Calcified tissue international 63 (1998), S. 312-319 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Key words: Ipriflavone—Bone formation—Rat perialveolar bone—Periodontal ligament—Osteoblasts.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract. The effect of ipriflavone (IP), a synthetic isoflavonoid derivative, on in vivo bone formation was studied in rat perialveolar bone by surgically producing a hole in the mandibular bone. The holes were filled either with powdered IP or with compounds containing no osteoinductive properties such as biostite and Htr (hard tissue replacement). In control animals, the holes were left to heal spontaneously. The animals were killed 3, 28, and 40 days after surgery and a detailed morphological and morphometric study was performed on the perialveolar bone surrounding the wounds. Three days after surgery (inflammatory phase) the bone wounds were occupied by hemorragic and inflammatory cells in both the untreated and IP-treated bone defects. Twenty-eight days after surgery, bone formation was evident with new bone spiculae particularly concentrated in the area of the bone lesion closest to the adjacent periodontal ligament. Morphometric measurements of the areas occupied by new bone showed that the synthesis of perialveolar bone was significantly stimulated by IP. The repair of the bone defects by new bone formation progressed by day 40, but only in the presence of IP were the original holes almost completely repaired. Conversely, biostite and Htr did not influence promotion of new bone formation. In conclusion, the results of the present study are consistent with a role of IP in stimulating osteogenesis and suggest that this compound could represent a potential therapeutic tool to promote repair of injured perialveolar bone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002239900533
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  • 9
    Digitale Medien
    Digitale Medien
    Investigation on the corrosion of brazed joints by means of scanning auger microprobe (1987)
    Springer
    Microchimica acta 91 (1987), S. 409-427 
    Details
    ISSN: 1436-5073
    Schlagwort(e): brazed joints ; corrosion ; Auger ; microanalysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract As a model experiment for the corrosion behaviour of brazed joints in water pipes made of stainless steel, some tens ofμan broad joints made of three different brazes (Ag/Cu/In/Ni, Ag/Cu/Sn, Ag/Cu) were exposed to streaming water at different Cl− concentrations. The samples were polarized. The three-dimensional distribution of the corrosion products, obtained by Auger mapping and depth profiling, supplied some information about the corrosion behaviour of the joints.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01199517
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  • 10
    Digitale Medien
    Digitale Medien
    Sequence of different types of nonlinear current oscillation in n-GaAs (1989)
    Springer
    Applied physics 48 (1989), S. 143-147 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 05.40 ; 72.70 ; 72.20J
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Self-generated chaotic current fluctuations in the post-breakdown regime of a n-GaAs layer at 4.2 K have been analyzed in detail. Without an external magnetic field only regular oscillations were observed. Increasing the magnetic field strength up to 100 mT generates a sequence of quasiperiodic and frequency-locking current oscillations and finally a Ruelle-Takens-Newhouse scenario with chaos. This may be understood by assuming two coupled oscillatory processes caused by dielectric relaxation and energy relaxation in the distribution of free carriers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01141276
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