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  • 1
    Electronic Resource
    Electronic Resource
    Transition to global stochasticity in a driven Morse oscillator (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 743-748 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the IR multiphton excitation and dissociation process of a Morse oscillator driven by an external sinusoidal field. Primary resonances and an infinite sequence of secondary resonances have been found that can be analyzed by using Chirikov's nonlinear resonance theory. The transition threshold to global stochasticity is also estimated based on the overlap criterion. Above the threshold dynamical flows are slowed down by the presence of cantori, as clearly demonstrated by the time-dependent dissociation rates calculated for several ensembles of initial points. A scaling law is found in the vicinity of the threshold with a critical exponent in close agreement with that predicted for the standard map.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320773
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  • 2
    Electronic Resource
    Electronic Resource
    Correlations between gas permeation and free-volume hole properties probed by positron annihilation spectroscopy (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 2365-2371 
    Details
    ISSN: 0887-6266
    Keywords: positron annihilation ; positronium ; free volume ; hole ; gas permeation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Free-volume hole sizes, fractions, and distributions in a series of polycarbonate-based polymers are measured by using positron annihilation lifetime (PAL) spectroscopy. Correlations between the obtained free-volume hole properties and gas diffusion coefficients are observed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331708
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  • 3
    Electronic Resource
    Electronic Resource
    Subnanometer hole properties of CO2-exposed polysulfone studied by positron annihilation lifetime spectroscopy (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 3049-3056 
    Details
    ISSN: 0887-6266
    Keywords: positron annihilation ; free volume ; polysulfone ; CO2 gas exposure ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Positron annihilation lifetime (PAL) spectroscopy has been employed to study subnanometer hole properties in polysulfone (PSF). In this study, hole properties of size, fraction, and distribution of PSF exposed to CO2 are reported. In the PSF/CO2 system, the hole size and fraction significantly increase and the free-volume distribution broadens as a function of CO2 pressure in the range of 0-1000 psi. Hysteresis in hole properties is observed during CO2 sorption/desorption cycle. The high sensitivity of PAL results due to CO2 exposure in PSF is explained in terms of the microstructural changes in the polymer matrix, i.e., filling penetrant and plasticization, gas hydrostatic pressure effect, and creation of free volumes and holes. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3049-3056, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of high pressure on the mechanical behavior of short fiber composites (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 844-850 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Three types of pressure dependent deformation processes have been observed for the short glass fiber reinforced composites of poly(vinyl chloride) (PVC). A unique deformation behavior, observed for the first time, features a sharp drop in stress followed by shear yielding in the matrix. Competitive pressure dependent failure processes in the composites are strongly affected by “debonding” at the fiber-matrix interface. A new general pressure dependent yield criterion for PVC and its composites was elucidated.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760241103
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  • 5
    Electronic Resource
    Electronic Resource
    Acoustic emission during irreversible deformation in short fiber reinforced poly(vinyl chloride) composites (1986)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 7 (1986), S. 26-35 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Acoustic emission (AE) during irreversible deformation in short glass fiber reinforced poly(vinyl chloride) (PVC) composites was studied using a piezoelectric crystal transducer. Compared to the well-coupled composites, many more AE events were observed during tensile deformation in the poorly-coupled composites, presumably due to failure at the fiber-matrix interface. No fiber fracture was detected in the tensile tests for either well-coupled or poorly-coupled composites. Irreversibility of acoustic emission was observed in repeated tensile loading experiments. Unlike PVC, the short fiber composites fractured during stress relaxation at 1 percent elongation. Studies of acoustic emission behavior during stress relaxation indicated that interfacial debonding is a time-dependent process. Relaxation fracture time was strongly increased by chemical coupling at the interface.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750070107
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  • 6
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    Abnormal assembly of membrane proteins in erythroid progenitors of patients with beta-thalassemia major (1996)
    American Society of Hematology
    Details
    Publication Date: 1996-03-01
    Description: The life threatening anemia in beta-thalassemia major (Cooley's anemia) is characterized by profound intramedullary lysis, the cause of which is incompletely understood. Using marrow obtained from beta thalassemia major patients undergoing allogeneic bone marrow transplantation in Pesaro Italy, it became possible to directly study the mechanism of the intramedullary hemolysis. Based on our previous studies, we hypothesized that the unmatched alpha globin chains would interfere with normal assembly of erythroid precursor membrane proteins. Patient and control erythroid precursors were reacted with monospecific polyclonal rabbit antibodies directed against spectrin, band 3, and band 4.1 and with a monoclonal anti-alpha globin chain antibody. Using laser confocal fluorescence microscopy, normal erythroid precursors show no alpha globin chain accumulation and exhibited uniformly smooth rim fluorescence of the three membrane proteins. In some thalassemic precursors, spectrin appeared to interact with large alpha globin accumulations, and in many of these cells the spectin appeared clumped and discontinuous. Band 4.1 interacted strongly with accumulations of alpha globin in thalassemic precursors to produce bizarrely clumped zones of abnormal band 4.1 distribution. Band 3 was incorporated smoothly into thalassemic erythroblast membranes. However, the proerythroblasts and basophilic erythroblasts were significantly deficient in band 3. Thus, accumulations of alpha globin in beta- thalassemia major colocalized with and disrupt band 4.1 and spectrin assembly into the membrane. The cause of deficient band 3 incorporation into thalassemic proerythroblast membranes remains unknown. These profound membrane alterations would likely contribute to the intramedullary lysis seen in Cooley's anemia.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology
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  • 7
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    Nonrandom association of free iron with membranes of sickle and beta- thalassemic erythrocytes (1993)
    American Society of Hematology
    Details
    Publication Date: 1993-11-15
    Description: To further define the nature of abnormal iron deposits on the membranes of pathologic red blood cells, we have used sickle cell anemia (HbSS), HbSC, and beta-thalassemic erythrocytes (RBCs) to prepare inside-out membranes (IOM) and insoluble membrane aggregates (AGGs) containing coclustered hemichrome and band 3. Study of IOM from HbSC and thalassemic patients showed that amounts of heme iron and, especially, free iron were much higher in patients who had undergone surgical splenectomy. The membrane AGGs from HbSS and beta-thalassemic RBCs contained much more globin than heme, with this discrepancy being variable from patient to patient. Although these AGGs were enriched (compared with the ghosts from which they were derived) for heme, as expected, less than 10% of total ghost heme was recovered in them. Remarkably, these AGGs also were enriched for nonheme iron, markedly so in some patients. Iron binding studies showed that the association of free iron with these hemichrome/band 3 AGGs is explained by the fact that free iron binds to denatured hemoglobin. These results document that free iron is nonrandomly associated with the membranes of sickle and beta-thalassemic RBCs. Whether this plays a causative role in the premature removal of such cells from the circulation remains to be seen.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology
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  • 8
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    Defective assembly of membrane proteins in erythroid precursors of beta- thalassemic mice (1994)
    American Society of Hematology
    Details
    Publication Date: 1994-07-15
    Description: beta-Thalassemic mice provide a useful model for studying the pathophysiology of human beta-thalassemia in that one can perform experiments that are difficult to perform in humans. The ease of access to beta-thalassemic mouse marrow provided the opportunity to explore the cause of the ineffective erythropoiesis that characterizes severe beta-thalassemia in mouse and man. We hypothesized that the accumulation of excess alpha-globin might interfere with the normal assembly of red blood cell (RBC) membrane proteins, thus contributing to the severe intramedullary lysis. Femoral marrow was obtained from normal and beta-thalassemic mice, and RBC precursors were purified (〉 90%) by panning and harvesting CD45- cells. The assembly of RBC membrane proteins was assessed by observing immunofluorescence patterns obtained on fixed permeabilized precursors using rabbit polyclonal antibodies directed against human spectrin, and band 4.1, and murine band 3. The distribution of the proteins was shown with a fluorescein- tagged goat antirabbit antibody. In contrast to normal mice, about 30% of intermediate and late stage erythroblasts in beta-thalassemic mice appear abnormal. Neither spectrin nor band 4.1 formed crisp rim fluorescence in these erythroid precursors of thalassemic mice, whereas assembly of band 3 appeared normal. Therefore, the assembly of membrane skeletal proteins is abnormal in murine beta-thalassemic erythroid precursors perhaps because of the deposition of unmatched alpha-globin chains.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology
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  • 9
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    Characterization of the autologous antibodies that opsonize erythrocytes with clustered integral membrane proteins (1993)
    American Society of Hematology
    Details
    Publication Date: 1993-06-01
    Description: In earlier studies we presented evidence that the clustering of the integral membrane protein, band 3, can serve as a signal for immune recognition and clearance of senescent or abnormal erythrocytes from circulation. In this study, we have exploited the capacity of 1 mmol/L Zn+2 to mildly and reversibly cluster band 3 in situ to characterize the nature of the autologous antibodies specific for the clustered state. We report that the autologous IgG elute almost exclusively in a high molecular weight complex with other proteins when C12E8 detergent extracts of Zn clustered membranes are chromatographed on Sepharose CL- 6B. The complex was also seen to contain complement component C3, hemoglobin, and a cross-linked oligomer of band 3. Autologous IgG and complement were virtually absent from all other fractions. When the band 3 clusters were disaggregated by removal of the Zn+2, the autologous IgG eluted from the erythrocyte surface. Collection of this IgG and use of the antibody in immunoblots of erythrocyte membranes showed that the band 3 monomer, dimer, and oligomers were the major antigenic species. Except for a minor unidentified band at approximately 78,000 d, no other proteins were significantly stained. Curiously, band 3 showed an uneven staining pattern, with oligomers and the leading edge of the monomers appearing more intensely than expected from their abundances in the Coomassie blue-stained gels. Typing of the same autologous IgG with monoclonal antibodies specific for the different subclasses of IgG showed the presence of only subtypes 2 and 3. Taken together, these data suggest that a specific population of autologous IgG recognizes sites of integral membrane protein clustering (a common lesion in senescent and abnormal red blood cells) and that the antigen within these clusters involves an aggregated state of band 3.
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    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology
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  • 10
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    Isolation, characterization, and immunoprecipitation studies of immune complexes from membranes of beta-thalassemic erythrocytes (1992)
    American Society of Hematology
    Details
    Publication Date: 1992-06-01
    Description: beta-Thalassemia, a hemoglobinopathy that results in the precipitation of denatured alpha-globin chains on the membrane, is characterized by erythrocytes with significantly reduced lifespans. We have demonstrated previously that hemoglobin denaturation on the membrane can promote clustering of integral membrane proteins, and that this clustering in turn leads to autologous antibody binding, complement fixation, and rapid removal of the cell by macrophages. To evaluate whether this pathway also occurs in beta-thalassemic cells, we have isolated and characterized the immune complexes from the membranes of these cells. We observe that autologous IgG-containing complexes obtained by either immunoprecipitation or simple centrifugation of nondenaturing detergent extracts of beta-thalassemic cell membranes contain globin, band 3, IgG, and complement as major components. Absorption spectra of these complexes demonstrate that the globin is, indeed, mainly in the form of hemichromes. Immunoblotting studies further show that much of the band 3 protein in the aggregates is covalently cross-linked to a dimeric or tetrameric form, consistent with the preference of the autologous IgG for clustered band 3. Although the insoluble aggregates constitute only approximately 1.6% of the total membrane protein, they still contain 27% of the total IgG and 35% of the total complement C3 on the thalassemic cell surface. Because cell surface IgG and complement component C3 are thought to trigger removal of erythrocytes from circulation, the hemichrome-induced clustering of band 3 may contribute to the beta-thalassemic cell's shortened lifespan.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology
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