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  • Chemistry  (16)
  • Environment Pollution  (9)
  • Molecular Sequence Data  (4)
  • LUNAR AND PLANETARY EXPLORATION
  • 1995-1999  (29)
  • 1998  (29)
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  • 1995-1999  (29)
Year
  • 1
    Electronic Resource
    Electronic Resource
    A theory for quasi-steady single-step thermal degradation of polymers (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 22 (1998), S. 109-118 
    Details
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A theory for approximately steady thermal degradation of solids is developed from a superset of nonlinear integral-differential equations. The theory extends previous work, using a degradation model that is more consistent than previously published models and fully accounts for surface radiation losses. The thermal decomposition of the solid is assumed to follow a single-step first-order Arrhenius reaction. A quasi-steady regime is identified and approximate solutions are compared with experimental results for PMMA and numerical results obtained by integrating the full model. The numerical solutions are found to compare well with experimental results and the approximate solutions compare well with the numerics. Furthermore, it is found that the quasi-steady mass loss rate gives a good estimate of the average mass loss rate even during thermally thin degradation. To simplify interpretation and to aid the analysis, the degradation kinetics are re-cast in terms of a critical temperature and a critical temperature range. Application of the theory to practical situations and other modelling approaches is also discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 14 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Interfacial phenomena: An in vitro study of the effect of calcium phosphate (Ca-P) ceramic on bone formation (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 464-474 
    Details
    ISSN: 0021-9304
    Keywords: calcium phosphate coatings ; magnetron sputtering ; osteoblast ; in vitro ; bone ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In previous studies we developed a RF magnetron sputter technique for the production of thin Ca-P coatings. With this technique coatings can be produced that vary in Ca/P ratio as well as in structural appearance. The aim of this investigation was to obtain more understanding of the biological behavior of these coatings by way of in vitro experiments. The effect of noncoated titanium (Ti) and three different Ca-P-sputtered surfaces on the proliferation and differentiation (morphology and matrix production) of osteoblast-like cells was studied. Proliferation was determined using counting procedures; morphology was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fluorescent markers and energy-dispersive X-ray microanalysis (EDX) were used to obtain quantitative and compositional information about the resultant calcified extracellular matrix (ECM). Results demonstrated that proliferation of the osteoblast-like cells was significantly (p 〈 0.05) higher on noncoated than on Ca-P-coated samples. On the other hand, more mineralized ECM was formed on the coated surfaces. In addition, TEM confirmed that the cells on the coated substrates were surrounded by ECM with collagen fibers embedded in crystallized, needle-shaped structures. On the basis of these findings, we concluded that: (1) the investigated Ca-P sputter coatings possess the capacity to activate the differentiation and expression of osteogenic cells, and (2) bone formation proceeds faster on Ca-P surfaces than on Ti substrates. Further, this bone-inductive effect appeared to be dependent on the Ca-P ratio of the deposited coatings. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 464-474, 1998.
    Additional Material: 14 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Scanning electron microscopic, transmission electron microscopic, and confocal laser scanning microscopic observation of fibroblasts cultured on microgrooved surfaces of bulk titanium substrata (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 425-433 
    Details
    ISSN: 0021-9304
    Keywords: surface topography ; plasma etching ; cellular orientation ; focal adhesion point ; in vitro ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: During this study, microtechnology and plasma etching were used to produce gratings 1.0 (TiD01), 2.0 (TiD02), 5.0 (TiD05), and 10.0 μm wide (TiD10) into commercially pure titanium wafers. After incubation of rat dermal fibroblast (RDFs) on these surfaces for 3 days, the cells were observed with scanning electron (SEM), transmission electron (TEM), and confocal laser scanning microscopy (CLSM). Results showed that the RDFs as a whole and their stress fibers oriented strictly parallel to the surface pattern on the TiD01 and TiD02 surfaces. On the TiD05 and TiD10 surfaces, this orientation was not observed. In addition, TEM and CLSM demonstrated that the focal adhesion points (FAP) were located mainly on the surface pattern ridges. TEM revealed that FAP were wrapped occasionally around the edges of the ridges. Only the RDFs on both the TiD05 and TiD10 surfaces protruded into the grooves and possessed FAP on the walls of the grooves. Attachment to the groove floor was observed only on the TiD10 textures. Comparison of these results with earlier observations on microtextured silicone rubber substrata suggests that material-specific properties do not influence the orientational effect of the surface texture on the observed RDF cellular behavior. The proliferation rate of the RDFs, however, seems to be much higher on titanium than on silicone rubber substrata. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 425-433, 1998.
    Additional Material: 13 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Microgrooved subcutaneous implants in the goat (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 634-641 
    Details
    ISSN: 0021-9304
    Keywords: biocompatibility ; subcutaneous implant ; implant surface ; microgrooves ; in vivo ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We investigated the behavior of microgrooved implants in soft tissue using polystyrene implantable disks, either smooth or microgrooved (1-10 μm) on both sides. The implants were placed subcutaneously in a goat for 1, 4, or 12 weeks. Light and transmission electron microscopy showed that fibrous capsule formation around the implants was fairly uniform. After 1 week the implants were covered with a fibrous capsule about 80 μm thick. The collagen matrix was loose, and many inflammatory cells were present. After 4 weeks the matrix was more dense and contained many newly formed blood vessels. At the implant surface a layer of inflammatory cells about 10 μm thick had accumulated. Finally, after 12 weeks the matrix had densified. One cellular layer of inflammatory cells was present at the implant surface. We carried out histomorphometric measurements of capsule thickness, inflammatory layer thickness, and the number of blood vessels. Capsule thickness appeared not to decrease with time. Further, these measurements showed that there were no differences in tissue reaction between smooth and microgrooved implants. On the basis of our observations, we suggest that 1 μm deep and 1-10 μm wide microgrooves do not influence tissue response around polystyrene implants in soft tissue. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 634-641, 1998.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Attachment, morphology, and protein expression of rat marrow stromal cells cultured on charged substrate surfaces (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 117-127 
    Details
    ISSN: 0021-9304
    Keywords: electrical stimulation ; cell attachment ; alkaline phosphatase ; osteopontin ; protein adsorption ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Although surface charge has been shown to affect the adhesion and morphology of a variety of cell types, the interactions of bone marrow stromal cells with charged surfaces still remain unclear. A novel electrical stimulation system was used to investigate the interactions between rat bone marrow stromal cells and charged substrates in this study. A conductive and transparent indium tin oxide (ITO) coating was used as an electret substrate. Rat marrow stromal cells were cultured on positive, negative, and uncharged ITO surfaces. Cell attachment, morphology, alkaline phosphatase activity, and expression of osteopontin and collagen type III were assessed using histochemical staining, immunolabeling, and fluorescence microscopy. Voltages of 0.7, 0.8, 0.9, and 1.0 V applied to the substrates created surface potentials but were insufficient to decompose the media. On positively charged ITO, cell attachment was enhanced in serum-supplemented and serum-free media. Furthermore, decreases in cell spreading, alkaline phosphatase activity, and osteopontin were observed in cells grown on the positively charged ITO. These data indicate that positively charged surfaces enhance cell attachment but suppress cell spreading and differentiation of rat marrow stromal cells. © 1998 John Wiley & Sons, Inc. J. Biomed Mater Res, 42, 117-127, 1998.
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  • 6
    Electronic Resource
    Electronic Resource
    Orientation of ECM protein deposition, fibroblast cytoskeleton, and attachment complex components on silicone microgrooved surfaces (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 291-300 
    Details
    ISSN: 0021-9304
    Keywords: surface topography ; actin ; vinculin ; fibronectin ; vitronectin ; grooves ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The microfilaments and vinculin-containing attachment complexes of rat dermal fibroblasts (RDF) incubated on microtextured surfaces were investigated with confocal laser scanning microscopy (CLSM) and digital image analysis (DIA). In addition, depositions of bovine and endogenous fibronectin and vitronectin were studied. Smooth and microtextured silicone substrata were produced that possessed parallel surface grooves with a groove and ridge width of 2.0, 5.0, and 10.0 μm. The groove depth was approximately 0.5 μm. CLSM and DIA make it possible to visualize and analyze intracellular and extracellular proteins and the underlying surface simultaneously. It was observed that the microfilaments and vinculin aggregates of the RDFs on the 2.0 μm grooved substrata were oriented along the surface grooves after 1, 3, 5, and 7 days of incubation while these proteins were significantly less oriented on the 5.0 and 10.0 μm grooved surfaces. Vinculin was located mainly on the surface ridges on all textured surfaces. In contrast, bovine and endogenous fibronectin and vitronectin were oriented along the surface grooves on all textured surfaces. These proteins did not seem to be hindered by the surface grooves since many groove-spanning filaments were found on all the microgrooved surfaces. In conclusion, it can be said that microtextured surfaces influence the orientation of intracellular and extracellular proteins. Although results corroborate three earlier published hypotheses, they do not justify a specific choice of any one of these hypotheses. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 291-300, 1998.
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of surface treatment on unalloyed titanium implants: Spectroscopic analyses (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 646-659 
    Details
    ISSN: 0021-9304
    Keywords: titanium ; surface treatment ; surface roughness ; surface composition ; surface energy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Surgical implant finishing and sterilization procedures were investigated to determine surface characteristics of unalloyed titanium (Ti). All specimens initially were cleaned with phosphoric acid and divided into five groups for comparisons of different surface treatments (C = cleaned as above, no further treatment; CP = C and passivated in nitric acid; CPS = CP and dry-heat sterilized; CPSS = CPS and resterilized; CS = C and dry-heat sterilized). Auger (AES), X-ray photoelectron (XPS), and Raman spectroscopic methods were used to examine surface compositions. The surface oxides formed by all treatments primarily were TiO2, with some Ti2O3 and possibly TiO. Significant concentrations of carbonaceous substances also were observed. The cleaning procedure alone resulted in residual phosphorus, primarily as phosphate groups along with some hydrogen phosphates. A higher percentage of physisorbed water appeared to be associated with the phosphorus. Passivation (with HNO3) alone removed phosphorus from the surface; specimens sterilized without prior passivation showed the thickest oxide and phosphorus profiles, suggesting that passivation alters the oxide characteristics either directly by altering the oxide structure or indirectly by removing moieties that alter the oxide. Raman spectroscopy showed no crystalline order in the oxide. Carbon, oxygen, phosphorus, and nitrogen presence were found to correlate with previously determined surface energy. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 646-659, 1998.
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  • 8
    Electronic Resource
    Electronic Resource
    Main-chain poly(arylene ether) phosphonium ionomers (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 781-785 
    Details
    ISSN: 0268-2605
    Keywords: phosphonium ; polymer ; monomer ; film ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(arylene ether) main-chain phosphonium ionomers were successfully synthesized and characterized. The reaction scheme involved first preparing the poly(arylene ether phosphine oxide) by a nucleophilic step or condensation polymerization of bisphenolates on activated aryl halides, wherein phenyl phosphine oxide was the activating group. High-molecular-weight, tough, film-forming polymers were produced with glass transition temperatures of 200°C or higher. The resulting materials were successfully reduced using phenylsilane in refluxing chlorobenzene. The derived phosphine or phosphine/phosphine oxide copolymer was reacted with alkyl halides to produce the phosphonium salts. The resulting materials showed enhanced hydrophilicity and in some cases could be successfully dispersed in water. In addition, chromophores such as Methyl Orange and Methyl Red were combined with the backbone ionomer to produce new film-forming, ionically linked species. The materials are of general interest for situations where water-dispersible intermediates, e.g. coatings, fiber sizings etc. are required. The phosphonium salts can be converted back to the phosphine oxide in fairly high yields by simple thermal methods and in quantitative yield by chemical methods (e.g. the Wittig reaction). © 1998 John Wiley & Sons, Ltd.
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  • 9
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    Structure of the amino-terminal protein interaction domain of STAT-4 (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-03-07
    Description: STATs (signal transducers and activators of transcription) are a family of transcription factors that are specifically activated to regulate gene transcription when cells encounter cytokines and growth factors. The crystal structure of an NH2-terminal conserved domain (N-domain) comprising the first 123 residues of STAT-4 was determined at 1.45 angstroms. The domain consists of eight helices that are assembled into a hook-like structure. The N-domain has been implicated in several protein-protein interactions affecting transcription, and it enables dimerized STAT molecules to polymerize and to bind DNA cooperatively. The structure shows that N-domains can interact through an extensive interface formed by polar interactions across one face of the hook. Mutagenesis of an invariant tryptophan residue at the heart of this interface abolished cooperative DNA binding by the full-length protein in vitro and reduced the transcriptional response after cytokine stimulation in vivo.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Vinkemeier, U -- Moarefi, I -- Darnell, J E Jr -- Kuriyan, J -- AI32489/AI/NIAID NIH HHS/ -- AI34420/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1998 Feb 13;279(5353):1048-52.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Molecular Cell Biology and Laboratories of Molecular Biophysics, The Rockefeller University, New York, NY 10021, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9461439" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Binding Sites ; Cell Line ; Crystallography, X-Ray ; DNA/metabolism ; DNA-Binding Proteins/*chemistry/genetics/metabolism ; Humans ; Hydrogen Bonding ; Interferon-gamma/pharmacology ; Models, Molecular ; Molecular Sequence Data ; Oligodeoxyribonucleotides/metabolism ; *Protein Conformation ; Protein Structure, Tertiary ; STAT1 Transcription Factor ; STAT4 Transcription Factor ; Signal Transduction ; Trans-Activators/*chemistry/genetics/metabolism ; Transcription, Genetic ; Transfection ; src Homology Domains
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    A viral mechanism for inhibition of the cellular phosphatase calcineurin (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-07-24
    Description: The transcription factor NFAT (nuclear factor of activated T cells) controls the expression of many immunomodulatory proteins. African swine fever virus inhibits proinflammatory cytokine expression in infected macrophages, and a viral protein A238L was found to display the activity of the immunosuppressive drug cyclosporin A by inhibiting NFAT-regulated gene transcription in vivo. This it does by binding the catalytic subunit of calcineurin and inhibiting calcineurin phosphatase activity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Miskin, J E -- Abrams, C C -- Goatley, L C -- Dixon, L K -- New York, N.Y. -- Science. 1998 Jul 24;281(5376):562-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Animal Health, Pirbright Laboratory, Pirbright, Surrey, GU24 0NF, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9677199" target="_blank"〉PubMed〈/a〉
    Keywords: African Swine Fever Virus/*physiology ; Amino Acid Sequence ; Animals ; Binding Sites ; Calcineurin/metabolism ; *Calcineurin Inhibitors ; Cell Nucleus/metabolism ; Cells, Cultured ; Cercopithecus aethiops ; Cyclosporine/pharmacology ; DNA-Binding Proteins/genetics/*metabolism ; Genes, Reporter ; Macrophages, Alveolar/*virology ; Molecular Sequence Data ; NF-kappa B/metabolism ; NFATC Transcription Factors ; *Nuclear Proteins ; Recombinant Proteins/metabolism ; Swine ; Transcription Factors/genetics/*metabolism ; *Transcription, Genetic ; Vero Cells ; Viral Proteins/genetics/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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