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  • Artikel: DFG Deutsche Nationallizenzen  (204)
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  • 1
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 77-85 
    ISSN: 0021-9304
    Schlagwort(e): implant ; titanium ; osteoblasts ; surface roughness ; 1α,25- (OH)2D3 ; differentiation ; local factor ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Surface roughness has been shown to affect differentiation and local factor production of MG63 osteoblast-like cells. This study examined whether surface roughness alters cellular response to circulating hormones such as 1α,25-(OH)2D3. Unalloyed titanium (Ti) disks were pretreated with HF/HNO3 (PT) and then were machined and acid-etched (MA). Ti disks also were sandblasted (SB), sandblasted and acid etched (CA), or plasma sprayed with Ti particles (PS). The surfaces, from smoothest to roughest, were: PT, MA, CA, SB, and PS. MG63 cells were cultured to confluence on standard tissue culture polystyrene (plastic) or the Ti surfaces and then treated for 24 h with either 10-8M or 10-7M 1α,25-(OH)2D3 or vehicle (control). Cellular response was measured by assaying cell number, cell layer alkaline phosphatase specific-activity, and the production of osteocalcin, latent (L) TGFβ, and PGE2. Alkaline phosphatase activity was affected by surface roughness; as the surface became rougher, the cells showed a significant increase in alkaline phosphatase activity. Addition of 1α,25-(OH)2D3 to the cultures caused a dose-dependent stimulation of alkaline phosphatase activity that was synergistic with the effect caused by surface roughness alone. 1α,25-(OH)2D3 also caused a synergistic increase in osteocalcin production as well as local factor (LTGFβ and PGE2) production on the rougher CA, SB, and PS surfaces, but it had no effect on the production on smooth surfaces. The inhibitory effect of surface roughness on cell number was not affected by 1α,25-(OH)2D3 except on the SB surface. 1α,25-(OH)2D3 decreased cell number, increased alkaline phosphatase activity and osteocalcin production, and had no effect on LTGFβ or PGE2 production by MG63 cells grown on tissue culture polystyrene. These data suggest that bone cell response to systemic hormones is modified by surface roughness and that surface roughness increases the responsiveness of MG63 cells to 1α,25-(OH)2D3. They also suggest that the endocrine system is actively involved in normal bone healing around implants. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 77-85, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 0021-9304
    Schlagwort(e): implant ; titanium ; osteoblasts ; prostaglandin ; indomethacin ; surface roughness ; 1α,25-(OH)2D3 ; differentiation ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Surface roughness affects proliferation, differentiation (alkaline phosphatase and osteocalcin), local factor production [transforming growth factor (TGFβ) and prostaglandin E2 (PGE2)], and response to 1,25-(OH)2D3 (1,25) of MG63 osteoblast-like cells. In this study, we examined whether the effect of surface roughness on MG63 cells is mediated by prostaglandins produced by the cells. Unalloyed titanium (Ti) disks were pretreated with HF/HNO3 (PT) and then machined and acid-etched (MA). Disks were also coarse grit-sandblasted (SB), coarse grit-sandblasted and acid-etched (CA), or plasma-sprayed with Ti particles (PS). The surfaces, from smoothest to roughest, were PT, MA, CA, SB, and PS. MG63 cells were cultured to confluence on the Ti disks in the presence or absence of 10-7M indomethacin (Indo), a specific inhibitor of cyclooxygenase activity, resulting in decreased prostaglandin production. When the cells reached confluence, cell number, cell layer alkaline phosphatase specific activity (ALPase), and osteocalcin (OC) and latent TGFβ (LTGFβ) production were determined. In addition, confluent cultures which had been grown in the absence of Indo were exposed to 10-7M 1,25, 10-7M Indo, or a combination of the two for 24 h. On the rougher surfaces, cell number was decreased and ALPase, OC, and LTGFβ were increased. When indomethacin was present throughout the culture period, the effect of surface roughness on cell number, OC, and LTGFβ was abolished. ALPase was reduced, but surface roughness-dependent effects were still observed. Addition of indomethacin to confluent cultures for 24 h had no effect on any of the parameters examined, with one exception: Cells cultured on MA surfaces exhibited a more differentiated phenotype. 1,25 increased all parameters examined on SB, CA, and PS surfaces. When indomethacin was added with 1,25, the 1,25-dependent effects on cell number and OC and LTGFβ production were abolished; however, ALPase was unaffected. This indicates that bone cell response to systemic hormones may be modified by implant surface roughness. This effect may be mediated, at least in part, by prostaglandins produced by the same cells. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 489-496, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 65-73 
    ISSN: 0887-6266
    Schlagwort(e): poly(ether ether ketone) (PEEK) ; poly(ether ketone ketone) (PEKK) ; solvent-induced crystallization ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The relationship between semicrystalline morphology and glass transition temperature has been investigated for solvent-crystallized poly(ether ether ketone) (PEEK) and poly(ether ketone ketone) (PEKK). Solvent-crystallized specimens of both PEEK and PEKK displayed a sizeable positive offset in Tg compared to quenched amorphous specimens as well as thermally crystallized specimens of comparable bulk crystallinity; the offset in Tg for the crystallized samples reflected the degree of constraint imposed on the amorphous segments by the crystallites. Small-angle X-ray scattering studies revealed markedly smaller crystal long periods (d) for the solvent-crystallized specimens compared to samples prepared by direct cold crystallization. The strong inverse correlation observed between Tg and interlamellar amorphous thickness (lA) based on a simple two-phase model was in excellent agreement with data reported previously for PEEK, and indicated the existence of a unique relationship between glass transition temperature and morphology in these poly(aryl ether ketones) over a wider range of sample preparation history and lamellar structure than was previously reported. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 65-73, 1998
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 461-470 
    ISSN: 0142-2421
    Schlagwort(e): W/TiN/Ti/Si contact structure ; MULSAM ; TEM ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The W/TiN/Ti/Si contact structures needed for ultra-large-scale integrated circuits have been studied using cross-sectional transmission electron microscopy (TEM) and multi-spectral Auger electron microscopy. Access to the Ti/Si interface for chemical characterization using SEM, Auger and electron energy-loss imaging and spectroscopy has been achieved by using a novel method of bevelled polishing of the silicon substrate material. Cross-sectional TEM was used to calibrate the depth scale in the MULSAM image sets, so allowing measurements of the thicknesses of various interfacial layers and the penetration of the ohmic contacts into the silicon. The TiN layer, providing adhesion of the tungsten as well as acting as a diffusion barrier, appears to have a domed shape, which penetrates the tungsten overlayer to a greater extent in the contact centres. The results of this work, combined with earlier, related, studies, enable a three-dimensional characterization of the bottom and sidewall structures in these contacts. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1457-1471 
    ISSN: 0887-624X
    Schlagwort(e): epoxy ; catalyst ; liquid crystalline ; kinetic ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Tetraalkylphosphonium-Tetrafluoroborate-Tetrafluoroboric Acid was used as a catalyst in the curing of a liquid crystalline epoxy. Under some conditions the Tetraalkylphosphonium-Tetrafluoroborate-Tetrafluoroboric Acid actually retarded the reaction. An extensive experimental and kinetic analysis is presented anda mechanism for the reaction retardation is proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1457-1471, 1998
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1855-1860 
    ISSN: 0887-624X
    Schlagwort(e): helical conformation ; stereospecific polymerization ; isotactic ; polyacetaldehyde ; polytrifluoroacetaldehyde (polyfluoral), polytrichloro-acetaldehyde (polychloral) ; polytribromoacetaldehyde (polybromal) ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Minimum potential energy helical conformations for a family of four isotactic polyacetaldehydes have been determined. Our results indicate that all of the polymers form irrational helices. Comparisons have been made with the reported structures for two of these stereoregular polymers based on earlier X-ray diffraction data. c-Axis values associated with the pitch of the helix for polyacetaldehyde and for polytrichloroacetaldehyde (polychloral) were experimentally measured to be 0.48 and 0.51 nm, respectively. Our calculated conformations afforded values for a helix pitch of 0.47 and 0.52 nm, respectively, which derive from a 3.9/1 helix for polyacetaldehyde and a 3.7/1 helix for polychloral. The structure for polytribromoacetaldehyde (polybromal) was predicted to be similar to that for polychloral. For polytrifluoroacetaldehyde (polyfluoral) and polyacetaldehyde, a number of helical conformations with similar energies were found. All of these conformations could be related to the polychloral helical structure. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1855-1860, 1998
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2653-2665 
    ISSN: 0887-624X
    Schlagwort(e): kinetics ; microwave cure ; thermal cure ; bisnadimide ; crosslinking ; mechanism ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetic studies of the crosslinking reaction of a nadic end-capped imide model compound, N,N′-(oxydi-3,4′-phenylene) bis(5-norbornene-2,3-dicarboximide), a bisnadimide, in thermal and microwave processes were investigated. The conversion of the endo isomer to exo isomer proceeds at a much lower temperature than the crosslinking reaction. The crosslinking reaction was monitored by the combined decrease in the infrared absorptions of the endo and exo isomers at 840 and 780 cm-1, respectively. The decrease in the concentration of starting materials follows first-order kinetics in the thermal and microwave processes. At the same temperatures (230 or 280°C), the crosslinking reaction proceeds at about 10 times faster in the microwave process than in the thermal process. Solid-state 13C-NMR showed no significant loss in C=C double bond resonance in the cured products by comparison with the starting material. This study provides direct evidence that the microwave process may be an efficient method to cure nadic end-capped polyimides. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2653-2665, 1998
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 262-272 
    ISSN: 0899-0042
    Schlagwort(e): airway ; beta2-agonist ; racemic ; eutomer ; distomer ; hyperreactivity ; bronchospasm ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Airways of asthma patients can become hyperresponsive to airway spasmogens following regular use of isoprenaline or β2-selective sympathomimetics. Hyperreactivity that results from acute exposure of animals to these drugs is pre-empted by vagal section (a procedure which does not influence spasmolytic efficacy of sympathomimetics), is not diminished by antagonism of β2-adrenoceptors and is not associated with loss of responsivity of β2-adrenoceptors in the airways. Since activation, modulation, or blockade of β2-adrenoceptors does not determine this form of hyperreactivity, the possibility that distomers may induce hyperreactivity must be considered. Ocular and vascular responses to distomers of sympathomimetics have long been recognised and, more recently, comparable observations have been made for the airways. Thus, reactivity of guinea-pig airways to spasmogens was increased following exposure to S-isoprenaline, S-salbutamol, or S-terbutaline and exposure to S-isoprenaline or S-salbutamol can intensify symptoms in asthmatics. Regular exposure to the racemate, especially during or following an allergic reaction, predisposes to expression of hyperreactivity, which is nullified, acutely, by the eutomer. These observations imply that biological effects of sympathomimetic distomers may contribute to morbidity and mortality in asthma patients. Chirality 10:262-272, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    ISSN: 0006-3525
    Schlagwort(e): structure-based design ; Vascular Cell Adhesion Molecule ; α4β1 ; integrins ; epitope transfer ; peptides ; receptor ; antagonists ; nmr spectroscopy ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Results from protein mutagenesis and x-ray crystallographic studies of the multidomain protein Vascular Cell Adhesion Molecule (VCAM) were used to design cyclic octapeptides that retain the critical structural and binding elements of the epitope of VCAM in the interaction with the integrin α4β1 (VLA-4). Changes in the activities of peptide analogues correlated with the relative activities of protein mutants of VCAM, and predicted the properties of two new mutants that bound α4β1 with improved affinity vs wild type protein. The nmr structures of two peptides revealed a high degree of similarity to the structure of the VCAM binding epitope. These results demonstrate that a compact binding epitope identified via protein structure-function studies may be transferred to a synthetically accessible small peptide with the key structure-activity relationships intact. © 1998 John Wiley & Sons, Inc. Biopoly 47: 265-275, 1998
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 3115-3125 
    ISSN: 0887-6266
    Schlagwort(e): interfacial thickness ; PPO ; SAN ; SMA ; neutron reflectivity NR ; binary interaction energies ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Estimates for the thickness of the interface between poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) and copolymers of styrene-acrylonitrile (SAN) and styrene-maleic anhydride (SMA) based on the theory of Helfand and Tagami are compared to neutron reflectivity (NR) measurements. Good agreement is found between the NR measurements and theoretical predictions that make use of a mean field binary interaction model and previously reported binary interaction energies. The techniques outlined in this work may be used to understand relationships between the mechanical properties of multiphase polymer blends and the fundamental thermodynamics of polymer interactions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3115-3125, 1998
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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