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  • Chemistry  (2,596)
  • Life and Medical Sciences  (326)
  • 1995-1999  (2,694)
  • 1925-1929
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  • 1
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We discuss issues in developing scalable parallel algorithms and focus on the distribution, as opposed to the replication, of key data structures. Replication of large data structures limits the maximum calculation size by imposing a low ratio of processors to memory. Only applications which distribute both data and computation across processors are truly scalable. The use of shared data structures that may be independently accessed by each process even in a distributed memory environment greatly simplifies development and provides a significant performance enhancement. We describe tools we have developed to support this programming paradigm. These tools are used to develop a highly efficient and scalable algorithm to perform self-consistent field calculations on molecular systems. A simple and classical strip-mining algorithm suffices to achieve an efficient and scalable Fock matrix construction in which all matrices are fully distributed. By strip mining over atoms, we also exploit all available sparsity and pave the way to adopting more sophisticated methods for summation of the Coulomb and exchange interactions. © 1996 by John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 41 (1996), S. 419-425 
    ISSN: 0959-8103
    Keywords: polyurethane ; cell growth ; phase separation ; hydrogen bonding index ; cytotoxicity ; Chemistry ; Polymer and Materials Science
    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: Polyurethanes (PU) with suitable soft segments have been found to be good blood-compatible polymers and have attracted much attention recently. In this study, various molar amounts of 4,4′-methylene bisphenyl isocyanate reacted with poly(tetramethylene oxide) were synthesized to explore the optimal ratio of hard/soft segments for cell attachment and proliferation in in vitro systems. Differential scanning calorimetry and dynamic mechanical analysis were used to determine the physical properties, hydrogen bonding index (HBI) and transmission electron microscopy to observe the phase-separation phenomena in the materials, and 3T3 fibroblast to evaluate the dependence of the cell proliferation at 37°C on the material properties. Our results show that cell attachment and proliferation are closely related to the cell growth surface, which in turn is controlled by (1) the ratio of hard to total segment concentration and (2) the recrystallization temperature (Tc) of PU. To obtain a good cell growth surface, the ratio of hard to total segment concentration is found to be between 0.4 and 0.6, and HBI is between 1.5 and 2.1. Furthermore, when the Tc of PU is near the physiology temperature, a stable surface for cell growth can be provided. The shorter molecules in the soft segment region can rearrange the molecular chain at 37°C.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 69-76 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Low to moderate molecular weight terpene-anhydride resins were synthesized and evaluated in coatings applications. The terpenes used were terepinolene, β-pinene, and alloocimene. The comononmers used were maleic or itaconic anhydride. The terpene-anhydride resins were used to formulate solvent-borne coatings with an epoxy or diol as a coreactant. The coatings were evaluated as films over aluminum or steel panels. When a diol was used as a coreactant, the film properties were relatively poor. When epoxy was used as a coreactant, the properties of the films were much improved in terms of resistance to solvent and hardness. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 1413-1425 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The adsorption of ethane from helium was measured in beds packed with 2.5 μm zeolite crystals and containing either a single hollow fiber or multiple fibers. THe single-fiber experiments indicate that the mass-transfer rate in bends containing zeolite 13X is limited by diffusion across the fiber wall and through macropores. FOr adsorption in single-fiber beds packed with zeolite 4A, mass transfer is limited by micropore diffusion within the particles. Breakthrough curves from beds containign 13X are adequately described with the linear driving force model, while curves from beds containing 4A are consistent with the Rosen model.Breakthrough curves from beds packed with zeolite 13X and containing multiple fibers can be predicted from the experiments with single-fiber beds when the fibers are evenly spaced. When fibers are unevenly spaced, the breakthrough curves are more disperse. Unevenly spaced fibers are the normal case. Even when fibers are evenly spaced, the productivity of hollow-fiber beds is expected to be no greater than that in conventional beds.
    Additional Material: 11 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 847-850 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 70 (1998), S. 1195-1208 
    ISSN: 0020-7608
    Keywords: GABAB analogs ; pharmacophoric pattern ; molecular similarity ; quantum chemical calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to determine the structural requirements that are important for GABAB binding affinity, a quantum-chemical-based conformational study has been performed, followed by a similarity analysis which includes 12 GABAB analogs. Due to the flexibility of the structures, a semigrid GABAB analog [2RS-(5,5-dimethyl) morpholinyl-acetic acid] has been used as a template for the amonium moiety in order to help to identify the active conformation. Both in vacuo, and solvent-simulated calculations, for the physiological media modeled as water molecules, have been compared, for this analog, at ab initio (G94, 6-31+G(d,p)) and semiempirical (PM3) levels, respectively. On the basis of this comparison, the results of in vacuo PM3 calculations have been chosen for the similarity analysis. We have included, in the calculations, a group of molecules heterogeneous enough to become representative of the different families that can bind to the GABAB receptor site. Following their comparison we report the leading characteristics that can be related to their binding capability and define a pharmacophoric pattern for GABAB analogs. The latter is compared with the one previously found for the binding affinity at the GABAA receptor site.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 1195-1208, 1998
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 645-653 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Collagen has been widely coated or grafted onto polymer surfaces to improve the biocompatibility of materials. To better support the growth of endothelial cells on polyurethane (PU), collagen was grafted to the carboxyl group enriched PU through 1,2-bis(2,3-epoxypropoxy)ethane linking. Our results demonstrated that collagen in various conditions may result in different forms being grafted to the PU substrate, which subsequently affected the growth of endothelial cells. Collagen predialyzed against physiological phosphate buffered saline (PBS) could be reconstituted into native type fibrils with a bigger diameter at 37°C than could collagen neutralized by titration with NaOH. At low temperature, titrated collagen formed flosslike fibrils packed in a ball with cobblestonelike morphology. The amount of collagen grafted was related to the condition of the collagen used, which in consequence affected the diameter of the collagen fibril formed and the growth of endothelial cells. In conclusion, reconstituted collagen fibrils formed from collagen in PBS at 37°C grafted in the highest amounts to an epoxy-PU substrate and that optimally supported the growth of endothelial cells. Such prepared materials may be potentially good vascular bioprosthetic materials and may provide a wide range of biological applications. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 176-183 
    ISSN: 0021-9304
    Keywords: hydroxyapatite ; crystallinity ; materials characterization ; alkaline phosphatase activity ; osteocalcin concentration ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The clinical success of dental implants is governed by implant surfaces and bone cell responses that promote rapid osseointegration and long-term stability. The specific objective of this study was to investigate osteoblast precursor cell responses to hydroxyapatite (HA) surfaces of different treatments. Since the nature of bone cell responses in vitro is influenced by the properties of HA ceramics, this study was divided into two components: a chemical and crystallographic characterization of the HA ceramics and an in vitro cell culture study. The sintered HA samples were observed to have the highest crystallite size as compared to the as-received HA and calcined HA samples. No differences in the surface roughness and chemical composition were observed among the sintered, calcined, and as-received HA surfaces. In concurrence with the X-ray diffraction, high resolution XPS resolution of Ca 2p also indicated a higher crystallinity on sintered HA samples as compared to the calcined and as-received HA samples. As indicated by increased alkaline phosphatase-specific activity, increased cell-surface and matrix-associated protein, and 1,25 (OH2) vitamin D3-stimulated osteocalcin production, a more differentiated osteoblast-like phenotype was observed on the sintered HA surfaces compared to the as-received HA and calcined HA surfaces. An increased osteoblast-like cell activity on the sintered HA surfaces suggested that the crystallite size of HA surfaces may play an important role in governing cellular response. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 176-183, 1998.
    Additional Material: 12 Ill.
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  • 9
    ISSN: 0021-9304
    Keywords: biodegradable barrier films ; canine periodontal defects ; rabbit subcutaneous implants ; mass loss ; polymer degradation rate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biodegradable barrier films were made by coagulating a solution of poly(DL-lactide) in N-methyl-2-pyrrolidone on porous polyethylene pads wetted with saline solution. The semisolid films were cut into 10 × 10 mm barriers and implanted subcutaneously in rabbits. At monthly intervals, the polymer implant sites were compared histologically to those implanted with USP negative control plastic. The polymer films were retrieved from the surrounding tissue, dried, weighed, and the changes in molecular weight determined using gel permeation chromatography. The molecular weight of the polymer decreased at a relatively constant rate over 5 months; however, no significant mass loss occurred until 5 months postimplantation. Also, no distinct histological differences were noted between the polymer barrier and the control plastic sites until 6 months when histiocytes and multinucleated giant cells showed a modest increase around fragmented polymer films. Similar barrier films also were fitted over naturally occurring buccal dehiscence defects in beagle dogs and the tissue sites compared histologically at 6 months to sham-operated control sites. New bone and dense connective tissues closely approximated segments of the remaining polymer and demonstrated the biocompatibility of the biodegradable films. Histomorphometric analyses of treated sites compared to sham controls showed that the polymer barrier is effective in promoting bone and cementum regeneration in periodontal defects in dogs. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 303-311, 1998.
    Additional Material: 7 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 621-623 
    ISSN: 0935-6304
    Keywords: GC-MS ; Catechin ; Epicatechin ; Flavonoids ; Plasma ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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