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  • 1
    ISSN: 0947-6539
    Keywords: biomineralization ; calcite ; crystal morphology ; mosaic structure ; symmetry reduction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organisms can exert a remarkable degree of control over crystal growth. One way of achieving this is by the adsorption of specialized macromolecules on specific planes of the growing crystals. With continued growth of the crystal, the macromolecules are incorporated inside the crystal bulk. Their presence does not change the crystal structure, but creates discontinuities in the perfect lattice. Here we study in detail three unusual cases of reduction in symmetry at the level of crystal domain shapes, induced by this controlled intercalation. We examined sponge spicules, which are single crystals of Mg-bearing calcite. They were specifically chosen for this study, because their morphologies do not reflect the hexagonal symmetry of calcite. Their crystal textures (coherence lengths and angular spreads) were characterized by high-resolution X-ray diffraction with well-collimated synchrotron radiation. The results are compared to analogous studies of synthetic calcite and Mg-bearing calcite. In all the selected spicules reduction in symmetry is observed in the coherence lengths among symmetry-related crystallographic directions. The reconstructed shapes of the domains of perfect structure closely match the specific spicule morphologies. The synthetic crystals show no such reduction in symmetry. Although the manner by which such exquisite control is achieved is not known, we envisage it involving a combination of oriented nucleation with either physical or stereochemically driven adsorption.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 80 (1968), S. 271-276 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chrom(II)-Salze lassen sich in der organischen Chemie für vielerlei Reduktionen verwenden; beispielsweise werden Alkylhalogenide in Alkane, günstig substituierte Olefine ebenfalls in Alkane und Alkine in trans-Olefine übergeführt. Einige Epoxyketone werden zu α,β-ungesättigten Ketonen oder β-Hydroxyketonen reduziert, und ein Nitrosteroid gab eine Hydroxy-hydroxyiminoverbindung. Die Reduktion von Alkylhalogeniden soll über freie Radikale verlaufen; das abgespaltene Halogenatom wird als Brücke zwischen zwei Chromatomen eingebaut.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 90 (1978), S. 1015-1016 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 619-647 
    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: The specific sorption capacities of poly(styrene-co-divinylbenzene) [i.e., (Sty)1-x (DVB)x samples for binary solutions of toluene (α = 1.98)] and a second solvent [i.e., heptane (α = 〈0.01), methanol (α = 〈0.06), acetone (α = 0.92) or chloroform (α = 3.00)] were correlated with the corresponding DVB mole fraction (x) in the sorbent polymer samples (0.01 〈 x 〈 0.11), with the volume fraction (z) of toluene in the sorbed binary liquid (which was cycled at least twice from z = 0 to z = 1 and back to z = 0 in increments of 0.1) and with the adsorption parameter (α) of the sorbed liquid. These correlations demonstrated that the sorption capacity during the initial transit from z = 0 to 1 reflects the molecular architecture in the original dry state. Once the samples have been swelled to saturation in toluene (z = 1), however, the “memory” of the former dry state is erased; thereafter the sorption capacity reflects only the architecture established in the fully swollen state, and the composition of the sorbed solution. The molecular nature of the solvent exchange processes is discussed in the text. © 1994 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1042-7147
    Keywords: X-ray and deep UV lithography ; Photoacid generators ; 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
    Notes: The X-ray (1.4 nm) and deep UV (248 nm) radiation responses of chemically amplified photoresists incorporating arylmethyl sulfone photoacid generators were evaluated. The arylmethyl sulfones were primarily derivatives of benzyl phenyl sulfone, selected to reveal the importance of desulfonylation and internal abstraction with regard to the photochemical efficiency of acid generation. At 1.4 nm, benzyl phenyl sulfone gave a much more sensitive resist than dibenzyl sulfone, while the methyl derivatives of benzyl phenyl sulfone did not give much improvement over the parent compound. This suggests that desulfonylation is more important than internal abstraction for increased photochemical efficiency. At 248 nm, similar trends were observed, but with some modifications arising from the variation in extinction coefficient among the sulfones. Sensitivities at or below 20 mJ/cm2 were obtained for both wavelength ranges.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 18 (1984), S. 547-559 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An in situ immunoradiometric assay was devised to quantitate human fibrinogen deposited on hemodialysis membrane, Cuprophane, from in vitro exposure to fibrinogen solution and from ex vivo extracorporally clinical use. The method requires a monospecific 125I-labeled antifibrinogen-IgG purified by DEAE chromatography and immunoadsorption. The labeled antifibrinogen IgG was shown to react specifically with fibrinogen adsorbed and immobilized (by glutaraldehyde) on Cuprophane. Other plasma proteins such as human albumin, IgG, or α-thrombin, adsorbed singly or coadsorbed with fibrinogen on the surface did not seem to affect the fibrinogen-antifibrinogen reaction. The presence of blood cells such as platelets and granulocytes with fibrinogen on Cuprophane reduced only slightly the uptake of 125I-antifibrinogen-IgG. The examination of fibrinogen-fibrin deposition on clinically used Cuprophane by this technique and by autoradiography of the same material following 125I-antifibrinogen-IgG conjugation indicated that the deposition of fibrinogen was heavy and heterogeneous. We concluded that this in situ method may be useful to monitor fibrinogen-fibrin deposition and adsorption of other plasma proteins that occur under in vitro, ex vivo, and in vivo conditions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 18 (1984), S. 695-705 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Human prothrombin in Tyrode's solution, in mock plasma (albumin, fibrinogen, and IgG mixture), and in citrated plasma adsorbs to Cuprophane, polyvinylchloride, and polyacrylonitrile surfaces. The adsorption of prothrombin is maximal in Tyrode's solution and minimal in plasma. The surface concentrations of prothrombin are highest on polyacrylonitrile, second on polyvinylchloride, and lowest on Cuprophane at all prothrombin concentrations tested in the bulk solution. Qualitative tests show that prothrombin adsorbed to polyvinylchloride can be activated by Taipan snake venom to generate thrombin that clots fibrinogen. However, more quantitative tests indicate that only part of the adsorbed prothrombin on all three materials can be activated to form thrombin exhibiting amidolytic activity. The partial reactivity of adsorbed prothrombin is further confirmed by release of 125I-peptide from surface bound 125I-prothrombin after treatment with Australian Taipan snake venom. Prothrombin bound to Cuprophane seems to promote granulocyte adhesion, but has no effect on platelet adhesion.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 22 (1988), S. 795-818 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tubular blood-contacting polymeric materials were modified by plasma polymerization and evaluated in the baboon with respect to their capacity to induce both acute and chronic arterial thrombosis. Polymer surface composition was determined by electron spectroscopy for chemical analysis. Steady-state arterial thromboembolism was initiated by introducing tubular segments into chronic arteriovenous shunts. Rates of platelet destruction induced by the test materials were calculated from 111In-platelet survival measurements. Nine plasma polymers based on tetrafluoroethylene, hexafluoroethane, hexafluoroethane/H2, and methane, when deposited on silicone rubber, consumed platelets at rates ranging from 1.1-5.6 × 108 platelets/cm2-day. Since these values were near the lower detection limit for this test system, the plasma polymers were considered relatively nonthrombogenic. Acute thrombus formation was initiated by inserting expanded Teflon (Gore-Tex PTFE) vascular grafts into the shunt system. 111In-platelet deposition was measured by scintillation camera imaging over a 1-h exposure period. Standard PTFE grafts (10 cm × 4 mm i. d.) accumulated approximately 1 × 1010 platelets over this interval. While modification of PTFE grafts with a plasma polymer based on hexafluoroethane/H2 did not alter graft surface morphology, platelet deposition was reduced by 87% as compared to the controls (p 〈 0.001). We conclude that both the surface chemistry and texture of prosthetic materials influence thrombogenesis. The method of plasma polymerization may be useful for assessing the importance of these variables independently and, perhaps, for minimizing certain adverse blood-material interactions.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 289-299 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This article reports on chemical reactions and the properties they generated in artificial bone materials termed “organoapatites.” These materials are synthesized using methodology we reported in the previous article of this series1. Two different processes were studied here for the transition from organoapatite particles to implants suitable for the restoration of the skeletal system. One process involved the hardening of powder compacts by beams of blue light derived from a lamp or a laser and the other involved pressure-induced interdiffusion of polymers. In both cases, the hardening reaction involved the formation of a polyion complex between two polyelectrolytes. In the photo-induced reaction an anionic electrolyte polymerizes to from the coulombic network and in the pressure-induced one, pressure forms the complex by interdiffusion of two polyions. Model reactions were studied using various polycations. Based on these results the organoapatite selected for the study was that containing dispersed poly(L-lysine) and sodium acrylate as the anionic monomer. The organomineral particles can be pressed at room temperature into objects of great physical integrity and hydrolytic stability relative to anorganic controls. The remarkable fact about these objects is that intimate molecular dispersion of only 2-3% by weight organic material provides integrity to the mineral network in an aqueous medium and also doubles its tensile strength. This integrity is essentially nonexistent in “anorganic” samples prepared by the same methodology used in organoapatite synthesis. The improvement in properties was most effectively produced by molecular bridges formed by photopolymerization. The photopolymerization leads to the “hardening” of pellets prepared by pressing of organoapatite powders. The reaction was found to be more facile in the microstructure of the organomineral, and it is potentially useful in the surgical application of organoapatites as artificial bone. © 1993 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 19 (1985), S. 813-825 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyclonal antihuman α-thrombin antibodies produced in rabbits reacted minimally (〈0.05%) in solution with human prothrombin. However, when prothrombin was adsorbed to artificial surfaces such as polyvinyl chloride (PVC), the crossreactivity of surface-bound prothrombin with antibody IgG to thrombin (〉95% purity) was shown to be significantly enhanced. On PVC, the molar ratios of antibody IgG to thrombin/prothrombin approached the same level as that of antibody IgG to thrombin/thrombin when thrombin was adsorbed to the same material. The analyses of antigen-antibodies interaction, in solution with a direct binding assay by immune precipitation at high-speed centrifugation (160,000 g, 30 min), and on solid-phase PVC, were accomplished by use of double-labeling technique, i.e., 131I-thrombin (or 131I-prothrombin) and 125I-antibody IgG to thrombin. The results appear to suggest that prothrombin adsorption to PVC has resulted in some molecular conformational changes so that immunologically the adsorbed prothrombin resembles that of adsorbed thrombin on the same PVC surface.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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