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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 1779-1784 
    ISSN: 0044-2313
    Keywords: Protonated sodium layer silicate hydrate ; 29Si-, 23Na- and 1H-MAS-NMR ; dehydration ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Chemistry of Kanemite [NaHSi2O5 · 3 H2O]xStarting from δ-Na2Si2O5 Kanemit was prepared by a direct exchange of Na+ by H+ in water containing reaction mixtures. By 29Si-, 23Na- and 1H-MAS-NMR investigations Kanemit was characterized as a layersilicate [NaHSi2O5 · 3 H2O]. By thermal treatment as well as by dehydration at room temperature under vacuum conditions a monohydrate is formed in which the layerstructure remains nearly unchanged. At temperatures between 100 and 110°C under normal conditions a hydrate phase of the composition [NaHSi2O5 · 0.25 H2O]x is prepared in which a changed silicate-layerstructure exists.
    Notes: Kanemit wurde aus δ-Na2Si2O5 durch einen direkten Austausch von Na+ gegen H+ in wasserhaltigem Reaktionsmedium hergestellt. Mit Hilfe von 29Si-, 23Na- und 1H-MAS-NMR-Untersuchungen wurde nachgewiesen, daß der Kanemit ein Schichtsilicat der Zusammensetzung [NaHSi2O5 · 3 H2O]x ist. Bei der thermischen, wie auch bei der Entwässerung im Vakuum bei Raumtemperatur entsteht ein Monohydrat, in dem die Schichtstruktur weitgehend erhalten bleibt. Bei Temperaturen zwischen 100 und 110°C läßt sich auch eine Hydratphase der Zusammensetzung [NaHSi2O5 · 0,25 H2O]x nachweisen, in der aber eine veränderte Schichtsilicatstruktur vorliegt.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We previously reported the use of polymeric delivery systems capable of sustained release of substances with molecular weights up to 2 × 106. The current study examined the tissue compatibilities of these slow-release agents and of other polymeric materials. To observe in vivo host responses to specific implants, tests were conducted in the rabbit cornea. The cornea as an implant site has several advantages compared to other organs including its clarity, avascularity, sensitivity, and convenient access to view. Corneas were examined using stereomicroscopy and histology. Two polymers suitable for sustained macromolecular release, poly(hydroxyethyl methacrylate), and alcohol-washed ethylene-vinyl acetate copolymer, were noninflammatory. Other polymers considered for sustained macromolecular release, such as polyacrylamide and poly(vinyl pyrrolidone), produced significant inflammation.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Bafilomycin A1, a specific inhibitor of H+-ATPases of the vacuolar type, was in the present study shown, at similar concentrations, to induce secretion of lysosomal enzyme and to elevate lysosomal pH in mouse macrophages. These results lend support to the previous suggestion of a triggering role for an increase in lysosomal pH and a permissive role for cytosolic pH in the exocytosis of macrophage lysosomal enzyme. Vacuolar H+-ATPases are present in the macrophage plasma membrane as well as in intracellular membranes, for example, those of the lysosomal and phagosomal compartments. Phagosomal acidification was shown to be achieved in part by a mechanism with a similar sensitivity to bafilomycin A1 as lysosomal H+ transport and in part by an early, bafilomycin A1-insensitive mechanism. We found a lesser sensitivity towards bafilomycin A1 of the lysosomal and phagosomal H+-ATPase than that localized in the plasma membrane, indicating differences among H+-ATPases at the subcellular level. Also, by attempts to mobilize lysosomal H+-ATPase to the plasma membrane, support was obtained for the notion that subcellular H+-ATPase populations differ and thus possibly could be differentially regulated. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 4
    ISSN: 0268-2605
    Keywords: magnetization reversal ; iron oxide particles ; SQUID ; atomic force microscopy ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report first measurements of the magnetization reversal of monodisperse 30 nm and 50 nm ferromagnetic Fe3O4 particles. These particles are produced in a carrier gas as an aerosol by spray pyrolysis. After production and size selection, they are precipitated on a silicon chip with a niobium SQUID (superconducting quantum interference device) incorporated on its surface. By changing a magnetic field in the plane of the SQUID, we can measure the magnetization reversal of the particles by the flux they induce into the SQUID. The angular dependence of this reversal is determined by rotating the magnetic field around the SQUID. Scanning electron microscope (SEM) images have confirmed the particle size and revealed the position of the collected particles. If the particle concentration is too high, we cannot detect changes in the magnetic moment of a single particle, but measure the magnetic properties of the whole assembly. If only a few particles are found on the SQUID loop the angular dependence of the magnetic reversal of a single particle can be measured; this result is compared with a simple model of magnetization reversal. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
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  • 5
    ISSN: 0193-7197
    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 , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A study conducted to determine the suitability of calcium carbonate (CaCO3) fillers in exterior PVC applications revealed that the surface-treated precipitated CaCO3s of average particle sizes 0.5 micron and 0.07 micron, in fact, minimized the initial yellowing of PVC seen on weathering. It is hypothesized that these particle-size CaCO3s, being optimum for light scattering, provide greater UV protection. Further, the high surface areas of these CaCO3s increase the capacity to neutralize the HCl responsible for yellowing of the PVC. The optimum filler level is 5 to 10 phr. At this loading level, long-term impact strength is also retained.
    Additional Material: 19 Ill.
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  • 6
    ISSN: 0193-7197
    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 , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Work reported earlier had shown that the addition of 0.07 micron stearate coated ultrafine precipitated CaCO3 (CUPCC) in medium to high molecular weight PVC resulted in a significant improvement in notched Izod impact strength. The improvement was much more dramatic when the filler loading exceeded 10 phr. The addition of CUPCC to low molecular weight PVC had practically no effect on the notched Izod impact strength at equivalent loadings. More recent studies have demonstrated that when CUPCC is added to an impact modified low molecular weight PVC, it dramatically enhances the efficiency of impact modifier. This was found to be consistent with threee general classes of commercially available impact modifiers used in this study. The ability to extend the impact modifier with CUPCC in low molecular weight PVC, which has gained a wide acceptance in injection molding operations, will result in significant cost savings. The effect of CUPCC addition on other key properties and cost benefits will also be presented.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    ISSN: 0193-7197
    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 , Process Engineering, Biotechnology, Nutrition Technology
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  • 8
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [Bis(trimethylsilyl) methylene] (diisopropylamino) borane: an Allene-Type N = B = C SystemThe title compound iPr2N=B=C(SiMe3)2 (4) is formed as a storable colourless liquid by the elimination of FSiMe3 from F-(iPr2N)B-C(SiMe3)3 (3) at 520°C. The compounds O=CHPh and Me3SiN3 are added to the B=C bond of 4 to give the [2 + 2] cycloaddition product 5 and the [2 + 3] cycloaddition product 6, respectively. The alkylideneaminoborane 4 crystallizes in the space group P21/n. Perpendicular planes through C2NB and BCSi2 define an allene-type structure with a linear N=B=C skeleton, bond lengths 136.3 (N=B) and 139.1 pm (B=C).
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  • 9
    ISSN: 0009-2940
    Keywords: Alkylidenoboranes ; 1,2-Oxaboretanes ; 1,2,4-Azasilaboretidines ; 2,3-Diiminoboretane ; Borylsilyldiazomethane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions at the BC Double Bond of iPr2N=B=C(SiMe3)2By thermal elimination of propene and migration of a methyl group at 500-600°C, the alkylidenoaminoborane iPr2N=B=C(SiMe3)2 (1b) is transformed to the azasilaboretidine [-N(iPr)=B(Me)-CH(SiMe3)-SiMe2-] (2). Protic agents HX (X = Cl, Br, OMe, OiPr, NMe2, NEt2) are added to 1b to give iPr2N=B(X)-CH(SiMe3)2 (3a-f); products 3g, h of the same type (X = O—CR=CH2, R = tBu, Ph) are formed from 1b and ketones MeRCO. Products iPr2N=B(X)-C(SiMe3)2-Y [X = Y = Br: 4; X = Me, Y = Li(tmeda): 5] are isolated from the reaction of 1b with the unpolar Br2 or with LiMe, respectively; adduct 5 can be hydrolyzed to 3i (X = Me, Y = H) by HCl. The bromoboration of 1b by MeBBr2 or BBr3 gives iPr2N=B(Br)-(Z)C(SiMe3)-BBrMe (Z = SiMe3: 6a; Z = SiMe2Br: 6b). The CO group of aldehydes RCHO [R = Me, tBu, C(Me)=CH2], ketones PhRCO (R = Me, Ph), and ethyl acetate undergo a [2+2] cycloaddition with 1b to give oxaboretanes [-B(NiPr2)-C(SiMe3)2-CRR′-O-] (7a-f); starting with HCONMe2, the cycloaddition to 1b is followed by ring opening and the migration of a silyl group to yield (iPr2N)B(OSiMe3)-C(SiMe3)=CH(NMe2) (8). Azides RN3 (R = Ph, PhCH2) may be added to 1b with loss of N2, azaboriridines [-(iPr2N)B—C(SiMe3)2-NR-] (9a, b) being formed, whereas Me3SiN3 gives the diazo compound (iPr2N)B[N(SiMe3)2]-C(SiMe3)=N2 (10). The formation of the boretane [-(iPr2N)B—C(SiMe3)2-C(=NtBu)-C(=NtBu)-] (11) is observed from the 2:1 reaction of tBuN≡C with 1b. The alkylidenoaminoborane H14C7N=B=C(SiMe3)2 (1c; H14C7N = 2,6-dimethylpiperidino) is synthesized by a procedure similar to the synthesis of 1b and gives reactions similar to those of 1b: thermal cyclisation to the azasilaboretidine 12, addition of HNMe2 to give 3j, [2 + 2] cycloaddition of RCHO (R = tBu, Ph) and Ph2CO to give 7g-i.
    Notes: Das Alkylidenaminoboran iPr2N=B=C(SiMe3)2 (1b) geht bei 500-600°C unter Propenabspaltung und Methylwanderung in das Azasilaboretidin [-N(iPr)=B(Me)-CH(SiMe3)-SiMe2-] (2) über. Protische Stoffe HX (X = Cl, Br, OMe, OiPr, NMe2, NEt2) addieren sich an 1b zu iPr2N=B(X)—CH(SiMe3)2 (3a-f); die Produkte 3g, h desselben Typs (X = O—CR=CH2; R = tBu, Ph) erhält man mit Ketonen MeRCO. Weiterhin kann man an 1b das unpolare Br2 sowie LiMe unter Bildung von iPr2N=B(X)—C(SiMe3)2-Y addieren [X = Y = Br: 4; X = Me, Y = Li(tmeda): 5]; 5 wird durch HCl zu 3i verseift (X = Me, Y = H). Die Bromoborierung von 1b mit MeBBr2 und BBr3 führt zu iPr2N=B(Br)—(Z)C(SiMe3)-BBrMe (Z = SiMe3: 6a; Z = SiMe2Br: 6b). Die CO-Gruppe von Aldehyden RCHO [R = Me, tBu, C(Me)=CH2], Ketonen PhRCO (R = Me, Ph) und Ethylacetat geht mit der BC-Bindung von 1b [2 + 2]-Cycloadditionen zu den Oxaboretanen [-B(NiPr2)-C(SiMe3)2-CRR′-O-] (7a-f) ein; im Falle von HCONMe2 folgt der Cycloaddition eine Silylverschiebung unter Ringöffnung zu (iPr2N)B(OSiMe3)-C(SiMe3)=CH(NMe2) (8). Azide RN3 (R = Ph, PhCH2) addieren sich an 1b unter Abspaltung von N2 zu den Azaboriridinen [-(iPr2N)B—C(SiMe3)2-NR-] (9a, b), während das Azid Me3SiN3 unter Silylwanderung die Diazoverbindung (iPr2N)B[N(SiMe3)2]-C(SiMe3)=N2 (10) ergibt. Mit tBuN≡C reagiert 1b im Verhältnis 2:1 zum Boretan [-(iPr2N)B—C(SiMe3)2-C(=NtBu)-C(=NtBu)-] (11). Das Alkylidenaminoboran H14C7Nd—B=C(SiMe3)2 (1c, H14C7N = 2,6-Dimethylpiperidino) bildet sich ähnlich und reagiert analog 1b: thermische Cyclisierung zum Azasilaboretidin 12, Addition von HNMe2 zu 3j, [2+2]-Cycloaddition von RCHO (R = tBu, Ph) und Ph2CO zu 7g-i.
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  • 10
    ISSN: 0009-2940
    Keywords: Methylenoboranes / (2 + 2)-Cycloadditions / Boraheterocycles / 1,3-Sigmatropic methyl shift ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 1.3-Methyl Shift along the Unsaturated BCSi SkeletonThe synthesis of the methoxy[tris(trimethylsilyl)methyl]boranes X-(MeO)B-C(SiMe3)3 (1a-d; X = Cl, Br, Ph, PhCH2) is described. The methylenoboranes Me-B=C(SiMe2Hal) (3a, b), the 2,3-dihydro-1H-1-sila-3-boraindene species 6, and the 1,2,3,4-tetrahydro-1-sila-3-boranaphthalene species 7 are formed by the thermal elimination of MeOSiMe3 from 1a/b or 1c or 1d, respectively. The boranes 3a, b undergo cyclodimerization at the B=C bond at 25 and 69°C, respectively, the diboretanes 4a, b being formed. The oxaboretanes 5a, b are isolated from the reaction of 3a, b with Ph2CO. The thermal elimination of MeOSiMe3 from Me′-(MeO)B-C(SiMe3)3 (1g;; Me′ = CD3) and subsequent addition of Ph2CO gives the oxboretanes 5g′/5g″ in the ratio of 1:6, showing that an equilibrium Me′-B=C(SiMe32 ⇄ Me - B=C(SiMe3(SiMe2Me′) with a statistical distribution of Me′ among seven methyl places is established in the hot tube before Ph2CO finally attacks the double bond. All these results are in accord with the primary formation of the methyleneboranes X-B=C(SiMe3)2 from 1a-d, followed by a 1,3-shift of Me along the unsaturated BCSi skeleton and the subsequent transformation into the isolated products.
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