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  • 1
    Electronic Resource
    Electronic Resource
    Collisionally Activated Dissociation of Some Bulkily Substituted Pyridinium Cations, II. Substituent Effect on Appearance Potential (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 177-181 
    Details
    ISSN: 0009-2940
    Keywords: Gas-phase dissociation ; Appearance energies ; Calculations, AM1 ; Pyridinium cations, N-benzyl-2,4,6-substituted ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Collisionally activated dissociations (CADs) of various pyridine-ring substituted N-benzylpyridinium cations in the gas phase form the substituted pyridine and benzyl carbocation. Appearance energies (AEs) are estimated quantitatively from the appearance thresholds of the corresponding fragment ion from the laser-desorbed pyridinium cations. MO calculations predict that such unimolecular dissociation processes lead initially to ion-molecule pairs (IMPs): some such IMPs are of significantly lower energy than the fully dissociated products. The AEs have also been compared with the energy differences [ΔΔHf=ΔHf(Py) + ΔHf(R+)  -  ΔHf(Py+R)] determined by AM1 calculations: in many cases these are quite close to the calculated energy differences; discrepancies are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250129
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  • 2
    Electronic Resource
    Electronic Resource
    Phase-mixed poly(ethylene glycol)/poly(trimethylolpropane triacrylate) semi-interpenetrating polymer networks obtained by rapid network formation (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2715-2725 
    Details
    ISSN: 0887-624X
    Keywords: semi-IPN ; PEG ; TMPTA ; phase separation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Semi-interpenetrating polymer networks (semi-IPNs) of poly(ethylene glycol) (PEG) in poly(trimethylolpropane triacrylate) (TMPTA) were synthesized from PEG melts in neat TMPTA monomer, using PEG of molecular weights from 4000 to 100,000 g/mol. Differential scanning calorimetry and transmission electron microscopy were used to examine phase separation occurring during network formation. The degree of phase separation was observed to depend upon the rate of PEG aggregation relative to the rate of network formation during TMPTA polymerization. Higher molecular weight PEG and acrylate-functionalized PEG formed more phase-mixed networks compared to lower molecular weight PEG; acetatefunctionalized PEG showed no difference from unmodified PEG in the extent of phase mixing. For networks that demonstrated phase separation, the PEG was observed to be in two states: some being phase mixed and solvent inextractable, and some being phase separated and solvent extractable. Phase-mixed networks could be obtained from this thermodynamically incompatible polymer pair utilizing rapid photopolymerization systems to overcome PEG phase aggregation and kinetically entrap the PEG in a nonequilibrium phase-mixed state. These mixed-phase semi-IPNs of PEG and TMPTA may be useful in biological applications where the presence of PEG is desired throughout the bulk matrix rather than as a surface graft to reduce biological interactions. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321412
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  • 3
    Electronic Resource
    Electronic Resource
    Modification of islet of langerhans surfaces with immunoprotective poly(ethylene glycol) coatings via interfacial photopolymerization (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 383-386 
    Details
    ISSN: 0006-3592
    Keywords: PEG coating ; islet of Langerhans ; insulin ; diabetes mellitus ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Poly(ethylene glycol) (PEG) has been used previously to alter immune interactions and systemic clearance of therapeutic proteins. We present herein chemical approaches for the conceptually similar treatment of therapeutic cells and tissues whereby immune and cell adhesive interactions may be reduced or interrupted, in the context of the transplantation of xenogeneic islets of Langerhans for the treatment of insulin-dependent diabetes mellitus. Visible-light-initiated interfacial photopolymerization of multifunctional PEG-based macromers was performed directly upon the surface of rat islets of Langerhans to produce conformal barrier hydrogel coatings with thickness of order 10 μ;m. The islets continued to be normal in ultrastructure and function as reflected by response to a glucose challenge in vitro. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440317
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  • 4
    Electronic Resource
    Electronic Resource
    Multifunctional poly(ethylene glycol) semi-interpenetrating polymer networks as highly selective adhesive substrates for bioadhesive peptide grafting (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 772-780 
    Details
    ISSN: 0006-3592
    Keywords: bioadhesion ; peptides ; poly(ethylene glycol) ; polymer networks ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Novel artificial extracellular matrices were synthesized in the form of semi-interpenetrating polymer networks containing copolymers of poly(ethylene glycol) and acrylic acid (PEG-co-AA) grafted with synthetic bioadhesive peptides onto exposed carboxylic acid moieties. These substrates were very resistant to cell adhesion, but when they were grafted with adhesive peptides they were highly biospecific in their ability to support cell adhesion. Extensive preadsorption of adhesive proteins or peptides did not render these materials cell adhesive; yet covalent grafting of adhesive peptides did render these materials highly cell adhesive even in the absence of serum proteins. Polymer networks containing immobilized PEG-co-AA were grafted with peptides at densities of 475 ± 40 pmol/cm2. Polymer networks containing immobilized PEG-co-AA N-terminally grafted with GRGDS supported cell adhesion efficiencies of 42 ± 4% 4 h after seeding and became confluent after 12 h. These cells displayed cell spreading and cytoskeletal grafted with inactive control peptides (GRDGS, GRGES, or no peptide) supported cell adhesion efficiencies of 0 ± 0%, even when challenged with high seeding densities (to 100,000 cell/cm2) over 14 days. These polymer networks are suitable substrates to investigate in vitro cell-surface interactions in the presence of serum proteins without nonspecific protein adsorption adhesion signals other than those immobilized for study.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430812
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  • 5
    Electronic Resource
    Electronic Resource
    Element-selective atomic emission detection for capillary GC of metal-containing compounds (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 669-676 
    Details
    ISSN: 0935-6304
    Keywords: Selective GC detection of metals ; Atomic emission detection ; Microwave-induced plasma ; Metal-containing compounds ; Metalloporphyrins ; Organomanganese ; Organotitanium ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Element-selective GC detection by microwave-induced plasma atomic emission spectroscopy has been used to examine a wide variety of compounds containing metals, non-metals, and metalloids. “Recipes”, or new selective detection schemes for use with the software of the computer-controlled system, have been developed for the selective detection of boron, aluminum, gallium, titanium, vanadium, chromium, manganese, rhenium, palladium, and platinum. Figures of merit including limits of detection, linear dynamic range, and spectral selectivity over carbon have been established for most of these elements. Gas chromatography - atomic emission detection (GC-AED) has been applied to the selective detection of vanadium, nickel, and iron in metalloporphyrins present in crude oil, manganese-selective detection of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline, and titanium-selective detection of reaction mixtures containing titanium catalysts or titanium boride molecular precursors.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240151008
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  • 6
    Electronic Resource
    Electronic Resource
    Atomic force microscopy of the banded structure of lyotropic polymers (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 15 (1994), S. 815-821 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No Abtract.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1994.030151102
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  • 7
    Electronic Resource
    Electronic Resource
    The addition of carbonyl compounds to tetramesitylgermasilene and dimesitylgermyleneDedicated to Prof. Adrian Gibbs Brook, a respected mentor and friend, on the occasion of his seventieth birthday. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 5 (1994), S. 293-303 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hexamesitylsiladigermirane, 1, has been photolyzed/thermolyzed in the presence of three representative carbonyl compounds: acetone, pivalaldehyde, and benzaldehyde. In each case, a [2 + 2] adduct between the carbonyl compound and Mes2Ge = SiMes2 was formed regioselectively to give a 2,3-silagermaoxetane. The 2,3-silagermaoxetanes have been fully characterized by IR and NMR (1H, 13C, and 29Si) spectroscopy and mass spectrometry. In two cases, the structures have been confirmed by X-ray crystallography: 4,4-dimethyl-2,2,3,3-tetramesityl-2,3-silagermaoxetane, 2a; crystals are triclinic, space group P1 with Z = 2 in a unit cell of dimensions a = 12.318(3) Å, b = 12.436(2) Å, c = 11.884(2) Å, α = 100.13(1)°, β = 103.80(2)°, and γ = 89.97(2)°. The structure was solved by direct methods and refined by least squares on the basis of 2955 observed reflections to R1 and wR2 values of 0.0600 and 0.1363, respectively. The structure of 4-tert-butyl-2,2,3,3-tetramesityl-2,3-silagermaoxetane, 2b, was also determined; crystals are monoclinic, space group Cc with Z = 4 in a unit cell of dimensions a = 11.306(2) Å, b = 21.292(4) Å, c = 16.524(2) Å, and β = 106.83(1)°. The structure was determined by direct methods and refined by full-matrix least squares on the basis of 1817 observed reflections to R1 and wR2 values of 0.0621 and 0.1681, respectively. An adduct between dimesitylgermylene and the carbonyl compound was also isolated in each reaction. The structure of the adduct appears to depend upon the steric bulk of the group attached to the carbonyl carbon.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hc.520050315
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  • 8
    Electronic Resource
    Electronic Resource
    Formic acid modified carbon dioxide as a mobile phase in capillary supercritical fluid chromatography (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 3 (1991), S. 47-57 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; modifiers ; formic acid ; mobile phase ; capillary columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A small percentage (0.3% w/w) of formic acid was added to supercritical carbon dioxide to increase mobile phase polarity and improve separation of polar solutes on three different commercially available capillary columns. Formic acid reduced retention and altered selectivity for several polar compounds. Thermodynamic studies revealed that the enthalpy of solvation was as much as 27 kcal mol-1 more negative when formic acid was added due to increased solute-solvent interactions. Entropy measurements show that formic acid modified mobile phase is more ordered than a pure carbon dioxide mobile phase, apparently as a result of modifier clustering around polar solutes. Van't Hoff plots for some very polar solutes showed a region of retrograde behavior at low temperatures and pressures, indicating an increase in modifier clustering. Comparisons between pure and modified mobile phases were also made by examining practical separations obtained with each, revealing differences in retention, selectivity and peak shape.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220030109
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal stability studies of a polyimide-polytetrafluoroethylene blend and its components (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 153-162 
    Details
    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-dielectric constant (∊r) polymers, such as polytetrafluoroethylene (PTFE), are an important component of advanced electronic products that transit data, since it is this physical property that largely determines a device's performance. For instance, the dielectric constant determines overall signal speed and proximity in that one circuit line can be placed to another, i.e., wiring density, while maintaining desired electrical characteristics. However, due to PTFE's inertness and intractability, significant challenges exist in the successful application of the polymer as an insulation material. One specific example is the lack of available methods to uniformly and controllably generate fine, high-density features in the neat fluoropolymer. Recently, it was reported that excellent structuring characteristics of PTFE can be achieved by sensitizing the fluoropolymer to excimer laser radiation using small quantities of an aromatic polyimide. An important physical property of the sensitization agent, in addition to interacting strongly with the laser's emitted energy, is suitable thermal stability due to PTFE's high-temperature processing requirements. Using multiple analysis techniques, the thermal decomposition behavior of PTFE, polyimide sensitizer, and resulting polymer blend have been evaluated. It was determined that the onset of decomposition for all systems is near or greater than 500°C. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070540202
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  • 10
    Electronic Resource
    Electronic Resource
    Avoidance of photoactivation in the epifluorescence video microscopic observation of thrombosis (1992)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 26 (1992), S. 1535-1542 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820261111
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