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  • 1
    Electronic Resource
    Electronic Resource
    Enantioselective binding of α-pinene and of some cyclohexanetriol derivatives by cyclodextrin hosts: A molecular modeling studyA preliminary report of some of this work was presented at the First Electronic Computational Chemistry Conference held on the Internet during November 1994. (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 931-939 
    Details
    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 have used molecular modeling to investigate the enantioselective separation of the monoterpene α-pinene on permethylated β-cyclodextrin and on α-cyclodextrin and the enantioselective separation of three cyclohexanetriol derivatives on permethylated β-cyclodextrin. Using the Consistent Valence Force Field (CVFF) from Insight/Discover, we have carried out systematic rigid-body docking grid searches on each of the optical antipodes of the organic guest molecules interacting with the cyclodextrins, followed by minimizations of the low-energy docked structures. A statistical mechanical analysis of the minimized energies yields data that agree in four out of five cases with the experimental elution order of enantiomers. The computed energies of the rigid-body docking before minimizations do not agree with the experimental results, suggesting that a conformational induced fit of the cyclodextrins upon binding of the organic guests may be involved in the mechanism of the chiral recognition. © 1996 by John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Extremely-low-frequency magnetic fields disrupt rhythmic slow activity in rat hippocampal slices (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 388-395 
    Details
    ISSN: 0197-8462
    Keywords: ELF magnetic fields ; hippocampus ; theta rhythm ; nitric oxide ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Several studies have indicated that weak, extremely-low-frequency (ELF; 1-100 Hz) magnetic fields affect brain electrical activity and memory processes in man and laboratory animals. Our studies sought to determine whether ELF magnetic fields could couple directly with brain tissue and affect neuronal activity in vitro. We used rat hippocampal slices to study field effects on a specific brain activity known as rhythmic slow activity (RSA), or theta rhythm, which occurs in 7-15 s bursts in the hippocampus during memory functions. RSA, which, in vivo, is a cholinergic activity, is induced in hippocampal slices by perfusion of the tissue with carbachol, a stable analog of acetylcholine. We previously demonstrated that the free radical nitric oxide (NO), synthesized in carbachol-treated hippocampal slices, lengthened and destabilized the intervals between successive RSA episodes. Here, we investigate the possibility that sinusoidal ELF magnetic fields could trigger the NO-dependent perturbation of the rate of occurrence of the RSA episodes. Carbachol-treated slices were exposed for 10 min epochs to 1 or 60 Hz magnetic fields with field intensities of 5.6, 56, or 560 μT (rms), or they were sham exposed. All exposures took place in the presence of an ambient DC field of 45 μT, with an angle of -66° from the horizontal plane. Sinusoidal 1 Hz fields at 56 and 560 μT, but not at 5.6 μT, triggered the irreversible destabilization of RSA intervals. Fields at 60 Hz resulted in similar, but not statistically significant, trends. Fields had no effects on RSA when NO synthesis was pharmacologically inhibited. However, field effects could take place when extracellular NO, diffusing from its cell of origin to the extracellular space, was chelated by hemoglobin. These results suggest that ELF magnetic fields exert a strong influence on NO systems in the brain; therefore, they could modulate the functional state of a variety of neuronal ensembles. © 1996 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Materials and design concepts for an intervertebral disc spacer. II. Multidurometer composite design (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 6 (1995), S. 117-123 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The main function of the intervertebral disc is to transmit and attenuate compressive and torsional forces, and stabilize the intervertebral joint. Unfortunately, the disc may be displaced or damaged due to trauma or disease causing the nucleus to herniate and protrude into the vertebral canal or intervertebral foramen. Pressure on the spinal nerve may cause pain or paralysis in the area of its distribution. At present, the surgical procedures used to alleviate this condition include disc excision, and/or spinal fusion. A more desirable situation would involve removing the nucleus pulposus and part or all of the annulus fibrosis and implanting a suitable biofunctional equivalent. Such a prostheis should attenuate stresses and prevent abnormal stress at adjacent intervertebral joints. Maintenance of normal disc height would prevent impingement of the posterior facet joints and facet joint syndrome. In a previous companion paper (J. Applied Biomat. 5:125-132; 1994), the mechanical behavior of disc prostheses manufactured from fiber reinforced, elastomeric thermoset resins were examined. In order to develop devices which were more practical from a manufacturing standpoint and extremely reproducible, the fiber reinforced thermoset resins were replaced by multi-durometer thermoplastic elastomeric materials. In the present paper, the mechanical properties of thermoplastic multicomponent desings have been investigated. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770060206
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular Tweezers as Synthetic Receptors: Molecular Recognition of Electron-Deficient Aromatic Substrates by Chemically Bonded Stationary Phases (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2741-2749 
    Details
    ISSN: 1434-193X
    Keywords: Supramolecular chemistry ; Molecular recognition ; HPLC-Bonded phases ; Arene-arene interactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and chromatographic properties of novel chemically-bonded stationary phases CBSP-1 and CBSP-2, containing substituted molecular tweezers with benzene and naphthalene spacer-units, are described. These phases selectively retain electron-deficient aromatic and quinoid analytes of appropriate size and topography, such as 1,4-dinitrobenzene, 1,2-, 1,3-, and 1,4-dicyanobenzenes, and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), in HPLC studies. The good qualitative correlation between the capacity factors k′ derived from the HPLC retention times and the association constants Ka obtained from binding studies in solution using molecular tweezers 1 and 2 as receptors, indicates that the mechanism of retention involves selective complexation by the molecular tweezers on the silica surface. As expected from the solution experiments, higher capacity factors and selectivities were obtained with CBSP-2 than with CBSP-1 because of a better structural fit of the naphthalene-spaced receptor with the aromatic analytes. Capacity factors, k′, and enthalpies of retention, ΔHR, were measured for four different aromatic analytes in 15 solvents. Chromatographic separation factors, α, were determined for seven structurally-related nitroaromatic compounds. The results of these measurements allow for the conclusion that the electrostatic nature and steric complementarity of the receptors and analytes is most important in determining selectivities.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Diffusion in gas separation membrane materials: A comparison and analysis of experimental characterization techniques (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1747-1755 
    Details
    ISSN: 0887-6266
    Keywords: kinetic sorption ; steady-state permeation/sorption ; polyimide ; carbon molecular sieve ; membrane separation processes ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Typically, materials with high-performance transport properties such as zeolites, carbon molecular sieves, or hyper rigid polymers are inherently difficult or impossible to characterize by steady-state membrane permeation experiments used for conventional polymers. Diffusion coefficients determined by transient sorption, a measurement easily performed on brittle media, are analyzed here and compared to those determined by steady-state permeation/sorption and transient permeation for a glassy polymer and a carbon molecular sieve. Average and local diffusion coefficients are extrapolated to zero upstream partial pressure to eliminate effects caused by concentration dependence. Good agreement between the techniques was observed for the glassy polymer. On the other hand, carbon molecular sieves, possessing a more complex morphology, exhibit a greater difference in diffusion coefficients determined by the various techniques. Nevertheless, comparison of the analysis techniques is shown to provide potentially valuable insights into the morphological features of such carbon molecular sieves. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1747-1755, 1998
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  • 6
    Electronic Resource
    Electronic Resource
    Phase separation of micellar solutions at extreme dilution: A study of polystyrene-b-poly(sodium acrylate) micelles in aqueous NaCl solutions (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1197-1212 
    Details
    ISSN: 0887-6266
    Keywords: block polyelectrolyte solutions ; micelles ; light scattering ; phase separation ; NaCl solutions ; extreme dilution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Micellar solutions of polystyrene-b-poly(sodium acrylate) copolymers in aqueous NaCl were studied by static light scattering (SLS). It was found that micellar solutions of the copolymer, at concentrations of NaCl at, or above, 2.0 mol dm-3, became turbid on dilution at constant salt concentration and at constant temperature. Turbidity arose from highly dilute solutions (typically at a concentration three orders of magnitude lower than the overlap concentration of the micelle, C*), but at concentrations above the expected critical micellization concentrations (c.m.c.s). The observed turbidity was attributed to the phase separation of the micellar phase. A systematic investigation of the phase separation phenomenon was performed. The effects of various parameters on the solution behavior of the micellar solutions were studied, including the effect of the concentration of NaCl, the effect of temperature, and the effect of the length of the hydrophilic, corona-forming poly(sodium acrylate) block. Phase separation was attributed to the presence of a very large excess of NaCl in the dilute micellar solutions. It was proposed that phase separation arose because of the reduced hydration of the polyion, the decreased electrostatic repulsion between the micelles, and the increase in the amount of ion binding, which occur in highly dilute salt solutions. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Biomechanical and histological analysis of an HA coated, arc deposited CPTi canine hip prosthesis (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 31 (1996), S. 465-474 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The interfacial shear strength and bone tissue response was investigated for an arc deposited (AD) commercially pure titanium implant surface, with (AD/HA) and without (AD) plasma-sprayed hydroxyapatite (HA) coating. Ten purpose bred coonhounds received bilateral femoral stem implantation (AD and AD/HA) in the proximal femurs (hemiarthroplasty). The femoral prosthesis consisted of a modular CoCr alloy head, modular Ti-6A1-4V neck, and a 10-mm diameter cylindrical Ti-6A1-4V femoral stem. The AD surface had 30-35% greater surface roughness than the AD/HA surface. The HA coating had a purity greater than 90% and a crystallinity greater than 65%. After 6, 12, and 24 weeks, the implants were retrieved and analyzed with mechanical testing, qualitative and quantitative histology, and electron microscopy. The AD/HA implants had equivalent interfacial shear strengths to the AD implants at all time periods. The AD/HA implants had significantly greater linear bone contact than the AD implants. The 6-week implants had significantly thicker cortical bone than the 12- and 24-week implants. The HA coating was very stable in vivo, evidenced by no thickness reduction at any time period. Qualitatively, the AD/HA implants primarily had bone contacting the implant surface with little fibrous tissue present, and the AD implants had bone and fibrous tissue contacting the implant surface. The electron microscopy analysis showed that the mechanically tested implants exhibited a mixed failure mode at the bone, HA coating, and titanium interfaces. © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Evaluation of poly(DTH carbonate), a tyrosine-derived degradable polymer, for orthopedic applications (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 1337-1348 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The polymerization of desaminotyrosinetyrosylhexyl ester (DTH) with phosgene gives rise to poly(DTH carbonate), a new pseudopoly(amino acid). To evaluate the performance of this bioabsorbable material in orthopedic applications, the tissue responses elicited by compression-molded pins of poly(DTH carbonate) and clinically used polydioxanone pins (PDS; Orthosorb®) were compared. The two types of pins were implanted in the paravertebral muscle and in the metaphyseal proximal tibia and distal femur of 10 White New Zealand Rabbits for 1, 2, 4, and 26 weeks. The tissue response was evaluated using histologic staining of softand hard-tissue sections, fluorescent bone marker incorporation, and backscattered electron imaging. In soft tissue, both poly(DTH carbonate) and PDS elicited a mild inflammatory response resulting in encapsulation. During the disintegration phase, the PDS implants triggered a foreign body response involving the phagocytosis of polymeric debris by histiocytes and giant cells. No such response was observed for poly(DTH carbonate). In hard tissue, close bone apposition was observed throughout the 26-week test period for poly(DTH carbonate) implants. At the 26-week time point, the poly(DTH carbonate) implants exhibited surface erosion and were penetrated by new bone. In contrast, an intervening fibrous tissue layer was always present between the PDS pins and the bone. At 26 weeks, the PDS implants had partially resorbed and a foreign body response characterized by infiltration of inflammatory cells, and bone resorption was observed in several of the implantation sites. This study indicates that poly(DTH carbonate) and PDS exhibit fundamentally different interactions with hard tissue, and that poly(DTH carbonate) is a promising orthopedic implant material. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820291105
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  • 9
    Electronic Resource
    Electronic Resource
    Vergleich von in Lösung und mit HPLC bestimmten Bildungsenthalpien über Wasserstoffbrücken gebundener Wirt-Gast-KomplexeQuantitative Host-Guest Complexation Studies Using Chemically Bonded Stationary Phases, 2. Mitteilung. - 1. Mitteilung: [1]. Diese Arbeit wurde von den National Institutes of Health gefördert (GM38010). (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 107 (1995), S. 2589-2592 
    Details
    ISSN: 0044-8249
    Keywords: Heterocyclen ; HPLC ; Supramolekulare Chemie ; Wasserstoffbrücken ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19951072119
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  • 10
    Electronic Resource
    Electronic Resource
    Hocheffektive, über Wasserstoffbrücken bindende Rezeptoren für GuanidinderivateDiese Arbeit wurde von den National Institutes of Health gefördert (GM 32937 und GM 38010). (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 107 (1995), S. 2321-2324 
    Details
    ISSN: 0044-8249
    Keywords: Molekulare Erkennung ; Nucleoside ; Wasserstoffbrücken ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19951071923
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