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  • Chemistry  (633)
  • Polymer and Materials Science  (370)
  • 1995-1999  (633)
  • 1996  (633)
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  • 1995-1999  (633)
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  • 1
    Electronic Resource
    Electronic Resource
    Surface roughness modulates the local production of growth factors and cytokines by osteoblast-like MG-63 cells (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 55-63 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Titanium (Ti) surface roughness affects proliferation, differentiation, and matrix production of MG-63 osteoblast-like cells. Cytokines and growth factors produced in the milieu surrounding an implant may also be influenced by its surface, thereby modulating the healing process. This study examined the effect of surface roughness on the production of two factors known to have potent effects on bone, prostaglandin E2 (PGE2) and transforming growth factor β1 (TGF-β1). MG-63 cells were cultured on Ti disks of varying roughness. The surfaces were ranked from smoothest to roughest: electropolished (EP), pretreated with hydrofluoric acid-nitric acid (PT), fine sand-blasted, etched with HCl and H2SO4, and washed (EA), coarse sand-blasted, etched with HCl and H2SO4, and washed (CA), and Ti plasma-sprayed (TPS). Cells were cultured in 24-well polystyrene (plastic) dishes as controls and to determine when confluence was achieved. Media were collected and cell number determined 24 h postconfluence. PGE2 and TGF-β1 levels in the conditioned media were determined using commercial radioimmunoassay and enzyme-linked immunosorbent assay kits, respectively. There was an inverse relationship between cell number and Ti surface roughness. Total PGE2 content in the media of cultures grown on the three roughest surfaces (FA, CA, and TPS) was significantly increased 1.5-4.0 times over that found in media of cultures grown on plastic or smooth surfaces. When PGE2 production was expressed per cell number, CA and TPS cultures exhibited six- to eightfold increases compared to cultures on plastic and smooth surfaces. There was a direct relationship between TGF-β1 production and surface roughness, both in terms of total TGF-β1 per culture and when normalized for cell number. TGF-β1 production on rough surfaces (CA and TPS) was three to five times higher than on plastic. These studies indicate that substrate surface roughness affects cytokine and growth factor production by MG-63 cells, suggesting that surface roughness may modulate the activity of cells interacting with an implant, and thereby affect tissue healing and implant success. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of titanium surface roughness on chondrocyte proliferation, matrix production, and differentiation depends on the state of cell maturation (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 30 (1996), S. 145-155 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Although it is well accepted that implant success is dependent on various surface properties, little is known about the effect of surface roughness on cell metabolism or differentiation, or whether the effects vary with the maturational state of the cells interacting with the implant. In the current study, we examined the effect of titanium (Ti) surface roughness on chondrocyte proliferation, differentiation, and matrix synthesis using cells derived from known stages of endochondral development. Chondrocytes derived from the resting zone (RCs) and growth zone (GCs) of rat costochondral cartilage were cultured on Ti disks that were prepared as follows: HF-HNO3-treated and washed (PT); PT-treated and electropolished (EP); fine sand-blasted, HCl-H2SO4-etched, and washed (FA); coarse sand-blasted, HCl-H2SO4-etched, and washed (CA); or Ti plasma-sprayed (TPS). Based on surface analysis, the Ti surfaces were ranked from smoothest to roughest: EP, PT, FA, CA, and TPS. Cell proliferation was assessed by cell number and [3H]-thymidine incorporation, and RNA synthesis was assessed by [3H]-uridine incorporation. Differentiation was determined by alkaline phosphatase specific activity (AL-Pase). Matrix production was measured by [3H]-proline incorporation into collagenase-digestible (CDP) and noncollagenase-digestible (NCP) protein and by [35S]-sulfate incorporation into proteoglycan. GCs required two trypsinizations for complete removal from the culture disks; the number of cells released by the first trypsinization was generally decreased with increasing surface roughness while that released by the second trypsinization was increased. In RC cultures, cell number was similarly decreased on the rougher surfaces; only minimal numbers of RCs were released by a second trypsinization. [3H]-thymidine incorporation by RCs decreased with increasing surface roughness while that by GCs was increased. [3H]-Uridine incorporation by both GCs and RCs was greater on rough surfaces. Conversely, ALPase in the cell layer and isolated cells of both cell types was significantly decreased. GC CDP and NCP production was significantly decreased on rough surfaces while CDP production by RC cells was significantly decreased on smooth surfaces. [35S]-sulfate incorporation by RCs and GCs was decreased on all surfaces compared to tissue culture plastic. The results of this study indicate that surface roughness affects chondrocyte proliferation, differentiation, and matrix synthesis, and that this regulation is cell maturation dependent. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    LC multiblock copolymers containing polysulfone segments. I. Synthesis and morphology (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 1819-1833 
    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: Multiblock copolymers offer the possibility to combine the properties of different polymers. Thus, new materials with tailor-made unique properties are available by coupling of different suitable polymeric segments. The goal of the work discussed in this paper was to combine advantageous properties of liquid-crystalline polymers (LCP) with those of polysulfone (PSU). Therefore, liquid crystalline poly(ethylene terephthalate-co-1,4-oxybenzoates) were connected with PSU oligomers. Chemically homogeneous multiblock copolymers with high molecular weight were obtained by a melt transesterification procedure. It was demonstrated by wide angle x-ray scattering (WAXS), polarizing microscopy, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) that the properties of the multiblock copolymers (solid phase structure, phase behavior, morphology, glass transition, and melting behavior) can be balanced by the segment length of the incorporated blocks. The investigations clearly reveal the existence of a two-phase structure. However, a change of properties compared to the corresponding homopolymers refers to certain interactions between the phase due to the chemical connection of the LCP and PSU segments. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrafast infrared spectroscopy in biomolecules: Active site dynamics of heme proteins (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 2 (1996), S. 277-299 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Rapid advances in the generation of intense tunable ultrashort mid-infrared (IR) laser pulses allow the use of ultrafast IR pump-probe and vibrational echo experiments to investigate the dynamics of the fundamental vibrational transition of CO bound to the active site of heme proteins. The studies were performed using a free-electron laser (FEL) and an experimental set up at the Stanford University FEL Center. These novel techniques are discussed in some detail. Pump-probe experiments on myoglobin-CO (MbCO) measure CO vibrational relaxation (VR). The VR process involves loss of vibrational excitation from CO to the protein and solvent. Infrared vibrational echoes measure CO vibrational dephasing. The quantum mechanical treatment of the force-correlation function description of vibrational dynamics in condensed phases is described briefly. A quantum mechanical treatment is needed to explain the temperature dependence of VR in Mb-CO from 10 to 300 K. A molecular-level description including elements of heme protein structure in the treatment of vibrational dynamics is also discussed. Vibrational relaxation of CO in Mb occurs on the 10-11-s time scale. VR was studied in proteins with single-site mutations, proteins from different species, and model heme compounds. A roughly linear relationship between carbonyl stretching frequency and VR rate has been observed. The dominant VR pathway is shown to involve anharmonic coupling from CO through the π-bonded network of the porphyrin, to porphyrin vibrations with frequencies 〉 400 cm-1. The heme protein influences VR of bound ligands at the active site primarily via altering the through π-bond coupling between CO and heme. Preliminary vibrational echo studies of the effects of protein conformational relaxation dynamics on ligand dephasing are also reported. © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of PTFE on Silicon Wafer Tribological Transfer Films by XPS, Imaging XPS and AFM (1996)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 24 (1996), S. 204-210 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Atomic force microscopy (AFM) shows that PTFE-on-silicon wafer tribological transfer films consist of narrow ribbons of PTFE, 〈1 μm wide and 〈10 nm high, aligned with the film draw direction. Within the ribbons the PTFE molecular chains are also aligned with the draw direction. Such materials are of interest as substrates for the epitaxial crystallization of polymers and small molecules. X-ray photoelectron spectroscopy demonstrates that the amount of PTFE put down increases with deposition temperature and pressure. The XPS azimuthal angle dependence at low electron take-off angle is consistent with the aligned ribbon morphology. Azimuthal and polar angle dependence and charging studies show that hydrocarbon contamination observed in the XPS spectrum is located on top of the silicon wafer substrate, in the channels between the PTFE ribbons. Imaging XPS confirms the pressure dependence of PTFE coverage, and at low deposition pressure reveals tracks of PTFE ∽100 μm wide, aligned with the film draw direction. Together with the AFM data this leads to a description of PTFE transfer films as fractal materials.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    NiH3IO6 · 6H2O  -  Kristallstruktur und Schwingungsspektren (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 845-852 
    Details
    ISSN: 0044-2313
    Keywords: Nickel orthoperiodate ; i.r., Raman spectra ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: NiH3IO6 · 6 H2O  -  Crystal Structures and Vibrational SpectraThe crystal structure of NiH3IO6 · 6 H2O has been determined by X-ray single-crystal diffraction (Pc, Z = 2, a = 516.74(9), b = 981.5(2), c = 1052.5(2) pm, β = 116.496(8)°) on the basis of 4169 unique reflections (R = 1.96%). The structure is built up of distorted Ni(H2O)62+ and H3IO62- octahedra linked by hydrogen bonding. IR and Raman spectra of both the title compound and isostructural MgH3IO6 · 6 H2O as well as of deuterated specimens are given. There are up to 14 different OH(OD) modes in the spectra of isotopically dilute samples due to the 15 different hydrogen positions of the structure. The internal modes of the meridional H3IO62- ions (pseudo C2v symmetry) are discussed with respect to that double T-shaped entity, which gives rise to only two instead of 3I—O, I—O(H), and OH stretches in the IR and Raman spectra, i.e. the same as for facial (C3v) structured ions.
    Notes: Die Kristallstruktur (Pc, Z = 2) von NiH3IO6 · 6 H2O wurde mittels Röntgen-Einkristallmessungen auf der Basis von 4169 symmetrieunabhängigen Reflexen bestimmt (R = 1,96%). IR- und Raman-Spektren von NiH3IO6 · 6 H2O und der isotypen Verbindung MgH3IO6 · 6 H2O sowie von deuterierten Präparaten werden mitgeteilt. Die Spektren isotypenverdünnter Proben zeigen bis zu 14 OH(OD)-Streckschwingungen entsprechend den 15 verschiedenen Wasserstoff-Positionen der Struktur. Die meridionalen H3IO62--Ionen (Pseudosymmetrie C2v) besitzen wegen der T-förmigen Anordnung der je 3 IO-und IOH-Gruppen nur je 2 IO-, IO(H)- und OH-Streckschwingungen in den IR- und Raman-Spektren und können daher schwingungsspektroskopisch nicht von H3IO62--Ionen mit facialer Struktur (C3v) unterschieden werden.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220516
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  • 7
    Electronic Resource
    Electronic Resource
    Zwitterionic polymerization of 1-[4-[(4-hydroxy-1-naphthyl)thio]butyl]quinuclidinium hydroxide inner salt (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 801-809 
    Details
    ISSN: 0887-624X
    Keywords: zwitterion ; hydroxide inner salt ; polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The zwitterion, 1-[4-[(4-hydroxy-1-naphthyl)thio]butyl]quinuclidinium hydroxide inner salt, was synthesized from tetrahydro-1-(4-hydroxy-1-naphthyl)thiophenium hydrochloride and quinuclidine and characterized by NMR and IR spectroscopy. Polymerization of the zwitterion was studied over the temperature range 175-225°C. The polymer was identified as poly(1,4-piperidinediylethyleneoxy-1,4-naphthylenethiotetramethylene) based on NMR and IR spectroscopy. The polymer was found to contain 3-butenylthio and 4-hydroxy-1-naphthyl end groups. Based on the signal area of the olefinic end group, the polymer M⊼n varied between 8500 and 13,000. The highest molecular weight was achieved at the lowest temperature, indicating that termination became more favored at higher temperature. A mechanism is proposed to describe the polymerization. © 1996 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    The polymerization rate of freshly nucleated particles during emulsion polymerization with micellar nucleation (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1747-1751 
    Details
    ISSN: 0887-624X
    Keywords: emulsion polymerization ; particle nucleation ; radical desorption ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple procedure was developed to account for the contribution of freshly nucleated particles to the total polymerization rate during micellar nucleation. It has been shown that the polymerization rate of the freshly nucleated particles cannot be described by a steady-state solution for a radical population balance over the particle size distribution, i.e., the classical Smith-Ewart recursion relation. Once nucleated, the particles grow for a significant period of time with one radical before either radical desorption or radical absorption, followed by instantaneous bimolecular termination, occur. For most emulsion polymerizations, radical desorption is the dominant process for radical loss of the freshly nucleated particles. A relation for the mean time that the freshly nucleated particles grow with one radical was derived. © 1996 John Wiley & Sons, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    Chaotic mixing of two similar fluids in the presence of a third dissimilar fluid (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3301-3309 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two-dimensional chaotic mixing of similar Newtonian fluids in the presence of an advected dissimilar minor phase fluid body with specified size, interfacial tension, and viscosity ratio was numerically investigated. Interfacial tension was sufficiently high to allow only small deformations in the dissimilar minor phase body. Mixing was confined to a rectangular cavity with periodically driven upper and lower surfaces. Regions of regular motion (i.e., islands) of comparable size to the minor phase body were eventually destroyed or replaced by the minor phase body. Islands persisted for longer times when the initial separation distance between the minor phase body and island was large or when the viscosity ratio was small. When interfacial tension was small enough to deform the minor phase body more readily, islands showed little indication of instability. Results suggest opportunities for improving mixing uniformity in practical processes and disclose how interactions between dissimilar fluids affect mixing.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690421202
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  • 10
    Electronic Resource
    Electronic Resource
    Perturbation analysis of Thomas and Windle's model of Case II transport (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2025-2035 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thomas and Windle's model of Case II transport is analyzed for a semiinfinite medium by a singular perturbation technique. Two adjacent boundary layers separate equilibrated and dry regions. A thin boundary layer of width ∼ O(M-1/2/ln M), where M (≫1) dictates how rapidly the mixture's viscosity decays with liquid concentration, sits next to the equilibrated outer left region. Here, quasi-steady diffusion balances relaxation. A thicker intermediate layer of width ∼ O(M-1/2) separates the lefthand boundary layer and the dry outer region on the right, where both relaxation and unsteady diffusion participate in the transport. Matching the solutions at leading order specifies the moving front's speed, v: v ∼ M1/2. The analysis indicates that relaxation significantly affects the nearly dry region just ahead of the moving front. This disagrees with the widely accepted view that ordinary diffusion dominates in the nearly dry righthand region. Approximating that ordinary diffusion dominates in this region leads to a stepexponential concentration profile at the front and a simple analytical solution for the front speed, v with the correct M scaling. This approximate result accurately predicts the values of v determined by direct numerical solutions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420723
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