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  • 1
    Electronic Resource
    Electronic Resource
    Role of Surface Effects in the Inelastic Background of X-ray Photoelectron Spectroscopy (1996)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 24 (1996), S. 490-496 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: We have derived a new deconvolution formula to obtain the original no-loss XPS spectra, the so-called source function, by taking surface effects into account. With this formula the primary XPS spectra of Au 4d and Au 4f are carried out from the experimental data. The primary excitation spectra are compared to the results derived by Tougaard’s method in which surface effects were neglected. The present result is markedly different from Tougaard’s result, which consists of a tail extending ∽50 eV below the peak. The result reveals that the influence of surface effects on the background removal of the spectra is considerably significant for the energy range ∽50 eV below the peak energy. It is also found that the large tail in Tougaard’s results can be essentially removed when surface effects are considered.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Ion Impacts and Nanostructures on Ge(111), In0.22Ga0.78As/GaAs(100) and Alpha Quartz Surfaces Observed by Atomic Force Microscopy (1996)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 24 (1996), S. 881-886 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Atomic force microscopy (AFM) is used to compare the topography of the ion-bombarded surfaces of Ge(111), atomically flat terraces on strained layers of In0.22Ga0.78As on GaAs and alpha quartz.Germanium samples were bombarded with 100 keV Ge+ ions at doses of up to 1016 ions cm-2. A cellular structure with a mean pore diameter of 50 nm was observed at greater detail but similar to that reported in earlier scanning electron microscope (SEM) measurements [I. H. Wilson, J. Appl. Phys. 53, 1698-1705 (1982)]. It is proposed that this structure is formed by the intersection of the etched surface with point defect clusters created in the dense collision cascade, and the combined effects of sputter etching, ion reflection and redeposition.Individual impact craters are observed on As+- and B+-bombarded In0.22Ga0.78As/GaAs (35 keV, 1011 ions cm-2) at the areal density identical to that of ion impacts. The craters arising from As+ bombardment are attributed to damage associated with nuclear stopping in the primary collision cascade.By contrast, alpha quartz samples bombarded with a wide range of ions (Pb, Ni, O, Si, Ar and In at doses of 1010-1011 ions cm-2) and energies (30 keV to 0.73 GeV) exhibit asperities (bumps). In the case of very high energy ions, the areal density of asperities is much less than that of ion impacts. The asperities are attributed to volume expansion associated with amorphous zone creation. In the case of very high energy ions, zone creation is attributed to energetic knock-on cascades directed back towards the surface.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    XPS Study of Mn Thin Films Grown on GaAs(001) Surfaces (1996)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 24 (1996), S. 653-656 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The composition-depth profile studies using x-ray photoelectron spectroscopy (XPS) are carried out for Mn thin films grown on GaAs(001) substrates at different substrate temperatures. The experimental results show that due to the interdiffusion and chemical reaction, an Mn-Ga-As mixed layer is formed between the Mn thin film and GaAs substrate. The thickness of the Mn-Ga-As mixed layer for the sample grown at 300 K is much thinner than that grown at 400 K. Because of the strong interdiffusion and chemical reaction, the overlayer on the GaAs substrate for the sample grown at 450 K is dominated by an Mn-Ga-As mixed layer, and no pure Mn area can be found on the top of the surface. The formation mechanism of γ-Mn grown on GaAs(001) surfaces is discussed.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Nylon 4/PVA blend membrane for dialysis (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1795-1804 
    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: To improve the hydrophilicity and enhance the transport flux of nylon 4 membrane for dialysis, this study attempts to utilize blending nylon 4 with poly(vinyl alcohol) (PVA). The instability of PVA in water can be obtained more easily than by other methods, such as chemical, γ-ray irradiated crosslinking, or high-temperature treatment used by previous researchers. The effects of maturation time of the casting solution, nylon 4/PVA ratios, and casting solvent compositions on esterification of PVA, salt permeability, water content, partition coefficient, diffusivity, and mechanical strength of membrances are studied. The membrane, prepared by casting solution of nylon 4/PVA = 9/1 wt % formic acid with 24-h maturation time, possesses permeabilities of NaCl and urea, 33.14 and 19.67 × 10-5 cm2/min, respectively.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070431003
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  • 5
    Electronic Resource
    Electronic Resource
    The influence of molecular weight on the large deformation behavior of SBS triblock copolymer elastomers (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 629-643 
    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: Engineering stress-strain properties were determined for two polystyrene-polybutadiene-polystyrene (SBS) triblock copolymer elastomers, one consisting of blocks of molecular weight 7000/43000/7000 and the other, 16000/85000/17000. In addition, various blends of these two materials were prepared in order to vary the number-average molecular weight of the blocks in a systematic way while maintaining polystyrene content in the range of 25-28 wt %. Samples were solvent cast from benzene or benzene/heptane mixtures and annealed before testing. Ring specimens were extended to rupture at varying strain rates on an Instron tensile tester. Results indicate that number-average molecular weight has a marked influence on stress-strain behavior over the range of molecular weights and testing conditions employed. The observed behavior is consistent with a systematic increase in the proportion of a mixed interfacial region between the pure polystyrene and polybutadiene domain as molecular weight decreases. The interfacial region contributes to mechanical hystersis, rate sensitivity, and toughness in the SBS materials. Scanning electron photomicrographs of fracture surfaces also showed systematic changes with molecular weight.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1977.070210305
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of hexane treatment on the permeation of silicone-coated polyethersulfone membranesIssued as NRCC No. 31483. (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 2169-2176 
    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: The polyethersulfone membranes were cast from casting solutions including poly(vinyl pyrrolidone) additive. The membranes were further dried, silicone-coated, and used for the permeation study with hydrogen and nitrogen gases. It has been found that solvent hexane which was included in the silicone rubber solution for surface coating increased the pore size on the membranes surface when poly(vinyl pyrrolidone) was present in the membrane. The above effect counteracted the pore size decrease by silicone coating, and, as a result, an H2/N2 permeability ratio of only 8.9 was achieved as compared with 28, which was obtained when the base polyethersulfone membrane was prepared from a casting solution without poly(vinyl pyrrolidone) additive.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410921
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  • 7
    Electronic Resource
    Electronic Resource
    Role of surfactant in composite latex particle morphology (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 487-499 
    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: Composite particles were prepared by seeded emulsion polymerization at 70°C using K2S2O8 as initiator and two different nonionic surfactants. Monodisperse polystyrene latex particles were used as seed and methyl methacrylate was used as second-stage monomer. When the surfactant, polyethylene oxide-propylene oxide (Pluronic F-108), was used, the final particle morphology showed that the PMMA (core) was partially covered by polystyrene. However, when nonyphenol polyethylene oxide (Igepal Co-990) was used as surfactant, one observed a reversed type of encapsulation (i.e., PS core is partially engulfed by PMMA). The interfacial tensions of the polymer phase against water containing the appropriate surfactant were measured by the drop-volume method and used in a mathematical model based on thermodynamic analysis to predict the equilibrium particle morphology. The observed particle morphologies were found to differ from the predicted morphologies at low conversion of the second-stage monomer but agreed with it at higher conversion.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070450313
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of azo-containing polydimethylsiloxanes and their copolymers with methyl methacrylate (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2613-2620 
    Details
    ISSN: 0887-624X
    Keywords: polydimethylsiloxane ; poly(methyl methacrylate) ; block copolymer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Azo group-containing polydimethylsiloxanes (PDMS-ACP), macroazoinitiators, were prepared by polycondensation reaction of 4,4′-azobis-4-cyanopentanoyl chloride (ACPC) with hydroxybutyl-terminated polydimethylsiloxane (PDMS) of varying molecular weights. The activation energy (Ea), activation enthalpy (ΔH
    Additional Material: 9 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Premelting thermal fluctuational base pair opening probability of poly(dA) · poly(dT) as predicted by the modified self-consistent phonon theory (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 139-148 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We employ a mean field, modified, self-consistent phonon theory to evaluate the single base-pair opening rate and the probability of a base pair in the amino proton exchangeable state for the homopolymer poly(dA) · poly(dT) at temperatures below the helix-coil transition region. Our calculated premelting single base-pair opening probabilities are in general agreement with several available experimental estimates from imino proton exchange and formaldehyde-induced DNA melting measurements. These calculated opening probabilities, however, are in disagreement with the prediction of the helix-coil transition theory. Possible reasons for the differences are discussed, especially the possible different definition of a meaningful open state in the premelting region. The premelting open state of the modified self-consistent phonon approximation theory seems to be appropriate to describe a solvent-accessible open configuration that is sufficient to facilitate important chemical reactions such as imino proton exchange and formaldehyde reaction with the bases. This can be compared with the completely unstacked open state of the helix-coil transition theory originally defined in the helix-coil transition region. We propose that the amino proton exchangeable state is different from the open state associated with melting and only involves the breaking of the amino interbase H bond. The agreement between the calculated and experimentally estimated probability of a base pair in the amino proton exchangeable state seems to support this hypothesis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310202
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  • 10
    Electronic Resource
    Electronic Resource
    A cooperative self-consistent microscopic theory of thermally induced melting of a repeat sequence DNA polymer (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 351-362 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We attempt to extend the modified self-consistent phonon theory to describe thermal fluctuational base-pair opening of repeat sequence DNA polymers in the helix-coil transition region as well as in the premelting region. A microscopic base-pair open state is introduced and the effect of this open state is taken into account self-consistently in a mean field system that models the DNA polymer. Our analysis indicates the structure of this open state changes with temperature in such a manner that on average a base pair opens and unstacks with its neighbors more completely as temperature increases. We apply this theory to a homopolymer - poly(dG) · poly(dC) to evaluate the base-pair opening probability in a temperature range from 273 to 366.5 K. At 366.5 K the system undergoes cooperative melting. Our calculated base-pair opening probabilities are in general agreement with several experimental estimates at room temperature. The calculated probabilities show typical melting curve behavior at temperatures close to the observed melting temperature. The cooperative modified self-consistent phonon approximation approach becomes a viable microscopic theory of melting. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330304
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