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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 21 (1975), S. 1158-1164 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method is presented for the numerical solution of nonlinear minimum-time control problems where at least one of the state variables is monotone. A coordinate transformation converts the problem with fixed end point and free end time to one of free end point and fixed end time. The transformed problem can be solved efficiently by the use of the gradient method with penalty functions to force the system to achieve target values of state variables. Application of the method is illustrated by the synthesis of a minimum-time temperature path for the thermally initiated bulk polymerization of styrene.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    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: Measurements of the density of a large number of experimental isotactic polypropylenes have shown that the specific volume is linearly related to per cent crystallinity as determined from x-ray data. The density is also linearly related to the absorbance of certain absorption bands in the infrared spectrum of isotactic polypropylene. The infrared data allow a determination of the density of the amorphous polymer which is in good agreement with literature values and with a value determined from the x-ray data by extrapolation to zero crystallinity. It is found that there is a rough, approximately linear correlation between crystallinity (by density) of unextracted polypropylene and the per cent insoluble residue remaining after extraction with boiling n-heptane or after successive extraction with other solvents and heptane. In all instances, the amount of residue exceeds the crystalline content. The crystallinity-insolubility relationship is influenced by molecular weight (as judged by intrinsic viscosity). An increase in crystallinity at constant [η] corresponds to an increase in insolubility; at constant crystallinity, a larger [η] corresponds to greater insolubility. In terms of density, the unextracted polymer may not be regarded as simply a mixture of two well-defined components, since the density of insoluble residue increases with the density of the whole polymer.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    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: Hydrocarbon-soluble oligomers were prepared by the acid-catalyzed condensation of alkylanilines with formaldehyde. Highest molecular weight oligomers (MW ∼ 6000) were obtained from alkylanilines prepared by the Friedel-Crafts alkylation of aniline with α-olefins. By NMR, it was shown that the oligomers contain structures corresponding to methylene-linked aromatic rings and methylene linked to both an aromatic ring and a nitrogen atom. The oligomers exhibit very good initial inhibition of metal corrosion in aqueous environment; and the inhibition is more persistent than that observed with monomeric analogs.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 293-306 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Strain transfer near hydroxyapatite (HA) coated canine hip implants was examined using simulated anatomical loading based on in vivo strain measurements. Strain changes near implants relative to intact control values were in excess of 100% for transverse and principal strains for zero time period (immediate postimplant) specimens. They were generally smaller (100% or less) for axial, transverse, and principal minimums in the same locations for 4 months postimplantation specimens.Cortical bone loss occurred in all implanted femora. The most extensive loss, up to 47%, occurred adjacent to the proximal section of the implant. Extensive trabecular bone formation, over 300% in some regions of each femur, was noted in all implanted femora.Backscattered electron imaging along the HA-coated sections of the implants showed extensive bone bonded to the coating. Normal light and UV light micrographs showed direct bone apposition to the implant surfaces and extensive bone formation in all test animals. Microscopy revealed no evidence of any soft tissue layer between the implant and bone. Bone was typically found in direct contact with the implant surface.Histomorphometry indicated that bone formation rates in the implanted femora were elevated, up to 850%, relative to controls. Fewer formation sites were noted on the posterior and lateral (in two cases zero sites). Mineral apposition rates (MAR) from two of the dogs were slightly elevated (from 110-113%) in the implanted femora relative to controls and depressed (to about 83% of controls) in a third. © 1994 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 6 (1995), S. 237-242 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Because of the recent trend in total hip arthroplasty to achieve direct contact of the endoprosthesis with cortical bone, comparison of bone apposition from cortical bone and cancellous bone was performed. The response of cortical and cancellous bone to hydroxylapatite was also compared. Implants in cortical bone demonstrated a higher interface shear strength and more bone apposition than those in cancellous bone over all time periods tested. Hydroxylapatite coating increased the interfacial shear and bone apposition in cortical bone at all time periods and in both the 3- and 6-week cancellous bone models. The potential effect of stress shielding (and subsequent bone resorption) by femoral stems ingrown with cortical bone is discussed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 141-152 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 ultra-high strength/modulus, extended chain polyethylene fiber (Spectra® fiber) composite has shown great potential as a lightweight armor material with its extraordinary capability of absorbing the kinetic energy of projectiles. But the relatively low melting point of this fiber (∼ 145°C) has caused concerns regarding the effect of temperature rise during the impact/penetration process on the performance as armor material. In this article, an analysis of temperature rise in projectile and the fiber composite during the impact/penetration process is described. Combining the simulation of impact deformation by finite element analysis and the simulation of temperature rise by a finite difference approximation of the related dynamic equations, the temperature rise caused by the projectile/composite interaction was estimated. Results show that there is a significant temperature rise at the projectile/composite interface due to the friction but that the short length of time involved in the process and the low thermal conductivity of Spectra fiber composite keep the temperature rise in a very small region (in the order of 0.001 cm) around the interface during the impact/penetration process. Consequently, the volume that is affected by the temperature rise is very small, in the order of total 0.001 cm3 around the projectile, and this is too small to generate any detectable effect on the armor performance. After the projectile is stopped, however, substantial heating of fiber composite can occur under specific conditions as the result of heat flow from the hot projectile embedded in the composite. This heating of fibers, however, is a postmortem effect and hence inconsequential to the ballistic performance of the composite armor.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 19 (1988), S. 203-212 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ultraviolet resonance Raman UVRR spectra, with 240 and 218 nm excitation, are reported for complexes of cis-NH32Pt2+ with dGMP 2-deoxyguanosine 5′-monophosphate having H or D at C-8. Previously reported UVRR effects of Pt binding to G are confirmed and extended. Excitation profiles recorded throughout the UV region are reported, together with cross-sections for the perchlorate ion, used as an internal standard. The excitation profiles show strong losses in enhancement associated with Pt binding for most of the guanine G UVRR bands in resonance with the UV electronic transitions of G. Hypochromic effects are involved, associated with diminished transition dipole moments due to the N-7-bound Pt, as are changes in Franck-Condon products. A new, weak resonance is seen in the excitation profiles at ca 220 nm, and is attributed to a Pt → G metal-ligand chargetransfer transition. Because bands showing large frequency shifts on Pt binding are selectively enhanced by this transition, 218 nm is the best wavelength for monitoring Pt binding to G in UVRR spectra. Even at this wavelength, Raman contributions from uncomplexed G and also A tend to obscure the Pt-bound G spectrum, as shown by the spectra of the dinucleotides d(GpG) and d(ApG) complexed with Pt(dien)2+ (dien = diethylenetriamine), although a marker for Pt-bound G can still be detected. The 218 nm-excited spectrum of cis-Pt[d(GpG)N-7(1), N-7(2)] shows clear evidence of both N(C-3′-endo) and S(C-2′-endo) sugar conformations, and also intensity alterations which may be associated with the ‘head-to-head’ arrangement of the Pt-bound G residues.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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