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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 6 (1982), S. 121-125 
    ISSN: 0148-7280
    Keywords: histidine decarboxylase ; preimplantation embryo ; blastocyst ; compaction ; histamine ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The present study determines the effect of a specific and an irreversible inhibitor of histidine decarboxylase (HDC), α-fluoromethylhistidine (α-FMH) on the mouse preimplantation embryo development in vitro. The embryo culture technique was used to assess the effect of α-FMH. Embryos recovered at 0800-0900 hr (AM) on day 3 of pregnancy were 4-8 cells, whereas those recovered at 1600-1630 hr were mostly 8-cell compacted embryos. Of the day 3-AM embryos, 81.3 ± 4.3% developed to blastocysts within 48 hr when cultured in the medium alone, but addition of α-FMH (0.19 or 0.38 mM) drastically reduced the blastocyst formation to 26.6 ± 7 or 16.8 ± 4.3%. Most of them were arrested before the compaction stage. Addition of L-histidine, the substrate for HDC, did not alter the inhibition of blastocyst formation in the presence of α-FMH (37.2 ± 10.9%). Of the day 3-PM embryos, 99.3 ± 0.7% developed to blastocyst stage when cultured in the medium alone and addition of α-FMH (0.19 or 0.38 mM) did not affect the embryo development (92.1 ± 4.3 or 81.9 ± 9.9% developed to blastocysts). The birth of healthy young following transfer of these blastocysts into pseudopregnant mice indicates normal development of the embryos under this condition. The results suggest that histamine synthesis may be required for the process of compaction and thus the formation of blastocyst.
    Additional Material: 1 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Journal of Vinyl and Additive Technology 1 (1995), S. 195-200 
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Among the various marine plastic debris, abandoned or lost fishing gear is a major pollutant, adversely affecting marine life and disturbing the ecological equilibrium. In an attempt to find a technological solution to recycling of the plastic fishing gear, two routes are evaluated. The first is melt reprocessing. Here, compatibilized blends and composites are prepared using various polymers - HDPE, nylon 6 (N6), nylon 66 (N66), etc. - obtained from melt reprocessing of fishnets. This approach involves cleaning, size reduction, melt extrusion and filtering, modification, and injection molding. Mechanical properties of blends and composites thus made are compared with commercial materials. The second approach uses these nets as organic fibrous reinforcements in polymeric matrices. N6 and N66 fibers obtained from fishnets are compounded with a thermoplastic polyurethane (TPU) matrix at temperatures below the melting point of nylons. Good adhesion between the fibers and the matrix is obtained because of the interaction between nylons and TPU. Addition of nylon fibers to the TPU matrix result in improved stiffness. Shore hardness, abrasion resistance, etc.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 16 (1995), S. 204-214 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In attempts to identify potential applications for refined commingled postconsumer plastics, a feedstock containing about 80% polyethylene (PE) and lesser amounts of poly(ethylene terephthalate) (PET), polystyrene (PS), polypropylene (PP), and poly(vinyl chloride) (PVC) was modified through functionalization with maleic anhydride in a co-rotating intermeshing twin-screw extruder. The modified and unmodified blends were compounded with various fillers and reinforcements such as glass fibers, mica flakes, talc, and calcium carbonate. Injection molded composites based on the modified matrix had, in general, superior mechanical and thermal properties. These findings are discussed in view of the improved adhesion resulting from reactions and/or enhanced polar interactions at phase boundaries. Several compounds prepared in this work had overall property data comparable to, or approaching those, of equivalent commercial HDPE molding compounds that are commonly used in “durable” applications.
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  • 4
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is noteworthy that the dehydro-Ala residue adopts an extended conformation that is different than those observed in dehydro-Phe, dehydro-Leu, and dehydro-Abu. The peptide N-Boc-L -Phe-dehydro-Ala-OCH3 (C18H24N2O5) was synthesized by the usual workup procedure and finally by converting N-Boc-L-Phe-L-Ser-OCH3 to N-Boc-L-Phe-dehydro-Ala-OCH3. It was crystallized from its solution in a methanol-water mixture at room temperature. The crystals belong to the monoclinic space group P21 with a = 9.577(1) Å, b = 5.195 (3) Å, c = 19.563 (3) Å, β = 94.67 (5)°, V = 970.1(6) Å3, Z = 2, dm = 1.201(5) Mg m-3, dc = 1.197 (5) Mg m-3. The structure was determined using direct method procedures. It was refined by a full-matrix least-squares procedure to an R value of 0.048 for 1370 observed reflections. The C2α-C2β distance is 1.327 (8) Å, while the bond angles N2-C2α-C2' and C1'-N2-C2α are 109.8 (5)° and 127.8 (5)°, respectively. The backbone adopts a nonspecific conformation with dehydro-Ala in a fully extended conformation with the following torsion angles: θl = 175.2 (4)°, ω, 0 = 170.2 (4)°, ø1 = 135.8 (5)°, ψ 1 = -22.6(6)°, ω1 = 168.5 (5)°, ψ2,= -170.3(5)°, ψ2T = -178.6(5)°', θT = 178.4(7)°. The rigid planar and trans conformation of dehydro-Ala forces Phe to adopt a strained conformation. The Boc group has a trans-trans conformation. The side-chain torsion angles of the Phe residue are χ1 = 63.3(6)°, χ12,1 = -92.1(6)°, χ12,2 = 89.5 (6)°. The observed conformation is stabilized by three nonlinear intramolecular C - H---O type of interactions. The crystal structure is stabilized by an intermolecular hydrogen bond N1 - H1---O2 of distance 2.938(7) Å along the b axis while the van der Waals forces are the stabilizing interactions in the ac plane. The low-energy conformation found by calculations corresponds to the solid state conformation established by the crystal structure analysis. © 1992 John Wiley & Sons, Inc.
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  • 5
    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: A comprehensive study of polyethylene extrusion was carried out with an instrumented extruder on several screws differing in geometry and paralleled with capillary rheometry of the extrudate leading to melt viscosity and elasticity functions. Assuming Oldroyd's constitutive equation for molten polyethylene and the extrudate melt temperature oscillation (ΔTm) as a measure of the process stability and an indication of melt mixing quality, it was found that the product of the dimensionless numbers (Deborah, De and Brinkman, Br) correlates well (r = 0.93) with ΔTm. Since the Br and De groups follow from the rheological characteristics of the melt and the extrusion process parameters, a relationship of type: ΔTm = a + b (De) (Br) appears useful in designing an extrusion process (for a polymer of known rheology) with respect to its stability, and indirectly, its mixing efficiency.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 1493-1499 
    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: This study was aimed at comparing vented extruder geometries and identifying scale-up parameters for melt devolatilization. Data are presented comparing single- and corotating twin-screw extruders for devolatilization of methyl methacrylate from poly(methyl methacrylate), and parameters are identified which characterize dynamic similarity for potential use in design and scale-up. These parameters include conventional process variables such as temperature, throughput, screw RPM, and degree of fill.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 20 (1996), S. 209-213 
    ISSN: 0363-9061
    Keywords: torsional surface waves ; geophysical prospecting ; earthquake damage ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: It is well known that an elastic homogeneous half-space does not allow torsional surface waves to propagate. The present paper attempts to find out the possibility of propagation of such waves in a viscoelastic half-space. The study reveals that although the homogeneous elastic half-space does not allow torsional surface waves to propagate, a viscoelastic half-space does so. The wave is damped due to the viscoelastic parameter. It has also been found that as the viscoelastic parameter decreases, the medium becomes elastic and the torsional surface waves ceases to propagate.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 20 (1996), S. 365-375 
    ISSN: 0363-9061
    Keywords: Rayleigh waves ; propagation ; heterogeneous incompressible substratum ; homogeneous incompressible half-space ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The paper studies the propagation of Rayleigh waves in an incompressible layer with general variation of rigidity as μ=μ0(1+bz)m resting over a homogeneous incompressible elastic half-space. Instead of using the Whittaker function, the expansion formula proposed by Newlands has been used for better results at shallow depths. As a particular case for m=1, the results have been shown to coincide with those obtained by Newlands. The velocities have been computed for different values of m and the results are presented in graphs.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 20 (1996), S. 287-294 
    ISSN: 0363-9061
    Keywords: torsional surface waves ; propagation ; hoterogeneous half-space ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The paper discusses the propagation of torsional surface wave in a homogeneous substratum over a half-space with linearly varying rigidity and density. The study reveals that under assumed conditions, a torsional surface wave propagates in the medium. The velocities of torsional surface waves have been calculated numerically and are presented in a number of graphs. It is also observed that for a stratum over a homogeneous half-space, the velocity of torsional surface waves coincides with that of Love waves. For a non-homogeneous half-space it is observed that the velocity of torsional surface waves is always higher than that of Love waves propagated in a homogeneous layer over a homogeneous half-space. An attempt is also made to assess the possible propagation of torsional surface waves in a half-space with linearly varying rigidity and density, lacking a superficial layer. It is concluded that such a half-space allows two solutions for torsional waves while a homogeneous half-space has one.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 17 (1993), S. 197-204 
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Additional Material: 2 Ill.
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