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  • Articles  (10)
  • Cell & Developmental Biology  (5)
  • Polymer and Materials Science  (5)
  • 1990-1994  (10)
  • Physics  (5)
  • Biology  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Partial swelling of latex particles with monomers (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 2049-2063 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two methods are described for experimentally determining the concentrations of monomer in both the aqueous phase and the latex particle phase during partial swelling of latex particles, and therefore also during intervall III of an emulsion polymerization. The ratio of the monomer concentrations in the aqueous phase, both below and at saturation, can be related to the volume fraction of polymer in the latex particles via the Vanzo equation. Comparison of theory and experiments for the methyl acrylate and poly(methyl acrylate-co-styrene) system shows that the monomer partitioning is insensitive to temperature, latex particle radius, polymer composition, polymer molecular weight and polymer cross-linking. Thermodynamic treatment of these and previously published partitioning results shows, at higher volume fractions of polymer, that the conformational entropy of mixing of monomer and polymer is the significant term determining the degree of partial latex particle swelling by monomer. Theoretical predictions of experimental results are quite insensitive to values of the Flory-Huggins interaction parameter and to the latex particle-water interfacial tension. A simple model is developed for the estimation of monomer partitioning which requires only the saturation monomer concentrations in the particle and aqueous phases.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930823
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of chain transfer agent on the entry of free radicals in emulsion polymerization (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 303-313 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The model of Maxwell et al. (Macromolecules 24, 1629 (1991)) for initiator efficiencies in emulsion polymerization has been extended to take into account the effect of added chain transfer agent (CTA). The model supposes that the rate-determining step for radical entry into latex particles is aqueous-phase propagation of the primary free radicals to a critical chain length z required for entry (forming species such as .MzSO-4, where M is a monomer entity and peroxodisulfate S2O2-8 is the initiator). The effect of CTA on the entry rate is assumed to occur by facilitating the production of aqueous-phase free-radical species (CTA.) by transfer between species such as .MzSO-4 (where n 〈 z) and CTA in the aqueous phase. The CTA. will be formed at a reasonable rate provided the CTA is not too water-insoluble (e.g. C12H25SH); it should also be capable of entering the latex particles rapidly because of its relative insolubility. If the monomer-derived .MnSO-4 tend to suffer aqueous-phase termination rather than entry, the overall rate of entry (and hence initiator efficiency) will be increased. This can explain the accelerating effect of intermediate molecular weight CTA's on emulsion polymerization of monomers such as butadiene, where z is large and hence initiator efficiency is very low in the absence of CTA, because most .MnSO-4 undergo termination rather than entry into the latex particles.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930201
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of thymosin β4 and thymosin β10 on actin structures in living cells (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 13-25 
    Details
    ISSN: 0886-1544
    Keywords: Tβ4 ; Tβ10 ; β-thymosins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The β-thymosins are a family of small proteins originally isolated from the thymus. Recently, two of the major mammalian isoforms, thymosin β4 (Tβ4) and thymosin β10 (Tβ10), are identified as significant actin monomer sequestering proteins which may be involved in regulating actin filament assembly. To study the cellular function of β-thymosins, we have used isoform-specific antibodies to determine their concentration and intracellular distribution, and examined the effects of inducing overexpression of Tβ4 and Tβ10 on actin filament structures. Immunofluorescence labeling of peritoneal macrophages showed that both β-thymosins are uniformly distributed within the cytoplasm. cDNA-mediated overexpression of β-thymosins in CV1 fibroblasts induced extensive loss of phalloidinstained actin stress fibers. Stress fibers in the cell center were more susceptible than those at the periphery. There was a decrease in the number of focal adhesions, as evidenced by a decrease in discrete vinculin staining and an increase in diffuse vinculin fluorescence. The majority of the transfected cells had normal shape in spite of extensive loss of actin filaments. Occasionally, cells overexpressing β-thymosin were observed to divide. In these cells, β-thymosin was excluded from the midbody which contains an actin filament-rich contractile ring. Our results indicate that Tβ4 and Tβ10 are functionally very similar and both are effective regulators of a large subset of actin filaments in living cells. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270103
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  • 4
    Electronic Resource
    Electronic Resource
    Vitamin D receptor alleles and bone physiology (1994)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 56 (1994), S. 307-314 
    Details
    ISSN: 0730-2312
    Keywords: vitamin D calcitriol ; bone ; genetics ; steroid hormone receptor ; vitamin D receptor ; retinoic acid receptor ; calcium ; homeostasis ; calcitonin ; parathyroid hormone ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The vitamin D endocrine system is central to the control of bone and calcium homeostasis. The active hormonal aform of vitamin D, 1,25 dihydroxyvitamin D (calcitriol), the circulating level of which is tightly regulated, acts through a specific receptor to mediate its genomic actions on almost every aspect of calcium homeostasis. Because of its transactivation function, it possible that a small difference in vitamin D receptor level could be amplified into a biologically significant alteration in physiological setpoint. The recent finding that polymorphisms in the vitamin D receptor gene are predictive of bone density (morrison et al., Nature 367:284-287, 1994) is the first example of an allelic effect in such a homeostatically controlled system. This raises the possibility that such central operators may exist in other regulatory pathways, and could expllain a large part of the observed “ormal” population distribution that exists for all physiological paraameters.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240560306
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  • 5
    Electronic Resource
    Electronic Resource
    A study of shear-stress relaxation anomalies in binary mixtures of monodisperse polystyrenes (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 943-950 
    Details
    ISSN: 0887-6266
    Keywords: stress relaxation anomalies of polystyrenes ; polystyrene rheology ; melt fracture ; binary blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report measurements of the nonlinear relaxation moduli after a step-shear strain of polystyrene solutions with nearly monodisperse and with bidisperse distributions of molecular weight. We find, as have others, that for monodisperse solutions with M/Me 〉 60, there are anomalies, such as an unusually low nonlinear modulus and a kink in a plot of shear stress versus time after the step strain. Here M is the polymer molecular weight and Me is the entanglement molecular weight. We find that in the bidisperse solutions the anomalies persist as long as Mw/Me 〉 60, where Mw is the weight-averaged molecular weight of the bidisperse solution. The persistence of the anomalies in bidisperse solutions disagrees with a theory of Marrucci and Grizzuti that attributes the anomalies to strain inhomogeneities similar to shear banding. The Marrucci-Grizzuti theory predicts that as little as 10% short chains in the bidisperse mix should eliminate the anomalies, whereas in the experiments reported here at least 30% is required. Nevertheless the way in which the anomalies disappear at high strains when one increases the fraction of low-molecular-weight component is qualitatively similar to the theoretical predictions and supports the notion that strain inhomogeneities occur in these systems. © 1992 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090300902
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  • 6
    Electronic Resource
    Electronic Resource
    Chlorinated polyolefins for asphalt binder modification (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 231-240 
    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 benefits obtained from the addition of small quantities of chlorinated polyolefins to paving grade asphalt binders were investigated. A chlorinated polyethylene plastomer, Tyrin 2552, and a chlorinated olefinic elastomer, Tyrin CM0730, were added to asphalt binders at 3 and 5 wt % and subsequently reactively processed to facilitate compatibilization. The mixtures were analyzed for rheological performance relating to fatigue and rutting as well as low-temperature fracture performance. The addition of small quantities of these polymers to the asphalt binders resulted in significant improvements over conventional modifiers at both the high and low temperature extremes. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070540209
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructural analysis of iridophore organellogenesis in a lizard, Sceloporus graciosus (Reptilia: Phrynosomatidae) (1991)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 209 (1991), S. 229-239 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Transmission electron microscopy (TEM) data from the ultrastructure of lizard skin iridophores (reflective dermal chromatophores) are used to illustrate the organellogenesis of small rectangular reflecting platelets, which are the color-generating components of these cells. During the development of reflecting platelets, crystals are deposited within double-membraned vesicles from electron-dense material located within the vesicles. The crystals are initially small but expand lengthwise eventually to fill the vesicle that contains them. The inner membrane then tightly surrounds the crystal whereas the outer membrane is much more loosely associated with the inner-membrane-bound crystal. These observations allow discussion of the possible origin of the precursor double-membraned vesicles from endoplasmic reticulum (ER) and Golgi-derived vesicles. A model is proposed that incorporates our findings and other published reports to explain the origin of the precursor double-membraned vesicles via three alternative pathways.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052090209
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  • 8
    Electronic Resource
    Electronic Resource
    Structural color production by constructive reflection from ordered collagen arrays in a bird (Philepitta castanea: Eurylaimidae) (1994)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 222 (1994), S. 61-72 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ordered hexagonal arrays of parallel collagen fibers produce the brilliant green structural color of the fleshy, supraorbital caruncles of male Velvet Asity (Philepitta castanea; Aves: Eurylaimidae). The collagen arrays are organized in larger macrofibrils that are packed irregularly within cone-shaped papillae that cover the surface of the caruncle. The color of the caruncle conforms closely to the wavelengths predicted by applying Bragg's Law of constructive reflection to measurements of the size and spatial organization of the collagen arrays. These observations constitute a novel mechanism of structural color production in animals. These collagen arrays are convergently similar to the smaller, highly structured collagen arrays in the mammalian cornea, which exploit the same physical mechanism to produce optical transparency. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052220107
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  • 9
    Electronic Resource
    Electronic Resource
    Polyoxirane as a mimic of crown ether in the initiation of “group-transfer” polymerization (1991)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 12 (1991), S. 653-655 
    Details
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1991.030121108
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  • 10
    Electronic Resource
    Electronic Resource
    Steel factor and c-Kit receptor: From mutants to a growth factor system (1993)
    New York, NY : Wiley-Blackwell
    BioEssays 15 (1993), S. 77-83 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mutations within the Steel and Dominant Spotting loci of mice have led to the recent identification of a growth factor/receptor system required for the normal development of germ cells, pigment cells and hematopoietic cells. Interactions between the products of these genes, Steel factor and c-Kit respectively, have now been demonstrated to influence various developmental processes, including survival, proliferation, and/or differentiation of cells in a tissue specific manner. In addition, our current understanding of the molecular basis of various Steel and Dominant Spotting alleles coupled with the emerging information on the expression pattern of steel factor and c-kit transcripts during development, is now beginning to explain the pleiotropic affects of these mutations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950150202
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