bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possibility of superconductive‐type enhanced conductivity in dna at room temperature
Authors: Ladik J. , Biczo G. , Redly J. 
Published: June 2010

AbstractApplying Little's formalism to investigate the possibility of superconductive regions at room temperature in organic polymers, we have calculated the Coulomb and effective attractive terms for the polycytosine homopoly‐nucleotide. Little's original idea that the effective interaction between the mobile electrons of the spine is due to the polarization of the side‐chain electrons has been extended to take into account the polarization of the σ electrons of the same systems which provide the mobile electrons.According to the results obtained for many intraband and interband scattering processes, the absolute value of the attractive term is larger than, or about the same as, that of the Coulomb term. Therefore, we cannot exclude the possibility of superconductive‐type enhanced conductivity in some regions of DNA. Finally, the effects of the finite dimensions of a cytosine molecule are discussed from the point of view of screening and thermodynamic fluctuations.
Polymerisation de polyethylene sur trichlorure de vanadium depose sur support. Morphologie du polymere naissant
Authors: Marchessault R. H. , Chanzy H. D. 
Published: June 2010

AbstractLa facilité avec laquelle VC13 se dépose sur différentes surfaces riches en électrons a été Utilisée pour obtenir des catalyseurs de polymérisation supportés sur différents supports plats. Si I'on polymérise de l'éthylène sur ces supports, des membranes de polyéthylène naissant sont obtenues et examinées au microscope électronique. Leur structure se compose d'agglomérats en forme de pustules reliés entre eux par une texture de rubans. Les pustules correspondent à l'encapsulation des cristaux de catalyseur tandis que les rubans sont engendrés par une action simultanée de polymérisation et de déplacement du catalyseur. Ainsi les donneurs d'électrons qui favorisent la désintégration des cristaux de VC13 ont pour effet de multiplier le nombre des rubans et agissent ainsi sur la morphologie. Par analyse thermique on peut obtenir des informations sur l'organisation cristalline moléculaire et supra‐moléculaire des membranes de polyéthylène naissant. Leur cristallinité varie de 74 à 86% tandis que la forme et le comportement des courbes de fusion confirme que la phase cristalline contient en majorité des cristallites où les chaǐnes sont dépliées. Par analyse thermique, on voit également que des membranes préparées à des températures plus élevées ont des degrés de cristallinité plus bas et un point de fusion plus élevé. Enfin, on remarque que par fusion, une membrane étirée de polyéthylène naissant engendre une phase fondue orientée et il est nécessaire de surchauffer les échantillons fondus au moins 40 degrés plus haut que le point de fusion pour obtenir un état fondu normal.
The realtionship between molecular weight and spherulitic growth rates in trans‐1, 4‐polyisoprene
Authors: Lovering Edward G. 
Published: June 2010

AbstractThe growth rate of high melt form spherulites in trans‐1,4‐polyisoprene was found to be Inversely proportional to the molecular weight up to Mn = 150,000. At higher molecular weights the dependence virtually ceases. The growth is given by:

Where ED is the free energy required to transport a crystallizing segment across the liquid‐crystal interface and ΔF2* is the free energy required to form a stable crystal nucleus. The relationship between molecular weight and spherulitic growth rate was not accounted for by the dependence of Tg on molecular weight, expressing ED by the WLF equation, nor by the dependence of ΔF2* on the molecular weight. The product of the end and lateral interfacial free energies of the crystallites is constant to M̄n = 40,000, above which it Increases with molecular weight. This has been attributed to a change in the crystallization mechanism near M̄n = 40,000, perhaps from a mechanism where most molecules crystallize within a single cyrstallite to one where each molecule is involved in several crystallites and the amorphous regions between them.
Steric stabilization of polymer suspensions in hydrocarbon media by adsorbed layers of graft copolymers
Authors: Osmond D. W. J. , Walbridge D. J. 
Published: June 2010

AbstractSterically stabilized dispersions of fine polymer particles in hydrocarbon media have been used for the study of the adsorption of amphipathic graft copolymers at polymer/hydrocarbon interfaces. The amount of graft copolymer adsorbed on the particle surfaces during the dispersion polymerization has been determined for a number of polymer substrates, over a range of particle sizes, and at different stabilizer concentrations. From these results the average surface spacing of the solvated component of the adsorbed graft copolymer has been calculated for solvated groups of low, medium and high molecular weight. In a limited number of cases the hydrodynamic steric barrier thickness has also been measured. These stabilizer spacing and barrier thickness values are compared with the dimensions of the solvated groups in free solution and the nature of the packing of these groups on the particle surface is discussed. Anomalous results obtained in a few cases are shown to be due to the mechanism of particle growth.
Stress softening in styrene‐butadiene block copolymers: Rheo‐optical studies
Authors: Fischer E. , Henderson J. F. 
Published: June 2010

AbstractThe stress‐strain and the optical properties of styrene/butadiene block polymers indicate that at strains below those at which finite extensibility of the polybutadiene chains become Important, the mechanical properties of the polymers are determined by the combined effects of the elastic deformation of the polybutadiene phase and the degree of interaction between the polystyrene regions. The process of stress‐softening in styrene/butadiene block polymers is due to the break‐up of polystyrene regions, rather than to flow and rupture of weak crosslinks. Some additional softening occurs in the polybutadiene phase due to loosening‐up of the polybutadiene network structure. Specimens which were softened to the same degree of internal strain of the polybutadiene phase had similar stress‐strain properties when account was taken of the filler effect of the polystyrene regions. Block polymers which were prestretched to a strain below the finite extensibility of the polybutadiene chains exhibited a stable network structure. At large strains non‐Gaussian behaviour of the polybutadiene chains, probably combined with a recoverable plastic deformation of the polystyrene regions, determined the stress‐strain properties of the block polymers. The stress‐strain and the optical studies of the original and the softened block polymers indicate that under the experimental conditions described here the physical crosslinks formed by the polystyrene regions were stable.
Solutions of diphilic copolymers: A quantitative approach to the analysis of fluctuating networks and antithixotropy
Authors: Frenkel S. Ya , Panov Yu. N. 
Published: June 2010

AbstractThe study of the concentration dependence of the molar apparent activation heat of viscous flow of MMA‐MAAc copolymer solutions in EDC (hydrogen bonded systems) permits to resolve three different concentration ranges. The first of them corresponds to the existence in the system of separate macromolecules and small associations, the second one corresponds to the co‐existence of an incomplete fluctuating network in equilibrium with associations and/or separate macromolecules, and the third one corresponds to the formation of a complete network including all the macromolecules present. The existence of the fluctuating network in the systems studied results in an antithixotropic strengthening of the solution structure in conditions of both shear and complex flow.
Application of differential scanning calorimetry to the identification of crosslinks in cellulose
Authors: Gilbert R. D. , Rhodes J. H. 
Published: June 2010

AbstractThermograms of reaction products of cellulose with dimethylolurea (DMU) or dimethylolethyleneurea (DMEU) homopolymers show the peak associated with cellulose decomposition is shifted up by as much as 20°C. Solubility measurements in cupriethylenediamine (Cuene) indicate the homopolymers are present as side groups on the cellulose. Cellulose reacted with DMU or its homopolymer is only insoluble in Cuene when oxymethylene crosslinks are simultaneously formed by CH2O. These crosslinks do not affect the thermal stability of cellulose. Linkages to DMEU or its homopolymer are relatively stable to alkaline hydrolysis and may be distinguished from oxymethylene linkages by comparison of thermograms and solubilities before and after acid hydrolysis. Comparison of thermograms of cellulose with those of the n‐methylol compounds, their homopolymers, physical mixtures of cellulose and the homopolymers, and reaction products of cellulose with DMU, DMEU, and CH2O, demonstrated that, depending upon the reaction conditions, CH2O evolution, in situ homopolymenzation, cellulose crosslinking by CH2O, by the n‐methylol compounds, and reaction with their oligomers may occur. Reaction variables, viz., pH, temperature, nature and concentration of catalyst, the time‐temperature interval between application of the n‐methylol compound and the final reaction, and the type of n‐methylol compound determine which reaction predominates. The modification of cellulose by DMU shows a greater dependence on catalyst type than does DMEU which readily polymerizes to low molecular‐weight products and evolves CH2O which crosslinks the cellulose.
Differences in absorption and emission properties of conalbumin and metal‐saturated conalbumin
Authors: Tan A. T. , Woodworth Robert C. 
Published: June 2010

AbstractThe stabilities of conalbumin and transition metal‐conalbumin complexes toward denaturants were studied by UV absorption and emission spectroscopy. The difference spectra of conalbumin and metal‐conalbumins in buffer, pH 8.0 vs. the same species in buffered 8 M urea were similar in shape with maxima at 286‐ and 292‐mμ and a negative absorption near 260‐mμ. The Δε292 for colored Fe‐, Cr‐, Cu‐, and Mn‐conalbumins was 5 × 103 less than that for conalbumin and colorless Co‐, Zn‐, Cd‐, Ni‐, and Mn‐conalbumins, indicating that two tryptophanyl residues were bound to or protected by metal ions in the former but not the latter cases. The F350 of conalbumin was quenched up to 65% on formation of the colored complexes, but not on formation of colorless complexes. The F350 of conalbumin was strongly quenched by increasing temperature (0 to 70°) or pH (5 to 12.5), whereas that of Fe+3‐conalbumin was essentially independent of these variables. These results indicate the presence of tryptophanyl residues, in addition to the known tyrosyl and histidyl residues, in conalbumin‐metal binding sites, and suggest that charge‐transfer interactions between these tryptophanyl residues and the bound metals is probably responsible, at least in part, for color formation, as well as for the marked increase in stability of these colored complexes.
Deoxyribonucleoprotein from sea urchin sperm: Preparation and thermal denaturation
Authors: Subirana Juan A. 
Published: June 2010

AbstractDeoxyribonucleohistone from sea urchin sperm has a marked tendency to form a gel upon suspension in distilled water. The gel can be disrupted by shear and soluble nucleoprotein is thus obtained. Soluble proteins from the microtubules of the sperm tail have a tendency to contaminate this preparation. At the same time they show some affinity with the nucleohistone. Histones are obtained from treated sperm and differences are reproducibly found at various stages of the preparation. From these results the factors which determine gel formation are discussed. The melting curves of the nucleoprotein are also studied. At low ionic strength a bimodal curve is obtained, probably due to an irregular distribution of histones on the DNA molecule. At high ionic strength a bimodal curve is also found, but in this case it is due to the turbidity of the nucleprotein solution.
Unfolding of a protein molecule in solution with ageing and thermal denaturation as determined by a reverse dye partition technique
Authors: Mukhopadhyay Sailes , Mitra Bhairab Chandra , Palit Santi R. 
Published: June 2010

AbstractA chloroform solution of an anionic dye bound to polymethyl methacrylate having an amino endgroup is partitioned with an extremely dilute solution (< 0.001 per cent) of a protein at a suitable pH. The amount of dye which gets transferred to the aqueous layer is a measure of the available excess of carboxyl over amino group of the protein. This value increases considerably with age and also with heat denaturation of the protein and so this gives an insight into conformational change or unfolding of the protein molecule as due to thermal denaturation and ageing characteristics.The same method has also been applied with success to determine, the carboxyl content of polyacrylamide (partially hydrolysed), carboxymethyl cellulose, gum arabie, copolymers containing acrylic, methacrylic and crotonic acids, and graft polymers containing acrylic acid.
Effect of the continuous medium on the color of discontinuous substrates. I. Empirical relationship between the light reflectance of dry textile samples and samples immersed in water
Authors: Goldfinger G. , Goldfinger Herta S. , Hersh S. P. , Leonard T. M. 
Published: June 2010

AbstractThe light reflectance between 380 nm and 700 nm of one white, one black, six red, and six blue cellulose triacetate fabric samples was measured. Each measurement was carried out once on a dry sample and once on a sample immersed in water. From the data a numerical relationship was derived which permits the prediction of “wet” color from “dry” color.
Optical rotatory properties and conformations of esters and polyesters of trans‐1,2‐cyclohexanedicarboxylic acid
Authors: Overberger C. G. , Montaudo G. , Furuyama Toshiuki , Goodman Murray 
Published: June 2010

AbstractThe conformational preferences of trans‐1,2‐cyclohexanedicarboxylic acid (1,2‐CH) and ester derivatives have been studied. The optical rotatory properties of these compounds are discussed in comparison with those of other cyclic dicarboxylic acids. A stereoregular polymer, poly[ethylene‐(+)‐trans‐1,2‐cyclohexane dicarboxylate] (1,2‐CHPE) has been synthesized, and its properties are compared with those of model compounds.
Volume dependence of the C2 correction in the Mooney‐Rivlin elastic equation of state
Authors: Mark J. E. 
Published: June 2010

AbstractStress‐strain isotherms at 25°C are reported for a series of unswollen networks of cis‐1, 4‐polybutadiene which differ both in degree of crosslinking and in the volume at which the crosslinks were introduced. The former quantity was varied by variation of the amount of high energy radiation used to bring about the crosslinking, the latter, by crosslinking the polymer in solution as well as in the bulk, undiluted state. The results are interpreted in terms of the equation f*/(α−α−2) = 2C1 + 2C2α−1 where f* is the force per unit area of the undistorted, unswollen sample, α is the relative length of the sample, and C1 and C2 are empirical constants, the latter serving as a measure of the departure of the dependence of stress on strain from that indicated by the statistical theory of rubber elasticity. At equal values of the “modulus” f*/(α−α−2), the correction C2 is found to be very small for networks prepared in solution and to increase markedly with increase in concentration of polymer in the system undergoing crosslinking. In addition, the networks prepared in solution exhibit considerably smaller nonequilibrium, relaxation effects than those crosslinked in the undiluted state.
Cationic polymerization of exo‐2‐methyl‐7‐oxabicyclo [2, 2, 1] heptane. II. Catalysis by PF5
Authors: Baccaredda M. , Giusti P. , Andruzzi F. , Cerrai P. , di Maina M. 
Published: June 2010

AbstractThe polymerization of exo‐2‐methyl‐7‐oxabicyclo[2, 2, 1] heptane by PF 5 in ethylene dichloride solution was investigated. The reaction was followed in vacuum dilatometers fitted with platinum wire electrodes, which allowed us to measure the variations of conductivity during the polymerization. The ultraviolet and visible spectra of the polymerizing solution have also been determined by a high vacuum technique. The conversion‐time curves showed an acceleration period which was gradually reduced by addition of water. The Rmax first increased with water concentration, reached a maximum at a α = [H2O] /[PF5] = 0.17, then decreased, and became zero at α = 1. The polymerizations gave limited yields at room temperature, which was not due to an equilibrium. At temperatures below O°C, 100% yields were obtained and experiments with a second addition of monomer showed that no termination was present but only transfer, as the second quantity of monomer was completely converted without increase of the molecular weight. The reaction mechanism is discussed.
Electron spin resonance study of trimethylolpropane monoallyl ether in radical polymerization
Authors: Doi Yukio , Ränby Bengt 
Published: June 2010

AbstractTrimethylolpropane monoallyl ether (TMP) was studied with an x‐band electron spin resonance (ESR) spectrometer by applying a flow method, developed by Dixon and Norman, in which TMP was subjected to hydroxyl radical attack. The observed ESR spectra were assigned to two radicals formed by addition of hydroxyl radical to TMP and one by abstraction of hydrogen from the allylic group of TMP. The ESR spectra from copolymerizing systems of vinyl acetate (VAc) and methyl acrylate (MA) with TMP were also studied. In the system VAc‐TMP, the ESR spectrum showed in addition to VAc radicals the presence of the three TMP radicals. In the system MA‐TMP, the ESR spectrum was mainly due to TMP radicals in which the allylic radicals were dominant. This result is consistent with the observation that polymerization of MA is strongly retarded by the addition of TMP, which is interpreted as due to the high reactivity of MA radicals to TMP monomer.
Donor‐acceptor complexes in copolymerization. VI. A proposed mechanism for the homopolymerization of comonomer complexes to alternating copolymers
Authors: Gaylord Norman G. 
Published: June 2010

AbstractAfter a brief review of the characteristics of the copolymerization of donor and acceptor monomers in the presence of metal halides, a mechanism is proposed for the formation of alternating copolymers. The charge‐transfer donor‐acceptor complex resulting from the interaction of a strong electron‐acceptor monomer and a strong electron‐donor monomer undergoes spontaneous or radical initiated homopolymerization to yield an equimolar alternating copolymer, irrespective of the initial monomer ratio. The formation of the [DA] complex is enhanced by complexation of the acceptor monomer with a metal halide or organometal halide. The homopolymerization of the (DA… [MX] occurs at a faster rate than conventional radical copolymerization. The spontaneous polymerization occurs when the equilibrium concentration of the complex is sufficiently high. The latter depends upon the electron‐donating strength of the donor monomer and the electron‐accepting strength of the acceptor monomer and the activator. Complex formation is favored at lower temperatures while polymerization may require thermal or catalytic activation. The complexes may be aligned in an ordered array or matrix, and polymerization proceeds through a rapid initial stage in which the molecular weight increases with conversion, followed by a slower stage in which the molecular weight remains constant at the highest level attained in the first stage, indicative of the first‐stage polymer acting as a template for the second‐stage polymerization. The proposed polymerization mechanism involves initiation by a head‐to‐head reaction of two complexes during which hydrogen abstraction or transfer occurs through a six‐membered cyclic transition state to generate a polymer chain with an attached terminal complex. The propagation reaction is head‐to‐tail and involves the addition of complexes to the chain end through hydrogen abstraction via a six‐membered cyclic transition state to regenerate the complex chain end.
Thermal behavior of elastomers at high rates of tensile straining
Authors: Glaser Z. R. , Eirich F. R. 
Published: June 2010

AbstractThe results of high strain‐rate tensile straining of a variety of elastomers at a number of temperatures are reported. Temperature increases, ΔT, occurring within the sample were measured during the deformation; i.e., the technique of adiabatic stretching was applied. The use of well characterized rubbers of different tendencies to crystallize upon elongation gave information on the changes in molecular packing, of the contribution from entanglements to the effective crosslink density, and of the effect of chemical and structural factors on mechanical behavior during rapid extension. An analysis of the effect of frictional heating, of deformational energy conversion, and of the anticipated enthalpy of crystallization was performed. The experimentally obtained temperature increases, the magnitude of the above three main factors which contribute to ΔT, and the amount of strain‐induced crystallization found are in agreement with theoretical considerations.
Relationship between structure of drawn polymers and molecular motion
Authors: Fischer E. W. , Goddar H. , Piesczek W. 
Published: June 2010

AbstractIn order to study the relationship between structure and molecular motion, drawn polymers are more suitable than isotropic samples since their morphology can be characterized more easily by quantitative methods such as small angle X‐ray scattering (SAXS) and electron microscopy (EM). The effects of changes in morphological structure on molecular motion are demonstrated by comparing the results of the SAXS and EM measurements with the dynamic mechanical behavior of drawn polyethylene. In addition the NMR broad line spectra of these samples were analyzed and the influence of annealing conditions and external stress was investigated.
Crystallization of poly(vinyl chloride) at high temperatures
Authors: Michel Alain , Guyot Alain 
Published: June 2010

AbstractA sample of poly(vinyl chloride) having a very good thermal stability and a high initial crystallinity was annealed between 80 and 260°C, either as it was or mixed with stabilizers, in sealed ampoules or in KBr pellets, and studied by X‐ray and IR techniques. When the sample is treated in glass ampoules, practically no changes in IR spectra are observed up to 240°C; the X‐ray diagrams, however, show an increase in the size of the crystallites but no increase in the amount of crystalline material. The melting point is observed by X‐ray between 250 and 260°C. If the sample is heated in the KBr pellets, it undergoes some stress which causes an increase of the crystalline IR bands at 604 and 635 cm−1, but no change in the X‐ray diagram. At higher temperatures, dehydrochlorination is enhanced by the KBr and involves chiefly the amorphous regions.