This book provides a broad survey of elastomers with special emphasis on materials with a rubber-like elasticity. As in the 3rd Edition, the emphasis remains on a unified treatment of the material; ...exploring topics from the chemical aspects such as elastomer synthesis and curing, through recent theoretical developments and characterization of equilibrium and dynamic properties, to the final applications of rubber, including tire engineering and manufacturing. Many advances have been made in polymer and elastomers research over the past ten years since the 3rd Edition was published. Updated material stresses the continuous relationship between the ongoing research in synthesis, physics, structure, and mechanics of rubber technology and industrial applications. Special attention is paid to recent advances in rubber-like elasticity theory and new processing techniques for elastomers. This new edition is comprised of 20% new material, including a new chapter on environmental issues and tire recycling.
Mice and men: An antibody conjugate with trans‐cyclooctene was administered to tumor‐bearing mice, and the resulting chemically tagged tumors were subsequently treated with an 111In‐labeled tetrazine ...probe in an inverse‐electron‐demand Diels–Alder reaction. The adduct was formed in a remarkable 52–57 % yield in vivo and used for non‐invasive pretargeted tumor imaging in mice (see picture).
Recent experimental results on the dynamics of glass-forming materials, particularly polymers, are surveyed. The focus is on aspects of the behavior that are connected to or correlated with ...structural relaxation. These results include the invariance to thermodynamic conditions (temperature, pressure, volume) of a number of propertiesbreadth of the relaxation dispersion, number of dynamically correlating molecules, Johari−Goldstein secondary relaxation time, onset of the dynamic crossover, and the product of temperature and specific volume with the latter raised to a material constantprovided the structural relaxation time is maintained constant. Additional salient experimental findings include the correlation of various high-frequency processes, usually measured in the glassy state, with properties of the equilibrium material above T g. These correlations indicate that the glass transition, although conventionally defined by the relaxation time becoming larger than experimental time scales (>100 s), has its beginning many orders of magnitude sooner. Also described herein are effects of spatial confinement on the glass transition; these can be dramatic, yet taken in toto are rather discombobulating. Such generally observed phenomena must be included in a comprehensive theory or model of the glass transition, since properties intimately connected to structural relaxation cannot be derived separately and be expected to exhibit such correlations by coincidence.
Atmospheric Chemistry of Iodine Saiz-Lopez, Alfonso; Plane, John M. C; Baker, Alex R ...
Chemical reviews,
03/2012, Letnik:
112, Številka:
3
Journal Article
Recenzirano
Odprti dostop
A comprehensive examination of the atmospheric chemistry of iodine is presented. Iodine accrues in aersols and is the topic of studies in photochemistry as well.
The manner in which the intermolecular potential u(r) governs structural relaxation in liquids is a long standing problem in condensed matter physics. Herein, we show, in agreement with recent ...experimental results, that diffusion coefficients for simulated Lennard-Jones m−6 liquids (8 ≤ m ≤ 36) in normal and moderately supercooled states are a unique function of the variable ργ/T, where ρ is density and T is temperature. The scaling exponent γ is a material specific constant whose magnitude is related to the steepness of the repulsive part of u(r), evaluated around the distance of closest approach between particles probed in the supercooled regime. Approximations of u(r) in terms of inverse power laws are also discussed.
In myelodysplastic syndromes (MDS), deletions of chromosome 7 or 7q are common and correlate with a poor prognosis. The relevant genes on chromosome 7 are unknown. We report here that EZH2, located ...at 7q36.1, is frequently targeted in MDS. Analysis of EZH2 deletions, missense and frameshift mutations strongly suggests that EZH2 is a tumor suppressor. As EZH2 functions as a histone methyltransferase, abnormal histone modification may contribute to epigenetic deregulation in MDS.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The viscoelastic glass-to-rubber softening transition is analyzed for various cross-linked polymers reinforced with filler particles. We find that the loss modulus peak corresponding to the segmental ...relaxation process (glass transition) is not significantly affected by the particle surface area in carbon black-filled polybutadiene or by silane chemical coupling of poly(styrene-co-butadiene) to silica. Large differences in shape and magnitude of the peak in the loss tangent (tan δ) vs temperature are noted for these materials; however, this is due to variations in the storage modulus at small strains in the rubbery state, which is influenced by the nature of the jammed filler network. The use of a simple relaxation model demonstrates this feature of the viscoelastic glass transition in filled rubber. It is not necessary to invoke concepts involving a mobility-restricted polymer layer near the filler surfaces to explain the viscoelastic results. Atomic force microscopy conducted with an ultrasharp tungsten tip indicates that there may be some stiffening of the elastomer in the proximity of filler particles, but this does not translate into an appreciable effect on the segmental dynamics in these materials.
An equation is derived that expresses the thermodynamic scaling exponent, γ, which superposes relaxation times τ and other measures of molecular mobility determined over a range of temperatures and ...densities, in terms of static physical quantities. The latter are available in the literature or can be measured at ambient pressure. We show for 13 materials, both molecular liquids and polymers, that the calculated γ are equivalent to the scaling exponents obtained directly by superpositioning. The assumptions of the analysis are that the glass transition T(g) is isochronal (i.e., τ(α) is constant at T(g), which is true by definition) and that the pressure derivative of the glass temperature is given by the first Ehrenfest relation. The latter, derived assuming continuity of the entropy at the glass transition, has been corroborated for many glass-forming materials at ambient pressure. However, we find that the Ehrenfest relation breaks down at elevated pressure; this limitation is of no consequence herein, since the appeal of the new equation is its applicability to ambient-pressure data. The ability to determine, from ambient-pressure measurements, the scaling exponent describing the high-pressure dynamics extends the applicability of this approach to a broader range of materials. Since γ is linked to the intermolecular potential, the new equation thus provides ready access to information about the forces between molecules.
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