10,515 research outputs found
GLOW DISCHARGE POLYMERIZATION.
In this review-paper the author summarizes some important aspects of ″polymer formation″ in the glow discharge polymerization or plasma polymerization, rather than presenting a bibliographical review of work. It is shown that glow discharge polymerization can be visualized as a process consisting of three discharge processes. These are (1) controlled discharge of monomer, (2) electric discharge (glow discharge), and (3) glow discharge polymerization of the monomer. Before the electric discharge is initiated, a steady-state flow of the monomer is generally established. During this controlled discharge of the monomer (without electric discharge), adsorption of the monomer onto the solid surfaces in a reactor and degassing of a substrate, etc., take place. The discussion is presented under headings - scope of polymer syntheses; processing factors of glow discharge polymerization; mechanism of polymer formation. Refs
Loose mechanochemical coupling of molecular motors
In living cells, molecular motors convert chemical energy into mechanical
work. Its thermodynamic energy efficiency, i.e. the ratio of output mechanical
work to input chemical energy, is usually high. However, using two-state
models, we found the motion of molecular motors is loosely coupled to the
chemical cycle. Only part of the input energy can be converted into mechanical
work. Others is dissipated into environment during substeps without
contributions to the macro scale unidirectional movement
Spontaneous alloying in binary metal microclusters - A molecular dynamics study -
Microcanonical molecular dynamics study of the spontaneous alloying(SA),
which is a manifestation of fast atomic diffusion in a nano-sized metal
cluster, is done in terms of a simple two dimensional binary Morse model.
Important features observed by Yasuda and Mori are well reproduced in our
simulation. The temperature dependence and size dependence of the SA phenomena
are extensively explored by examining long time dynamics. The dominant role of
negative heat of solution in completing the SA is also discussed. We point out
that a presence of melting surface induces the diffusion of core atoms even if
they are solid-like. In other words, the {\it surface melting} at substantially
low temperature plays a key role in attaining the SA.Comment: 15 pages, 12 fgures, Submitted to Phys.Rev.
A Study Of Surface Dynamics Of Polymers. II. Investigation By Plasma Surface Implantation Of Fluorine–containing Moieties
Macromolecules at the surface of a polymeric solid have considerable mobility, and the specific arrangement of functional groups of macromolecules at the surface is dictated by the environmental conditions in which the surface is placed. Consequently, the change of environmental conditions, such as immersion in water or placement in a biological surrounding, could cause a considerable degree of change in the surface characteristics of a polymer from those evaluated in the laboratory against ambient air. The mobile nature of a polymer surface can be investigated by surface‐implanting fluorine‐containing moieties, mainly—CF3, by the plasma implantation technique and following the disappearance and reappearance of fluorine atoms on the surface. The disappearance rates (based on the immersion time in water at room temperature) of ESCA F1s signals, the decay rates of (advancing) contact angle of water, and the recovery of these values on heat treatment of water‐immersed samples were measured as a function of crystallinity of polymer samples (at three levels of crystallinity) for poly (ethylene terephthalate) and nylon 6. Copyright © 1988 John Wiley & Sons, Inc
In situ imaging of microstructure formation in electronic interconnections
The development of microstructure during melting, reactive wetting and solidification of solder pastes on Cu-plated printed circuit boards has been studied by synchrotron radiography. Using Sn-3.0Ag-0.5Cu/Cu and Sn-0.7Cu/Cu as examples, we show that the interfacial Cu6Sn5 layer is present within 0.05 s of wetting, and explore the kinetics of flux void formation at the interface between the liquid and the Cu6Sn5 layer. Quantification of the nucleation locations and anisotropic growth kinetics of primary Cu6Sn5 crystals reveals a competition between the nucleation of Cu6Sn5 in the liquid versus growth of Cu6Sn5 from the existing Cu6Sn5 layer. Direct imaging confirms that the β-Sn nucleates at/near the Cu6Sn5 layer in Sn-3.0Ag-0.5Cu/Cu joints
Electrodynamic trapping of spinless neutral atoms with an atom chip
Three dimensional electrodynamic trapping of neutral atoms has been
demonstrated. By applying time-varying inhomogeneous electric fields with
micron-sized electrodes, nearly strontium atoms in the state
have been trapped with a lifetime of 80 ms. In order to design the electrodes,
we numerically analyzed the electric field and simulated atomic trajectories in
the trap, which showed reasonable agreement with the experiment.Comment: 4pages, 4figures, to appear in Phys. Rev. Let
Global NLO Analysis of Nuclear Parton Distribution Functions
Nuclear parton distribution functions (NPDFs) are determined by a global
analysis of experimental measurements on structure-function ratios
F_2^A/F_2^{A'} and Drell-Yan cross section ratios
\sigma_{DY}^A/\sigma_{DY}^{A'}, and their uncertainties are estimated by the
Hessian method. The NPDFs are obtained in both leading order (LO) and
next-to-leading order (NLO) of \alpha_s. As a result, valence-quark
distributions are relatively well determined, whereas antiquark distributions
at x>0.2 and gluon distributions in the whole x region have large
uncertainties. The NLO uncertainties are slightly smaller than the LO ones;
however, such a NLO improvement is not as significant as the nucleonic case.Comment: 3 pages, LaTeX, 4 eps files, to be published in the AIP proceedings
of the 9th International Workshop on Neutrino Factories, Superbeams and
Betabeams (NuFact07), Okayama, Japan, August 6 - 11, 2007. A code for
calculating our nuclear parton distribution functions and their uncertainties
can be obtained from http://research.kek.jp/people/kumanos/nuclp.htm
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