Debye (unité)

Le debye (symbole D) est une unité de moment dipolaire. Cette unité appartient au système d'unités CGS et ne fait pas partie du système d'unités SI. Dans les unités SI, = . Son nom vient du physicien et chimiste Peter J. W. Debye qui effectua des recherches sur les molécules polaires. Le debye est défini comme mesurant . Historiquement, le debye était défini comme le moment dipolaire d'un couple de charges de signes contraires mais d'une même valeur de statcoulomb (ou "e.s.u." (pour "electrostatic unit") dans une littérature plus ancienne), séparées d'un ångström, ceci donnant une unité pratique pour les moments dipolaires moléculaires. Le debye est encore utilisé en physique atomique et en chimie. En effet, les moments dipolaires des atomes et des molécules sont du même ordre de grandeur que l'unité atomique de moment dipolaire (produit du rayon de Bohr a, c'est-à-dire la longueur de la liaison, et de la charge élémentaire e ) qui vaut environ . Les unités SI sont incommodément

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Electric dipole moment

The electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. The SI unit for electric d

Dipole

In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways: *An electric dipole deals with the separation of the positive and negative electric charges found in any electromag

Système CGS

Le système CGS est un système d'unités de mesure des grandeurs physiques, où les unités de base de la mécanique sont le centimètre (pour les longueurs), le gramme (pour les masses) et la seconde (po

MSE-422: Advanced metallurgy

This course covers the metallurgy, processing and properties of modern high-performance metals and alloys (e.g. advanced steels, Ni-base, Ti-base, High Entropy Alloys etc.). In addition, the principles of computational alloy design as well as approaches for a sustainable metallurgy will be addressed

MSE-304: Surfaces and interfaces

This lecture introduces the basic concepts used to describe the atomic or molecular structure of surfaces and interfaces and the underlying thermodynamic concepts. The influence of interfaces on the properties of materials is also discussed.

PHYS-423: Plasma I

Following an introduction of the main plasma properties, the fundamental concepts of the fluid and kinetic theory of plasmas are introduced. Applications concerning laboratory, space, and astrophysical plasmas are discussed throughout the course.

Partial Molar and Specific Volumes of Polyelectrolytes: Comparison of Experimental and Predicted Values in Salt-free Solutions

Artur Bartkowiak, David Hunkeler, Christine Wandrey

The partial molar volume, .hivin.V, and the partial sp. vol., .hivin.n, were estd. for more than 25 polyelectrolyte structures. The materials investigated by d. measurements in highly dild. aq. solns. (c < 10-2 monomol/L) included both synthetic polyelectrolytes and chem. modified natural polymers. Through a detailed anal., related to the chem. structure and macromol. parameters, a linear dependence between the copolymer compn. and the partial vols. could be identified for diallyldimethylammonium chloride/acrylamide copolymers. Additivity could also be shown for sodium cellulose sulfate having various degrees of substitution. For a homologous series of poly(vinylbenzyltrialkylammonium chloride)s, a linear correlation between the molar mass of the monomer unit and the partial molar volume was obtained. No influence of the d.p. was obsd. as long as the contour length exceeds the Debye length. The exptl. results were used to evaluate the general applicability of the additivity schemes of Durchschlag and Zipper, as well as Gianni and Lepori, to polyelectrolytes. Agreement between exptl. and calcd. partial vols. strongly depends on the chem. structures. In the case of the synthetic polycations, the deviations are in a similar range for both models though somewhat smaller for the Gianni/Lepori model. The use of the Durchschlag/Zipper model yields much better agreement for the anionic biopolymers with deviations generally less than 3%. The tendency of the empirical models is correct; however, the precision may be improved by regressing of parameters from the exptl. results. The new exptl. data may also be useful in polyelectrolyte characterization. [on SciFinder (R)]

1999

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A gauge invariant Debye mass and the complex heavy-quark potential

Yannis Burnier

Following the original idea of Debye, we define and extract a gauge-invariant screening mass from the complex static in-medium heavy-quark potential V-Q (Q) over bar, recently obtained from lattice QCD. To this end we derive a formula using concepts from both effective-and classical field theories that faithfully reproduces both the screened real-and the imaginary part of the lattice potential with a single temperature dependent fit parameter m(D)(T). Using values of the real part of V-Q (Q) over bar in a gluonic medium, we obtain Debye masses compatible with HTL perturbation theory. (C) 2015 The Authors. Published by Elsevier B.V.

Elsevier2016

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Concentration regimes in polyelectrolyte solutions

Christine Wandrey

A general description of the electrolytic cond. behavior of highly charged strong polyelectrolytes in dil. and semidilute aq. solns. is presented. For the first time this model considers the effects of the molar mass, charge d. (for charge distances less than the Bjerrum length), polyelectrolyte concn., and the ionic strength adjusted by both the polyelectrolyte concn. (cp in monomol L-1) and added simple salt concn. (cs in mol L-1). Above the overlap concn. (c*) the molar mass influence is weak; below c* the equiv. cond. (L) increases strongly when cp decreases (cp > cs). The following relations were found: Lmax .apprx. cs-1/5 and Lmax .apprx. M-2/5 (M is molar mass). The cond. behavior can be qual. explained in terms of Manning's theory with an addnl. change of the interaction parameter fc. An empirical dependence of fc on the ratio of the Debye length to the contour length (lD/L) was found. Three concn. regimes differing in the polyion-counterion interaction were identified; these are characterized by the conditions: (lD/L < 4p)-1/2, (4p)-1/2 < lD/L < 1, and lD/L > 1, resp. The model describes polyelectrolyte solns. characterized by arbitrary (including zero) salt concn. [on SciFinder (R)]

1999

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