Surface heterogeneity and surface area from linear inverse gas chromatography. Application to glass fibers

A new method of measuring surface heterogeneity of non-porous adsorbents by inverse gas chromatography (IGC) is developed. In contrast with the methods described in the literature which are based on nonlinear chromatography (thermodynamics of adsorption) this method is based on linear chromatography (kinetics of adsorption). The mass balance equation of linear chromatography with axial diffusion term and the Langmuir kinetic equation on an open (non-porous) heterogeneous surface are solved by the method of Laplace transforms. The expressions for four semi-invariants of an elution profile are obtained. These are linear combinations of the moments of the distribution of sites in residence time of adsorbed molecule with coefficients determined from elution profile of non-adsorbing gas. Four semi-invariants of elution profiles of benzene and methane on a column packed with E-glass fiber were determined experimentally at temperatures around 100 degrees C. The mean, the standard deviation of the normal distribution in adsorption energy as well as the sticking coefficient and pre-exponential factor of the Frenkel equation are determined for benzene on E-glass. A method of the specific surface determination from linear IGC is proposed.     

The effective magnetic permeability of a two-phase fibred ferromagnetic composite

The magnetic properties of a two-phase fiber composite are theoretically studied. One of the phases is a ferromagnet with a highly nonlinear field dependence of the local magnetic permeability and a negligible hysteresis loop. The dependences of the effective magnetic permeability (both along and across the fibers) on the external magnetic field and on ferromagnetic phase concentration are found. A steep rise in the effective transverse permeability is revealed near the percolation threshold.     

Effect of isotropic stress on dislocation bias factor in bcc iron: an atomistic study

The effect of externally applied stress on the dislocation bias factor (BF) in bcc iron has been studied using a combination of atomistic static calculations and finite element integration. Three kinds of dislocations were considered, namely, a₀/2〈1 1 1〉{1 1 0} screw, a₀/2〈1 1 1〉{1 1 0} edge and a₀〈1 0 0〉{0 0 1} edge dislocations. The computations reveal that the isotropic crystal expansion leads to an increasing or constant dislocation bias, depending on the Burgers vector and type of dislocation. On the other hand, compressive stress reduces the dislocation bias for all the dislocations studied. Variation of the dislocation BF depending on dislocation type and Burgers vector is discussed by analysing the modification of the interaction energy landscape and the capture efficiency values for the vacancy and self-interstitial atom.     

Glide of dislocations in <1 1 1>{3 2 1} slip system: an atomistic study

Atomistic calculations are performed to investigate plastic slip in the <1?1?1>{3?2?1} system in body-centred cubic iron. Several modern interatomic potentials, developed over the last decade, are applied to compute the stacking fault γ-line energy in the {3?2?1} plane and the results are compared with the ab initio prediction. The applied potentials have shown strong deviations, but several potentials acquired good qualitative agreement with the ab initio data. Depending on the applied potential, the lowest value of the Peierls stress for the edge dislocation (ED) is 50 MPa (Ackland and Bacon from 1997) and the highest is 550 MPa (Dudarev and Derlet from 2005), while for the screw dislocation it is much higher, in the range 1–2 GPa. At finite temperature, however, the flow stress of the ED is found to decrease exponentially reaching a negligible value at about 200 K, irrespective of the applied potential. On the basis of the data obtained using Ackland–Mendelev potential from 2004, we conclude that the slip resistance of the <1?1?1>{3?2?1} system is in between the resistance of the <1?1?1>{1?1?0} and <1?1?1>{1?1?2} slip systems.     

The permeability and remanent magnetization of a randomly inhomogeneous two-phase medium

A randomly inhomogeneous composite consisting of two, ferromagnetic and nonmagnetic (para-or diamagnetic), phases is considered. The dependence of the effective permeability of the composite on the concentration of the ferromagnetic phase and on the applied magnetic field is found for the case of the negligible hysteresis loop. When the hysteresis loop is appreciable, the remanent magnetization as a function of the ferromagnet concentration is calculated.     

The multi-functional aspect of scanning holographic microscopy: a review(Invited Paper)

Recent developments in scanning holographic microscopy that offer the prospects of new quantitative tools and imaging modalities in bio, micro, and nano sciences are reviewed. The versatility of the method is emphasized. Scanning holography can operate in an incoherent mode for fluorescence imaging, in a coherent mode for quantitative phase imaging, or in a tomographic mode for axial sectioning and rejection of the out-of-focus haze. Possible applications are illustrated with examples, and future prospects ...     

SYNTHESIS AND STRUCTURE OF A BINUCLEAR Pd(II) CHLORANILATE COMPLEX

Journal of Structural Chemistry - A binuclear complex of palladium (Et3NH)2[Pd2(ca)2(μ-Cl)2]·2CH3CN is synthesized by ligand-exchange reaction between [PdCl2(PhCN)2] and (Et3NH)2ca...     

Analysis of fully discrete approximations to parabolic problems with rough or distribution-valued initial data

Summary. We consider fully discrete approximations to a parabolic initial-boundary value problem with rough or distribution-valued initial data in two space dimensions. For discretization in time and space, we apply single step methods and the standard Galerkin method with piecewise linear test functions, respectively. For spatial discretization of the initial condition, we are however forced to use more involved constructions. Our main result is stability and error estimates of the discrete solutions. Received October 21, 1999 / Revised version received May 3, 2001 / Published online December 18, 2001     

Long-term stability of variable stepsize approximations of semigroups

This paper is concerned with the stability of rational one-step approximations of semigroups. Particular emphasis is laid on long-term stability bounds. The analysis is based on a general Banach space framework and allows variable stepsize sequences. Under reasonable assumptions on the stepsize sequence, asymptotic stability bounds for general semigroups are derived. The bounds are typical in the sense that they contain, in general, a factor that grows with the number of steps. Under additional hypotheses on the approximation, more favorable stability bounds are obtained for the subclass of holomorphic semigroups.

     

Performance of the low pressure MWPCs for f ission fragments under a high background

Two couples of low pressure multi-wire proportional chambers (MWPC) were located in the target chamber to detect fission fragments in a hypernuclei producing experiment at Thomas Jefferson National Laboratory (Jlab). In the experiment, a continuous wave (CW) electron beam was applied to form hypernuclei by electromagnetic interaction. In the target chamber, the high energy (1.853 GeV) and high intensity (500 nA) primary electron beam caused a high particle background, which influenced the detection of the fission fragments. This report described the design of the MWPCs and studied the fission-fragment detecting performance of them under such a high background. The efficiency of the MWPCs was given with the help of a high resolution kaon spectrometer. At the same time, the background particles were discussed with a Monte Carlo code based on GEANT4.