Interaction of Point Defects with Grain Boundaries in fcc Metals

Structures of several symmetrical tilt grain boundaries (GBs) with different tilt axes in Cu and Al and their interaction with vacancies and interstitials are studied using atomistic computer simulations with embedded-atom potentials. The lowest defect formation energy in a GB is found to correlate with the GB energy in both Cu and Al. Importantly, vacancies and self-interstitials in GBs have comparable formation energies, suggesting that both defects are equally important for GB diffusion and other properties. Vacancies in GBs can be either localized at certain sites or be delocalized over several sites. Some GB sites do not support a stable vacancy at all. Self-interstitial atoms can occupy relatively open interatomic positions, form split dumbbell configurations, or give rise to highly delocalized displacement zones. These structural forms of point defects have been observed across the whole set of twelve GBs in Cu and six GBs in Al studied in this paper as well as in our previous work [Interface Science 11, 131–148 (2003)]. It is suggested that these structural forms are general to all GBs in fcc metals. They can be explained by the existence of internal stresses and alternating tension and compression regions in the GB core.     

Application of polyfluorophenazines to dichroic fluorescent dyes in guest-host liquid crystal displays

Novel dichroic fluorescent 2- and 2,7-disubstituted perfluorophenazines exhibit emission maxima in the range 570-600 nm in MLC-2039. The order parameter of fluorescence was observed in the range 0.29-0.49.     

Calcite and fluorite as catalyst for the Knövenagel condensation of malononitrile and methyl cyanoacetate under solvent-free conditions

When milled together with calcite or fluorite, malononitrile and methyl cyanoacetate readily underwent Knövenagel condensation with aromatic aldehydes, giving the corresponding arylidenemalononitriles and (E)-α-cyanocinnamic esters in good to excellent yield.     

Evaluation of a quantitative method for trace impurities in arsenous acids by synchrotron radiation X-ray fluorescence spectrometry and inductively coupled plasma-atomic emission spectrometry.

Thirteen arsenous acid samples of known origins and refining methods were collected. Each sample was subjected to quantitative analysis of any impurity elements present using synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The trace elements selected were Sn, Sb and Bi for the reasons that they were considered not to be changed by their circumstances and that they showed high sensitivity to SR-XRF. These results obtained by both methods were compared and the correlation between these two methods was determined. The quantification of trace impurities obtained by SR-XRF using As as an internal standard showed good agreement with the results obtained by ICP-AES. The discrimination of refining method became possible by the comparison of these impurities' contents measured with non-destructive SR-XRF using several arsenous acid particles.     

Critical exponent and critical blow-up for quasilinear parabolic equations

B ₂-groups are special (torsion-free) abelian Butler groups. The interest in this class of groups comes from representation theory. A particular functor, also called Butler functor, connects algebraic properties of the category of free abelian groups with (a few) distinguished subgroups with these Butler groups. This helps to understand Butler groups and caused lots of activities on Butler groups. Butler groups were originally defined for finite rank, however a homological connection discovered by Bican and Salce opened the investigation of Butler groups of infinite rank. Despite the fact that classifications of Butler groups are possible under restriction even for infinite rank (see a forthcoming paper by Files and Göbel [Mathematische Zeitschrift]), general structure theorems are impossible. This is supported by the following very special case of the Main Theorem of this paper, showing that any ring with a free additive group is an endomorphism ring of a Butler group. The result implies the existence of large indecomposable or of large superdecomposable Butler groups as well as the existence of counter-examples for Kaplansky’s test problems.     

Local magnetic field and muon site in CeAs

We report on zero field and longitudinal field μSR experiments on a CeAs single crystal between 3.3 and 12 K. Below the antiferromagnetic transition at 7.5 K a spontaneously precessing signal with a saturation frequency of \approx25 MHz representing the full sample amplitude has been found. From an analysis of the field dependence of the relaxation rate of this signal in \langle 100\rangle and \langle 110\rangle crystal orientation parallel to the muon spin and the applied longitudinal field, a \langle 100\rangle orientation of the local field at the muon site is concluded. This supports an AF‐I single‐\veck magnetic ordering. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thin-layer chromatographic behaviour and separation of rare earths in silica gel-aqueous alkali metal chloride systems

Summary The thin-layer chromatographic behaviour of all the rare earths except Pm on silica gel in aqueous solutions of five alkali metal chlorides has been surveyed. The Rf-values and the logarithms of the separation factors relative to Gd vary in a regular and peculiar way with increasing atomic number, through a reflection of the strong tetrad effect. A discussion concerning the effects on the Rf-values of the solvent cations and the solvent anions, and typical chromatograms for the separations of multi-component mixtures containing adjacent lanthanoids are also presented.     

Structure comparison between Th2Zn17-type and TbCu7-type Sm–Fe intermetallic compounds and their nitrides by means of 57Fe-Mössbauer spectroscopy

Samarium–iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th₂Zn₁₇-type and a TbCu₇-type structure, respectively. Structure comparison between these types was investigated for Sm–Fe intermetallic compounds and their nitrides by ⁵⁷Fe-Mössbauer spectroscopy.     

Fast Encoding Method for Image Vector Quantization Based on Multiple Appropriate Features to Estimate Euclidean Distance

The encoding process of finding the best-matched codeword (winner) for a certain input vector in image vector quantization (VQ) is computationally very expensive due to a lot of k-dimensional Euclidean distance computations. In order to speed up the VQ encoding process, it is beneficial to firstly estimate how large the Euclidean distance is between the input vector and a candidate codeword by using appropriate low dimensional features of a vector instead of an immediate Euclidean distance computation. If the estimated Euclidean distance is large enough, it implies that the current candidate codeword could not be a winner so that it can be rejected safely and thus avoid actual Euclidean distance computation. Sum (1-D), L₂ norm (1-D) and partial sums (2-D) of a vector are used together as the appropriate features in this paper because they are the first three simplest features. Then, four estimations of Euclidean distance between the input vector and a codeword are connected to each other by the Cauchy–Schwarz inequality to realize codeword rejection. For typical standard images with very different details (Lena, F-16, Pepper and Baboon), the final remaining must-do actual Euclidean distance computations can be eliminated obviously and the total computational cost including all overhead can also be reduced obviously compared to the state-of-the-art EEENNS method meanwhile keeping a full search (FS) equivalent PSNR.     

Thickness and Surface Profile Measurement by a Sinusoidal Wavelength-Scanning Interferometer

We propose a sinusoidal wavelength-scanning interferometer for measuring thickness and surface profile of a thin film. The interference signal contains phase modulation amplitude Z and phase $aL which are related to the positions and profiles of the reflecting surfaces, respectively. By reducing the difference between the detected signal and the estimated signal using the multidimensional nonlinear least-squares algorithm, we estimate values of Z and $aL. Experimental results show that the front and rear surfaces of a silica glass plate of 20 $mUm-thickness could be measured with an error less than 10 nm.