Hamiltonian spatial structure for three-dimensional water waves in a moving frame of reference

Summary The governing equations for three-dimensional time-dependent water waves in a moving frame of reference are reformulated in terms of the energy and momentum flux. The novelty of this approach is that time-independent motions of the system—that is, motions that are steady in a moving frame of reference—satisfy a partial differential equation, which is shown to be Hamiltonian. The theory of Hamiltonian evolution equations (canonical variables, Poisson brackets, symplectic form, conservation laws) is applied to the spatial Hamiltonian system derived for pure gravity waves. The addition of surface tension changes the spatial Hamiltonian structure in such a way that the symplectic operator becomes degenerate, and the properties of this generalized Hamiltonian system are also studied. Hamiltonian bifurcation theory is applied to the linear spatial Hamiltonian system for capillary-gravity waves, showing how new waves can be found in this framework.     

萃取法富集XRF光谱测定岩石,土壤中的痕量元素

本文研究了用10%N_(7402)-MIBK萃取预富集,以XRFS测定岩石、土壤中Pb、Zn、Cu、Cd、Mo、Bi、Sn等痕量元素的方法,并研究了背景对检出限的影响,选Sm作内标。确定了样品分解,薄样制备方法和测定条件,检出限较直接粉末压片法约降低两个数量级,精密度通常优于4%,本法分析结果与标样推荐值吻合。     

Non-stoichiometry and properties of ternary semiconductor phases of variable composition based on IV-VI compounds

An overview and analysis of our experimental data on the crystal structure, mechanical, thermal, galvanomagnetic and thermoelectric properties vs composition of the ternary semiconductor phases based on IV-Te compounds in the IV-X-Te systems (IV-Ge, Sn, Pb; X-Cu, Ag, Cd, In, Ga, Bi, Sb, Mn, V) are given. The separate and joint effect of deviation from stoichiometry and cation substitution on the IV-X-Te phase properties is established using the method of ‘controlled atomic defects’. Some general regularities and new physical phenomena connected with simultaneous presence of intrinsic and impurity point defects are detected. The influence of the cation substitution on the intrinsic defect equilibrium is established. It is shown that critical phenomena of percolation nature are observed in the range of small impurity contents as well as small intrinsic defect concentrations. Principally new models of the energy band structure of IV-X-Te ternary phases, which take into consideration a high concentration of non-stoichiometric defects, are proposed. The role of long- and short-range ordering is discussed. The formation of complexes as a result of chemical interaction between impurity and host atoms is detected. The above-mentioned phenomena are common for ternary phases and should be taken into account when developing materials for different applications.     

Solid phase extraction GC/ECD method for the analysis of organochlorine pesticides in wildlife plasma

A gas chromatographic method for the analysis of nine organo-chlorine pesticides in wildlife plasma is described. Reversed-phase solid phase extraction is utilized to extract the organochlorine pesticides from plasma. This is followed by a normal phase solid phase extraction clean-up as the pesticides are recovered by elution with hexane:ethyl ether (1:1) and quantified by gas chromatogra-phy/electron capture detection. Method limits of detection range from 7.0–25 μg/L. The mean recovery for all pesticides is 81%.     

Modification of the NRTL model for ternary and quaternary liquid-liquid equilibrium calculations

The original NRTL model is modified for the correlation of ternary liquid-liquid equilibria. The ternary expression of the modified NRTL model includes three additional ternary parameters and the ternary terms vanish when a ternary system degenerates to a binary. The ability of the modified NRTL model has been evaluated in the calculations of ternary vapor-liquid-liquid equilibria and quaternary liquid-liquid equilibria.     

Extraction chromatographic studies of Ti(IV) with cyanex 301 as impregnant—Recovery from red mud

Summary A silica gel column impregnated with bis-(2,4,4-trimethylpentyl)dithiophosphinic acid has been studied for the uptake of Ti(IV). Its chemical stability has been examined and its regeneration power checked. The stoichiometry of the extracted species is proposed and the loading capacity of the column material for Ti(IV) assessed. Some important binary separations of Ti(IV) from commonly associated metal ions have been achieved and the column has been used to recover high-purity titanium from red mud, a secondary sector material.     

A descent algorithm for solving monotone variational inequalities and monotone complementarity problems

The paper provides a descent algorithm for solving certain monotone variational inequalities and shows how this algorithm may be used for solving certain monotone complementarity problems. Convergence is proved under natural monotonicity and smoothness conditions; neither symmetry nor strict monotonicity is required.The author is grateful to two anonymous referees for their very valuable comments on an earlier draft of this paper.     

Phase stability in the LnCa2Mn2O7 (Ln=Pr, Nd, Sm and Gd) Ruddlesden-Popper series

The synthesis of the Ruddlesden-Popper series, LnCa₂Mn₂O₇, (Ln=Pr, Nd, Sm and Gd) is described and their structure and electronic properties investigated. The reduction in size of the A-site cation causes an increase in the distortion of their orthorhombic structures (space group Cmcm). All of these compounds form with a perovskite impurity, the amount of which increases on reduction of the cation size. The synthesis temperature also alters the amount of perovskite impurity in the phase, but only to a lower limit, implying the perovskite phase is intrinsic to the material and that a phase equilibrium exists between the layered Ruddlesden-Popper and perovskite phases, which is controlled by the cation size. The magnetic susceptibility show transitions characteristic of the perovskite phase, therefore little direct information can be obtained about the Ruddlesden-Popper phases, except that ferromagnetism is not observed in any of these materials.     

Lindemann law revisited

Summary Traditionally, Lindemann law has gained a fame of unpredictable validity, since it apparently provides agreement with experiment which varies ?randomly? from excellent to very poor. Under the hypothesis that such incoherent results might have been originated by inaccurate data, we carefully reanalyse its validity. We use an integral quasiharmonic formulation which minimizes the effect of experimental errors, and compare the results from different sources whenever available. The agreement with experiment is found to be very good for all the cases considered, and namely for metals (Al, Ag, Au, Cu, Fe), ionic crystals (KCl, NaCl, RbCl) and complex sinthetic polycrystals (forsterite), in the sense that Lindemann law inaccuracy is much smaller than the experimental scatter. Different types of simple spectra are tried (Debye and Brillouin), but minimal differences are detected. This suggests that melting is relatively insensitive to the specific shape of the spectrum.

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Riassunto Tradizionalmente, la legge di Lindemann ha fama di grande imprevedibilità, in quanto l'accordo coi dati sperimentali varia da ottimo a pessimo in maniera del tutto casuale. Ipotizzando che tale incoerenza nei risultati possa essere originata da errori sperimentali, ne rianalizziamo accuratamente la validità utilizzando una formulazione quasi armonica che minimizza l'effetto dell'inaccuratezza sperimentale e confrontando i risultati di tutte le diverse fonti disponibili. L'accordo coi dati è ottimo in tutti i casi considerati e cioè per i metalli (Al, Ag, Au, Cu, Fe), cristalli ionici (KCl, NaCl, RbCl) e policristalli complessi (forsterite), nel senso che l'inaccuratezza della legge di Lindemann è molto piú piccola dello scatter sperimentale. Le minime differenze trovate utilizzando diversi tipi di spettro (Debye and Brillouin) suggeriscono che la fusione sia influenzata in maniera ridotta dalla forma specifica dello spettro.

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Резюме Традиционно закон Линдемана имеет репутацию закона с непредсказуемой применимостью, т.к. дает согласие с экспериментом, которое изменяется ?случайно? от превосходного до плохого. Используя гипотезу, что некогерентные результаты могут возникать из неточных данных, мы заново анализируем применимость закона. Мы используем интегральную квазигармоническую формулировку, которая минимизируем влияние экспериментальных погрешностей, и сравниваем результаты из различиных имеющихся источников. Получается очень хорошее согласие с экспериментом для всех рассмотренных случаев: для металлов (Al, Ag, Au, Cu, Fe), ионных кристаллов (KCl, NaCl, RbCl) и сложных синтетических поликристаллов, т.е. погрешность закона Линдемана оказывается много меньше экспериментального разброса. Исследуются различные типы простых спектров (Дебая и Вриллюэна), получаются минимальные различия. Предполагается, что плавление относительно не чувствительно к конкретной форме спектра.