Analysis of Carbamates as Fluorescent 1-Dimethylamino-naphthalene-5-sulfonate Esters

The fluorigenic labelling of several N-methyl carbamates is carried out using 1-dimethyl-aminonaphthalene-5-sulfonyl chloride (dansyl chloride). Prior to chromatography the carbamates are reacted in aqueous solution with the dansyl chloride. The derivative is extracted from the solution with n-hexane and subsequently spotted on a thin-layer plate for chromatography. For each N-methyl carbamate, two highly fluorescent spots are obtained. One is common to all N-methyl carbamates studied, whereas the other is characteristic of each individual carbamate. N.m.r. and infrared spectroscopic data indicate that the common spot is the methylamine derivative, and the second spot is the derivative from the phenyl moiety of each carbamate. The sensitivity of the method is less than one nanogram and has been successfully applied to the analysis of natural water samples.     

Three‐dimensional computation for flow‐induced vibrations in in‐line and cross‐flow directions of a circular cylinder

We present numerical results for in‐line and cross‐flow vibrations of a circular cylinder, which is immersed in a uniform flow and is elastically supported by damper‐spring systems to compute vibrations of a rigid cylinder. In the case of a circular cylinder with a low Scruton number, it is well‐known that two types of self‐excited vibrations appear in the in‐line direction in the range of low reduced velocities. On the other hand, a cross‐flow vibration of the circular cylinder can be excited in the range of high reduced velocities. Therefore, we compute the flow‐induced vibrations of the circular cylinder in the wide range of the reduced velocities at low and high Scruton numbers and discuss about excitation mechanisms in the in‐line and cross‐flow directions. Copyright © 2011 John Wiley & Sons, Ltd.     

On the ion exchange defects in aluminosilicate lattices

Summary Samples of synthetic leucite and boron-substituted leucite are investigated by infrared spectroscopy and spectrally resolved thermoluminescence. Evidence is obtained in favour of the assumption that point defects in aluminosilicate lattices are originated by exchanges of Si⁺⁴ and Al⁺³ ions lying in different cells.     

Effect of Fe substitution on the thermal expansion of the highT c superconductor Y1Ba2Cu3O y

Thermal expansion measurements have been carried out on Fe substituted superconducting compounds Y₁Ba₂(Cu_1−x Fe _x )₃O _y (0<x<4%) using a high resolution dilatometer employing the three terminal capacitance technique. The experimental set up is sensitive enough to detect changes in α of less than 10⁻⁸K⁻¹. Results show that the jump Δα in the coefficient of linear thermal expansion at the superconducting transition temperature,T _c, increases almost linearly with Fe concentration. The normal state thermal expansion coefficient α first decreases, attains a minimum value aroundx=1% and then increases for higher Fe concentrations. The oxygen content per unit formula is almost constant up tox=1% and then increases rapidly withx. It has also been observed that the anomalous behaviour of α around 260 K observed by Meingastet al [22] for Fe concentrationx=5% is due to inadequate annealing of the sample.     

工作机械相对振动的研究

本文对工作机械的相对振动进行了理论和实验研究。分析了相对振动的激励和合成原理,提出了工件和工具同相振动和异相振动、同相域以及相对振动放大因子等概念。在此基础上指出了减小相对振动的途径,以作为设计和改造工作机械的参考。     

Effect of optical-phonon scattering on the energy distribution of hot electrons in semiconductors at low temperature

Summary The variational method is used in finding the solution of the transport equation for a system of hot electrons inn-Ge atT=20 K in the presence of high electric field. The role of the emission of optical phonons by hot electrons together with the effect of electron capture by repulsive centres on the formulation of the distribution function are studied. It is shown that the emission of optical phonons plays a dominant role in the formulation of the distribution. The influence of electron capture is very small, it may become appreciable at higher trap concentrations. The obtained distribution function is then used in calculating the capture rate of electrons by negatively charged centres. It is shown that the capture rate increases with electric field.

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Riassunto Il metodo variazionale è usato per trovare la soluzione dell'equazione di transporto per un sistema di elettroni caldi inn-Ge aT=20 K in presenza di grande campo elettrico. Si studiano il ruolo dell'emissione di fononi ottici da elettroni caldi insieme con l'effetto della cattura degli elettroni da centri di repulsione sulla formulazione della funzione di distribuzione. Si mostra che l'emissione di fononi ottici svolge un ruolo dominante nella formulazione della distribuzione. L'influenza della cattura degli elettroni è molto piccola, può diventare apprezzabile a piú grande concentrazione di trappole. La funzione di distribuzione ottenuta è quindi usata nel calcolare il rapporto di cattura degli elettroni da centri a carica negativa. Si mostra che il rapporto di cattura cresce col campo elettrico.

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Резюме Используется вариационный метод для нахождения решения транспортного уравнения для системы горячих электронов вn-Ge приT=20 К при наличии сильного электрического поля. Исследуется роля испускания оптических фононов горячими электронами и эффект эахвата электпонов отталкивающими центрами при определении функции распредения. Показывается, что испускание оптических фононов играет доминируюэую роль при образовании функции распределения. Влияние захвата электронов очень мало и становится существенным при более высоких концентрациях ловушек. Полученная функция распределения используется при вычис-лении интенсивности захвата злектпонов отрицательно заряженными центрами. Показывается, что интенсивность захвата увеличивается с возрастанием электрического поля.

     

Equiconvergence of some complex interpolatory polynomials

Summary Walsh showed the close relation between the Lagrange interpolant in then ^th roots of unity and the corresponding Taylor expansion for functions belonging to a certain class of analytic functions. Recent extensions of this phenomena to Hermite interpolation and other linear processes of interpolation have been surveyed in [3, 5]. Following a recent idea of L. Yuanren [7], we show how new relations between other linear operators can be derived which exhibit Walsh equiconvergence.Dedicated to R. S. Varga on the occasion of his sixtieth birthdayThese authors were supported by NSERC A3094     

A shape-optimization technique for the capillary surface problem

Summary The problem of the construction of an equilibrium surface taking the surface tension into account leads to Laplace-Young equation which is a nonlinear elliptic free-boundary problem. In contrast to Orr et al. where an iterative technique is used for direct solution of the equation for problems with simple geometry, we propose here an alternative approach based on shape optimization techniques. The shape of the domain of the liquid is varied to attain the optimality condition. Using optimal control theory to derive expressions for the gradient, a numerical scheme is proposed and simple model problems are solved to validate the scheme.     

Tracking poles and representing Hankel operators directly from data

Summary We propose and analyse a method of estimating the poles near the unit circleT of a functionG whose values are given at a grid of points onT: we give an algorithm for performing this estimation and prove a convergence theorem. The method is to identify the phase for an estimate by considering the peaks of the absolute value ofG onT, and then to estimate the modulus by seeking a bestL ² fit toG over a small arc by a first order rational function. These pole estimates lead to the construction of a basis ofL ² which is well suited to the numerical representation of the Hankel operator with symbolG and thereby to the numerical solution of the Nehari problem (computing the bestH , analytic, approximation toG relative to theL norm), as analysed in [HY]. We present the results of numerical tests of these algorithms.Partially supported by grants from the AFOSR and NSF     

Stable in situ sorting and minimum data movement

In this paper, we describe an algorithm to stably sort an array ofn elements using only a linear number of data movements and constant extra space, albeit in quadratic time. It was not known previously whether such an algorithm existed. When the input contains only a constant number of distinct values, we present a sequence ofin situ stable sorting algorithms makingO(n lg^(k+1) n+kn) comparisons (lg^(K) means lg iteratedk times and lg* the number of times the logarithm must be taken to give a result 0) andO(kn) data movements for any fixed valuek, culminating in one that makesO(n lg*n) comparisons and data movements. Stable versions of quicksort follow from these algorithms.Research supported by Natural Sciences and Engineering Research Council of Canada grant No.A-8237 and the Information Technology Research Centre of Ontario.Supported in part by a Research Initiation Grant from the Virginia Engineering Foundation.