Hydrolytic potentiometric titration of sulphate with application in the analysis of waters

Sulphate is precipitated with barium ion, and excess of barium is precipitated with chromate, excess of which immediately hydrolyses at the end-point to give a sharp jump in pH, measured with a glass electrode. A 1:1 methanol/water medium is optimal. Application to waters requires pretreatment with a cation-exchange resin. River, potable and mineral waters containing 20–2000 mg l^?1 sulpate were analysed accurately with relative standard deviations of 1–2%.     

Solution of the Schrödinger equation for two different molecular potentials by the Nikiforov-Uvarov method

In this study, the solution of the Schr?dinger equation by a method developed by Nikiforov and Uvarov which is not based on the manipulation of formal power series has been schematically presented. The method gives elegant, easy and exact solutions of the Schr?dinger equation. In order to demonstrate the applications of the method, solutions of the Schr?dinger equation for the well-known pseudo-harmonic oscillator and a new symmetrical potential proposed by the authors are given. The concrete energy spectra and corresponding wave functions are obtained. The superiority and the limitations of the method compared to other methods have also been emphasized. Received: 20 November 1996 / Accepted: 1 October 1997     

Universal decay of the classical Loschmidt echo of neutrally stable mixing dynamics

We provide analytical and numerical evidence that the classical mixing systems, which lack exponential sensitivity on initial conditions, exhibit universal decay of the Loschmidt echo which turns out to be a function of a single scaled time variable delta(2/5)t, where delta is the strength of perturbation. The role of dynamical instability and entropy production is discussed.     

Novel liquid crystals based on [1]benzothieno[3,2- b][1]benzothiophene

Four series of new [1]benzothieno[3,2- b][1]benzothiophene derivatives have been synthesized. In the non-chiral series a SmA phase occurs, while the chiral series exhibits a rather wide antiferroelectric SmC^A* phase just below the SmA phase. The SmA-SmC^A* phase transition has been studied using DSC and dielectric spectroscopy. In the SmC^A* phase the spontaneous quantities have been measured. The tilt angle shows a typical temperature dependence and the values of spontaneous polarization are rather moderate. The length of the helical pitch increases on increasing the length of the non-chiral alkyl chain.     

de Sitter gauge theories and induced gravities

The European Physical Journal C - Pure de Sitter, anti de Sitter, and orthogonal gauge theories in four-dimensional Euclidean spacetime are studied. It is shown that, if the theory is...     

Minimal and Pseudo-Umbilical Rotational Surfaces in Euclidean Space {\mathbb{E}^4}

In this paper we study general rotational surfaces in ${\mathbb{E}^4}$ whose meridian curves lie in two-dimensional planes. We firstly find all minimal general rotational surfaces by solving the differential equation that characterizes minimal general rotational surfaces. Then we determine all pseudo-umbilical general rotational surfaces in ${\mathbb{E}^4}$ .