On Commutativity of Rings With Derivations

Let R be a ring and d : R → R a derivation of R. In the present paper we investigate commutativity of R satisfying any one of the properties (i)d([x,y]) = [x,y], (ii)d(x o y) = xoy, (iii)d(x) o d(y) = 0, or (iv)d(x) o d(y) = x o y, for all x, y in some apropriate subset of R.     

Tests for liquid chromatographs

Summary The paper describes tests for liquid chromatographs to assess the autosampler and pump flow rate precision; suitability of the instrument for normal phase chromatography; UV detector performance; and external band broadening characteristics. Tests for mixing and proportioning characteristics of solvent pumps and performance of diode array detectors are also considered. These tests are designed to evaluate the performance of both newly released liquid chromatography equipment and equipment already in operation. Data from evaluations carried out by instrument manufacturer’s and suppliers is reported and discussed. This data offers specifications to a common format for initial selection of instruments prior to purchase.     

On topological properties of poly honeycomb networks

Topological indices are numerical parameters of a graph which characterize its topology and are usually graph invariant. In QSAR/QSPR study, physico-chemical properties and topological indices such as the Randi?, the atom-bond connectivity (ABC) and the geometric-arithmetic (GA) indices are used to predict the bioactivity of chemical compounds. Graph theory has found a considerable use in this area of research. In this paper, we study poly honeycomb networks which are generated by a honeycomb network of dimension n and derive analytical closed results for the general Randi? index \(R_\alpha (G)\) for different values of \(\alpha \), for a David derived network \((\textit{DD}(n))\) of dimension n, a dominating David derived network \((\textit{DDD}(n))\) of dimension n as well as a regular triangulene silicate network of dimension n. We also compute the general first Zagreb, ABC, GA, \(\textit{ABC}_4\) and \(\textit{GA}_5\) indices for these poly honeycomb networks for the first time and give closed formulas of these degree based indices in case of poly honeycomb networks.     

Crystallographic report: Chlorodimethyltin(IV) piperidine‐1‐carbodithioate

Me₂Sn(S₂CN(CH₂)₅)Cl contains five‐coordinated tin with a bidentate dithiocarbamate ligand spanning equatorial and axial positions in a distorted trigonal bipyramidal geometry. Copyright © 2005 John Wiley & Sons, Ltd.     

Spectrophotometric determination of tranexamic acid in pharmaceutical bulk and dosage forms.

In this study, a simple, fast, accurate and sensitive spectrophotometric method has been developed for the determination of tranexamic acid in bulk and pharmaceutical preparations. The method is based on the reaction of ninhydrin with the primary amino group of tranexamic acid in the basic medium at pH 8.0. The reaction produces a bluish-purple color which absorbs maximally at 565 nm. Beer's law was obeyed in the range of 3-40 microg ml(-1) with molar absorptivity of 5.093 x 10(3) L mol(-1) cm(-1). The effects of various factors such as temperature, heating time, concentration of reagent, color stability and interferences were investigated to optimize the procedure. The results have been validated analytically and statistically. The proposed method has been applied for the determination of tranexamic acid in bulk and pharmaceutical preparations with good results.     

A note on the negative absorption of electromagnetic waves at the cyclotron resonance of plasma electrons

The quantum interpretation of the negative absorption of electromagnetic waves at the cyclotron resonance of plasma is given, and the conditions under which the negative absorption takes placs are examined.     

Integration of Markov and Linear Programming Models to Assess the Farmgate and National Consequences of Adopting New Bovine Reproductive Technologies in the United Kingdom Agriculture

Despite many advances in biotechnology being futuristic, in some industries such technological improvements are now becoming generally available for absorption into commercial practice. The new reproductive technologies for bovine animals are such an example. For a regulated industry like agriculture, an ex ante evaluation of the impact of their adoption is the concern of policy makers. This paper describes a modelling strategy devised to assess these impacts, using a sequence of stochastic, financial and linear programming models. A set of individual farm type models were developed and later extended to a national model to simulate the interactions that occur between dairy and beef enterprises and the competition between them for resources on individual farms. Restraints reflecting national policies such as quotas on milk production and industry support through subsidies are built into the model to explore several scenarios. These models are used to assess the impact of new technologies on dairy and beef production nationally and for regions which have been identified by the Ministry of Agriculture, Fisheries and Food.     

Gamma-Radiolysis of water-insoluble heteroxylans

Chemical and structural changes of two-insoluble heteroxylans of different origin after -irradiation treatment were studied by IR spectroscopy and sugar analysis of the obtained polymeric fractions. Radiolytic degradation in solid states was found to be an effective fragmentation method for structural analysis of complex insoluble polysaccharides.     

Stability analysis for a nonlinear coupled system of fractional hybrid delay differential equations

The main objective of this research work is to establish existence results as well as to study qualitative aspects of the proposed coupled system of fractional hybrid delay differential equations (FHDDEs). Using the hybrid fixed point theory, we establish appropriate results for the existence of at least one solution to our problem. The powerful tools of functional analysis and dynamical systems are applied to derive different kinds of stability analysis. These include Ulam-Hyers (UH), generalized Ulam-Hyers (GUH), Ulam-Hyers-Rassias (UHR), and generalized Ulam-Hyers-Rassias (GUHR). In order to provide the authenticity of the our results, an illustrative example is given to wind up the present research work.