Wall NMR in the weak ferromagnets YCrO3 and LuCrO3

Complex NMR spectra, consisting of a maximum of six resonance lines, were observed in the domain walls of YCrO₃ and LuCrO₃ and studied as a function of temperature and the in-plane magnetic field. The distribution of the NMR frequency across the domain wall was calculated taking into account the anisotropy of hyperfine fields and quadrupolar interactions. The calculated frequency distribution was used to simulate the shape of the NMR spectra in YCrO₃. The analysis of theoretical spectra in the centext of our experimental results and in particular the asymmetric behaviour of resonance lines in a magnetic field indicate the critical importance of the relaxation processes on the shape of NMR spectra. This conclusion was confirmed by an experiment in which the relaxation was simulated in YFeO₃. The NMR spectrum in LuCrO₃ can be explained by the same model.     

An equity approach to stream water quality management

A model for stream water quality management with particular emphasis on applicability in Turkey is developed via mathematical programming. A new criterion of equity is introduced and the model is formulated as a quadratic programming problem with two objectives, namely equity among dischargers and minimization of total cost. The model is also applied to a hypothetical stream and compared with other more common water quality management programs.     

Bestimmung der Geschwindigkeitskonstante der Bromierungsreaktion von Acetanilid mittels Titrationsmethode in diffuser Schicht an der rotierenden Ring-Scheiben-Elektrode

The kinetics of the bromination of acetanilide has been studied with the diffusion layer titration method. The results have been obtained using the apparatus which consists of the ring-disc electrode and an amperostat-potentiostat system. Dependence of the ring current on the disc current has been determined as a function of rotation speeds of the electrode, of the solution concentration and temperature. It has been shown the bromination reaction of acetanilide exhibits by first order kinetics. In that case Br₂ and Br₃ ^? are the brominating species. The rate of bromination changes with the concentration of the Br^? ions. This reaction rate depends on reactions of molecular bromine with acetanilide. For 0.033<[Br^?]<0.173M the rate constant changes in the following range: $$17530M^{ - 1} s^{ - 1}< k< 6400M^{ - 1} s^{ - 1} ([H + ] = 1,34;T = 298K)$$      

Studies on poly(ethylene terephthalate)/cotton blends by differential scanning calorimetry

DSC curves of polyster/cotton blends indicate that the glass transition temperature,T _g, of cotton varies with the blend composition. Standard curves for quality control purposes are presented and are based on either the cotton or PET transition peak areas. Factors that contribute to the size of the peak areas were determined: a composition coefficient factor and a thermal coefficient factor.

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Zusammenfassung Die DSC-Kurven von Polyster/Baumwoll-Gemischen zeigen, dass die Glas-Übergangstemperatur (T _g der Baumwolle sich mit der Zusammensetzung des Gemisches ändert. Standardkurven für Qualitätskontrollen werden gezeigt, welche auf den Übergangspeakflächen der Baumwolle oder des PETs beruhen. Die zur Grösse der Peakfläche beitragenden Faktoren wurden bestimmt: ein Zusammensetzungskoeffizient und ein thermischer Koeffizient.

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Résumé Les courbes DSC des combinaisons polyester/coton indiquent que la température de transition vitreuseT _g du coton varie avec la composition. On présente des courbes types pour le contrôle de la qualité d'après les surfaces des pics de transition du coton ou du PET. On a déterminé les facteurs qui influencent la dimension des surfaces des pics: l'un est en rapport avec la composition et l'autre avec le coefficient thermique.

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Synthesis of (±)-heliannuol C

A synthesis of (±)-heliannuol C is described involving Bargellini condensation, Dieckmann cyclization and ortho-ester Claisen rearrangement followed by a regioselective epoxide reduction. A new CuI-catalyzed [2+2] cycloaddition reaction is also described.     

Snakes and perturbed random walks

We study some properties of random walks perturbed at extrema, which are generalizations of the walks considered, e.g., by Davis (1999) and Tóth (1996). This process can also be viewed as a version of an excited random walk, recently studied by many authors. We obtain several properties related to the range of the process with infinite memory and prove the strong law, the central limit theorem, and the criterion for the recurrence of the perturbed walk with finite memory. We also state some open problems. Our methods are predominantly combinatorial and do not involve complicated analytic techniques.     

RAPTA complexes containing N‐substituted Tetrazole scaffolds: Synthesis,characterization and Antiproliferative activity

This work describes the synthesis of a series of Ru(II)‐Arene (Arene=p‐cymene, benzene) complexes using different N‐substituted tetrazole ligands and their PTA analogues. All the complexes have been characterized thoroughly using different analytical techniques. Antiproliferative activity of the synthesized complexes against different cell lines indicates remarkable activity of certain complexes up to nanomolar level. In few cases introduction of water soluble PTA (PTA = 1,3,5‐ triaza‐7‐phospha‐tricyclo‐[3.3.1.1]decane) ligand induce significant cytotoxic activity in the ruthenium complex with respect to their chloro analogues, particularly against Jurkat and MCF‐7 cell lines. Interaction with different biomolecules and stability of the RAPTA complexes have been explored in pseudo‐pharmacological conditions.