From electrochromic phenomena to energy harvesting and storage—an overview of solid state ionics research at the Institute of Solid State Physics,University of Latvia

Journal of Solid State Electrochemistry - Solid state ionics is one of the key research topics of the Institute of Solid State Physics, University of Latvia since its establishment. The research...     

Synthesis and cytotoxicity of silylalkylthio‐substituted N‐heterocycles and their hydroselenites

New hydroselenites of the different silylalkylthio‐substituted N‐heterocycles have been prepared by the reaction of selenium dioxide with N‐heterocycles in an aqueous medium. Their structure was confirmed by ¹H, ¹³C, and ⁷⁷Se NMR data. Most of these silylalkylthio‐substituted N‐heterocycles and their hydroselenites have an expressed cytotoxic activity on the MG‐22A (mouse hepatoma), HT‐1080 (human fibrosarcoma), B16 (mouse melanoma), and Neuro 2A (mouse neuroblastoma) cell lines. Some of the hydroselenites exhibit free‐radical protection simultaneously with a high cytotoxic effect. The substances studied were also active in vivoagainst sarcoma S‐180. Copyright © 2003 John Wiley & Sons, Ltd.     

Determination of chemical purity and isotopic composition of natural and carbon-13-labeled arsenobetaine bromide standards by quantitative1H-NMR

In this study, we report the characterization of three arsenobetaine-certified reference materials by quantitative NMR. We have synthesized an arsenobetaine bromide high-purity standard of natural isotopic composition (ABET-1) and two carbon-13-labeled isotopic standards (BBET-1 and CBET-1). Assignments of the chemical purity and isotopic composition are not trivial in the case of arsenobetaine, and in this study we utilized quantitative¹H-NMR techniques for the determination of the mass fractions (chemical purity). The isotopic purity of all three standards was also assessed by NMR from the carbon-13 satellite signals. The standards are non-hygroscopic, high-purity (ca. 0.99 g/g), and the carbon-13 enrichment for both isotopic standards is x(¹³C)≈0.99. These standards are designed for use as primary calibrators for mass spectrometric determination of arsenobetaine in environmental samples.     

Decomposing Euclidean space with a small number of smooth sets

Let the cardinal invariant denote the least number of continuously smooth -dimensional surfaces into which -dimensional Euclidean space can be decomposed. It will be shown to be consistent that is greater than . These cardinals will be shown to be closely related to the invariants associated with the problem of decomposing continuous functions into differentiable ones.