Torsion-free crystallographic groups with indecomposable holonomy group II.

Let K be a principal ideal domain, G a finite group, and M a KG-module which is a free K-module of finite rank on which G acts faithfully. A generalized crystallographic group is a non-split extension C of M by G such that conjugation in C induces the G-module structure on M. ( When K = Z, these are just the classical crystallographic groups.) The dimension of C is the K-rank of M, the holonomy group of C is G, and C is indecomposable if M is an indecomposable KG-module. We study indecomposable torsion-free generalized crystallographic groups with holonomy group G when K is Z, or its localization Z((p)) at the prime p, or the ring Z(p) of p-adic integers. We prove that the dimensions of such groups with G non-cyclic of order p(2) are unbounded. For K = Z, we show that there are infinitely many non-isomorphic such groups with G the alternating group of degree 4 and we study the dimensions of such groups with G cyclic of certain orders

Постать М. П. Василенка в публікаціях української діаспори (The Figure of Mykola Vasylenko in Publications of Ukrainian Diaspora)

Автором досліджено інтелектуальну спадщину української діаспори, яка присвячена вивченню постаті відомого вченого та громадського діяча М.П. Василенка. У своїх працях увагу йому приділяли історики, публіцисти та інші дослідники. Їх науковий доробок про вченого представлений дослідженнями загального плану, статтями про його наукову та політичну діяльність на сторінках різних діаспорних видань, зокрема в «Українському історику». Окремо розглянуто публікації мемуарного характеру, як важливі джерела до вивчення особи М. Василенка. До них відносяться спогади його дружини Н. Полонської-Василенко, істориків Л. Окиншевича, Д. Дорошенка, гетьмана П. Скоропадського. (The author studies the intellectual heritage of the Ukrainian diaspora, which represented by the study of famous scholar and public figure Mykola Vasylenko. Many historians, journalists and other researchers paid attention to him in their studies. Their academic works about Vasylenko are mainly presented in forms of articles about his scholarly and political activities in various diaspora`s publications, particularly in Ukrainian Historian. The memoirs, considered as important sources in the study of Vasylenko heritage, are published separately. These are the memories of his wife N. Polonska-Vasylenko and historians L. Okynshevych, D. Doroshenko, and Hetman P. Skoropadskyi.

Наукова діяльність Миколи Василенка наприкінці ХІХ – на поч. ХХ ст. (Mykola Vasylenco' scientific activity at the end of XIX – the beginning of XX century)

У статті проаналізовано участь Миколи Василенка в науковому житті підросійської України на межі ХІХ – ХХ ст., становлення і трансформацію його наукових поглядів. Зроблено висновки про домінування у нього «українського» компонента наукового світогляду з початку ХХ ст., а особливо після ознайомлення з працями Михайла Грушевського. (This article is an attempt to analyze the scientific works by M.Vasylenko which have been written until 1917. From the beginning of his work young scientist was most interested in General Theory of Law and State. His scholar authority was greatly increasing. His publications in ‘The Brockhaus and Efron Encyclopedic Dictionary’ contained forward scientific ideas. The scholar was one of the most active members of The Nestor the Chronicler Historical Community. From 1909 to 1917 M.Vasylenko joined different scientific associations such as Ukrainian Scientific Association and The Taras Shevchenko Scientific Society. The analysis of scientific works by M.Vasylenko shows the Ukrainian element of his mentality become more intensive at that time. M. Hrushevskyi influenced M.Vasylenko in this way. M.Vasylenko moved on M. Hrushevskyi’ historical concept and also popularized his works, and actively reviewed it. The most obvious proof of the scientist’s move to the position of the national-centered conception of Ukrainian history is contained in ‘The Essays on the History of Western Rus and Ukraine’, his the most famous research.

Tunable electrophysical properties of composites nano-CdS/polyvinyl alcohol

Electrical d.c. conductivity of nano-CdS/polyvinyl alcohol composites with different nanoparticle concentrations and its temperature dependence were studied. The composites demonstrate increasing resistivity with CdS nanoparticles content. The currentevoltage characteristics of composites exhibit non-ohmic superlinear behavior that is interpreted in terms of space-charges-limited currents. Temperature dependence of resistivity is characterized by high temperature coefficient of resistivity which is favorable for applications in flexible, easy-to-shape thermistors. The tunability of the thermal sensitivity of CdS/polyvinyl alcohol composites was analyzed

Phosphorescence of CdS nanoparticles in polymer matrix as an indication of host-guest interaction

We report on the observation of the long-lasting low-temperature photoluminescence decay in the hybrid system nano-CdS/polyvinyl alcohol with a characteristic time of about 1.7 s. The origin of the phosphorescence is ascribed to the accumulation of photo-excited excitons in the traps within the polymeric matrix with subsequent transfer of the excitation to the embedded CdS nanoparticles

Retardation of nanoparticles growth by doping

The process of doping of CdS nanoparticles with Mn during colloidal synthesis is analyzed by EPR and optical studies. Analysis of EPR results demonstrated that Mn2+ ions are successfully incorporated into the nanoparticles and occupy the crystal sites both in the bulk of a NP and near the surface of a NP. Optical absorption measurements revealed the retardation of absorption edge shift during the growth for Mn-doped CdS NPs as compared to the undoped CdS NPs. It was concluded that the presence of Mn in the solution leads to the inhibition of NPs growth

Effects of Ultraviolet Light on Optical Properties of Colloidal CdS Nanoparticles Embedded in Polyvinyl Alcohol (PVA) Matrix

CdS nanoparticles have been synthesized in aqueous solution using polyvinyl alcohol (PVA) as a capping reagent. The effects of exposure by ultraviolet (UV) light on optical properties of nanocomposites consisting of colloidal CdS nanoparticles and a polymer PVA matrix were studied by employing photoluminescence (PL) spectroscopy. It is shown that UV-induced changes of the photoluminescence intensity in PVA are caused by creation and healing of non-radiative recombination centers. It is also concluded that in the nanocomposites, the UV-induced changes of the PL intensity are predominantly governed by processes at the NP/PVA interfaceFinancial support from the Swedish Institute via Visby program is greatly appreciated

Synthesis of Capped AIIBVI Nanoparticles for Fluorescent Biomarkers

The conditions for growing CdS nanoparticles suitable for the visualization of biological tissues were theoretically studied and experimentally checked. The optimal ranges for pH values and precursors’ concentrations were determined. The applicability of the mercaptoethanol-capped nanoparticles for in vitro luminescence visualization of several cellular forms in histological specimens of human placenta has been prove