46 research outputs found

    Relative concentration and structure of native defects in GaP

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    The native defects in the compound semiconductor GaP have been studied using a pseudopotential density functional theory method in order to determine their relative concentrations and the most stable charge states. The electronic and atomic structures are presented and the defect concentrations are estimated using calculated formation energies. Relaxation effects are taken into account fully and produce negative-U charge transfer levels for VP and PGa. The concentration of VGa is in good agreement with the results of positron annihilation experiments. The charge transfer levels presented compare qualitatively well with experiments where available. The effect of stoichiometry on the defect concentrations is also described and is shown to be considerable. The lowest formation energies are found for PGa +2 in p-type and VGa −3 in n-type GaP under P-rich conditions, and for GaP −2 in n-type GaP under Ga-rich conditions. Finally, the finite size errors arising from the use of supercells with periodic boundary conditions are examined

    European lipodystrophy registry: Background and structure

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    Background: Lipodystrophy syndromes comprise a group of extremely rare and heterogeneous diseases characterized by a selective loss of adipose tissue in the absence of nutritional deprivation or catabolic state. Because of the rarity of each lipodystrophy subform, research in this area is difficult and international co-operation mandatory. Therefore, in 2016, the European Consortium of Lipodystrophies (ECLip) decided to create a registry for patients with lipodystrophy. Results: The registry was build using the information technology Open Source Registry System for Rare Diseases in the EU (OSSE), an open-source software and toolbox. Lipodystrophy specific data forms were developed based on current knowledge of typical signs and symptoms of lipodystrophy. The platform complies with the new General Data Protection Regulation (EU) 2016/679 by ensuring patient pseudonymization, informational separation of powers, secure data storage and security of communication, user authentication, person specific access to data, and recording of access granted to any data. Inclusion criteria are all patients with any form of lipodystrophy (with the exception of HIV-associated lipodystrophy). So far 246 patients from nine centres (Amsterdam, Bologna, Izmir, Leipzig, M\ufcnster, Moscow, Pisa, Santiago de Compostela, Ulm) have been recruited. With the help from the six centres on the brink of recruitment (Cambridge, Lille, Nicosia, Paris, Porto, Rome) this number is expected to double within the next one or 2 years. Conclusions: A European registry for all patients with lipodystrophy will provide a platform for improved research in the area of lipodystrophy. All physicians from Europe and neighbouring countries caring for patients with lipodystrophy are invited to participate in the ECLip Registry. Study registration: ClinicalTrials.gov (NCT03553420). Registered 14 March 2018, retrospectively registered

    Body weight, metabolism and clock genes

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    Biological rhythms are present in the lives of almost all organisms ranging from plants to more evolved creatures. These oscillations allow the anticipation of many physiological and behavioral mechanisms thus enabling coordination of rhythms in a timely manner, adaption to environmental changes and more efficient organization of the cellular processes responsible for survival of both the individual and the species. Many components of energy homeostasis exhibit circadian rhythms, which are regulated by central (suprachiasmatic nucleus) and peripheral (located in other tissues) circadian clocks. Adipocyte plays an important role in the regulation of energy homeostasis, the signaling of satiety and cellular differentiation and proliferation. Also, the adipocyte circadian clock is probably involved in the control of many of these functions. Thus, circadian clocks are implicated in the control of energy balance, feeding behavior and consequently in the regulation of body weight. In this regard, alterations in clock genes and rhythms can interfere with the complex mechanism of metabolic and hormonal anticipation, contributing to multifactorial diseases such as obesity and diabetes. The aim of this review was to define circadian clocks by describing their functioning and role in the whole body and in adipocyte metabolism, as well as their influence on body weight control and the development of obesity

    Національна доповідь про стан і перспективи розвитку освіти в Україні: монографія (До 30-річчя незалежності України)

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    The publication provides a comprehensive analysis of the state and development of national education over the 30 years of Ukraine’s independence, identifies current problems in education, ascertains the causes of their emergence, offers scientifically reasoned ways to modernise domestic education in the context of globalisation, European integration, innovative development, and national self-identification. Designed for legislators, state officials, education institutions leaders, teaching and academic staff, the general public, all those who seek to increase the competitiveness of Ukrainian education in the context of civilisation changes.У виданні здійснено всебічний аналіз стану і розвитку національної освіти за 30-річний період незалежності України, визначено актуальні проблеми освітньої сфери, виявлено причини їх виникнення, запропоновано науково обґрунтовані шляхи модернізації вітчизняної освіти в умовах глобалізації, європейської інтеграції, інноваційного розвитку та національної самоідентифікації. Розраховано на законодавців, державних управлінців, керівників закладів освіти, педагогічних і науково-педагогічних працівників, широку громадськість, усіх, хто прагне підвищення конкурентоспроможності української освіти в контексті цивілізаційних змін

    Neutron spectrometry method for determination of hydogen content in metal hydrides

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    Nondestructive method for analysis of stoichiometric ratio in metal hydrides has been developed. It is based on analysis of total neutron cross sections for hydride samples measured in the area of slow neutrons with use of neutron spectrometry time of flight method. As on titanium hydride example, it is shown, that measurement and analysis of total neutron cross sections for samples TiHn allow to evaluate the value of ratio metal-hydrogen in hydride (n) with accu¬racy ~ 1 %

    Luminescent and Optically Detected Magnetic Resonance Studies of CdS/PVA Nanocomposite

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    A series of solid nanocomposites containing CdS nanoparticles in polymeric matrix with varied conditions on the interface particle/polymer was fabricated and studied by photoluminescence (PL) and optically detected magnetic resonance (ODMR) methods. The results revealed interface-related features in both PL and ODMR spectra. The revealed paramagnetic centers are concluded to be involved in the processes of photo-excited carriers relaxation.Funding Agencies|Volkswagen Foundation; Swedish Institute via Visby program; National Academy of Science of Ukraine [26/17-H]</p

    Evidence for a phosphorus-related interfacial defect complex at a GaP/GaNP heterojunction

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    Optically detected magnetic resonance (ODMR) studies of molecular beam epitaxial GaNP/GaP structures reveal presence of a P-related complex defect, evident from its resolved hyperfine interaction between an unpaired electronic spin (S=1/2) and a nuclear spin (I = ½) of a 31P atom. The principal axis of the defect is concluded to be along a &lt;111&gt; crystallographic direction from angular dependence of the ODMR spectrum, restricting the P atom (either a PGa antisite or a Pi interstitial) and its partner in the complex defect to be oriented along this direction. The principal values of the electronic g-tensor and hyperfine interaction tensor are determined as: g┴=2.013, g║=2.002, and A┴=130´10-4 cm-1, A║=330´10-4 cm-1, respectively. The interface nature of the defect is clearly manifested by the absence of the ODMR lines originating from two out of four equivalent &lt;111&gt; orientations. Defect formation is shown to be facilitated by nitrogen ion bombardment under non-equilibrium growth conditions and the defect is thermally stable upon post-growth thermal annealing.Original Publication: Daniel Dagnelund, I. P Vorona, L. S. Vlasenko, X. J. Wang, A. Utsumi, Y. Furukawa, A. Wakahara, H. Yonezu, I. A. Buyanova and W. M. Chen, Evidence for a phosphorus-related interfacial defect complex at a GaP/GaNP heterojunction, 2010, Physical Review B Condensed Matter, (81), , 115334. http://dx.doi.org/10.1103/PhysRevB.81.115334 Copyright: American Physical Society http://www.aps.org/</p

    Dielectric resonator in rectangular ??(102) cavity for electron paramagnetic resonance study of thin films

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    The improved compared to a rectangular TE(102 )cavity geometry of a dielectric resonator (DR) suitable for studying thin films and coatings has been calculated and experimentally verified. It is shown that electron paramagnetic resonance (EPR) signal of SiOx films can be enhanced by using as the DR of two rectangular parallelepipeds fabricated from BaTi4O9 + 8.5% ZnO ceramics (epsilon=36) with dimension of 5.64x5.5 x 5.9 mm(3 )and a gap of up to 0.5 mm between them. Located inside a standard rectangular metal TE(102 )cavity of the X-band EPR spectrometer, the DR increases the filling factor by 5-12 times depending on the size of a sample studied. The experimental use of the DR allows to increase the EPR signal of the 950 nm SiOx thin film by a factor of approximately 4.Funding Agencies|National Academy of Sciences of Ukraine [0118U002317, 0118U002317s]; Swedish Foundation for Strategic Research (SSF) [UKR22-0040]</p

    Optically detected magnetic resonance study of relaxation/emission processes in the nanoparticle-polymer composite

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    Two nanocomposites containing CdS nanoparticles in polymeric matrices were studied using the photoluminescence (PL) and optically detected magnetic resonance (ODMR) methods. Due to equal sizes of NPs in the composites (~5 nm) but different matrices – the oxygen-containing polymer PVA (polyvinyl alcohol) and oxygen-free polymer PEI (polyethyleneimine) – differences of nanocomposites properties are predominantly caused by different interfacial conditions. ODMR spectra have revealed five types of centers related to the PL emission – four centers involved in radiative recombination and one center related to non-radiative recombination processes. The oxygen-related interfacial center in CdS/PVA (LK1-center) and sulfur vacancy center in CdS/PEI (Vs-center) were identified
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