Influence of interface structure on electronic properties and Schottky barriers in Fe/GaAs magnetic junctions

The electronic and magnetic properties of Fe/GaAs(001) magnetic junctions are investigated using first-principles density-functional calculations. Abrupt and intermixed interfaces are considered, and the dependence of charge transfer, magnetization profiles, Schottky barrier heights, and spin polarization of densities of states on interface structure is studied. With As-termination, an abrupt interface with Fe is favored, while Ga-terminated GaAs favors the formation of an intermixed layer with Fe. The Schottky barrier heights are particularly sensitive to the abruptness of the interface. A significant density of states in the semiconducting gap arises from metal interface states. These spin-dependent interface states lead to a significant minority spin polarization of the density of states at the Fermi level that persists well into the semiconductor, providing a channel for the tunneling of minority spins through the Schottky barrier. These interface-induced gap states and their dependence on atomic structure at the interface are discussed in connection with potential spin-injection applications.Comment: 9 pages, 9 figures, to appear in PR

Innovations of the Beginning of the Sixth Millennium BC in the Northern Pontic Steppe

This study focuses on the pottery-bearing ("Neolithic") sites of the northern Azov Sea region. The vessels ornamented with comb imprints appeared there in the sixth millennium BC. In the light of a recent re-dating of the Rakushechny Yar site sequence, the sites of the northern Azov region appeared to be the earliest evidence for this innovation. The innovation in the ceramic assemblage is accompanied by an innovative lithic tool set. The latter included macro-blades and fan-shaped end-scrapers, which were previously unknown in the studied region. Their reanalysis (including new field work at the single-layer site of Chapaevka) helped formulate a hypothesis of maritime transmission of comb-ornamented ceramics in the Black and Azov Sea. This hypothesis will stimulate further discussions regarding the ways of Neolithization in Eastern Europe. It underlines the connections between Balkan "classic"Neolithic and pottery-bearing sites of the Ukrainian Steppe. The impressed ware from Makri and other mainland Greek sites is treated as the closest analogy to the finds of the northern Azov Sea region

Optical transitions and nature of Stokes shift in spherical CdS quantum dots

We study the structure of the energy spectra along with the character of the states participating in optical transitions in colloidal CdS quantum dots (QDs) using the {\sl ab initio} accuracy charge patching method combined with the %pseudopotential based folded spectrum calculations of electronic structure of thousand-atom nanostructures. In particular, attention is paid to the nature of the large resonant Stokes shift observed in CdS quantum dots. We find that the top of the valence band state is bright, in contrast with the results of numerous {\bf k$\cdot$p} calculations, and determine the limits of applicability of the {\bf k$\cdot$p} approach. The calculated electron-hole exchange splitting suggests the spin-forbidden valence state may explain the nature of the ``dark exciton'' in CdS quantum dots.Comment: 5 pages, 4 figure

Verifying the chronology of Ukrainian Neolithic

This paper addresses the earliest Neolithic phases in Ukraine: aspects relating to the chronology, methods and time of Neolithisation. In general, the earliest Neolithisation relates to the times of the Linear Pottery culture. Nevertheless, Ukraine has numerous eco-zones so the process could have been different in other zones. The authors emphasize that the key to getting closer to solving this problem is the chronology-re-dating and validation program. Hitherto dates of one culture or period of culture have been treated against each other. This article presents a small series of AMS from well-defined contexts of four sites, previously dated by the Kyiv radiocarbon facility. The results are compared with existing dates in order to establish the validity of existing chronologies for the Neolithic of Ukraine. Obtained results allowed the authors to conclude that the Kyiv dates should not be obligatorily treated as wrong. Furthermore, the authors reopened the discussion to establish what was the role of LBK and Azov-Dnieper culture communities in spreading farming and herding in Ukraine during the second half of the VIth millennium BC

Impurity complexes and conductivity of Ga-doped ZnO

Using hybrid functional theory together with experimental measurements, we investigate the influence of gallium impurities and their complexes on electrical properties of ZnO. In contrast to the behavior of isolated Ga impurities and native defects, the calculated formation energies of Ga complexes are consistent with our experimental data. We show that for high levels of Ga doping the acceptor behavior of GaZn-VZn and GaZn-Oi complexes explains the conductivity measurements and compensation levels in ZnO. The computed binding energies of these complexes are also consistent with the binding energies obtained from the measurements of the temperature dependence of carrier mobility. Our results show that the formation of defect complexes, often overlooked by theory, can be indispensable in capturing the defect physics

Exergic balance and efficiency of reverse osmosis modules

In this paper the option of using exergy analysis method is proposed for preparing make-up water by reverse osmosis systems (ROS), which are spreading in the reconstruction of the chemical departments of Ukrainian nuclear power plants. The estimation of exergy efficiency of water purification by membrane units is made and the nature of influence of the ROS main parameters on thermodynamic efficiency is identified. The conclusion on the possible ways of facilities improvement is drawn

Анальгезивна та протизапальна дії похідних 5,7-діацил- 3-H(алкіл)-6-арил-5Н-[1,2,4]тріазоло[3,4-b][1,3,4]тіадіазину

The search for new analgesic and anti-inflammatory drugs, exceeding by efficacy and/or safety the existinganalogues is very important and relevant. The nitrogenous heterocycles are promising in this respect, in particular,the compounds containing an imidazole triazol and tіadiazin moiety. The aim of the current study was to investigatethe antiexudative and antinociceptive activity of new derivatives of 5,7-diacyl-3-H(alkyl)-6-aryl-5H[1,2,4]triazol[3,4-b][1,3,4]thiadiazine.The antinociceptive and antiexudative activity studies were carried out on the white nonlinear mice. Theexperimental evaluation of specific activity was carried out on the models “Hot plate”, acetic acid induced writhing(antinociceptive action) and carrageenan edema (antiexudative action). The substance was used in a single oral routadministration in a dose of 25 mg/kg. Ketorolac was used as a reference product in the dose of 25 mg/kg (models“Hot plate”, acetic acid induced writhing). Diclofenac was used as a reference product in the dose of 25 mg/kg onthe model carrageenan edema. The experimental study showed the antinociceptive and antiexudative effects of thederivatives. The antinociceptive activity of 5,7-diacyl-3-H(alkіl)-6-aryl-5H[1,2,4]triazol[3,4-b][1,3,4]tіadiazin derivatiesrelated to the modification structure in the para position of benzene ring. The antiexudative activity is associated withacetyl groups thiadiazine ring. The most promising compound IFT_247 showed a significant antinociceptive effect,which is comparable to an active comparator ketorolac: “Hot plate” +232.46 % and +112.71 %; acetic acid inducedwrithing -66.67 % and -61.02 %, respectively.Поиск новых анальгезирующих и противовоспалительных препаратов, превосходящих по эффектив-ности и/или безопасности существующие аналоги, важен и актуален. В этом отношении перспективныазотистые гетероциклы, в частности соединения, содержащие в себе триазоловый и тиадиазиновыйфрагменты.Была поставлена цель исследовать антиноцицептивную и антиэксудативную активность новыхпроизводных 5,7-диацил-3-H(алкил)-6-арил-5Н-[1,2,4]триазоло[3,4-b][1,3,4]тиадиазина.Исследование проведено на белых нелинейных мышах обоего пола. Оценено антиноцицептивную иантиэксудативную активность пяти производных 5,7-диацил-3-H(алкил)-6-арил-5Н-[1,2,4]триазоло[3,4-b][1,3,4]тиадиазина на моделях “горячей пластины, уксуснокислых “корчей” (антиноцицептивный эффект)и каррагенинового отека (антиэкссудативное действие) при однократном внутрижелудочном введении вдозе 25 мг/кг. В качестве препаратов сравнения использовали кеторолак в дозе 25 мг/кг (“горячая пласти-на”, уксуснокислые “корчи”) и диклофенак натрия в дозе 25 мг/кг (каррагениновый отек). Исследованныесоединения показали наличие достоверного антиноцицептивного и антиэкссудативного эффектов.Антиноцицептивная активность ряда связана с модификацией структуры 5,7-диацил-3-H(алкил)-6-арил-5Н-[1,2,4]триазоло[3,4-b][1,3,4]тиадиазина в параположении бензольного кольца. Антиэкссудативнаяактивность – с ацетиловыми группами тиадиазинового кольца. Наиболее перспективным являетсясоединение IFT_247, проявляющее значительный анальгезирующий эффект в эксперименте и не усту-пающее по активности препарату сравнения – кеторолаку: “горячая пластина” – +232,46 и +112,71 %;уксуснокислые “корчи” – -66,67 и -61,02 % соответственно.Пошук нових анальгезивних і протизапальних препаратів, що переважають за ефективністю та/абобезпекою існуючі аналоги, є важливим і актуальним. У цьому відношенні перспективні азотисті гетеро-цикли, зокрема сполуки, що містять у собі тріазоловий і тіадіазиновий фрагменти.Було поставлено мету дослідити антиноцицептивну та антиексудативну активність нових похідних5,7-діацил-3-H(алкіл)-6-арил-5Н-[1,2,4]тріазоло[3,4-b][1,3,4]тіадіазину.Дослідження проведено на білих нелінійних мишах обох статей. Оцінено антиноцицептивну йантиексудативну активність п’яти похідних 5,7-діацил-3-H(алкіл)-6-арил-5Н-[1,2,4]тріазоло[3,4-b][1,3,4]тіадіазину на моделях “гарячої пластини”, оцтовокислих “корчів” (антиноцицептивний ефект) ікарагенінового набряку (антиексудативна дія) при одноразовому внутрішньошлунковому введенні в дозі25 мг/кг. Як препарати порівняння використовували кеторолак у дозі 25 мг/кг (“гаряча пластина”, оцтовокислі“корчі”) і диклофенак натрію в дозі 25 мг/кг (карагеніновий набряк). Досліджені сполуки показали наявністьдостовірного антиноцицептивного й антиексудативного ефектів. Антиноцицептивна активністьряду пов’язана з модифікацією структури 5,7-діацил-3-H(алкіл)-6-арил-5Н-[1,2,4]тріазоло[3,4-b][1,3,4]тіадіазину в параположенні бензольного кільця. Антиексудативна активність – з ацетиловими групамитіадіазинового кільця. Найбільш перспективною є сполука IFT_247, що проявляє значний анальгезивнийефект в експерименті й не поступається за активністю препарату порівняння – кеторолаку: “гарячапластина” – +232,46 і +112,71 %; оцтовокислі “корчі” – -66,67 і -61,02 % відповідно