排序方式: 共有59条查询结果,搜索用时 15 毫秒
31.
Alfred Pollak Branko Stanovnik Prof. Dr. Miha Tišler Janja Venetič-Fortuna 《Monatshefte für Chemie / Chemical Monthly》1975,106(2):473-481
Reactions between some halogenated heterocycles and heterocyclic N-oxides with compounds containing reactive methylene groups are described and the structures of the products were studied. 相似文献
32.
Brina Dojer Amalija Golobi? Zvonko Jagli?i? Matja? Kristl Miha Drofenik 《Monatshefte für Chemie / Chemical Monthly》2012,19(5):175-180
Abstract
A new coordination compound of zinc fluoride and hydroxylammonium, (NH3OH)2ZnF4, was obtained after dissolving zinc powder in hydrofluoric acid (40%) and adding solid hydroxylammonium fluoride. The colourless crystals were characterised chemically, magnetically, structurally by single-crystal X-ray diffraction analysis, and thermogravimetrically by TGA and DSC analysis. The structure consists of NH3OH+ cations and ZnF6 octahedra in which the metal ion lies on the inversion centre. Each of the ZnF6 octahedra shares four of its vertices in a way that each vertex is shared between two octahedra. Oxygen and nitrogen atoms of hydroxylammonium cations are donors of hydrogen bonds. Hydroxylamonium fluorozincate crystallizes monoclinic, P21/c, with cell parameters a = 8.1604(4) ?, b = 5.8406(3) ?, c = 5.6586(2) ? and β = 94.745(3)°. The compound decomposes above 373 K in four steps, obtaining ZnO as the final residue. Magnetic properties of the compound were studied between 2 and 300 K, giving the prevailing diamagnetic behaviour with room temperature susceptibility of −9 × 10−5 emu mol−1. 相似文献33.
Matja? Kristl Brina Dojer Amalija Golobi? Miha Drofenik 《Journal of fluorine chemistry》2010,131(9):907-914
The first layered hydroxylammonium fluorometalates, (NH3OH)2CuF4 and (NH3OH)2CoF4, were prepared by the reaction of solid NH3OHF and the aqueous solution of copper or cobalt in HF. Both compounds crystallize in monoclinic, P21/c, unit cell with parameters: a = 7.9617(2) Å, b = 5.9527(2) Å, c = 5.8060(2) Å, β = 95.226(2)° for (NH3OH)2CuF4 and a = 8.1764(3) Å, b = 5.8571(2) Å, c = 5.6662(2) Å, β = 94.675(3)° for (NH3OH)2CoF4, respectively. Magnetic susceptibility was measured between 2 K and 300 K giving the effective Bohr magneton number of 2.1 for Cu and 5.2 BM for Co. At low temperatures both complexes undergo a transition to magnetically ordered phase. The thermal decomposition of both compounds was studied by TG, DSC and X-ray powder diffraction. The thermal decomposition of (NH3OH)2CuF4 is a complex process, yielding NH4CuF3 as an intermediate product and impure Cu2O as the final residue, while (NH3OH)2CoF4 decomposes in two steps, obtaining CoF2 after the first step and CoO as the final product. 相似文献
34.
In this paper, we consider various problems concerning quasi-matchings and semi-matchings in bipartite graphs, which generalize the classical problem of determining a perfect matching in bipartite graphs. We prove a generalization of Hall’s marriage theorem, and present an algorithm that solves the problem of determining a lexicographically minimum -quasi-matching (that is a set of edges in a bipartite graph such that in one set of the bipartition every vertex has at least incident edges from , where is a so-called need mapping, while on the other side of the bipartition the distribution of degrees with respect to is lexicographically minimum). We obtain that finding a lexicographically minimum quasi-matching is equivalent to minimizing any strictly convex function on the degrees of the A-side of a quasi-matching and use this fact to prove a more general statement: the optima of any component-based strictly convex cost function on any subset of -sphere in are precisely the lexicographically minimal elements of this subset. We also present an application in designing optimal CDMA-based wireless sensor networks. 相似文献
35.
Jagli?i? Z Zentková M Mihalik M Arnold Z Drofenik M Kristl M Dojer B Kasuni? M Golobi? A Jagodi? M 《J Phys Condens Matter》2012,24(5):056002
The magnetic properties of layered hydroxylammonium fluorocobaltate (NH(3)OH)(2)CoF(4) were investigated by measuring its dc magnetic susceptibility in zero-field-cooled (ZFC) and field-cooled (FC) regimes, its frequency dependent ac susceptibility, its isothermal magnetization curves after ZFC and FC regimes, and its heat capacity. Effects of pressure and magnetic field on magnetic phase transitions were studied by susceptibility and heat capacity measurements, respectively. The system undergoes a magnetic phase transition from a paramagnetic state to a canted antiferromagnetic state exhibiting a weak ferromagnetic behavior at T(C) = 46.5 K and an antiferromagnetic transition at T(N) = 2.9 K. The most spectacular manifestation of the complex magnetic behavior in this system is a shift of the isothermal magnetization hysteresis loop in a temperature range below 20 K after the FC regime-an exchange bias phenomenon. We investigated the exchange bias as a function of the magnetic field during cooling and as a function of temperature. The observed exchange bias was attributed to the large exchange anisotropy which exists due to the quasi-2D structure of the layered (NH(3)OH)(2)CoF(4) material. 相似文献
36.
Dritan Topi Janja Babi
Katarina Pavi
-Vrta
Gabrijela Tav
ar-Kalcher Breda Jakovac-Strajn 《Molecules (Basel, Switzerland)》2021,26(1)
In this study, ten Fusarium toxins were analysed in wheat and maize commodities from Albania. In total, 71 samples of wheat and 45 samples of maize were collected from different producing regions. The analytical procedure consisted of a simple one-step sample extraction followed by the determination of toxins using liquid chromatography coupled with tandem mass spectrometry. Fusarium toxins were found in 23% of the analysed wheat samples and in 78% of maize samples. In maize samples, most often fumonisins B1 (FB1) and B2 (FB2) were found. They were present in 76% of samples. They were detected in all positive samples except in one with concentrations ranging from 59.9 to 16,970 μg/kg. The sum of FB1 and FB2 exceeded the EU maximum permitted level (4000 μg/kg) in 31% of maize samples. In wheat samples, the only detected Fusarium mycotoxin was deoxynivalenol (DON), present in 23% of samples. In one sample with the concentration of 1916 μg/kg, the EU maximum permitted level (1250 μg/kg) was exceeded. This is the first report on the presence of Fusarium toxins in wheat and maize grains cultivated in Albania. 相似文献
37.
In gene therapy and DNA vaccination, RNA removal from DNA preparations is vital and is typically achieved by the addition of ribonuclease into the sample. Removal of ribonuclease from DNA samples requires an additional purification step. An alternative is the implementation of immobilized ribonuclease. In our work, ribonuclease was covalently coupled onto the surface of methacrylate monoliths via epoxy or imidazole carbamate groups. Various immobilization conditions were tested by changing immobilization pH. Ribonuclease immobilized on the monolith via imidazole carbamate groups at pH 9 was found to be six times more active than the ribonuclease immobilized on the monolith via epoxy groups. Under optimal immobilization conditions the Michaelis-Menten constant, Km, for cytidine-2,3-cyclic monophosphate, and turnover number, k3 were 0.52 mM and 4.6s(-1), respectively, and mirrored properties of free enzyme. Enzyme reactor was found to efficiently eliminate RNA contaminants from DNA samples. It was active for several weeks of operation and processed 300 column volumes of sample. Required residence time to eliminate RNA was estimated to be around 0.5 min enabling flow rates above 1 column volume per min. 相似文献
38.
Reverse micelles present self-assembled multi-molecular entities formed within specific compositional ranges of water-in-oil microemulsions. The structure of a reverse micelle is typically represented as nano-sized droplet of a polar liquid phase, capped by a monolayer of surfactant molecules, and uniformly distributed within a non-polar, oil phase. Although their role in serving as primitive membranes for encapsulation of primordial self-replicating chemical cycles that anticipated the very origins of life has been proposed, their first application for 'parent(hesis)ing' chemical reactions with an aim to produce 'templated' 2D arrays of nanoparticles dates back to only 25 years ago. Reverse micelles have since then been depicted as passive nano-reactors that via their shapes template the growing crystalline nuclei into narrowly dispersed or even perfectly uniform nano-sized particles. Despite this, numerous examples can be supported, where from deviations from the simple unilateral correlations between size and shape distribution of reverse micelles and the particles formed within may be reasonably implied. A rather richer, dynamical role of reverse micelles, with potential significance in the research and design of complex, self-assembly synthesis pathways, as well as possible adoption of their application as an aspect of biomimetic approach, is suggested herein. 相似文献
39.
Krzysztof Kozak Jadwiga Mazur Janja Vaupotič Dominik Grządziel Ivan Kobal Khaled M.H. Omran 《Isotopes in environmental and health studies》2013,49(2):274-282
Natural radioactivity is one of the essential components of the environment. Unlike the Sudety mountains area in Poland, the Tatra Mountains were not the subject of wide survey as regards the levels of natural radioactivity. Especially, the concentrations of radon (natural radioactive gas) have not been investigated there in terms of their possible negative health impact. Within the frame of bilateral cooperation between the Institute of Nuclear Physics in Kraków, Poland, and the Jo?ef Stefan Institute in Ljubljana, Slovenia, the measurements of natural radioactive elements in old uranium mines in the Tatra National Park were performed in June 2010. The investigated sites were located in Dolina Bia?ego (The Valley of the White). One of the mines is situated near the tourist path. The paper presents the results of complex measurements of natural radioactivity in both uranium drifts. The concentration of radon gas inside the mining drifts exceeded 28,000 Bq m?3. Also, very high gamma dose rates were observed (up to 5600 nSv h?1). The maximum concentrations of natural radioactive elements (potassium 40K, radium 226Ra, thorium 232Th) in rock samples amounted to 535, 2137, and 18 Bq kg?1, respectively. The effective dose rates due to radon and thoron inhalation have been assessed as 0.013 mSv h?1 (for the lowest concentration) and 0.121 mSv h?1 (for the highest concentration). 相似文献
40.
Brina Dojer Amalija Golobič Zvonko Jagličić Matjaž Kristl Miha Drofenik 《Monatshefte für Chemie / Chemical Monthly》2012,18(1):73-78