Synthesis and characterization of MnCrO4, a new mixed-valence antiferromagnet

A new orthorhombic phase, MnCrO4, isostructural with MCrO 4 (M = Mg, Co, Ni, Cu, Cd) was prepared by evaporation of an aqueous solution, (NH4)2Cr2O7 + 2 Mn(NO 3)2, followed by calcination at 400 C. It is characterized by redox titration, Rietveld analysis of the X-ray diffraction pattern, Cr K edge and Mn K edge XANES, ESR, magnetic susceptibility, specific heat and resistivity measurements. In contrast to the high-pressure MnCrO4 phase where both cations are octahedral, the new phase contains Cr in a tetrahedral environment suggesting the charge balance Mn2+Cr 6+O4. However, the positions of both X-ray absorption K edges, the bond lengths and the ESR data suggest the occurrence of some mixed-valence character in which the mean oxidation state of Mn is higher than 2 and that of Cr is lower than 6. Both the magnetic susceptibility and the specific heat data indicate an onset of a three-dimensional antiferromagnetic order at TN ≈ 42 K, which was confirmed also by calculating the spin exchange interactions on the basis of first principles density functional calculations. Dynamic magnetic studies (ESR) corroborate this scenario and indicate appreciable short-range correlations at temperatures far above T N. MnCrO4 is a semiconductor with activation energy of 0.27 eV; it loses oxygen on heating above 400 C to form first Cr 2O3 plus Mn3O4 and then Mn 1.5Cr1.5O4 spinel. © 2013 American Chemical Society

Особенности микроэлементного статуса у детей с острой крапивницей

Background: The increase in the occurrence of allergic dermatoses, especially in young children, is one of the urgent problems of pediatrics. The development of allergic reactions may be caused by changes in microelements balance of the body. Objective: Our aim was to study the features of the microelement status in children with acute urticaria.Methods: A comparative study included patients with acute urticaria of varying severity and healthy children (I and IIA groups of health). Study of microelement was carried out in hair samples by X-ray analysis.Results: The study revealed lower content of zinc in hair in patients with urticaria (n = 40) (48 compared to 146 mcg/g in 23 children of control group, p < 0.001). It also revealed lower content of calcium (447 and 2428 mcg/g respectively; p = 0.001) as well as higher content of sulfur (33860 and 26447 mcg/g respectively; p = 0.001) and potassium (537 and 312 mcg/g respectively; p = 0.001). Differences in the iron, nickel, copper, and chlorine content in hair in comparable groups were not detected. There was no association of microelements content with a burdened hereditary allergologic anamnesis.Conclusion: Children with urticaria have dismicroelemntosis, characterized by a decrease in zinc and calcium content, and an increase in the concentration of sulfur and potassium.Увеличение частоты встречаемости аллергических дерматозов, особенно у детей раннего возраста, является одной из актуальных проблем педиатрии. Развитие аллергических реакций может быть следствием изменения баланса микроэлементов в организме.Цель исследования: изучить особенности микроэлементного статуса у детей с острой крапивницей.Методы: в сравнительное исследование включали больных с острой крапивницей различной степени тяжести и здоровых детей (I и IIA группы здоровья). Изучение микроэлементного статуса осуществляли в пробах волос методом рентгенофлуоресцентного анализа.Результаты: у пациентов с крапивницей (n = 40) установлено более низкое содержание в волосах цинка (48 в сравнении со 146 мкг/г у 23 детей контрольной группы; р < 0,001) и кальция (447 и 2428 мкг/г, соответственно; р = 0,001), а также более высокое содержание серы (33 860 и 26 447 мкг/г, соответственно; р = 0,001) и калия (537 и 312 мкг/г, соответственно; р = 0,001). Различий в сравниваемых группах по содержанию в волосах железа, никеля, меди и хлора не обнаружено. Исключена и связь содержания микроэлементов с отягощенным наследственным аллергологическим анамнезом.Заключение: у детей с крапивницей установлено наличие дисмикроэлементоза, характеризующегося снижением содержания цинка и кальция, повышением концентрации серы и калия

Investigation of the Morphological, Atomic and Electronic Structural Changes CuOx Nanoparticles and CNT in a Nanocomposite CuOx CNT SEM and X ray Spectroscopic Studies

Morphology, atomic and electronic structure of CuOx/CNT nanocomposite synthesized by electrochemical method were investigated using methods scanning electron microscopy (SEM), X-ray absorption spectroscopy (XANES and NEXAFS) and X-ray photoelectron spectroscopy (XPS). It has been shown that by the formation of a nanocomposite changes in morphology, oxidation state and phase composition of CuOx nanoparticles in comparison with the initial particles were observed. The initial oxidation of carbon nanotube (CNT) surface leads to reduction ability of the formation of chemical bonds between the nanoparticles and tubes.</jats:p

Electronic structure of hydrogenated carbon nanotubes studied bycore level spectroscopy

The high resolution near edge X ray absorption fine structure spectroscopy and X ray photoelectron spectroscopy were used to elucidate the nature of chemical bonding between carbon and hydrogen atoms on the surface and inside hydrogenated single walled carbon nanotubes H SWNTs . The measured spectra showed formation of chemical bonding between the hydrogen and carbon atoms in H SWNTs.In order to obtain a detailed understanding origin of the chemical bond between C and H atoms, density functional calculations and theoretical analysis of experimental NEXAFS spectra were carried ou

SiO2ZrO2 Thin Films as Low Temperature NO2 and O3 Sensors

Thin SiO2ZrO2films were prepared, up to 0.2 μm thick, by means of the sol–gel technology and characterized by a Scanning electron microscopy and X-ray diffraction. It is shown the presence of monoclinic, cubic and tetragonal phases of ZrO2in the SiO2matrix. The crystallites sizes depend on the annealing temperature of the film and amount to 35 and 56 nm for the films annealed at 773 and 973 K, respectively. The films resistance is rather sensitive to the presence of NO2and O3impurity in air at lower operating temperatures in the range of 30-60°C.</jats:p

Hydrogenated carbon nanotubes x ray absorption spectroscopy and ab initio simulation analysis

The paper presents the results of investigation of the chemical bond formation in hydrogenated single walled carbon nanotubes using X ray absorption spectroscopy. All measurements were performed with the use of synchrotron radiation at BESSY II. The C1s absorption spectra point to formation of covalent chemical bonding between the hydrogen and carbon atoms in H SWNTs. The investigation of the H SWNT local structure has been carried out on the basis of the semi empirical PM6 method MOPAC 2009 and Finite Difference method. The possibility of H SWNTs dehydrogenation was also investigate

CuOx Films for NO2 Detection Microstructurel Characterization

Copper oxides films as promising materials for gas sensors applications were studied. Copper oxide films were deposited onto Si SiO2 substrates using a citrate sol gel method with the subsequent temperature treatment at 150 500 amp; 8304;C. These films were characterized by means of secondary electron microscopy SEM and X ray absorption near edge structure XANES spectroscopy. The prepared films were utilized in NO2 sensors. The dependences of the NO2 response on the operating temperature and NO2 concentration 10 200 ppm were investigated. The maximum NO2 response was achieved for the film annealed at 250 amp; 8304;