Realization of the one-dimensional anisotropic XY model in a Tb(III)-W(V) chain compound

We report the magnetic behavior of the one-dimensional (1D) cyanido-bridged chain complex [Tb(pzam) 3(H 2O)M(CN) 8] •H 2O, where M = W(V). The system shows qualitatively similar magnetic behavior with its already reported M = Mo(V): a broad anomaly in the specific heat ascribed to the magnetic interactions, a transition to three-dimensional magnetic order at T C = 1.15 K, and comparable magnetization and susceptibility. However, substituting the Mo(V) ion by the larger W(V) causes a drastic change in the symmetry of the Tb(III) g tensor, whereby the magnetic interaction between the Tb(III) and M(V) changes from Ising type into an anisotropic XY exchange. We analyze the data in terms of theoretical predictions for the 1D XYZ Hamiltonian and we find an excellent agreement between the theory and experimental data (J x = 1.89 K, J y = 2J x, J z = 0). © 2012 American Physical Society.This research was supported by a Veni grant from the Netherlands Organization for Scientific Research (NWO) to S.T.. We acknowledge Spanish MINECO for Grants MAT2009-13977-C03 and CSD2007-00010.Peer Reviewe

Plasma-assisted Oxidation of Cu(100) and Cu(111)

Oxidized copper surfaces have attracted significant attention in recent years due to their unique catalytic properties, including their enhanced hydrocarbon selectivity during the electrochemical reduction of CO2. Although oxygen plasma has been used to create highly active copper oxide electrodes for CO2RR, how such treatment alters the copper surface is still poorly understood. Here, we study the oxidation of Cu(100) and Cu(111) surfaces by sequential exposure to a low-pressure oxygen plasma at room temperature. We used scanning tunnelling microscopy (STM), low energy electron microscopy (LEEM), X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure spectroscopy (NEXAFS) and low energy electron diffraction (LEED) for the comprehensive characterization of the resulting oxide films. O2-plasma exposure initially induces the growth of 3-dimensional oxide islands surrounded by an O-covered Cu surface. With ongoing plasma exposure, the islands coalesce and form a closed oxide film. Utilizing spectroscopy, we traced the evolution of metallic Cu, Cu2O and CuO species upon oxygen plasma exposure and found a dependence of the surface structure and chemical state on the substrate's orientation. On Cu(100) the oxide islands grow with a lower rate than on the (111) surface. Furthermore, while on Cu(100) only Cu2O is formed during the initial growth phase, both Cu2O and CuO species are simultaneously generated on Cu(111). Finally, prolonged oxygen plasma exposure results in a sandwiched film structure with CuO at the surface and Cu2O at the interface to the metallic support. A stable CuO(111) surface orientation is identified in both cases, aligned to the Cu(111) support, but with two coexisting rotational domains on Cu(100). These findings illustrate the possibility of tailoring the oxidation state, structure and morphology of metallic surfaces for a wide range of applications through oxygen plasma treatments

Mechanistic implications of the active species involved in the oxidation of hydrocarbons by iron complexes of pyrazine-2-carboxylic acid

The reactivity towards H2O2 of the complexes [Fe(pca)2(py)2]·py (1) and Na2{[Fe(pca3)]2O}·2H2O·CH3CN (2) (where pca− is pyrazine-2-carboxylate) and their catalytic activity in the oxidation of hydrocarbons is reported. Addition of H2O2 to 1 results in the formation of a dinuclear Fe(III)–(µ-O)–Fe(III) species characterized spectroscopically and by cyclic voltammetry. By contrast, treatment of 2 with H2O2 results in the formation of mononuclear iron(II) complexes, [Fe(pca)2(solvent)2]. The experimental results indicate that the catalytic activity of the starting complexes 1 and 2 is strongly dependent on the species formed in solution.

Plasma Functionalization of Silica Bilayer Polymorphs

Ultrathin silica films are considered suitable two-dimensional model systems for the study of fundamental chemical and physical properties of all-silica zeolites and their derivatives, as well as novel supports for the stabilization of single atoms. In the present work, we report the creation of a new model catalytic support based on the surface functionalization of different silica bilayer (BL) polymorphs with well-defined atomic structures. The functionalization is carried out by means of in situ H-plasma treatments at room temperature. Low energy electron diffraction and microscopy data indicate that the atomic structure of the films remains unchanged upon treatment. Comparing the experimental results (photoemission and infrared absorption spectra) with density functional theory simulations shows that H2 is added via the heterolytic dissociation of an interlayer Si–O–Si siloxane bond and the subsequent formation of a hydroxyl and a hydride group in the top and bottom layers of the silica film, respectively. Functionalization of the silica films constitutes the first step into the development of a new type of model system of single-atom catalysts where metal atoms with different affinities for the functional groups can be anchored in the SiO2 matrix in well-established positions. In this way, synergistic and confinement effects between the active centers can be studied in a controlled manner

Dynamics and geometric properties of the k-Trigonometric model

We analyze the dynamics and the geometric properties of the Potential Energy Surfaces (PES) of the k-Trigonometric Model (kTM), defined by a fully-connected k-body interaction. This model has no thermodynamic transition for k=1, a second order one for k=2, and a first order one for k>2. In this paper we i) show that the single particle dynamics can be traced back to an effective dynamical system (with only one degree of freedom); ii) compute the diffusion constant analytically; iii) determine analytically several properties of the self correlation functions apart from the relaxation times which we calculate numerically; iv) relate the collective correlation functions to the ones of the effective degree of freedom using an exact Dyson-like equation; v) using two analytical methods, calculate the saddles of the PES that are visited by the system evolving at fixed temperature. On the one hand we minimize |grad V|^2, as usually done in the numerical study of supercooled liquids and, on the other hand, we compute the saddles with minimum distance (in configuration space) from initial equilibrium configurations. We find the same result from the two calculations and we speculate that the coincidence might go beyond the specific model investigated here.Comment: 36 pages, 13 figure

Coupling of morphological instability and kinetic instability: Chemical waves in hydrogen oxidation on a bimetallic Ni/Rh(111) surface

The oxidation and reduction of a bimetallic Ni/Rh model catalyst during the water forming O2+H2 reaction is studied with low-energy electron microscopy, microspot-low-energy electron diffraction, and x-ray photoemission electron microscopy. Oxidation of a submonolayer Ni film results in the formation of three-dimensional (3D) NiO nanoparticles. Reduction of 3D-NiO in H2 produces a dispersed two-dimensional film of metallic Ni. Chemical waves during the O2+H2 reaction involve a cyclic transformation between 3D-NiO and 2D-NiO

Статистическая оценка сопутствующих патологических процессов при аденоме простаты

Department of morphopathology, Department of urology and surgical nephrology, Nicolae Tesmitsanu State University of Medicine and FarmacyThis study aims to assess the statistical figures of morphopathological aspects of prostatic adenoma using the methods of statistical processing and analyzing to determine the informative indices of variability and the trend of the development of the pathological processes concurrent to the Benign Prostate Hiperplasia (BPH). It has been found that in 30 patients aged 45-68 along with BPH the pathological processes with a predominance of the inflammatory, dystrophic and discirculatory ones, involving all the structural elements of the adenoma and its bordering zones, have been identified. The level of activity of the processes, including the inflammatory processes in the peripheral area has been found out. The inflammatory processes of moderate and emphasized activity (the IInd and IIId degrees) have made up a maximum frequency and accounted for 77% of the cases, being followed by circulatory disorders of the IInd and IIId degrees of activity, what has corresponded to 76% of cases. В данном исследовании отражена статистическая оценка морфопатологических аспектов, выявленных при аденоме простаты, использованы методы статистической обработки и анализа для выявления информативных параметров вариабельности, а также тенденции развития патологических процессов, которые сопутствуют доброкачественной гиперплазии простаты (ДГП). Установлено, что у 30 пациентов в возрасте 45-68 лет, одновременно с ДГП присутствуют патологические процессы, преимущественно воспалительные, дисциркуляторные и дистрофические, включающие все структурные элементы аденомы и ее пограничной зоны. Выявлена степень активности процессов, в том числе на периферии, что соответствовало зоне энуклеации аденомы. Воспалительные процессы умеренной и выраженной степени активности (II-III степень) соответствовали максимальной частоте и составили 77% случаев, за ними следовали дисциркуляторные нарушения II-III степени, которые составили 76%

Statistical-mechanical formulation of Lyapunov exponents

We show how the Lyapunov exponents of a dynamic system can in general be expressed in terms of the free energy of a (non-Hermitian) quantum many-body problem. This puts their study as a problem of statistical mechanics, whose intuitive concepts and techniques of approximation can hence be borrowed.Comment: 10 pages, 3 figures, RevTex

Терапевтические возможности лечения артериальной гипертензии у детей

Arterial hypertension is a major health problem in developed and developing countries, affecting approximately one billion people in the world and its evolution is affects primarily younger people, by that representing a major public health problem due to its major complications. In the treatment of arterial hypertension in children, it is very important the non-medical treatment, knowing the fact that among other risk factors, obesity plays a huge role and also life style changes, which are the first choice for treatment. The possibilities to treat arterial hypertension in children are limited, despite the large numbers of drugs for the adult population and continuous progress in this direction. This article is a summary of literature sources, referring to non-medical and pharmacological treatment, evaluate the most important classes of drugs accepted and used in the treatment of arterial hypertension in children, allowing us to focus on the recently introduced drugs to treat arterial hypertension in children and teenagers.Артериальная гипертензия является одной из основных проблем здравоохранения как в развитых, так и в развивающихся странах. Поражает, примерно, один миллиард людей во всём мире, имеет на сегодняшний день тенденцию к уменьшению возрастной категории и представляет собой серьезную проблему общественного здравоохранения в связи с её серьезными осложнениями и возрастающей заболеваемостью. Исходя из того, что ессенциальная артериальная гипертензия является результатом ожирения, а также множества факторов риска, в лечении артериальной гипертензии у детей особое значение уделяется немедикаментозным методам, которые преследуют изменение стиля жизни, как метод первого выбора. Несмотря на то, что существует огромное множество антигипертензивных препаратов и существенный прогресс в контроле артериальной гипертензии у взрослого населения, возможности назначения лечения для детей ограничены. Данная статья представляет собой литературный обзор немедикаментозного и медикаментозного лечения артериальной гипертензии, что позволяет оценить наиболее важные классы современных медицинских препаратов, разрешённых для лечения артериальной гипертензии у детей и подростков