Investigation of growth conditions, crystal structure and surface morphology of SmS films fabricated by MOCVD technique

The polycrystalline SmS films were fabricated by MOCVD technique using a number of ditiocarbamates, synthesized by different techniques. The growth kinetics and temperature dependencies of the film growth rate are investigated, which allowed us to determine the activation energies and the reaction type. The investigations of the structure and surface morphology of films were carried out. The technological conditions are determined providing the fabrication of single-phase SmS films of cubic modification with the most ordered crystal structure

Relativistic instant-form approach to the structure of two-body composite systems

A new approach to the electroweak properties of two-particle composite systems is developed. The approach is based on the use of the instant form of relativistic Hamiltonian dynamics. The main novel feature of this approach is the new method of construction of the matrix element of the electroweak current operator. The electroweak current matrix element satisfies the relativistic covariance conditions and in the case of the electromagnetic current also the conservation law automatically. The properties of the system as well as the approximations are formulated in terms of form factors. The approach makes it possible to formulate relativistic impulse approximation in such a way that the Lorentz-covariance of the current is ensured. In the electromagnetic case the current conservation law is ensured, too. The results of the calculations are unambiguous: they do not depend on the choice of the coordinate frame and on the choice of "good" components of the current as it takes place in the standard form of light--front dynamics. Our approach gives good results for the pion electromagnetic form factor in the whole range of momentum transfers available for experiments at present time, as well as for lepton decay constant of pion.Comment: 26 pages, Revtex, 5 figure

Reforming of bioethanol in the system with reverse vortex air/Сo₂ flow of “Tornado” type with liquid electrode

In this paper we studied the reforming of bioethanol using the combined system that includes a plasma processing and handling in the pyrolysis chamber. As the plasma source was used plasma-liquid system with back-vortex flow of gas (a mixture of air and CO₂) and liquid electrode. Carbon dioxide was added in reforming the system to influence the plasma-chemical processes in the conversion of hydrocarbons. As the working fluid was used ethanol solution in distilled water (ratio C₂H₅OH/H₂O = 1/9,5). The system was investigated by emission spectroscopy, current-voltage characteristics, gas chromatography.Изучено реформирование биоэтанола с использованием комбинированной системы, которая включает плазменную обработку и обработку в пиролитической камере. В качестве источника плазмы была использована плазменно-жидкостная система с обратновихревым потоком газа (смесь воздуха и СО₂) и жидким электродом. Углекислый газ добавлялся в систему при реформировании для того, чтобы влиять на плазмохимические процессы конверсии углеводородов. В качестве рабочей жидкости использовался раствор этилового спирта в дистиллированной воде (соотношение C₂H₅OH/H₂O = 1/9, 5).Система была исследована с помощью эмиссионной спектроскопии, вольт-амперных характеристик, газовой хроматографии.Вивчено реформування біоетанолу з використанням комбінованої системи, яка включає плазмову обробку і обробку в піролітичній камері. В якості джерела плазми було використано плазмово-рідинну систему зі зворотновихровим потоком газу (суміш повітря і СО₂) з рідким електродом. Вуглекислий газ додавався в систему під час реформування для того, щоб впливати на плазмохімічні процеси конверсії вуглеводнів. В якості робочої рідини використовувався розчин етилового спирту в дистильованій воді (співвідношення C₂H₅OH/H₂O = 1/9, 5). Система була досліджена за допомогою емісійної спектроскопії, вольт-амперних характеристик, газової хроматографії

Time of arrival through interacting environments: Tunneling processes

We discuss the propagation of wave packets through interacting environments. Such environments generally modify the dispersion relation or shape of the wave function. To study such effects in detail, we define the distribution function P_{X}(T), which describes the arrival time T of a packet at a detector located at point X. We calculate P_{X}(T) for wave packets traveling through a tunneling barrier and find that our results actually explain recent experiments. We compare our results with Nelson's stochastic interpretation of quantum mechanics and resolve a paradox previously apparent in Nelson's viewpoint about the tunneling time.Comment: Latex 19 pages, 11 eps figures, title modified, comments and references added, final versio

Open string wavefunctions in flux compactifications

We consider compactifications of type I supergravity on manifolds with SU(3) structure, in the presence of RR fluxes and magnetized D9-branes, and analyze the generalized Dirac and Laplace-Beltrami operators associated to the D9-brane worldvolume fields. These compactifications are T-dual to standard type IIB toroidal orientifolds with NSNS and RR 3-form fluxes and D3/D7 branes. By using techniques of representation theory and harmonic analysis, the spectrum of open string wavefunctions can be computed for Lie groups and their quotients, as we illustrate with explicit twisted tori examples. We find a correspondence between irreducible unitary representations of the Kaloper-Myers algebra and families of Kaluza-Klein excitations. We perform the computation of 2- and 3-point couplings for matter fields in the above flux compactifications, and compare our results with those of 4d effective supergravity.Comment: 89 pages, 4 figures. v3: more typos corrected, version published in JHE

Mild oxidative functionalization of cycloalkanes catalyzed by novel dicopper(II) cores

The search for new transition metal based catalytic systems that are active in the oxidative functionalization of such inert substrates as saturated hydrocarbons continues to be an important research direction in molecular catalysis. In the present study, two new copper(II) coordination compounds, namely a discrete dimer [Cu2(μ-H2tea)2(nfa)2]·2H2O (1) and a 1D coordination polymer [Cu2(μ-H2tea)2(μ-Htma)]n·4nH2O (2) were synthesized and applied as homogeneous catalysts for the mild oxidative functionalization of cycloalkanes (cyclopentane, cyclohexane, cycloheptane, and cyclooctane). Both products 1 and 2 were self-assembled in aqueous medium from copper(II) nitrate, triethanolamine (H3tea), sodium hydroxide, and 2-naphthoic (Hnfa) or trimesic (H3tma) acids, isolated as stable crystalline solids, and fully characterized by standard methods including single-crystal X-ray diffraction. Their structures feature a similar type of dicopper(II) triethanolaminate cores that are decorated by terminal or bridging aromatic carboxylate ligands. Two model catalytic reactions were investigated, namely the oxidation of cycloalkanes by H2O2 to produce cycloalkyl hydroperoxides as intermediate products and then a mixture of cyclic alcohols and ketones as final products, and the carboxylation of cycloalkanes with CO/S2O82−/H2O to form cycloalkanecarboxylic acids as main products. These model reactions undergo under very mild conditions (50−60 °C) and show good efficiency. Substrate scope, selectivity features, and the effects of reaction parameters were investigated and discussed in detail. This study widens the family of multicopper(II) cores capable of catalyzing the oxidative functionalization of saturated hydrocarbons under mild conditions. © 2021 Elsevier B.V