Temperature dependence of self-trapped exciton luminescence in nanostructured hafnia powder

The intrinsic optical properties and peculiarities of the energy structure of hafnium dioxide largely determine the prospects for applying the latter in new generation devices of optoelectronics and nanoelectronics. In this work, we have studied the diffuse reflectance spectra at room temperature for a nominally pure nanostructured $HfO_2$ powder with a monoclinic crystal structure and, as well its photoluminescence in the temperature range of 40 - 300 K. We have also estimated the bandgap $E_g$ under the assumption made for indirect (5.31 eV) and direct (5.61 eV) allowed transitions. We have detected emission with a 4.2 eV maximum at T < 200 K and conducted an analysis of the experimental dependencies to evaluate the activation energies of thermal quenching (140 meV) and enhancement (3 meV) processes. Accounting for both the temperature behavior of the spectral characteristics and the estimation of the Huang-Rhys factor S >> 1 has shown that radiative decay of self-trapped excitons forms the mechanism of the indicated emission. In this case, the localization is mainly due to the interaction of holes with active vibrational modes of oxygen atoms in non-equivalent ($O_{3f}$ and $O_{4f}$) crystal positions. Thorough study of the discussed excitonic effects can advance development of hafnia-based structures with a controlled optical response.Comment: 21 pages, 7 figures, 2 tables, 56 references. Keywords: hafnium dioxide, self-trapped exciton, F-center, thermal quenching of luminescence, luminescence enhacement, Huang-Rhys factor, effective phonon energy, bandgap widt

Laboratory workshop on instrumental specialties of physic-technological institute of UrFU. Part 2

The article discusses new laboratory works, included into the laboratory practical work on subjects related to microprocessor technique and the sensors, currently used on the instrumental specialties of physico-technological instituteВ статье обсуждается новые лабораторные работы, включенные в лабораторный практикум по дисциплинам, связанным с микропроцессорной техникой и первичными датчиками, использующимися в настоящее время на приборостроительных специальностях физико-технологического институт

On The Universality Class Of Little String Theories

We propose that Little String Theories in six dimensions are quasilocal quantum field theories. Such field theories obey a modification of Wightman axioms which allows Wightman functions (i.e. vacuum expectation values of products of fundamental fields) to grow exponentially in momentum space. Wightman functions of quasilocal fields in x-space violate microlocality at short distances. With additional assumptions about the ultraviolet behavior of quasilocal fields, one can define approximately local observables associated to big enough compact regions. The minimum size of such a region can be interpreted as the minimum distance which observables can probe. We argue that for Little String Theories this distance is of order {\sqrt N}/M_s.Comment: 25 pages, late

Luminescence in anion-deficient hafnia nanotubes

Hafnia-based nanostructures and other high-k dielectrics are promising wide-gap materials for developing new opto- and nanoelectronics devices. They possess a unique combination of physical and chemical properties such as insensitivity to electrical and optical degradation, radiation damage stability, a high specific surface area, and an increased concentration of the appropriate active electron-hole centers. The present paper aims to investigate the structural, optical, and luminescent properties of anodized non-stoichiometric $HfO_2$ nanotubes. As-grown amorphous hafnia nanotubes and nanotubes annealed at 700{\deg}C with a monoclinic crystal lattice served as samples. It has been shown that the bandgap $E_g$ for direct allowed transitions amounts to $5.65\pm0.05$ eV for amorphous and $5.51\pm0.05$ eV for monoclinic nanotubes. For the first time, we have studied the features of the intrinsic cathodoluminescence and photoluminescence of the obtained nanotubular $HfO_2$ structures with an atomic deficiency in the anion sublattice at temperatures of 10 and 300 K. A broad emission band with a maximum of 2.3-2.4 eV has been revealed. We have also conducted an analysis of the kinetic dependencies of the observed photoluminescence for synthesized $HfO_2$ samples in the millisecond range at room temperature. It showed that there are several types of optically active capture and emission centers based on vacancy states in the $O_{3f}$ and $O_{4f}$ positions with different coordination numbers and a varied number of localized charge carriers ($V^0$, $V^-$, and $V^{2-}$). The uncovered regularities can be used to optimize the functional characteristics of developed-surface luminescent media based on nanotubular and nanoporous modifications of hafnia.Comment: 15 pages, 6 figures, 3 tables, 50 reference

MODERN TREATMENT MINIMALLY INVASIVE TECHNOLOGIES RENOVASCULAR HYPERTENSION

The purpose of the research was the study of the effectiveness of balloon angioplasty and stenting of renal arteries to improve the microcirculation of the kidneys in patients with renovascular hypertension. During the period from 2010 to 2012 inclusive in the vascular compartment BSMU clinic were examined and treated 32 patients with renal artery stenosis. Inclusion criteria were: presence of verified violations of regional circulation in the kidney, the presence of symptomatic renovascular hypertension. Measures the average systolic and diastolic blood pressure mast. Patients received antihypertensive treatment to endovascular treatment. Treatment with antihypertensive medication was effective only in 9.8 % of cases. Diagnostic angiography of the renal arteries was performed using angiographic complex INNOVA 3131 IQ. After analyzing the data, the question of stenting or balloon angioplasty. After a detailed survey of 32 patients underwent endovascular intervention for renal artery 6 balloon angioplasty and stenting 26. Following the procedure, the hypotensive effect was observed in all cases. Evaluation of the results showed a significant reduction in the maximum rise in systolic blood pressure by 28 %, diastolic - 21 %. After endovascular intervention, the mean systolic blood pressure decreased by 10%, the average diastolic blood pressure - 15 %. Mean arterial pressure decreased by 8 %. In a review of the effectiveness of endovascular procedures with the original length and the degree of hypertension. Thus, roentgenendovascular treatment improves microcirculation in the renal tissue, which leads to the hypotensive effect of a predominantly marked reduction of maximum systolic blood pressure

PROGRAMMABLE-GAIN AMPLIFIER FOR SENSOR APPLICATIONS

Programmable-gain amplifier for measuring sensor signals is designed. This amplifier contains various buffering cascades and filters, making this amplifier compatible with different kinds of sensors

Clinical Experience of Luminescent Diagnostics of Precancerous Diseases and Cervical Cancer

The article summarizes the experience of using luminescent diagnostics with the use of ytterbium porphyrin complexes in gynecology and oncology. A pharmaceutical composition based on the Yb complex of 2,4-dimethoxyhematoporphyrin IX was used as the luminescent markers within the infrared range. The determination of luminescence characteristics (luminescence intensity) was carried out using a laserfiber fluorimeter in the range of 900-1100 nm. A new method for diagnosis of cervical disease has been proposed. The method of luminescent diagnostics allows to conduct a survey of a large number of patients in a short time. The method of luminescent diagnostics using the ytterbium complexes of porphyrins is not invasive. The method can be used as a screening. Differences between normal and pathologically altered cervical tissue have been identified and differences between pathological changes in the cervix HSIL (CIN II, CIN III) and cervical cancer are reliable. Keywords: Cervical cancer, squamous cell carcinoma, diagnosis of cervical cancer, squamous intraepithelial lesions of high grade – HSIL, luminescent diagnostics, luminescing in the near infrared (NIR) spectral region, porphyrins, ytterbium complexes of porphyrins

Level of Stress in Students with the Disturbance of Nasal Breathing and Comorbid Disorders

Background. The progressive increase of the number of schoolchildren with adaptation disorders and low level of health in recent years determines the need to assess the characteristics of the psychosomatic status in children and adolescents with various types of somatic pathology, including diseases of ENT organs, accompanied by nasal breathing disorders and hypoxia. It is also necessary to determine the severity of stress in children, for timely prevention and correction of these disorders.Aim: to assess the level of stress in schoolchildren with nasal breathing disorders against the background of nasal diseases and concomitant psychosomatic disorders.Materials and methods. 481 schoolchildren aged 12–17 (boys and girls) were examined. Nasal breathing disorders were assessed by a comprehensive ENT examination, including rhinoscopy, radiography of the sinuses, and olfactometry. The presence and severity of stress were determined by the questionnaire “Social factors and stress”.Results. We found that the high level of stress in children with nasal breathing disorders on the background of ENT pathology is more often associated with the high frequency and severity of psychosomatic symptoms: the presence of dorsalgia, asthenic syndrome, chronic headache and frequent episodes of abdominal pain. Moderately and significantly increased levels of stress associated with the presence of children with hypertension, asthenic syndrome, frequent abdominal pain, frequent pain in the cervical spine, panic disorders.Conclusions. Thus, the presence of certain psychosomatic complaints in children with nasal breathing disorders is directly related to the level of stress, which is important to take into account when planning preventive and corrective measures aimed at increasing the adaptive capacity and stress resistance of children. The studies illustrate the need to assess the psychosomatic status and the level of stress in schoolchildren with nasal breathing disorders taking into account their existing comorbid disorders of the psychosomatic spectrum

Nonlinear electrochemical relaxation around conductors

We analyze the simplest problem of electrochemical relaxation in more than one dimension - the response of an uncharged, ideally polarizable metallic sphere (or cylinder) in a symmetric, binary electrolyte to a uniform electric field. In order to go beyond the circuit approximation for thin double layers, our analysis is based on the Poisson-Nernst-Planck (PNP) equations of dilute solution theory. Unlike most previous studies, however, we focus on the nonlinear regime, where the applied voltage across the conductor is larger than the thermal voltage. In such strong electric fields, the classical model predicts that the double layer adsorbs enough ions to produce bulk concentration gradients and surface conduction. Our analysis begins with a general derivation of surface conservation laws in the thin double-layer limit, which provide effective boundary conditions on the quasi-neutral bulk. We solve the resulting nonlinear partial differential equations numerically for strong fields and also perform a time-dependent asymptotic analysis for weaker fields, where bulk diffusion and surface conduction arise as first-order corrections. We also derive various dimensionless parameters comparing surface to bulk transport processes, which generalize the Bikerman-Dukhin number. Our results have basic relevance for double-layer charging dynamics and nonlinear electrokinetics in the ubiquitous PNP approximation.Comment: 25 pages, 17 figures, 4 table