VARIATIONS IN SOLAR ACTIVITY AND CHANGES IN THE LEVEL OF KHAKASSIA SALT LAKES IN THE LAST MILLENNIUM

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Phonon Localization in One-Dimensional Quasiperiodic Chains

Quasiperiodic long range order is intermediate between spatial periodicity and disorder, and the excitations in 1D quasiperiodic systems are believed to be transitional between extended and localized. These ideas are tested with a numerical analysis of two incommensurate 1D elastic chains: Frenkel-Kontorova (FK) and Lennard-Jones (LJ). The ground state configurations and the eigenfrequencies and eigenfunctions for harmonic excitations are determined. Aubry's "transition by breaking the analyticity" is observed in the ground state of each model, but the behavior of the excitations is qualitatively different. Phonon localization is observed for some modes in the LJ chain on both sides of the transition. The localization phenomenon apparently is decoupled from the distribution of eigenfrequencies since the spectrum changes from continuous to Cantor-set-like when the interaction parameters are varied to cross the analyticity--breaking transition. The eigenfunctions of the FK chain satisfy the "quasi-Bloch" theorem below the transition, but not above it, while only a subset of the eigenfunctions of the LJ chain satisfy the theorem.Comment: This is a revised version to appear in Physical Review B; includes additional and necessary clarifications and comments. 7 pages; requires revtex.sty v3.0, epsf.sty; includes 6 EPS figures. Postscript version also available at http://lifshitz.physics.wisc.edu/www/koltenbah/koltenbah_homepage.htm

Random Tilings: Concepts and Examples

We introduce a concept for random tilings which, comprising the conventional one, is also applicable to tiling ensembles without height representation. In particular, we focus on the random tiling entropy as a function of the tile densities. In this context, and under rather mild assumptions, we prove a generalization of the first random tiling hypothesis which connects the maximum of the entropy with the symmetry of the ensemble. Explicit examples are obtained through the re-interpretation of several exactly solvable models. This also leads to a counterexample to the analogue of the second random tiling hypothesis about the form of the entropy function near its maximum.Comment: 32 pages, 42 eps-figures, Latex2e updated version, minor grammatical change

Dual-gated bilayer graphene hot electron bolometer

Detection of infrared light is central to diverse applications in security, medicine, astronomy, materials science, and biology. Often different materials and detection mechanisms are employed to optimize performance in different spectral ranges. Graphene is a unique material with strong, nearly frequency-independent light-matter interaction from far infrared to ultraviolet, with potential for broadband photonics applications. Moreover, graphene's small electron-phonon coupling suggests that hot-electron effects may be exploited at relatively high temperatures for fast and highly sensitive detectors in which light energy heats only the small-specific-heat electronic system. Here we demonstrate such a hot-electron bolometer using bilayer graphene that is dual-gated to create a tunable bandgap and electron-temperature-dependent conductivity. The measured large electron-phonon heat resistance is in good agreement with theoretical estimates in magnitude and temperature dependence, and enables our graphene bolometer operating at a temperature of 5 K to have a low noise equivalent power (33 fW/Hz1/2). We employ a pump-probe technique to directly measure the intrinsic speed of our device, >1 GHz at 10 K.Comment: 5 figure

The study of the dynamics of clinical and laboratory-instrumental parameters in hypertensive patients with obesity who underwent COVID-19-associated pneumonia

BACKGROUND: According  to the results of the ESSE-RF study, the frequency of obesity in the population  reached 29.7%. Obesity is one of the main risk factors for the development of cardiovascular diseases. Features of the course of COVID-19 in patients with obesity is a very urgent problem.AIM: The aim of the study was a comparative investigation of clinical and laboratory-instrumental parameters in AH patients with or without obesity who had COVID-19 associated pneumonia, to identify the role of obesity as a potential predictor of post-COVID cardiovascular complications 3 months after discharge from the hospital.MATERIALS AND METHODS: Materials and methods. The study included 174 patients with COVID-19-associated pneumonia. Group 1 included 78 patients with AH without obesity, group 2 — 96 patients with AH and obesity. All patients were tested with a blood sample at the time of admission and 3 months after discharge from the hospital. We assessed parameters of general blood test, biochemistry, hemostasis, inflammation biomarkers — concentration of C-reactive protein (CRP), highly sensitive CRP (hs-CRP), homocysteine, IL-6, etc. All patients initially underwent computed tomography  of the chest. In both groups, 24-hour blood pressure monitoring was performed using BPLaB device, according to the standard protocol; echocardiography using  an expert class ultrasound diagnostic  system Vivid S70. The study is registered with the Clinical Trials.gov database Identifier: NCT04501822.RESULTS: Results. The biomarker that significantly distinguished the both groups of patients, as well as subgroups according to the degree of obesity was the concentration of maxCRP and hs-CRP, which was significantly higher in group 2. In addition, the registered maximum values of MPO, NT-proBNP, IL-1,6, TNA-α and NRL parameters in group 2 of patients with 2–3 degrees of obesity, may indicate the highest probability of developing  delayed adverse cardiovascular complications  in this group of patients. Mean systolic blood pressure, variability of systolic and diastolic blood pressure, and heart rate at night were significantly  higher in AH patients with obesity. Numerous correlations of obesity with laboratory and instrumental parameters have been registered, which may indicate an increased likelihood of delayed unwanted cardiovascular complications in this particular group of patients. Multiple regression showed that obesity is an independent predictor of an increase in LDH, hs-CRP and right atrium.CONCLUSION: Dynamic control of the studied parameters in patients with AH and OB registered an increased concentration of CRP at the initial stage and 3 months after treatment, with a general trend towards a decrease in the increased initial structural parameters of ECHO CG. The logistic regression method showed that the presence of OB in patients with AH is an independent factor causing increased levels of immune inflammation (CRP), a marker of tissue destruction (LDH), and load on the right atrium

Secondary crystalline phases identification in Cu2ZnSnSe4 thin films: contributions from Raman scattering and photoluminescence

In this work, we present the Raman peak positions of the quaternary pure selenide compound Cu2ZnSnSe4 (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, Cu2SnSe3, ZnSe, SnSe, SnSe2, MoSe2 and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials’ model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.info:eu-repo/semantics/publishedVersio

Бурение осадков оз. Каракель (долина р. Теберда) и перспективы реконструкции истории оледенения и климата голоцена на Кавказе

Lacustrine sediments represent an important data source for glacial and palaeoclimatic reconstructions. Having a number of certain advantages, they can be successfully used as a means of specification of glacier situation and age of moraine deposits, as well as a basis for detailed climatic models of the Holocene. The article focuses on the coring of sediments of Lake Kakakel (Western Caucasus) that has its goal to clarify the Holocene climatic history for the region, providing the sampling methods, lithologic description of the sediment core, obtained radiocarbon dating and the element composition of the sediments. The primary outlook over the results of coring of the sediments of the Lake Karakyol helped to reconsider the conventional opinion on the glacial fluctuations in the valley of Teberda and to assume the future possibility for high-definition palaeoclimatic reconstruction for Western Caucasus.Озёрные отложения – важный источник данных для реконструкции колебаний ледников и изменений климата. Рассмотрены первые результаты бурения осадков оз. Каракель (долина р. Теберда, Западный Кавказ), выполненного для реконструкции голоценовой истории оледенения и климата в регионе. Описаны методика отбора образцов и особенности стратиграфии керна донных отложений оз. Каракель, приведены три радиоуглеродные датировки, позволившие оценить скорости осадконакопления в верхней части толщи (поздний голоцен). Датировка нижнего слоя озёрных отложений – 11 700 л.н. (календарный возраст) – одновременно представляет собой оценку минимального возраста морены, подпруживающей оз. Каракель

VARIATIONS IN SOLAR ACTIVITY AND CHANGES IN THE LEVEL OF KHAKASSIA SALT LAKES IN THE LAST MILLENNIUM

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