Thermodynamics of Electrolytes on Anisotropic Lattices

The phase behavior of ionic fluids on simple cubic and tetragonal (anisotropic) lattices has been studied by grand canonical Monte Carlo simulations. Systems with both the true lattice Coulombic potential and continuous-space $1/r$ electrostatic interactions have been investigated. At all degrees of anisotropy, only coexistence between a disordered low-density phase and an ordered high-density phase with the structure similar to ionic crystal was found, in contrast to recent theoretical predictions. Tricritical parameters were determined to be monotonously increasing functions of anisotropy parameters which is consistent with theoretical calculations based on the Debye-H\"uckel approach. At large anisotropies a two-dimensional-like behavior is observed, from which we estimated the dimensionless tricritical temperature and density for the two-dimensional square lattice electrolyte to be $T^*_{tri}=0.14$ and $\rho^*_{tri} = 0.70$.Comment: submitted to PR

Critical behavior of the fluctuation heat capacity near the glass transition of metallic glasses

The high-frequency shear modulus of five Zr-, Pd-, Cu-based conventional and two high-entropy bulk metallic glasses was measured in a wide temperature range up to the beginning of crystallization. Using these data and general thermodynamic relations, the "fluctuation" heat capacity $\Delta C_f$ determined by local structural fluctuations in the defect regions is introduced and calculated. It is found that $\Delta C_f$ temperature dependence for all metallic glasses has a large peak located slightly below or above the glass transition temperature but clearly lower than the crystallization onset temperature. The form of this peak resembles the characteristic $\lambda$-peak typical for order-disorder phase transitions. It is suggested that this $\Delta C_f$-peak reflects certain underlying critical phenomenon. The critical temperature $T_0$ (peak temperature) and corresponding critical index $\alpha$ are determined. Averaged over all seven metallic glasses under investigation in the initial and relaxed states, the critical index $\alpha=0.26$. The results obtained indicate that the fluctuations of thermal energy near the glass transition bear the marks of a continuous phase transition. However, the derived critical index is between those corresponding to a second-order phase transition ($\alpha\approx 0.1$) and a critical transition characterized by a tricritical point ($\alpha \approx 0.5$).Comment: 18 pages, 4 figure

Fermi-liquid theory of the surface impedance of a metal in a normal magnetic field

In this paper we present detailed theoretical analysis of the frequency and/or magnetic field dependence of the surface impedance of a metal at the anomalous skin effect. We calculate the surface impedance in the presence of a magnetic field directed along the normal to the metal surface. The effects of the Fermi-liquid interactions on the surface impedance are studied. It is shown that the cyclotron resonance in a normal magnetic field may be revealed {\it only and exclusively} in such metals whose Fermi surfaces include segments where its Gaussian curvature turns zero. The results could be applied to extract extra informations concerning local anomalies in the Fermi surface curvature in conventional and quasi-two-dimensional metals.Comment: 10 pages, 1 figure, text added and rearranged, computational details are moved into Appendice

The behavior of radioactive metals (Am, Eu, Sr) during the processing of radioactive graphite in salt melts

The behavior of Am, Eu, Sr radionuclides was investigated by thermodynamic modeling method at heating of radioactive graphite in NaCl - KCl - Na2CO3 - K2CO3 molten salt with additives of nickel oxide NiO. The integrated thermodynamic analysis was carried out by means of TERRA software in temperature range 373-3273 K to determine possible composition of condensed and gaseous phases. It was established that americium is in gaseous state in temperature range 2773-3273 K. Europium is in the forms of gaseous EuO and Eu in temperature range 2373-3273 K. Strontium is in the forms of gaseous SrCl2, SrCl, Sr, SrO in temperature range 2373-3273 K. © Published under licence by IOP Publishing Ltd

CALCULATION OF COMPRESSIBILITY IN MOLTEN MIXTURES OF POTASSIUM HALIDES BY MOLECULAR DYNAMICS SIMULATION

Calculation of the isothermal compressibility of molten potassium halides by the molecular dynamics method is carried out. It is shown that as the radii differences between the anions of the constituent binary mixture increase, the interparticle interactions in the system increase. This is manifested in a greater deviation from the additivity of the isothermal compressibility of the KCl-KI mixture as compared to the KBr-KI mixture

Investigation of transition frequencies of two acoustically coupled bubbles using a direct numerical simulation technique

The theoretical results regarding the ``transition frequencies'' of two acoustically interacting bubbles have been verified numerically. The theory provided by Ida [Phys. Lett. A 297 (2002) 210] predicted the existence of three transition frequencies per bubble, each of which has the phase difference of $\pi /2$ between a bubble's pulsation and the external sound field, while previous theories predicted only two natural frequencies which cause such phase shifts. Namely, two of the three transition frequencies correspond to the natural frequencies, while the remaining does not. In a subsequent paper [M. Ida, Phys. Rev. E 67 (2003) 056617], it was shown theoretically that transition frequencies other than the natural frequencies may cause the sign reversal of the secondary Bjerknes force acting between pulsating bubbles. In the present study, we employ a direct numerical simulation technique that uses the compressible Navier-Stokes equations with a surface-tension term as the governing equations to investigate the transition frequencies of two coupled bubbles by observing their pulsation amplitudes and directions of translational motion, both of which change as the driving frequency changes. The numerical results reproduce the recent theoretical predictions, validating the existence of the transition frequencies not corresponding to the natural frequency.Comment: 18 pages, 8 figures, in pres

Quantitative visualization assessment of the vascular wall in patients with surgical pathology of the aortic valve, aorta and brachiocephalic arteries

Objective: Identification of the quantitative characteristics of changes in the arterial wall according to ultrasound, CT and MRI; development of the roadmap for the use of radiology diagnostic methods.Material and methods: 548 studies of 483 patients with atherosclerosis were analyzed (15 ultrasound studies, 483 – CTA and 50 – MRI). In the comparison group (n = 17) in patients without atherosclerosis, an analysis of MRI data of the aortic wall was performed. According to CTA, signs of atherosclerotic degeneration were assessed. According to the MRI data, indicators of aortic distensibility, Young’s modulus of the aortic wall (MPa), systolic distension of the aorta (ml), aortic wall enhancement index during contrast enhancement were calculated.Results: During the performance of ultrasound in all cases (n = 15), the analysis of the elastic properties of the aortic wall is difficult due to the artifact from calcification. Adverse CT signs of the occurrence of intraoperative vascular complications: the presence of an intraluminal thrombus, an uneven internal aortic contour of more than half of the circumference with an aortic wall thickness of more than 5 mm. According to MRI data in patients with atherosclerosis, aortic distensibility was reduced to 14.42 ± 2.95%, Young’s modulus for the aortic wall was 0.77 ± 0.26 MPa, the index of contrast enhancement of the aortic wall was 1.73 ± 0.5, the volume of systolic aortic distension was 11.48 ± 1.84 ml. In patients with vascular events in the perioperative period, systolic aortic dilatation was 9.2 ml.Conclusion: The signs which are expedient to consider when making a decision on surgical treatment have been identified. Significant limitations were identified in the assessment of elasticity by ultrasound. The wider use of MRI in atherosclerotic lesions looks promising

Observation of Magnetic Monopoles in Spin Ice

Excitations from a strongly frustrated system, the kagome ice state of the spin ice Dy2Ti2O7 under magnetic fields along a [111] direction, have been studied. They are theoretically proposed to be regarded as magnetic monopoles. Neutron scattering measurements of spin correlations show that close to the critical point the monopoles are fluctuating between high- and low-density states, supporting that the magnetic Coulomb force acts between them. Specific heat measurements show that monopole-pair creation obeys an Arrhenius law, indicating that the density of monopoles can be controlled by temperature and magnetic field.Comment: 5 pages, 4 figures; International Conference on Neutron Scattering 2009 (May 7); J. Phys. Soc. Jpn. 78, No.10 (2009) (Received Aug 11, 2009; accepted Sept 8, 2009; published Oct 13, 2009

Объемный анализ компьютерно-томографической ангиографии при лечении расслоения грудной аорты на примере с семилетним периодом наблюдения

Purpose. To establish the methods for estimating the volume of the true and false aortic canals applying computed tomography angiography (CTA) to a clinical case with hybrid stent-graft thoracic aorta with distal stent-graftinduced new entry associated (d-SINE) in the long-term follow-up period in comparison with a widely used technique of measuring diameters of the aorta on different levels.Materials and methods. Sequential analysis of CTA in a 7-year follow-up was performed. Aorta was divided into 3 segments, in each segment total aortic volumes (AV), volume of the true canal (TC), and volume of functional lumen of the false canal (FLFC) were calculated. The following were mathematically calculated: volume of the false canal (FC) via difference in volume between AV and TC, volume of the thrombosed lumen of FC as the difference between FC and FLFC, the coefficient of FC thrombosis, the degree of stent-graft opening. Mathematical assessment of excess volume of the graft was performed.Results. Modelling of aortic cavity, evaluation of changes in the volumes of TC and FC during a long-term follow-up, analysis of the factors inducing the development of the d-SINE syndrome were performed. When comparing the volume of the graft and the volume of the implantation zone, an excess of 234% was found, while the opening of the graft was 80%. When using the reference method based on the diameter of the true lumen of the aorta, the excess was 22% during one-year follow-up period showing no changes subsequently.Conclusion. Potentially, the method of measuring volumes based on CTA results can be used to complement the generally accepted method based on measuring diameters, since it does not require additional financial resources and has the potential to estimate effectiveness of treatment and identify complications predictors in the postoperative period to determine indications for reoperation. Цель исследования: разработать методику расчета объема истинного и ложного каналов аорты по данным компьютерно-томографической ангиографии (КТА) на клиническом примере пациента после гибридного протезирования грудного отдела аорты и с развитием дистального стент-ассоциированного надрыва интимы (d-SINE) в отдаленном периоде наблюдения в сравнении с широко используемой методикой измерения диаметров аорты на разных уровнях.Материал и методы. Выполнен последовательный анализ данных КТА аорты 7-летнего периода наблюдения. Аорта разделялась на 3 сегмента, в каждом сегменте рассчитывались общий объемы аорты (ОА), объем истинного канала (ИК), объем функционирующего просвета ложного канала (ФЛК). Математически вычислялись: объем ложного канала путем разности значений объемов между ОА и ИК, объем тромбированного просвета ЛК (ТЛК) как разность ЛК и ФЛК, коэффициент тромбоза ЛК, степень раскрываемости протеза. Проведена математическая оценка превышения объема протеза.Результаты. На клиническом примере проведены моделирование полости аорты и оценка изменений объемов истинного и ложного каналов при длительном наблюдении. Проведен анализ факторов, способствующих развитию синдрома d-SINE. При сравнении объема протеза и объема зоны имплантации выявлено превышение в 234%, раскрытие протеза при этом составило 80% от должного. При использовании референтного метода, основанного на диаметре истинного просвета аорты, превышение было не столь значимым и составило 22% через год после операции и без изменений в последующий период.Заключение. Потенциально методика измерения объемов по данным КТА может применяться в качестве дополняющей к общепринятой методике, основанной на измерении диаметров, поскольку не требует дополнительных затрат от здравоохранения и имеет потенциал в плане оценки эффективности проведенного лечения и выявления предикторов осложнений в послеоперационном периоде для определения показаний к повторному оперативному вмешательству

Реакция ледников Полярного Урала на современные изменения климата

Monitoring of glacier mass balance is usually focused on analysis of middle and large glaciers, so small glaciers on the verge of extinction remain out of the attention of researchers. Studies of glaciers of the Polar Urals, begun in the mid-twentieth century, present in this respect interesting information. The series of observations of them is the longest among other glaciers of the mountainous regions of the Russian mainland in the polar latitudes. New results of quantitative assessment of changes in the size and mass balance of glaciers in this region are presented. To estimate the geodetic balance of the IGAN Glacier, data from photogeodetic surveys of 1963, data of ground-based DGPS surveys of 2008 and 2018 together with a fragment of the digital elevation model (DEM) of the ArcticDEM v3.0 of 2016 were used. Using these data, the DEM of its surface was calculated as of 1963, 2008, and 2018, and the changes in the glacier volume were estimated for the period from 1963 to 2018, during which the glacier had lost 19.7 million m3 of ice, of which 3.2 million m3 were lost in the last decade. The average decrease in the surface height was 18.94±3.22 m, and the maximum – 53.5±1.0 m. In 1963–2008, the specific massbalance was equal to −317±59 mm w.e./year, while in 2008–2018 −336±61 mm/year. Estimation of changes in the size of 30 glaciers of the Polar Urals made from images of the Sentinel-2 satellite had shown that in 2000– 2018 the glaciers lost 2.02 km2 (about 28%) of the area. In comparison with the period of 1953–2000, the average annual rate of reduction of their area doubled and amounted to 0.112 km2/year (1.54%/year). Magnitudes of the reduction of individual glaciers are not identical. Within the selection of 30 glaciers, they vary from 7.1% (the Terentyev Glacier) to 61.1% (the Oleniy Glacier). The analysis of changes in temperature and precipitation in 2000–2018 allows us making the conclusion that the reason for the accelerated reduction of glaciers in the Polar Urals in these years is the rise of summer air temperature since beginning of the twentieth century by 1.5 °C, to which the lowering of winter precipitation was added in the last decade.По данным фотогеодезических съёмок 1963 г., наземных DGPS‐съёмок 2008 и 2018 гг. и космических снимков оценены изменения геодезического баланса ледника ИГАН и размеров 30 ледников Полярного Урала с 1953 по 2018 г. По сравнению с 1953 г. площадь ледников продолжает сокращаться с возрастающей скоростью; с начала ХХI в. она увеличилась в 2 раза. С 1953 г. ледник ИГАН потерял 19,7 млн м3 льда, его высота в среднем понизилась на 19 м