KINETICS OF OXIDATION OF THE ALLOY VT18U

Исследования проведены на экспериментальном сплаве типа ВТ18У с применением методов электронной микроскопии и термогравиметрии. Цель – изучить кинетику окисления сплава при различных температурах в течение 24 часов.Work was carried out on an experimental alloy type VT18U using the methods of electron microscopy and thermogravimetry. The purpose of this work is to study the kinetics of oxidation of the alloy at different temperatures for 24 hours

Why Are Alkali Halide Solid Surfaces Not Wetted By Their Own Melt?

Alkali halide (100) crystal surfaces are anomalous, being very poorly wetted by their own melt at the triple point. We present extensive simulations for NaCl, followed by calculations of the solid-vapor, solid-liquid, and liquid-vapor free energies showing that solid NaCl(100) is a nonmelting surface, and that its full behavior can quantitatively be accounted for within a simple Born-Meyer-Huggins-Fumi-Tosi model potential. The incomplete wetting is traced to the conspiracy of three factors: surface anharmonicities stabilizing the solid surface; a large density jump causing bad liquid-solid adhesion; incipient NaCl molecular correlations destabilizing the liquid surface. The latter is pursued in detail, and it is shown that surface short-range charge order acts to raise the surface tension because incipient NaCl molecular formation anomalously reduces the surface entropy of liquid NaCl much below that of solid NaCl(100).Comment: 4 pages, 3 figure

Cardiovascular pathology in diff erent forms of primary hyperparathyroidism

Objective: To study the frequency and features of the clinical course of cardiovascular pathology in patients with diff erent clinical forms of primary hyperparathyroidism (PHPT). Materials and Methods: A retrospective analysis of case histories of 48 patients who received inpatient treatment for PHPT in the endocrinological or surgical departments of two large hospitals in Arkhangelsk from 2005 to 2015 was performed.Results: Among the revealed cases of PHPT, the symptomatic form of PHPT was the most common (88%). Th e analysis showed a high frequency of arterial hypertension (AH) (69%) with a more severe course in patients with a mixed form of PHPT. Th e level of parathyroid hormone (PTH) was higher in patients with AH compared with patients without hypertension and PHPT (p = 0.008). Left ventricular hypertrophy was detected in 60% of patients with a mixed form of PHPT. In a mild form, this complication was not observed. Th e relationship between the level of total blood calcium and PTH and the interventricular septum thickness was revealed by the results of echocardiography (p = 0.036 and p = 0.012). Th e inverse relationship between the duration of the QT interval and the level of ionized blood calcium was shown (p = 0.022).Conclusions: Changes in phosphorus-calcium metabolism provoked by PHPT aff ect the state of the cardiovascular system, which determines the need for increased attention of various specialists to this type of complications in PHPT, timely indication of treatment, and improvement of the quality of patient’s life

The influence of modification by superdispersed powders on the lead-tin-base bronze structure

The paper presents data on the influence of additives of the pre-treated aluminium oxide powder on the structure of cast lead-tin-based bronzes. Different quantities of the modifier, based on the superdispersed aluminum oxide powder, were added to the bronze melt. The studies have shown that addition of a small amount of aluminum oxide powder (0.07... 0.25 %) allows modifying the micro structure of the obtained castings. This modification includes grain refinement, reduction of the matrix dendrites size of tin solid solution in copper, as well as formation of spherical inclusions of the low-melting phase - lead. In this case, the addition of such modifier influences weakly the morphology and the quantity of solid eutectoid inclusions based on electron compound Cu[31] Sn[8]

Comparative analysis of clinical manifestations of primary hyperparathyroidisis by results of hospitalizations and screening for hypercalcia in the Arkhangelsk region

Objective: to compare the forms and clinical course of primary hypeparathyroidism in hospitalized patients over a ten-year period, with patients identified by a routine analysis of blood calcium in Arkhangelsk region.Material and methods: At the first stage, a retrospective analysis of 48 case histories of patients who received inpatient treatment for PHPT in two multidisciplinary hospitals in Arkhangelsk from 2005 to 2015 was carried out. At the second stage, a screening of blood calcium was performed in patients of large outpatient clinic in Arkhangelsk from March 1 to March 31, 2015, as a result of which 21 cases of the first established PHPT were detected. A comparative analysis of the clinical course was carried out in two groups of patients with PHPT compared with the control group.Results: patients with PHPT detected during screening showed a higher incidence of mild forms of the disease (38 %), a higher level of bone mineral density in all parts of the skeleton according to dual-energy X-ray absorptiometry, and a lower incidence of nephrolithiasis (24 % vs. 69 %) compared with hospitalized patients, among which the manifest forms of the disease prevailed (88 %), fibrocystic osteitis was detected in 44 % of cases, and coral nephrolithiasis - in 10% of cases.Conclusion: a routine study of blood calcium levels helps to identify primary hyperparathyroidism at earlier stages to prevent the development of severe complications and invalidisation of patients

Cr2O3/Al-Al2O3 composite catalysts for hydrocarbons dehydrogenation prepared from aluminum nanopowder

Aluminum nanopowder (10–150 nm) was treated hydrothermally in mild conditions (60–95 °C, at atmospheric pressure), and an aluminum-alumina composite with high porosity and specific surface area was obtained. Cr2O3/Al-Al2O3 catalysts were prepared using the aluminum-alumina composite by impregnation techniques and tested in dehydrogenation of C4-hydrocarbons. It was shown that aluminum-alumina composites had high chemical and phase purity, specific surface area of 150–350 m2/g and the average pore size of 8–13 nm, that is favorable for application as support for catalysts. Cr2O3/Al-Al2O3 catalysts had high activity and selectivity in dehydrogenation of n- and i-butane (conversion of 44–80 mol.% and selectivity >85% at temperatures of 540–610 °C), that is comparable ones for commercial catalysts for CATOFIN, STAR processes

Influence of ultrafine particles on structure, mechanical properties, and strengthening of ductile cast iron

Integrated assessment of the influence of an ultrafine mixture TiO2 + ZrO2 + Na3AlF6 on the formation of the structure, mechanical properties, and strengthening of ductile cast iron was made in the paper. The structural-phase composition of ductile cast iron was studied by means of scanning electron microscopy and a transmission electron microscope. Plastic deformation was determined during testing of uniaxial compression. The change in the structural state of the alloy and in its mechanical properties was observed. Quantitative assessment of contributions of separate physical mechanisms to strengthening characteristics of unmodified and modified ductile cast iron was made

Tuberous sclerosis syndrome: a typical case of a rare disease

The article is devoted to a rare hereditary disease from the group of phak omatoses with an autosomal dominant type of inheritance — Pringle — Burnevill disease. The questions of the prevalence of the disease, the variability of the clinical picture, the timeliness of the clinical diagnosis are considered. Particular attention is paid to skin manifestations and their differential diagnosis. A clinical case of this disease is described