Heat capacity of a thin membrane at very low temperature

We calculate the dependence of heat capacity of a free standing thin membrane on its thickness and temperature. A remarkable fact is that for a given temperature there exists a minimum in the dependence of the heat capacity on the thickness. The ratio of the heat capacity to its minimal value for a given temperature is a universal function of the ratio of the thickness to its value corresponding to the minimum. The minimal value of the heat capacitance for given temperature is proportional to the temperature squared. Our analysis can be used, in particular, for optimizing support membranes for microbolometers

Comparative analysis of the structure and internal stress in Ti-6Al-4V alloys manufactured by 3D printing and processing with screw extrusion

Study is based on the compare characterization of the structure and evaluation of the residual internal stresses in Ti-6Al-4V samples manufactured by the 3D printing (selective laser melting) and in the Ti-6Al-4V samples obtained with using of the severe plastic deformation by screw extrusion. The microstructure and residual stresses were examined by transmission electron microscope and X-ray diffractometer. High tensile internal residual stresses in the 3D printed sample were found. The high compressive residual internal stresses were found in the hot pressed and in the twisted samples. It was shown that arising of the high residual stresses in the studied samples under various technological processes occurred in various ways. The residual stresses in the severe plastic deformed samples arose due to non-uniform volumetric plastic deformation. In 3D printed sample, the residual tensile stresses arose from both phase (martensitic) transformation and thermal deformation. © Published under licence by IOP Publishing Ltd

Oxygen and nitrogen concentrations in the Ti-6Al-4V alloy manufactured by direct metal laser sintering (DMLS) process

Published ArticleTwo machines from two scientific centers (Russia and South Africa) were used for the manufacturing of the Ti6Al4V alloys by the direct metal laser sintering. The chemical composition of powders complies with the ASTM F-136 (grade 5), ASTM B348 (grade 23) standard for medical applications. Analysis of the oxygen and nitrogen contamination in DMLS alloys was done with Van de Graaff accelerator with two Mega Volts. It is found that structures of the samples manufactured with two different machines used the same regimes are close to each other. TEM studies found the metastable martensitic structure and silicon nitride Si3N4. It was found that the oxygen and nitrogen contents in both samples are within the normal range for medical grade titanium alloys

Microstructure and mechanical properties of Al-12Si produced by selective laser melting

Al-12Si specimens are produced by selective laser melting (SLM) from gas atomized powders. Installation for the production of powder is original. All specimens were prepared using the EOSINT M 280 device. A fine cellular structure is observed with residual free Si along the cellular boundaries. Room temperature tensile tests reveal remarkable mechanical behavior: the samples show yield and tensile strengths of about 102 MPa and 425 MPa, respectively, along with fracture strain of 12%. The study of crack surface morphology was shown by the example of a sample. Except the spherical pores, the interface of the molten pool also appears on the fracture surface, which indicates a mixture of fragile and ductile fracture. Additionally, the agglomerated silicon group appears also on the fracture surface. © Published under licence by IOP Publishing Ltd

Microstructure and mechanical properties of Al-12Si produced by selective laser melting

Al-12Si specimens are produced by selective laser melting (SLM) from gas atomized powders. Installation for the production of powder is original. All specimens were prepared using the EOSINT M 280 device. A fine cellular structure is observed with residual free Si along the cellular boundaries. Room temperature tensile tests reveal remarkable mechanical behavior: the samples show yield and tensile strengths of about 102 MPa and 425 MPa, respectively, along with fracture strain of 12%. The study of crack surface morphology was shown by the example of a sample. Except the spherical pores, the interface of the molten pool also appears on the fracture surface, which indicates a mixture of fragile and ductile fracture. Additionally, the agglomerated silicon group appears also on the fracture surface. © Published under licence by IOP Publishing Ltd

Functional activity of the oral endothelium in persons, with chronic periodontitis during treatment with plasmolifting

Chronic periodontitis as an osteoimmune disease of the oral cavity is accompanied by a change in the functional activity of endotheliocytes. Moreover, abnormal vascularization exacerbates periodontal inflammation, as it promotes the transmigration of a larger number of immunocompetent cells, the influx of inflammatory mediators and cytokines.The aim of our work was to study the functional activity of the endothelium of the vessels of the oral cavity in persons suffering from chronic periodontitis in the treatment of plasmolifting.Materials and methods. Under observation were 30 patients diagnosed with chronic generalized periodontitis of moderate severity at the age of 35 (32.50; 40.00) years, with no severe somatic pathology (main group). The comparison group included 20 people aged 38 (34.00; 45.00) years with no inflammatory diseases in the oral cavity. All patients underwent local anti-inflammatory therapy and sanitation of periodontal pockets, correction of occlusal contacts, curettage, plasma lifting. Oral fluid concentration of soluble adhesion molecules ICAM-1 and VCAM-1, endothelin-1, qualitative and quantitative composition of microflora were determined.Results. After the treatment with plasmolifting, a noticeable relief of the activity of the inflammatory process was observed. In patients with chronic periodontitis, Porphyromonas gingivalis was found in 100 % of cases in a titer of 5.73 (4.9; 6.7) lg (gEq/sample), in 62.5 % – Prevotella intermedia in a titer of 4.5 (3.0; 5.5) lg (gEq/sample). Against the background of therapy, decrease of the occurrence of the microorganism and of the number of microorganisms was observed. The concentration of the soluble form of VCAM-1 in the oral fluid of patients with chronic periodontitis exceeded the values of the control group by 38.3 times (p = 0.000001), and ICAM-1 – by 18.1 times (p = 0.00001). Against the background of plasmolifting therapy, the level of the studied substances decreased, but exceeded the control values by 25.2 and 6.4 times, respectively. The content of endothelin in the oral fluid in patients with periodontitis exceeded the values of healthy individuals by 40.7 % (p = 0.003), during therapy its values decreased, but did not reach the level of healthy volunteers (p = 0.04)

Goltsov phenomenon as a natural-technogenic electromagnetic discharge of the lithosphere

The article presents data on an unusual natural phenomenon that occurred on November 30, 1984 in the village of Goltsovka, Zmeinogorsky District, Altai Territory. It manifested itself in the passage above the village of a luminous ball, which was accompanied by an impact on the surface of the earth and led to some damage to structures and buildings. A detailed description of this unusual phenomenon in the published scientific literature, as far as we know, is practically absent. The article describes this phenomenon, based on data collected soon after the event, with the addition of upto-date clarifying information. A comparison is made with several known cases of ball lightning and a whirlwind. The conclusion is made about an unusually large energy release in the Goltsovka event

Морфометрические параметры разнокачественности семян моркови и факторы их определяющие.

Relevance.The contribution of varietal and environmental factors to the variability of the length of the endosperm and the embryo of carrot seeds was studied. Materials and methods. The objects of study were the original seeds of Rogneda, Lubava and Chernozemochka, Chantene 2461 and Boyarynya varieties. The seeds were grown at the Voronezh and West Siberian experimental stations. The linear dimensions of the seed and endosperm were measured using a caliper. The length of the embryo was measured using a microscope (Micromed) and a video eyepiece (DCM 300 MD) at х40 magnification. Statistical processing of the research data two-factor experiment was carried out using analysis of variance. Differences in the compared parameters were considered statistically significant at p 0.05.Results. The linear dimensions of all the main elements of seeds, as well as the index of Ie/z on average for three years significantly differed in the studied carrot varieties (P < 0.001). The maximum length of the seed (3.14±0.02 mm), the length of the endosperm (2.66±0.02 mm) and the length of the embryo (1.23±0.03 mm) on average for three years was observed in the Rogneda variety. The average coefficient of variation (V) of seed length was minimal and varied from 10.1% to 12.9%. The average values of the coefficient of variation (V) for the length of the endosperm varied in a wider range from 12.0% to 14.6%. The length of the embryo had a maximum level of variability from 18.7% in the Rogneda variety to 20.3% in the Chernozemochka variety 21.3%. The variety factor had a predominant influence (from 50.8 % to 86.5 %) on the size of the seed and its morphological elements. The contribution of the environmental conditions of the year of reproduction to the formation of morphometric parameters did not exceed 22.3 %. This allowed us to draw a conclusion about the prospects of selection and the possibility of selective changes in the morphological parameters of the seed. Актуальность. Изучен вклад сортового и экологического факторов в изменчивость длины эндосперма и зародыша семян моркови.  Материал и методы. Объектами для изучения служили оригинальные семена сортов Рогнеда, Любава и Черноземочка, Шантенэ 2461 и Боярыня. Семена выращены на Воронежской и Западно-Сибирской опытных станциях. Измерение линейных размеров семени и эндосперма осуществляли штангенциркулем. Длину зародыша измеряли с помощью микроскопа (Микромед) и видеоокуляра (DCM 300 MD) при x40 увеличении. Статистическую обработку данных исследований двухфакторного опыта проводили с помощью дисперсионного анализа. Различия сравниваемых параметров считали статистически значимыми при Р 0,05.Результаты. Линейные размеры всех основных элементов семян, а также индекс Iэ/з в среднем за три года существенно отличались у изученных сортов моркови (Р < 0,001). Максимальная длина семени (3,14±0,02 мм), длина эндосперма (2,66±0,02 мм) и длина зародыша (1,23±0,03 мм) в среднем за три года отмечена у сорта Рогнеда. Средние значения коэффициента вариации (V) длины семени были минимальными и изменялись от 10,1% до 12,9%. Средние значения коэффициента вариации (V) для длины эндосперма изменялись в более широких пределах от 12,0% до 14,6%. Длина зародыша имела максимальный уровень вариабельности от 18,7% у сорта Рогнеда до 20,3% у сорта Черноземочка 21,3%. Фактор сорта оказывал преобладающее влияние (от 50,8% до 86,5%) на размер семени и его морфологические элементы. Вклад фактора экологических условий года репродукции в формирование морфометрических параметров не превышал 22,3%. Это позволило сделать вывод о перспективности отбора и возможности селекционного изменения морфологических параметров семени, которые определяют технологические, посевные и другие их свойства.