Influence of spin polarization on resistivity of a two-dimensional electron gas in Si MOSFET at metallic densities

Positive magnetoresistance (PMR) of a silicon MOSFET in parallel magnetic fields B has been measured at high electron densities n >> n_c where n_c is the critical density of the metal-insulator transition (MIT). It turns out that the normalized PMR curves, R(B)/R(0), merge together when the field is scaled according to B/B_c(n) where B_c is the field in which electrons become fully spin polarized. The values of B_c have been calculated from the simple equality between the Zeeman splitting energy and the Fermi energy taking into account the experimentally measured dependence of the spin susceptibility on the electron density. This extends the range of validity of the scaling all the way to a deeply metallic regime far away from MIT. The subsequent analysis of PMR for low n >~ n_c demonstrated that the merging of the initial parts of curves can bee achieved only with taking into account the temperature dependence of B_c. It is also shown that the shape of the PMR curves at strong magnetic fields is affected by a crossover from a purely two-dimensional (2D) electron transport to a regime where out-of-plane carrier motion becomes important (quasi-three-dimensional regime).Comment: 5 pages, including 6 figures; misprints corrected; Europhys. Lett. (in press

Electron transport in a slot-gate Si MOSFET

The transversal and longitudinal resistance in the quantum Hall effect regime was measured in a Si MOSFET sample in which a slot-gate allows one to vary the electron density and filling factor in different parts of the sample. In case of unequal gate voltages, the longitudinal resistances on the opposite sides of the sample differ from each other because the originated Hall voltage difference is added to the longitudinal voltage only on one side depending on the gradient of the gate voltages and the direction of the external magnetic field. After subtracting the Hall voltage difference, the increase in longitudinal resistance is observed when electrons on the opposite sides of the slot occupy Landau levels with different spin orientations.Comment: To appear in Europhys. Let

Fixed nitrogen in agriculture and its role in agrocenoses

Received: February 23rd, 2021 ; Accepted: May 12th, 2021 ; Published: May 19th, 2021 ; Correspondence: [email protected] typical low-humus black soils in short crop rotations with legumes (25–33%) and without them, it was found that depending on the set of crops in crop rotation and application of fertilizer rates, nitrogen yield per crop is from 355 kg ha-1 to 682 kg ha-1 . The recommended fertilization system provided nitrogen compensation for crop yields by only 31–76%. Hence, in the plant-fertilizer system nitrogen deficiency varies from 161 to 370 kg ha-1 . The greatest nitrogen deficiency in the soil is observed in crop rotation without the use of fertilizers with the following crop rotation: peas-winter wheat-grain maize-spring barley. The main source of nitrogen for plants is soil nitrogen. In crop rotations with legumes, biological nitrogen is supplied from the air, which in quantitative terms per rotation in crop rotations with peas is 109–288 kg ha-1 , with soybeans 264–312, and with alfalfa 486 kg ha-1 . Biological nitrogen in crop rotations with peas and soybeans is reimbursed from 25 to 62%, in crop rotation without legumes - 9% (non-symbiotic nitrogen fixation), and in crop rotation with alfalfa - 89% of the total nitrogen removal with the crop

Post-trocar hernias after laparoscopic cholecystectomy

Catedra chirurgie generală, Universitatea din Transnistria, Tiraspol, Republica Moldova, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Aplicarea în practică a colecistectomiilor laparoscopice (CEL) nu a exclus riscul de apariție a herniilor ventrale postoperatorii. Herniile se dezvoltă în locurile de plasare a trocarelor și poartă denumirea de „hernii post-trocar” – HPT. Acestea alcătuiesc circa 0,3-1,1% din numărul total al herniilor ventrale postoperatorii și demonstrează o tendință spre creștere. Conform datelor literaturii, HPT în 0,9% cazuri se formează lângă ombilic și în 0,1% cazuri au o altă localizare. Material și metode: Analiza este bazată pe experiența tratamentului a 19 pacienți cu HPT după CEL pe parcursul a 10 ani (2002-2013). În această perioadă în Clinică au fost efectuate 1112 CEL. Rata formării herniilor a constituit 1,7%. Vîrsta medie a bolnavilor – 54 ani. Intervalul de la momentul apariției herniei – de la 1 la 3 ani. La 16 (1,4%) bolnavi au avut loc supurații de plagă postoperatorie paraombilicală. Diastaza mușchilor recți de gradul 1-2 a fost diagnosticată la 14 (1,2%) bolnavi. În 18 (1,6%) cazuri hernia s-a localizat paraombilical și într-un caz pe peretele abdominal lateral. HPT se caracterizează printr-o discordanță între dimensiunile porților și a sacului herniar. Rezultate: La 2 pacienți a fost depistată prezența a 2 defecte a liniei albe abdominale. Absența în 10 (0,8%) cazuri a ligaturilor aponeurotice în regiunea herniei indică lipsa suturării defectului liniei albe după prima operație. În 3 (0,2%) cazuri cu dimensiunile defectului herniar <2 cm a fost efectuată autoplastia aponeurotică după Sapejco. În celelalte cazuri (defectul herniar >3 cm și prezența diastazei mușchilor recți) s-a efectuat hernioplastia cu lambou autodermal. Cazuri de complicații și recidive postoperatorii nu au fost înregistrate. Concluzii: Profilaxia HPT după CEL necesită suturarea prudentă a defectului aponeurotic în locul plasării trocarelor cu diametrul peste 1 cm. La pacienții de vârstă avansată și la bătrîni regiunea paraombilicală reprezintă o zonă de risc pentru dezvoltarea HPT.Introduction: The implementation of laparoscopic cholecystectomies (LCE) did not exclude the formation of post-operative hernia. Hernia appears in the place of trocar ports („post-trocar hernia” – PTH). PTH represents 0.3-1.1% of total number of post-operative hernias and tends to increase. According to the literature in 0.9% cases hernias are formed around the umbilicus, and in 0.1% – in other areas. Material and methods: The analysis is based on the experience of surgical treatment of 19 patients with PTH after LCE within 10 years (2002-2013). During this period were performed 1112 LCE. The rate of hernia was 1.7%. The mean age of the patients was 54 years. The interval from the hernia development was 1-3 years. After surgery 16 patients had infection of paraumbilical wound. The diastasis of rectus abdominis muscles grade 1-2 was diagnosed in 14 (1.2%) patients. Hernia was formed in 18 (1.6%) patients in paraumbilical region and in 1 case on the lateral abdominal wall. The peculiar feature of PTH is the mismatch of hernia ring size with size of the hernia sac. Results: In 2 patients was noted presence of 2 defects of the white line of the abdomen. The absence of aponeurotic sutures in the area of hernias in 10 (0.8%) patients indicated that white line defect after first operation was not sutured. In 3 (0.2%) cases of hernia 3 cm and the diastasis of the rectus abdominis muscles repair was performed by hernioplasty with autodermal implant. There were no complications or recurrences after surgery. Conclusions: Prevention of PTH after LCE requires careful suturing of aponeurotic defect in the site of trocar placement with diameter greater than 1 cm. In patients with advanced age and elderly the paraumbilical area represents the risk site for development of PTH

Methane Pyrolysis over Carbon Catalysts

Methane pyrolysis at the temperature range of 550-1000 °C in gas flow reactor with fixed bed of mixed  catalysts based on carbon materials of various structure (fullerene cocoons, fullerene black, vacuum black, cathode deposit, onion-like carbon, glassy carbon, carbon fibers, mineral shungite and graphite) has been studied. Methane pyrolysis products, including stoichiometric amount of hydrogen are C3-C4 alkanes, C2-C4 alkenes, aromatics and pyrolytic carbon. Methane pyrolysis is carried out both on a catalytic surface and in a volume and contribution of the surface is determined by pyrolysis temperature. Materials with curved carbon surface show an activity in methane dehydrogenation at lower temperatures, than materials with planar basic structure elements. Materials with a small specific surface area favor methane aromatization at 950–1000 °C with formation of mainly benzene, toluene and naphthalene. The primary activation of C–H bond in methane at temperatures of lower than 850 °C, as well as the multiple dehydrogenation conversions resulting in the formation of pyrolytic carbon and its precursors (aromatics), are, probably, heterogeneous reactions

Deratization Activities in the Jewish Autonomous Region in the Post-Flooding Period

Represented is a quantitative characteristic of the objects and facilities in the Jewish Autonomous Region exposed to the flooding-2013. Justified is the necessity for implementation of preventive measures against increase in the activity of HFRS natural foci; showed are the data on disinfestation organization for the prevention of natural-focal infection during the high water and post-flooding period in 2013. Displayed are the results of deratization efficacy control in various administrative units of the entity, calculated using Abbot formula, as well as results of investigation of small rodent population density at the natural stations and substantiation of the barrier disinfestation carrying out. Specified are the areas of the continuous and barrier disinfestation, indicators of Hanta Virus contamination of the rodents caught while performing control over efficacy of deratization works

Potential of using cultivated dermal fibroblasts on the biodegradable polymeric matrices for treating skin damages in the experiment

ФИБРОБЛАСТЫЭКСПЕРИМЕНТЫ НА ЖИВОТНЫХБИОМЕДИЦИНСКИЕ ИССЛЕДОВАНИЯБИОДЕГРАДАЦИЯСОЕДИНИТЕЛЬНОЙ ТКАНИ КЛЕТКИКРЫСЫ ЛИНИИ WISTARКОЖА /ПОВРЕЖДДЕКСТРАНА ФОСФАТПОЛИЛАКТИДРАНЫ ЗАЖИВЛЕНИЕКЛЕТОК ТРАНСПЛАНТАЦИЯКЛЕТОЧНАЯ ТЕРАПИЯЦель. Оценить возможность применения культивированных дермальных фибробластов на полимер- ных биодеградируемых матрицах для лечения повреждений кожного покрова в эксперименте. Материал и методы. Исследование выполнено на 90 крысах линии Wistar массой тела 180-200 г, с чистыми ранами диаметром 2,5 см. Было сформировано 6 групп – по животных в каждой. Культуру дер- мальных фибробластов выделяли из кожи новорожденных крыс; для накопления необходимой биомассы клеток проводили субпассирование. В 1 группе (контроль) клеточные биопрепараты не применялись. В группах 2-6 для лечения экспериментальных ран были использованы биодеградируемые матрицы (фосфат декстрана либо полилактид) как без клеточного биопрепарата, так и с содержанием культивированных фибробластов в количестве от 250?103 до 700?103 клеток на один раневой дефект. Выводы о влиянии дермаль- ных фибробластов на полимерных биодеградируемых матрицах на раневой процесс делали на основании сравнительного анализа результатов компьютерной планиметрии и морфологического исследования. Результаты. На всех этапах (7, 14, 21, 28 сутки) эксперимента минимальная скорость заживления была зарегистрированы в группе 1. Шестая группа, в которой в рану вносили полилактид, содержащий 700?103 клеток, характеризовалась максимальными – относительно остальных групп – значениями скоро- сти заживления. В микропрепаратах 6 группы на 21 сутки эксперимента отмечена полная эпителизация ра- невого дефекта. Выявлено наличие сильной прямой корреляционной связи между количеством трансплан- тированных клеток и скоростью заживления раневых дефектов на 7 сутки (?=0,923), 14 сутки (?=0,924), а также 21 сутки эксперимента (?=0,914). Заключение. В условиях эксперимента установлено, что локальное применение культивированных дермальных фибробластов на полимерных биодеградируемых матрицах (фосфат декстрана и полилактид) ведет к достоверному сокращению сроков эпителизации раневых дефектов.Objectives. To evaluate the possibility of using of cultivated dermal fibroblasts on the biodegradable polymeric matrices for treating skin damages in the experiment. Methods. The study was performed on 90 rats of Wistar line (180-200 g weight) with pure wounds (D-2,5cm). Six groups were formed, 15 animals per each group. The culture of dermal fibroblasts was isolated from the skin of newborn rats; to accumulate the required biomass of cells subpassage was carried out. The cellular biological products were not applied in group 1 (control). Biodegradable matrices (dextran phosphate or polylactide) were used for treating wounds in the groups 2-6 as matrices without cellular biological product and matrices with cultured fibroblasts (250?103 to 700?103 cells per wound). Conclusion about the impact of biodegradable polymeric matrices with dermal fibroblasts on the wound healing was made on the basis of a comparative analysis of the results of digital planimetry and morphological studies. Results. At all stages (7, 14, 21, 28 days) minimal rate of healing was registered in the first group. The sixth group, where polylactide containing 700?103 cells was added in the wound, is characterized by the biggest values of the healing rate – with respect to other groups. Complete epithelization of the wound defects in the micropreparations of the sixth group was marked by the 21st day of the experiment. The strong direct correlation between the number of transplanted cells and wound rate healing was detected on the 7th day (?=0,923), the 14th day (?=0,924), and the 21st day of the experiment (?=0,914). Conclusion. In the experiment it has been found out, that local application of the cultivated dermal fibroblasts on biodegradable polymer matrices (dextran phosphate and polylactide) results in a significant reduction of terms of the wound epithelization