Effect of Screening on Spin Polarization in a Two-Dimensional Electron Gas

The experimentally observed amazing dependence of a critical magnetic field Bc of a full field-induced spin polarization and a spin susceptibility of a two-dimensional electron gas on the electron density can be explained by screening of the Coulomb potential. The possibility of spontaneous full spin polarization expected at lower electron densities also crucially depends on screening.Comment: 7 pages, 3 figure

A comparative analysis of single-port and four-port laparoscopic cholecystectomies in patients with chronic calculous cholecystitis

The objective: To conduct a comparative analysis of the results of single-port and four-port laparoscopic cholecystectomies in patients with chronic calculous cholecystitis. Materials and methods. During 2015 – 2017 years 214 patients underwent surgery for chronic calculous cholecystitis. All patients were divided into 2 groups. The first group consisted of 102 (47.6%) patients, who underwent single-port laparoscopic cholecystectomy (SILC). The second included 112 (52.3%), for whom standard laparoscopic cholecystectomy was performed. The results in both groups were compared on the following criteria: 1) patient characteristics: age, sex and body mass index (BMI); 2) the duration of surgical intervention; 3) the total time of the patient hospitalisation; 4) the presence of drainage in the abdominal cavity; 5) anaesthetic assessment of the patient's physical condition prior to surgical intervention (classification of ASA); 6) the level of pain within 6 hours after the operation – visual analogue scale (VAS; from 0 to 10, where 0 – no pain, 10 – maximum pain); 7) the necessity for the administration of opioid analgesics in the postoperative period; 8) the presence of complications arose during surgery (bleeding, injury of the common bile duct, gallbladder perforation, leak of bile into the abdominal cavity); 9) the postoperative quality of life, cosmetic outcome (evaluation was performed using the 4-Likert scale. Results. When choosing access to remove the gallbladder, it is important to evaluate carefully the patient's data before surgery. The age of the patient, the presence of concomitant diseases, BMI, patient tolerance to the expected mode of operation play an important role. The history of proven acute cholecystitis, frequent biliary colics determine the performance of laparoscopic 4-ports cholecystectomy. Umbilical hernia can be used to place a port for interference through one-port access. When planning a single-port operation, one should be aware of the possibility of intra-operational occurrence of technical difficulties that may require the installation of additional trochars. Conclusions. The single-port method is a modern safe operation, one of the alternatives to the traditional four-port cholecystectomy, which causes the best cosmetic result of a low level of postoperative pain. Both technologies should not be opposed, but, on the contrary, it is necessary to combine and connect the advantages of both technologies in order to achieve the optimal result of surgical treatment

In the transmission of the 1.4 drawbar category mobile power vehicle on the performance indicators of machine and tractor units

The aim of the work is to scientifically substantiate a way to improve the technical, economic and agrotechnological performance indicators of machine-tractor units, compiled on the basis of traction power equipment of category 1.4, the main technological operations in the cultivation of various crops by reducing the level of dynamic processes in their connections. It is established that the elastic damping mechanism with nonlinear characteristics and optimal parameters installed in front of the drive shaft of the power transmission of a traction power tool of category 1.4 provides favorable conditions for the functioning of all links of machine-tractor units for agricultural purposes, with them the main technological operations are performed, which contributes to the improvement of its technical, economic and agrotechnological indicators. The installation of an elastic-damping mechanism with nonlinear characteristics and optimal parameters in front of the drive shaft of the tractor traction category 1.4 provides an increase in productivity by more than 8% while reducing specific fuel consumption by 9% or more, as well as improving the quality performance of machine-tractor units when they perform basic technological operations

The dependence of the functional parameters of a tractor of traction class 1,4 as part of a cultivator unit on the type of tire model of size 18,4r-38 on propellers

The aim of the work: to establish the functional indicators of a cultivator unit based on a wheeled mobile power vehicle of traction class 1.4 when its driving wheels are equipped with tires of size 18.4R-38 of various models (206B, TM300S, VL-32). The increase in the performance indicators of the functioning of any machine-tractor unit depends largely on its working speed and the width of the grip, which implies the use of mobile energy means with high traction and energy indicators at the lowest level of dynamic processes in the links of the machine-tractor unit. For wheeled mobile power equipment, the achievement of high traction and energy indicators is determined by the properties of the tires of the driving wheels. Analysis of traction test data showed that the MTZ-80 tractor with VL-32 tires mounted on the propellers had the best traction performance compared to other tested models

Optimization of The Soil Agrophysical Properties for Spring Rape on Leached Black Soil

An important agronomic task in cultivating spring rape is improving the physical properties of leached black soil, which are extremely important for increasing its productivity. A central role in the physics of these soils is played by studying its density, which helps regulate the soil processes and maintain favorable conditions for spring rape. According to the studies, the highest productivity of spring rape is observed in the case of the arable layer density of 1.00 – 1.10 g/cm3. Moreover, in the case of soil density of 1.10 g/cm3, productivity is better by 5.6 – 8.5 % than in the case of 1.00 g/cm3. The number of seeds per pod has increased especially strongly (by 13.8 %). In the subsurface layer (30 – 40 cm), soil density of 1.10 – 1.20 g/cm3 is optimal for spring rape growth and development

Marketing research in a transition economy of the turbulent world

The aim of the study is to clarify what factors and how exactly to act in market research in the transition economy of Ukraine. The hypothesis raised is the conduct of market research in a transition economy is affected by factors related to global economic trends, the state of development of marketing theory and market research in the world and in Ukraine. Their study was carried out through the use of general scientific methods of abstraction, a systematic approach to the study of socioeconomic processes and the participation of relevant theoretical concepts. Among the most relevant results is that the analysis confirms our hypothesis that the conduct of market research in the underdeveloped oligarchic transitive economy of Ukraine is influenced by three groups of factors related to the trends of the world economy, the state of development of marketing theory and market research, as well as characteristics of the transitive economy. The market research market size calculation is based on certain expert assumptions and may not fully reflect the actual situation. On the other hand, the practice of market research is influenced not only by theoretical developments but also by the state of its market. The result of the investigation makes it possible to take into account the particularities of the type of economy in transition in Ukraine

ІНСТРУМЕНТАЛЬНЕ ВИЗНАЧЕННЯ ІНСОЛЯЦІЇ В РАЙОНІ М. ОДЕСИ

Використання сонячних установок (СУ) знижує споживання органічного палива і, відповідно, антропогенне навантаження на довкілля. Основним параметром при проектуванні СУ є величина інсоляції. В роботі за вимірами метеостанції уточнено середньо місячну та середньо рокову інсоляцію в м. Одесі. Проведено співставлення отриманих величин з літературними даними. Проведено розрахунок приведених витрат при використанні сонячної установки чи котла на природному газі для гарячого водопостачання. Показано, що з урахуванням податків за викиди шкідливих речовин приведені витрати для сонячної установки на 31 % більші

Multilayered antifriction nanostraction covering for lubrication in the tribocoupling

In article principles of creation of a new way of the lubrication a wheel-rail tribosystem by drawing on a lateral side of a rail head of a multilayered antifriction nanostructurial covering possessing property of blocking negative segregation phenomena in metals of a wheel and a rail are considered