Analytic approximation of solutions of parabolic partial differential equations with variable coefficients

A complete family of solutions for the one-dimensional reaction-diffusion equation $$u_{xx}(x,t)-q(x)u(x,t) = u_t(x,t)$$ with a coefficient $q$ depending on $x$ is constructed. The solutions represent the images of the heat polynomials under the action of a transmutation operator. Their use allows one to obtain an explicit solution of the noncharacteristic Cauchy problem for the considered equation with sufficiently regular Cauchy data as well as to solve numerically initial boundary value problems. In the paper the Dirichlet boundary conditions are considered however the proposed method can be easily extended onto other standard boundary conditions. The proposed numerical method is shown to reveal good accuracy.Comment: 8 pages, 1 figure. Minor updates to the tex

Lidar investigations of M-zone

The creation of pulse dye lasers tuned to resonant line of meteor produced admixtures of atmospheric constituents has made it possible to begin lidar investigations of the vertical distribution of mesospheric sodium concentration and its dynamics in the upper atmosphere. The observed morning increase of sodium concentration in the vertical column is probably caused by diurnal variations of sporadic meteors. The study of the dynamics of the sodium column concentration in the period of meteor streams activity confirms the suggestion of cosmic origin of these atoms. The short lived increase of sodium concentration brought about by a meteor stream, however, exceeds by one order the level of the sporadic background

Transmutations for Darboux transformed operators with applications

We solve the following problem. Given a continuous complex-valued potential q_1 defined on a segment [-a,a] and let q_2 be the potential of a Darboux transformed Schr\"odinger operator. Suppose a transmutation operator T_1 for the potential q_1 is known such that the corresponding Schr\"odinger operator is transmuted into the operator of second derivative. Find an analogous transmutation operator T_2 for the potential q_2. It is well known that the transmutation operators can be realized in the form of Volterra integral operators with continuously differentiable kernels. Given a kernel K_1 of the transmutation operator T_1 we find the kernel K_2 of T_2 in a closed form in terms of K_1. As a corollary interesting commutation relations between T_1 and T_2 are obtained which then are used in order to construct the transmutation operator for the one-dimensional Dirac system with a scalar potential

Prospective Observational Study on acute Appendicitis Worldwide (POSAW)

Background: Acute appendicitis (AA) is the most common surgical disease, and appendectomy is the treatment of choice in the majority of cases. A correct diagnosis is key for decreasing the negative appendectomy rate. The management can become difficult in case of complicated appendicitis. The aim of this study is to describe the worldwide clinical and diagnostic work-up and management of AA in surgical departments.Methods: This prospective multicenter observational study was performed in 116 worldwide surgical departments from 44 countries over a 6-month period (April 1, 2016-September 30, 2016). All consecutive patients admitted to surgical departments with a clinical diagnosis of AA were included in the study.Results: A total of 4282 patients were enrolled in the POSAW study, 1928 (45%) women and 2354 (55%) men, with a median age of 29 years. Nine hundred and seven (21.2%) patients underwent an abdominal CT scan, 1856 (43.3%) patients an US, and 285 (6.7%) patients both CT scan and US. A total of 4097 (95.7%) patients underwent surgery; 1809 (42.2%) underwent open appendectomy and 2215 (51.7%) had laparoscopic appendectomy. One hundred eighty-five (4.3%) patients were managed conservatively. Major complications occurred in 199 patients (4.6%). The overall mortality rate was 0.28%.Conclusions: The results of the present study confirm the clinical value of imaging techniques and prognostic scores. Appendectomy remains the most effective treatment of acute appendicitis. Mortality rate is low.</p

Global validation of the WSES Sepsis Severity Score for patients with complicated intra-abdominal infections : a prospective multicentre study (WISS Study)

Background: To validate a new practical Sepsis Severity Score for patients with complicated intra-abdominal infections (cIAIs) including the clinical conditions at the admission (severe sepsis/septic shock), the origin of the cIAIs, the delay in source control, the setting of acquisition and any risk factors such as age and immunosuppression. Methods: The WISS study (WSES cIAIs Score Study) is a multicenter observational study underwent in 132 medical institutions worldwide during a four-month study period (October 2014-February 2015). Four thousand five hundred thirty-three patients with a mean age of 51.2 years (range 18-99) were enrolled in the WISS study. Results: Univariate analysis has shown that all factors that were previously included in the WSES Sepsis Severity Score were highly statistically significant between those who died and those who survived (p <0.0001). The multivariate logistic regression model was highly significant (p <0.0001, R-2 = 0.54) and showed that all these factors were independent in predicting mortality of sepsis. Receiver Operator Curve has shown that the WSES Severity Sepsis Score had an excellent prediction for mortality. A score above 5.5 was the best predictor of mortality having a sensitivity of 89.2 %, a specificity of 83.5 % and a positive likelihood ratio of 5.4. Conclusions: WSES Sepsis Severity Score for patients with complicated Intra-abdominal infections can be used on global level. It has shown high sensitivity, specificity, and likelihood ratio that may help us in making clinical decisions.Peer reviewe

Prospective Observational Study on acute Appendicitis Worldwide (POSAW)

Acute appendicitis (AA) is the most common surgical disease, and appendectomy is the treatment of choice in the majority of cases. A correct diagnosis is key for decreasing the negative appendectomy rate. The management can become difficult in case of complicated appendicitis. The aim of this study is to describe the worldwide clinical and diagnostic work-up and management of AA in surgical departments.info:eu-repo/semantics/publishedVersio

Проверка износостойких и прирабатываемых покритий

Some results of works on installation creation on incision, for check of various systems of coatings (wearproof, and abradable sealing, etc.) are resulted. Problems are stated at creation of installation and criterion which were necessary for considering by technical project working out. Some calculations for definition of operating modes, installations which should provide pos­sibility to model to (simulate) covering work on various types of propellers both modern, and created in the future are resulted. Namely, installation should provide a wide temperature span and speeds of incision etc. Offered test method of coverings will allow to devide out expenses to incision on check of again developed coverings, and also to devide out terms on check of again developed coveringsOne of propeller key parameters influencing its EFFICIENCY is the radial clearance be­tween unshrouded blade high-pressure turbines and stator high-pressure turbine. Various types of coatings which provide an optimum positive allowance at the expense of local development of a covering are applied to radial clearance optimization on all power setting,   and not admitting deterioration of blades both system of active regulating of a radial clearance. Before decision making about conducting of test of a covering on the propeller it is necessary to execute great volume of checks (adhesion, thermo cycles etc.). Since covering test for the propeller demands considerable expenses - fuel, propeller assemblage etc., and thus on tests there can be defects because of an inefficient run in covering (deterioration of blades high-pressure turbine or a covering weathering). For decrease in risks and expenses of the coatings connected with test on the propeller, it is necessary to execute test of a covering for incision in conditions as much as possible approached to real on the propeller for what installation for check of run in turbine and compressor coatings has been designed and made.For definition of demanded magnitudes calculations by definition a radial velocity of incision (rapprochement) of a rotor and the stator are carried out. The analysis of temperatures and speeds of incision on available propellers. Приведены некоторые результаты работ по созданию установки по врезанию, для проверки различных систем покрытий (износостойких, прирабатываемых и т.п.). Из­ложены проблемы при создании установки и критерии, которые было необходимо учесть при разработке технического задания. Приведены некоторые расчеты для определения режимов работы, установки, которые должны обеспечивать возможность моделировать (имитировать) работу покрытия на различных типах двигателей как современных, так и создаваемых в будущем. А именно, установка должна обеспечивать широкий диапазон температур и скоростей врезания и т.д. Предложенный метод испытаний покрытий на врезание позволит сократить затраты по проверке вновь разрабатываемых покрытий, а также сократить сроки по проверке вновь разрабатываемых покрытий.

A complex method for prophylaxis of laparoscopic cholecystectomy complications

The clinical examination and treatment results were analyzed in 1282 patients, in whom laparoscopic cholecystectomy, using complex method of the complications prophylaxis, was performed for calculous cholecystitis. The complications have had occurred in 21 (1.64%) patients, the conversion necessity--in 10 (0.78%), 3 (0.23%) patients died

Delayed presentation of blunt duodenal injuries in children. Case report and review of literature

Background. Duodenal injuries are rare in children and classically present following a fall over the handle bar. Retroperitoneal location of the duodenum may lead to delay in diagnosis, and missed injuries are associated with increased morbidity and mortality. Case report. A 5-year-old child was admitted to the National Trauma Center, in Tirana (Albania), 28 hours after a Motor Vehicle Crash (MVC), complaining of mild abdominal pain. He was febrile (39°C) and had a white blood cells count of 18,000 mm3. On physical exam he had mild tenderness. Plain abdominal X-rays and Focused Abdominal Sonography for Trauma (FAST) were negative for free air or free fluid. The CT scan of the abdomen demonstrated free air and fluid in the retroperitoneal space. At laparatomy, a perforation of the second portion of the duodenum was found. A single layer suture repair of the duodenum with wide drainage was performed. The patient was discharged from the hospital tolerating oral feeding 8 days later. Conclusion. Duodenal injuries in children are rare. Most duodenal hematomas are managed non-operatively. This is a case of MCV with delayed presentation that was treated surgically for perforation successfully