Backward scattering of low-energy antiprotons by highly charged and neutral uranium: Coulomb glory

Collisions of antiprotons with He-, Ne-, Ni-like, bare, and neutral uranium are studied theoretically for scattering angles close to 180$^{\circ}$ and antiproton energies with the interval 100 eV -- 10 keV. We investigate the Coulomb glory effect which is caused by a screening of the Coulomb potential of the nucleus and results in a prominent maximum of the differential cross section in the backward direction at some energies of the incident particle. We found that for larger numbers of electrons in the ion the effect becomes more pronounced and shifts to higher energies of the antiproton. On the other hand, a maximum of the differential cross section in the backward direction can also be found in the scattering of antiprotons on a bare uranium nucleus. The latter case can be regarded as a manifestation of the screening property of the vacuum-polarization potential in non-relativistic collisions of heavy particles.Comment: 14 pages, 5 figure

РАСЧЕТ ТЕРМОДИНАМИЧЕСКИХ СВОЙСТВ ПЕРРЕНАТОВ МЕТАЛЛОВ И ИХ ИСПОЛЬЗОВАНИЕ ПРИ МОДЕЛИРОВАНИИ ПОДГОТОВКИ ПРОБ К ХИМИЧЕСКОМУ АНАЛИЗУ

Thermodynamic properties, namely standard molar enthalpy of formation (ΔHf°298), standard molar entropy (S°298), and temperature dependence of heat capacity (Ср(Т)) of crystalline metal perrhenates, were assessed by the semi-empirical methods. In this work, ΔHf°298, S°298 and coefficients a, b and c for Cp = а + 0.001×b×T + 105×c×T –2equation were calculated using several methods and averaged. These thermodynamic properties were calculated for the following perrhenates metals: Li, N, K, Rb, Cs, Cu, Ba, Fe, Ca, Cd, Co, Mg, Mn, Pb, Sr, Zn, Al, Crи Fe. The calculated values of the thermodynamic properties were in good accordance with the known literature data. New data were applied to the thermodynamic simulation of rhenium-containing sample pretreatment processes for the chemical analysis. The thermodynamic simulation of the sintering sample with the magnesium oxide with/without oxidizing agents was carried out using HSC 6.1 software with new data about the perrhenates. According to the calculated results, the addition of the oxidizing agent (NaNO3 or K2S2O7) to the magnesium oxide was needed and its presence ensured the rhenium transition into the solution without losses. In this case, rhenium was present at the temperature of the sintering predominantly as NaReO4c or KReO4c. Calculation results and estimation of perrhenates thermodynamic properties could be used for the thermodynamic simulation of different processes as well as in analytical chemistry and in metallurgy.Keywords: perrhenates, thermodynamic properties, thermodynamic simulation, sintering, oxidizing agent, rhenium(Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.4.015 O.V. Melchakova1, P.V. Zaitceva1, A.V. Maiorova1,2, T.V. Kulikova1,2, N.V. Pechishcheva1, K.Yu. Shunyaev1,21Institute of Metallurgy of the Ural Branch of the Russian academy of Sciences, 101, Amundsen street, Ekaterinburg, 620016, Russian Federation, 2Ural Federal University named after the first President of Russia B.N. Yeltsin,19, Mira street, Ekaterinburg, 620002, Russian FederationС помощью полуэмпирических методов оценены термодинамические свойства перренатов металлов (Li, Na, K, Rb, Cs, Cu, Ba, Fe, Ca, Cd, Co, Mg, Mn, Pb, Sr, Zn, Al, Crи Fe) в кристаллическом состоянии: стандартная энтальпия образования (ΔH°298), стандартная энтропия (S°298)и температурная зависимость теплоемкости (Ср(Т)) в диапазоне температур 298.15 – 1200 K. Методы, основанные на методе групповых составляющих, были использованы для оценки ΔH°298 (эмпирический метод Ле Вана, инкрементный метод и метод Мостафа)и S°298 (инкрементный метод Кумока и правило Неймана – Коппа). Для расчета коэффициентов a, b, c в уравнении Cp = а + 0.001×b×T + 105×c×T –2 были использованы аддитивный метод, эмпирические формулы Абашидзе и Цагарейшвили и метод Мостафа. Значения величин, полученные различными методами, были усреднены и использованы в термодинамическом моделировании. С использованием программного комплекса HSC 6.1, дополненного рассчитанными и усредненными термодинамическими свойствами перренатов металлов, выполнено термодинамическое моделирование процесса спекания ренийсодержащих материалов. Рассмотрено спекание проб, содержащих рений, с оксидом магния в отсутствии и присутствии окислительной добавки (NaNO3 или K2S2O7). Показано, что добавление окислительной добавки приводит к минимизации газообразных потерь рения в процессе спекания. Полученные теоретические результаты согласуются с экспериментальными, что говорит о применимости рассчитанных нами термодинамических свойств перренатов металлов. Рассчитанные термодинамические свойства перренатов металлов могут быть использованы для различных термодинамических расчетов как в аналитической химии, так и в металлургии.Ключевые слова: перренаты, термодинамические свойства, термодинамическое моделирование, спекание, окислительная добавка, ренийDOI: http://dx.doi.org/10.15826/analitika.2019.23.4.01

Assessment of serological tests for antibodies to different antigens of the SARS-CoV-2 virus: comparison of six immunoassays

The new coronavirus SARS-CoV-2 has become a global challenge to medicine and, in particular, laboratory diagnostics. The study of the antibodies’ level to SARS-CoV-2 can be used as a confirmation test in the diagnosis of a disease, but it becomes of paramount importance in assessing population immunity resulting from a disease or vaccination, as well as in selection of convalescent plasma donors. The kits developed in our country and abroad for detecting antibodies to the SARS-CoV-2 virus differ both in the methods of testing and in the used coronavirus antigens to which the antibodies are directed. The aim of this study was to compare the diagnostic sensitivity and specificity of five kits for the detection of IgG antibodies to the SARS-CoV-2 virus, based on different diagnostic methods. Serum samples from 137 COVID-19 convalescents and 166 donors of blood and its components were examined. The control group consisted of 50 blood sera collected at the beginning of 2019 and 19 sera collected in 2018 (before the advent of the SARS-CoV-2 virus) and stored at -70 °C. Testing was carried out in analytical systems: rapid test “COVID-19 IgM/IgG Rapid Test (Colloidal Gold)” (China), on an automatic immunochemical analyzer Abbott Architect™ i2000 and kit “SARS-CoV2-IgG” (Abbot, Chicago , IL USA), by the chemiluminescence method using an automatic analyzer of the CL series and kits of the “Mindray” company (China) “SARS-CoV-2 IgM” and “SARS-CoV-2 IgG” and by the enzyme immunoassay method on the kits of the companies “Diagnostic Systems” Ltd (Russia, Nizhny Novgorod) “DS-IFA-ANTI-SARS-CoV-2-G”, “Xema” Ltd (Federal State Budgetary Institution “National Medical Research Center of Hematology” of the Ministry of Health of Russia) “SARS-CoV-2-IgG-IFA” and “Vector-Best” CJSC (Russia, Novosibirsk)” SARS-COV-2-IgM-IFA-BEST” and “SARS-COV-2-IgG-IFABEST”. When comparing the results of testing 137 plasma samples on the Vector-Best and Mindray kits for IgG antibodies, 127 samples were positive, 7 samples were negative on both kits, the discrepancy was 2.2%. In the study of IgM antibodies, 32.1% were positive, and 52.6% were negative in both kits. The discrepancy rate was 15.3%. Out of 166 samples, 1 serum (0.6%) was negative in 5 kits. On the Mindray kit, IgG antibodies to the antigens of the SARS-CoV-2 virus were detected in 165 samples (99.4%), on Vector-Best – in 164 sera (98.8%), on Diagnostic systems – in 151 (90.96%), on Xema – in 154 (92.8%), and on Abbott – in 155 samples (93.4%). At the same time, 135 (81.33%) samples were positive in all kits, while 30 samples had discordant results (18.07%), and in 9 sera, specific IgG was not detected in 2 or more kits. ROC analysis revealed a high diagnostic value of all tested kits (AUC from 0.908 to 0.998), which indicates a high quality of the separation model of positive and negative samples (p < 0.001). With the cut-off set by the manufacturers, the sensitivity and specificity ranged from 82.8% and 93.3% for the Diagnostic Systems kit to 99.4% and 95.8% for the VectorBest kit. The calculated correlation coefficients were higher between kits with a similar composition of the antigen used in the kits; therefore, it is better to monitor the dynamics of antibodies by diagnostic kits from the same manufacturer

Web Based Postgraduate Thesis/Dessertation System - A Prototype

With the advancement of information communication technology in Malaysia, education field should take advantage to upgrade their learning and management techniques. Students should be allowed to learn anytime, anywhere and at their own place. However administration and lecture should be able to manage their work more effective and flexible. The web-based system is effective way to learning and managing education works. This report outlines the development of a web-based postgraduate thesis/dissertation management system (WPTS), which aimed to assist thesis/dissertation administration, supervisor and students in the better integration during students doing the thesis/dissertation works. This prototype system base on case study with a group of MSC(IT), administration, lecturer and students who participate in thesis/dissertation management activities. This report also presenting the tests conducted with users, it also contributed some perspective regarding benefits that gain by administration, supervisor and students, and recommends future application of the approach

Analysis of the RC catalog sample in the region overlapping with the regions of the FIRST and SDSS surveys: I. Identification of sources with the VLSS, TXS, NVSS, FIRST, and GB6 catalogs

Radio sources of the RC catalog produced in 1980--1985 at RATAN-600 radio telescope based on a deep survey of a sky strip centered on the declination of the SS 433 source are optically identified in the region overlapping with FIRST and SDSS surveys (about 132 square degrees). The NVSS catalog was used as the reference catalog for refining the coordinates of the radio sources. The morphology is found for about 75% of the objects of the sample and the ratio of single, double and multicomponent radio sources is computed based on FIRST radio maps. The 74, 365, 1400, and 4850 MHz data of the VLSS, TXS, NVSS, FIRST, and GB6 catalogs are used to analyze the shape of the spectra.Comment: 16 pages, 3 figure

Developing a Ballistic Software Kit to Estimate Vehicle Characteristics at the Draft Design Stage

The article describes a ballistic software kit to calculate a moving vehicle trajectory in atmosphere and space. Such software gives an opportunity to accelerate the acquisition of flying vehicle’s ballistic parameters at the stage of draft design. It contributes to improving collaboration efficiency between adjacent departments involved in the project. The developed software kit includes three different programs: Trajectory-LAND© (motion in atmosphere with possible correction of a trajectory), Trajectory-SPACE© (motion in the non-central gravity field with possible simulation of maneuvers), Trajectory-LAUNCH© (launch-vehicle’s insertion into the orbit with possible defining the impact points of separated stages). Each of the software concedes the addition of computational modules to use the solution results of the basic task. Implemented mathematical models permit to take into account the influence of main perturbations on the flying vehicle during the flight. For illustration purposes, the article gives some examples of using each of the programs and their block-diagrams.The developed software implements some algorithms, which allow attaining the convergence of numerical simulation of differential equations of motion. This problem arises, for example, while determining an attitude in case the stages have already separated from the launch vehicle. The mathematical conversion from Rodriguez-Hamilton parameters into Euler’s angles disables us to obtain reliable values of attitude angles due to the limitations for existing area of inverse trigonometric functions being used. Incorrect values of pitch lead to raw and roll channels divergences. Moreover, the mistakes in attitude determination lead to mistakes in obtained values of attack angle, which is included into the forms for aerodynamic forces and torques. As a result, the solution of system of differential equations is a failure when a flying vehicle enters the height of 30-35 km. The similar situations happen also when using other software of the kit. So there are special logical and mathematical tricks to overcome these difficulties.The free accessible software available for the trajectory calculation is either inappropriate for solving the regarded tasks, in principle, or is functionally limited. The real analogues are available either at the rocket and space enterprises, or in research institutes, and a high cost disables their licensing use, especially, in state educational institutions. Besides, such software often falls within the restrictions on double-purpose technology circulation. In spite of the existing non-commercial analogues the developed software kit allows the transformation of the program while dealing with various tasks in new projects. This kit holds an intermediate niche between approximate estimations of vehicle’s ballistic properties at the stage of technical proposal and accurate calculations to be performed, usually, only for final version of the flying vehicle.</p