Charge inhomogeneities due to smooth ripples in graphene sheets

We study the effect of the curved ripples observed in the free standing graphene samples on the electronic structure of the system. We model the ripples as smooth curved bumps and compute the Green's function of the Dirac fermions in the curved surface. Curved regions modify the Fermi velocity that becomes a function of the point on the graphene surface and induce energy dependent oscillations in the local density of states around the position of the bump. The corrections are estimated to be of a few percent of the flat density at the typical energies explored in local probes such as scanning tunnel microscopy that should be able to observe the predicted correlation of the morphology with the electronics. We discuss the connection of the present work with the recent observation of charge anisotropy in graphene and propose that it can be used as an experimental test of the curvature effects.Comment: 9 pages, 5 figures. v2: Abstract and discussion about experimental consequences expande

Educational Tourism: Tribute to Fashion or New Educational Opportunities?

The relevance of this article lies in the need to study educational tourism as one of the ways to motivate students in educational process.  The article discusses new technologies in the educational process, which must be made more saturated and practically applicable. Visualization and the ability to implement the acquired knowledge can interest students and increase their interest in learning the information included in the curriculum. The purpose of the study is to analyze the importance of educational tourism for students. Research methods: As research methods, the following ones were used: questionnaire survey of participants of educational tours and free-style interviews with teachers and organizers of educational tourism, allowing identifying such characteristics of educational tourism’s value for students as awareness of participants about the project, previous personal experience, interest and satisfaction with the project. Research results: the article considers the importance of educational tourism from the point of view of its participants like students, accompanying teachers, from the point of view of the organizers of the tourist and educational project. The novelty and originality of the research lies in the fact that educational tourism is considered as an alternative to educational activities, which allows not only to make a trip, but also to acquire new knowledge, skills and abilities during it, which will be learned much better than just memorizing the material from the book. It is shown that the value of educational tourism can be assessed if there is knowledge about its components such as interest and personal experience of its participants, satisfaction or dissatisfaction with certain elements of the educational tour, awareness of the project possibilities, features of the organization and implementation of the tour. It is revealed that educational tourism performs not only directly educational, but also socially significant functions for society. The study shows that the project participants perceive the educational component easily and without difficulties and there is a high interest of students in educational tours. It is revealed that the accompanying notes a positive dynamic in the interest in the educational process after participation in the project. Both its participants and its organizers perceive the possibility of expanding the project positively. It is determined that the greatest difficulty in the organization of educational tourism is caused by the lack of support of state structures, which in turn causes difficulty in entering new sites where the project can be implemented. It is shown that the educational component of the project is positively evaluated by both direct consumers and teachers in terms of the correctness in the construction of the narrative and semantic parts. It is shown that to the positive aspects of educational tourism can be attributed the emotional involvement of participants in the educational process during the excursion service, as well as increasing the level of their interest in further study. Practical significance: the data obtained in this work can be used in social psychology, pedagogy, age psychology, pedagogical psychology, as well as for further theoretical development of this issue

Physical properties of thermoelectric zinc antimonide using first-principles calculations

We report first principles calculations of the structural, electronic, elastic and vibrational properties of the semiconducting orthorhombic ZnSb compound. We study also the intrinsic point defects in order to eventually improve the thermoelectric properties of this already very promising thermoelectric material. Concerning the electronic properties, in addition to the band structure, we show that the Zn (Sb) crystallographically equivalent atoms are not exactly equivalent from the electronic point of view. Lattice dynamics, elastic and thermodynamic properties are found to be in good agreement with experiments and they confirm the non equivalency of the zinc and antimony atoms from the vibrational point of view. The calculated elastic properties show a relatively weak anisotropy and the hardest direction is the y direction. We observe the presence of low energy modes involving both Zn and Sb atoms at about 5-6 meV, similarly to what has been found in Zn4Sb3 and we suggest that the interactions of these modes with acoustic phonons could explain the relatively low thermal conductivity of ZnSb. Zinc vacancies are the most stable defects and this explains the intrinsic p-type conductivity of ZnSb.Comment: 33 pages, 8 figure

Innovative Methods in Management and Raising the Quality of Higher Professional Education in Russia

Economic and political changes in contemporary society lead to reforms of many social spheres. The system of education in general and higher professional education in particular is no exception. The issue of ensuring the quality of education has recently attracted great attention in all countries of the world. The key problem of reforming education is raising its quality. In this paper, the object of research was the quality of education provided by higher education institutions. The authors have conducted the analysis of models for raising the quality of education and qualimetry of the laboratory work quality based on a survey of teachers and students. The QFD method was described by the example of its application in five universities of the Russian Federation. It has been proved that this method can provide the university with a planning tool with which higher education institutions can provide services that fully meet the requirements of customers (students, parents, employers, the state and society as a whole), thereby ensuring the suitability of the system to meet external requirements – the Fitness-for-Purpose approach (building goals based on the external environment). In addition, it has also been substantiated that the application of this method in the system of higher professional education will ensure the suitability of the system to achieve its own goals - the Fitness-for-Purpose approach (development, improvement, effective management). Thus, the QFD method will make it possible to support of all types of coordinated activities for the leadership and management of higher education institutions in relation to quality, as well as a set of developed regulatory and methodological documents that determine the content, technologies, methods and means of work of all officials, teachers and students to further improve the quality of educational process, thereby ensuring the competitiveness of higher education institutions and effective development on the global market of educational service

ОПРЕДЕЛЕНИЕ УРАНА В ВОДНЫХ РАСТВОРАХ МЕТОДОМ ВРЕМЯПРОЛЕТНОЙ МАСС-СПЕКТРОМЕТРИИ С ИМПУЛЬСНЫМ ТЛЕЮЩИМ РАЗРЯДОМ ПОСЛЕ ЕГО КОНЦЕНТРИРОВАНИЯ ОКИСЛЕННЫМИ УГЛЕРОДНЫМИ НАНОТРУБКАМИ

The pollution of the environment with uranium dictates the need to control the concentration of this element in natural waters to the permissible limits for the stability of the ecosystems and public health. In 2011, WHO set maximum permissible concentration of uranium in water to 0.03 ppm due to the strong toxicity and radioactivity of uranium in water. Therefore, the continuous monitoring of uranium content is an important task for the safety and health of the citizens. To determine the low uranium content in natural waters, the conservation of the studied solutions is necessary. However, this method of storage and transportation is not always simple. In the current paper, as a convenient method of concentrating uranium, preserving the sample and transporting it, we used the method of sorbing uranium on sorbents. Single-layer carbon nanotubes were used as sorbents. Their surfaces were modified using wet chemical oxidation and synthesis with Aerosil A-380 silica. Two schemes were considered for concentrating the uranium on the surface of the sorbent: individual carbon nanotubes and nanotubes modified with silica. The direct analysis was used to determine the content of uranium in the sorbent, namely, time-of-flight mass spectrometry with the pulsed glow discharge (GDMS). The most effective approach for the determination of uranium in water was the sorption of uranium on the tablet consisting of oxidized nanotubes modified with silica. The limit of detection in this case was 0.2 ppb.Keywords: mass-spectrometry, pulsed glow discharge, environment, direct analysis, uranium, carbon nanotubes  DOI: http://dx.doi.org/10.15826/analitika.2020.24.2.001Titova A.D1, Postnov V.N.1, Savinov S.S.1, Stolyarova N.V.2, Ivanenko N.B.2, Chuchina V.A.1, Gubal A.R.1, Ganeev A.A.1,21Saint-Petersburg State University (SPBU),Universitetskaya emb., 7/9, Saint-Petersburg, 199034, Russian Federation2Institute of Toxicology of Federal Medico-Biological Agency,ul. Bekhtereva, 1, Saint-Petersburg, 192019, Russian FederationЗагрязнение окружающей среды ураном диктует необходимость контроля концентрации этого элемента в природных водах до допустимых пределов, что необходимо для стабильности экосистем и здоровья населения. Из-за сильной токсичности и радиоактивности в 2011 году ВОЗ установила предельно допустимую концентрацию урана в воде – 0.03 ppm. При транспортировке проб природной воды с низким содержанием урана (на уровне ПДК) их консервируют. В качестве удобного способа транспортировки пробы и одновременного концентрирования урана в данной работе предложено сорбировать его на однослойных углеродных нанотрубках. Поверхность углеродных нанотрубок предварительно модифицировали химическим окислением и обрабатывали кремнеземом аэросил А-380. Рассматривали два варианта концентрирования урана на поверхность сорбента: индивидуальные и модифицированные кремнеземом углеродные нанотрубки. Для анализа использовали прямой метод определения содержания урана в сорбенте − времяпролетную масс-спектрометрию с импульсным тлеющим разрядом (GD-MS). Показано, что наиболее эффективным подходом для определения урана в воде стала сорбция урана на таблетку, состоящую из модифицированных кремнеземом окисленных нанотрубок. Предел обнаружения при этом составил 0.2 ppb.Ключевые слова: масс-спектрометрия, импульсный тлеющий разряд, окружающая среда, прямой анализ, уран, углеродные нанотрубкиDOI: http://dx.doi.org/10.15826/analitika.2020.24.2.00

Vitamin D (steroid hormone) and the nervous system diseases (literature review)

The present review aims to summarize the activities of vitamin D effects on the nervous system and to clarify a vitamin D role in brain diseases, in the pathogenesis or as a serum biomarker for the disease development and severity. Objective: correlation between chronic nervous system diseases and vitamin D level. Methods: a literature research in PubMed and in Russian electronic resources by keywords: vitamin D, brain diseases, chronic nervous system diseases. Results. Vitamin D as a neurosteroid hormone stimulates cerebral activity in both adult and embryonic brain regulates the activity of neural circuits which are responsible for locomotor, reward-dependent and emotional behavior. Patients with autism spectrum disorders, schizophrenia, Alzheimer disease, multiple sclerosis, Parkinson disease and sleep disorders have been shown to have low level of vitamin D. Discussion. Data are controversial, a further study of vitamin D hypovitaminosis significance is essential for the nervous system chronic diseases manifestation and evaluation of the vitamin D dietary supplement efficiency in patients with the nervous system pathology

Analysis of Protein Markers in Plasma of Patients with Drug Dependence Syndrome: Observational Clinical Study

Background. In drug addiction treatment, the diagnostic process is based on the chemical toxicological determination of the intoxication substrate or its metabolite. Laboratory monitoring and prediction issues that could form the basis of secondary prevention remain unresolved. Specific nervous tissue proteins are considered to be the most promising laboratory markers of drug pathology.Objective — to determine some potential biomarkers of protein-chemical nature in the plasma of patients with drug dependence syndrome.Methods. The study was conducted according to the design of an observational clinical trial at the Narcological Dispensary of Krasnodar Krai in the period from 07.2021 to 07.2022. The main group (group 2) included 31 patients diagnosed with substance dependence syndrome. The control group (group 1, n = 15) consisted of healthy subjects submitted to occupational medical examinations. During the detoxification-stabilization therapy and rehabilitation, 5 proteins were determined in the plasma: brainand glial-derived neurotrophic factors, neuron-specific enolase, alpha-synuclein and calcium-binding protein S100B. Statistical analysis of the data involved the Mann-Whitney test for comparing the values of the control and experimental groups and the Wilcoxon test for comparing the values of one group obtained at different stages of observation. The calculations were carried out using StatPlus version 7 (AnalystSoft Inc., USA).Results. A total of 31 patients were included in the main group, 18 of them were followed up with a diagnosis of opioid dependence syndrome (n = 11) or psychostimulant dependence syndrome (n = 7). Patients dropped out of the study due to their refusal to participate in the study or undergo rehabilitation, or due to relapse of the disease. When admitted to the hospital, patients indicated a 45% decrease in brain-derived neurotrophic factor in the plasma ( p < 0.001), and a 3.9-fold decrease after rehabilitation course ( p < 0.001). Glial-derived neurotrophic factor in the plasma exceeded the controls 1.9 times ( p < 0.001) upon admission to hospital, but rapidly returned to normal values thereafter. Level of neuron-specific enolase in the plasma was also poor, 36% lower than the controls ( p <0.001), but approached the control values by the end of rehabilitation.Conclusion. The study obtained data indicating the changes in neurotrophic factors in the blood plasma of patients with opioid or psychostimulant dependence. The rehabilitation period was marked by a relatively rapid improving level of neurotrophins; however, brain-derived neurotrophic factor remained reduced despite the successful treatment, which may indicate the irreversible changes