Broadband reflectionless metasheets: Frequency-selective transmission and perfect absorption

Energy of propagating electromagnetic waves can be fully absorbed in a thin lossy layer, but only in a narrow frequency band, as follows from the causality principle. On the other hand, it appears that there are no fundamental limitations on broadband matching of thin absorbing layers. However, known thin absorbers produce significant reflections outside of the resonant absorption band. In this paper we explore possibilities to realize a thin absorbing layer which produces no reflected waves in a very wide frequency range, while the transmission coefficient has a narrow peak of full absorption. Here we show, both theoretically and experimentally, that a wide-band-matched thin resonant absorber, invisible in reflection, can be realized if one and the same resonant mode of the absorbing array unit cells is utilized to create both electric and magnetic responses. We test this concept using chiral particles in each unit cells, arranged in a periodic planar racemic array, utilizing chirality coupling in each unit cell but compensating the field coupling at the macroscopic level. We prove that the concept and the proposed realization approach also can be used to create non-reflecting layers for full control of transmitted fields. Our results can have a broad range of potential applications over the entire electromagnetic spectrum including, for example, perfect ultra-compact wave filters and selective multi-frequency sensors.Comment: 9 pages, 10 figure

Changes in Cognitive Functions of Pupils under Conditions of Iodine Deficiency

Clinical and physiological examination of 38 children which latent hypothyroidism (the main group) and 176 apparently healthy persons of intact region (the control group) at the age from 8 to 17 years living in endemic region was carried out. To determine the functional state of the thyroid gland in blood serum the content of total triiodothyronine (Т3), total and free thyroxin (Т4, fТ4), thyroid-stimulating hormone (TSH) of adenohypophysis were determined as well as urinary iodine level was examined. The cognitive functions were characterized by the indices of attention as the result of correction test and rate of sensomotor reactions which were evaluated using modified Schulte tables. It was detected that in all children with latent hypothyroidism regardless of age work accuracy rate decreased, attention span increased slowly, fatigue developed early and rate of information analysis significantly reduced already within the first 5 minutes in comparison with analogical data in healthy children. When being tested children of the control group made fewer mistakes, the tempo of doing tasks remained higher for 5 minutes. There was a correlation between the indices of correction test, sensomotor reactions and data of thyroid status of pupils

Problems and prospects of development of ecological tourism in Ireland

The paper presents the research on the development of ecological tourism in Ireland. The basic directions and problems of development of ecotourism. Income from ecotourism in the country was analyzed in the article, as well as the model for the attraction of tourists to Irelan

Features of high-strength composite material structure creation

The basis of technology proposed is use of a sol-gel method for preventing polycrystalline corundum fiber from crystallization during heating to high temperature and for low-temperature synthesis of prescribed phases in a corundum matrix with the aim of improving the operating properties of composite materials based on corundum. As a result of firing a charge based on corundum powder modified with tetraethoxysilane and polycrystalline corundum fiber modified with ethylsilicate-32 at 1360°C materials are created with very good strength properties. The materials exhibit electrical insulation properties and are stable in ionized gas streams at the level of known analogs as a result of creating self-reinforced mullite and β-SiC corundum matrix, reinforced with polycrystalline fiber and rapidly sintered due to presence of silicon oxynitride

Some Structural and Chemical Changes in Endocardial Endothelium of Rats in Emotional and Pain Stress Complicated by Hypercholesterolemia

The objective of the research was to study the content of some neutral lipids of endocardial endothelium in rats in relation to structural changes occurring in it, in the co-existence of emotional and pain stress, as well as alimentary hypercholesterolemia. Materials and methods. The electric-impulse model was used for stress modeling. Alimentary hypercholesterolemia was modeled feeding animals an atherogenic diet. The concentration of triacylglycerols, free and esterified cholesterol were examined using the method of thin-layer chromatography performed on silica gel. The concentration of free fatty acids was determined using the radiochemical method. The state of endocardial endothelium was studied with the help of light microscopy; the impression smears obtained from macro preparations of ventricle were analyzed.Results. In co-existence of stress and hypercholesterolemia, significant increase in free cholesterol as well as free fatty acid concentration was noticed. This essentially exceeded the analogical indices under the action of stress only. Structural changes in the endocardium followed by desquamation of separate endotheliocytes were the result of stress reaction. In the action of both pathogenic factors, this process was intensified; layer-by-layer exfoliation of endotheliocytes was observed. Conclusions. In acute emotional and pain stress, changes in lipid spectrum of membrane structures of endocardial endotheliocytes the main manifestation of which is the accumulation of free cholesterol in cells and increase in the levels of free fatty acids take place. The increase in the number of desquamated endothelial cells is the result of stress action as well. Alimentary hypercholesterolemia significantly increases such pathological changes. 

Russian entrepreneurship in the context of the economic crisis: tendencies, problems and prospects

The objective of the article is to analyze the main trends of entrepreneurship in Russia and identify areas of its activation to support sustainable economic growth and economic security. The article presents the authors’ approach to the definition of entrepreneurial activit

Modeling of spirals with equal dielectric, magnetic, and chiral susceptibilities

In this article, we study spiral particles with optimized design parameters, which can make possible the realization of media with equal dielectric, magnetic, and chiral susceptibilities. Two different spiral structures are investigated: the canonical spiral (which consists of a split loop with two straight-wire sections, orthogonal to the loop plane and connected to the edges of the gap) and the true helix (which is obtained by bending a wire with a constant pitch angle). The transmission and reflection coefficients of arrays of spiral particles are obtained under plane wave excitation by numerical simulation. The properties of slabs formed by periodic chiral and racemic arrays of spirals are investigated. Good agreement is found between the presented results and the previously reported theoretical and experimental studies

Oxidation resistance of nano-reinforced PC-refractories modified with phenol formaldehyde resin. Part 4. Thermodynamic evaluation of phase formation within Mg–O–C–Al, Mg–O–C–Ni and МgO‒Al₂O₃‒NiO‒SiO₂ systems using SiC + Al + Ni (NiO) complex antioxidant

Results are given for the synthesis and co-existence of phases formed from components of complex organic- inorganic antioxidant formed during modification of phenol-formaldehyde resin (PFR) and graphite with silica alkoxide and inorganic or organic nickel precursors. Thermodynamic analysis is given for the Mg–Al–C and Mg–O–Ni–C systems. It is shown that the periclase and carbon can coexist with aluminum and nickel, and also that oxidized antioxidants Al₂O₃ and NiO can interact respectively with the periclase and with the synthesized SiC formed during modification of PFR with silica. In considering the NiO‒MgO‒Al₂O₃‒SiO₂ system it is established that during service noble spinel will be synthesized from the complex antioxidant components, facilitating an increase in PC-refractory durability in service

Особливості формування соціального пакету для фахівців фармації в аптечних закладах

Aim. To study the features of forming a social package (SP) for pharmacy specialists (PS) in pharmacy institutions and the directions of their targeted implementation in modern conditions. Materials and methods. The results of personal research, such scientific methods as sample observations, desk and analytical analysis, comparison, abstract-logical, synthesis, sociological (questionnaire), expert assessments were used. Results. Issues of social protection of PS have been given attention since the days of the planned economy. At the same time, the study of the features of forming SP for PS in pharmacy institutions as a necessary tool for the implementation of social protection was insufficient. According to the results of a survey of respondents, our research determined the motivational needs of PS when forming SP in pharmacy institutions, the expediency of taking into account certain groups of employees in them, the expediency of considering the age of PS, the attitude to the fulfillment of additional obligations and functions by PS when forming SP, the availability of ways to satisfy the needs of PS and employers in the formation of SP, the components of SP that are preferred by PS at the level of pharmacy institutions, possible directions for supporting PS in modern conditions of exposure to increased risks. Conclusions. It has been found that when forming SP for PS at the level of pharmacy institutions it is necessary to focus on certain features. For this purpose, the expediency of considering certain groups of employees, possible ways to meet the needs of PS and employers, the list of components of SP, the expediency fulfilling additional obligations and functions by PS in the formation of SP have been studied. The directions of support of PS when forming SP in pharmacy institutions in modern conditions have been outlined. In the complex, this will allow to increase the motivation in the professional activities of PS, their social protection and the quality of pharmaceutical provision, medical, civil and military institutions in general.Мета – дослідити особливості формування соціального пакету (СП) для фахівців фармації (ФФ) в аптечних закладах та напрями його адресної реалізації в сучасних умовах. Матеріали та методи – результати особистих досліджень, наукові методи: вибіркові спостереження, кабінетний та аналітичний аналіз, порівняння, абстрактно-логічний, синтезу, соціологічні (анкетування), експертних оцінок. Результати дослідження. Питанням соціального захисту ФФ приділяють увагу з часів планової економіки. Разом із тим, вивчення особливостей формування СП для ФФ в аптечних закладах як необхідного інструменту реалізації соціального захисту не є достатнє. За результатами досліджень визначено мотиваційні потреби ФФ під час формування СП в аптечних закладах, доцільність враховувати окремі групи працівників, вік, ставлення до виконання додаткових зобов’язань і функцій, наявність шляхів задоволеності потреб ФФ і роботодавців, складові СП, яким надають переваги ФФ на рівні аптечних закладів, можливі напрями підтримки ФФ у сучасних умовах впливу підвищених ризиків. Висновки. З’ясовано, що під час формування СП для ФФ на рівні аптечних закладів необхідно орієнтуватись на певні особливості. Для цього досліджено доцільність враховувати окремі групи працівників, можливі шляхи забезпечення потреб ФФ і роботодавців, перелік складових СП, виконання ФФ додаткових зобов’язань і функцій. Окреслено напрями підтримки ФФ під час формування СП в аптечних закладах у сучасних умовах. У комплексі це дозволить підвищити мотивацію у професійній діяльності ФФ, їх соціальний захист, а також якість фармацевтичного забезпечення медичних цивільних і військових установ загалом