Temperature dependent graphene suspension due to thermal Casimir interaction

Thermal effects contributing to the Casimir interaction between objects are usually small at room temperature and they are difficult to separate from quantum mechanical contributions at higher temperatures. We propose that the thermal Casimir force effect can be observed for a graphene flake suspended in a fluid between substrates at the room temperature regime. The properly chosen materials for the substrates and fluid induce a Casimir repulsion. The balance with the other forces, such as gravity and buoyancy, results in a stable temperature dependent equilibrium separation. The suspended graphene is a promising system due to its potential for observing thermal Casimir effects at room temperature.Comment: 5 pages, 4 figures, in APL production 201

Strong exciton-plasmon coupling in semiconducting carbon nanotubes

We study theoretically the interactions of excitonic states with surface electromagnetic modes of small-diameter (~1 nm) semiconducting single-walled carbon nanotubes. We show that these interactions can result in strong exciton-surface-plasmon coupling. The exciton absorption line shape exhibits Rabi splitting ~0.1 eV as the exciton energy is tuned to the nearest interband surface plasmon resonance of the nanotube. We also show that the quantum confined Stark effect may be used as a tool to control the exciton binding energy and the nanotube band gap in carbon nanotubes in order, e.g., to bring the exciton total energy in resonance with the nearest interband plasmon mode. The exciton-plasmon Rabi splitting we predict here for an individual carbon nanotube is close in its magnitude to that previously reported for hybrid plasmonic nanostructures artificially fabricated of organic semiconductors on metallic films. We expect this effect to open up paths to new tunable optoelectronic device applications of semiconducting carbon nanotubes.Comment: 22 pages, 8 figures, accepted for PR

Spontaneous decay of excited atomic states near a carbon nanotube

Spontaneous decay process of an excited atom placed inside or outside (near the surface) a carbon nanotube is analyzed. Calculations have been performed for various achiral nanotubes. The effect of the nanotube surface has been demonstrated to dramatically increase the atomic spontaneous decay rate -- by 6 to 7 orders of magnitude compared with that of the same atom in vacuum. Such an increase is associated with the nonradiative decay via surface excitations in the nanotube.Comment: 8 pages, 3 figure

Chemical analysis of aerosol in the Venusian cloud layer by reaction gas chromatography on board the Vega landers

The experiment on sulfuric acid aerosol determination in the Venusian cloud layer on board the Vega landers is described. An average content of sulfuric acid of approximately 1 mg/cu m was found for the samples taken from the atmosphere at heights from 63 to 48 km and analyzed with the SIGMA-3 chromatograph. Sulfur dioxide (SO2) was revealed in the gaseous sample at the height of 48 km. From the experimental results and blank run measurements, a suggestion is made that the Venusian cloud layer aerosol consists of more complicated particles than the sulfuric acid water solution does

Фенологія нересту плоскирки (Blicca bjoerkna) у біотопах природного заповідника «Дніпровсько-Орільський» залежно від сезонної зміни температур

This paper examines the relationship between climatic conditions and the phenology of spawning of the white bream Blicca bjoerkna (Linnaeus, 1758) in natural habitats of the "Dnipro-Orylskiy" Nature Reserve. The characteristic of spawning distribution is symmetric, as the asymmetry coefficients do not significantly differ from zero. The distribution of the timing of spawning and its duration are also characterized by excesses, which do not significantly differ from zero alternatives. Analysis of meteorological data for the period of study allowed us to determine the trends in temperature variation, which correlate with the temperature of the water. Spawning events in any given year take place entirely within an upward temperature progression that can be accurately described by a linear equation in the form: Y = b + a · x, where Y – ten-day average temperature; x – the order of decades for I–VI months of the year, a and b – the parameters of the equation. The same equation can be used to describe downward movements in the temperature for decades during the VII–XII months of the year. Regression parameters and coefficients of determination have the following environmental sense. For the ascending temperature branch the regression coefficient b will decrease in proportion to the increase in the contrast between winter and summer temperatures. Due to the fact that linear approximation is a certain generalization of the sinusoid natural course of temperature, it should be borne in mind that the highest summer temperatures are close to the change in direction in the course of temperature from increase to decrease. Therefore, the coefficient b will largely depend on the minimum winter temperatures and should be interpreted as a marker of the coldness of the winter. This interpretation is all the more justified because we are concerned here with assessment of the impact on fish spawning, and the processes that precede spawning events clearly have importance for their explanation. Changes in the direction of the course of temperature which occur after spawning have no value in explaining spawning. If we consider coefficient b beyond the environmental context, then certainly this figure depends on the coldness of the winter and equally on the warmness of the summer. Similar considerations lead us to interpret the coefficient b of a descending branch as a marker of the warmness of the summer. Comparison of the ascending temperature branch of the current year and the descending branch of the previous year gives the coefficient of correlation between these parameters of linear regression r = –0.10, P = 0.39. This result confirms our assumption that the coefficient b of a descending branch is a marker of the warmness of summer, because if it were a marker of the coldness of a winter, then the coefficient of correlation parameters for the temperature course that are common for this winter would be statistically significant. In addition, the absence of connections indicates that these coefficients provide independent and additional information about the weather conditions. Coefficient a for the ascending branch characterizes the rate of warming during the spring, ie the rate of onset of summer, and for the descending branch – the rate of cooling in the fall, that is the speed of the onset of winter. The linear model reflects the general trend of warming in spring and cooling in autumn. In reality, the course of temperature change is by its nature a complex oscillatory process. Therefore the coefficient of determination of linear regression indicates the extent of correspondence of the real process to the linear model. Significant deviations from the general trend lead to a reduction in the coefficient of determination. These variations are the result of processes of sharp warming, alternating with periods of abrupt cooling. The more such events occur, the smaller the coefficient of determination. Thus, to describe the timing of spawning events we can examine the impact on them of such factors as regression model parameters for the current year for the ascending branch of temperature changes and parameters for the model of the previous year for the descending branch of temperature changes. As a result of our studies, we found that during the period 1997–2015 the typical course of temperature during the year is characterized by two branches: ascending and descending. The data obtained support the hypothesis that the onset of the various phases of spawning (the beginning of spawning, the end of spawning, spawning duration) is explained by temperature variation of the current year up to the spawning event and by temperature variation in the preceding year. The timing of the spawning of B. bjoerkna can be described at a statistically significant level by multidimensional factors reflecting the peculiarities of weather conditions and habitat type. The colder the previous summer and the winter of the current year and the fewer variables there are in the course of temperature, the later spawning occurs. The warmer the previous summer and the colder the winter of the current year, the later the spawning ends. Temperature variability in the course of temperature contributes to an earlier completion of spawning. There is a strong correlation between the beginning and the end of the spawning season so the impact of environmental factors at the beginning of spawning is also reflected in the timing of the end of spawning. The influence of conditions in the current year on the end of spawning is conditioned by the timing of the onset of spawning and the impact of weather conditions of the previous year on the end of spawning has independent significance. Установлено залежності фенології нересту плоскирки Bliccabjoerkna (Linnaeus, 1758) у біотопах природного заповідника «Дніпровсько-Орільський» від кліматичних умов. Протягом 1997–2015 рр. нерест плоскирки починався у діапазоні від 29 квітня до 23 травня (на 118–142-гу добу поточного року), а закінчувався в діапазоні від 20 травня до 12 червня (на 139–162-гу добу). Таким чином, нерест тривав 10–30 діб. Типовий хід температури протягом року характеризується наявністю двох гілок: висхідної та низхідної. Одержано дані, які підтверджують гіпотезу про те, що для пояснення часу настання етапів нересту значення має хід температури цього року до моменту настання події (початок нересту, кінець нересту, тривалість нересту) та хід температур минулого року. Терміни початку нересту плоскирки статистично вірогідно можуть бути описані за допомогою багатовимірних факторів, які відображають особливості метеорологічних умов та типів біотопу. Нерест настає тим пізніше, чим холодніші минуле літо та поточна зима, а також чим менш варіабельний хід температур. Кінець нересту настає тим пізніше, чим тепліше попереднє літо та чим холодніша зима. Варіабельність ходу температур сприяє ранньому завершенню нересту. Між термінами початку та кінця нересту існує сильний кореляційний зв’язок, тому вплив екологічних факторів на початок нересту віддзеркалюється також у термінах кінця нересту. Вплив умов поточного року на кінцевий термін нересту опосередковується терміном початку нересту, а вплив метеорологічних умов минулого року на термін закінчення нересту має самостійне значення

Конкуренція представників родини Бичкові (Gobiidae) з іншими видами риб водойм Придніпров’я

The paper analyzes the species’ composition of Gobiidae, their quantitative and qualitative parameters in the coastal zone of the Pridneproovye water bodies. The structural and functional features of organization of coastal Gobies groups in the explored territory have been investigated, as well as characteristics of spatial arrangement of Gobiidae family representatives in water bodies and rivers and their role in the coastal groups of fishes. In the waters of Dnipropetrovsk region there were recorded 8 species of the Gobies family: round goby Neogobius melanostomus (Pallas, 1814), big-headed goby N. kessleri (Gunter, 1861), monkey goby N. fluviatilis (Pallas, 1814), goad goby N. gymnotrachelus (Kessler, 1857), toad goby Mesogobius batrachocephalus (Pallas, 1814), tube-nosed goby Proterorhinus marmoratus (Pallas, 1814), starry goby Benthophilus stellatus (Sauvage, 1874), Brauner’s tadpole goby Benthophiloides brauneri (Beling et Iljin, 1927). The gobies are quickly settled in various water bodies. The highest numbers of Gobiidae were registered in Dneprovsky water basin – 113.8 specimens/100 m2. The dominant among the Gobiidae is monkey goby, and subdominant is round goby. The main food competitor of monkey goby are juveniles of commercial fish. In Samara river the index of trophic niche overlap between goby and roach reaches 0.95, between goby and silver bream – 0.91, between goby and crucian carp – 0.88, between goby and rudd – 0.87, between goby and common bream – 0.62. The number and biomass indicators in Samara river have fallen due to trophic competition between new aggressive fish species – pumpkinseed and Gobiidae. In the Ingulets river the total overlap of trophic niches is observed between N. fluviatilis and black-striped pipefish (1.0), almost complete overlap is recorded between monkey goby and pumpkinseed (0.97). It is found that native species of Dnipropetrovsk region (including commercial species) undergo intense trophic pressure on the part of low value, “weed” or alien speciesПроаналізовано видовий склад родини Бичкові у прибережній зоні водойм Придніпров’я. Досліджено структурно-функціональні особливості організації прибережних угруповань бичкових. Проаналізовано особливості просторового розподілу Gobiidae на акваторії річок і водосховищ, їх роль у літоральних угрупованнях риб. У водоймах Дніпропетровської області зареєстровано 8 видів родини Gobiidae: Neogobius melanostomus, N. kessleri, N. fluviatilis, N. gymnotrachelus, Mesogobius batrachocephalus, Proterorhinus marmoratus, Benthophilus stellatus, B. brauneri. Бички швидко розселяються по різних водоймах. Найбільша чисельність бичкових відмічена для акваторій Дніпровського водосховища (113,8 екз./100 м2). Видом-домінантом серед Gobiidae є N. fluviatilis, субдомінантом – N. melanostomus. Головними трофічними конкурентами N. fluviatilis є молодь промислових риб. У р. Самара (притока Дніпровського водосховища) коефіцієнти перекриття трофічних ніш між бичком і пліткою досягають 0,95, плоскиркою – 0,91, карасем сріблястим – 0,88, краснопіркою – 0,87, лящем – 0,62. У р. Інгулець, яка впадає у Каховське водосховище, повне перекриття трофічної ніші спостерігається між N. fluviatilis та Syngnathus abaster nigrolineatus (1,0), майже повне – між бичком і новим агресивним видом іхтіофауни Придніпров’я – Lepomis gibbosus (0,97). Аборигенні риби водойм Дніпропетровської області (у тому числі промислові) піддаються потужному трофічному пресингу з боку малоцінних, «смітних» або чужорідних виді

Study of antimicrobial activity and technology optimization of Calendulae flos galenicals

The article presents materials on optimization of manufacture technology for Calendulae flos galenicals with medium level of antibacterial activity. For antibacterial study of extracts, we used agar well diffusion method. In our research, we utilized six test-strain microorganisms: E. coli ATCC 25922, S. aureus ATCC 25923, P. vulgaris ATCC 4636, P. aeruginosa ATCC 27853, C. albicans ATCC 885/653, and B. subtilis ATCC 6633. We have found that the maximum level of extracts’ antimicrobial activity is achieved in the range of ethanol content in the extractant from 70 to 97 % v/

Confinement-Induced Nonlocality and Casimir Force in Transdimensional Systems

We study within the framework of the Lifshitz theory the long-range Casimir force for in-plane isotropic and anisotropic free-standing transdimensional material slabs. In the former case, we show that the confinement-induced nonlocality not only weakens the attraction of ultrathin slabs but also changes the distance dependence of the material-dependent correction to the Casimir force to go as $\sim\!1/\!\sqrt{l}$ contrary to the $\sim\!1/l$ dependence of that of the local Lifshitz force. In the latter case, we use closely packed array of parallel aligned single-wall carbon nanotubes in a dielectric layer of finite thickness to demonstrate strong orientational anisotropy and crossover behavior for the inter-slab attractive force in addition to its reduction with decreasing slab thickness. We give physical insight as to why such a pair of ultrathin slabs prefers to stick together in the perpendicularly oriented manner, rather than in the parallel relative orientation as one would customarily expect.Comment: 20 pages, 4 figures, 52 reference

Aspects and issues of marketing authorisation and use of medicinal products for COVID-19 prevention during the pandemic

At the end of 2019, an outbreak of a new coronavirus began in the city of Wuhan (Hubei Province) in the People's Republic of China. The outbreak turned into a pandemic. In the shortest possible time, national and international manufacturers developed preventive COVID-19 vaccines, and the population was vaccinated. During pandemics, accelerated approval of vaccines is an important factor that shortens the time to market with the aim of mass vaccination. The experience of rapidly developing and introducing vaccines into routine practice is not only important for managing the current pandemic, but also valuable in case of extremely likely future ones. The aim of this study was to analyse the main issues associated with assessing the safety and efficacy of vaccines for COVID-19 prevention during their registration and widespread use amid the pandemic and ongoing SARS-CoV-2 evolution. The vaccines for COVID-19 prevention were developed and introduced into healthcare practice very rapidly and under the circumstances of the pandemic, and the use of these vaccines has surfaced a number of concerns requiring further research. The most important issues identified in the performed analysis include, but are not limited to the need for accelerated assessment of the safety and immunogenicity of new vaccines; the lack of immune correlates of protection against SARS-CoV-2; the waning of antibody immunity over time, motivating the need to determine revaccination and post-recovery vaccination timelines; and the emergence of mutant SARS-CoV-2 variants. One of noteworthy aspects is the need to develop recommendations for updating the strain composition of registered COVID-19 vaccines. According to the conclusions, the level of herd immunity, including vaccine-induced protection, plays a certain role in virus evolution during the pandemic. If COVID-19 becomes seasonal, which is a probable scenario, regular revaccination can be essential