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

Population structure of the spawning roach Rutilus rutilus in water bodies of the Dniprovs’ko-Orilsky nature reserve

Розглянуто стан популяції фонового виду іхтіофауни заповідника – Rutilus rutilus Linnaeus, 1758. Вивчено базові популяційні параметри виду. Надано оцінку сучасному стану та визначено перспективи подальшого існування плітки у водоймах заповідника.Розглянуто стан популяції фонового виду іхтіофауни заповідника – Rutilus rutilus Linnaeus, 1758. Вивчено базові популяційні параметри виду. Надано оцінку сучасному стану та визначено перспективи подальшого існування плітки у водоймах заповідника.The population state of Rutilus rutilus Linnaeus, 1758, which is a common species in the reserve, is under consideration. Basic population parameters of the species have been studied. Assessment of modern state and determination of further perspectives of the roach existence in the reserve’s basins have been done

Структура нерестової популяції ляща (Abramis brama) водойм Дніпровсько-Орільського природного заповідника

The population state of important food fish Abramis brama L. in the Dniprovsko-Orelsky Nature Reserve is under consideration . Basic population parameters of the species have been studied. Assessment of modern state and determination of perspectives of further existence of the roach in the Reserve’s basins have been done.Розглянуто стан популяції цінного промислового виду іхтіофауни Дніпровського водосховища – Abramis brama Linnaeus, 1758 на акваторії Дніпровсько-Орільського природного заповідника. Визначено основні популяційні характеристики виду у водоймах заповідника. Надано оцінку сучасному стану нерестової популяції та розглянуто перспективи подальшого існування ляща на акваторії заповідника. Розглянуто стан популяції цінного промислового виду іхтіофауни Дніпровського водосховища – Abramis brama Linnaeus, 1758 на акваторії Дніпровсько-Орільського природного заповідника. Визначено основні популяційні характеристики виду у водоймах заповідника. Надано оцінку сучасному стану нерестової популяції та розглянуто перспективи подальшого існування ляща на акваторії заповідника.

Фауна риб прибережної зони дншровсько-орільського заповідника на сучасному етапі розвитку Іхтюценозу

Status of groups of coastal fish in water bodies ofthenaturereserve, anddynamicsoftheirquantitativeandqualitativeparameters isconsidered. Responses of fish communities to changes occurring in floodplain lakes were recorded,with thedeterminationoftheirunderlyingfactors, andmeasuresonmaintaininghomeostasis of this group of aquatic organisms and optimizationoftheirrecoveryandreproductionarerecommended.Розглянуто стан угруповань риб прибережної зони водойм заповідника, динаміку їх кількі- сних та якісних параметрів. Відмічено реакції іхтіоценозів на зміни, які відбуваються в заплав- них озерах, та визначено вплив факторів, що їх обумовлюють. Рекомендовано заходи щодо під- тримки гомеостазу цієї групи водних організмів та оптимізаціїїх відновлення і відтворення.Розглянуто стан угруповань риб прибережної зони водойм заповідника, динаміку їх кількі- сних та якісних параметрів. Відмічено реакції іхтіоценозів на зміни, які відбуваються в заплав- них озерах, та визначено вплив факторів, що їх обумовлюють. Рекомендовано заходи щодо під- тримки гомеостазу цієї групи водних організмів та оптимізаціїїх відновлення і відтворення

Triboelectric Backgrounds to radio-based UHE Neutrino Exeperiments

The triboelectric effect broadly includes any process in which force applied at a boundary layer results in displacement of surface charge, leading to the generation of an electrostatic potential. Wind blowing over granular surfaces, such as snow, can induce a potential difference, with subsequent coronal discharge. Nanosecond timescale discharges can lead to radio-frequency emissions with characteristics similar to piezoelectric-induced discharges. For Antarctic-sited experiments seeking detection of radio-frequency signals generated by collisions of cosmic rays or neutrinos with atmospheric or englacial molecular targets, triboelectric emissions from the surface pose a potential background. This is particularly true for experiments in which radio antennas are buried ~(1--100) m below the snow surface, and seeking to validate neutrino detection strategies by measurement of down-coming radio-frequency emissions from extensive air showers. Herein, after summarizing extant evidence for wind-induced triboelectric effects previously reported elsewhere, we detail additional analysis using archival data collected with the RICE and AURA experiments at the South Pole. We broadly characterize those radio-frequency emissions based on source location, and time-domain and also frequency-domain characteristics. We find that: a) For wind velocities in excess of 10-12 m/s, triboelectric background triggers can dominate data-taking, b) frequency spectra for triboelectric events are generally shifted to the low-end of the regime to which current radio experiments are typically sensitive (100-200 MHz), c) there is an apparent preference for tribo-electric discharges from metal surface structures, consistent with a model in which localized, above-surface structures provide a repository for transported charge

Assessment of the impact of seasonal patterns climatic conditions on spawning events of the white bream Blicca bjoerkna (Linnaeus, 1758) in astronomical and biological time

This paper describes spawning events of the white bream Blicca bjoerkna (Linnaeus, 1758 )in astronomical and biological time depending on seasonal patterns of climatic conditions. The research was conducted in the "Dnipro-Orilskiy" Nature Reserve (Ukraine) during the years 1997–2015 in four habitat types. The timing of the spawning event (start, end) was evaluated using astronomical time (number of days from January 1 each year), with correction for the lunar and the semilunar cycle, and using biological time (number of days from the end of spawning in the previous year to the beginning and end of spawning in the current year). The spawning phenology of the white bream was found to be dependent on the dynamics of weather conditions over time. Patterns of varying climatic regimes which are expressed by means of multivariate principal component are the most informative predictors of the spawning events. Evaluation of occurrence of spawning events in astronomic or biological time gives somewhat different models of the impact of climate regimes. The impact of the principal components indicating variability of rainfall during the year in which spawning occurs is statistically significant for almost all regression models. Models using the solar calendar are also more sensitive to the course of air temperatures within the year when spawning occurred. Correction of time based on the lunar cycle allows us to assess events which are sensitive also to the temperature and rainfall variation during the second half of the previous year. Biological time was shown to be sensitive to environmental influences over time from the end of spawning in the previous year to spawning in any given year

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