Radio echo in the turbulent corona and simulations of solar drift-pair radio bursts

Drift-pair bursts are an unusual type of solar low-frequency radio emission, which appear in the dynamic spectra as two parallel drifting bright stripes separated in time. Recent imaging spectroscopy observations allowed for the quantitative characterization of the drifting pairs in terms of source size, position, and evolution. Here, the drift-pair parameters are qualitatively analyzed and compared with the newly developed Monte Carlo ray-tracing technique simulating radio-wave propagation in the inhomogeneous anisotropic turbulent solar corona. The results suggest that drift-pair bursts can be formed due to a combination of refraction and scattering processes, with the trailing component being the result of turbulent reflection (turbulent radio echo). The formation of drift-pair bursts requires an anisotropic scattering with the level of plasma density fluctuations comparable to that in type III bursts, but with a stronger anisotropy at the inner turbulence scale. The anisotropic radio-wave scattering model can quantitatively reproduce the key properties of drift-pair bursts: the apparent source size and its increase with time at a given frequency, the parallel motion of the source centroid positions, and the delay between the burst components. The trailing component is found to be virtually cospatial and following the main component. The simulations suggest that drift-pair bursts are likely to be observed closer to the disk center and below 100 MHz due to the effects of free–free absorption and scattering. The exciter of drift pairs is consistent with propagating packets of whistlers, allowing for a fascinating way to diagnose the plasma turbulence and the radio emission mechanism

LEARNING TO PREDICT CLOSED QUESTIONS ON STACK OVERFLOW // Ученые записки КФУ. Физико-математические науки 2013 том155 N4

В статье рассматривается задача прогнозирования вероятности того, что вопрос на сервисе Stack Overflow - популярном вопросно-ответном ресурсе, посвященном разработке программного обеспечения - будет закрыт модератором. Задача, данные и метрика оценки качества были предложены в рамках открытого конкурса по машинному обучению на сервисе Kaggle. В процессе решения задачи мы использовали широкий набор признаков для классификации, в том числе признаки, описывающие личные характеристики пользователя, взаимодействие пользователей друг с другом, а также содержание вопросов, в том числе тематическое. В процессе классификации протестировано несколько алгоритмов машинного обучения. По результатам эксперимента были выявлены наиболее важные признаки: личные характеристики пользователя и тематические признаки вопроса. Наилучшие результаты были получены с помощью алгоритма, реализованного в библиотеке Vowpal Wabbit, - интерактивного обучения на основе стохастического градиентного спуска. Наилучшая полученная нами оценка попадает в топ-5 лучших результатов в финальной таблице, но получена после даты завершения конкурса

Sex estimation based on the anthropometric measurements of thyroid cartilage using discriminant analysis

Abstract Background The morphometric analysis of the individual bones of the human skeleton can be used to estimate the sex of unidentified corpses. Our aims were as follows: to test whether thyroid cartilage can be used for forensic purposes as a predictor of biological sex; to establish the level of sexual dimorphism of the thyroid cartilage in a sample of adult subjects from a population of European Russia; and to test the accuracy of the morphometric parameters obtained from the thyroid cartilage. Results The thyroid cartilage from 100 adults of known age (50 males and 50 females) was obtained during forensic examination; morphometric tests were conducted using Vernier Digital ROKTOOLS ABS DIN 862 0-200/6 inch with measurement accuracy ± 0.01 mm. The measured parameters were N = 31 for each subject. Intra- and inter-observer reproducibility was tested. Multivariate statistical analysis was applied to the measurements. To check the data set for normal distribution, the Kolmogorov-Smirnov test was used. Finally, to estimate the sex of the observed individuals, a stepwise discriminant analysis was conducted, using the Wilks' lambda selection method. The most significant parameters were the outer distance between bases of inferior horn; the inner distance between distal ends of inferior horns; distance between distal ends of left superior and inferior horns; left superior horn length (distance between left superior horn distal end and base); distance between superior and inferior notches; thyroid angle; left lamina height (vertical line along left lamina middle); horizontal distance between anterior intermedium line and the right lamina posterior edge; distance between inferior thyroid notch and line connecting left and right thyroid laminae; and left superior horn thickness at mid-line. The stepwise discriminant analysis resulted in an equation with ten parameters. Conclusions The results of the current study indicated that in the European Russian population, the equation obtained in the stepwise discriminant analysis makes it possible to predict sex with a probability of 100% on the validation set. On the test set, the resultant accuracy was 100% for females and 100% for males. Our findings confirm the scientific evidence that the thyroid cartilage has a pronounced sexual dimorphism

Generation of GeV protons from 1 PW laser interaction with near critical density targets

The propagation of ultra intense laser pulses through matter is connected with the generation of strong moving magnetic fields in the propagation channel as well as the formation of a thin ion filament along the axis of the channel. Upon exiting the plasma the magnetic field displaces the electrons at the back of the target, generating a quasistatic electric field that accelerates and collimates ions from the filament. Two-dimensional Particle-in-Cell simulations show that a 1 PW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to an energy of 1.3 GeV. Scaling laws and optimal conditions for proton acceleration are established considering the energy depletion of the laser pulse.Comment: 26 pages, 8 figure

Innovative nuclear energy systems : state-of-the art survey on evaluation and aggregation judgment measures applied to performance comparison

This paper summarizes the experience gained in the application of multi-criteria decision making and uncertainty treatment methods to a comparative assessment of nuclear energy systems and related nuclear fuel cycles. These judgment measures provide a means for comprehensive evaluation according to different conflicting criteria, such as costs, benefits and risks, which are inevitably associated with the deployment of advanced technologies. Major findings and recommendations elaborated in international and national projects and studies are reviewed and discussed. A careful analysis is performed for multi-criteria comparative assessment of nuclear energy systems and nuclear fuel cycles on the basis of various evaluation and screening results. The purpose of this paper is to discuss the lessons learned, to share the identified solutions, and indicate promising future directions

Apophis planetary defense campaign

We describe results of a planetary defense exercise conducted during the close approach to Earth by the near-Earth asteroid (99942) Apophis during 2020 December–2021 March. The planetary defense community has been conducting observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. These community-led global exercises were carried out with the support of NASA's Planetary Defense Coordination Office and the International Asteroid Warning Network. The Apophis campaign is the third in our series of planetary defense exercises. The goal of this campaign was to recover, track, and characterize Apophis as a potential impactor to exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication. Based on the campaign results, we present lessons learned about our ability to observe and model a potential impactor. Data products derived from astrometric observations were available for inclusion in our risk assessment model almost immediately, allowing real-time updates to the impact probability calculation and possible impact locations. An early NEOWISE diameter measurement provided a significant improvement in the uncertainty on the range of hypothetical impact outcomes. The availability of different characterization methods such as photometry, spectroscopy, and radar provided robustness to our ability to assess the potential impact risk

Phenological shifts of abiotic events, producers and consumers across a continent

Ongoing climate change can shift organism phenology in ways that vary depending on species, habitats and climate factors studied. To probe for large-scale patterns in associated phenological change, we use 70,709 observations from six decades of systematic monitoring across the former Union of Soviet Socialist Republics. Among 110 phenological events related to plants, birds, insects, amphibians and fungi, we find a mosaic of change, defying simple predictions of earlier springs, later autumns and stronger changes at higher latitudes and elevations. Site mean temperature emerged as a strong predictor of local phenology, but the magnitude and direction of change varied with trophic level and the relative timing of an event. Beyond temperature-associated variation, we uncover high variation among both sites and years, with some sites being characterized by disproportionately long seasons and others by short ones. Our findings emphasize concerns regarding ecosystem integrity and highlight the difficulty of predicting climate change outcomes. The authors use systematic monitoring across the former USSR to investigate phenological changes across taxa. The long-term mean temperature of a site emerged as a strong predictor of phenological change, with further imprints of trophic level, event timing, site, year and biotic interactions.Peer reviewe

Chronicles of nature calendar, a long-term and large-scale multitaxon database on phenology

We present an extensive, large-scale, long-term and multitaxon database on phenological and climatic variation, involving 506,186 observation dates acquired in 471 localities in Russian Federation, Ukraine, Uzbekistan, Belarus and Kyrgyzstan. The data cover the period 1890-2018, with 96% of the data being from 1960 onwards. The database is rich in plants, birds and climatic events, but also includes insects, amphibians, reptiles and fungi. The database includes multiple events per species, such as the onset days of leaf unfolding and leaf fall for plants, and the days for first spring and last autumn occurrences for birds. The data were acquired using standardized methods by permanent staff of national parks and nature reserves (87% of the data) and members of a phenological observation network (13% of the data). The database is valuable for exploring how species respond in their phenology to climate change. Large-scale analyses of spatial variation in phenological response can help to better predict the consequences of species and community responses to climate change.Peer reviewe

Heterogeneous world model and collaborative scenarios of transition to globally sustainable nuclear energy systems

The International Atomic Energy Agency's International Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO) is to help ensure that nuclear energy is available to contribute to meeting global energy needs of the 21st century in a sustainable manner. The INPRO task titled “Global scenarios” is to develop global and regional nuclear energy scenarios that lead to a global vision of sustainable nuclear energy in the 21st century. Results of multiple studies show that the criteria for developing sustainable nuclear energy cannot be met without innovations in reactor and nuclear fuel cycle technologies. Combining different reactor types and associated fuel chains creates a multiplicity of nuclear energy system arrangements potentially contributing to global sustainability of nuclear energy. In this, cooperation among countries having different policy regarding fuel cycle back end would be essential to bring sustainability benefits from innovations in technology to all interested users. INPRO has developed heterogeneous global model to capture countries’ different policies regarding the back end of the nuclear fuel cycle in regional and global scenarios of nuclear energy evolution and applied in a number of studies performed by participants of the project. This paper will highlight the model and major conclusions obtained in the studies