Two-dimensional nonstationary model of the propagation of an electron beam in a vacuum

A two dimensional nonstationary model of the propagation of a relativistic electron beam injected into a vacuum is considered. Collision effects are ignored and there are no external fields. Two types of the electron current propagation are shown from the computer simulation of the Maxwell-Vlasov equations

Solitary wave interaction in a compact equation for deep-water gravity waves

In this study we compute numerical traveling wave solutions to a compact version of the Zakharov equation for unidirectional deep-water waves recently derived by Dyachenko & Zakharov (2011) Furthermore, by means of an accurate Fourier-type spectral scheme we find that solitary waves appear to collide elastically, suggesting the integrability of the Zakharov equation.Comment: 8 pages, 5 figures, 23 references. Other author's papers can be downloaded at http://www.lama.univ-savoie.fr/~dutykh/ . arXiv admin note: text overlap with arXiv:1204.288

The EMCCD-Based Speckle Interferometer of the BTA 6-m Telescope: Description and First Results

The description is given for the speckle interferometer of the BTA 6-m telescope of the SAO RAS based on a new detector with an electron multiplication CCD. The main components of the instrument are microscope objectives, interference filters and atmospheric dispersion correction prisms. The PhotonMAX-512B CCD camera using a back-illuminated CCD97 allows up to 20 speckle images (with 512$\times$512 pix resolution) per second storage on the hard drive. Due to high quantum efficiency (93% in the maximum at 550 nm), and high transmission of its optical elements, the new camera can be used for diffraction-limited (0.02$''$) image reconstruction of $15^{m}$ stars under good seeing conditions. The main advantages of the new system over the previous generation BTA speckle interferometer are examined.Comment: 18 pages, 14 figure

Freely decaying weak turbulence for sea surface gravity waves

We study numerically the generation of power laws in the framework of weak turbulence theory for surface gravity waves in deep water. Starting from a random wave field, we let the system evolve numerically according to the nonlinear Euler equations for gravity waves in infinitely deep water. In agreement with the theory of Zakharov and Filonenko, we find the formation of a power spectrum characterized by a power law of the form of $|{\bf k}|^{-2.5}$.Comment: 4 pages, 3 figure

Speckle Interferometry of Metal-Poor Stars in the Solar Neighborhood.II

The results of speckle interferometric observations of 115 metal-poor stars [m/H]<-1 within 250 pc from the Sun and with proper motions mu <= 0.2"/yr, made with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, are reported. Close companions with separations ranging from 0.034" to 1" were observed for 12 objects - G76-21, G59-1, G63-46, G135-16, G168-42, G141-47, G142-44, G190-10, G28-43, G217-8, G130-7, and G89-14 - eight of them are astrometrically resolved for the first time. The newly resolved systems include one triple star - G190-10. If combined with spectroscopic and visual data, our results imply a single:binary:triple:quadruple star ratio of 147:64:9:1 for a sample of 221 primary components of halo and thick-disk stars

Влияние пандемии COVID-19 на показатели заболеваемости злокачественными опухолями, подлежащими скринингу в рамках диспансеризации (популяционное исследование)

Background. During the COVID-19 pandemic, annual adult check-ups have been postponed, resulting in cancer screening disruption.The aim of the study was to evaluate changes in the incidence and stage distribution of malignancies included in the screening program during the COVID-19 pandemic using the Arkhangelsk Regional Cancer Registry (ARRC).Material and Methods. We assessed the changes of the incidence rates and stage distribution for the colon, rectum, lung, breast, cervix, uterine body, ovary, prostate and kidney cancers over the periods 2018–19 and 2020–21. Results. A total of 12354 cases with 9 cancers were selected: 6680 for the period 2018–19 and 5674 (-15.1 %) for the period 2020-21. The most significant decrease in crude and age-standardized incidence rates was registered in patients with lung (-18.0–18.1 %), rectum (-25.1–25.9 %) and cervix (-33.6–36.9 %) cancers, p&lt;0.001. The decrease was not signifcant in patients with breast, uterine body, and kidney cancers. The proportion of patients with stage I decreased in lung cancer (-20.0 %, from 14.8 % to 11.8 %), rectum (-20.2 %, from 20.9 % to 16.7 %), and uterine cervix (-37.1 %, from 53.2 % to 33.5 %). In prostate and kidney cancers, the proportion of patients with stage I increased by 30 % (from 19.5 % to 25.4 %) and 17.6 % (from 45.9 % to 54.0 %), respectively. A signifcant reduction in the proportion of early stages during the COVID-19 pandemic was observed in lung and cervical cancer. Conclusion Postponed health checkups due to COVID-19 pandemic disruptions have led to substantial reductions in new cancers being diagnosed, mainly for cervical, lung, colon and rectal cancers. No signifcant changes were observed for other cancers. Further analysis of mortality and survival of cancer patients is required. Key words: health checkup, cancer screening, COVID-19 pandemic, cancer incidence, stage distribution&gt;˂0.001. The decrease was not significant in patients with breast, uterine body, and kidney cancers. The proportion of patients with stage I decreased in lung cancer (-20.0 %, from 14.8 % to 11.8 %), rectum (-20.2 %, from 20.9 % to 16.7 %), and uterine cervix (-37.1 %, from 53.2 % to 33.5 %). In prostate and kidney cancers, the proportion of patients with stage I increased by 30 % (from 19.5 % to 25.4 %) and 17.6 % (from 45.9 % to 54.0 %), respectively. A significant reduction in the proportion of early stages during the COVID-19 pandemic was observed in lung and cervical cancer.Conclusion. Postponed health checkups due to COVID-19 pandemic disruptions have led to substantial reductions in new cancers being diagnosed, mainly for cervical, lung, colon and rectal cancers. No significant changes were observed for other cancers. Further analysis of mortality and survival of cancer patients is required. Актуальность. В период пандемии COVID-19 была приостановлена диспансеризация отдельных групп взрослого населения (ДОГВН), что могло привести к ухудшению скрининга ряда злокачественных новообразований (ЗНО).Цель исследования ‒ оценить изменения заболеваемости и стадийной структуры ЗНО, включенных в программу скрининга в рамках ДОГВН, во время пандемии COVID-19 по данным Архангельского областного канцер-регистра (АОКР).Материал и методы. Оценивали динамику показателей заболеваемости и распределения по стадии при индексных ЗНО (иЗНО) ободочной, прямой кишки, легкого, молочной железы, шейки, тела матки, яичников, предстательной железы и почки в периоды 2018–19 гг. и 2020–21 гг.Результаты. Всего отобрано 12354 случая заболевания при девяти иЗНО: в 2018–19 гг. выявлено 6680, в 2020–21 гг. – 5674 (-15,1 %). Наиболее выраженное снижение «грубых» и стандартизованных по возрасту показателей заболеваемости зарегистрировано при раке легкого (-18,0–18,1 %), прямой кишки (-25,1–25,9 %) и шейки матки (-33,6–36,9 %), различия статистически значимы (р&lt;0,001). Снижение было статистически незначимым при раке молочной железы, тела матки, почки. Доля больных I стадии уменьшалась при раке легкого (на 20,0 %, с 14,8 до 11,8 %), прямой кишки (на 20,2 %, с 20,9 до 16,7 %), шейки матки (на 37,1 %, с 53,2 до 33,5 %). При раке предстательной железы и почки зарегистрировано увеличение доли I стадии на 30 % (с 19,5 до 25,4 %) и 17,6 % (с 45,9 до 54,0 %) соответственно. В возрастных группах скрининга в рамках ДОГВН значимое снижение доли ранних стадий в период пандемии COVID-19 наблюдали при раке легкого и шейки матки. Заключение. Ограничение ДОГВН в период пандемии привело к уменьшению числа выявленных иЗНО в основном за счет ранних стадий при раке шейки матки, легкого, ободочной и прямой кишки. При других иЗНО эти изменения были не столь явными. В дальнейшем требуется анализ смертности и выживаемости больных иЗНО. Ключевые слова: диспансеризация взрослого населения, скрининг рака, индексные злокачественные новообразования, пандемия COVID-19, заболеваемость, распределение по стадии.&gt;˂ 0,001). Снижение было статистически незначимым при раке молочной железы, тела матки, почки. Доля больных I стадии уменьшалась при раке легкого (на 20,0 %, с 14,8 до 11,8 %), прямой кишки (на 20,2 %, с 20,9 до 16,7 %), шейки матки (на 37,1 %, с 53,2 до 33,5 %). При раке предстательной железы и почки зарегистрировано увеличение доли I стадии на 30 % (с 19,5 до 25,4 %) и 17,6 % (с 45,9 до 54,0 %) соответственно. В возрастных группах скрининга в рамках ДОГВН значимое снижение доли ранних стадий в период пандемии COVID-19 наблюдали при раке легкого и шейки матки.Заключение. Ограничение ДОГВН в период пандемии привело к уменьшению числа выявленных иЗНО в основном за счет ранних стадий при раке шейки матки, легкого, ободочной и прямой кишки. При других иЗНО эти изменения были не столь явными. В дальнейшем требуется анализ смертности и выживаемости больных иЗНО.

Discovery of a young low-mass brown dwarf transiting a fast-rotating F-type star by the Galactic Plane eXoplanet (GPX) survey

We announce the discovery of GPX-1 b, a transiting brown dwarf with a mass of $19.7\pm 1.6$ $M_{\mathrm{Jup}}$ and a radius of $1.47\pm0.10$ $R_{\mathrm{Jup}}$, the first sub-stellar object discovered by the Galactic Plane eXoplanet (GPX) survey. The brown dwarf transits a moderately bright ($V$ = 12.3 mag) fast-rotating F-type star with a projected rotational velocity $v\sin{ i_*}=40\pm10$ km/s. We use the isochrone placement algorithm to characterize the host star, which has effective temperature $7000\pm200$ K, mass $1.68\pm0.10$ $M_{\mathrm{Sun}}$, radius $1.56\pm0.10$ $R_{\mathrm{Sun}}$ and approximate age $0.27_{-0.15}^{+0.09}$ Gyr. GPX-1 b has an orbital period of $\sim$1.75 d, and a transit depth of $0.90\pm0.03$ %. We describe the GPX transit detection observations, subsequent photometric and speckle-interferometric follow-up observations, and SOPHIE spectroscopic measurements, which allowed us to establish the presence of a sub-stellar object around the host star. GPX-1 was observed at 30-min integrations by TESS in Sector 18, but the data is affected by blending with a 3.4 mag brighter star 42 arcsec away. GPX-1 b is one of about two dozen transiting brown dwarfs known to date, with a mass close to the theoretical brown dwarf/gas giant planet mass transition boundary. Since GPX-1 is a moderately bright and fast-rotating star, it can be followed-up by the means of Doppler tomography.Comment: 13 pages, 13 figures, accepted to MNRAS in May 202