The quest for companions to post-common envelope binaries: I. Searching a sample of stars from the CSS and SDSS

As part of an ongoing collaboration between student groups at high schools and professional astronomers, we have searched for the presence of circum-binary planets in a bona-fide unbiased sample of twelve post-common envelope binaries (PCEBs) from the Catalina Sky Survey (CSS) and the Sloan Digital Sky Survey (SDSS). Although the present ephemerides are significantly more accurate than previous ones, we find no clear evidence for orbital period variations between 2005 and 2011 or during the 2011 observing season. The sparse long-term coverage still permits O-C variations with a period of years and an amplitude of tens of seconds, as found in other systems. Our observations provide the basis for future inferences about the frequency with which planet-sized or brown-dwarf companions have either formed in these evolved systems or survived the common envelope (CE) phase.Comment: accepted by A&

On Unbounded Composition Operators in L2L^2-Spaces

Fundamental properties of unbounded composition operators in $L^2$-spaces are studied. Characterizations of normal and quasinormal composition operators are provided. Formally normal composition operators are shown to be normal. Composition operators generating Stieltjes moment sequences are completely characterized. The unbounded counterparts of the celebrated Lambert's characterizations of subnormality of bounded composition operators are shown to be false. Various illustrative examples are supplied

Efficiency of Using Cryptocurrencies as an Investment Asset

The study of the effectiveness of using cryptocurrencies as an investment resource was conducted on the basis of testing the hypothesis that the introduction of leading cryptocurrencies that are components of the CRIX index into the investment portfolio improves its quality (efficiency). Cryptocurrency investment opportunities are explored on the basis of statistics for July 2016-June 2019. An average annual return on investment (ROI), which is adjusted for passive income on an investment asset (PI), is used to evaluate investment performance. In this study, cryptocurrencies are compared with the following alternative investment areas: Forex market, equities (companies with the highest weights in Nasdaq 100, Euro STOXX 50), commodities, government bonds, real estate. The criteria were determined by the increase in the Sharpe ratio of the investment portfolio and its average annual return. Optimization of investment portfolios without cryptocurrencies and with them was performed on the basis of the Markowitz model. The result shows the confirmation of the hypothesis: the introduction of 3 cryptocurrencies – Bitcoin, Ripple, Litecoin – in the proportions of 2.31%, 1%, 1%, respectively, increased the Sharpe ratio of the investment portfolio by 3.29 points, and the coefficient of return by 9.42 percentage points while increasing the risk by only 0.51 percentage points. This result indicates that the quality (increase in efficiency) of the investment portfolio due to the introduction of cryptocurrencies and the ability to control the investment risk of the portfolio despite the high volatility of cryptocurrencies. This proves the investment (speculative) function of crypto-assets, which can be the basis for developing a model of accounting for crypto-assets

МОРФОГЕНЕЗ ЖОВЧНИХ ПРОТОК ЛЮДИНИ В ЕМБРІОНАЛЬНОМУ ПЕРІОДІ

Numerous publications in scientific periodical press are indicative of an extraordinary interest of scientists in the issues of intrauterine morphogenesis. The study deals with the issue of prenatal morphogenesis of extrahepatic biliary ducts, since developmental defects of this segment of the digestive system constitute approximately 6-8 % out of all developmental defects. The objective of the study is to specify regularities of the spatial-temporal dynamics of the prenatal morphogenesis of the extrahepatic bile ducts. The investigation resulted in the following: the rudiment of the common bile duct in embryos of 4,0-5,0 mm of the parietococcygeal length is in the form of a hollow epithelial cord connecting the hepatic diverticulum with the ventral wall of the primary intestine. Physiological atresia of the common bile duct occurs in embryos of 8,5-11,0 mm of the parietococcygeal length due to intensive epithelial proliferation. Recanalization of the common bile duct is completed at the later stages of the intrauterine development.Многочисленные публикации в научной периодеческой прессе свидетельствует о чрезвычайной заинтересованости ученых проблемой внутриутробного морфогенеза. Исследование посвящено проблеме пренатального морфогенеза внепеченочных желчных путей так как пороки развития этого сегмента пищеварительной системы составляют около 6-8 % от всех пороков рахвития. Целью исследования является выяснение закономерностей пространственно-временной динамики пренатального морфогенеза внепеченочных желчных проток. В результате исследования установлено: у зародышей 4,0-5,0 мм теменно-копчиковой длинны зачаток общей желчной протоки являет собой полый эпителиальный тяж, который соеденяет печеночный дивертикул с вентральной стенкой первичной кишки. Физиологическая атрезия общей желчной протоки возникает у зародышей 8,5-11,0 мм теменно-копчиковой длинны в следствии интенсивной пролиферации эпителия. Реканализация общей желчной протоки заканчивается на более поздних этапах внутриутробного развития.Численні публікації в науковій періодичній пресі свідчать про надзвичайну зацікавленість науковців проблемою внутрішньоутробного морфогенезу. Дослідження присвячене проблемі пренатального морфогенезу позапечінкових жовчних проток, адже вади розвитку цього сегмента травної системи складають близько 6-8 % від усіх вад розвитку. Метою дослідження є зʼясування закономірностей просторово-часової динаміки пренатального морфогенезу позапечінкових жовчних проток. В результаті дослідження встановлено: у зародків 4,0-5,0 мм тім’яно-куприкової довжини зачаток спільної жовчної протоки являє собою порожнистий епітеліальний тяж, який з’єднує печінковий дивертикул з вентральною стінкою первинної кишки. Фізіологічна атрезія спільної жовчної протоки виникає в зародків 8,5-11,0 мм тім’яно-куприкової довжини в наслідок інтенсивної проліферації епітелію. Реканалізація спільної жовчної протоки завершується на пізніших етепах внутрішньоутробного розвитку