Screening of cosmological constant for De Sitter Universe in non-local gravity, phantom-divide crossing and finite-time future singularities

We investigate de Sitter solutions in non-local gravity as well as in non-local gravity with Lagrange constraint multiplier. We examine a condition to avoid a ghost and discuss a screening scenario for a cosmological constant in de Sitter solutions. Furthermore, we explicitly demonstrate that three types of the finite-time future singularities can occur in non-local gravity and explore their properties. In addition, we evaluate the effective equation of state for the universe and show that the late-time accelerating universe may be effectively the quintessence, cosmological constant or phantom-like phases. In particular, it is found that there is a case in which a crossing of the phantom divide from the non-phantom (quintessence) phase to the phantom one can be realized when a finite-time future singularity occurs. Moreover, it is demonstrated that the addition of an $R^2$ term can cure the finite-time future singularities in non-local gravity. It is also suggested that in the framework of non-local gravity, adding an $R^2$ term leads to possible unification of the early-time inflation with the late-time cosmic acceleration.Comment: 42 pages, no figure, version accepted for publication in General Relativity and Gravitatio

Neutron Majorana mass from exotic instantons

We show how a Majorana mass for the Neutron could result from non-perturbative quantum gravity effects peculiar to string theory. In particular, "exotic instantons" in un-oriented string compactifications with D-branes extending the (supersymmetric) standard model could indirectly produce an effective operator delta{m} n^t n+h.c. In a specific model with an extra vector-like pair of `quarks', acquiring a large mass proportional to the string mass scale (exponentially suppressed by a function of the string moduli fields), delta{m} can turn out to be as low as 10^{-24}-10^{-25} eV. The induced neutron-antineutron oscillations could take place with a time scale tau_{n\bar{n}} > 10^8 s, that could be tested by the next generation of experiments. On the other hand, proton decay and FCNC's are automatically strongly suppressed and are compatible with the current experimental limits. Depending on the number of brane intersections, the model may also lead to the generation of Majorana masses for R-handed neutrini. Our proposal could also suggest neutron-neutralino or neutron-axino oscillations, with implications in UCN, Dark Matter Direct Detection, UHECR and Neutron-Antineutron oscillations. This suggests to improve the limits on neutron-antineutron oscillations, as a possible test of string theory and quantum gravity.Comment: 35 pages, 11 figures. More comments on neutron-neutralino mixin

Phosphatidylinositol(4,5)bisphosphate coordinates actin-mediated mobilization and translocation of secretory vesicles to the plasma membrane of chromaffin cells

ORP5 and ORP8, members of the oxysterol-binding protein (OSBP)-related proteins (ORP) family, are endoplasmic reticulum membrane proteins implicated in lipid trafficking. ORP5 and ORP8 are reported to localize to endoplasmic reticulum-plasma membrane junctions via binding to phosphatidylinositol-4-phosphate (PtdIns(4)P), and act as a PtdIns(4)P/phosphatidylserine counter exchanger between the endoplasmic reticulum and plasma membrane. Here we provide evidence that the pleckstrin homology domain of ORP5/8 via PtdIns(4,5)P 2, and not PtdIns(4)P binding mediates the recruitment of ORP5/8 to endoplasmic reticulum-plasma membrane contact sites. The OSBP-related domain of ORP8 can extract and transport multiple phosphoinositides in vitro, and knocking down both ORP5 and ORP8 in cells increases the plasma membrane level of PtdIns(4,5)P 2 with little effect on PtdIns(4)P. Overall, our data show, for the first time, that phosphoinositides other than PtdIns(4)P can also serve as co-exchangers for the transport of cargo lipids by ORPs.ORP5/8 are endoplasmic reticulum (ER) membrane proteins implicated in lipid trafficking that localize to ER-plasma membrane (PM) contacts and maintain membrane homeostasis. Here the authors show that PtdIns(4,5)P 2 plays a critical role in the targeting and function of ORP5/8 at the PM

Популяционный иммунитет к SARS-COV-2 населения Калиниградской области в эпидемический сезон COVID-19

Introduction. The COVID-19 pandemic was announced by WHO in February 2020. In the Kaliningrad region, the first case (imported) was registered in early March 2020, the beginning of the epidemic increase fell on the 14th week. 2020, and the peak incidence was reached in the 22nd week of the year, after which there was a steady decrease in the number of cases. The study of population immunity was carried out at the 32nd week during the period of the lowest level of intensity of the epidemic process.Purpose of the study. Assessment of the assessment of the level of population immunity to the SARS-CoV-2 virus among the population of the Kaliningrad region during the period of the epidemic incidence of the population of COVID-19.Materials and methods. The study was carried out as part of the first stage of the Rospotrebnadzor program to assess population immunity to SARS-CoV-2 among the population of the Russian Federation. The selection of volunteers for the study was carried out by a questionnaire survey and subsequent randomization. The analysis includes the results of a survey of 2675 people. The number of volunteers in age groups ranged from 314 to 493 people. The results obtained were processed by the methods of variation statistics.Results. The results obtained showed that the average seroprevalence in the population was 50.2%, while the highest seroprevalence was found in the child age group 1-17 years (66.9%) and among persons aged 18-29 (57.0). No significant gender differences were found (men – 48,3 ± 1,6%, women – 51,1 ± 1,1%). The distribution of the proportion of seropositive people in the settlements of the region varied from 33,9% to 59.6%. The largest share of seroprevalence in the representative samples was found among people engaged in art / creativity (55,3%), the smallest – among educational workers (42,0%). Among COVID-19 convalescents, the level of humoral immunity reached 94,6%. Most of the seropositive volunteers (95,2%) did not have any symptoms of COVID-19, that is, they belonged to the category of asymptomatic carriers.Output. The results of a survey of a representative cohort of volunteers in the Kaliningrad region showed that they are characterized by a high level of population immunity, which makes it possible to expect a decrease in.Введение. Пандемия COVID-19 была объявлена Всемирная организация здравоохранения в феврале 2020 г. В Калининградской области первый случай (завозной) зарегистрировали в начале марта 2020 г., начало эпидемического нарастания пришлось на 14-ю неделю 2020 г., а пик заболеваемости был достигнут на 22-й неделе года, после чего отмечалось устойчивое снижение количества заболевший. Исследование популяционного иммунитета было проведено на 32-й неделе в период самого низкого уровня напряженности эпидемического процесса.Цель. Оценка уровня популяционного иммунитета к вирусу SARS-CoV-2 среди населения Калининградской области в период эпидемической заболеваемости населения COVID-19.Материалы и методы. Исследование проведено в рамках первого этапа программы Роспотребнадзора по оценке популяционного иммунитета к SARS-CoV-2 среди населения Российской Федерации. Отбор волонтеров для исследования проводили методом анкетирования и последующей рандомизации. В анализ включены результаты обследования 2675 человек. Количество волонтеров в возрастных группах варьировало от 314 до 493 человек. Полученные результаты обрабатывали методами вариационной статистики.Результаты. Полученные результаты показали, что средняя серопревалентность по популяции составила 50,2%, при этом набольшая серопревалентность была выявлена в детской возрастной группе 1–17 лет (66,9%) и среди лиц в возрасте 18–29 лет (57,0). Достоверных половых различий не установлено (мужчины – 48,3±1,6%, женщины – 51,1±1,1%). Распределение доли серопозитивных по населенным пунктам области варьировало от 33,9% до 59,6%. Наибольшая доля серопревалентных в репрезентативных выборках выявлена среди лиц, занятых искусством/творчеством (55,3%), наименьшая – среди работников образования (42,0%). Среди реконвалесцентов COVID-19 уровень гуморального иммунитета достиг 94,6%. Большая часть серопозитивных волонтеров (95,2%) не имела каких-либо симптомов COVID-19, то есть относилась к категории бессимптомных носителей.Выводы. Результаты обследования репрезентативной когорты волонтеров Калининградской области показали, что для них характерен высокий уровень популяционного иммунитета, позволяющий ожидать снижения напряженности эпидемического процесса.