On analytical solutions of f(R) modified gravity theories in FLRW cosmologies

A novel analytical method for f(R) modified theories without matter in Friedmann-Lemaitre-Robertson-Walker spacetimes is introduced. The equation of motion for the scale factor in terms of cosmic time is reduced to the equation for the evolution of the Ricci scalar R with the Hubble parameter H. The solution of equation of motion for actions of the form of power law in Ricci scalar R, is presented with a detailed elaboration of the action quadratic in R. The reverse use of the introduced method is exemplified in finding functional forms f(R) which lead to specified scale factor functions. The analytical solutions are corroborated by numerical calculations with excellent agreement. Possible further applications to the phases of inflationary expansion and late-time acceleration as well as f(R) theories with radiation are outlined.Comment: 16 pages, 6 figures. v2: minor changes, references added. v3: minor changes, more references added. v4: version to appear in IJMPD. v5: DOI and journal reference adde

Inheritance of signs of «many-flowered» common wheat and evaluation of productivity of the spike of F2 hybrids

Parameters of spike productivity in plants varieties Novosibirskaya 67 (N67), Saratovskaya 29 (S29), Puza-4 and «many-flowered» line Skle 123-09 were assessed in two years with different weather conditions. It was shown that «many-flowered» line Skle 123-09 is significantly higher in the number of grains per spike and number of grains per spikelet than varieties N67, S29 and Puza-4, and that the expression of «many-flowering» depends on the environmental conditions and the genetic background. It was shown that the «many-flowering» is a genetic trait and is therefore workable. A study of hybrids F2 С29×Skle123-09, N67×Skle 123-09, P-4×Skle 123-09 isolated plants with fan-shaped cones and a high number of grains per spikelet as Skle 123-09 and having the best performance of other features as ear varieties recipients. The seeds of these plants will be used to secure «flowering». Two-factor analysis of variance showed that the number of grains per spike knotted depends on growing conditions, genotype and their interaction. Variability of grains per spikelet in drought-resistant varieties of S29 and Puza-4 is mainly dependent on the genotype and, to a lesser extent, on the «genotype×environment» interaction. In variety N67 created for West Siberia, only genotype is a factor. The weight of a grain per ear primarily is primarily affected by «genotype×environment» (almost 60 %), while the influence of «genotype×environmental» was half as strong. The variability of «masse of one grain» in F2 hybrids (S29, P-4×Skle123-09) is influenced by environmental factors, genotype and their interplay. Genotype accounts for the highest impact (> 70 %). F2 hybrids (N67×Skle 123-09) share the greatest variability in the «genotype×environment» interaction (77 %)

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

Protein kinase Cepsilon is important for migration of neuroblastoma cells

<p>Abstract</p> <p>Background</p> <p>Migration is important for the metastatic capacity and thus for the malignancy of cancer cells. There is limited knowledge on regulatory factors that promote the migration of neuroblastoma cells. This study investigates the hypothesis that protein kinase C (PKC) isoforms regulate neuroblastoma cell motility.</p> <p>Methods</p> <p>PKC isoforms were downregulated with siRNA or modulated with activators and inhibitors. Migration was analyzed with scratch and transwell assays. Protein phosphorylation and expression levels were measured with Western blot.</p> <p>Results</p> <p>Stimulation with 12-<it>O</it>-tetradecanoylphorbol-13-acetate (TPA) induced migration of SK-N-BE(2)C neuroblastoma cells. Treatment with the general protein kinase C (PKC) inhibitor GF109203X and the inhibitor of classical isoforms Gö6976 inhibited migration while an inhibitor of PKCβ isoforms did not have an effect. Downregulation of PKCε, but not of PKCα or PKCδ, with siRNA led to a suppression of both basal and TPA-stimulated migration. Experiments using PD98059 and LY294002, inhibitors of the Erk and phosphatidylinositol 3-kinase (PI3K) pathways, respectively, showed that PI3K is not necessary for TPA-induced migration. The Erk pathway might be involved in TPA-induced migration but not in migration driven by PKCε. TPA induced phosphorylation of the PKC substrate myristoylated alanine-rich C kinase substrate (MARCKS) which was suppressed by the PKC inhibitors. Treatment with siRNA oligonucleotides against different PKC isoforms before stimulation with TPA did not influence the phosphorylation of MARCKS.</p> <p>Conclusion</p> <p>PKCε is important for migration of SK-N-BE(2)C neuroblastoma cells. Neither the Erk pathway nor MARCKS are critical downstream targets of PKCε but they may be involved in TPA-mediated migration.</p

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.

Targeting RNS/caveolin-1/MMP signaling cascades to protect against cerebral ischemia-reperfusion injuries: potential application for drug discovery

Reactive nitrogen species (RNS) play important roles in mediating cerebral ischemia-reperfusion injury. RNS activate multiple signaling pathways and participate in different cellular events in cerebral ischemia-reperfusion injury. Recent studies have indicated that caveolin-1 and matrix metalloproteinase (MMP) are important signaling molecules in the pathological process of ischemic brain injury. During cerebral ischemia-reperfusion, the production of nitric oxide (NO) and peroxynitrite (ONOO-), two representative RNS, down-regulates the expression of caveolin-1 (Cav-1) and, in turn, further activates nitric oxide synthase (NOS) to promote RNS generation. The increased RNS further induce MMP activation and mediate disruption of the blood-brain barrier (BBB), aggravating the brain damage in cerebral ischemia-reperfusion injury. Therefore, the feedback interaction among RNS/Cav-1/MMPs provides an amplified mechanism for aggravating ischemic brain damage during cerebral ischemia-reperfusion injury. Targeting the RNS/Cav-1/MMP pathway could be a promising therapeutic strategy for protecting against cerebral ischemia-reperfusion injury. In this mini-review article, we highlight the important role of the RNS/Cav-1/MMP signaling cascades in ischemic stroke injury and review the current progress of studies seeking therapeutic compounds targeting the RNS/Cav-1/MMP signaling cascades to attenuate cerebral ischemia-reperfusion injury. Several representative natural compounds, including calycosin-7-O-β-D-glucoside, baicalin, Momordica charantia polysaccharide (MCP), chlorogenic acid, lutein and lycopene, have shown potential for targeting the RNS/Cav-1/MMP signaling pathway to protect the brain in ischemic stroke. Therefore, the RNS/Cav-1/MMP pathway is an important therapeutic target in ischemic stroke treatment.published_or_final_versio