On Nonlocal Modified Gravity and its Cosmological Solutions

During hundred years of General Relativity (GR), many significant gravitational phenomena have been predicted and discovered. General Relativity is still the best theory of gravity. Nevertheless, some (quantum) theoretical and (astrophysical and cosmological) phenomenological difficulties of modern gravity have been motivation to search more general theory of gravity than GR. As a result, many modifications of GR have been considered. One of promising recent investigations is Nonlocal Modified Gravity. In this article we present a brief review of some nonlocal gravity models with their cosmological solutions, in which nonlocality is expressed by an analytic function of the d'Alembert-Beltrami operator $\Box$. Some new results are also presented.Comment: 16 page

Nonlocal de Sitter gravity and its exact cosmological solutions

This paper is devoted to a simple nonlocal de Sitter gravity model and its exact vacuum cosmological solutions. In the Einstein-Hilbert action with $\Lambda$ term, we introduce nonlocality by the following way: $R - 2 \Lambda = \sqrt{R-2\Lambda}\ \sqrt{R-2\Lambda} \to \sqrt{R-2\Lambda}\ F(\Box)\ \sqrt{R-2\Lambda} ,$where${F} (\Box) = 1 + \sum_{n= 1}^{+\infty} \big( f_n \Box^n + f_{-n} \Box^{-n} \big) $is an analytic function of the d'Alembert-Beltrami operator$\Box$and its inverse$\Box^{-1}$. By this way,$R$and$\Lambda$enter with the same form into nonlocal version as they are in the local one, and nonlocal operator$F(\Box)$is dimensionless. The corresponding equations of motion for gravitational field$g_{\mu\nu}$are presented. The first step in finding some exact cosmological solutions is solving the equation$\Box \sqrt{R-2\Lambda} = q \sqrt{R-2\Lambda} , $where$ q =\zeta \Lambda \quad (\zeta \in \mathbb{R})$is an eigenvalue and$\sqrt{R-2\Lambda}$is an eigenfunction of the operator$\Box .$ We presented and discussed several exact cosmological solutions for homogeneous and isotropic universe. One of these solutions mimics effects that are usually assigned to dark matter and dark energy. Some other solutions are examples of the nonsingular bounce ones in flat, closed and open universe. There are also singular and cyclic solutions. All these cosmological solutions are a result of nonlocality and do not exist in the local de Sitter case.Comment: 27 pages, 5 figures. Comments welcom

О нелокальной модифицированной гравитации

In the last hundred years many significant gravitational phenomena have been predicted anddiscovered by General Relativity (GR), which is still the best theory of gravity. Nevertheless,due to the great observational discoveries of 20th century some (quantum) theoretical and(astrophysical and cosmological) phenomenological difficulties of modern gravity have beenmotivation to search more general theory of gravity than GR. As a result, many modificationsof GR have been considered. One of promising recent investigations is Nonlocal ModifiedGravity. In this article we present a review of some nonlocal gravity models with theirexact cosmological solutions, in which nonlocality is expressed by an analytic function of thed’Alembert–Beltrami operator. Some of obtained solutions contain effects which are usuallyassigned to the dark matter and dark energy.За последние сто лет многие существенные гравитационные явления были предсказаны и обнаружены Общей теорией относительности (GR), которая до сих пор остается лучшей теорией гравитации. Тем не менее, из-за великих наблюдательных открытий 20-го века некоторые (квантовые) теоретические и (астрофизические и космологические) феноменологические трудности современной гравитации были мотивацией для поиска болееобщей теории гравитации, чем ОТО. В результате были рассмотрены многие модификации ТО. Одним из многообещающих недавних исследований является нелокальная модифицированная гравитация. В этой статье мы представляем обзор некоторых нелокальных гравитационных моделей с их точными космологическими решениями, в которых нелокальность выражается аналитической функцией от оператора Даламбера — Бельтрами. Некоторые из полученных решений содержат эффекты, которые обычно присваиваютсятемной материи и темной энергии

Evaluating the Role of LVI as an Indicator for Adverse Outcomes in Patients with Upper Tract Urothelial Carcinoma and its Histological Subtypes

Lymphvascular invasion (LVI) is recognized as an adverse prognostic factor in many cancers. Our aim is to assess the prognostic ability of LVI in UTUC urothelial carcinoma (UC) and micropapillary urothelial carcinoma (MPUC) subtypes as a predictor of overall survival (OS) using a large North American cohort. Our cohort included 9750 cM0 UTUC patients who underwent a radical nephroureterectomy (RNU), between 2004 and 2015, within the National Cancer Database (NCDB). The main variable of interest was LVI status, and its interaction with pathological nodal (pN) status. Kaplan-Meier curves were used to estimate the OS. Cox regression analysis tested the impact of LVI status on OS after accounting for covariates. In patients with UC at 5-years post-RNU, the OS rates were 60.2%, 29.9%, 28.9%, and 20.8% in patient with pN0 without LVI, pN0 with LVI, pN+ without LVI, and pN+ with LVI, respectively (p Our report is the first to examine the impact of LVI on OS in a large North American nationwide cohort. It indicates that LVI is associated with reduced OS in patients with UTUC treated surgically

Review of retrospective dosimetry techniques for external ionising radiation exposures

The current focus on networking and mutual assistance in the management of radiation accidents or incidents has demonstrated the importance of a joined-up approach in physical and biological dosimetry. To this end, the European Radiation Dosimetry Working Group 10 on 'Retrospective Dosimetry' has been set up by individuals from a wide range of disciplines across Europe. Here, established and emerging dosimetry methods are reviewed, which can be used immediately and retrospectively following external ionising radiation exposure. Endpoints and assays include dicentrics, translocations, premature chromosome condensation, micronuclei, somatic mutations, gene expression, electron paramagnetic resonance, thermoluminescence, optically stimulated luminescence, neutron activation, haematology, protein biomarkers and analytical dose reconstruction. Individual characteristics of these techniques, their limitations and potential for further development are reviewed, and their usefulness in specific exposure scenarios is discussed. Whilst no single technique fulfils the criteria of an ideal dosemeter, an integrated approach using multiple techniques tailored to the exposure scenario can cover most requirements. © The Author 2010. Published by Oxford University Press. All rights reserved

Aneuploidy and Confined Chromosomal Mosaicism in the Developing Human Brain

BACKGROUND: Understanding the mechanisms underlying generation of neuronal variability and complexity remains the central challenge for neuroscience. Structural variation in the neuronal genome is likely to be one important mechanism for neuronal diversity and brain diseases. Large-scale genomic variations due to loss or gain of whole chromosomes (aneuploidy) have been described in cells of the normal and diseased human brain, which are generated from neural stem cells during intrauterine period of life. However, the incidence of aneuploidy in the developing human brain and its impact on the brain development and function are obscure. METHODOLOGY/PRINCIPAL FINDINGS: To address genomic variation during development we surveyed aneuploidy/polyploidy in the human fetal tissues by advanced molecular-cytogenetic techniques at the single-cell level. Here we show that the human developing brain has mosaic nature, being composed of euploid and aneuploid neural cells. Studying over 600,000 neural cells, we have determined the average aneuploidy frequency as 1.25-1.45% per chromosome, with the overall percentage of aneuploidy tending to approach 30-35%. Furthermore, we found that mosaic aneuploidy can be exclusively confined to the brain. CONCLUSIONS/SIGNIFICANCE: Our data indicates aneuploidization to be an additional pathological mechanism for neuronal genome diversification. These findings highlight the involvement of aneuploidy in the human brain development and suggest an unexpected link between developmental chromosomal instability, intercellural/intertissular genome diversity and human brain diseases