Purely radiative irrotational dust spacetimes

We consider irrotational dust spacetimes in the full non-linear regime which are "purely radiative" in the sense that the gravitational field satisfies the covariant transverse conditions div(H) = div(E) = 0. Within this family we show that the Bianchi class A spatially homogeneous dust models are uniquely characterised by the condition that $H$ is diagonal in the shear-eigenframe.Comment: 6 pages, ERE 2006 conference, minor correction

Purely radiative perfect fluids with degenerate shear tensor

We consider non-rotating geodesic perfect fluid spacetimes which are purely radiative in the sense that the gravitational field satisfies the covariant transverse conditions div H = div E = 0. We show that when the shear tensor S is degenerate, H, E and S necessarily commute and hence the resulting spacetimes are hypersurface homogeneous of Bianchi class A (modulo some purely electric exceptions).Comment: 8 pages, references added, typos corrected, simplified some algebraic manipulation

Effects of Synaptic and Myelin Plasticity on Learning in a Network of Kuramoto Phase Oscillators

Models of learning typically focus on synaptic plasticity. However, learning is the result of both synaptic and myelin plasticity. Specifically, synaptic changes often co-occur and interact with myelin changes, leading to complex dynamic interactions between these processes. Here, we investigate the implications of these interactions for the coupling behavior of a system of Kuramoto oscillators. To that end, we construct a fully connected, one-dimensional ring network of phase oscillators whose coupling strength (reflecting synaptic strength) as well as conduction velocity (reflecting myelination) are each regulated by a Hebbian learning rule. We evaluate the behavior of the system in terms of structural (pairwise connection strength and conduction velocity) and functional connectivity (local and global synchronization behavior). We find that for conditions in which a system limited to synaptic plasticity develops two distinct clusters both structurally and functionally, additional adaptive myelination allows for functional communication across these structural clusters. Hence, dynamic conduction velocity permits the functional integration of structurally segregated clusters. Our results confirm that network states following learning may be different when myelin plasticity is considered in addition to synaptic plasticity, pointing towards the relevance of integrating both factors in computational models of learning.Comment: 39 pages, 15 figures This work is submitted in Chaos: An Interdisciplinary Journal of Nonlinear Scienc

Purely radiative perfect fluids

We study `purely radiative' (div E = div H = 0) and geodesic perfect fluids with non-constant pressure and show that the Bianchi class A perfect fluids can be uniquely characterized --modulo the class of purely electric and (pseudo-)spherically symmetric universes-- as those models for which the magnetic and electric part of the Weyl tensor and the shear are simultaneously diagonalizable. For the case of constant pressure the same conclusion holds provided one also assumes that the fluid is irrotational.Comment: 12 pages, minor grammatical change

Increasing the number of embryos transferred from two to three, does not increase pregnancy rates in good prognosis patients

Background: To compare the pregnancy outcomes after two embryos versus three embryos transfers (ETs) in women undergoing in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles. Materials and Methods: This retrospective study was performed on three hundred eighty seven women with primary infertility and with at least one fresh embryo in good quality in order to transfer at each IVF/ICSI cycle, from September 2006 to June 2010. Patients were categorized into two groups according to the number of ET as follows: ET2 and ET3 groups, indicating two and three embryos were respectively transferred. Pregnancy outcomes were compared between ET2 and ET3 groups. Chi square and student t tests were used for data analysis. Results: Clinical pregnancy and live birth rates were similar between two groups. The rates of multiple pregnancies were 27 and 45.2 in ET2 and ET3 groups, respectively. The rate of multiple pregnancies in young women was significantly increased when triple instead of double embryos were transferred. Logistic regression analysis indicated two significant prognostic variables for live birth that included number and quality of transferred embryos; it means that the chance of live birth following ICSI treatment increased 3.2-fold when the embryo with top quality (grade A) was transferred, but the number of ET had an inverse relationship with live birth rate; it means that probability of live birth in women with transfer of two embryos was three times greater than those who had three ET. Conclusion: Due to the difficulty of implementation of the elective single-ET technique in some infertility centers in the world, we suggest transfer of double instead of triple embryos when at least one good quality embryo is available for transfer in women aged 39 years or younger. However, to reduce the rate of multiple pregnancies, it is recommended to consider the elective single ET strategy. � 2015, Royan Institute (ACECR). All rights reserved

Diagnostic value of D-dimer�s serum level in Iranian patients with cerebral venous thrombosis

Cerebral venous thrombosis (CVT) is a longterm debilitating vascular brain disease with high morbidity and mortality. It may be associated with rise in D-dimer level. The aim of this study was to examine this potential association and identify the critical D-dimer cut-off level corresponding to increase the risk of CVT. This case-control study was conducted on two groups of patients with and without CVT attending the Rasool Akram Hospital (Iran) during 2014 and 2015. D-dimer levels were measured by the rapid sensitive D-dimer assay. Data were analyzed by Spearman�s correlation coefficient test, independent-samples t-test, backward-selection multiple linear regression and multiple binary logistic regression analyses. Sensitivity-specificity tests were used to detect D-dimer cut-off for CVT. Differences between the D-dimer levels of the case and control groups were significant (P<0.001). It showed that each level of increase in the number of symptoms could increase the risk of thrombosis occurrence for about 3.5 times. All symptom types except for headache were associated with D-dimer level, while headache has negative association with D-dimer level. D-dimer cut-off point for CVT diagnosis was estimated at 350 ng/mg. We concluded that D-dimer serum level significantly rises in CVT patients. A rounded cut-off point of 350 ng/mg can be used as a diagnostic criterion for CVT prediction. © L. Hashami et al., 2016

The effect of six weeks yoga exercises on quality of life in infertile women with polycystic ovary syndrome (Pcos)

Introduction: Infertility is one of the main concerns of human societies and PCOS is considered as the most common reason of women's infertility due to ovulation disorders. Infertility has been considered as the main cause of psychopathy disorders and reduced quality of life in PCOS patients. Exercise is a non-pharmaceutical method in treatment of PCOS that yoga is a recommended exercise for this disease. This study was performed with aim to determine the effect of 6 weeks yoga on the quality of life in infertile women with PCOS. Methods: This clinical randomized trial was performed on 61 infertile women with PCOS undergoing infertility treatment referred to the Tehran Sarem Hospital in 2015-2015. The qualified subjects were divided to two groups of case and control. Then, all the subjects completed the demographic profile and fertility questionnaires and modified PCOS questionnaire. Then, the case group performed yoga for 6 weeks and the control group did not receive any intervention. After 6 weeks, the questionnaires were again completed. Data were analyzed by SPSS software (version 21) and independent t-test, paired t-test, Mann-Whitney, Chi-square, Mac-Nemar, and Wilcoxon test. P<0.05 was considered statistically significant Results: Yoga exercise for 6 weeks had significant effect on the scores of quality of life and Hirsotism (p=0.001), weight (p= 0.010), Acnea (p= 0.001), infertility (p= 0.001), Emotional (p<0.001), menstrual disorders (p<0.001) and total score (p<0.001). Conclusion: Yoga as a meditation exercise for 6 weeks can improve the score of quality of life in women with PCOS undergoing infertility treatment. Therefore, this exercise as an effective and low-cost method can be used for improvement of life quality in these women. © 2019, Mashhad University of Medical Sciences. All rights reserved

Detailed investigation of downstream TLR signaling in the follicular cells of women with endometriosis

Background: Inflammatory responses within the peritoneal cavity may result in endometrial dysfunction in women with endometriosis. The true causes of this disease remain poorly understood. It is hypothesized that downstream toll-like receptors (TLRs) inflammatory cytokines in response to pathogens may be associated with endometriosis. So, this study was aimed at evaluating the expression of TLRs signaling and endometriosis-associated inflammatory responses. Methods: Totally, 20 infertile endometriosis patients and 20 normal women undergoing controlled ovarian stimulation were enrolled. The cellular pellet and supernatant were obtained by centrifugation of follicular fluid (FF). Evaluation of TLRs and their signaling pathway gene expression was performed on cellular pellets using quantitative-PCR. The supernatant was used for determination of cytokine protein expression by ELISA. The results are expressed as mean±SEM and a p<0.05 was considered statistically significant. Results: Quantitative-PCR analysis suggested that TLR1, 5, 6, 7, 8, 10, MYD88, NF-ĸB, IL-10 and TGF-β genes expression significantly increased in patients compared to the control group (p<0.05). TLR3, 9, INF-β genes expression was significantly lower in endometriosis than control group (p<0.05). There was no significant difference in the expression of TLR2, TLR4, TIRAP, TRIF, TRAM, and IRF3 between two groups. Also, significant increase in the levels of IL-6, IL-8 and MIF protein in FF of endometriosis group was detected in comparison with normal women (p<0.05). Conclusion: The expression of TLR downstream signaling in the follicular cells can initiate inflammatory responses and changes in the FF cytokine profile which in turn may induce endometriosis and infertility disorder. © 2020 Avicenna Research Institute. All rights reserved

Magnetic sensing for microstructural assessment of power station steels: magnetic Barkhausen noise and minor loop measurements

There are currently no techniques available to monitor the microstructural condition of power station steel components in-service (at elevated temperatures). Electromagnetic (EM) inspection methods have the potential to provide a solution to this problem. Tests have been carried out on power generation steel (P9 and T22) samples with different microstructural states using major and minor B-H loop measurements and correlations established between EM properties and material properties such as Vickers hardness. These correlations will be used to develop a field deployable tool for the quantification of degradation in power station steels