Stability of planar shear flow in the presence of electro-convectioncross-flow is presented. Emphasis is put on understanding

International audienceThe first complete study of linear, modal and non-modal stability of the EHD electroconvection problem with and without how electroconvection changes the stability characteristics of the plane Poiseuille flow

Linear stability of Poiseuille flow over a steady spanwise Stokes layer

The temporal linear stability of plane Poiseuille flow modified by spanwise forcing applied at the walls is considered. The forcing consists of a stationary streamwise distribution of spanwise velocity that generates a steady transversal Stokes layer, known to reduce skin-friction drag in a turbulent flow with little energetic cost. A large numerical study is carried out, where the effects of both the physical and the discretization parameters are thoroughly explored, for three representative subcritical values of the Reynolds number Re. Results show that the spanwise Stokes layer significantly affects the linear stability of the system. For example, at Re=2000 the wall forcing is found to more than double the negative real part of the least-stable eigenvalue, and to decrease by nearly a factor of 4 the maximum transient growth of perturbation energy. These observations are Re dependent and further improve at higher Re. Comments on the physical implications of the obtained results are provided, suggesting that spanwise forcing might be effective to obtain at the same time a delayed transition to turbulence and a reduced turbulent friction

Linear stability of Poiseuille flow over a steady spanwise Stokes layer

The temporal linear stability of plane Poiseuille flow modified by spanwise forcing applied at the walls is considered. The forcing consists of a stationary streamwise distribution of spanwise velocity that generates a steady transversal Stokes layer, known to reduce skin-friction drag in a turbulent flow with little energetic cost. A large numerical study is carried out, where the effects of both the physical and the discretization parameters are thoroughly explored, for three representative subcritical values of the Reynolds number Re. Results show that the spanwise Stokes layer significantly affects the linear stability of the system. For example, at Re=2000 the wall forcing is found to more than double the negative real part of the least-stable eigenvalue, and to decrease by nearly a factor of four the maximum transient growth of perturbation energy. These observations are Re-dependent and further improve at higher $Re$. Comments on the physical implications of the obtained results are provided, suggesting that spanwise forcing might be effective to obtain at the same time a delayed transition to turbulence and a reduced turbulent friction.Comment: Under consideration by PR

Modal and nonmodal stability analysis of electrohydrodynamic flow with and without cross-flow

We report the results of a complete modal and nonmodal linear stability analysis of the electrohydrodynamic flow (EHD) for the problem of electroconvection in the strong injection region. Convective cells are formed by Coulomb force in an insulating liquid residing between two plane electrodes subject to unipolar injection. Besides pure electroconvection, we also consider the case where a cross-flow is present, generated by a streamwise pressure gradient, in the form of a laminar Poiseuille flow. The effect of charge diffusion, often neglected in previous linear stability analyses, is included in the present study and a transient growth analysis, rarely considered in EHD, is carried out. In the case without cross-flow, a non-zero charge diffusion leads to a lower linear stability threshold and thus to a more unstable low. The transient growth, though enhanced by increasing charge diffusion, remains small and hence cannot fully account for the discrepancy of the linear stability threshold between theoretical and experimental results. When a cross-flow is present, increasing the strength of the electric field in the high-$Re$ Poiseuille flow yields a more unstable flow in both modal and nonmodal stability analyses. Even though the energy analysis and the input-output analysis both indicate that the energy growth directly related to the electric field is small, the electric effect enhances the lift-up mechanism. The symmetry of channel flow with respect to the centerline is broken due to the additional electric field acting in the wall-normal direction. As a result, the centers of the streamwise rolls are shifted towards the injector electrode, and the optimal spanwise wavenumber achieving maximum transient energy growth increases with the strength of the electric field

Thrombotic microangiopathies during pregnancy : The obstetrical and neonatal perspective

Thrombotic Microangiopathies during pregnancy and puerperium are very rare and, if undiagnosed, can be lifethreating. Pregnancy and postpartum can represent a trigger in predisposed patients. Therefore, obstetricians are usually the first to observe clinical symptoms and laboratory abnormalities suggestive of Thrombotic Microangiopathies. The aim of this review is to briefly describe the obstetrical and perinatal outcome of these entities and highlight the clues for a correct diagnosis of pregnancy-related Thrombotic Microangiopathies. (C) 2019 Elsevier B.V. All rights reserved.Peer reviewe

Low molecular weight heparin use during pregnancy and risk of postpartum hemorrhage: a systematic review and meta-analysis

INTRODUCTION: Postpartum hemorrhage (PPH) is the leading cause of maternal mortality worldwide with a prevalence rate of approximately 6%. Although most cases of PPH have no identifiable risk factors, the incidence of PPH has been associated to the thromboprophylaxis in pregnancy with low molecular weight heparin (LMWH). Thus, the aim of the study is to evaluate the risk of PPH in cases of pregnant women exposed to LMWH. MATERIALS AND METHODS: Electronic research was performed in OVID, Scopus, ClinicalTrials.gov, MEDLINE, the PROSPERO International Prospective Register of Systematic Reviews, EMBASE, and the Cochrane Central Register of Controlled Trials through April 2016. We included randomized controlled trials, cohort and case-control studies of women who underwent thromboprophylaxis with LMWH during pregnancy compared to a control group (either placebo or no treatment). The primary outcome was the incidence of PPH. The summary measures were reported as relative risk (RR) or as mean differences (MD) with 95% confidence interval (CI). RESULTS: Eight studies including 22,162 women were analyzed. Of the 22,162 women, 1320 (6%) were administered LMWH, 20,842 (94%) women formed the nonexposed group (control group). Women treated with LMWH had a higher risk of PPH (RR 1.45, 95%CI 1.02-2.05) compared to controls; there was no difference in mean of blood loss at delivery (MD -32.90, 95%CI 68.72-2.93) and in risk of blood transfusion at delivery (RR 1.24, 95%CI 0.62-2.51), respectively. CONCLUSIONS: Women who receive LMWH during pregnancy have a significantly higher risk of developing PPH. Women who receive LMWH during pregnancy have neither significantly higher mean blood loss at delivery nor higher risk of blood transfusion

Risk of preeclampsia in of women who underwent chorionic villus sampling

OBJECTIVE: To assess the risk of preeclampsia in women who underwent chorionic villus sampling (CVS). STUDY DESIGN: This is a retrospective, single-center, cohort study. All consecutive singleton gestations who underwent chorionic villus sampling from January 2014 to January 2016 were included in the study. The primary outcome was the incidence of preeclampsia. Subgroup analysis in women with beta thalassemic trait was performed. Logistic regression, presented as adjusted odds ratio (aOR) with the 95% of confidence interval (CI), was performed. RESULTS: Five hundred forty-seven women who underwent CVS, and 1532 women who did not were analyzed. Women who underwent CVS had a significantly lower risk of preeclampsia (4.4 versus 8.0%; aOR 0.53, 95%CI 0.34-0.83), and late-onset preeclampsia (3.3 versus 6.1%; aOR 0.52, 95%CI 0.31-0.87). No statistically significant differences were found in preeclampsia with severe features, early-onset preeclampsia, and preterm birth (PTB). Women who underwent CVS due to thalassemic trait had a lower incidence of preeclampsia compare to those women who did not undergo CVS (3.3 versus 8.0%; aOR 0.39, 95%CI 0.14-0.87), while no differences were found comparing women who underwent CVS due to thalassemic trait with women who underwent CVS due to other reasons. CONCLUSIONS: Women who underwent first trimester CVS had a lower risk of preeclampsia compared to those who did not

Effects of exercise during pregnancy in women with short cervix: Secondary analysis from the Italian Pessary Trial in singletons

OBJECTIVE: To evaluate effects of exercise during pregnancy in asymptomatic singleton pregnancies without prior spontaneous preterm birth (SPTB) but with short transvaginal ultrasound cervical length (TVU CL). STUDY DESIGN: This is a secondary analysis of the Italian Pessary Trial for the Italian Preterm Birth Prevention (IPP) Working Group. In the original prospective randomized controlled trial asymptomatic singleton pregnancies without prior SPTB but with TVU CL ≤ 25 mm at 18 0/6-23 6/7 weeks were randomized into 1:1 ratio to either cervical pessary or no pessary. During their follow-up visits, women were asked about their activity. For the purpose of this secondary analysis, women were classified in the following groups, using the information obtained in the follow-up visit one month after randomization: 1) Exercise group, defined as women performing exercise ≥2 days a week for ≥20 min each day. 2) No exercise group, defined as women performing exercise <2 days a week for ≥20 min each day. The primary outcome of this secondary analysis was PTB < 37 weeks. RESULTS: 300 women were included in this analysis. 99 (33.0%) were included in the exercise group. 201 (67.0%) were included in the no exercise group. Of the 201 women in the no exercise group, 90 (44.8%) affirmed that they had reduced their activity after the diagnosis of short cervix despite the research staff recommendations, while the other 111 (55.2%) women performed a sedentary life style even before the diagnosis of short cervix. PTB < 37 weeks occurred in 22 women (22.2%) in the exercise group, and 66 women (32.8%) in the no exercise group (aOR 0.65, 95% CI 0.33-1.03). CONCLUSION: In asymptomatic singleton pregnancies with short cervix, performing exercise ≥2 days a week for ≥20 min each day does not increase the risk of PTB but is indeed associated with a non-significant reduction in PTB < 37 weeks by 32%

Mast Cells in Peritoneal Fluid From Women With Endometriosis and Their Possible Role in Modulating Sperm Function

Endometriosis is a local pelvic inflammatory process, frequently associated with infertility, with altered function of immune-related cells in the peritoneal environment. Mast cells are known to be key players of the immune system and have been recently involved in endometriosis and in infertility, with their mediators directly suppressing sperm motility. In this study, we evaluated the mast cell population and their mediators in the peritoneal fluid of infertile patients with endometriosis and their impact on human sperm motility. Peritoneal fluids, collected by laparoscopy from 11 infertile patients with endometriosis and 9 fertile controls were evaluated for the presence of mast cells, tryptase levels and their effect on sperm motility. Furthermore, an in vitro model of mast cells-sperm interaction in peritoneal fluid was set up, using LAD2 cell line as a mast cell model, and analyzed from a functional as well as a morphological point of view. Mast cell peritoneal fluid population and its main mediator, tryptase, is more represented in endometriosis confirming an involvement of these cells in this disease. Anyway it appears unlikely that tryptase enriched peritoneal fluid, which fails to inhibit sperm motility, could contribute to endometriosis associated infertility. Despite of this, sperm interaction with the mast cell surface (LAD2) induced a significantly mast cell-degranulation response in the peritoneal fluid from endometriosis which could directly modulate sperm function other than motility. This evidence lead us to suppose that there is, between these elements, an interrelationship which deserves further studies

Incidence of toxoplasmosis in pregnancy in Campania: A population-based study on screening, treatment, and outcome

INTRODUCTION: The aim of this study was to evaluate the incidence of toxoplasmosis infection during pregnancy and to describe the characteristics of the serological status, management, follow-up and treatment. MATERIAL AND METHODS: This is a population-based cohort study of women referred for suspected toxoplasmosis during pregnancy from January, 2001 to December, 2012. Suspected toxoplasmosis was defined as positive IgM antibody during pregnancy. Women with suspected toxoplasmosis during pregnancy were classified into three groups: seroconversion, suspected infection, or no infection in pregnancy. Women in the first and second group were treated according to local protocol, and amniocentesis with toxoplasmosis PCR detection and serial detailed ultrasound scans were offered. Neonates were investigated for congenital toxoplasmosis at birth and were monitored for at least one year after birth. RESULTS: During the study period, there were 738,588 deliveries in Campania. Of them 1159 (0.2%) were referred to our Institution for suspected toxoplasmosis during pregnancy: 183 (15.8%) women were classified as seroconversion, 381 (32.9%) were suspected infection, and 595 (51.3%) were not infected in pregnancy. Neonatal outcome was available for 476 pregnancies, including 479 neonates (3 twins, 473 singletons), out of the 564 pregnancies with seroconversion or suspected infection. 384 (80.2%) babies were not infected at birth and at follow-up, 67 (14.0%) had congenital toxoplasmosis, 10 (2.1%) were voluntary induced termination of pregnancy, 15 (3.1%) were spontaneous miscarriage, and 4 (0.8%) were stillbirth (of which one counted already in the infected cohort). Considering cases of congenital toxoplasmosis, the transmission rate in women with seroconversion was 32.9% (52/158), and in women with suspected infection was 4.7% (15/321). CONCLUSIONS: Toxoplasmosis is uncommon in pregnancy with overall incidence of seroconversion and suspected infection in pregnancy of 0.8 per 1000 live births and incidence of congenital toxoplasmosis 0.1 per 1000 live births when applying a strict protocol of screening, follow-up, and treatment. 51.3% (595/1159) of women referred to our center for suspected infection were actually considered not infected