Solar models and electron screening

We investigate the sensitivity of the solar model to changes in the nuclear reaction screening factors. We show that the sound speed profile as determined by helioseismology certainly rules out changes in the screening factors exceeding more than 10%. A slightly improved solar model could be obtained by enhancing screening by about 5% over the Salpeter value. We also discuss how envelope properties of the Sun depend on screening, too. We conclude that the solar model can be used to help settling the on-going dispute about the ``correct'' screening factors.Comment: accepted for publication by Astron. Astrophy

Factors associated with depressive mood at the onset of multiple sclerosis - an analysis of 781 patients of the German NationMS cohort

BACKGROUND: Depression has a major impact on the disease burden of multiple sclerosis (MS). Analyses of overlapping MS and depression risk factors [smoking, vitamin D (25-OH-VD) and Epstein-Barr virus (EBV) infection] and sex, age, disease characteristics and neuroimaging features associated with depressive symptoms in early MS are scarce. OBJECTIVES: To assess an association of MS risk factors with depressive symptoms within the German NationMS cohort. DESIGN: Cross-sectional analysis within a multicenter observational study. METHODS: Baseline data of n = 781 adults with newly diagnosed clinically isolated syndrome or relapsing-remitting MS qualified for analysis. Global and region-specific magnetic resonance imaging (MRI)-volumetry parameters were available for n = 327 patients. Association of demographic factors, MS characteristics and risk factors [sex, age, smoking, disease course, presence of current relapse, expanded disability status scale (EDSS) score, fatigue (fatigue scale motor cognition), 25-OH-VD serum concentration, EBV nuclear antigen-1 IgG (EBNA1-IgG) serum levels] and depressive symptoms (Beck Depression Inventory-II, BDI-II) was tested as a primary outcome by multivariable linear regression. Non-parametric correlation and group comparison were performed for associations of MRI parameters and depressive symptoms. RESULTS: Mean age was 34.3 years (95% confidence interval: 33.6-35.0). The female-to-male ratio was 2.3:1. At least minimal depressive symptoms (BDI-II > 8) were present in n = 256 (32.8%), 25-OH-VD deficiency (<20 ng/ml) in n = 398 (51.0%), n = 246 (31.5%) participants were smokers. Presence of current relapse [coefficient (c) = 1.48, p = 0.016], more severe fatigue (c = 0.26, p < 0.0001), lower 25-OH-VD (c = -0.03, p = 0.034) and smoking (c = 0.35, p = 0.008) were associated with higher BDI-II scores. Sex, age, disease course, EDSS, month of visit, EBNA1-IgG levels and brain volumes at baseline were not. CONCLUSION: Depressive symptoms need to be assessed in early MS. Patients during relapse seem especially vulnerable to depressive symptoms. Contributing factors such as fatigue, vitamin D deficiency and smoking, could specifically be targeted in future interventions and should be investigated in prospective studies

Stellar evolution models with overshooting based on 3-equation non-local theories - I. Physical basis and the computation of the dissipation rate

Context. Convective overshoot mixing is a critical ingredient of stellar structure models but is treated in most cases by ad hoc extensions of the mixing-length theory for convection. Advanced theories that are both more physical and numerically treatable are needed.Aims. Convective flows in stellar interiors are highly turbulent. This poses a number of numerical challenges for the modelling of convection in stellar interiors. We included an effective turbulence model in a 1D stellar evolution code in order to treat non-local effects within the same theory.Methods. We used a turbulent convection model that relies on the solution of second order moment equations. We implemented this into a state-of-the-art 1D stellar evolution code. To overcome a deficit in the original form of the model, we took the dissipation due to buoyancy waves in the overshooting zone into account.Results. We compute stellar models of intermediate mass main-sequence stars of between 1.5 and 8 M⊙. Overshoot mixing from the convective core and modified temperature gradients within and above it emerge naturally as a solution of the turbulent convection model equations.Conclusions. For a given set of model parameters, the overshooting extent determined from the turbulent convection model is comparable to other overshooting descriptions, the free parameters of which had been adjusted to match observations. The relative size of the mixed cores decreases with decreasing stellar mass without additional adjustments. We find that the dissipation by buoyancy waves constitutes a necessary and relevant extension of the turbulent convection model in use

Laparoscopic neurolysis of the sacral plexus and the sciatic nerve for extensive endometriosis of the pelvic wall

Background: The aim of this study is to report on the feasibility of laparoscopic neurolysis of the plexus sacralis and the sciatic nerve in deep endometriotic infiltration of the lateral pelvic wall. Methods: A transperitoneal approach to the pelvic nerves combined with the LANN technique for intraoperative assessment of the function of the exposed nerves permit exposure and sparing of all somatic nerves during resection of the endometriotic lesion. Results: We report on our short experience with 21 patients who underwent this technique for the treatment of endometriotic infiltration of the sacral plexus at different levels. Conclusion: In young patients with chronic unilateral sciatica or unilateral pudendal neuralgia - Alcock's canal syndrome - where no neurological/orthopedic etiologies have been found, endometriotic infiltration of the lateral pelvic wall has to be implicated as a potential etiology and an indication for laparoscopy must be discussed. Laparoscopic neurolysis of the pelvic somatic nerves is a feasible procedure for trained laparoscopic surgeons who have a good knowledge of the retroperitoneal pelvic (neuro)anatomy. © Georg Thieme Verlag KG Stuttgart