Two-dimensional Stellar Evolution Code Including Arbitrary Magnetic Fields. I. Mathematical Techniques and Test Cases

A high-precision two-dimensional stellar evolution code has been developed for studying solar variability due to structural changes produced by varying internal magnetic fields of arbitrary configurations. Specifically, we are interested in modeling the effects of a dynamo-type field on the detailed internal structure and on the global parameters of the Sun. The high precision is required to model both very small solar changes (of the order of 10-4) and short timescales (of the order of 1 yr). It is accomplished by using the mass coordinate to replace the radial coordinate, by using fixed and adjustable time steps, a realistic stellar atmosphere, and element diffusion, and by adjusting the grid points. We have also built into the code the potential to subsequently include rotation and turbulence. The current code has been tested for several cases, including its ability to reproduce the one-dimensional results

Two-Dimensional Stellar Evolution Code Including Arbitrary Magnetic Fields. II. Precision Improvement and Inclusion of Turbulence and Rotation

In the second paper of this series we pursue two objectives. First, in order to make the code more sensitive to small effects, we remove many approximations made in Paper I. Second, we include turbulence and rotation in the two-dimensional framework. The stellar equilibrium is described by means of a set of five differential equations, with the introduction of a new dependent variable, namely the perturbation to the radial gravity, that is found when the non-radial effects are considered in the solution of the Poisson equation; following the scheme of the first paper, we write the equations in such a way that the two-dimensional effects can be easily disentangled. The key concept introduced in this series is the equipotential surface. We use the underlying cause-effect relation to develop a recurrence relation to calculate the equipotential surface functions for uniform rotation, differential rotation, rotation-like toroidal magnetic fields and turbulence. We also develop a more precise code to numerically solve the two-dimensional stellar structure and evolution equations based on the equipotential surface calculations. We have shown that with this formulation we can achieve the precision required by observations by appropriately selecting the convergence criterion. Several examples are presented to show that the method works well. Since we are interested in modeling the effects of a dynamo-type field on the detailed envelope structure and global properties of the Sun, the code has been optimized for short timescales phenomena (down to 1 yr). The time dependence of the code has so far been tested exclusively to address such problems.Comment: 56 pages, 8 figures, submitted to ApJ

Increased rate of abdominal surgery both before and after diagnosis of celiac disease

BACKGROUND: The detection of celiac disease (CD) is suboptimal. AIMS: We hypothesized that misdiagnosis is leading to diagnostic delays, and examine this assertion by determining if patients have increased risk of abdominal surgery before CD diagnosis. METHODS: Through biopsy reports from Sweden's 28 pathology departments we identified all individuals with CD (Marsh stage 3; n=29,096). Using hospital-based data on inpatient and outpatient surgery recorded in the Swedish Patient Register, we compared abdominal surgery (appendectomy, laparotomy, biliary tract surgery, and uterine surgery) with that in 144,522 controls matched for age, sex, county and calendar year. Conditional logistic regression estimated odds ratios (ORs). RESULTS: 4064 (14.0%) individuals with CD and 15,760 (10.9%) controls had a record of earlier abdominal surgery (OR=1.36, 95% CI=1.31-1.42). Risk estimates were highest in the first year after surgery (OR=2.00; 95% CI=1.79-2.22). Appendectomy, laparotomy, biliary tract surgery, and uterine surgery were all associated with having a later CD diagnosis. Of note, abdominal surgery was also more common after CD diagnosis (hazard ratio=1.34; 95% CI=1.29-1.39). CONCLUSIONS: There is an increased risk of abdominal surgery both before and after CD diagnosis. Surgical complications associated with CD may best explain these outcomes. Medical nihilism and lack of CD awareness may be contributing to outcomes