Systematic Study of L-Shell Opacity at Stellar Interior Temperatures.

The first systematic study of opacity dependence on atomic number at stellar interior temperatures is used to evaluate discrepancies between measured and modeled iron opacity [J. E. Bailey et al., Nature (London) 517, 56 (2015)NATUAS0028-083610.1038/nature14048]. High-temperature (>180 eV) chromium and nickel opacities are measured with ±6%-10% uncertainty, using the same methods employed in the previous iron experiments. The 10%-20% experiment reproducibility demonstrates experiment reliability. The overall model-data disagreements are smaller than for iron. However, the systematic study reveals shortcomings in models for density effects, excited states, and open L-shell configurations. The 30%-45% underestimate in the modeled quasicontinuum opacity at short wavelengths was observed only from iron and only at temperature above 180 eV. Thus, either opacity theories are missing physics that has nonmonotonic dependence on the number of bound electrons or there is an experimental flaw unique to the iron measurement at temperatures above 180 eV.

A higher-than-predicted measurement of iron opacity at solar interior temperatures.

Nearly a century ago it was recognized that radiation absorption by stellar matter controls the internal temperature profiles within stars. Laboratory opacity measurements, however, have never been performed at stellar interior conditions, introducing uncertainties in stellar models. A particular problem arose when refined photosphere spectral analysis led to reductions of 30-50 per cent in the inferred amounts of carbon, nitrogen and oxygen in the Sun. Standard solar models using the revised element abundances disagree with helioseismic observations that determine the internal solar structure using acoustic oscillations. This could be resolved if the true mean opacity for the solar interior matter were roughly 15 per cent higher than predicted, because increased opacity compensates for the decreased element abundances. Iron accounts for a quarter of the total opacity at the solar radiation/convection zone boundary. Here we report measurements of wavelength-resolved iron opacity at electron temperatures of 1.9-2.3 million kelvin and electron densities of (0.7-4.0) × 10(22) per cubic centimetre, conditions very similar to those in the solar region that affects the discrepancy the most: the radiation/convection zone boundary. The measured wavelength-dependent opacity is 30-400 per cent higher than predicted. This represents roughly half the change in the mean opacity needed to resolve the solar discrepancy, even though iron is only one of many elements that contribute to opacity.

Ionization balance in inertial confinement fusion hohlraums.

We present the first x-ray spectroscopic measurements of the ionization balance in inertial confinement fusion hohlraums supported by 4omega Thomson scattering diagnostics. The experimental data show agreement with non-LTE radiation-hydrodynamic calculations of the averaged Au charge state and electron temperatures. These findings are consistent with the successful integrated modeling of the hohlraum radiation fields. Comparisons with detailed synthetic spectra calculations show that the experimental ionization distribution is slightly shifted indicating nonsteady state kinetics.

Splenic conservation in the management of large splenic cysts: case report and literature review.

The majority of splenic cysts occur as a result of parasitic infection, most commonly in countries where hydatid disease is endemic. In the Western world however, their occurrence is extremely rare and aetiology less clear. Approximately 800 cases of non-parasitic splenic cysts have been reported in the world literature to date. Their presentation ranges from that of an incidental finding on abdominal examination to catastrophic intraperitoneal haemorrhage. The methods of treatment of splenic cysts are protean with no universally accepted policy. We report a case of a massive splenic cyst in an adolescent female treated by partial splenectomy. We also present a review of the pertinent literature on this subject paying special attention to the role of conservative surgery with preservation of normal splenic tissue.

Low-flow cardiopulmonary bypass produces greater pulmonary dysfunction than circulatory arrest.

BACKGROUND: Deep hypothermic circulatory arrest (DHCA) is used during the repair of congenital heart disease in neonates. However, because of concern about neurologic injury after DHCA, there is increasing use of continuous deep hypothermic low-flow cardiopulmonary bypass (DHCPB). This study examines the effects of DHCPB versus DHCA on pulmonary dynamics in 1-week-old piglets (weight range, 2.5 to 3.5 kg). METHODS: Animals were placed on CPB (37 degrees C) at 100 mL.kg-1.min-1, cooled to 18 degrees C, and then assigned to one of two groups: DHCPB (n = 7), 25 to 50 mL.kg-1.min-1 DHCPB for 90 minutes; or DHCA (n = 8), DHCA for 90 minutes. Animals were rewarmed to 37 degrees C, weaned from CPB, and observed for 30 minutes. Static pulmonary compliance and pulmonary vascular resistance index were assessed before CPB, 5 minutes after CPB, and 30 minutes after CPB. RESULTS: There was greater impairment of static pulmonary compliance after DHCPB compared with 90 minutes of DHCA. There was a trend toward higher pulmonary vascular resistance index in the DHCPB group; however, significance was not reached. CONCLUSIONS: Deep hypothermic low flow cardiopulmonary bypass produces greater pulmonary dysfunction than DHCA, manifested by decreased static pulmonary compliance. If DHCPB is used in place of DHCA in congenital heart operations, close attention to ventilatory and fluid management is mandatory in the postoperative period to prevent further worsening of pulmonary dysfunction.

Review of techniques used to image aortic dissection.

This article describes the imaging of aortic dissection from the perspective of a multidisciplinary imaging team. The relative merits of radiography, aortography, computed tomography, magnetic resonance imaging, ultrasound and nuclear medicine are described. Each technique has unique advantages for initial diagnosis, confirmation and follow-up. In recent years, ultrasound, computed tomography and magnetic resonance imaging have seen increased use for diagnosis of the condition.