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.

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.

Spectroscopic modeling and characterization of a collisionally confined laser-ablated plasma plume.

Plasma plumes produced by laser ablation are an established method for manufacturing the high quality stoichiometrically complex thin films used for a variety of optical, photoelectric, and superconducting applications. The state and reproducibility of the plasma close to the surface of the irradiated target plays a critical role in producing high quality thin films. Unfortunately, this dense plasma has historically eluded quantifiable characterization. The difficulty in modeling the plume formation arises in the accounting for the small amount of energy deposited into the target when physical properties of these exotic target materials are not known. In this work we obtain the high density state of the plasma plume through the use of an experimental spectroscopic technique and a custom spectroscopic model. In addition to obtaining detailed temperature and density profiles, issues regarding line broadening and opacity for spectroscopic characterization will be addressed for this unique environment.

Spectroscopic characterization of an ultrashort-pulse-laser-driven Ar cluster target incorporating both Boltzmann and particle-in-cell models.

A model that solves simultaneously both the electron and atomic kinetics was used to generate a synthetic He alpha and satellite x-ray spectra to characterize a high intensity ultrashort laser driven Ar cluster target experiment. In particular, level populations were obtained from a detailed collisional-radiative model where collisional rates were computed from a time varying electron distribution function obtained from the solution of the zero-dimensional Boltzmann equation. In addition, a particle-in-cell simulation was used to model the laser interaction with the cluster target and provided the initial electron energy distribution function (EEDF) for the Boltzmann solver. This study suggests that a high density average, high, of 3.2 x 10(20) cm(-3) was held by the system for a time, delta tau, of 5.7 ps, and during this time the plasma was in a highly nonequilibrium state in both the EEDF and the ion level populations.

Atomic physics modeling of transmission spectra of Sc-doped aerogel foams to support OMEGA experiments.

We present synthetic transmission spectra generated with PrismSPECT utilizing both the ATBASE model and the Los Alamos opacity library (OPLIB) to evaluate whether an alternative choice in atomic data will impact modeling of experimental data from radiation transport experiments using Sc-doped aerogel foams (ScSi6O12 at 75 mg/cm3 density). We have determined that in the 50-200 eV Te range there is a significant difference in the 1s-3p spectra, especially below 100 eV, and for Te = 200 eV above 5000 eV in photon energy. Examining synthetic spectra generated using OPLIB with 300 resolving power reveals spectral sensitivity to Te changes of ∼3 eV.

Metabolic replacement of kidney function in uremic animals with a bioartificial kidney containing human cells.

Current renal substitution therapy with hemodialysis or hemofiltration has been an important life-sustaining technology, but it still has suboptimal clinical outcomes in patients with end-stage renal disease or acute renal failure. This therapy replaces the small solute clearance function of the glomerulus but does not replace the metabolic and endocrinologic functions of the tubular cells. This article shows that the combination of a synthetic hemofiltration cartridge and a renal tubule cell assist device (RAD) containing human cells in an extracorporeal circuit replaces filtration, metabolic, and endocrinologic functions in acutely uremic dogs. The RAD maintained excellent performance and durability characteristics for 24 hours of continuous use in the uremic animals. The RAD increased ammonia excretion, glutathione metabolism, and 1,25-dihydroxyvitamin D3 production. Cardiovascular stability in the animals was documented in these studies during this extracorporeal treatment. With these results, clinical evaluation of this device in the treatment of severely ill patients with acute renal failure in an intensive care unit has been initiated.

Sister-chromatid exchanges induced in swine lymphocytes by chronic oral doses of dimethylbenzanthracene.

Sister-chromatid exchanges were scored at 3-week intervals in lymphocytes of female swine ingesting daily doses of 1.25 or 2.50 mg/kg of 7,12-dimethylbenzanthracene (DMBA) for 160 days. Exchanges increased with time for about 120 days then reached a plateau at approximately 2.5 times their pretreatment level. No increase in chromosome aberrations could be identified as resulting from ingestion of the chemical. Week-old progeny of animals that had ingested the chemical throughout pregnancy showed no increase of exchanges in their peripheral lymphocytes.

Species variation in BrdUrd-induced sister-chromatid exchanges.

Peripheral blood lymphocytes from cattle, pigs, sheep and humans were cultured in the presence of 0.5, 1, 2, 5, 10 or 20 micrograms/ml of BrdUrd. Sister-chromatid exchanges were scored in 25 second-division metaphases from each donor at each level of the chemical. Dose--response curves for all 4 species increased steeply to 2 micrograms/ml; above this level, SCE numbers increased less rapidly but maintained a linear relationship to increasing BrdUrd concentration. Comparisons of the straight-line portions of the dose--response curves showed human cells to be significantly more sensitive to increasing BrdUrd level than cow or pig cells and different from sheep at the 10% level of confidence.

Accumulation of SCEs in lymphocytes during chronic ingestion of a mutagen.

Studies in 2 large-animal species have shown that continued ingestion of a mutagen increases sister chromatid exchanges (SCE) in circulating lymphocytes at rates directly related to the accumulated dose but differing between species. Groups of 3 pigs received daily oral doses of 0, 1.25, or 2.50 mg/kg body weight of 7,12-dimethylbenzanthracene (DMBA) for 160 consecutive da; similar groups of sheep received 0, 0.625, or 1.25 mg/kg daily for up to 114 da. Lymphocytes taken at 3-wk intervals from pigs and every 2 wk from sheep were cultured, and 25 randomly selected second-division metaphases from each culture were scored for SCE. Swine lymphocytes had elevated numbers of SCE at the earliest sampling times after DMBA feeding was begun. Sister chromatid exchanges continued to increase gradually among pigs consuming 1.25 mg/kg/da for 160 da whereas those on 2.5 mg/kg tended to plateau at approximately 2.5 times their pretreatment level after some 80 da. Sheep treated with comparable levels of DMBA (1.25 mg/kg) exhibited a much more rapid rise in SCE than pigs; within 40 da their SCEs were at 4 times the control level and animals were exhibiting toxicity symptoms. Low-dose sheep also showed a rapid initial increase but plateaued at about 2.5 times the control level beyond 40 da.

In vitro evaluation of liquid antacid products.

The in vitro neutralizing capacities, sodium content, and cost of 21 nonprescription antacid products were compared. A 5-ml sample of each antacid product was placed in a beaker using a pipette. The pipette was rinsed three times wtih purified water 5 ml, and the mixture was stirred with a magnetic stirring rod. After one minute, 1.0 N hydrochloride acid 30 ml was added to the mixture and stirring was continued for 15 minutes. The pH was then measured. Using a burette, sufficient 0.5 N sodium hydroxide was added to the mixture to raise the pH stable value to 3.5. Samples were tested in duplicate. Manufacturers were requested to provide sodium content for the antacid products, and costs were obtained based on wholesale prices. Neutralizing capacity of the antacids ranged from 1.3 to 8.7 meq/ml. Of the 21 products, 17 contained at least 90% of the claimed neutralizing capacity, as required by FDA. One product did not qualify as an antacid by FDA standards. Sodium content has been reduced in may preparations and may no longer be a factor in choosing an antacid. Chronic therapy with antacids can be expensive, and it costs more to deliver a given amount of neutralizing capacity with less concentrated antacids.

Mitotic response and sister chromatid exchanges in lymphocytes cultured in sera from different sources.

The numbers of sister chromatid exchanges in lymphocytes grown in varying concentrations of serum from different sources indicated that some sera contain a factor, probably introduced as a contaminant, which induces SCEs. Sera from 6 animals showed no evidence of a difference in baseline SCE levels due to the donor of the serum.

A black female with the 48, XXXX chromosome constitution.

The case of a 19-year-old severly mentally retarded Black female with a 48,XXXX chromosome constitution is reported. She had low-set ears, minimum webbing of the neck, small inverted nipples, and tapering of the extremities. All ten digital patterns of the fingers were ulnar loops, resulting in a marked reduction of dermal ridge counts.