All-Order Full-Coulomb Quantum Spectral Line-Shape Calculations.

Understanding how atoms interact with hot dense matter is essential for astrophysical and laboratory plasmas. Interactions in high-density plasmas broaden spectral lines, providing a rare window into interactions that govern, for example, radiation transport in stars. However, up to now, spectral line-shape theories employed at least one of three common approximations: second-order Taylor treatment of broadening operator, dipole-only interactions between atom and plasma, and classical treatment of perturbing electrons. In this Letter, we remove all three approximations simultaneously for the first time and test the importance for two applications: neutral hydrogen and highly ionized magnesium and oxygen. We found 15%-50% change in the spectral line widths, which are sufficient to impact applications including white-dwarf mass determination, stellar-opacity research, and laboratory plasma diagnostics.

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.

Erratum: Measurement of Preheat Due to Nonlocal Electron Transport in Warm Dense Matter [Phys. Rev. Lett. 120, 025002 (2018)].

This corrects the article DOI: 10.1103/PhysRevLett.120.025002.

Effect of Electron Capture on Spectral Line Broadening in Hot Dense Plasmas.

Accurate calculation of spectral line broadening is important for many hot, dense plasma applications. However, calculated line widths have significantly underestimated measured widths for Δn=0 lines of Li-like ions, which is known as the isolated-line problem. In this Letter, scrutinization of the line-width derivation reveals that the commonly used expression neglects a potentially important contribution from electron-capture. Line-width calculations including this process are performed with two independent codes, both of which removed the discrepancies at temperatures below 10 eV. The revised calculations also suggest the remaining discrepancy scales more strongly with electron temperature than the atomic number as was previously suggested.

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.

Evaluation of Plasmodium vivax malaria recurrence in Brazil.

BACKGROUND: Control of vivax malaria in endemic areas requires management of recurrence. The Brazilian National Malaria Surveillance System (SIVEP-Malária) records every case of malaria in Brazil, but is not designed to differentiate between primary and recurrent infections. The aim of this study was to explore whether the information provided by SIVEP-Malária could be used to identify Plasmodium vivax recurrences, its risk factors and evaluate the effectiveness of short course primaquine (7-9 days: total dose 3-4.2 mg/kg) in preventing relapses. METHODS: In this observational retrospective cohort study, data matching of SIVEP-Malária records was undertaken using bloom filters to identify potential recurrences defined as microscopically-confirmed P. vivax episodes from the same individual occurring within a year. Generalized Estimation Equation (GEE) models were used to determine predictors of recurrence. Extended Cox-based conditional Prentice-Williams-Peterson models (PWP) models were used to evaluate time to recurrence. RESULTS: Between June 1, 2014 and May 31, 2015, 26,295 episodes fulfilled the criteria of potential recurrence among 154,970 reported malaria episodes. Age ≤ 3 years, being male, literate, not-indigenous and having domestic working activities were identified as risk factors for recurrence. There was no difference in time to recurrence or recurrence frequency between patients treated with 14-day or 7-9 day primaquine regimens (HR = 1.02, 0.96-1.09) and RR = 0.97 (0.90-1.04), respectively. The use of chloroquine alone was associated with a 1.43 (1.29-1.58, p < 0.0001) increased risk of P. vivax recurrence compared to patients who used chloroquine combined with short-course primaquine, the Brazilian standard of care. This was RR = 2.06 (1.48-2.86, p < 0.0001), RR = 1.90 (1.60-2.25, p = 0.0001) and RR = 1.14 (1.00-1.29, p = 0.05) for recurrences occurring between 3-28, 29-60 and > 60 days, respectively. PWP models showed that the time to recurrence was longer in recipients of both primaquine and artemisinin-based combination therapy (ACT) compared to patients treated with chloroquine alone or with concomitant primaquine, HR = 2.2 (1.62-2.99, p < 0.0001), HR = 1.27 (0.97-1.66, p = 0.08), respectively. CONCLUSION: Short course primaquine was as effective as 14-day regimens and associated with a halving of the risk and delay in time to recurrence of P. vivax infections in comparison to chloroquine alone. The study demonstrates the feasibility of using record linkage on routine surveillance data to identify potential P. vivax recurrences, associated risk factors and impact of treatment.

Measurement of Preheat Due to Nonlocal Electron Transport in Warm Dense Matter.

This Letter presents a novel approach to study electron transport in warm dense matter. It also includes the first x-ray Thomson scattering (XRTS) measurement from low-density CH foams compressed by a strong laser-driven shock at the OMEGA laser facility. The XRTS measurement is combined with velocity interferometry (VISAR) and optical pyrometry (SOP) providing a robust measurement of thermodynamic conditions in the shock. Evidence of significant preheat contributing to elevated temperatures reaching 17.5-35 eV in shocked CH foam is measured by XRTS. These measurements are complemented by abnormally high shock velocities observed by VISAR and early emission seen by SOP. These results are compared to radiation hydrodynamics simulations that include first-principles treatment of nonlocal electron transport in warm dense matter with excellent agreement. Additional simulations confirm that the x-ray contribution to this preheat is negligible.

Benchmark Experiment for Photoionized Plasma Emission from Accretion-Powered X-Ray Sources.

The interpretation of x-ray spectra emerging from x-ray binaries and active galactic nuclei accreted plasmas relies on complex physical models for radiation generation and transport in photoionized plasmas. These models have not been sufficiently experimentally validated. We have developed a highly reproducible benchmark experiment to study spectrum formation from a photoionized silicon plasma in a regime comparable to astrophysical plasmas. Ionization predictions are higher than inferred from measured absorption spectra. Self-emission measured at adjustable column densities tests radiation transport effects, demonstrating that the resonant Auger destruction assumption used to interpret black hole accretion spectra is inaccurate.

Predicting excitation energies in warm and hot dense matter.

In a dense plasma environment, the energy levels of an ion shift relative to the isolated ion values. This shift is reflected in the optical spectrum of the plasma and can be measured in, for example, emission experiments. In this work we use a recently developed method of modeling electronic states in warm dense matter to predict these level energies. In this model excited state energies are calculated directly by enforcing constrained one-electron occupation factors, thus allowing the calculation of specific transition and ionization energies. This model includes plasma effects self-consistently, so the effect of continuum lowering is included in an ab initio sense. We use the model to calculate the K-edge and K-alpha energies of solid density magnesium, aluminum, and silicon over a range of temperatures, finding close agreement with experimental results. We also calculate the ionization potential depression to compare to widely used models and investigate the effects of temperature on the lowering of the continuum.

Excited states in warm and hot dense matter.

Accurate modeling of warm and hot dense matter is challenging in part due to the multitude of excited states that must be considered. Here, we present a variational framework that models these excited states. In this framework an excited state is defined by a set of effective one-electron occupation factors, and the corresponding energy is defined by the effective one-body energy with an exchange and correlation term. The variational framework is applied to an atom-in-plasma model (a generalization of the so-called average atom model). Comparisons with a density functional theory based average atom model generally reveal good agreement in the calculated pressure, but our model also gives access to the excitation energies and charge state distributions.

Development of improved higher-order correction for the NIF opacity spectrometer.

X-ray opacity measurements on the National Ignition Facility (NIF) are in the process of reproducing earlier measurements from the Sandia Z Facility, in particular for oxygen and iron plasmas. These measurements have the potential to revise our understanding of the "solar problem" and of the hot degenerate Q class white dwarf structure by probing plasma conditions near the base of their convection zones. Accurate opacity measurements using soft x-ray Bragg crystal spectrometers require correction for higher-order diffraction effects. Extending prior work in this area [Dutra et al., Review of Scientific Instruments 93, 113527 (2022)], we have developed a new method to remove higher-order spectral components from NIF opacity spectrometer data. By modeling absorption and backlighting continuum spectra and subtracting the second- and third-order components from the measured data, we are able to perform this correction while avoiding imprinting first-order model line features onto the data.

Electron- and proton-impact excitation of hydrogenlike uranium in relativistic collisions.

The K shell excitation of H-like uranium (U(91+)) in relativistic collisions with different gaseous targets has been studied at the experimental storage ring at GSI Darmstadt. By performing measurements with different targets as well as with different collision energies, we were able to observe for the first time the effect of electron-impact excitation (EIE) process in the heaviest hydrogenlike ion. The large fine-structure splitting in H-like uranium allowed us to unambiguously resolve excitation into different L shell levels. State-of-the-art calculations performed within the relativistic framework which include excitation mechanisms due to both protons (nucleus) and electrons are in good agreement with the experimental findings. Moreover, our experimental data clearly demonstrate the importance of including the generalized Breit interaction in the treatment of the EIE process.

2nd and 3rd order spectral energy corrections with penumbral de-blurring methodology for opacity platform used on the National Ignition Facility.

The Opacity Spectrometer (OpSpec) used in the National Ignition Facility's opacity experiments measures x-ray spectra from 0.9 to 2.1 keV from the different experimental regions: the backlight source, emission source, and the absorption region with the transmission calculated from these regions. The OpSpec designs have gone through several iterations to help improve the signal-to-noise ratio, remove alternate crystal plane reflections, and improve spectral resolution, which helps to increase the validity of the opacity measurements. However, the source spans well outside the current working spectral range, and higher-order reflections are intrinsic to the crystal, which increases the overall signal seen in the data regions. The recorded data are the convolution of 1st order transmission, higher-order reflections, and the penumbra blurring. This work represents the details for deconvolving the 2nd and 3rd order spectral energy corrections with a penumbral de-blurring to correct the relative measurement of x-ray intensity of different spectral energies and further analysis of datasets relevant to the opacity experiments.

Polymorphism in the pvcrt-o and pvmdr-1 genes of Plasmodium vivax associated with a better prognosis for malaria.

The early molecular identification of strains of Plasmodium vivax that have a worse prognosis is important to stratify the risk of complications and choice of conduct made by medical teams. Thus, the aim of the present study was to associate the presence of polymorphisms in the pvmdr-1 and pvcrt-o resistance genes of P. vivax in patients with better or worse prognosis. This cross-sectional epidemiological study was conducted based on data obtained from the records of 120 patients diagnosed with malaria in the Brazilian Amazon. The T958M and F1076L mutations of the pvmdr-1 gene had a frequency of 3.3 and 4.2%, respectively, and primo-infected patients had a 17 times greater chance of being infected with protozoa with the T958M mutation compared to patients with previous episodes. Regarding pvcrt-o, the C393T and T786C polymorphisms had a frequency of 14.2 and 3.3%, respectively, and self-declared white patients had a 3.1 times greater chance of being infected with protozoa with the C393T polymorphism. In addition, patients with this pvcrt-o polymorphism had lower concentrations of C-reactive protein, indicating a better prognosis. These data present clues of genetic indicators useful for assessing the virulence of the parasite and the prognosis of patients with vivax malaria.

Sub-keV design for the National Ignition Facility's soft x-ray Opacity Spectrometer (OpSpec) and expansion plans for time-resolved measurements.

When compared with the National Ignition Facility's (NIF) original soft x-ray opacity spectrometer, which used a convex cylindrical design, an elliptically shaped design has helped to increase the signal-to-noise ratio and eliminated nearly all reflections from alternate crystal planes. The success of the elliptical geometry in the opacity experiments has driven a new elliptical geometry crystal with a spectral range covering 520-1100 eV. When coupled with the primary elliptical geometry, which spans 1000-2100 eV, the new sub-keV elliptical geometry helps to cover the full iron L-shell and major oxygen transitions important to solar opacity experimentation. The new design has been built and tested by using a Henke x-ray source and shows the desired spectral coverage. Additional plans are underway to expand these opacity measurements into a mode of time-resolved detection, ∼1 ns gated, but considerations for the detector size and photometrics mean a crystal geometry redesign. The new low-energy geometry, including preliminary results from the NIF opacity experiments, is presented along with the expansion plans into a time-resolved platform.

Time-dependent density functional theory applied to average atom opacity.

We focus on studying the opacity of iron, chromium, and nickel plasmas at conditions relevant to experiments carried out at Sandia National Laboratories [J. E. Bailey et al., Nature (London) 517, 56 (2015)NATUAS0028-083610.1038/nature14048]. We calculate the photoabsorption cross sections and subsequent opacity for plasmas using linear-response time-dependent density functional theory (TD-DFT). Our results indicate that the physics of channel mixing accounted for in linear-response TD-DFT leads to an increase in the opacity in the bound-free quasicontinuum, where the Sandia experiments indicate that models underpredict iron opacity. However, the increase seen in our calculations is only in the range of 5%-10%. Further, we do not see any change in this trend for chromium and nickel. This behavior indicates that channel mixing effects do not explain the trends in opacity observed in the Sandia experiments.

Microsatellite loci: determining the genetic variability of Plasmodium vivax.

OBJECTIVE: To describe the genetic diversity of Plasmodium vivax isolates from different areas in the Brazilian Amazon using 11 polymorphic microsatellites and to evaluate the correlation between microsatellite variation and repeat array length. METHODS: Microsatellites with variable repeat units and array lengths were selected using in silico search of the P. vivax genome. We designed primers and amplified the selected loci in DNA obtained from patients with P. vivax acute infections. RESULTS: Positive correlation between repeat array length and microsatellite variation was detected independently of the size of repeat unit (di, tri, or tetranucleotide). We used these markers to describe the genetic variability of P. vivax isolates from four geographic regions of the Brazilian Amazon. Substantial variability was observed among P. vivax isolates within populations, concurrent with high levels of multiple-clone infections and high linkage disequilibrium. Overall, structured populations were observed with moderate to high genetic differentiation. CONCLUSION: The markers studied are useful tools for assessing population structure of P. vivax, as demonstrated for Brazilian populations and for searching for evidence of recent selection events associated with different phenotypes, such as drug resistance.

Inhibitory properties of the antibody response to Plasmodium vivax Duffy binding protein in an area with unstable malaria transmission.

The function of the Plasmodium vivax Duffy binding protein (DBP) during the erythrocyte invasion process is critical for successful parasite growth and pathogenesis in human infections. Although DBP is the subject of intensive malaria vaccine research, investigations on the functional proprieties of anti-DBP antibodies in the human population have been limited [Infect Immun68 (2000) 3164]. In the present study, we examined the ability of sera from different populations of the Brazilian Amazon--an area of markedly unstable malaria transmission--to inhibit the erythrocyte-binding function of the DBP ligand domain (region II, DBP(II)). We found that long-term exposure to malaria in the Amazon area elicits DBP-specific antibodies that inhibit the binding of different DBP(II) variants to erythrocytes. Despite the great variability of inhibitory antibody responses observed among study participants, we observed a positive correlation between erythrocyte binding-inhibitory activity and enzyme-linked immunosorbent assay anti-DBP antibodies. Of importance, there was a non-significant tendency towards increased levels of anti-DBP antibodies among individuals with asymptomatic P. vivax infections.

Association between particular polymorphic residues on apical membrane antigen 1 (AMA-1) and platelet levels in patients with vivax malaria.

Apical membrane antigen 1 (AMA-1) is an immunogenic type 1 integral membrane protein, present in all Plasmodium spp., that probably has a role in the initiation of the invasion process of the erythrocyte. The DNA sequence of variable domain I of the Plasmodium vivax ama1 gene was sequenced in Brazilian isolates obtained from thrombocytopenic patients (n = 32) and patients with normal platelet counts (n = 22). There was a significant negative correlation between parasite density and platelet counts. It was concluded that there is an additional effect of sequence on platelet counts. The presence of amino-acid residues Y(193) and S(210) was associated significantly with normal platelet counts in P. vivax malaria, independent of the level of parasitaemia (p <0.0001). These data have implications for AMA-1-based vaccine design and suggest the possible use of this molecule as a marker of morbidity.