Origins and Scaling of Hot-Electron Preheat in Ignition-Scale Direct-Drive Inertial Confinement Fusion Experiments.

Planar laser-plasma interaction (LPI) experiments at the National Ignition Facility (NIF) have allowed access for the first time to regimes of electron density scale length (∼500 to 700 µm), electron temperature (∼3 to 5 keV), and laser intensity (6 to 16×10^{14} W/cm^{2}) that are relevant to direct-drive inertial confinement fusion ignition. Unlike in shorter-scale-length plasmas on OMEGA, scattered-light data on the NIF show that the near-quarter-critical LPI physics is dominated by stimulated Raman scattering (SRS) rather than by two-plasmon decay (TPD). This difference in regime is explained based on absolute SRS and TPD threshold considerations. SRS sidescatter tangential to density contours and other SRS mechanisms are observed. The fraction of laser energy converted to hot electrons is ∼0.7% to 2.9%, consistent with observed levels of SRS. The intensity threshold for hot-electron production is assessed, and the use of a Si ablator slightly increases this threshold from ∼4×10^{14} to ∼6×10^{14} W/cm^{2}. These results have significant implications for mitigation of LPI hot-electron preheat in direct-drive ignition designs.

Developing an Experimental Basis for Understanding Transport in NIF Hohlraum Plasmas.

We report on the first multilocation electron temperature (T_{e}) and flow measurements in an ignition hohlraum at the National Ignition Facility using the novel technique of mid-Z spectroscopic tracer "dots." The measurements define a low resolution "map" of hohlraum plasma conditions and provide a basis for the first multilocation tests of particle and energy transport physics in a laser-driven x-ray cavity. The data set is consistent with classical heat flow near the capsule but reduced heat flow near the laser entrance hole. We evaluate the role of kinetic effects, self-generated magnetic fields, and instabilities in causing spatially dependent heat transport in the hohlraum.

Measurement of Hydrodynamic Growth near Peak Velocity in an Inertial Confinement Fusion Capsule Implosion using a Self-Radiography Technique.

First measurements of hydrodynamic growth near peak implosion velocity in an inertial confinement fusion (ICF) implosion at the National Ignition Facility were obtained using a self-radiographing technique and a preimposed Legendre mode 40, λ=140 µm, sinusoidal perturbation. These are the first measurements of the total growth at the most unstable mode from acceleration Rayleigh-Taylor achieved in any ICF experiment to date, showing growth of the areal density perturbation of ∼7000×. Measurements were made at convergences of ∼5 to ∼10× at both the waist and pole of the capsule, demonstrating simultaneous measurements of the growth factors from both lines of sight. The areal density growth factors are an order of magnitude larger than prior experimental measurements and differed by ∼2× between the waist and the pole, showing asymmetry in the measured growth factors. These new measurements significantly advance our ability to diagnose perturbations detrimental to ICF implosions, uniquely intersecting the change from an accelerating to decelerating shell, with multiple simultaneous angular views.

Thin shell, high velocity inertial confinement fusion implosions on the national ignition facility.

Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165 µm in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Early results have shown good repeatability, with up to 1/2 the neutron yield coming from α-particle self-heating.

2D X-ray radiography of imploding capsules at the national ignition facility.

First measurements of the in-flight shape of imploding inertial confinement fusion (ICF) capsules at the National Ignition Facility (NIF) were obtained by using two-dimensional x-ray radiography. The sequence of area-backlit, time-gated pinhole images is analyzed for implosion velocity, low-mode shape and density asymmetries, and the absolute offset and center-of-mass velocity of the capsule shell. The in-flight shell is often observed to be asymmetric even when the concomitant core self-emission is round. A ∼ 15 µm shell asymmetry amplitude of the Y(40) spherical harmonic mode was observed for standard NIF ICF hohlraums at a shell radius of ∼ 200 µm (capsule at ∼ 5× radial compression). This asymmetry is mitigated by a ∼ 10% increase in the hohlraum length.

Hot-spot mix in ignition-scale inertial confinement fusion targets.

Mixing of plastic ablator material, doped with Cu and Ge dopants, deep into the hot spot of ignition-scale inertial confinement fusion implosions by hydrodynamic instabilities is diagnosed with x-ray spectroscopy on the National Ignition Facility. The amount of hot-spot mix mass is determined from the absolute brightness of the emergent Cu and Ge K-shell emission. The Cu and Ge dopants placed at different radial locations in the plastic ablator show the ablation-front hydrodynamic instability is primarily responsible for hot-spot mix. Low neutron yields and hot-spot mix mass between 34(-13,+50) ng and 4000(-2970,+17 160) ng are observed.

Comparison of 3 agar media in Fung double tubes and Petri plates to detect and enumerate Clostridium spp. in broiler chicken intestines.

Clostridium perfringens is an anaerobic, spore-forming bacterium that may lead to necrotic enteritis, resulting in poor feed efficiency and increased mortality in chickens. It is estimated that C. perfringens infects almost 1 million people in the United States every year. The objective of this research was to compare the Fung double tube (FDT) and conventional Petri plates using 3 different media to detect and enumerate Clostridium spp. in chicken intestines. Nine Cobb 500 broilers were randomly selected and euthanized at 21 and 42 d of age for a total of 18 samples. The jejunum and ileum from each broiler were harvested and studied in 2 methods and 3 media combinations, utilizing a 2 × 3 factorial totaling 6 treatments. The 2 methods were FDT and conventional Petri plates, and the 3 media were Shahidi-Ferguson Perfringens (SFP) with egg yolk supplement, polymyxin B, and kanamycin (E); SFP with polymyxin B and kanamycin (P); and SFP with d-cycloserine (C). Enumerations were performed after 24 h of incubation at 37°C. At 21 d, counts using medium C with FDT (4.51 log10 cfu/g) and plates (2.38 log10 cfu/g) were higher (P < 0.05) than using media E or P. On d 42, there were no differences among plate treatments and medium E had the highest counts (0.98 log10 cfu/g). Of all the FDT, medium C (5.35 log10 cfu/g) had the highest counts (P < 0.05), followed by medium P (3.54 log10 cfu/g). This study illustrates that the FDT method is able to enumerate Clostridium spp. at higher levels (P < 0.001) than the conventional Petri plate method; therefore, the FDT should be implemented and further explored.

Velocity and timing of multiple spherically converging shock waves in liquid deuterium.

The fuel entropy and required drive energy for an inertial confinement fusion implosion are set by a sequence of shocks that must be precisely timed to achieve ignition. This Letter reports measurements of multiple spherical shock waves in liquid deuterium that facilitate timing inertial confinement fusion shocks to the required precision. These experiments produced the highest shock velocity observed in liquid deuterium (U(s) = 135 km/s at ∼2500 GPa) and also the first observation of convergence effects on the shock velocity. Simulations model the shock-timing results well when a nonlocal transport model is used in the coronal plasma.

Hospitalization budget impact during the COVID-19 pandemic in Spain.

OBJECTIVES: The aim was to determine the direct impact of the COVID-19 pandemic on Spain's health budget. METHODS: Budget impact analyses based on retrospective data from patients with suspected severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) admitted to a Spanish hospital between February 26 and May 21, 2020. Direct medical costs from the perspective of the hospital were calculated. We analyzed diagnostic tests, drugs, medical and nursing care, and isolation ward and ICU stays for three cohorts: patients seen in the emergency room only, hospitalized patients who tested positive for SARS-CoV-2, and patients who tested negative. RESULTS: The impact on the hospital's budget for the 3 months was calculated at €15,633,180, 97.4% of which was related to health care and hospitalization. ICU stays accounted for 5.3% of the total costs. The mean cost per patient was €10,744. The main costs were staffing costs (10,131 to 11,357 €/patient for physicians and 10,274 to 11,215 €/patient for nurses). Scenario analysis showed that the range of hospital expenditure was between €14,693,256 and €16,524,924. The median impact of the pandemic on the Spanish health budget in the sensitivity analysis using bootstrapped individual data was €9357 million (interquartile range [IQR], 9071 to 9689) for the conservative scenario (113,588 hospital admissions and 11,664 ICU admissions) and €10,385 million (IQR, 110,030 to 10,758) for the worst-case scenario (including suspected cases). CONCLUSION: The impact of COVID-19 on the Spanish public health budget (12.3% of total public health expenditure) is greater than multiple sclerosis, cancer and diabetes cost.

X-ray diffraction at the National Ignition Facility.

We report details of an experimental platform implemented at the National Ignition Facility to obtain in situ powder diffraction data from solids dynamically compressed to extreme pressures. Thin samples are sandwiched between tamper layers and ramp compressed using a gradual increase in the drive-laser irradiance. Pressure history in the sample is determined using high-precision velocimetry measurements. Up to two independently timed pulses of x rays are produced at or near the time of peak pressure by laser illumination of thin metal foils. The quasi-monochromatic x-ray pulses have a mean wavelength selectable between 0.6 Å and 1.9 Å depending on the foil material. The diffracted signal is recorded on image plates with a typical 2θ x-ray scattering angle uncertainty of about 0.2° and resolution of about 1°. Analytic expressions are reported for systematic corrections to 2θ due to finite pinhole size and sample offset. A new variant of a nonlinear background subtraction algorithm is described, which has been used to observe diffraction lines at signal-to-background ratios as low as a few percent. Variations in system response over the detector area are compensated in order to obtain accurate line intensities; this system response calculation includes a new analytic approximation for image-plate sensitivity as a function of photon energy and incident angle. This experimental platform has been used up to 2 TPa (20 Mbar) to determine the crystal structure, measure the density, and evaluate the strain-induced texturing of a variety of compressed samples spanning periods 2-7 on the periodic table.

Image-plate sensitivity to x rays at 2 to 60 keV.

The sensitivity of Fuji SR and MS image plates (IPs) used in x-ray spectrometers on OMEGA and the National Ignition Facility has been measured using two techniques. A set of radioisotopes has been used to constrain image-plate sensitivity between 6 and 60 keV, while a Manson source has been used to expose image plates to x rays at energies between 1.5 and 8 keV. These data have shown variation in sensitivity on the order of 5% for a given IP type and scanner settings. The radioisotope technique has also been used to assess IP fading properties for MS-type plates over long times. IP sensitivity as a function of scanner settings and pixel size has been systematically examined, showing variations of up to a factor of 2 depending on the IP type. Cross-calibration of IP scanners at different facilities is necessary to produce a consistent absolute sensitivity curve spanning the energy range of 2-60 keV.

Efficacy and adverse effects of collagenase use in the treatment of Dupuytren's disease: a meta-analysis.

AIMS: The aim of this meta-analysis was to assess the safety and efficacy of collagenase clostridium histolyticum compared with fasciectomy and percutaneous needle fasciotomy (PNF) for Dupuytren's disease. MATERIALS AND METHODS: We systematically searched PubMed, EMBASE, LILACS, Web of Science, Cochrane, Teseo and the ClinicalTrials.gov registry for clinical trials and cohort or case-control studies which compared the clinical outcomes and adverse effects of collagenase with those of fasciectomy or PNF. Of 1345 articles retrieved, ten were selected. They described the outcomes of 425 patients treated with collagenase and 418 treated by fasciectomy or PNF. Complications were assessed using inverse-variance weighted odds ratios (ORs). Clinical efficacy was assessed by differences between the means for movement of the joint before and after treatment. Dose adjustment was applied in all cases. RESULTS: Random-effects modelling showed that patients treated with collagenase had 3.24 increased odds of adverse effects compared with those treated by fasciectomy (OR 4.39) or PNF (OR 1.72,). The effect was lost when only major complications were assessed. Joint movement analysis revealed a difference between means of less than 10%, indicating equivalent clinical efficacy in the short and medium term for collagenase and fasciectomy. We were unable to analyse this for PNF due to a shortage of data. CONCLUSION: There were no significant differences in effect size between collagenase and fasciectomy. The use of collagenase was associated with a higher overall risk of adverse effects than both fasciectomy and PNF. Cite this article: Bone Joint J 2018;100-B:73-80.

Progress towards a more predictive model for hohlraum radiation drive and symmetry.

For several years, we have been calculating the radiation drive in laser-heated gold hohlraums using flux-limited heat transport with a limiter of 0.15, tabulated values of local thermodynamic equilibrium gold opacity, and an approximate model for not in a local thermodynamic equilibrium (NLTE) gold emissivity (DCA_2010). This model has been successful in predicting the radiation drive in vacuum hohlraums, but for gas-filled hohlraums used to drive capsule implosions, the model consistently predicts too much drive and capsule bang times earlier than measured. In this work, we introduce a new model that brings the calculated bang time into better agreement with the measured bang time. The new model employs (1) a numerical grid that is fully converged in space, energy, and time, (2) a modified approximate NLTE model that includes more physics and is in better agreement with more detailed offline emissivity models, and (3) a reduced flux limiter value of 0.03. We applied this model to gas-filled hohlraum experiments using high density carbon and plastic ablator capsules that had hohlraum He fill gas densities ranging from 0.06 to 1.6 mg/cc and hohlraum diameters of 5.75 or 6.72 mm. The new model predicts bang times to within ±100 ps for most experiments with low to intermediate fill densities (up to 0.85 mg/cc). This model predicts higher temperatures in the plasma than the old model and also predicts that at higher gas fill densities, a significant amount of inner beam laser energy escapes the hohlraum through the opposite laser entrance hole.

Capsule implosions for continuum x-ray backlighting of opacity samples at the National Ignition Facility.

Direct drive implosions of plastic capsules have been performed at the National Ignition Facility to provide a broad-spectrum (500-2000 eV) X-ray continuum source for X-ray transmission spectroscopy. The source was developed for the high-temperature plasma opacity experimental platform. Initial experiments using 2.0 mm diameter polyalpha-methyl styrene capsules with ∼20 µm thickness have been performed. X-ray yields of up to ∼1 kJ/sr have been measured using the Dante multichannel diode array. The backlighter source size was measured to be ∼100 µm FWHM, with ∼350 ps pulse duration during the peak emission stage. Results are used to simulate transmission spectra for a hypothetical iron opacity sample at 150 eV, enabling the derivation of photometrics requirements for future opacity experiments.

A technique for measuring the quality of an elliptically bent pentaerythritol [PET(002)] crystal.

We present a technique for determining the X-ray spectral quality from each region of an elliptically curved PET(002) crystal. The investigative technique utilizes the shape of the crystal rocking curve which changes significantly as the radius of curvature changes. This unique quality information enables the spectroscopist to verify where in the spectral range that the spectrometer performance is satisfactory and where there are regions that would show spectral distortion. A collection of rocking curve measurements for elliptically curved PET(002) has been built up in our X-ray laboratory. The multi-lamellar model from the XOP software has been used as a guide and corrections were applied to the model based upon measurements. But, the measurement of RI at small radius of curvature shows an anomalous behavior; the multi-lamellar model fails to show this behavior. The effect of this anomalous RI behavior on an X-ray spectrometer calibration is calculated. It is compared to the multi-lamellar model calculation which is completely inadequate for predicting RI for this range of curvature and spectral energies.

Association of Beta2-Positive Clostridium perfringens Type A With Focal Duodenal Necrosis in Egg-Laying Chickens in the United States.

Focal duodenal necrosis (FDN) is a poorly understood intestinal disease of egg layers, and has been associated with drops in egg production and decreased egg weights. The etiology of this disease is still unknown, but the condition has been associated with Clostridium colinum and Clostridium perfringens. In order to investigate the etiology, duodenal samples were taken from hens with FDN. The hens originated from table egg layer farms in three states. The samples were examined by histopathology, bacteriology, and immunohistochemistry. Macroscopically, all samples contained focal to multifocal, variably sized, reddened or brownish gray areas of mucosal erosion. Histopathology revealed mild to severe heterophilic and lymphoplasmacytic enteritis with loss of enterocytes at the villous tips, luminal fibrinonecrotic exudate, and variable numbers of Gram-positive and Gram-negative rod-shaped bacteria within the lesions in 16/30 samples. Clostridium perfringens was isolated by anaerobic bacteriology from 4/13 samples that had characteristic microscopic lesions of FDN. Polymerase chain reaction (PCR) revealed that all four isolates were Type A C. perfringens, positive for beta2 gene and negative for necrotic enteritis toxin B and enterotoxin genes. PCR for Clostridium colinum applied to DNA extracted from frozen intestinal samples yielded negative results in 14/14 duodenal samples. Immunohistochemistry (IHC) for 7C. perfringens, alpha and beta2 toxins stained a few to numerous long rod-shaped bacteria present in the lesions. IHC for alpha and beta2 toxins also stained enterocytes at the villous tips, inflammatory cells in the lamina propria, as well as degenerated and sloughed enterocytes present within the luminal exudate. These findings suggest that C. perfringens may play a role in the development of FDN. Experimental challenge studies with these isolates still need to be performed in order to reproduce the disease and fulfill Koch's postulates.

Acute Hemolysis with Renal Failure due to Clostridium Bacteremia in a Patient with AML.

We present a case of acute hemolytic anemia, renal failure, and Clostridium perfringens bacteremia in a patient with acute myelogenous leukemia. The high fatality of C. perfringens bacteremia requires that clinicians recognize and rapidly treat patients at risk for this infection. Although other hemolytic processes are in the differential diagnosis of these events, the presence of high fever, chills, and rapidly positive blood cultures may help narrow the diagnosis. Most cases of C. perfringens bacteremia have a concomitant coinfection, which makes broad spectrum empiric therapy essential. There is a high mortality rate of C. perfringens infections associated with leukemia.

Development of a krypton-doped gas symmetry capsule platform for x-ray spectroscopy of implosion cores on the NIF.

The electron temperature at stagnation of an ICF implosion can be measured from the emission spectrum of high-energy x-rays that pass through the cold material surrounding the hot stagnating core. Here we describe a platform developed on the National Ignition Facility where trace levels of a mid-Z dopant (krypton) are added to the fuel gas of a symcap (symmetry surrogate) implosion to allow for the use of x-ray spectroscopy of the krypton line emission.

Observation of hohlraum-wall motion with spectrally selective x-ray imaging at the National Ignition Facility.

The high fuel capsule compression required for indirect drive inertial confinement fusion requires careful control of the X-ray drive symmetry throughout the laser pulse. When the outer cone beams strike the hohlraum wall, the plasma ablated off the hohlraum wall expands into the hohlraum and can alter both the outer and inner cone beam propagations and hence the X-ray drive symmetry especially at the final stage of the drive pulse. To quantitatively understand the wall motion, we developed a new experimental technique which visualizes the expansion and stagnation of the hohlraum wall plasma. Details of the experiment and the technique of spectrally selective x-ray imaging are discussed.

Characterization of an aromatic amino acid aminotransferase from Rhizobium leguminosarum biovar trifolii.

The most abundant aromatic amino acid aminotransferase of Rhizobium leguminosarum biovar trifolii was partially purified. The molecular mass of the enzyme was estimated to be 53 kDa by gel filtration. The enzyme transaminated aromatic amino acids and histidine. It used aromatic keto acids and alpha-ketoglutaric and oxalacetic acids as amino-group acceptors. The optimum temperature was 35 degrees C. Using phenylalanine and alpha-ketoglutaric acid as substrates the activation energy was 46.2 kJ.mol-1 and for the couple tryptophan:alpha-ketoglutaric acid it was 70.3 kJ.mol-1. The optimum pH was different for each substrate: 7.3 for phenylalanine, 7.9 for histidine and 8.7 for tryptophan.