Laser-direct-drive fusion target design with a high-Z gradient-density pusher shell.

Laser-direct-drive fusion target designs with solid deuterium-tritium (DT) fuel, a high-Z gradient-density pusher shell (GDPS), and a Au-coated foam layer have been investigated through both 1D and 2D radiation-hydrodynamic simulations. Compared with conventional low-Z ablators and DT-push-on-DT targets, these GDPS targets possess certain advantages of being instability-resistant implosions that can be high adiabat (α≥8) and low hot-spot and pusher-shell convergence (CR_{hs}≈22 and CR_{PS}≈17), and have a low implosion velocity (v_{imp}<3×10^{7}cm/s). Using symmetric drive with laser energies of 1.9 to 2.5MJ, 1D lilac simulations of these GDPS implosions can result in neutron yields corresponding to ≳50-MJ energy, even with reduced laser absorption due to the cross-beam energy transfer (CBET) effect. Two-dimensional draco simulations show that these GDPS targets can still ignite and deliver neutron yields from 4 to ∼10MJ even if CBET is present, while traditional DT-push-on-DT targets normally fail due to the CBET-induced reduction of ablation pressure. If CBET is mitigated, these GDPS targets are expected to produce neutron yields of >20MJ at a driven laser energy of ∼2MJ. The key factors behind the robust ignition and moderate energy gain of such GDPS implosions are as follows: (1) The high initial density of the high-Z pusher shell can be placed at a very high adiabat while the DT fuel is maintained at a relatively low-entropy state; therefore, such implosions can still provide enough compression ρR>1g/cm^{2} for sufficient confinement; (2) the high-Z layer significantly reduces heat-conduction loss from the hot spot since thermal conductivity scales as ∼1/Z; and (3) possible radiation trapping may offer an additional advantage for reducing energy loss from such high-Z targets.

Time-dependent density-functional-theory calculations of the nonlocal electron stopping range for inertial confinement fusion applications.

Nonlocal electron transport is important for understanding laser-target coupling for laser-direct-drive (LDD) inertial confinement fusion (ICF) simulations. Current models for the nonlocal electron mean free path in radiation-hydrodynamic codes are based on plasma-physics models developed decades ago; improvements are needed to accurately predict the electron conduction in LDD simulations of ICF target implosions. We utilized time-dependent density functional theory (TD-DFT) to calculate the electron stopping power (SP) in the so-called conduction-zone plasmas of polystyrene in a wide range of densities and temperatures relevant to LDD. Compared with the modified Lee-More model, the TD-DFT calculations indicated a lower SP and a higher stopping range for nonlocal electrons. We fit these electron SP calculations to obtain a global analytical model for the electron stopping range as a function of plasma conditions and the nonlocal electron kinetic energy. This model was implemented in the one-dimensional radiation-hydrodynamic code lilac to perform simulations of LDD ICF implosions, which are further compared with simulations by the standard modified Lee-More model. Results from these integrated simulations are discussed in terms of the implications of this TD-DFT-based mean-free-path model to ICF simulations.

Proof-of-Principle Experiment on the Dynamic Shell Formation for Inertial Confinement Fusion.

In the dynamic-shell (DS) concept [V. N. Goncharov et al., Novel Hot-Spot Ignition Designs for Inertial Confinement Fusion with Liquid-Deuterium-Tritium Spheres, Phys. Rev. Lett. 125, 065001 (2020).PRLTAO0031-900710.1103/PhysRevLett.125.065001] for laser-driven inertial confinement fusion the deuterium-tritium fuel is initially in the form of a homogeneous liquid inside a wetted-foam spherical shell. This fuel is ignited using a conventional implosion, which is preceded by a initial compression of the fuel followed by its expansion and dynamic formation of a high-density fuel shell with a low-density interior. This Letter reports on a scaled-down, proof-of-principle experiment on the OMEGA laser demonstrating, for the first time, the feasibility of DS formation. A shell is formed by convergent shocks launched by laser pulses at the edge of a plasma sphere, with the plasma itself formed as a result of laser-driven compression and relaxation of a surrogate plastic-foam ball target. Three x-ray diagnostics, namely, 1D spatially resolved self-emission streaked imaging, 2D self-emission framed imaging, and backlighting radiography, have shown good agreement with the predicted evolution of the DS and its stability to low Legendre mode perturbations introduced by laser irradiation and target asymmetries.

Inverse Bremsstrahlung Absorption.

Inverse bremsstrahlung absorption was measured based on transmission through a finite-length plasma that was thoroughly characterized using spatially resolved Thomson scattering. Expected absorption was then calculated using the diagnosed plasma conditions while varying the absorption model components. To match data, it is necessary to account for (i) the Langdon effect; (ii) laser-frequency (rather than plasma-frequency) dependence in the Coulomb logarithm, as is typical of bremsstrahlung theories but not transport theories; and (iii) a correction due to ion screening. Radiation-hydrodynamic simulations of inertial confinement fusion implosions have to date used a Coulomb logarithm from the transport literature and no screening correction. We anticipate that updating the model for collisional absorption will substantially revise our understanding of laser-target coupling for such implosions.

Average-atom model with Siegert states.

In plasmas, electronic states can be well-localized bound states or itinerant free states, or something in between. In self-consistent treatments of plasma electronic structure such as the average-atom model, all states must be accurately resolved in order to achieve a converged numerical solution. This is a challenging numerical and algorithmic problem in large part due to the continuum of free states which is relatively expensive and difficult to resolve accurately. Siegert states are an appealing alternative. They form a complete eigenbasis with a purely discrete spectrum while still being equivalent to a representation in terms of the usual bound states and free states. However, many of their properties are unintuitive, and it is not obvious that they are suitable for self-consistent plasma electronic structure calculations. Here it is demonstrated that Siegert states can be used to accurately solve an average-atom model and offer advantages over the traditional finite-difference approach, including a concrete physical picture of pressure ionization and continuum resonances.

Multiple scattering theory for dense plasmas.

Dense plasmas occur in stars, giant planets, and in inertial fusion experiments. Accurate modeling of the electronic structure of these plasmas allows for prediction of material properties that can in turn be used to simulate these astrophysical objects and terrestrial experiments. But modeling them remains a challenge. Here we explore the Korringa-Kohn-Rostoker Green's function (KKR-GF) method for this purpose. We find that it is able to predict equation of state in good agreement with other state-of-the-art methods, where they are accurate and viable. In addition, it is shown that the computational cost does not significantly change with temperature, in contrast with other approaches. Moreover, the method does not use pseudopotentials-core states are calculated self consistently. We conclude that KKR-GF is a very promising method for dense plasma simulation.

Muscle Quality, Strength, and Lower Extremity Physical Performance in the Baltimore Longitudinal Study of Aging.

BACKGROUND: Muscle quality is defined as the force generated by each volumetric unit of muscle tissue. No consensus exists on an optimal measure of muscle quality, impeding comparison across studies and implementation in clinical settings. It is unknown whether muscle quality measures that rely on complex and expensive tests, such as isokinetic dynamometry and computerized tomography correlate with lower extremity performance (LEP) any better than measures derived from simpler and less expensive tests, such as grip strength (Grip) and appendicular lean mass (ALM) assessed by DXA. Additionally, whether muscle quality is more strongly associated with LEP than strength has not been fully tested. OBJECTIVES: This study compares the concurrent validity of alternative measures of muscle quality and characterizes their relationship with LEP. We also whether muscle quality correlates more strongly with LEP than strength alone. DESIGN: Cross-sectional analysis. SETTING: Community. PARTICIPANTS: 365 men and 345 women 65 years of age and older in the Baltimore Longitudinal Study of Aging. MEASURES: Thigh cross-sectional area (TCSA), isokinetic and isometric knee extension strength (ID), BMI adjusted ALM (ALMBMI) from DXA, and Grip. Concurrent validity was assessed as the percent variance of different measures of LEP explained by each muscle quality measure. In addition, we compared LEP relationships between each measure of strength and its correspondent value of muscle quality. Confidence intervals for differences in percent variance were calculated by bootstrapping. RESULTS: Grip/ALMBMI explained as much variance as ID/TCSA across all LEP measures in women and most in men. Across all LEP measures, strength explained as much variance of LEP as muscle quality. CONCLUSIONS: Grip/ALMBMI and ID/TCSA measures had similar correlations with LEP. Muscle quality did not outperform strength. Although evaluating muscle quality may be useful to assess age-related mechanisms of change in muscle strength, measures of strength alone may suffice to understand the relationship between muscle and LEP.

Comparative effectiveness of venous thromboembolism prophylaxis options for the patient undergoing total hip and knee replacement: a network meta-analysis.

Essentials Despite trial data, guidelines have not endorsed direct oral Xa inhibitors above other options. We provide profiles of venous thromboembolism and hemorrhage risk for 12 options. Direct oral Xa inhibitors had a favorable profile compared with low-molecular-weight heparin. Other options did not have favorable profiles compared with low-molecular-weight heparin. SUMMARY: Background There are numerous trials and several meta-analyses comparing venous thromboembolism (VTE) prophylaxis options after total hip and knee replacement (THR and TKR). None have included simultaneous comparison of new with older options. Objective To measure simultaneously the relative risk of VTE and hemorrhage for 12 prophylaxis options. Methods We abstracted VTE and hemorrhage information from randomized controlled trials published between January 1990 and June 2016 comparing 12 prophylaxis options. We then constructed networks to compute the relative risk for each option, relative to once-daily dosing with low-molecular-weight heparin (LMWH) Low. Results Main: Relative to LMWH Low, direct oral Xa inhibitors had the lowest risk of total deep vein thrombosis (DVT)-asymptomatic and symptomatic- (odds ratio [OR], 0.45; 95% confidence interval [CI], 0.35-0.57), translating to 53-139 fewer DVTs per 1000 patients. Vitamin K antagonists (VKAs) titrated to International Normalized Ratio [INR] 2-3 predicted 56% more DVT events (OR, 1.56; 95% CI, 1.14-2.14). Aspirin performed similarly (OR, 0.80; 95% CI, 0.34-1.86), although small numbers prohibit firm conclusions. Direct oral Xa inhibitors did not lead to significantly more bleeding (OR, 1.21; 95% CI, 0.79-1.90). Secondary: Relative to LMWH Low, direct oral Xa inhibitors prevented 4-fold more symptomatic DVTs (OR, 0.25; 95% CI, 0.13-0.47). Conclusions Relative to LMWH Low, direct oral Xa inhibitors had a more favorable profile of VTE and hemorrhage risk, whereas VKAs had a less favorable profile. The profile of other agents was not more or less favorable. Clinicians should consider these profiles when selecting prophylaxis options.

Mother-to-child transmission of GB virus C in a cohort of women coinfected with GB virus C and HIV in Bangkok, Thailand.

BACKGROUND: GB virus C (GBV-C) is an apathogenic virus that inhibits human immunodeficiency virus (HIV) replication in vitro. Mother-to-child transmission (MTCT) of GBV-C has been observed in multiple small studies. Our study examined the rate and correlates of MTCT of GBV-C in a large cohort of GBV-C-HIV-coinfected pregnant women in Thailand. METHODS: Maternal delivery plasma specimens from 245 GBV-C-HIV-infected women and specimens from their infants at 4 or 6 months of age were tested for GBV-C RNA. Associations with MTCT of GBV-C were examined using logistic regression. RESULTS: One hundred one (41%) of 245 infants acquired GBV-C infection. MTCT of GBV-C was independently associated with maternal antiretroviral therapy (adjusted odds ratio [AOR], 5.21 [95% confidence interval {CI}, 2.12-12.81]), infant HIV infection (AOR, 0.05 [95% CI, 0.01-0.26]), maternal GBV-C load (8.0 log(10) copies/mL: AOR, 86.77 [95% CI, 15.27-481.70]; 7.0-7.9 log(10) copies/mL: AOR, 45.62 [95% CI, 8.41-247.51]; 5.0-6.9 log(10) copies/mL: AOR, 9.07 [95% CI, 1.85-44.33]: reference, <5 log(10) viral copies/mL), and caesarean delivery (AOR, 0.26 [95% CI, 0.12-0.59]). CONCLUSIONS: Associations with maternal GBV-C load and mode of delivery suggest transmission during pregnancy and delivery. Despite mode of delivery being a common risk factor for virus transmission, GBV-C and HIV were rarely cotransmitted. The mechanisms by which maternal receipt of antiretroviral therapy might increase MTCT of GBV-C are unknown.

HIV seroconversion during pregnancy and risk for mother-to-infant transmission.

Pregnant women infected with HIV-1 were enrolled in a prospective mother-to-infant transmission study from 1992 through 1994 in Bangkok. In participating hospitals, voluntary HIV testing was routinely offered at the beginning of antenatal care and again in the middle of the third trimester of pregnancy. Women who seroconverted to HIV during pregnancy were compared with women who had tested positive on their first antenatal test. Maternal HIV RNA levels were determined during pregnancy, at delivery, and postpartum using RNA polymerase chain reaction (PCR), and infection status in infants was determined by DNA PCR. No infants were breast-fed, but prophylactic antiretroviral therapy was not yet used in Thailand to prevent transmission from mother to infant. Among enrolled women, 16 who seroconverted during pregnancy and 279 who were HIV-1-seropositive at their first antenatal test gave birth. Median plasma RNA levels at delivery were similar for the two groups (17,505 and 20,845 copies/ml, respectively; p =.8). Two (13.3%) of 15 infants born to women who seroconverted and 66 (24.8%) of 266 infants born to previously HIV-seropositive women were infected with HIV (p =.5). There was no increased risk for mother-to-infant HIV transmission and no significant difference in viral load at delivery between HIV-infected women who seroconverted to HIV during pregnancy and those who were HIV-seropositive when first tested.

Safety of late in utero exposure to zidovudine in infants born to human immunodeficiency virus-infected mothers: Bangkok. Bangkok Collaborative Perinatal HIV Transmission Study Group.

BACKGROUND: Short-course zidovudine (ZDV) given in the late antenatal period can reduce mother-infant human immunodeficiency virus (HIV) transmission by one half. Because this intervention is being implemented in developing countries, evidence of its safety is needed. METHODS: In a randomized, double-blinded, placebo-controlled trial in Bangkok, HIV-infected pregnant women received either ZDV (300 mg twice daily from 36 weeks' gestation until labor, then every 3 hours until delivery) or an identical placebo regimen. Infants were evaluated at birth and at 1, 2, 4, 6, 9, 12, 15, and 18 months of age. Growth, clinical events, and hematologic and immunologic measurements were compared between treatment groups. RESULTS: Of the 395 children born (196 in ZDV group and 199 in placebo group), 330 were uninfected, 55 were infected, and 10 had indeterminate infection status. Overall, 319 children (81%) completed 18 months of follow-up, and 14 (4%) died before 18 months of age. Among uninfected children, the mean hematocrit was lower in the ZDV group at birth (49.1% vs 51.5%) but not at later ages; mean weight, height, head circumference, and CD4(+) and CD8(+) T lymphocyte counts were similar in both groups at all ages. Five uninfected children in the ZDV group but only one in the placebo group had a febrile convulsion. No other signs suggestive of mitochondrial dysfunction and no tumors were observed. Among infected children, an estimated 62% in the ZDV group and 77% in the placebo group survived free of Centers for Disease Control and Prevention class C disease during the 18-month follow-up. CONCLUSIONS: No significant adverse events were associated with short-course ZDV during 18 months of follow-up in this population.

Placental abnormalities associated with human immunodeficiency virus type 1 infection and perinatal transmission in Bangkok, Thailand.

The effects of human immunodeficiency virus (HIV) type 1 on the placenta and the role of the placenta in mother-to-child HIV-1 transmission are not well understood. Placentas from 78 HIV-infected and 158 HIV-uninfected women were examined as part of a prospective perinatal HIV transmission study in Bangkok. HIV-infected women were more likely than HIV-uninfected women to have chorioamnionitis (odds ratio [OR], 2.1; P=.03), placental membrane inflammation (PMI; OR, 2. 7; P=.02), and deciduitis (OR, 2.3; P=.03) and less likely to have villitis (OR, 0.3; P=.02). However, among HIV-infected women, fewer women who transmitted infection to their child had chorioamnionitis (relative risk [RR], 0.2; P=.03), funisitis (RR, 0.4; P=.1), or PMI (RR undefined; P=.03). These findings suggest that, in this population, HIV-infected women are at increased risk for placental membrane inflammatory lesions, but that placental inflammatory lesions are not associated with increased perinatal HIV transmission.

HIV-infected women delivering without antenatal care in a large Bangkok hospital, 1997.

The aim was to estimate the proportion of HIV-infected women giving birth at a large Bangkok hospital who had not received antenatal care (ANC) and to identify predictors of not receiving ANC. At Rajavithi Hospital, Bangkok, women with ANC are routinely tested for HIV at their first antenatal visit; women without ANC are routinely tested at delivery. Hospital staff interview all HIV-infected women and record sociodemographic and HIV risk factor information in a delivery room log book. We abstracted and analyzed data recorded in this log book for all HIV-infected women who gave birth at Rajavithi Hospital in 1997. Of 303 HIV-infected women who gave birth, 75% had received ANC at Rajavithi Hospital, 10% had received ANC at other locations, and 15% had not received ANC. On multivariate analysis, HIV-infected women who had received ANC were more likely to work or have partners who worked in construction (25% vs 11%; adjusted odds ratio [AOR]; 2.6; p = 0.03) or have a history of injection drug use (4% vs 0.4%; AOR = 20.8; p = 0.02) than those who had not received ANC, but were less likely to report their current partner as a risk factor for acquiring HIV infection (22% vs. 40%; AOR = 0.4; p = 0.05). Because a substantial number of HIV-infected women give birth in this large Bangkok hospital without receiving ANC, interventions are needed to increase the number of HIV-infected women who receive ANC and to prevent perinatal HIV transmission from HIV-infected pregnant women who have not received ANC.

Early diagnosis of HIV-1-infected infants in Thailand using RNA and DNA PCR assays sensitive to non-B subtypes.

OBJECTIVES: To evaluate the sensitivity and specificity of RNA and DNA polymerase chain reaction (PCR) for early diagnosis of perinatal HIV-1 infection and to investigate early viral dynamics in infected infants. DESIGN: A cohort study of 395 non-breastfed infants born to HIV-infected mothers in a randomized clinical trial of short-course antenatal zidovudine. METHODS: Infant venous blood specimens collected at birth, 2 months, and 6 months of age were tested by qualitative DNA and quantitative RNA PCR (Roche Amplicor). To determine sensitivity and specificity of DNA and RNA PCR, results were compared with later DNA PCR results and to antibody results at 18 months. The HIV-1 subtype of the mother's infection was determined by peptide serotyping. RESULTS: In the study, 92% of mothers were infected with subtype E. DNA PCR sensitivity was 38% (20 of 53) at birth, and 100% at 2 months (53 of 53) and 6 months (47 of 47). RNA PCR sensitivity was 47% (25 of 53) at birth and 100% (53 of 53) at 2 months. All samples that tested DNA-positive tested RNA-positive. Specificity was 100% for both DNA and RNA testing at all timepoints. For infected infants, the median viral load of RNA-positive specimens was 407,000 copies/ml (5.6 log10) at birth, 3, 700,000 copies/ml (6.6 log10) at 2 months, and 1,700,000 copies/ml (6.2 log10) at 6 months. Infant RNA levels at 2 and 6 months did not differ by maternal zidovudine exposure, or RNA level at birth. CONCLUSION: This RNA PCR assay performed well for diagnosing perinatal HIV subtype E infection, detecting nearly half of infected infants at birth, and 100% at 2 and 6 months, with 100% specificity. Infected infant viral RNA levels were very high at 2 and 6 months, and were unaffected by maternal zidovudine treatment.

Evaluating a new strategy for prophylaxis to prevent Pneumocystis carinii pneumonia in HIV-exposed infants in Thailand. Bangkok Collaborative Perinatal HIV Transmission Study Group.

OBJECTIVE: To evaluate a strategy for prophylaxis against Pneumocystis carinii pneumonia (PCP) for infants in Thailand. METHODS: HIV-infected women were offered trimethoprim-sulfamethoxazole for PCP prophylaxis for their children at 1-2 months of age. When the children reached 6 months of age, investigators simulated a decision to continue or stop prophylaxis on the basis of clinical criteria, and compared their decisions with results of polymerase chain reaction (PCR) testing for HIV. We calculated the proportions of children who received and completed prophylaxis, and compared the rates of pneumonia and death from pneumonia with rates from an earlier prospective cohort. RESULTS: Of 395 eligible infants, 383 (97%) started prophylaxis. By 6 months of age, 10 (2.6%) were lost to follow-up, three (0.8%) were non-adherent, seven (2%) had stopped because of adverse events, four (1%) had died, and 359 (94%) still received prophylaxis. At 6 months of age, 30 (70%) of 43 HIV-infected children and 16 (5%) of 316 uninfected children met the clinical criteria to continue prophylaxis. The incidence of pneumonia at 1 to 6 months of age was 22% (15/68) in the earlier cohort, and 13% (6/46) in the recent cohort [relative risk (RR) 0.6, 95% confidence interval (CI) 0.3-1.4; P= 0.22]; mortality rates were 9% and 4%, respectively (RR 0.5; 95% CI 0.1-2.3; P = 0.47). CONCLUSION: This PCP prophylaxis strategy appeared to be acceptable and safe, may have reduced morbidity and mortality from pneumonia, and should be considered in developing countries where early laboratory diagnosis of perinatal HIV infection is unavailable.

Lack of association between human immunodeficiency virus type 1 antibody in cervicovaginal lavage fluid and plasma and perinatal transmission, in Thailand.

To determine the association between human immunodeficiency virus type 1 (HIV)-specific antibody and RNA levels in cervicovaginal lavage (CVL) samples and plasma, zidovudine treatment, and perinatal transmission, HIV subtype E gp160-specific IgG and IgA were serially measured in a subset of 74 HIV-infected women in a placebo-controlled trial of zidovudine, beginning at 36 weeks of gestation. HIV IgG was detected in 100% of plasma and 97% of CVL samples; HIV IgA was consistently detected in 62% of plasma and 31% of CVL samples. Antibody titers in CVL samples correlated better with the RNA level in CVL samples than with plasma antibody titers. Zidovudine did not affect antibody titers. Perinatal HIV transmission was not associated with antibody in CVL samples or plasma. HIV-specific antibody is present in the cervicovaginal canal of HIV-infected pregnant women; its correlation with the RNA level in CVL fluid suggests local antibody production. However, there was no evidence that these antibodies protected against perinatal HIV transmission.

Human immunodeficiency virus-related tuberculosis and primary drug resistance in Bangkok, Thailand.

SETTING: Central Chest Hospital, a 500-bed referral hospital near Bangkok with a large out-patient department. OBJECTIVES: To determine human immunodeficiency virus (HIV) seroprevalence among patients with pulmonary tuberculosis (TB), and compare HIV-positive and HIV-negative TB patients. DESIGN: From July 1995 through June 1996, a cross-sectional study was conducted of newly registered adults (> or =16 years old) with suspected pulmonary TB. RESULTS: Of 2587 newly registered patients with suspected pulmonary TB, 2019 (78%) received HIV pretest counseling and 1816 (90%) consented to testing. Of these, 364 (20%) were HIV-seropositive. Among 1091 patients with bacteriologically confirmed TB, HIV seroprevalence was 22%. HIV-positive patients were more likely to be young, unemployed, single men and to have a history of injection drug use. HIV-positive patients with first-episode TB were more likely to have Mycobacterium tuberculosis strains resistant to isoniazid (10.9% vs 3.5%; P < 0.001), rifampicin (9.4% vs 2.9%; P < 0.001), and at least isoniazid and rifampicin (multidrug-resistant TB [MDR-TB]; 5.2% vs 0.4%; P < 0.001). CONCLUSIONS: HIV prevalence is high among TB patients at this Bangkok hospital and is associated with drug resistance, including a 12 times higher risk of MDR-TB. These findings underscore the urgent need to assure adherence to complete, effective TB treatment regimens for all patients, including persons who are potentially difficult to manage such as injection drug users.