Demonstration of improved laser preheat with a cryogenically cooled magnetized liner inertial fusion platform

We report on progress implementing and testing cryogenically cooled platforms for Magnetized Liner Inertial Fusion (MagLIF) experiments. Two cryogenically cooled experimental platforms were developed: an integrated platform fielded on the Z pulsed power generator that combines magnetization, laser preheat, and pulsed-power-driven fuel compression and a laser-only platform in a separate chamber that enables measurements of the laser preheat energy using shadowgraphy measurements. The laser-only experiments suggest that ∼89% ± 10% of the incident energy is coupled to the fuel in cooled targets across the energy range tested, significantly higher than previous warm experiments that achieved at most 67% coupling and in line with simulation predictions. The laser preheat configuration was applied to a cryogenically cooled integrated experiment that used a novel cryostat configuration that cooled the MagLIF liner from both ends. The integrated experiment, z3576, coupled 2.32 ± 0.25 kJ preheat energy to the fuel, the highest to-date, demonstrated excellent temperature control and nominal current delivery, and produced one of the highest pressure stagnations as determined by a Bayesian analysis of the data.

Harmonic Generation and Inverse Cascade in the z-Pinch Driven, Preseeded Multimode, Magneto-Rayleigh-Taylor Instability

The magneto-Rayleigh-Taylor instability (MRTI) plays an essential role in astrophysical systems and in magneto-inertial fusion, where it is known to be an important degradation mechanism of confinement and target performance. In this Letter, we show for the first time experimental evidence of mode mixing and the onset of an inverse-cascade process resulting from the nonlinear coupling of two discrete preseeded axial modes (400- and 550-μm wavelengths) on an Al liner that is magnetically imploded using the 20-MA, 100-ns rise-time Z Machine at Sandia National Laboratories. Four radiographs captured the temporal evolution of the MRTI. We introduce a novel unfold technique to analyze the experimental radiographs and compare the results to simulations and to a weakly nonlinear model. We find good quantitative agreement with simulations using the radiation magnetohydrodynamics code hydra. Spectral analysis of the MRTI time evolution obtained from the simulations shows evidence of harmonic generation, mode coupling, and the onset of an inverse-cascade process. The experiments provide a benchmark for future work on the MRTI and motivate the development of new analytical theories to better understand this instability.

Performance Scaling in Magnetized Liner Inertial Fusion Experiments

We present experimental results from the first systematic study of performance scaling with drive parameters for a magnetoinertial fusion concept. In magnetized liner inertial fusion experiments, the burn-averaged ion temperature doubles to 3.1 keV and the primary deuterium-deuterium neutron yield increases by more than an order of magnitude to 1.1×10^{13} (2 kJ deuterium-tritium equivalent) through a simultaneous increase in the applied magnetic field (from 10.4 to 15.9 T), laser preheat energy (from 0.46 to 1.2 kJ), and current coupling (from 16 to 20 MA). Individual parametric scans of the initial magnetic field and laser preheat energy show the expected trends, demonstrating the importance of magnetic insulation and the impact of the Nernst effect for this concept. A drive-current scan shows that present experiments operate close to the point where implosion stability is a limiting factor in performance, demonstrating the need to raise fuel pressure as drive current is increased. Simulations that capture these experimental trends indicate that another order of magnitude increase in yield on the Z facility is possible with additional increases of input parameters.

Wave kinetics of drift-wave turbulence and zonal flows beyond the ray approximation

Inhomogeneous drift-wave turbulence can be modeled as an effective plasma where drift waves act as quantumlike particles and the zonal-flow velocity serves as a collective field through which they interact. This effective plasma can be described by a Wigner-Moyal equation (WME), which generalizes the quasilinear wave-kinetic equation (WKE) to the full-wave regime, i.e., resolves the wavelength scale. Unlike waves governed by manifestly quantumlike equations, whose WMEs can be borrowed from quantum mechanics and are commonly known, drift waves have Hamiltonians very different from those of conventional quantum particles. This causes unusual phase-space dynamics that is typically not captured by the WKE. We demonstrate how to correctly model this dynamics with the WME instead. Specifically, we report full-wave phase-space simulations of the zonal-flow formation (zonostrophic instability), deterioration (tertiary instability), and the so-called predator-prey oscillations. We also show how the WME facilitates analysis of these phenomena, namely, (i) we show that full-wave effects critically affect the zonostrophic instability, particularly its nonlinear stage and saturation; (ii) we derive the tertiary-instability growth rate; and (iii) we demonstrate that, with full-wave effects retained, the predator-prey oscillations do not require zonal-flow collisional damping, contrary to previous studies. We also show how the famous Rayleigh-Kuo criterion, which has been missing in wave-kinetic theories of drift-wave turbulence, emerges from the WME.

The role of faecal diversion in low rectal cancer: a review of 1791 patients having rectal resection with anastomosis for cancer, with and without a proximal stoma

AIM

The morbidity of anastomotic dehiscence may be mitigated by a defunctioning stoma, but it is unclear if it is required for most low rectal anastomoses. Preoperative risk factors leading to anastomotic complications and the indications for faecal diversion have yet to be clearly defined.

METHOD

Using the American College of Surgeons-National Surgical Quality Improvement Project (ACS-NSQIP) participant-use file, patients were identified who underwent low anterior resection with anastomosis for cancer at the 211 participating hospitals in 2005-08.

RESULTS

A total of 1791 patients underwent low anterior resection. Patients were subdivided into two groups based on the level of the anastomosis. Of these 1266 patients had a low pelvic anastomosis (LPA) and 525 a coloanal anastomosis (CAA). In the LPA group, 606 patients had a stoma and 660 had no stoma. There were no differences in wound complications, sepsis or septic shock. Patients who had a stoma were more likely to have postoperative acute renal failure (1.7 vs 0.5%, P = 0.0485, OR 3.674). In the CAA group, 352 had a stoma and 173 had no stoma. In patients without faecal diversion, there was a significantly greater incidence of sepsis (8.7 vs 3.7%, P = 0.022, OR 2.47), septic shock (3.5 vs 0.57%, P = 0.018, OR 6.29) and need for reoperation (11 vs 1.7%, P = 0.0001, OR 7.11). Hospital length of stay was significantly longer with CAA and no stoma. On multivariate analysis, not having a stoma with a CAA was a risk factor for serious postoperative morbidity.

CONCLUSION

While a defunctioning stoma with a coloanal anastomosis seems to protect from postoperative sepsis, septic shock and need for reoperation, it is likely that it is overused in rectal cancer surgery.

Filamin A mutations cause periventricular heterotopia with Ehlers-Danlos syndrome

OBJECTIVE

To define the clinical, radiologic, and genetic features of periventricular heterotopia (PH) with Ehlers-Danlos syndrome (EDS).

METHODS

Exonic sequencing and single stranded conformational polymorphism (SSCP) analysis was performed on affected individuals. Linkage analysis using microsatellite markers on the X-chromosome was performed on a single pedigree. Western blotting evaluated for loss of filamin A (FLNA) protein and Southern blotting assessed for any potential chromosome rearrangement in this region.

RESULTS

The authors report two familial cases and nine additional sporadic cases of the EDS-variant form of PH, which is characterized by nodular brain heterotopia, joint hypermobility, and development of aortic dilatation in early adulthood. MRI typically demonstrated bilateral nodular PH, indistinguishable from PH due to FLNA mutations. Exonic sequencing or SSCP analyses of FLNA revealed a 2762 delG single base pair deletion in one affected female. Another affected female harbored a C116 single point mutation, resulting in an A39G change. A third affected female had a 4147 delG single base pair deletion. One pedigree with no detectable exonic mutation demonstrated positive linkage to the FLNA locus Xq28, an affected individual in this family also had no detectable FLNA protein, but no chromosomal rearrangement was detected.

CONCLUSION

These results suggest that the Ehlers-Danlos variant of periventricular heterotopia (PH), in part, represents an overlapping syndrome with X-linked dominant PH due to filamin A mutations.

Analysis of initial CT findings after endovascular repair of abdominal aortic aneurysm

PURPOSE

To determine the spectrum and frequency of specific computed tomographic (CT) findings in the acute period after endovascular repair of abdominal aortic aneurysm (AAA).

MATERIALS AND METHODS

CT images obtained 1--3 days after endograft placement were evaluated in 88 patients. The images were analyzed for stent position, appearance of endograft components, perigraft leak, and postoperative findings including air and acute thrombus within the aneurysm and air surrounding the femoral-femoral bypass graft. Findings that could be misinterpreted as perigraft leak were evaluated.

RESULTS

Fifteen (17%) of 88 patients had perigraft leak in the acute postoperative period. The bare segment of the proximal self-expanding stent covered one or both renal arteries in 54 (61%) patients. One patient had CT evidence of renovascular compromise. Postoperative air was within the aneurysmal sac in 51 (58%) patients and surrounded the femoral-femoral bypass graft in 67 (94%) of 71 patients in whom the grafts were evaluated with CT. Mottled attenuation within the aneurysmal sac was seen in 50 (57%) patients. Forty-six (52%) patients had calcifications within longstanding thrombus. In 31 (35%) patients, findings that could have been misinterpreted as perigraft leak were identified.

CONCLUSION

Accurate analysis of CT findings after endovascular AAA repair requires careful review of all available CT images (preprocedural and pre- and postcontrast) and clear understanding of specific stent-graft components and placement.

Clindamycin and gentamicin for aerobic and anaerobic sepsis

Thirty-eight adult patients with serious pleuropulmonary, soft-tissue, bone, and intra-abdominal infections caused by combinations of aerobic, facultative, and anaerobic bacteria were treated with parenterally given clindamycin phosphate and gentamicin sulfate and surgery when appropriate. Nine had associated bacteremia. In 29, infections failed to respond to other therapeutic regimens, which included penicillins, cephalosporins, aminoglycosides, and chloramphenicol. Results with clindamycin and gentamicin were excellent and were attributed primarily to the activity of clindamycin against anaerobes, particularly Bacteroides fragilis. Serum concentrations of clindamycin surpassed by manyfold the minimal inhibitory concentrations (MICs) for anaerobes. Serum concentrations of gentamicin did not consistently surpass the MICs for Enterobacteriaceae and Pseudomonas aeruginosa, although those organisms were consistently gentamicinsusceptible by disk diffusion susceptibility tests. Persistent colonization with Enterobacteriaceae, P aeruginosa, enterococci, or Candida were common, and occasionally they were significant in prolonging the clinical courses of patients with extensive infections.

In vitro activity of gentamicin and minocycline alone and in combination against bacteria associated with intra-abdominal sepsis

The minimal inhibitory concentrations of gentamicin and minocycline alone and in combination were determined by a broth microdilution method for 100 aerobic, facultative, and anaerobic isolates representative of pathogens recovered from patients with intra-abdominal sepsis. Gentamicin inhibited all strains of Klebsiella, Enterobacter, and Pseudomonas aeruginosa in concentrations of 0.4 to 3.1 mug/ml and all strains of Escherichia coli and Proteus mirabilis in concentrations of 0.8 to 12.5 mug/ml. Whereas minocycline did not consistently inhibit these organisms in concentrations of 1.6 mug or less/ml, it did act synergistically with gentamicin against 43% of the Enterobacteriaceae tested in clinically achievable concentrations; significant synergy was most common with E. coli (60%). Minocycline inhibited 62% of Bacteroides fragilis, 71% of Clostridium, 40% of anaerobic cocci, and 40% of enterococci tested in concentrations of 1.6 mug or less/ml. Whereas gentamicin rarely inhibited these organisms in concentrations of 6.2 mug or less/ml, it did act synergistically with minocycline against 20% of B. fragilis, 67% of Clostridium, 22% of anaerobic cocci, and 22% of enterococci (which had minimal inhibitory concentrations of minocycline within the range tested) at clinically achievable concentrations. Although only four (13%) of the 30 isolates resistant to both gentamicin and minocycline alone were inhibited by clinically achievable concentrations of the combination, the observed synergy, particularly against strains of E. coli, was considered to be of potential clinical usefulness. Antagonism between gentamicin and minocycline was not observed at the concentrations tested.

Nafcillin treatment of Staphylococcus aureus meningitis

Serial serum and cerebrospinal fluid nafcillin concentrations were determined in a patient successfully treated with nafcillin (200 mg/kg per day) for Staphylococcus aureus bacteremia and meningitis. Nafcillin and methicillin cerebrospinal fluid concentrations were compared.

Idiopathic hypertrophic subaortic stenosis in pregnancy

The coexistence of pregnancy and idiopathic hypertrophic subaortic stenosis is a potentially dangerous combination. We report a 23-year-old white woman with idiopathic hypertrophic subaortic stenosis and pregnancy who presented with severe symptoms (Class IV) and modest outflow obstruction associated with marked mitral regurgitation. After delivery, the evidence for significant mitral regurgitation regressed, while the outflow obstruction seemed unchanged. However, she returned to Functional Class II. We review the mechanisms by which pregnancy and labor may alter the hemodynamics of idiopathic hypertrophic subaortic stenosis and we discuss recommendations for the management of these patients during pregnancy, labor, and the immediate postpartum period. We conclude that despite increasing symptoms, most women with diopathic hypertrophic subaortic stenosis can tolerate pregnancy and a vaginal delivery.