Under hypersonic entry conditions into an atmosphere, gas may be ionized via shock waves to create a weakly ionized plasma. Accurate kinetic modeling of these flows is essential for deriving ...macroscopic properties relevant to vehicular design, such as surface heat flux. Of particular interest are regions with a high degree of charge separation. One region is the plasma sheath at the vehicle surface, whose self-induced electric fields lead to ion acceleration and thus increased heat flux to the vehicle. The second region is the interface between the shock front and the ambient freestream gas, whose field structure is not well understood. Due to statistical scatter and the computational cost associated with simulating high density flows with electric field effects, these regions have yet to be fully characterized by prior investigations using traditional particle-based kinetic modeling. In this study, we explore both regions by developing a one-dimensional numerical model of a rarefied, hypersonic shock layer for a helium atmosphere. The model employs the grid-based direct kinetic method, which directly solves the Boltzmann-Poisson-BGK equations for a discretized velocity distribution function. The charge density, ion and electron currents, and convective heat flux are computed and compared with results from the standard direct simulation Monte Carlo model, which invokes the ambipolar diffusion approximation to simulate plasma dynamics. Additionally, the electric field and magnitude of charge separation are evaluated throughout the flowfield to assess the validity of the quasineutral assumption along the stagnation streamline.
We report precision determinations of the beam-normal single spin asymmetries (A_{n}) in the elastic scattering of 0.95 and 2.18 GeV electrons off ^{12}C, ^{40}Ca, ^{48}Ca, and ^{208}Pb at very ...forward angles where the most detailed theoretical calculations have been performed. The first measurements of A_{n} for ^{40}Ca and ^{48}Ca are found to be similar to that of ^{12}C, consistent with expectations and thus demonstrating the validity of theoretical calculations for nuclei with Z≤20. We also report A_{n} for ^{208}Pb at two new momentum transfers (Q^{2}) extending the previous measurement. Our new data confirm the surprising result previously reported, with all three data points showing significant disagreement with the results from the Z≤20 nuclei. These data confirm our basic understanding of the underlying dynamics that govern A_{n} for nuclei containing ≲50 nucleons, but point to the need for further investigation to understand the unusual A_{n} behavior discovered for scattering off ^{208}Pb.
We report a precision measurement of the parity-violating asymmetry A PV in the elastic scattering of longitudinally polarized electrons from 208 Pb . We measure APV=550±16(stat)±8(syst) parts per ...billion, leading to an extraction of the neutral weak form factor FW(Q2=0.00616 GeV2)=0.368±0.013 . Combined with our previous measurement, the extracted neutron skin thickness is Rn−Rp=0.283±0.071 fm. The result also yields the first significant direct measurement of the interior weak density of 208 Pb: ρW0=− 0.0796 ± 0.0036 ( exp ) ± 0.0013 ( theo ) fm−3 leading to the interior baryon density ρb0 = 0.1480 ± 0.0036 ( exp ) ± 0.0013 ( theo ) fm −3. The measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.
We report a precision measurement of the parity-violating asymmetry A_{PV} in the elastic scattering of longitudinally polarized electrons from ^{208}Pb. We measure A_{PV}=550±16(stat)±8(syst) parts ...per billion, leading to an extraction of the neutral weak form factor F_{W}(Q^{2}=0.00616 GeV^{2})=0.368±0.013. Combined with our previous measurement, the extracted neutron skin thickness is R_{n}-R_{p}=0.283±0.071 fm. The result also yields the first significant direct measurement of the interior weak density of ^{208}Pb: ρ_{W}^{0}=-0.0796±0.0036(exp)±0.0013(theo) fm^{-3} leading to the interior baryon density ρ_{b}^{0}=0.1480±0.0036(exp)±0.0013(theo) fm^{-3}. The measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.
Sarcopenia, the loss of muscle mass and function, has been linked to morbidity and mortality in several orthopedic procedures. At present, there is a paucity of data concerning sarcopenia in adult ...spinal deformity (ASD) surgery and particularly with respect to the most complex techniques performed on this population such as pedicle subtraction osteotomy (PSO). Due to the high surgical burden placed on patients undergoing PSOs, appropriate patient selection is critical for minimizing complications.
The aim of this study was to 1) determine if sarcopenia was an independent risk factor for complications in ASD patients undergoing PSO, and 2) define discrete categories of complication risk based on sarcopenia severity.
Single-center retrospective review.
Seventy-three ASD patients who underwent PSO.
The primary outcome measure was the presence of any 2-year complication: cardiac, pulmonary, neurologic, dural tear, epidural hematoma, wound infection, proximal junctional kyphosis (PJK), nonunion and revision surgery. Secondary outcome measures included intraoperative blood loss (EBL) and length of stay (LOS).
We identified 73 ASD patients with available lumbar CT/MRI scans who underwent PSO with spinal fusion ≥5 levels at a tertiary care center from 2005-2014. Sarcopenia was assessed based on the psoas-lumbar vertebral index (PLVI), a validated marker for central sarcopenia. The PLVI was calculated by dividing a patient's average iliopsoas cross-sectional area (CSA) by the CSA of the L4 vertebrae. Using stratum-specific likelihood ratio (SSLR) analysis, patients were separated into three distinct sarcopenia groups based on complication risk. Cutoffs generated through SSLR were confirmed using multivariable regression controlling for demographic and surgical factors.
The mean age of the cohort was 61±8 years, 75% female. The mean PLVI was 0.84±0.28, with 47% of patients having any complication. Patients with a complication had a 27% lower PLVI on average than those without complications (0.76 vs. 0.91, p=0.021). SSLR analysis produced 3 complication categories: 32% complication rate for PLVI ≥ 0.81; 61% for PLVI 0.60-0.80; and 69% for PLVI < 0.60. Relative to patients with PLVI ≥ 0.81, those with PLVI 0.60-0.80 and PLVI < 0.60 had 3.2x and 4.3x greater odds of developing a complication, respectively (p<0.05 for both). With respect to individual complications, patients with PLVI < 1.0 had significantly higher risk of PJK (34% vs. 0%, p=0.022), while patients with PLVI < 0.8 had significantly higher risk of wound infection (12% vs. 0%, p=0.028) and dural tear (14% vs. 0%, p=0.019). There were no significant associations between sarcopenia, EBL and LOS (p>0.05 for all).
Increasing severity of sarcopenia is associated with significantly and incrementally increased risk of complications following PSO for ASD surgery. We define PLVI cutoffs (0.60 and 0.81) below which complication risk is significantly increased.
This abstract does not discuss or include any applicable devices or drugs.
A 66-year-old woman with polymyositis and recurrent urinary tract infections presented with lumbar pain and progressive lower extremity neuropathy. Imaging showed lytic destruction of the vertebral ...bone from L2 to L4 with extension into adjacent musculature. Histological examination demonstrated Michaelis-Gutmann bodies consistent with malakoplakia. The patient underwent revision T12-sacrum posterior fusion, L2-5 laminectomy, and anterior L3-4 corpectomy, followed by L2-4 anterior stabilization and a 6-week course of ceftriaxone. At 3 months postoperatively, she was asymptomatic without recurrence.
Malakoplakia of bone should be considered in the differential diagnosis of lytic bone lesions and can be effectively treated with surgical debulking with penetrative antibiotics.
The Alliance for Academic Internal Medicine (AAIM) supports the need for a uniform subspecialty fellowship training and advanced residency training start date. At present, training programs and their ...sponsoring institutions vary widely in the timing of institutional orientation and fellowship/advanced residency training start dates. Some institutions conduct orientation programs before the scheduled completion of the initial training program, which leads to conflicts for the resident between current and future obligations. AAIM believes that requiring residents to report for fellowship before completion of residency training is disruptive to medical education, creates unnecessary stress for the residents, and risks, violating federal labor laws and Center for Medicare and Medicaid Services graduate medical education funding rules. Adoption of Jul 1, 2015 as the earliest start date for all training and orientation activities can be endorsed internally by AAIM institutions and would resolve these conflicts. Here, Barrett et al examine AAIM adoption of a uniform subspecialty fellowship and other advanced training.
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