Descriptive Analysis of Orthopaedic Surgery Residency Program Directors.

The purpose of this study was to analyze the demographics and backgrounds of U.S. orthopaedic surgery residency program directors (PDs). We collected publicly available information on 189 orthopaedic surgery residency PDs. Of those PDs, 90% were male MDs with an average age of 52. The average age at PD appointment was 45. The average duration of appointment was 7 years. About 81% of programs were university-affiliated, and 61% were in an urban environment. PDs attended 100 medical schools, 129 residencies, and 96 fellowships. of PDs, 87% completed fellowships, commonly in trauma and sports medicine. There was no significant difference between male and female PDs when comparing age, academic appointment, or urban/rural environment. Most female PDs (89%) were at university-based hospitals. Of PDs at osteopathic-focused programs, 28% had an MD/PD. No program with an allopathic focus had a DO/PD. Lastly, 38% of PDs worked at the center where they completed residency. (Journal of Surgical Orthopaedic Advances 31(4):252-255, 2022).

Development of Clostridium septicum gas gangrene as an adverse effect of clindamycin-induced Clostridium difficile infection in a pediatric patient.

Clostridium myonecrosis or gas gangrene is a life-threatening infection characterized by either traumatic or atraumatic etiology. It has been widely described in patients with traumatic open wounds and in immunocompromised patients, including malignancy. A third source can result from natural flora in the gastrointestinal tract after bowel ischemia. This is a rare occurrence and is even less commonly described in the pediatric population. We present a pediatric patient who developed Clostridium septicum myonecrosis as an iatrogenic complication from clindamycin-induced Clostridium difficile ischemic colitis.

Comparison of treecodes for computing electrostatic potentials in charged particle systems with disjoint targets and sources.

In molecular simulations, it is sometimes necessary to compute the electrostatic potential at M target sites due to a disjoint set of N charged source particles. Direct summation requires O(MN) operations, which is prohibitively expensive when M and N are large. Here, we consider two alternative tree-based methods that reduce the cost. The standard particle-cluster treecode partitions the N sources into an octree and applies a far-field approximation, whereas a recently developed cluster-particle treecode instead partitions the M targets into an octree and applies a near-field approximation. We compare the two treecodes with direct summation and document their accuracy, CPU run time, and memory usage. We find that the particle-cluster treecode is faster when N > M, that is, when the sources outnumber the targets, and conversely, the cluster-particle treecode is faster when M > N, that is, when the targets outnumber the sources. Hence, the two treecodes provide useful tools for computing electrostatic potentials in charged particle systems with disjoint targets and sources.

Periodic Coulomb Tree Method: An Alternative to Parallel Particle Mesh Ewald.

Particle mesh Ewald (PME) is generally the method of choice for handling electrostatics in simulations with periodic boundary conditions. The excellent efficiency of PME on low processor counts is largely due to the use of the fast Fourier transform (FFT). However, due to the FFT's high communication cost, PME scales poorly in parallel. We develop a periodic Coulomb tree (PCT) method for electrostatic interactions in periodic boundary conditions as an alternative to PME in parallel simulations. We verify the accuracy of PCT by comparison of structural and dynamical properties of three different systems obtained via MD simulations using PME and PCT and provide parallel timing comparisons of the two methods on up to 1024 cores.

Advanced Potential Energy Surfaces for Molecular Simulation.

Advanced potential energy surfaces are defined as theoretical models that explicitly include many-body effects that transcend the standard fixed-charge, pairwise-additive paradigm typically used in molecular simulation. However, several factors relating to their software implementation have precluded their widespread use in condensed-phase simulations: the computational cost of the theoretical models, a paucity of approximate models and algorithmic improvements that can ameliorate their cost, underdeveloped interfaces and limited dissemination in computational code bases that are widely used in the computational chemistry community, and software implementations that have not kept pace with modern high-performance computing (HPC) architectures, such as multicore CPUs and modern graphics processing units (GPUs). In this Feature Article we review recent progress made in these areas, including well-defined polarization approximations and new multipole electrostatic formulations, novel methods for solving the mutual polarization equations and increasing the MD time step, combining linear-scaling electronic structure methods with new QM/MM methods that account for mutual polarization between the two regions, and the greatly improved software deployment of these models and methods onto GPU and CPU hardware platforms. We have now approached an era where multipole-based polarizable force fields can be routinely used to obtain computational results comparable to state-of-the-art density functional theory while reaching sampling statistics that are acceptable when compared to that obtained from simpler fixed partial charge force fields.