Model of charge transfer collisions between C60 and slow ions.

A semiclassical model describing the charge transfer collisions of C60 fullerene with different slow ions has been developed to analyze available observations. These data reveal multiple Breit-Wigner-like peaks in the cross sections, with subsequent peaks of reactive cross sections decreasing in magnitude. Calculations of charge transfer probabilities, quasi-resonant cross sections, and cross sections for reactive collisions have been performed using semiempirical interaction potentials between fullerenes and ion projectiles. All computations have been carried out with realistic wave functions for C60's valence electrons derived from the simplified jellium model. The quality of these electron wave functions has been successfully verified by comparing theoretical calculations and experimental data on the small angle cross sections of resonant C60+C60 + collisions. Using the semiempirical potentials to describe resonant scattering phenomena in C60 collisions with ions and Landau-Zener charge transfer theory, we calculated theoretical cross sections for various C60 charge transfer and fragmentation reactions which agree with experiments.

Characterizing stages of COVID-19 epidemics: a nonlinear physics perspective based on amplitude equations.

The relevant dynamics underlying COVID-19 waves is described from an amplitude space perspective. To this end, the amplitude dynamics of infected populations is considered in different stages of epidemic waves. Eigenvectors and their corresponding amplitudes are derived analytically for low-dimensional models and by means of computational methods for high-dimensional models. It is shown that the amplitudes of all eigenvectors as functions of time can be tracked through the diverse stages of COVID-19 waves featuring jumps at the stage boundaries. In particular, it is shown that under certain circumstances the initial, outbreak stage and the final, subsiding stage of an epidemic wave are primarily determined by the unstable eigenvector of the initial stage and its corresponding remnant vector of the final stage. The corresponding amplitude captures most of the dynamics of the emerging and subsiding epidemics such that the problem at hand effectively becomes one dimensional leading to a dramatic reduction of the complexity of the problem at hand. Explicitly demonstrated for the first-wave COVID-19 epidemics of the year 2020 in the state of New York and Pakistan are given.

Boids in a loop: Self-propelled particles within a flexible boundary.

We numerically explore the behavior of repelling and aligning self-propelled polar particles (boids) in two dimensions enclosed by a damped flexible and elastic loop-shaped boundary. We observe disordered, polar ordered, jammed, and circulating states. The latter produce a rich variety of boundary shapes, including circles, ovals, irregulars, ruffles, or sprockets, depending upon the bending moment of the boundary and the boundary to particle mass ratio. With the exception of the circulating states with nonround boundaries, states resemble those exhibited by attracting self-propelled particles, but here the confining boundary acts in place of a cohesive force. We attribute the formation of ruffles to instability mediated by pressure on the boundary when the speed of waves on the boundary approximately matches the self-propelled particle's swim speed.

Managed care and children with special health care needs.

Providing care to children with special health care needs within a managed care environment presents special challenges for providers and parents alike. The goal of managed care is to contain costs by encouraging or requiring members to obtain services through a designated network. In managed care programs, children and families may experience limited access to specialized care and services, along with decreased fragmentation inherent in fee-for-service care. For providers, managed care creates financial risk while offering opportunities for acquiring new skills and knowledge. The primary care provider assumes a central role in creating a medical home that links the child and family to a single provider who is an ongoing resource and partner in care. To provide comprehensive, coordinated, family-centered care, the medical home provider must learn about a variety of services available within the community and guide parents in learning how to access the services that meet their child's needs. Pediatric nurse practitioners can play a significant role in ensuring that children receive the most appropriate care.

Radiation exposure has increased in trauma patients over time.

BACKGROUND: Computed tomography (CT) scans have become imaging modalities of choice in trauma centers. The purposes of this study were to evaluate the trend of radiation exposure in acute trauma patients. Our hypothesis was that radiation dosage and charges would increase over time without change in patient acuity or outcome. METHODS: Five hundred consecutive trauma patients were retrospectively reviewed for the years 2002, 2005, and 2008. Total number of CT scans, plain radiographs, and total radiation dosage (milliSieverts [mSV]) were determined. Charges were calculated. Injury severity scores and mortality were determined. RESULTS: The mean number of CT scans for category 1 patients in 2002, 2005, and 2008 was 1.5, 3.1, and 4.6, respectively (p = 0.01). This trend was similar in category 2 patients: 2.0, 3.5, 5.1, respectively (p < 0.01). Significant decreases in plain radiography were noted concurrently. This contributed to increased total radiation exposure to categories 1 and 2 patients over 2002, 2005, and 2008: 12.0 mSV, 23.6 mSV, and 33.6 mSV (p = 0.02); and 17.5 mSV, 24.1 mSV, and 37.5 mSV (p < 0.001), respectively. Charges for diagnostic imaging per patient also increased for categories 1 and 2 patients over 2002, 2005, and 2008: $2,933, $4,656, and $6,677; and $4,105, $5,344, and $7,365, respectively (all p < 0.01). Over the course of a year for 4,800 trauma patients treated at our hospital, this is expected to accrue additional charges of $13 million. CONCLUSION: The number of CT scans per trauma patient has more than doubled over 6 years, generating more radiation exposure and charges per patient, despite no change in mortality or injury severity. Judicious use of advanced imaging may control risks and costs without compromising care. LEVEL OF EVIDENCE: III, retrospective.

Crankshaft effect after posterior spinal fusion and unit rod instrumentation in children with cerebral palsy.

Radiographs and charts were reviewed for all children with cerebral palsy who underwent posterior-only spinal fusion with the unit rod for neuromuscular scoliosis by the senior author from 1989 through 1996. Fifty patients were found to have an open triradiate cartilage at the time of fusion. A single observer obtained measurements of the preoperative, postoperative, and most recent spine films using the standard Cobb angle. Amount of change was calculated over the respective periods. Forty-three patients had at least 2 years of clinical follow-up. Twenty-nine patients had more than 2 years of both radiographic (mean, 4.6 years) and clinical follow-up (mean, 4.8 years) with a closed triradiate cartilage on their most recent films. In this group, the mean absolute curve change over the length of radiographic follow-up was 0.6 degrees (range, -9-14). None of the 43 patients with at least 2 years of clinical follow-up (mean, 4.5 years) had any radiographic change that was clinically significant on chart review. Therefore posterior spinal fusion alone with unit rod instrumentation is adequate treatment to control crankshaft deformity in skeletally immature children with neuromuscular scoliosis due to cerebral palsy.

Trisomy 21 associated with ovarian dysgerminoma.

A 13-year-old G(0)P(0) white female with trisomy 21 presented with a complex pelvic mass. She underwent resection of the mass and complete staging for what was found to be a stage IIIC completely resected dysgerminoma. She was treated with three cycles of bleomycin, etoposide, and cisplatin chemotherapy and remains free of disease 1 year later. This association is presented as a rare case that may illustrate the relative increase in germ cell neoplasms in female patients with Down's syndrome. While the association of seminoma with Down's syndrome has been documented in a number of cases in males, the female counterpart of this tumor, dysgerminoma, in trisomy 21 has been reported quite infrequently. The potential for germ cell tumors in both male and female trisomy 21 is therefore illustrated.