3,741 research outputs found

    Electric and magnetic radial diffusion coefficients using the Van Allen probes data

    Get PDF
    ULF waves are a common occurrence in the inner magnetosphere and they contribute to particle motion, significantly, at times. We used the magnetic and the electric field data from the Electric and Magnetic Field Instrument Suite and Integrated Sciences (EMFISIS) and the Electric Field and Waves instruments (EFW) on board the Van Allen Probes to estimate the ULF wave power in the compressional component of the magnetic field and the azimuthal component of the electric field, respectively. Using L∗, Kp, and magnetic local time (MLT) as parameters, we conclude that the noon sector contains higher ULF Pc-5 wave power compared with the other MLT sectors. The dawn, dusk, and midnight sectors have no statistically significant difference between them. The drift-averaged power spectral densities are used to derive the magnetic and the electric component of the radial diffusion coefficient. Both components exhibit little to no energy dependence, resulting in simple analytic models for both components. More importantly, the electric component is larger than the magnetic component by one to two orders of magnitude for almost all L∗ and Kp; thus, the electric field perturbations are more effective in driving radial diffusion of charged particles in the inner magnetosphere. We also present a comparison of the Van Allen Probes radial diffusion coefficients, including the error estimates, with some of the previous published results. This allows us to gauge the large amount of uncertainty present in such estimates

    Difference in Postoperative Outcomes and Perioperative Resource Utilization Between General Surgeons and Pediatric Surgeons: A Systematic Review

    Get PDF
    Background: Both general surgeons (GS) and pediatric surgeons (PS) perform a high volume of appendectomies in pediatric patients, but there is a paucity of data on these outcomes based on surgeon training. We performed a systematic review and meta-analysis to compare postoperative outcomes and perioperative resource utilization for pediatric appendectomies.Methods: We searched PubMed to identify articles examining the association between surgeon specialization and outcomes for pediatric patients undergoing appendectomies. Study selection, data extraction, risk of bias assessment, and quality assessment were performed by one reviewer, with another reviewer to resolve discrepancies.Results: We identified 4799 articles, with 98.4% (4724/2799) concordance after initial review. Following resolution of discrepancies, 16 studies met inclusion criteria. Of the studies that reported each outcome, GS and PS demonstrated similar rates of readmission within 30 days (pooled RR 1.61 95% CI 0.66, 2.55) wound infections (pooled RR 1.07, 95% CI .55, 1.60), use of laparoscopic surgery (pooled RR 1.87, 95% CI .21, 3.53), postoperative complications (pooled RR 1.40, 95% CI .83, 1.97), use of preoperative imaging (pooled RR .98,95% CI .90, 1.05), and intra-abdominal abscesses (pooled RR .80, 95% CI .03, 1.58). Patients treated by GS did have a significantly higher risk of negative appendectomies (pooled RR 1.47, 95% CI 1.10, 1.84) when compared to PS.Discussion: This is the first meta-analysis to compare outcomes for pediatric appendectomies performed by GS compared to PS. Patient outcomes and resource utilization were similar among PS and GS, except for negative appendectomies were significantly more likely with GS

    Evaluation of an integrated primary care-led dementia shared care program in Singapore: An effectiveness and cost-effectiveness study

    Get PDF
    Aim: With an aging Singapore population, there is an increasing demand for dementia care. The present study aimed to evaluate the effectiveness and cost-effectiveness of the Primary Care Dementia Clinic (PCDC) in comparison with the Memory Clinic (MC; hospital-based) and other polyclinics. Methods: A quasi-experimental design was implemented. Effectiveness of PCDC was assessed through caregiver satisfaction, quality of life (caregiver-rated) and adverse events rates. Quality-of-Life measures using the EuroQol 5 Dimension Questionnaire (EQ-5D) at baseline, 6 months and 12 months was assessed. Costs were calculated from a societal perspective. The incremental cost-effectiveness of the PCDC was compared with MC and other polyclinics. Results: The present study showed that quality of life and the rate of adverse events at 12 months were similar between the three groups. Caregiver satisfaction at 12 months was higher in the PCDC group when compared with other polyclinics. There were no observed differences in societal cost between the three groups. At 6-month follow up, direct medical costs for PCDC were significantly lower that of other polyclinics. At 12-month follow up, PCDC patients had higher Quality Adjusted Life Years (QALYs) compared with the MC group. Conclusion: PCDC provided effective care, similar to care at MC and better than care at other polyclinics. Caregiver satisfaction was higher for the PCDC group, and PCDC patients had lower direct medical costs at 6-month follow up. Given these findings, adopting a PCDC model in other polyclinics in Singapore can be beneficial for optimal right siting of patients.Nakul Saxena, Pradeep Paul George, Kelvin WS Teo, Woan Shin Tan, Charis Ng, Bee Hoon Heng, Cindy Ying Ying Yeo, Philomena Anthony, Colin Tan, Kang Yih Low, Valerie Wu, Noorhazlina Binte Ali and Mei Sian Chon

    Polarized Virtual Photon Structure Function g2Îłg_2^\gamma and Twist-3 Effects in QCD

    Full text link
    We investigate the twist-3 effects in the polarized virtual photon structure. The structure functions g1γg_1^\gamma and g2γg_2^\gamma of polarized photon could be experimentally studied in the future polarized epep or e+e−e^+e^- colliders. The leading contributions to g1γg_1^\gamma are the twist-2 effects, while another structure function g2γg_2^\gamma, which only exists for the virtual photon target, receives not only the twist-2 but also twist-3 contributions. We first show that the twist-3 effects actually exist in the box-diagram contributions and we extract the twist-3 part, which can also be reproduced by the pure QED operator product expansion. We then calculate the non-trivial lowest moment (n=3n=3) of the twist-3 contribution to g2γg_2^\gamma in QCD. For large NcN_c (the number of colors), the QCD analysis of the twist-3 effects in the flavor nonsinglet part of g2γg_2^\gamma becomes tractable and we can obtain its moments in a compact form for all nn.Comment: 27 pages, LaTeX, 9 eps figures, eqsection.sty file included, Appendix A added, some minor changes for Fig.
    • 

    corecore