Recent Advances in Understanding Particle Acceleration Processes in Solar Flares

We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares, inspired by RHESSI observations. The individual articles are to appear in Space Science Reviews (2011

Identifying optimal techniques for laparoscopic sleeve gastrectomy based on outcomes of surgeons ranked by safety and efficacy

Background: Considerable technical variation exists when performing laparoscopic sleeve gas-trectomy (SG). However, little is known about which techniques are associated with optimal outcomes. Objective: To identify technique-specific variables common among surgeons with the best out-comes for SG based on rankings for safety and efficacy. Methods: Practicing surgeons (n = 30) voluntarily submitted a video of a typical SG between 2015-2016. Technique-specific data was captured from each video as well as a survey questionnaire and included: bougie size, stapler vendor, type of staple loads, oversewing, imbricating, use of buttressing, use of fibrin sealant, intraoperative leak test, intraoperative endoscopy and drain placement. Surgeon-specific operative times, risk-adjusted 30-day complication rates as well as 1-year patient reported outcomes were obtained from cases performed by surgeons during the study period (n = 7,023) using a state-wide bariatric-specific data registry. Surgeons were ranked using a composite score based on 4 outcome variables for safety (overall and severe complications, hemorrhage and reoperation rates) and 2 outcome variables for efficacy (weight loss and satisfaction rate). Pearson\u27s r coefficient was calculated to identify a correlation between surgeon rankings for safety vs. efficacy. Univariate analysis was performed to identify technique-specific variables associated with surgeons in the top and bottom quartiles for safety and efficacy. Results: Surgeons ranked in the top quartile for safety (n = 7) had an overall complication rate of 2.87% (0%-4.9%), severe complication rate of 0.46% (0%-1%), hemorrhage rate of 0.29% (0%-1.1%) and reoperation rate of 0.11% (0%-0.6%). Surgeons ranked in the top quartile for efficacy (n = 8) had patients with a mean excess body weight loss of 61.3% (58%-63.6%) and a satisfaction rate of 89.6% (87.5%-93.3%) at 1 year after surgery. There was no correlation between surgeon\u27s rankings for safety and efficacy (r = 0.12, p = 0.52). Surgeons ranked in the top quartile for safety and efficacy had shorter operative times than surgeons in the bottom quartiles (64 min vs 89 min, p\0.0001 and 75 min vs 95 min, p\0.0001, respectively). Surgeons ranked in the top quartile for safety were more likely to use buttressing material (71.4% vs 16.7%, p = 0.05). The remaining technique-specific variables were not significantly different between top and bottom quartiles. Conclusions: Surgeon rankings for safety did not correlate with those for efficacy. The safest surgeons were more likely to use buttressing material, otherwise, there were no unique technique-specific variables among top performers. Top ranked surgeons had faster operative times, indicating that there may be other metrics of technical quality that correlate to optimal outcomes

Predictors of one-year follow-up patient survey completion after bariatric surgery

Background: The impact of bariatric surgery on comorbidity remission and quality of life requires long term evaluation of outcomes. Most MBSAQIP centers struggle to achieve lifelong, in-person, follow-up for bariatric surgery patients. An alternative strategy utilizes patient completed surveys. Identification of patient and site specific factors associated with survey completion may provide valuable information for practices seeking to maximize follow-up rates This study aims to identify factors that are associated with patients\u27 completion rates of previously validated one-year follow-up surveys after bariatric surgery. Methods: Using clinical registry data from the Michigan Bariatric Surgery Collaborative, we included all patients who underwent bariatric surgery at 38 unique hospitals from January 2012 thru October 2015. Procedure type, demographic data, co-morbidities, and 30-day postoperative complications were evaluated for significant predictors of follow-up. Hospital specific rates of survey completion were compared. Results: A total of 24,781 patients underwent bariatric surgery during the study period and 11,125 (44.9%) completed one-year follow-up surveys. Compared to Roux-en-Y gastric bypass, the follow-up rate was lower after laparoscopic adjustable gastric banding (OR= 0.49; CI = 0.41-0.58) but higher after sleeve gastrectomy (OR= 1.22; CI= 0.82-1.80). Better follow-up was noted with annual household incomes 4 $10,000 (OR= 1.54; CI= 1.39-1.70), college graduates (OR= 1.38; CI= 1.28-1.49), older age (OR= 1.02; CI= 1.02-1.03) and those who were married or living with a significant other (OR = 1.3; CI= 1.23-1.37). Serious postoperative complications, private insurance, Black race, and tobacco use were associated with lower follow-up rates (all p\u3c 0.0001). During the study period, average follow-up rates increased from 28% in 2012 to 52% in 2015 (Figure 1). Follow-up rates at the hospital level ranged from 0% to 81% per year. Six hospitals (16%) had persistently high follow-up rates (≥ 42% per year) while rates increased 20% to 40% in 10 hospitals (26%) and 4 40% in 9 hospitals (24%). Conclusion: Procedure type, socioeconomic factors and serious complications have significant associations with completion of one-year follow-up surveys after bariatric surgery. Certain hospitals had improved rates of follow-up indicating that hospitals pecific protocols may play an important role in obtaining followup data. Elucidation of these systematic follow-up protocols may allow optimization of long term data acquisition

Regulation of SR-BI protein levels by phosphorylation of its associated protein, PDZK1

Scavenger receptor class B type I (SR-BI) is a high-density lipoprotein (HDL) receptor that mediates the selective uptake of HDL cholesterol and cholesterol secretion into bile in the liver. Previously, we identified an SR-BI-associated protein, termed PDZK1, from rat liver membrane extracts. PDZK1 contains four PSD-95/Dlg/ZO-1 (PDZ) domains, the first of which in the N-terminal region is responsible for the association with SR-BI. PDZK1 controls hepatic SR-BI expression in a posttranscriptional fashion both in cell culture and in vivo. In this study, we demonstrated that the C-terminal region of PDZK1 is crucial for up-regulating SR-BI protein expression. Metabolic labeling experiments and phosphoamino acid analysis revealed that PDZK1 is phosphorylated at Ser residues within this region. Point-mutation analysis demonstrated that PDZK1 is phosphorylated at Ser-509. Interestingly, a mutant PDZK1, in which Ser-509 was replaced with Ala, lost the ability to up-regulate SR-BI protein. We identified Ser-509 of PDZK1 as the residue that is phosphorylated by the cAMP-dependent PKA in vitro as well as in cell culture. Ser-509 of PDZK1 in rat liver was also phosphorylated, as shown by an Ab that specifically detects phosphorylated Ser-509. Administration of glucagon to Wistar rats increased PDZK1 phosphorylation as well as hepatic SR-BI and PDZK1 expression while it decreased plasma HDL levels, indicating that PDZK1 phosphorylation is hormonally regulated. These findings suggest that phosphorylation of PDZK1 has an important role in the regulation of hepatic SR-BI expression and, thus, influences plasma HDL levels