Magnon-phonon hybridization in 2D antiferromagnet MnPSe3.

Magnetic excitations in van der Waals (vdW) materials, especially in the two-dimensional (2D) limit, are an exciting research topic from both the fundamental and applied perspectives. Using temperature-dependent, magneto-Raman spectroscopy, we identify the hybridization of two-magnon excitations with two phonons in manganese phosphorus triselenide (MnPSe3), a magnetic vdW material that hosts in-plane antiferromagnetism. Results from first-principles calculations of the phonon and magnon spectra further support our identification. The Raman spectra's rich temperature dependence through the magnetic transition displays an avoided crossing behavior in the phonons' frequency and a concurrent decrease in their lifetimes. We construct a model based on the interaction between a discrete level and a continuum that reproduces these observations. Our results imply a strong hybridization between each phonon and a two-magnon continuum. This work demonstrates that the magnon-phonon interactions can be observed directly in Raman scattering and provides deep insight into these interactions in 2D magnetic materials.

Laparoscopic versus open insertion of the peritoneal catheter in ventriculoperitoneal shunt placement: review of 810 consecutive cases.

OBJECT: Traditional ventriculoperitoneal (VP) shunt surgery involves insertion of the distal catheter by minilaparotomy. However, minilaparotomy may be a significant source of morbidity during shunt surgery. Laparoscopic insertion of the distal catheter is an alternative technique that may simplify and improve the safety of shunt surgery. METHODS: The authors performed a retrospective review of hospital records of all patients undergoing new VP shunt insertion at a tertiary care center between 2004 and 2009. Patient characteristics and outcomes were compared between patients undergoing open or laparoscopic insertion of the distal catheter. Independent variables in the analysis included age, sex, race, body mass index, surgical technique, previous VP shunt placement, previous abdominal procedures, American Society of Anesthesiology (ASA) score, and indication for shunt placement. Dependent variables included the occurrence of shunt failure, cause of shunt failure, complications, length of stay (LOS), LOS after shunt placement, estimated blood loss, and operative time. RESULTS: The authors identified 810 patients who met the inclusion criteria; open or laparoscopic distal catheter insertion was performed in 335 and 475 patients, respectively. There were no significant differences between the groups regarding age, race, ASA score, or indication for shunt placement. The most common indication was hydrocephalus due to subarachnoid hemorrhage, followed by tumor-associated hydrocephalus, normal pressure hydrocephalus (NPH), and hydrocephalus due to trauma. The incidence of shunt failure was not statistically different between cohorts, occurring in 20.0% of laparoscopic and 20.9% of open catheter placement cases (p = 0.791). With analysis of causes of shunt failure, shunt obstruction occurred significantly more often in the open surgery cohort (p = 0.012). In patients with a known cause shunt obstruction, distal obstruction occurred in 35.7% of the open cohort obstructions and 4.8% of the laparoscopic cohort obstructions (p = 0.014). The relative risk of distal obstruction in open cases compared with laparoscopic cases was 7.50. Infections occurred in 8.2% of laparoscopic cases compared with 6.6% of open cases (p = 0.419). Within the NPH subgroup, the laparoscopically treated patients had significantly more overdrainage (p = 0.040), whereas those in the open cohort experienced significantly more shunt obstructions (p = 0.034). Laparoscopically treated patients had shorter operative times (p < 0.0005), inpatient LOS (p < 0.001), and inpatient LOS after VP shunt placement (p = 0.01) as well as less blood loss (p = 0.058). CONCLUSIONS: To our knowledge this is the largest reported comparison of distal VP shunt catheter insertion techniques. Compared with minilaparotomy, the laparoscopic approach was associated with decreased time in the operating room and a decreased LOS. Moreover, laparoscopy was associated with fewer distal shunt obstructions. Laparoscopic shunt surgery is a viable alternative to traditional shunt surgery.

Elective surgical case cancellation in the Veterans Health Administration system: identifying areas for improvement.

BACKGROUND: This study evaluated elective surgical case cancellation (CC) rates, reasons for these cancellations, and identified areas for improvement within the Veterans Health Administration (VA) system. METHODS: CC data for 2006 were collected from the scheduling software for 123 VA facilities. Surveys were distributed to 40 facilities (10 highest and 10 lowest CC rates for high- and low-volume facilities). CC reasons were standardized and piloted at 5 facilities. RESULTS: Of 329,784 cases scheduled by 9 surgical specialties, 40,988 (12.4%) were cancelled. CC reasons (9,528) were placed into 6 broad categories: patient (35%), work-up/medical condition change (28%), facility (20%), surgeon (8%), anesthesia (1%), and miscellaneous (8%). Survey results show areas for improvement at the facility level and a standardized list of 28 CC reasons was comprehensive. CONCLUSIONS: Interventions that decrease cancellations caused by patient factors, inadequate work-up, and facility factors are needed to reduce overall elective surgical case cancellations.

Laparoscopic versus open approach for implantation of the peritoneal catheter during ventriculoperitoneal shunt placement.

BACKGROUND: Ventriculoperitoneal shunt (VPS) is the mainstay of therapy for hydrocephalus. The aim of this study is to compare outcomes of laparoscopic (LVPS) versus open (OVPS) techniques for placement of distal VPS catheters. METHODS: All patients undergoing new VPS placement at a tertiary care center between January 2004 and August 2007 were included. Univariate analysis was performed. Wilcoxon rank-sum, chi-square, and Fisher's exact tests were used to make comparisons between LVPS and OVPS groups. Stepwise backward logistic regression was performed to predict complications requiring operative intervention. A Kaplan-Meier estimate of the survival function was calculated for shunt survival. All data is presented as median and range unless otherwise specified. RESULTS: Five hundred thirty-five consecutive patients underwent 579 VPS (258 LVPS, 321 OVPS). Median age (52.0 years) and American Society of Anesthesiologists (ASA) score (3) were similar in LVPS and OVPS groups. Body mass index (BMI) [27.8 (17.0-64.9) kg/m(2) versus 25.9 (12.3-44.4) kg/m(2), p = 0.007], previous operations [0.8 +/- 0.9 versus 0.6 +/- 0.7, p = 0.004 (mean +/- standard deviation)], estimated blood loss (EBL) [20 (0-175) ml versus 25 (0-500) ml, p < 0.001], operating room (OR) time [37.5 (17.0-152.0) min versus 52.0 (20.0-197.0) min, p < 0.001], and length of stay (LOS) [11 (1-77) days versus 14 (1-225) days, p = 0.016] were statistically different between the LVPS and OVPS groups, respectively. LVPS abdominal complication rate of 5.8% and OVPS rate of 6.9% were similar (p = 0.611). Previous abdominal operation [odds ratio (OR) 1.673, 95% confidence interval (CI) 1.100-2.543, p = 0.016] and previous VPS (OR 1.929, 95% CI 1.147-3.243, p = 0.016) were significant predictors of complications requiring operative intervention. Kaplan-Meier analysis demonstrated no difference in survival between LVPS and OVPS groups (p = 0.538), with overall shunt survival of 86.4% at 6 months and 83.0% at 1 year. CONCLUSIONS: LVPS is associated with decreased OR time, less blood loss, and shorter LOS with no difference in complication rate when compared OVPS. The laparoscopic approach for VPS is a safe, effective, and readily reproducible alternative to the traditional open approach.

Pancreatic resection with islet cell autotransplant for the treatment of severe chronic pancreatitis.

Pancreatic resection can alleviate pain in properly selected patients with severe chronic pancreatitis (CP), although the apancreatic state causes "brittle" diabetes. Islet auto-transplantation (IAT) after resection can decrease diabetes-related morbidity. Twenty-six consecutive patients with CP who underwent 27 pancreatic resections with IAT from April 2005 to December 2007 were evaluated in this retrospective case control study. Data were collected by chart and operative note reviews and query of hospital databases. Subgroup analysis was performed on 21 cases of total pancreatectomy and six cases of pancreaticoduodenectomy (PD). Mean age was 43.8 years and 46.2 per cent of patients were female. The most common etiology of CP was alcoholism (34.6%), followed by idiopathic causes (30.8%) and pancreatic divisum (23.1%). There was no mortality and the complication rate was 56 per cent. Islet equivalents infused and islet equivalents/gram of pancreas were 82,094 and 2,739 respectively. Mean discharge insulin dose was 10.7 units/day. Mean follow-up was 6.5 months. At 6 months, 80 per cent of patients reporting had decreased or eliminated their use of narcotic medication and all total pancreatectomy patients required insulin (mean 23 units/day). In appropriately selected patients, pancreatic resection with IAT is safe and effective for the treatment of intractable pain associated with CP.