Analytical Approximations of Critical Clearing Time for Parametric Analysis of Power System Transient Stability

An analytic approximation for the critical clearing time (CCT) metric is derived from direct methods for power system stability. The formula has been designed to incorporate as many features of transient stability analysis as possible such as different fault locations and different post-fault network states. The purpose of this metric is to analyse trends in stability (in terms of CCT) of power systems under the variation of a system parameter. The performance of this metric to measure stability trends is demonstrated on an aggregated power network, the so-called two machine infinite bus network, by varying load parameters in the full bus admittance matrix using numerical continuation. The metric is compared to two other expressions for the CCT which incorporate additional non-linearities present in the model

Value of individual surgeon performance metrics as quality assurance measures in oesophagogastric cancer surgery

Background Surgeon‐level operative mortality is widely seen as a measure of quality after gastric and oesophageal resection. This study aimed to evaluate this alongside a compound‐level outcome analysis. Methods Consecutive patients who underwent treatment including surgery delivered by a multidisciplinary team, which included seven specialist surgeons, were studied. The primary outcome was death within 30 days of surgery; secondary outcomes were anastomotic leak, Clavien–Dindo morbidity score, lymph node harvest, circumferential resection margin (CRM) status, disease‐free (DFS), and overall (OS) survival. Results The median number of annual resections per surgeon was 10 (range 5–25), compared with 14 (5–25) for joint consultant teams (P = 0·855). The median annual surgeon‐level mortality rate was 0 (0–9) per cent versus an overall network annual operative mortality rate of 1·8 (0–3·7) per cent. Joint consultant team procedures were associated with fewer operative deaths (0·5 per cent versus 3·4 per cent at surgeon level; P = 0·027). The median surgeon anastomotic leak rate was 12·4 (range 9–20) per cent (P = 0·625 versus the whole surgical range), overall morbidity 46·5 (31–60) per cent (P = 0·066), lymph node harvest 16 (9–29) (P < 0·001), CRM positivity 32·0 (16–46) per cent (P = 0·003), 5‐year DFS rate 44·8 (29–60) per cent and OS rate 46·5 (35–53) per cent. No designated metrics were independently associated with DFS or OS in multivariable analysis. Conclusion Annual surgeon‐level metrics demonstrated wide variations (fivefold), but these performance metrics were not associated with survival

Temporal variability and statistics of the Strehl ratio in adaptive-optics images

We have investigated the temporal variability and statistics of the "instantaneous" Strehl ratio. The observations were carried out with the 3.63-m AEOS telescope equipped with a high-order adaptive optics system. In this paper Strehl ratio is defined as the peak intensity of a single short exposure. We have also studied the behaviour of the phase variance computed on the reconstructed wavefronts. We tested the Marechal approximation and used it to explain the observed negative skewness of the Strehl ratio distribution. The estimate of the phase variance is shown to fit a three-parameter Gamma distribution model. We show that simple scaling of the reconstructed wavefronts has a large impact on the shape of the Strehl ratio distribution.Comment: submitted to PAS

Diabetes and prediabetes in patients with hepatitis B residing in North America

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115977/1/hep28110-sup-0001-suppinfo01.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/115977/2/hep28110.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/115977/3/hep28110_am.pd

Propensity score analysis of 18-FDG PET/CT-enhanced staging in patients undergoing surgery for esophageal cancer

Purpose PET/CT is now integral to the staging pathway for potentially curable esophageal cancer (EC), primarily to identify distant metastases undetected by computed tomography. The aim of this study was to analyze the effect of PET/CT introduction on survival and assess patterns of recurrence after esophagectomy. Methods A longitudinal cohort of EC patients staged between 1998 and 2016 were considered for inclusion. After co-variate adjustment using propensity scoring, a cohort of 496 patients (273 pre-PET/CT and 223 post-PET/CT) who underwent esophagectomy [median age 63 years (31–80), 395 males, 425 adenocarcinomas, 71 squamous cell carcinomas, 325 neoadjuvant therapy] were included. The primary outcome measure was overall survival (OS) based on intention to treat. Results Three-year OS pre-PET/CT was 42.5% compared with 57.8% post-PET/CT (Chi2 6.571, df 1, p = 0.004). On multivariable analysis, pT stage (HR 1.496 [95% CI 1.28–1.75], p < 0.0001), pN stage (HR 1.114 [95% CI 1.04–1.19], p = 0.001) and PET/CT staging (HR 0.688 [95% CI 0.53–0.89] p = 0.004) were independently associated with OS. Recurrent cancer was observed in 125 patients (51.4%) pre-PET/CT, compared with 74 patients post-PET/CT (37.8%, p = 0.004), and was less likely to be distant recurrence after PET/CT introduction (39.5 vs. 27.0%, p = 0.006). Conclusions Enhanced PET/CT staging is an important modality and independent factor associated with improved survival in patients undergoing esophagectomy for cancer

Competition between Magnetic and Structural Transition in CrN

CrN is observed to undergo a paramagnetic to antiferromagnetic transition accompanied by a shear distortion from cubic NaCl-type to orthorhombic structure. Our first-principle plane wave and ultrasoft pseudopotential calculations confirm that the distorted antiferromagnetic phase with spin configuration arranged in double ferromagnetic sheets along [110] is the most stable. Antiferromagnetic ordering leads to a large depletion of states around Fermi level, but it does not open a gap. Simultaneous occurence of structural distortion and antiferromagnetic order is analyzed.Comment: 10 pages, 10 figure