Analysis of defect structure in silicon. Characterization of samples from UCP ingot 5848-13C

Statistically significant quantitative structural imperfection measurements were made on samples from ubiquitous crystalline process (UCP) Ingot 5848 - 13 C. Important trends were noticed between the measured data, cell efficiency, and diffusion length. Grain boundary substructure appears to have an important effect on the conversion efficiency of solar cells from Semix material. Quantitative microscopy measurements give statistically significant information compared to other microanalytical techniques. A surface preparation technique to obtain proper contrast of structural defects suitable for QTM analysis was perfected

Silicon sheet growth development for the large area silicon sheet task of the low cost solar array project. Quantitative analysis of defects in silicon

The various steps involved in obtaining quantitative information of structural defects in crystalline silicon samples are described. Procedures discussed include: (1) chemical polishing; (2) chemical etching; and (3) automated image analysis of samples on the QTM 720 System

Quantitative analysis of defects in silicon: Silicon sheet growth development for the large area silicon sheet task of the low cost solar array project

The various steps involved in the chemical polishing and etching of silicon samples are described and the data on twins, grain boundaries and dislocation pits from fifty-three (53) samples are discussed

Accelerating Asymptotically Exact MCMC for Computationally Intensive Models via Local Approximations

We construct a new framework for accelerating Markov chain Monte Carlo in posterior sampling problems where standard methods are limited by the computational cost of the likelihood, or of numerical models embedded therein. Our approach introduces local approximations of these models into the Metropolis-Hastings kernel, borrowing ideas from deterministic approximation theory, optimization, and experimental design. Previous efforts at integrating approximate models into inference typically sacrifice either the sampler's exactness or efficiency; our work seeks to address these limitations by exploiting useful convergence characteristics of local approximations. We prove the ergodicity of our approximate Markov chain, showing that it samples asymptotically from the \emph{exact} posterior distribution of interest. We describe variations of the algorithm that employ either local polynomial approximations or local Gaussian process regressors. Our theoretical results reinforce the key observation underlying this paper: when the likelihood has some \emph{local} regularity, the number of model evaluations per MCMC step can be greatly reduced without biasing the Monte Carlo average. Numerical experiments demonstrate multiple order-of-magnitude reductions in the number of forward model evaluations used in representative ODE and PDE inference problems, with both synthetic and real data.Comment: A major update of the theory and example

Quantitative analysis of defects in silicon. Silicon sheet growth development for the large are silicon sheet task of the low-cost solar array project

One hundred and seventy four silicon sheet samples were analyzed for twin boundary density, dislocation pit density, and grain boundary length. Procedures were developed for the quantitative analysis of the twin boundary and dislocation pit densities using a QTM-720 Quantitative Image Analyzing system. The QTM-720 system was upgraded with the addition of a PDP 11/03 mini-computer with dual floppy disc drive, a digital equipment writer high speed printer, and a field-image feature interface module. Three versions of a computer program that controls the data acquisition and analysis on the QTM-720 were written. Procedures for the chemical polishing and etching were also developed

Analysis of defect structure in silicon. Characterization of SEMIX material. Silicon sheet growth development for the large area silicon sheet task of the low-cost solar array project

Statistically significant quantitative structural imperfection measurements were made on samples from ubiquitous crystalline process (UCP) Ingot 5848 - 13C. Important correlation was obtained between defect densities, cell efficiency, and diffusion length. Grain boundary substructure displayed a strong influence on the conversion efficiency of solar cells from Semix material. Quantitative microscopy measurements gave statistically significant information compared to other microanalytical techniques. A surface preparation technique to obtain proper contrast of structural defects suitable for quantimet quantitative image analyzer (QTM) analysis was perfected and is used routinely. The relationships between hole mobility and grain boundary density was determined. Mobility was measured using the van der Pauw technique, and grain boundary density was measured using quantitative microscopy technique. Mobility was found to decrease with increasing grain boundary density

Analysis of defect structure in silicon. Silicon sheet growth development for the large area silicon sheet task of the Low-Cost Solar array Project

One hundred ninety-three silicon sheet samples, approximately 880 square centimeters, were analyzed for twin boundary density, dislocation pit density, and grain boundary length. One hundred fifteen of these samples were manufactured by a heat exchanger method, thirty-eight by edge defined film fed growth, twenty-three by the silicon on ceramics process, and ten by the dendritic web process. Seven solar cells were also step-etched to determine the internal defect distribution on these samples. Procedures were developed or the quantitative characterization of structural defects such as dislocation pits, precipitates, twin & grain boundaries using a QTM 720 quantitative image analyzing system interfaced with a PDP 11/03 mini computer. Characterization of the grain boundary length per unit area for polycrystalline samples was done by using the intercept method on an Olympus HBM Microscope

A study of serum sodium levels in decompensated chronic liver disease and its clinical significance.

Decompensated Chronic Liver Disease is associated with disturbances in regulation of water balance leading on to abnormalities in serum sodium. Various studies have established a correlation between serum sodium levels and survival in these patients. Dilutional Hyponatremia due to impaired free water clearance is the most common dysnatremia while hypernatremia due to cathartic use has also been reported in few studies. The aim of this study was to study the serum sodium levels in patients with DCLD and to establish its significance. Hyponatremia is more common in DCLD and low serum sodium levels are associated with increased frequency of complications such as hepatic encephalopathy, hepatorenal syndrome, spontaneous bacterial peritonitis and GI bleeding. Lower serum sodium levels were associated with increased MELD CPS score and mortality indicating the inverse relationship between serum sodium levels and severity of the disease

Maximum Likelihood Estimation for Single Particle, Passive Microrheology Data with Drift

Volume limitations and low yield thresholds of biological fluids have led to widespread use of passive microparticle rheology. The mean-squared-displacement (MSD) statistics of bead position time series (bead paths) are either applied directly to determine the creep compliance [Xu et al (1998)] or transformed to determine dynamic storage and loss moduli [Mason & Weitz (1995)]. A prevalent hurdle arises when there is a non-diffusive experimental drift in the data. Commensurate with the magnitude of drift relative to diffusive mobility, quantified by a P\'eclet number, the MSD statistics are distorted, and thus the path data must be "corrected" for drift. The standard approach is to estimate and subtract the drift from particle paths, and then calculate MSD statistics. We present an alternative, parametric approach using maximum likelihood estimation that simultaneously fits drift and diffusive model parameters from the path data; the MSD statistics (and consequently the compliance and dynamic moduli) then follow directly from the best-fit model. We illustrate and compare both methods on simulated path data over a range of P\'eclet numbers, where exact answers are known. We choose fractional Brownian motion as the numerical model because it affords tunable, sub-diffusive MSD statistics consistent with typical 30 second long, experimental observations of microbeads in several biological fluids. Finally, we apply and compare both methods on data from human bronchial epithelial cell culture mucus.Comment: 29 pages, 12 figure

Early postoperative outcomes of dunking pancreatojejunostomy

Background: There is no gold standard method for pancreatico-enteric reconstruction.  In our department, dunking pancreatojejunostomy (DPJ) and Duct to mucosa PJ technique are done as per surgeon’s choice.  In this study, authors evaluate the early postoperative outcomes following DPJ based on ISGPS (2007).Methods: A Retrospective analysis of prospectively collected data from January 2008 to December 2015. Detailed information on these patients was maintained on a prospectively held computerized database. Routine drain amylase estimations are being done on POD 3and 5 for all patients undergoing pancreatic resections and on all subsequent days if output is suggestive of pancreatic fistula. Details of patients who have undergone pancreatic resection with duct to mucosa type of pancreato-intestinal anastomosis during the same period (64 patients) were also collected prospectively and analysed. DPJ and Duct to mucosa groups were not comparable with respect to age, duct size, pancreatic gland texture and co-morbidities. Hence direct comparison between the two groups has not been carried out.Results: A total of 75 of 139 pancreatic resections with pancreatointestinal anastomosis who had dunking PJ and fulfilled the study criteria were analysed; none were excluded for analysing early outcomes. 19 out of 75 (25.5%) developed grade ‘A’ POPF, five out of 75 (6.6%) developed Grade ‘B’ POPF and three out of 75 (3.3%) developed Grade ‘C’ POPF. 20 out of 75 (26.6%) had grade ‘A’ DGE, five out of 75 (6.6%) had grade ‘B’ DGE. PPH occurred in four out of 75 (5.3%), two out of four were early PPH, one was managed by coiling and other by re-laparotomy, two were late PPH both managed by coiling of the pseudo aneurysms. There was no 30-day mortality.Conclusions: Dunking (Invagiantion) pancreatojejunostomy has accepatable early outcomes with clinically significant/relevant postoperative pancreatic fistula rates of Grade B (6.6%) and Grade C (4%), delayed gastric emptying (33.2%) and post pancreatic hemorrhage (5.3%) rates. The outcomes are comparable with Duct-to-mucosa PJ mentioned in literature