Effects of Volume Changes on the Thermal Performance of PCM Layers Subjected to Oscillations of the Ambient Temperature: Transient and Steady Periodic Regimes.

The Stefan problem regarding the formation of several liquid-solid interfaces produced by the oscillations of the ambient temperature around the melting point of a phase change material has been addressed by several authors. Numerical and semi-analytical methods have been used to find the thermal response of a phase change material under these type of boundary conditions. However, volume changes produced by the moving fronts and their effects on the thermal performance of phase change materials have not been addressed. In this work, volume changes are incorporated through an additional equation of motion for the thickness of the system. The thickness of the phase change material becomes a dynamic variable of motion by imposing total mass conservation. The modified equation of motion for each interface is obtained by coupling mass conservation with a local energy-mass balance at each front. The dynamics of liquid-solid interface configurations is analyzed in the transient and steady periodic regimes. Finite element and heat balance integral methods are used to verify the consistency of the solutions to the proposed model. The heat balance integral method is modified and adapted to find approximate solutions when two fronts collide, and the temperature profiles are not smooth. Volumetric corrections to the sensible and latent heat released (absorbed) are introduced during front formation, annihilation, and in the presence of two fronts. Finally, the thermal energy released by the interior surface is estimated through the proposed model and compared with the solutions obtained through models proposed by other authors.

Association between circulating levels of sex steroid hormones and Barrett's esophagus in men: a case-control analysis.

BACKGROUND & AIMS: Esophageal adenocarcinoma is believed to result from the progression of gastroesophageal reflux disease to erosive esophagitis and re-epithelialization of the esophagus with a columnar cell population termed Barrett's esophagus (BE). Men develop BE and esophageal adenocarcinoma more frequently than women, yet little is known about the mechanisms of this difference. We assessed whether sex steroid hormones were associated with BE in a male population. METHODS: We analyzed data from the Barrett's Esophagus Early Detection Case Control Study, based at the Walter Reed National Military Medical Center. Blood samples were collected from 174 men with BE and 213 men without BE (controls, based on endoscopic analysis); 13 sex steroid hormones were measured by mass spectrometry and sex hormone binding globulin was measured by enzyme-linked immunosorbent assay. We also calculated free estradiol, free testosterone, and free dihydrotestosterone (DHT). We used multivariable logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) adjusted for age, race, smoking status, alcohol consumption, body mass index, heartburn, regurgitation, and gastroesophageal symptom score (excluding heartburn and regurgitation). RESULTS: Levels of free testosterone and free DHT were associated positively with BE risk; patients in the highest quartile for these hormones were most likely to have BE (free testosterone: OR, 5.36; 95% CI, 2.21-13.03; P = .0002; free DHT: OR, 4.25; 95% CI, 1.87-9.66; P = .001). Level of estrone sulfate was associated inversely with BE risk (P for trend = .02). No other hormone was associated with BE risk. Relationships were not modified by age or BMI. CONCLUSIONS: In an analysis of men, levels of free testosterone and free DHT were significantly associated with BE.

The role of endoscopy in the management of GERD.

We recommend that uncomplicated GERD be diagnosed on the basis of typical symptoms without the use of diagnostic testing, including EGD. We recommend EGD for patients who have symptoms suggesting complicated GERD or alarm symptoms. We recommend that EGD not be routinely performed solely for the assessment of extraesophageal GERD symptoms. We recommend that endoscopic findings of reflux esophagitis be classified according to an accepted grading scale or described in detail. We suggest that repeat EGD be performed in patients with severe erosive esophagitis after at least an 8-week course of PPI therapy to exclude underlying BE or dysplasia. 44BB We recommend against obtaining tissue samples from endoscopically normal tissue to diagnose GERD or exclude BE in adults. We suggest that endoscopy be considered in patients with multiple risk factors for Barrett's esophagus. We recommend that tissue samples be obtained to confirm endoscopically suspected Barrett's esophagus. We suggest that endoscopic antireflux therapy be considered for selected patients with uncomplicated GERD after careful discussion with the patient regarding potential adverse effects, benefits, and other available therapeutic options.

Existing and emerging therapies for irritable bowel syndrome.

INTRODUCTION: Irritable bowel syndrome is a common disorder that is associated with a significant impact on both affected individuals and society. While the pathophysiology of irritable bowel syndrome remains unknown, knowledge regarding the normal and abnormal functions of the gut and its complex interaction with the body's nervous systems continues to shed light on the multifactorial origins of irritable bowel syndrome symptoms. This article provides an overview of the current knowledge of the therapeutic approaches to irritable bowel syndrome. AREAS COVERED: A search of the online bibliographic databases MEDLINE and EMBASE was performed in order to identify all relevant articles published between 1980 and 2010. The search was enhanced with the use of a medical librarian. Bibliographies from potentially relevant articles were manually searched. EXPERT OPINION: The therapeutic options for irritable bowel syndrome are rapidly evolving beyond traditional symptom-based therapies, such as fiber, antispasmodics, antidiarrheals and laxatives, and are moving toward agents with organ-specific receptor selectivity directed, in many cases, at specific gastrointestinal functions.

Endoscopic ultrasound does not accurately stage early adenocarcinoma or high-grade dysplasia of the esophagus.

BACKGROUND & AIMS: Patients with esophageal high-grade dysplasia or mucosal esophageal cancer can be successfully treated by endoscopy. We performed a systematic review of the literature to determine whether endoscopic ultrasound (EUS) correctly predicts the T-stage of early esophageal cancers, compared with pathology specimens obtained by using endoscopic mucosal resection (EMR) or surgery. METHODS: Standard systematic review methods were used to perform reference searches, determine eligibility, abstract data, and analyze data. When possible, individual patient-level data were abstracted, in addition to publication-level aggregate data. RESULTS: Twelve studies had sufficient information to abstract and review for quality; 8 had individual patient-level data (n = 132). Compared with surgical or EMR pathology staging, EUS had T-stage concordance of 65%, including all studies (n = 12), but only 56% concordance when limited to individual patient-level data. Factors such as initial biopsy pathology (high-grade dysplasia vs early-stage cancer) did not appear to affect the concordance of staging between EUS and EMR/surgical staging. CONCLUSIONS: EUS is not sufficiently accurate in determining the T-stage of high-grade dysplasias or superficial adenocarcinomas; other means of staging, such as EMR, should be used.