Modeling of Stochastic Wind Based on Operational Flight Data Using Karhunen-Loève Expansion Method.

Wind has a significant influence on the operational flight safety. To quantify the influence of the wind characteristics, a wind series generator is required in simulations. This paper presents a method to model the stochastic wind based on operational flight data using the Karhunen-Loève expansion. The proposed wind model allows us to generate new realizations of wind series, which follow the original statistical characteristics. To improve the accuracy of this wind model, a vine copula is used in this paper to capture the high dimensional dependence among the random variables in the expansions. Besides, the proposed stochastic model based on the Karhunen-Loève expansion is compared with the well-known von Karman turbulence model based on the spectral representation in this paper. Modeling results of turbulence data validate that the Karhunen-Loève expansion and the spectral representation coincide in the stationary process. Furthermore, construction results of the non-stationary wind process from operational flights show that the generated wind series have a good match in the statistical characteristics with the raw data. The proposed stochastic wind model allows us to integrate the new wind series into the Monte Carlo Simulation for quantitative assessments.

Review on novel concepts of columnar lined esophagus.

BACKGROUND: Columnar lined esophagus (CLE) is a marker for gastroesophageal reflux and associates with an increased cancer risk among those with Barrett's esophagus. Recent studies fostered the development of integrated CLE concepts. METHODS: Using PubMed, we conducted a review of studies on novel histopathological concepts of nondysplastic CLE. RESULTS: Two histopathological concepts-the squamo-oxyntic gap (SOG) and the dilated distal esophagus (DDE), currently model our novel understanding of CLE. As a consequence of reflux, SOG interposes between the squamous lined esophagus and the oxyntic mucosa of the proximal stomach. Thus the SOG describes the histopathology of CLE within the tubular esophagus and the DDE, which is known to develop at the cost of a shortened lower esophageal sphincter and foster increased acid gastric reflux. Histopathological studies of the lower end of the esophagus indicate, that the DDE is reflux damaged, dilated, gastric type folds forming esophagus and cannot be differentiated from proximal stomach by endoscopy. While the endoscopically visible squamocolumnar junction (SCJ) defines the proximal limit of the SOG, the assessment of the distal limit requires the histopathology of measured multilevel biopsies. Within the SOG, CLE types distribute along a distinct zonation with intestinal metaplasia (IM; Barrett's esophagus) and/or cardiac mucosa (CM) at the SCJ and oxyntocardiac mucosa (OCM) within the distal portion of the SOG. The zonation follows the pH-gradient across the distal esophagus. Diagnosis of SOG and DDE includes endoscopy, histopathology of measured multi-level biopsies from the distal esophagus, function, and radiologic tests. CM and OCM do not require treatment and are surveilled in 5 year intervals, unless they associate with life quality impairing symptoms, which demand medical or surgical therapy. In the presence of an increased cancer risk profile, it is justified to consider radiofrequency ablation (RFA) of IM within clinical studies in order to prevent the progression to dysplasia and cancer. Dysplasia justifies RFA ± endoscopic resection. CONCLUSIONS: SOG and DDE represent novel concepts fusing the morphological and functional aspects of CLE. Future studies should examine the impact of SOG and DDE for monitoring and management of gastroesophageal reflux disease (GERD).

The cardia: esophageal or gastric? Critical reviewing the anatomy and histopathology of the esophagogastric junction.

BACKGROUND: Discrepancy exists regarding the anatomical allocation of the cardia: esophageal or gastric. With this review we aimed to clarify this issue. METHODS: Using PUB MED, Scopus and Google we analyzed the recent literature (1889-2012) regarding the "esophageal" vs. the "gastric" cardia. RESULTS: The synonymous use of the term cardia to describe the anti reflux mechanism within the distal portion of the esophagus and the proximal segment of the stomach nourished the misunderstanding, that the cardia represents a normal anatomical structure interposed between the tubular esophagus and the body of the stomach. Anatomical, histopathological and physiological studies revealed that what has been taken for gastric cardia in fact represents reflux damaged dilated distal esophagus (DDE). Since DDE is covered by columnar lined esophagus (CLE) it cannot be differentiated from the proximal stomach during regular endoscopy. However, the histopathology of multi level biopsies obtained from the endoscopically suspected esophagogastric junction (EGJ) serves to allocate the origin of the columnar lined foregut, esophageal (cardiac, oxyntocardiac mucosa, intestinal metaplasia) vs. gastric (oxyntic mucosa). CONCLUSIONS: Neither the esophagus nor the stomach contains a "cardia". The recent misconceptions regarding the foregut anatomy explain, why the innermost coverage of the reflux damaged esophagus is termed "cardiac mucosa". Thus the term should be reserved to name the histopathology of cardiac and oxyntocardiac mucosa, which develop due to gastroesophageal reflux within the distal esophagus.