Comparison of extended and ensemble based Kalman filters with low and high resolution primitive equation ocean models

International audienceKalman filters are widely used for data assimilation into ocean models. The aim of this study is to discuss the relevance of these filters with high resolution ocean models. This was investigated through the comparison of two advanced Kalman filters: the singular evolutive extended Kalman (SEEK) filter and its ensemble-based variant, called SEIK filter. The two filters were implemented with the Princeton Ocean model (POM) considering a low spatial resolution configuration (Mediterranean sea model) and a very high one (Pagasitikos Gulf coastal model). It is shown that the two filters perform reasonably well when applied with the low resolution model. However, when the high resolution model is considered, the behavior of the SEEK filter seriously degrades because of strong model nonlinearities while the SEIK filter remains remarkably more stable. Based on the assumption of prior Gaussian distributions, the linear analysis step of the latter can still be improved though

WHOI cable : time domain numerical simulation of moored and towed oceanographic systems

This report presents a numerical framework for analyzing the statics and dynamics of cable strctures commonly encountered in oceanographic engineering practice. The numerical program, WHOI Cable, features a nonlinear solver that includes the effects of geometric and material nonlinearties, bending stiffness for seamless modeling of slack cables, and a model for the interaction of cable segments with the seafoor. The program solves both surface and subsurface single-point mooring problems, systems with both ends anchored on the bottom, and towing and drifter problems. Forcing includes waves, current, ship speed, and pay-out of cable. The programs that make-up WHOI Cable run under Unix, DOS, and Windows. There is a familiar Windows-style interface available for Windows 95 and Windows NT platforms. In the report, the mathematical and numerical framework for WHOI Cable is described, followed by detailed instructions for formulating problem input files and running the codes. Examples are included in an appendix to highlight the range of problems that WHOI Cable can solve.Funding was provided by the Office of Naval Research through grants NOOOl4-92-J-1269 and N00014-95-1-0106 and an Office of Naval Research Graduate Fellowship

Eastern Mediterranean biogeochemical flux model: simulations of the pelagic ecosystem

International audienceDuring the second phase (2003?2006) of the Mediterranean ocean Forecasting System Project (MFS) named Toward Environmental Predictions (MFSTEP) one of the three major aims was the development of numerical forecasting systems. In this context a generic Biochemical Flux Model (BFM) was developed and coupled with hydrodynamic models already operating at basin scale as well as at regional areas. In the Eastern Mediterranean basin the BFM was coupled with the Aegean Levantine Eddy Resolving MOdel (ALERMO). The BFM is a generic highly complex model based on ERSEM and although a detailed description of the model and its sub models is beyond the scope of this work a short presentation of the main processes, paying emphasis on the parameter values used is presented. Additionally the performance of the model is evaluated with some preliminary results being qualitatively compared against field observations. The model at its present form is rather promising reproducing all major important features even though there are inefficiencies mostly related to primary and bacterial productivity rates

Evidence Linking Obstructive Sleep Apnea to Hypertension

Obstructive sleep apnea (OSA) has been linked to hypertension in several experimental, epidemiological, and clinical studies. Animal modes of sleep apnea have provided strong evidence for a causal relationship with hypertension. Studies in humans have demonstrated that patients with sleep apnea have an increased blood pressure and a higher incidence of hypertension.  The most compelling evidence linking OSA and hypertension was provided by data from the Wisconsin Sleep Cohort Study. This study has demonstrated a dose-response association between sleep-disordered breathing at baseline and the presence of de novo hypertension 4 years later.  The odds ratios for the presence of hypertension at the 4-year follow-up study according to the apnea-hypopnea index (AHI) at base line were estimated after adjustment for baseline hypertension status, body mass index (BMI), neck and waist circumference, age, gender, and weekly use of alcohol and tobacco. Relative to the reference category of an AHI of 0 events per hour at baseline, the odds ratios for the presence of hypertension at follow-up were 1.42 (95% confidence intervals-CI 1.13-1.78) with an AHI of 0.1-4.9 events per hour at base line as compared with none, 2.03 (95% CI 1.29-3.17) with an AHI of 5.0-14.9 events per hour, and 2.89 (95% CI 1.46-5.64) with an AHI of 15.0 or more events per hour. These findings suggest two important concepts. First, sleep-disordered breathing is a risk factor for hypertension in the general population. Second, even sleep apnea that is considered mild may also contribute significantly to overall blood pressure levels...(excerpt

First Diagnosed Heart Failure Due to Churg-Strauss Syndrome. A Case Report

Churg Strauss Syndrome (CSS)is an autoimmune condition that causes inflammation of small and medium-sized blood vessels. It is a non-infectious systemic vasculitis, which affects mainly the lungs but also other tissues and organs. CSS is considered a highly variable condition in terms of its presentation and its course. The most serious complication of the vasculitic stage is congestive heart failure with reduced ejection fraction. We present a case with first diagnosed heart failure because of CSS and review of the literature

Cardiac Amyloidosis : Mini Review and a Case Report

Amyloidosis is a rare heterogeneous group of systemic disorders, which result due to extra cellular deposition of an insoluble, amorphous, eosinophilic, substance known as amyloid. The disease is often characterized by a restrictive cardiomyopathy with a poor prognosis and survival. The treatment of cardiac amyloidosis depends on the underlying etiology. However, the diagnosis of the type of cardiac amyloidosis is not always straightforward. We present here a case of cardiac amyloidosis and we discuss the different forms

Imaging groundwater infiltration dynamics in the karst vadose zone with long-term ERT monitoring

Water infiltration and recharge processes in karst systems are complex and difficult to measure with conventional hydrological methods. In particular, temporarily saturated groundwater reservoirs hosted in the vadose zone can play a buffering role in water infiltration. This results from the pronounced porosity and permeability contrasts created by local karstification processes of carbonate rocks. Analyses of time-lapse 2-D geoelectrical imaging over a period of 3 years at the Rochefort Cave Laboratory (RCL) site in south Belgium highlight variable hydrodynamics in a karst vadose zone. This represents the first long-term and permanently installed electrical resistivity tomography (ERT) monitoring in a karst landscape. The collected data were compared to conventional hydrological measurements (drip discharge monitoring, soil moisture and water conductivity data sets) and a detailed structural analysis of the local geological structures providing a thorough understanding of the groundwater infiltration. Seasonal changes affect all the imaged areas leading to increases in resistivity in spring and summer attributed to enhanced evapotranspiration, whereas winter is characterised by a general decrease in resistivity associated with a groundwater recharge of the vadose zone. Three types of hydrological dynamics, corresponding to areas with distinct lithological and structural features, could be identified via changes in resistivity: (D1) upper conductive layers, associated with clay-rich soil and epikarst, showing the highest variability related to weather conditions; (D2) deeper and more resistive limestone areas, characterised by variable degrees of porosity and clay contents, hence showing more diffuse seasonal variations; and (D3) a conductive fractured zone associated with damped seasonal dynamics, while showing a great variability similar to that of the upper layers in response to rainfall events. This study provides detailed images of the sources of drip discharge spots traditionally monitored in caves and aims to support modelling approaches of karst hydrological processes

Pulmonary Embolism: Clinical Features and Diagnosis

Pulmonary embolism is a lethal yet treatable disease. Given the significant overlap of symptoms and signs between the presentation of pulmonary embolism and acute coronary syndromes, it becomes clear that emergency room physicians must be familiar with the diagnosis of pulmonary embolism. A critical issue is always to consider pulmonary embolism in the differential diagnosis of chest pain. However, the clinical diagnosis of pulmonary embolism remains problematic due to the nonspecific presenting symptoms, signs, electrocardiographic abnormalities, arterial blood gas and chest X-ray findings. D-dimers are becoming a widely available useful laboratory tool in the diagnosis of suspected pulmonary embolism. In this concise overview, the diagnostic value of clinical assessment in patients with possible pulmonary embolism will be explored