On the role of the Jeffreys'sheltering mechanism in the sustain of extreme water waves

The effect of the wind on the sustain of extreme water waves is investigated experimentally and numerically. A series of experiments conducted in the Large Air-Sea Interactions Facility (LASIF) showed that a wind blowing over a strongly nonlinear short wave group due to the linear focusing of a modulated wave train may increase the life time of the extreme wave event. The expriments suggested that the air flow separation that occurs on the leeward side of the steep crests may sustain longer the maximum of modulation of the focusing-defocusing cycle. Based on a Boundary-Integral Equation Method and a pressure distribution over the steep crests given by the Jeffreys'sheltering theory, similar numerical simulations have confirmed the experimental resultsComment: accept\'{e} pour publication 200

Numerical and experimental simulations of wind effect on rogue waves

http://www.cosis.net/abstracts/EGU05/00368/EGU05-J-00368.pdfRogue wave generation can be explained on the basis of spatio-temporal focusing concept. The paper reports on a series of numerical simulations based on a BIEMmethod and their comparison with experiments. The modulated wave trains are numericallygenerated by a paddle and the wind effect is described by the introductionof wind-induced current. The time-variable frequency of the paddle is chosento produce a rogue wave (due to spatio-temporal focusing) at a given fetch. Numericalsimulations are performed for different values of wind-drift current (us =0, 20, 25, 30, 40, 50cm.s−1), corresponding to the experimental values of wind speed(U = 0, 4, 5, 6, 8, 10m.s−1). It is shown that the shift of the focusing point increasesas u2s, as predicted theoretically (Pelinovsky & Kharif, 2005). A spreading of the focusingarea and a weak decrease of the rogue wave amplification are observed asthe wind speed increases. Experiments showed that the amplification increases as thewind speed increases (Giovanangeli & al., 2004). This disagreement suggests that theamplification of the rogue wave may be due the direct effect of the wind on the freesurface which is not taken into account in the numerical model

Influence of wind on extreme wave events: Experimental and numerical approaches

International audienceThe influence of wind on extreme wave events is investigated experimentally and numerically. A series of experiments conducted in the Large Air-Sea Interactions Facility (LASIF) shows that a wind blowing over a short wave group due to the dispersive focusing of a longer frequency modulated wave train (chirped wave packet) may increase the time duration of the extreme wave event by delaying the defocusing stage. A detailed analysis of the experimental results suggests that the air flow separation that occurs on the leeward side of the steep crests may sustain longer the maximum of modulation of the focusing-defocusing cycle. Furthermore it is found that the frequency downshifting observed during the formation of the extreme wave event is more important when the wind velocity is larger. The experiments have pointed out that the transfer of momentum and energy is strongly increased during extreme wave events. Two series of numerical simulations have been performed using a pressure distribution over the steep crests given by the Jeffreys'sheltering theory. The first series corresponding to the dispersive focusing confirms the experimental results. The second series that corresponds to extreme wave events due to modulational instability shows that wind sustains steep waves which then evolve into breaking waves. Furthermore, it was shown numerically that during extreme wave events the wind-driven current may play a significant role in their persistence

Variété et distribution des sujets d'actualité sur Internet: Une analyse quantitative de l'information en ligne

http://mots.revues.org/19832International audienceThe pluralism of news is supposed to be ensured by the multiplicity of the sources on the Internet. Based on thousands articles from all categories of websites, the ­lexicometric analysis of the titles and the identification of topical issues both highlight a more uneven reality. While websites deal with a wide diversity of issues during a whole day, they simultaneously focus on a few major issues, which treatment and wordings are often quite redundant.Sur Internet, la multiplicité des sources est censée garantir le pluralisme de l'information. Portant sur des milliers d'articles issus de toutes catégories de sites, l'analyse lexicométrique des titres et l'identification des sujets de l'actualité donnent à voir une réalité plus contrastée. La grande variété des sujets abordés sur la toile se traduit simutanément par une concentration sur quelques sujets majeurs, souvent traités de façon redondante jusque dans leur formulation

Impact of Complex-Logic Cell Layout on the Single-Event Transient Sensitivity

International audienceThe design methodology based on standard cells is widely used in a broad range of VLSI applications. Further, several optimization algorithms can be employed to address different constraints such as power consumption or reliability. This work evaluates the implications of the usage of complex-logic cells from a 45 nm Standard-Cell library to the Single-Event Transient sensitivity under heavy ions. Results show that even though a reduction in the layout area is obtained when adopting complex-logic gates, a slight reduction in the total sensitive area of the circuit is observed. Moreover, the effectiveness of logical masking can be suppressed, leading to a higher SET cross-section

Gated blood-pool SPECT evaluation of changes after radiofrequency catheter ablation of accessory pathways Evidence for persistent ventricular preexcitation despite successful therapy

AbstractOBJECTIVESThis study was designed to prospectively evaluate the effects of radiofrequency ablation in Wolff-Parkinson-White (WPW) syndrome by scintigraphic analysis.BACKGROUNDThe functional changes triggered by radiofrequency current ablation of atrioventricular accessory pathways are not fully known.METHODSForty-four patients with WPW syndrome were consecutively investigated before and 48 h after radiofrequency therapy. Fourteen patients had right sided atrioventricular pathways and 30 patients had left sided bypass-tracts. Planar gated imaging and gated blood pool tomography were performed in all of these patients.RESULTSA significant increase in the left ventricular ejection fraction (LVEF) was demonstrated in patients with left preexcitation (62.2 ± 7.9% before ablation against 64.4 ± 6.3% after ablation, p = 0.02) but not for those with right sided anomalous pathway. Phase analysis only gave significant differences following ablation of right sided pathways (left-to-right phase difference = 14.4 ± 13.8° before ablation versus 7.5 ± 7.2° after ablation, p < 0.05). Early abnormal ventricular contraction persisted in 12 patients with right accessory pathways and in 8 patients with left accessory pathways despite the complete disappearance of any abnormal conduction as proven electrophysiologically.CONCLUSIONSFollowing catheter ablation of atrioventricular accessory pathways: 1) an improvement of left ventricular function may be seen, particularly in patients with left sided accessory pathways, and 2) unexpected persistence of local ventricular preexcitation at the site of successful ablation may be detected

Incidental chest radiographic findings in adult patients with acute cough

PURPOSE Imaging may produce unexpected or incidental findings with consequences for patients and ordering of future investigations. Chest radiography in patients with acute cough is among the most common reasons for imaging in primary care, but data on associated incidental findings are lacking. We set out to describe the type and prevalence of incidental chest radiography findings in primary care patients with acute cough. METHODS We report on data from a cross-sectional study in 16 European primary care networks on 3,105 patients with acute cough, all of whom were undergoing chest radiography as part of a research study workup. Apart from assessment for specified signs of pneumonia and acute bronchitis, local radiologists were asked to evaluate any additional finding on the radiographs. For the 2,823 participants with good-quality chest radiographs, these findings were categorized according to clinical relevance based on previous research evidence and analyzed for type and prevalence by network, sex, age, and smoking status. RESULTS Incidental findings were reported in 19% of all participants, and ranged from 0% to 25% by primary care network, with the network being an independent contributor (P < .001). Of all participants 3% had clinically relevant incidental findings. Suspected nodules and shadows were reported in 1.8%. Incidental findings were more common is older participants and smokers (P < .001). CONCLUSIONS Clinically relevant incidental findings on chest radiographs in primary care adult patients with acute cough are uncommon, and prevalence varies by setting

Antivirals for influenza-Like Illness? A randomised Controlled trial of Clinical and Cost effectiveness in primary CarE (ALIC4 E): the ALIC4 E protocol

INTRODUCTION: Effective management of seasonal and pandemic influenza is a high priority internationally. Guidelines in many countries recommend antiviral treatment for older people and individuals with comorbidity at increased risk of complications. However, antivirals are not often prescribed in primary care in Europe, partly because its clinical and cost effectiveness has been insufficiently demonstrated by non-industry funded and pragmatic studies. METHODS AND ANALYSIS: Antivirals for influenza-Like Illness? An rCt of Clinical and Cost effectiveness in primary CarE is a European multinational, multicentre, open-labelled, non-industry funded, pragmatic, adaptive-platform, randomised controlled trial. Initial trial arms will be best usual primary care and best usual primary care plus treatment with oseltamivir for 5 days. We aim to recruit at least 2500 participants ≥1 year presenting with influenza-like illness (ILI), with symptom duration ≤72 hours in primary care over three consecutive periods of confirmed high influenza incidence. Participant outcomes will be followed up to 28 days by diary and telephone. The primary objective is to determine whether adding antiviral treatment to best usual primary care is effective in reducing time to return to usual daily activity with fever, headache and muscle ache reduced to minor severity or less. Secondary objectives include estimating cost-effectiveness, benefits in subgroups according to age (64 years), severity of symptoms at presentation (low, medium and high), comorbidity (yes/no), duration of symptoms (≤48 hours/>48-72 hours), complications (hospital admission and pneumonia), use of additional prescribed medication including antibiotics, use of over-the-counter medicines and self-management of ILI symptoms. ETHICS AND DISSEMINATION: Research ethics committee (REC) approval was granted by the NRES Committee South Central (Oxford B) and Clinical Trial Authority (CTA) approval by The Medicines and Healthcare products Regulatory Agency. All participating countries gained national REC and CTA approval as required. Dissemination of results will be through peer-reviewed scientific journals and conference presentations

Impact of Cardiovascular Risk Factors on Carotid Intima-Media Thickness and Degree of Severity: A Cross-Sectional Study

OBJECTIVE: Age, hypertension, dyslipidemia and diabetes are common cardiovascular risk factors (CVRFs) that contribute to the development of atherosclerosis in cardiovascular system including carotid artery disease. However, the impact of these risk factors on the increased carotid intima-media thickness (cIMT) and degree of carotid severity remains to be further clarified. This study aims to evaluate the relationship between CVRFs and degree of carotid severity and cIMT in high-risk subjects. METHODS: Four thousand and three hundred ninety-four subjects with one or more risk factors were retrospectively reviewed in this study. Patients were divided into different groups based on age, the type and quantity of CVRFs. cIMT and degree of carotid artery stenosis were measured and analyzed based on carotid ultrasound imaging with findings compared to the CVRFs to determine the correlation between these variables. RESULTS: Aging was significantly associated with degree of severity (P &lt; 0.05) and cIMT was significantly increased with age (P &lt; 0.05). Individual CVRF analysis shows that hypertension was more related to the degree of severity than dyslipidemia and diabetes with corresponding abnormal cIMT rates being 79.39%, 72.98% and 32.37%, respectively. The prevalence of carotid atherosclerosis were 20.06%, 22.88% and 28.63%, respectively corresponding to patients with zero, one and more than one chronic diseases. The percentage of abnormal cIMT in hypertensive patient group with dyslipidemia is significantly higher than the other groups (P&lt; 0.05). CONCLUSIONS: This study shows a direct correlation between the degree of carotid severity and cIMT and cardiovascular risk factors, especially with age and hypertension. Carotid atherosclerosis is closely related to the number of cardiovascular risk factors