Statistical Evaluation of the Shock Wave Boundary Layer Interaction Phenomenon

Turbulent velocity and thermal correlations from direct numerical simulation data of a spatially growing compressible turbulent boundary layer interacting with an impinging shock are discussed. The cross-stream variation of the velocity second-moments and the thermal fluxes one boundary layer thickness upstream of the shock impingement point are discussed. Other correlations are examined to further statistically quantify the effect of the oblique shock-turbulence interaction

Post-shock downstream evolution of turbulent boundary layer based on quadrant analysis

Quadrant analysis is one of the technique that commonly used to detect and to quantify the composition of occurrence of different turbulent events (e.g. ejections and sweeps) in a turbulent boundary layer. In the present communication the post-shock behaviour of the supersonic turbulent boundary layer will be presented on the basis of above mentioned analysis. In addition the effect of two different wall-temperature conditions will also be investigated

The Karachi intracranial stenosis study (KISS) Protocol: an urban multicenter case-control investigation reporting the clinical, radiologic and biochemical associations of intracranial stenosis in Pakistan.

Background: Intracranial stenosis is the most common cause of stroke among Asians. It has a poor prognosis with a high rate of recurrence. No effective medical or surgical treatment modality has been developed for the treatment of stroke due to intracranial stenosis. We aim to identify risk factors and biomarkers for intracranial stenosis and to develop techniques such as use of transcranial doppler to help diagnose intracranial stenosis in a cost-effective manner. Methods/Design: The Karachi Intracranial Stenosis Study (KISS) is a prospective, observational, case-control study to describe the clinical features and determine the risk factors of patients with stroke due to intracranial stenosis and compare them to those with stroke due to other etiologies as well as to unaffected individuals. We plan to recruit 200 patients with stroke due to intracranial stenosis and two control groups each of 150 matched individuals. The first set of controls will include patients with ischemic stroke that is due to other atherosclerotic mechanisms specifically lacunar and cardioembolic strokes. The second group will consist of stroke free individuals. Standardized interviews will be conducted to determine demographic, medical, social, and behavioral variables along with baseline medications. Mandatory procedures for inclusion in the study are clinical confirmation of stroke by a healthcare professional within 72 hours of onset, 12 lead electrocardiogram, and neuroimaging. In addition, lipid profile, serum glucose, creatinine and HbA1C will be measured in all participants. Ancillary tests will include carotid ultrasound, transcranial doppler and magnetic resonance or computed tomography angiogram to rule out concurrent carotid disease. Echocardiogram and other additional investigations will be performed at these centers at the discretion of the regional physicians. Discussion: The results of this study will help inform locally relevant clinical guidelines and effective public health and individual interventions

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

ETUDE NUMERIQUE DE L'INFLUENCE DE L'IMPACT D'UNE ONDE DE CHOC ET D'UN TRANSFERT DE CHALEUR SUR UNE COUCHE LIMITE EN DEVELOPPEMENT

As a prerequesite for relevant model development and improvement of design methodologies for supersonic vehicles, this study aims at investigating the influence of wall heat-transfer and shock interaction on the turbulence structure of supersonic boundary layers. The numerical strategy relies on the full resolution of threedimensional compressible Navier-Stokes equations by means of state-of-art high-order WENO and compact schemes. A fully-developped turbulent boundary layer is simulated by means of upstream wall perturbations triggering the transition in order to dispose of fully-reliable data upstream of the analysis region. Insipient separation conditions and two different wall thermal boundary conditions (adiabatic and cold) are considered. The analysis focuses on the evolution of mean and turbulent flow properties along the interaction region and in the relaxation region downstream of the shock-system. The strong influence of the mean pressure gradient is quantified through the analysis of mean flow profiles and boundary layer integral parameters. The anisotropic amplification of turbulent quantities through the interaction region is characterized and the turbulent events associated with the modification of the turbulence structure of the perturbed boundary layer are identified. The mean and turbulent thermal fields are shown to be strongly modified by the wall cooling which significantly dampens more particularly the turbulent thermal quantities levels across the boundary layer. In addition, a reduction of the upstream influence and separation lengths by the wall cooling are evidenced along with a faster recovery process downstream of the shock-system.Dans l'optique de développer à terme des modèles pertinents et in fine améliorer le design de véhicules supersoniques, cette étude propose une analyse détaillée de l'influence d'un choc et d'un transfert de chaleur sur la structure de la turbulence au sein d'une couche limite supersonique. La stratégie numérique utilisée repose sur des simulations numériques directes des équations de Navier-Stokes à l'aide de schémas WENO et compact d'ordre élevé. Le développement complet de la couche limite est simulé à l'aide d'un forçage amont à la paroi afin de s'assurer du plus haut degré de réalisme dans la zone d'étude. Des conditions de séparation naissante et deux conditions thermiques de paroi (adiabatique et refroidie) sont considérées. L'analyse se concentre sur l'altération des caractéristiques moyennes et turbulentes à travers la zone d'interaction et au sein de la zone de relaxation, sur la base de profils moyens et de paramètres intégraux. L'amplification anisotrope des variables turbulentes est quantifiée tandis que les évènements turbulents associés à la modification de la structure globale sont identifiés. La forte modification des champs thermiques moyens et turbulents par le refroidissement est mise en exergue, notamment la diminution significative des quantités turbulentes à travers la couche. Par ailleurs, la réduction à la fois des longueurs d'influence amont, de séparation et de relaxation est mise en évidence

Abusive Supervision Impact on Employees’ Creativity: A Mediated-Moderated Perspective

The drive for the current study was to describe the findings carried out to understand abusive supervision and employees’ creativity in business organizations. This research investigated the effect of abusive supervision on employees’ creativity. The influence of employment insecurity as a mediating variable and the moderating role of locus of control has also been examined. The study was based on Hobfoll’s conservation of resources theory. The data were collected using a self-administered questionnaire from 500 employees working in different business organizations in Pakistan. To analyze the data, the study employed path analytic approaches using multilevel modeling in Mplus 7.1. The empirical analysis has confirmed that abusive supervision and employment insecurity have a significant negative impact on employees’ creativity. Employment infectivity partially mediates the effect of abusive supervision on employees’ creativity. Moderation analysis was performed and established that the locus of control moderates the effect of abusive supervision on employment insecurity as well as the effect of employment insecurity on employees’ creativity. The current research has contributed towards developing a better understanding of the studied variables, i.e., abusive supervision, employment insecurity, locus of control, and employees’ creativity. To the best of authors’ knowledge these variables have been studied together here for the first time. The study also forwarded practical recommendations for managers and entrepreneurs