Towards LES of bubble-laden channel flows:Sub-grid scale closures for momentum advection

This paper presents an a-posteriori assessment of different LES sub-grid scale closures for momentum advection in the context of bubble-laden channel flows. The numerical approach is based on the Volume-of-Fluid method in combination with the onefluid formulation of the incompressible Navier-Stokes equations. To study the behavior of different subgrid scale models, a turbulent bubble-laden downflow channel is simulated at a friction Reynolds number of ReΤ = 590. The setup is chosen such that the bubbles are nearly spherical, but mildly wobbling. Both functional models of eddy viscosity type and scale similarity type models are used to close the sub-grid scale stresses. The results are compared to a direct numerical simulation of the same setup. It is found that the stream-wise volumetric flow rate depends strongly on the closure model as well as the grid resolution. While some models lead to an improvement compared to the LES without an explicit model, the comparably dissipative nature of the QUICK scheme prevents a clear assessment of some more advanced modeling strategies

Towards LES of bubble-laden channel flows: sub-gridscale closures for momentum advection

This paper presents an a-posteriori assessmentof different LES sub-grid scale closures for momentumadvection in the context of bubble-laden channelflows. The numerical approach is based on theVolume-of-Fluid method in combination with the onefluidformulation of the incompressible Navier-Stokesequations. To study the behavior of different subgridscale models, a turbulent bubble-laden downflowchannel is simulated at a friction Reynolds number ofRe = 590. The setup is chosen such that the bubblesare nearly spherical, but mildly wobbling. Both functionalmodels of eddy viscosity type and scale similaritytype models are used to close the sub-grid scalestresses. The results are compared to a direct numericalsimulation of the same setup. It is found that thestream-wise volumetric flow rate depends strongly onthe closure model as well as the grid resolution. Whilesome models lead to an improvement compared to theLES without an explicit model, the comparably dissipativenature of the QUICK scheme prevents a clearassessment of some more advanced modeling strategies

Towards LES of bubble-laden channel flows: sub-gridscale closures for momentum advection

This paper presents an a-posteriori assessmentof different LES sub-grid scale closures for momentumadvection in the context of bubble-laden channelflows. The numerical approach is based on theVolume-of-Fluid method in combination with the onefluidformulation of the incompressible Navier-Stokesequations. To study the behavior of different subgridscale models, a turbulent bubble-laden downflowchannel is simulated at a friction Reynolds number ofRe = 590. The setup is chosen such that the bubblesare nearly spherical, but mildly wobbling. Both functionalmodels of eddy viscosity type and scale similaritytype models are used to close the sub-grid scalestresses. The results are compared to a direct numericalsimulation of the same setup. It is found that thestream-wise volumetric flow rate depends strongly onthe closure model as well as the grid resolution. Whilesome models lead to an improvement compared to theLES without an explicit model, the comparably dissipativenature of the QUICK scheme prevents a clearassessment of some more advanced modeling strategies

A nomenclature for restriction enzymes, DNA methyltransferases, homing endonucleases and their genes

A nomenclature is described for restriction endonucleases, DNA methyltransferases, homing endonucleases and related genes and gene products. It provides explicit categories for the many different Type II enzymes now identified and provides a system for naming the putative genes found by sequence analysis of microbial genomes

A hospital-site controlled intervention using audit and feedback to implement guidelines concerning inappropriate treatment of catheter-associated asymptomatic bacteriuria

<p>Abstract</p> <p>Background</p> <p>Catheter-associated urinary tract infection (CAUTI) is one of the most common hospital-acquired infections. However, many cases treated as hospital-acquired CAUTI are actually asymptomatic bacteriuria (ABU). Evidence-based guidelines recommend that providers neither screen for nor treat ABU in most catheterized patients, but there is a significant gap between these guidelines and clinical practice. Our objectives are (1) to evaluate the effectiveness of an audit and feedback intervention for increasing guideline-concordant care concerning catheter-associated ABU and (2) to measure improvements in healthcare providers' knowledge of and attitudes toward the practice guidelines associated with the intervention.</p> <p>Methods/Design</p> <p>The study uses a controlled pre/post design to test an intervention using audit and feedback of healthcare providers to improve their compliance with ABU guidelines. The intervention and the control sites are two VA hospitals. For objective 1 we will review medical records to measure the clinical outcomes of inappropriate screening for and treatment of catheter-associated ABU. For objective 2 we will survey providers' knowledge and attitudes. Three phases of our protocol are proposed: the first 12-month phase will involve observation of the baseline incidence of inappropriate screening for and treatment of ABU at both sites. This surveillance for clinical outcomes will continue at both sites throughout the study. Phase 2 consists of 12 months of individualized audit and feedback at the intervention site and guidelines distribution at both sites. The third phase, also over 12 months, will provide unit-level feedback at the intervention site to assess sustainability. Healthcare providers at the intervention site during phase 2 and at both sites during phase 3 will complete pre/post surveys of awareness and familiarity (knowledge), as well as of acceptance and outcome expectancy (attitudes) regarding the relevant practice guidelines.</p> <p>Discussion</p> <p>Our proposal to bring clinical practice in line with published guidelines has significant potential to decrease overdiagnosis of CAUTI and associated inappropriate antibiotic use. Our study will also provide information about how to maximize effectiveness of audit and feedback to achieve guideline adherence in the inpatient setting.</p> <p>Trial Registration</p> <p><a href="http://www.clinicaltrials.gov/ct2/show/NCT01052545">NCT01052545</a></p