Stripe formation in horizontally oscillating granular suspensions

We present the results of an experimental study of pattern formation in horizontally oscillating granular suspensions. Starting from a homogeneous state, the suspension turns into a striped pattern within a specific range of frequencies and amplitudes of oscillation. We observe an initial development of layered structures perpendicular to the vibration direction and a gradual coarsening of the stripes. However, both processes gradually slow down and eventually saturate. The probability distribution of the stripe width approaches a nonmonotonic steady-state form which can be approximated by a Poisson distribution. We observe similar structures in MD simulations of soft spherical particles coupled to the motion of the surrounding fluid.Comment: 7 pages, 8 figures, to appear in Europhys. Lett. (2014

Engineered Thermally Sprayed Electrodes for Hydrogen Production by Alkaline Water Electrolysis

Alkaline water electrolysis is one of the most promising methods for producing high purity hydrogen to be used as a clean and renewable energy carrier. However, due to the high costs of the electrolysers in addition to high energy consumption of the electrolysis process, this method is still not used for large scale hydrogen production in industrial applications. The costs associated with the materials and energy loss of this technology can be reduced by decreasing the hydrogen evolution overpotentials by using durable and inexpensive electrocatalysts with high intrinsic activities and large active surface areas. The main objective of this work is to manufacture cathode electrodes for the hydrogen evolution reaction (HER) with modified surface structures and large effective areas, using different thermal spray techniques. For this purpose, new methodologies for manufacturing the electrodes are introduced while the surface morphology of the electrodes is designed and engineered by the coating processes. Nickel is used as electrode material as it shows high electrocatalytic activity, has high stability in alkaline solutions and is relatively inexpensive compared to noble metals with the best activities. Suspension plasma spray (SPS), high velocity oxy-fuel (HVOF) and cold spray are introduced as novel methods for producing nickel electrodes for the HER. A combination of atmospheric and suspension plasma spray, with optimized parameters toward enhancement of the electrode surface area, is effectively used for development of multiscale electrode surface structures with micron and nanosized features. In addition, the surface texture of the electrodes is engineered by deposition of three-dimensional fin arrays by employing mesh screens when either the combined atmospheric and suspension plasma spray or HVOF processes were used. For these electrodes the surface area was mainly enhanced by deposition of the particles at normal and off-normal angles. The produced hierarchical multiscale electrode structures enhanced the electrocatalytic activity for the HER by increasing the accessibility of the electrode surface to the electrolyte besides facilitating the hydrogen bubble detachment. Finally, cold spray was used to manufacture the electrodes with large activities by peening of the electrode surface by the solid-state nickel particles during the deposition process. The activity of the electrodes was enhanced by increasing the surface defects and changing the electronic structure of the electrodes induced by the peening effect

Experimental Investigation on Churning Power Loss of Splash Lubricated Worm Gear

Churning power losses are a complex phenomenon that produces critical power losses when considering the splash lubrication of gear units. This article describes the method to investigate the churning power loss in a worm gearbox. A particular test rig was designed and fabricated to experiment on single start worm gear incompletely submerged in an oil bath. The direct torque measurement technique was used to determine the churning power losses. Experiments have been conducted to determine the impact of a variety of operating conditions on churning power losses, including worm speeds, gear immersion depth, lubricant temperatures, and lubricant type (mineral and synthetic). It was found that the churning losses were significantly affected by the worm shaft orientation, speed of gear, and the depth of immersion (static head). The lubricant's temperature is more essential than the type of lubricant in terms of churning power loss

How nurse educators promote reflective thinking in a college of nursing in KwaZulu-Natal.

Thesis (M.A.)-University of KwaZulu-Natal, 2007.There is a great deal of literature and a number of research studies that have been carried out on reflective practice, models and frameworks of reflection and teaching strategies that successfully promote reflective thinking. This study addresses the need to adopt teaching - learning approaches in nursing education that develop a link between theory and practice in a meaningful way. Reflective thinking is one such approach which is gaining popularity. Reflection is claimed as a goal in many teacher education programmes but the application of reflective teaching strategies has been problematic. This study was aimed at exploring how nurse educators of the Nursing Colleges in KwaZulu-Natal promoted reflective thinking in their teaching. Three of the four Nursing Colleges chosen for data collection were from the greater Durban Metropolitan area because of the accessibility of the participants. There were seventy-two participants in the study. A quantitative design was used, followed by statistical analysis of the data. Data was collected by means of a questionnaire which included structured and semi-structured questions. What emerged in this study is the need for Nurse Educators to take cogniscance of determining appropriate teaching strategies that would develop reflective thinking skills amongst learners. However, the findings indicate that most Nurse Educators do utilize teaching strategies that promote reflective thinking, but a large percentage still use the lecture method as the primary teaching strategy

Diagnostic Accuracy of Rapid Antigen Tests for COVID-19 Detection: A Systematic Review With Meta-analysis

Introduction: Reverse transcription-polymerase chain reaction (RT-PCR) to detect SARS-CoV-2 is time-consuming and sometimes not feasible in developing nations. Rapid antigen test (RAT) could decrease the load of diagnosis. However, the efficacy of RAT is yet to be investigated comprehensively. Thus, the current systematic review and meta-analysis were conducted to evaluate the diagnostic accuracy of RAT against RT-PCR methods as the reference standard. Methods: We searched the MEDLINE/Pubmed and Embase databases for the relevant records. The QUADAS-2 tool was used to assess the quality of the studies. Diagnostic accuracy measures [i.e., sensitivity, specificity, diagnostic odds ratio (DOR), positive likelihood ratios (PLR), negative likelihood ratios (NLR), and the area under the curve (AUC)] were pooled with a random-effects model. All statistical analyses were performed with Meta-DiSc (Version 1.4, Cochrane Colloquium, Barcelona, Spain). Results: After reviewing retrieved records, we identified 60 studies that met the inclusion criteria. The pooled sensitivity and specificity of the rapid antigen tests against the reference test (the real-time PCR) were 69% (95% CI: 68–70) and 99% (95% CI: 99–99). The PLR, NLR, DOR and the AUC estimates were found to be 72 (95% CI: 44–119), 0.30 (95% CI: 0.26–0.36), 316 (95% CI: 167–590) and 97%, respectively. Conclusion: The present study indicated that using RAT kits is primarily recommended for the early detection of patients suspected of having COVID-19, particularly in countries with limited resources and laboratory equipment. However, the negative RAT samples may need to be confirmed using molecular tests, mainly when the symptoms of COVID-19 are present. Keywords: COVID-19, SARS-CoV-2, rapid antigen test, specificity, sensitivity, meta-analysi

Diagnostic Accuracy of Pyrazinamide Susceptibility Testing in Mycobacterium tuberculosis: A Systematic Review with Meta-Analysis

Introduction: Pyrazinamide (PZA) susceptibility testing plays a critical role in determining the appropriate treatment regimens for multidrug-resistant tuberculosis. We conducted a systematic review and meta-analysis to evaluate the diagnostic accuracy of sequencing PZA susceptibility tests against culture-based susceptibility testing methods as the reference standard. Methods: We searched the MEDLINE/PubMed, Embase, and Web of Science databases for the relevant records. The QUADAS-2 tool was used to assess the quality of the studies. Diagnostic accuracy measures (i.e., sensitivity and specificity) were pooled with a random-effects model. All statistical analyses were performed with Meta-DiSc (version 1.4, Cochrane Colloquium, Barcelona, Spain), STATA (version 14, Stata Corporation, College Station, TX), and RevMan (version 5.3, The Nordic Cochrane Centre, the Cochrane Collaboration, Copenhagen, Denmark) software. Results: A total of 72 articles, published between 2000 and 2019, comprising data for 8,701 isolates of Mycobacterium tuberculosis were included in the final analysis. The pooled sensitivity and specificity of the PZA sequencing test against all reference tests (the combination of BACTEC mycobacteria growth indicator tube 960 (MGIT 960), BACTEC 460, and proportion method) were 87% (95% CI: 85–88) and 94.7% (95% CI: 94–95). The positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and the area under the curve estimates were found to be 12.0 (95% CI: 9.0–16.0), 0.17 (95% CI: 0.13–0.21), 106 (95% CI: 71–158), and 96%, respectively. Deek's test result indicated a low likelihood for publication bias (p = 0.01). Conclusions: Our analysis indicated that PZA sequencing may be used in combination with conventional tests due to the advantage of the time to result and in scenarios where culture tests are not feasible. Further work to improve molecular tests would benefit from the availability of standardized reference standards and improvements to the methodology