Heat transfer enhancement through periodic flow area variations in microchannels

In this study, annular microchannels with a microscale gap of 300 μm were implemented through the concentric superposition of two macro-sized cylinders. Flow area variations along the streamwise direction were created by introducing sinusoidal wave profiles on either the inner or outer wall of the annular gap while keeping the other wall flat. These variations introduced re-entrant effects along the flow direction. Numerical studies using the finite volume method were performed to elucidate the single-phase, steady-state thermal and hydrodynamic performances of the wavy channels, using water as the fluid medium, with an operating Reynolds number range of 800–2200. The predicted results were validated using the available measured data and classical correlations. This study demonstrated the viability of attaining enhanced heat transfer rates of up to 360% of the original straight channel through the inducement of flow area variations with single wavy-walled channels. Despite magnifications of the friction factors, the single wavy-walled channels attained a 120% increment in heat transfer coefficient when evaluated at the same pumping power. Overall, single-walled wavy passages were deemed suitable for heat exchanger designs demanding very high heat removal rates and efficiencies while the conventional serpentine channels were apt for moderately enhancing heat transfer while requiring low pumping power.Accepted versio

Experimental investigation on the effects of bifurcation angle on enhanced microscale heat transfer in macro geometry

The effectiveness of microscale heat transfer in macro geometry has been demonstrated to produce comparable heat transfer performance to that of conventional microchannels. For this research, a microchannel was created by fitting an insert with nominal diameter 19.4 mm concentrically within a hollow cylinder with inner diameter 20.0 mm, thereby producing a microchannel with an annular gap of 300 µm. Surface profiles on the insert were optimised to recover pressure loss, aiming to address the increased pumping requirements that accompany the improvement in heat transfer capabilities. A bifurcation angle was incorporated into the offset fin geometry design. The increased heat removal capability at the same pumping power and the reduction of pumping power for the same heat removal duty for three different bifurcation angles, namely 70, 75 and 80 degrees, were investigated with respect to parallel channels. The experimental study was conducted at a constant heat flux of 500 W at Reynolds number ranging from 690 to 4600. The amount of fluid in the microchannel, heat transfer area, rate of heat supplied, average channel gap size, channel length and fin height were kept constant. Experimental results successfully validated the effectiveness of bifurcation angles in the recovery of pressure loss across the microchannel. As compared to parallel channels, the 80-degrees bifurcating fins displayed the highest enhancement of the heat transfer coefficient and greatest reduction of the pumping power, which are 27% enhanced and 52% reduced respectively, at a given heat removal duty.Accepted versio

A review of image processing and quantification analysis for solid oxide fuel cell

The purpose of this study is to investigate the approaches applied to analyze solid oxide fuel cell (SOFC) microstructural properties. Both manual and automated image processing approaches applied on SOFC microstructural images which are obtained from several types of tomography such as dual-beam focused ion beam with scanning electron microscopy (FIB-SEM), Electron Backscatter Diffraction (EBSD) and others are discussed. In fact, to achieve a realistic and accurate SOFC microstructural properties, such as average diameter, volume fraction, triple phase boundary (TPB), area interface density and tortuosity factor, the approaches of image processing and quantification are crucial for a reliable image generation for quantification purposes. The microstructural properties are optimized to improve SOFC electrode performance. Therefore, the image processing and quantification approaches are outlined and reviewed. Despite the automated image processing and quantification algorithms significantly outperform manual image processing and quantification approaches in terms of computing speed when evaluating and measuring microstructural properties, the efficiency and productivity are still extremely taken into concern. As a result, image processing and quantification approaches are concluded and presented respectively in this paper

Synergic interplay of the La motif, RRM1 and the interdomain linker of LARP6 in the recognition of collagen mRNA expands the RNA binding repertoire of the La module

The La-related proteins (LARPs) form a diverse group of RNA-binding proteins characterized by the possession of a composite RNA binding unit, the La module. The La module comprises two domains, the La motif (LaM) and the RRM1, which together recognize and bind to a wide array of RNA substrates. Structural information regarding the La module is at present restricted to the prototypic La protein, which acts as an RNA chaperone binding to 3′ UUU(OH) sequences of nascent RNA polymerase III transcripts. In contrast, LARP6 is implicated in the regulation of collagen synthesis and interacts with a specific stem-loop within the 5′ UTR of the collagen mRNA. Here, we present the structure of the LaM and RRM1 of human LARP6 uncovering in both cases considerable structural variation in comparison to the equivalent domains in La and revealing an unprecedented fold for the RRM1. A mutagenic study guided by the structures revealed that RNA recognition requires synergy between the LaM and RRM1 as well as the participation of the interdomain linker, probably in realizing tandem domain configurations and dynamics required for substrate selectivity. Our study highlights a considerable complexity and plasticity in the architecture of the La module within LARPs

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Critical care admission following elective surgery was not associated with survival benefit: prospective analysis of data from 27 countries

This was an investigator initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (UK) Professorship held by RP. The study was sponsored by Queen Mary University of London