Analysis of the airflow features and ventilation efficiency of an Ultra-Clean-Air operating theatre by qDNS simulations and experimental validation.

Ultra-Clean-Air (UCA) operating theatres aim to minimise surgical instrument contamination and wound infection through high flow rates of ultra-clean air, reducing the presence of Microbe Carrying Particles (MCPs). This study investigates the airflow patterns and ventilation characteristics of a UCA operating theatre (OT) under standard ventilation system operating conditions, considering both empty and partially occupied scenarios. Utilising a precise computational model, quasi-Direct Numerical Simulations (qDNS) were conducted to delineate flow velocity profiles, energy spectra, distributions of turbulent kinetic energy, energy dissipation rate, local Kolmogorov scales, and pressure-based coherent structures. These results were also complemented by a tracer gas decay analysis following ASHRAE standard guidelines. Simulations showed that contrary to the intended laminar regime, the OT's geometry inherently fosters a predominantly turbulent airflow, sustained until evacuation through the exhaust vents, and facilitating recirculation zones irrespective of occupancy level. Notably, the occupied scenario demonstrated superior ventilation efficiency, a phenomenon attributed to enhanced kinetic energy induced by the additional obstructions. The findings underscore the critical role of UCA-OT design in mitigating MCP dissemination, highlighting the potential to augment the design to optimise airflow across a broader theatre spectrum, thereby diminishing recirculation zones and consequently reducing the propensity for Surgical Site Infections (SSIs). The study advocates for design refinements to harness the turbulent dynamics beneficially, steering towards a safer surgical environment.

Mass Spectrometry Multiplexed Detection of SARS-CoV-2.

Testing of large populations for virus infection is now a reality worldwide due to the coronavirus (SARS-CoV-2) pandemic. The demand for SARS-CoV-2 testing using alternatives other than PCR led to the development of mass spectrometry (MS)-based assays. However, MS for SARS-CoV-2 large-scale testing have some downsides, including complex sample preparation and slow data analysis. Here, we describe a high-throughput targeted proteomics method to detect SARS-CoV-2 directly from nasopharyngeal and oropharyngeal swabs. This strategy employs fully automated sample preparation mediated by magnetic particles, followed by detection of SARS-CoV-2 nucleoprotein peptides by turbulent flow chromatography coupled with tandem mass spectrometry.

Current status and future trends on automated multidimensional separation techniques employing sorbent-based extraction columns.

Determination of target analytes present in complex matrices requires a suitable sample preparation approach to efficiently remove the analytes of interest from a medium containing several interferers while at the same time preconcentrating them aiming to improve the output signal detection. Online multidimensional solid-phase separation techniques have been widely used for the analysis of different contaminants in complex matrices such as food, environmental, and biological samples, among others. These online techniques usually consist of two steps performed in two different columns (extraction and analytical column), the first being employed to extract the analytes of interest from the original medium and the latter to separate them from the interferers. The extraction column in multidimensional techniques presents a relevant role since their variations as building material (usually a tube), sorbent material, modes of application, and so on can significantly influence the extraction success. The main features of such columns are subject of constant research aiming improvements directly related to the performance of the separation techniques that utilize multidimensional analysis. The present review highlights the main features of extraction columns online coupled to chromatographic techniques, inclusive for in-tube solid-phase microextraction, online solid phase and turbulent flow, aiming the determination of analytes present at very low concentrations in complex matrices. It will critically describe and discuss some of the most common instrumental set up as well as comments on recent applications of these multidimensional techniques. Besides that, the authors have described some properties and enhancements of the extraction columns that are used as first dimension on these systems, such as type of column material (poly (ether ether ketone), fused silica, stainless steel, and other materials) and the way that the extractive phase is accommodated inside the tubing (filled and open tubular). Practical applications of this approach in fields such as environment, food, and bioanalysis are also presented and discussed.

Sonic anemometry and sediment traps to evaluate the effectiveness of windbreaks in preventing wind erosion

The present work analyzes the effectiveness of windbreaks against wind erosion through the study of streamline patterns and turbulent flow by means of sonic anemometry and sediment traps. To this end, windbreaks composed of plastic meshes (7.5 m long and 0.7 m tall) were used. Windbreaks are a good means to reduce wind erosion, as they produce a positive effect on the characteristics of air currents that are related to wind erosion processes. Due to their ease of installation and dismantling, plastic meshes are widely used in areas where they are not required permanently. In our study, the use of a mesh of 13 × 30 threads cm2 and 39 % porosity resulted in an average reduction of 85 % in face velocity at a height of 0.4 m and a distance of 1 m from the windbreak. The turbulence intensity i increased behind the windbreak because the reduction of mean of air speed on the leeside caused by the flow of air through the windbreak. Fluctuation levels, however, remained stable. The mean values of turbulence kinetic energy k decreased by 65 % to 86 % at a distance of 1 m from the windbreak and at a height of 0.4 m. The windbreak reduces erosion and sediment transportation 2 m downwind (2.9 times the windbreak height). Nevertheless, sediment transportation was not reduced at a height of 1.0 m and the effect of the windbreak was not observed at a distance of 6 m downwind (8.6 m times the windbreak height).(AU)

Sonic anemometry and sediment traps to evaluate the effectiveness of windbreaks in preventing wind erosion

The present work analyzes the effectiveness of windbreaks against wind erosion through the study of streamline patterns and turbulent flow by means of sonic anemometry and sediment traps. To this end, windbreaks composed of plastic meshes (7.5 m long and 0.7 m tall) were used. Windbreaks are a good means to reduce wind erosion, as they produce a positive effect on the characteristics of air currents that are related to wind erosion processes. Due to their ease of installation and dismantling, plastic meshes are widely used in areas where they are not required permanently. In our study, the use of a mesh of 13 × 30 threads cm2 and 39 % porosity resulted in an average reduction of 85 % in face velocity at a height of 0.4 m and a distance of 1 m from the windbreak. The turbulence intensity i increased behind the windbreak because the reduction of mean of air speed on the leeside caused by the flow of air through the windbreak. Fluctuation levels, however, remained stable. The mean values of turbulence kinetic energy k decreased by 65 % to 86 % at a distance of 1 m from the windbreak and at a height of 0.4 m. The windbreak reduces erosion and sediment transportation 2 m downwind (2.9 times the windbreak height). Nevertheless, sediment transportation was not reduced at a height of 1.0 m and the effect of the windbreak was not observed at a distance of 6 m downwind (8.6 m times the windbreak height).

Estudio de la transferencia de calor en un octavo del conjunto combustible del reactor nuclear de alto desempeño refrigerado por agua supercrítica / Heat transfer study in one eighth of the high performance supercritical water-cooled reactor fuel assembly

El reactor nuclear de agua ligera de alto desempeño es la versión europea del reactor refrigerado por agua supercrítica, propuesto como uno de los candidatos para la Generación IV de reactores nucleares. En este trabajo se evaluó la capacidad para predecir el comportamiento de la transferencia de calor hacia el agua supercrítica en los subcanales de 1/8 del conjunto combustible del HPLWR, mediante códigos de la Dinámica de Fluidos Computacional utilizando dos modelos de turbulencia: el modelo de esfuerzos de Reynolds, desarrollado por Speziale y el modelo k-ω de transporte de esfuerzos cortantes. Se realizó un estudio de sensibilidad de malla que garantizó la independencia de los resultados numéricos respecto del tamaño y distribución de los elementos de la malla. Se calcularon las distribuciones axiales de temperatura en la envoltura y en los elementos combustibles, además de las distribuciones de temperatura del agua en la zona refrigerante y en la zona moderadora. Se compararon los resultados de los dos modelos de turbulencia y se mostró que no se obtuvo ninguna diferencia apreciable en los valores de la temperatura promedio del agua supercrítica calculada con los modelos de turbulencia utilizados. Sin embargo, los resultados numéricos utilizando el modelo de turbulencia SST mostraron mayores valores de temperatura del combustible y de temperatura superficial de la envoltura de los elementos combustibles que los calculados con el modelo SSG

The high-performance light-water nuclear reactor is the European version of the supercritical water-cooled reactor, proposed as one of the candidates for Generation IV of nuclear reactors. This paper assesses the ability to predict the heat transfer behavior to supercritical water in the sub-channels of the 1/8 HPLWR fuel assembly by codes of Computational Fluid Dynamics using two models of turbulence (the Reynolds stress model developed by Speziale and the k-ω shear stress transport model). A mesh sensitivity study was performed to guarantee the independence of the numerical results regardless the size and distribution of the mesh elements. Temperature distributions were calculated in the fuel rods, in the clad, and in water both in the cooling zone and moderator zone. The results of the two turbulence models were compared. No appreciable difference was obtained in the values of the supercritical water average temperature calculated with the turbulence models used. However, the numerical results using the SST turbulence model show higher values regarding the temperature of both fuel rods and clad surface compared to those calculated with the SSG model

On-line approaches for the determination of residues and contaminants in complex samples.

The determination of residues and contaminants in complex matrices such as in the case of food, environmental, and biological samples requires a combination of several steps to succeed in the aimed goal. At least three independent steps are integrated to provide the best available situation to deal with such matrices: (1) a sample preparation technique is employed to isolate the target compounds from the rest of the matrix; (2) a chromatographic (second) step further "purifies" the isolated compounds from the co-extracted matrix interferences; (3) a spectroscopy-based device acts as chromatographic detector (ideally containing a tandem high-resolution mass analyzer) for the qualitative and quantitative analysis. These techniques can be operated in different modes including the off-line and the on-line modes. The present report focus the on-line coupling techniques aiming the determination of analytes present in complex matrices. The fundamentals of these approaches as well as the most common set ups are presented and discussed, as well as a review on the recent applications of these two approaches to the fields of bioanalytical, environmental, and food analysis are critically discussed.

Three-dimensional computational fluid dynamics modeling of particle uptake by an occupational air sampler using manually-scaled and adaptive grids.

This work presents fluid flow and particle trajectory simulation studies to determine the aspiration efficiency of a horizontally oriented occupational air sampler using computational fluid dynamics (CFD). Grid adaption and manual scaling of the grids were applied to two sampler prototypes based on a 37-mm cassette. The standard k-ε model was used to simulate the turbulent air flow and a second order streamline-upwind discretization scheme was used to stabilize convective terms of the Navier-Stokes equations. Successively scaled grids for each configuration were created manually and by means of grid adaption using the velocity gradient in the main flow direction. Solutions were verified to assess iterative convergence, grid independence and monotonic convergence. Particle aspiration efficiencies determined for both prototype samplers were undistinguishable, indicating that the porous filter does not play a noticeable role in particle aspiration. Results conclude that grid adaption is a powerful tool that allows to refine specific regions that require lots of detail and therefore better resolve flow detail. It was verified that adaptive grids provided a higher number of locations with monotonic convergence than the manual grids and required the least computational effort.