scholarly journals Exposure of Ophthalmologists to Patients' Exhaled Droplets in Clinical Practice: A Numerical Simulation of SARS-CoV-2 Exposure Risk

2021 ◽  
Vol 9 ◽  
Author(s):  
Yanchao Fan ◽  
Li Liu ◽  
Hui Zhang ◽  
Yingping Deng ◽  
Yi Wang ◽  
...  
Keyword(s):  
Microscopic Examination ◽  
Numerical Models ◽  
Working Environment ◽  
Diagnostic Process ◽  
Slit Lamp ◽  
Infectious Risk ◽  
Direct Exposure ◽  
Indirect Exposure ◽  
Dynamics Simulations ◽  
Ophthalmoscopic Examination

Background: Lack of quantification of direct and indirect exposure of ophthalmologists during ophthalmic diagnostic process makes it hard to estimate the infectious risk of aerosol pathogen faced by ophthalmologists at working environment.Methods: Accurate numerical models of thermal manikins and computational fluid dynamics simulations were used to investigate direct (droplet inhalation and mucosal deposition) and indirect exposure (droplets on working equipment) within a half-minute procedure. Three ophthalmic examination or treatment scenarios (direct ophthalmoscopic examination, slit-lamp microscopic examination, and ophthalmic operation) were selected as typical exposure distance, two breathing modes (normal breathing and coughing), three levels of ambient RH (40, 70, and 95%) and three initial droplet sizes (50, 70, and 100 μm) were considered as common working environmental condition.Results: The exposure of an ophthalmologist to a patient's expiratory droplets during a direct ophthalmoscopic examination was found to be 95 times that of a person during normal interpersonal interaction at a distance of 1 m and 12.1, 8.8, and 9.7 times that of an ophthalmologist during a slit-lamp microscopic examination, a surgeon during an ophthalmic operation and an assistant during an ophthalmic operation, respectively. The ophthalmologist's direct exposure to droplets when the patient cough-exhaled was ~7.6 times that when the patient breath-exhaled. Compared with high indoor RH, direct droplet exposure was higher and indirect droplet exposure was lower when the indoor RH was 40%.Conclusion: During the course of performing ophthalmic examinations or treatment, ophthalmologists typically face a high risk of SARS-CoV-2 infection by droplet transmission.

Experimental Validation of Existing Numerical Models for the Interaction of Fluid Transients With In-Line Air Pockets

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Jane Alexander ◽  
Pedro J. Lee ◽  
Mark Davidson ◽  
Huan-Feng Duan ◽  
Zhao Li ◽  
...  
Keyword(s):  
Time Delay ◽  
Wave Speed ◽  
Numerical Models ◽  
Diagnostic Process ◽  
Air Pocket ◽  
Fluid Transients ◽  
Entrapped Air ◽  
Air Pockets ◽  
The Given ◽  
Potential Tool

Entrapped air in pipeline systems can compromise the operation of the system by blocking flow and raising pumping costs. Fluid transients are a potential tool for characterizing entrapped air pockets, and a numerical model which is able to accurately predict transient pressures for a given air volume represents an asset to the diagnostic process. This paper presents a detailed study on our current capability for modeling and predicting the dynamics of an inline air pocket, and is one of a series of articles within a broader context on air pocket dynamics. This paper presents an assessment of the accuracy of the variable wave speed and accumulator models for modeling air pockets. The variable wave speed model was found to be unstable for the given conditions, while the accumulator model is affected by amplitude and time-delay errors. The time-delay error could be partially overcome by combining the two models.

Exposure to genocide and the risk of schizophrenia: a population-based study

2015 ◽  
Vol 46 (4) ◽  
pp. 855-863 ◽  
Author(s):  
S. Z. Levine ◽  
I. Levav ◽  
Y. Goldberg ◽  
I. Pugachova ◽  
Y. Becher ◽  
...  
Keyword(s):  
Cox Regression ◽  
Population Based ◽  
In Utero ◽  
Sensitivity Analyses ◽  
Critical Periods ◽  
Population Based Study ◽  
Regression Modelling ◽  
Direct Exposure ◽  
The Holocaust ◽  
Indirect Exposure

BackgroundNo evidence exists on the association between genocide and the incidence of schizophrenia. This study aims to identify critical periods of exposure to genocide on the risk of schizophrenia.MethodThis population-based study comprised of all subjects born in European nations where the Holocaust occurred from 1928 to 1945, who immigrated to Israel by 1965 and were indexed in the Population Register (N = 113 932). Subjects were followed for schizophrenia disorder in the National Psychiatric Case Registry from 1950 to 2014. The population was disaggregated to compare groups that immigrated before (indirect exposure: n = 8886, 7.8%) or after (direct exposure: n = 105 046, 92.2%) the Nazi or fascist era of persecutions began. The latter group was further disaggregated to examine likely initial prenatal or postnatal genocide exposures. Cox regression modelling was computed to compare the risk of schizophrenia between the groups, adjusting for confounders.ResultsThe likely direct group was at a statistically (p < 0.05) greater risk of schizophrenia (hazard ratio = 1.27, 95% confidence interval 1.06–1.51) than the indirect group. Also, the likely combined in utero and postnatal, and late postnatal (over age 2 years) exposure subgroups were statistically at greater risk of schizophrenia than the indirect group (p < 0.05). The likely in utero only and early postnatal (up to age 2 years) exposure subgroups compared with the indirect exposure group did not significantly differ. These results were replicated across three sensitivity analyses.ConclusionsThis study showed that genocide exposure elevated the risk of schizophrenia, and identified in utero and postnatal (combined) and late postnatal (age over 2 years) exposures as critical periods of risk.

Circular Cylinder Exposed to Cross Flow Fluid Forces – Parameters of Influence – Limits of Numerical Models

2003 ◽  
Author(s):  
Christoph Reichel ◽  
Klaus Strohmeier
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Models ◽  
Lift Coefficient ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Rigid Cylinder ◽  
Fluid Forces ◽  
Wide Range ◽  
Dynamics Simulations

In many technical fields, e.g. heat exchangers, circular cylinders are involved in Fluid Structure Interaction (FSI) problems. Therefore correct frequency and magnitude of fluid forces, respectively Strouhal number, drag and lift coefficient are needed. If fluid forces are evaluated with Computational Fluid Dynamics (CFD), mostly flow around a rigid cylinder is used to verify model and numerical methods. Unfortunately experimental as well as numerical results show great variation, making verification and testing of models difficult. Reynolds number is regarded as main influencing parameter for a rigid cylinder in cross flow. Most of experimental deviations can be related to other parameters, which differ from experiment to experiment. In this paper such parameters are specified and it is shown, that a closer look is needed, if one really wants to verify a model. Besides experimental results, which can be found in literature, some parameters are investigated by numerical simulation. Like experiments CFD (Computational Fluid Dynamics) simulations show a huge bandwidth of results, even when the same turbulence model is used. Flow around cylinders separates over a wide range of Reynolds numbers. It will be demonstrated that, using CFD, large deviations in fluid forces can often be related to miscalculation of the point of separation.

Forming Tool Use Representations: A Neurophysiological Investigation into Tool Exposure

2011 ◽  
Vol 23 (10) ◽  
pp. 2920-2934 ◽  
Author(s):  
John Christopher Mizelle ◽  
Teresa Tang ◽  
Nikta Pirouz ◽  
Lewis A. Wheaton
Keyword(s):  
Learning Strategies ◽  
Tool Use ◽  
Motor Planning ◽  
Hemispheric Dominance ◽  
Neural Activation ◽  
The Novel ◽  
Beta Band ◽  
Related Information ◽  
Direct Exposure ◽  
Indirect Exposure

Prior work has identified a common left parietofrontal network for storage of tool-related information for various tasks. How these representations become established within this network on the basis of different modes of exposure is unclear. Here, healthy subjects engaged in physical practice (direct exposure) with familiar and unfamiliar tools. A separate group of subjects engaged in video-based observation (indirect exposure) of the same tools to understand how these learning strategies create representations. To assess neural mechanisms engaged for pantomime after different modes of exposure, a pantomime task was performed for both tools while recording neural activation with high-density EEG. Motor planning–related neural activation was evaluated using beta band (13–22 Hz) event-related desynchronization. Hemispheric dominance was assessed, and activation maps were generated to understand topography of activations. Comparison of conditions (effects of tool familiarity and tool exposure) was performed with standardized low-resolution brain electromagnetic tomography. Novel tool pantomime following direct exposure resulted in greater activations of bilateral parietofrontal regions. Activations following indirect training varied by tool familiarity; pantomime of the familiar tool showed greater activations in left parietofrontal areas, whereas the novel tool showed greater activations at right temporoparieto-occipital areas. These findings have relevance to the mechanisms for understanding motor-related behaviors involved in new tools that we have little or no experience with and can extend into advancing theories of tool use motor learning.

scholarly journals Multiscale Modelling of Nanoindentation

2007 ◽  
Vol 345-346 ◽  
pp. 925-930 ◽  
Author(s):  
Hyung Jun Chang ◽  
Heung Nam Han ◽  
Marc Fivel
Keyword(s):  
Finite Element Modelling ◽  
Numerical Models ◽  
Dislocation Dynamics ◽  
Nanoindentation Test ◽  
Discrete Dislocation Dynamics ◽  
The Past ◽  
Discrete Dislocation ◽  
The World ◽  
Continuum Description ◽  
Dynamics Simulations

Nanoindentation is an interesting technique used to probe the local mechanical properties of a material. Although this test has been widely used and developed over the world during the past few years, it remains a lot of uncertainties regarding the interpretation of nanoindentation data. In this study, we propose to simulate the nanoindentation test of FCC single crystals like Cu or Ni using three numerical models. At the lowest scale, molecular dynamics simulations give details of the nucleation of the first dislocations induced by the indentation. At an intermediate scale, discrete dislocation dynamics simulations are performed to study the evolution of the dislocation microstructure during the loading. Finally, at the upper scale, 3D finite element modelling using crystal plasticity constitutive equations give a continuum description of the indentation induced plasticity. It is shown how the different models are interconnected together.

Investigation of a Diffuser-Volute Combination With Variable Cross-Sectional Area for Centrifugal Fans

2016 ◽  
Author(s):  
Tore Fischer ◽  
Manuel Rudersdorf ◽  
Sebastian Burgmann ◽  
Thorsten kleine Sextro ◽  
Joerg R. Seume
Keyword(s):  
Numerical Models ◽  
Cross Sectional Area ◽  
Experimental Investigations ◽  
Variable Cross ◽  
Centrifugal Fan ◽  
Sectional Area ◽  
Cross Sectional ◽  
Centrifugal Fans ◽  
Flow Mechanisms ◽  
Dynamics Simulations

The present paper focuses on the potential efficiency improvements and the stable operating range of a centrifugal fan for fuel cell applications. Improvements will be achieved by variability of the cross-sectional area of diffuser and volute by use of a moving backplate. The investigation consists of three parts: The first part describes the design and the performance prediction of a diffuser-volute combination with a variable cross-sectional area, based on empirical correlations and low-resolution CFD (Computational Fluid Dynamics) simulations. For the second part, high-resolution 360 degree CFD simulations are used to gain deeper insight into the flow mechanisms and their influence on fan performance. The last part presents the experimental investigations carried out to validate the numerical models. For this purpose, a demonstrator of the fan including a diffuser-volute combination with variable cross-sectional area is manufactured and investigated using optical PIV (Particle Image Velocimetry) measurements.

Calculations of Scald Burns: Effects of Water Temperature, Exposure Duration, and Clothing

2010 ◽  
Author(s):  
Nessa Johnson ◽  
John Abraham ◽  
Zach Helgeson
Keyword(s):  
Elevated Temperatures ◽  
Burn Injury ◽  
Tissue Injury ◽  
Numerical Models ◽  
Blood Perfusion ◽  
Visual Observation ◽  
Hot Water ◽  
Appropriate Treatment ◽  
Direct Exposure ◽  
Temperature Exposure

A numerical model has been constructed to assess the depth of injury incurred when skin is exposed to heated water. The model includes an extended duration which occurs when clothing, saturated with hot water is kept in contact with the skin after the direct exposure has ended. The model takes data from a broad summary of the literature which examines the ranges of reported tissue thicknesses, tissue thermophysical properties, and blood perfusion. Water temperatures ranging from 60–90°C and total exposure durations up to 110 seconds were modeled. As expected, longer durations and elevated temperatures lead to a greater extent of tissue injury. Calculated values of tissue injury were compared with prior injury reports. These reports, taken from the literature, reinforce the present calculations. It is seen that numerical models can accurately predict burn injury as observed in clinical settings, in fact, the calculations of burn injury presented here provide more information for the appropriate treatment of burn injuries compared to visual observation.

scholarly journals PSII-19 Stallion exposure fails to alter circulating LH concentrations or hasten ovulation in seasonally anestrous mares

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 240-241
Author(s):  
Chelsea D Sinclair ◽  
Jeffrey Stevenson ◽  
Abigail Jager ◽  
Nathan Long ◽  
Timothy Rozell ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Direct Contact ◽  
Treatment Initiation ◽  
Similar Increase ◽  
Short Day ◽  
Male Effect ◽  
Direct Exposure ◽  
Indirect Exposure ◽  
One Way Anova

Abstract Introduction of males to seasonally anestrous females has been shown to increase LH concentrations and hasten the first ovulation in ewes and does. Investigation of the male effect in mares has not been well-studied. The objective of this study was to determine if direct or indirect exposure to a stallion would result in a similar increase in LH and hasten first ovulation in anestrous mares. In late February, mares were stratified by parity and age and randomly assigned to 3 treatments (n = 7 per treatment): DXP (direct exposure; mares housed adjacent to stallion and allowed direct contact for 2 h on 3 d/wk by placing the stallion into a cage in the center of a tease pen), IXP (indirect exposure; mares housed adjacent to stallion but not allowed direct contact), and CON (control; mares housed away from stallion and not allowed direct or indirect exposure). During the first, third, and fifth days of treatment, blood was collected hourly for 8 h beginning just before treatment initiation for later analysis of LH. Concentrations of LH were analyzed for repeated measures and time from the first day of treatment to ovulation was analyzed using one-way ANOVA. The interval from treatment initiation to first ovulation did not differ (P &gt; 0.05) among treatments: 36.3±6.7, 36.9±6.7, and 48.3±4.2 d for DXP, IXP, and CON, respectively. Although treatments did not affect (P &gt; 0.05) LH concentration, a significant day effect (P &lt; 0.05) was detected with LH concentrations being greater on the fifth treatment day compared with the first and third days. Results signify that stallion exposure to anestrous mares failed to elicit the same effects that have been observed in short-day breeders, thus indicating that stallion exposure may not be beneficial in the management of anestrous mares.

scholarly journals Differences of Cytotoxicity of Orthodontic Bands Assessed by Survival Tests inSaccharomyces cerevisiae

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Tatiana Siqueira Gonçalves ◽  
Luciane Macedo de Menezes ◽  
Luciele Gonzaga Ribeiro ◽  
Catieli Gobetti Lindholz ◽  
Renata Medina-Silva
Keyword(s):  
Artificial Saliva ◽  
Survival Rates ◽  
Negative Control ◽  
Yeast Cells ◽  
Orthodontic Appliances ◽  
Slight Reduction ◽  
Yeast Viability ◽  
Direct Exposure ◽  
Indirect Exposure ◽  
Laser Soldering

The aim of this study was to evaluate the cytotoxicity induced by orthodontic bands through survival tests onSaccharomyces cerevisiae,a microorganism that presents several genetic and biochemical characteristics similar to human cells. Three groups of bands were evaluated: silver soldered (SSB), laser soldered (LSB), and bands without any solder (WSB). Yeast cells were directly exposed to the bands and indirectly, when a previous elution of the metals in artificial saliva was performed. The negative control was composed of yeast cells or artificial saliva not exposed to any kind of metal. In the direct exposure experiments, all tested groups of bands induced a slight reduction in yeast viability compared to the control. This effect was more intense for the SSB, although not statistically significant. For the indirect exposure experiments, the SSB induced a statistically significant decrease in cell viability compared to the LSB. There were no significant differences between the survival rates of the negative control and the LSB group in both direct and saliva tests. SSBs were cytotoxic, whilst LSBs were not, confirming that laser soldering may be a more biocompatible alternative for use in connecting wires to orthodontic appliances.

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