scholarly journals Factors affecting aerosol size distribution during various dental procedures

2021 ◽  
Author(s):  
Shruti Choudhary ◽  
Michael J Durkin ◽  
Daniel C Stoeckel ◽  
Heidi M Steinkamp ◽  
Martin H Thornhill ◽  
...  
Keyword(s):  
Particulate Matter ◽  
High Speed ◽  
High Volume ◽  
Routine Care ◽  
Mitigation Strategies ◽  
Aerosol Size Distribution ◽  
Dental Clinic ◽  
Factors Affecting ◽  
Dental Procedures ◽  
The Impact

Objectives: To determine the impact of various aerosol mitigation interventions and establish duration of aerosol persistence in a variety of dental clinic configurations. Methods: We performed aerosol measurement studies in endodontic, orthodontic, periodontic, pediatric, and general dentistry clinics. We used an optical aerosol spectrometer and wearable particulate matter sensors to measure real-time aerosol concentration from the vantage point of the dentist during routine care in a variety of clinic configurations (e.g, open bay, single room, partitioned operatories). We compared the impact of aerosol mitigation strategies [ventilation and high-volume evacuation (HVE)] and prevalence of particulate matter in the dental clinic environment before, during and after high-speed drilling, slow speed drilling and ultrasonic scaling procedures. Results: Conical and ISOVAC HVE were superior to standard tip evacuation for aerosol-generating procedures. When aerosols were detected in the environment, they were rapidly dispersed within minutes of completing the aerosol-generating procedure. Few aerosols were detected in dental clinics, regardless of configuration, when conical and ISOVAC HVE were used. Conclusions: Dentists should consider using conical or ISOVAC HVE rather than standard tip evacuators to reduce aerosols generated during routine clinical practice. Furthermore, when such effective aerosol mitigation strategies are employed, dentists need not leave dental chairs fallow between patients as aerosols are rapidly dispersed. Clinical Significance: ISOVAC HVE is highly effective in reducing aerosol emissions. With adequate ventilation and HVE use, dental fallow time can be reduced to 5 minutes.

scholarly journals Examining partial proportional odds model in analyzing severity of high-speed railway accident

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Jing Wang ◽  
Yinghan Wang ◽  
Yichuan Peng ◽  
Jian John Lu
Keyword(s):  
High Speed ◽  
Proportional Odds Model ◽  
Impact Factors ◽  
Proportional Odds ◽  
High Speed Railway ◽  
Severity Level ◽  
Content Type ◽  
Factors Affecting ◽  
Partial Proportional Odds Model ◽  
The Impact

Purpose The operation safety of the high-speed railway has been widely concerned. Due to the joint influence of the environment, equipment, personnel and other factors, accidents are inevitable in the operation process. However, few studies focused on identifying contributing factors affecting the severity of high-speed railway accidents because of the difficulty in obtaining field data. This study aims to investigate the impact factors affecting the severity of the general high-speed railway. Design/methodology/approach A total of 14 potential factors were examined from 475 data. The severity level is categorized into four levels by delay time and the number of subsequent trains that are affected by the accident. The partial proportional odds model was constructed to relax the constraint of the parallel line assumption. Findings The results show that 10 factors are found to significantly affect accident severity. Moreover, the factors including automation train protection (ATP) system fault, platform screen door and train door fault, traction converter fault and railway clearance intrusion by objects have an effect on reducing the severity level. On the contrary, the accidents caused by objects hanging on the catenary, pantograph fault, passenger misconducting or sudden illness, personnel intrusion of railway clearance, driving on heavy rain or snow and train collision against objects tend to be more severe. Originality/value The research results are very useful for mitigating the consequences of high-speed rail accidents.

scholarly journals Prediction of source contributions to urban background PM<sub>10</sub> concentrations in European cities: a case study for an episode in December 2016 using EMEP/MSC-W rv4.15 and LOTOS-EUROS v2.0 – Part 1: The country contributions

2020 ◽  
Vol 13 (4) ◽  
pp. 1787-1807 ◽  
Author(s):  
Matthieu Pommier ◽  
Hilde Fagerli ◽  
Michael Schulz ◽  
Alvaro Valdebenito ◽  
Richard Kranenburg ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Emission Reduction ◽  
Total Concentration ◽  
Large Fraction ◽  
Mitigation Strategies ◽  
Grid Cells ◽  
Source Attribution ◽  
European Cities ◽  
Guideline Value ◽  
The Impact

Abstract. A large fraction of the urban population in Europe is exposed to particulate matter levels above the WHO guideline value. To make more effective mitigation strategies, it is important to understand the influence on particulate matter (PM) from pollutants emitted in different European nations. In this study, we evaluate a country source contribution forecasting system aimed at assessing the domestic and transboundary contributions to PM in major European cities for an episode in December 2016. The system is composed of two models (EMEP/MSC-W rv4.15 and LOTOS-EUROS v2.0), which allows the consideration of differences in the source attribution. We also compared the PM10 concentrations, and both models present satisfactory agreement in the 4 d forecasts of the surface concentrations, since the hourly concentrations can be highly correlated with in situ observations. The correlation coefficients reach values of up to 0.58 for LOTOS-EUROS and 0.50 for EMEP for the urban stations; the values are 0.58 for LOTOS-EUROS and 0.72 for EMEP for the rural stations. However, the models underpredict the highest hourly concentrations measured by the urban stations (mean underestimation of 36 %), which is to be expected given the relatively coarse model resolution used (0.25∘ longitude × 0.125∘ latitude). For the source attribution calculations, LOTOS-EUROS uses a labelling technique, while the EMEP/MSC-W model uses a scenario having reduced anthropogenic emissions, and then it is compared to a reference run where no changes are applied. Different percentages (5 %, 15 %, and 50 %) for the reduced emissions in the EMEP/MSC-W model were used to test the robustness of the methodology. The impact of the different ways to define the urban area for the studied cities was also investigated (i.e. one model grid cell, nine grid cells, and grid cells covering the definition given by the Global Administrative Areas – GADM). We found that the combination of a 15 % emission reduction and a larger domain (nine grid cells or GADM) helps to preserve the linearity between emission and concentrations changes. The nonlinearity, related to the emission reduction scenario used, is suggested by the nature of the mismatch between the total concentration and the sum of the concentrations from different calculated sources. Even limited, this nonlinearity is observed in the NO3-, NH4+, and H2O concentrations, which is related to gas–aerosol partitioning of the species. The use of a 15 % emission reduction and of a larger city domain also causes better agreement on the determination of the main country contributors between both country source calculations. Over the 34 European cities investigated, PM10 was dominated by domestic emissions for the studied episode (1–9 December 2016). The two models generally agree on the dominant external country contributor (68 % on an hourly basis) to PM10 concentrations. Overall, 75 % of the hourly predicted PM10 concentrations of both models have the same top five main country contributors. Better agreement on the dominant country contributor for primary (emitted) species (70 % is found for primary organic matter (POM) and 80 % for elemental carbon – EC) than for the inorganic secondary component of the aerosol (50 %), which is predictable due to the conceptual differences in the source attribution used by both models. The country contribution calculated by the scenario approach depends on the chemical regime, which largely impacts the secondary components, unlike the calculation using the labelling approach.

scholarly journals A Preliminary Assessment of the Impacts of Multiple Temporal-scale Variations in Particulate Matter on its Source Apportionment

2018 ◽  
Author(s):  
Xing Peng ◽  
Jian Gao ◽  
Guoliang Shi ◽  
Xurong Shi ◽  
Yanqi Huangfu ◽  
...  
Keyword(s):  
Time Series ◽  
Particulate Matter ◽  
Source Apportionment ◽  
Chemical Species ◽  
Principal Component ◽  
Temporal Scale ◽  
Mitigation Strategies ◽  
Total Variance ◽  
Secondary Source ◽  
The Impact

Abstract. Time series of pollutant concentrations consist of variations at different time scales that are attributable to many processes/sources (data noise, source intensities, meteorological conditions, climate, etc.). Improving the knowledge of the impact of multiple temporal-scale components on pollutant variations and pollution levels can provide useful information for suitable mitigation strategies for pollutant control during a high pollution episode. To investigate the source factors driving these variations, the Kolmogorov-Zurbenko (KZ) filter was used to decompose the time series of PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 μm) and chemical species into intra-day, diurnal, synoptic, and baseline temporal-scale components (TS components). The synoptic TS component has the largest amplitude and relative contributions (about 50 %) to the total variance of SO42−, NH4+, and OC concentrations. The diurnal TS component has the largest relative contributions to the total variance of PM2.5, NO3−, EC, Ca, and Fe concentrations, ranging from 32 % to 47 %. To investigate the source impacts on PM2.5 from different TS components, four datasets RI (intra-day removed), RD (diurnal removed), RS (synoptic removed), and RBL (baseline removed) were created by respectively removing the intra-day, diurnal, synoptic, and baseline TS component from the original datasets. Multilinear Engine 2 (ME-2) and/or principal component analysis was applied to these four datasets as well as the original datasets for source apportionment. ME-2 solutions using the original and RI dataset identify crustal dust contributions. For the solutions from original, RI, RD, and RS datasets, the total primary source impacts are close, ranging from 35.1 to 40.4 μg m−3 during the entire sampling period. For the secondary source impacts, solutions from the original, RI and RD dataset give similar source impacts (about 30 μg m−3), which were higher than the impacts derived from the RS datasets (21.2 μg m−3).

The impact of high speed, high volume traffic axes on brown bears in Slovenia

2003 ◽  
Vol 111 (2) ◽  
pp. 191-204 ◽  
Author(s):  
Petra Kaczensky ◽  
Felix Knauer ◽  
Blaz Krze ◽  
Marco Jonozovic ◽  
Miha Adamic ◽  
...  
Keyword(s):  
High Speed ◽  
High Volume ◽  
Brown Bears ◽  
The Impact

Factors affecting the administration of adjuvant therapy in patients with pancreatic adenocarcinoma.

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. e15087-e15087
Author(s):  
Pablo Emilio Serrano Aybar ◽  
Peter Tae Wan Kim ◽  
Kenneth Leung ◽  
Sean P. Cleary ◽  
Steven Gallinger ◽  
...  
Keyword(s):  
Adjuvant Therapy ◽  
Pancreatic Adenocarcinoma ◽  
Multivariate Logistic Regression Analysis ◽  
Major Complication ◽  
High Volume ◽  
Lower Probability ◽  
Node Negative ◽  
Factors Affecting ◽  
Major Complications ◽  
The Impact

e15087 Background: Adjuvant therapy for pancreatic adenocarcinoma is now considered standard of care. The proportion of patients receiving adjuvant therapy (ADT) following pancreatic resection is a good quality indicator of cancer care. The aim of this study was to evaluate factors associated with receiving ADT in patients with pancreatic cancer. Methods: Between years 2000-2010, all patients undergoing pancreaticoduodenectomy for pancreatic adenocarcinoma at a single high-volume hepatotopancreatobiliary center were evaluated. The impact of demographic, peri-operative and pathological risk factors affecting the administration of ADT were analyzed using univariate and multivariate logistic regression analysis. Results: There were 258 patients identified. Median age was 65 (37-84) years, 54% were females. There was a 15% margin positivity rate, 14% pancreatic leak rate, 14.7% major complication rate, and 1.2% 90 day/in-hospital mortality rate. Overall, 160/258 (70%) of patients received adjuvant therapy. On multivariate analysis; age, presence of major complications, node-negative disease and earlier era (2000-2004) were significantly associated with a lower probability of receiving ADT. Reasons for not receiving ADT were; patient preference: 20/67 (32%), not recommended: 14/67 (23%), disease recurrence: 12/67 (9.5%) and being medically unfit for ADT: 18/67 (11.5%). None of these reasons were different between time-periods except for fewer patients being offered ADT from 2000-2005 (15.4% vs. 2.5%, p <0.001). Conclusions: Thirty percent of patients do not receive ADT following pancreatectomy. Those with advanced age; node-negative disease and those who had major complications after pancreaticoduodenectomy were less likely to receive ADT. The impact of these factors should be taken into account when considering the administration of ADT.

scholarly journals FACTORS AFFECTING THE USE OF 4G SERVICES: THE CASE OF VIETNAM

2019 ◽  
pp. 61-74
Author(s):  
Binh Tran Duy ◽  
Tran Huu Ai
Keyword(s):  
Technology Adoption ◽  
Service Quality ◽  
High Speed ◽  
Perceived Value ◽  
Strong Relationship ◽  
Service Users ◽  
Factors Affecting ◽  
Value Perception ◽  
Actual Use ◽  
The Impact

4G services open the door for conversation and data communications by means of high-speed mobile connection. However, the actual use of the 4G speeds is still below expectations. Therefore, it is important to understand the interaction of factors involved in the adoption of this technology. Previous studies have shown that such variables as convenience, efficient service quality and variety of services, perceived value and price are important factors in the course of 4G technology adoption. In this study, the authors examine the impact of these factors on own sample of the 4G service users. Our research results demonstrate that: 1) price, convenience and varied services are important predictors of value perception; 2) there is a relationship between diversity of services and the sense of value mediated by convenience and 3) perceived value has a strong relationship with the intention to buy.

scholarly journals Characteristics and Extent of Particulate Matter Emissions of a Ropeway Public Mobility System in the City Center of Perugia (Central Italy)

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1356
Author(s):  
Beatrice Moroni ◽  
Stefano Crocchianti ◽  
Federica Bruschi ◽  
Chiara Petroselli ◽  
Alessandro Di Menno di Bucchianico ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Central Italy ◽  
Road Dust ◽  
High Volume ◽  
Atmospheric Particulate Matter ◽  
Aerosol Sampling ◽  
City Center ◽  
Mobility System ◽  
The Impact ◽  
The City

Minimetrò (MM) is a ropeway public mobility system that has been in operation in the city of Perugia for about ten years to integrate with urban mobility and lighten vehicular traffic in the historic city center. The purpose of this work was to evaluate the impact of MM as a source of pollutants in the urban context, and the exposure of people in the cabins and the platforms along the MM line. These topics have been investigated by means of intensive measurement and sampling campaigns performed in February and June 2015 on three specific sites of the MM line representative of different sources and levels of urban pollution. Stationary and dynamic measurements of particle size distribution, nanoparticle and black carbon aerosol number and mass concentrations measurements were performed by means of different bench and portable instruments. Aerosol sampling was carried out using low volume and high-volume aerosol samplers, and the samples nalysed by off-line methods. Results show that MM is a considerable source of atmospheric particulate matter having characteristics very similar to those of the common urban road dust in Perugia. In the lack of clear indications on road dust effect, the contribution of MM to the aerosol in Perugia cannot be neglected.

scholarly journals Impacts of a railway tunnel on the streams baseflow verified by means of numerical modelling

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Leonardo Piccinini ◽  
Valentina Vincenzi
Keyword(s):  
Numerical Modelling ◽  
High Speed ◽  
Three Dimensional ◽  
Tracer Tests ◽  
Maximum Flow ◽  
Mitigation Strategies ◽  
Railway Tunnel ◽  
Flow Measurements ◽  
Railway Line ◽  
The Impact

The high-speed railway line between Bologna and Florence (Italy) is mostly developed underground through the Tuscan-Emilian Apennine, and the tunnels severely impacted groundwater and surface water. The 15-km-long Firenzuola tunnel crosses siliciclastic turbidites: during drilling, water inrushes occurred at fault and fracture zones, and the tunnel continues to drain the aquifer. The water table dropped below the level of the valleys, and gaining streams transformed into losing streams or ran completely dry, as did many springs. Hydrological observations and two multitracer tests have previously characterized the stream-tunnel connections and the impact processes. In the framework of planning mitigation strategies to minimize impacts on stream baseflow, three-dimensional numerical modelling with MODFLOW (the EPM approach) is applied to evaluate the artificial minimum flow needed to maintain flow continuity along the stream during the recession phase. The establishment of the two presented models is based on hydrogeological monitoring data and the results of flow measurements and tracer tests. Maximum flow rates subtracted from stream baseflow by the tunnel along the connection structures are calculated for two streams with major impacts.

scholarly journals Mitigation strategies for communication networks induced impairments in autonomous microgrids control: A review

2021 ◽  
Vol 5 (4) ◽  
pp. 342-375
Author(s):  
Olayanju Sunday Akinwale ◽  
◽  
Dahunsi Folasade Mojisola ◽  
Ponnle A. Akinlolu ◽  
◽  
...  
Keyword(s):  
High Speed ◽  
Renewable Energy Sources ◽  
Congestion Management ◽  
Mitigation Strategies ◽  
Topology Design ◽  
Effective Control ◽  
Control Methods ◽  
Cyber Attack ◽  
Secondary Control ◽  
The Impact

<abstract> <p>The advancement in communication technology and the availability of intelligent electronic devices (IEDs) have impacted positively on the penetration of renewable energy sources (RES) into the main electricity grid. High penetration of RES also come along with greater demand for more effective control approaches, congestion management techniques, and microgrids optimal dispatch. Most of the secondary control methods of microgrid systems in the autonomous mode require communication links between the distributed generators (DGs) for sharing power information and data for control purposes. This article gives ample review on the communication induced impairments in islanded microgrids. In the review, attention is given to communication induced delay, data packet loss, and cyber-attack that degrades optimal operations of islanded microgrids. The review also considered impairments modelling, the impact of impairments on microgrids operation and management, and the control methods employed in mitigating some of their negative impacts. The paper revealed that innovative control solutions for impairment mitigation rather than the development of new high-speed communication infrastructure should be implemented for microgrid control. It was also pointed out that a sparse communication graph is the basis for communication topology design for distributed secondary control in the microgrid.</p> </abstract>

scholarly journals The Spatial-Temporal Distribution and Control Measures Evaluation of Droplets and Aerosol Cloud in Dental Procedures

2021 ◽  
Author(s):  
Chao Yuan ◽  
Hongtao Yang ◽  
Siyuan Zheng ◽  
Xiangyu Sun ◽  
Xiaochi Chen ◽  
...  
Keyword(s):  
High Speed ◽  
Control Measure ◽  
Operation Mode ◽  
Temporal Distribution ◽  
High Volume ◽  
Control Measures ◽  
Aerosol Cloud ◽  
Dental Procedures ◽  
Air Purifier ◽  
And Control

Abstract Background: Droplets and aerosol cloud generating procedures in dentistry can increase the risk of airborne transmission of diseases such as COVID-19. To gain insight into the diffusion of spatters and possible preventive measures, we measured the particle spatial-temporal distribution characteristic and evaluated the effectiveness of the control measures.Methods: We conducted an experiment to observe the emitted spatters obtained during the simulated dental preparation by using high-speed videography. We measured the particle size distributions by laser diffraction and preliminarily estimated its velocity. We qualitatively and quantitatively described the spatial-temporal distributions of spatters and their control measure effects. Results: Majority of the dental spatters were small droplets (diameter less than 50 μm). A large number of smallest droplets (diameter less than 10 μm) were generated by high-speed air turbine handpiece. At the oral outlet, the speed of large droplets could exceed 2.63 m/s, and the speed of aerosol clouds ranged from 0.31–2.37 m/s. The evolution of the spatters showed that the more fully developed the state, the greater the number of spatters and the wider the contamination range. When the operation mode was moved from the central incisor to the first molar, the spatter direction became increasingly concentrated, and the velocities were enhanced. Larger droplets randomly moved along trajectories and rapidly settled. The aerosol cloud tended to float as a mass that interacted with the surrounding air. The high-volume evacuation could effectively clear away most of the dental spatters. The suction air purifier could change the diffusion direction of the spatters, compress the contamination range, and control aerosol escape into surrounding air. Conclusions: Our view is that we should combine the ‘point’ control measure (high-volume evacuation) and ‘area’ control measure (suction air purifier) to reduce the scope of pollution and prevent the aerosol escape into the surroundings. The study contributes to devising more accurate infection control guidelines, establishing appropriate interventions for different oral treatments, and minimizing the spread of respiratory diseases so that we can reduce cost and achieve the best results when medical resources are limited.

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