Concentration Of Small Particles Research Articles

Substantially elevated TSH, not traditional clinical subclinical thyroid disorder groupings, are associated with smaller LDL-P mean size: ELSA-Brasil

LDL appears to drive atherogenesis in overt hypothyroidism, but in subclinical dysfunction, its role is not completely elucidated. The aim of this study was to evaluate subfractions of LDL in subclinical (SC) thyroid disorders. Individuals were divided into three groups by baseline thyroid function (SC hypothyroidism, euthyroidism, and SC hyperthyroidism). LDL particle (LDL-P) subfractions were analyzed by Nuclear Magnetic Resonance (NMR) spectroscopy. The association between LDL-P subfractions and thyroid groups and quintiles was evaluated by linear regression models. We evaluated 3304 participants (54.1% women, 51.2% white, mean age 50.6±8.7 years). In the univariate analysis, small LDL particle concentrations (SLDL-P) were not different between SC hypo- and hyperthyroidism compared to euthyroid individuals (p=0.485 and p=0.314, respectively). Large LDL-P (LDL-P) levels also did not differ in SC hyperthyroidism and SC hypothyroidism compared to euthyroidism (p=0.698 and 0.788 respectively). Intermediate LDL-P levels were not different across the groups. These numbers did not materially change in multivariate analysis. However, we also analyzed LDL subfractions according to quintiles of TSH. We showed that in the higher TSH quintile LDL subfractions presented a significantly smaller mean size of LDL subfractions compared to the first quintile. SC thyroid disorders are not associated with significant changes in LDL-P subfractions measured by NMR spectroscopy. However, it seems that the LDL mean size decreases as TSH levels increase, which may represent a more atherogenic lipid profile.

A modified classic‐micromechanics approach to predict effective elastic properties of nanoparticles reinforced polymers

AbstractThe purpose of this study is to develop modified analytical models using micromechanical methods that can effectively estimate the elastic modulus of a polymeric composite material containing nanoparticle fillers. Relying on the Eigen‐strain concept in nanoparticle and matrix, Eshelby correlations initially developed for solid defects are revised. Also, an improved Mori–Tanaka and self‐consistent model were proposed based on the modified Eshelby equivalent inclusion approach, accordingly. The effective elastic properties including Young's modulus and Poisson's ratio were estimated using new models and compared to the conventional and previously developed micromechanical models. Also, the estimated values were validated using the experimentally determined elastic properties. For the experimental program, CB/Elastomer nanocomposite specimens were fabricated and tested. Numerical computations indicate that the new models can well and more accurately predict the experiment at the small particle concentration.

Healthy lifestyle, metabolomics and incident type 2 diabetes in a population-based cohort from Spain

BackgroundThe contribution of metabolomic factors to the association of healthy lifestyle with type 2 diabetes risk is unknown. We assessed the association of a composite measure of lifestyle with plasma metabolite profiles and incident type 2 diabetes, and whether relevant metabolites can explain the prospective association between healthy lifestyle and incident type 2 diabetes.MethodsA Healthy Lifestyle Score (HLS) (5-point scale including diet, physical activity, smoking status, alcohol consumption and BMI) was estimated in 1016 Hortega Study participants, who had targeted plasma metabolomic determinations at baseline examination in 2001–2003, and were followed-up to 2015 to ascertain incident type 2 diabetes.ResultsThe HLS was cross-sectionally associated with 32 (out of 49) plasma metabolites (2.5% false discovery rate). In the subset of 830 participants without prevalent type 2 diabetes, the rate ratio (RR) and rate difference (RD) of incident type 2 diabetes (n cases = 51) per one-point increase in HLS was, respectively, 0.69 (95% CI, 0.51, 0.93), and − 8.23 (95% CI, − 16.34, − 0.13)/10,000 person-years. In single-metabolite models, most of the HLS-related metabolites were prospectively associated with incident type 2 diabetes. In probit Bayesian Kernel Machine Regression, these prospective associations were mostly driven by medium HDL particle concentration and phenylpropionate, followed by small LDL particle concentration, which jointly accounted for ~ 50% of the HLS-related decrease in incident type 2 diabetes.ConclusionsThe HLS showed a strong inverse association with incident type 2 diabetes, which was largely explained by plasma metabolites measured years before the clinical diagnosis.

Impacts of low concentrations of nanoplastics on leaf litter decomposition and food quality for detritivores in streams

In forested streams, leaf litter decomposition is a vital ecosystem process, governed primarily by aquatic hyphomycetes. These fungi are crucial mediators of nutrients and energy to invertebrates and higher trophic levels. Very little information is available on the impact of low concentrations of different sizes of nanoplastic particles (NPPs) on leaf litter decomposition and aquatic hyphomycetes communities. Besides, NPPs impact on leaf litter nutritional quality and invertebrate feeding behaviour is unknown. We conducted a microcosm assay with varying concentrations (0–25 μg L-1) of small (100 nm; SNPPs) and large (1000 nm; LNPPs) plastic particles to assess their impact on leaf litter decomposition, sporulation rates and community structure of aquatic hyphomycetes. Furthermore, leaf litter was retrieved and fed to invertebrates to assess feeding rates. Our results indicated that leaf litter decomposition, fungal sporulation and abundance were significantly affected by NPPs concentrations and sizes. By contrast, leaf litter nutritional quality was impacted only by sizes. The NPPs, particularly SNPPs, augmented leaf litter polyunsaturated fatty acids (18–31%), consequently improving food quality; however, invertebrates' feeding rates were not impacted. Overall, our study provides novel insights on the risks posed by NPPs with pronounced impact at the basal trophic level.

Effects of Alirocumab on Triglyceride Metabolism: A Fat-Tolerance Test and Nuclear Magnetic Resonance Spectroscopy Study.

Background: PCSK9 antibodies strongly reduce LDL cholesterol. The effects of PCSK9 antibodies on triglyceride metabolism are less pronounced. The present study aimed to investigate in detail the effects of alirocumab on triglycerides, triglyceride-rich lipoproteins, and lipase regulators. Methods: A total of 24 patients with an indication for treatment with PCSK9 antibodies were recruited. There were two visits at the study site: the first before initiation of treatment with alirocumab and the second after 10 weeks of treatment. Fat-tolerance tests, nuclear magnetic resonance spectroscopy, and enzyme-linked immunosorbent assays were performed to analyze lipid metabolism. Results: A total of 21 participants underwent the first and second investigation. Among these, two participants only received alirocumab twice and 19 patients completed the trial per protocol. All of them had atherosclerotic vascular disease. There was no significant effect of alirocumab treatment on fasting triglycerides, post-prandial triglycerides, or lipoprotein-lipase regulating proteins. Total, large, and small LDL particle concentrations decreased, while the HDL particle concentration increased (all p < 0.001). Mean total circulating PCSK9 markedly increased in response to alirocumab treatment (p < 0.001). Whereas PCSK9 increased more than three-fold in all 19 compliant patients, it remained unchanged in those two patients with two injections only. Conclusion: Significant effects of alirocumab on triglyceride metabolism were not detectable in the ALIROCKS trial. The total circulating PCSK9 concentration might be a useful biomarker to differentiate non-adherence from non-response to PCSK9 antibodies.

Geochemistry of street dust in Tyumen, Russia: influence of traffic load.

This study investigates the elemental composition, organic carbon content, pH values, and particle size characteristics in 50 road dust samples collected from Tyumen, a large city in Western Siberia (Russia). The content of 62 major and trace elements was studied using atomic emission spectrometry (ICP-AES) и inductively coupled plasma spectrometry (ICP-MS). It was revealed that the dust has an alkaline reaction pH = 7.4-10.2 and low organic carbon content (0.07-2.9%). The grain size distribution of the road dust samples revealed that the predominant grain size fraction was of 100-250μm. The content of small particles (PM2 and PM10) representing the greatest environmental hazard is minimal on roads with an average traffic intensity. Studies have shown that the main road dust pollutants in Tyumen are Ni, Sb, Cr, Zn, and Co. The average geoaccumulation index (Igeo) values are ranked as Ni (2.2) > Sb (1.5) > Cr (1.3) > Zn (0.4) > Co (0.4) > Cu (0.2). The contamination evaluation through enrichment factor (EF) calculation showed that road dust is highly enriched in Ni and significantly in Cr and Sb. More than 80% of Zn, Co, and Cu and more than 90% of Ni, Sb, and Cr come from anthropogenic sources. The average concentration of Ni and Cr in the road dust of Tyumen is one order of magnitude higher than in other cities of the Earth where similar studies were carried out. The high Ni content is associated with the composition of local soils and roadways, increased content in vehicle exhaust gasses, and abrasion of metal parts. Calculations of the total enrichment index Ze showed that the level of road dust pollution in most of Tyumen's territory is hazardous.

An adaptable direct simulation Monte Carlo method for simulating acoustic agglomeration of solid particles

An adaptable direct simulation Monte Carlo (DSMC) method that settles the challenge of coexistence of agglomeration and rebound as a consequence of inter-particle collisions was developed to simulate acoustic agglomeration of solid particles. The method was validated against experimental data under a range of operational conditions. Based on this, the evolution of particle size distribution, agglomeration efficiency and agglomeration behavior with time was numerically investigated. The effect of restitution coefficient on the performance of acoustic agglomeration was also examined. The results show that the occurrence of acoustic agglomeration yields a significant decrease in the number concentration of small particles and a small increase in the number concentration of large particles. Moreover, a worse performance of acoustic agglomeration at a higher restitution coefficient is observed. This study demonstrated the power of the proposed method in simulating the acoustic agglomeration and provided a fundamental approach for investigating the dispersed gas-solid two-phase flows.

Microphysical characteristics of precipitating cumulus cloud based on airborne Ka-band cloud radar and droplet measurements

Based on cloud-probe data and airborne Ka-band cloud radar data collected in Baoding on 5 August 2018, the microphysical structural characteristics of cumulus (Cu) cloud at the precipitation stage were investigated. The cloud droplets in the Cu cloud were found to be significantly larger than those in stratiform (STF) cloud. In the Cu cloud, most cloud particles were between 7 and 10 μm in diameter, while in the STF cloud the majority of cloud particles grew no larger than 2 μm. The sensitivity of cloud properties to aerosols varied with height. The cloud droplet effective radius showed a negative relationship with the aerosol number concentration (Na) in the cloud planetary boundary layer (PBL) and upper layer above the PBL. However, the cloud droplet concentration (Nc) varied little with decreased Na in the high liquid water content region above 1500 m. High Na values of between 300 and 1853 cm−3 were found in the PBL, and the maximum Na was sampled near the surface in August in the Hebei region, which was lower than that in autumn and winter. High radar reflectivity corresponded to large FCDP (fast cloud droplet probe) particle concentrations and small aerosol particle concentrations, and vice versa for low radar reflectivity. Strong updrafts in the Cu cloud increased the peak radius and Nc, and broadened cloud droplet spectrum; lower air temperature was favorable for particle condensational growth and produced larger droplets.摘要在积云中, 大多数云粒子的直径在7到10微米之间, 而在层云中, 大多数云粒子的直径不超过2微米. 云滴有效半径与云中行星边界层(PBL)及PBL上层的气溶胶数浓度(Na)呈负相关. 在1500米以上的高液态水含量区域, 云滴浓度(Nc)变化不大, Na含量降低. 高雷达反射率对应于大的FCDP云粒子浓度和小的气溶胶粒子浓度. 积云中的强上升气流增加了云滴的峰值半径和数浓度, 拓宽了云滴谱; 较低的空气温度有利于粒子的凝结增长, 并产生较大的液滴.

Investigation of Metal and Trace Elements of Cenospheres from Lignite High-Calcium Fly Ash (Thailand)

High-calcium fly ashes contain a large content of small particles including cenospheres of chemical constituents known to be similar to fly ash and the parent coal. Coal fly ash contains metal and trace elements that may leach out during disposal or utilization. This work aimed to understand an overview of cenosphere characteristics relating to fly ash and leaching study. To our knowledge, this is the first report on metal and trace element leaching of cenospheres separated from high-calcium (28.9 wt.%) class C fly ash produced from the Mae Moh coal-fired thermal power plant in Thailand. In this study, the cenospheres were separated from fly ash by a wet separation process (sink-float method) using water as medium. Physical properties, morphology, chemical composition, the mineral phases of cenospheres and fly ash have been characterized. Extraction was carried out by acid digestion; the selected metal and trace elements in this study are Mg, Al, Zn, Pb, Cd, Cr, and Cu; the obtained environmentally available concentrations of cenospheres were analyzed in comparison to those of fly ash. The concentrations of Cu, Cr, Pb, and Cd elements of interest in the leachates obtained from the toxicity characteristic leaching procedure (TCLP) showed the tendency to decrease in that order. All the elements were found below the permissible limit values regarding Thailand soil quality standards. Association of the heavy metal trace elements in cenospheres and fly ash was discussed in in terms of physico-chemical-geochemistry correlating with the leaching concentrations.

Effect of BaTiO3Nanofillers on the Energy Storage Performance of Polymer Nanocomposites

AbstractPolymer nanocomposite is a promising substitute for the charge‐storage dielectric material in capacitors. Barium titanate/polycarbonate (BT/PC) nanocomposite is one of the system due to its comprehensive excellent dielectric properties. As the dielectric response of nanocomposite depends strongly on the size of the fillers, concentration of fillers in the composite system. In this study, BT/PC nanocomposites (BT = 1‐5%) with thickness of 100 µm were fabricated to reveal the effect of the fillers on the energy storage performance of the polymer nanocomposites. Owing to the variable concentration and good dispersibility of the nanofillers, the nanocomposites with small concentration of BT particles show more uniform and denser microstructures. Moreover, with the increase of filler concentration, dielectric results indicate a breakdown strength enhancement in the nanocomposites with BT fillers, which is quite different from the nanocomposites with normal fillers, and therefore leads to the superior energy storage performance. This study demonstrates a strategy of obtaining large dielectric constants and energy densities in ceramic/polymer composites for energy storage device applications.

One-dimensional narrow-band conductors

We review one-dimensional lattice models and the corresponding results that describe the low-temperature properties of quasi-one-dimensional lattice systems with long-range interaction. A widely known example is narrow-band low-dimensional conductors with long-range interelectron repulsion. The models deal with particles that live on the one-dimensional host lattice (chain), translation invariant or disordered, and interact via the long-range repulsive potential. The results are presented concerning the translation invariant host chain, in particular: the low-temperature thermodynamics incommensurable ground states and related devil-staircase form of various characteristics as functions of pertinent parameters, the self-localization of particles, a new branch of elementary excitations, etc. In the disordered case, where the sites of the host chain fluctuate randomly around the sites of the periodic chain, the low-temperature thermodynamics and the structure of the ground state are discussed in the framework of a certain model, which we call the cluster model and which seems to be a fairly reasonable approximation for low temperatures and small concentration of particles. Using analytical and numerical tools we analyze the thermodynamics and the ground state of the model. The latter proves to be a sequence of random domains and we study in detail their distribution.

Abstract P139: Diet-induced Shifts In HDL Profiles Are Associated With Changes In Immune Parameters

Introduction: Preclinical and population-based studies have demonstrated immunomodulatory and anti-inflammatory properties of HDL; however, it is unclear whether diet-induced changes in HDL profiles can directly impact markers of immune inflammation. Hypothesis: We hypothesized that daily consumption of different egg-based diets, which have been shown to differentially impact serum lipids and lipoprotein profiles, would induce changes in HDL parameters that correspond to shifts in clinical and molecular immune markers. Methods: Healthy men and women (18-35y, BMI &lt; 30kg/m 2 or &lt; 30% body fat for men and &lt; 40% body fat for women, n = 26) participated in a 16-week randomized, crossover intervention trial (NCT03577223), in which they consumed an egg-free diet for 4 weeks, followed by a 4-week diet containing either 3 whole eggs or 3 egg whites per day. Participants then followed a 4-week egg-free diet washout period, before switching to the alternative whole egg or egg white diet treatment. Fasting lipoprotein profiles, complete blood cell counts, and gene expression in peripheral blood mononuclear cells (PBMCs) was measured at the end of each diet period. Results: While no changes in total HDL particles, average HDL particle diameter, or the concentration of small (7.4-8.0 nm) or medium (8.1-9.5 nm) HDL particles was observed, the concentration of large HDL particles (10.8nm) was increased by whole egg intake as compared to intake of egg whites. A trend toward increased apolipoprotein A1 during the whole egg diet period as compared to the egg-free diet period was additionally observed. In line with our hypothesis, changes in large HDL concentrations between whole egg vs. egg white periods were inversely correlated with total white blood cell counts and absolute lymphocyte counts. CD8A mRNA expression in PBMCs was inversely correlated with concentrations of total and large HDL particles. Importantly, while serum choline and betaine were increased by whole egg intake compared to the other diet periods, no differences in pro-atherogenic and inflammatory trimethylamine-N-oxide (TMAO) between diet periods was observed. Conclusion: These findings suggest that diet-induced changes in HDL profiles are directly associated with changes in immune parameters.

Serum levels of small HDL particles are negatively correlated with death or lung transplantation in an observational study of idiopathic pulmonary fibrosis.

Serum lipoproteins, such as high-density lipoproteins (HDL), may influence disease severity in idiopathic pulmonary fibrosis (IPF). Here, we investigated associations between serum lipids and lipoproteins and clinical end-points in IPF. Clinical data and serum lipids were analysed from a discovery cohort (59 IPF subjects, 56 healthy volunteers) and validated using an independent, multicentre cohort (207 IPF subjects) from the Pulmonary Fibrosis Foundation registry. Associations between lipids and clinical end-points (forced vital capacity, 6-min walk distance, gender age physiology (GAP) index, death or lung transplantation) were examined using Pearson's correlation and multivariable analyses. Serum concentrations of small HDL particles measured using nuclear magnetic resonance spectroscopy (S-HDLPNMR) correlated negatively with the GAP index in the discovery cohort of IPF subjects. The negative correlation of S-HDLPNMR with GAP index was confirmed in the validation cohort of IPF subjects. Higher levels of S-HDLPNMR were associated with lower odds of death or its competing outcome, lung transplantation (OR 0.9 for each 1-μmol·L-1 increase in S-HDLPNMR, p<0.05), at 1, 2 and 3 years from study entry in a combined cohort of all IPF subjects. Higher serum levels of S-HDLPNMR are negatively correlated with the GAP index, as well as with lower observed mortality or lung transplantation in IPF subjects. These findings support the hypothesis that S-HDLPNMR may modify mortality risk in patients with IPF.

High-latitude precipitation: Snowfall regimes at two distinct sites in Scandinavia

AbstractThe prevailing snowfall regimes at two Scandinavian sites, Haukeliseter, Norway and Kiruna, Sweden, are documented using ground-based in-situ and remote sensing methods. Micro Rain Radar (MRR) profiles indicate three distinct snowfall regimes occur at both sites: shallow, deep, and intermittent snowfall. The shallow snowfall regime produces the lowest mean snowfall rates and radar echo tops are confined below 1.5 km above ground level (AGL). Shallow snowfall occurs under areas of large scale subsidence with a moist boundary layer and dry air aloft. The atmospheric ridge coinciding with shallow snowfall is highly anomalous over Haukeliseter, but is more common in Kiruna where shallow snowfall was frequently observed. The shallow snowfall particle size distributions (PSDs) are broad with lower particle concentrations than other regimes, especially small particles. Deep snowfall events exhibit MRR profiles that extend above 2 km AGL, and tend to be associated with weak low pressure and high relative humidity throughout the troposphere. The PSDs in deep events are narrower with high concentrations of small particles. Increasing MRR reflectivity towards the surface suggests aggregation as a possible growth process during deep snowfall events. The heaviest mean snowfall rates are associated with intermittent events that are characterized by deep MRR profiles, but have variations in intensity and height. The intermittent regime is associated with anomalous, deep low pressure along the coast of Norway, and enhanced relative humidity at lower levels. The PSDs reveal high concentrations of small and large particles. The analysis reveals that there are unique characteristics of shallow, deep, and intermittent snowfall regimes that are common between the sites.

A Study of Creatinine Level among Patients with Dyslipidemia and Type 2 Diabetes Mellitus using Multilayer Perceptron and Multiple Linear Regression.

Background and Objective:Dyslipidemia is one of the most important risk factors for coronary heart disease with diabetes mellitus. Diabetic dyslipidemia is correlated with reduced concentrations of high-density lipoprotein cholesterol, elevated concentrations of plasma triglycerides, and increased concentrations of dense small particles of low-density lipoprotein cholesterol. Furthermore, dyslipidemia is one of the factors that accelerate renal failure in patients with nephropathy that is observed to be higher in these patients. This paper aims to propose the variable selection using the multilayer perceptron (MLP) neural network methodology before performing the multiple linear regression (MLR) modeling. Dataset consists of patient with Dyslipidemia, and Type 2 Diabetes Mellitus was selected to illustrate the design-build methodology. According to clinical expert's opinion and based on their assessment, these variables were chosen, which comprises the level of creatinine, urea, total cholesterol, uric acid, sodium, and HbA1c.Materials and Methods:At the first stage, all the selected variables will be a screen for their clinical important point of view, and it was found that creatinine has a significant relationship to the level of urea reading, a total of cholesterol reading, and the level of uric acid reading. By considering the level of significance, α = 0.05, these three variables are being selected and used for the input of the MLP model. Then, the MLR is being applied according to the best variable obtained through MLP process.Results:Through the testing/out-sample mean squared error (MSE), the performance of MLP was assessed. MSE is an indication of the distance from the actual findings from our estimates. The smallest MSE of the MLP shows the best variable selection combination in the model.Conclusion:In this research paper, we also provide the R syntax for MLP better illustration. The key factors associated with creatinine were urea, total cholesterol, and uric acid in patients with dyslipidemia and type 2 diabetes mellitus.

Dietary Strawberries Improve Cardiometabolic Risks in Adults With Obesity and Elevated Serum LDL-Cholesterol in a Randomized Controlled Crossover Trial

Abstract Objectives Dietary berries, such as strawberries are rich in bioactive compounds and have been shown to lower cardiometabolic risks. We examined the dose-response effects of two dietary achievable doses of strawberries on glycemic control and lipid profiles in adults. Methods In this 14-week randomized controlled crossover study, adults with obesity and elevated serum LDL-cholesterol were assigned to one of the three arms for four weeks separated by a one-week washout period: control powder, one serving strawberries (low dose: 13 g powder/day), and 2.5 servings strawberries (high dose: 32 g powder/day). Participants were instructed to follow their usual diet and lifestyle while refraining from consuming other berries and related products throughout the study. Blood samples and anthropometric measures were collected at baseline and at the end of each four-week phase of intervention. Results Thirty-three participants completed all three phases of the trial [(mean ± SD): Age: 53 ± 13 y; BMI: 33 ± 3.0 kg/m2). Outcome measures were analyzed using a mixed model analysis of variance with statistical significance set at P &amp;lt; 0.05. Findings revealed significant reduction in fasting insulin as well as homeostatic model of assessment of insulin resistance (HOMA-IR) following the high dose strawberries when compared to the low dose strawberry and control phases. Glucose and conventional lipid profiles did not differ among groups. Total and small LDL particle concentrations (nuclear magnetic resonance-determined) were significantly decreased in the high dose strawberry group compared to control and low dose group (P &amp;lt; 0.05). Conclusions These data suggest that consuming strawberries at two and half servings for four weeks significantly improves insulin resistance and LDL particle profiles in adults with features of the metabolic syndrome. Funding Sources Supported by the NIH grant U54GM104938 (Oklahoma Shared Clinical and Translational Resource), OUHSC and the California Strawberry Commission.

Effects of size polydispersity on segregation of spherical particles in rotating drum.

To get insight into the segregation process of a polydisperse granular materials flow, we numerically investigated the migration process of particles in a rotating drum operating in the rolling regime by means of the discrete element method. Particle migration is analyzed through the variation of the proportion of particles in different zones where the flow property is characterized. The proportion of particles in different zones of the drum shows to increase in the center of the flow radially and axially where a higher concentration of small particles is observed, while its decreases in other zones with a higher concentration of larger particles. Interestingly, we find that the migration process of particles leads to radial and axial segregation which is caused by a combination between the exerted fluctuation forces on particles and its surrounding pressure gradient.

The efficacy of an extraoral scavenging device on reducing aerosol particles\u2009\u2264\u20095\u2009\xb5m during dental aerosol-generating procedures: an exploratory pilot study in a university setting

Objective/aimTo identify small particle concentrations (eight categories: ≤0.1 µm × ≤5.0 µm) induced by aerosol-generating procedures (AGPs; high-speed tooth preparation, ultrasonic scaling; air polishing) under high-flow suction with a 16-mm intraoral cannula with and without an additional mobile extraoral scavenger (EOS) device during student training.Materials and methodsTwenty tests were performed (16.94 m2 room without ventilation with constant temperature (26.7 (1.1) °C and humidity (56.53 (4.20)%)). Data were collected 2 min before, 2 min during, and 6 min after AGPs. The EOS device and the air sampler for particle counting were placed 0.35 m from the open mouth of a manikin head. The particle number concentration (PN, counts/m3) was measured to calculate ΔPN (ΔPN = [post-PN] − [pre-PN]).ResultsMean ΔPN (SD) ranged between −8.65E+06 (2.86E+07) counts/m3 for 0.15 µm and 6.41E+04 (2.77E+05) counts/m3 for 1.0 µm particles. No significant differences were found among the AGP groups (p > 0.05) or between the AGP and control groups (p > 0.05). With an EOS device, lower ΔPN was detected for smaller particles by high-speed tooth preparation (0.1–0.3 µm; p < 0.001).DiscussionA greater reduction in the number of smaller particles generated by the EOS device was found for high-speed tooth preparation. Low ΔPN by all AGPs demonstrated the efficacy of high-flow suction.ConclusionsThe additional use of an EOS device should be carefully considered when performing treatments, such as high-speed tooth preparation, that generate particularly small particles when more people are present and all other protective options have been exhausted.

Aircraft Measurements of the Microphysical Properties of Stratiform Clouds with Embedded Convection

The presence of embedded convection in stratiform clouds strongly affects ice microphysical properties and precipitation formation. In situ aircraft measurements, including upward and downward spirals and horizontal penetrations, were performed within both embedded convective cells and stratiform regions of a mixed-phase stratiform cloud system on 22 May 2017. Supercooled liquid water measurements, particle size distributions, and particle habits in different cloud regions were discussed with the intent of characterizing the riming process and determining how particle size distributions vary from convective to stratiform regions. Significant amounts of supercooled liquid water, with maxima up to 0.6 g m−3, were observed between −3°C and −6°C in the embedded convective cells while the peak liquid water content was generally less than 0.1 g m−3 in the stratiform regions. There are two distinct differences in particle size distributions between convective and stratiform regions. One difference is the significant shift toward larger particles from upper −15°C to lower −10°C in the convective region, with the maximum particle dimensions increasing from less than 6000 μm to over 1 cm. The particles larger than 1 cm at −10°C are composed of dendrites and their aggregates. The other difference is the large concentrations of small particles (25–205 μm) at temperatures between −3°C and −5°C in the convective region, where rimed ice particles and needles coexist. Needle regions are observed from three of the five spirals, but only the cloud conditions within the convective region fit into the Hallett-Mossop criteria.

Bridging the gap between particle-scale forces and continuum modelling of size segregation: application to bedload transport

Abstract