Diameter Standard Deviation Research Articles

Mechanical, Compositional, and Structural Properties of the Post-natal Mouse Achilles Tendon

During post-natal development, tendons undergo a well orchestrated process whereby extensive structural and compositional changes occur in synchrony to produce a normal tissue. Conversely, during the repair response to injury, structural and compositional changes occur, but in this case, a mechanically inferior tendon is produced. As a result, the process of development has been postulated as a potential paradigm through which improved adult tissue healing may occur. In this study we measured the mechanical, compositional, and structural properties in the post-natal mouse Achilles tendon at 4, 7, 10, 14, 21, and 28 days old. Throughout post-natal development, the mechanical properties, collagen content, fibril diameter mean, and fibril diameter standard deviation increased. Biglycan expression decreased and decorin expression and fiber organization were unchanged. This study provides a new mouse model that can be used to quantitatively examine mechanical development, as well as compositional and structural changes and biological mechanisms, during post-natal tendon development. This model is advantageous due to the large number of genetically modified mice and commercially available assays that are not available in other animal models. A mouse model therefore allows future mechanistic studies to build on this work.

Estimation of (co)variance components and genetic parameters for growth and wool traits of Chinese superfine merino sheep with the use of a multi-trait animal model

The aim of the current study was to estimate genetic parameters for birth weight (BW), weaning weight (WW), weaning staple length (WSL), yearling liveweight (YLW), and greasy fleece weight (YGFW), staple length (YSL), mean fiber diameter (YFD), fiber diameter standard deviation (YFDSD) and fiber diameter variation (YFDCV) at first shearing, which are essential to design a selection breeding program for Chinese superfine merino sheep. Data was collected on progeny from eight birth years (2001–2008) in the Chinese superfine merino breeding flock maintained at Xinjiang Gongnaisi Fine Wool Sheep Breeding Farm, Xinjiang, China. (Co)Variance components and genetic parameters were estimated by average information restricted maximum likelihood (AIREML) with a multi-trait animal model, and primarily 6 single-trait models for each trait were used to determine the most appropriate model for multi-trait analyses with Akaike's Information Criterion (AIC). Estimates of direct heritability were 0.15 for BW, 0.27 for WSL, 0.16 for WW, 0.23 for YLW, 0.32 for YSL, 0.17 for YGFW, 0.22 for YFD, 0.02 for YFDSD and 0.09 for YFDCV. Maternal heritability estimates for BW and YGFW were 0.15 and 0.05, respectively. Direct genetic correlations among studied traits ranged from − 0.85 (YGFW–YFDCV) to 0.87 (WSL–YSL). Phenotypic and environmental correlation estimates were generally lower than those of genetic correlation. Low to moderate direct heritability estimates for growth at different age, fiber diameter, fleece weight and staple length imply that selection for these traits results in lower to moderate genetic gain. Our results herein lay a practical foundation for performing an optimal breeding program in Chinese superfine merino.

Characteristics of Fe-Cr-Al Alloy Nanopowders Prepared by Electrical Wire Explosion Process under Liquid Media

Fe-Cr-Al alloy nanopowders were successfully prepared by electrical wire explosion method in ethyl alcohol media. The formation of Fe-Cr-Al alloy nanopowder was monitored by X-ray diffraction. The alloy powders have spherical shape and nanometer size. The alloy powders prepared by the electrical wire explosion method have main crystal structures of bcc Fe-Cr alloy. The geometric mean diameter and geometric standard deviation of an alloy powder formed from a wire with diameter of 0.1 mm were 10.2 nm and 1.62, respectively. However, the geometric mean diameter and geometric standard deviation of an alloy powder formed from a wire with diameter of 0.2 mm were 15.4 nm and 1.66, respectively. These values indicate that the particle size of the alloy powders prepared by the EWE method was increased with wire diameter. Fe, Cr, and Al components are uniformly dispersed inside the powder.

Development and application of a model (ExDoM) for calculating the respiratory tract dose and retention of particles under variable exposure conditions

The ExDoM is a model for calculating the human exposure and the deposition, dose, clearance, and finally retention of aerosol particles in the respiratory tract at specific times during and after exposure, under variable exposure conditions. Specifically, the model incorporates an exposure module which allows the user to set variable or static exposure conditions (exposure concentration, physical exertion levels, and different environments) or in the case of the physical exertion levels and exposure environment to choose from a list of typical exposure scenarios (activity pattern, exposure environment, and physical exertion level). The exposure concentration can refer to total particulate matter (PM) concentration or chemically resolved particles of variant size distributions. The aerosol size parameters can be introduced to the model either directly as median aerodynamic diameter and geometric standard deviation or are estimated by the model from measurement data. The model treats monodisperse or polydisperse aerosol size distributions. The human respiratory tract (RT) model of the International Commission on Radiological protection (ICRP Publication 66) is utilized for the respiratory tract deposition calculations. The above together with the dose and clearance/retention modules can be used to study together exposure and dose of chemically resolved particles of variant size distributions. The ExDoM model implementation in order to study the exposure and dose of particles in the human RT is demonstrated at two locations. In particular, the dose and retention of particles to RT and the mass transferred to the gastrointestinal tract and blood capillaries are estimated for an adult Caucasian male exposed to PM10 at a coastal remote site in the eastern Mediterranean. In addition, the regional lung doses of specific chemical components of PM10 (inorganic ions and carbonaceous compounds) during realistic exposure conditions outdoors at a residential background area in Oslo, Norway, were assessed. The results from the two studies showed that the dose was enhanced for the carbonaceous fine fraction of particles in the alveolar region of the lung whereas the dose of crustal material dominated in the extrathoracic region.

Fugitive Dust Emission Source Profiles and Assessment of Selected Control Strategies for Particulate Matter at Gravel Processing Sites in Taiwan

Particles emitted from gravel processing sites are one contributor to worsening air quality in Taiwan. Major pollution sources at gravel processing sites include gravel and sand piles, unpaved roads, material crushers, and bare ground. This study analyzed fugitive dust emission characteristics at each pollution source using several types of particle samplers, including total suspended particulates (TSP), suspended particulate (PM10), fine suspended particulate (PM2.5), particulate sizer, and dust-fall collectors. Furthermore, silt content and moisture in the gravel were measured to develop particulate emission factors. The results showed that TSP (<100 µm) concentrations at the boundary of gravel sites ranged from 280 to 1290 µg/m3, which clearly exceeds the Taiwan hourly air quality standard of 500 µg/m3. Moreover, PM10 concentrations, ranging from 135 to 550 µg/m3, were also above the daily air quality standard of 125 µg/m3 and approximately 1.2 and 1.5 times the PM2.5 concentrations, ranging from 105 to 470 µg/m3. The size distribution analysis reveals that mass mean diameter and geometric standard deviation ranged from 3.2 to 5.7 µm and from 2.82 to 5.51, respectively. In this study, spraying surfactant was the most effective control strategy to abate windblown dust from unpaved roads, having a control efficiency of approximately 93%, which is significantly higher than using paved road strategies with a control efficiency of approximately 45%. For paved roads, wet suppression provided the best dust control efficiencies ranging from 50 to 83%. Re-vegetation of disturbed ground had dust control efficiencies ranging from 48 to 64%.

Phenotypic associations with fibre curvature standard deviation in cashmere

Cashmere fibre curvature (crimp) impacts on the softness and quality of cashmere textiles, the efficiency of cashmere processing and cashmere production. This study investigated the relationship between cashmere fibre curvature standard deviation (FCSD) and other fleece attributes, and how this relationship differs with animal and farm attributes, for 10 commercial cashmere flocks in Australia. Data was analysed using general linear model analysis. Nineteen parameters were recorded for 1168 goats. Following log transformation, the best model for FCSD included farm, goat age, mean fibre diameter, fibre curvature, fibre diameter standard deviation, cashmere yield, cashmere staple length and live weight and the interactions between these terms. The percentage variance accounted for was 82%. Mean fibre diameter and fibre curvature accounted for 55% of the variation in FCSD and farm accounted for 41% of the variation. Cumulatively mean fibre diameter, fibre curvature and farm accounted for 75% of the variation existing in FCSD. For the other terms, age added 2% and the remaining measurements a further 5% to variation accounted for by the best model. Environmental (farm-effects) on FCSD are large and may explain the difficulties cashmere growers experience when they evaluate cashmere goats. Increasing the fibre curvature of cashmere was associated with an increase in cashmere FCSD, but for some combinations of farm and MFD the increase in FCSD was ≈35°/mm while with other combinations the increase was ≈5°/mm as fibre curvature increased. At a given fibre curvature the response of FCSD to mean fibre diameter differed substantially between farms, from strong negative to strong positive. Increasing cashmere yield from 20 to 55% was associated with decline in FCSD. Increasing fibre diameter SD from 3 to 5 μm increased FCSD by 6°/mm, increasing staple length and live weight were associated with small declines in FCSD. There was strong evidence of an age effect that differed with farms, but there were few clear cut trends in FCSD with increasing age. The results suggest that farm based influences are affecting the point at which fibre keratinisation is completed and thus influencing the variation in FCSD. We conclude that, because the differences between farms in the relationship been fibre curvature standard deviation, mean fibre diameter and fibre curvature are great, it is unlikely that crimp rate and crimp definition will be good indicators of cashmere fineness across farms.

Evaluation of metered dose inhaler (MDI) formulations of ciclosporin

Our purpose was to evaluate metered dose inhaler (MDI) formulations of cyclosporin (cyclosporine) for aerodynamic properties, chemical stability and bioactivity. Ciclosporin formulations (0.1, 0.5 and 1.0% w/w) were prepared in hydrofluoroalkane (HFA) propellants (134a and 227) containing 3 and 6% ethanol. Aerodynamic properties of the MDI formulations were analysed using an eight-stage Andersen cascade impactor and respirable mass and non-respirable mass, mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were determined from the impaction profiles. The chemical stability of 0.1% ciclosporin in HFA 227 containing 3% ethanol formulation stored at room temperature and 40 degrees C was evaluated by HPLC at 0, 14, 30 and 90 days. The bioactivity of ciclosporin MDI formulations was evaluated by determining the ciclosporin-mediated inhibition of interleukin-2 (IL-2) release from human Jurkat cells stimulated with phorbol 12-myristate 13-acetate (PMA). As ethanol concentration increased from 3 to 6%, respirable mass decreased from 2.3 mg per five actuations to 0.04 mg per five actuations for HFA 227 formulations, and from 1.5 mg to 0.09 mg per five actuations for HFA 134a formulations. The MMAD for both HFA 134a and 227 formulations increased with an increase in ciclosporin concentration. HPLC analysis showed ciclosporin to be extremely stable in HFA 227 at room temperature and 40 degrees C. Stimulation of Jurkat cells with PMA released significant amounts of IL-2, which was inhibited by ciclosporin in a dose-dependent manner. This study shows the feasibility of developing chemically stable and bioactive HFA-based MDI formulations of ciclosporin.

Nanoparticle Transport and Coagulation in Bends of Circular Cross Section via a New Moment Method

Transport of nanoparticles and coagulation is simulated with the combination of CFD in a circular bend. The Taylor-expansion moment method (TEMOM) is employed to study dynamics of nanoparticles with Brownian motion, based on the flow field from numerical simulation. A fully developed flow pattern in the present simulation is compared with previous numerical results for validating the model and computational code. It is found that for the simulated particulate flow system, the particle mass concentration, number concentration, particle polydispersity, mean particle diameter and geometric standard deviation over cross-section increase with time. The distribution of particle mass concentration at different time is independent of the initial particle size. More particles are concentrated at outer edge of the bend. Coagulation plays more important role at initial stage than that in the subsequent period. The increase of Reynolds number and initial particle size leads to the increase of particle number concentration. The particle polydispersity, mean particle diameter and geometric standard deviation increase with decreasing Reynolds number and initial particle size.

Synthesis, Structure and Growth Mechanism of Size and Shape Tunable Au/Ag Bimetallic Nanoparticles

AbstractBy simply adding ascorbic acid in advance of AgNO3, the size and shape controllable Au/Ag bimetallic nanoparticles (NP) were prepared in the traditional Au growth solution free of seed at room temperature. The size distribution of NP is well uniform with ca. 10%–15% standard deviation in diameter. By changing CTAB concentration, the size and shape of NPs are tunable. After researching the surface‐enhanced Raman spectroscopy (SERS) behavior of the prepared NPs, an enhancement factor varied from 4.3×104 to 1.1×105 was obtained for the NP centered at ca. (64±8) nm. Electrochemical cyclic voltammetric results revealed that the so formed nanoparticles were Au riched Au/Ag bimetallic NP, and this formation might be due to the disproportionation reaction of Au+ prompted by Ag+ and the under potential deposition process of Ag+ on Au.

Development of Budesonide Microparticles Using Spray-Drying Technology for Pulmonary Administration: Design, Characterization, In Vitro Evaluation, and In Vivo Efficacy Study

The purpose of this research was to generate, characterize, and investigate the in vivo efficacy of budesonide (BUD) microparticles prepared by spray-drying technology with a potential application as carriers for pulmonary administration with sustained-release profile and improved respirable fraction. Microspheres and porous particles of chitosan (drug/chitosan, 1:2) were prepared by spray drying using optimized process parameters and were characterized for different physicochemical parameters. Mass median aerodynamic diameter and geometric standard deviation for conventional, microspheres, and porous particles formulations were 2.75, 4.60, and 4.30 microm and 2.56, 1.75, and 2.54, respectively. Pharmacokinetic study was performed in rats by intratracheal administration of either placebo or developed dry powder inhalation (DPI) formulation. Pharmacokinetic parameters were calculated (Ka, Ke, T(max), C(max), AUC, and Vd) and these results indicated that developed formulations extended half life compared to conventional formulation with onefold to fourfold improved local and systemic bioavailability. Estimates of relative bioavailability suggested that developed formulations have excellent lung deposition characteristics with extended T(1/2) from 9.4 to 14 h compared to conventional formulation. Anti-inflammatory activity of BUD and developed formulations was compared and found to be similar. Cytotoxicity was determined in A549 alveolar epithelial cell line and found to be not toxic. In vivo pulmonary deposition of developed conventional formulation was studied using gamma scintigraphy and results indicated potential in vitro-in vivo correlation in performance of conventional BUD DPI formulation. From the DPI formulation prepared with porous particles, the concentration of BUD increased fourfold in the lungs, indicating pulmonary targeting potential of developed formulations.

Estimate of confidence intervals for geometric mean diameter and geometric standard deviation of lognormal size distribution

Confidence of particle size distribution, which is the size distribution of sample particles selected from a large population with lognormal size distribution, has been studied theoretically. Theoretical equations were derived from the basic formulas commonly used in statistics to estimate confidence intervals for geometric mean diameter and geometric standard deviation. Computer simulation has provided size distribution of sample particles by random sampling in order to confirm the theoretical equations. For both geometric mean diameter and geometric standard deviation, the confidence intervals were calculated so that both values of population were placed approximately in the middle of the intervals. The tendencies for the intervals to decrease with an increase in sample particle number and/or significance level, and with a decrease in geometric standard deviation, were reasonable in statistics. The proposed theoretical equations should be useful for estimating confidence of lognormal size distribution.

Calibration of the Modified Electrical Low-Pressure Impactor (ELPI) for Use with Pressurized Pharmaceutical Aerosols

The modified Electrical Low Pressure Impactor (ELPI) is currently being used in several laboratories to determine inherent electrostatic charge of pharmaceutical aerosols as a function of their particle size. However, the ELPI appears to underestimate the aerodynamic particle size distributions (aPSDs) of pressurized metered dose inhalers (pMDIs), casting doubt upon the manufacturer's calibration. In the present study, four commercially available pMDIs with a range of aPSDs were used to recalibrate cutoff diameters (d50s) of the ELPI stages using a reference ACI. Particle size analyses were performed in a mensurated ACI and a calibrated modified ELPI (n = 5); stage coating was employed in both instruments. The ACI data were fitted to a lognormal cumulative distribution function by nonlinear regression analysis. Best estimates for mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) for each pMDI were obtained and used in combination with impaction results from the modified ELPI to determine new d50s for each of the ELPI stages by numerical methods. Ventolin HFA was employed to validate the new ELPI d50 values. The curve-fitting procedure produced excellent fits of the ACI data for all the calibration pMDIs, which were well modeled as mono-modal and lognormally distributed. The mean d50s obtained following recalibration of the modified ELPI were found to deviate increasingly from the manufacturer-supplied values as aerodynamic diameter decreased. Ventolin HFA's MMAD determined using the modified ELPI with the manufacturer-supplied d50s was 2.06 +/- 0.08 microm. The MMAD calculated using the recalibrated d50s was 2.63 +/- 0.09 microm, which was statistically indistinguishable (p = 0.0852) from that determined for Ventolin HFA using the ACI (2.73 +/- 0.09 microm). In the absence of a comprehensive recalibration of the ELPI using monodisperse aerosols, the mean d50s for stages 4-12 of ELPI reported offer a practical way of analyzing the aPSD of pharmaceutical aerosols based on the collection and chemical analysis of ELPI deposition data.

Superparamagnetic nanoparticles as targeted probes for diagnostic and therapeutic applications.

Superparamagnetic nanoparticles (NPs) have been attractive for medical diagnostics and therapeutics due to their unique magnetic properties and their ability to interact with various biomolecules of interest. The solution phase based chemical synthesis provides a near precise control on NP size, and monodisperse magnetic NPs with standard deviation in diameter of less than 10% are now routinely available. Upon controlled surface functionalization and coupling with fragments of DNA strands, proteins, peptides or antibodies, these NPs can be well-dispersed in biological solutions and used for drug delivery, magnetic separation, magnetic resonance imaging contrast enhancement and magnetic fluid hyperthermia. This Perspective reviews the common syntheses and controlled surface functionalization of monodisperse Fe(3)O(4)-based superparamagnetic NPs. It further outlines the exciting application potentials of these NPs in magnetic resonance imaging and drug delivery.

Funções de pedo-transferência para a curva de retenção da água no solo

Pedotransfer functions allow prediction of the soil hydraulic characteristics from basic soil data. In this study pedotransfer functions were developed in order to obtain three specific points of the soil water retention curve: field capacity, wilting point and maximum capacity, which were considered to be correspondent to the water held in soil against suctions of 0.25 kPa, 9.8 kPa and 1554 kPa. The basic properties of soil used were particle size distribution, organic content, bulk density, depth of the layer and the statistical variables geometric mean diameter and geometric standard deviation of the soil particles. The method for building the functions was multiple linear regression analysis with 304 measurements of soil layers from numerous soil families from different locals in Portugal. The adjusted coefficient of determination of the pedotransfer functions was higher than 0.84. The validation of pedotranfer functions was made with a regional, independent data set of 55 measurements, obtained in this study for a particular irrigation area in Alentejo. The correlation coefficient obtained between the values predicted with the pedotransfer functions and the measured ones, for water retained in the soil at 0.25 kPa, 9.8 kPa e 1554 kPa was, respectively, 0.90, 0.73 and 0.85 which were considered significant at the 0.1% probability level.

Modeling of Gravitational Wet Scrubbers with Electrostatic Enhancement

AbstractConventional gravitational wet scrubbers, which generally perform removal of fine particles with low efficiency, cannot meet new standards for pollution emissions. One way of improving the collection efficiency of fine particles is to impose additional electrostatic forces upon particles by means of particle‐charging, or droplet‐charging, or even opposite‐charging of particles and droplets. A Monte Carlo method for population balance modeling is presented to describe the particle removal processes of gravitational wet scrubbers with electrostatic enhancement, in such a way that the grade collection efficiency and particle size distribution are calculated quantitatively. Numerical results show that, the grade collection efficiency of submicron particles is only ca. 5 % in conventional wet scrubbers. However, it reaches ca. 25 % in particle‐charging wet scrubbers, ca. 70 % in droplet‐charging wet scrubbers, and even above 99 % in opposite‐charging wet scrubbers. Furthermore, population balance modeling is used to optimize the operational parameters of the droplet‐charging wet scrubbers by means of the quantitative comparison of the grade collection efficiency. It is found that the operational parameters that are beneficial to the high‐efficiency removal of fine particles are faster gas velocity, slower droplet velocity, larger liquid‐to‐gas flow ratio, larger charge‐to‐mass ratio of droplets, smaller geometric mean diameter and smaller geometric standard deviation of droplets.

Implications to fleece evaluation derived from sources of variation contributing to cashmere fibre curvature

Cashmere fibre curvature (crimp) has important impact on the softness and quality of cashmere textiles, the efficiency of cashmere processing and cashmere production. This work was aimed to quantify the magnitude and direction of factors affecting cashmere fibre curvature, with data collected from 11 Australian commercial cashmere farms, using general linear model analysis. Nineteen parameters were recorded for 1244 goats. Following log transformation the best model for fibre curvature included farm, age, clean washing yield, mean fibre diameter, cashmere yield, fibre diameter standard deviation, and live weight and the interactions between these terms. The percentage variance accounted for was 71.7%. Mean fibre diameter alone accounted for 39% of the variation in fibre curvature and farm accounted for 49% of the variation. Cumulatively mean fibre diameter and farm accounted for 66.6% of the variation existing in fibre curvature. For the other terms, age added 2.2% and the other fibre measurements a further 2.9% to variation accounted for by the best model. Results suggest that within a farm, using cashmere fibre crimp frequency to estimate mean fibre diameter has a correlation of 0.72—provided the trained observers perform as well as the calibrated laboratory equipment. On the other hand, however, results indicate fibre curvature not to be a reasonable indicator of mean fibre diameter differences across farms. Farm-effects on fibre curvature are large and may explain the difficulties cashmere growers experience when they visit other farms to visually evaluate cashmere goats prior to purchase. This work indicated that heavier goats are likely to produce cashmere with a lower fibre curvature. As this relationship did not differ between farms, it is reasonable to conclude that all goats exhibit this phenotypic response. Using cashmere fibre curvature (crimp frequency) as a tool for changing mean fibre diameter or selecting homogenous batches of fibre for sale will be reasonably effective within a farm, but is not a reasonable indicator and predictor of mean fibre diameter differences between farms.

Determinants of cashmere production: The contribution of fleece measurements and animal growth on farms

To identify fleece and animal growth characteristics that are associated with cashmere production, the magnitude and direction of factors affecting cashmere production using fleece and live body weight measurements available to the cashmere producer were modelled. Data was collected from 11 Australian commercial cashmere farms. Following log transformation of clean cashmere weight, the best general linear model for predicting clean cashmere weight included: farm, mean fibre diameter, fibre diameter standard deviation, cashmere fibre curvature and fibre curvature standard deviation, cashmere staple length, clean washing yield, live body weight, live body weight change, and interactions between these parameters. The best general linear model did not include variables for age and sex cohorts. The variance accounted for was 67.6%. The residual standard deviation was 0.115. A majority of the variation regarding clean cashmere production (58%) was related to farm, staple length and mean fibre diameter. To obtain an understanding of how the responses of clean cashmere weight to fleece and growth measurements varied with farm, regression coefficients in the general linear model were modelled as possibly correlated random effects, using REML mixed model analysis. On a typical farm, greater clean cashmere weight was associated with longer staple length, greater mean fibre diameter, greater fibre diameter standard deviation, greater fibre curvature, greater fibre curvature standard deviation and greater live body weight. Farms recorded responses varying from negative to positive for washing yield and live body weight change. It was concluded that fleece characteristics and animal growth (but not age and sex) are primary determinants of cashmere production. However, the way these characteristics affect cashmere production varies from farm to farm.

Estimating the number of droplets and drug particles emitted from MDIs.

The objective of this paper is to assess the number of drug particles or droplets contained in metered dose inhaler (MDI) aerosols. Equations were developed to estimate this. The number of drug particles was estimated to be as high as about 300 million for QVAR solution MDIs and as low as 670,000 for Beclovent MDIs. The number of particles in MDI aerosols was shown to be highly dependent on the mass median aerodynamic diameter (MMAD) and geometric standard deviation, and to a lesser extent the total mass of the aerosol. It was demonstrated that when the number of particles are calculated assuming that the aerosol is monodisperse and using the MMAD as the particle size, the number of particles are significantly underestimated. The number of droplets atomized from HFA-134a MDIs was estimated to range from about 220 million to about 1.1 billion droplets per actuation. For solution MDIs, each of the atomized droplets contains drug and thus the number of drug particles is the same as the number of atomized droplets. However, for suspension MDI formulations many of the droplets do not contain any micronized drug particles and the number of drug particles is much lower than the number of atomized droplets.

Comparison of Continuous Monitor (TEOM) and Gravimetric Sampler Particulate Matter Concentrations

Tapered element oscillating microbalance (TEOM) samplers may offer significant advantages to state air pollution regulatory agencies and air quality researchers in terms of reduced labor and data processing requirements through an automated particulate matter (PM) monitoring system. However, previous research has shown that TEOM samplers may not report accurate PM concentrations due to the operating characteristics of the automated system. This article presents the results of a multiyear study using collocated TEOM and gravimetric samplers configured to measure TSP concentrations from a Texas cattle feedlot. The objective of this work was to define the relationship between PM concentrations measured by TEOM and gravimetric samplers and characterize the influence of concentration intensity and particle size on that relationship. The results show that there was a significant positive linear relationship between the concentrations measured by the TEOM and gravimetric TSP samplers (p-values < 0.001). It was observed that in general, the TEOM samplers reported lower TSP concentrations than the collocated gravimetric TSP sampler. Further investigation into these results indicated that the difference in the concentration measured by the TEOM sampler versus the gravimetric TSP sampler (known as the TEOM measurement error) is correlated with the concentration measured by the gravimetric TSP sampler, but the nature of that relationship varies by location. However, linear relationships were observed between the measurement error of the TEOM samplers and the mass median diameter and geometric standard deviation of the collocated gravimetric TSP sample.

Measurement of local specific interfacial area in bubble columns via a non-isokinetic withdrawal method coupled to electro-optical detector

Precise measurement of gas–liquid interfacial surface area is essential to reactor design and operation. Mass transfer from the gas phase to the liquid phase is often a key feature that controls the overall process. Measurement of gas–liquid interfacial area is often made through a separate measurement of the gas holdup and bubble size with complex and/or sophisticated methods. In this work, an inexpensive method is presented for the simultaneous determination of both local gas holdup and bubble diameter. The method is based on the withdrawal of the air–liquid dispersion under non-isokinetic conditions and on bubble counting via a simple optical device. The method was calibrated in a bubble column with several withdrawal pressures using coalescing and non-coalescing media. During the same calibration experiment, gas holdup was also measured manometrically and individual bubble diameters were measured by a photographic method. With a vacuum pressure of 3 kPa, local interfacial area measured with the withdrawal method produced a relative error below 13%, compared to the manometric/photographic method. The method was then used to characterize local specific interfacial area in a bubble column under several operating conditions with coalescing and non-coalescing media. In coalescing media and with superficial gas velocities ( v g ) from 0.25 to 3.5 cm/s, the average interfacial area ranged from 17 to 197 m - 1 . With non-coalescing media the average interfacial area ranged from 40 to 560 m - 1 . Under the test condition it was observed that gas holdup is a parameter that has a greater distribution (standard deviation from 30% to 70%) than the volume-mean bubble diameter (standard deviation from 6% to 12%). It is shown that a model previously developed for characterizing gas holdup homogeneity is also suitable for characterizing interfacial area homogeneity.