Effect of crystal size distribution on thermoelectric performance for Lanthanum-doped strontium titanate bulk material

NASA Astrophysics Data System (ADS)

Zhang, Boyu; Wang, Jun; Yaer, Xinba; Huo, Zhenzhen; Wu, Yin; Li, Yan; Miao, Lei; Liu, Chengyan; Zou, Tao; Ma, Wen

2015-07-01

Effect of crystal size distribution on thermoelectric performance of Lanthanum-doped strontium titanate (La-SrTiO3) ceramics are investigated in this study. Thermoelectric performance measurement, coupled with microstructure studies, shows that the electrical conductivity strongly depends on the crystal size, potential barrier on the grain boundary and porosity. Meantime, because the average potential barriers height are increased along with the reduction of crystal size, the Seebeck coefficients are increased by energy filtering effect at the large number of grain boundaries. As a result, by controlling of crystal size distribution, ZT value of La-SrTiO3 is improved.

Resonance-induced multimodal body-size distributions in ecosystems

PubMed Central

Lampert, Adam; Tlusty, Tsvi

2013-01-01

The size of an organism reflects its metabolic rate, growth rate, mortality, and other important characteristics; therefore, the distribution of body size is a major determinant of ecosystem structure and function. Body-size distributions often are multimodal, with several peaks of abundant sizes, and previous studies suggest that this is the outcome of niche separation: species from distinct peaks avoid competition by consuming different resources, which results in selection of different sizes in each niche. However, this cannot explain many ecosystems with several peaks competing over the same niche. Here, we suggest an alternative, generic mechanism underlying multimodal size distributions, by showing that the size-dependent tradeoff between reproduction and resource utilization entails an inherent resonance that may induce multiple peaks, all competing over the same niche. Our theory is well fitted to empirical data in various ecosystems, in which both model and measurements show a multimodal, periodically peaked distribution at larger sizes, followed by a smooth tail at smaller sizes. Moreover, we show a universal pattern of size distributions, manifested in the collapse of data from ecosystems of different scales: phytoplankton in a lake, metazoans in a stream, and arthropods in forests. The demonstrated resonance mechanism is generic, suggesting that multimodal distributions of numerous ecological characters emerge from the interplay between local competition and global migration. PMID:23248320

Predictive modelling of grain-size distributions from marine electromagnetic profiling data using end-member analysis and a radial basis function network

NASA Astrophysics Data System (ADS)

Baasch, B.; Müller, H.; von Dobeneck, T.

2018-07-01

In this work, we present a new methodology to predict grain-size distributions from geophysical data. Specifically, electric conductivity and magnetic susceptibility of seafloor sediments recovered from electromagnetic profiling data are used to predict grain-size distributions along shelf-wide survey lines. Field data from the NW Iberian shelf are investigated and reveal a strong relation between the electromagnetic properties and grain-size distribution. The here presented workflow combines unsupervised and supervised machine-learning techniques. Non-negative matrix factorization is used to determine grain-size end-members from sediment surface samples. Four end-members were found, which well represent the variety of sediments in the study area. A radial basis function network modified for prediction of compositional data is then used to estimate the abundances of these end-members from the electromagnetic properties. The end-members together with their predicted abundances are finally back transformed to grain-size distributions. A minimum spatial variation constraint is implemented in the training of the network to avoid overfitting and to respect the spatial distribution of sediment patterns. The predicted models are tested via leave-one-out cross-validation revealing high prediction accuracy with coefficients of determination (R2) between 0.76 and 0.89. The predicted grain-size distributions represent the well-known sediment facies and patterns on the NW Iberian shelf and provide new insights into their distribution, transition and dynamics. This study suggests that electromagnetic benthic profiling in combination with machine learning techniques is a powerful tool to estimate grain-size distribution of marine sediments.

Predictive modelling of grain size distributions from marine electromagnetic profiling data using end-member analysis and a radial basis function network

NASA Astrophysics Data System (ADS)

Baasch, B.; M"uller, H.; von Dobeneck, T.

2018-04-01

In this work we present a new methodology to predict grain-size distributions from geophysical data. Specifically, electric conductivity and magnetic susceptibility of seafloor sediments recovered from electromagnetic profiling data are used to predict grain-size distributions along shelf-wide survey lines. Field data from the NW Iberian shelf are investigated and reveal a strong relation between the electromagnetic properties and grain-size distribution. The here presented workflow combines unsupervised and supervised machine learning techniques. Nonnegative matrix factorisation is used to determine grain-size end-members from sediment surface samples. Four end-members were found which well represent the variety of sediments in the study area. A radial-basis function network modified for prediction of compositional data is then used to estimate the abundances of these end-members from the electromagnetic properties. The end-members together with their predicted abundances are finally back transformed to grain-size distributions. A minimum spatial variation constraint is implemented in the training of the network to avoid overfitting and to respect the spatial distribution of sediment patterns. The predicted models are tested via leave-one-out cross-validation revealing high prediction accuracy with coefficients of determination (R2) between 0.76 and 0.89. The predicted grain-size distributions represent the well-known sediment facies and patterns on the NW Iberian shelf and provide new insights into their distribution, transition and dynamics. This study suggests that electromagnetic benthic profiling in combination with machine learning techniques is a powerful tool to estimate grain-size distribution of marine sediments.

Differentiating gold nanorod samples using particle size and shape distributions from transmission electron microscope images

NASA Astrophysics Data System (ADS)

Grulke, Eric A.; Wu, Xiaochun; Ji, Yinglu; Buhr, Egbert; Yamamoto, Kazuhiro; Song, Nam Woong; Stefaniak, Aleksandr B.; Schwegler-Berry, Diane; Burchett, Woodrow W.; Lambert, Joshua; Stromberg, Arnold J.

2018-04-01

Size and shape distributions of gold nanorod samples are critical to their physico-chemical properties, especially their longitudinal surface plasmon resonance. This interlaboratory comparison study developed methods for measuring and evaluating size and shape distributions for gold nanorod samples using transmission electron microscopy (TEM) images. The objective was to determine whether two different samples, which had different performance attributes in their application, were different with respect to their size and/or shape descriptor distributions. Touching particles in the captured images were identified using a ruggedness shape descriptor. Nanorods could be distinguished from nanocubes using an elongational shape descriptor. A non-parametric statistical test showed that cumulative distributions of an elongational shape descriptor, that is, the aspect ratio, were statistically different between the two samples for all laboratories. While the scale parameters of size and shape distributions were similar for both samples, the width parameters of size and shape distributions were statistically different. This protocol fulfills an important need for a standardized approach to measure gold nanorod size and shape distributions for applications in which quantitative measurements and comparisons are important. Furthermore, the validated protocol workflow can be automated, thus providing consistent and rapid measurements of nanorod size and shape distributions for researchers, regulatory agencies, and industry.

Random Distribution Pattern and Non-adaptivity of Genome Size in a Highly Variable Population of Festuca pallens

PubMed Central

Šmarda, Petr; Bureš, Petr; Horová, Lucie

2007-01-01

Background and Aims The spatial and statistical distribution of genome sizes and the adaptivity of genome size to some types of habitat, vegetation or microclimatic conditions were investigated in a tetraploid population of Festuca pallens. The population was previously documented to vary highly in genome size and is assumed as a model for the study of the initial stages of genome size differentiation. Methods Using DAPI flow cytometry, samples were measured repeatedly with diploid Festuca pallens as the internal standard. Altogether 172 plants from 57 plots (2·25 m2), distributed in contrasting habitats over the whole locality in South Moravia, Czech Republic, were sampled. The differences in DNA content were confirmed by the double peaks of simultaneously measured samples. Key Results At maximum, a 1·115-fold difference in genome size was observed. The statistical distribution of genome sizes was found to be continuous and best fits the extreme (Gumbel) distribution with rare occurrences of extremely large genomes (positive-skewed), as it is similar for the log-normal distribution of the whole Angiosperms. Even plants from the same plot frequently varied considerably in genome size and the spatial distribution of genome sizes was generally random and unautocorrelated (P > 0·05). The observed spatial pattern and the overall lack of correlations of genome size with recognized vegetation types or microclimatic conditions indicate the absence of ecological adaptivity of genome size in the studied population. Conclusions These experimental data on intraspecific genome size variability in Festuca pallens argue for the absence of natural selection and the selective non-significance of genome size in the initial stages of genome size differentiation, and corroborate the current hypothetical model of genome size evolution in Angiosperms (Bennetzen et al., 2005, Annals of Botany 95: 127–132). PMID:17565968

Size distributions of micro-bubbles generated by a pressurized dissolution method

NASA Astrophysics Data System (ADS)

Taya, C.; Maeda, Y.; Hosokawa, S.; Tomiyama, A.; Ito, Y.

2012-03-01

Size of micro-bubbles is widely distributed in the range of one to several hundreds micrometers and depends on generation methods, flow conditions and elapsed times after the bubble generation. Although a size distribution of micro-bubbles should be taken into account to improve accuracy in numerical simulations of flows with micro-bubbles, a variety of the size distribution makes it difficult to introduce the size distribution in the simulations. On the other hand, several models such as the Rosin-Rammler equation and the Nukiyama-Tanazawa equation have been proposed to represent the size distribution of particles or droplets. Applicability of these models to the size distribution of micro-bubbles has not been examined yet. In this study, we therefore measure size distribution of micro-bubbles generated by a pressurized dissolution method by using a phase Doppler anemometry (PDA), and investigate the applicability of the available models to the size distributions of micro-bubbles. Experimental apparatus consists of a pressurized tank in which air is dissolved in liquid under high pressure condition, a decompression nozzle in which micro-bubbles are generated due to pressure reduction, a rectangular duct and an upper tank. Experiments are conducted for several liquid volumetric fluxes in the decompression nozzle. Measurements are carried out at the downstream region of the decompression nozzle and in the upper tank. The experimental results indicate that (1) the Nukiyama-Tanasawa equation well represents the size distribution of micro-bubbles generated by the pressurized dissolution method, whereas the Rosin-Rammler equation fails in the representation, (2) the bubble size distribution of micro-bubbles can be evaluated by using the Nukiyama-Tanasawa equation without individual bubble diameters, when mean bubble diameter and skewness of the bubble distribution are given, and (3) an evaluation method of visibility based on the bubble size distribution and bubble number density is proposed, and the evaluated visibility agrees well with the visibility measured in the upper tank.

Long-Tailed Distributions in Biological Systems:. Revisit to Lognormals

NASA Astrophysics Data System (ADS)

Kobayashi, N.; Kohyama, K.; Moriyama, O.; Sasaki, Y.; Matsushita, M.; Matsushita, S.

2007-07-01

Long-tailed distributions in biological systems have been studied. First, we found that lognormal distributions show excellent fit with various data for the duration distribution of disability in aged people, irrespective of their severity and gender. The robust lognormal distribution of disability implies that the incidence of diseases can be completed by many independent subprocesses in succession. Next, we studied food fragmentation by human mastication. A lognormal distribution well fits to the entire region for masticated food fragments for a small number of chewing strokes. Furthermore, the tail of the fragment-size distribution changes from the lognormal distribution to a power-law one as the chewing stroke number increases. The good data fitting by the lognormal and power-law distribution implies that two functions of mastication, a sequential fragmentation with cascade and randomness and a lower threshold for fragment size, may affect the size distribution of masticated food fragments.

Implications of Atmospheric Test Fallout Data for Nuclear Winter.

NASA Astrophysics Data System (ADS)

Baker, George Harold, III

1987-09-01

Atmospheric test fallout data have been used to determine admissable dust particle size distributions for nuclear winter studies. The research was originally motivated by extreme differences noted in the magnitude and longevity of dust effects predicted by particle size distributions routinely used in fallout predictions versus those used for nuclear winter studies. Three different sets of historical data have been analyzed: (1) Stratospheric burden of Strontium -90 and Tungsten-185, 1954-1967 (92 contributing events); (2) Continental U.S. Strontium-90 fallout through 1958 (75 contributing events); (3) Local Fallout from selected Nevada tests (16 events). The contribution of dust to possible long term climate effects following a nuclear exchange depends strongly on the particle size distribution. The distribution affects both the atmospheric residence time and optical depth. One dimensional models of stratospheric/tropospheric fallout removal were developed and used to identify optimum particle distributions. Results indicate that particle distributions which properly predict bulk stratospheric activity transfer tend to be somewhat smaller than number size distributions used in initial nuclear winter studies. In addition, both ^{90}Sr and ^ {185}W fallout behavior is better predicted by the lognormal distribution function than the prevalent power law hybrid function. It is shown that the power law behavior of particle samples may well be an aberration of gravitational cloud stratification. Results support the possible existence of two independent particle size distributions in clouds generated by surface or near surface bursts. One distribution governs late time stratospheric fallout, the other governs early time fallout. A bimodal lognormal distribution is proposed to describe the cloud particle population. The distribution predicts higher initial sunlight attenuation and lower late time attenuation than the power law hybrid function used in initial nuclear winter studies.

Zipf's law and city size distribution: A survey of the literature and future research agenda

NASA Astrophysics Data System (ADS)

Arshad, Sidra; Hu, Shougeng; Ashraf, Badar Nadeem

2018-02-01

This study provides a systematic review of the existing literature on Zipf's law for city size distribution. Existing empirical evidence suggests that Zipf's law is not always observable even for the upper-tail cities of a territory. However, the controversy with empirical findings arises due to sample selection biases, methodological weaknesses and data limitations. The hypothesis of Zipf's law is more likely to be rejected for the entire city size distribution and, in such case, alternative distributions have been suggested. On the contrary, the hypothesis is more likely to be accepted if better empirical methods are employed and cities are properly defined. The debate is still far from to be conclusive. In addition, we identify four emerging areas in Zipf's law and city size distribution research including the size distribution of lower-tail cities, the size distribution of cities in sub-national regions, the alternative forms of Zipf's law, and the relationship between Zipf's law and the coherence property of the urban system.

Experimental study on pore structure and performance of sintered porous wick

NASA Astrophysics Data System (ADS)

He, Da; Wang, Shufan; Liu, Rutie; Wang, Zhubo; Xiong, Xiang; Zou, Jianpeng

2018-02-01

Porous wicks were prepared via powder metallurgy using NH4HCO3 powders as pore-forming agent. The pore-forming agent particle size was varied to control the pore structure and equivalent pore size distribution feature of porous wick. The effect of pore-forming agent particle size on the porosity, pore structures, equivalent pore size distribution and capillary pumping performance were investigated. Results show that with the particle size of pore-forming agent decrease, the green density and the volume shrinkage of the porous wicks gradually increase and the porosity reduces slightly. There are two types of pores inside the porous wick, large-sized prefabricated pores and small-sized gap pores. With the particle size of pore-forming agent decrease, the size of the prefabricated pores becomes smaller and the distribution tends to be uniform. Gap pores and prefabricated pores inside the wick can make up different types of pore channels. The equivalent pore size of wick is closely related to the structure of pore channels. Furthermore, the equivalent pore size distribution of wick shows an obvious double-peak feature when the pore-forming agent particle size is large. With the particle size of pore-forming agent decrease, the two peaks of equivalent pore size distribution approach gradually to each other, resulting in a single-peak feature. Porous wick with single-peak feature equivalent pore size distribution possesses the better capillary pumping performances.

Transient Properties of Probability Distribution for a Markov Process with Size-dependent Additive Noise

NASA Astrophysics Data System (ADS)

Yamada, Yuhei; Yamazaki, Yoshihiro

2018-04-01

This study considered a stochastic model for cluster growth in a Markov process with a cluster size dependent additive noise. According to this model, the probability distribution of the cluster size transiently becomes an exponential or a log-normal distribution depending on the initial condition of the growth. In this letter, a master equation is obtained for this model, and derivation of the distributions is discussed.

Characterizing temporal changes of agricultural particulate matter number concentrations

NASA Astrophysics Data System (ADS)

Docekal, G. P.; Mahmood, R.; Larkin, G. P.; Silva, P. J.

2017-12-01

It is widely accepted among literature that particulate matter (PM) are of detriment to human health and the environment as a whole. These effects can vary depending on the particle size. This study examines PM size distributions and number concentrations at a poultry house. Despite much literature on PM concentrations at agricultural facilities, few studies have looked at the size distribution of particles at such facilities from the nucleation up through the coarse mode. Two optical particle counters (OPCs) were placed, one inside of a chicken house, and one on the outside of an exhaust fan to determine particle size distributions. In addition, a scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) sampled poultry house particles to give sizing information from a full size range of 10 nm - 20 mm. The data collected show several different types of events where observed size distributions changed. While some of these are due to expected dust generation events producing coarse mode particles, others suggest particle nucleation and accumulation events at the smaller size ranges that also occurred. The data suggest that agricultural facilities have an impact one the presence of PM in the environment beyond just generation of coarse mode dust. Data for different types of size distribution changes observed will be discussed.

Particle size distributions by transmission electron microscopy: an interlaboratory comparison case study

PubMed Central

Rice, Stephen B; Chan, Christopher; Brown, Scott C; Eschbach, Peter; Han, Li; Ensor, David S; Stefaniak, Aleksandr B; Bonevich, John; Vladár, András E; Hight Walker, Angela R; Zheng, Jiwen; Starnes, Catherine; Stromberg, Arnold; Ye, Jia; Grulke, Eric A

2015-01-01

This paper reports an interlaboratory comparison that evaluated a protocol for measuring and analysing the particle size distribution of discrete, metallic, spheroidal nanoparticles using transmission electron microscopy (TEM). The study was focused on automated image capture and automated particle analysis. NIST RM8012 gold nanoparticles (30 nm nominal diameter) were measured for area-equivalent diameter distributions by eight laboratories. Statistical analysis was used to (1) assess the data quality without using size distribution reference models, (2) determine reference model parameters for different size distribution reference models and non-linear regression fitting methods and (3) assess the measurement uncertainty of a size distribution parameter by using its coefficient of variation. The interlaboratory area-equivalent diameter mean, 27.6 nm ± 2.4 nm (computed based on a normal distribution), was quite similar to the area-equivalent diameter, 27.6 nm, assigned to NIST RM8012. The lognormal reference model was the preferred choice for these particle size distributions as, for all laboratories, its parameters had lower relative standard errors (RSEs) than the other size distribution reference models tested (normal, Weibull and Rosin–Rammler–Bennett). The RSEs for the fitted standard deviations were two orders of magnitude higher than those for the fitted means, suggesting that most of the parameter estimate errors were associated with estimating the breadth of the distributions. The coefficients of variation for the interlaboratory statistics also confirmed the lognormal reference model as the preferred choice. From quasi-linear plots, the typical range for good fits between the model and cumulative number-based distributions was 1.9 fitted standard deviations less than the mean to 2.3 fitted standard deviations above the mean. Automated image capture, automated particle analysis and statistical evaluation of the data and fitting coefficients provide a framework for assessing nanoparticle size distributions using TEM for image acquisition. PMID:26361398

Particle size distribution properties in mixed-phase monsoon clouds from in situ measurements during CAIPEEX

NASA Astrophysics Data System (ADS)

Patade, Sachin; Prabha, T. V.; Axisa, D.; Gayatri, K.; Heymsfield, A.

2015-10-01

A comprehensive analysis of particle size distributions measured in situ with airborne instrumentation during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) is presented. In situ airborne observations in the developing stage of continental convective clouds during premonsoon (PRE), transition, and monsoon (MON) period at temperatures from 25 to -22°C are used in the study. The PRE clouds have narrow drop size and particle size distributions compared to monsoon clouds and showed less development of size spectra with decrease in temperature. Overall, the PRE cases had much lower values of particle number concentrations and ice water content compared to MON cases, indicating large differences in the ice initiation and growth processes between these cloud regimes. This study provided compelling evidence that in addition to dynamics, aerosol and moisture are important for modulating ice microphysical processes in PRE and MON clouds through impacts on cloud drop size distribution. Significant differences are observed in the relationship of the slope and intercept parameters of the fitted particle size distributions (PSDs) with temperature in PRE and MON clouds. The intercept values are higher in MON clouds than PRE for exponential distribution which can be attributed to higher cloud particle number concentrations and ice water content in MON clouds. The PRE clouds tend to have larger values of dispersion of gamma size distributions than MON clouds, signifying narrower spectra. The relationships between PSDs parameters are presented and compared with previous observations.

Body size distributions signal a regime shift in a lake ecosystem

USGS Publications Warehouse

Spanbauer, Trisha; Allen, Craig R.; Angeler, David G.; Eason, Tarsha; Fritz, Sherilyn C.; Garmestani, Ahjond S.; Nash, Kirsty L.; Stone, Jeffery R.; Stow, Craig A.; Sundstrom, Shana M.

2016-01-01

Communities of organisms, from mammals to microorganisms, have discontinuous distributions of body size. This pattern of size structuring is a conservative trait of community organization and is a product of processes that occur at multiple spatial and temporal scales. In this study, we assessed whether body size patterns serve as an indicator of a threshold between alternative regimes. Over the past 7000 years, the biological communities of Foy Lake (Montana, USA) have undergone a major regime shift owing to climate change. We used a palaeoecological record of diatom communities to estimate diatom sizes, and then analysed the discontinuous distribution of organism sizes over time. We used Bayesian classification and regression tree models to determine that all time intervals exhibited aggregations of sizes separated by gaps in the distribution and found a significant change in diatom body size distributions approximately 150 years before the identified ecosystem regime shift. We suggest that discontinuity analysis is a useful addition to the suite of tools for the detection of early warning signals of regime shifts.

Log-Normal Distribution of Cosmic Voids in Simulations and Mocks

NASA Astrophysics Data System (ADS)

Russell, E.; Pycke, J.-R.

2017-01-01

Following up on previous studies, we complete here a full analysis of the void size distributions of the Cosmic Void Catalog based on three different simulation and mock catalogs: dark matter (DM), haloes, and galaxies. Based on this analysis, we attempt to answer two questions: Is a three-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we find here that all void size distributions of these data samples satisfy the three-parameter log-normal distribution whether the environment is dominated by DM, haloes, or galaxies. In addition, the shape parameters of the three-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and between the variance of the void size distribution and the maximum tree depth, directly from the simulated data. In addition to this, we find that the percentage of voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central density reaches ≥3.84% in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius.

Particle size distribution of main-channel-bed sediments along the upper Mississippi River, USA

USGS Publications Warehouse

Remo, Jonathan; Heine, Ruben A.; Ickes, Brian

2016-01-01

In this study, we compared pre-lock-and-dam (ca. 1925) with a modern longitudinal survey of main-channel-bed sediments along a 740-km segment of the upper Mississippi River (UMR) between Davenport, IA, and Cairo, IL. This comparison was undertaken to gain a better understanding of how bed sediments are distributed longitudinally and to assess change since the completion of the UMR lock and dam navigation system and Missouri River dams (i.e., mid-twentieth century). The comparison of the historic and modern longitudinal bed sediment surveys showed similar bed sediment sizes and distributions along the study segment with the majority (> 90%) of bed sediment samples having a median diameter (D50) of fine to coarse sand. The fine tail (≤ D10) of the sediment size distributions was very fine to medium sand, and the coarse tail (≥ D90) of sediment-size distribution was coarse sand to gravel. Coarsest sediments in both surveys were found within or immediately downstream of bedrock-floored reaches. Statistical analysis revealed that the particle-size distributions between the survey samples were statistically identical, suggesting no overall difference in main-channel-bed sediment-size distribution between 1925 and present. This was a surprising result given the magnitude of river engineering undertaken along the study segment over the past ~ 90 years. The absence of substantial differences in main-channel-bed-sediment size suggests that flow competencies within the highly engineered navigation channel today are similar to conditions within the less-engineered historic channel.

Species distribution model transferability and model grain size - finer may not always be better.

PubMed

Manzoor, Syed Amir; Griffiths, Geoffrey; Lukac, Martin

2018-05-08

Species distribution models have been used to predict the distribution of invasive species for conservation planning. Understanding spatial transferability of niche predictions is critical to promote species-habitat conservation and forecasting areas vulnerable to invasion. Grain size of predictor variables is an important factor affecting the accuracy and transferability of species distribution models. Choice of grain size is often dependent on the type of predictor variables used and the selection of predictors sometimes rely on data availability. This study employed the MAXENT species distribution model to investigate the effect of the grain size on model transferability for an invasive plant species. We modelled the distribution of Rhododendron ponticum in Wales, U.K. and tested model performance and transferability by varying grain size (50 m, 300 m, and 1 km). MAXENT-based models are sensitive to grain size and selection of variables. We found that over-reliance on the commonly used bioclimatic variables may lead to less accurate models as it often compromises the finer grain size of biophysical variables which may be more important determinants of species distribution at small spatial scales. Model accuracy is likely to increase with decreasing grain size. However, successful model transferability may require optimization of model grain size.

Numerical modeling of the tensile strength of a biological granular aggregate: Effect of the particle size distribution

NASA Astrophysics Data System (ADS)

Heinze, Karsta; Frank, Xavier; Lullien-Pellerin, Valérie; George, Matthieu; Radjai, Farhang; Delenne, Jean-Yves

2017-06-01

Wheat grains can be considered as a natural cemented granular material. They are milled under high forces to produce food products such as flour. The major part of the grain is the so-called starchy endosperm. It contains stiff starch granules, which show a multi-modal size distribution, and a softer protein matrix that surrounds the granules. Experimental milling studies and numerical simulations are going hand in hand to better understand the fragmentation behavior of this biological material and to improve milling performance. We present a numerical study of the effect of granule size distribution on the strength of such a cemented granular material. Samples of bi-modal starch granule size distribution were created and submitted to uniaxial tension, using a peridynamics method. We show that, when compared to the effects of starch-protein interface adhesion and voids, the granule size distribution has a limited effect on the samples' yield stress.

Effects of composition of grains of debris flow on its impact force

NASA Astrophysics Data System (ADS)

Tang, jinbo; Hu, Kaiheng; Cui, Peng

2017-04-01

Debris flows compose of solid material with broad size distribution from fine sand to boulders. Impact force imposed by debris flows is a very important issue for protection engineering design and strongly influenced by their grain composition. However, this issue has not been studied in depth and the effects of grain composition not been considered in the calculation of the impact force. In this present study, the small-scale flume experiments with five kinds of compositions of grains for debris flow were carried out to study the effect of the composition of grains of debris flow on its impact force. The results show that the impact force of debris flow increases with the grain size, the hydrodynamic pressure of debris flow is calibrated based on the normalization parameter dmax/d50, in which dmax is the maximum size and d50 is the median size. Furthermore, a log-logistic statistic distribution could be used to describe the distribution of magnitude of impact force of debris flow, where the mean and the variance of the present distribution increase with grain size. This distribution proposed in the present study could be used to the reliability analysis of structures impacted by debris flow.

Habitat structure and body size distributions: Cross-ecosystem comparison for taxa with determinate and indeterminate growth

USGS Publications Warehouse

Nash, Kirsty L.; Allen, Craig R.; Barichievy, Chris; Nystrom, Magnus; Sundstrom, Shana M.; Graham, Nicholas A.J.

2014-01-01

Habitat structure across multiple spatial and temporal scales has been proposed as a key driver of body size distributions for associated communities. Thus, understanding the relationship between habitat and body size is fundamental to developing predictions regarding the influence of habitat change on animal communities. Much of the work assessing the relationship between habitat structure and body size distributions has focused on terrestrial taxa with determinate growth, and has primarily analysed discontinuities (gaps) in the distribution of species mean sizes (species size relationships or SSRs). The suitability of this approach for taxa with indeterminate growth has yet to be determined. We provide a cross-ecosystem comparison of bird (determinate growth) and fish (indeterminate growth) body mass distributions using four independent data sets. We evaluate three size distribution indices: SSRs, species size–density relationships (SSDRs) and individual size–density relationships (ISDRs), and two types of analysis: looking for either discontinuities or abundance patterns and multi-modality in the distributions. To assess the respective suitability of these three indices and two analytical approaches for understanding habitat–size relationships in different ecosystems, we compare their ability to differentiate bird or fish communities found within contrasting habitat conditions. All three indices of body size distribution are useful for examining the relationship between cross-scale patterns of habitat structure and size for species with determinate growth, such as birds. In contrast, for species with indeterminate growth such as fish, the relationship between habitat structure and body size may be masked when using mean summary metrics, and thus individual-level data (ISDRs) are more useful. Furthermore, ISDRs, which have traditionally been used to study aquatic systems, present a potentially useful common currency for comparing body size distributions across terrestrial and aquatic ecosystems.

Effects of the turnover rate on the size distribution of firms: An application of the kinetic exchange models

NASA Astrophysics Data System (ADS)

Chakrabarti, Anindya S.

2012-12-01

We address the issue of the distribution of firm size. To this end we propose a model of firms in a closed, conserved economy populated with zero-intelligence agents who continuously move from one firm to another. We then analyze the size distribution and related statistics obtained from the model. There are three well known statistical features obtained from the panel study of the firms i.e., the power law in size (in terms of income and/or employment), the Laplace distribution in the growth rates and the slowly declining standard deviation of the growth rates conditional on the firm size. First, we show that the model generalizes the usual kinetic exchange models with binary interaction to interactions between an arbitrary number of agents. When the number of interacting agents is in the order of the system itself, it is possible to decouple the model. We provide exact results on the distributions which are not known yet for binary interactions. Our model easily reproduces the power law for the size distribution of firms (Zipf’s law). The fluctuations in the growth rate falls with increasing size following a power law (though the exponent does not match with the data). However, the distribution of the difference of the firm size in this model has Laplace distribution whereas the real data suggests that the difference of the log of sizes has the same distribution.

Gas Bubble Migration and Trapping in Porous Media: Pore-Scale Simulation

NASA Astrophysics Data System (ADS)

Mahabadi, Nariman; Zheng, Xianglei; Yun, Tae Sup; van Paassen, Leon; Jang, Jaewon

2018-02-01

Gas bubbles can be naturally generated or intentionally introduced in sediments. Gas bubble migration and trapping affect the rate of gas emission into the atmosphere or modify the sediment properties such as hydraulic and mechanical properties. In this study, the migration and trapping of gas bubbles are simulated using the pore-network model extracted from the 3D X-ray image of in situ sediment. Two types of bubble size distribution (mono-sized and distributed-sized cases) are used in the simulation. The spatial and statistical bubble size distribution, residual gas saturation, and hydraulic conductivity reduction due to the bubble trapping are investigated. The results show that the bubble size distribution becomes wider during the gas bubble migration due to bubble coalescence for both mono-sized and distributed-sized cases. And the trapped bubble fraction and the residual gas saturation increase as the bubble size increases. The hydraulic conductivity is reduced as a result of the gas bubble trapping. The reduction in hydraulic conductivity is apparently observed as bubble size and the number of nucleation points increase.

Particle morphology characterization and manipulation in biomass slurries and the effect on rheological properties and enzymatic conversion.

PubMed

Dibble, Clare J; Shatova, Tatyana A; Jorgenson, Jennie L; Stickel, Jonathan J

2011-01-01

An improved understanding of how particle size distribution relates to enzymatic hydrolysis performance and rheological properties could enable enhanced biochemical conversion of lignocellulosic feedstocks. Particle size distribution can change as a result of either physical or chemical manipulation of a biomass sample. In this study, we employed image processing techniques to measure slurry particle size distribution and validated the results by showing that they are comparable to those from laser diffraction and sieving. Particle size and chemical changes of biomass slurries were manipulated independently and the resulting yield stress and enzymatic digestibility of slurries with different size distributions were measured. Interestingly, reducing particle size by mechanical means from about 1 mm to 100 μm did not reduce the yield stress of the slurries over a broad range of concentrations or increase the digestibility of the biomass over the range of size reduction studied here. This is in stark contrast to the increase in digestibility and decrease in yield stress when particle size is reduced by dilute-acid pretreatment over similar size ranges. Copyright © 2011 American Institute of Chemical Engineers (AIChE).

Colony size-frequency distribution of pocilloporid juvenile corals along a natural environmental gradient in the Red Sea.

PubMed

Lozano-Cortés, Diego F; Berumen, Michael L

2016-04-30

Coral colony size-frequency distributions can be used to assess population responses to local environmental conditions and disturbances. In this study, we surveyed juvenile pocilloporids, herbivorous fish densities, and algal cover in the central and southern Saudi Arabian Red Sea. We sampled nine reefs with different disturbance histories along a north-south natural gradient of physicochemical conditions (higher salinity and wider temperature fluctuations in the north, and higher turbidity and productivity in the south). Since coral populations with negatively skewed size-frequency distributions have been associated with unfavorable environmental conditions, we expected to find more negative distributions in the southern Red Sea, where corals are potentially experiencing suboptimal conditions. Although juvenile coral and parrotfish densities differed significantly between the two regions, mean colony size and size-frequency distributions did not. Results suggest that pocilloporid colony size-frequency distribution may not be an accurate indicator of differences in biological or oceanographic conditions in the Red Sea. Copyright © 2015 Elsevier Ltd. All rights reserved.

Variability of the occurrence frequency of solar flares as a function of peak hard X-ray rate

NASA Technical Reports Server (NTRS)

Bai, T.

1993-01-01

We study the occurrence frequency of solar flares as a function of the hard X-ray peak count rate, using observations of the Solar Maximum Mission. The size distributions are well represented by power-law distributions with negative indices. As a better alternative to the conventional method, we devise a maximum likelihood method of determining the power-law index of the size distribution. We find that the power-law index of the size distribution changes with time and with the phase of the 154-day periodicity. The size distribution is steeper during the maximum years of solar cycle 21 (1980 and 1981) than during the declining phase (1982-1984). The size distribution, however, is flatter during the maximum phase of the 154-day periodicity than during the minimum phase. The implications of these findings are discussed.

Analysis of field size distributions, LACIE test sites 5029, 5033, and 5039, Anhwei Province, People's Republic of China

NASA Technical Reports Server (NTRS)

Podwysocki, M. H.

1976-01-01

A study was made of the field size distributions for LACIE test sites 5029, 5033, and 5039, People's Republic of China. Field lengths and widths were measured from LANDSAT imagery, and field area was statistically modeled. Field size parameters have log-normal or Poisson frequency distributions. These were normalized to the Gaussian distribution and theoretical population curves were made. When compared to fields in other areas of the same country measured in the previous study, field lengths and widths in the three LACIE test sites were 2 to 3 times smaller and areas were smaller by an order of magnitude.

Mass and number size distributions of emitted particulates at five important operation units in a hazardous industrial waste incineration plant.

PubMed

Lin, Chi-Chi; Huang, Hsiao-Lin; Hsiao, Wen-Yuan

2016-01-01

Past studies indicated particulates generated by waste incineration contain various hazardous compounds. The aerosol characteristics are very important for particulate hazard control and workers' protection. This study explores the detailed characteristics of emitted particulates from each important operation unit in a rotary kiln-based hazardous industrial waste incineration plant. A dust size analyzer (Grimm 1.109) and a scanning mobility particle sizer (SMPS) were used to measure the aerosol mass concentration, mass size distribution, and number size distribution at five operation units (S1-S5) during periods of normal operation, furnace shutdown, and annual maintenance. The place with the highest measured PM10 concentration was located at the area of fly ash discharge from air pollution control equipment (S5) during the period of normal operation. Fine particles (PM2.5) constituted the majority of the emitted particles from the incineration plant. The mass size distributions (elucidated) made it clear that the size of aerosols caused by the increased particulate mass, resulting from work activities, were mostly greater than 1.5 μm. Whereas the number size distributions showed that the major diameters of particulates that caused the increase of particulate number concentrations, from work activities, were distributed in the sub micrometer range. The process of discharging fly ash from air pollution control equipment can significantly increase the emission of nanoparticles. The mass concentrations and size distributions of emitted particulates were different at each operation unit. This information is valuable for managers to take appropriate strategy to reduce the particulate emission and associated worker exposure.

Characterizing the size distribution of particles in urban stormwater by use of fixed-point sample-collection methods

USGS Publications Warehouse

Selbig, William R.; Bannerman, Roger T.

2011-01-01

The U.S Geological Survey, in cooperation with the Wisconsin Department of Natural Resources (WDNR) and in collaboration with the Root River Municipal Stormwater Permit Group monitored eight urban source areas representing six types of source areas in or near Madison, Wis. in an effort to improve characterization of particle-size distributions in urban stormwater by use of fixed-point sample collection methods. The types of source areas were parking lot, feeder street, collector street, arterial street, rooftop, and mixed use. This information can then be used by environmental managers and engineers when selecting the most appropriate control devices for the removal of solids from urban stormwater. Mixed-use and parking-lot study areas had the lowest median particle sizes (42 and 54 (u or mu)m, respectively), followed by the collector street study area (70 (u or mu)m). Both arterial street and institutional roof study areas had similar median particle sizes of approximately 95 (u or mu)m. Finally, the feeder street study area showed the largest median particle size of nearly 200 (u or mu)m. Median particle sizes measured as part of this study were somewhat comparable to those reported in previous studies from similar source areas. The majority of particle mass in four out of six source areas was silt and clay particles that are less than 32 (u or mu)m in size. Distributions of particles ranging from 500 (u or mu)m were highly variable both within and between source areas. Results of this study suggest substantial variability in data can inhibit the development of a single particle-size distribution that is representative of stormwater runoff generated from a single source area or land use. Continued development of improved sample collection methods, such as the depth-integrated sample arm, may reduce variability in particle-size distributions by mitigating the effect of sediment bias inherent with a fixed-point sampler.

Particle size distributions in chondritic meteorites: Evidence for pre-planetesimal histories

NASA Astrophysics Data System (ADS)

Simon, J. I.; Cuzzi, J. N.; McCain, K. A.; Cato, M. J.; Christoffersen, P. A.; Fisher, K. R.; Srinivasan, P.; Tait, A. W.; Olson, D. M.; Scargle, J. D.

2018-07-01

Magnesium-rich silicate chondrules and calcium-, aluminum-rich refractory inclusions (CAIs) are fundamental components of primitive chondritic meteorites. It has been suggested that concentration of these early-formed particles by nebular sorting processes may lead to accretion of planetesimals, the planetary bodies that represent the building blocks of the terrestrial planets. In this case, the size distributions of the particles may constrain the accretion process. Here we present new particle size distribution data for Northwest Africa 5717, a primitive ordinary chondrite (ungrouped 3.05) and the well-known carbonaceous chondrite Allende (CV3). Instead of the relatively narrow size distributions obtained in previous studies (Ebel et al., 2016; Friedrich et al., 2015; Paque and Cuzzi, 1997, and references therein), we observed broad size distributions for all particle types in both meteorites. Detailed microscopic image analysis of Allende shows differences in the size distributions of chondrule subtypes, but collectively these subpopulations comprise a composite "chondrule" size distribution that is similar to the broad size distribution found for CAIs. Also, we find accretionary 'dust' rims on only a subset (∼15-20%) of the chondrules contained in Allende, which indicates that subpopulations of chondrules experienced distinct histories prior to planetary accretion. For the rimmed subset, we find positive correlation between rim thickness and chondrule size. The remarkable similarity between the size distributions of various subgroups of particles, both with and without fine grained rims, implies a common size sorting process. Chondrite classification schemes, astrophysical disk models that predict a narrow chondrule size population and/or a common localized formation event, and conventional particle analysis methods must all be critically reevaluated. We support the idea that distinct "lithologies" in NWA 5717 are nebular aggregates of chondrules. If ≥cm-sized aggregates of chondrules can form it will have implications for planet formation and suggests the sticking stage is where the preferential size physics is operating.

Particle Size Distributions in Chondritic Meteorites: Evidence for Pre-Planetesimal Histories

NASA Technical Reports Server (NTRS)

Simon, J. I.; Cuzzi, J. N.; McCain, K. A.; Cato, M. J.; Christoffersen, P. A.; Fisher, K. R.; Srinivasan, P.; Tait, A. W.; Olson, D. M.; Scargle, J. D.

2018-01-01

Magnesium-rich silicate chondrules and calcium-, aluminum-rich refractory inclusions (CAIs) are fundamental components of primitive chondritic meteorites. It has been suggested that concentration of these early-formed particles by nebular sorting processes may lead to accretion of planetesimals, the planetary bodies that represent the building blocks of the terrestrial planets. In this case, the size distributions of the particles may constrain the accretion process. Here we present new particle size distribution data for Northwest Africa 5717, a primitive ordinary chondrite (ungrouped 3.05) and the well-known carbonaceous chondrite Allende (CV3). Instead of the relatively narrow size distributions obtained in previous studies (Ebel et al., 2016; Friedrich et al., 2015; Paque and Cuzzi, 1997, and references therein), we observed broad size distributions for all particle types in both meteorites. Detailed microscopic image analysis of Allende shows differences in the size distributions of chondrule subtypes, but collectively these subpopulations comprise a composite "chondrule" size distribution that is similar to the broad size distribution found for CAIs. Also, we find accretionary 'dust' rims on only a subset (approximately 15-20 percent) of the chondrules contained in Allende, which indicates that subpopulations of chondrules experienced distinct histories prior to planetary accretion. For the rimmed subset, we find positive correlation between rim thickness and chondrule size. The remarkable similarity between the size distributions of various subgroups of particles, both with and without fine grained rims, implies a common size sorting process. Chondrite classification schemes, astrophysical disk models that predict a narrow chondrule size population and/or a common localized formation event, and conventional particle analysis methods must all be critically reevaluated. We support the idea that distinct "lithologies" in NWA 5717 are nebular aggregates of chondrules. If greater than or equal to centimeter-sized aggregates of chondrules can form it will have implications for planet formation and suggests the sticking stage is where the preferential size physics is operating.

LOG-NORMAL DISTRIBUTION OF COSMIC VOIDS IN SIMULATIONS AND MOCKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, E.; Pycke, J.-R., E-mail: er111@nyu.edu, E-mail: jrp15@nyu.edu

2017-01-20

Following up on previous studies, we complete here a full analysis of the void size distributions of the Cosmic Void Catalog based on three different simulation and mock catalogs: dark matter (DM), haloes, and galaxies. Based on this analysis, we attempt to answer two questions: Is a three-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we find here that all void size distributions of thesemore » data samples satisfy the three-parameter log-normal distribution whether the environment is dominated by DM, haloes, or galaxies. In addition, the shape parameters of the three-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and between the variance of the void size distribution and the maximum tree depth, directly from the simulated data. In addition to this, we find that the percentage of voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central density reaches ≥3.84% in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius.« less

Dermally adhered soil: 2. Reconstruction of dry-sieve particle-size distributions from wet-sieve data.

PubMed

Choate, LaDonna M; Ranville, James F; Bunge, Annette L; Macalady, Donald L

2006-10-01

In the evaluation of soil particle-size effects on environmental processes, particle-size distributions are measured by either wet or dry sieving. Commonly, size distributions determined by wet and dry sieving differ because some particles disaggregate in water. Whereas the dry-sieve distributions are most relevant to the study of soil adherence to skin, soil can be recovered from skin only by washing with the potential for disaggregation whether or not it is subsequently wet or dry sieved. Thus, the possibility exists that wet-sieving measurements of the particle sizes that adhered to the skin could be skewed toward the smaller fractions. This paper provides a method by which dry-sieve particle-size distributions can be reconstructed from wet-sieve particle-size distributions for the same soil. The approach combines mass balances with a series of experiments in which wet sieving was applied to dry-sieve fractions from the original soil. Unless the soil moisture content is high (i.e., greater than or equal to the water content after equilibration with water-saturated air), only the soil particles of diameters less than about 63 microm adhere to the skin. Because of this, the adhering particle-size distribution calculated using the reconstruction method was not significantly different from the wet-sieving determinations.

Effects of grain size distribution on the packing fraction and shear strength of frictionless disk packings.

PubMed

Estrada, Nicolas

2016-12-01

Using discrete element methods, the effects of the grain size distribution on the density and the shear strength of frictionless disk packings are analyzed. Specifically, two recent findings on the relationship between the system's grain size distribution and its rheology are revisited, and their validity is tested across a broader range of distributions than what has been used in previous studies. First, the effects of the distribution on the solid fraction are explored. It is found that the distribution that produces the densest packing is not the uniform distribution by volume fractions as suggested in a recent publication. In fact, the maximal packing fraction is obtained when the grading curve follows a power law with an exponent close to 0.5 as suggested by Fuller and Thompson in 1907 and 1919 [Trans Am. Soc. Civ. Eng. 59, 1 (1907) and A Treatise on Concrete, Plain and Reinforced (1919), respectively] while studying mixtures of cement and stone aggregates. Second, the effects of the distribution on the shear strength are analyzed. It is confirmed that these systems exhibit a small shear strength, even if composed of frictionless particles as has been shown recently in several works. It is also found that this shear strength is independent of the grain size distribution. This counterintuitive result has previously been shown for the uniform distribution by volume fractions. In this paper, it is shown that this observation keeps true for different shapes of the grain size distribution.

Planetarium instructional efficacy: A research synthesis

NASA Astrophysics Data System (ADS)

Brazell, Bruce D.

The purpose of the current study was to explore the instructional effectiveness of the planetarium in astronomy education using meta-analysis. A review of the literature revealed 46 studies related to planetarium efficacy. However, only 19 of the studies satisfied selection criteria for inclusion in the meta-analysis. Selected studies were then subjected to coding procedures, which extracted information such as subject characteristics, experimental design, and outcome measures. From these data, 24 effect sizes were calculated in the area of student achievement and five effect sizes were determined in the area of student attitudes using reported statistical information. Mean effect sizes were calculated for both the achievement and the attitude distributions. Additionally, each effect size distribution was subjected to homogeneity analysis. The attitude distribution was found to be homogeneous with a mean effect size of -0.09, which was not significant, p = .2535. The achievement distribution was found to be heterogeneous with a statistically significant mean effect size of +0.28, p < .05. Since the achievement distribution was heterogeneous, the analog to the ANOVA procedure was employed to explore variability in this distribution in terms of the coded variables. The analog to the ANOVA procedure revealed that the variability introduced by the coded variables did not fully explain the variability in the achievement distribution beyond subject-level sampling error under a fixed effects model. Therefore, a random effects model analysis was performed which resulted in a mean effect size of +0.18, which was not significant, p = .2363. However, a large random effect variance component was determined indicating that the differences between studies were systematic and yet to be revealed. The findings of this meta-analysis showed that the planetarium has been an effective instructional tool in astronomy education in terms of student achievement. However, the meta-analysis revealed that the planetarium has not been a very effective tool for improving student attitudes towards astronomy.

Modelling study on the three-dimensional neutron depolarisation response of the evolving ferrite particle size distribution during the austenite-ferrite phase transformation in steels

NASA Astrophysics Data System (ADS)

Fang, H.; van der Zwaag, S.; van Dijk, N. H.

2018-07-01

The magnetic configuration of a ferromagnetic system with mono-disperse and poly-disperse distribution of magnetic particles with inter-particle interactions has been computed. The analysis is general in nature and applies to all systems containing magnetically interacting particles in a non-magnetic matrix, but has been applied to steel microstructures, consisting of a paramagnetic austenite phase and a ferromagnetic ferrite phase, as formed during the austenite-to-ferrite phase transformation in low-alloyed steels. The characteristics of the computational microstructures are linked to the correlation function and determinant of depolarisation matrix, which can be experimentally obtained in three-dimensional neutron depolarisation (3DND). By tuning the parameters in the model used to generate the microstructure, we studied the effect of the (magnetic) particle size distribution on the 3DND parameters. It is found that the magnetic particle size derived from 3DND data matches the microstructural grain size over a wide range of volume fractions and grain size distributions. A relationship between the correlation function and the relative width of the particle size distribution was proposed to accurately account for the width of the size distribution. This evaluation shows that 3DND experiments can provide unique in situ information on the austenite-to-ferrite phase transformation in steels.

Size distribution and growth rate of crystal nuclei near critical undercooling in small volumes

NASA Astrophysics Data System (ADS)

Kožíšek, Z.; Demo, P.

2017-11-01

Kinetic equations are numerically solved within standard nucleation model to determine the size distribution of nuclei in small volumes near critical undercooling. Critical undercooling, when first nuclei are detected within the system, depends on the droplet volume. The size distribution of nuclei reaches the stationary value after some time delay and decreases with nucleus size. Only a certain maximum size of nuclei is reached in small volumes near critical undercooling. As a model system, we selected recently studied nucleation in Ni droplet [J. Bokeloh et al., Phys. Rev. Let. 107 (2011) 145701] due to available experimental and simulation data. However, using these data for sample masses from 23 μg up to 63 mg (corresponding to experiments) leads to the size distribution of nuclei, when no critical nuclei in Ni droplet are formed (the number of critical nuclei < 1). If one takes into account the size dependence of the interfacial energy, the size distribution of nuclei increases to reasonable values. In lower volumes (V ≤ 10-9 m3) nucleus size reaches some maximum extreme size, which quickly increases with undercooling. Supercritical clusters continue their growth only if the number of critical nuclei is sufficiently high.

PARTICLE SIZE DISTRIBUTIONS FROM SELECT RESIDENCES PARTICIPATING IN THE NERL RTP PM PANEL STUDY

EPA Science Inventory

Particle Size Distributions from Select Residences Participating in the NERL RTP PM Panel Study. Alan Vette, Ronald Williams, and Michael Riediker, U.S. Environmental Protection Agency, National Exposure Research Laboratory, Research Triangle Park, NC 27711; Jonathan Thornburg...

Effects of dust size distribution on dust acoustic waves in two-dimensional unmagnetized dusty plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

He Guangjun; Duan Wenshan; Tian Duoxiang

2008-04-15

For unmagnetized dusty plasma with many different dust grain species containing both hot isothermal electrons and ions, both the linear dispersion relation and the Kadomtsev-Petviashvili equation for small, but finite amplitude dust acoustic waves are obtained. The linear dispersion relation is investigated numerically. Furthermore, the variations of amplitude, width, and propagation velocity of the nonlinear solitary wave with an arbitrary dust size distribution function are studied as well. Moreover, both the power law distribution and the Gaussian distribution are approximately simulated by using appropriate arbitrary dust size distribution functions.

Physicochemical Characterization of Capstone Depleted Uranium Aerosols II: Particle Size Distributions as a Function of Time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Yung-Sung; Kenoyer, Judson L.; Guilmette, Raymond A.

2009-03-01

The Capstone Depleted Uranium (DU) Aerosol Study, which generated and characterized aerosols containing depleted uranium from perforation of armored vehicles with large-caliber DU penetrators, incorporated a sampling protocol to evaluated particle size distributions. Aerosol particle size distribution is an important parameter that influences aerosol transport and deposition processes as well as the dosimetry of the inhaled particles. These aerosols were collected on cascade impactor substrates using a pre-established time sequence following the firing event to analyze the uranium concentration and particle size of the aerosols as a function of time. The impactor substrates were analyzed using beta spectrometry, and themore » derived uranium content of each served as input to the evaluation of particle size distributions. Activity median aerodynamic diameters (AMADs) of the particle size distributions were evaluated using unimodal and bimodal models. The particle size data from the impactor measurements was quite variable. Most size distributions measured in the test based on activity had bimodal size distributions with a small particle size mode in the range of between 0.2 and 1.2 um and a large size mode between 2 and 15 um. In general, the evolution of particle size over time showed an overall decrease of average particle size from AMADs of 5 to 10 um shortly after perforation to around 1 um at the end of the 2-hr sampling period. The AMADs generally decreased over time because of settling. Additionally, the median diameter of the larger size mode decreased with time. These results were used to estimate the dosimetry of inhaled DU particles.« less

Detailed mass size distributions of atmospheric aerosol species in the Negev desert, Israel, during ARACHNE-96

NASA Astrophysics Data System (ADS)

Maenhaut, Willy; Ptasinski, Jacek; Cafmeyer, Jan

1999-04-01

As part of the 1996 summer intensive of the Aerosol, RAdiation and CHemistry Experiment (ARACHNE-96), the mass size distribution of various airborne particulate elements was studied at a remote site in the Negev Desert, Israel. Aerosol collections were made with 8-stage PIXE International cascade impactors (PCIs) and 12-stage small deposit area low pressure impactors (SDIs) and the samples were analyzed by PIXE for about 20 elements. The mineral elements (Al, Si, Ca, Ti, Fe) exhibited a unimodal size distribution which peaked at about 6 μm, but the contribution of particles larger than 10 μm was clearly more pronounced during the day than during night. Sulphur and Br had a tendency to exhibit two modes in the submicrometer size range, with diameters at about 0.3 and 0.6 μm, respectively. The elements V and Ni, which are indicators of residual fuel burning, showed essentially one fine mode (at 0.3 μm) in addition to a coarse mode which represented the mineral dust contribution. Overall, good agreement was observed between the mass size distributions from the PCI and SDI devices. The PCI was superior to the SDI for studying the size distribution in the coarse size range, but the SDI was clearly superior for unravelling the various modes in the submicrometer size range.

Modeling of mineral dust in the atmosphere: Sources, transport, and optical thickness

NASA Technical Reports Server (NTRS)

Tegen, Ina; Fung, Inez

1994-01-01

A global three-dimensional model of the atmospheric mineral dust cycle is developed for the study of its impact on the radiative balance of the atmosphere. The model includes four size classes of minearl dust, whose source distributions are based on the distributions of vegetation, soil texture and soil moisture. Uplift and deposition are parameterized using analyzed winds and rainfall statistics that resolve high-frequency events. Dust transport in the atmosphere is simulated with the tracer transport model of the Goddard Institute for Space Studies. The simulated seasonal variations of dust concentrations show general reasonable agreement with the observed distributions, as do the size distributions at several observing sites. The discrepancies between the simulated and the observed dust concentrations point to regions of significant land surface modification. Monthly distribution of aerosol optical depths are calculated from the distribution of dust particle sizes. The maximum optical depth due to dust is 0.4-0.5 in the seasonal mean. The main uncertainties, about a factor of 3-5, in calculating optical thicknesses arise from the crude resolution of soil particle sizes, from insufficient constraint by the total dust loading in the atmosphere, and from our ignorance about adhesion, agglomeration, uplift, and size distributions of fine dust particles (less than 1 micrometer).

Analytic modeling of aerosol size distributions

NASA Technical Reports Server (NTRS)

Deepack, A.; Box, G. P.

1979-01-01

Mathematical functions commonly used for representing aerosol size distributions are studied parametrically. Methods for obtaining best fit estimates of the parameters are described. A catalog of graphical plots depicting the parametric behavior of the functions is presented along with procedures for obtaining analytical representations of size distribution data by visual matching of the data with one of the plots. Examples of fitting the same data with equal accuracy by more than one analytic model are also given.

Body size distributions signal a regime shift in a lake ...

EPA Pesticide Factsheets

Communities of organisms, from mammals to microorganisms, have discontinuous distributions of body size. This pattern of size structuring is a conservative trait of community organization and is a product of processes that occur at multiple spatial and temporal scales. In this study, we assessed whether body size patterns serve as an indicator of a threshold between alternative regimes. Over the past 7000 years, the biological communities of Foy Lake (Montana,USA) have undergone a major regime shift owing to climate change. We used a palaeoecological record of diatom communities to estimate diatom sizes, and then analysed the discontinuous distribution of organism sizes over time. We used Bayesian classification and regression tree models to determine that all time intervals exhibited aggregations of sizes separated by gaps in the distribution and found a significant change in diatom body size distributions approximately 150 years before the identified ecosystem regime shift. We suggest that discontinuity analysis is a useful addition to the suite of tools for the detection of early warning signals of regime shifts. Communities of organisms from mammals to microorganisms have discontinuous distributions of body size. This pattern of size structuring is a conservative trait of community organization and is a product of processes that occur at discrete spatial and temporal scales within ecosystems. Here, a paleoecological record of diatom community change is use

Specific Features in Measuring Particle Size Distributions in Highly Disperse Aerosol Systems

NASA Astrophysics Data System (ADS)

Zagaynov, V. A.; Vasyanovich, M. E.; Maksimenko, V. V.; Lushnikov, A. A.; Biryukov, Yu. G.; Agranovskii, I. E.

2018-06-01

The distribution of highly dispersed aerosols is studied. Particular attention is given to the diffusion dynamic approach, as it is the best way to determine particle size distribution. It shown that the problem can be divided into two steps: directly measuring particle penetration through diffusion batteries and solving the inverse problem (obtaining a size distribution from the measured penetrations). No reliable way of solving the so-called inverse problem is found, but it can be done by introducing a parametrized size distribution (i.e., a gamma distribution). The integral equation is therefore reduced to a system of nonlinear equations that can be solved by elementary mathematical means. Further development of the method requires an increase in sensitivity (i.e., measuring the dimensions of molecular clusters with radioactive sources, along with the activity of diffusion battery screens).

Rapid measurement of sub-micrometer aerosol size distribution using a fast integrated mobility spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yang; Pinterich, Tamara; Wang, Jian

We present rapid measurement of submicron particle size distributions enables the characterization of aerosols with fast changing properties, and is often necessary for measurements onboard mobile platforms (e.g., research aircraft). Aerosol mobility size distribution is commonly measured by a scanning mobility particle sizer (SMPS), which relies on voltage scanning or stepping to classify particles of different sizes, and may take up to several minutes to obtain a complete size spectrum of aerosol particles. The recently developed fast integrated mobility spectrometer (FIMS) with enhanced dynamic size range classifies and detects particles from 10 to ~600 nm simultaneously, allowing submicron aerosol mobilitymore » size distributions to be captured at a time resolution of 1 second. In this study, we present a detailed data inversion routine for deriving aerosol size distribution from FIMS measurements. The inversion routine takes into consideration the FIMS transfer function, particle penetration efficiency in the FIMS, and multiple charging of aerosols. The accuracy of the FIMS measurement is demonstrated by comparing parallel FIMS and SMPS measurements of stable aerosols with a wide range of size spectrum shapes, including ambient aerosols and aerosols classified by a differential mobility analyzer (DMA). The FIMS and SMPS-derived size distributions show excellent agreements for all aerosols tested. In addition, total number concentrations of ambient aerosols were integrated from 1 Hz FIMS size distributions, and compared with those directly measured by a condensation particle counter (CPC) operated in parallel. Finally, the integrated and measured total particle concentrations agree well within 5%.« less

Rapid measurement of sub-micrometer aerosol size distribution using a fast integrated mobility spectrometer

DOE PAGES

Wang, Yang; Pinterich, Tamara; Wang, Jian

2018-03-30

We present rapid measurement of submicron particle size distributions enables the characterization of aerosols with fast changing properties, and is often necessary for measurements onboard mobile platforms (e.g., research aircraft). Aerosol mobility size distribution is commonly measured by a scanning mobility particle sizer (SMPS), which relies on voltage scanning or stepping to classify particles of different sizes, and may take up to several minutes to obtain a complete size spectrum of aerosol particles. The recently developed fast integrated mobility spectrometer (FIMS) with enhanced dynamic size range classifies and detects particles from 10 to ~600 nm simultaneously, allowing submicron aerosol mobilitymore » size distributions to be captured at a time resolution of 1 second. In this study, we present a detailed data inversion routine for deriving aerosol size distribution from FIMS measurements. The inversion routine takes into consideration the FIMS transfer function, particle penetration efficiency in the FIMS, and multiple charging of aerosols. The accuracy of the FIMS measurement is demonstrated by comparing parallel FIMS and SMPS measurements of stable aerosols with a wide range of size spectrum shapes, including ambient aerosols and aerosols classified by a differential mobility analyzer (DMA). The FIMS and SMPS-derived size distributions show excellent agreements for all aerosols tested. In addition, total number concentrations of ambient aerosols were integrated from 1 Hz FIMS size distributions, and compared with those directly measured by a condensation particle counter (CPC) operated in parallel. Finally, the integrated and measured total particle concentrations agree well within 5%.« less

Effective Ice Particle Densities for Cold Anvil Cirrus

NASA Technical Reports Server (NTRS)

Heymsfield, Andrew J.; Schmitt, Carl G.; Bansemer, Aaron; Baumgardner, Darrel; Weinstock, Elliot M.; Smith, Jessica

2002-01-01

This study derives effective ice particle densities from data collected from the NASA WB-57F aircraft near the tops of anvils during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) in southern Florida in July 2002. The effective density, defined as the ice particle mass divided by the volume of an equivalent diameter liquid sphere, is obtained for particle populations and single sizes containing mixed particle habits using measurements of condensed water content and particle size distributions. The mean effective densities for populations decrease with increasing slopes of the gamma size distributions fitted to the size distributions. The population-mean densities range from near 0.91 g/cu m to 0.15 g/cu m. Effective densities for single sizes obey a power-law with an exponent of about -0.55, somewhat less steep than found from earlier studies. Our interpretations apply to samples where particle sizes are generally below 200-300 microns in maximum dimension because of probe limitations.

Random-growth urban model with geographical fitness

NASA Astrophysics Data System (ADS)

Kii, Masanobu; Akimoto, Keigo; Doi, Kenji

2012-12-01

This paper formulates a random-growth urban model with a notion of geographical fitness. Using techniques of complex-network theory, we study our system as a type of preferential-attachment model with fitness, and we analyze its macro behavior to clarify the properties of the city-size distributions it predicts. First, restricting the geographical fitness to take positive values and using a continuum approach, we show that the city-size distributions predicted by our model asymptotically approach Pareto distributions with coefficients greater than unity. Then, allowing the geographical fitness to take negative values, we perform local coefficient analysis to show that the predicted city-size distributions can deviate from Pareto distributions, as is often observed in actual city-size distributions. As a result, the model we propose can generate a generic class of city-size distributions, including but not limited to Pareto distributions. For applications to city-population projections, our simple model requires randomness only when new cities are created, not during their subsequent growth. This property leads to smooth trajectories of city population growth, in contrast to other models using Gibrat’s law. In addition, a discrete form of our dynamical equations can be used to estimate past city populations based on present-day data; this fact allows quantitative assessment of the performance of our model. Further study is needed to determine appropriate formulas for the geographical fitness.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.

2005-01-01

Cloud microphysics are inevitable affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds, Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effect of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, a detailed spectral-bin microphysical scheme was implemented into the the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral-bim microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e., pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e., 33 bins). Atmospheric aerosols are also described using number density size-distribution functions.

Regression modeling of particle size distributions in urban storm water: advancements through improved sample collection methods

USGS Publications Warehouse

Fienen, Michael N.; Selbig, William R.

2012-01-01

A new sample collection system was developed to improve the representation of sediment entrained in urban storm water by integrating water quality samples from the entire water column. The depth-integrated sampler arm (DISA) was able to mitigate sediment stratification bias in storm water, thereby improving the characterization of suspended-sediment concentration and particle size distribution at three independent study locations. Use of the DISA decreased variability, which improved statistical regression to predict particle size distribution using surrogate environmental parameters, such as precipitation depth and intensity. The performance of this statistical modeling technique was compared to results using traditional fixed-point sampling methods and was found to perform better. When environmental parameters can be used to predict particle size distributions, environmental managers have more options when characterizing concentrations, loads, and particle size distributions in urban runoff.

Particle size distribution of the radon progeny and ambient aerosols in the Underground Tourist Route "Liczyrzepa" Mine in Kowary Adit

NASA Astrophysics Data System (ADS)

Wołoszczuk, Katarzyna; Skubacz, Krystian

2018-01-01

Central Laboratory for Radiological Protection, in cooperation with Central Mining Institute performed measurements of radon concentration in air, potential alpha energy concentration (PAEC), particle size distribution of the radon progeny and ambient aerosols in the Underground Tourist-Educational Route "Liczyrzepa" Mine in Kowary Adit. A research study was developed to investigate the appropriate dose conversion factors for short-lived radon progeny. The particle size distribution of radon progeny was determined using Radon Progeny Particle Size Spectrometer (RPPSS). The device allows to receive the distribution of PAEC in the particle size range from 0.6 nm to 2494 nm, based on their activity measured on 8 stages composed of impaction plates or diffusion screens. The measurements of the ambient airborne particle size distribution were performed in the range from a few nanometres to about 20 micrometres using Aerodynamic Particle Sizer (APS) spectrometer and the Scanning Mobility Particle Sizer Spectrometer (SMPS).

Quantification of the evolution of firm size distributions due to mergers and acquisitions.

PubMed

Lera, Sandro Claudio; Sornette, Didier

2017-01-01

The distribution of firm sizes is known to be heavy tailed. In order to account for this stylized fact, previous economic models have focused mainly on growth through investments in a company's own operations (internal growth). Thereby, the impact of mergers and acquisitions (M&A) on the firm size (external growth) is often not taken into consideration, notwithstanding its potential large impact. In this article, we make a first step into accounting for M&A. Specifically, we describe the effect of mergers and acquisitions on the firm size distribution in terms of an integro-differential equation. This equation is subsequently solved both analytically and numerically for various initial conditions, which allows us to account for different observations of previous empirical studies. In particular, it rationalises shortcomings of past work by quantifying that mergers and acquisitions develop a significant influence on the firm size distribution only over time scales much longer than a few decades. This explains why M&A has apparently little impact on the firm size distributions in existing data sets. Our approach is very flexible and can be extended to account for other sources of external growth, thus contributing towards a holistic understanding of the distribution of firm sizes.

Inferred Lunar Boulder Distributions at Decimeter Scales

NASA Technical Reports Server (NTRS)

Baloga, S. M.; Glaze, L. S.; Spudis, P. D.

2012-01-01

Block size distributions of impact deposits on the Moon are diagnostic of the impact process and environmental effects, such as target lithology and weathering. Block size distributions are also important factors in trafficability, habitability, and possibly the identification of indigenous resources. Lunar block sizes have been investigated for many years for many purposes [e.g., 1-3]. An unresolved issue is the extent to which lunar block size distributions can be extrapolated to scales smaller than limits of resolution of direct measurement. This would seem to be a straightforward statistical application, but it is complicated by two issues. First, the cumulative size frequency distribution of observable boulders rolls over due to resolution limitations at the small end. Second, statistical regression provides the best fit only around the centroid of the data [4]. Confidence and prediction limits splay away from the best fit at the endpoints resulting in inferences in the boulder density at the CPR scale that can differ by many orders of magnitude [4]. These issues were originally investigated by Cintala and McBride [2] using Surveyor data. The objective of this study was to determine whether the measured block size distributions from Lunar Reconnaissance Orbiter Camera - Narrow Angle Camera (LROC-NAC) images (m-scale resolution) can be used to infer the block size distribution at length scales comparable to Mini-RF Circular Polarization Ratio (CPR) scales, nominally taken as 10 cm. This would set the stage for assessing correlations of inferred block size distributions with CPR returns [6].

Interpretations of family size distributions: The Datura example

NASA Astrophysics Data System (ADS)

Henych, Tomáš; Holsapple, Keith A.

2018-04-01

Young asteroid families are unique sources of information about fragmentation physics and the structure of their parent bodies, since their physical properties have not changed much since their birth. Families have different properties such as age, size, taxonomy, collision severity and others, and understanding the effect of those properties on our observations of the size-frequency distribution (SFD) of family fragments can give us important insights into the hypervelocity collision processes at scales we cannot achieve in our laboratories. Here we take as an example the very young Datura family, with a small 8-km parent body, and compare its size distribution to other families, with both large and small parent bodies, and created by both catastrophic and cratering formation events. We conclude that most likely explanation for the shallower size distribution compared to larger families is a more pronounced observational bias because of its small size. Its size distribution is perfectly normal when its parent body size is taken into account. We also discuss some other possibilities. In addition, we study another common feature: an offset or "bump" in the distribution occurring for a few of the larger elements. We hypothesize that it can be explained by a newly described regime of cratering, "spall cratering", which controls the majority of impact craters on the surface of small asteroids like Datura.

Sound absorption by suspensions of nonspherical particles: Measurements compared with predictions using various particle sizing techniques

NASA Astrophysics Data System (ADS)

Richards, Simon D.; Leighton, Timothy G.; Brown, Niven R.

2003-10-01

Knowledge of the particle size distribution is required in order to predict ultrasonic absorption in polydisperse particulate suspensions. This paper shows that the method used to measure the particle size distribution can lead to important differences in the predicted absorption. A reverberation technique developed for measuring ultrasonic absorption by suspended particles is used to measure the absorption in suspensions of nonspherical particles. Two types of particulates are studied: (i) kaolin (china clay) particles which are platelike in form; and (ii) calcium carbonate particles which are more granular. Results are compared to theoretical predictions of visco-inertial absorption by suspensions of spherical particles. The particle size distributions, which are required for these predictions, are measured by laser diffraction, gravitational sedimentation and centrifugal sedimentation, all of which assume spherical particles. For a given sample, each sizing technique yields a different size distribution, leading to differences in the predicted absorption. The particle size distributions obtained by gravitational and centrifugal sedimentation are reinterpreted to yield a representative size distribution of oblate spheroids, and predictions for absorption by these spheroids are compared with the measurements. Good agreement between theory and measurement for the flat kaolin particles is obtained, demonstrating that these particles can be adequately represented by oblate spheroids.

The Size Frequency Distribution of Small Main-Belt Asteroids

NASA Technical Reports Server (NTRS)

Burt, Brian J.; Trilling, David E.; Hines, Dean C.; Stapelfeldt, Karl R.; Rebull, Luisa M.; Fuentes, Cesar I.; Hulsebus, Alan

2012-01-01

The asteroid size distribution informs us about the formation and composition of the Solar System. We build on our previous work in which we harvest serendipitously observed data of the Taurus region and measure the brightness and size distributions of Main-belt asteroids. This is accomplished with the highly sensitive MIPS 24 micron channel. We expect to catalog 104 asteroids, giving us a statistically significant data set. Results from this investigation will allow us to characterize the total population of small, Main-belt asteroids. Here we will present new results on the completeness of our study; on the presence of size distribution variations with inclination and radial distance in the belt; and early result on other archival fields.

Microstructure characterization of 316L deformed at high strain rates using EBSD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yvell, K., E-mail: kyv@du.se

2016-12-15

Specimens from split Hopkinson pressure bar experiments, at strain rates between ~ 1000–9000 s{sup −1} at room temperature and 500 °C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations > 2° can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneousmore » and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain. - Highlights: •Only changes in strain, not strain rate, gave differences in the microstructure. •A bimodal lognormal size distribution was found to describe the size distribution. •Variation of the subgrain fraction sizes agrees with models for heterogeneous slip. •Variation of subgrain size with strain describes part of the stress strain curve.« less

Effects of Climate Change on Subterranean Termite Territory Size: A Simulation Study

PubMed Central

Lee, Sang-Hee; Chon, Tae-Soo

2011-01-01

In order to study how climate change affects the territory size of subterranean termites, a lattice model was used to simulate the foraging territory of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), and the minimized local rules that are based on empirical data from the development of termites' foraging territory was applied. A landscape was generated by randomly assigning values ranging from 0.0 to 1.0 to each lattice site, which represented the spatially distributed property of the landscape. At the beginning of the simulation run, N territory seeds - one for each founding pair, were randomly distributed on the lattice space. The territories grew during the summer and shrank during the winter. In the model, the effects of climate change were demonstrated by changes in two variables: the period of the summer season, T, and the percentage of the remaining termite cells, σ, after the shrinkage. The territory size distribution was investigated in the size descending order for the values of T (= 10, 15, ... , 50) and σ (= 10, 15, ... , 50) at a steady state after a sufficiently long time period. The distribution was separated into two regions: the larger-sized territories and the smaller-sized territories. The slope, m, of the distribution of territory size on a semi-log scale for the larger-sized territories was maximal with T (45 ≤ T ≤ 50) in the maximal range and with σ in the optimal range (30 ≤ σ ≤ 40), regardless of the value of N. The results suggest that the climate change can influence the termite territory size distribution under the proper balance of T and σ in combination. PMID:21870966

Dependence of Microlensing on Source Size and Lens Mass

NASA Astrophysics Data System (ADS)

Congdon, A. B.; Keeton, C. R.

2007-11-01

In gravitational lensed quasars, the magnification of an image depends on the configuration of stars in the lensing galaxy. We study the statistics of the magnification distribution for random star fields. The width of the distribution characterizes the amount by which the observed magnification is likely to differ from models in which the mass is smoothly distributed. We use numerical simulations to explore how the width of the magnification distribution depends on the mass function of stars, and on the size of the source quasar. We then propose a semi-analytic model to describe the distribution width for different source sizes and stellar mass functions.

Feasibility study of in-situ characterization of size distribution of air voids in concrete pavements.

DOT National Transportation Integrated Search

2013-06-01

This report concerns a feasibility study on the use of a non-destructive and non-invasive method to determine the size distribution of air voids in fresh concrete, which will be used for laying concrete pavement. A preliminary review of different tec...

A Computational Study of the Modification of Raindrop Size Distributions in Subcloud Downdrafts.

DTIC Science & Technology

1981-08-01

Schumann (1939) and Findeisen (1939). It is characterized by a raindrop distribution consisting of many small droplets and a few large drops; all large...rain by means of sequential rain drop size distributions. Quart. J. Roy. Meteor. Soc., 88, 301-314. Findeisen , W., 1939: Zur Frage der

A size-structured model of bacterial growth and reproduction.

PubMed

Ellermeyer, S F; Pilyugin, S S

2012-01-01

We consider a size-structured bacterial population model in which the rate of cell growth is both size- and time-dependent and the average per capita reproduction rate is specified as a model parameter. It is shown that the model admits classical solutions. The population-level and distribution-level behaviours of these solutions are then determined in terms of the model parameters. The distribution-level behaviour is found to be different from that found in similar models of bacterial population dynamics. Rather than convergence to a stable size distribution, we find that size distributions repeat in cycles. This phenomenon is observed in similar models only under special assumptions on the functional form of the size-dependent growth rate factor. Our main results are illustrated with examples, and we also provide an introductory study of the bacterial growth in a chemostat within the framework of our model.

Fragment size distribution in viscous bag breakup of a drop

NASA Astrophysics Data System (ADS)

Kulkarni, Varun; Bulusu, Kartik V.; Plesniak, Michael W.; Sojka, Paul E.

2015-11-01

In this study we examine the drop size distribution resulting from the fragmentation of a single drop in the presence of a continuous air jet. Specifically, we study the effect of Weber number, We, and Ohnesorge number, Oh on the disintegration process. The regime of breakup considered is observed between 12 <= We <= 16 for Oh <= 0.1. Experiments are conducted using phase Doppler anemometry. Both the number and volume fragment size probability distributions are plotted. The volume probability distribution revealed a bi-modal behavior with two distinct peaks: one corresponding to the rim fragments and the other to the bag fragments. This behavior was suppressed in the number probability distribution. Additionally, we employ an in-house particle detection code to isolate the rim fragment size distribution from the total probability distributions. Our experiments showed that the bag fragments are smaller in diameter and larger in number, while the rim fragments are larger in diameter and smaller in number. Furthermore, with increasing We for a given Ohwe observe a large number of small-diameter drops and small number of large-diameter drops. On the other hand, with increasing Oh for a fixed We the opposite is seen.

Characterizations of particle size distribution of the droplets exhaled by sneeze

PubMed Central

Han, Z. Y.; Weng, W. G.; Huang, Q. Y.

2013-01-01

This work focuses on the size distribution of sneeze droplets exhaled immediately at mouth. Twenty healthy subjects participated in the experiment and 44 sneezes were measured by using a laser particle size analyser. Two types of distributions are observed: unimodal and bimodal. For each sneeze, the droplets exhaled at different time in the sneeze duration have the same distribution characteristics with good time stability. The volume-based size distributions of sneeze droplets can be represented by a lognormal distribution function, and the relationship between the distribution parameters and the physiological characteristics of the subjects are studied by using linear regression analysis. The geometric mean of the droplet size of all the subjects is 360.1 µm for unimodal distribution and 74.4 µm for bimodal distribution with geometric standard deviations of 1.5 and 1.7, respectively. For the two peaks of the bimodal distribution, the geometric mean (the geometric standard deviation) is 386.2 µm (1.8) for peak 1 and 72.0 µm (1.5) for peak 2. The influences of the measurement method, the limitations of the instrument, the evaporation effects of the droplets, the differences of biological dynamic mechanism and characteristics between sneeze and other respiratory activities are also discussed. PMID:24026469

Comparing particle-size distributions in modern and ancient sand-bed rivers

NASA Astrophysics Data System (ADS)

Hajek, E. A.; Lynds, R. M.; Huzurbazar, S. V.

2011-12-01

Particle-size distributions yield valuable insight into processes controlling sediment supply, transport, and deposition in sedimentary systems. This is especially true in ancient deposits, where effects of changing boundary conditions and autogenic processes may be detected from deposited sediment. In order to improve interpretations in ancient deposits and constrain uncertainty associated with new methods for paleomorphodynamic reconstructions in ancient fluvial systems, we compare particle-size distributions in three active sand-bed rivers in central Nebraska (USA) to grain-size distributions from ancient sandy fluvial deposits. Within the modern rivers studied, particle-size distributions of active-layer, suspended-load, and slackwater deposits show consistent relationships despite some morphological and sediment-supply differences between the rivers. In particular, there is substantial and consistent overlap between bed-material and suspended-load distributions, and the coarsest material found in slackwater deposits is comparable to the coarse fraction of suspended-sediment samples. Proxy bed-load and slackwater-deposit samples from the Kayenta Formation (Lower Jurassic, Utah/Colorado, USA) show overlap similar to that seen in the modern rivers, suggesting that these deposits may be sampled for paleomorphodynamic reconstructions, including paleoslope estimation. We also compare grain-size distributions of channel, floodplain, and proximal-overbank deposits in the Willwood (Paleocene/Eocene, Bighorn Basin, Wyoming, USA), Wasatch (Paleocene/Eocene, Piceance Creek Basin, Colorado, USA), and Ferris (Cretaceous/Paleocene, Hanna Basin, Wyoming, USA) formations. Grain-size characteristics in these deposits reflect how suspended- and bed-load sediment is distributed across the floodplain during channel avulsion events. In order to constrain uncertainty inherent in such estimates, we evaluate uncertainty associated with sample collection, preparation, analytical particle-size analysis, and statistical characterization in both modern and ancient settings. We consider potential error contributions and evaluate the degree to which this uncertainty might be significant in modern sediment-transport studies and ancient paleomorphodynamic reconstructions.

Probing the stochastic property of endoreduplication in cell size determination of Arabidopsis thaliana leaf epidermal tissue

PubMed Central

2017-01-01

Cell size distribution is highly reproducible, whereas the size of individual cells often varies greatly within a tissue. This is obvious in a population of Arabidopsis thaliana leaf epidermal cells, which ranged from 1,000 to 10,000 μm2 in size. Endoreduplication is a specialized cell cycle in which nuclear genome size (ploidy) is doubled in the absence of cell division. Although epidermal cells require endoreduplication to enhance cellular expansion, the issue of whether this mechanism is sufficient for explaining cell size distribution remains unclear due to a lack of quantitative understanding linking the occurrence of endoreduplication with cell size diversity. Here, we addressed this question by quantitatively summarizing ploidy profile and cell size distribution using a simple theoretical framework. We first found that endoreduplication dynamics is a Poisson process through cellular maturation. This finding allowed us to construct a mathematical model to predict the time evolution of a ploidy profile with a single rate constant for endoreduplication occurrence in a given time. We reproduced experimentally measured ploidy profile in both wild-type leaf tissue and endoreduplication-related mutants with this analytical solution, further demonstrating the probabilistic property of endoreduplication. We next extended the mathematical model by incorporating the element that cell size is determined according to ploidy level to examine cell size distribution. This analysis revealed that cell size is exponentially enlarged 1.5 times every endoreduplication round. Because this theoretical simulation successfully recapitulated experimentally observed cell size distributions, we concluded that Poissonian endoreduplication dynamics and exponential size-boosting are the sources of the broad cell size distribution in epidermal tissue. More generally, this study contributes to a quantitative understanding whereby stochastic dynamics generate steady-state biological heterogeneity. PMID:28926847

Slip-Size Distribution and Self-Organized Criticality in Block-Spring Models with Quenched Randomness

NASA Astrophysics Data System (ADS)

Sakaguchi, Hidetsugu; Kadowaki, Shuntaro

2017-07-01

We study slowly pulling block-spring models in random media. Second-order phase transitions exist in a model pulled by a constant force in the case of velocity-strengthening friction. If external forces are slowly increased, nearly critical states are self-organized. Slips of various sizes occur, and the probability distributions of slip size roughly obey power laws. The exponent is close to that in the quenched Edwards-Wilkinson model. Furthermore, the slip-size distributions are investigated in cases of Coulomb friction, velocity-weakening friction, and two-dimensional block-spring models.

Spatial Distribution of Bed Particles in Natural Boulder-Bed Streams

NASA Astrophysics Data System (ADS)

Clancy, K. F.; Prestegaard, K. L.

2001-12-01

The Wolman pebble count is used to obtain the size distribution of bed particles in natural streams. Statistics such as median particle size (D50) are used in resistance calculations. Additional information such as bed particle heterogeneity may also be obtained from the particle distribution, which is used to predict sediment transport rates (Hey, 1979), (Ferguson, Prestegaard, Ashworth, 1989). Boulder-bed streams have an extreme range of particles in the particle size distribution ranging from sand size particles to particles larger than 0.5-m. A study of a natural boulder-bed reach demonstrated that the spatial distribution of the particles is a significant factor in predicting sediment transport and stream bed and bank stability. Further experiments were performed to test the limits of the spatial distribution's effect on sediment transport. Three stream reaches 40-m in length were selected with similar hydrologic characteristics and spatial distributions but varying average size particles. We used a grid 0.5 by 0.5-m and measured four particles within each grid cell. Digital photographs of the streambed were taken in each grid cell. The photographs were examined using image analysis software to obtain particle size and position of the largest particles (D84) within the reach's particle distribution. Cross section, topography and stream depth were surveyed. Velocity and velocity profiles were measured and recorded. With these data and additional surveys of bankfull floods, we tested the significance of the spatial distributions as average particle size decreases. The spatial distribution of streambed particles may provide information about stream valley formation, bank stability, sediment transport, and the growth rate of riparian vegetation.

Sampling the structure and chemical order in assemblies of ferromagnetic nanoparticles by nuclear magnetic resonance

PubMed Central

Liu, Yuefeng; Luo, Jingjie; Shin, Yooleemi; Moldovan, Simona; Ersen, Ovidiu; Hébraud, Anne; Schlatter, Guy; Pham-Huu, Cuong; Meny, Christian

2016-01-01

Assemblies of nanoparticles are studied in many research fields from physics to medicine. However, as it is often difficult to produce mono-dispersed particles, investigating the key parameters enhancing their efficiency is blurred by wide size distributions. Indeed, near-field methods analyse a part of the sample that might not be representative of the full size distribution and macroscopic methods give average information including all particle sizes. Here, we introduce temperature differential ferromagnetic nuclear resonance spectra that allow sampling the crystallographic structure, the chemical composition and the chemical order of non-interacting ferromagnetic nanoparticles for specific size ranges within their size distribution. The method is applied to cobalt nanoparticles for catalysis and allows extracting the size effect from the crystallographic structure effect on their catalytic activity. It also allows sampling of the chemical composition and chemical order within the size distribution of alloyed nanoparticles and can thus be useful in many research fields. PMID:27156575

Size distribution spectrum of noninertial particles in turbulence

NASA Astrophysics Data System (ADS)

Saito, Izumi; Gotoh, Toshiyuki; Watanabe, Takeshi

2018-05-01

Collision-coalescence growth of noninertial particles in three-dimensional homogeneous isotropic turbulence is studied. Smoluchowski's coagulation equation describes the evolution of the size distribution of particles in this system. By applying a methodology based on turbulence theory, the equation is shown to have a steady-state solution, which corresponds to the Kolmogorov-type power-law spectrum. Direct numerical simulations of turbulence and Lagrangian particles are conducted. The result shows that the size distribution in a statistically steady state agrees accurately with the theoretical prediction.

Description of Particle Size, Distribution, and Behavior of Talc Preparations Commercially Available Within the United States.

PubMed

Gilbert, Christopher R; Furman, Benjamin R; Feller-Kopman, David J; Haouzi, Philippe

2018-01-01

Widespread use of talc pleurodesis remains controversial for many providers concerned by adverse events such as respiratory failure, which are sometimes fatal. Particle talc size has been implicated in these adverse effects, mainly on the basis of animal studies utilizing large amounts of talc or in observational studies performed on different continents with different talc preparations and doses. Our aim was to determine the particle size and distribution of only the commercially available US-talc preparations and whether the fluid content can affect this distribution. Commercially available US talc was evaluated under scanning electron microscopy and dynamic light scattering (DLS). Distribution of talc particle size was obtained in saline and various protein-based solutions. Talc particle size by DLS was performed with commercially available Sterile Talc Powder and Sclerosol Intrapleural Aerosol. Sterile Talc Powder demonstrated a median diameter of 26.57 μm with a range of particle sizes from 0.399 μm to 100.237 μm. Sclerosol demonstrated a median diameter of 24.49 μm with a range of particle sizes from 0.224 μm to 100.237 μm. The exposure of talc to a protein rich environment (bovine serum albumin and human pleural fluid) led to the development of measureable, new, larger aggregated particle (>100 μm). Currently available US talc seems to have size characteristics similar to previous described "graded" talc preparations. The exposure of talc to a protein rich environment seems to modify the overall distribution of talc particle size when examined by DLS.

Bayesian inference on earthquake size distribution: a case study in Italy

NASA Astrophysics Data System (ADS)

Licia, Faenza; Carlo, Meletti; Laura, Sandri

2010-05-01

This paper is focused on the study of earthquake size statistical distribution by using Bayesian inference. The strategy consists in the definition of an a priori distribution based on instrumental seismicity, and modeled as a power law distribution. By using the observed historical data, the power law is then modified in order to obtain the posterior distribution. The aim of this paper is to define the earthquake size distribution using all the seismic database available (i.e., instrumental and historical catalogs) and a robust statistical technique. We apply this methodology to the Italian seismicity, dividing the territory in source zones as done for the seismic hazard assessment, taken here as a reference model. The results suggest that each area has its own peculiar trend: while the power law is able to capture the mean aspect of the earthquake size distribution, the posterior emphasizes different slopes in different areas. Our results are in general agreement with the ones used in the seismic hazard assessment in Italy. However, there are areas in which a flattening in the curve is shown, meaning a significant departure from the power law behavior and implying that there are some local aspects that a power law distribution is not able to capture.

Andean Condor (Vultur gryphus) in Ecuador: Geographic Distribution, Population Size and Extinction Risk.

PubMed

Naveda-Rodríguez, Adrián; Vargas, Félix Hernán; Kohn, Sebastián; Zapata-Ríos, Galo

2016-01-01

The Andean Condor (Vultur gryphus) in Ecuador is classified as Critically Endangered. Before 2015, standardized and systematic estimates of geographic distribution, population size and structure were not available for this species, hampering the assessment of its current status and hindering the design and implementation of effective conservation actions. In this study, we performed the first quantitative assessment of geographic distribution, population size and population viability of Andean Condor in Ecuador. We used a methodological approach that included an ecological niche model to study geographic distribution, a simultaneous survey of 70 roosting sites to estimate population size and a population viability analysis (PVA) for the next 100 years. Geographic distribution in the form of extent of occurrence was 49 725 km2. During a two-day census, 93 Andean Condors were recorded and a population of 94 to 102 individuals was estimated. In this population, adult-to-immature ratio was 1:0.5. In the modeled PVA scenarios, the probability of extinction, mean time to extinction and minimum population size varied from zero to 100%, 63 years and 193 individuals, respectively. Habitat loss is the greatest threat to the conservation of Andean Condor populations in Ecuador. Population size reduction in scenarios that included habitat loss began within the first 15 years of this threat. Population reinforcement had no effects on the recovery of Andean Condor populations given the current status of the species in Ecuador. The population size estimate presented in this study is the lower than those reported previously in other countries where the species occur. The inferences derived from the population viability analysis have implications for Condor management in Ecuador. This study highlights the need to redirect efforts from captive breeding and population reinforcement to habitat conservation.

Andean Condor (Vultur gryphus) in Ecuador: Geographic Distribution, Population Size and Extinction Risk

PubMed Central

Naveda-Rodríguez, Adrián; Vargas, Félix Hernán; Kohn, Sebastián; Zapata-Ríos, Galo

2016-01-01

The Andean Condor (Vultur gryphus) in Ecuador is classified as Critically Endangered. Before 2015, standardized and systematic estimates of geographic distribution, population size and structure were not available for this species, hampering the assessment of its current status and hindering the design and implementation of effective conservation actions. In this study, we performed the first quantitative assessment of geographic distribution, population size and population viability of Andean Condor in Ecuador. We used a methodological approach that included an ecological niche model to study geographic distribution, a simultaneous survey of 70 roosting sites to estimate population size and a population viability analysis (PVA) for the next 100 years. Geographic distribution in the form of extent of occurrence was 49 725 km2. During a two-day census, 93 Andean Condors were recorded and a population of 94 to 102 individuals was estimated. In this population, adult-to-immature ratio was 1:0.5. In the modeled PVA scenarios, the probability of extinction, mean time to extinction and minimum population size varied from zero to 100%, 63 years and 193 individuals, respectively. Habitat loss is the greatest threat to the conservation of Andean Condor populations in Ecuador. Population size reduction in scenarios that included habitat loss began within the first 15 years of this threat. Population reinforcement had no effects on the recovery of Andean Condor populations given the current status of the species in Ecuador. The population size estimate presented in this study is the lower than those reported previously in other countries where the species occur. The inferences derived from the population viability analysis have implications for Condor management in Ecuador. This study highlights the need to redirect efforts from captive breeding and population reinforcement to habitat conservation. PMID:26986004

A demographic study of the exponential distribution applied to uneven-aged forests

Treesearch

Jeffrey H. Gove

2016-01-01

A demographic approach based on a size-structured version of the McKendrick-Von Foerster equation is used to demonstrate a theoretical link between the population size distribution and the underlying vital rates (recruitment, mortality and diameter growth) for the population of individuals whose diameter distribution is negative exponential. This model supports the...

Recovering 3D particle size distributions from 2D sections

NASA Astrophysics Data System (ADS)

Cuzzi, Jeffrey N.; Olson, Daniel M.

2017-03-01

We discuss different ways to convert observed, apparent particle size distributions from 2D sections (thin sections, SEM maps on planar surfaces, etc.) into true 3D particle size distributions. We give a simple, flexible, and practical method to do this; show which of these techniques gives the most faithful conversions; and provide (online) short computer codes to calculate both 2D-3D recoveries and simulations of 2D observations by random sectioning. The most important systematic bias of 2D sectioning, from the standpoint of most chondrite studies, is an overestimate of the abundance of the larger particles. We show that fairly good recoveries can be achieved from observed size distributions containing 100-300 individual measurements of apparent particle diameter.

Quantification of the evolution of firm size distributions due to mergers and acquisitions

PubMed Central

Sornette, Didier

2017-01-01

The distribution of firm sizes is known to be heavy tailed. In order to account for this stylized fact, previous economic models have focused mainly on growth through investments in a company’s own operations (internal growth). Thereby, the impact of mergers and acquisitions (M&A) on the firm size (external growth) is often not taken into consideration, notwithstanding its potential large impact. In this article, we make a first step into accounting for M&A. Specifically, we describe the effect of mergers and acquisitions on the firm size distribution in terms of an integro-differential equation. This equation is subsequently solved both analytically and numerically for various initial conditions, which allows us to account for different observations of previous empirical studies. In particular, it rationalises shortcomings of past work by quantifying that mergers and acquisitions develop a significant influence on the firm size distribution only over time scales much longer than a few decades. This explains why M&A has apparently little impact on the firm size distributions in existing data sets. Our approach is very flexible and can be extended to account for other sources of external growth, thus contributing towards a holistic understanding of the distribution of firm sizes. PMID:28841683

Study the fragment size distribution in dynamic fragmentation of laser shock loding tin

NASA Astrophysics Data System (ADS)

He, Weihua; Xin, Jianting; Chu, Genbai; Shui, Min; Xi, Tao; Zhao, Yongqiang; Gu, Yuqiu

2017-06-01

Characterizing the distribution of fragment size produced from dynamic fragmentation process is very important for fundamental science like predicting material dymanic response performance and for a variety of engineering applications. However, only a few data about fragment mass or size have been obtained due to its great challenge in its dynamic measurement. This paper would focus on investigating the fragment size distribution from the dynamic fragmentation of laser shock-loaded metal. Material ejection of tin sample with wedge shape groove in the free surface is collected with soft recovery technique. Via fine post-shot analysis techniques including X-ray micro-tomography and the improved watershed method, it is found that fragments can be well detected. To characterize their size distributions, a random geometric statistics method based on Poisson mixtures was derived for dynamic heterogeneous fragmentation problem, which leads to a linear combinational exponential distribution. Finally we examined the size distribution of laser shock-loaded tin with the derived model, and provided comparisons with other state-of-art models. The resulting comparisons prove that our proposed model can provide more reasonable fitting result for laser shock-loaded metal.

Single-size thermometric measurements on a size distribution of neutral fullerenes.

PubMed

Cauchy, C; Bakker, J M; Huismans, Y; Rouzée, A; Redlich, B; van der Meer, A F G; Bordas, C; Vrakking, M J J; Lépine, F

2013-05-10

We present measurements of the velocity distribution of electrons emitted from mass-selected neutral fullerenes, performed at the intracavity free electron laser FELICE. We make use of mass-specific vibrational resonances in the infrared domain to selectively heat up one out of a distribution of several fullerene species. Efficient energy redistribution leads to decay via thermionic emission. Time-resolved electron kinetic energy distributions measured give information on the decay rate of the selected fullerene. This method is generally applicable to all neutral species that exhibit thermionic emission and provides a unique tool to study the stability of mass-selected neutral clusters and molecules that are only available as part of a size distribution.

Objective assessment of the effect of pupil size upon the power distribution of multifocal contact lenses.

PubMed

Papadatou, Eleni; Del Águila-Carrasco, Antonio J; Esteve-Taboada, José J; Madrid-Costa, David; Cerviño-Expósito, Alejandro

2017-01-01

To analytically assess the effect of pupil size upon the refractive power distributions of different designs of multifocal contact lenses. Two multifocal contact lenses of center-near design and one multifocal contact lens of center-distance design were used in this study. Their power profiles were measured using the NIMO TR1504 device (LAMBDA-X, Belgium). Based on their power profiles, the power distribution was assessed as a function of pupil size. For the high addition lenses, the resulting refractive power as a function of viewing distance (far, intermediate, and near) and pupil size was also analyzed. The power distribution of the lenses was affected by pupil size differently. One of the lenses showed a significant spread in refractive power distribution, from about -3 D to 0 D. Generally, the power distribution of the lenses expanded as the pupil diameter became greater. The surface of the lens dedicated for each distance varied substantially with the design of the lens. In an experimental basis, our results show how the lenses power distribution is affected by the pupil size and underlined the necessity of careful evaluation of the patient's visual needs and the optical properties of a multifocal contact lens for achieving the optimal visual outcome.

Hydroacoustic Evaluation of Juvenile Salmonid Passage and Distribution at Lookout Point Dam, 2010

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Fenton; Johnson, Gary E.; Royer, Ida M.

2011-07-01

This report presents the results of an evaluation of juvenile salmonid passage and distribution at Lookout Point Dam (LOP) on the Middle Fork Willamette River. The study was conducted by the Pacific Northwest National Laboratory for the U.S. Army Corps of Engineers, Portland District (USACE). The goal of the study was to provide fish passage and distribution data to support decisions on long-term measures to enhance downstream passage at LOP and others dams in USACE’s Willamette Valley Project in response to the listing of Upper Willamette River Spring Chinook salmon (Oncorhynchus tshawytscha) and Upper Willamette River steelhead (O. mykiss) asmore » threatened under the Endangered Species Act. During the year-long study period - February 1, 2010 to January 31, 2011the objectives of the hydroacoustic evaluation of fish passage and distribution at LOP were to: 1. Estimate passage rates, run timing, horizontal distribution, and diel distribution at turbine penstock intakes for smolt-size fish. 2. Estimate passage rates, run timing and diel distribution at turbine penstock intakes for small-size fish. 3. Estimate passage rates and run timing at the regulating outlets for smolt-size fish. 4. Estimate vertical distribution of smolt-size fish in the forebay near the upstream face of the dam. The fixed-location hydroacoustic technique was used to accomplish the objectives of this study. Transducers (420 kHz) were deployed in each penstock intake, above each RO entrance, and on the dam face; a total of nine transducers (2 single-beam and 7 split-beam) were used. We summarize the findings from the hydroacoustic evaluation of juvenile salmonid passage and distribution at LOP during February 2010 through January 2011 as follows. • Fish passage rates for smolt-size fish (> ~90 mm) were highest during December-January and lowest in mid-summer through early fall. • During the entire study period, an estimated total of 142,463 fish ± 4,444 (95% confidence interval) smolt-size fish passed through turbine penstock intakes. • Diel periodicity of smolt-size fish showing crepuscular peaks was evident in fish passage into turbine penstock intakes. • Run timing for small-size fish (~65-90 mm) peaked (702 fish) on December 18. Downstream passage of small-size juvenile fish was variable, occurring on two days in the spring, eight days in the summer, and at times throughout late fall and winter. A total of 7,017 ± 690 small-size fish passed through the turbine penstock intakes during the study period. • Relatively few fish passed into the ROs when they were open in summer (2 fish/d) and winter (8 fish/d). • Fish were surface-oriented with 62-80% above 10 m deep. The highest percentage of fish (30-60%) was in the 5-10 m depth bin. We draw the following conclusions from the study. • The non-obtrusive hydroacoustic data from this study are reliable because passage estimates and patterns were similar with those observed in the direct capture data from the tailrace screw trap and were consistent with distribution patterns observed in other studies of juvenile salmonid passage at dams. • Fish passage at LOP was apparently affected but not dominated by dam operations and reservoir elevation. • The surface-oriented vertical distribution of fish we observed supports development of surface passage or collector devices. In summary, the high-resolution spatially and temporally data reported herein provide detailed estimates of vertical, horizontal, diel, daily, and seasonal passage and distributions at LOP during March 2010 through January 2011. This information is applicable to management decisions on design and development of surface passage and collections devices to help restore Chinook salmon populations in the Middle Fork Willamette River watershed above Lookout Point Dam.« less

New Measurements of the Particle Size Distribution of Apollo 11 Lunar Soil 10084

NASA Technical Reports Server (NTRS)

McKay, D.S.; Cooper, B.L.; Riofrio, L.M.

2009-01-01

We have initiated a major new program to determine the grain size distribution of nearly all lunar soils collected in the Apollo program. Following the return of Apollo soil and core samples, a number of investigators including our own group performed grain size distribution studies and published the results [1-11]. Nearly all of these studies were done by sieving the samples, usually with a working fluid such as Freon(TradeMark) or water. We have measured the particle size distribution of lunar soil 10084,2005 in water, using a Microtrac(TradeMark) laser diffraction instrument. Details of our own sieving technique and protocol (also used in [11]). are given in [4]. While sieving usually produces accurate and reproducible results, it has disadvantages. It is very labor intensive and requires hours to days to perform properly. Even using automated sieve shaking devices, four or five days may be needed to sieve each sample, although multiple sieve stacks increases productivity. Second, sieving is subject to loss of grains through handling and weighing operations, and these losses are concentrated in the finest grain sizes. Loss from handling becomes a more acute problem when smaller amounts of material are used. While we were able to quantitatively sieve into 6 or 8 size fractions using starting soil masses as low as 50mg, attrition and handling problems limit the practicality of sieving smaller amounts. Third, sieving below 10 or 20microns is not practical because of the problems of grain loss, and smaller grains sticking to coarser grains. Sieving is completely impractical below about 5- 10microns. Consequently, sieving gives no information on the size distribution below approx.10 microns which includes the important submicrometer and nanoparticle size ranges. Finally, sieving creates a limited number of size bins and may therefore miss fine structure of the distribution which would be revealed by other methods that produce many smaller size bins.

Lognormal Behavior of the Size Distributions of Animation Characters

NASA Astrophysics Data System (ADS)

Yamamoto, Ken

This study investigates the statistical property of the character sizes of animation, superhero series, and video game. By using online databases of Pokémon (video game) and Power Rangers (superhero series), the height and weight distributions are constructed, and we find that the weight distributions of Pokémon and Zords (robots in Power Rangers) follow the lognormal distribution in common. For the theoretical mechanism of this lognormal behavior, the combination of the normal distribution and the Weber-Fechner law is proposed.

Asymmetric competition causes multimodal size distributions in spatially structured populations

PubMed Central

Velázquez, Jorge; Allen, Robert B.; Coomes, David A.; Eichhorn, Markus P.

2016-01-01

Plant sizes within populations often exhibit multimodal distributions, even when all individuals are the same age and have experienced identical conditions. To establish the causes of this, we created an individual-based model simulating the growth of trees in a spatially explicit framework, which was parametrized using data from a long-term study of forest stands in New Zealand. First, we demonstrate that asymmetric resource competition is a necessary condition for the formation of multimodal size distributions within cohorts. By contrast, the legacy of small-scale clustering during recruitment is transient and quickly overwhelmed by density-dependent mortality. Complex multi-layered size distributions are generated when established individuals are restricted in the spatial domain within which they can capture resources. The number of modes reveals the effective number of direct competitors, while the separation and spread of modes are influenced by distances among established individuals. Asymmetric competition within local neighbourhoods can therefore generate a range of complex size distributions within even-aged cohorts. PMID:26817778

Seasonal evolution of the Arctic marginal ice zone and its power-law obeying floe size distribution

NASA Astrophysics Data System (ADS)

Zhang, J.; Stern, H. L., III; Schweiger, A. J. B.; Steele, M.; Hwang, P. B.

2017-12-01

A thickness, floe size, and enthalpy distribution (TFED) sea ice model, implemented numerically into the Pan-arctic Ice-Ocean Modeling and Assimilation System (PIOMAS), is used to investigate the seasonal evolution of the Arctic marginal ice zone (MIZ) and its floe size distribution. The TFED sea ice model, by coupling the Zhang et al. [2015] sea ice floe size distribution (FSD) theory with the Thorndike et al. [1975] ice thickness distribution (ITD) theory, simulates 12-category FSD and ITD explicitly and jointly. A range of ice thickness and floe size observations were used for model calibration and validation. The model creates FSDs that generally obey a power law or upper truncated power law, as observed by satellites and aerial surveys. In this study, we will examine the role of ice fragmentation and lateral melting in altering FSDs in the Arctic MIZ. We will also investigate how changes in FSD impact the seasonal evolution of the MIZ by modifying the thermodynamic processes.

Nanoparticles and metrology: a comparison of methods for the determination of particle size distributions

NASA Astrophysics Data System (ADS)

Coleman, Victoria A.; Jämting, Åsa K.; Catchpoole, Heather J.; Roy, Maitreyee; Herrmann, Jan

2011-10-01

Nanoparticles and products incorporating nanoparticles are a growing branch of nanotechnology industry. They have found a broad market, including the cosmetic, health care and energy sectors. Accurate and representative determination of particle size distributions in such products is critical at all stages of the product lifecycle, extending from quality control at point of manufacture to environmental fate at the point of disposal. Determination of particle size distributions is non-trivial, and is complicated by the fact that different techniques measure different quantities, leading to differences in the measured size distributions. In this study we use both mono- and multi-modal dispersions of nanoparticle reference materials to compare and contrast traditional and novel methods for particle size distribution determination. The methods investigated include ensemble techniques such as dynamic light scattering (DLS) and differential centrifugal sedimentation (DCS), as well as single particle techniques such as transmission electron microscopy (TEM) and microchannel resonator (ultra high-resolution mass sensor).

Temperature dependence of the size distribution function of InAs quantum dots on GaAs(001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arciprete, F.; Fanfoni, M.; Patella, F.

2010-04-15

We present a detailed atomic-force-microscopy study of the effect of annealing on InAs/GaAs(001) quantum dots grown by molecular-beam epitaxy. Samples were grown at a low growth rate at 500 deg. C with an InAs coverage slightly greater than critical thickness and subsequently annealed at several temperatures. We find that immediately quenched samples exhibit a bimodal size distribution with a high density of small dots (<50 nm{sup 3}) while annealing at temperatures greater than 420 deg. C leads to a unimodal size distribution. This result indicates a coarsening process governing the evolution of the island size distribution function which is limitedmore » by the attachment-detachment of the adatoms at the island boundary. At higher temperatures one cannot ascribe a single rate-determining step for coarsening because of the increased role of adatom diffusion. However, for long annealing times at 500 deg. C the island size distribution is strongly affected by In desorption.« less

Permeability-Selectivity Analysis of Microfiltration and Ultrafiltration Membranes: Effect of Pore Size and Shape Distribution and Membrane Stretching.

PubMed

Siddiqui, Muhammad Usama; Arif, Abul Fazal Muhammad; Bashmal, Salem

2016-08-06

We present a modeling approach to determine the permeability-selectivity tradeoff for microfiltration and ultrafiltration membranes with a distribution of pore sizes and pore shapes. Using the formulated permeability-selectivity model, the effect of pore aspect ratio and pore size distribution on the permeability-selectivity tradeoff of the membrane is analyzed. A finite element model is developed to study the effect of membrane stretching on the distribution of pore sizes and shapes in the stretched membrane. The effect of membrane stretching on the permeability-selectivity tradeoff of membranes is also analyzed. The results show that increasing pore aspect ratio improves membrane performance while increasing the width of pore size distribution deteriorates the performance. It was also found that the effect of membrane stretching on the permeability-selectivity tradeoff is greatly affected by the uniformity of pore distribution in the membrane. Stretching showed a positive shift in the permeability-selectivity tradeoff curve of membranes with well-dispersed pores while in the case of pore clustering, a negative shift in the permeability-selectivity tradeoff curve was observed.

[Study of inversion and classification of particle size distribution under dependent model algorithm].

PubMed

Sun, Xiao-Gang; Tang, Hong; Yuan, Gui-Bin

2008-05-01

For the total light scattering particle sizing technique, an inversion and classification method was proposed with the dependent model algorithm. The measured particle system was inversed simultaneously by different particle distribution functions whose mathematic model was known in advance, and then classified according to the inversion errors. The simulation experiments illustrated that it is feasible to use the inversion errors to determine the particle size distribution. The particle size distribution function was obtained accurately at only three wavelengths in the visible light range with the genetic algorithm, and the inversion results were steady and reliable, which decreased the number of multi wavelengths to the greatest extent and increased the selectivity of light source. The single peak distribution inversion error was less than 5% and the bimodal distribution inversion error was less than 10% when 5% stochastic noise was put in the transmission extinction measurement values at two wavelengths. The running time of this method was less than 2 s. The method has advantages of simplicity, rapidity, and suitability for on-line particle size measurement.

Sample size determination for mediation analysis of longitudinal data.

PubMed

Pan, Haitao; Liu, Suyu; Miao, Danmin; Yuan, Ying

2018-03-27

Sample size planning for longitudinal data is crucial when designing mediation studies because sufficient statistical power is not only required in grant applications and peer-reviewed publications, but is essential to reliable research results. However, sample size determination is not straightforward for mediation analysis of longitudinal design. To facilitate planning the sample size for longitudinal mediation studies with a multilevel mediation model, this article provides the sample size required to achieve 80% power by simulations under various sizes of the mediation effect, within-subject correlations and numbers of repeated measures. The sample size calculation is based on three commonly used mediation tests: Sobel's method, distribution of product method and the bootstrap method. Among the three methods of testing the mediation effects, Sobel's method required the largest sample size to achieve 80% power. Bootstrapping and the distribution of the product method performed similarly and were more powerful than Sobel's method, as reflected by the relatively smaller sample sizes. For all three methods, the sample size required to achieve 80% power depended on the value of the ICC (i.e., within-subject correlation). A larger value of ICC typically required a larger sample size to achieve 80% power. Simulation results also illustrated the advantage of the longitudinal study design. The sample size tables for most encountered scenarios in practice have also been published for convenient use. Extensive simulations study showed that the distribution of the product method and bootstrapping method have superior performance to the Sobel's method, but the product method was recommended to use in practice in terms of less computation time load compared to the bootstrapping method. A R package has been developed for the product method of sample size determination in mediation longitudinal study design.

Effect of grading fingerling hybrid catfish (Channel Catfish X Blue Catfish) on growth, production, feed conversion, and foodfish size distribution.

USDA-ARS?s Scientific Manuscript database

Hybrid catfish production ponds often produce a wide size range of fish and payments to farmers may be reduced due to discounts for larger fish. This study was conducted to determine effect of grading hybrid catfish fingerlings on the size distribution of harvested foodfish. Three 0.25-acre ponds we...

Vertical distribution of the prokaryotic cell size in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

La Ferla, R.; Maimone, G.; Azzaro, M.; Conversano, F.; Brunet, C.; Cabral, A. S.; Paranhos, R.

2012-12-01

Distributions of prokaryotic cell size and morphology were studied in different areas of the Mediterranean Sea by using image analysis on samples collected from surface down to bathypelagic layers (max depth 4,900 m) in the Southern Tyrrhenian, Southern Adriatic and Eastern Mediterranean Seas. Distribution of cell size of prokaryotes in marine ecosystem is very often not considered, which makes our study first in the context of prokaryotic ecology. In the deep Mediterranean layers, an usually-not-considered form of carbon sequestration through prokaryotic cells has been highlighted, which is consistent with an increase in cell size with the depth of the water column. A wide range in prokaryotic cell volumes was observed (between 0.045 and 0.566 μm3). Increase in cell size with depth was opposed to cell abundance distribution. Our results from microscopic observations were confirmed by the increasing HNA/LNA ratio (HNA, cells with high nucleic acid content; LNA, cells with low nucleic acid content) along the water column. Implications of our results on the increasing cell size with depth are in the fact that the quantitative estimation of prokaryotic biomass changes along the water column and the amount of carbon sequestered in the deep biota is enhanced.

Effects of resource-dependent cannibalism on population size distribution and individual life history in a case-bearing caddisfly

PubMed Central

Okuda, Noboru

2018-01-01

Resource availability often determines the intensity of cannibalism, which has a considerable effect on population size distribution and individual life history. Larvae of the caddisfly Psilotreta kisoensis build portable cases from sedimentary sands and often display cannibalism. For this species, the availability of preferable case material is a critical factor that affects larval fitness, and material is locally variable depending on the underlying geology. In this study, we investigated how sand quality as a case material determines cannibalism frequency among larvae and, in turn, how the differential cannibalism frequency affects the body-size distribution and voltinism. Rearing experiments within a cohort revealed that a bimodal size distribution developed regardless of material quality. However, as the preferable material became abundant, the proportion of larger to smaller individuals increased. Consecutive experiments suggested that smaller larvae were more frequently cannibalized by larger ones and excluded from the population when preferable smooth material was abundant. This frequent cannibalism resulted in a bimodal size distribution with a significantly higher proportion of larger compared to smaller individuals. The size-dependent cannibalism was significantly suppressed when the larvae were raised in an environment with a scarcity of the preferable case material. This is probably because larvae cannot enjoy the benefit of rapid growth by cannibalism due to the difficulties in enlarging their case. At low cannibalism the growth of smaller individuals was stunted, and this was probably due to risk of cannibalism by larger individuals. This growth reduction in small individuals led to a bimodal size-distribution but with a lower proportion of larger to smaller individuals compared to at high cannibalism. A field study in two streams showed a similar size distribution of larvae as was found in the rearing experiment. The bimodal ratio has consequences for life history, since a size-bimodal population causes a cohort splitting: only larvae that were fully grown at 1 year had a univoltine life cycle, whereas larvae with a stunted growth continued their larval life for another year (semivoltine). This study suggests that availability of preferable case building material is an important factor that affects cannibalism, which in turn affects larval population size structure and cohort splitting. PMID:29466375

Effects of resource-dependent cannibalism on population size distribution and individual life history in a case-bearing caddisfly.

PubMed

Okano, Jun-Ichi; Okuda, Noboru

2018-01-01

Resource availability often determines the intensity of cannibalism, which has a considerable effect on population size distribution and individual life history. Larvae of the caddisfly Psilotreta kisoensis build portable cases from sedimentary sands and often display cannibalism. For this species, the availability of preferable case material is a critical factor that affects larval fitness, and material is locally variable depending on the underlying geology. In this study, we investigated how sand quality as a case material determines cannibalism frequency among larvae and, in turn, how the differential cannibalism frequency affects the body-size distribution and voltinism. Rearing experiments within a cohort revealed that a bimodal size distribution developed regardless of material quality. However, as the preferable material became abundant, the proportion of larger to smaller individuals increased. Consecutive experiments suggested that smaller larvae were more frequently cannibalized by larger ones and excluded from the population when preferable smooth material was abundant. This frequent cannibalism resulted in a bimodal size distribution with a significantly higher proportion of larger compared to smaller individuals. The size-dependent cannibalism was significantly suppressed when the larvae were raised in an environment with a scarcity of the preferable case material. This is probably because larvae cannot enjoy the benefit of rapid growth by cannibalism due to the difficulties in enlarging their case. At low cannibalism the growth of smaller individuals was stunted, and this was probably due to risk of cannibalism by larger individuals. This growth reduction in small individuals led to a bimodal size-distribution but with a lower proportion of larger to smaller individuals compared to at high cannibalism. A field study in two streams showed a similar size distribution of larvae as was found in the rearing experiment. The bimodal ratio has consequences for life history, since a size-bimodal population causes a cohort splitting: only larvae that were fully grown at 1 year had a univoltine life cycle, whereas larvae with a stunted growth continued their larval life for another year (semivoltine). This study suggests that availability of preferable case building material is an important factor that affects cannibalism, which in turn affects larval population size structure and cohort splitting.

Distribution of the two-sample t-test statistic following blinded sample size re-estimation.

PubMed

Lu, Kaifeng

2016-05-01

We consider the blinded sample size re-estimation based on the simple one-sample variance estimator at an interim analysis. We characterize the exact distribution of the standard two-sample t-test statistic at the final analysis. We describe a simulation algorithm for the evaluation of the probability of rejecting the null hypothesis at given treatment effect. We compare the blinded sample size re-estimation method with two unblinded methods with respect to the empirical type I error, the empirical power, and the empirical distribution of the standard deviation estimator and final sample size. We characterize the type I error inflation across the range of standardized non-inferiority margin for non-inferiority trials, and derive the adjusted significance level to ensure type I error control for given sample size of the internal pilot study. We show that the adjusted significance level increases as the sample size of the internal pilot study increases. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Particle size analysis of some water/oil/water multiple emulsions.

PubMed

Ursica, L; Tita, D; Palici, I; Tita, B; Vlaia, V

2005-04-29

Particle size analysis gives useful information about the structure and stability of multiple emulsions, which are important characteristics of these systems. It also enables the observation of the growth process of particles dispersed in multiple emulsions, accordingly, the evolution of their dimension in time. The size of multiple particles in the seven water/oil/water (W/O/W) emulsions was determined by measuring the particles size observed during the microscopic examination. In order to describe the distribution of the size of multiple particles, the value of two parameters that define the particle size was calculated: the arithmetical mean diameter and the median diameter. The results of the particle size analysis in the seven multiple emulsions W/O/W studied are presented as histograms of the distribution density immediately, 1 and 3 months after the preparation of each emulsion, as well as by establishing the mean and the median diameter of particles. The comparative study of the distribution histograms and of the mean and median diameters of W/O/W multiple particles indicates that the prepared emulsions are fine and very fine dispersions, stable, and presenting a growth of the abovementioned diameters during the study.

Statistical analyses support power law distributions found in neuronal avalanches.

PubMed

Klaus, Andreas; Yu, Shan; Plenz, Dietmar

2011-01-01

The size distribution of neuronal avalanches in cortical networks has been reported to follow a power law distribution with exponent close to -1.5, which is a reflection of long-range spatial correlations in spontaneous neuronal activity. However, identifying power law scaling in empirical data can be difficult and sometimes controversial. In the present study, we tested the power law hypothesis for neuronal avalanches by using more stringent statistical analyses. In particular, we performed the following steps: (i) analysis of finite-size scaling to identify scale-free dynamics in neuronal avalanches, (ii) model parameter estimation to determine the specific exponent of the power law, and (iii) comparison of the power law to alternative model distributions. Consistent with critical state dynamics, avalanche size distributions exhibited robust scaling behavior in which the maximum avalanche size was limited only by the spatial extent of sampling ("finite size" effect). This scale-free dynamics suggests the power law as a model for the distribution of avalanche sizes. Using both the Kolmogorov-Smirnov statistic and a maximum likelihood approach, we found the slope to be close to -1.5, which is in line with previous reports. Finally, the power law model for neuronal avalanches was compared to the exponential and to various heavy-tail distributions based on the Kolmogorov-Smirnov distance and by using a log-likelihood ratio test. Both the power law distribution without and with exponential cut-off provided significantly better fits to the cluster size distributions in neuronal avalanches than the exponential, the lognormal and the gamma distribution. In summary, our findings strongly support the power law scaling in neuronal avalanches, providing further evidence for critical state dynamics in superficial layers of cortex.

Use of the truncated shifted Pareto distribution in assessing size distribution of oil and gas fields

USGS Publications Warehouse

Houghton, J.C.

1988-01-01

The truncated shifted Pareto (TSP) distribution, a variant of the two-parameter Pareto distribution, in which one parameter is added to shift the distribution right and left and the right-hand side is truncated, is used to model size distributions of oil and gas fields for resource assessment. Assumptions about limits to the left-hand and right-hand side reduce the number of parameters to two. The TSP distribution has advantages over the more customary lognormal distribution because it has a simple analytic expression, allowing exact computation of several statistics of interest, has a "J-shape," and has more flexibility in the thickness of the right-hand tail. Oil field sizes from the Minnelusa play in the Powder River Basin, Wyoming and Montana, are used as a case study. Probability plotting procedures allow easy visualization of the fit and help the assessment. ?? 1988 International Association for Mathematical Geology.

Size distributions of polycyclic aromatic hydrocarbons in urban atmosphere: sorption mechanism and source contributions to respiratory deposition

NASA Astrophysics Data System (ADS)

Lv, Yan; Li, Xiang; Xu, Ting Ting; Cheng, Tian Tao; Yang, Xin; Chen, Jian Min; Iinuma, Yoshiteru; Herrmann, Hartmut

2016-03-01

In order to better understand the particle size distribution of polycyclic aromatic hydrocarbons (PAHs) and their source contribution to human respiratory system, size-resolved PAHs have been studied in ambient aerosols at a megacity Shanghai site during a 1-year period (2012-2013). The results showed the PAHs had a bimodal distribution with one mode peak in the fine-particle size range (0.4-2.1 µm) and another mode peak in the coarse-particle size range (3.3-9.0 µm). Along with the increase in ring number of PAHs, the intensity of the fine-mode peak increased, while the coarse-mode peak decreased. Plotting of log(PAH / PM) against log(Dp) showed that all slope values were above -1, suggesting that multiple mechanisms (adsorption and absorption) controlled the particle size distribution of PAHs. The total deposition flux of PAHs in the respiratory tract was calculated as being 8.8 ± 2.0 ng h-1. The highest lifetime cancer risk (LCR) was estimated at 1.5 × 10-6, which exceeded the unit risk of 10-6. The LCR values presented here were mainly influenced by accumulation mode PAHs which came from biomass burning (24 %), coal combustion (25 %), and vehicular emission (27 %). The present study provides us with a mechanistic understanding of the particle size distribution of PAHs and their transport in the human respiratory system, which can help develop better source control strategies.

Simultaneous Comparison of Two Roller Compaction Techniques and Two Particle Size Analysis Methods.

PubMed

Saarinen, Tuomas; Antikainen, Osmo; Yliruusi, Jouko

2017-11-01

A new dry granulation technique, gas-assisted roller compaction (GARC), was compared with conventional roller compaction (CRC) by manufacturing 34 granulation batches. The process variables studied were roll pressure, roll speed, and sieve size of the conical mill. The main quality attributes measured were granule size and flow characteristics. Within granulations also the real applicability of two particle size analysis techniques, sieve analysis (SA) and fast imaging technique (Flashsizer, FS), was tested. All granules obtained were acceptable. In general, the particle size of GARC granules was slightly larger than that of CRC granules. In addition, the GARC granules had better flowability. For example, the tablet weight variation of GARC granules was close to 2%, indicating good flowing and packing characteristics. The comparison of the two particle size analysis techniques showed that SA was more accurate in determining wide and bimodal size distributions while FS showed narrower and mono-modal distributions. However, both techniques gave good estimates for mean granule sizes. Overall, SA was a time-consuming but accurate technique that provided reliable information for the entire granule size distribution. By contrast, FS oversimplified the shape of the size distribution, but nevertheless yielded acceptable estimates for mean particle size. In general, FS was two to three orders of magnitude faster than SA.

Influence of multidroplet size distribution on icing collection efficiency

NASA Technical Reports Server (NTRS)

Chang, H.-P.; Kimble, K. R.; Frost, W.; Shaw, R. J.

1983-01-01

Calculation of collection efficiencies of two-dimensional airfoils for a monodispersed droplet icing cloud and a multidispersed droplet is carried out. Comparison is made with the experimental results reported in the NACA Technical Note series. The results of the study show considerably improved agreement with experiment when multidroplet size distributions are employed. The study then investigates the effect of collection efficiency on airborne particle droplet size sampling instruments. The biased effect introduced due to sampling from different collection volumes is predicted.

Coupled CFD-PBE Predictions of Renal Stone Size Distributions in the Nephron in Microgravity

NASA Technical Reports Server (NTRS)

Kassemi, Mohammad; Griffin, Elise; Thompson, David

2016-01-01

In this paper, a deterministic model is developed to assess the risk of critical renal stone formation for astronauts during space travel. A Population Balance Equation (PBE) model is used to compute the size distribution of a population of nucleating, growing and agglomerating renal calculi as they are transported through different sections of the nephron. The PBE model is coupled to a Computational Fluid Dynamics (CFD) model that solves for steady state flow of urine and transport of renal calculi along with the concentrations of ionic species, calcium and oxalate, in the nephron using an Eulerian two-phase mathematical framework. Parametric simulation are performed to study stone size enhancement and steady state volume fraction distributions in the four main sections of the nephron under weightlessness conditions. Contribution of agglomeration to the stone size distribution and effect of wall friction on the stone volume fraction distributions are carefully examined. Case studies using measured astronaut urinary calcium and oxalate concentrations in microgravity as input indicate that under nominal conditions the largest stone sizes developed in Space will be still considerably below the critical range for problematic stone development. However, results also indicate that the highest stone volume fraction occurs next to the tubule and duct walls. This suggests that there is an increased potential for wall adhesion with the possibility of evolution towards critical stone sizes.

A technique for production of nanocrystalline cellulose with a narrow size distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Wen; Holbery, James D.; Li, Kaichang

2009-02-01

Nanocrystalline cellulose (NCC) was prepared by sulfuric acid hydrolysis of microcrystalline cellulose. A differential centrifugation technique was studied to obtain NCC whiskers with a narrow size distribution. It was shown that the volume of NCC in different fractions had an inverse relationship with relative centrifugal force (RCF). The length of NCC whiskers was also fractionized by differential RCF. The aspect ratio of NCC in different fractions had a relatively narrow range. This technique provides an easy way of producing NCC whiskers with a narrow size distribution.

Effect of rapid thermal annealing temperature on the dispersion of Si nanocrystals in SiO2 matrix

NASA Astrophysics Data System (ADS)

Saxena, Nupur; Kumar, Pragati; Gupta, Vinay

2015-05-01

Effect of rapid thermal annealing temperature on the dispersion of silicon nanocrystals (Si-NC's) embedded in SiO2 matrix grown by atom beam sputtering (ABS) method is reported. The dispersion of Si NCs in SiO2 is an important issue to fabricate high efficiency devices based on Si-NC's. The transmission electron microscopy studies reveal that the precipitation of excess silicon is almost uniform and the particles grow in almost uniform size upto 850 °C. The size distribution of the particles broadens and becomes bimodal as the temperature is increased to 950 °C. This suggests that by controlling the annealing temperature, the dispersion of Si-NC's can be controlled. The results are supported by selected area diffraction (SAED) studies and micro photoluminescence (PL) spectroscopy. The discussion of effect of particle size distribution on PL spectrum is presented based on tight binding approximation (TBA) method using Gaussian and log-normal distribution of particles. The study suggests that the dispersion and consequently emission energy varies as a function of particle size distribution and that can be controlled by annealing parameters.

Size Class Distribution of Quercus engelmannii (Engelmann Oak) on the Santa Rosa Plateau, Riverside County, California

Treesearch

Earl W. Lathrop; Chris Osborne; Anna Rochester; Kevin Yeung; Samuel Soret; Rochelle Hopper

1991-01-01

Size class distribution of Quercus engelmannii (Engelmann oak) on the Santa Rosa Plateau was studied to understand whether current recruitment of young oaks is sufficient to maintain the population in spite of high natural mortality and impacts of development in some portions of the plateau woodland. Sapling-size oaks (1-10 cm dbh) made up 5.56 pct...

Improvement of Galilean refractive beam shaping system for accurately generating near-diffraction-limited flattop beam with arbitrary beam size.

PubMed

Ma, Haotong; Liu, Zejin; Jiang, Pengzhi; Xu, Xiaojun; Du, Shaojun

2011-07-04

We propose and demonstrate the improvement of conventional Galilean refractive beam shaping system for accurately generating near-diffraction-limited flattop beam with arbitrary beam size. Based on the detailed study of the refractive beam shaping system, we found that the conventional Galilean beam shaper can only work well for the magnifying beam shaping. Taking the transformation of input beam with Gaussian irradiance distribution into target beam with high order Fermi-Dirac flattop profile as an example, the shaper can only work well at the condition that the size of input and target beam meets R(0) ≥ 1.3 w(0). For the improvement, the shaper is regarded as the combination of magnifying and demagnifying beam shaping system. The surface and phase distributions of the improved Galilean beam shaping system are derived based on Geometric and Fourier Optics. By using the improved Galilean beam shaper, the accurate transformation of input beam with Gaussian irradiance distribution into target beam with flattop irradiance distribution is realized. The irradiance distribution of the output beam is coincident with that of the target beam and the corresponding phase distribution is maintained. The propagation performance of the output beam is greatly improved. Studies of the influences of beam size and beam order on the improved Galilean beam shaping system show that restriction of beam size has been greatly reduced. This improvement can also be used to redistribute the input beam with complicated irradiance distribution into output beam with complicated irradiance distribution.

Relationship between Defect Size and Fatigue Life Distributions in Al-7 Pct Si-Mg Alloy Castings

NASA Astrophysics Data System (ADS)

Tiryakioğlu, Murat

2009-07-01

A new method for predicting the variability in fatigue life of castings was developed by combining the size distribution for the fatigue-initiating defects and a fatigue life model based on the Paris-Erdoğan law for crack propagation. Two datasets for the fatigue-initiating defects in Al-7 pct Si-Mg alloy castings, reported previously in the literature, were used to demonstrate that (1) the size of fatigue-initiating defects follow the Gumbel distribution; (2) the crack propagation model developed previously provides respectable fits to experimental data; and (3) the method developed in the present study expresses the variability in both datasets, almost as well as the lognormal distribution and better than the Weibull distribution.

Seed-parent fecundity distributions in bee-pollinated forage legume polycrosses

USDA-ARS?s Scientific Manuscript database

Modeling expected fecundity distributions in bee-pollinated forage legume polycrosses allows more accurate assessment of effective polycross size and its inbreeding consequences. In this study, polycross size (N) standardized seed-parent fecundity frequencies [(Pfi – (1/N))/(1/N)] were modeled on 16...

Size and moisture distribution characteristics of walnuts and their components

USDA-ARS?s Scientific Manuscript database

The objective of this study was to determine the size characteristics and moisture content (MC) distributions of individual walnuts and their components, including hulls, shells and kernels under different harvest conditions. Measurements were carried out for three walnut varieties, Tulare, Howard a...

Reconstruction of sediment transport pathways in modern microtidal sand flat by multiple classification analysis

NASA Astrophysics Data System (ADS)

Yamashita, S.; Nakajo, T.; Naruse, H.

2009-12-01

In this study, we statistically classified the grain size distribution of the bottom surface sediment on a microtidal sand flat to analyze the depositional processes of the sediment. Multiple classification analysis revealed that two types of sediment populations exist in the bottom surface sediment. Then, we employed the sediment trend model developed by Gao and Collins (1992) for the estimation of sediment transport pathways. As a result, we found that statistical discrimination of the bottom surface sediment provides useful information for the sediment trend model while dealing with various types of sediment transport processes. The microtidal sand flat along the Kushida River estuary, Ise Bay, central Japan, was investigated, and 102 bottom surface sediment samples were obtained. Then, their grain size distribution patterns were measured by the settling tube method, and each grain size distribution parameter (mud and gravel contents, mean grain size, coefficient of variance (CV), skewness, kurtosis, 5, 25, 50, 75, and 95 percentile) was calculated. Here, CV is the normalized sorting value divided by the mean grain size. Two classical statistical methods—principal component analysis (PCA) and fuzzy cluster analysis—were applied. The results of PCA showed that the bottom surface sediment of the study area is mainly characterized by grain size (mean grain size and 5-95 percentile) and the CV value, indicating predominantly large absolute values of factor loadings in primal component (PC) 1. PC1 is interpreted as being indicative of the grain-size trend, in which a finer grain-size distribution indicates better size sorting. The frequency distribution of PC1 has a bimodal shape and suggests the existence of two types of sediment populations. Therefore, we applied fuzzy cluster analysis, the results of which revealed two groupings of the sediment (Cluster 1 and Cluster 2). Cluster 1 shows a lower value of PC1, indicating coarse and poorly sorted sediments. Cluster 1 sediments are distributed around the branched channel from Kushida River and show an expanding distribution from the river mouth toward the northeast direction. Cluster 2 shows a higher value of PC1, indicating fine and well-sorted sediments; this cluster is distributed in a distant area from the river mouth, including the offshore region. Therefore, Cluster 1 and Cluster 2 are interpreted as being deposited by fluvial and wave processes, respectively. Finally, on the basis of this distribution pattern, the sediment trend model was applied in areas dominated separately by fluvial and wave processes. Resultant sediment transport patterns showed good agreement with those obtained by field observations. The results of this study provide an important insight into the numerical models of sediment transport.

Size distributions of air showers accompanied with high energy gamma ray bundles observed at Mt. Chacaltaya

NASA Technical Reports Server (NTRS)

Matano, T.; Machida, M.; Tsuchima, I.; Kawasumi, N.; Honda, K.; Hashimoto, K.; Martinic, N.; Zapata, J.; Navia, C. E.; Aquirre, C.

1985-01-01

Size distributions of air showers accompanied with bundle of high energy gamma rays and/or large size bursts under emulsion chambers, to study the composition of primary cosmic rays and also characteristics of high energy nuclear interaction. Air showers initiated by particles with a large cross section of interaction may develop from narrow region of the atmosphere near the top. Starting levels of air showers by particles with smaller cross section fluctuate in wider region of the atmosphere. Air showers of extremely small size accompanied with bundle of gamma rays may be ones initiated by protons at lower level after penetrating deep atmosphere without interaction. It is determined that the relative size distribution according to the total energy of bundle of gamma rays and the total burst size observed under 15 cm lead absorber.

Study on extrusion process of SiC ceramic matrix

NASA Astrophysics Data System (ADS)

Dai, Xiao-Yuan; Shen, Fan; Ji, Jia-You; Wang, Shu-Ling; Xu, Man

2017-11-01

In this thesis, the extrusion process of SiC ceramic matrix has been systematically studied.The effect of different cellulose content on the flexural strength and pore size distribution of SiC matrix was discussed.Reselts show that with the increase of cellulose content, the flexural strength decreased.The pore size distribution in the sample was 1um-4um, and the 1um-2um concentration was more concentrated. It is found that the cellulose content has little effect on the pore size distribution.When the cellulose content is 7%, the flexural strength of the sample is 40.9Mpa. At this time, the mechanical properties of the sample are the strongest.

Does Litter Size Variation Affect Models of Terrestrial Carnivore Extinction Risk and Management?

PubMed Central

Devenish-Nelson, Eleanor S.; Stephens, Philip A.; Harris, Stephen; Soulsbury, Carl; Richards, Shane A.

2013-01-01

Background Individual variation in both survival and reproduction has the potential to influence extinction risk. Especially for rare or threatened species, reliable population models should adequately incorporate demographic uncertainty. Here, we focus on an important form of demographic stochasticity: variation in litter sizes. We use terrestrial carnivores as an example taxon, as they are frequently threatened or of economic importance. Since data on intraspecific litter size variation are often sparse, it is unclear what probability distribution should be used to describe the pattern of litter size variation for multiparous carnivores. Methodology/Principal Findings We used litter size data on 32 terrestrial carnivore species to test the fit of 12 probability distributions. The influence of these distributions on quasi-extinction probabilities and the probability of successful disease control was then examined for three canid species – the island fox Urocyon littoralis, the red fox Vulpes vulpes, and the African wild dog Lycaon pictus. Best fitting probability distributions differed among the carnivores examined. However, the discretised normal distribution provided the best fit for the majority of species, because variation among litter-sizes was often small. Importantly, however, the outcomes of demographic models were generally robust to the distribution used. Conclusion/Significance These results provide reassurance for those using demographic modelling for the management of less studied carnivores in which litter size variation is estimated using data from species with similar reproductive attributes. PMID:23469140

Does litter size variation affect models of terrestrial carnivore extinction risk and management?

PubMed

Devenish-Nelson, Eleanor S; Stephens, Philip A; Harris, Stephen; Soulsbury, Carl; Richards, Shane A

2013-01-01

Individual variation in both survival and reproduction has the potential to influence extinction risk. Especially for rare or threatened species, reliable population models should adequately incorporate demographic uncertainty. Here, we focus on an important form of demographic stochasticity: variation in litter sizes. We use terrestrial carnivores as an example taxon, as they are frequently threatened or of economic importance. Since data on intraspecific litter size variation are often sparse, it is unclear what probability distribution should be used to describe the pattern of litter size variation for multiparous carnivores. We used litter size data on 32 terrestrial carnivore species to test the fit of 12 probability distributions. The influence of these distributions on quasi-extinction probabilities and the probability of successful disease control was then examined for three canid species - the island fox Urocyon littoralis, the red fox Vulpes vulpes, and the African wild dog Lycaon pictus. Best fitting probability distributions differed among the carnivores examined. However, the discretised normal distribution provided the best fit for the majority of species, because variation among litter-sizes was often small. Importantly, however, the outcomes of demographic models were generally robust to the distribution used. These results provide reassurance for those using demographic modelling for the management of less studied carnivores in which litter size variation is estimated using data from species with similar reproductive attributes.

Characterization of Raman Scattering in Solid Samples with Different Particle Sizes and Elucidation on the Trends of Particle Size-Dependent Intensity Variations in Relation to Changes in the Sizes of Laser Illumination and Detection Area.

PubMed

Duy, Pham K; Chun, Seulah; Chung, Hoeil

2017-11-21

We have systematically characterized Raman scatterings in solid samples with different particle sizes and investigated subsequent trends of particle size-induced intensity variations. For this purpose, both lactose powders and pellets composed of five different particle sizes were prepared. Uniquely in this study, three spectral acquisition schemes with different sizes of laser illuminations and detection windows were employed for the evaluation, since it was expected that the experimental configuration would be another factor potentially influencing the intensity of the lactose peak, along with the particle size itself. In both samples, the distribution of Raman photons became broader with the increase in particle size, as the mean free path of laser photons, the average photon travel distance between consecutive scattering locations, became longer under this situation. When the particle size was the same, the Raman photon distribution was narrower in the pellets since the individual particles were more densely packed in a given volume (the shorter mean free path). When the size of the detection window was small, the number of photons reaching the detector decreased as the photon distribution was larger. Meanwhile, a large-window detector was able to collect the widely distributed Raman photons more effectively; therefore, the trends of intensity change with the variation in particle size were dissimilar depending on the employed spectral acquisition schemes. Overall, the Monte Carlo simulation was effective at probing the photon distribution inside the samples and helped to support the experimental observations.

[Experimental study on particle size distributions of an engine fueled with blends of biodiesel].

PubMed

Lu, Xiao-Ming; Ge, Yun-Shan; Han, Xiu-Kun; Wu, Si-Jin; Zhu, Rong-Fu; He, Chao

2007-04-01

The purpose of this study is to obtain the particle size distributions of an engine fueled biodiesel and its blends. A turbocharged DI diesel engine was tested on a dynamometer. A pump of 80 L/min and fiber glass filters with diameter of 90 mm were used to sample engine particles in exhaust pipe. Sampling duration was 10 minutes. Particle size distributions were measured by a laser diffraction particle size analyzer. Results indicated that higher engine speed resulted in smaller particle sizes and narrower distributions. The modes on distribution curves and mode variation were larger with dry samples than with wet samples (dry: around 10 - 12 microm vs. wet: around 4 - 10 microm). At low speed, Sauter mean diameter d32 of dry samples was the biggest with B100, the smallest with diesel fuel, and among them with B20, while at high speed, d32 the biggest with B20, the smallest with B100, and in middle with diesel. Median diameter d(0.5) also reflected the results. Except for 2 000 r/min, d32 of wet with B20 is the biggest, the smallest with diesel, and in middle with B100. The large mode variation resulted in increase of d32.

A POSSIBLE DIVOT IN THE SIZE DISTRIBUTION OF THE KUIPER BELT'S SCATTERING OBJECTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shankman, C.; Gladman, B. J.; Kaib, N.

Via joint analysis of a calibrated telescopic survey, which found scattering Kuiper Belt objects, and models of their expected orbital distribution, we explore the scattering-object (SO) size distribution. Although for D > 100 km the number of objects quickly rise as diameters decrease, we find a relative lack of smaller objects, ruling out a single power law at greater than 99% confidence. After studying traditional ''knees'' in the size distribution, we explore other formulations and find that, surprisingly, our analysis is consistent with a very sudden decrease (a divot) in the number distribution as diameters decrease below 100 km, whichmore » then rises again as a power law. Motivated by other dynamically hot populations and the Centaurs, we argue for a divot size distribution where the number of smaller objects rises again as expected via collisional equilibrium. Extrapolation yields enough kilometer-scale SOs to supply the nearby Jupiter-family comets. Our interpretation is that this divot feature is a preserved relic of the size distribution made by planetesimal formation, now ''frozen in'' to portions of the Kuiper Belt sharing a ''hot'' orbital inclination distribution, explaining several puzzles in Kuiper Belt science. Additionally, we show that to match today's SO inclination distribution, the supply source that was scattered outward must have already been vertically heated to the of order 10 Degree-Sign .« less

Simulation on Poisson and negative binomial models of count road accident modeling

NASA Astrophysics Data System (ADS)

Sapuan, M. S.; Razali, A. M.; Zamzuri, Z. H.; Ibrahim, K.

2016-11-01

Accident count data have often been shown to have overdispersion. On the other hand, the data might contain zero count (excess zeros). The simulation study was conducted to create a scenarios which an accident happen in T-junction with the assumption the dependent variables of generated data follows certain distribution namely Poisson and negative binomial distribution with different sample size of n=30 to n=500. The study objective was accomplished by fitting Poisson regression, negative binomial regression and Hurdle negative binomial model to the simulated data. The model validation was compared and the simulation result shows for each different sample size, not all model fit the data nicely even though the data generated from its own distribution especially when the sample size is larger. Furthermore, the larger sample size indicates that more zeros accident count in the dataset.

The Development of Midlatitude Cirrus Models for MODIS Using FIRE-I, FIRE-II, and ARM In Situ Data

NASA Technical Reports Server (NTRS)

Nasiri, Shaima L.; Baum, Bryan A.; Heymsfield, Andrew J.; Yang, Ping; Poellot, Michael R.; Kratz, David P.; Hu, Yong-Xiang

2002-01-01

Detailed in situ data from cirrus clouds have been collected during dedicated field Campaigns, but the use of the size and habit distribution data has been lagging in the development of more realistic cirrus scattering models. In this study, the authors examine the use of in situ cirrus data collected during three field campaigns to develop more realistic midlatitude cirrus microphysical models. Data are used from the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE)-I (1986) and FIRE-II (1991) campaigns and from a recent Atmospheric Radiation Measurement (ARM) Program campaign held in March-April of 2000. The microphysical models are based on measured vertical distributions of both particle size and particle habit and are used to develop new scattering models for a suite of moderate-resolution imaging spectroradiometer (MODIS) bands spanning visible. near-infrared, and infrared wavelengths. The sensitivity of the resulting scattering properties to the underlying assumptions of the assumed particle size and habit distributions are examined. It is found that the near-infrared bands are sensitive not only to the discretization of the size distribution but also to the assumed habit distribution. In addition. the results indicate that the effective diameter calculated from a given size distribution tends to be sensitive to the number of size bins that are used to discretize the data and also to the ice-crystal habit distribution.

Understanding the role of pore size homogeneity in the water transport through graphene layers.

PubMed

Su, Jiaye; Zhao, Yunzhen; Fang, Chang

2018-06-01

Graphene is a versatile 2D material and attracts an increasing amount of attention from a broad scientific community, including novel nanofluidic devices. In this work, we use molecular dynamics simulations to study the pressure driven water transport through graphene layers, focusing on the pore size homogeneity, realized by the arrangement of two pore sizes. For a given layer number, we find that water flux exhibits an excellent linear behavior with pressure, in agreement with the prediction of the Hagen-Poiseuille equation. Interestingly, the flux for concentrated pore size distribution is around two times larger than that of a uniform distribution. More surprisingly, under a given pressure, the water flux changes in an opposite way for these two distributions, where the flux ratio almost increases linearly with the layer number. For the largest layer number, more distributions suggest the same conclusion that higher water flux can be attained for more concentrated pore size distributions. Similar differences for the water translocation time and occupancy are also identified. The major reason for these results should clearly be due to the hydrogen bond and density profile distributions. Our results are helpful to delineate the exquisite role of pore size homogeneity, and should have great implications for the design of high flux nanofluidic devices and inversely the detection of pore structures.

Understanding the role of pore size homogeneity in the water transport through graphene layers

NASA Astrophysics Data System (ADS)

Su, Jiaye; Zhao, Yunzhen; Fang, Chang

2018-06-01

Graphene is a versatile 2D material and attracts an increasing amount of attention from a broad scientific community, including novel nanofluidic devices. In this work, we use molecular dynamics simulations to study the pressure driven water transport through graphene layers, focusing on the pore size homogeneity, realized by the arrangement of two pore sizes. For a given layer number, we find that water flux exhibits an excellent linear behavior with pressure, in agreement with the prediction of the Hagen–Poiseuille equation. Interestingly, the flux for concentrated pore size distribution is around two times larger than that of a uniform distribution. More surprisingly, under a given pressure, the water flux changes in an opposite way for these two distributions, where the flux ratio almost increases linearly with the layer number. For the largest layer number, more distributions suggest the same conclusion that higher water flux can be attained for more concentrated pore size distributions. Similar differences for the water translocation time and occupancy are also identified. The major reason for these results should clearly be due to the hydrogen bond and density profile distributions. Our results are helpful to delineate the exquisite role of pore size homogeneity, and should have great implications for the design of high flux nanofluidic devices and inversely the detection of pore structures.

Prediction of the size distributions of methanol-ethanol clusters detected in VUV laser/time-of-flight mass spectrometry.

PubMed

Liu, Yi; Consta, Styliani; Shi, Yujun; Lipson, R H; Goddard, William A

2009-06-25

The size distributions and geometries of vapor clusters equilibrated with methanol-ethanol (Me-Et) liquid mixtures were recently studied by vacuum ultraviolet (VUV) laser time-of-flight (TOF) mass spectrometry and density functional theory (DFT) calculations (Liu, Y.; Consta, S.; Ogeer, F.; Shi, Y. J.; Lipson, R. H. Can. J. Chem. 2007, 85, 843-852). On the basis of the mass spectra recorded, it was concluded that the formation of neutral tetramers is particularly prominent. Here we develop grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) frameworks to compute cluster size distributions in vapor mixtures that allow a direct comparison with experimental mass spectra. Using the all-atom optimized potential for liquid simulations (OPLS-AA) force field, we systematically examined the neutral cluster size distributions as functions of pressure and temperature. These neutral cluster distributions were then used to derive ionized cluster distributions to compare directly with the experiments. The simulations suggest that supersaturation at 12 to 16 times the equilibrium vapor pressure at 298 K or supercooling at temperature 240 to 260 K at the equilibrium vapor pressure can lead to the relatively abundant tetramer population observed in the experiments. Our simulations capture the most distinct features observed in the experimental TOF mass spectra: Et(3)H(+) at m/z = 139 in the vapor corresponding to 10:90% Me-Et liquid mixture and Me(3)H(+) at m/z = 97 in the vapors corresponding to 50:50% and 90:10% Me-Et liquid mixtures. The hybrid GCMC scheme developed in this work extends the capability of studying the size distributions of neat clusters to mixed species and provides a useful tool for studying environmentally important systems such as atmospheric aerosols.

Power laws, discontinuities and regional city size distributions

USGS Publications Warehouse

Garmestani, A.S.; Allen, Craig R.; Gallagher, C.M.

2008-01-01

Urban systems are manifestations of human adaptation to the natural environment. City size distributions are the expression of hierarchical processes acting upon urban systems. In this paper, we test the entire city size distributions for the southeastern and southwestern United States (1990), as well as the size classes in these regions for power law behavior. We interpret the differences in the size of the regional city size distributions as the manifestation of variable growth dynamics dependent upon city size. Size classes in the city size distributions are snapshots of stable states within urban systems in flux.

Size Distribution and Dispersion of Droplets Generated by Impingement of Breaking Waves on Oil Slicks

NASA Astrophysics Data System (ADS)

Li, C.; Miller, J.; Wang, J.; Koley, S. S.; Katz, J.

2017-10-01

This laboratory experimental study investigates the temporal evolution of the size distribution of subsurface oil droplets generated as breaking waves entrain oil slicks. The measurements are performed for varying wave energy, as well as large variations in oil viscosity and oil-water interfacial tension, the latter achieved by premixing the oil with dispersant. In situ measurements using digital inline holography at two magnifications are applied for measuring the droplet sizes and Particle Image Velocimetry (PIV) for determining the temporal evolution of turbulence after wave breaking. All early (2-10 s) size distributions have two distinct size ranges with different slopes. For low dispersant to oil ratios (DOR), the transition between them could be predicted based on a turbulent Weber (We) number in the 2-4 range, suggesting that turbulence plays an important role. For smaller droplets, all the number size distributions have power of about -2.1, and for larger droplets, the power decreases well below -3. The measured steepening of the size distribution over time is predicted by a simple model involving buoyant rise and turbulence dispersion. Conversely, for DOR 1:100 and 1:25 oils, the diameter of slope transition decreases from ˜1 mm to 46 and 14 µm, respectively, much faster than the We-based prediction, and the size distribution steepens with increasing DOR. Furthermore, the concentration of micron-sized droplets of DOR 1:25 oil increases for the first 10 min after entrainment. These phenomena are presumably caused by the observed formation and breakup oil microthreads associated with tip streaming.

Characteristic fragment size distributions in dynamic fragmentation

NASA Astrophysics Data System (ADS)

Zhou, Fenghua; Molinari, Jean-François; Ramesh, K. T.

2006-06-01

The one-dimensional fragmentation of a dynamically expanding ring (Mott's problem) is studied numerically to obtain the fragment signatures under different strain rates. An empirical formula is proposed to calculate an average fragment size. Rayleigh distribution is found to describe the statistical properties of the fragment populations.

Effects of soil surface roughness on interrill erosion processes and sediment particle size distribution

USDA-ARS?s Scientific Manuscript database

Soil surface roughness significantly impacts runoff and erosion under rainfall. Few previous studies on runoff generation focused on the effects of soil surface roughness on the sediment particle size distribution (PSD), which greatly affects interrill erosion and sedimentation processes. To address...

Distribution of normal superficial ocular vessels in digital images.

PubMed

Banaee, Touka; Ehsaei, Asieh; Pourreza, Hamidreza; Khajedaluee, Mohammad; Abrishami, Mojtaba; Basiri, Mohsen; Daneshvar Kakhki, Ramin; Pourreza, Reza

2014-02-01

To investigate the distribution of different-sized vessels in the digital images of the ocular surface, an endeavor which may provide useful information for future studies. This study included 295 healthy individuals. From each participant, four digital photographs of the superior and inferior conjunctivae of both eyes, with a fixed succession of photography (right upper, right lower, left upper, left lower), were taken with a slit lamp mounted camera. Photographs were then analyzed by a previously described algorithm for vessel detection in the digital images. The area (of the image) occupied by vessels (AOV) of different sizes was measured. Height, weight, fasting blood sugar (FBS) and hemoglobin levels were also measured and the relationship between these parameters and the AOV was investigated. These findings indicated a statistically significant difference in the distribution of the AOV among the four conjunctival areas. No significant correlations were noted between the AOV of each conjunctival area and the different demographic and biometric factors. Medium-sized vessels were the most abundant vessels in the photographs of the four investigated conjunctival areas. The AOV of the different sizes of vessels follows a normal distribution curve in the four areas of the conjunctiva. The distribution of the vessels in successive photographs changes in a specific manner, with the mean AOV becoming larger as the photos were taken from the right upper to the left lower area. The AOV of vessel sizes has a normal distribution curve and medium-sized vessels occupy the largest area of the photograph. Copyright © 2013 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

The interplay of various sources of noise on reliability of species distribution models hinges on ecological specialisation.

PubMed

Soultan, Alaaeldin; Safi, Kamran

2017-01-01

Digitized species occurrence data provide an unprecedented source of information for ecologists and conservationists. Species distribution model (SDM) has become a popular method to utilise these data for understanding the spatial and temporal distribution of species, and for modelling biodiversity patterns. Our objective is to study the impact of noise in species occurrence data (namely sample size and positional accuracy) on the performance and reliability of SDM, considering the multiplicative impact of SDM algorithms, species specialisation, and grid resolution. We created a set of four 'virtual' species characterized by different specialisation levels. For each of these species, we built the suitable habitat models using five algorithms at two grid resolutions, with varying sample sizes and different levels of positional accuracy. We assessed the performance and reliability of the SDM according to classic model evaluation metrics (Area Under the Curve and True Skill Statistic) and model agreement metrics (Overall Concordance Correlation Coefficient and geographic niche overlap) respectively. Our study revealed that species specialisation had by far the most dominant impact on the SDM. In contrast to previous studies, we found that for widespread species, low sample size and low positional accuracy were acceptable, and useful distribution ranges could be predicted with as few as 10 species occurrences. Range predictions for narrow-ranged species, however, were sensitive to sample size and positional accuracy, such that useful distribution ranges required at least 20 species occurrences. Against expectations, the MAXENT algorithm poorly predicted the distribution of specialist species at low sample size.

Tin particle size measurements in high explosively driven shockwave experiments using Mie scattering method

NASA Astrophysics Data System (ADS)

Monfared, Shabnam; Buttler, William; Schauer, Martin; Lalone, Brandon; Pack, Cora; Stevens, Gerald; Stone, Joseph; Special Technologies Laboratory Collaboration; Los Alamos National Laboratory Team

2014-03-01

Los Alamos National Laboratory is actively engaged in the study of material failure physics to support the hydrodynamic models development, where an important failure mechanism of explosively shocked metals causes mass ejection from the backside of a shocked surface with surface perturbations. Ejecta models are in development for this situation. Our past work has clearly shown that the total ejected mass and mass-velocity distribution sensitively link to the wavelength and amplitude of these perturbations. While we have had success developing ejecta mass and mass-velocity models, we need to better understand the size and size-velocity distributions of the ejected mass. To support size measurements we have developed a dynamic Mie scattering diagnostic based on a CW laser that permits measurement of the forward attenuation cross-section combined with a dynamic mass-density and mass-velocity distribution, as well as a measurement of the forward scattering cross-section at 12 angles (5- 32.5 degrees) in increments of 2.5 degrees. We compare size distribution followed from Beers law with attenuation cross-section and mass measurement to the dynamic size distribution determined from scattering cross-section alone. We report results from our first quality experiments.

Simultaneous Measurements of Nanoaerosols and Radioactive Aerosols Containing the Short-lived Radon Isotopes.

PubMed

Otahal, P P S; Burian, I; Ondracek, J; Zdimal, V; Holub, R F

2017-11-01

The activity size distribution of the Equilibrium-Equivalent Concentration (EER) of 222Rn is one of the most important parameters for the estimation of radiation dose by inhalation of radon decay products. A series of measurements of the EER activity size distribution were performed by the screen diffusion battery in Radon-Aerosol chamber (10 m3) at the National Institute for Nuclear, Chemical, and Biological Protection (SUJCHBO). These measurements were performed at different levels of radon concentration. For this study, the Graded Screen Array Diffusion Battery (GSA DB), developed by the SUJCHBO (based on Earl Knutson and Robert F Holub design), consists of 10 screens and backup filter used to collect all particles that penetrated the screens. The measuring range of this GSA DB allows measuring the radioactive nanoaerosols in the size range from 0.5 to 100 nm. The Earl Knutson algorithm was used for EER activity size distribution evaluation. The results of EER activity size distribution were subsequently compared with the aerosol particle size distribution measured by Scanning Mobility Particle Sizer Spectrometer (SMPS 3936 N, TSI Inc., MN, USA). © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Solvent effect in sonochemical synthesis of metal-alloy nanoparticles for use as electrocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okoli, Celest U.; Kuttiyiel, Kurian A.; Cole, Jesse

Nanomaterials are now widely used in the fabrication of electrodes and electrocatalysts. In this paper, we report a sonochemical study of the synthesis of molybdenum and palladium alloy nanomaterials supported on functionalized carbon material in various solvents: hexadecane, ethanol, ethylene glycol, polyethylene glycol (PEG 400) and Ionic liquids (ILs). The objective was to identify simple and more environmentally friendly design and fabrication methods for nanomaterial synthesis that are suitable as electrocatalysts in electrochemical applications. The particles size and distribution of nanomaterials were compared on two different carbons as supports: activated carbon and multiwall carbon nanotubes (MWCNTs). The results show thatmore » carbon materials functionalized with ILs in ethanol/deionized water mixture solvent produced smaller particles sizes (3.00 ± 0.05 nm) with uniform distribution while in PEG 400, functionalized materials produced 4.00 ± 1 nm sized particles with uneven distribution (range). In hexadecane solvents with Polyvinylpyrrolidone (PVP) as capping ligands, large particle sizes (14.00 ± 1 nm) were produced with wide particle size distribution. Finally, the metal alloy nanoparticles produced in ILs without any external reducing agent have potential to exhibit a higher catalytic activity due to smaller particle size and uniform distribution.« less

Comparison of two probability distributions used to model sizes of undiscovered oil and gas accumulations: Does the tail wag the assessment?

USGS Publications Warehouse

Attanasi, E.D.; Charpentier, R.R.

2002-01-01

Undiscovered oil and gas assessments are commonly reported as aggregate estimates of hydrocarbon volumes. Potential commercial value and discovery costs are, however, determined by accumulation size, so engineers, economists, decision makers, and sometimes policy analysts are most interested in projected discovery sizes. The lognormal and Pareto distributions have been used to model exploration target sizes. This note contrasts the outcomes of applying these alternative distributions to the play level assessments of the U.S. Geological Survey's 1995 National Oil and Gas Assessment. Using the same numbers of undiscovered accumulations and the same minimum, medium, and maximum size estimates, substitution of the shifted truncated lognormal distribution for the shifted truncated Pareto distribution reduced assessed undiscovered oil by 16% and gas by 15%. Nearly all of the volume differences resulted because the lognormal had fewer larger fields relative to the Pareto. The lognormal also resulted in a smaller number of small fields relative to the Pareto. For the Permian Basin case study presented here, reserve addition costs were 20% higher with the lognormal size assumption. ?? 2002 International Association for Mathematical Geology.

Solvent effect in sonochemical synthesis of metal-alloy nanoparticles for use as electrocatalysts

DOE PAGES

Okoli, Celest U.; Kuttiyiel, Kurian A.; Cole, Jesse; ...

2017-10-03

Nanomaterials are now widely used in the fabrication of electrodes and electrocatalysts. In this paper, we report a sonochemical study of the synthesis of molybdenum and palladium alloy nanomaterials supported on functionalized carbon material in various solvents: hexadecane, ethanol, ethylene glycol, polyethylene glycol (PEG 400) and Ionic liquids (ILs). The objective was to identify simple and more environmentally friendly design and fabrication methods for nanomaterial synthesis that are suitable as electrocatalysts in electrochemical applications. The particles size and distribution of nanomaterials were compared on two different carbons as supports: activated carbon and multiwall carbon nanotubes (MWCNTs). The results show thatmore » carbon materials functionalized with ILs in ethanol/deionized water mixture solvent produced smaller particles sizes (3.00 ± 0.05 nm) with uniform distribution while in PEG 400, functionalized materials produced 4.00 ± 1 nm sized particles with uneven distribution (range). In hexadecane solvents with Polyvinylpyrrolidone (PVP) as capping ligands, large particle sizes (14.00 ± 1 nm) were produced with wide particle size distribution. Finally, the metal alloy nanoparticles produced in ILs without any external reducing agent have potential to exhibit a higher catalytic activity due to smaller particle size and uniform distribution.« less

Characterization of titanium dioxide nanoparticles in food products: analytical methods to define nanoparticles.

PubMed

Peters, Ruud J B; van Bemmel, Greet; Herrera-Rivera, Zahira; Helsper, Hans P F G; Marvin, Hans J P; Weigel, Stefan; Tromp, Peter C; Oomen, Agnes G; Rietveld, Anton G; Bouwmeester, Hans

2014-07-09

Titanium dioxide (TiO2) is a common food additive used to enhance the white color, brightness, and sometimes flavor of a variety of food products. In this study 7 food grade TiO2 materials (E171), 24 food products, and 3 personal care products were investigated for their TiO2 content and the number-based size distribution of TiO2 particles present in these products. Three principally different methods have been used to determine the number-based size distribution of TiO2 particles: electron microscopy, asymmetric flow field-flow fractionation combined with inductively coupled mass spectrometry, and single-particle inductively coupled mass spectrometry. The results show that all E171 materials have similar size distributions with primary particle sizes in the range of 60-300 nm. Depending on the analytical method used, 10-15% of the particles in these materials had sizes below 100 nm. In 24 of the 27 foods and personal care products detectable amounts of titanium were found ranging from 0.02 to 9.0 mg TiO2/g product. The number-based size distributions for TiO2 particles in the food and personal care products showed that 5-10% of the particles in these products had sizes below 100 nm, comparable to that found in the E171 materials. Comparable size distributions were found using the three principally different analytical methods. Although the applied methods are considered state of the art, they showed practical size limits for TiO2 particles in the range of 20-50 nm, which may introduce a significant bias in the size distribution because particles <20 nm are excluded. This shows the inability of current state of the art methods to support the European Union recommendation for the definition of nanomaterials.

The Microphysical Structure of Extreme Precipitation as Inferred from Ground-Based Raindrop Spectra.

NASA Astrophysics Data System (ADS)

Uijlenhoet, Remko; Smith, James A.; Steiner, Matthias

2003-05-01

The controls on the variability of raindrop size distributions in extreme rainfall and the associated radar reflectivity-rain rate relationships are studied using a scaling-law formalism for the description of raindrop size distributions and their properties. This scaling-law formalism enables a separation of the effects of changes in the scale of the raindrop size distribution from those in its shape. Parameters controlling the scale and shape of the scaled raindrop size distribution may be related to the microphysical processes generating extreme rainfall. A global scaling analysis of raindrop size distributions corresponding to rain rates exceeding 100 mm h1, collected during the 1950s with the Illinois State Water Survey raindrop camera in Miami, Florida, reveals that extreme rain rates tend to be associated with conditions in which the variability of the raindrop size distribution is strongly number controlled (i.e., characteristic drop sizes are roughly constant). This means that changes in properties of raindrop size distributions in extreme rainfall are largely produced by varying raindrop concentrations. As a result, rainfall integral variables (such as radar reflectivity and rain rate) are roughly proportional to each other, which is consistent with the concept of the so-called equilibrium raindrop size distribution and has profound implications for radar measurement of extreme rainfall. A time series analysis for two contrasting extreme rainfall events supports the hypothesis that the variability of raindrop size distributions for extreme rain rates is strongly number controlled. However, this analysis also reveals that the actual shapes of the (measured and scaled) spectra may differ significantly from storm to storm. This implies that the exponents of power-law radar reflectivity-rain rate relationships may be similar, and close to unity, for different extreme rainfall events, but their prefactors may differ substantially. Consequently, there is no unique radar reflectivity-rain rate relationship for extreme rain rates, but the variability is essentially reduced to one free parameter (i.e., the prefactor). It is suggested that this free parameter may be estimated on the basis of differential reflectivity measurements in extreme rainfall.

Family size, the physical environment, and socioeconomic effects across the stature distribution.

PubMed

Carson, Scott Alan

2012-04-01

A neglected area in historical stature studies is the relationship between stature and family size. Using robust statistics and a large 19th century data set, this study documents a positive relationship between stature and family size across the stature distribution. The relationship between material inequality and health is the subject of considerable debate, and there was a positive relationship between stature and wealth and an inverse relationship between stature and material inequality. After controlling for family size and wealth variables, the paper reports a positive relationship between the physical environment and stature. Copyright © 2012 Elsevier GmbH. All rights reserved.

Measuring Compartment Size and Gas Solubility in Marine Mammals

DTIC Science & Technology

2014-09-30

analyzed by gas chromatography . Injection of the sample into the gas chromatograph is done using a sample loop to minimize volume injection error. We...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Measuring Compartment Size and Gas Solubility in Marine...study is to develop methods to estimate marine mammal tissue compartment sizes, and tissue gas solubility. We aim to improve the data available for

Size and Velocity Distributions of Particles and Droplets in Spray Combustion Systems.

DTIC Science & Technology

1984-11-01

constructed, calibrated, and successfully applied. Our efforts to verify the performance and accuracy of this diagnostic led to a parallel research...array will not be an acceptable detection system for size distribution measurements by this method. VI. Conclusions This study has led to the following...radiation is also useful particle size analysis by ensemble multiangle scattering. One problem for all multiwavelength or multiaricle diagnostics for

Quality of the log-geometric distribution extrapolation for smaller undiscovered oil and gas pool size

USGS Publications Warehouse

Chenglin, L.; Charpentier, R.R.

2010-01-01

The U.S. Geological Survey procedure for the estimation of the general form of the parent distribution requires that the parameters of the log-geometric distribution be calculated and analyzed for the sensitivity of these parameters to different conditions. In this study, we derive the shape factor of a log-geometric distribution from the ratio of frequencies between adjacent bins. The shape factor has a log straight-line relationship with the ratio of frequencies. Additionally, the calculation equations of a ratio of the mean size to the lower size-class boundary are deduced. For a specific log-geometric distribution, we find that the ratio of the mean size to the lower size-class boundary is the same. We apply our analysis to simulations based on oil and gas pool distributions from four petroleum systems of Alberta, Canada and four generated distributions. Each petroleum system in Alberta has a different shape factor. Generally, the shape factors in the four petroleum systems stabilize with the increase of discovered pool numbers. For a log-geometric distribution, the shape factor becomes stable when discovered pool numbers exceed 50 and the shape factor is influenced by the exploration efficiency when the exploration efficiency is less than 1. The simulation results show that calculated shape factors increase with those of the parent distributions, and undiscovered oil and gas resources estimated through the log-geometric distribution extrapolation are smaller than the actual values. ?? 2010 International Association for Mathematical Geology.

Effect of particle size distribution on the separation efficiency in liquid chromatography.

PubMed

Horváth, Krisztián; Lukács, Diána; Sepsey, Annamária; Felinger, Attila

2014-09-26

In this work, the influence of the width of particle size distribution (PSD) on chromatographic efficiency is studied. The PSD is described by lognormal distribution. A theoretical framework is developed in order to calculate heights equivalent to a theoretical plate in case of different PSDs. Our calculations demonstrate and verify that wide particle size distributions have significant effect on the separation efficiency of molecules. The differences of fully porous and core-shell phases regarding the influence of width of PSD are presented and discussed. The efficiencies of bimodal phases were also calculated. The results showed that these packings do not have any advantage over unimodal phases. Copyright © 2014 Elsevier B.V. All rights reserved.

Robust organelle size extractions from elastic scattering measurements of single cells (Conference Presentation)

NASA Astrophysics Data System (ADS)

Cannaday, Ashley E.; Draham, Robert; Berger, Andrew J.

2016-04-01

The goal of this project is to estimate non-nuclear organelle size distributions in single cells by measuring angular scattering patterns and fitting them with Mie theory. Simulations have indicated that the large relative size distribution of organelles (mean:width≈2) leads to unstable Mie fits unless scattering is collected at polar angles less than 20 degrees. Our optical system has therefore been modified to collect angles down to 10 degrees. Initial validations will be performed on polystyrene bead populations whose size distributions resemble those of cell organelles. Unlike with the narrow bead distributions that are often used for calibration, we expect to see an order-of-magnitude improvement in the stability of the size estimates as the minimum angle decreases from 20 to 10 degrees. Scattering patterns will then be acquired and analyzed from single cells (EMT6 mouse cancer cells), both fixed and live, at multiple time points. Fixed cells, with no changes in organelle sizes over time, will be measured to determine the fluctuation level in estimated size distribution due to measurement imperfections alone. Subsequent measurements on live cells will determine whether there is a higher level of fluctuation that could be attributed to dynamic changes in organelle size. Studies on unperturbed cells are precursors to ones in which the effects of exogenous agents are monitored over time.

Structure analysis and size distribution of particulate matter from candles and kerosene combustion in burning chamber

NASA Astrophysics Data System (ADS)

Baitimirova, M.; Osite, A.; Katkevics, J.; Viksna, A.

2012-08-01

Burning of candles generates particulate matter of fine dimensions that produces poor indoor air quality, so it may cause harmful impact on human health. In this study solid aerosol particles of burning of candles of different composition and kerosene combustion were collected in a closed laboratory system. Present work describes particulate matter collection for structure analysis and the relationship between source and size distribution of particulate matter. The formation mechanism of particulate matter and their tendency to agglomerate also are described. Particles obtained from kerosene combustion have normal size distribution. Whereas, particles generated from the burning of stearin candles have distribution shifted towards finer particle size range. If an additive of stearin to paraffin candle is used, particle size distribution is also observed in range of towards finer particles. A tendency to form agglomerates in a short time is observed in case of particles obtained from kerosene combustion, while in case of particles obtained from burning of candles of different composition such a tendency is not observed. Particles from candles and kerosene combustion are Aitken and accumulation mode particles

Pore size distribution effect on rarefied gas transport in porous media

NASA Astrophysics Data System (ADS)

Hori, Takuma; Yoshimoto, Yuta; Takagi, Shu; Kinefuchi, Ikuya

2017-11-01

Gas transport phenomena in porous media are known to strongly influence the performance of devices such as gas separation membranes and fuel cells. Knudsen diffusion is a dominant flow regime in these devices since they have nanoscale pores. Many experiments have shown that these porous media have complex structures and pore size distributions; thus, the diffusion coefficient in these media cannot be easily assessed. Previous studies have reported that the characteristic pore diameter of porous media can be defined in light of the pore size distribution; however, tortuosity factor, which is necessary for the evaluation of diffusion coefficient, is still unknown without gas transport measurements or simulations. Thus, the relation between pore size distributions and tortuosity factors is required to obtain the gas transport properties. We perform numerical simulations to prove the relation between them. Porous media are numerically constructed while satisfying given pore size distributions. Then, the mean-square displacement simulation is performed to obtain the tortuosity factors of the constructed porous media.. This paper is based on results obtained from a project commissioned by the New Energy and Industrial Development Organization (NEDO).

Fabrication strategy for amphiphilic microcapsules with narrow size distribution by premix membrane emulsification.

PubMed

Wei, Yi; Wang, Yuxia; Wang, Lianyan; Hao, Dongxia; Ma, Guanghui

2011-10-15

Amphiphilic co-polymer, which can maintain the stability of proteins and increase the protein loading efficiency, is considered as an exploring-worthy biodegrade polymer for drug delivery. However, amphiphilic microcapsules prepared by conventional methods, such like mechanical stirring and spray-drying methods, exhibit broad size distributions due to its hydrophilic sequences, leading to poor reproducibility. In this study, we employed poly(monomethoxypoly ethylene glycol-co-D,L-lactide) (mPEG-PLA, PELA), one of common amphiphilic polymers, as model to focus on investigating the process parameters and mechanisms to prepare PELA microcapsules with narrow size distribution and regular sphericity by combining premix membrane emulsification and double emulsion technique. The coarse double emulsion with broad size distribution was repeatedly pressed through Shirasu Porous Glass (SPG) membrane with relatively high pressure to form the fine emulsion with narrow size distribution. Then, the microcapsules with narrow size distribution can be obtained by solvent extraction method. It was found that it was more difficult to obtain PELA microcapsules with narrow size distribution and smooth surface due to its amphiphilic property, compared with the cases of PLA and PLGA. The smooth surface morphology was found to be related to several factors including internal water phase with less volume, slower stirring rate during solidification and using ethyl acetate as oil phase. It was also found that mass ratio of hydrophilic mPEG, stabilizer PVA concentration in external water phase and transmembrane pressure played important role on the distribution of microcapsules size. The suitable preparation conditions were determined as follows: for the membrane with pore size of 2.8 μm, the mass ratio of PLA/mPEG was 19:1, volume ratio of W(1)/O was 1:10 and O/W(2) was 1:5, PVA concentration (w/v) was 1.0%, magnetic stirring rate during solidification was 60 rpm and 300 kPa was chosen as transmembrane pressure. There was a linear relationship between the diameter of microcapsules and the pore size of the membranes. Finally, by manipulating the process parameters, PELA microcapsules with narrow size distributions (coefficient of variation was less than 15%), smooth morphology and various sizes, were obtained. Most importantly, the key factors affecting fabrication have been revealed and mechanisms were illustrated in detail, which would shed light on the research of amphiphilic polymer formulation. Copyright © 2011 Elsevier B.V. All rights reserved.

Global distribution of clay-size minerals on land surface for biogeochemical and climatological studies

PubMed Central

Ito, Akihiko; Wagai, Rota

2017-01-01

Clay-size minerals play important roles in terrestrial biogeochemistry and atmospheric physics, but their data have been only partially compiled at global scale. We present a global dataset of clay-size minerals in the topsoil and subsoil at different spatial resolutions. The data of soil clay and its mineralogical composition were gathered through a literature survey and aggregated by soil orders of the Soil Taxonomy for each of the ten groups: gibbsite, kaolinite, illite/mica, smectite, vermiculite, chlorite, iron oxide, quartz, non-crystalline, and others. Using a global soil map, a global dataset of soil clay-size mineral distribution was developed at resolutions of 2' to 2° grid cells. The data uncertainty associated with data variability and assumption was evaluated using a Monte Carlo method, and validity of the clay-size mineral distribution obtained in this study was examined by comparing with other datasets. The global soil clay data offer spatially explicit studies on terrestrial biogeochemical cycles, dust emission to the atmosphere, and other interdisciplinary earth sciences. PMID:28829435

Techniques for determining partial size distribution of particulate matter: Laser diffraction versus electrical sensing zone

USDA-ARS?s Scientific Manuscript database

The study of health impacts, emission estimation of particulate matter (PM), and development of new control technologies require knowledge of PM characteristics. Among these PM characteristics, the particle size distribution (PSD) is perhaps the most important physical parameter governing particle b...

A Bayesian Nonparametric Meta-Analysis Model

ERIC Educational Resources Information Center

Karabatsos, George; Talbott, Elizabeth; Walker, Stephen G.

2015-01-01

In a meta-analysis, it is important to specify a model that adequately describes the effect-size distribution of the underlying population of studies. The conventional normal fixed-effect and normal random-effects models assume a normal effect-size population distribution, conditionally on parameters and covariates. For estimating the mean overall…

Biosimilar versus patented erythropoietins: learning from 5 years of European and Japanese experience.

PubMed

Bocquet, François; Paubel, Pascal; Fusier, Isabelle; Cordonnier, Anne-Laure; Sinègre, Martine; Le Pen, Claude

2015-02-01

Patent expiries on leading biologics are creating new momentum in the market for biosimilars (copies of off-patent biologics), paving the way for their development. However, little is known about the factors influencing the competition between biosimilars and their reference products (REF). The aim of this study was to analyse key global erythropoietin (EPO) markets and factors affecting biosimilar EPO (BIOSIM-EPO) uptakes, and to identify countries where BIOSIM-EPOs have gained significant market shares. Inclusion criteria for countries in the study were a biosimilar regulatory framework similar to the EU framework, and biological market value higher than US$2.5 billion. Factors evaluated included EPO market size, EPO retail/hospital distribution mix, national incentives to use biosimilars and BIOSIM-EPO/REF price differences. IMS Health provided EPO consumption in volumes, values, and EPO ex-manufacturer prices from 2007 to 2012. Japan: large-sized market, mixed retail/hospital distribution, no incentives, low BIOSIM-EPO uptake (6.8 % in 2012). France: large-sized market, dominant retail distribution, no incentives, low BIOSIM-EPO uptake (5.8 %). Spain and Italy: medium-sized market, dominant hospital distribution, no incentives, moderate BIOSIM-EPO uptakes (11.5 and 8.6 %). Germany: small-sized market, dominant retail distribution, presence of incentives, high BIOSIM-EPO uptake (30.4 %). UK: small-sized market, mixed retail/hospital distribution, no incentives, low BIOSIM-EPO uptake (2.0 %). BIOSIM-EPO/REF price differences play no role at a global level (-10.8 % in Germany and -26.9 % in Japan). EPO markets have proven to be highly country-specific. EPO market sizes, EPO retail/hospital distribution mixes and BIOSIM-EPO/REF price differences may not be determining factors of BIOSIM-EPO uptakes. Prescription and substitution incentives to use BIOSIM-EPO appear to be determining factors in Germany. The heterogeneity of national EPO markets makes it impossible to outline country profile types with significant BIOSIM-EPO penetrations.

Using sediment particle size distribution to evaluate sediment sources in the Tobacco Creek Watershed

NASA Astrophysics Data System (ADS)

Liu, Cenwei; Lobb, David; Li, Sheng; Owens, Philip; Kuzyk, ZouZou

2014-05-01

Lake Winnipeg has recently brought attention to the deteriorated water quality due to in part to nutrient and sediment input from agricultural land. Improving water quality in Lake Winnipeg requires the knowledge of the sediment sources within this ecosystem. There are a variety of environmental fingerprinting techniques have been successfully used in the assessment of sediment sources. In this study, we used particle size distribution to evaluate spatial and temporal variations of suspended sediment and potential sediment sources collected in the Tobacco Creek Watershed in Manitoba, Canada. The particle size distribution of suspended sediment can reflect the origin of sediment and processes during sediment transport, deposition and remobilization within the watershed. The objectives of this study were to quantify visually observed spatial and temporal changes in sediment particles, and to assess the sediment source using a rapid and cost-effective fingerprinting technique based on particle size distribution. The suspended sediment was collected by sediment traps twice a year during rainfall and snowmelt periods from 2009 to 2012. The potential sediment sources included the top soil of cultivated field, riparian area and entire profile from stream banks. Suspended sediment and soil samples were pre-wet with RO water and sieved through 600 μm sieve before analyzing. Particle size distribution of all samples was determined using a Malvern Mastersizer 2000S laser diffraction with the measurement range up to 600μm. Comparison of the results for different fractions of sediment showed significant difference in particle size distribution of suspended sediment between snowmelt and rainfall events. An important difference of particle size distribution also found between the cultivated soil and forest soil. This difference can be explained by different land uses which provided a distinct fingerprint of sediment. An overall improvement in water quality can be achieved by managing sediment according to the identified sediment sources in the watershed.

Changes in Arctic Sea Ice Thickness and Floe Size

NASA Astrophysics Data System (ADS)

Zhang, J.; Schweiger, A. J. B.; Stern, H. L., III; Steele, M.

2016-12-01

A thickness, floe size, and enthalpy distribution sea ice model was implemented into the Pan-arctic Ice-Ocean Modeling and Assimilation System (PIOMAS) by coupling the Zhang et al. [2015] sea ice floe size distribution (FSD) theory with the Thorndike et al. [1975] ice thickness distribution (ITD) theory in order to explicitly simulate multicategory FSD and ITD simultaneously. A range of ice thickness and floe size observations were used for model calibration and validation. The expanded, validated PIOMAS was used to study sea ice response to atmospheric and oceanic changes in the Arctic, focusing on the interannual variability and trends of ice thickness and floe size over the period 1979-2015. It is found that over the study period both ice thickness and floe size have been decreasing steadily in the Arctic. The simulated ice thickness shows considerable spatiotemporal variability in recent years. As the ice cover becomes thinner and weaker, the model simulates an increasing number of small floes (at the low end of the FSD), which affects sea ice properties, particularly in the marginal ice zone.

Optical extinction dependence on wavelength and size distribution of airborne dust

NASA Astrophysics Data System (ADS)

Pangle, Garrett E.; Hook, D. A.; Long, Brandon J. N.; Philbrick, C. R.; Hallen, Hans D.

2013-05-01

The optical scattering from laser beams propagating through atmospheric aerosols has been shown to be very useful in describing air pollution aerosol properties. This research explores and extends that capability to particulate matter. The optical properties of Arizona Road Dust (ARD) samples are measured in a chamber that simulates the particle dispersal of dust aerosols in the atmospheric environment. Visible, near infrared, and long wave infrared lasers are used. Optical scattering measurements show the expected dependence of laser wavelength and particle size on the extinction of laser beams. The extinction at long wavelengths demonstrates reduced scattering, but chemical absorption of dust species must be considered. The extinction and depolarization of laser wavelengths interacting with several size cuts of ARD are examined. The measurements include studies of different size distributions, and their evolution over time is recorded by an Aerodynamic Particle Sizer. We analyze the size-dependent extinction and depolarization of ARD. We present a method of predicting extinction for an arbitrary ARD size distribution. These studies provide new insights for understanding the optical propagation of laser beams through airborne particulate matter.

Cell-size distribution in epithelial tissue formation and homeostasis

PubMed Central

Primo, Luca; Celani, Antonio

2017-01-01

How cell growth and proliferation are orchestrated in living tissues to achieve a given biological function is a central problem in biology. During development, tissue regeneration and homeostasis, cell proliferation must be coordinated by spatial cues in order for cells to attain the correct size and shape. Biological tissues also feature a notable homogeneity of cell size, which, in specific cases, represents a physiological need. Here, we study the temporal evolution of the cell-size distribution by applying the theory of kinetic fragmentation to tissue development and homeostasis. Our theory predicts self-similar probability density function (PDF) of cell size and explains how division times and redistribution ensure cell size homogeneity across the tissue. Theoretical predictions and numerical simulations of confluent non-homeostatic tissue cultures show that cell size distribution is self-similar. Our experimental data confirm predictions and reveal that, as assumed in the theory, cell division times scale like a power-law of the cell size. We find that in homeostatic conditions there is a stationary distribution with lognormal tails, consistently with our experimental data. Our theoretical predictions and numerical simulations show that the shape of the PDF depends on how the space inherited by apoptotic cells is redistributed and that apoptotic cell rates might also depend on size. PMID:28330988

Cell-size distribution in epithelial tissue formation and homeostasis.

PubMed

Puliafito, Alberto; Primo, Luca; Celani, Antonio

2017-03-01

How cell growth and proliferation are orchestrated in living tissues to achieve a given biological function is a central problem in biology. During development, tissue regeneration and homeostasis, cell proliferation must be coordinated by spatial cues in order for cells to attain the correct size and shape. Biological tissues also feature a notable homogeneity of cell size, which, in specific cases, represents a physiological need. Here, we study the temporal evolution of the cell-size distribution by applying the theory of kinetic fragmentation to tissue development and homeostasis. Our theory predicts self-similar probability density function (PDF) of cell size and explains how division times and redistribution ensure cell size homogeneity across the tissue. Theoretical predictions and numerical simulations of confluent non-homeostatic tissue cultures show that cell size distribution is self-similar. Our experimental data confirm predictions and reveal that, as assumed in the theory, cell division times scale like a power-law of the cell size. We find that in homeostatic conditions there is a stationary distribution with lognormal tails, consistently with our experimental data. Our theoretical predictions and numerical simulations show that the shape of the PDF depends on how the space inherited by apoptotic cells is redistributed and that apoptotic cell rates might also depend on size. © 2017 The Author(s).

Size Effect on Specific Energy Distribution in Particle Comminution

NASA Astrophysics Data System (ADS)

Xu, Yongfu; Wang, Yidong

A theoretical study is made to derive an energy distribution equation for the size reduction process from the fractal model for the particle comminution. Fractal model is employed as a valid measure of the self-similar size distribution of comminution daughter products. The tensile strength of particles varies with particle size in the manner of a power function law. The energy consumption for comminuting single particle is found to be proportional to the 5(D-3)/3rd order of the particle size, D being the fractal dimension of particle comminution daughter. The Weibull statistics is applied to describe the relationship between the breakage probability and specific energy of particle comminution. A simple equation is derived for the breakage probability of particles in view of the dependence of fracture energy on particle size. The calculated exponents and Weibull coefficients are generally in conformity with published data for fracture of particles.

Influence of the operating parameters of the needle-plate electrostatic precipitator on the size distribution of aerosol particles

NASA Astrophysics Data System (ADS)

Arsenov, P. V.; Efimov, A. A.; Protas, N. V.; Ivanov, V. V.

2018-03-01

The influence of the operating parameters (voltage and aerosol flow rate) of the needle-plate electrostatic precipitator (NP-ESP) on the size distribution of aerosol particles has been studied. The NP-ESP consists of a needle and a plate located in the plastic tube used as aerosol transport duct. Alumina (Al2O3) particles were synthesized by a spark discharge and used as a test aerosol with a size range from 25 to 500 nm. It was found that the average particle size decreases with increasing voltage and aerosol flow rate through the NP-ESP. It was also found that the average particle size can be reduced more than in 2 times in comparison with the initial size distribution at a voltage and aerosol flow rate through the NP-ESP are equal to 16 kV and 250 l/min, respectively.

An Investigation of Aerosol Measurements from the Halogen Occultation Experiment: Validation, Size Distributions, Composition, and Relation to Other Chemical Species

NASA Technical Reports Server (NTRS)

Deshler, Terry; Hervig, Mark E.

1998-01-01

The efforts envisioned within the original proposal (accepted February 1994) and the extension of this proposal (accepted February 1997) included measurement validations, the retrieval of aerosol size distributions and distribution moments, aerosol correction studies, and investigations of polar stratospheric clouds. A majority of the results from this grant have been published. The principal results from this grant are discussed.

Discontinuous pore fluid distribution under microgravity--KC-135 flight investigations

NASA Technical Reports Server (NTRS)

Reddi, Lakshmi N.; Xiao, Ming; Steinberg, Susan L.

2005-01-01

Designing a reliable plant growth system for crop production in space requires the understanding of pore fluid distribution in porous media under microgravity. The objective of this experimental investigation, which was conducted aboard NASA KC-135 reduced gravity flight, is to study possible particle separation and the distribution of discontinuous wetting fluid in porous media under microgravity. KC-135 aircraft provided gravity conditions of 1, 1.8, and 10(-2) g. Glass beads of a known size distribution were used as porous media; and Hexadecane, a petroleum compound immiscible with and lighter than water, was used as wetting fluid at residual saturation. Nitrogen freezer was used to solidify the discontinuous Hexadecane ganglia in glass beads to preserve the ganglia size changes during different gravity conditions, so that the blob-size distributions (BSDs) could be measured after flight. It was concluded from this study that microgravity has little effect on the size distribution of pore fluid blobs corresponding to residual saturation of wetting fluids in porous media. The blobs showed no noticeable breakup or coalescence during microgravity. However, based on the increase in bulk volume of samples due to particle separation under microgravity, groups of particles, within which pore fluid blobs were encapsulated, appeared to have rearranged themselves under microgravity.

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.

The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately andin situusing crystallographic methods owing to the small size of such particles (<5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormal size distribution.more » The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. This work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.« less

Body frame size in school children is related to the amount of adipose tissue in different depots but not to adipose distribution.

PubMed

Guzmán-de la Garza, Francisco J; González Ayala, Alejandra E; Gómez Nava, Marisol; Martínez Monsiváis, Leislie I; Salinas Martínez, Ana M; Ramírez López, Erik; Mathiew Quirós, Alvaro; Garcia Quintanilla, Francisco

2017-09-10

The main aim of this study was to test the hypothesis that body frame size is related to the amount of fat in different adipose tissue depots and to fat distribution in schoolchildren. Children aged between 5 and 10 years were included in this cross-sectional study (n = 565). Body frame size, adiposity markers (anthropometric, skinfolds thickness, and ultrasound measures), and fat distribution indices were analyzed. Correlation coefficients adjusted by reliability were estimated and analyzed by sex; the significance of the difference between two correlation coefficients was assessed using the Fisher z-transformation. The sample included primarily urban children; 58.6% were normal weight, 16.1% overweight, 19.6% obese, and the rest were underweight. Markers of subcutaneous adiposity, fat mass and fat-free mass, and preperitoneal adiposity showed higher and significant correlations with the sum of the biacromial + bitrochanteric diameter than with the elbow diameter, regardless of sex. The fat distribution conicity index presented significant but weak correlations; and visceral adipose tissue, hepatic steatosis, and the waist-for-hip ratio were not significantly correlated with body frame size measures. Body frame size in school children was related to the amount of adipose tissue in different depots, but not adipose distribution. More studies are needed to confirm this relationship and its importance to predict changes in visceral fat deposition during growth. © 2017 Wiley Periodicals, Inc.

Development of Portable Aerosol Mobility Spectrometer for Personal and Mobile Aerosol Measurement

PubMed Central

Kulkarni, Pramod; Qi, Chaolong; Fukushima, Nobuhiko

2017-01-01

We describe development of a Portable Aerosol Mobility Spectrometer (PAMS) for size distribution measurement of submicrometer aerosol. The spectrometer is designed for use in personal or mobile aerosol characterization studies and measures approximately 22.5 × 22.5 × 15 cm and weighs about 4.5 kg including the battery. PAMS uses electrical mobility technique to measure number-weighted particle size distribution of aerosol in the 10–855 nm range. Aerosol particles are electrically charged using a dual-corona bipolar corona charger, followed by classification in a cylindrical miniature differential mobility analyzer. A condensation particle counter is used to detect and count particles. The mobility classifier was operated at an aerosol flow rate of 0.05 L/min, and at two different user-selectable sheath flows of 0.2 L/min (for wider size range 15–855 nm) and 0.4 L/min (for higher size resolution over the size range of 10.6–436 nm). The instrument was operated in voltage stepping mode to retrieve the size distribution, which took approximately 1–2 minutes, depending on the configuration. Sizing accuracy and resolution were probed and found to be within the 25% limit of NIOSH criterion for direct-reading instruments (NIOSH 2012). Comparison of size distribution measurements from PAMS and other commercial mobility spectrometers showed good agreement. The instrument offers unique measurement capability for on-person or mobile size distribution measurements of ultrafine and nanoparticle aerosol. PMID:28413241

Study on Sumbawa gold ore liberation using rod mill: effect of rod-number and rotational speed on particle size distribution

NASA Astrophysics Data System (ADS)

Prasetya, A.; Mawadati, A.; Putri, A. M. R.; Petrus, H. T. B. M.

2018-01-01

Comminution is one of crucial steps in gold ore processing used to liberate the valuable minerals from gaunge mineral. This research is done to find the particle size distribution of gold ore after it has been treated through the comminution process in a rod mill with various number of rod and rotational speed that will results in one optimum milling condition. For the initial step, Sumbawa gold ore was crushed and then sieved to pass the 2.5 mesh and retained on the 5 mesh (this condition was taken to mimic real application in artisanal gold mining). Inserting the prepared sample into the rod mill, the observation on effect of rod-number and rotational speed was then conducted by variating the rod number of 7 and 10 while the rotational speed was varied from 60, 85, and 110 rpm. In order to be able to provide estimation on particle distribution of every condition, the comminution kinetic was applied by taking sample at 15, 30, 60, and 120 minutes for size distribution analysis. The change of particle distribution of top and bottom product as time series was then treated using Rosin-Rammler distribution equation. The result shows that the homogenity of particle size and particle size distribution is affected by rod-number and rotational speed. The particle size distribution is more homogeneous by increasing of milling time, regardless of rod-number and rotational speed. Mean size of particles do not change significantly after 60 minutes milling time. Experimental results showed that the optimum condition was achieved at rotational speed of 85 rpm, using rod-number of 7.

Effects of Surface and Subsurface Bed Material Composition on Gravel Transport and Flow Competence Relations—Possibilities for Prediction

NASA Astrophysics Data System (ADS)

Bunte, K.; Abt, S. R.; Swingle, K. W.; Cenderelli, D. A.; Gaeuman, D. A.

2014-12-01

Bedload transport and flow competence relations are difficult to predict in coarse-bedded steep streams where widely differing sediment supply, bed stability, and complex flow hydraulics greatly affect amounts and sizes of transported gravel particles. This study explains how properties of bed material surface and subsurface size distributions are directly related to gravel transport and may be used for prediction of gravel transport and flow competence relations. Gravel transport, flow competence, and bed material size were measured in step-pool and plane-bed streams. Power functions were fitted to gravel transport QB=aQb and flow competence Dmax=cQd relations; Q is water discharge. Frequency distributions of surface FDsurf and subsurface FDsub bed material were likewise described by power functions FDsurf=hD j and FDsub=kDm fitted over six 0.5-phi size classes within 4 to 22.4 mm. Those gravel sizes are typically mobile even in moderate floods. Study results show that steeper subsurface bed material size distributions lead to steeper gravel transport and flow competence relations, whereas larger amounts of sediment contained in those 6 size bedmaterial classes (larger h and k) flatten the relations. Similarly, steeper surface size distributions decrease the coefficients of the gravel transport and flow competence relations, whereas larger amounts of sediment within the six bed material classes increase the intercepts of gravel transport and flow competence relations. Those relations are likely causative in streams where bedload stems almost entirely from the channel bed as opposed to direct (unworked) contributions from hillslopes and tributaries. The exponent of the subsurface bed material distribution m predicted the gravel transport exponent b with r2 near 0.7 and flow competence exponent d with r2 near 0.5. The intercept of bed surface distributions h increased the intercept a of gravel transport and c of the flow competence relations with r2 near 0.6.

The effect of voxel size on dose distribution in Varian Clinac iX 6 MV photon beam using Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Yani, Sitti; Dirgayussa, I. Gde E.; Rhani, Moh. Fadhillah; Haryanto, Freddy; Arif, Idam

2015-09-01

Recently, Monte Carlo (MC) calculation method has reported as the most accurate method of predicting dose distributions in radiotherapy. The MC code system (especially DOSXYZnrc) has been used to investigate the different voxel (volume elements) sizes effect on the accuracy of dose distributions. To investigate this effect on dosimetry parameters, calculations were made with three different voxel sizes. The effects were investigated with dose distribution calculations for seven voxel sizes: 1 × 1 × 0.1 cm3, 1 × 1 × 0.5 cm3, and 1 × 1 × 0.8 cm3. The 1 × 109 histories were simulated in order to get statistical uncertainties of 2%. This simulation takes about 9-10 hours to complete. Measurements are made with field sizes 10 × 10 cm2 for the 6 MV photon beams with Gaussian intensity distribution FWHM 0.1 cm and SSD 100.1 cm. MC simulated and measured dose distributions in a water phantom. The output of this simulation i.e. the percent depth dose and dose profile in dmax from the three sets of calculations are presented and comparisons are made with the experiment data from TTSH (Tan Tock Seng Hospital, Singapore) in 0-5 cm depth. Dose that scored in voxels is a volume averaged estimate of the dose at the center of a voxel. The results in this study show that the difference between Monte Carlo simulation and experiment data depend on the voxel size both for percent depth dose (PDD) and profile dose. PDD scan on Z axis (depth) of water phantom, the big difference obtain in the voxel size 1 × 1 × 0.8 cm3 about 17%. In this study, the profile dose focused on high gradient dose area. Profile dose scan on Y axis and the big difference get in the voxel size 1 × 1 × 0.1 cm3 about 12%. This study demonstrated that the arrange voxel in Monte Carlo simulation becomes important.

[Studies on the size distribution of airborne microbes at home in Beijing].

PubMed

Fang, Zhi-Guo; Sun, Ping; Ouyang, Zhi-Yun; Liu, Peng; Sun, Li; Wang, Xiao-Yong

2013-07-01

The effect of airborne microbes on human health not only depends on their compositions (genera and species), but also on their concentrations and sizes. Moreover, there are different mechanisms of airborne microbes of different sizes with different effects on human health. The size distributions and median diameters were investigated in detail with imitated six-stage Andersen sampler in 31 selected family homes with children in Beijing. Results showed that there was similar distribution characteristics of airborne microbes in different home environment, different season, different child's sex, and different apartment's architecture, but different distribution characteristics between airborne bacteria and fungi were observed in family homes in Beijing. In general, although airborne bacteria and fungi were plotted with normal logarithmic distribution, the particle percentage of airborne bacteria increased gradually from stage 1 (> 8.2 microm) to stage 5 (1.0-2.0 microm), and then decreased dramatically in stage 6 (< 1.0 microm), the percentage of airborne fungi increased gradually from stage 1 to stage 4 (2.0-3.5 microm), and then decreased dramatically from stage 4 to stage 6. The size distributions of dominant fungi were different in different fungal genera. Cladosporium, Penicillium and Aspergillus were recorded with normal logarithmic distribution, with the highest percentage detected in stage 4, and Alternaria were observed with skew distribution, with the highest percentage detected in stage 2 (5.0-10.4 microm). Finally, the median diameters of airborne bacteria were larger than those of airborne fungi, and the lowest median diameter of airborne bacteria and fungi was found in winter, while there were no significant variations of airborne bacterial and fungal median diameters in spring, summer and autumn in a year in this study.

The influence of wildfires on aerosol size distributions in rural areas.

PubMed

Alonso-Blanco, E; Calvo, A I; Fraile, R; Castro, A

2012-01-01

The number of particles and their size distributions were measured in a rural area, during the summer, using a PCASP-X. The aim was to study the influence of wildfires on particle size distributions. The comparative studies carried out reveal an average increase of around ten times in the number of particles in the fine mode, especially in sizes between 0.10 and 0.14 μm, where the increase is of nearly 20 times. An analysis carried out at three different points in time--before, during, and after the passing of the smoke plume from the wildfires--shows that the mean geometric diameter of the fine mode in the measurements affected by the fire is smaller than the one obtained in the measurements carried out immediately before and after (0.14 μm) and presents average values of 0.11 μm.

The Influence of Wildfires on Aerosol Size Distributions in Rural Areas

PubMed Central

Alonso-Blanco, E.; Calvo, A. I.; Fraile, R.; Castro, A.

2012-01-01

The number of particles and their size distributions were measured in a rural area, during the summer, using a PCASP-X. The aim was to study the influence of wildfires on particle size distributions. The comparative studies carried out reveal an average increase of around ten times in the number of particles in the fine mode, especially in sizes between 0.10 and 0.14 μm, where the increase is of nearly 20 times. An analysis carried out at three different points in time—before, during, and after the passing of the smoke plume from the wildfires—shows that the mean geometric diameter of the fine mode in the measurements affected by the fire is smaller than the one obtained in the measurements carried out immediately before and after (0.14 μm) and presents average values of 0.11 μm. PMID:22629191

A case study of highly time-resolved evolution of aerosol chemical composition and optical properties during severe haze pollution in Shanghai, China

NASA Astrophysics Data System (ADS)

Zhu, W.; Cheng, Z.; Lou, S.

2017-12-01

Despite of extensive efforts into characterization of the sources in severe haze pollution periods in the megacity of Shanghai, the study of aerosol composition, mass-size distribution and optical properties to PM1 in the pollution periods remain poorly understood. Here we conducted a 47days real-time measurement of submicron aerosol (PM1) composition and size distribution by a High-Resolution Time-of-Flight Aerosol Mass spectrometer (HR-TOF-AMS), particle light scattering by a Cavity Attenuated Phase Shift ALBedo monitor (CAPS-ALB) and Photoacoustic Extinctionmeter (PAX) in Shanghai, China, from November 28, 2016 to January 12, 2017. The average PM1 concentration was 85.9(±14.7) μg/m3 during the pollution period, which was nearly 4 times higher than that of clean period. Increased scattering coefficient during EP was associated with higher secondary inorganic aerosols and organics. We also observed organics mass size distribution for different pollution extents showing different distribution characteristics. There were no obvious differences for ammonium nitrate and ammonium sulfate among the pollution periods, which represented single peak distributions, and peaks ranged at 650-700nm and 700nm, respectively. A strong relationship can be expected between PM1 compounds mass concentration size distribution and scattering coefficient, suggesting that chemical composition, size distribution of the particles and their variations could also contribute to the extinction coefficients. Organics and secondary inorganic species to particle light scattering were quantified. The results showed that organics and ammonium nitrate were the largest contribution to scattering coefficients of PM1. The contribution of (NH4)2SO4 to the light scattering exceeded that of NH4NO3 during clean period due to the enhanced sulfate concentrations. Our results elucidate substantial changes of aerosol composition, formation mechanisms, size distribution and optical properties due to local emissions, region transports and meteorological changes in the pollution period.

Effects of Vertex Activity and Self-organized Criticality Behavior on a Weighted Evolving Network

NASA Astrophysics Data System (ADS)

Zhang, Gui-Qing; Yang, Qiu-Ying; Chen, Tian-Lun

2008-08-01

Effects of vertex activity have been analyzed on a weighted evolving network. The network is characterized by the probability distribution of vertex strength, each edge weight and evolution of the strength of vertices with different vertex activities. The model exhibits self-organized criticality behavior. The probability distribution of avalanche size for different network sizes is also shown. In addition, there is a power law relation between the size and the duration of an avalanche and the average of avalanche size has been studied for different vertex activities.

Box-Cox transformation of firm size data in statistical analysis

NASA Astrophysics Data System (ADS)

Chen, Ting Ting; Takaishi, Tetsuya

2014-03-01

Firm size data usually do not show the normality that is often assumed in statistical analysis such as regression analysis. In this study we focus on two firm size data: the number of employees and sale. Those data deviate considerably from a normal distribution. To improve the normality of those data we transform them by the Box-Cox transformation with appropriate parameters. The Box-Cox transformation parameters are determined so that the transformed data best show the kurtosis of a normal distribution. It is found that the two firm size data transformed by the Box-Cox transformation show strong linearity. This indicates that the number of employees and sale have the similar property as a firm size indicator. The Box-Cox parameters obtained for the firm size data are found to be very close to zero. In this case the Box-Cox transformations are approximately a log-transformation. This suggests that the firm size data we used are approximately log-normal distributions.

Study of vesicle size distribution dependence on pH value based on nanopore resistive pulse method

NASA Astrophysics Data System (ADS)

Lin, Yuqing; Rudzevich, Yauheni; Wearne, Adam; Lumpkin, Daniel; Morales, Joselyn; Nemec, Kathleen; Tatulian, Suren; Lupan, Oleg; Chow, Lee

2013-03-01

Vesicles are low-micron to sub-micron spheres formed by a lipid bilayer shell and serve as potential vehicles for drug delivery. The size of vesicle is proposed to be one of the instrumental variables affecting delivery efficiency since the size is correlated to factors like circulation and residence time in blood, the rate for cell endocytosis, and efficiency in cell targeting. In this work, we demonstrate accessible and reliable detection and size distribution measurement employing a glass nanopore device based on the resistive pulse method. This novel method enables us to investigate the size distribution dependence of pH difference across the membrane of vesicles with very small sample volume and rapid speed. This provides useful information for optimizing the efficiency of drug delivery in a pH sensitive environment.

A numerical determination of the evolution of cloud drop spectra due to condensation on natural aerosol particles

NASA Technical Reports Server (NTRS)

Lee, I. Y.; Haenel, G.; Pruppacher, H. R.

1980-01-01

The time variation in size of aerosol particles growing by condensation is studied numerically by means of an air parcel model which allows entrainment of air and aerosol particles. Particles of four types of aerosols typically occurring in atmospheric air masses were considered. The present model circumvents any assumption about the size distribution and chemical composition of the aerosol particles by basing the aerosol particle growth on actually observed size distributions and on observed amounts of water taken up under equilibrium by a deposit of the aerosol particles. Characteristic differences in the drop size distribution, liquid water content and supersaturation were found for the clouds which evolved from the four aerosol types considered.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.

2004-01-01

Cloud microphysics are inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles (i.e., pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail). Each type is described by a special size distribution function containing many categories (i.e. 33 bins). Atmospheric aerosols are also described using number density size-distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep cloud systems in the west Pacific warm pool region, in the sub-tropics (Florida) and in the mid-latitude using identical thermodynamic conditions but with different concentrations of CCN: a low 'clean' concentration and a high 'dirty' concentration.

Comparison of aerosol volume size distributions between column and surface measurements downwind of Seoul, Korea

NASA Astrophysics Data System (ADS)

Park, J. S.; Choi, Y.; Ghim, Y. S.

2015-12-01

The aerosol volume size distribution is one of the most important parameters in retrieving aerosol optical properties and studying radiative forcing. The column-integrated aerosol volume size distribution for AERONET was obtained from inversion product level 1.5 (22 bins between 0.1 and 30 μm in diameter) from the measurements of CIMEL sunphotometer (CE-318); that for SKYNET was obtained using skyrad.pack V5 (20 bins, 0.02-33 μm) from the measurements of PREDE skyradiometer (POM-02). The aerosol volume size distribution at the surface was measured using a wide range aerosol spectrometer system consisting of a scanning mobility particle scanner (Grimm, Model 5.419; 89 bins, 0.005-0.35 μm) and an optical particle counter (Grimm, Model 1.109; 31 bins, 0.27-34 μm). The measurement was conducted in Yongin, downwind of Seoul, Korea, from April 30 to June 27, 2015. The measurement site is located on the rooftop of a five-story building on the hill (37.34°N, 127.27°E, 167 m above sea level) in the global campus of Hankuk University of Foreign Studies. To investigate the discrepancy in effective diameter and fine mode volume fraction, we compared the volume size distributions when the measurement time coincided within 5 minutes because the measurement intervals were different between instruments.

Modeling and Scaling of the Distribution of Trade Avalanches in a STOCK Market

NASA Astrophysics Data System (ADS)

Kim, Hyun-Joo

We study the trading activity in the Korea Stock Exchange by considering trade avalanches. A series of successive trading with small trade time interval is regarded as a trade avalanche of which the size s is defined as the number of trade in a series of successive trades. We measure the distribution of trade avalanches sizes P(s) and find that it follows the power-law behavior P(s) ~ s-α with the exponent α ≈ 2 for two stocks with the largest number of trades. A simple stochastic model which describes the power-law behavior of the distribution of trade avalanche size is introduced. In the model it is assumed that the some trades induce the accompanying trades, which results in the trade avalanches and we find that the distribution of the trade avalanche size also follows power-law behavior with the exponent α ≈ 2.

How the Assumed Size Distribution of Dust Minerals Affects the Predicted Ice Forming Nuclei

NASA Technical Reports Server (NTRS)

Perlwitz, Jan P.; Fridlind, Ann M.; Garcia-Pando, Carlos Perez; Miller, Ron L.; Knopf, Daniel A.

2015-01-01

The formation of ice in clouds depends on the availability of ice forming nuclei (IFN). Dust aerosol particles are considered the most important source of IFN at a global scale. Recent laboratory studies have demonstrated that the mineral feldspar provides the most efficient dust IFN for immersion freezing and together with kaolinite for deposition ice nucleation, and that the phyllosilicates illite and montmorillonite (a member of the smectite group) are of secondary importance.A few studies have applied global models that simulate mineral specific dust to predict the number and geographical distribution of IFN. These studies have been based on the simple assumption that the mineral composition of soil as provided in data sets from the literature translates directly into the mineral composition of the dust aerosols. However, these tables are based on measurements of wet-sieved soil where dust aggregates are destroyed to a large degree. In consequence, the size distribution of dust is shifted to smaller sizes, and phyllosilicates like illite, kaolinite, and smectite are only found in the size range 2 m. In contrast, in measurements of the mineral composition of dust aerosols, the largest mass fraction of these phyllosilicates is found in the size range 2 m as part of dust aggregates. Conversely, the mass fraction of feldspar is smaller in this size range, varying with the geographical location. This may have a significant effect on the predicted IFN number and its geographical distribution.An improved mineral specific dust aerosol module has been recently implemented in the NASA GISS Earth System ModelE2. The dust module takes into consideration the disaggregated state of wet-sieved soil, on which the tables of soil mineral fractions are based. To simulate the atmospheric cycle of the minerals, the mass size distribution of each mineral in aggregates that are emitted from undispersed parent soil is reconstructed. In the current study, we test the null-hypothesis that simulating the presence of a large mass fraction of phyllosilicates in dust aerosols in the size range 2 m, in comparison to a simple model assumption where this is neglected, does not yield a significant effect on the magnitude and geographical distribution of the predicted IFN number. Results from sensitivity experiments are presented as well.

Evaluation of the degree of mixing of combinations of dry syrup, powder, and fine granule products in consideration of particle size distribution using near infrared spectrometry.

PubMed

Yamamoto, Yoshihisa; Suzuki, Toyofumi; Matsumoto, Mika; Ohtani, Michiteru; Hayano, Shuichi; Fukami, Toshiro; Tomono, Kazuo

2012-01-01

We used near infrared (NIR) spectroscopy to evaluate the degree of mixing of blended dry syrup (DS) products whose particle sizes are not specified in the Revised 16th Edition of the Japanese Pharmacopoeia, and also evaluated the degree of mixing when powder products or fine granule products were added to DS products. The data obtained were used to investigate the relationship between the particle size distributions of the products studied and the degree of mixing. We found that the particle size distribution characteristics of the 15 DS products studied can be broadly classified into 5 types. Combinations of frequently prescribed products were selected to represent 4 of the 5 particle size distribution types and were blended with a mortar and pestle. The coefficient of variation (CV) decreased as the percent mass of Asverin® Dry Syrup 2% (Asverin-DS) increased in blends of Periactin® Powder 1% (Periactin) and Asverin-DS, indicating an improved degree of mixing (uniformity). In contrast, in blends of Periactin and Mucodyne® DS 33.3%, mixing a combination at a 1:1 mass ratio 40 times resulted in a CV of 20%. Other mixing frequencies and mass ratios resulted in a CV by 50% to 70%, indicating a very poor degree of mixing (poor uniformity). These results suggest that when combining different DSs, or a DS with a powder or fine granule product, the blending obtained with a mortar and pestle improves as the particle size distributions of the components approach each other and as the ranges of the distributions narrow.

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

DOE PAGES

Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.; ...

2017-04-13

The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately and in situ using crystallographic methods owing to the small size of such particles (<5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormalmore » size distribution. The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. As a result, this work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.« less

Modelling and validation of particle size distributions of supported nanoparticles using the pair distribution function technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.

The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately and in situ using crystallographic methods owing to the small size of such particles (<5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormalmore » size distribution. The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. As a result, this work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.« less

Accounting for parameter uncertainty in the definition of parametric distributions used to describe individual patient variation in health economic models.

PubMed

Degeling, Koen; IJzerman, Maarten J; Koopman, Miriam; Koffijberg, Hendrik

2017-12-15

Parametric distributions based on individual patient data can be used to represent both stochastic and parameter uncertainty. Although general guidance is available on how parameter uncertainty should be accounted for in probabilistic sensitivity analysis, there is no comprehensive guidance on reflecting parameter uncertainty in the (correlated) parameters of distributions used to represent stochastic uncertainty in patient-level models. This study aims to provide this guidance by proposing appropriate methods and illustrating the impact of this uncertainty on modeling outcomes. Two approaches, 1) using non-parametric bootstrapping and 2) using multivariate Normal distributions, were applied in a simulation and case study. The approaches were compared based on point-estimates and distributions of time-to-event and health economic outcomes. To assess sample size impact on the uncertainty in these outcomes, sample size was varied in the simulation study and subgroup analyses were performed for the case-study. Accounting for parameter uncertainty in distributions that reflect stochastic uncertainty substantially increased the uncertainty surrounding health economic outcomes, illustrated by larger confidence ellipses surrounding the cost-effectiveness point-estimates and different cost-effectiveness acceptability curves. Although both approaches performed similar for larger sample sizes (i.e. n = 500), the second approach was more sensitive to extreme values for small sample sizes (i.e. n = 25), yielding infeasible modeling outcomes. Modelers should be aware that parameter uncertainty in distributions used to describe stochastic uncertainty needs to be reflected in probabilistic sensitivity analysis, as it could substantially impact the total amount of uncertainty surrounding health economic outcomes. If feasible, the bootstrap approach is recommended to account for this uncertainty.

A generalized threshold model for computing bed load grain size distribution

NASA Astrophysics Data System (ADS)

Recking, Alain

2016-12-01

For morphodynamic studies, it is important to compute not only the transported volumes of bed load, but also the size of the transported material. A few bed load equations compute fractional transport (i.e., both the volume and grain size distribution), but many equations compute only the bulk transport (a volume) with no consideration of the transported grain sizes. To fill this gap, a method is proposed to compute the bed load grain size distribution separately to the bed load flux. The method is called the Generalized Threshold Model (GTM), because it extends the flow competence method for threshold of motion of the largest transported grain size to the full bed surface grain size distribution. This was achieved by replacing dimensional diameters with their size indices in the standard hiding function, which offers a useful framework for computation, carried out for each indices considered in the range [1, 100]. New functions are also proposed to account for partial transport. The method is very simple to implement and is sufficiently flexible to be tested in many environments. In addition to being a good complement to standard bulk bed load equations, it could also serve as a framework to assist in analyzing the physics of bed load transport in future research.

Tuning Aerosol Particle Size Distribution of Metered Dose Inhalers Using Cosolvents and Surfactants

PubMed Central

Saleem, Imran Y.; Smyth, Hugh D. C.

2013-01-01

Objectives. The purpose of these studies was to understand the influence of cosolvent and surfactant contributions to particle size distributions emitted from solution metered dose inhalers (pMDIs) based on the propellant HFA 227. Methods. Two sets of formulations were prepared: (a) pMDIs-HFA 227 containing cosolvent (5–15% w/w ethanol) with constant surfactant (pluronic) concentration and (b) pMDIs-HFA 227 containing surfactant (0–5.45% w/w pluronic) with constant cosolvent concentration. Particle size distributions emitted from these pMDIs were analyzed using aerodynamic characterization (inertial impaction) and laser diffraction methods. Results. Both cosolvent and surfactant concentrations were positively correlated with median particle sizes; that is, drug particle size increased with increasing ethanol and pluronic concentrations. However, evaluation of particle size distributions showed that cosolvent caused reduction in the fine particle mode magnitude while the surfactant caused a shift in the mode position. These findings highlight the different mechanisms by which these components influence droplet formation and demonstrate the ability to utilize the different effects in formulations of pMDI-HFA 227 for independently modulating particle sizes in the respirable region. Conclusion. Potentially, the formulation design window generated using these excipients in combination could be used to match the particle size output of reformulated products to preexisting pMDI products. PMID:23984381

A note on power and sample size calculations for the Kruskal-Wallis test for ordered categorical data.

PubMed

Fan, Chunpeng; Zhang, Donghui

2012-01-01

Although the Kruskal-Wallis test has been widely used to analyze ordered categorical data, power and sample size methods for this test have been investigated to a much lesser extent when the underlying multinomial distributions are unknown. This article generalizes the power and sample size procedures proposed by Fan et al. ( 2011 ) for continuous data to ordered categorical data, when estimates from a pilot study are used in the place of knowledge of the true underlying distribution. Simulations show that the proposed power and sample size formulas perform well. A myelin oligodendrocyte glycoprotein (MOG) induced experimental autoimmunce encephalomyelitis (EAE) mouse study is used to demonstrate the application of the methods.

Vesicle sizing by static light scattering: a Fourier cosine transform approach

NASA Astrophysics Data System (ADS)

Wang, Jianhong; Hallett, F. Ross

1995-08-01

A Fourier cosine transform method, based on the Rayleigh-Gans-Debye thin-shell approximation, was developed to retrieve vesicle size distribution directly from the angular dependence of scattered light intensity. Its feasibility for real vesicles was partially tested on scattering data generated by the exact Mie solutions for isotropic vesicles. The noise tolerance of the method in recovering unimodal and biomodal distributions was studied with the simulated data. Applicability of this approach to vesicles with weak anisotropy was examined using Mie theory for anisotropic hollow spheres. A primitive theory about the first four moments of the radius distribution about the origin, excluding the mean radius, was obtained as an alternative to the direct retrieval of size distributions.

Straight from the source's mouth; a quantitative study of grain-size export for an entire active rift, the Corinth Rift, central Greece

NASA Astrophysics Data System (ADS)

Watkins, Stephen E.; Whittaker, Alexander C.; Bell, Rebecca E.; Brooke, Sam A. S.; McNeill, Lisa C.; Gawthorpe, Robert L.

2017-04-01

The volumes, grain sizes and characteristics of sediment supplied from source catchments fundamentally controls basin stratigraphy. However, to date, few studies have constrained sediment budgets, including grain size, released into an active rift basin at a regional scale. The Gulf of Corinth, central Greece, is one of the most rapidly extending rifts in the world, with geodetic measurements of 5 mm/yr in the East to 15 mm/yr in the West. It has well-constrained climatic and tectonic boundary conditions and bedrock lithologies are well-characterised. It is therefore an ideal natural laboratory to study the grain-size export for a rift. In the field, we visited the river mouths of 49 catchments draining into the Corinth Gulf, which in total drain 83% of the rift. At each site, hydraulic geometries, surface grain-size of channel bars and full-weighted grain-size distributions of river sediment were obtained. The surface grain-size was measured using the Wolman point count method and the full-weighted grain-size distribution of the bedload by in-situ sieving. In total, approximately 17,000 point counts and 3 tonnes of sediment were processed. The grain-size distributions show an overall increase from East to West on the southern coast of the gulf, with largest grain-sizes exported from the Western rift catchments. D84 ranges from 20 to 110 mm, however 50% of D84 grain-sizes are less than 40 mm. Subsequently, we derived the full Holocene sediment budget for the Corinth Gulf by combining our grain size data with catchment sediment fluxes, constrained using the BQART model and calibrated to known Holocene sediment volumes in the basin from seismic data (c.f. Watkins et al., in review). This is the first time such a budget has been derived for the Corinth Rift. Finally, our estimates of sediment budgets and grain sizes were compared to regional uplift constraints, fault distributions, slip rates and lithology to identify the relative importance of these controls on sediment supply to the basin.

Pore water colloid properties in argillaceous sedimentary rocks.

PubMed

Degueldre, Claude; Cloet, Veerle

2016-11-01

The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay colloid concentration is expected to be very low (<1ppb, for 10-100nm) which restricts their relevance for radionuclide transport. Copyright © 2016. Published by Elsevier B.V.

Study of physical properties of metal oxide nanoparticles obtained in acoustoplasma discharge

NASA Astrophysics Data System (ADS)

Bulychev, N. A.; Kazaryan, M. A.; Zakharyan, A. R.; Bodryshev, V. V.; Kirichenko, M. N.; Shevchenko, S. N.; Yakunin, V. G.; Timoshenko, V. Y.; Bychenko, A. B.

2018-04-01

Nanoparticles of tungsten, copper, iron, and zinc oxides were synthesized in acoustoplasma discharge. Their size distribution was studied by electron microscopy and laser correlation spectroscopy. Ultrasound was found to narrow significantly the size distribution width of zinc oxide nanoparticles. Water suspensions of zinc oxide nanoparticles showed photoluminescence in red and near infrared spectral ranges, which makes them a promising material for luminescent diagnostics of biological systems.

Limits of the memory coefficient in measuring correlated bursts

NASA Astrophysics Data System (ADS)

Jo, Hang-Hyun; Hiraoka, Takayuki

2018-03-01

Temporal inhomogeneities in event sequences of natural and social phenomena have been characterized in terms of interevent times and correlations between interevent times. The inhomogeneities of interevent times have been extensively studied, while the correlations between interevent times, often called correlated bursts, are far from being fully understood. For measuring the correlated bursts, two relevant approaches were suggested, i.e., memory coefficient and burst size distribution. Here a burst size denotes the number of events in a bursty train detected for a given time window. Empirical analyses have revealed that the larger memory coefficient tends to be associated with the heavier tail of the burst size distribution. In particular, empirical findings in human activities appear inconsistent, such that the memory coefficient is close to 0, while burst size distributions follow a power law. In order to comprehend these observations, by assuming the conditional independence between consecutive interevent times, we derive the analytical form of the memory coefficient as a function of parameters describing interevent time and burst size distributions. Our analytical result can explain the general tendency of the larger memory coefficient being associated with the heavier tail of burst size distribution. We also find that the apparently inconsistent observations in human activities are compatible with each other, indicating that the memory coefficient has limits to measure the correlated bursts.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Khain, A.; Simpson, S.; Johnson, D.; Li, X.; Remer, L.

2003-01-01

Cloud microphysics are inevitable affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distribution parameterized as spectral bin microphysics are needed to explicitly study the effect of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensembel (GCE) model. The formulation for the explicit spectral-bim microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e., pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), groupel and frozen drops/hall] Each type is described by a special size distribution function containing many categories (i.e., 33 bins). Atmospheric aerosols are also described using number density size-distribution functions.A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep cloud systems in the west Pacific warm pool region and in the mid-latitude using identical thermodynamic conditions but with different concentrations of CCN: a low "clean" concentration and a high "dirty" concentration. Besides the initial differences in aerosol concentration, preliminary results indicate that the low CCN concentration case produces rainfall at the surface sooner than the high CCN case but has less cloud water mass aloft. Because the spectral-bim model explicitly calculates and allows for the examination of both the mass and number concentration of cpecies in each size category, a detailed analysis of the instantaneous size spectrum can be obtained for the two cases. It is shown that since the low CCN case produces fever droplets, larger size develop due to greater condencational and collectional growth, leading to a broader size spectrum in comparison to the high CCN case.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Khain, A.; Simpson, S.; Johnson, D.; Li, X.; Remer, L.

2003-01-01

Cloud microphysics are inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e.,pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e. 33 bins). Atmospheric aerosols are also described using number density size-distribution functions.A spectral-bin microphysical model is very expensive from a from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep tropical clouds in the west Pacific warm pool region using identical thermodynamic conditions but with different concentrations of CCN: a low "clean" concentration and a high "dirty" concentration. Besides the initial differences in aerosol concentration, preliminary results indicate that the low CCN concentration case produces rainfall at the surface sooner than the high CCN case but has less cloud water mass aloft. Because the spectral-bin model explicitly calculates and allows for the examination of both the mass and number concentration of species in each size categor, a detailed analysis of the instantaneous size spectrum can be obtained for the two cases. It is shown that since the low CCN case produces fewer droplets, larger sized develop due to the greater condensational and collectional growth, leading to a broader size spectrum in comparison to the high CCN case.

Improved Time-Lapsed Angular Scattering Microscopy of Single Cells

NASA Astrophysics Data System (ADS)

Cannaday, Ashley E.

By measuring angular scattering patterns from biological samples and fitting them with a Mie theory model, one can estimate the organelle size distribution within many cells. Quantitative organelle sizing of ensembles of cells using this method has been well established. Our goal is to develop the methodology to extend this approach to the single cell level, measuring the angular scattering at multiple time points and estimating the non-nuclear organelle size distribution parameters. The diameters of individual organelle-size beads were successfully extracted using scattering measurements with a minimum deflection angle of 20 degrees. However, the accuracy of size estimates can be limited by the angular range detected. In particular, simulations by our group suggest that, for cell organelle populations with a broader size distribution, the accuracy of size prediction improves substantially if the minimum angle of detection angle is 15 degrees or less. The system was therefore modified to collect scattering angles down to 10 degrees. To confirm experimentally that size predictions will become more stable when lower scattering angles are detected, initial validations were performed on individual polystyrene beads ranging in diameter from 1 to 5 microns. We found that the lower minimum angle enabled the width of this delta-function size distribution to be predicted more accurately. Scattering patterns were then acquired and analyzed from single mouse squamous cell carcinoma cells at multiple time points. The scattering patterns exhibit angular dependencies that look unlike those of any single sphere size, but are well-fit by a broad distribution of sizes, as expected. To determine the fluctuation level in the estimated size distribution due to measurement imperfections alone, formaldehyde-fixed cells were measured. Subsequent measurements on live (non-fixed) cells revealed an order of magnitude greater fluctuation in the estimated sizes compared to fixed cells. With our improved and better-understood approach to single cell angular scattering, we are now capable of reliably detecting changes in organelle size predictions due to biological causes above our measurement error of 20 nm, which enables us to apply our system to future studies of the investigation of various single cell biological processes.

Self-narrowing of size distributions of nanostructures by nucleation antibunching

NASA Astrophysics Data System (ADS)

Glas, Frank; Dubrovskii, Vladimir G.

2017-08-01

We study theoretically the size distributions of ensembles of nanostructures fed from a nanosize mother phase or a nanocatalyst that contains a limited number of the growth species that form each nanostructure. In such systems, the nucleation probability decreases exponentially after each nucleation event, leading to the so-called nucleation antibunching. Specifically, this effect has been observed in individual nanowires grown in the vapor-liquid-solid mode and greatly affects their properties. By performing numerical simulations over large ensembles of nanostructures as well as developing two different analytical schemes (a discrete and a continuum approach), we show that nucleation antibunching completely suppresses fluctuation-induced broadening of the size distribution. As a result, the variance of the distribution saturates to a time-independent value instead of growing infinitely with time. The size distribution widths and shapes primarily depend on the two parameters describing the degree of antibunching and the nucleation delay required to initiate the growth. The resulting sub-Poissonian distributions are highly desirable for improving size homogeneity of nanowires. On a more general level, this unique self-narrowing effect is expected whenever the growth rate is regulated by a nanophase which is able to nucleate an island much faster than it is refilled from a surrounding macroscopic phase.

Note: Evaluation of slurry particle size analyzers for chemical mechanical planarization process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Sunjae; Kulkarni, Atul; Qin, Hongyi

In the chemical mechanical planarization (CMP) process, slurry particle size is important because large particles can cause defects. Hence, selection of an appropriate particle measuring system is necessary in the CMP process. In this study, a scanning mobility particle sizer (SMPS) and dynamic light scattering (DLS) were compared for particle size distribution (PSD) measurements. In addition, the actual particle size and shape were confirmed by transmission electron microscope (TEM) results. SMPS classifies the particle size according to the electrical mobility, and measures the particle concentration (single particle measurement). On the other hand, the DLS measures the particle size distribution bymore » analyzing scattered light from multiple particles (multiple particle measurement). For the slurry particles selected for evaluation, it is observed that SMPS shows bi-modal particle sizes 30 nm and 80 nm, which closely matches with the TEM measurements, whereas DLS shows only single mode distribution in the range of 90 nm to 100 nm and showing incapability of measuring small particles. Hence, SMPS can be a better choice for the evaluation of CMP slurry particle size and concentration measurements.« less

A new mechanistic approach for the further development of a population with established size bimodality

USGS Publications Warehouse

Heerman, Lisa; DeAngelis, Donald L.; Borcherding, Jost

2017-01-01

Usually, the origin of a within-cohort bimodal size distribution is assumed to be caused by initial size differences or by one discrete period of accelerated growth for one part of the population. The aim of this study was to determine if more continuous pathways exist allowing shifts from the small to the large fraction within a bimodal age-cohort. Therefore, a Eurasian perch population, which had already developed a bimodal size-distribution and had differential resource use of the two size-cohorts, was examined. Results revealed that formation of a bimodal size-distribution can be a continuous process. Perch from the small size-cohort were able to grow into the large size-cohort by feeding on macroinvertebrates not used by their conspecifics. The diet shifts were accompanied by morphological shape changes. Intra-specific competition seemed to trigger the development towards an increasing number of large individuals. A stage-structured matrix model confirmed these assumptions. The fact that bimodality can be a continuous process is important to consider for the understanding of ecological processes and links within ecosystems.

A new mechanistic approach for the further development of a population with established size bimodality

PubMed Central

DeAngelis, Donald L.; Borcherding, Jost

2017-01-01

Usually, the origin of a within-cohort bimodal size distribution is assumed to be caused by initial size differences or by one discrete period of accelerated growth for one part of the population. The aim of this study was to determine if more continuous pathways exist allowing shifts from the small to the large fraction within a bimodal age-cohort. Therefore, a Eurasian perch population, which had already developed a bimodal size-distribution and had differential resource use of the two size-cohorts, was examined. Results revealed that formation of a bimodal size-distribution can be a continuous process. Perch from the small size-cohort were able to grow into the large size-cohort by feeding on macroinvertebrates not used by their conspecifics. The diet shifts were accompanied by morphological shape changes. Intra-specific competition seemed to trigger the development towards an increasing number of large individuals. A stage-structured matrix model confirmed these assumptions. The fact that bimodality can be a continuous process is important to consider for the understanding of ecological processes and links within ecosystems. PMID:28650963

The geometry of proliferating dicot cells.

PubMed

Korn, R W

2001-02-01

The distributions of cell size and cell cycle duration were studied in two-dimensional expanding plant tissues. Plastic imprints of the leaf epidermis of three dicot plants, jade (Crassula argentae), impatiens (Impatiens wallerana), and the common begonia (Begonia semperflorens) were made and cell outlines analysed. The average, standard deviation and coefficient of variance (CV = 100 x standard deviation/average) of cell size were determined with the CV of mother cells less than the CV for daughter cells and both are less than that for all cells. An equation was devised as a simple description of the probability distribution of sizes for all cells of a tissue. Cell cycle durations as measured in arbitrary time units were determined by reconstructing the initial and final sizes of cells and they collectively give the expected asymmetric bell-shaped probability distribution. Given the features of unequal cell division (an average of 11.6% difference in size of daughter cells) and the size variation of dividing cells, it appears that the range of cell size is more critically regulated than the size of a cell at any particular time.

Observed oil and gas field size distributions: A consequence of the discovery process and prices of oil and gas

USGS Publications Warehouse

Drew, L.J.; Attanasi, E.D.; Schuenemeyer, J.H.

1988-01-01

If observed oil and gas field size distributions are obtained by random samplings, the fitted distributions should approximate that of the parent population of oil and gas fields. However, empirical evidence strongly suggests that larger fields tend to be discovered earlier in the discovery process than they would be by random sampling. Economic factors also can limit the number of small fields that are developed and reported. This paper examines observed size distributions in state and federal waters of offshore Texas. Results of the analysis demonstrate how the shape of the observable size distributions change with significant hydrocarbon price changes. Comparison of state and federal observed size distributions in the offshore area shows how production cost differences also affect the shape of the observed size distribution. Methods for modifying the discovery rate estimation procedures when economic factors significantly affect the discovery sequence are presented. A primary conclusion of the analysis is that, because hydrocarbon price changes can significantly affect the observed discovery size distribution, one should not be confident about inferring the form and specific parameters of the parent field size distribution from the observed distributions. ?? 1988 International Association for Mathematical Geology.

Laboratory and field evaluations of the LISST-100 instrument for suspended particle size determinations

USGS Publications Warehouse

Gartner, J.W.; Cheng, R.T.; Wang, P.-F.; Richter, K.

2001-01-01

Advances in technology have resulted in a new instrument that is designed for in-situ determination of particle size spectra. Such an instrument that can measure undisturbed particle size distributions is much needed for sediment transport studies. The LISST-100 (Laser In-Situ Scattering and Transmissometry) uses the principle of laser diffraction to obtain the size distribution and volume concentration of suspended material in 32 size classes logarithmically spaced between 1.25 and 250 ??m. This paper describes a laboratory evaluation of the ability of LISST-100 to determine particle sizes using suspensions of single size, artificial particles. Findings show the instrument is able to determine particle size to within about 10% with increasing error as particle size increases. The instrument determines volume (or mass) concentration using a volume conversion factor Cv. This volume conversion factor is theoretically a constant. In the laboratory evaluation Cv is found to vary by a factor of about three over the particle size range between 5 and 200 ??m. Results from field studies in South San Francisco Bay show that values of mass concentration of suspended marine sediments estimated by LISST-100 agree favorably with estimates from optical backscatterance sensors if an appropriate value of Cv, according to mean size, is used and the assumed average particle (aggregate) density is carefully chosen. Analyses of size distribution of suspended materials in South San Francisco Bay over multiple tide cycles suggest the likelihood of different sources of sediment because of different size characteristics during flood and ebb cycles. ?? 2001 Elsevier Science B.V.

Stochastic transformation of points in polygons according to the Voronoi tessellation: microstructural description.

PubMed

Di Vito, Alessia; Fanfoni, Massimo; Tomellini, Massimo

2010-12-01

Starting from a stochastic two-dimensional process we studied the transformation of points in disks and squares following a protocol according to which at any step the island size increases proportionally to the corresponding Voronoi tessera. Two interaction mechanisms among islands have been dealt with: coalescence and impingement. We studied the evolution of the island density and of the island size distribution functions, in dependence on island collision mechanisms for both Poissonian and correlated spatial distributions of points. The island size distribution functions have been found to be invariant with the fraction of transformed phase for a given stochastic process. The n(Θ) curve describing the island decay has been found to be independent of the shape (apart from high correlation degrees) and interaction mechanism.

Airborne Aerosol Closure Studies During PRIDE

NASA Technical Reports Server (NTRS)

Redemann, Jens; Livingston, John M.; Russell, Philip B.; Schmid, Beat; Reid, Jeff

2000-01-01

The Puerto Rico Dust Experiment (PRIDE) was conducted during June/July of 2000 to study the properties of Saharan dust aerosols transported across the Atlantic Ocean to the Caribbean Islands. During PRIDE, the NASA Ames Research Center six-channel (380 - 1020 nm) airborne autotracking sunphotometer (AATS-6) was operated aboard a Piper Navajo airplane alongside a suite of in situ aerosol instruments. The in situ aerosol instrumentation relevant to this paper included a Forward Scattering Spectrometer Probe (FSSP-100) and a Passive Cavity Aerosol Spectrometer Probe (PCASP), covering the radius range of approx. 0.05 to 10 microns. The simultaneous and collocated measurement of multi-spectral aerosol optical depth and in situ particle size distribution data permits a variety of closure studies. For example, vertical profiles of aerosol optical depth obtained during local aircraft ascents and descents can be differentiated with respect to altitude and compared to extinction profiles calculated using the in situ particle size distribution data (and reasonable estimates of the aerosol index of refraction). Additionally, aerosol extinction (optical depth) spectra can be inverted to retrieve estimates of the particle size distributions, which can be compared directly to the in situ size distributions. In this paper we will report on such closure studies using data from a select number of vertical profiles at Cabras Island, Puerto Rico, including measurements in distinct Saharan Dust Layers. Preliminary results show good agreement to within 30% between mid-visible aerosol extinction derived from the AATS-6 optical depth profiles and extinction profiles forward calculated using 60s-average in situ particle size distributions and standard Saharan dust aerosol refractive indices published in the literature. In agreement with tendencies observed in previous studies, our initial results show an underestimate of aerosol extinction calculated based on the in situ size distributions relative to the extinction obtained from the sunphotometer measurements. However, a more extensive analysis of all available AATS-6 and in situ size distribution data is necessary to ascertain whether the preliminary results regarding the degree of extinction closure is representative of the entire range of dust conditions encountered in PRIDE. Finally, we will compare the spectral extinction measurements obtained in PRIDE to similar data obtained in Saharan dust layers encountered above the Canary Islands during ACE-2 (Aerosol Characterization Experiment) in July 1997. Thus, the evolution of Saharan dust spectral properties during its transport across the Atlantic can be investigated, provided the dust origin and microphysical properties are found to be comparable.

Assessment of optimum threshold and particle shape parameter for the image analysis of aggregate size distribution of concrete sections

NASA Astrophysics Data System (ADS)

Ozen, Murat; Guler, Murat

2014-02-01

Aggregate gradation is one of the key design parameters affecting the workability and strength properties of concrete mixtures. Estimating aggregate gradation from hardened concrete samples can offer valuable insights into the quality of mixtures in terms of the degree of segregation and the amount of deviation from the specified gradation limits. In this study, a methodology is introduced to determine the particle size distribution of aggregates from 2D cross sectional images of concrete samples. The samples used in the study were fabricated from six mix designs by varying the aggregate gradation, aggregate source and maximum aggregate size with five replicates of each design combination. Each sample was cut into three pieces using a diamond saw and then scanned to obtain the cross sectional images using a desktop flatbed scanner. An algorithm is proposed to determine the optimum threshold for the image analysis of the cross sections. A procedure was also suggested to determine a suitable particle shape parameter to be used in the analysis of aggregate size distribution within each cross section. Results of analyses indicated that the optimum threshold hence the pixel distribution functions may be different even for the cross sections of an identical concrete sample. Besides, the maximum ferret diameter is the most suitable shape parameter to estimate the size distribution of aggregates when computed based on the diagonal sieve opening. The outcome of this study can be of practical value for the practitioners to evaluate concrete in terms of the degree of segregation and the bounds of mixture's gradation achieved during manufacturing.

SU-E-T-374: Evaluation and Verification of Dose Calculation Accuracy with Different Dose Grid Sizes for Intracranial Stereotactic Radiosurgery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, C; Schultheiss, T

Purpose: In this study, we aim to evaluate the effect of dose grid size on the accuracy of calculated dose for small lesions in intracranial stereotactic radiosurgery (SRS), and to verify dose calculation accuracy with radiochromic film dosimetry. Methods: 15 intracranial lesions from previous SRS patients were retrospectively selected for this study. The planning target volume (PTV) ranged from 0.17 to 2.3 cm{sup 3}. A commercial treatment planning system was used to generate SRS plans using the volumetric modulated arc therapy (VMAT) technique using two arc fields. Two convolution-superposition-based dose calculation algorithms (Anisotropic Analytical Algorithm and Acuros XB algorithm) weremore » used to calculate volume dose distribution with dose grid size ranging from 1 mm to 3 mm with 0.5 mm step size. First, while the plan monitor units (MU) were kept constant, PTV dose variations were analyzed. Second, with 95% of the PTV covered by the prescription dose, variations of the plan MUs as a function of dose grid size were analyzed. Radiochomic films were used to compare the delivered dose and profile with the calculated dose distribution with different dose grid sizes. Results: The dose to the PTV, in terms of the mean dose, maximum, and minimum dose, showed steady decrease with increasing dose grid size using both algorithms. With 95% of the PTV covered by the prescription dose, the total MU increased with increasing dose grid size in most of the plans. Radiochromic film measurements showed better agreement with dose distributions calculated with 1-mm dose grid size. Conclusion: Dose grid size has significant impact on calculated dose distribution in intracranial SRS treatment planning with small target volumes. Using the default dose grid size could lead to under-estimation of delivered dose. A small dose grid size should be used to ensure calculation accuracy and agreement with QA measurements.« less

The Effect of Small Sample Size on Measurement Equivalence of Psychometric Questionnaires in MIMIC Model: A Simulation Study.

PubMed

Jamali, Jamshid; Ayatollahi, Seyyed Mohammad Taghi; Jafari, Peyman

2017-01-01

Evaluating measurement equivalence (also known as differential item functioning (DIF)) is an important part of the process of validating psychometric questionnaires. This study aimed at evaluating the multiple indicators multiple causes (MIMIC) model for DIF detection when latent construct distribution is nonnormal and the focal group sample size is small. In this simulation-based study, Type I error rates and power of MIMIC model for detecting uniform-DIF were investigated under different combinations of reference to focal group sample size ratio, magnitude of the uniform-DIF effect, scale length, the number of response categories, and latent trait distribution. Moderate and high skewness in the latent trait distribution led to a decrease of 0.33% and 0.47% power of MIMIC model for detecting uniform-DIF, respectively. The findings indicated that, by increasing the scale length, the number of response categories and magnitude DIF improved the power of MIMIC model, by 3.47%, 4.83%, and 20.35%, respectively; it also decreased Type I error of MIMIC approach by 2.81%, 5.66%, and 0.04%, respectively. This study revealed that power of MIMIC model was at an acceptable level when latent trait distributions were skewed. However, empirical Type I error rate was slightly greater than nominal significance level. Consequently, the MIMIC was recommended for detection of uniform-DIF when latent construct distribution is nonnormal and the focal group sample size is small.

The Effect of Small Sample Size on Measurement Equivalence of Psychometric Questionnaires in MIMIC Model: A Simulation Study

PubMed Central

Jafari, Peyman

2017-01-01

Evaluating measurement equivalence (also known as differential item functioning (DIF)) is an important part of the process of validating psychometric questionnaires. This study aimed at evaluating the multiple indicators multiple causes (MIMIC) model for DIF detection when latent construct distribution is nonnormal and the focal group sample size is small. In this simulation-based study, Type I error rates and power of MIMIC model for detecting uniform-DIF were investigated under different combinations of reference to focal group sample size ratio, magnitude of the uniform-DIF effect, scale length, the number of response categories, and latent trait distribution. Moderate and high skewness in the latent trait distribution led to a decrease of 0.33% and 0.47% power of MIMIC model for detecting uniform-DIF, respectively. The findings indicated that, by increasing the scale length, the number of response categories and magnitude DIF improved the power of MIMIC model, by 3.47%, 4.83%, and 20.35%, respectively; it also decreased Type I error of MIMIC approach by 2.81%, 5.66%, and 0.04%, respectively. This study revealed that power of MIMIC model was at an acceptable level when latent trait distributions were skewed. However, empirical Type I error rate was slightly greater than nominal significance level. Consequently, the MIMIC was recommended for detection of uniform-DIF when latent construct distribution is nonnormal and the focal group sample size is small. PMID:28713828

Methane Leaks from Natural Gas Systems Follow Extreme Distributions.

PubMed

Brandt, Adam R; Heath, Garvin A; Cooley, Daniel

2016-11-15

Future energy systems may rely on natural gas as a low-cost fuel to support variable renewable power. However, leaking natural gas causes climate damage because methane (CH 4 ) has a high global warming potential. In this study, we use extreme-value theory to explore the distribution of natural gas leak sizes. By analyzing ∼15 000 measurements from 18 prior studies, we show that all available natural gas leakage data sets are statistically heavy-tailed, and that gas leaks are more extremely distributed than other natural and social phenomena. A unifying result is that the largest 5% of leaks typically contribute over 50% of the total leakage volume. While prior studies used log-normal model distributions, we show that log-normal functions poorly represent tail behavior. Our results suggest that published uncertainty ranges of CH 4 emissions are too narrow, and that larger sample sizes are required in future studies to achieve targeted confidence intervals. Additionally, we find that cross-study aggregation of data sets to increase sample size is not recommended due to apparent deviation between sampled populations. Understanding the nature of leak distributions can improve emission estimates, better illustrate their uncertainty, allow prioritization of source categories, and improve sampling design. Also, these data can be used for more effective design of leak detection technologies.

Methane Leaks from Natural Gas Systems Follow Extreme Distributions

DOE PAGES

Brandt, Adam R.; Heath, Garvin A.; Cooley, Daniel

2016-10-14

Future energy systems may rely on natural gas as a low-cost fuel to support variable renewable power. However, leaking natural gas causes climate damage because methane (CH 4) has a high global warming potential. In this study, we use extreme-value theory to explore the distribution of natural gas leak sizes. By analyzing ~15,000 measurements from 18 prior studies, we show that all available natural gas leakage datasets are statistically heavy-tailed, and that gas leaks are more extremely distributed than other natural and social phenomena. A unifying result is that the largest 5% of leaks typically contribute over 50% of themore » total leakage volume. While prior studies used lognormal model distributions, we show that lognormal functions poorly represent tail behavior. Our results suggest that published uncertainty ranges of CH 4 emissions are too narrow, and that larger sample sizes are required in future studies to achieve targeted confidence intervals. Additionally, we find that cross-study aggregation of datasets to increase sample size is not recommended due to apparent deviation between sampled populations. Finally, understanding the nature of leak distributions can improve emission estimates, better illustrate their uncertainty, allow prioritization of source categories, and improve sampling design. Also, these data can be used for more effective design of leak detection technologies.« less

Methane Leaks from Natural Gas Systems Follow Extreme Distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, Adam R.; Heath, Garvin A.; Cooley, Daniel

Future energy systems may rely on natural gas as a low-cost fuel to support variable renewable power. However, leaking natural gas causes climate damage because methane (CH 4) has a high global warming potential. In this study, we use extreme-value theory to explore the distribution of natural gas leak sizes. By analyzing ~15,000 measurements from 18 prior studies, we show that all available natural gas leakage datasets are statistically heavy-tailed, and that gas leaks are more extremely distributed than other natural and social phenomena. A unifying result is that the largest 5% of leaks typically contribute over 50% of themore » total leakage volume. While prior studies used lognormal model distributions, we show that lognormal functions poorly represent tail behavior. Our results suggest that published uncertainty ranges of CH 4 emissions are too narrow, and that larger sample sizes are required in future studies to achieve targeted confidence intervals. Additionally, we find that cross-study aggregation of datasets to increase sample size is not recommended due to apparent deviation between sampled populations. Finally, understanding the nature of leak distributions can improve emission estimates, better illustrate their uncertainty, allow prioritization of source categories, and improve sampling design. Also, these data can be used for more effective design of leak detection technologies.« less

Characterization and variability of particle size distributions in Hudson Bay, Canada

NASA Astrophysics Data System (ADS)

Xi, Hongyan; Larouche, Pierre; Tang, Shilin; Michel, Christine

2014-06-01

Particle size distribution (PSD) plays a significant role in many aspects of aquatic ecosystems, including phytoplankton dynamics, sediment fluxes, and optical scattering from particulates. As of yet, little is known on the variability of particle size distribution in marine ecosystems. In this study, we investigated the PSD properties and variability in Hudson Bay based on measurements from a laser diffractometer (LISST-100X Type-B) in concert with biogeochemical parameters collected during summer 2010. Results show that most power-law fitted PSD slopes ranged from 2.5 to 4.5, covering nearly the entire range observed for natural waters. Offshore waters showed a predominance of smaller particles while near the coast, the effect of riverine inputs on PSD were apparent. Particulate inorganic matter contributed more to total suspended matter in coastal waters leading to lower PSD slopes than offshore. The depth distribution of PSD slopes shows that larger particles were associated with the pycnocline. Below the pycnocline, smaller particles dominated the spectra. A comparison between a PSD slope-based method to derive phytoplankton size class (PSC) and pigment-based derived PSC showed the two methods agreed relatively well. This study provides valuable baseline information on particle size properties and phytoplankton composition estimates in a sub-arctic environment subject to rapid environmental change.

Sample size determination for logistic regression on a logit-normal distribution.

PubMed

Kim, Seongho; Heath, Elisabeth; Heilbrun, Lance

2017-06-01

Although the sample size for simple logistic regression can be readily determined using currently available methods, the sample size calculation for multiple logistic regression requires some additional information, such as the coefficient of determination ([Formula: see text]) of a covariate of interest with other covariates, which is often unavailable in practice. The response variable of logistic regression follows a logit-normal distribution which can be generated from a logistic transformation of a normal distribution. Using this property of logistic regression, we propose new methods of determining the sample size for simple and multiple logistic regressions using a normal transformation of outcome measures. Simulation studies and a motivating example show several advantages of the proposed methods over the existing methods: (i) no need for [Formula: see text] for multiple logistic regression, (ii) available interim or group-sequential designs, and (iii) much smaller required sample size.

STUDYING THE EFFECTS OF CALCIUM AND MAGNESIUM ON SIZE-DISTRIBUTED NITRATE AND AMMONIUM WITH EQUISOLV II. (R823186)

EPA Science Inventory

Abstract

A chemical equilibrium code was improved and used to show that calcium and magnesium have a large yet different effect on the aerosol size distribution in different regions of Los Angeles. In the code, a new technique of solving individual equilibrium equation...

Environmental DNA particle size distribution from Brook Trout (Salvelinus fontinalis)

Treesearch

Taylor M. Wilcox; Kevin S. McKelvey; Michael K. Young; Winsor H. Lowe; Michael K. Schwartz

2015-01-01

Environmental DNA (eDNA) sampling has become a widespread approach for detecting aquatic animals with high potential for improving conservation biology. However, little research has been done to determine the size of particles targeted by eDNA surveys. In this study, we conduct particle distribution analysis of eDNA from a captive Brook Trout (Salvelinus fontinalis) in...

Application of Aerosol Hygroscopicity Measured at the Atmospheric Radiation Measurement Program's Southern Great Plains Site to Examine Composition and Evolution

NASA Technical Reports Server (NTRS)

Gasparini, Roberto; Runjun, Li; Collins, Don R.; Ferrare, Richard A.; Brackett, Vincent G.

2006-01-01

A Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) was used to measure submicron aerosol size distributions, hygroscopicity, and occasionally volatility during the May 2003 Aerosol Intensive Operational Period (IOP) at the Central Facility of the Atmospheric Radiation Measurement Program's Southern Great Plains (ARM SGP) site. Hygroscopic growth factor distributions for particles at eight dry diameters ranging from 0.012 micrometers to 0.600 micrometers were measured throughout the study. For a subset of particle sizes, more detailed measurements were occasionally made in which the relative humidity or temperature to which the aerosol was exposed was varied over a wide range. These measurements, in conjunction with backtrajectory clustering, were used to infer aerosol composition and to gain insight into the processes responsible for evolution. The hygroscopic growth of both the smallest and largest particles analyzed was typically less than that of particles with dry diameters of about 0.100 micrometers. It is speculated that condensation of secondary organic aerosol on nucleation mode particles is largely responsible for the minimal hygroscopic growth observed at the smallest sizes considered. Growth factor distributions of the largest particles characterized typically contained a nonhygroscopic mode believed to be composed primarily of dust. A model was developed to characterize the hygroscopic properties of particles within a size distribution mode through analysis of the fixed size hygroscopic growth measurements. The performance of this model was quantified through comparison of the measured fixed size hygroscopic growth factor distributions with those simulated through convolution of the size-resolved concentration contributed by each of the size modes and the mode-resolved hygroscopicity. This transformation from sizeresolved hygroscopicity to mode-resolved hygroscopicity facilitated examination of changes in the hygroscopic properties of particles within a size distribution mode that accompanied changes in the sizes of those particles. This model was used to examine three specific cases in which the sampled aerosol evolved slowly over a period of hours or days.

Phylogenetic analyses suggest that diversification and body size evolution are independent in insects.

PubMed

Rainford, James L; Hofreiter, Michael; Mayhew, Peter J

2016-01-08

Skewed body size distributions and the high relative richness of small-bodied taxa are a fundamental property of a wide range of animal clades. The evolutionary processes responsible for generating these distributions are well described in vertebrate model systems but have yet to be explored in detail for other major terrestrial clades. In this study, we explore the macro-evolutionary patterns of body size variation across families of Hexapoda (insects and their close relatives), using recent advances in phylogenetic understanding, with an aim to investigate the link between size and diversity within this ancient and highly diverse lineage. The maximum, minimum and mean-log body lengths of hexapod families are all approximately log-normally distributed, consistent with previous studies at lower taxonomic levels, and contrasting with skewed distributions typical of vertebrate groups. After taking phylogeny and within-tip variation into account, we find no evidence for a negative relationship between diversification rate and body size, suggesting decoupling of the forces controlling these two traits. Likelihood-based modeling of the log-mean body size identifies distinct processes operating within Holometabola and Diptera compared with other hexapod groups, consistent with accelerating rates of size evolution within these clades, while as a whole, hexapod body size evolution is found to be dominated by neutral processes including significant phylogenetic conservatism. Based on our findings we suggest that the use of models derived from well-studied but atypical clades, such as vertebrates may lead to misleading conclusions when applied to other major terrestrial lineages. Our results indicate that within hexapods, and within the limits of current systematic and phylogenetic knowledge, insect diversification is generally unfettered by size-biased macro-evolutionary processes, and that these processes over large timescales tend to converge on apparently neutral evolutionary processes. We also identify limitations on available data within the clade and modeling approaches for the resolution of trees of higher taxa, the resolution of which may collectively enhance our understanding of this key component of terrestrial ecosystems.

Contrasting Size Distributions of Chondrules and Inclusions in Allende CV3

NASA Technical Reports Server (NTRS)

Fisher, Kent R.; Tait, Alastair W.; Simon, Jusin I.; Cuzzi, Jeff N.

2014-01-01

There are several leading theories on the processes that led to the formation of chondrites, e.g., sorting by mass, by X-winds, turbulent concentration, and by photophoresis. The juxtaposition of refractory inclusions (CAIs) and less refractory chondrules is central to these theories and there is much to be learned from their relative size distributions. There have been a number of studies into size distributions of particles in chondrites but only on relatively small scales primarily for chondrules, and rarely for both Calcium Aluminum-rich Inclusions (CAIs) and chondrules in the same sample. We have implemented macro-scale (25 cm diameter sample) and high-resolution microscale sampling of the Allende CV3 chondrite to create a complete data set of size frequencies for CAIs and chondrules.

The variance of dispersion measure of high-redshift transient objects as a probe of ionized bubble size during reionization

NASA Astrophysics Data System (ADS)

Yoshiura, Shintaro; Takahashi, Keitaro

2018-01-01

The dispersion measure (DM) of high-redshift (z ≳ 6) transient objects such as fast radio bursts can be a powerful tool to probe the intergalactic medium during the Epoch of Reionization. In this paper, we study the variance of the DMs of objects with the same redshift as a potential probe of the size distribution of ionized bubbles. We calculate the DM variance with a simple model with randomly distributed spherical bubbles. It is found that the DM variance reflects the characteristics of the probability distribution of the bubble size. We find that the variance can be measured precisely enough to obtain the information on the typical size with a few hundred sources at a single redshift.

The Italian primary school-size distribution and the city-size: a complex nexus

NASA Astrophysics Data System (ADS)

Belmonte, Alessandro; di Clemente, Riccardo; Buldyrev, Sergey V.

2014-06-01

We characterize the statistical law according to which Italian primary school-size distributes. We find that the school-size can be approximated by a log-normal distribution, with a fat lower tail that collects a large number of very small schools. The upper tail of the school-size distribution decreases exponentially and the growth rates are distributed with a Laplace PDF. These distributions are similar to those observed for firms and are consistent with a Bose-Einstein preferential attachment process. The body of the distribution features a bimodal shape suggesting some source of heterogeneity in the school organization that we uncover by an in-depth analysis of the relation between schools-size and city-size. We propose a novel cluster methodology and a new spatial interaction approach among schools which outline the variety of policies implemented in Italy. Different regional policies are also discussed shedding lights on the relation between policy and geographical features.

The effect of caster wheel diameter and mass distribution on drag forces in manual wheelchairs.

PubMed

Zepeda, Rene; Chan, Franco; Sawatzky, Bonita

2016-01-01

This study proposes a way to reduce energy losses in the form of rolling resistance friction during manual wheelchair propulsion by increasing the size of the front caster wheels and adjusting the weight distribution. Drag tests were conducted using a treadmill and a force transducer. Three different casters diameter (4 in., 5 in., and 6 in.) and six different mass distribution combinations (based on percentage of total weight on the caster wheels) were studied. A two-way analysis of variance test was performed to compare caster size and weight distribution contribution with drag force of an ultralight wheelchair. The 4 in. caster contributed significantly more drag, but only when weight was 40% or greater over the casters. Weight distribution contributed more to drag regardless of the casters used.

Relationships between annual plant productivity, nitrogen deposition and fire size in low-elevation California desert scrub

USGS Publications Warehouse

Rao, Leela E.; Matchett, John R.; Brooks, Matthew L.; Johns, Robert; Minnich, Richard A.; Allen, Edith B.

2014-01-01

Although precipitation is correlated with fire size in desert ecosystems and is typically used as an indirect surrogate for fine fuel load, a direct link between fine fuel biomass and fire size has not been established. In addition, nitrogen (N) deposition can affect fire risk through its fertilisation effect on fine fuel production. In this study, we examine the relationships between fire size and precipitation, N deposition and biomass with emphasis on identifying biomass and N deposition thresholds associated with fire spreading across the landscape. We used a 28-year fire record of 582 burns from low-elevation desert scrub to evaluate the relationship of precipitation, N deposition and biomass with the distribution of fire sizes using quantile regression. We found that models using annual biomass have similar predictive ability to those using precipitation and N deposition at the lower to intermediate portions of the fire size distribution. No distinct biomass threshold was found, although within the 99th percentile of the distribution fire size increased with greater than 125 g m–2 of winter fine fuel production. The study did not produce an N deposition threshold, but did validate the value of 125 g m–2 of fine fuel for spread of fires.

Reynolds number scaling to predict droplet size distribution in dispersed and undispersed subsurface oil releases.

PubMed

Li, Pu; Weng, Linlu; Niu, Haibo; Robinson, Brian; King, Thomas; Conmy, Robyn; Lee, Kenneth; Liu, Lei

2016-12-15

This study was aimed at testing the applicability of modified Weber number scaling with Alaska North Slope (ANS) crude oil, and developing a Reynolds number scaling approach for oil droplet size prediction for high viscosity oils. Dispersant to oil ratio and empirical coefficients were also quantified. Finally, a two-step Rosin-Rammler scheme was introduced for the determination of droplet size distribution. This new approach appeared more advantageous in avoiding the inconsistency in interfacial tension measurements, and consequently delivered concise droplet size prediction. Calculated and observed data correlated well based on Reynolds number scaling. The relation indicated that chemical dispersant played an important role in reducing the droplet size of ANS under different seasonal conditions. The proposed Reynolds number scaling and two-step Rosin-Rammler approaches provide a concise, reliable way to predict droplet size distribution, supporting decision making in chemical dispersant application during an offshore oil spill. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interference from Proteins and Surfactants on Particle Size Distributions Measured by Nanoparticle Tracking Analysis (NTA).

PubMed

Bai, Kelvin; Barnett, Gregory V; Kar, Sambit R; Das, Tapan K

2017-04-01

Characterization of submicron protein particles continues to be challenging despite active developments in the field. NTA is a submicron particle enumeration technique, which optically tracks the light scattering signal from suspended particles undergoing Brownian motion. The submicron particle size range NTA can monitor in common protein formulations is not well established. We conducted a comprehensive investigation with several protein formulations along with corresponding placebos using NTA to determine submicron particle size distributions and shed light on potential non-particle origin of size distribution in the range of approximately 50-300 nm. NTA and DLS are performed on polystyrene size standards as well as protein and placebo formulations. Protein formulations filtered through a 20 nm filter, with and without polysorbate-80, show NTA particle counts. As such, particle counts above 20 nm are not expected in these solutions. Several other systems including positive and negative controls were studied using NTA and DLS. These apparent particles measured by NTA are not observed in DLS measurements and may not correspond to real particles. The intent of this article is to raise awareness about the need to interpret particle counts and size distribution from NTA with caution.

Primary particle diameter differentiation and bimodality identification by five analytical methods using gold nanoparticle size distributions synthesized by pulsed laser ablation in liquids

NASA Astrophysics Data System (ADS)

Letzel, Alexander; Gökce, Bilal; Menzel, Andreas; Plech, Anton; Barcikowski, Stephan

2018-03-01

For a known material, the size distribution of a nanoparticle colloid is a crucial parameter that defines its properties. However, measured size distributions are not easy to interpret as one has to consider weighting (e.g. by light absorption, scattering intensity, volume, surface, number) and the way size information was gained. The radius of a suspended nanoparticle can be given as e.g. sphere equivalent, hydrodynamic, Feret or radius of gyration. In this study, gold nanoparticles in water are synthesized by pulsed-laser ablation (LAL) and fragmentation (LFL) in liquids and characterized by various techniques (scanning transmission electron microscopy (STEM), small-angle X-ray scattering (SAXS), analytical disc centrifugation (ADC), dynamic light scattering (DLS) and UV-vis spectroscopy with Mie-Gans Theory) to study the comparability of different analytical techniques and determine the method that is preferable for a given task related to laser-generated nanoparticles. In particular, laser-generated colloids are known to be bimodal and/or polydisperse, but bimodality is sometimes not analytically resolved in literature. In addition, frequently reported small size shifts of the primary particle mode around 10 nm needs evaluation of its statistical significance related to the analytical method. Closely related to earlier studies on SAXS, different colloids in defined proportions are mixed and their size as a function of the nominal mixing ratio is analyzed. It is found that the derived particle size is independent of the nominal mixing ratio if the colloid size fractions do not overlap considerably. Conversely, the obtained size for colloids with overlapping size fractions strongly depends on the nominal mixing ratio since most methods cannot distinguish between such fractions. Overall, SAXS and ADC are very accurate methods for particle size analysis. Further, the ability of different methods to determine the nominal mixing ratio of sizes fractions is studied experimentally.

ELISPOTs Produced by CD8 and CD4 Cells Follow Log Normal Size Distribution Permitting Objective Counting

PubMed Central

Karulin, Alexey Y.; Karacsony, Kinga; Zhang, Wenji; Targoni, Oleg S.; Moldovan, Ioana; Dittrich, Marcus; Sundararaman, Srividya; Lehmann, Paul V.

2015-01-01

Each positive well in ELISPOT assays contains spots of variable sizes that can range from tens of micrometers up to a millimeter in diameter. Therefore, when it comes to counting these spots the decision on setting the lower and the upper spot size thresholds to discriminate between non-specific background noise, spots produced by individual T cells, and spots formed by T cell clusters is critical. If the spot sizes follow a known statistical distribution, precise predictions on minimal and maximal spot sizes, belonging to a given T cell population, can be made. We studied the size distributional properties of IFN-γ, IL-2, IL-4, IL-5 and IL-17 spots elicited in ELISPOT assays with PBMC from 172 healthy donors, upon stimulation with 32 individual viral peptides representing defined HLA Class I-restricted epitopes for CD8 cells, and with protein antigens of CMV and EBV activating CD4 cells. A total of 334 CD8 and 80 CD4 positive T cell responses were analyzed. In 99.7% of the test cases, spot size distributions followed Log Normal function. These data formally demonstrate that it is possible to establish objective, statistically validated parameters for counting T cell ELISPOTs. PMID:25612115

A Novel Approach of Using Ground CNTs as the Carbon Source to Fabricate Uniformly Distributed Nano-Sized TiCx/2009Al Composites.

PubMed

Wang, Lei; Qiu, Feng; Ouyang, Licheng; Wang, Huiyuan; Zha, Min; Shu, Shili; Zhao, Qinglong; Jiang, Qichuan

2015-12-17

Nano-sized TiC x /2009Al composites (with 5, 7, and 9 vol% TiC x ) were fabricated via the combustion synthesis of the 2009Al-Ti-CNTs system combined with vacuum hot pressing followed by hot extrusion. In the present study, CNTs were used as the carbon source to synthesize nano-sized TiC x particles. An attempt was made to correlate the effect of ground CNTs by milling and the distribution of synthesized nano-sized TiC x particles in 2009Al as well as the tensile properties of nano-sized TiC x /2009Al composites. Microstructure analysis showed that when ground CNTs were used, the synthesized nano-sized TiC x particles dispersed more uniformly in the 2009Al matrix. Moreover, when 2 h-milled CNTs were used, the 5, 7, and 9 vol% nano-sized TiC x /2009Al composites had the highest tensile properties, especially, the 9 vol% nano-sized TiC x /2009Al composites. The results offered a new approach to improve the distribution of in situ nano-sized TiC x particles and tensile properties of composites.

A Novel Approach of Using Ground CNTs as the Carbon Source to Fabricate Uniformly Distributed Nano-Sized TiCx/2009Al Composites

PubMed Central

Wang, Lei; Qiu, Feng; Ouyang, Licheng; Wang, Huiyuan; Zha, Min; Shu, Shili; Zhao, Qinglong; Jiang, Qichuan

2015-01-01

Nano-sized TiCx/2009Al composites (with 5, 7, and 9 vol% TiCx) were fabricated via the combustion synthesis of the 2009Al-Ti-CNTs system combined with vacuum hot pressing followed by hot extrusion. In the present study, CNTs were used as the carbon source to synthesize nano-sized TiCx particles. An attempt was made to correlate the effect of ground CNTs by milling and the distribution of synthesized nano-sized TiCx particles in 2009Al as well as the tensile properties of nano-sized TiCx/2009Al composites. Microstructure analysis showed that when ground CNTs were used, the synthesized nano-sized TiCx particles dispersed more uniformly in the 2009Al matrix. Moreover, when 2 h-milled CNTs were used, the 5, 7, and 9 vol% nano-sized TiCx/2009Al composites had the highest tensile properties, especially, the 9 vol% nano-sized TiCx/2009Al composites. The results offered a new approach to improve the distribution of in situ nano-sized TiCx particles and tensile properties of composites. PMID:28793749

Resource distribution and group size in the common langur Semnopithecus entellus in southern India.

PubMed

Vasudev, Divya; Kumar, Ajith; Sinha, Anindya

2008-07-01

We investigated the influence of resource abundance and distribution on the group size and composition of the common langur Semnopithecus entellus in the contiguous forests of Bandipur National Park, Mudumalai Wildlife Sanctuary and Nagarahole National Park in southern India. We also explored any additional effect of predator pressure and the risk of take-over on the same attributes. Data on group composition and vegetation were collected from January to May 2006. The size and composition of 94 bisexual groups were obtained. The group size varied from 7 to 40 and the groups included unimale and multimale groups. Thirty-five all-male groups were encountered. Vegetation was sampled from 17 grids of dimension 1 km x 1 km, each containing twelve 25 m x 25 m plots. The list of food species was compiled from previous studies and observations made during the study period. The mean basal area of all the food trees within each plot and its coefficient of variation at the level of the grid were used to represent resource abundance and distribution, respectively. The number of adult females and males within groups were analyzed separately to test for differential effects on age-sex categories. Group size increased as resources became spatially more heterogeneous. The abundance of resources had a negative effect on group size. This study did not find evidence supporting the direct effect of predator presence or of the risk of take-over. Contrary to what were expected, adult males reacted more strongly and predictably to resources than did adult females. The group attributes and their relationship with food resource abundance and distribution differed between two sites in the study area possibly owing to langur subspecies differences.

The evolution of biomass-burning aerosol size distributions due to coagulation: dependence on fire and meteorological details and parameterization

NASA Astrophysics Data System (ADS)

Sakamoto, Kimiko M.; Laing, James R.; Stevens, Robin G.; Jaffe, Daniel A.; Pierce, Jeffrey R.

2016-06-01

Biomass-burning aerosols have a significant effect on global and regional aerosol climate forcings. To model the magnitude of these effects accurately requires knowledge of the size distribution of the emitted and evolving aerosol particles. Current biomass-burning inventories do not include size distributions, and global and regional models generally assume a fixed size distribution from all biomass-burning emissions. However, biomass-burning size distributions evolve in the plume due to coagulation and net organic aerosol (OA) evaporation or formation, and the plume processes occur on spacial scales smaller than global/regional-model grid boxes. The extent of this size-distribution evolution is dependent on a variety of factors relating to the emission source and atmospheric conditions. Therefore, accurately accounting for biomass-burning aerosol size in global models requires an effective aerosol size distribution that accounts for this sub-grid evolution and can be derived from available emission-inventory and meteorological parameters. In this paper, we perform a detailed investigation of the effects of coagulation on the aerosol size distribution in biomass-burning plumes. We compare the effect of coagulation to that of OA evaporation and formation. We develop coagulation-only parameterizations for effective biomass-burning size distributions using the SAM-TOMAS large-eddy simulation plume model. For the most-sophisticated parameterization, we use the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) to build a parameterization of the aged size distribution based on the SAM-TOMAS output and seven inputs: emission median dry diameter, emission distribution modal width, mass emissions flux, fire area, mean boundary-layer wind speed, plume mixing depth, and time/distance since emission. This parameterization was tested against an independent set of SAM-TOMAS simulations and yields R2 values of 0.83 and 0.89 for Dpm and modal width, respectively. The size distribution is particularly sensitive to the mass emissions flux, fire area, wind speed, and time, and we provide simplified fits of the aged size distribution to just these input variables. The simplified fits were tested against 11 aged biomass-burning size distributions observed at the Mt. Bachelor Observatory in August 2015. The simple fits captured over half of the variability in observed Dpm and modal width even though the freshly emitted Dpm and modal widths were unknown. These fits may be used in global and regional aerosol models. Finally, we show that coagulation generally leads to greater changes in the particle size distribution than OA evaporation/formation does, using estimates of OA production/loss from the literature.

A statistical approach to estimate the 3D size distribution of spheres from 2D size distributions

USGS Publications Warehouse

Kong, M.; Bhattacharya, R.N.; James, C.; Basu, A.

2005-01-01

Size distribution of rigidly embedded spheres in a groundmass is usually determined from measurements of the radii of the two-dimensional (2D) circular cross sections of the spheres in random flat planes of a sample, such as in thin sections or polished slabs. Several methods have been devised to find a simple factor to convert the mean of such 2D size distributions to the actual 3D mean size of the spheres without a consensus. We derive an entirely theoretical solution based on well-established probability laws and not constrained by limitations of absolute size, which indicates that the ratio of the means of measured 2D and estimated 3D grain size distribution should be r/4 (=.785). Actual 2D size distribution of the radii of submicron sized, pure Fe0 globules in lunar agglutinitic glass, determined from backscattered electron images, is tested to fit the gamma size distribution model better than the log-normal model. Numerical analysis of 2D size distributions of Fe0 globules in 9 lunar soils shows that the average mean of 2D/3D ratio is 0.84, which is very close to the theoretical value. These results converge with the ratio 0.8 that Hughes (1978) determined for millimeter-sized chondrules from empirical measurements. We recommend that a factor of 1.273 (reciprocal of 0.785) be used to convert the determined 2D mean size (radius or diameter) of a population of spheres to estimate their actual 3D size. ?? 2005 Geological Society of America.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.; Johnson, D.; Remer, L.

2004-01-01

Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensembel (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e. 33 bins). Atmospheric aerosols are also described using number density size distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep tropical clouds in the west Pacific warm pool region and in the mid-latitude continent with different concentrations of CCN: a low "c1ean"concentration and a high "dirty" concentration. In addition, differences and similarities between bulk microphysics and spectral-bin microphysical schemes will be examined and discussed.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.; Johnson, D.; Remer, L.

2004-01-01

Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, r d a U production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensembe1 (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and platelike), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e. 33 bins). Atmospheric aerosols are also described using number density size-distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep tropical clouds in the west Pacific warm pool region and in the mid-latitude continent with different concentrations of CCN: a low "c1ean"concentration and a high "dirty" concentration. In addition, differences and similarities between bulk microphysics and spectral-bin microphysical schemes will be examined and discussed.

Improving Sensitivity in Ultrasound Molecular Imaging by Tailoring Contrast Agent Size Distribution: In Vivo Studies

PubMed Central

Streeter, Jason E.; Gessner, Ryan; Miles, Iman; Dayton, Paul A.

2010-01-01

Molecular imaging with ultrasound relies on microbubble contrast agents (MCAs) selectively adhering to a ligand-specific target. Prior studies have shown that only small quantities of microbubbles are retained at their target sites, therefore, enhancing contrast sensitivity to low concentrations of microbubbles is essential to improve molecular imaging techniques. In order to assess the effect of MCA diameter on imaging sensitivity, perfusion and molecular imaging studies were performed with microbubbles of varying size distributions. To assess signal improvement and MCA circulation time as a function of size and concentration, blood perfusion was imaged in rat kidneys using nontargeted size-sorted MCAs with a Siemens Sequoia ultrasound system (Siemans, Mountain View, CA) in cadence pulse sequencing (CPS) mode. Molecular imaging sensitivity improvements were studied with size-sorted αvβ3-targeted bubbles in both fibrosarcoma and R3230 rat tumor models. In perfusion imaging studies, video intensity and contrast persistence was ≈8 times and ≈3 times greater respectively, for “sorted 3-micron” MCAs (diameter, 3.3 ± 1.95 μm) when compared to “unsorted” MCAs (diameter, 0.9 ± 0.45 μm) at low concentrations. In targeted experiments, application of sorted 3-micron MCAs resulted in a ≈20 times video intensity increase over unsorted populations. Tailoring size-distributions results in substantial imaging sensitivity improvement over unsorted populations, which is essential in maximizing sensitivity to small numbers of MCAs for molecular imaging. PMID:20236606

Head and facial anthropometry of mixed-race US Army male soldiers for military design and sizing: a pilot study.

PubMed

Yokota, Miyo

2005-05-01

In the United States, the biologically admixed population is increasing. Such demographic changes may affect the distribution of anthropometric characteristics, which are incorporated into the design of equipment and clothing for the US Army and other large organizations. The purpose of this study was to examine multivariate craniofacial anthropometric distributions between biologically admixed male populations and single racial groups of Black and White males. Multivariate statistical results suggested that nose breadth and lip length were different between Blacks and Whites. Such differences may be considered for adjustments to respirators and chemical-biological protective masks. However, based on this pilot study, multivariate anthropometric distributions of admixed individuals were within the distributions of single racial groups. Based on the sample reported, sizing and designing for the admixed groups are not necessary if anthropometric distributions of single racial groups comprising admixed groups are known.

Illustration of distributed generation effects on protection system coordination

NASA Astrophysics Data System (ADS)

Alawami, Hussain Adnan

Environmental concerns, market forces, and emergence of new technologies have recently resulted in restructuring electric utility from vertically integrated networks to competitive deregulated entities. Distributed generation (DG) is playing a major role in such deregulated markets. When they are installed in small amounts and small sizes, their impacts on the system may be negligible. When their penetration levels increase as well as their sizes, however, they may start affecting the system performance from more than one aspect. Power system protection needs to be re-assessed after the emergence of DG. This thesis attempts to illustrate the impact of DG on the power system protection coordination. It will study the operation of the impedance relays, fuses, reclosers and overcurrent relays when a DG is added to the distribution network. Different DG sizes, distances from the network and locations within the distribution system will be considered. Power system protection coordination is very sensitive to the DG size where it is not for the DG distance. DG location has direct impact on the operation of the protective devices especially when it is inserted in the middle point of the distribution system. Key Words, Distributed Generation, Impedance relay, fuses, reclosers, overcurrent relays, power system protection coordination.

Particle size distribution: A key factor in estimating powder dustiness.

PubMed

López Lilao, Ana; Sanfélix Forner, Vicenta; Mallol Gasch, Gustavo; Monfort Gimeno, Eliseo

2017-12-01

A wide variety of raw materials, involving more than 20 samples of quartzes, feldspars, nephelines, carbonates, dolomites, sands, zircons, and alumina, were selected and characterised. Dustiness, i.e., a materials' tendency to generate dust on handling, was determined using the continuous drop method. These raw materials were selected to encompass a wide range of particle sizes (1.6-294 µm) and true densities (2650-4680 kg/m 3 ). The dustiness of the raw materials, i.e., their tendency to generate dust on handling, was determined using the continuous drop method. The influence of some key material parameters (particle size distribution, flowability, and specific surface area) on dustiness was assessed. In this regard, dustiness was found to be significantly affected by particle size distribution. Data analysis enabled development of a model for predicting the dustiness of the studied materials, assuming that dustiness depended on the particle fraction susceptible to emission and on the bulk material's susceptibility to release these particles. On the one hand, the developed model allows the dustiness mechanisms to be better understood. In this regard, it may be noted that relative emission increased with mean particle size. However, this did not necessarily imply that dustiness did, because dustiness also depended on the fraction of particles susceptible to be emitted. On the other hand, the developed model enables dustiness to be estimated using just the particle size distribution data. The quality of the fits was quite good and the fact that only particle size distribution data are needed facilitates industrial application, since these data are usually known by raw materials managers, thus making additional tests unnecessary. This model may therefore be deemed a key tool in drawing up efficient preventive and/or corrective measures to reduce dust emissions during bulk powder processing, both inside and outside industrial facilities. It is recommended, however, to use the developed model only if particle size, true density, moisture content, and shape lie within the studied ranges.

Role of Sample Processing Strategies at the European Union National Reference Laboratories (NRLs) Concerning the Analysis of Pesticide Residues.

PubMed

Hajeb, Parvaneh; Herrmann, Susan S; Poulsen, Mette E

2017-07-19

The guidance document SANTE 11945/2015 recommends that cereal samples be milled to a particle size preferably smaller than 1.0 mm and that extensive heating of the samples should be avoided. The aim of the present study was therefore to investigate the differences in milling procedures, obtained particle size distributions, and the resulting pesticide residue recovery when cereal samples were milled at the European Union National Reference Laboratories (NRLs) with their routine milling procedures. A total of 23 NRLs participated in the study. The oat and rye samples milled by each NRL were sent to the European Union Reference Laboratory on Cereals and Feedingstuff (EURL) for the determination of the particle size distribution and pesticide residue recovery. The results showed that the NRLs used several different brands and types of mills. Large variations in the particle size distributions and pesticide extraction efficiencies were observed even between samples milled by the same type of mill.

Physico-chemical characterization of grain dust in storage air of Bangalore.

PubMed

Mukherjee, A K; Nag, D P; Kakde, Y; Babu, K R; Prdkash, M N; Rao, S R

1998-06-01

An Anderson personal cascade impactor was used to study the particle mass size distribution in the storage air of two major grain storage centers in Bangalore. Dust levels in storage air as well as the personal exposures of workers were determined along with a detailed study on the particle size distribution. Protein and carbohydrate content of the dust were also determined respectively in the phosphate buffer saline (PBS) and water extracts by using the standard analytical techniques. Personal exposures in both of the grain storage centers have been found to be much above the limit prescribed by ACGIH (1995-96). But the results of particle size analysis showed a higher particle mass distribution in the non-respirable size range. The mass median diameters (MMD) of the storage air particulate of both the centers were found to be beyond the respirable range. Presence of protein and carbohydrate in the storage air dust is indicative of the existence of glyco-proteins, mostly of membrane origin.

Freeze-drying of nanosuspensions, 1: freezing rate versus formulation design as critical factors to preserve the original particle size distribution.

PubMed

Beirowski, Jakob; Inghelbrecht, Sabine; Arien, Albertina; Gieseler, Henning

2011-05-01

It has been recently reported in the literature that using a fast freezing rate during freeze-drying of drug nanosuspensions is beneficial to preserve the original particle size distribution. All freezing rates studied were obtained by utilizing a custom-made apparatus and were then indirectly related to conventional vial freeze-drying. However, a standard freeze-dryer is only capable of achieving moderate freezing rates in the shelf fluid circulation system. Therefore, it was the purpose of the present study to evaluate the possibility to establish a typical freezing protocol applicable to a standard freeze-drying unit in combination with an adequate choice of cryoprotective excipients and steric stabilizers to preserve the original particle size distribution. Six different drug nanosuspensions containing itraconazole as a drug model were studied using freeze-thaw experiments and a full factorial design to reveal major factors for the stabilization of drug nanosuspensions and the corresponding interactions. In contrast to previous reports, the freezing regime showed no significant influence on preserving the original particle size distribution, suggesting that the concentrations of both the steric stabilizer and the cryoprotective agent are optimized. Moreover, it could be pinpointed that the combined effect of steric stabilizer and cryoprotectant clearly contribute to nanoparticle stability. Copyright © 2010 Wiley-Liss, Inc.

A Phase Field Study of the Effect of Microstructure Grain Size Heterogeneity on Grain Growth

NASA Astrophysics Data System (ADS)

Crist, David J. D.

Recent studies conducted with sharp-interface models suggest a link between the spatial distribution of grain size variance and average grain growth rate. This relationship and its effect on grain growth rate was examined using the diffuse-interface Phase Field Method on a series of microstructures with different degrees of grain size gradation. Results from this work indicate that the average grain growth rate has a positive correlation with the average grain size dispersion for phase field simulations, confirming previous observations. It is also shown that the grain growth rate in microstructures with skewed grain size distributions is better measured through the change in the volume-weighted average grain size than statistical mean grain size. This material is based upon work supported by the National Science Foundation under Grant No. 1334283. The NSF project title is "DMREF: Real Time Control of Grain Growth in Metals" and was awarded by the Civil, Mechanical and Manufacturing Innovation division under the Designing Materials to Revolutionize and Engineer our Future (DMREF) program.

Effect of the slope and initial moisture content on soil loss, aggregate and particle size distribution

NASA Astrophysics Data System (ADS)

Szabó, Judit Alexandra; Jakab, Gergely; Szabó, Boglárka

2015-04-01

Soil structure degradation has effect through the soil water balance and nutrient supply on the agricultural potential of an area. The soil erosion process comprises two phases: detachment and transport by water. To study the transport phase nozzle type laboratory-scale rainfall simulator was used with constant 80 mmhr-1 intensity on an arable haplic Cambisol. Measuring the aggregate and particle size distribution of the soil loss gives a good approach the erosion process. The primary objective of this study was to examine the sediment concentration, and detect the quality and quantity change of the soil loss during a single precipitation under six treatment combinations (recently tilled and crusty soil surface on two different slope steepness, inland inundation and drought soil conditions). Soil loss were collected continually, and separated per aggregate size fractions with sieves in three rounds during a rain to measure the weights. The particle size distribution was measured with Horiba LA-950 particle size analyzer. In general the ratio of the macro aggregates decreases and the ratio of the micro aggregates and clay fraction increases in the sediment with time during the precipitation due to the raindrop impact. Sediment concentration depends on the slope steepness, as from steeper slopes the runoff can transport bigger amount of sediment, but from the tilled surface bigger aggregates were washing down. Micro aggregate fraction is one of the indicators of good soil structure. The degradation of micro aggregates occurs in steeper slopes and the most erosive time period depends on the micromorphology of the surface. And while the aggregate size distribution of the soil loss of the treatments shows high variety of distribution and differs from the original soil, the particle size distribution of each aggregate size fraction shows similar trends except the 50-250 µm fraction where the fine sand fraction is dominating instead of the loam. This anomaly may be connected with the TC content of this fraction, but more research is needed. In agricultural areas micro aggregate fraction plays important role in nutrient supply thus understanding the erosion process is necessary because of the better protection in the future.

Estimation of Effect Size from a Series of Experiments Involving Paired Comparisons.

ERIC Educational Resources Information Center

Gibbons, Robert D.; And Others

1993-01-01

A distribution theory is derived for a G. V. Glass-type (1976) estimator of effect size from studies involving paired comparisons. The possibility of combining effect sizes from studies involving a mixture of related and unrelated samples is also explored. Resulting estimates are illustrated using data from previous psychiatric research. (SLD)

Calculations of the variability of ice cloud radiative properties at selected solar wavelengths

NASA Technical Reports Server (NTRS)

Welch, R. M.; Zdunkowski, W. G.; Cox, S. K.

1980-01-01

This study shows that there is surprising little difference in values of reflectance, absorptance, and transmittance for many of the intermediate-size particle spectra. Particle size distributions with mode radii ranging from approximately 50 to 300 microns, irrespective of particle shape and nearly independent of the choice of size distribution representation, give relatively similar flux values. The very small particle sizes, however, have significantly larger values of reflectance and transmittance with corresponding smaller values of absorptance than do the larger particle sizes. The very large particle modes produce very small values of reflectance and transmittance along with very large values of absorptance. Such variations are particularly noticeable when plotted as a function of wavelength.

Sedimentation field flow fractionation and optical absorption spectroscopy for a quantitative size characterization of silver nanoparticles.

PubMed

Contado, Catia; Argazzi, Roberto; Amendola, Vincenzo

2016-11-04

Many advanced industrial and biomedical applications that use silver nanoparticles (AgNPs), require that particles are not only nano-sized, but also well dispersed, not aggregated and not agglomerated. This study presents two methods able to give rapidly sizes of monodispersed AgNPs suspensions in the dimensional range of 20-100nm. The first method, based on the application of Mie's theory, determines the particle sizes from the values of the surface plasmon resonance wavelength (SPR MAX ), read from the optical absorption spectra, recorded between 190nm and 800nm. The computed sizes were compared with those determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) and resulted in agreement with the nominal values in a range between 13% (for 20nm NPs) and 1% (for 100nm NPs), The second method is based on the masterly combination of the Sedimentation Field Flow Fractionation (SdFFF - now sold as Centrifugal FFF-CFFF) and the Optical Absorption Spectroscopy (OAS) techniques to accomplish sizes and quantitative particle size distributions for monodispersed, non-aggregated AgNPs suspensions. The SdFFF separation abilities, well exploited to size NPs, greatly benefits from the application of Mie's theory to the UV-vis signal elaboration, producing quantitative mass-based particle size distributions, from which trusted number-sized particle size distributions can be derived. The silver mass distributions were verified and supported by detecting off-line the Ag concentration with the graphite furnace atomic absorption spectrometry (GF-AAS). Copyright © 2016 Elsevier B.V. All rights reserved.

Investigation of pore size and energy distributions by statistical physics formalism applied to agriculture products

NASA Astrophysics Data System (ADS)

Aouaini, Fatma; Knani, Salah; Yahia, Manel Ben; Bahloul, Neila; Ben Lamine, Abdelmottaleb; Kechaou, Nabil

2015-12-01

In this paper, we present a new investigation that allows determining the pore size distribution (PSD) in a porous medium. This PSD is achieved by using the desorption isotherms of four varieties of olive leaves. This is by the means of statistical physics formalism and Kelvin's law. The results are compared with those obtained with scanning electron microscopy. The effect of temperature on the distribution function of pores has been studied. The influence of each parameter on the PSD is interpreted. A similar function of adsorption energy distribution, AED, is deduced from the PSD.

A new stochastic algorithm for inversion of dust aerosol size distribution

NASA Astrophysics Data System (ADS)

Wang, Li; Li, Feng; Yang, Ma-ying

2015-08-01

Dust aerosol size distribution is an important source of information about atmospheric aerosols, and it can be determined from multiwavelength extinction measurements. This paper describes a stochastic inverse technique based on artificial bee colony (ABC) algorithm to invert the dust aerosol size distribution by light extinction method. The direct problems for the size distribution of water drop and dust particle, which are the main elements of atmospheric aerosols, are solved by the Mie theory and the Lambert-Beer Law in multispectral region. And then, the parameters of three widely used functions, i.e. the log normal distribution (L-N), the Junge distribution (J-J), and the normal distribution (N-N), which can provide the most useful representation of aerosol size distributions, are inversed by the ABC algorithm in the dependent model. Numerical results show that the ABC algorithm can be successfully applied to recover the aerosol size distribution with high feasibility and reliability even in the presence of random noise.

Scaling and allometry in the building geometries of Greater London

NASA Astrophysics Data System (ADS)

Batty, M.; Carvalho, R.; Hudson-Smith, A.; Milton, R.; Smith, D.; Steadman, P.

2008-06-01

Many aggregate distributions of urban activities such as city sizes reveal scaling but hardly any work exists on the properties of spatial distributions within individual cities, notwithstanding considerable knowledge about their fractal structure. We redress this here by examining scaling relationships in a world city using data on the geometric properties of individual buildings. We first summarise how power laws can be used to approximate the size distributions of buildings, in analogy to city-size distributions which have been widely studied as rank-size and lognormal distributions following Zipf [ Human Behavior and the Principle of Least Effort (Addison-Wesley, Cambridge, 1949)] and Gibrat [ Les Inégalités Économiques (Librarie du Recueil Sirey, Paris, 1931)]. We then extend this analysis to allometric relationships between buildings in terms of their different geometric size properties. We present some preliminary analysis of building heights from the Emporis database which suggests very strong scaling in world cities. The data base for Greater London is then introduced from which we extract 3.6 million buildings whose scaling properties we explore. We examine key allometric relationships between these different properties illustrating how building shape changes according to size, and we extend this analysis to the classification of buildings according to land use types. We conclude with an analysis of two-point correlation functions of building geometries which supports our non-spatial analysis of scaling.

History of water-column anoxia in the Black Sea indicated by pyrite framboid size distributions

USGS Publications Warehouse

Wilkin, R.T.; Arthur, M.A.; Dean, W.E.

1997-01-01

A detailed study of size distributions of framboidal pyrite in Holocene Black Sea sediments establishes the timing of a change from deposition under an oxic water column to deposition under an anoxic and sulfidic water column. In the most recent carbonate-rich sediments (Unit I) and in the organic carbon-rich sapropel (Unit II), framboid size distributions are remarkably uniform (mean diameter= 5 ??m); over 95% of the framboids in Unit I and Unit II are < 7 ??m in diameter. These properties of framboidal pyrite are consistent with framboid nucleation and growth within an anoxic and sulfidic water column, followed by transport to the sediment-water interface, cessation of pyrite growth due to the exhaustion of reactive iron, and subsequent burial. In contrast, the organic carbon-poor sediments of lacustrine Unit III contain pyrite framboids that are generally much larger in size (mean diameter = 10 ??m). In Unit III, over 95% of the framboids are < 25 ??m in diameter, 40% of framboids are between 7 ??m and 25 ??m, and framboids up to 50 ??m in diameter are present. This distribution of sizes suggests framboid nucleation and growth within anoxic sediment porewaters. These new data on size distributions of framboidal pyrite confirm that the development of water-column anoxia in the Black Sea coincided with the initiation of deposition of laminated Unit II sapropels.

Fluctuations in email size

NASA Astrophysics Data System (ADS)

Matsubara, Yoshitsugu; Musashi, Yasuo

2017-12-01

The purpose of this study is to explain fluctuations in email size. We have previously investigated the long-term correlations between email send requests and data flow in the system log of the primary staff email server at a university campus, finding that email size frequency follows a power-law distribution with two inflection points, and that the power-law property weakens the correlation of the data flow. However, the mechanism underlying this fluctuation is not completely understood. We collected new log data from both staff and students over six academic years and analyzed the frequency distribution thereof, focusing on the type of content contained in the emails. Furthermore, we obtained permission to collect "Content-Type" log data from the email headers. We therefore collected the staff log data from May 1, 2015 to July 31, 2015, creating two subdistributions. In this paper, we propose a model to explain these subdistributions, which follow log-normal-like distributions. In the log-normal-like model, email senders -consciously or unconsciously- regulate the size of new email sentences according to a normal distribution. The fitting of the model is acceptable for these subdistributions, and the model demonstrates power-law properties for large email sizes. An analysis of the length of new email sentences would be required for further discussion of our model; however, to protect user privacy at the participating organization, we left this analysis for future work. This study provides new knowledge on the properties of email sizes, and our model is expected to contribute to the decision on whether to establish upper size limits in the design of email services.

Broadening of Cloud Droplet Size Distributions and Warm Rain Initiation Associated with Turbulence: An Overview

DOE PAGES

Lu, Chunsong; Liu, Yangang; Niu, Shengjie; ...

2017-10-12

In the paper of warm clouds, there are many outstanding questions. Cloud droplet size distributions are much wider, and warm rain is initiated in a shorter time and with a shallower cloud depth than theoretical expectations. This review summarizes the studies related to the effects of turbulent fluctuations and turbulent entrainment-mixing on the broadening of droplet size distributions and warm rain initiation, including observational, laboratorial, numerical, and theoretical achievements. Particular attention is paid to studies by Chinese scientists since the 1950s, since most results have been published in Chinese. The review reveals that high-resolution observations and simulations, and laboratory experimentsmore » are needed because knowledge of the detailed physical processes involved in the effects of turbulence and entrainment-mixing on cloud microphysics still remains elusive.« less

Broadening of Cloud Droplet Size Distributions and Warm Rain Initiation Associated with Turbulence: An Overview

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Chunsong; Liu, Yangang; Niu, Shengjie

In the paper of warm clouds, there are many outstanding questions. Cloud droplet size distributions are much wider, and warm rain is initiated in a shorter time and with a shallower cloud depth than theoretical expectations. This review summarizes the studies related to the effects of turbulent fluctuations and turbulent entrainment-mixing on the broadening of droplet size distributions and warm rain initiation, including observational, laboratorial, numerical, and theoretical achievements. Particular attention is paid to studies by Chinese scientists since the 1950s, since most results have been published in Chinese. The review reveals that high-resolution observations and simulations, and laboratory experimentsmore » are needed because knowledge of the detailed physical processes involved in the effects of turbulence and entrainment-mixing on cloud microphysics still remains elusive.« less

Suppression of nucleation mode particles by biomass burning in an urban environment: a case study.

PubMed

Agus, Emily L; Lingard, Justin J N; Tomlin, Alison S

2008-08-01

Measurements of concentrations and size distributions of particles 4.7 to 160 nm were taken using an SMPS during the bonfire and firework celebrations on Bonfire Night in Leeds, UK, 2006. These celebrations provided an opportunity to study size distributions in a unique atmospheric pollution situation during and following a significant emission event due to open biomass burning. A log-normal fitting program was used to determine the characteristics of the modal groups present within hourly averaged size distributions. Results from the modal fitting showed that on bonfire night the smallest nucleation mode, which was present before and after the bonfire event and on comparison weekends, was not detected within the size distribution. In addition, there was a significant shift in the modal diameters of the remaining modes during the peak of the pollution event. Using the concept of a coagulation sink, the atmospheric lifetimes of smaller particles were significantly reduced during the pollution event, and thus were used to explain the disappearance of the smallest nucleation mode as well as changes in particle count mean diameters. The significance for particle mixing state is discussed.

Studies on remote sensing method of particle size and water density distribution in mists and clouds using laser radar techniques

NASA Technical Reports Server (NTRS)

Shimizu, H.; Kobayasi, T.; Inaba, H.

1979-01-01

A method of remote measurement of the particle size and density distribution of water droplets was developed. In this method, the size of droplets is measured from the Mie scattering parameter which is defined as the total-to-backscattering ratio of the laser beam. The water density distribution is obtained by a combination of the Mie scattering parameter and the extinction coefficient of the laser beam. This method was examined experimentally for the mist generated by an ultrasonic mist generator and applied to clouds containing rain and snow. Compared with the conventional sampling method, the present method has advantages of remote measurement capability and improvement in accuracy.

Forecasting distributions of large federal-lands fires utilizing satellite and gridded weather information

USGS Publications Warehouse

Preisler, H.K.; Burgan, R.E.; Eidenshink, J.C.; Klaver, Jacqueline M.; Klaver, R.W.

2009-01-01

The current study presents a statistical model for assessing the skill of fire danger indices and for forecasting the distribution of the expected numbers of large fires over a given region and for the upcoming week. The procedure permits development of daily maps that forecast, for the forthcoming week and within federal lands, percentiles of the distributions of (i) number of ignitions; (ii) number of fires above a given size; (iii) conditional probabilities of fires greater than a specified size, given ignition. As an illustration, we used the methods to study the skill of the Fire Potential Index an index that incorporates satellite and surface observations to map fire potential at a national scale in forecasting distributions of large fires. ?? 2009 IAWF.

Particle size distribution and respiratory deposition estimates of airborne perfluoroalkyl acids during the haze period in the megacity of Shanghai.

PubMed

Guo, Mengjie; Lyu, Yan; Xu, Tingting; Yao, Bo; Song, Weihua; Li, Mei; Yang, Xin; Cheng, Tiantao; Li, Xiang

2018-03-01

This study presents the particle size distribution and respiratory deposition estimates of airborne perfluoroalkyl acids (PFAAs) during the haze period. Size-segregated haze aerosols were collected from an urban location in Shanghai using an eight-stage air sampler. The samples were analyzed for eight PFAAs using ultra-high-performance liquid chromatography tandem triple quadrupole mass spectrometry. The quantification results showed that the concentrations of particle-bound Σ 8PFAAs ranged from 0.26 to 1.90 ng m -3 (mean: 1.44 ng m -3 ). All of the measured PFAAs particle size distributions had a bimodal mode that peaked respectively in accumulation size range (0.4 < Dp < 2.1 μm) and coarse size ranges (Dp > 2.1 μm), but the width of each distribution somewhat varied by compound. The emission source, molecular weight, and volatility of the PFAAs were important factors influencing the size distribution of particle-bound PFAAs. Of these compounds, PFUnDA presented a strong accumulation in the fine size range (average 75% associated with particles <2.1 μm), followed by PFOA (69%) and PFDA (64%). The human risk assessment of PFOS via inhalation was addressed and followed the same pattern as the size distribution, with a 2-fold higher risk for the fine particle fraction compared to the coarse particle fraction at urban sites. Approximately 30.3-82.0% of PFAA deposition (∑PFAA: 72.5%) in the alveolar region was associated with particles <2.1 μm, although the contribution of fine particles to the total PFAAs concentration in urban air was only 28-57% (∑8PFAAs: 48%). These results suggested that fine particles are significant contributors to the deposition of PFAAs in the alveolar region of the lung. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Particle Size Distribution and Pollutant Speciation Analyses of Stormwater Runoff in the Ancient Town of Suzhou].

PubMed

Li, Huai; Wu, Wei; Tian, Yong-jing; Huang, Tian-yin

2016-02-15

The particle size distribution (PSD) and its transformation processes in the stormwater runoffs in the ancient town of Suzhou were studied based on the particles size analyses, the water-quality monitoring data and the parameters of the rainfall-runoff models. The commercial districts, the modern residential area, the old residential area, the traffic area and the landscape tourist area were selected as the five functional example areas in the ancient town of Suzhou. The effects of antecedent dry period, the rainfall intensity and the amount of runoffs on the particle size distributions were studied, and the existing forms of the main pollutants in different functional areas and their possible relations were analyzed as well. The results showed that the particle size distribution, the migration processes and the output characteristics in the stormwater runoffs were greatly different in these five functional areas, which indicated different control measures for the pollution of the runoffs should be taken in the design process. The antecedent dry period, the rainfall intensity and the amount of runoffs showed significant correlations with the particle size distribution, showing these were the important factors. The output of the particles was greatly influenced by the flow scouring in the early period of the rainfall, and the correlations between the amount of runoffs and the particle migration ability presented significant difference in 30% (early period) and 70% (later period) of the runoff volume. The major existence form of the output pollutants was particle, and the correlation analyses of different diameter particles showed that the particles smaller than 150 microm were the dominant carrier of the pollutants via adsorption and accumulation processes.

1H and 2H NMR studies of benzene confined in porous solids: melting point depression and pore size distribution.

PubMed

Aksnes, D W; Kimtys, L

2004-01-01

The pore size distributions of four controlled pore glasses and three silica gels with nominal diameters in the range 4-24 nm were determined by measuring the 1H and 2H NMR signals from the non-frozen fraction of confined benzene and perdeuterated benzene as a function of temperature, in steps of ca. 0.1-1 K. The liquid and solid components of the adsorbate were distinguished, on the basis of the spin-spin relaxation time T2, by employing a spin-echo sequence. The experimental intensity curves of the liquid component are well represented by a sum of two error functions. The mean melting point depression of benzene and perdeuterated benzene confined in the four controlled pore glasses, with pore radius R, follows the simplified Gibbs-Thompson equation DeltaT=kp/R with a kp value of 44 K nm. As expected, the kp value mainly determines the position of the pore size distribution curve, i.e., the mean pore radius, while the transition width determines the shape of the pore size distribution curve. The excellent agreement between the results from the 1H and 2H measurements shows that the effect of the background absorption from protons in physisorbed water and silanol groups is negligible under the experimental conditions used. The overall pore size distributions determined by NMR are in reasonable agreement with the results specified by the manufacturer, or measured by us using the N2 sorption technique. The NMR method, which is complementary to the conventional gas sorption method, is particularly appropriate for studying pore sizes in the mesoporous range.

Application of Lorenz curve to interpret concentration of contraception and fertility in a population.

PubMed

Ghanma, M A; Rider, R V; Sirageldin, I

1984-01-01

The Lorenz Curve, originally developed to measure the concentration of wealth in a population, was used to describe the distribution of contraceptive practice in Jordan. Data from the 1976 Jordan Fertility Study, carried out as part of the World Fertility Survey program, was used in the analysis. The application of the Automatic Interaction Detector program to the survey's sample population of 3611 women of reproductive age divided the sample into 6 mutually exclusive groups on the basis of residence, education, and whether desired family size was attained or not attained. These 3 characteristics accounted for a major portion of the variation in contraceptive practice. These subgroups, in ascending order by the proportion practicing contraception, were: 1) rural women with unattained desired family size; 2) urban, illiterate women with unattained desired family size; 3) rural women with attained desired family size; 4) urban, literate women with unattained desired family size; 5) urban, illiterate women with attained desired family size; and 6) urban, literate women with attained desired family size. The cumulative proportion of the sample in each ordered subdivision was plotted on the X axis of a graph, and the cumulative proportion of those practicing contraception was plotted on the Y axis of the graph. A line connecting the intersection of the points on the X and Y axis was then drawn. The resultant line was a concave ascending line. If contraceptive practice was evenly distributed in the population, the line would be a straight diagonal line. The plotted curved line indicated that contraceptive practice was unevenly distributed in the population. 2 indexes for measuring the area between the diagonal and the line resulting from plotting the observed distribution for each subgroup was used to assess the degree of concentration of contraceptive practice in the population. The indexes also indicated that contraceptive practice was unequally distributed. When separate curves were plotted for the subgroups with attained desired family size and the subgroups without attained desired family size, it was apparent that the distribution of contraceptive practice was more uniform among those with attained desired family size than among the other 3 subgroups. A curve for the distribution of births was then plotted on the same graph. This curve was not a true application of the Lorenz Curve since it was based on the order of the subdivisions by birth rates. The resultant line approached the straight diagonal line and indicated that the distribution of births was fairly evenly distributed in the population. The uneven distribution of contraceptive practice and the uniform distribution of births suggests that contraceptive practice in this population is ineffective. This may be a characteristic of populations in the early stages of fertility control.

Particle size distribution of airborne Aspergillus fumigatus spores emitted from compost using membrane filtration

NASA Astrophysics Data System (ADS)

Deacon, L. J.; Pankhurst, L. J.; Drew, G. H.; Hayes, E. T.; Jackson, S.; Longhurst, P. J.; Longhurst, J. W. S.; Liu, J.; Pollard, S. J. T.; Tyrrel, S. F.

Information on the particle size distribution of bioaerosols emitted from open air composting operations is valuable in evaluating potential health impacts and is a requirement for improved dispersion simulation modelling. The membrane filter method was used to study the particle size distribution of Aspergillus fumigatus spores in air 50 m downwind of a green waste compost screening operation at a commercial facility. The highest concentrations (approximately 8 × 10 4 CFU m -3) of culturable spores were found on filters with pore diameters in the range 1-2 μm which suggests that the majority of spores are emitted as single cells. The findings were compared to published data collected using an Andersen sampler. Results were significantly correlated ( p < 0.01) indicating that the two methods are directly comparable across all particles sizes for Aspergillus spores.

The Italian primary school-size distribution and the city-size: a complex nexus

PubMed Central

Belmonte, Alessandro; Di Clemente, Riccardo; Buldyrev, Sergey V.

2014-01-01

We characterize the statistical law according to which Italian primary school-size distributes. We find that the school-size can be approximated by a log-normal distribution, with a fat lower tail that collects a large number of very small schools. The upper tail of the school-size distribution decreases exponentially and the growth rates are distributed with a Laplace PDF. These distributions are similar to those observed for firms and are consistent with a Bose-Einstein preferential attachment process. The body of the distribution features a bimodal shape suggesting some source of heterogeneity in the school organization that we uncover by an in-depth analysis of the relation between schools-size and city-size. We propose a novel cluster methodology and a new spatial interaction approach among schools which outline the variety of policies implemented in Italy. Different regional policies are also discussed shedding lights on the relation between policy and geographical features. PMID:24954714

Evidence for Natural Variability in Marine Stratocumulus Cloud Properties Due to Cloud-Aerosol

NASA Technical Reports Server (NTRS)

Albrecht, Bruce; Sharon, Tarah; Jonsson, Haf; Minnis, Patrick; Minnis, Patrick; Ayers, J. Kirk; Khaiyer, Mandana M.

2004-01-01

In this study, aircraft observations from the Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter are used to characterize the variability in drizzle, cloud, and aerosol properties associated with cloud rifts and the surrounding solid clouds observed off the coast of California. A flight made on 16 July 1999 provided measurements directly across an interface between solid and rift cloud conditions. Aircraft instrumentation allowed for measurements of aerosol, cloud droplet, and drizzle spectra. CCN concentrations were measured in addition to standard thermodynamic variables and the winds. A Forward Scatter Spectrometer Probe (FSSP) measured size distribution of cloud-sized droplets. A Cloud Imaging Probe (CIP) was used to measure distributions of drizzle-sized droplets. Aerosol distributions were obtained from a Cloud Aerosol Scatterprobe (CAS). The CAS probe measured aerosols, cloud droplets and drizzle-sized drops; for this study. The CAS probe was used to measure aerosols in the size range of 0.5 micron - 1 micron. Smaller aerosols were characterized using an Ultrafine Condensation Particle Counter (CPC) sensor. The CPC was used to measure particles with diameters greater than 0.003 micron. By subtracting different count concentrations measured with the CPC, this probe was capable of identifying ultrafine particles those falling in the size range of 3 nanometers - 7 nanometers that are believed to be associated with new particle production.

The effect of microscopic friction and size distributions on conditional probability distributions in soft particle packings

NASA Astrophysics Data System (ADS)

Saitoh, Kuniyasu; Magnanimo, Vanessa; Luding, Stefan

2017-10-01

Employing two-dimensional molecular dynamics (MD) simulations of soft particles, we study their non-affine responses to quasi-static isotropic compression where the effects of microscopic friction between the particles in contact and particle size distributions are examined. To quantify complicated restructuring of force-chain networks under isotropic compression, we introduce the conditional probability distributions (CPDs) of particle overlaps such that a master equation for distribution of overlaps in the soft particle packings can be constructed. From our MD simulations, we observe that the CPDs are well described by q-Gaussian distributions, where we find that the correlation for the evolution of particle overlaps is suppressed by microscopic friction, while it significantly increases with the increase of poly-dispersity.

Hybrid approach combining multiple characterization techniques and simulations for microstructural analysis of proton exchange membrane fuel cell electrodes

NASA Astrophysics Data System (ADS)

Cetinbas, Firat C.; Ahluwalia, Rajesh K.; Kariuki, Nancy; De Andrade, Vincent; Fongalland, Dash; Smith, Linda; Sharman, Jonathan; Ferreira, Paulo; Rasouli, Somaye; Myers, Deborah J.

2017-03-01

The cost and performance of proton exchange membrane fuel cells strongly depend on the cathode electrode due to usage of expensive platinum (Pt) group metal catalyst and sluggish reaction kinetics. Development of low Pt content high performance cathodes requires comprehensive understanding of the electrode microstructure. In this study, a new approach is presented to characterize the detailed cathode electrode microstructure from nm to μm length scales by combining information from different experimental techniques. In this context, nano-scale X-ray computed tomography (nano-CT) is performed to extract the secondary pore space of the electrode. Transmission electron microscopy (TEM) is employed to determine primary C particle and Pt particle size distributions. X-ray scattering, with its ability to provide size distributions of orders of magnitude more particles than TEM, is used to confirm the TEM-determined size distributions. The number of primary pores that cannot be resolved by nano-CT is approximated using mercury intrusion porosimetry. An algorithm is developed to incorporate all these experimental data in one geometric representation. Upon validation of pore size distribution against gas adsorption and mercury intrusion porosimetry data, reconstructed ionomer size distribution is reported. In addition, transport related characteristics and effective properties are computed by performing simulations on the hybrid microstructure.

Size distributions of coastal ocean suspended particulate inorganic matter: Amorphous silica and clay minerals and their dynamics

NASA Astrophysics Data System (ADS)

Zhang, Xiaodong; Stavn, Robert H.; Falster, Alexander U.; Rick, Johannes J.; Gray, Deric; Gould, Richard W.

2017-04-01

Particulate inorganic matter (PIM) is a key component in estuarine and coastal systems and plays a critical role in trace metal cycling. Better understanding of coastal dynamics and biogeochemistry requires improved quantification of PIM in terms of its concentration, size distribution, and mineral species composition. The angular pattern of light scattering contains detailed information about the size and composition of particles. These volume scattering functions (VSFs) were measured in Mobile Bay, Alabama, USA, a dynamic, PIM dominated coastal environment. From measured VSFs, we determined through inversion the particle size distributions (PSDs) of major components of PIM, amorphous silica and clay minerals. An innovation here is the extension of our reported PSDs significantly into the submicron range. The PSDs of autochthonous amorphous silica exhibit two unique features: a peak centered at about 0.8 μm between 0.2 and 4 μm and a very broad shoulder essentially extending from 4 μm to >100 μm. With an active and steady particle source from blooming diatoms, the shapes of amorphous silica PSDs for sizes <10 μm varied little across the study area, but showed more particles of sizes >10 μm inside the bay, likely due to wind-induced resuspension of larger frustules that have settled. Compared to autochthonous amorphous silica, the allochthonous clay minerals are denser and exhibit relatively narrower PSDs with peaks located between 1 and 4 μm. Preferential settling of larger mineral particles as well as the smaller but denser illite component further narrowed the size distributions of clay minerals as they were being transported outside the bay. The derived PSDs also indicated a very dynamic situation in Mobile Bay when a cold weather front passed through during the experiment. With northerly winds of speeds up to 15 m s-1, both amorphous silica and clay minerals showed a dramatic increase in concentration and broadening in size distribution outside the exit of the barrier islands, indicative of wind-induced resuspension and subsequent advection of particles out of Mobile Bay. While collectively recognized as the PIM, amorphous silica and clay minerals, as shown in this study, possess very different size distributions. Considering how differences in PSDs and the associated particle areas will effect differences in sorption/desorption properties of these components, the results also demonstrate the potential of applying VSF-inversion in studying biogeochemistry in the estuarine-coastal ocean system.

Ejected Particle Size Distributions from Shocked Metal Surfaces

DOE PAGES

Schauer, M. M.; Buttler, W. T.; Frayer, D. K.; ...

2017-04-12

Here, we present size distributions for particles ejected from features machined onto the surface of shocked Sn targets. The functional form of the size distributions is assumed to be log-normal, and the characteristic parameters of the distribution are extracted from the measured angular distribution of light scattered from a laser beam incident on the ejected particles. We also found strong evidence for a bimodal distribution of particle sizes with smaller particles evolved from features machined into the target surface and larger particles being produced at the edges of these features.

Ejected Particle Size Distributions from Shocked Metal Surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schauer, M. M.; Buttler, W. T.; Frayer, D. K.

Here, we present size distributions for particles ejected from features machined onto the surface of shocked Sn targets. The functional form of the size distributions is assumed to be log-normal, and the characteristic parameters of the distribution are extracted from the measured angular distribution of light scattered from a laser beam incident on the ejected particles. We also found strong evidence for a bimodal distribution of particle sizes with smaller particles evolved from features machined into the target surface and larger particles being produced at the edges of these features.

Preparation of gold nanoparticles and determination of their particles size via different methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iqbal, Muhammad; Usanase, Gisele; Oulmi, Kafia

Graphical abstract: Preparation of gold nanoparticles via NaBH{sub 4} reduction method, and determination of their particle size, size distribution and morphology by using different techniques. - Highlights: • Gold nanoparticles were synthesized by NaBH{sub 4} reduction method. • Excess of reducing agent leads to tendency of aggregation. • The particle size, size distribution and morphology were investigated. • Particle size was determined both experimentally as well as theoretically. - Abstract: Gold nanoparticles have been used in various applications covering both electronics, biosensors, in vivo biomedical imaging and in vitro biomedical diagnosis. As a general requirement, gold nanoparticles should be preparedmore » in large scale, easy to be functionalized by chemical compound of by specific ligands or biomolecules. In this study, gold nanoparticles were prepared by using different concentrations of reducing agent (NaBH{sub 4}) in various formulations and their effect on the particle size, size distribution and morphology was investigated. Moreover, special attention has been dedicated to comparison of particles size measured by various techniques, such as, light scattering, transmission electron microscopy, UV spectrum using standard curve and particles size calculated by using Mie theory and UV spectrum of gold nanoparticles dispersion. Particle size determined by various techniques can be correlated for monodispersed particles and excess of reducing agent leads to increase in the particle size.« less

Vessel Sampling and Blood Flow Velocity Distribution With Vessel Diameter for Characterizing the Human Bulbar Conjunctival Microvasculature.

PubMed

Wang, Liang; Yuan, Jin; Jiang, Hong; Yan, Wentao; Cintrón-Colón, Hector R; Perez, Victor L; DeBuc, Delia C; Feuer, William J; Wang, Jianhua

2016-03-01

This study determined (1) how many vessels (i.e., the vessel sampling) are needed to reliably characterize the bulbar conjunctival microvasculature and (2) if characteristic information can be obtained from the distribution histogram of the blood flow velocity and vessel diameter. Functional slitlamp biomicroscope was used to image hundreds of venules per subject. The bulbar conjunctiva in five healthy human subjects was imaged on six different locations in the temporal bulbar conjunctiva. The histograms of the diameter and velocity were plotted to examine whether the distribution was normal. Standard errors were calculated from the standard deviation and vessel sample size. The ratio of the standard error of the mean over the population mean was used to determine the sample size cutoff. The velocity was plotted as a function of the vessel diameter to display the distribution of the diameter and velocity. The results showed that the sampling size was approximately 15 vessels, which generated a standard error equivalent to 15% of the population mean from the total vessel population. The distributions of the diameter and velocity were not only unimodal, but also somewhat positively skewed and not normal. The blood flow velocity was related to the vessel diameter (r=0.23, P<0.05). This was the first study to determine the sampling size of the vessels and the distribution histogram of the blood flow velocity and vessel diameter, which may lead to a better understanding of the human microvascular system of the bulbar conjunctiva.

Discrete hierarchy of sizes and performances in the exchange-traded fund universe

NASA Astrophysics Data System (ADS)

Vandermarliere, B.; Ryckebusch, J.; Schoors, K.; Cauwels, P.; Sornette, D.

2017-03-01

Using detailed statistical analyses of the size distribution of a universe of equity exchange-traded funds (ETFs), we discover a discrete hierarchy of sizes, which imprints a log-periodic structure on the probability distribution of ETF sizes that dominates the details of the asymptotic tail. This allows us to propose a classification of the studied universe of ETFs into seven size layers approximately organized according to a multiplicative ratio of 3.5 in their total market capitalization. Introducing a similarity metric generalizing the Herfindhal index, we find that the largest ETFs exhibit a significantly stronger intra-layer and inter-layer similarity compared with the smaller ETFs. Comparing the performance across the seven discerned ETF size layers, we find an inverse size effect, namely large ETFs perform significantly better than the small ones both in 2014 and 2015.

Particle Size Characteristics of Fluvial Suspended Sediment in Proglacial Streams, King George Island, South Shetland Island

NASA Astrophysics Data System (ADS)

Szymczak, Ewa

2017-12-01

In this study, the characterization of particle size distribution of suspended sediment that is transported by streams (Ornithologist Creek, Ecology Glacier Creeks, Petrified Forest Creek, Czech Creek, Vanishing Creek, Italian Creek) in the area of the Arctowski Polish Antarctic Station is presented. During the first period of the summer season, the aforementioned streams are supplied by the melting snow fields, while later on, by thawing permafrost. The water samples were collected from the streams at monthly intervals during the Antarctic summer season (January - March) of 2016. The particle size distribution was measured in the laboratory with a LISST-25X laser diffraction particle size analyser. According to Sequoia Scientific Inc., LISST-25X can measure particle sizes (Sauter Mean Diameter) between 2.50 and 500 μm. The results of particle size measurements were analysed in relation to flow velocity (0.18-0.89 m/s), the cross-sectional parameters of the streams, suspended sediment concentration (0.06-167.22 mg/dm3) and the content of particulate organic matter (9.8-84.85%). Overall, the mean particle size ranged from 28.8 to 136 μm. The grain size of well-sorted sediments ranged from 0.076 to 0.57, with the skewness and kurtosis values varying from -0.1 to 0.4, and from 0.67 to 1.3, respectively. Based on the particle size characteristics of suspended sediment, the streams were divided into two groups. For most of the streams, the sediment was very well sorted, while fine sand and very fine sand were dominant fractions displaying symmetric and platykurtic distributions, respectively. Only in two streams, the suspended sediment consisted of silt-size grains, well or moderately well sorted, with coarse-skewness and mostly mesokurtic distribution. The C-M chart suggested that the transportation processes of suspended sediment included the suspended mode only. The grain-size distribution of suspended sediment was mainly influenced by the stream runoff, surface sediment type and biological processes.

Criticality in finite dynamical networks

NASA Astrophysics Data System (ADS)

Rohlf, Thimo; Gulbahce, Natali; Teuscher, Christof

2007-03-01

It has been shown analytically and experimentally that both random boolean and random threshold networks show a transition from ordered to chaotic dynamics at a critical average connectivity Kc in the thermodynamical limit [1]. By looking at the statistical distributions of damage spreading (damage sizes), we go beyond this extensively studied mean-field approximation. We study the scaling properties of damage size distributions as a function of system size N and initial perturbation size d(t=0). We present numerical evidence that another characteristic point, Kd exists for finite system sizes, where the expectation value of damage spreading in the network is independent of the system size N. Further, the probability to obtain critical networks is investigated for a given system size and average connectivity k. Our results suggest that, for finite size dynamical networks, phase space structure is very complex and may not exhibit a sharp order-disorder transition. Finally, we discuss the implications of our findings for evolutionary processes and learning applied to networks which solve specific computational tasks. [1] Derrida, B. and Pomeau, Y. (1986), Europhys. Lett., 1, 45-49

Variability in group size and the evolution of collective action.

PubMed

Peña, Jorge; Nöldeke, Georg

2016-01-21

Models of the evolution of collective action typically assume that interactions occur in groups of identical size. In contrast, social interactions between animals occur in groups of widely dispersed size. This paper models collective action problems as two-strategy multiplayer games and studies the effect of variability in group size on the evolution of cooperative behavior under the replicator dynamics. The analysis identifies elementary conditions on the payoff structure of the game implying that the evolution of cooperative behavior is promoted or inhibited when the group size experienced by a focal player is more or less variable. Similar but more stringent conditions are applicable when the confounding effect of size-biased sampling, which causes the group-size distribution experienced by a focal player to differ from the statistical distribution of group sizes, is taken into account. Copyright © 2015 Elsevier Ltd. All rights reserved.

Numerical simulation for the magnetic force distribution in electromagnetic forming of small size flat sheet

NASA Astrophysics Data System (ADS)

Chen, Xiaowei; Wang, Wenping; Wan, Min

2013-12-01

It is essential to calculate magnetic force in the process of studying electromagnetic flat sheet forming. Calculating magnetic force is the basis of analyzing the sheet deformation and optimizing technical parameters. Magnetic force distribution on the sheet can be obtained by numerical simulation of electromagnetic field. In contrast to other computing methods, the method of numerical simulation has some significant advantages, such as higher calculation accuracy, easier using and other advantages. In this paper, in order to study of magnetic force distribution on the small size flat sheet in electromagnetic forming when flat round spiral coil, flat rectangular spiral coil and uniform pressure coil are adopted, the 3D finite element models are established by software ANSYS/EMAG. The magnetic force distribution on the sheet are analyzed when the plane geometries of sheet are equal or less than the coil geometries under fixed discharge impulse. The results showed that when the physical dimensions of sheet are less than the corresponding dimensions of the coil, the variation of induced current channel width on the sheet will cause induced current crowding effect that seriously influence the magnetic force distribution, and the degree of inhomogeneity of magnetic force distribution is increase nearly linearly with the variation of induced current channel width; the small size uniform pressure coil will produce approximately uniform magnetic force distribution on the sheet, but the coil is easy to early failure; the desirable magnetic force distribution can be achieved when the unilateral placed flat rectangular spiral coil is adopted, and this program can be take as preferred one, because the longevity of flat rectangular spiral coil is longer than the working life of small size uniform pressure coil.

Body-size trends of the extinct giant shark Carcharocles megalodon: a deep-time perspective on marine apex predators.

PubMed

Pimiento, Catalina; Balk, Meghan A

2015-06-01

The extinct shark Carcharocles megalodon is one of the largest marine apex predators ever to exist. Nonetheless, little is known about its body-size variations through time and space. Here, we studied the body-size trends of C. megalodon through its temporal and geographic range to better understand its ecology and evolution. Given that this species was the last of the megatooth lineage, a group of species that shows a purported size increase through time, we hypothesized that C. megalodon also displayed this trend, increasing in size over time and reaching its largest size prior to extinction. We found that C. megalodon body-size distribution was left-skewed (suggesting a long-term selective pressure favoring larger individuals), and presented significant geographic variation (possibly as a result of the heterogeneous ecological constraints of this cosmopolitan species) over geologic time. Finally, we found that stasis was the general mode of size evolution of C. megalodon (i.e., no net changes over time), contrasting with the trends of the megatooth lineage and our hypothesis. Given that C. megalodon is a relatively long-lived species with a widely distributed fossil record, we further used this study system to provide a deep-time perspective to the understanding of the body-size trends of marine apex predators. For instance, our results suggest that (1) a selective pressure in predatory sharks for consuming a broader range of prey may favor larger individuals and produce left-skewed distributions on a geologic time scale; (2) body-size variations in cosmopolitan apex marine predators may depend on their interactions with geographically discrete communities; and (3) the inherent characteristics of shark species can produce stable sizes over geologic time, regardless of the size trends of their lineages.

Empirical evidence for multi-scaled controls on wildfire size distributions in California

NASA Astrophysics Data System (ADS)

Povak, N.; Hessburg, P. F., Sr.; Salter, R. B.

2014-12-01

Ecological theory asserts that regional wildfire size distributions are examples of self-organized critical (SOC) systems. Controls on SOC event-size distributions by virtue are purely endogenous to the system and include the (1) frequency and pattern of ignitions, (2) distribution and size of prior fires, and (3) lagged successional patterns after fires. However, recent work has shown that the largest wildfires often result from extreme climatic events, and that patterns of vegetation and topography may help constrain local fire spread, calling into question the SOC model's simplicity. Using an atlas of >12,000 California wildfires (1950-2012) and maximum likelihood estimation (MLE), we fit four different power-law models and broken-stick regressions to fire-size distributions across 16 Bailey's ecoregions. Comparisons among empirical fire size distributions across ecoregions indicated that most ecoregion's fire-size distributions were significantly different, suggesting that broad-scale top-down controls differed among ecoregions. One-parameter power-law models consistently fit a middle range of fire sizes (~100 to 10000 ha) across most ecoregions, but did not fit to larger and smaller fire sizes. We fit the same four power-law models to patch size distributions of aspect, slope, and curvature topographies and found that the power-law models fit to a similar middle range of topography patch sizes. These results suggested that empirical evidence may exist for topographic controls on fire sizes. To test this, we used neutral landscape modeling techniques to determine if observed fire edges corresponded with aspect breaks more often than expected by random. We found significant differences between the empirical and neutral models for some ecoregions, particularly within the middle range of fire sizes. Our results, combined with other recent work, suggest that controls on ecoregional fire size distributions are multi-scaled and likely are not purely SOC. California wildfire ecosystems appear to be adaptive, governed by stationary and non-stationary controls, which may be either exogenous or endogenous to the system.

Analysis of exosome purification methods using a model liposome system and tunable-resistive pulse sensing

NASA Astrophysics Data System (ADS)

Lane, Rebecca E.; Korbie, Darren; Anderson, Will; Vaidyanathan, Ramanathan; Trau, Matt

2015-01-01

Exosomes are vesicles which have garnered interest due to their diagnostic and therapeutic potential. Isolation of pure yields of exosomes from complex biological fluids whilst preserving their physical characteristics is critical for downstream applications. In this study, we use 100 nm-liposomes from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol as a model system as a model system to assess the effect of exosome isolation protocols on vesicle recovery and size distribution using a single-particle analysis method. We demonstrate that liposome size distribution and ζ-potential are comparable to extracted exosomes, making them an ideal model for comparison studies. Four different purification protocols were evaluated, with liposomes robustly isolated by three of them. Recovered yields varied and liposome size distribution was unaltered during processing, suggesting that these protocols do not induce particle aggregation. This leads us to conclude that the size distribution profile and characteristics of vesicles are stably maintained during processing and purification, suggesting that reports detailing how exosomes derived from tumour cells differ in size to those from normal cells are reporting a real phenomenon. However, we hypothesize that larger particles present in most purified exosome samples represent co-purified contaminating non-exosome debris. These isolation techniques are therefore likely nonspecific and may co-isolate non-exosome material of similar physical properties.

Experimental Study of the Possibility to Make a Mortar with Ternary Sand (Natural and Artificial Fine Aggregates)

NASA Astrophysics Data System (ADS)

Baali, L.; Naceri, A.; Rahmouni, Z.; Mehidi, M. W. Noui

This experimental study investigates the possibility to make a mortar with a ternary sand (natural and artificial fine aggregates). This method is utilized to correct the particle size distribution of various sands used in mortar. For this investigation, three sands have been used: a dune sand (DS), a slag sand (SS), and brick sand (BS) at different proportions in mortar. After crushing, the artificial fine aggregate (blast furnace slag and waste brick fine aggregate) was sifted in order to use it as fine aggregate. The effect of the quality and grain size distribution of natural fine aggregate (i.e., DS) and artificial fine aggregates (i.e., SS and BS) on the physical properties of ternary sand confected (density, porosity, fineness modulus, equivalent sand, particle size distribution, water absorption) and properties of fresh and hardened mortar were analysed. In the same way for this study, the physical properties and chemical compositions of DS, SS, BS and cement were investigated. The results obtained show that the mechanical strength on mortar depends of the nature and particle size distribution of sand studied. The reuse of this recycled material (slag blast furnace and waste brick) in the industry would contribute to the protection of the environment. This study shows the potential of this method to make mortar with ternary sand (natural and artificial fine aggreagates) in order to improve the physical properties of sand. Utilising natural and artificial fine aggregates to produce quality mortar should yield significant environmental benefits.

Size-biased distributions in the generalized beta distribution family, with applications to forestry

Treesearch

Mark J. Ducey; Jeffrey H. Gove

2015-01-01

Size-biased distributions arise in many forestry applications, as well as other environmental, econometric, and biomedical sampling problems. We examine the size-biased versions of the generalized beta of the first kind, generalized beta of the second kind and generalized gamma distributions. These distributions include, as special cases, the Dagum (Burr Type III),...

The Role of Aerosols on Precipitation Processes: Cloud Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Matsui, T.

2012-01-01

Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, a detailed spectral-bin microphysical scheme was implemented into the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e., 33 bins). Atmospheric aerosols are also described using number density size-distribution functions. The model is tested by studying the evolution of deep cloud systems in the west Pacific warm pool region, the sub-tropics (Florida) and midlatitudes using identical thermodynamic conditions but with different concentrations of CCN: a low "clean" concentration and a high "dirty" concentration. Results indicate that the low CCN concentration case produces rainfall at the surface sooner than the high CeN case but has less cloud water mass aloft. Because the spectral-bin model explicitly calculates and allows for the examination of both the mass and number concentration of species in each size category, a detailed analysis of the instantaneous size spectrum can be obtained for these cases. It is shown that since the low (CN case produces fewer droplets, larger sizes develop due to greater condensational and collection growth, leading to a broader size spectrum in comparison to the high CCN case. Sensitivity tests were performed to identify the impact of ice processes, radiation and large-scale influence on cloud-aerosol interactive processes, especially regarding surface rainfall amounts and characteristics (i.e., heavy or convective versus light or stratiform types). In addition, an inert tracer was included to follow the vertical redistribution of aerosols by cloud processes. We will also give a brief review from observational evidence on the role of aerosol on precipitation processes.

A normative inference approach for optimal sample sizes in decisions from experience

PubMed Central

Ostwald, Dirk; Starke, Ludger; Hertwig, Ralph

2015-01-01

“Decisions from experience” (DFE) refers to a body of work that emerged in research on behavioral decision making over the last decade. One of the major experimental paradigms employed to study experience-based choice is the “sampling paradigm,” which serves as a model of decision making under limited knowledge about the statistical structure of the world. In this paradigm respondents are presented with two payoff distributions, which, in contrast to standard approaches in behavioral economics, are specified not in terms of explicit outcome-probability information, but by the opportunity to sample outcomes from each distribution without economic consequences. Participants are encouraged to explore the distributions until they feel confident enough to decide from which they would prefer to draw from in a final trial involving real monetary payoffs. One commonly employed measure to characterize the behavior of participants in the sampling paradigm is the sample size, that is, the number of outcome draws which participants choose to obtain from each distribution prior to terminating sampling. A natural question that arises in this context concerns the “optimal” sample size, which could be used as a normative benchmark to evaluate human sampling behavior in DFE. In this theoretical study, we relate the DFE sampling paradigm to the classical statistical decision theoretic literature and, under a probabilistic inference assumption, evaluate optimal sample sizes for DFE. In our treatment we go beyond analytically established results by showing how the classical statistical decision theoretic framework can be used to derive optimal sample sizes under arbitrary, but numerically evaluable, constraints. Finally, we critically evaluate the value of deriving optimal sample sizes under this framework as testable predictions for the experimental study of sampling behavior in DFE. PMID:26441720

Microphysical Processes Affecting the Pinatubo Volcanic Plume

NASA Technical Reports Server (NTRS)

Hamill, Patrick; Houben, Howard; Young, Richard; Turco, Richard; Zhao, Jingxia

1996-01-01

In this paper we consider microphysical processes which affect the formation of sulfate particles and their size distribution in a dispersing cloud. A model for the dispersion of the Mt. Pinatubo volcanic cloud is described. We then consider a single point in the dispersing cloud and study the effects of nucleation, condensation and coagulation on the time evolution of the particle size distribution at that point.

A stochastic differential equations approach for the description of helium bubble size distributions in irradiated metals

NASA Astrophysics Data System (ADS)

Seif, Dariush; Ghoniem, Nasr M.

2014-12-01

A rate theory model based on the theory of nonlinear stochastic differential equations (SDEs) is developed to estimate the time-dependent size distribution of helium bubbles in metals under irradiation. Using approaches derived from Itô's calculus, rate equations for the first five moments of the size distribution in helium-vacancy space are derived, accounting for the stochastic nature of the atomic processes involved. In the first iteration of the model, the distribution is represented as a bivariate Gaussian distribution. The spread of the distribution about the mean is obtained by white-noise terms in the second-order moments, driven by fluctuations in the general absorption and emission of point defects by bubbles, and fluctuations stemming from collision cascades. This statistical model for the reconstruction of the distribution by its moments is coupled to a previously developed reduced-set, mean-field, rate theory model. As an illustrative case study, the model is applied to a tungsten plasma facing component under irradiation. Our findings highlight the important role of stochastic atomic fluctuations on the evolution of helium-vacancy cluster size distributions. It is found that when the average bubble size is small (at low dpa levels), the relative spread of the distribution is large and average bubble pressures may be very large. As bubbles begin to grow in size, average bubble pressures decrease, and stochastic fluctuations have a lessened effect. The distribution becomes tighter as it evolves in time, corresponding to a more uniform bubble population. The model is formulated in a general way, capable of including point defect drift due to internal temperature and/or stress gradients. These arise during pulsed irradiation, and also during steady irradiation as a result of externally applied or internally generated non-homogeneous stress fields. Discussion is given into how the model can be extended to include full spatial resolution and how the implementation of a path-integral approach may proceed if the distribution is known experimentally to significantly stray from a Gaussian description.

Identifying airborne metal particles sources near an optoelectronic and semiconductor industrial park

NASA Astrophysics Data System (ADS)

Chen, Ho-Wen; Chen, Wei-Yea; Chang, Cheng-Nan; Chuang, Yen-Hsun; Lin, Yu-Hao

2016-06-01

The recently developed Central Taiwan Science Park (CTSP) in central Taiwan is home to an optoelectronic and semiconductor industrial cluster. Therefore, exploring the elemental compositions and size distributions of airborne particles emitted from the CTSP would help to prevent pollution. This study analyzed size-fractionated metal-rich particle samples collected in upwind and downwind areas of CTSP during Jan. and Oct. 2013 by using micro-orifice uniform deposited impactor (MOUDI). Correlation analysis, hierarchical cluster analysis and particle mass-size distribution analysis are performed to identify the source of metal-rich particle near the CTSP. Analyses of elemental compositions and particle size distributions emitted from the CTSP revealed that the CTSP emits some metals (V, As, In Ga, Cd and Cu) in the ultrafine particles (< 1 μm). The statistical analysis combines with the particle mass-size distribution analysis could provide useful source identification information. In airborne particles with the size of 0.32 μm, Ga could be a useful pollution index for optoelectronic and semiconductor emission in the CTSP. Meanwhile, the ratios of As/Ga concentration at the particle size of 0.32 μm demonstrates that humans near the CTSP would be potentially exposed to GaAs ultrafine particles. That is, metals such as Ga and As and other metals that are not regulated in Taiwan are potentially harmful to human health.

Simulating galactic dust grain evolution on a moving mesh

NASA Astrophysics Data System (ADS)

McKinnon, Ryan; Vogelsberger, Mark; Torrey, Paul; Marinacci, Federico; Kannan, Rahul

2018-05-01

Interstellar dust is an important component of the galactic ecosystem, playing a key role in multiple galaxy formation processes. We present a novel numerical framework for the dynamics and size evolution of dust grains implemented in the moving-mesh hydrodynamics code AREPO suited for cosmological galaxy formation simulations. We employ a particle-based method for dust subject to dynamical forces including drag and gravity. The drag force is implemented using a second-order semi-implicit integrator and validated using several dust-hydrodynamical test problems. Each dust particle has a grain size distribution, describing the local abundance of grains of different sizes. The grain size distribution is discretised with a second-order piecewise linear method and evolves in time according to various dust physical processes, including accretion, sputtering, shattering, and coagulation. We present a novel scheme for stochastically forming dust during stellar evolution and new methods for sub-cycling of dust physics time-steps. Using this model, we simulate an isolated disc galaxy to study the impact of dust physical processes that shape the interstellar grain size distribution. We demonstrate, for example, how dust shattering shifts the grain size distribution to smaller sizes resulting in a significant rise of radiation extinction from optical to near-ultraviolet wavelengths. Our framework for simulating dust and gas mixtures can readily be extended to account for other dynamical processes relevant in galaxy formation, like magnetohydrodynamics, radiation pressure, and thermo-chemical processes.

Membrane emulsification to produce perfume microcapsules

NASA Astrophysics Data System (ADS)

Pan, Xuemiao

Microencapsulation is an efficient technology to deliver perfume oils from consumer products onto the surface of fabrics. Microcapsules having uniform size/mechanical strength, may provide better release performance. Membrane emulsification in a dispersion cell followed by in-situ polymerization was used to prepare narrow size distribution melamine-formaldehyde (MF) microcapsules containing several types of oil-based fragrances or ingredients. Investigated in this study are the parameters impacting to the size and size distribution of the droplets and final MF microcapsules. A pilot plant-scale cross-flow membrane system was also used to produce MF microcapsules, demonstrating that the membrane emulsification process has potential to be scaled up for industrial applications. In this study, health and environmental friendly poly (methyl methacrylate) (PMMA) microcapsules with narrow size distribution were also prepared for the first time using the dispersion cell membrane emulsification system. Characterization methods previously used for thin-shell microcapsules were expanded to analyse microcapsules with thick shells. The intrinsic mechanical properties of thick shells were determined using a micromanipulation technique and finite element analysis (FEM). The microcapsules structure was also considered in the determination of the permeability and diffusivity of the perfume oils in good solvents..

Body size distribution of the dinosaurs.

PubMed

O'Gorman, Eoin J; Hone, David W E

2012-01-01

The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size.

Body Size Distribution of the Dinosaurs

PubMed Central

O’Gorman, Eoin J.; Hone, David W. E.

2012-01-01

The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size. PMID:23284818

Extreme value statistics analysis of fracture strengths of a sintered silicon nitride failing from pores

NASA Technical Reports Server (NTRS)

Chao, Luen-Yuan; Shetty, Dinesh K.

1992-01-01

Statistical analysis and correlation between pore-size distribution and fracture strength distribution using the theory of extreme-value statistics is presented for a sintered silicon nitride. The pore-size distribution on a polished surface of this material was characterized, using an automatic optical image analyzer. The distribution measured on the two-dimensional plane surface was transformed to a population (volume) distribution, using the Schwartz-Saltykov diameter method. The population pore-size distribution and the distribution of the pore size at the fracture origin were correllated by extreme-value statistics. Fracture strength distribution was then predicted from the extreme-value pore-size distribution, usin a linear elastic fracture mechanics model of annular crack around pore and the fracture toughness of the ceramic. The predicted strength distribution was in good agreement with strength measurements in bending. In particular, the extreme-value statistics analysis explained the nonlinear trend in the linearized Weibull plot of measured strengths without postulating a lower-bound strength.

Thermodynamics of Macromolecular Association in Heterogeneous Crowding Environments: Theoretical and Simulation Studies with a Simplified Model.

PubMed

Ando, Tadashi; Yu, Isseki; Feig, Michael; Sugita, Yuji

2016-11-23

The cytoplasm of a cell is crowded with many different kinds of macromolecules. The macromolecular crowding affects the thermodynamics and kinetics of biological reactions in a living cell, such as protein folding, association, and diffusion. Theoretical and simulation studies using simplified models focus on the essential features of the crowding effects and provide a basis for analyzing experimental data. In most of the previous studies on the crowding effects, a uniform crowder size is assumed, which is in contrast to the inhomogeneous size distribution of macromolecules in a living cell. Here, we evaluate the free energy changes upon macromolecular association in a cell-like inhomogeneous crowding system via a theory of hard-sphere fluids and free energy calculations using Brownian dynamics trajectories. The inhomogeneous crowding model based on 41 different types of macromolecules represented by spheres with different radii mimics the physiological concentrations of macromolecules in the cytoplasm of Mycoplasma genitalium. The free energy changes of macromolecular association evaluated by the theory and simulations were in good agreement with each other. The crowder size distribution affects both specific and nonspecific molecular associations, suggesting that not only the volume fraction but also the size distribution of macromolecules are important factors for evaluating in vivo crowding effects. This study relates in vitro experiments on macromolecular crowding to in vivo crowding effects by using the theory of hard-sphere fluids with crowder-size heterogeneity.

Combining spray nozzle simulators with meshes: characterization of rainfall intensity and drop properties

NASA Astrophysics Data System (ADS)

Carvalho, Sílvia C. P.; de Lima, João L. M. P.; de Lima, M. Isabel P.

2013-04-01

Rainfall simulators can be a powerful tool to increase our understanding of hydrological and geomorphological processes. Nevertheless, rainfall simulators' design and operation might be rather demanding, for achieving specific rainfall intensity distributions and drop characteristics. The pressurized simulators have some advantages over the non-pressurized simulators: drops do not rely on gravity to reach terminal velocity, but are sprayed out under pressure; pressurized simulators also yield a broad range of drop sizes in comparison with drop-formers simulators. The main purpose of this study was to explore in the laboratory the potential of combining spray nozzle simulators with meshes in order to change rainfall characteristics (rainfall intensity and diameters and fall speed of drops). Different types of spray nozzles were tested, such as single full-cone and multiple full-cone nozzles. The impact of the meshes on the simulated rain was studied by testing different materials (i.e. plastic and steel meshes), square apertures and wire thicknesses, and different vertical distances between the nozzle and the meshes underneath. The diameter and fall speed of the rain drops were measured using a Laser Precipitation Monitor (Thies Clima). The rainfall intensity range and coefficients of uniformity of the sprays and the drop size distribution, fall speed and kinetic energy were analysed. Results show that when meshes intercept drop trajectories the spatial distribution of rainfall intensity and the drop size distribution are affected. As the spray nozzles generate typically small drop sizes and narrow drop size distributions, meshes can be used to promote the formation of bigger drops and random their landing positions.

A Facile pH Controlled Citrate-Based Reduction Method for Gold Nanoparticle Synthesis at Room Temperature.

PubMed

Tyagi, Himanshu; Kushwaha, Ajay; Kumar, Anshuman; Aslam, Mohammed

2016-12-01

The synthesis of gold nanoparticles using citrate reduction process has been revisited. A simplified room temperature approach to standard Turkevich synthesis is employed to obtain fairly monodisperse gold nanoparticles. The role of initial pH alongside the concentration ratio of reactants is explored for the size control of Au nanoparticles. The particle size distribution has been investigated using UV-vis spectroscopy and transmission electron microscope (TEM). At optimal pH of 5, gold nanoparticles obtained are highly monodisperse and spherical in shape and have narrower size distribution (sharp surface plasmon at 520 nm). For other pH conditions, particles are non-uniform and polydisperse, showing a red-shift in plasmon peak due to aggregation and large particle size distribution. The room temperature approach results in highly stable "colloidal" suspension of gold nanoparticles. The stability test through absorption spectroscopy indicates no sign of aggregation for a month. The rate of reduction of auric ionic species by citrate ions is determined via UV absorbance studies. The size of nanoparticles under various conditions is thus predicted using a theoretical model that incorporates nucleation, growth, and aggregation processes. The faster rate of reduction yields better size distribution for optimized pH and reactant concentrations. The model involves solving population balance equation for continuously evolving particle size distribution by discretization techniques. The particle sizes estimated from the simulations (13 to 25 nm) are close to the experimental ones (10 to 32 nm) and corroborate the similarity of reaction processes at 300 and 373 K (classical Turkevich reaction). Thus, substitution of experimentally measured rate of disappearance of auric ionic species into theoretical model enables us to capture the unusual experimental observations.

Particle size distribution of mainstream tobacco and marijuana smoke. Analysis using the electrical aerosol analyzer.

PubMed

Anderson, P J; Wilson, J D; Hiller, F C

1989-07-01

Accurate measurement of cigarette smoke particle size distribution is important for estimation of lung deposition. Most prior investigators have reported a mass median diameter (MMD) in the size range of 0.3 to 0.5 micron, with a small geometric standard deviation (GSD), indicating few ultrafine (less than 0.1 micron) particles. A few studies, however, have suggested the presence of ultrafine particles by reporting a smaller count median diameter (CMD). Part of this disparity may be due tot he inefficiency to previous sizing methods in measuring ultrafine size range, to evaluate size distribution of smoke from standard research cigarettes, commercial filter cigarettes, and from marijuana cigarettes with different delta 9-tetrahydrocannabinol contents. Four 35-cm3, 2-s puffs were generated at 60-s intervals, rapidly diluted, and passed through a charge neutralizer and into a 240-L chamber. Size distribution for six cigarettes of each type was measured, CMD and GSD were determined from a computer-generated log probability plot, and MMD was calculated. The size distribution parameters obtained were similar for all cigarettes tested, with an average CMD of 0.1 micron, a MMD of 0.38 micron, and a GSD of 2.0. The MMD found using the EAA is similar to that previously reported, but the CMD is distinctly smaller and the GSD larger, indicating the presence of many more ultrafine particles. These results may explain the disparity of CMD values found in existing data. Ultrafine particles are of toxicologic importance because their respiratory tract deposition is significantly higher than for particles 0.3 to 0.5 micron and because their large surface area facilitates adsorption and delivery of potentially toxic gases to the lung.

Grain size distribution and microstructures of experimentally sheared granitoid gouge at coseismic slip rates - Criteria to distinguish seismic and aseismic faults?

NASA Astrophysics Data System (ADS)

Stünitz, Holger; Keulen, Nynke; Hirose, Takehiro; Heilbronner, Renée

2010-01-01

Microstructures and grain size distribution from high velocity friction experiments are compared with those of slow deformation experiments of Keulen et al. (2007, 2008) for the same material (Verzasca granitoid). The mechanical behavior of granitoid gouge in fast velocity friction experiments at slip rates of 0.65 and 1.28 m/s and normal stresses of 0.4-0.9 MPa is characterized by slip weakening in a typical exponential friction coefficient vs displacement relationship. The grain size distributions yield similar D-values (slope of frequency versus grain size curve = 2.2-2.3) as those of slow deformation experiments (D = 2.0-2.3) for grain sizes larger than 1 μm. These values are independent of the total displacement above a shear strain of about γ = 20. The D-values are also independent of the displacement rates in the range of ˜1 μm/s to ˜1.3 m/s and do not vary in the normal stress range between 0.5 MPa and 500 MPa. With increasing displacement, grain shapes evolve towards more rounded and less serrated grains. While the grain size distribution remains constant, the progressive grain shape evolution suggests that grain comminution takes place by attrition at clast boundaries. Attrition produces a range of very small grain sizes by crushing with a D <-value = 1. The results of the study demonstrate that most cataclastic and gouge fault zones may have resulted from seismic deformation but the distinction of seismic and aseismic deformation cannot be made on the basis of grain size distribution.

A New Bond Albedo for Performing Orbital Debris Brightness to Size Transformations

NASA Technical Reports Server (NTRS)

Mulrooney, Mark K.; Matney, Mark J.

2008-01-01

We have developed a technique for estimating the intrinsic size distribution of orbital debris objects via optical measurements alone. The process is predicated on the empirically observed power-law size distribution of debris (as indicated by radar RCS measurements) and the log-normal probability distribution of optical albedos as ascertained from phase (Lambertian) and range-corrected telescopic brightness measurements. Since the observed distribution of optical brightness is the product integral of the size distribution of the parent [debris] population with the albedo probability distribution, it is a straightforward matter to transform a given distribution of optical brightness back to a size distribution by the appropriate choice of a single albedo value. This is true because the integration of a powerlaw with a log-normal distribution (Fredholm Integral of the First Kind) yields a Gaussian-blurred power-law distribution with identical power-law exponent. Application of a single albedo to this distribution recovers a simple power-law [in size] which is linearly offset from the original distribution by a constant whose value depends on the choice of the albedo. Significantly, there exists a unique Bond albedo which, when applied to an observed brightness distribution, yields zero offset and therefore recovers the original size distribution. For physically realistic powerlaws of negative slope, the proper choice of albedo recovers the parent size distribution by compensating for the observational bias caused by the large number of small objects that appear anomalously large (bright) - and thereby skew the small population upward by rising above the detection threshold - and the lower number of large objects that appear anomalously small (dim). Based on this comprehensive analysis, a value of 0.13 should be applied to all orbital debris albedo-based brightness-to-size transformations regardless of data source. Its prima fascia genesis, derived and constructed from the current RCS to size conversion methodology (SiBAM Size-Based Estimation Model) and optical data reduction standards, assures consistency in application with the prior canonical value of 0.1. Herein we present the empirical and mathematical arguments for this approach and by example apply it to a comprehensive set of photometric data acquired via NASA's Liquid Mirror Telescopes during the 2000-2001 observing season.

The effects of variable dust size and charge on dust acoustic waves propagating in a hybrid Cairns–Tsallis complex plasma

NASA Astrophysics Data System (ADS)

El-Taibany, W. F.; El-Siragy, N. M.; Behery, E. E.; Elbendary, A. A.; Taha, R. M.

2018-05-01

The propagation characteristics of dust acoustic waves (DAWs) in a dusty plasma consisting of variable size dust grains, hybrid Cairns-Tsallis-distributed electrons, and nonthermal ions are studied. The charging of the dust grains is described by the orbital-motion-limited theory and the size of the dust grains obeys the power law dust size distribution. To describe the nonlinear propagation of the DAWs, a Zakharov-Kuznetsov equation is derived using a reductive perturbation method. It is found that the nonthermal and nonextensive parameters influence the main properties of DAWs. Moreover, our results reveal that the rarefactive waves can propagate mainly in the proposed plasma model while compressive waves can be detected for a very small range of the distribution parameters of plasma species, and the DAWs are faster and wider for smaller size dust grains. Applications of the present results to dusty plasma observations are briefly discussed.

The Influence of Crystal Size Distributions on the Rheology of Magmas: New Insights From Analog Experiments

NASA Astrophysics Data System (ADS)

Klein, Johannes; Mueller, Sebastian P.; Castro, Jonathan M.

2017-11-01

This study examines the influence of particle-size distributions on the rheology of particle suspensions by using analog experiments with spherical glass beads in silicone oil as a magma equivalent. The analyses of 274 individual particle-bearing suspensions of varying modality (unimodality, bimodality, trimodality, and tetramodality), as well as of polymodal suspensions with specific defined skewness and variance, are the first data set of its kind and provide important insights into the relationship between the solid particles of a suspension and its rheological behavior. Since the relationship between the rheology of particle-bearing suspensions and its maximum packing fraction ϕm is well established by several theoretical models, the results of the analog experiments of this study reveal that the polydispersity γ exerts the largest influence on ϕm. Consequently, the estimation of the polydispersity γ of a particle-size distribution is essential for estimating the viscosity of that given suspension.

An improved methodology of asymmetric flow field flow fractionation hyphenated with inductively coupled mass spectrometry for the determination of size distribution of gold nanoparticles in dietary supplements.

PubMed

Mudalige, Thilak K; Qu, Haiou; Linder, Sean W

2015-11-13

Engineered nanoparticles are available in large numbers of commercial products claiming various health benefits. Nanoparticle absorption, distribution, metabolism, excretion, and toxicity in a biological system are dependent on particle size, thus the determination of size and size distribution is essential for full characterization. Number based average size and size distribution is a major parameter for full characterization of the nanoparticle. In the case of polydispersed samples, large numbers of particles are needed to obtain accurate size distribution data. Herein, we report a rapid methodology, demonstrating improved nanoparticle recovery and excellent size resolution, for the characterization of gold nanoparticles in dietary supplements using asymmetric flow field flow fractionation coupled with visible absorption spectrometry and inductively coupled plasma mass spectrometry. A linear relationship between gold nanoparticle size and retention times was observed, and used for characterization of unknown samples. The particle size results from unknown samples were compared to results from traditional size analysis by transmission electron microscopy, and found to have less than a 5% deviation in size for unknown product over the size range from 7 to 30 nm. Published by Elsevier B.V.

Particle-size dependence on metal(loid) distributions in mine wastes: Implications for water contamination and human exposure

USGS Publications Warehouse

Kim, C.S.; Wilson, K.M.; Rytuba, J.J.

2011-01-01

The mining and processing of metal-bearing ores has resulted in contamination issues where waste materials from abandoned mines remain in piles of untreated and unconsolidated material, posing the potential for waterborne and airborne transport of toxic elements. This study presents a systematic method of particle size separation, mass distribution, and bulk chemical analysis for mine tailings and adjacent background soil samples from the Rand historic mining district, California, in order to assess particle size distribution and related trends in metal(loid) concentration as a function of particle size. Mine tailings produced through stamp milling and leaching processes were found to have both a narrower and finer particle size distribution than background samples, with significant fractions of particles available in a size range (???250 ??m) that could be incidentally ingested. In both tailings and background samples, the majority of trace metal(loid)s display an inverse relationship between concentration and particle size, resulting in higher proportions of As, Cr, Cu, Pb and Zn in finer-sized fractions which are more susceptible to both water- and wind-borne transport as well as ingestion and/or inhalation. Established regulatory screening levels for such elements may, therefore, significantly underestimate potential exposure risk if relying solely on bulk sample concentrations to guide remediation decisions. Correlations in elemental concentration trends (such as between As and Fe) indicate relationships between elements that may be relevant to their chemical speciation. ?? 2011 Elsevier Ltd.

The Role of pH in Controlling Size and Distribution of Silver Nanoparticles using Biosynthesis from Diospyros discolor Willd. (Ebenaceae)

NASA Astrophysics Data System (ADS)

Nurfadhilah, M.; Nolia, I.; Handayani, W.; Imawan, C.

2018-05-01

The silver nanoparticles generated by biosynthesis have a quite diverse result, both in size and shape. Structures of silver nanoparticles can be controlled by modifying the parameters of the biosynthesis such as the ratio between the precursors and reducing agents, as well as pH of the solution. In this study, the pH of Diospyros discolor (Bisbul) leaves aqueous extract was varied to 4, 7, 9, and 11. The extract then was added to 1 mM AgNO3 precursor (1:2; v/v ratio). The result of the silver nanoparticles characterized using spectrophotometer UV-Vis to find if there was any absorbance peak formed between 400 nm to 500 nm. TEM characterization was used to determine the size and shape of silver nanoparticles, and PSA was used to see their size distribution and stability. The higher pH tends to produce smaller silver nanoparticles rapidly. The synthesis parameters that were varied in this research have affected the size, size distribution patterns, and stability of silver nanoparticles.

Determination of grain-size characteristics from electromagnetic seabed mapping data: A NW Iberian shelf study

NASA Astrophysics Data System (ADS)

Baasch, Benjamin; Müller, Hendrik; von Dobeneck, Tilo; Oberle, Ferdinand K. J.

2017-05-01

The electric conductivity and magnetic susceptibility of sediments are fundamental parameters in environmental geophysics. Both can be derived from marine electromagnetic profiling, a novel, fast and non-invasive seafloor mapping technique. Here we present statistical evidence that electric conductivity and magnetic susceptibility can help to determine physical grain-size characteristics (size, sorting and mud content) of marine surficial sediments. Electromagnetic data acquired with the bottom-towed electromagnetic profiler MARUM NERIDIS III were analysed and compared with grain size data from 33 samples across the NW Iberian continental shelf. A negative correlation between mean grain size and conductivity (R=-0.79) as well as mean grain size and susceptibility (R=-0.78) was found. Simple and multiple linear regression analyses were carried out to predict mean grain size, mud content and the standard deviation of the grain-size distribution from conductivity and susceptibility. The comparison of both methods showed that multiple linear regression models predict the grain-size distribution characteristics better than the simple models. This exemplary study demonstrates that electromagnetic benthic profiling is capable to estimate mean grain size, sorting and mud content of marine surficial sediments at a very high significance level. Transfer functions can be calibrated using grains-size data from a few reference samples and extrapolated along shelf-wide survey lines. This study suggests that electromagnetic benthic profiling should play a larger role for coastal zone management, seafloor contamination and sediment provenance studies in worldwide continental shelf systems.

Particle-size distribution modified effective medium theory and validation by magneto-dielectric Co-Ti substituted BaM ferrite composites

NASA Astrophysics Data System (ADS)

Li, Qifan; Chen, Yajie; Harris, Vincent G.

2018-05-01

This letter reports an extended effective medium theory (EMT) including particle-size distribution functions to maximize the magnetic properties of magneto-dielectric composites. It is experimentally verified by Co-Ti substituted barium ferrite (BaCoxTixFe12-2xO19)/wax composites with specifically designed particle-size distributions. In the form of an integral equation, the extended EMT formula essentially takes the size-dependent parameters of magnetic particle fillers into account. It predicts the effective permeability of magneto-dielectric composites with various particle-size distributions, indicating an optimal distribution for a population of magnetic particles. The improvement of the optimized effective permeability is significant concerning magnetic particles whose properties are strongly size dependent.

The Effect of Size Fraction in Analyses of Benthic Foraminifera Assemblages: A Case Study Comparing Assemblages from the >125 μm and >150 μm Size Fractions

NASA Astrophysics Data System (ADS)

Weinkauf, Manuel F. G.; Milker, Yvonne

2018-05-01

Benthic Foraminifera assemblages are employed for past environmental reconstructions, as well as for biomonitoring studies in recent environments. Despite their established status for such applications, and existing protocols for sample treatment, not all studies using benthic Foraminifera employ the same methodology. For instance, there is no broad practical consensus whether to use the >125 µm or >150 µm size fraction for benthic foraminiferal assemblage analyses. Here, we use early Pleistocene material from the Pefka E section on the Island of Rhodes (Greece), which has been counted in both size fractions, to investigate whether a 25 µm difference in the counted fraction is already sufficient to have an impact on ecological studies. We analysed the influence of the difference in size fraction on studies of biodiversity as well as multivariate assemblage analyses of the sample material. We found that for both types of studies, the general trends remain the same regardless of the chosen size fraction, but in detail significant differences emerge which are not consistently distributed between samples. Studies which require a high degree of precision can thus not compare results from analyses that used different size fractions, and the inconsistent distribution of differences makes it impossible to develop corrections for this issue. We therefore advocate the consistent use of the >125 µm size fraction for benthic foraminiferal studies in the future.

Secondary atomization in the combustion of electrostatic sprays

NASA Technical Reports Server (NTRS)

Gomez, Alessandro; Chen, Gung

1993-01-01

The combustion of electrosprays in a laminar counterflow diffusion flame has been experimentally studied by measuring droplet size and velocity distributions and gas-phase temperature. Detailed examination of the evolution of droplet size distribution as droplets approach the flame shows that, if substantial evaporation occurs before droplets 'interact' with the flame, the size distribution becomes bimodal. A secondary, sharp peak, in fact, develops in correspondence of diameters about one order of magnitude smaller than the mean. No evaporation mechanism can account for the development of such bimodality, that can be explained only in terms of a disintegration of droplets into finer fragments of size much smaller than the parent ones. This fission is of electric nature and it occurs when the repulsion of electric charges overcomes the surface tension cohesive force ultimately leading to a disintegration into finer fragments at or about the so-called Rayleigh limit. We here report on the first observation in combustion environments of such 'explosions'. If, on the other hand, droplets enter the very high temperature region before exploding, there appears to be no evidence of bimodality in their size distribution. In this case, in fact, flame chemi-ions may neutralize the charge on the droplets and thus prevent disruption.

An In Situ Method for Sizing Insoluble Residues in Precipitation and Other Aqueous Samples

PubMed Central

Axson, Jessica L.; Creamean, Jessie M.; Bondy, Amy L.; Capracotta, Sonja S.; Warner, Katy Y.; Ault, Andrew P.

2015-01-01

Particles are frequently incorporated into clouds or precipitation, influencing climate by acting as cloud condensation or ice nuclei, taking up coatings during cloud processing, and removing species through wet deposition. Many of these particles, particularly ice nuclei, can remain suspended within cloud droplets/crystals as insoluble residues. While previous studies have measured the soluble or bulk mass of species within clouds and precipitation, no studies to date have determined the number concentration and size distribution of insoluble residues in precipitation or cloud water using in situ methods. Herein, for the first time we demonstrate that Nanoparticle Tracking Analysis (NTA) is a powerful in situ method for determining the total number concentration, number size distribution, and surface area distribution of insoluble residues in precipitation, both of rain and melted snow. The method uses 500 μL or less of liquid sample and does not require sample modification. Number concentrations for the insoluble residues in aqueous precipitation samples ranged from 2.0–3.0(±0.3)×108 particles cm−3, while surface area ranged from 1.8(±0.7)–3.2(±1.0)×107 μm2 cm−3. Number size distributions peaked between 133–150 nm, with both single and multi-modal character, while surface area distributions peaked between 173–270 nm. Comparison with electron microscopy of particles up to 10 μm show that, by number, > 97% residues are <1 μm in diameter, the upper limit of the NTA. The range of concentration and distribution properties indicates that insoluble residue properties vary with ambient aerosol concentrations, cloud microphysics, and meteorological dynamics. NTA has great potential for studying the role that insoluble residues play in critical atmospheric processes. PMID:25705069

Intercomparison and Evaluation of Global Aerosol Microphysical Properties Among Aerocom Models of a Range of Complexity

NASA Technical Reports Server (NTRS)

Mann, G. W.; Carslaw, K. S.; Reddington, C. L.; Pringle, K. J.; Schulz, M.; Asmi, A.; Spracklen, D. V.; Ridley, D. A.; Woodhouse, M. T.; Lee, L. A.;

Stratospheric aerosol particle size distribution based on multi-color polarization measurements of the twilight sky

NASA Astrophysics Data System (ADS)

Ugolnikov, Oleg S.; Maslov, Igor A.

2018-03-01

Polarization measurements of the twilight background with Wide-Angle Polarization Camera (WAPC) are used to detect the depolarization effect caused by stratospheric aerosol near the altitude of 20 km. Based on a number of observations in central Russia in spring and summer 2016, we found the parameters of lognormal size distribution of aerosol particles. This confirmed the previously published results of the colorimetric method as applied to the same twilights. The mean particle radius (about 0.1 micrometers) and size distribution are also in agreement with the recent data of in situ and space-based remote sensing of stratospheric aerosol. Methods considered here provide two independent techniques of the stratospheric aerosol study based on the twilight sky analysis.

[Distribution of atmospheric ultrafine particles during haze weather in Hangzhou].

PubMed

Chen, Qiu-Fang; Sun, Zai; Xie, Xiao-Fang

2014-08-01

Atmospheric ultrafine particles (UFPs) were monitored with fast mobility particle sizer (FMPS) in continuous haze weather and the haze fading process during December 6 to 11, 2013 in Hangzhou. Particle concentration and size distribution were studied associated with meteorological factors. The results showed that number concentrations were the highest at night and began to reduce in the morning. There was a small peak at 8 o'clock in the morning and 18 o'clock in the afternoon. It showed an obvious peak traffic source, which indicated that traffic emissions played a great role in the atmospheric pollution. During haze weather, the highest number concentration of UFPs reached 8 x 10(4) cm(-3). Particle size spectrum distribution was bimodal, the peak particle sizes were 15 nm and 100 nm respectively. Majority of UFPs were Aitken mode and Accumulation mode and the size of most particles concentrated near 100 nm. Average CMD(count medium diameter) was 85.89 nm. During haze fading process, number concentration and particles with size around 100 nm began to reduce and peak size shifted to small size. Nuclear modal particles increased and were more than accumulation mode. Average CMD was 58.64 nm. Meteorological factors such as the visibility and wind were negatively correlated with the particle number concentration. Correlation coefficient R were -0.225 and - 0.229. The humidity was correlated with number concentration. Correlation coefficient R was 0.271. The atmosphere was stable in winter and the level temperature had small correlation with number concentration. Therefore, study on distribution of atmospheric ultrafine particles during haze weather had the significance on the formation mechanism and control of haze weather.

Planar Laser Imaging of Sprays for Liquid Rocket Studies

NASA Technical Reports Server (NTRS)

Lee, W.; Pal, S.; Ryan, H. M.; Strakey, P. A.; Santoro, Robert J.

1990-01-01

A planar laser imaging technique which incorporates an optical polarization ratio technique for droplet size measurement was studied. A series of pressure atomized water sprays were studied with this technique and compared with measurements obtained using a Phase Doppler Particle Analyzer. In particular, the effects of assuming a logarithmic normal distribution function for the droplet size distribution within a spray was evaluated. Reasonable agreement between the instrument was obtained for the geometric mean diameter of the droplet distribution. However, comparisons based on the Sauter mean diameter show larger discrepancies, essentially because of uncertainties in the appropriate standard deviation to be applied for the polarization ratio technique. Comparisons were also made between single laser pulse (temporally resolved) measurements with multiple laser pulse visualizations of the spray.

Survival distributions impact the power of randomized placebo-phase design and parallel groups randomized clinical trials.

PubMed

Abrahamyan, Lusine; Li, Chuan Silvia; Beyene, Joseph; Willan, Andrew R; Feldman, Brian M

2011-03-01

The study evaluated the power of the randomized placebo-phase design (RPPD)-a new design of randomized clinical trials (RCTs), compared with the traditional parallel groups design, assuming various response time distributions. In the RPPD, at some point, all subjects receive the experimental therapy, and the exposure to placebo is for only a short fixed period of time. For the study, an object-oriented simulation program was written in R. The power of the simulated trials was evaluated using six scenarios, where the treatment response times followed the exponential, Weibull, or lognormal distributions. The median response time was assumed to be 355 days for the placebo and 42 days for the experimental drug. Based on the simulation results, the sample size requirements to achieve the same level of power were different under different response time to treatment distributions. The scenario where the response times followed the exponential distribution had the highest sample size requirement. In most scenarios, the parallel groups RCT had higher power compared with the RPPD. The sample size requirement varies depending on the underlying hazard distribution. The RPPD requires more subjects to achieve a similar power to the parallel groups design. Copyright © 2011 Elsevier Inc. All rights reserved.

Electric wind in a Differential Mobility Analyzer

DOE PAGES

Palo, Marus; Meelis Eller; Uin, Janek; ...

2015-10-25

Electric wind -- the movement of gas, induced by ions moving in an electric field -- can be a distorting factor in size distribution measurements using Differential Mobility Analyzers (DMAs). The aim of this study was to determine the conditions under which electric wind occurs in the locally-built VLDMA (Very Long Differential Mobility Analyzer) and TSI Long-DMA (3081) and to describe the associated distortion of the measured spectra. Electric wind proved to be promoted by the increase of electric field strength, aerosol layer thickness, particle number concentration and particle size. The measured size spectra revealed three types of distortion: wideningmore » of the size distribution, shift of the mode of the distribution to smaller diameters and smoothing out the peaks of the multiply charged particles. Electric wind may therefore be a source of severe distortion of the spectrum when measuring large particles at high concentrations.« less

Do detailed simulations with size-resolved microphysics reproduce basic features of observed cirrus ice size distributions?

NASA Astrophysics Data System (ADS)

Fridlind, A. M.; Atlas, R.; van Diedenhoven, B.; Ackerman, A. S.; Rind, D. H.; Harrington, J. Y.; McFarquhar, G. M.; Um, J.; Jackson, R.; Lawson, P.

2017-12-01

It has recently been suggested that seeding synoptic cirrus could have desirable characteristics as a geoengineering approach, but surprisingly large uncertainties remain in the fundamental parameters that govern cirrus properties, such as mass accommodation coefficient, ice crystal physical properties, aggregation efficiency, and ice nucleation rate from typical upper tropospheric aerosol. Only one synoptic cirrus model intercomparison study has been published to date, and studies that compare the shapes of observed and simulated ice size distributions remain sparse. Here we amend a recent model intercomparison setup using observations during two 2010 SPARTICUS campaign flights. We take a quasi-Lagrangian column approach and introduce an ensemble of gravity wave scenarios derived from collocated Doppler cloud radar retrievals of vertical wind speed. We use ice crystal properties derived from in situ cloud particle images, for the first time allowing smoothly varying and internally consistent treatments of nonspherical ice capacitance, fall speed, gravitational collection, and optical properties over all particle sizes in our model. We test two new parameterizations for mass accommodation coefficient as a function of size, temperature and water vapor supersaturation, and several ice nucleation scenarios. Comparison of results with in situ ice particle size distribution data, corrected using state-of-the-art algorithms to remove shattering artifacts, indicate that poorly constrained uncertainties in the number concentration of crystals smaller than 100 µm in maximum dimension still prohibit distinguishing which parameter combinations are more realistic. When projected area is concentrated at such sizes, the only parameter combination that reproduces observed size distribution properties uses a fixed mass accommodation coefficient of 0.01, on the low end of recently reported values. No simulations reproduce the observed abundance of such small crystals when the projected area is concentrated at larger sizes. Simulations across the parameter space are also compared with MODIS collection 6 retrievals and forward simulations of cloud radar reflectivity and mean Doppler velocity. Results motivate further in situ and laboratory measurements to narrow parameter uncertainties in models.

Modeling of the silane FBR system

NASA Technical Reports Server (NTRS)

Dudokovic, M. P.; Ramachandran, P. A.; Lai, S.

1984-01-01

Development of a mathematical model for fluidized bed pyrolysis of silane that relates production rate and product properties (size, size distribution, presence or absence of fines) with bed size and operating conditions (temperature, feed concentration, flow rate, seed size, etc.) and development of user oriented algorithm for the model are considered. A parameter sensitivity study of the model was also developed.

Size distribution of Portuguese firms between 2006 and 2012

NASA Astrophysics Data System (ADS)

Pascoal, Rui; Augusto, Mário; Monteiro, A. M.

2016-09-01

This study aims to describe the size distribution of Portuguese firms, as measured by annual sales and total assets, between 2006 and 2012, giving an economic interpretation for the evolution of the distribution along the time. Three distributions are fitted to data: the lognormal, the Pareto (and as a particular case Zipf) and the Simplified Canonical Law (SCL). We present the main arguments found in literature to justify the use of distributions and emphasize the interpretation of SCL coefficients. Methods of estimation include Maximum Likelihood, modified Ordinary Least Squares in log-log scale and Nonlinear Least Squares considering the Levenberg-Marquardt algorithm. When applying these approaches to Portuguese's firms data, we analyze if the evolution of estimated parameters in both lognormal power and SCL is in accordance with the known existence of a recession period after 2008. This is confirmed for sales but not for assets, leading to the conclusion that the first variable is a best proxy for firm size.

The effect of particle shape and size distribution on the acoustical properties of mixtures of hemp particles.

PubMed

Glé, Philippe; Gourdon, Emmanuel; Arnaud, Laurent; Horoshenkov, Kirill-V; Khan, Amir

2013-12-01

Hemp concrete is an attractive alternative to traditional materials used in building construction. It has a very low environmental impact, and it is characterized by high thermal insulation. Hemp aggregate particles are parallelepiped in shape and can be organized in a plurality of ways to create a considerable proportion of open pores with a complex connectivity pattern, the acoustical properties of which have never been examined systematically. Therefore this paper is focused on the fundamental understanding of the relations between the particle shape and size distribution, pore size distribution, and the acoustical properties of the resultant porous material mixture. The sound absorption and the transmission loss of various hemp aggregates is characterized using laboratory experiments and three theoretical models. These models are used to relate the particle size distribution to the pore size distribution. It is shown that the shape of particles and particle size control the pore size distribution and tortuosity in shiv. These properties in turn relate directly to the observed acoustical behavior.

STREAMBED PARTICLE SIZE FROM PEBBLE COUNTS USING VISUALLY ESTIMATED SIZE CLSASES: JUNK OR USEFUL DATA?

EPA Science Inventory

In large-scale studies, it is often neither feasible nor necessary to obtain the large samples of 400 particles advocated by many geomorphologists to adequately quantify streambed surface particle-size distributions. Synoptic surveys such as U.S. Environmental Protection Agency...

Study into the correlation of dominant pore throat size and SIP relaxation frequency

NASA Astrophysics Data System (ADS)

Kruschwitz, Sabine; Prinz, Carsten; Zimathies, Annett

2016-12-01

There is currently a debate within the SIP community about the characteristic textural length scale controlling relaxation time of consolidated porous media. One idea is that the relaxation time is dominated by the pore throat size distribution or more specifically the modal pore throat size as determined in mercury intrusion capillary pressure tests. Recently new studies on inverting pore size distributions from SIP data were published implying that the relaxation mechanisms and controlling length scale are well understood. In contrast new analytical model studies based on the Marshall-Madden membrane polarization theory suggested that two relaxation processes might compete: the one along the short narrow pore (the throat) with one across the wider pore in case the narrow pores become relatively long. This paper presents a first systematically focused study into the relationship of pore throat sizes and SIP relaxation times. The generality of predicted trends is investigated across a wide range of materials differing considerably in chemical composition, specific surface and pore space characteristics. Three different groups of relaxation behaviors can be clearly distinguished. The different behaviors are related to clay content and type, carbonate content, size of the grains and the wide pores in the samples.

Potential source identification for aerosol concentrations over a site in Northwestern India

NASA Astrophysics Data System (ADS)

Payra, Swagata; Kumar, Pramod; Verma, Sunita; Prakash, Divya; Soni, Manish

2016-03-01

The collocated measurements of aerosols size distribution (ASD) and aerosol optical thickness (AOT) are analyzed simultaneously using Grimm aerosol spectrometer and MICROTOP II Sunphotometer over Jaipur, capital of Rajasthan in India. The contrast temperature characteristics during winter and summer seasons of year 2011 are investigated in the present study. The total aerosol number concentration (TANC, 0.3-20 μm) during winter season was observed higher than in summer time and it was dominated by fine aerosol number concentration (FANC < 2 μm). Particles smaller than 0.8 μm (at aerodynamic size) constitute ~ 99% of all particles in winter and ~ 90% of particles in summer season. However, particles greater than 2 μm contribute ~ 3% and ~ 0.2% in summer and winter seasons respectively. The aerosols optical thickness shows nearly similar AOT values during summer and winter but corresponding low Angstrom Exponent (AE) values during summer than winter, respectively. In this work, Potential Source Contribution Function (PSCF) analysis is applied to identify locations of sources that influenced concentrations of aerosols over study area in two different seasons. PSCF analysis shows that the dust particles from Thar Desert contribute significantly to the coarse aerosol number concentration (CANC). Higher values of the PSCF in north from Jaipur showed the industrial areas in northern India to be the likely sources of fine particles. The variation in size distribution of aerosols during two seasons is clearly reflected in the log normal size distribution curves. The log normal size distribution curves reveals that the particle size less than 0.8 μm is the key contributor in winter for higher ANC.

Geometry and Topology of Two-Dimensional Dry Foams: Computer Simulation and Experimental Characterization.

PubMed

Tong, Mingming; Cole, Katie; Brito-Parada, Pablo R; Neethling, Stephen; Cilliers, Jan J

2017-04-18

Pseudo-two-dimensional (2D) foams are commonly used in foam studies as it is experimentally easier to measure the bubble size distribution and other geometric and topological properties of these foams than it is for a 3D foam. Despite the widespread use of 2D foams in both simulation and experimental studies, many important geometric and topological relationships are still not well understood. Film size, for example, is a key parameter in the stability of bubbles and the overall structure of foams. The relationship between the size distribution of the films in a foam and that of the bubbles themselves is thus a key relationship in the modeling and simulation of unstable foams. This work uses structural simulation from Surface Evolver to statistically analyze this relationship and to ultimately formulate a relationship for the film size in 2D foams that is shown to be valid across a wide range of different bubble polydispersities. These results and other topological features are then validated using digital image analysis of experimental pseudo-2D foams produced in a vertical Hele-Shaw cell, which contains a monolayer of bubbles between two plates. From both the experimental and computational results, it is shown that there is a distribution of sizes that a film can adopt and that this distribution is very strongly dependent on the sizes of the two bubbles to which the film is attached, especially the smaller one, but that it is virtually independent of the underlying polydispersity of the foam.

Determination of the cumulus size distribution from LANDSAT pictures

NASA Technical Reports Server (NTRS)

Karg, E.; Mueller, H.; Quenzel, H.

1983-01-01

Varying insolation causes undesirable thermic stress to the receiver of a solar power plant. The rapid change of insolation depends on the size distribution of the clouds; in order to measure these changes, it is suitable to determine typical cumulus size distributions. For this purpose, LANDSAT-images are adequate. Several examples of cumulus size distributions will be presented and their effects on the operation of a solar power plant are discussed.

Unfolding sphere size distributions with a density estimator based on Tikhonov regularization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weese, J.; Korat, E.; Maier, D.

1997-12-01

This report proposes a method for unfolding sphere size distributions given a sample of radii that combines the advantages of a density estimator with those of Tikhonov regularization methods. The following topics are discusses in this report to achieve this method: the relation between the profile and the sphere size distribution; the method for unfolding sphere size distributions; the results based on simulations; and the experimental data comparison.

Effect of sodium azide addition and aging storage on casein micelle size

NASA Astrophysics Data System (ADS)

Sinaga, H.; Deeth, H.; Bhandari, B.

2018-02-01

Casein micelles affected most of milk properties, therefore the use sodium azide as milk preservation is not expected to alter milk properties during storage, including the casein micelle size. The aim of this study was to analyse casein micelle size after the addition of sodium azide during storage. The experiment was performed as a complete block randomised design with three replications. The addition of 0.02-0.10% Na-azide do not lead to any noticeable differences in average casein size at the same day and show similar trend after 14 day-storage. At concentration of 0.02% sodium azide (Na-azide), the size of pasteurised milk did not change up to 12 days, while the size of raw skim milk slightly increased by ageing time at day 5. The treated concentration did not affect the size distribution, except for milk with 0.02% Na-azide which had narrower distribution compared to other treated and control milk. The finding from this study suggests that the role of Na-azide in this experiments during storage at 4°C is only for preventing the microbial growth.

Effect of microfluidization on casein micelle size of bovine milk

NASA Astrophysics Data System (ADS)

Sinaga, H.; Deeth, H.; Bhandari, B.

2018-02-01

The properties of milk are likely to be dependent on the casein micelle size, and various processing technologies produce particular change in the average size of casein micelles. The main objective of this study was to manipulate casein micelle size by subjecting milk to microfluidizer. The experiment was performed as a complete block randomised design with three replications. The sample was passed through the microfluidizer at the set pressure of 83, 97, 112 and 126 MPa for one, two, three, four, five and six cycles, except for the 112 MPa. The results showed that microfluidized milk has smaller size by 3% with pressure up to 126 MPa. However, at each pressure, no further reduction was observed after increasing the passed up to 6 cycles. Although the average casein micelle size was similar, elevating pressure resulted in narrower size distribution. In contrast, increasing the number of cycles had little effect on casein micelle distribution. The finding from this study can be applied for future work to characterize the fundamental and functional properties of the treated milk.

Preliminary investigation on the effects of primary airflow to coal particle distribution in coal-fired boilers

NASA Astrophysics Data System (ADS)

Noor, N. A. W. Mohd; Hassan, H.; Hashim, M. F.; Hasini, H.; Munisamy, K. M.

2017-04-01

This paper presents an investigation on the effects of primary airflow to coal fineness in coal-fired boilers. In coal fired power plant, coal is pulverized in a pulverizer, and it is then transferred to boiler for combustion. Coal need to be ground to its desired size to obtain maximum combustion efficiency. Coarse coal particle size may lead to many performance problems such as formation of clinker. In this study, the effects of primary airflow to coal particles size and coal flow distribution were investigated by using isokinetic coal sampling and computational fluid dynamic (CFD) modelling. Four different primary airflows were tested and the effects to resulting coal fineness were recorded. Results show that the optimum coal fineness distribution is obtained at design primary airflow. Any reduction or increase of air flow rate results in undesirable coal fineness distribution.

Structural and Morphological Evaluation of Nano-Sized MoSi2 Powder Produced by Mechanical Milling

NASA Astrophysics Data System (ADS)

Sameezadeh, Mahmood; Farhangi, Hassan; Emamy, Masoud

Nano-sized intermetallic powders have received great attention owing to their property advantages over conventional micro-sized counterparts. In the present study nano-sized MoSi2 powder has been produced successfully from commercially available MoSi2 (3 μm) by a mechanical milling process carried out for a period of 100 hours. The effects of milling time on size and morphology of the powders were studied by SEM and TEM and image analyzing system. The results indicate that the as-received micrometric powder with a wide size distribution of irregular shaped morphology changes to a narrow size distribution of nearly equiaxed particles with the progress of attrition milling up to 100 h, reaching an average particle size of 71 nm. Structural evolution of milled samples was characterized by XRD to determine the crystallite size and lattice microstrain using Williamson-Hall method. According to the results, the crystallite size of the powders decreases continuously down to 23 nm with increasing milling time up to 100 h and this size refinement is more rapid at the early stages of the milling process. On the other hand, the lattice strain increases considerably with milling up to 65 h and further milling causes no significant changes of lattice strain.

Probability density of aperture-averaged irradiance fluctuations for long range free space optical communication links.

PubMed

Lyke, Stephen D; Voelz, David G; Roggemann, Michael C

2009-11-20

The probability density function (PDF) of aperture-averaged irradiance fluctuations is calculated from wave-optics simulations of a laser after propagating through atmospheric turbulence to investigate the evolution of the distribution as the aperture diameter is increased. The simulation data distribution is compared to theoretical gamma-gamma and lognormal PDF models under a variety of scintillation regimes from weak to strong. Results show that under weak scintillation conditions both the gamma-gamma and lognormal PDF models provide a good fit to the simulation data for all aperture sizes studied. Our results indicate that in moderate scintillation the gamma-gamma PDF provides a better fit to the simulation data than the lognormal PDF for all aperture sizes studied. In the strong scintillation regime, the simulation data distribution is gamma gamma for aperture sizes much smaller than the coherence radius rho0 and lognormal for aperture sizes on the order of rho0 and larger. Examples of how these results affect the bit-error rate of an on-off keyed free space optical communication link are presented.

An in situ USAXS-SAXS-WAXS study of precipitate size distribution evolution in a model Ni-based alloy.

PubMed

Andrews, Ross N; Serio, Joseph; Muralidharan, Govindarajan; Ilavsky, Jan

2017-06-01

Intermetallic γ' precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS-SAXS-WAXS) analysis can be used to evaluate the temporal evolution of an alloy's precipitate size distribution (PSD) and phase structure during in situ heat treatment. Analysis of PSDs from USAXS-SAXS data employs either least-squares fitting of a preordained PSD model or a maximum entropy (MaxEnt) approach, the latter avoiding a priori definition of a functional form of the PSD. However, strong low- q scattering from grain boundaries and/or structure factor effects inhibit MaxEnt analysis of typical alloys. This work describes the extension of Bayesian-MaxEnt analysis methods to data exhibiting structure factor effects and low- q power law slopes and demonstrates their use in an in situ study of precipitate size evolution during heat treatment of a model Ni-Al-Si alloy.

An in situ USAXS–SAXS–WAXS study of precipitate size distribution evolution in a model Ni-based alloy1

PubMed Central

Andrews, Ross N.; Serio, Joseph; Muralidharan, Govindarajan; Ilavsky, Jan

2017-01-01

Intermetallic γ′ precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS–SAXS–WAXS) analysis can be used to evaluate the temporal evolution of an alloy’s precipitate size distribution (PSD) and phase structure during in situ heat treatment. Analysis of PSDs from USAXS–SAXS data employs either least-squares fitting of a preordained PSD model or a maximum entropy (MaxEnt) approach, the latter avoiding a priori definition of a functional form of the PSD. However, strong low-q scattering from grain boundaries and/or structure factor effects inhibit MaxEnt analysis of typical alloys. This work describes the extension of Bayesian–MaxEnt analysis methods to data exhibiting structure factor effects and low-q power law slopes and demonstrates their use in an in situ study of precipitate size evolution during heat treatment of a model Ni–Al–Si alloy. PMID:28656039

Cell Size Regulation in Bacteria

NASA Astrophysics Data System (ADS)

Amir, Ariel

2014-05-01

Various bacteria such as the canonical gram negative Escherichia coli or the well-studied gram positive Bacillus subtilis divide symmetrically after they approximately double their volume. Their size at division is not constant, but is typically distributed over a narrow range. Here, we propose an analytically tractable model for cell size control, and calculate the cell size and interdivision time distributions, as well as the correlations between these variables. We suggest ways of extracting the model parameters from experimental data, and show that existing data for E. coli supports partial size control, and a particular explanation: a cell attempts to add a constant volume from the time of initiation of DNA replication to the next initiation event. This hypothesis accounts for the experimentally observed correlations between mother and daughter cells as well as the exponential dependence of size on growth rate.

Physical characterization of fine particulate matter inside the public transit buses fueled by biodiesel in Toledo, Ohio.

PubMed

Shandilya, Kaushik K; Kumar, Ashok

2011-06-15

This study presents the physical characteristics of fine particulate matter (PM) collected inside the urban-public transit buses in Toledo, OH. These buses run on 20% biodiesel blended with ultra-low sulfur diesel (ULSD) (B20). For risk analysis, it is crucial to know the modality of the size distribution and the shape factor of PM collected inside the bus. The number-size distribution, microstructure, and aspect ratio of fine PM filter samples collected in the urban-public transit buses were measured for three years (2007-2009), using an environmental scanning electron microscope (ESEM) coupled with energy dispersive X-ray spectrometry (EDX). Only the reproducible results from repeated experiments on ESEM and size distribution obtained by the GRIMM dust monitor were used in this study. The size distribution was found bi-modal in the winter and fall months and was primarily uni-modal during spring and summer. The aspect ratio for different filter samples collected inside the bus range from 2.4 to 3.6 in average value, with standard deviation ranging from 0.9 to 7.4. The square-shaped and oblong-shaped particles represent the single inhalable particle's morphology characteristics in the air of the Toledo transit buses. Copyright © 2011 Elsevier B.V. All rights reserved.

Examination of a high resolution laser optical plankton counter and FlowCAM for measuring plankton concentration and size

NASA Astrophysics Data System (ADS)

Kydd, Jocelyn; Rajakaruna, Harshana; Briski, Elizabeta; Bailey, Sarah

2018-03-01

Many commercial ships will soon begin to use treatment systems to manage their ballast water and reduce the global transfer of harmful aquatic organisms and pathogens in accordance with upcoming International Maritime Organization regulations. As a result, rapid and accurate automated methods will be needed to monitoring compliance of ships' ballast water. We examined two automated particle counters for monitoring organisms ≥ 50 μm in minimum dimension: a High Resolution Laser Optical Plankton Counter (HR-LOPC), and a Flow Cytometer with digital imaging Microscope (FlowCAM), in comparison to traditional (manual) microscopy considering plankton concentration, size frequency distributions and particle size measurements. The automated tools tended to underestimate particle concentration compared to standard microscopy, but gave similar results in terms of relative abundance of individual taxa. For most taxa, particle size measurements generated by FlowCAM ABD (Area Based Diameter) were more similar to microscope measurements than were those by FlowCAM ESD (Equivalent Spherical Diameter), though there was a mismatch in size estimates for some organisms between the FlowCAM ABD and microscope due to orientation and complex morphology. When a single problematic taxon is very abundant, the resulting size frequency distribution curves can become skewed, as was observed with Asterionella in this study. In particular, special consideration is needed when utilizing automated tools to analyse samples containing colonial species. Re-analysis of the size frequency distributions with the removal of Asterionella from FlowCAM and microscope data resulted in more similar curves across methods with FlowCAM ABD having the best fit compared to the microscope, although microscope concentration estimates were still significantly higher than estimates from the other methods. The results of our study indicate that both automated tools can generate frequency distributions of particles that might be particularly useful if correction factors can be developed for known differences in well-studied aquatic ecosystems.

Grain Growth and Precipitation Behavior of Iridium Alloy DOP-26 During Long Term Aging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, Dean T.; Muralidharan, Govindarajan; Fox, Ethan E.

The influence of long term aging on grain growth and precipitate sizes and spatial distribution in iridium alloy DOP-26 was studied. Samples of DOP-26 were fabricated using the new process, recrystallized for 1 hour (h) at 1375 C, then aged at either 1300, 1400, or 1500 C for times ranging from 50 to 10,000 h. Grain size measurements (vertical and horizontal mean linear intercept and horizontal and vertical projection) and analyses of iridium-thorium precipitates (size and spacing) were made on the longitudinal, transverse, and rolling surfaces of the as-recrystallized and aged specimens from which the two-dimensional spatial distribution and meanmore » sizes of the precipitates were obtained. The results obtained from this study are intended to provide input to grain growth models.« less

A combined experimental and numerical study on upper airway dosimetry of inhaled nanoparticles from an electrical discharge machine shop.

PubMed

Tian, Lin; Shang, Yidan; Chen, Rui; Bai, Ru; Chen, Chunying; Inthavong, Kiao; Tu, Jiyuan

2017-07-12

Exposure to nanoparticles in the workplace is a health concern to occupational workers with increased risk of developing respiratory, cardiovascular, and neurological disorders. Based on animal inhalation study and human lung tumor risk extrapolation, current authoritative recommendations on exposure limits are either on total mass or number concentrations. Effects of particle size distribution and the implication to regional airway dosages are not elaborated. Real time production of particle concentration and size distribution in the range from 5.52 to 98.2 nm were recorded in a wire-cut electrical discharge machine shop (WEDM) during a typical working day. Under the realistic exposure condition, human inhalation simulations were performed in a physiologically realistic nasal and upper airway replica. The combined experimental and numerical study is the first to establish a realistic exposure condition, and under which, detailed dose metric studies can be performed. In addition to mass concentration guided exposure limit, inhalation risks to nano-pollutant were reexamined accounting for the actual particle size distribution and deposition statistics. Detailed dosimetries of the inhaled nano-pollutants in human nasal and upper airways with respect to particle number, mass and surface area were discussed, and empirical equations were developed. An astonishing enhancement of human airway dosages were detected by current combined experimental and numerical study in the WEDM machine shop. Up to 33 folds in mass, 27 folds in surface area and 8 folds in number dosages were detected during working hours in comparison to the background dosimetry measured at midnight. The real time particle concentration measurement showed substantial emission of nano-pollutants by WEDM machining activity, and the combined experimental and numerical study provided extraordinary details on human inhalation dosimetry. It was found out that human inhalation dosimetry was extremely sensitive to real time particle concentration and size distribution. Averaged particle concentration over 24-h period will inevitably misrepresent the sensible information critical for realistic inhalation risk assessment. Particle size distribution carries very important information in determining human airway dosimetry. A pure number or mass concentration recommendation on the exposure limit at workplace is insufficient. A particle size distribution, together with the deposition equations, is critical to recognize the actual exposure risks. In addition, human airway dosimetry in number, mass and surface area varies significantly. A complete inhalation risk assessment requires the knowledge of toxicity mechanisms in response to each individual metric. Further improvements in these areas are needed.

Matilda: A mass filtered nanocluster source

NASA Astrophysics Data System (ADS)

Kwon, Gihan

Cluster science provides a good model system for the study of the size dependence of electronic properties, chemical reactivity, as well as magnetic properties of materials. One of the main interests in cluster science is the nanoscale understanding of chemical reactions and selectivity in catalysis. Therefore, a new cluster system was constructed to study catalysts for applications in renewable energy. Matilda, a nanocluster source, consists of a cluster source and a Retarding Field Analyzer (RFA). A moveable AJA A310 Series 1"-diameter magnetron sputtering gun enclosed in a water cooled aggregation tube served as the cluster source. A silver coin was used for the sputtering target. The sputtering pressure in the aggregation tube was controlled, ranging from 0.07 to 1torr, using a mass flow controller. The mean cluster size was found to be a function of relative partial pressure (He/Ar), sputtering power, and aggregation length. The kinetic energy distribution of ionized clusters was measured with the RFA. The maximum ion energy distribution was 2.9 eV/atom at a zero pressure ratio. At high Ar flow rates, the mean cluster size was 20 ˜ 80nm, and at a 9.5 partial pressure ratio, the mean cluster size was reduced to 1.6nm. Our results showed that the He gas pressure can be optimized to reduce the cluster size variations. Results from SIMION, which is an electron optics simulation package, supported the basic function of an RFA, a three-element lens and the magnetic sector mass filter. These simulated results agreed with experimental data. For the size selection experiment, the channeltron electron multiplier collected ionized cluster signal at different positions during Ag deposition on a TEM grid for four and half hours. The cluster signal was high at the position for neutral clusters, which was not bent by a magnetic field, and the signal decreased rapidly far away from the neutral cluster region. For cluster separation according to mass to charge ratio in a magnetic sector mass filter, the ion energy of the cluster and its distribution must be precisely controlled by acceleration or deceleration. To verify the size separation, a high resolution microscope was required. Matilda provided narrow particle sized distribution from atomic scale to 4nm in size with different pressure ratio without additional mass filter. It is very economical way to produce relatively narrow particle size distribution.

Studying the Binomial Distribution Using LabVIEW

ERIC Educational Resources Information Center

George, Danielle J.; Hammer, Nathan I.

2015-01-01

This undergraduate physical chemistry laboratory exercise introduces students to the study of probability distributions both experimentally and using computer simulations. Students perform the classic coin toss experiment individually and then pool all of their data together to study the effect of experimental sample size on the binomial…

Rank Diversity of Languages: Generic Behavior in Computational Linguistics

PubMed Central

Cocho, Germinal; Flores, Jorge; Gershenson, Carlos; Pineda, Carlos; Sánchez, Sergio

2015-01-01

Statistical studies of languages have focused on the rank-frequency distribution of words. Instead, we introduce here a measure of how word ranks change in time and call this distribution rank diversity. We calculate this diversity for books published in six European languages since 1800, and find that it follows a universal lognormal distribution. Based on the mean and standard deviation associated with the lognormal distribution, we define three different word regimes of languages: “heads” consist of words which almost do not change their rank in time, “bodies” are words of general use, while “tails” are comprised by context-specific words and vary their rank considerably in time. The heads and bodies reflect the size of language cores identified by linguists for basic communication. We propose a Gaussian random walk model which reproduces the rank variation of words in time and thus the diversity. Rank diversity of words can be understood as the result of random variations in rank, where the size of the variation depends on the rank itself. We find that the core size is similar for all languages studied. PMID:25849150

Rank diversity of languages: generic behavior in computational linguistics.

PubMed

Cocho, Germinal; Flores, Jorge; Gershenson, Carlos; Pineda, Carlos; Sánchez, Sergio

2015-01-01

Statistical studies of languages have focused on the rank-frequency distribution of words. Instead, we introduce here a measure of how word ranks change in time and call this distribution rank diversity. We calculate this diversity for books published in six European languages since 1800, and find that it follows a universal lognormal distribution. Based on the mean and standard deviation associated with the lognormal distribution, we define three different word regimes of languages: "heads" consist of words which almost do not change their rank in time, "bodies" are words of general use, while "tails" are comprised by context-specific words and vary their rank considerably in time. The heads and bodies reflect the size of language cores identified by linguists for basic communication. We propose a Gaussian random walk model which reproduces the rank variation of words in time and thus the diversity. Rank diversity of words can be understood as the result of random variations in rank, where the size of the variation depends on the rank itself. We find that the core size is similar for all languages studied.

Effect of wire size on maxillary arch force/couple systems for a simulated high canine malocclusion.

PubMed

Major, Paul W; Toogood, Roger W; Badawi, Hisham M; Carey, Jason P; Seru, Surbhi

2014-12-01

To better understand the effects of copper nickel titanium (CuNiTi) archwire size on bracket-archwire mechanics through the analysis of force/couple distributions along the maxillary arch. The hypothesis is that wire size is linearly related to the forces and moments produced along the arch. An Orthodontic Simulator was utilized to study a simplified high canine malocclusion. Force/couple distributions produced by passive and elastic ligation using two wire sizes (Damon 0.014 and 0.018 inch) measured with a sample size of 144. The distribution and variation in force/couple loading around the arch is a complicated function of wire size. The use of a thicker wire increases the force/couple magnitudes regardless of ligation method. Owing to the non-linear material behaviour of CuNiTi, this increase is less than would occur based on linear theory as would apply for stainless steel wires. The results demonstrate that an increase in wire size does not result in a proportional increase of applied force/moment. This discrepancy is explained in terms of the non-linear properties of CuNiTi wires. This non-proportional force response in relation to increased wire size warrants careful consideration when selecting wires in a clinical setting. © 2014 British Orthodontic Society.

Undersampling power-law size distributions: effect on the assessment of extreme natural hazards

USGS Publications Warehouse

Geist, Eric L.; Parsons, Thomas E.

2014-01-01

The effect of undersampling on estimating the size of extreme natural hazards from historical data is examined. Tests using synthetic catalogs indicate that the tail of an empirical size distribution sampled from a pure Pareto probability distribution can range from having one-to-several unusually large events to appearing depleted, relative to the parent distribution. Both of these effects are artifacts caused by limited catalog length. It is more difficult to diagnose the artificially depleted empirical distributions, since one expects that a pure Pareto distribution is physically limited in some way. Using maximum likelihood methods and the method of moments, we estimate the power-law exponent and the corner size parameter of tapered Pareto distributions for several natural hazard examples: tsunamis, floods, and earthquakes. Each of these examples has varying catalog lengths and measurement thresholds, relative to the largest event sizes. In many cases where there are only several orders of magnitude between the measurement threshold and the largest events, joint two-parameter estimation techniques are necessary to account for estimation dependence between the power-law scaling exponent and the corner size parameter. Results indicate that whereas the corner size parameter of a tapered Pareto distribution can be estimated, its upper confidence bound cannot be determined and the estimate itself is often unstable with time. Correspondingly, one cannot statistically reject a pure Pareto null hypothesis using natural hazard catalog data. Although physical limits to the hazard source size and by attenuation mechanisms from source to site constrain the maximum hazard size, historical data alone often cannot reliably determine the corner size parameter. Probabilistic assessments incorporating theoretical constraints on source size and propagation effects are preferred over deterministic assessments of extreme natural hazards based on historic data.

Pore size distribution calculation from 1H NMR signal and N2 adsorption-desorption techniques

NASA Astrophysics Data System (ADS)

Hassan, Jamal

2012-09-01

The pore size distribution (PSD) of nano-material MCM-41 is determined using two different approaches: N2 adsorption-desorption and 1H NMR signal of water confined in silica nano-pores of MCM-41. The first approach is based on the recently modified Kelvin equation [J.V. Rocha, D. Barrera, K. Sapag, Top. Catal. 54(2011) 121-134] which deals with the known underestimation in pore size distribution for the mesoporous materials such as MCM-41 by introducing a correction factor to the classical Kelvin equation. The second method employs the Gibbs-Thompson equation, using NMR, for melting point depression of liquid in confined geometries. The result shows that both approaches give similar pore size distribution to some extent, and also the NMR technique can be considered as an alternative direct method to obtain quantitative results especially for mesoporous materials. The pore diameter estimated for the nano-material used in this study was about 35 and 38 Å for the modified Kelvin and NMR methods respectively. A comparison between these methods and the classical Kelvin equation is also presented.

In vitro ovine articular chondrocyte proliferation: experiments and modelling.

PubMed

Mancuso, L; Liuzzo, M I; Fadda, S; Pisu, M; Cincotti, A; Arras, M; La Nasa, G; Concas, A; Cao, G

2010-06-01

This study focuses on analysis of in vitro cultures of chondrocytes from ovine articular cartilage. Isolated cells were seeded in Petri dishes, then expanded to confluence and phenotypically characterized by flow cytometry. The sigmoidal temporal profile of total counts was obtained by classic haemocytometry and corresponding cell size distributions were measured electronically using a Coulter Counter. A mathematical model recently proposed (1) was adopted for quantitative interpretation of these experimental data. The model is based on a 1-D (that is, mass-structured), single-staged population balance approach capable of taking into account contact inhibition at confluence. The model's parameters were determined by fitting measured total cell counts and size distributions. Model reliability was verified by predicting cell proliferation counts and corresponding size distributions at culture times longer than those used when tuning the model's parameters. It was found that adoption of cell mass as the intrinsic characteristic of a growing chondrocyte population enables sigmoidal temporal profiles of total counts in the Petri dish, as well as cell size distributions at 'balanced growth', to be adequately predicted.

The Equilibrium Allele Frequency Distribution for a Population with Reproductive Skew

PubMed Central

Der, Ricky; Plotkin, Joshua B.

2014-01-01

We study the population genetics of two neutral alleles under reversible mutation in a model that features a skewed offspring distribution, called the Λ-Fleming–Viot process. We describe the shape of the equilibrium allele frequency distribution as a function of the model parameters. We show that the mutation rates can be uniquely identified from this equilibrium distribution, but the form of the offspring distribution cannot itself always be so identified. We introduce an estimator for the mutation rate that is consistent, independent of the form of reproductive skew. We also introduce a two-allele infinite-sites version of the Λ-Fleming–Viot process, and we use it to study how reproductive skew influences standing genetic diversity in a population. We derive asymptotic formulas for the expected number of segregating sites as a function of sample size and offspring distribution. We find that the Wright–Fisher model minimizes the equilibrium genetic diversity, for a given mutation rate and variance effective population size, compared to all other Λ-processes. PMID:24473932

COMPARISON OF TWO PARTICLE-SIZE SPECTROMETERS FOR AMBIENT AEROSOL MEASUREMENTS. (R827354C002)

EPA Science Inventory

There is an ongoing debate on the question which size fraction of particles in ambient air may be responsible for human health effects observed in epidemiological studies. Since there is no single instrument available for the measurement of the particle-size distribution over ...

Estimation of surface area concentration of workplace incidental nanoparticles based on number and mass concentrations

NASA Astrophysics Data System (ADS)

Park, J. Y.; Ramachandran, G.; Raynor, P. C.; Kim, S. W.

2011-10-01

Surface area was estimated by three different methods using number and/or mass concentrations obtained from either two or three instruments that are commonly used in the field. The estimated surface area concentrations were compared with reference surface area concentrations (SAREF) calculated from the particle size distributions obtained from a scanning mobility particle sizer and an optical particle counter (OPC). The first estimation method (SAPSD) used particle size distribution measured by a condensation particle counter (CPC) and an OPC. The second method (SAINV1) used an inversion routine based on PM1.0, PM2.5, and number concentrations to reconstruct assumed lognormal size distributions by minimizing the difference between measurements and calculated values. The third method (SAINV2) utilized a simpler inversion method that used PM1.0 and number concentrations to construct a lognormal size distribution with an assumed value of geometric standard deviation. All estimated surface area concentrations were calculated from the reconstructed size distributions. These methods were evaluated using particle measurements obtained in a restaurant, an aluminum die-casting factory, and a diesel engine laboratory. SAPSD was 0.7-1.8 times higher and SAINV1 and SAINV2 were 2.2-8 times higher than SAREF in the restaurant and diesel engine laboratory. In the die casting facility, all estimated surface area concentrations were lower than SAREF. However, the estimated surface area concentration using all three methods had qualitatively similar exposure trends and rankings to those using SAREF within a workplace. This study suggests that surface area concentration estimation based on particle size distribution (SAPSD) is a more accurate and convenient method to estimate surface area concentrations than estimation methods using inversion routines and may be feasible to use for classifying exposure groups and identifying exposure trends.

Comparing Aircraft Observations of Snowfall to Forecasts Using Single or Two Moment Bulk Water Microphysics Schemes

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.

2010-01-01

High resolution weather forecast models with explicit prediction of hydrometeor type, size distribution, and fall speed may be useful in the development of precipitation retrievals, by providing representative characteristics of frozen hydrometeors. Several single or double-moment microphysics schemes are currently available within the Weather Research and Forecasting (WRF) model, allowing for the prediction of up to three ice species. Each scheme incorporates different assumptions regarding the characteristics of their ice classes, particularly in terms of size distribution, density, and fall speed. In addition to the prediction of hydrometeor content, these schemes must accurately represent the vertical profile of water vapor to account for possible attenuation, along with the size distribution, density, and shape characteristics of ice crystals that are relevant to microwave scattering. An evaluation of a particular scheme requires the availability of field campaign measurements. The Canadian CloudSat/CALIPSO Validation Project (C3VP) obtained measurements of ice crystal shapes, size distributions, fall speeds, and precipitation during several intensive observation periods. In this study, C3VP observations obtained during the 22 January 2007 synoptic-scale snowfall event are compared against WRF model output, based upon forecasts using four single-moment and two double-moment schemes available as of version 3.1. Schemes are compared against aircraft observations by examining differences in size distribution, density, and content. In addition to direct measurements from aircraft probes, simulated precipitation can also be converted to equivalent, remotely sensed characteristics through the use of the NASA Goddard Satellite Data Simulator Unit. Outputs from high resolution forecasts are compared against radar and satellite observations emphasizing differences in assumed crystal shape and size distribution characteristics.

General herpetological collecting is size-based for five Pacific lizards

USGS Publications Warehouse

Rodda, Gordon H.; Yackel Adams, Amy A.; Campbell, Earl W.; Fritts, Thomas H.

2015-01-01

Accurate estimation of a species’ size distribution is a key component of characterizing its ecology, evolution, physiology, and demography. We compared the body size distributions of five Pacific lizards (Carlia ailanpalai, Emoia caeruleocauda, Gehyra mutilata, Hemidactylus frenatus, and Lepidodactylus lugubris) from general herpetological collecting (including visual surveys and glue boards) with those from complete censuses obtained by total removal. All species exhibited the same pattern: general herpetological collecting undersampled juveniles and oversampled mid-sized adults. The bias was greatest for the smallest juveniles and was not statistically evident for newly maturing and very large adults. All of the true size distributions of these continuously breeding species were skewed heavily toward juveniles, more so than the detections obtained from general collecting. A strongly skewed size distribution is not well characterized by the mean or maximum, though those are the statistics routinely reported for species’ sizes. We found body mass to be distributed more symmetrically than was snout–vent length, providing an additional rationale for collecting and reporting that size measure.

Particle size distributions and the vertical distribution of suspended matter in the upwelling region off Oregon

NASA Technical Reports Server (NTRS)

Kitchen, J. C.

1977-01-01

Various methods of presenting and mathematically describing particle size distribution are explained and evaluated. The hyperbolic distribution is found to be the most practical but the more complex characteristic vector analysis is the most sensitive to changes in the shape of the particle size distributions. A method for determining onshore-offshore flow patterns from the distribution of particulates was presented. A numerical model of the vertical structure of two size classes of particles was developed. The results show a close similarity to the observed distributions but overestimate the particle concentration by forty percent. This was attributed to ignoring grazing by zooplankton. Sensivity analyses showed the size preference was most responsive to the maximum specific growth rates and nutrient half saturation constants. The verical structure was highly dependent on the eddy diffusivity followed closely by the growth terms.

Body Size Diversity and Frequency Distributions of Neotropical Cichlid Fishes (Cichliformes: Cichlidae: Cichlinae)

PubMed Central

Steele, Sarah E.; López-Fernández, Hernán

2014-01-01

Body size is an important correlate of life history, ecology and distribution of species. Despite this, very little is known about body size evolution in fishes, particularly freshwater fishes of the Neotropics where species and body size diversity are relatively high. Phylogenetic history and body size data were used to explore body size frequency distributions in Neotropical cichlids, a broadly distributed and ecologically diverse group of fishes that is highly representative of body size diversity in Neotropical freshwater fishes. We test for divergence, phylogenetic autocorrelation and among-clade partitioning of body size space. Neotropical cichlids show low phylogenetic autocorrelation and divergence within and among taxonomic levels. Three distinct regions of body size space were identified from body size frequency distributions at various taxonomic levels corresponding to subclades of the most diverse tribe, Geophagini. These regions suggest that lineages may be evolving towards particular size optima that may be tied to specific ecological roles. The diversification of Geophagini appears to constrain the evolution of body size among other Neotropical cichlid lineages; non-Geophagini clades show lower species-richness in body size regions shared with Geophagini. Neotropical cichlid genera show less divergence and extreme body size than expected within and among tribes. Body size divergence among species may instead be present or linked to ecology at the community assembly scale. PMID:25180970

Parallel Measurements of Light Scattering and Characterization of Marine Particles in Water: An Evaluation of Methodology

DTIC Science & Technology

2008-01-01

A second objective is to characterize variability in the volume scattering function and particle size distribution for various optical water types...volume scattering function (VSF) and the particle size distribution (PSD) • Analysis of in situ optical measurements and particle size distributions ...SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION /AVAILABILITY STATEMENT Approved for public release; distribution unlimited 13. SUPPLEMENTARY

Effect of solvent type on the nanoparticle formation of atorvastatin calcium by the supercritical antisolvent process.

PubMed

Kim, Min-Soo; Song, Ha-Seung; Park, Hee Jun; Hwang, Sung-Joo

2012-01-01

The aims of this study were to identify how the solvent selection affects particle formation and to examine the effect of the initial drug solution concentration on mean particle size and particle size distribution in the supercritical antisolvent (SAS) process. Amorphous atorvastatin calcium was precipitated from seven different solvents using the SAS process. Particles with mean particle size ranging between 62.6 and 1493.7 nm were obtained by varying organic solvent type and solution concentration. By changing the solvent, we observed large variations in particle size and particle size distribution, accompanied by different particle morphologies. Particles obtained from acetone and tetrahydrofuran (THF) were compact and spherical fine particles, whereas those from N-methylpyrrolidone (NMP) and dimethylsulfoxide (DMSO) were agglomerated, with rough surfaces and relatively larger particle sizes. Interestingly, the mean particle size of atorvastatin calcium increased with an increase in the boiling point of the organic solvent used. Thus, for atorvastatin particle formation via the SAS process, particle size was determined mainly by evaporation of the organic solvent into the antisolvent phase. In addition, the mean particle size was increased with increasing drug solution concentration. In this study, from the aspects of particle size and solvent toxicity, acetone was the better organic solvent for controlling nanoparticle formation of atorvastatin calcium.

Near-infrared scattering as a dust diagnostic

NASA Astrophysics Data System (ADS)

Saajasto, Mika; Juvela, Mika; Malinen, Johanna

2018-06-01

Context. Regarding the evolution of dust grains from diffuse regions of space to dense molecular cloud cores, many questions remain open. Scattering at near-infrared wavelengths, or "cloudshine", can provide information on cloud structure, dust properties, and the radiation field that is complementary to mid-infrared "coreshine" and observations of dust emission at longer wavelengths. Aims: We examine the possibility of using near-infrared scattering to constrain the local radiation field and the dust properties, the scattering and absorption efficiency, the size distribution of the grains, and the maximum grain size. Methods: We use radiative transfer modelling to examine the constraints provided by the J, H, and K bands in combination with mid-infrared surface brightness at 3.6 μm. We use spherical one-dimensional and elliptical three-dimensional cloud models to study the observable effects of different grain size distributions with varying absorption and scattering properties. As an example, we analyse observations of a molecular cloud in Taurus, TMC-1N. Results: The observed surface brightness ratios of the bands change when the dust properties are changed. However, even a change of ±10% in the surface brightness of one band changes the estimated power-law exponent of the size distribution γ by up to 30% and the estimated strength of the radiation field KISRF by up to 60%. The maximum grain size Amax and γ are always strongly anti-correlated. For example, overestimating the surface brightness by 10% changes the estimated radiation field strength by 20% and the exponent of the size distribution by 15%. The analysis of our synthetic observations indicates that the relative uncertainty of the parameter distributions are on average Amax, γ 25%, and the deviation between the estimated and correct values ΔQ < 15%. For the TMC-1N observations, a maximum grain size Amax > 1.5μm and a size distribution with γ > 4.0 have high probability. The mass weighted average grain size is ⟨am⟩ = 0.113μm. Conclusions: We show that scattered infrared light can be used to derive meaningful limits for the dust parameters. However, errors in the surface brightness data can result in considerable uncertainties on the derived parameters.

The morphology of cometary dust: Subunit size distributions down to tens of nanometres

NASA Astrophysics Data System (ADS)

Mannel, Thurid; Bentley, Mark; Boakes, Peter; Jeszenszky, Harald; Levasseur-Regourd, Anny-Chantal; Schmied, Roland; Torkar, Klaus

2017-04-01

The Rosetta orbiter carried a dedicated analysis suite for cometary dust. One of the key instruments was MIDAS (Micro-Imaging Dust Analysis System), an atomic force microscope that scanned the surfaces of hundreds of (sub-)micrometre particles in 3D with resolutions down to nanometres. This provided the opportunity to study the morphology of the smallest cometary dust; initial investigation revealed that the particles are agglomerates of smaller subunits [1] with different structural properties [2]. To understand the (surface-) structure of the dust particles and the origin of their smallest building blocks, a number of particles were investigated in detail and the size distribution of their subunits determined [3]. Here we discuss the subunit size distributions ranging from tens of nanometres to a few micrometres. The differences between the subunit size distributions for particles collected pre-perihelion, close to perihelion, and during a huge outburst are examined, as well as the dependence of subunit size on particle size. A case where a particle was fragmented in consecutive scans allows a direct comparison of fragment and subunit size distributions. Finally, the small end of the subunit size distribution is investigated: the smallest determined sizes will be reviewed in the context of other cometary missions, interplanetary dust particles believed to originate from comets, and remote observations. It will be discussed if the smallest subunits can be interpreted as fundamental building blocks of our early Solar System and if their origin was in our protoplanetary disc or the interstellar material. References: [1] M.S. Bentley, R. Schmied, T. Mannel et al., Aggregate dust particles at comet 67P/Chruyumov-Gerasimenko, Nature, 537, 2016. doi:10.1038/nature19091 [2] T. Mannel, M.S. Bentley, R. Schmied et al., Fractal cometary dust - a window into the early Solar system, MNRAS, 462, 2016. doi:10.1093/mnras/stw2898 [3] R. Schmied, T. Mannel, H. Jeszenszky, M.S. Bentley, Properties of cometary dust down to the nanometre scale, poster at the conference 'Comets: A new vision after Rosetta/Philae' in Toulouse, 14-18 November 2016.

New algorithm and system for measuring size distribution of blood cells

NASA Astrophysics Data System (ADS)

Yao, Cuiping; Li, Zheng; Zhang, Zhenxi

2004-06-01

In optical scattering particle sizing, a numerical transform is sought so that a particle size distribution can be determined from angular measurements of near forward scattering, which has been adopted in the measurement of blood cells. In this paper a new method of counting and classification of blood cell, laser light scattering method from stationary suspensions, is presented. The genetic algorithm combined with nonnegative least squared algorithm is employed to inverse the size distribution of blood cells. Numerical tests show that these techniques can be successfully applied to measuring size distribution of blood cell with high stability.

Nonstandard convergence to jamming in random sequential adsorption: The case of patterned one-dimensional substrates

NASA Astrophysics Data System (ADS)

Verma, Arjun; Privman, Vladimir

2018-02-01

We study approach to the large-time jammed state of the deposited particles in the model of random sequential adsorption. The convergence laws are usually derived from the argument of Pomeau which includes the assumption of the dominance, at large enough times, of small landing regions into each of which only a single particle can be deposited without overlapping earlier deposited particles and which, after a certain time are no longer created by depositions in larger gaps. The second assumption has been that the size distribution of gaps open for particle-center landing in this large-time small-gaps regime is finite in the limit of zero gap size. We report numerical Monte Carlo studies of a recently introduced model of random sequential adsorption on patterned one-dimensional substrates that suggest that the second assumption must be generalized. We argue that a region exists in the parameter space of the studied model in which the gap-size distribution in the Pomeau large-time regime actually linearly vanishes at zero gap sizes. In another region, the distribution develops a threshold property, i.e., there are no small gaps below a certain gap size. We discuss the implications of these findings for new asymptotic power-law and exponential-modified-by-a-power-law convergences to jamming in irreversible one-dimensional deposition.

Three-dimensional cluster formation and structure in heterogeneous dose distribution of intensity modulated radiation therapy.

PubMed

Chao, Ming; Wei, Jie; Narayanasamy, Ganesh; Yuan, Yading; Lo, Yeh-Chi; Peñagarícano, José A

2018-05-01

To investigate three-dimensional cluster structure and its correlation to clinical endpoint in heterogeneous dose distributions from intensity modulated radiation therapy. Twenty-five clinical plans from twenty-one head and neck (HN) patients were used for a phenomenological study of the cluster structure formed from the dose distributions of organs at risks (OARs) close to the planning target volumes (PTVs). Initially, OAR clusters were searched to examine the pattern consistence among ten HN patients and five clinically similar plans from another HN patient. Second, clusters of the esophagus from another ten HN patients were scrutinized to correlate their sizes to radiobiological parameters. Finally, an extensive Monte Carlo (MC) procedure was implemented to gain deeper insights into the behavioral properties of the cluster formation. Clinical studies showed that OAR clusters had drastic differences despite similar PTV coverage among different patients, and the radiobiological parameters failed to positively correlate with the cluster sizes. MC study demonstrated the inverse relationship between the cluster size and the cluster connectivity, and the nonlinear changes in cluster size with dose thresholds. In addition, the clusters were insensitive to the shape of OARs. The results demonstrated that the cluster size could serve as an insightful index of normal tissue damage. The clinical outcome of the same dose-volume might be potentially different. Copyright © 2018 Elsevier B.V. All rights reserved.

Charge-induced secondary atomization in diffusion flames of electrostatic sprays

NASA Technical Reports Server (NTRS)

Gomez, Alessandro; Chen, Gung

1994-01-01

The combustion of electrostatic sprays of heptane in laminar counterflow diffusion flames was experimentally studied by measuring droplet size and velocity distributions, as well as the gas-phase temperature. A detailed examination of the evolution of droplet size distribution as droplets approach the flame shows that, if substantial evaporation occurs before droplets interact with the flame, an initially monodisperse size distribution becomes bimodal. A secondary sharp peak in the size histogram develops in correspondence of diameters about one order of magnitude smaller than the mean. No evaporation mechanism can account for the development of such bimodality, that can be explained only in terms of a disintegration of droplets into finer fragments of size much smaller than that of the parent. Other evidence in support of this interpretation is offered by the measurements of droplet size-velocity correlation and velocity component distributions, showing that, as a consequence of the ejection process, the droplets responsible for the secondary peak have velocities uncorrelated with the mean flow. The fission is induced by the electric charge. When a droplet evaporates, in fact, the electric charge density on the droplet surface increases while the droplet shrinks, until the so-called Rayleigh limit is reached at which point the repulsion of electric charges overcomes the surface tension cohesive force, ultimately leading to a disintegraton into finer fragments. We report on the first observation of such fissions in combustion environments. If, on the other hand, insufficient evaporation has occurred before droplets enter the high temperature region, there appears to be no significant evidence of bimodality in their size distribution. In this case, in fact, the concentration of flame chemi-ions or, in the case of positively charged droplets, electrons may be sufficient for them to neutralize the charge on the droplets and to prevent disruption.

The relationship between mammal faunas and climatic instability since the Last Glacial Maximum: A Nearctic vs. Western Palearctic comparison

NASA Astrophysics Data System (ADS)

Torres-Romero, Erik Joaquín; Varela, Sara; Fisher, Jason T.; Olalla-Tárraga, Miguel Á.

2017-07-01

Climate has played a key role in shaping the geographic patterns of biodiversity. The imprint of Quaternary climatic fluctuations is particularly evident on the geographic distribution of Holarctic faunas, which dramatically shifted their ranges following the alternation of glacial-interglacial cycles during the Pleistocene. Here, we evaluate the existence of differences between climatically stable and unstable regions - defined on the basis of climatic change velocity since the Last Glacial Maximum - in the geographic distribution of several biological attributes of extant terrestrial mammals of the Nearctic and Western Palearctic regions. Specifically, we use a macroecological approach to assess the dissimilarities in species richness, range size, body size, longevity and litter size of species that inhabit regions with contrasting histories of climatic stability. While several studies have documented how the distributional ranges of animals can be affected by long-term historic climatic fluctuations, there is less evidence on the species-specific traits that determine their responsiveness under such climatic instability. We find that climatically unstable areas have more widespread species and lower mammal richness than stable regions in both continents. We detected stronger signatures of historical climatic instability on the geographic distribution of body size in the Nearctic region, possibly reflecting lagged responses to recolonize deglaciated regions. However, the way that animals respond to climatic fluctuations varies widely among species and we were unable to find a relationship between climatic instability and other mammal life-history traits (longevity and litter size) in any of the two biogeographic regions. We, therefore, conclude that beyond some biological traits typical of macroecological analyses such as geographic range size and body size, it is difficult to infer the responsiveness of species distributions to climate change solely based on particular life-history traits.

Influence of pore size distributions on decomposition of maize leaf residue: evidence from X-ray computed micro-tomography

NASA Astrophysics Data System (ADS)

Negassa, Wakene; Guber, Andrey; Kravchenko, Alexandra; Rivers, Mark

2014-05-01

Soil's potential to sequester carbon (C) depends not only on quality and quantity of organic inputs to soil but also on the residence time of the applied organic inputs within the soil. Soil pore structure is one of the main factors that influence residence time of soil organic matter by controlling gas exchange, soil moisture and microbial activities, thereby soil C sequestration capacity. Previous attempts to investigate the fate of organic inputs added to soil did not allow examining their decomposition in situ; the drawback that can now be remediated by application of X-ray computed micro-tomography (µ-CT). The non-destructive and non-invasive nature of µ-CT gives an opportunity to investigate the effect of soil pore size distributions on decomposition of plant residues at a new quantitative level. The objective of this study is to examine the influence of pore size distributions on the decomposition of plant residue added to soil. Samples with contrasting pore size distributions were created using aggregate fractions of five different sizes (<0.05, 0.05-0.1, 0.10-05, 0.5-1.0 and 1.0-2.0 mm). Weighted average pore diameters ranged from 10 µm (<0.05 mm fraction) to 104 µm (1-2 mm fraction), while maximum pore diameter were in a range from 29 µm (<0.05 mm fraction) to 568 µm (1-2 mm fraction) in the created soil samples. Dried pieces of maize leaves 2.5 mg in size (equivalent to 1.71 mg C g-1 soil) were added to half of the studied samples. Samples with and without maize leaves were incubated for 120 days. CO2 emission from the samples was measured at regular time intervals. In order to ensure that the observed differences are due to differences in pore structure and not due to differences in inherent properties of the studied aggregate fractions, we repeated the whole experiment using soil from the same aggregate size fractions but ground to <0.05 mm size. Five to six replicated samples were used for intact and ground samples of all sizes with and without leaves. Two replications of the intact aggregate fractions of all sizes with leaves were subjected to µ-CT scanning before and after incubation, whereas all the remaining replications of both intact and ground aggregate fractions of <0.05, 0.05-0.1, and 1.0-2.0 mm sizes with leaves were scanned with µ-CT after the incubation. The µ-CT image showed that approximately 80% of the leaves in the intact samples of large aggregate fractions (0.5-1.0 and 1.0-2.0 mm) was decomposed during the incubation, while only 50-60% of the leaves were decomposed in the intact samples of smaller sized fractions. Even lower percent of leaves (40-50%) was decomposed in the ground samples, with very similar leaf decomposition observed in all ground samples regardless of the aggregate fraction size. Consistent with µ-CT results, the proportion of decomposed leaf estimated with the conventional mass loss method was 48% and 60% for the <0.05 mm and 1.0-2.0 mm soil size fractions of intact aggregates, and 40-50% in ground samples, respectively. The results of the incubation experiment demonstrated that, while greater C mineralization was observed in samples of all size fractions amended with leaf, the effect of leaf presence was most pronounced in the smaller aggregate fractions (0.05-0.1 mm and 0.05 mm) of intact aggregates. The results of the present study unequivocally demonstrate that differences in pore size distributions have a major effect on the decomposition of plant residues added to soil. Moreover, in presence of plant residues, differences in pore size distributions appear to also influence the rates of decomposition of the intrinsic soil organic material.

Size distribution of particle-phase molecular markers during a severe winter pollution episode.

PubMed

Kleeman, Michael J; Riddle, Sarah G; Jakober, Chris A

2008-09-01

Airborne particulate matter was collected using filter samplers and cascade impactors in six size fractions below 1.8 microm during a severe winter air pollution event at three sites in the Central Valley of California. The smallest size fraction analyzed was 0.056 < Dp <0.1 microm particle diameter, which accounts for the majority of the mass in the ultrafine (PM0.1) size range. Separate samples were collected during the daytime (10 a.m. to 6 p.m. PST) and nighttime (8 p.m. to 8 a.m. PST) to characterize diurnal patterns. Each sample was extracted with organic solvents and analyzed using gas chromatography mass spectrometry for molecular markers that can be used for size-resolved source apportionment calculations. Colocated impactor and filter measurements were highly correlated (R8 > 0.8) for retene, benzo[ghi]flouranthene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, perylene, indeno[1,2,3-cd]pyrene, benzo[ghi]perylene, coronene, MW302 polycyclic aromatic hydrocarbon (PAHs), 17beta(H)-21alpha(H)-30-norhopane, 17alpha(H)-21beta(H)-hopane, alphabetabeta-20R-C29-ethylcholestane, levoglucosan, and cholesterol. Of these compounds, levoglucosan was present in the highest concentration (60-2080 ng m(-3)) followed by cholesterol (6-35 ng m(-3)), PAHs (2-38 ng m(-3)), and hopanes and steranes (0-2 ng m(-3)). Nighttime concentrations were higher than daytime concentrations in all cases. Organic compound size distributions were generally similar to the total carbon size distributions during the nighttime but showed greater variability during the daytime. This may reflect the dominance of fresh emission in the stagnant surface layer during the evening hours and the presence of aged organic aerosol at the surface during the daytime when the atmosphere is better mixed. All of the measured organic compound particle size distributions had a single mode that peaked somewhere between 0.18 and 0.56 microm, but the width of each distribution varied by compound. Cholesterol generally had the broadest particle size distribution, while benzo[ghi]perylene and 17alpha(H)-21beta(H)-29-norhopane generally had sharper peaks. The difference between the size distributions of the various particle-phase organic compounds reflects the fact that these compounds exist in particles emitted from different sources. The results of the current study will prove useful for size-resolved source apportionment exercises.

Study of sandy soil grain-size distribution on its deformation properties

NASA Astrophysics Data System (ADS)

Antropova, L. B.; Gruzin, A. V.; Gildebrandt, M. I.; Malaya, L. D.; Nikulina, V. B.

2018-04-01

As a rule, new oil and gas fields' development faces the challenges of providing construction objects with material and mineral resources, for example, medium sand soil for buildings and facilities footings of the technological infrastructure under construction. This problem solution seems to lie in a rational usage of the existing environmental resources, soils included. The study was made of a medium sand soil grain-size distribution impact on its deformation properties. Based on the performed investigations, a technique for controlling sandy soil deformation properties was developed.

Particle size, size distribution and morphological evaluation of glass fiber reinforced plastic (GRP) industrial by-product.

PubMed

Mazzoli, Alida; Moriconi, Giacomo

2014-12-01

The waste management of glass fiber reinforced polymer (GRP) materials, in particular those made with thermosetting resins, is a critical issue for the composites industry because these materials cannot be reprocessed. Therefore, most thermosetting GRP waste is presently sent to landfill, in spite of the significant environmental impact caused by their disposal in this way. The limited GRP waste recycling worldwide is mostly due to its intrinsic thermosetting properties, lack of characterization data and unavailability of viable recycling and recovery routes. One of the possibility for re-using GRP industrial by-product is in form of powder as a partial aggregate replacement or filler addition in cement based composites for applications in sustainable construction materials and technologies. However, the feasibility of this kind of reutilization strongly depends on the morphology and particle size distribution of a powder made up of polymer granules and glass fibers. In the present study, the use of image analysis method, based on scanning electron microscopy (SEM) and ImageJ processing program, is proposed in order to evaluate the morphology of the particles and measure the particle size and size distribution of fine GRP waste powder. The obtained results show a great potential of such a method in order to be considered as a standardized method of measurement and analysis in order to characterize the grain size and size distribution of GRP particles before exploiting any compatibility issue for its recycling management. Copyright © 2014 Elsevier Ltd. All rights reserved.

Investigation of Physicochemical Drug Properties to Prepare Fine Globular Granules Composed of Only Drug Substance in Fluidized Bed Rotor Granulation.

PubMed

Mise, Ryohei; Iwao, Yasunori; Kimura, Shin-Ichiro; Osugi, Yukiko; Noguchi, Shuji; Itai, Shigeru

2015-01-01

The effect of some drug properties (wettability and particle size distribution) on granule properties (mean particle size, particle size distribution, sphericity, and granule strength) were investigated in a high (>97%) drug-loading formulation using fluidized bed rotor granulation. Three drugs: acetaminophen (APAP); ibuprofen (IBU); and ethenzamide (ETZ) were used as model drugs based on their differences in wettability and particle size distribution. Granules with mean particle sizes of 100-200 µm and a narrow particle size distribution (PSD) could be prepared regardless of the drug used. IBU and ETZ granules showed a higher sphericity than APAP granules, while APAP and ETZ granules exhibited higher granule strength than IBU. The relationship between drug and granule properties suggested that the wettability and the PSD of the drugs were critical parameters affecting sphericity and granule strength, respectively. Furthermore, the dissolution profiles of granules prepared with poorly water-soluble drugs (IBU and ETZ) showed a rapid release (80% release in 20 min) because of the improved wettability with granulation. The present study demonstrated for the first time that fluidized bed rotor granulation can prepare high drug-loaded (>97%) globular granules with a mean particle size of less than 200 µm and the relationship between physicochemical drug properties and the properties of the granules obtained could be readily determined, indicating the potential for further application of this methodology to various drugs.

The clouds of Venus. II - An investigation of the influence of coagulation on the observed droplet size distribution

NASA Technical Reports Server (NTRS)

Rossow, W. B.

1977-01-01

An approximate numerical technique is used to investigate the influence of coagulation, sedimentation and turbulent motions on the observed droplet size distribution in the upper layers of the Venus clouds. If the cloud mass mixing ratio is less than 0.000001 at 250 K or the eddy diffusivity throughout the cloud is greater than 1,000,000 sq cm per sec, then coagulation is unimportant. In this case, the observed droplet size distribution is the initial size distribution produced by the condensation of the droplets. It is found that all cloud models with droplet formation near the cloud top (e.g., a photochemical model) must produce the observed droplet size distribution by condensation without subsequent modification by coagulation. However, neither meteoritic or surface dust can supply sufficient nucleating particles to account for the observed droplet number density. If the cloud droplets are formed near the cloud bottom, the observed droplet size distribution can be produced solely by the interaction of coagulation and dynamics; all information about the initial size distribution is lost. If droplet formation occurs near the cloud bottom, the lower atmosphere of Venus is oxidizing rather than reducing.

Size characterization of airborne SiO2 nanoparticles with on-line and off-line measurement techniques: an interlaboratory comparison study

NASA Astrophysics Data System (ADS)

Motzkus, C.; Macé, T.; Gaie-Levrel, F.; Ducourtieux, S.; Delvallee, A.; Dirscherl, K.; Hodoroaba, V.-D.; Popov, I.; Popov, O.; Kuselman, I.; Takahata, K.; Ehara, K.; Ausset, P.; Maillé, M.; Michielsen, N.; Bondiguel, S.; Gensdarmes, F.; Morawska, L.; Johnson, G. R.; Faghihi, E. M.; Kim, C. S.; Kim, Y. H.; Chu, M. C.; Guardado, J. A.; Salas, A.; Capannelli, G.; Costa, C.; Bostrom, T.; Jämting, Å. K.; Lawn, M. A.; Adlem, L.; Vaslin-Reimann, S.

2013-10-01

Results of an interlaboratory comparison on size characterization of SiO2 airborne nanoparticles using on-line and off-line measurement techniques are discussed. This study was performed in the framework of Technical Working Area (TWA) 34—"Properties of Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS) in the project no. 3 "Techniques for characterizing size distribution of airborne nanoparticles". Two types of nano-aerosols, consisting of (1) one population of nanoparticles with a mean diameter between 30.3 and 39.0 nm and (2) two populations of non-agglomerated nanoparticles with mean diameters between, respectively, 36.2-46.6 nm and 80.2-89.8 nm, were generated for characterization measurements. Scanning mobility particle size spectrometers (SMPS) were used for on-line measurements of size distributions of the produced nano-aerosols. Transmission electron microscopy, scanning electron microscopy, and atomic force microscopy were used as off-line measurement techniques for nanoparticles characterization. Samples were deposited on appropriate supports such as grids, filters, and mica plates by electrostatic precipitation and a filtration technique using SMPS controlled generation upstream. The results of the main size distribution parameters (mean and mode diameters), obtained from several laboratories, were compared based on metrological approaches including metrological traceability, calibration, and evaluation of the measurement uncertainty. Internationally harmonized measurement procedures for airborne SiO2 nanoparticles characterization are proposed.

Droplet Sizing Research Program.

DTIC Science & Technology

1986-03-10

of size and velocity distributions is needed. For example, fuel spray studies, aer- osol studies, flue gas desulfurization , spray drying, paint...techniques are presented chronologic- ally since there is a logical development as a function of time. Most of the significant technical accomplishments...U3U 0 0 ILI N signals with an apparently different size by using the following logic : droplets that produce a certain visibility are associated with a

Size-isolation of ultrasound-mediated phase change perfluorocarbon droplets using differential centrifugation.

PubMed

Mercado, Karla P; Radhakrishnan, Kirthi; Stewart, Kyle; Snider, Lindsay; Ryan, Devin; Haworth, Kevin J

2016-05-01

Perfluorocarbon droplets that are capable of an ultrasound-mediated phase transition have applications in diagnostic and therapeutic ultrasound. Techniques to modify the droplet size distribution are of interest because of the size-dependent acoustic response of the droplets. Differential centrifugation has been used to isolate specific sizes of microbubbles. In this work, differential centrifugation was employed to isolate droplets with diameters between 1 and 3 μm and 2 and 5 μm from an initially polydisperse distribution. Further, an empirical model was developed for predicting the droplet size distribution following differential centrifugation and to facilitate the selection of centrifugation parameters for obtaining desired size distributions.

Size-isolation of ultrasound-mediated phase change perfluorocarbon droplets using differential centrifugation

PubMed Central

Mercado, Karla P.; Radhakrishnan, Kirthi; Stewart, Kyle; Snider, Lindsay; Ryan, Devin; Haworth, Kevin J.

2016-01-01

Perfluorocarbon droplets that are capable of an ultrasound-mediated phase transition have applications in diagnostic and therapeutic ultrasound. Techniques to modify the droplet size distribution are of interest because of the size-dependent acoustic response of the droplets. Differential centrifugation has been used to isolate specific sizes of microbubbles. In this work, differential centrifugation was employed to isolate droplets with diameters between 1 and 3 μm and 2 and 5 μm from an initially polydisperse distribution. Further, an empirical model was developed for predicting the droplet size distribution following differential centrifugation and to facilitate the selection of centrifugation parameters for obtaining desired size distributions. PMID:27250199

Optimizing Mississippi aggregates for concrete bridge decks.

DOT National Transportation Integrated Search

2012-12-01

AASHTO M 43 Standard Specification for Sizes of Aggregate for Road and Bridge Construction : addresses particle size distribution of material included in various maximum nominal size aggregates. This : particle size distribution requires additi...

Quantitative Research on the Minimum Wage

ERIC Educational Resources Information Center

Goldfarb, Robert S.

1975-01-01

The article reviews recent research examining the impact of minimum wage requirements on the size and distribution of teenage employment and earnings. The studies measure income distribution, employment levels and effect on unemployment. (MW)

Fracture size and transmissivity correlations: Implications for transport simulations in sparse three-dimensional discrete fracture networks following a truncated power law distribution of fracture size

NASA Astrophysics Data System (ADS)

Hyman, J. D.; Aldrich, G.; Viswanathan, H.; Makedonska, N.; Karra, S.

2016-08-01

We characterize how different fracture size-transmissivity relationships influence flow and transport simulations through sparse three-dimensional discrete fracture networks. Although it is generally accepted that there is a positive correlation between a fracture's size and its transmissivity/aperture, the functional form of that relationship remains a matter of debate. Relationships that assume perfect correlation, semicorrelation, and noncorrelation between the two have been proposed. To study the impact that adopting one of these relationships has on transport properties, we generate multiple sparse fracture networks composed of circular fractures whose radii follow a truncated power law distribution. The distribution of transmissivities are selected so that the mean transmissivity of the fracture networks are the same and the distributions of aperture and transmissivity in models that include a stochastic term are also the same. We observe that adopting a correlation between a fracture size and its transmissivity leads to earlier breakthrough times and higher effective permeability when compared to networks where no correlation is used. While fracture network geometry plays the principal role in determining where transport occurs within the network, the relationship between size and transmissivity controls the flow speed. These observations indicate DFN modelers should be aware that breakthrough times and effective permeabilities can be strongly influenced by such a relationship in addition to fracture and network statistics.

Fracture size and transmissivity correlations: Implications for transport simulations in sparse three-dimensional discrete fracture networks following a truncated power law distribution of fracture size

NASA Astrophysics Data System (ADS)

Hyman, J.; Aldrich, G. A.; Viswanathan, H. S.; Makedonska, N.; Karra, S.

2016-12-01

We characterize how different fracture size-transmissivity relationships influence flow and transport simulations through sparse three-dimensional discrete fracture networks. Although it is generally accepted that there is a positive correlation between a fracture's size and its transmissivity/aperture, the functional form of that relationship remains a matter of debate. Relationships that assume perfect correlation, semi-correlation, and non-correlation between the two have been proposed. To study the impact that adopting one of these relationships has on transport properties, we generate multiple sparse fracture networks composed of circular fractures whose radii follow a truncated power law distribution. The distribution of transmissivities are selected so that the mean transmissivity of the fracture networks are the same and the distributions of aperture and transmissivity in models that include a stochastic term are also the same.We observe that adopting a correlation between a fracture size and its transmissivity leads to earlier breakthrough times and higher effective permeability when compared to networks where no correlation is used. While fracture network geometry plays the principal role in determining where transport occurs within the network, the relationship between size and transmissivity controls the flow speed. These observations indicate DFN modelers should be aware that breakthrough times and effective permeabilities can be strongly influenced by such a relationship in addition to fracture and network statistics.

Microstructure as a function of the grain size distribution for packings of frictionless disks: Effects of the size span and the shape of the distribution.

PubMed

Estrada, Nicolas; Oquendo, W F

2017-10-01

This article presents a numerical study of the effects of grain size distribution (GSD) on the microstructure of two-dimensional packings of frictionless disks. The GSD is described by a power law with two parameters controlling the size span and the shape of the distribution. First, several samples are built for each combination of these parameters. Then, by means of contact dynamics simulations, the samples are densified in oedometric conditions and sheared in a simple shear configuration. The microstructure is analyzed in terms of packing fraction, local ordering, connectivity, and force transmission properties. It is shown that the microstructure is notoriously affected by both the size span and the shape of the GSD. These findings confirm recent observations regarding the size span of the GSD and extend previous works by describing the effects of the GSD shape. Specifically, we find that if the GSD shape is varied by increasing the proportion of small grains by a certain amount, it is possible to increase the packing fraction, increase coordination, and decrease the proportion of floating particles. Thus, by carefully controlling the GSD shape, it is possible to obtain systems that are denser and better connected, probably increasing the system's robustness and optimizing important strength properties such as stiffness, cohesion, and fragmentation susceptibility.

4D Imaging of Salt Precipitation during Evaporation from Saline Porous Media Influenced by the Particle Size Distribution

NASA Astrophysics Data System (ADS)

Norouzi Rad, M.; Shokri, N.

2014-12-01

Understanding the physics of water evaporation from saline porous media is important in many processes such as evaporation from porous media, vegetation, plant growth, biodiversity in soil, and durability of building materials. To investigate the effect of particle size distribution on the dynamics of salt precipitation in saline porous media during evaporation, we applied X-ray micro-tomography technique. Six samples of quartz sand with different grain size distributions were used in the present study enabling us to constrain the effects of particle and pore sizes on salt precipitation patterns and dynamics. The pore size distributions were computed using the pore-scale X-ray images. The packed beds were saturated with NaCl solution of 3 Molal and the X-ray imaging was continued for one day with temporal resolution of 30 min resulting in pore scale information about the evaporation and precipitation dynamics. Our results show more precipitation at the early stage of the evaporation in the case of sand with the larger particle size due to the presence of fewer evaporation sites at the surface. The presence of more preferential evaporation sites at the surface of finer sands significantly modified the patterns and thickness of the salt crust deposited on the surface such that a thinner salt crust was formed in the case of sand with smaller particle size covering larger area at the surface as opposed to the thicker patchy crusts in samples with larger particle sizes. Our results provide new insights regarding the physics of salt precipitation in porous media during evaporation.

Combining gas-phase electrophoretic mobility molecular analysis (GEMMA), light scattering, field flow fractionation and cryo electron microscopy in a multidimensional approach to characterize liposomal carrier vesicles

PubMed Central

Gondikas, Andreas; von der Kammer, Frank; Hofmann, Thilo; Marchetti-Deschmann, Martina; Allmaier, Günter; Marko-Varga, György; Andersson, Roland

2017-01-01

For drug delivery, characterization of liposomes regarding size, particle number concentrations, occurrence of low-sized liposome artefacts and drug encapsulation are of importance to understand their pharmacodynamic properties. In our study, we aimed to demonstrate the applicability of nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analyser (nES GEMMA) as a suitable technique for analyzing these parameters. We measured number-based particle concentrations, identified differences in size between nominally identical liposomal samples, and detected the presence of low-diameter material which yielded bimodal particle size distributions. Subsequently, we compared these findings to dynamic light scattering (DLS) data and results from light scattering experiments coupled to Asymmetric Flow-Field Flow Fractionation (AF4), the latter improving the detectability of smaller particles in polydisperse samples due to a size separation step prior detection. However, the bimodal size distribution could not be detected due to method inherent limitations. In contrast, cryo transmission electron microscopy corroborated nES GEMMA results. Hence, gas-phase electrophoresis proved to be a versatile tool for liposome characterization as it could analyze both vesicle size and size distribution. Finally, a correlation of nES GEMMA results with cell viability experiments was carried out to demonstrate the importance of liposome batch-to-batch control as low-sized sample components possibly impact cell viability. PMID:27639623

Spatial organization of surface nanobubbles and its implications in their formation process.

PubMed

Lhuissier, Henri; Lohse, Detlef; Zhang, Xuehua

2014-02-21

We study the size and spatial distribution of surface nanobubbles formed by the solvent exchange method to gain insight into the mechanism of their formation. The analysis of Atomic Force Microscopy (AFM) images of nanobubbles formed on a hydrophobic surface reveals that the nanobubbles are not randomly located, which we attribute to the role of the history of nucleation during the formation. Moreover, the size of each nanobubble is found to be strongly correlated with the area of the bubble-depleted zone around it. The precise correlation suggests that the nanobubbles grow by diffusion of the gas from the bulk rather than by diffusion of the gas adsorbed on the surface. Lastly, the size distribution of the nanobubbles is found to be well described by a log-normal distribution.

Structural characterization of casein micelles: shape changes during film formation.

PubMed

Gebhardt, R; Vendrely, C; Kulozik, U

2011-11-09

The objective of this study was to determine the effect of size-fractionation by centrifugation on the film structure of casein micelles. Fractionated casein micelles in solution were asymmetrically distributed with a small distribution width as measured by dynamic light scattering. Films prepared from the size-fractionated samples showed a smooth surface in optical microscopy images and a homogeneous microstructure in atomic force micrographs. The nano- and microstructure of casein films was probed by micro-beam grazing incidence small angle x-ray scattering (μGISAXS). Compared to the solution measurements, the sizes determined in the film were larger and broadly distributed. The measured GISAXS patterns clearly deviate from those simulated for a sphere and suggest a deformation of the casein micelles in the film. © 2011 IOP Publishing Ltd

Asteroid collisions: Target size effects and resultant velocity distributions

NASA Technical Reports Server (NTRS)

Ryan, Eileen V.

1993-01-01

To study the dynamic fragmentation of rock to simulate asteroid collisions, we use a 2-D, continuum damage numerical hydrocode which models two-body impacts. This hydrocode monitors stress wave propagation and interaction within the target body, and includes a physical model for the formation and growth of cracks in rock. With this algorithm we have successfully reproduced fragment size distributions and mean ejecta speeds from laboratory impact experiments using basalt, and weak and strong mortar as target materials. Using the hydrocode, we have determined that the energy needed to fracture a body has a much stronger dependence on target size than predicted from most scaling theories. In addition, velocity distributions obtained indicate that mean ejecta speeds resulting from large-body collisions do not exceed escape velocities.

Estimating the mean and standard deviation of environmental data with below detection limit observations: Considering highly skewed data and model misspecification.

PubMed

Shoari, Niloofar; Dubé, Jean-Sébastien; Chenouri, Shoja'eddin

2015-11-01

In environmental studies, concentration measurements frequently fall below detection limits of measuring instruments, resulting in left-censored data. Some studies employ parametric methods such as the maximum likelihood estimator (MLE), robust regression on order statistic (rROS), and gamma regression on order statistic (GROS), while others suggest a non-parametric approach, the Kaplan-Meier method (KM). Using examples of real data from a soil characterization study in Montreal, we highlight the need for additional investigations that aim at unifying the existing literature. A number of studies have examined this issue; however, those considering data skewness and model misspecification are rare. These aspects are investigated in this paper through simulations. Among other findings, results show that for low skewed data, the performance of different statistical methods is comparable, regardless of the censoring percentage and sample size. For highly skewed data, the performance of the MLE method under lognormal and Weibull distributions is questionable; particularly, when the sample size is small or censoring percentage is high. In such conditions, MLE under gamma distribution, rROS, GROS, and KM are less sensitive to skewness. Related to model misspecification, MLE based on lognormal and Weibull distributions provides poor estimates when the true distribution of data is misspecified. However, the methods of rROS, GROS, and MLE under gamma distribution are generally robust to model misspecifications regardless of skewness, sample size, and censoring percentage. Since the characteristics of environmental data (e.g., type of distribution and skewness) are unknown a priori, we suggest using MLE based on gamma distribution, rROS and GROS. Copyright © 2015 Elsevier Ltd. All rights reserved.

Grain boundary crystallography in polycrystalline yttria-stabilised cubic zirconia

NASA Astrophysics Data System (ADS)

Kini, Maya K.

2018-07-01

Properties of grain boundaries such as grain boundary energy, mobility and diffusion are reported to depend strongly on their crystallography. While studies on ceramic bicrystals with low Σ misorientations have shown highly ordered structures and low energies, studies on dense polycrystalline ceramics often show the significance of grain boundary planes. In the present study, grain boundary plane distributions were studied for yttria-stabilised cubic zirconia with varying grain sizes using Electron Back Scattered Diffraction technique combined with a stereological approach. Despite nearly isotropic grain boundary plane distributions, a highly anisotropic grain boundary character distribution is observed for specific misorientations. Certain low-energy symmetric tilts such as Σ3 and Σ11 are found to occur with high frequencies across the grain size range studied, leading to an inverse correlation between GB energy and frequency of occurrence, consistent with other ceramics studied in literature.

Modeling of Grain Size Distribution of Tsunami Sand Deposits in V-shaped Valley of Numanohama During the 2011 Tohoku Tsunami

NASA Astrophysics Data System (ADS)

Gusman, A. R.; Satake, K.; Goto, T.; Takahashi, T.

2016-12-01

Estimating tsunami amplitude from tsunami sand deposit has been a challenge. The grain size distribution of tsunami sand deposit may have correlation with tsunami inundation process, and further with its source characteristics. In order to test this hypothesis, we need a tsunami sediment transport model that can accurately estimate grain size distribution of tsunami deposit. Here, we built and validate a tsunami sediment transport model that can simulate grain size distribution. Our numerical model has three layers which are suspended load layer, active bed layer, and parent bed layer. The two bed layers contain information about the grain size distribution. This numerical model can handle a wide range of grain sizes from 0.063 (4 ϕ) to 5.657 mm (-2.5 ϕ). We apply the numerical model to simulate the sedimentation process during the 2011 Tohoku earthquake in Numanohama, Iwate prefecture, Japan. The grain size distributions at 15 sample points along a 900 m transect from the beach are used to validate the tsunami sediment transport model. The tsunami deposits are dominated by coarse sand with diameter of 0.5 - 1 mm and their thickness are up to 25 cm. Our tsunami model can well reproduce the observed tsunami run-ups that are ranged from 16 to 34 m along the steep valley in Numanohama. The shapes of the simulated grain size distributions at many sample points located within 300 m from the shoreline are similar to the observations. The differences between observed and simulated peak of grain size distributions are less than 1 ϕ. Our result also shows that the simulated sand thickness distribution along the transect is consistent with the observation.

Constraining ejecta particle size distributions with light scattering

NASA Astrophysics Data System (ADS)

Schauer, Martin; Buttler, William; Frayer, Daniel; Grover, Michael; Lalone, Brandon; Monfared, Shabnam; Sorenson, Daniel; Stevens, Gerald; Turley, William

2017-06-01

The angular distribution of the intensity of light scattered from a particle is strongly dependent on the particle size and can be calculated using the Mie solution to Maxwell's equations. For a collection of particles with a range of sizes, the angular intensity distribution will be the sum of the contributions from each particle size weighted by the number of particles in that size bin. The set of equations describing this pattern is not uniquely invertible, i.e. a number of different distributions can lead to the same scattering pattern, but with reasonable assumptions about the distribution it is possible to constrain the problem and extract estimates of the particle sizes from a measured scattering pattern. We report here on experiments using particles ejected by shockwaves incident on strips of triangular perturbations machined into the surface of tin targets. These measurements indicate a bimodal distribution of ejected particle sizes with relatively large particles (median radius 2-4 μm) evolved from the edges of the perturbation strip and smaller particles (median radius 200-600 nm) from the perturbations. We will briefly discuss the implications of these results and outline future plans.

Can airborne ultrasound monitor bubble size in chocolate?

NASA Astrophysics Data System (ADS)

Watson, N.; Hazlehurst, T.; Povey, M.; Vieira, J.; Sundara, R.; Sandoz, J.-P.

2014-04-01

Aerated chocolate products consist of solid chocolate with the inclusion of bubbles and are a popular consumer product in many countries. The volume fraction and size distribution of the bubbles has an effect on their sensory properties and manufacturing cost. For these reasons it is important to have an online real time process monitoring system capable of measuring their bubble size distribution. As these products are eaten by consumers it is desirable that the monitoring system is non contact to avoid food contaminations. In this work we assess the feasibility of using an airborne ultrasound system to monitor the bubble size distribution in aerated chocolate bars. The experimental results from the airborne acoustic experiments were compared with theoretical results for known bubble size distributions using COMSOL Multiphysics. This combined experimental and theoretical approach is used to develop a greater understanding of how ultrasound propagates through aerated chocolate and to assess the feasibility of using airborne ultrasound to monitor bubble size distribution in these systems. The results indicated that a smaller bubble size distribution would result in an increase in attenuation through the product.

Time-dependent solutions for a stochastic model of gene expression with molecule production in the form of a compound Poisson process.

PubMed

Jędrak, Jakub; Ochab-Marcinek, Anna

2016-09-01

We study a stochastic model of gene expression, in which protein production has a form of random bursts whose size distribution is arbitrary, whereas protein decay is a first-order reaction. We find exact analytical expressions for the time evolution of the cumulant-generating function for the most general case when both the burst size probability distribution and the model parameters depend on time in an arbitrary (e.g., oscillatory) manner, and for arbitrary initial conditions. We show that in the case of periodic external activation and constant protein degradation rate, the response of the gene is analogous to the resistor-capacitor low-pass filter, where slow oscillations of the external driving have a greater effect on gene expression than the fast ones. We also demonstrate that the nth cumulant of the protein number distribution depends on the nth moment of the burst size distribution. We use these results to show that different measures of noise (coefficient of variation, Fano factor, fractional change of variance) may vary in time in a different manner. Therefore, any biological hypothesis of evolutionary optimization based on the nonmonotonic dependence of a chosen measure of noise on time must justify why it assumes that biological evolution quantifies noise in that particular way. Finally, we show that not only for exponentially distributed burst sizes but also for a wider class of burst size distributions (e.g., Dirac delta and gamma) the control of gene expression level by burst frequency modulation gives rise to proportional scaling of variance of the protein number distribution to its mean, whereas the control by amplitude modulation implies proportionality of protein number variance to the mean squared.

Birth order and sibship size: evaluation of the role of selection bias in a case-control study of non-Hodgkin's lymphoma.

PubMed

Mensah, F K; Willett, E V; Simpson, J; Smith, A G; Roman, E

2007-09-15

Substantial heterogeneity has been observed among case-control studies investigating associations between non-Hodgkin's lymphoma and familial characteristics, such as birth order and sibship size. The potential role of selection bias in explaining such heterogeneity is considered within this study. Selection bias according to familial characteristics and socioeconomic status is investigated within a United Kingdom-based case-control study of non-Hodgkin's lymphoma diagnosed during 1998-2001. Reported distributions of birth order and maternal age are each compared with expected reference distributions derived using national birth statistics from the United Kingdom. A method is detailed in which yearly data are used to derive expected distributions, taking account of variability in birth statistics over time. Census data are used to reweight both the case and control study populations such that they are comparable with the general population with regard to socioeconomic status. The authors found little support for an association between non-Hodgkin's lymphoma and birth order or family size and little evidence for an influence of selection bias. However, the findings suggest that between-study heterogeneity could be explained by selection biases that influence the demographic characteristics of participants.

Modeling the Impact of Drizzle and 3D Cloud Structure on Remote Sensing of Effective Radius

NASA Technical Reports Server (NTRS)

Platnick, Steven; Zinner, Tobias; Ackerman, S.

2008-01-01

Remote sensing of cloud particle size with passive sensors like MODIS is an important tool for cloud microphysical studies. As a measure of the radiatively relevant droplet size, effective radius can be retrieved with different combinations of visible through shortwave infrared channels. MODIS observations sometimes show significantly larger effective radii in marine boundary layer cloud fields derived from the 1.6 and 2.1 pm channel observations than for 3.7 pm retrievals. Possible explanations range from 3D radiative transport effects and sub-pixel cloud inhomogeneity to the impact of drizzle formation on the droplet distribution. To investigate the potential influence of these factors, we use LES boundary layer cloud simulations in combination with 3D Monte Carlo simulations of MODIS observations. LES simulations of warm cloud spectral microphysics for cases of marine stratus and broken stratocumulus, each for two different values of cloud condensation nuclei density, produce cloud structures comprising droplet size distributions with and without drizzle size drops. In this study, synthetic MODIS observations generated from 3D radiative transport simulations that consider the full droplet size distribution will be generated for each scene. The operational MODIS effective radius retrievals will then be applied to the simulated reflectances and the results compared with the LES microphysics.

High-resolution, submicron particle size distribution analysis using gravitational-sweep sedimentation.

PubMed Central

Mächtle, W

1999-01-01

Sedimentation velocity is a powerful tool for the analysis of complex solutions of macromolecules. However, sample turbidity imposes an upper limit to the size of molecular complexes currently amenable to such analysis. Furthermore, the breadth of the particle size distribution, combined with possible variations in the density of different particles, makes it difficult to analyze extremely complex mixtures. These same problems are faced in the polymer industry, where dispersions of latices, pigments, lacquers, and emulsions must be characterized. There is a rich history of methods developed for the polymer industry finding use in the biochemical sciences. Two such methods are presented. These use analytical ultracentrifugation to determine the density and size distributions for submicron-sized particles. Both methods rely on Stokes' equations to estimate particle size and density, whereas turbidity, corrected using Mie's theory, provides the concentration measurement. The first method uses the sedimentation time in dispersion media of different densities to evaluate the particle density and size distribution. This method works provided the sample is chemically homogeneous. The second method splices together data gathered at different sample concentrations, thus permitting the high-resolution determination of the size distribution of particle diameters ranging from 10 to 3000 nm. By increasing the rotor speed exponentially from 0 to 40,000 rpm over a 1-h period, size distributions may be measured for extremely broadly distributed dispersions. Presented here is a short history of particle size distribution analysis using the ultracentrifuge, along with a description of the newest experimental methods. Several applications of the methods are provided that demonstrate the breadth of its utility, including extensions to samples containing nonspherical and chromophoric particles. PMID:9916040

WE-AB-204-07: Spatiotemporal Distribution of the FDG PET Tracer in Solid Tumors: Contributions of Diffusion and Convection Mechanisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soltani, M; Sefidgar, M; Bazmara, H

2015-06-15

Purpose: In this study, a mathematical model is utilized to simulate FDG distribution in tumor tissue. In contrast to conventional compartmental modeling, tracer distributions across space and time are directly linked together (i.e. moving beyond ordinary differential equations (ODEs) to utilizing partial differential equations (PDEs) coupling space and time). The diffusion and convection transport mechanisms are both incorporated to model tracer distribution. We aimed to investigate the contributions of these two mechanisms on FDG distribution for various tumor geometries obtained from PET/CT images. Methods: FDG transport was simulated via a spatiotemporal distribution model (SDM). The model is based on amore » 5K compartmental model. We model the fact that tracer concentration in the second compartment (extracellular space) is modulated via convection and diffusion. Data from n=45 patients with pancreatic tumors as imaged using clinical FDG PET/CT imaging were analyzed, and geometrical information from the tumors including size, shape, and aspect ratios were classified. Tumors with varying shapes and sizes were assessed in order to investigate the effects of convection and diffusion mechanisms on FDG transport. Numerical methods simulating interstitial flow and solute transport in tissue were utilized. Results: We have shown the convection mechanism to depend on the shape and size of tumors whereas diffusion mechanism is seen to exhibit low dependency on shape and size. Results show that concentration distribution of FDG is relatively similar for the considered tumors; and that the diffusion mechanism of FDG transport significantly dominates the convection mechanism. The Peclet number which shows the ratio of convection to diffusion rates was shown to be of the order of 10−{sup 3} for all considered tumors. Conclusion: We have demonstrated that even though convection leads to varying tracer distribution profiles depending on tumor shape and size, the domination of the diffusion phenomenon prevents these factors from modulating FDG distribution.« less

Finite-size analysis of continuous-variable measurement-device-independent quantum key distribution

NASA Astrophysics Data System (ADS)

Zhang, Xueying; Zhang, Yichen; Zhao, Yijia; Wang, Xiangyu; Yu, Song; Guo, Hong

2017-10-01

We study the impact of the finite-size effect on the continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) protocol, mainly considering the finite-size effect on the parameter estimation procedure. The central-limit theorem and maximum likelihood estimation theorem are used to estimate the parameters. We also analyze the relationship between the number of exchanged signals and the optimal modulation variance in the protocol. It is proved that when Charlie's position is close to Bob, the CV-MDI QKD protocol has the farthest transmission distance in the finite-size scenario. Finally, we discuss the impact of finite-size effects related to the practical detection in the CV-MDI QKD protocol. The overall results indicate that the finite-size effect has a great influence on the secret-key rate of the CV-MDI QKD protocol and should not be ignored.

Effect of dynamic high pressure on emulsifying and encapsulant properties of cashew tree gum.

PubMed

Porto, Bruna Castro; Cristianini, Marcelo

2018-04-15

Dynamic high pressure (DHP) has been applied in the physical modification of biopolymers as polysaccharides, proteins and gums. It is known that DHP is able to promote degradation of polysaccharides (e.g. molecular weight reduction). However, few studies have assessed the effect of DHP on the emulsifying and encapsulating properties of polysaccharides. Thus, this study aimed to investigate the effect of DHP on the emulsifying (average droplet size and particle size distribution, optical and confocal scanning laser microscopy, rheology, zeta potential and electric conductivity, creaming index, and turbidity) and encapsulating (scanning electronic microscopy, flavor retention, average droplet size, and particle size distribution) properties of cashew tree gum (CG). The application of DHP process improved the emulsifying capacity of cashew tree gum (CG) by reducing the medium droplet size (D3,2 and D4,3), increasing the turbidity and improving the emulsion stability. However, no effect of DHP was observed on the encapsulating capacity of CG. Copyright © 2018 Elsevier Ltd. All rights reserved.

Importance of aggregation and small ice crystals in cirrus clouds, based on observations and an ice particle growth model

NASA Technical Reports Server (NTRS)

Mitchell, David L.; Chai, Steven K.; Dong, Yayi; Arnott, W. Patrick; Hallett, John

1993-01-01

The 1 November 1986 FIRE I case study was used to test an ice particle growth model which predicts bimodal size spectra in cirrus clouds. The model was developed from an analytically based model which predicts the height evolution of monomodal ice particle size spectra from the measured ice water content (IWC). Size spectra from the monomodal model are represented by a gamma distribution, N(D) = N(sub o)D(exp nu)exp(-lambda D), where D = ice particle maximum dimension. The slope parameter, lambda, and the parameter N(sub o) are predicted from the IWC through the growth processes of vapor diffusion and aggregation. The model formulation is analytical, computationally efficient, and well suited for incorporation into larger models. The monomodal model has been validated against two other cirrus cloud case studies. From the monomodal size spectra, the size distributions which determine concentrations of ice particles less than about 150 mu m are predicted.

Simulating Bubble Plumes from Breaking Waves with a Forced-Air Venturi

NASA Astrophysics Data System (ADS)

Long, M. S.; Keene, W. C.; Maben, J. R.; Chang, R. Y. W.; Duplessis, P.; Kieber, D. J.; Beaupre, S. R.; Frossard, A. A.; Kinsey, J. D.; Zhu, Y.; Lu, X.; Bisgrove, J.

2017-12-01

It has been hypothesized that the size distribution of bubbles in subsurface seawater is a major factor that modulates the corresponding size distribution of primary marine aerosol (PMA) generated when those bubbles burst at the air-water interface. A primary physical control of the bubble size distribution produced by wave breaking is the associated turbulence that disintegrates larger bubbles into smaller ones. This leads to two characteristic features of bubble size distributions: (1) the Hinze scale which reflects a bubble size above which disintegration is possible based on turbulence intensity and (2) the slopes of log-linear regressions of the size distribution on either side of the Hinze scale that indicate the state of plume evolution or age. A Venturi with tunable seawater and forced air flow rates was designed and deployed in an artificial PMA generator to produce bubble plumes representative of breaking waves. This approach provides direct control of turbulence intensity and, thus, the resulting bubble size distribution characterizable by observations of the Hinze scale and the simulated plume age over a range of known air detrainment rates. Evaluation of performance in different seawater types over the western North Atlantic demonstrated that the Venturi produced bubble plumes with parameter values that bracket the range of those observed in laboratory and field experiments. Specifically, the seawater flow rate modulated the value of the Hinze scale while the forced-air flow rate modulated the plume age parameters. Results indicate that the size distribution of sub-surface bubbles within the generator did not significantly modulate the corresponding number size distribution of PMA produced via bubble bursting.

Size distribution of magnetic iron oxide nanoparticles using Warren-Averbach XRD analysis

NASA Astrophysics Data System (ADS)

Mahadevan, S.; Behera, S. P.; Gnanaprakash, G.; Jayakumar, T.; Philip, J.; Rao, B. P. C.

2012-07-01

We use the Fourier transform based Warren-Averbach (WA) analysis to separate the contributions of X-ray diffraction (XRD) profile broadening due to crystallite size and microstrain for magnetic iron oxide nanoparticles. The profile shape of the column length distribution, obtained from WA analysis, is used to analyze the shape of the magnetic iron oxide nanoparticles. From the column length distribution, the crystallite size and its distribution are estimated for these nanoparticles which are compared with size distribution obtained from dynamic light scattering measurements. The crystallite size and size distribution of crystallites obtained from WA analysis are explained based on the experimental parameters employed in preparation of these magnetic iron oxide nanoparticles. The variation of volume weighted diameter (Dv, from WA analysis) with saturation magnetization (Ms) fits well to a core shell model wherein it is known that Ms=Mbulk(1-6g/Dv) with Mbulk as bulk magnetization of iron oxide and g as magnetic shell disorder thickness.

Time-evolution of grain size distributions in random nucleation and growth crystallization processes

NASA Astrophysics Data System (ADS)

Teran, Anthony V.; Bill, Andreas; Bergmann, Ralf B.

2010-02-01

We study the time dependence of the grain size distribution N(r,t) during crystallization of a d -dimensional solid. A partial differential equation, including a source term for nuclei and a growth law for grains, is solved analytically for any dimension d . We discuss solutions obtained for processes described by the Kolmogorov-Avrami-Mehl-Johnson model for random nucleation and growth (RNG). Nucleation and growth are set on the same footing, which leads to a time-dependent decay of both effective rates. We analyze in detail how model parameters, the dimensionality of the crystallization process, and time influence the shape of the distribution. The calculations show that the dynamics of the effective nucleation and effective growth rates play an essential role in determining the final form of the distribution obtained at full crystallization. We demonstrate that for one class of nucleation and growth rates, the distribution evolves in time into the logarithmic-normal (lognormal) form discussed earlier by Bergmann and Bill [J. Cryst. Growth 310, 3135 (2008)]. We also obtain an analytical expression for the finite maximal grain size at all times. The theory allows for the description of a variety of RNG crystallization processes in thin films and bulk materials. Expressions useful for experimental data analysis are presented for the grain size distribution and the moments in terms of fundamental and measurable parameters of the model.

Distribution of genotype network sizes in sequence-to-structure genotype-phenotype maps.

PubMed

Manrubia, Susanna; Cuesta, José A

2017-04-01

An essential quantity to ensure evolvability of populations is the navigability of the genotype space. Navigability, understood as the ease with which alternative phenotypes are reached, relies on the existence of sufficiently large and mutually attainable genotype networks. The size of genotype networks (e.g. the number of RNA sequences folding into a particular secondary structure or the number of DNA sequences coding for the same protein structure) is astronomically large in all functional molecules investigated: an exhaustive experimental or computational study of all RNA folds or all protein structures becomes impossible even for moderately long sequences. Here, we analytically derive the distribution of genotype network sizes for a hierarchy of models which successively incorporate features of increasingly realistic sequence-to-structure genotype-phenotype maps. The main feature of these models relies on the characterization of each phenotype through a prototypical sequence whose sites admit a variable fraction of letters of the alphabet. Our models interpolate between two limit distributions: a power-law distribution, when the ordering of sites in the prototypical sequence is strongly constrained, and a lognormal distribution, as suggested for RNA, when different orderings of the same set of sites yield different phenotypes. Our main result is the qualitative and quantitative identification of those features of sequence-to-structure maps that lead to different distributions of genotype network sizes. © 2017 The Author(s).

Pharmacokinetics, tissue distribution, and excretion of zinc oxide nanoparticles

PubMed Central

Baek, Miri; Chung, Hae-Eun; Yu, Jin; Lee, Jung-A; Kim, Tae-Hyun; Oh, Jae-Min; Lee, Won-Jae; Paek, Seung-Min; Lee, Jong Kwon; Jeong, Jayoung; Choy, Jin-Ho; Choi, Soo-Jin

2012-01-01

Background This study explored the pharmacokinetics, tissue distribution, and excretion profile of zinc oxide (ZnO) nanoparticles with respect to their particle size in rats. Methods Two ZnO nanoparticles of different size (20 nm and 70 nm) were orally administered to male and female rats, respectively. The area under the plasma concentration-time curve, tissue distribution, excretion, and the fate of the nanoparticles in organs were analyzed. Results The plasma zinc concentration of both sizes of ZnO nanoparticles increased during the 24 hours after administration in a dose-dependent manner. They were mainly distributed to organs such as the liver, lung, and kidney within 72 hours without any significant difference being found according to particle size or rat gender. Elimination kinetics showed that a small amount of ZnO nanoparticles was excreted via the urine, while most of nanoparticles were excreted via the feces. Transmission electron microscopy and x-ray absorption spectroscopy studies in the tissues showed no noticeable ZnO nanoparticles, while new Zn-S bonds were observed in tissues. Conclusion ZnO nanoparticles of different size were not easily absorbed into the bloodstream via the gastrointestinal tract after a single oral dose. The liver, lung, and kidney could be possible target organs for accumulation and toxicity of ZnO nanoparticles was independent of particle size or gender. ZnO nanoparticles appear to be absorbed in the organs in an ionic form rather than in a particulate form due to newly formed Zn-S bonds. The nanoparticles were mainly excreted via the feces, and smaller particles were cleared more rapidly than the larger ones. ZnO nanoparticles at a concentration below 300 mg/kg were distributed in tissues and excreted within 24 hours. These findings provide crucial information on possible acute and chronic toxicity of ZnO nanoparticles in potential target organs. PMID:22811602

The time-evolution of DCIS size distributions with applications to breast cancer growth and progression.

PubMed

Dowty, James G; Byrnes, Graham B; Gertig, Dorota M

2014-12-01

Ductal carcinoma in situ (DCIS) lesions are non-invasive tumours of the breast that are thought to precede most invasive breast cancers (IBCs). As individual DCIS lesions are initiated, grow and invade (i.e. become IBC), the size distribution of the DCIS lesions present in a given human population will evolve. We derive a differential equation governing this evolution and show, for given assumptions about growth and invasion, that there is a unique distribution which does not vary with time. Further, we show that any initial distribution converges to this stationary distribution exponentially quickly. Therefore, it is reasonable to assume that the stationary distribution governs the size of DCIS lesions in human populations which are relatively stable with respect to the determinants of breast cancer. Based on this assumption and the size data of 110 DCIS lesions detected in a mammographic screening programme between 1993 and 2000, we produce maximum likelihood estimates for certain growth and invasion parameters. Assuming that DCIS size is proportional to a positive power p of the time since tumour initiation, we estimate p to be 0.50 with a 95% confidence interval of (0.35, 0.71). Therefore, we estimate that DCIS lesions follow a square-root growth law and hence that they grow rapidly when small and relatively slowly when large. Our approach and results should be useful for other mathematical studies of cancer, especially those investigating biological mechanisms of invasion. © The Authors 2013. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.

Composition of Metallic Elements and Size Distribution of Fine and Ultrafine Particles in a Steelmaking Factory.

PubMed

Marcias, Gabriele; Fostinelli, Jacopo; Catalani, Simona; Uras, Michele; Sanna, Andrea Maurizio; Avataneo, Giuseppe; De Palma, Giuseppe; Fabbri, Daniele; Paganelli, Matteo; Lecca, Luigi Isaia; Buonanno, Giorgio; Campagna, Marcello

2018-06-07

The characteristics of aerosol, in particular particle size and chemical composition, can have an impact on human health. Particle size distribution and chemical composition is a necessary parameter in occupational exposure assessment conducted in order to understand possible health effects. The aim of this study was to characterize workplace airborne particulate matter in a metallurgical setting by synergistically using two different approaches; Methodology: Analysis of inhalable fraction concentrations through traditional sampling equipment and ultrafine particles (UFP) concentrations and size distribution was conducted by an Electric Low-Pressure Impactor (ELPI+™). The determination of metallic elements (ME) in particles was carried out by inductively coupled plasma mass spectrometry; Results: Inhalable fraction and ME concentrations were below the limits set by Italian legislation and the American Conference of Governmental Industrial Hygienists (ACGIH, 2017). The median of UFP was between 4.00 × 10⁴ and 2.92 × 10⁵ particles/cm³. ME concentrations determined in the particles collected by ELPI show differences in size range distribution; Conclusions: The adopted synergistic approach enabled a qualitative and quantitative assessment of the particles in steelmaking factories. The results could lead to a better knowledge of occupational exposure characterization, in turn affording a better understanding of occupational health issues due to metal fumes exposure.

Development of flurbiprofen-loaded nanoparticles with a narrow size distribution using sucrose.

PubMed

Oh, Dong Hoon; Yan, Yi-Dong; Kim, Dong Wuk; Kim, Jong Oh; Yong, Chul Soon; Choi, Han-Gon

2014-02-01

A novel flurbiprofen-loaded nanoemulsion which gave uniform emulsion droplets with a narrow size distribution was previously reported to be prepared using membrane emulsification method. The purpose of this study is to develop a novel flurbiprofen-loaded nanoparticle with a narrow size distribution and improved bioavailability. The nanoparticle was prepared by solidifying nanoemulsion using sucrose as a carrier via spray drying method. Its physicochemical properties were investigated using SEM, DSC and PXRD. Furthermore, dissolution and bioavailability in rats were evaluated compared to a flurbiprofen-loaded commercial product. The flurbiprofen-loaded nanoparticles with flurbiprofen/sucrose/surfactant mixture (1/20/2, weight ratio) gave good solidification and no stickiness. They associated with about 70,000-fold improved drug solubility and had a mean size of about 300 nm with a narrow size distribution. Flurbiprofen was present in a changed amorphous state in these nanoparticles. Moreover, the nanoparticles gave significantly shorter Tmax, and higher AUC and Cmax of the drug compared to the commercial product (p < 0.05). In particular, they showed about nine-fold higher AUC of the drug than did the commercial product. These flurbiprofen-loaded nanoparticles prepared with sucrose by the membrane emulsification and spray drying method would be a potential candidate for orally delivering poorly water-soluble flurbiprofen with enhanced bioavailability.

Growth models and the expected distribution of fluctuating asymmetry

USGS Publications Warehouse

Graham, John H.; Shimizu, Kunio; Emlen, John M.; Freeman, D. Carl; Merkel, John

2003-01-01

Multiplicative error accounts for much of the size-scaling and leptokurtosis in fluctuating asymmetry. It arises when growth involves the addition of tissue to that which is already present. Such errors are lognormally distributed. The distribution of the difference between two lognormal variates is leptokurtic. If those two variates are correlated, then the asymmetry variance will scale with size. Inert tissues typically exhibit additive error and have a gamma distribution. Although their asymmetry variance does not exhibit size-scaling, the distribution of the difference between two gamma variates is nevertheless leptokurtic. Measurement error is also additive, but has a normal distribution. Thus, the measurement of fluctuating asymmetry may involve the mixing of additive and multiplicative error. When errors are multiplicative, we recommend computing log E(l) − log E(r), the difference between the logarithms of the expected values of left and right sides, even when size-scaling is not obvious. If l and r are lognormally distributed, and measurement error is nil, the resulting distribution will be normal, and multiplicative error will not confound size-related changes in asymmetry. When errors are additive, such a transformation to remove size-scaling is unnecessary. Nevertheless, the distribution of l − r may still be leptokurtic.

Ionic Size Effects: Generalized Boltzmann Distributions, Counterion Stratification, and Modified Debye Length.

PubMed

Liu, Bo; Liu, Pei; Xu, Zhenli; Zhou, Shenggao

2013-10-01

Near a charged surface, counterions of different valences and sizes cluster; and their concentration profiles stratify. At a distance from such a surface larger than the Debye length, the electric field is screened by counterions. Recent studies by a variational mean-field approach that includes ionic size effects and by Monte Carlo simulations both suggest that the counterion stratification is determined by the ionic valence-to-volume ratios. Central in the mean-field approach is a free-energy functional of ionic concentrations in which the ionic size effects are included through the entropic effect of solvent molecules. The corresponding equilibrium conditions define the generalized Boltzmann distributions relating the ionic concentrations to the electrostatic potential. This paper presents a detailed analysis and numerical calculations of such a free-energy functional to understand the dependence of the ionic charge density on the electrostatic potential through the generalized Boltzmann distributions, the role of ionic valence-to-volume ratios in the counterion stratification, and the modification of Debye length due to the effect of ionic sizes.

Ionic Size Effects: Generalized Boltzmann Distributions, Counterion Stratification, and Modified Debye Length

PubMed Central

Liu, Bo; Liu, Pei; Xu, Zhenli; Zhou, Shenggao

2013-01-01

Near a charged surface, counterions of different valences and sizes cluster; and their concentration profiles stratify. At a distance from such a surface larger than the Debye length, the electric field is screened by counterions. Recent studies by a variational mean-field approach that includes ionic size effects and by Monte Carlo simulations both suggest that the counterion stratification is determined by the ionic valence-to-volume ratios. Central in the mean-field approach is a free-energy functional of ionic concentrations in which the ionic size effects are included through the entropic effect of solvent molecules. The corresponding equilibrium conditions define the generalized Boltzmann distributions relating the ionic concentrations to the electrostatic potential. This paper presents a detailed analysis and numerical calculations of such a free-energy functional to understand the dependence of the ionic charge density on the electrostatic potential through the generalized Boltzmann distributions, the role of ionic valence-to-volume ratios in the counterion stratification, and the modification of Debye length due to the effect of ionic sizes. PMID:24465094

Characterization of micron-size hydrogen clusters using Mie scattering.

PubMed

Jinno, S; Tanaka, H; Matsui, R; Kanasaki, M; Sakaki, H; Kando, M; Kondo, K; Sugiyama, A; Uesaka, M; Kishimoto, Y; Fukuda, Y

2017-08-07

Hydrogen clusters with diameters of a few micrometer range, composed of 10 8-10 hydrogen molecules, have been produced for the first time in an expansion of supercooled, high-pressure hydrogen gas into a vacuum through a conical nozzle connected to a cryogenic pulsed solenoid valve. The size distribution of the clusters has been evaluated by measuring the angular distribution of laser light scattered from the clusters. The data were analyzed based on the Mie scattering theory combined with the Tikhonov regularization method including the instrumental functions, the validity of which was assessed by performing a calibration study using a reference target consisting of standard micro-particles with two different sizes. The size distribution of the clusters was found discrete peaked at 0.33 ± 0.03, 0.65 ± 0.05, 0.81 ± 0.06, 1.40 ± 0.06 and 2.00 ± 0.13 µm in diameter. The highly reproducible and impurity-free nature of the micron-size hydrogen clusters can be a promising target for laser-driven multi-MeV proton sources with the currently available high power lasers.

Reciprocal-space mapping of epitaxic thin films with crystallite size and shape polydispersity.

PubMed

Boulle, A; Conchon, F; Guinebretière, R

2006-01-01

A development is presented that allows the simulation of reciprocal-space maps (RSMs) of epitaxic thin films exhibiting fluctuations in the size and shape of the crystalline domains over which diffraction is coherent (crystallites). Three different crystallite shapes are studied, namely parallelepipeds, trigonal prisms and hexagonal prisms. For each shape, two cases are considered. Firstly, the overall size is allowed to vary but with a fixed thickness/width ratio. Secondly, the thickness and width are allowed to vary independently. The calculations are performed assuming three different size probability density functions: the normal distribution, the lognormal distribution and a general histogram distribution. In all cases considered, the computation of the RSM only requires a two-dimensional Fourier integral and the integrand has a simple analytical expression, i.e. there is no significant increase in computing times by taking size and shape fluctuations into account. The approach presented is compatible with most lattice disorder models (dislocations, inclusions, mosaicity, ...) and allows a straightforward account of the instrumental resolution. The applicability of the model is illustrated with the case of an yttria-stabilized zirconia film grown on sapphire.

Catch of channel catfish with tandem-set hoop nets and gill nets in lentic systems of Nebraska

USGS Publications Warehouse

Richters, Lindsey K.; Pope, Kevin L.

2011-01-01

Twenty-six Nebraska water bodies representing two ecosystem types (small standing waters and large standing waters) were surveyed during 2008 and 2009 with tandem-set hoop nets and experimental gill nets to determine if similar trends existed in catch rates and size structures of channel catfish Ictalurus punctatus captured with these gears. Gear efficiency was assessed as the number of sets (nets) that would be required to capture 100 channel catfish given observed catch per unit effort (CPUE). Efficiency of gill nets was not correlated with efficiency of hoop nets for capturing channel catfish. Small sample sizes prohibited estimation of proportional size distributions in most surveys; in the four surveys for which sample size was sufficient to quantify length-frequency distributions of captured channel catfish, distributions differed between gears. The CPUE of channel catfish did not differ between small and large water bodies for either gear. While catch rates of hoop nets were lower than rates recorded in previous studies, this gear was more efficient than gill nets at capturing channel catfish. However, comparisons of size structure between gears may be problematic.

Size Determination of Aqueous C60 by Asymmetric Flow Field-Flow Fractionation (AF4) and in-Line Dynamic Light Scattering

EPA Science Inventory

To date, studies on the environmental behaviour of aggregated aqueous fullerene nanomaterials have used the entire size distribution of fullerene aggregates and do not distinguish between different aggregate size classes. This is a direct result of the lack of analytical methods ...

Measurements in liquid fuel sprays

NASA Technical Reports Server (NTRS)

Chigier, N.; Mao, C. P.

1985-01-01

A ground test facility is being established at NASA Lewis Research Center to simulate the environmental and flight conditions needed to study adverse weather effects. One of the most important components is the water spray system which consists of many nozzles fitted on spray bars. Water is injected through air-assisted atomizers to generate uniform size drops to simulate icing in clouds. The primary objective is to provide experimental data on drop size distribution over a wide range of operating conditions. Correlation equations for mean drop size and initial injection parameters are being determined to assist in the design and modification of the Altitude Wind Tunnel. Special emphasis is being placed on the study of the aerodynamic structure of the air-assisted atomizer sprays. Detailed measurements of the variation of drop size distribution and velocity as a function of time and space are being made. Accurate initial and boundary conditions are being provided for computer model evaluation.

Understanding asteroid collisional history through experimental and numerical studies

NASA Technical Reports Server (NTRS)

Davis, Donald R.; Ryan, Eileen V.; Weidenschilling, S. J.

1991-01-01

Asteroids can lose angular momentum due to so called splash effect, the analog to the drain effect for cratering impacts. Numerical code with the splash effect incorporated was applied to study the simultaneous evolution of asteroid sized and spins. Results are presented on the spin changes of asteroids due to various physical effects that are incorporated in the described model. The goal was to understand the interplay between the evolution of sizes and spins over a wide and plausible range of model parameters. A single starting population was used both for size distribution and the spin distribution of asteroids and the changes in the spins were calculated over solar system history for different model parameters. It is shown that there is a strong coupling between the size and spin evolution, that the observed relative spindown of asteroids approximately 100 km diameter is likely to be the result of the angular momentum splash effect.

Understanding asteroid collisional history through experimental and numerical studies

NASA Astrophysics Data System (ADS)

Davis, Donald R.; Ryan, Eileen V.; Weidenschilling, S. J.

1991-06-01

Asteroids can lose angular momentum due to so called splash effect, the analog to the drain effect for cratering impacts. Numerical code with the splash effect incorporated was applied to study the simultaneous evolution of asteroid sized and spins. Results are presented on the spin changes of asteroids due to various physical effects that are incorporated in the described model. The goal was to understand the interplay between the evolution of sizes and spins over a wide and plausible range of model parameters. A single starting population was used both for size distribution and the spin distribution of asteroids and the changes in the spins were calculated over solar system history for different model parameters. It is shown that there is a strong coupling between the size and spin evolution, that the observed relative spindown of asteroids approximately 100 km diameter is likely to be the result of the angular momentum splash effect.

Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation.

PubMed

He, Qian; Freakley, Simon J; Edwards, Jennifer K; Carley, Albert F; Borisevich, Albina Y; Mineo, Yuki; Haruta, Masatake; Hutchings, Graham J; Kiely, Christopher J

2016-09-27

The identity of active species in supported gold catalysts for low temperature carbon monoxide oxidation remains an unsettled debate. With large amounts of experimental evidence supporting theories of either gold nanoparticles or sub-nm gold species being active, it was recently proposed that a size-dependent activity hierarchy should exist. Here we study the diverging catalytic behaviours after heat treatment of Au/FeO x materials prepared via co-precipitation and deposition precipitation methods. After ruling out any support effects, the gold particle size distributions in different catalysts are quantitatively studied using aberration corrected scanning transmission electron microscopy (STEM). A counting protocol is developed to reveal the true particle size distribution from HAADF-STEM images, which reliably includes all the gold species present. Correlation of the populations of the various gold species present with catalysis results demonstrate that a size-dependent activity hierarchy must exist in the Au/FeO x catalyst.

Effects of age condition on the distribution and integrity of inorganic fillers in dental resin composites.

PubMed

D'Alpino, Paulo Henrique Perlatti; Svizero, Nádia da Rocha; Bim Júnior, Odair; Valduga, Claudete Justina; Graeff, Carlos Frederico de Oliveira; Sauro, Salvatore

2016-06-01

The aim of this study is to evaluate the distribution of the filler size along with the zeta potential, and the integrity of silane-bonded filler surface in different types of restorative dental composites as a function of the material age condition. Filtek P60 (hybrid composite), Filtek Z250 (small-particle filled composite), Filtek Z350XT (nanofilled composite), and Filtek Silorane (silorane composite) (3M ESPE) were tested at different stage condition (i.e., fresh/new, aged, and expired). Composites were submitted to an accelerated aging protocol (Arrhenius model). Specimens were obtained by first diluting each composite specimen in ethanol and then dispersed in potassium chloride solution (0.001 mol%). Composite fillers were characterized for their zeta potential, mean particle size, size distribution, via poly-dispersion dynamic light scattering. The integrity of the silane-bonded surface of the fillers was characterized by FTIR. The material age influenced significantly the outcomes; Zeta potential, filler characteristics, and silane integrity varied both after aging and expiration. Silorane presented the broadest filler distribution and lowest zeta potential. Nanofilled and silorane composites exhibited decreased peak intensities in the FTIR analysis, indicating a deficiency of the silane integrity after aging or expiry time. Regardless to the material condition, the hybrid and the small-particle-filled composites were more stable overtime as no significant alteration in filler size distribution, diameter, and zeta potential occurred. A deficiency in the silane integrity in the nanofilled and silorane composites seems to be affected by the material stage condition. The materials conditions tested in this study influenced the filler size distribution, the zeta potential, and integrity of the silane adsorbed on fillers in the nanofilled and silorane composites. Thus, this may result in a decrease of the clinical performance of aforementioned composites, in particular, if these are used after inappropriate storage conditions.

A General Class of Signed Rank Tests for Clustered Data when the Cluster Size is Potentially Informative

PubMed Central

Datta, Somnath; Nevalainen, Jaakko; Oja, Hannu

2012-01-01

SUMMARY Rank based tests are alternatives to likelihood based tests popularized by their relative robustness and underlying elegant mathematical theory. There has been a serge in research activities in this area in recent years since a number of researchers are working to develop and extend rank based procedures to clustered dependent data which include situations with known correlation structures (e.g., as in mixed effects models) as well as more general form of dependence. The purpose of this paper is to test the symmetry of a marginal distribution under clustered data. However, unlike most other papers in the area, we consider the possibility that the cluster size is a random variable whose distribution is dependent on the distribution of the variable of interest within a cluster. This situation typically arises when the clusters are defined in a natural way (e.g., not controlled by the experimenter or statistician) and in which the size of the cluster may carry information about the distribution of data values within a cluster. Under the scenario of an informative cluster size, attempts to use some form of variance adjusted sign or signed rank tests would fail since they would not maintain the correct size under the distribution of marginal symmetry. To overcome this difficulty Datta and Satten (2008; Biometrics, 64, 501–507) proposed a Wilcoxon type signed rank test based on the principle of within cluster resampling. In this paper we study this problem in more generality by introducing a class of valid tests employing a general score function. Asymptotic null distribution of these tests is obtained. A simulation study shows that a more general choice of the score function can sometimes result in greater power than the Datta and Satten test; furthermore, this development offers the user a wider choice. We illustrate our tests using a real data example on spinal cord injury patients. PMID:23074359

A General Class of Signed Rank Tests for Clustered Data when the Cluster Size is Potentially Informative.

PubMed

Datta, Somnath; Nevalainen, Jaakko; Oja, Hannu

2012-09-01

Rank based tests are alternatives to likelihood based tests popularized by their relative robustness and underlying elegant mathematical theory. There has been a serge in research activities in this area in recent years since a number of researchers are working to develop and extend rank based procedures to clustered dependent data which include situations with known correlation structures (e.g., as in mixed effects models) as well as more general form of dependence.The purpose of this paper is to test the symmetry of a marginal distribution under clustered data. However, unlike most other papers in the area, we consider the possibility that the cluster size is a random variable whose distribution is dependent on the distribution of the variable of interest within a cluster. This situation typically arises when the clusters are defined in a natural way (e.g., not controlled by the experimenter or statistician) and in which the size of the cluster may carry information about the distribution of data values within a cluster.Under the scenario of an informative cluster size, attempts to use some form of variance adjusted sign or signed rank tests would fail since they would not maintain the correct size under the distribution of marginal symmetry. To overcome this difficulty Datta and Satten (2008; Biometrics, 64, 501-507) proposed a Wilcoxon type signed rank test based on the principle of within cluster resampling. In this paper we study this problem in more generality by introducing a class of valid tests employing a general score function. Asymptotic null distribution of these tests is obtained. A simulation study shows that a more general choice of the score function can sometimes result in greater power than the Datta and Satten test; furthermore, this development offers the user a wider choice. We illustrate our tests using a real data example on spinal cord injury patients.

Size distribution and sorption of polychlorinated biphenyls during haze episodes

NASA Astrophysics Data System (ADS)

Zhu, Qingqing; Liu, Guorui; Zheng, Minghui; Zhang, Xian; Gao, Lirong; Su, Guijin; Liang, Yong

2018-01-01

There is a lack of studies on the size distribution of polychlorinated biphenyls (PCBs) during haze days, and their sorption mechanisms on aerosol particles remain unclear. In this study, PCBs in particle-sized aerosols from urban atmospheres of Beijing, China were investigated during haze and normal days. The concentrations, gas/particle partitioning, size distribution, and associated human daily intake of PCBs via inhalation were compared during haze days and normal days. Compared with normal days, higher particle mass-associated PCB levels were measured during haze days. The concentrations of ∑PCBs in particulate fractions were 11.9-134 pg/m3 and 6.37-14.9 pg/m3 during haze days and normal days, respectively. PCBs increased with decreasing particle size (>10 μm, 10-2.5 μm, 2.5-1.0 μm, and ≤1.0 μm). During haze days, PCBs were overwhelmingly associated with a fine particle fraction of ≤1.0 μm (64.6%), while during normal days the contribution was 33.7%. Tetra-CBs were the largest contributors (51.8%-66.7%) both in the gas and particle fractions during normal days. The profiles in the gas fraction were conspicuously different than those in the PM fractions during haze days, with di-CBs predominating in the gas fraction and higher homologues (tetra-CBs, penta-CBs, and hexa-CBs) concurrently accounting for most of the PM fractions. The mean-normalized size distributions of particulate mass and PCBs exhibited unimodal patterns, and a similar trend was observed for PCBs during both days. They all tended to be in the PM fraction of 1.0-2.5 μm. Adsorption might be the predominating mechanism for the gas-particle partitioning of PCBs during haze days, whereas absorption might be dominative during normal days.

Mass or total surface area with aerosol size distribution as exposure metrics for inflammatory, cytotoxic and oxidative lung responses in rats exposed to titanium dioxide nanoparticles.

PubMed

Noël, A; Truchon, G; Cloutier, Y; Charbonneau, M; Maghni, K; Tardif, R

2017-04-01

There is currently no consensus on the best exposure metric(s) for expressing nanoparticle (NP) dose. Although surface area has been extensively studied for inflammatory responses, it has not been as thoroughly validated for cytotoxicity or oxidative stress effects. Since inhaled NPs deposit and interact with lung cells based on agglomerate size, we hypothesize that mass concentration combined with aerosol size distribution is suitable for NP risk assessment. The objective of this study was to evaluate different exposure metrics for inhaled 5 nm titanium dioxide aerosols composed of small (SA < 100 nm) or large (LA > 100 nm) agglomerates at 2, 7, and 20 mg/m 3 on rat lung inflammatory, cytotoxicity, and oxidative stress responses. We found a significant positive correlation ( r = 0.98, p < 0.01) with the inflammatory reaction, measured by the number of neutrophils and the mass concentration when considering all six (SA + LA) aerosols. This correlation was similar ( r = 0.87) for total surface area. Regarding cytotoxicity and oxidative stress responses, measured by lactate dehydrogenase and 8-isoprostane, respectively, and mass or total surface area as an exposure metric, we observed significant positive correlations only with SA aerosols for both the mass concentration and size distribution ( r > 0.91, p < 0.01), as well as for the total surface area ( r > 0.97, p < 0.01). These data show that mass or total surface area concentrations alone are insufficient to adequately predict oxidant and cytotoxic pulmonary effects. Overall, our study indicates that considering NP size distribution along with mass or total surface area concentrations contributes to a more mechanistic discrimination of pulmonary responses to NP exposure.

A novel approach for fit analysis of thermal protective clothing using three-dimensional body scanning.

PubMed

Lu, Yehu; Song, Guowen; Li, Jun

2014-11-01

The garment fit played an important role in protective performance, comfort and mobility. The purpose of this study is to quantify the air gap to quantitatively characterize a three-dimensional (3-D) garment fit using a 3-D body scanning technique. A method for processing of scanned data was developed to investigate the air gap size and distribution between the clothing and human body. The mesh model formed from nude and clothed body was aligned, superimposed and sectioned using Rapidform software. The air gap size and distribution over the body surface were analyzed. The total air volume was also calculated. The effects of fabric properties and garment size on air gap distribution were explored. The results indicated that average air gap of the fit clothing was around 25-30 mm and the overall air gap distribution was similar. The air gap was unevenly distributed over the body and it was strongly associated with the body parts, fabric properties and garment size. The research will help understand the overall clothing fit and its association with protection, thermal and movement comfort, and provide guidelines for clothing engineers to improve thermal performance and reduce physiological burden. Copyright © 2014 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Effects of Droplet Size on Intrusion of Sub-Surface Oil Spills

NASA Astrophysics Data System (ADS)

Adams, Eric; Chan, Godine; Wang, Dayang

2014-11-01

We explore effects of droplet size on droplet intrusion and transport in sub-surface oil spills. Negatively buoyant glass beads released continuously to a stratified ambient simulate oil droplets in a rising multiphase plume, and distributions of settled beads are used to infer signatures of surfacing oil. Initial tests used quiescent conditions, while ongoing tests simulate currents by towing the source and a bottom sled. Without current, deposited beads have a Gaussian distribution, with variance increasing with decreasing particle size. Distributions agree with a model assuming first order particle loss from an intrusion layer of constant thickness, and empirically determined flow rate. With current, deposited beads display a parabolic distribution similar to that expected from a source in uniform flow; we are currently comparing observed distributions with similar analytical models. Because chemical dispersants have been used to reduce oil droplet size, our study provides one measure of their effectiveness. Results are applied to conditions from the `Deep Spill' field experiment, and the recent Deepwater Horizon oil spill, and are being used to provide ``inner boundary conditions'' for subsequent far field modeling of these events. This research was made possible by grants from Chevron Energy Technology Co., through the Chevron-MITEI University Partnership Program, and BP/The Gulf of Mexico Research Initiative, GISR.

Adsorption energy distribution of carbon tetrachloride on carbon nanofiber arrays prepared by template synthesis

NASA Astrophysics Data System (ADS)

Wu, Chi-Hsin; Shr, Jin-Fang; Wu, Chu-Fu; Hsieh, Chien-Te

2008-02-01

The influence of pore size distribution on adsorption energy distributions (AEDs) of aligned carbon nanofiber (CNF) arrays in vapor phase was conducted in the present study. A template-assisted synthesis was employed to fabricate aligned CNF arrays with different pore size distributions (PSDs). Adsorption isotherms of CCl 4 onto the CNF arrays were investigated within an entire pressure of 0.05-0.18 atm at 30 °C. The adsorptive surface coverage was found to decrease with the average pore size, indicating the presence of heterogeneity for gas adsorption. An AED model was postulated to describe the heterogeneous surface consisting of numerous surface pitchwises that obey a localized Langmuir model. It was found that all CNF arrays exhibit a similar Gaussian-type AED, in where the peak adsorption energy shifts to a higher energy with decreasing the pore size of CNFs. This finding can be ascribed to a fact that micropores are major providers of adsorption sites, whereas in mesopores only weaker adsorption is observed, thus resulting in the shift of energy distribution. An excellent prediction to the adsorption isotherms of CCl 4 by the AED model indicates that the PSD of CNFs acts a crucial factor in affecting the adsorptive coverage.

Particle size-dependent organ distribution of gold nanoparticles after intravenous administration.

PubMed

De Jong, Wim H; Hagens, Werner I; Krystek, Petra; Burger, Marina C; Sips, Adriënne J A M; Geertsma, Robert E

2008-04-01

A kinetic study was performed to determine the influence of particle size on the in vivo tissue distribution of spherical-shaped gold nanoparticles in the rat. Gold nanoparticles were chosen as model substances as they are used in several medical applications. In addition, the detection of the presence of gold is feasible with no background levels in the body in the normal situation. Rats were intravenously injected in the tail vein with gold nanoparticles with a diameter of 10, 50, 100 and 250 nm, respectively. After 24 h, the rats were sacrificed and blood and various organs were collected for gold determination. The presence of gold was measured quantitatively with inductively coupled plasma mass spectrometry (ICP-MS). For all gold nanoparticle sizes the majority of the gold was demonstrated to be present in liver and spleen. A clear difference was observed between the distribution of the 10 nm particles and the larger particles. The 10 nm particles were present in various organ systems including blood, liver, spleen, kidney, testis, thymus, heart, lung and brain, whereas the larger particles were only detected in blood, liver and spleen. The results demonstrate that tissue distribution of gold nanoparticles is size-dependent with the smallest 10nm nanoparticles showing the most widespread organ distribution.

Measurement and dynamics of the spatial distribution of an electron localized at a metal-dielectric interface

NASA Astrophysics Data System (ADS)

Bezel, Ilya; Gaffney, Kelly J.; Garrett-Roe, Sean; Liu, Simon H.; Miller, André D.; Szymanski, Paul; Harris, Charles B.

2004-01-01

The ability of time- and angle-resolved two-photon photoemission to estimate the size distribution of electron localization in the plane of a metal-adsorbate interface is discussed. It is shown that the width of angular distribution of the photoelectric current is inversely proportional to the electron localization size within the most common approximations in the description of image potential states. The localization of the n=1 image potential state for two monolayers of butyronitrile on Ag(111) is used as an example. For the delocalized n=1 state, the shape of the signal amplitude as a function of momentum parallel to the surface changes rapidly with time, indicating efficient intraband relaxation on a 100 fs time scale. For the localized state, little change was observed. The latter is related to the constant size distribution of electron localization, which is estimated to be a Gaussian with a 15±4 Å full width at half maximum in the plane of the interface. A simple model was used to study the effect of a weak localization potential on the overall width of the angular distribution of the photoemitted electrons, which exhibited little sensitivity to the details of the potential. This substantiates the validity of the localization size estimate.

In Situ Study on the Evolution of Multimodal Particle Size Distributions of ZnO Quantum Dots: Some General Rules for the Occurrence of Multimodalities.

PubMed

Schindler, Torben; Walter, Johannes; Peukert, Wolfgang; Segets, Doris; Unruh, Tobias

2015-12-10

Properties of small semiconductor nanoparticles (NPs) are strongly governed by their size. Precise characterization is a key requirement for tailored dispersities and thus for high-quality devices. Results of a careful analysis of particle size distributions (PSDs) of ZnO are presented combining advantages of UV/vis absorption spectroscopy, analytical ultracentrifugation, and small-angle X-ray scattering (SAXS). Our study reveals that careful cross-validation of these different methods is mandatory to end up with reliable resolution. PSDs of ZnO NPs are multimodal on a size range of 2-8 nm, a finding that is not yet sufficiently addressed. In the second part of our work the evolution of PSDs was studied using in situ SAXS. General principles for the appearance of multimodalities covering a temperature range between 15 and 45 °C were found which are solely determined by the aging state indicated by the size of the medium-sized fraction. Whenever this fraction exceeds a critical diameter, a new multimodality is identified, independent of the particular time-temperature combination. A fraction of larger particles aggregates first before a fraction of smaller particles is detected. Fixed multimodalities have not yet been addressed adequately and could only be evidenced due to careful size analysis.

CHARACTERIZATION OF INDOOR-OUTDOOR AEROSOL CONCENTRATION RELATIONSHIPS DURING THE FRESNO PM EXPOSURE STUDIES

EPA Science Inventory

Particle size distributions were measured indoors and outdoors of a single, detached residence during the Fresno particulate matter exposure studies in winter (February 1-28, 1999) and spring (April 18-May 16, 1999). Data was collected for particle sizes ranging from about 0....

Investigating the effect of sputtering conditions on the physical properties of aluminum thin film and the resulting alumina template

NASA Astrophysics Data System (ADS)

Taheriniya, Shabnam; Parhizgar, Sara Sadat; Sari, Amir Hossein

2018-06-01

To study the alumina template pore size distribution as a function of Al thin film grain size distribution, porous alumina templates were prepared by anodizing sputtered aluminum thin films. To control the grain size the aluminum samples were sputtered with the rate of 0.5, 1 and 2 Å/s and the substrate temperature was either 25, 75 or 125 °C. All samples were anodized for 120 s in 1 M sulfuric acid solution kept at 1 °C while a 15 V potential was being applied. The standard deviation value for samples deposited at room temperature but with different rates is roughly 2 nm in both thin film and porous template form but it rises to approximately 4 nm with substrate temperature. Samples with the average grain size of 13, 14, 18.5 and 21 nm respectively produce alumina templates with an average pore size of 8.5, 10, 15 and 16 nm in that order which shows the average grain size limits the average pore diameter in the resulting template. Lateral correlation length and grain boundary effect are other factors that affect the pore formation process and pore size distribution by limiting the initial current density.

A Year-round Observation of Size Distribution of Aerosol Particles at the Cape Ochiishi, Japan

NASA Astrophysics Data System (ADS)

Miura, K.; Mukai, H.; Hashimoto, S.; Uematsu, M.

2010-12-01

New particle formation by nucleation of gas-phase compounds emitted from marine biogenic sources is very important for climate change. To clarify the mechanism of the formation, size distributions of submicron aerosols have been measured at the Cape Ochiishi, facing the North Western Pacific Ocean where primary productivity is high. A test observation was done from 22nd May to 18th June 2008 and a year-round observation has been performed from 16th October 2009 to 7th September 2010. The size distribution from 10 nm to 487 nm in diameter was measured with a scanning mobility particle sizer (SMPS, TSI 3034). Sample air was dried to lower than 40%. Transport of sulfate, organic carbon (OC), and black carbon (BC) was estimated with Chemical weather FORecasting System (CFORS), developed by Prof. Uno, Kyushu University, Japan. Existence of inversion layer was estimated with temperature profile measured at surface, 10m, 30m, and 50m in altitude. The burst of the particles smaller than 20nm in diameter continuing longer than 3 hrs was observed ten times until 3rd November 2009. Two were observed in early summer and the other was in autumn. Banana shape was faintly observed five times. Transport of sulfate, OC, and BC was observed 3, 8, 9 times, respectively. Source of air mass was estimated with these elements, weather map, and wind direction. Five air masses were estimated to continental. Clearly nucleation related to marine sources was not observed. The size distribution of burst evens of maritime and continental air mass showed the shift of mode to larger diameter. Strong inversion of temperature was observed once. The value of size distribution did not show high. Minimum value of size distribution was observed in the strong rain on 27th October. Acknowledgments This study was partly supported by the Grant-in-Aids for Scientific Research on Priority Areas from the Ministry of Education, Culture, Sports, Science and Technology, Japan (18067005). The observation was performed at the monitoring station of the National Institute for Environmental Studies.

Determining Size Distribution at the Phoenix Landing Site

NASA Astrophysics Data System (ADS)

Mason, E. L.; Lemmon, M. T.

2016-12-01

Dust aerosols play a crucial role in determining atmospheric radiative heating on Mars through absorption and scattering of sunlight. How dust scatters and absorbs light is dependent on size, shape, composition, and quantity. Optical properties of the dust have been well constrained in the visible and near infrared wavelengths using various methods [Wolff et al. 2009, Lemmon et al. 2004]. In addition, the dust is nonspherical, and irregular shapes have shown to work well in determining effective particle size [Pollack et al. 1977]. Variance of the size distribution is less constrained but constitutes an important parameter in fully describing the dust. The Phoenix Lander's Surface Stereo Imager performed several cross-sky brightness surveys to determine the size distribution and scattering properties of dust in the wavelength range of 400 to 1000 nm. In combination with a single-layer radiative transfer model, these surveys can be used to help constrain variance of the size distribution. We will present a discussion of seasonal size distribution as it pertains to the Phoenix landing site.

Size-segregated urban aerosol characterization by electron microscopy and dynamic light scattering and influence of sample preparation

NASA Astrophysics Data System (ADS)

Marvanová, Soňa; Kulich, Pavel; Skoupý, Radim; Hubatka, František; Ciganek, Miroslav; Bendl, Jan; Hovorka, Jan; Machala, Miroslav

2018-04-01

Size-segregated particulate matter (PM) is frequently used in chemical and toxicological studies. Nevertheless, toxicological in vitro studies working with the whole particles often lack a proper evaluation of PM real size distribution and characterization of agglomeration under the experimental conditions. In this study, changes in particle size distributions during the PM sample manipulation and also semiquantitative elemental composition of single particles were evaluated. Coarse (1-10 μm), upper accumulation (0.5-1 μm), lower accumulation (0.17-0.5 μm), and ultrafine (<0.17 μm) PM fractions were collected by high volume cascade impactor in Prague city center. Particles were examined using electron microscopy and their elemental composition was determined by energy dispersive X-ray spectroscopy. Larger or smaller particles, not corresponding to the impaction cut points, were found in all fractions, as they occur in agglomerates and are impacted according to their aerodynamic diameter. Elemental composition of particles in size-segregated fractions varied significantly. Ns-soot occurred in all size fractions. Metallic nanospheres were found in accumulation fractions, but not in ultrafine fraction where ns-soot, carbonaceous particles, and inorganic salts were identified. Dynamic light scattering was used to measure particle size distribution in water and in cell culture media. PM suspension of lower accumulation fraction in water agglomerated after freezing/thawing the sample, and the agglomerates were disrupted by subsequent sonication. Ultrafine fraction did not agglomerate after freezing/thawing the sample. Both lower accumulation and ultrafine fractions were stable in cell culture media with fetal bovine serum, while high agglomeration occurred in media without fetal bovine serum as measured during 24 h.

Orphan therapies: making best use of postmarket data.

PubMed

Maro, Judith C; Brown, Jeffrey S; Dal Pan, Gerald J; Li, Lingling

2014-08-01

Postmarket surveillance of the comparative safety and efficacy of orphan therapeutics is challenging, particularly when multiple therapeutics are licensed for the same orphan indication. To make best use of product-specific registry data collected to fulfill regulatory requirements, we propose the creation of a distributed electronic health data network among registries. Such a network could support sequential statistical analyses designed to detect early warnings of excess risks. We use a simulated example to explore the circumstances under which a distributed network may prove advantageous. We perform sample size calculations for sequential and non-sequential statistical studies aimed at comparing the incidence of hepatotoxicity following initiation of two newly licensed therapies for homozygous familial hypercholesterolemia. We calculate the sample size savings ratio, or the proportion of sample size saved if one conducted a sequential study as compared to a non-sequential study. Then, using models to describe the adoption and utilization of these therapies, we simulate when these sample sizes are attainable in calendar years. We then calculate the analytic calendar time savings ratio, analogous to the sample size savings ratio. We repeat these analyses for numerous scenarios. Sequential analyses detect effect sizes earlier or at the same time as non-sequential analyses. The most substantial potential savings occur when the market share is more imbalanced (i.e., 90% for therapy A) and the effect size is closest to the null hypothesis. However, due to low exposure prevalence, these savings are difficult to realize within the 30-year time frame of this simulation for scenarios in which the outcome of interest occurs at or more frequently than one event/100 person-years. We illustrate a process to assess whether sequential statistical analyses of registry data performed via distributed networks may prove a worthwhile infrastructure investment for pharmacovigilance.

The effects of surfactant and electrolyte concentrations on the size of nanochitosan during storage

NASA Astrophysics Data System (ADS)

Primaningtyas, Annisa; Budhijanto, Wiratni; Fahrurrozi, Mohammad; Kusumastuti, Yuni

2017-05-01

The nano-sized particle of chitosan (nanochitosan) is a potential natural preservative agent for fresh fish and fish product preservation. Theoretically, nano-sized particles exert strong van der Waals force to each other so that the problem associated with nanochitosan is agglomeration that leads to size instability during storage. Size stability is of importance in the application of nanochitosan as an antimicrobial agent because it considerably affects the antimicrobial activity of chitosan. In this study, the formulation of nanochitosan was optimized with respect to the two major factors in colloid dispersion theory, which were the presence of surfactant and electrolyte. Polysorbate-80 was chosen as the representative of food grade surfactant while NaCl was used as the electrolyte. The purposes of this study were to evaluate the effect of polysorbate-80 concentration and to determine the effect of NaCl ions on the particle size of nanochitosan for at least one month storage period. Data were analyzed using Analysis of Variance (ANOVA) to identify the factors significantly affect the size stability. The dynamics of particle size distribution during storage was measured by Particle Size Analyzer (PSA). The result showed that surfactant did not significantly affect the particle size stability. On the other hand, the addition of electrolyte into the colloidal dispersion of nanochitosan consistently stabilized and also narrowed the particle size distribution during storage in the range of 175-391 nm.

Pharmacokinetics, Metabolism, Distribution and Permeability of Nanomedicine.

PubMed

Ravindran, Selvan; Suthar, Jitendra Kumar; Rokade, Rutuja; Deshpande, Pooja; Singh, Pooja; Pratinidhi, Ashutosh; Khambadkhar, Rajeshree; Utekar, Srushti

2018-01-01

Medical application of nanotechnology is termed as Nanomedicine and is widely used in healthcare industries. Nanotechnology has helped Physicians, Scientists and Technologists to understand the changes in cellular levels to develop nanomedicines and address the challenges faced by the healthcare sectors. Nanoparticles with less than 1nm in size have been used as drug delivery and gene delivery systems to accelerate the drug action in humans. Size of nanomaterials is akin to that of biomolecules and expected to have better interactions. Hence, its utility for various biomedical applications is explored. Pharmacokinetics, metabolism, permeability, distribution and elimination studies of nanoparticles are essential to understand its potency, toxicity threshold and confirm its safe use in humans. Reports were available for toxicity studies on nanoparticles, but work on metabolism, pharmacokinetics, distribution and permeability of nanomedicine is limited. Hence, the main focus of this review article is about metabolism, pharmacokinetics, permeability and biodistribution of nanomaterials used in nanomedicine. Nanomedicine is increasingly becoming important in the treatment of diseases and diagnosis. Size of the particle plays an important role. As the particle size decreases its effect to cure the disease increases. Pharmacokinetics, bioavailability, half-life, metabolism, biodistribution and permeability of nanomedicine were found to be better than that of microsized drugs. In vitro and In vivo ADME (Absorption, Distribution, Metabolism and Excretion) studies are mandatory for pharmaceutical organic drugs. Similarly, nanomaterials should be subjected to both in vitro and in vivo ADME studies. Thus, nanomedicine can assist in the development of safe personalized medicine in humans. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Methods for estimating 2D cloud size distributions from 1D observations

DOE PAGES

Romps, David M.; Vogelmann, Andrew M.

2017-08-04

The two-dimensional (2D) size distribution of clouds in the horizontal plane plays a central role in the calculation of cloud cover, cloud radiative forcing, convective entrainment rates, and the likelihood of precipitation. Here, a simple method is proposed for calculating the area-weighted mean cloud size and for approximating the 2D size distribution from the 1D cloud chord lengths measured by aircraft and vertically pointing lidar and radar. This simple method (which is exact for square clouds) compares favorably against the inverse Abel transform (which is exact for circular clouds) in the context of theoretical size distributions. Both methods also performmore » well when used to predict the size distribution of real clouds from a Landsat scene. When applied to a large number of Landsat scenes, the simple method is able to accurately estimate the mean cloud size. Finally, as a demonstration, the methods are applied to aircraft measurements of shallow cumuli during the RACORO campaign, which then allow for an estimate of the true area-weighted mean cloud size.« less

Methods for estimating 2D cloud size distributions from 1D observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romps, David M.; Vogelmann, Andrew M.

The two-dimensional (2D) size distribution of clouds in the horizontal plane plays a central role in the calculation of cloud cover, cloud radiative forcing, convective entrainment rates, and the likelihood of precipitation. Here, a simple method is proposed for calculating the area-weighted mean cloud size and for approximating the 2D size distribution from the 1D cloud chord lengths measured by aircraft and vertically pointing lidar and radar. This simple method (which is exact for square clouds) compares favorably against the inverse Abel transform (which is exact for circular clouds) in the context of theoretical size distributions. Both methods also performmore » well when used to predict the size distribution of real clouds from a Landsat scene. When applied to a large number of Landsat scenes, the simple method is able to accurately estimate the mean cloud size. Finally, as a demonstration, the methods are applied to aircraft measurements of shallow cumuli during the RACORO campaign, which then allow for an estimate of the true area-weighted mean cloud size.« less

On sample size of the kruskal-wallis test with application to a mouse peritoneal cavity study.

PubMed

Fan, Chunpeng; Zhang, Donghui; Zhang, Cun-Hui

2011-03-01

As the nonparametric generalization of the one-way analysis of variance model, the Kruskal-Wallis test applies when the goal is to test the difference between multiple samples and the underlying population distributions are nonnormal or unknown. Although the Kruskal-Wallis test has been widely used for data analysis, power and sample size methods for this test have been investigated to a much lesser extent. This article proposes new power and sample size calculation methods for the Kruskal-Wallis test based on the pilot study in either a completely nonparametric model or a semiparametric location model. No assumption is made on the shape of the underlying population distributions. Simulation results show that, in terms of sample size calculation for the Kruskal-Wallis test, the proposed methods are more reliable and preferable to some more traditional methods. A mouse peritoneal cavity study is used to demonstrate the application of the methods. © 2010, The International Biometric Society.

Relation between self-organized criticality and grain aspect ratio in granular piles

NASA Astrophysics Data System (ADS)

Denisov, D. V.; Villanueva, Y. Y.; Lőrincz, K. A.; May, S.; Wijngaarden, R. J.

2012-05-01

We investigate experimentally whether self-organized criticality (SOC) occurs in granular piles composed of different grains, namely, rice, lentils, quinoa, and mung beans. These four grains were selected to have different aspect ratios, from oblong to oblate. As a function of aspect ratio, we determined the growth (β) and roughness (α) exponents, the avalanche fractal dimension (D), the avalanche size distribution exponent (τ), the critical angle (γ), and its fluctuation. At superficial inspection, three types of grains seem to have power-law-distributed avalanches with a well-defined τ. However, only rice is truly SOC if we take three criteria into account: a power-law-shaped avalanche size distribution, finite size scaling, and a universal scaling relation relating characteristic exponents. We study SOC as a spatiotemporal fractal; in particular, we study the spatial structure of criticality from local observation of the slope angle. From the fluctuation of the slope angle we conclude that greater fluctuation (and thus bigger avalanches) happen in piles consisting of grains with larger aspect ratio.

Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition

PubMed Central

Schmale, Julia; Henning, Silvia; Henzing, Bas; Keskinen, Helmi; Sellegri, Karine; Ovadnevaite, Jurgita; Bougiatioti, Aikaterini; Kalivitis, Nikos; Stavroulas, Iasonas; Jefferson, Anne; Park, Minsu; Schlag, Patrick; Kristensson, Adam; Iwamoto, Yoko; Pringle, Kirsty; Reddington, Carly; Aalto, Pasi; Äijälä, Mikko; Baltensperger, Urs; Bialek, Jakub; Birmili, Wolfram; Bukowiecki, Nicolas; Ehn, Mikael; Fjæraa, Ann Mari; Fiebig, Markus; Frank, Göran; Fröhlich, Roman; Frumau, Arnoud; Furuya, Masaki; Hammer, Emanuel; Heikkinen, Liine; Herrmann, Erik; Holzinger, Rupert; Hyono, Hiroyuki; Kanakidou, Maria; Kiendler-Scharr, Astrid; Kinouchi, Kento; Kos, Gerard; Kulmala, Markku; Mihalopoulos, Nikolaos; Motos, Ghislain; Nenes, Athanasios; O’Dowd, Colin; Paramonov, Mikhail; Petäjä, Tuukka; Picard, David; Poulain, Laurent; Prévôt, André Stephan Henry; Slowik, Jay; Sonntag, Andre; Swietlicki, Erik; Svenningsson, Birgitta; Tsurumaru, Hiroshi; Wiedensohler, Alfred; Wittbom, Cerina; Ogren, John A.; Matsuki, Atsushi; Yum, Seong Soo; Myhre, Cathrine Lund; Carslaw, Ken; Stratmann, Frank; Gysel, Martin

2017-01-01

Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment. PMID:28291234

Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition

NASA Astrophysics Data System (ADS)

Schmale, Julia; Henning, Silvia; Henzing, Bas; Keskinen, Helmi; Sellegri, Karine; Ovadnevaite, Jurgita; Bougiatioti, Aikaterini; Kalivitis, Nikos; Stavroulas, Iasonas; Jefferson, Anne; Park, Minsu; Schlag, Patrick; Kristensson, Adam; Iwamoto, Yoko; Pringle, Kirsty; Reddington, Carly; Aalto, Pasi; Äijälä, Mikko; Baltensperger, Urs; Bialek, Jakub; Birmili, Wolfram; Bukowiecki, Nicolas; Ehn, Mikael; Fjæraa, Ann Mari; Fiebig, Markus; Frank, Göran; Fröhlich, Roman; Frumau, Arnoud; Furuya, Masaki; Hammer, Emanuel; Heikkinen, Liine; Herrmann, Erik; Holzinger, Rupert; Hyono, Hiroyuki; Kanakidou, Maria; Kiendler-Scharr, Astrid; Kinouchi, Kento; Kos, Gerard; Kulmala, Markku; Mihalopoulos, Nikolaos; Motos, Ghislain; Nenes, Athanasios; O'Dowd, Colin; Paramonov, Mikhail; Petäjä, Tuukka; Picard, David; Poulain, Laurent; Prévôt, André Stephan Henry; Slowik, Jay; Sonntag, Andre; Swietlicki, Erik; Svenningsson, Birgitta; Tsurumaru, Hiroshi; Wiedensohler, Alfred; Wittbom, Cerina; Ogren, John A.; Matsuki, Atsushi; Yum, Seong Soo; Myhre, Cathrine Lund; Carslaw, Ken; Stratmann, Frank; Gysel, Martin

2017-03-01

Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment.

Determination of hydrogen abundance in selected lunar soils

NASA Technical Reports Server (NTRS)

Bustin, Roberta

1987-01-01

Hydrogen was implanted in lunar soil through solar wind activity. In order to determine the feasibility of utilizing this solar wind hydrogen, it is necessary to know not only hydrogen abundances in bulk soils from a variety of locations but also the distribution of hydrogen within a given soil. Hydrogen distribution in bulk soils, grain size separates, mineral types, and core samples was investigated. Hydrogen was found in all samples studied. The amount varied considerably, depending on soil maturity, mineral types present, grain size distribution, and depth. Hydrogen implantation is definitely a surface phenomenon. However, as constructional particles are formed, previously exposed surfaces become embedded within particles, causing an enrichment of hydrogen in these species. In view of possibly extracting the hydrogen for use on the lunar surface, it is encouraging to know that hydrogen is present to a considerable depth and not only in the upper few millimeters. Based on these preliminary studies, extraction of solar wind hydrogen from lunar soil appears feasible, particulary if some kind of grain size separation is possible.

40 CFR Table F-3 to Subpart F of... - Critical Parameters of Idealized Ambient Particle Size Distributions

Code of Federal Regulations, 2010 CFR

2010-07-01

... Ambient Particle Size Distributions F Table F-3 to Subpart F of Part 53 Protection of Environment... Ambient Particle Size Distributions Idealized Distribution Fine Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m3) Coarse Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m3) PM2.5/PM10 Ratio FRM Sampler...

40 CFR Table F-3 to Subpart F of... - Critical Parameters of Idealized Ambient Particle Size Distributions

Code of Federal Regulations, 2013 CFR

2013-07-01

... Ambient Particle Size Distributions F Table F-3 to Subpart F of Part 53 Protection of Environment... Ambient Particle Size Distributions Idealized Distribution Fine Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m 3) Coarse Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m 3) PM 2.5/PM 10 Ratio FRM Sampler...

40 CFR Table F-3 to Subpart F of... - Critical Parameters of Idealized Ambient Particle Size Distributions

Code of Federal Regulations, 2012 CFR

2012-07-01

... Ambient Particle Size Distributions F Table F-3 to Subpart F of Part 53 Protection of Environment... Ambient Particle Size Distributions Idealized Distribution Fine Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m3) Coarse Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m3) PM2.5/PM10 Ratio FRM Sampler...

40 CFR Table F-3 to Subpart F of... - Critical Parameters of Idealized Ambient Particle Size Distributions

Code of Federal Regulations, 2011 CFR

2011-07-01

... Ambient Particle Size Distributions F Table F-3 to Subpart F of Part 53 Protection of Environment... Ambient Particle Size Distributions Idealized Distribution Fine Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m3) Coarse Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m3) PM2.5/PM10 Ratio FRM Sampler...

40 CFR Table F-3 to Subpart F of... - Critical Parameters of Idealized Ambient Particle Size Distributions

Code of Federal Regulations, 2014 CFR

2014-07-01

... Ambient Particle Size Distributions F Table F-3 to Subpart F of Part 53 Protection of Environment... Ambient Particle Size Distributions Idealized Distribution Fine Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m3) Coarse Particle Mode MMD (µm) Geo. Std. Dev. Conc. (µg/m3) PM 2.5/PM 10 Ratio FRM Sampler...

Three-phase boundary length in solid-oxide fuel cells: A mathematical model

NASA Astrophysics Data System (ADS)

Janardhanan, Vinod M.; Heuveline, Vincent; Deutschmann, Olaf

A mathematical model to calculate the volume specific three-phase boundary length in the porous composite electrodes of solid-oxide fuel cell is presented. The model is exclusively based on geometrical considerations accounting for porosity, particle diameter, particle size distribution, and solids phase distribution. Results are presented for uniform particle size distribution as well as for non-uniform particle size distribution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taheri, M; Teslich, N; Lu, J P

An in situ method for studying the role of laser energy on the microstructural evolution of polycrystalline Si is presented. By monitoring both laser energy and microstructural evolution simultaneously in the dynamic transmission electron microscope, information on grain size and defect concentration can be correlated directly with processing conditions. This proof of principle study provides fundamental scientific information on the crystallization process that has technological importance for the development of thin film transistors. In conclusion, we successfully developed a method for studying UV laser processing of Si films in situ on nanosecond time scales, with ultimate implications for TFT applicationmore » improvements. In addition to grain size distribution as a function of laser energy density, we found that grain size scaled with laser energy in general. We showed that nanosecond time resolution allowed us to see the nucleation and growth front during processing, which will help further the understanding of microstructural evolution of poly-Si films for electronic applications. Future studies, coupled with high resolution TEM, will be performed to study grain boundary migration, intergranular defects, and grain size distribution with respect to laser energy and adsorption depth.« less

Effect of site on sedimentological characteristics and metal pollution in two semi-enclosed embayments of great freshwater reservoir: Lake Nasser, Egypt

NASA Astrophysics Data System (ADS)

Farhat, Hassan I.; Aly, Walid

2018-05-01

This study was carried out to assess the effect of site on the spatial variations of sedimentological characteristics and heavy metal pollution of two semi-enclosed embayments of Lake Nasser. Grain Size, texture and mode of transportation as well as some heavy metals and organic matter were assessed in sediment samples from those embayments. The results indicated that the grain size of the lake sediments was affected by site variation. Moreover, heavy metal distribution in the sediments was mainly directed by grain size distribution and organic matter, though, the organic matter was more critical than grain size in controlling heavy metals distribution in each embayment. The main source of heavy metals in studied embayments was concluded to be the metals brought with flood waters rather than being of anthropogenic origin. The results also indicated the association of studied metals with Fe and Mn oxides of suspended matters and dissolved solids which come with flood water and trapped and settled to the bottom sediment in the stagnation period. Measured indices indicated that southern embayment is more polluted than northern one, which could be explained on the basis that the southern embayment reserves larger amounts of suspended matter coming with the flood than northern embayment.

Does increasing the size of bi-weekly samples of records influence results when using the Global Trigger Tool? An observational study of retrospective record reviews of two different sample sizes.

PubMed

Mevik, Kjersti; Griffin, Frances A; Hansen, Tonje E; Deilkås, Ellen T; Vonen, Barthold

2016-04-25

To investigate the impact of increasing sample of records reviewed bi-weekly with the Global Trigger Tool method to identify adverse events in hospitalised patients. Retrospective observational study. A Norwegian 524-bed general hospital trust. 1920 medical records selected from 1 January to 31 December 2010. Rate, type and severity of adverse events identified in two different samples sizes of records selected as 10 and 70 records, bi-weekly. In the large sample, 1.45 (95% CI 1.07 to 1.97) times more adverse events per 1000 patient days (39.3 adverse events/1000 patient days) were identified than in the small sample (27.2 adverse events/1000 patient days). Hospital-acquired infections were the most common category of adverse events in both the samples, and the distributions of the other categories of adverse events did not differ significantly between the samples. The distribution of severity level of adverse events did not differ between the samples. The findings suggest that while the distribution of categories and severity are not dependent on the sample size, the rate of adverse events is. Further studies are needed to conclude if the optimal sample size may need to be adjusted based on the hospital size in order to detect a more accurate rate of adverse events. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

PM 10, PM 2.5 and PM 1.0—Emissions from industrial plants—Results from measurement programmes in Germany

NASA Astrophysics Data System (ADS)

Ehrlich, C.; Noll, G.; Kalkoff, W.-D.; Baumbach, G.; Dreiseidler, A.

Emission measurement programmes were carried out at industrial plants in several regions of Germany to determine the fine dust in the waste gases; the PM 10, PM 2.5 and PM 1.0 fractions were sampled using a cascade impactor technique. The installations tested included plants used for: combustion (brown coal, heavy fuel oil, wood), cement production, glass production, asphalt mixing, and processing plants for natural stones and sand, ceramics, metallurgy, chemical production, spray painting, wood processing/chip drying, poultry farming and waste treatment. In addition waste gas samples were taken from small-scale combustion units, like domestic stoves, firing lignite briquettes or wood. In total 303 individual measurement results were obtained during 106 different measurement campaigns. In the study it was found that in more than 70% of the individual emission measurement results from industrial plants and domestic stoves the PM 10 portion amounted to more than 90% and the PM 2.5 portion between 50% and 90% of the total PM (particulate matter) emission. For thermal industrial processes the PM 1.0 portion constituted between 20% and 60% of the total PM emission. Typical particle size distributions for different processes were presented as cumulative frequency distributions and as frequency distributions. The particle size distributions determined for the different plant types show interesting similarities and differences depending on whether the processes are thermal, mechanical, chemical or mixed. Consequently, for the groups of plant investigated, a major finding of this study has been that the particle size distribution is a characteristic of the industrial process. Attempts to correlate particle size distributions of different plants to different gas cleaning technologies did not lead to usable results.

Preparing rock powder specimens of controlled size distribution

NASA Technical Reports Server (NTRS)

Blum, P.

1968-01-01

Apparatus produces rock powder specimens of the size distribution needed in geological sampling. By cutting grooves in the surface of the rock sample and then by milling these shallow, parallel ridges, the powder specimen is produced. Particle size distribution is controlled by changing the height and width of ridges.

The influence of polymeric membrane gas spargers on hydrodynamics and mass transfer in bubble column bioreactors.

PubMed

Tirunehe, Gossaye; Norddahl, B

2016-04-01

Gas sparging performances of a flat sheet and tubular polymeric membranes were investigated in 3.1 m bubble column bioreactor operated in a semi batch mode. Air-water and air-CMC (Carboxymethyl cellulose) solutions of 0.5, 0.75 and 1.0 % w/w were used as interacting gas-liquid mediums. CMC solutions were employed in the study to simulate rheological properties of bioreactor broth. Gas holdup, bubble size distribution, interfacial area and gas-liquid mass transfer were studied in the homogeneous bubbly flow hydrodynamic regime with superficial gas velocity (U(G)) range of 0.0004-0.0025 m/s. The study indicated that the tubular membrane sparger produced the highest gas holdup and densely populated fine bubbles with narrow size distribution. An increase in liquid viscosity promoted a shift in bubble size distribution to large stable bubbles and smaller specific interfacial area. The tubular membrane sparger achieved greater interfacial area and an enhanced overall mass transfer coefficient (K(L)a) by a factor of 1.2-1.9 compared to the flat sheet membrane.

Collective philanthropy: describing and modeling the ecology of giving.

PubMed

Gottesman, William L; Reagan, Andrew James; Dodds, Peter Sheridan

2014-01-01

Reflective of income and wealth distributions, philanthropic gifting appears to follow an approximate power-law size distribution as measured by the size of gifts received by individual institutions. We explore the ecology of gifting by analysing data sets of individual gifts for a diverse group of institutions dedicated to education, medicine, art, public support, and religion. We find that the detailed forms of gift-size distributions differ across but are relatively constant within charity categories. We construct a model for how a donor's income affects their giving preferences in different charity categories, offering a mechanistic explanation for variations in institutional gift-size distributions. We discuss how knowledge of gift-sized distributions may be used to assess an institution's gift-giving profile, to help set fundraising goals, and to design an institution-specific giving pyramid.

Influence of the weighing bar position in vessel on measurement of cement’s particle size distribution by using the buoyancy weighing-bar method

NASA Astrophysics Data System (ADS)

Tambun, R.; Sihombing, R. O.; Simanjuntak, A.; Hanum, F.

2018-02-01

The buoyancy weighing-bar method is a new simple and cost-effective method to determine the particle size distribution both settling and floating particle. In this method, the density change in a suspension due to particle migration is measured by weighing buoyancy against a weighing-bar hung in the suspension, and then the particle size distribution is calculated using the length of the bar and the time-course change in the mass of the bar. The apparatus of this method consists of a weighing-bar and an analytical balance with a hook for under-floor weighing. The weighing bar is used to detect the density change in suspension. In this study we investigate the influences of position of weighing bar in vessel on settling particle size distribution measurements of cement by using the buoyancy weighing-bar method. The vessel used in this experiment is graduated cylinder with the diameter of 65 mm and the position of weighing bar is in center and off center of vessel. The diameter of weighing bar in this experiment is 10 mm, and the kerosene is used as a dispersion liquids. The results obtained show that the positions of weighing bar in vessel have no significant effect on determination the cement’s particle size distribution by using buoyancy weighing-bar method, and the results obtained are comparable to those measured by using settling balance method.

Size-frequency distribution, growth, and mortality of snow crab (Chionoecetes opilio) and arctic lyre crab (Hyas coarctatus) in the chukchi sea from 2009 to 2013

NASA Astrophysics Data System (ADS)

Groß, Jasmin; Konar, Brenda; Brey, Thomas; Grebmeier, Jacqueline M.

2017-10-01

The snow crab Chionoecetes opilio and Arctic lyre crab Hyas coarctatus are prominent members of the Chukchi Sea epifaunal community. A better understanding of their life history will aid in determining their role in this ecosystem in light of the changing climate and resource development. In this study, the size frequency distribution, growth, and mortality of these two crab species was examined in 2009, 2010, 2012, and 2013 to determine temporal and spatial patterns within the eastern Chukchi Sea, and to identify potential environmental drivers of the observed patterns. Temporally, the mean size of both sexes of C. opilio and H. coarctatus decreased significantly from 2009 to 2013, with the number of rare maximum sized organisms decreasing significantly to near absence in the latter two study years. Spatially, the mean size of male and female crabs of both species showed a latitudinal trend, decreasing from south to north in the investigation area. Growth of both sexes of C. opilio and H. coarctatus was linear over the sampled size range, and mortality was highest in the latter two study years. Life history features of both species related to different environmental parameters in different years, ranging from temperature, the sediment carbon to nitrogen ratio of the organic content, and sediment grain size distribution. Likely explanations for the observed temporal and spatial variability are ontogenetic migrations of mature crabs to warmer areas possibly due to cooler water temperatures in the latter two study years, or interannual fluctuations, which have been reported for C. opilio populations in other areas where successful waves of recruitment were estimated to occur in eight year intervals. Further research is suggested to determine if the spatial and temporal patterns found in this study are part of the natural variability in this system or if they are an indication of long-term trends.

Retrieval of Droplet size Density Distribution from Multiple field of view Cross polarized Lidar Signals: Theory and Experimental Validation

DTIC Science & Technology

2016-06-02

Retrieval of droplet-size density distribution from multiple-field-of-view cross-polarized lidar signals: theory and experimental validation...theoretical and experimental studies of mul- tiple scattering and multiple-field-of-view (MFOV) li- dar detection have made possible the retrieval of cloud...droplet cloud are typical of Rayleigh scattering, with a signature close to a dipole (phase function quasi -flat and a zero-depolarization ratio

Interpretation of size-exclusion chromatography for the determination of molecular-size distribution of human immunoglobulins.

PubMed

Christians, S; Schluender, S; van Treel, N D; Behr-Gross, M-E

2016-01-01

Molecular-size distribution by size-exclusion chromatography (SEC) [1] is used for the quantification of unwanted aggregated forms in therapeutic polyclonal antibodies, referred to as human immunoglobulins (Ig) in the European Pharmacopoeia. Considering not only the requirements of the monographs for human normal Ig (0338, 0918 and 2788) [2-4], but also the general chapter on chromatographic techniques (2.2.46) [5], several chromatographic column types are allowed for performing this test. Although the EDQM knowledge database gives only 2 examples of suitable columns as a guide for the user, these monographs permit the use of columns with different lengths and diameters, and do not prescribe either particle size or pore size, which are considered key characteristics of SEC columns. Therefore, the columns used may differ significantly from each other with regard to peak resolution, potentially resulting in ambiguous peak identity assignment. In some cases, this may even lead to situations where the manufacturer and the Official Medicines Control Laboratory (OMCL) in charge of Official Control Authority Batch Release (OCABR) have differing molecular-size distribution profiles for aggregates of the same batch of Ig, even though both laboratories follow the requirements of the relevant monograph. In the present study, several formally acceptable columns and the peak integration results obtained therewith were compared. A standard size-exclusion column with a length of 60 cm and a particle size of 10 µm typically detects only 3 Ig fractions, namely monomers, dimers and polymers. This column type was among the first reliable HPLC columns on the market for this test and very rapidly became the standard for many pharmaceutical manufacturers and OMCLs for batch release testing. Consequently, the distribution of monomers, dimers and polymers was established as the basis for the interpretation of the results of the molecular-size distribution test in the relevant monographs. However, modern columns with a smaller particle size provide better resolution and also reveal a class of components designated here as oligomers. This publication addresses the interpretation of the SEC test for Ig with respect to the following questions: - how can molecular-size distribution tests benefit from the use of the most recent column technology without changing the sense of well-established quality parameters? - is it possible to mathematically define a way to interpret chromatograms generated with various column types with the same fractionation range but different resolution power? - how should oligomers be considered regarding compliance with compendial specifications?

Combination of Cation Exchange and Quantized Ostwald Ripening for Controlling Size Distribution of Lead Chalcogenide Quantum Dots

DOE PAGES

Zhang, Changwang; Xia, Yong; Zhang, Zhiming; ...

2017-03-22

A new strategy for narrowing the size distribution of colloidal quantum dots (QDs) was developed by combining cation exchange and quantized Ostwald ripening. Medium-sized reactant CdS(e) QDs were subjected to cation exchange to form the target PbS(e) QDs, and then small reactant CdS(e) QDs were added which were converted to small PbS(e) dots via cation exchange. The small-sized ensemble of PbS(e) QDs dissolved completely rapidly and released a large amount of monomers, promoting the growth and size-focusing of the medium-sized ensemble of PbS(e) QDs. The addition of small reactant QDs can be repeated to continuously reduce the size distribution. Themore » new method was applied to synthesize PbSe and PbS QDs with extremely narrow size distributions and as a bonus they have hybrid surface passivation. In conclusion, the size distribution of prepared PbSe and PbS QDs are as low as 3.6% and 4.3%, respectively, leading to hexagonal close packing in monolayer and highly ordered three-dimensional superlattice.« less

Combination of Cation Exchange and Quantized Ostwald Ripening for Controlling Size Distribution of Lead Chalcogenide Quantum Dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Changwang; Xia, Yong; Zhang, Zhiming

A new strategy for narrowing the size distribution of colloidal quantum dots (QDs) was developed by combining cation exchange and quantized Ostwald ripening. Medium-sized reactant CdS(e) QDs were subjected to cation exchange to form the target PbS(e) QDs, and then small reactant CdS(e) QDs were added which were converted to small PbS(e) dots via cation exchange. The small-sized ensemble of PbS(e) QDs dissolved completely rapidly and released a large amount of monomers, promoting the growth and size-focusing of the medium-sized ensemble of PbS(e) QDs. The addition of small reactant QDs can be repeated to continuously reduce the size distribution. Themore » new method was applied to synthesize PbSe and PbS QDs with extremely narrow size distributions and as a bonus they have hybrid surface passivation. In conclusion, the size distribution of prepared PbSe and PbS QDs are as low as 3.6% and 4.3%, respectively, leading to hexagonal close packing in monolayer and highly ordered three-dimensional superlattice.« less

Effects of the underlying topology on perturbation spreading in the Axelrod model for cultural dissemination

NASA Astrophysics Data System (ADS)

Kim, Yup; Cho, Minsoo; Yook, Soon-Hyung

2011-10-01

We study the effects of the underlying topologies on a single feature perturbation imposed to the Axelrod model of consensus formation. From the numerical simulations we show that there are successive updates which are similar to avalanches in many self-organized criticality systems when a perturbation is imposed. We find that the distribution of avalanche size satisfies the finite-size scaling (FSS) ansatz on two-dimensional lattices and random networks. However, on scale-free networks with the degree exponent γ≤3 we show that the avalanche size distribution does not satisfy the FSS ansatz. The results indicate that the disordered configurations on two-dimensional lattices or on random networks are still stable against the perturbation in the limit N (network size) →∞. However, on scale-free networks with γ≤3 the perturbation always drives the disordered phase into an ordered phase. The possible relationship between the properties of phase transition of the Axelrod model and the avalanche distribution is also discussed.

Effect of Temperature on the Size Distribution, Shell Properties, and Stability of Definity®.

PubMed

Shekhar, Himanshu; Smith, Nathaniel J; Raymond, Jason L; Holland, Christy K

2018-02-01

Physical characterization of an ultrasound contrast agent (UCA) aids in its safe and effective use in diagnostic and therapeutic applications. The goal of this study was to investigate the impact of temperature on the size distribution, shell properties, and stability of Definity ® , a U.S. Food and Drug Administration-approved UCA used for left ventricular opacification. A Coulter counter was modified to enable particle size measurements at physiologic temperatures. The broadband acoustic attenuation spectrum and size distribution of Definity ® were measured at room temperature (25 °C) and physiologic temperature (37 °C) and were used to estimate the viscoelastic shell properties of the agent at both temperatures. Attenuation and size distribution was measured over time to assess the effect of temperature on the temporal stability of Definity ® . The attenuation coefficient of Definity ® at 37 °C was as much as 5 dB higher than the attenuation coefficient measured at 25 °C. However, the size distributions of Definity ® at 25 °C and 37 °C were similar. The estimated shell stiffness and viscosity decreased from 1.76 ± 0.18 N/m and 0.21 × 10 -6  ± 0.07 × 10 -6 kg/s at 25 °C to 1.01 ± 0.07 N/m and 0.04 × 10 -6  ± 0.04 × 10 -6 kg/s at 37 °C, respectively. Size-dependent differences in dissolution rates were observed within the UCA population at both 25 °C and 37 °C. Additionally, cooling the diluted UCA suspension from 37 °C to 25 °C accelerated the dissolution rate. These results indicate that although temperature affects the shell properties of Definity ® and can influence the stability of Definity ® , the size distribution of this agent is not affected by a temperature increase from 25 °C to 37 °C. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

Sensing Size through Clustering in Non-Equilibrium Membranes and the Control of Membrane-Bound Enzymatic Reactions

PubMed Central

Vagne, Quentin; Turner, Matthew S.; Sens, Pierre

2015-01-01

The formation of dynamical clusters of proteins is ubiquitous in cellular membranes and is in part regulated by the recycling of membrane components. We show, using stochastic simulations and analytic modeling, that the out-of-equilibrium cluster size distribution of membrane components undergoing continuous recycling is strongly influenced by lateral confinement. This result has significant implications for the clustering of plasma membrane proteins whose mobility is hindered by cytoskeletal “corrals” and for protein clustering in cellular organelles of limited size that generically support material fluxes. We show how the confinement size can be sensed through its effect on the size distribution of clusters of membrane heterogeneities and propose that this could be regulated to control the efficiency of membrane-bound reactions. To illustrate this, we study a chain of enzymatic reactions sensitive to membrane protein clustering. The reaction efficiency is found to be a non-monotonic function of the system size, and can be optimal for sizes comparable to those of cellular organelles. PMID:26656912

Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

USGS Publications Warehouse

Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

2011-01-01

The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

Genome-wide analysis of macrosatellite repeat copy number variation in worldwide populations: evidence for differences and commonalities in size distributions and size restrictions

PubMed Central

2013-01-01

Background Macrosatellite repeats (MSRs), usually spanning hundreds of kilobases of genomic DNA, comprise a significant proportion of the human genome. Because of their highly polymorphic nature, MSRs represent an extreme example of copy number variation, but their structure and function is largely understudied. Here, we describe a detailed study of six autosomal and two X chromosomal MSRs among 270 HapMap individuals from Central Europe, Asia and Africa. Copy number variation, stability and genetic heterogeneity of the autosomal macrosatellite repeats RS447 (chromosome 4p), MSR5p (5p), FLJ40296 (13q), RNU2 (17q) and D4Z4 (4q and 10q) and X chromosomal DXZ4 and CT47 were investigated. Results Repeat array size distribution analysis shows that all of these MSRs are highly polymorphic with the most genetic variation among Africans and the least among Asians. A mitotic mutation rate of 0.4-2.2% was observed, exceeding meiotic mutation rates and possibly explaining the large size variability found for these MSRs. By means of a novel Bayesian approach, statistical support for a distinct multimodal rather than a uniform allele size distribution was detected in seven out of eight MSRs, with evidence for equidistant intervals between the modes. Conclusions The multimodal distributions with evidence for equidistant intervals, in combination with the observation of MSR-specific constraints on minimum array size, suggest that MSRs are limited in their configurations and that deviations thereof may cause disease, as is the case for facioscapulohumeral muscular dystrophy. However, at present we cannot exclude that there are mechanistic constraints for MSRs that are not directly disease-related. This study represents the first comprehensive study of MSRs in different human populations by applying novel statistical methods and identifies commonalities and differences in their organization and function in the human genome. PMID:23496858

Particle size distribution of aerosols sprayed from household hand-pump sprays containing fluorine-based and silicone-based compounds.

PubMed

Kawakami, Tsuyoshi; Isama, Kazuo; Ikarashi, Yoshiaki

2015-01-01

Japan has published safety guideline on waterproof aerosol sprays. Furthermore, the Aerosol Industry Association of Japan has adopted voluntary regulations on waterproof aerosol sprays. Aerosol particles of diameter less than 10 µm are considered as "fine particles". In order to avoid acute lung injury, this size fraction should account for less than 0.6% of the sprayed aerosol particles. In contrast, the particle size distribution of aerosols released by hand-pump sprays containing fluorine-based or silicone-based compounds have not been investigated in Japan. Thus, the present study investigated the aerosol particle size distribution of 16 household hand-pump sprays. In 4 samples, the ratio of fine particles in aerosols exceeded 0.6%. This study confirmed that several hand-pump sprays available in the Japanese market can spray fine particles. Since the hand-pump sprays use water as a solvent and their ingredients may be more hydrophilic than those of aerosol sprays, the concepts related to the safety of aerosol-sprays do not apply to the hand pump sprays. Therefore, it may be required for the hand-pump spray to develop a suitable method for evaluating the toxicity and to establish the safety guideline.

The social architecture of capitalism

NASA Astrophysics Data System (ADS)

Wright, Ian

2005-02-01

A dynamic model of the social relations between workers and capitalists is introduced. The model self-organises into a dynamic equilibrium with statistical properties that are in close qualitative and in many cases quantitative agreement with a broad range of known empirical distributions of developed capitalism, including the power-law firm size distribution, the Laplace firm and GDP growth distribution, the lognormal firm demises distribution, the exponential recession duration distribution, the lognormal-Pareto income distribution, and the gamma-like firm rate-of-profit distribution. Normally these distributions are studied in isolation, but this model unifies and connects them within a single causal framework. The model also generates business cycle phenomena, including fluctuating wage and profit shares in national income about values consistent with empirical studies. The generation of an approximately lognormal-Pareto income distribution and an exponential-Pareto wealth distribution demonstrates that the power-law regime of the income distribution can be explained by an additive process on a power-law network that models the social relation between employers and employees organised in firms, rather than a multiplicative process that models returns to investment in financial markets. A testable consequence of the model is the conjecture that the rate-of-profit distribution is consistent with a parameter-mix of a ratio of normal variates with means and variances that depend on a firm size parameter that is distributed according to a power-law.

Detecting tree-fall gap disturbances in tropical rain forests with airborne lidar

NASA Astrophysics Data System (ADS)

Espirito-Santo, F. D. B.; Saatchi, S.; Keller, M.

2017-12-01

Forest inventory studies in the Amazon indicate a large terrestrial carbon sink. However, field plots may fail to represent forest mortality processes at landscape-scales of tropical forests. Here we characterize the frequency distribution of tree-fall gap disturbances in natural forests of tropical forests using a novel combination of forest inventory and airborne lidar data. We quantify gap size frequency distribution along vertical and horizontal dimensions in ten Neotropical forest canopies distributed across gradients of climate and landscapes using airborne lidar measurements. We assessed all canopy openings related to each class of tree height which yields a three dimensional structure of the distribution of canopy gaps. Gap frequency distributions from lidar CHM data vary markedly with minimum gap size thresholds, but we found that natural forest disturbances (tree-fall gaps) follow a power-law distribution with narrow range of power-law exponents (-1.2 to -1.3). These power-law exponents from gap frequency distributions provide insights into how natural forest disturbances are distributed over tropical forest landscape.

A Comparative Study of T1 and T2 Relaxation in Shale

NASA Astrophysics Data System (ADS)

Keating, K.; Obasi, C. C.; Pashin, J. C.

2015-12-01

Nuclear magnetic resonance (NMR) relaxation measurement have been used extensively in petroleum and, more recently, in groundwater resource evaluation to estimate the porosity, pore-size distributions, permeability, fluid saturation, and fluid mobility. In shale, the transverse decay rate of NMR signal is sensitive to the microporosity, but is also affected by the paramagnetic contributions of clay and other iron-bearing minerals. Furthermore, contrasts in the magnetic susceptibility of the mineral matrix and pore fluids that result in an inhomogeneous magnetic field within the pore space results in an extra term in transverse relaxation. These issues can cause errors in NMR-based estimates of pore-size distribution and permeability. In this study we compare T1 and T2 relaxation time distributions in order to study the molecular mechanism of relaxation in brine-saturated mixtures of clay and other common minerals. We collected measurements on a range of mixtures of clay minerals common in shale (illite, glauconite, celadonite, chamosite, montmorillonite and kaolinite) and pyrite. To constrain the interpretation of the NMR data, we measured the magnetic susceptibility and surface area of all samples. We are confident that by accounting for the presence and variations of clay and pyrite in shale, we can substantially improve both the NMR estimate of pore-size distribution and permeability.

Analysis of Genetic Algorithm for Rule-Set Production (GARP) modeling approach for predicting distributions of fleas implicated as vectors of plague, Yersinia pestis, in California.

PubMed

Adjemian, Jennifer C Z; Girvetz, Evan H; Beckett, Laurel; Foley, Janet E

2006-01-01

More than 20 species of fleas in California are implicated as potential vectors of Yersinia pestis. Extremely limited spatial data exist for plague vectors-a key component to understanding where the greatest risks for human, domestic animal, and wildlife health exist. This study increases the spatial data available for 13 potential plague vectors by using the ecological niche modeling system Genetic Algorithm for Rule-Set Production (GARP) to predict their respective distributions. Because the available sample sizes in our data set varied greatly from one species to another, we also performed an analysis of the robustness of GARP by using the data available for flea Oropsylla montana (Baker) to quantify the effects that sample size and the chosen explanatory variables have on the final species distribution map. GARP effectively modeled the distributions of 13 vector species. Furthermore, our analyses show that all of these modeled ranges are robust, with a sample size of six fleas or greater not significantly impacting the percentage of the in-state area where the flea was predicted to be found, or the testing accuracy of the model. The results of this study will help guide the sampling efforts of future studies focusing on plague vectors.

Empirical study of the tails of mutual fund size

NASA Astrophysics Data System (ADS)

Schwarzkopf, Yonathan; Farmer, J. Doyne

2010-06-01

The mutual fund industry manages about a quarter of the assets in the U.S. stock market and thus plays an important role in the U.S. economy. The question of how much control is concentrated in the hands of the largest players is best quantitatively discussed in terms of the tail behavior of the mutual fund size distribution. We study the distribution empirically and show that the tail is much better described by a log-normal than a power law, indicating less concentration than, for example, personal income. The results are highly statistically significant and are consistent across fifteen years. This contradicts a recent theory concerning the origin of the power law tails of the trading volume distribution. Based on the analysis in a companion paper, the log-normality is to be expected, and indicates that the distribution of mutual funds remains perpetually out of equilibrium.

The size distribution of interstellar grains

NASA Technical Reports Server (NTRS)

Witt, Adolf N.

1987-01-01

Three major areas involving interstellar grains were investigated. First, studies were performed of scattering in reflection nebulae with the goal of deriving scattering characteristics of dust grains such as the albedo and the phase function asymmetry throughout the visible and the ultraviolet. Secondly, studies were performed of the wavelength dependence of interstellar extinction designed to demonstrate the wide range of grain size distributions naturally occurring in individual clouds in different parts of the galaxy. And thirdly, studies were also performed of the ultraviolet powered emission of dust grains in the 0.5 to 1.0 micron wavelength range in reflection nebulae. Findings considered of major importance are highlighted.

Multi-shell spherical GaAs /AlxGa1-x As quantum dot shells-size distribution as a mechanism to generate intermediate band energy levels

NASA Astrophysics Data System (ADS)

Rodríguez-Magdaleno, K. A.; Pérez-Álvarez, R.; Martínez-Orozco, J. C.; Pernas-Salomón, R.

2017-04-01

In this work the generation of an intermediate band of energy levels from multi-shell spherical GaAs /AlxGa1-x As quantum dot shells-size distribution is reported. Within the effective mass approximation the electronic structure of a GaAs spherical quantum-dot surrounded by one, two and three shells is studied in detail using a numerically stable transfer matrix method. We found that a shells-size distribution characterized by continuously wider GaAs domains is a suitable mechanism to generate the intermediate band whose width is also dependent on the Aluminium concentration x. Our results suggest that this effective mechanism can be used for the design of wider intermediate band than reported in other quantum systems with possible solar cells enhanced performance.

Active control of impulsive noise with symmetric α-stable distribution based on an improved step-size normalized adaptive algorithm

NASA Astrophysics Data System (ADS)

Zhou, Yali; Zhang, Qizhi; Yin, Yixin

2015-05-01

In this paper, active control of impulsive noise with symmetric α-stable (SαS) distribution is studied. A general step-size normalized filtered-x Least Mean Square (FxLMS) algorithm is developed based on the analysis of existing algorithms, and the Gaussian distribution function is used to normalize the step size. Compared with existing algorithms, the proposed algorithm needs neither the parameter selection and thresholds estimation nor the process of cost function selection and complex gradient computation. Computer simulations have been carried out to suggest that the proposed algorithm is effective for attenuating SαS impulsive noise, and then the proposed algorithm has been implemented in an experimental ANC system. Experimental results show that the proposed scheme has good performance for SαS impulsive noise attenuation.

Distribution of binder in granules produced by means of twin screw granulation.

PubMed

Fonteyne, Margot; Fussell, Andrew Luke; Vercruysse, Jurgen; Vervaet, Chris; Remon, Jean Paul; Strachan, Clare; Rades, Thomas; De Beer, Thomas

2014-02-28

According to the quality by design principle processes may not remain black-boxes and full process understanding is required. The granule size distribution of granules produced via twin screw granulation is often found to be bimodal. The aim of this study was to gain a better understanding of binder distribution within granules produced via twin screw granulation in order to investigate if an inhomogeneous spread of binder is causing this bimodal size distribution. Theophylline-lactose-polyvinylpyrrolidone K30 (PVP) (30-67.5-2.5%, w/w) was used as a model formulation. The intra-granular distribution of PVP was evaluated by means of hyperspectral coherent anti-Stokes Raman scattering (CARS) microscopy. For the evaluated formulation, no PVP rich zones were detected when applying a lateral spatial resolution of 0.5 μm, indicating that PVP is homogenously distributed within the granules. Copyright © 2013 Elsevier B.V. All rights reserved.

Fabrication and evaluation of low-cost agarose-zinc nanoporous composite matrix: influence of adsorbent density and size distribution on the performance of expanded beds.

PubMed

Asghari, Fateme; Jahanshahi, Mohsen

2012-09-28

Expanded bed adsorption (EBA), a promising and practical separation technique for adsorption of nanobioproduct/bioproduct, has been widely studied in the past two decades. The development of adsorbent with the special design for expanded bed process is a challenging course. To reduce the costs of adsorbent preparation, fine zinc powder was used as the inexpensive densifier. A series of matrices named Ag-Zn were prepared by water-in-oil emulsification method. The structure and morphology of the prepared matrix were studied by the optical microscope (OM) and scanning electron microscopy (SEM). The physical properties as a function of zinc powder ratio to agarose slurry were measured. The prepared matrices had regular spherical shape, and followed logarithmic normal size distribution with the range of 75-330 μm, mean diameter of 140.54-191.11 μm, wet density of 1.33-2.01 g/ml, water content of 0.45-0.75, porosity of 0.86-0.97 and pore size of about 40-90 nm. The bed expansion factor at the range of 2-3 was examined. The obtained results indicated that the expansion factor was decreased with increasing of matrix density. In addition, it was found that matrices with large particle size were suitable for high operation flow rate. The hydrodynamic properties were determined in expanded bed by the residence time distribution method (RTD). The effects of flow velocity, expansion factor and density of matrix on the hydrodynamic properties were also investigated. Moreover, the influence of particle size distribution on the performance of expanded bed has been studied. Therefore, three different particle size fractions (65-140, 215-280 and 65-280 μm) were assessed. The results indicated that dispersion in liquid-solid expanded beds increased with increasing flow rate and expansion factor; and matrix with a wide particle size distribution leaded to a reduced axial dispersion compared to matrices with a narrow size distribution. The axial dispersion coefficient also enhanced with the increasing of matrix density. It was found that flow rate was the most essential factor to effect on the hydrodynamic characteristics in the bed. For all the prepared matrices, the values of axial mixing coefficients (D(axl)) were smaller than 1.0 × 10⁻⁵ m²/s when flow velocities in expanded bed were less than 700 cm/h. All the results indicate that the prepared matrix show good expansion and stability in expanded bed; and it is suitable for expanded bed processes as an economical adsorbent. Copyright © 2012 Elsevier B.V. All rights reserved.

Size distribution of submarine landslides along the U.S. Atlantic margin

USGS Publications Warehouse

Chaytor, J.D.; ten Brink, Uri S.; Solow, A.R.; Andrews, B.D.

2009-01-01

Assessment of the probability for destructive landslide-generated tsunamis depends on the knowledge of the number, size, and frequency of large submarine landslides. This paper investigates the size distribution of submarine landslides along the U.S. Atlantic continental slope and rise using the size of the landslide source regions (landslide failure scars). Landslide scars along the margin identified in a detailed bathymetric Digital Elevation Model (DEM) have areas that range between 0.89??km2 and 2410??km2 and volumes between 0.002??km3 and 179??km3. The area to volume relationship of these failure scars is almost linear (inverse power-law exponent close to 1), suggesting a fairly uniform failure thickness of a few 10s of meters in each event, with only rare, deep excavating landslides. The cumulative volume distribution of the failure scars is very well described by a log-normal distribution rather than by an inverse power-law, the most commonly used distribution for both subaerial and submarine landslides. A log-normal distribution centered on a volume of 0.86??km3 may indicate that landslides preferentially mobilize a moderate amount of material (on the order of 1??km3), rather than large landslides or very small ones. Alternatively, the log-normal distribution may reflect an inverse power law distribution modified by a size-dependent probability of observing landslide scars in the bathymetry data. If the latter is the case, an inverse power-law distribution with an exponent of 1.3 ?? 0.3, modified by a size-dependent conditional probability of identifying more failure scars with increasing landslide size, fits the observed size distribution. This exponent value is similar to the predicted exponent of 1.2 ?? 0.3 for subaerial landslides in unconsolidated material. Both the log-normal and modified inverse power-law distributions of the observed failure scar volumes suggest that large landslides, which have the greatest potential to generate damaging tsunamis, occur infrequently along the margin. ?? 2008 Elsevier B.V.

The effects of plasma inhomogeneity on the nanoparticle coating in a low pressure plasma reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pourali, N.; Foroutan, G.

2015-10-15

A self-consistent model is used to study the surface coating of a collection of charged nanoparticles trapped in the sheath region of a low pressure plasma reactor. The model consists of multi-fluid plasma sheath module, including nanoparticle dynamics, as well as the surface deposition and particle heating modules. The simulation results show that the mean particle radius increases with time and the nanoparticle size distribution is broadened. The mean radius is a linear function of time, while the variance exhibits a quadratic dependence. The broadening in size distribution is attributed to the spatial inhomogeneity of the deposition rate which inmore » turn depends on the plasma inhomogeneity. The spatial inhomogeneity of the ions has strong impact on the broadening of the size distribution, as the ions contribute both in the nanoparticle charging and in direct film deposition. The distribution width also increases with increasing of the pressure, gas temperature, and the ambient temperature gradient.« less

Properties and Fluxes of Primary Marine Aerosol Generated Via Detrainment of Turbulence-Modulated Bubble Plumes from Fresh North Atlantic Seawater

NASA Astrophysics Data System (ADS)

Keene, W. C.; Long, M. S.; Duplessis, P.; Kieber, D. J.; Maben, J. R.; Frossard, A. A.; Kinsey, J. D.; Beaupre, S. R.; Lu, X.; Chang, R.; Zhu, Y.; Bisgrove, J.

2017-12-01

During a September-October 2016 cruise of the R/V Endeavor in the western North Atlantic Ocean, primary marine aerosol (PMA) was produced in a high capacity generator during day and night via detrainment of bubbles from biologically productive and oligotrophic seawater. The turbulent mixing of clean air and seawater in a Venturi nozzle produced bubble plumes with tunable size distributions. Physicochemical characteristics of size-resolved PMA and seawater were measured. PMA number production efficiencies per unit air detrained (PEnum) increased with increasing detainment rate. For given conditions, PEnum values summed over size distributions were roughly ten times greater than those for frits whereas normalized size distributions were similar. Results show that bubble size distributions significantly modulated number production fluxes but not relative shapes of corresponding size distributions. In contrast, mass production efficiencies (PEmass) decreased with increasing air detrainment and were similar to those for frits, consistent with the hypothesis that bubble rafts on the seawater surface modulate emissions of larger jet droplets that dominate PMA mass production. Production efficiencies of organic matter were about three times greater than those for frits whereas organic enrichment factors integrated over size distributions were similar.

Development, primacy, and systems of cities.

PubMed

El-shakhs, S

1972-10-01

The relationship between the evolutionary changes in the city size distribution of nationally defined urban systems and the process of socioeconomic development is examined. Attention is directed to the problems of defining and measuring changes in city size distributions, using the results to test empirically the relationship of such changes to the development process. Existing theoretical structures and empirical generalizations which have tried to explain or to describe, respectively, the hierarchical relationships of cities are represented by central place theory and rank size relationships. The problem is not that deviations exist but that an adequate definition is lacking of urban systems on the 1 hand, and a universal measure of city size distribution, which could be applied to any system irrespective of its level of development, on the other. The problem of measuring changes in city size distributions is further compounded by the lack of sufficient reliable information about different systems of cities for the purposes of empirical comparative analysis. Changes in city size distributions have thus far been viewed largely within the framework of classic equilibrium theory. A more differentiated continuum of the development process should replace the bioplar continuum of underdeveloped developed countries in relating changes in city size distribution with development. Implicit in this distinction is the view that processes which influence spatial organization during the early formative stages of development are inherently different from those operating during the more advanced stages. 2 approaches were used to examine the relationship between national levels of development and primacy: a comparative analysis of a large number of countries at a given point in time; and a historical analysis of a limited sample of 2 advanced countries, the US and Great Britain. The 75 countries included in this study cover a wide range of characteristics. The study found a significant association between the degree of primacy of distributions of cities and their socioeconomic level of development; and the form of the primacy curve (or its evolution with development) seemed to follow a consistent pattern in which the peak of primacy obtained during the stages of socioeconomic transition with countries being less primate in either direction from that peak. This pattern is the result of 2 reverse influences of the development process on the spatial structure of countries--centralization and concentration beginning with the rise of cities and a decentralization and spread effect accompanying the increasing influence and importance of the periphery and structural changes in the pattern of authority.

Bubble size statistics during reionization from 21-cm tomography

NASA Astrophysics Data System (ADS)

Giri, Sambit K.; Mellema, Garrelt; Dixon, Keri L.; Iliev, Ilian T.

2018-01-01

The upcoming SKA1-Low radio interferometer will be sensitive enough to produce tomographic imaging data of the redshifted 21-cm signal from the Epoch of Reionization. Due to the non-Gaussian distribution of the signal, a power spectrum analysis alone will not provide a complete description of its properties. Here, we consider an additional metric which could be derived from tomographic imaging data, namely the bubble size distribution of ionized regions. We study three methods that have previously been used to characterize bubble size distributions in simulation data for the hydrogen ionization fraction - the spherical-average (SPA), mean-free-path (MFP) and friends-of-friends (FOF) methods - and apply them to simulated 21-cm data cubes. Our simulated data cubes have the (sensitivity-dictated) resolution expected for the SKA1-Low reionization experiment and we study the impact of both the light-cone (LC) and redshift space distortion (RSD) effects. To identify ionized regions in the 21-cm data we introduce a new, self-adjusting thresholding approach based on the K-Means algorithm. We find that the fraction of ionized cells identified in this way consistently falls below the mean volume-averaged ionized fraction. From a comparison of the three bubble size methods, we conclude that all three methods are useful, but that the MFP method performs best in terms of tracking the progress of reionization and separating different reionization scenarios. The LC effect is found to affect data spanning more than about 10 MHz in frequency (Δz ∼ 0.5). We find that RSDs only marginally affect the bubble size distributions.

The asymptotic behavior in a reversible random coagulation-fragmentation polymerization process with sub-exponential decay

NASA Astrophysics Data System (ADS)

Dong, Siqun; Zhao, Dianli

2018-01-01

This paper studies the subcritical, near-critical and supercritical asymptotic behavior of a reversible random coagulation-fragmentation polymerization process as N → ∞, with the number of distinct ways to form a k-clusters from k units satisfying f(k) =(1 + o (1)) cr-ke-kαk-β, where 0 < α < 1 and β > 0. When the cluster size is small, its distribution is proved to converge to the Gaussian distribution. For the medium clusters, its distribution will converge to Poisson distribution in supercritical stage, and no large clusters exist in this stage. Furthermore, the largest length of polymers of size N is of order ln N in the subcritical stage under α ⩽ 1 / 2.

Optical granulometric analysis of sedimentary deposits by color segmentation-based software: OPTGRAN-CS

NASA Astrophysics Data System (ADS)

Chávez, G. Moreno; Sarocchi, D.; Santana, E. Arce; Borselli, L.

2015-12-01

The study of grain size distribution is fundamental for understanding sedimentological environments. Through these analyses, clast erosion, transport and deposition processes can be interpreted and modeled. However, grain size distribution analysis can be difficult in some outcrops due to the number and complexity of the arrangement of clasts and matrix and their physical size. Despite various technological advances, it is almost impossible to get the full grain size distribution (blocks to sand grain size) with a single method or instrument of analysis. For this reason development in this area continues to be fundamental. In recent years, various methods of particle size analysis by automatic image processing have been developed, due to their potential advantages with respect to classical ones; speed and final detailed content of information (virtually for each analyzed particle). In this framework, we have developed a novel algorithm and software for grain size distribution analysis, based on color image segmentation using an entropy-controlled quadratic Markov measure field algorithm and the Rosiwal method for counting intersections between clast and linear transects in the images. We test the novel algorithm in different sedimentary deposit types from 14 varieties of sedimentological environments. The results of the new algorithm were compared with grain counts performed manually by the same Rosiwal methods applied by experts. The new algorithm has the same accuracy as a classical manual count process, but the application of this innovative methodology is much easier and dramatically less time-consuming. The final productivity of the new software for analysis of clasts deposits after recording field outcrop images can be increased significantly.

Multi-Instrument Manager Tool for Data Acquisition and Merging of Optical and Electrical Mobility Size Distributions

NASA Astrophysics Data System (ADS)

Tritscher, Torsten; Koched, Amine; Han, Hee-Siew; Filimundi, Eric; Johnson, Tim; Elzey, Sherrie; Avenido, Aaron; Kykal, Carsten; Bischof, Oliver F.

2015-05-01

Electrical mobility classification (EC) followed by Condensation Particle Counter (CPC) detection is the technique combined in Scanning Mobility Particle Sizers(SMPS) to retrieve nanoparticle size distributions in the range from 2.5 nm to 1 μm. The detectable size range of SMPS systems can be extended by the addition of an Optical Particle Sizer(OPS) that covers larger sizes from 300 nm to 10 μm. This optical sizing method reports an optical equivalent diameter, which is often different from the electrical mobility diameter measured by the standard SMPS technique. Multi-Instrument Manager (MIMTM) software developed by TSI incorporates algorithms that facilitate merging SMPS data sets with data based on optical equivalent diameter to compile single, wide-range size distributions. Here we present MIM 2.0, the next-generation of the data merging tool that offers many advanced features for data merging and post-processing. MIM 2.0 allows direct data acquisition with OPS and NanoScan SMPS instruments to retrieve real-time particle size distributions from 10 nm to 10 μm, which we show in a case study at a fireplace. The merged data can be adjusted using one of the merging options, which automatically determines an overall aerosol effective refractive index. As a result an indirect and average characterization of aerosol optical and shape properties is possible. The merging tool allows several pre-settings, data averaging and adjustments, as well as the export of data sets and fitted graphs. MIM 2.0 also features several post-processing options for SMPS data and differences can be visualized in a multi-peak sample over a narrow size range.

Effect of Bimodal Grain Size Distribution on Scatter in Toughness

NASA Astrophysics Data System (ADS)

Chakrabarti, Debalay; Strangwood, Martin; Davis, Claire

2009-04-01

Blunt-notch tests were performed at -160 °C to investigate the effect of a bimodal ferrite grain size distribution in steel on cleavage fracture toughness, by comparing local fracture stress values for heat-treated microstructures with uniformly fine, uniformly coarse, and bimodal grain structures. An analysis of fracture stress values indicates that bimodality can have a significant effect on toughness by generating high scatter in the fracture test results. Local cleavage fracture values were related to grain size distributions and it was shown that the largest grains in the microstructure, with an area percent greater than approximately 4 pct, gave rise to cleavage initiation. In the case of the bimodal grain size distribution, the large grains from both the “fine grain” and “coarse grain” population initiate cleavage; this spread in grain size values resulted in higher scatter in the fracture stress than in the unimodal distributions. The notch-bend test results have been used to explain the difference in scatter in the Charpy energies for the unimodal and bimodal ferrite grain size distributions of thermomechanically controlled rolled (TMCR) steel, in which the bimodal distribution showed higher scatter in the Charpy impact transition (IT) region.

Biophysical characterization of influenza virus subpopulations using field flow fractionation and multiangle light scattering: correlation of particle counts, size distribution and infectivity.

PubMed

Wei, Ziping; McEvoy, Matt; Razinkov, Vladimir; Polozova, Alla; Li, Elizabeth; Casas-Finet, Jose; Tous, Guillermo I; Balu, Palani; Pan, Alfred A; Mehta, Harshvardhan; Schenerman, Mark A

2007-09-01

Adequate biophysical characterization of influenza virions is important for vaccine development. The influenza virus vaccines are produced from the allantoic fluid of developing chicken embryos. The process of viral replication produces a heterogeneous mixture of infectious and non-infectious viral particles with varying states of aggregation. The study of the relative distribution and behavior of different subpopulations and their inter-correlation can assist in the development of a robust process for a live virus vaccine. This report describes a field flow fractionation and multiangle light scattering (FFF-MALS) method optimized for the analysis of size distribution and total particle counts. The FFF-MALS method was compared with several other methods such as transmission electron microscopy (TEM), atomic force microscopy (AFM), size exclusion chromatography followed by MALS (SEC-MALS), quantitative reverse transcription polymerase chain reaction (RT Q-PCR), median tissue culture dose (TCID(50)), and the fluorescent focus assay (FFA). The correlation between the various methods for determining total particle counts, infectivity and size distribution is reported. The pros and cons of each of the analytical methods are discussed.

Thermal hysteresis kinetic effects of spin crossover nanoparticulated systems studied by FORC diagram method on an Ising-like model

NASA Astrophysics Data System (ADS)

Atitoaie, Alexandru; Stoleriu, Laurentiu; Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian

2016-04-01

The scientific community is manifesting a high research interest on spin crossover compounds and their recently synthesized nanoparticles, due to their various appealing properties, such as the bistability between a diamagnetic low spin state and a paramagnetic high spin state (HS), inter-switchable by temperature or pressure changes, light irradiation or magnetic field. The utility of these compounds showing hysteresis covers a broad area of applications, from the development of more efficient designs of temperature and pressure sensors to automotive and aeronautic industries and even a new type of molecular actuators. We are proposing in this work a study regarding the kinetic effects and the distribution of reversible and irreversible components on the thermal hysteresis of spin crossover nanoparticulated systems. We are considering here tridimensional systems with different sizes and also systems of nanoparticles with a Gaussian size distribution. The correlations between the kinetics of the thermal hysteresis, the distributions of sizes and intermolecular interactions and the transition temperature distributions were established by using the FORC (First Order Reversal Curves) method using a Monte Carlo technique within an Ising-like system.

Aircraft microwave observations and simulations of deep convection from 18 to 183 GHz. II - Model results

NASA Technical Reports Server (NTRS)

Yeh, Hwa-Young M.; Prasad, N.; Mack, Robert A.; Adler, Robert F.

1990-01-01

In this June 29, 1986 case study, a radiative transfer model is used to simulate the aircraft multichannel microwave brightness temperatures presented in the Adler et al. (1990) paper and to study the convective storm structure. Ground-based radar data are used to derive hydrometeor profiles of the storm, based on which the microwave upwelling brightness temperatures are calculated. Various vertical hydrometeor phase profiles and the Marshall and Palmer (M-P, 1948) and Sekhon and Srivastava (S-S, 1970) ice particle size distributions are experimented in the model. The results are compared with the aircraft radiometric data. The comparison reveals that the M-P distribution well represents the ice particle size distribution, especially in the upper tropospheric portion of the cloud; the S-S distribution appears to better simulate the ice particle size at the lower portion of the cloud, which has a greater effect on the low-frequency microwave upwelling brightness temperatures; and that, in deep convective regions, significant supercooled liquid water (about 0.5 g/cu m) may be present up to the -30 C layer, while in less convective areas, frozen hydrometeors are predominant above -10 C level.

Impact of geometrical properties on permeability and fluid phase distribution in porous media

NASA Astrophysics Data System (ADS)

Lehmann, P.; Berchtold, M.; Ahrenholz, B.; Tölke, J.; Kaestner, A.; Krafczyk, M.; Flühler, H.; Künsch, H. R.

2008-09-01

To predict fluid phase distribution in porous media, the effect of geometric properties on flow processes must be understood. In this study, we analyze the effect of volume, surface, curvature and connectivity (the four Minkowski functionals) on the hydraulic conductivity and the water retention curve. For that purpose, we generated 12 artificial structures with 800 3 voxels (the units of a 3D image) and compared them with a scanned sand sample of the same size. The structures were generated with a Boolean model based on a random distribution of overlapping ellipsoids whose size and shape were chosen to fulfill the criteria of the measured functionals. The pore structure of sand material was mapped with X-rays from synchrotrons. To analyze the effect of geometry on water flow and fluid distribution we carried out three types of analysis: Firstly, we computed geometrical properties like chord length, distance from the solids, pore size distribution and the Minkowski functionals as a function of pore size. Secondly, the fluid phase distribution as a function of the applied pressure was calculated with a morphological pore network model. Thirdly, the permeability was determined using a state-of-the-art lattice-Boltzmann method. For the simulated structure with the true Minkowski functionals the pores were larger and the computed air-entry value of the artificial medium was reduced to 85% of the value obtained from the scanned sample. The computed permeability for the geometry with the four fitted Minkowski functionals was equal to the permeability of the scanned image. The permeability was much more sensitive to the volume and surface than to curvature and connectivity of the medium. We conclude that the Minkowski functionals are not sufficient to characterize the geometrical properties of a porous structure that are relevant for the distribution of two fluid phases. Depending on the procedure to generate artificial structures with predefined Minkowski functionals, structures differing in pore size distribution can be obtained.