WorldWideScience

Sample records for colony size distributions

  1. Application of ant colony optimisation in distribution transformer sizing

    African Journals Online (AJOL)

    This study proposes an optimisation method for transformer sizing in power system using ant colony optimisation and a verification of the process by MATLAB software. The aim is to address the issue of transformer sizing which is a major challenge affecting its effective performance, longevity, huge capital cost and power ...

  2. application of ant colony optimisation in distribution transformer sizing

    African Journals Online (AJOL)

    HP

    E-mail addresses: 1 folorunsoo@abuad.edu.ng, 2 patrick.oriaifo@uniben.edu, 3 neville.idiagi@uniben.edu,. 4 emma.ogujor@uniben.edu.ng. ABSTRACT. This study proposes an optimisation method for transformer sizing in power system using ant colony optimisation and a verification of the process by MATLAB software.

  3. Foraging arena size and structural complexity affect the dynamics of food distribution in ant colonies.

    Science.gov (United States)

    Buczkowski, Grzegorz; VanWeelden, Matthew

    2010-12-01

    Food acquisition by ant colonies is a complex process that starts with acquiring food at the source (i.e., foraging) and culminates with food exchange in or around the nest (i.e., feeding). While ant foraging behavior is relatively well understood, the process of food distribution has received little attention, largely because of the lack of methodology that allows for accurate monitoring of food flow. In this study, we used the odorous house ant, Tapinoma sessile (Say) to investigate the effect of foraging arena size and structural complexity on the rate and the extent of spread of liquid carbohydrate food (sucrose solution) throughout a colony. To track the movement of food, we used protein marking and double-antibody sandwich enzyme-linked immunosorbent assay, DAS-ELISA. Variation in arena size, in conjunction with different colony sizes, allowed us to test the effect of different worker densities on food distribution. Results demonstrate that both arena size and colony size have a significant effect on the spread of the food and the number of workers receiving food decreased as arena size and colony size increased. When colony size was kept constant and arena size increased, the percentage of workers testing positive for the marker decreased, most likely because of fewer trophallactic interactions resulting from lower worker density. When arena size was kept constant and colony size increased, the percentage of workers testing positive decreased. Nonrandom (clustered) worker dispersion and a limited supply of food may have contributed to this result. Overall, results suggest that food distribution is more complete is smaller colonies regardless of the size of the foraging arena and that colony size, rather than worker density, is the primary factor affecting food distribution. The structural complexity of foraging arenas ranged from simple, two-dimensional space (empty arenas) to complex, three-dimensional space (arenas filled with mulch). The structural

  4. Quantifying the effect of colony size and food distribution on harvester ant foraging.

    Directory of Open Access Journals (Sweden)

    Tatiana P Flanagan

    Full Text Available Desert seed-harvester ants, genus Pogonomyrmex, are central place foragers that search for resources collectively. We quantify how seed harvesters exploit the spatial distribution of seeds to improve their rate of seed collection. We find that foraging rates are significantly influenced by the clumpiness of experimental seed baits. Colonies collected seeds from larger piles faster than randomly distributed seeds. We developed a method to compare foraging rates on clumped versus random seeds across three Pogonomyrmex species that differ substantially in forager population size. The increase in foraging rate when food was clumped in larger piles was indistinguishable across the three species, suggesting that species with larger colonies are no better than species with smaller colonies at collecting clumped seeds. These findings contradict the theoretical expectation that larger groups are more efficient at exploiting clumped resources, thus contributing to our understanding of the importance of the spatial distribution of food sources and colony size for communication and organization in social insects.

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

    KAUST Repository

    Lozano-Cortes, Diego

    2015-10-29

    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.

  6. A framework for analysis of abortive colony size distributions using a model of branching processes in irradiated normal human fibroblasts.

    Directory of Open Access Journals (Sweden)

    Tetsuya Sakashita

    Full Text Available BACKGROUND: Clonogenicity gives important information about the cellular reproductive potential following ionizing irradiation, but an abortive colony that fails to continue to grow remains poorly characterized. It was recently reported that the fraction of abortive colonies increases with increasing dose. Thus, we set out to investigate the production kinetics of abortive colonies using a model of branching processes. METHODOLOGY/PRINCIPAL FINDINGS: We firstly plotted the experimentally determined colony size distribution of abortive colonies in irradiated normal human fibroblasts, and found the linear relationship on the log-linear or log-log plot. By applying the simple model of branching processes to the linear relationship, we found the persistent reproductive cell death (RCD over several generations following irradiation. To verify the estimated probability of RCD, abortive colony size distribution (≤ 15 cells and the surviving fraction were simulated by the Monte Carlo computational approach for colony expansion. Parameters estimated from the log-log fit demonstrated the good performance in both simulations than those from the log-linear fit. Radiation-induced RCD, i.e. excess probability, lasted over 16 generations and mainly consisted of two components in the early (<3 generations and late phases. Intriguingly, the survival curve was sensitive to the excess probability over 5 generations, whereas abortive colony size distribution was robust against it. These results suggest that, whereas short-term RCD is critical to the abortive colony size distribution, long-lasting RCD is important for the dose response of the surviving fraction. CONCLUSIONS/SIGNIFICANCE: Our present model provides a single framework for understanding the behavior of primary cell colonies in culture following irradiation.

  7. Inverse estimation of the spheroidal particle size distribution using Ant Colony Optimization algorithms in multispectral extinction technique

    Science.gov (United States)

    He, Zhenzong; Qi, Hong; Wang, Yuqing; Ruan, Liming

    2014-10-01

    Four improved Ant Colony Optimization (ACO) algorithms, i.e. the probability density function based ACO (PDF-ACO) algorithm, the Region ACO (RACO) algorithm, Stochastic ACO (SACO) algorithm and Homogeneous ACO (HACO) algorithm, are employed to estimate the particle size distribution (PSD) of the spheroidal particles. The direct problems are solved by the extended Anomalous Diffraction Approximation (ADA) and the Lambert-Beer law. Three commonly used monomodal distribution functions i.e. the Rosin-Rammer (R-R) distribution function, the normal (N-N) distribution function, and the logarithmic normal (L-N) distribution function are estimated under dependent model. The influence of random measurement errors on the inverse results is also investigated. All the results reveal that the PDF-ACO algorithm is more accurate than the other three ACO algorithms and can be used as an effective technique to investigate the PSD of the spheroidal particles. Furthermore, the Johnson's SB (J-SB) function and the modified beta (M-β) function are employed as the general distribution functions to retrieve the PSD of spheroidal particles using PDF-ACO algorithm. The investigation shows a reasonable agreement between the original distribution function and the general distribution function when only considering the variety of the length of the rotational semi-axis.

  8. Colony size-frequency distributions among different populations of the scleractinan coral Siderastrea stellata in Southwestern Atlantic: implications for life history patterns

    Directory of Open Access Journals (Sweden)

    Monica Moraes Lins de Barros

    2006-12-01

    Full Text Available Colony size-frequency distributions of reef corals may be used to infer growth potential and population responses upon environmental changes. The present paper compares the size structure of colonies of Siderastrea stellata Verrill, 1868,among 11 sites, six of them distributed along a gradient of sediment deposition in Abrolhos, Bahia, Brazil (18º S. Results indicated that the population structure is likely to be influenced by local conditions, rather than large scale factors, such as latitude. The 11 distributions, however, showed higher frequencies of small size classes. Class 1 (up to 2.5 cm diameter was always present and the frequency of colonies from size class 3 (10 cm diameter tended to decrease in all sites. Comparison among the six Abrolhos sites showed that S. stellata has advantages at sites with intermediate sedimentation, where colonies attain larger sizes, probably, reflecting a higher survivorship over time. The present study showed that, despite the influence of environmental conditions on parameters of the populations such as size of colony, the life history strategy of S. stellata reflects a local adaptation that allows its development and survivorship in shallow waters and horizontal substrates, sites characterized by high mortality rates.Distribuições de freqüências de classes de tamanho de colônias de corais recifais, associadas a dados de fecundidade e crescimento, podem ser utilizadas para inferir o potencial de crescimento e respostas da população frente às variações ambientais. Apresentamos análise da estrutura de tamanho de colônias do coral Siderastrea stellata Verrill, 1868, em 11 locais, seis desses distribuídos ao longo de um gradiente de sedimentação em Abrolhos, Bahia, Brasil (18ºS. Os resultados demonstraram ausência de um padrão latitudinal, indicando maior influência de fatores locais. Em Abrolhos, locais com taxas de deposição de sedimento intermediárias apresentaram os maiores

  9. COMPARISON OF BACTERIAL FORAGING OPTIMIZATION AND ARTIFICIAL BEE COLONY OPTIMIZATION TECHNIQUE FOR DISTRIBUTED GENERATION SIZING AND PLACEMENT IN AN ELECTRICAL DISTRIBUTION SYSTEM

    OpenAIRE

    J. A. Baskar*, Dr. R. Hariprakash (IITM), Dr. M. Vijayakumar

    2017-01-01

    Integration of Distributed Generation (DG) in an electrical distribution system has increased recently due to voltage improvement, line loss reduction, environmental advantages, and postponement of system upgrading, and increasing reliability. Improper location and capacity of DG may affect the voltage stability on the Distribution System (DS). Optimization techniques are tools used to predict size and locate the DG units in the system, so as to utilize these units optimally within certain li...

  10. Population regulation in Magellanic penguins: what determines changes in colony size?

    Directory of Open Access Journals (Sweden)

    Luciana M Pozzi

    Full Text Available Seabirds are often studied at individual colonies, but the confounding effects of emigration and mortality processes in open populations may lead to inappropriate conclusions on the mechanisms underlying population changes. Magellanic penguin (Spheniscus magellanicus colonies of variable population sizes are distributed along the Argentine coastline. In recent decades, several population and distributional changes have occurred, with some colonies declining and others newly established or increasing. We integrated data of eight colonies scattered along ∼600 km in Northern Patagonia (from 41°26´S, 65°01´W to 45°11´S, 66°30´W, Rio Negro and Chubut provinces and conducted analysis in terms of their growth rates, production of young and of the dependence of those vital rates on colony age, size, and location. We contrasted population trends estimated from abundance data with those derived from population modeling to understand if observed growth rates were attainable under closed population scenarios. Population trends were inversely related to colony size, suggesting a density dependent growth pattern. All colonies located in the north--which were established during the last decades--increased at high rates, with the smallest, recently established colonies growing at the fastest rate. In central-southern Chubut, where colonies are the oldest, the largest breeding aggregations declined, but smaller colonies remained relatively stable. Results provided strong evidence that dispersal played a major role in driving local trends. Breeding success was higher in northern colonies, likely mediated by favorable oceanographic conditions. However, mean foraging distance and body condition of chicks at fledging were influenced by colony size. Recruitment of penguins in the northern area may have been triggered by a combination of density dependence, likely exacerbated by less favorable oceanographic conditions in the southern sector. Our results

  11. Recruitment strategies and colony size in social insects

    NARCIS (Netherlands)

    Planque, R.; van den Berg, G.J.B.; Franks, N.R.

    2010-01-01

    Ants use a great variety of recruitment methods to forage for food or find new nests, including tandem running, group recruitment and scent trails. It has been known for some time that there is a loose correlation across many taxa between species-specific mature colony size and recruitment method.

  12. Field evidence for aseasonality of reproduction and colony size in ...

    African Journals Online (AJOL)

    The giant mole-rat, Fukomys mechowii is a cooperatively breeding subterranean mole-rat exhibiting a reproductive division of labour in which usually one, or occasionally two, females are responsible for procreation. In a field study that involved complete excavation of 32 burrow systems, mean colony size was 9.9 ...

  13. Ant colony optimization algorithm for continuous domains based on position distribution model of ant colony foraging.

    Science.gov (United States)

    Liu, Liqiang; Dai, Yuntao; Gao, Jinyu

    2014-01-01

    Ant colony optimization algorithm for continuous domains is a major research direction for ant colony optimization algorithm. In this paper, we propose a distribution model of ant colony foraging, through analysis of the relationship between the position distribution and food source in the process of ant colony foraging. We design a continuous domain optimization algorithm based on the model and give the form of solution for the algorithm, the distribution model of pheromone, the update rules of ant colony position, and the processing method of constraint condition. Algorithm performance against a set of test trials was unconstrained optimization test functions and a set of optimization test functions, and test results of other algorithms are compared and analyzed to verify the correctness and effectiveness of the proposed algorithm.

  14. Seasonality in oestrus and litter size in an assistance dog breeding colony in the United Kingdom.

    Science.gov (United States)

    Wigham, Eleanor E; Moxon, Rachel S; England, Gary C W; Wood, James L N; Morters, Michelle K

    2017-10-07

    Evidence of seasonality in oestrus in bitches within specialist breeding programmes, such as those for assistance dogs, may support colony management through tailoring the distribution of resources required for breeding throughout the year. However, at present there are conflicting data regarding seasonality in oestrus (and litter size) in domestic dogs. The primary objective of this study was to investigate seasonal variations in oestrus and litter size in a large assistance dog breeding colony in the UK in order to optimise colony management. The authors analysed the annual distribution of 3624 observations of oestrus collected from 568 brood bitches from January 2005 to June 2014. The authors also evaluated the relationship between month and litter size for 1609 litters observed during the same period. There was no evidence of regular seasonal variations in oestrus or litter size by meteorological season or month. The lack of seasonality in oestrus may be a function of dogs in the UK, particularly valuable breeding bitches, being exposed to fairly constant environmental conditions throughout the year as a consequence of artificial light and heating during the winter months. The authors' findings suggest that special consideration of the annual distribution of oestrus and litter size is unnecessary for the management of assistance dog breeding colonies similar to those in the UK. © British Veterinary Association (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  15. Multimodal Raindrop Size Distributions.

    Science.gov (United States)

    Sauvageot, Henri; Koffi, Manlandon

    2000-08-01

    The raindrop size distributions (DSDs) observed over a short span usually have an erratic shape, with several relative maxima. This multimodal structure is studied from disdrometer data acquired in tropical and midlatitude areas. It is shown that some modes of DSDs have a persistence larger than several minutes and can be spotted from one DSD to the next one as they migrate through the size classes. It is demonstrated that Nm, the number of modes of DSDs, for diameter larger than 2 mm, is not related to the mean rain rate but depends on the rain-rate fluctuations. Statistical evidence of such a relation is given. The spread of DSDs is found to be dependent on its multimodal structure, that is, on Nm. The large values of Nm are associated with low values of slope and intercept N0 of the fitted exponential distribution.In order to explain the dependence of the DSD shape on Nm, a conceptual model is proposed in which the modes are interpreted as resulting from an overlapping of rain shafts. The associated DSD is termed a synthetic drop size distribution (SDSD). It is shown that the overlapping of rain shafts generated from a sequence of rain cells of increasing intensity, such as observed at the leading edge of a convective system, results in undersloping SDSDs. In the reverse configuration, that is, with a sequence of rain cells with decreasing intensity, such as observed at the ending edge of a convective system, it results in oversloping SDSDs. Observations in agreement with these conclusions are presented. The readability of the modal structure of the DSDs depends on several factors in such a way that an apparent multimodal structure is not necessary for a DSD to be an SDSD. It is suggested that most of the DSDs observed at the ground are synthetic DSDs.

  16. Coloniality of birds in the Kalahari – spatial distribution of trees and nests of the Sociable Weaver (Philetairus socius)

    CSIR Research Space (South Africa)

    Rösner, S

    2010-01-01

    Full Text Available and distribution of suitable nesting trees influences the variability of colony size and spatial distribution of colonies in two study sites in the Kalahari, South Africa. We used spatial statistics to describe characteristics of point patterns. Nests of communal...

  17. Mesoscale variability in intact and ghost colonies of Phaeocystis antarctica in the Ross Sea: Distribution and abundance

    Science.gov (United States)

    Smith, Walker O.; McGillicuddy, Dennis J.; Olson, Elise B.; Kosnyrev, Valery; Peacock, Emily E.; Sosik, Heidi M.

    2017-02-01

    Phaeocystis, a genus with a cosmopolitan distribution and a polymorphic life cycle, was observed during summer in the Ross Sea, Antarctica, where large blooms of this haptophyte regularly occur. The mesoscale vertical and horizontal distributions of colonies of Phaeocystis antarctica were assessed using a towed Video Plankton Recorder (VPR). The mean size of colonies was 1.20 mm, and mean abundances within the three VPR surveys were 4.86, 1.96, and 11.5 mL- 1. In addition to the typical spherical, transparent colonies, the VPR quantified an optically dissimilar form of colony that had a distinctive translucent appearance. It also measured the abundance of collapsed colonies, similar to those observed previously from cultures and mesocosms, which we called "ghost colonies". The translucent colonial form had a different distribution than the more common colonial form, and at times was more abundant. Relative to intact colonies, the ghost colonies occurred less frequently, with mean abundances in the three surveys being 0.01, 0.08, and 0.0004 mL- 1. Ghost colonies generally were found below the euphotic zone, where they often were in greater abundance than intact colonies. However, the relationship of ghost colonies to intact P. antarctica colonies was not direct or consistent, suggesting that the formation of ghost colonies from living colonies and their appearance within the water column were not tightly coupled. Given their relative scarcity and low carbon content, it is unlikely that ghost colonies contribute substantially to vertical flux; however, it is possible that we did not sample periods of major flux events, and as a result minimized the importance of ghost colonies to vertical flux. They do, however, represent a poorly documented feature of polar haptophyte life cycles.

  18. Measuring coral size-frequency distribution using stereo video technology, a comparison with in situ measurements.

    Science.gov (United States)

    Turner, Joseph A; Polunin, Nicholas V C; Field, Stuart N; Wilson, Shaun K

    2015-05-01

    Coral colony size-frequency distribution data offer valuable information about the ecological status of coral reefs. Such data are usually collected by divers in situ, but stereo video is being increasingly used for monitoring benthic marine communities and may be used to collect size information for coral colonies. This study compared the size-frequency distributions of coral colonies obtained by divers measuring colonies 'in situ' with digital video imagery collected using stereo video and later processed using computer software. The size-frequency distributions of the two methods were similar for corymbose colonies, although distributions were different for massive, branching and all colonies combined. The differences are mainly driven by greater abundance of colonies >50 cm and fewer colonies 5 cm and was able to record measurements on 87% of the colonies detected. However, stereo video only detected 57% of marked colonies coral recruits. Estimates of colony size made with the stereo video were smaller than the in situ technique for all growth forms, particularly for massive morphologies. Despite differences in size distributions, community assessments, which incorporated genera, growth forms and size, were similar between the two techniques. Stereo video is suitable for monitoring coral community demographics and provided data similar to in situ measure for corymbose corals, but the ability to accurately measure massive and branching coral morphologies appeared to decline with increasing colony size.

  19. Foraging Distance and Population Size of Juvenile Colonies of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae) in Laboratory Extended Arenas.

    Science.gov (United States)

    Su, Nan-Yao; Osbrink, Weste; Kakkar, Garima; Mullins, Aaron; Chouvenc, Thomas

    2017-08-01

    The relationship between colony size and foraging distance was examined in extended foraging arenas with juvenile colonies of the Formosan subterranean termite, Coptotermes formosanus Shiraki. Our results showed that as long as royal pairs are present, larger colonies foraged at longer distances, and the oldest workers distributed farther away from the central nest. The results agree with the scaling model that predicts a large foraging range for animals of larger body size. An analysis of published data from population survey studies and field trials of bait toxicants showed that field colonies of the eastern subterranean termite, Reticulitermes flavipes (Kollar), follow the scaling model, while C. formosanus colonies were inconsistent with the model prediction. Reasons for the inconsistency with field data of C. formosanus are discussed. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  20. a Missing Link? - Mesoscale Distributions of Colonial Phaeocystis Antarctica and its Ghost Colonies in the Ross Sea

    Science.gov (United States)

    Smith, W.; McGillicuddy, D. J., Jr.; Olson, E.; Sosik, H. M.; Peacock, E.

    2016-02-01

    It is well established that the haptophyte Phaeocystis antarctica is a dominant member of the Ross Sea phytoplankton, contributing more than half of the annual production. Its broad spatial distribution has been documented by ship sampling, but its mesoscale variations are poorly known. In the PRISM (Processes Regulating Iron Supply at the Mesoscale) project in 2011, we deployed a Video Plankton Recorder (VPR) for 24 h between selected locations that had been identified by satellite images to have eddy-like features. As P. antarctica colonies are far larger than the VPR's camera resolution (2 mm vs. 40 µm), we were able to quantify colonial contributions to total fluorescence and particulate organic carbon, resolving distances of a few kms and depths of ca. 1 m. Within these surveys, we found unusual forms of colonies, which we subsequently deemed "ghost colonies"; that is, colonies that have largely lost their cells and have collapsed. While ghost colonies generally were located deeper in the water column than intact colonies, not all surface Phaeocystis blooms were associated with ghost colonies. For example, in one survey ghost colonies and intact colonial forms were present throughout the water column, but with distributions separated by depth; while in another survey, their distributions appeared to be spatially distinct in the horizontal. We hypothesize that ghost colonies are formed upon extreme micronutrient stress, which causes colonies to sink and cells to be liberated from colonies. Considerable mesoscale variability was noted in P. antarctica distributions and was related to oceanographic features. The mesoscale variations in both P. antarctica and its ghost colonies potentially have significant impacts on vertical fluxes and biogeochemical cycles in the Ross Sea.

  1. Aerosol Size Distributions In Auckland.

    Czech Academy of Sciences Publication Activity Database

    Coulson, G.; Olivares, G.; Talbot, Nicholas

    2016-01-01

    Roč. 50, č. 1 (2016), s. 23-28 E-ISSN 1836-5876 Institutional support: RVO:67985858 Keywords : aerosol size distribution * particle number concentration * roadside Subject RIV: CF - Physical ; Theoretical Chemistry

  2. Bubble size distribution of foam

    NARCIS (Netherlands)

    den Engelsen, C.W.; den Engelsen, C.W.; Isarin, J.C.; Warmoeskerken, Marinus; Groot Wassink, J.; Groot Wassink, J.

    2002-01-01

    A procedure based upon image analysis has been adopted to study the influence of several physical parameters on bubble size in foam. A procedure has been described to account for the distribution of bubble size. Foam was generated in a rotor-stator mixer. In the present research, the nature of the

  3. The global distribution of ammonia emissions from seabird colonies

    Science.gov (United States)

    Riddick, S. N.; Dragosits, U.; Blackall, T. D.; Daunt, F.; Wanless, S.; Sutton, M. A.

    2012-08-01

    Seabird colonies represent a significant source of atmospheric ammonia (NH3) in remote maritime systems, producing a source of nitrogen that may encourage plant growth, alter terrestrial plant community composition and affect the surrounding marine ecosystem. To investigate seabird NH3 emissions on a global scale, we developed a contemporary seabird database including a total seabird population of 261 million breeding pairs. We used this in conjunction with a bioenergetics model to estimate the mass of nitrogen excreted by all seabirds at each breeding colony. The results combined with the findings of mid-latitude field studies of volatilization rates estimate the global distribution of NH3 emissions from seabird colonies on an annual basis. The largest uncertainty in our emission estimate concerns the potential temperature dependence of NH3 emission. To investigate this we calculated and compared temperature independent emission estimates with a maximum feasible temperature dependent emission, based on the thermodynamic dissociation and solubility equilibria. Using the temperature independent approach, we estimate global NH3 emissions from seabird colonies at 404 Gg NH3 per year. By comparison, since most seabirds are located in relatively cold circumpolar locations, the thermodynamically dependent estimate is 136 Gg NH3 per year. Actual global emissions are expected to be within these bounds, as other factors, such as non-linear interactions with water availability and surface infiltration, moderate the theoretical temperature response. Combining sources of error from temperature (±49%), seabird population estimates (±36%), variation in diet composition (±23%) and non-breeder attendance (±13%), gives a mid estimate with an overall uncertainty range of NH3 emission from seabird colonies of 270 [97-442] Gg NH3 per year. These emissions are environmentally relevant as they primarily occur as "hot-spots" in otherwise pristine environments with low anthropogenic

  4. Colony formation and colony size do not reflect the onset of replicative senescence in human fibroblasts

    NARCIS (Netherlands)

    Maier, Andrea B.; Maier, Ilko L.; Van Heemst, Diana; Westendorp, Rudi G.J.

    2008-01-01

    Replicative senescence of human fibroblasts in vitro has been used as a model for in vivo aging. The onset of replicative senescence varies between several months to years. A colony formation assay, critically dependent on growth speed, can be performed within weeks, and has been reported being an

  5. Spatial Distribution of Lactococcus lactis Colonies Modulates the Production of Major Metabolites during the Ripening of a Model Cheese.

    Science.gov (United States)

    Le Boucher, Clémentine; Gagnaire, Valérie; Briard-Bion, Valérie; Jardin, Julien; Maillard, Marie-Bernadette; Dervilly-Pinel, Gaud; Le Bizec, Bruno; Lortal, Sylvie; Jeanson, Sophie; Thierry, Anne

    2015-10-23

    In cheese, lactic acid bacteria are immobilized at the coagulation step and grow as colonies. The spatial distribution of bacterial colonies is characterized by the size and number of colonies for a given bacterial population within cheese. Our objective was to demonstrate that different spatial distributions, which lead to differences in the exchange surface between the colonies and the cheese matrix, can influence the ripening process. The strategy was to generate cheeses with the same growth and acidification of a Lactococcus lactis strain with two different spatial distributions, big and small colonies, to monitor the production of the major ripening metabolites, including sugars, organic acids, peptides, free amino acids, and volatile metabolites, over 1 month of ripening. The monitored metabolites were qualitatively the same for both cheeses, but many of them were more abundant in the small-colony cheeses than in the big-colony cheeses over 1 month of ripening. Therefore, the results obtained showed that two different spatial distributions of L. lactis modulated the ripening time course by generating moderate but significant differences in the rates of production or consumption for many of the metabolites commonly monitored throughout ripening. The present work further explores the immobilization of bacteria as colonies within cheese and highlights the consequences of this immobilization on cheese ripening. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  6. Spatial Distribution of Lactococcus lactis Colonies Modulates the Production of Major Metabolites during the Ripening of a Model Cheese

    Science.gov (United States)

    Le Boucher, Clémentine; Gagnaire, Valérie; Briard-Bion, Valérie; Jardin, Julien; Maillard, Marie-Bernadette; Dervilly-Pinel, Gaud; Le Bizec, Bruno; Lortal, Sylvie; Jeanson, Sophie

    2015-01-01

    In cheese, lactic acid bacteria are immobilized at the coagulation step and grow as colonies. The spatial distribution of bacterial colonies is characterized by the size and number of colonies for a given bacterial population within cheese. Our objective was to demonstrate that different spatial distributions, which lead to differences in the exchange surface between the colonies and the cheese matrix, can influence the ripening process. The strategy was to generate cheeses with the same growth and acidification of a Lactococcus lactis strain with two different spatial distributions, big and small colonies, to monitor the production of the major ripening metabolites, including sugars, organic acids, peptides, free amino acids, and volatile metabolites, over 1 month of ripening. The monitored metabolites were qualitatively the same for both cheeses, but many of them were more abundant in the small-colony cheeses than in the big-colony cheeses over 1 month of ripening. Therefore, the results obtained showed that two different spatial distributions of L. lactis modulated the ripening time course by generating moderate but significant differences in the rates of production or consumption for many of the metabolites commonly monitored throughout ripening. The present work further explores the immobilization of bacteria as colonies within cheese and highlights the consequences of this immobilization on cheese ripening. PMID:26497453

  7. Efficient distribution of toy products using ant colony optimization algorithm

    Science.gov (United States)

    Hidayat, S.; Nurpraja, C. A.

    2017-12-01

    CV Atham Toys (CVAT) produces wooden toys and furniture, comprises 13 small and medium industries. CVAT always attempt to deliver customer orders on time but delivery costs are high. This is because of inadequate infrastructure such that delivery routes are long, car maintenance costs are high, while fuel subsidy by the government is still temporary. This study seeks to minimize the cost of product distribution based on the shortest route using one of five Ant Colony Optimization (ACO) algorithms to solve the Vehicle Routing Problem (VRP). This study concludes that the best of the five is the Ant Colony System (ACS) algorithm. The best route in 1st week gave a total distance of 124.11 km at a cost of Rp 66,703.75. The 2nd week route gave a total distance of 132.27 km at a cost of Rp 71,095.13. The 3rd week best route gave a total distance of 122.70 km with a cost of Rp 65,951.25. While the 4th week gave a total distance of 132.27 km at a cost of Rp 74,083.63. Prior to this study there was no effort to calculate these figures.

  8. The distribution of depleted uranium contamination in Colonie, NY, USA.

    Science.gov (United States)

    Lloyd, N S; Chenery, S R N; Parrish, R R

    2009-12-20

    Uranium oxide particles were dispersed into the environment from a factory in Colonie (NY, USA) by prevailing winds during the 1960s and '70s. Uranium concentrations and isotope ratios from bulk soil samples have been accurately measured using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) without the need for analyte separation chemistry. The natural range of uranium concentrations in the Colonie soils has been estimated as 0.7-2.1 microg g(-1), with a weighted geometric mean of 1.05 microg g(-1); the contaminated soil samples comprise uranium up to 500+/-40 microg g(-1). A plot of (236)U/(238)U against (235)U/(238)U isotope ratios describes a mixing line between natural uranium and depleted uranium (DU) in bulk soil samples; scatter from this line can be accounted for by heterogeneity in the DU particulate. The end-member of DU compositions aggregated in these bulk samples comprises (2.05+/-0.06) x 10(-3)(235)U/(238)U, (3.2+/-0.1)x10(-5)(236)U/(238)U, and (7.1+/-0.3) x 10(-6)(234)U/(238)U. The analytical method is sensitive to as little as 50 ng g(-1) DU mixed with the natural uranium occurring in these soils. The contamination footprint has been mapped northward from site, and at least one third of the uranium in a soil sample from the surface 5 cm, collected 5. 1km NNW of the site, is DU. The distribution of contamination within the surface soil horizon follows a trend of exponential decrease with depth, which can be approximated by a simple diffusion model. Bioturbation by earthworms can account for dispersal of contaminant from the soil surface, in the form of primary uranium oxide particulates, and uranyl species that are adsorbed to organic matter. Considering this distribution, the total mass of uranium contamination emitted from the factory is estimated to be c. 4.8 tonnes.

  9. On the Size Distribution of Sand

    DEFF Research Database (Denmark)

    Sørensen, Michael

    2016-01-01

    by Bagnold and confirmed in numerous empirical studies. The model implies that the size distribution of a sand deposit is a logarithmic normal-inverse Gaussian (NIG) distribution, which is one of the generalized hyperbolic distributions. The model modifies a previous model, which implied a log-normal size-distribution......, variance and skewness of the log-size distribution to the physical parameters of the model. The results might be useful when comparing empirical size-distributions from different deposits. It is argued that size-distributions with the same general shape as the NIG-distributions can be obtained also when......A model is presented of the development of the size distribution of sand while it is transported from a source to a deposit. The model provides a possible explanation of the log-hyperbolic shape that is frequently found in unimodal grain size distributions in natural sand deposits, as pointed out...

  10. Colony size is linked to paternity frequency and paternity skew in yellowjacket wasps and hornets.

    Science.gov (United States)

    Loope, Kevin J; Chien, Chun; Juhl, Michael

    2014-12-30

    The puzzle of the selective benefits of multiple mating and multiple paternity in social insects has been a major focus of research in evolutionary biology. We examine paternity in a clade of social insects, the vespine wasps (the yellowjackets and hornets), which contains species with high multiple paternity as well as species with single paternity. This group is particularly useful for comparative analyses given the wide interspecific variation in paternity traits despite similar sociobiology and ecology of the species in the genera Vespula, Dolichovespula and Vespa. We describe the paternity of 5 species of yellowjackets (Vespula spp.) and we perform a phylogenetically controlled comparative analysis of relatedness, paternity frequency, paternity skew, colony size, and nest site across 22 vespine taxa. We found moderate multiple paternity in four small-colony Vespula rufa-group species (effective paternity 1.5 - 2.1), and higher multiple paternity in the large-colony Vespula flavopilosa (effective paternity ~3.1). Our comparative analysis shows that colony size, but not nest site, predicts average intracolony relatedness. Underlying this pattern, we found that greater colony size is associated with both higher paternity frequency and reduced paternity skew. Our results support hypotheses focusing on the enhancement of genetic diversity in species with large colonies, and run counter to the hypothesis that multiple paternity is adaptively maintained due to sperm limitation associated with large colonies. We confirm the patterns observed in taxonomically widespread analyses by comparing closely related species of wasps with similar ecology, behavior and social organization. The vespine wasps may be a useful group for experimental investigation of the benefits of multiple paternity in the future.

  11. Foraging distance and population size of juvenile colonies of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae) in laboratory extended arenas

    Science.gov (United States)

    The relationship between colony size and foraging distance was examined in extended foraging arenas with incipient colonies of the Formosan subterranean termite, Coptotermes formosanus Shiraki. Our results showed that as long as the royal pairs are present, larger colonies foraged at longer distance...

  12. Vocal activity as a low cost and scalable index of seabird colony size.

    Science.gov (United States)

    Borker, Abraham L; McKown, Matthew W; Ackerman, Joshua T; Eagles-Smith, Collin A; Tershy, Bernie R; Croll, Donald A

    2014-08-01

    Although wildlife conservation actions have increased globally in number and complexity, the lack of scalable, cost-effective monitoring methods limits adaptive management and the evaluation of conservation efficacy. Automated sensors and computer-aided analyses provide a scalable and increasingly cost-effective tool for conservation monitoring. A key assumption of automated acoustic monitoring of birds is that measures of acoustic activity at colony sites are correlated with the relative abundance of nesting birds. We tested this assumption for nesting Forster's terns (Sterna forsteri) in San Francisco Bay for 2 breeding seasons. Sensors recorded ambient sound at 7 colonies that had 15-111 nests in 2009 and 2010. Colonies were spaced at least 250 m apart and ranged from 36 to 2,571 m(2) . We used spectrogram cross-correlation to automate the detection of tern calls from recordings. We calculated mean seasonal call rate and compared it with mean active nest count at each colony. Acoustic activity explained 71% of the variation in nest abundance between breeding sites and 88% of the change in colony size between years. These results validate a primary assumption of acoustic indices; that is, for terns, acoustic activity is correlated to relative abundance, a fundamental step toward designing rigorous and scalable acoustic monitoring programs to measure the effectiveness of conservation actions for colonial birds and other acoustically active wildlife. © 2014 Society for Conservation Biology.

  13. Foraging pattern, colony distribution, and foraging range of the Florida harvester ant, Pogonomyrmex badius

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, J.S. (Savannah River Ecology Laboratory); Gentry, J.B.; Aiken, S.C.

    1981-12-01

    This report describes the foraging pattern of the Florida harvester ant Pogonomyrmex badius in a high-density population of colonies. The foraging pattern has both promoted and been influenced by the colony distribution. Pogonomyrmex badius forages from short trails which extend into a surrounding foraging range. Direction of foraging trails is influenced by the location of a colony's near neighbors. Seasonal nest relocations always occur along a foraging trail, usually the main trail. Foraging ranges are not actively defended, but are used almost exclusively by foragers from a single colony. Foraging ranges will be extended into an area abandoned by neighboring foragers, indicating that forager presence may define each colony's range. Colony distribution has remained essentially the same for several years, despite seasonal nest relocations and addition of new colonies. Establishment of trails and exclusive foraging ranges by each colony minimizes encounters with neighboring foragers and guarantees access to available resources; this pattern also promotes maintenance of the existing colony distribution and partitioning of resources.

  14. Foraging pattern, colony distribution, and foraging range of the Florida harvester ant Pogonomyrmex badius

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, J.S.; Gentry, J.B.

    1981-12-01

    This report describes the foraging pattern of the Florida harvester ant Pogonomyrmex badius in a high-density population of colonies. The foraging pattern has both promoted and been influenced by the colony distribution. Pogonomyrmex badius forages from short trails which extend into a surrounding foraging range. Direction of foraging trails is influenced by the location of a colony's near neighbors. Seasonal nest relocations always occur along a foraging trail, usually the main trail. Foraging ranges are not actively defended, but are used almost exclusively by foragers from a single colony. Foraging ranges will be extended into an area abondoned by neighboring foragers, indicating that forager presence may define each colony's range. Colony distribution has remained essentially the same for several years, despite seasonal nest relocations and addition of new colonies. Establishment of trails and exclusive foraging ranges by each colony minimizes encounters with neighboring foragers and guarantees access to available resources; this pattern also pomotes maintenance of the existing colony distribution and partitioning of resources.

  15. The distribution of depleted uranium contamination in Colonie, NY, USA

    OpenAIRE

    Lloyd, N.S.; Chenery, S.R.N.; Parrish, R. R.

    2009-01-01

    Uranium oxide particles were dispersed into the environment from a factory in Colonie (NY, USA) by prevailing winds during the 1960’s and ’70’s. Uranium concentrations and isotope ratios from bulk soil samples have been accurately measured using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) without the need for analyte separation chemistry. The natural range of uranium concentrations in the Colonie soils has been estimated as 0.7 – 2.1 μg g-1, with a weighted geometric mea...

  16. Modeling particle size distributions by the Weibull distribution function

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Zhigang (Rogers Tool Works, Rogers, AR (United States)); Patterson, B.R.; Turner, M.E. Jr (Univ. of Alabama, Birmingham, AL (United States))

    1993-10-01

    A method is proposed for modeling two- and three-dimensional particle size distributions using the Weibull distribution function. Experimental results show that, for tungsten particles in liquid phase sintered W-14Ni-6Fe, the experimental cumulative section size distributions were well fit by the Weibull probability function, which can also be used to compute the corresponding relative frequency distributions. Modeling the two-dimensional section size distributions facilitates the use of the Saltykov or other methods for unfolding three-dimensional (3-D) size distributions with minimal irregularities. Fitting the unfolded cumulative 3-D particle size distribution with the Weibull function enables computation of the statistical distribution parameters from the parameters of the fit Weibull function.

  17. Aggregate size distributions in hydrophobic flocculation

    Directory of Open Access Journals (Sweden)

    Chairoj Rattanakawin

    2003-07-01

    Full Text Available The evolution of aggregate (floc size distributions resulting from hydrophobic flocculation has been investigated using a laser light scattering technique. By measuring floc size distributions it is possible to distinguish clearly among floc formation, growth and breakage. Hydrophobic flocculation of hematite suspensions with sodium oleate under a variety of agitating conditions produces uni-modal size distributions. The size distribution of the primary particles is shifted to larger floc sizes when the dispersed suspension is coagulated by pH adjustment. By adding sodium oleate to the pre-coagulated suspension, the distribution progresses further to the larger size. However, prolonged agitation degrades the formed flocs, regressing the distribution to the smaller size. Median floc size derived from the distribution is also used as performance criterion. The median floc size increases rapidly at the initial stage of the flocculation, and decreases with the extended agitation time and intensity. Relatively weak flocs are produced which may be due to the low dosage of sodium oleate used in this flocculation study. It is suggested that further investigation should focus on optimum reagent dosage and non-polar oil addition to strengthen these weak flocs.

  18. Body Size Distribution of the Dinosaurs

    Science.gov (United States)

    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

  19. Body size distribution of the dinosaurs.

    Science.gov (United States)

    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.

  20. Population trends and distribution of Common Murre Uria aalge colonies in Washington, 1996-2015

    Science.gov (United States)

    Thomas, Susan M; Lyons, James E.

    2017-01-01

    Periodic assessments of population trends and changes in spatial distribution are valuable for managing marine birds and their breeding habitats, particularly when evaluating long-term response to threats such as oil spills, predation pressure, and changing ocean conditions. We evaluated recent trends in abundance and distribution of the Common Murre Uria aalge within Copalis, Quillayute Needles, and Flattery Rocks National Wildlife Refuges, which include all murre colonies in Washington except one, off-refuge, on Tatoosh Island. In 1996-2001 and 2010-2015, aerial photographic surveys were conducted during the incubation phase (mid-June through mid-July) each year. Using images from film (1996-2001) and digital (2010-2015) cameras that included all parts of each colony, we manually counted murres. We estimated population trend as annual percent change in whole-colony counts using an overdispersed Poisson regression model. Overall, numbers of murres counted at breeding colonies in Washington increased by 8.8% per year (95% CI 3.0%-14.9%) during 1996–2015. The overall statewide increase was driven by an increase at colonies in northern Washington of approximately 11% per year (95% CI 4.5%-17.8%). Despite an increasing trend, abundance remains lower than levels in the late 1970s, and the spatial distribution has changed. Colonies in southern Washington - where murres were historically the most abundant - are no longer active, or only minimally so, whereas colonies in the north - which were rarely active in the early 1970s - are now the largest. There was high variability in spatial distribution among years, a pattern that indicates a need for coordinated monitoring and movement studies throughout the California Current System to understand dispersal and colonization. Our results indicate that future management of refuge islands could protect both current and historic colony locations, given the patterns of colony dynamics and the uncertainty about long-term effects

  1. Aggregate size distributions in sweep flocculation

    Directory of Open Access Journals (Sweden)

    Chairoj Rattanakawin

    2005-09-01

    Full Text Available The evolution of aggregate size distributions resulting from sweep flocculation has been investigated using laser light scattering technique. By measuring the (volume distributions of floc size, it is possible to distinguish clearly among floc formation, growth and breakage. Sweep flocculation of stable kaolin suspensions with ferric chloride under conditions of the rapid/slow mixing protocol produces uni-modal size distributions. The size distribution is shifted to larger floc size especially during the rapid mixing step. The variation of the distributions is also shown in the plot of cumulative percent finer against floc size. From this plot, the distributions maintain the same S-shape curves over the range of the mixing intensities/times studied. A parallel shift of the curves indicates that self-preserving size distribution occurred in this flocculation. It is suggested that some parameters from mathematical functions derived from the curves could be used to construct a model and predict the flocculating performance. These parameters will be useful for a water treatment process selection, design criteria, and process control strategies. Thus the use of these parameters should be employed in any further study.

  2. Particle size distribution instrument. Topical report 13

    Energy Technology Data Exchange (ETDEWEB)

    Okhuysen, W.; Gassaway, J.D.

    1995-04-01

    The development of an instrument to measure the concentration of particles in gas is described in this report. An in situ instrument was designed and constructed which sizes individual particles and counts the number of occurrences for several size classes. Although this instrument was designed to detect the size distribution of slag and seed particles generated at an experimental coal-fired magnetohydrodynamic power facility, it can be used as a nonintrusive diagnostic tool for other hostile industrial processes involving the formation and growth of particulates. Two of the techniques developed are extensions of the widely used crossed beam velocimeter, providing simultaneous measurement of the size distribution and velocity of articles.

  3. The ecological benefits of larger colony size may promote polygyny in ants.

    Science.gov (United States)

    Boulay, R; Arnan, X; Cerdá, X; Retana, J

    2014-12-01

    How polygyny evolved in social insect societies is a long-standing question. This phenomenon, which is functionally similar to communal breeding in vertebrates, occurs when several queens come together in the same nest to lay eggs that are raised by workers. As a consequence, polygyny drastically reduces genetic relatedness among nestmates. It has been suggested that the short-term benefits procured by group living may outweigh the costs of sharing the same nesting site and thus contribute to organisms rearing unrelated individuals. However, tests of this hypothesis are still limited. To examine the evolutionary emergence of polygyny, we reviewed the literature to build a data set containing life-history traits for 149 Palearctic ant species and combined this data set with a reconstructed phylogeny. We show that monogyny is the ancestral state and that polygyny has evolved secondarily and independently throughout the phylogenetic tree. The occurrence of polygyny is significantly correlated with larger colony size, dependent colony founding and ecological dominance. Although polydomy (when a colony simultaneously uses several connected nests) tends to occur more frequently in polygynous species, this trend is not significant when phylogenetic history is accounted for. Overall, our results indicate that polygyny may have evolved in ants in spite of the reduction in nestmate relatedness because large colony size provides immediate ecological advantages, such as the more efficient use of temporal food resources. We suggest that the competitive context of ant communities may have provided the conditions necessary for the evolution of polygyny in some clades. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

  4. Understanding animal group-size distributions.

    Directory of Open Access Journals (Sweden)

    Michael Griesser

    Full Text Available One of the most striking aspects of animal groups is their remarkable variation in size, both within and between species. While a number of mechanistic models have been proposed to explain this variation, there are few comprehensive datasets against which these models have been tested. In particular, we only vaguely understand how environmental factors and behavioral activities affect group-size distributions. Here we use observations of House sparrows (Passer domesticus to investigate the factors determining group-size distribution. Over a wide range of conditions, we observed that animal group sizes followed a single parameter distribution known as the logarithmic distribution. This single parameter is the mean group size experienced by a randomly chosen individual (including the individual itself. For sparrows, the experienced mean group size, and hence the distribution, was affected by four factors: morning temperature, place, behavior and the degree of food spillage. Our results further indicate that the sparrows regulate the mean group size they experience, either by groups splitting more or merging less when local densities are high. We suggest that the mean experienced group size provides a simple but general tool for assessing the ecology and evolution of grouping.

  5. Particle size distribution predicts particulate phosphorus removal

    National Research Council Canada - National Science Library

    River, Mark; Richardson, Curtis J

    2018-01-01

    ... particles, based on a continuous particle size distribution. This information can help improve the design of stormwater Best management practices to reduce PP loading in both urban and agricultural watersheds.

  6. The exponential age distribution and the Pareto firm size distribution

    OpenAIRE

    Coad, Alex

    2008-01-01

    Recent work drawing on data for large and small firms has shown a Pareto distribution of firm size. We mix a Gibrat-type growth process among incumbents with an exponential distribution of firm's age, to obtain the empirical Pareto distribution.

  7. Bubble Size Distributions in Coastal Seas

    NARCIS (Netherlands)

    Leeuw, G. de; Cohen, L.H.

    1995-01-01

    Bubble size distributions have been measured with an optical system that is based on imaging of a small sample volume with a CCD camera system, and processing of the images to obtain the size of individual bubbles in the diameter range from 30 to lOOO^m. This bubble measuring system is deployed from

  8. Latitudinal gradients in sea ice and primary production determine Arctic seabird colony size in Greenland.

    Science.gov (United States)

    Laidre, Kristin L; Heide-Jørgensen, Mads Peter; Nyeland, Jens; Mosbech, Anders; Boertmann, David

    2008-12-07

    Sea ice loss will indirectly alter energy transfer through the pelagic food web and ultimately impact apex predators. We quantified spring-time trends in sea ice recession around each of 46 thick-billed murre (Uria lomvia) colonies in west Greenland across 20 degrees of latitude and investigated the magnitude and timing of the associated spring-time primary production. A geographical information system was used to extract satellite-based observations of sea ice concentration from the Nimbus-7 scanning multichannel microwave radiometer (SMMR, 1979-1987) and the Defence Meteorological Satellite Programs Special Sensor Microwave/Imager (SSMI, 1987-2004), and satellite-based observations of chlorophyll a from the moderate resolution imaging spectroradiometer (MODIS: EOS-Terra satellite) in weekly intervals in circular buffers around each colony site (150 km in radius). Rapid recession of high Arctic seasonal ice cover created a temporally predictable primary production bloom and associated trophic cascade in water gradually exposed to solar radiation. This pattern was largely absent from lower latitudes where little to no sea ice resulted in a temporally variable primary production bloom driven by nutrient cycling and upwelling uncoupled to ice. The relationship between the rate and variability of sea ice recession and colony size of thick-billed murres shows that periodical confinement of the trophic cascade at high latitudes determines the carrying capacity for Arctic seabirds during the breeding period.

  9. Particle Size Distributions in Atmospheric Clouds

    Science.gov (United States)

    Paoli, Roberto; Shariff, Karim

    2003-01-01

    In this note, we derive a transport equation for a spatially integrated distribution function of particles size that is suitable for sparse particle systems, such as in atmospheric clouds. This is done by integrating a Boltzmann equation for a (local) distribution function over an arbitrary but finite volume. A methodology for evolving the moments of the integrated distribution is presented. These moments can be either tracked for a finite number of discrete populations ('clusters') or treated as continuum variables.

  10. Effects of within-colony competition on body size asymmetries and reproductive skew in a social spider

    DEFF Research Database (Denmark)

    Grinsted, Lena; Bilde, Trine

    2013-01-01

    Reproductive partitioning is a key component of social organization in groups of cooperative organisms. In colonies of permanently social spiders of the genus Stegodyphus less than half of the females reproduce, while all females, including nonreproducers, perform suicidal allo-maternal care. Some...... not increase over the course of the experiment, suggesting that body size variation is shaped at an early stage. This might facilitate task specialization within colonies and ensure colony-level reproductive output by early allocation of reproductive roles. We suggest that reproductive skew in social spiders...

  11. Determination of size distribution using neural networks

    NARCIS (Netherlands)

    Stevens, JH; Nijhuis, JAG; Spaanenburg, L; Mohammadian, M

    1999-01-01

    In this paper we present a novel approach to the estimation of size distributions of grains in water from images. External conditions such as the concentrations of grains in water cannot be controlled. This poses problems for local image analysis which tries to identify and measure single grains.

  12. Suspended sediment concentration and particle size distribution ...

    Indian Academy of Sciences (India)

    ... particle size distribution (PSD) were correlated with HMC by using bivariate and multivariate regression models. Proposed models were then selected based on statistical criteria. The results showed high correlation between dissolved and particulate chromium content with efficiency coefficients beyond 77% ( > 0.001).

  13. to medium-sized water distribution systems

    African Journals Online (AJOL)

    Framework for optimizing chlorine dose in small- to medium-sized water distribution systems: A case of a residential neighbourhood in Lahore, Pakistan. ... The bulk decay coefficient (Kb) was determined in the laboratory, whereas the wall decay coefficient (Kw) was estimated by calibrating the simulation results with the ...

  14. The relationship between canopy cover and colony size of the wood ant Formica lugubris--implications for the thermal effects on a keystone ant species.

    Directory of Open Access Journals (Sweden)

    Yi-Huei Chen

    Full Text Available Climate change may affect ecosystems and biodiversity through the impacts of rising temperature on species' body size. In terms of physiology and genetics, the colony is the unit of selection for ants so colony size can be considered the body size of a colony. For polydomous ant species, a colony is spread across several nests. This study aims to clarify how climate change may influence an ecologically significant ant species group by investigating thermal effects on wood ant colony size. The strong link between canopy cover and the local temperatures of wood ant's nesting location provides a feasible approach for our study. Our results showed that nests were larger in shadier areas where the thermal environment was colder and more stable compared to open areas. Colonies (sum of nests in a polydomous colony also tended to be larger in shadier areas than in open areas. In addition to temperature, our results supported that food resource availability may be an additional factor mediating the relationship between canopy cover and nest size. The effects of canopy cover on total colony size may act at the nest level because of the positive relationship between total colony size and mean nest size, rather than at the colony level due to lack of link between canopy cover and number of nests per colony. Causal relationships between the environment and the life-history characteristics may suggest possible future impacts of climate change on these species.

  15. Image Analysis for Particle Size Distribution

    OpenAIRE

    Shanthi, C; R. Kingsley Porpatham; Pappa, N.

    2014-01-01

    Particle size distribution (PSD) affects properties of particulate materials and is used for denoting their quality and performance. Among many techniques available to measure PSD, many are quite often offline methods and are time consuming. Also methods like sieving involve, handling of the material physically and electromagnetically, which is healthy, if avoided for certain materials. Thus the need for an online PSD analyzer and the advent of digital image processing has rendered the drift ...

  16. Indoor aerosol size distributions in a gymnasium.

    Science.gov (United States)

    Castro, Amaya; Calvo, Ana I; Alves, Célia; Alonso-Blanco, Elisabeth; Coz, Esther; Marques, Liliana; Nunes, Teresa; Fernández-Guisuraga, Jose Manuel; Fraile, Roberto

    2015-08-15

    In this study, an indoor/outdoor monitoring program was carried out in a gymnasium at the University of Leon, Spain. The main goal was a characterization of aerosol size distributions in a university gymnasium under different conditions and sports activities (with and without magnesia alba) and the study of the mass fraction deposited in each of the parts of the respiratory tract. The aerosol particles were measured in 31 discrete channels (size ranges) using a laser spectrometer probe. Aerosol size distributions were studied under different conditions: i) before sports activities, ii) activities without using magnesia alba, iii) activities using magnesia alba, iv) cleaning procedures, and v) outdoors. The aerosol refractive index and density indoors were estimated from the aerosol composition: 1.577-0.003i and 2.055 g cm(-3), respectively. Using the estimated density, the mass concentration was calculated, and the evolution of PM1, PM2.5 and PM10 for different activities was assessed. The quality of the air in the gymnasium was strongly influenced by the use of magnesia alba (MgCO3) and the number of gymnasts who were training. Due to the climbing chalk and the constant process of resuspension, average PM10 concentrations of over 440 μg m(-3) were reached. The maximum daily concentrations ranged from 500 to 900 μg m(-3). Particle size determines the place in the respiratory tract where the deposition occurs. For this reason, the inhalable, thoracic, tracheobronchial and respirable fractions were assessed for healthy adults and high risk people, according to international standards. The estimations show that, for healthy adults, up to 300 μg m(-3) can be retained by the trachea and bronchi, and 130 μg m(-3) may reach the alveolar region. The different physical activities and the attendance rates in the sports facility have a significant influence on the concentration and size distributions observed. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Particle size distribution in ground biological samples.

    Science.gov (United States)

    Koglin, D; Backhaus, F; Schladot, J D

    1997-05-01

    Modern trace and retrospective analysis of Environmental Specimen Bank (ESB) samples require surplus material prepared and characterized as reference materials. Before the biological samples could be analyzed and stored for long periods at cryogenic temperatures, the materials have to be pre-crushed. As a second step, a milling and homogenization procedure has to follow. For this preparation, a grinding device is cooled with liquid nitrogen to a temperature of -190 degrees C. It is a significant condition for homogeneous samples that at least 90% of the particles should be smaller than 200 microns. In the German ESB the particle size distribution of the processed material is determined by means of a laser particle sizer. The decrease of particle sizes of deer liver and bream muscles after different grinding procedures as well as the consequences of ultrasonic treatment of the sample before particle size measurements have been investigated.

  18. Remote Laser Diffraction Particle Size Distribution Analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Batcheller, Thomas Aquinas; Huestis, Gary Michael; Bolton, Steven Michael

    2001-03-01

    In support of a radioactive slurry sampling and physical characterization task, an “off-the-shelf” laser diffraction (classical light scattering) particle size analyzer was utilized for remote particle size distribution (PSD) analysis. Spent nuclear fuel was previously reprocessed at the Idaho Nuclear Technology and Engineering Center (INTEC—formerly recognized as the Idaho Chemical Processing Plant) which is on DOE’s INEEL site. The acidic, radioactive aqueous raffinate streams from these processes were transferred to 300,000 gallon stainless steel storage vessels located in the INTEC Tank Farm area. Due to the transfer piping configuration in these vessels, complete removal of the liquid can not be achieved. Consequently, a “heel” slurry remains at the bottom of an “emptied” vessel. Particle size distribution characterization of the settled solids in this remaining heel slurry, as well as suspended solids in the tank liquid, is the goal of this remote PSD analyzer task. A Horiba Instruments Inc. Model LA-300 PSD analyzer, which has a 0.1 to 600 micron measurement range, was modified for remote application in a “hot cell” (gamma radiation) environment. This technology provides rapid and simple PSD analysis, especially down in the fine and microscopic particle size regime. Particle size analysis of these radioactive slurries down in this smaller range was not previously achievable—making this technology far superior than the traditional methods used. Successful acquisition of this data, in conjunction with other characterization analyses, provides important information that can be used in the myriad of potential radioactive waste management alternatives.

  19. Infestation and distribution of the mite Varroa destructor in colonies of africanized bees

    Directory of Open Access Journals (Sweden)

    G. Moretto

    Full Text Available Whereas in several parts of the world varroa is the major pest affecting apiculture, in others the parasite is unknown to many beekeepers because its damage to bees is minor. The impact of the mite Varroa destructor is related to the climatic conditions and the races of Apis mellifera bees in each region where the pest exists. In the present study, the current level of infestation by the mite was assessed to determine the evolution of the pest in Africanized bee colonies in Southern Brazil. This level of infestation was considered low: approximately two mites per one hundred adult bees. This result is similar to that obtained for the same apiary almost five years ago and for others distributed in various regions of Brazil. In the present study, we also estimated the total varroa population and its distribution among brood and adults in each bee colony.

  20. Sample size calculations for skewed distributions.

    Science.gov (United States)

    Cundill, Bonnie; Alexander, Neal D E

    2015-04-02

    Sample size calculations should correspond to the intended method of analysis. Nevertheless, for non-normal distributions, they are often done on the basis of normal approximations, even when the data are to be analysed using generalized linear models (GLMs). For the case of comparison of two means, we use GLM theory to derive sample size formulae, with particular cases being the negative binomial, Poisson, binomial, and gamma families. By simulation we estimate the performance of normal approximations, which, via the identity link, are special cases of our approach, and for common link functions such as the log. The negative binomial and gamma scenarios are motivated by examples in hookworm vaccine trials and insecticide-treated materials, respectively. Calculations on the link function (log) scale work well for the negative binomial and gamma scenarios examined and are often superior to the normal approximations. However, they have little advantage for the Poisson and binomial distributions. The proposed method is suitable for sample size calculations for comparisons of means of highly skewed outcome variables.

  1. A natural antipredation experiment: predator control and reduced sea ice increases colony size in a long-lived duck.

    Science.gov (United States)

    Hanssen, Sveinn A; Moe, Børge; Bårdsen, Bård-Jørgen; Hanssen, Frank; Gabrielsen, Geir W

    2013-09-01

    Anthropogenic impact on the environment and wildlife are multifaceted and far-reaching. On a smaller scale, controlling for predators has been increasing the yield from local natural prey resources. Globally, human-induced global warming is expected to impose severe negative effects on ecosystems, an effect that is expected to be even more pronounced in the scarcely populated northern latitudes. The clearest indication of a changing Arctic climate is an increase in both air and ocean temperatures leading to reduced sea ice distribution. Population viability is for long-lived species dependent on adult survival and recruitment. Predation is the main mortality cause in many bird populations, and egg predation is considered the main cause of reproductive failure in many birds. To assess the effect of predation and climate, we compared population time series from a natural experiment where a trapper/down collector has been licensed to actively protect breeding common eiders Somateria mollissima (a large seaduck) by shooting/chasing egg predators, with time series from another eider colony located within a nature reserve with no manipulation of egg predators. We found that actively limiting predator activity led to an increase in the population growth rate and carrying capacity with a factor of 3-4 compared to that found in the control population. We also found that population numbers were higher in years with reduced concentration of spring sea ice. We conclude that there was a large positive impact of human limitation of egg predators, and that this lead to higher population growth rate and a large increase in size of the breeding colony. We also report a positive effect of warming climate in the high arctic as reduced sea-ice concentrations was associated with higher numbers of breeding birds.

  2. Particle size distribution predicts particulate phosphorus removal.

    Science.gov (United States)

    River, Mark; Richardson, Curtis J

    2018-01-01

    Particulate phosphorus (PP) is often the largest component of the total phosphorus (P) load in stormwater. Fine-resolution measurement of particle sizes allows us to investigate the mechanisms behind the removal of PP in stormwater wetlands, since the diameter of particles influences the settling velocity and the amount of sorbed P on a particle. In this paper, we present a novel method to estimate PP, where we measure and count individual particles in stormwater and use the total surface area as a proxy for PP. Our results show a strong relationship between total particle surface area and PP, which we use to put forth a simple mechanistic model of PP removal via gravitational settling of individual mineral particles, based on a continuous particle size distribution. This information can help improve the design of stormwater Best management practices to reduce PP loading in both urban and agricultural watersheds.

  3. Electronic cigarette aerosol particle size distribution measurements.

    Science.gov (United States)

    Ingebrethsen, Bradley J; Cole, Stephen K; Alderman, Steven L

    2012-12-01

    The particle size distribution of aerosols produced by electronic cigarettes was measured in an undiluted state by a spectral transmission procedure and after high dilution with an electrical mobility analyzer. The undiluted e-cigarette aerosols were found to have particle diameters of average mass in the 250-450 nm range and particle number concentrations in the 10(9) particles/cm(3) range. These measurements are comparable to those observed for tobacco burning cigarette smoke in prior studies and also measured in the current study with the spectral transmission method and with the electrical mobility procedure. Total particulate mass for the e-cigarettes calculated from the size distribution parameters measured by spectral transmission were in good agreement with replicate determinations of total particulate mass by gravimetric filter collection. In contrast, average particle diameters determined for e-cigarettes by the electrical mobility method are in the 50 nm range and total particulate masses calculated based on the suggested diameters are orders of magnitude smaller than those determined gravimetrically. This latter discrepancy, and the very small particle diameters observed, are believed to result from almost complete e-cigarette aerosol particle evaporation at the dilution levels and conditions of the electrical mobility analysis. A much smaller degree, ~20% by mass, of apparent particle evaporation was observed for tobacco burning cigarette smoke. The spectral transmission method is validated in the current study against measurements on tobacco burning cigarette smoke, which has been well characterized in prior studies, and is supported as yielding an accurate characterization of the e-cigarette aerosol particle size distribution.

  4. Particle Size Distribution in Aluminum Manufacturing Facilities.

    Science.gov (United States)

    Liu, Sa; Noth, Elizabeth M; Dixon-Ernst, Christine; Eisen, Ellen A; Cullen, Mark R; Hammond, S Katharine

    2014-10-01

    As part of exposure assessment for an ongoing epidemiologic study of heart disease and fine particle exposures in aluminum industry, area particle samples were collected in production facilities to assess instrument reliability and particle size distribution at different process areas. Personal modular impactors (PMI) and Minimicro-orifice uniform deposition impactors (MiniMOUDI) were used. The coefficient of variation (CV) of co-located samples was used to evaluate the reproducibility of the samplers. PM2.5 measured by PMI was compared to PM2.5 calculated from MiniMOUDI data. Mass median aerodynamic diameter (MMAD) and concentrations of sub-micrometer (PM1.0) and quasi-ultrafine (PM0.56) particles were evaluated to characterize particle size distribution. Most of CVs were less than 30%. The slope of the linear regression of PMI_PM2.5 versus MiniMOUDI_PM2.5 was 1.03 mg/m3 per mg/m3 (± 0.05), with correlation coefficient of 0.97 (± 0.01). Particle size distribution varied substantively in smelters, whereas it was less variable in fabrication units with significantly smaller MMADs (arithmetic mean of MMADs: 2.59 μm in smelters vs. 1.31 μm in fabrication units, p = 0.001). Although the total particle concentration was more than two times higher in the smelters than in the fabrication units, the fraction of PM10 which was PM1.0 or PM0.56 was significantly lower in the smelters than in the fabrication units (p particles were similar in these two types of facilities. It would appear, studies evaluating ultrafine particle exposure in aluminum industry should focus on not only the smelters, but also the fabrication facilities.

  5. Particle Size Distribution in Aluminum Manufacturing Facilities

    Science.gov (United States)

    Liu, Sa; Noth, Elizabeth M.; Dixon-Ernst, Christine; Eisen, Ellen A.; Cullen, Mark R.; Hammond, S. Katharine

    2015-01-01

    As part of exposure assessment for an ongoing epidemiologic study of heart disease and fine particle exposures in aluminum industry, area particle samples were collected in production facilities to assess instrument reliability and particle size distribution at different process areas. Personal modular impactors (PMI) and Minimicro-orifice uniform deposition impactors (MiniMOUDI) were used. The coefficient of variation (CV) of co-located samples was used to evaluate the reproducibility of the samplers. PM2.5 measured by PMI was compared to PM2.5 calculated from MiniMOUDI data. Mass median aerodynamic diameter (MMAD) and concentrations of sub-micrometer (PM1.0) and quasi-ultrafine (PM0.56) particles were evaluated to characterize particle size distribution. Most of CVs were less than 30%. The slope of the linear regression of PMI_PM2.5 versus MiniMOUDI_PM2.5 was 1.03 mg/m3 per mg/m3 (± 0.05), with correlation coefficient of 0.97 (± 0.01). Particle size distribution varied substantively in smelters, whereas it was less variable in fabrication units with significantly smaller MMADs (arithmetic mean of MMADs: 2.59 μm in smelters vs. 1.31 μm in fabrication units, p = 0.001). Although the total particle concentration was more than two times higher in the smelters than in the fabrication units, the fraction of PM10 which was PM1.0 or PM0.56 was significantly lower in the smelters than in the fabrication units (p < 0.001). Consequently, the concentrations of sub-micrometer and quasi-ultrafine particles were similar in these two types of facilities. It would appear, studies evaluating ultrafine particle exposure in aluminum industry should focus on not only the smelters, but also the fabrication facilities. PMID:26478760

  6. Field evidence for colony size and aseasonality of breeding and in ...

    African Journals Online (AJOL)

    Ansell's mole-rat, Fukomys anselli, is a cooperatively breeding bathyergid endemic to the Lusaka Province of Zambia. During a 12-month field study involving the capture of 33 colonies of mole-rats, the number of occupants, breeding females and sex ratio within colonies were recorded. While thirty of these social groups ...

  7. Queen-worker caste ratio depends on colony size in the pharaoh ant (Monomorium pharaonis)

    DEFF Research Database (Denmark)

    Schmidt, Anna Mosegaard; Linksvayer, Timothy Arnold; Boomsma, Jacobus Jan

    2011-01-01

    The success of an ant colony depends on the simultaneous presence of reproducing queens and nonreproducing workers in a ratio that will maximize colony growth and reproduction. Despite its presumably crucial role, queen–worker caste ratios (the ratio of adult queens to workers) and the factors......, for the first time in a social insect, we confirmed the general life history prediction by Smith and Fretwell (Am Nat 108:499–506, 1974) that offspring number varies more than offspring size. Our findings document a high level of plasticity in energy allocation toward female castes and suggest that polygynous...

  8. Simulation study of territory size distributions in subterranean termites.

    Science.gov (United States)

    Jeon, Wonju; Lee, Sang-Hee

    2011-06-21

    In this study, on the basis of empirical data, we have simulated the foraging tunnel patterns of two subterranean termites, Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar), using a two-dimensional model. We have defined a territory as a convex polygon containing a tunnel pattern and explored the effects of competition among termite territory colonies on the territory size distribution in the steady state that was attained after a sufficient simulation time. In the model, territorial competition was characterized by a blocking probability P(block) that quantitatively describes the ease with which a tunnel stops its advancement when it meets another tunnel; higher P(block) values imply easier termination. In the beginning of the simulation run, N=10, 20,…,100 territory seeds, representing the founding pair, were randomly distributed on a square area. When the territory density was less (N=20), the differences in the territory size distributions for different P(block) values were small because the territories had sufficient space to grow without strong competitions. Further, when the territory density was higher (N>20), the territory sizes increased in accordance with the combinational effect of P(block) and N. In order to understand these effects better, we introduced an interference coefficient γ. We mathematically derived γ as a function of P(block) and N: γ(N,P(block))=a(N)P(block)/(P(block)+b(N)). a(N) and b(N) are functions of N/(N+c) and d/(N+c), respectively, and c and d are constants characterizing territorial competition. The γ function is applicable to characterize the territoriality of various species and increases with both the P(block) values and N; higher γ values imply higher limitations of the network growth. We used the γ function, fitted the simulation results, and determined the c and d values. In addition, we have briefly discussed the predictability of the present model by comparing it with our previous lattice model

  9. Grain size distribution in sheared polycrystals

    Science.gov (United States)

    Sarkar, Tanmoy; Biswas, Santidan; Chaudhuri, Pinaki; Sain, Anirban

    2017-12-01

    Plastic deformation in solids induced by external stresses is of both fundamental and practical interest. Using both phase field crystal modeling and molecular dynamics simulations, we study the shear response of monocomponent polycrystalline solids. We subject mesocale polycrystalline samples to constant strain rates in a planar Couette flow geometry for studying its plastic flow, in particular its grain deformation dynamics. As opposed to equilibrium solids where grain dynamics is mainly driven by thermal diffusion, external stress/strain induce a much higher level of grain deformation activity in the form of grain rotation, coalescence, and breakage, mediated by dislocations. Despite this, the grain size distribution of this driven system shows only a weak power-law correction to its equilibrium log-normal behavior. We interpret the grain reorganization dynamics using a stochastic model.

  10. An argument for compositional crystal size distributions

    Science.gov (United States)

    Cashman, Katharine; Riker, Jenny

    2017-04-01

    Crystal size distribution (CSD) measurements have long been used to quantify the crystal content of igneous samples and, by extension, the crystal residence time in magmatic systems. In the simplest systems, crystals nucleate and grow continuously and resulting CSDs produce log linear distributions that can be used to determine the dominant crystal size and total crystal number. Most magmatic systems are not simple, however, and most measured CSDs are not linear. Instead CSDs are commonly curved, with steep linear segments denoting the smallest (groundmass) crystals and flatter linear-to-curved segments recording the larger crystal population. Several explanations have been given for this pattern. There is growing evidence, however, that many crystals are inherited from other parts of the magmatic system (antecrysts); for this reason, measured CSDs are commonly interpreted by fitting the curve with two separate linear trends that, in turn, are used to infer conditions of both pre-eruptive (antecrysts) and syn-eruptive (groundmass) magma storage. There is a problem with this interpretation, however, as many antecrysts have overgrown rims that reflect growth from the transporting melt, growth that was probably synchronous with formation of the groundmass population. Moreover, the rims can contribute substantially to the overall volume of the inherited crystals. From this perspective, the CSD segment representing the large crystal population cannot be interpreted as a single crystallization event, but instead records the combined size of inherited core and overgrown rim. At the same time, both the magnitude and the kinetics of the crystallization event that caused the groundmass crystallization are underestimated when the rims of the large crystals are not included as part of this late-stage event. Here we use examples from both crystallization experiments and natural samples to illustrate the effects of rim growth on CSD form and interpretation. In the case of

  11. Parameterizing Size Distribution in Ice Clouds

    Energy Technology Data Exchange (ETDEWEB)

    DeSlover, Daniel; Mitchell, David L.

    2009-09-25

    PARAMETERIZING SIZE DISTRIBUTIONS IN ICE CLOUDS David L. Mitchell and Daniel H. DeSlover ABSTRACT An outstanding problem that contributes considerable uncertainty to Global Climate Model (GCM) predictions of future climate is the characterization of ice particle sizes in cirrus clouds. Recent parameterizations of ice cloud effective diameter differ by a factor of three, which, for overcast conditions, often translate to changes in outgoing longwave radiation (OLR) of 55 W m-2 or more. Much of this uncertainty in cirrus particle sizes is related to the problem of ice particle shattering during in situ sampling of the ice particle size distribution (PSD). Ice particles often shatter into many smaller ice fragments upon collision with the rim of the probe inlet tube. These small ice artifacts are counted as real ice crystals, resulting in anomalously high concentrations of small ice crystals (D < 100 µm) and underestimates of the mean and effective size of the PSD. Half of the cirrus cloud optical depth calculated from these in situ measurements can be due to this shattering phenomenon. Another challenge is the determination of ice and liquid water amounts in mixed phase clouds. Mixed phase clouds in the Arctic contain mostly liquid water, and the presence of ice is important for determining their lifecycle. Colder high clouds between -20 and -36 oC may also be mixed phase but in this case their condensate is mostly ice with low levels of liquid water. Rather than affecting their lifecycle, the presence of liquid dramatically affects the cloud optical properties, which affects cloud-climate feedback processes in GCMs. This project has made advancements in solving both of these problems. Regarding the first problem, PSD in ice clouds are uncertain due to the inability to reliably measure the concentrations of the smallest crystals (D < 100 µm), known as the “small mode”. Rather than using in situ probe measurements aboard aircraft, we employed a treatment of ice

  12. Costs of task allocation with local feedback: Effects of colony size and extra workers in social insects and other multi-agent systems.

    Science.gov (United States)

    Radeva, Tsvetomira; Dornhaus, Anna; Lynch, Nancy; Nagpal, Radhika; Su, Hsin-Hao

    2017-12-01

    Adaptive collective systems are common in biology and beyond. Typically, such systems require a task allocation algorithm: a mechanism or rule-set by which individuals select particular roles. Here we study the performance of such task allocation mechanisms measured in terms of the time for individuals to allocate to tasks. We ask: (1) Is task allocation fundamentally difficult, and thus costly? (2) Does the performance of task allocation mechanisms depend on the number of individuals? And (3) what other parameters may affect their efficiency? We use techniques from distributed computing theory to develop a model of a social insect colony, where workers have to be allocated to a set of tasks; however, our model is generalizable to other systems. We show, first, that the ability of workers to quickly assess demand for work in tasks they are not currently engaged in crucially affects whether task allocation is quickly achieved or not. This indicates that in social insect tasks such as thermoregulation, where temperature may provide a global and near instantaneous stimulus to measure the need for cooling, for example, it should be easy to match the number of workers to the need for work. In other tasks, such as nest repair, it may be impossible for workers not directly at the work site to know that this task needs more workers. We argue that this affects whether task allocation mechanisms are under strong selection. Second, we show that colony size does not affect task allocation performance under our assumptions. This implies that when effects of colony size are found, they are not inherent in the process of task allocation itself, but due to processes not modeled here, such as higher variation in task demand for smaller colonies, benefits of specialized workers, or constant overhead costs. Third, we show that the ratio of the number of available workers to the workload crucially affects performance. Thus, workers in excess of those needed to complete all tasks

  13. Colony size, cell number, carbon and nitrogen contents of Phaeocystis pouchetii from western Norway

    NARCIS (Netherlands)

    Verity, Peter G.; Whipple, S. J.; Nejstgaard, J. C.; Alderkamp, A.-C.

    Phaeocystis pouchetii is an ecologically important colony-forming marine phytoplankton species in northern hemisphere cold waters. It plays a central role in the processing of biogeochemically important elements in the upper ocean during spring blooms. Here, we report highly significant quantitative

  14. A new stochastic algorithm for inversion of dust aerosol size distribution

    Science.gov (United States)

    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.

  15. Effects of particle size distribution in thick film conductors

    Science.gov (United States)

    Vest, R. W.

    1983-01-01

    Studies of particle size distribution in thick film conductors are discussed. The distribution of particle sizes does have an effect on fired film density but the effect is not always positive. A proper distribution of sizes is necessary, and while the theoretical models can serve as guides to selecting this proper distribution, improved densities can be achieved by empirical variations from the predictions of the models.

  16. Diatom cell size, coloniality and motility: trade-offs between temperature, salinity and nutrient supply with climate change.

    Directory of Open Access Journals (Sweden)

    Filip Svensson

    Full Text Available Reduction in body size has been proposed as a universal response of organisms, both to warming and to decreased salinity. However, it is still controversial if size reduction is caused by temperature or salinity on their own, or if other factors interfere as well. We used natural benthic diatom communities to explore how "body size" (cells and colonies and motility change along temperature (2-26°C and salinity (0.5-7.8 gradients in the brackish Baltic Sea. Fourth-corner analysis confirmed that small cell and colony sizes were associated with high temperature in summer. Average community cell volume decreased linearly with 2.2% per °C. However, cells were larger with artificial warming when nutrient concentrations were high in the cold season. Average community cell volume increased by 5.2% per °C of artificial warming from 0 to 8.5°C and simultaneously there was a selection for motility, which probably helped to optimize growth rates by trade-offs between nutrient supply and irradiation. Along the Baltic Sea salinity gradient cell size decreased with decreasing salinity, apparently mediated by nutrient stoichiometry. Altogether, our results suggest that climate change in this century may polarize seasonality by creating two new niches, with elevated temperature at high nutrient concentrations in the cold season (increasing cell size and elevated temperature at low nutrient concentrations in the warm season (decreasing cell size. Higher temperature in summer and lower salinity by increased land-runoff are expected to decrease the average cell size of primary producers, which is likely to affect the transfer of energy to higher trophic levels.

  17. Evaluation of droplet size distributions using univariate and multivariate approaches

    DEFF Research Database (Denmark)

    Gauno, M.H.; Larsen, C.C.; Vilhelmsen, T.

    2013-01-01

    of the distribution. The current study was aiming to compare univariate and multivariate approach in evaluating droplet size distributions. As a model system, the atomization of a coating solution from a two-fluid nozzle was investigated. The effect of three process parameters (concentration of ethyl cellulose...... in ethanol, atomizing air pressure, and flow rate of coating solution) on the droplet size and droplet size distribution using a full mixed factorial design was used. The droplet size produced by a two-fluid nozzle was measured by laser diffraction and reported as volume based size distribution......Pharmaceutically relevant material characteristics are often analyzed based on univariate descriptors instead of utilizing the whole information available in the full distribution. One example is droplet size distribution, which is often described by the median droplet size and the width...

  18. How Sample Size Affects a Sampling Distribution

    Science.gov (United States)

    Mulekar, Madhuri S.; Siegel, Murray H.

    2009-01-01

    If students are to understand inferential statistics successfully, they must have a profound understanding of the nature of the sampling distribution. Specifically, they must comprehend the determination of the expected value and standard error of a sampling distribution as well as the meaning of the central limit theorem. Many students in a high…

  19. Sequestration and Distribution Characteristics of Cd(II by Microcystis aeruginosa and Its Role in Colony Formation

    Directory of Open Access Journals (Sweden)

    Xiangdong Bi

    2016-01-01

    Full Text Available To investigate the sequestration and distribution characteristics of Cd(II by Microcystis aeruginosa and its role in Microcystis colony formation, M. aeruginosa was exposed to six different Cd(II concentrations for 10 days. Cd(II exposure caused hormesis in the growth of M. aeruginosa. Low concentrations of Cd(II significantly induced formation of small Microcystis colonies (P93% of Cd(II was sequestrated in the groups with lower added concentrations of Cd(II. More than 80% of the sequestrated Cd(II was bioadsorbed by bEPS. The Pearson correlation coefficients of exterior and interior factors related to colony formation of M. aeruginosa revealed that Cd(II could stimulate the production of IPS and bEPS via increasing Cd(II bioaccumulation and bioadsorption. Increased levels of cross-linking between Cd(II and bEPS stimulated algal cell aggregation, which eventually promoted the formation of Microcystis colonies.

  20. Concentration and size distribution of particles in abstracted groundwater.

    Science.gov (United States)

    van Beek, C G E M; de Zwart, A H; Balemans, M; Kooiman, J W; van Rosmalen, C; Timmer, H; Vandersluys, J; Stuyfzand, P J

    2010-02-01

    Particle number concentrations have been counted and particle size distributions calculated in groundwater derived by abstraction wells. Both concentration and size distribution are governed by the discharge rate: the higher this rate the higher the concentration and the higher the proportion of larger particles. However, the particle concentration in groundwater derived from abstraction wells, with high groundwater flow velocities, is much lower than in groundwater from monitor wells, with minimal flow velocities. This inconsistency points to exhaustion of the particle supply in the aquifer around wells due to groundwater abstraction for many years. The particle size distribution can be described with the help of a power law or Pareto distribution. Comparing the measured particle size distribution with the Pareto distribution shows that particles with a diameter >7 microm are under-represented. As the particle size distribution is dependent on the flow velocity, so is the value of the "Pareto" slope beta. (c) 2009 Elsevier Ltd. All rights reserved.

  1. Bubble size distribution and inner surface in a bubble flow

    Science.gov (United States)

    Žitek, P.; Valenta, V.

    2017-09-01

    This paper follows the reports [4] and gives instructions on how to theoretically determine the bubble size and its distribution using the distribution function of Nukiyama-Tanasawa with friction factors.

  2. On the problem of solving the optimization for continuous space based on information distribution function of ant colony algorithm

    Science.gov (United States)

    Min, Huang; Na, Cai

    2017-06-01

    These years, ant colony algorithm has been widely used in solving the domain of discrete space optimization, while the research on solving the continuous space optimization was relatively little. Based on the original optimization for continuous space, the article proposes the improved ant colony algorithm which is used to Solve the optimization for continuous space, so as to overcome the ant colony algorithm’s disadvantages of searching for a long time in continuous space. The article improves the solving way for the total amount of information of each interval and the due number of ants. The article also introduces a function of changes with the increase of the number of iterations in order to enhance the convergence rate of the improved ant colony algorithm. The simulation results show that compared with the result in literature[5], the suggested improved ant colony algorithm that based on the information distribution function has a better convergence performance. Thus, the article provides a new feasible and effective method for ant colony algorithm to solve this kind of problem.

  3. The equilibrium size distribution of rouleaux.

    OpenAIRE

    Perelson, A S; Wiegel, F.W.

    1982-01-01

    Rouleaux are formed by the aggregation of red blood cells in the presence of macromolecules that bridge the membranes of adherent erythrocytes. We compute the size and degree of branching of rouleaux for macroscopic systems in thermal equilibrium in the absence of fluid flow. Using techniques from statistical mechanics, analytical expressions are derived for (a) the average number of rouleaux consisting of n cells and having m branch points; (b) the average number of cells per rouleau; (c) th...

  4. Artificial Bee Colony Algorithm for Transient Performance Augmentation of Grid Connected Distributed Generation

    Science.gov (United States)

    Chatterjee, A.; Ghoshal, S. P.; Mukherjee, V.

    In this paper, a conventional thermal power system equipped with automatic voltage regulator, IEEE type dual input power system stabilizer (PSS) PSS3B and integral controlled automatic generation control loop is considered. A distributed generation (DG) system consisting of aqua electrolyzer, photovoltaic cells, diesel engine generator, and some other energy storage devices like flywheel energy storage system and battery energy storage system is modeled. This hybrid distributed system is connected to the grid. While integrating this DG with the onventional thermal power system, improved transient performance is noticed. Further improvement in the transient performance of this grid connected DG is observed with the usage of superconducting magnetic energy storage device. The different tunable parameters of the proposed hybrid power system model are optimized by artificial bee colony (ABC) algorithm. The optimal solutions offered by the ABC algorithm are compared with those offered by genetic algorithm (GA). It is also revealed that the optimizing performance of the ABC is better than the GA for this specific application.

  5. Improved mathematical models for particle-size distribution data ...

    African Journals Online (AJOL)

    Prior studies have suggested that particle-size distribution data of soils is central and helpful in this regard. This study proposes two improved mathematical models to describe and represent the varied particle-size distribution (PSD) data for tropically weathered residual (TWR) soils. The theoretical analysis and the ...

  6. Concentration and size distribution of particles in abstracted groundwater

    NARCIS (Netherlands)

    Van Beek, C.G.E.M.; de Zwart, A.H.; Balemans, M.; Kooiman, J.W.; van Rosmalen, C.; Timmer, H.; Vandersluys, J.; Stuijfzand, P.J.

    2010-01-01

    Particle number concentrations have been counted and particle size distributions calculated in groundwater derived by abstraction wells. Both concentration and size distribution are governed by the discharge rate: the higher this rate the higher the concentration and the higher the proportion of

  7. Grist size distribution and gelatinization temperature of malted ...

    African Journals Online (AJOL)

    The effect of particle size distribution of sorghum malt grist on gelatinization temperature of the sorghum mash was assessed with respect to sorghum variety ICSV400. This was with a view to determining the possible relationship between the grist size distribution and the temperature at which the mash from such grist will ...

  8. Bubble Size Distributions on the North Atlantic and North Sea

    NARCIS (Netherlands)

    Leeuw, G. de; Cohen, L.H.

    2002-01-01

    Bubble size distributions were measured at open sea with optical bubble measuring systems(BMS)deployed from buoys at depths from 0.4 to l.5m. The BMS measures the bubbles in a small sample volume that is monitored with a video camera. The images are analyzed to obtain bubble size distributions in

  9. Evolution of the floc size distribution of cohesive sediments

    NARCIS (Netherlands)

    Mietta, F.

    2010-01-01

    This thesis focuses on the flocculation process of cohesive sediment (mud) and in particular on the time evolution of the floc size distribution. Mud is mainly observed in estuarine environment and its settling velocity is strongly affected by its floc size distribution. Small flocs (1-50

  10. An Inquiry into the nature, causes and distribution of wealth in the Cape Colony, 1652-1795

    NARCIS (Netherlands)

    Fourie, J.

    2012-01-01

    Three important questions about the Dutch Cape Colony are investigated in this dissertation: 1) how affluent were Cape settlers, 2) what were the causes of such wealth, and 3) how was the wealth distributed? Using a variety of statistical sources, most notably the detailed probate inventories and

  11. On the particle-size distribution function of cometary dust

    Science.gov (United States)

    Sekanina, Z.

    1980-01-01

    The characterization of the particle size distribution in cometary tails is considered. The particle-size related distribution function of the acceleration exerted on the cometary particle by solar radiation pressure used by Finson and Probstein (1968) is introduced, and distribution functions observed for the comets Arend-Roland 1957 III, Bennett 1970 II and Seki-Lines 1962 III are illustrated. It is pointed out that although the distribution functions have features in common, the rate of decrease of the distribution towards zero acceleration (large particles) is not well determined. An approximation for the size distribution in this range obtained from a photometric study of anomalous cometary tails is presented, and used to formulate an a priori distribution law which can be used to approximate all types of expected distributions by varying three key parameters.

  12. A machine learning approach for predicting atmospheric aerosol size distributions

    Science.gov (United States)

    Rudiger, Joshua J.; Book, Kevin; deGrassie, John Stephen; Hammel, Stephen; Baker, Brooke

    2017-09-01

    An accurate model and parameterization of aerosol concentration is needed to predict the performance of electro-optical imaging systems. Current models have been shown to vary widely in their ability to accurately predict aerosol size distributions and subsequent scattering properties of the atmosphere. One of the more prevalent methods for modeling particle size spectra consists of fitting a modified gamma function to measurement data, however this limits the distribution to a single mode. Machine learning models have been shown to predict complex multimodal aerosol particle size spectra. Here we establish an empirical model for predicting aerosol size spectra using machine learning techniques. This is accomplished through measurements of aerosols size distributions over the course of eight months. The machine learning models are shown to extend the functionality of Advanced Navy Aerosol Model (ANAM), developed to model the size distribution of aerosols in the maritime environment.

  13. Improved Root Normal Size Distributions for Liquid Atomization

    Science.gov (United States)

    2015-11-01

    Introduction First introduced by Tate and Marshall (1953), root normal size distributions are commonly used to describe aerosol size distributions, and...eight different equations. The first of these equations is as follows: mCDM  (2...of experiments impose a minimum droplet size minD or, equivalently, mCDM minmin  due to optical resolution or other practical factors. If the

  14. Changes in concentration and size distribution of aerosols during ...

    Indian Academy of Sciences (India)

    Measurements of the concentration and size distribution of aerosol particles in the size-ranges of 0.5–20 m and 16–700 nm diameters were made during six fog episodes over the south Indian Ocean. Observations show that concentrations of particles of all sizes start decreasing 1–2 hours before the occurrence of fog.

  15. The Colonial Origins of Inequality : Exploring the Causes and Consequences of Land Distribution

    NARCIS (Netherlands)

    Frankema, Ewout

    2006-01-01

    The colonial heritage of high land inequality in Latin American countries is still, after nearly two centuries of independence, one of the crucial underpinnings of its persistent high levels of income inequality. This paper assesses the colonial strategy of land redistribution in a global

  16. Optimal Sizing of a Stand-Alone Hybrid Power System Based on Battery/Hydrogen with an Improved Ant Colony Optimization

    Directory of Open Access Journals (Sweden)

    Weiqiang Dong

    2016-09-01

    Full Text Available A distributed power system with renewable energy sources is very popular in recent years due to the rapid depletion of conventional sources of energy. Reasonable sizing for such power systems could improve the power supply reliability and reduce the annual system cost. The goal of this work is to optimize the size of a stand-alone hybrid photovoltaic (PV/wind turbine (WT/battery (B/hydrogen system (a hybrid system based on battery and hydrogen (HS-BH for reliable and economic supply. Two objectives that take the minimum annual system cost and maximum system reliability described as the loss of power supply probability (LPSP have been addressed for sizing HS-BH from a more comprehensive perspective, considering the basic demand of load, the profit from hydrogen, which is produced by HS-BH, and an effective energy storage strategy. An improved ant colony optimization (ACO algorithm has been presented to solve the sizing problem of HS-BH. Finally, a simulation experiment has been done to demonstrate the developed results, in which some comparisons have been done to emphasize the advantage of HS-BH with the aid of data from an island of Zhejiang, China.

  17. Effect of land cover, habitat fragmentation and ant colonies on the distribution and abundance of shrews in southern California

    Science.gov (United States)

    Laakkonen, Juha; Fisher, Robert N.; Case, Ted J.

    2001-01-01

    Because effects of habitat fragmentation and anthropogenic disturbance on native animals have been relatively little studied in arid areas and in insectivores, we investigated the roles of different land covers, habitat fragmentation and ant colonies on the distribution and abundance of shrews, Notiosorex crawfordi and Sorex ornatus, in southern California.Notiosorex crawfordi was the numerically dominant species (trap-success rate 0·52) occurring in 21 of the 22 study sites in 85% of the 286 pitfall arrays used in this study.Sorex ornatus was captured in 14 of the sites, in 52% of the arrays with a total trap-success rate of 0·2. Neither of the species was found in one of the sites.The population dynamics of the two shrew species were relatively synchronous during the 4–5-year study; the peak densities usually occurred during the spring. Precipitation had a significant positive effect, and maximum temperature a significant negative effect on the trap-success rate of S. ornatus.Occurrence and abundance of shrews varied significantly between sites and years but the size of the landscape or the study site had no effect on the abundance of shrews. The amount of urban edge had no significant effect on the captures of shrews but increased edge allows invasion of the Argentine ants, which had a highly significant negative impact on the abundance of N. crawfordi.At the trap array level, the percentage of coastal sage scrub flora had a significant positive, and the percentage of other flora had a significant negative effect on the abundance of N. crawfordi. The mean canopy height and the abundance of N. crawfordi had a significant positive effect on the occurrence of S. ornatus.Our study suggests that the loss of native coastal sage scrub flora and increasing presence of Argentine ant colonies may significantly effect the distribution and abundance of N. crawfordi. The very low overall population densities of both shrew species in most study sites make both species

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

    Science.gov (United States)

    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

  19. Pore-size-distribution of cationic polyacrylamide hydrogels

    Energy Technology Data Exchange (ETDEWEB)

    Kremer, M.; Prausnitz, J.M.

    1992-06-01

    The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga's mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

  20. Pore-size-distribution of cationic polyacrylamide hydrogels. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Kremer, M.; Prausnitz, J.M.

    1992-06-01

    The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga`s mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

  1. Measuring firm size distribution with semi-nonparametric densities

    Science.gov (United States)

    Cortés, Lina M.; Mora-Valencia, Andrés; Perote, Javier

    2017-11-01

    In this article, we propose a new methodology based on a (log) semi-nonparametric (log-SNP) distribution that nests the lognormal and enables better fits in the upper tail of the distribution through the introduction of new parameters. We test the performance of the lognormal and log-SNP distributions capturing firm size, measured through a sample of US firms in 2004-2015. Taking different levels of aggregation by type of economic activity, our study shows that the log-SNP provides a better fit of the firm size distribution. We also formally introduce the multivariate log-SNP distribution, which encompasses the multivariate lognormal, to analyze the estimation of the joint distribution of the value of the firm's assets and sales. The results suggest that sales are a better firm size measure, as indicated by other studies in the literature.

  2. Inversion of spheroid particle size distribution in wider size range and aspect ratio range

    Directory of Open Access Journals (Sweden)

    Tang Hong

    2013-01-01

    Full Text Available The non-spherical particle sizing is very important in the aerosol science, and it can be determined by the light extinction measurement. This paper studies the effect of relationship of the size range and aspect ratio range on the inversion of spheroid particle size distribution by the dependent mode algorithm. The T matrix method and the geometric optics approximation method are used to calculate the extinction efficiency of the spheroids with different size range and aspect ratio range, and the inversion of spheroid particle size distribution in these different ranges is conducted. Numerical simulation indicates that a fairly reasonable representation of the spheroid particle size distribution can be obtained when the size range and aspect ratio range are suitably chosen.

  3. Methods of assessing grain-size distribution during grain growth

    DEFF Research Database (Denmark)

    Tweed, Cherry J.; Hansen, Niels; Ralph, Brian

    1985-01-01

    This paper considers methods of obtaining grain-size distributions and ways of describing them. In order to collect statistically useful amounts of data, an automatic image analyzer is used, and the resulting data are subjected to a series of tests that evaluate the differences between two related...... distributions (before and after grain growth). The distributions are measured from two-dimensional sections, and both the data and the corresponding true three-dimensional grain-size distributions (obtained by stereological analysis) are collected. The techniques described here are illustrated by reference...

  4. Appendix B: Summary of TEM Particle Size Distribution Datasets

    Science.gov (United States)

    As discussed in the main text (see Section 5.3.2), calculation of the concentration of asbestos fibers in each of the bins of potential interest requires particle size distribution data derived using transmission electron microscopy (TEM).

  5. Body-size distribution, biomass estimates and life histories of ...

    African Journals Online (AJOL)

    The body-size distributions and biomass estimates of Caenis (Ephemeroptera: Caenidae), Cloeon (Ephemeroptera: Baetidae), Coenagrionidae (Odonata), Micronecta (Hemiptera: Corixidae), Chironominae (Diptera: Chironomidae) and Orthocladiinae (Diptera: Chironomidae), the most common and abundant insect taxa ...

  6. Size distribution measurements and chemical analysis of aerosol components

    Energy Technology Data Exchange (ETDEWEB)

    Pakkanen, T.A.

    1995-12-31

    The principal aims of this work were to improve the existing methods for size distribution measurements and to draw conclusions about atmospheric and in-stack aerosol chemistry and physics by utilizing size distributions of various aerosol components measured. A sample dissolution with dilute nitric acid in an ultrasonic bath and subsequent graphite furnace atomic absorption spectrometric analysis was found to result in low blank values and good recoveries for several elements in atmospheric fine particle size fractions below 2 {mu}m of equivalent aerodynamic particle diameter (EAD). Furthermore, it turned out that a substantial amount of analyses associated with insoluble material could be recovered since suspensions were formed. The size distribution measurements of in-stack combustion aerosols indicated two modal size distributions for most components measured. The existence of the fine particle mode suggests that a substantial fraction of such elements with two modal size distributions may vaporize and nucleate during the combustion process. In southern Norway, size distributions of atmospheric aerosol components usually exhibited one or two fine particle modes and one or two coarse particle modes. Atmospheric relative humidity values higher than 80% resulted in significant increase of the mass median diameters of the droplet mode. Important local and/or regional sources of As, Br, I, K, Mn, Pb, Sb, Si and Zn were found to exist in southern Norway. The existence of these sources was reflected in the corresponding size distributions determined, and was utilized in the development of a source identification method based on size distribution data. On the Finnish south coast, atmospheric coarse particle nitrate was found to be formed mostly through an atmospheric reaction of nitric acid with existing coarse particle sea salt but reactions and/or adsorption of nitric acid with soil derived particles also occurred. Chloride was depleted when acidic species reacted

  7. Bipartite producer consumer networks and the size distribution of firms

    Science.gov (United States)

    Dahui, Wang; Li, Zhou; Zengru, Di

    2006-05-01

    A bipartite producer-consumer network is constructed to describe the industrial structure. The edges from consumer to producer represent the choices of the consumer for the final products and the degree of producer can represent its market share. So the size distribution of firms can be characterized by producer's degree distribution. The probability for a producer receiving a new consumption is determined by its competency described by initial attractiveness and the self-reinforcing mechanism in the competition described by preferential attachment. The cases with constant total consumption and with growing market are studied. The following results are obtained: (1) Without market growth and a uniform initial attractiveness a, the final distribution of firm sizes is Gamma distribution for a>1 and is exponential for a=1. If amarket, the size distribution of firms obeys the power-law. The exponent is affected by the market growth and the initial attractiveness of the firms.

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

    Science.gov (United States)

    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),...

  9. Numerical methods for integrating particle-size frequency distributions

    Science.gov (United States)

    Weltje, Gert Jan; Roberson, Sam

    2012-07-01

    This article presents a suite of numerical methods contained within a Matlab toolbox for constructing complete particle-size distributions from diverse particle-size data. These centre around the application of a constrained cubic-spline interpolation to logit-transformed cumulative percentage frequency data. This approach allows for the robust prediction of frequency values for a set of common particle-size categories. The scheme also calculates realistic, smoothly tapering tails for open-ended distributions using a non-linear extrapolation algorithm. An inversion of established graphic measures to calculate graphic cumulative percentiles is also presented. The robustness of the interpolation-extrapolation model is assessed using particle-size data from 4885 sediment samples from The Netherlands. The influence of the number, size and position of particle-size categories on the accuracy of modeled particle-size distributions was investigated by running a series of simulations using the empirical data set. Goodness-of-fit statistics between modeled distributions and input data are calculated by measuring the Euclidean distance between log-ratio transformed particle-size distributions. Technique accuracy, estimated as the mean goodness-of-fit between repeat sample measurements, was used to identify optimum model parameters. Simulations demonstrate that the data can be accurately characterized by 22 equal-width particle-size categories and 63 equiprobable particle-size categories. Optimal interpolation parameters are highly dependent on the density and position of particle-size categories in the original data set and on the overall level of technique accuracy.

  10. A multivariate rank test for comparing mass size distributions

    KAUST Repository

    Lombard, F.

    2012-04-01

    Particle size analyses of a raw material are commonplace in the mineral processing industry. Knowledge of particle size distributions is crucial in planning milling operations to enable an optimum degree of liberation of valuable mineral phases, to minimize plant losses due to an excess of oversize or undersize material or to attain a size distribution that fits a contractual specification. The problem addressed in the present paper is how to test the equality of two or more underlying size distributions. A distinguishing feature of these size distributions is that they are not based on counts of individual particles. Rather, they are mass size distributions giving the fractions of the total mass of a sampled material lying in each of a number of size intervals. As such, the data are compositional in nature, using the terminology of Aitchison [1] that is, multivariate vectors the components of which add to 100%. In the literature, various versions of Hotelling\\'s T 2 have been used to compare matched pairs of such compositional data. In this paper, we propose a robust test procedure based on ranks as a competitor to Hotelling\\'s T 2. In contrast to the latter statistic, the power of the rank test is not unduly affected by the presence of outliers or of zeros among the data. © 2012 Copyright Taylor and Francis Group, LLC.

  11. Size distribution and roundness of clasts within pseudotachylytes of ...

    Indian Academy of Sciences (India)

    They carry quartz as well as feldspar clasts with sizes of few mm in diameter; the clast sizes show a modified Power law distribution with finer ones (<1000 μm2) deviating from linearity. The shape of the clasts shows a high degree of roundness (<0.4) due to thermal decrepitation. In a large instance, devitrification has ...

  12. Optimum size distribution of sorghum grist for brewing purposes ...

    African Journals Online (AJOL)

    The effect of particle size distribution of malted sorghum grist on extract yield and lautering performance was assessed. Sorghum grist particle size evaluation was carried out by sieve analysis after milling. The malted sorghum grist with proportions of coarse, fine, and flour particles in the ratio of 0.36: 0.25: 0.39 respectively ...

  13. The dune size distribution and scaling relations of barchan dunefields

    NARCIS (Netherlands)

    Duran Vinent, Orencio; Schwämmle, V.; Lind, P.G.; Herrmann, H.J.

    2009-01-01

    Barchan dunes emerge as a collective phenomena involving the generation of thousands of them in so called barchan dune fields. By measuring the size and position of dunes in Moroccan barchan dune fields, we find that these dunes tend to distribute uniformly in space and follow an unique size

  14. Effects of Mixtures on Liquid and Solid Fragment Size Distributions

    Science.gov (United States)

    2016-05-01

    these will be called Type IV Gamma size distributions. This is a short but opaque definition . Laney (2015b) gives a longer but clearer definition of Type...as described below, the available evidence indicates that, by the definitions introduced here, it may be better described as a compound size...bins, too few size bins, fixed bin widths, or inadequately- varying bin widths. Overpopulated bins – which typically occur for smaller fragments

  15. Modelling complete particle-size distributions from operator estimates of particle-size

    Science.gov (United States)

    Roberson, Sam; Weltje, Gert Jan

    2014-05-01

    Estimates of particle-size made by operators in the field and laboratory represent a vast and relatively untapped data archive. The wide spatial distribution of particle-size estimates makes them ideal for constructing geological models and soil maps. This study uses a large data set from the Netherlands (n = 4837) containing both operator estimates of particle size and complete particle-size distributions measured by laser granulometry. This study introduces a logit-based constrained-cubic-spline (CCS) algorithm to interpolate complete particle-size distributions from operator estimates. The CCS model is compared to four other models: (i) a linear interpolation; (ii) a log-hyperbolic interpolation; (iii) an empirical logistic function; and (iv) an empirical arctan function. Operator estimates were found to be both inaccurate and imprecise; only 14% of samples were successfully classified using the Dutch classification scheme for fine sediment. Operator estimates of sediment particle-size encompass the same range of values as particle-size distributions measured by laser analysis. However, the distributions measured by laser analysis show that most of the sand percentage values lie between zero and one, so the majority of the variability in the data is lost because operator estimates are made to the nearest 1% at best, and more frequently to the nearest 5%. A method for constructing complete particle-size distributions from operator estimates of sediment texture using a logit constrained cubit spline (CCS) interpolation algorithm is presented. This model and four other previously published methods are compared to establish the best approach to modelling particle-size distributions. The logit-CCS model is the most accurate method, although both logit-linear and log-linear interpolation models provide reasonable alternatives. Models based on empirical distribution functions are less accurate than interpolation algorithms for modelling particle-size distributions in

  16. Juvenile Penaeid Shrimp Density, Spatial Distribution and Size ...

    African Journals Online (AJOL)

    The effects of habitat characteristics (mangrove creek, sandflat, mudflat and seagrass meadow) water salinity, temperature, and depth on the density, spatial distribution and size distribution of juveniles of five commercially important penaied shrimp species (Metapenaus monoceros, M. stebbingi, Fenneropenaeus indicus, ...

  17. The Seasonal Evolution of Sea Ice Floe Size Distribution

    Science.gov (United States)

    2015-09-30

    occur in the appearance and morphology of the Arctic sea ice cover over and annual cycle. These photos were taken over the pack ice near SHEBA in May...causing flexural failure and breaking of the ice cover. In the interior of the Arctic ice pack (e.g. Beaufort Sea ) where waves are not prevalent...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. “The Seasonal Evolution of Sea Ice Floe Size Distribution

  18. Sequestration and Distribution Characteristics of Cd(II) by Microcystis aeruginosa and Its Role in Colony Formation.

    Science.gov (United States)

    Bi, Xiangdong; Yan, Ran; Li, Fenxiang; Dai, Wei; Jiao, Kewei; Zhou, Qixing; Liu, Qi

    2016-01-01

    To investigate the sequestration and distribution characteristics of Cd(II) by Microcystis aeruginosa and its role in Microcystis colony formation, M. aeruginosa was exposed to six different Cd(II) concentrations for 10 days. Cd(II) exposure caused hormesis in the growth of M. aeruginosa. Low concentrations of Cd(II) significantly induced formation of small Microcystis colonies (P bEPS) contents of M. aeruginosa significantly (P 93% of Cd(II) was sequestrated in the groups with lower added concentrations of Cd(II). More than 80% of the sequestrated Cd(II) was bioadsorbed by bEPS. The Pearson correlation coefficients of exterior and interior factors related to colony formation of M. aeruginosa revealed that Cd(II) could stimulate the production of IPS and bEPS via increasing Cd(II) bioaccumulation and bioadsorption. Increased levels of cross-linking between Cd(II) and bEPS stimulated algal cell aggregation, which eventually promoted the formation of Microcystis colonies.

  19. Resource selection models are useful in predicting fine-scale distributions of black-footed ferrets in prairie dog colonies

    Science.gov (United States)

    Eads, David A.; Jachowski, David S.; Biggins, Dean E.; Livieri, Travis M.; Matchett, Marc R.; Millspaugh, Joshua J.

    2012-01-01

    Wildlife-habitat relationships are often conceptualized as resource selection functions (RSFs)—models increasingly used to estimate species distributions and prioritize habitat conservation. We evaluated the predictive capabilities of 2 black-footed ferret (Mustela nigripes) RSFs developed on a 452-ha colony of black-tailed prairie dogs (Cynomys ludovicianus) in the Conata Basin, South Dakota. We used the RSFs to project the relative probability of occurrence of ferrets throughout an adjacent 227-ha colony. We evaluated performance of the RSFs using ferret space use data collected via postbreeding spotlight surveys June–October 2005–2006. In home ranges and core areas, ferrets selected the predicted "very high" and "high" occurrence categories of both RSFs. Count metrics also suggested selection of these categories; for each model in each year, approximately 81% of ferret locations occurred in areas of very high or high predicted occurrence. These results suggest usefulness of the RSFs in estimating the distribution of ferrets throughout a black-tailed prairie dog colony. The RSFs provide a fine-scale habitat assessment for ferrets that can be used to prioritize releases of ferrets and habitat restoration for prairie dogs and ferrets. A method to quickly inventory the distribution of prairie dog burrow openings would greatly facilitate application of the RSFs.

  20. Cell-size distribution in epithelial tissue formation and homeostasis.

    Science.gov (United States)

    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).

  1. Size Effect on Specific Energy Distribution in Particle Comminution

    Science.gov (United States)

    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.

  2. Crater size distributions on Ganymede and Callisto: fundamental issues

    Science.gov (United States)

    Wagner, Roland; Schmedemann, Nico; Werner, Stefanie; Ivanov, Boris; Stephan, Katrin; Jaumann, Ralf

    2015-04-01

    Crater size distributions on the two largest Jovian satellites Ganymede and Callisto and the origin of impactors are subject of intense and controversial debates. In this paper, we reinvestigate crater size distributions measured in surface units derived from a recently published global geologic map, based on Voyager and Galileo SSI images at a scale of 1 km/pxl (Collins G. C. et al. (2013), U. S. Geol. Surv., Sci. Inv. Map 3237). These units are used as a context to units mapped in more detail at higher resolution in Galileo SSI images. We focus on the following fundamental issues: (1) Similarity between shapes of crater distributions on the Galilean satellites and on inner solar system bodies; (2) production versus equilibrium distributions; (3) apex/antapex variations in crater distributions. First, our results show a strong similarity in shape between the crater distributions on the most densely cratered regions on Ganymede and Callisto with those in the lunar highlands. We conclude that the shape of the crater distributions on these two Jovian satellites implies the craters were preferentially formed from members of a collisionally evolved projectile family, derived either from Main Belt asteroids as candidates of impactors on the Jovian satellites, or from projectiles stemming from the outer solar system which have undergone collisional evolution, resulting in a size distribution similar to those of Main Belt asteroids. Second, the complex shape of the crater distributions on Ganymede and Callisto indicates they are mostly production distributions and can be used to infer the underlying shape of the projectile size distribution. Locally, equilibrium distributions occur, especially at smaller sub-kilometer diameters. Third, the most densely cratered regions on both satellites do not show apex-antapex variations in crater frequency, as inferred for bodies from heliocentric orbits (e.g., Zahnle K. et al. (2003), Icarus 163, 263-289). This indicates that these

  3. Nutrient flow and distribution in conventional cage, enriched colony, and aviary layer houses.

    Science.gov (United States)

    Lin, Xing Jun; Zhang, Ruihong; Jiang, Shumei; Elmashad, Hamed M; Mitloehner, Frank

    2016-01-01

    This study was carried out to measure the mass flow and distribution of nutrients (N, C, S, P, and K) as well as solids and moisture in conventional cage (CC), enriched colony (EC), and aviary (AV) laying-hen houses with Lohmann LSL lite hens located on a commercial laying-hen farm in Iowa. The weight of consumed feed and water, and amounts of eggs and manure production were collected weekly from each house for 2 entire flocks for a total of 28 mo. Samples of feed, egg, manure, litter, and hens were regularly taken and analyzed for total solids and nutrients (N, C, S, P, and K). The nutrient losses to the atmosphere were calculated using a mass balance approach. The losses of nutrients were calculated by subtracting the nutrient contents in eggs, manure, and layer body weight gain from the nutrients intake. The research results showed that the feed intake and manure production rates were similar in the 3 houses. The average nutrient intake in feed, in g d(-1) hen(-1), for the 3 houses was 42.0 C, 2.96 N, 0.36 S, 0.55 P, and 0.79 K. The nutrient intake was partitioned as follow: C - 18% in eggs, 28% in manure, and 54% in air losses; N - 34% in eggs, 58% in manure, and 8% in air losses; S - 26% in eggs, 68% in manure, and 6% in air losses; P - 17% in eggs, 79% in manure, and 3.1% in air losses; and K - 9% in eggs, 89% in manure, and 1.6% in air losses. Manure removed from the EC house was drier than manure from the CC or AV house. Among the 3 hen houses studied, the EC house had the lowest nutrient losses and the AV house had the highest losses. Nutrient loss in CC was statistically similar to EC. But loss of N, C, and S in AV differed from CC and EC. Furthermore, the loss of P and K in the 3 housing systems was statistically similar. The AV had a doubled mortality rate compared to CC and EC. © 2015 Poultry Science Association Inc.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    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 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. 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.

  5. Lognormal Behavior of the Size Distributions of Animation Characters

    Science.gov (United States)

    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.

  6. Particle size distribution in ferrofluid macro-clusters

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Wah-Keat, E-mail: wklee@bnl.gov [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700S. Cass Avenue, Argonne, IL 60439 (United States); Ilavsky, Jan [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700S. Cass Avenue, Argonne, IL 60439 (United States)

    2013-03-15

    Under an applied magnetic field, many commercial and concentrated ferrofluids agglomerate and form large micron-sized structures. Although large diameter particles have been implicated in the formation of these macro-clusters, the question of whether the particle size distribution of the macro-clusters are the same as the original fluid remains open. Some studies suggest that these macro-clusters consist of larger particles, while others have shown that there is no difference in the particle size distribution between the macro-clusters and the original fluid. In this study, we use X-ray imaging to aid in a sample (diluted EFH-1 from Ferrotec) separation process and conclusively show that the average particle size in the macro-clusters is significantly larger than those in the original sample. The average particle size in the macro-clusters is 19.6 nm while the average particle size of the original fluid is 11.6 nm. - Highlights: Black-Right-Pointing-Pointer X-ray imaging was used to isolate ferrofluid macro-clusters under an applied field. Black-Right-Pointing-Pointer Small angle X-ray scattering was used to determine particle size distributions. Black-Right-Pointing-Pointer Results show that macro-clusters consist of particles that are larger than average.

  7. Rank-Size Distribution of Notes in Harmonic Music: Hierarchic Shuffling of Distributions

    Science.gov (United States)

    Del Río, Manuel Beltrán; Cocho, Germinal

    We trace the rank size distribution of notes in harmonic music, which on previous works we suggested was much better represented by the Two-parameter, first class Beta distribution than the customary power law, to the ranked mixing of distributions dictated by the harmonic and instrumental nature of the piece. The same representation is shown to arise in other fields by the same type of ranked shuffling of distributions. We include the codon content of intergenic DNA sequences and the ranked distribution of sizes of trees in a determined area as examples. We show that the fittings proposed increase their accuracy with the number of distributions that are mixed and ranked.

  8. Global patterns of city size distributions and their fundamental drivers.

    Directory of Open Access Journals (Sweden)

    Ethan H Decker

    Full Text Available Urban areas and their voracious appetites are increasingly dominating the flows of energy and materials around the globe. Understanding the size distribution and dynamics of urban areas is vital if we are to manage their growth and mitigate their negative impacts on global ecosystems. For over 50 years, city size distributions have been assumed to universally follow a power function, and many theories have been put forth to explain what has become known as Zipf's law (the instance where the exponent of the power function equals unity. Most previous studies, however, only include the largest cities that comprise the tail of the distribution. Here we show that national, regional and continental city size distributions, whether based on census data or inferred from cluster areas of remotely-sensed nighttime lights, are in fact lognormally distributed through the majority of cities and only approach power functions for the largest cities in the distribution tails. To explore generating processes, we use a simple model incorporating only two basic human dynamics, migration and reproduction, that nonetheless generates distributions very similar to those found empirically. Our results suggest that macroscopic patterns of human settlements may be far more constrained by fundamental ecological principles than more fine-scale socioeconomic factors.

  9. Particle size and metal distributions in anaerobically digested pig slurry.

    Science.gov (United States)

    Marcato, Claire E; Pinelli, Eric; Pouech, Philippe; Winterton, Peter; Guiresse, Maritxu

    2008-05-01

    Particle size distribution and trace element patterns were studied in a full-scale anaerobic digestion plant treating pig slurry. Mass balance was established for major (N, P, K, Ca, Fe, Mg and S) and minor (Al, Cu, Mn and Zn) elements. Most of the elements were conserved through the process but part of the P, Ca, Mg and Mn was deposited as crystals lining the digester. In the dry matter of the slurry, Cu and Zn occurred at between 170 and 2600 mg kg(-1) due to pig diet supplements. Analyses of particle size distributions in raw and digested slurries showed a general shift in distribution towards larger sizes due to degradation of small and easily degradable particles as well as formation of large microbial filaments. Graded sieving of digested slurry showed metals to be mainly present on 3-25 microm particles. Less than 2% Cu and Zn was removed by passage through a 250 microm rotary screen.

  10. Production, depreciation and the size distribution of firms

    Science.gov (United States)

    Ma, Qi; Chen, Yongwang; Tong, Hui; Di, Zengru

    2008-05-01

    Many empirical researches indicate that firm size distributions in different industries or countries exhibit some similar characters. Among them the fact that many firm size distributions obey power-law especially for the upper end has been mostly discussed. Here we present an agent-based model to describe the evolution of manufacturing firms. Some basic economic behaviors are taken into account, which are production with decreasing marginal returns, preferential allocation of investments, and stochastic depreciation. The model gives a steady size distribution of firms which obey power-law. The effect of parameters on the power exponent is analyzed. The theoretical results are given based on both the Fokker-Planck equation and the Kesten process. They are well consistent with the numerical results.

  11. Linear Model for Optimal Distributed Generation Size Predication

    Directory of Open Access Journals (Sweden)

    Ahmed Al Ameri

    2017-01-01

    Full Text Available This article presents a linear model predicting optimal size of Distributed Generation (DG that addresses the minimum power loss. This method is based fundamentally on strong coupling between active power and voltage angle as well as between reactive power and voltage magnitudes. This paper proposes simplified method to calculate the total power losses in electrical grid for different distributed generation sizes and locations. The method has been implemented and tested on several IEEE bus test systems. The results show that the proposed method is capable of predicting approximate optimal size of DG when compared with precision calculations. The method that linearizes a complex model showed a good result, which can actually reduce processing time required. The acceptable accuracy with less time and memory required can help the grid operator to assess power system integrated within large-scale distribution generation.

  12. Isometric size-scaling of metabolic rate and the size abundance distribution of phytoplankton

    Science.gov (United States)

    Huete-Ortega, María; Cermeño, Pedro; Calvo-Díaz, Alejandra; Marañón, Emilio

    2012-01-01

    The relationship between phytoplankton cell size and abundance has long been known to follow regular, predictable patterns in near steady-state ecosystems, but its origin has remained elusive. To explore the linkage between the size-scaling of metabolic rate and the size abundance distribution of natural phytoplankton communities, we determined simultaneously phytoplankton carbon fixation rates and cell abundance across a cell volume range of over six orders of magnitude in tropical and subtropical waters of the Atlantic Ocean. We found an approximately isometric relationship between carbon fixation rate and cell size (mean slope value: 1.16; range: 1.03–1.32), negating the idea that Kleiber's law is applicable to unicellular autotrophic protists. On the basis of the scaling of individual resource use with cell size, we predicted a reciprocal relationship between the size-scalings of phytoplankton metabolic rate and abundance. This prediction was confirmed by the observed slopes of the relationship between phytoplankton abundance and cell size, which have a mean value of −1.15 (range: −1.29 to −0.97), indicating that the size abundance distribution largely results from the size-scaling of metabolic rate. Our results imply that the total energy processed by carbon fixation is constant along the phytoplankton size spectrum in near steady-state marine ecosystems. PMID:22171079

  13. Fluctuation-induced spreading of size distribution in condensation kinetics.

    Science.gov (United States)

    Dubrovskii, V G

    2009-10-28

    One of the major results of condensation theory is the time independence of the size distribution shape (in terms of a certain invariant size) at the stage of regular growth of particles. This property follows directly from the simplified Zeldovich equation in the continuous form, where the fluctuation term is neglected. We show that the time invariance is broken by the fluctuation-induced spreading of the size spectrum. We first analyze the linear kinetic equations for the distributions p(i)(t) with the growth rates of the form i(alpha). Exact solutions demonstrate the increase in dispersion with time as sqft[t] at alpha=0 and the time-independent dispersion at alpha=1. From the asymptotic analysis of the continuous Zeldovich equation with fractional alpha, it is shown that the distribution spreading always occurs at alphasolutions for the size distribution have the form of a diffusionlike Gaussian. In the case of constant material influx, the spectrum width increases with mean size z as sqrt[z] irrespective of alpha. We present a diagram of different growth scenarios and show that the time spreading occurs in the majority of condensing systems. Some numerical estimates for the effect of spectrum spreading are also presented.

  14. Estimation of Nanoparticle Size Distributions by Image Analysis

    DEFF Research Database (Denmark)

    Fisker, Rune; Carstensen, Jens Michael; Hansen, Mikkel Fougt

    2000-01-01

    . In this paper, we present an automated image analysis technique based on a deformable ellipse model that can perform this task. Results of using this technique are shown for both nearly spherical particles and more irregularly shaped particles. The technique proves to be a very useful tool for nanoparticle......Knowledge of the nanoparticle size distribution is important for the interpretation of experimental results in many studies of nanoparticle properties. An automated method is needed for accurate and robust estimation of particle size distribution from nanoparticle images with thousands of particles...

  15. Saturn's rings - Particle size distributions for thin layer model

    Science.gov (United States)

    Zebker, H. A.; Marouf, E. A.; Tyler, G. L.

    1985-01-01

    A model incorporating limited interaction between the incident energy and particles in the ring is considered which appears to be consistent with the multiple scattering process in Saturn's rings. The model allows for the small physical thickness of the rings and can be used to relate Voyager 1 observations of 3.6- and 13-cm wavelength microwave scatter from the rings to the ring particle size distribution function for particles with radii ranging from 0.001 to 20 m. This limited-scatter model yields solutions for particle size distribution functions for eight regions in the rings, which exhibit approximately inverse-cubic power-law behavior.

  16. Space Shuttle exhausted aluminum oxide - A measured particle size distribution

    Science.gov (United States)

    Cofer, W. R., III; Purgold, G. C.; Edahl, R. A.; Winstead, E. L.

    1991-01-01

    Aluminum oxide (A2O3) particles were collected from the Space Shuttle exhaust plume immediately following the launch of STS-34 on October 18, 1989. A2O3 samples were obtained at 2.4, 3.0, 3.2, and 7.4 km in altitude. The samples were analyzed using SEM to develope particle size distributions. There were no indications that the particle size distribution changed as a function of altitude. The particle number concentrations per cubic meter of air sampled for the four collections was found to fit an exponential expression.

  17. Tactical Size Unit as Distribution in a Data Farming Environment

    Directory of Open Access Journals (Sweden)

    Esa Lappi

    2016-02-01

    Full Text Available In agent based models, the agents are usually platforms (individual soldiers, tanks, helicopters, etc., not military units. In the Sandis software, the agents can be platoon size units. As there are about 30 soldiers in a platoon, there is a need for strength distribution in simulations. The contribution of this paper is a conceptual model of the platoon level agent, the needed mathematical models and concepts, and references earlier studies of how simulations have been conducted in a data farming environment with platoon/squad size unit agents with strength distribution.

  18. Obtaining the size distribution of fault gouges with polydisperse bearings.

    Science.gov (United States)

    Lind, Pedro G; Baram, Reza M; Herrmann, Hans J

    2008-02-01

    We generalize a recent study of random space-filling bearings to a more realistic situation, where the spacing offset varies randomly during the space-filling procedure, and show that it reproduces well the size distributions observed in recent studies of real fault gouges. In particular, we show that the fractal dimensions of random polydisperse bearings sweep predominantly the low range of values in the spectrum of fractal dimensions observed along real faults, which strengthen the evidence that polydisperse bearings may explain the occurrence of seismic gaps in nature. In addition, the influence of different distributions on the offset is studied and we find that a uniform distribution is the best choice for reproducing the size distribution of fault gouges.

  19. Particle size distributions of several commonly used seeding aerosols

    Science.gov (United States)

    Crosswy, F. L.

    1985-01-01

    During the course of experimentation, no solid particle powder could be found which produced an aerosol with a narrow particle size distribution when fluidization was the only flow process used in producing the aerosol. The complication of adding particle size fractionation processes to the aerosol generation effort appears to be avoidable. In this regard, a simple sonic orifice is found to be effective in reducing the percentage of agglomerates in the several metal oxide powders tested. Marginally beneficial results are obtained for a 0.5/99.5 percent by weight mixture of the flow agent and metal oxide powder. However, agglomeration is observed to be enhanced when the flow agent percentage is increased to 5 percent. Liquid atomization using the Collison nebulizer as well as a version of the Laskin nozzle resulted in polydispersed aerosols with particle size distributions heavily weighted by the small particle end of the size spectrum. The aerosol particle size distributions produced by the vaporization/condensation seeder are closer to the ideal monodispersed aerosol than any of the other aerosols tested. In addition, this seeding approach affords a measure of control over particle size and particle production rate.

  20. Size distributions of gold nanoclusters studied by liquid chromatography

    Energy Technology Data Exchange (ETDEWEB)

    WILCOXON,JESS P.; MARTIN,JAMES E.; PROVENCIO,PAULA P.

    2000-05-23

    The authors report high pressure liquid chromatography, (HPLC), and transmission electron microscopy, (TEM), studies of the size distributions of nanosize gold clusters dispersed in organic solvents. These metal clusters are synthesized in inverse micelles at room temperature and those investigated range in diameter from 1--10 nm. HPLC is sensitive enough to discern changes in hydrodynamic volume corresponding to only 2 carbon atoms of the passivating agent or metal core size changes of less than 4 {angstrom}. The authors have determined for the first time how the total cluster volume (metal core + passivating organic shell) changes with the size of the passivating agent.

  1. Size Evolution and Stochastic Models: Explaining Ostracod Size through Probabilistic Distributions

    Science.gov (United States)

    Krawczyk, M.; Decker, S.; Heim, N. A.; Payne, J.

    2014-12-01

    The biovolume of animals has functioned as an important benchmark for measuring evolution throughout geologic time. In our project, we examined the observed average body size of ostracods over time in order to understand the mechanism of size evolution in these marine organisms. The body size of ostracods has varied since the beginning of the Ordovician, where the first true ostracods appeared. We created a stochastic branching model to create possible evolutionary trees of ostracod size. Using stratigraphic ranges for ostracods compiled from over 750 genera in the Treatise on Invertebrate Paleontology, we calculated overall speciation and extinction rates for our model. At each timestep in our model, new lineages can evolve or existing lineages can become extinct. Newly evolved lineages are assigned sizes based on their parent genera. We parameterized our model to generate neutral and directional changes in ostracod size to compare with the observed data. New sizes were chosen via a normal distribution, and the neutral model selected new sizes differentials centered on zero, allowing for an equal chance of larger or smaller ostracods at each speciation. Conversely, the directional model centered the distribution on a negative value, giving a larger chance of smaller ostracods. Our data strongly suggests that the overall direction of ostracod evolution has been following a model that directionally pushes mean ostracod size down, shying away from a neutral model. Our model was able to match the magnitude of size decrease. Our models had a constant linear decrease while the actual data had a much more rapid initial rate followed by a constant size. The nuance of the observed trends ultimately suggests a more complex method of size evolution. In conclusion, probabilistic methods can provide valuable insight into possible evolutionary mechanisms determining size evolution in ostracods.

  2. The Particle-Size Toolbox: 3D modelling of particle-size distributions in the subsurface

    Science.gov (United States)

    Roberson, Sam; Weltje, Gert Jan

    2014-05-01

    This paper presents a Matlab toolbox for creating three-dimensional models of complete particle-size distributions in the subsurface. Three modules comprise the toolbox: (i) integration; (ii) optimization, and (iii) interpolation. The integration module accepts a wide variety of input data from boreholes and surface samples. These are converted into a common format. Particle-size data are integrated using a combination of interpolation or Gaussian simulation techniques. Data can be calibrated to minimise the influence of different analytical techniques. Data optimisation relies on subdividing the integrated data into geological units and gridding borehole data to a regular cell size. The optimization step applies principal component analysis to quantify and exclude noise from the data based on individual geological unit volumes. Typically two to three principal components are then used for interpolation. The interpolation module involves standard semi-variogram modelling, cross-validation and interpolation procedures. These can run in Matlab using mGstat, or in Geovariances Isatis via batch processing. Interpolated principal component scores are back-transformed into complete particle-size distributions. Uncertainty in the modelled distributions is quantified by back-transforming the error variance to derive an upper and lower distribution envelope. These data can be used to derive a single measure of uncertainty for each particle-size distribution: the simplicial distance metric.

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

    Science.gov (United States)

    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

  4. particle size distribution and control on bitumen saturation of some ...

    African Journals Online (AJOL)

    vicadmin

    The bitumen saturation analysis was carried out with the use of toluene. The result of sedimentological and particle size distribution studies showed that the sands are medium grained, moderately sorted and mesokurtic. The grain morphology can be described as having low to high sphericity, with shapes generally ...

  5. Article size distribution and control on Bitumen saturation of some ...

    African Journals Online (AJOL)

    The bitumen saturation analysis was carried out with the use of toluene. The result of sedimentological and particle size distribution studies showed that the sands are medium grained, moderately sorted and mesokurtic. The grain morphology can be described as having low to high sphericity, with shapes generally ...

  6. The degree distribution of fixed act-size collaboration networks

    Indian Academy of Sciences (India)

    There are a large number of fixed act-size collaboration networks [11]. For ex- ample, each football team has eleven players. In athletic sports or other items, the number of players is fixed, etc. In this paper, we propose a new approach to provide a rigorous proof for the existence of the degree distribution of this model, and ...

  7. Tracing Particle Size Distribution Curves Using an Analogue Circuit.

    Science.gov (United States)

    Bisschop, F. De; Segaert, O.

    1986-01-01

    Proposes an analog circuit for use in sedimentation analysis of finely divided solid materials. Discusses a method of particle size distribution analysis and provides schematics of the circuit with list of components as well as a discussion about the operation of the circuit. (JM)

  8. Fish species composition, size structure and distribution in non ...

    African Journals Online (AJOL)

    Fish diversity studies in littoral non-trawlable areas of Lake Victoria (Tanzania) were undertaken during six systematic surveys (November 2000 to December 2002). Information on fish species composition, size structure as well as spatial and temporal distribution was generated from gill-netting, beach-seining and electric ...

  9. Pore-size distributions of N-isopropylacrylamide (NIPA) hydrogels

    Energy Technology Data Exchange (ETDEWEB)

    Walther, D.H.; Blanch, H.W.; Prausnitz, J.M. [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering]|[Lawrence Berkeley Lab., CA (United States)

    1993-11-01

    Pore-size distributions have been measured for N-isopropylacrylamide (NIPA) hydrogels at 25 and 32{degrees}C with swelling capacities 11.3 and 6.0 g swollen gel per g dry gel. The mixed-solute-exclusion method (introduced by Kuga) was used to obtain the experimental solute-exclusion curve which represents the amount of imbibed liquid inside the gel inaccessible for a solute of radius r. The pore-size distributions were obtained by using Casassa`s Brownian-motion model and numerically solving the Fredholm integral equation. The pore-size distributions of temperature-sensitive NIPA hydrogels are strongly dependent on temperature which determines swelling capacity. With increasing swelling capacity (from 6.0 to 11.3), the pore-size distribution shifts to higher mode values (27.3 to 50.6 {angstrom}) and to higher variance (1.07{center_dot}10{sup 3} to 3.58{center_dot}10{sup 3} {angstrom}{sup 2}).

  10. Improved Mathematical Models for Particle-Size Distribution Data

    African Journals Online (AJOL)

    BirukEdimon

    1. IMPROVED MATHEMATICAL MODELS FOR PARTICLE-SIZE. DISTRIBUTION DATA REPRESENTATION OF TROPICAL. WEATHERED RESIDUAL SOILS. Addiszemen Teklay1, Messele Haile2, Alemayehu Teferra2, andE. J. Murray3. 1. School of Civil & Water Resources Engineering, Bahirdar Institute of Technology,. 2.

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

    Science.gov (United States)

    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...

  12. Size distribution and structure of Barchan dune fields

    DEFF Research Database (Denmark)

    Duran, O.; Schwämmle, Veit; Lind, P. G.

    2011-01-01

    as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields...

  13. Particle size distribution of selected electronic nicotine delivery system products.

    Science.gov (United States)

    Oldham, Michael J; Zhang, Jingjie; Rusyniak, Mark J; Kane, David B; Gardner, William P

    2018-01-31

    Dosimetry models can be used to predict the dose of inhaled material, but they require several parameters including particle size distribution. The reported particle size distributions for aerosols from electronic nicotine delivery system (ENDS) products vary widely and don't always identify a specific product. A low-flow cascade impactor was used to determine the particle size distribution [mass median aerodynamic diameter (MMAD); geometric standard deviation (GSD)] from 20 different cartridge based ENDS products. To assess losses and vapor phase amount, collection efficiency of the system was measured by comparing the collected mass in the impactor to the difference in ENDS product mass. The levels of nicotine, glycerin, propylene glycol, water, and menthol in the formulations of each product were also measured. Regardless of the ENDS product formulation, the MMAD of all tested products was similar and ranged from 0.9 to 1.2 μm with a GSD ranging from 1.7 to 2.2. There was no consistent pattern of change in the MMAD and GSD as a function of number of puffs (cartridge life). The collection efficiency indicated that 9%-26% of the generated mass was deposited in the collection system or was in the vapor phase. The particle size distribution data are suitable for use in aerosol dosimetry programs. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  14. Effects of Particle Size Distribution on Bioremediation of Crude Oil ...

    African Journals Online (AJOL)

    ... microbial characteristics for a period of 42days. The parameters examined were: moisture content, particle size distribution, total hydrocarbon content, soil pH, available nitrogen, available phosphorus, total heterotrophic bacteria and fungi count. The analysis of the soil characteristics throughout the remediation period ...

  15. Size distribution of airborne particles in animal houses

    NARCIS (Netherlands)

    Lai, T.L.H.; Aarnink, A.J.A.; Cambra-Lopez, M.; Huynh, T.T.T.; Parmentier, H.K.; Groot Koerkamp, P.W.G.

    2011-01-01

    The objective of this study was to determine concentration and size distribution of airborne particles inside and outside animal houses for broilers, broiler breeder (with bedding); layers (floor or aviary housing system); turkeys (with bedding), pigs: fatteners (traditional house, low emission

  16. Size distribution of airborne particles in animal houses

    NARCIS (Netherlands)

    Lai, T.L.H.; Aarnink, A.J.A.; Cambra-López, M.; Huynh, T.T.T.; Parmentier, H.K.; Groot Koerkamp, P.W.G.

    2014-01-01

    The concentration and size distribution of airborne particles were measured inside and outside typical animal houses such as broilers, broiler breeders (both floor housing with litter); layers (floor housing system and aviary housing system); turkeys (floor housing with litter), pigs: fattening pigs

  17. Comparison of aerosol size distribution in coastal and oceanic environments

    NARCIS (Netherlands)

    Kusmierczyk-Michulec, J.T.; Eijk, A.M.J. van

    2006-01-01

    The results of applying the empirical orthogonal functions (EOF) method to decomposition and approximation of aerosol size distributions are presented. A comparison was made for two aerosol data sets, representing coastal and oceanic environments. The first data set includes measurements collected

  18. [Characterization of bubble size distribution in ES-DAF unit].

    Science.gov (United States)

    Chen, Fu-tai; Zuo, Hua; Li, Jiu-yi; Fan, Zheng-hong; Luan, Zhao-kun

    2004-01-01

    ES-DAF unit was introduced and studied in this paper. Without a costly air saturator, ES-DAF consists of an ejector and a static mixer between the pressure side and suction side of the recycle rotary pump. The bubble size distribution in this novel unit was studied by using a CCD imagination through a microscope. The bubble size decreased with the increase of cycle ratio or the decrease of superficial air-water ratio. These results suggest that smaller bubbles would be formed when the initial number of nucleation sites increase by enhancing the turbulence intensity in the saturation system. The bubble size distribution became lower and wider with the increase of saturation pressure because of more frequent bubble collision and coalescence.

  19. Size distribution and structure of Barchan dune fields

    Directory of Open Access Journals (Sweden)

    O. Durán

    2011-07-01

    Full Text Available Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009, we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was based on a mean-field model ignoring the spatial distribution of dune fields. Here, we present a simplified dune field model that includes the spatial evolution of individual dunes as well as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields but fail to reproduce their homogeneity along the wind direction.

  20. Estimating a distribution function of the tumor size at metastasis.

    Science.gov (United States)

    Xu, J L; Prorok, P C

    1998-09-01

    In studying the relationship between the size of primary cancers and the occurrence of metastases, two quantities are of prime importance. The first is the distribution of tumor size at the point of metastatic transition, while the second is the probability that detectable metastases are present when cancer comes to medical attention. Kimmel and Flehinger (1991, Biometrics 47, 987-1004) developed a general nonparametric model and studied its two limiting cases. Because of unidentifiablity of their general model, a new identifiable model is introduced by making the hazard function for detecting a metastatic cancer a constant. The new model includes Kimmel and Flehinger's (1991) second limiting model as a special case. An estimator of the tumor size distribution at metastases is proposed. The result is applied to a set of colorectal cancer data.

  1. Lognormal field size distributions as a consequence of economic truncation

    Science.gov (United States)

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

    1985-01-01

    The assumption of lognormal (parent) field size distributions has for a long time been applied to resource appraisal and evaluation of exploration strategy by the petroleum industry. However, frequency distributions estimated with observed data and used to justify this hypotheses are conditional. Examination of various observed field size distributions across basins and over time shows that such distributions should be regarded as the end result of an economic filtering process. Commercial discoveries depend on oil and gas prices and field development costs. Some new fields are eliminated due to location, depths, or water depths. This filtering process is called economic truncation. Economic truncation may occur when predictions of a discovery process are passed through an economic appraisal model. We demonstrate that (1) economic resource appraisals, (2) forecasts of levels of petroleum industry activity, and (3) expected benefits of developing and implementing cost reducing technology are sensitive to assumptions made about the nature of that portion of (parent) field size distribution subject to economic truncation. ?? 1985 Plenum Publishing Corporation.

  2. Particle size distributions and the vertical distribution of suspended matter in the upwelling region off Oregon

    Science.gov (United States)

    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.

  3. Bringing Home the Trash: Do Colony-Based Differences in Foraging Distribution Lead to Increased Plastic Ingestion in Laysan Albatrosses?

    Science.gov (United States)

    Young, Lindsay C.; Vanderlip, Cynthia; Duffy, David C.; Afanasyev, Vsevolod; Shaffer, Scott A.

    2009-01-01

    When searching for prey, animals should maximize energetic gain, while minimizing energy expenditure by altering their movements relative to prey availability. However, with increasing amounts of marine debris, what once may have been ‘optimal’ foraging strategies for top marine predators, are leading to sub-optimal diets comprised in large part of plastic. Indeed, the highly vagile Laysan albatross (Phoebastria immutabilis) which forages throughout the North Pacific, are well known for their tendency to ingest plastic. Here we examine whether Laysan albatrosses nesting on Kure Atoll and Oahu Island, 2,150 km apart, experience different levels of plastic ingestion. Twenty two geolocators were deployed on breeding adults for up to two years. Regurgitated boluses of undigestable material were also collected from chicks at each site to compare the amount of plastic vs. natural foods. Chicks from Kure Atoll were fed almost ten times the amount of plastic compared to chicks from Oahu despite boluses from both colonies having similar amounts of natural food. Tracking data indicated that adults from either colony did not have core overlapping distributions during the early half of the breeding period and that adults from Kure had a greater overlap with the putative range of the Western Garbage Patch corroborating our observation of higher plastic loads at this colony. At-sea distributions also varied throughout the year suggesting that Laysan albatrosses either adjusted their foraging behavior according to constraints on time away from the nest or to variation in resources. However, in the non-breeding season, distributional overlap was greater indicating that the energy required to reach the foraging grounds was less important than the total energy available. These results demonstrate how a marine predator that is not dispersal limited alters its foraging strategy throughout the reproductive cycle to maximize energetic gain and how this has led to differences in

  4. Bringing home the trash: do colony-based differences in foraging distribution lead to increased plastic ingestion in Laysan albatrosses?

    Directory of Open Access Journals (Sweden)

    Lindsay C Young

    Full Text Available When searching for prey, animals should maximize energetic gain, while minimizing energy expenditure by altering their movements relative to prey availability. However, with increasing amounts of marine debris, what once may have been 'optimal' foraging strategies for top marine predators, are leading to sub-optimal diets comprised in large part of plastic. Indeed, the highly vagile Laysan albatross (Phoebastria immutabilis which forages throughout the North Pacific, are well known for their tendency to ingest plastic. Here we examine whether Laysan albatrosses nesting on Kure Atoll and Oahu Island, 2,150 km apart, experience different levels of plastic ingestion. Twenty two geolocators were deployed on breeding adults for up to two years. Regurgitated boluses of undigestable material were also collected from chicks at each site to compare the amount of plastic vs. natural foods. Chicks from Kure Atoll were fed almost ten times the amount of plastic compared to chicks from Oahu despite boluses from both colonies having similar amounts of natural food. Tracking data indicated that adults from either colony did not have core overlapping distributions during the early half of the breeding period and that adults from Kure had a greater overlap with the putative range of the Western Garbage Patch corroborating our observation of higher plastic loads at this colony. At-sea distributions also varied throughout the year suggesting that Laysan albatrosses either adjusted their foraging behavior according to constraints on time away from the nest or to variation in resources. However, in the non-breeding season, distributional overlap was greater indicating that the energy required to reach the foraging grounds was less important than the total energy available. These results demonstrate how a marine predator that is not dispersal limited alters its foraging strategy throughout the reproductive cycle to maximize energetic gain and how this has led to

  5. Modelling of Recent Changes In The Urban Particle Size Distribution

    Science.gov (United States)

    Gentry, J.; Heyder, J.; Kreyling, W. G.; Heinrich, J.; Wichmann, H. E.

    Measurements of the particle size distribution in the environment of the East German city of Erfurt over the last decade showed a constant or slight increase in the number of particles smaller than 0.1 µm (ultrafine particles) and a decrease in the number of larger particles (fine particles) confirmed by a 3-4 fold decrease in PM2 . This effect .5 may be attributed to a possible increase in ultrafine particle emission, a decrease in fine particle emission and consequently by less scavenging of ultrafine by fine parti- cles. Numerical protocols were developed to examine this conjecture supporting their validity. The measurement protocol, the implications of the increase in ultrafine par- ticles along with a decrease in micron size particles, and the development of a nu- merical code (mathematical model?) to examine this phenomenon are discussed. The codes were developed to simulate coagulation with broad distributions. The simula- tions quantitatively examine the effect of the reduction of micron sized particles on ul- trafine particle persistence. They indicate the necessity of a continual source of micron sized particles, since sedimentation would eliminate such particles without continual renewal. The code is described in detail, with particular attention paid to the effect of the coagulation kernel used in the particle balance equations. These simulations sug- gest that it is important to use coagulation kernels appropriate for the transition regime. Otherwise the collision of similarly sized ultrafine particles are underestimated. Sev- eral protocols accounting for different continual source terms are studied.

  6. Control of Distributions and Sizes of Nanocomposite Carbon Particles

    Science.gov (United States)

    Feng, P. X.

    Microscale to nanoscale carbon and carbon nitride particles and films were synthesized by using plasma discharge sputtering deposition techniques. Experimental results indicated that sizes and distributions of the particles were directly determined by both discharge voltage and bias voltage. Sputtering deposition at high discharge voltages yielded large sizes (micrometer order) of particles with a high disorder of distribution. Whereas sputtering deposition at low discharge voltages yielded nanoscale of particles that uniformly distributed on the surface of the substrate. Ar laser beam in combination with an optical microscope has been used, enabling one to remove these particles and to achieve preferred distributions of the particles. Low growth rate of the films was found at the low voltage discharge sputtering deposition. Bias voltage was employed during the experiments in order to speed up the growth rate and increase nitrogen content inside the carbon nitride film. With an increase of the bias voltage up to 5 kV, nanoparticles appeared in two-dimensional, sunflower type of cluster distributions. Typical G, D, and C=N bands in the Raman spectra of the samples were identified.

  7. Improved understanding of the searching behavior of ant colony optimization algorithms applied to the water distribution design problem

    Science.gov (United States)

    Zecchin, A. C.; Simpson, A. R.; Maier, H. R.; Marchi, A.; Nixon, J. B.

    2012-09-01

    Evolutionary algorithms (EAs) have been applied successfully to many water resource problems, such as system design, management decision formulation, and model calibration. The performance of an EA with respect to a particular problem type is dependent on how effectively its internal operators balance the exploitation/exploration trade-off to iteratively find solutions of an increasing quality. For a given problem, different algorithms are observed to produce a variety of different final performances, but there have been surprisingly few investigations into characterizing how the different internal mechanisms alter the algorithm's searching behavior, in both the objective and decision space, to arrive at this final performance. This paper presents metrics for analyzing the searching behavior of ant colony optimization algorithms, a particular type of EA, for the optimal water distribution system design problem, which is a classical NP-hard problem in civil engineering. Using the proposed metrics, behavior is characterized in terms of three different attributes: (1) the effectiveness of the search in improving its solution quality and entering into optimal or near-optimal regions of the search space, (2) the extent to which the algorithm explores as it converges to solutions, and (3) the searching behavior with respect to the feasible and infeasible regions. A range of case studies is considered, where a number of ant colony optimization variants are applied to a selection of water distribution system optimization problems. The results demonstrate the utility of the proposed metrics to give greater insight into how the internal operators affect each algorithm's searching behavior.

  8. Recovering 3D Particle Size Distributions from 2D Sections

    Science.gov (United States)

    Cuzzi, Jeffrey N.; Olson, Daniel A.

    2016-01-01

    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. Proper determination of particle size distributions in chondrites - for chondrules, CAIs, and metalgrains - is of basic importance for assessing the processes of formation and/or of accretion of theseparticles into their parent bodies. To date, most information of this sort is gathered from 2D samplescut from a rock such as in microscopic analysis of thin sections, or SEM maps of planar surfaces(Dodd 1976, Hughes 1978a,b; Rubin and Keil 1984, Rubin and Grossman 1987, Grossman et al1988, Rubin 1989, Metzler et al 1992, Kuebler et al 1999, Nelson and Rubin 2002, Schneider et al 2003, Hezel et al 2008; Fisher et al 2014; for an exhaustive review with numerous references seeFriedrich et al 2014). While qualitative discrimination between chondrite types can readily be doneusing data of this sort, any deeper exploration of the processes by which chondrite constituents werecreated or emplaced into their parent requires a more quantitative approach.

  9. Raindrop Size Distribution Observation for GPM/DPR algorithm development

    Science.gov (United States)

    Nakagawa, Katsuhiro; Hanado, Hiroshi; Nishikawa, Masanori; Nakamura, Kenji; Kaneko, Yuki; Kawamura, Seiji; Iwai, Hironori; Minda, Haruya; Oki, Riko

    2013-04-01

    In order to evaluate and improve the accuracy of rainfall intensity from space-borne radars (TRMM/PR and GPM/DPR), it is important to estimate the rain attenuation, namely the k-Z relationship (k is the specific attenuation, Z is the radar reflectivity) correctly. National Institute of Information and Communications Technology (NICT) developed the mobile precipitation observation system for the dual Ka-band radar field campaign for GPM/DPR algorithm development. The precipitation measurement instruments are installed on the roof of container. The installed instruments for raindrop size distribution (DSD) measurements are 2-dimensional Video disdtrometer (2DVD), Joss-type disdrometer, and Laser Optical disdrometr (Parsival). 2DVD and Persival can measure not only raindrop size distribution but also ice and snow size distribution. Observations using the mobile precipitation observation system were performed in Okinawa Island, in Tsukuba, over the slope of Mt. Fuji, in Nagaoka, and in Sapporo Japan. Using these observed DSD data in the different provinces, the characteristics of DSD itself are analyzed and the k-Z relationship is estimated for evaluation and improvement of the TRMM/PR and GPM/DPR algorithm.

  10. Multifractal Characterization of Pore Size Distributions of Peat Soil

    Directory of Open Access Journals (Sweden)

    Joko Sampurno

    2016-08-01

    Full Text Available This paper discusses a multifractal analysis of the microscopic structure of peat soil. The aim of this study was to apply the multifractal technique to analyze the properties of five slices of peat soil (L1-L5. Binary images (220 x 220 pixels, with a conversion value of 9.41 μm/pixel were made from the thin slices and then analyzed. This analysis was conducted to obtain the relationship between physical parameters and complexity parameters. The results showed that the spectrum of f(α can describe well the pore size distribution and average size of pores correlated with the value of D(0. A high value of the average pore size is followed by a low D value and vice versa.

  11. An overview of aerosol particle sensors for size distribution measurement

    Directory of Open Access Journals (Sweden)

    Panich Intra

    2007-08-01

    Full Text Available Fine aerosols are generally referred to airborne particles of diameter in submicron or nanometer size range. Measurement capabilities are required to gain understanding of these particle dynamics. One of the most important physical and chemical parameters is the particle size distribution. The aim of this article is to give an overview of recent development of already existing sensors for particle size distribution measurement based on electrical mobility determination. Available instruments for particle size measurement include a scanning mobility particle sizer (SMPS, an electrical aerosol spectrometer (EAS, an engine exhaust particle sizer (EEPS, a bipolar charge aerosol classifier (BCAC, a fast aerosol spectrometer (FAS a differential mobility spectrometer (DMS, and a CMU electrical mobility spectrometer (EMS. The operating principles, as well as detailed physical characteristics of these instruments and their main components consisting of a particle charger, a mobility classifier, and a signal detector, are described. Typical measurements of aerosol from various sources by these instruments compared with an electrical low pressure impactor (ELPI are also presented.

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

    Science.gov (United States)

    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.

  13. Application of flower pollination algorithm for optimal placement and sizing of distributed generation in Distribution systems

    Directory of Open Access Journals (Sweden)

    P. Dinakara Prasad Reddy

    2016-05-01

    Full Text Available Distributed generator (DG resources are small, self contained electric generating plants that can provide power to homes, businesses or industrial facilities in distribution feeders. By optimal placement of DG we can reduce power loss and improve the voltage profile. However, the values of DGs are largely dependent on their types, sizes and locations as they were installed in distribution feeders. The main contribution of the paper is to find the optimal locations of DG units and sizes. Index vector method is used for optimal DG locations. In this paper new optimization algorithm i.e. flower pollination algorithm is proposed to determine the optimal DG size. This paper uses three different types of DG units for compensation. The proposed methods have been tested on 15-bus, 34-bus, and 69-bus radial distribution systems. MATLAB, version 8.3 software is used for simulation.

  14. Morphology, size distribution and elemental composition of several dental debris

    Science.gov (United States)

    Abe, Shigeaki; Iwadera, Nobuki; Esaki, Mitsue; Aoyama, Ken-Ichi; Akasaka, Tsukasa; Uo, Motohiro; Morita, Manabu; Yawaka, Yasutaka; Watari, Fumio

    2012-12-01

    We investigated morphologies, size distributions and elemental compositions of dental debris formed by cutting/grinding teeth or dental alloys. The average size of debris formed by cutting/grinding dental alloy was around 100 μm and that of teeth was 20 μm. The debris formed by grinding with diamond or carborundum point had isotropic irregular shape, while the debris formed by cutting with carbide bar had characteristic lathe-cut shape. The elemental analysis indicated that the debris formed by grinding dental alloy with carborundum point consisted of not only the particles of the alloy but also the particles of Si compounds with the size of around 10 μm. The particles of Si compounds would be formed by abrasion of the grinding instrument (carborundum, SiC). Similarly, the debris formed by grinding with diamond point also contained submicro-sized particles consisting of C compounds. The results indicate that the morphology and composition of dental debris are varied depending on the combination between the workpiece and the cutting/grinding materials and that the dental debris consist of both the workpiece and the cutting/grinding materials in some combination. In addition, some of the debris of tooth had the size less than 2 μm, which has a potential to induce inflammation. Though the inflammation can be expected at low level, it is required to investigate the details in future.

  15. Cometary coma dust size distribution from in situ IR spectra

    Science.gov (United States)

    Rinaldi, G.; Della Corte, V.; Fulle, M.; Capaccioni, F.; Rotundi, A.; Ivanovski, S. L.; Bockelée-Morvan, D.; Filacchione, G.; D'Aversa, E.; Capria, M. T.; Tozzi, G. P.; Erard, S.; Leyrat, C.; Palomba, E.; Longobardo, A.; Ciarniello, M.; Taylor, F.; Mottola, S.; Salatti, M.

    2017-07-01

    Dust is the most abundant component in cometary comae. Here, we investigate the dust size distribution in 67P/Churyumov-Gerasimenko (67P/CG) using data from the Rosetta spacecraft that was in close proximity to the comet from 2014 August to 2016 September. The Visual, Infrared and Thermal Imaging Spectrometer (VIRTIS-M), spectral range of 0.25-5 μm, and the Grain Impact Analyser and Dust Accumulator (GIADA), both part of the Rosetta payload, together provide a powerful means to characterize the dust coma properties. On March 28, Rosetta performed a flyby close to the nucleus that allowed GIADA to detect a large amount of dust particles used to constraint the differential size distribution power-law index of -2.2 ± 0.3. In April 2015, VIRTIS-M observed the spectral radiance in the wavelength range of 1-5 μm. A simple radiative transfer model has been applied to simulate the VIRTIS-M radiances, thus allowing to infer the dust properties. We assumed an optically thin dust coma and spherical amorphous carbon particles in the size range between 0.1 to 1000 μm. We obtained the infrared data best fit with a differential dust size distribution power-law index of -3.1_{-0.1}^{+3}. This index matches the one determined using GIADA March 2015 data indicating that, before perihelion, the inner coma radiance is dominated by particles larger than 10 μm; and the dust coma did not change its properties during most of the 67P/CG inbound orbit.

  16. Universal scaling of grain size distributions during dislocation creep

    Science.gov (United States)

    Aupart, Claire; Dunkel, Kristina G.; Angheluta, Luiza; Austrheim, Håkon; Ildefonse, Benoît; Malthe-Sørenssen, Anders; Jamtveit, Bjørn

    2017-04-01

    Grain size distributions are major sources of information about the mechanisms involved in ductile deformation processes and are often used as paleopiezometers (stress gauges). Several factors have been claimed to influence the stress vs grain size relation, including the water content (Jung & Karato 2001), the temperature (De Bresser et al., 2001), the crystal orientation (Linckens et al., 2016), the presence of second phase particles (Doherty et al. 1997; Cross et al., 2015), and heterogeneous stress distributions (Platt & Behr 2011). However, most of the studies of paleopiezometers have been done in the laboratory under conditions different from those in natural systems. It is therefore essential to complement these studies with observations of naturally deformed rocks. We have measured olivine grain sizes in ultramafic rocks from the Leka ophiolite in Norway and from Alpine Corsica using electron backscatter diffraction (EBSD) data, and calculated the corresponding probability density functions. We compared our results with samples from other studies and localities that have formed under a wide range of stress and strain rate conditions. All distributions collapse onto one universal curve in a log-log diagram where grain sizes are normalized by the mean grain size of each sample. The curve is composed of two straight segments with distinct slopes for grains above and below the mean grain size. These observations indicate that a surprisingly simple and universal power-law scaling describes the grain size distribution in ultramafic rocks during dislocation creep irrespective of stress levels and strain rates. Cross, Andrew J., Susan Ellis, and David J. Prior. 2015. « A Phenomenological Numerical Approach for Investigating Grain Size Evolution in Ductiley Deforming Rocks ». Journal of Structural Geology 76 (juillet): 22-34. doi:10.1016/j.jsg.2015.04.001. De Bresser, J. H. P., J. H. Ter Heege, and C. J. Spiers. 2001. « Grain Size Reduction by Dynamic

  17. Building predictive models of soil particle-size distribution

    Directory of Open Access Journals (Sweden)

    Alessandro Samuel-Rosa

    2013-04-01

    Full Text Available Is it possible to build predictive models (PMs of soil particle-size distribution (psd in a region with complex geology and a young and unstable land-surface? The main objective of this study was to answer this question. A set of 339 soil samples from a small slope catchment in Southern Brazil was used to build PMs of psd in the surface soil layer. Multiple linear regression models were constructed using terrain attributes (elevation, slope, catchment area, convergence index, and topographic wetness index. The PMs explained more than half of the data variance. This performance is similar to (or even better than that of the conventional soil mapping approach. For some size fractions, the PM performance can reach 70 %. Largest uncertainties were observed in geologically more complex areas. Therefore, significant improvements in the predictions can only be achieved if accurate geological data is made available. Meanwhile, PMs built on terrain attributes are efficient in predicting the particle-size distribution (psd of soils in regions of complex geology.

  18. Shape, size, and distribution of magnetic particles in Bjurbole chondrules

    Science.gov (United States)

    Nava, David F.

    1994-01-01

    Chondrules from the Bjurbole chondritic meteorite (L4) exhibit saturation remanence magnetization (SIRM) values which vary over three orders of magnitude. REM values (Natural Remanence Magnetization/SIRM) for Allende (C3V) and Chainpur (LL3) are less than 0.01 but in Bjurbole some chondrules were found to have REM values greater than 0.1 with several greater than 0.2. REM values greater than 0.1 are abnormal and cannot be acquired during weak field cooling. If exposure to a strong field (whatever the source) during the chondrules' history is responsible for the high REM values, was such history associated with a different processing which might have resulted in different shape, size, and distribution of metal particles compared to chondrules having REM values of less than 0.01? Furthermore, magnetic hysteresis results show a broad range of magnetic hardness and other intrinsic magnetic properties. These features must be related to (1) size and amount of metal; and (2) properties of, and amount of, tetrataenite in the chondrules (all chondrules thus far subjected to thermomagnetic analysis show the presence of tetrataenite). A scanning electron microscopy (SEM) study is underway to determine the relationship between the shape, size, and distribution of metal particles within individual chondrules and the magnetic properties of these chondrules. Results from the SEM study in conjunction with magnetic property data may also help to discern effects from possible lightning strikes in the nebula prior to incorporation of the chondrules into the parent body.

  19. Estimation of Raindrop size Distribution over Darjeeling (India)

    Science.gov (United States)

    Mehta, Shyam; Mitra, Amitabha

    2016-07-01

    A study of rain drop size distribution (DSD) model over Darjeeling (27001'N, 88015'E), India, has been carried out using a Micro Rain Radar (MRR). In this article on the basis of MRR which measured DSD (number of rain drop size and rain rates with the time interval of one minute), at the particular heights and the different rain rates. It starts the simulating data for using the general formula moment of the gamma DSD; however, Applying the method by DSD model of exponential, lognormal, and gamma, to check the true estimation of drop size distributions and it has been estimated by the lower order moments and higher order moments for gamma Distributions. It shows the DSD at different altitudes from 150 m to 2000 m, in the vertical steps of 500 m. however it has been simulated the DSD data about 2 km out of 4.5 km. (I). At the height of 150 m where most of DSD behaves gamma Distributions according to the moments order of low and the moments order of high, However, where occupying low concentrations for any rain rates, (ii). Upper altitudes from 450 m to 2000 m as where as shown most of DSD behaves gamma Distributions according to the moments order of high only, However, where occupying high concentrations for any rain rates. DSD at the altitudes of 2 km and even more 4.5 km (as not shown) but every height behaves more or less similar manner except at the height of 150 m, The DSD of empirical model has been derived on the basis of fit parameters evaluated from experimental data. It is observed that data fits well in gamma distribution for Darjeeling. And relation between slope (ΛɅ) and shape (μµ) which bears the best resemblance at the height of 150m (ground surface) at the lower order moments by the linear fit for any rain rates. In higher altitudes obtained where shape (μ) and slope (ΛɅ) which is not making any resemblance by the linear fit or polynomial fit for any rain rates in Darjeeling.

  20. [Research on particle size and size distribution of nanocrystals in urines by laser light scattering method].

    Science.gov (United States)

    Wan, Mu-Hua; Zhao, Mei-Xia; Ouyang, Jian-Ming

    2009-01-01

    In the present paper laser light scattering method was used to investigate the particle size and size distribution of nanoparticles simultaneously in urines of lithogenic patients and healthy persons. This method is economic, rapid, accurate and easy to operate. The results showed that healthy urines are more stable than lithogenic urines. In urines of healthy human, the ultrafine crystals were well scattered and not aggregated with a smaller size. However, the ultrafine crystals in lithogenic urine have a broad size distribution, which increases the aggregation trend of nanocrystals. Based on the intensity-autocorrelation curve, the stability of urine samples of both healthy human and lithogenic patients was comparatively investigated. The relationship between the measurement results and the methods of handling sample was studied. The results show that a stable urine sample can be obtained by diluting the urine with a ratio of 20%, then centrifuging it at 4,000 round per minute for 15 minutes or filtrating it with 1.2 microm cellulose acetate filter. The results of laser light scattering method are consistent with that obtained by transmission electron microscopy (TEM). The reasons for the stability of urines are explained from the points of Van der Waals force, urine viscosity, pH value, ionic strength, surface charge and zeta potential of the ultrafine crystals, and so on. The results in this paper provide a new thought for preventing formation and recurrence of urinary stones.

  1. An effective inversion algorithm for retrieving bimodal aerosol particle size distribution from spectral extinction data

    Science.gov (United States)

    He, Zhenzong; Qi, Hong; Yao, Yuchen; Ruan, Liming

    2014-12-01

    The Ant Colony Optimization algorithm based on the probability density function (PDF-ACO) is applied to estimate the bimodal aerosol particle size distribution (PSD). The direct problem is solved by the modified Anomalous Diffraction Approximation (ADA, as an approximation for optically large and soft spheres, i.e., χ≫1 and |m-1|≪1) and the Beer-Lambert law. First, a popular bimodal aerosol PSD and three other bimodal PSDs are retrieved in the dependent model by the multi-wavelength extinction technique. All the results reveal that the PDF-ACO algorithm can be used as an effective technique to investigate the bimodal PSD. Then, the Johnson's SB (J-SB) function and the modified beta (M-β) function are employed as the general distribution function to retrieve the bimodal PSDs under the independent model. Finally, the J-SB and M-β functions are applied to recover actual measurement aerosol PSDs over Beijing and Shanghai obtained from the aerosol robotic network (AERONET). The numerical simulation and experimental results demonstrate that these two general functions, especially the J-SB function, can be used as a versatile distribution function to retrieve the bimodal aerosol PSD when no priori information about the PSD is available.

  2. A quantitative method for clustering size distributions of elements

    Science.gov (United States)

    Dillner, Ann M.; Schauer, James J.; Christensen, William F.; Cass, Glen R.

    A quantitative method was developed to group similarly shaped size distributions of particle-phase elements in order to ascertain sources of the elements. This method was developed and applied using data from two sites in Houston, TX; one site surrounded by refineries, chemical plants and vehicular and commercial shipping traffic, and the other site, 25 miles inland surrounded by residences, light industrial facilities and vehicular traffic. Twenty-four hour size-segregated (0.056fluid catalytic cracking unit catalysts, fuel oil burning, a coal-fired power plant, and high-temperature metal working. The clustered elements were generally attributed to different sources at the two sites during each sampling day indicating the diversity of local sources that impact heavy metals concentrations in the region.

  3. Method for measuring the size distribution of airborne rhinovirus

    Energy Technology Data Exchange (ETDEWEB)

    Russell, M.L.; Goth-Goldstein, R.; Apte, M.G.; Fisk, W.J.

    2002-01-01

    About 50% of viral-induced respiratory illnesses are caused by the human rhinovirus (HRV). Measurements of the concentrations and sizes of bioaerosols are critical for research on building characteristics, aerosol transport, and mitigation measures. We developed a quantitative reverse transcription-coupled polymerase chain reaction (RT-PCR) assay for HRV and verified that this assay detects HRV in nasal lavage samples. A quantitation standard was used to determine a detection limit of 5 fg of HRV RNA with a linear range over 1000-fold. To measure the size distribution of HRV aerosols, volunteers with a head cold spent two hours in a ventilated research chamber. Airborne particles from the chamber were collected using an Andersen Six-Stage Cascade Impactor. Each stage of the impactor was analyzed by quantitative RT-PCR for HRV. For the first two volunteers with confirmed HRV infection, but with mild symptoms, we were unable to detect HRV on any stage of the impactor.

  4. New finite-size correction for local alignment score distributions

    Directory of Open Access Journals (Sweden)

    Park Yonil

    2012-06-01

    Full Text Available Abstract Background Local alignment programs often calculate the probability that a match occurred by chance. The calculation of this probability may require a “finite-size” correction to the lengths of the sequences, as an alignment that starts near the end of either sequence may run out of sequence before achieving a significant score. Findings We present an improved finite-size correction that considers the distribution of sequence lengths rather than simply the corresponding means. This approach improves sensitivity and avoids substituting an ad hoc length for short sequences that can underestimate the significance of a match. We use a test set derived from ASTRAL to show improved ROC scores, especially for shorter sequences. Conclusions The new finite-size correction improves the calculation of probabilities for a local alignment. It is now used in the BLAST+ package and at the NCBI BLAST web site (http://blast.ncbi.nlm.nih.gov.

  5. Simulation of soot size distribution in an ethylene counterflow flame

    KAUST Repository

    Zhou, Kun

    2014-01-06

    Soot, an aggregate of carbonaceous particles produced during the rich combustion of fossil fuels, is an undesirable pollutant and health hazard. Soot evolution involves various dynamic processes: nucleation soot formation from polycyclic aromatic hydrocarbons (PAHs) condensation PAHs condensing on soot particle surface surface processes hydrogen-abstraction-C2H2-addition, oxidation coagulation two soot particles coagulating to form a bigger particle This simulation work investigates soot size distribution and morphology in an ethylene counterflow flame, using i). Chemkin with a method of moments to deal with the coupling between vapor consumption and soot formation; ii). Monte Carlo simulation of soot dynamics.

  6. Changes in protein size distribution during wheat flour cake processing

    OpenAIRE

    Dewaest, Marine; Villemejane, Cindy; Berland, Sophie; Michon, Camille; Verel, Aliette

    2017-01-01

    Aggregation of egg and wheat proteins during cake mixing and baking was monitored by SE-HPLC after sequential extraction of dough and baked cakes in SDS-buffer first and then in SDS/DTE buffer. Three cake recipes were compared, including either only egg, only flour, or both flour and egg proteins. Dough mixing did not result in any changes in protein solubility or size distribution. Baking promoted protein aggregation and quickly resulted in the solubility loss of all proteins within the firs...

  7. Spread of plague among black-tailed prairie dogs is associated with colony spatial characteristics

    Science.gov (United States)

    Johnson, T.L.; Cully, J.F.; Collinge, S.K.; Ray, C.; Frey, C.M.; Sandercock, B.K.

    2011-01-01

    Sylvatic plague (Yersinia pestis) is an exotic pathogen that is highly virulent in black-tailed prairie dogs (Cynomys ludovicianus) and causes widespread colony losses and individual mortality rates >95%. We investigated colony spatial characteristics that may influence inter-colony transmission of plague at 3 prairie dog colony complexes in the Great Plains. The 4 spatial characteristics we considered include: colony size, Euclidean distance to nearest neighboring colony, colony proximity index, and distance to nearest drainage (dispersal) corridor. We used multi-state mark-recapture models to determine the relationship between these colony characteristics and probability of plague transmission among prairie dog colonies. Annual mapping of colonies and mark-recapture analyses of disease dynamics in natural colonies led to 4 main results: 1) plague outbreaks exhibited high spatial and temporal variation, 2) the site of initiation of epizootic plague may have substantially influenced the subsequent inter-colony spread of plague, 3) the long-term effect of plague on individual colonies differed among sites because of how individuals and colonies were distributed, and 4) colony spatial characteristics were related to the probability of infection at all sites although the relative importance and direction of relationships varied among sites. Our findings suggest that conventional prairie dog conservation management strategies, including promoting large, highly connected colonies, may need to be altered in the presence of plague. ?? 2011 The Wildlife Society.

  8. Optimal placement and sizing of multiple distributed generating units in distribution

    Directory of Open Access Journals (Sweden)

    D. Rama Prabha

    2016-06-01

    Full Text Available Distributed generation (DG is becoming more important due to the increase in the demands for electrical energy. DG plays a vital role in reducing real power losses, operating cost and enhancing the voltage stability which is the objective function in this problem. This paper proposes a multi-objective technique for optimally determining the location and sizing of multiple distributed generation (DG units in the distribution network with different load models. The loss sensitivity factor (LSF determines the optimal placement of DGs. Invasive weed optimization (IWO is a population based meta-heuristic algorithm based on the behavior of weeds. This algorithm is used to find optimal sizing of the DGs. The proposed method has been tested for different load models on IEEE-33 bus and 69 bus radial distribution systems. This method has been compared with other nature inspired optimization methods. The simulated results illustrate the good applicability and performance of the proposed method.

  9. Light scattering by lunar-like particle size distributions

    Science.gov (United States)

    Goguen, Jay D.

    1991-01-01

    A fundamental input to models of light scattering from planetary regoliths is the mean phase function of the regolith particles. Using the known size distribution for typical lunar soils, the mean phase function and mean linear polarization for a regolith volume element of spherical particles of any composition were calculated from Mie theory. The two contour plots given here summarize the changes in the mean phase function and linear polarization with changes in the real part of the complex index of refraction, n - ik, for k equals 0.01, the visible wavelength 0.55 micrometers, and the particle size distribution of the typical mature lunar soil 72141. A second figure is a similar index-phase surface, except with k equals 0.1. The index-phase surfaces from this survey are a first order description of scattering by lunar-like regoliths of spherical particles of arbitrary composition. They form the basis of functions that span a large range of parameter-space.

  10. Geographic structure of adelie penguin populations: overlap in colony-specific foraging areas

    Science.gov (United States)

    Ainley, D.G.; Ribic, C.A.; Ballard, G.; Heath, S.; Gaffney, I.; Karl, B.J.; Barton, K.J.; Wilson, P.R.; Webb, S.

    2004-01-01

    the study, when foraging trips of the large colony were very long, parents lost mass, and chick meals were smaller. In light of existing data on prey abundance in neritic waters in Antarctica suggesting that krill are relatively evenly distributed and in high abundance in the Southern Ross Sea, we conclude that penguins depleted or changed the availability of their prey, that the degree of alteration was a function of colony size, and that the large colony affected the location (and perhaps ultimately the size) of foraging areas for the smaller colonies. It appears, therefore, that foraging dynamics play a role in the geographic structuring of colonies in this species. ?? 2004 by the Ecological Society of America.

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

    NARCIS (Netherlands)

    Saitoh, K.; Magnanimo, Vanessa; Luding, Stefan

    2016-01-01

    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

  12. Size distribution analysis of influenza virus particles using size exclusion chromatography.

    Science.gov (United States)

    Vajda, Judith; Weber, Dennis; Brekel, Dominik; Hundt, Boris; Müller, Egbert

    2016-09-23

    Size exclusion chromatography is a standard method in quality control of biopharmaceutical proteins. In contrast, vaccine analysis is often based on activity assays. The hemagglutination assay is a widely accepted influenza quantification method, providing no insight in the size distribution of virus particles. Capabilities of size exclusion chromatography to complement the hemagglutination assay are investigated. The presented method is comparatively robust regarding different buffer systems, ionic strength and additive concentrations. Addition of 200mM arginine or sodium chloride is necessary to obtain complete virus particle recovery. 0.5 and 1.0M arginine increase the hydrodynamic radius of the whole virus particles by 5nm. Sodium citrate induces virus particle aggregation. Results are confirmed by dynamic light scattering. Retention of a H1N1v strain correlates with DNA contents between 5ng/mL and 670ng/mL. Quantitative elution of the virus preparations is verified on basis of hemagglutination activity. Elution of hemagglutination inducing compounds starts at a flow channel diameter of 7000nm. The universal applicability is demonstrated with three different influenza virus samples, including an industrially produced, pandemic vaccine strain. Size distribution of the pandemic H1N1v 5258, H1N1 PR/8/34, and H3N2 Aichi/2/68 preparations spreads across inter- and intra-particle volume and extends to the secondary interaction dominated range. Thus, virus particle debris seems to induce hemagglutination. Fragments generated by 0.5% Triton™ X-100 treatment increase overall hemagglutination activity. Copyright © 2016 The Author(s). Published by Elsevier B.V. All rights reserved.

  13. Determining particle size distributions in the inhalable size range for wood dust collected by air samplers.

    Science.gov (United States)

    Harper, Martin; Muller, Brian S; Bartolucci, Al

    2002-10-01

    In the absence of methods for determining particle size distributions in the inhalable size range with good discrimination, the samples collected by personal air sampling devices can only be characterized by their total mass. This parameter gives no information regarding the size distribution of the aerosol or the size-selection characteristics of different samplers in field use conditions. A method is described where the particles collected by a sampler are removed, suspended, and re-deposited on a mixed cellulose-ester filter, and examined by optical microscopy to determine particle aerodynamic diameters. This method is particularly appropriate to wood dust particles which are generally large and close to rectangular prisms in shape. Over 200 wood dust samples have been collected in three different wood-products industries, using the traditional closed-face polystyrene/acrylonitrile cassette, the Institute of Occupational Medicine inhalable sampler, and the Button sampler developed by the University of Cincinnati. A portion of these samples has been analyzed to determine the limitations of this method. Extensive quality control measures are being developed to improve the robustness of the procedure, and preliminary results suggest the method has an accuracy similar to that required of National Institute for Occupational Safety and Health (NIOSH) methods. The results should provide valuable insights into the collection characteristics of the samplers and the impact of these characteristics on comparison of sampler results to present and potential future limit values. The NIOSH Deep South Education and Research Center has a focus on research into hazards of the forestry and associated wood-products industry, and it is hoped to expand this activity in the future.

  14. Raindrop size distributions and storm classification in Mexico City

    Science.gov (United States)

    Amaro-Loza, Alejandra; Pedrozo-Acuña, Adrián; Agustín| Breña-Naranjo, José

    2017-04-01

    Worldwide, the effects of urbanization and land use change have caused alterations to the hydrological response of urban catchments. This observed phenomenon implies high resolution measurements of rainfall patterns. The work provides the first dataset of raindrop size distributions and storm classification, among others, across several locations of Mexico City. Data were derived from a recent established network of laser optical disdrometers (LOD) and retrieving measurements of rainrate, reflectivity, number of drops, drop diameter & velocity, and kinetic energy, at a 1-minute resolution. Moreover, the comparison of hourly rainfall patterns revealed the origin and classification of storms into three types: stratiform, transition and convective, by means of its corresponding reflectivity and rainrate relationship (Z-R). Finally, a set of rainfall statistics was applied to evaluate the performance of the LOD disdrometer and weighing precipitation gauge (WPG) data at different aggregated timescales. It was found that WPG gauge estimates remain below the precipitation amounts measured by the LOD.

  15. Retrieval of spherical particle size distribution with an improved Tikhonov iteration method

    OpenAIRE

    Tang Hong

    2012-01-01

    The problem of retrieval for spherical particle size distribution in the independent mode is studied, and an improved Tikhonov iteration method is proposed. In this method, the particle size distribution is retrieved from the light extinction data through the Phillips-Twomey method firstly in the independent mode, and then the obtained inversion results of the particle size distribution is used as the initial distribution and the final retrieved particle size distribution is obtained. S...

  16. Event-based total suspended sediment particle size distribution model

    Science.gov (United States)

    Thompson, Jennifer; Sattar, Ahmed M. A.; Gharabaghi, Bahram; Warner, Richard C.

    2016-05-01

    One of the most challenging modelling tasks in hydrology is prediction of the total suspended sediment particle size distribution (TSS-PSD) in stormwater runoff generated from exposed soil surfaces at active construction sites and surface mining operations. The main objective of this study is to employ gene expression programming (GEP) and artificial neural networks (ANN) to develop a new model with the ability to more accurately predict the TSS-PSD by taking advantage of both event-specific and site-specific factors in the model. To compile the data for this study, laboratory scale experiments using rainfall simulators were conducted on fourteen different soils to obtain TSS-PSD. This data is supplemented with field data from three construction sites in Ontario over a period of two years to capture the effect of transport and deposition within the site. The combined data sets provide a wide range of key overlooked site-specific and storm event-specific factors. Both parent soil and TSS-PSD in runoff are quantified by fitting each to a lognormal distribution. Compared to existing regression models, the developed model more accurately predicted the TSS-PSD using a more comprehensive list of key model input parameters. Employment of the new model will increase the efficiency of deployment of required best management practices, designed based on TSS-PSD, to minimize potential adverse effects of construction site runoff on aquatic life in the receiving watercourses.

  17. Size distribution of PM at Cape Verde - Santiago Island

    Science.gov (United States)

    Pio, C.; Nunes, T.; Cardoso, J.; Caseiro, A.; Cerqueira, M.; Custodio, D.; Freitas, M. C.; Almeida, S. M.

    2012-04-01

    The archipelago of Cape Verde is located on the eastern North Atlantic, about 500 km west of the African coast. Its geographical location, inside the main area of dust transport over tropical Atlantic and near the coast of Africa, is strongly affected by mineral dust from the Sahara and the Sahel regions. In the scope of the CVDust project a surface field station was implemented in the surroundings of Praia City, Santiago Island (14° 55' N e 23° 29' W, 98 m at sea level), where aerosol sampling throughout different samplers was performed during one year. To study the size distribution of aerosol, an optical dust monitor (Grimm 180), from 0.250 to 32 μm in 31 size channels, was running almost continuously from January 2011 to December 2011. The performance of Grimm 180 to quantify PM mass concentration in an area affected by the transport of Saharan dust particles was evaluated throughout the sampling period by comparison with PM10 mass concentrations obtained with the gravimetric reference method (PM10 TSI High-Volume, PM10 Partisol and PM10 TCR-Tecora). PM10 mass concentration estimated with the Grimm 180 dust monitor, an optical counter, showed a good correlation with the reference gravimetric method, with R2= 0.94 and a linear regression equation of PM10Grimm = 0.81PM10TCR- 5.34. The number and mass size distribution of PM at ground level together with meteorological and back trajectories were analyzed and compared for different conditions aiming at identifying different signatures related to sources and dust transport. January and February, the months when most Saharan dust events occurred, showed the highest concentrations, with PM10 daily average of 66.6±60.2 μg m-3 and 91.6±97.4 μg m-3, respectively. During these months PM1 and PM2.5 accounted for less than 11% and 47% of PM10 respectively, and the contribution of fine fractions (PM1 and PM2.5) to PM mass concentrations tended to increase for the other months. During Saharan dust events, the PM2

  18. CHANGES IN THE DISTRIBUTION OF SUBTERRANEAN TERMITE COLONIES (ISOPTERA: RHINOTERMITIDAE) IN CITY PARK, NEW ORLEANS, LOUISIANA IN THE AFTERMATH OF HURRICANE KATRINA

    Science.gov (United States)

    Termite activity had been continuously monitored in four sections of City Park since 2002. Between 2002 and 2005, 12 distinct Formosan subterranean termite, Coptotermes formosanus Shiraki, colonies had been delineated using mark-release-recapture techniques. This study examines how the distribution ...

  19. A new technique based on Artificial Bee Colony Algorithm for optimal sizing of stand-alone photovoltaic system

    Directory of Open Access Journals (Sweden)

    Ahmed F. Mohamed

    2014-05-01

    Full Text Available One of the most recent optimization techniques applied to the optimal design of photovoltaic system to supply an isolated load demand is the Artificial Bee Colony Algorithm (ABC. The proposed methodology is applied to optimize the cost of the PV system including photovoltaic, a battery bank, a battery charger controller, and inverter. Two objective functions are proposed: the first one is the PV module output power which is to be maximized and the second one is the life cycle cost (LCC which is to be minimized. The analysis is performed based on measured solar radiation and ambient temperature measured at Helwan city, Egypt. A comparison between ABC algorithm and Genetic Algorithm (GA optimal results is done. Another location is selected which is Zagazig city to check the validity of ABC algorithm in any location. The ABC is more optimal than GA. The results encouraged the use of the PV systems to electrify the rural sites of Egypt.

  20. A new technique based on Artificial Bee Colony Algorithm for optimal sizing of stand-alone photovoltaic system.

    Science.gov (United States)

    Mohamed, Ahmed F; Elarini, Mahdi M; Othman, Ahmed M

    2014-05-01

    One of the most recent optimization techniques applied to the optimal design of photovoltaic system to supply an isolated load demand is the Artificial Bee Colony Algorithm (ABC). The proposed methodology is applied to optimize the cost of the PV system including photovoltaic, a battery bank, a battery charger controller, and inverter. Two objective functions are proposed: the first one is the PV module output power which is to be maximized and the second one is the life cycle cost (LCC) which is to be minimized. The analysis is performed based on measured solar radiation and ambient temperature measured at Helwan city, Egypt. A comparison between ABC algorithm and Genetic Algorithm (GA) optimal results is done. Another location is selected which is Zagazig city to check the validity of ABC algorithm in any location. The ABC is more optimal than GA. The results encouraged the use of the PV systems to electrify the rural sites of Egypt.

  1. Differential colony size, cell length, and cellular proteome of Escherichia coli isolated from urine vs. stone nidus of kidney stone patients.

    Science.gov (United States)

    Tavichakorntrakool, Ratree; Boonsiri, Patcharee; Prasongwatana, Vitoon; Lulitanond, Aroonlug; Wongkham, Chaisiri; Thongboonkerd, Visith

    2017-03-01

    Escherichia coli is associated with kidney stone disease, as a cause or an effect (secondary or recurrent urinary tract infection, UTI). Defining phenotypic or functional differences between E. coli inside stone nidus (ECS, associated with infection-induced stone) and outside the stone (i.e. from urine) (ECU, represented secondary infection) would be helpful to better understand bacterial involvement in this disease. ECS and ECU were isolated from 100 stone formers and subjected to antimicrobial susceptibility test, ERIC-PCR genotyping, determination of biofilm formation, bacterial colony size on agar plate and cell length in broth, 2-DE, nanoLC-MS/MS, protein network analysis, and pyruvate dehydrogenase (PDH) activity assay. From 100 stone formers, 36 had positive bacterial culture, of which 5 pairs had identical antimicrobial susceptibility patterns and comparable ERIC-PCR genotypes. ECS had smaller colony size and longer cell length than ECU. 2-DE proteomic analysis revealed significantly differential levels of proteins involved in carbohydrate metabolism, stress response, and RNA/protein metabolism. Functional validation demonstrated lower PDH activity in ECS. All these differential phenotypic and cellular proteome findings might be adaptive response of E. coli from remote infection to survive within the stone matrix that subsequently caused recurrent UTI in kidney stone patients. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Particle size distribution and property of bacteria attached to carbon fines in drinking water treatment

    Directory of Open Access Journals (Sweden)

    Wang Leilei

    2008-06-01

    Full Text Available The quantitative change and size distribution of particles in the effluents from a sand filter and a granular activated carbon (GAC filter in a drinking water treatment plant were investigated. The average total concentration of particles in the sand filter effluent during a filter cycle was 148 particles/mL, 27 of which were larger than 2 µm in size. The concentration in the GAC effluent (561 particles/mL was significantly greater than that in the sand filter effluent. The concentration of particles larger than 2 µm in the GAC filter effluent reached 201 particles/mL, with the amount of particles with sizes between 2 µm and 15 µm increasing. The most probable number (MPN of carbon fines reached 43 unit/L after six hours and fines between 0.45 µm and 8.0 µm accounted for more than 50%. The total concentration of outflowing bacteria in the GAC filter effluent, 350 CFU (colony-forming units/mL, was greater than that in the sand filter effluent, 210 CFU/mL. The desorbed bacteria concentration reached an average of 310 CFU/mg fines. The disinfection efficiency of desorbed bacteria was lower than 40% with 1.5 mg/L of chlorine. The disinfection effect showed that the inactivation rate with 2.0 mg/L of chloramine (90% was higher than that with chlorine (70%. Experimental results indicated that the high particle concentration in raw water and sedimentation effluent led to high levels of outflowing particles in the sand filter effluent. The activated carbon fines in the effluent accounted for a small proportion of the total particle amount, but the existing bacteria attached to carbon fines may influence the drinking water safety. The disinfection efficiency of desorbed bacteria was lower than that of free bacteria with chlorine, and the disinfection effect on bacteria attached to carbon fines with chloramine was better than that with only chlorine.

  3. Size Dependence of Dust Distribution around the Earth Orbit

    Energy Technology Data Exchange (ETDEWEB)

    Ueda, Takahiro; Takeuchi, Taku [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo, 152-8551 (Japan); Kobayashi, Hiroshi; Ishihara, Daisuke; Kondo, Toru; Kaneda, Hidehiro, E-mail: t.ueda@geo.titech.ac.jp [Graduate School of Science, Nagoya University, Nagoya, Aichi, 464-8602 (Japan)

    2017-05-01

    In the solar system, interplanetary dust particles (IDPs) originating mainly from asteroid collisions and cometary activities drift to Earth orbit due to Poynting–Robertson drag. We analyzed the thermal emission from IDPs that was observed by the first Japanese infrared astronomical satellite, AKARI . The observed surface brightness in the trailing direction of the Earth orbit is 3.7% greater than that in the leading direction in the 9 μ m band and 3.0% in the 18 μ m band. In order to reveal dust properties causing leading–trailing surface brightness asymmetry, we numerically integrated orbits of the Sun, the Earth, and a dust particle as a restricted three-body problem including radiation from the Sun. The initial orbits of particles are determined according to the orbits of main-belt asteroids or Jupiter-family comets. Orbital trapping in mean motion resonances results in a significant leading–trailing asymmetry so that intermediate sized dust (∼10–100 μ m) produces a greater asymmetry than zodiacal light. The leading–trailing surface brightness difference integrated over the size distribution of the asteroidal dust is obtained to be 27.7% and 25.3% in the 9 μ m and 18 μ m bands, respectively. In contrast, the brightness difference for cometary dust is calculated as 3.6% and 3.1% in the 9 μ m and 18 μ m bands, respectively, if the maximum dust radius is set to be s {sub max} = 3000 μ m. Taking into account these values and their errors, we conclude that the contribution of asteroidal dust to the zodiacal infrared emission is less than ∼10%, while cometary dust of the order of 1 mm mainly accounts for the zodiacal light in infrared.

  4. Analytical Approach for Loss Minimization in Distribution Systems by Optimum Placement and Sizing of Distributed Generation

    Directory of Open Access Journals (Sweden)

    Bakshi Surbhi

    2016-01-01

    Full Text Available Distributed Generation has drawn the attention of industrialists and researchers for quite a time now due to the advantages it brings loads. In addition to cost-effective and environmentally friendly, but also brings higher reliability coefficient power system. The DG unit is placed close to the load, rather than increasing the capacity of main generator. This methodology brings many benefits, but has to address some of the challenges. The main is to find the optimal location and size of DG units between them. The purpose of this paper is distributed generation by adding an additional means to reduce losses on the line. This paper attempts to optimize the technology to solve the problem of optimal location and size through the development of multi-objective particle swarm. The problem has been reduced to a mathematical optimization problem by developing a fitness function considering losses and voltage distribution line. Fitness function by using the optimal value of the size and location of this algorithm was found to be minimized. IEEE-14 bus system is being considered, in order to test the proposed algorithm and the results show improved performance in terms of accuracy and convergence rate.

  5. ESTIMATING SOIL PARTICLE-SIZE DISTRIBUTION FOR SICILIAN SOILS

    Directory of Open Access Journals (Sweden)

    Vincenzo Bagarello

    2009-09-01

    Full Text Available The soil particle-size distribution (PSD is commonly used for soil classification and for estimating soil behavior. An accurate mathematical representation of the PSD is required to estimate soil hydraulic properties and to compare texture measurements from different classification systems. The objective of this study was to evaluate the ability of the Haverkamp and Parlange (HP and Fredlund et al. (F PSD models to fit 243 measured PSDs from a wide range of 38 005_Bagarello(547_33 18-11-2009 11:55 Pagina 38 soil textures in Sicily and to test the effect of the number of measured particle diameters on the fitting of the theoretical PSD. For each soil textural class, the best fitting performance, established using three statistical indices (MXE, ME, RMSE, was obtained for the F model with three fitting parameters. In particular, this model performed better in the fine-textured soils than the coarse-textured ones but a good performance (i.e., RMSE < 0.03 was detected for the majority of the investigated soil textural classes, i.e. clay, silty-clay, silty-clay-loam, silt-loam, clay-loam, loamy-sand, and loam classes. Decreasing the number of measured data pairs from 14 to eight determined a worse fitting of the theoretical distribution to the measured one. It was concluded that the F model with three fitting parameters has a wide applicability for Sicilian soils and that the comparison of different PSD investigations can be affected by the number of measured data pairs.

  6. Queen Size Variation in the Ponerine Ant Ponera coarctata (Hymenoptera: Formicidae

    Directory of Open Access Journals (Sweden)

    J. Liebig

    1995-01-01

    Full Text Available Queens of Ponera coarctata show a pronounced variation in size as measured by ommatidia number and Weber's alitrunk length. Isometric size variation and the normal distribution of size categories indicate that, despite these differences, only one queen morph exists. Queen size varies less within colonies than between colonies, and thus appears to be colony specific. Ovary length apparently varies with queen size. Similar size variations as in queens also occured in males, but not in workers.

  7. Optimal Placement and Sizing of Renewable Distributed Generations and Capacitor Banks into Radial Distribution Systems

    Directory of Open Access Journals (Sweden)

    Mahesh Kumar

    2017-06-01

    Full Text Available In recent years, renewable types of distributed generation in the distribution system have been much appreciated due to their enormous technical and environmental advantages. This paper proposes a methodology for optimal placement and sizing of renewable distributed generation(s (i.e., wind, solar and biomass and capacitor banks into a radial distribution system. The intermittency of wind speed and solar irradiance are handled with multi-state modeling using suitable probability distribution functions. The three objective functions, i.e., power loss reduction, voltage stability improvement, and voltage deviation minimization are optimized using advanced Pareto-front non-dominated sorting multi-objective particle swarm optimization method. First a set of non-dominated Pareto-front data are called from the algorithm. Later, a fuzzy decision technique is applied to extract the trade-off solution set. The effectiveness of the proposed methodology is tested on the standard IEEE 33 test system. The overall results reveal that combination of renewable distributed generations and capacitor banks are dominant in power loss reduction, voltage stability and voltage profile improvement.

  8. Particle size distributions from laboratory-scale biomass fires using fast response instruments

    Science.gov (United States)

    S Hosseini; L. Qi; D. Cocker; D. Weise; A. Miller; M. Shrivastava; J.W. Miller; S. Mahalingam; M. Princevac; H. Jung

    2010-01-01

    Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date, particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distributions in...

  9. Firm-size distribution and price-cost margins in Dutch manufacturing

    NARCIS (Netherlands)

    Y.M. Prince (Yvonne); A.R. Thurik (Roy)

    1993-01-01

    textabstractIndustrial economists surmise a relation between the size distribution of firms and performance. Usually, attention is focused on the high end of the size distribution. The widely used 4-firm seller concentration, C4, ignores what happens at the low end of the size distribution. An

  10. Reduction in soil aggregate size distribution due to wind erosion

    Science.gov (United States)

    Swet, Nitzan; Katra, Itzhak

    2017-04-01

    Soil erosion process by wind causes emission of fine soil particles, and thus alters the topsoil's properties, fertility, and erodibility. Topsoil resistance to erosion depends on its physicochemical properties, especially on the soil aggregation. Although the key role of aggregates in soil erodibility, quantitative information on the relations between soil aggregate size distribution (ASD) and erosion is still lucking. This study focuses on ASD analyses before and after soil erosion by wind. Wind tunnel experiments and soil analyses were conducted on semiarid loess topsoils with different initial conditions of aggregation. The results show that in all initial soil conditions saltation of sand particles caused the breakdown of macro-aggregates > 500 µm, resulting in increase of micro-aggregates (63-250 µm). The micro-aggregate production increases with the wind shear velocity (up to 0.61 m s-1) for soils with available macro-aggregates. The findings highlight dynamics in soil aggregation in response to erosion process, and therefore the significance of ASD in quantifying soil degradation and soil loss potential.

  11. Coarse and fine root plants affect pore size distributions differently.

    Science.gov (United States)

    Bodner, G; Leitner, D; Kaul, H-P

    Small scale root-pore interactions require validation of their impact on effective hydraulic processes at the field scale. Our objective was to develop an interpretative framework linking root effects on macroscopic pore parameters with knowledge at the rhizosphere scale. A field experiment with twelve species from different families was conducted. Parameters of Kosugi's pore size distribution (PSD) model were determined inversely from tension infiltrometer data. Measured root traits were related to pore variables by regression analysis. A pore evolution model was used to analyze if observed pore dynamics followed a diffusion like process. Roots essentially conditioned soil properties at the field scale. Rooting densities higher than 0.5 % of pore space stabilized soil structure against pore loss. Coarse root systems increased macroporosity by 30 %. Species with dense fine root systems induced heterogenization of the pore space and higher micropore volume. We suggested particle re-orientation and aggregate coalescence as main underlying processes. The diffusion type pore evolution model could only partially capture the observed PSD dynamics. Root systems differing in axes morphology induced distinctive pore dynamics. Scaling between these effective hydraulic impacts and processes at the root-pore interface is essential for plant based management of soil structure.

  12. An alternative method for determining particle-size distribution of forest road aggregate and soil with large-sized particles

    Science.gov (United States)

    Hakjun Rhee; Randy B. Foltz; James L. Fridley; Finn Krogstad; Deborah S. Page-Dumroese

    2014-01-01

    Measurement of particle-size distribution (PSD) of soil with large-sized particles (e.g., 25.4 mm diameter) requires a large sample and numerous particle-size analyses (PSAs). A new method is needed that would reduce time, effort, and cost for PSAs of the soil and aggregate material with large-sized particles. We evaluated a nested method for sampling and PSA by...

  13. Comparisons of Particulate Size Distributions from Multiple Combustion Strategies

    Science.gov (United States)

    Zhang, Yizhou

    In this study, a comparison of particle size distribution (PSD) measurements from eight different combustion strategies was conducted at four different load-speed points. The PSDs were measured using a scanning mobility particle sizer (SMPS) together with a condensation particle counter (CPC). To study the influence of volatile particles, PSD measurements were performed with and without a volatile particle remover (thermodenuder, TD) at both low and high dilution ratios. The common engine platform utilized in the experiment helps to eliminate the influence of background particulate and ensures similarity in dilution conditions. The results show a large number of volatile particles were present under LDR sample conditions for most of the operating conditions. The use of a TD, especially when coupled with HDR, was demonstrated to be effective at removing volatile particles and provided consistent measurements across all combustion strategies. The PSD comparison showed that gasoline premixed combustion strategies such as HCCI and GCI generally have low PSD magnitudes for particle sizes greater than the Particle Measurement Programme (PMP) cutoff diameter (23 nm), and the PSDs were highly nuclei-mode particle dominated. The strategies using diesel as the only fuel (DLTC and CDC) generally showed the highest particle number emissions for particles larger than 23 nm and had accumulation-mode particle dominated PSDs. A consistent correlation between the increase of the direct-injection of diesel fuel and a higher fraction of accumulation-mode particles was observed over all combustion strategies. A DI fuel substitution study and injector nozzle geometry study were conducted to better understand the correlation between PSD shape and DI fueling. It was found that DI fuel properties has a clear impact on PSD behavior for CDC and NG DPI. Fuel with lower density and lower sooting tendency led to a nuclei-mode particle dominated PSD shape. For NG RCCI, accumulation

  14. Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model.

    Science.gov (United States)

    Doğan, İlker; van de Sanden, Mauritius C M

    2015-08-22

    Analysis of the size distribution of nanocrystals is a critical requirement for the processing and optimization of their size-dependent properties. The common techniques used for the size analysis are transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). These techniques, however, are not suitable for analyzing the nanocrystal size distribution in a fast, non-destructive and a reliable manner at the same time. Our aim in this work is to demonstrate that size distribution of semiconductor nanocrystals that are subject to size-dependent phonon confinement effects, can be quantitatively estimated in a non-destructive, fast and reliable manner using Raman spectroscopy. Moreover, mixed size distributions can be separately probed, and their respective volumetric ratios can be estimated using this technique. In order to analyze the size distribution, we have formulized an analytical expression of one-particle PCM and projected it onto a generic distribution function that will represent the size distribution of analyzed nanocrystal. As a model experiment, we have analyzed the size distribution of free-standing silicon nanocrystals (Si-NCs) with multi-modal size distributions. The estimated size distributions are in excellent agreement with TEM and PL results, revealing the reliability of our model.

  15. Evaluating the role of genome downsizing and size thresholds from genome size distributions in angiosperms.

    Science.gov (United States)

    Zenil-Ferguson, Rosana; Ponciano, José M; Burleigh, J Gordon

    2016-07-01

    Whole-genome duplications (WGDs) can rapidly increase genome size in angiosperms. Yet their mean genome size is not correlated with ploidy. We compared three hypotheses to explain the constancy of genome size means across ploidies. The genome downsizing hypothesis suggests that genome size will decrease by a given percentage after a WGD. The genome size threshold hypothesis assumes that taxa with large genomes or large monoploid numbers will fail to undergo or survive WGDs. Finally, the genome downsizing and threshold hypothesis suggests that both genome downsizing and thresholds affect the relationship between genome size means and ploidy. We performed nonparametric bootstrap simulations to compare observed angiosperm genome size means among species or genera against simulated genome sizes under the three different hypotheses. We evaluated the hypotheses using a decision theory approach and estimated the expected percentage of genome downsizing. The threshold hypothesis improves the approximations between mean genome size and simulated genome size. At the species level, the genome downsizing with thresholds hypothesis best explains the genome size means with a 15% genome downsizing percentage. In the genus level simulations, the monoploid number threshold hypothesis best explains the data. Thresholds of genome size and monoploid number added to genome downsizing at species level simulations explain the observed means of angiosperm genome sizes, and monoploid number is important for determining the genome size mean at the genus level. © 2016 Botanical Society of America.

  16. Quantitative analysis of crystal/grain sizes and their distributions in 2D and 3D

    DEFF Research Database (Denmark)

    Berger, Alfons; Herwegh, Marco; Schwarz, Jens-Oliver

    2011-01-01

    We review methods to estimate the average crystal (grain) size and the crystal (grain) size distribution in solid rocks. Average grain sizes often provide the base for stress estimates or rheological calculations requiring the quantification of grain sizes in a rock’s microstructure. The primary...... root) to calculate statistical parameters as the mean, median, mode or the skewness of a crystal size distribution. The finally calculated average grain sizes have to be compatible between the different grain size estimation approaches in order to be properly applied, for example, in paleo......, although the primary calculations were obtained in different ways. In order to present an average grain size, we propose to use the area-weighted and volume-weighted mean in the case of unimodal grain size distributions, respectively, for 2D and 3D measurements. The shape of the crystal size distribution...

  17. Effect of inoculum size and water activity on the time to visible growth of Penicillium chrysogenum colony.

    Science.gov (United States)

    Burgain, Anaïs; Bensoussan, Maurice; Dantigny, Philippe

    2013-05-15

    In order to assess the effect of the inoculum size on the time to visible growth for Penicillium chrysogenum, the correlation described by González et al. (González, H.H.L., Resnik, S.L., Vaamonde, G., 1987. Influence of inoculum size on growth rate and lag phase of fungi isolate from Argentine corn. International Journal of Food Microbiology 4, 111-117) was compared to the model introduced by Gougouli et al. (Gougouli, M., Kalantzi, K., Beletsiotis, E., Koutsoumanis, K.P., 2011. Development and application of predictive models for fungal growth as tools to improve quality control in yogurt production. Food Microbiology 28, 1453-1462). Based on the regression coefficient, the latter model performed better than the former one to fit the data obtained for P. chrysogenum grown on Potato Dextrose Agar at 25 °C. Inoculum sizes in the range 10(1)-10(5) spores were tested at 0.930, 0.950, 0.970, and 0.995 aw. By extrapolation of the straight line, the model of Gougouli et al. (2011) provided accurate estimations of the time to visible growth for a single spore inoculum, tvg (N=1). In order to avoid experiments at reduced water activities, the influence of water activity on the model parameters, and on the ratio tvg (N=1) over the germination time was assessed. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. The Hierarchy Model of the Size Distribution of Centres

    NARCIS (Netherlands)

    J. Tinbergen (Jan)

    1968-01-01

    textabstractWe know that human beings live in centres, that is, cities, towns and villages of different size. Both large and small centres have a number of advantages and disadvantages, different for different people and this is why we have a whole range of sizes. Statistically, we even find that

  19. Diverging geometric and magnetic size distributions of iron oxide nanocrystals

    NARCIS (Netherlands)

    Luigjes, B.|info:eu-repo/dai/nl/31412330X; Woudenberg, S.M.C.; de Groot, R.; Meeldijk, J.D.|info:eu-repo/dai/nl/323921647; Torres Galvis, H.M.|info:eu-repo/dai/nl/314116249; de Jong, K.P.|info:eu-repo/dai/nl/06885580X; Philipse, A.P.|info:eu-repo/dai/nl/073532894; Erné, B.H.|info:eu-repo/dai/nl/141937378

    2011-01-01

    An important reason to prepare magnetic nanoparticles of uniform size and shape is to ensure uniform magnetic properties. However, here, we demonstrate that magnetic iron oxide crystals of 20 nm or less with a low polydispersity of the geometric size can nevertheless have a strikingly broad

  20. Local Pore Size Correlations Determine Flow Distributions in Porous Media.

    Science.gov (United States)

    Alim, Karen; Parsa, Shima; Weitz, David A; Brenner, Michael P

    2017-10-06

    The relationship between the microstructure of a porous medium and the observed flow distribution is still a puzzle. We resolve it with an analytical model, where the local correlations between adjacent pores, which determine the distribution of flows propagated from one pore downstream, predict the flow distribution. Numerical simulations of a two-dimensional porous medium verify the model and clearly show the transition of flow distributions from δ-function-like via Gaussians to exponential with increasing disorder. Comparison to experimental data further verifies our numerical approach.

  1. A grain size distribution model for non-catalytic gas-solid reactions

    NARCIS (Netherlands)

    Heesink, Albertus B.M.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

    1993-01-01

    A new model to describe the non-catalytic conversion of a solid by a reactant gas is proposed. This so-called grain size distribution (GSD) model presumes the porous particle to be a collection of grains of various sizes. The size distribution of the grains is derived from mercury porosimetry

  2. Particle size distribution and physico-chemical composition of clay ...

    African Journals Online (AJOL)

    Loss on Ignition (LOI) was by gravimetry. The data obtained on the alkaline metals, alkali metals, silica, sesquioxides/titanium, pH and Loss on ignition (LOI) reveal a general reduction in composition as particles sizes reduces. However, Mg (MgO) increased (16.09% - 30.86%) through <300μm to <44μm as sieved sizes ...

  3. Semivarying coefficient models for capture-recapture data: colony size estimation for the little penguin Eudyptula minor.

    Science.gov (United States)

    Stoklosa, Jakub; Dann, Peter; Huggins, Richard

    2014-09-01

    To accommodate seasonal effects that change from year to year into models for the size of an open population we consider a time-varying coefficient model. We fit this model to a capture-recapture data set collected on the little penguin Eudyptula minor in south-eastern Australia over a 25 year period using Jolly-Seber type estimators and nonparametric P-spline techniques. The time-varying coefficient model identified strong changes in the seasonal pattern across the years which we further examined using functional data analysis techniques. To evaluate the methodology we also conducted several simulation studies that incorporate seasonal variation. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. The limit distribution of the maximum increment of a random walk with regularly varying jump size distribution

    DEFF Research Database (Denmark)

    Mikosch, Thomas Valentin; Rackauskas, Alfredas

    2010-01-01

    In this paper, we deal with the asymptotic distribution of the maximum increment of a random walk with a regularly varying jump size distribution. This problem is motivated by a long-standing problem on change point detection for epidemic alternatives. It turns out that the limit distribution...... of the maximum increment of the random walk is one of the classical extreme value distributions, the Fréchet distribution. We prove the results in the general framework of point processes and for jump sizes taking values in a separable Banach space...

  5. Size distribution of rare earth elements in coal ash

    Science.gov (United States)

    Scott, Clinton T.; Deonarine, Amrika; Kolker, Allan; Adams, Monique; Holland, James F.

    2015-01-01

    Rare earth elements (REEs) are utilized in various applications that are vital to the automotive, petrochemical, medical, and information technology industries. As world demand for REEs increases, critical shortages are expected. Due to the retention of REEs during coal combustion, coal fly ash is increasingly considered a potential resource. Previous studies have demonstrated that coal fly ash is variably enriched in REEs relative to feed coal (e.g, Seredin and Dai, 2012) and that enrichment increases with decreasing size fractions (Blissett et al., 2014). In order to further explore the REE resource potential of coal ash, and determine the partitioning behavior of REE as a function of grain size, we studied whole coal and fly ash size-fractions collected from three U.S commercial-scale coal-fired generating stations burning Appalachian or Powder River Basin coal. Whole fly ash was separated into , 5 um, to 5 to 10 um and 10 to 100 um particle size fractions by mechanical shaking using trace-metal clean procedures. In these samples REE enrichments in whole fly ash ranges 5.6 to 18.5 times that of feedcoals. Partitioning results for size separates relative to whole coal and whole fly ash will also be reported. 

  6. Macrophage colony-stimulating factor (CSF1) controls monocyte production and maturation and the steady-state size of the liver in pigs.

    Science.gov (United States)

    Sauter, Kristin A; Waddell, Lindsey A; Lisowski, Zofia M; Young, Rachel; Lefevre, Lucas; Davis, Gemma M; Clohisey, Sara M; McCulloch, Mary; Magowan, Elizabeth; Mabbott, Neil A; Summers, Kim M; Hume, David A

    2016-09-01

    Macrophage colony-stimulating factor (CSF1) is an essential growth and differentiation factor for cells of the macrophage lineage. To explore the role of CSF1 in steady-state control of monocyte production and differentiation and tissue repair, we previously developed a bioactive protein with a longer half-life in circulation by fusing pig CSF1 with the Fc region of pig IgG1a. CSF1-Fc administration to pigs expanded progenitor pools in the marrow and selectively increased monocyte numbers and their expression of the maturation marker CD163. There was a rapid increase in the size of the liver, and extensive proliferation of hepatocytes associated with increased macrophage infiltration. Despite the large influx of macrophages, there was no evidence of liver injury and no increase in circulating liver enzymes. Microarray expression profiling of livers identified increased expression of macrophage markers, i.e., cytokines such as TNF, IL1, and IL6 known to influence hepatocyte proliferation, alongside cell cycle genes. The analysis also revealed selective enrichment of genes associated with portal, as opposed to centrilobular regions, as seen in hepatic regeneration. Combined with earlier data from the mouse, this study supports the existence of a CSF1-dependent feedback loop, linking macrophages of the liver with bone marrow and blood monocytes, to mediate homeostatic control of the size of the liver. The results also provide evidence of safety and efficacy for possible clinical applications of CSF1-Fc. Copyright © 2016 the American Physiological Society.

  7. Size Distribution Imaging by Non-Uniform Oscillating-Gradient Spin Echo (NOGSE) MRI

    National Research Council Canada - National Science Library

    Shemesh, Noam; Álvarez, Gonzalo A; Frydman, Lucio

    2015-01-01

    .... These size distributions play fundamental roles in defining the physicochemical, biophysical and physiological properties of a wide variety of systems - ranging from advanced catalytic materials...

  8. The Modelled Raindrop Size Distribution of Skudai, Peninsular Malaysia, Using Exponential and Lognormal Distributions

    Directory of Open Access Journals (Sweden)

    Mahadi Lawan Yakubu

    2014-01-01

    Full Text Available This paper presents the modelled raindrop size parameters in Skudai region of the Johor Bahru, western Malaysia. Presently, there is no model to forecast the characteristics of DSD in Malaysia, and this has an underpinning implication on wet weather pollution predictions. The climate of Skudai exhibits local variability in regional scale. This study established five different parametric expressions describing the rain rate of Skudai; these models are idiosyncratic to the climate of the region. Sophisticated equipment that converts sound to a relevant raindrop diameter is often too expensive and its cost sometimes overrides its attractiveness. In this study, a physical low-cost method was used to record the DSD of the study area. The Kaplan-Meier method was used to test the aptness of the data to exponential and lognormal distributions, which were subsequently used to formulate the parameterisation of the distributions. This research abrogates the concept of exclusive occurrence of convective storm in tropical regions and presented a new insight into their concurrence appearance.

  9. The modelled raindrop size distribution of Skudai, Peninsular Malaysia, using exponential and lognormal distributions.

    Science.gov (United States)

    Yakubu, Mahadi Lawan; Yusop, Zulkifli; Yusof, Fadhilah

    2014-01-01

    This paper presents the modelled raindrop size parameters in Skudai region of the Johor Bahru, western Malaysia. Presently, there is no model to forecast the characteristics of DSD in Malaysia, and this has an underpinning implication on wet weather pollution predictions. The climate of Skudai exhibits local variability in regional scale. This study established five different parametric expressions describing the rain rate of Skudai; these models are idiosyncratic to the climate of the region. Sophisticated equipment that converts sound to a relevant raindrop diameter is often too expensive and its cost sometimes overrides its attractiveness. In this study, a physical low-cost method was used to record the DSD of the study area. The Kaplan-Meier method was used to test the aptness of the data to exponential and lognormal distributions, which were subsequently used to formulate the parameterisation of the distributions. This research abrogates the concept of exclusive occurrence of convective storm in tropical regions and presented a new insight into their concurrence appearance.

  10. fish species and size distribution and abundance in different areas ...

    African Journals Online (AJOL)

    Tanzania Fisheries Research Institute. 1 PO Box 9750, Dar es Salaam. 2 PO Box 78850, Dar es ... areas and size structure variations according to depth in Lake Victoria, Tanzania. Data were collected using a bottom trawl net during .... ammonia, nitrate, nitrite and phosphate) was done in the laboratory using the Palintest.

  11. The effect of surface albedo and grain size distribution on ...

    African Journals Online (AJOL)

    Sand dams are very useful in arid and semi arid lands (ASALs) as facilities for water storage and conservation. Soils in ASALs are mainly sandy and major water loss is by evaporation and infiltration. This study investigated the effect of sand media characteristics, specifically surface albedo, grain size and stratification on ...

  12. Changes in concentration and size distribution of aerosols during ...

    Indian Academy of Sciences (India)

    and continues until 10–20 minutes before the onset of fog when particle concentrations in all size ranges rapidly increase by one/two orders of magnitude in ~20 minutes. Thereafter ..... in sufficient concentrations to sustain the formation and growth of new particles. Thereafter, loss of par- ticles by sedimentation will cause ...

  13. Current distribution and population size of the Blue Swallow Hirundo ...

    African Journals Online (AJOL)

    Two surveys of Blue Swallows were conducted in the southern Tanzanian highland grasslands in order to determine the habitat preferences and estimate the size of this subpopulation. During the 2008/09 and 2012 surveys, a total distance of 3 635 km was travelled in search of Blue Swallows (at an altitude of above 1 400 ...

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

    Science.gov (United States)

    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

  15. Single-Size Thermometric Measurements on a Size Distribution of Neutral Fullerenes

    NARCIS (Netherlands)

    Cauchy, C.; Bakker, J. M.; Huismans, Y.; Rouzee, A.; Redlich, B.; van der Meer, A. F. G.; Bordas, C.; Vrakking, M. J. J.; Lepine, F.

    2013-01-01

    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

  16. Size effect on strength and lifetime probability distributions of ...

    Indian Academy of Sciences (India)

    ments and ships, as well as computer circuits, chips and MEMS, should be designed for failure ... The theory is shown to match the experimentally observed systematic deviations of strength and lifetime histograms of industrial ceramics from the Weibull distribution. ... A probabilistic theory was recently developed to model.

  17. Spatial Analysis of Particle Size Distribution of Soils Formed on ...

    African Journals Online (AJOL)

    ... and silt and silt clay ratio (r = 0.77, p<0.01). It was observed that clay, sand and silt + clay bear similar distribution in the field as shown by the prediction contour maps. These variables could receive similar treatment in precision farming, enhance knowledge of pedogenesis and sustainable environmental management.

  18. Size effect on strength and lifetime probability distributions of ...

    Indian Academy of Sciences (India)

    The empirical approach is sufficient for perfectly brittle and perfectly ductile structures since the cumulative distribution function (cdf) of random strength is known, making it possible to extrapolate to the tail from the mean and variance. However, the empirical approach does not apply to structures consisting of quasibrittle ...

  19. Determination of Size Distributions in Nanocrystalline Powders by TEM, XRD and SAXS

    DEFF Research Database (Denmark)

    Jensen, Henrik; Pedersen, Jørgen Houe; Jørgensen, Jens Erik

    2006-01-01

    Crystallite size distributions and particle size distributions were determined by TEM, XRD, and SAXS for three commercially available TiO2 samples and one homemade. The theoretical Guinier Model was fitted to the experimental data and compared to analytical expressions. Modeling of the XRD spectra...... the size distribution obtained from the XRD experiments; however, a good agreement was obtained between the two techniques. Electron microscopy, SEM and TEM, confirmed the primary particle sizes, the size distributions, and the shapes obtained by XRD and SAXS. The SSEC78 powder and the commercially...... available powders showed different morphologies. The SSEC78 powder showed the narrowest sizes distribution while UV100 and TiO2_5nm consisted of the smallest primary particles. SSEC78, UV100, and TiO2_5nm consisted of both primary particles as well as a secondary structure comprised of nanosized primary...

  20. Dust generation in powders: Effect of particle size distribution

    OpenAIRE

    Chakravarty Somik; Le Bihan Olivier; Fischer Marc; Morgeneyer Martin

    2017-01-01

    This study explores the relationship between the bulk and grain-scale properties of powders and dust generation. A vortex shaker dustiness tester was used to evaluate 8 calcium carbonate test powders with median particle sizes ranging from 2μm to 136μm. Respirable aerosols released from the powder samples were characterised by their particle number and mass concentrations. All the powder samples were found to release respirable fractions of dust particles which end up decreasing with time. Th...

  1. Lunar impact flashes - tracing the NEO size distribution

    Science.gov (United States)

    Avdellidou, Chrysa; Koschny, Detlef; NELIOTA Team

    2017-10-01

    Almost 20 years ago, we started to monitor the lunar surface with small telescopes to detect light flashes resulting from the hypervelocity collisions of meteoroids. The initial purpose was to understand the flux of impactors on Earth. The estimation of the flux of near Earth Objects (NEOs) is important not only for the protection of the human civilisation (meter-sized, see Chelyabinsk event in 2013), but also for the protection of the space assets (cm-sized objects). Apart from the NEO flux, the lunar surface helps the study of the impact events per se. The European Space Agency (ESA) is directing and funding lunar observations at 1.2 m Kryoneri telescope in Peloponnese, Greece. This telescope is equipped with a dichroic beam-splitter that directs the light onto two sCMOS cameras, that observe in visible and infrared wavelengths, using Rc and Ic Cousin filters respectively. Currently it is the largest telescope in the world that performs dedicated lunar impact flashes observations. We present the first flash observations in two bands, allowing us to measure flash temperatures for the first time. We find that the temperatures have a range that agrees with the theoretical approaches. Since the temperature can now be calculated, we have a more accurate estimation of the impactor’s mass and the size of the radiated ejecta plume.Having the Moon as a large-scale laboratory, new horizons are set towards the understanding of the nature of impacts, the impactor's material type and the energy partitioning, that is a constant puzzle in impact studies. This can now happen as more impact parameters can be determined and combined, such as the impactor’s mass and speed, flash luminosity, radiating volume, crater size when applicable etc. Future statistics can determine the different lunar regolith properties at different impact sites, especially during a meteoroid stream where the impactors share a common origin and possibly composition.

  2. The Seasonal Evolution of Sea Ice Floe Size Distribution

    Science.gov (United States)

    2013-09-30

    DRI, which is expected to include images from the MEDEA /National Security and Climate Change Research Program and the Center for Southeastern...This project is a new start in FY13, with funds awarded in April 2013. To date we have: (1) Determined the seasonal evolution of floe size...from the MEDEA /National Security Climate Change Research Program and SAR imagery from the Center for Southeastern Tropical Advanced Remote Sensing

  3. Body size diversity and frequency distributions of Neotropical cichlid fishes (Cichliformes: Cichlidae: Cichlinae.

    Directory of Open Access Journals (Sweden)

    Sarah E Steele

    Full Text Available 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.

  4. Characteristics of dust particles abraded from pesticide treated seeds: 1. Size distribution using different measuring techniques.

    Science.gov (United States)

    Foqué, Dieter; Zwertvaegher, Ingrid Ka; Devarrewaere, Wouter; Verboven, Pieter; Nuyttens, David

    2017-07-01

    Particle size is one of the most important properties affecting the driftability and behaviour of dust particles abraded from pesticide dressed seeds during sowing. Three particle sizing techniques were used determine the particle size distribution of dust abraded from seeds from six different species. Important differences in dust particle size distribution between species were observed with the finest dust for rapeseed and the coarsest dust for barley. Wet laser diffraction and sonic sieving particle size results correlated well while micro-CT is able to deliver three-dimensional information and additional physical particle properties (shape, porosity). All particle sizing techniques have their (dis)advantages and none of them is able to perfectly describe the real size distribution of non-spherical particles. The particle size information gathered can be used in dust drift prediction models, risk assessment tools and will help to better understand the dust drift phenomenon. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  5. Numerical simulation of the vertical migration of Microcystis (cyanobacteria colonies based on turbulence drag

    Directory of Open Access Journals (Sweden)

    Hongru Zhao

    2016-11-01

    Full Text Available The vertical migration and accumulation of Microcystis is an important process in water blooms, and colony migration is influenced by colony size and wind-wave disturbance. The vertical migration of Microcystis colonies in turbulence can be simulated in a numerical model. In this study, we model such migration by coupling the colony size and hydrodynamics, including the gravity, colony buoyancy, and the viscous drag force of turbulence. The turbulence intensity was represented by the turbulent kinetic energy (KZ; the larger the KZ, the stronger the wind-wave disturbance. The simulated vertical distribution of Microcystis well agreed with the measured values in a laboratory experiment indicating that our model can simulate the vertical distribution of Microcystis under different hydrodynamic conditions. We also found a size-dependent critical turbulent kinetic energy (TKZ, such that if the turbulent kinetic energy of water exceeds the critical value (i.e., KZ > TKZ, the colonies sink under the drag forces of turbulence; conversely, if KZ < TKZ, the colonies can overcome the turbulent mixing and float. The TKZ of each colony was linearly related to colony diameter. The model is crucial for prediction and prevention of water blooms. The simulated threshold turbulent kinetic energy, at which water blooms disappear in Lake Taihu (a large freshwater lake in the Yangtze Delta, Jiangsu Province, China, was 55.5 cm2 s−2. 

  6. Endotoxins in cotton: washing effects and size distribution

    Energy Technology Data Exchange (ETDEWEB)

    Olenchock, S.A.; Mull, J.C.; Jones, W.G.

    1983-01-01

    Endotoxin contamination was measured in washed and unwashed cottons from three distinct growing areas, California, Mississippi, and Texas. The data show differences in endotoxin contamination based upon the geographic source of the cotton. It is also shown that washing bulk cotton before the carding process results in lower endotoxin in the cotton dust. Washing conditions can affect the endotoxin levels, and all size fractions of the airborne dust contain quantifiable endotoxin contamination. Endotoxin analyses provide a simple and reliable method for monitoring the cleanliness of cotton or airborne cotton dusts.

  7. Estimation of pore size distribution using concentric double pulsed-field gradient NMR.

    Science.gov (United States)

    Benjamini, Dan; Nevo, Uri

    2013-05-01

    Estimation of pore size distribution of well calibrated phantoms using NMR is demonstrated here for the first time. Porous materials are a central constituent in fields as diverse as biology, geology, and oil drilling. Noninvasive characterization of monodisperse porous samples using conventional pulsed-field gradient (PFG) NMR is a well-established method. However, estimation of pore size distribution of heterogeneous polydisperse systems, which comprise most of the materials found in nature, remains extremely challenging. Concentric double pulsed-field gradient (CDPFG) is a 2-D technique where both q (the amplitude of the diffusion gradient) and φ (the relative angle between the gradient pairs) are varied. A recent prediction indicates this method should produce a more accurate and robust estimation of pore size distribution than its conventional 1-D versions. Five well defined size distribution phantoms, consisting of 1-5 different pore sizes in the range of 5-25 μm were used. The estimated pore size distributions were all in good agreement with the known theoretical size distributions, and were obtained without any a priori assumption on the size distribution model. These findings support that in addition to its theoretical benefits, the CDPFG method is experimentally reliable. Furthermore, by adding the angle parameter, sensitivity to small compartment sizes is increased without the use of strong gradients, thus making CDPFG safe for biological applications. Copyright © 2013 Elsevier Inc. All rights reserved.

  8. Distribution of dislocation source length and the size dependent yield strength in freestanding thin films

    NARCIS (Netherlands)

    Shishvan, Siamak Soleymani; Van der Giessen, Erik

    A method is proposed to estimate the size-dependent yield strength of columnar-grained freestanding thin films. The estimate relies on assuming a distribution of the size of Frank-Read sources, which is then translated into a log-normal distribution of the source strength, depending on film

  9. Dust coagulation and fragmentation in molecular clouds. II. The opacity of the dust aggregate size distribution

    NARCIS (Netherlands)

    Ormel, C.W.; Min, M.|info:eu-repo/dai/nl/277318416; Tielens, A. G. G. M.; Dominik, C.; Paszun, D.

    2011-01-01

    The dust size distribution in molecular clouds can be strongly affected by ice-mantle formation and (subsequent) grain coagulation. Following previous work where the dust size distribution has been calculated from a state-of-the art collision model for dust aggregates that involves both coagulation

  10. A model study of the size and composition distribution of aerosols in an aircraft exhaust

    Energy Technology Data Exchange (ETDEWEB)

    Sorokin, A.A. [SRC `ECOLEN`, Moscow (Russian Federation)

    1997-12-31

    A two-dimensional, axisymmetric flow field model which includes water and sulphate aerosol formation represented by moments of the size and composition distribution function is used to calculate the effect of radial turbulent jet mixing on the aerosol size distribution and mean modal composition. (author) 6 refs.

  11. Control over Particle Size Distribution by Autoclaving Poloxamer-Stabilized Trimyristin Nanodispersions.

    Science.gov (United States)

    Göke, Katrin; Roese, Elin; Arnold, Andreas; Kuntsche, Judith; Bunjes, Heike

    2016-09-06

    Lipid nanoparticles are under investigation as delivery systems for poorly water-soluble drugs. The particle size in these dispersions strongly influences important pharmaceutical properties like biodistribution and drug loading capacity; it should be below 500 nm for direct injection into the bloodstream. Consequently, small particles with a narrow particle size distribution are desired. Hitherto, there are, however, only limited possibilities for the preparation of monodisperse, pharmaceutically relevant dispersions. In this work, the effect of autoclaving at 121 °C on the particle size distribution of lipid nanoemulsions and -suspensions consisting of the pharmaceutically relevant components trimyristin and poloxamer 188 was studied. Additionally, the amount of emulsifier needed to stabilize both untreated and autoclaved particles was assessed. In our study, four dispersions of mean particle sizes from 45 to 150 nm were prepared by high-pressure melt homogenization. The particle size distribution before and after autoclaving was characterized using static and dynamic light scattering, differential scanning calorimetry, and transmission electron microscopy. Asymmetrical flow field-flow fractionation was used for particle size distribution analyses and for the determination of free poloxamer 188. Upon autoclaving, the mean particle size increased to up to 200 nm, but not proportionally to the initial size. At the same time, the particle size distribution width decreased remarkably. Heat treatment thus seems to be a promising approach to achieve the desired narrow particle size distribution of such dispersions. Related to the lipid content, suspension particles needed more emulsifier for stabilization than emulsion droplets, and smaller particles more than larger ones.

  12. Strict monandry in the ponerine army ant genus Simopelta suggests that colony size and complexity drive mating system evolution in social insects

    DEFF Research Database (Denmark)

    Kronauer, Daniel J C; O'Donnell, Sean; Boomsma, Jacobus J

    2011-01-01

    Altruism in social insects has evolved between closely related full-siblings. It is therefore of considerable interest why some groups have secondarily evolved low within-colony relatedness, which in turn affects the relatedness incentives of within-colony cooperation and conflict. The highest qu...

  13. ON ESTIMATION AND HYPOTHESIS TESTING OF THE GRAIN SIZE DISTRIBUTION BY THE SALTYKOV METHOD

    Directory of Open Access Journals (Sweden)

    Yuri Gulbin

    2011-05-01

    Full Text Available The paper considers the problem of validity of unfolding the grain size distribution with the back-substitution method. Due to the ill-conditioned nature of unfolding matrices, it is necessary to evaluate the accuracy and precision of parameter estimation and to verify the possibility of expected grain size distribution testing on the basis of intersection size histogram data. In order to review these questions, the computer modeling was used to compare size distributions obtained stereologically with those possessed by three-dimensional model aggregates of grains with a specified shape and random size. Results of simulations are reported and ways of improving the conventional stereological techniques are suggested. It is shown that new improvements in estimating and testing procedures enable grain size distributions to be unfolded more efficiently.

  14. A correction algorithm for particle size distribution measurements made with the forward-scattering spectrometer probe

    Science.gov (United States)

    Lock, James A.; Hovenac, Edward A.

    1989-01-01

    A correction algorithm for evaluating the particle size distribution measurements of atmospheric aerosols obtained with a forward-scattering spectrometer probe (FSSP) is examined. A model based on Poisson statistics is employed to calculate the average diameter and rms width of the particle size distribution. The dead time and coincidence errors in the measured number density are estimated. The model generated data are compared with a Monte Carlo simulation of the FSSP operation. It is observed that the correlation between the actual and measured size distribution is nonlinear. It is noted that the algorithm permits more accurate calculation of the average diameter and rms width of the distribution compared to uncorrected measured quantities.

  15. Efficient immune-GA method for DNOs in sizing and placement of distributed generation units

    OpenAIRE

    Soroudi, Alireza; Ehsan, Mehdi

    2011-01-01

    This paper proposes a hybrid heuristic optimization method based on genetic algorithm and immune systems to maximize the benefits of Distribution Network Operators (DNOs) accrued due to sizing and placement of Distributed Generation (DG) units in distribution networks. The effects of DG units in reducing the reinforcement costs and active power losses of distribution network have been investigated. In the presented method, the integration of DG units in distribution network is done considerin...

  16. Bimodal distribution of the magnetic dipole moment in nanoparticles with a monomodal distribution of the physical size

    NARCIS (Netherlands)

    van Rijssel, Jozef; Kuipers, Bonny W M; Erne, Ben

    2015-01-01

    High-frequency applications of magnetic nanoparticles, such as therapeutic hyperthermia and magnetic particle imaging, are sensitive to nanoparticle size and dipole moment. Usually, it is assumed that magnetic nanoparticles with a log-normal distribution of the physical size also have a log-normal

  17. Bimodal distribution of the magnetic dipole moment in nanoparticles with a monomodal distribution of the physical size

    Energy Technology Data Exchange (ETDEWEB)

    Rijssel, Jos van; Kuipers, Bonny W.M.; Erné, Ben H., E-mail: B.H.Erne@uu.nl

    2015-04-15

    High-frequency applications of magnetic nanoparticles, such as therapeutic hyperthermia and magnetic particle imaging, are sensitive to nanoparticle size and dipole moment. Usually, it is assumed that magnetic nanoparticles with a log-normal distribution of the physical size also have a log-normal distribution of the magnetic dipole moment. Here, we test this assumption for different types of superparamagnetic iron oxide nanoparticles in the 5–20 nm range, by multimodal fitting of magnetization curves using the MINORIM inversion method. The particles are studied while in dilute colloidal dispersion in a liquid, thereby preventing hysteresis and diminishing the effects of magnetic anisotropy on the interpretation of the magnetization curves. For two different types of well crystallized particles, the magnetic distribution is indeed log-normal, as expected from the physical size distribution. However, two other types of particles, with twinning defects or inhomogeneous oxide phases, are found to have a bimodal magnetic distribution. Our qualitative explanation is that relatively low fields are sufficient to begin aligning the particles in the liquid on the basis of their net dipole moment, whereas higher fields are required to align the smaller domains or less magnetic phases inside the particles. - Highlights: • Multimodal fits of dilute ferrofluids reveal when the particles are multidomain. • No a priori shape of the distribution is assumed by the MINORIM inversion method. • Well crystallized particles have log-normal TEM and magnetic size distributions. • Defective particles can combine a monomodal size and a bimodal dipole moment.

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

    Science.gov (United States)

    1984-11-01

    optimal value. the quality of reconstruction of particle size distribution degrades.The values of Omsa were set at 1°. 30 and 100. In the present case m.x...diffraction particle size measurements on 45 pm poly- styrene latex spheres in a water flow cell. The ensemble scattering method assumed that the...form it is possible in theory to determine the range of the diffraction signature given by Eqs. 5 refractive indez along with the size distribution and

  19. On the behavior of mud floc size distribution : Model calibration and model behavior

    NARCIS (Netherlands)

    Mietta, F.; Chassagne, C.; Verney, R.; Winterwerp, J.C.

    2011-01-01

    In this paper, we study a population balance equation (PBE) where flocs are distributed into classes according to their mass. Each class i contains i primary particles with mass mp and size Lp. All differently sized flocs can aggregate, binary breakup into two equally sized flocs is used, and the

  20. Trough models: Universality classes, distribution of avalanches, and cluster sizes

    Science.gov (United States)

    Leung, Kwan-Tai

    1992-11-01

    Extensions of the one-dimensional two-state trough model introduced by Carlson, Chayes, Grannan, and Swindle (CCGS) [Phys. Rev. A 42, 2467 (1990)] are considered. In particular, I investigate what kinds of physical processes are relevant to its scaling behavior. Short-range rearrangements of trough positions (slide events), which were neglected by CCGS, are shown to be irrelevant. By a simple modification of the dynamics, however, I obtain universality classes characterized by a single parameter. For trough models in general, including the two-state and the ``limited local'' sandpile models, asymptotically exact relations between the distribution of trough-trough distances and that of the mass of avalanches are derived. They yield moment relations in agreement with Krug's [J. Stat. Phys. 66, 1635 (1992)]. All results are verified by simulations.

  1. A GENERALIZED CLASS OF TRANSFORMATION MATRICES FOR THE RECONSTRUCTION OF SPHERE SIZE DISTRIBUTIONS FROM SECTION CIRCLE SIZE DISTRIBUTIONS

    Directory of Open Access Journals (Sweden)

    Willi Pabst

    2017-03-01

    Full Text Available A generalized formulation of transformation matrices is given for the reconstruction of sphere diameter distributions from their section circle diameter distributions. This generalized formulation is based on a weight shift parameter that can be adjusted from 0 to 1. It includes the well-known Saltykov and Cruz-Orive transformations as special cases (for parameter values of 0 and 0.5, respectively. The physical meaning of this generalization is explained (showing, among others, that the Woodhead transformation should be bounded by the Saltykov transformation on the one side and by our transformation from the other and its numerical performance is investigated. In particular, it is shown that our generalized transformation is numerically highly unstable, i.e. introduces numerical artefacts (oscillations or even unphysical negative sphere frequencies into the reconstruction, and can lead to completely wrong results when a critical value of the parameter (usually in the range 0.7-0.9, depending on the type of distribution is exceeded. It is shown that this numerical instability is an intrinsic feature of these transformations that depends not only on the weight shift parameter value and is affected both by the type and the position of the distribution. It occurs in a natural way also for the Cruz-Orive and other transformations with finite weight shift parameter values and is not just caused by inadequate input data (e.g. as a consequence of an insufficient number of objects counted, as commonly assumed. Finally it is shown that an even more general class of transformation matrices can be defined that includes, in addition to the aformentioned transformations, also the Wicksell transformation.

  2. First-principles derivation of static avalanche-size distributions.

    Science.gov (United States)

    Le Doussal, Pierre; Wiese, Kay Jörg

    2012-06-01

    We study the energy minimization problem for an elastic interface in a random potential plus a quadratic well. As the position of the well is varied, the ground state undergoes jumps, called shocks or static avalanches. We introduce an efficient and systematic method to compute the statistics of avalanche sizes and manifold displacements. The tree-level calculation, i.e., mean-field limit, is obtained by solving a saddle-point equation. Graphically, it can be interpreted as the sum of all tree graphs. The 1-loop corrections are computed using results from the functional renormalization group. At the upper critical dimension the shock statistics is described by the Brownian force model (BFM), the static version of the so-called Alessandro-Beatrice-Bertotti-Montorsi (ABBM) model in the nonequilibrium context of depinning. This model can itself be treated exactly in any dimension and its shock statistics is that of a Lévy process. Contact is made with classical results in probability theory on the Burgers equation with Brownian initial conditions. In particular we obtain a functional extension of an evolution equation introduced by Carraro and Duchon, which recursively constructs the tree diagrams in the field theory.

  3. Estimating Functions of Distributions Defined over Spaces of Unknown Size

    Directory of Open Access Journals (Sweden)

    David H. Wolpert

    2013-10-01

    Full Text Available We consider Bayesian estimation of information-theoretic quantities from data, using a Dirichlet prior. Acknowledging the uncertainty of the event space size m and the Dirichlet prior’s concentration parameter c, we treat both as random variables set by a hyperprior. We show that the associated hyperprior, P(c, m, obeys a simple “Irrelevance of Unseen Variables” (IUV desideratum iff P(c, m = P(cP(m. Thus, requiring IUV greatly reduces the number of degrees of freedom of the hyperprior. Some information-theoretic quantities can be expressed multiple ways, in terms of different event spaces, e.g., mutual information. With all hyperpriors (implicitly used in earlier work, different choices of this event space lead to different posterior expected values of these information-theoretic quantities. We show that there is no such dependence on the choice of event space for a hyperprior that obeys IUV. We also derive a result that allows us to exploit IUV to greatly simplify calculations, like the posterior expected mutual information or posterior expected multi-information. We also use computer experiments to favorably compare an IUV-based estimator of entropy to three alternative methods in common use. We end by discussing how seemingly innocuous changes to the formalization of an estimation problem can substantially affect the resultant estimates of posterior expectations.

  4. General expression for the component size distribution in infinite configuration networks.

    Science.gov (United States)

    Kryven, Ivan

    2017-05-01

    In the infinite configuration network the links between nodes are assigned randomly with the only restriction that the degree distribution has to match a predefined function. This work presents a simple equation that gives for an arbitrary degree distribution the corresponding size distribution of connected components. This equation is suitable for fast and stable numerical computations up to the machine precision. The analytical analysis reveals that the asymptote of the component size distribution is completely defined by only a few parameters of the degree distribution: the first three moments, scale, and exponent (if applicable). When the degree distribution features a heavy tail, multiple asymptotic modes are observed in the component size distribution that, in turn, may or may not feature a heavy tail.

  5. Size Distributions and Characterization of Native and Ground Samples for Toxicology Studies

    Science.gov (United States)

    McKay, David S.; Cooper, Bonnie L.; Taylor, Larry A.

    2010-01-01

    This slide presentation shows charts and graphs that review the particle size distribution and characterization of natural and ground samples for toxicology studies. There are graphs which show the volume distribution versus the number distribution for natural occurring dust, jet mill ground dust, and ball mill ground dust.

  6. Methods for determining particle size distribution and growth rates between 1 and 3 nm using the Particle Size Magnifier

    CERN Document Server

    Lehtipalo, Katrianne; Kontkanen, Jenni; Kangasluoma, Juha; Franchin, Alessandro; Wimmer, Daniela; Schobesberger, Siegfried; Junninen, Heikki; Petäjä, Tuukka; Sipilä, Mikko; Mikkilä, Jyri; Vanhanen, Joonas; Worsnop, Douglas R; Kulmala, Markku

    2014-01-01

    The most important parameters describing the atmospheric new particle formation process are the particle formation and growth rates. These together determine the amount of cloud condensation nuclei attributed to secondary particle formation. Due to difficulties in detecting small neutral particles, it has previously not been possible to derive these directly from measurements in the size range below about 3 nm. The Airmodus Particle Size Magnifier has been used at the SMEAR II station in Hyytiälä, southern Finland, and during nucleation experiments in the CLOUD chamber at CERN for measuring particles as small as about 1 nm in mobility diameter. We developed several methods to determine the particle size distribution and growth rates in the size range of 1–3 nm from these data sets. Here we introduce the appearance-time method for calculating initial growth rates. The validity of the method was tested by simulations with the Ion-UHMA aerosol dynamic model.

  7. Intensity and degree of segregation in bimodal and multimodal grain size distributions

    Science.gov (United States)

    Katra, Itzhak; Yizhaq, Hezi

    2017-08-01

    The commonly used grain size analysis technique which applies moments (sorting, skewness and kurtosis) is less useful in the case of sediments with bimodal size distributions. Herein we suggest a new simple method for analyzing the degree of grain size segregation in sand-sized sediment that has clear bimodal size distributions. Two main features are used to characterize the bimodal distribution: grain diameter segregation, which is the normalized difference between coarse and fine grain diameters, and the frequency segregation which is the normalized difference in frequencies between two modes. The new defined indices can be calculated from frequency plot curves and can be graphically represented on a two dimensional coordinate system showing the dynamical aspects of the size distribution. The results enable comparison between granular samples from different locations and/or times to shed new light on the dynamic processes involved in grain size segregation of sediments. We demonstrate here the use of this method to analyze bimodal distributions of aeolian granular samples mostly from aeolian megaripples. Six different aeolian cases were analyzed to highlight the method's applicability, which is relevant to wide research themes in the Earth and environmental sciences, and can furthermore be easily adapted to analyze polymodal grain size distributions.

  8. Influence of stress-path on pore size distribution in granular materials

    Science.gov (United States)

    Das, Arghya; Kumar, Abhinav

    2017-06-01

    Pore size distribution is an important feature of granular materials in the context of filtration and erosion in soil hydraulic structures. Present study focuses on the evolution characteristics of pore size distribution for numerically simulated granular assemblies while subjected to various compression boundary constrain, namely, conventional drained triaxial compression, one-dimensional or oedometric compression and isotropic compression. We consider the effects initial packing of the granular assembly, loose or dense state. A simplified algorithm based on Delaunay tessellation is used for the estimation of pore size distribution for the deforming granular assemblies at various stress states. The analyses show that, the evolution of pore size is predominantly governed by the current porosity of the granular assembly while the stress path or loading process has minimal influence. Further it has also been observed that pore volume distribution reaches towards a critical distribution at the critical porosity during shear enhanced loading process irrespective of the deformation mechanism either compaction or dilation.

  9. Shear strength and microstructure of polydisperse packings: The effect of size span and shape of particle size distribution.

    Science.gov (United States)

    Azéma, Emilien; Linero, Sandra; Estrada, Nicolas; Lizcano, Arcesio

    2017-08-01

    By means of extensive contact dynamics simulations, we analyzed the effect of particle size distribution (PSD) on the strength and microstructure of sheared granular materials composed of frictional disks. The PSDs are built by means of a normalized β function, which allows the systematic investigation of the effects of both, the size span (from almost monodisperse to highly polydisperse) and the shape of the PSD (from linear to pronouncedly curved). We show that the shear strength is independent of the size span, which substantiates previous results obtained for uniform distributions by packing fraction. Notably, the shear strength is also independent of the shape of the PSD, as shown previously for systems composed of frictionless disks. In contrast, the packing fraction increases with the size span, but decreases with more pronounced PSD curvature. At the microscale, we analyzed the connectivity and anisotropies of the contacts and forces networks. We show that the invariance of the shear strength with the PSD is due to a compensation mechanism which involves both geometrical sources of anisotropy. In particular, contact orientation anisotropy decreases with the size span and increases with PSD curvature, while the branch length anisotropy behaves inversely.

  10. Influence of density-dependent competition on foraging and migratory behavior of a subtropical colonial seabird.

    Science.gov (United States)

    Lamb, Juliet S; Satgé, Yvan G; Jodice, Patrick G R

    2017-08-01

    Density-dependent competition for food resources influences both foraging ecology and reproduction in a variety of animals. The relationship between colony size, local prey depletion, and reproductive output in colonial central-place foragers has been extensively studied in seabirds; however, most studies have focused on effects of intraspecific competition during the breeding season, while little is known about whether density-dependent resource depletion influences individual migratory behavior outside the breeding season. Using breeding colony size as a surrogate for intraspecific resource competition, we tested for effects of colony size on breeding home range, nestling health, and migratory patterns of a nearshore colonial seabird, the brown pelican (Pelecanus occidentalis), originating from seven breeding colonies of varying sizes in the subtropical northern Gulf of Mexico. We found evidence for density-dependent effects on foraging behavior during the breeding season, as individual foraging areas increased linearly with the number of breeding pairs per colony. Contrary to our predictions, however, nestlings from more numerous colonies with larger foraging ranges did not experience either decreased condition or increased stress. During nonbreeding, individuals from larger colonies were more likely to migrate, and traveled longer distances, than individuals from smaller colonies, indicating that the influence of density-dependent effects on distribution persists into the nonbreeding period. We also found significant effects of individual physical condition, particularly body size, on migratory behavior, which in combination with colony size suggesting that dominant individuals remain closer to breeding sites during winter. We conclude that density-dependent competition may be an important driver of both the extent of foraging ranges and the degree of migration exhibited by brown pelicans. However, the effects of density-dependent competition on breeding

  11. An Empirical Bayes Mixture Model for Effect Size Distributions in Genome-Wide Association Studies

    DEFF Research Database (Denmark)

    Thompson, Wesley K.; Wang, Yunpeng; Schork, Andrew J.

    2015-01-01

    for discovery, and polygenic risk prediction. To this end, previous work has used effect-size models based on various distributions, including the normal and normal mixture distributions, among others. In this paper we propose a scale mixture of two normals model for effect size distributions of genome...... minimizing discrepancies between the parametric mixture model and resampling-based nonparametric estimates of replication effect sizes and variances. We describe in detail the implications of this model for estimation of the non-null proportion, the probability of replication in de novo samples, the local...

  12. Methods of computing vocabulary size for the two-parameter rank distribution

    Science.gov (United States)

    Edmundson, H. P.; Fostel, G.; Tung, I.; Underwood, W.

    1972-01-01

    A summation method is described for computing the vocabulary size for given parameter values in the 1- and 2-parameter rank distributions. Two methods of determining the asymptotes for the family of 2-parameter rank-distribution curves are also described. Tables are computed and graphs are drawn relating paris of parameter values to the vocabulary size. The partial product formula for the Riemann zeta function is investigated as an approximation to the partial sum formula for the Riemann zeta function. An error bound is established that indicates that the partial product should not be used to approximate the partial sum in calculating the vocabulary size for the 2-parameter rank distribution.

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

    Science.gov (United States)

    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

    2013-11-01

    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

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

    Science.gov (United States)

    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

  15. Concentrations and Size Distributions of Bacteria-Containing Particles over Oceans from China to the Arctic Ocean

    Directory of Open Access Journals (Sweden)

    Ming Li

    2017-05-01

    Full Text Available During the third China Arctic Research Expedition (July–September 2008, size-resolved measurements of bacteria-containing particles (BCPs in the marine boundary layer (MBL air were conducted during a cruise through the East China Sea, the Yellow Sea, the Japan Sea, the Okhotsk Sea, the Bering Sea, the Chukchi Sea, and the Arctic Ocean. The concentrations of total airborne BCPs (TBCPs, non-salt tolerant airborne BCPs (NSBCPs, and salt tolerant airborne BCPs (SBCPs varied from 29 to 955 CFU m−3 (CFU = Colony Forming Unit, 16 to 919 CFU m−3, and 4 to 276 CFU m−3, with an average value of 275, 182, and 92 CFU m−3, respectively. Although the SBCP concentrations were less than the NSBCP concentrations when averaged over all measurements, there are several cases where the reverse is true (e.g., in the high Arctic Ocean. During the cruise, the TBCP sizes were dominated by the diameter >4.7 μm fraction (accounted for 46.3% on average, while the fine fraction (diameter <2.1 μm accounted for 27.8%. For NSBCPs and SBCPs, the coarse fraction also was the dominant fraction over most regions. The influence of local meteorological conditions on the abundance, size distributions, and species of airborne bacteria is discussed. Notably, in the atmosphere over the Arctic Ocean the abundance of airborne bacteria was apparently related to the distribution of sea ice. As cultivation based methodologies may underestimate the environmental bacterial communities, it is expected that the abundance of bacteria in the ambient air would be higher than that observed in this study. In order to distinguish different species of bacteria, molecular biological techniques (e.g., 16S rDNA analysis are required for identification in future investigations.

  16. Undersampling power-law size distributions: effect on the assessment of extreme natural hazards

    Science.gov (United States)

    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.

  17. Effect of Particle Size Distribution on Slurry Rheology: Nuclear Waste Simulant Slurries

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Jaehun; Oh, Takkeun; Luna, Maria L.; Schweiger, Michael J.

    2011-07-05

    Controlling the rheological properties of slurries has been of great interest in various industries such as cosmetics, ceramic processing, and nuclear waste treatment. Many physicochemical parameters, such as particle size, pH, ionic strength, and mass/volume fraction of particles, can influence the rheological properties of slurry. Among such parameters, the particle size distribution of slurry would be especially important for nuclear waste treatment because most nuclear waste slurries show a broad particle size distribution. We studied the rheological properties of several different low activity waste nuclear simulant slurries having different particle size distributions under high salt and high pH conditions. Using rheological and particle size analysis, it was found that the percentage of colloid-sized particles in slurry appears to be a key factor for rheological characteristics and the efficiency of rheological modifiers. This behavior was shown to be coupled with an existing electrostatic interaction between particles under a low salt concentration. Our study suggests that one may need to implement the particle size distribution as a critical factor to understand and control rheological properties in nuclear waste treatment plants, such as the U.S. Department of Energy’s Hanford and Savannah River sites, because the particle size distributions significantly vary over different types of nuclear waste slurries.

  18. Particle Size Distributions Measured in the Stratospheric Plumes of Three Rockets During the ACCENT Missions

    Science.gov (United States)

    Wiedinmyer, C.; Brock, C. A.; Reeves, J. M.; Ross, M. N.; Schmid, O.; Toohey, D.; Wilson, J. C.

    2001-12-01

    The global impact of particles emitted by rocket engines on stratospheric ozone is not well understood, mainly due to the lack of comprehensive in situ measurements of the size distributions of these emitted particles. During the Atmospheric Chemistry of Combustion Emissions Near the Tropopause (ACCENT) missions in 1999, the NASA WB-57F aircraft carried the University of Denver N-MASS and FCAS instruments into the stratospheric plumes from three rockets. Size distributions of particles with diameters from 4 to approximately 2000 nm were calculated from the instrument measurements using numerical inversion techniques. The data have been averaged over 30-second intervals. The particle size distributions observed in all of the rocket plumes included a dominant mode near 60 nm diameter, probably composed of alumina particles. A smaller mode at approximately 25 nm, possibly composed of soot particles, was seen in only the plumes of rockets that used liquid oxygen and kerosene as a propellant. Aircraft exhaust emitted by the WB-57F was also sampled; the size distributions within these plumes are consistent with prior measurements in aircraft plumes. The size distributions for all rocket intercepts have been fitted to bimodal, lognormal distributions to provide input for global models of the stratosphere. Our data suggest that previous estimates of the solid rocket motor alumina size distributions may underestimate the alumina surface area emission index, and so underestimate the particle surface area available for heterogeneous chlorine activation reactions in the global stratosphere.

  19. Bacterial colonies in solid media and foods: a review on their growth and interactions with the micro-environment

    Directory of Open Access Journals (Sweden)

    Sophie eJeanson

    2015-12-01

    Full Text Available Bacteria, either indigenous or added, are immobilised in solid foods where they grow as colonies. Since the 80’s, relatively few research groups have explored the implications of bacteria growing as colonies and mostly focused on pathogens in large colonies on agar/gelatine media. It is only recently that high resolution imaging techniques and biophysical characterisation techniques increased the understanding of the growth of bacterial colonies, for different sizes of colonies, at the microscopic level and even down to the molecular level. This review covers the studies on bacterial colony growth in agar or gelatine media mimicking the food environment and in model cheese. The following conclusions have been brought to light.Firstly, under unfavourable conditions, mimicking food conditions, the immobilisation of bacteria always constrains their growth in comparison with planktonic growth and increases the sensibility of bacteria to environmental stresses. Secondly, the spatial distribution describes both the distance between colonies and the size of the colonies as a function of the initial level of population. By studying the literature, we concluded that there systematically exists a threshold that distinguishes micro-colonies (radius 200 µm. Micro-colonies growth resembles planktonic growth and no pH microgradients could be observed. Macro-colonies growth is slower than planktonic growth and pH microgradients could be observed in and around them due to diffusion limitations which occur around, but also inside the macro-colonies. Diffusion limitations of milk proteins have been demonstrated in a model cheese around and in the bacterial colonies. In conclusion, the impact of immobilisation is predominant for macro-colonies in comparison with micro-colonies. However, the interaction between the colonies and the food matrix itself remains to be further investigated at the microscopic scale.

  20. Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment.

    Science.gov (United States)

    Jeanson, Sophie; Floury, Juliane; Gagnaire, Valérie; Lortal, Sylvie; Thierry, Anne

    2015-01-01

    Bacteria, either indigenous or added, are immobilized in solid foods where they grow as colonies. Since the 80's, relatively few research groups have explored the implications of bacteria growing as colonies and mostly focused on pathogens in large colonies on agar/gelatine media. It is only recently that high resolution imaging techniques and biophysical characterization techniques increased the understanding of the growth of bacterial colonies, for different sizes of colonies, at the microscopic level and even down to the molecular level. This review covers the studies on bacterial colony growth in agar or gelatine media mimicking the food environment and in model cheese. The following conclusions have been brought to light. Firstly, under unfavorable conditions, mimicking food conditions, the immobilization of bacteria always constrains their growth in comparison with planktonic growth and increases the sensibility of bacteria to environmental stresses. Secondly, the spatial distribution describes both the distance between colonies and the size of the colonies as a function of the initial level of population. By studying the literature, we concluded that there systematically exists a threshold that distinguishes micro-colonies (radius 200 μm). Micro-colonies growth resembles planktonic growth and no pH microgradients could be observed. Macro-colonies growth is slower than planktonic growth and pH microgradients could be observed in and around them due to diffusion limitations which occur around, but also inside the macro-colonies. Diffusion limitations of milk proteins have been demonstrated in a model cheese around and in the bacterial colonies. In conclusion, the impact of immobilization is predominant for macro-colonies in comparison with micro-colonies. However, the interaction between the colonies and the food matrix itself remains to be further investigated at the microscopic scale.

  1. Distribution Functions of Sizes and Fluxes Determined from Supra-Arcade Downflows

    Science.gov (United States)

    McKenzie, D.; Savage, S.

    2011-01-01

    The frequency distributions of sizes and fluxes of supra-arcade downflows (SADs) provide information about the process of their creation. For example, a fractal creation process may be expected to yield a power-law distribution of sizes and/or fluxes. We examine 120 cross-sectional areas and magnetic flux estimates found by Savage & McKenzie for SADs, and find that (1) the areas are consistent with a log-normal distribution and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution nor a normal distribution. As a demonstration of the applicability of these findings to improved understanding of reconnection, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution.

  2. Development of a simplified optical technique for the simultaneous measurement of particle size distribution and velocity

    Science.gov (United States)

    Smith, J. L.

    1983-01-01

    Existing techniques were surveyed, an experimental procedure was developed, a laboratory test model was fabricated, limited data were recovered for proof of principle, and the relationship between particle size distribution and amplitude measurements was illustrated in an effort to develop a low cost, simplified optical technique for measuring particle size distributions and velocities in fluidized bed combustors and gasifiers. A He-Ne laser illuminated Rochi Rulings (range 10 to 500 lines per inch). Various samples of known particle size distributions were passed through the fringe pattern produced by the rulings. A photomultiplier tube converted light from the fringe volume to an electrical signal which was recorded using an oscilloscope and camera. The signal amplitudes were correlated against the known particle size distributions. The correlation holds true for various samples.

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

    Science.gov (United States)

    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.

  4. Enhanced resolution particle size distributions by multiple angle photon correlation spectroscopy

    Science.gov (United States)

    Bott, Steven E.

    1989-01-01

    Photon correlation spectroscopy (PCS) has become a method of choice for measuring submicrometer particles. It is capable of rapid, accurate measurements of mean particle size. Since the measurements are nonperturbing, it is ideal for monitoring systems undergoing dynamic changes. Despite its widespread acceptance, the information content of PCS measurements for particle size distributions is low and provides limited resolution. A method is presented whereby PCS measurements made at several scattering angles plus the angular distribution of light scattered from the particles are combined in a single simultaneous analysis to effect an enhanced resolution particle size distribution. The efficacy of the method is assessed by recovering size distributions from computer simulated data and by comparisons of conventional PCS measurements of polystyrene spheres with those made by the new method.

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

    Science.gov (United States)

    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).

  6. NON-COHESIVE SOILS’ COMPRESSIBILITY AND UNEVEN GRAIN-SIZE DISTRIBUTION RELATION

    Directory of Open Access Journals (Sweden)

    Anatoliy Mirnyy

    2016-03-01

    Full Text Available This paper presents the results of laboratory investigation of soil compression phases with consideration of various granulometric composition. Materials and Methods Experimental soil box with microscale video recording for compression phases studies is described. Photo and video materials showing the differences of microscale particle movements were obtained for non-cohesive soils with different grain-size distribution. Results The analysis of the compression tests results and elastic and plastic deformations separation allows identifying each compression phase. It is shown, that soil density is correlating with deformability parameters only for the same grain-size distribution. Basing on the test results the authors suggest that compaction ratio is not sufficient for deformability estimating without grain-size distribution taken into account. Discussion and Conclusions Considering grain-size distribution allows refining technological requirements for artificial soil structures, backfills, and sand beds. Further studies could be used for developing standard documents, SP45.13330.2012 in particular.

  7. Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition

    NARCIS (Netherlands)

    Schmale, J.; Henning, S.; Henzing, B.; Keskinen, H.; Sellegri, K.; Ovadnevaite, J.; Bougiatioti, A.; Kalivitis, N.; Stavroulas, I.; Jefferson, A.; Park, M.; Schlag, P.; Kristensson, A.; Iwamoto, Y.; Pringle, K.; Reddington, C.; Aalto, P.; Äijälä, M.; Baltensperger, U.; Bialek, J.; Birmili, W.; Bukowiecki, N.; Ehn, M.; Fjæraa, A.M.; Fiebig, M.; Frank, G.; Fröhlich, R.; Frumau, A.; Furuya, M.; Hammer, E.; Heikkinen, L.; Herrmann, E.; Holzinger, R.; Hyono, H.; Kanakidou, M.; Kiendler-Scharr, A.; Kinouchi, K.; Kos, G.; Kulmala, M.; Mihalopoulos, N.; Motos, G.; Nenes, A.; O'Dowd, C.; Paramonov, M.; Petäjä, T.; Picard, D.; Poulain, L.; Prévôt, A.S.H.; Slowik, J.; Sonntag, A.; Swietlicki, E.; Svenningsson, B.; Tsurumaru, H.; Wiedensohler, A.; Wittbom, C.; Ogren, J.A.; Matsuki, A.; Yum, S.S.; Myhre, C.L.; Carslaw, K.; Stratmann, F.; Gysel, M.

    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

  8. Forms of density regulation and (quasi-) stationary distributions of population sizes in birds

    DEFF Research Database (Denmark)

    Sæther, Bernt-Erik; Engen, Steinar; Grøtan, Vidar

    2008-01-01

    that have grown from very small population sizes followed by a period of fluctuations around K. We then use these parameters to estimate the quasi-stationary distribution of population size. There were often large uncertainties in these parameters specifying the form of density regulation that were...... generally independent of the duration of the study period. In contrast, precision in the estimates of environmental variance increased with the length of the time series. In most of the populations, a large proportion of the probability density of the (quasi-) stationary distribution of population sizes...... was located at intermediate population sizes relative to K. Thus, we suggest that the (quasi-) stationary distribution of population sizes represents a useful summary statistic that in many cases provides a more robust characterisation of basic population dynamics (e.g. range of variation in population...

  9. Effect of Lithium Ions on Copper Nanoparticle Size, Shape, and Distribution

    Directory of Open Access Journals (Sweden)

    Kyung-Deok Jang

    2012-01-01

    Full Text Available Copper nanoparticles were synthesized using lithium ions to increase the aqueous electrical conductivity of the solution and precisely control the size, shape, and size distribution of the particles. In this study, the conventional approach of increasing particle size by the concentration of copper ions and PGPPE in a copper chloride solution was compared to increasing the concentration of lithium chloride when the copper chloride concentration was held constant. Particle size and shape were characterized by TEM, and the size distribution of the particles at different concentrations was obtained by particle size analysis. Increasing the concentration of copper ion in the solution greatly increased the aqueous electric conductivity and the size of the particles but led to a wide size distribution ranging from 150 nm to 400 nm and rough particle morphology. The addition of lithium ions increased the size of the particles, but maintains them in a range of 250 nm. In addition the particles exhibited spherical shape as determined by TEM. The addition of lithium ions to the solution has the potential to synthesize nanoparticles with optimal characteristics for printing applications by maintaining a narrow size range and spherical shape.

  10. Characterizations of particle size distribution of the droplets exhaled by sneeze.

    Science.gov (United States)

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

    2013-11-06

    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.

  11. Evolution of electrical distribution grid sizing considering self-consumption of local renewable production

    OpenAIRE

    Rogeau, Antoine; Barbier, Thibaut; Girard, Robin; Kong, Nicolas

    2017-01-01

    International audience; In the last decades, renewable energy sources have been increasing their shares in the world energy market. In addition to the ecological benefits, this trend can have adjunct benefits, for example for distribution system operators: a gain in their grid sizing. Indeed, installation of decentralized production, when used in a self-consumption approach, can lead to reduction of the consumption peaks. This work is willing to quantify what grid sizing reduction a distribut...

  12. Bed load size distribution and flow conditions in a high mountain catchment of Central Pyrenees

    OpenAIRE

    Martínez Castroviejo, Ricardo

    1990-01-01

    The bed load size distribution caused by different types of flow are compared in a high mountain catchment located in the upper Gallego river basin (Central Spanish’ Pyrenees). Three kinds of hydrologic events could be defined: those triggered by heavy autumn rainfalls, those originated by isolated summer rainstorms and those promoted by snowmelting. Each one is characterized by a peculiar bed load size distribution. Thus, it could be demonstrated that the coarser fractions, above 30 mm in di...

  13. Are range-size distributions consistent with species-level heritability?

    DEFF Research Database (Denmark)

    Borregaard, Michael Krabbe; Gotelli, Nicholas; Rahbek, Carsten

    2012-01-01

    The concept of species-level heritability is widely contested. Because it is most likely to apply to emergent, species-level traits, one of the central discussions has focused on the potential heritability of geographic range size. However, a central argument against range-size heritability has...... been that it is not compatible with the observed shape of present-day species range-size distributions (SRDs), a claim that has never been tested. To assess this claim, we used forward simulation of range-size evolution in clades with varying degrees of range-size heritability, and compared the output...

  14. Particle size distribution of major inorganic species in atmospheric aerosols from Majorca (Spain).

    Science.gov (United States)

    Mateu, J.; Forteza, R.; Cerdà, V.; Colom-Altés, M.

    1995-09-01

    Atmospheric aerosols collected by means of a cascade impaction system at the campus of the University of the Balearic Islands (Majorca, Spain) from November 1993 to February 1994 were analysed for chloride, nitrate, sulphate, ammonium, calcium, magnesium, sodium and potassium. Based on particle size distribution, the species studied were classified into three groups: (a) concentration decrease with particle size (sulphate and ammonium), (b) concentration increase with particle size (chloride, calcium, magnesium and sodium), and ( c) independent of particle size (nitrate and potassium). A principal component analysis (PCA) revealed a clear relationship between particle size and analyte origin. Also, the origin of sulphate and potassium fine and coarse particles was found to be different.

  15. Model independent determination of colloidal silica size distributions via analytical ultracentrifugation

    NARCIS (Netherlands)

    Planken, K.L.|info:eu-repo/dai/nl/304841099; Kuipers, B.W.M.|info:eu-repo/dai/nl/304841110; Philipse, A.P.|info:eu-repo/dai/nl/073532894

    2008-01-01

    We report a method to determine the particle size distribution of small colloidal silica spheres via analytical ultracentrifugation and show that the average particle size, variance, standard deviation, and relative polydispersity can be obtained from a single sedimentation velocity (SV) analytical

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

    Science.gov (United States)

    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 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.

  17. Sediment - size distribution of innershelf off Gopalpur, Orissa coast using EOF analysis

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, T.V.R.; Rao, K.M.; Rao, M.M.M.; Lakshminarayana, S.; Murthy, K.S.R.

    Function (EOF) analysis carried out for the above units on grain-size distribution of the sediments in the ø - size class revealed that the first three ø - dependant eigen function viz. c1, (ø), c2 (ø) and c3 (ø) account for more than 95% of variance...

  18. Characterization of Nanocrystal Size Distribution Using Raman Spectroscopy with a Multi-particle Phonon Confinement Model

    NARCIS (Netherlands)

    Dogan, I.; M. C. M. van de Sanden,

    2015-01-01

    We demonstrate how to determine the size distribution of semiconductor nanocrystals in a quantitative manner using Raman spectroscopy employing an analytically defined multi-particle phonon confinement model. Results obtained are in excellent agreement with the other size analysis techniques like

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

    Science.gov (United States)

    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 st...

  20. Particle size distributions from laboratory-scale biomass fires using fast response instruments

    Directory of Open Access Journals (Sweden)

    S. Hosseini

    2010-08-01

    Full Text Available Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date, particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distributions in well controlled repeatable lab scale biomass fires for southwestern United States fuels with focus on chaparral. The combustion laboratory at the United States Department of Agriculture-Forest Service's Fire Science Laboratory (USDA-FSL, Missoula, MT provided a repeatable combustion and dilution environment ideal for measurements. For a variety of fuels tested the major mode of particle size distribution was in the range of 29 to 52 nm, which is attributable to dilution of the fresh smoke. Comparing mass size distribution from FMPS and APS measurement 51–68% of particle mass was attributable to the particles ranging from 0.5 to 10 μm for PM10. Geometric mean diameter rapidly increased during flaming and gradually decreased during mixed and smoldering phase combustion. Most fuels produced a unimodal distribution during flaming phase and strong biomodal distribution during smoldering phase. The mode of combustion (flaming, mixed and smoldering could be better distinguished using the slopes in MCE (Modified Combustion Efficiency vs. geometric mean diameter than only using MCE values.

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

    Science.gov (United States)

    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

  2. Laboratory study of the particle-size distribution of Decabromodiphenyl ether (BDE-209) in ambient air.

    Science.gov (United States)

    Su, Peng-hao; Hou, Chun-yan; Sun, Dan; Feng, Dao-lun; Halldorson, Thor; Ding, Yong-sheng; Li, Yi-fan; Tomy, Gregg T

    2016-02-01

    Laboratory measurements for particle-size distribution of Decabromodiphenyl ether (BDE-209) were performed in a 0.5 m(3) sealed room at 25 °C. BDE-209 was manually bounded to ambient particles. An electrostatic field-sampler was employed to collect particles. The number of collected particles (n(i,j), i and j was the class of particle diameter and applied voltage on electrostatic field-sampler sampler, respectively) and the corresponding mass of BDE-209 in collected particles (m(∑i,j)) were determined in a series of 6 experiments. The particle-size distribution coefficient (ki) was calculated through equations related to n(i,j) and m(∑i,j), and the particle-size distribution of BDE-209 was determined by ki·n(i,j). Results revealed that BDE-209 distributed in particles of all size and were not affiliated with fine particles as in field measurements. The particle size-fraction should be taken into account when discussing the particle-size distribution of BDE-209 in ambient air due to the normalized coefficients (normalized to k1) and were approximately in the same order of magnitude for each diameter class. The method described in the present study was deemed feasible in determining the particle-size distribution of BDE-209 from vaporization sources and helpful to understanding the instinct rule of particle-size distribution of BDE-209, and potentially feasible for other SVOCs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Size distributions of water-soluble organic carbon in ambient aerosols and its size-resolved thermal characteristics

    Science.gov (United States)

    Yu, Jian Zhen; Yang, Hong; Zhang, Hongyi; Lau, Alexis K. H.

    Aerosol mass size distributions of water-soluble organic carbon (WSOC) were studied at a coastal site in Hong Kong. Eleven sets of 72-h samples were collected using an eight-stage impactor sampler over three seasons in 2000-2001. Regardless of air mass origins being mainly marine or continental, WSOC exhibited bimodal size distributions with a dominant fine mode and a minor coarse mode in the size range of >0.43 μm. The two modes had a mass mean aerodynamic diameter (MMAD) of 0.7±0.1 and 4.0±0.3 μm, respectively. The fine WSOC accounted for the major proportion of the total WSOC, ranging from two-thirds to four-fifths. The WSOC mixtures were resolved into 3-5 peaks under controlled progressive heating and combustion conditions. A positive matrix factorization analysis deconvoluted the WSOC mixtures into three component groups of different thermal behaviors. The three groups of WSOC species were postulated to be low, medium, and high molecular weight (MW) polar compounds on the basis of their thermal evolution features. On average, they accounted for 21%, 39%, and 40% of fine WSOC (2.1 μm) was largely made of the low MW polar compound group. The low MW group had a bimodal distribution with a dominant coarse mode, likely associated with sea salt aerosols. The medium and the high MW groups had a single mode distribution in the droplet mode, both with an average MMAD of 0.7±0.1 μm. Their droplet mode presence indicated that they were associated with cloud-processed particles. There is evidence to suggest that the high MW group was likely secondary in origin, formed during cloud processing.

  4. Effects of pore-size and shape distributions on diffusion pore imaging by nuclear magnetic resonance.

    Science.gov (United States)

    Kuder, Tristan Anselm; Laun, Frederik Bernd

    2015-08-01

    In medical imaging and porous media research, NMR diffusion measurements are extensively used to investigate the structure of diffusion restrictions such as cell membranes. Recently, several methods have been proposed to unambiguously determine the shape of arbitrary closed pores or cells filled with an NMR-visible medium by diffusion experiments. The first approach uses a combination of a long and a short diffusion-weighting gradient pulse, while the other techniques employ short gradient pulses only. While the eventual aim of these methods is to determine pore-size and shape distributions, the focus has been so far on identical pores. Thus, the aim of this work is to investigate the ability of these different methods to resolve pore-size and orientation distributions. Simulations were performed comparing the various pore imaging techniques employing different distributions of pore size and orientation and varying timing parameters. The long-narrow gradient profile is most advantageous to investigate pore distributions, because average pore images can be directly obtained. The short-gradient methods suppress larger pores or induce a considerable blurring. Moreover, pore-shape-specific artifacts occur; for example, the central part of a distribution of cylinders may be largely underestimated. Depending on the actual pore distribution, short-gradient methods may nonetheless yield good approximations of the average pore shape. Furthermore, the application of short-gradient methods can be advantageous to differentiate whether pore-size distributions or intensity distributions, e.g., due to surface relaxation, are predominant.

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

    Energy Technology Data Exchange (ETDEWEB)

    Shankman, C.; Gladman, B. J. [Department of Physics and Astronomy, University of British Columbia, 6224 Agriculture Road, Vancouver, BC V6T 1Z1 (Canada); Kaib, N. [Department of Physics and Astronomy, Queens University (Canada); Kavelaars, J. J. [National Research Council of Canada, Victoria, BC V9E 2E7 (Canada); Petit, J. M. [Institut UTINAM, CNRS-Universite de Franche-Comte, Besancon (France)

    2013-02-10

    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, which 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 .

  6. Methane Bubble Size Distributions, Flux, and Dissolution in a Freshwater Lake.

    Science.gov (United States)

    Delwiche, Kyle B; Hemond, Harold F

    2017-12-05

    The majority of methane produced in many anoxic sediments is released via ebullition. These bubbles are subject to dissolution as they rise, and dissolution rates are strongly influenced by bubble size. Current understanding of natural methane bubble size distributions is limited by the difficulty in measuring bubble sizes over wide spatial or temporal scales. Our custom optical bubble size sensors recorded bubble sizes and release timing at 8 locations in Upper Mystic Lake, MA continuously for 3 months. Bubble size distributions were spatially heterogeneous even over relatively small areas experiencing similar flux, suggesting that localized sediment conditions are important to controlling bubble size. There was no change in bubble size distributions over the 3 month sampling period, but mean bubble size was positively correlated with daily ebullition flux. Bubble data was used to verify the performance of a widely used bubble dissolution model, and the model was then used to estimate that bubble dissolution accounts for approximately 10% of methane accumulated in the hypolimnion during summer stratification, and at most 15% of the diffusive air-water-methane flux from the epilimnion.

  7. Colony formation in the cyanobacterium Microcystis.

    Science.gov (United States)

    Xiao, Man; Li, Ming; Reynolds, Colin S

    2018-02-22

    and inhibit the growth of less-buoyant species in deeper layers. Over time, accompanying species may fail to maintain viable populations, allowing Microcystis to dominate. Microcystis blooms can be controlled by artificial mixing. Microcystis colonies and non-buoyant phytoplankton will be exposed to identical light conditions if they are evenly distributed over the water column. In that case, green algae and diatoms, which generally have a higher growth rate than Microcystis, will be more successful. Under such mixing conditions, other phytoplankton taxa could recover and the dominance of Microcystis would be reduced. This review advances our understanding of the factors and mechanisms affecting Microcystis colony formation and size in the field and laboratory through synthesis of current knowledge. The main transition pathways of morphological changes in Microcystis provide an example of the phenotypic plasticity of organisms during morphological evolution from a unicellular to multicellular state. We emphasise that the mechanisms and factors influencing competition among various close morphospecies are sometimes paradoxical because these morphospecies are potentially a single species. Further work is required to clarify the colony-forming process in different Microcystis morphospecies and the seasonal variation in this process. This will allow researchers to grow laboratory cultures that more closely reflect field morphologies and to optimise artificial mixing to manage blooms more effectively. © 2018 Cambridge Philosophical Society.

  8. Colony Dimorphism in Bradyrhizobium Strains

    Science.gov (United States)

    Sylvester-Bradley, Rosemary; Thornton, Philip; Jones, Peter

    1988-01-01

    Ten isolates of Bradyrhizobium spp. which form two colony types were studied; the isolates originated from a range of legume species. The two colony types differed in the amount of gum formed or size or both, depending on the strain. Whole 7-day-old colonies of each type were subcultured to determine the proportion of cells which had changed to the other type. An iterative computerized procedure was used to determine the rate of switching per generation between the two types and to predict proportions reached at equilibrium for each strain. The predicted proportions of the wetter (more gummy) or larger colony type at equilibrium differed significantly between strains, ranging from 0.9999 (strain CIAT 2383) to 0.0216 (strain CIAT 2469), because some strains switched faster from dry to wet (or small to large) and others switched faster from wet to dry (or large to small). Predicted equilibrium was reached after about 140 generations in strain USDA 76. In all but one strain (CIAT 3030) the growth rate of the wetter colony type was greater than or similar to that of the drier type. The mean difference in generation time between the two colony types was 0.37 h. Doubling times calculated for either colony type after 7 days of growth on the agar surface ranged from 6.0 to 7.3 h. The formation of two persistent colony types by one strain (clonal or colony dimorphism) may be a common phenomenon among Bradyrhizobium strains. Images PMID:16347599

  9. Statistical analysis of bubble and crystal size distributions: Formulations and procedures

    Science.gov (United States)

    Proussevitch, Alexander A.; Sahagian, Dork L.; Tsentalovich, Evgeni P.

    2007-07-01

    Bubble and crystal size distributions have previously been described only by either exponential or power law functions. Within this limited framework, it has not been possible to characterize size distributions in a fully quantitative manner. We have developed an analytical and computational formulation with which to characterize and study crystal and bubble size distributions (BSD). This formulation demonstrates that all distributions known to date belong to the logarithmic family of statistical distributions. Four functions within the logarithmic family are best suited to natural bubbles and crystals (log normal, logistic, Weibull, and exponential). This characterization is supported by the fact that the power law function widely used for crystal and bubble size analysis is not a statistical distribution function, but rather represents an approximation of the upper regions (larger bubbles/crystals) of the logistic distribution, whose sizes are much larger than the mode. The coefficients for each of the four logarithmic functions can be derived by 1) best fit exceedance function of the logarithmic distribution, and 2) best fit of the linear transformation of the distribution probability density. A close match of the coefficients derived by the above two methods can be used as an indicator of correct function fitting (choice of initial values). Function fitting by exceedance curves leads to the most accurate statistical results, but has certain strict limitations, including 1) a requirement to rescale the base distribution function; 2) a higher failure rate for function fitting than that for distribution density; 3) uncertainty in observational data error estimates; and 4) unsuitability for visual interpretation. The most productive approach to visualization and interpretation of size distributions is through linear transformation of logarithmic distributions on the basis of probability densities. This also makes it possible to 1) clearly discern bimodal

  10. Dust Particle Size Distribution Inversion Based on the Multi Population Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Jiandong Mao Juan Li

    2014-01-01

    Full Text Available The aerosol number size distribution is the main parameter for characterizing aerosol optical properties and physical properties, it has a major influence on radiation forcing. With regard to some disadvantages in the traditional methods, a method based on the multi population genetic algorithm (MPGA is proposed and employed to retrieve the aerosol size distribution of dust particles. The MPGA principles and design are presented in detail. The MPGA has better performance compared with conventional methods. In order to verify the feasibility of the inversion method, the measured aerosol optical thickness (AOT data of dust particles taken by a sun photometer are used and a series of comparisons between the simple genetic algorithm (SGA and MPGA are carried out. The results show that the MPGA presents better properties when compared with the SGA with smaller inversion errors, smaller population size and fewer generation numbers to retrieve the aerosol size distribution. The MPGA inversion method is analyzed using the background day, dust storm event and seasonal size distribution. The method proposed in this study has important applications and reference value for aerosol particle size distribution inversion.

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

    Directory of Open Access Journals (Sweden)

    Sandro Claudio Lera

    Full Text Available 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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  14. New method to estimate the sample size for calculation of a proportion assuming binomial distribution.

    Science.gov (United States)

    Vallejo, Adriana; Muniesa, Ana; Ferreira, Chelo; de Blas, Ignacio

    2013-10-01

    Nowadays the formula to calculate the sample size for estimate a proportion (as prevalence) is based on the Normal distribution, however it would be based on a Binomial distribution which confidence interval was possible to be calculated using the Wilson Score method. By comparing the two formulae (Normal and Binomial distributions), the variation of the amplitude of the confidence intervals is relevant in the tails and the center of the curves. In order to calculate the needed sample size we have simulated an iterative sampling procedure, which shows an underestimation of the sample size for values of prevalence closed to 0 or 1, and also an overestimation for values closed to 0.5. Attending to these results we proposed an algorithm based on Wilson Score method that provides similar values for the sample size than empirically obtained by simulation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Particle size distribution effects on gas-particle mass transfer within electrostatic precipitators.

    Science.gov (United States)

    Clack, Herek L

    2006-06-15

    Varying degrees of mercury capture and transformation have been reported across electrostatic precipitators (ESPs). Previous analyses have shown that the dominant mass transfer mechanism responsible for mercury capture within ESPs is gas-particle mass transfer during particulate collection. Whereas previous analyses assumed dispersions of uniform size, the present analysis reveals the effects of polydispersity on both gas-particle mass transfer and particle collection within an ESP. The analysis reveals that the idealized monodisperse particle size distribution provides the highest gas-particle mass transfer but results in the lowest particle collection efficiency (% mass). As the particle size distribution broadens, gas-particle mass transfer decreases and particle collection efficiency increases. The results suggest that more than just reporting mean particle diameter provided by the sorbent manufacturer, pilot- and field-tests of sorbent injection for mercury emissions control need to experimentally measure the particle size distribution of the sorbent as it is injected in order to facilitate interpretation of their results.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  18. Deconvolution of the particle size distribution of ProRoot MTA and MTA Angelus.

    Science.gov (United States)

    Ha, William Nguyen; Shakibaie, Fardad; Kahler, Bill; Walsh, Laurence James

    2016-01-01

    Objective Mineral trioxide aggregate (MTA) cements contain two types of particles, namely Portland cement (PC) (nominally 80% w/w) and bismuth oxide (BO) (20%). This study aims to determine the particle size distribution (PSD) of PC and BO found in MTA. Materials and methods The PSDs of ProRoot MTA (MTA-P) and MTA Angelus (MTA-A) powder were determined using laser diffraction, and compared to samples of PC (at three different particle sizes) and BO. The non-linear least squares method was used to deconvolute the PSDs into the constituents. MTA-P and MTA-A powders were also assessed with scanning electron microscopy. Results BO showed a near Gaussian distribution for particle size, with a mode distribution peak at 10.48 μm. PC samples milled to differing degrees of fineness had mode distribution peaks from 19.31 down to 4.88 μm. MTA-P had a complex PSD composed of both fine and large PC particles, with BO at an intermediate size, whereas MTA-A had only small BO particles and large PC particles. Conclusions The PSD of MTA cement products is bimodal or more complex, which has implications for understanding how particle size influences the overall properties of the material. Smaller particles may be reactive PC or unreactive radiopaque agent. Manufacturers should disclose particle size information for PC and radiopaque agents to prevent simplistic conclusions being drawn from statements of average particle size for MTA materials.

  19. Five Days Granulocyte Colony-Stimulating Factor Treatment Increases Bone Formation and Reduces Gap Size of a Rat Segmental Bone Defect: A Pilot Study

    Directory of Open Access Journals (Sweden)

    Marietta Herrmann

    2018-02-01

    Full Text Available Bone is an organ with high natural regenerative capacity and most fractures heal spontaneously when appropriate fracture fixation is provided. However, additional treatment is required for patients with large segmental defects exceeding the endogenous healing potential and for patients suffering from fracture non-unions. These cases are often associated with insufficient vascularization. Transplantation of CD34+ endothelial progenitor cells (EPCs has been successfully applied to promote neovascularization of bone defects, however including extensive ex vivo manipulation of cells. Here, we hypothesized, that treatment with granulocyte colony-stimulating factor (G-CSF may improve bone healing by mobilization of CD34+ progenitor cells into the circulation, which in turn may facilitate vascularization at the defect site. In this pilot study, we aimed to characterize the different cell populations mobilized by G-CSF and investigate the influence of cell mobilization on the healing of a critical size femoral defect in rats. Cell mobilization was investigated by flow cytometry at different time points after five consecutive daily G-CSF injections. In a pilot study, bone healing of a 4.5-mm critical femoral defect in F344 rats was compared between a saline-treated control group and a G-CSF treatment group. In vivo microcomputed tomography and histology were applied to compare bone formation in both treatment groups. Our data revealed that leukocyte counts show a peak increase at the first day after the last G-CSF injection. In addition, we found that CD34+ progenitor cells, including EPCs, were significantly enriched at day 1, and further increased at day 5 and day 11. Upregulation of monocytes, granulocytes and macrophages peaked at day 1. G-CSF treatment significantly increased bone volume and bone density in the defect, which was confirmed by histology. Our data show that different cell populations are mobilized by G-CSF treatment in cell specific

  20. Austenite Grain Size Estimtion from Chord Lengths of Logarithmic-Normal Distribution

    Directory of Open Access Journals (Sweden)

    Adrian H.

    2017-12-01

    Full Text Available Linear section of grains in polyhedral material microstructure is a system of chords. The mean length of chords is the linear grain size of the microstructure. For the prior austenite grains of low alloy structural steels, the chord length is a random variable of gamma- or logarithmic-normal distribution. The statistical grain size estimation belongs to the quantitative metallographic problems. The so-called point estimation is a well known procedure. The interval estimation (grain size confidence interval for the gamma distribution was given elsewhere, but for the logarithmic-normal distribution is the subject of the present contribution. The statistical analysis is analogous to the one for the gamma distribution.

  1. 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

    Science.gov (United States)

    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.

  2. Simulation and analysis of the soot particle size distribution in a turbulent nonpremixed flame

    KAUST Repository

    Lucchesi, Marco

    2017-02-05

    A modeling framework based on Direct Simulation Monte Carlo (DSMC) is employed to simulate the evolution of the soot particle size distribution in turbulent sooting flames. The stochastic reactor describes the evolution of soot in fluid parcels following Lagrangian trajectories in a turbulent flow field. The trajectories are sampled from a Direct Numerical Simulation (DNS) of a n-heptane turbulent nonpremixed flame. The DSMC method is validated against experimentally measured size distributions in laminar premixed flames and found to reproduce quantitatively the experimental results, including the appearance of the second mode at large aggregate sizes and the presence of a trough at mobility diameters in the range 3–8 nm. The model is then applied to the simulation of soot formation and growth in simplified configurations featuring a constant concentration of soot precursors and the evolution of the size distribution in time is found to depend on the intensity of the nucleation rate. Higher nucleation rates lead to a higher peak in number density and to the size distribution attaining its second mode sooner. The ensemble-averaged PSDF in the turbulent flame is computed from individual samples of the PSDF from large sets of Lagrangian trajectories. This statistical measure is equivalent to time-averaged, scanning mobility particle size (SMPS) measurements in turbulent flames. Although individual trajectories display strong bimodality as in laminar flames, the ensemble-average PSDF possesses only one mode and a long, broad tail, which implies significant polydispersity induced by turbulence. Our results agree very well with SMPS measurements available in the literature. Conditioning on key features of the trajectory, such as mixture fraction or radial locations does not reduce the scatter in the size distributions and the ensemble-averaged PSDF remains broad. The results highlight and explain the important role of turbulence in broadening the size distribution of

  3. Unravelling the size distribution of social groups with information theory in complex networks

    Science.gov (United States)

    Hernando, A.; Villuendas, D.; Vesperinas, C.; Abad, M.; Plastino, A.

    2010-07-01

    The minimization of Fisher’s information (MFI) approach of Frieden et al. [Phys. Rev. E 60, 48 (1999)] is applied to the study of size distributions in social groups on the basis of a recently established analogy between scale invariant systems and classical gases [Phys. A 389, 490 (2010)]. Going beyond the ideal gas scenario is seen to be tantamount to simulating the interactions taking place, for a competitive cluster growth process, in a scale-free ideal network - a non-correlated network with a connection-degree’s distribution that mimics the scale-free ideal gas density distribution. We use a scaling rule that allows one to classify the final cluster-size distributions using only one parameter that we call the competitiveness, which can be seen as a measure of the strength of the interactions. We find that both empirical city-size distributions and electoral results can be thus reproduced and classified according to this competitiveness-parameter, that also allow us to infer the maximum number of stable social relationships that one person can maintain, known as the Dunbar number, together with its standard deviation. We discuss the importance of this number in connection with the empirical phenomenon known as “six-degrees of separation”. Finally, we show that scaled city-size distributions of large countries follow, in general, the same universal distribution.

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

    Science.gov (United States)

    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.

  5. Particle-size distribution of airborne poly- and perfluorinated alkyl substances.

    Science.gov (United States)

    Dreyer, A; Kirchgeorg, T; Weinberg, I; Matthias, V

    2015-06-01

    Eleven particle-size-segregated samples were taken to investigate the particle-size distribution of perfluoroalkyl substances (PFASs) using two five stage impactors in parallel. Samples were extracted with methanol and detected by HPLC/MS-MS. Investigation yielded reproducible results for the parallel samples over the entire sampling period. Particle-size distribution varied between perfluorooctane sulfonate (PFOS) and other perfluoroalkyl sulfonates (PFSAs), perfluorooctane carboxylate (PFOA) and other perfluoroalkyl carboxylates (PFCAs) and n-methyl-perfluorooctanesulfonamido ethanol (MeFOSE). Whereas PFOA and MeFOSE were predominantly observed in smallest size fraction (size fractions between 1.38 and 3.81μm. The reason for this different behaviour remained unclear and indicated a complex atmospheric PFAS processing and sampling which should be further investigated and optimized, respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Effects of Particle Size Distribution on the Burn Ability of Limestone

    Directory of Open Access Journals (Sweden)

    Ismaila E. SULEIMAN

    2013-11-01

    Full Text Available The effect of particle size reduction on the burn ability of Limestone was investigated using the limestone obtained from Obajana Cement Mines. Limestone samples were grinded and were classified into following particles size distribution: 90µm, 200µm, 250µm and 500µm graduated in different sieve sizes. The decomposition rates of these samples were monitored under the same temperature condition in a pre-heated furnace of 1000°C and at constant time interval of 0-35 minutes. From the results of the investigation, the material with particle size distribution of 90µm has the fastest reaction rate of 0.1369g/min and highest lime conversion of 52.0 weight percent; loss on ignition being 48 weight percent. This reaction rate increases as the particle size decreases from 500µm to 90µm.

  7. The uniqueness of firm size distribution function from tent-shaped growth rate distribution

    Science.gov (United States)

    Ishikawa, Atushi

    2007-09-01

    Employing profits data of Japanese firms in 2003 and 2004, we report the proof that a Non-Gibrat's law in the middle scale region of profits is unique under the law of detailed balance. This uniquely leads to the probability distribution function (pdf) of profits. In the proof, two approximations are employed. The pdf of growth rate is described as tent-shaped exponential functions and the value of the origin of the growth rate distribution is constant. These approximations are confirmed in the database. The resultant profits pdf fits with the empirical data consistently. This guarantees the validity of the approximations.

  8. Optimal placement and sizing of wind / solar based DG sources in distribution system

    Science.gov (United States)

    Guan, Wanlin; Guo, Niao; Yu, Chunlai; Chen, Xiaoguang; Yu, Haiyang; Liu, Zhipeng; Cui, Jiapeng

    2017-06-01

    Proper placement and sizing of Distributed Generation (DG) in distribution system can obtain maximum potential benefits. This paper proposes quantum particle swarm algorithm (QPSO) based wind turbine generation unit (WTGU) and photovoltaic (PV) array placement and sizing approach for real power loss reduction and voltage stability improvement of distribution system. Performance modeling of wind and solar generation system are described and classified into PQ\\PQ (V)\\PI type models in power flow. Considering the WTGU and PV based DGs in distribution system is geographical restrictive, the optimal area and DG capacity limits of each bus in the setting area need to be set before optimization, the area optimization method is proposed . The method has been tested on IEEE 33-bus radial distribution systems to demonstrate the performance and effectiveness of the proposed method.

  9. Finite-size effects on return interval distributions for weakest-link-scaling systems

    Science.gov (United States)

    Hristopulos, Dionissios T.; Petrakis, Manolis P.; Kaniadakis, Giorgio

    2014-05-01

    The Weibull distribution is a commonly used model for the strength of brittle materials and earthquake return intervals. Deviations from Weibull scaling, however, have been observed in earthquake return intervals and the fracture strength of quasibrittle materials. We investigate weakest-link scaling in finite-size systems and deviations of empirical return interval distributions from the Weibull distribution function. Our analysis employs the ansatz that the survival probability function of a system with complex interactions among its units can be expressed as the product of the survival probability functions for an ensemble of representative volume elements (RVEs). We show that if the system comprises a finite number of RVEs, it obeys the κ-Weibull distribution. The upper tail of the κ-Weibull distribution declines as a power law in contrast with Weibull scaling. The hazard rate function of the κ-Weibull distribution decreases linearly after a waiting time τc∝n1/m, where m is the Weibull modulus and n is the system size in terms of representative volume elements. We conduct statistical analysis of experimental data and simulations which show that the κ Weibull provides competitive fits to the return interval distributions of seismic data and of avalanches in a fiber bundle model. In conclusion, using theoretical and statistical analysis of real and simulated data, we demonstrate that the κ-Weibull distribution is a useful model for extreme-event return intervals in finite-size systems.

  10. Finite-size effects on return interval distributions for weakest-link-scaling systems.

    Science.gov (United States)

    Hristopulos, Dionissios T; Petrakis, Manolis P; Kaniadakis, Giorgio

    2014-05-01

    The Weibull distribution is a commonly used model for the strength of brittle materials and earthquake return intervals. Deviations from Weibull scaling, however, have been observed in earthquake return intervals and the fracture strength of quasibrittle materials. We investigate weakest-link scaling in finite-size systems and deviations of empirical return interval distributions from the Weibull distribution function. Our analysis employs the ansatz that the survival probability function of a system with complex interactions among its units can be expressed as the product of the survival probability functions for an ensemble of representative volume elements (RVEs). We show that if the system comprises a finite number of RVEs, it obeys the κ-Weibull distribution. The upper tail of the κ-Weibull distribution declines as a power law in contrast with Weibull scaling. The hazard rate function of the κ-Weibull distribution decreases linearly after a waiting time τ(c) ∝ n(1/m), where m is the Weibull modulus and n is the system size in terms of representative volume elements. We conduct statistical analysis of experimental data and simulations which show that the κ Weibull provides competitive fits to the return interval distributions of seismic data and of avalanches in a fiber bundle model. In conclusion, using theoretical and statistical analysis of real and simulated data, we demonstrate that the κ-Weibull distribution is a useful model for extreme-event return intervals in finite-size systems.

  11. The size distributions of asteroid families in the SDSS Moving Object Catalog 4

    Science.gov (United States)

    Parker, A.; Ivezić, Ž.; Jurić, M.; Lupton, R.; Sekora, M. D.; Kowalski, A.

    2008-11-01

    Asteroid families, traditionally defined as clusters of objects in orbital parameter space, often have distinctive optical colors. We show that the separation of family members from background interlopers can be improved with the aid of SDSS colors as a qualifier for family membership. Based on an ˜88,000 object subset of the Sloan Digital Sky Survey Moving Object Catalog 4 with available proper orbital elements, we define 37 statistically robust asteroid families with at least 100 members (12 families have over 1000 members) using a simple Gaussian distribution model in both orbital and color space. The interloper rejection rate based on colors is typically ˜10% for a given orbital family definition, with four families that can be reliably isolated only with the aid of colors. About 50% of all objects in this data set belong to families, and this fraction varies from about 35% for objects brighter than an H magnitude of 13 and rises to 60% for objects fainter than this. The fraction of C-type objects in families decreases with increasing H magnitude for H>13, while the fraction of S-type objects above this limit remains effectively constant. This suggests that S-type objects require a shorter timescale for equilibrating the background and family size distributions via collisional processing. The size distribution varies significantly among families, and is typically different from size distributions for background populations. The size distributions for 15 families display a well-defined change of slope and can be modeled as a "broken" double power-law. Such "broken" size distributions are twice as likely for S-type familes than for C-type families (73% vs. 36%), and are dominated by dynamically old families. The remaining families with size distributions that can be modeled as a single power law are dominated by young families (families. No such slope-color correlation is discernible for families whose size distribution follows a single power law. For several

  12. Stable Size Distribution of Amyloid Plaques Over the Course of Alzheimer Disease

    Science.gov (United States)

    Serrano-Pozo, Alberto; Mielke, Matthew L.; Muzitansky, Alona; Gómez-Isla, Teresa; Growdon, John H.; Bacskai, Brian J.; Betensky, Rebecca A.; Frosch, Matthew P.; Hyman, Bradley T.

    2012-01-01

    Amyloid-β plaques are a key pathological feature of Alzheimer disease (AD), but whether plaque sizes increase or stabilize over the course of AD is unknown. We measured the size distribution of total immunoreactive (10D5-positive) and dense-core (Thioflavine-S-positive) plaques in the temporal neocortex of a large group of AD and plaque-bearing age-matched non-demented subjects to test the hypothesis that amyloid plaques continue to grow along with the progression of the disease. The size of amyloid-β (10D5)-positive plaques did not differ between groups whereas dense-core plaques from the AD group were slightly larger than those in the non-demented group (~25%–30%, p = 0.01). Within the AD group, dense-core plaque size did not independently correlate with duration of clinical disease (from 4 to 21 years, p = 0.68), whereas 10D5-positive plaque size correlated negatively with disease duration (p = 0.01). By contrast, an earlier age of symptom onset strongly predicted a larger postmortem plaque size; this effect was independent of disease duration and the presence of the APOEε4 allele (p = 0.0001). We conclude that plaques vary in size among patients, with larger size distributions correlating with an earlier age of onset, but plaques do not substantially increase in size over the clinical course of the disease. PMID:22805771

  13. Ultrasonic attenuation of polycrystalline materials with a distribution of grain sizes.

    Science.gov (United States)

    Arguelles, Andrea P; Turner, Joseph A

    2017-06-01

    Elastic wave scattering at grain boundaries in polycrystalline media can be quantified to determine microstructural properties. The amplitude drop observed for coherent wave propagation (attenuation) as well as diffuse-field scattering events have been extensively studied. In all cases, the scattering shows a clear dependence on grain size, grain shape, and microstructural texture. Models used to quantify scattering experiments are often developed assuming dependence on a single spatial length scale, usually, mean grain diameter. However, several microscopy studies suggest that most metals have a log normal distribution of grain sizes. In this study, grain size distribution is discussed within the context of previous attenuation models valid for arbitrary crystallite symmetries. Results are presented for titanium using a range of distribution means and widths assuming equiaxed grains and no preferred crystallographic orientation. The longitudinal and shear attenuations are shown to vary with respect to the frequency dependence for varying distribution widths even when the volumetric mean grain size is held constant. Furthermore, the results suggest that grain size estimates based on attenuation can have large errors if the distribution is neglected. This work is anticipated to play an important role in microstructural characterization research associated with ultrasonic scattering.

  14. Particle size distributions in Saturn's rings from Voyager 1 radio occultation

    Science.gov (United States)

    Marouf, E. A.; Tyler, G. L.; Zebker, H. A.; Simpson, R. A.; Eshleman, V. R.

    1983-01-01

    Information on Saturn ring particle sizes obtained with the Voyager 1 ring occultation experiment is discussed. The theory underlying the determination of the particle size distribution is presented, including differential extinction and inversion of the scattered signal. Experimental observations and results for the observed spectra, differential cross sections, suprameter and sub- to suprameter size distributions are presented. The size and mass distributions both cut off sharply at about 4-5 m; the mass distribution peaks over the 3-4 m size range for four ring system features at 1.35, 1.51, 2.01, and 2.12 Saturn radii. A power-law type model is consistent with the data over a limited size range of 0.01 to 1 m. The fractional contribution of the suprameter particles to the microwave opacity for the four features appears to be about 1/3, 1/3, 2/3, and 1, respectively, and their cumulative surface mass per unit area are about 11, 16, 41, and 132 g/sq cm if the particles are solid water ice.

  15. Effect of particle size distribution on the rheology of oil-coal slurries

    Energy Technology Data Exchange (ETDEWEB)

    Hao, L.; Wang, Y.; Xiong, C. [China University of Mining and Technology, Beijing (China)

    2007-02-15

    The rheological behaviour of Shenhua coal-oil slurry was studied as a function of solids concentration, particle size and size distribution. At a certain particle size distribution the apparent viscosity of coal slurry increases with the increase of solid concentration. Coal slurries were found to exhibit a wide spectrum of flow behaviour ranging from Newtonian at low concentrations to shear-thinning and pseudoplastic with a yield stress at higher concentrations. By adding a narrow-sized coarse coal fraction to the finer coal slurry, a flow characteristics optimum coarse-to-fine particle ratio of 40:60 exists at which the slurry is Newtonian. The significant improvement in the rheological behavior with changing the particle size distribution may be explained in terms of spatial rearrangement of the particles and apparent dilution effect. The results indicate that, with a careful control of the particle size distribution, it is possible to prepare an optimum oil-coal slurry which has a low viscosity but with high solids loadings. 10 refs., 4 figs., 3 tabs.

  16. Size distribution of particles in Saturn’s rings from aggregation and fragmentation

    Science.gov (United States)

    Brilliantov, Nikolai; Krapivsky, P. L.; Bodrova, Anna; Spahn, Frank; Hayakawa, Hisao; Stadnichuk, Vladimir; Schmidt, Jürgen

    2015-01-01

    Saturn’s rings consist of a huge number of water ice particles, with a tiny addition of rocky material. They form a flat disk, as the result of an interplay of angular momentum conservation and the steady loss of energy in dissipative interparticle collisions. For particles in the size range from a few centimeters to a few meters, a power-law distribution of radii, ∼r−q with q≈3, has been inferred; for larger sizes, the distribution has a steep cutoff. It has been suggested that this size distribution may arise from a balance between aggregation and fragmentation of ring particles, yet neither the power-law dependence nor the upper size cutoff have been established on theoretical grounds. Here we propose a model for the particle size distribution that quantitatively explains the observations. In accordance with data, our model predicts the exponent q to be constrained to the interval 2.75≤q≤3.5. Also an exponential cutoff for larger particle sizes establishes naturally with the cutoff radius being set by the relative frequency of aggregating and disruptive collisions. This cutoff is much smaller than the typical scale of microstructures seen in Saturn’s rings. PMID:26183228

  17. Bubble size distribution in acoustic droplet vaporization via dissolution using an ultrasound wide-beam method.

    Science.gov (United States)

    Xu, Shanshan; Zong, Yujin; Li, Wusong; Zhang, Siyuan; Wan, Mingxi

    2014-05-01

    Performance and efficiency of numerous cavitation enhanced applications in a wide range of areas depend on the cavitation bubble size distribution. Therefore, cavitation bubble size estimation would be beneficial for biological and industrial applications that rely on cavitation. In this study, an acoustic method using a wide beam with low pressure is proposed to acquire the time intensity curve of the dissolution process for the cavitation bubble population and then determine the bubble size distribution. Dissolution of the cavitation bubbles in saline and in phase-shift nanodroplet emulsion diluted with undegassed or degassed saline was obtained to quantify the effects of pulse duration (PD) and acoustic power (AP) or peak negative pressure (PNP) of focused ultrasound on the size distribution of induced cavitation bubbles. It was found that an increase of PD will induce large bubbles while AP had only a little effect on the mean bubble size in saline. It was also recognized that longer PD and higher PNP increases the proportions of large and small bubbles, respectively, in suspensions of phase-shift nanodroplet emulsions. Moreover, degassing of the suspension tended to bring about smaller mean bubble size than the undegassed suspension. In addition, condensation of cavitation bubble produced in diluted suspension of phase-shift nanodroplet emulsion was involved in the calculation to discuss the effect of bubble condensation in the bubble size estimation in acoustic droplet vaporization. It was shown that calculation without considering the condensation might underestimate the mean bubble size and the calculation with considering the condensation might have more influence over the size distribution of small bubbles, but less effect on that of large bubbles. Without or with considering bubble condensation, the accessible minimum bubble radius was 0.4 or 1.7 μm and the step size was 0.3 μm. This acoustic technique provides an approach to estimate the size

  18. Synthesis and toxicity characterization of carbon coated iron oxide nanoparticles with highly defined size distributions.

    Science.gov (United States)

    Mendes, Rafael Gregorio; Koch, Britta; Bachmatiuk, Alicja; El-Gendy, Ahmed Aboud; Krupskaya, Yulia; Springer, Armin; Klingeler, Rüdiger; Schmidt, Oliver; Büchner, Bernd; Sanchez, Samuel; Rümmeli, Mark Hermann

    2014-01-01

    Iron oxide nanoparticles hold great promise for future biomedical applications. To this end numerous studies on iron oxide nanoparticles have been conducted. One aspect these studies reveal is that nanoparticle size and shape can trigger different cellular responses through endocytic pathways, cell viability and early apoptosis. However, systematic studies investigating the size dependence of iron oxide nanoparticles with highly defined diameters across multiple cells lines are not available yet. Iron oxide nanoparticles with well-defined size distributions were prepared. All samples were thoroughly characterized and the cytotoxicity for four standard cell lines (HeLa Kyoto, human osteosarcoma (U2OS), mouse fibroblasts (NIH 3T3) and mouse macrophages (J7442)) where investigated. Our findings show that small differences in size distribution (ca. 10nm) of iron oxide nanoparticles do not influence cytotoxicity, while uptake is size dependent. Cytotoxicity is dose-dependent. Broad distributions of nanoparticles are more easily internalized as compared to the narrow distributions for two of the cell lines tested (HeLa Kyoto and mouse macrophages (J7442)). The data indicate that it is not feasible to probe changes in cytotoxicity within a small size range (10nm). However, TEM investigations of the nanoparticles indicate that cellular uptake is size dependent. The present work compares narrow and broad distributions for various samples of carbon-coated iron oxide nanoparticles. The data highlights that cells differentiate between nanoparticle sizes as indicated by differences in cellular uptake. This information provides valuable knowledge to better understand the interaction of nanoparticles and cells. © 2013.

  19. Particle size distributions in a DC-cast and rolled AA3104 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ekstroem, H.-E.; Oestensson, L. [Graenges Technol., Finspang (Sweden); Hagstroem, J.

    2000-07-01

    Particle size distributions in an AA3104 alloy homogenised at different temperatures have been determined using both scanning electron microscope with a field emission electron gun (FEG-SEM) and transmission electron microscope (TEM). Constituent particles and dispersoids were measured at different depths for two hot rolled gauges. The measured area size distributions are transformed to 3D distributions using a modified Johnson-Saltykov method assuming different shapes of the particles and considering the information depth in the SEM and the TEM foil thickness. The analysis shows that the assumptions made regarding information depths have a large influence on the 3D size distributions and consequently also on calculated Zener drag. The very inhomogeneous particle distribution in the ingots makes it important to spread out the selected image fields to achieve reliable statistics also during the measurements on the hot bands. The TEM and FEG-SEM measurements give results in excellent agreement. Calculation of the Zener drag from the mean particle diameter and volume fraction gives values 4-5 times larger than those obtained using a more rigorous method considering the particle size distribution. (orig.)

  20. Effect of Particle Size Distribution on Ammonium Sulphate Dried in a Rotary Dryer

    Directory of Open Access Journals (Sweden)

    Susianto Susianto

    2010-08-01

    Full Text Available The aim of this work is to study theoretically, by mathematical model development, the effect of particle size distribution on the performance of rotary dryer to dry ammonium sulphate fertilizer assuming plug flow with axial dispersion pattern (PFDA model for solid particle flow. The mathematical model development was carried out by combining the drying processes model with particle size distribution model. Particle size distribution models used are Rosin-Rommler model and Gamma distribution model. For simplicity, the model of drying processes of solid particles in the rotary dryer was developed by assuming of uniform air conditions (temperature and humidity along the rotary dryer as in the entry conditions. The resulting differential equations were solved analytically under Matlab 6.1 facility.Since this model, solid hold up, and axial dispersion number were obtained from empirical correlations in the literatures. The drying rate of ammonium sulphate fertilizer in rotary dryer was estimated using isothermal diffusion model with effective diffusivity of moisture in the particle obtained from previous study [2]. Using Gamma function distribution, this research showed that for the value of the coefficient of variance (CV less than 0.5, particle size distribution does not have significant effect on dryer performance. For the value of CV greater than 0.5, the dryer performance increase (or outlet solid moisture content decrease with increasing the value of CV. The application of Rosin-Rammler model gives lower prediction of outlet solid moisture content compared to the application of Gamma function model.

  1. Methods for obtaining true particle size distributions from cross section measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lord, Kristina Alyse [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    Sectioning methods are frequently used to measure grain sizes in materials. These methods do not provide accurate grain sizes for two reasons. First, the sizes of features observed on random sections are always smaller than the true sizes of solid spherical shaped objects, as noted by Wicksell [1]. This is the case because the section very rarely passes through the center of solid spherical shaped objects randomly dispersed throughout a material. The sizes of features observed on random sections are inversely related to the distance of the center of the solid object from the section [1]. Second, on a plane section through the solid material, larger sized features are more frequently observed than smaller ones due to the larger probability for a section to come into contact with the larger sized portion of the spheres than the smaller sized portion. As a result, it is necessary to find a method that takes into account these reasons for inaccurate particle size measurements, while providing a correction factor for accurately determining true particle size measurements. I present a method for deducing true grain size distributions from those determined from specimen cross sections, either by measurement of equivalent grain diameters or linear intercepts.

  2. Tuning aerosol particle size distribution of metered dose inhalers using cosolvents and surfactants.

    Science.gov (United States)

    Saleem, Imran Y; Smyth, Hugh D C

    2013-01-01

    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. 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. 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. 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.

  3. Introduction of a Nozzle Throat Diameter Dependency into the SRM Dust Size Distribution

    Science.gov (United States)

    Stabroth, S.; Wegener, P.; Oswald, M.; Wiedemann, C.; Klinkrad, H.; Vörsmann, P.

    In the exhaust gas of SRM (Solid Rocket Motor) firings, a considerable amount of very small aluminium oxide (Al2O3) particles is generally included. In order to increase motor performance and to dampen burn instabilities, aluminium is used as an additive in the propellant. During the burn process this aluminium is transformed into Al2O3. A large number of small dust particles (nozzle. The ESA space debris population model MASTER-2001 considers 1,032 SRM firings with the associated generation of SRM slag and dust. The resulting Al2O3 population is a major contribution to the micron size space debris environment in Earth orbit. For the modelling of each SRM dust release event a detailed knowledge of the size distribution is essential. However, the knowledge of the particle size distribution after passing the nozzle throat is poor. The current dust implementation in the MASTER-2001 space debris model therefore assumes an average motor size, since information on the actual motor size is normally not available in common databases. Thus, a fixed distribution is identically used for large upper stages as well as small apogee motors. This assumption can lead to an over-representation of large dust in regions, where mainly apogee motors are used (i.e. GEO) and an under-representation in lower altitudes, where large stages predominate. In this paper, a concept for the improvement of SRM dust size modelling is discussed. It will be shown that an introduction of a nozzle throat diameter dependency into the dust size distribution could lead to a more precise modelling of SRM dust release events. Investigations showed that there is a good correlation between the propellant mass flow and the nozzle's throat diameter, which is in turn the determining term for the actual diameter distribution. Based on this correlation, the paper will outline a size distribution taking into account the actual motor size. The improved SRM dust size distribution is going to be used by the MASTER-2005

  4. Asymptotic distributions of coalescence times and ancestral lineage numbers for populations with temporally varying size.

    Science.gov (United States)

    Chen, Hua; Chen, Kun

    2013-07-01

    The distributions of coalescence times and ancestral lineage numbers play an essential role in coalescent modeling and ancestral inference. Both exact distributions of coalescence times and ancestral lineage numbers are expressed as the sum of alternating series, and the terms in the series become numerically intractable for large samples. More computationally attractive are their asymptotic distributions, which were derived in Griffiths (1984) for populations with constant size. In this article, we derive the asymptotic distributions of coalescence times and ancestral lineage numbers for populations with temporally varying size. For a sample of size n, denote by Tm the mth coalescent time, when m + 1 lineages coalesce into m lineages, and An(t) the number of ancestral lineages at time t back from the current generation. Similar to the results in Griffiths (1984), the number of ancestral lineages, An(t), and the coalescence times, Tm, are asymptotically normal, with the mean and variance of these distributions depending on the population size function, N(t). At the very early stage of the coalescent, when t → 0, the number of coalesced lineages n - An(t) follows a Poisson distribution, and as m → n, $$n\\left(n-1\\right){T}_{m}/2N\\left(0\\right)$$ follows a gamma distribution. We demonstrate the accuracy of the asymptotic approximations by comparing to both exact distributions and coalescent simulations. Several applications of the theoretical results are also shown: deriving statistics related to the properties of gene genealogies, such as the time to the most recent common ancestor (TMRCA) and the total branch length (TBL) of the genealogy, and deriving the allele frequency spectrum for large genealogies. With the advent of genomic-level sequencing data for large samples, the asymptotic distributions are expected to have wide applications in theoretical and methodological development for population genetic inference.

  5. Influence of grain size distribution on dynamic shear modulus of sands

    Science.gov (United States)

    Dyka, Ireneusz; Srokosz, Piotr E.; Bujko, Marcin

    2017-11-01

    The paper presents the results of laboratory tests, that verify the correlation between the grain-size characteristics of non-cohesive soils and the value of the dynamic shear modulus. The problem is a continuation of the research performed at the Institute of Soil Mechanics and Rock Mechanics in Karlsruhe, by T. Wichtmann and T. Triantafyllidis, who derived the extension of the applicability of the Hardin's equation describing the explicite dependence between the grain size distribution of sands and the values of dynamic shear modulus. For this purpose, piezo-ceramic bender elements generating elastic waves were used to investigate the mechanical properties of the specimens with artificially generated particle distribution. The obtained results confirmed the hypothesis that grain size distribution of non-cohesive soils has a significant influence on the dynamic shear modulus, but at the same time they have shown that obtaining unambiguous results from bender element tests is a difficult task in practical applications.

  6. On computational approaches for size-and-shape distributions from sedimentation velocity analytical ultracentrifugation.

    Science.gov (United States)

    Schuck, Peter

    2010-07-01

    Sedimentation velocity analytical ultracentrifugation has become a very popular technique to study size distributions and interactions of macromolecules. Recently, a method termed two-dimensional spectrum analysis (2DSA) for the determination of size-and-shape distributions was described by Demeler and colleagues (Eur Biophys J 2009). It is based on novel ideas conceived for fitting the integral equations of the size-and-shape distribution to experimental data, illustrated with an example but provided without proof of the principle of the algorithm. In the present work, we examine the 2DSA algorithm by comparison with the mathematical reference frame and simple well-known numerical concepts for solving Fredholm integral equations, and test the key assumptions underlying the 2DSA method in an example application. While the 2DSA appears computationally excessively wasteful, key elements also appear to be in conflict with mathematical results. This raises doubts about the correctness of the results from 2DSA analysis.

  7. Geostatistical analysis of tree size distributions in the southern Kalahari obtained from remotely sensed data

    Science.gov (United States)

    Moustakas, Aristides; Chorti, Arsenia; Hristopulos, Dionissios T.

    2007-10-01

    We propose using geostatistical methods for the spatial analysis of data pertaining to the size of trees (in terms of canopy surface area) obtained by means of remote sensing methods. Geostatistical methods are suitable because the locations of the trees are at the nodes of an unstructured grid. More specifically, we present a semivariogram analysis to detect correlations in the tree size spatial distribution, and we apply a novel method of anisotropy analysis to search for possible anisotropy in the size distribution. We use a combination of aerial photographs and satellite images in four snapshots covering 37 years to investigate the temporal behavior in addition to the spatial distribution at a single time. The aerial photographs were taken in 1964, 1984, 1993, and the IKONOS satellite image in 2001. We follow a study area covering over 139 ha and over 2,000 tree individuals. Our plots are located in the Southern Kalahari savanna near the city of Kimberley, South Africa.

  8. Advanced analysis of polymer emulsions: Particle size and particle size distribution by field-flow fractionation and dynamic light scattering.

    Science.gov (United States)

    Makan, Ashwell C; Spallek, Markus J; du Toit, Madeleine; Klein, Thorsten; Pasch, Harald

    2016-04-15

    Field flow fractionation (FFF) is an advanced fractionation technique for the analyses of very sensitive particles. In this study, different FFF techniques were used for the fractionation and analysis of polymer emulsions/latexes. As model systems, a pure acrylic emulsion and emulsions containing titanium dioxide were prepared and analyzed. An acrylic emulsion polymerization was conducted, continuously sampled from the reactor and subsequently analyzed to determine the particle size, radius of gyration in specific, of the latex particles throughout the polymerization reaction. Asymmetrical flow field-flow fractionation (AF4) and sedimentation field-flow fractionation (SdFFF), coupled to a multidetector system, multi-angle laser light scattering (MALLS), ultraviolet (UV) and refractive index (RI), respectively, were used to investigate the evolution of particle sizes and particle size distributions (PSDs) as the polymerization progressed. The obtained particle sizes were compared against batch-mode dynamic light scattering (DLS). Results indicated differences between AF4 and DLS results due to DLS taking hydration layers into account, whereas both AF4 and SdFFF were coupled to MALLS detection, hence not taking the hydration layer into account for size determination. SdFFF has additional separation capabilities with a much higher resolution compared to AF4. The calculated radii values were 5 nm larger for SdFFF measurements for each analyzed sample against the corresponding AF4 values. Additionally a low particle size shoulder was observed for SdFFF indicating bimodality in the reactor very early during the polymerization reaction. Furthermore, different emulsions were mixed with inorganic species used as additives in cosmetics and coatings such as TiO2. These complex mixtures of species were analyzed to investigate the retention and particle interaction behavior under different AF4 experimental conditions, such as the mobile phase. The AF4 system was coupled online

  9. Polycyclic aromatic hydrocarbons in urban atmosphere of Guangzhou, China: Size distribution characteristics and size-resolved gas-particle partitioning

    Science.gov (United States)

    Yu, Huan; Yu, Jian Zhen

    2012-07-01

    Size distributions of thirteen polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), and organic carbon (OC) in the range of 0.01-18 μm were measured using a nano Micro-Orifice Uniform Deposit Impactor (nano-MOUDI) in an urban location in Guangzhou, China in July 2006. PAH size distributions were fit with five modes and the respective mass median aerodynamic diameters (MMAD) are: Aitken mode (MMAD: ˜0.05 μm), three accumulation modes AMI, AMII, AMIII (MMAD: 0.13-0.17 μm, 0.4-0.45 μm, and 0.9-1.2 μm, respectively), and coarse mode (MMAD: 4-6 μm). Seven-ring PAH was mainly in AMII and AMIII. Five- and six-ring PAHs were found to be abundant in all the three AM. Three- and four-ring PAHs had a significant presence in the coarse mode in addition to the three AM. Size-resolved gas-particle partition coefficients of PAHs (Kp) were estimated using measured EC and OC data. The Kp values of a given PAH could differ by a factor of up to ˜7 on particles in different size modes, with the highest Kp associated with the AMI particles and the lowest Kp associated with the coarse mode particles. Comparison of calculated overall Kp with measured Kp values in Guangzhou by Yang et al. (2010) shows that adsorption on EC appeared to be the dominant mechanism driving the gas-particle partitioning of three- and four-ring PAHs while absorption in OM played a dominant role for five- and six-ring PAHs. The calculated equilibrium timescales of repartitioning indicate that five- to seven-ring PAHs could not achieve equilibrium partitioning within their typical residence time in urban atmospheres, while three- and four-ring PAHs could readily reach new equilibrium states in particles of all sizes. A partitioning flux is therefore proposed to replace the equilibrium assumption in modeling PAH transport and fate.

  10. Effects of different block size distributions in pressure transient response of naturally fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Montazeri, G.H. [Islamic Azad University, Mahshahr (Iran, Islamic Republic of). Dept. of Chemical and Petroleum Engineering], E-mail: montazeri_gh@yahoo.com; Tahami, S.A. [Mad Daneshgostar Tabnak Co. (MDT),Tehran (Iran, Islamic Republic of); Moradi, B.; Safari, E. [Iranian Central Oil Fields Co, Tehran (Iran, Islamic Republic of)], E-mail: morady.babak@gmail.com

    2011-07-15

    This paper presents a model for pressure transient and derivative analysis for naturally fractured reservoirs by a formulation of inter porosity flow incorporating variations in matrix block size, which is inversely related to fracture intensity. Geologically realistic Probability Density Functions (PDFs) of matrix block size, such as uniform, bimodal, linear and exponential distributions, are examined and pseudo-steady-state and transient models for inter porosity flow are assumed. The results have been physically interpreted, and, despite results obtained by other authors, it was found that the shape of pressure derivative curves for different PDFs are basically identical within some ranges of block size variability, inter porosity skin, PDFs parameters and matrix storage capacity. This tool can give an insight on the distribution of block sizes and shapes, together with other sources of information such as Logs and geological observations. (author)

  11. Martensitic transformations in nanostructured nitinol: Finite element modeling of grain size and distribution effects

    DEFF Research Database (Denmark)

    Liu, Hong-Sheng; Mishnaevsky, Leon

    2013-01-01

    transformation are totally suppressed. Graded and localized distributions of grain sizes of nitinol were compared with nitinol samples with homogeneous grain size distribution. In the materials with localized region of small grains, it was observed that the martensite rich regions form first on the border......A computational model of martensitic phase transformation in nanostructured nitinol is developed which takes into account the grain size effect. On the basis of the theoretical analysis of the thermodynamic transformation criterion and the energy barrier for phase transformation......, it was demonstrated that the energy barrier for martensitic phase transformation in nanocrystalline nitinol increase drastically with decreasing the grain size. Finite element simulations of phase transformations and structure evolution in nanocrystalline nitinol under mechanical (tensile) loading are carried out...

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

    Science.gov (United States)

    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.

  13. Decoding Size Distribution Patterns in Marine and Transitional Water Phytoplankton: From Community to Species Level

    Science.gov (United States)

    Roselli, Leonilde; Basset, Alberto

    2015-01-01

    Understanding the mechanisms of phytoplankton community assembly is a fundamental issue of aquatic ecology. Here, we use field data from transitional (e.g. coastal lagoons) and coastal water environments to decode patterns of phytoplankton size distribution into organization and adaptive mechanisms. Transitional waters are characterized by higher resource availability and shallower well-mixed water column than coastal marine environments. Differences in physico-chemical regime between the two environments have been hypothesized to exert contrasting selective pressures on phytoplankton cell morphology (size and shape). We tested the hypothesis focusing on resource availability (nutrients and light) and mixed layer depth as ecological axes that define ecological niches of phytoplankton. We report fundamental differences in size distributions of marine and freshwater diatoms, with transitional water phytoplankton significantly smaller and with higher surface to volume ratio than marine species. Here, we hypothesize that mixing condition affecting size-dependent sinking may drive phytoplankton size and shape distributions. The interplay between shallow mixed layer depth and frequent and complete mixing of transitional waters may likely increase the competitive advantage of small phytoplankton limiting large cell fitness. The nutrient regime appears to explain the size distribution within both marine and transitional water environments, while it seem does not explain the pattern observed across the two environments. In addition, difference in light availability across the two environments appear do not explain the occurrence of asymmetric size distribution at each hierarchical level. We hypothesize that such competitive equilibria and adaptive strategies in resource exploitation may drive by organism’s behavior which exploring patch resources in transitional and marine phytoplankton communities. PMID:25974052

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

    Science.gov (United States)

    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.

  15. Mie forward scattering - Improved semiempirical approximation with application to particle size distribution inversion

    Science.gov (United States)

    Fymat, A. L.; Mease, K. D.

    1981-01-01

    The approximation of Penndorf (1962) and Shifrin-Punina (1968) to the Mie solution at forward scattering angles are extended to small size parameters. The proposed semiempirical approximation accurately represents the Mie results down to x = 0.5-1 for refractive index m = 1.33, and to x = 2.0 for larger index values. The implications of the result for the inversion of particle size distribution from single scattering data in the forward direction are discussed.

  16. A novel methodology to study polymodal particle size distributions produced during continuous wet granulation.

    Science.gov (United States)

    Mendez Torrecillas, Carlota; Halbert, Gavin W; Lamprou, Dimitrios A

    2017-03-15

    It is important during powder granulation to obtain particles of a homogeneous size especially in critical situations such as pharmaceutical manufacture. To date, homogeneity of particle size distribution has been defined by the use of the d50 combined with the span of the particle size distribution, which has been found ineffective for polymodal particle size distributions. This work focuses on demonstrating the limitations of the span parameter to quantify homogeneity and proposes a novel improved metric based on the transformation of a typical particle size distribution curve into a homogeneity factor which can vary from 0 to 100%. The potential of this method as a characterisation tool has been demonstrated through its application to the production of granules using two different materials. The workspace of an 11mm twin screw granulator was defined for two common excipients (α-lactose monohydrate and microcrystalline cellulose). Homogeneity of the obtained granules varied dramatically from 0 to 95% in the same workspace, allowing identification of critical process parameters (e.g. feed rate, liquid/solid ratio, torque velocities). In addition it defined the operational conditions required to produce the most homogeneous product within the range 5μm-2.2mm from both materials. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Measurement of Bubble Size Distribution Based on Acoustic Propagation in Bubbly Medium

    Science.gov (United States)

    Wu, Xiongjun; Hsiao, Chao-Tsung; Choi, Jin-Keun; Chahine, Georges

    2013-03-01

    Acoustic properties are strongly affected by bubble size distribution in a bubbly medium. Measurement of the acoustic transmission becomes increasingly difficulty as the void fraction of the bubbly medium increases due to strong attenuation, while acoustic reflection can be measured more easily with increasing void fraction. The ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright, an instrument for bubble size measurement that is under development tries to take full advantage of the properties of acoustic propagation in bubbly media to extract bubble size distribution. Properties of both acoustic transmission and reflection in the bubbly medium from a range of short single-frequency bursts of acoustic waves at different frequencies are measured in an effort to deduce the bubble size distribution. With the combination of both acoustic transmission and reflection, assisted with validations from photography, the ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright has the potential to measure bubble size distributions in a wider void fraction range. This work was sponsored by Department of Energy SBIR program

  18. Porous media grain size distribution and hydrodynamic forces effects on transport and deposition of suspended particles.

    Science.gov (United States)

    Ahfir, Nasre-Dine; Hammadi, Ahmed; Alem, Abdellah; Wang, HuaQing; Le Bras, Gilbert; Ouahbi, Tariq

    2017-03-01

    The effects of porous media grain size distribution on the transport and deposition of polydisperse suspended particles under different flow velocities were investigated. Selected Kaolinite particles (2-30μm) and Fluorescein (dissolved tracer) were injected in the porous media by step input injection technique. Three sands filled columns were used: Fine sand, Coarse sand, and a third sand (Mixture) obtained by mixing the two last sands in equal weight proportion. The porous media performance on the particle removal was evaluated by analysing particles breakthrough curves, hydro-dispersive parameters determined using the analytical solution of convection-dispersion equation with a first order deposition kinetics, particles deposition profiles, and particle-size distribution of the recovered and the deposited particles. The deposition kinetics and the longitudinal hydrodynamic dispersion coefficients are controlled by the porous media grain size distribution. Mixture sand is more dispersive than Fine and Coarse sands. More the uniformity coefficient of the porous medium is large, higher is the filtration efficiency. At low velocities, porous media capture all sizes of suspended particles injected with larger ones mainly captured at the entrance. A high flow velocity carries the particles deeper into the porous media, producing more gradual changes in the deposition profile. The median diameter of the deposited particles at different depth increases with flow velocity. The large grain size distribution leads to build narrow pores enhancing the deposition of the particles by straining. Copyright © 2016. Published by Elsevier B.V.

  19. A uniform measurement expression for cross method comparison of nanoparticle aggregate size distributions

    DEFF Research Database (Denmark)

    Dudkiewicz, Agnieszka; Wagner, Stephan; Lehner, Angela

    2015-01-01

    plasma mass spectrometry detection (AF4-ICP-MS). Transformed size distributions are then compared between the methods and conclusions drawn on methods’ measurement accuracy, limits of detection and quantification related to the synthetic amorphous silca’s size. Two out of the six tested methods (GEMMA...... and AF4-ICP-MS) cross validate the MED distributions between each other, providing a true measurement. The measurement accuracy of other four techniques is shown to be compromised either by the high limit of detection and quantification (CLS, NTA, Wet-SEM) or the sample preparation that is biased...

  20. Effect of substrate pretreatment on particle size distribution in a full-scale research biogas plant.

    Science.gov (United States)

    Naegele, Hans-Joachim; Mönch-Tegeder, Matthias; Haag, Nicola Leonard; Oechsner, Hans

    2014-11-01

    The objective of this study was to investigate the pretreatment effects of high-fibre substrate on particle size distribution in a full-scale agricultural biogas plant (BGP). Two digesters, one fed with pretreated material and one with untreated material, were investigated for a period of 90days. Samples from different positions and heights were taken with a special probe sampling system and put through a wet sieve. The results show that on average 58.0±8.6% of the particles in both digesters are fine fraction (particles (13.1%) with a length >4mm was measured in the untreated digester. However, the volume distribution over all positions and heights did not show a clear and uniform distribution of particles. These results reveal that substrate pretreatment has an effect on particle size in the fermenting substrate, but due to the uneven distribution mixing, is not homogeneous within the digester. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Soot Particle Size Distribution Functions in a Turbulent Non-Premixed Ethylene-Nitrogen Flame

    KAUST Repository

    Boyette, Wesley

    2017-02-21

    A scanning mobility particle sizer with a nano differential mobility analyzer was used to measure nanoparticle size distribution functions in a turbulent non-premixed flame. The burner utilizes a premixed pilot flame which anchors a C2H4/N2 (35/65) central jet with ReD = 20,000. Nanoparticles in the flame were sampled through a N2-filled tube with a 500- μm orifice. Previous studies have shown that insufficient dilution of the nanoparticles can lead to coagulation in the sampling line and skewed particle size distribution functions. A system of mass flow controllers and valves were used to vary the dilution ratio. Single-stage and two-stage dilution systems were investigated. A parametric study on the effect of the dilution ratio on the observed particle size distribution function indicates that particle coagulation in the sampling line can be eliminated using a two-stage dilution process. Carbonaceous nanoparticle (soot) concentration particle size distribution functions along the flame centerline at multiple heights in the flame are presented. The resulting distributions reveal a pattern of increasing mean particle diameters as the distance from the nozzle along the centerline increases.

  2. Fragment size distribution statistics in dynamic fragmentation of laser shock-loaded tin

    Directory of Open Access Journals (Sweden)

    Weihua He

    2017-06-01

    Full Text Available This work investigates the geometric statistics method to characterize the size distribution of tin fragments produced in the laser shock-loaded dynamic fragmentation process. In the shock experiments, the ejection of the tin sample with etched V-shape groove in the free surface are collected by the soft recovery technique. Subsequently, the produced fragments are automatically detected with the fine post-shot analysis techniques including the X-ray micro-tomography and the improved watershed method. To characterize the size distributions of the fragments, a theoretical random geometric statistics model based on Poisson mixtures is derived for dynamic heterogeneous fragmentation problem, which reveals linear combinational exponential distribution. The experimental data related to fragment size distributions of the laser shock-loaded tin sample are examined with the proposed theoretical model, and its fitting performance is compared with that of other state-of-the-art fragment size distribution models. The comparison results prove that our proposed model can provide far more reasonable fitting result for the laser shock-loaded tin.

  3. The variability of tidewater-glacier calving: origin of event-size and interval distributions

    CERN Document Server

    Chapuis, Anne

    2012-01-01

    Calving activity at the front of tidewater glaciers is characterized by a large variability in iceberg sizes and inter-event intervals. We present calving-event data obtained from continuous observations of the fronts of two tidewater glaciers on Svalbard, and show that the distributions of event sizes and inter-event intervals can be reproduced by a simple calving model focusing on the mutual interplay between calving and the destabilization of the glacier front. The event-size distributions of both the field and the model data extend over several orders of magnitude and resemble power laws. The distributions of inter-event intervals are broad, but have a less pronounced tail. In the model, the width of the size distribution increases with the calving susceptibility of the glacier front, a parameter measuring the effect of calving on the stress in the local neighborhood of the calving region. Inter-event interval distributions, in contrast, are insensitive to the calving susceptibility. Above a critical susc...

  4. Estimation of T-cell repertoire diversity and clonal size distribution by Poisson abundance models.

    Science.gov (United States)

    Sepúlveda, Nuno; Paulino, Carlos Daniel; Carneiro, Jorge

    2010-02-28

    The answer to many fundamental questions in Immunology requires the quantitative characterization of the T-cell repertoire, namely T cell receptor (TCR) diversity and clonal size distribution. An increasing number of repertoire studies are based on sequencing of the TCR variable regions in T-cell samples from which one tries to estimate the diversity of the original T-cell populations. Hitherto, estimation of TCR diversity was tackled either by a "standard" method that assumes a homogeneous clonal size distribution, or by non-parametric methods, such as the abundance-coverage and incidence-coverage estimators. However, both methods show caveats. On the one hand, the samples exhibit clonal size distributions with heavy right tails, a feature that is incompatible with the assumption of an equal frequency of every TCR sequence in the repertoire. Thus, this "standard" method produces inaccurate estimates. On the other hand, non-parametric estimators are robust in a wide range of situations, but per se provide no information about the clonal size distribution. This paper redeploys Poisson abundance models from Ecology to overcome the limitations of the above inferential procedures. These models assume that each TCR variant is sampled according to a Poisson distribution with a specific sampling rate, itself varying according to some Exponential, Gamma, or Lognormal distribution, or still an appropriate mixture of Exponential distributions. With these models, one can estimate the clonal size distribution in addition to TCR diversity of the repertoire. A procedure is suggested to evaluate robustness of diversity estimates with respect to the most abundant sampled TCR sequences. For illustrative purposes, previously published data on mice with limited TCR diversity are analyzed. Two of the presented models are more consistent with the data and give the most robust TCR diversity estimates. They suggest that clonal sizes follow either a Lognormal or an appropriate mixture of

  5. Equations for hydraulic conductivity estimation from particle size distribution: A dimensional analysis

    Science.gov (United States)

    Wang, Ji-Peng; François, Bertrand; Lambert, Pierre

    2017-09-01

    Estimating hydraulic conductivity from particle size distribution (PSD) is an important issue for various engineering problems. Classical models such as Hazen model, Beyer model, and Kozeny-Carman model usually regard the grain diameter at 10% passing (d10) as an effective grain size and the effects of particle size uniformity (in Beyer model) or porosity (in Kozeny-Carman model) are sometimes embedded. This technical note applies the dimensional analysis (Buckingham's ∏ theorem) to analyze the relationship between hydraulic conductivity and particle size distribution (PSD). The porosity is regarded as a dependent variable on the grain size distribution in unconsolidated conditions. It indicates that the coefficient of grain size uniformity and a dimensionless group representing the gravity effect, which is proportional to the mean grain volume, are the main two determinative parameters for estimating hydraulic conductivity. Regression analysis is then carried out on a database comprising 431 samples collected from different depositional environments and new equations are developed for hydraulic conductivity estimation. The new equation, validated in specimens beyond the database, shows an improved prediction comparing to using the classic models.

  6. Classification of spray nozzles based on droplet size distributions and wind tunnel tests.

    Science.gov (United States)

    De Schamphelerie, M; Spanoghe, P; Nuyttens, D; Baetens, K; Cornelis, W; Gabriels, D; Van der Meeren, P

    2006-01-01

    Droplet size distribution of a pesticide spray is recognised as a main factor affecting spray drift. As a first approximation, nozzles can be classified based on their droplet size spectrum. However, the risk of drift for a given droplet size distribution is also a function of spray structure, droplet velocities and entrained air conditions. Wind tunnel tests to determine actual drift potentials of the different nozzles have been proposed as a method of adding an indication of the risk of spray drift to the existing classification based on droplet size distributions (Miller et al, 1995). In this research wind tunnel tests were performed in the wind tunnel of the International Centre for Eremology (I.C.E.), Ghent University, to determine the drift potential of different types and sizes of nozzles at various spray pressures. Flat Fan (F) nozzles Hardi ISO 110 02, 110 03, 110 04, 110 06; Low-Drift (LD) nozzles Hardi ISO 110 02, 110 03, 110 04 and Injet Air Inclusion (AI) nozzles Hardi ISO 110 02, 110 03, 110 04 were tested at a spray pressures of 2, 3 and 4 bar. The droplet size spectra of the F and the LD nozzles were measured with a Malvern Mastersizer at spray pressures 2 bar, 3 bar and 4 bar. The Malvern spectra were used to calculate the Volume Median Diameters (VMD) of the sprays.

  7. THE SENSITIVITY OF THE CATALYST EFFECTIVENESS FACTOR TO PORE SIZE DISTRIBUTION

    Directory of Open Access Journals (Sweden)

    Z. Bensetiti

    1997-09-01

    Full Text Available A model is proposed for the average effective diffusivity for an arbitrary pore size distribution. It is shown that the average diffusivity must also depend on the distribution of the catalyst sites. The reaction diffusivity is compared with the average diffusivities defined by Wakao and Smith (1962 and Johnson and Stewart (1965. For the methanol dehydration and n-butene isomerization, the reaction diffusivity gives a better estimation of the effectiveness factor than the other models

  8. Influence of Milling Process of Roasted Cocoa Beans on Size Distribution Change of Cocoa Cotyledon

    Directory of Open Access Journals (Sweden)

    Sukrisno Widyotomo

    2007-05-01

    Full Text Available One of important steps in secondarycocoa process is deshelling cocoa beans roasted. The aim of deshelling is to enrich cotyledon cocoa surface area which affects to reduce energy and processing time with good quality of the chocolate product. The objective of this research is to study the influence of milling process on physical characteristic change of cocoa beans roasted such as size distribution change, geometrical diameter average, uniformity index, fineness modulus, and average dimension of cotyledoncocoa roasted. The Indonesian Coffee and Cocoa Research Institute has designed and tested deshelling of roasted cocoa beans which will be used in this research. Before deshelling process, C grade bulk cocoa beans has been roasted up to 2.5—3% water contents. The result showed that optimal milling process by rotary cutter type milling unit has good size distribution change, geometrical diameter average, uniformity index, fineness modulus, and average dimension on 500 rpm rotary speed and 2.8 m/s air flow. On optimal process condition, 74.5% of cocoa cotyledon roasted has diameter size between 2.0—4.75 mm, 2.116 mm average of geometrical diameter, 0.864 mm average dimension, 3.052 fineness modulus, and 80% as crude size particel-20% as temperate size particel on uniformity index. Therefore, more than 80% of cocoa cotyledon roasted has diameter size between 2.0—4.75 mm with 700—900 rpm rotary cutter speed. Average of geometric diameter was 1.65—2.19 mm, and the dimension average was 0.69—0.89 mm. Uniformity index was crude size particle up to 80—90%, and in temperate size particle10—20%. Fineness modulus value was 2.73—3.09. Key words: cocoa, milling, size distribution, roasted beans.

  9. Colony social stress differentially alters blood pressure and resistance-sized mesenteric artery reactivity in SHR/y and WKY male rats.

    Science.gov (United States)

    Toot, Jonathan D; Reho, John J; Novak, Jacqueline; Dunphy, Gail; Ely, Daniel L; Ramirez, Rolando J

    2011-01-01

    Increased sympathetic nervous system (SNS) activity, testosterone, and spontaneously hypertensive rat Y chromosome (SHR Yc) play a role in a genetic model of hypertension. Male rats with the SHR Yc and Wistar-Kyoto (WKY) autosomes (denoted SHR/y) exhibit these characteristics when compared to rats with the WKY Yc and WKY autosomes (denoted WKY). We hypothesized that chronic social stress will increase blood pressure and SNS activity more in SHR/y males compared to WKY males, resulting in increased myogenic reactivity along with decreased vasoconstriction of small mesenteric arteries. SHR/y and WKY males were housed in strain- specific colonies (10 males with 10 females) or as controls (10 males). Systolic blood pressure (SBP) and blood samples were collected prior to termination. Second-order mesenteric arteries were studied using a pressure arteriograph in which myogenic reactivity and phenylephrine (PE) responsiveness were measured. SHR/y colony SBP, and circulating norepinephrine and testosterone concentrations were elevated compared to control and WKY colony males (p social stress elevated both SNS activity and testosterone level which may be responsible for the increased mesenteric artery myogenic reactivity, and SBP as noted in SHR/y males.

  10. Finite Size Effects on the Real-Space Pair Distribution Function of Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Gilbert, Benjamin

    2008-10-01

    The pair distribution function (PDF) method is a powerful approach for the analysis of the structure of nanoparticles. An important approximation used in nanoparticle PDF simulations is the incorporation of a form factor describing nanoparticle size and shape. The precise effect of the form factor on the PDF is determined by both particle shape and structure if these characteristics are both anisotropic and correlated. The correct incorporation of finite size effects is important for distinguishing and quantifying the structural consequences of small particle size in nanomaterials.

  11. Comprehensive Characterization Of Ultrafine Particulate Emission From 2007 Diesel Engines: PM Size Distribution, Loading And Indidividual Particle Size And Composition.

    Science.gov (United States)

    Zelenyuk, A.; Cuadra-Rodriguez, L. A.; Imre, D.; Shimpi, S.; Warey, A.

    2006-12-01

    The strong absorption of solar radiation by black carbon (BC) impacts the atmospheric radiative balance in a complex and significant manner. One of the most important sources of BC is vehicular emissions, of which diesel represents a significant fraction. To address this issue the EPA has issues new stringent regulations that will be in effect in 2007, limiting the amount of particulate mass that can be emitted by diesel engines. The new engines are equipped with aftertreatments that reduce PM emissions to the point, where filter measurements are subject to significant artifacts and characterization by other techniques presents new challenges. We will present the results of the multidisciplinary study conducted at the Cummins Technical Center in which a suite of instruments was deployed to yield comprehensive, temporally resolved information on the diesel exhaust particle loadings and properties in real-time: Particle size distributions were measured by Engine Exhaust Particle Sizer (EEPS) and Scanning Mobility Particle Sizer (SMPS). Total particle diameter concentration was obtained using Electrical Aerosol Detector (EAD). Laser Induced Incandescence and photoacoustic techniques were used to monitor the PM soot content. Single Particle Laser Ablation Time-of- flight Mass Spectrometer (SPLAT) provided the aerodynamic diameter and chemical composition of individual diesel exhaust particles. Measurements were conducted on a number of heavy duty diesel engines operated under variety of operating conditions, including FTP transient cycles, ramped-modal cycles and steady states runs. We have also characterized PM emissions during diesel particulate filter regeneration cycles. We will present a comparison of PM characteristics observed during identical cycles, but with and without the use of aftertreatment. A total of approximately 100,000 individual particles were sized and their composition characterized by SPLAT. The aerodynamic size distributions of the characterized

  12. Optimum siting and sizing of a large distributed generator in a mesh connected system

    Energy Technology Data Exchange (ETDEWEB)

    Elnashar, Mohab M.; El Shatshat, Ramadan; Salama, Magdy M.A. [Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario (Canada)

    2010-06-15

    This paper proposes a new approach to optimally determine the appropriate size and location of the distributed generator (DG) in a large mesh connected system. This paper presents a visual optimization approach in which the planner plays an important role in determining the optimal siting and sizing of the DG through the choice of the appropriate weight factors of the parameters included in the optimization technique according to the system deficiencies. Losses, voltage profile and short circuit level are used in the algorithm to determine the optimum sizes and locations of the DG. The short circuit level parameter is introduced to represent the protective device requirements in the selection of the size and location of the DG. The proposed technique has been tested on the IEEE 24 - bus mesh connected test system. The obtained results showed clearly that the optimal size and location can be simply determined through the proposed approach. (author)

  13. Number size distributions and seasonality of submicron particles in Europe 2008-2009

    Science.gov (United States)

    Asmi, A.; Wiedensohler, A.; Laj, P.; Fjaeraa, A.-M.; Sellegri, K.; Birmili, W.; Weingartner, E.; Baltensperger, U.; Zdimal, V.; Zikova, N.; Putaud, J.-P.; Marinoni, A.; Tunved, P.; Hansson, H.-C.; Fiebig, M.; Kivekäs, N.; Lihavainen, H.; Asmi, E.; Ulevicius, V.; Aalto, P. P.; Swietlicki, E.; Kristensson, A.; Mihalopoulos, N.; Kalivitis, N.; Kalapov, I.; Kiss, G.; de Leeuw, G.; Henzing, B.; Harrison, R. M.; Beddows, D.; O'Dowd, C.; Jennings, S. G.; Flentje, H.; Weinhold, K.; Meinhardt, F.; Ries, L.; Kulmala, M.

    2011-06-01

    Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community. We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes) are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types. The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l.) with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional coverage of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the

  14. Passive acoustic measurement of bedload grain size distribution using self-generated noise

    Science.gov (United States)

    Petrut, Teodor; Geay, Thomas; Gervaise, Cédric; Belleudy, Philippe; Zanker, Sebastien

    2018-01-01

    Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.

  15. A statistical analysis of North East Atlantic (submicron aerosol size distributions

    Directory of Open Access Journals (Sweden)

    M. Dall'Osto

    2011-12-01

    Full Text Available The Global Atmospheric Watch research station at Mace Head (Ireland offers the possibility to sample some of the cleanest air masses being imported into Europe as well as some of the most polluted being exported out of Europe. We present a statistical cluster analysis of the physical characteristics of aerosol size distributions in air ranging from the cleanest to the most polluted for the year 2008. Data coverage achieved was 75% throughout the year. By applying the Hartigan-Wong k-Means method, 12 clusters were identified as systematically occurring. These 12 clusters could be further combined into 4 categories with similar characteristics, namely: coastal nucleation category (occurring 21.3 % of the time, open ocean nucleation category (occurring 32.6% of the time, background clean marine category (occurring 26.1% of the time and anthropogenic category (occurring 20% of the time aerosol size distributions. The coastal nucleation category is characterised by a clear and dominant nucleation mode at sizes less than 10 nm while the open ocean nucleation category is characterised by a dominant Aitken mode between 15 nm and 50 nm. The background clean marine aerosol exhibited a clear bimodality in the sub-micron size distribution, with although it should be noted that either the Aitken mode or the accumulation mode may dominate the number concentration. However, peculiar background clean marine size distributions with coarser accumulation modes are also observed during winter months. By contrast, the continentally-influenced size distributions are generally more monomodal (accumulation, albeit with traces of bimodality. The open ocean category occurs more often during May, June and July, corresponding with the North East (NE Atlantic high biological period. Combined with the relatively high percentage frequency of occurrence (32.6%, this suggests that the marine biota is an important source of new nano aerosol particles in NE Atlantic Air.

  16. Body size abundance distributions of nano- and micro-phytoplankton guilds in coastal marine ecosystems

    Science.gov (United States)

    Sabetta, Letizia; Fiocca, Annita; Margheriti, Lucia; Vignes, Fabio; Basset, Alberto; Mangoni, Olga; Carrada, Gian Carlo; Ruggieri, Nicoletta; Ianni, Carmela

    2005-06-01

    This study focuses on body size-abundance distributions of nano- and micro-phytoplankton guilds in coastal marine areas of the Southern Adriatic-Ionian region. The aim of the study was to evaluate the occurrence of common patterns of body size-abundance distributions in relation to physical, chemical and biological environmental forcing factors and to taxonomic composition of phytoplankton guilds. This paper is based on data collected during four oceanographic cruises carried out seasonally along the Southern Apulian coast (Adriatic and Ionian Seas, SE Italy) as a part of the INTERREG II Italy-Greece Program. The study was performed at 21 stations located on 7 transects perpendicular to the coastline, with 3 stations per transect at a distance of 3, 9 and 15 NM from the coastline. At each station, profiles of the major physical features of the water were determined and water samples were collected for phytoplankton and nutrient analysis. Overall, 320 nano- and micro-phytoplankton taxa were identified, 76% of which at species level, with phytoplankton cells ranging in size from 0.008 to 4697.54 ng. Body size-abundance distributions showed some common features: they were relatively invariant (average similarity 65%) with respect to taxonomic composition (average similarity 32%), right skewed (90%), leptokurtic (77%) and log normal (76%). Moreover, abiotic, biotic and spatial ecosystem components accounted for up to 75% of body size-abundance distribution variation. The results of this study suggest that body size-abundance distributions are an intrinsic property of marine phytoplankton communities, emphasising functional dependence on ecological constraints related to trophic factors and intra-guild coexistence relationships.

  17. Effect of particle size and distribution of the sizing agent on the carbon fibers surface and interfacial shear strength (IFSS) of its composites

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, R.L. [Open Project of State Key Laboratory Breeding Base for Mining Disaster Prevention and Control, Shandong University of Science and Technology (China); School of Materials Science and Engineering, Shandong University of Science and Technology, 266590 Qingdao (China); Liu, Y. [School of Materials Science and Engineering, Shandong University of Science and Technology, 266590 Qingdao (China); Huang, Y.D., E-mail: rlzhit@126.com [School of Chemical Engineering and Technology, State Key laboratory of Urban Water Resource and Environment Department of Applied Chemistry, Harbin Institute of Technology, 150001 Harbin (China); Liu, L. [School of Chemical Engineering and Technology, State Key laboratory of Urban Water Resource and Environment Department of Applied Chemistry, Harbin Institute of Technology, 150001 Harbin (China)

    2013-12-15

    Effect of particle size and distribution of the sizing agent on the performance of carbon fiber and carbon fiber composites has been investigated. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize carbon fiber surface topographies. At the same time, the single fiber strength and Weibull distribution were also studied in order to investigate the effect of coatings on the fibers. The interfacial shear strength and hygrothermal aging of the carbon fiber/epoxy resin composites were also measured. The results indicated that the particle size and distribution is important for improving the surface of carbon fibers and its composites performance. Different particle size and distribution of sizing agent has different contribution to the wetting performance of carbon fibers. The fibers sized with P-2 had higher value of IFSS and better hygrothermal aging resistant properties.

  18. Effect of dust size distribution on ion-acoustic solitons in dusty plasmas with different dust grains

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Dong-Ning; Yang, Yang; Yan, Qiang [Northwest Normal University, College of Physics and Electronic Engineering (China); Wang, Xiao-Yun [Lanzhou Jiao Tong University, Department of Mathematics and Physics (China); Duan, Wen-Shan, E-mail: duanws@126.com [Northwest Normal University, College of Physics and Electronic Engineering (China)

    2017-02-15

    Theoretical studies are carried out for ion acoustic solitons in multicomponent nonuniform plasma considering the dust size distribution. The Korteweg−de Vries equation for ion acoustic solitons is given by using the reductive perturbation technique. Two special dust size distributions are considered. The dependences of the width and amplitude of solitons on dust size parameters are shown. It is found that the properties of a solitary wave depend on the shape of the size distribution function of dust grains.

  19. INDIGENOUS SPACES IN COLONIAL DOCUMENTS

    Directory of Open Access Journals (Sweden)

    Bartira Ferraz Barbosa

    2004-12-01

    Full Text Available The indigenous spaces constituted at the beginning of the colonial period represented a threat to the plans of implantation and development of the Portuguese-Brazilian colonial economy. Although little studied, they were distributed along the coast and inland of the captaincy of Pernambuco as the documents selected for this study point out. It is a question of the analysis of sources about cultures, spaces and indigenous frontiers, subjects that did not receive in-depth interpretations when studying the growth of Portuguese or Dutch colonial space.

  20. Deconvolution of the particle size distribution of ProRoot MTA and MTA Angelus

    Science.gov (United States)

    Ha, William Nguyen; Shakibaie, Fardad; Kahler, Bill; Walsh, Laurence James

    2016-01-01

    Abstract Objective Mineral trioxide aggregate (MTA) cements contain two types of particles, namely Portland cement (PC) (nominally 80% w/w) and bismuth oxide (BO) (20%). This study aims to determine the particle size distribution (PSD) of PC and BO found in MTA. Materials and methods The PSDs of ProRoot MTA (MTA-P) and MTA Angelus (MTA-A) powder were determined using laser diffraction, and compared to samples of PC (at three different particle sizes) and BO. The non-linear least squares method was used to deconvolute the PSDs into the constituents. MTA-P and MTA-A powders were also assessed with scanning electron microscopy. Results BO showed a near Gaussian distribution for particle size, with a mode distribution peak at 10.48 μm. PC samples milled to differing degrees of fineness had mode distribution peaks from 19.31 down to 4.88 μm. MTA-P had a complex PSD composed of both fine and large PC particles, with BO at an intermediate size, whereas MTA-A had only small BO particles and large PC particles. Conclusions The PSD of MTA cement products is bimodal or more complex, which has implications for understanding how particle size influences the overall properties of the material. Smaller particles may be reactive PC or unreactive radiopaque agent. Manufacturers should disclose particle size information for PC and radiopaque agents to prevent simplistic conclusions being drawn from statements of average particle size for MTA materials. PMID:27335899

  1. Aerosol number size distributions over a coastal semi urban location: Seasonal changes and ultrafine particle bursts

    Energy Technology Data Exchange (ETDEWEB)

    Babu, S. Suresh, E-mail: s_sureshbabu@vssc.gov.in [Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022 (India); Kompalli, Sobhan Kumar [Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022 (India); Moorthy, K. Krishna [Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560 012 (India)

    2016-09-01

    Number-size distribution is one of the important microphysical properties of atmospheric aerosols that influence aerosol life cycle, aerosol-radiation interaction as well as aerosol-cloud interactions. Making use of one-yearlong measurements of aerosol particle number-size distributions (PNSD) over a broad size spectrum (~ 15–15,000 nm) from a tropical coastal semi-urban location-Trivandrum (Thiruvananthapuram), the size characteristics, their seasonality and response to mesoscale and synoptic scale meteorology are examined. While the accumulation mode contributed mostly to the annual mean concentration, ultrafine particles (having diameter < 100 nm) contributed as much as 45% to the total concentration, and thus constitute a strong reservoir, that would add to the larger particles through size transformation. The size distributions were, in general, bimodal with well-defined modes in the accumulation and coarse regimes, with mode diameters lying in the range 141 to 167 nm and 1150 to 1760 nm respectively, in different seasons. Despite the contribution of the coarse sized particles to the total number concentration being meager, they contributed significantly to the surface area and volume, especially during transport of marine air mass highlighting the role of synoptic air mass changes. Significant diurnal variation occurred in the number concentrations, geometric mean diameters, which is mostly attributed to the dynamics of the local coastal atmospheric boundary layer and the effect of mesoscale land/sea breeze circulation. Bursts of ultrafine particles (UFP) occurred quite frequently, apparently during periods of land-sea breeze transitions, caused by the strong mixing of precursor-rich urban air mass with the cleaner marine air mass; the resulting turbulence along with boundary layer dynamics aiding the nucleation. These ex-situ particles were observed at the surface due to the transport associated with boundary layer dynamics. The particle growth rates from

  2. The limit distribution of the maximum increment of a random walk with dependent regularly varying jump sizes

    DEFF Research Database (Denmark)

    Mikosch, Thomas Valentin; Moser, Martin

    2013-01-01

    We investigate the maximum increment of a random walk with heavy-tailed jump size distribution. Here heavy-tailedness is understood as regular variation of the finite-dimensional distributions. The jump sizes constitute a strictly stationary sequence. Using a continuous mapping argument acting...... on the point processes of the normalized jump sizes, we prove that the maximum increment of the random walk converges in distribution to a Fréchet distributed random variable....

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

    Science.gov (United States)

    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.

  4. Use of commercial vessels in survey augmentation: the size-frequency distribution

    Directory of Open Access Journals (Sweden)

    Eric N. Powell

    2006-09-01

    Full Text Available The trend towards use of commercial vessels to enhance survey data requires assessment of the advantages and limitations of various options for their use. One application is to augment information on size-frequency distributions obtained in multispecies trawl surveys where stratum boundaries and sampling density are not optimal for all species. Analysis focused on ten recreationally and commercially important species: bluefish, butterfish, Loligo squid, weakfish, summer flounder, winter flounder, silver hake (whiting, black sea bass, striped bass, and scup (porgy. The commercial vessel took 59 tows in the sampled domain south of Long Island, New York and the survey vessel 18. Black sea bass, Loligo squid, and summer flounder demonstrated an onshore-offshore gradient such that smaller fish were caught disproportionately inshore and larger fish offshore. Butterfish, silver hake, and weakfish were characterized by a southwest-northeast gradient such that larger fish were caught disproportionately northeast of the southwestern-most sector. All sizes of scup, striped bass, and bluefish were caught predominately inshore. Winter flounder were caught predominately offshore. The commercial vessel was characterized by an increased frequency of large catches for most species. Consequently, patchiness was assayed to be higher by the commercial vessel in nearly all cases. The size-frequency distribution obtained by the survey vessel for six of the ten species, bluefish, butterfish, Loligo squid, summer flounder, weakfish, and silver hake, could not be obtained by chance from the size-frequency distribution obtained by the commercial vessel. The difference in sample density did not significantly influence the size-frequency distribution. Of the six species characterized by significant differences in size-frequency distribution between boats, all but one was patchy at the population level and all had one or more size classes so characterized. Although the

  5. A Design of Experiment Study of Nanoprecipitation and Nano Spray Drying as Processes to Prepare PLGA Nano- and Microparticles with Defined Sizes and Size Distributions.

    Science.gov (United States)

    Draheim, Christina; de Crécy, Francois; Hansen, Steffi; Collnot, Eva-Maria; Lehr, Claus-Michael

    2015-08-01

    Aim of this study was to explore the potential of a design of experiments approach to nanoprecipitation (NPR) and nano spray drying (NSD) as processes for preparing poly (lactic-co-glycolic acid, PLGA) nano- and microparticles. In particular, we determined the feasible size range, critical factors influencing particle size, size distribution or yield, and the robustness towards variations of the batch size. A fractional factorial design for response surface was applied to study the influence on continuous, categorical and discrete factors. NPR yielded nanoparticles (150-200 nm) with narrow size distribution (PDI drug delivery systems, as well as to optimize these processes regarding particle size, size distribution and yield. Such understanding of these processes is instrumental for their subsequent scale up and quality control as needed for preclinical and clinical test batches.

  6. Assessing tephra total grain-size distribution: Insights from field data analysis

    Science.gov (United States)

    Costa, A.; Pioli, L.; Bonadonna, C.

    2016-06-01

    The Total Grain-Size Distribution (TGSD) of tephra deposits is crucial for hazard assessment and provides fundamental insights into eruption dynamics. It controls both the mass distribution within the eruptive plume and the sedimentation processes and can provide essential information on the fragmentation mechanisms. TGSD is typically calculated by integrating deposit grain-size at different locations. The result of such integration is affected not only by the number, but also by the spatial distribution and distance from the vent of the sampling sites. In order to evaluate the reliability of TGSDs, we assessed representative sampling distances for pyroclasts of different sizes through dedicated numerical simulations of tephra dispersal. Results reveal that, depending on wind conditions, a representative grain-size distribution of tephra deposits down to ∼100 μm can be obtained by integrating samples collected at distances from less than one tenth up to a few tens of the column height. The statistical properties of TGSDs representative of a range of eruption styles were calculated by fitting the data with a few general distributions given by the sum of two log-normal distributions (bi-Gaussian in Φ-units), the sum of two Weibull distributions, and a generalized log-logistic distribution for the cumulative number distributions. The main parameters of the bi-lognormal fitting correlate with height of the eruptive columns and magma viscosity, allowing general relationships to be used for estimating TGSD generated in a variety of eruptive styles and for different magma compositions. Fitting results of the cumulative number distribution show two different power law trends for coarse and fine fractions of tephra particles, respectively. Our results shed light on the complex processes that control the size of particles being injected into the atmosphere during volcanic explosive eruptions and represent the first attempt to assess TGSD on the basis of pivotal physical

  7. Polarimetric weather radar retrieval of raindrop size distribution by means of a regularized artificial neural network

    NARCIS (Netherlands)

    Vulpiani, G.; Marzano, F.S.; Chandrasekar, V.; Berne, A.D.; Uijlenhoet, R.

    2006-01-01

    The raindrop size distribution (RSD) is a critical factor in estimating rain intensity using advanced dual-polarized weather radars. A new neural-network algorithm to estimate the RSD from S-band dual-polarized radar measurements is presented. The corresponding rain rates are then computed assuming

  8. A century of shocks : The evolution of the German city size distribution 1925-1999

    NARCIS (Netherlands)

    Bosker, Maarten; Brakman, Steven; Garretsen, Harry; Schramm, Marc

    This paper uses empirical evidence on the evolution and structure of the West-German city size distribution to assess the relevance of three different theories of urban growth. The West-German case is of particular interest as Germany's urban system has been subject to some of history's largest

  9. Ripening and Focusing of Aggregate Size Distributions with Overall Volume Growth

    Directory of Open Access Journals (Sweden)

    Jürgen eVollmer

    2014-04-01

    Full Text Available We explore the evolution of the aggregate size distribution in systems where aggregates grow by diffusive accretion of mass. Supersaturation is controlled in such a way that the overall aggregate volume grows linearly in time. Classical Ostwald ripening, which is recovered in the limit of vanishing overall growth, constitutes an unstable solution of the dynamics. In the presence of overall growth evaporation of aggregates always drives the dynamics into a new, qualitatively different growth regime where ripening ceases, and growth proceeds at a constant number density of aggregates. We provide a comprehensive description of the evolution of the aggregate size distribution in the constant density regime: the size distribution does not approach a universal shape, and even for moderate overall growth rates the standard deviation of the aggregate radius decays monotonically. The implications of this theory for the focusing of aggregate size distributions are discussed for a range of different settings including the growth of tiny rain droplets in clouds, as long as they do not yet feel gravity, and the synthesis of nano-particles and quantum dots.

  10. VIMS Stellar Occultations and the Particle-Size Distribution of Saturn's Rings

    Science.gov (United States)

    Harbison, Rebecca A.; Nicholson, Philip D.

    2017-10-01

    Occultations of rings have proven to be a useful way to measure the particle-size distribution of the bodies making up the ring. During stellar occultations of Saturn's rings observed by Cassini, we have observed 'gap overshoots' or 'horns': places near a sharp edge of the rings, such as the gaps of A Ring, where the transmission of starlight appears to exceed unity. This excess light is due to starlight forward-scattered from the nearby ring into the detector. In this work, we model these `horns' in terms of a truncated power law particle-size distribution. Due to the geometry of the observations and the observation wavelength of 2.92 microns, chosen to minimize reflected ringshine, our observations are sensitive to the distribution of ring particles from the millimeter to decimeter range, which we model this using a truncated power law size distribution. Using data from 2005 through 2017, we confirm results seen in other wavelength regimes that show the steepening of the power-law index and decrease in minimum particle size after the Encke Gap and out to the edge fo the A Ring and use the Keeler Gap to further constrain this trend.

  11. Significant effect of grain size distribution on compaction rates in granular aggregates

    NARCIS (Netherlands)

    Niemeijer, André; Elsworth, Derek; Marone, Chris

    2009-01-01

    We investigate the role of pressure solution in deformation of upper- to mid-crustal rocks using aggregates of halite as a room temperature analog for fluid-assisted deformation processes in the Earth's crust. Experiments evaluate the effects of initial grain size distribution on macroscopic

  12. Bimodal grain-size distribution of Chinese loess, and its palaeoclimatic implications

    NARCIS (Netherlands)

    Sun, D.G.; Bloemendal, J.; Rea, D.K.; An, Z.S.; Vandenberghe, J.; Lu, H.; Su, R.; Liu, T.S.

    2004-01-01

    Grain-size analysis indicates that Chinese loess generally shows a bimodal distribution with a coarse and a fine component. The coarse component, comprising the main part of the loess, has pronounced kurtosis and is well sorted, which is interpreted to be the product of dust storms generated by

  13. Effect of dust size distribution and dust charge fluctuation on dust ion ...

    Indian Academy of Sciences (India)

    The effects of dust size distribution and dust charge fluctuation of dust grains on the small but finite amplitude nonlinear dust ion-acoustic shock waves, in an unmagnetized multi-ion dusty plasma which contains negative ions, positive ions and electrons, are studied in this paper. A Burgers equation and its stationary ...

  14. Particle-size distribution and void fraction of geometric random packings

    NARCIS (Netherlands)

    Brouwers, Jos

    2006-01-01

    This paper addresses the geometric random packing and void fraction of polydisperse particles. It is demonstrated that the bimodal packing can be transformed into a continuous particle-size distribution of the power law type. It follows that a maximum packing fraction of particles is obtained when

  15. Flow rate through microfilters: Influence of the pore size distribution, hydrodynamic interactions, wall slip, and inertia

    DEFF Research Database (Denmark)

    Jensen, Kaare Hartvig; Valente, Andre X. C. N.; Stone, Howard A.

    2014-01-01

    to obtain an analytical formula for the pressure drop across the microfilter versus the flow rate that accounts for the non-uniform distribution of pore sizes, the hydrodynamic interactions between the pores given their layout pattern, and wall slip. Further, we discuss inertial effects and their order...

  16. Particle size distribution effect on burn rate of ammonium nitrate based propellant

    NARCIS (Netherlands)

    Miedema, J.R.; Klein, A.J.J.; Zee, F.W.M.

    1995-01-01

    Burn rate control of a Phase Stabilised Ammonium Nitrate (PSAN) propellant by specific surface area (SSA) tuning of the PSAN oxidiser resulted in unexpected effects of applying a new batch of PSAN having a different particle size distribution. Analysis of the deviations and consultation of

  17. Effect of dust size distribution and dust charge fluctuation on dust ion ...

    Indian Academy of Sciences (India)

    2016-06-17

    Jun 17, 2016 ... Dusty plasma; dust-acoustic shock wave; dust size distribution; adiabatic dust charge variation; negative ions. PACS Nos 52.27.Lw; 52.35.Tc; 52.35.Mw. 1. Introduction ... processes has relation to some phenomena including. Landau damping, collisions between charged particles and neutrals and ...

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

    Science.gov (United States)

    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...

  19. M(H) dependence and size distribution of SPIONs measured by atomic magnetometry

    CERN Document Server

    Colombo, Simone; Grujic, Zoran D; Dolgovskiy, Vladimir; Weis, Antoine

    2016-01-01

    We demonstrate that the quasistatic recording of the magnetic excitation function M(H) of superparamagnetic iron oxide magnetic nanoparticle (SPION) suspensions by an atomic magnetometer allows a precise determination of the sample's iron mass content mFe and the particle size distribution.

  20. A Stochastic Theory for Deep Bed Filtration Accounting for Dispersion and Size Distributions

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Bedrikovetsky, P. G.

    2010-01-01

    We develop a stochastic theory for filtration of suspensions in porous media. The theory takes into account particle and pore size distributions, as well as the random character of the particle motion, which is described in the framework of the theory of continuous-time random walks (CTRW). In th...

  1. Size distribution in African catfish (Clarias gariepinus) affects feeding behaviour but not growth

    NARCIS (Netherlands)

    Matos Martins, de C.I.; Aanyu, M.; Schrama, J.W.; Verreth, J.A.J.

    2005-01-01

    The goal of this study is to evaluate the effect of size distribution on growth performance and feeding behaviour in juveniles of African catfish. Two thousand sibling fish were grown for 8 weeks until the start of the experiment. Afterwards fish were individually weighed, manually selected and

  2. Estimates of zooplankton abundance and size distribution with the Optical Plankton Counter (OPC)

    DEFF Research Database (Denmark)

    Wieland, Kai; Petersen, D.; Schnack, D.

    1997-01-01

    The capability of the Optical Plankton Count er (OPC) to examine the abundance and size distribution of zooplankton was tested in Storfjorden, Norway, in June 1993. Selected material obtained from net sampling was measured with a laboratory version of the OPC and compared with microscope analysis...

  3. Characterization of hollow fiber hemo-dialysis membranes: pore size distribution and performance

    NARCIS (Netherlands)

    Broek, A.P.; Broek, Arnold P.; Teunis, Herman A.; Teunis, Hermannus A.; Bargeman, D.; Bargeman, Derk; Sprengers, Erik D.; Smolders, C.A.; Smolders, C.A.

    1992-01-01

    The effect of two commonly used sterilization methods for artificial kidneys on the morphology and performance of hollow fiber Hemophan® hemodialysis membranes was studied. A relatively new membrane characterization method, thermoporometry, was used to determine the pore size distributions and

  4. INFLUENCE OF ELECTROPHORETIC DEPOSITION PARAMETERS ON PORE SIZE DISTRIBUTION OF DOPED NANO ALUMINA PLATES

    Directory of Open Access Journals (Sweden)

    Mostafa Milani

    2016-10-01

    Full Text Available Doped nano alumina powders were successfully deposited as a thick film by electrophoretic deposition (EPD. A mixture of ethanol, cation salts of alumina dopants and iodine was used for dispersion system. Mg- Y- La- and Ce- salts add to ethanol and deposited with alumina powders on to substrate. The effects of suspension power loading, deposition time, electrode distance and applied potential simultaneously on density, pore size distribution and cell current density of alumina nanoparticles were examined. The weight of deposition increased with time and voltage increased and electrode distance decreased. In all applied voltages in higher suspension concentration, weight of deposition are sufficiently high but the density of the film are clearly better in low and high voltages than medium voltage. In constant suspension concentration with increasing in applied voltage, deposition rate increased and current decreased faster than medium voltage, which limits the homogeneous deposition forming and decreased density. Low applied voltages provided better pore size distribution and narrow and steep slope in middle of pore size distribution plot. High density samples with best pore size distribution achieved in lower rate deposition and assisted to better densification at sintering step in doped alumina plates.

  5. Pore size distribution effect on rarefied gas transport in porous media

    Science.gov (United States)

    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).

  6. Oscillating bubble concentration and its size distribution using acoustic emission spectra.

    Science.gov (United States)

    Avvaru, Balasubrahmanyam; Pandit, Aniruddha B

    2009-01-01

    New method has been proposed for the estimation of size and number density distribution of oscillating bubbles in a sonochemical reactor using acoustic emission spectra measurements. Bubble size distribution has been determined using Minnaert's equation [M. Minnaert, On musical air bubbles and sound of running water, Philanthr. Mag. 16 (1933) 235], i.e., size of oscillating bubble is inversely related to the frequency of its volume oscillations. Decomposition of the pressure signal measured by the hydrophone in frequency domain of FFT spectrum and then inverse FFT reconstruction of the signal at each frequency level has been carried out to get the information about each of the bubble/cavity oscillation event. The number mean radius of the bubble size is calculated to be in the range of 50-80 microm and it was not found to vary much with the spatial distribution of acoustic field strength of the ultrasound processor used in the work. However, the number density of the oscillating bubbles and the nature of the distribution were found to vary in different horizontal planes away from the driving transducer surface in the ultrasonic bath. A separate set of experiments on erosion assessment studies were carried out using a thin aluminium foil, revealing a phenomena of active region of oscillating bubbles at antinodal points of the stationary waves, identical to the information provided by the acoustic emission spectra at the same location in the ultrasonic bath.

  7. Sizing stack and battery of a fuel cell hybrid distribution truck

    NARCIS (Netherlands)

    Y. Shen; P. van den Bosch; Edwin Tazelaar; Bram Veenhuizen; T. Hofman

    2012-01-01

    An existing fuel cell hybrid distribution truck, built for demonstration purposes, is used as a case study to investigate the effect of stack (kW) and battery (kW, kWh) sizes on the hydrogen consumption of the vehicle. Three driving cycles, the NEDC for Low Power vehicles, CSC and JE05 cycle, define

  8. Influence of surface charge distributions and particle size distributions on particle attachment in granular media filtration.

    Science.gov (United States)

    Kim, Jinkeun; Nason, Jeffrey A; Lawler, Desmond F

    2008-04-01

    Filtration experiments were performed with a laboratory-scale filter using spherical glass beads with 0.55 mm diameter as collectors. Suspensions were made with Min-U-Sil 5 particles, and two different methods (pH control and polymer dosing) were used for destabilization. In the pH control experiments, all particles had negative surface charge, and those with lower (absolute value) charge were selectively attached to the collectors, especially during the early stage of filtration. This selective attachment of the lower charged particles caused the zeta potential distribution (ZPD) of the effluent to move to a more negative range. However, the ZPD of the effluent did not continue moving to more negative values during the later stages of filtration, and this result was attributed to two reasons: ripening effects and detachment of flocs. In the polymer experiments, substantial differences were found between experiments performed with negatively charged particles (underdosing) and those with positively charged particles (overdosing). With under-dosing, the results were similar to the pH control experiments (which also had negatively charged particles), but with overdosing, the effluent's ZPDs in the early stages did not overlap with those of the influent and more highly charged particles were removed more efficiently than lesser-charged particles. It is hypothesized that, despite a substantial period of pre-equilibration of media and coagulant, this equilibrium shifted when particles were also added. It was assumed that coagulant molecules previously adsorbed to the particles desorbed and subsequently attached to the filter media because of surface area differences in the particle and filter media.

  9. Direct Online Determination of Laser-Induced Particle Size Distribution by ICPMS.

    Science.gov (United States)

    Donard, Ariane; Claverie, Fanny; Pointurier, Fabien; Blitz Frayret, Céline; Svatosova, Barbora; Pécheyran, Christophe

    2017-09-05

    The characterization of the aerosol (size, composition, and concentration) generated by Laser Ablation is of great interest due to its impact on the analytical performances when coupled to Inductively Coupled Plasma Mass Spectrometry (ICPMS). The capabilities of High Resolution ICPMS as a direct tool to characterize nanoparticles produced by femtosecond Laser Ablation of pure copper are presented. An analytical protocol, similar to the "single particle ICPMS" technique used to characterize the size distribution of nanoparticles in solution, was developed in order to observe the signals of individual particles produced by a single ablation shot. A Visual Basic for Applications (VBA) data processing was developed to count and sort the particles as a function of their size and thus determine the particle size distribution. To check the reliability of the method, the results were compared to a more conventional technique, namely, Electrical Low Pressure Impaction (ELPI) for 4000 shots. Detection limit for the particles produced by the laser ablation of a copper foil is of a few attograms corresponding to a nanoparticle of 14 nm. The direct online determination of particle size by ICPMS gave similar results than ELPI for copper particles ejected during the ablation shot by shot at a fixed spot, from 1 to 100 shots. Particles larger than 159 nm represented less than 1% of the aerosol whose distribution was centered on 25-51 nm.

  10. Particle size distributions of currently used pesticides in ambient air of an agricultural Mediterranean area

    Science.gov (United States)

    Coscollà, Clara; Muñoz, Amalia; Borrás, Esther; Vera, Teresa; Ródenas, Milagros; Yusà, Vicent

    2014-10-01

    This work presents first data on the particle size distribution of 16 pesticides currently used in Mediterranean agriculture in the atmosphere. Particulate matter air samples were collected using a cascade impactor distributed into four size fractions in a rural site of Valencia Region, during July to September in 2012 and from May to July in 2013. A total of 16 pesticides were detected, including six fungicides, seven insecticides and three herbicides. The total concentrations in the particulate phase (TSP: Total Suspended Particulate) ranged from 3.5 to 383.1 pg m-3. Most of the pesticides (such as carbendazim, tebuconazole, chlorpyrifos-ethyl and chlorpyrifos-methyl) were accumulated in the ultrafine-fine (<1 μm) and coarse (2.5-10 μm) particle size fractions. Others like omethoate, dimethoate and malathion were presented only in the ultrafine-fine size fraction (<1 μm). Finally, diuron, diphenylamine and terbuthylazine-desethyl-2-OH also show a bimodal distribution but mainly in the coarse size fractions.

  11. Prediction of bulk powder flow performance using comprehensive particle size and particle shape distributions.

    Science.gov (United States)

    Yu, Weili; Muteki, Koji; Zhang, Lin; Kim, Gloria

    2011-01-01

    The purpose of this study is to establish a modeling approach that can be used to predict bulk powder flowability of pharmaceutical materials from their particle size and shape distributions. To build and validate the model, 23 commonly used pharmaceutical excipients and 38 binary blends were fully characterized for their particle size and shape distributions. The particle size and shape of each sample was characterized by multiple descriptors to fully reflect their morphological characteristics. The flow properties of these materials were analyzed using the Schulze Ring Shear Tester at a fixed humidity condition. A partial least squares (PLS) approach was used to build the mathematical model. Several different modeling approaches were attempted and the best method was identified as using a combination of formulation composition and particle size and shape distributions of single-component powder systems. The PLS model was shown to provide excellent predictions of powder flow function coefficient (FFC) of up to approximately 20. The results also revealed that both particle size and shape play an important role in determining the powder flow behavior. Copyright © 2010 Wiley-Liss, Inc. and the American Pharmacists Association

  12. Vertical distribution of the prokaryotic cell size in the Mediterranean Sea

    Science.gov (United States)

    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.

  13. Explicit expressions of the Pietra index for the generalized function for the size distribution of income

    Science.gov (United States)

    Sarabia, José María; Jordá, Vanesa

    2014-12-01

    The importance of the Pietra index in socioeconomic systems and econophysics has been highlighted by Eliazar and Sokolov (2010). In this paper, we obtain closed expressions for the Pietra index for the generalized function for the size of income proposed by McDonald (1984). This family is composed of three classes of distributions: the generalized gamma distribution (GG), the generalized beta of the first kind (GB1) and the generalized beta of the second kind (GB2). For the different distributions, we obtain closed and simple expressions of the Pietra index, which can be easily computed. We also obtain the Pietra index for other relevant income models including finite mixtures of distributions and the κ-generalized distribution (Clementi et al., 2008). Finally, two empirical applications with real income data are given.

  14. Evaluation and interpretation of bubble size distributions in pulsed megasonic fields

    Science.gov (United States)

    Hauptmann, M.; Struyf, H.; De Gendt, S.; Glorieux, C.; Brems, S.

    2013-05-01

    The occurrence of acoustic cavitation is incorporating a multitude of interdependent effects that strongly depend on the bubble size. Therefore, bubble size control would be beneficial for biological and industrial processes that rely on acoustic cavitation. A pulsed acoustic field can result in bubble size control and the repeated dissolution and reactivation ("recycling") of potentially active bubbles. As a consequence, a pulsed field can strongly enhance cavitation activity. In this paper, we present a modified methodology for the evaluation of the active bubble size distribution by means of a combination of cavitation noise measurements and ultrasonic pulsing. The key component of this modified methodology is the definition of an upper size limit, below which bubbles—in between subsequent pulses—have to dissolve, in order to be sustainably recycled. This upper limit makes it possible to explain and link the enhancement of cavitation activity to a bubble size distribution. The experimentally determined bubble size distributions for different power densities are interpreted in the frame of numerical calculations of the oscillatory responses of the bubbles to the intermittent driving sound field. The distributions are found to be shaped by the size dependent interplay between bubble pulsations, rectified diffusion, coalescence, and the development of parametrically amplified shape instabilities. Also, a phenomenological reactivation-deactivation model is proposed to explain and quantify the observed enhancement of cavitation activity under pulsed, with respect to continuous sonication. In this model, the pulse-duration determines the magnitude of the reactivation of partially dissolved bubbles and the deactivation of activated bubbles by coalescence. It is shown that the subsequent recycling of previously active bubbles leads to an accumulation of cavitation activity, which saturates after a certain number of pulses. The model is fitted to the experimental

  15. Concentration and particle size distribution of polycyclic aromatic hydrocarbons formed by thermal cooking.

    Science.gov (United States)

    Saito, E; Tanaka, N; Miyazaki, A; Tsuzaki, M

    2014-06-15

    The concentration and particle size distribution of 19 major polycyclic aromatic hydrocarbons (PAHs) emitted by thermal cooking were investigated. Corn, trout, beef, prawns, and pork were selected for grilling. The PAHs in the oil mist emitted when the food was grilled were collected according to particle size range and analysed by GC/MS. Much higher concentrations of PAHs were detected in the oil mist emitted by grilled pork, trout, and beef samples, which were rich in fat. The main components of the cooking exhaust were 3- and 4-ring PAHs, regardless of food type. The particle size distribution showed that almost all the PAHs were concentrated in particles with diameters of particles with diameters of 90% of the PAHs would reach the alveolar region of the lungs. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Saturn's rings: Particle composition and size distribution as constrained by microwave observations. I - Radar observations

    Science.gov (United States)

    Cuzzi, J. N.; Pollack, J. B.

    1978-01-01

    The radar backscattering characteristics of compositional and structural models of Saturn's rings are calculated and compared with observations of the absolute value, wavelength dependence, and degree of depolarization of the rings' radar cross section (reflectivity). The doubling method is used to calculate reflectivities for systems that are many particles thick using optical depths derived from observations at visible wavelengths. If the rings are many particles thick, irregular centimeter- to meter-sized particles composed primarily of water ice attain sufficiently high albedos and scattering efficiencies to explain the radar observations. In that case, the wavelength independence of radar reflectivity implies the existence of a broad particle size distribution; a narrower size distribution is also a possibility. Particles of primarily silicate composition are ruled out by the radar observations. Purely metallic particles may not be ruled out on the basis of existing radar observations. A monolayer of very large ice 'particles' that exhibit multiple internal scattering may not yet be ruled out.

  17. Pore-size distribution and compressibility of coarse sandy subsoil with added biochar

    DEFF Research Database (Denmark)

    Petersen, C. T.; Hansen, E.; Larsen, H. H.

    2016-01-01

    the effects of two fine-grained gasification biochars made of straw (LTST) and other materials (LTSN) and of one fast pyrolysis straw biochar (FPST) on pore-size distribution and soil compressibility when added to coarse sandy subsoil. Water retention and therefore pore-size distribution were affected...... systematically. All biochars converted drainable pore space with pore diameters in the range 60–300 µm into water-retaining pores of size 0.2–60 µm, which was taken as an estimate of available water capacity (AWC). Effects were linear over the whole range of biochar (0–4% by mass). The effect of LTST and LTSN...

  18. Effect of ground granulated blast furnace slag particle size distribution on paste rheology: A preliminary model

    Science.gov (United States)

    Kashani, Alireza; Provis, John L.; van Deventer, Jannie S. J.

    2013-06-01

    Ground granulated blast furnace slag is widely combined with Portland cement as a supplementary material, and is also used in alkali-activated binders (geopolymers) and in supersulfated cements, which are potential replacements for Portland cement with significantly reduced carbon dioxide emissions. The rheology of a cementitious material is important in terms of its influence on workability, especially in self leveling concretes. The current research investigates the effects of different particle size distributions of slag particles on paste rheology. Rheological measurements results show a direct relationship between the modal particle size and the yield stress of the paste. An empirical model is introduced to calculate the yield stress value of each paste based on the particle size distribution, and applied to a range of systems at single water to solids ratio. The model gives a very good match with the experimental data.

  19. Stationary Size Distributions of Growing Cells with Binary and Multiple Cell Division

    Science.gov (United States)

    Rading, M. M.; Engel, T. A.; Lipowsky, R.; Valleriani, A.

    2011-10-01

    Populations of unicellular organisms that grow under constant environmental conditions are considered theoretically. The size distribution of these cells is calculated analytically, both for the usual process of binary division, in which one mother cell produces always two daughter cells, and for the more complex process of multiple division, in which one mother cell can produce 2 n daughter cells with n=1,2,3,… . The latter mode of division is inspired by the unicellular algae Chlamydomonas reinhardtii. The uniform response of the whole population to different environmental conditions is encoded in the individual rates of growth and division of the cells. The analytical treatment of the problem is based on size-dependent rules for cell growth and stochastic transition processes for cell division. The comparison between binary and multiple division shows that these different division processes lead to qualitatively different results for the size distribution and the population growth rates.

  20. The measurement of aerosol size distributions (AMAD) in buildings on BNFL`s Sellafield site

    Energy Technology Data Exchange (ETDEWEB)

    Kelso, S.M.; Wraight, J.C. [British Nuclear Fuels plc, Sellafield (United Kingdom)

    1996-07-01

    Cascade centripeters were used to make measurements of aerosol activity size distributions in several buildings involved in the reprocessing of Magnox Nuclear Reactor Fuel on BNFL`s Sellafield site. Whilst the 50 measurements made demonstrate significant variations in size distribution between buildings (2.8 {mu}m-4.2 {mu}m) and even between sampling locations within particular buildings (1.9 {mu}m-9.0 {mu}m), they demonstrate consistently larger particle sizes than the 1 {mu}m AMAD default value recommended in ICRP Publication 30 and provide further empirical support for the adoption of a 5 {mu}m AMAD default value as most recently proposed in ICRP Publication 66 for workplaces. (Author).

  1. The size distribution of spatiotemporal extreme rainfall clusters around the globe

    Science.gov (United States)

    Traxl, D.; Boers, N.; Rheinwalt, A.; Goswami, B.; Kurths, J.

    2016-09-01

    The scaling behavior of rainfall has been extensively studied both in terms of event magnitudes and in terms of spatial extents of the events. Different heavy-tailed distributions have been proposed as candidates for both instances, but statistically rigorous treatments are rare. Here we combine the domains of event magnitudes and event area sizes by a spatiotemporal integration of 3-hourly rain rates corresponding to extreme events derived from the quasi-global high-resolution rainfall product Tropical Rainfall Measuring Mission 3B42. A maximum likelihood evaluation reveals that the distribution of spatiotemporally integrated extreme rainfall cluster sizes over the oceans is best described by a truncated power law, calling into question previous statements about scale-free distributions. The observed subpower law behavior of the distribution's tail is evaluated with a simple generative model, which indicates that the exponential truncation of an otherwise scale-free spatiotemporal cluster size distribution over the oceans could be explained by the existence of land masses on the globe.

  2. Functional Stereology for 3D Particle Size Distributions from 2D Observations: a Practical Approach

    Science.gov (United States)

    Proussevitch, A. A.; Sahagian, D. L.; Jutzeler, M.

    2010-12-01

    Functional stereology applies known deconvolution techniques to obtain 3D size distributions from 2D cross-section data based on an assumption that both 2D and 3D statistics have known distribution functions with unknown parameters. A new stereological approach enables us to solve this problem by utilizing function minimization to find parameters of the distribution functions. There is no limit to continuous distribution function types that could be used, such as Gaussian, Logistic, Weibull, Gamma, and others. As compared to previously known 2D to 3D conversion methods (e.g. Sahagian and Proussevitch, 1998), functional stereology has much greater practical application to non-spherical particles/objects because it is free of uncontrollable error propagation for all particles shapes. The new practical method of functional stereology has been implemented in Stereonet software adapted for both a) direct logarithmic scales of particle/voids volumes, and b) Phi units of linear dimensions (-log2 of size). Applications of the method include distribution of voids/bubbles in all types of volcanic rocks, pore networks in sedimentary rocks, mineral and grain sizes, volcanic clasts, breccia, and texture features of a wide range of rock formations. Such applications demonstrate utility of this functional stereology approach.

  3. Determination of nanoparticle size distribution together with density or molecular weight by 2D analytical ultracentrifugation

    KAUST Repository

    Carney, Randy P.

    2011-06-07

    Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (?P) and particle diameter (dp) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations. 2011 Macmillan Publishers Limited. All rights reserved.

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

    Science.gov (United States)

    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.

  5. Effect of ship structure and size on grounding and collision damage distributions

    DEFF Research Database (Denmark)

    Pedersen, Preben Terndrup; Zhang, Shengming

    2000-01-01

    It has been argued that a major shortcoming in the International Maritime Organization (IMO) Interim Guidelines for Approval of Alternative Methods of Design and Construction of Oil Tankers in Collision and Grounding is that grounding and collision damages normalized by the main dimensions...... of the ship have the same probability density distributions regardless of a particular structural design and ship size.The present paper explores analytical methods for assessing the overall effect of structural design on the damage distributions in accidental grounding and collisions. The results...... are expressed in simple expressions involving structural dimensions and the building material of the ships. The study shows that the density distribution for collision and grounding damages normalized by the main dimensions of the ship depends on the size of the ship. A larger ship has a higher probability...

  6. Theoretical size distribution of fossil taxa: analysis of a null model

    Directory of Open Access Journals (Sweden)

    Hughes Barry D

    2007-03-01

    Full Text Available Abstract Background This article deals with the theoretical size distribution (of number of sub-taxa of a fossil taxon arising from a simple null model of macroevolution. Model New species arise through speciations occurring independently and at random at a fixed probability rate, while extinctions either occur independently and at random (background extinctions or cataclysmically. In addition new genera are assumed to arise through speciations of a very radical nature, again assumed to occur independently and at random at a fixed probability rate. Conclusion The size distributions of the pioneering genus (following a cataclysm and of derived genera are determined. Also the distribution of the number of genera is considered along with a comparison of the probability of a monospecific genus with that of a monogeneric family.

  7. Scaling of size distributions of C60 and C70 fullerene surface islands

    Science.gov (United States)

    Dubrovskii, V. G.; Berdnikov, Y.; Olyanich, D. A.; Mararov, V. V.; Utas, T. V.; Zotov, A. V.; Saranin, A. A.

    2017-06-01

    We present experimental data and a theoretical analysis for the size distributions of C60 and C70 surface islands deposited onto In-modified Si(111)√3 × √3-Au surface under different conditions. We show that both fullerene islands feature an analytic Vicsek-Family scaling shape where the scaled size distributions are given by a power law times an incomplete beta-function with the required normalization. The power exponent in this distribution corresponds to the fractal shape of two-dimensional islands, confirmed by the experimentally observed morphologies. Quite interestingly, we do not see any significant difference between C60 and C70 fullerenes in terms of either scaling parameters or temperature dependence of the diffusion constants. In particular, we deduce the activation energy for surface diffusion of ED = 140 ± 10 meV for both types of fullerenes.

  8. Seasonal cycle and modal structure of particle number size distribution at Dome C, Antarctica

    Directory of Open Access Journals (Sweden)

    E. Järvinen

    2013-08-01

    Full Text Available We studied new particle formation and modal behavior of ultrafine aerosol particles on the high East Antarctic plateau at the Concordia station, Dome C (75°06' S, 123°23' E. Aerosol particle number size distributions were measured in the size range 10–600 nm from 14 December 2007 to 7 November 2009. We used an automatic algorithm for fitting up to three modes to the size distribution data. The total particle number concentration was low with the median of 109 cm−3. There was a clear seasonal cycle in the total particle number and the volume concentrations. The concentrations were at their highest during the austral summer with the median values of 260 cm−3 and 0.086 μm3 cm−3, and at their lowest during the austral winter with corresponding values of 15 cm−3 and 0.009 μm3 cm−3. New particle formation events were determined from the size distribution data. During the measurement period, natural new particle formation was observed on 60 days and for 15 of these days the particle growth rates from 10 to 25 nm in size could be determined. The median particle growth rate during all these events was 2.5 nm h−1 and the median formation rate of 10 nm particles was 0.023 cm−3 s−1. Most of the events were similar to those observed at other continental locations, yet also some variability in event types was observed. Exceptional features in Dome C were the winter events that occurred during dark periods, as well as the events for which the growth could be followed during several consecutive days. We called these latter events slowly growing events. This paper is the first one to analyze long-term size distribution data from Dome C, and also the first paper to show that new particle formation events occur in central Antarctica.

  9. The Effect of Solid Constituent Particle Size Distributions on TP-H1148 Propellant Slag

    Science.gov (United States)

    May, Douglas H.; Miles, William L.; Taylor, David S.; Rackham, Jon L.

    1997-01-01

    Special aluminum and ammonium perchlorate (AP) particle size distributions were prepared for a matrix of five-inch diameter, center-perforated (CP) motor tests to measure the aluminum oxide slag response in Space Shuttle Reusable Solid Rocket Motor (RSRM) propellant. Previous tests of TP-H1148 propellant in five-inch CP spin motors have shown a correlation between aluminum particle size and generated slag. The motors for this study were cast from thirteen five-gallon propellant mixes which used five particle size levels of aluminum powder, five of unground AP and three of ground AP. Aluminum had the greatest effect on slag formation, the more coarse fractions causing greater slag quantities and larger slag particles. Unground AP had about half the effect of aluminum with the coarser fractions again producing more and larger sized slag particles. The variation in ground AP did not have a significant effect on slag formation. Quench bomb tests showed the same trends as the spin motors, that is, larger aluminum and AP particle size distributions generated larger slag particles leaving the propellant surface. Cured propellant mechanical properties were also impacted by particle size variation.

  10. [Study on the grain-size distribution of polycyclic aromatic hydrocarbons in Yangtze River sediment].

    Science.gov (United States)

    Feng, Jing-lan; Niu, Jun-feng

    2007-07-01

    Sediments collected from Yangtze River were separated into five size fractions ( > 200 microm, 200 - 125 microm, 125 - 63 microm, 63 - 25 microm, sediments. Sigma PAHs concentrations ranged from 26.1 to 7135.9 ng/g and varied largely among the different size fractions. The highest Sigma PAHs concentration (7135.9 ng/g) was associated with the largest size fraction ( > 200 microm) while the fine silt fraction (63 - 25 microm) contained the lowest Sigma PAHs concentration, 26.1 ng/g. Although the PAHs concentrations difference among different fractions was great, the composition of PAHs in the five size fractions showed similar pattern dominated by PAHs with three or more rings. Sediment particles less than 25 microm contributed 75% of the Sigma PAHs, while comprising 38.6% of bulk sediment dry weight. A significant positive correlation (p size fractions demonstrated that TOC was important for PAHs distribution in sediments. Additionally, sediment organic matter type and structure also played an important role in PAHs distribution in different grain size fractions.

  11. Sampling surface particle size distributions and stability analysis of deep channel in the Pearl River Estuary

    Science.gov (United States)

    Feng, Hao-chuan; Zhang, Wei; Zhu, Yu-liang; Lei, Zhi-yi; Ji, Xiao-mei

    2017-06-01

    Particle size distributions (PSDs) of bottom sediments in a coastal zone are generally multimodal due to the complexity of the dynamic environment. In this paper, bottom sediments along the deep channel of the Pearl River Estuary (PRE) are used to understand the multimodal PSDs' characteristics and the corresponding depositional environment. The results of curve-fitting analysis indicate that the near-bottom sediments in the deep channel generally have a bimodal distribution with a fine component and a relatively coarse component. The particle size distribution of bimodal sediment samples can be expressed as the sum of two lognormal functions and the parameters for each component can be determined. At each station of the PRE, the fine component makes up less volume of the sediments and is relatively poorly sorted. The relatively coarse component, which is the major component of the sediments, is even more poorly sorted. The interrelations between the dynamics and particle size of the bottom sediment in the deep channel of the PRE have also been investigated by the field measurement and simulated data. The critical shear velocity and the shear velocity are calculated to study the stability of the deep channel. The results indicate that the critical shear velocity has a similar distribution over large part of the deep channel due to the similar particle size distribution of sediments. Based on a comparison between the critical shear velocities derived from sedimentary parameters and the shear velocities obtained by tidal currents, it is likely that the depositional area is mainly distributed in the northern part of the channel, while the southern part of the deep channel has to face higher erosion risk.

  12. MinSORTING: an Excel macro for modelling sediment composition and grain-size distribution

    Science.gov (United States)

    Resentini, Alberto; Malusà, Marco G.; Garzanti, Eduardo

    2013-04-01

    Detrital mineral analyses are gaining increasing attention in the geosciences as new single-grain analytical techniques are constantly improving their resolution, and consequently widening their range of application, including sedimentary petrology, tectonic geomorphology and archaeology (Mange and Wright, 2007; von Eynatten and Dunkl, 2012). We present here MinSORTING, a new tool to quickly predict the size distribution of various minerals and rock fragments in detrital sediments, based on the physical laws that control sedimentation by tractive wind or water currents (Garzanti et al., 2008). The input values requested by the software are the sediment mean size, sorting, fluid type (seawater, freshwater, air) and standard sediment composition chosen from a given array including nine diverse tectonic settings. MinSORTING calculates the bulk sediment density and the settling velocity. The mean size of each single detrital component, assumed as lognormally-distributed, is calculated from its characteristic size-shift with respect to bulk sediment mean size, dependent in turn on its density and shape. The final output of MinSORTING is the distribution of each single detrital mineral in each size classes (at the chosen 0.25, 0.5 or 1 phi intervals). This allows geochronolgists to select the most suitable grain size of sediment to be sampled in the field, as well as the most representative size-window for analysis. Also, MinSORTING provides an estimate of the volume/weight of the fractions not considered in both sizes finer and coarser than the selected size-window. A beta version of the software is available upon request from: alberto.resentini@unimib.it Mange, M., and Wright, D. (eds), 2007. Heavy minerals in use. Developments in Sedimentology Series, 58. Elsevier, Amsterdam. Garzanti, E., Andò, S., Vezzoli, G., 2008. Settling-equivalence of detrital minerals and grain-size dependence of sediment composition. Earth and Planetary Science Letters 273, 138-151. von

  13. A comparative study of submicron particle sizing platforms: accuracy, precision and resolution analysis of polydisperse particle size distributions.

    Science.gov (United States)

    Anderson, Will; Kozak, Darby; Coleman, Victoria A; Jämting, Åsa K; Trau, Matt

    2013-09-01

    The particle size distribution (PSD) of a polydisperse or multimodal system can often be difficult to obtain due to the inherent limitations in established measurement techniques. For this reason, the resolution, accuracy and precision of three new and one established, commercially available and fundamentally different particle size analysis platforms were compared by measuring both individual and a mixed sample of monodisperse, sub-micron (220, 330, and 410 nm - nominal modal size) polystyrene particles. The platforms compared were the qNano Tunable Resistive Pulse Sensor, Nanosight LM10 Particle Tracking Analysis System, the CPS Instruments's UHR24000 Disc Centrifuge, and the routinely used Malvern Zetasizer Nano ZS Dynamic Light Scattering system. All measurements were subjected to a peak detection algorithm so that the detected particle populations could be compared to 'reference' Transmission Electron Microscope measurements of the individual particle samples. Only the Tunable Resistive Pulse Sensor and Disc Centrifuge platforms provided the resolution required to resolve all three particle populations present in the mixed 'multimodal' particle sample. In contrast, the light scattering based Particle Tracking Analysis and Dynamic Light Scattering platforms were only able to detect a single population of particles corresponding to either the largest (410 nm) or smallest (220 nm) particles in the multimodal sample, respectively. When the particle sets were measured separately (monomodal) each platform was able to resolve and accurately obtain a mean particle size within 10% of the Transmission Electron Microscope reference values. However, the broadness of the PSD measured in the monomodal samples deviated greatly, with coefficients of variation being ~2-6-fold larger than the TEM measurements across all four platforms. The large variation in the PSDs obtained from these four, fundamentally different platforms, indicates that great care must still be taken in

  14. Aethina tumida (Coleoptera: Nitidulidae) and Oplostomus haroldi (Coleoptera: Scarabaeidae): Occurrence in Kenya, Distribution within Honey Bee Colonies, and Response to Host Odors

    Science.gov (United States)

    Aethina tumida Murray is considered a minor parasitic pest of African honey bee colonies, but little information is available on other coleopteran pests. We surveyed for A. tumida and other beetles in honey bee colonies at four major beekeeping locations: Watamu, Chawia-Taita, Matuu, and Nairobi in...

  15. The morphology of cometary dust: Subunit size distributions down to tens of nanometres

    Science.gov (United States)

    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

  16. 40 CFR Table F-3 to Subpart F of... - Critical Parameters of Idealized Ambient Particle Size Distributions

    Science.gov (United States)

    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...

  17. Particle size distribution of brominated flame retardants in house dust from Japan

    Directory of Open Access Journals (Sweden)

    Natsuko Kajiwara

    2016-06-01

    Full Text Available The present study was conducted to examine the concentrations, profiles, and mass distributions of polybrominated diphenyl ethers (PBDEs, hexabromocyclododecanes (HBCDs, and polybrominated dibenzo-p-dioxins/furans (PBDD/Fs based on the particle sizes of house dust samples from five homes in Japan. After removal of impurities from house dust from vacuum cleaner bags, selected indoor dust samples were size fractionated (>2 mm, 1–2 mm, 0.5–1 mm, 250–500 μm, 106–250 μm, 53–106 μm, and 250 μm in size and fluffy dust were included. The conclusion is that particulate dust <250 μm in size without fluffy dust should be used to analyze dust for brominated flame retardants.

  18. Pore size distribution, strength, and microstructure of portland cement paste containing metal hydroxide waste

    Energy Technology Data Exchange (ETDEWEB)

    Majid, Z.A.; Mahmud, H.; Shaaban, M.G.

    1996-12-31

    Stabilization/solidification of hazardous wastes is used to convert hazardous metal hydroxide waste sludge into a solid mass with better handling properties. This study investigated the pore size development of ordinary portland cement pastes containing metal hydroxide waste sludge and rice husk ash using mercury intrusion porosimetry. The effects of acre and the addition of rice husk ash on pore size development and strength were studied. It was found that the pore structures of mixes changed significantly with curing acre. The pore size shifted from 1,204 to 324 {angstrom} for 3-day old cement paste, and from 956 to 263 {angstrom} for a 7-day old sample. A reduction in pore size distribution for different curing ages was also observed in the other mixtures. From this limited study, no conclusion could be made as to any correlation between strength development and porosity. 10 refs., 6 figs., 3 tabs.

  19. Tumor Microvasculature: Endothelial Leakiness and Endothelial Pore Size Distribution in a Breast Cancer Model

    Directory of Open Access Journals (Sweden)

    E.E. Uzgiris

    2008-01-01

    Full Text Available Tumor endothelial leakiness is quantified in a rat mammary adenocarcinoma model using dynamic contrast enhancement MRI and contrast agents of widely varying sizes. The contrast agents were constructed to be of globular configuration and have their uptake rate into tumor interstitium be driven by the same diffusion process and limited only by the availability of endothelial pores of passable size. It was observed that the endothelial pore distribution has a steep power law dependence on size, r−β, with an exponent of −4.1. The model of large pore dominance in tumor leakiness as reported in some earlier investigation with fluorescent probes and optical chamber methods is rejected for this tumor model and a number of other tumor types including chemically induced tumors. This steep power law dependence on size is also consistent with observations on human breast cancer.

  20. Refined Synthesis and Characterization of Controlled Diameter, Narrow Size Distribution Microparticles for Aerospace Research Applications

    Science.gov (United States)

    Tiemsin, Pacita I.; Wohl, Christopher J.

    2012-01-01

    Flow visualization using polystyrene microspheres (PSL)s has enabled researchers to learn a tremendous amount of information via particle based diagnostic techniques. To better accommodate wind tunnel researchers needs, PSL synthesis via dispersion polymerization has been carried out at NASA Langley Research Center since the late 1980s. When utilizing seed material for flow visualization, size and size distribution are of paramount importance. Therefore, the work described here focused on further refinement of PSL synthesis and characterization. Through controlled variation of synthetic conditions (chemical concentrations, solution stirring speed, temperature, etc.) a robust, controllable procedure was developed. The relationship between particle size and salt concentration, MgSO4, was identified enabling the determination of PSL diameters a priori. Suggestions of future topics related to PSL synthesis, stability, and size variation are also described.

  1. State-Of-The-Art in Microgrid-Integrated Distributed Energy Storage Sizing

    Directory of Open Access Journals (Sweden)

    Ibrahim Alsaidan

    2017-09-01

    Full Text Available Distributed energy storage (DES plays an important role in microgrid operation and control, as it can potentially improve local reliability and resilience, reduce operation cost, and mitigate challenges caused by high penetration renewable generation. However, to ensure an acceptable economic and technical performance, DES must be optimally sized and placed. This paper reviews the existing DES sizing methods for microgrid applications and presents a generic sizing method that enables microgrid planners to efficiently determine the optimal DES size, technology, and location. The proposed method takes into consideration the impact of DES operation on its lifetime to enhance the obtained results accuracy and practicality. The presented model can be used for both grid-tied (considering both grid-connected and islanded modes and isolated microgrids.

  2. SIZE DISTRIBUTION AND RATE OF PRODUCTION OF AIRBORNE PARTICULATE MATTER GENERATED DURING METAL CUTTING

    Energy Technology Data Exchange (ETDEWEB)

    M.A. Ebadian, Ph.D.; S.K. Dua, Ph.D., C.H.P.; Hillol Guha, Ph.D.

    2001-01-01

    During deactivation and decommissioning activities, thermal cutting tools, such as plasma torch, laser, and gasoline torch, are used to cut metals. These activities generate fumes, smoke and particulates. These airborne species of matter, called aerosols, may be inhaled if suitable respiratory protection is not used. Inhalation of the airborne metallic aerosols has been reported to cause ill health effects, such as acute respiratory syndrome and chromosome damage in lymphocytes. In the nuclear industry, metals may be contaminated with radioactive materials. Cutting these metals, as in size reduction of gloveboxes and tanks, produces high concentrations of airborne transuranic particles. Particles of the respirable size range (size < 10 {micro}m) deposit in various compartments of the respiratory tract, the fraction and the site in the respiratory tract depending on the size of the particles. The dose delivered to the respiratory tract depends on the size distribution of the airborne particulates (aerosols) and their concentration and radioactivity/toxicity. The concentration of airborne particulate matter in an environment is dependent upon the rate of their production and the ventilation rate. Thus, measuring aerosol size distribution and generation rate is important for (1) the assessment of inhalation exposures of workers, (2) the selection of respiratory protection equipment, and (3) the design of appropriate filtration systems. Size distribution of the aerosols generated during cutting of different metals by plasma torch was measured. Cutting rates of different metals, rate of generation of respirable mass, as well as the fraction of the released kerf that become respirable were determined. This report presents results of these studies. Measurements of the particles generated during cutting of metal plates with a plasma arc torch revealed the presence of particles with mass median aerodynamic diameters of particles close to 0.2 {micro}m, arising from

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

    Science.gov (United States)

    Ding, Wenfeng; Huang, Chihua

    2017-10-01

    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 this issue, a rainfall-simulation experiment was conducted with treatments that included two different initial soil surface roughnesses and two rainfall intensities. Soil surface roughness was determined by using photogrammetric method. For each simulated event, runoff and sediment samples were collected at different experimental times. The effective (undispersed) PSD of each sediment sample and the ultimate (after dispersion) PSD were used to investigate the detachment and transport mechanisms involved in sediment movement. The results show that soil surface roughness significantly delayed runoff initiation, but had no significant effect on the steady runoff rate. However, a significant difference in the soil loss rate was observed between the smooth and rough soil surfaces. Sediments from smooth soil surfaces were more depleted in clay-size particles, but more enriched in sand-size particles than those from rough soil surfaces, suggesting that erosion was less selective on smooth than on rough soil surfaces. The ratio of different sizes of transported sediment to the soil matrix indicates that most of the clay was eroded in the form of aggregates, silt-size particles were transported mainly as primary particles, and sand-size particles were predominantly aggregates of finer particles. Soil surface roughness has a crucial effect on the sediment size distribution and erosion processes. Significant differences of the enrichment ratios for the effective PSD and the ultimate PSD were observed under the two soil surface roughness treatments. These findings demonstrate that we should consider each particle size separately rather than use only the total sediment discharge in

  4. Lifestyle intervention improves lipoprotein particle size and distribution without weight loss in obese Latino adolescents.

    Science.gov (United States)

    Ryder, J R; Vega-López, S; Ortega, R; Konopken, Y; Shaibi, G Q

    2013-10-01

    Childhood obesity is associated with a pro-atherogenic phenotype contributing to increased cardiovascular disease (CVD) risk. This single-arm pilot study examined the effects of a lifestyle intervention on lipoprotein particle size and cholesterol distribution in obese Latino adolescents. Fifteen obese Latino adolescents (15.0 ± 1.0 years) completed a 12-week nutrition education and exercise intervention. Low-density lipoprotein (LDL) particle size and distribution of cholesterol in lipoprotein subclasses were determined via polyacrylamide gel electrophoresis. The intervention resulted in increases in mean LDL particle size (269.3 ± 3.4 to 271.6 ± 2.9 Å, P = 0.0003) and cholesterol in large high-density lipoprotein (HDL) subfractions (22.4 ± 11.2 to 26.8 ± 10.6% area, P = 0.007) along with decreases of cholesterol in small LDL (1.6 ± 2.0 to 0.6 ± 1.2% area, P  0.05) and suggest that lifestyle modification in obese youth may reduce cardiovascular risk by shifting lipoprotein particle size and cholesterol distribution to a less atherogenic phenotype. © 2013 The Authors. Pediatric Obesity © 2013 International Association for the Study of Obesity.

  5. The particle-size distribution in the dust ejected from IRC +10216

    Science.gov (United States)

    Jura, M.

    1994-01-01

    We propose that in the outer envelope (more than 15 sec from the star) around IRC +10216 the grains are amorphous carbon spheres of radius a with a size distribution of the form n(a) approximately equals d(exp -3.5) exp (-a/a(sub 0)) and a(sub 0) approximately equals 0.10 micrometers. Small grains (a much less than a(sub 0)) are required to explain the shielding of circumstellar molecules against destruction by interstellar ultraviolet radiation. Larger grains (a much greater than a(sub 0)) are required to explain the observed circumstellar polarization at the K band. In this model approximately 0.1% of the mass in the ejected dust is contained in particles that are larger than 1 micrometer in diameter. If the size distribution of the ejected SiC particles is similar to the size distribution that we derive for the amorphous carbon grains, then at least some of the micron-sized SiC inclusions in meteorites thought to originate from mass-losing carbon stars may have been produced in the outflows from stars such as IRC +10216.

  6. Effects of the confining solvent on the size distribution of silver NPs by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Oseguera-Galindo, D. O., E-mail: david.omar0927@hotmail.com; Martinez-Benitez, A.; Chavez-Chavez, A.; Gomez-Rosas, G.; Perez-Centeno, A.; Santana-Aranda, M. A., E-mail: miguelangelsantana@gmail.com [CUCEI, Universidad de Guadalajara, Departamento de Fisica (Mexico)

    2012-09-15

    Laser ablation of a silver target confined in acetone, ethanol, methanol, propanol, and distilled water allowed us to obtain silver nanoparticles with different size distributions. We employed a pulsed Nd:YAG laser ({lambda} = 532 nm, 0.5 J/pulse) with a high fluence of 64 J/cm{sup 2} with a scanning density of 2,500 pulses/cm{sup 2}, having overlapping of consecutive pulses. The analysis of transmission electron micrographs showed that the smaller particle sizes were obtained confining the target in propanol, while the larger ones were obtained employing ethanol. Nanoparticle size distributions were fitted with two Gaussian peaks in all five cases, being the smaller sizes the most frequent. Predominant peaks were centered at 4.8 and 13.9 nm in propanol and ethanol, respectively, having a broader distribution for the nanoparticles obtained in ethanol. Furthermore, comparison of electron micrographs taken the day of synthesis and 4 and 9 months later in the case of water and propanol, respectively, shows that nanoparticle suspension is more stable in propanol.

  7. [Elemental size distribution of airborne fine and ultrafine particulate matters in the suburb of Shanghai, China].

    Science.gov (United States)

    Lin, Jun; Liu, Wei; Li, Yan; Bao, Liang-Man; Li, Yu-Lan; Xu, Zhong-Yang; Wu, Wei-Wei; Chen, Dong-Liang; He, Wei

    2009-04-15

    The elemental size distributions of airborne fine/ultrafine particulate matters in the suburb of Shanghai were studied using synchrotron X-ray fluorescence. Median mass aerodynamic diameter (MMAD), elemental correlation coefficient as well as enrichment factor (EF) of each size fraction were calculated to characterize the sources of elements in fine/ultrafine particulate matters. Ca and Ti distributed mainly in coarse particles (> 2 microm) with size independent enrichment factors between 0.1 and 3.2, and the correlation coefficient between Ca and Ti was as high as 0.933, which implied strong contribution from nature sources, such as soil dusts and resuspended dusts. However, V, Cr, Mn, Ni, Zn, Cu, Pb, Cl, S mainly distributed in 0.1-1.0 microm particulate matters with MMAD between 0.56-0.94 microm. The EF of V, Cr, Ni, Cu, Zn, Pb increased with decreasing particle size. The highest EF were found for Pb in ultrafine particulate matters (MMAD of 1.3 microm. The results indicated non-negligible influences of remote transmission of anthropogenic pollutions.

  8. Linking canopy leaf area and light environments with tree size distributions to explain Amazon forest demography.

    Science.gov (United States)

    Stark, Scott C; Enquist, Brian J; Saleska, Scott R; Leitold, Veronika; Schietti, Juliana; Longo, Marcos; Alves, Luciana F; Camargo, Plinio B; Oliveira, Raimundo C

    2015-07-01

    Forest biophysical structure - the arrangement and frequency of leaves and stems - emerges from growth, mortality and space filling dynamics, and may also influence those dynamics by structuring light environments. To investigate this interaction, we developed models that could use LiDAR remote sensing to link leaf area profiles with tree size distributions, comparing models which did not (metabolic scaling theory) and did allow light to influence this link. We found that a light environment-to-structure link was necessary to accurately simulate tree size distributions and canopy structure in two contrasting Amazon forests. Partitioning leaf area profiles into size-class components, we found that demographic rates were related to variation in light absorption, with mortality increasing relative to growth in higher light, consistent with a light environment feedback to size distributions. Combining LiDAR with models linking forest structure and demography offers a high-throughput approach to advance theory and investigate climate-relevant tropical forest change. © 2015 John Wiley & Sons Ltd/CNRS.

  9. Exposure Hazard to Bisphenol A for Labor and Particle Size Distribution at Polycarbonate Molding Plants.

    Science.gov (United States)

    Chao, Yuchan; Chen, Jinluh; Yang, Weinduo; Ho, Tsunghan; Yen, Fusan

    2015-06-01

    This research provides an insight into exposure information and particle size distributions of Bisphenol A (BPA), a common environmental hormone, at polycarbonate (PC) molding plants in southern Taiwan. The inhalable dust sampler as IOM and the micro-orifice uniform deposition impactor (MOUDI) were used for samples collection to evaluate the level and particle size distribution of BPA in PC molding plants. All collected samples were analyzed by high performance liquid chromatography (HPLC) for BPA concentrations. BPA concentrations detected from the plant using optical grade PC material ranged from 32.28 to 44.97 μg/m(3), which were significantly higher than BPA concentrations (16.16 to 19.39 μg/m(3)) detected from the plant using food grade PC material. Under working environment, the particle size distribution showed a single mode distribution, with a MMAD of 0.84μm and a GSD of 1.97. Emission of BPA increased during heating process and most of BPA particles deposited in the nasal cavity (63.37%), following by alveolus (30.7%), and trachea-bronchus (5.93%). It is of importance that proper personal protection should be taken upon the BPA particulates released during the molding process at PC molding plants.

  10. Aerosol Optical Properties and Determination of Aerosol Size Distribution in Wuhan, China

    Directory of Open Access Journals (Sweden)

    Wei Gong

    2014-01-01

    Full Text Available Columnar aerosol volume size distributions from March 2012 to February 2013 in Wuhan, China, were investigated with a focus on monthly and seasonal variations in the aerosol optical depths (AODs and Ångström exponents. AOD is wavelength dependent, and for AOD at, for example, 500 nm, the seasonal averaged AOD value decreased in the order of winter (~0.84, spring (~0.83, summer (~0.76 and autumn (~0.55. The Ångström exponent suggested that the aerosol sizes in summer (~1.22, winter (~1.14, autumn (~1.06 and spring (~0.99 varied from fine to coarse particles. The Ångström exponent and AOD could provide a qualitative evaluation of ASD. Moreover, aerosol size distribution (ASD was larger in winter than the other three seasons, especially from 1.0 µm to 15 µm due to heavy anthropogenic aerosol and damp climate. The ASD spectral shape showed a bimodal distribution in autumn, winter, and spring, with one peak (<0.1 in the fine mode range and the other (>0.14 in the coarse mode range. However, there appeared to be a trimodal distribution during summer, with two peaks in the coarse mode, which might be due to the hygroscopic growth of the local particles and the generation of aerosol precursor resulting from the extreme-high temperature and relative humidity.

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

    Science.gov (United States)

    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.

  12. Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions

    Energy Technology Data Exchange (ETDEWEB)

    Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; Ciochetto, David; Niedermeier, Dennis; Ovchinnikov, Mikhail; Shaw, Raymond A.; Yang, Fan

    2016-11-28

    The influence of aerosol concentration on cloud droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud droplet growth and fallout. As aerosol concentration is increased the cloud droplet mean diameter decreases as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics (τc < τt) for high aerosol concentration, and slow microphysics (τc > τt) for low aerosol concentration; here, τc is the phase relaxation time and τt is the turbulence correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as τs-1c-1 + τt-1, and the measurements are in excellent agreement with this finding. This finding underscores the importance of droplet size dispersion for the aerosol indirect effect: increasing aerosol concentration not only suppresses precipitation formation through reduction of the mean droplet diameter, but perhaps more importantly, through narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol / slow microphysics limit are likely of leading importance for precipitation formation.

  13. Lung deposited surface area size distributions of particulate matter in different urban areas

    Science.gov (United States)

    Kuuluvainen, Heino; Rönkkö, Topi; Järvinen, Anssi; Saari, Sampo; Karjalainen, Panu; Lähde, Tero; Pirjola, Liisa; Niemi, Jarkko V.; Hillamo, Risto; Keskinen, Jorma

    2016-07-01

    Lung deposited surface area (LDSA) concentration is considered as a relevant metric for the negative health effects of aerosol particles. We report for the first time the size distributions of the LDSA measured in urban air. The measurements were carried out in the metropolitan area of Helsinki, including mobile laboratory and stationary measurements in different outdoor environments, such as traffic sites, a park area, the city center and residential areas. The main instrument in this study was an electrical low pressure impactor (ELPI), which was calibrated in the field to measure the LDSA concentration. The calibration factor was determined to be 60 μm2/(cm3 pA). In the experiments, the LDSA size distributions were found to form two modes at the traffic sites and in the city center. Both of these traffic related particle modes, the nucleation mode and the soot mode, had a clear contribution to the total LDSA concentration. The average total concentrations varied from 12 to 94 μm2/cm3, measured in the park area and at the traffic site next to a major road, respectively. The LDSA concentration was found to correlate with the mass of fine particles (PM2.5), but the relation of these two metrics varied between different environments, emphasizing the influence of traffic on the LDSA. The results of this study provide valuable information on the total concentrations and size distributions of the LDSA for epidemiological studies. The size distributions are especially important in estimating the contribution of outdoor concentrations on the concentrations inside buildings and vehicles through size-dependent penetration factors.

  14. Joint inversion of NMR and SIP data to estimate pore size distribution of geomaterials

    Science.gov (United States)

    Niu, Qifei; Zhang, Chi

    2018-03-01

    There are growing interests in using geophysical tools to characterize the microstructure of geomaterials because of the non-invasive nature and the applicability in field. In these applications, multiple types of geophysical data sets are usually processed separately, which may be inadequate to constrain the key feature of target variables. Therefore, simultaneous processing of multiple data sets could potentially improve the resolution. In this study, we propose a method to estimate pore size distribution by joint inversion of nuclear magnetic resonance (NMR) T2 relaxation and spectral induced polarization (SIP) spectra. The petrophysical relation between NMR T2 relaxation time and SIP relaxation time is incorporated in a nonlinear least squares problem formulation, which is solved using Gauss-Newton method. The joint inversion scheme is applied to a synthetic sample and a Berea sandstone sample. The jointly estimated pore size distributions are very close to the true model and results from other experimental method. Even when the knowledge of the petrophysical models of the sample is incomplete, the joint inversion can still capture the main features of the pore size distribution of the samples, including the general shape and relative peak positions of the distribution curves. It is also found from the numerical example that the surface relaxivity of the sample could be extracted with the joint inversion of NMR and SIP data if the diffusion coefficient of the ions in the electrical double layer is known. Comparing to individual inversions, the joint inversion could improve the resolution of the estimated pore size distribution because of the addition of extra data sets. The proposed approach might constitute a first step towards a comprehensive joint inversion that can extract the full pore geometry information of a geomaterial from NMR and SIP data.

  15. Effect of the Pore Size Distribution on the Displacement Efficiency of Multiphase Flow in Porous Media

    Directory of Open Access Journals (Sweden)

    Yang Yongfei

    2016-01-01

    Full Text Available Due to the complexity of porous media, it is difficult to use traditional experimental methods to study the quantitative impact of the pore size distribution on multiphase flow. In this paper, the impact of two pore distribution function types for three-phase flow was quantitatively investigated based on a three-dimensional pore-scale network model. The results show that in the process of wetting phase displacing the non-wetting phase without wetting films or spreading layers, the displacement efficiency was enhanced with the increase of the two function distribution’s parameters, which are the power law exponent in the power law distribution and the average pore radius or standard deviation in the truncated normal distribution, and vice versa. Additionally, the formation of wetting film is better for the process of displacement.

  16. Creating a Bimodal Drop-Size Distribution in the NASA Glenn Icing Research Tunnel

    Science.gov (United States)

    King-Steen, Laura E.; Ide, Robert F.

    2017-01-01

    The Icing Research Tunnel at NASA Glenn has demonstrated that they can create a drop-size distribution that matches the FAA Part 25 Appendix O FZDZ, MVD distributions that are measured when the two nozzle sets are sprayed simultaneously closely matched what was found by combining the two individual distributions analytically. Additionally, distributions were compared between spraying all spraybars and also by spraying only every-other spraybar, and were found to match within 4%. The cloud liquid water content uniformity for this condition has been found to be excellent. It should be noted, however, that the liquid water content for this condition in the IRT is much higher than the requirement specified in Part 25 Appendix O.

  17. Dependence of exponents on text length versus finite-size scaling for word-frequency distributions

    Science.gov (United States)

    Corral, Álvaro; Font-Clos, Francesc

    2017-08-01

    Some authors have recently argued that a finite-size scaling law for the text-length dependence of word-frequency distributions cannot be conceptually valid. Here we give solid quantitative evidence for the validity of this scaling law, using both careful statistical tests and analytical arguments based on the generalized central-limit theorem applied to the moments of the distribution (and obtaining a novel derivation of Heaps' law as a by-product). We also find that the picture of word-frequency distributions with power-law exponents that decrease with text length [X. Yan and P. Minnhagen, Physica A 444, 828 (2016), 10.1016/j.physa.2015.10.082] does not stand with rigorous statistical analysis. Instead, we show that the distributions are perfectly described by power-law tails with stable exponents, whose values are close to 2, in agreement with the classical Zipf's law. Some misconceptions about scaling are also clarified.

  18. Effect of Temperature on the Size Distribution, Shell Properties, and Stability of Definity®.

    Science.gov (United States)

    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.

  19. Grain Size Distribution in Mudstones: A Question of Nature vs. Nurture

    Science.gov (United States)

    Schieber, J.

    2011-12-01

    Grain size distribution in mudstones is affected by the composition of the source material, the processes of transport and deposition, and post-depositional diagenetic modification. With regard to source, it does make a difference whether for example a slate belt is eroded vs a stable craton. The former setting tends to provide a broad range of detrital quartz in the sub 62 micron size range in addition to clays and greenschist grade rock fragments, whereas the latter may be biased towards coarser quartz silt (30-60 microns), in addition to clays and mica flakes. In flume experiments, when fine grained materials are transported in turbulent flows at velocities that allow floccules to transfer to bedload, a systematic shift of grain size distribution towards an increasingly finer grained suspended load is observed as velocity is lowered. This implies that the bedload floccules are initially constructed of only the coarsest clay particles at high velocities, and that finer clay particles become incorporated into floccules as velocity is lowered. Implications for the rock record are that clay beds deposited from decelerating flows should show subtle internal grading of coarser clay particles; and that clay beds deposited from continuous fast flows should show a uniform distribution of coarse clays. Still water settled clays should show a well developed lower (coarser) and upper (finer) subdivision. A final complication arises when diagenetic processes, such as the dissolution of biogenic silica, give rise to diagenetic quartz grains in the silt to sand size range. This diagenetic silica precipitates in fossil cavities and pore spaces of uncompacted muds, and on casual inspection can be mistaken for detrital quartz. In distal mudstone successions close to 100 % of "apparent" quartz silt can be of that origin, and reworking by bottom currents can further enhance a detrital perception by producing rippled and laminated silt beds. Although understanding how size

  20. In situ exhaust cloud measurements. [particle size distribution and cloud physics of rocket exhaust clouds

    Science.gov (United States)

    Wornom, D.

    1980-01-01

    Airborne in situ exhaust cloud measurements were conducted to obtain definitions of cloud particle size range, Cl2 content, and HCl partitioning. Particle size distribution data and Cl2 measurements were made during the May, August, and September 1977 Titan launches. The measurements of three basic effluents - HCl, NO sub X, and particles - against minutes after launch are plotted. The maximum observed HCl concentration to the maximum Cl2 concentration are compared and the ratios of the Cl2 to the HCl is calculated.

  1. A simple algorithm for measuring particle size distributions on an uneven background from TEM images

    DEFF Research Database (Denmark)

    Gontard, Lionel Cervera; Ozkaya, Dogan; Dunin-Borkowski, Rafal E.

    2011-01-01

    Nanoparticles have a wide range of applications in science and technology. Their sizes are often measured using transmission electron microscopy (TEM) or X-ray diffraction. Here, we describe a simple computer algorithm for measuring particle size distributions from TEM images in the presence...... of an uneven background. The approach is based on adaptive thresholding, making use of local threshold values that change with spatial coordinate. The algorithm allows particles to be detected and characterized with greater accuracy than using more conventional methods, in which a global threshold is used. Its...

  2. Pore Size Distribution in Chicken Eggs as Determined by Mercury Porosimetry

    Directory of Open Access Journals (Sweden)

    La Scala Jr N

    2000-01-01

    Full Text Available In this study we investigated the application of mercury porosimetry technique into the determination of porosity features in 28 week old hen eggshells. Our results have shown that the majority of the pores have sizes between 1 to 10 mu m in the eggshells studied. By applying mercury porosimetry technique we were able to describe the porosity features better, by determining a pore size distribution in the eggshells. Here, we introduce mercury porosimetry technique as a new routine technique applied into the study of eggshells.

  3. The effect of particle size distributions on the microstructural evolution during sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Tikare, V.; Frandsen, Henrik Lund

    2013-01-01

    Microstructural evolution and sintering behavior of powder compacts composed of spherical particles with different particle size distributions (PSDs) were simulated using a kinetic Monte Carlo model of solid state sintering. Compacts of monosized particles, normal PSDs with fixed mean particle...... PSDs, but the final grain sizes were smaller. These behaviors are explained by the smallest grains in the broader PSDs being consumed very quickly by larger neighboring grains. The elimination of the small grains reduces both the total number of necks and the neck area between particles, which in turn...

  4. The size distribution of interstellar dust particles as determined from polarization: Infinite cylinders

    Science.gov (United States)

    Kim, Sang-Hee; Martin, P. G.

    1994-08-01

    To extract the size distribution of polarizing dust grains from the wavelength dependence of interstellar linear polarization as objectively as possible, we have used the maximum-entropy method (MEM), as in an earlier study of size distributions based on extinction (Kim, Martin, & Hendry). There are additional complications using polarization data since polarization depends on shape and alignment. In this first investigation, we adopted infinite cylinders with perfect spinning alignment. To constrain a wide range of sizes it is necessary to use data from the infrared to the far-ultraviolet. Much of our analysis is based on bare silicate grains. The modified Serkowski law represents interstellar polarization quite well for the wavelength range 0.3 to 2 micrometers using one parameter, lambdamax, the wavelength at which the polarization is maximum. Recent ultraviolet polarimetric observations of eight stars of differing lambdamax indicate that extrapolation of the modified Serkowski curve into the ultraviolet produces a reasonable approximation for larger lambdamax (greater than or approximately 0.55 micrometer), but for smaller lambdamax there is an excess of polarization observed. Therefore, we have investigated how the size distribution of the polarizing grains changes with lambdamax simply by fitting the modified Serkowski curve evaluated for lambdamax = 0.55, 0.615, and 0.68 micrometers. But for HD 25443 (lambdamax = 0.49 micrometer) which shows super-Serkowski behavi or, and for HD 197770 (lambdamax = 0.51 micrometers) which might exhibit a 2175 A polarization bump, we combined the modified Serkowski curve in the infrared and optical with the actual far-ultraviolet data. The size distributions found for silicates bear little resemblance to a power law. Instead, when expressed as contributions to the total mass, they peak roughly at 0.14 micrometer and are skewed, with the relative rate of decrease to larger and smaller sizes depending on lambdamax. For the

  5. Simulation of the evolution of particle size distributions in a vehicle exhaust plume with unconfined dilution by ambient air.

    Science.gov (United States)

    Jiang, Pengzhi; Lignell, David O; Kelly, Kerry E; Lighty, JoAnn S; Sarofim, Adel F; Montgomery, Christopher J

    2005-04-01

    Over the past several years, numerous studies have linked ambient concentrations of particulate matter (PM) to adverse health effects, and more recent studies have identified PM size and surface area as important factors in determining the health effects of PM. This study contributes to a better understanding of the evolution of particle size distributions in exhaust plumes with unconfined dilution by ambient air. It combines computational fluid dynamics (CFD) with an aerosol dynamics model to examine the effects of different streamlines in an exhaust plume, ambient particle size distributions, and vehicle and wind speed on the particle size distribution in an exhaust plume. CFD was used to calculate the flow field and gas mixing for unconfined dilution of a vehicle exhaust plume, and the calculated dilution ratios were then used as input to the aerosol dynamics simulation. The results of the study show that vehicle speed affected the particle size distribution of an exhaust plume because increasing vehicle speed caused more rapid dilution and inhibited coagulation. Ambient particle size distributions had an effect on the smaller sized particles (approximately 10 nm range under some conditions) and larger sized particles (>2 microm) of the particle size distribution. The ambient air particle size distribution affects the larger sizes of the exhaust plume because vehicle exhaust typically contains few particles larger than 2 microm. Finally, the location of a streamline in the exhaust plume had little effect on the particle size distribution; the particle size distribution along any streamline at a distance x differed by less than 5% from the particle size distributions along any other streamline at distance x.

  6. On the Steady-State System Size Distribution for a Discrete-Time Geo/G/1 Repairable Queue

    Directory of Open Access Journals (Sweden)

    Renbin Liu

    2014-01-01

    Full Text Available This paper studies a discrete-time N-policy Geo/G/1 queueing system with feedback and repairable server. With a probabilistic analysis method and renewal process theory, the steady-state system size distribution is derived. Further, the steady-state system size distribution derived in this work is extremely suitable for numerical calculations. Numerical example illustrates the important application of steady-state system size distribution in system capacity design for a network access proxy system.

  7. Yield stress of ultrafine-grained or nanocrystalline materials with a bimodal grain size distribution

    Science.gov (United States)

    Pande, C. S.; DeGiorgi, V. G.; E Moser, A.

    2018-02-01

    An attractive processing route for enhancing the yield strength of high-strength nanocrystalline metals and alloys while maintaining high ductility is to develop a bimodal grain size distribution (GSD), in which, supposedly, the finer grains provide strength, and the coarser grains maintain or even enhance ductility. We present a theoretical model predicting the strength of such a system, and show, analytically, how the yield stress is related to the various parameters of the bimodal GSD, such as volume fraction of the two components of the bimodal distribution and their standard deviations.

  8. Improved Multiobjective Harmony Search Algorithm with Application to Placement and Sizing of Distributed Generation

    Directory of Open Access Journals (Sweden)

    Wanxing Sheng

    2014-01-01

    Full Text Available To solve the comprehensive multiobjective optimization problem, this study proposes an improved metaheuristic searching algorithm with combination of harmony search and the fast nondominated sorting approach. This is a kind of the novel intelligent optimization algorithm for multiobjective harmony search (MOHS. The detailed description and the algorithm formulating are discussed. Taking the optimal placement and sizing issue of distributed generation (DG in distributed power system as one example, the solving procedure of the proposed method is given. Simulation result on modified IEEE 33-bus test system and comparison with NSGA-II algorithm has proved that the proposed MOHS can get promising results for engineering application.

  9. Massive-scale aircraft observations of giant sea-salt aerosol particle size distributions in atmospheric marine boundary layers

    Science.gov (United States)

    Jensen, J. B.

    2015-12-01

    iant sea-salt aerosol particles (dry radius, rd > 0.5 μm) occur nearly everywhere in the marine boundary layer and frequently above. This study presents observations of atmospheric sea-salt size distributions in the range 0.7 Chile and the 2011 ICE-T in the Caribbean. In each deployment, size distributions using hundreds of slides are used to relate fitted log-normal size distributions parameters to wind speed, altitude and other atmospheric conditions. The size distributions provide a unique observational set for initializing cloud models with coarse-mode aerosol particle observations for marine atmospheres.

  10. Grain size distributions and their effects on auto-acoustic compaction

    Science.gov (United States)

    Taylor, S.; Brodsky, E. E.

    2013-12-01

    dependent on the largest grain sizes present in the mixture. Establishing governing rules for how mixtures of grain sizes interact will aid our understanding of how the different fault gouge configurations and size distributions observed in natural systems affect shear behavior and earthquake stability on faults.

  11. A Study of Cirrus Ice Particle Size Distribution Using TC4 Observations

    Science.gov (United States)

    Tian, Lin; Heymsfield, Gerald M.; Li, Lihua; Heymsfield, Andrew J.; Bansemer, Aaron; Twohy, Cynthia H.; Srivastava, Ramesh C.

    2010-01-01

    An analysis of two days of in situ observations of ice particle size spectra, in convectively generated cirrus, obtained during NASA s Tropical Composition, Cloud, and Climate Coupling (TC4) mission is presented. The observed spectra are examined for their fit to the exponential, gamma, and lognormal function distributions. Characteristic particle size and concentration density scales are determined using two (for the exponential) or three (for the gamma and lognormal functions) moments of the spectra. It is shown that transformed exponential, gamma, and lognormal distributions should collapse onto standard curves. An examination of the transformed spectra, and of deviations of the transformed spectra from the standard curves, shows that the lognormal function provides a better fit to the observed spectra.

  12. Particle size distribution of suspended solids in the Chesapeake Bay entrance and adjacent shelf waters

    Science.gov (United States)

    Byrnes, M. R.; Oertel, G. F.

    1981-01-01

    Characteristics of suspended solids, including total suspended matter, total suspended inorganics, total suspended organics, particle size distribution, and the presence of the ten most prominent particle types were determined. Four research vessels simultaneously collected samples along four transects. Samples were collected within a 2-hour period that coincided with the maximum ebb penetration of Chesapeake Bay outwelling. The distribution of primary and secondary particle size modes indicate the presence of a surface or near-surface plume, possibly associated with three sources: (1) runoff, (2) resuspension of material within the Bay, and/or (3) resuspension of material in the area of shoals at the Bay mouth. Additional supportive evidence for this conclusion is illustrated with ocean color scanner data.

  13. Graphite nodule count and size distribution in thin-walled ductile cast iron

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Tiedje, Niels Skat

    2008-01-01

    Graphite nodule count and size distribution have been analysed in thin walled ductile cast iron. The 2D nodule counts have been converted into 3D nodule count by using Finite Difference Method (FDM). Particles having a diameter smaller than 5 µm should be neglected in the nodule count as these ar......Graphite nodule count and size distribution have been analysed in thin walled ductile cast iron. The 2D nodule counts have been converted into 3D nodule count by using Finite Difference Method (FDM). Particles having a diameter smaller than 5 µm should be neglected in the nodule count...... as these are inclusions and micro porosities that do not influence the solidification morphology. If there are many small graphite nodules as in thin walled castings only 3D nodule count calculated by FDM will give reliable results. 2D nodule count and 3D nodule count calculated by simple equations will give too low...

  14. Weakest-Link Scaling and Finite Size Effects on Recurrence Times Distribution

    CERN Document Server

    Hristopulos, Dionissios T; Kaniadakis, Giorgio

    2013-01-01

    Tectonic earthquakes result from the fracturing of the Earth's crust due to the loading induced by the motion of the tectonic plates. Hence, the statistical laws of earthquakes must be intimately connected to the statistical laws of fracture. The Weibull distribution is a commonly used model of earthquake recurrence times (ERT). Nevertheless, deviations from Weibull scaling have been observed in ERT data and in fracture experiments on quasi-brittle materials. We propose that the weakest-link-scaling theory for finite-size systems leads to the kappa-Weibull function, which implies a power-law tail for the ERT distribution. We show that the ERT hazard rate function decreases linearly after a waiting time which is proportional to the system size (in terms of representative volume elements) raised to the inverse of the Weibull modulus. We also demonstrate that the kappa-Weibull can be applied to strongly correlated systems by means of simulations of a fiber bundle model.

  15. Conservation of bubble size distribution during gas reactive absorption in bubble column reactors

    Directory of Open Access Journals (Sweden)

    P. L.C. LAGE

    1999-12-01

    Full Text Available Conservation of the bubble size distribution function was applied to the reactive absorption of carbon dioxide in a bubble column reactor. The model developed was solved by the method of characteristics and by a Monte Carlo method. Simulations were carried out using simplified models for the liquid phase and for the gas-liquid mass transfer. Predictions of gas holdup and outlet gas composition showed that the concept of a mean bubble diameter is not applicable when the bubble size distribution is reasonably polydispersed. In these cases, the mass mean velocity and the numerical mean velocity of the bubbles are very different. Therefore, quantification of the polydispersion of bubbles was shown to be essential to gas-phase hydrodynamics modeling.

  16. Investigation of the PAH size distribution in a compact HII region

    Science.gov (United States)

    Ohsawa, Ryou

    2013-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are excited by absorbing UV photons and emit the strong emission features in the infrared. The PAH emission features can be a good estimator of star formation rates (SFRs). On the other hand, PAHs are destroyed in harsh environments like HII regions. Two mechanisms are suggested for PAH destruction; sputtering and photo-dissociation. It is not observationally investigated which process is dominant in HII regions. We invent a method to identify the dominating destruction process in terms of the size distribution of PAHs. We propose the near-infrared imaging observations of a compact HII region M1-78 with the Gemini/NIRI. We investigate the variation in the PAH size distribution in M1-78 and discuss which destruction process is dominant in HII regions.

  17. A new apparatus for real-time assessment of the particle size distribution of disintegrating tablets.

    Science.gov (United States)

    Quodbach, Julian; Kleinebudde, Peter

    2014-11-01

    The aim of this study is the introduction of a novel apparatus that is capable of continuously measuring the particle size reduction of disintegrating tablets and analysis of the obtained results. The apparatus is constructed such that no particles pass directly through the pumping system. Thereby, the overall energy input into the particle suspension is reduced, and continuous measurement is possible without rapid destruction of the generated particles. The detected particle sizes at the beginning and at the end of the measurement differ greatly, depending on the applied disintegrant. The median particle sizes at the end of the measurement vary between 621.5 and 178.0 μm for different disintegrants. It is demonstrated that the particle size reduction follows an exponential function and that the fit parameters can be used to describe the disintegration behavior. A strong correlation between the median particle size of crospovidone disintegrants and generated particle size of the tablets is observed. This could be due to a more homogeneous distribution of the disintegrant particles in the tablets. Similar trends are observed for sodium starch glycolate and croscarmellose sodium. The new apparatus provides an innovative method to describe disintegrant effectiveness and efficiency. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  18. Effects of particle size distribution on some physical, chemical and functional properties of unripe banana flour.

    Science.gov (United States)

    Savlak, Nazlı; Türker, Burcu; Yeşilkanat, Nazlıcan

    2016-12-15

    The objective of this study was to examine the effect of particle size distribution on physical, chemical and functional properties of unripe banana flour for the first time. A pure triploid (AAA group) of Musa acuminata subgroup Cavendish (°Brix;0.2, pH;4.73, titratable acidity; 0.56g/100g malic acid, total solids; 27.42%) which was supplied from Gazipaşa, Antalya, Turkey from October 2014 to October 2015 was used. Size fractions of Particle size significantly effected color, water absorbtion index and wettability. L(∗) value decreased, a(∗) and b(∗) values decreased by increasing particle size (r(2)=-0.94, r(2)=0.72, r(2)=0.73 respectively). Particles under 212μm had the lowest rate of wettability (83.40s). A negative correlation between particle size and wettability (r(2)=-0.75) and positive correlation between particle size and water absorption index (r(2)=0.94) was observed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Effect of sulfate and carbonate minerals on particle-size distributions in arid soils

    Science.gov (United States)

    Goossens, Dirk; Buck, Brenda J.; Teng, Yuazxin; Robins, Colin; Goldstein, Harland L.

    2014-01-01

    Arid soils pose unique problems during measurement and interpretation of particle-size distributions (PSDs) because they often contain high concentrations of water-soluble salts. This study investigates the effects of sulfate and carbonate minerals on grain-size analysis by comparing analyses in water, in which the minerals dissolve, and isopropanol (IPA), in which they do not. The presence of gypsum, in particular, substantially affects particle-size analysis once the concentration of gypsum in the sample exceeds the mineral’s solubility threshold. For smaller concentrations particle-size results are unaffected. This is because at concentrations above the solubility threshold fine particles cement together or bind to coarser particles or aggregates already present in the sample, or soluble mineral coatings enlarge grains. Formation of discrete crystallites exacerbates the problem. When soluble minerals are dissolved the original, insoluble grains will become partly or entirely liberated. Thus, removing soluble minerals will result in an increase in measured fine particles. Distortion of particle-size analysis is larger for sulfate minerals than for carbonate minerals because of the much higher solubility in water of the former. When possible, arid soils should be analyzed using a liquid in which the mineral grains do not dissolve, such as IPA, because the results will more accurately reflect the PSD under most arid soil field conditions. This is especially important when interpreting soil and environmental processes affected by particle size.

  20. Element enrichment factor calculation using grain-size distribution and functional data regression.

    Science.gov (United States)

    Sierra, C; Ordóñez, C; Saavedra, A; Gallego, J R

    2015-01-01

    In environmental geochemistry studies it is common practice to normalize element concentrations in order to remove the effect of grain size. Linear regression with respect to a particular grain size or conservative element is a widely used method of normalization. In this paper, the utility of functional linear regression, in which the grain-size curve is the independent variable and the concentration of pollutant the dependent variable, is analyzed and applied to detrital sediment. After implementing functional linear regression and classical linear regression models to normalize and calculate enrichment factors, we concluded that the former regression technique has some advantages over the latter. First, functional linear regression directly considers the grain-size distribution of the samples as the explanatory variable. Second, as the regression coefficients are not constant values but functions depending on the grain size, it is easier to comprehend the relationship between grain size and pollutant concentration. Third, regularization can be introduced into the model in order to establish equilibrium between reliability of the data and smoothness of the solutions. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. What can size distributions within cohorts tell us about ecological processes in fish larvae?

    Directory of Open Access Journals (Sweden)

    Arild Folkvord

    2009-10-01

    Full Text Available Marine fish larvae are subject to variable environments, which is probably reflected in their growth and survival rates. Mortality rates are generally high and size-dependent. At the species level, these mortality rates are usually accompanied by correspondingly high growth rates. Here we provide examples from experimental studies with Atlantic cod (Gadus morhua and Atlantic herring (Clupea harengus larvae, in which multiple cohorts were followed over time. Body size, prey concentrations, and temperature are shown to influence growth rates. We present a method based on cumulative size distributions (CSDs for visualizing variability of sizes within cohorts over time. Analysis of CSDs revealed size-selective mortality and variations among populations in size- and temperature-dependent growth throughout ontogeny. We found that cod larvae consistently exhibit higher growth rates than herring larvae. While cod larvae may have an advantage over herring larvae when food availability is high, herring were more able to survive at low food concentrations than cod. Cod and herring seem to represent two growth strategies: cod larvae are relatively small at hatching and a high growth rate appears to be a prerequisite for success, whereas herring larvae are initially large, but grow more slowly.

  2. Sample size calculation for differential expression analysis of RNA-seq data under Poisson distribution.

    Science.gov (United States)

    Li, Chung-I; Su, Pei-Fang; Guo, Yan; Shyr, Yu

    2013-01-01

    Sample size determination is an important issue in the experimental design of biomedical research. Because of the complexity of RNA-seq experiments, however, the field currently lacks a sample size method widely applicable to differential expression studies utilising RNA-seq technology. In this report, we propose several methods for sample size calculation for single-gene differential expression analysis of RNA-seq data under Poisson distribution. These methods are then extended to multiple genes, with consideration for addressing the multiple testing problem by controlling false discovery rate. Moreover, most of the proposed methods allow for closed-form sample size formulas with specification of the desired minimum fold change and minimum average read count, and thus are not computationally intensive. Simulation studies to evaluate the performance of the proposed sample size formulas are presented; the results indicate that our methods work well, with achievement of desired power. Finally, our sample size calculation methods are applied to three real RNA-seq data sets.

  3. An Instrument Employing a Coronal Discharge for the Determination of Droplet-Size Distribution in Clouds

    Science.gov (United States)

    Brun, Rinaldo J.; Levine, Joseph; Kleinknecht, Kenneth S.

    1951-01-01

    A flight instrument that uses electric means for measuring the droplet-size distribution in above-freezing clouds has been devised and given preliminary evaluation in flight. An electric charge is placed on the droplets and they are separated aerodynamically according to their mass. Because the charge placed on the droplets is a. function of the droplet size, the size spectrum can 'be determined by measurement of the charge deposited on cylinders of several different sizes placed to intercept the charged droplets. An expression for the rate of charge acquisition by a water droplet in a field of coronal discharge is derived. The results obtained in flight with an instrument based on the method described indicate that continuous records of droplet-size spectrum variations in clouds can be obtained. The experimental instrument was used to evaluate the method and was not refined to the extent necessary for obtaining conclusive meteorological data. The desirable features of an instrument based on the method described are (i) The instrument can be used in clouds with temperatures above freezing; (2) the size and the shape of the cylinders do not change during the exposure time; (3) the readings are instantaneous and continuous; (4) the available sensitivity permits the study of variations in cloud structures of less than 200 feet in extent.

  4. Measurement of an electronic cigarette aerosol size distribution during a puff

    OpenAIRE

    Belka Miloslav; Lizal Frantisek; Jedelsky Jan; Jicha Miroslav; Pospisil Jiri

    2017-01-01

    Electronic cigarettes (e-cigarettes) have become very popular recently because they are marketed as a healthier alternative to tobacco smoking and as a useful tool to smoking cessation. E-cigarettes use a heating element to create an aerosol from a solution usually consisting of propylene glycol, glycerol, and nicotine. Despite the wide spread of e-cigarettes, information about aerosol size distributions is rather sparse. This can be caused by the relative newness of e-cigarettes and by the d...

  5. Metrological assessment of a portable analyzer for monitoring the particle size distribution of ultrafine particles.

    Science.gov (United States)

    Stabile, Luca; Cauda, Emanuele; Marini, Sara; Buonanno, Giorgio

    2014-08-01

    Adverse health effects caused by worker exposure to ultrafine particles have been detected in recent years. The scientific community focuses on the assessment of ultrafine aerosols in different microenvironments in order to determine the related worker exposure/dose levels. To this end, particle size distribution measurements have to be taken along with total particle number concentrations. The latter are obtainable through hand-held monitors. A portable particle size distribution analyzer (Nanoscan SMPS 3910, TSI Inc.) was recently commercialized, but so far no metrological assessment has been performed to characterize its performance with respect to well-established laboratory-based instruments such as the scanning mobility particle sizer (SMPS) spectrometer. The present paper compares the aerosol monitoring capability of the Nanoscan SMPS to the laboratory SMPS in order to evaluate whether the Nanoscan SMPS is suitable for field experiments designed to characterize particle exposure in different microenvironments. Tests were performed both in a Marple calm air chamber, where fresh diesel particulate matter and atomized dioctyl phthalate particles were monitored, and in microenvironments, where outdoor, urban, indoor aged, and indoor fresh aerosols were measured. Results show that the Nanoscan SMPS is able to properly measure the particle size distribution for each type of aerosol investigated, but it overestimates the total particle number concentration in the case of fresh aerosols. In particular, the test performed in the Marple chamber showed total concentrations up to twice those measured by the laboratory SMPS-likely because of the inability of the Nanoscan SMPS unipolar charger to properly charge aerosols made up of aggregated particles. Based on these findings, when field test exposure studies are conducted, the Nanoscan SMPS should be used in tandem with a condensation particle counter in order to verify and correct the particle size distribution data

  6. Optimizing the grain size distribution for talc-magnesite ore flotation

    OpenAIRE

    kvarla Jiøí; Zeleòák Fridrich

    2001-01-01

    Flotation is the only separation method with an universal utilization. Along with the separation of particulate valuable or hazardous components from primary and seconadry mineral raw materials, it is of usage in biotechnologies and water cleaning. The success of the flotation separation crucially depends on the particle size distribution or composition of the ore charge entering the process. The paper deals with the problem of flotation treatment of talc-magnesite ore. The main components of...

  7. Transformation and Self-Similarity Properties of Gamma and Weibull Fragment Size Distributions

    Science.gov (United States)

    2015-12-01

    Cambridge University Press, 2006 N. Bremond and E. Villermaux, Atomization by Jet Impact, Journal of Fluid Mechanics, 549, 273-306, 2006 N. Bremond...Entropy Formalism for Prediction of Drop-Size Distribution in Sprays: Application to Pressure Swirl Atomizers, Atomization and Sprays, 6(5), 601-622...2012 J. Eggers and E. Villermaux, Physics of Liquid Jets , Reports on Progress in Physics, 71(3), 036601, 2008 H. J. Empie, S. J. Lien, W. Yang

  8. High-Resolution UV Holography Lens for Particle Size Distribution Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Malone, Morris Kaufman; Capelle, Gene; Grover, Mike; Sorenson, Dan; Pazuchanics, Pete

    2010-01-01

    A high-resolution UV holography relay lens, shown in Figure 1, has been developed for measuring particle size distributions down to 0.5 μm in a 12-mm-diameter by 5-mm-thick volume. This work has been selected by an independent judging panel and editors of R&D Magazine as a recipient of a 2009 R&D 100 Award. This award recognizes the 100 most technologically significant products introduced during the past year.

  9. Feasibility Study of In-situ Characterization of Size Distribution of Air Voids in Concrete Pavements

    OpenAIRE

    Li, Kai Ming; Tong, Bao N; Liu, Sheng

    2013-01-01

    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 techniques suggested that the measurement of the p-wave velocity of ultrasound pulses transmitted through a fresh concrete specimen offers the most straightforward approach. This report describes an experimental study to address the design of an expe...

  10. [Impacts of Sediment Disturbance on the Distribution of Suspended Particle Size and Phosphorus].

    Science.gov (United States)

    Guo, Jun-rui; Li, Da-peng; Liu, Yan-jian

    2016-04-15

    To clarify the influence of the sediments disturbance on the particle size distribution of suspended solids, and the influence of particle distribution on the forms of dissolved phosphorous in the overlaying water, the sediments and overlying water from Meiliang Bay, Taihu Lake, were used to conduct the indoor simulation experiments to investigate the particle size of suspended solids according to the Ubbelobde particle size criteria and the distribution of phosphorus compounds in the overlying water under the disturbance circumstances. The results indicated that the average proportions of small (0-10 microm), middle (10-20 microm) and large (> or = 20 microm) diameter particles presented different trends of increasing, decreasing and staying stable, respectively. It indicated the possible transformation of particle size of suspended solids from small-middle diameter to large diameter. In addition, the data of DTP/TP and DIP/TP showed a periodical variation with the corresponding periodical variety of particle diameter in suspended solids, while ns obvious variety of DTP and DIP was observed. It suggested that disturbance enhanced the ability of phosphorus immobilization by suspended solids. On the other band, the percentages of DTP in TP and DIP in TP were 19% and 13% under the disturbance, respectively, and they were obviously lower than those (DTP/TP, 80% and DIP/TP, 69% ) in the control. It indicated that tbs transformation of particle size of suspended solids from small-middle diameter to large diameter due to disturbance was in favor of tbe adsorption and sedimentation of dissolved phosphorus. Accordingly, the formation of particle phosphorus was enhanced. Therefore, it delayed the development of eutrophication in the water body.

  11. Sulphate aerosol size distributions at Mumbai, India, during the INDOEX-FFP (1998)

    Energy Technology Data Exchange (ETDEWEB)

    Venkataraman, C.; Sinha, P.; Bammi, S. [Indian Inst. of Technology, Bombay (India). Centre for Environmental Science and Engineering

    2001-05-01

    Sulphate size distributions were measured at the coastal station of Mumbai (formerly Bombay) through 1998, during the Indian ocean experiment (INDOEX) first field phase (FFP), to fill current gaps in size-resolved aerosol chemical composition data. The paper examines meteorological, seasonal and source-contribution effects on sulphate aerosol and discusses potential effects of sulphate on regional climate. Sulphate size-distributions were largely trimodal with a condensation mode (mass median aerodynamic diameter or MMAD 0.6{mu}m), a droplet mode (MMAD 1.9-2.4{mu}m) and a coarse mode (MMAD 5{mu}m). Condensation mode sulphate mass-fractions were highest in winter, consistent with the high meteorological potential for gas-to-particle conversion along with low relative humidity (RH). The droplet mode concentrations and MMADs were larger in the pre-monsoon and winter than in monsoon, implying predominance in larger sized particles within this mode. In these seasons the high RH, and consequently aerosol water in the droplet mode, would favour aerosol-phase partitioning and reactions of SO{sub 2}. Coarse mode sulphate concentrations were lowest in the monsoon, when continental contribution to sulphate was low and washout was efficient. In winter and pre-monsoon, coarse mode sulphate concentrations were somewhat higher, likely from SO{sub 2} gas-to-particle conversion. Low daytime sulphate concentrations with a large coarse fraction, along with largely onshore winds, indicated marine aerosol predominance. High nighttime sulphate concentrations and a coincident large fine fraction indicated contributions from anthropogenic/industrial sources or from gas-to-particle conversion. Monthly mean sulphate concentrations increased with increasing SO{sub 2} concentrations, RH and easterly wind direction, indicating the importance of gas-to-particle conversion and industrial sources located to the east. Atmospheric chemistry effects on sulphate size distributions in Mumbai

  12. Sulphate aerosol size distributions at Mumbai, India, during the INDOEX-FFP (1998)

    Science.gov (United States)

    Venkataraman, Chandra; Sinha, Prashant; Bammi, Sachin

    Sulphate size distributions were measured at the coastal station of Mumbai (formerly Bombay) through 1998, during the Indian ocean experiment (INDOEX) first field phase (FFP), to fill current gaps in size-resolved aerosol chemical composition data. The paper examines meteorological, seasonal and source-contribution effects on sulphate aerosol and discusses potential effects of sulphate on regional climate. Sulphate size-distributions were largely trimodal with a condensation mode (mass median aerodynamic diameter or MMAD 0.6 μm), a droplet mode (MMAD 1.9-2.4 μm) and a coarse mode (MMAD 5 μm). Condensation mode sulphate mass-fractions were highest in winter, consistent with the high meteorological potential for gas-to-particle conversion along with low relative humidity (RH). The droplet mode concentrations and MMADs were larger in the pre-monsoon and winter than in monsoon, implying sulphate predominance in larger sized particles within this mode. In these seasons the high RH, and consequently greater aerosol water in the droplet mode, would favour aerosol-phase partitioning and reactions of SO 2. Coarse mode sulphate concentrations were lowest in the monsoon, when continental contribution to sulphate was low and washout was efficient. In winter and pre-monsoon, coarse mode sulphate concentrations were somewhat higher, likely from SO 2 gas-to-particle conversion. Low daytime sulphate concentrations with a large coarse fraction, along with largely onshore winds, indicated marine aerosol predominance. High nighttime sulphate concentrations and a coincident large fine fraction indicated contributions from anthropogenic/industrial sources or from gas-to-particle conversion. Monthly mean sulphate concentrations increased with increasing SO 2 concentrations, RH and easterly wind direction, indicating the importance of gas-to-particle conversion and industrial sources located to the east. Atmospheric chemistry effects on sulphate size distributions in Mumbai, indicated

  13. Dependence of pulsed focused ultrasound induced thrombolysis on duty cycle and cavitation bubble size distribution.

    Science.gov (United States)

    Xu, Shanshan; Zong, Yujin; Feng, Yi; Liu, Runna; Liu, Xiaodong; Hu, Yaxin; Han, Shimin; Wan, Mingxi

    2015-01-01

    In this study, we investigated the relationship between the efficiency of pulsed, focused ultrasound (FUS)-induced thrombolysis, the duty cycle (2.3%, 9%, and 18%) and the size distribution of cavitation bubbles. The efficiency of thrombolysis was evaluated through the degree of mechanical fragmentation, namely the number, mass, and size of clot debris particles. First, we found that the total number and mass of clot debris particles were highest when a duty cycle of 9% was used and that the mean diameter of clot debris particles was smallest. Second, we found that the size distribution of cavitation bubbles was mainly centered around the linear resonance radius (2.5μm) of the emission frequency (1.2MHz) of the FUS transducer when a 9% duty cycle was used, while the majority of cavitation bubbles became smaller or larger than the linear resonance radius when a 2.3% or 18% duty cycle was used. In addition, the inertial cavitation dose from the treatment performed at 9% duty cycle was much higher than the dose obtained with the other two duty cycles. The data presented here suggest that there is an optimal duty cycle at which the thrombolysis efficiency and cavitation activity are strongest. They further indicate that using a pulsed FUS may help control the size distribution of cavitation nuclei within an active size range, which we found to be near the linear resonance radius of the emission frequency of the FUS transducer. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Effect of particle size distribution and chlorophyll content on beam attenuation spectra

    Science.gov (United States)

    Kitchen, J. C.; Zaneveld, J. R. V.; Pak, H.

    1982-01-01

    The relationships between beam attenuation spectra, chlorophyll and pheophytin pigment concentrations, and particle size distributions are examined for a coastal region believed to have negligible concentrations of terrestrially derived dissolved organic compounds but large quantities of phytoplankton and resuspended sediments. It was found that the slope of the beam attenuation spectra increases when the hyperbolic slope of the size distribution increases. The magnitude of this increase in slope was consistent with calculations based on a range of particle diameters from 0.5 to 30 microns so that it would be possible to predict the slope of the particle size distribution if the slope of the beam attenuation spectra is known. The ratio of chlorophyll and pheophytin pigments to suspended volume concentrations affected the beam attenuation spectra to a lesser degree and in a more complex manner. Because of the strong effect of slope, it was concluded that the chlorophyll and pheophytin pigment content of suspended particles could not be efficiently predicted by means of beam attenuation measurements.

  15. Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation.

    Science.gov (United States)

    Shiraiwa, Manabu; Yee, Lindsay D; Schilling, Katherine A; Loza, Christine L; Craven, Jill S; Zuend, Andreas; Ziemann, Paul J; Seinfeld, John H

    2013-07-16

    Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process.

  16. Influence of grain size distribution on dynamic shear modulus of sands

    Directory of Open Access Journals (Sweden)

    Dyka Ireneusz

    2017-11-01

    Full Text Available The paper presents the results of laboratory tests, that verify the correlation between the grain-size characteristics of non-cohesive soils and the value of the dynamic shear modulus. The problem is a continuation of the research performed at the Institute of Soil Mechanics and Rock Mechanics in Karlsruhe, by T. Wichtmann and T. Triantafyllidis, who derived the extension of the applicability of the Hardin’s equation describing the explicite dependence between the grain size distribution of sands and the values of dynamic shear modulus. For this purpose, piezo-ceramic bender elements generating elastic waves were used to investigate the mechanical properties of the specimens with artificially generated particle distribution. The obtained results confirmed the hypothesis that grain size distribution of non-cohesive soils has a significant influence on the dynamic shear modulus, but at the same time they have shown that obtaining unambiguous results from bender element tests is a difficult task in practical applications.

  17. Anthropogenic Landscape Homogenization: Size-distribution of Wetlands in Mid-western Prairie Landscapes (Invited)

    Science.gov (United States)

    Basu, N. B.; Stunkel, K.; Van Meter, K. J.

    2013-12-01

    The Prairie Pothole Region, extending from the Des Moines Lobe in Iowa into Canada, is a landscape dotted with thousands of glacially formed depressional wetlands. Vast areas of these wetlands have been drained for agriculture. Consequent losses in ecological and hydrological services have been recognized in the recent past, and restoration efforts are underway. Effective restoration requires understanding the distribution and connectivity of the original wetland network, and the effects of human interventions in altering it. The objective of our study was to (1) understand the size-distribution and spatial organization of depressional features in the Des Moines Lobe, (2) explore the role of human impacts on the same, and (3) understand how losses have impacted aquatic ecosystem services. We found that the size-frequency relationship of the depressional features follows a power law distribution that varies based on the landform type and the size of the study area. We compared depressions based on 1m LIDAR DEM with current wetlands based on National Wetlands Inventory (NWI) data to evaluate the effects of human disturbance on the landscape. The LIDAR captures the depressional areas that correspond to wetlands before the landscape was extensively tile-drained, while NWI captures the features of the existing wetlands in the area. Results show that we have preferentially drained larger and smaller wetlands, effectively homogenizing the landscape. Modeling is used to explore the role of homogenization on aquatic ecosystem responses.

  18. Size and shape distribution of magnetic nanoparticles in disordered systems: computer simulations of superparamagnetic resonance spectra

    Science.gov (United States)

    Kliava, Janis; Berger, René

    1999-11-01

    A new model is proposed in order to account for the superparamagnetic resonance spectra arising from the ferromagnetic particles dispersed in a diamagnetic matrix (e.g., ferrofluids, partially devitrified glasses). The model explicitly takes into account non-sphericity of magnetic nanoparticles in a joint distribution density of sizes and demagnetising factors. The distribution in particle shapes is shown to take an important part in determining the superparamagnetic resonance spectra. By computer simulating the resonance spectra of annealed iron-containing borate and sol-gel silica glasses, characteristics of size and shape distributions of magnetic nanoparticles are evaluated. As the anneal temperature is increased from 456°C to 480°C, the most probable diameter of the magnetic particles formed in the borate glass is increased from 3.4 to 4.7 nm, while their shapes become better ordered. The mean size of particles formed in the sol-gel silica glass is small, ca. 3.0 nm, and their shapes are less ordered in comparison with the borate glass.

  19. Large Scale Behavior and Droplet Size Distributions in Crude Oil Jets and Plumes

    Science.gov (United States)

    Katz, Joseph; Murphy, David; Morra, David

    2013-11-01

    The 2010 Deepwater Horizon blowout introduced several million barrels of crude oil into the Gulf of Mexico. Injected initially as a turbulent jet containing crude oil and gas, the spill caused formation of a subsurface plume stretching for tens of miles. The behavior of such buoyant multiphase plumes depends on several factors, such as the oil droplet and bubble size distributions, current speed, and ambient stratification. While large droplets quickly rise to the surface, fine ones together with entrained seawater form intrusion layers. Many elements of the physics of droplet formation by an immiscible turbulent jet and their resulting size distribution have not been elucidated, but are known to be significantly influenced by the addition of dispersants, which vary the Weber Number by orders of magnitude. We present experimental high speed visualizations of turbulent jets of sweet petroleum crude oil (MC 252) premixed with Corexit 9500A dispersant at various dispersant to oil ratios. Observations were conducted in a 0.9 m × 0.9 m × 2.5 m towing tank, where large-scale behavior of the jet, both stationary and towed at various speeds to simulate cross-flow, have been recorded at high speed. Preliminary data on oil droplet size and spatial distributions were also measured using a videoscope and pulsed light sheet. Sponsored by Gulf of Mexico Research Initiative (GoMRI).

  20. Correlation of Red Blood Cell Aggregate Size with Transmitted Light Intensity Distributions

    Science.gov (United States)

    Hitt, Darren L.

    1998-11-01

    Under sufficiently low shear rates, such as those encountered in the microcirculation, human red blood cells are known to form aggregate structures (`rouleaux'). These aggregates may range in size from a simple chain containing only a few cells to complex three-dimensional structures containing tens of cells. Previous studies have attempted to characterize the aggregate size by examining the spatial distribution of transmitted light intensity resulting from transillumination of the blood flow. For experiments performed in vitro and in vivo, spectral analysis of the transmitted light intensities has shown that the presence of aggregates in the flow can linked with an increase in the spectral power at small wavenumbers. The magnitudes of the affected wavenumbers correspond to structures considerably larger than individual cells. A precise numerical correlation, however, is difficult to establish. In this work, computer simulations of aggregating blood flow are used along with statistical considerations in an attempt to better correlate the observed spectral trends with actual aggregate size.