Nonsphericity Index and Size Ratio Identify Morphologic Differences between Growing and Stable Aneurysms in a Longitudinal Study of 93 Cases.

Science.gov (United States)

Chien, A; Xu, M; Yokota, H; Scalzo, F; Morimoto, E; Salamon, N

2018-01-25

Recent studies have strongly associated intracranial aneurysm growth with increased risk of rupture. Identifying aneurysms that are likely to grow would be beneficial to plan more effective monitoring and intervention strategies. Our hypothesis is that for unruptured intracranial aneurysms of similar size, morphologic characteristics differ between aneurysms that continue to grow and those that do not. From aneurysms in our medical center with follow-up imaging dates in 2015, ninety-three intracranial aneurysms (23 growing, 70 stable) were selected. All CTA images for the aneurysm diagnosis and follow-up were collected, a total of 348 3D imaging studies. Aneurysm 3D geometry for each imaging study was reconstructed, and morphologic characteristics, including volume, surface area, nonsphericity index, aspect ratio, and size ratio were calculated. Morphologic characteristics were found to differ between growing and stable groups. For aneurysms of 7 mm, volume ( P differ between those that are growing and those that are stable. The nonsphericity index, in particular, was found to be higher among growing aneurysms. The size ratio was found to be the second most significant parameter associated with growth. © 2018 by American Journal of Neuroradiology.

Research on pyrolysis characteristics and kinetics of super fine and conventional pulverized coal

International Nuclear Information System (INIS)

Zhang Chaoqun; Jiang Xiumin; Wei Lihong; Wang Hui

2007-01-01

Based on isothermal thermogravimetric analysis (TGA) and kinetic equations, the optimization toolbox of MATLAB was applied to study the effects of particle size and heating rate on the pyrolysis characteristics and kinetics and to obtain the mechanism function and kinetic parameters of Yuanbaoshan coal at four different particle sizes and heating rates. The pyrolysis characteristics of the samples were analyzed using thermogravimetric (TG) curves and differential thermogravimetric (DTG) curves. The results show that the coal pyrolysis process is strongly affected by heating rate and particle size. As the heating rate increases, the temperature of volatile matter initiation increases, the total volatile matter evolved decreases and the DTG peak shifts toward higher temperature. As the particle size decreases, the temperature of volatile matter initiation of the coal sample decreases and the maximum rate of mass loss increases. In the pyrolysis of coal, the activation energies of the samples were found to increase with growing particle size and decreasing heating rate for both of the devolatilization temperature stages. In the lower temperature stage, the coal samples show a great difference in mechanism function at different particle sizes and heating rates

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.

Bone cell kinetics in the metaphysis of the growing long bone of the rat

International Nuclear Information System (INIS)

Kimmel, D.B.; Jee, W.S.

1976-01-01

The growing long bone metaphysis of rats was studied in a cell kinetic and morphometric analysis using tritiated thymidine as a tracer of cells. The results showed striking differences in the distribution and movements of osteoprogenitor and osteoblasts as compared to the osteoclasts. The results also showed a deficiency in cell production in the proliferating bone cells in the metaphysis. A new model of bone cell origin, proliferation, and movements in the metaphysis is proposed; osteoblasts and osteoprogenitor cells, the bone surface cells endemic to the metaphysis, are a continuum in adding bone forming cells and forming new bone on the calcified cartilage cores of the metaphysis. The osteoclasts, on the other hand, arise from mononuclear blood cells brought to the metaphysis through metaphyseal blood vessel spaces near the growth cartilage-metaphyseal junction

Photophysics of size-selected InP nanocrystals: Exciton recombination kinetics

International Nuclear Information System (INIS)

Kim, S.; Wolters, R.H.; Heath, J.R.

1996-01-01

We report here on the size-dependent kinetics of exciton recombination in a III endash V quantum dot system, InP. The measurements reported include various frequency dependent quantum yields as a function of temperature, frequency dependent luminescence decay curves, and time-gated emission spectra. This data is fit to a three-state quantum model which has been previously utilized to explain photophysical phenomena in II endash VI quantum dots. The initial photoexcitation is assumed to place an electron in a (delocalized) bulk conduction band state. Activation barriers for trapping and detrapping of the electron to surface states, as well as activation barriers for surface-state radiationless relaxation processes are measured as a function of particle size. The energy barrier to detrapping is found to be the major factor limiting room temperature band-edge luminescence. This barrier increases with decreasing particle size. For 30 A particles, this barrier is found to be greater than 6 kJ/mol emdash a barrier which is more than an order of magnitude larger than that previously found for 32 A CdS nanocrystals. copyright 1996 American Institute of Physics

Model for analyzing growth kinetics of a slowly growing Mycobacterium sp

International Nuclear Information System (INIS)

Lambrecht, R.S.; Carriere, J.F.; Collins, M.T.

1988-01-01

This report describes a simple method for quantifying viable mycobacteria and for determining generation time. We used statistical models and computer analysis of growth curves generated for the slowly growing mycobacterium Mycobacterium paratuberculosis under controlled conditions to derive a mathematical formula relating the dependent variable, growth, to the independent variables, log10 number of organisms in the inoculum (inoculum size) and incubation time. Growth was measured by a radiometric method which detects 14 CO 2 release during metabolism of a 14 C-labeled substrate. The radiometric method allowed for early detection of growth and detected as few as three viable bacteria. The coefficient of variation between culture vials inoculated with the same number of M. paratuberculosis was 0.083. Radiometric measurements were highly correlated to spectrophotometric and plate count methods for measuring growth (r = 0.962 and 0.992, respectively). The proportion of the total variability explained by the model in a goodness of fit test was 0.9994. Application of the model to broth cultures provided accurate estimates of the number of M. paratuberculosis (standard error = 0.21, log10 scale) and the growth rate (coefficient of variation, 0.03). Generation time was observed to be dependent upon the number of organisms in the inoculum. The model accurately described all phases of growth of M. paratuberculosis and can likely be applied to other slowly growing microorganisms

Effects of Prepolymerized Particle Size and Polymerization Kinetics on Volumetric Shrinkage of Dental Modeling Resins

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Tae-Yub Kwon

2014-01-01

Full Text Available Dental modeling resins have been developed for use in areas where highly precise resin structures are needed. The manufacturers claim that these polymethyl methacrylate/methyl methacrylate (PMMA/MMA resins show little or no shrinkage after polymerization. This study examined the polymerization shrinkage of five dental modeling resins as well as one temporary PMMA/MMA resin (control. The morphology and the particle size of the prepolymerized PMMA powders were investigated by scanning electron microscopy and laser diffraction particle size analysis, respectively. Linear polymerization shrinkage strains of the resins were monitored for 20 minutes using a custom-made linometer, and the final values (at 20 minutes were converted into volumetric shrinkages. The final volumetric shrinkage values for the modeling resins were statistically similar (P>0.05 or significantly larger (P<0.05 than that of the control resin and were related to the polymerization kinetics (P<0.05 rather than the PMMA bead size (P=0.335. Therefore, the optimal control of the polymerization kinetics seems to be more important for producing high-precision resin structures rather than the use of dental modeling resins.

Controlling drug delivery kinetics from mesoporous titania thin films by pore size and surface energy

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Karlsson J

2015-07-01

Full Text Available Johan Karlsson, Saba Atefyekta, Martin Andersson Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden Abstract: The osseointegration capacity of bone-anchoring implants can be improved by the use of drugs that are administrated by an inbuilt drug delivery system. However, to attain superior control of drug delivery and to have the ability to administer drugs of varying size, including proteins, further material development of drug carriers is needed. Mesoporous materials have shown great potential in drug delivery applications to provide and maintain a drug concentration within the therapeutic window for the desired period of time. Moreover, drug delivery from coatings consisting of mesoporous titania has shown to be promising to improve healing of bone-anchoring implants. Here we report on how the delivery of an osteoporosis drug, alendronate, can be controlled by altering pore size and surface energy of mesoporous titania thin films. The pore size was varied from 3.4 nm to 7.2 nm by the use of different structure-directing templates and addition of a swelling agent. The surface energy was also altered by grafting dimethylsilane to the pore walls. The drug uptake and release profiles were monitored in situ using quartz crystal microbalance with dissipation (QCM-D and it was shown that both pore size and surface energy had a profound effect on both the adsorption and release kinetics of alendronate. The QCM-D data provided evidence that the drug delivery from mesoporous titania films is controlled by a binding–diffusion mechanism. The yielded knowledge of release kinetics is crucial in order to improve the in vivo tissue response associated to therapeutic treatments. Keywords: mesoporous titania, controlled drug delivery, release kinetics, alendronate, QCM-D

Kinetic Assembly of Near-IR Active Gold Nanoclusters using Weakly Adsorbing Polymers to Control Size

Science.gov (United States)

Tam, Jasmine M.; Murthy, Avinash K.; Ingram, Davis R.; Nguyen, Robin; Sokolov, Konstantin V.; Johnston, Keith P.

2013-01-01

Clusters of metal nanoparticles with an overall size less than 100 nm and high metal loadings for strong optical functionality, are of interest in various fields including microelectronics, sensors, optoelectronics and biomedical imaging and therapeutics. Herein we assemble ~5 nm gold particles into clusters with controlled size, as small as 30 nm and up to 100 nm, which contain only small amounts of polymeric stabilizers. The assembly is kinetically controlled with weakly adsorbing polymers, PLA(2K)-b-PEG(10K)-b-PLA(2K) or PEG (MW = 3350), by manipulating electrostatic, van der Waals (VDW), steric, and depletion forces. The cluster size and optical properties are tuned as a function of particle volume fractions and polymer/gold ratios to modulate the interparticle interactions. The close spacing between the constituent gold nanoparticles and high gold loadings (80–85% w/w gold) produce a strong absorbance cross section of ~9×10−15 m2 in the NIR at 700 nm. This morphology results from VDW and depletion attractive interactions that exclude the weakly adsorbed polymeric stabilizer from the cluster interior. The generality of this kinetic assembly platform is demonstrated for gold nanoparticles with a range of surface charges from highly negative to neutral, with the two different polymers. PMID:20361735

Comparative analysis of mineral and secundary raw materials screening kinetics

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Stojanović Aleksandra

2015-01-01

Full Text Available Efficiency of screening shows screening performance compared to an ideal screening to achieve a complete separation of the fractions without the presence of grains of size less than the mesh openings left on sieve and grains of size larger than the mesh opening that passed through the sieve. Efficiency is growing rapidly and after a certain time is reduced. This is explained by the fact that the speed of screening depends on the percentage of 'small', 'small-to large' and 'large' grain. The paper shows how for the given grain, their shape and density affect the kinetics of screening.

Role of rumen butyrate in regulation of nitrogen utilization and urea nitrogen kinetics in growing sheep.

Science.gov (United States)

Agarwal, U; Hu, Q; Baldwin, R L; Bequette, B J

2015-05-01

Butyrate, a major rumen VFA, has been indirectly linked to enhancement of urea recycling on the basis of increased expression of urea transporter in the rumen epithelia of steers fed a rumen butyrate-enhancing diet. Two studies were conducted to quantify the effect of elevated rumen butyrate concentrations on N balance, urea kinetics and rumen epithelial proliferation. Wether sheep (n= 4), fitted with a rumen cannula, were fed a pelleted ration (∼165 g CP/kg DM, 10.3 MJ ME/kg DM) at 1.8 × ME requirement. In Exp. 1, sheep were infused intraruminally with either an electrolyte buffer solution (Con-Buf) or butyrate dissolved in the buffer solution (But-Buf) during 8-d periods in a balanced crossover design. In Exp. 2, sheep were infused intraruminally with either sodium acetate (Na-Ac) or sodium butyrate (Na-But) for 9 d. All solutions were adjusted to pH 6.8 and 8.0 in Exp. 1 and 2, respectively, and VFA were infused at 10% of ME intake. [15N2] urea was continuously infused intravenously for the last 5 d of each period, and total urine and feces were collected. In Exp. 1, 2H5-phenylalanine was continuously infused intravenously over the last 12 h, after which a biopsy from the rumen papillae was taken for measurement of fractional protein synthesis rate (FSR). Butyrate infusion treatments increased (P = 0.1 in Exp. 1; P urea entry (synthesis) rate was reduced ( urea kinetics were not altered by But-Buf compared with Con-Buf. These studies are the first to directly assess the role of butyrate in urea recycling and its effects on rumen papillae protein turnover in growing lambs. Under the feeding conditions used and the rate of continuous butyrate infusion into the rumen in the present studies, butyrate does not affect overall N retention in growing sheep. However, butyrate may play a role in the redistribution of urea N fluxes in the overall scheme of N metabolism.

Studying the effect of particle size and coating type on the blood kinetics of superparamagnetic iron oxide nanoparticles.

Science.gov (United States)

Roohi, Farnoosh; Lohrke, Jessica; Ide, Andreas; Schütz, Gunnar; Dassler, Katrin

2012-01-01

Magnetic resonance imaging (MRI), one of the most powerful imaging techniques available, usually requires the use of an on-demand designed contrast agent to fully exploit its potential. The blood kinetics of the contrast agent represent an important factor that needs to be considered depending on the objective of the medical examination. For particulate contrast agents, such as superparamagnetic iron oxide nanoparticles (SPIOs), the key parameters are particle size and characteristics of the coating material. In this study we analyzed the effect of these two properties independently and systematically on the magnetic behavior and blood half-life of SPIOs. Eleven different SPIOs were synthesized for this study. In the first set (a), seven carboxydextran (CDX)-coated SPIOs of different sizes (19-86 nm) were obtained by fractionating a broadly size-distributed CDX-SPIO. The second set (b) contained three SPIOs of identical size (50 nm) that were stabilized with different coating materials, polyacrylic acid (PAA), poly-ethylene glycol, and starch. Furthermore, small PAA-SPIOs (20 nm) were synthesized to gain a global insight into the effects of particle size vs coating characteristics. Saturation magnetization and proton relaxivity were determined to represent the magnetic and imaging properties. The blood half-life was analyzed in rats using MRI, time-domain nuclear magnetic resonance, and inductively coupled plasma optical emission spectrometry. By changing the particle size without modifying any other parameters, the relaxivity r(2) increased with increasing mean particle diameter. However, the blood half-life was shorter for larger particles. The effect of the coating material on magnetic properties was less pronounced, but it had a strong influence on blood kinetics depending on the ionic character of the coating material. In this report we systematically demonstrated that both particle size and coating material influence blood kinetics and magnetic properties of

Morphological evolution of dissolving feldspar particles with anisotropic surface kinetics and implications for dissolution rate normalization and grain size dependence: A kinetic modeling study

Science.gov (United States)

Zhang, Li; Lüttge, Andreas

2009-11-01

With previous two-dimensional (2D) simulations based on surface-specific feldspar dissolution succeeding in relating the macroscopic feldspar kinetics to the molecular-scale surface reactions of Si and Al atoms ( Zhang and Lüttge, 2008, 2009), we extended our modeling effort to three-dimensional (3D) feldspar particle dissolution simulations. Bearing on the same theoretical basis, the 3D feldspar particle dissolution simulations have verified the anisotropic surface kinetics observed in the 2D surface-specific simulations. The combined effect of saturation state, pH, and temperature on the surface kinetics anisotropy has been subsequently evaluated, found offering diverse options for morphological evolution of dissolving feldspar nanoparticles with varying grain sizes and starting shapes. Among the three primary faces on the simulated feldspar surface, the (1 0 0) face has the biggest dissolution rate across an extensively wide saturation state range and thus acquires a higher percentage of the surface area upon dissolution. The slowest dissolution occurs to either (0 0 1) or (0 1 0) faces depending on the bond energies of Si-(O)-Si ( ΦSi-O-Si/ kT) and Al-(O)-Si ( ΦAl-O-Si/ kT). When the ratio of ΦSi-O-Si/ kT to ΦAl-O-Si/ kT changes from 6:3 to 7:5, the dissolution rates of three primary faces change from the trend of (1 0 0) > (0 1 0) > (0 0 1) to the trend of (1 0 0) > (0 0 1) > (0 1 0). The rate difference between faces becomes more distinct and accordingly edge rounding becomes more significant. Feldspar nanoparticles also experience an increasing degree of edge rounding from far-from-equilibrium to close-to-equilibrium. Furthermore, we assessed the connection between the continuous morphological modification and the variation in the bulk dissolution rate during the dissolution of a single feldspar particle. Different normalization treatments equivalent to the commonly used mass, cube assumption, sphere assumption, geometric surface area, and reactive

Anomalous size effect in conductivity of Bi films of small thickness

International Nuclear Information System (INIS)

Anopchenko, A.S.; Kashirin, V.Yu.; Komnik, Yu.F.

1995-01-01

Experimental data are obtained at helium temperature, which describe the kinetic properties (conductivity, magnetoresistance and Hall coefficient) of Bi films whose thicknesses are within 100-500 A. The small-thickness Bi films display an anomalous size effect- the growing conductivity at decreasing thickness, and pronounced quantum interference effects - weak electron localization and enhancing electron-electron interaction in a disordered system. The information derived on the kinetic properties of the films is used to identify the character of the changes in the electron and hole concentrations and mobilities with a decreasing thickness. The isotropy of the properties in the films plane due to the axial texture has permitted us to use the equations for a conductor with two types of charge carriers. The used kinetic characteristics correctly take into account the contribution of the quantum corrections related to quantum interference. It is found that the concentration of the charge carries increases appreciably (by about two orders of magnitude) as the film thickness decreases to 100 A, which determines the anomalous size effect in the conductivity of the films

Studying the effect of particle size and coating type on the blood kinetics of superparamagnetic iron oxide nanoparticles

Directory of Open Access Journals (Sweden)

Roohi F

2012-08-01

Full Text Available Farnoosh Roohi, Jessica Lohrke, Andreas Ide, Gunnar Schütz, Katrin DasslerMR and CT Contrast Media Research, Bayer Pharma AG, Berlin, GermanyPurpose: Magnetic resonance imaging (MRI, one of the most powerful imaging techniques available, usually requires the use of an on-demand designed contrast agent to fully exploit its potential. The blood kinetics of the contrast agent represent an important factor that needs to be considered depending on the objective of the medical examination. For particulate contrast agents, such as superparamagnetic iron oxide nanoparticles (SPIOs, the key parameters are particle size and characteristics of the coating material. In this study we analyzed the effect of these two properties independently and systematically on the magnetic behavior and blood half-life of SPIOs.Methods: Eleven different SPIOs were synthesized for this study. In the first set (a, seven carboxydextran (CDX-coated SPIOs of different sizes (19–86 nm were obtained by fractionating a broadly size-distributed CDX–SPIO. The second set (b contained three SPIOs of identical size (50 nm that were stabilized with different coating materials, polyacrylic acid (PAA, polyethylene glycol, and starch. Furthermore, small PAA–SPIOs (20 nm were synthesized to gain a global insight into the effects of particle size vs coating characteristics. Saturation magnetization and proton relaxivity were determined to represent the magnetic and imaging properties. The blood half-life was analyzed in rats using MRI, time-domain nuclear magnetic resonance, and inductively coupled plasma optical emission spectrometry.Results: By changing the particle size without modifying any other parameters, the relaxivity r2 increased with increasing mean particle diameter. However, the blood half-life was shorter for larger particles. The effect of the coating material on magnetic properties was less pronounced, but it had a strong influence on blood kinetics depending on the

Growing vertical ZnO nanorod arrays within graphite: efficient isolation of large size and high quality single-layer graphene.

Science.gov (United States)

Ding, Ling; E, Yifeng; Fan, Louzhen; Yang, Shihe

2013-07-18

We report a unique strategy for efficiently exfoliating large size and high quality single-layer graphene directly from graphite into DMF dispersions by growing ZnO nanorod arrays between the graphene layers in graphite.

Low Temperature Synthesis of CdSe Quantum Dots with Amine Derivative and Their Chemical Kinetics

Science.gov (United States)

Seongmi Hwang,; Youngmin Choi,; Sunho Jeong,; Hakyun Jung,; Chang Gyoun Kim,; Teak-Mo Chung,; Beyong-Hwan Ryu,

2010-05-01

The chemical kinetics of growing CdSe nanocrystals was studied in order to investigate the effects of amine capping agents on the size of resulting quantum dots (QDs). CdSe QDs were prepared in phenyl ether, and the amine ligand dependence of QD size was determined. The results show that the size of CdSe nanocrystals can be regulated by controlling reaction rate, with smaller QDs being formed in slower processes. The results of photoluminescence (PL) studies show that the emission wavelengths of the QDs well correlate with particle size. This simple process for forming different-sized QDs, which uses a cheap solvent and various capping agents, has the potential for preparing CdSe nanocrystals more economically.

Growing Mouse Oocytes Transiently Activate Folate Transport via Folate Receptors As They Approach Full Size.

Science.gov (United States)

Meredith, Megan; MacNeil, Allison H; Trasler, Jacquetta M; Baltz, Jay M

2016-06-01

The folate cycle is central to cellular one-carbon metabolism, where folates are carriers of one-carbon units that are critical for synthesis of purines, thymidylate, and S-adenosylmethionine, the universal methyl donor that forms the cellular methyl pool. Although folates are well-known to be important for early embryo and fetal development, their role in oogenesis has not been clearly established. Here, folate transport proteins were detected in developing neonatal ovaries and growing oocytes by immunohistochemistry, Western blot, and immunofluorescence. The folate receptors FOLR1 and FOLR2 as well as reduced folate carrier 1 (RFC1, SLC19A1 protein) each appeared to be present in follicular cells including granulosa cells. In growing oocytes, however, only FOLR2 immunoreactivity appeared abundant. Localization of apparent FOLR2 immunofluorescence near the plasma membrane increased with oocyte growth and peaked in oocytes as they neared full size. We assessed folate transport using the model folate leucovorin (folinic acid). Unexpectedly, there was a transient burst of folate transport activity for a brief period during oocyte growth as they neared full size, while folate transport was otherwise undetectable for the rest of oogenesis and in fully grown germinal vesicle stage oocytes. This folate transport was inhibited by dynasore, an inhibitor of endocytosis, but insensitive to the anion transport inhibitor stilbene 4-acetamido-40-isothiocyanato-stilbene-2,20-disulfonic acid, consistent with folate receptor-mediated transport but not with RFC1-mediated transport. Thus, near the end of their growth, growing oocytes may take up folates that could support the final stage of oogenesis or be stored to provide the endogenous folates needed in early embryogenesis. © 2016 by the Society for the Study of Reproduction, Inc.

Kinetics of growing the disordered antiphase domains in titanium carbohydride TiC0.50H0.21

International Nuclear Information System (INIS)

Khidirov, I.; Sotvoldiev, D.I.

2010-01-01

For establishing formation and growth laws of the disordered nanostructures (the antiphase domains) in the nonstoichiometric titanium carbohydride with cubic NaCl type structure we quenched the titanium carbohydride TiC 0.50 H 0.21 from 1000 deg C followed by annealing at 500, 600, 700, 800 deg C with 24 hour ageing. Neutron diffraction patterns were recorded after each annealing temperature. The half-width of the superstructure (111) reflection is shown to decrease with increasing the annealing temperature that testified on the disordered nanostructure size growing with temperature. The sizes of the disordered nanostructure formed at various temperatures and their dependence D = f(T) were determined on the basis of the neutron diffraction data. (authors)

Size effects in tin-based lead-free solder joints: Kinetics of bond formation and mechanical characteristics

Science.gov (United States)

Abdelhadi, Ousama Mohamed Omer

Continuous miniaturization of microelectronic interconnects demands smaller joints with comparable microstructural and structural sizes. As the size of joints become smaller, the volume of intermetallics (IMCs) becomes comparable with the joint size. As a result, the kinetics of bond formation changes and the types and thicknesses of IMC phases that form within the constrained region of the bond varies. This dissertation focuses on investigating combination effects of process parameters and size on kinetics of bond formation, resulting microstructure and the mechanical properties of joints that are formed under structurally constrained conditions. An experiment is designed where several process parameters such as time of bonding, temperature, and pressure, and bond thickness as structural chracteristic, are varied at multiple levels. The experiment is then implemented on the process. Scanning electron microscope (SEM) is then utilized to determine the bond thickness, IMC phases and their thicknesses, and morphology of the bonds. Electron backscatter diffraction (EBSD) is used to determine the grain size in different regions, including the bulk solder, and different IMC phases. Physics-based analytical models have been developed for growth kinetics of IMC compounds and are verified using the experimental results. Nanoindentation is used to determine the mechanical behavior of IMC phases in joints in different scales. Four-point bending notched multilayer specimen and four-point bending technique were used to determine fracture toughness of the bonds containing IMCs. Analytical modeling of peeling and shear stresses and fracture toughness in tri-layer four-point bend specimen containing intermetallic layer was developed and was verified and validated using finite element simulation and experimental results. The experiment is used in conjunction with the model to calculate and verify the fracture toughness of Cu6Sn5 IMC materials. As expected two different IMC phases

Modeling uptake kinetics of cadmium by field-grown lettuce

Energy Technology Data Exchange (ETDEWEB)

Chen Weiping [Department of Environmental Sciences, University of California, 900 University Avenue, Riverside, CA 92521 (United States)], E-mail: chenweip@yahoo.com.cn; Li Lianqing [Institute of Resources, Ecosystem and Environment of Agriculture, Nanjing Agricultural University, Nanjing 210095 (China); Chang, Andrew C.; Wu Laosheng [Department of Environmental Sciences, University of California, 900 University Avenue, Riverside, CA 92521 (United States); Kwon, Soon-Ik [Agricultural Environmental and Ecology Division, National Institute of Agricultural Science and Technology, Suwon 441-707 (Korea, Republic of); Bottoms, Rick [Desert Research and Extension Center, 1004 East Holton Road, El Centro, CA 92243 (United States)

2008-03-15

Cadmium uptake by field grown Romaine lettuce treated with P-fertilizers of different Cd levels was investigated over an entire growing season. Results indicated that the rate of Cd uptake at a given time of the season can be satisfactorily described by the Michaelis-Menten kinetics, that is, plant uptake increases as the Cd concentration in soil solution increases, and it gradually approaches a saturation level. However, the rate constant of the Michaelis-Menten kinetics changes over the growing season. Under a given soil Cd level, the cadmium content in plant tissue decreases exponentially with time. To account for the dynamic nature of Cd uptake, a kinetic model integrating the time factor was developed to simulate Cd plant uptake over the growing season: C{sub Plant} = C{sub Solution} . PUF{sub max} . exp[-b . t], where C{sub Plant} and C{sub Solution} refer to the Cd content in plant tissue and soil solution, respectively, PUF{sub max} and b are kinetic constants. - A kinetic model was developed to evaluate the uptake of Cd under field conditions.

Modeling uptake kinetics of cadmium by field-grown lettuce

International Nuclear Information System (INIS)

Chen Weiping; Li Lianqing; Chang, Andrew C.; Wu Laosheng; Kwon, Soon-Ik; Bottoms, Rick

2008-01-01

Cadmium uptake by field grown Romaine lettuce treated with P-fertilizers of different Cd levels was investigated over an entire growing season. Results indicated that the rate of Cd uptake at a given time of the season can be satisfactorily described by the Michaelis-Menten kinetics, that is, plant uptake increases as the Cd concentration in soil solution increases, and it gradually approaches a saturation level. However, the rate constant of the Michaelis-Menten kinetics changes over the growing season. Under a given soil Cd level, the cadmium content in plant tissue decreases exponentially with time. To account for the dynamic nature of Cd uptake, a kinetic model integrating the time factor was developed to simulate Cd plant uptake over the growing season: C Plant = C Solution . PUF max . exp[-b . t], where C Plant and C Solution refer to the Cd content in plant tissue and soil solution, respectively, PUF max and b are kinetic constants. - A kinetic model was developed to evaluate the uptake of Cd under field conditions

Cell proliferation kinetics and radiation response in 9L tumor spheroids

Energy Technology Data Exchange (ETDEWEB)

Sweigert, S.E.

1984-05-01

Cell kinetic parameters, including population doubling-time, cell cycle time, and growth fraction, were measured in 9L gliosarcoma spheroids. These parameters were studied as the spheroids grew from 50 ..mu..m to over 900 ..mu..m in diameter. Experiments relating the cell kinetic parameters to the radiation response of 9L spheroids were also carried out. The major findings were that the average cell cycle time (T/sub c/), is considerably longer in large spheroids than in exponentially-growing monolayers, the radiosensitivity of noncycling (but still viable) cells in spheroids is not significantly different from that of cycling spheroid cells, and the radiation-induced division delay is approximately twice as long in spheroid cells as in monolayer cells given equal radiation doses. The cell loss factor for spheroids of various sizes was calculated, by using the measured kinetic parameters in the basic equations for growth of a cell population. 157 references, 6 figures, 3 tables.

Cell proliferation kinetics and radiation response in 9L tumor spheroids

International Nuclear Information System (INIS)

Sweigert, S.E.

1984-05-01

Cell kinetic parameters, including population doubling-time, cell cycle time, and growth fraction, were measured in 9L gliosarcoma spheroids. These parameters were studied as the spheroids grew from 50 μm to over 900 μm in diameter. Experiments relating the cell kinetic parameters to the radiation response of 9L spheroids were also carried out. The major findings were that the average cell cycle time (T/sub c/), is considerably longer in large spheroids than in exponentially-growing monolayers, the radiosensitivity of noncycling (but still viable) cells in spheroids is not significantly different from that of cycling spheroid cells, and the radiation-induced division delay is approximately twice as long in spheroid cells as in monolayer cells given equal radiation doses. The cell loss factor for spheroids of various sizes was calculated, by using the measured kinetic parameters in the basic equations for growth of a cell population. 157 references, 6 figures, 3 tables

Effects of growth rate, cell size, motion, and elemental stoichiometry on nutrient transport kinetics.

Science.gov (United States)

Flynn, Kevin J; Skibinski, David O F; Lindemann, Christian

2018-04-01

Nutrient acquisition is a critical determinant for the competitive advantage for auto- and osmohetero- trophs alike. Nutrient limited growth is commonly described on a whole cell basis through reference to a maximum growth rate (Gmax) and a half-saturation constant (KG). This empirical application of a Michaelis-Menten like description ignores the multiple underlying feedbacks between physiology contributing to growth, cell size, elemental stoichiometry and cell motion. Here we explore these relationships with reference to the kinetics of the nutrient transporter protein, the transporter rate density at the cell surface (TRD; potential transport rate per unit plasma-membrane area), and diffusion gradients. While the half saturation value for the limiting nutrient increases rapidly with cell size, significant mitigation is afforded by cell motion (swimming or sedimentation), and by decreasing the cellular carbon density. There is thus potential for high vacuolation and high sedimentation rates in diatoms to significantly decrease KG and increase species competitive advantage. Our results also suggest that Gmax for larger non-diatom protists may be constrained by rates of nutrient transport. For a given carbon density, cell size and TRD, the value of Gmax/KG remains constant. This implies that species or strains with a lower Gmax might coincidentally have a competitive advantage under nutrient limited conditions as they also express lower values of KG. The ability of cells to modulate the TRD according to their nutritional status, and hence change the instantaneous maximum transport rate, has a very marked effect upon transport and growth kinetics. Analyses and dynamic models that do not consider such modulation will inevitably fail to properly reflect competitive advantage in nutrient acquisition. This has important implications for the accurate representation and predictive capabilities of model applications, in particular in a changing environment.

Unravelling the dependence of hydrogen oxidation kinetics on the size of Pt nanoparticles by in operando nanoplasmonic temperature sensing

DEFF Research Database (Denmark)

Wettergren, Kristina; Hellman, Anders; Cavalca, Filippo Carlo

2015-01-01

We use a noninvasive nanoscale optical-temperature measurement method based on localized surface plasmon resonance to investigate the particle size-dependence of the hydrogen oxidation reaction kinetics on model supported Pt nanocatalysts at atmospheric pressure in operando. With decreasing average...

In-stream nutrient uptake kinetics along stream size and development gradients in a rapidly developing mountain resort watershed

Science.gov (United States)

Covino, T.; McGlynn, B.; McNamarra, R.; Gardner, K.

2012-04-01

Land use / land cover (LULC) change including mountain resort development often lead to increased nutrient loading to streams, however the potential influence on stream ecosystem nutrient uptake kinetics and transport remain poorly understood. Given the deleterious impacts elevated nutrient loading can have on aquatic ecosystems, it is imperative to improve understanding of nutrient retention capacities across stream scales and watershed development intensities. We performed seventeen nutrient addition experiments on six streams across the West Fork Gallatin Watershed, Montana, USA, to quantify nitrogen (N) uptake kinetics and retention dynamics across stream sizes (1st to 4th order) and along a mountain resort development gradient. We observed that stream N uptake kinetics and spiraling parameters varied across streams of different development intensity and scale. In more developed watersheds we observed a fertilization affect, however, none of the streams exhibited saturation with respect to N. Additionally, we observed that elevated loading led to increased biomass and retentive capacities in developed streams that helped maintain export at low levels during baseflow. Our results indicate that LULC can enhance in-stream uptake of limiting nutrients and highlight the value of characterizing uptake kinetic curves from ambient to saturation.

The ontogeny of sexual size dimorphism of a moth: when do males and females grow apart?

Directory of Open Access Journals (Sweden)

R Craig Stillwell

Full Text Available Sexual dimorphism in body size (sexual size dimorphism is common in many species. The sources of selection that generate the independent evolution of adult male and female size have been investigated extensively by evolutionary biologists, but how and when females and males grow apart during ontogeny is poorly understood. Here we use the hawkmoth, Manduca sexta, to examine when sexual size dimorphism arises by measuring body mass every day during development. We further investigated whether environmental variables influence the ontogeny of sexual size dimorphism by raising moths on three different diet qualities (poor, medium and high. We found that size dimorphism arose during early larval development on the highest quality food treatment but it arose late in larval development when raised on the medium quality food. This female-biased dimorphism (females larger increased substantially from the pupal-to-adult stage in both treatments, a pattern that appears to be common in Lepidopterans. Although dimorphism appeared in a few stages when individuals were raised on the poorest quality diet, it did not persist such that male and female adults were the same size. This demonstrates that the environmental conditions that insects are raised in can affect the growth trajectories of males and females differently and thus when dimorphism arises or disappears during development. We conclude that the development of sexual size dimorphism in M. sexta occurs during larval development and continues to accumulate during the pupal/adult stages, and that environmental variables such as diet quality can influence patterns of dimorphism in adults.

Ozone disintegration kinetics in the reactor for tyres decomposition

International Nuclear Information System (INIS)

Golota, V.I.; Manujlenko, O.V.; Taran, G.V.; Pis'menetskij, A.S.; Zamuriev, A.A.

2010-01-01

The results of theoretical and experimental research of ozone disintegration kinetics in the chemical reactor which is developed for decomposition of tyres in the ozone-air environment are presented. Analytical expression for dependence of ozone concentration in the reactor from time and from parameters of the task, such as volume speed of ozone-air mixture feed on a reactor input, concentration of ozone on the input to the reactor, volume speed of output of the used mixture, reactor size, and square of its internal surface is obtained. It is shown that at the same speed of ozone-air mixture pro rolling through the reactor, with growth of ozone concentration on the input, value of stationary concentration in the reactor grows, remaining always less than concentration on the input. It is also shown that at the same ozone concentration on the input, with growth of speed of ozone-air mixture pro rolling through the reactor, value of stationary ozone concentration in the reactor also grows, remaining always less than ozone concentration on the input. The ozone disintegration kinetics in the reactor in a wide range of speed of ozone-air mixture pro rolling through the reactor (0.15, 0.30, 0.45, 0.60 m3/hour) and various ozone concentration on the input (5, 10, 15, 20 g/m3) is experimentally studied. It is shown that experimental results with good accuracy coincide with the theoretical. Direct experiment showed the essential influence of the internal surface of the reactor on the ozone disintegration kinetics.

Organization of growing random networks

International Nuclear Information System (INIS)

Krapivsky, P. L.; Redner, S.

2001-01-01

The organizational development of growing random networks is investigated. These growing networks are built by adding nodes successively, and linking each to an earlier node of degree k with an attachment probability A k . When A k grows more slowly than linearly with k, the number of nodes with k links, N k (t), decays faster than a power law in k, while for A k growing faster than linearly in k, a single node emerges which connects to nearly all other nodes. When A k is asymptotically linear, N k (t)∼tk -ν , with ν dependent on details of the attachment probability, but in the range 2 -2 power-law tail, where s is the component size. The out component has a typical size of order lnt, and it provides basic insights into the genealogy of the network

Fine kinetics of natural physical ageing in glassy As10Se90

International Nuclear Information System (INIS)

Balitska, V.; Golovchak, R.; Kozdras, A.; Shpotyuk, O.

2014-01-01

Sigmoid behavior of natural physical ageing in glassy As 10 Se 90 reveals multi-step-wise growing kinetics of enthalpy losses. Phenomenological description of this kinetics can be adequately developed in terms of first-order relaxation processes, tending atomic structure from initial towards more thermodynamically equilibrium state. This kinetics is shown to obey characteristic stretched exponential behavior originated from a number of growing steps, attributed to the interconnected processes of chalcogen chain alignment and cooperative shrinkage of glass network

Disordering kinetics in surface overlayers

International Nuclear Information System (INIS)

Jesina, A.; Tringides, M.C.

1993-01-01

The disordering kinetics of the O/W(110)-p(2x1)+p(2x2) overlayer, prepared initially in a well-ordered state, are studied with low-energy electron diffraction profile analysis. The decay of the peak intensity, used as a measure of the growing disorder, cannot be fitted to a power law as in the case of ordering processes. The full width at half maximum of the time-dependent structure factor S(q,t) is constant with time, which suggests that the average size remains constant. Diffusion activation energy extracted for the temperature dependence of the disordering is 1.0±0.05 eV, which is different from the value of 0.6 eV measured in ordering processes. The difference can be explained by the adsorbate-adsorbate interactions, which contribute differently to the diffusion barrier, in the two experiments

Effect of Pore Size and Pore Connectivity on Unidirectional Capillary Penetration Kinetics in 3-D Porous Media using Direct Numerical Simulation

Science.gov (United States)

Fu, An; Palakurthi, Nikhil; Konangi, Santosh; Comer, Ken; Jog, Milind

2017-11-01

The physics of capillary flow is used widely in multiple fields. Lucas-Washburn equation is developed by using a single pore-sized capillary tube with continuous pore connection. Although this equation has been extended to describe the penetration kinetics into porous medium, multiple studies have indicated L-W does not accurately predict flow patterns in real porous media. In this study, the penetration kinetics including the effect of pore size and pore connectivity will be closely examined since they are expected to be the key factors effecting the penetration process. The Liquid wicking process is studied from a converging and diverging capillary tube to the complex virtual 3-D porous structures with Direct Numerical Simulation (DNS) using the Volume-Of-Fluid (VOF) method within the OpenFOAM CFD Solver. Additionally Porous Medium properties such as Permeability (k) , Tortuosity (τ) will be also analyzed.

Stoichiometry and kinetics of poly-{beta}-hydroxybutyrate metabolism in aerobic, slow growing, activated sludge cultures

Energy Technology Data Exchange (ETDEWEB)

Beun, J.J.; Paletta, F.; Loosdrecht, M.C.M. Van; Heijnen, J.J.

2000-02-20

This paper discusses the poly-{beta}-hydroxybutyrate (PHB) metabolism in aerobic, slow growing, activated sludge cultures, based on experimental data and on a metabolic model. The dynamic conditions which occur in activated sludge processes were simulated in a 2-L sequencing batch reactor (SBR) by subjecting a mixed microbial population to successive periods of external substrate availability (feast period) and no external substrate availability (famine period). Under these conditions intracellular storage and consumption of PHB was observed. It appeared that in the feast period, 66% to almost 100% of the substrate consumed is used for storage of PHB, the remainder is used for growth and maintenance processes. Furthermore, it appeared that at high sludge retention time (SRT) the growth rate in the feast and famine periods was the same. With decreasing SRT the growth rate in the feast period increased relative to the growth rate in the famine period. Acetate consumption and PHB production in the feast period both proceeded with a zero-order rate in acetate and PHB concentration respectively. PHB consumption in the famine period could best be described kinetically with a nth order degradation equation in PHB concentration. The obtained results are discussed in the context of the general activated sludge models.

Prediction and validation of burnout curves for Goettelborn char using reaction kinetics determined in shock tube experiments

Energy Technology Data Exchange (ETDEWEB)

Moors, J.H.J.; Banin, V.E.; Haas, J.H.P.; Weber, R.; Veefkind, A. [Eindhoven University of Technology, Eindhoven (Netherlands). Dept. of Applied Physics

1999-01-01

Using a shock tube facility the combustion characteristics of pulverised char ({lt} 10 {mu}m) were measured. A prediction was made for the burnout behaviour of a commercial sized char particle (75-90 {mu}m) in different ambient conditions using a `pseudo kinetic` approach. In this approach the kinetic rate of a surface containing micro pores is determined and these `pseudo kinetics` are then applied to the larger particle not taking into account the micro pores. Comparison of the predictions with measurements done with an isothermal plug flow reactor showed this approach to be valid within experimental error for low burnout. A linear decrease of the kinetic reaction rate with burnout is shown to predict the burnout behaviour in the complete range of burnout. A possible explanation for this linear decrease could be a growing fraction of non-combustible material in the char particles during burnout. 11 refs., 6 figs., 2 tabs.

Passage kinetics of dry matter and neutral detergent fibre through the gastro-intestinal tract of growing beef heifers fed a high-concentrate diet measured with internal ð13C and external markers

NARCIS (Netherlands)

Daniel, J.B.; Laar, van H.; Warner, D.; Dijkstra, J.; Navarro-Villa, A.; Pellikaan, W.F.

2014-01-01

Fractional rumen passage rates (K1) are fundamental in feed evaluation systems for ruminants to predict the extent of nutrient degradation. Data on passage kinetics of growing beef cattle fed high-concentrate diets are scarce and mainly rely on external passage markers which do not provide

Extraction Kinetics and Molecular Size Fractionation of Humic Substances From Two Brazilian Soils

Directory of Open Access Journals (Sweden)

Dick Deborah Pinheiro

1999-01-01

Full Text Available In the present study, the extraction behaviour of humic substances (HS from an Oxisol and a Mollisol from South Brazil, by using 0.1 and 0.5 mol L-1 NaOH and 0.15 mol L-1 neutral pyrophosphate solutions, respectively, was systematically studied. The kinetics and efficiency of HS extraction were evaluated by means of UV/Vis spectroscopy. The isolated humic acids (HA and fulvic acids (FA were size-classified by multistage ultrafiltration (six fractions in the molecular weight range of 1 to 100 kDa. The obtained data show that the HS extraction yield depended not only on the extractant, but also on the soil type. Within 3 h approximately 90% of the soluble HS could be extracted following complex extraction kinetics by both methods and none or little structural modification was verified as observed from their stable extinction ratio E350/E550. In the Mollisol the pyrophosphate extraction was more effective, suggesting that a great part of HS occurred as macromolecules bonded to clay minerals and aggregated between themselves through cationic bridges. In the Oxisol a higher HS yield was verified with the alkaline method, presumably due to HS fixation onto the oxide surface by H-bonds and/or surface complexation reactions. In general, HS extracted by the pyrophosphate procedure showed higher molecular weights than those extracted by NaOH.

Nucleation of diindenoperylene and pentacene at thermal and hyperthermal incident kinetic energies

Energy Technology Data Exchange (ETDEWEB)

Kish, Edward R.; Desai, Tushar V.; Greer, Douglas R.; Engstrom, James R., E-mail: jre7@cornell.edu [School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853 (United States); Woll, Arthur R. [Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York 14853 (United States)

2015-05-15

The authors have examined the nucleation of diindenoperylene (DIP) on SiO{sub 2} employing primarily atomic force microscopy and focusing on the effect of incident kinetic energy employing both thermal and supersonic sources. For all incident kinetic energies examined (E{sub i} = 0.09–11.3 eV), the nucleation of DIP is homogeneous and the dependence of the maximum island density on the growth rate is described by a power law. A critical nucleus of approximately two molecules is implicated by our data. A re-examination of the nucleation of pentacene on SiO{sub 2} gives the same major result that the maximum island density is determined by the growth rate, and it is independent of the incident kinetic energy. These observations are readily understood by factoring in the size of the critical nucleus in each case, and the island density, which indicates that diffusive transport of molecules to the growing islands dominate the dynamics of growth in the submonolayer regime.

Improvement of aging kinetics and precipitate size refinement in Mg–Sn alloys by hafnium additions

Energy Technology Data Exchange (ETDEWEB)

Behdad, S. [Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States); Zhou, L. [Department of Materials Science and Engineering and Advanced Materials Processing and Analysis Center, University of Central Florida, Orlando, FL 32816 (United States); Henderson, H.B.; Manuel, M.V. [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States); Sohn, Y. [Department of Materials Science and Engineering and Advanced Materials Processing and Analysis Center, University of Central Florida, Orlando, FL 32816 (United States); Agarwal, A. [Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States); Boesl, B., E-mail: bboesl@fiu.edu [Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States)

2016-01-10

Two Mg–Sn alloys were microalloyed by addition of Hafnium and their age-hardening response was studied at 200 °C. Time to reach peak hardness was significantly reduced and improved by Hf addition. TEM study showed Hf clusters in the close vicinity and at the surface of Mg{sub 2}Sn precipitates, which confirms that Hf clusters act as additional nucleation centers for Mg{sub 2}Sn precipitate formation. Our results support the validity of thermokinetic criterion proposed by Mendis for selection of microalloying elements in order to refine precipitate size, accelerate aging kinetics and enhance peak hardness.

Who receives bank loans? A study of lending officers' assessments of loans to growing small and medium-sized enterprises

OpenAIRE

Bruns, Volker

2004-01-01

This thesis explores factors that influence lending officers' assessments of credit requests from growing small and medium-sized enterprises (SMEs). Building on asymmetric information theory, factors identified in previous research are grouped into the theoretical categories of risk-assessment, risk-alignment, and risk-shifting. Hypotheses are developed as to what influences lending officers' credit assessments. In addition, it is hypothesized that risk-taking proclivity interacts with other ...

Isoconversional kinetics of thermally stimulated processes

CERN Document Server

Vyazovkin, Sergey

2015-01-01

The use of isoconversional kinetic methods for analysis of thermogravimetric and calorimetric data on thermally stimulated processes is quickly growing in popularity. The purpose of this book is to create the first comprehensive resource on the theory and applications of isoconversional methodology. The book introduces the reader to the kinetics of physical and chemical condensed phase processes that occur as a result of changing temperature and discusses how isoconversional analysis can provide important kinetic insights into them. The book will help the readers to develop a better understanding of the methodology, and promote its efficient usage and successful development.

Kinetics of diuron and amitrole adsorption from aqueous solution on activated carbons.

Science.gov (United States)

Fontecha-Cámara, M A; López-Ramón, M V; Pastrana-Martínez, L M; Moreno-Castilla, C

2008-08-15

A study was conducted on the adsorption kinetics of diuron and amitrole from aqueous solutions on activated carbons of different particle sizes and on an activated carbon fiber. Different kinetic models were applied to the experimental results obtained. A pseudo-second-order rate equation fitted the adsorption kinetics data better than a pseudo-first-order rate equation. Amitrole showed faster adsorption kinetics compared with diuron because of the smaller size of the former herbicide, despite its lower driving force for adsorption. Both reaction rate constants increased when the particle size decreased. The activated carbon fiber and the activated carbon of smallest particle size (0.03 mm) showed similar adsorption kinetics. The intraparticle diffusion rate constant increased with higher initial concentration of herbicides in solution and with lower particle size of the adsorbent. This is because the rise in initial concentration increased the amount adsorbed at equilibrium, and the reduction in particle size increased the number of collisions between adsorbate and adsorbent particles. Demineralization of the activated carbon with particle size of 0.5mm had practically no effect on the adsorption kinetics.

Kinetics and Photodegradation Study of Aqueous Methyl tert-Butyl Ether Using Zinc Oxide: The Effect of Particle Size

Directory of Open Access Journals (Sweden)

Zaki S. Seddigi

2013-01-01

Full Text Available Zinc oxide of different average particle sizes 25 nm, 59 nm, and 421 nm as applied in the photodegradation of MTBE. This study was carried out in a batch photoreactor having a high pressure mercury lamp. Zinc oxide of particle size of 421 nm was found to be the most effective in degrading MTBE in an aqueous solution. On using this type of ZnO in a solution of 100 ppm MTBE, the concentration of MTBE has decreased to 5.1 ppm after a period of five hours. The kinetics of the photocatalytic degradation of MTBE was found to be a first order reaction.

Barrierless growth of precursor-free, ultrafast laser-fragmented noble metal nanoparticles by colloidal atom clusters - A kinetic in situ study.

Science.gov (United States)

Jendrzej, Sandra; Gökce, Bilal; Amendola, Vincenzo; Barcikowski, Stephan

2016-02-01

Unintended post-synthesis growth of noble metal colloids caused by excess amounts of reactants or highly reactive atom clusters represents a fundamental problem in colloidal chemistry, affecting product stability or purity. Hence, quantified kinetics could allow defining nanoparticle size determination in dependence of the time. Here, we investigate in situ the growth kinetics of ps pulsed laser-fragmented platinum nanoparticles in presence of naked atom clusters in water without any influence of reducing agents or surfactants. The nanoparticle growth is investigated for platinum covering a time scale of minutes to 50days after nanoparticle generation, it is also supplemented by results obtained from gold and palladium. Since a minimum atom cluster concentration is exceeded, a significant growth is determined by time resolved UV/Vis spectroscopy, analytical disc centrifugation, zeta potential measurement and transmission electron microscopy. We suggest a decrease of atom cluster concentration over time, since nanoparticles grow at the expense of atom clusters. The growth mechanism during early phase (<1day) of laser-synthesized colloid is kinetically modeled by rapid barrierless coalescence. The prolonged slow nanoparticle growth is kinetically modeled by a combination of coalescence and Lifshitz-Slyozov-Wagner kinetic for Ostwald ripening, validated experimentally by the temperature dependence of Pt nanoparticle size and growth quenching by Iodide anions. Copyright © 2015. Published by Elsevier Inc.

Fine kinetics of natural physical ageing in glassy As{sub 10}Se{sub 90}

Energy Technology Data Exchange (ETDEWEB)

Balitska, V. [Institute of Materials, Scientific Research Company “Carat”, 202 Stryjska Str., 79031 Lviv (Ukraine); Lviv State University of Vital Activity Safety, 35, Kleparivska Str., Lviv 79007 (Ukraine); Golovchak, R. [Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN 37044 (United States); Kozdras, A. [Faculty of Physics of Opole Technical University, 75, Ozimska Str., Opole 45370 (Poland); Shpotyuk, O., E-mail: shpotyuk@novas.lviv.ua [Institute of Materials, Scientific Research Company “Carat”, 202 Stryjska Str., 79031 Lviv (Ukraine); Institute of Physics, Jan Dlugosz University, Al. Armii Krajowej 13/15, Czestochowa 42201 (Poland)

2014-02-01

Sigmoid behavior of natural physical ageing in glassy As{sub 10}Se{sub 90} reveals multi-step-wise growing kinetics of enthalpy losses. Phenomenological description of this kinetics can be adequately developed in terms of first-order relaxation processes, tending atomic structure from initial towards more thermodynamically equilibrium state. This kinetics is shown to obey characteristic stretched exponential behavior originated from a number of growing steps, attributed to the interconnected processes of chalcogen chain alignment and cooperative shrinkage of glass network.

Organization of growing random networks

Energy Technology Data Exchange (ETDEWEB)

Krapivsky, P. L.; Redner, S.

2001-06-01

The organizational development of growing random networks is investigated. These growing networks are built by adding nodes successively, and linking each to an earlier node of degree k with an attachment probability A{sub k}. When A{sub k} grows more slowly than linearly with k, the number of nodes with k links, N{sub k}(t), decays faster than a power law in k, while for A{sub k} growing faster than linearly in k, a single node emerges which connects to nearly all other nodes. When A{sub k} is asymptotically linear, N{sub k}(t){similar_to}tk{sup {minus}{nu}}, with {nu} dependent on details of the attachment probability, but in the range 2{lt}{nu}{lt}{infinity}. The combined age and degree distribution of nodes shows that old nodes typically have a large degree. There is also a significant correlation in the degrees of neighboring nodes, so that nodes of similar degree are more likely to be connected. The size distributions of the in and out components of the network with respect to a given node{emdash}namely, its {open_quotes}descendants{close_quotes} and {open_quotes}ancestors{close_quotes}{emdash}are also determined. The in component exhibits a robust s{sup {minus}2} power-law tail, where s is the component size. The out component has a typical size of order lnt, and it provides basic insights into the genealogy of the network.

Kinetic Behavior of Aggregation-Exchange Growth Process with Catalyzed-Birth

International Nuclear Information System (INIS)

Han Anjia; Chen Yu; Lin Zhenquan; Ke Jianhong

2007-01-01

We propose an aggregation model of a two-species system to mimic the growth of cities' population and assets, in which irreversible coagulation reactions and exchange reactions occur between any two aggregates of the same species, and the monomer-birth reactions of one species occur by the catalysis of the other species. In the case with population-catalyzed birth of assets, the rate kernel of an asset aggregate B k of size k grows to become an aggregate B k+1 through a monomer-birth catalyzed by a population aggregate A j of size j is J(k,j) = Jkj λ . And in mutually catalyzed birth model, the birth rate kernels of population and assets are H(k,j) = Hkj η and J(k,j) = Jkj λ , respectively. The kinetics of the system is investigated based on the mean-field theory. In the model of population-catalyzed birth of assets, the long-time asymptotic behavior of the assets aggregate size distribution obeys the conventional or modified scaling form. In mutually catalyzed birth system, the asymptotic behaviors of population and assets obey the conventional scaling form in the case of η = λ = 0, and they obey the modified scaling form in the case of η = 0,λ = 1. In the case of η = λ = 1, the total mass of population aggregates and that of asset aggregates both grow much faster than those in population-catalyzed birth of assets model, and they approaches to infinite values in finite time.

Real-time imaging of vertically aligned carbon nanotube array growth kinetics

International Nuclear Information System (INIS)

Puretzky, A A; Eres, G; Rouleau, C M; Ivanov, I N; Geohegan, D B

2008-01-01

In situ time-lapse photography and laser irradiation are applied to understand unusual coordinated growth kinetics of vertically aligned carbon nanotube arrays including pauses in growth, retraction, and local equilibration in length. A model is presented which explains the measured kinetics and determines the conditions for diffusion-limited growth. Laser irradiation of the growing nanotube arrays is first used to prove that the nanotubes grow from catalyst particles at their bases, and then increase their growth rate and terminal lengths

Effect of Growing Size of Interaction Neighbors on the Evolution of Cooperation in Spatial Snowdrift Game

International Nuclear Information System (INIS)

Zhang Juanjuan; Sun Shiwen; Wang Li; Xia Chengyi; Wang Juan; Wang Zhen

2012-01-01

In this paper, we study the influence of the size of interaction neighbors (k) on the evolution of cooperation in the spatial snowdrift game. At first, we consider the effects of noise K and cost-to-benefit ratio r, the simulation results indicate that the evolution of cooperation depends on the combined action of noise and cost-to-benefit ratio. For a lower r, the cooperators are multitudinous and the cooperation frequency ultimately increases to 1 as the increase of noise. However, for a higher r, the defectors account for the majority of the game and dominate the game if the noise is large enough. Then we mainly investigate how k influences the evolution of cooperation by varying the noise in detail. We find that the frequency of cooperators is closely related to the size of neighborhood and cost-to-benefit ratio r. In the case of lower r, the augmentation of k plays no positive role in promoting the cooperation as compared with that of k = 4, while for higher r the cooperation is improved for a growing size of neighborhood. At last, based on the above discussions, we explore the cluster-forming mechanism among the cooperators. The current results are beneficial to further understand the evolution of cooperation in many natural, social and biological systems. (general)

Two-Step Production of Phenylpyruvic Acid from L-Phenylalanine by Growing and Resting Cells of Engineered Escherichia coli: Process Optimization and Kinetics Modeling.

Directory of Open Access Journals (Sweden)

Ying Hou

Full Text Available Phenylpyruvic acid (PPA is widely used in the pharmaceutical, food, and chemical industries. Here, a two-step bioconversion process, involving growing and resting cells, was established to produce PPA from l-phenylalanine using the engineered Escherichia coli constructed previously. First, the biotransformation conditions for growing cells were optimized (l-phenylalanine concentration 20.0 g·L-1, temperature 35°C and a two-stage temperature control strategy (keep 20°C for 12 h and increase the temperature to 35°C until the end of biotransformation was performed. The biotransformation conditions for resting cells were then optimized in 3-L bioreactor and the optimized conditions were as follows: agitation speed 500 rpm, aeration rate 1.5 vvm, and l-phenylalanine concentration 30 g·L-1. The total maximal production (mass conversion rate reached 29.8 ± 2.1 g·L-1 (99.3% and 75.1 ± 2.5 g·L-1 (93.9% in the flask and 3-L bioreactor, respectively. Finally, a kinetic model was established, and it was revealed that the substrate and product inhibition were the main limiting factors for resting cell biotransformation.

Two-Step Production of Phenylpyruvic Acid from L-Phenylalanine by Growing and Resting Cells of Engineered Escherichia coli: Process Optimization and Kinetics Modeling.

Science.gov (United States)

Hou, Ying; Hossain, Gazi Sakir; Li, Jianghua; Shin, Hyun-Dong; Liu, Long; Du, Guocheng; Chen, Jian

2016-01-01

Phenylpyruvic acid (PPA) is widely used in the pharmaceutical, food, and chemical industries. Here, a two-step bioconversion process, involving growing and resting cells, was established to produce PPA from l-phenylalanine using the engineered Escherichia coli constructed previously. First, the biotransformation conditions for growing cells were optimized (l-phenylalanine concentration 20.0 g·L-1, temperature 35°C) and a two-stage temperature control strategy (keep 20°C for 12 h and increase the temperature to 35°C until the end of biotransformation) was performed. The biotransformation conditions for resting cells were then optimized in 3-L bioreactor and the optimized conditions were as follows: agitation speed 500 rpm, aeration rate 1.5 vvm, and l-phenylalanine concentration 30 g·L-1. The total maximal production (mass conversion rate) reached 29.8 ± 2.1 g·L-1 (99.3%) and 75.1 ± 2.5 g·L-1 (93.9%) in the flask and 3-L bioreactor, respectively. Finally, a kinetic model was established, and it was revealed that the substrate and product inhibition were the main limiting factors for resting cell biotransformation.

Two-Step Production of Phenylpyruvic Acid from L-Phenylalanine by Growing and Resting Cells of Engineered Escherichia coli: Process Optimization and Kinetics Modeling

Science.gov (United States)

Hou, Ying; Hossain, Gazi Sakir; Li, Jianghua; Shin, Hyun-dong; Liu, Long; Du, Guocheng; Chen, Jian

2016-01-01

Phenylpyruvic acid (PPA) is widely used in the pharmaceutical, food, and chemical industries. Here, a two-step bioconversion process, involving growing and resting cells, was established to produce PPA from l-phenylalanine using the engineered Escherichia coli constructed previously. First, the biotransformation conditions for growing cells were optimized (l-phenylalanine concentration 20.0 g·L−1, temperature 35°C) and a two-stage temperature control strategy (keep 20°C for 12 h and increase the temperature to 35°C until the end of biotransformation) was performed. The biotransformation conditions for resting cells were then optimized in 3-L bioreactor and the optimized conditions were as follows: agitation speed 500 rpm, aeration rate 1.5 vvm, and l-phenylalanine concentration 30 g·L−1. The total maximal production (mass conversion rate) reached 29.8 ± 2.1 g·L−1 (99.3%) and 75.1 ± 2.5 g·L−1 (93.9%) in the flask and 3-L bioreactor, respectively. Finally, a kinetic model was established, and it was revealed that the substrate and product inhibition were the main limiting factors for resting cell biotransformation. PMID:27851793

Fischer-Tropsch synthesis: Support and cobalt cluster size effects on kinetics over Co/Al{sub 2}O{sub 3} and Co/SiO{sub 2} catalysts

Energy Technology Data Exchange (ETDEWEB)

Wenping Ma; Gary Jacobs; Dennis E. Sparks; Muthu K. Gnanamani; Venkat Ramana Rao Pendyala; Chia H. Yen; Jennifer L.S. Klettlinger; Thomas M. Tomsik; Burtron H. Davis [University of Kentucky, Lexington, KY (USA). Center for Applied Energy Research

2011-02-15

The influence of support type and cobalt cluster size (i.e., with average diameters falling within the range of 8-40 nm) on the kinetics of Fischer-Tropsch synthesis (FT) were investigated by kinetic tests employing a CSTR and two Co/{gamma}-Al{sub 2}O{sub 3} catalysts having different average pore sizes, and two Co/SiO{sub 2} catalysts prepared on the same support but having different loadings. A kinetic model -r{sub CO}=kP{sup a}{sub co}P{sup b}{sub H2}/(1 + mP{sub H2O}/P{sub H2}) that contains a water effect constant 'm' was used to fit the experimental data obtained with all four catalysts. Kinetic parameters suggest that both support type and average Co particle size impact FT behavior. Cobalt cluster size influenced kinetic parameters such as reaction order, rate constant, and the water effect parameter.Decreasing the average Co cluster diameter by about 30% led to an increase in the intrinsic reaction rate constant k, defined on a per g of catalyst basis, by 62-102% for the {gamma}-Al{sub 2}O{sub 3} and SiO{sub 2}-supported cobalt catalysts. Moreover, less inhibition by adsorbed CO and greater H{sub 2} dissociation on catalysts having smaller Co particles was suggested by the higher a and lower b values obtained for the measured reaction orders. Irrespective of support type, the catalysts having smaller average Co particles were more sensitive to water. Comparing the catalysts having strong interactions between cobalt and support (Co/Al{sub 2}O{sub 3}) to the ones with weak interactions (Co/SiO{sub 2}), the water effect parameters were found to be positive (indicating a negative influence on CO conversion) and negative (denoting a positive effect on CO conversion), respectively. Greater a and a/b values were observed for both Al{sub 2}O{sub 3}-supported Co catalysts, implying greater inhibition of the FT rate by strongly adsorbed CO on Co/Al{sub 2}O{sub 3} relative to Co/SiO{sub 2}. 78 refs., 4 figs., 3 tabs.

Nucleation and Growth Kinetics from LaMer Burst Data.

Science.gov (United States)

Chu, Daniel B K; Owen, Jonathan S; Peters, Baron

2017-10-12

In LaMer burst nucleation, the individual nucleation events happen en masse, quasi-simultaneously, and at nearly identical homogeneous conditions. These properties make LaMer burst nucleation important for applications that require monodispersed particles and also for theoretical analyses. Sugimoto and co-workers predicted that the number of nuclei generated during a LaMer burst depends only on the solute supply rate and the growth rate, independent of the nucleation kinetics. Some experiments confirm that solute supply kinetics control the number of nuclei, but flaws in the original theoretical analysis raise questions about the predicted roles of growth and nucleation kinetics. We provide a rigorous analysis of the coupled equations that govern concentrations of nuclei and solutes. Our analysis confirms that the number of nuclei is largely determined by the solute supply and growth rates, but our predicted relationship differs from that of Sugimoto et al. Moreover, we find that additional nucleus size dependent corrections should emerge in systems with slow growth kinetics. Finally, we show how the nucleation kinetics determine the particle size distribution. We suggest that measured particle size distributions might therefore provide ways to test theoretical models of homogeneous nucleation kinetics.

Stability analysis of non-autonomous reaction-diffusion systems: the effects of growing domains

KAUST Repository

Madzvamuse, Anotida; Gaffney, Eamonn A.; Maini, Philip K.

2009-01-01

By using asymptotic theory, we generalise the Turing diffusively-driven instability conditions for reaction-diffusion systems with slow, isotropic domain growth. There are two fundamental biological differences between the Turing conditions on fixed and growing domains, namely: (i) we need not enforce cross nor pure kinetic conditions and (ii) the restriction to activator-inhibitor kinetics to induce pattern formation on a growing biological system is no longer a requirement. Our theoretical findings are confirmed and reinforced by numerical simulations for the special cases of isotropic linear, exponential and logistic growth profiles. In particular we illustrate an example of a reaction-diffusion system which cannot exhibit a diffusively-driven instability on a fixed domain but is unstable in the presence of slow growth. © Springer-Verlag 2009.

Stability analysis of non-autonomous reaction-diffusion systems: the effects of growing domains

KAUST Repository

Madzvamuse, Anotida

2009-08-29

By using asymptotic theory, we generalise the Turing diffusively-driven instability conditions for reaction-diffusion systems with slow, isotropic domain growth. There are two fundamental biological differences between the Turing conditions on fixed and growing domains, namely: (i) we need not enforce cross nor pure kinetic conditions and (ii) the restriction to activator-inhibitor kinetics to induce pattern formation on a growing biological system is no longer a requirement. Our theoretical findings are confirmed and reinforced by numerical simulations for the special cases of isotropic linear, exponential and logistic growth profiles. In particular we illustrate an example of a reaction-diffusion system which cannot exhibit a diffusively-driven instability on a fixed domain but is unstable in the presence of slow growth. © Springer-Verlag 2009.

Study of the synthesis of copper nanoparticles: the role of capping and kinetic towards control of particle size and stability

Energy Technology Data Exchange (ETDEWEB)

Granata, Giuseppe, E-mail: giuseppe.granata@aoni.waseda.jp; Yamaoka, Taishi [Waseda University, School of Creative Science and Engineering (Japan); Pagnanelli, Francesca [Sapienza University of Rome, Department of Chemistry (Italy); Fuwa, Akio [Waseda University, School of Creative Science and Engineering (Japan)

2016-05-15

The synthesis of copper nanoparticles (CuNPs) by surfactant-assisted chemical reduction method was studied aiming to identify and quantify the role of kinetic and capping on particle size distribution. The use of a strong and a mild reducing agent (hydrazine, d-glucose) has been investigated as well as the use of three different capping agents: cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP). Experimental tests were arranged according to factorial designs. CuNPs were characterized by XRD, FE-SEM and UV–Vis spectrophotometry. Particle size distribution was determined by image analysis and significance of investigated factors was statistically assessed by analysis of variance. Under the investigated conditions, CTAB was found capable of preventing oxidation but it had a significant positive effect on nanoparticle size (about 40 and 30 nm); SDS determined a good size control but no stabilization, whilst PVP could provide both size control (significant negative effect of about 15 and 25 nm) and stability. Average size of CuNPs can be significantly reduced of about 50 nm by replacing d-glucose with hydrazine.Graphical Abstract.

An 'attachment kinetics-based' volume of fraction method for organic crystallization: a fluid-dynamic approach to macromolecular-crystal engineering

International Nuclear Information System (INIS)

Lappa, Marcello

2003-01-01

This analysis exhibits a strong interdisciplinary nature and deals with advances in protein (crystal) engineering models and computational methods as well as with novel results on the relative importance of 'controlling forces' in macromolecular crystal growth. The attention is focused in particular on microgravity fluid-dynamic aspects. From a numerical point of view, the growing crystal gives rise to a moving boundary problem. A 'kinetic-coefficient-based' volume tracking method is specifically and carefully developed according to the complex properties and mechanisms of macromolecular protein crystal growth taking into account the possibility of anisotropic (faceted) surface-orientation-dependent growth. The method is used to shed some light on the interplay of surface attachment kinetics and mass transport (diffusive or convective) in liquid phase and on several mechanisms still poorly understood. It is shown that the size of a growing crystal plays a 'critical role' in the relative importance of surface effects and in determining the intensity of convection. Convective effects, in turn, are found to impact growth rates, macroscopic structures of precipitates, particle size and morphology as well as the mechanisms driving growth. The paper introduces a novel computational method (that simulates the growth due to the slow addition of solute molecules to a lattice and can handle the shape of organic growing crystals under the influence of natural convection) and, at the same time, represents a quite exhaustive attempt to help organic crystal growers to discern the complex interrelations among the various parameters under one's control (that are not independent of one another) and to elaborate rational guidelines relating to physical factors that can influence the probability of success in crystallizing protein substances

Thermal decomposition kinetics of ammonium uranyl carbonate

International Nuclear Information System (INIS)

Kim, E.H.; Park, J.J.; Park, J.H.; Chang, I.S.; Choi, C.S.; Kim, S.D.

1994-01-01

The thermal decomposition kinetics of AUC [ammonium uranyl carbonate; (NH 4 ) 4 UO 2 (CO 3 ) 3 [ in an isothermal thermogravimetric (TG) reactor under N 2 atmosphere has been determined. The kinetic data can be represented by the two-dimensional nucleation and growth model. The reaction rate increases and activation energy decreases with increasing particle size and precipitation time which appears in the particle size larger than 30 μm in the mechano-chemical phenomena. (orig.)

Study of aniline polymerization reactions through the particle size formation in acidic and neutral medium

Science.gov (United States)

Aribowo, Slamet; Hafizah, Mas Ayu Elita; Manaf, Azwar; Andreas

2018-04-01

In the present paper, we reported particle size kinetic studies on the conducting polyaniline (PANI) which synthesized through a chemical oxidative polymerization technique from aniline monomer. PANI was prepared using ammonium persulfate (APS) as oxidizing agent which carried out in acidic and neutral medium at various batch temperatures of respectively 20, 30 and 50 °C. From the studies, it was noticed that the complete polymerization reaction progressed within 480 minutes duration time. The pH of the solution during reaction kinetic reached values 0.8 - to 1.2 in acidic media, while in the neutral media the pH value reached values 3.8 - 4.9. The batch temperature controlled the polymerization reaction in which the reaction progressing, which followed by the temperature rise of solution above the batch temperature before settled down to the initial temperature. An increment in the batch temperature gave highest rise in the solution temperature for the two media which cannot be more than 50 °C. The final product of polymerization reaction was PANI confirmed by Fourier Transform Infra-Red (FTIR) spectrophotometer for molecule structure identification. The averages particle size of PANI which carried out in the two different media is evidently similar in the range 30 - 40 μm and insensitive to the batch temperature. However, the particle size of PANI which obtained from the polymerization reaction at a batch temperature of 50 °C under acidic condition reached ˜53.1 μm at the tip of the propagation stage which started in the first 5 minutes. The size is obviously being the largest among the batch temperatures. Whereas, under neutral condition the particle size is much larger which reached the size 135 μm at the batch temperature of 20 °C. It is concluded that the particle size formation during the polymerization reaction being one of the important parameter to determine particle growing of polymer which indicated the reaction kinetics mechanism of synthesize

Kinetic considerations in the choice of treatment schedules for neuraxis radiotherapy

International Nuclear Information System (INIS)

Wheldon, T.E.

1993-01-01

Neuraxis radiotherapy of radiosensitive tumours such as medulloblastoma is usually carried out using conventionally sized fractions and a shrinking field technique. Plowman and Doughty (Br.J.Radiol., 64 (1991) 603-607) have proposed a partial transmission block (PTB) technique which entails the use of small daily doses over a conventional time period. Radiobiological analysis suggests that, although the PTB technique may be adequate for slowly growing tumours, therapeutic efficacy is likely to be compromised where the tumour doubling time is short. Accelerated hyperfractionation (twice daily fractions) provides a possible alternative to both conventional scheduling and the PTB technique. Direct measurement of the kinetics of tumour cells in CSF, where possible, may provide useful guidance in the choice of regimes. (author)

Colony Size Affects the Efficacy of Bait Containing Chlorfluazuron Against the Fungus-Growing Termite Macrotermes gilvus (Blattodea: Termitidae).

Science.gov (United States)

Lee, Ching-Chen; Neoh, Kok-Boon; Lee, Chow-Yang

2014-12-01

The efficacy of chitin synthesis inhibitors (CSIs) against fungus-growing termites is known to vary. In this study, 0.1% chlorfluazuron (CFZ) cellulose bait was tested against medium and large field colonies of Macrotermes gilvus (Hagen). The termite mounds were dissected to determine the health of the colony. Individual termites (i.e., workers and larvae) and fungus combs were subjected to gas chromatography-mass spectrometry (GC-MS) analysis to detect the presence of CFZ. In this study, 540.0 ± 25.8 g (or equivalent to 540.0 ± 25.8 mg active ingredient) and 680.0 ± 49.0 g (680.0 ± 49.0 mg active ingredient) of bait matrix were removed by the medium- and large-sized colonies, respectively, after baiting. All treated medium-sized colonies were moribund. The dead termites were scattered in the mound, larvae were absent, population size had decreased by 90%, and the queens appeared unhealthy. In contrast, no or limited effects were found in large-sized colonies. Only trace amounts of CFZ were detected in workers, larvae, and fungus combs, and the population of large-sized colonies had declined by only up to 40%. This might be owing to the presence of large amount of basidiomycete fungus and a drastic decrease of CFZ content per unit fungus comb (a main food source of larvae) in the large-sized colonies, and hence reduced the toxic effect and longer time is required to accumulate the lethal dose in larvae. Nevertheless, we do not deny the possibility of CSI bait eliminating or suppressing the higher termite if the test colonies could pick up adequate lethal dose by installing more bait stations and prolonging the baiting period. © 2014 Entomological Society of America.

Kinetic modeling of solid-state partitioning phase transformation with simultaneous misfit accommodation

International Nuclear Information System (INIS)

Song, Shaojie; Liu, Feng

2016-01-01

Considering a spherical misfitting precipitate growing into a finite elastic-perfectly plastic supersaturated matrix, a kinetic modeling for such solid-state partitioning phase transformation is presented, where the interactions of interface migration, solute diffusion and misfit accommodation are analyzed. The linkage between interface migration and solute diffusion proceeds through interfacial composition and interface velocity; their effects on misfit accommodation are mainly manifested in an effective transformation strain, which depends on instantaneous composition field and precipitate size. Taking γ to α transformation of a binary Fe-0.5 at.% C alloy under both isothermal and continuous cooling conditions as examples, the effects of misfit accommodation on the coupling interface migration and solute diffusion are well evaluated and discussed. For the isothermal transformation, a counterbalancing influence between mechanical and chemical driving forces is found so that the mixed-mode transformation kinetics is not sensitive with respect to the elastic–plastic accommodation of the effective misfit strain. Different from the isothermal process, during the continuous cooling condition, the effects of misfit accommodation on the kinetics of solid-state partitioning phase transformation are mainly manifested in the great decrease of the transformation starting temperature and the thermodynamic equilibrium composition. The present kinetic modeling was applied to predict the experimentally measured γ/α transformation of Fe-0.47 at.% C alloy conducted with a cooling rate of 10 K min −1 and a good agreement was achieved.

Entanglement in correlated random spin chains, RNA folding and kinetic roughening

International Nuclear Information System (INIS)

Rodríguez-Laguna, Javier; Santalla, Silvia N; Ramírez, Giovanni; Sierra, Germán

2016-01-01

Average block entanglement in the 1D XX-model with uncorrelated random couplings is known to grow as the logarithm of the block size, in similarity to conformal systems. In this work we study random spin chains whose couplings present long range correlations, generated as gaussian fields with a power-law spectral function. Ground states are always planar valence bond states, and their statistical ensembles are characterized in terms of their block entropy and their bond-length distribution, which follow power-laws. We conjecture the existence of a critical value for the spectral exponent, below which the system behavior is identical to the case of uncorrelated couplings. Above that critical value, the entanglement entropy violates the area law and grows as a power law of the block size, with an exponent which increases from zero to one. Interestingly, we show that XXZ models with positive anisotropy present the opposite behavior, and strong correlations in the couplings lead to lower entropies. Similar planar bond structures are also found in statistical models of RNA folding and kinetic roughening, and we trace an analogy between them and quantum valence bond states. Using an inverse renormalization procedure we determine the optimal spin-chain couplings which give rise to a given planar bond structure, and study the statistical properties of the couplings whose bond structures mimic those found in RNA folding. (paper)

Kinetics of self-assembled InN quantum dots grown on Si (111) by plasma-assisted MBE

International Nuclear Information System (INIS)

Kumar, Mahesh; Roul, Basanta; Bhat, Thirumaleshwara N.; Rajpalke, Mohana K.; Sinha, Neeraj; Kalghatgi, A. T.; Krupanidhi, S. B.

2011-01-01

One of the scientific challenges of growing InN quantum dots (QDs), using Molecular beam epitaxy (MBE), is to understand the fundamental processes that control the morphology and distribution of QDs. A systematic manipulation of the morphology, optical emission, and structural properties of InN/Si (111) QDs is demonstrated by changing the growth kinetics parameters such as flux rate and growth time. Due to the large lattice mismatch, between InN and Si (∼8%), the dots formed from the Strannski–Krastanow (S–K) growth mode are dislocated. Despite the variations in strain (residual) and the shape, both the dot size and pair separation distribution show the scaling behavior. We observed that the distribution of dot sizes, for samples grown under varying conditions, follow the scaling function.

Difference in postprandial GLP-1 response despite similar glucose kinetics after consumption of wheat breads with different particle size in healthy men

DEFF Research Database (Denmark)

Eelderink, Coby; Noort, Martijn W J; Sozer, Nesli

2017-01-01

PURPOSE: Underlying mechanisms of the beneficial health effects of low glycemic index starchy foods are not fully elucidated yet. We varied the wheat particle size to obtain fiber-rich breads with a high and low glycemic response and investigated the differences in postprandial glucose kinetics...... and metabolic response after their consumption. METHODS: Ten healthy male volunteers participated in a randomized, crossover study, consuming (13)C-enriched breads with different structures; a control bread (CB) made from wheat flour combined with wheat bran, and a kernel bread (KB) where 85 % of flour...... in a difference in glucose response and kinetics, but in a pronounced difference in GLP-1 response. Thus, changing the processing conditions of wheat for baking bread can influence the metabolic response beyond glycemia and may therefore influence health....

Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

Science.gov (United States)

Bang, Junhyeok; Kim, Youg-Sung; Park, C. H.; Gao, F.; Zhang, S. B.

2014-06-01

Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (VZn - Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of VZn compared to VO, more VZn-abundant clusters are formed than VO-abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (VZn - Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to VO donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.

Propagation of electro-kinetic waves in magnetized GaN semiconductor with nano-sized ion colloids

Energy Technology Data Exchange (ETDEWEB)

Saxena, Ajay [Government College, Garoth, Dist. Mandsaur (M P) (India); Sharma, Giriraj, E-mail: grsharma@gmail.com [SRJ Government Girls’ College, Neemuch (M P) (India); Jat, K. L. [Swami Vivekanand Government P G College, Neemuch (M P) (India); Rishi, M. P. [Shahid Bhagat Singh Government P G College, Jaora, Dist Ratlam (M P) (India)

2015-07-31

Based on hydrodynamic model of multi-component plasma, an analytical study on propagation of longitudinal electro-kinetic (LEK) waves in wurtzite and zincblende structures of GaN is carried out. Nano-sized ion colloids (NICs) are embedded in the sample by the technique of ion-implantation. The implanted NICs are considered massive by an order as compared to the host lattice points and do not participate in Based LEK perturbations. Though, the NICs are continuously bombarded by the electrons as well as the holes yet, the former acquires a net negative charge owing to relatively higher mobility of electrons and consequently results into depletion of electron density in the medium. It i s found that the presence of charged NICs significantly modifies the dispersion and amplification characteristics of LEK waves in magnetized GaN semiconductor plasma and their role becomes increasingly effective as the fraction of charge on them increases.

Propagation of electro-kinetic waves in magnetized GaN semiconductor with nano-sized ion colloids

International Nuclear Information System (INIS)

Saxena, Ajay; Sharma, Giriraj; Jat, K. L.; Rishi, M. P.

2015-01-01

Based on hydrodynamic model of multi-component plasma, an analytical study on propagation of longitudinal electro-kinetic (LEK) waves in wurtzite and zincblende structures of GaN is carried out. Nano-sized ion colloids (NICs) are embedded in the sample by the technique of ion-implantation. The implanted NICs are considered massive by an order as compared to the host lattice points and do not participate in Based LEK perturbations. Though, the NICs are continuously bombarded by the electrons as well as the holes yet, the former acquires a net negative charge owing to relatively higher mobility of electrons and consequently results into depletion of electron density in the medium. It i s found that the presence of charged NICs significantly modifies the dispersion and amplification characteristics of LEK waves in magnetized GaN semiconductor plasma and their role becomes increasingly effective as the fraction of charge on them increases

Physisorption kinetics

CERN Document Server

Kreuzer, Hans Jürgen

1986-01-01

This monograph deals with the kinetics of adsorption and desorption of molecules physisorbed on solid surfaces. Although frequent and detailed reference is made to experiment, it is mainly concerned with the theory of the subject. In this, we have attempted to present a unified picture based on the master equation approach. Physisorption kinetics is by no means a closed and mature subject; rather, in writing this monograph we intended to survey a field very much in flux, to assess its achievements so far, and to give a reasonable basis from which further developments can take off. For this reason we have included many papers in the bibliography that are not referred to in the text but are of relevance to physisorption. To keep this monograph to a reasonable size, and also to allow for some unity in the presentation of the material, we had to omit a number of topics related to physisorption kinetics. We have not covered to any extent the equilibrium properties of physisorbed layers such as structures, phase tr...

Numerical Simulation of the Kinetic Critical Nucleus

OpenAIRE

Sanada, Masaaki; Nishioka, Kazumi; Okada, Masahumi; Maksimov, Igor, L.

1997-01-01

Our main interest is to see whether the number density indicates a peak at the kinetically stable critical nucleus due to its kinetical stability. We have numerically calculated the time evolution of the number densities of clusters in the case of water vapor nucleation. We employ the condition in which the difference between the size of the thermodynamic crtitical nucleus and that of the kinetic one is appreciable. The results show that the peak does not appear in the number densities of clu...

Agglomerative clustering of growing squares

NARCIS (Netherlands)

Castermans, Thom; Speckmann, Bettina; Staals, Frank; Verbeek, Kevin; Bender, M.A.; Farach-Colton, M.; Mosteiro, M.A.

2018-01-01

We study an agglomerative clustering problem motivated by interactive glyphs in geo-visualization. Consider a set of disjoint square glyphs on an interactive map. When the user zooms out, the glyphs grow in size relative to the map, possibly with different speeds. When two glyphs intersect, we wish

Difference in postprandial GLP-1 response despite similar glucose kinetics after consumption of wheat breads with different particle size in healthy men.

Science.gov (United States)

Eelderink, Coby; Noort, Martijn W J; Sozer, Nesli; Koehorst, Martijn; Holst, Jens J; Deacon, Carolyn F; Rehfeld, Jens F; Poutanen, Kaisa; Vonk, Roel J; Oudhuis, Lizette; Priebe, Marion G

2017-04-01

Underlying mechanisms of the beneficial health effects of low glycemic index starchy foods are not fully elucidated yet. We varied the wheat particle size to obtain fiber-rich breads with a high and low glycemic response and investigated the differences in postprandial glucose kinetics and metabolic response after their consumption. Ten healthy male volunteers participated in a randomized, crossover study, consuming 13 C-enriched breads with different structures; a control bread (CB) made from wheat flour combined with wheat bran, and a kernel bread (KB) where 85 % of flour was substituted with broken wheat kernels. The structure of the breads was characterized extensively. The use of stable isotopes enabled calculation of glucose kinetics: rate of appearance of exogenous glucose, endogenous glucose production, and glucose clearance rate. Additionally, postprandial plasma concentrations of glucose, insulin, glucagon, incretins, cholecystokinin, and bile acids were analyzed. Despite the attempt to obtain a bread with a low glycemic response by replacing flour by broken kernels, the glycemic response and glucose kinetics were quite similar after consumption of CB and KB. Interestingly, the glucagon-like peptide-1 (GLP-1) response was much lower after KB compared to CB (iAUC, P bread did not result in a difference in glucose response and kinetics, but in a pronounced difference in GLP-1 response. Thus, changing the processing conditions of wheat for baking bread can influence the metabolic response beyond glycemia and may therefore influence health.

Sperm length evolution in the fungus-growing ants

DEFF Research Database (Denmark)

Baer, B.; Dijkstra, M. B.; Mueller, U. G.

2009-01-01

-growing ants, representing 9 of the 12 recognized genera, and mapped these onto the ant phylogeny. We show that average sperm length across species is highly variable and decreases with mature colony size in basal genera with singly mated queens, suggesting that sperm production or storage constraints affect...... the evolution of sperm length. Sperm length does not decrease further in multiply mating leaf-cutting ants, despite substantial further increases in colony size. In a combined analysis, sexual dimorphism explained 63.1% of the variance in sperm length between species. As colony size was not a significant...... predictor in this analysis, we conclude that sperm production trade-offs in males have been the major selective force affecting sperm length across the fungus-growing ants, rather than storage constraints in females. The relationship between sperm length and sexual dimorphism remained robust...

Chemistry and kinetics of size-selected cobalt cluster cations at thermal energies. I. Reactions with CO

Science.gov (United States)

Guo, B. C.; Kerns, K. P.; Castleman, A. W., Jr.

1992-06-01

The chemistry and kinetics of size-selected Co+n cluster-ion (n=2-8) reactions with CO are studied using a selected ion drift tube affixed with a laser vaporization source operated under well-defined thermal conditions. All reactions studied in the present work are found to be association reactions. Their absolute rate constants, which are determined quantitatively, are found to have a strong dependence on cluster size. Similar to the cases of reactions with many other reactants such as H2 and CH4, Co+4 and Co+5 display a higher reactivity toward the CO molecule than do clusters of neighboring size. The multiple-collision conditions employed in the present work have enabled a determination of the maximum coordination number of CO molecules bound onto each Co+n cluster. It is found that the tetramer tends to bond 12 CO molecules, the pentamer 14 CO, hexamer 16 CO, and so on. The results are interpreted in terms of Lauher's calculation and the polyhedral skeletal electron pair theory. All the measured maximum coordination numbers correlate extremely well with the predictions of these theories, except for the trimer where the measured number is one CO less than the predicted value. The good agreement between experiment and theory enables one to gain some insight into the geometric structure of the clusters. Based on the present findings, the cobalt tetramer cation is interpreted to have a tetrahedral structure, the pentamer a trigonal bipyramid, and the hexamer an octahedral structure. Other cluster structures are also discussed.

Controlling the size and morphology of Au@Pd core-shell nanocrystals by manipulating the kinetics of seeded growth.

Science.gov (United States)

Li, Jing; Zheng, Yiqun; Zeng, Jie; Xia, Younan

2012-06-25

This article reports a systematic study of the seed-mediated growth of Au@Pd core-shell nanocrystals with a variety of controlled sizes and morphologies. The key to the success of this synthesis is to manipulate the reaction kinetics by tuning a set of reaction parameters, including the type and concentration of capping agent, the amount of ascorbic acid used as the reducing agent, and the injection rate used for the precursor solution. Starting from Au nanospheres of 11 nm in diameter as the seeds, Au@Pd core-shell nanocrystals with a number of morphologies, including octahedra, concave octahedra, rectangular bars, cubes, concave cubes, and dendrites, could all be obtained by simply altering the reaction rate. For the first time, it was possible to generate Au@Pd nanocrystals with concave structures on the surfaces while their sizes were kept below 20 nm. In addition, the as-prepared Au@Pd nanocubes can be used as seeds to generate Au@Pd@Au and Au@Pd@Au@Pd nanocrystals with multishelled structures. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Monte Carlo criticality calculations accelerated by a growing neutron population

International Nuclear Information System (INIS)

Dufek, Jan; Tuttelberg, Kaur

2016-01-01

Highlights: • Efficiency is significantly improved when population size grows over cycles. • The bias in the fission source is balanced to other errors in the source. • The bias in the fission source decays over the cycle as the population grows. - Abstract: We propose a fission source convergence acceleration method for Monte Carlo criticality simulation. As the efficiency of Monte Carlo criticality simulations is sensitive to the selected neutron population size, the method attempts to achieve the acceleration via on-the-fly control of the neutron population size. The neutron population size is gradually increased over successive criticality cycles so that the fission source bias amounts to a specific fraction of the total error in the cumulative fission source. An optimal setting then gives a reasonably small neutron population size, allowing for an efficient source iteration; at the same time the neutron population size is chosen large enough to ensure a sufficiently small source bias, such that does not limit accuracy of the simulation.

Kinetics of zigzag domain boundaries in gadolinium molybdate

International Nuclear Information System (INIS)

Alekseev, A.N.; Proklov, A.L.; Tikhomirova, N.A.; Shuvalov, L.A.; AN SSSR, Moscow. Inst. Kristallografii)

1987-01-01

Kinetics of zigzag domain boundaries (3DB) in ferroelectric gadolinium molybdate (GMO) crystal was investigated at different amplitude, duration and growth rate of external electric field. The results verify the difference between shifting rates of two 3DB constituents of wedge-shaped systems, growing with field change rate increase

Influential factors of formation kinetics of flocs produced by water treatment coagulants.

Science.gov (United States)

Wu, Chunde; Wang, Lin; Hu, Bing; Ye, Jian

2013-05-01

The growth rate and size of floc formation is of great importance in water treatment especially in coagulation process. The floc formation kinetics and the coagulation efficiency of synthetic water were investigated by using an on-line continuous optical photometric dispersion analyze and the analysis of water quality. Experimental conditions such as alum dosage, pH value for coagulation, stirring intensity and initial turbidity were extensively examined. The photometric dispersion analyze results showed that coagulation of kaolin suspensions with two coagulants (alum and polyaluminium chloride) could be taken as a two-phase process: slow and rapid growth periods. Operating conditions with higher coagulant doses, appropriate pH and average shear rate might be particularly advantageous. The rate of overall floc growth was mainly determined by a combination of hydraulic and water quality conditions such as pH and turbidity. The measurement of zeta potential indicates that polyaluminium chloride exhibited higher charge-neutralizing ability than alum and achieved lower turbidities than alum for equivalent Al dosages. Under the same operating conditions, the alum showed a higher grow rate, but with smaller floc size.

Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

International Nuclear Information System (INIS)

Bang, Junhyeok; Zhang, S. B.; Kim, Youg-Sung; Park, C. H.; Gao, F.

2014-01-01

Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (V Zn  − Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of V Zn compared to V O , more V Zn -abundant clusters are formed than V O -abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (V Zn  − Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to V O donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.

A question of balance: Kinetic balance for electrons and positrons

International Nuclear Information System (INIS)

Dyall, Kenneth G.

2012-01-01

Graphical abstract: Kinetic balance for both electrons and positrons is achieved by applying the correct relation for positive and negative energy states separately and then using the electron and positron eigensolutions from the separate diagonalizations of the Hamiltonian as a dual basis. Highlights: ► Kinetic balance for electrons and positrons is achieved in a dual atomic basis. ► Dual atomic balance alleviates, but does not eliminate, energy prolapse. ► Positron affinities converge quicker with basis set size with dual atomic balance. - Abstract: The kinetic balance criterion used in current relativistic basis set codes is satisfied by the electron solutions of the Dirac equation, but not the positron solutions. A proposal for applying kinetic balance to both sets of solutions is presented. The method is applied along with “normal” kinetic balance to one-electron systems, to investigate its possible relation to prolapse, and to the positron affinity of F − , to investigate the kinetic energy deficiency for positron solutions. The new method reduces but does not eliminate prolapse for energy-optimized basis sets, and provides faster and smoother convergence with basis set size for the positron affinity.

Nonequilibrium electron energy-loss kinetics in metal clusters

CERN Document Server

Guillon, C; Fatti, N D; Vallee, F

2003-01-01

Ultrafast energy exchanges of a non-Fermi electron gas with the lattice are investigated in silver clusters with sizes ranging from 4 to 26 nm using a femtosecond pump-probe technique. The results yield evidence for a cluster-size-dependent slowing down of the short-time energy losses of the electron gas when it is strongly athermal. A constant rate is eventually reached after a few hundred femtoseconds, consistent with the electron gas internal thermalization kinetics, this behaviour reflecting evolution from an individual to a collective electron-lattice type of coupling. The timescale of this transient regime is reduced in small nanoparticles, in agreement with speeding up of the electron-electron interactions with size reduction. The experimental results are in quantitative agreement with numerical simulations of the electron kinetics.

Stiffness Confinement Method with Pseudo Absorption for Spatial Kinetics

International Nuclear Information System (INIS)

Park, Beom Woo; Joo, Han Gyu; Chao, Yungan

2013-01-01

The primary advantage of the SCM is that it is possible to use larger time step sizes. This advantage comes from the fact because the SCM involves the solution of an eigenvalue problem instead of the ordinary form of a fixed source problem. Since using a large time step size is strongly desired in the direct whole core transport calculation for transient problems, we investigate here the SCM for spatial kinetics first with a simple one-dimensional, one-group diffusion equation and propose an improved formulation. The performance of the improved SCM for spatial kinetics is assessed by comparing the SCM solutions with the standard method solutions employing the Crank-Nicholson method with exponential transform. The stiffness confinement method for spatial kinetics was refined with the pseudo absorption term representing the dynamic frequencies. It was verified that the proposed SCM works much better than the Crank-Nicholson method with exponential transform in that time step sizes larger than 20 msec can be using in a super prompt-critical transient involving 1.5$ reactivity insertion

Stiffness Confinement Method with Pseudo Absorption for Spatial Kinetics

Energy Technology Data Exchange (ETDEWEB)

Park, Beom Woo; Joo, Han Gyu [Seoul National Univ., Seoul (Korea, Republic of); Chao, Yungan [Retired in China, Beijing (China)

2013-05-15

The primary advantage of the SCM is that it is possible to use larger time step sizes. This advantage comes from the fact because the SCM involves the solution of an eigenvalue problem instead of the ordinary form of a fixed source problem. Since using a large time step size is strongly desired in the direct whole core transport calculation for transient problems, we investigate here the SCM for spatial kinetics first with a simple one-dimensional, one-group diffusion equation and propose an improved formulation. The performance of the improved SCM for spatial kinetics is assessed by comparing the SCM solutions with the standard method solutions employing the Crank-Nicholson method with exponential transform. The stiffness confinement method for spatial kinetics was refined with the pseudo absorption term representing the dynamic frequencies. It was verified that the proposed SCM works much better than the Crank-Nicholson method with exponential transform in that time step sizes larger than 20 msec can be using in a super prompt-critical transient involving 1.5$ reactivity insertion.

Intrinsic noise analyzer: a software package for the exploration of stochastic biochemical kinetics using the system size expansion.

Science.gov (United States)

Thomas, Philipp; Matuschek, Hannes; Grima, Ramon

2012-01-01

The accepted stochastic descriptions of biochemical dynamics under well-mixed conditions are given by the Chemical Master Equation and the Stochastic Simulation Algorithm, which are equivalent. The latter is a Monte-Carlo method, which, despite enjoying broad availability in a large number of existing software packages, is computationally expensive due to the huge amounts of ensemble averaging required for obtaining accurate statistical information. The former is a set of coupled differential-difference equations for the probability of the system being in any one of the possible mesoscopic states; these equations are typically computationally intractable because of the inherently large state space. Here we introduce the software package intrinsic Noise Analyzer (iNA), which allows for systematic analysis of stochastic biochemical kinetics by means of van Kampen's system size expansion of the Chemical Master Equation. iNA is platform independent and supports the popular SBML format natively. The present implementation is the first to adopt a complementary approach that combines state-of-the-art analysis tools using the computer algebra system Ginac with traditional methods of stochastic simulation. iNA integrates two approximation methods based on the system size expansion, the Linear Noise Approximation and effective mesoscopic rate equations, which to-date have not been available to non-expert users, into an easy-to-use graphical user interface. In particular, the present methods allow for quick approximate analysis of time-dependent mean concentrations, variances, covariances and correlations coefficients, which typically outperforms stochastic simulations. These analytical tools are complemented by automated multi-core stochastic simulations with direct statistical evaluation and visualization. We showcase iNA's performance by using it to explore the stochastic properties of cooperative and non-cooperative enzyme kinetics and a gene network associated with

Intrinsic noise analyzer: a software package for the exploration of stochastic biochemical kinetics using the system size expansion.

Directory of Open Access Journals (Sweden)

Philipp Thomas

Full Text Available The accepted stochastic descriptions of biochemical dynamics under well-mixed conditions are given by the Chemical Master Equation and the Stochastic Simulation Algorithm, which are equivalent. The latter is a Monte-Carlo method, which, despite enjoying broad availability in a large number of existing software packages, is computationally expensive due to the huge amounts of ensemble averaging required for obtaining accurate statistical information. The former is a set of coupled differential-difference equations for the probability of the system being in any one of the possible mesoscopic states; these equations are typically computationally intractable because of the inherently large state space. Here we introduce the software package intrinsic Noise Analyzer (iNA, which allows for systematic analysis of stochastic biochemical kinetics by means of van Kampen's system size expansion of the Chemical Master Equation. iNA is platform independent and supports the popular SBML format natively. The present implementation is the first to adopt a complementary approach that combines state-of-the-art analysis tools using the computer algebra system Ginac with traditional methods of stochastic simulation. iNA integrates two approximation methods based on the system size expansion, the Linear Noise Approximation and effective mesoscopic rate equations, which to-date have not been available to non-expert users, into an easy-to-use graphical user interface. In particular, the present methods allow for quick approximate analysis of time-dependent mean concentrations, variances, covariances and correlations coefficients, which typically outperforms stochastic simulations. These analytical tools are complemented by automated multi-core stochastic simulations with direct statistical evaluation and visualization. We showcase iNA's performance by using it to explore the stochastic properties of cooperative and non-cooperative enzyme kinetics and a gene network

Intrinsic Noise Analyzer: A Software Package for the Exploration of Stochastic Biochemical Kinetics Using the System Size Expansion

Science.gov (United States)

Grima, Ramon

2012-01-01

The accepted stochastic descriptions of biochemical dynamics under well-mixed conditions are given by the Chemical Master Equation and the Stochastic Simulation Algorithm, which are equivalent. The latter is a Monte-Carlo method, which, despite enjoying broad availability in a large number of existing software packages, is computationally expensive due to the huge amounts of ensemble averaging required for obtaining accurate statistical information. The former is a set of coupled differential-difference equations for the probability of the system being in any one of the possible mesoscopic states; these equations are typically computationally intractable because of the inherently large state space. Here we introduce the software package intrinsic Noise Analyzer (iNA), which allows for systematic analysis of stochastic biochemical kinetics by means of van Kampen’s system size expansion of the Chemical Master Equation. iNA is platform independent and supports the popular SBML format natively. The present implementation is the first to adopt a complementary approach that combines state-of-the-art analysis tools using the computer algebra system Ginac with traditional methods of stochastic simulation. iNA integrates two approximation methods based on the system size expansion, the Linear Noise Approximation and effective mesoscopic rate equations, which to-date have not been available to non-expert users, into an easy-to-use graphical user interface. In particular, the present methods allow for quick approximate analysis of time-dependent mean concentrations, variances, covariances and correlations coefficients, which typically outperforms stochastic simulations. These analytical tools are complemented by automated multi-core stochastic simulations with direct statistical evaluation and visualization. We showcase iNA’s performance by using it to explore the stochastic properties of cooperative and non-cooperative enzyme kinetics and a gene network associated with

The influence of temperature on kinetics in solid-state fermentation

NARCIS (Netherlands)

Smits, J.P.; Rinzema, A.; Tramper, J.; Sonsbeek, H.M. van; Hage, J.C.; Kaynak, A.; Knol, W.

1998-01-01

In this paper, correlations between temperature and kinetics of Trichoderma reesei QM9414 growing on wheat bran are described in terms of glucosamine production, oxygen consumption, and carbon dioxide production. Maximum growth temperature (T(max)) being approximately 314 K, is estimated by

CRYSTALLIZATION KINETICS OF AMMONIUM PERCHLORATE IN AN AGITATED VESSEL

Directory of Open Access Journals (Sweden)

Nahidh Kaseer

2013-05-01

Full Text Available 31Overall crystal growth kinetics for ammonium perchlorate in laboratory scale batch  agitated vessel crystallizer have been determined from batch experiments performed in an integral mode. The effects of temperature between 30-60ºC, seed size 0.07, 0.120 and 0.275 mm and stirrer speed 160, 340, and 480 rpm, on the kinetics of crystal growth were investigated. Two different methods, viz. polynomial fitting and initial derivative were used to predict the kinetics expression. In general both methods gave comparable results for growth kinetics estimation. The order of growth process is not more than two. The activation energy for crystal growth of ammonium perchlorate was determined and found  to be equal to 5.8 kJ/ mole.            Finally, the influence of the affecting parameters on the crystal growth rate gives general expression that had an obvious dependence of the growth rate on each variables of concern (temperature, seed size, and stirrer speed .The general overall growth rate expression had shown that super saturation is the most significant variable. While the positive dependence of the stirrer speed demonstrates the importance of the diffusional step in the growth rate model. Moreover, the positive dependence of the seed size demonstrate the importance of the surface integration  step in the growth rate model. All the studied variables tend to suggest that the growth rate characteristics  of ammonium perchlorate from aqueous solution commenced in a batch crystallizer are diffusion kinetic controlled process.

Combined effect of pulse density and grid cell size on predicting and mapping aboveground carbon in fast-growing Eucalyptus forest plantation using airborne LiDAR data.

Science.gov (United States)

Silva, Carlos Alberto; Hudak, Andrew Thomas; Klauberg, Carine; Vierling, Lee Alexandre; Gonzalez-Benecke, Carlos; de Padua Chaves Carvalho, Samuel; Rodriguez, Luiz Carlos Estraviz; Cardil, Adrián

2017-12-01

LiDAR remote sensing is a rapidly evolving technology for quantifying a variety of forest attributes, including aboveground carbon (AGC). Pulse density influences the acquisition cost of LiDAR, and grid cell size influences AGC prediction using plot-based methods; however, little work has evaluated the effects of LiDAR pulse density and cell size for predicting and mapping AGC in fast-growing Eucalyptus forest plantations. The aim of this study was to evaluate the effect of LiDAR pulse density and grid cell size on AGC prediction accuracy at plot and stand-levels using airborne LiDAR and field data. We used the Random Forest (RF) machine learning algorithm to model AGC using LiDAR-derived metrics from LiDAR collections of 5 and 10 pulses m -2 (RF5 and RF10) and grid cell sizes of 5, 10, 15 and 20 m. The results show that LiDAR pulse density of 5 pulses m -2 provides metrics with similar prediction accuracy for AGC as when using a dataset with 10 pulses m -2 in these fast-growing plantations. Relative root mean square errors (RMSEs) for the RF5 and RF10 were 6.14 and 6.01%, respectively. Equivalence tests showed that the predicted AGC from the training and validation models were equivalent to the observed AGC measurements. The grid cell sizes for mapping ranging from 5 to 20 also did not significantly affect the prediction accuracy of AGC at stand level in this system. LiDAR measurements can be used to predict and map AGC across variable-age Eucalyptus plantations with adequate levels of precision and accuracy using 5 pulses m -2 and a grid cell size of 5 m. The promising results for AGC modeling in this study will allow for greater confidence in comparing AGC estimates with varying LiDAR sampling densities for Eucalyptus plantations and assist in decision making towards more cost effective and efficient forest inventory.

Size-dependent mortality rate profiles.

Science.gov (United States)

Roa-Ureta, Ruben H

2016-08-07

Knowledge of mortality rates is crucial to the understanding of population dynamics in populations of free-living fish and invertebrates in marine and freshwater environments, and consequently to sustainable resource management. There is a well developed theory of population dynamics based on age distributions that allow direct estimation of mortality rates. However, for most cases the aging of individuals is difficult or age distributions are not available for other reasons. The body size distribution is a widely available alternative although the theory underlying the formation of its shape is more complicated than in the case of age distributions. A solid theory of the time evolution of a population structured by any physiological variable has been developed in 1960s and 1970s by adapting the Hamilton-Jacobi formulation of classical mechanics, and equations to estimate the body size-distributed mortality profile have been derived for simple cases. Here I extend those results with regards to the size-distributed mortality profile to complex cases of non-stationary populations, individuals growing according to a generalised growth model and seasonally patterned recruitment pulses. I apply resulting methods to two cases in the marine environment, a benthic crustacean population that was growing during the period of observation and whose individuals grow with negative acceleration, and a sea urchin coastal population that is undergoing a stable cycle of two equilibrium points in population size whose individuals grow with varying acceleration that switches sign along the size range. The extension is very general and substantially widens the applicability of the theory. Copyright © 2016 Elsevier Ltd. All rights reserved.

Kinetic compartmental analysis of carnitine metabolism in the dog

International Nuclear Information System (INIS)

Rebouche, C.J.; Engel, A.G.

1983-01-01

This study was undertaken to quantitate the dynamic parameters of carnitine metabolism in the dog. Six mongrel dogs were given intravenous injections of L-[methyl-3H]carnitine and the specific radioactivity of carnitine was followed in plasma and urine for 19-28 days. The data were analyzed by kinetic compartmental analysis. A three-compartment, open-system model [(a) extracellular fluid, (b) cardiac and skeletal muscle, (c) other tissues, particularly liver and kidney] was adopted and kinetic parameters (carnitine flux, pool sizes, kinetic constants) were derived. In four of six dogs the size of the muscle carnitine pool obtained by kinetic compartmental analysis agreed (+/- 5%) with estimates based on measurement of carnitine concentrations in different muscles. In three of six dogs carnitine excretion rates derived from kinetic compartmental analysis agreed (+/- 9%) with experimentally measured values, but in three dogs the rates by kinetic compartmental analysis were significantly higher than the corresponding rates measured directly. Appropriate chromatographic analyses revealed no radioactive metabolites in muscle or urine of any of the dogs. Turnover times for carnitine were (mean +/- SEM): 0.44 +/- 0.05 h for extracellular fluid, 232 +/- 22 h for muscle, and 7.9 +/- 1.1 h for other tissues. The estimated flux of carnitine in muscle was 210 pmol/min/g of tissue. Whole-body turnover time for carnitine was 62.9 +/- 5.6 days (mean +/- SEM). Estimated carnitine biosynthesis ranged from 2.9 to 28 mumol/kg body wt/day. Results of this study indicate that kinetic compartmental analysis may be applicable to study of human carnitine metabolism

Finite size effects in phase transformation kinetics in thin films and surface layers

International Nuclear Information System (INIS)

Trofimov, Vladimir I.; Trofimov, Ilya V.; Kim, Jong-Il

2004-01-01

In studies of phase transformation kinetics in thin films, e.g. crystallization of amorphous films, until recent time is widely used familiar Kolmogorov-Johnson-Mehl-Avrami (KJMA) statistical model of crystallization despite it is applicable only to an infinite medium. In this paper a model of transformation kinetics in thin films based on a concept of the survival probability for randomly chosen point during transformation process is presented. Two model versions: volume induced transformation (VIT) when the second-phase grains nucleate over a whole film volume and surface induced transformation (SIT) when they form on an interface with two nucleation mode: instantaneous nucleation at transformation onset and continuous one during all the process are studied. At VIT-process due to the finite film thickness effects the transformation profile has a maximum in a film middle, whereas that of the grains population reaches a minimum inhere, the grains density is always higher than in a volume material, and the thinner film the slower it transforms. The transformation kinetics in a thin film obeys a generalized KJMA equation with parameters depending on a film thickness and in limiting cases of extremely thin and thick film it reduces to classical KJMA equation for 2D- and 3D-system, respectively

Simulation methods with extended stability for stiff biochemical Kinetics

Directory of Open Access Journals (Sweden)

Rué Pau

2010-08-01

Full Text Available Abstract Background With increasing computer power, simulating the dynamics of complex systems in chemistry and biology is becoming increasingly routine. The modelling of individual reactions in (biochemical systems involves a large number of random events that can be simulated by the stochastic simulation algorithm (SSA. The key quantity is the step size, or waiting time, τ, whose value inversely depends on the size of the propensities of the different channel reactions and which needs to be re-evaluated after every firing event. Such a discrete event simulation may be extremely expensive, in particular for stiff systems where τ can be very short due to the fast kinetics of some of the channel reactions. Several alternative methods have been put forward to increase the integration step size. The so-called τ-leap approach takes a larger step size by allowing all the reactions to fire, from a Poisson or Binomial distribution, within that step. Although the expected value for the different species in the reactive system is maintained with respect to more precise methods, the variance at steady state can suffer from large errors as τ grows. Results In this paper we extend Poisson τ-leap methods to a general class of Runge-Kutta (RK τ-leap methods. We show that with the proper selection of the coefficients, the variance of the extended τ-leap can be well-behaved, leading to significantly larger step sizes. Conclusions The benefit of adapting the extended method to the use of RK frameworks is clear in terms of speed of calculation, as the number of evaluations of the Poisson distribution is still one set per time step, as in the original τ-leap method. The approach paves the way to explore new multiscale methods to simulate (biochemical systems.

Catastrophic Disruption Threshold and Maximum Deflection from Kinetic Impact

Science.gov (United States)

Cheng, A. F.

2017-12-01

The use of a kinetic impactor to deflect an asteroid on a collision course with Earth was described in the NASA Near-Earth Object Survey and Deflection Analysis of Alternatives (2007) as the most mature approach for asteroid deflection and mitigation. The NASA DART mission will demonstrate asteroid deflection by kinetic impact at the Potentially Hazardous Asteroid 65803 Didymos in October, 2022. The kinetic impactor approach is considered to be applicable with warning times of 10 years or more and with hazardous asteroid diameters of 400 m or less. In principle, a larger kinetic impactor bringing greater kinetic energy could cause a larger deflection, but input of excessive kinetic energy will cause catastrophic disruption of the target, leaving possibly large fragments still on collision course with Earth. Thus the catastrophic disruption threshold limits the maximum deflection from a kinetic impactor. An often-cited rule of thumb states that the maximum deflection is 0.1 times the escape velocity before the target will be disrupted. It turns out this rule of thumb does not work well. A comparison to numerical simulation results shows that a similar rule applies in the gravity limit, for large targets more than 300 m, where the maximum deflection is roughly the escape velocity at momentum enhancement factor β=2. In the gravity limit, the rule of thumb corresponds to pure momentum coupling (μ=1/3), but simulations find a slightly different scaling μ=0.43. In the smaller target size range that kinetic impactors would apply to, the catastrophic disruption limit is strength-controlled. A DART-like impactor won't disrupt any target asteroid down to significantly smaller size than the 50 m below which a hazardous object would not penetrate the atmosphere in any case unless it is unusually strong.

Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

Energy Technology Data Exchange (ETDEWEB)

Bang, Junhyeok; Zhang, S. B., E-mail: zhangs9@rpi.edu, E-mail: kimyongsung@gmail.com [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Kim, Youg-Sung, E-mail: zhangs9@rpi.edu, E-mail: kimyongsung@gmail.com [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Department of Nano Science, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Park, C. H. [Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Busan 609-735 (Korea, Republic of); Gao, F. [Pacific Northwest National Laboratory, MS K8-93, P.O. Box 999, Richland, Washington 99352 (United States)

2014-06-23

Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (V{sub Zn} − Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of V{sub Zn} compared to V{sub O}, more V{sub Zn}-abundant clusters are formed than V{sub O}-abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (V{sub Zn} − Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to V{sub O} donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.

Kinetic mixing and the supersymmetric gauge hierarchy

International Nuclear Information System (INIS)

Dienes, K.R.; Kolda, C.; March-Russell, J.

1997-01-01

The most general Lagrangian for a model with two U(1) gauge symmetries contains a renormalizable operator which mixes their gauge kinetic terms. Such kinetic mixing can be generated at arbitrarily high scales but will not be suppressed by large masses. In models whose supersymmetry (SUSY)-breaking hidden sectors contain U(1) gauge factors, we show that such terms will generically arise and communicate SUSY breaking to the visible sector through mixing with hypercharge. In the context of the usual supergravity- or gauge-mediated communication scenarios with D-terms of order the fundamental scale of SUSY breaking, this effect can destabilize the gauge hierarchy. Even in models for which kinetic mixing is suppressed or the D-terms are arranged to be small, this effect is a potentially large correction to the soft scalar masses and therefore introduces a new measurable low-energy parameter. We calculate the size of kinetic mixing both in field theory and in string theory, and argue that appreciable kinetic mixing is a generic feature of string models. We conclude that the possibility of kinetic mixing effects cannot be ignored in model building and in phenomenological studies of the low-energy SUSY spectra. (orig.)

A new mathematical model for coal flotation kinetics

OpenAIRE

Guerrero-Pérez, Juan Sebastián; Barraza-Burgos, Juan Manuel

2017-01-01

Abstract This study describes the development and formulation of a novel mathematical model for coal flotation kinetic. The flotation rate was considered as a function of chemical, operating and petrographic parameters for a global flotation order n. The equation for flotation rate was obtained by dimensional analysis using the Rayleigh method. It shows the dependency of flotation kinetic on operating parameters, such as air velocity and particle size; chemical parameters, such as reagents do...

The kinetics of fossil resin extraction from a flotation concentrate

Energy Technology Data Exchange (ETDEWEB)

Li, L.; Yu, Q.; Miller, J.D. [Univ. of Utah, Salt Lake City, UT (United States)

1995-11-01

The kinetics of fossil resin extraction from a flotation concentrate by heptane were investigated as a function of process variables using monosize particles. Experimental results provide for a better understanding of the refining process and the basis for subsequent design and construction of a continuous resin refining circuit. Based on the effect of process variables (particle size, stirring speed, and temperature) the resin extraction rate appears to be controlled by surface solvation phenomena. The initial extraction rate was found to be inversely proportional to the initial particle size and a kinetic model is being developed to describe the experimental results.

Cluster-cluster aggregation kinetics and primary particle growth of soot nanoparticles in flame by light scattering and numerical simulations.

Science.gov (United States)

di Stasio, Stefano; Konstandopoulos, Athanasios G; Kostoglou, Margaritis

2002-03-01

The agglomeration kinetics of growing soot generated in a diffusion atmospheric flame are here studied in situ by light scattering technique to infer cluster morphology and size (fractal dimension D(f) and radius of gyration R(g)). SEM analysis is used as a standard reference to obtain primary particle size D(P) at different residence times. The number N(P) of primary particles per aggregate and the number concentration n(A) of clusters are evaluated on the basis of the measured angular patterns of the scattered light intensity. The major finding is that the kinetics of the coagulation process that yields to the formation of chain-like aggregates by soot primary particles (size 10 to 40 nm) can be described with a constant coagulation kernel beta(c,exp)=2.37x10(-9) cm3/s (coagulation constant tau(c) approximately = 0.28 ms). This result is in nice accord with the Smoluchowski coagulation equation in the free molecular regime, and, vice versa, it is in contrast with previous studies conducted by invasive (ex situ) techniques, which claimed the evidence in flames of coagulation rates much larger than the kinetic theory predictions. Thereafter, a number of numerical simulations is implemented to compare with the experimental results on primary particle growth rate and on the process of aggregate reshaping that is observed by light scattering at later residence times. The restructuring process is conjectured to occur, for not well understood reasons, as a direct consequence of the atomic rearrangement in the solid phase carbon due to the prolonged residence time within the flame. Thus, on one side, it is shown that the numerical simulations of primary size history compare well with the values of primary size from SEM experiment with a growth rate constant of primary diameter about 1 nm/s. On the other side, the evolution of aggregate morphology is found to be predictable by the numerical simulations when the onset of a first-order "thermal" restructuring mechanism is

Effect of particle size on thermal decomposition of alkali metal picrates

International Nuclear Information System (INIS)

Liu, Rui; Zhang, Tonglai; Yang, Li; Zhou, Zunning

2014-01-01

Graphical abstract: The smaller-sized picrate has greater gas emission than do its larger counterpart. The small size effect reduces the thermal decomposition activation energy, accelerates the reaction rate, and promotes the reaction activity. - Highlights: • Picrates were prepared into three micron sizes by microemulsion synthesis. • Thermal decomposition kinetics and thermodynamics were studied by DPTA and DSC. • Smaller-sized picrate has higher activity and faster reaction rate. • Particle size effect on thermal decomposition kinetics and thermodynamics was revealed. - Abstract: Three alkali metal picrates, KPA, RbPA and CsPA, were prepared into three micron sizes by microemulsion synthesis, and their thermal decomposition behaviors were investigated by DPTA at different temperatures and by DSC at different heating rates. The smaller-sized picrate has greater gas emission and smaller kinetic and thermodynamic parameters than do its larger counterpart. It can be attributed to the decreasing particle size which leads to the high surface energy, the fast mass and heat transfer, and the increasing active sites on the reaction interface. The small size effect and surface effect cause the autocatalysis which reduces the activation energy and promotes the reaction activity. The particle size does not affect the reaction mechanism. However, the picrates with different central alkali metals exhibit different reaction mechanisms even though they are of the same size. This is because the central metal determines the bond energy and consequently affects the stability of picrate

Effect of particle size on thermal decomposition of alkali metal picrates

Energy Technology Data Exchange (ETDEWEB)

Liu, Rui; Zhang, Tonglai, E-mail: ztlbit@bit.edu.cn; Yang, Li; Zhou, Zunning

2014-05-01

Graphical abstract: The smaller-sized picrate has greater gas emission than do its larger counterpart. The small size effect reduces the thermal decomposition activation energy, accelerates the reaction rate, and promotes the reaction activity. - Highlights: • Picrates were prepared into three micron sizes by microemulsion synthesis. • Thermal decomposition kinetics and thermodynamics were studied by DPTA and DSC. • Smaller-sized picrate has higher activity and faster reaction rate. • Particle size effect on thermal decomposition kinetics and thermodynamics was revealed. - Abstract: Three alkali metal picrates, KPA, RbPA and CsPA, were prepared into three micron sizes by microemulsion synthesis, and their thermal decomposition behaviors were investigated by DPTA at different temperatures and by DSC at different heating rates. The smaller-sized picrate has greater gas emission and smaller kinetic and thermodynamic parameters than do its larger counterpart. It can be attributed to the decreasing particle size which leads to the high surface energy, the fast mass and heat transfer, and the increasing active sites on the reaction interface. The small size effect and surface effect cause the autocatalysis which reduces the activation energy and promotes the reaction activity. The particle size does not affect the reaction mechanism. However, the picrates with different central alkali metals exhibit different reaction mechanisms even though they are of the same size. This is because the central metal determines the bond energy and consequently affects the stability of picrate.

Land use/land cover and scale influences on in-stream nitrogen uptake kinetics

Science.gov (United States)

Covino, Tim; McGlynn, Brian; McNamara, Rebecca

2012-06-01

Land use/land cover change often leads to increased nutrient loading to streams; however, its influence on stream ecosystem nutrient transport remains poorly understood. Given the deleterious impacts elevated nutrient loading can have on aquatic ecosystems, it is imperative to improve understanding of nutrient retention capacities across stream scales and watershed development gradients. We performed 17 nutrient addition experiments on six streams across the West Fork Gallatin Watershed, Montana, USA, to quantify nitrogen uptake kinetics and retention dynamics across stream sizes (first to fourth order) and along a watershed development gradient. We observed that stream nitrogen (N) uptake kinetics and spiraling parameters varied across streams of different development intensity and scale. In more developed watersheds we observed a fertilization affect. This fertilization affect was evident as increased ash-free dry mass, chlorophylla, and ambient and maximum uptake rates in developed as compared to undeveloped streams. Ash-free dry mass, chlorophylla, and the number of structures in a subwatershed were significantly correlated to nutrient spiraling and kinetic parameters, while ambient and average annual N concentrations were not. Additionally, increased maximum uptake capacities in developed streams contributed to low in-stream nutrient concentrations during the growing season, and helped maintain watershed export at low levels during base flow. Our results indicate that land use/land cover change can enhance in-stream uptake of limiting nutrients and highlight the need for improved understanding of the watershed dynamics that control nutrient export across scales and development intensities for mitigation and protection of aquatic ecosystems.

Investigation of nucleation kinetics in H2SO4 vapor through modeling of gas phase kinetics coupled with particle dynamics

Science.gov (United States)

Carlsson, Philip T. M.; Zeuch, Thomas

2018-03-01

We have developed a new model utilizing our existing kinetic gas phase models to simulate experimental particle size distributions emerging in dry supersaturated H2SO4 vapor homogeneously produced by rapid oxidation of SO2 through stabilized Criegee-Intermediates from 2-butene ozonolysis. We use a sectional method for simulating the particle dynamics. The particle treatment in the model is based on first principles and takes into account the transition from the kinetic to the diffusion-limited regime. It captures the temporal evolution of size distributions at the end of the ozonolysis experiment well, noting a slight underrepresentation of coagulation effects for larger particle sizes. The model correctly predicts the shape and the modes of the experimentally observed particle size distributions. The predicted modes show an extremely high sensitivity to the H2SO4 evaporation rates of the initially formed H2SO4 clusters (dimer to pentamer), which were arbitrarily restricted to decrease exponentially with increasing cluster size. In future, the analysis presented in this work can be extended to allow a direct validation of quantum chemically predicted stabilities of small H2SO4 clusters, which are believed to initiate a significant fraction of atmospheric new particle formation events. We discuss the prospects and possible limitations of the here presented approach.

Twin-domain size and bulk oxygen in-diffusion kinetics of YBa 2Cu 3O 6+x studied by neutron powder diffraction and gas volumetry

Science.gov (United States)

Poulsen, H. F.; Andersen, N. H.; Lebech, B.

1991-02-01

We report experimental results of twin-domain size and bulk oxygen in-diffusion kinetics of YBa 2Cu 3O 6+ x, which supplement a previous and simultaneous study of the structural phase diagram and oxygen equilibrium partial pressure. Analysis of neutron powder diffraction peak broadening show features which are identified to result from temperature independent twin-domain formation in to different orthorhombic phases with domain sizes and 250 and 350Å, respectively. The oxygen in-diffusion flow shows simple relaxation type behaviour J=J 0 exp( {-t}/{τ}) despite a rather broad particle size distribution. At higher temperatures, τ is activated with activation energies 0.55 and 0.25 eV in the tetragonal and orthorhombic phases, respectively. Comparison between twin-domain sizes and bulk oxygen in-diffusion time constants indicates that the twin-domain boundaries may contribute to the effective bulk oxygen in-diffusion. All our results may be interpreted in terms of the 2D ASYNNNI model description of the oxygen basal plane ordering, and they suggest that recent first principles interaction parameters should be modified.

A homeostatic clock sets daughter centriole size in flies

Science.gov (United States)

Aydogan, Mustafa G.; Steinacker, Thomas L.; Novak, Zsofia A.; Baumbach, Janina; Muschalik, Nadine

2018-01-01

Centrioles are highly structured organelles whose size is remarkably consistent within any given cell type. New centrioles are born when Polo-like kinase 4 (Plk4) recruits Ana2/STIL and Sas-6 to the side of an existing “mother” centriole. These two proteins then assemble into a cartwheel, which grows outwards to form the structural core of a new daughter. Here, we show that in early Drosophila melanogaster embryos, daughter centrioles grow at a linear rate during early S-phase and abruptly stop growing when they reach their correct size in mid- to late S-phase. Unexpectedly, the cartwheel grows from its proximal end, and Plk4 determines both the rate and period of centriole growth: the more active the centriolar Plk4, the faster centrioles grow, but the faster centriolar Plk4 is inactivated and growth ceases. Thus, Plk4 functions as a homeostatic clock, establishing an inverse relationship between growth rate and period to ensure that daughter centrioles grow to the correct size. PMID:29500190

Dust Effects on Nucleation Kinetics and Nanoparticle Product Size Distributions: Illustrative Case Study of a Prototype Ir(0)n Transition-Metal Nanoparticle Formation System.

Science.gov (United States)

Özkar, Saim; Finke, Richard G

2017-07-05

The question is addressed if dust is kinetically important in the nucleation and growth of Ir(0) n nanoparticles formed from [Bu 4 N] 5 Na 3 (1,5-COD)Ir I ·P 2 W 15 Nb 3 O 62 (hereafter [(COD)Ir·POM] 8- ), reduced by H 2 in propylene carbonate solvent. Following a concise review of the (often-neglected) literature addressing dust in nucleation phenomena dating back to the late 1800s, the nucleation and growth kinetics of the [(COD)Ir·POM] 8- precatalyst system are examined for the effects of 0.2 μm microfiltration of the solvent and precatalyst solution, of rinsing the glassware with that microfiltered solvent, of silanizing the glass reaction vessel, for the addition of nucleation apparent rate "constant" k 1obs(bimol) is shown to be slowed by a factor of ∼5 to ∼7.6, depending on the precise experiment and its conditions, just by the filtration of the precatalyst solution using a 0.20 μm filter and rinsing the glassware surface with 0.20 μm filtered propylene carbonate solvent; (ii) that simply employing a 0.20 μm filtration step narrows the size distribution of the resulting Ir(0) n nanoparticles by a factor of 2.4 from ±19 to ±8%, a remarkable result; (iii) that the narrower size distribution can be accounted for by the slowed nucleation rate constant, k 1obs(bimol) , and by the unchanged autocatalytic growth rate constant, k 2obs(bimol) , that is, by the increased ratio of k 2obs(bimol) /k 1obs(bimol) that further separates nucleation from growth in time for filtered vs unfiltered solutions; and (iv) that five lines of evidence indicate that the filterable component of the solution, which has nucleation rate-enhancing and size-dispersion broadening effects, is dust.

Particle growth kinetics over the Amazon rainforest

Science.gov (United States)

Pinterich, T.; Andreae, M. O.; Artaxo, P.; Kuang, C.; Longo, K.; Machado, L.; Manzi, A. O.; Martin, S. T.; Mei, F.; Pöhlker, C.; Pöhlker, M. L.; Poeschl, U.; Shilling, J. E.; Shiraiwa, M.; Tomlinson, J. M.; Zaveri, R. A.; Wang, J.

2016-12-01

Aerosol particles larger than 100 nm play a key role in global climate by acting as cloud condensation nuclei (CCN). Most of these particles, originated from new particle formation or directly emitted into the atmospheric, are initially too small to serve as CCN. These small particles grow to CCN size mainly through condensation of secondary species. In one extreme, the growth is dictated by kinetic condensation of very low-volatility compounds, favoring the growth of the smallest particles; in the other extreme, the process is driven by Raoult's law-based equilibrium partitioning of semi-volatile organic compound, favoring the growth of larger particles. These two mechanisms can lead to very different production rates of CCN. The growth of particles depends on a number of parameters, including the volatility of condensing species, particle phase, and diffusivity inside the particles, and this process is not well understood in part due to lack of ambient data. Here we examine atmospheric particle growth using high-resolution size distributions measured onboard the DOE G-1 aircraft during GoAmazon campaign, which took place from January 2014 to December 2015 near Manaus, Brazil, a city surrounded by natural forest for over 1000 km in every direction. City plumes are clearly identified by the strong enhancement of nucleation and Aitken mode particle concentrations over the clean background. As the plume traveled downwind, particle growth was observed, and is attributed to condensation of secondary species and coagulation (Fig.1). Observed aerosol growth is modeled using MOSAIC (Model for Simulating Aerosol Interactions and Chemistry), which dynamically partitions multiple compounds to all particle size bins by taking into account compound volatility, gas-phase diffusion, interfacial mass accommodation, particle-phase diffusion, and particle-phase reaction. The results from both wet and dry seasons will be discussed.

Relativistic distances, sizes, lengths

International Nuclear Information System (INIS)

Strel'tsov, V.N.

1992-01-01

Such notion as light or retarded distance, field size, formation way, visible size of a body, relativistic or radar length and wave length of light from a moving atom are considered. The relation between these notions is cleared up, their classification is given. It is stressed that the formation way is defined by the field size of a moving particle. In the case of the electromagnetic field, longitudinal sizes increase proportionally γ 2 with growing charge velocity (γ is the Lorentz-factor). 18 refs

Crystallization kinetics in Si-1 at%Sn during rapid solidification in undercooled melt

Science.gov (United States)

Kuribayashi, K.; Ozawa, S.; Nagayama, K.; Inatomi, Y.

2017-06-01

In order to elucidate the cause of the morphological transition of crystals growing in an undercooled melt of semiconducting materials, we carried out the containerless solidification of undoped Si and Si-1 at%Sn using a CO2 laser-equipped electromagnetic levitator (EML). The crystallization of these materials was successfully achieved under controlled undercooling. The relation between the shape of growing crystals and the degree of undercooling in Si-1 at%Sn was similar to that in undoped Si; that is, plate-like needle crystals were observed at low undercooling, whereas at medium and high undercooling the shape of growing crystals changed to massive dendrites. The grain-size of as-solidified samples of Si-1 at%Sn was remarkably small compared with that of undoped Si. The surface morphologies of samples solidified by dropping the melt onto a chill plate of mirror-polished silicon consisted of typical twin-related dendrites. On the other hand, samples that were dropped from the undercooled state consisted of twin-free dendrites. The nucleation rate of two-dimensional nuclei calculated on the basis of two mechanisms, which are the twin-plane re-entrant edge mechanism and the twin-free mechanism, suggested that the morphological transition to twin-free dendrites from twin-related dendrites occurs when the degree of undercooling becomes larger than the critical value. These results indicate that the cause of the morphological transition of Si growing in the undercooled melt is not the roughening transition of the crystal-melt interface but the transition of the nucleation kinetics to the twin-free mechanism from the twin-related mechanism.

Kinetics of small particle activation in supersaturated vapors

Energy Technology Data Exchange (ETDEWEB)

McGraw, R.; Wang, J.

2010-08-29

We examine the nucleated (with barrier) activation of perfectly wetting (zero contact angle) particles ranging from bulk size down to one nanometer. Thermodynamic properties of the particles, coated with liquid layers of varying thickness and surrounded by vapor, are analyzed. Nano-size particles are predicted to activate at relative humidity below the Kelvin curve on crossing a nucleation barrier, located at a critical liquid layer thickness such that the total particle size (core + liquid layer) equals the Kelvin radius (Fig. 1). This barrier vanishes precisely as the critical layer thickness approaches the thin layer limit and the Kelvin radius equals the radius of the particle itself. These considerations are similar to those included in Fletcher's theory (Fletcher, 1958) however the present analysis differs in several important respects. Firstly, where Fletcher used the classical prefactor-exponent form for the nucleation rate, requiring separate estimation of the kinetic prefactor, we solve a diffusion-drift equation that is equivalent to including the full Becker-Doering (BD) multi-state kinetics of condensation/evaporation along the growth coordinate. We also determine the mean first passage time (MFPT) for barrier crossing (Wedekind et al., 2007), which is shown to provide a generalization of BD nucleation kinetics especially useful for barrier heights that are considerably lower than those typically encountered in homogeneous vapor-liquid nucleation, and make explicit comparisons between the MFPT and BD kinetic models. Barrier heights for heterogeneous nucleation are computed by a thermo-dynamic area construction introduced recently to model deliquescence and efflorescence of small particles (McGraw and Lewis, 2009). In addition to providing a graphical representation of the activation process that offers new insights, the area construction provides a molecular approach that avoids explicit use of the interfacial tension. Typical barrier profiles for

Phase transformation kinetics of Voronoi cells in space tessellation governed by the Kolmogorov–Johnson–Mehl–Avrami model

Energy Technology Data Exchange (ETDEWEB)

Tomellini, Massimo, E-mail: tomellini@uniroma2.it

2017-03-26

On the basis of the Kolmogorov–Johnson–Mehl–Avrami (KJMA) method for space tessellation the kinetics of Voronoi cell filling, by central grain growth, has been studied as a function of the cell size. This is done by solving an integral equation for which a class of solutions is obtained in closed form, where the cell-size probability density is the Gamma distribution function. The computation gives the time evolution of the mean grain size, as a function of cell volume, which is further employed for describing the grain-size probability density function. The present approach is applied to determine, analytically, the exact grain-size distribution function in 1D and the size distributions in 2D and 3D through approximation. - Highlights: • The kinetics of cell filling is determined for Poisson–Voronoi tessellation in dD. • The kinetics is obtained in closed form by solving an integral equation. • Connection between the evolution of the mean grain and the size distribution is studied. • The exact grain-size distribution function is determined, analytically, in 1D.

Influence of growing conditions on heavy metals content in cultivated mushrooms

International Nuclear Information System (INIS)

Kmitene, L.

1997-01-01

The aim of the research was to investigate the influence of growing terms, microclimate conditions and growing medium on the mushroom harvest and quality. Champignons were grown according to the Polish technology. Pleurotus ostreatus was grown in perforate sacks using chopped wheat straw. Mycelium was sowed in different terms. It was established that the harvest of mushrooms, especially their quality, depends not only on growing conditions, but also on the kind of mushrooms, composte quality, mushroom size (diameter of cap), picking of mushrooms, storage time and other conditions. The technology of mushroom growing will be developed after studying all the factors determining the content of heavy metals and radiation in mushrooms

Mutant number distribution in an exponentially growing population

Science.gov (United States)

Keller, Peter; Antal, Tibor

2015-01-01

We present an explicit solution to a classic model of cell-population growth introduced by Luria and Delbrück (1943 Genetics 28 491-511) 70 years ago to study the emergence of mutations in bacterial populations. In this model a wild-type population is assumed to grow exponentially in a deterministic fashion. Proportional to the wild-type population size, mutants arrive randomly and initiate new sub-populations of mutants that grow stochastically according to a supercritical birth and death process. We give an exact expression for the generating function of the total number of mutants at a given wild-type population size. We present a simple expression for the probability of finding no mutants, and a recursion formula for the probability of finding a given number of mutants. In the ‘large population-small mutation’ limit we recover recent results of Kessler and Levine (2014 J. Stat. Phys. doi:10.1007/s10955-014-1143-3) for a fully stochastic version of the process.

Estimation of kinetic and thermodynamic ligand-binding parameters using computational strategies.

Science.gov (United States)

Deganutti, Giuseppe; Moro, Stefano

2017-04-01

Kinetic and thermodynamic ligand-protein binding parameters are gaining growing importance as key information to consider in drug discovery. The determination of the molecular structures, using particularly x-ray and NMR techniques, is crucial for understanding how a ligand recognizes its target in the final binding complex. However, for a better understanding of the recognition processes, experimental studies of ligand-protein interactions are needed. Even though several techniques can be used to investigate both thermodynamic and kinetic profiles for a ligand-protein complex, these procedures are very often laborious, time consuming and expensive. In the last 10 years, computational approaches have enormous potential in providing insights into each of the above effects and in parsing their contributions to the changes in both kinetic and thermodynamic binding parameters. The main purpose of this review is to summarize the state of the art of computational strategies for estimating the kinetic and thermodynamic parameters of a ligand-protein binding.

Kinetic models of controllable pore growth of anodic aluminum oxide membrane

Science.gov (United States)

Huang, Yan; Zeng, Hong-yan; Zhao, Ce; Qu, Ye-qing; Zhang, Pin

2012-06-01

An anodized Al2O3 (AAO) membrane with apertures about 72 nm in diameter was prepared by two-step anodic oxidation. The appearance and pore arrangement of the AAO membrane were characterized by energy dispersive x-ray spectroscopy and scanning electron microscopy. It was confirmed that the pores with high pore aspect ratio were parallel, well-ordered, and uniform. The kinetics of pores growth in the AAO membrane was derived, and the kinetic models showed that pores stopped developing when the pressure ( σ) trended to equal the surface tension at the end of anodic oxidation. During pore expansion, the effects of the oxalic acid concentration and expansion time on the pore size were investigated, and the kinetic behaviors were explained with two kinetic models derived in this study. They showed that the pore size increased with extended time ( r= G· t+ G'), but decreased with increased concentration ( r = - K·ln c- K') through the derived mathematic formula. Also, the values of G, G', K, and K' were derived from our experimental data.

Uncertainty quantification for hyperbolic and kinetic equations

CERN Document Server

Pareschi, Lorenzo

2017-01-01

This book explores recent advances in uncertainty quantification for hyperbolic, kinetic, and related problems. The contributions address a range of different aspects, including: polynomial chaos expansions, perturbation methods, multi-level Monte Carlo methods, importance sampling, and moment methods. The interest in these topics is rapidly growing, as their applications have now expanded to many areas in engineering, physics, biology and the social sciences. Accordingly, the book provides the scientific community with a topical overview of the latest research efforts.

Growth kinetics of metastable (331) nanofacet on Au and Pt(110) surfaces

International Nuclear Information System (INIS)

Ndongmouo, U.T.; Houngninou, E.; Hontinfinde, F.

2006-12-01

A theoretical epitaxial growth model with realistic barriers for surface diffusion is investigated by means of kinetic Monte Carlo simulations to study the growth modes of metastable (331) nanofacets on Au and Pt(110) surfaces. The results show that under experimental atomic fluxes, the (331) nanofacets grow by 2D nucleation at low temperature in the submonolayer regime. A metastable growth phase diagram that can be useful to experimentalists is presented and looks similar to the one found for the stationary growth of the bcc(001) surface in the kinetic 6-vertex model. (author)

Molecular size evolution of oligomers in organic aerosols collected in urban atmospheres and generated in a smog chamber.

Science.gov (United States)

Kalberer, Markus; Sax, Mirjam; Samburova, Vera

2006-10-01

Only a minor fraction of the total organic aerosol mass can be resolved on a molecular level. High molecular weight compounds in organic aerosols have recently gained much attention because this class of compound potentially explains a major fraction of the unexplained organic aerosol mass. These compounds have been identified with different mass spectrometric methods, and compounds with molecular masses up to 1000 Da are found in secondary organic aerosols (SOA) generated from aromatic and terpene precursors in smog chamber experiments. Here, we apply matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to SOA particles from two biogenic precursors, alpha-pinene and isoprene. Similar oligomer patterns are found in these two SOA systems, but also in SOA from trimethylbenzene, an anthropogenic SOA precursor. However, different maxima molecular sizes were measured for these three SOA systems. While oligomers in alpha-pinene and isoprene have sizes mostly below 600-700 Da, they grow up to about 1000 Da in trimethylbenzene-SOA. The final molecular size of the oligomers is reached early during the particle aging process, whereas other particle properties related to aging, such as the overall acid concentration or the oligomer concentration, increase continuously over a much longer time scale. This kinetic behavior of the oligomer molecular size growth can be explained by a chain growth kinetic regime. Similar oligomer mass patterns were measured in aqueous extracts of ambient aerosol samples (measured with the same technique). Distinct differences between summer and winter were observed. In summer a few single mass peaks were measured with much higher intensity than in winter, pointing to a possible difference in the formation processes of these compounds in winter and summer.

The Comparative Kinetics of Ca, Sr, and Ra within the Yellow-Bellied Turtle. Trachemys scripta, as influenced by Dietary Calcium, Season, Age and Sex of the Animal

International Nuclear Information System (INIS)

Hinton, T.G.; Pinder, J.E.; Hinton, T.G.; Whicker, F.W.

1988-01-01

Most of the data on assimilation and retention of radionuclides by animals is from homeothermic mammals. The assimilation and retention of radionuclides have only recently been investigated in reptiles. In both groups, interesting conjectures can be made concerning the kinetics of radionuclides in relation to temperature and to the abundance of the radioisotope chemical analogue. Temperature plays an important role in the metabolism and behavior of ectotherms and can thus affect radionuclide kinetics. The abundance of chemical analogues has been shown to decrease the assimilation and retention of radionuclides in homeotherms but such relationships have not been well documented in vertebrate ectotherms. The kinetics of Ca, Sr, and Ra in the freshwater turtle, Trachemys scripta is studied. It is ectothermic and 40% of its wet mass is comprised of a calcareous shell. What role does the shell play in calcium homeostasis, and how do the kinetics of analogous radioisotopes behave in such a calcium-rich system. T. scripta have a long life span of 20-30 years. They demonstrate reserved sexual dimorphism with females being larger, and they grow continuously, which results in large ranges in adult body size. Much of the winter is spent in hibernation. The spring is an active period related to mating, yet one in which little food is consumed. How do such oscillating changes in metabolic rate, as well as differences in body size, affect radionuclide elimination. To address such questions, radionuclide assimilation and retention as influenced by the amount of stable calcium in the turtle diet, season of the year and age and sex of the animal, are examined. The results demonstrate the complex nature of radionuclide kinetics within ectotherms and give insights into the basic biology of turtles

Size, density and composition of cell-mineral aggregates formed during anoxygenic phototrophic Fe(II) oxidation: Impact on modern and ancient environments

DEFF Research Database (Denmark)

Posth, Nicole R.; Huelin, Sonia; Konhauser, Kurt O.

2010-01-01

Cell-Fe(III) mineral aggregates produced by anoxygenic Fe(II)-oxidizing photoautotrophic microorganisms (photoferrotrophs) may be influential in the modern Fe cycle and were likely an integral part of ancient biogeochemical cycles on early Earth. While studies have focused on the environmental...... conditions under which modern photoferrotrophs grow and the kinetics, physiology and mechanism of Fe(II) oxidation, no systematic analyses of the physico-chemical characteristics of those aggregates, such as shape, size, density and chemical composition, have as yet been conducted. Herein, experimental...... results show most aggregates are bulbous or ragged in shape, with an average particle size of 10-40??m, and densities that typically range between 2.0 and 2.4g/cm 3; the cell fraction of the aggregates increased and their density decreased with initial Fe(II) concentration. The mineralogy of the ferric...

Kinetic theory of nonlinear transport phenomena in complex plasmas

International Nuclear Information System (INIS)

Mishra, S. K.; Sodha, M. S.

2013-01-01

In contrast to the prevalent use of the phenomenological theory of transport phenomena, a number of transport properties of complex plasmas have been evaluated by using appropriate expressions, available from the kinetic theory, which are based on Boltzmann's transfer equation; in particular, the energy dependence of the electron collision frequency has been taken into account. Following the recent trend, the number and energy balance of all the constituents of the complex plasma and the charge balance on the particles is accounted for; the Ohmic loss has also been included in the energy balance of the electrons. The charging kinetics for the complex plasma comprising of uniformly dispersed dust particles, characterized by (i) uniform size and (ii) the Mathis, Rumpl, and Nordsieck power law of size distribution has been developed. Using appropriate expressions for the transport parameters based on the kinetic theory, the system of equations has been solved to investigate the parametric dependence of the complex plasma transport properties on the applied electric field and other plasma parameters; the results are graphically illustrated.

Fully kinetic simulations of megajoule-scale dense plasma focus

Energy Technology Data Exchange (ETDEWEB)

Schmidt, A.; Link, A.; Tang, V.; Halvorson, C.; May, M. [Lawrence Livermore National Laboratory, Livermore California 94550 (United States); Welch, D. [Voss Scientific, LLC, Albuquerque, New Mexico 87108 (United States); Meehan, B. T.; Hagen, E. C. [National Security Technologies, LLC, Las Vegas, Nevada 89030 (United States)

2014-10-15

Dense plasma focus (DPF) Z-pinch devices are sources of copious high energy electrons and ions, x-rays, and neutrons. Megajoule-scale DPFs can generate 10{sup 12} neutrons per pulse in deuterium gas through a combination of thermonuclear and beam-target fusion. However, the details of the neutron production are not fully understood and past optimization efforts of these devices have been largely empirical. Previously, we reported on the first fully kinetic simulations of a kilojoule-scale DPF and demonstrated that both kinetic ions and kinetic electrons are needed to reproduce experimentally observed features, such as charged-particle beam formation and anomalous resistivity. Here, we present the first fully kinetic simulation of a MegaJoule DPF, with predicted ion and neutron spectra, neutron anisotropy, neutron spot size, and time history of neutron production. The total yield predicted by the simulation is in agreement with measured values, validating the kinetic model in a second energy regime.

Marijuana growing operations in British Columbia revisited, 1997-2003

Energy Technology Data Exchange (ETDEWEB)

Plecas, D.; Malm, A.; Kinney, B. [University College of the Fraser Valley, Abbotsford, BC (Canada). Dept. of Criminology and Criminal Justice]|[University College of the Fraser Valley, Abbotsford, BC (Canada). International Centre for Urban Research Studies

2005-03-01

The results of a comprehensive study of marihuana cultivation in British Columbia were presented. This report describes the incidents of marihuana grow operations coming to the attention of the police; the characteristics of marihuana growing operations; the suspects involved; the actions taken by the police and courts; and penalty. The study confirms that these operations which are dispersed throughout the province are increasing in both size and sophistication. The average number of kilograms of harvested marihuana seized per grow operation tripled from 1997 to 2003. In addition, the number of high intensity lights seized per operation also grew, leading to an associated increase in the average amount of electricity theft per operation. About 1 in 5 grow operations involved hydro theft. The average cost associated with hydro theft per operation was about $2,880 in 1997 and $3,740 in 2003. In 2003, it is estimated that growers stole more than $3,200,000 from BC Hydro. In addition to electricity by-passes, 15 per cent of indoor grow operations contained hazards such as weapons, explosives, and other drugs. 25 tabs., 34 figs.

Plasma kinetics of 14C-uric acid in bulls

International Nuclear Information System (INIS)

Cetinkaya, N.

1999-01-01

Plasma kinetics of uric acid were followed by 14C labelled uric acid to measure the effects of feed intake upon kinetic parameters. Two bulls (average L W 346±79 kg) were given an intravenous administration of a tracer (8-14C-uric acid, 250μCi/50 ml) by single injection via a jugular catheter. Animals were fed a mixed diet containing 30% wheat straw and 70% compounded feed as 95 and 60 % of the voluntary intake. Voluntary intakes were 8 kg/d as fed for two bulls. Blood samples, were collected at 0, 0.5,1, 2, 3, 4, 6, 8, 12, 16, 24 and 28 h after tracer administration. Fractional rates of clearance from the blood and pool size of compartments in the blood were estimated using plasma 8-14C-counts, following the method proposed by Chen and Franklin. The mean values of fractional rates (K 2,1 , K 1,2 ) and compartments pool size (V 1 , V 2 ) and the total pool size of compartments I and 2 at 60% and 95% feeding level were 1.97 and 1.44, 1.06 and 0.78; 76.9 L and 94.5 L, 137.01 L and 163.51 L; 214.0 L and 250.3 L respectively. Plasma kinetic parameters of 14C-uric acid were not affected at different feed intakes

Asymptotic size determines species abundance in the marine size spectrum

DEFF Research Database (Denmark)

Andersen, Ken Haste; Beyer, Jan

2006-01-01

The majority of higher organisms in the marine environment display indeterminate growth; that is, they continue to grow throughout their life, limited by an asymptotic size. We derive the abundance of species as a function of their asymptotic size. The derivation is based on size-spectrum theory......, where population structure is derived from physiology and simple arguments regarding the predator-prey interaction. Using a hypothesis of constant satiation, which states that the average degree of satiation is independent of the size of an organism, the number of individuals with a given size is found...... to be proportional to the weight raised to the power -2.05, independent of the predator/prey size ratio. This is the first time the spectrum exponent has been derived solely on the basis of processes at the individual level. The theory furthermore predicts that the parameters in the von Bertalanffy growth function...

Competing role of catalysis-coagulation and catalysis-fragmentation in kinetic aggregation behaviours

International Nuclear Information System (INIS)

Li Xiao-Dong; Lin Zhen-Quan; Song Mei-Xia; Ke Jian-Hong

2010-01-01

We propose a kinetic aggregation model where species A aggregates evolve by the catalysis-coagulation and the catalysis-fragmentation, while the catalyst aggregates of the same species B or C perform self-coagulation processes. By means of the generalized Smoluchowski rate equation based on the mean-field assumption, we study the kinetic behaviours of the system with the catalysis-coagulation rate kernel K(i,j;l) ∝ l ν and the catalysis-fragmentation rate kernel F(i,j;l) ∝ l μ , where l is the size of the catalyst aggregate, and ν and μ are two parameters reflecting the dependence of the catalysis reaction on the size of the catalyst aggregate. The relation between the values of parameters ν and μ reflects the competing roles between the two catalysis processes in the kinetic evolution of species A. It is found that the competing roles of the catalysis-coagulation and catalysis-fragmentation in the kinetic aggregation behaviours are not determined simply by the relation between the two parameters ν and μ, but also depend on the values of these two parameters. When ν > μ and ν ≥ 0, the kinetic evolution of species A is dominated by the catalysis-coagulation and its aggregate size distribution a k (t) obeys the conventional or generalized scaling law; when ν k (t) approaches the scale-free form; and in other cases, a balance is established between the two competing processes at large times and a k (t) obeys a modified scaling law. (cross-disciplinary physics and related areas of science and technology)

Thermodynamics versus Kinetics Dichotomy in the Linear Self-Assembly of Mixed Nanoblocks.

Science.gov (United States)

Ruiz, L; Keten, S

2014-06-05

We report classical and replica exchange molecular dynamics simulations that establish the mechanisms underpinning the growth kinetics of a binary mix of nanorings that form striped nanotubes via self-assembly. A step-growth coalescence model captures the growth process of the nanotubes, which suggests that high aspect ratio nanostructures can grow by obeying the universal laws of self-similar coarsening, contrary to systems that grow through nucleation and elongation. Notably, striped patterns do not depend on specific growth mechanisms, but are governed by tempering conditions that control the likelihood of depropagation and fragmentation.

Mutant number distribution in an exponentially growing population

International Nuclear Information System (INIS)

Keller, Peter; Antal, Tibor

2015-01-01

We present an explicit solution to a classic model of cell-population growth introduced by Luria and Delbrück (1943 Genetics 28 491–511) 70 years ago to study the emergence of mutations in bacterial populations. In this model a wild-type population is assumed to grow exponentially in a deterministic fashion. Proportional to the wild-type population size, mutants arrive randomly and initiate new sub-populations of mutants that grow stochastically according to a supercritical birth and death process. We give an exact expression for the generating function of the total number of mutants at a given wild-type population size. We present a simple expression for the probability of finding no mutants, and a recursion formula for the probability of finding a given number of mutants. In the ‘large population-small mutation’ limit we recover recent results of Kessler and Levine (2014 J. Stat. Phys. doi:10.1007/s10955-014-1143-3) for a fully stochastic version of the process. (paper)

Reactive extraction of lactic acid using alamine 336 in MIBK : equilibria and kinetics

NARCIS (Netherlands)

Wasewar, Kailas L.; Heesink, A. Bert M.; Versteeg, Geert F.; Pangarkar, Vishwas G.

2002-01-01

Lactic acid is an important commercial product and extracting it out of aqueous solution is a growing requirement in fermentation based industries and recovery from waste streams. The design of an amine extraction process requires (i) equilibrium and (ii) kinetic data for the acid–amine (solvent)

Structural stability of nano-sized clusters

NARCIS (Netherlands)

De Hosson, JTM; Palasantzas, G; Vystavel, T; Koch, S; Ovidko,; Pande, CS; Krishnamoorti, R; Lavernia, E; Skandan, G

2004-01-01

This contribution presents challenges to control the microstructure in nano-structured materials via a relatively new approach, i.e. using a so-called nanocluster source. An important aspect is that the cluster size distribution is monodisperse and that the kinetic energy of the clusters during

Cluster growing process and a sequence of magic numbers

DEFF Research Database (Denmark)

Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

2003-01-01

demonstrate that in this way all known global minimum structures of the Lennard-Jones (LJ) clusters can be found. Our method provides an efficient tool for the calculation and analysis of atomic cluster structure. With its use we justify the magic number sequence for the clusters of noble gas atoms......We present a new theoretical framework for modeling the cluster growing process. Starting from the initial tetrahedral cluster configuration, adding new atoms to the system, and absorbing its energy at each step, we find cluster growing paths up to the cluster sizes of more than 100 atoms. We...

Pore geometry of ceramic device: The key factor of drug release kinetics

Directory of Open Access Journals (Sweden)

Čolović B.

2013-01-01

Full Text Available Release kinetics of tigecycline, a potential antibiotic in treatment of osteomyelitis, from calcium hydroxyapatite (CHA, as one of the most important ceramic materials in bone tissue engineering, was investigated in this study. Tigecycline, in solid state, was mixed with CHA powder and the obtained mixture was compressed into tablets using two different pressures. These tablets were immersed in a phosphate-buffered saline solution and tigecycline release was measured by a UV-VIS spectrophotometer. The total release time was 5 or 28 days, depending on the pressure applied during compression. It was shown that there is a close relationship between pore sizes and drug release rate. The drug release kinetics was interpreted on the base of pore sizes and pore size distribution. [Projekat Ministarstva nauke Republike Srbije, br. 172026

Amorphization kinetics of Zr3Fe under electron irradiation

International Nuclear Information System (INIS)

Motta, A.T.; Howe, L.M.; Okamoto, P.R.

1992-10-01

0.9 MeV electron irradiations were performed at 28--220 K in a high-voltage electron microscope (HVEM). By measuring onset, spread and final size of the amorphous region, factoring in the Guassian distribution of the beam, a kinetic description of the amorphization in terms of dose, dose rate and temperature was obtained. The critical temperature for amorphization by electron irradiation was found to be ∼220 K, compared to 570--625 K for 40 Ar ion irradiation. Also, the dose-to-amorphization increased exponentially with temperature. Results indicated that the rate of growth of the amorphous region under the electron beam decreased with increasing temperature and the does-to-amorphization decreased with increasing dose rate. The size of the amorphous region saturated after a region dose, the final size decreasing with increasing temperature, and it was argued that this is related to the existence of a critical dose rate, which increased with temperature, below which no amorphization occurred. The above observations can be understood in the framework of the kinetics of damage accumulation under irradiation

Rapidly growing ovarian endometrioid adenocarcinoma involving the vagina: A case report

Directory of Open Access Journals (Sweden)

Sunghun Na

2011-12-01

Conclusion: Epithelial ovarian cancer may grow very rapidly. The frequent measurement of tumor size by ultrasonography may provide important information on detection in a subset of ovarian carcinomas that develop from preexisting, detectable lesions.

Equilibria and kinetics for reactive extraction of lactic acid using Alamine 336 in decanol

NARCIS (Netherlands)

Wasewar, Kailas L.; Heesink, A. Bert M.; Versteeg, Geert F.; Pangarkar, Vishwas G.

2002-01-01

Lactic acid is an important commercial product and extracting this from aqueous solution is a growing requirement in fermentation-based industries. The design of an amine extraction process requires (i) equilibrium and (ii) kinetic data for the acid–amine (solvent) system used. The equilibrium

Equilibria and kinetics for reactive extraction of lactic acid using Alamine 336 in decanol

NARCIS (Netherlands)

Wasewar, Kailas L.; Heesink, Albertus B.M.; Versteeg, Geert; Pangarkar, Vishwas G.

2002-01-01

Lactic acid is an important commercial product and extracting this from aqueous solution is a growing requirement in fermentation-based industries. The design of an amine extraction process requires (i) equilibrium and (ii) kinetic data for the acid-amine (solvent) system used. The equilibrium

A new study of the kinetics of curd production in the process of cheese manufacture.

Science.gov (United States)

Muñoz, Susana Vargas; Torres, Maykel González; Guerrero, Francisco Quintanilla; Talavera, Rogelio Rodríguez

2017-11-01

We studied the role played by temperature and rennet concentration in the coagulation process for cheese manufacture and the evaluation of their kinetics. We concluded that temperature is the main factor that determines the kinetics. The rennet concentration was unimportant probably due to the fast action of the enzyme chymosin. The Dynamic light scattering technique allowed measuring the aggregate's size and their formation kinetics. The volume fraction of solids was determined from viscosity measurements, showing profiles that are in agreement with the size profiles. The results indicate that the formation of the aggregates for rennet cheese is strongly dependent on temperature and rennet concentration. The results revealed that at 35·5 °C the volume fraction of solids has the maximum slope, indicating that at this temperature the curd is formed rapidly. The optimal temperature throughout the process was established. Second-order kinetics were obtained for the process. We observed a quadratic dependence between the rennet volume and the volume fraction of solids (curd), thereby indicating that the kinetics of the curd production should be of order two.

STRATEGIES AND KINETICS OF PHOTOACCLIMATION IN 3 ANTARCTIC NANOPHYTOFLAGELLATES

NARCIS (Netherlands)

BUMA, AGJ; NOORDELOOS, AAM; LARSEN, J

Three Antarctic nanophytoflagellates (two cryptophyte species and a Pyramimonas sp.) were compared for their capacity to photoacclimate and for their kinetic responses in changing photic environments. Division rate, cell size, cellular fluorescence, and chlorophyll a content were measured during

Uniqueness of thermodynamic projector and kinetic basis of molecular individualism

Science.gov (United States)

Gorban, Alexander N.; Karlin, Iliya V.

2004-05-01

Three results are presented: First, we solve the problem of persistence of dissipation for reduction of kinetic models. Kinetic equations with thermodynamic Lyapunov functions are studied. Uniqueness of the thermodynamic projector is proven: There exists only one projector which transforms any vector field equipped with the given Lyapunov function into a vector field with the same Lyapunov function for a given anzatz manifold which is not tangent to the Lyapunov function levels. Second, we use the thermodynamic projector for developing the short memory approximation and coarse-graining for general nonlinear dynamic systems. We prove that in this approximation the entropy production increases. ( The theorem about entropy overproduction.) In example, we apply the thermodynamic projector to derive the equations of reduced kinetics for the Fokker-Planck equation. A new class of closures is developed, the kinetic multipeak polyhedra. Distributions of this type are expected in kinetic models with multidimensional instability as universally as the Gaussian distribution appears for stable systems. The number of possible relatively stable states of a nonequilibrium system grows as 2 m, and the number of macroscopic parameters is in order mn, where n is the dimension of configuration space, and m is the number of independent unstable directions in this space. The elaborated class of closures and equations pretends to describe the effects of “molecular individualism”. This is the third result.

Study on the agglomeration kinetics of uranium peroxide

International Nuclear Information System (INIS)

Bertrand, M.; Mojica Rodriguez, L.A.; Muhr, H.; Plasari, E.; Auger, F.

2016-01-01

Considering the previous study dealing with thermodynamic and kinetic phenomena (nucleation and crystal growth) during the uranium peroxide precipitation, this work focuses on the agglomeration mechanism. It provides the results obtained from the experiments carried out in a mixed suspension - mixed product removal (MSMPR) mixer operating at steady state. The influence of the operating parameters on the uranium peroxide agglomerates was studied in order to identify the agglomeration kernel. The method is based on the resolution of the population balance equation using the method of moments and the experimental particle size distributions. The results lead to a size-independent kernel directly proportional to the crystal growth rate. Under the stirring conditions studied, the agglomeration appears to be significantly reduced by mixing which results in a kernel inversely proportional to the average shear rate. The agglomeration kinetic law obtained in this study will be used for the process modelling in a further study. (authors)

Study on the agglomeration kinetics of uranium peroxide

Energy Technology Data Exchange (ETDEWEB)

Bertrand, M.; Mojica Rodriguez, L.A. [CEA, Centre de Marcoule, Nuclear Energy Division, RadioChemistry and Process Department, 17171, Bagnols-sur-Ceze 30207 (France); Muhr, H.; Plasari, E. [Reaction and Process Engineering Laboratory, CNRS, University of Lorraine. 1 rue Grandville, BP 20451, Nancy 54001 (France); Auger, F. [Areva Mines/SEPA. 2 route de Lavaugrasse, Bessines-sur-Gartempe 87250 (France)

2016-07-01

Considering the previous study dealing with thermodynamic and kinetic phenomena (nucleation and crystal growth) during the uranium peroxide precipitation, this work focuses on the agglomeration mechanism. It provides the results obtained from the experiments carried out in a mixed suspension - mixed product removal (MSMPR) mixer operating at steady state. The influence of the operating parameters on the uranium peroxide agglomerates was studied in order to identify the agglomeration kernel. The method is based on the resolution of the population balance equation using the method of moments and the experimental particle size distributions. The results lead to a size-independent kernel directly proportional to the crystal growth rate. Under the stirring conditions studied, the agglomeration appears to be significantly reduced by mixing which results in a kernel inversely proportional to the average shear rate. The agglomeration kinetic law obtained in this study will be used for the process modelling in a further study. (authors)

Atomic size effect on critical cooling rate and glass formation

International Nuclear Information System (INIS)

Jalali, Payman; Li Mo

2005-01-01

Atomic size effect on critical cooling rate and glass formability in a model binary system is investigated using molecular dynamics simulation. To isolate atomic size effect from the rest of the factors that critically influence the glass formation, a hard sphere model is employed in conjunction with a newly developed densification method. The glass formability is defined as a set of optimal conditions that result in the slowest cooling rate of the glass-forming liquid. Critical cooling rates are identified from extensive molecular dynamics simulations. A kinetic glass-forming diagram is mapped out that marks the boundary between the glass-forming regions and competing crystalline phases in terms of the parameters of the atomic size ratio and alloy concentration. It is found that the potency of the atomic size difference on glass formation is influenced greatly by the competing metastable and equilibrium crystalline phases in the system, and the kinetic processes leading to the formation of these phases. The mechanisms of the atomic size effect on topological instability of crystal packing and glass formation are discussed

Non-kinetic capabilities: complementing the kinetic prevalence to targeting

OpenAIRE

Ducheine, P.

2014-01-01

Targeting is used in military doctrine to describe a military operational way, using (military) means to influence a target (or addressee) in order to achieve designated political and/or military goals. The four factors italicized are used to analyse non-kinetic targeting, complementing our knowledge and understanding of the kinetic prevalence. Paradoxically, non-kinetic targeting is not recognized as a separate concept: kinetic and non-kinetic are intertwined facets of targeting. Kinetic tar...

A conservative scheme of drift kinetic electrons for gyrokinetic simulation of kinetic-MHD processes in toroidal plasmas

Science.gov (United States)

Bao, J.; Liu, D.; Lin, Z.

2017-10-01

A conservative scheme of drift kinetic electrons for gyrokinetic simulations of kinetic-magnetohydrodynamic processes in toroidal plasmas has been formulated and verified. Both vector potential and electron perturbed distribution function are decomposed into adiabatic part with analytic solution and non-adiabatic part solved numerically. The adiabatic parallel electric field is solved directly from the electron adiabatic response, resulting in a high degree of accuracy. The consistency between electrostatic potential and parallel vector potential is enforced by using the electron continuity equation. Since particles are only used to calculate the non-adiabatic response, which is used to calculate the non-adiabatic vector potential through Ohm's law, the conservative scheme minimizes the electron particle noise and mitigates the cancellation problem. Linear dispersion relations of the kinetic Alfvén wave and the collisionless tearing mode in cylindrical geometry have been verified in gyrokinetic toroidal code simulations, which show that the perpendicular grid size can be larger than the electron collisionless skin depth when the mode wavelength is longer than the electron skin depth.

Tissue distribution and excretion kinetics of orally administered silica nanoparticles in rats

Science.gov (United States)

Lee, Jeong-A; Kim, Mi-Kyung; Paek, Hee-Jeong; Kim, Yu-Ri; Kim, Meyoung-Kon; Lee, Jong-Kwon; Jeong, Jayoung; Choi, Soo-Jin

2014-01-01

Purpose The effects of particle size on the tissue distribution and excretion kinetics of silica nanoparticles and their biological fates were investigated following a single oral administration to male and female rats. Methods Silica nanoparticles of two different sizes (20 nm and 100 nm) were orally administered to male and female rats, respectively. Tissue distribution kinetics, excretion profiles, and fates in tissues were analyzed using elemental analysis and transmission electron microscopy. Results The differently sized silica nanoparticles mainly distributed to kidneys and liver for 3 days post-administration and, to some extent, to lungs and spleen for 2 days post-administration, regardless of particle size or sex. Transmission electron microscopy and energy dispersive spectroscopy studies in tissues demonstrated almost intact particles in liver, but partially decomposed particles with an irregular morphology were found in kidneys, especially in rats that had been administered 20 nm nanoparticles. Size-dependent excretion kinetics were apparent and the smaller 20 nm particles were found to be more rapidly eliminated than the larger 100 nm particles. Elimination profiles showed 7%–8% of silica nanoparticles were excreted via urine, but most nanoparticles were excreted via feces, regardless of particle size or sex. Conclusion The kidneys, liver, lungs, and spleen were found to be the target organs of orally-administered silica nanoparticles in rats, and this organ distribution was not affected by particle size or animal sex. In vivo, silica nanoparticles were found to retain their particulate form, although more decomposition was observed in kidneys, especially for 20 nm particles. Urinary and fecal excretion pathways were determined to play roles in the elimination of silica nanoparticles, but 20 nm particles were secreted more rapidly, presumably because they are more easily decomposed. These findings will be of interest to those seeking to predict

Kinetic formation of silver-copper nanoparticles and its characterization

Science.gov (United States)

Zulkafi, Nurul Hikmah; Idrus, Nor Faeqah; Jai, Junaidah; Hadi, Abdul

2017-12-01

A study of the kinetic formation of silver-copper nanoparticles in aqueous medium on the basis of size distribution and its characterization has been carried out and reported in this paper. The Ag-Cu nanoparticles were synthesized through polyol method that using Ethylene Glycol (H2C6O12) as a reduction agent and solvent and Polyoxyethylene-(80)-Sorbitan Monooleate (Tween 80) as a stabilizer. The kinetic formation of Ag-Cu nanoparticles was observed using Dynamic Light Scattering (DLS) and characterized by using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Transmission Electron Microscope (TEM). The XRD analysis results confirmed that size distribution was strongly dependent on molarity of precursors of silver (AgNO3) and copper (Cu(NO3)2.3H2O). The FESEM and TEM analysis indicated the existence of Ag and Cu nanoparticles in the core-shell shape. The silver-copper nanoparticles were spherical and uniform particles size with the average size of about 28 nm and 38 nm for silver and copper, respectively. DLS observation showed the growth of nanoparticles at the temperature of 140°C as the effect of reaction time at 1, 2, 3, 4 and 5 hours.

Dynamic Model of Basic Oxygen Steelmaking Process Based on Multizone Reaction Kinetics: Modeling of Decarburization

Science.gov (United States)

Rout, Bapin Kumar; Brooks, Geoffrey; Akbar Rhamdhani, M.; Li, Zushu; Schrama, Frank N. H.; Overbosch, Aart

2018-03-01

In a previous study by the authors (Rout et al. in Metall Mater Trans B 49:537-557, 2018), a dynamic model for the BOF, employing the concept of multizone kinetics was developed. In the current study, the kinetics of decarburization reaction is investigated. The jet impact and slag-metal emulsion zones were identified to be primary zones for carbon oxidation. The dynamic parameters in the rate equation of decarburization such as residence time of metal drops in the emulsion, interfacial area evolution, initial size, and the effects of surface-active oxides have been included in the kinetic rate equation of the metal droplet. A modified mass-transfer coefficient based on the ideal Langmuir adsorption equilibrium has been proposed to take into account the surface blockage effects of SiO2 and P2O5 in slag on the decarburization kinetics of a metal droplet in the emulsion. Further, a size distribution function has been included in the rate equation to evaluate the effect of droplet size on reaction kinetics. The mathematical simulation indicates that decarburization of the droplet in the emulsion is a strong function of the initial size and residence time. A modified droplet generation rate proposed previously by the authors has been used to estimate the total decarburization rate by slag-metal emulsion. The model's prediction shows that about 76 pct of total carbon is removed by reactions in the emulsion, and the remaining is removed by reactions at the jet impact zone. The predicted bath carbon by the model has been found to be in good agreement with the industrially measured data.

Dynamic Model of Basic Oxygen Steelmaking Process Based on Multizone Reaction Kinetics: Modeling of Decarburization

Science.gov (United States)

Rout, Bapin Kumar; Brooks, Geoffrey; Akbar Rhamdhani, M.; Li, Zushu; Schrama, Frank N. H.; Overbosch, Aart

2018-06-01

In a previous study by the authors (Rout et al. in Metall Mater Trans B 49:537-557, 2018), a dynamic model for the BOF, employing the concept of multizone kinetics was developed. In the current study, the kinetics of decarburization reaction is investigated. The jet impact and slag-metal emulsion zones were identified to be primary zones for carbon oxidation. The dynamic parameters in the rate equation of decarburization such as residence time of metal drops in the emulsion, interfacial area evolution, initial size, and the effects of surface-active oxides have been included in the kinetic rate equation of the metal droplet. A modified mass-transfer coefficient based on the ideal Langmuir adsorption equilibrium has been proposed to take into account the surface blockage effects of SiO2 and P2O5 in slag on the decarburization kinetics of a metal droplet in the emulsion. Further, a size distribution function has been included in the rate equation to evaluate the effect of droplet size on reaction kinetics. The mathematical simulation indicates that decarburization of the droplet in the emulsion is a strong function of the initial size and residence time. A modified droplet generation rate proposed previously by the authors has been used to estimate the total decarburization rate by slag-metal emulsion. The model's prediction shows that about 76 pct of total carbon is removed by reactions in the emulsion, and the remaining is removed by reactions at the jet impact zone. The predicted bath carbon by the model has been found to be in good agreement with the industrially measured data.

Experimental investigations and modeling of devolatilization based on superimposed kinetics of biomass

DEFF Research Database (Denmark)

Trubetskaya, Anna; Jensen, Anker Degn

A non-isothermal one-dimensional model has been developed to describe biomass pyrolysis at fast heating rate (600-104 Ks-1), high temperatures (up to 1500C) and is valid for different biomass particle sizes (< 10 mm). The model was developedto estimate the yields of volatile gas and char. The mod...... the charyield of woody and herbaceous biomass particles using one fixed set of kinetic parameters valid for woody andherbaceous biomass....... relies on the concept applied in fast pyrolysis of cellulose throughthe formation of an intermediate liquid (so called metaplast) which reacts further to char and gas. The kinetics of the fastpyrolysis was described by the Broido-Shafizadeh scheme.The influence of particle size and shape was included...... obtained in the wire mesh and drop tube reactors. Thus, the modelincluding these two parameters provides an acceptable fit of char yield to the experimental data. The present results showedthat the proposed kinetic model for the fast biomass pyrolysis is relatively simple and predicts reasonably accurately...

Solving point reactor kinetic equations by time step-size adaptable numerical methods

International Nuclear Information System (INIS)

Liao Chaqing

2007-01-01

Based on the analysis of effects of time step-size on numerical solutions, this paper showed the necessity of step-size adaptation. Based on the relationship between error and step-size, two-step adaptation methods for solving initial value problems (IVPs) were introduced. They are Two-Step Method and Embedded Runge-Kutta Method. PRKEs were solved by implicit Euler method with step-sizes optimized by using Two-Step Method. It was observed that the control error has important influence on the step-size and the accuracy of solutions. With suitable control errors, the solutions of PRKEs computed by the above mentioned method are accurate reasonably. The accuracy and usage of MATLAB built-in ODE solvers ode23 and ode45, both of which adopt Runge-Kutta-Fehlberg method, were also studied and discussed. (authors)

Kinetics of transesterification of methyl acetate and n-octanol catalyzed by cation exchange resins

Energy Technology Data Exchange (ETDEWEB)

Liu, Yong; Gao, Li; Li, Xiying; Mao, Liqun [Henan University, Kaifeng (China); Wei, Min [Henan University of Technology, Zhengzhou (China)

2013-05-15

The transesterification kinetics of methyl acetate with n-octanol to octyl acetate and methanol were studied using Amberlyst 15 as catalyst in a batch stirred reactor. The influence of the agitation speed, particle size, temperature, catalyst loading, and initial reactants molar ratio was investigated in detail. A pseudo-homogeneous (PH) kinetic model was applied to correlate the experimental data in the temperature range of 313.15 K to 328.15 K. The estimated kinetic parameters made the calculated results in good agreement with the experimental data. A kinetic model describing the transesterification reaction catalyzed by cation exchange resins was developed.

Firm size and taxes

OpenAIRE

Chongvilaivan, Aekapol; Jinjarak, Yothin

2010-01-01

The scale dependence in firm growth (smaller firms grow faster) is systematically reflected in the size distribution. This paper studies whether taxes affect the equilibrium firm size distribution in a cross-country context. The main finding is that the empirical association between firm growth and corporate tax (VAT) is positive (negative), with notable differences in the response of manufacturing firms and that of the others. We draw implications for recent debate on the impact of taxes and...

Kinetics of in situ combustion. SUPRI TR 91

Energy Technology Data Exchange (ETDEWEB)

Mamora, D.D.; Ramey, H.J. Jr.; Brigham, W.E.; Castanier, L.M.

1993-07-01

Oxidation kinetic experiments with various crude oil types show two reaction peaks at about 250{degree}C (482{degree}F) and 400{degree}C (725{degree}F). These experiments lead to the conclusion that the fuel during high temperature oxidation is an oxygenated hydrocarbon. A new oxidation reaction model has been developed which includes two partially-overlapping reactions: namely, low-temperature oxidation followed by high-temperature oxidation. For the fuel oxidation reaction, the new model includes the effects of sand grain size and the atomic hydrogen-carbon (H/C) and oxygen-carbon (O/C) ratios of the fuel. Results based on the new model are in good agreement with the experimental data. Methods have been developed to calculate the atomic H/C and O/C ratios. These methods consider the oxygen in the oxygenated fuel, and enable a direct comparison of the atomic H/C ratios obtained from kinetic and combustion tube experiments. The finding that the fuel in kinetic tube experiments is an oxygenated hydrocarbon indicates that oxidation reactions are different in kinetic and combustion tube experiments. A new experimental technique or method of analysis will be required to obtain kinetic parameters for oxidation reactions encountered in combustion tube experiments and field operations.

Comparing kinetic curves in liquid chromatography

Science.gov (United States)

Kurganov, A. A.; Kanat'eva, A. Yu.; Yakubenko, E. E.; Popova, T. P.; Shiryaeva, V. E.

2017-01-01

Five equations for kinetic curves which connect the number of theoretical plates N and time of analysis t 0 for five different versions of optimization, depending on the parameters being varied (e.g., mobile phase flow rate, pressure drop, sorbent grain size), are obtained by means of mathematical modeling. It is found that a method based on the optimization of a sorbent grain size at fixed pressure is most suitable for the optimization of rapid separations. It is noted that the advantages of the method are limited by an area of relatively low efficiency, and the advantage of optimization is transferred to a method based on the optimization of both the sorbent grain size and the drop in pressure across a column in the area of high efficiency.

A few more comments on secularly growing loop corrections in strong electric fields

International Nuclear Information System (INIS)

Akhmedov, E.T.; Popov, F.K.

2015-01-01

We extend the observations of our previous paper http://dx.doi.org/10.1007/JHEP09(2014)071 [http://arxiv.org/abs/1405.5285]. particular, we show that the secular growth of the loop corrections to the two-point correlation functions is gauge independent: we observe the same growth in the case of the static gauge for the constant background electric field. Furthermore we solve the kinetic equation describing photon production from the background fields, which was derived in our previous paper and allows one to sum up leading secularly growing corrections from all loops. Finally, we show that in the constant electric field background the one-loop correction to the current of the produced pairs is not zero: it also grows with time and violates time translational and reversal invariance of QED on the constant electric field background.

Size control of Au NPs supported by pH operation

Science.gov (United States)

Ichiji, Masumi; Akiba, Hiroko; Hirasawa, Izumi

2017-07-01

Au NPs are expected to become useful functional particles, as particle gun used for plant gene transfer and also catalysts. We have studied PSD (particle size distribution) control of Au NPs by reduction crystallization. Previous study found out importance of seeds policy and also feeding profile. In this paper, effect of pH in the reduction crystallization was investigated to clarify the possibility of Au NPs PSD control by pH operation and also their growth process. Au NPs of size range 10-600 nm were obtained in single-jet system using ascorbic acid (AsA) as a reducing agent with adjusting pH of AsA. Au NPs are found to grow in the process of nucleation, agglomeration, agglomeration growth and surface growth. Au NPs tend to grow by agglomeration and become larger size in lower pH regions, and to grow only by surface growth and become smaller size in higher pH regions.

Probing static disorder in Arrhenius kinetics by single-molecule force spectroscopy.

Science.gov (United States)

Kuo, Tzu-Ling; Garcia-Manyes, Sergi; Li, Jingyuan; Barel, Itay; Lu, Hui; Berne, Bruce J; Urbakh, Michael; Klafter, Joseph; Fernández, Julio M

2010-06-22

The widely used Arrhenius equation describes the kinetics of simple two-state reactions, with the implicit assumption of a single transition state with a well-defined activation energy barrier DeltaE, as the rate-limiting step. However, it has become increasingly clear that the saddle point of the free-energy surface in most reactions is populated by ensembles of conformations, leading to nonexponential kinetics. Here we present a theory that generalizes the Arrhenius equation to include static disorder of conformational degrees of freedom as a function of an external perturbation to fully account for a diverse set of transition states. The effect of a perturbation on static disorder is best examined at the single-molecule level. Here we use force-clamp spectroscopy to study the nonexponential kinetics of single ubiquitin proteins unfolding under force. We find that the measured variance in DeltaE shows both force-dependent and independent components, where the force-dependent component scales with F(2), in excellent agreement with our theory. Our study illustrates a novel adaptation of the classical Arrhenius equation that accounts for the microscopic origins of nonexponential kinetics, which are essential in understanding the rapidly growing body of single-molecule data.

A message-passing approach to random constraint satisfaction problems with growing domains

International Nuclear Information System (INIS)

Zhao, Chunyan; Zheng, Zhiming; Zhou, Haijun; Xu, Ke

2011-01-01

Message-passing algorithms based on belief propagation (BP) are implemented on a random constraint satisfaction problem (CSP) referred to as model RB, which is a prototype of hard random CSPs with growing domain size. In model RB, the number of candidate discrete values (the domain size) of each variable increases polynomially with the variable number N of the problem formula. Although the satisfiability threshold of model RB is exactly known, finding solutions for a single problem formula is quite challenging and attempts have been limited to cases of N ∼ 10 2 . In this paper, we propose two different kinds of message-passing algorithms guided by BP for this problem. Numerical simulations demonstrate that these algorithms allow us to find a solution for random formulas of model RB with constraint tightness slightly less than p cr , the threshold value for the satisfiability phase transition. To evaluate the performance of these algorithms, we also provide a local search algorithm (random walk) as a comparison. Besides this, the simulated time dependence of the problem size N and the entropy of the variables for growing domain size are discussed

Influence of the interaction volume on the kinetic energy resolution of a velocity map imaging spectrometer

International Nuclear Information System (INIS)

Zhang Peng; Feng Zheng-Peng; Luo Si-Qiang; Wang Zhe

2016-01-01

We investigate the influence of the interaction volume on the energy resolution of a velocity map imaging spectrometer. The simulation results show that the axial interaction size has a significant influence on the resolution. This influence is increased for a higher kinetic energy. We further show that the radial interaction size has a minor influence on the energy resolution for the electron or ion with medium energy, but it is crucial for the resolution of the electron or ion with low kinetic energy. By tracing the flight trajectories we show how the electron or ion energy resolution is influenced by the interaction size. (paper)

Organic Field-Effect Transistors: A 3D Kinetic Monte Carlo Simulation of the Current Characteristics in Micrometer-Sized Devices

KAUST Repository

Li, Haoyuan; Li, Yuan; Li, Hong; Bredas, Jean-Luc

2017-01-01

The electrical properties of organic field-effect transistors (OFETs) are usually characterized by applying models initially developed for inorganic-based devices, which often implies the use of approximations that might be inappropriate for organic semiconductors. These approximations have brought limitations to the understanding of the device physics associated with organic materials. A strategy to overcome this issue is to establish straightforward connections between the macroscopic current characteristics and microscopic charge transport in OFETs. Here, a 3D kinetic Monte Carlo model is developed that goes beyond both the conventional assumption of zero channel thickness and the gradual channel approximation to simulate carrier transport and current. Using parallel computing and a new algorithm that significantly improves the evaluation of electric potential within the device, this methodology allows the simulation of micrometer-sized OFETs. The current characteristics of representative OFET devices are well reproduced, which provides insight into the validity of the gradual channel approximation in the case of OFETs, the impact of the channel thickness, and the nature of microscopic charge transport.

Organic Field-Effect Transistors: A 3D Kinetic Monte Carlo Simulation of the Current Characteristics in Micrometer-Sized Devices

KAUST Repository

Li, Haoyuan

2017-01-16

The electrical properties of organic field-effect transistors (OFETs) are usually characterized by applying models initially developed for inorganic-based devices, which often implies the use of approximations that might be inappropriate for organic semiconductors. These approximations have brought limitations to the understanding of the device physics associated with organic materials. A strategy to overcome this issue is to establish straightforward connections between the macroscopic current characteristics and microscopic charge transport in OFETs. Here, a 3D kinetic Monte Carlo model is developed that goes beyond both the conventional assumption of zero channel thickness and the gradual channel approximation to simulate carrier transport and current. Using parallel computing and a new algorithm that significantly improves the evaluation of electric potential within the device, this methodology allows the simulation of micrometer-sized OFETs. The current characteristics of representative OFET devices are well reproduced, which provides insight into the validity of the gradual channel approximation in the case of OFETs, the impact of the channel thickness, and the nature of microscopic charge transport.

The thermodynamic and kinetic interactions of He interstitial clusters with bubbles in W

Energy Technology Data Exchange (ETDEWEB)

Perez, Danny, E-mail: danny-perez@lanl.gov; Sandoval, Luis; Voter, Arthur F. [Theoretical Division T-1, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Uberuaga, Blas P. [Materials Science and Technology MST-8, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2016-05-28

Due to its enviable properties, tungsten is a leading candidate plasma facing material in nuclear fusion reactors. However, like many other metals, tungsten is known to be affected by the high doses of helium atoms incoming from the plasma. Indeed, the implanted interstitial helium atoms cluster together and, upon reaching a critical cluster size, convert into substitutional nanoscale He bubbles. These bubbles then grow by absorbing further interstitial clusters from the matrix. This process can lead to deleterious changes in microstructure, degradation of mechanical properties, and contamination of the plasma. In order to better understand the growth process, we use traditional and accelerated molecular dynamics simulations to investigate the interactions between interstitial He clusters and pre-existing bubbles. These interactions are characterized in terms of thermodynamics and kinetics. We show that the proximity of the bubble leads to an enhancement of the trap mutation rate and, consequently, to the nucleation of satellite bubbles in the neighborhood of existing ones. We also uncover a number of mechanisms that can lead to the subsequent annihilation of such satellite nanobubbles.

Grow, Baby, Grow

Science.gov (United States)

Maybe you quit smoking during your pregnancy. Or maybe you struggled and weren’t able to stay quit. Now that your baby is here, trying to stay away from smoking is still important. That’s because the chemicals in smoke can make it harder for your baby to grow like he or she should.

Phase transformation kinetics and microstructure of NiTi shape

Indian Academy of Sciences (India)

Phase transformation kinetics and microstructure of NiTi shape memory alloy: ... by 1.4687 J. In addition, entropy of the alloys decreases by 0.2335 J (g ∘ C) − 1 ... is an obvious difference in the grain sizes of the unpressured sample and the ...

On the second kinetic order thermoluminescent glow curves

International Nuclear Information System (INIS)

Dang Thanh Luong; Nguyen Hao Quang; Hoang Minh Giang

1995-01-01

The kinetic parameters of thermoluminescent material such as CaF 2 -N and CaSO 4 -Dy with the different grain sizes are investigated in detail using the least square method of fitting. It was found that the activation energy E (or trap depth) and peak temperature T m ax are changed with the elapsed time between the irradiation and read-out for the low temperature glow curve peaks. The similar TL glow curve shapes are obtained for the different CaSO 4 -Dy grain size. (author). 7 refs., 5 figs., 2 tabs

Kinetic energy budgets near the turbulent/nonturbulent interface in jets

Science.gov (United States)

Taveira, Rodrigo R.; da Silva, Carlos B.

2013-01-01

The dynamics of the kinetic energy near the turbulent/nonturbulent (T/NT) interface separating the turbulent from the irrotational flow regions is analysed using three direct numerical simulations of turbulent planar jets, with Reynolds numbers based on the Taylor micro-scale across the jet shear layer in the range Reλ ≈ 120-160. Important levels of kinetic energy are already present in the irrotational region near the T/NT interface. The mean pressure and kinetic energy are well described by the Bernoulli equation in this region and agree with recent results obtained from rapid distortion theory in the turbulent region [M. A. C. Teixeira and C. B. da Silva, "Turbulence dynamics near a turbulent/non-turbulent interface," J. Fluid Mech. 695, 257-287 (2012)], 10.1017/jfm.2012.17 while the normal Reynolds stresses agree with the theoretical predictions from Phillips ["The irrotational motion outside a free turbulent boundary," Proc. Cambridge Philos. Soc. 51, 220 (1955)], 10.1017/S0305004100030073. The use of conditional statistics in relation to the distance from the T/NT interface allow a detailed study of the build up of kinetic energy across the T/NT interface, pointing to a very different picture than using classical statistics. Conditional kinetic energy budgets show that apart from the viscous dissipation of kinetic energy, the maximum of all the mechanisms governing the kinetic energy are concentrated in a very narrow region distancing about one to two Taylor micro-scales from the T/NT interface. The (total and fluctuating) kinetic energy starts increasing in the irrotational region by pressure-velocity interactions - a mechanism that can act at distance, and continue to grow by advection (for the total kinetic energy) and turbulent diffusion (for the turbulent kinetic energy) inside the turbulent region. These mechanisms tend to occur preferentially around the core of the large-scale vortices existing near T/NT interface. The production of turbulent

Multiscale approaches to protein-mediated interactions between membranes—relating microscopic and macroscopic dynamics in radially growing adhesions

International Nuclear Information System (INIS)

Bihr, Timo; Smith, Ana-Suncana; Seifert, Udo

2015-01-01

Macromolecular complexation leading to coupling of two or more cellular membranes is a crucial step in a number of biological functions of the cell. While other mechanisms may also play a role, adhesion always involves the fluctuations of deformable membranes, the diffusion of proteins and the molecular binding and unbinding. Because these stochastic processes couple over a multitude of time and length scales, theoretical modeling of membrane adhesion has been a major challenge. Here we present an effective Monte Carlo scheme within which the effects of the membrane are integrated into local rates for molecular recognition. The latter step in the Monte Carlo approach enables us to simulate the nucleation and growth of adhesion domains within a system of the size of a cell for tens of seconds without loss of accuracy, as shown by comparison to 10 6 times more expensive Langevin simulations. To perform this validation, the Langevin approach was augmented to simulate diffusion of proteins explicitly, together with reaction kinetics and membrane dynamics. We use the Monte Carlo scheme to gain deeper insight to the experimentally observed radial growth of micron sized adhesion domains, and connect the effective rate with which the domain is growing to the underlying microscopic events. We thus demonstrate that our technique yields detailed information about protein transport and complexation in membranes, which is a fundamental step toward understanding even more complex membrane interactions in the cellular context. (paper)

Explosive sport training and torque kinetics in children.

Science.gov (United States)

Dotan, Raffy; Mitchell, Cameron J; Cohen, Rotem; Gabriel, David; Klentrou, Panagiota; Falk, Bareket

2013-07-01

A high rate of force development (RFD) is often more important than maximal force in daily and sports activities. In children, resistance training has been shown to increase maximal force. It is unclear whether, or to what extent, can children improve RFD and force kinetics. For this study, we compared strength and force kinetics of boy gymnasts with those of untrained boys and untrained men. Eight boy gymnasts (age, 9.5 ± 1.2 y), 20 untrained boys (age, 10.1 ± 1.3 y), and 20 untrained men (age, 22.9 ± 4.4 y) performed maximal, explosive, isometric elbow flexions (EF) and knee flexions (KF). Peak torque (maximal voluntary contraction (MVC)), elapsed times to 10%-100% MVC, peak rate of torque development (RTDpk), and other kinetics parameters were determined. When gymnasts were compared with untrained boys, size-normalized EF MVC was 11%-20% higher, RTDpk was 32% higher, and times to 30% and 80% MVC were 16% and 55% shorter, respectively (p kinetics parameters were similar. These findings highlight the specificity of gymnastics training, which markedly elevated the torque kinetics of young, prepubertal boys to adult levels, but only moderately affected peak torque. It is suggested that neurologic adaptations, such as enhanced firing and activation rates or increased type II motor-unit recruitment, as well as changes in musculotendinous stiffness, could explain these findings.

Batch study, equilibrium and kinetics of adsorption of naphthalene using waste tyre rubber granules

Directory of Open Access Journals (Sweden)

Felix A. Aisien

2014-04-01

Full Text Available The potential use of waste tyre rubber granules (WTRG for the batch adsorption of naphthalene from aqueous solutions was investigated. The effect of various operational variables such as contact time, initial naphthalene concentration, adsorbent dose, size of adsorbent particles, and temperature of solution on the adsorption capacity of WTRG was evaluated. The adsorption of naphthalene by WTRG was a fast kinetic process with an equilibrium contact time of 60 min. A low temperature (5°C, small adsorbent particle size (0.212 mm and higher adsorbent dosage favored the adsorption process. Results of isotherm studies revealed that adsorption of naphthalene was best described by the Langmuir isotherm equation (R2=0.997 while the kinetics of the process was best described by the Lagergren pseudofirst order kinetic equation (R2=0.998. This study has demonstrated the suitability of WTRG for the removal of naphthalene from aqueous solution.

Mathematical modeling of CA125 kinetics in recurrent ovarian cancer (ROC) patients treated with chemotherapy and predictive value of early modeled kinetic parameters in CALYPSO trial: A GCIG study

DEFF Research Database (Denmark)

You, Benoit; Colomban, Olivier; Heywood, Mark

2011-01-01

Background: Although CA125 kinetic profiles may be related with relapse risk in ovarian cancer patients treated with chemotherapy, no reliable kinetic parameters have been reported. Mathematical modeling may help describe CA125 decline dynamically and determine parameters predictive of relapse....... Methods: Data from CALYPSO phase III trial data comparing 2 carboplatin-based regimens in ROC patients were analyzed. Based on population kinetic approach (Monolix software), a semi-mechanistic model was used to fit serum log (CA125) concentration-time profiles with following parameters: tumor growth rate...... the first 50 treatment days were tested regarding progression free survival (PFS) against other reported prognostic factors using Cox-models: treatment arm; platinum-free interval (PFI), metastatic site number, largest tumor size, elevated WBC and measurable disease. Results: The CA125 kinetics from 898...

The Effect of pH and High-Pressure Homogenization on Droplet Size

Directory of Open Access Journals (Sweden)

Ah Pis Yong

2017-12-01

Full Text Available The aims of this study are to revisit the effect of high pressure on homogenization and the influence of pH on the emulsion droplet sizes. The high-pressure homogenization (HPH involves two stages of processing, where the first stage involves in blending the coarse emulsion by a blender, and the second stage requires disruption of the coarse emulsion into smaller droplets by a high-pressure homogenizer. The pressure range in this review is in between 10-500 MPa. The homogenised droplet sizes can be reduced by increasing the homogenization recirculation, and there is a threshold point beyond that by applying pressure only, the size cannot be further reduced. Normally, homogenised emulsions are classified by their degree of kinetic stability. Dispersed phase present in the form of droplets while continuous phase also known as suspended droplets. With a proper homogenization recirculation and pressure, a more kinetically stable emulsion can be produced. The side effects of increasing homogenization pressure are that it can cause overprocessing of the emulsion droplets where the droplet sizes become larger rather than the expected smaller size. This can cause kinetic instability in the emulsion. The droplet size is usually measured by dynamic light scattering or by laser light scattering technique. The type of samples used in this reviews are such as chocolate and vanilla based powders; mean droplet sizes samples; basil oil; tomato; lupin protein; oil; skim milk, soymilk; coconut milk; tomato homogenate; corn; egg-yolk, rapeseed and sunflower; Poly(4-vinylpyridine/silica; and Complex 1 until complex 4 approaches from author case study. A relationship is developed between emulsion size and pH. Results clearly show that lower pH offers smaller droplet of emulsion and the opposite occurs when the pH is increased.

Kinetic modelling and mechanism of dye adsorption on unburned carbon

Energy Technology Data Exchange (ETDEWEB)

Wang, S.B.; Li, H.T. [Curtin University of Technology, Perth, WA (Australia). Dept. of Chemical Engineering

2007-07-01

Textile dyeing processes are among the most environmentally unfriendly industrial processes by producing coloured wastewaters. The adsorption method using unburned carbon from coal combustion residue was studied for the decolourisation of typical acidic and basic dyes. It was discovered that the unburned carbon showed high adsorption capacity at 1.97 x 10{sup -4} and 5.27 x 10{sup -4} mol/g for Basic Violet 3 and Acid Black 1, respectively. The solution pH, particle size and temperature significantly influenced the adsorption capacity. Higher solution pH favoured the adsorption of basic dye while reduced the adsorption of acid dye. The adsorption of dye increased with increasing temperature but decreased with increasing particle size. Sorption kinetic data indicated that the adsorption kinetics followed the pseudo-second-order model. The adsorption mechanism consisted of two processes, external diffusion and intraparticle diffusion, and the external diffusion was the dominating process.

Play School: Where Children and Families Learn and Grow Together

Science.gov (United States)

McDermott, Lori Berger

2012-01-01

A growing body of national research confirms that significant levels of learning and growth occur during early childhood, and that it is important, from a public policy perspective, to increase access to quality programs and services that support the development of skills and attitudes children need to succeed. Clearly, no one-size-fits-all…

Kinetic energy of throughfall in a highly diverse forest ecosystem in the humid subtropics

Science.gov (United States)

Geißler, Christian; Kühn, Peter; Scholten, Thomas

2010-05-01

After decades of research it is generally accepted that vegetation is a key factor in controlling soil erosion. Therefore, in ecosystems where erosion is a serious problem, afforestation is a common measure against erosion. Most of the studies in the last decades focused on agricultural systems and less attention was paid to natural systems. To understand the mechanisms preventing soil erosion in natural systems the processes have to be studied in detail and gradually. The first step and central research question is on how the canopies of the tree layer alter the properties of rainfall and generate throughfall. Kinetic energy is a widely used parameter to estimate the erosion potential of open field rainfall and throughfall. In the past, numerous studies have shown that vegetation of a certain height enhances the kinetic energy under the canopy (Chapman 1948, Mosley 1982, Vis 1986, Hall & Calder 1993, Nanko et al. 2006, Nanko et al. 2008) in relation to open field rainfall. This is mainly due to a shift in the drop size distribution to less but larger drops possessing a higher amount of kinetic energy. In vital forest ecosystems lower vegetation (shrubs, herbs) as well as a continuous litter layer protects the forest soil from the impact of large drops. The influence of biodiversity, specific forest stands or single species in this process system is still in discussion. In the present study calibrated splash cups (after Ellison 1947, Geißler et al. under review) have been used to detect differences in kinetic energy on the scale of specific species and on the scale of forest stands of contrasting age and biodiversity in a natural forest ecosystem. The splash cups have been calibrated experimentally using a laser disdrometer. The results show that the kinetic energy of throughfall produced by the tree layer increases with the age of the specific forest stand. The average throughfall kinetic energy (J m-2) is about 2.6 times higher in forests than under open field

Going from microscopic to macroscopic on nonuniform growing domains.

Science.gov (United States)

Yates, Christian A; Baker, Ruth E; Erban, Radek; Maini, Philip K

2012-08-01

Throughout development, chemical cues are employed to guide the functional specification of underlying tissues while the spatiotemporal distributions of such chemicals can be influenced by the growth of the tissue itself. These chemicals, termed morphogens, are often modeled using partial differential equations (PDEs). The connection between discrete stochastic and deterministic continuum models of particle migration on growing domains was elucidated by Baker, Yates, and Erban [Bull. Math. Biol. 72, 719 (2010)] in which the migration of individual particles was modeled as an on-lattice position-jump process. We build on this work by incorporating a more physically reasonable description of domain growth. Instead of allowing underlying lattice elements to instantaneously double in size and divide, we allow incremental element growth and splitting upon reaching a predefined threshold size. Such a description of domain growth necessitates a nonuniform partition of the domain. We first demonstrate that an individual-based stochastic model for particle diffusion on such a nonuniform domain partition is equivalent to a PDE model of the same phenomenon on a nongrowing domain, providing the transition rates (which we derive) are chosen correctly and we partition the domain in the correct manner. We extend this analysis to the case where the domain is allowed to change in size, altering the transition rates as necessary. Through application of the master equation formalism we derive a PDE for particle density on this growing domain and corroborate our findings with numerical simulations.

Size scaling of static friction.

Science.gov (United States)

Braun, O M; Manini, Nicola; Tosatti, Erio

2013-02-22

Sliding friction across a thin soft lubricant film typically occurs by stick slip, the lubricant fully solidifying at stick, yielding and flowing at slip. The static friction force per unit area preceding slip is known from molecular dynamics (MD) simulations to decrease with increasing contact area. That makes the large-size fate of stick slip unclear and unknown; its possible vanishing is important as it would herald smooth sliding with a dramatic drop of kinetic friction at large size. Here we formulate a scaling law of the static friction force, which for a soft lubricant is predicted to decrease as f(m)+Δf/A(γ) for increasing contact area A, with γ>0. Our main finding is that the value of f(m), controlling the survival of stick slip at large size, can be evaluated by simulations of comparably small size. MD simulations of soft lubricant sliding are presented, which verify this theory.

Kinetic Typography

DEFF Research Database (Denmark)

van Leeuwen, Theo; Djonov, Emilia

2014-01-01

After discussing broad cultural drivers behind the development of kinetic typography, the chapter outlines an approach to analysing kinetic typography which is based on Halliday's theory of transitivity, as applied by Kress and Van Leeuwen to visual images.......After discussing broad cultural drivers behind the development of kinetic typography, the chapter outlines an approach to analysing kinetic typography which is based on Halliday's theory of transitivity, as applied by Kress and Van Leeuwen to visual images....

Size effects in lithium ion batteries

International Nuclear Information System (INIS)

Yao Hu-Rong; Yin Ya-Xia; Guo Yu-Gao

2016-01-01

Size-related properties of novel lithium battery materials, arising from kinetics, thermodynamics, and newly discovered lithium storage mechanisms, are reviewed. Complementary experimental and computational investigations of the use of the size effects to modify electrodes and electrolytes for lithium ion batteries are enumerated and discussed together. Size differences in the materials in lithium ion batteries lead to a variety of exciting phenomena. Smaller-particle materials with highly connective interfaces and reduced diffusion paths exhibit higher rate performance than the corresponding bulk materials. The thermodynamics is also changed by the higher surface energy of smaller particles, affecting, for example, secondary surface reactions, lattice parameter, voltage, and the phase transformation mechanism. Newly discovered lithium storage mechanisms that result in superior storage capacity are also briefly highlighted. (topical review)

Exploring the chemical kinetics of partially oxidized intermediates by combining experiments, theory, and kinetic modeling.

Science.gov (United States)

Hoyermann, Karlheinz; Mauß, Fabian; Olzmann, Matthias; Welz, Oliver; Zeuch, Thomas

2017-07-19

Partially oxidized intermediates play a central role in combustion and atmospheric chemistry. In this perspective, we focus on the chemical kinetics of alkoxy radicals, peroxy radicals, and Criegee intermediates, which are key species in both combustion and atmospheric environments. These reactive intermediates feature a broad spectrum of chemical diversity. Their reactivity is central to our understanding of how volatile organic compounds are degraded in the atmosphere and converted into secondary organic aerosol. Moreover, they sensitively determine ignition timing in internal combustion engines. The intention of this perspective article is to provide the reader with information about the general mechanisms of reactions initiated by addition of atomic and molecular oxygen to alkyl radicals and ozone to alkenes. We will focus on critical branching points in the subsequent reaction mechanisms and discuss them from a consistent point of view. As a first example of our integrated approach, we will show how experiment, theory, and kinetic modeling have been successfully combined in the first infrared detection of Criegee intermediates during the gas phase ozonolysis. As a second example, we will examine the ignition timing of n-heptane/air mixtures at low and intermediate temperatures. Here, we present a reduced, fuel size independent kinetic model of the complex chemistry initiated by peroxy radicals that has been successfully applied to simulate standard n-heptane combustion experiments.

Kinetic Uptake Studies of Powdered Materials in Solution

Directory of Open Access Journals (Sweden)

Mohamed H. Mohamed

2015-06-01

Full Text Available Challenges exist for the study of time dependent sorption processes for heterogeneous systems, especially in the case of dispersed nanomaterials in solvents or solutions because they are not well suited to conventional batch kinetic experiments. In this study, a comparison of batch versus a one-pot setup in two variable configurations was evaluated for the study of uptake kinetics in heterogeneous (solid/solution systems: (i conventional batch method; (ii one-pot system with dispersed adsorbent in solution with a semi-permeable barrier (filter paper or dialysis tubing for in situ sampling; and (iii one-pot system with an adsorbent confined in a semi-permeable barrier (dialysis tubing or filter paper barrier with ex situ sampling. The sorbent systems evaluated herein include several cyclodextrin-based polyurethane materials with two types of phenolic dyes: p-nitrophenol and phenolphthalein. The one-pot kinetics method with in situ (Method ii or ex situ (Method iii sampling described herein offers significant advantages for the study of heterogeneous sorption kinetics of highly dispersed sorbent materials with particles sizes across a range of dimensions from the micron to nanometer scale. The method described herein will contribute positively to the development of advanced studies for heterogeneous sorption processes where an assessment of the relative uptake properties is required at different experimental conditions. The results of this study will be advantageous for the study of nanomaterials with significant benefits over batch kinetic studies for a wide range of heterogeneous sorption processes.

The size effects upon shock plastic compression of nanocrystals

Science.gov (United States)

Malygin, G. A.; Klyavin, O. V.

2017-10-01

For the first time a theoretical analysis of scale effects upon the shock plastic compression of nanocrystals is implemented in the context of a dislocation kinetic approach based on the equations and relationships of dislocation kinetics. The yield point of crystals τy is established as a quantitative function of their cross-section size D and the rate of shock deformation as τy ɛ2/3 D. This dependence is valid in the case of elastic stress relaxation on account of emission of dislocations from single-pole Frank-Read sources near the crystal surface.

Kinetics model development of cocoa bean fermentation

Science.gov (United States)

Kresnowati, M. T. A. P.; Gunawan, Agus Yodi; Muliyadini, Winny

2015-12-01

Although Indonesia is one of the biggest cocoa beans producers in the world, Indonesian cocoa beans are oftenly of low quality and thereby frequently priced low in the world market. In order to improve the quality, adequate post-harvest cocoa processing techniques are required. Fermentation is the vital stage in series of cocoa beans post harvest processing which could improve the quality of cocoa beans, in particular taste, aroma, and colours. During the fermentation process, combination of microbes grow producing metabolites that serve as the precursors for cocoa beans flavour. Microbial composition and thereby their activities will affect the fermentation performance and influence the properties of cocoa beans. The correlation could be reviewed using a kinetic model that includes unstructured microbial growth, substrate utilization and metabolic product formation. The developed kinetic model could be further used to design cocoa bean fermentation process to meet the expected quality. Further the development of kinetic model of cocoa bean fermentation also serve as a good case study of mixed culture solid state fermentation, that has rarely been studied. This paper presents the development of a kinetic model for solid-state cocoa beans fermentation using an empirical approach. Series of lab scale cocoa bean fermentations, either natural fermentations without starter addition or fermentations with mixed yeast and lactic acid bacteria starter addition, were used for model parameters estimation. The results showed that cocoa beans fermentation can be modelled mathematically and the best model included substrate utilization, microbial growth, metabolites production and its transport. Although the developed model still can not explain the dynamics in microbial population, this model can sufficiently explained the observed changes in sugar concentration as well as metabolic products in the cocoa bean pulp.

Influence of austenite grain size on recrystallisation-precipitation interaction in a V-microalloyed steel

International Nuclear Information System (INIS)

Quispe, A.; Medina, S.F.; Gomez, M.; Chaves, J.I.

2007-01-01

By means of torsion tests using small specimens, the influence of austenite grain size on strain induced precipitation kinetics has been determined in a vanadium microalloyed steel. Determination of recrystallisation-precipitation-time-temperature (RPTT) diagrams for two austenite grain sizes allows values of the aforementioned magnitudes to be determined. An ample discussion is made of the quantitative influence found and its relation with nucleation and growth mechanisms of precipitates. The results are compared with the quantitative influence exerted by the other variables, reaching the conclusion that the austenite grain size has a notable influence on strain induced precipitation kinetics which should not be underestimated. Finally, the influence of austenite grain size is included in a strain induced precipitation model constructed by the authors of this work and which also takes into account the other aforementioned variables

The effects of one-dimensional glide on the reaction kinetics of interstitial clusters

DEFF Research Database (Denmark)

Heinisch, H.L.; Singh, B.N.; Golubov, S.I.

2000-01-01

is therefore 'mixed 1D/3D migration' along a 3D path consisting of 1D segments, The defect reaction kinetics under mixed 1D/3D diffusion are different from pure 1D diffusion and pure 3D diffusion, both of which can be formulated within analytical rate theory models of microstructure evolution under irradiation....... Atomic-scale kinetic Monte Carlo (kMC) defect migration simulations are used to investigate the effects of mixed 1D/3D migration on defect reaction kinetics as a guide for implementing mixed 1D/3D migration into the analytical rate theory. The functional dependence of the sink strength on the size...

Repair kinetics in tissues

International Nuclear Information System (INIS)

Thames, H.D.

1989-01-01

Monoexponential repair kinetics is based on the assumption of a single, dose-independent rate of repair of sublethal injury in the target cells for tissue injury after exposure to ionizing radiation. Descriptions of the available data based on this assumption have proved fairly successful for both acutely responding (skin, lip mucosa, gut) and late-responding (lung, spinal cord) normal tissues. There are indications of biphasic exponential repair in both categories, however. Unfortunately, the data usually lack sufficient resolution to permit unambiguous determination of the repair rates. There are also indications that repair kinetics may depend on the size of the dose. The data are conflicting on this account, however, with suggestions of both faster and slower repair after larger doses. Indeed, experiments that have been explicitly designed to test this hypothesis show either no effect (gut, spinal cord), faster repair after higher doses (lung, kidney), or slower repair after higher doses (skin). Monoexponential repair appears to be a fairly accurate description that provides an approximation to a more complicated picture, the elucidation of whose details will, however, require very careful and extensive experimental study. (author). 30 refs.; 1 fig

Parallelized Seeded Region Growing Using CUDA

Directory of Open Access Journals (Sweden)

Seongjin Park

2014-01-01

Full Text Available This paper presents a novel method for parallelizing the seeded region growing (SRG algorithm using Compute Unified Device Architecture (CUDA technology, with intention to overcome the theoretical weakness of SRG algorithm of its computation time being directly proportional to the size of a segmented region. The segmentation performance of the proposed CUDA-based SRG is compared with SRG implementations on single-core CPUs, quad-core CPUs, and shader language programming, using synthetic datasets and 20 body CT scans. Based on the experimental results, the CUDA-based SRG outperforms the other three implementations, advocating that it can substantially assist the segmentation during massive CT screening tests.

Application of neutron radiography and tomography for analysis of root morphology of growing ginseng

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyun Ho; Sung, Bong Jae; Park, Jong Yoon [Geumsan Agricultural Development and Technology Center, Geumsan (Korea, Republic of); Sim, Cheul Muu; Kim, Young Jin; Lee, Seung Wook [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

2005-07-01

The shape of main root of ginseng is very important for its commercial value. The morphology of main root is predominantly determined by the root-growing pattern in one year after transplantation of ginseng seedling(one years root). There are many factors affecting the root growing of young ginseng but no systematic approach has been applied to find the effects of various factors. The main reason for this was no method was sought to see the root shapes non-destructively. Neutron radiography is thought to be an appropriate NDT method for root morphology examination in ginseng and a study on using NR for the research on ginseng is being conducted. Considering that the live plants should be moved to the reactor site for their examination of four or five times per year at least, the pot growing method is indispensable. The pot should contain enough soils for growing-up of ginseng and its maximum size is limited to have good contrast in neutron radiography image of ginseng root. Thus, a preliminary radiographic study was performed to find the proper size of ginseng pot using the NR facility of HANARO. Several pots will be prepared for young ginsengs and they will be examined for about one year.

Application of neutron radiography and tomography for analysis of root morphology of growing ginseng

International Nuclear Information System (INIS)

Kim, Hyun Ho; Sung, Bong Jae; Park, Jong Yoon; Sim, Cheul Muu; Kim, Young Jin; Lee, Seung Wook

2005-01-01

The shape of main root of ginseng is very important for its commercial value. The morphology of main root is predominantly determined by the root-growing pattern in one year after transplantation of ginseng seedling(one years root). There are many factors affecting the root growing of young ginseng but no systematic approach has been applied to find the effects of various factors. The main reason for this was no method was sought to see the root shapes non-destructively. Neutron radiography is thought to be an appropriate NDT method for root morphology examination in ginseng and a study on using NR for the research on ginseng is being conducted. Considering that the live plants should be moved to the reactor site for their examination of four or five times per year at least, the pot growing method is indispensable. The pot should contain enough soils for growing-up of ginseng and its maximum size is limited to have good contrast in neutron radiography image of ginseng root. Thus, a preliminary radiographic study was performed to find the proper size of ginseng pot using the NR facility of HANARO. Several pots will be prepared for young ginsengs and they will be examined for about one year

How cells grow and divide: mathematical analysis confirms demand for the cell cycle

International Nuclear Information System (INIS)

Kwon, Hyun Woong; Choi, M Y

2012-01-01

Eukaryotes usually grow through cell growth and division. How cells grow and divide is essential to life because too small or too large cells cannot function well. In order for an organism to survive even under a condition where cell growth and division processes are independent of each other, cells must have an appropriate growth factor, growth rate and division rate. To determine them, we derive a time evolution equation for the size distribution of cells from the master equation describing changes in the cell size due to growth and in the total number of cells due to division. It is found that long-time behaviors of moments of the size distribution divide the parameter space, consisting of the growth factor and the ratio of the division rate to the growth rate, into infinitely many regions. Examining the properties of each region, we conclude that growth with a small growth factor may be disastrous; this demonstrates the demand for the cell cycle consisting of coordinated growth and division processes. (paper)

Rapidly- growing firms and their main characteristics: a longitudinal study from United States

DEFF Research Database (Denmark)

Keen, Christian; Etemad, Hamid

2011-01-01

concerning the theoretical relations between high-growth and location, size and temporal characteristics of the high-growth enterprises. Using non parametric tests, we analyze a 21-year longitudinal database of privately held rapidly growing enterprises from the USA. This analysis indicates that these firms...... are relatively smaller enterprises and their high growth rates are not restricted to a particular location, industrial region, size or time period. The findings of this analysis point to a population of high-growth enterprises with diverse locations, sizes and times with important implications for scholarly...

Kinetics and mechanisms of the oxide film growth on the surface of α-Fe in transitional domains

International Nuclear Information System (INIS)

Mukhambetov, D.G.; Berber, N.N.; Kargin, D.B.; Chalaya, O.V.

2003-01-01

The object of this work was to study the kinetics of the α-Fe surface oxidation with prevailing cubic texture at temperatures of 450-500 deg. C. The basic conformity to natural laws and mechanisms of the two-phase thin oxide films grows are determined. (author)

Copper Root Pruning and Container Cavity Size Influence Longleaf Pine Growth through Five Growing Seasons

Science.gov (United States)

James D. Haywood; Shi-Jean Susana Sung; Mary Anne Sword Sayer

2012-01-01

However, type and size of container can influence field performance. In this study, longleaf pine seedlings were grown in Beaver Plastics Styroblocks either without a copper treatment (Superblock) or with a copper oxychloride coating (Copperblock) and with three sizes of cavities that were 60, 108, and 164 ml. Seedlings from the six container types (two types of...

Child–adult differences in the kinetics of torque development

Science.gov (United States)

DOTAN, RAFFY; MITCHELL, CAMERON; COHEN, ROTEM; GABRIEL, DAVID; KLENTROU, PANAGIOTA; FALK, BAREKET

2013-01-01

Children have lower size-normalised maximal voluntary force, speed, and power than adults. It has been hypothesised that these and other age-related performance differences are due to lesser type-II motor-unit utilisation in children. This should be manifested as slower force kinetics in explosive muscle contractions. The purpose of this study was to investigate the nature of child–adult force-kinetics differences and whether the latter could support that hypothesis. Untrained boys (n = 20) and men (n = 20) (10.1 ± 1.3 and 22.9 ± 4.4 years, respectively), performed maximal, explosive, isometric elbow flexions and knee extensions on a Biodex dynamometer. Peak torque (MVC), times to 10–100% MVC, and other kinetics parameters were determined. The boys’ body-mass-normalised knee extension MVC, peak rate of torque development, and %MVC at 100 ms were 26, 17 and 23% lower compared with the men and their times to 30% and 80% MVC were 24 and 48% longer, respectively. Elbow flexion kinetics showed similar or greater differences. The findings illuminate boys’ inherent disadvantage in tasks requiring speed or explosive force. It is demonstrated that the extent of the boys–men kinetics disparity cannot be explained by muscle-composition and/or musculo-tendinous-stiffness differences. We suggest therefore that the findings indirectly support children’s lower utilisation of type-II motor units. PMID:23320937

Blood lactate kinetics in normal and stress-susceptible pigs

International Nuclear Information System (INIS)

Darrah, P.S.; Beitz, D.C.; Topel, D.G.; Christian, L.L.

1981-01-01

In vitro rates of lactate metabolism were determined in stress-susceptible (SS) and stress-resistant (SR) pigs. Three SR and three SS pigs were given 20 muCi of [U-/sup 14/C] L-lactate by a single injection method and resting blood lactate kinetics were measured. Seventeen blood samples were taken during the 60 min after injection. Lactate was separated from the deproteinized plasma by silicic acid column chromatography, and specific radioactivity was determined. Kinetic characteristics were calculated from plots of specific activity versus time. Pigs met steady-state requirements during the sampling period. There were no differences in kinetic characteristics of resting SS and SR pigs. Later, a second isotope injection was given after 5 min of electrical stress. Lactate pool sizes increased similarly in both types of pigs after stress; however, SS pigs had greater plasma lactate concentrations after stress. It is concluded that SS and SR pigs respond differently to stress but have similar capacities to metabolize lactate while resting

Uranium oxidation kinetics monitored by in-situ X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Zalkind, S., E-mail: shimonzl@nrcn.org.il; Rafailov, G.; Halevy, I.; Livneh, T.; Rubin, A.; Maimon, H.; Schweke, D.

2017-03-15

The oxidation kinetics of U-0.1 wt%Cr at oxygen pressures of 150 Torr and the temperature range of 90–150 °C was studied by means of in-situ X-ray diffraction (XRD). A “breakaway” in the oxidation kinetics is found at ∼0.25 μm, turning from a parabolic to a linear rate law. At the initial stage of oxidation the growth plane of UO{sub 2}(111) is the prominent one. As the oxide thickens, the growth rate of UO{sub 2}(220) plane increases and both planes grow concurrently. The activation energies obtained for the oxide growth are Q{sub parabolic} = 17.5 kcal/mol and Q{sub linear} = 19 kcal/mol. Enhanced oxidation around uranium carbide (UC) inclusions is clearly observed by scanning electron microscopy (SEM).

On the origin of the cobalt particle size effects in Fischer−Tropsch catalysis

NARCIS (Netherlands)

den Breejen, J.P.|info:eu-repo/dai/nl/304837318; Radstake, P.B.|info:eu-repo/dai/nl/304829587; Bezemer, G.L.; Bitter, J.H.|info:eu-repo/dai/nl/160581435; Froseth, V.; Holmen, A.; de Jong, K.P.|info:eu-repo/dai/nl/06885580X

2009-01-01

The effects of metal particle size in catalysis are of prime scientific and industrial importance and call for a better understanding. In this paper the origin of the cobalt particle size effects in Fischer−Tropsch (FT) catalysis was studied. Steady-State Isotopic Transient Kinetic Analysis (SSITKA)

Application of a small molecule radiopharmaceutical concept to improve kinetics

International Nuclear Information System (INIS)

Jeong, Jae Min

2016-01-01

Recently, large molecules or nanoparticles are actively studied as radiopharmaceuticals. However, their kinetics is problematic because of a slow penetration through the capillaries and slow distribution to the target. To improve the kinetics, a two-step targeting method can be applied by using small molecules and very rapid copper-free click reaction. Although this method might have limitations such as internalization of the first targeted conjugate, it will provide high target-to-non-target ratio imaging of radiopharmaceuticals. The majority of radiopharmaceuticals belong to small molecules of which the molecular weight is less than 2000 Da, and the molecular size is smaller than 2 nm generally. The outstanding feature of the small molecule radiopharmaceuticals compared to large molecules is with their kinetics. Their distribution to target and clearance from non-target tissues are very rapid, which is the essential requirement of radiopharmaceuticals. In conclusion, the small molecule radiopharmaceuticals generally show excellent biodistribution properties; however, they show poor efficiency of radioisotope delivery. Large molecule or nanoparticle radiopharmaceuticals have advantages of multimodal and efficient delivery, but lower target-to-non-target ratio. Two-step targeting using a bio-orthogonal copper-free click reaction can be a solution of the problem of large molecule or nanoparticle radiopharmaceuticals. The majority of radiopharmaceuticals belong to small molecules of which the molecular weight is less than 2000 Da, and the molecular size is smaller than 2 nm generally. The outstanding feature of the small molecule radiopharmaceuticals compared to large molecules is with their kinetics. Their distribution to target and clearance from non-target tissues are very rapid, which is the essential requirement of radiopharmaceuticals

Application of a small molecule radiopharmaceutical concept to improve kinetics

Energy Technology Data Exchange (ETDEWEB)

Jeong, Jae Min [Dept. of Nuclear Medicine, Seoul National University College of Medicine, Seoul (Korea, Republic of)

2016-06-15

Recently, large molecules or nanoparticles are actively studied as radiopharmaceuticals. However, their kinetics is problematic because of a slow penetration through the capillaries and slow distribution to the target. To improve the kinetics, a two-step targeting method can be applied by using small molecules and very rapid copper-free click reaction. Although this method might have limitations such as internalization of the first targeted conjugate, it will provide high target-to-non-target ratio imaging of radiopharmaceuticals. The majority of radiopharmaceuticals belong to small molecules of which the molecular weight is less than 2000 Da, and the molecular size is smaller than 2 nm generally. The outstanding feature of the small molecule radiopharmaceuticals compared to large molecules is with their kinetics. Their distribution to target and clearance from non-target tissues are very rapid, which is the essential requirement of radiopharmaceuticals. In conclusion, the small molecule radiopharmaceuticals generally show excellent biodistribution properties; however, they show poor efficiency of radioisotope delivery. Large molecule or nanoparticle radiopharmaceuticals have advantages of multimodal and efficient delivery, but lower target-to-non-target ratio. Two-step targeting using a bio-orthogonal copper-free click reaction can be a solution of the problem of large molecule or nanoparticle radiopharmaceuticals. The majority of radiopharmaceuticals belong to small molecules of which the molecular weight is less than 2000 Da, and the molecular size is smaller than 2 nm generally. The outstanding feature of the small molecule radiopharmaceuticals compared to large molecules is with their kinetics. Their distribution to target and clearance from non-target tissues are very rapid, which is the essential requirement of radiopharmaceuticals.

Comparison of NBG-18, NBG-17, IG-110 and IG-11 oxidation kinetics in air

Science.gov (United States)

Lee, Jo Jo; Ghosh, Tushar K.; Loyalka, Sudarshan K.

2018-03-01

The oxidation rates of several nuclear-grade graphites, NBG-18, NBG-17, IG-110 and IG-11, were measured in air using thermogravimetry. Kinetic parameters and oxidation behavior for each grade were compared by coke type, filler grain size and microstructure. The thickness of the oxidized layer for each grade was determined by layer peeling and direct density measurements. The results for NBG-17 and IG-11 were compared with those available in the literature and our recently reported results for NBG-18 and IG-110 oxidation in air. The finer-grained graphites IG-110 and IG-11 were more oxidized than medium-grained NBG-18 and NBG-17 because of deeper oxidant penetration, higher porosity and higher probability of available active sites. Variation in experimental conditions also had a marked effect on the reported kinetic parameters by several studies. Kinetic parameters such as activation energy and transition temperature were sensitive to air flow rates as well as sample size and geometry.

Striking dynamics and kinetic properties of boxing and MMA gloves

Directory of Open Access Journals (Sweden)

Benjamin Lee

2014-08-01

Full Text Available With the growing popularity of Mixed Martial Arts (MMA as a competitive sport, questions regarding the dynamic response and properties of MMA gloves arise. High-energy impacts from punches are very similar to boxing yet MMA competition requires the use of 4 oz fingerless glove, compared to the larger full enclosure boxing glove. This work assessed the kinetic properties and strike dynamics of MMA gloves and compared findings with traditional boxing gloves. Gloves mounted on a molded fist were impacted repetitively on an instrumental anvil designed for impact, over a 5 hour period resulting in 10,000 continuous and consistent strikes. Kinetic data from impacts were sampled at the beginning of the data collection and subsequently every 30 minutes (every 1,000 strikes. MMA gloves produced 4-5 times greater peak force and 5 times faster load rate compared to the boxing glove. However, MMA gloves also showed signs of material fatigue, with peak force increasing by 35% and rate of loading increasing by 60% over the duration of the test. Boxing glove characteristics did deteriorate but to a lesser extent. In summary, the kinetic properties of MMA glove differed substantially from the boxing glove resulting in impacts characterized by higher peak forces and more rapid development of force. Material properties including stiffness and thickness play a role in the kinetic characteristics upon impact, and can be inferred to alter injury mechanisms of blunt force trauma.

Microstructure and hydrogen sorption kinetics of Mg nanopowders with catalyst

International Nuclear Information System (INIS)

Revesz, A.; Fatay, D.; Spassov, T.

2007-01-01

MgH 2 powders were ball-milled with and without catalysts (Nb 2 O 5 ) under hydrogen in a high-energy mill for 10 h. Morphological, structural and microstructural characterization of the nanocomposites, including particle and crystallite size distribution were carried out before and after hydrogen absorption. In order to study the above-mentioned microstructural parameters imaging and X-ray scattering techniques (high-resolution X-ray diffractometry) have been employed. The effect of the particle and grain size on the hydriding/dehydriding kinetics of ball-milled MgH 2 + catalyst powders was analyzed. The grain and particle size reduction enhances substantially the hydriding/dehydriding

Cesium removal and kinetics equilibrium: Precipitation kinetics

International Nuclear Information System (INIS)

Barnes, M.J.

1999-01-01

This task consisted of both non-radioactive and radioactive (tracer) tests examining the influence of potentially significant variables on cesium tetraphenylborate precipitation kinetics. The work investigated the time required to reach cesium decontamination and the conditions that affect the cesium precipitation kinetics

Kinetic modelling for zinc (II) ions biosorption onto Luffa cylindrica

International Nuclear Information System (INIS)

Oboh, I.; Aluyor, E.; Audu, T.

2015-01-01

The biosorption of Zinc (II) ions onto a biomaterial - Luffa cylindrica has been studied. This biomaterial was characterized by elemental analysis, surface area, pore size distribution, scanning electron microscopy, and the biomaterial before and after sorption, was characterized by Fourier Transform Infra Red (FTIR) spectrometer. The kinetic nonlinear models fitted were Pseudo-first order, Pseudo-second order and Intra-particle diffusion. A comparison of non-linear regression method in selecting the kinetic model was made. Four error functions, namely coefficient of determination (R 2 ), hybrid fractional error function (HYBRID), average relative error (ARE), and sum of the errors squared (ERRSQ), were used to predict the parameters of the kinetic models. The strength of this study is that a biomaterial with wide distribution particularly in the tropical world and which occurs as waste material could be put into effective utilization as a biosorbent to address a crucial environmental problem

Characteristics of phosphorus adsorption by sediment mineral matrices with different particle sizes

Directory of Open Access Journals (Sweden)

Yang Xiao

2013-07-01

Full Text Available The particle size of sediment is one of the main factors that influence the phosphorus physical adsorption on sediment. In order to eliminate the effect of other components of sediment on the phosphorus physical adsorption the sediment mineral matrices were obtained by removing inorganic matter metal oxides, and organic matter from natural sediments, which were collected from the Nantong reach of the Yangtze River. The results show that an exponential relationship exists between the median particle size (D50 and specific surface area (Sg of the sediment mineral matrices, and the fine sediment mineral matrix sample has a larger specific surface area and pore volume than the coarse sediment particles. The kinetic equations were used to describe the phosphorus adsorption process of the sediment mineral matrices, including the Elovich equation, quasi-first-order adsorption kinetic equation, and quasi-second-order adsorption kinetic equation. The results show that the quasi-second-order adsorption kinetic equation has the best fitting effect. Using the mass conservation and Langmuir adsorption kinetic equations, a formula was deduced to calculate the equilibrium adsorption capacity of the sediment mineral matrices. The results of this study show that the phosphorus adsorption capacity decreases with the increase of D50, indicating that the specific surface area and pore volume are the main factors in determining the phosphorus adsorption capacity of the sediment mineral matrices. This study will help understand the important role of sediment in the transformation of phosphorus in aquatic environments.

Growing media [Chapter 5

Science.gov (United States)

Douglass F. Jacobs; Thomas D. Landis; Tara Luna

2009-01-01

Selecting the proper growing medium is one of the most important considerations in nursery plant production. A growing medium can be defined as a substance through which roots grow and extract water and nutrients. In native plant nurseries, a growing medium can consist of native soil but is more commonly an "artificial soil" composed of materials such as peat...

Analysis and simulation of phase transformation kinetics of zeolite A from amorphous phases

CERN Document Server

Marui, Y; Uchida, H; Takiyama, H

2003-01-01

Experiments on transformation rates of zeolite A from amorphous phases at different feed rates to alter the particle size of the amorphous phases were carried out to analyze the kinetics of the transformation, and were analyzed by performing simulation of the transformation. A clear dependence of the induction time for nucleation of zeolite A crystals on the surface area of the amorphous phase was recognized, indicating that the nucleation of zeolite A was heterogeneous and the nucleation rate was almost proportional to the size of the amorphous particles. From the simulation, the mechanism of the transformation was found to be heterogeneous nucleation of zeolite A crystals on the surface of amorphous particles followed by solution mediated phase transformation, and the transformation kinetics were well reproduced at different feed rates. (author)

Coarsening kinetics of γ' precipitates in the Ni-Al-Mo system

International Nuclear Information System (INIS)

Wang Tao; Sheng Guang; Liu Zikui; Chen Longqing

2008-01-01

The effect of Mo on the microstructure evolution and coarsening kinetics of γ' precipitates in the Ni-Al-Mo system is studied using phase-field simulations with inputs from thermodynamic, kinetic and lattice parameter databases. For alloys of different compositions, the precipitate morphology and the statistical information of precipitate sizes are predicted as a function of annealing time. It is observed that increasing Mo content leads to a change of the precipitate morphology from being cuboidal to spherical as well as a reduction in the coarsening rate. Comparison between simulated results and existing experimental microstructure morphologies and coarsening rates shows good agreements

Effective computation of stochastic protein kinetic equation by reducing stiffness via variable transformation

Energy Technology Data Exchange (ETDEWEB)

Wang, Lijin, E-mail: ljwang@ucas.ac.cn [School of Mathematical Sciences, University of Chinese Academy of Sciences, Beijing 100049 (China)

2016-06-08

The stochastic protein kinetic equations can be stiff for certain parameters, which makes their numerical simulation rely on very small time step sizes, resulting in large computational cost and accumulated round-off errors. For such situation, we provide a method of reducing stiffness of the stochastic protein kinetic equation by means of a kind of variable transformation. Theoretical and numerical analysis show effectiveness of this method. Its generalization to a more general class of stochastic differential equation models is also discussed.

Simulation study of effects of initial particle size distribution on dissolution

International Nuclear Information System (INIS)

Wang, G.; Xu, D.S.; Ma, N.; Zhou, N.; Payton, E.J.; Yang, R.; Mills, M.J.; Wang, Y.

2009-01-01

Dissolution kinetics of γ' particles in binary Ni-Al alloys with different initial particle size distributions (PSD) is studied using a three-dimensional (3D) quantitative phase field model. By linking model inputs directly to thermodynamic and atomic mobility databases, microstructural evolution during dissolution is simulated in real time and length scales. The model is first validated against analytical solution for dissolution of a single γ' particle in 1D and numerical solution in 3D before it is applied to investigate the effects of initial PSD on dissolution kinetics. Four different types of PSD, uniform, normal, log-normal and bimodal, are considered. The simulation results show that the volume fraction of γ' particles decreases exponentially with time, while the temporal evolution of average particle size depends strongly on the initial PSD

Effects of butter naturally enriched with conjugated linoleic acid and vaccenic acid on blood lipids and LDL particle size in growing pigs

Directory of Open Access Journals (Sweden)

Haug Anna

2008-08-01

Full Text Available Abstract Background Cow milk is a natural source of the cis 9, trans 11 isomer of conjugated linoleic acid (c9,t11-CLA and trans vaccenic acid (VA. These fatty acids may be considered as functional foods, and the concentration in milk can be increased by e.g. sunflower oil supplementation to the dairy cow feed. The objective of this study was to compare the effects of regular butter with a special butter naturally enriched in c9,t11-CLA and VA on plasma lipids in female growing pigs. The experimental period lasted for three weeks and the two diets provided daily either 5.0 g c9,t11-CLA plus 15.1 g VA or 1.3 g c9,t11-CLA plus 3.6 g VA. Results The serum concentrations of c9,t11-CLA, VA and alpha-linolenic acid were increased and myristic (14:0 and palmitic acid (16:0 were reduced in the pigs fed the CLA+VA-rich butter-diet compared to regular butter, but no differences in plasma concentrations of triacylglycerol, cholesterol, HDL-cholesterol, LDL-cholesterol, LDL particle size distribution or total cholesterol/HDL cholesterol were observed among the two dietary treatment groups. Conclusion Growing pigs fed diets containing butter naturally enriched in about 20 g c9,t11-CLA plus VA daily for three weeks, had increased serum concentrations of alpha-linolenic acid and decreased myristic and palmitic acid compared to pigs fed regular butter, implying a potential benefit of the CLA+VA butter on serum fatty acid composition. Butter enriched in CLA+VA does not appear to have significant effect on the plasma lipoprotein profile in pigs.

Effects of butter naturally enriched with conjugated linoleic acid and vaccenic acid on blood lipids and LDL particle size in growing pigs

Science.gov (United States)

Haug, Anna; Sjøgren, Per; Hølland, Nina; Müller, Hanne; Kjos, Nils P; Taugbøl, Ole; Fjerdingby, Nina; Biong, Anne S; Selmer-Olsen, Eirik; Harstad, Odd M

2008-01-01

Background Cow milk is a natural source of the cis 9, trans 11 isomer of conjugated linoleic acid (c9,t11-CLA) and trans vaccenic acid (VA). These fatty acids may be considered as functional foods, and the concentration in milk can be increased by e.g. sunflower oil supplementation to the dairy cow feed. The objective of this study was to compare the effects of regular butter with a special butter naturally enriched in c9,t11-CLA and VA on plasma lipids in female growing pigs. The experimental period lasted for three weeks and the two diets provided daily either 5.0 g c9,t11-CLA plus 15.1 g VA or 1.3 g c9,t11-CLA plus 3.6 g VA. Results The serum concentrations of c9,t11-CLA, VA and alpha-linolenic acid were increased and myristic (14:0) and palmitic acid (16:0) were reduced in the pigs fed the CLA+VA-rich butter-diet compared to regular butter, but no differences in plasma concentrations of triacylglycerol, cholesterol, HDL-cholesterol, LDL-cholesterol, LDL particle size distribution or total cholesterol/HDL cholesterol were observed among the two dietary treatment groups. Conclusion Growing pigs fed diets containing butter naturally enriched in about 20 g c9,t11-CLA plus VA daily for three weeks, had increased serum concentrations of alpha-linolenic acid and decreased myristic and palmitic acid compared to pigs fed regular butter, implying a potential benefit of the CLA+VA butter on serum fatty acid composition. Butter enriched in CLA+VA does not appear to have significant effect on the plasma lipoprotein profile in pigs. PMID:18759970

Kinetics of ion exchange in the chelating resin Dowex A-1

International Nuclear Information System (INIS)

Matsuzuru, Hideo; Wadachi, Yoshiki

1975-01-01

The kinetics of ion exchanges of Ag + , Zn 2+ and Cr 3+ at extremely low concentrations on the chelating resin Dowex A-1 has been studied by means of finite volume method. The rate of exchanges for both Ag + and Zn 2+ is dependent on the ionic strength, particle size of the resin and reaction temperature. At higher ionic strength (0.1 - 0.05) the kinetics is controlled by particle diffusion, whereas at lower ionic one (0.01 - 0.001) film diffusion is predominant. The apparent activation energy obtained is 3.84 kcal/mol for Ag + and 3.91 kcal/mol for Zn 2+ . The exchange rate of Cr 3+ obeys a first-order rate equation independent of the ionic strength and particle size of the resin. The apparent activation energy is 15.5 kcal/mol. These results support the view that the rate-determining step of this reaction is chelate formation reaction. (auth.)

Estimation of Adjoint-Weighted Kinetics Parameters in Monte Carlo Wieland Calculations

International Nuclear Information System (INIS)

Choi, Sung Hoon; Shim, Hyung Jin

2013-01-01

The effective delayed neutron fraction, β eff , and the prompt neutron generation time, Λ, in the point kinetics equation are weighted by the adjoint flux to improve the accuracy of the reactivity estimate. Recently the Monte Carlo (MC) kinetics parameter estimation methods by using the self-consistent adjoint flux calculated in the MC forward simulations have been developed and successfully applied for the research reactor analyses. However these adjoint estimation methods based on the cycle-by-cycle genealogical table require a huge memory size to store the pedigree hierarchy. In this paper, we present a new adjoint estimation in which the pedigree of a single history is utilized by applying the MC Wielandt method. The effectiveness of the new method is demonstrated in the kinetics parameter estimations for infinite homogeneous two-group problems and the Godiva critical facility

Nucleation theory with delayed interactions: an application to the early stages of the receptor-mediated adhesion/fusion kinetics of lipid vesicles.

Science.gov (United States)

Raudino, Antonio; Pannuzzo, Martina

2010-01-28

A semiquantitative theory aimed to describe the adhesion kinetics between soft objects, such as living cells or vesicles, has been developed. When rigid bodies are considered, the adhesion kinetics is successfully described by the classical Derjaguin, Landau, Verwey, and Overbeek (DLVO) picture, where the energy profile of two approaching bodies is given by a two asymmetrical potential wells separated by a barrier. The transition probability from the long-distance to the short-distance minimum defines the adhesion rate. Conversely, soft bodies might follow a different pathway to reach the short-distance minimum: thermally excited fluctuations give rise to local protrusions connecting the approaching bodies. These transient adhesion sites are stabilized by short-range adhesion forces (e.g., ligand-receptor interactions between membranes brought at contact distance), while they are destabilized both by repulsive forces and by the elastic deformation energy. Above a critical area of the contact site, the adhesion forces prevail: the contact site grows in size until the complete adhesion of the two bodies inside a short-distance minimum is attained. This nucleation mechanism has been developed in the framework of a nonequilibrium Fokker-Planck picture by considering both the adhesive patch growth and dissolution processes. In addition, we also investigated the effect of the ligand-receptor pairing kinetics at the adhesion site in the time course of the patch expansion. The ratio between the ligand-receptor pairing kinetics and the expansion rate of the adhesion site is of paramount relevance in determining the overall nucleation rate. The theory enables one to self-consistently include both thermodynamics (energy barrier height) and dynamic (viscosity) parameters, giving rise in some limiting cases to simple analytical formulas. The model could be employed to rationalize fusion kinetics between vesicles, provided the short-range adhesion transition is the rate

Magnetic agglomeration method for size control in the synthesis of magnetic nanoparticles

Science.gov (United States)

Huber, Dale L [Albuquerque, NM

2011-07-05

A method for controlling the size of chemically synthesized magnetic nanoparticles that employs magnetic interaction between particles to control particle size and does not rely on conventional kinetic control of the reaction to control particle size. The particles are caused to reversibly agglomerate and precipitate from solution; the size at which this occurs can be well controlled to provide a very narrow particle size distribution. The size of particles is controllable by the size of the surfactant employed in the process; controlling the size of the surfactant allows magnetic control of the agglomeration and precipitation processes. Agglomeration is used to effectively stop particle growth to provide a very narrow range of particle sizes.

Heparin kinetics

International Nuclear Information System (INIS)

Swart, C.A.M. de.

1983-01-01

The author has studied the kinetics of heparin and heparin fractions after intravenous administration in humans and in this thesis the results of this study are reported. Basic knowledge about the physico-chemical properties of heparin and its interactions with proteins resulting in anticoagulant and lipolytic effects are discussed in a review (chapter II), which also comprises some clinical aspects of heparin therapy. In chapter III the kinetics of the anticoagulant effect are described after intravenous administration of five commercial heparin preparations. A mathematical model is presented that fits best to these kinetics. The kinetics of the anticoagulant and lipolytic effects after intravenous injection of various 35 S-radiolabelled heparin fractions and their relationship with the disappearance of the radiolabel are described in chapter IV. Chapter V gives a description of the kinetics of two radiolabels after injection of in vitro formed complexes consisting of purified, 125 I-radiolabelled antithrombin III and various 35 S-radiolabelled heparin fractions. (Auth.)

Anomalous roughness of turbulent interfaces with system size dependent local roughness exponent

International Nuclear Information System (INIS)

Balankin, Alexander S.; Matamoros, Daniel Morales

2005-01-01

In a system far from equilibrium the system size can play the role of control parameter that governs the spatiotemporal dynamics of the system. Accordingly, the kinetic roughness of interfaces in systems far from equilibrium may depend on the system size. To get an insight into this problem, we performed a detailed study of rough interfaces formed in paper combustion experiments. Using paper sheets of different width λ, we found that the turbulent flame fronts display anomalous multi-scaling characterized by non-universal global roughness exponent α and by the system size dependent spectrum of local roughness exponents, ζ q (λ)=ζ 1 (1)q -ω λ φ q =0.93q -0.15 . The structure factor of turbulent flame fronts also exhibits unconventional scaling dependence on λ. These results are expected to apply to a broad range of far from equilibrium systems when the kinetic energy fluctuations exceed a certain critical value.

Kinetics of coal pyrolysis

Energy Technology Data Exchange (ETDEWEB)

Seery, D.J.; Freihaut, J.D.; Proscia, W.M. (United Technologies Research Center, East Hartford, CT (USA)); Howard, J.B.; Peters, W.; Hsu, J.; Hajaligol, M.; Sarofim, A. (Massachusetts Inst. of Tech., Cambridge, MA (USA)); Jenkins, R.; Mallin, J.; Espindola-Merin, B. (Pennsylvania State Univ., University Park, PA (USA)); Essenhigh, R.; Misra, M.K. (Ohio State Univ., Columbus, OH (USA))

1989-07-01

This report contains results of a coordinated, multi-laboratory investigation of coal devolatilization. Data is reported pertaining to the devolatilization for bituminous coals over three orders of magnitude in apparent heating rate (100 to 100,000 + {degree}C/sec), over two orders of magnitude in particle size (20 to 700 microns), final particle temperatures from 400 to 1600{degree}C, heat transfer modes ranging from convection to radiative, ambient pressure ranging from near vacuum to one atmosphere pressure. The heat transfer characteristics of the reactors are reported in detail. It is assumed the experimental results are to form the basis of a devolatilization data base. Empirical rate expressions are developed for each phase of devolatilization which, when coupled to an awareness of the heat transfer rate potential of a particular devolatilization reactor, indicate the kinetics emphasized by a particular system reactor plus coal sample. The analysis indicates the particular phase of devolatilization that will be emphasized by a particular reactor type and, thereby, the kinetic expressions appropriate to that devolatilization system. Engineering rate expressions are developed from the empirical rate expressions in the context of a fundamental understanding of coal devolatilization developed in the course of the investigation. 164 refs., 223 figs., 44 tabs.

Tissue distribution and excretion kinetics of orally administered silica nanoparticles in rats

Directory of Open Access Journals (Sweden)

Lee JA

2014-12-01

Full Text Available Jeong-A Lee,1 Mi-Kyung Kim,1 Hee-Jeong Paek,1 Yu-Ri Kim,2 Meyoung-Kon Kim,2 Jong-Kwon Lee,3 Jayoung Jeong,3 Soo-Jin Choi1 1Department of Food Science and Technology, Seoul Women’s University, Seoul, Republic of Korea; 2Department of Biochemistry and Molecular Biology, Korea University Medical School and College, Seoul, Republic of Korea; 3Toxicological Research Division, National Institute of Food and Drug Safety Evaluation, Chungchungbuk–do, Republic of Korea Purpose: The effects of particle size on the tissue distribution and excretion kinetics of silica nanoparticles and their biological fates were investigated following a single oral administration to male and female rats. Methods: Silica nanoparticles of two different sizes (20 nm and 100 nm were orally administered to male and female rats, respectively. Tissue distribution kinetics, excretion profiles, and fates in tissues were analyzed using elemental analysis and transmission electron microscopy. Results: The differently sized silica nanoparticles mainly distributed to kidneys and liver for 3 days post-administration and, to some extent, to lungs and spleen for 2 days post-administration, regardless of particle size or sex. Transmission electron microscopy and energy dispersive spectroscopy studies in tissues demonstrated almost intact particles in liver, but partially decomposed particles with an irregular morphology were found in kidneys, especially in rats that had been administered 20 nm nanoparticles. Size-dependent excretion kinetics were apparent and the smaller 20 nm particles were found to be more rapidly eliminated than the larger 100 nm particles. Elimination profiles showed 7%–8% of silica nanoparticles were excreted via urine, but most nanoparticles were excreted via feces, regardless of particle size or sex. Conclusion: The kidneys, liver, lungs, and spleen were found to be the target organs of orally-administered silica nanoparticles in rats, and this organ

A novel microculture kinetic assay (MiCK assay) for malignant cell growth and chemosensitivity.

Science.gov (United States)

Kravtsov, V D

1994-01-01

The THERMOmax microplate reader was adapted for monitoring the growth kinetics of human leukaemic OCI/AML-2 and mouse tumour J-774.1 cell lines in continuous culture. Fluid evaporation from wells, CO2 escape and contamination were prevented by hermetic sealing of the microcultures in wells of a 96-well microplate, thus enabling the cells to grow exponentially for 72 h under the conditions of the incubated microplate reader. For both OCI/AML-2 cells, which grow in suspension, and adherent J-774.1 cells, a linear correlation was demonstrated between the number of unstained cells seeded in a given microplate well and the optical density (OD) of that well. Therefore, the OD/time curve of the culture could be deemed to be its growth curve. By the use of the linear fit equation, the actual number of the cells in the wells was computable at any time point of the assay. In the chemosensitivity test, an inhibitory effect of ARA-C on the growth of the cells could be estimated by viewing of the growth curves plotted on the screen. The maximum kinetic rates (Vmax) of the curves in the control and the ARA-C-treated wells were compared, yielding a growth inhibition index (GII). Comparison of results of the kinetic chemosensitivity assay with those of a [3H]thymidine incorporation assay revealed that the novel assay is suitable for precise quantitation of the cell chemosensitivity, is more informative and has the added technical advantage of performance without recourse to radioactive or chemically hazardous substances.

Theory of Nanocluster Size Distributions from Ion Beam Synthesis

Energy Technology Data Exchange (ETDEWEB)

Yuan, C.W.; Yi, D.O.; Sharp, I.D.; Shin, S.J.; Liao, C.Y.; Guzman, J.; Ager III, J.W.; Haller, E.E.; Chrzan, D.C.

2008-06-13

Ion beam synthesis of nanoclusters is studied via both kinetic Monte Carlo simulations and the self-consistent mean-field solution to a set of coupled rate equations. Both approaches predict the existence of a steady state shape for the cluster size distribution that depends only on a characteristic length determined by the ratio of the effective diffusion coefficient to the ion flux. The average cluster size in the steady state regime is determined by the implanted species/matrix interface energy.

Simulation of growing grains under orientation relation - dependent quadruple point dragging

International Nuclear Information System (INIS)

Ito, K

2015-01-01

The growth behaviour of a specified grain embedded in matrix grains, for which the migration mobility of the quadruple points depended on the relation between the orientations of the growing and shrinking grains, was studied using a modified Potts MC-type threedimensional simulation. Large embedded grains continued to grow without being overcome by coarsening matrix grains, whereas small embedded grains disappeared, under the influence of the relative mobilities of the quadruple points, the composition of the matrix grain texture and the width of the grain size distribution of the matrix grains. These results indicate that orientation relation-dependent quadruple point dragging can affect the recrystallization texture during the grain coarsening stage. (paper)

Modelling the role of compositional fluctuations in nucleation kinetics

International Nuclear Information System (INIS)

Ženíšek, J.; Kozeschnik, E.; Svoboda, J.; Fischer, F.D.

2015-01-01

The classical nucleation theory of precipitate nucleation in interstitial/substitutional alloys is applied to account for the influence of spatial A–B composition fluctuations in an A–B–C matrix on the kinetics of nucleation of (A,B) 3 C precipitates. A and B are substitutional elements in the matrix and C is an interstitial component, assumed to preferentially bind to B atoms. All lattice sites are considered as potential nucleation sites. The fluctuations of chemical composition result in a local variation of the nucleation probability. The nucleation sites are eliminated from the system if they are located in a C-depleted diffusion zone belonging to an already nucleated and growing precipitate. The chemistry is that of an Fe–Cr–C system, and the specific interface energy is treated as a free parameter. Random, regular and homogeneous A–B distributions in the matrix are simulated and compared for various values of the interface energy. An increasing enhancement of the role of compositional fluctuations on nucleation kinetics with increasing interface energy and decreasing chemical driving force is observed

Stopped-flow kinetic studies of poly(amidoamine) dendrimer-calf thymus DNA to form dendriplexes.

Science.gov (United States)

Dey, Debabrata; Kumar, Santosh; Maiti, Souvik; Dhara, Dibakar

2013-11-07

Poly(amidoamine) (PAMAM) dendrimers are known to be highly efficient nonviral carriers in gene delivery. Dendrimer-mediated transfection is known to be a function of the dendrimer to DNA charge ratio as well as the size of the dendrimer. In the present study, the binding kinetics of four PAMAM dendrimers (G1, G2, G3, and G4) with calf thymus DNA (CT-DNA) has been studied using stopped-flow fluorescence spectroscopy. The effect of dendrimer-to-DNA charge ratio and dendrimer generation on the binding kinetics was investigated. In most cases, the results of dendrimer-CT-DNA binding can be explained by a two-step reaction mechanism: a rapid electrostatic binding between the dendrimer and DNA, followed by a conformational change of the dendrimer-DNA complex that ultimately leads to DNA condensation. It was observed that the charge ratio on the dendrimer and the DNA phosphate groups, as well as the dendrimer generation (size), has a marked effect on the kinetics of binding between the DNA and the dendrimers. The rate constant (k'1) of the first step was much higher compared to that of the second step (k'2), and both were found to increase with an increase in dendrimer concentration. Among the four generations of dendrimers, G4 exhibited significantly faster binding kinetics compared to the three smaller generation dendrimers.

Growing hairs in shorn cattle

Directory of Open Access Journals (Sweden)

Cecília José Veríssimo

2013-12-01

Full Text Available The shearing operation can provide double benefits to the cattle: they can become more heat tolerant and the tick infestation decreases. The cattle tick Rhipicephalus (Boophilus microplus causes great losses to dairy cattle, especially to the Holstein cattle because they are very susceptible to this tick. Its control is becoming each day more difficult, owing to the increasing resistance to acaricides they are acquiring. The objective of this work was to study the growing of haircoat following shearing. We made our experiment with 17 animals, 7 females and 10 males. They were shaved on the anterior third (head, neck, dewlap, scapula and arm of one side, at random. The work was performed in two steps: they were shorn for the first time on August 2nd 2012, with a size 10 blade in a clipper Oster model GoldenA5, which left the fur coat 2 mm long. Then we evaluated the hair length growing by collecting fortnightly three sample of hairs in the middle of the scapula, with  electric pliers, modified for this purpose, in both sides of the animals, sheared and non-sheared, until 30 days after this shearing. The three hair samples were put inside a little plastic bag per animal. Meanwhile, as we thought that the animals shearing had to be done closer to the skin, we decided to shear them again (in the same side shorn before, on October 2nd 2012. We changed our procedure using the same machine, but now with a blade size 30, which left the fur coat 1mm thick. After that, we collected again, fortnightly, samples of hairs on both sides during 2 months. The 10 longest hairs in the plastig bag were measured using a graph paper and the average per animal was calculated in each data and blade. A random design was applied for statistical analysis, the hair length of both sides, sheared and non sheared were compared by a two related samples tests – Wilcoxon, in a non parametric test, using the SPSSP 12.0 program, in each data within each blade. Using blade size

Grain growth kinetics of ringwoodite and majorite garnet mixtures and implications for the rheology of the transition zone

Science.gov (United States)

Ezad, I.; Dobson, D. P.; Brodholt, J. P.; Thomson, A.; Hunt, S.

2017-12-01

The grain size of the transition zone is a poorly known but important geophysical parameter. Among others, the grain size may control the rheology, seismic attenuation and radiative thermal conductivity of the mantle. However, the grain size of the transition zone minerals ringwoodite (Mg,Fe)2SiO4 and majorite garnet MgSiO3 under appropriate zone conditions is currently unknown and there are very few experiments with which to constrain it. In order to determine the grain size of the transition zone, the grain growth kinetics must be determined for a range of mantle compositions. We have, therefore, experimentally determined the grain growth kinetics of the lowermost transition zone minerals through multi anvil experiments at University College London (UCL). This is achieved through a comprehensive set of time series experiments at pressures of 21 GPa and temperatures relevant to the transition zone. We have also determined the effect of varying water content, oxygen fugacity, iron content and aluminium content also discussed by Dobson and Mariani., (2014). Our initial grain growth experiments conducted at 1200°C and 1400°C at 18 GPa show extremely slow grain growth kinetics; time series experiments extended to 105.8 seconds are unable to produce grains larger than 100 nm. This suggests that fine-grained material at the base of the transition zone will persist on geological timescales. Such small grains size suggests that diffusion creep might be the dominant deformation mechanism in this region. Reference: Dobson, D.P., Mariani, E., 2014. The kinetics of the reaction of majorite plus ferropericlase to ringwoodite: Implications for mantle upwellings crossing the 660 km discontinuity. Earth Planet. Sci. Lett. 408, 110-118. doi:10.1016/j.epsl.2014.10.009

Evaporation kinetics and phase of laboratory and ambient secondary organic aerosol

Science.gov (United States)

Vaden, Timothy D.; Imre, Dan; Beránek, Josef; Shrivastava, Manish; Zelenyuk, Alla

2011-01-01

Field measurements of secondary organic aerosol (SOA) find significantly higher mass loads than predicted by models, sparking intense effort focused on finding additional SOA sources but leaving the fundamental assumptions used by models unchallenged. Current air-quality models use absorptive partitioning theory assuming SOA particles are liquid droplets, forming instantaneous reversible equilibrium with gas phase. Further, they ignore the effects of adsorption of spectator organic species during SOA formation on SOA properties and fate. Using accurate and highly sensitive experimental approach for studying evaporation kinetics of size-selected single SOA particles, we characterized room-temperature evaporation kinetics of laboratory-generated α-pinene SOA and ambient atmospheric SOA. We found that even when gas phase organics are removed, it takes ∼24 h for pure α-pinene SOA particles to evaporate 75% of their mass, which is in sharp contrast to the ∼10 min time scale predicted by current kinetic models. Adsorption of “spectator” organic vapors during SOA formation, and aging of these coated SOA particles, dramatically reduced the evaporation rate, and in some cases nearly stopped it. Ambient SOA was found to exhibit evaporation behavior very similar to that of laboratory-generated coated and aged SOA. For all cases studied in this work, SOA evaporation behavior is nearly size-independent and does not follow the evaporation kinetics of liquid droplets, in sharp contrast with model assumptions. The findings about SOA phase, evaporation rates, and the importance of spectator gases and aging all indicate that there is need to reformulate the way SOA formation and evaporation are treated by models. PMID:21262848

Nonlinear generation of kinetic-scale waves by magnetohydrodynamic Alfvén waves and nonlocal spectral transport in the solar wind

Energy Technology Data Exchange (ETDEWEB)

Zhao, J. S.; Wu, D. J. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing (China); Voitenko, Y.; De Keyser, J., E-mail: js_zhao@pmo.ac.cn [Solar-Terrestrial Centre of Excellence, Space Physics Division, Belgian Institute for Space Aeronomy, Ringlaan-3-Avenue Circulaire, B-1180 Brussels (Belgium)

2014-04-20

We study the nonlocal nonlinear coupling and generation of kinetic Alfvén waves (KAWs) and kinetic slow waves (KSWs) by magnetohydrodynamic Alfvén waves (MHD AWs) in conditions typical for the solar wind in the inner heliosphere. This cross-scale process provides an alternative to the turbulent energy cascade passing through many intermediate scales. The nonlinearities we study are proportional to the scalar products of wave vectors and hence are called 'scalar' ones. Despite the strong Landau damping of kinetic waves, we found fast growing KAWs and KSWs at perpendicular wavelengths close to the ion gyroradius. Using the parametric decay formalism, we investigate two independent decay channels for the pump AW: forward decay (involving co-propagating product waves) and backward decay (involving counter-propagating product waves). The growth rate of the forward decay is typically 0.05 but can exceed 0.1 of the pump wave frequency. The resulting spectral transport is nonlocal and anisotropic, sharply increasing perpendicular wavenumbers but not parallel ones. AWs and KAWs propagating against the pump AW grow with about the same rate and contribute to the sunward wave flux in the solar wind. Our results suggest that the nonlocal decay of MHD AWs into KAWs and KSWs is a robust mechanism for the cross-scale spectral transport of the wave energy from MHD to dissipative kinetic scales in the solar wind and similar media.

Growth and maximum size of tiger sharks (Galeocerdo cuvier) in Hawaii.

Science.gov (United States)

Meyer, Carl G; O'Malley, Joseph M; Papastamatiou, Yannis P; Dale, Jonathan J; Hutchinson, Melanie R; Anderson, James M; Royer, Mark A; Holland, Kim N

2014-01-01

Tiger sharks (Galecerdo cuvier) are apex predators characterized by their broad diet, large size and rapid growth. Tiger shark maximum size is typically between 380 & 450 cm Total Length (TL), with a few individuals reaching 550 cm TL, but the maximum size of tiger sharks in Hawaii waters remains uncertain. A previous study suggested tiger sharks grow rather slowly in Hawaii compared to other regions, but this may have been an artifact of the method used to estimate growth (unvalidated vertebral ring counts) compounded by small sample size and narrow size range. Since 1993, the University of Hawaii has conducted a research program aimed at elucidating tiger shark biology, and to date 420 tiger sharks have been tagged and 50 recaptured. All recaptures were from Hawaii except a single shark recaptured off Isla Jacques Cousteau (24°13'17″N 109°52'14″W), in the southern Gulf of California (minimum distance between tag and recapture sites  =  approximately 5,000 km), after 366 days at liberty (DAL). We used these empirical mark-recapture data to estimate growth rates and maximum size for tiger sharks in Hawaii. We found that tiger sharks in Hawaii grow twice as fast as previously thought, on average reaching 340 cm TL by age 5, and attaining a maximum size of 403 cm TL. Our model indicates the fastest growing individuals attain 400 cm TL by age 5, and the largest reach a maximum size of 444 cm TL. The largest shark captured during our study was 464 cm TL but individuals >450 cm TL were extremely rare (0.005% of sharks captured). We conclude that tiger shark growth rates and maximum sizes in Hawaii are generally consistent with those in other regions, and hypothesize that a broad diet may help them to achieve this rapid growth by maximizing prey consumption rates.

Understanding release kinetics of biopolymer drug delivery microcapsules for biomedical applications

International Nuclear Information System (INIS)

Desai, Salil; Perkins, Jessica; Harrison, Benjamin S.; Sankar, Jag

2010-01-01

Drug delivery and dosage concentrations are considered as major focal points in conventional as well as battlefield emergency medicine. The concept of localizing drug delivery via microcapsules is an evolving field to confine the adverse side effects of high concentration drug doses. This paper focuses on understanding release kinetics through biopolymer microcapsules for time-dependent drug release. Calcium alginate microcapsules were manufactured using a direct-write inkjet technique. Rhodamine 6G was used as the release agent to observe the release kinetics from calcium alginate beads in distilled water. A design of experiments was constructed to compare the effect of the microcapsule diameter and different concentrations of calcium chloride (M) and sodium alginate (%, w/v) solutions on the release kinetics profiles of the microcapsules. This research gives insight to identify favorable sizes of microcapsules and concentrations of sodium alginate and calcium chloride solutions for controlled release behavior of drug delivery microcapsules.

Association of footprint measurements with plantar kinetics: a linear regression model.

Science.gov (United States)

Fascione, Jeanna M; Crews, Ryan T; Wrobel, James S

2014-03-01

The use of foot measurements to classify morphology and interpret foot function remains one of the focal concepts of lower-extremity biomechanics. However, only 27% to 55% of midfoot variance in foot pressures has been determined in the most comprehensive models. We investigated whether dynamic walking footprint measurements are associated with inter-individual foot loading variability. Thirty individuals (15 men and 15 women; mean ± SD age, 27.17 ± 2.21 years) walked at a self-selected speed over an electronic pedography platform using the midgait technique. Kinetic variables (contact time, peak pressure, pressure-time integral, and force-time integral) were collected for six masked regions. Footprints were digitized for area and linear boundaries using digital photo planimetry software. Six footprint measurements were determined: contact area, footprint index, arch index, truncated arch index, Chippaux-Smirak index, and Staheli index. Linear regression analysis with a Bonferroni adjustment was performed to determine the association between the footprint measurements and each of the kinetic variables. The findings demonstrate that a relationship exists between increased midfoot contact and increased kinetic values in respective locations. Many of these variables produced large effect sizes while describing 38% to 71% of the common variance of select plantar kinetic variables in the medial midfoot region. In addition, larger footprints were associated with larger kinetic values at the medial heel region and both masked forefoot regions. Dynamic footprint measurements are associated with dynamic plantar loading kinetics, with emphasis on the midfoot region.

4He adsorbed in cylindrical silica nanopores: Effect of size on the single-atom mean kinetic energy

International Nuclear Information System (INIS)

Andreani, C.; Senesi, R.; Pantalei, C.

2007-01-01

This paper reports a study of the short-time dynamics of helium confined in silica nanopores (xerogel powder), with average pore diameters of 24 and 160 A. The longitudinal momentum distribution of helium adsorbed in xerogels has been determined via deep inelastic neutron scattering (DINS) measurements performed on the VESUVIO spectrometer at the ISIS spallation source. DINS measurements, in the attosecond time scale (i.e., 10 -16 -10 -15 s), were performed at a temperature of T=2.5 K and saturated vapor pressure conditions, with 95% pore volume filling. The average wave-vector transfer q was about 130 A -1 . For confined helium, significant changes in the values of the single-particle mean kinetic energies K > are found in the bulk phase. These are 32.6±8.7 K for the 24 A and 24.4±5.3 K for the 160 A pore diameters, remarkably higher than K >=16.2±0.4 K, the value of normal liquid 4 He at T=2.5 K and saturated vapor pressure conditions. The results are interpreted in terms of a model where 4 He atoms are arranged in concentric annuli along the cylindrical pore axis, with K > mainly dependent on the ratio between the atomic 'effective' diameter and the pore diameter. The number of solid layers close to pore surface is found to be strongly pore-size dependent with one single solid layer for 24 A diameter pore and three solid layers for 160 A diameter pore

Kinetic theory of age-structured stochastic birth-death processes

Science.gov (United States)

Greenman, Chris D.; Chou, Tom

2016-01-01

Classical age-structured mass-action models such as the McKendrick-von Foerster equation have been extensively studied but are unable to describe stochastic fluctuations or population-size-dependent birth and death rates. Stochastic theories that treat semi-Markov age-dependent processes using, e.g., the Bellman-Harris equation do not resolve a population's age structure and are unable to quantify population-size dependencies. Conversely, current theories that include size-dependent population dynamics (e.g., mathematical models that include carrying capacity such as the logistic equation) cannot be easily extended to take into account age-dependent birth and death rates. In this paper, we present a systematic derivation of a new, fully stochastic kinetic theory for interacting age-structured populations. By defining multiparticle probability density functions, we derive a hierarchy of kinetic equations for the stochastic evolution of an aging population undergoing birth and death. We show that the fully stochastic age-dependent birth-death process precludes factorization of the corresponding probability densities, which then must be solved by using a Bogoliubov--Born--Green--Kirkwood--Yvon-like hierarchy. Explicit solutions are derived in three limits: no birth, no death, and steady state. These are then compared with their corresponding mean-field results. Our results generalize both deterministic models and existing master equation approaches by providing an intuitive and efficient way to simultaneously model age- and population-dependent stochastic dynamics applicable to the study of demography, stem cell dynamics, and disease evolution.

Growing Mouse Oocytes Transiently Activate Folate Transport via Folate Receptors As They Approach Full Size1

OpenAIRE

Meredith, Megan; MacNeil, Allison H.; Trasler, Jacquetta M.; Baltz, Jay M.

2016-01-01

The folate cycle is central to cellular one-carbon metabolism, where folates are carriers of one-carbon units that are critical for synthesis of purines, thymidylate, and S-adenosylmethionine, the universal methyl donor that forms the cellular methyl pool. Although folates are well-known to be important for early embryo and fetal development, their role in oogenesis has not been clearly established. Here, folate transport proteins were detected in developing neonatal ovaries and growing oocyt...

Investigation of Chemical Kinetics on Soot Formation Event of n-Heptane Spray Combustion

DEFF Research Database (Denmark)

Pang, Kar Mun; Jangi, Mehdi; Bai, Xue-Song

2014-01-01

. Numerical computation is performed using OpenFOAM and chemistry coordinate mapping (CCM) approach is used to expedite the calculation. Three n-heptane kinetic mechanisms with different chemistry sizes and comprehensiveness in oxidation pathways and soot precursor formation are adopted. The three examined...

Kinetics of lipid-nanoparticle-mediated intracellular mRNA delivery and function

Science.gov (United States)

Zhdanov, Vladimir P.

2017-10-01

mRNA delivery into cells forms the basis for one of the new and promising ways to treat various diseases. Among suitable carriers, lipid nanoparticles (LNPs) with a size of about 100 nm are now often employed. Despite high current interest in this area, the understanding of the basic details of LNP-mediated mRNA delivery and function is limited. To clarify the kinetics of mRNA release from LNPs, the author uses three generic models implying (i) exponential, (ii) diffusion-controlled, and (iii) detachment-controlled kinetic regimes, respectively. Despite the distinct differences in these kinetics, the associated transient kinetics of mRNA translation to the corresponding protein and its degradation are shown to be not too sensitive to the details of the mRNA delivery by LNPs (or other nanocarriers). In addition, the author illustrates how this protein may temporarily influence the expression of one gene or a few equivalent genes. The analysis includes positive or negative regulation of the gene transcription via the attachment of the protein without or with positive or negative feedback in the gene expression. Stable, bistable, and oscillatory schemes have been scrutinized in this context.

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

Science.gov (United States)

Sakashita, Tetsuya; Hamada, Nobuyuki; Kawaguchi, Isao; Ouchi, Noriyuki B; Hara, Takamitsu; Kobayashi, Yasuhiko; Saito, Kimiaki

2013-01-01

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. 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 (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. Our present model provides a single framework for understanding the behavior of primary cell colonies in culture following irradiation.

Kinetics of sub-spinodal dewetting of thin films of thickness dependent viscosity.

Science.gov (United States)

Kotni, Tirumala Rao; Khanna, Rajesh; Sarkar, Jayati

2017-05-04

An alternative explanation of the time varying and very low growth exponents in dewetting of polymer films like polystyrene films is presented based on non-linear simulations. The kinetics of these films is explored within the framework of experimentally observed thickness dependent viscosity. These films exhibit sub-spinodal dewetting via formation of satellite holes in between primary dewetted holes under favorable conditions of excess intermolecular forces and film thicknesses. We find that conditions responsible for sub-spinodal dewetting concurrently lead to remarkable changes in the kinetics of dewetting of even primary holes. For example, the radius of the hole grows in time with a power-law growth exponent sequence of [Formula: see text], in contrast to the usual  ∼4/5. This is due to the cumulative effect of reduced rim mobility due to thickness dependent viscosity and hindrance created by satellite holes.

Stochastic theory of interfacial enzyme kinetics: A kinetic Monte Carlo study

International Nuclear Information System (INIS)

Das, Biswajit; Gangopadhyay, Gautam

2012-01-01

Graphical abstract: Stochastic theory of interfacial enzyme kinetics is formulated. Numerical results of macroscopic phenomenon of lag-burst kinetics is obtained by using a kinetic Monte Carlo approach to single enzyme activity. Highlights: ► An enzyme is attached with the fluid state phospholipid molecules on the Langmuir monolayer. ► Through the diffusion, the enzyme molecule reaches the gel–fluid interface. ► After hydrolysing a phospholipid molecule it predominantly leaves the surface in the lag phase. ► The enzyme is strictly attached to the surface with scooting mode of motion and the burst phase appears. - Abstract: In the spirit of Gillespie’s stochastic approach we have formulated a theory to explore the advancement of the interfacial enzyme kinetics at the single enzyme level which is ultimately utilized to obtain the ensemble average macroscopic feature, lag-burst kinetics. We have provided a theory of the transition from the lag phase to the burst phase kinetics by considering the gradual development of electrostatic interaction among the positively charged enzyme and negatively charged product molecules deposited on the phospholipid surface. It is shown that the different diffusion time scales of the enzyme over the fluid and product regions are responsible for the memory effect in the correlation of successive turnover events of the hopping mode in the single trajectory analysis which again is reflected on the non-Gaussian distribution of turnover times on the macroscopic kinetics in the lag phase unlike the burst phase kinetics.

Kinetics and mechanism of DNA repair

International Nuclear Information System (INIS)

Meldrum, R.A.; Wharton, C.W.; Shall, S.

1990-01-01

Experiments are described in which the feasibility of using caged dideoxy and other nucleoside triphosphate analogues for trapping breaks induced by u.v. radiation damage to mammalian cell DNA is evaluated. These nucleotide analogues that have a photolabile 1-(2-nitrophenyl)ethyl-protecting group attached to the γ-phosphate are placed in situ by permeabilizing cells by exposure to hypo-osmotic medium. The nucleoside triphosphate is released by a 351 nm u.v. laser pulse whence it may incorporate in the growing chain of DNA induced by the excision-repair process and terminate chain elongation. If the photoreleased dideoxynucleoside trisphosphate is isotopically labelled in the α-phosphate position the break is trapped and labelled. Incorporation of radioactivity into trichloroacetic acid insoluble material in these experiments confirms their potential for use in studies of the kinetics of mammalian cell DNA repair. (author)

Comparison of micronucleus frequencies and proliferation kinetics in three X-irradiated cell lines

International Nuclear Information System (INIS)

Kaffenberger, W.; Becker, K.; Beuningen, D. van

1990-01-01

The kinetics of the occurrence of micronuclei was correlated with the survival of three mammalian cell lines of human, monkey, and mouse origin after irradiation with 240 kV X-rays. Particular attention was paid to the evaluation of the individual proliferation kinetics of the cell lines as well as to the characterization of micronuclei subpopulation with respect to size and possible biological importance using DNA and BUdR labelling techniques, fluorescence microscopy, and image analysis. The results demonstrate very characteristic size distributions of micronuclei for the three cell lines independent of radiation dose and time after irradiation. A close correlation between cell death and the occurrence of micronuclei (expressed as a calculated 'MN index') after irradiation could be established only when the kinetics of progression of cells through the cell cycle (e.g. the doubling time) and the biological characteristics of micronuclei (e.g. BUdR positivity, the micronucleus frequencies, and the number of micronuclei per main nucleus) were taken into account. Therefore, the micronucleus assay might not be useful as a quantitative perdictive assay in vivo but may allow qualitative estimations of radiation damage only because the necessary proliferation parameters of the cells might not be possible to establish in vivo. (orig.) [de

Kinetics of barium sulphate reaction crystallization in crystallizers with internal circulation

Directory of Open Access Journals (Sweden)

J. Koralewska

2008-06-01

Full Text Available Kinetic calculation results describing the observed nucleation and growth rates of barium sulphate crystals precipitated in an integrated reaction-crystallization process in a barium sulphate-ammonium chloride-water system are presented and analyzed. The scope of experiments included two continuous model DTM-type crystallizers (Draft Tube Magma with internal circulation of the suspension forced by a liquid jet-pump device responsible for stable and intensive enough ascending/descending flow of BaSO4 crystal magma in a mixing chamber. For comparison purposes the experimental data corresponding to a continuous DT (Draft Tube crystallizer with propeller agitator are presented and discussed. The various types of laboratory crystallizers used were fed with concentrated water solution of barium chloride (of 10 or 24 mass % and - in a stoichiometric proportion - crystalline ammonium sulphate, assuming isothermal (348 K and hydrodynamic (average residence time of suspension in a crystallizer: 900 s process conditions. The observed nucleation and growth rates of barium sulphate crystals were estimated on the basis of crystal size distributions (CSDs using convenient calculation scheme derived for an MSMPR (Mixed Suspension Mixed Product Removal model approach. Considering the experimental population density distribution courses, a size-dependent growth (SDG phenomenon was taken into account in the kinetic calculations. Five SDG kinetic models recommended in the accessible literature were used for kinetic parameter values estimation. It was proved statistically, that Rojkowski’s two SDG models (hyperbolic and exponential best suit for our own experimental data description. The experimental data presented can be practically applied for improving the constructions of liquid jet-pump DTM crystallizers recommended for reaction crystallization of sparingly soluble inorganic salts (especially for high concentrations of reaction substrates in the modern

Prediction of the filtrate particle size distribution from the pore size distribution in membrane filtration: Numerical correlations from computer simulations

Science.gov (United States)

Marrufo-Hernández, Norma Alejandra; Hernández-Guerrero, Maribel; Nápoles-Duarte, José Manuel; Palomares-Báez, Juan Pedro; Chávez-Rojo, Marco Antonio

2018-03-01

We present a computational model that describes the diffusion of a hard spheres colloidal fluid through a membrane. The membrane matrix is modeled as a series of flat parallel planes with circular pores of different sizes and random spatial distribution. This model was employed to determine how the size distribution of the colloidal filtrate depends on the size distributions of both, the particles in the feed and the pores of the membrane, as well as to describe the filtration kinetics. A Brownian dynamics simulation study considering normal distributions was developed in order to determine empirical correlations between the parameters that characterize these distributions. The model can also be extended to other distributions such as log-normal. This study could, therefore, facilitate the selection of membranes for industrial or scientific filtration processes once the size distribution of the feed is known and the expected characteristics in the filtrate have been defined.

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

Science.gov (United States)

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

2013-05-10

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

Equilibrium and Kinetic Sorption of Some Heavy Metals from Aqueous Waste Solutions Using p (AAc-HEMA)

International Nuclear Information System (INIS)

El-Sayed, A.H.; Khalil, F.H.; Elnesr, E.; Mansour, T.; El-Gammal, B.; El -Sabbah, M.M.B.

2013-01-01

Removal of heavy metals from aqueous waste solution using poly acrylic acid / 2-hydroxy ethyle methacrylate ( p-AAc/ HEMA) was investigated. Experiments were carried out as function of contact time, initial concentration, ph, particle size and temperature. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. The results indicated that poly acrylic acid / 2-hydroxy ethyle methacrylate (p-AAc/ HEMA) is suitable as adsorbent material for adsorption of Sr 2+ , Co 2+ , Cd 2+ , Zn 2+ , Nd 3+ and Eu 3+ radio active nuclei from aqueous solutions.

Measuring kinetic drivers of pneumolysin pore structure.

Science.gov (United States)

Gilbert, Robert J C; Sonnen, Andreas F-P

2016-05-01

Most membrane attack complex-perforin/cholesterol-dependent cytolysin (MACPF/CDC) proteins are thought to form pores in target membranes by assembling into pre-pore oligomers before undergoing a pre-pore to pore transition. Assembly during pore formation is into both full rings of subunits and incomplete rings (arcs). The balance between arcs and full rings is determined by a mechanism dependent on protein concentration in which arc pores arise due to kinetic trapping of the pre-pore forms by the depletion of free protein subunits during oligomerization. Here we describe the use of a kinetic assay to study pore formation in red blood cells by the MACPF/CDC pneumolysin from Streptococcus pneumoniae. We show that cell lysis displays two kinds of dependence on protein concentration. At lower concentrations, it is dependent on the pre-pore to pore transition of arc oligomers, which we show to be a cooperative process. At higher concentrations, it is dependent on the amount of pneumolysin bound to the membrane and reflects the affinity of the protein for its receptor, cholesterol. A lag occurs before cell lysis begins; this is dependent on oligomerization of pneumolysin. Kinetic dissection of cell lysis by pneumolysin demonstrates the capacity of MACPF/CDCs to generate pore-forming oligomeric structures of variable size with, most likely, different functional roles in biology.

Physical kinetics

International Nuclear Information System (INIS)

Lifschitz, E.M.; Pitajewski, L.P.

1983-01-01

The textbook covers the subject under the following headings: kinetic gas theory, diffusion approximation, collisionless plasma, collisions within the plasma, plasma in the magnetic field, theory of instabilities, dielectrics, quantum fluids, metals, diagram technique for nonequilibrium systems, superconductors, and kinetics of phase transformations

Biorock Electric Reefs Grow Back Severely Eroded Beaches in Months

Directory of Open Access Journals (Sweden)

Thomas J. F. Goreau

2017-10-01

Full Text Available Severely eroded beaches on low lying islands in Indonesia were grown back in a few months—believed to be a record—using an innovative method of shore protection, Biorock electric reef technology. Biorock shore protection reefs are growing limestone structures that get stronger with age and repair themselves, are cheaper than concrete or rock sea walls and breakwaters, and are much more effective at shore protection and beach growth. Biorock reefs are permeable, porous, growing, self-repairing structures of any size or shape, which dissipate wave energy by internal refraction, diffraction, and frictional dissipation. They do not cause reflection of waves like hard sea walls and breakwaters, which erodes the sand in front of, and then underneath, such structures, until they collapse. Biorock reefs stimulate settlement, growth, survival, and resistance to the environmental stress of all forms of marine life, restoring coral reefs, sea grasses, biological sand production, and fisheries habitat. Biorock reefs can grow back eroded beaches and islands faster than the rate of sea level rise, and are the most cost-effective method of shore protection and adaptation to global sea level rise for low lying islands and coasts.

Precipitation kinetics in binary Fe–Cu and ternary Fe–Cu–Ni alloys via kMC method

Directory of Open Access Journals (Sweden)

Yi Wang

2017-08-01

Full Text Available The precipitation kinetics of coherent Cu rich precipitates (CRPs in binary Fe–Cu and ternary Fe–Cu–Ni alloys during thermal aging was modelled by the kinetic Monte Carlo method (kMC. A good agreement of the precipitation kinetics of Fe–Cu was found between the simulation and experimental results, as observed by means of advancement factor and cluster number density. This agreement was obtained owing to the correct description of the fast cluster mobility. The simulation results indicate that the effects of Ni are two-fold: Ni promotes the nucleation of Cu clusters; while the precipitation kinetics appears to be delayed by Ni addition during the coarsening stage. The apparent delayed precipitation kinetics is revealed to be related with the cluster mobility, which are reduced by Ni addition. The reduction effect of the cluster mobility weakens when the CRPs sizes increase. The results provide a view angle on the effects of solute elements upon Cu precipitation kinetics through the consideration of the non-conventional cluster growth mechanism, and kMC is verified to be a powerful approach on that.

Controllable Growth of Large-Size Crystalline MoS2 and Resist-Free Transfer Assisted with a Cu Thin Film

Science.gov (United States)

Lin, Ziyuan; Zhao, Yuda; Zhou, Changjian; Zhong, Ren; Wang, Xinsheng; Tsang, Yuen Hong; Chai, Yang

2015-12-01

Two-dimensional MoS2 is a promising material for future nanoelectronics and optoelectronics. It has remained a great challenge to grow large-size crystalline and high surface coverage monolayer MoS2. In this work, we investigate the controllable growth of monolayer MoS2 evolving from triangular flakes to continuous thin films by optimizing the concentration of gaseous MoS2, which has been shown a both thermodynamic and kinetic growth factor. A single-crystal monolayer MoS2 larger than 300 μm was successfully grown by suppressing the nuclei density and supplying sufficient source. Furthermore, we present a facile process of transferring the centimeter scale MoS2 assisted with a copper thin film. Our results show the absence of observable residues or wrinkles after we transfer MoS2 from the growth substrates onto flat substrates using this technique, which can be further extended to transfer other two-dimensional layered materials.

Kinetics of tracheid development explain conifer tree-ring structure.

Science.gov (United States)

Cuny, Henri E; Rathgeber, Cyrille B K; Frank, David; Fonti, Patrick; Fournier, Meriem

2014-09-01

Conifer tree rings are generally composed of large, thin-walled cells of light earlywood followed by narrow, thick-walled cells of dense latewood. Yet, how wood formation processes and the associated kinetics create this typical pattern remains poorly understood. We monitored tree-ring formation weekly over 3 yr in 45 trees of three conifer species in France. Data were used to model cell development kinetics, and to attribute the relative importance of the duration and rate of cell enlargement and cell wall deposition on tree-ring structure. Cell enlargement duration contributed to 75% of changes in cell diameter along the tree rings. Remarkably, the amount of wall material per cell was quite constant along the rings. Consequently, and in contrast with widespread belief, changes in cell wall thickness were not principally attributed to the duration and rate of wall deposition (33%), but rather to the changes in cell size (67%). Cell enlargement duration, as the main driver of cell size and wall thickness, contributed to 56% of wood density variation along the rings. This mechanistic framework now forms the basis for unraveling how environmental stresses trigger deviations (e.g. false rings) from the normal tree-ring structure. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Pyrolysis kinetics and thermodynamic parameters of castor (Ricinus communis) residue using thermogravimetric analysis.

Science.gov (United States)

Kaur, Ravneet; Gera, Poonam; Jha, Mithilesh Kumar; Bhaskar, Thallada

2018-02-01

Castor plant is a fast-growing, perennial shrub from Euphorbiaceae family. More than 50% of the residue is generated from its stems and leaves. The main aim of this work is to study the pyrolytic characteristics, kinetics and thermodynamic properties of castor residue. The TGA experiments were carried out from room temperature to 900 °C under an inert atmosphere at different heating rates of 5, 10, 15, 20, 30 and 40 °C/min. The kinetic analysis was carried using different models namely Kissinger, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The average E ɑ calculated by FWO and KAS methods were 167.10 and 165.86 kJ/mole respectively. Gibbs free energy varied from 150.62-154.33 to 150.59-154.65 kJ/mol for FWO and KAS respectively. The HHV of castor residue was 14.43 MJ/kg, considered as potential feedstock for bio-energy production. Kinetic and thermodynamic results will be useful input for the design of pyrolytic process using castor residue as feedstock. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adsorption kinetics of 201Tl and migration of 99mTc in natural soils

International Nuclear Information System (INIS)

Rodriguez N, C. E.; Monroy G, F.; Fernandez R, E.; Anguiano A, J.

2012-10-01

The safety is very important in facilities where radioactive wastes are stored. One of the necessary characteristics of the site where these wastes will be disposed is the soil permeability, since a waterproof terrain avoids the diffusion and radionuclide transport in the leakages case. The objective of this work is to study the adsorption kinetics of 201 Tl and the migration of 99m Tc in natural soil samples. The adsorption kinetics was determined starting from the obtaining of the retention coefficient of the thallium (static method) at different contact times. The technetium diffusion was studied by means of the dynamic method with different soil particles sizes. The results showed that the thallium is totally adsorbed starting from 20 h of contact among this and the mean. On the other hand, the technetium is very mobile in the soil, since it was possible to extract the majority of the tracer with little solvent. Also, it was found that for each soil gram the double water will be needed to leach the technetium almost in its entirety. Moreover, influence exists of the particle size in the migration velocity from the radiotracer to the most mobile being in major sizes than 2 mm that in minor size. (Author)

Large litter sizes

DEFF Research Database (Denmark)

Sandøe, Peter; Rutherford, K.M.D.; Berg, Peer

2012-01-01

This paper presents some key results and conclusions from a review (Rutherford et al. 2011) undertaken regarding the ethical and welfare implications of breeding for large litter size in the domestic pig and about different ways of dealing with these implications. Focus is primarily on the direct...... possible to achieve a drop in relative piglet mortality and the related welfare problems. However, there will be a growing problem with the need to use foster or nurse sows which may have negative effects on both sows and piglets. This gives rise to new challenges for management....

The nonlocal electron kinetics for a low-pressure glow discharge dusty plasma

Science.gov (United States)

Liang, Yonggan; Wang, Ying; Li, Hui; Tian, Ruihuan; Yuan, Chengxun; Kudryavtsev, A. A.; Rabadanov, K. M.; Wu, Jian; Zhou, Zhongxiang; Tian, Hao

2018-05-01

The nonlocal electron kinetic model based on the Boltzmann equation is developed in low-pressure argon glow discharge dusty plasmas. The additional electron-dust elastic and inelastic collision processes are considered when solving the kinetic equation numerically. The orbital motion limited theory and collision enhanced collection approximation are employed to calculate the dust surface potential. The electron energy distribution function (EEDF), effective electron temperature Teff, and dust surface potential are investigated under different plasma and dust conditions by solving the Boltzmann and the dust charging current balance equations self-consistently. A comparison of the calculation results obtained from nonlocal and local kinetic models is made. It is shown that the appearance of dust particles leads to a deviation of the EEDF from its original profile for both nonlocal and local kinetic models. With the increase in dust density and size, the effective electron temperature and dust surface potential decrease due to the high-energy electron loss on the dust surface. Meanwhile, the nonlocal and local results differ much from each other under the same calculation condition. It is concluded that, for low-pressure (PR ≤ 1 cm*Torr) glow discharge dusty plasmas, the existence of dust particles will amplify the difference of local and nonlocal EEDFs, which makes the local kinetic model more improper to determine the main parameters of the positive column. The nonlocal kinetic model should be used for the calculation of the EEDFs and dusty plasma parameters.

Influence of deformation on dolomite rim growth kinetics

Science.gov (United States)

Helpa, Vanessa; Rybacki, Erik; Grafulha Morales, Luiz Fernando; Dresen, Georg

2015-04-01

Using a gas-deformation apparatus stacks of oriented calcite (CaCO3) and magnesite (MgCO3) single crystals were deformed at T = 750° C and P = 400 MPa to examine the influence of stress and strain on magnesio-calcite and dolomite (CaMg[CO3]2) growth kinetics. Triaxial compression and torsion tests performed at constant stresses between 7 and 38 MPa and test durations between 4 and 171 hours resulted in bulk strains of 0.03-0.2 and maximum shear strains of 0.8-5.6, respectively. The reaction rims consist of fine-grained (2-7 μm) dolomite with palisade-shaped grains growing into magnesite reactants and equiaxed granular dolomite grains next to calcite. In between dolomite and pure calcite, magnesio-calcite grains evolved with an average grain size of 20-40 μm. Grain boundaries tend to be straighter at high bulk strains and equilibrium angles at grain triple junctions are common within the magnesio-calcite layer. Transmission electron microscopy shows almost dislocation free palisades and increasing dislocation density within granular dolomite towards the magnesio-calcite boundary. Within magnesio-calcite grains, dislocations are concentrated at grain boundaries. Variation of time at fixed stress (˜17 MPa) yields a parabolic time dependence of dolomite rim width, indicating diffusion-controlled growth, similar to isostatic rim growth behavior. In contrast, the magnesio-calcite layer growth is enhanced compared to isostatic conditions. Triaxial compression at given time shows no significant change of dolomite rim thickness (11±2 μm) and width of magnesio-calcite layers (33±5 μm) with increasing stress. In torsion experiments, reaction layer thickness and grain size decrease from the center (low stress/strain) to the edge (high strain/stress) of samples. Chemical analysis shows nearly stoichiometric composition of dolomite palisades, but enhanced Ca content within granular grains, indicating local disequilibrium with magnesio-calcite, in particular for twisted

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...

Fresh tar (from biomass gasification) destruction with downstream catalysts: comparison of their intrinsic activity with a realistic kinetic model

Energy Technology Data Exchange (ETDEWEB)

Corella, J.; Narvaez, I.; Orio, A. [Complutense Univ. of Madrid (Spain). Dept. of Chemical Engineering

1996-12-31

A model for fresh tar destruction over catalysts placed downstream a biomass gasifier is presented. It includes the stoichio-metry and the calculation of the kinetic constants for the tar destruction. Catalysts studied include commercial Ni steam reforming catalysts and calcinated dolomites. Kinetic constants for tar destruction are calculated for several particle sizes, times- on-stream and temperatures of the catalyst and equivalence ratios in the gasifier. Such intrinsic kinetic constants allow a rigorous or scientific comparison of solids and conditions to be used in an advanced gasification process. (orig.) 4 refs.

Fresh tar (from biomass gasification) destruction with downstream catalysts: comparison of their intrinsic activity with a realistic kinetic model

Energy Technology Data Exchange (ETDEWEB)

Corella, J; Narvaez, I; Orio, A [Complutense Univ. of Madrid (Spain). Dept. of Chemical Engineering

1997-12-31

A model for fresh tar destruction over catalysts placed downstream a biomass gasifier is presented. It includes the stoichio-metry and the calculation of the kinetic constants for the tar destruction. Catalysts studied include commercial Ni steam reforming catalysts and calcinated dolomites. Kinetic constants for tar destruction are calculated for several particle sizes, times- on-stream and temperatures of the catalyst and equivalence ratios in the gasifier. Such intrinsic kinetic constants allow a rigorous or scientific comparison of solids and conditions to be used in an advanced gasification process. (orig.) 4 refs.

Characters of neutron noise in full-size molten salt reactor

International Nuclear Information System (INIS)

Wang, Jiangmeng; Cao, Xinrong

2015-01-01

Highlights: • The larger system size makes full-size MSR deviate from point kinetic behavior. • The increasing velocity has non-monotonic effect on the effective delayed neutron fraction. • The amplitude of Green’s function at low frequencies is inversely proportional to the effective delayed neutron fraction. • The range of plateau region is smaller due to the more prominent point kinetic effect. - Abstract: In the present paper, the frequency-dependent and space-dependent behavior of the neutron noise in a full-size Molten Salt Reactor (MSR) is investigated. The theoretical models considering the fuel circulation are established based on one-group neutron diffusion theory. Green’s function of the neutron noise induced by a propagating perturbation is introduced with linear noise theory, due to the small perturbation. The equations are numerically calculated by developing a code, in which the eigenfunction expansion method is adopted. The static results show that the effective delayed neutron fraction changes non-monotonically with the increasing fuel velocity. In the dynamic case, the results are compared to those obtained in 1D MSR and a traditional reactor, in order to figure out the effects of both the fuel circulation and the system size. It is found that there is no difference in 1D and 3D MSR systems from the view of fuel circulation, i.e., the fuel circulation enhances the spatial neutronic coupling and leads to the stronger point kinetic effect. The more prominent space-dependent effect founded in 3D traditional reactors is also observed in the MSR, due to the looser neutronic coupling and the unique singularity of Green’s function in the location of the perturbation. Another interesting finding is that Green’s function for low frequencies changes non-monotonically with increasing velocity. The largest magnitude of Green’s function is observed at the velocity where the effective delayed neutron fraction reaches its minimum. Finally, the

Nanometer sized structures grown by pulsed laser deposition

KAUST Repository

ElZein, Basma

2015-10-01

Nanometer sized materials can be produced by exposing a target to a laser source to remove material from the target and deposit the removed material onto a surface of a substrate to grow a thin film in a vacuum chamber

Crystallization kinetics of the borax decahydrate

Science.gov (United States)

Ceyhan, A. A.; Sahin, Ö.; Bulutcu, A. N.

2007-03-01

The growth and dissolution rates of borax decahydrate have been measured as a function of supersaturation for various particle sizes at different temperature ranges of 13 and 50 °C in a laboratory-scale fluidized bed crystallizer. The values of mass transfer coefficient, K, reaction rate constant, kr and reaction rate order, r were determined. The relative importances of diffusion and integration resistance were described by new terms named integration and diffusion concentration fraction. It was found that the overall growth rate of borax decahydrate is mainly controlled by integration (reaction) steps. It was also estimated that the dissolution region of borax decahydrate, apart from other materials, is controlled by diffusion and surface reaction. Increasing the temperature and particle size cause an increase in the values of kinetic parameters ( Kg, kr and K). The activation energies of overall, reaction and mass transfer steps were determined as 18.07, 18.79 and 8.26 kJmol -1, respectively.

Particle size-dependent organ distribution of gold nanoparticles after intravenous administration

NARCIS (Netherlands)

De Jong, Wim H.; Hagens, Werner I.; Krystek, Petra; Burger, Marina C.; Sips, Adriënne J A M; Geertsma, Robert E.

2008-01-01

A kinetic study was performed to determine the influence of particle size on the in vivo tissue distribution of spherical-shaped gold nanoparticles in the rat. Gold nanoparticles were chosen as model substances as they are used in several medical applications. In addition, the detection of the

Kinetics of phase transformations

International Nuclear Information System (INIS)

Thompson, M.O.; Aziz, M.J.; Stephenson, G.B.

1992-01-01

This volume contains papers presented at the Materials Research Society symposium on Kinetics of Phase Transformations held in Boston, Massachusetts from November 26-29, 1990. The symposium provided a forum for research results in an exceptionally broad and interdisciplinary field. Presentations covered nearly every major class of transformations including solid-solid, liquid-solid, transport phenomena and kinetics modeling. Papers involving amorphous Si, a dominant topic at the symposium, are collected in the first section followed by sections on four major areas of transformation kinetics. The symposium opened with joint sessions on ion and electron beam induced transformations in conjunction with the Surface Chemistry and Beam-Solid Interactions: symposium. Subsequent sessions focused on the areas of ordering and nonlinear diffusion kinetics, solid state reactions and amorphization, kinetics and defects of amorphous silicon, and kinetics of melting and solidification. Seven internationally recognized invited speakers reviewed many of the important problems and recent results in these areas, including defects in amorphous Si, crystal to glass transformations, ordering kinetics, solid-state amorphization, computer modeling, and liquid/solid transformations

Nonlinear oxidation kinetics of nickel cermets

International Nuclear Information System (INIS)

Galinski, Henning; Bieberle-Huetter, Anja; Rupp, Jennifer L.M.; Gauckler, Ludwig J.

2011-01-01

The oxidation of a cermet of screen-printed nickel (Ni) and gadolinia-doped ceria (CGO) with an approximate median porosity of 50 vol.% has been studied via in situ X-ray diffraction and focused ion beam nanotomography in the temperature range 773-848 K. The oxidation kinetics of Ni to NiO is found to be highly nonlinear with an apparent activation energy of 2.8(2) eV in this temperature range. The nonlinear oxidation kinetics found is in good agreement with theoretical works on oxide growth driven by nonlinear inbuilt fields. Stress-induced Kirkendall void formation has been identified as the physical process that enhances the oxidation of Ni/CGO cermets. Compressive stresses within the Ni matrix result from the thermal expansion mismatch of Ni and CGO and cause plastic deformation as they exceed the yield stress of the Ni matrix. The pore size distribution of Kirkendall voids formed has been measured by FIB nanotomography and shows a significant temperature dependence. It is shown that even one cycle of reoxidation changes irreversibly the microstructure of the cermet which can be interpreted as the onset and main contribution to the mechanical degradation of the cermet.

Application of a validated gasification model to determine the impact of coal particle grinding size on carbon conversion

KAUST Repository

Kumar, Mayank; Ghoniem, Ahmed F.

2013-01-01

In this paper, we describe the implementation of a comprehensive, previously validated multiscale model of entrained flow gasification to examine the impact of particle size on the gasification process in two different gasifier designs; the MHI and the GE gasifier. We show that the impact of the particle size depends on whether the char conversion process is kinetically limited or boundary layer diffusion-limited. Fine grinding helps accelerate char conversion under diffusion-control conditions, whereas the impact is not as noticeable under kinetic-control operation. The availability of particular gasification agents, namely O2 in the earlier sections of the gasifier or CO2 and H2O in the latter sections, as well as the temperature, are shown to have an impact on the relative importance of kinetics versus diffusion limitation. © 2013 Elsevier Ltd. All rights reserved.

Application of a validated gasification model to determine the impact of coal particle grinding size on carbon conversion

KAUST Repository

Kumar, Mayank

2013-06-01

In this paper, we describe the implementation of a comprehensive, previously validated multiscale model of entrained flow gasification to examine the impact of particle size on the gasification process in two different gasifier designs; the MHI and the GE gasifier. We show that the impact of the particle size depends on whether the char conversion process is kinetically limited or boundary layer diffusion-limited. Fine grinding helps accelerate char conversion under diffusion-control conditions, whereas the impact is not as noticeable under kinetic-control operation. The availability of particular gasification agents, namely O2 in the earlier sections of the gasifier or CO2 and H2O in the latter sections, as well as the temperature, are shown to have an impact on the relative importance of kinetics versus diffusion limitation. © 2013 Elsevier Ltd. All rights reserved.

Adsorption of cadmium from aqueous solution onto untreated coffee grounds: Equilibrium, kinetics and thermodynamics

Energy Technology Data Exchange (ETDEWEB)

Azouaou, N., E-mail: azouaou20@yahoo.fr [Laboratory of Reaction Genius, Faculty of Mechanical and Processes Genius, University of Sciences and Technology Houari - Boumediene, USTHB, BP no 32 El Alia bab ezzouar, 16111 Algiers (Algeria); Sadaoui, Z. [Laboratory of Reaction Genius, Faculty of Mechanical and Processes Genius, University of Sciences and Technology Houari - Boumediene, USTHB, BP no 32 El Alia bab ezzouar, 16111 Algiers (Algeria); Djaafri, A. [Central laboratory, SEAAL, 97 Parc ben omar, Kouba, Algiers (Algeria); Mokaddem, H. [Laboratory of Reaction Genius, Faculty of Mechanical and Processes Genius, University of Sciences and Technology Houari - Boumediene, USTHB, BP no 32 El Alia bab ezzouar, 16111 Algiers (Algeria)

2010-12-15

Adsorption can be used as a cost effective and efficient technique for the removal of toxic heavy metals from wastewater. Waste materials with no further treatment such as coffee grounds from cafeterias may act as adsorbents for the removal of cadmium. Batch kinetic and equilibrium experiments were conducted to study the effects of contact time, adsorbent dose, initial pH, particle size, initial concentration of cadmium and temperature. Three adsorption isotherm models namely, Langmuir, Freundlich and Dubinin-Radushkevich were used to analyse the equilibrium data. The Langmuir isotherm which provided the best correlation for Cd{sup 2+} adsorption onto coffee grounds, shows that the adsorption was favourable and the adsorption capacity found was equal to 15.65 mg g{sup -1}. Thermodynamic parameters were evaluated and the adsorption was exothermic. The equilibrium was achieved less than 120 min. The adsorption kinetic data was fitted with first and second order kinetic models. Finally it was concluded that the cadmium adsorption kinetic onto coffee grounds was well fitted by second order kinetic model rather than first order model. The results suggest that coffee grounds have high possibility to be used as effective and economical adsorbent for Cd{sup 2+} removal.

Adsorption of cadmium from aqueous solution onto untreated coffee grounds: Equilibrium, kinetics and thermodynamics

International Nuclear Information System (INIS)

Azouaou, N.; Sadaoui, Z.; Djaafri, A.; Mokaddem, H.

2010-01-01

Adsorption can be used as a cost effective and efficient technique for the removal of toxic heavy metals from wastewater. Waste materials with no further treatment such as coffee grounds from cafeterias may act as adsorbents for the removal of cadmium. Batch kinetic and equilibrium experiments were conducted to study the effects of contact time, adsorbent dose, initial pH, particle size, initial concentration of cadmium and temperature. Three adsorption isotherm models namely, Langmuir, Freundlich and Dubinin-Radushkevich were used to analyse the equilibrium data. The Langmuir isotherm which provided the best correlation for Cd 2+ adsorption onto coffee grounds, shows that the adsorption was favourable and the adsorption capacity found was equal to 15.65 mg g -1 . Thermodynamic parameters were evaluated and the adsorption was exothermic. The equilibrium was achieved less than 120 min. The adsorption kinetic data was fitted with first and second order kinetic models. Finally it was concluded that the cadmium adsorption kinetic onto coffee grounds was well fitted by second order kinetic model rather than first order model. The results suggest that coffee grounds have high possibility to be used as effective and economical adsorbent for Cd 2+ removal.

Size-density metrics, leaf area, and productivity in eastern white pine

Science.gov (United States)

J. C. Innes; M. J. Ducey; J. H. Gove; W. B. Leak; J. P. Barrett

2005-01-01

Size-density metrics are used extensively for silvicultural planning; however, they operate on biological assumptions that remain relatively untested. Using data from 12 even-aged stands of eastern white pine (Pinus strobus L.) growing in southern New Hampshire, we compared size-density metrics with stand productivity and its biological components,...

Kinetic Models for Topological Nearest-Neighbor Interactions

Science.gov (United States)

Blanchet, Adrien; Degond, Pierre

2017-12-01

We consider systems of agents interacting through topological interactions. These have been shown to play an important part in animal and human behavior. Precisely, the system consists of a finite number of particles characterized by their positions and velocities. At random times a randomly chosen particle, the follower, adopts the velocity of its closest neighbor, the leader. We study the limit of a system size going to infinity and, under the assumption of propagation of chaos, show that the limit kinetic equation is a non-standard spatial diffusion equation for the particle distribution function. We also study the case wherein the particles interact with their K closest neighbors and show that the corresponding kinetic equation is the same. Finally, we prove that these models can be seen as a singular limit of the smooth rank-based model previously studied in Blanchet and Degond (J Stat Phys 163:41-60, 2016). The proofs are based on a combinatorial interpretation of the rank as well as some concentration of measure arguments.

Can reduced stocking rates and natural forage utilization produce market sized catfish from fingerlings in one growing season

Science.gov (United States)

The purpose of this study was to determine the feasibility of growing marketable channel catfish Ictalurus punctatus from pond-run fingerlings (15.9 g/fish) using low stocking densities (7,413 or 14,826 fish/ha) and electrified bug lights to enhance natural forage available to fish. Even at low sto...

Seeking kinetic pathways relevant to the structural evolution of metal nanoparticles

International Nuclear Information System (INIS)

Haldar, Paramita; Chatterjee, Abhijit

2015-01-01

Understanding the kinetic pathways that cause metal nanoparticles to structurally evolve over time is essential for predicting their shape and size distributions and catalytic properties. Consequently, we need detailed kinetic models that can provide such information. Most kinetic Monte Carlo models used for metal systems contain a fixed catalogue of atomic moves; the catalogue is largely constructed based on our physical understanding of the material. In some situations, it is possible that an incorrect picture of the overall dynamics is obtained when kinetic pathways that are relevant to the dynamics are missing from the catalogue. Hence, a computational framework that can systematically determine the relevant pathways is required. This work intends to fulfil this requirement. Examples involving an Ag nanoparticle are studied to illustrate how molecular dynamics (MD) calculations can be employed to find the relevant pathways in a system. Since pathways that are unlikely to be selected at short timescales can become relevant at longer times, the accuracy of the catalogue is maintained by continually seeking these pathways using MD. We discuss various aspects of our approach, namely, defining the relevance of atomic moves to the dynamics and determining when additional MD is required to ensure the desired accuracy, as well as physical insights into the Ag nanoparticle. (paper)

Heterogeneous kinetics of the reduction of chromium (VI) by elemental iron

International Nuclear Information System (INIS)

Fiuza, Antonio; Silva, Aurora; Carvalho, Goreti; Fuente, Antonio V. de la; Delerue-Matos, Cristina

2010-01-01

Zero valent iron (ZVI) has been extensively used as a reactive medium for the reduction of Cr(VI) to Cr(III) in reactive permeable barriers. The kinetic rate depends strongly on the superficial oxidation of the iron particles used and the preliminary washing of ZVI increases the rate. The reaction has been primarily modelled using a pseudo-first-order kinetics which is inappropriate for a heterogeneous reaction. We assumed a shrinking particle type model where the kinetic rate is proportional to the available iron surface area, to the initial volume of solution and to the chromium concentration raised to a power α which is the order of the chemical reaction occurring at surface. We assumed α = 2/3 based on the likeness to the shrinking particle models with spherical symmetry. Kinetics studies were performed in order to evaluate the suitability of this approach. The influence of the following parameters was experimentally studied: initial available surface area, chromium concentration, temperature and pH. The assumed order for the reaction was confirmed. In addition, the rate constant was calculated from data obtained in different operating conditions. Digital pictures of iron balls were periodically taken and the image treatment allowed for establishing the time evolution of their size distribution.

Complexes between ovalbumin nanoparticles and linoleic acid: Stoichiometric, kinetic and thermodynamic aspects.

Science.gov (United States)

Sponton, Osvaldo E; Perez, Adrián A; Carrara, Carlos R; Santiago, Liliana G

2016-11-15

Stoichiometric, kinetic and thermodynamic aspects of complex formation between heat-induced aggregates of ovalbumin (ovalbumin nanoparticles, OVAn) and linoleic acid (LA) were evaluated. Extrinsic fluorescence data were fitted to modified Scatchard model yielding the following results: n: 49±2 LA molecules bound per OVA monomer unit and Ka: 9.80±2.53×10(5)M. Kinetic and thermodynamic properties were analyzed by turbidity measurements at different LA/OVA monomer molar ratios (21.5-172) and temperatures (20-40°C). An adsorption approach was used and a pseudo-second-order kinetics was found for LA-OVAn complex formation. This adsorption process took place within 1h. Thermodynamic parameters indicated that LA adsorption on OVAn was a spontaneous, endothermic and entropically-driven process, highlighting the hydrophobic nature of the LA and OVAn interaction. Finally, Atomic Force Microscopy imaging revealed that both OVAn and LA-OVAn complexes have a roughly rounded form with size lower than 100nm. Copyright © 2016 Elsevier Ltd. All rights reserved.

Achieving 3-D Nanoparticle Assembly in Nanocomposite Thin Films via Kinetic Control

Energy Technology Data Exchange (ETDEWEB)

Huang, Jingyu; Xiao, Yihan; Xu, Ting [UCB

2017-02-20

Nanocomposite thin films containing well-ordered nanoparticle (NP) assemblies are ideal candidates for the fabrication of metamaterials. Achieving 3-D assembly of NPs in nanocomposite thin films is thermodynamically challenging as the particle size gets similar to that of a single polymer chain. The entropic penalties of polymeric matrix upon NP incorporation leads to NP aggregation on the film surface or within the defects in the film. Controlling the kinetic pathways of assembly process provides an alternative path forward by arresting the system in nonequilibrium states. Here, we report the thin film 3-D hierarchical assembly of 20 nm NPs in supramolecules with a 30 nm periodicity. By mediating the NP diffusion kinetics in the supramolecular matrix, surface aggregation of NPs was suppressed and NPs coassemble with supramolecules to form new 3-D morphologies in thin films. The present studies opened a viable route to achieve designer functional composite thin films via kinetic control.

Comparison of drop size and velocity measurements by a laser precipitation meter and low-speed photography for an agriculture sprinkler

Science.gov (United States)

Kinetic energy of water droplets has a substantial effect on development of a soil surface seal and infiltration rate of bare soil. Methods for measuring sprinkler droplet size and velocity needed to calculate droplet kinetic energy have been developed and tested over the past 50 years, each with ad...

Precipitation kinetics of a continuous precipitator, with application to the precipitation of ammonium polyuranate

International Nuclear Information System (INIS)

Hoyt, R.C.

1978-04-01

A mathematical model describing the kinetics of continuous precipitation was developed which accounts for crystal nucleation, crystal growth, primary coagulation, and secondary coagulation. Population density distributions, average particle sizes, dominant particle sizes, and suspension density fractions of the crystallites, primary agglomerates, and secondary agglomerates leaving the continuous precipitator can be determined. This kinetic model was applied to the continuous precipitation of ammonium polyuranate, which consists of: (1) elementary crystals, (2) clusters or primary coagulated particles, and (3) agglomerates or secondary coagulated particles. The crystallites are thin, submicron, hexagonal platelets. The clusters had an upper size limit of about 7 μ in diameter and contained numerous small voids (less than 0.3 μm) due to the packing of the crystallites. The agglomerates had an upper size limit of about 40 μm in diameter and contained large voids (approximately 1 μm). The particle size distribution and particle structure of the ammonium polyuranate precipitate can be controlled through proper regulation of the precipitation conditions. The ratio of clusters to agglomerates can be best controlled through the uranium concentration, and the cohesiveness or internal bonding strength of the particles can be controlled with the ammonium to uranium reacting feed mole ratio. These two conditions, in conjunction with the residence time, will determine the nucleation rates, growth rates, and size distributions of the particles leaving the continuous precipitator. With proper control of these physical particle characteristics, the use of pore formers, ball-milling, and powder blending can probably be eliminated from the nuclear fuel fabrication process, substantially reducing the cost

Precipitation kinetics of a continuous precipitator, with application to the precipitation of ammonium polyuranate

Energy Technology Data Exchange (ETDEWEB)

Hoyt, R.C.

1978-04-01

A mathematical model describing the kinetics of continuous precipitation was developed which accounts for crystal nucleation, crystal growth, primary coagulation, and secondary coagulation. Population density distributions, average particle sizes, dominant particle sizes, and suspension density fractions of the crystallites, primary agglomerates, and secondary agglomerates leaving the continuous precipitator can be determined. This kinetic model was applied to the continuous precipitation of ammonium polyuranate, which consists of: (1) elementary crystals, (2) clusters or primary coagulated particles, and (3) agglomerates or secondary coagulated particles. The crystallites are thin, submicron, hexagonal platelets. The clusters had an upper size limit of about 7 ..mu.. in diameter and contained numerous small voids (less than 0.3 ..mu..m) due to the packing of the crystallites. The agglomerates had an upper size limit of about 40 ..mu..m in diameter and contained large voids (approximately 1 ..mu..m). The particle size distribution and particle structure of the ammonium polyuranate precipitate can be controlled through proper regulation of the precipitation conditions. The ratio of clusters to agglomerates can be best controlled through the uranium concentration, and the cohesiveness or internal bonding strength of the particles can be controlled with the ammonium to uranium reacting feed mole ratio. These two conditions, in conjunction with the residence time, will determine the nucleation rates, growth rates, and size distributions of the particles leaving the continuous precipitator. With proper control of these physical particle characteristics, the use of pore formers, ball-milling, and powder blending can probably be eliminated from the nuclear fuel fabrication process, substantially reducing the cost.

Socio-economic determinants of growing trees on farms in the middle hills of Nepal

DEFF Research Database (Denmark)

Oli, B.N.; Treue, Thorsten; Larsen, Helle Overgaard

2015-01-01

were found. The Shannon–Wiener index was 2.46 and Simpson’s Dominance index was 0.15. Trees on farmland contributed on average 43 % of households’ firewood and fodder consumption. Apparent determinants of tree growing were identified through OLS regression; they included size of land and livestock......On-farm tree growing is potentially important for livelihood strategies and forest conservation, and varies greatly according to local contexts. A detailed knowledge base is therefore needed, requiring, inter alia, the documentation of factors associated with growing trees on farms. The present...... study surveyed 304 randomly sampled households in ten community forestry user groups in Nepal, eliciting data on demographics, income and consumption of tree products. All trees on households’ farm land were registered by species. Farmers had on average 65 trees per hectare and a total of 92 species...

Kinetics in radiation chemistry

International Nuclear Information System (INIS)

Hummel, A.

1987-01-01

In this chapter the authors first briefly review the kinetics of first- and second-order processes for continuous and pulsed irradiation, without taking the effects of nonhomogeneous formation of the species into consideration. They also discuss diffusion controlled reactions under conditions where interactions of more than two particles can be neglected, first the kinetics of the diffusion-controlled reaction of randomly generated species (homogeneous reaction) and then that of isolated pairs of reactants. The latter is often called geminate kinetics when dealing with pairs of oppositely charged species; they shall use this term for the kinetics of isolated pairs in general. In the last section they discuss briefly the kinetics of groups of more than two reactants

Characterization of gas-aerosol interaction kinetics using morphology dependent stimulated Raman scattering

International Nuclear Information System (INIS)

Aker, P.M.

1993-01-01

This study is aimed at characterizing the influence of aerosol surface structure on the kinetics of gas-aerosol interactions. Changes in gas phase chemical reaction rates as a function of exposure to a specific aerosol are measured with aerosols having different surface properties due to the composition and/or temperature of the material making up the aerosol. The kinetic data generated can be used directly in atmospheric modeling calculations. The surface structure of the aerosol is using morphology-dependent enhancement of simulated Raman scattering (MDSRS). Detailed dynamics of gas-aerosol interactions can be obtained by correlating the change in the reaction rate with change in surface structure and by monitoring the change in aerosol surface structure during, the course of the reaction. This dynamics information can be used to generate kinetic data for systems which are similar in nature to those studied, but are not amenable to laboratory investigation. We show here that increased MDSRS sensitivity is achieved by using an excitation laser source that has a narrow linewidth and we have been able to detect sulfate anion concentrations much lower than previously reported. We have shown that the linewidth of the MDSRS mode excited in a droplet is limited by the laser linewidth. This is a positive result for it eases our ability to quantify the MDSRS gain equation. This result also suggests that MDSRS signal size should be independent of droplet size, and preliminary experiments confirm this hypothesis

Kinetic equation solution by inverse kinetic method

International Nuclear Information System (INIS)

Salas, G.

1983-01-01

We propose a computer program (CAMU) which permits to solve the inverse kinetic equation. The CAMU code is written in HPL language for a HP 982 A microcomputer with a peripheral interface HP 9876 A ''thermal graphic printer''. The CAMU code solves the inverse kinetic equation by taking as data entry the output of the ionization chambers and integrating the equation with the help of the Simpson method. With this program we calculate the evolution of the reactivity in time for a given disturbance

Hydrolytic Activation Kinetics of the Herbicide Benzobicyclon in Simulated Aquatic Systems.

Science.gov (United States)

Williams, Katryn L; Tjeerdema, Ronald S

2016-06-22

Herbicide resistance is a growing concern for weeds in California rice fields. Benzobicyclon (BZB; 3-(2-chloro-4-(methylsulfonyl)benzoyl)-2-phenylthiobicyclo[3.2.1]oct-2-en-4-one) has proven successful against resistant rice field weeds in Asia. A pro-herbicide, BZB forms the active agent, benzobicyclon hydrolysate (BH), in water; however, the transformation kinetics are not understood for aquatic systems, particularly flooded California rice fields. A quantitative experiment was performed to assess the primary mechanism and kinetics of BZB hydrolysis to BH. Complete conversion to BH was observed for all treatments. Basic conditions (pH 9) enhanced the reaction, with half-lives ranging from 5 to 28 h. Dissolved organic carbon (DOC) hindered transformation, which is consistent with other base-catalyzed hydrolysis reactions. BH was relatively hydrolytically stable, with 18% maximum loss after 5 days. Results indicate BZB is an efficient pro-herbicide under aqueous conditions such as those of a California rice field, although application may be best suited for fields with recirculating tailwater systems.

Introduction to chemical kinetics

CERN Document Server

Soustelle, Michel

2013-01-01

This book is a progressive presentation of kinetics of the chemical reactions. It provides complete coverage of the domain of chemical kinetics, which is necessary for the various future users in the fields of Chemistry, Physical Chemistry, Materials Science, Chemical Engineering, Macromolecular Chemistry and Combustion. It will help them to understand the most sophisticated knowledge of their future job area. Over 15 chapters, this book present the fundamentals of chemical kinetics, its relations with reaction mechanisms and kinetic properties. Two chapters are then devoted to experimental re

Effect of pH and inoculum size on pentachlorophenol degradation ...

African Journals Online (AJOL)

The success of this depends on finding strains able to degrade PCP in a changeable environment. The aim of this work was to study the influence of pH of the medium and the effect of inoculum size on pentachlorophenol degradation by Pseudomonas sp. A study of PCP degradation kinetics was performed to assess such ...

Highly polygenic variation in environmental perception determines dauer larvae formation in growing populations of Caenorhabditis elegans.

Directory of Open Access Journals (Sweden)

James W M Green

Full Text Available Determining how complex traits are genetically controlled is a requirement if we are to predict how they evolve and how they might respond to selection. This requires understanding how distinct, and often more simple, life history traits interact and change in response to environmental conditions. In order to begin addressing such issues, we have been analyzing the formation of the developmentally arrested dauer larvae of Caenorhabditis elegans under different conditions.We find that 18 of 22 previously identified quantitative trait loci (QTLs affecting dauer larvae formation in growing populations, assayed by determining the number of dauer larvae present at food patch exhaustion, can be recovered under various environmental conditions. We also show that food patch size affects both the ability to detect QTLs and estimates of effect size, and demonstrate that an allele of nath-10 affects dauer larvae formation in growing populations. To investigate the component traits that affect dauer larvae formation in growing populations we map, using the same introgression lines, QTLs that affect dauer larvae formation in response to defined amounts of pheromone. This identifies 36 QTLs, again demonstrating the highly polygenic nature of the genetic variation underlying dauer larvae formation.These data indicate that QTLs affecting the number of dauer larvae at food exhaustion in growing populations of C. elegans are highly reproducible, and that nearly all can be explained by variation affecting dauer larvae formation in response to defined amounts of pheromone. This suggests that most variation in dauer larvae formation in growing populations is a consequence of variation in the perception of the food and pheromone environment (i.e. chemosensory variation and in the integration of these cues.

Large intradiploic growing skull fracture of the posterior fossa

International Nuclear Information System (INIS)

Hamamcioglu, M. Kemal; Hicdonmez, Tufan; Kilincer, Cumhur; Cobanoglu, Sebahattin

2006-01-01

Growing skull fractures (GSFs) are rare complications of head injury and mostly occur in infancy and early childhood. Location in the posterior fossa and intradiploic development of a GSF is very uncommon. We report a 7-year-old boy with a large, 9 x 7 x 4-cm, occipital intradiploic GSF. The lesion developed progressively over a period of 5 years following a documented occipital linear fracture. This case of a GSF developing from a known occipital linear fracture demonstrates that a GSF may reach a considerable size and, although uncommon, intradiploic development and occipital localization of a GSF is possible. (orig.)

Mechanisms and kinetics of granulated sewage sludge combustion.

Science.gov (United States)

Kijo-Kleczkowska, Agnieszka; Środa, Katarzyna; Kosowska-Golachowska, Monika; Musiał, Tomasz; Wolski, Krzysztof

2015-12-01

This paper investigates sewage sludge disposal methods with particular emphasis on combustion as the priority disposal method. Sewage sludge incineration is an attractive option because it minimizes odour, significantly reduces the volume of the starting material and thermally destroys organic and toxic components of the off pads. Additionally, it is possible that ashes could be used. Currently, as many as 11 plants use sewage sludge as fuel in Poland; thus, this technology must be further developed in Poland while considering the benefits of co-combustion with other fuels. This paper presents the results of experimental studies aimed at determining the mechanisms (defining the fuel combustion region by studying the effects of process parameters, including the size of the fuel sample, temperature in the combustion chamber and air velocity, on combustion) and kinetics (measurement of fuel temperature and mass changes) of fuel combustion in an air stream under different thermal conditions and flow rates. The combustion of the sludge samples during air flow between temperatures of 800 and 900°C is a kinetic-diffusion process. This process determines the sample size, temperature of its environment, and air velocity. The adopted process parameters, the time and ignition temperature of the fuel by volatiles, combustion time of the volatiles, time to reach the maximum temperature of the fuel surface, maximum temperature of the fuel surface, char combustion time, and the total process time, had significant impacts. Copyright © 2015 Elsevier Ltd. All rights reserved.

Supercritical kinetic analysis in simplified system of fuel debris using integral kinetic model

International Nuclear Information System (INIS)

Tuya, Delgersaikhan; Obara, Toru

2016-01-01

Highlights: • Kinetic analysis in simplified weakly coupled fuel debris system was performed. • The integral kinetic model was used to simulate criticality accidents. • The fission power and released energy during simulated accident were obtained. • Coupling between debris regions and its effect on the fission power was obtained. - Abstract: Preliminary prompt supercritical kinetic analyses in a simplified coupled system of fuel debris designed to roughly resemble a melted core of a nuclear reactor were performed using an integral kinetic model. The integral kinetic model, which can describe region- and time-dependent fission rate in a coupled system of arbitrary geometry, was used because the fuel debris system is weakly coupled in terms of neutronics. The results revealed some important characteristics of coupled systems, such as the coupling between debris regions and the effect of the coupling on the fission rate and released energy in each debris region during the simulated criticality accident. In brief, this study showed that the integral kinetic model can be applied to supercritical kinetic analysis in fuel debris systems and also that it can be a useful tool for investigating the effect of the coupling on consequences of a supercritical accident.

Aggregation kinetics and structure of cryoimmunoglobulins clusters

CERN Document Server

De Spirito, M; Bassi, F A; Di Stasio, E; Giardina, B; Arcovito, G

2002-01-01

Cryoimmunoglobulins are pathological antibodies characterized by a temperature-dependent reversible insolubility. Rheumatoid factors (RF) are immunoglobulins possessing anti-immunoglobulin activity and usually consist of an IgM antibody that recognizes IgG as antigen. These proteins are present in sera of patients affected by a large variety of different pathologies, such as HCV infection, neoplastic and autoimmune diseases. Aggregation and precipitation of cryoimmunoglobulins, leading to vasculiti, are physical phenomena behind such pathologies. A deep knowledge of the physico-chemical mechanisms regulating such phenomena plays a fundamental role in biological and clinical applications. In this work, a preliminary investigation of the aggregation kinetics and of the final macro- molecular structure of the aggregates is presented. Through static light scattering techniques, the gyration radius R/sub g/ and the fractal dimension D/sub m/ of the growing clusters have been determined. However, while the initial ...

Effect of planting density and growing media on growth and yield of strawberry

International Nuclear Information System (INIS)

Tariq, R.; Qureshi, K.M.; Hassan, I.; Rasheed, M.; Qureshi, U.S.

2013-01-01

Strawberry (Fragaria ananasa), belonging to Rosaceae family, is a rich source of vitamins and minerals with delicate flavors. It is perishable crop which is exceedingly in demand for its taste, profitability, high yield and good quality. To make the plant growth successful in the container, the requirement of special media is very important step because plant growth is largely depended on the physiochemical properties of the growing media used. Winter strawberry production in a greenhouse using high plant densities and various media may be a viable alternative to open-field production system. Planting density can be increased thrice by using different production systems. Studies were conducted to see the impact of different planting densities and media on growth and yield of strawberry. The treatments were T 1 = Control, with normal planting distance of 30 cm x 60 cm and growing media silt, sand and farm yard manure (FYM); T 2 = 15 cm 2 x 30 cm and silt, sand and FYM; T 3 = 30 cm x 60 cm and coir; T 4 = 15 cm x 30 cm and coir; T 5 = 30 cm x 60 cm and peat moss; T 6 = 15 cm x 30 cm and 5 6 peat moss. Results showed that plants grown at low planting distance on all growth media showed more pronounced results as compared to high planting distance. Plants grown in peat moss at both planting densities moderately increased the plant height, canopy size, leaf area, number of fruits, fruit size, fruit weight and titratable acidity. A significant increase in fresh and dry weight of leaves, number of leaves, fruit yield in term of fruit number, fruit size and fruit weight, and fruit quality with high ascorbic acid contents were observed. On the other hand, plants grown in silt, sand and FYM (1 : 1 : 1) at both planting densities showed significant increment in vegetative growth resulting in early flowering with more flowers per plant, better fruit setting and fruit set percentage, greater fruit size and weight but fruit number per plant was reduced which lowered the overall

Metabolism of tRNAs in growing cells of Escherichia coli illuminated with near-ultraviolet light

International Nuclear Information System (INIS)

Hajnsdorf, E.; Favre, A.

1986-01-01

The tRNA metabolism which accompanies illumination of growing E. coli cells has been examined in conditions that led to growth delay. The in vivo formation of the 8-13 link was followed by a fluorimetric procedure and revealed pseudo-first order kinetics very close to those obtained in vitro under the same illumination conditions. Comparison of these kinetics with published radiochromatographic data suggests the transient formation during illumination of a new RNase-T 2 -resistant dinucleotide in tRNA distinct from the 8-13 link. Under illumination some tRNA molecules lack one or more bases in a specific position in the sequence. During the growth lag, uracil incorporation into nucleic acids occurs at between 4-8% of the rate normally observed during exponential growth. However, the pyrimidine ribonucleoside triphosphate pools are strongly perturbed after illumination. Comparison of exogenous [ 3 H]uracil incorporation into two strains proficient or deficient in uracil biosynthesis suggests a derepression of the endogenous path after light treatment. In addition, the UTP-to-CTP conversion is inhibited. In spite of preferential incorporation of exogenously labelled uracil in tRNA after illumination, a possible pyrimidine base turnover cannot be proved. (author)

Drying kinetics characteristic of Indonesia lignite coal (IBC) using lab scale fixed bed reactor

Energy Technology Data Exchange (ETDEWEB)

Kang, TaeJin; Jeon, DoMan; Namkung, Hueon; Jang, DongHa; Jeon, Youngshin; Kim, Hyungtaek [Ajou Univ., Suwon (Korea, Republic of). Div. of Energy Systems Research

2013-07-01

Recent instability of energy market arouse a lot of interest about coal which has a tremendous amount of proven coal reserves worldwide. South Korea hold the second rank by importing 80 million tons of coal in 2007 following by Japan. Among various coals, there is disused coal. It's called Low Rank Coal (LRC). Drying process has to be preceded before being utilized as power plant. In this study, drying kinetics of LRC is induced by using a fixed bed reactor. The drying kinetics was deduced from particle size, the inlet gas temperature, the drying time, the gas velocity, and the L/D ratio. The consideration on Reynold's number was taken for correction of gas velocity, particle size, and the L/D ratio was taken for correction packing height of coal. It can be found that active drying of free water and phase boundary reaction is suitable mechanism through the fixed bed reactor experiments.

The body size of the oil-collecting bee Tetrapedia diversipes (Apidae)

OpenAIRE

Pinto da Silva,Carlos; Silva,Adriana; Duran Cordeiro,Guaraci; Alves dos Santos ,Isabel

2015-01-01

The body size of bees can affect their fitness in many ways. There is an indirect relationship between the size of the mother and the size of her progeny. This is so because large mothers use larger nests and brood cells and have higher foraging capacity than small mothers, and consequently large mothers supply a larger amount of food to their larvae, which grow larger. We analyzed the relationship between body size of individual oil-collecting bees of the species Tetrapedia diversipes and th...

Role of tomography in providing radionuclide distribution and kinetic data

International Nuclear Information System (INIS)

Budinger, T.F.; Derenzo, S.E.; Huesman, R.H.

1981-01-01

A major limitation in radionuclide dosimetry has been the lack of human organ-specific radionuclide distribution and kinetic data because methods of acquiring sequential quantitative information from volumes of interest were not available. Developments in emission computed tomography instrumentation and associated algorithms have overcome this basic limitation, thus allowing in vivo noninvasive tissue distribution studies to be performed. Five aspects of kinetic data acquisition using tomography are: (1) the resolution volume for quantitative work is about two times larger than the system resolution element size as defined by a spread function criterion of full width at half (peak) maximum; (2) scattered radiation might account for 30% of the activity in a given resolution volume and must be taken into account for accurate calculations; (3) proper attenuation compensation must be made to yield quantitative data, particularly with single photon tomography; (4) for dosimetry studies with short half-life labels, multisection systems with dynamic imaging capabilities commensurate with the half-life are needed; (5) the biological conditions such as patient disease and dietary history and the specific activity of the radiopharmaceutical are factors of prime importance in the distribution kinetics

EXPERIENCE GROWING A FRY WALLEYE (STIZOSTEDION LUCIOPERCA UNDER DIFFERENT PRODUCTION TECHNOLOGIES

Directory of Open Access Journals (Sweden)

V. Martsenuk

2014-09-01

Full Text Available Purpose. The question of growing and cultivation technology a fry walleye (Stizostedion Sander lucioperca, in various conditions of intensification and cultivation of the objects on the example of Ukraine, Poland and Czech Republic. Methodology. Some of the research conducted in JSC "Lebedynska RMS." There was a corresponding work of herd sires and fry. Also used published articles and monographs using statistical analysis methods. Findings. The existing technology of breeding and raising perch as in natural waters and artificial reproduction. Also, this is a clear description of the biology walleye in the early stages postembryogenesis perch. Also highlighted key points in the technology of the object at different aquaculture technologies. Originality. On the basis of existing technologies were analyzed current methods for growing and perch are to be brought in fish farms Ukraine, depending on the technical capabilities of enterprises. Practical value. Comparative review of technology growing perch allows farmers to introduce more appropriate technology of walleye for your own needs. Since it is directly a particular manufacturer planting material of the object is necessary to choose the most suitable and perfect technology, based on the existing herd sires, space, equipment and ability to use hormonal stimulation. So can use the following methods of breeding walleye: natural spawning, uncontrolled; controlled natural spawning; spawning in lake; artificial spawning; spawning outside-seasonal. During the early stages of walleye can identify a number of critical periods greatly affect the possibility of wound development: small body size at the final stage of resorption of yolk sac; small size of the cavity; feed intake in the water column; high sensitivity to stress; belonging to the group of fish with a closed bladder; great demands on environmental conditions; relative preferences heat; penchant for cannibalism.

Fast Search and Adaptive Resolution for Complex Particle Kinetics

Science.gov (United States)

Larson, David J.

2005-10-01

A new plasma simulation algorithm, intended to bridge the gap between Eulerian fluid and kinetic regimes, is now being used for a variety of applications in ICF and weapon effects. The CPK method (Complex Particle Kinetic) concept [1] uses an ensemble of macro-particles with a Gaussian spatial profile and a Mawellian velocity distribution to represent particle distributions in phase space. Time evolution is modeled by a combination of Lagrangian motion and internal evolution within each individual macro-particle. Collisional particle-particle interactions [2] are facilitated by sorting particles into bins depending of the particle size. Different bin levels are connected by a linked list. Searching for neighboring particles is highly efficient because the search is limited to particles in neighboring bins with the possibility of interaction. The bin structure also allows the computation of various spatial moments at different resolutions. Combining the results of the moment calculations yields information on where and when increased resolution is necessary. We will present details of the particle binning process along with progress towards our goal of simulating the transition from continuum to fully kinetic physics. [1] D. W. Hewett, J. Comp. Phys. 189 (2003). [2] D. J. Larson, J. Comp. Phys. 188 (2003).

Principles of chemical kinetics

CERN Document Server

House, James E

2007-01-01

James House's revised Principles of Chemical Kinetics provides a clear and logical description of chemical kinetics in a manner unlike any other book of its kind. Clearly written with detailed derivations, the text allows students to move rapidly from theoretical concepts of rates of reaction to concrete applications. Unlike other texts, House presents a balanced treatment of kinetic reactions in gas, solution, and solid states. The entire text has been revised and includes many new sections and an additional chapter on applications of kinetics. The topics covered include quantitative rela

[The early expressive vocabulary size in simultaneous bilingual growing-up infants - a diagnostic relevant criterion?].

Science.gov (United States)

Kiese-Himmel, C; Sellner, L; Bockmann, A-K

2013-08-01

Bilingual young children's early expressive vocabulary size and its composition (as one domain of the language development) should be examined to find out whether children with a risk for delayed language development may be identified in this way. 30 bilingual kindergarten infants from Berlin (with simultaneous language acquisition; second language German) and 30 monolingual German infants from the greater areas of Stuttgart and Heidelberg were pair matched (mean chronological age 22.5 [SD 3.1] months; min 16; max 26). The German expressive vocabulary checklist Elternfragebogen zur Wort-schatzentwicklung im frühen Kindesalter (ELAN; Bockmann & Kiese-Himmel, 2006) was filled out by all parents. In addition, parents of bilingual infants completed the adaption of the German vocabulary checklist Sprachbeurteilung durch Eltern (SBE-2-KT; v. Suchodoletz & Sachse, 2008) for the second mother tongue. The monolinguals' word sum in the ELAN (145.7; SD 75.8) differed significantly (p=0.001) from the bilinguals' word sum (78.3; SD 78.9 words). In contrast, bilinguals did not significantly differ in their overall expressive vocabulary size (ELAN+SBE-2-KT: 101.2; SD 77.0 words) from their monolingual counterparts (ELAN). Because bilinguals had a similar sized overall early vocabulary (both languages) like monolingual German-learning infants, the diagnostic criterion to identify late talkers with 24 months of age (less than 50 German words and no word combinations) should not be applied to bilingually infants with simultaneously double language acquisition. © Georg Thieme Verlag KG Stuttgart · New York.

Airline's choice of aircraft size-explanations and implications

NARCIS (Netherlands)

Rietveld, P.; Givoni, M.

2009-01-01

When facing a growth in demand, airlines tend to respond more by means of increasing frequencies than by increasing aircraft size. At many of the world's largest airports there are fewer than 100 passengers per air transport movement, although congestion and delays are growing. Furthermore, demand

Microstructural characterization and grain growth kinetics of atomized Fe-6%Si alloy

Energy Technology Data Exchange (ETDEWEB)

Florio Filho, A.; Bolfarini, C.; Kiminami, C.S. [Dept. de Engenharia de Materiais, Univ. Federal de Sao Carlos, Sao Carlos SP (Brazil)

2001-07-01

The microstructural characterization of the overspray powders is considered an important step to evaluate the as-cast microstructure of preforms fabricated by spray forming process. The particles generated during the high pressure gas atomization fly toward a substrate located at the middle height into the atomization chamber and consolidate to a dense deposit. The solidification process begins already during the flight of the droplets and high cooling rate can be achieved by the droplets of the molten metal during the atomization step. Consequently, the microstructure of the preform has some typical features presented by rapidly solidified metals as low level of porosity and segregation and it is strongly influenced by the thermal history of the droplets during flight. In the present work the microstructure of the particles of the Fe-6%Si alloy was analysed by light microscopy and scanning electron microscopy (SEM). The experimental determination of the kinetic exponent n for grain boundary migration in both powder and preform was determined by isothermal treatment under argon atmosphere. It has been stated that the larger the particle size the greater the grain size in Fe-6%Si alloy. It was observed also that the interface morphology is strongly related to the particle size. Furthermore, the grain growth kinetic in the preform seems to not obey the migration mechanism where the self diffusion of elemental Fe drive the boundary displacement. (orig.)

Temperature Sensitivity of Soil Respiration to Nitrogen Fertilization: Varying Effects between Growing and Non-Growing Seasons

Science.gov (United States)

Liu, Qingfang; Wang, Rui; Li, Rujian; Hu, Yaxian; Guo, Shengli

2016-01-01

Nitrogen (N) fertilization has a considerable effect on food production and carbon cycling in agro-ecosystems. However, the impacts of N fertilization rates on the temperature sensitivity of soil respiration (Q10) were controversial. Five N rates (N0, N45, N90, N135, and N180) were applied to a continuous winter wheat (Triticum aestivum L.) crop on the semi-arid Loess Plateau, and the in situ soil respiration was monitored during five consecutive years from 2008 to 2013. During the growing season, the mean soil respiration rates increased with increasing N fertilization rates, peaking at 1.53 μmol m−2s−1 in the N135 treatment. A similar dynamic pattern was observed during the non-growing season, yet on average with 7.3% greater soil respiration rates than the growing season. In general for all the N fertilization treatments, the mean Q10 value during the non-growing season was significantly greater than that during the growing season. As N fertilization rates increased, the Q10 values did not change significantly in the growing season but significantly decreased in the non-growing season. Overall, N fertilization markedly influenced soil respirations and Q10 values, in particular posing distinct effects on the Q10 values between the growing and non-growing seasons. PMID:27992576

Plasma kinetic theory

International Nuclear Information System (INIS)

Elliott, J.A.

1993-01-01

Plasma kinetic theory is discussed and a comparison made with the kinetic theory of gases. The plasma is described by a modified set of fluid equations and it is shown how these fluid equations can be derived. (UK)

Shape transition of endotaxial islands growth from kinetically constrained to equilibrium regimes

Energy Technology Data Exchange (ETDEWEB)

Li, Zhi-Peng, E-mail: LI.Zhipeng@nims.go.jp [Department of Physics, National University of Singapore, 2 Science Drive 3, S117542 Singapore (Singapore); Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tok, Engsoon [Department of Physics, National University of Singapore, 2 Science Drive 3, S117542 Singapore (Singapore); Foo, Yonglim [Institute of Materials Research and Engineering, 3 Research Link, S117602 Singapore (Singapore)

2013-09-01

Graphical abstract: - Highlights: • All Fe{sub 13}Ge{sub 8} islands will grow into Ge(0 0 1) substrate at temperatures from 350 to 675 °C. • Shape transition occurred from kinetically constrained to equilibrium regime. • All endotaxial islands can be clarified into two types. • The mechanisms of endotaxial growth and shape transition have been rationalized. - Abstract: A comprehensive study of Fe grown on Ge(0 0 1) substrates has been conducted at elevated temperatures, ranging from 350 to 675 °C. All iron germinide islands, with the same Fe{sub 13}Ge{sub 8} phase, grow into the Ge substrate with the same epitaxial relationship. Shape transition occurs from small square islands (low temperatures), to elongated orthogonal islands or orthogonal nanowires (intermediate temperatures), and then finally to large square orthogonal islands (high temperatures). According to both transmission electron microscopy (TEM) and atomic force microscopy (AFM) investigations, all islands can be defined as either type-I or type-II. Type-I islands usually form at kinetically constrained growth regimes, like truncated pyramids. Type-II islands usually appear at equilibrium growth regimes forming a dome-like shape. Based on a simple semi-quantitative model, type-II islands have a lower total energy per volume than type-I, which is considered as the dominant mechanism for this type of shape transition. Moreover, this study not only elucidates details of endotaxial growth in the Fe–Ge system, but also suggests the possibility of controlled fabrication of temperature-dependent nanostructures, especially in materials with dissimilar crystal structures.

Spatially Different Tissue-Scale Diffusivity Shapes ANGUSTIFOLIA3 Gradient in Growing Leaves.

Science.gov (United States)

Kawade, Kensuke; Tanimoto, Hirokazu; Horiguchi, Gorou; Tsukaya, Hirokazu

2017-09-05

The spatial gradient of signaling molecules is pivotal for establishing developmental patterns of multicellular organisms. It has long been proposed that these gradients could arise from the pure diffusion process of signaling molecules between cells, but whether this simplest mechanism establishes the formation of the tissue-scale gradient remains unclear. Plasmodesmata are unique channel structures in plants that connect neighboring cells for molecular transport. In this study, we measured cellular- and tissue-scale kinetics of molecular transport through plasmodesmata in Arabidopsis thaliana developing leaf primordia by fluorescence recovery assays. These trans-scale measurements revealed biophysical properties of diffusive molecular transport through plasmodesmata and revealed that the tissue-scale diffusivity, but not the cellular-scale diffusivity, is spatially different along the leaf proximal-to-distal axis. We found that the gradient in cell size along the developmental axis underlies this spatially different tissue-scale diffusivity. We then asked how this diffusion-based framework functions in establishing a signaling gradient of endogenous molecules. ANGUSTIFOLIA3 (AN3) is a transcriptional co-activator, and as we have shown here, it forms a long-range signaling gradient along the leaf proximal-to-distal axis to determine a cell-proliferation domain. By genetically engineering AN3 mobility, we assessed each contribution of cell-to-cell movement and tissue growth to the distribution of the AN3 gradient. We constructed a diffusion-based theoretical model using these quantitative data to analyze the AN3 gradient formation and demonstrated that it could be achieved solely by the diffusive molecular transport in a growing tissue. Our results indicate that the spatially different tissue-scale diffusivity is a core mechanism for AN3 gradient formation. This provides evidence that the pure diffusion process establishes the formation of the long-range signaling

N-(2-PIRYDYLAMINO METHYLENEBISPHOSPHONIC ACID AS A SOLE SOURCE OF A FUNGI FUSARIUM STRAINS GROWING

Directory of Open Access Journals (Sweden)

Teresa Krzyśko-Łupicka

2016-09-01

The results of growth kinetics of the studied Fusarium fungi in the presence of N-(2-pirydyloamino methyle-nobisphosphonic acid, were expressed by dry weight [g·dm-3]. Only Fusarium oxysporum XVI has been capa-ble to grow in acidic medium (pH 4.0 using N-(2-pirydylamino methylene-bisphosphonic acid as an alterna-tive source of phosphorus. In these conditions the N-(2-pirydylamino methylenebisphosphonic acid degrada-tion was carried out to utilize phosphorus compounds as a source of nutrient components for this strain. The presence of N-(2-pirydylamino methylenebisphosphonic acid receded a growth rate of mycelium but did not have an effect on spores of tested fungi.

Passage kinetics of digesta in horses fed with coastcross hay ground to different degrees

Directory of Open Access Journals (Sweden)

Vinicius Pimentel Silva

2014-10-01

Full Text Available This study was conducted to evaluate the kinetics, physicochemical characteristics and particle size of digesta in the right ventral colon (RVC of horses fed coastcross hay ground to different degrees. Four horses fitted with cannulae in the RVC were used and were fed the following forms of hay: long, chopped, ground to 5 mm and ground to 3 mm. A Latin Square 4x4 study design was used. Each experimental period included 10 days for diet adaptation, four days for feces collection and one day for digesta collection. The kinetics of the particulate and solute phases of digesta were evaluated based on the mean retention time (MRT, passage rate (k and transit time (TT using two external markers: Cr-NDF and Co-EDTA. The TT of solid phase digesta was 3 hours longer (P0.05 in k or MRT in either the liquid or solid phase of digesta as a function of the different degrees of hay grinding. However, the liquid phase of digesta presented a higher k than the solid phase, with values of 3.28 and 2.73 h-1 being obtained, respectively. The smallest particle size and the lowest neutral detergent fiber contents in colon digesta were observed when hay ground to 3 mm was offered, leading to values of 0.51 mm and 53.46%, respectively. Grinding the hay increased the transit time of the liquid phase in the digestive tract of the horses, whereas no change in the kinetics of the solid phase digesta was observed. The grinding of hay reduced the NDF and the average particle size in the right ventral colon.

Kinetics of a Migration－Driven Aggregation－Fragmentation Process

Institute of Scientific and Technical Information of China (English)

ZHUANGYou-Yi; LINZhen-Quan; KEJian-Hon~

2003-01-01

We propose a reversible model of the migration-driven aggregation-fragmentation process with the symmetric migration rate kernels K (k; j) = K′(k; j) =λkjv and the constant aggregation rates I1, I2 and fragmentation rates Jl, J2. Based on the mean-field theory, we investigate the evolution behavior of the aggregate size distributions in several cases with different values of index v. We find that the fragmentation reaction plays a more important role in the kinetic behaviors of the system than the aggregation and migration. When Jl = 0 and J2 = O, the aggregate size distributions αk(t) and bk(t) obey the conventional scaling law, while when Jl > 0 and J2 > O, they obey the modified scaling law with an exponential scaling function. The total mass of either species remains conserved.

Testing machine for fatigue crack kinetic investigation in specimens under bending

International Nuclear Information System (INIS)

Panasyuk, V.V.; Ratych, L.V.; Dmytrakh, I.N.

1978-01-01

A kinematic diagram of testing mashine for the investigation of fatigue crack kinetics in prismatic specimens, subjected to pure bending is described. Suggested is a technique of choosing an optimum ratio of the parameters of ''the testing machine-specimen'' system, which provide the stabilization of the stress intensity coefficient for a certain region of crack development under hard loading. On the example of the 40KhS and 15Kh2MFA steel specimens the pliability of the machine constructed according to the described diagram and designed for the 30ONxm maximum bending moment. The results obtained can be used in designing of the testing machines for studying pure bending under hard loading and in choosing the sizes of specimens with rectangular cross sections for investigations into the kinetics of the fatigue crack

Kinetics of Infection-Driven Growth Model with Birth and Death

International Nuclear Information System (INIS)

Yang Shunyou; Zhu Shengqing; Ke Jianhong; Lin Zhenquan

2008-01-01

We propose a two-species infection model, in which an infected aggregate can gain one monomer from a healthy one due to infection when they meet together. Moreover, both the healthy and infected aggregates may lose one monomer because of self-death, but a healthy aggregate can spontaneously yield a new monomer. Consider a simple system in which the birth/death rates are directly proportional to the aggregate size, namely, the birth and death rates of the healthy aggregate of size k are J 1 k and J 2 k while the self-death rate of the infected aggregate of size k is J 3 k. We then investigate the kinetics of such a system by means of rate equation approach. For the J 1 > J 2 case, the aggregate size distribution of either species approaches the generalized scaling form and the typical size of either species increases wavily at large times. For the J 1 = J 2 case, the size distribution of healthy aggregates approaches the generalized scaling form while that of infected aggregates satisfies the modified scaling form. For the J 1 2 case, the size distribution of healthy aggregates satisfies the modified scaling form, but that of infected aggregates does not scale

From an equilibrium based MOF adsorbent to a kinetic selective carbon molecular sieve for paraffin/iso-paraffin separation

KAUST Repository

Li, Baiyan

2016-11-04

We unveil a unique kinetic driven separation material for selectively removing linear paraffins from iso-paraffins via a molecular sieving mechanism. Subsequent carbonization and thermal treatment of CD-MOF-2, the cyclodextrin metal-organic framework, afforded a carbon molecular sieve with a uniform and reduced pore size of ca. 5.0 Å, and it exhibited highly selective kinetic separation of n-butane and n-pentane from iso-butane and iso-pentane, respectively. © The Royal Society of Chemistry.

Kinetic methods for measuring the temperature of clusters and nanoparticles in molecular beams

International Nuclear Information System (INIS)

Makarov, Grigorii N

2011-01-01

The temperature (internal energy) of clusters and nanoparticles is an important physical parameter which affects many of their properties and the character of processes they are involved in. At the same time, determining the temperature of free clusters and nanoparticles in molecular beams is a rather complicated problem because the temperature of small particles depends on their size. In this paper, recently developed kinetic methods for measuring the temperature of clusters and nanoparticles in molecular beams are reviewed. The definition of temperature in the present context is given, and how the temperature affects the properties of and the processes involving the particles is discussed. The temperature behavior of clusters and nanoparticles near a phase transition point is analyzed. Early methods for measuring the temperature of large clusters are briefly described. It is shown that, compared to other methods, new kinetic methods are more universal and applicable for determining the temperature of clusters and nanoparticles of practically any size and composition. The future development and applications of these methods are outlined. (reviews of topical problems)

Modeling Hybridization Kinetics of Gene Probes in a DNA Biochip Using FEMLAB

Science.gov (United States)

Munir, Ahsan; Waseem, Hassan; Williams, Maggie R.; Stedtfeld, Robert D.; Gulari, Erdogan; Tiedje, James M.; Hashsham, Syed A.

2017-01-01

Microfluidic DNA biochips capable of detecting specific DNA sequences are useful in medical diagnostics, drug discovery, food safety monitoring and agriculture. They are used as miniaturized platforms for analysis of nucleic acids-based biomarkers. Binding kinetics between immobilized single stranded DNA on the surface and its complementary strand present in the sample are of interest. To achieve optimal sensitivity with minimum sample size and rapid hybridization, ability to predict the kinetics of hybridization based on the thermodynamic characteristics of the probe is crucial. In this study, a computer aided numerical model for the design and optimization of a flow-through biochip was developed using a finite element technique packaged software tool (FEMLAB; package included in COMSOL Multiphysics) to simulate the transport of DNA through a microfluidic chamber to the reaction surface. The model accounts for fluid flow, convection and diffusion in the channel and on the reaction surface. Concentration, association rate constant, dissociation rate constant, recirculation flow rate, and temperature were key parameters affecting the rate of hybridization. The model predicted the kinetic profile and signal intensities of eighteen 20-mer probes targeting vancomycin resistance genes (VRGs). Predicted signal intensities and hybridization kinetics strongly correlated with experimental data in the biochip (R2 = 0.8131). PMID:28555058

Modeling Hybridization Kinetics of Gene Probes in a DNA Biochip Using FEMLAB

Directory of Open Access Journals (Sweden)

Ahsan Munir

2017-05-01

Full Text Available Microfluidic DNA biochips capable of detecting specific DNA sequences are useful in medical diagnostics, drug discovery, food safety monitoring and agriculture. They are used as miniaturized platforms for analysis of nucleic acids-based biomarkers. Binding kinetics between immobilized single stranded DNA on the surface and its complementary strand present in the sample are of interest. To achieve optimal sensitivity with minimum sample size and rapid hybridization, ability to predict the kinetics of hybridization based on the thermodynamic characteristics of the probe is crucial. In this study, a computer aided numerical model for the design and optimization of a flow-through biochip was developed using a finite element technique packaged software tool (FEMLAB; package included in COMSOL Multiphysics to simulate the transport of DNA through a microfluidic chamber to the reaction surface. The model accounts for fluid flow, convection and diffusion in the channel and on the reaction surface. Concentration, association rate constant, dissociation rate constant, recirculation flow rate, and temperature were key parameters affecting the rate of hybridization. The model predicted the kinetic profile and signal intensities of eighteen 20-mer probes targeting vancomycin resistance genes (VRGs. Predicted signal intensities and hybridization kinetics strongly correlated with experimental data in the biochip (R2 = 0.8131.

Kinetic analysis of cooking losses from beef and other animal muscles heated in a water bath--effect of sample dimensions and prior freezing and ageing.

Science.gov (United States)

Oillic, Samuel; Lemoine, Eric; Gros, Jean-Bernard; Kondjoyan, Alain

2011-07-01

Cooking loss kinetics were measured on cubes and parallelepipeds of beef Semimembranosus muscle ranging from 1 cm × 1 cm × 1 cm to 7 cm × 7 cm × 28 cm in size. The samples were water bath-heated at three different temperatures, i.e. 50°C, 70°C and 90°C, and for five different times. Temperatures were simulated to help interpret the results. Pre-freezing the sample, difference in ageing time, and in muscle fiber orientation had little influence on cooking losses. At longer treatment times, the effects of sample size disappeared and cooking losses depended only on the temperature. A selection of the tests was repeated on four other beef muscles and on veal, horse and lamb Semimembranosus muscle. Kinetics followed similar curves in all cases but resulted in different final water contents. The shape of the kinetics curves suggests first-order kinetics. Copyright © 2011 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved.

Differences in inhibition by beta-arabinofuranosyladenine (araA) of radiation induced DNA damage repair in exponentially growing and plateau-phase CHO-cells

International Nuclear Information System (INIS)

Iliakis, G.; Seaner, R.

1988-01-01

The effect of beta-arabinofuranosyladenine (araA) on the repair of radiation induced DNA damage, as measured by the DNA unwinding technique, was studied in exponentially growing and plateau-phase CHO-cells after exposure to X-rays. Induction of DNA damage by radiation was found to be similar in exponentially growing and plateau-phase cells. In the absence of araA, repair of radiation induced DNA damage proceeded with similar kinetics in exponentially growing and plateau-phase cells. AraA at concentrations between 0-1500 μM inhibited DNA repair both in exponentially growing and in plateau-phase cells. However, the degree of inhibition was significantly higher (by a factor of 3) in plateau-phase cells. A similar degree of repair inhibition by araA was observed in plateau-phase cells treated in their conditioned medium, as well as in plateau-phase cells that were transferred in fresh growth medium just before treatment initiation. These results indicate the importance of biochemical parameters associated with alterations in the growth state of the cells for the inhibitory effect of araA and may help in the elucidation of the molecular mechanism(s) underlying repair inhibition by inhibitors of DNA replication. (orig.)

Kinetics and mass-transfer phenomena in anaerobic granular sludge.

Science.gov (United States)

Gonzalez-Gil, G; Seghezzo, L; Lettinga, G; Kleerebezem, R

2001-04-20

The kinetic properties of acetate-degrading methanogenic granular sludge of different mean diameters were assessed at different up-flow velocities (V(up)). Using this approach, the influence of internal and external mass transfer could be estimated. First, the apparent Monod constant (K(S)) for each data set was calculated by means of a curve-fitting procedure. The experimental results revealed that variations in the V(up) did not affect the apparent K(S)-value, indicating that external mass-transport resistance normally can be neglected. With regard to the granule size, a clear increase in K(S) was found at increasing granule diameters. The experimental data were further used to validate a dynamic mathematical biofilm model. The biofilm model was able to describe reaction-diffusion kinetics in anaerobic granules, using a single value for the effective diffusion coefficient in the granules. This suggests that biogas formation did not influence the diffusion-rates in the granular biomass. Copyright 2001 John Wiley & Sons, Inc.

Kinetic Interface

DEFF Research Database (Denmark)

2009-01-01

A kinetic interface for orientation detection in a video training system is disclosed. The interface includes a balance platform instrumented with inertial motion sensors. The interface engages a participant's sense of balance in training exercises.......A kinetic interface for orientation detection in a video training system is disclosed. The interface includes a balance platform instrumented with inertial motion sensors. The interface engages a participant's sense of balance in training exercises....

Mesoscopic dynamics of diffusion-influenced enzyme kinetics.

Science.gov (United States)

Chen, Jiang-Xing; Kapral, Raymond

2011-01-28

A particle-based mesoscopic model for enzyme kinetics is constructed and used to investigate the influence of diffusion on the reactive dynamics. Enzymes and enzyme-substrate complexes are modeled as finite-size soft spherical particles, while substrate, product, and solvent molecules are point particles. The system is evolved using a hybrid molecular dynamics-multiparticle collision dynamics scheme. Both the nonreactive and reactive dynamics are constructed to satisfy mass, momentum, and energy conservation laws, and reversible reaction steps satisfy detailed balance. Hydrodynamic interactions among the enzymes and complexes are automatically accounted for in the dynamics. Diffusion manifests itself in various ways, notably in power-law behavior in the evolution of the species concentrations. In accord with earlier investigations, regimes where the product production rate exhibits either monotonic or nonmonotonic behavior as a function of time are found. In addition, the species concentrations display both t(-1/2) and t(-3/2) power-law behavior, depending on the dynamical regime under investigation. For high enzyme volume fractions, cooperative effects influence the enzyme kinetics. The time dependent rate coefficient determined from the mass action rate law is computed and shown to depend on the enzyme concentration. Lifetime distributions of substrate molecules newly released in complex dissociation events are determined and shown to have either a power-law form for rebinding to the same enzyme from which they were released or an exponential form for rebinding to different enzymes. The model can be used and extended to explore a variety of issues related concentration effects and diffusion on enzyme kinetics.

Mesoscopic dynamics of diffusion-influenced enzyme kinetics

Science.gov (United States)

Chen, Jiang-Xing; Kapral, Raymond

2011-01-01

A particle-based mesoscopic model for enzyme kinetics is constructed and used to investigate the influence of diffusion on the reactive dynamics. Enzymes and enzyme-substrate complexes are modeled as finite-size soft spherical particles, while substrate, product, and solvent molecules are point particles. The system is evolved using a hybrid molecular dynamics-multiparticle collision dynamics scheme. Both the nonreactive and reactive dynamics are constructed to satisfy mass, momentum, and energy conservation laws, and reversible reaction steps satisfy detailed balance. Hydrodynamic interactions among the enzymes and complexes are automatically accounted for in the dynamics. Diffusion manifests itself in various ways, notably in power-law behavior in the evolution of the species concentrations. In accord with earlier investigations, regimes where the product production rate exhibits either monotonic or nonmonotonic behavior as a function of time are found. In addition, the species concentrations display both t^{-1/2} and t^{-3/2} power-law behavior, depending on the dynamical regime under investigation. For high enzyme volume fractions, cooperative effects influence the enzyme kinetics. The time dependent rate coefficient determined from the mass action rate law is computed and shown to depend on the enzyme concentration. Lifetime distributions of substrate molecules newly released in complex dissociation events are determined and shown to have either a power-law form for rebinding to the same enzyme from which they were released or an exponential form for rebinding to different enzymes. The model can be used and extended to explore a variety of issues related concentration effects and diffusion on enzyme kinetics.

Growing media constituents determine the microbial nitrogen conversions in organic growing media for horticulture.

Science.gov (United States)

Grunert, Oliver; Reheul, Dirk; Van Labeke, Marie-Christine; Perneel, Maaike; Hernandez-Sanabria, Emma; Vlaeminck, Siegfried E; Boon, Nico

2016-05-01

Vegetables and fruits are an important part of a healthy food diet, however, the eco-sustainability of the production of these can still be significantly improved. European farmers and consumers spend an estimated €15.5 billion per year on inorganic fertilizers and the production of N-fertilizers results in a high carbon footprint. We investigated if fertilizer type and medium constituents determine microbial nitrogen conversions in organic growing media and can be used as a next step towards a more sustainable horticulture. We demonstrated that growing media constituents showed differences in urea hydrolysis, ammonia and nitrite oxidation and in carbon dioxide respiration rate. Interestingly, mixing of the growing media constituents resulted in a stimulation of the function of the microorganisms. The use of organic fertilizer resulted in an increase in amoA gene copy number by factor 100 compared to inorganic fertilizers. Our results support our hypothesis that the activity of the functional microbial community with respect to nitrogen turnover in an organic growing medium can be improved by selecting and mixing the appropriate growing media components with each other. These findings contribute to the understanding of the functional microbial community in growing media and its potential role towards a more responsible horticulture. © 2016 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

The influence of the texture and microstructure of a Zr-2.5Nb substrate upon the oxidation kinetics

International Nuclear Information System (INIS)

Lin, J.; Cao Xiaohui; Szpunar, J.A.

2002-01-01

The thin oxide layer growing on the zirconium alloy is dense and adherent and therefore is protective against further oxidation and hydrogen ingress, which is deleterious to zirconium pressure tube used in nuclear power stations because it facilitates formation of zirconium hydrides. Heat treatment and other surface modification methods were applied to zirconium alloys and the texture was investigated. Thermogravimetric analytic (TGA) was used for oxidation kinetics studies. The oxidation kinetics data show the variation of the oxidation rate due to the difference of texture and microstructure and the oxidation resistance is improved after the substrate is cold worked and heat treated. After cold work and heat treatment, the texture of substrate changes from (11-20)[1-100] to (11-23)[1-100]. (orig.)

A unified approach to model uptake kinetics of trace elements in complex aqueous – solid solution systems

International Nuclear Information System (INIS)

Thien, Bruno M.J.; Kulik, Dmitrii A.; Curti, Enzo

2014-01-01

Highlights: • There are several models able to describe trace element partitioning in growing minerals. • To describe complex systems, those models must be embedded in a geochemical code. • We merged two models into a unified one suitable for implementation in a geochemical code. • This unified model was tested against coprecipitation experimental data. • We explored how our model reacts to solution depletion effects. - Abstract: Thermodynamics alone is usually not sufficient to predict growth-rate dependencies of trace element partitioning into host mineral solid solutions. In this contribution, two uptake kinetic models were analyzed that are promising in terms of mechanistic understanding and potential for implementation in geochemical modelling codes. The growth Surface Entrapment Model (Watson, 2004) and the Surface Reaction Kinetic Model (DePaolo, 2011) were shown to be complementary, and under certain assumptions merged into a single analytical expression. This Unified Uptake Kinetics Model was implemented in GEMS3K and GEM-Selektor codes ( (http://gems.web.psi.ch)), a Gibbs energy minimization package for geochemical modelling. This implementation extends the applicability of the unified uptake kinetics model to accounting for non-trivial factors influencing the trace element partitioning into solid solutions, such as the changes in aqueous solution composition and speciation, or the depletion effects in closed geochemical systems

Kinetics and

Directory of Open Access Journals (Sweden)

Mojtaba Ahmadi

2016-11-01

Full Text Available The aqueous degradation of Reactive Yellow 84 (RY84 by potassium peroxydisulfate (K2S2O8 has been studied in laboratory scale experiments. The effect of the initial concentrations of potassium peroxydisulfate and RY84, pH and temperature on RY84 degradation were also examined. Experimental data were analyzed using first and second-order kinetics. The degradation kinetics of RY84 of the potassium peroxydisulfate process followed the second-order reaction kinetics. These rate constants have an extreme values similar to of 9.493 mM−1min−1 at a peroxydisulfate dose of 4 mmol/L. Thermodynamic parameters such as activation (Ea and Gibbs free energy (ΔG° were also evaluated. The negative value of ΔGo and Ea shows the spontaneous reaction natural conditions and exothermic nature.

Short communication: Glucose kinetics in dairy heifers limit-fed a low- or high-forage ration at four levels of nitrogen intake

Science.gov (United States)

The objective of this research was to evaluate the effect of level of forage and nitrogen (N) intake on glucose kinetics in growing dairy heifers. Eight Holstein heifers (beginning at 362 ± 7 kg body weight (BW) and 12.3 ± 0.4 months of age) were fed eight rations according to a split-plot, 4 x 4 La...

Estimation of the growth kinetics for the cooling crystallisation of paracetamol and ethanol solutions

Science.gov (United States)

Mitchell, Niall A.; Ó'Ciardhá, Clifford T.; Frawley, Patrick J.

2011-08-01

This work details the estimation of the growth kinetics of paracetamol in ethanol solutions for cooling crystallisation processes, by means of isothermal seeded batch experiments. The growth kinetics of paracetamol crystals were evaluated in isolation, with the growth rate assumed to be size independent. Prior knowledge of the Metastable Zone Width (MSZW) was required, so that supersaturation ratios of 1.7-1.1 could be induced in solution without the occurrence of nucleation. The technique involved the utilisation of two in-situ Process Analytical Techniques (PATs), with a Focused Beam Reflectance Measurement (FBRM ®) utilised to ensure that negligible nucleation occurred and an Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) probe employed for online monitoring of solute concentration. Initial Particle Size Distributions (PSDs) were used in conjunction with desupersaturation profiles to determine the growth rate as a function of temperature and supersaturation. Furthermore, the effects of seed loading and size on the crystal growth rate were investigated. A numerical model, incorporating the population balance equation and the method of moments, was utilised to describe the crystal growth process. Experimental parameters were compared to the model simulation, with the accuracy of the model validated by means of the final product PSDs and solute concentration.

A growing danger: the risks posed by marihuana grow-ops

Energy Technology Data Exchange (ETDEWEB)

Bradley, F. [Canadian Electricity Association (Canada)

2005-02-01

The proliferation of sophisticated illegal indoor multi-plant marihuana cultivation operations is discussed, focusing primarily on public health and safety issues. Public health issues arise from the high level of molds and pollens caused by high humidity, which can cause asthma, respiratory conditions and allergies, particularly among children, and the likelihood of deadly levels of carbon monoxide build-up resulting from faulty rerouting of the residence's ventilation system. Safety issues discussed are: fires and electrocutions associated with the use of electrical diversions or bipasses to circumvent utility meters, the chemical and electrical hazards involved in investigating and dismantling growing operations, the significant dangers to utility crews who must repair illegal electrical bypasses, injuries by the booby-traps planted to protect the operation from other criminals or law enforcement agents, and the physical danger from the violence, including homicide and assaults, carried out by operators to exert control over production and distribution. Although in general, there is a relaxed attitude towards marihuana use in Canada. there is growing evidence of increasing public concern over large-scale growing operations. Nevertheless, to date operators of grow-ops have been dealt with lightly by the justice system. For example, in British Columbia 11,733 cases have come to the attention of police during the 1997 to 2000 period. Of these about half were dealt with informally (i.e. 'no case' seizures) and 2,255 cases led to at least one offender being convicted. The majority of convictions did not result in custodial dispositions. Only 18 per cent of the cases resulted in prison sentences, the average term being only 4.5 months.

Investigating the conformational stability of prion strains through a kinetic replication model.

Directory of Open Access Journals (Sweden)

Mattia Zampieri

2009-07-01

Full Text Available Prion proteins are known to misfold into a range of different aggregated forms, showing different phenotypic and pathological states. Understanding strain specificities is an important problem in the field of prion disease. Little is known about which PrP(Sc structural properties and molecular mechanisms determine prion replication, disease progression and strain phenotype. The aim of this work is to investigate, through a mathematical model, how the structural stability of different aggregated forms can influence the kinetics of prion replication. The model-based results suggest that prion strains with different conformational stability undergoing in vivo replication are characterizable in primis by means of different rates of breakage. A further role seems to be played by the aggregation rate (i.e. the rate at which a prion fibril grows. The kinetic variability introduced in the model by these two parameters allows us to reproduce the different characteristic features of the various strains (e.g., fibrils' mean length and is coherent with all experimental observations concerning strain-specific behavior.

Stoichiometry and kinetics of single and mixed substrate uptake in Aspergillus niger.

Science.gov (United States)

Lameiras, Francisca; Ras, Cor; Ten Pierick, Angela; Heijnen, Joseph J; van Gulik, Walter M

2018-02-01

In its natural environment, the filamentous fungus Aspergillus niger grows on decaying fruits and plant material, thereby enzymatically degrading the lignocellulosic constituents (lignin, cellulose, hemicellulose, and pectin) into a mixture of mono- and oligosaccharides. To investigate the kinetics and stoichiometry of growth of this fungus on lignocellulosic sugars, we carried out batch cultivations on six representative monosaccharides (glucose, xylose, mannose, rhamnose, arabinose, and galacturonic acid) and a mixture of these. Growth on these substrates was characterized in terms of biomass yields, oxygen/biomass ratios, and specific conversion rates. Interestingly, in combination, some of the carbon sources were consumed simultaneously and some sequentially. With a previously developed protocol, a sequential chemostat cultivation experiment was performed on a feed mixture of the six substrates. We found that the uptake of glucose, xylose, and mannose could be described with a Michaelis-Menten-type kinetics; however, these carbon sources seem to be competing for the same transport systems, while the uptake of arabinose, galacturonic acid, and rhamnose appeared to be repressed by the presence of other substrates.

Rhizobia symbiosis of seven leguminous species growing along Xindian riverbank of Northern Taiwan

Directory of Open Access Journals (Sweden)

Cheng-Tai Huang

2018-01-01

Full Text Available Legume-rhizobia symbioses of seven leguminous species growing along Xindian riverbank of Northern Taiwan were investigated in this study. These legumes form either determinate or indeterminate types of root nodules. The determinate nodules of Alysicarpus vaginalis, Desmodium. triflorum, D. heterophyllum, Sesbania cannabina and the indeterminate nodules of Mimosa pudica harbored bacteroids of morphological uniformity (length of 1-3 μm, while the indeterminate nodules of Crotalaria zanzibarica and Trifolium repens contained bacteroids of highly pleomorphism (size varying from 1 to 5 μm. The enclosed bacteria were isolated from respective nodules, and twenty slow-growing and nine fast-growing rhizobial isolates were recovered. The slow-growing isolates were classified to the genus Bradyrhizobium based on the 16S rRNA sequences, whereas the fast-growing rhizobia comprise four genera, Neorhizobium, Rhizobium, Cupriavidus and Paraburkholderia. Results of stable isotope analyses revealed that the seven leguminous species had similar and consistently negative δ15N values in leaves (mean of -1.2 ‰, whereas the values were positive (varying from 3.7 to 7.3 ‰ in the nodules. These values were significantly higher in the indeterminate nodules than those in the determinate ones. In addition, variations in the values of leaf δ13C (varying from -29 to -34‰ among the seven legumes were measured, indicating their photosynthetic water use efficiencies were different. This is the first field survey to report the rhizobial diversity and the nutrient relationships of sympatric legume in Taiwan.

Slow VO2 off-kinetics in skeletal muscle is associated with fast PCr off-kinetics--and inversely.

Science.gov (United States)

Korzeniewski, Bernard; Zoladz, Jerzy A

2013-09-01

The computer model of the bioenergetic system in skeletal muscle, developed previously, was used to study the effect of the characteristic decay time of the parallel activation of oxidative phosphorylation [τ(OFF)] during muscle recovery on the muscle oxygen consumption rate (Vo2) and phosphocreatine (PCr) work-to-rest transition (off)-kinetics and on the relationship between the Vo2 and PCr rest-to-work transition (on)- and off-kinetics in moderate and heavy exercise. An increase in τ(OFF) slows down the initial phase of the muscle Vo2 off-kinetics and accelerates the PCr off-kinetics. As a result, the relationship between the initial phase of the Vo2 off-kinetics (lasting approximately 3-60 s in computer simulations) and the PCr off-kinetics is inverse: the slower the former, the faster the latter. A faster initial phase of the Vo2 off-kinetics is associated with a slower late phase of the Vo2 off-kinetics, and as a result, the integral of Vo2 above baseline during recovery, representing the oxygen debt, is identical in all cases [values of τ(OFF)] for a given PCr decrease. Depending on τ(OFF), the muscle Vo2 on-kinetics was either equally fast or slower than the Vo2 off-kinetics in moderate exercise and always slower in heavy exercise. PCr on-kinetics was always faster than PCr off-kinetics. This study clearly demonstrates that τ(OFF) has a pronounced impact on the mutual relations between the muscle Vo2 and PCr on- and off-kinetics.

From atoms to layers: in situ gold cluster growth kinetics during sputter deposition

Science.gov (United States)

Schwartzkopf, Matthias; Buffet, Adeline; Körstgens, Volker; Metwalli, Ezzeldin; Schlage, Kai; Benecke, Gunthard; Perlich, Jan; Rawolle, Monika; Rothkirch, André; Heidmann, Berit; Herzog, Gerd; Müller-Buschbaum, Peter; Röhlsberger, Ralf; Gehrke, Rainer; Stribeck, Norbert; Roth, Stephan V.

2013-05-01

The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources.The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction

Holographic kinetic k-essence model

Energy Technology Data Exchange (ETDEWEB)

Cruz, Norman [Departamento de Fisica, Facultad de Ciencia, Universidad de Santiago de Chile, Casilla 307, Santiago (Chile)], E-mail: ncruz@lauca.usach.cl; Gonzalez-Diaz, Pedro F.; Rozas-Fernandez, Alberto [Colina de los Chopos, Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain)], E-mail: a.rozas@cfmac.csic.es; Sanchez, Guillermo [Departamento de Matematica y Ciencia de la Computacion, Facultad de Ciencia, Universidad de Santiago de Chile, Casilla 307, Santiago (Chile)], E-mail: gsanchez@usach.cl

2009-08-31

We consider a connection between the holographic dark energy density and the kinetic k-essence energy density in a flat FRW universe. With the choice c{>=}1, the holographic dark energy can be described by a kinetic k-essence scalar field in a certain way. In this Letter we show this kinetic k-essential description of the holographic dark energy with c{>=}1 and reconstruct the kinetic k-essence function F(X)

Synthesis of Ag-Cu and Ag-Cu{sub 2}O alloy nanoparticles using a seed-mediated polyol process, thermodynamic and kinetic aspects

Energy Technology Data Exchange (ETDEWEB)

Niknafs, Yasaman; Amirjani, Amirmostafa; Marashi, Pirooz, E-mail: pmarashi@aut.ac.ir; Fatmehsari, Davoud Haghshenas

2017-03-01

In this paper, Ag, Ag-Cu and Ag-Cu{sub 2}O nanoparticles were synthesized using a modified polyol method. Size, shape and composition of the obtained nanostructures were effectively controlled by adjusting the kinetic and thermodynamic conditions. Response surface methodology was employed to consider the interaction of parameters and to develop a polynomial equation for predicting the size of the silver nanoparticles. The precisely controlled silver nanoaprticles were used as the seeds for the formation of alloyed nanoparticles. By manipulating the involved parameters, both spherical and cubical Ag-Cu and Ag-Cu{sub 2}O nanostructures are obtainable in the size range of 90–100 nm. The morphological, optical and compositional characteristics of the obtained nanostructures were studied using SEM, FE-SEM, UV–Vis, EDS and XRD. - Highlights: • Synthesis of Ag, Ag-Cu and Ag-Cu{sub 2}O alloy nanostructures. • RSM was successfully employed for predicting the size of the AgNPs. • Size and composition tuning by adjusting the kinetic and thermodynamic conditions.

Dissolution of kinetics of nanoscale liquid Pb/Bi inclusions at a grain boundary in aluminium

DEFF Research Database (Denmark)

Prokofjev, Sergei I.; Johnson, Erik; Zhilin, Victor M.

2008-01-01

of the inclusions was observed until their complete disappearance. Digitized video recordings of the process of dissolution were used to obtain the dependence of the inclusion size with time. The kinetics of the dissolution of the grain boundary inclusions can be described with a model where it is assumed...

Reflected kinetics model for nuclear space reactor kinetics and control scoping calculations

Energy Technology Data Exchange (ETDEWEB)

Washington, K.E.

1986-05-01

The objective of this research is to develop a model that offers an alternative to the point kinetics (PK) modelling approach in the analysis of space reactor kinetics and control studies. Modelling effort will focus on the explicit treatment of control drums as reactivity input devices so that the transition to automatic control can be smoothly done. The proposed model is developed for the specific integration of automatic control and the solution of the servo mechanism problem. The integration of the kinetics model with an automatic controller will provide a useful tool for performing space reactor scoping studies for different designs and configurations. Such a tool should prove to be invaluable in the design phase of a space nuclear system from the point of view of kinetics and control limitations.

Reflected kinetics model for nuclear space reactor kinetics and control scoping calculations

International Nuclear Information System (INIS)

Washington, K.E.

1986-05-01

The objective of this research is to develop a model that offers an alternative to the point kinetics (PK) modelling approach in the analysis of space reactor kinetics and control studies. Modelling effort will focus on the explicit treatment of control drums as reactivity input devices so that the transition to automatic control can be smoothly done. The proposed model is developed for the specific integration of automatic control and the solution of the servo mechanism problem. The integration of the kinetics model with an automatic controller will provide a useful tool for performing space reactor scoping studies for different designs and configurations. Such a tool should prove to be invaluable in the design phase of a space nuclear system from the point of view of kinetics and control limitations

Kinetic theory of rf current drive and helicity injection

International Nuclear Information System (INIS)

Mett, R.R.

1992-01-01

Current drive and helicity injection by plasma waves are examined with the use of kinetic theory. The Vlasov equation yields a general current drive formula that contains resonant and nonresonant (ponderomotivelike) contributions. Standard quasilinear current drive is described by the former, while helicity current drive may be contained in the latter. Since direct analytical comparison of the sizes of the two terms is, in general, difficult, a new approach is taken. Solution of the drift-kinetic equation shows that the standard Landau damping/transit time magnetic pumping quasilinear diffusion coefficient is the only contribution to steady-state current drive to leading order in ε=ρ L /l, where ρ L is the Larmor radius and l is the inhomogeneity scale length. All nonresonant contributions, including the helicity, appear at higher order, after averages are taken over a flux surface, over azimuth, and over time. Consequently, at wave frequencies well below the electron cyclotron frequency, a wave helicity flux perpendicular to the magnetic field does not influence the parallel motion of electrons to leading order and therefore will not drive a significant current. Any current associated with a wave helicity flux is then either ion current (and thus inefficient) or electron current stemming from effects not included in the drift-kinetic treatment, such as cyclotron, collisional, or nonlinear (i.e., not quasilinear)

LLNL Chemical Kinetics Modeling Group

Energy Technology Data Exchange (ETDEWEB)

Pitz, W J; Westbrook, C K; Mehl, M; Herbinet, O; Curran, H J; Silke, E J

2008-09-24

The LLNL chemical kinetics modeling group has been responsible for much progress in the development of chemical kinetic models for practical fuels. The group began its work in the early 1970s, developing chemical kinetic models for methane, ethane, ethanol and halogenated inhibitors. Most recently, it has been developing chemical kinetic models for large n-alkanes, cycloalkanes, hexenes, and large methyl esters. These component models are needed to represent gasoline, diesel, jet, and oil-sand-derived fuels.

Controlled formation of Ni(DMG)2 microrods/tubes by manipulating the kinetics of chemical reactions and their application in naked-eye sensors.

Science.gov (United States)

Qin, Jianli; Wang, Bo; Zhang, Xiujuan; Zhang, Xiaohong

2012-08-01

We have demonstrated controlled preparation of Ni(DMG)2 microrods/tubes via chemical reaction method. By manipulating the reaction kinetics via the concentration of reactants, shapes of the resulting microstructures can be easily tuned from microrods to microtubes. Size of the resulting products can also be controlled through changing the reaction temperatures. It was proposed that under high reactants' concentrations, molecules will prefer to grow at corners or edges of nuclei with high free energies, to reduce the total energy in the system, which would lead to partial or complete hollow interiors and eventually resulted in mircotubes. The fact that DMG show high selectivity with Ni2+ and accompanied with obvious color change enable us to fabricate test strip for naked-eye detection of Ni2+. Benefit from the large surface areas of DMG nanoparticles on the test strip, the detection limit is improved by two orders over that of conventional solution method. This strategy is sensitive, simple and easy to handle, thus expected to possess potentials for the practical Ni2+ detection applications.

Numerical simulation of stochastic point kinetic equation in the dynamical system of nuclear reactor

International Nuclear Information System (INIS)

Saha Ray, S.

2012-01-01

Highlights: ► In this paper stochastic neutron point kinetic equations have been analyzed. ► Euler–Maruyama method and Strong Taylor 1.5 order method have been discussed. ► These methods are applied for the solution of stochastic point kinetic equations. ► Comparison between the results of these methods and others are presented in tables. ► Graphs for neutron and precursor sample paths are also presented. -- Abstract: In the present paper, the numerical approximation methods, applied to efficiently calculate the solution for stochastic point kinetic equations () in nuclear reactor dynamics, are investigated. A system of Itô stochastic differential equations has been analyzed to model the neutron density and the delayed neutron precursors in a point nuclear reactor. The resulting system of Itô stochastic differential equations are solved over each time-step size. The methods are verified by considering different initial conditions, experimental data and over constant reactivities. The computational results indicate that the methods are simple and suitable for solving stochastic point kinetic equations. In this article, a numerical investigation is made in order to observe the random oscillations in neutron and precursor population dynamics in subcritical and critical reactors.

Gyrocenter-gauge kinetic theory

International Nuclear Information System (INIS)

Qin, H.; Tang, W.M.; Lee, W.W.

2000-01-01

Gyrocenter-gauge kinetic theory is developed as an extension of the existing gyrokinetic theories. In essence, the formalism introduced here is a kinetic description of magnetized plasmas in the gyrocenter coordinates which is fully equivalent to the Vlasov-Maxwell system in the particle coordinates. In particular, provided the gyroradius is smaller than the scale-length of the magnetic field, it can treat high frequency range as well as the usual low frequency range normally associated with gyrokinetic approaches. A significant advantage of this formalism is that it enables the direct particle-in-cell simulations of compressional Alfven waves for MHD applications and of RF waves relevant to plasma heating in space and laboratory plasmas. The gyrocenter-gauge kinetic susceptibility for arbitrary wavelength and arbitrary frequency electromagnetic perturbations in a homogeneous magnetized plasma is shown to recover exactly the classical result obtained by integrating the Vlasov-Maxwell system in the particle coordinates. This demonstrates that all the waves supported by the Vlasov-Maxwell system can be studied using the gyrocenter-gauge kinetic model in the gyrocenter coordinates. This theoretical approach is so named to distinguish it from the existing gyrokinetic theory, which has been successfully developed and applied to many important low-frequency and long parallel wavelength problems, where the conventional meaning of gyrokinetic has been standardized. Besides the usual gyrokinetic distribution function, the gyrocenter-gauge kinetic theory emphasizes as well the gyrocenter-gauge distribution function, which sometimes contains all the physics of the problems being studied, and whose importance has not been realized previously. The gyrocenter-gauge distribution function enters Maxwell's equations through the pull-back transformation of the gyrocenter transformation, which depends on the perturbed fields. The efficacy of the gyrocenter-gauge kinetic approach is

Selective toxin effects on faster and slower growing individuals in the formation of hormesis at the population level - A case study with Lactuca sativa and PCIB.

Science.gov (United States)

Belz, Regina G; Sinkkonen, Aki

2016-10-01

Natural plant populations have large phenotypic plasticity that enhances acclimation to local stress factors such as toxin exposures. While consequences of high toxin exposures are well addressed, effects of low-dose toxin exposures on plant populations are seldom investigated. In particular, the importance of 'selective low-dose toxicity' and hormesis, i.e. stimulatory effects, has not been studied simultaneously. Since selective toxicity can change the size distribution of populations, we assumed that hormesis alters the size distribution at the population level, and investigated whether and how these two low-dose phenomena coexist. The study was conducted with Lactuca sativa L. exposed to the auxin-inhibitor 2-(p-chlorophenoxy)-2-methylpropionic acid (PCIB) in vitro. In two separate experiments, L. sativa was exposed to 12 PCIB doses in 24 replicates (50 plants/replicate). Shoot/root growth responses at the population level were compared to the fast-growing (≥90% percentile) and the slow-growing subpopulations (≤10% percentile) by Mann-Whitney U testing and dose-response modelling. In the formation of pronounced PCIB hormesis at the population level, low-dose effects proved selective, but widely stimulatory which seems to counteract low-dose selective toxicity. The selectivity of hormesis was dose- and growth rate-dependent. Stimulation occurred at lower concentrations and stimulation percentage was higher among slow-growing individuals, but partly or entirely masked at the population level by moderate or negligible stimulation among the faster growing individuals. We conclude that the hormetic effect up to the maximum stimulation may be primarily facilitated by an increase in size of the most slow-growing individuals, while thereafter it seems that mainly the fast-growing individuals contributed to the observed hormesis at the population level. As size distribution within a population is related to survival, our study hints that selective effects on slow

Tunable Rare Earth fcu-MOF Platform: Access to Adsorption Kinetics Driven Gas/Vapor Separations via Pore Size Contraction

KAUST Repository

Xue, Dongxu; Belmabkhout, Youssef; Shekhah, Osama; Jiang, Hao; Adil, Karim; Cairns, Amy J; Eddaoudi, Mohamed

2015-01-01

Reticular chemistry approach was successfully employed to deliberately construct new rare-earth (RE, i.e. Eu3+, Tb3+ and Y3+) fcu metal‒organic frameworks (MOFs) with restricted window apertures. Controlled and selective access to the resultant contracted fcu-MOF pores permits the achievement of the requisite sorbate cut-off ideal for selective adsorption kinetics separation and/or molecular sieving of gases and vapors. Predetermined reaction conditions that permitted the formation in-situ of the 12-connected RE hexanuclear molecular building block (MBB) and the establishment of the RE-fcu-MOF plat-form, especially in the presence of 2-fluorobenzoic acid (2-FBA) as a modulator and a structure directing agent, were used to synthesize isostructural RE-1,4-NDC-fcu-MOFs based on a relatively bulkier 2-connected bridging ligand, namely 1,4-naphthalenedicarboxylate (1,4-NDC). The subsequent RE-1,4-NDC-fcu-MOF structural features, contracted windows/pores and high concentration of open metal sites combined with exceptional hydrothermal and chemical stabilities, yielded nota-ble gas/solvent separation properties, driven mostly by adsorption kinetics as exemplified in this work for n-butane/methane, butanol/methanol and butanol/water pair systems.

Tunable Rare Earth fcu-MOF Platform: Access to Adsorption Kinetics Driven Gas/Vapor Separations via Pore Size Contraction

KAUST Repository

Xue, Dongxu

2015-03-31

Reticular chemistry approach was successfully employed to deliberately construct new rare-earth (RE, i.e. Eu3+, Tb3+ and Y3+) fcu metal‒organic frameworks (MOFs) with restricted window apertures. Controlled and selective access to the resultant contracted fcu-MOF pores permits the achievement of the requisite sorbate cut-off ideal for selective adsorption kinetics separation and/or molecular sieving of gases and vapors. Predetermined reaction conditions that permitted the formation in-situ of the 12-connected RE hexanuclear molecular building block (MBB) and the establishment of the RE-fcu-MOF plat-form, especially in the presence of 2-fluorobenzoic acid (2-FBA) as a modulator and a structure directing agent, were used to synthesize isostructural RE-1,4-NDC-fcu-MOFs based on a relatively bulkier 2-connected bridging ligand, namely 1,4-naphthalenedicarboxylate (1,4-NDC). The subsequent RE-1,4-NDC-fcu-MOF structural features, contracted windows/pores and high concentration of open metal sites combined with exceptional hydrothermal and chemical stabilities, yielded nota-ble gas/solvent separation properties, driven mostly by adsorption kinetics as exemplified in this work for n-butane/methane, butanol/methanol and butanol/water pair systems.

Tunable Rare Earth fcu-MOF Platform: Access to Adsorption Kinetics Driven Gas/Vapor Separations via Pore Size Contraction.

Science.gov (United States)

Xue, Dong-Xu; Belmabkhout, Youssef; Shekhah, Osama; Jiang, Hao; Adil, Karim; Cairns, Amy J; Eddaoudi, Mohamed

2015-04-22

Reticular chemistry approach was successfully employed to deliberately construct new rare-earth (RE, i.e., Eu(3+), Tb(3+), and Y(3+)) fcu metal-organic frameworks (MOFs) with restricted window apertures. Controlled and selective access to the resultant contracted fcu-MOF pores permits the achievement of the requisite sorbate cutoff, ideal for selective adsorption kinetics based separation and/or molecular sieving of gases and vapors. Predetermined reaction conditions that permitted the formation in situ of the 12-connected RE hexanuclear molecular building block (MBB) and the establishment of the first RE-fcu-MOF platform, especially in the presence of 2-fluorobenzoic acid (2-FBA) as a modulator and a structure directing agent, were used to synthesize isostructural RE-1,4-NDC-fcu-MOFs based on a relatively bulkier 2-connected bridging ligand, namely 1,4-naphthalenedicarboxylate (1,4-NDC). The subsequent RE-1,4-NDC-fcu-MOF structural features, contracted windows/pores and high concentration of open metal sites combined with exceptional hydrothermal and chemical stabilities, yielded notable gas/solvent separation properties, driven mostly by adsorption kinetics as exemplified in this work for n-butane/methane, butanol/methanol, and butanol/water pair systems.

Kinetics of adsorption of dyes from aqueous solution using activated carbon prepared from waste apricot

International Nuclear Information System (INIS)

Onal, Yunus

2006-01-01

Adsorbent (WA11Zn5) has been prepared from waste apricot by chemical activation with ZnCl 2 . Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by N 2 adsorption and DFT plus software. Adsorption of three dyes, namely, Methylene Blue (MB), Malachite Green (MG), Crystal Violet (CV), onto activated carbon in aqueous solution was studied in a batch system with respect to contact time, temperature. The kinetics of adsorption of MB, MG and CV have been discussed using six kinetic models, i.e., the pseudo-first-order model, the pseudo-second-order model, the Elovich equation, the intraparticle diffusion model, the Bangham equation, the modified Freundlich equation. Kinetic parameters and correlation coefficients were determined. It was shown that the second-order kinetic equation could describe the adsorption kinetics for three dyes. The dyes uptake process was found to be controlled by external mass transfer at earlier stages (before 5 min) and by intraparticle diffusion at later stages (after 5 min). Thermodynamic parameters, such as ΔG, ΔH and ΔS, have been calculated by using the thermodynamic equilibrium coefficient obtained at different temperatures and concentrations. The thermodynamics of dyes-WA11Zn5 system indicates endothermic process

Functional Size Measurement applied to UML-based user requirements

NARCIS (Netherlands)

van den Berg, Klaas; Dekkers, Ton; Oudshoorn, Rogier; Dekkers, T.

There is a growing interest in applying standardized methods for Functional Size Measurement (FSM) to Functional User Requirements (FUR) based on models in the Unified Modelling Language (UML). No consensus exists on this issue. We analyzed the demands that FSM places on FURs. We propose a

Tissue tropisms, infection kinetics, histologic lesions, and antibody response of the MR766 strain of Zika virus in a murine model.

Science.gov (United States)

Kawiecki, Anna B; Mayton, E Handly; Dutuze, M Fausta; Goupil, Brad A; Langohr, Ingeborg M; Del Piero, Fabio; Christofferson, Rebecca C

2017-04-18

The appearance of severe Zika virus (ZIKV) disease in the most recent outbreak has prompted researchers to respond through the development of tools to quickly characterize transmission and pathology. We describe here another such tool, a mouse model of ZIKV infection and pathogenesis using the MR766 strain of virus that adds to the growing body of knowledge regarding ZIKV kinetics in small animal models. We infected mice with the MR766 strain of ZIKV to determine infection kinetics via serum viremia. We further evaluated infection-induced lesions via histopathology and visualized viral antigen via immunohistochemical labeling. We also investigated the antibody response of recovered animals to both the MR766 and a strain from the current outbreak (PRVABC59). We demonstrate that the IRF3/7 DKO mouse is a susceptible, mostly non-lethal model well suited for the study of infection kinetics, pathological progression, and antibody response. Infected mice presented lesions in tissues that have been associated with ZIKV infection in the human population, such as the eyes, male gonads, and central nervous system. In addition, we demonstrate that infection with the MR766 strain produces cross-neutralizing antibodies to the PRVABC59 strain of the Asian lineage. This model provides an additional tool for future studies into the transmission routes of ZIKV, as well as for the development of antivirals and other therapeutics, and should be included in the growing list of available tools for investigations of ZIKV infection and pathogenesis.

Numerical Simulations of Two-Phase Flow in a Self-Aerated Flotation Machine and Kinetics Modeling

KAUST Repository

Fayed, Hassan E.; Ragab, Saad

2015-01-01

A new boundary condition treatment has been devised for two-phase flow numerical simulations in a self-aerated minerals flotation machine and applied to a Wemco 0.8 m3 pilot cell. Airflow rate is not specified a priori but is predicted by the simulations as well as power consumption. Time-dependent simulations of two-phase flow in flotation machines are essential to understanding flow behavior and physics in self-aerated machines such as the Wemco machines. In this paper, simulations have been conducted for three different uniform bubble sizes (db = 0.5, 0.7 and 1.0 mm) to study the effects of bubble size on air holdup and hydrodynamics in Wemco pilot cells. Moreover, a computational fluid dynamics (CFD)-based flotation model has been developed to predict the pulp recovery rate of minerals from a flotation cell for different bubble sizes, different particle sizes and particle size distribution. The model uses a first-order rate equation, where models for probabilities of collision, adhesion and stabilization and collisions frequency estimated by Zaitchik-2010 model are used for the calculation of rate constant. Spatial distributions of dissipation rate and air volume fraction (also called void fraction) determined by the two-phase simulations are the input for the flotation kinetics model. The average pulp recovery rate has been calculated locally for different uniform bubble and particle diameters. The CFD-based flotation kinetics model is also used to predict pulp recovery rate in the presence of particle size distribution. Particle number density pdf and the data generated for single particle size are used to compute the recovery rate for a specific mean particle diameter. Our computational model gives a figure of merit for the recovery rate of a flotation machine, and as such can be used to assess incremental design improvements as well as design of new machines.

Numerical Simulations of Two-Phase Flow in a Self-Aerated Flotation Machine and Kinetics Modeling

Directory of Open Access Journals (Sweden)

Hassan Fayed

2015-03-01

Full Text Available A new boundary condition treatment has been devised for two-phase flow numerical simulations in a self-aerated minerals flotation machine and applied to a Wemco 0.8 m3 pilot cell. Airflow rate is not specified a priori but is predicted by the simulations as well as power consumption. Time-dependent simulations of two-phase flow in flotation machines are essential to understanding flow behavior and physics in self-aerated machines such as the Wemco machines. In this paper, simulations have been conducted for three different uniform bubble sizes (db = 0.5, 0.7 and 1.0 mm to study the effects of bubble size on air holdup and hydrodynamics in Wemco pilot cells. Moreover, a computational fluid dynamics (CFD-based flotation model has been developed to predict the pulp recovery rate of minerals from a flotation cell for different bubble sizes, different particle sizes and particle size distribution. The model uses a first-order rate equation, where models for probabilities of collision, adhesion and stabilization and collisions frequency estimated by Zaitchik-2010 model are used for the calculation of rate constant. Spatial distributions of dissipation rate and air volume fraction (also called void fraction determined by the two-phase simulations are the input for the flotation kinetics model. The average pulp recovery rate has been calculated locally for different uniform bubble and particle diameters. The CFD-based flotation kinetics model is also used to predict pulp recovery rate in the presence of particle size distribution. Particle number density pdf and the data generated for single particle size are used to compute the recovery rate for a specific mean particle diameter. Our computational model gives a figure of merit for the recovery rate of a flotation machine, and as such can be used to assess incremental design improvements as well as design of new machines.

Numerical Simulations of Two-Phase Flow in a Self-Aerated Flotation Machine and Kinetics Modeling

KAUST Repository

Fayed, Hassan E.

2015-03-30

A new boundary condition treatment has been devised for two-phase flow numerical simulations in a self-aerated minerals flotation machine and applied to a Wemco 0.8 m3 pilot cell. Airflow rate is not specified a priori but is predicted by the simulations as well as power consumption. Time-dependent simulations of two-phase flow in flotation machines are essential to understanding flow behavior and physics in self-aerated machines such as the Wemco machines. In this paper, simulations have been conducted for three different uniform bubble sizes (db = 0.5, 0.7 and 1.0 mm) to study the effects of bubble size on air holdup and hydrodynamics in Wemco pilot cells. Moreover, a computational fluid dynamics (CFD)-based flotation model has been developed to predict the pulp recovery rate of minerals from a flotation cell for different bubble sizes, different particle sizes and particle size distribution. The model uses a first-order rate equation, where models for probabilities of collision, adhesion and stabilization and collisions frequency estimated by Zaitchik-2010 model are used for the calculation of rate constant. Spatial distributions of dissipation rate and air volume fraction (also called void fraction) determined by the two-phase simulations are the input for the flotation kinetics model. The average pulp recovery rate has been calculated locally for different uniform bubble and particle diameters. The CFD-based flotation kinetics model is also used to predict pulp recovery rate in the presence of particle size distribution. Particle number density pdf and the data generated for single particle size are used to compute the recovery rate for a specific mean particle diameter. Our computational model gives a figure of merit for the recovery rate of a flotation machine, and as such can be used to assess incremental design improvements as well as design of new machines.

Some current problems in atmospheric ozone chemistry; role of chemical kinetics

Energy Technology Data Exchange (ETDEWEB)

Cox, R.A.

1987-03-01

A review is given on selected aspects of the reaction mechanisms of current interest in the chemistry of atmospheric ozone. Atmospheric ozone is produced and removed by a complex series of elementary gas-phase photochemical reactions involving O/sub x/, HO/sub x/, NO/sub x/, CIO/sub x/ and hydrocarbon species. At the present time there is a good knowledge of the basic processes involved in ozone chemistry in the stratosphere and the troposphere and the kinetics of most of the key reactions are well defined. There are a number of difficulties in the theoretical descriptions of observed ozone behaviour which may be due to uncertainties in the chemistry. Examples are the failure to predict present day ozone in the photochemically controlled region above 35 Km altitude and the large reductions in the ozone column in the Antartic Spring which has been observed in recent years. In the troposphere there is growing evidence that ozone and other trace gases have changed appreciably from pre-industrial concentrations, due to chemical reactions involving man-made pollutants. Quantitative investigation of the mechanisms by which these changes may occur requires a sound laboratory kinetics data base.

Tracer kinetics of plants carbon allocation with continuously produced 11CO2

International Nuclear Information System (INIS)

Fares, Y.; Goeschl, J.D.; Magnuson, C.E.; Strain, B.R.

1988-01-01

Parameters of carbon allocation dynamics in plants were measured using 11 CO 2 and tracer kinetics techniques. Mechanical agitation reduced carbon export rate (CER) by 33% in cotton seedling's leaf, while storage rate and export pool size increased. Carbon storage and export rates of C 4 bunch grasses were higher in the afternoon than in the morning in spite of the decrease in CER. Water stress of cotton seedlings caused reduction in CER, and increase in exportable products concentrations and rate of storage. By the third stress day, measurable decreases in CER, transpiration, export rate and export pool size were recorded. (author) 17 refs.; 8 figs.; 1 tab

Drug kinetics release from Eudragit – Tenofovir@SiOC tablets

Energy Technology Data Exchange (ETDEWEB)

Tamayo, A., E-mail: aitanath@icv.csic.es [Ceramics and Glass Institute, CSIC, Madrid (Spain); Mazo, M.A. [Ceramics and Glass Institute, CSIC, Madrid (Spain); Veiga, M.D.; Ruiz-Caro, R.; Notario-Pérez, F. [Dpt. Pharmaceutical Technology, Faculty of Pharmacy, Complutense University of Madrid, Madrid (Spain); Rubio, J. [Ceramics and Glass Institute, CSIC, Madrid (Spain)

2017-06-01

A novel drug release system has been obtained in form of tablets from Eudragit® RS and tenofovir loaded on porous silicon oxycarbide glasses (SiOC). Active carbon (AC) and mesoporous silica (MCM-41) have also been used for comparative purposes. The porous silicon oxycarbide presents a bimodal mesopore size distribution that is maintained after functionalization with amino groups. We have studied the adsorption kinetics and adsorption equilibrium when the materials are loaded with tenofovir and, in all cases, pseudo-second order kinetics and Langmuir isotherm have been revealed as the most representative models describing the kinetic and thermodynamic parameters. Besides, the tenofovir adsorption on these materials turns out to be a favorable process. In vitro release of tenofovir has been studied in simulated vaginal medium by applying different release models. Continuous tenofovir release for > 20 days has been obtained for the SiOC material functionalized with amine groups. We concluded that the drug release occurs in two steps that involve a drug diffusion step through the material pores and diffusion through the swollen polymer. The interactions between the tenofovir drug and de amine groups of the functionalized silicon oxycarbide also play an important role in the release process. - Highlights: • Kinetic and thermodinamic parameters of the adsorption of tenofovir on porous substrates have been obtained. • Sustained release of TFV for > 20 days in SVF when it is supported on SiOC and manufactured as Eudragit®RS-containing tablets. • Release described by a two-step process involving diffusion through SiOC matrix and subsequent diffusion through the polymer.

Carcass traits and meat quality of different slow growing and fast growing broiler chickens

Directory of Open Access Journals (Sweden)

M. Oblakova

2017-12-01

Full Text Available Abstract. The experiment was conducted in the breeder farm of department Population genetics, reproduction and technologies of poultry and rabbits at the Agriculture Institute of Stara Zagora. Five lines from the National Gene Pool of Bulgaria: line Ss (Sussex, line E (Barred Plymouth Rock, line NG (New Hampshire, line F (NG x Red Rhode Island, line L (White Plymouth Rock were used as maternal forms in the crossing schedule and line M (Cornish as a paternal form for production of slow-growing broilers. The birds were grown to 84 days. Feeding was done with compound feeds according to the age: starter (1/14 days of age, grower (14/28 days of age, finisher (28/84 days of age. By the end of the experiment, slaughter analysis was performed with 3 female and 3 male broiler chickens per group with live weight corresponding to the average of each genotype. The live weight was determined, as well as the grill weight, the weights of cuts (breast, thighs, wings, edible offal (heart, liver, gizzard and abdominal fat. On the basis of these data, the slaughter yield and body parts ratios were calculated. The data for the live body weights of birds at slaughtering indicated the highest values for group V – 4040g, followed by groups ІV and ІІ – 3271.67g and 3186.67g, respectively (p<0.05. There was a statistically significant difference between the sexes with superiority of male birds (p<0.001. In the other 3 groups, breast meat percentage ranged from 19.48 to 19.84%. The share of thighs from the grill was the greatest in slow-growing chickens from group II – 33.01%, followed by group І – 32.35%, group IV – 32.18%, and the lowest- in groups ІІІ and V (31.91% and 31.18%, respectively. The analysis of data exhibited a significant effect of the genotype on water content of breast meat (resp. Dry matter, with lower values in slow-growing birds from group III – 73.19% (p<0.05, whereas in the other groups it ranged between 73.44 and 73.62%. The

Mechanotransduction mechanisms in growing spherically structured tissues

Science.gov (United States)

Littlejohns, Euan; Dunlop, Carina M.

2018-04-01

There is increasing experimental interest in mechanotransduction in multi-cellular tissues as opposed to single cells. This is driven by a growing awareness of the importance of physiologically relevant three-dimensional culture and of cell–cell and cell–gel interactions in directing growth and development. The paradigm biophysical technique for investigating tissue level mechanobiology in this context is to grow model tissues in artificial gels with well-defined mechanical properties. These studies often indicate that the stiffness of the encapsulating gel can significantly alter cellular behaviours. We demonstrate here potential mechanisms linking tissue growth with stiffness-mediated mechanotransduction. We show how tissue growth in gel systems generates points at which there is a significant qualitative change in the cellular stress and strain experienced. We show analytically how these potential switching points depend on the mechanical properties of the constraining gel and predict when they will occur. Significantly, we identify distinct mechanisms that act separately in each of the stress and strain fields at different times. These observations suggest growth as a potential physical mechanism coupling gel stiffness with cellular mechanotransduction in three-dimensional tissues. We additionally show that non-proliferating areas, in the case that the constraining gel is soft compared with the tissue, will expand and contract passively as a result of growth. Central compartment size is thus seen to not be a reliable indicator on its own for growth initiation or active behaviour.

Kinetics and hybrid kinetic-fluid models for nonequilibrium gas and plasmas

International Nuclear Information System (INIS)

Crouseilles, N.

2004-12-01

For a few decades, the application of the physics of plasmas has appeared in different fields like laser-matter interaction, astrophysics or thermonuclear fusion. In this thesis, we are interested in the modeling and the numerical study of nonequilibrium gas and plasmas. To describe such systems, two ways are usually used: the fluid description and the kinetic description. When we study a nonequilibrium system, fluid models are not sufficient and a kinetic description have to be used. However, solving a kinetic model requires the discretization of a large number of variables, which is quite expensive from a numerical point of view. The aim of this work is to propose a hybrid kinetic-fluid model thanks to a domain decomposition method in the velocity space. The derivation of the hybrid model is done in two different contexts: the rarefied gas context and the more complicated plasmas context. The derivation partly relies on Levermore's entropy minimization approach. The so-obtained model is then discretized and validated on various numerical test cases. In a second stage, a numerical study of a fully kinetic model is presented. A collisional plasma constituted of electrons and ions is considered through the Vlasov-Poisson-Fokker-Planck-Landau equation. Then, a numerical scheme which preserves total mass and total energy is presented. This discretization permits in particular a numerical study of the Landau damping. (author)

Oxygen no longer plays a major role in Body Size Evolution

Science.gov (United States)

Datta, H.; Sachson, W.; Heim, N. A.; Payne, J.

2015-12-01

When observing the long-term relationship between atmospheric oxygen and the maximum size in organisms across the Geozoic (~3.8 Ga - present), it appears that as oxygen increases, organism size grows. However, during the Phanerozoic (541 Ma - Present) oxygen levels varied, so we set out to test the hypothesis that oxygen levels drive patterns marine animal body size evolution. Expected decreases in maximum size due to a lack of oxygen do not occur, and instead, body size continues to increase regardless. In the oxygen data, a relatively low atmospheric oxygen percentage can support increasing body size, so our research tries to determine whether lifestyle affects body size in marine organisms. The genera in the data set were organized based on their tiering, motility, and feeding, such as a pelagic, fully-motile, predator. When organisms fill a certain ecological niche to take advantage of resources, they will have certain life modes, rather than randomly selected traits. For example, even in terrestrial environments, large animals have to constantly feed themselves to support their expensive terrestrial lifestyle which involves fairly consistent movement, and the structural support necessary for that movement. Only organisms with access to high energy food sources or large amounts of food can support themselves, and that is before they expend energy elsewhere. Organisms that expend energy frugally when active or have slower metabolisms in comparison to body size have a more efficient lifestyle and are generally able to grow larger, while those who have higher energy demands like predators are limited to comparatively smaller sizes. Therefore, in respect to the fossil record and modern measurements of animals, the metabolism and lifestyle of an organism dictate its body size in general. With this further clarification on the patterns of evolution, it will be easier to observe and understand the reasons for the ecological traits of organisms today.

Tantalum high-temperature oxidation kinetics

International Nuclear Information System (INIS)

Grigor'ev, Yu.M.; Sarkisyan, A.A.; Merzhanov, A.G.

1981-01-01

Kinetics of heat release and scale growth during tantalum oxidation within 650-1300 deg C temperature range in oxygen-containing media is investigated. Kinetic equations and temperature and pressure dependences of constants are ound Applicability of the kinetic Lorie mechanism for the description of the tantalum oxidation kinetics applicably to rapid-passing processes is shown. It is stated that the process rate (reaction ability) is determined by adsorption desorption factors on the external surface of the ''protective'' oxide for the ''linear'' oxidation stage [ru

High-temperature dehydration of talc: a kinetics study using in situ X-ray powder diffraction

Science.gov (United States)

Wang, Duojun; Yi, Li; Huang, Bojin; Liu, Chuanjiang

2015-06-01

High-temperature in situ X-ray powder diffraction patterns were used to study the dehydration kinetics of natural talc with a size of 10-15 µm. The talc was annealed from 1073 to 1223 K, and the variations in the characteristic peaks corresponding to talc with the time were recorded to determine the reaction progress. The decomposition of talc occurred, and peaks corresponding to talc and peaks corresponding to enstatite and quartz were observed. The enstatite and talc exhibited a topotactic relationship. The dehydration kinetics of talc was studied as a function of temperature between 1073 and 1223 K. The kinetics data could be modeled using an Avrami equation that considers nucleation and growth processes ? where n varies from 0.4 to 0.8. The rate constant (k) equation for the natural talc is ? The reaction mechanism for the dehydration of talc is a heterogeneous nucleation and growth mechanism.

Cultural systems for growing potatoes in space

Science.gov (United States)

Tibbitts, T.; Bula, R.; Corey, R.; Morrow, R.

1988-01-01

Higher plants are being evaluated for life support to provide needed food, oxygen and water as well as removal of carbon dioxide from the atmosphere. The successful utilization of plants in space will require the development of not only highly productive growing systems but also highly efficient bioregenerative systems. It will be necessary to recycle all inedible plant parts and all human wastes so that the entire complement of elemental compounds can be reused. Potatoes have been proposed as one of the desirable crops because they are 1) extremely productive, yielding more than 100 metric tons per hectare from field plantings, 2) the edible tubers are high in digestible starch (70%) and protein (10%) on a dry weight basis, 3) up to 80% of the total plant production is in tubers and thus edible, 4) the plants are easily propagated either from tubers or from tissue culture plantlets, 5) the tubers can be utilized with a minimum of processing, and 6) potatoes can be prepared in a variety of different forms for the human diet (Tibbitts et al., 1982). However potatoes have a growth pattern that complicates the development of growing the plants in controlled systems. Tubers are borne on underground stems that are botanically termed 'rhizomes', but in common usage termed 'stolons'. The stolons must be maintained in a dark, moist area with sufficient provision for enlargement of tubers. Stems rapidly terminate in flowers forcing extensive branching and spreading of plants so that individual plants will cover 0.2 m2 or more area. Thus the growing system must be developed to provide an area that is darkened for tuber and root growth and of sufficient size for plant spread. A system developed for growing potatoes, or any plants, in space will have certain requirements that must be met to make them a useful part of a life support system. The system must 1) be constructed of materials, and involve media, that can be reused for many successive cycles of plant growth, 2

Muscular Oxygen Uptake Kinetics in Aged Adults.

Science.gov (United States)

Koschate, J; Drescher, U; Baum, K; Eichberg, S; Schiffer, T; Latsch, J; Brixius, K; Hoffmann, U

2016-06-01

Pulmonary oxygen uptake (V˙O2) kinetics and heart rate kinetics are influenced by age and fitness. Muscular V˙O2 kinetics can be estimated from heart rate and pulmonary V˙O2. In this study the applicability of a test using pseudo-random binary sequences in combination with a model to estimate muscular V˙O2 kinetics was tested. Muscular V˙O2 kinetics were expected to be faster than pulmonary V˙O2 kinetics, slowed in aged subjects and correlated with maximum V˙O2 and heart rate kinetics. 27 elderly subjects (73±3 years; 81.1±8.2 kg; 175±4.7 cm) participated. Cardiorespiratory kinetics were assessed using the maximum of cross-correlation functions, higher maxima implying faster kinetics. Muscular V˙O2 kinetics were faster than pulmonary V˙O2 kinetics (0.31±0.1 vs. 0.29±0.1 s; p=0.004). Heart rate kinetics were not correlated with muscular or pulmonary V˙O2 kinetics or maximum V˙O2. Muscular V˙O2 kinetics correlated with maximum V˙O2 (r=0.35; p=0.033). This suggests, that muscular V˙O2 kinetics are faster than estimates from pulmonary V˙O2 and related to maximum V˙O2 in aged subjects. In the future this experimental approach may help to characterize alterations in muscular V˙O2 under various conditions independent of motivation and maximal effort. © Georg Thieme Verlag KG Stuttgart · New York.

Deposition of caesium and strontium substances on growing crops: Effects and countermeasures

International Nuclear Information System (INIS)

Bengtsson, S.

2010-01-01

Full text: To investigate how the two radionuclides caesium ( 134 Cs) and strontium ( 85 Sr) are taken up and transported to the harvested parts (the seeds) by fallout in a growing crop. Further on how this is related to the size and time of the fallout. From the information collected recommendation of suitable countermeasures at different scenarios to prevent further spreading to food stuff can be suggested. In the project a number of field trials where artificial deposited by the two radionuclides 134 Cs and 85 Sr in a contaminated rainfall, on the two agricultural crops Brassica napus L. (spring rape) and Triticum aestivum L. (spring wheat). The trial contained different treatments where the radionuclides where deposited by a rainfall simulator at different growing stages of the crops. The field trial continues for two more years and the reason for that is due to the variation of the climate for the different years. The radionuclides were applied in the form of a wet deposition and the rainfall was about 1 mm m -1 with a concentration of 20 kBq m -1 for each radionuclide. Samples were taken from the plots at the day(s) after the treatment of contaminated rainfall, both from the latest treated plots and from the earlier treated plots. The hypotheses are: 1. That the size of the deposition and the time in relation to the development stages of the crop will steer how much caesium and strontium that are coughed, detained and transferred to the harvested parts. 2. That the levels of caesium and strontium in the harvested parts of the crops are related to the insensitivity of the rainfall after a deposition and also how long time the first intensive rain will occur. 3. That the size of caesium and strontium in harvested plant parts are related to the size of uptake throw the leaves. 4. If the deposition of caesium and strontium will be the same, the levels of caesium will be much higher than strontium in the harvested parts. (author)

Oxygen tension measurements of tumors growing in mice

International Nuclear Information System (INIS)

Adam, Markus F.; Dorie, Mary Jo; Brown, J. Martin

1999-01-01

Purpose: Clinical studies using the Eppendorf histograph have shown that patients whose tumors have a low pO 2 have worse local control after radiotherapy, and have higher metastatic rates. Because preclinical studies of methods of overcoming, or exploiting, hypoxia generally use transplanted tumors in mice, we have compared the oxygenation of mouse tumors with human tumors to determine the appropriateness of the transplanted mouse model for such preclinical studies. Methods and Materials: We evaluated the oxygenation status of subcutaneous (s.c.) tissue and of 12 intradermally (i.d.)- and 7 s.c.-growing mouse or human transplanted tumors in mice using the Eppendorf histograph, and compared the values obtained with measurements of human head and neck nodes. Results: The normal tissue pO 2 profile of air-breathing mice showed a nearly Gaussian distribution (38.2 ± 14.9 mmHg). Breathing 10% O 2 or carbogen resulted in dramatic changes in normal tissue oxygenation. Tumors growing intradermally in the back of air-breathing mice were extremely hypoxic and resistant to expected changes in oxygenation (carbogen breathing, size, and use of anesthetics). Tumors growing s.c. in the foot showed higher oxygen profiles with marked changes in oxygenation when exposing the animals to different levels of oxygen. However, the oxygenation of the mouse tumors transplanted in either site was only a fraction of that of the majority of human tumors. Conclusion: Experimental mouse tumors are markedly hypoxic, with median values of 10-20% of those of human tumors. Hence, mouse tumors are probably good models for the most hypoxic human tumors that respond poorly to radiotherapy; however, caution has to be exercised in extrapolating data from mouse to man

Hydrothermal decomposition of industrial jarosite in alkaline media: The rate determining step of the process kinetics

Directory of Open Access Journals (Sweden)

González-Ibarra A.A.

2016-01-01

Full Text Available This work examines the role of NaOH and Ca(OH2 on the hydrothermal decomposition of industrial jarosite deposited by a Mexican company in a tailings dam. The industrial jarosite is mainly composed by natrojarosite and contains 150 g Ag/t, showing a narrow particle size distribution, as revealed by XRD, fire assay, SEM-EDS and laser-diffraction analysis. The effect of the pH, when using NaOH or Ca(OH2 as alkalinizing agent was studied by carrying out decomposition experiments at different pH values and 60°C in a homogeneous size particle system (pH = 8, 9, 10 and 11 and in a heterogeneous size particle system (pH = 11. Also, the kinetic study of the process and the controlling step of the decomposition reaction when NaOH and Ca(OH2 are used was determined by fitting the data obtained to the shrinking core model for spherical particles of constant size. These results, supported by chemical (EDS, morphological (SEM and mapping of elements (EDS analysis of a partially reacted jarosite particle allowed to conclude that when NaOH is used, the process kinetics is controlled by the chemical reaction and when Ca(OH2 is used, the rate determining step is changed to a diffusion control through a layer of solid products.

Mathematical study of chemical kinetics schemes. Application to air pollution models; Etude mathematique de schemas de cinetique chimique. Application a des modeles de pollution atmospherique

Energy Technology Data Exchange (ETDEWEB)

Billette, E.

1997-06-23

Complex chemical kinetics modelling is relevant in numerous fields related to the petroleum industry, for instance engine combustion, petrochemistry and atmospheric pollution. Many numerical difficulties are encountered in the computation of these models, mainly due to the large size, the non-linearity and the stiffness of the associated ordinary differential systems. We first studied systems that have an asymptotic behaviour which may be derived from an algebraic analysis. Then we reviewed different methods that make possible the reduction of size and stiffness for chemical kinetics-related differential systems, and suggest possible improvements for some of those methods. We also studied their application to atmospheric chemistry models. Finally, we started to extend those reduction methods to partial differential systems that include, in addition to chemical kinetics, other phenomena such as species emission, advection or diffusion. (author) 44 refs.

Adsorption analysis equilibria and kinetics

CERN Document Server

Do, Duong D

1998-01-01

This book covers topics of equilibria and kinetics of adsorption in porous media. Fundamental equilibria and kinetics are dealt with for homogeneous as well as heterogeneous particles. Five chapters of the book deal with equilibria and eight chapters deal with kinetics. Single component as well as multicomponent systems are discussed. In kinetics analysis, we deal with the various mass transport processes and their interactions inside a porous particle. Conventional approaches as well as the new approach using Maxwell-Stefan equations are presented. Various methods to measure diffusivity, such

Tritiated water uptake kinetics in tissue-free water and organically-bound fractions of tomato plants

International Nuclear Information System (INIS)

Spencer, F.S.

1984-03-01

The kinetics of tritiated water (HTO) vapour uptake into tissue-free water tritium (TFWT) and organically bound tritium (OBT) fractions of tomato, Lycopersicon esculentum Mill., cv Vendor, were investigated under controlled growing conditions. Most uptake data fitted a first-order kinetic model, C t = C ∞ (1-e -kt ), where C t is the tritium concentration at time t, Ca the steady-state concentration and k the uptake rate constant. During atmospheric-HTO exposure with clean-water irrigation in open pots the TFWT k values were 0.024 ± 0.023 h -1 for new foliage, 0.104 ± 0.067 h -1 for old foliage and 0.042 ± to 0.136 h -1 for new green fruit. OBT uptake rate constants were 20 percent less for new foliage and 76 percent less for new green fruit. Under steady-state conditions the ratio of tritium specific activities of TWFT to atmospheric HTO were 0.43 in new foliage, 0.46 in old foliage and 0.19 in green fruit. Within the plant, OBT and TFWT ratios were 0.70 for new foliage, 0.63 for old foliage (maximum) and between 0.72 and 1.92 for green fruit. The greater than unity tritium specific activity ratios in green fruit were not attributed to tritium enrichment but rather to the translocation of foliar OBT to the growing fruit which contained lower specific activity TFWT derived from soil water

Can differences in phosphorus uptake kinetics explain the distribution of cattail and sawgrass in the Florida Everglades?

Directory of Open Access Journals (Sweden)

McKee Karen L

2010-02-01

Full Text Available Abstract Background Cattail (Typha domingensis has been spreading in phosphorus (P enriched areas of the oligotrophic Florida Everglades at the expense of sawgrass (Cladium mariscus spp. jamaicense. Abundant evidence in the literature explains how the opportunistic features of Typha might lead to a complete dominance in P-enriched areas. Less clear is how Typha can grow and acquire P at extremely low P levels, which prevail in the unimpacted areas of the Everglades. Results Apparent P uptake kinetics were measured for intact plants of Cladium and Typha acclimated to low and high P at two levels of oxygen in hydroponic culture. The saturated rate of P uptake was higher in Typha than in Cladium and higher in low-P acclimated plants than in high-P acclimated plants. The affinity for P uptake was two-fold higher in Typha than in Cladium, and two- to three-fold higher for low-P acclimated plants compared to high-P acclimated plants. As Cladium had a greater proportion of its biomass allocated to roots, the overall uptake capacity of the two species at high P did not differ. At low P availability, Typha increased biomass allocation to roots more than Cladium. Both species also adjusted their P uptake kinetics, but Typha more so than Cladium. The adjustment of the P uptake system and increased biomass allocation to roots resulted in a five-fold higher uptake per plant for Cladium and a ten-fold higher uptake for Typha. Conclusions Both Cladium and Typha adjust P uptake kinetics in relation to plant demand when P availability is high. When P concentrations are low, however, Typha adjusts P uptake kinetics and also increases allocation to roots more so than Cladium, thereby improving both efficiency and capacity of P uptake. Cladium has less need to adjust P uptake kinetics because it is already efficient at acquiring P from peat soils (e.g., through secretion of phosphatases, symbiosis with arbuscular mycorrhizal fungi, nutrient conservation growth

Adsorption of Pb(II) ions from aqueous solution by native and activated bentonite: Kinetic, equilibrium and thermodynamic study

Energy Technology Data Exchange (ETDEWEB)

Kul, Ali Riza [Yuzuncu Yil University, Faculty of Art and Science, Department of Chemistry, 65080 Van (Turkey); Koyuncu, Huelya, E-mail: hkoyuncu@yyu.edu.tr [Forensic Medicine Foundation, Felek Street No. 45, 06300 Kecioren, Ankara (Turkey)

2010-07-15

In this study, the adsorption kinetics, equilibrium and thermodynamics of Pb(II) ions on native (NB) and acid activated (AAB) bentonites were examined. The specific surface areas, pore size and pore-size distributions of the samples were fully characterized. The adsorption efficiency of Pb(II) onto the NB and AAB was increased with increasing temperature. The kinetics of adsorption of Pb(II) ions was discussed using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model. The initial sorption rate and the activation energy were also calculated. The activation energy of the sorption was calculated as 16.51 and 13.66 kJ mol{sup -1} for NB and AAB, respectively. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherm equations at different temperatures. R{sub L} separation factor for Langmuir and the n value for Freundlich isotherm show that Pb(II) ions are favorably adsorbed by NB and AAB. Thermodynamic quantities such as Gibbs free energy ({Delta}G), the enthalpy ({Delta}H) and the entropy change of sorption ({Delta}S) were determined as about -5.06, 10.29 and 0.017 kJ mol{sup -1} K{sup -1}, respectively for AAB. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously.

Oil accumulation kinetic along ripening in four olive cultivars varying for fruit size

Directory of Open Access Journals (Sweden)

Breton Catherine

2009-01-01

Full Text Available To determine whether oil accumulation pattern is parallel to drupe olive (Olea europaea L growth and if common climatic parameters may influence oil content we conducted an experiment in rainfed orchards with four olive cultivars, Amygdalolia, Arbequina, Lucques, and Olivière, differing by fruit size at maturity. Fruits were harvested weekly from July to November. They were counted and weighted before being crushed. Fat content was determined on dry matter using a Minispec RMN. Common climatic parameters were recorded. Variance analyses showed stage effects highly significant. Results showed three different patterns for fruit growth. Dry matter accumulated broadly similarly and the weekly rates were positively correlated with fruit size. Oil accumulation is mostly independent of climatic variation and probably depends on genetic programmes for each cultivar. We defined the main steps and events for olive fruit ripening according to recent knowledge on fruit development.

KiMoSys: a web-based repository of experimental data for KInetic MOdels of biological SYStems.

Science.gov (United States)

Costa, Rafael S; Veríssimo, André; Vinga, Susana

2014-08-13

The kinetic modeling of biological systems is mainly composed of three steps that proceed iteratively: model building, simulation and analysis. In the first step, it is usually required to set initial metabolite concentrations, and to assign kinetic rate laws, along with estimating parameter values using kinetic data through optimization when these are not known. Although the rapid development of high-throughput methods has generated much omics data, experimentalists present only a summary of obtained results for publication, the experimental data files are not usually submitted to any public repository, or simply not available at all. In order to automatize as much as possible the steps of building kinetic models, there is a growing requirement in the systems biology community for easily exchanging data in combination with models, which represents the main motivation of KiMoSys development. KiMoSys is a user-friendly platform that includes a public data repository of published experimental data, containing concentration data of metabolites and enzymes and flux data. It was designed to ensure data management, storage and sharing for a wider systems biology community. This community repository offers a web-based interface and upload facility to turn available data into publicly accessible, centralized and structured-format data files. Moreover, it compiles and integrates available kinetic models associated with the data.KiMoSys also integrates some tools to facilitate the kinetic model construction process of large-scale metabolic networks, especially when the systems biologists perform computational research. KiMoSys is a web-based system that integrates a public data and associated model(s) repository with computational tools, providing the systems biology community with a novel application facilitating data storage and sharing, thus supporting construction of ODE-based kinetic models and collaborative research projects.The web application implemented using Ruby

Predicting rainfall erosivity by momentum and kinetic energy in Mediterranean environment

Science.gov (United States)

Carollo, Francesco G.; Ferro, Vito; Serio, Maria A.

2018-05-01

Rainfall erosivity is an index that describes the power of rainfall to cause soil erosion and it is used around the world for assessing and predicting soil loss on agricultural lands. Erosivity can be represented in terms of both rainfall momentum and kinetic energy, both calculated per unit time and area. Contrasting results on the representativeness of these two variables are available: some authors stated that momentum and kinetic energy are practically interchangeable in soil loss estimation while other found that kinetic energy is the most suitable expression of rainfall erosivity. The direct and continuous measurements of momentum and kinetic energy by a disdrometer allow also to establish a relationship with rainfall intensity at the study site. At first in this paper a comparison between the momentum-rainfall intensity relationships measured at Palermo and El Teularet by an optical disdrometer is presented. For a fixed rainfall intensity the measurements showed that the rainfall momentum values measured at the two experimental sites are not coincident. However both datasets presented a threshold value of rainfall intensity over which the rainfall momentum assumes a quasi-constant value. Then the reliability of a theoretically deduced relationship, linking momentum, rainfall intensity and median volume diameter, is positively verified using measured raindrop size distributions. An analysis to assess which variable, momentum or kinetic energy per unit area and time, is the best predictor of erosivity in Italy and Spain was also carried out. This investigation highlighted that the rainfall kinetic energy per unit area and time can be substituted by rainfall momentum as index for estimating the rainfall erosivity, and this result does not depend on the site where precipitation occurs. Finally, rainfall intensity measurements and soil loss data collected from the bare plots equipped at Sparacia experimental area were used to verify the reliability of some

Stable solutions of a scalar conservation law for particle-size segregation in dense granular avalanches

OpenAIRE

Shearer, M.; Gray, J. M N T; Thornton, A. R.

2008-01-01

Dense, dry granular avalanches are very efficient at sorting the larger particles towards the free surface of the flow, and finer grains towards the base, through the combined processes of kinetic sieving and squeeze expulsion. This generates an inversely graded particle-size distribution, which is fundamental to a variety of pattern formation mechanisms, as well as subtle size-mobility feedback effects, leading to the formation of coarse-grained lateral levees that create channels in geophys...

Present status on numerical algorithms and benchmark tests for point kinetics and quasi-static approximate kinetics

International Nuclear Information System (INIS)

Ise, Takeharu

1976-12-01

Review studies have been made on algorithms of numerical analysis and benchmark tests on point kinetics and quasistatic approximate kinetics computer codes to perform efficiently benchmark tests on space-dependent neutron kinetics codes. Point kinetics methods have now been improved since they can be directly applied to the factorization procedures. Methods based on Pade rational function give numerically stable solutions and methods on matrix-splitting are interested in the fact that they are applicable to the direct integration methods. An improved quasistatic (IQ) approximation is the best and the most practical method; it is numerically shown that the IQ method has a high stability and precision and the computation time which is about one tenth of that of the direct method. IQ method is applicable to thermal reactors as well as fast reactors and especially fitted for fast reactors to which many time steps are necessary. Two-dimensional diffusion kinetics codes are most practicable though there exist also three-dimensional diffusion kinetics code as well as two-dimensional transport kinetics code. On developing a space-dependent kinetics code, in any case, it is desirable to improve the method so as to have a high computing speed for solving static diffusion and transport equations. (auth.)

Granulocyte kinetics

International Nuclear Information System (INIS)

Peters, A.M.; Lavender, J.P.; Saverymuttu, S.H.

1985-01-01

By using density gradient materials enriched with autologous plasma, the authors have been able to isolate granulocutes from other cellular elements and label them with In-111 without separation from a plasma environment. The kinetic behavior of these cells suggests that phenomena attributed to granulocyte activation are greatly reduced by this labeling. Here, they review their study of granulocyte kinetics in health and disease in hope of quantifying sites of margination and identifying principal sites of destruction. The three principle headings of the paper are distribution, life-span, and destruction

Dynamic Model of Basic Oxygen Steelmaking Process Based on Multi-zone Reaction Kinetics: Model Derivation and Validation

Science.gov (United States)

Rout, Bapin Kumar; Brooks, Geoff; Rhamdhani, M. Akbar; Li, Zushu; Schrama, Frank N. H.; Sun, Jianjun

2018-04-01

A multi-zone kinetic model coupled with a dynamic slag generation model was developed for the simulation of hot metal and slag composition during the basic oxygen furnace (BOF) operation. The three reaction zones (i) jet impact zone, (ii) slag-bulk metal zone, (iii) slag-metal-gas emulsion zone were considered for the calculation of overall refining kinetics. In the rate equations, the transient rate parameters were mathematically described as a function of process variables. A micro and macroscopic rate calculation methodology (micro-kinetics and macro-kinetics) were developed to estimate the total refining contributed by the recirculating metal droplets through the slag-metal emulsion zone. The micro-kinetics involves developing the rate equation for individual droplets in the emulsion. The mathematical models for the size distribution of initial droplets, kinetics of simultaneous refining of elements, the residence time in the emulsion, and dynamic interfacial area change were established in the micro-kinetic model. In the macro-kinetics calculation, a droplet generation model was employed and the total amount of refining by emulsion was calculated by summing the refining from the entire population of returning droplets. A dynamic FetO generation model based on oxygen mass balance was developed and coupled with the multi-zone kinetic model. The effect of post-combustion on the evolution of slag and metal composition was investigated. The model was applied to a 200-ton top blowing converter and the simulated value of metal and slag was found to be in good agreement with the measured data. The post-combustion ratio was found to be an important factor in controlling FetO content in the slag and the kinetics of Mn and P in a BOF process.

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).

Thermodynamics and kinetics of graphene chemistry: a graphene hydrogenation prototype study.

Science.gov (United States)

Pham, Buu Q; Gordon, Mark S

2016-12-07

The thermodynamic and kinetic controls of graphene chemistry are studied computationally using a graphene hydrogenation reaction and polyaromatic hydrocarbons to represent the graphene surface. Hydrogen atoms are concertedly chemisorped onto the surface of graphene models of different shapes (i.e., all-zigzag, all-armchair, zigzag-armchair mixed edges) and sizes (i.e., from 16-42 carbon atoms). The second-order Z-averaged perturbation theory (ZAPT2) method combined with Pople double and triple zeta basis sets are used for all calculations. It is found that both the net enthalpy change and the barrier height of graphene hydrogenation at graphene edges are lower than at their interior surfaces. While the thermodynamic product distribution is mainly determined by the remaining π-islands of functionalized graphenes (Phys. Chem. Chem. Phys., 2013, 15, 3725-3735), the kinetics of the reaction is primarily correlated with the localization of the electrostatic potential of the graphene surface.

Design of slurry bubble column reactors: novel technique for optimum catalyst size selection contractual origin of the invention

Science.gov (United States)

Gamwo, Isaac K [Murrysville, PA; Gidaspow, Dimitri [Northbrook, IL; Jung, Jonghwun [Naperville, IL

2009-11-17

A method for determining optimum catalyst particle size for a gas-solid, liquid-solid, or gas-liquid-solid fluidized bed reactor such as a slurry bubble column reactor (SBCR) for converting synthesis gas into liquid fuels considers the complete granular temperature balance based on the kinetic theory of granular flow, the effect of a volumetric mass transfer coefficient between the liquid and the gas, and the water gas shift reaction. The granular temperature of the catalyst particles representing the kinetic energy of the catalyst particles is measured and the volumetric mass transfer coefficient between the gas and liquid phases is calculated using the granular temperature. Catalyst particle size is varied from 20 .mu.m to 120 .mu.m and a maximum mass transfer coefficient corresponding to optimum liquid hydrocarbon fuel production is determined. Optimum catalyst particle size for maximum methanol production in a SBCR was determined to be in the range of 60-70 .mu.m.

Kinetics of Scheelite Conversion in Sulfuric Acid

Science.gov (United States)

Shen, Leiting; Li, Xiaobin; Zhou, Qiusheng; Peng, Zhihong; Liu, Guihua; Qi, Tiangui; Taskinen, Pekka

2018-02-01

Complete conversion of scheelite in H2SO4 solution plays a key role in exploration of cleaner technology for producing ammonium paratungstate. In this work, the factors influencing scheelite conversion were investigated experimentally to model its kinetics. The results indicated that the conversion rate increases with increasing temperature and reducing particle size, but is almost independent of stirring speed. Moreover, although the conversion rate increases with increasing initial H2SO4 concentration (≤ 1.25 mol/L), it decreases rapidly at 1.5 mol/L H2SO4 after 10 min due to formation of a H2WO4 layer. The experimental data agree quite well with the shrinking core model under chemical reaction control in ≤ 1.25 mol/L H2SO4 solution, and the kinetic equation was established as: 1- ( 1- α )^{ 1 / 3} = 2 2 2 5 4 6. 6\\cdot C_{{{H}_{ 2} {SO}_{ 4} }}^{ 1. 2 2 6} \\cdot r_{ 0}^{ - 1} \\cdot e^{{ - 3 9 2 6 0/RT}} \\cdot t (t, min). This work could contribute to better understanding of scheelite conversion in H2SO4 solution and development of a new route for ammonium paratungstate production.

Kinetic evolutionary behavior of catalysis-select migration

International Nuclear Information System (INIS)

Wu Yuan-Gang; Lin Zhen-Quan; Ke Jian-Hong

2012-01-01

We propose a catalysis-select migration driven evolution model of two-species (A- and B-species) aggregates, where one unit of species A migrates to species B under the catalysts of species C, while under the catalysts of species D the reaction will become one unit of species B migrating to species A. Meanwhile the catalyst aggregates of species C perform self-coagulation, as do the species D aggregates. We study this catalysis-select migration driven kinetic aggregation phenomena using the generalized Smoluchowski rate equation approach with C species catalysis-select migration rate kernel K(k;i,j) = Kkij and D species catalysis-select migration rate kernel J(k;i,j)= Jkij. The kinetic evolution behaviour is found to be dominated by the competition between the catalysis-select immigration and emigration, in which the competition is between JD 0 and KC 0 (D 0 and C 0 are the initial numbers of the monomers of species D and C, respectively). When JD 0 −KC 0 > 0, the aggregate size distribution of species A satisfies the conventional scaling form and that of species B satisfies a modified scaling form. And in the case of JD 0 −KC 0 0 −KC 0 > 0 case. (interdisciplinary physics and related areas of science and technology)

Kinetics of particle deposition at heterogeneous surfaces

Science.gov (United States)

Stojiljković, D. Lj.; Vrhovac, S. B.

2017-12-01

The random sequential adsorption (RSA) approach is used to analyze adsorption of spherical particles of fixed diameter d0 on nonuniform surfaces covered by square cells arranged in a square lattice pattern. To characterize such pattern two dimensionless parameters are used: the cell size α and the cell-cell separation β, measured in terms of the particle diameter d0. Adsorption is assumed to occur if the particle (projected) center lies within a cell area. We focus on the kinetics of deposition process in the case when no more than a single disk can be placed onto any square cell (α deposition process is not consistent with the power law behavior. However, if the geometry of the pattern approaches towards ;noninteracting conditions; (β > 1), when adsorption on each cell can be decoupled, approach of the coverage fraction θ(t) to θJ becomes closer to the exponential law. Consequently, changing the pattern parameters in the present model allows to interpolate the deposition kinetics between the continuum limit and the lattice-like behavior. Structural properties of the jammed-state coverings are studied in terms of the radial distribution function g(r) and spatial distribution of particles inside the cell. Various, non-trivial spatial distributions are observed depending on the geometry of the pattern.

Probabilistic approach to lysozyme crystal nucleation kinetics.

Science.gov (United States)

Dimitrov, Ivaylo L; Hodzhaoglu, Feyzim V; Koleva, Dobryana P

2015-09-01

Nucleation of lysozyme crystals in quiescent solutions at a regime of progressive nucleation is investigated under an optical microscope at conditions of constant supersaturation. A method based on the stochastic nature of crystal nucleation and using discrete time sampling of small solution volumes for the presence or absence of detectable crystals is developed. It allows probabilities for crystal detection to be experimentally estimated. One hundred single samplings were used for each probability determination for 18 time intervals and six lysozyme concentrations. Fitting of a particular probability function to experimentally obtained data made possible the direct evaluation of stationary rates for lysozyme crystal nucleation, the time for growth of supernuclei to a detectable size and probability distribution of nucleation times. Obtained stationary nucleation rates were then used for the calculation of other nucleation parameters, such as the kinetic nucleation factor, nucleus size, work for nucleus formation and effective specific surface energy of the nucleus. The experimental method itself is simple and adaptable and can be used for crystal nucleation studies of arbitrary soluble substances with known solubility at particular solution conditions.

The Relationship between Offshoring Strategies and Firm Performance: Impact of innovation, absorptive capacity and firm size

NARCIS (Netherlands)

M.W. Roza-van Vuren (Marja)

2011-01-01

textabstractHow do offshoring strategies impact firm performance? And how are innovation, absorptive capacity and firm size influencing this relationship? This research investigates how firms of varying size, well-established firms and growing firms may profit from relocating business activities to

Irreversible processes kinetic theory

CERN Document Server

Brush, Stephen G

2013-01-01

Kinetic Theory, Volume 2: Irreversible Processes deals with the kinetic theory of gases and the irreversible processes they undergo. It includes the two papers by James Clerk Maxwell and Ludwig Boltzmann in which the basic equations for transport processes in gases are formulated, together with the first derivation of Boltzmann's ""H-theorem"" and a discussion of this theorem, along with the problem of irreversibility.Comprised of 10 chapters, this volume begins with an introduction to the fundamental nature of heat and of gases, along with Boltzmann's work on the kinetic theory of gases and s

Kinetic Behaviors of a Competitive Population and Fitness System in Exchange-Driven Growth

International Nuclear Information System (INIS)

Lu Ke; Lin Zhenquan; Sun Yunfei

2008-01-01

We proposed an aggregation model of two species aggregates of fitness and population to study the interaction between the two species in their exchange-driven processes of the same species by introducing the monomer birth of fitness catalyzed by the population, where the fitness aggregates perform self-death process and the population aggregates perform self-birth process. The kinetic behaviors of the aggregate size distributions of the fitness and population were analyzed by the rate equation approach with their exchange rate kernel K 1 (k,j) = K 1 kj and K 2 (k,j) = K 2 kj, the fitness aggregate's self-death rate kernel J 1 (k) = J 1 k, population aggregate's self-birth rate kernel J 2 (k) = J 2 k and population-catalyzed fitness birth rate kernel I(k,j) = Ikj v . The kinetic behavior of the fitness was found depending crucially on the parameter v, which reflects the dependence of the population-catalyzed fitness birth rate on the size of the catalyst (population) aggregate. (i) In the v ≤ 0 case, the effect of catalyzed-birth of fitness is rather weak and the exchange-driven aggregation and self-death of the fitness dominate the process, and the fitness aggregate size distribution a k (t) does not have scale form. (ii) When v > 0, the effect of the population-catalyzed birth of fitness gets strong enough, and the catalyzed-birth and self-death of the fitness aggregates, together with the self-birth of the population aggregates dominate the evolution process of the fitness aggregates. The aggregate size distribution a k (t) approaches a generalized scaling form

Drug-Target Kinetics in Drug Discovery.

Science.gov (United States)

Tonge, Peter J

2018-01-17

The development of therapies for the treatment of neurological cancer faces a number of major challenges including the synthesis of small molecule agents that can penetrate the blood-brain barrier (BBB). Given the likelihood that in many cases drug exposure will be lower in the CNS than in systemic circulation, it follows that strategies should be employed that can sustain target engagement at low drug concentration. Time dependent target occupancy is a function of both the drug and target concentration as well as the thermodynamic and kinetic parameters that describe the binding reaction coordinate, and sustained target occupancy can be achieved through structural modifications that increase target (re)binding and/or that decrease the rate of drug dissociation. The discovery and deployment of compounds with optimized kinetic effects requires information on the structure-kinetic relationships that modulate the kinetics of binding, and the molecular factors that control the translation of drug-target kinetics to time-dependent drug activity in the disease state. This Review first introduces the potential benefits of drug-target kinetics, such as the ability to delineate both thermodynamic and kinetic selectivity, and then describes factors, such as target vulnerability, that impact the utility of kinetic selectivity. The Review concludes with a description of a mechanistic PK/PD model that integrates drug-target kinetics into predictions of drug activity.

Specific cesium activity in freshwater fish and the size effect

International Nuclear Information System (INIS)

Kulikov, A.O.; Ryabov, I.N.; USSR Academy of Sciences, Moscow

1992-01-01

The specific Cs-137 activity of muscle tissues of silver carp (Hypophthalmichthys molitrix) from the cooling pond of the Chernobyl nuclear power plant caught in 1987 and 1988 increased almost linearly with fish weight ('size effect') in contrast to liver tissue, whose specific activity remained independent of weight. A kinetic model for uptake and excretion was developed to describe the size effect in muscle tissue by introducing a weight-dependent Cs biological half-time to fish. Similar size effects of specific Cs-137 activity were also found for other species of fish from cooling pond, but were primarily attributed to changes in feeding habits with increasing weight of fish rather than to metabolic changes in feeding habits with both of muscle and liver tissue increased with fish weight for those species in contrast to silver carp. (author). 12 refs.; 12 figs.; 1 tab

Basic dye decomposition kinetics in a photocatalytic slurry reactor

International Nuclear Information System (INIS)

Wu, C.-H.; Chang, H.-W.; Chern, J.-M.

2006-01-01

Wastewater effluent from textile plants using various dyes is one of the major water pollutants to the environment. Traditional chemical, physical and biological processes for treating textile dye wastewaters have disadvantages such as high cost, energy waste and generating secondary pollution during the treatment process. The photocatalytic process using TiO 2 semiconductor particles under UV light illumination has been shown to be potentially advantageous and applicable in the treatment of wastewater pollutants. In this study, the dye decomposition kinetics by nano-size TiO 2 suspension at natural solution pH was experimentally studied by varying the agitation speed (50-200 rpm), TiO 2 suspension concentration (0.25-1.71 g/L), initial dye concentration (10-50 ppm), temperature (10-50 deg. C), and UV power intensity (0-96 W). The experimental results show the agitation speed, varying from 50 to 200 rpm, has a slight influence on the dye decomposition rate and the pH history; the dye decomposition rate increases with the TiO 2 suspension concentration up to 0.98 g/L, then decrease with increasing TiO 2 suspension concentration; the initial dye decomposition rate increases with the initial dye concentration up to a certain value depending upon the temperature, then decreases with increasing initial dye concentration; the dye decomposition rate increases with the UV power intensity up to 64 W to reach a plateau. Kinetic models have been developed to fit the experimental kinetic data well

Thermal hysteresis kinetic effects of spin crossover nanoparticulated systems studied by FORC diagram method on an Ising-like model

International Nuclear Information System (INIS)

Atitoaie, Alexandru; Stoleriu, Laurentiu; Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian

2016-01-01

The scientific community is manifesting a high research interest on spin crossover compounds and their recently synthesized nanoparticles, due to their various appealing properties, such as the bistability between a diamagnetic low spin state and a paramagnetic high spin state (HS), inter-switchable by temperature or pressure changes, light irradiation or magnetic field. The utility of these compounds showing hysteresis covers a broad area of applications, from the development of more efficient designs of temperature and pressure sensors to automotive and aeronautic industries and even a new type of molecular actuators. We are proposing in this work a study regarding the kinetic effects and the distribution of reversible and irreversible components on the thermal hysteresis of spin crossover nanoparticulated systems. We are considering here tridimensional systems with different sizes and also systems of nanoparticles with a Gaussian size distribution. The correlations between the kinetics of the thermal hysteresis, the distributions of sizes and intermolecular interactions and the transition temperature distributions were established by using the FORC (First Order Reversal Curves) method using a Monte Carlo technique within an Ising-like system.

Thermal hysteresis kinetic effects of spin crossover nanoparticulated systems studied by FORC diagram method on an Ising-like model

Energy Technology Data Exchange (ETDEWEB)

Atitoaie, Alexandru, E-mail: atitoaie@phys-iasi.ro [Department. of Physics, “Alexandru Ioan Cuza” University, 700506 Iasi (Romania); National Institute of Research and Development for Technical Physics, Iasi (Romania); Stoleriu, Laurentiu [Department. of Physics, “Alexandru Ioan Cuza” University, 700506 Iasi (Romania); Tanasa, Radu [Department. of Physics, “Alexandru Ioan Cuza” University, 700506 Iasi (Romania); Department of Engineering, University of Cambridge, CB2 1PZ Cambridge (United Kingdom); Stancu, Alexandru; Enachescu, Cristian [Department. of Physics, “Alexandru Ioan Cuza” University, 700506 Iasi (Romania)

2016-04-01

The scientific community is manifesting a high research interest on spin crossover compounds and their recently synthesized nanoparticles, due to their various appealing properties, such as the bistability between a diamagnetic low spin state and a paramagnetic high spin state (HS), inter-switchable by temperature or pressure changes, light irradiation or magnetic field. The utility of these compounds showing hysteresis covers a broad area of applications, from the development of more efficient designs of temperature and pressure sensors to automotive and aeronautic industries and even a new type of molecular actuators. We are proposing in this work a study regarding the kinetic effects and the distribution of reversible and irreversible components on the thermal hysteresis of spin crossover nanoparticulated systems. We are considering here tridimensional systems with different sizes and also systems of nanoparticles with a Gaussian size distribution. The correlations between the kinetics of the thermal hysteresis, the distributions of sizes and intermolecular interactions and the transition temperature distributions were established by using the FORC (First Order Reversal Curves) method using a Monte Carlo technique within an Ising-like system.

Kinetics of a new phase formation in supersaturated solid solutions. 1. Dilute one-component systems

International Nuclear Information System (INIS)

Dubinko, V.I.

1991-07-01

A complete set of kinetic equations describing the diffusion decay of supersaturated solutions, as well as the formation of new-phase fluctuations in equilibrium systems, is derived. A novel method of determining forward and backward reaction rates entering the master equation is proposed which does not require the use of any reference cluster size distribution, either the constrained or the true equilibrium one, employed in all modifications of the classical nucleation theory. Instead, this reference distribution can be obtained as an equilibrium solution of the present master equation. The main advantage of this method is the possibility to take into account various factors affecting the diffusion decay, such as the reaction kinetics at the precipitate surfaces and the diffusion kinetics in the mother phase with account of elastic interaction between nucleating species and their clusters. The latter is of a key importance in the irradiation environment considered in the forthcoming second part of the article. (author). 3 refs

Kinetic-Scale Magnetic Turbulence and Finite Larmor Radius Effects at Mercury

Science.gov (United States)

Uritsky, V. M.; Slavin, J. A.; Khazanov, G. V.; Donovan, E. F.; Boardsen, S. A.; Anderson, B. J.; Korth, H.

2011-01-01

We use a nonstationary generalization of the higher-order structure function technique to investigate statistical properties of the magnetic field fluctuations recorded by MESSENGER spacecraft during its first flyby (01/14/2008) through the near-Mercury space environment, with the emphasis on key boundary regions participating in the solar wind - magnetosphere interaction. Our analysis shows, for the first time, that kinetic-scale fluctuations play a significant role in the Mercury's magnetosphere up to the largest resolvable timescale (approx.20 s) imposed by the signal nonstationariry, suggesting that turbulence at this plane I is largely controlled by finite Larmor radius effects. In particular, we report the presence of a highly turbulent and extended foreshock system filled with packets of ULF oscillations, broad-band intermittent fluctuations in the magnetosheath, ion-kinetic turbulence in the central plasma sheet of Mercury's magnetotail, and kinetic-scale fluctuations in the inner current sheet encountered at the outbound (dawn-side) magnetopause. Overall, our measurements indicate that the Hermean magnetosphere, as well as the surrounding region, are strongly affected by non-MHD effects introduced by finite sizes of cyclotron orbits of the constituting ion species. Physical mechanisms of these effects and their potentially critical impact on the structure and dynamics of Mercury's magnetic field remain to be understood.

Optimizing Greenhouse Rice Production: What Is the Best Pot Size?

OpenAIRE

Eddy, Robert; Acosta, Kevin; Liu, Yisi; Russell, Michael

2016-01-01

This publication describes our studies to determine the best pot size to optimize greenhouse rice production. We recommend 9-cm (4-inch) diameter square pot. Pots as small as 7-cm diameter yielded seed. This version is updated to include observations of larger pots with multiple plants. Photos of the plants growing under differing pot sizes are provided. This document is one entry in a series of questions and answers originally posted to the Purdue University Department of Horticulture & L...

Investigation on CO catalytic oxidation reaction kinetics of faceted perovskite nanostructures loaded with Pt

KAUST Repository

Yin, S. M.

2017-01-18

Perovskite lead titanate nanostructures with specific {111}, {100} and {001} facets exposed, have been employed as supports to investigate the crystal facet effect on the growth and CO catalytic activity of Pt nanoparticles. The size, distribution and surface chemical states of Pt on the perovskite supports have been significantly modified, leading to a tailored conversion temperature and catalytic kinetics towards CO catalytic oxidation.

Investigation on CO catalytic oxidation reaction kinetics of faceted perovskite nanostructures loaded with Pt

KAUST Repository

Yin, S. M.; Duanmu, J. J.; Zhu, Yihan; Yuan, Y. F.; Guo, S. Y.; Yang, J. L.; Ren, Z. H.; Han, G. R.

2017-01-01

Perovskite lead titanate nanostructures with specific {111}, {100} and {001} facets exposed, have been employed as supports to investigate the crystal facet effect on the growth and CO catalytic activity of Pt nanoparticles. The size, distribution and surface chemical states of Pt on the perovskite supports have been significantly modified, leading to a tailored conversion temperature and catalytic kinetics towards CO catalytic oxidation.

The Kinetics of Chirality Assignment in Catalytic Single Walled Carbon Nanotube Growth

OpenAIRE

Xu, Ziwei; Yan, Tianying; Ding, Feng

2014-01-01

Chirality-selected single-walled carbon nanotubes (SWCNTs) ensure a great potential of building ~1 nm sized electronics. However, the reliable method for chirality-selected SWCNT is still pending. Here we present a theoretical study on the SWCNT's chirality assignment and control during the catalytic growth. This study reveals that the chirality of a SWCNT is determined by the kinetic incorporation of the pentagon formation during SWCNT nucleation. Therefore, chirality is randomly assigned on...

Improved hydrogen sorption kinetics in wet ball milled Mg hydrides

Energy Technology Data Exchange (ETDEWEB)

Meng, Li

2011-05-04

In this work, wet ball milling method is used in order to improve hydrogen sorption behaviour due to its improved microstructure of solid hydrogen materials. Compared to traditional ball milling method, wet ball milling has benefits on improvement of MgH{sub 2} microstructure and further influences on its hydrogen sorption behavior. With the help of solvent tetrahydrofuran (THF), wet ball milled MgH{sub 2} powder has much smaller particle size and its specific surface area is 7 times as large as that of dry ball milled MgH{sub 2} powder. Although after ball milling the grain size is decreased a lot compared to as-received MgH{sub 2} powder, the grain size of wet ball milled MgH{sub 2} powder is larger than that of dry ball milled MgH{sub 2} powder due to the lubricant effect of solvent THF during wet ball milling. The improved particle size and specific surface area of wet ball milled MgH{sub 2} powder is found to be determining its hydrogen sorption kinetics especially at relatively low temperatures. And it also shows good cycling sorption behavior, which decides on its industrial applicability. With three different catalysts MgH{sub 2} powder shows improved hydrogen sorption behavior as well as the cyclic sorption behavior. Among them, the Nb{sub 2}O{sub 5} catalyst is found to be the most effective one in this work. Compared to the wet ball milled MgH{sub 2} powder, the particle size and specific surface area of the MgH{sub 2} powder with catalysts are similar to the previous ones, while the grain size of the MgH{sub 2} with catalysts is much finer. In this case, two reasons for hydrogen sorption improvement are suggested: one is the reduction of the grain size. The other may be as pointed out in some literatures that formation of new oxidation could enhance the hydrogen sorption kinetics, which is also the reason why its hydrogen capacity is decreased compared to without catalysts. After further ball milling, the specific surface area of wet ball milled Mg

A kinetics database and scripts for PHREEQC

Science.gov (United States)

Hu, B.; Zhang, Y.; Teng, Y.; Zhu, C.

2017-12-01

Kinetics of geochemical reactions has been increasingly used in numerical models to simulate coupled flow, mass transport, and chemical reactions. However, the kinetic data are scattered in the literature. To assemble a kinetic dataset for a modeling project is an intimidating task for most. In order to facilitate the application of kinetics in geochemical modeling, we assembled kinetics parameters into a database for the geochemical simulation program, PHREEQC (version 3.0). Kinetics data were collected from the literature. Our database includes kinetic data for over 70 minerals. The rate equations are also programmed into scripts with the Basic language. Using the new kinetic database, we simulated reaction path during the albite dissolution process using various rate equations in the literature. The simulation results with three different rate equations gave difference reaction paths at different time scale. Another application involves a coupled reactive transport model simulating the advancement of an acid plume in an acid mine drainage site associated with Bear Creek Uranium tailings pond. Geochemical reactions including calcite, gypsum, and illite were simulated with PHREEQC using the new kinetic database. The simulation results successfully demonstrated the utility of new kinetic database.

Non-Selective Evolution of Growing Populations.

Directory of Open Access Journals (Sweden)

Karl Wienand

Full Text Available Non-selective effects, like genetic drift, are an important factor in modern conceptions of evolution, and have been extensively studied for constant population sizes (Kimura, 1955; Otto and Whitlock, 1997. Here, we consider non-selective evolution in the case of growing populations that are of small size and have varying trait compositions (e.g. after a population bottleneck. We find that, in these conditions, populations never fixate to a trait, but tend to a random limit composition, and that the distribution of compositions "freezes" to a steady state. This final state is crucially influenced by the initial conditions. We obtain these findings from a combined theoretical and experimental approach, using multiple mixed subpopulations of two Pseudomonas putida strains in non-selective growth conditions (Matthijs et al, 2009 as model system. The experimental results for the population dynamics match the theoretical predictions based on the Pólya urn model (Eggenberger and Pólya, 1923 for all analyzed parameter regimes. In summary, we show that exponential growth stops genetic drift. This result contrasts with previous theoretical analyses of non-selective evolution (e.g. genetic drift, which investigated how traits spread and eventually take over populations (fixate (Kimura, 1955; Otto and Whitlock, 1997. Moreover, our work highlights how deeply growth influences non-selective evolution, and how it plays a key role in maintaining genetic variability. Consequently, it is of particular importance in life-cycles models (Melbinger et al, 2010; Cremer et al, 2011; Cremer et al, 2012 of periodically shrinking and expanding populations.

Some Aspects of Extended Kinetic Equation

Directory of Open Access Journals (Sweden)

Dilip Kumar

2015-09-01

Full Text Available Motivated by the pathway model of Mathai introduced in 2005 [Linear Algebra and Its Applications, 396, 317–328] we extend the standard kinetic equations. Connection of the extended kinetic equation with fractional calculus operator is established. The solution of the general form of the fractional kinetic equation is obtained through Laplace transform. The results for the standard kinetic equation are obtained as the limiting case.

Thermodynamic and kinetic theory of nucleation, deliquescence and efflorescence transitions in the ensemble of droplets on soluble particles.

Science.gov (United States)

Shchekin, Alexander K; Shabaev, Ilya V; Hellmuth, Olaf

2013-02-07

Thermodynamic and kinetic peculiarities of nucleation, deliquescence and efflorescence transitions in the ensemble of droplets formed on soluble condensation nuclei from a solvent vapor have been considered. The interplay of the effects of solubility and the size of condensation nuclei has been analyzed. Activation barriers for the deliquescence and phase transitions and for the reverse efflorescence transition have been determined as functions of the relative humidity of the vapor-gas atmosphere, initial size, and solubility of condensation nuclei. It has been demonstrated that, upon variations in the relative humidity of the atmosphere, the crossover in thermodynamically stable and unstable variables of the droplet state takes place. The physical meaning of stable and unstable variables has been clarified. The kinetic equations for establishing equilibrium and steady distributions of binary droplets have been solved. The specific times for relaxation, deliquescence and efflorescence transitions have been calculated.

A Novel Selective Inverse Agonist of the CB2 Receptor as a Radiolabeled Tool Compound for Kinetic Binding Studies.

Science.gov (United States)

Martella, Andrea; Sijben, Huub; Rufer, Arne C; Grether, Uwe; Fingerle, Juergen; Ullmer, Christoph; Hartung, Thomas; IJzerman, Adriaan P; van der Stelt, Mario; Heitman, Laura H

2017-10-01

The endocannabinoid system, and in particular the cannabinoid type 2 receptor (CB2R), raised the interest of many medicinal chemistry programs for its therapeutic relevance in several (patho)physiologic processes. However, the physico-chemical properties of tool compounds for CB2R (e.g., the radioligand [ 3 H]CP55,940) are not optimal, despite the research efforts in developing effective drugs to target this system. At the same time, the importance of drug-target binding kinetics is growing since the kinetic binding profile of a ligand may provide important insights for the resulting in vivo efficacy. In this context we synthesized and characterized [ 3 H]RO6957022, a highly selective CB2R inverse agonist, as a radiolabeled tool compound. In equilibrium and kinetic binding experiments [ 3 H]RO6957022 showed high affinity for human CB2R with fast association ( k on ) and moderate dissociation ( k off ) kinetics. To demonstrate the robustness of [ 3 H]RO6957022 binding, affinity studies were carried out for a wide range of CB2R reference ligands, spanning the range of full, partial, and inverse agonists. Finally, we used [ 3 H]RO6957022 to study the kinetic binding profiles (i.e., k on and k off values) of selected synthetic and endogenous (i.e., 2-arachidonoylglycerol, anandamide, and noladin ether) CB2R ligands by competition association experiments. All tested ligands, and in particular the endocannabinoids, displayed distinct kinetic profiles, shedding more light on their mechanism of action and the importance of association rates in the determination of CB2R affinity. Altogether, this study shows that the use of a novel tool compound, i.e., [ 3 H]RO6957022, can support the development of novel ligands with a repertoire of kinetic binding profiles for CB2R. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

Kinetics of Sub-Micron Grain Size Refinement in 9310 Steel

Science.gov (United States)

Kozmel, Thomas; Chen, Edward Y.; Chen, Charlie C.; Tin, Sammy

2014-05-01

Recent efforts have focused on the development of novel manufacturing processes capable of producing microstructures dominated by sub-micron grains. For structural applications, grain refinement has been shown to enhance mechanical properties such as strength, fatigue resistance, and fracture toughness. Through control of the thermo-mechanical processing parameters, dynamic recrystallization mechanisms were used to produce microstructures consisting of sub-micron grains in 9310 steel. Starting with initial bainitic grain sizes of 40 to 50 μm, various levels of grain refinement were observed following hot deformation of 9310 steel samples at temperatures and strain rates ranging from 755 K to 922 K (482 °C and 649 °C) and 1 to 0.001/s, respectively. The resulting deformation microstructures were characterized using scanning electron microscopy and electron backscatter diffraction techniques to quantify the extent of carbide coarsening and grain refinement occurring during deformation. Microstructural models based on the Zener-Holloman parameter were developed and modified to include the effect of the ferrite/carbide interactions within the system. These models were shown to effectively correlate microstructural attributes to the thermal mechanical processing parameters.

Satellite Formation during Coalescence of Unequal Size Drops

KAUST Repository

Zhang, F. H.

2009-03-12

The coalescence of a drop with a flat liquid surface pinches off a satellite from its top, in the well-known coalescence cascade, whereas the coalescence of two equally sized drops does not appear to leave such a satellite. Herein we perform experiments to identify the critical diameter ratio of two drops, above which a satellite is produced during their coalescence. We find that the critical parent ratio is as small as 1.55, but grows monotonically with the Ohnesorge number. The daughter size is typically about 50% of the mother drop. However, we have identified novel pinch-off dynamics close to the critical size ratio, where the satellite does not fully separate, but rather goes directly into a second stage of the coalescence cascade, thus generating a much smaller satellite droplet.

Satellite Formation during Coalescence of Unequal Size Drops

KAUST Repository

Zhang, F. H.; Li, E. Q.; Thoroddsen, Sigurdur T

2009-01-01

The coalescence of a drop with a flat liquid surface pinches off a satellite from its top, in the well-known coalescence cascade, whereas the coalescence of two equally sized drops does not appear to leave such a satellite. Herein we perform experiments to identify the critical diameter ratio of two drops, above which a satellite is produced during their coalescence. We find that the critical parent ratio is as small as 1.55, but grows monotonically with the Ohnesorge number. The daughter size is typically about 50% of the mother drop. However, we have identified novel pinch-off dynamics close to the critical size ratio, where the satellite does not fully separate, but rather goes directly into a second stage of the coalescence cascade, thus generating a much smaller satellite droplet.

Kinetics of incorporation/redistribution of photosensitizer hypericin to/from high-density lipoproteins.

Science.gov (United States)

Joniova, Jaroslava; Buriankova, Luboslava; Buzova, Diana; Miskovsky, Pavol; Jancura, Daniel

2014-11-20

By means of fluorescence spectroscopy we have studied the kinetics of interaction of a photosensitizer hypericin (Hyp) with high-density lipoproteins (HDL). Hyp is incorporated into HDL molecules as monomer till ratio Hyp/HDL ∼8:1 and above this ratio forms non-fluorescent aggregates. This number is different from that found in the case of Hyp incorporation into low-density lipoprotein (LDL) molecules (8:1 vs 30:1). The difference is mainly attributed to the smaller size of HDL in comparison with LDL molecule. Biphasic kinetics of Hyp association with HDL was observed. The rapid phase of incorporation is completed within seconds, while the slow one lasts several minutes. The kinetics of the association of Hyp molecules with free HDL, Hyp/HDL=10:1 complex and the redistribution of Hyp from Hyp/HDL=70:1 complex to free HDL molecules reveal a qualitative similar characteristics of these processes with those observed for the interaction of Hyp with LDL. However, the incorporation of Hyp into HDL in the "slow" phase is more rapid than to LDL and extend of Hyp penetration into lipoproteins in the fast phase is also much higher in the case of HDL. The lower concentration of cholesterol molecules in outer shell of HDL particles is probably the determining factor for the more rapid kinetics of Hyp incorporation to and redistribution from these molecules when comparing with LDL particles. Copyright © 2014 Elsevier B.V. All rights reserved.

Experimental conditions affecting the kinetics of aqueous HCN polymerization as revealed by UV-vis spectroscopy.

Science.gov (United States)

Marín-Yaseli, Margarita R; Moreno, Miguel; de la Fuente, José L; Briones, Carlos; Ruiz-Bermejo, Marta

2018-02-15

HCN polymerization is one of the most important and fascinating reactions in prebiotic chemistry, and interest in HCN polymers in the field of materials science is growing. However, little is known about the kinetics of the HCN polymerization process. In the present study, a first approach to the kinetics of two sets of aqueous HCN polymerizations, from NH 4 CN and NaCN, at middle temperatures between 4 and 38°C, has been carried out. For each series, the presence of air and salts in the reaction medium has been systematically explored. A previous kinetic analysis was conducted during the conversion of the insoluble black HCN polymers obtained as gel fractions in these precipitation polymerizations for a reaction of one month, where a limit conversion was achieved at the highest polymerization temperature. The kinetic description of the gravimetric data for this complex system shows a clear change in the linear dependence with the polymerization temperature for the reaction from NH 4 CN, besides a relevant catalytic effect of ammonium, in comparison with those data obtained from the NaCN series. These results also demonstrated the notable influence of air, oxygen, and the saline medium in HCN polymer formation. Similar conclusions were reached when the sol fractions were monitored by UV-vis spectroscopy, and a Hill type correlation was used to describe the polymerization profiles obtained. This technique was chosen because it provides an easy, prompt and fast method to follow the evolution of the liquid or continuous phase of the process under study. Copyright © 2017 Elsevier B.V. All rights reserved.

Cheap heat grows in fields

International Nuclear Information System (INIS)

Haluza, I.

2006-01-01

Slovak farmers resemble the peasants from the film T he Magnificent Seven . They keep complaining about their fate but consider any innovation as an interference. And that is why they still have not started growing fast-growing wood although the number of heating plants processing bio-mass from forests and fields is growing. Natural gas is expensive and coal creates pollution. Energy from biomass is becoming a good business and also creates new business opportunities - growing the raw material it needs. Such heating plants usually use waste from wood processing companies and Slovak Forests (Lesy SR) has also started deliveries of chip wood from old forests. There are plantations of fast growing wood suitable for heat production of over 500-thousand hectares throughout the EU. This is about 10% of Slovakian's area where the first plantations are also already being set up. The first promising plantation project was launched this spring. And this is not a project launched and backed by a big company but a starting up businessman, Miroslav Forgac from Kosice. He founded his company, Forgim, last winter. Without big money involved and thank to a new business idea he managed to persuade farmers to set up the first plantations. He supplied the seedlings and the business has started with 75 ha of plantations around Trnava, Sala, Komarno, Lucenec, Poprad and Kosice. He is gradually signing contracts with other landowners and next year the area of plantations is set to grow by 1500 ha. Plantations of fast growing trees such as willow, poplar and acacia regenerate by new trees growing out of the roots of the old and from cut trees so from one seedling and one investment there can be several harvests. Swedish willows from Forgim regenerate 20 to 25 years after the first planting. And only then new seedlings have to be purchased. Using special machines that even cut the wood to wood chips the plantations can be 'harvested' every three years. Unlike crops, the fields do not

The kinetic stabilizer: Issues and opportunities

International Nuclear Information System (INIS)

Post, R.F.

2002-01-01

Five decades of fusion research have resulted in a solid base of understanding of the physics of plasma confinement by magnetic fields, including documentation of the role of the topology of the magnetic fields, i.e., 'open' or 'closed' field lines, in determining the confinement. Without known exception, closed systems, such as tokamaks, stellarators, or reversed-field pinches, have confinement times that are dominated by turbulence. As a result, to produce net fusion power, closed systems must be so large in size as to raise questions as to their practicality. By contrast, there are examples of open (mirror-based) systems where turbulence, if present at all, was at such low levels as to have a negligible influence on the confinement. Specifically, members of a subset of open systems, those with axisymmetric fields, have demonstrated cross-field transport rates that agree with classical predictions, opening up the possibility of fusion power systems that would be much smaller than their closed-field counterparts. Standing in the way of implementing axisymmetric mirror-based fusion systems is the MHD-unstable nature of their equilibria. The kinetic stabilizer represents a proposed way to overcome this difficulty, one based on theory that has been confirmed in the gas dynamic trap (GDT) axisymmetric mirror experiment in Novosibirsk, Russia. MHD-stabilization in the GDT arises from the presence of a sufficient density of effluent plasma on the outwardly expanding field lines outside the mirrors. However, in those mirror-based fusion systems, such as tandem-mirrors, that would operate at lower plasma collisionalities than the GDT, the effluent plasma density would be too low for this stabilization method to be effective. The kinetic stabilizer overcomes this difficulty by using ion beams injected from ion sources located far out on the expanding field lines beyond the outer mirror. These ion beams, aimed at small angles to the field lines, are compressed, stagnated

Template-directed nucleation and growth of CdS nanocrystal: the role of helical and nonhelical nanofibers on their shape and size

International Nuclear Information System (INIS)

Bose, Partha Pratim; Banerjee, Arindam

2010-01-01

This study describes the use of chiral nature of synthetic self-assembled nanofibers for nucleation and growth of Cadmium sulfide (CdS) nanocrystals with different sizes and shapes in room temperature. The templates are built by immobilizing a peptide capping agent on the surface of synthetic self-assembled helical or nonhelical nanofibers and CdS nanocrystals were allowed to grow on them. It is observed that there are differences in shapes and sizes of the nanocrystals depending on the chiral nature of the nanofibers on which they were growing. Even the CdS nanocrystals grown on different chiral and achiral nanofibers differ markedly in their photoluminescence properties. Thus, here we introduce a new way of using chirality of nanofibers to nucleate and grow CdS nanocrystals of different shape, size, and optical property.

Unusual fast-growing ovarian cystic teratoma during pregnancy presenting with intracystic fat "floating balls" appearance.

Science.gov (United States)

Donnadieu, Anne Claire; Deffieux, Xavier; Le Ray, Camille; Mordefroid, Marie; Frydman, René; Fernandez, Hervé

2006-12-01

A large ovarian cyst was diagnosed at 22 weeks' of gestation in a 32-year-old woman. The ultrasonographic appearance of the ovarian cyst was unusual with multiple mobile, spherical echogenic structures floating in the cystic mass, called intracystic "fat balls." Right adnexectomy was performed by laparotomy at 28 weeks' of gestation, because of rapid growth and overall size exceeding 20 cm. Pathological examination confirmed ovarian cystic teratoma. Usually, dermoid cysts are slow-growing, even in premenopausal women. The exact mechanism related to the fast growth during pregnancy is unknown. It could be related to an unusual pattern of estrogen (E)/P receptors expression in the cystic teratoma. This case shows that a fast-growing, mature ovarian cystic teratoma may occur during pregnancy.

Study on copper kinetics in processing sulphide ore mixed with copper and zinc with sulfuric acid leaching under pressure

Science.gov (United States)

Wen-bo, LUO; Ji-kun, WANG; Yin, GAN

2018-01-01

Sulphide ore mixed with copper and zinc is processed with pressure acid leaching. Research is conducted on the copper kinetic. The stirring rate is set at 600 rpm which could eliminate the influence of external diffusions. Research is conducted on the factors affecting the copper leaching kinetic are temperature, pressure, concentration of sulfuric acid, particle size. The result shows that the apparent activity energy is 50.7 KJ/mol. We could determine that the copper leaching process is shrinking core model of chemical reaction control and work out the leaching equation.

Vlasov simulations of kinetic Alfvén waves at proton kinetic scales

Energy Technology Data Exchange (ETDEWEB)

Vásconez, C. L. [Dipartimento di Fisica, Università della Calabria, I-87036 Cosenza (Italy); Observatorio Astronómico de Quito, Escuela Politécnica Nacional, Quito (Ecuador); Valentini, F.; Veltri, P. [Dipartimento di Fisica, Università della Calabria, I-87036 Cosenza (Italy); Camporeale, E. [Centrum Wiskunde and Informatica, Amsterdam (Netherlands)

2014-11-15

Kinetic Alfvén waves represent an important subject in space plasma physics, since they are thought to play a crucial role in the development of the turbulent energy cascade in the solar wind plasma at short wavelengths (of the order of the proton gyro radius ρ{sub p} and/or inertial length d{sub p} and beyond). A full understanding of the physical mechanisms which govern the kinetic plasma dynamics at these scales can provide important clues on the problem of the turbulent dissipation and heating in collisionless systems. In this paper, hybrid Vlasov-Maxwell simulations are employed to analyze in detail the features of the kinetic Alfvén waves at proton kinetic scales, in typical conditions of the solar wind environment (proton plasma beta β{sub p} = 1). In particular, linear and nonlinear regimes of propagation of these fluctuations have been investigated in a single-wave situation, focusing on the physical processes of collisionless Landau damping and wave-particle resonant interaction. Interestingly, since for wavelengths close to d{sub p} and β{sub p} ≃ 1 (for which ρ{sub p} ≃ d{sub p}) the kinetic Alfvén waves have small phase speed compared to the proton thermal velocity, wave-particle interaction processes produce significant deformations in the core of the particle velocity distribution, appearing as phase space vortices and resulting in flat-top velocity profiles. Moreover, as the Eulerian hybrid Vlasov-Maxwell algorithm allows for a clean almost noise-free description of the velocity space, three-dimensional plots of the proton velocity distribution help to emphasize how the plasma departs from the Maxwellian configuration of thermodynamic equilibrium due to nonlinear kinetic effects.

Preparation of steam activated carbon from rubberwood sawdust (Hevea brasiliensis) and its adsorption kinetics

Energy Technology Data Exchange (ETDEWEB)

Prakash Kumar, B.G. [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600 025 (India); Shivakamy, K. [Centralised Waste Management Facility, Bhabha Atomic Research Centre, Kalpakkam 603 102 (India); Miranda, Lima Rose [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600 025 (India); Velan, M. [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600 025 (India)]. E-mail: velan@annauniv.edu

2006-08-25

Activated carbon was produced from a biowaste product, rubberwood sawdust (RWSD) using steam in a high temperature fluidized bed reactor. Experiments were carried out to investigate the influence of various process parameters such as activation time, activation temperature, particle size and fluidising velocity on the quality of the activated carbon. The activated carbon was characterized based on its iodine number, methylene blue number, Brauner Emmet Teller (BET) surface area and surface area obtained using the ethylene glycol mono ethyl ether (EGME) retention method. The best quality activated carbon was obtained at an activation time and temperature of 1 h and 750 deg. C for an average particle size of 0.46 mm. The adsorption kinetics shows that pseudo-second-order rate fitted the adsorption kinetics better than pseudo-first-order rate equation. The adsorption capacity of carbon produced from RWSD was found to be 1250 mg g{sup -1} for the Bismark Brown dye. The rate constant and diffusion coefficient for intraparticle transport were determined for steam activated carbon. The characteristic of the prepared activated carbon was found comparable to the commercial activated carbon.

Promotion of alternative-sized personal protective equipment.

Science.gov (United States)

Flynn, Michael A; Keller, Brenna; DeLaney, Sheli C

2017-12-01

With more diversity in the workforce, companies are producing PPE such as hard hats, safety glasses, coveralls, foot protection, and safety harnesses for a larger range of body shapes and sizes. However, gray literature reports suggest that barriers exist to getting alternate sized PPE from the manufacturer to the workers who need it. The purpose of this study is to determine the extent to which alternative-sized PPE is marketed. A web-based review of seven major manufacturers of PPE was conducted to determine: (a) whether or not they offer alternative-sized products, (b) if these products are clearly labeled, and (c) if images used to display PPE are representative of a diverse workforce. Of the seven PPE manufacturers investigated, six had at least one product that was marketed as gender and/or size alternatives however, alternative sizes were more common for larger body types. Alternative-sized products rarely included size charts, and the models used to display PPE were overwhelmingly white males of average size. Despite the growing availability of alternative-sized PPE, it can be difficult to find these products, which suggests that they are rarely promoted or labeled as alternative-sized. Our study indicates that companies should expand their product lines and more aggressively market and promote these items. Guidance on how to properly fit their products would also be extremely helpful to the end-user. Manufacturers could improve the availability of alternative-sized PPE and increase their promotion of these products on their websites and in their catalogs. Individual companies and safety professionals may assist in this process by demonstrating demand for alternative-sized PPE. Published by Elsevier Ltd.

Chemical kinetics and reaction mechanism

International Nuclear Information System (INIS)

Jung, Ou Sik; Park, Youn Yeol

1996-12-01

This book is about chemical kinetics and reaction mechanism. It consists of eleven chapters, which deal with reaction and reaction speed on reaction mechanism, simple reaction by rate expression, reversible reaction and simultaneous reaction, successive reaction, complicated reaction mechanism, assumption for reaction mechanism, transition state theory, successive reaction and oscillating reaction, reaction by solution, research method high except kinetics on reaction mechanism, high reaction of kinetics like pulsed radiolysis.

Economic Cost-Analysis of the Impact of Container Size on Transplanted Tree Value

Directory of Open Access Journals (Sweden)

Lauren M. Garcia Chance

2017-04-01

Full Text Available The benefits and costs of varying container sizes have yet to be fully evaluated to determine which container size affords the most advantageous opportunity for consumers. To determine value of the tree following transplant, clonal replicates of Vitex agnus-castus L. [Chaste Tree], Acer rubrum L. var. drummondii (Hook. & Arn. ex Nutt. Sarg. [Drummond Red Maple], and Taxodium distichum (L. Rich. [Baldcypress] were grown under common conditions in each of five container sizes 3.5, 11.7, 23.3, 97.8 or 175.0 L, respectively (#1, 3, 7, 25 or 45. In June 2013, six trees of each container size and species were transplanted to a sandy clay loam field in College Station, Texas. To determine the increase in value over a two-year post-transplant period, height and caliper measurements were taken at the end of nursery production and again at the end of the second growing season in the field, October 2014. Utilizing industry standards, initial costs of materials and labor were then compared with the size of trees after two years. Replacement cost analysis after two growing seasons indicated a greater increase in value for 11.7 and 23.3 L trees compared to losses in value for some 175.0 L trees. In comparison with trees from larger containers, trees from smaller size containers experienced shorter establishment times and increased growth rates, thus creating a quicker return on investment for trees transplanted from the smaller container sizes.

Kinetic modelling of enzymatic starch hydrolysis

NARCIS (Netherlands)

Bednarska, K.A.

2015-01-01

Kinetic modelling of enzymatic starch hydrolysis – a summary

K.A. Bednarska

The dissertation entitled ‘Kinetic modelling of enzymatic starch hydrolysis’ describes the enzymatic hydrolysis and kinetic modelling of liquefaction and saccharification of wheat starch.

Quantitative study of bundle size effect on thermal conductivity of single-walled carbon nanotubes

Science.gov (United States)

Feng, Ya; Inoue, Taiki; An, Hua; Xiang, Rong; Chiashi, Shohei; Maruyama, Shigeo

2018-05-01

Compared with isolated single-walled carbon nanotubes (SWNTs), thermal conductivity is greatly impeded in SWNT bundles; however, the measurement of the bundle size effect is difficult. In this study, the number of SWNTs in a bundle was determined based on the transferred horizontally aligned SWNTs on a suspended micro-thermometer to quantitatively study the effect of the bundle size on thermal conductivity. Increasing the bundle size significantly degraded the thermal conductivity. For isolated SWNTs, thermal conductivity was approximately 5000 ± 1000 W m-1 K-1 at room temperature, three times larger than that of the four-SWNT bundle. The logarithmical deterioration of thermal conductivity resulting from the increased bundle size can be attributed to the increased scattering rate with neighboring SWNTs based on the kinetic theory.

Growing container seedlings: Three considerations

Science.gov (United States)

Kas Dumroese; Thomas D. Landis

2015-01-01

The science of growing reforestation and conservation plants in containers has continually evolved, and three simple observations may greatly improve seedling quality. First, retaining stock in its original container for more than one growing season should be avoided. Second, strongly taprooted species now being grown as bareroot stock may be good candidates...

Effect of electromagnetic radiation on the kinetics of grinding a mineral

International Nuclear Information System (INIS)

Lopez M, A.; Delgadillo G, J. A.; Vega C, H. R.

2015-10-01

In this study the effect of kinetic grinding of a mineral was investigated when is pre treated with ionizing electromagnetic radiation. This radiation is with 15 MeV photons produced by a Linac for Radiotherapy. The results for the irradiated sample with respect to the non-irradiated indicate that there were changes in the structure of the minerals in the sample under study. Changes were observed through scanning electron microscopy and X-ray diffraction, combined with the refinement of the diffraction profiles by the Rietveld method using the software Maud Program. The grinding kinetics shows a constant distribution of slightly greater size through time used for the irradiated sample. A reduction of 11.2% of the Bond (Wi) work index was reached, going from 10.91 to 9.69 kw h/t for the irradiated sample. This parameter represents the fracture toughness of a mineral. The results indicate greater efficiency of energy applied to the grinding of the irradiated sample with respect to the non-irradiated. (Author)

Mortality as a bivariate function of age and size in indeterminate growers

DEFF Research Database (Denmark)

Colchero, Fernando; Schaible, Ralf

2014-01-01

Mortality in organisms that grow indefinitely, known as indeterminate growers, is thought to be driven primarily by size. However, a number of ageing mechanisms also act as functions of age. Thus, to explain mortality in these species, both size and age need to be explicitly modelled. Here we...... contribution of age, as a proxy for chronological deterioration, is of typical senescence; while a seemingly senescent population can have underlying age-related negative senescence, which is, however, overcome by negative underlying size effects. We show how inference about these unobserved processes can...

A critical look at the kinetic models of thermoluminescence-II. Non-first order kinetics

International Nuclear Information System (INIS)

Sunta, C M; Ayta, W E F; Chubaci, J F D; Watanabe, S

2005-01-01

Non-first order (FO) kinetics models are of three types; second order (SO), general order (GO) and mixed order (MO). It is shown that all three of these have constraints in their energy level schemes and their applicable parameter values. In nature such restrictions are not expected to exist. The thermoluminescence (TL) glow peaks produced by these models shift their position and change their shape as the trap occupancies change. Such characteristics are very unlike those found in samples of real materials. In these models, in general, retrapping predominates over recombination. It is shown that the quasi-equilibrium (QE) assumption implied in the derivation of the TL equation of these models is quite valid, thus disproving earlier workers' conclusion that QE cannot be held under retrapping dominant conditions. However notwithstanding their validity, they suffer from the shortcomings as stated above and have certain lacunae. For example, the kinetic order (KO) parameter and the pre-exponential factor which are assumed to be the constant parameters of the GO kinetics expression turn out to be variables when this expression is applied to plausible physical models. Further, in glow peak characterization using the GO expression, the quality of fit is found to deteriorate when the best fitted value of KO parameter is different from 1 and 2. This means that the found value of the basic parameter, namely the activation energy, becomes subject to error. In the MO kinetics model, the value of the KO parameter α would change with dose, and thus in this model also, as in the GO model, no single value of KO can be assigned to a given glow peak. The paper discusses TL of real materials having characteristics typically like those of FO kinetics. Theoretically too, a plausible physical model of TL emission produces glow peaks which have characteristics of FO kinetics under a wide variety of parametric combinations. In the background of the above findings, it is suggested that

Fluorescence kinetics and positron annihilation kinetics investigations in cadmium sulfide crystals

Energy Technology Data Exchange (ETDEWEB)

Grillot, E; Bancie-Grillot, M; Egee, M [Reims Univ., 51 (France)

1976-03-01

Fluorescence kinetics and positrons annihilation kinetics investigations on CdS crystals, either very pure or with increasing contents of Ag-ions, led to similar and complementary results. Ag-ions mainly fill the cadmium vacancies of the lattice, building red emission luminogene centres, while green 'edge-emission' ones are destroyed. These latter, which involve an excited level active for high energy series fluorescence, seems actually related to cadmium vacancies.

Thin film growing by the laser ablation technique: possibilities for growing of dosimetric materials

International Nuclear Information System (INIS)

Rojas R, E.M.; Melo M, M.; Enriquez Z, E.; Fernandez G, M.; Haro P, E.; Hernandez P, J.L.

2005-01-01

In this talk we will present the basics about the laser ablation technique and how it is used for thin film growing, either as a single film or a stack of thin films, as well as some methods to characterize in real time the film thickness. Finally, we will discuss the possibilities of using laser ablation for growing thin films with applications to dosimetry. (Author)

''FUR'' - one size suits all

International Nuclear Information System (INIS)

Rutland, M.; Que, L.; Hassan, I.M.

2000-01-01

This work used amalgamated data from previous projects in order to test the concept that when organ function is expressed in terms of tracer kinetics, the results are independent of patient size or gender. Dynamic gamma camera studies were analysed by measuring the rate of movement of tracers from the blood into various organs. These rates were expressed as a ''fractional uptake rate'' (FUR), which is the fraction of tracer in the blood taken up by the organ per unit time. As these values were small, it was convenient to express the FUR per million seconds. The FUR was calculated using the expression FUR = SLOPE (of Rutland-Patlak plot), multiplied by B(0) (the blood curve value back-extrapolated to time zero), and divided by the TOTAL amount of tracer injected. Data were used from adult patients between the ages of 20 and 49 years who had normal organ function. Organ/tracer groups studied were the skeletal uptake of 99m Tc-MDP, the renal uptake of 99m Tc-MAG3, the renal uptake of 99m Tc-MDP, the renal uptake of 99m Tc-DTPA, the hepatic uptake of 99m Tc-colloid, the splenic uptake of 99m Tc-colloid, and the hepatic uptake of 99m Tc-DISIDA. Each organ/tracer group was divided into three subgroups according to patient size (smallest, middle and largest), and also into subgroups according to gender. Comparison of these subgroups did not show any significant size- or gender-related differences in FUR values. It is concluded that for patients with normally functioning organs the FUR is independent of patient size or gender. Thus, the FUR is a valuable way of expressing organ function, particularly in patients with unusual or rapidly changing body size, such as children. (orig.)

Determination of the crystal-melt interface kinetic coefficient from molecular dynamics simulations

International Nuclear Information System (INIS)

Monk, J; Mendelev, M I; Yang, Y; Asta, M; Hoyt, J J; Sun, D Y

2010-01-01

kinetic coefficient determination for any given classical MD system. The model also elucidates that the magnitude of the temperature gradients obtained in simulations with a single thermostat depends on the length of the simulation system normal to the interface; the need for the corrections discussed in this paper can thus be gauged from a study of the dependence of the calculated kinetic coefficient on system size

Nanometer-size surface modification produced by single, low energy, highly charged ions

International Nuclear Information System (INIS)

Stockli, M.P.

1994-01-01

Atomically flat surfaces of insulators have been bombarded with low energy, highly charged ions to search for nanometer-size surface modifications. It is expected that the high electron deficiency of highly charged ions will capture and/or remove many of the insulator's localized electrons when impacting on an insulating surface. The resulting local electron deficiency is expected to locally disintegrate the insulator through a open-quotes Coulomb explosionclose quotes forming nanometer-size craters. Xe ions with charge states between 10+ and 45+ and kinetic energies between 0 and 10 keV/q were obtained from the KSU-CRYEBIS, a CRYogenic Electron Beam Ion Source and directed onto various insulating materials. Mica was favored as target material as atomically flat surfaces can be obtained reliably through cleaving. However, the authors observations with an atomic force microscope have shown that mica tends to defoliate locally rather than disintegrate, most likely due to the small binding forces between adjacent layers. So far the authors measurements indicate that each ion produces one blister if the charge state is sufficiently high. The blistering does not seem to depend very much on the kinetic energy of the ions

The formation and growing properties of poly(ethylene terephthalate) fiber growing media after thermo-oxidative treatment

International Nuclear Information System (INIS)

Chang, C.P.; Lin, S.M.

2007-01-01

This research uses three kinds of recycled synthetic fibers that all possess excellent thermal plasticity property as raw material to develop a new firm cultivation media: polyethylene terephthalate, polyamide and polypropylene. One can not only freely control plants cultivation growing condition by changing bulk density of the media, but also solve disposal problem after usage by applying thermal oxidative treatment during manufacturing processes. The water content, air permeability and formation conditions of these fiber growing media that are required in plants growing habitat were discussed, and compared the fallout with rockwool (RW) growing media that is commonly used at present days. The results indicated that the polyethylene terephthalate fiber media could attain best formation characteristics among these fibers at the same bulk density range. Furthermore, the fiber media that were thermo-oxidative treated at 240-260 deg. C could obtained above 90% total porosity, 23-49% air capacity and 48-68% water availability, water contents raised from 1735-1094 to 2145-1156% under bulk densities of 0.03-0.09 g/cm 3 , which conforms to the common plant growing habitat conditions. Its performance well surpasses the rockwool growing media. We also discovered that the thermo-oxidative treated polyethylene terephthalate (PET) fiber media could be easily broken down and become powdery by exerting pressure, thus greatly reduce its volume and effectively improve disposal processes that are difficult presently for the huge refuse create by rockwool

Rethinking wave-kinetic theory applied to zonal flows

Science.gov (United States)

Parker, Jeffrey

2017-10-01

Over the past two decades, a number of studies have employed a wave-kinetic theory to describe fluctuations interacting with zonal flows. Recent work has uncovered a defect in this wave-kinetic formulation: the system is dominated by the growth of (arbitrarily) small-scale zonal structures. Theoretical calculations of linear growth rates suggest, and nonlinear simulations confirm, that this system leads to the concentration of zonal flow energy in the smallest resolved scales, irrespective of the numerical resolution. This behavior results from the assumption that zonal flows are extremely long wavelength, leading to the neglect of key terms responsible for conservation of enstrophy. A corrected theory, CE2-GO, is presented; it is free of these errors yet preserves the intuitive phase-space mathematical structure. CE2-GO properly conserves enstrophy as well as energy, and yields accurate growth rates of zonal flow. Numerical simulations are shown to be well-behaved and not dependent on box size. The steady-state limit simplifies into an exact wave-kinetic form which offers the promise of deeper insight into the behavior of wavepackets. The CE2-GO theory takes its place in a hierarchy of models as the geometrical-optics reduction of the more complete cumulant-expansion statistical theory CE2. The new theory represents the minimal statistical description, enabling an intuitive phase-space formulation and an accurate description of turbulence-zonal flow dynamics. This work was supported by an NSF Graduate Research Fellowship, a US DOE Fusion Energy Sciences Fellowship, and US DOE Contract Nos. DE-AC52-07NA27344 and DE-AC02-09CH11466.

Simple mass transport model for metal uptake by marine macroalgae growing at different rates

Energy Technology Data Exchange (ETDEWEB)

Rice, D.L.

1984-01-01

Although algae growing at different rates may exhibit different concentrations of a given metal, such differences in algal chemistry may or may not reflect actual effects of environmental growth factors on the kinetics of metal uptake. Published data on uptake of rubidium, cadmium, and manganese by the green seaweed Ulva fasciata Delile grown at different rates in open system sea water was interpreted using the model. Differences in exposure time to sea water of relatively old and relatively young thalli were responsible for significant decreases in algal rubidium and cadmium concentrations with increases in specific growth rate. The biomass-specific growth rates of uptake of these two metals did not vary with growth rate. Both algal concentrations and specific rates of uptake of manganese increase significantly with increasing growth rate, thus indicating a distinct link between the kinetics of manganese uptake and metabolic rate. Under some circumstances, seaweed bioassay coupled with an interpretive model may provide the only reasonable approach to the study of chemical uptake-growth phenomena. In practice, if the residence time of sea water in culture chambers is sufficiently low to preclude pseudo-closed system artifacts, differences in trace metal concentrations between input and output sea water may be difficult to detect. In the field and in situ experiments based on time-series monitoring of changes in the water chemistry would be technically difficult or perhaps impossible to perform. 13 references, 1 figure.

New Methods for Processing and Quantifying VO2 Kinetics to Steady State: VO2 Onset Kinetics

Directory of Open Access Journals (Sweden)

Craig R. McNulty

2017-09-01

Full Text Available Current methods of oxygen uptake (VO2 kinetics data handling may be too simplistic for the complex physiology involved in the underlying physiological processes. Therefore, the aim of this study was to quantify the VO2 kinetics to steady state across the full range of sub-ventilatory threshold work rates, with a particular focus on the VO2 onset kinetics. Ten healthy, moderately trained males participated in five bouts of cycling. Each bout involved 10 min at a percentage of the subject's ventilation threshold (30, 45, 60, 75, 90% from unloaded cycling. The VO2 kinetics was quantified using the conventional mono-exponential time constant (tau, τ, as well as the new methods for VO2 onset kinetics. Compared to linear modeling, non-linear modeling caused a deterioration of goodness of fit (main effect, p < 0.001 across all exercise intensities. Remainder kinetics were also improved using a modified application of the mono-exponential model (main effect, p < 0.001. Interestingly, the slope from the linear regression of the onset kinetics data is similar across all subjects and absolute exercise intensities, and thereby independent of subject fitness and τ. This could indicate that there are no functional limitations between subjects during this onset phase, with limitations occurring for the latter transition to steady state. Finally, the continuing use of mono-exponential modeling could mask important underlying physiology of more instantaneous VO2 responses to steady state. Consequently, further research should be conducted on this new approach to VO2 onset kinetics.

Kinetic and isotherm studies of Cu(II) biosorption onto valonia tannin resin

Energy Technology Data Exchange (ETDEWEB)

Sengil, I. Ayhan [Department of Environmental Engineering, Engineering Faculty, Sakarya University, 54100 Sakarya (Turkey)], E-mail: asengil@sakarya.edu.tr; Ozacar, Mahmut [Department of Chemistry, Science and Arts Faculty, Sakarya University, 54100 Sakarya (Turkey); Tuerkmenler, Harun [Institute of Sciences and Technology, Sakarya University, 54040 Sakarya (Turkey)

2009-03-15

The biosorption of Cu(II) from aqueous solutions by valonia tannin resin was investigated as a function of particle size, initial pH, contact time and initial metal ion concentration. The aim of this study was to understand the mechanisms that govern copper removal and find a suitable equilibrium isotherm and kinetic model for the copper removal in a batch reactor. The experimental isotherm data were analysed using the Langmuir, Freundlich and Temkin equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analysed using four sorption kinetic models - the pseudo-first- and second-order equations, the Elovich and the intraparticle diffusion model equation - to determine the best fit equation for the biosorption of copper ions onto valonia tannin resin. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process, whereas the Elovich equation also fits the experimental data well.

A kinetic model of municipal sludge degradation during non-catalytic wet oxidation.

Science.gov (United States)

Prince-Pike, Arrian; Wilson, David I; Baroutian, Saeid; Andrews, John; Gapes, Daniel J

2015-12-15

Wet oxidation is a successful process for the treatment of municipal sludge. In addition, the resulting effluent from wet oxidation is a useful carbon source for subsequent biological nutrient removal processes in wastewater treatment. Owing to limitations with current kinetic models, this study produced a kinetic model which predicts the concentrations of key intermediate components during wet oxidation. The model was regressed from lab-scale experiments and then subsequently validated using data from a wet oxidation pilot plant. The model was shown to be accurate in predicting the concentrations of each component, and produced good results when applied to a plant 500 times larger in size. A statistical study was undertaken to investigate the validity of the regressed model parameters. Finally the usefulness of the model was demonstrated by suggesting optimum operating conditions such that volatile fatty acids were maximised. Copyright © 2015 Elsevier Ltd. All rights reserved.

Growth kinetics of tin oxide nanocrystals in colloidal suspensions under hydrothermal conditions

International Nuclear Information System (INIS)

Lee, Eduardo J.H.; Ribeiro, Caue; Longo, Elson; Leite, Edson R.

2006-01-01

Colloidal suspensions of tin oxide nanocrystals were synthesized at room temperature by the hydrolysis reaction of tin chloride (II), in an ethanolic solution. The coarsening kinetics of such nanocrystals was studied by submitting the as-prepared suspensions to hydrothermal treatments at temperatures of 100, 150 and 200 deg. C for periods between 60 and 12,000 min. Transmission electron microscopy (TEM) was used to characterize the samples (i.e. distribution of nanocrystal size, average particle radius and morphology). The results show that the usual Ostwald ripening coarsening mechanism does not fit well the experimental data, which is an indicative that this process is not significant for SnO 2 nanocrystals, in the studied experimental conditions. The morphology evolution of the nanocrystals upon hydrothermal treatment indicates that growth by oriented attachment (OA) should be significant. A kinetic model that describes OA growth is successfully applied to fit the data

Fibril growth kinetics link buffer conditions and topology of 3D collagen I networks.

Science.gov (United States)

Kalbitzer, Liv; Pompe, Tilo

2018-02-01

Three-dimensional fibrillar networks reconstituted from collagen I are widely used as biomimetic scaffolds for in vitro and in vivo cell studies. Various physicochemical parameters of buffer conditions for in vitro fibril formation are well known, including pH-value, ion concentrations and temperature. However, there is a lack of a detailed understanding of reconstituting well-defined 3D network topologies, which is required to mimic specific properties of the native extracellular matrix. We screened a wide range of relevant physicochemical buffer conditions and characterized the topology of the reconstituted 3D networks in terms of mean pore size and fibril diameter. A congruent analysis of fibril formation kinetics by turbidimetry revealed the adjustment of the lateral growth phase of fibrils by buffer conditions to be key in the determination of pore size and fibril diameter of the networks. Although the kinetics of nucleation and linear growth phase were affected by buffer conditions as well, network topology was independent of those two growth phases. Overall, the results of our study provide necessary insights into how to engineer 3D collagen matrices with an independent control over topology parameters, in order to mimic in vivo tissues in in vitro experiments and tissue engineering applications. The study reports a comprehensive analysis of physicochemical conditions of buffer solutions to reconstitute defined 3D collagen I matrices. By a combined analysis of network topology, i.e., pore size and fibril diameter, and the kinetics of fibril formation we can reveal the dependence of 3D network topology on buffer conditions, such as pH-value, phosphate concentration and sodium chloride content. With those results we are now able to provide engineering strategies to independently tune the topology parameters of widely used 3D collagen scaffolds based on the buffer conditions. By that, we enable the straightforward mimicking of extracellular matrices of in vivo

Kinetics of the hydrogen production reaction in a copper-chlorine water splitting plant

International Nuclear Information System (INIS)

Zamfirescu, C.; Naterer, G.F.; Dincer, I.

2009-01-01

The exothermic reaction of HCl with particulate Cu occurs during hydrogen production step in the thermochemical copper-chlorine (Cu-Cl) water splitting cycle. In this paper, this chemical reaction is modeled kinetically, and a parametric study is performed to determine the influences of particle size, temperature and molar ratios on the reaction kinetics. It is determined that the residence time of copper particles varies between 10 and 100 s, depending on the operating conditions. The hydrogen conversion at equilibrium varies between 55 and 85%, depending on the reaction temperature. The heat flux at the particle surface, caused by the exothermic enthalpy of reaction, reaches about 3,000 W/m 2 when the particle shrinks to 0.1% from its initial size. A numerical algorithm is developed to solve the moving boundary Stefan problem with a chemical reaction. It predicts the shrinking of copper particles based on the hypothesis that the chemical reaction and heat transfer are decoupled. The model allows for estimation of the temperature of the copper particle, assumed spherical, in the radial direction. The maximum temperature at the interface is higher than the melting point of CuCl by 10-50 o C, depending on the assumed operating conditions. (author)

Effect of the critical size of initial voids on stress-induced migration

International Nuclear Information System (INIS)

Aoyagi, Minoru

2004-01-01

The stress-induced migration phenomenon is one of the problems related to the reliability of metal interconnections in semiconductor devices. This phenomenon causes voids and fractures in interconnections. The basic feature of this phenomenon is vacancy migration to minute initial voids. Expanding initial voids grow into larger voids and fractures. The purpose of this work is to theoretically clarify the effects of residual thermal stress and void surface stress on the behavior of the initial voids which exist immediately after a passivation process. Using a spherical metal sample with a spherical void under external stress, vacancy absorption or emission was investigated between the void surface and the sample surface. The behavior of vacancies and atoms was also investigated in interconnections under residual thermal stress. We show that the void or sample surface becomes a vacancy sink or source, depending on the mutual relationship between the surface stress due to the surface-free energy and the residual thermal stress. We also reveal that the initial voids, which exist immediately after a passivation process, grow into larger voids and fractures when the size of the initial voids exceeds the critical size. If the size of the initial void can be controlled to below the critical size, voids and fractures do not occur

Zinc and Copper Release Kinetics in a Calcareous Soil amended with Manure and Vermicompost

Directory of Open Access Journals (Sweden)

hamid reza motaghian

2017-02-01

Full Text Available Introduction: Use of organic fertilizers such as vermicompost in agricultural soils with low organic matter content is almost considered as a one way for adding nutrients in these soils. However, application of these fertilizers may affect micronutrient release characteristics. Micronutrient release Kinetics in soils especially in amended soils give information about potential of amended soils to release these elements into solution. Although it is important to study kinetics of micronutrient release from soils to identify soil micronutrients buffering capacity, little attention has been paid to micronutrients desorption rate studies especially in amended soils. The rate of release micronutrients from soil solid phase by considering micronutrients as adsorbed ions or in mineral forms is an important parameter in nutrition of plants by microelements and a dynamic factor that regulates its continuous supply to growing plants; nonetheless, little attention has been paid to micronutrients kinetics inrelease studies. Material and Methods: In this study, kinetics of zinc (Zn and copper (Cu were compared in one calcareous soil amended with 0, 0.5, and 1% (w/w of manure and vermicompost in a completely randomized design and then amended and un-amended soils were incubated at field capacity, for 30 days. After incubation period, amended and un-amended soils were air-dried and were prepared to kinetics study. Kinetics of Zn and Cu release were studied by successive extraction with DTPA-TEA solution. Two grams of the amended and un-amended soils, in triplicate, suspended in 20 ml DTPA-TEA solution were equilibrated at 25±10C for 1, 8, 24, 48, 72, 96, 120, 144, 168, 336 and 504 h by shaking for 15 min. before incubation and 15 min. before the suspensions were centrifuged. Seven drops of toluene were added to each 1000 ml of extractant to inhibit microbial activity. Zinc and copper desorption with time was fitted by using different equations (Zero

Particle size dependence of biogenic secondary organic aerosol molecular composition

Science.gov (United States)

Tu, Peijun; Johnston, Murray V.

2017-06-01

Formation of secondary organic aerosol (SOA) is initiated by the oxidation of volatile organic compounds (VOCs) in the gas phase whose products subsequently partition to the particle phase. Non-volatile molecules have a negligible evaporation rate and grow particles at their condensation rate. Semi-volatile molecules have a significant evaporation rate and grow particles at a much slower rate than their condensation rate. Particle phase chemistry may enhance particle growth if it transforms partitioned semi-volatile molecules into non-volatile products. In principle, changes in molecular composition as a function of particle size allow non-volatile molecules that have condensed from the gas phase (a surface-limited process) to be distinguished from those produced by particle phase reaction (a volume-limited process). In this work, SOA was produced by β-pinene ozonolysis in a flow tube reactor. Aerosol exiting the reactor was size-selected with a differential mobility analyzer, and individual particle sizes between 35 and 110 nm in diameter were characterized by on- and offline mass spectrometry. Both the average oxygen-to-carbon (O / C) ratio and carbon oxidation state (OSc) were found to decrease with increasing particle size, while the relative signal intensity of oligomers increased with increasing particle size. These results are consistent with oligomer formation primarily in the particle phase (accretion reactions, which become more favored as the volume-to-surface-area ratio of the particle increases). Analysis of a series of polydisperse SOA samples showed similar dependencies: as the mass loading increased (and average volume-to-surface-area ratio increased), the average O / C ratio and OSc decreased, while the relative intensity of oligomer ions increased. The results illustrate the potential impact that particle phase chemistry can have on biogenic SOA formation and the particle size range where this chemistry becomes important.

Particle size dependence of biogenic secondary organic aerosol molecular composition

Directory of Open Access Journals (Sweden)

P. Tu

2017-06-01

Full Text Available Formation of secondary organic aerosol (SOA is initiated by the oxidation of volatile organic compounds (VOCs in the gas phase whose products subsequently partition to the particle phase. Non-volatile molecules have a negligible evaporation rate and grow particles at their condensation rate. Semi-volatile molecules have a significant evaporation rate and grow particles at a much slower rate than their condensation rate. Particle phase chemistry may enhance particle growth if it transforms partitioned semi-volatile molecules into non-volatile products. In principle, changes in molecular composition as a function of particle size allow non-volatile molecules that have condensed from the gas phase (a surface-limited process to be distinguished from those produced by particle phase reaction (a volume-limited process. In this work, SOA was produced by β-pinene ozonolysis in a flow tube reactor. Aerosol exiting the reactor was size-selected with a differential mobility analyzer, and individual particle sizes between 35 and 110 nm in diameter were characterized by on- and offline mass spectrometry. Both the average oxygen-to-carbon (O ∕ C ratio and carbon oxidation state (OSc were found to decrease with increasing particle size, while the relative signal intensity of oligomers increased with increasing particle size. These results are consistent with oligomer formation primarily in the particle phase (accretion reactions, which become more favored as the volume-to-surface-area ratio of the particle increases. Analysis of a series of polydisperse SOA samples showed similar dependencies: as the mass loading increased (and average volume-to-surface-area ratio increased, the average O ∕ C ratio and OSc decreased, while the relative intensity of oligomer ions increased. The results illustrate the potential impact that particle phase chemistry can have on biogenic SOA formation and the particle size range where this chemistry becomes