Study of spectroscopic properties of nanosized particles of core-shell morphology

NASA Astrophysics Data System (ADS)

Bzhalava, T. N.; Kervalishvili, P. J.

2018-03-01

Method of studying spectroscopic properties of nanosized particles and estimation of resonance wavelength range for determination of specific and unique “spectral” signatures in purpose of sensing, identification of nanobioparticles, viruses is proposed. Elaboration of relevant models of viruses, estimation of spectral response on interaction of electromagnetic (EM) field and viral nanoparticle is the goal of proposed methodology. Core-shell physical model is used as the first approximation of shape-structure of virion. Theoretical solution of EM wave scattering on single spherical virus-like particle (VLP) is applied for determination of EM fields in the areas of core, shell and surrounding medium of (VLP), as well as scattering and absorption characteristics. Numerical results obtained by computer simulation for estimation of EM “spectra” of bacteriophage T7 demonstrate the strong dependence of spectroscopic characteristics on core-shell related electric and geometric parameters of VLP in resonance wavelengths range. Expected spectral response is observable on far-field characterizations. Obtained analytical EM field expressions, modelling technique in complement with experimental spectroscopic methods should be the way of providing the virus spectral signatures, important in bioparticles characterization.

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core. Structure, dissolution in cell culture media, and biological impact on macrophages

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

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H.

Widespread use of silver nanoparticles raises questions of environmental impact and toxicity. Both silver particles and silver ions formed by particle dissolution may impact biological systems. Therefore it is important to understand the characteristics of silver nanoparticles and their stability in relevant media. The synthesis route can impact physical and chemical characteristics of the particles and we report the characterization and solution stability of three types of silver nanoparticles (20 nm particles with and without gold cores and 110 nm particles with gold cores) in cell culture media with serum proteins: FBS10%/RPMI. These nanoparticles were synthesized in aqueous solution andmore » characterized using both in situ and ex situ analysis methods. Dissolution studies were carried at particle concentrations from 1 µg/ml to 50 µg/ml. Particles with gold cores had smaller crystallite size and higher apparent solubility than pure silver particles. A dissolution model was found to describe the time variation of particle size and amount of dissolved silver for particle loadings above 9 µg/ml. An effective solubility product obtained from fitting the data was higher for the 20 nm gold core particles in comparison to the pure silver or 110 nm particles. Dissolution of the nanoparticles was enhanced by presence of serum proteins contained in fetal bovine serum. In addition, the protocol of the dispersion in the medium was found to influence particle agglomeration and dissolution. Results show that particle structure can impact the concentration of dissolved silver and the dose to which cells would be exposed during in vitro studies.« less

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core. Structure, dissolution in cell culture media, and biological impact on macrophages

DOE PAGES

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H.; ...

2015-07-15

Widespread use of silver nanoparticles raises questions of environmental impact and toxicity. Both silver particles and silver ions formed by particle dissolution may impact biological systems. Therefore it is important to understand the characteristics of silver nanoparticles and their stability in relevant media. The synthesis route can impact physical and chemical characteristics of the particles and we report the characterization and solution stability of three types of silver nanoparticles (20 nm particles with and without gold cores and 110 nm particles with gold cores) in cell culture media with serum proteins: FBS10%/RPMI. These nanoparticles were synthesized in aqueous solution andmore » characterized using both in situ and ex situ analysis methods. Dissolution studies were carried at particle concentrations from 1 µg/ml to 50 µg/ml. Particles with gold cores had smaller crystallite size and higher apparent solubility than pure silver particles. A dissolution model was found to describe the time variation of particle size and amount of dissolved silver for particle loadings above 9 µg/ml. An effective solubility product obtained from fitting the data was higher for the 20 nm gold core particles in comparison to the pure silver or 110 nm particles. Dissolution of the nanoparticles was enhanced by presence of serum proteins contained in fetal bovine serum. In addition, the protocol of the dispersion in the medium was found to influence particle agglomeration and dissolution. Results show that particle structure can impact the concentration of dissolved silver and the dose to which cells would be exposed during in vitro studies.« less

The Correlation Entropy as a Measure of the Complexity of High-Lying Single-Particle Modes

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

Stoyanov, Chavdar; Zelevinsky, Vladimir; Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824-1321

Highly-excited single-particle states in nuclei are coupled with the excitations of a more complex character, first of all with collective phonon-like modes of the core. In the framework of the quasiparticle-phonon model we consider the structure of resulting complex configurations using the 1k17/2 orbital in 209Pb as an example. The eigenstates of the model carry significant degree of complexity that can be quantified with the aid of correlational invariant entropy. With artificially enhanced particle-core coupling, the system undergoes the doubling phase transition with the quasiparticle strength concentrated in two repelling peaks.

Examining Model Atmospheric Particles Inside and Out

NASA Astrophysics Data System (ADS)

Wingen, L. M.; Zhao, Y.; Fairhurst, M. C.; Perraud, V. M.; Ezell, M. J.; Finlayson-Pitts, B. J.

2017-12-01

Atmospheric particles scatter incoming solar radiation and act as cloud condensation nuclei (CCN), thereby directly and indirectly affecting the earth's radiative balance and reducing visibility. These atmospheric particles may not be uniform in composition. Differences in the composition of a particle's outer surface from its core can arise during particle growth, (photo)chemical aging, and exchange of species with the gas phase. The nature of the surface on a molecular level is expected to impact growth mechanisms as well as their ability to act as CCN. Model laboratory particle systems are explored using direct analysis in real time-mass spectrometry (DART-MS), which is sensitive to surface composition, and contrasted with average composition measurements using high resolution, time-of-flight aerosol mass spectrometry (HR-ToF-AMS). Results include studies of the heterogeneous reactions of amines with solid dicarboxylic acid particles, which are shown to generate aminium dicarboxylate salts at the particle surface, leaving an unreacted core. Combination of both mass spectrometric techniques reveals a trend in reactivity of C3-C7 dicarboxylic acids with amines and allows calculation of the DART probe depth into the particles. The results of studies on additional model systems that are currently being explored will also be reported.

Magnetic field directed assembly of superstructures of ferrite-ferroelectric core-shell nanoparticles and studies on magneto-electric interactions

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

Srinivasan, G., E-mail: srinivas@oakland.edu; Sreenivasulu, G.; Benoit, Crystal

2015-05-07

Composites of ferromagnetic and ferroelectric are of interest for studies on mechanical strain mediated magneto-electric (ME) interactions and for useful technologies. Here, we report on magnetic-field-assisted-assembly of barium titanate (BTO)-nickel ferrite (NFO) core-shell particles into linear chains and 2D/3D arrays and measurements of ME effects in such assemblies. First, we synthesized the core-shell nano-particles with 50–600 nm BTO and 10–200 nm NFO by chemical self-assembly by coating the ferroic particles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst via the “click” reaction. The core-shell structure was confirmed with electron microscopy and scanning probe microscopy. Wemore » obtained superstructure of the core-shell particles by subjecting them to a magnetic field gradient that exerts an attractive force on the particles and align them toward the regions of high field strengths. At low particle concentration, linear chains were formed and they evolved into 2D and 3D arrays at high particle concentrations. Magnetoelectric characterization on unassembled films and assembled arrays has been performed through measurements of low-frequency ME voltage coefficient (MEVC) by subjecting the sample to a bias magnetic field and an ac magnetic field. The MEVC is higher for field-assembled samples than for unassembled films and is found to be sensitive to field orientation with a higher MEVC for magnetic fields parallel to the array direction than for magnetic fields perpendicular to the array. A maximum MEVC of 20 mV/cm Oe, one of the highest reported for any bulk nanocomposite, is measured across the array thickness. A model is provided for ME coupling in the superstructures of BTO-NFO particulate composites. First, we estimated the MEVC for a free-standing BTO-NFO core-shell particle and then extended the model to include an array of linear chains of the particles. The theoretical estimates are in qualitative agreement with the data.« less

Magnetic field directed assembly of superstructures of ferrite-ferroelectric core-shell nanoparticles and studies on magneto-electric interactions

NASA Astrophysics Data System (ADS)

Srinivasan, G.; Sreenivasulu, G.; Benoit, Crystal; Petrov, V. M.; Chavez, F.

2015-05-01

Composites of ferromagnetic and ferroelectric are of interest for studies on mechanical strain mediated magneto-electric (ME) interactions and for useful technologies. Here, we report on magnetic-field-assisted-assembly of barium titanate (BTO)-nickel ferrite (NFO) core-shell particles into linear chains and 2D/3D arrays and measurements of ME effects in such assemblies. First, we synthesized the core-shell nano-particles with 50-600 nm BTO and 10-200 nm NFO by chemical self-assembly by coating the ferroic particles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst via the "click" reaction. The core-shell structure was confirmed with electron microscopy and scanning probe microscopy. We obtained superstructure of the core-shell particles by subjecting them to a magnetic field gradient that exerts an attractive force on the particles and align them toward the regions of high field strengths. At low particle concentration, linear chains were formed and they evolved into 2D and 3D arrays at high particle concentrations. Magnetoelectric characterization on unassembled films and assembled arrays has been performed through measurements of low-frequency ME voltage coefficient (MEVC) by subjecting the sample to a bias magnetic field and an ac magnetic field. The MEVC is higher for field-assembled samples than for unassembled films and is found to be sensitive to field orientation with a higher MEVC for magnetic fields parallel to the array direction than for magnetic fields perpendicular to the array. A maximum MEVC of 20 mV/cm Oe, one of the highest reported for any bulk nanocomposite, is measured across the array thickness. A model is provided for ME coupling in the superstructures of BTO-NFO particulate composites. First, we estimated the MEVC for a free-standing BTO-NFO core-shell particle and then extended the model to include an array of linear chains of the particles. The theoretical estimates are in qualitative agreement with the data.

Linking hygroscopicity and the surface microstructure of model inorganic salts, simple and complex carbohydrates, and authentic sea spray aerosol particles.

PubMed

Estillore, Armando D; Morris, Holly S; Or, Victor W; Lee, Hansol D; Alves, Michael R; Marciano, Meagan A; Laskina, Olga; Qin, Zhen; Tivanski, Alexei V; Grassian, Vicki H

2017-08-09

Individual airborne sea spray aerosol (SSA) particles show diversity in their morphologies and water uptake properties that are highly dependent on the biological, chemical, and physical processes within the sea subsurface and the sea surface microlayer. In this study, hygroscopicity data for model systems of organic compounds of marine origin mixed with NaCl are compared to data for authentic SSA samples collected in an ocean-atmosphere facility providing insights into the SSA particle growth, phase transitions and interactions with water vapor in the atmosphere. In particular, we combine single particle morphology analyses using atomic force microscopy (AFM) with hygroscopic growth measurements in order to provide important insights into particle hygroscopicity and the surface microstructure. For model systems, a range of simple and complex carbohydrates were studied including glucose, maltose, sucrose, laminarin, sodium alginate, and lipopolysaccharides. The measured hygroscopic growth was compared with predictions from the Extended-Aerosol Inorganics Model (E-AIM). It is shown here that the E-AIM model describes well the deliquescence transition and hygroscopic growth at low mass ratios but not as well for high ratios, most likely due to a high organic volume fraction. AFM imaging reveals that the equilibrium morphology of these single-component organic particles is amorphous. When NaCl is mixed with the organics, the particles adopt a core-shell morphology with a cubic NaCl core and the organics forming a shell similar to what is observed for the authentic SSA samples. The observation of such core-shell morphologies is found to be highly dependent on the salt to organic ratio and varies depending on the nature and solubility of the organic component. Additionally, single particle organic volume fraction AFM analysis of NaCl : glucose and NaCl : laminarin mixtures shows that the ratio of salt to organics in solution does not correspond exactly for individual particles - showing diversity within the ensemble of particles produced even for a simple two component system.

Dissipation and Rheology of Sheared Soft-Core Frictionless Disks Below Jamming

NASA Astrophysics Data System (ADS)

Vâgberg, Daniel; Olsson, Peter; Teitel, S.

2014-05-01

We use numerical simulations to investigate the effect that different models of energy dissipation have on the rheology of soft-core frictionless disks, below jamming in two dimensions. We find that it is not necessarily the mass of the particles that determines whether a system has Bagnoldian or Newtonian rheology, but rather the presence or absence of large connected clusters of particles. We demonstrate the key role that tangential dissipation plays in the formation of such clusters and in several models find a transition from Bagnoldian to Newtonian rheology as the packing fraction ϕ is varied. For each model, we show that appropriately scaled rheology curves approach a well defined limit as the mass of the particles decreases and collisions become strongly inelastic.

Investigation of the particle-core structure of odd-mass nuclei in the NpNn scheme

NASA Astrophysics Data System (ADS)

Bucurescu, D.; Cata, G.; Cutoiu, D.; Dragulescu, E.; Ivasu, M.; Zamfir, N. V.; Gizon, A.; Gizon, J.

1989-10-01

The NpNn scheme is applied to data related to collective band structures determined by the unique parity shell model orbitals in odd-A nuclei from the mass regions A≌80-100 and A≌130. Simple systematics are obtained which give a synthetic picture of the evolution of the particle-core coupling in these nuclear regions.

Optical properties of light absorbing carbon aggregates mixed with sulfate: assessment of different model geometries for climate forcing calculations.

PubMed

Kahnert, Michael; Nousiainen, Timo; Lindqvist, Hannakaisa; Ebert, Martin

2012-04-23

Light scattering by light absorbing carbon (LAC) aggregates encapsulated into sulfate shells is computed by use of the discrete dipole method. Computations are performed for a UV, visible, and IR wavelength, different particle sizes, and volume fractions. Reference computations are compared to three classes of simplified model particles that have been proposed for climate modeling purposes. Neither model matches the reference results sufficiently well. Remarkably, more realistic core-shell geometries fall behind homogeneous mixture models. An extended model based on a core-shell-shell geometry is proposed and tested. Good agreement is found for total optical cross sections and the asymmetry parameter. © 2012 Optical Society of America

Acceleration of the Particle Swarm Optimization for Peierls-Nabarro modeling of dislocations in conventional and high-entropy alloys

NASA Astrophysics Data System (ADS)

Pei, Zongrui; Eisenbach, Markus

2017-06-01

Dislocations are among the most important defects in determining the mechanical properties of both conventional alloys and high-entropy alloys. The Peierls-Nabarro model supplies an efficient pathway to their geometries and mobility. The difficulty in solving the integro-differential Peierls-Nabarro equation is how to effectively avoid the local minima in the energy landscape of a dislocation core. Among the other methods to optimize the dislocation core structures, we choose the algorithm of Particle Swarm Optimization, an algorithm that simulates the social behaviors of organisms. By employing more particles (bigger swarm) and more iterative steps (allowing them to explore for longer time), the local minima can be effectively avoided. But this would require more computational cost. The advantage of this algorithm is that it is readily parallelized in modern high computing architecture. We demonstrate the performance of our parallelized algorithm scales linearly with the number of employed cores.

Deep particle bed dryout model based on flooding

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

Kuan, P.

1987-01-01

Examination of the damaged Three Mile island Unit 2 (TMI-2) reactor indicates that a deep (approx. 1-m) bed of relatively large (approx. 1-mm) particles was formed in the core. Cooling of such beds is crucial to the arrest of core damage progression. The Lipinski model, based on flows in the bed, has been used to predict the coolability, but uncertainties exist in the turbulent permeability. Models based on flooding at the top of the bed either have a dimensional viscosity term, or no viscosity dependence, thus limiting their applicability. This paper presents a dimensionless correlation based on flooding data thatmore » involves a liquid Reynolds number. The derived dryout model from this correlation is compared with data for deep beds of large particles at atmospheric pressure, and with other models over a wide pressure range. It is concluded that the present model can give quite accurate predictions for the dryout heat flux of particle beds formed during a light water reactor accident and it is easy to use and agrees with the Lipinski n = 5 model, which requires iterative calculations.« less

Scattering of 42-MeV alpha particles from Cu-65

NASA Technical Reports Server (NTRS)

Stewart, W. M.; Seth, K. K.

1972-01-01

The extended particle-core coupling model was used to predict the properties of low-lying levels of Cu-65. A 42-MeV alpha particle cyclotron beam was used for the experiment. The experiment included magnetic analysis of the incident beam and particle detection by lithium-drifted silicon semiconductors. Angular distributions were measured for 10 to 50 degrees in the center of mass system. Data was reduced by fitting the peaks with a skewed Gaussian function using a least squares computer program with a linear background search. The energy calibration of each system was done by pulsar, and the excitation energies are accurate to + or - 25 keV. The simple weak coupling model cannot account for the experimentally observed quantities of the low-lying levels of Cu-65. The extended particle-core calculation showed that the coupling is not weak and that considerable configuration mixing of the low-lying states results.

FEM analysis of magnetic flake composites

NASA Astrophysics Data System (ADS)

Claassen, J. H.

2009-07-01

A composite comprised of layered flake-like magnetic particles embedded in an insulating medium has been proposed as a low permeability, low loss core material. This would be an alternative to "distributed air gap" compressed powder cores that are widely used for inductors in power applications. Since the lowest loss metallic materials are manufactured in the form of very thin sheets, the particles after pulverizing would be in the form of flakes. The effective permeability and average core loss have been computed for model systems of flake composites in a two-dimensional approximation. The core loss is modeled by eddy current dissipation in the low-frequency limit, where the conductor thickness is much less than the skin depth. It is found that useful values of permeability should be obtained for a modest filling fraction of magnetic material, in contrast to the powder cores which require a value close to unity. The core loss will scale as the inverse of filling fraction, with a small additional enhancement due to perpendicular field components. It is thus expected that useful core materials may be attainable without the necessity of large compaction forces.

Advanced tokamak research with integrated modeling in JT-60 Upgrade

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

Hayashi, N.

2010-05-15

Researches on advanced tokamak (AT) have progressed with integrated modeling in JT-60 Upgrade [N. Oyama et al., Nucl. Fusion 49, 104007 (2009)]. Based on JT-60U experimental analyses and first principle simulations, new models were developed and integrated into core, rotation, edge/pedestal, and scrape-off-layer (SOL)/divertor codes. The integrated models clarified complex and autonomous features in AT. An integrated core model was implemented to take account of an anomalous radial transport of alpha particles caused by Alfven eigenmodes. It showed the reduction in the fusion gain by the anomalous radial transport and further escape of alpha particles. Integrated rotation model showed mechanismsmore » of rotation driven by the magnetic-field-ripple loss of fast ions and the charge separation due to fast-ion drift. An inward pinch model of high-Z impurity due to the atomic process was developed and indicated that the pinch velocity increases with the toroidal rotation. Integrated edge/pedestal model clarified causes of collisionality dependence of energy loss due to the edge localized mode and the enhancement of energy loss by steepening a core pressure gradient just inside the pedestal top. An ideal magnetohydrodynamics stability code was developed to take account of toroidal rotation and clarified a destabilizing effect of rotation on the pedestal. Integrated SOL/divertor model clarified a mechanism of X-point multifaceted asymmetric radiation from edge. A model of the SOL flow driven by core particle orbits which partially enter the SOL was developed by introducing the ion-orbit-induced flow to fluid equations.« less

Fiber Bragg grating filter using evaporated induced self assembly of silica nano particles

NASA Astrophysics Data System (ADS)

Hammarling, Krister; Zhang, Renyung; Manuilskiy, Anatoliy; Nilsson, Hans-Erik

2014-03-01

In the present work we conduct a study of fiber filters produced by evaporation of silica particles upon a MM-fiber core. A band filter was designed and theoretically verified using a 2D Comsol simulation model of a 3D problem, and calculated in the frequency domain in respect to refractive index. The fiber filters were fabricated by stripping and chemically etching the middle part of an MM-fiber until the core was exposed. A mono layer of silica nano particles were evaporated on the core using an Evaporation Induced Self-Assembly (EISA) method. The experimental results indicated a broader bandwidth than indicated by the simulations which can be explained by the mismatch in the particle size distributions, uneven particle packing and finally by effects from multiple mode angles. Thus, there are several closely connected Bragg wavelengths that build up the broader bandwidth. The experimental part shows that it is possible by narrowing the particle size distributing and better control of the particle packing, the filter effectiveness can be greatly improved.

Fines migration during CO 2 injection: Experimental results interpreted using surface forces

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

Xie, Quan; Saeedi, Ali; Delle Piane, Claudio

The South West Hub project is one of the Australian Flagship Carbon Capture and Storage projects located in the south-west of Western Australia. To evaluate the injectivity potential during the forthcoming full-scale CO 2 injection, we conducted three core-flooding experiments using reservoir core plugs from the well Harvey-1. We aimed to investigate in this paper whether the injection of CO 2 leads to fines migration and permeability reduction due to the relatively high kaolinite content (up to 13%) in the injection interval of the target formation (i.e. the Wonnerup Member of the Lesueur Formation). We imaged the core samples beforemore » flooding to verify the presence of kaolinite at the pore-scale using scanning electron microscopy (SEM). We also examined the pore network of the core plugs before and after the core-flooding experiments using Nuclear Magnetic Resonance (NMR). Moreover, to gain a better understanding of any kaolinite fines migration, we delineated surface force using two models based on Derjaguin-Landau-Verwey-Overbeek (denoted by DLVO) theory coupled hydrodynamic force: (1) sphere/flat model representing interaction between kaolinite/quartz, and (2) flat/flat model representing interaction between kaolinite/kaolinite. Our core-flooding experimental results showed that CO 2/brine injection triggered moderate to significant reduction in the permeability of the core samples with a negligible porosity change. NMR measurements supported the core-flooding results, suggesting that the relatively large pores disappeared in favour of a higher proportion of the medium to small pores after flooding. The DLVO calculations showed that some kaolinite particles probably lifted off and detached from neighbouring kaolinite particles rather than quartz grains. Moreover, the modelling results showed that the kaolinite fines migration would not occur under normal reservoir multiphase flow conditions. This is not because of the low hydrodynamic force. It is rather because the geometries of the particles dominate their interplay. Finally and overall, both of the experimental and analytical modelling results point to the fines migration to be the most likely cause of the permeability impairment observed during core-flooding experiments.« less

Fines migration during CO 2 injection: Experimental results interpreted using surface forces

DOE PAGES

Xie, Quan; Saeedi, Ali; Delle Piane, Claudio; ...

2017-09-04

The South West Hub project is one of the Australian Flagship Carbon Capture and Storage projects located in the south-west of Western Australia. To evaluate the injectivity potential during the forthcoming full-scale CO 2 injection, we conducted three core-flooding experiments using reservoir core plugs from the well Harvey-1. We aimed to investigate in this paper whether the injection of CO 2 leads to fines migration and permeability reduction due to the relatively high kaolinite content (up to 13%) in the injection interval of the target formation (i.e. the Wonnerup Member of the Lesueur Formation). We imaged the core samples beforemore » flooding to verify the presence of kaolinite at the pore-scale using scanning electron microscopy (SEM). We also examined the pore network of the core plugs before and after the core-flooding experiments using Nuclear Magnetic Resonance (NMR). Moreover, to gain a better understanding of any kaolinite fines migration, we delineated surface force using two models based on Derjaguin-Landau-Verwey-Overbeek (denoted by DLVO) theory coupled hydrodynamic force: (1) sphere/flat model representing interaction between kaolinite/quartz, and (2) flat/flat model representing interaction between kaolinite/kaolinite. Our core-flooding experimental results showed that CO 2/brine injection triggered moderate to significant reduction in the permeability of the core samples with a negligible porosity change. NMR measurements supported the core-flooding results, suggesting that the relatively large pores disappeared in favour of a higher proportion of the medium to small pores after flooding. The DLVO calculations showed that some kaolinite particles probably lifted off and detached from neighbouring kaolinite particles rather than quartz grains. Moreover, the modelling results showed that the kaolinite fines migration would not occur under normal reservoir multiphase flow conditions. This is not because of the low hydrodynamic force. It is rather because the geometries of the particles dominate their interplay. Finally and overall, both of the experimental and analytical modelling results point to the fines migration to be the most likely cause of the permeability impairment observed during core-flooding experiments.« less

Influence of particle size and shell thickness of core-shell packing materials on optimum experimental conditions in preparative chromatography.

PubMed

Horváth, Krisztián; Felinger, Attila

2015-08-14

The applicability of core-shell phases in preparative separations was studied by a modeling approach. The preparative separations were optimized for two compounds having bi-Langmuir isotherms. The differential mass balance equation of chromatography was solved by the Rouchon algorithm. The results show that as the size of the core increases, larger particles can be used in separations, resulting in higher applicable flow rates, shorter cycle times. Due to the decreasing volume of porous layer, the loadability of the column dropped significantly. As a result, the productivity and economy of the separation decreases. It is shown that if it is possible to optimize the size of stationary phase particles for the given separation task, the use of core-shell phases are not beneficial. The use of core-shell phases proved to be advantageous when the goal is to build preparative column for general purposes (e.g. for purification of different products) in small scale separations. Copyright © 2015 Elsevier B.V. All rights reserved.

Lower Bound on the Mean Square Displacement of Particles in the Hard Disk Model

NASA Astrophysics Data System (ADS)

Richthammer, Thomas

2016-08-01

The hard disk model is a 2D Gibbsian process of particles interacting via pure hard core repulsion. At high particle density the model is believed to show orientational order, however, it is known not to exhibit positional order. Here we investigate to what extent particle positions may fluctuate. We consider a finite volume version of the model in a box of dimensions 2 n × 2 n with arbitrary boundary configuration, and we show that the mean square displacement of particles near the center of the box is bounded from below by c log n. The result generalizes to a large class of models with fairly arbitrary interaction.

Interrelating the breakage and composition of mined and drill core coal

NASA Astrophysics Data System (ADS)

Wilson, Terril Edward

Particle size distribution of coal is important if the coal is to be beneficiated, or if a coal sales contract includes particle size specifications. An exploration bore core sample of coal ought to be reduced from its original cylindrical form to a particle size distribution and particle composition that reflects, insofar as possible, a process stream of raw coal it represents. Often, coal cores are reduced with a laboratory crushing machine, the product of which does not match the raw coal size distribution. This study proceeds from work in coal bore core reduction by Australian investigators. In this study, as differentiated from the Australian work, drop-shatter impact breakage followed by dry batch tumbling in steel cylinder rotated about its transverse axis are employed to characterize the core material in terms of first-order and zeroth-order breakage rate constants, which are indices of the propensity of the coal to degrade during excavation and handling. Initial drop-shatter and dry tumbling calibrations were done with synthetic cores composed of controlled low-strength concrete incorporating fly ash (as a partial substitute for Portland cement) in order to reduce material variables and conserve difficult-to-obtain coal cores. Cores of three different coalbeds--Illinois No. 6, Upper Freeport, and Pocahontas No. 5 were subjected to drop-shatter and dry batch tumbling tests to determine breakage response. First-order breakage, characterized by a first-order breakage index for each coal, occurred in the drop-shatter tests. First- and zeroth-order breakage occurred in dry batch tumbling; disappearance of coarse particles and creation of fine particles occurred in a systematic way that could be represented mathematically. Certain of the coal cores available for testing were dry and friable. Comparison of coal preparation plant feed with a crushed bore core and a bore core prepared by drop-shatter and tumbling (all from the same Illinois No.6 coal mining property) indicated that the size distribution and size fraction composition of the drop-shattered/tumbled core more closely resembled the plant feed than the crushed core. An attempt to determine breakage parameters (to allow use of selection and breakage functions and population balance models in the description of bore core size reduction) was initiated. Rank determination of the three coal types was done, indicating that higher rank associates with higher breakage propensity. The two step procedure of drop-shatter and dry batch tumbling simulates the first-order (volume breakage) and zeroth-order (abrasion of particle surfaces) that occur in excavation and handling operations, and is appropriate for drill core reduction prior to laboratory analysis.

Tracking Water Diffusion Fronts in a Highly Viscous Aerosol Particle

NASA Astrophysics Data System (ADS)

Bastelberger, Sandra; Krieger, Ulrich; Peter, Thomas

2016-04-01

Field measurements indicate that atmospheric secondary aerosol particles can be present in a highly viscous, glassy state [1]. In contrast to liquid state particles, the gas phase equilibration is kinetically limited and governed by condensed phase diffusion. In recent water diffusion experiments on highly viscous single aerosol particles levitated in an electrodynamic balance (EDB) we observed a characteristic shift behavior of the Mie whispering gallery modes (WGM) indicative of the changing radial structure of the particle, thus providing us with an experimental method to track the diffusion process inside the particle. When a highly viscous, homogeneous particle is exposed to an abrupt increase in relative humidity, the rapid gas phase diffusion and strong concentration dependence of the diffusion coefficient in the condensed phase lead to extremely steep water concentration gradients inside the particle, reminiscent of diffusion fronts. The resulting quasi step-like concentration profile motivates the introduction of a simple core-shell model describing the morphology of the non-equilibrium particle during humidification. The subsequent particle growth and reduction of the shell refractive index can be observed as red and blueshift behavior of the WGM, respectively. The shift pattern can be attributed to a core-shell radius ratio and particle radius derived from model calculations [2]. If supplemented with growth information obtained from the WGM redshift and thermodynamic equilibrium data, we can infer a comprehensive picture of the time evolution of the diffusion fronts in the framework of our core-shell model. The measured time dependent concentration profile is then compared with simulations solving the non-linear diffusion equation [3] [1] Virtanen, A., et al., Nature, 467, 824-827, 2010 [2] Kaiser, T., Schweiger, G., Computers in Physics, Vol. 7, No. 6, 682-686, Nov/Dec 1993 [3] Zobrist, B., Soonsin, V., Luo, B.P., Peter, T. et al., Phys. Chem. Chem. Phys., 13,3514-3526, 2011

Parameter Sensitivity Study of the Unreacted-Core Shrinking Model: A Computer Activity for Chemical Reaction Engineering Courses

ERIC Educational Resources Information Center

Tudela, Ignacio; Bonete, Pedro; Fullana, Andres; Conesa, Juan Antonio

2011-01-01

The unreacted-core shrinking (UCS) model is employed to characterize fluid-particle reactions that are important in industry and research. An approach to understand the UCS model by numerical methods is presented, which helps the visualization of the influence of the variables that control the overall heterogeneous process. Use of this approach in…

Magneto thermal conductivity of superconducting Nb with intermediate level of impurity

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

L.S. Sharath Chandra, M.K. Chattopadhyay, S.B. Roy, V.C. Sahni, G.R. Myneni

2012-03-01

Niobium materials with intermediate purity level are used for fabrication of superconducting radio frequency cavities (SCRF), and thermal conductivity is an important parameter influencing the performance of such SCRF cavities. We report here the temperature and magnetic field dependence of thermal conductivity {kappa} for superconducting niobium (Nb) samples, for which the electron mean free path I{sub e}, the phonon mean free path I{sub g}, and the vortex core diameter 2r{sub C} are of the same order of magnitude. The measured thermal conductivity is analyzed using the effective gap model (developed for I{sub e} >> 2r{sub C} (Dubeck et al 1963more » Phys. Rev. Lett. 10 98)) and the normal core model (developed for I{sub e} << 2r{sub C} (Ward and Dew-Hughes 1970 J. Phys. C: Solid St. Phys. 3 2245)). However, it is found that the effective gap model is not suitable for low temperatures when I{sub e} {approx} 2r{sub C}. The normal core model, on the other hand, is able to describe {kappa}(T,H) over the entire temperature range except in the field regime between H{sub C1} and H{sub C2} i.e. in the mixed state. It is shown that to understand the complete behavior of {kappa} in the mixed state, the scattering of quasi-particles from the vortex cores and the intervortex quasi-particle tunneling are to be invoked. The quasi-particle scattering from vortices for the present system is understood in terms of the framework of Sergeenkov and Ausloos (1995 Phys. Rev. B 52 3614) extending their approach to the case of Nb. The intervortex tunneling is understood within the framework of Schmidbauer et al (1970 Z. Phys. 240 30). Analysis of the field dependence of thermal conductivity shows that while the quasi-particle scattering from vortices dominates in the low fields, the intervortex quasi-particle tunneling dominates in high fields. Analysis of the temperature dependence of thermal conductivity shows that while the quasi-particle scattering is dominant at low temperatures, the intervortex quasi-particle tunneling is dominant at high temperatures.« less

Characterization of the lipid and protein organization in HBsAg viral particles by steady-state and time-resolved fluorescence spectroscopy.

PubMed

Greiner, Vanille J; Egelé, Caroline; Oncul, Sule; Ronzon, Frédéric; Manin, Catherine; Klymchenko, Andrey; Mély, Yves

2010-08-01

Hepatitis B surface antigen (HBsAg) particles, produced in the yeast Hansenula polymorpha, are 20 nm particles, composed of S surface viral proteins and host-derived lipids. Since the detailed structure of these particles is still missing, we further characterized them by fluorescence techniques. Fluorescence correlation spectroscopy indicated that the particles are mainly monomeric, with about 70 S proteins per particle. The S proteins were characterized through the intrinsic fluorescence of their thirteen Trp residues. Fluorescence quenching and time-resolved fluorescence experiments suggest the presence of both low emissive embedded Trp residues and more emissive Trp residues at the surface of the HBsAg particles. The low emission of the embedded Trp residues is consistent with their close proximity in alpha-helices. Furthermore, S proteins exhibit restricted movement, as expected from their tight association with lipids. The lipid organization of the particles was studied using viscosity-sensitive DPH-based probes and environment sensitive 3-hydroxyflavone probes, and compared to lipid vesicles and low density lipoproteins (LDLs), taken as models. Like LDLs, the HBsAg particles were found to be composed of an ordered rigid lipid interface, probably organized as a phospholipid monolayer, and a more hydrophobic and fluid inner core, likely composed of triglycerides and free fatty acids. However, the lipid core of HBsAg particles was substantially more polar than the LDL one, probably due to its larger content in proteins and its lower content in sterols. Based on our data, we propose a structural model for HBsAg particles where the S proteins deeply penetrate into the lipid core. Copyright 2010 Elsevier Masson SAS. All rights reserved.

Acceleration of the Particle Swarm Optimization for Peierls–Nabarro modeling of dislocations in conventional and high-entropy alloys

DOE PAGES

Pei, Zongrui; Max-Planck-Inst. fur Eisenforschung, Duseldorf; Eisenbach, Markus

2017-02-06

Dislocations are among the most important defects in determining the mechanical properties of both conventional alloys and high-entropy alloys. The Peierls-Nabarro model supplies an efficient pathway to their geometries and mobility. The difficulty in solving the integro-differential Peierls-Nabarro equation is how to effectively avoid the local minima in the energy landscape of a dislocation core. Among the other methods to optimize the dislocation core structures, we choose the algorithm of Particle Swarm Optimization, an algorithm that simulates the social behaviors of organisms. By employing more particles (bigger swarm) and more iterative steps (allowing them to explore for longer time), themore » local minima can be effectively avoided. But this would require more computational cost. The advantage of this algorithm is that it is readily parallelized in modern high computing architecture. We demonstrate the performance of our parallelized algorithm scales linearly with the number of employed cores.« less

Development of magnetic luminescent core/shell nanocomplex particles with fluorescence using Rhodamine 6G

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

Lee, Hee Uk; Song, Yoon Seok; Park, Chulhwan

2012-12-15

Graphical abstract: Display Omitted Highlights: ► A simple method was developed to synthesize Co-B/SiO{sub 2}/dye/SiO{sub 2} composite particles. ► The magnetic particle shows that highly luminescent and core/shell particles are formed. ► Such core/shell particles can be easily suspended in water. ► The magnetic particles could detect fluorescence for the application of biosensor. -- Abstract: A simple and reproducible method was developed to synthesize a novel class of Co-B/SiO{sub 2}/dye/SiO{sub 2} composite core/shell particles. Using a single cobalt core, Rhodamine 6G of organic dye molecules was entrapped in a silica shell, resulting in core/shell particles of ∼200 nm diameter. Analysesmore » using a variety of techniques such as transmission electron microscopy, X-ray photoelectron spectroscopy, vibration sample magnetometry, confocal laser scanning microscopy, and fluorescence intensity demonstrated that dye molecules were trapped inside the core/shell particles. A photoluminescence investigation showed that highly luminescent and photostable core/shell particles were formed. Such core/shell particles can be easily suspended in water. The synthesized magnetic particles could be used to detect fluorescence on glass substrate arrays for bioassay and biosensor applications.« less

Facile fabrication of core-in-shell particles by the slow removal of the core and its use in the encapsulation of metal nanoparticles.

PubMed

Choi, Won San; Koo, Hye Young; Kim, Dong-Yu

2008-05-06

Core-in-shell particles with controllable core size have been fabricated from core-shell particles by means of the controlled core-dissolution method. These cores in inorganic shells were employed as scaffolds for the synthesis of metal nanoparticles. After dissolution of the cores, metal nanoparticles embedded in cores were encapsulated into the interior of shell, without any damage or change. This article describes a very simple method for deriving core-in-shell particles with controllable core size and encapsulation of nanoparticles into the interior of shell.

Structures of p -shell double-Λ hypernuclei studied with microscopic cluster models

NASA Astrophysics Data System (ADS)

Kanada-En'yo, Yoshiko

2018-03-01

0 s -orbit Λ states in p -shell double-Λ hypernuclei (Z Λ Λ A ), Li Λ Λ 8 , Li Λ Λ 9 , Be Λ Λ 10 ,11 ,12 , B Λ Λ 12 ,13 , and C Λ Λ 14 are investigated. Microscopic cluster models are applied to core nuclear part and a potential model is adopted for Λ particles. The Λ -core potential is a folding potential obtained with effective G -matrix Λ -N interactions, which reasonably reproduce energy spectra of Z Λ A -1 . System dependence of the Λ -Λ binding energies is understood by the core polarization energy from nuclear size reduction. Reductions of nuclear sizes and E 2 transition strengths by Λ particles are also discussed.

Core-shell microspheres with porous nanostructured shells for liquid chromatography.

PubMed

Ahmed, Adham; Skinley, Kevin; Herodotou, Stephanie; Zhang, Haifei

2018-01-01

The development of new stationary phases has been the key aspect for fast and efficient high-performance liquid chromatography separation with relatively low backpressure. Core-shell particles, with a solid core and porous shell, have been extensively investigated and commercially manufactured in the last decade. The excellent performance of core-shell particles columns has been recorded for a wide range of analytes, covering small and large molecules, neutral and ionic (acidic and basic), biomolecules and metabolites. In this review, we first introduce the advance and advantages of core-shell particles (or more widely known as superficially porous particles) against non-porous particles and fully porous particles. This is followed by the detailed description of various methods used to fabricate core-shell particles. We then discuss the applications of common silica core-shell particles (mostly commercially manufactured), spheres-on-sphere particles and core-shell particles with a non-silica shell. This review concludes with a summary and perspective on the development of stationary phase materials for high-performance liquid chromatography applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two moment dust and water ice in the MarsWRF GCM

NASA Astrophysics Data System (ADS)

Lee, Christopher; Richardson, Mark I.; Newman, Claire E.; Mischna, Michael A.

2016-10-01

A new two moment dust and water ice microphysics scheme has been developed for the MarsWRF General Circulation Model based on the Morrison and Gettelman (2008) scheme, and includes temperature dependent nucleation processes and energetically constrained condensation and evaporation. Dust consumed in the formation of water ice is also tracked by the model.The two moment dust scheme simulates dust particles in the Martian atmosphere using a Gamma distribution with fixed radius for lifted particles. Within the atmosphere the particle distribution is advected and sedimented within the two moment framework, obviating the requirement for lossy conversion between the continuous Gamma distribution and discritized bins found in some Mars microphysics schemes. Water ice is simulated using the same Gamma distribution and advected and sedimented in the same way. Water ice nucleation occurs heterogeneously onto dust particles with temperature dependent contact parameters (e.g. Trainer et al., 2009) and condensation and evaporation follows energetic constraints (e.g. Pruppacher and Klett, 1980; Montmessin et al., 2002) allowing water ice particles to grow in size where necessary. Dust particles are tracked within the ice cores as nucleation occurs, and dust cores advect and sediment along with their parent ice particle distributions. Radiative properties of dust and water particles are calculated as a function of the effective radius of the particles and the distribution width. The new microphysics scheme requires 5 tracers to be tracked as the moments of the dust, water ice, and ice core. All microphysical processes are simulated entirely within the two moment framework without any discretization of particle sizes.The effect of this new microphysics scheme on dust and water ice cloud distribution will be discussed and compared with observations from TES and MCS.

Thermal-Hydraulic Transient Analysis of a Packed Particle Bed Reactor Fuel Element

DTIC Science & Technology

1990-06-01

long fuel elements, arranged to form a core , were analyzed for an up-power transient from 0 MWt to approximately 18 MWt. The simple model significantly...VARIATIONS IN FUEL ELEMENT GEOMETRY ............. 60 4.4 VARIATIONS IN THE MANNER OF TRANSIENT CONTROL ..... 62 4.5 CORE REPRESENTATION BY MULTIPLE FUEL ...the HTGR , however, the PBR packs small fuel particles between inner and outer retention elements, designated as frits. The PBR is appropriate for a

Extension of the XGC code for global gyrokinetic simulations in stellarator geometry

NASA Astrophysics Data System (ADS)

Cole, Michael; Moritaka, Toseo; White, Roscoe; Hager, Robert; Ku, Seung-Hoe; Chang, Choong-Seock

2017-10-01

In this work, the total-f, gyrokinetic particle-in-cell code XGC is extended to treat stellarator geometries. Improvements to meshing tools and the code itself have enabled the first physics studies, including single particle tracing and flux surface mapping in the magnetic geometry of the heliotron LHD and quasi-isodynamic stellarator Wendelstein 7-X. These have provided the first successful test cases for our approach. XGC is uniquely placed to model the complex edge physics of stellarators. A roadmap to such a global confinement modeling capability will be presented. Single particle studies will include the physics of energetic particles' global stochastic motions and their effect on confinement. Good confinement of energetic particles is vital for a successful stellarator reactor design. These results can be compared in the core region with those of other codes, such as ORBIT3d. In subsequent work, neoclassical transport and turbulence can then be considered and compared to results from codes such as EUTERPE and GENE. After sufficient verification in the core region, XGC will move into the stellarator edge region including the material wall and neutral particle recycling.

Bipolarons in one-dimensional extended Peierls-Hubbard models

NASA Astrophysics Data System (ADS)

Sous, John; Chakraborty, Monodeep; Krems, Roman; Berciu, Mona

2017-04-01

We study two particles in an infinite chain and coupled to phonons by interactions that modulate their hopping as described by the Peierls/Su-Schrieffer-Heeger (SSH) model. In the case of hard-core bare particles, we show that exchange of phonons generates effective nearest-neighbor repulsion between particles and also gives rise to interactions that move the pair as a whole. The two-polaron phase diagram exhibits two sharp transitions, leading to light dimers at strong coupling and the flattening of the dimer dispersion at some critical values of the parameters. This dimer (quasi)self-trapping occurs at coupling strengths where single polarons are mobile. On the other hand, in the case of soft-core particles/ spinfull fermions, we show that phonon-mediated interactions are attractive and result in strongly bound and mobile bipolarons in a wide region of parameter space. This illustrates that, depending on the strength of the phonon-mediated interactions and statistics of bare particles, the coupling to phonons may completely suppress or strongly enhance quantum transport of correlated particles. This work was supported by NSERC of Canada and the Stewart Blusson Quantum Matter Institute.

Mechanism of formation and nanostructure of Stöber silica particles

NASA Astrophysics Data System (ADS)

Masalov, V. M.; Sukhinina, N. S.; Kudrenko, E. A.; Emelchenko, G. A.

2011-07-01

The formation of silica nano- and microparticles has been studied during growth by the modified Stöber-Fink-Bohn (SFB) method. It has been experimentally found that the density and fractal structure of particles vary with size as they grow from 70 to 2200 nm. We propose a model of particle structure which is a dense primary particle core and is composed of concentric secondary particle shells terminating in dense primary particle layers.

Seed-Surface Grafting Precipitation Polymerization for Preparing Microsized Optically Active Helical Polymer Core/Shell Particles and Their Application in Enantioselective Crystallization.

PubMed

Zhao, Biao; Lin, Jiangfeng; Deng, Jianping; Liu, Dong

2018-05-14

Core/shell particles constructed by polymer shell and silica core have constituted a significant category of advanced functional materials. However, constructing microsized optically active helical polymer core/shell particles still remains as a big academic challenge due to the lack of effective and universal preparation methods. In this study, a seed-surface grafting precipitation polymerization (SSGPP) strategy is developed for preparing microsized core/shell particles with SiO 2 as core on which helically substituted polyacetylene is covalently bonded as shell. The resulting core/shell particles exhibit fascinating optical activity and efficiently induce enantioselective crystallization of racemic threonine. Taking advantage of the preparation strategy, novel achiral polymeric and hybrid core/shell particles are also expected. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Packing in protein cores

NASA Astrophysics Data System (ADS)

Gaines, J. C.; Clark, A. H.; Regan, L.; O'Hern, C. S.

2017-07-01

Proteins are biological polymers that underlie all cellular functions. The first high-resolution protein structures were determined by x-ray crystallography in the 1960s. Since then, there has been continued interest in understanding and predicting protein structure and stability. It is well-established that a large contribution to protein stability originates from the sequestration from solvent of hydrophobic residues in the protein core. How are such hydrophobic residues arranged in the core; how can one best model the packing of these residues, and are residues loosely packed with multiple allowed side chain conformations or densely packed with a single allowed side chain conformation? Here we show that to properly model the packing of residues in protein cores it is essential that amino acids are represented by appropriately calibrated atom sizes, and that hydrogen atoms are explicitly included. We show that protein cores possess a packing fraction of φ ≈ 0.56 , which is significantly less than the typically quoted value of 0.74 obtained using the extended atom representation. We also compare the results for the packing of amino acids in protein cores to results obtained for jammed packings from discrete element simulations of spheres, elongated particles, and composite particles with bumpy surfaces. We show that amino acids in protein cores pack as densely as disordered jammed packings of particles with similar values for the aspect ratio and bumpiness as found for amino acids. Knowing the structural properties of protein cores is of both fundamental and practical importance. Practically, it enables the assessment of changes in the structure and stability of proteins arising from amino acid mutations (such as those identified as a result of the massive human genome sequencing efforts) and the design of new folded, stable proteins and protein-protein interactions with tunable specificity and affinity.

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages

PubMed Central

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H.; Baer, Donald R.; Smith, Jordan N.; Liu, Chongxuan; Kodali, Vamsi; Thrall, Brian D.; Chen, Shu; Porter, Alexandra E.; Ryan, Mary P.

2015-01-01

Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies. PMID:26178265

Comparison of 20 nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages.

PubMed

Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H; Baer, Donald R; Smith, Jordan N; Liu, Chongxuan; Kodali, Vamsi; Thrall, Brian D; Chen, Shu; Porter, Alexandra E; Ryan, Mary P

2015-09-15

Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies.

Uptake of bright fluorophore core-silica shell nanoparticles by biological systems

PubMed Central

Zane, Andrew; McCracken, Christie; Knight, Deborah A; Young, Tanya; Lutton, Anthony D; Olesik, John W; Waldman, W James; Dutta, Prabir K

2015-01-01

Nanoparticles are used in a variety of consumer applications. Silica nanoparticles in particular are common, including as a component of foods. There are concerns that ingested nano-silica particles can cross the intestinal epithelium, enter the circulation, and accumulate in tissues and organs. Thus, tracking these particles is of interest, and fluorescence spectroscopic methods are well-suited for this purpose. However, nanosilica is not fluorescent. In this article, we focus on core-silica shell nanoparticles, using fluorescent Rhodamine 6G, Rhodamine 800, or CdSe/CdS/ZnS quantum dots as the core. These stable fluorophore/silica nanoparticles had surface characteristics similar to those of commercial silica particles. Thus, they were used as model particles to examine internalization by cultured cells, including an epithelial cell line relevant to the gastrointestinal tract. Finally, these particles were administered to mice by gavage, and their presence in various organs, including stomach, small intestine, cecum, colon, kidney, lung, brain, and spleen, was examined. By combining confocal fluorescence microscopy with inductively coupled plasma mass spectrometry, the presence of nanoparticles, rather than their dissolved form, was established in liver tissues. PMID:25759579

Fused-core particle technology as an alternative to sub-2-microm particles to achieve high separation efficiency with low backpressure.

PubMed

Cunliffe, Jennifer M; Maloney, Todd D

2007-12-01

Fused-Core particles have recently been introduced as an alternative to using sub-2-microm particles in chromatographic separations. Fused-Core particles are composed of a 1.7 microm solid core surrounded by a 0.5 microm porous silica layer (d(p) = 2.7 microm) to reduce mass transfer and increase peak efficiency. The performance of two commercially available Fused-Core particles (Advanced Materials Technology Halo C18 and Supelco Ascentis Express C18) was compared with sub-2-microm particles from Waters, Agilent, and Thermo Scientific. Although the peak efficiencies were only approximately 80% of those obtained by the Waters Acquity particles, the 50% lower backpressure allowed columns to be coupled in series to increase peak efficiency to 92,750 plates. The low backpressure and high efficiencies of the Fused-Core particles offer a viable alternative to using sub-2-microm particles and very-high-pressure LC instrumentation.

Entrapment of carbon dioxide with chitosan-based core-shell particles containing changeable cores.

PubMed

Dong, Yanrui; Fu, Yinghao; Lin, Xia; Xiao, Congming

2016-08-01

Water-soluble chitosan-based core-shell particles that contained changeable cores were successfully applied to anchor carbon dioxide. The entrapment capacity of the particles for carbon dioxide (EC) depended on the cores. It was found that EC of the particles contained aqueous cores was higher than that of the beads with water-soluble chitosan gel cores, which was confirmed with thermogravimetric analysis. In addition, calcium ions and sodium hydroxide were introduced within the particles to examine their effect on the entrapment. EC of the particles was enhanced with sodium hydroxide when the cores were WSC gel. The incorporation of calcium ions was helpful for stabilizing carbon dioxide through the formation of calcium carbonate, which was verified with Fourier transform infrared spectra and scanning electron microscopy/energy-dispersive spectrometry. This phenomenon meant the role of calcium ions for fixating carbon dioxide was significant. Copyright © 2016 Elsevier B.V. All rights reserved.

High-lying single-particle modes, chaos, correlational entropy, and doubling phase transition

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

Stoyanov, Chavdar; Zelevinsky, Vladimir

Highly excited single-particle states in nuclei are coupled with the excitations of a more complex character, first of all with collective phononlike modes of the core. In the framework of the quasiparticle-phonon model, we consider the structure of resulting complex configurations, using the 1k{sub 17/2} orbital in {sup 209}Pb as an example. Although, on the level of one- and two-phonon admixtures, the fully chaotic Gaussian orthogonal ensemble regime is not reached, the eigenstates of the model carry a significant degree of complexity that can be quantified with the aid of correlational invariant entropy. With artificially enhanced particle-core coupling, the systemmore » undergoes the doubling phase transition with the quasiparticle strength concentrated in two repelling peaks. This phase transition is clearly detected by correlational entropy.« less

Deleterious Thermal Effects Due To Randomized Flow Paths in Pebble Bed, and Particle Bed Style Reactors

NASA Technical Reports Server (NTRS)

Moran, Robert P.

2013-01-01

A review of literature associated with Pebble Bed and Particle Bed reactor core research has revealed a systemic problem inherent to reactor core concepts which utilize randomized rather than structured coolant channel flow paths. For both the Pebble Bed and Particle Bed Reactor designs; case studies reveal that for indeterminate reasons, regions within the core would suffer from excessive heating leading to thermal runaway and localized fuel melting. A thermal Computational Fluid Dynamics model was utilized to verify that In both the Pebble Bed and Particle Bed Reactor concepts randomized coolant channel pathways combined with localized high temperature regions would work together to resist the flow of coolant diverting it away from where it is needed the most to cooler less resistive pathways where it is needed the least. In other words given the choice via randomized coolant pathways the reactor coolant will take the path of least resistance, and hot zones offer the highest resistance. Having identified the relationship between randomized coolant channel pathways and localized fuel melting it is now safe to assume that other reactor concepts that utilize randomized coolant pathways such as the foam core reactor are also susceptible to this phenomenon.

Changes of ns-soot mixing states and shapes in an urban area during CalNex

NASA Astrophysics Data System (ADS)

Adachi, Kouji; Buseck, Peter R.

2013-05-01

Aerosol particles from megacities influence the regional and global climate as well as the health of their occupants. We used transmission electron microscopes (TEMs) to study aerosol particles collected from the Los Angeles area during the 2010 CalNex campaign. We detected major amounts of ns-soot, defined as consisting of carbon nanospheres, sulfate, sea salt, and organic aerosol (OA) and lesser amounts of brochosome particles from leaf hoppers. Ns-soot-particle shapes, mixing states, and abundances varied significantly with sampling times and days. Within plumes having high CO2 concentrations, much ns-soot was compacted and contained a relatively large number of carbon nanospheres. Ns-soot particles from both CalNex samples and Mexico City, the latter collected in 2006, had a wide range of shapes when mixed with other aerosol particles, but neither sets showed spherical ns-soot nor the core-shell configuration that is commonly used in optical calculations. Our TEM observations and light-absorption calculations of modeled particles indicate that, in contrast to ns-soot particles that are embedded within other materials or have the hypothesized core-shell configurations, those attached to other aerosol particles hardly enhance their light absorption. We conclude that the ways in which ns-soot mixes with other particles explain the observations of smaller light amplification by ns-soot coatings than model calculations during the CalNex campaign and presumably in other areas.

Core protein cleavage by signal peptide peptidase is required for hepatitis C virus-like particle assembly

PubMed Central

Ait-Goughoulte, Malika; Hourioux, Christophe; Patient, Romuald; Trassard, Sylvie; Brand, Denys; Roingeard, Philippe

2006-01-01

SUMMARY Hepatitis C virus (HCV) core protein, expressed with a Semliki forest virus (SFV) replicon, self-assembles into HCV-like particles (HCV-LP) at the endoplasmic reticulum (ER) membrane, providing an opportunity to study HCV assembly and morphogenesis by electron microscopy. We used this model to investigate whether the processing of the HCV core protein by the signal peptide peptidase (SPP) is required for the HCV-LP assembly. We designed several mutants as there are conflicting reports concerning the cleavage of mutant proteins by SPP. Production of the only core mutant protein that escaped SPP processing led to the formation of multiple layers of electron-dense ER membrane, with no evidence of HCV-LP assembly. Our data shed light on the HCV core residues involved in SPP cleavage and suggest that this cleavage is essential for HCV assembly. PMID:16528035

Stress relaxation in pre-stressed aluminum core–shell particles: X-ray diffraction study, modeling, and improved reactivity

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

Levitas, Valery I.; McCollum, Jena; Pantoya, Michelle L.

Stress relaxation in aluminum micron-scale particles covered by alumina shell after pre-stressing by thermal treatment and storage was measured using X-ray diffraction with synchrotron radiation. Pre-stressing was produced by annealing Al particles at 573K followed by fast cooling. While averaged dilatational strain in Al core was negligible for untreated particles, it was measured at 4.40×10 -5 and 2.85×10 -5 after 2 and 48 days of storage. Consistently, such a treatment leads to increase in flame propagation speed for Al+CuO mixture by 37% and 25%, respectively. Analytical model for creep in alumna shell and stress relaxation in Al core-alumina shellmore » structure is developed and activation energy and pre-exponential multiplier are estimated. The effect of storage temperature and annealing temperature on the kinetics of stress relaxation was evaluated theoretically. These results provide estimates for optimizing Al reactivity with the holding time at annealing temperature and allowable time for storage of Al particles for various environmental temperatures.« less

Stress relaxation in pre-stressed aluminum core–shell particles: X-ray diffraction study, modeling, and improved reactivity

DOE PAGES

Levitas, Valery I.; McCollum, Jena; Pantoya, Michelle L.; ...

2016-05-30

Stress relaxation in aluminum micron-scale particles covered by alumina shell after pre-stressing by thermal treatment and storage was measured using X-ray diffraction with synchrotron radiation. Pre-stressing was produced by annealing Al particles at 573K followed by fast cooling. While averaged dilatational strain in Al core was negligible for untreated particles, it was measured at 4.40×10 -5 and 2.85×10 -5 after 2 and 48 days of storage. Consistently, such a treatment leads to increase in flame propagation speed for Al+CuO mixture by 37% and 25%, respectively. Analytical model for creep in alumna shell and stress relaxation in Al core-alumina shellmore » structure is developed and activation energy and pre-exponential multiplier are estimated. The effect of storage temperature and annealing temperature on the kinetics of stress relaxation was evaluated theoretically. These results provide estimates for optimizing Al reactivity with the holding time at annealing temperature and allowable time for storage of Al particles for various environmental temperatures.« less

Verification of Electromagnetic Physics Models for Parallel Computing Architectures in the GeantV Project

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

Amadio, G.; et al.

An intensive R&D and programming effort is required to accomplish new challenges posed by future experimental high-energy particle physics (HEP) programs. The GeantV project aims to narrow the gap between the performance of the existing HEP detector simulation software and the ideal performance achievable, exploiting latest advances in computing technology. The project has developed a particle detector simulation prototype capable of transporting in parallel particles in complex geometries exploiting instruction level microparallelism (SIMD and SIMT), task-level parallelism (multithreading) and high-level parallelism (MPI), leveraging both the multi-core and the many-core opportunities. We present preliminary verification results concerning the electromagnetic (EM) physicsmore » models developed for parallel computing architectures within the GeantV project. In order to exploit the potential of vectorization and accelerators and to make the physics model effectively parallelizable, advanced sampling techniques have been implemented and tested. In this paper we introduce a set of automated statistical tests in order to verify the vectorized models by checking their consistency with the corresponding Geant4 models and to validate them against experimental data.« less

Influence of Shell Thickness on the Colloidal Stability of Magnetic Core-Shell Particle Suspensions

PubMed Central

Neville, Frances; Moreno-Atanasio, Roberto

2018-01-01

We present a Discrete Element study of the behavior of magnetic core-shell particles in which the properties of the core and the shell are explicitly defined. Particle cores were considered to be made of pure iron and thus possessed ferromagnetic properties, while particle shells were considered to be made of silica. Core sizes ranged between 0.5 and 4.0 μm with the actual particle size of the core-shell particles in the range between 0.6 and 21 μm. The magnetic cores were considered to have a magnetization of one tenth of the saturation magnetization of iron. This study aimed to understand how the thickness of the shell hinders the formation of particle chains. Chain formation was studied with different shell thicknesses and particle sizes in the presence and absence of an electrical double layer force in order to investigate the effect of surface charge density on the magnetic core-shell particle interactions. For core sizes of 0.5 and 4.0 μm the relative shell thicknesses needed to hinder the aggregation process were approximately 0.4 and 0.6 respectively, indicating that larger core sizes are detrimental to be used in applications in which no flocculation is needed. In addition, the presence of an electrical double layer, for values of surface charge density of less than 20 mC/m2, could stop the contact between particles without hindering their vertical alignment. Only when the shell thickness was considerably larger, was the electrical double layer able to contribute to the full disruption of the magnetic flocculation process. PMID:29922646

Influence of Shell Thickness on the Colloidal Stability of Magnetic Core-Shell Particle Suspensions.

PubMed

Neville, Frances; Moreno-Atanasio, Roberto

2018-01-01

We present a Discrete Element study of the behavior of magnetic core-shell particles in which the properties of the core and the shell are explicitly defined. Particle cores were considered to be made of pure iron and thus possessed ferromagnetic properties, while particle shells were considered to be made of silica. Core sizes ranged between 0.5 and 4.0 μm with the actual particle size of the core-shell particles in the range between 0.6 and 21 μm. The magnetic cores were considered to have a magnetization of one tenth of the saturation magnetization of iron. This study aimed to understand how the thickness of the shell hinders the formation of particle chains. Chain formation was studied with different shell thicknesses and particle sizes in the presence and absence of an electrical double layer force in order to investigate the effect of surface charge density on the magnetic core-shell particle interactions. For core sizes of 0.5 and 4.0 μm the relative shell thicknesses needed to hinder the aggregation process were approximately 0.4 and 0.6 respectively, indicating that larger core sizes are detrimental to be used in applications in which no flocculation is needed. In addition, the presence of an electrical double layer, for values of surface charge density of less than 20 mC/m 2 , could stop the contact between particles without hindering their vertical alignment. Only when the shell thickness was considerably larger, was the electrical double layer able to contribute to the full disruption of the magnetic flocculation process.

Preparation and characterization of SiO2-coated submicron-sized L10 Fe-Pt particles

NASA Astrophysics Data System (ADS)

Hayashi, Yoshiaki; Ogawa, Tomoyuki; Ishiyama, Kazushi

2018-05-01

The development of magnets with higher performance is attracting increasing interest. The optimization of their microstructure is essential to enhance their properties, and a microstructure comprising magnetically isolated hard magnetic grains of a single-domain size has been proposed as an ideal structure for enhancing the coercivity of magnets. To obtain magnets with an ideal structure, we consider the fabrication of magnets by an approach based on core/shell nanoparticles with a hard magnetic core and a non-magnetic shell. In this study, to obtain particles for our proposed approach, we attempted to fabricate L10 Fe-Pt/SiO2-core/shell particles with submicron-sized cores less than the critical single-domain size. The fabrication of such core/shell particles was confirmed from morphology observations and XRD analysis of the particles. Although the formation of more desirable core/shell particles with submicron-sized single-crystal cores in the single-domain size range was not achieved, the fabricated core/shell particles showed a high coercivity of 25 kOe.

Particle bed reactor modeling

NASA Technical Reports Server (NTRS)

Sapyta, Joe; Reid, Hank; Walton, Lew

1993-01-01

The topics are presented in viewgraph form and include the following: particle bed reactor (PBR) core cross section; PBR bleed cycle; fuel and moderator flow paths; PBR modeling requirements; characteristics of PBR and nuclear thermal propulsion (NTP) modeling; challenges for PBR and NTP modeling; thermal hydraulic computer codes; capabilities for PBR/reactor application; thermal/hydralic codes; limitations; physical correlations; comparison of predicted friction factor and experimental data; frit pressure drop testing; cold frit mask factor; decay heat flow rate; startup transient simulation; and philosophy of systems modeling.

Ice Particle Transport Analysis With Phase Change for the E(sup 3) Turbofan Engine Using LEWICE3D Version 3.2

NASA Technical Reports Server (NTRS)

Bidwell, Colin, S.

2012-01-01

Ice Particle trajectory calculations with phase change were made for the Energy Efficient Engine (E(sup 3)) using the LEWICE3D Version 3.2 software. The particle trajectory computations were performed using the new Glenn Ice Particle Phase Change Model which has been incorporated into the LEWICE3D Version 3.2 software. The E(sup 3) was developed by NASA and GE in the early 1980 s as a technology demonstrator and is representative of a modern high bypass turbofan engine. The E(sup 3) flow field was calculated using the NASA Glenn ADPAC turbomachinery flow solver. Computations were performed for the low pressure compressor of the E(sup 3) for a Mach 0.8 cruise condition at 11,887 m assuming a standard warm day for ice particle sizes of 5, 20, and 100 microns and a free stream particle concentration of 0.3 g/cu m. The impingement efficiency results showed that as particle size increased average impingement efficiencies and scoop factors increased for the various components. The particle analysis also showed that the amount of mass entering the inner core decreased with increased particle size because the larger particles were less able to negotiate the turn into the inner core due to particle inertia. The particle phase change analysis results showed that the larger particles warmed less as they were transported through the low pressure compressor. Only the smallest 5 micron particles were warmed enough to produce melting and the amount of melting was relatively small with a maximum average melting fraction of 0.836. The results also showed an appreciable amount of particle sublimation and evaporation for the 5 micron particles entering the engine core (22 percent).

Characterization of core–shell MOF particles by depth profiling experiments using on-line single particle mass spectrometry

DOE PAGES

Cahill, J. F.; Fei, H.; Cohen, S. M.; ...

2015-01-05

Materials with core-shell structures have distinct properties that lend themselves to a variety of potential applications. Characterization of small particle core-shell materials presents a unique analytical challenge. Herein, single particles of solid-state materials with core-shell structures were measured using on-line aerosol time-of-flight mass spectrometry (ATOFMS). Laser 'depth profiling' experiments verified the core-shell nature of two known core-shell particle configurations (< 2 mu m diameter) that possessed inverted, complimentary core-shell compositions (ZrO2@SiO2 versus SiO2@ZrO2). The average peak area ratios of Si and Zr ions were calculated to definitively show their core-shell composition. These ratio curves acted as a calibrant for anmore » uncharacterized sample - a metal-organic framework (MOF) material surround by silica (UiO-66(Zr)@SiO2; UiO = University of Oslo). ATOFMS depth profiling was used to show that these particles did indeed exhibit a core-shell architecture. The results presented here show that ATOFMS can provide unique insights into core-shell solid-state materials with particle diameters between 0.2-3 mu m.« less

Identifying a New Mechanism of HIV Core Formation | Center for Cancer Research

Cancer.gov

During the maturation of human immunodeficiency virus 1 (HIV-1), viral particles transition from a noninfectious form to an infectious one, and this conversion requires the cleavage of the HIV-1 Gag polyprotein. Gag is made up of three structural proteins—matrix (MA), capsid (CA), and nucleocapsid (NC)—connected by linkers. MA anchors Gag in the membrane, CA surrounds the HIV-1 core, and NC packages the viral RNA within the core. Current models of the development of HIV-1 suggest that when CA is cleaved from Gag it dissociates from the membrane and moves into the virus interior before nucleating, in a concentration-dependent manner, into the core, which is the last step in virus maturation. The core is thought to grow from its narrow end stopping only when it reaches the opposite side of the virus membrane. Since blocking the formation of infectious viral particles is an important therapeutic strategy, it is critical to understand the detailed mechanism of core maturation.

A novel approach to a fine particle coating using porous spherical silica as core particles.

PubMed

Ishida, Makoto; Uchiyama, Jumpei; Isaji, Keiko; Suzuki, Yuta; Ikematsu, Yasuyuki; Aoki, Shigeru

2014-08-01

Abstract The applicability of porous spherical silica (PSS) was evaluated as core particles for pharmaceutical products by comparing it with commercial core particles such as mannitol (NP-108), sucrose and microcrystalline cellulose spheres. We investigated the physical properties of core particles, such as particle size distribution, flow properties, crushing strength, plastic limit, drying rate, hygroscopic property and aggregation degree. It was found that PSS was a core particle of small particle size, low friability, high water adsorption capacity, rapid drying rate and lower occurrence of particle aggregation, although wettability is a factor to be carefully considered. The aggregation and taste-masking ability using PSS and NP-108 as core particles were evaluated at a fluidized-bed coating process. The functional coating under the excess spray rate shows different aggregation trends and dissolution profiles between PSS and NP-108; thereby, exhibiting the formation of uniform coating under the excess spray rate in the case of PSS. This expands the range of the acceptable spray feed rates to coat fine particles, and indicates the possibility of decreasing the coating time. The results obtained in this study suggested that the core particle, which has a property like that of PSS, was useful in overcoming such disadvantages as large particle size, which feels gritty in oral cavity; particle aggregation; and the long coating time of the particle coating process. These results will enable the practical fine particle coating method by increasing the range of optimum coating conditions and decreasing the coating time in fluidized bed technology.

Practical comparison of 2.7 microm fused-core silica particles and porous sub-2 microm particles for fast separations in pharmaceutical process development.

PubMed

Abrahim, Ahmed; Al-Sayah, Mohammad; Skrdla, Peter; Bereznitski, Yuri; Chen, Yadan; Wu, Naijun

2010-01-05

Fused-core silica stationary phases represent a key technological advancement in the arena of fast HPLC separations. These phases are made by fusing a 0.5 microm porous silica layer onto 1.7 microm nonporous silica cores. The reduced intra-particle flow path of the fused particles provides superior mass transfer kinetics and better performance at high mobile phase velocities, while the fused-core particles provide lower pressure than sub-2 microm particles. In this work, chromatographic performance of the fused-core particles (Ascentis Express) was investigated and compared to that of sub-2 microm porous particles (1.8 microm Zorbax Eclipse Plus C18 and 1.7 microm Acquity BEH C18). Specifically, retention, selectivity, and loading capacity were systematically compared for these two types of columns. Other chromatographic parameters such as efficiency and pressure drop were also studied. Although the fused-core column was found to provide better analyte shape selectivity, both columns had similar hydrophobic, hydrogen bonding, total ion-exchange, and acidic ion-exchange selectivities. As expected, the retention factors and sample loading capacity on the fused-core particle column were slightly lower than those for the sub-2 microm particle column. However, the most dramatic observation was that similar efficiency separations to the sub-2 microm particles could be achieved using the fused-core particles, without the expense of high column back pressure. The low pressure of the fused-core column allows fast separations to be performed routinely on a conventional LC system without significant loss in efficiency or resolution. Applications to the HPLC impurity profiling of drug substance candidates were performed using both types of columns to validate this last point.

Control of particle and power exhaust in pellet fuelled ITER DT scenarios employing integrated models

NASA Astrophysics Data System (ADS)

Wiesen, S.; Köchl, F.; Belo, P.; Kotov, V.; Loarte, A.; Parail, V.; Corrigan, G.; Garzotti, L.; Harting, D.

2017-07-01

The integrated model JINTRAC is employed to assess the dynamic density evolution of the ITER baseline scenario when fuelled by discrete pellets. The consequences on the core confinement properties, α-particle heating due to fusion and the effect on the ITER divertor operation, taking into account the material limitations on the target heat loads, are discussed within the integrated model. Using the model one can observe that stable but cyclical operational regimes can be achieved for a pellet-fuelled ITER ELMy H-mode scenario with Q  =  10 maintaining partially detached conditions in the divertor. It is shown that the level of divertor detachment is inversely correlated with the core plasma density due to α-particle heating, and thus depends on the density evolution cycle imposed by pellet ablations. The power crossing the separatrix to be dissipated depends on the enhancement of the transport in the pedestal region being linked with the pressure gradient evolution after pellet injection. The fuelling efficacy of the deposited pellet material is strongly dependent on the E  ×  B plasmoid drift. It is concluded that integrated models like JINTRAC, if validated and supported by realistic physics constraints, may help to establish suitable control schemes of particle and power exhaust in burning ITER DT-plasma scenarios.

Design of Aerosol Coating Reactors: Precursor Injection

PubMed Central

Buesser, Beat; Pratsinis, Sotiris E.

2013-01-01

Particles are coated with thin shells to facilitate their processing and incorporation into liquid or solid matrixes without altering core particle properties (coloristic, magnetic, etc.). Here, computational fluid and particle dynamics are combined to investigate the geometry of an aerosol reactor for continuous coating of freshly-made titanium dioxide core nanoparticles with nanothin silica shells by injection of hexamethyldisiloxane (HMDSO) vapor downstream of TiO2 particle formation. The focus is on the influence of HMDSO vapor jet number and direction in terms of azimuth and inclination jet angles on process temperature and coated particle characteristics (shell thickness and fraction of uncoated particles). Rapid and homogeneous mixing of core particle aerosol and coating precursor vapor facilitates synthesis of core-shell nanoparticles with uniform shell thickness and high coating efficiency (minimal uncoated core and free coating particles). PMID:23658471

Molecular Dynamics Studies of Overbased Detergents on a Water Surface.

PubMed

Bodnarchuk, M S; Dini, D; Heyes, D M; Breakspear, A; Chahine, S

2017-07-25

Molecular dynamics (MD) simulations are reported of model overbased detergent nanoparticles on a model water surface which mimic their behavior on a Langmuir trough or large water droplet in engine oil. The simulations predict that the structure of the nanoparticle on a water surface is different to when it is immersed in a bulk hydrophobic solvent. The surfactant tails are partly directed out of the water, while the carbonate core maximizes its extent of contact with the water. Umbrella sampling calculations of the potential of mean force between two particles showed that they are associated with varying degrees with a maximum binding free energy of ca. 10 k B T for the salicylate stabilized particle, ca. 8 k B T for a sulfurized alkyl phenate stabilized particle, and ca. 5 k B T for a sulfonate stabilized particle. The differences in the strength of attraction depend on the proximity of nearest approach and the energy penalty associated with the disruption of the hydration shell of water molecules around the calcium carbonate core when the two particles approach. This is greatest for the sulfonate particle, which partially loses the surfactant ions to the solution, and least for the salicylate, which forms the weakest water "cage". The particles are separated by a water hydration layer, even at the point of closest approach.

Space charge induced resonance excitation in high intensity rings

NASA Astrophysics Data System (ADS)

Cousineau, S.; Lee, S. Y.; Holmes, J. A.; Danilov, V.; Fedotov, A.

2003-03-01

We present a particle core model study of the space charge effect on high intensity synchrotron beams, with specific emphasis on the Proton Storage Ring (PSR) at Los Alamos National Laboratory. Our particle core model formulation includes realistic lattice focusing and dispersion. We transport both matched and mismatched beams through real lattice structure and compare the results with those of an equivalent uniform-focusing approximation. The effects of lattice structure and finite momentum spread on the resonance behavior are specifically targeted. Stroboscopic maps of the mismatched envelope are constructed and show high-order resonances and stochastic effects that dominate at high mismatch or high intensity. We observe the evolution of the envelope phase-space structure during a high intensity PSR beam accumulation. Finally, we examine the envelope-particle parametric resonance condition and discuss the possibility for halo growth in synchrotron beams due to this mechanism.

Large enhanced dielectric permittivity in polyaniline passivated core-shell nano magnetic iron oxide by plasma polymerization

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

Joy, Lija K.; Sooraj, V.; Sethulakshmi, N.

2014-03-24

Commercial samples of Magnetite with size ranging from 25–30 nm were coated with polyaniline by using radio frequency plasma polymerization to achieve a core shell structure of magnetic nanoparticle (core)–Polyaniline (shell). High resolution transmission electron microscopy images confirm the core shell architecture of polyaniline coated iron oxide. The dielectric properties of the material were studied before and after plasma treatment. The polymer coated magnetite particles exhibited a large dielectric permittivity with respect to uncoated samples. The dielectric behavior was modeled using a Maxwell–Wagner capacitor model. A plausible mechanism for the enhancement of dielectric permittivity is proposed.

Adsorption of hairy particles with mobile ligands: Molecular dynamics and density functional study

NASA Astrophysics Data System (ADS)

Borówko, M.; Sokołowski, S.; Staszewski, T.; Pizio, O.

2018-01-01

We study models of hairy nanoparticles in contact with a hard wall. Each particle is built of a spherical core with a number of ligands attached to it and each ligand is composed of several spherical, tangentially jointed segments. The number of segments is the same for all ligands. Particular models differ by the numbers of ligands and of segments per ligand, but the total number of segments is constant. Moreover, our model assumes that the ligands are tethered to the core in such a manner that they can "slide" over the core surface. Using molecular dynamics simulations we investigate the differences in the structure of a system close to the wall. In order to characterize the distribution of the ligands around the core, we have calculated the end-to-end distances of the ligands and the lengths and orientation of the mass dipoles. Additionally, we also employed a density functional approach to obtain the density profiles. We have found that if the number of ligands is not too high, the proposed version of the theory is capable to predict the structure of the system with a reasonable accuracy.

Energetic ion leakage from foreshock transient cores

NASA Astrophysics Data System (ADS)

Liu, Terry Z.; Angelopoulos, Vassilis; Hietala, Heli

2017-07-01

Earth's foreshock is filled with backstreaming particles that can interact with the ambient solar wind and its discontinuities to form foreshock transients. Many foreshock transients have a core with low dynamic pressure that can significantly perturb the bow shock and the magnetosphere-ionosphere system. Foreshock transients have also been recently recognized as sites of particle acceleration, which may be important for seeding the parent shock with energetic particles. A relevant step of this seeding would be energetic ion leakage into the surrounding foreshock environment. On the other hand, such leakage would also suppress the energetic particle flux contrast across foreshock transients' boundaries masking their perceived contribution to ion energization. To further examine this hypothesis of ion leakage, we report on multipoint case studies of three foreshock transient events selected from a large database. The cases were selected to exemplify, in increasing complexity, the nature and consequences of energetic ion leakage. Ion energy dispersion, observed upstream and/or downstream of the foreshock transients, is explained with a simple, ballistic model of ions leaking from the foreshock transients. Larger energies are required for leaked ions to reach the spacecraft as the distance between the transient and spacecraft increases. Our model, which explains well the observed ion energy dispersion and velocity distributions, can also be used to reveal the shape of the foreshock transients in three dimensions. Our results suggest that ion leakage from foreshock transient cores needs to be accounted for both in statistical studies and in global models of ion acceleration under quasi-parallel foreshock conditions.

GRAVITATIONAL ACCRETION OF PARTICLES ONTO MOONLETS EMBEDDED IN SATURN's RINGS

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

Yasui, Yuki; Ohtsuki, Keiji; Daisaka, Hiroshi, E-mail: y.yasui@whale.kobe-u.ac.jp, E-mail: ohtsuki@tiger.kobe-u.ac.jp

2014-12-20

Using a local N-body simulation, we examine gravitational accretion of ring particles onto moonlet cores in Saturn's rings. We find that gravitational accretion of particles onto moonlet cores is unlikely to occur in the C ring and probably difficult in the inner B ring as well provided that the cores are rigid water ice. Dependence of particle accretion on ring thickness changes when the radial distance from the planet and/or the density of particles is varied: the former determines the size of the core's Hill radius relative to its physical size, while the latter changes the effect of self-gravity ofmore » accreted particles. We find that particle accretion onto high-latitude regions of the core surface can occur even if the rings' vertical thickness is much smaller than the core radius, although redistribution of particles onto the high-latitude regions would not be perfectly efficient in outer regions of the rings such as the outer A ring, where the size of the core's Hill sphere in the vertical direction is significantly larger than the core's physical radius. Our results suggest that large boulders recently inferred from observations of transparent holes in the C ring are not formed locally by gravitational accretion, while propeller moonlets in the A ring would be gravitational aggregates formed by particle accretion onto dense cores. Our results also imply that the main bodies of small satellites near the outer edge of Saturn's rings may have been formed in rather thin rings.« less

Fabrication of sub-micrometer-sized jingle bell-shaped hollow spheres from multilayered core-shell particles.

PubMed

Gu, Shunchao; Kondo, Tomohiro; Mine, Eiichi; Nagao, Daisuke; Kobayashi, Yoshio; Konno, Mikio

2004-11-01

Jingle bell-shaped hollow spheres were fabricated starting from multilayered particles composed of a silica core, a polystyrene inner shell, and a titania outer shell. Composite particles of silica core-polystyrene shell, synthesized by coating a 339-nm-sized silica core with a polystyrene shell of thickness 238 nm in emulsion polymerization, were used as core particles for a succeeding titania-coating. A sol-gel method was employed to form the titania outer shell with a thickness of 37 nm. The inner polystyrene shell in the multilayered particles was removed by immersing them in tetrahydrofuran. These successive procedures could produce jingle bell-shaped hollow spheres that contained a silica core in the titania shell.

Folic acid-functionalized magnetic ZnFe2O4 hollow microsphere core/mesoporous silica shell composite particles: synthesis and application in drug release.

PubMed

Yang, Dandan; Wei, Kaiwei; Liu, Qi; Yang, Yong; Guo, Xue; Rong, Hongren; Cheng, Mei-Ling; Wang, Guoxiu

2013-07-01

A drug delivery system was designed by deliberately combining the useful functions into one entity, which was composed of magnetic ZnFe2O4 hollow microsphere as the core, and mesoporous silica with folic acid molecules as the outer shell. Amine groups coated magnetic ZnFe2O4 hollow microsphere core/mesoporous silica shell (MZHM-MSS-NH2) composite particles were first synthesized by a one-pot direct co-condensation method. Subsequently a novel kind of folic acid-functionalized magnetic ZnFe2O4 hollow microsphere core/mesoporous silica shell (MZHM-MSS-NHFA) composite particles were synthesized by conjugating folic acid as targeted molecule to MZHM-MSS-NH2. Ibuprofen, a well-known antiphlogistic drug, was used as a model drug to assess the loading and releasing behavior of the composite microspheres. The results show that the MZHM-MSS-NHFA system has the higher capacity of drug storage and good sustained drug-release property. Copyright © 2013 Elsevier B.V. All rights reserved.

Combined synthesis and in situ coating of nanoparticles in the gas phase

NASA Astrophysics Data System (ADS)

Lähde, Anna; Raula, Janne; Kauppinen, Esko I.

2008-12-01

Combined gas phase synthesis and coating of sodium chloride (NaCl) and lactose nanoparticles has been developed using an aerosol flow reactor. Nano-sized core particles were produced by the droplet-to-particle method and coated in situ by the physical vapour deposition of L-leucine vapour. The saturation of L-leucine in the reactor determined the resulting particle size and size distribution. In general, particle size increased with the addition of L-leucine and notable narrowing of the core particle size distribution was observed. In addition, homogeneous nucleation of the vapour, i.e. formation of pure L-leucine particles, was observed depending on the saturation conditions of L-leucine as well as the core particle characteristics. The effects of core particle properties, i.e. size and solid-state characteristics, on the coating process were studied by comparing the results for coated NaCl and lactose particles. During deposition, L-leucine formed a uniform coating on the surface of the core particles. The coating stabilised the nanoparticles and prevented the sintering of particles during storage.

Optimization and design of pigments for heat-insulating coatings

NASA Astrophysics Data System (ADS)

Wang, Guang-Hai; Zhang, Yue

2010-12-01

This paper reports that heat insulating property of infrared reflective coatings is obtained through the use of pigments which diffuse near-infrared thermal radiation. Suitable structure and size distribution of pigments would attain maximum diffuse infrared radiation and reduce the pigment volume concentration required. The optimum structure and size range of pigments for reflective infrared coatings are studied by using Kubelka—Munk theory, Mie model and independent scattering approximation. Taking titania particle as the pigment embedded in an inorganic coating, the computational results show that core-shell particles present excellent scattering ability, more so than solid and hollow spherical particles. The optimum radius range of core-shell particles is around 0.3 ~ 1.6 μm. Furthermore, the influence of shell thickness on optical parameters of the coating is also obvious and the optimal thickness of shell is 100-300 nm.

Modelling the optical properties of aerosols in a chemical transport model

NASA Astrophysics Data System (ADS)

Andersson, E.; Kahnert, M.

2015-12-01

According to the IPCC fifth assessment report (2013), clouds and aerosols still contribute to the largest uncertainty when estimating and interpreting changes to the Earth's energy budget. Therefore, understanding the interaction between radiation and aerosols is both crucial for remote sensing observations and modelling the climate forcing arising from aerosols. Carbon particles are the largest contributor to the aerosol absorption of solar radiation, thereby enhancing the warming of the planet. Modelling the radiative properties of carbon particles is a hard task and involves many uncertainties arising from the difficulties of accounting for the morphologies and heterogeneous chemical composition of the particles. This study aims to compare two ways of modelling the optical properties of aerosols simulated by a chemical transport model. The first method models particle optical properties as homogeneous spheres and are externally mixed. This is a simple model that is particularly easy to use in data assimilation methods, since the optics model is linear. The second method involves a core-shell internal mixture of soot, where sulphate, nitrate, ammonia, organic carbon, sea salt, and water are contained in the shell. However, by contrast to previously used core-shell models, only part of the carbon is concentrated in the core, while the remaining part is homogeneously mixed with the shell. The chemical transport model (CTM) simulations are done regionally over Europe with the Multiple-scale Atmospheric Transport and CHemistry (MATCH) model, developed by the Swedish Meteorological and Hydrological Institute (SMHI). The MATCH model was run with both an aerosol dynamics module, called SALSA, and with a regular "bulk" approach, i.e., a mass transport model without aerosol dynamics. Two events from 2007 are used in the analysis, one with high (22/12-2007) and one with low (22/6-2007) levels of elemental carbon (EC) over Europe. The results of the study help to assess the significance of aerosol morphology for modelling radiative forcing and aerosol optical properties relevant to interpreting remote sensing observations. The uncertainties introduced by the optics model are gauged by comparing them to model uncertainties related to the inclusion or omission of aerosol dynamic processes.

Synthesis and characterization of magnetic and non-magnetic core-shell polyepoxide micrometer-sized particles of narrow size distribution.

PubMed

Omer-Mizrahi, Melany; Margel, Shlomo

2009-01-15

Core polystyrene microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxy ethanol. Uniform polyglycidyl methacrylate/polystyrene core-shell micrometer-sized particles were prepared by emulsion polymerization at 73 degrees C of glycidyl methacrylate in the presence of the core polystyrene microspheres. Core-shell particles with different properties (size, surface morphology and composition) have been prepared by changing various parameters belonging to the above seeded emulsion polymerization process, e.g., volumes of the monomer glycidyl methacrylate and the crosslinker monomer ethylene glycol dimethacrylate. Magnetic Fe(3)O(4)/polyglycidyl methacrylate/polystyrene micrometer-sized particles were prepared by coating the former core-shell particles with magnetite nanoparticles via a nucleation and growth mechanism. Characterization of the various particles has been accomplished by routine methods such as light microscopy, SEM, FTIR, BET and magnetic measurements.

Predictable Particle Engineering: Programming the Energy Level, Carrier Generation, and Conductivity of Core-Shell Particles.

PubMed

Yuan, Conghui; Wu, Tong; Mao, Jie; Chen, Ting; Li, Yuntong; Li, Min; Xu, Yiting; Zeng, Birong; Luo, Weiang; Yu, Lingke; Zheng, Gaofeng; Dai, Lizong

2018-06-20

Core-shell structures are of particular interest in the development of advanced composite materials as they can efficiently bring different components together at nanoscale. The advantage of this structure greatly relies on the crucial design of both core and shell, thus achieving an intercomponent synergistic effect. In this report, we show that decorating semiconductor nanocrystals with a boronate polymer shell can easily achieve programmable core-shell interactions. Taking ZnO and anatase TiO 2 nanocrystals as inner core examples, the effective core-shell interactions can narrow the band gap of semiconductor nanocrystals, change the HOMO and LUMO levels of boronate polymer shell, and significantly improve the carrier density of core-shell particles. The hole mobility of core-shell particles can be improved by almost 9 orders of magnitude in comparison with net boronate polymer, while the conductivity of core-shell particles is at most 30-fold of nanocrystals. The particle engineering strategy is based on two driving forces: catechol-surface binding and B-N dative bonding and having a high ability to control and predict the shell thickness. Also, this approach is applicable to various inorganic nanoparticles with different components, sizes, and shapes.

Ionization of the Earth's Upper Atmosphere in Large Energetic Particle Events

NASA Astrophysics Data System (ADS)

Wolff, E.; Burrows, J.; Kallenrode, M.; von Koenig, M.; Kuenzi, K. F.; Quack, M.

2001-12-01

Energetic charged particles ionize the upper terrestrial atmosphere. Sofar, chemical consequences of precipitating particles have been discussed for solar protons with energies up to a few hundred MeV. We present a refined model for the interaction of energetic particles with the atmosphere based on a Monte-Carlo simulation. The model includes higher energies and other particle species, such as energetic solar electrons. Results are presented for well-known solar events, such as July 14, 2000, and are extrapolated to extremely large events, such as Carrington's white light flare in 1859, which from ice cores has been identified ass the largest impulsive NO3 event in the interval 1561 -- 1994 (McCracken et al., 2001).

Gold/silver core-shell 20 nm nanoparticles extracted from citrate solution examined by XPS

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

Engelhard, Mark H.; Smith, Jordan N.; Baer, Donald R.

Silver nanoparticles of many types are widely used in consumer and medical products. The surface chemistry of particles and the coatings that form during synthesis or use in many types of media can significantly impact the behaviors of particles including dissolution, transformation and biological or environmental impact. Consequently it is useful to be able to extract information about the thickness of surface coatings and other attributes of nanoparticles produced in a variety of ways. It has been demonstrated that X-ray Photoelectron Spectroscopy (XPS) can be reliably used to determine the thickness of organic and other nanoparticles coatings and shells. However,more » care is required to produce reliable and consistent information. Here we report the XPS spectra from gold/silver core-shell nanoparticles of nominal size 20 nm removed from a citrate saturated solution after one and two washing cycles. The Simulation of Electron Spectra for Surface Analysis (SESSA) program had been used to model peak amplitudes to obtain information on citrate coatings that remain after washing and demonstrate the presence of the gold core. This data is provided so that others can compare use of SESSA or other modeling approaches to quantify the nature of coatings to those already published and to explore the impacts particle non-uniformities on XPS signals from core-shell nanoparticles.« less

Engineering hepatitis B virus core particles for targeting HER2 receptors in vitro and in vivo.

PubMed

Mohamed Suffian, Izzat Fahimuddin Bin; Wang, Julie Tzu-Wen; Hodgins, Naomi O; Klippstein, Rebecca; Garcia-Maya, Mitla; Brown, Paul; Nishimura, Yuya; Heidari, Hamed; Bals, Sara; Sosabowski, Jane K; Ogino, Chiaki; Kondo, Akihiko; Al-Jamal, Khuloud T

2017-03-01

Hepatitis B Virus core (HBc) particles have been studied for their potential as drug delivery vehicles for cancer therapy. HBc particles are hollow nano-particles of 30-34 nm diameter and 7 nm thick envelopes, consisting of 180-240 units of 21 kDa core monomers. They have the capacity to assemble/dis-assemble in a controlled manner allowing encapsulation of various drugs and other biomolecules. Moreover, other functional motifs, i.e. receptors, receptor binding sequences, peptides and proteins can be expressed. This study focuses on the development of genetically modified HBc particles to specifically recognise and target human epidermal growth factor receptor-2 (HER2)-expressing cancer cells, in vitro and in vivo, for future cancer therapy. The non-specific binding capacity of wild type HBc particles was reduced by genetic deletion of the sequence encoding arginine-rich domains. A specific HER2-targeting was achieved by expressing the Z HER2 affibodies on the HBc particles surface. In vitro studies showed specific uptake of Z HER2 -ΔHBc particles in HER2 expressing cancer cells. In vivo studies confirmed positive uptake of Z HER2 -ΔHBc particles in HER2-expressing tumours, compared to non-targeted ΔHBc particles in intraperitoneal tumour-bearing mice models. The present results highlight the potential of these nanocarriers in targeting HER2-positive metastatic abdominal cancer following intra-peritoneal administration. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Two-component Gaussian core model: Strong-coupling limit, Bjerrum pairs, and gas-liquid phase transition.

PubMed

Frydel, Derek; Levin, Yan

2018-01-14

In the present work, we investigate a gas-liquid transition in a two-component Gaussian core model, where particles of the same species repel and those of different species attract. Unlike a similar transition in a one-component system with particles having attractive interactions at long separations and repulsive interactions at short separations, a transition in the two-component system is not driven solely by interactions but by a specific feature of the interactions, the correlations. This leads to extremely low critical temperature, as correlations are dominant in the strong-coupling limit. By carrying out various approximations based on standard liquid-state methods, we show that a gas-liquid transition of the two-component system poses a challenging theoretical problem.

Two-component Gaussian core model: Strong-coupling limit, Bjerrum pairs, and gas-liquid phase transition

NASA Astrophysics Data System (ADS)

Frydel, Derek; Levin, Yan

2018-01-01

In the present work, we investigate a gas-liquid transition in a two-component Gaussian core model, where particles of the same species repel and those of different species attract. Unlike a similar transition in a one-component system with particles having attractive interactions at long separations and repulsive interactions at short separations, a transition in the two-component system is not driven solely by interactions but by a specific feature of the interactions, the correlations. This leads to extremely low critical temperature, as correlations are dominant in the strong-coupling limit. By carrying out various approximations based on standard liquid-state methods, we show that a gas-liquid transition of the two-component system poses a challenging theoretical problem.

Exact diagonalization of quantum lattice models on coprocessors

NASA Astrophysics Data System (ADS)

Siro, T.; Harju, A.

2016-10-01

We implement the Lanczos algorithm on an Intel Xeon Phi coprocessor and compare its performance to a multi-core Intel Xeon CPU and an NVIDIA graphics processor. The Xeon and the Xeon Phi are parallelized with OpenMP and the graphics processor is programmed with CUDA. The performance is evaluated by measuring the execution time of a single step in the Lanczos algorithm. We study two quantum lattice models with different particle numbers, and conclude that for small systems, the multi-core CPU is the fastest platform, while for large systems, the graphics processor is the clear winner, reaching speedups of up to 7.6 compared to the CPU. The Xeon Phi outperforms the CPU with sufficiently large particle number, reaching a speedup of 2.5.

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

Cai Xiaoming; Chen Shu; Wang Yupeng

The superfluid-to-Anderson-insulator transition of a strongly repulsive Bose gas is studied in a one-dimensional incommensurate optical lattice. In the hard-core limit, the Bose-Fermi mapping allows us to deal with the system using the exact numerical method. Based on the Aubry-Andre model, we exploit the phase transition of the hard-core boson system from the superfluid phase with all single-particle states extended to the Bose-glass phase with all the single-particle states being Anderson localized as the strength of the incommensurate potential increases relative to the hopping amplitude. We evaluate the superfluid fraction, one-particle density matrices, momentum distributions, the natural orbitals, and theirmore » occupations. All of these quantities show that there exists a superfluid-to-insulator phase transition in the system.« less

Brightness temperature - obtaining the physical properties of a non-equipartition plasma

NASA Astrophysics Data System (ADS)

Nokhrina, E. E.

2017-06-01

The limit on the intrinsic brightness temperature, attributed to `Compton catastrophe', has been established being 1012 K. Somewhat lower limit of the order of 1011.5 K is implied if we assume that the radiating plasma is in equipartition with the magnetic field - the idea that explained why the observed cores of active galactic nuclei (AGNs) sustained the limit lower than the `Compton catastrophe'. Recent observations with unprecedented high resolution by the RadioAstron have revealed systematic exceed in the observed brightness temperature. We propose means of estimating the degree of the non-equipartition regime in AGN cores. Coupled with the core-shift measurements, the method allows us to independently estimate the magnetic field strength and the particle number density at the core. We show that the ratio of magnetic energy to radiating plasma energy is of the order of 10-5, which means the flow in the core is dominated by the particle energy. We show that the magnetic field obtained by the brightness temperature measurements may be underestimated. We propose for the relativistic jets with small viewing angles the non-uniform magnetohydrodynamic model and obtain the expression for the magnetic field amplitude about two orders higher than that for the uniform model. These magnetic field amplitudes are consistent with the limiting magnetic field suggested by the `magnetically arrested disc' model.

Dark-matter admixed white dwarfs

NASA Astrophysics Data System (ADS)

Leung, Shing Chi; Chu, Ming Chung; Lin, Lap Ming; Wong, Ka Wing

2014-03-01

We study the equilibrium structures of white dwarfs (WD) with dark matter cores formed by non-self-annihilating dark matter (DM) particles with masses ranging from 1 GeV to 100 GeV, assuming in form of an ideal degenerate Fermi gas inside the stars. For DM particles of mass 10 GeV and 100 GeV, we find that stable stellar models exist only if the mass of the DM core inside the star is less than O and -3)Msun , respectively. The global properties of these stars, and the corresponding Chandrasekhar mass (CM) limits, are essentially the same as those of traditional WD models without DM. Nevertheless, in the 10 GeV case, the gravitational attraction of the DM core is strong enough to squeeze the normal matter in the core region to densities above neutron drip. For the 1 GeV case, the DM core inside the star can be as massive as O and affects the global structure of the star significantly. The radius of a stellar model with DM can be about two times smaller than that of a traditional WD. Furthermore, the CM limit can be decreased by as much as 40%. Our results may have implications on the extent to which type Ia supernovae can be regarded as standard candles. This work is partially supported by a grant from the Research Grant Council of the Hong Kong Special Administrative Region, China (Project No. 400910).

Polychlorinated Biphenyls in a Temperate Alpine Glacier: 2. Model Results of Chemical Fate Processes.

PubMed

Steinlin, Christine; Bogdal, Christian; Pavlova, Pavlina A; Schwikowski, Margit; Lüthi, Martin P; Scheringer, Martin; Schmid, Peter; Hungerbühler, Konrad

2015-12-15

We present results from a chemical fate model quantifying incorporation of polychlorinated biphenyls (PCBs) into the Silvretta glacier, a temperate Alpine glacier located in Switzerland. Temperate glaciers, in contrast to cold glaciers, are glaciers where melt processes are prevalent. Incorporation of PCBs into cold glaciers has been quantified in previous studies. However, the fate of PCBs in temperate glaciers has never been investigated. In the model, we include melt processes, inducing elution of water-soluble substances and, conversely, enrichment of particles and particle-bound chemicals. The model is validated by comparing modeled and measured PCB concentrations in an ice core collected in the Silvretta accumulation area. We quantify PCB incorporation between 1900 and 2010, and discuss the fate of six PCB congeners. PCB concentrations in the ice core peak in the period of high PCB emissions, as well as in years with strong melt. While for lower-chlorinated PCB congeners revolatilization is important, for higher-chlorinated congeners, the main processes are storage in glacier ice and removal by particle runoff. This study gives insight into PCB fate and dynamics and reveals the effect of snow accumulation and melt processes on the fate of semivolatile organic chemicals in a temperate Alpine glacier.

Particle Filter-Based Recursive Data Fusion With Sensor Indexing for Large Core Neutron Flux Estimation

NASA Astrophysics Data System (ADS)

Tamboli, Prakash Kumar; Duttagupta, Siddhartha P.; Roy, Kallol

2017-06-01

We introduce a sequential importance sampling particle filter (PF)-based multisensor multivariate nonlinear estimator for estimating the in-core neutron flux distribution for pressurized heavy water reactor core. Many critical applications such as reactor protection and control rely upon neutron flux information, and thus their reliability is of utmost importance. The point kinetic model based on neutron transport conveniently explains the dynamics of nuclear reactor. The neutron flux in the large core loosely coupled reactor is sensed by multiple sensors measuring point fluxes located at various locations inside the reactor core. The flux values are coupled to each other through diffusion equation. The coupling facilitates redundancy in the information. It is shown that multiple independent data about the localized flux can be fused together to enhance the estimation accuracy to a great extent. We also propose the sensor anomaly handling feature in multisensor PF to maintain the estimation process even when the sensor is faulty or generates data anomaly.

A New Innovative Spherical Cermet Nuclear Fuel Element to Achieve an Ultra-Long Core Life for use in Grid-Appropriate LWRs

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

Senor, David J.; Painter, Chad L.; Geelhood, Ken J.

2007-12-01

Spherical cermet fuel elements are proposed for use in the Atoms For Peace Reactor (AFPR-100) concept. AFPR-100 is a small-scale, inherently safe, proliferation-resistant reactor that would be ideal for deployment to nations with emerging economies that decide to select nuclear power for the generation of carbon-free electricity. The basic concept of the AFPR core is a water-cooled fixed particle bed, randomly packed with spherical fuel elements. The flow of coolant within the particle bed is at such a low rate that the bed does not fluidize. This report summarizes an approach to fuel fabrication, results associated with fuel performance modeling,more » core neutronics and thermal hydraulics analyses demonstrating a ~20 year core life, and a conclusion that the proliferation resistance of the AFPR reactor concept is high.« less

Synthesis of suitable SiO2 nano particles as the core in core-shell nanostructured materials.

PubMed

Ghahari, Mehdi; Aghababazadeh, Roya; Ebadzadeh, Touradj; Mirhabibi, Alireza; Brydson, Rik; Fabbri, Paola; Najafi, Farhod

2011-06-01

The effect of surfactant on the luminescent intensity of SiO2 @Y2O3:Eu3+ particles with a core shell structure is described. Core-shell particles are used in phosphor materials and employing spherical particles with a narrow size distribution is vital for the enhancement of luminescent properties. Three kinds of different surfactants were used to synthesis SiO2 nano particles via a sol gel process. The results demonstrated that comb polycarboxylic acid surfactant had a significant influence on the morphology and particle size distribution. Somehow, particles with 100 nm size and narrow size distribution were produced. These particles had relatively uniform packing, unlike particles produced with other surfactants or without surfactant which had irregular assembly. The photoluminescence intensity of SiO2 @Y2O3:Eu3+ particles that was synthesized by comb polycarboxylic acid surfactant was higher than those which were produced without surfactant.

Comparison of experimental and modeled absorption enhancement by black carbon (BC) cored polydisperse aerosols under hygroscopic conditions.

PubMed

Shamjad, P M; Tripathi, S N; Aggarwal, S G; Mishra, S K; Joshi, Manish; Khan, Arshad; Sapra, B K; Ram, Kirpa

2012-08-07

The quantification of the radiative impacts of light absorbing ambient black carbon (BC) particles strongly depends on accurate measurements of BC mass concentration and absorption coefficient (β(abs)). In this study, an experiment has been conducted to quantify the influence of hygroscopic growth of ambient particles on light absorption. Using the hygroscopic growth factor (i.e., Zdanovskii-Stokes-Robinson (ZSR) approach), a model has been developed to predict the chemical composition of particles based on measurements, and the absorption and scattering coefficients are derived using a core-shell assumption with light extinction estimates based on Mie theory. The estimated optical properties agree within 7% for absorption coefficient and 30% for scattering coefficient with that of measured values. The enhancement of absorption is found to vary according to the thickness of the shell and BC mass, with a maximum of 2.3 for a shell thickness of 18 nm for the particles. The findings of this study underline the importance of considering aerosol-mixing states while calculating their radiative forcing.

Effects of complex internal structures on rheology of multiple emulsions particles in 2D from a boundary integral method.

PubMed

Wang, Jingtao; Liu, Jinxia; Han, Junjie; Guan, Jing

2013-02-08

A boundary integral method is developed to investigate the effects of inner droplets and asymmetry of internal structures on rheology of two-dimensional multiple emulsion particles with arbitrary numbers of layers and droplets within each layer. Under a modest extensional flow, the number increment of layers and inner droplets, and the collision among inner droplets subject the particle to stronger shears. In addition, the coalescence or release of inner droplets changes the internal structure of the multiple emulsion particles. Since the rheology of such particles is sensitive to internal structures and their change, modeling them as the core-shell particles to obtain the viscosity equation of a single particle should be modified by introducing the time-dependable volume fraction Φ(t) of the core instead of the fixed Φ. An asymmetric internal structure induces an oriented contact and merging of the outer and inner interface. The start time of the interface merging is controlled by adjusting the viscosity ratio and enhancing the asymmetry, which is promising in the controlled release of inner droplets through hydrodynamics for targeted drug delivery.

Particle levitation and guidance in hollow-core photonic crystal fiber.

PubMed

Benabid, Fetah; Knight, J; Russell, P

2002-10-21

We report the guidance of dry micron-sized dielectric particles in hollow core photonic crystal fiber. The particles were levitated in air and then coupled to the air-core of the fiber using an Argon ion laser beam operating at a wavelength of 514 nm. The diameter of the hollow core of the fiber is 20 m . A laser power of 80 mW was sufficient to levitate a 5 m diameter polystyrene sphere and guide it through a ~150 mm long hollow-core crystal photonic fiber. The speed of the guided particle was measured to be around 1 cm/s.

Application of hepatitis B core particles produced by human primary hepatocellular carcinoma (PLC/342) propagated in nude mice to the determination of anti-HBc by passive hemagglutination.

PubMed

Miyamoto, K; Itoh, Y; Tsuda, F; Matsui, T; Tanaka, T; Miyamoto, H; Naitoh, S; Imai, M; Usuda, S; Nakamura, T

1986-05-22

Human primary hepatocellular carcinoma (PLC/342), carried by nude mice, produces hepatitis B core particles as well as hepatitis B surface antigen particles. Core particles purified form PLC/342 tumors displayed epitopes of hepatitis B core antigen (HBcAg) but not epitopes of hepatitis B e antigen (HBeAg) on their surface, unlike core particles prepared from Dane particles, derived from plasma of asymptomatic carriers, that expressed epitopes of both HBcAg and HBeAg. Core particles obtained from PLC/342 tumors were applied to the determination of antibody to HBcAg (anti-HBc) by passive hemagglutination. The assay detected anti-HBc not only in individuals with persistent infection with hepatitis B virus and in those who had recovered from transient infection, but also in patients with acute type B hepatitis, indicating that it can detect anti-HBc of either IgG or IgM class. A liberal availability of core particles from tumors carried by nude mice, taken together with an easy applicability of the method, would make the passive hemagglutination for anti-HBc a valuable tool in clinical and epidemiological studies, especially in places where sophisticated methods are not feasible.

SAXS analysis of single- and multi-core iron oxide magnetic nanoparticles

PubMed Central

Szczerba, Wojciech; Costo, Rocio; Morales, Maria del Puerto; Thünemann, Andreas F.

2017-01-01

This article reports on the characterization of four superparamagnetic iron oxide nanoparticles stabilized with dimercaptosuccinic acid, which are suitable candidates for reference materials for magnetic properties. Particles p1 and p2 are single-core particles, while p3 and p4 are multi-core particles. Small-angle X-ray scattering analysis reveals a lognormal type of size distribution for the iron oxide cores of the particles. Their mean radii are 6.9 nm (p1), 10.6 nm (p2), 5.5 nm (p3) and 4.1 nm (p4), with narrow relative distribution widths of 0.08, 0.13, 0.08 and 0.12. The cores are arranged as a clustered network in the form of dense mass fractals with a fractal dimension of 2.9 in the multi-core particles p3 and p4, but the cores are well separated from each other by a protecting organic shell. The radii of gyration of the mass fractals are 48 and 44 nm, and each network contains 117 and 186 primary particles, respectively. The radius distributions of the primary particle were confirmed with transmission electron microscopy. All particles contain purely maghemite, as shown by X-ray absorption fine structure spectroscopy. PMID:28381973

Extinction cross section measurements for a single optically trapped particle

NASA Astrophysics Data System (ADS)

Cotterell, Michael I.; Preston, Thomas C.; Mason, Bernard J.; Orr-Ewing, Andrew J.; Reid, Jonathan P.

2015-08-01

Bessel beam (BB) optical traps have become widely used to confine single and multiple aerosol particles across a broad range of sizes, from a few microns to < 200 nm in radius. The radiation pressure force exerted by the core of a single, zeroth-order BB incident on a particle can be balanced by a counter-propagating gas flow, allowing a single particle to be trapped indefinitely. The pseudo non-diffracting nature of BBs enables particles to be confined over macroscopic distances along the BB core propagation length; the position of the particle along this length can be finely controlled by variation of the BB laser power. This latter property is exploited to optimize the particle position at the center of the TEM00 mode of a high finesse optical cavity, allowing cavity ring-down spectroscopy (CRDS) to be performed on single aerosol particles and their optical extinction cross section, σext, measured. Further, the variation in the light from the illuminating BB elastically scattered by the particle is recorded as a function of scattering angle. Such intensity distributions are fitted to Lorenz-Mie theory to determine the particle radius. The trends in σext with particle radius are modelled using cavity standing wave Mie simulations and a particle's varying refractive index with changing relative humidity is determined. We demonstrate σext measurements on individual sub-micrometer aerosol particles and determine the lowest limit in particle size that can be probed by this technique. The BB-CRDS method will play a key role in reducing the uncertainty associated with atmospheric aerosol radiative forcing, which remains among the largest uncertainties in climate modelling.

Nanotomography and Micromagnetic Modelling of Remanence Carriers in the Semarkona LL3.0 Chondrite: A New View of the Vortex State

NASA Astrophysics Data System (ADS)

Harrison, R. J.; Einsle, J. F.; Williams, W.; Ó Conbhuí, P.; Fu, R. R.; Weiss, B. P.; Kasama, T.

2015-12-01

Dusty-olivine chondrules are carriers of stable pre-accretionary remanence, and have recently been used to obtain the first reliable estimate of the magnetic field of the early solar nebula. Here we show how the magnetic architecture of a single dusty olivine grain from the Semarkona LL3.0 ordinary chondrite meteorite can be fully characterised in three-dimensions, using a combination of Focussed-Ion-Beam nanotomography (FIB-nt), electron tomography and finite-element micromagnetic modelling. We present a 3D volume reconstruction of a dusty olivine grain, obtained by selective milling through a region of interest in a series of sequential 20 nm slices, which are then imaged using scanning electron microscopy. The data provide a quantitative description of the iron particle ensemble, including the distribution of particle sizes, shapes, interparticle spacings and preferred orientations. Iron particles are predominantly oblate ellipoids. Particles nucleate on dislocation networks and are loosely arranged in a series of parallel sheets with their shortest dimension oriented normal to the sheets and their longest dimensions preferentially aligned within the sheets. Individual particle geometries are converted to a finite-element mesh and used to perform micromagnetic simulations. The majority of particles adopt a single vortex state, with 'bulk' spins that rotate around a central vortex core. The results challenge pre-conceived ideas about the remanence carrying properties of vortex states. We find that remanence is carried by bulk spins rather than the vortex core. Although the orientation of the core is determined by the ellipsoidal geometry (parallel to the major axis for prolate ellipsoids; parallel to the minor axis for oblate ellipsoids), the remanence vectors generally lie at large angles (and in many cases antiparallel) to the core magnetisation. Even in the case of prolate particles, the resulting remanence vector can make a large angle of ~50° to the expected easy axis. The results reconcile the predicted and observed directions of remanence anisotropy, and demonstrate how this combination of nanotomography and micromagnetics will become an essential component of future single-crystal paleomagnetic studies.

Energetic powder

DOEpatents

Jorgensen, Betty S.; Danen, Wayne C.

2003-12-23

Fluoroalkylsilane-coated metal particles. The particles have a central metal core, a buffer layer surrounding the core, and a fluoroalkylsilane layer attached to the buffer layer. The particles may be prepared by combining a chemically reactive fluoroalkylsilane compound with an oxide coated metal particle having a hydroxylated surface. The resulting fluoroalkylsilane layer that coats the particles provides them with excellent resistance to aging. The particles can be blended with oxidant particles to form energetic powder that releases chemical energy when the buffer layer is physically disrupted so that the reductant metal core can react with the oxidant.

Shapes of Soot Particles Embedded in Organic Material and Sulfates

NASA Astrophysics Data System (ADS)

Adachi, K.; Buseck, P. R.

2008-12-01

Three-dimensional (3D) shapes of aerosol particles collected from Mexico City during the MILAGRO (Megacity Initiative: Local and Global Research Observations) campaign were analyzed using electron tomography (ET). Mexico City is a representative tropical megacity, where pollution is heavy and photochemical reaction is rapid. Its aerosol particles are of interest because of their effects on the regional and global climate and on health. We used ET to study soot particles that are embedded in organic material, commonly with sulfates, collected from Mexico City plumes. They comprise more than 50 % of the aerosol particles with aerodynamic diameters between 50 and 300 nm. ET combines a series of transmission electron microscope (TEM) images obtained in different viewing directions into representations that display the 3D digitized objects. By using the 3D data, we determined the volume ratios of the various component materials in individual internally mixed particles. In our samples, organic materials dominate, and soot and sulfate commonly occupy up to 10 volume %. The mean fractal dimension, which indicates the complexity of aggregates, of soot particles is 2.2 (± 0.2), suggesting that they retain their chain-like structure when embedded in organic material rather than being highly compacted. Their 3D images show that soot particles tend to be near the surface of the embedding particle rather than in the core, i.e., a core-shell model is inappropriate. Their morphological features indicate that the soot particles have lower absorption of sunlight by a few tens of percent relative to that of the compacted or concentrically coated particles assumed in current climate models.

Analysis of Particle Transport in DIII-D H-mode Plasma with a Generalized Pinch-Diffusion Model

NASA Astrophysics Data System (ADS)

Owen, L. W.; Stacey, W. M.; Groebner, R. J.; Callen, J. D.; Bonnin, X.

2009-11-01

Interpretative analyses of particle transport in the pedestal region of H-mode plasmas typically yield diffusion coefficients that are very small (<0.1 m^2/s) in the steep gradient region when a purely diffusive particle flux is fitted to the experimental density gradients. Previous evaluation of the particle and momentum balance equations using the experimental data indicated that the pedestal profiles are consistent with transport described by a pinch-diffusion particle flux relation [1]. This type of model is used to calculate the diffusion coefficient and pinch velocity in the core for an inter-ELM H-mode plasma in the DIII-D discharge 98889. Full-plasma SOPLS simulations using neutral beam particle and energy sources from ONETWO calculations and the model transport coefficients show good agreement with the measured density pedestal profile. 6pt [1] W.M. Stacey and R.J. Groebner, Phys. Plasmas 12, 042504 (2005).

Continuum theory for cluster morphologies of soft colloids.

PubMed

Kosmrlj, A; Pauschenwein, G J; Kahl, G; Ziherl, P

2011-06-09

We introduce a continuum description of the thermodynamics of colloids with a core-corona architecture. In the case of thick coronas, their overlap can be treated approximately by replacing the exact one-particle density distribution by a suitably shaped step profile, which provides a convenient way of modeling the spherical, columnar, lamellar, and inverted cluster morphologies predicted by numerical simulations and the more involved theories. We use the model to study monodisperse particles with the hard-core/square-shoulder pair interaction as the simplest representatives of the core-corona class. We derive approximate analytical expressions for the enthalpies of the cluster morphologies which offer a clear insight into the mechanisms at work, and we calculate the lattice spacing and the cluster size for all morphologies of the phase sequence as well as the phase-transition pressures. By comparing the results with the exact crystalline minimum-enthalpy configurations, we show that the accuracy of the theory increases with shoulder width. We discuss possible extensions of the theory that could account for the finite-temperature effects.

Efficient numerical technique for calculating the properties of interacting dimers in the Peierls-Hubbard model

NASA Astrophysics Data System (ADS)

Sous, John; Chakraborty, Monodeep; Krems, Roman; Berciu, Mona

2017-04-01

We develop a method to compute the Green's function for two particles in an infinite chain and coupled to phonons by interactions that modulate their hopping as described by the Peierls/Su-Schrieffer-Heeger (SSH) model. The method is based on a variational approximation to the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy and is shown to agree with exact digaonalization calculations. We show that the properties of bipolarons arising in such models is qualitatively different from those of the well-studied Holstein bipolarons. In particular, we show that depending on the particle statistics, strongly bound bipolarons may or may not form. In the case of hard-core bosons, we demonstrate novel effects for dimers such as sharp transitions and self-trapping. In the case of soft-core particles/ spinfull fermions, we show that the mediated interactions lead to overscreeing of the bare Hubbard U repulsion resulting in the formation of strongly bound bipolarons. This work was supported by NSERC of Canada and the Stewart Blusson Quantum Matter Institute.

Improved Thermoplastic/Iron-Particle Transformer Cores

NASA Technical Reports Server (NTRS)

Wincheski, Russell A.; Bryant, Robert G.; Namkung, Min

2004-01-01

A method of fabricating improved transformer cores from composites of thermoplastic matrices and iron-particles has been invented. Relative to commercially available laminated-iron-alloy transformer cores, the cores fabricated by this method weigh less and are less expensive. Relative to prior polymer-matrix/ iron-particle composite-material transformer cores, the cores fabricated by this method can be made mechanically stronger and more magnetically permeable. In addition, whereas some prior cores have exhibited significant eddy-current losses, the cores fabricated by this method exhibit very small eddy-current losses. The cores made by this method can be expected to be attractive for use in diverse applications, including high-signal-to-noise transformers, stepping motors, and high-frequency ignition coils. The present method is a product of an experimental study of the relationships among fabrication conditions, final densities of iron particles, and mechanical and electromagnetic properties of fabricated cores. Among the fabrication conditions investigated were molding pressures (83, 104, and 131 MPa), and molding temperatures (250, 300, and 350 C). Each block of core material was made by uniaxial-compression molding, at the applicable pressure/temperature combination, of a mixture of 2 weight percent of LaRC (or equivalent high-temperature soluble thermoplastic adhesive) with 98 weight percent of approximately spherical iron particles having diameters in the micron range. Each molded block was cut into square cross-section rods that were used as core specimens in mechanical and electromagnetic tests. Some of the core specimens were annealed at 900 C and cooled slowly before testing. For comparison, a low-carbon-steel core was also tested. The results of the tests showed that density, hardness, and rupture strength generally increased with molding pressure and temperature, though the correlation was rather weak. The weakness of the correlation was attributed to the pores in the specimens. The maximum relative permeabilities of cores made without annealing ranged from 30 to 110, while those of cores made with annealing ranged from 900 to 1,400. However, the greater permeabilities of the annealed specimens were not associated with noticeably greater densities. The major practical result of the investigation was the discovery of an optimum distribution of iron-particle sizes: It was found that eddy-current losses in the molded cores were minimized by using 100 mesh (corresponding to particles with diameters less than or equal to 100 m) iron particles. The effect of optimization of particle sizes on eddy-current losses is depicted in the figure.

Aerosol fabrication methods for monodisperse nanoparticles

DOEpatents

Jiang, Xingmao; Brinker, C Jeffrey

2014-10-21

Exemplary embodiments provide materials and methods for forming monodisperse particles. In one embodiment, the monodisperse particles can be formed by first spraying a nanoparticle-containing dispersion into aerosol droplets and then heating the aerosol droplets in the presence of a shell precursor to form core-shell particles. By removing either the shell layer or the nanoparticle core of the core-shell particles, monodisperse nanoparticles can be formed.

Structural model of the 50S subunit of E.Coli ribosomes from solution scattering

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

Svergun, D.I.; Koch, M.H.J.; Pedersen, J.S.

1994-12-31

The application of new methods of small-angle scattering data interpretation to a contrast variation study of the 50S ribosomal subunit of Escherichia coli in solution is described. The X-ray data from contrast variation with sucrose are analyzed in terms of the basic scattering curves from the volume inaccessible to sucrose and from the regions inside this volume occupied mainly by RNA and by proteins. From these curves models of the shape of the 50S and its RNA-rich core are evaluated and positioned so that their difference produces a scattering curve which is in good agreement with the scattering from themore » protein moiety. Basing on this preliminary model, the X-ray and neutron contrast variation data of the 50S subunit in aqueous solutions are interpreted in the frame of the advanced two-phase model described by the shapes of the 50S subunit and its RNA-rich core taking into account density fluctuations inside the RNA and the protein moiety. The shape of the envelope of the 50S subunit and of the RNA-rich core are evaluated with a resolution of about 40A. The shape of the envelope is in good agreement with the models of the 50S subunit obtained from electron microscopy on isolated particles. The shape of the RNA-rich core correlates well with the model of the entire particle determined by the image reconstruction from ordered sheets indicating that the latter model which is based on the subjective contouring of density maps is heavily biased towards the RNA.« less

Martian Dust Devils: Laboratory Simulations of Particle Threshold

NASA Technical Reports Server (NTRS)

Greeley, Ronald; Balme, Matthew R.; Iverson, James D.; Metzger, Stephen; Mickelson, Robert; Phoreman, Jim; White, Bruce

2003-01-01

An apparatus has been fabricated to simulate terrestrial and Martian dust devils. Comparisons of surface pressure profiles through the vortex core generated in the apparatus with both those in natural dust devils on Earth and those inferred for Mars are similar and are consistent with theoretical Rankine vortex models. Experiments to determine particle threshold under Earth ambient atmospheric pressures show that sand (particles > 60 micron in diameter) threshold is analogous to normal boundary-layer shear, in which the rotating winds of the vortex generate surface shear and hence lift. Lower-pressure experiments down to approx. 65 mbar follow this trend for sand-sized particles. However, smaller particles (i.e., dust) and all particles at very low pressures (w 10-60 mbar) appear to be subjected to an additional lift function interpreted to result from the strong decrease in atmospheric pressure centered beneath the vortex core. Initial results suggest that the wind speeds required for the entrainment of grains approx. 2 microns in diameter (i.e., Martian dust sizes) are about half those required for entrainment by boundary layer winds on both Earth and Mars.

Dark gamma-ray bursts

NASA Astrophysics Data System (ADS)

Brdar, Vedran; Kopp, Joachim; Liu, Jia

2017-03-01

Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stellar interior, also its DM core heats up and contracts, so that the DM density increases rapidly during the final stages of stellar evolution. We argue that, counterintuitively, the annihilation burst is more intense if DM annihilation is a p -wave process than for s -wave annihilation because in the former case, more DM particles survive until the supernova. If among the DM annihilation products are particles like dark photons that can escape the exploding star and decay to standard model particles later, the annihilation burst results in a flash of gamma rays accompanying the supernova. For a galactic supernova, this "dark gamma-ray burst" may be observable in the Čerenkov Telescope Array.

Modeling anoxic aggregates in the ocean - implications for nitrogen, sulfur and trace metal cycling

NASA Astrophysics Data System (ADS)

Bianchi, D.; Weber, T. S.; Deutsch, C.

2016-02-01

Anoxic conditions are uncommon in the open ocean, and mostly confined to the cores of oxygen minimum zones (OMZs). When oxygen runs out, a suite of alternative electron acceptors are used, leading to denitrification and, rarely in open waters, sulfate reduction. Anoxic conditions have been shown to develop inside millimeter-scale organic particles and aggregates, establishing microscale gradients that could sustain diverse microbial communities along a sequence of redox niches. We develop a model of the biogeochemistry of anoxic aggregates that includes aerobic and anaerobic reactions in a diffusion-limited environment, and present analytical and numerical solutions for the conditions that allow denitrification and sulfate reduction inside aggregates. The model is applied to realistic size spectra of particles sinking through the water column, and used to estimate the potential for particle-bound denitrification and sulfate reduction in the global ocean. We show that anoxia inside aggregates may be common throughout low oxygen waters, extending the niche of denitrifying metabolisms beyond fully anoxic zones. In the OMZ cores, aggregates can sustain pockets of sulfate reduction in otherwise non-sulfidic waters, depending on ambient nitrate concentrations, particle respiration rates, and other factors. We further discuss the implications for nitrogen, sulfur and trace metal cycling in the ocean.

DNA compaction by poly (amido amine) dendrimers of ammonia cored and ethylene diamine cored

NASA Astrophysics Data System (ADS)

Qamhieh, K.; Al-Shawwa, J.

2017-06-01

The complexes build-up of DNA and soft particles poly amidoamine (PAMAM) dendrimers of ammonia cored of generations (G1-G6) and ethylenediamine cored of generations (G1-G10) have been studied, using a new theoretical model developed by Qamhieh and coworkers. The model describes the interaction between linear polyelectrolyte (LPE) chain and ion-penetrable spheres. Many factors affecting LPE/dendrimer complex have been investigated such as dendrimer generation, the Bjerrum length, salt concentration, and rigidity of the LPE chain represented by the persistence length. It is found that the wrapping chain length around dendrimer increases by increasing dendrimer`s generation, Bjerrum length, and salt concentration, while decreases by increasing the persistence length of the LPE chain. Also we can conclude that the wrapping length of LPE chain around ethylenediamine cored dendrimers is larger than its length around ammonia cored dendrimers.

Investigating phonon-mediated interactions with polar molecules

NASA Astrophysics Data System (ADS)

Sous, John; Madison, Kirk; Berciu, Mona; Krems, Roman

2017-04-01

We show that an ensemble of polar molecules in an optical lattice realizes the Peierls polaron model for hard-core particles/ pseudospins. We analyze the quasiparticle spectrum in the one-particle subspace, the two-particle subspace and at finite concentrations. We derive an effective model that describes the low-energy behavior of the system. We show that the Hamiltonian includes phonon-mediated repulsions and phonon-mediated ``pair-hopping'' terms which move the particle pair as a whole. We show that microwave excitations of the system exhibit signatures of these interactions. These results pave the way for the experimental observation of phonon-mediated repulsion. This work was supported by NSERC of Canada and the Stewart Blusson Quantum Matter Institute.

Porous Core-Shell Nanostructures for Catalytic Applications

NASA Astrophysics Data System (ADS)

Ewers, Trevor David

Porous core-shell nanostructures have recently received much attention for their enhanced thermal stability. They show great potential in the field of catalysis, as reactant gases can diffuse in and out of the porous shell while the core particle is protected from sintering, a process in which particles coalesce to form larger particles. Sintering is a large problem in industry and is the primary cause of irreversible deactivation. Despite the obvious advantages of high thermal stability, porous core-shell nanoparticles can be developed to have additional interactive properties from the combination of the core and shell together, rather than just the core particle alone. This dissertation focuses on developing new porous core-shell systems in which both the core and shell take part in catalysis. Two types of systems are explored; (1) yolk-shell nanostructures with reducible oxide shells formed using the Kirkendall effect and (2) ceramic-based porous oxide shells formed using sol-gel chemistry. Of the Kirkendall-based systems, Au FexOy and Cu CoO were synthesized and studied for catalytic applications. Additionally, ZnO was explored as a potential shelling material. Sol-gel work focused on optimizing synthetic methods to allow for coating of small gold particles, which remains a challenge today. Mixed metal oxides were explored as a shelling material to make dual catalysts in which the product of a reaction on the core particle becomes a reactant within the shell.

Symplectic no-core shell-model approach to intermediate-mass nuclei

NASA Astrophysics Data System (ADS)

Tobin, G. K.; Ferriss, M. C.; Launey, K. D.; Dytrych, T.; Draayer, J. P.; Dreyfuss, A. C.; Bahri, C.

2014-03-01

We present a microscopic description of nuclei in the intermediate-mass region, including the proximity to the proton drip line, based on a no-core shell model with a schematic many-nucleon long-range interaction with no parameter adjustments. The outcome confirms the essential role played by the symplectic symmetry to inform the interaction and the winnowing of shell-model spaces. We show that it is imperative that model spaces be expanded well beyond the current limits up through 15 major shells to accommodate particle excitations, which appear critical to highly deformed spatial structures and the convergence of associated observables.

Evaluation of shrinking core model in leaching process of Pomalaa nickel laterite using citric acid as leachant at atmospheric conditions

NASA Astrophysics Data System (ADS)

Wanta, K. C.; Perdana, I.; Petrus, H. T. B. M.

2016-11-01

Most of kinetics studies related to leaching process used shrinking core model to describe physical phenomena of the process. Generally, the model was developed in connection with transport and/or reaction of reactant components. In this study, commonly used internal diffusion controlled shrinking core model was evaluated for leaching process of Pomalaa nickel laterite using citric acid as leachant. Particle size was varied at 60-70, 100-120, -200 meshes, while the operating temperature was kept constant at 358 K, citric acid concentration at 0.1 M, pulp density at 20% w/v and the leaching time was for 120 minutes. Simulation results showed that the shrinking core model was inadequate to closely approach the experimental data. Meanwhile, the experimental data indicated that the leaching process was determined by the mobility of product molecules in the ash layer pores. In case of leaching resulting large product molecules, a mathematical model involving steps of reaction and product diffusion might be appropriate to develop.

Synthesis of highly monodisperse particles composed of a magnetic core and fluorescent shell.

PubMed

Nagao, Daisuke; Yokoyama, Mikio; Yamauchi, Noriko; Matsumoto, Hideki; Kobayashi, Yoshio; Konno, Mikio

2008-09-02

Highly monodisperse particles composed of a magnetic silica core and fluorescent polymer shell were synthesized with a combined technique of heterocoagulation and soap-free emulsion polymerization. Prior to heterocoagulation, monodisperse, submicrometer-sized silica particles were prepared with the Stober method, and magnetic nanoparticles were prepared with a modified Massart method in which a cationic silane coupling agent of N-trimethoxysilylpropyl- N, N, N-trimethylammonium chloride was added just after coprecipitation of Fe (2+) and Fe (3+). The silica particles with negative surface potential were heterocoagulated with the magnetic nanoparticles with positive surface potential. The magnetic silica particles obtained with the heterocoagulation were treated with sodium silicate to modify their surfaces with silica. In the formation of a fluorescent polymer shell onto the silica-coated magnetic silica cores, an amphoteric initiator of 2,2'-azobis[ N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057) was used to control the colloidal stability of the magnetic cores during the polymer coating. The polymerization of St in the presence of a hydrophobic fluorophore of pyrene could coat the cores with fluorescent polymer shells, resulting in monodisperse particles with a magnetic silica core and fluorescent polymer shell. Measurements of zeta potential for the composite particles in different pH values indicated that the composite particles had an amphoteric property originating from VA-057 initiator.

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

Martin, William R.; Lee, John C.; baxter, Alan

Information and measured data from the intial Fort St. Vrain (FSV) high temperature gas reactor core is used to develop a benchmark configuration to validate computational methods for analysis of a full-core, commercial HTR configuration. Large uncertainties in the geometry and composition data for the FSV fuel and core are identified, including: (1) the relative numbers of fuel particles for the four particle types, (2) the distribution of fuel kernel diameters for the four particle types, (3) the Th:U ratio in the initial FSV core, (4) and the buffer thickness for the fissile and fertile particles. Sensitivity studies were performedmore » to assess each of these uncertainties. A number of methods were developed to assist in these studies, including: (1) the automation of MCNP5 input files for FSV using Python scripts, (2) a simple method to verify isotopic loadings in MCNP5 input files, (3) an automated procedure to conduct a coupled MCNP5-RELAP5 analysis for a full-core FSV configuration with thermal-hydraulic feedback, and (4) a methodology for sampling kernel diameters from arbitrary power law and Gaussian PDFs that preserved fuel loading and packing factor constraints. A reference FSV fuel configuration was developed based on having a single diameter kernel for each of the four particle types, preserving known uranium and thorium loadings and packing factor (58%). Three fuel models were developed, based on representing the fuel as a mixture of kernels with two diameters, four diameters, or a continuous range of diameters. The fuel particles were put into a fuel compact using either a lattice-bsed approach or a stochastic packing methodology from RPI, and simulated with MCNP5. The results of the sensitivity studies indicated that the uncertainties in the relative numbers and sizes of fissile and fertile kernels were not important nor were the distributions of kernel diameters within their diameter ranges. The uncertainty in the Th:U ratio in the intial FSV core was found to be important with a crude study. The uncertainty in the TRISO buffer thickness was estimated to be unimportant but the study was not conclusive. FSV fuel compacts and a regular FSV fuel element were analyzed with MCNP5 and compared with predictions using a modified version of HELIOS that is capable of analyzing TRISO fuel configurations. The HELIOS analyses were performed by SSP. The eigenvalue discrepancies between HELIOS and MCNP5 are currently on the order of 1% but these are still being evaluated. Full-core FSV configurations were developed for two initial critical configurations - a cold, clean critical loading and a critical configuration at 70% power. MCNP5 predictions are compared to experimental data and the results are mixed. Analyses were also done for the pulsed neutron experiments that were conducted by GA for the initial FSV core. MCNP5 was used to model these experiments and reasonable agreement with measured results has been observed.« less

Covalent immobilization of molecularly imprinted polymer nanoparticles using an epoxy silane.

PubMed

Kamra, Tripta; Chaudhary, Shilpi; Xu, Changgang; Johansson, Niclas; Montelius, Lars; Schnadt, Joachim; Ye, Lei

2015-05-01

Molecularly imprinted polymers (MIPs) can be used as antibody mimics to develop robust chemical sensors. One challenging problem in using MIPs for sensor development is the lack of reliable conjugation chemistry that allows MIPs to be fixed on transducer surface. In this work, we study the use of epoxy silane to immobilize MIP nanoparticles on model transducer surfaces without impairing the function of the immobilized nanoparticles. The MIP nanoparticles with a core-shell structure have selective molecular binding sites in the core and multiple amino groups in the shell. The model transducer surface is functionalized with a self-assembled monolayer of epoxy silane, which reacts with the core-shell MIP particles to enable straightforward immobilization. The whole process is characterized by studying the treated surfaces after each preparation step using atomic force microscopy, scanning electron microscopy, fluorescence microscopy, contact angle measurements and X-ray photoelectron spectroscopy. The microscopy results show that the MIP particles are immobilized uniformly on surface. The photoelectron spectroscopy results further confirm the action of each functionalization step. The molecular selectivity of the MIP-functionalized surface is verified by radioligand binding analysis. The particle immobilization approach described here has a general applicability for constructing selective chemical sensors in different formats. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Combustion of metal agglomerates in a solid rocket core flow

NASA Astrophysics Data System (ADS)

Maggi, Filippo; Dossi, Stefano; DeLuca, Luigi T.

2013-12-01

The need for access to space may require the use of solid propellants. High thrust and density are appealing features for different applications, spanning from boosting phase to other service applications (separation, de-orbiting, orbit insertion). Aluminum is widely used as a fuel in composite solid rocket motors because metal oxidation increases enthalpy release in combustion chamber and grants higher specific impulse. Combustion process of metal particles is complex and involves aggregation, agglomeration and evolution of reacting particulate inside the core flow of the rocket. It is always stated that residence time should be enough in order to grant complete metal oxidation but agglomerate initial size, rocket grain geometry, burning rate, and other factors have to be reconsidered. New space missions may not require large rocket systems and metal combustion efficiency becomes potentially a key issue to understand whether solid propulsion embodies a viable solution or liquid/hybrid systems are better. A simple model for metal combustion is set up in this paper. Metal particles are represented as single drops trailed by the core flow and reacted according to Beckstead's model. The fluid dynamics is inviscid, incompressible, 1D. The paper presents parametric computations on ideal single-size particles as well as on experimental agglomerate populations as a function of operating rocket conditions and geometries.

Shock wave propagation in layered planetary embryos

NASA Astrophysics Data System (ADS)

Arkani-Hamed, Jafar; Ivanov, Boris A.

2014-05-01

The propagation of impact-induced shock wave inside a planetary embryo is investigated using the Hugoniot equations and a new scaling law, governing the particle velocity variations along a shock ray inside a spherical body. The scaling law is adopted to determine the impact heating of a growing embryo in its early stage when it is an undifferentiated and uniform body. The new scaling law, similar to other existing scaling laws, is not suitable for a large differentiated embryo consisting of a silicate mantle overlying an iron core. An algorithm is developed in this study on the basis of the ray theory in a spherically symmetric body which relates the shock parameters at the top of the core to those at the base of the mantle, thus enabling the adoption of scaling laws to estimate the impact heating of both the mantle and the core. The algorithm is applied to two embryo models: a simple two-layered model with a uniform mantle overlying a uniform core, and a model where the pre-shock density and acoustic velocity of the embryo are radially dependent. The former illustrates details of the particle velocity, shock pressure, and temperature increase behind the shock front in a 2D axisymmetric geometry. The latter provides a means to compare the results with those obtained by a hydrocode simulation. The agreement between the results of the two techniques in revealing the effects of the core-mantle boundary on the shock wave transmission across the boundary is encouraging.

Going beyond the second virial coefficient in the hadron resonance gas model

NASA Astrophysics Data System (ADS)

Bugaev, K. A.; Sagun, V. V.; Ivanytskyi, A. I.; Yakimenko, I. P.; Nikonov, E. G.; Taranenko, A. V.; Zinovjev, G. M.

2018-02-01

We develop a novel formulation of the hadron resonance gas model which, besides a hard-core repulsion, explicitly accounts for the surface tension induced by the interaction between the particles. Such an equation of state allows us to go beyond the Van der Waals approximation for any number of different hard-core radii. A comparison with the Carnahan-Starling equation of state shows that the new model is valid for packing fractions 0.2-0.22, while the usual Van der Waals model is inapplicable at packing fractions above 0.1-0.11. Moreover, it is shown that the equation of state with induced surface tension is softer than the one of hard spheres and remains causal at higher particle densities. The great advantage of our model is that there are only two equations to be solved and neither their number nor their form depend on the values of the hard-core radii used for different hadronic resonances. Such an advantage leads to a significant mathematical simplification compared to other versions of truly multi-component hadron resonance gas models. Using this equation of state we obtain a high-quality fit of the ALICE hadron multiplicities measured at the center-of-mass energy 2.76 TeV per nucleon and we find that the dependence of χ2 / ndf on the temperature has a single global minimum in the traditional hadron resonance gas model with the multi-component hard-core repulsion. Also we find two local minima of χ2 / ndf in the model in which the proper volume of each hadron is proportional to its mass. However, it is shown that in the latter model a second local minimum located at higher temperatures always appears far above the limit of its applicability.

Polystyrene Core-Silica Shell Particles with Defined Nanoarchitectures as a Versatile Platform for Suspension Array Technology.

PubMed

Sarma, Dominik; Gawlitza, Kornelia; Rurack, Knut

2016-04-19

The need for rapid and high-throughput screening in analytical laboratories has led to significant growth in interest in suspension array technologies (SATs), especially with regard to cytometric assays targeting a low to medium number of analytes. Such SAT or bead-based assays rely on spherical objects that constitute the analytical platform. Usually, functionalized polymer or silica (SiO2) microbeads are used which each have distinct advantages and drawbacks. In this paper, we present a straightforward synthetic route to highly monodisperse SiO2-coated polystyrene core-shell (CS) beads for SAT with controllable architectures from smooth to raspberry- and multilayer-like shells by varying the molecular weight of poly(vinylpyrrolidone) (PVP), which was used as the stabilizer of the cores. The combination of both organic polymer core and a structurally controlled inorganic SiO2 shell in one hybrid particle holds great promises for flexible next-generation design of the spherical platform. The particles were characterized by electron microscopy (SEM, T-SEM, and TEM), thermogravimetry, flow cytometry, and nitrogen adsorption/desorption, offering comprehensive information on the composition, size, structure, and surface area. All particles show ideal cytometric detection patterns and facile handling due to the hybrid structure. The beads are endowed with straightforward modification possibilities through the defined SiO2 shells. We successfully implemented the particles in fluorometric SAT model assays, illustrating the benefits of tailored surface area which is readily available for small-molecule anchoring. Very promising assay performance was shown for DNA hybridization assays with quantification limits down to 8 fmol.

High-Speed Particle-in-Cell Simulation Parallelized with Graphic Processing Units for Low Temperature Plasmas for Material Processing

NASA Astrophysics Data System (ADS)

Hur, Min Young; Verboncoeur, John; Lee, Hae June

2014-10-01

Particle-in-cell (PIC) simulations have high fidelity in the plasma device requiring transient kinetic modeling compared with fluid simulations. It uses less approximation on the plasma kinetics but requires many particles and grids to observe the semantic results. It means that the simulation spends lots of simulation time in proportion to the number of particles. Therefore, PIC simulation needs high performance computing. In this research, a graphic processing unit (GPU) is adopted for high performance computing of PIC simulation for low temperature discharge plasmas. GPUs have many-core processors and high memory bandwidth compared with a central processing unit (CPU). NVIDIA GeForce GPUs were used for the test with hundreds of cores which show cost-effective performance. PIC code algorithm is divided into two modules which are a field solver and a particle mover. The particle mover module is divided into four routines which are named move, boundary, Monte Carlo collision (MCC), and deposit. Overall, the GPU code solves particle motions as well as electrostatic potential in two-dimensional geometry almost 30 times faster than a single CPU code. This work was supported by the Korea Institute of Science Technology Information.

The adenovirus major core protein VII is dispensable for virion assembly but is essential for lytic infection

PubMed Central

Suomalainen, Maarit; Zheng, Yueting; Boucke, Karin

2017-01-01

The Adenovirus (Ad) genome within the capsid is tightly associated with a virus-encoded, histone-like core protein—protein VII. Two other Ad core proteins, V and X/μ, also are located within the virion and are loosely associated with viral DNA. Core protein VII remains associated with the Ad genome during the early phase of infection. It is not known if naked Ad DNA is packaged into the capsid, as with dsDNA bacteriophage and herpesviruses, followed by the encapsidation of viral core proteins, or if a unique packaging mechanism exists with Ad where a DNA-protein complex is simultaneously packaged into the virion. The latter model would require an entirely new molecular mechanism for packaging compared to known viral packaging motors. We characterized a virus with a conditional knockout of core protein VII. Remarkably, virus particles were assembled efficiently in the absence of protein VII. No changes in protein composition were evident with VII−virus particles, including the abundance of core protein V, but changes in the proteolytic processing of some capsid proteins were evident. Virus particles that lack protein VII enter the cell, but incoming virions did not escape efficiently from endosomes. This greatly diminished all subsequent aspects of the infectious cycle. These results reveal that the Ad major core protein VII is not required to condense viral DNA within the capsid, but rather plays an unexpected role during virus maturation and the early stages of infection. These results establish a new paradigm pertaining to the Ad assembly mechanism and reveal a new and important role of protein VII in early stages of infection. PMID:28628648

Shaped nanocrystal particles and methods for making the same

DOEpatents

Alivisatos, A Paul [Oakland, CA; Scher, Erik C [Menlo Park, CA; Manna, Liberato [Berkeley, CA

2011-11-22

Shaped nanocrystal particles and methods for making shaped nanocrystal particles are disclosed. One embodiment includes a method for forming a branched, nanocrystal particle. It includes (a) forming a core having a first crystal structure in a solution, (b) forming a first arm extending from the core having a second crystal structure in the solution, and (c) forming a second arm extending from the core having the second crystal structure in the solution.

Shaped nanocrystal particles and methods for making the same

DOEpatents

Alivisatos, A. Paul; Scher, Erik C; Manna, Liberato

2013-12-17

Shaped nanocrystal particles and methods for making shaped nanocrystal particles are disclosed. One embodiment includes a method for forming a branched, nanocrystal particle. It includes (a) forming a core having a first crystal structure in a solution, (b) forming a first arm extending from the core having a second crystal structure in the solution, and (c) forming a second arm extending from the core having the second crystal structure in the solution.

Shaped nanocrystal particles and methods for working the same

DOEpatents

Alivisatos, A. Paul; Sher, Eric C.; Manna, Liberato

2007-12-25

Shaped nanocrystal particles and methods for making shaped nanocrystal particles are disclosed. One embodiment includes a method for forming a branched, nanocrystal particle. It includes (a) forming a core having a first crystal structure in a solution, (b) forming a first arm extending from the core having a second crystal structure in the solution, and (c) forming a second arm extending from the core having the second crystal structure in the solution.

Shaped Nonocrystal Particles And Methods For Making The Same

DOEpatents

Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

2005-02-15

Shaped nanocrystal particles and methods for making shaped nanocrystal particles are disclosed. One embodiment includes a method for forming a branched, nanocrystal particle. It includes (a) forming a core having a first crystal structure in a solution, (b) forming a first arm extending from the core having a second crystal structure in the solution, and (c) forming a second arm extending from the core having the second crystal structure in the solution.

Microscopic Shell Model Calculations for sd-Shell Nuclei

NASA Astrophysics Data System (ADS)

Barrett, Bruce R.; Dikmen, Erdal; Maris, Pieter; Shirokov, Andrey M.; Smirnova, Nadya A.; Vary, James P.

Several techniques now exist for performing detailed and accurate calculations of the structure of light nuclei, i.e., A ≤ 16. Going to heavier nuclei requires new techniques or extensions of old ones. One of these is the so-called No Core Shell Model (NCSM) with a Core approach, which involves an Okubo-Lee-Suzuki (OLS) transformation of a converged NCSM result into a single major shell, such as the sd-shell. The obtained effective two-body matrix elements can be separated into core and single-particle (s.p.) energies plus residual two-body interactions, which can be used for performing standard shell-model (SSM) calculations. As an example, an application of this procedure will be given for nuclei at the beginning ofthe sd-shell.

Method for producing chemical energy

DOEpatents

Jorgensen, Betty S.; Danen, Wayne C.

2004-09-21

Fluoroalkylsilane-coated metal particles having a central metal core, a buffer layer surrounding the core, and a fluoroalkylsilane layer attached to the buffer layer are prepared by combining a chemically reactive fluoroalkylsilane compound with an oxide coated metal particle having a hydroxylated surface. The resulting fluoroalkylsilane layer that coats the particles provides them with excellent resistance to aging. The particles can be blended with oxidant particles to form energetic powder that releases chemical energy when the buffer layer is physically disrupted so that the reductant metal core can react with the oxidant.

Effect of non-metallic precipitates and grain size on core loss of non-oriented electrical silicon steels

NASA Astrophysics Data System (ADS)

Wang, Jiayi; Ren, Qiang; Luo, Yan; Zhang, Lifeng

2018-04-01

In the current study, the number density and size of non-metallic precipitates and the size of grains on the core loss of the 50W800 non-oriented electrical silicon steel sheets were investigated. The number density and size of precipitates and grains were statistically analyzed using an automatic scanning electron microscope (ASPEX) and an optical microscope. Hypothesis models were established to reveal the physical feature for the function of grain size and precipitates on the core loss of the steel. Most precipitates in the steel were AlN particles smaller than 1 μm so that were detrimental to the core loss of the steel. These finer AlN particles distributed on the surface of the steel sheet. The relationship between the number density of precipitates (x in number/mm2 steel area) and the core loss (P1.5/50 in W/kg) was regressed as P1.5/50 = 4.150 + 0.002 x. The average grain size was approximately 25-35 μm. The relationship between the core loss and grain size (d in μm) was P1.5/50 = 3.851 + 20.001 d-1 + 60.000 d-2.

Changes in atmospheric chemical composition determined from ice core records in southwestern Siberia during the twentieth century

NASA Astrophysics Data System (ADS)

Joswiak, Daniel R.

The presented research includes analysis and interpretation of the upper 50 m of a deep ice core which was drilled at 49°48'22"N, 86°33'52" (4115 m.a.s.l.) on the Belukha Plateau, Altai, in southwestern Siberia. The main goal was to examine variability of geochemical records preserved in the ice in relation to climatic and environmental changes; and to determine the main aerosol sources using ground- and upper-level meteorological data. Ion chromatography was used to determine concentrations of anions (SO4, NO3, NO2, Cl), cations (NH4, Ca, K, Mg, Na), the carboxylic (organic) acids acetate (CH3COOH), formate (HCOOH), oxalate (C2O4), and methanesulfonic acid (CH3SO 3H). Major ion concentrations were dominated by sulfate (30.3%), nitrate (18.1%), formate (15.0%), and ammonium (12.4%). Highest concentrations were observed for sulfate; over 1460 ppb. Laser particle counting was used to determine size resolved number concentrations of particles ranging from 0.5 to 16.0 mum. Logarithmic distribution of particles was observed, with over 90% of the particle number concentration coming from particles less than 1.4 mum. Particle mass, calculated from the number concentration, revealed the greatest contribution (59%) to mass arrived with medium size particles (4.0-8.0 microm). Back-trajectories were modeled using NOAA's Hyplit model were modeled for the four days of maximum annual precipitation during a year of increased (1991) and decreased (1990) ion and particle concentrations. Principle components factor analysis was used to determine the main aerosol sources. The upper 50 m covers the time period from 1917 to 2002. Glacier flow models indicated the full depth of 170 m should provide over 1000 years of records. Insoluble particle concentrations preserved in the ice core were affected mainly by climatic conditions including precipitation regimes and wind speed variability. The small size particles (0.5-1.0 mm) are transported inter-continentally and associated with background atmospheric concentrations in the middle-troposphere. The large size particles (4.0-16.0 mum) are deposited from the atmosphere rapidly compared to small particles and were transported to high elevations from the central Asian desert sources. All size particles were found to be negatively correlated with average monthly temperatures indicating low temperatures during the dry particle deposition. During the first half of the 20th Century, soluble ions were dominated by organic acids; indicating mainly natural sources from vegetation and biomass burning. Ion profiles associated with human activities such as fuel combustion (SO4, NO3) significantly increased in concentration from the mid-1950s; coinciding with population growth in large industrialized cities upwind from the study location. Highest correlations between major ions and the ground and upper level wind speed were observed for SO4, indicating long-range transport of pollution to the Altai Mountains. Ion profiles associated with central Asian dust (Ca, Mg) and with sea salt aerosols (Na, Cl) were mainly influenced by climatic factors, and average concentrations did not significantly change during the 20th Century. Factor analysis revealed that ions typically associated with biomass burning (NH4, K) were not resolvable as indicators of separate aerosol source. The organic acid components better preserve forest fire signatures at this study location. The back-trajectories exhibited several notable differences in transport paths of air masses. The trajectories modeled for 1991 show a farther transport distance with significant time of transfer over heavily populated regions of Europe and Russia. The modeled back-trajectories over the Middle-East on two heaviest precipitation days in 1991 provided evidence of the large oil fires in Kuwait, appeared as increased concentrations in sulfate, nitrate, and organic acids. The modeled back-trajectories for 1990 show more localized transport paths or transport over sparsely populated Arctic and Polar Regions. Correlations were not found between the ice core geochemistry and the upper-level wind direction, illustrating the greater importance of the pathways of air masses arriving to the study location. Event-scale modeling of air mass back-trajectories showed a prospective method in determination of transport and source of pollutants preserved in snow and ice.

Electrocatalysts having gold monolayers on platinum nanoparticle cores, and uses thereof

DOEpatents

Adzic, Radoslav; Zhang, Junliang

2010-04-27

The invention relates to gold-coated particles useful as fuel cell electrocatalysts. The particles are composed of an electrocatalytically active core at least partially encapsulated by an outer shell of gold or gold alloy. The invention more particularly relates to such particles having a noble metal-containing core, and more particularly, a platinum or platinum alloy core. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

Microstructures and performance of CaO-based ceramic cores with different particle size distributions for investment casting

NASA Astrophysics Data System (ADS)

Zhou, P. P.; Wu, G. Q.; Tao, Y.; Cheng, X.; Zhao, J. Q.; Nan, H.

2018-02-01

A series of calcium-based ceramic cores for casting titanium alloy were prepared by mixing different amounts of coarse and fine powders through injection molding. The effects of particle size on the microstructures and properties of the ceramic cores were investigated using quantitative and statistical analysis methods. It is found that the shrinkage and room-temperature strength of the ceramic cores were enhanced as increasing the contents of fine particles. Moreover, the creep resistance of the ceramic cores increased initially and then decreased. The increase in the fine particle content of the cores reduced the number and mean diameter of pores after sintering. The grain boundary density decreased firstly and then increased. The flexural strength of the ceramic cores at room temperature decreased with increasing porosity of ceramic cores, whereas the creep resistance increased with decreasing grain boundary density. A core exhibiting the optimal property was obtained when mixing 65 wt% of coarse powders (75-150 μm) and 35 wt% of fine powders (25-48 μm).

Competition between crystallization and glassification for particles with short-ranged attraction. Possible applications to protein crystallization

NASA Astrophysics Data System (ADS)

Zaccarelli, E.; Sciortino, F.; Tartaglia, P.; Foffi, G.; McCullagh, G. D.; Lawlor, A.; Dawson, K. A.

2002-11-01

We discuss the phase behaviour of spherical hard-core particles, with an attractive potential, as described by a hard-core Yukawa model. The ratio of the range of the attraction to the diameter of the particles is an important control parameter of the problem. Upon decreasing the range of the attraction, the phase diagram changes quite significantly, with the liquid-gas transition becoming metastable, and the crystal being in equilibrium with the fluid, with no intervening liquid. We also study the glass transition lines and, crucially, find that the situation, being very simple for pure repulsive potentials, becomes much richer in competition between glass and crystal phases for short-range attractions. Also a transition between attractive and repulsive glass appears somewhat in analogy with the isostructural equilibrium transition between two crystals.

Modeling analysis of pulsed magnetization process of magnetic core based on inverse Jiles-Atherton model

NASA Astrophysics Data System (ADS)

Liu, Yi; Zhang, He; Liu, Siwei; Lin, Fuchang

2018-05-01

The J-A (Jiles-Atherton) model is widely used to describe the magnetization characteristics of magnetic cores in a low-frequency alternating field. However, this model is deficient in the quantitative analysis of the eddy current loss and residual loss in a high-frequency magnetic field. Based on the decomposition of magnetization intensity, an inverse J-A model is established which uses magnetic flux density B as an input variable. Static and dynamic core losses under high frequency excitation are separated based on the inverse J-A model. Optimized parameters of the inverse J-A model are obtained based on particle swarm optimization. The platform for the pulsed magnetization characteristic test is designed and constructed. The hysteresis curves of ferrite and Fe-based nanocrystalline cores at high magnetization rates are measured. The simulated and measured hysteresis curves are presented and compared. It is found that the inverse J-A model can be used to describe the magnetization characteristics at high magnetization rates and to separate the static loss and dynamic loss accurately.

Unit: Model for Matter, Inspection Pack, National Trial Print.

ERIC Educational Resources Information Center

Australian Science Education Project, Toorak, Victoria.

Mental and physical models are treated in the Australian Science Education Project trial unit prepared for students in a transitional stage between concrete and abstract reasoning. Students are introduced to the particle model of matter through a series of core activities, including a combination game using nuts and bolts, culminating in a…

Development of property-transfer models for estimating the hydraulic properties of deep sediments at the Idaho National Engineering and Environmental Laboratory, Idaho

USGS Publications Warehouse

Winfield, Kari A.

2005-01-01

Because characterizing the unsaturated hydraulic properties of sediments over large areas or depths is costly and time consuming, development of models that predict these properties from more easily measured bulk-physical properties is desirable. At the Idaho National Engineering and Environmental Laboratory, the unsaturated zone is composed of thick basalt flow sequences interbedded with thinner sedimentary layers. Determining the unsaturated hydraulic properties of sedimentary layers is one step in understanding water flow and solute transport processes through this complex unsaturated system. Multiple linear regression was used to construct simple property-transfer models for estimating the water-retention curve and saturated hydraulic conductivity of deep sediments at the Idaho National Engineering and Environmental Laboratory. The regression models were developed from 109 core sample subsets with laboratory measurements of hydraulic and bulk-physical properties. The core samples were collected at depths of 9 to 175 meters at two facilities within the southwestern portion of the Idaho National Engineering and Environmental Laboratory-the Radioactive Waste Management Complex, and the Vadose Zone Research Park southwest of the Idaho Nuclear Technology and Engineering Center. Four regression models were developed using bulk-physical property measurements (bulk density, particle density, and particle size) as the potential explanatory variables. Three representations of the particle-size distribution were compared: (1) textural-class percentages (gravel, sand, silt, and clay), (2) geometric statistics (mean and standard deviation), and (3) graphical statistics (median and uniformity coefficient). The four response variables, estimated from linear combinations of the bulk-physical properties, included saturated hydraulic conductivity and three parameters that define the water-retention curve. For each core sample,values of each water-retention parameter were estimated from the appropriate regression equation and used to calculate an estimated water-retention curve. The degree to which the estimated curve approximated the measured curve was quantified using a goodness-of-fit indicator, the root-mean-square error. Comparison of the root-mean-square-error distributions for each alternative particle-size model showed that the estimated water-retention curves were insensitive to the way the particle-size distribution was represented. Bulk density, the median particle diameter, and the uniformity coefficient were chosen as input parameters for the final models. The property-transfer models developed in this study allow easy determination of hydraulic properties without need for their direct measurement. Additionally, the models provide the basis for development of theoretical models that rely on physical relationships between the pore-size distribution and the bulk-physical properties of the media. With this adaptation, the property-transfer models should have greater application throughout the Idaho National Engineering and Environmental Laboratory and other geographic locations.

The Morphology of Emulsion Polymerized Latex Particles

DOE R&D Accomplishments Database

Wignall, G. D.; Ramakrishnan, V. R.; Linne, M. A.; Klein, A.; Sperling, L. H.; Wai, M. P.; Gelman, R. A.; Fatica, M. G.; Hoerl, R. H.; Fisher, L. W.

1987-11-01

Under monomer starved feed conditions, emulsion polymerization of perdeuterated methyl methacrylate and styrene in the presence of preformed polymethylmethacrylate latexes resulted in particles with a core-shell morphology, as determined by small-angle neutron scattering (SANS) analysis for a hollow sphere. The locus of polymerization of the added deuterated monomer is therefore at the particle surface. In similar measurements a statistical copolymer of styrene and methyl methacrylate was used as seed particles for further polymerization of trideuteromethyl methacrylate. The resulting polymer latex was again shown to have a core-shell morphological structure as determined by SANS. SANS experiments were also undertaken on polystyrene latexes polymerized by equilibrium swelling methods, with deuterated polymer forming the first or second step. The experiments covered a molecular weight range of 6 x 10{sup 4} 10{sup 6} the molecular weights are consistent with the experimental errors, indicating that the deuterium labeled molecules are randomly distributed in the latex. These results led to the finding that the polymer chains were constrained in the latex particles by factors of 2 to 4 from the relaxed coil dimensions. For M < 10{sup 6} g/mol SANS gave zero angle scattering intensities much higher than expected on the basis of a random distribution of labeled molecules. Several models were examined, including the possible development of core-shell structures at lower molecular weights.

How changing the particle structure can speed up protein mass transfer kinetics in liquid chromatography.

PubMed

Gritti, Fabrice; Horvath, Krisztian; Guiochon, Georges

2012-11-09

The mass transfer kinetics of a few compounds (uracil, 112 Da), insulin (5.5 kDa), lysozyme (13.4 kDa), and bovine serum albumin (BSA, 67 kDa) in columns packed with several types of spherical particles was investigated under non-retained conditions, in order to eliminate the poorly known contribution of surface diffusion to overall sample diffusivity across the porous particles in RPLC. Diffusivity across particles is then minimum. Based on the porosity of the particles accessible to analytes, it was accurately estimated from the elution times, the internal obstruction factor (using Pismen correlation), and the hindrance diffusion factor (using Renkin correlation). The columns used were packed with fully porous particles 2.5 μm Luna-C(18) 100 Å, core-shell particles 2.6 μm Kinetex-C(18) 100 Å, 3.6 μm Aeris Widepore-C(18) 200 Å, and prototype 2.7 μm core-shell particles (made of two concentric porous shells with 100 and 300 Å average pore size, respectively), and with 3.3 μm non-porous silica particles. The results demonstrate that the porous particle structure and the solid-liquid mass transfer resistance have practically no effect on the column efficiency for small molecules. For them, the column performance depends principally on eddy dispersion (packing homogeneity), to a lesser degree on longitudinal diffusion (effective sample diffusivity along the packed bed), and only slightly on the solid-liquid mass transfer resistance (sample diffusivity across the particle). In contrast, for proteins, this third HETP contribution, hence the porous particle structure, together with eddy dispersion govern the kinetic performance of columns. Mass transfer kinetics of proteins was observed to be fastest for columns packed with core-shell particles having either a large core-to-particle ratio or having a second, external, shell made of a thin porous layer with large mesopores (200-300 Å) and a high porosity (~/=0.5-0.7). The structure of this external shell seems to speed up the penetration of proteins into the particles. A stochastic model of the penetration of bulky proteins driven by a concentration gradient across an infinitely thin membrane of known porosity and pore size is suggested to explain this mechanism. Yet, under retained conditions, surface diffusion speeds up the mass transfer into the mesopores and levels the kinetic performance of particles built with either one or two porous shells. Copyright © 2012 Elsevier B.V. All rights reserved.

Control of the shell structural properties and cavity diameter of hollow magnesium fluoride particles.

PubMed

Nandiyanto, Asep Bayu Dani; Ogi, Takashi; Okuyama, Kikuo

2014-03-26

Control of the shell structural properties [i.e., thickness (8-25 nm) and morphology (dense and raspberry)] and cavity diameter (100-350 nm) of hollow particles was investigated experimentally, and the results were qualitatively explained based on the available theory. We found that the selective deposition size and formation of the shell component on the surface of a core template played important roles in controlling the structure of the resulting shell. To achieve the selective deposition size and formation of the shell component, various process parameters (i.e., reaction temperature and charge, size, and composition of the core template and shell components) were tested. Magnesium fluoride (MgF2) and polystyrene spheres were used as models for shell and core components, respectively. MgF2 was selected because, to the best of our knowledge, the current reported approaches to date were limited to synthesis of MgF2 in film and particle forms only. Therefore, understanding how to control the formation of MgF2 with various structures (both the thickness and morphology) is a prospective for advanced lens synthesis and applications.

Apportionment of polycyclic aromatic hydrocarbon sources in lower Fox River, USA, sediments by a chemical mass balance model

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

Su, M.C.; Christensen, E.R.; Karls, J.F.

Four sediment cores were collected from the lower Fox River, Wisconsin, USA, to identify possible sources of polycyclic aromatic hydrocarbons (PAHs) using a chemical mass balance model. The cores, which were obtained in 1995 from areas close to Green Bay, Wisconsin, USA, had total PAH concentrations between 19.3 and 0.34 ppm. To determine historical trends of PAH inputs, {sup 210}Pb and {sup 137}Cs dating was used, and elemental carbon particle analysis was done to characterize particles from the combustion of coal, wood, and petroleum. Source fingerprints were taken from the literature. Their results indicate that coke oven emissions, highway dust,more » coal gasification, and wood burning are likely sources of PAHs in the lower Fox River. Coke oven emissions are in the range of 40 to 90% of total PAHs, and this fraction decreases from 1930 to 1990, except in core Fox River-A (FR-A). The overall highway dust (HWY) contribution is between 10 and 75%, and this fraction increases from 1930 to present, except in core FR-A. The wood burning (WB) contribution is less than 7% in cores FR-B, FR-C, and FR-D. In core FR-A, a maximum ({approximately}23%) is found around 1960. The contribution of wood burning has changed from less than 6% in 1950 to between 3 and 10% in 1995. Evidence of aerobic biodegradation or photolysis in the sediment of phenanthrene, with a half-life of approximately 0.5 years has been found at the site of core FR-D, which is the shallowest (1.1 m) of the four core sites.« less

Implications for Post-processing Nucleosynthesis of Core-collapse Supernova Models with Lagrangian Particles

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

Harris, J. Austin; Hix, W. Raphael; Chertkow, Merek A.

In this paper, we investigate core-collapse supernova (CCSN) nucleosynthesis with self-consistent, axisymmetric (2D) simulations performed using the neutrino hydrodynamics code Chimera. Computational costs have traditionally constrained the evolution of the nuclear composition within multidimensional CCSN models to, at best, a 14-species α-network capable of tracking onlymore » $$(\\alpha ,\\gamma )$$ reactions from 4He to 60Zn. Such a simplified network limits the ability to accurately evolve detailed composition and neutronization or calculate the nuclear energy generation rate. Lagrangian tracer particles are commonly used to extend the nuclear network evolution by incorporating more realistic networks into post-processing nucleosynthesis calculations. However, limitations such as poor spatial resolution of the tracer particles; inconsistent thermodynamic evolution, including misestimation of expansion timescales; and uncertain determination of the multidimensional mass cut at the end of the simulation impose uncertainties inherent to this approach. Finally, we present a detailed analysis of the impact of such uncertainties for four self-consistent axisymmetric CCSN models initiated from solar-metallicity, nonrotating progenitors of 12, 15, 20, and 25 $${M}_{\\odot }$$ and evolved with the smaller α-network to more than 1 s after the launch of an explosion.« less

Implications for Post-processing Nucleosynthesis of Core-collapse Supernova Models with Lagrangian Particles

NASA Astrophysics Data System (ADS)

Harris, J. Austin; Hix, W. Raphael; Chertkow, Merek A.; Lee, C. T.; Lentz, Eric J.; Messer, O. E. Bronson

2017-07-01

We investigate core-collapse supernova (CCSN) nucleosynthesis with self-consistent, axisymmetric (2D) simulations performed using the neutrino hydrodynamics code Chimera. Computational costs have traditionally constrained the evolution of the nuclear composition within multidimensional CCSN models to, at best, a 14-species α-network capable of tracking only (α ,γ ) reactions from 4He to 60Zn. Such a simplified network limits the ability to accurately evolve detailed composition and neutronization or calculate the nuclear energy generation rate. Lagrangian tracer particles are commonly used to extend the nuclear network evolution by incorporating more realistic networks into post-processing nucleosynthesis calculations. However, limitations such as poor spatial resolution of the tracer particles inconsistent thermodynamic evolution, including misestimation of expansion timescales and uncertain determination of the multidimensional mass cut at the end of the simulation impose uncertainties inherent to this approach. We present a detailed analysis of the impact of such uncertainties for four self-consistent axisymmetric CCSN models initiated from solar-metallicity, nonrotating progenitors of 12, 15, 20, and 25 {M}⊙ and evolved with the smaller α-network to more than 1 s after the launch of an explosion.

Implications for Post-processing Nucleosynthesis of Core-collapse Supernova Models with Lagrangian Particles

DOE PAGES

Harris, J. Austin; Hix, W. Raphael; Chertkow, Merek A.; ...

2017-06-26

In this paper, we investigate core-collapse supernova (CCSN) nucleosynthesis with self-consistent, axisymmetric (2D) simulations performed using the neutrino hydrodynamics code Chimera. Computational costs have traditionally constrained the evolution of the nuclear composition within multidimensional CCSN models to, at best, a 14-species α-network capable of tracking onlymore » $$(\\alpha ,\\gamma )$$ reactions from 4He to 60Zn. Such a simplified network limits the ability to accurately evolve detailed composition and neutronization or calculate the nuclear energy generation rate. Lagrangian tracer particles are commonly used to extend the nuclear network evolution by incorporating more realistic networks into post-processing nucleosynthesis calculations. However, limitations such as poor spatial resolution of the tracer particles; inconsistent thermodynamic evolution, including misestimation of expansion timescales; and uncertain determination of the multidimensional mass cut at the end of the simulation impose uncertainties inherent to this approach. Finally, we present a detailed analysis of the impact of such uncertainties for four self-consistent axisymmetric CCSN models initiated from solar-metallicity, nonrotating progenitors of 12, 15, 20, and 25 $${M}_{\\odot }$$ and evolved with the smaller α-network to more than 1 s after the launch of an explosion.« less

Comparison of settling particles and sediments at IMAGES coring site in the northwestern North Pacific — Effect of resuspended particles on paleorecords

NASA Astrophysics Data System (ADS)

Kawahata, Hodaka; Minoshima, Kayo; Ishizaki, Yui; Yamaoka, Kyoko; Gupta, Lallan P.; Nagao, Masayuki; Kuroyanagi, Azumi

2009-12-01

In order to understand settling process of particles in high sedimentation area, one mooring of sediment trap was deployed right above the IMAGES coring site in the northwestern North Pacific. In spite of two large maxima of settling particle fluxes in June-July 2002 and October-early January 2003, organic matter (OM) and carbonate showed higher peaks in June-July while lithogenics showed a large peak in October-early January with degraded OM (low aspartic acid/beta-alanine (Asp/Bala) and glutamic acid/gamma-aminobutyric (Glu/Gaba) ratios). Fresh OM production peaked in June-July 2002 and April-May 2003. Thus a large export production occurred in spring-early summer (April-June). Alkenone production was enhanced mainly in June-July. The mean alkenone SST of the settling particles was rather consistent with the observed annual mean SST and alkenone SST determined from the surface sediments. On the other hand, the maximum lithogenic flux along with the degradation of OM indicated that a significant amount of resuspended matter contaminated the bottom sediments. Based upon idealized model, the current and settling speeds make fractionation by size and density of resuspended particles during the settling process. Accumulation rates of lithogenics were ~ 5 times those in the sediment traps, which indicate large contribution of resuspended particles to settling particles especially during October-early January, when the Tsugaru current showed high current speed. These observations call our attention to carefully reconstruct paleo-environments based upon lithogenics and several other proxies such as biogenic silica, which would be biased for example in the record of IMAGES core at Site Shimokita located on the gentle continental slope.

Enhanced stability of a chimeric hepatitis B core antigen virus-like-particle (HBcAg-VLP) by a C-terminal linker-hexahistidine-peptide.

PubMed

Schumacher, Jens; Bacic, Tijana; Staritzbichler, René; Daneschdar, Matin; Klamp, Thorsten; Arnold, Philipp; Jägle, Sabrina; Türeci, Özlem; Markl, Jürgen; Sahin, Ugur

2018-04-13

Virus-like-particles (VLPs) are attractive nanoparticulate scaffolds for broad applications in material/biological sciences and medicine. Prior their functionalization, specific adaptations have to be carried out. These adjustments frequently lead to disordered particles, but the particle integrity is an essential factor for the VLP suitability. Therefore, major requirements for particle stabilization exist. The objective of this study was to evaluate novel stabilizing elements for functionalized chimeric hepatitis B virus core antigen virus-like particles (HBcAg-VLP), with beneficial characteristics for vaccine development, imaging or delivery. The effects of a carboxy-terminal polyhistidine-peptide and an intradimer disulfide-bridge on the stability of preclinically approved chimeric HBcAg-VLPs were assessed. We purified recombinant chimeric HBcAg-VLPs bearing different modified C-termini and compared their physical and chemical particle stability by quantitative protein-biochemical and biophysical techniques. We observed lower chemical resistance of T = 3- compared to T = 4-VLP (triangulation number) capsids and profound impairment of accessibility of hexahistidine-peptides in assembled VLPs. Histidines attached to the C-terminus were associated with superior mechanical and/or chemical particle stability depending on the number of histidine moieties. A molecular modeling approach based on cryo-electron microscopy and biolayer interferometry revealed the underlying structural mechanism for the strengthening of the integrity of VLPs. Interactions triggering capsid stabilization occur on a highly conserved residue on the basis of HBcAg-monomers as well as on hexahistidine-peptides of adjacent monomers. This new stabilization mechanism appears to mimic an evolutionary conserved stabilization concept for hepadnavirus core proteins. These findings establish the genetically simply transferable C-terminal polyhistidine-peptide as a general stabilizing element for chimeric HBcAg-VLPs to increase their suitability.

Understanding the mechanism of proteasome 20S core particle gating

PubMed Central

Latham, Michael P.; Sekhar, Ashok; Kay, Lewis E.

2014-01-01

The 20S core particle proteasome is a molecular machine playing an important role in cellular function by degrading protein substrates that no longer are required or that have become damaged. Regulation of proteasome activity occurs, in part, through a gating mechanism controlling the sizes of pores at the top and bottom ends of the symmetric proteasome barrel and restricting access to catalytic sites sequestered in the lumen of the structure. Although atomic resolution models of both open and closed states of the proteasome have been elucidated, the mechanism by which gates exchange between these states remains to be understood. Here, this is investigated by using magnetization transfer NMR spectroscopy focusing on the 20S proteasome core particle from Thermoplasma acidophilum. We show from viscosity-dependent proteasome gating kinetics that frictional forces originating from random solvent motions are critical for driving the gating process. Notably, a small effective hydrodynamic radius (EHR; <4Å) is obtained, providing a picture in which gate exchange proceeds through many steps involving only very small segment sizes. A small EHR further suggests that the kinetics of gate interconversion will not be affected appreciably by large viscogens, such as macromolecules found in the cell, so long as they are inert. Indeed, measurements in cell lysate reveal that the gate interconversion rate decreases only slightly, demonstrating that controlled studies in vitro provide an excellent starting point for understanding regulation of 20S core particle function in complex, biologically relevant environments. PMID:24706783

Extreme-Scale Stochastic Particle Tracing for Uncertain Unsteady Flow Analysis

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

Guo, Hanqi; He, Wenbin; Seo, Sangmin

2016-11-13

We present an efficient and scalable solution to estimate uncertain transport behaviors using stochastic flow maps (SFM,) for visualizing and analyzing uncertain unsteady flows. SFM computation is extremely expensive because it requires many Monte Carlo runs to trace densely seeded particles in the flow. We alleviate the computational cost by decoupling the time dependencies in SFMs so that we can process adjacent time steps independently and then compose them together for longer time periods. Adaptive refinement is also used to reduce the number of runs for each location. We then parallelize over tasks—packets of particles in our design—to achieve highmore » efficiency in MPI/thread hybrid programming. Such a task model also enables CPU/GPU coprocessing. We show the scalability on two supercomputers, Mira (up to 1M Blue Gene/Q cores) and Titan (up to 128K Opteron cores and 8K GPUs), that can trace billions of particles in seconds.« less

Control of the Speed of a Light-Induced Spin Transition through Mesoscale Core-Shell Architecture.

PubMed

Felts, Ashley C; Slimani, Ahmed; Cain, John M; Andrus, Matthew J; Ahir, Akhil R; Abboud, Khalil A; Meisel, Mark W; Boukheddaden, Kamel; Talham, Daniel R

2018-05-02

The rate of the light-induced spin transition in a coordination polymer network solid dramatically increases when included as the core in mesoscale core-shell particles. A series of photomagnetic coordination polymer core-shell heterostructures, based on the light-switchable Rb a Co b [Fe(CN) 6 ] c · mH 2 O (RbCoFe-PBA) as core with the isostructural K j Ni k [Cr(CN) 6 ] l · nH 2 O (KNiCr-PBA) as shell, are studied using temperature-dependent powder X-ray diffraction and SQUID magnetometry. The core RbCoFe-PBA exhibits a charge transfer-induced spin transition (CTIST), which can be thermally and optically induced. When coupled to the shell, the rate of the optically induced transition from low spin to high spin increases. Isothermal relaxation from the optically induced high spin state of the core back to the low spin state and activation energies associated with the transition between these states were measured. The presence of a shell decreases the activation energy, which is associated with the elastic properties of the core. Numerical simulations using an electro-elastic model for the spin transition in core-shell particles supports the findings, demonstrating how coupling of the core to the shell changes the elastic properties of the system. The ability to tune the rate of optically induced magnetic and structural phase transitions through control of mesoscale architecture presents a new approach to the development of photoswitchable materials with tailored properties.

Trafficking of Hepatitis C Virus Core Protein during Virus Particle Assembly

PubMed Central

Counihan, Natalie A.; Rawlinson, Stephen M.; Lindenbach, Brett D.

2011-01-01

Hepatitis C virus (HCV) core protein is directed to the surface of lipid droplets (LD), a step that is essential for infectious virus production. However, the process by which core is recruited from LD into nascent virus particles is not well understood. To investigate the kinetics of core trafficking, we developed methods to image functional core protein in live, virus-producing cells. During the peak of virus assembly, core formed polarized caps on large, immotile LDs, adjacent to putative sites of assembly. In addition, LD-independent, motile puncta of core were found to traffic along microtubules. Importantly, core was recruited from LDs into these puncta, and interaction between the viral NS2 and NS3-4A proteins was essential for this recruitment process. These data reveal new aspects of core trafficking and identify a novel role for viral nonstructural proteins in virus particle assembly. PMID:22028650

Density functional description of size-dependent effects at nucleation on neutral and charged nanoparticles

NASA Astrophysics Data System (ADS)

Shchekin, Alexander K.; Lebedeva, Tatiana S.

2017-03-01

A numerical study of size-dependent effects in the thermodynamics of a small droplet formed around a solid nanoparticle has been performed within the square-gradient density functional theory. The Lennard-Jones fluid with the Carnahan-Starling model for the hard-sphere contribution to intermolecular interaction in liquid and vapor phases and interfaces has been used for description of the condensate. The intermolecular forces between the solid core and condensate molecules have been taken into account with the help of the Lennard-Jones part of the total molecular potential of the core. The influence of the electric charge of the particle has been considered under assumption of the central Coulomb potential in the medium with dielectric permittivity depending on local condensate density. The condensate density profiles and equimolecular radii for equilibrium droplets at different values of the condensate chemical potential have been computed in the cases of an uncharged solid core with the molecular potential, a charged core without molecular potential, and a core with joint action of the Coulomb and molecular potentials. The appearance of stable equilibrium droplets even in the absence of the electric charge has been commented. As a next step, the capillary, disjoining pressure, and electrostatic contributions to the condensate chemical potential have been considered and compared with the predictions of classical thermodynamics in a wide range of values of the droplet and the particle equimolecular radii. With the help of the found dependence of the condensate chemical potential in droplet on the droplet size, the activation barrier for nucleation on uncharged and charged particles has been computed as a function of the vapor supersaturation. Finally, the work of droplet formation and the work of wetting the particle have been found as functions of the droplet size.

Porous metal oxide particles and their methods of synthesis

DOEpatents

Chen, Fanglin; Liu, Qiang

2013-03-12

Methods are generally disclosed for synthesis of porous particles from a solution formed from a leaving agent, a surfactant, and a soluble metal salt in a solvent. The surfactant congregates to form a nanoparticle core such that the metal salt forms about the nanoparticle core to form a plurality of nanoparticles. The solution is heated such that the leaving agent forms gas bubbles in the solution, and the plurality of nanoparticles congregate about the gas bubbles to form a porous particle. The porous particles are also generally disclosed and can include a particle shell formed about a core to define an average diameter from about 0.5 .mu.m to about 50 .mu.m. The particle shell can be formed from a plurality of nanoparticles having an average diameter of from about 1 nm to about 50 nm and defined by a metal salt formed about a surfactant core.

Nonequilibrium dynamics of one-dimensional hard-core anyons following a quench: complete relaxation of one-body observables.

PubMed

Wright, Tod M; Rigol, Marcos; Davis, Matthew J; Kheruntsyan, Karén V

2014-08-01

We demonstrate the role of interactions in driving the relaxation of an isolated integrable quantum system following a sudden quench. We consider a family of integrable hard-core lattice anyon models that continuously interpolates between noninteracting spinless fermions and strongly interacting hard-core bosons. A generalized Jordan-Wigner transformation maps the entire family to noninteracting fermions. We find that, aside from the singular free-fermion limit, the entire single-particle density matrix and, therefore, all one-body observables relax to the predictions of the generalized Gibbs ensemble (GGE). This demonstrates that, in the presence of interactions, correlations between particles in the many-body wave function provide the effective dissipation required to drive the relaxation of all one-body observables to the GGE. This relaxation does not depend on translational invariance or the tracing out of any spatial domain of the system.

3D Study of the Morphology and Dynamics of Zeolite Nucleation.

PubMed

Melinte, Georgian; Georgieva, Veselina; Springuel-Huet, Marie-Anne; Nossov, Andreï; Ersen, Ovidiu; Guenneau, Flavien; Gedeon, Antoine; Palčić, Ana; Bozhilov, Krassimir N; Pham-Huu, Cuong; Qiu, Shilun; Mintova, Svetlana; Valtchev, Valentin

2015-12-07

The principle aspects and constraints of the dynamics and kinetics of zeolite nucleation in hydrogel systems are analyzed on the basis of a model Na-rich aluminosilicate system. A detailed time-series EMT-type zeolite crystallization study in the model hydrogel system was performed to elucidate the topological and temporal aspects of zeolite nucleation. A comprehensive set of analytical tools and methods was employed to analyze the gel evolution and complement the primary methods of transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR) spectroscopy. TEM tomography reveals that the initial gel particles exhibit a core-shell structure. Zeolite nucleation is topologically limited to this shell structure and the kinetics of nucleation is controlled by the shell integrity. The induction period extends to the moment when the shell is consumed and the bulk solution can react with the core of the gel particles. These new findings, in particular the importance of the gel particle shell in zeolite nucleation, can be used to control the growth process and properties of zeolites formed in hydrogels. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

PubMed

Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

2016-04-21

We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.

Monte Carlo Simulation of Nanoparticle Encapsulation in Flames

NASA Technical Reports Server (NTRS)

Sun, Z.; Huertas, J. I.; Axelbaum, R. L.

1999-01-01

Two critical challenges facing the application of flames for synthesis of nanopowder materials are: (1) overcoming formation of agglomerates and (2) ensuring that the highly reactive nanopowders that are synthesized in flames can be produced in such a manner that their purity is maintained during subsequent processing. Agglomerates are produced in flames because particle formation occurs in a high temperature and high number density environment. They are undesirable in most advanced applications of powders. For example, agglomerates have a deleterious effect on compaction density, leading to voids when nanopowders are consolidated. Efforts to avoid agglomeration in flames without substantially reducing particle number density and, consequently, production rate, have had limited success. Powder purity must also be maintained during subsequent handling of nanopowders and this poses a significant challenge for any synthesis route because nanopowders, particularly metals and non-oxide ceramic powders, are inherently reactive. Impurities acquired during handling of nanopowders have slowed the advancement of the nanostructured materials industry. One promising approach that has been proposed to address these problems is nano-encapsulation. In this approach, the core particles are encapsulated in a removable material while they are within the flame but before excessive agglomeration has occurred. Condensation can be very rapid so that core particles are trapped within the condensed material and agglomeration is limited. Nano-encapsulation also addresses the handling concerns for post-synthesis processing. Results have shown that when nano-encapsulated powders are exposed to atmosphere the core particles are protected from oxidation and/or hydrolysis. Thus, handling of the powders does not require extreme care. If, for example, at the time of consolidation the encapsulation material is removed by vacuum annealing, the resulting powder remains unagglomerated and free of impurities. In this work, we described a novel aerosol model that has been developed to simulate particle encapsulation in flames. The model will ultimately be coupled to a one-dimensional spherical flame code and compared to results from microgravity flame experiments.

Full-Color Biomimetic Photonic Materials with Iridescent and Non-Iridescent Structural Colors.

PubMed

Kawamura, Ayaka; Kohri, Michinari; Morimoto, Gen; Nannichi, Yuri; Taniguchi, Tatsuo; Kishikawa, Keiki

2016-09-23

The beautiful structural colors in bird feathers are some of the brightest colors in nature, and some of these colors are created by arrays of melanin granules that act as both structural colors and scattering absorbers. Inspired by the color of bird feathers, high-visibility structural colors have been created by altering four variables: size, blackness, refractive index, and arrangement of the nano-elements. To control these four variables, we developed a facile method for the preparation of biomimetic core-shell particles with melanin-like polydopamine (PDA) shell layers. The size of the core-shell particles was controlled by adjusting the core polystyrene (PSt) particles' diameter and the PDA shell thicknesses. The blackness and refractive index of the colloidal particles could be adjusted by controlling the thickness of the PDA shell. The arrangement of the particles was controlled by adjusting the surface roughness of the core-shell particles. This method enabled the production of both iridescent and non-iridescent structural colors from only one component. This simple and novel process of using core-shell particles containing PDA shell layers can be used in basic research on structural colors in nature and their practical applications.

Single-wall nanohorn structure and distribution of incorporated materials

NASA Astrophysics Data System (ADS)

Maigne, Alan; Gloter, Alexandre; Ajima, Kumiko; Colliex, Christian; Iijima, Sumio

2005-03-01

Single-wall carbon nanohorns (SWNHs) are unique spherical-aggregates of single-wall carbon quasi-nanotubes. So far, the observable area has been limited to the aggregate surfaces. We studied core-region structure with TEM using thickness measurement method, EELS, and EDS, and found that carbon density was uniform over the whole aggregate. This result allows to modelize the core-region and to clarify previous models of SWNHs. We used same tools to investigate the incorporation of materials such as fullerenes or platinium compounds. We found that particles can even be incorporated in the core-region and that their distribution in the aggregate depends on their concentration. The information available with these models should be useful in the study of SWNH applications to, for example, drug delivery system.

Review of the fermionic dark matter model applied to galactic structures

NASA Astrophysics Data System (ADS)

Krut, A.; Argüelles, C. R.; Rueda, J.; Ruffini, R.

2015-12-01

Baryonic components (e.g. bulge and disk) of galactic structures are assumed to be embedded in an isothermal dark matter halo of fermionic nature. Besides the Pauli principle only gravitational interaction is considered. Using the underlying Fermi-Dirac phase space distribution, typical of collisionless relaxation processes, it yields an one-parameter family of scaled solutions which reproduces the observed flat rotation curves in galaxies, and additionally predicts a degenerate core through their centers. In order to provide the right DM halo properties of galaxies a set of four parameters (particle mass, degeneracy parameter at the galactic center, central density and the velocity dispersion) is necessary. The more general density profile shows three regimes depending on radius: an almost uniform very dense quantum core followed by a steep fall, a plateau in the diluted regime and a Boltzmannian tail representing the halo. In contrast to purely Boltzmannian configurations the fermionic DM model containing a quantum core allows to determine the particle mass. We show that the quantum core can be well approximated by a polytrope of index n = 3/2, while the halo can be perfectly described by an isothermal sphere with a halo scale length radius equal to approximately 3/4 of the King-radius.

Review of the fermionic dark matter model applied to galactic structures

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

Krut, A.; Argüelles, C. R.; Rueda, J.

2015-12-17

Baryonic components (e.g. bulge and disk) of galactic structures are assumed to be embedded in an isothermal dark matter halo of fermionic nature. Besides the Pauli principle only gravitational interaction is considered. Using the underlying Fermi-Dirac phase space distribution, typical of collisionless relaxation processes, it yields an one-parameter family of scaled solutions which reproduces the observed flat rotation curves in galaxies, and additionally predicts a degenerate core through their centers. In order to provide the right DM halo properties of galaxies a set of four parameters (particle mass, degeneracy parameter at the galactic center, central density and the velocity dispersion)more » is necessary. The more general density profile shows three regimes depending on radius: an almost uniform very dense quantum core followed by a steep fall, a plateau in the diluted regime and a Boltzmannian tail representing the halo. In contrast to purely Boltzmannian configurations the fermionic DM model containing a quantum core allows to determine the particle mass. We show that the quantum core can be well approximated by a polytrope of index n = 3/2, while the halo can be perfectly described by an isothermal sphere with a halo scale length radius equal to approximately 3/4 of the King-radius.« less

Grafting Modification of the Reactive Core-Shell Particles to Enhance the Toughening Ability of Polylactide

PubMed Central

Li, Zhaokun; Song, Shixin; Zhao, Xuanchen; Lv, Xue; Sun, Shulin

2017-01-01

In order to overcome the brittleness of polylactide (PLA), reactive core-shell particles (RCS) with polybutadiene as core and methyl methacrylate-co-styrene-co-glycidyl methacrylate as shell were prepared to toughen PLA. Tert-dodecyl mercaptan (TDDM) was used as chain transfer agent to modify the grafting properties (such as grafting degree, shell thickness, internal and external grafting) of the core-shell particles. The introduction of TDDM decreased the grafting degree, shell thickness and the Tg of the core phase. When the content of TDDM was lower than 1.15%, the RCS particles dispersed in the PLA matrix uniformly—otherwise, agglomeration took place. The addition of RCS particles induced a higher cold crystallization temperature and a lower melting temperature of PLA which indicated the decreased crystallization ability of PLA. Dynamic mechanical analysis (DMA) results proved the good miscibility between PLA and the RCS particles and the increase of TDDM in RCS induced higher storage modulus of PLA/RCS blends. Suitable TDDM addition improved the toughening ability of RCS particles for PLA. In the present research, PLA/RCS-T4 (RCS-T4: the reactive core-shell particles with 0.76 wt % TDDM addition) blends displayed much better impact strength than other blends due to the easier cavitation/debonding ability and good dispersion morphology of the RCS-T4 particles. When the RCS-T4 content was 25 wt %, the impact strength of PLA/RCS-T4 blend reached 768 J/m, which was more than 25 times that of the pure PLA. PMID:28813019

Grafting Modification of the Reactive Core-Shell Particles to Enhance the Toughening Ability of Polylactide.

PubMed

Li, Zhaokun; Song, Shixin; Zhao, Xuanchen; Lv, Xue; Sun, Shulin

2017-08-16

In order to overcome the brittleness of polylactide (PLA), reactive core-shell particles (RCS) with polybutadiene as core and methyl methacrylate-co-styrene-co-glycidyl methacrylate as shell were prepared to toughen PLA. Tert-dodecyl mercaptan (TDDM) was used as chain transfer agent to modify the grafting properties (such as grafting degree, shell thickness, internal and external grafting) of the core-shell particles. The introduction of TDDM decreased the grafting degree, shell thickness and the T g of the core phase. When the content of TDDM was lower than 1.15%, the RCS particles dispersed in the PLA matrix uniformly-otherwise, agglomeration took place. The addition of RCS particles induced a higher cold crystallization temperature and a lower melting temperature of PLA which indicated the decreased crystallization ability of PLA. Dynamic mechanical analysis (DMA) results proved the good miscibility between PLA and the RCS particles and the increase of TDDM in RCS induced higher storage modulus of PLA/RCS blends. Suitable TDDM addition improved the toughening ability of RCS particles for PLA. In the present research, PLA/RCS-T4 (RCS-T4: the reactive core-shell particles with 0.76 wt % TDDM addition) blends displayed much better impact strength than other blends due to the easier cavitation/debonding ability and good dispersion morphology of the RCS-T4 particles. When the RCS-T4 content was 25 wt %, the impact strength of PLA/RCS-T4 blend reached 768 J/m, which was more than 25 times that of the pure PLA.

Universal analytical scattering form factor for shell-, core-shell, or homogeneous particles with continuously variable density profile shape.

PubMed

Foster, Tobias

2011-09-01

A novel analytical and continuous density distribution function with a widely variable shape is reported and used to derive an analytical scattering form factor that allows us to universally describe the scattering from particles with the radial density profile of homogeneous spheres, shells, or core-shell particles. Composed by the sum of two Fermi-Dirac distribution functions, the shape of the density profile can be altered continuously from step-like via Gaussian-like or parabolic to asymptotically hyperbolic by varying a single "shape parameter", d. Using this density profile, the scattering form factor can be calculated numerically. An analytical form factor can be derived using an approximate expression for the original Fermi-Dirac distribution function. This approximation is accurate for sufficiently small rescaled shape parameters, d/R (R being the particle radius), up to values of d/R ≈ 0.1, and thus captures step-like, Gaussian-like, and parabolic as well as asymptotically hyperbolic profile shapes. It is expected that this form factor is particularly useful in a model-dependent analysis of small-angle scattering data since the applied continuous and analytical function for the particle density profile can be compared directly with the density profile extracted from the data by model-free approaches like the generalized inverse Fourier transform method. © 2011 American Chemical Society

CALCINATION AND SINTERING MODELS FOR APPLICATION TO HIGH-TEMPERATURE, SHORT-TIME SULFATION OF CALCIUM-BASED SORBENTS

EPA Science Inventory

To simulate the staged availability of transient high surface area CaO observed in high-temperature flow-reactor data, the rate of calcination of CaCO3 or Ca(OH)2 is described by an empirical modification of the shrinking-core model. The physical model depicts particle decomposi...

Shape evolution of a core-shell spherical particle under hydrostatic pressure.

PubMed

Colin, Jérôme

2012-03-01

The morphological evolution by surface diffusion of a core-shell spherical particle has been investigated theoretically under hydrostatic pressure when the shear modulii of the core and shell are different. A linear stability analysis has demonstrated that depending on the pressure, shear modulii, and radii of both phases, the free surface of the composite particle may be unstable with respect to a shape perturbation. A stability diagram finally emphasizes that the roughness development is favored in the case of a hard shell with a soft core.

Free-Standing and Self-Crosslinkable Hybrid Films by Core-Shell Particle Design and Processing.

PubMed

Vowinkel, Steffen; Paul, Stephen; Gutmann, Torsten; Gallei, Markus

2017-11-15

The utilization and preparation of functional hybrid films for optical sensing applications and membranes is of utmost importance. In this work, we report the convenient and scalable preparation of self-crosslinking particle-based films derived by directed self-assembly of alkoxysilane-based cross-linkers as part of a core-shell particle architecture. The synthesis of well-designed monodisperse core-shell particles by emulsion polymerization is the basic prerequisite for subsequent particle processing via the melt-shear organization technique. In more detail, the core particles consist of polystyrene (PS) or poly(methyl methacrylate) (PMMA), while the comparably soft particle shell consists of poly(ethyl acrylate) (PEA) and different alkoxysilane-based poly(methacrylate)s. For hybrid film formation and convenient self-cross-linking, different alkyl groups at the siloxane moieties were investigated in detail by solid-state Magic-Angle Spinning Nuclear Magnetic Resonance (MAS, NMR) spectroscopy revealing different crosslinking capabilities, which strongly influence the properties of the core or shell particle films with respect to transparency and iridescent reflection colors. Furthermore, solid-state NMR spectroscopy and investigation of the thermal properties by differential scanning calorimetry (DSC) measurements allow for insights into the cross-linking capabilities prior to and after synthesis, as well as after the thermally and pressure-induced processing steps. Subsequently, free-standing and self-crosslinked particle-based films featuring excellent particle order are obtained by application of the melt-shear organization technique, as shown by microscopy (TEM, SEM).

Coordination Chemistry Inside Polymeric Nanoreactors: Interparticle Metal Exchange and Ionic Compound Vectorization in Phosphine-Functionalized Amphiphilic Polymer Latexes.

PubMed

Chen, Si; Gayet, Florence; Manoury, Eric; Joumaa, Ahmad; Lansalot, Muriel; D'Agosto, Franck; Poli, Rinaldo

2016-04-25

Stable latexes of hierarchically organized core-cross-linked polymer micelles that are functionalized at the core with triphenylphosphine (TPP@CCM) have been investigated by NMR spectroscopic analysis at both natural (ca. pH 5) and strongly basic (pH 13.6) pH values after core swelling with toluene. The core-shell interface structuring forces part of the hydrophilic poly(ethylene oxide) (PEO) chains to reside inside the hydrophobic core at both pH values. Loading the particle cores with [Rh(acac)(CO)2 ] (acac=acetylacetonate) at various Rh/P ratios yielded polymer-supported [Rh(acac)(CO)(TPP)] (TPP=triphenylphosphine). The particle-to-particle rhodium migration is very fast at natural pH, but slows down dramatically at high pH, whereas the size distribution of the nanoreactors remains unchanged. The slow migration at pH 13.6 leads to the generation of polymer-anchored [Rh(OH)(CO)(TPP)2 ], which is also generated immediately upon the addition of NaOH to the particles with a [Rh(acac)(CO)] loading of 50 %. Similarly, treatment of the same particles with NaCl yielded polymer-anchored [RhCl(CO)(TPP)2 ]. Interparticle coupling occurs during these rapid processes. These experiments prove that the major contribution to metal migration is direct core-core contact. The slow migration at the high pH value, however, must result from a pathway that does not involve core-core contact. The facile penetration of the polymer cores by NaOH and NaCl results from the presence of shell-linked poly(ethylene oxide) methyl ether functions both outside and inside the polymer core-shell interface. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Leaching behavior of copper from waste printed circuit boards with Brønsted acidic ionic liquid

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

Huang, Jinxiu; Chen, Mengjun, E-mail: kyling@swust.edu.cn; Chen, Haiyan

2014-02-15

Highlights: • A Brønsted acidic ILs was used to leach Cu from WPCBs for the first time. • The particle size of WPCBs has significant influence on Cu leaching rate. • Cu leaching rate was higher than 99% under the optimum leaching conditions. • The leaching process can be modeled with shrinking core model, and the E{sub a} was 25.36 kJ/mol. - Abstract: In this work, a Brønsted acidic ionic liquid, 1-butyl-3-methyl-imidazolium hydrogen sulfate ([bmim]HSO{sub 4}), was used to leach copper from waste printed circuit boards (WPCBs, mounted with electronic components) for the first time, and the leaching behavior ofmore » copper was discussed in detail. The results showed that after the pre-treatment, the metal distributions were different with the particle size: Cu, Zn and Al increased with the increasing particle size; while Ni, Sn and Pb were in the contrary. And the particle size has significant influence on copper leaching rate. Copper leaching rate was higher than 99%, almost 100%, when 1 g WPCBs powder was leached under the optimum conditions: particle size of 0.1–0.25 mm, 25 mL 80% (v/v) ionic liquid, 10 mL 30% hydrogen peroxide, solid/liquid ratio of 1/25, 70 °C and 2 h. Copper leaching by [bmim]HSO{sub 4} can be modeled with the shrinking core model, controlled by diffusion through a solid product layer, and the kinetic apparent activation energy has been calculated to be 25.36 kJ/mol.« less

Gyrokinetic modelling of the quasilinear particle flux for plasmas with neutral-beam fuelling

NASA Astrophysics Data System (ADS)

Narita, E.; Honda, M.; Nakata, M.; Yoshida, M.; Takenaga, H.; Hayashi, N.

2018-02-01

A quasilinear particle flux is modelled based on gyrokinetic calculations. The particle flux is estimated by determining factors, namely, coefficients of off-diagonal terms and a particle diffusivity. In this paper, the methodology to estimate the factors is presented using a subset of JT-60U plasmas. First, the coefficients of off-diagonal terms are estimated by linear gyrokinetic calculations. Next, to obtain the particle diffusivity, a semi-empirical approach is taken. Most experimental analyses for particle transport have assumed that turbulent particle fluxes are zero in the core region. On the other hand, even in the stationary state, the plasmas in question have a finite turbulent particle flux due to neutral-beam fuelling. By combining estimates of the experimental turbulent particle flux and the coefficients of off-diagonal terms calculated earlier, the particle diffusivity is obtained. The particle diffusivity should reflect a saturation amplitude of instabilities. The particle diffusivity is investigated in terms of the effects of the linear instability and linear zonal flow response, and it is found that a formula including these effects roughly reproduces the particle diffusivity. The developed framework for prediction of the particle flux is flexible to add terms neglected in the current model. The methodology to estimate the quasilinear particle flux requires so low computational cost that a database consisting of the resultant coefficients of off-diagonal terms and particle diffusivity can be constructed to train a neural network. The development of the methodology is the first step towards a neural-network-based particle transport model for fast prediction of the particle flux.

Computational modeling of lava domes using particle dynamics to investigate the effect of conduit flow mechanics on flow patterns

NASA Astrophysics Data System (ADS)

Husain, Taha Murtuza

Large (1--4 x 106 m3) to major (> 4 x 106 m3) dome collapses for andesitic lava domes such as Soufriere Hills Volcano, Montserrat are observed for elevated magma discharge rates (6--13 m3/s). The gas rich magma pulses lead to pressure build up in the lava dome that result in structural failure of the over steepened canyon-like walls which may lead to rockfall or pyroclastic flow. This indicates that dome collapse intimately related to magma extrusion rate. Variation in magma extrusion rate for open-system magma chambers is observed to follow alternating periods of high and low activity. Periodic behavior of magma exhibits a rich diversity in the nature of its eruptive history due to variation in magma chamber size, total crystal content, linear crystal growth rate and magma replenishment rate. Distinguished patterns of growth were observed at different magma flow rates ranging from endogenous to exogenous dome growth for magma with varying strengths. Determining the key parameters that control the transition in flow pattern of the magma during its lava dome building eruption is the main focus. This dissertation examines the mechanical effects on the morphology of the evolving lava dome on the extrusion of magma from a central vent using a 2D particle dynamics model. The particle dynamics model is coupled with a conduit flow model that incorporates the kinetics of crystallization and rheological stiffening to investigate important mechanisms during lava dome building eruptions. Chapter I of this dissertation explores lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional carapace that caps a ductile magma core. Extrusion rate and magma rheology together with crystallization temperature and volatile content govern the distribution of strength in the composite structure. This new model is calibrated against existing observational models of lava dome growth. Chapter II of this dissertation explores the effects of a spectrum of different rheological regimes, on eruptive style and morphologic evolution of lava domes, using a two-dimensional (2D) particle-dynamics model for a spreading viscoplastic (Bingham) fluid. We assume that the ductile magma core of a 2-D synthetic lava dome develops finite yield strength, and that deformable frictional talus evolves from a carapace that caps the magma core. Our new model is calibrated against an existing analytical model for a spreading viscoplastic lava dome and is further compared against observational data of lava dome growth. Chapter III of this dissertation explores different lava-dome styles by developing a two-dimensional particle-dynamics model. These growth patterns range from endogenous lava dome growth comprising expansion of a ductile dome core to the exogenous extrusion of a degassed lava plug resulting in generation of a lava spine. We couple conduit flow dynamics with surface growth of the evolving lava dome, fueled by an open-system magma chamber undergoing continuous replenishment. The conduit flow model accounts for the variation in rheology of ascending magma that results from degassing-induced crystallization. Chapter IV of this dissertation explores the Variation in the extruding lava flow patterns range from endogenous dome growth with a ductile core to the exogenous extrusion of a degassed lava plug that results in the generation of a spine. The variations are a manifestation of the changes in the magma rheology which is governed by magma composition and rate of decompression of the ascending magma. We simulate using a two-dimensional particle-dynamics model, the cyclic behavior of lava dome growth with endogenous growth at high discharge rates followed by exogenous extrusion of rheologically stiffened lava due to degassing induced crystallization at low discharge rates. We couple conduit flow dynamics with surface growth of the evolving lava dome which is fueled by an overpressured reservoir undergoing constant replenishment. The periodic behavior between magma chamber pressure and discharge rate is reproduced as a result of the temporal and spatial change in magma viscosity controlled by crystallization kinetics. Dimensionless numbers are used to map the flow behaviors with the changing extrusion regime. A dimensionless plot identifying the flow transition region during the growth cycle of an evolving lava dome in its lava dome eruptive period is presented. The plot provides a the threshold value of a dimensionless strength parameter (pi 2 < 3.31 x 10-4) below which the transition in flow pattern occurs from endogenously evolving lava dome with a ductile core to the development of a shear lobe for short or long lived periodic episode of the extrusion of magma. (Abstract shortened by UMI.).

In vitro protease cleavage and computer simulations reveal the HIV-1 capsid maturation pathway

NASA Astrophysics Data System (ADS)

Ning, Jiying; Erdemci-Tandogan, Gonca; Yufenyuy, Ernest L.; Wagner, Jef; Himes, Benjamin A.; Zhao, Gongpu; Aiken, Christopher; Zandi, Roya; Zhang, Peijun

2016-12-01

HIV-1 virions assemble as immature particles containing Gag polyproteins that are processed by the viral protease into individual components, resulting in the formation of mature infectious particles. There are two competing models for the process of forming the mature HIV-1 core: the disassembly and de novo reassembly model and the non-diffusional displacive model. To study the maturation pathway, we simulate HIV-1 maturation in vitro by digesting immature particles and assembled virus-like particles with recombinant HIV-1 protease and monitor the process with biochemical assays and cryoEM structural analysis in parallel. Processing of Gag in vitro is accurate and efficient and results in both soluble capsid protein and conical or tubular capsid assemblies, seemingly converted from immature Gag particles. Computer simulations further reveal probable assembly pathways of HIV-1 capsid formation. Combining the experimental data and computer simulations, our results suggest a sequential combination of both displacive and disassembly/reassembly processes for HIV-1 maturation.

Low-temperature behavior of core-softened models: water and silica behavior.

PubMed

Jagla, E A

2001-06-01

A core-softened model of a glass forming fluid is numerically studied in the limit of very low temperatures. The model shows two qualitatively different behaviors depending on the strength of the attraction between particles. For no or low attraction, the changes of density as a function of pressure are smooth, although hysteretic due to mechanical metastabilities. For larger attraction, sudden changes of density upon compressing and decompressing occur. This global mechanical instability is correlated to the existence of a thermodynamic first-order amorphous-amorphous transition. The two different behaviors obtained correspond qualitatively to the different phenomenology observed in silica and water.

DNA of a Human Hepatitis B Virus Candidate

PubMed Central

Robinson, William S.; Clayton, David A.; Greenman, Richard L.

1974-01-01

Particles containing DNA polymerase (Dane particles) were purified from the plasma of chronic carriers of hepatitis B antigen. After a DNA polymerase reaction with purified Dane particle preparations treated with Nonidet P-40 detergent, Dane particle core structures containing radioactive DNA product were isolated by sedimentation in a sucrose density gradient. The radioactive DNA was extracted with sodium dodecyl sulfate and isolated by band sedimentation in a preformed CsCl gradient. Examination of the radioactive DNA band by electron microscopy revealed exclusively circular double-stranded DNA molecules approximately 0.78 μm in length. Identical circular molecules were observed when DNA was isolated by a similar procedure from particles that had not undergone a DNA polymerase reaction. The molecules were completely degraded by DNase 1. When Dane particle core structures were treated with DNase 1 before DNA extraction, only 0.78-μm circular DNA molecules were detected. Without DNase treatment of core structures, linear molecules with lengths between 0.5 and 12 μm, in addition to the 0.78-μm circles were found. These results suggest that the 0.78-μm circular molecules were in a protected position within Dane particle cores and the linear molecules were not within core structures. Length measurements on 225 circular molecules revealed a mean length of 0.78 ± 0.09 μm which would correspond to a molecular weight of around 1.6 × 106. The circular molecules probably serve as primer-template for the DNA polymerase reaction carried out by Dane particle cores. Thermal denaturation and buoyant density measurements on the Dane particle DNA polymerase reaction product revealed a guanosine plus cytosine content of 48 to 49%. Images PMID:4847328

Emergency deployable core catcher

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

Rosewell, M.P.

An emergency melt down core catcher apparatus for a nuclear reactor having a retrofitable eutectic solute holding vessel connected to a core containment vessel with particle transferring fluid and particles or granules of solid eutectic solute materials contained therein and transferable by automatically operated valve means to transport and position the solid eutectic solute material in a position below the core to catch and react with any partial or complete melt down of the fuel core.

Development and validation of a critical gradient energetic particle driven Alfven eigenmode transport model for DIII-D tilted neutral beam experiments

DOE PAGES

Waltz, Ronald E.; Bass, Eric M.; Heidbrink, William W.; ...

2015-10-30

Recent experiments with the DIII-D tilted neutral beam injection (NBI) varying the beam energetic particle (EP) source profiles have provided strong evidence that unstable Alfven eigenmodes (AE) drive stiff EP transport at a critical EP density gradient. Here the critical gradient is identified by the local AE growth rate being equal to the local ITG/TEM growth rate at the same low toroidal mode number. The growth rates are taken from the gyrokinetic code GYRO. Simulation show that the slowing down beam-like EP distribution has a slightly lower critical gradient than the Maxwellian. The ALPHA EP density transport code, used tomore » validate the model, combines the low-n stiff EP critical density gradient AE mid-core transport with the energy independent high-n ITG/TEM density transport model controling the central core EP density profile. For the on-axis NBI heated DIII-D shot 146102, while the net loss to the edge is small, about half the birth fast ions are transported from the central core r/a < 0.5 and the central density is about half the slowing down density. Lastly, these results are in good agreement with experimental fast ion pressure profiles inferred from MSE constrained EFIT equilibria.« less

Modeling and Detection of Ice Particle Accretion in Aircraft Engine Compression Systems

NASA Technical Reports Server (NTRS)

May, Ryan D.; Simon, Donald L.; Guo, Ten-Huei

2012-01-01

The accretion of ice particles in the core of commercial aircraft engines has been an ongoing aviation safety challenge. While no accidents have resulted from this phenomenon to date, numerous engine power loss events ranging from uneventful recoveries to forced landings have been recorded. As a first step to enabling mitigation strategies during ice accretion, a detection scheme must be developed that is capable of being implemented on board modern engines. In this paper, a simple detection scheme is developed and tested using a realistic engine simulation with approximate ice accretion models based on data from a compressor design tool. These accretion models are implemented as modified Low Pressure Compressor maps and have the capability to shift engine performance based on a specified level of ice blockage. Based on results from this model, it is possible to detect the accretion of ice in the engine core by observing shifts in the typical sensed engine outputs. Results are presented in which, for a 0.1 percent false positive rate, a true positive detection rate of 98 percent is achieved.

Discussion on Microwave-Matter Interaction Mechanisms by In Situ Observation of "Core-Shell" Microstructure during Microwave Sintering.

PubMed

Liu, Wenchao; Xu, Feng; Li, Yongcun; Hu, Xiaofang; Dong, Bo; Xiao, Yu

2016-02-23

This research aims to deepen the understanding of the interaction mechanisms between microwave and matter in a metal-ceramic system based on in situ synchrotron radiation computed tomography. A special internal "core-shell" microstructure was discovered for the first time and used as an indicator for the interaction mechanisms between microwave and matter. Firstly, it was proved that the microwave magnetic field acted on metal particles by way of inducing an eddy current in the surface of the metal particles, which led to the formation of a "core-shell" microstructure in the metal particles. On this basis, it was proposed that the ceramic particles could change the microwave field and open a way for the microwave, thereby leading to selective heating in the region around the ceramic particles, which was verified by the fact that all the "core-shell" microstructure was located around ceramic particles. Furthermore, it was indicated that the ceramic particles would gather the microwaves, and might lead to local heating in the metal-ceramic contact region. The focusing of the microwave was proved by the quantitative analysis of the evolution rate of the "core-shell" microstructure in a different region. This study will help to reveal the microwave-matter interaction mechanisms during microwave sintering.

CQPSO scheduling algorithm for heterogeneous multi-core DAG task model

NASA Astrophysics Data System (ADS)

Zhai, Wenzheng; Hu, Yue-Li; Ran, Feng

2017-07-01

Efficient task scheduling is critical to achieve high performance in a heterogeneous multi-core computing environment. The paper focuses on the heterogeneous multi-core directed acyclic graph (DAG) task model and proposes a novel task scheduling method based on an improved chaotic quantum-behaved particle swarm optimization (CQPSO) algorithm. A task priority scheduling list was built. A processor with minimum cumulative earliest finish time (EFT) was acted as the object of the first task assignment. The task precedence relationships were satisfied and the total execution time of all tasks was minimized. The experimental results show that the proposed algorithm has the advantage of optimization abilities, simple and feasible, fast convergence, and can be applied to the task scheduling optimization for other heterogeneous and distributed environment.

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

Lyn, Rodney K.; Department of Chemistry, University of Ottawa, Ottawa; Kennedy, David C.

Research highlights: {yields} Hepatitis C virus uses lipid droplets (LD) onto which HCV core proteins bind. {yields} HCV core proteins on LDs facilitate viral particle assembly. {yields} We used a novel combination of CARS, two-photon fluorescence, and DIC microscopies. {yields} Particle tracking experiments show that core slowly affects LD localization. {yields} Particle tracking measured the change in speed and directionality of LD movement. -- Abstract: The hepatitis C virus (HCV) is a global health problem, with limited treatment options and no vaccine available. HCV uses components of the host cell to proliferate, including lipid droplets (LD) onto which HCV coremore » proteins bind and facilitate viral particle assembly. We have measured the dynamics of HCV core protein-mediated changes in LDs and rates of LD movement on microtubules using a combination of coherent anti-Stokes Raman scattering (CARS), two-photon fluorescence (TPF), and differential interference contrast (DIC) microscopies. Results show that the HCV core protein induces rapid increases in LD size. Particle tracking experiments show that HCV core protein slowly affects LD localization by controlling the directionality of LD movement on microtubules. These dynamic processes ultimately aid HCV in propagating and the molecules and interactions involved represent novel targets for potential therapeutic intervention.« less

Multifunctional particles for melanoma-targeted drug delivery.

PubMed

Wadajkar, Aniket S; Bhavsar, Zarna; Ko, Cheng-Yu; Koppolu, Bhanuprasanth; Cui, Weina; Tang, Liping; Nguyen, Kytai T

2012-08-01

New magnetic-based core-shell particles (MBCSPs) were developed to target skin cancer cells while delivering chemotherapeutic drugs in a controlled fashion. MBCSPs consist of a thermo-responsive shell of poly(N-isopropylacrylamide-acrylamide-allylamine) and a core of poly(lactic-co-glycolic acid) (PLGA) embedded with magnetite nanoparticles. To target melanoma cancer cells, MBCSPs were conjugated with Gly-Arg-Gly-Asp-Ser (GRGDS) peptides that specifically bind to the α(5)β(3) receptors of melanoma cells. MBCSPs consist of unique multifunctional and controlled drug delivery characteristics. Specially, they can provide dual drug release mechanisms (a sustained release of drugs through degradation of PLGA core and a controlled release in response to changes in temperature via thermo-responsive polymer shell), and dual targeting mechanisms (magnetic localization and receptor-mediated targeting). Results from in vitro studies indicate that GRGDS-conjugated MBCSPs have an average diameter of 296 nm and exhibit no cytotoxicity towards human dermal fibroblasts up to 500 μg ml(-1). Further, a sustained release of curcumin from the core and a temperature-dependent release of doxorubicin from the shell of MBCSPs were observed. The particles also produced a dark contrast signal in magnetic resonance imaging. Finally, the particles were accumulated at the tumor site in a B16F10 melanoma orthotopic mouse model, especially in the presence of a magnet. Results indicate great potential of MBCSPs as a platform technology to target, treat and monitor melanoma for targeted drug delivery to reduce side effects of chemotherapeutic reagents. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A pathway for the growth of core-shell Pt-Pd nanoparticles

DOE PAGES

Narula, Chaitanya Kumar; Yang, Xiaofan; Li, Chen; ...

2015-10-12

In this study, the aging of both Pt-Pd nanoparticles and core-shell Pt-Pd nanoparticles has been reported to result in alloying of Pt with Pd. In comparison to monometallic Pt catalysts, the growth of Pd-Pt bimetallics is slower; however, the mechanism of growth of particles and the mechanism by which Pd improves the hydrothermal durability of bimetallic Pd-Pt particles remains uncertain. In our work on hydrothermal aging of core-shell Pt-Pd nanoparticles, synthesized by solution methods, with varying Pd:Pt ratio of 1:4, 1:1, and 4:1, we compare the growth of core-shell Pt-Pd nanoparticles and find that particles grow by migrating and joiningmore » together. The unique feature of the observed growth is that Pd shells from both particles open up and join, allowing the cores to merge. At high temperatures, alloying occurs in good agreement with reports by other workers.« less

Polyethylenimine-immobilized core-shell nanoparticles: synthesis, characterization, and biocompatibility test.

PubMed

Ratanajanchai, Montri; Soodvilai, Sunhapas; Pimpha, Nuttaporn; Sunintaboon, Panya

2014-01-01

Herein, we prepared PEI-immobilized core-shell particles possessing various types of polymer cores via a visible light-induced surfactant-free emulsion polymerization (SFEP) of three vinyl monomers: styrene (St), methyl methacrylate (MMA), and 2-hydroxyethyl methacrylate (HEMA). An effect of monomers on the polymerization and characteristics of resulting products was investigated. Monomers with high polarity can provide high monomer conversion, high percentage of grafted PEI, stable particles with uniform size distribution but less amino groups per particles. All prepared nanoparticles exhibited a core-shell nanostructure, containing PEI on the shell with hydrodynamic size around 140-230nm. For in-vitro study in Caco-2 cells, we found that the incorporation of PEI into these core-shell nanoparticles can significantly reduce its cytotoxic effect and also be able to internalized within the cells. Accordingly, these biocompatible particles would be useful for various biomedical applications, including gene transfection and intracellular drug delivery. © 2013.

Photoreactive, core-shell cross-linked/hollow microspheres prepared by delayed addition of cross-linker in dispersion polymerization for antifouling and immobilization of protein.

PubMed

Wang, Shengliu; Yue, Kai; Liu, Lianying; Yang, Wantai

2013-01-01

When dispersion polymerization of styrene (St) had run for 3h, after particle rapidly growing stage, 4,4'-dimethacryloyloxybenzophenone (DMABP) cross-linker was added to reaction system and photoreactive, core(PSt)-shell(Poly(St-co-DMABP)) particles with rich benzophenone (BP) groups on surface were prepared. Polymerization of DMABP could occurred mainly on the preformed core of PSt because its diffusion could be impeded by (1) compactness of particles formed at the moment of cross-linker addition (more than 80% of monomer had been consumed, particles were no longer fully swollen by monomer), (2) reduced polarity of continuous phase, and (3) immediate occurrence of cross-linking. Subsequently, photoreactive, cross-linked hollow particles were yielded by removal of uncross-linked core in THF. SEM and TEM observation demonstrated the formation of core-shell structure and improvement of shell thickness when DMABP content increased. UV-vis spectra analysis on polymer dissolved in THF indicated that there is no polymer of DMABP in core. FTIR spectra analysis and XPS measurement further revealed that BP component on particle surface was enriched when amount of DMABP increased. Finally, an anti-fouling polymer (poly (ethylene glycol), PEG) and protein of mouse IgG was immobilized on particle surface under UV irradiation, as confirmed by FTIR spectra analysis, SEM observation and TMB color reaction. Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.

Full-Color Biomimetic Photonic Materials with Iridescent and Non-Iridescent Structural Colors

PubMed Central

Kawamura, Ayaka; Kohri, Michinari; Morimoto, Gen; Nannichi, Yuri; Taniguchi, Tatsuo; Kishikawa, Keiki

2016-01-01

The beautiful structural colors in bird feathers are some of the brightest colors in nature, and some of these colors are created by arrays of melanin granules that act as both structural colors and scattering absorbers. Inspired by the color of bird feathers, high-visibility structural colors have been created by altering four variables: size, blackness, refractive index, and arrangement of the nano-elements. To control these four variables, we developed a facile method for the preparation of biomimetic core-shell particles with melanin-like polydopamine (PDA) shell layers. The size of the core-shell particles was controlled by adjusting the core polystyrene (PSt) particles’ diameter and the PDA shell thicknesses. The blackness and refractive index of the colloidal particles could be adjusted by controlling the thickness of the PDA shell. The arrangement of the particles was controlled by adjusting the surface roughness of the core-shell particles. This method enabled the production of both iridescent and non-iridescent structural colors from only one component. This simple and novel process of using core-shell particles containing PDA shell layers can be used in basic research on structural colors in nature and their practical applications. PMID:27658446

Structural Color Tuning: Mixing Melanin-Like Particles with Different Diameters to Create Neutral Colors.

PubMed

Kawamura, Ayaka; Kohri, Michinari; Yoshioka, Shinya; Taniguchi, Tatsuo; Kishikawa, Keiki

2017-04-18

We present the ability to tune structural colors by mixing colloidal particles. To produce high-visibility structural colors, melanin-like core-shell particles composed of a polystyrene (PSt) core and a polydopamine (PDA) shell, were used as components. The results indicated that neutral structural colors could be successfully obtained by simply mixing two differently sized melanin-like PSt@PDA core-shell particles. In addition, the arrangements of the particles, which were important factors when forming structural colors, were investigated by mathematical processing using a 2D Fourier transform technique and Voronoi diagrams. These findings provide new insights for the development of structural color-based ink applications.

Experimental and numerical study of steam gasification of a single charcoal particle

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

Mermoud, F.; Van de Steene, L.; Golfier, F.

2006-04-15

The present work deals with a study coupling experiments and modeling of charcoal gasification by steam at large particle scale. A reliable set of experiments was first established using a specially developed 'macro-TG' apparatus where a particle was suspended and continuously weighed during its gasification. The main control parameters of a fixed-bed process were modified separately: steam gasification of beech charcoal spheres of different diameters (10 to 30 mm) was studied at different temperatures (830 to 1030{sup o}C), different steam partial pressures (0.1 to 0.4 atm H{sub 2}O), and different gas velocities around the particle (0.09 to 0.30 m/s). Simulationsmore » with the particle model were performed for each case. Confrontations with experimental data indicate that the model predictions are both qualitatively and quantitatively satisfactory, with an accuracy of 7%, until 60% of conversion, despite the fact that the phenomena of reactive surface evolution and particle fracturing are not well understood. Anisotropy and peripheral fragmentation make the end of the process difficult to simulate. Finally, an analysis of the thermochemical situation is proposed: it is demonstrated that the usual homogeneous or shrinking core particle models are not satisfying and that only the assumption of thermal equilibrium between the particle and the surrounding gas is valid for a model at bed scale. (author)« less

Modes of interaction between nanostructured metal and a conducting mirror as a function of separation and incident polarization

NASA Astrophysics Data System (ADS)

Bonnie, F.; Arnold, M. D.; Smith, G. B.; Gentle, A. R.

2013-09-01

The optical resonances that occur in nanostructured metal layers are modulated in thin film stacks if the nanostructured layer is separated from a reflecting conducting layer by various thicknesses of thin dielectric. We have measured and modeled the optical response of interacting silver layers, with alumina spacer thickness ranging from a few nm to 50 nm, for s- and p-polarized incident light, and a range of incident angles. Standard thin film models, including standard effective medium models for the nanostructured layer, will break down for spacer thickness below a critical threshold. For example, with polarisation in the film plane and some nano-islands, it may occur at around 10 nm depending on spacer refractive index. Of particular interest here are novel effects observed with the onset of percolation in the nanolayer. Hot spot effects can be modified by nearby mirrors. Other modes to consider include (a) a two-particle mode involving a particle and its mirror image (b) A Fano resonance from hybridisation of localized and de-localised plasmon modes (c) a Babinet's core-(partial) shell particle with metal core-dielectric shell in metal (d) spacing dependent phase modulation (e) the impact of field gradients induced by the mirror at the nano-layer.

Role of core excitation in (d ,p ) transfer reactions

NASA Astrophysics Data System (ADS)

Deltuva, A.; Ross, A.; Norvaišas, E.; Nunes, F. M.

2016-10-01

Background: Recent work found that core excitations can be important in extracting structure information from (d ,p ) reactions. Purpose: Our objective is to systematically explore the role of core excitation in (d ,p ) reactions and to understand the origin of the dynamical effects. Method: Based on the particle-rotor model of n +10Be , we generate a number of models with a range of separation energies (Sn=0.1 -5.0 MeV), while maintaining a significant core excited component. We then apply the latest extension of the momentum-space-based Faddeev method, including dynamical core excitation in the reaction mechanism to all orders, to the 10Be(d ,p )11Be -like reactions, and study the excitation effects for beam energies Ed=15 -90 MeV. Results: We study the resulting angular distributions and the differences between the spectroscopic factor that would be extracted from the cross sections, when including dynamical core excitation in the reaction, and that of the original structure model. We also explore how different partial waves affect the final cross section. Conclusions: Our results show a strong beam-energy dependence of the extracted spectroscopic factors that become smaller for intermediate beam energies. This dependence increases for loosely bound systems.

The Role of Nanoparticle Surface Functionality in the Disruption of Model Cell Membranes

PubMed Central

Moghadam, Babak Y.; Hou, Wen-Che; Corredor, Charlie; Westerhoff, Paul; Posner, Jonathan D.

2012-01-01

Lipid bilayers are biomembranes common to cellular life and constitute a continuous barrier between cells and their environment. Understanding the interaction of engineered nanomaterials (ENMs) with lipid bilayers is an important step toward predicting subsequent biological effects. In this study, we assess the effect of varying the surface functionality and concentration of 10 nm-diameter gold (Au) and titanium dioxide (TiO2) ENMs on the disruption of negatively charged lipid bilayer vesicles (liposomes) using a dye leakage assay. Our findings show that Au ENMs having both positive and negative surface charge induce leakage that reaches a steady state after several hours. Positively charged particles with identical surface functionality and different core composition show similar leakage effects and result in faster and greater leakage than negatively charged particles, which suggests that surface functionality, not particle core composition, is a critical factor in determining the interaction between ENMs and lipid bilayers. The results suggest that particles permanently adsorb to bilayers and that only one positively charged particle is required to disrupt a liposome and trigger leakage of its entire contents in contrast to mellitin molecules, the most widely studied membrane lytic peptide, which requires hundred of molecules to generate leakage. PMID:22921268

TWO-DIMENSIONAL CORE-COLLAPSE SUPERNOVA SIMULATIONS WITH THE ISOTROPIC DIFFUSION SOURCE APPROXIMATION FOR NEUTRINO TRANSPORT

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

Pan, Kuo-Chuan; Liebendörfer, Matthias; Hempel, Matthias

2016-01-20

The neutrino mechanism of core-collapse supernova is investigated via non-relativistic, two-dimensional (2D), neutrino radiation–hydrodynamic simulations. For the transport of electron flavor neutrinos, we use the interaction rates defined by Bruenn and the isotropic diffusion source approximation (IDSA) scheme, which decomposes the transported particles into trapped-particle and streaming-particle components. Heavy neutrinos are described by a leakage scheme. Unlike the “ray-by-ray” approach in some other multidimensional supernova models, we use cylindrical coordinates and solve the trapped-particle component in multiple dimensions, improving the proto-neutron star resolution and the neutrino transport in angular and temporal directions. We provide an IDSA verification by performing one-dimensionalmore » (1D) and 2D simulations with 15 and 20 M{sub ⊙} progenitors from Woosley et al. and discuss the difference between our IDSA results and those existing in the literature. Additionally, we perform Newtonian 1D and 2D simulations from prebounce core collapse to several hundred milliseconds postbounce with 11, 15, 21, and 27 M{sub ⊙} progenitors from Woosley et al. with the HS(DD2) equation of state. General-relativistic effects are neglected. We obtain robust explosions with diagnostic energies E{sub dia} ≳ 0.1–0.5 B (1 B ≡ 10{sup 51} erg) for all considered 2D models within approximately 100–300 ms after bounce and find that explosions are mostly dominated by the neutrino-driven convection, although standing accretion shock instabilities are observed as well. We also find that the level of electron deleptonization during collapse dramatically affects the postbounce evolution, e.g., the neglect of neutrino–electron scattering during collapse will lead to a stronger explosion.« less

Drift of suspended ferromagnetic particles due to the Magnus effect

NASA Astrophysics Data System (ADS)

Denisov, S. I.; Pedchenko, B. O.

2017-01-01

A minimal system of equations is introduced and applied to study the drift motion of ferromagnetic particles suspended in a viscous fluid and subjected to a time-periodic driving force and a nonuniformly rotating magnetic field. It is demonstrated that the synchronized translational and rotational oscillations of these particles are accompanied by their drift in a preferred direction, which occurs under the action of the Magnus force. We calculate both analytically and numerically the drift velocity of particles characterized by single-domain cores and nonmagnetic shells and show that there are two types of drift, unidirectional and bidirectional, which can be realized in suspensions composed of particles with different core-shell ratios. The possibility of using the phenomenon of bidirectional drift for the separation of core-shell particles in suspensions is also discussed.

Investigations on the magnetization behavior of magnetic composite particles

NASA Astrophysics Data System (ADS)

Eichholz, Christian; Knoll, Johannes; Lerche, Dietmar; Nirschl, Hermann

2014-11-01

In life sciences the application of surface functionalized magnetic composite particles is establishing in diagnostics and in downstream processing of modern biotechnology. These magnetic composite particles consist of non-magnetic material, e.g. polystyrene, which serves as a matrix for the second magnetic component, usually colloidal magnetite. Because of the multitude of magnetic cores these magnetic beads show a complex magnetization behavior which cannot be described with the available approaches for homogeneous magnetic material. Therefore, in this work a new model for the magnetization behavior of magnetic composite particles is developed. By introducing an effective magnetization and considering an overall demagnetization factor the deviation of the demagnetization of homogeneously magnetized particles is taken into account. Calculated and experimental results show a good agreement which allows for the verification of the adapted model of particle magnetization. Besides, a newly developed magnetic analyzing centrifuge is used for the characterization of magnetic composite particle systems. The experimental results, also used for the model verification, give both, information about the magnetic properties and the interaction behavior of particle systems. By adding further components to the particle solution, such as salts or proteins, industrial relevant systems can be reconstructed. The analyzing tool can be used to adapt industrial processes without time-consuming preliminary tests with large samples in the process equipments.

Role of cleavage at the core-E1 junction of hepatitis C virus polyprotein in viral morphogenesis.

PubMed

Pène, Véronique; Lemasson, Matthieu; Harper, Francis; Pierron, Gérard; Rosenberg, Arielle R

2017-01-01

In hepatitis C virus (HCV) polyprotein sequence, core protein terminates with E1 envelope signal peptide. Cleavage by signal peptidase (SP) separates E1 from the complete form of core protein, anchored in the endoplasmic reticulum (ER) membrane by the signal peptide. Subsequent cleavage of the signal peptide by signal-peptide peptidase (SPP) releases the mature form of core protein, which preferentially relocates to lipid droplets. Both of these cleavages are required for the HCV infectious cycle, supporting the idea that HCV assembly begins at the surface of lipid droplets, yet SPP-catalyzed cleavage is dispensable for initiation of budding in the ER. Here we have addressed at what step(s) of the HCV infectious cycle SP-catalyzed cleavage at the core-E1 junction is required. Taking advantage of the sole system that has allowed visualization of HCV budding events in the ER lumen of mammalian cells, we showed that, unexpectedly, mutations abolishing this cleavage did not prevent but instead tended to promote the initiation of viral budding. Moreover, even though no viral particles were released from Huh-7 cells transfected with a full-length HCV genome bearing these mutations, intracellular viral particles containing core protein protected by a membrane envelope were formed. These were visualized by electron microscopy as capsid-containing particles with a diameter of about 70 nm and 40 nm before and after delipidation, respectively, comparable to intracellular wild-type particle precursors except that they were non-infectious. Thus, our results show that SP-catalyzed cleavage is dispensable for HCV budding per se, but is required for the viral particles to acquire their infectivity and secretion. These data support the idea that HCV assembly occurs in concert with budding at the ER membrane. Furthermore, capsid-containing particles did not accumulate in the absence of SP-catalyzed cleavage, suggesting the quality of newly formed viral particles is controlled before secretion.

Role of cleavage at the core-E1 junction of hepatitis C virus polyprotein in viral morphogenesis

PubMed Central

Pène, Véronique; Lemasson, Matthieu; Harper, Francis; Pierron, Gérard; Rosenberg, Arielle R.

2017-01-01

In hepatitis C virus (HCV) polyprotein sequence, core protein terminates with E1 envelope signal peptide. Cleavage by signal peptidase (SP) separates E1 from the complete form of core protein, anchored in the endoplasmic reticulum (ER) membrane by the signal peptide. Subsequent cleavage of the signal peptide by signal-peptide peptidase (SPP) releases the mature form of core protein, which preferentially relocates to lipid droplets. Both of these cleavages are required for the HCV infectious cycle, supporting the idea that HCV assembly begins at the surface of lipid droplets, yet SPP-catalyzed cleavage is dispensable for initiation of budding in the ER. Here we have addressed at what step(s) of the HCV infectious cycle SP-catalyzed cleavage at the core-E1 junction is required. Taking advantage of the sole system that has allowed visualization of HCV budding events in the ER lumen of mammalian cells, we showed that, unexpectedly, mutations abolishing this cleavage did not prevent but instead tended to promote the initiation of viral budding. Moreover, even though no viral particles were released from Huh-7 cells transfected with a full-length HCV genome bearing these mutations, intracellular viral particles containing core protein protected by a membrane envelope were formed. These were visualized by electron microscopy as capsid-containing particles with a diameter of about 70 nm and 40 nm before and after delipidation, respectively, comparable to intracellular wild-type particle precursors except that they were non-infectious. Thus, our results show that SP-catalyzed cleavage is dispensable for HCV budding per se, but is required for the viral particles to acquire their infectivity and secretion. These data support the idea that HCV assembly occurs in concert with budding at the ER membrane. Furthermore, capsid-containing particles did not accumulate in the absence of SP-catalyzed cleavage, suggesting the quality of newly formed viral particles is controlled before secretion. PMID:28437468

Particle acceleration at shocks in the inner heliosphere

NASA Astrophysics Data System (ADS)

Parker, Linda Neergaard

This dissertation describes a study of particle acceleration at shocks via the diffusive shock acceleration mechanism. Results for particle acceleration at both quasi-parallel and quasi-perpendicular shocks are presented to address the question of whether there are sufficient particles in the solar wind thermal core, modeled as either a Maxwellian or kappa- distribution, to account for the observed accelerated spectrum. Results of accelerating the theoretical upstream distribution are compared to energetic observations at 1 AU. It is shown that the particle distribution in the solar wind thermal core is sufficient to explain the accelerated particle spectrum downstream of the shock, although the shape of the downstream distribution in some cases does not follow completely the theory of diffusive shock acceleration, indicating possible additional processes at work in the shock for these cases. Results show good to excellent agreement between the theoretical and observed spectral index for one third to one half of both quasi-parallel and quasi-perpendicular shocks studied herein. Coronal mass ejections occurring during periods of high solar activity surrounding solar maximum can produce shocks in excess of 3-8 shocks per day. During solar minimum, diffusive shock acceleration at shocks can generally be understood on the basis of single independent shocks and no other shock necessarily influences the diffusive shock acceleration mechanism. In this sense, diffusive shock acceleration during solar minimum may be regarded as Markovian. By contrast, diffusive shock acceleration of particles at periods of high solar activity (e.g. solar maximum) see frequent, closely spaced shocks that include the effects of particle acceleration at preceding and following shocks. Therefore, diffusive shock acceleration of particles at solar maximum cannot be modeled on the basis of diffusive shock acceleration as a single, independent shock and the process is essentially non-Markovian. A multiple shock model is developed based in part on the box model of (Protheroe and Stanev, 1998; Moraal and Axford, 1983; Ball and Kirk, 1992; Drury et al. 1999) that accelerates particles at multiple shocks and decompresses the particles between shocks via two methods. The first method of decompression is based on the that used by Melrose and Pope (1993), which adiabatically decompresses particles between shocks. The second method solves the cosmic ray transport equation and adiabatically decompresses between shocks and includes the loss of particles through convection and diffusion. The transport method allows for the inclusion of a temporal variability and thus allows for a more representative frequency distribution of shocks. The transport method of decompression and loss is used to accelerate particles at seventy-three shocks in a thirty day time period. Comparisons with observations taken at 1 AU during the same time period are encouraging as the model is able to reproduce the observed amplitude of the accelerated particles and in part the variability. This work provides the basis for developing more sophisticated models that can be applied to a suite of observations

ReaDDy - A Software for Particle-Based Reaction-Diffusion Dynamics in Crowded Cellular Environments

PubMed Central

Schöneberg, Johannes; Noé, Frank

2013-01-01

We introduce the software package ReaDDy for simulation of detailed spatiotemporal mechanisms of dynamical processes in the cell, based on reaction-diffusion dynamics with particle resolution. In contrast to other particle-based reaction kinetics programs, ReaDDy supports particle interaction potentials. This permits effects such as space exclusion, molecular crowding and aggregation to be modeled. The biomolecules simulated can be represented as a sphere, or as a more complex geometry such as a domain structure or polymer chain. ReaDDy bridges the gap between small-scale but highly detailed molecular dynamics or Brownian dynamics simulations and large-scale but little-detailed reaction kinetics simulations. ReaDDy has a modular design that enables the exchange of the computing core by efficient platform-specific implementations or dynamical models that are different from Brownian dynamics. PMID:24040218

Random close packing in protein cores

NASA Astrophysics Data System (ADS)

Ohern, Corey

Shortly after the determination of the first protein x-ray crystal structures, researchers analyzed their cores and reported packing fractions ϕ ~ 0 . 75 , a value that is similar to close packing equal-sized spheres. A limitation of these analyses was the use of `extended atom' models, rather than the more physically accurate `explicit hydrogen' model. The validity of using the explicit hydrogen model is proved by its ability to predict the side chain dihedral angle distributions observed in proteins. We employ the explicit hydrogen model to calculate the packing fraction of the cores of over 200 high resolution protein structures. We find that these protein cores have ϕ ~ 0 . 55 , which is comparable to random close-packing of non-spherical particles. This result provides a deeper understanding of the physical basis of protein structure that will enable predictions of the effects of amino acid mutations and design of new functional proteins. We gratefully acknowledge the support of the Raymond and Beverly Sackler Institute for Biological, Physical, and Engineering Sciences, National Library of Medicine training grant T15LM00705628 (J.C.G.), and National Science Foundation DMR-1307712 (L.R.).

Shock compression of Fe-Ni-Si system to 280 GPa: Implications for the composition of the Earth's outer core

NASA Astrophysics Data System (ADS)

Zhang, Youjun; Sekine, Toshimori; He, Hongliang; Yu, Yin; Liu, Fusheng; Zhang, Mingjian

2014-07-01

The shock Hugoniot of an Fe-9 wt %Ni-10 wt %Si system as a model of the Earth's core has been measured up to ~280 GPa using a two-stage light-gas gun. The samples had an average density of 6.853 (±0.036) g/cm3. The relationship between shock velocity (Us) and particle velocity (up) can be described by Us (km/s) = 3.95 (±0.15) + 1.53 (±0.05) up (km/s). The calculated Hugoniot temperatures and the melting curve indicate that the model composition melts above a shock pressure of ~168 GPa, which is significantly lower than the shock-melting pressure of iron (~225 GPa). A comparison of the pressure-density (P-ρ) profiles between the model composition and the preliminary reference Earth model gives a silicon content close to 10 wt %, necessary to compensate the density deficit in the Earth's outer core from seismological observations, if silicon is present as a major light element in the Fe-Ni core system.

Character of energy flow in air shower core

NASA Technical Reports Server (NTRS)

Mizushima, K.; Asakimori, K.; Maeda, T.; Kameda, T.; Misaki, Y.

1985-01-01

Energy per charged particle near the core of air showers was measured by 9 energy flow detectors, which were the combination of Cerenkov counters and scintillators. Energy per particle of each detector was normalized to energy at 2m from the core. The following results were obtained as to the energy flow: (1) integral frequency distribution of mean energy per particle (averaged over 9 detectors) is composed of two groups separated distinctly; and (2) showers contained in one group show an anisotropy of arrival direction.

Graphics Processing Unit Acceleration of Gyrokinetic Turbulence Simulations

NASA Astrophysics Data System (ADS)

Hause, Benjamin; Parker, Scott; Chen, Yang

2013-10-01

We find a substantial increase in on-node performance using Graphics Processing Unit (GPU) acceleration in gyrokinetic delta-f particle-in-cell simulation. Optimization is performed on a two-dimensional slab gyrokinetic particle simulation using the Portland Group Fortran compiler with the OpenACC compiler directives and Fortran CUDA. Mixed implementation of both Open-ACC and CUDA is demonstrated. CUDA is required for optimizing the particle deposition algorithm. We have implemented the GPU acceleration on a third generation Core I7 gaming PC with two NVIDIA GTX 680 GPUs. We find comparable, or better, acceleration relative to the NERSC DIRAC cluster with the NVIDIA Tesla C2050 computing processor. The Tesla C 2050 is about 2.6 times more expensive than the GTX 580 gaming GPU. We also see enormous speedups (10 or more) on the Titan supercomputer at Oak Ridge with Kepler K20 GPUs. Results show speed-ups comparable or better than that of OpenMP models utilizing multiple cores. The use of hybrid OpenACC, CUDA Fortran, and MPI models across many nodes will also be discussed. Optimization strategies will be presented. We will discuss progress on optimizing the comprehensive three dimensional general geometry GEM code.

Core-shell fuel cell electrodes

DOEpatents

Adzic, Radoslav; Bliznakov, Stoyan; Vukmirovic, Miomir

2017-07-25

Embodiments of the disclosure relate to electrocatalysts. The electrocatalyst may include at least one gas-diffusion layer having a first side and a second side, and particle cores adhered to at least one of the first and second sides of the at least one gas-diffusion layer. The particle cores includes surfaces adhered to the at least one of the first and second sides of the at least one gas-diffusion layer and surfaces not in contact with the at least one gas-diffusion layer. Furthermore, a thin layer of catalytically atoms may be adhered to the surfaces of the particle cores not in contact with the at least one gas-diffusion layer.

Tandem Fusion of Hepatitis B Core Antigen Allows Assembly of Virus-Like Particles in Bacteria and Plants with Enhanced Capacity to Accommodate Foreign Proteins

PubMed Central

Peyret, Hadrien; Gehin, Annick; Thuenemann, Eva C.; Blond, Donatienne; El Turabi, Aadil; Beales, Lucy; Clarke, Dean; Gilbert, Robert J. C.; Fry, Elizabeth E.; Stuart, David I.; Holmes, Kris; Stonehouse, Nicola J.; Whelan, Mike; Rosenberg, William; Lomonossoff, George P.; Rowlands, David J.

2015-01-01

The core protein of the hepatitis B virus, HBcAg, assembles into highly immunogenic virus-like particles (HBc VLPs) when expressed in a variety of heterologous systems. Specifically, the major insertion region (MIR) on the HBcAg protein allows the insertion of foreign sequences, which are then exposed on the tips of surface spike structures on the outside of the assembled particle. Here, we present a novel strategy which aids the display of whole proteins on the surface of HBc particles. This strategy, named tandem core, is based on the production of the HBcAg dimer as a single polypeptide chain by tandem fusion of two HBcAg open reading frames. This allows the insertion of large heterologous sequences in only one of the two MIRs in each spike, without compromising VLP formation. We present the use of tandem core technology in both plant and bacterial expression systems. The results show that tandem core particles can be produced with unmodified MIRs, or with one MIR in each tandem dimer modified to contain the entire sequence of GFP or of a camelid nanobody. Both inserted proteins are correctly folded and the nanobody fused to the surface of the tandem core particle (which we name tandibody) retains the ability to bind to its cognate antigen. This technology paves the way for the display of natively folded proteins on the surface of HBc particles either through direct fusion or through non-covalent attachment via a nanobody. PMID:25830365

Pebble Accretion in Turbulent Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Xu, Ziyan; Bai, Xue-Ning; Murray-Clay, Ruth A.

2017-09-01

It has been realized in recent years that the accretion of pebble-sized dust particles onto planetary cores is an important mode of core growth, which enables the formation of giant planets at large distances and assists planet formation in general. The pebble accretion theory is built upon the orbit theory of dust particles in a laminar protoplanetary disk (PPD). For sufficiently large core mass (in the “Hill regime”), essentially all particles of appropriate sizes entering the Hill sphere can be captured. However, the outer regions of PPDs are expected to be weakly turbulent due to the magnetorotational instability (MRI), where turbulent stirring of particle orbits may affect the efficiency of pebble accretion. We conduct shearing-box simulations of pebble accretion with different levels of MRI turbulence (strongly turbulent assuming ideal magnetohydrodynamics, weakly turbulent in the presence of ambipolar diffusion, and laminar) and different core masses to test the efficiency of pebble accretion at a microphysical level. We find that accretion remains efficient for marginally coupled particles (dimensionless stopping time {τ }s˜ 0.1{--}1) even in the presence of strong MRI turbulence. Though more dust particles are brought toward the core by the turbulence, this effect is largely canceled by a reduction in accretion probability. As a result, the overall effect of turbulence on the accretion rate is mainly reflected in the changes in the thickness of the dust layer. On the other hand, we find that the efficiency of pebble accretion for strongly coupled particles (down to {τ }s˜ 0.01) can be modestly reduced by strong turbulence for low-mass cores.

Composite fluorescent nanoparticles for biomedical imaging.

PubMed

Pansare, Vikram J; Bruzek, Matthew J; Adamson, Douglas H; Anthony, John; Prud'homme, Robert K

2014-04-01

In the rapidly expanding field of biomedical imaging, there is a need for nontoxic, photostable, and nonquenching fluorophores for fluorescent imaging. We have successfully encapsulated a new, extremely hydrophobic, pentacene-based fluorescent dye within polymeric nanoparticles (NPs) or nanocarriers (NCs) via the Flash NanoPrecipitation (FNP) process. Nanoparticles and dye-loaded micelles were formulated by FNP and characterized by dynamic light scattering, fluorescence spectroscopy, UV-VIS absorbance spectroscopy, and confocal microscopy. These fluorescent particles were loaded from less than 1% to 78% by weight core loading and the fluorescence maximum was found to be at 2.3 wt.%. The particles were also stably formed at 2.3% core loading from 20 up to 250 nm in diameter with per-particle fluorescence scaling linearly with the NC core volume. The major absorption peaks are at 458, 575, and 625 nm, and the major emission peaks at 635 and 695 nm. In solution, the Et-TP5 dye displays a strong concentration-dependent ratio of the emission intensities of the first two emission peaks, whereas in the nanoparticle core the spectrum is independent of concentration over the entire concentration range. A model of the fluorescence quenching was consistent with Förster resonant energy transfer as the cause of the quenching observed for Et-TP5. The Förster radius calculated from the absorption and emission spectra of Et-TP5 is 4.1 nm, whereas the average dye spacing in the particles at the maximum fluorescence is 3.9 nm. We have successfully encapsulated Et-TP5, a pentacene derivative dye previously only used in light-emitting diode applications, within NCs via the FNP process. The extreme hydrophobicity of the dye keeps it encapsulated in the NC core, its extended pentacene structure gives it relatively long wavelength emission at 695 nm, and the pentacene structure, without oxygen or nitrogen atoms in its core, makes it highly resistant to photobleaching. Its bulky side groups minimize self-quenching and localization within the nanoparticle core prevents interaction of the dye with biological surfaces, or molecules in diagnostic assays. Loading of dye in the NP core allows 25 times more dye to be delivered than if it were conjugated onto the nanocarrier surface. The utility of the dye for quantifying nanoparticle binding is demonstrated. Studies to extend the wavelength range of these pentacene dyes into the near infra-red are underway.

Structural and magnetic properties of multi-core nanoparticles analysed using a generalised numerical inversion method

PubMed Central

Bender, P.; Bogart, L. K.; Posth, O.; Szczerba, W.; Rogers, S. E.; Castro, A.; Nilsson, L.; Zeng, L. J.; Sugunan, A.; Sommertune, J.; Fornara, A.; González-Alonso, D.; Barquín, L. Fernández; Johansson, C.

2017-01-01

The structural and magnetic properties of magnetic multi-core particles were determined by numerical inversion of small angle scattering and isothermal magnetisation data. The investigated particles consist of iron oxide nanoparticle cores (9 nm) embedded in poly(styrene) spheres (160 nm). A thorough physical characterisation of the particles included transmission electron microscopy, X-ray diffraction and asymmetrical flow field-flow fractionation. Their structure was ultimately disclosed by an indirect Fourier transform of static light scattering, small angle X-ray scattering and small angle neutron scattering data of the colloidal dispersion. The extracted pair distance distribution functions clearly indicated that the cores were mostly accumulated in the outer surface layers of the poly(styrene) spheres. To investigate the magnetic properties, the isothermal magnetisation curves of the multi-core particles (immobilised and dispersed in water) were analysed. The study stands out by applying the same numerical approach to extract the apparent moment distributions of the particles as for the indirect Fourier transform. It could be shown that the main peak of the apparent moment distributions correlated to the expected intrinsic moment distribution of the cores. Additional peaks were observed which signaled deviations of the isothermal magnetisation behavior from the non-interacting case, indicating weak dipolar interactions. PMID:28397851

Hypersonic vibrations of Ag@SiO2 (cubic core)-shell nanospheres.

PubMed

Sun, Jing Ya; Wang, Zhi Kui; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau; Tran, Toan Trong; Lu, Xianmao

2010-12-28

The intriguing optical and catalytic properties of metal-silica core-shell nanoparticles, inherited from their plasmonic metallic cores together with the rich surface chemistry and increased stability offered by their silica shells, have enabled a wide variety of applications. In this work, we investigate the confined vibrational modes of a series of monodisperse Ag@SiO(2) (cubic core)-shell nanospheres synthesized using a modified Stöber sol-gel method. The particle-size dependence of their mode frequencies has been mapped by Brillouin light scattering, a powerful tool for probing hypersonic vibrations. Unlike the larger particles, the observed spheroidal-like mode frequencies of the smaller ones do not scale with inverse diameter. Interestingly, the onset of the deviation from this linearity occurs at a smaller particle size for higher-energy modes than for lower-energy ones. Finite element simulations show that the mode displacement profiles of the Ag@SiO(2) core-shells closely resemble those of a homogeneous SiO(2) sphere. Simulations have also been performed to ascertain the effects that the core shape and the relative hardness of the core and shell materials have on the vibrations of the core-shell as a whole. As the vibrational modes of a particle have a bearing on its thermal and mechanical properties, the findings would be of value in designing core-shell nanostructures with customized thermal and mechanical characteristics.

ANIMAL MODELS: CARDIOVASCULAR DISEASE, CNS INJURY AND ULTRAFINE PARTICLE BIOKINETICS

EPA Science Inventory

The Animal Core studies will help to answer the question of why subpopulations are at increased risk of adverse health outcomes following PM exposure. They will identify the cellular and molecular mechanisms which underlie cardiovascular susceptibility. Exposure-response rel...

Fabrication of poly(o-anisidine) coated silica core-shell microspheres and their electrorheological response

NASA Astrophysics Data System (ADS)

Lee, Chul Joo; Choi, Hyoung Jin

2017-11-01

In this work, silica/poly(o-anisidine) (POA) core-shell structured microspheres were synthesized by coating the silica core surface with POA with a help of a chemical grafting agent, N-[(3-trimethoxylsilyl)-propyl] aniline. The synthesized silica microspheres were then applied as a polymer/inorganic composite particle-based electrorheological (ER) fluid. The morphology of the silica/POA microspheres was examined by using both transmission electron microscopy and scanning electron microscopy, while their thermal properties and chemical structure were checked by thermogravimetric analysis and Fourier-transform infrared spectroscopy, respectively. The ER properties of the silica/POA particle-based ER fluid were examined by using a Couette-type rotational rheometer equipped with a high-voltage power supplier and analyzed by the Bingham model and modified Mason number. In order to obtain additional information about the electrical polarization properties, the dielectric spectra were measured by an LCR meter and fitted by using the Cole-Cole equation. Furthermore, suspension stability of the ER fluid was tested using Turbiscan.

Suspended-Bed Reactor preliminary design, /sup 233/U--/sup 232/Th cycle. Final report (revised)

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

Karam, R.A.; Alapour, A.; Lee, C.C.

1977-11-01

The preliminary design Suspended-Bed Reactor is described. Coated particles about 2 mm in diameter are used as the fuel. The coatings consist of three layers: (1) low density pyrolytic graphite, 70 ..mu.. thick, (2) silicon carbide pressure vessel, 30 ..mu.. thick, and (3) ZrC layer, 50 ..mu.. thick, to protect the pressure vessel from moisture and oxygen. The fuel kernel can be either uranium-thorium dicarbide or metal. The coated particles are suspended by helium gas (coolant) in a cluster of pressurized tubes. The upward flow of helium fluidizes the coated particles. As the flow rate increases, the bed of particlesmore » is lifted upward to the core section. The particles are restrained at the upper end of the core by a suitable screen. The overall particle density in the core is just enough for criticality condition. Should the helium flow cease, the bed in the core section will collapse, and the particles will flow downward into the section where the increased physical spacings among the tubes brings about a safe shutdown. By immersing this section of the tubes in a large graphite block to serve as a heat sink, dissipation of decay heat becomes manageable. This eliminates the need for emergency core cooling systems.« less

Equations of state for neutron stars and core-collapse supernovae

NASA Astrophysics Data System (ADS)

Oertel, Micaela; Providência, Constança

2018-04-01

Modelling compact stars is a complex task which depends on many ingredients, among others the properties of dense matter. In this contribution models for the equation of state (EoS) of dense matter will be discussed, relevant for the description of core-collapse supernovae, compact stars and compact star mergers. Such EoS models have to cover large ranges in baryon number density, temperature and isospin asymmetry. The characteristics of matter change dramatically within these ranges, from a mixture of nucleons, nuclei, and electrons to uniform, strongly interacting matter containing nucleons, and possibly other particles such as hyperons or quarks. Some implications for compact star astrophysics will be highlighted, too.

Nucleation mode particles with a nonvolatile core in the exhaust of a heavy duty diesel vehicle.

PubMed

Rönkkö, Topi; Virtanen, Annele; Kannosto, Jonna; Keskinen, Jorma; Lappi, Maija; Pirjola, Liisa

2007-09-15

The characteristics of the nucleation mode particles of a Euro IV heavy-duty diesel vehicle exhaust were studied. The NOx and PM emissions of the vehicle were controlled through the use of cooled EGR and high-pressure fuel injection techniques; no exhaust gas after-treatment was used. Particle measurements were performed in vehicle laboratory and on road. Nucleation mode dominated the particle number size distribution in all the tested driving conditions. According to the on-road measurements, the nucleation mode was already formed after 0.7 s residence time in the atmosphere and no significant changes were observed for longer residence times. The nucleation mode was insensitive to the fuel sulfur content, dilution air temperature, and relative humidity. An increase in the dilution ratio decreased the size of the nucleation mode particles. This behavior was observed to be linked to the total hydrocarbon concentration in the diluted sample. In volatility measurements, the nucleation mode particles were observed to have a nonvolatile core with volatile species condensed on it. The results indicate that the nucleation mode particles have a nonvolatile core formed before the dilution process. The core particles have grown because of the condensation of semivolatile material, mainly hydrocarbons, during the dilution.

Modelling the Centers of Galaxies

NASA Technical Reports Server (NTRS)

Smith, B. F.; Miller, R. H.; Young, Richard E. (Technical Monitor)

1997-01-01

The key to studying central regions by means of nobody numerical experiments is to concentrate on the central few parsecs of a galaxy, replacing the remainder of the galaxy by a suitable boundary condition, rather after the manner in which stellar interiors can be studied without a detailed stellar atmosphere by replacing the atmosphere with a boundary condition. Replacements must be carefully designed because the long range gravitational force means that the core region is sensitive to mass outside that region and because particles can exchange between the outer galaxy and the core region. We use periodic boundary conditions, coupled with an iterative procedure to generate initial particle loads in isothermal equilibrium. Angular momentum conservation is ensured for problems including systematic rotation by a circular reflecting boundary and by integrating in a frame that rotates with the mean flow. Mass beyond the boundary contributes to the gravitational potential, but does not participate in the dynamics. A symplectic integration scheme has been developed for rotating coordinate systems. This combination works well, leading to robust configurations. Some preliminary results with this combination show that: (1) Rotating systems are extremely sensitive to non-axisymmetric external potentials, and (2) that a second core, orbiting near the main core (like the M31 second core system), shows extremely rapid orbital decay. The experimental setups will be discussed, along with preliminary results.

The effects of substrate size, surface area, and density on coat thickness of multi-particulate dosage forms.

PubMed

Heinicke, Grant; Matthews, Frank; Schwartz, Joseph B

2005-01-01

Drugs layering experiments were performed in a fluid bed fitted with a rotor granulator insert using diltiazem as a model drug. The drug was applied in various quantities to sugar spheres of different mesh sizes to give a series of drug-layered sugar spheres (cores) of different potency, size, and weight per particle. The drug presence lowered the bulk density of the cores in proportion to the quantity of added drug. Polymer coating of each core lot was performed in a fluid bed fitted with a Wurster insert. A series of polymer-coated cores (pellets) was removed from each coating experiment. The mean diameter of each core and each pellet sample was determined by image analysis. The rate of change of diameter on polymer addition was determined for each starting size of core and compared to calculated values. The core diameter was displaced from the line of best fit through the pellet diameter data. Cores of different potency with the same size distribution were made by layering increasing quantities of drug onto sugar spheres of decreasing mesh size. Equal quantities of polymer were applied to the same-sized core lots and coat thickness was measured. Weight/weight calculations predict equal coat thickness under these conditions, but measurable differences were found. Simple corrections to core charge weight in the Wurster insert were successfully used to manufacture pellets having the same coat thickness. The sensitivity of the image analysis technique in measuring particle size distributions (PSDs) was demonstrated by measuring a displacement in PSD after addition of 0.5% w/w talc to a pellet sample.

Wire Composition: Its Effect on Metal Disintegration and Particle Formation in Twin-Wire Arc-Spraying Process

NASA Astrophysics Data System (ADS)

Tillmann, W.; Abdulgader, M.

2013-03-01

The wire tips in twin-wire arc-spraying (TWAS) are heated in three different zones. A high-speed camera was used to observe the melting behavior, metal breakup, and particle formation under different operating conditions. In zone (I), the wire tips are melted (liquidus metal) and directly atomized in the form of smaller droplets. Their size is a function of the specific properties of the molten metal and the exerting aerodynamic forces. Zone (II) is directly beneath zone (I) and the origin of the extruded metal sheets at the wire tips. The extruded metal sheets in the case of cored wires are shorter than those observed while using solid wires. In this study, the effects of adjustable parameters and powder filling on melting behavior, particle formation, and process instability were revealed, and a comparison between solid and cored wires was made. The findings can improve the accuracy of the TWAS process modeling.

HCV Core Residues Critical for Infectivity Are Also Involved in Core-NS5A Complex Formation

PubMed Central

Gawlik, Katarzyna; Baugh, James; Chatterji, Udayan; Lim, Precious J.; Bobardt, Michael D.; Gallay, Philippe A.

2014-01-01

Hepatitis C virus (HCV) infection is a major cause of liver disease. The molecular machinery of HCV assembly and particle release remains obscure. A better understanding of the assembly events might reveal new potential antiviral strategies. It was suggested that the nonstructural protein 5A (NS5A), an attractive recent drug target, participates in the production of infectious particles as a result of its interaction with the HCV core protein. However, prior to the present study, the NS5A-binding site in the viral core remained unknown. We found that the D1 domain of core contains the NS5A-binding site with the strongest interacting capacity in the basic P38-K74 cluster. We also demonstrated that the N-terminal basic residues of core at positions 50, 51, 59 and 62 were required for NS5A binding. Analysis of all substitution combinations of R50A, K51A, R59A, and R62A, in the context of the HCVcc system, showed that single, double, triple, and quadruple mutants were fully competent for viral RNA replication, but deficient in secretion of viral particles. Furthermore, we found that the extracellular and intracellular infectivity of all the mutants was abolished, suggesting a defect in the formation of infectious particles. Importantly, we showed that the interaction between the single and quadruple core mutants and NS5A was impaired in cells expressing full-length HCV genome. Interestingly, mutations of the four basic residues of core did not alter the association of core or NS5A with lipid droplets. This study showed for the first time that basic residues in the D1 domain of core that are critical for the formation of infectious extracellular and intracellular particles also play a role in core-NS5A interactions. PMID:24533158

Light Absorption Enhancement of Black Carbon Aerosol Constrained by Particle Morphology.

PubMed

Wu, Yu; Cheng, Tianhai; Liu, Dantong; Allan, James D; Zheng, Lijuan; Chen, Hao

2018-06-19

The radiative forcing of black carbon aerosol (BC) is one of the largest sources of uncertainty in climate change assessments. Contrasting results of BC absorption enhancement ( E abs ) after aging are estimated by field measurements and modeling studies, causing ambiguous parametrizations of BC solar absorption in climate models. Here we quantify E abs using a theoretical model parametrized by the complex particle morphology of BC in different aging scales. We show that E abs continuously increases with aging and stabilizes with a maximum of ∼3.5, suggesting that previous seemingly contrast results of E abs can be explicitly described by BC aging with corresponding particle morphology. We also report that current climate models using Mie Core-Shell model may overestimate E abs at a certain aging stage with a rapid rise of E abs , which is commonly observed in the ambient. A correction coefficient for this overestimation is suggested to improve model predictions of BC climate impact.

Neutron dose rate analysis on HTGR-10 reactor using Monte Carlo code

NASA Astrophysics Data System (ADS)

Suwoto; Adrial, H.; Hamzah, A.; Zuhair; Bakhri, S.; Sunaryo, G. R.

2018-02-01

The HTGR-10 reactor is cylinder-shaped core fuelled with kernel TRISO coated fuel particles in the spherical pebble with helium cooling system. The outlet helium gas coolant temperature outputted from the reactor core is designed to 700 °C. One advantage HTGR type reactor is capable of co-generation, as an addition to generating electricity, the reactor was designed to produce heat at high temperature can be used for other processes. The spherical fuel pebble contains 8335 TRISO UO2 kernel coated particles with enrichment of 10% and 17% are dispersed in a graphite matrix. The main purpose of this study was to analysis the distribution of neutron dose rates generated from HTGR-10 reactors. The calculation and analysis result of neutron dose rate in the HTGR-10 reactor core was performed using Monte Carlo MCNP5v1.6 code. The problems of double heterogeneity in kernel fuel coated particles TRISO and spherical fuel pebble in the HTGR-10 core are modelled well with MCNP5v1.6 code. The neutron flux to dose conversion factors taken from the International Commission on Radiological Protection (ICRP-74) was used to determine the dose rate that passes through the active core, reflectors, core barrel, reactor pressure vessel (RPV) and a biological shield. The calculated results of neutron dose rate with MCNP5v1.6 code using a conversion factor of ICRP-74 (2009) for radiation workers in the radial direction on the outside of the RPV (radial position = 220 cm from the center of the patio HTGR-10) provides the respective value of 9.22E-4 μSv/h and 9.58E-4 μSv/h for enrichment 10% and 17%, respectively. The calculated values of neutron dose rates are compliant with BAPETEN Chairman’s Regulation Number 4 Year 2013 on Radiation Protection and Safety in Nuclear Energy Utilization which sets the limit value for the average effective dose for radiation workers 20 mSv/year or 10μSv/h. Thus the protection and safety for radiation workers to be safe from the radiation source has been fulfilled. From the result analysis, it can be concluded that the model of calculation result of neutron dose rate for HTGR-10 core has met the required radiation safety standards.

Formation and cleaning function of physically cross-linked dual strengthened water-soluble chitosan-based core-shell particles.

PubMed

Dong, Yanrui; Xiao, Congming

2017-09-01

Facile and mild ionic cross-linking and freezing/thawing technologies were applied to prepare double strengthened core-shell particles by using water-soluble chitosan (WSC), sodium alginate (SA) and poly(vinyl alcohol) (PVA) as starting materials. The aqueous solution contained WSC and PVA was dropped in ethanol to form beads. The beads were converted into WSC/PVA hydrogel particles by being subjected to three freeze/thaw cycles. Subsequently, ionic cross-linked hydrogel layer was formed around each WSC/PVA particle to generate core-shell particulates. Fourier transform infrared spectra confirmed the combination among various components. Dynamic mechanical thermal analysis indicated that the storage modulus of the core-shell hydrogel was improved obviously. Thermogravimetric analysis exhibited the thermal stability of the particles was also enhanced by incorporation of PVA. It was found that the particles were able to adsorb carbon dioxide, lead ion and copper ion. The adsorption capacities of dry particles toward carbon dioxide, Pb(II) and Cu(II) could reach 199.62, 39.28 and 26.03mg/g, respectively. The rates of the particles for binding Pb(II) and Cu(II) at initial stage were 26.57 and 4.30%/min, respectively. These experimental results suggested that the particles were an efficient sorbent for removing hazardous substances such as carbon dioxide and heavy-metal ions. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of core/shell structure on magnetic induction heating promotion in Fe3O4/γ-Fe2O3 magnetic nanoparticles for hyperthermia

NASA Astrophysics Data System (ADS)

Lee, Shih-Chi; Fu, Chao-Ming; Chang, Fu-Hsiung

2013-10-01

Fe3O4/γ-Fe2O3 core-shell magnetic nanoparticles have demonstrated superior heating efficiency by applying the alternating magnetic field. The magnetic induction heating properties of core-shell magnetic nanoparticles were analyzed by the rate-dependent hysteresis model, taken into account the magnetic anisotropies and actual size distribution of particles. The analyzed results have disclosed the significance of magnetic anisotropies and shell-thickness to the promotion of magnetic induction heating performance. Further experiments about the cancer cells with uptake of these core-shell magnetic nanoparticles conjugated biocompatible cationic liposomes have achieved in vitro intracellular magnetically induced hyperthermia under a weak alternating magnetic field.

PARTICLE IMAGE VELOCIMETRY MEASUREMENTS IN A REPRESENTATIVE GAS-COOLED PRISMATIC REACTOR CORE MODEL: FLOW IN THE COOLANT CHANNELS AND INTERSTITIAL BYPASS GAPS

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

Thomas E. Conder; Richard Skifton; Ralph Budwig

Core bypass flow is one of the key issues with the prismatic Gas Turbine-Modular Helium Reactor, and it refers to the coolant that navigates through the interstitial, non-cooling passages between the graphite fuel blocks instead of traveling through the designated coolant channels. To determine the bypass flow, a double scale representative model was manufactured and installed in the Matched Index-of-Refraction flow facility; after which, stereo Particle Image Velocimetry (PIV) was employed to measure the flow field within. PIV images were analyzed to produce vector maps, and flow rates were calculated by numerically integrating over the velocity field. It was foundmore » that the bypass flow varied between 6.9-15.8% for channel Reynolds numbers of 1,746 and 4,618. The results were compared to computational fluid dynamic (CFD) pre-test simulations. When compared to these pretest calculations, the CFD analysis appeared to under predict the flow through the gap.« less

Material with core-shell structure

DOEpatents

Luhrs, Claudia [Rio Rancho, NM; Richard, Monique N [Ann Arbor, MI; Dehne, Aaron [Maumee, OH; Phillips, Jonathan [Rio Rancho, NM; Stamm, Kimber L [Ann Arbor, MI; Fanson, Paul T [Brighton, MI

2011-11-15

Disclosed is a material having a composite particle, the composite particle including an outer shell and a core. The core is made from a lithium alloying material and the outer shell has an inner volume that is greater in size than the core of the lithium alloying material. In some instances, the outer mean diameter of the outer shell is less than 500 nanometers and the core occupies between 5 and 99% of the inner volume. In addition, the outer shell can have an average wall thickness of less than 100 nanometers.

LARC-1: a Los Alamos release calculation program for fission product transport in HTGRs during the LOFC accident

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

Carruthers, L.M.; Lee, C.E.

1976-10-01

The theoretical and numerical data base development of the LARC-1 code is described. Four analytical models of fission product release from an HTGR core during the loss of forced circulation accident are developed. Effects of diffusion, adsorption and evaporation of the metallics and precursors are neglected in this first LARC model. Comparison of the analytic models indicates that the constant release-renormalized model is adequate to describe the processes involved. The numerical data base for release constants, temperature modeling, fission product release rates, coated fuel particle failure fraction and aged coated fuel particle failure fractions is discussed. Analytic fits and graphicmore » displays for these data are given for the Ft. St. Vrain and GASSAR models.« less

How temperature determines formation of maghemite nanoparticles

NASA Astrophysics Data System (ADS)

Girod, Matthias; Vogel, Stefanie; Szczerba, Wojciech; Thünemann, Andreas F.

2015-04-01

We report on the formation of polymer-stabilized superparamagnetic single-core and multi-core maghemite nanoparticles. The particle formation was carried out by coprecipitation of Fe(II) and Fe(III) sulfate in a continuous aqueous process using a micromixer system. Aggregates containing 50 primary particles with sizes of 2 nm were formed at a reaction temperature of 30 °C. These particles aggregated further with time and were not stable. In contrast, stable single-core particles with a diameter of 7 nm were formed at 80 °C as revealed by small-angle X-ray scattering (SAXS) coupled in-line with the micromixer for particle characterization. X-ray diffraction and TEM confirmed the SAXS results. X-ray absorption near-edge structure spectroscopy (XANES) identified the iron oxide phase as maghemite.

Controlled Release from Core-Shell Nanoporous Silica Particles for Corrosion Inhibition of Aluminum Alloys

DOE PAGES

Jiang, Xingmao; Jiang, Ying-Bing; Liu, Nanguo; ...

2011-01-01

Ceriumore » m (Ce) corrosion inhibitors were encapsulated into hexagonally ordered nanoporous silica particles via single-step aerosol-assisted self-assembly. The core/shell structured particles are effective for corrosion inhibition of aluminum alloy AA2024-T3. Numerical simulation proved that the core-shell nanostructure delays the release process. The effective diffusion coefficient elucidated from release data for monodisperse particles in water was 1.0 × 10 − 14  m 2 s for Ce 3+ compared to 2.5 × 10 − 13  m 2 s for NaCl. The pore size, pore surface chemistry, and the inhibitor solubility are crucial factors for the application. Microporous hydrophobic particles encapsulating a less soluble corrosion inhibitor are desirable for long-term corrosion inhibition.« less

Core-shell fuel cell electrodes

DOEpatents

Adzic, Radoslav; Bliznakov, Stoyan; Vukmirovic, Miomir

2017-12-26

Embodiments of the disclosure relate to membrane electrode assemblies. The membrane electrode assembly may include at least one gas-diffusion layer having a first side and a second side, and particle cores adhered to at least one of the first and second sides of the at least one gas-diffusion layer. The particle cores includes surfaces adhered to the at least one of the first and second sides of the at least one gas-diffusion layer and surfaces not in contact with the at least one gas-diffusion layer. Furthermore, a thin layer of catalytically atoms may be adhered to the surfaces of the particle cores not in contact with the at least one gas-diffusion layer.

Isocratic and gradient impedance plot analysis and comparison of some recently introduced large size core-shell and fully porous particles.

PubMed

Vanderheyden, Yoachim; Cabooter, Deirdre; Desmet, Gert; Broeckhoven, Ken

2013-10-18

The intrinsic kinetic performance of three recently commercialized large size (≥4μm) core-shell particles packed in columns with different lengths has been measured and compared with that of standard fully porous particles of similar and smaller size (5 and 3.5μm, respectively). The kinetic performance is compared in both absolute (plot of t0 versus the plate count N or the peak capacity np for isocratic and gradient elution, respectively) and dimensionless units. The latter is realized by switching to so-called impedance plots, a format which has been previously introduced (as a plot of t0/N(2) or E0 versus Nopt/N) and has in the present study been extended from isocratic to gradient elution (where the impedance plot corresponds to a plot of t0/np(4) versus np,opt(2)/np(2)). Both the isocratic and gradient impedance plot yielded a very similar picture: the clustered impedance plot curves divide into two distinct groups, one for the core-shell particles (lowest values, i.e. best performance) and one for the fully porous particles (highest values), confirming the clear intrinsic kinetic advantage of core-shell particles. If used around their optimal flow rate, the core-shell particles displayed a minimal separation impedance that is about 40% lower than the fully porous particles. Even larger gains in separation speed can be achieved in the C-term regime. Copyright © 2013 Elsevier B.V. All rights reserved.

Electrocatalysts having platium monolayers on palladium, palladium alloy, and gold alloy core-shell nanoparticles, and uses thereof

DOEpatents

Adzic, Radoslav; Mo, Yibo; Vukmirovic, Miomir; Zhang, Junliang

2010-12-21

The invention relates to platinum-coated particles useful as fuel cell electrocatalysts. The particles are composed of a noble metal or metal alloy core at least partially encapsulated by an atomically thin surface layer of platinum atoms. The invention particularly relates to such particles having a palladium, palladium alloy, gold alloy, or rhenium alloy core encapsulated by an atomic monolayer of platinum. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

Pre-Stressing Micron-Scale Aluminum Core-Shell Particles to Improve Reactivity

PubMed Central

Levitas, Valery I.; McCollum, Jena; Pantoya, Michelle

2015-01-01

The main direction in increasing reactivity of aluminum (Al) particles for energetic applications is reduction in their size down to nanoscale. However, Al nanoparticles are 30–50 times more expensive than micron scale particles and possess safety and environmental issues. Here, we improved reactivity of Al micron scale particles by synthesizing pre-stressed core-shell structures. Al particles were annealed and quenched to induce compressive stresses in the alumina passivation shell surrounding Al core. This thermal treatment was designed based on predictions of the melt-dispersion mechanism (MDM); a theory describing Al particle reaction under high heating rate. For all anneal treatment temperatures, experimental flame propagation rates for Al combined with nanoscale copper oxide (CuO) are in quantitative agreement with the theoretical predictions based on the MDM. The best treatment increases flame rate by 36% and achieves 68% of that for the best Al nanoparticles. PMID:25597747

Effective stochastic generator with site-dependent interactions

NASA Astrophysics Data System (ADS)

Khamehchi, Masoumeh; Jafarpour, Farhad H.

2017-11-01

It is known that the stochastic generators of effective processes associated with the unconditioned dynamics of rare events might consist of non-local interactions; however, it can be shown that there are special cases for which these generators can include local interactions. In this paper, we investigate this possibility by considering systems of classical particles moving on a one-dimensional lattice with open boundaries. The particles might have hard-core interactions similar to the particles in an exclusion process, or there can be many arbitrary particles at a single site in a zero-range process. Assuming that the interactions in the original process are local and site-independent, we will show that under certain constraints on the microscopic reaction rules, the stochastic generator of an unconditioned process can be local but site-dependent. As two examples, the asymmetric zero-temperature Glauber model and the A-model with diffusion are presented and studied under the above-mentioned constraints.

Coagulation of grains in static and collapsing protostellar clouds

NASA Technical Reports Server (NTRS)

Weidenschilling, S. J.; Ruzmaikina, T. V.

1993-01-01

The wavelength dependence of extinction in the diffuse interstellar medium implies that it is produced by particles of dominant size of approximately 10(exp -5) cm. There is some indication that in the cores of dense molecular clouds, sub-micron grains can coagulate to form larger particles; this process is probably driven by turbulence. The most primitive meteorites (carbonaceous chondrites) are composed of particles with a bimodal size distribution with peaks near 1 micron (matrix) and 1 mm (chondrules). Models for chondrule formation that involve processing of presolar material by chemical reactions or through an accretion shock during infall assume that aggregates of the requisite mass could form before or during collapse. The effectiveness of coagulation during collapse has been disputed; it appears to depend on specific assumptions. The first results of detailed numerical modeling of spatial and temporal variations of particle sizes in presolar clouds, both static and collapsing, is reported in this article.

Biomimetic synthesis of raspberry-like hybrid polymer-silica core-shell nanoparticles by templating colloidal particles with hairy polyamine shell.

PubMed

Pi, Mengwei; Yang, Tingting; Yuan, Jianjun; Fujii, Syuji; Kakigi, Yuichi; Nakamura, Yoshinobu; Cheng, Shiyuan

2010-07-01

The nanoparticles composed of polystyrene core and poly[2-(diethylamino)ethyl methacrylate] (PDEA) hairy shell were used as colloidal templates for in situ silica mineralization, allowing the well-controlled synthesis of hybrid silica core-shell nanoparticles with raspberry-like morphology and hollow silica nanoparticles by subsequent calcination. Silica deposition was performed by simply stirring a mixture of the polymeric core-shell particles in isopropanol, tetramethyl orthosilicate (TMOS) and water at 25 degrees C for 2.5h. No experimental evidence was found for nontemplated silica formation, which indicated that silica deposition occurred exclusively in the PDEA shell and formed PDEA-silica hybrid shell. The resulting hybrid silica core-shell particles were characterized by transmission electron microscopy (TEM), thermogravimetry, aqueous electrophoresis, and X-ray photoelectron spectroscopy. TEM studies indicated that the hybrid particles have well-defined core-shell structure with raspberry morphology after silica deposition. We found that the surface nanostructure of hybrid nanoparticles and the composition distribution of PDEA-silica hybrid shell could be well controlled by adjusting the silicification conditions. These new hybrid core-shell nanoparticles and hollow silica nanoparticles would have potential applications for high-performance coatings, encapsulation and delivery of active organic molecules. 2010 Elsevier B.V. All rights reserved.

Structural, Mechanistic, and Antigenic Characterization of the Human Astrovirus Capsid

PubMed Central

York, Royce L.; Yousefi, Payam A.; Bogdanoff, Walter; Haile, Sara; Tripathi, Sarvind

2015-01-01

ABSTRACT Human astroviruses (HAstVs) are nonenveloped, positive-sense, single-stranded RNA viruses that are a leading cause of viral gastroenteritis. HAstV particles display T=3 icosahedral symmetry formed by 180 copies of the capsid protein (CP), which undergoes proteolytic maturation to generate infectious HAstV particles. Little is known about the molecular features that govern HAstV particle assembly, maturation, infectivity, and immunogenicity. Here we report the crystal structures of the two main structural domains of the HAstV CP: the core domain at 2.60-Å resolution and the spike domain at 0.95-Å resolution. Fitting of these structures into the previously determined 25-Å-resolution electron cryomicroscopy density maps of HAstV allowed us to characterize the molecular features on the surfaces of immature and mature T=3 HAstV particles. The highly electropositive inner surface of HAstV supports a model in which interaction of the HAstV CP core with viral RNA is a driving force in T=3 HAstV particle formation. Additionally, mapping of conserved residues onto the HAstV CP core and spike domains in the context of the immature and mature HAstV particles revealed dramatic changes to the exposure of conserved residues during virus maturation. Indeed, we show that antibodies raised against mature HAstV have reactivity to both the HAstV CP core and spike domains, revealing for the first time that the CP core domain is antigenic. Together, these data provide new molecular insights into HAstV that have practical applications for the development of vaccines and antiviral therapies. IMPORTANCE Astroviruses are a leading cause of viral diarrhea in young children, immunocompromised individuals, and the elderly. Despite the prevalence of astroviruses, little is known at the molecular level about how the astrovirus particle assembles and is converted into an infectious, mature virus. In this paper, we describe the high-resolution structures of the two main astrovirus capsid proteins. Fitting these structures into previously determined low-resolution maps of astrovirus allowed us to characterize the molecular surfaces of immature and mature astroviruses. Our studies provide the first evidence that astroviruses undergo viral RNA-dependent assembly. We also provide new insight into the molecular mechanisms that lead to astrovirus maturation and infectivity. Finally, we show that both capsid proteins contribute to the adaptive immune response against astrovirus. Together, these studies will help to guide the development of vaccines and antiviral drugs targeting astrovirus. PMID:26656707

Numerical modeling of oil shale fragmentation experiments

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

Kuszmaul, J.S.

The economic development of modified in situ oil shale retorting will benefit from the ability to design a blasting scheme that creates a rubble bed of uniform permeability. Preparing such a design depends upon successfully predicting how a given explosive charge and firing sequence will fracture the oil shale. Numerical models are used to predict the extent of damage caused by a particular explosive charge. Recent single-blastwell cratering tests provided experimental measurements of the extent of damage induced by an explosion. Measuring rock damage involved crater excavation, rubble screening, crater elevation surveys, and posttest extraction of cores. These measurements weremore » compared to the damage calculated by the numerical model. Core analyses showed that the damage varied greatly from layer to layer. The numerical results also show this effect, indicating that rock damage is highly dependent on oil shale grade. The computer simulation also calculated particle velocities and dynamic stress amplitudes in the rock; predicted values agree with experimental measurements. Calculated rock fragmentation compared favorably with fragmentation measured by crater excavation and by core analysis. Because coring provides direct inspection of rock fragmentation, the use of posttest coring in future experiments is recommended.« less

High-performance multiprocessor architecture for a 3-D lattice gas model

NASA Technical Reports Server (NTRS)

Lee, F.; Flynn, M.; Morf, M.

1991-01-01

The lattice gas method has recently emerged as a promising discrete particle simulation method in areas such as fluid dynamics. We present a very high-performance scalable multiprocessor architecture, called ALGE, proposed for the simulation of a realistic 3-D lattice gas model, Henon's 24-bit FCHC isometric model. Each of these VLSI processors is as powerful as a CRAY-2 for this application. ALGE is scalable in the sense that it achieves linear speedup for both fixed and increasing problem sizes with more processors. The core computation of a lattice gas model consists of many repetitions of two alternating phases: particle collision and propagation. Functional decomposition by symmetry group and virtual move are the respective keys to efficient implementation of collision and propagation.

Role of core excitation in ( d , p ) transfer reactions

DOE PAGES

Deltuva, A.; Ross, A.; Norvaišas, E.; ...

2016-10-24

In our recent work we found that core excitations can be important in extracting structure information from (d,p) reactions. Our objective is to systematically explore the role of core excitation in (d,p) reactions and to understand the origin of the dynamical effects. Based on the particle-rotor model of n+Be 10, we generate a number of models with a range of separation energies (S n=0.1–5.0 MeV), while maintaining a significant core excited component. We then apply the latest extension of the momentum-space-based Faddeev method, including dynamical core excitation in the reaction mechanism to all orders, to the Be 10(d,p)Be 11-like reactions,more » and study the excitation effects for beam energies E d=15–90 MeV. We study the resulting angular distributions and the differences between the spectroscopic factor that would be extracted from the cross sections, when including dynamical core excitation in the reaction, and that of the original structure model. We also explore how different partial waves affect the final cross section. Our results show a strong beam-energy dependence of the extracted spectroscopic factors that become smaller for intermediate beam energies. Finally, this dependence increases for loosely bound systems.« less

Occurrence of dead core in catalytic particles containing immobilized enzymes: analysis for the Michaelis-Menten kinetics and assessment of numerical methods.

PubMed

Pereira, Félix Monteiro; Oliveira, Samuel Conceição

2016-11-01

In this article, the occurrence of dead core in catalytic particles containing immobilized enzymes is analyzed for the Michaelis-Menten kinetics. An assessment of numerical methods is performed to solve the boundary value problem generated by the mathematical modeling of diffusion and reaction processes under steady state and isothermal conditions. Two classes of numerical methods were employed: shooting and collocation. The shooting method used the ode function from Scilab software. The collocation methods included: that implemented by the bvode function of Scilab, the orthogonal collocation, and the orthogonal collocation on finite elements. The methods were validated for simplified forms of the Michaelis-Menten equation (zero-order and first-order kinetics), for which analytical solutions are available. Among the methods covered in this article, the orthogonal collocation on finite elements proved to be the most robust and efficient method to solve the boundary value problem concerning Michaelis-Menten kinetics. For this enzyme kinetics, it was found that the dead core can occur when verified certain conditions of diffusion-reaction within the catalytic particle. The application of the concepts and methods presented in this study will allow for a more generalized analysis and more accurate designs of heterogeneous enzymatic reactors.

Postcollapse Evolution of Globular Clusters

NASA Astrophysics Data System (ADS)

Makino, Junichiro

1996-11-01

A number of globular clusters appear to have undergone core collapse, in the sense that their predicted collapse times are much shorter than their current ages. Simulations with gas models and the Fokker-Planck approximation have shown that the central density of a globular cluster after the collapse undergoes nonlinear oscillation with a large amplitude (gravothermal oscillation). However, the question whether such an oscillation actually takes place in real N-body systems has remained unsolved because an N-body simulation with a sufficiently high resolution would have required computing resources of the order of several GFLOPS-yr. In the present paper, we report the results of such a simulation performed on a dedicated special-purpose computer, GRAPE-4. We have simulated the evolution of isolated point-mass systems with up to 32,768 particles. The largest number of particles reported previously is 10,000. We confirm that gravothermal oscillation takes place in an N-body system. The expansion phase shows all the signatures that are considered to be evidence of the gravothermal nature of the oscillation. At the maximum expansion, the core radius is ˜1% of the half-mass radius for the run with 32,768 particles. The maximum core size, rc, depends on N as ∝ N-1/3.

On Maximal Hard-Core Thinnings of Stationary Particle Processes

NASA Astrophysics Data System (ADS)

Hirsch, Christian; Last, Günter

2018-02-01

The present paper studies existence and distributional uniqueness of subclasses of stationary hard-core particle systems arising as thinnings of stationary particle processes. These subclasses are defined by natural maximality criteria. We investigate two specific criteria, one related to the intensity of the hard-core particle process, the other one being a local optimality criterion on the level of realizations. In fact, the criteria are equivalent under suitable moment conditions. We show that stationary hard-core thinnings satisfying such criteria exist and are frequently distributionally unique. More precisely, distributional uniqueness holds in subcritical and barely supercritical regimes of continuum percolation. Additionally, based on the analysis of a specific example, we argue that fluctuations in grain sizes can play an important role for establishing distributional uniqueness at high intensities. Finally, we provide a family of algorithmically constructible approximations whose volume fractions are arbitrarily close to the maximum.

Fabrication of polyacrylate core-shell nanoparticles via spray drying method

NASA Astrophysics Data System (ADS)

Chen, Pengpeng; Cheng, Zenghui; Chu, Fuxiang; Xu, Yuzhi; Wang, Chunpeng

2016-05-01

Fine polyacrylate particles are thought to be environmental plastisols for car industry. However, these particles are mainly dried through demulsification of the latexes, which is not reproducible and hard to be scaled up. In this work, a spray drying method had been applied to the plastisols-used acrylate latex. By adjusting the core/shell ratio, spray drying process of the latex was fully studied. Scanning electronic microscopy observation of the nanoparticles before and after spray drying indicated that the core-shell structures could be well preserved and particles were well separated by spray drying if the shell was thick enough. Otherwise, the particles fused into each other and core-shell structures were destroyed. Polyacrylate plastisols were developed using diisononylphthalate as a plasticizer, and plastigels were obtained after heat treatment of the sols. Results showed that the shell thickness also had a great influence on the storage stability of the plastisols and mechanical properties of the plastigels.

SOLAR INTERACTING PROTONS VERSUS INTERPLANETARY PROTONS IN THE CORE PLUS HALO MODEL OF DIFFUSIVE SHOCK ACCELERATION AND STOCHASTIC RE-ACCELERATION

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

Kocharov, L.; Laitinen, T.; Vainio, R.

2015-06-10

With the first observations of solar γ-rays from the decay of pions, the relationship of protons producing ground level enhancements (GLEs) on the Earth to those of similar energies producing the γ-rays on the Sun has been debated. These two populations may be either independent and simply coincident in large flares, or they may be, in fact, the same population stemming from a single accelerating agent and jointly distributed at the Sun and also in space. Assuming the latter, we model a scenario in which particles are accelerated near the Sun in a shock wave with a fraction transported backmore » to the solar surface to radiate, while the remainder is detected at Earth in the form of a GLE. Interplanetary ions versus ions interacting at the Sun are studied for a spherical shock wave propagating in a radial magnetic field through a highly turbulent radial ray (the acceleration core) and surrounding weakly turbulent sector in which the accelerated particles can propagate toward or away from the Sun. The model presented here accounts for both the first-order Fermi acceleration at the shock front and the second-order, stochastic re-acceleration by the turbulence enhanced behind the shock. We find that the re-acceleration is important in generating the γ-radiation and we also find that up to 10% of the particle population can find its way to the Sun as compared to particles escaping to the interplanetary space.« less

Simulation of bipolar charge transport in nanocomposite polymer films

NASA Astrophysics Data System (ADS)

Lean, Meng H.; Chu, Wei-Ping L.

2015-03-01

This paper describes 3D particle-in-cell simulation of bipolar charge injection and transport through nanocomposite film comprised of ferroelectric ceramic nanofillers in an amorphous polymer matrix. The classical electrical double layer (EDL) model for a monopolar core is extended (eEDL) to represent the nanofiller by replacing it with a dipolar core. Charge injection at the electrodes assumes metal-polymer Schottky emission at low to moderate fields and Fowler-Nordheim tunneling at high fields. Injected particles migrate via field-dependent Poole-Frenkel mobility and recombine with Monte Carlo selection. The simulation algorithm uses a boundary integral equation method for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit assuring robust and rapid convergence. The model is capable of simulating a wide dynamic range spanning leakage current to pre-breakdown. Simulation results for BaTiO3 nanofiller in amorphous polymer matrix indicate that charge transport behavior depend on nanoparticle polarization with anti-parallel orientation showing the highest leakage conduction and therefore lowest level of charge trapping in the interaction zone. Charge recombination is also highest, at the cost of reduced leakage conduction charge. The eEDL model predicts the meandering pathways of charge particle trajectories.

PARFUME Theory and Model basis Report

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

Darrell L. Knudson; Gregory K Miller; G.K. Miller

2009-09-01

The success of gas reactors depends upon the safety and quality of the coated particle fuel. The fuel performance modeling code PARFUME simulates the mechanical, thermal and physico-chemical behavior of fuel particles during irradiation. This report documents the theory and material properties behind vari¬ous capabilities of the code, which include: 1) various options for calculating CO production and fission product gas release, 2) an analytical solution for stresses in the coating layers that accounts for irradiation-induced creep and swelling of the pyrocarbon layers, 3) a thermal model that calculates a time-dependent temperature profile through a pebble bed sphere or amore » prismatic block core, as well as through the layers of each analyzed particle, 4) simulation of multi-dimensional particle behavior associated with cracking in the IPyC layer, partial debonding of the IPyC from the SiC, particle asphericity, and kernel migration (or amoeba effect), 5) two independent methods for determining particle failure probabilities, 6) a model for calculating release-to-birth (R/B) ratios of gaseous fission products that accounts for particle failures and uranium contamination in the fuel matrix, and 7) the evaluation of an accident condition, where a particle experiences a sudden change in temperature following a period of normal irradiation. The accident condi¬tion entails diffusion of fission products through the particle coating layers and through the fuel matrix to the coolant boundary. This document represents the initial version of the PARFUME Theory and Model Basis Report. More detailed descriptions will be provided in future revisions.« less

Soft template synthesis of yolk/silica shell particles.

PubMed

Wu, Xue-Jun; Xu, Dongsheng

2010-04-06

Yolk/shell particles possess a unique structure that is composed of hollow shells that encapsulate other particles but with an interstitial space between them. These structures are different from core/shell particles in that the core particles are freely movable in the shell. Yolk/shell particles combine the properties of each component, and can find potential applications in catalysis, lithium ion batteries, and biosensors. In this Research News article, a soft-template-assisted method for the preparation of yolk/silica shell particles is presented. The demonstrated method is simple and general, and can produce hollow silica spheres incorporated with different particles independent of their diameters, geometry, and composition. Furthermore, yolk/mesoporous silica shell particles and multishelled particles are also prepared through optimization of the experimental conditions. Finally, potential applications of these particles are discussed.

Electrostatic interactions between diffuse soft multi-layered (bio)particles: beyond Debye-Hückel approximation and Deryagin formulation.

PubMed

Duval, Jérôme F L; Merlin, Jenny; Narayana, Puranam A L

2011-01-21

We report a steady-state theory for the evaluation of electrostatic interactions between identical or dissimilar spherical soft multi-layered (bio)particles, e.g. microgels or microorganisms. These generally consist of a rigid core surrounded by concentric ion-permeable layers that may differ in thickness, soft material density, chemical composition and degree of dissociation for the ionogenic groups. The formalism allows the account of diffuse interphases where distributions of ionogenic groups from one layer to the other are position-dependent. The model is valid for any number of ion-permeable layers around the core of the interacting soft particles and covers all limiting situations in terms of nature of interacting particles, i.e. homo- and hetero-interactions between hard, soft or entirely porous colloids. The theory is based on a rigorous numerical solution of the non-linearized Poisson-Boltzmann equation including radial and angular distortions of the electric field distribution within and outside the interacting soft particles in approach. The Gibbs energy of electrostatic interaction is obtained from a general expression derived following the method by Verwey and Overbeek based on appropriate electric double layer charging mechanisms. Original analytical solutions are provided here for cases where interaction takes place between soft multi-layered particles whose size and charge density are in line with Deryagin treatment and Debye-Hückel approximation. These situations include interactions between hard and soft particles, hard plate and soft particle or soft plate and soft particle. The flexibility of the formalism is highlighted by the discussion of few situations which clearly illustrate that electrostatic interaction between multi-layered particles may be partly or predominantly governed by potential distribution within the most internal layers. A major consequence is that both amplitude and sign of Gibbs electrostatic interaction energy may dramatically change depending on the interplay between characteristic Debye length, thickness of ion-permeable layers and their respective protolytic features (e.g. location, magnitude and sign of charge density). This formalism extends a recent model by Ohshima which is strictly limited to interaction between soft mono-shell particles within Deryagin and Debye-Hückel approximations under conditions where ionizable sites are completely dissociated.

Co-encapsulation of CdSe/ZnS and CeO2 nanoparticles in waterborne polymer dispersions: enhancement of fluorescence emission under sunlight.

PubMed

De San Luis, Alicia; Paulis, Maria; Leiza, Jose Ramon

2017-11-15

Hybrid core/shell polymer particles with co-encapsulated quantum dots (QDs) (CdSe/ZnS) and CeO 2 nanoparticles have been synthesized in a two stage semi-batch emulsion polymerization process. In the first stage, both inorganic nanoparticles are incorporated into cross-linked polystyrene (PS) particles by miniemulsion polymerization. This hybrid dispersion is then used as the seed to produce the core/shell particles by starved feeding of methyl methacrylate and divinylbenzene (MMA/DVB) monomers. The core/shell hybrid dispersions maintained in the dark exhibit stable fluorescence emission over time, and notably their fluorescence intensity increases under sunlight, likely due to the effect of the co-encapsulated CeO 2 nanoparticles that change the optical properties of the environment of the quantum dot particles. The fluorescence increase depends on the QD : CeO 2 ratio, with the 1 : 2 ratio resulting in the highest increase (280%). Furthermore, a film forming hybrid latex has been synthesized using the former core/shell PS/QD/CeO 2 /PMMA particles as seeds and feeding under semi-batch conditions methyl methacrylate, butyl acrylate and acrylic acid. Films cast from this core/shell/shell hybrid dispersion also exhibit fluorescence, and as for the core/shell latex the fluorescence increases under sunlight exposure. Interestingly, the increase in the film is at least two times higher than that in the latex, which is attributed to the additional effect of the neighboring coalesced particles containing CeO 2 affecting the environment of the QDs.

Vaporizing particle velocimeter

NASA Technical Reports Server (NTRS)

Weinstein, Leonard M. (Inventor)

1992-01-01

A velocimeter measures flow characteristics of a flow traveling through a chamber in a given direction. Tracer particles are entrained in the flow and a source of radiant energy produces an output stream directed transversely to the chamber, having a sufficient intensity to vaporize the particles as they pass through the output stream. Each of the vaporized particles explodes to produce a shock wave and a hot core, and a flow visualization system tracks the motion of the hot cores and shock waves to measure the velocity of each tracer particle and the temperature of the flow around the tracer.

Free Electrons to Molecular Bonds and Back: Closing the Energetic Oxygen Reduction (ORR)-Oxygen Evolution (OER) Cycle Using Core-Shell Nanoelectrocatalysts.

PubMed

Strasser, Peter

2016-11-15

Nanomaterial science and electrocatalytic science have entered a successful "nanoelectrochemical" symbiosis, in which novel nanomaterials offer new frontiers for studies on electrocatalytic charge transfer, while electrocatalytic processes give meaning and often practical importance to novel nanomaterial concepts. Examples of this fruitful symbiosis are dealloyed core-shell nanoparticle electrocatalysts, which often exhibit enhanced kinetic charge transfer rates at greatly improved atom-efficiency. As such, they represent ideal electrocatalyst architectures for the acidic oxygen reduction reaction to water (ORR) and the acidic oxygen evolution reaction from water (OER) that require scarce Pt- and Ir-based catalysts. Together, these two reactions constitute the "O-cycle", a key elemental process loop in the field of electrochemical energy interconversion between electricity (free electrons) and molecular bonds (H 2 O/O 2 ), realized in the combination of water electrolyzers and hydrogen/oxygen fuel cells. In this Account, we describe our recent efforts to design, synthesize, understand, and test noble metal-poor dealloyed Pt and Ir core-shell nanoparticles for deployment in acidic polymer electrolyte membrane (PEM) electrolyzers and PEM fuel cells. Spherical dealloyed Pt core-shell particles, derived from PtNi 3 precursor alloys, showed favorable ORR activity. More detailed size-activity correlation studies further revealed that the 6-8 nm diameter range is a most desirable initial particle size range in order to maximize the particle Ni content after ORR testing and to preserve performance stability. Similarly, dealloyed and oxidized IrO x core-shell particles derived from Ni-rich Ir-Ni precursor particles proved highly efficient oxygen evolution reaction (OER) catalysts in acidic conditions. In addition to the noble metal savings in the particle cores, the Pt core-shell particles are believed to benefit in terms of their mass-based electrochemical kinetics from surface lattice strain effects that tune the adsorption energies and barriers of elementary steps. The molecular mechanism of the kinetic benefit of the dealloyed IrO x particle needs more attention, but there is mounting evidence for ligand hole effects in defect-rich IrO x shells that generate preactive oxygen centers.

Effects of Heat Treatment on the Magnetic Properties of Polymer-Bound Iron Particle Cores

NASA Technical Reports Server (NTRS)

Namkung, M.; Wincheski, B.; Bryant, R. G.

1998-01-01

Spherical iron particles of three different size distributions, 6-10 microns in diameter, 100 mesh and 30-80 mesh, were mixed with 2.0 wt. % of soluble imide and compression molded at 300 C under 131 MPa. Post fabrication heat treatments were performed at 960 C for 6 hours resulting in a significant enhancement of the permeability in low field region for all the specimens except for the one made of 30-80 mesh particles. The rate of core loss of these specimens at a magnetic induction of 5 kG measured up to 1 kHz shows a noticeable increase after heat treatment which, along with the permeability enhancement, can be explained by the coalescence of particles forming a network of conductivity paths in the specimens. The scanning electron micrographs taken for the 6-10 micron particle specimens show no evidence of heat treatment-induced grain growth. The untreated specimens show a very weak f(sup 2) dependence of the core loss which clearly indicates a negligible contribution from the eddy current loss. In particular, an almost perfect linearity was found in the frequency dependence of the core loss of the untreated specimen made of 100 mesh iron particles.

Effects of Heat Treatment on the Magnetic Properties of Polymer-Bound Iron Particle Cores

NASA Technical Reports Server (NTRS)

Namkung, M.; Wincheski, B.; Bryant, R. G.; Buchman, A.

1998-01-01

Spherical iron particles of three different size distributions, 6-10 micrometers in diameter, 100 mesh and 30-80 mesh, were mixed with 2.0 wt % of soluble imide and compression molded at 300 C under 131 MPa. Post-fabrication heat treatments were performed at 960 C for 6 h resulting in a significant enhancement of the permeability in low field region for all the specimens except for the one made of 30-80 mesh particles. The rate of core loss of these specimens at a magnetic induction of 5 kG measured up to 1 kHz shows a noticeable. increase after heat treatment which, along with the permeability enhancement, can be explained by the coalescence of particles forming a network of conductivity paths in the specimens. ne scanning electron micrographs taken for the 6-10 micrometer particle specimens show no evidence of heat treatment-induced grain growth. The untreated specimens show a very weak f(sup 2) -dependence of the core loss which clearly indicates a negligible contribution from the eddy current loss. In particular, an almost perfect linearity was found in the frequency dependence of the core loss of the untreated specimen made of 100 mesh iron particles.

Dependence of Aerosol Light Absorption and Single-Scattering Albedo On Ambient Relative Humidity for Sulfate Aerosols with Black Carbon Cores

NASA Technical Reports Server (NTRS)

Redemann, Jens; Russell, Philip B.; Hamill, Patrick

2001-01-01

Atmospheric aerosols frequently contain hygroscopic sulfate species and black carbon (soot) inclusions. In this paper we report results of a modeling study to determine the change in aerosol absorption due to increases in ambient relative humidity (RH), for three common sulfate species, assuming that the soot mass fraction is present as a single concentric core within each particle. Because of the lack of detailed knowledge about various input parameters to models describing internally mixed aerosol particle optics, we focus on results that were aimed at determining the maximum effect that particle humidification may have on aerosol light absorption. In the wavelength range from 450 to 750 nm, maximum absorption humidification factors (ratio of wet to 'dry=30% RH' absorption) for single aerosol particles are found to be as large as 1.75 when the RH changes from 30 to 99.5%. Upon lesser humidification from 30 to 80% RH, absorption humidification for single particles is only as much as 1.2, even for the most favorable combination of initial ('dry') soot mass fraction and particle size. Integrated over monomodal lognormal particle size distributions, maximum absorption humidification factors range between 1.07 and 1.15 for humidification from 30 to 80% and between 1.1 and 1.35 for humidification from 30 to 95% RH for all species considered. The largest humidification factors at a wavelength of 450 nm are obtained for 'dry' particle size distributions that peak at a radius of 0.05 microns, while the absorption humidification factors at 700 nm are largest for 'dry' size distributions that are dominated by particles in the radius range of 0.06 to 0.08 microns. Single-scattering albedo estimates at ambient conditions are often based on absorption measurements at low RH (approx. 30%) and the assumption that aerosol absorption does not change upon humidification (i.e., absorption humidification equal to unity). Our modeling study suggests that this assumption alone can introduce absolute errors in estimates of the midvisible single-scattering albedo of up to 0.05 for realistic dry particle size distributions. Our study also indicates that this error increases with increasing wavelength. The potential errors in aerosol single-scattering albedo derived here are comparable in magnitude and in addition to uncertainties in single-scattering albedo estimates that are based on measurements of aerosol light absorption and scattering.

Bidirectional Lipid Droplet Velocities Are Controlled by Differential Binding Strengths of HCV Core DII Protein

PubMed Central

Lyn, Rodney K.; Hope, Graham; Sherratt, Allison R.; McLauchlan, John; Pezacki, John Paul

2013-01-01

Host cell lipid droplets (LD) are essential in the hepatitis C virus (HCV) life cycle and are targeted by the viral capsid core protein. Core-coated LDs accumulate in the perinuclear region and facilitate viral particle assembly, but it is unclear how mobility of these LDs is directed by core. Herein we used two-photon fluorescence, differential interference contrast imaging, and coherent anti-Stokes Raman scattering microscopies, to reveal novel core-mediated changes to LD dynamics. Expression of core protein’s lipid binding domain II (DII-core) induced slower LD speeds, but did not affect directionality of movement on microtubules. Modulating the LD binding strength of DII-core further impacted LD mobility, revealing the temporal effects of LD-bound DII-core. These results for DII-core coated LDs support a model for core-mediated LD localization that involves core slowing down the rate of movement of LDs until localization at the perinuclear region is accomplished where LD movement ceases. The guided localization of LDs by HCV core protein not only is essential to the viral life cycle but also poses an interesting target for the development of antiviral strategies against HCV. PMID:24223760

Synthesis of Cu/SiO2 Core-Shell Particles Using Hyperbranched Polyester as Template and Dispersant

NASA Astrophysics Data System (ADS)

Han, Wensong

2017-07-01

Third-generation hyperbranched polyester (HBPE3) was synthesized by stepwise polymerization with N, N-diethylol-3-amine methylpropionate as AB2 monomer and pentaerythritol as core molecule. Then, Cu particles were prepared by reduction of copper nitrate with ascorbic acid in aqueous solution using HBPE3 as template. Finally, Cu/SiO2 particles were prepared by coating silica on the surface of Cu particles. The structure and morphology of the samples were characterized by Fourier-transform infrared (FT-IR) spectrometry, x-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results confirmed the formation of the silica coating on the surface of Cu and that the Cu/SiO2 particles had spherical shape with particle size in the range of 0.8 μm to 2 μm. Compared with pure Cu, the synthesized Cu/SiO2 core-shell particles exhibited better oxidation resistance at high temperature. Moreover, the oxidation resistance of the Cu/SiO2 particles increased significantly with increasing tetraethyl orthosilicate (TEOS) concentration.

Modeling photoacoustic spectral features of micron-sized particles

NASA Astrophysics Data System (ADS)

Strohm, Eric M.; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael C.

2014-10-01

The photoacoustic signal generated from particles when irradiated by light is determined by attributes of the particle such as the size, speed of sound, morphology and the optical absorption coefficient. Unique features such as periodically varying minima and maxima are observed throughout the photoacoustic signal power spectrum, where the periodicity depends on these physical attributes. The frequency content of the photoacoustic signals can be used to obtain the physical attributes of unknown particles by comparison to analytical solutions of homogeneous symmetric geometric structures, such as spheres. However, analytical solutions do not exist for irregularly shaped particles, inhomogeneous particles or particles near structures. A finite element model (FEM) was used to simulate photoacoustic wave propagation from four different particle configurations: a homogeneous particle suspended in water, a homogeneous particle on a reflecting boundary, an inhomogeneous particle with an absorbing shell and non-absorbing core, and an irregularly shaped particle such as a red blood cell. Biocompatible perfluorocarbon droplets, 3-5 μm in diameter containing optically absorbing nanoparticles were used as the representative ideal particles, as they are spherical, homogeneous, optically translucent, and have known physical properties. The photoacoustic spectrum of micron-sized single droplets in suspension and on a reflecting boundary were measured over the frequency range of 100-500 MHz and compared directly to analytical models and the FEM. Good agreement between the analytical model, FEM and measured values were observed for a droplet in suspension, where the spectral minima agreed to within a 3.3 MHz standard deviation. For a droplet on a reflecting boundary, spectral features were correctly reproduced using the FEM but not the analytical model. The photoacoustic spectra from other common particle configurations such as particle with an absorbing shell and a biconcave-shaped red blood cell were also investigated, where unique features in the power spectrum could be used to identify them.

Fabrication of PLA/CaCO3 hybrid micro-particles as carriers for water-soluble bioactive molecules.

PubMed

Kudryavtseva, Valeriya L; Zhao, Li; Tverdokhlebov, Sergei I; Sukhorukov, Gleb B

2017-09-01

We propose the use of polylactic acid/calcium carbonate (PLA/CaCO 3 ) hybrid micro-particles for achieving improved encapsulation of water-soluble substances. Biodegradable porous CaCO 3 microparticles can be loaded with wide range of bioactive substance. Thus, the formation of hydrophobic polymeric shell on surface of these loaded microparticles results on encapsulation and, hence, sealing internal cargo and preventing their release in aqueous media. In this study, to encapsulate proteins, we explore the solid-in-oil-in-water emulsion method for fabricating core/shell PLA/CaCO 3 systems. We used CaCO 3 particles as a protective core for encapsulated bovine serum albumin, which served as a model protein system. We prepared a PLA coating using dichloromethane as an organic solvent and polyvinyl alcohol as a surfactant for emulsification; in addition, we varied experimental parameters such as surfactant concentration and polymer-to-CaCO 3 ratio to determine their effect on particle-size distribution, encapsulation efficiency and capsule permeability. The results show that the particle size decreased and the size distribution narrowed as the surfactant concentration increased in the external aqueous phase. In addition, when the CaCO 3 /PLA mass ratio dropped below 0.8, the hybrid micro-particles were more likely to resist treatment by ethylenediaminetetraacetic acid and thus retained their bioactive cargos within the polymer-coated micro-particles. Copyright © 2017 Elsevier B.V. All rights reserved.

Silica Nanoparticles for Intracellular Protein Delivery: a Novel Synthesis Approach Using Green Fluorescent Protein

NASA Astrophysics Data System (ADS)

Schmidt, Sarah; Tavernaro, Isabella; Cavelius, Christian; Weber, Eva; Kümper, Alexander; Schmitz, Carmen; Fleddermann, Jana; Kraegeloh, Annette

2017-09-01

In this study, a novel approach for preparation of green fluorescent protein (GFP)-doped silica nanoparticles with a narrow size distribution is presented. GFP was chosen as a model protein due to its autofluorescence. Protein-doped nanoparticles have a high application potential in the field of intracellular protein delivery. In addition, fluorescently labelled particles can be used for bioimaging. The size of these protein-doped nanoparticles was adjusted from 15 to 35 nm using a multistep synthesis process, comprising the particle core synthesis followed by shell regrowth steps. GFP was selectively incorporated into the silica matrix of either the core or the shell or both by a one-pot reaction. The obtained nanoparticles were characterised by determination of particle size, hydrodynamic diameter, ζ-potential, fluorescence and quantum yield. The measurements showed that the fluorescence of GFP was maintained during particle synthesis. Cellular uptake experiments demonstrated that the GFP-doped nanoparticles can be used as stable and effective fluorescent probes. The study reveals the potential of the chosen approach for incorporation of functional biological macromolecules into silica nanoparticles, which opens novel application fields like intracellular protein delivery.

Development of SSUBPIC code for modeling the neutral gas depletion effect in helicon discharges

NASA Astrophysics Data System (ADS)

Kollasch, Jeffrey; Sovenic, Carl; Schmitz, Oliver

2017-10-01

The SSUBPIC (steady-state unstructured-boundary particle-in-cell) code is being developed to model helicon plasma devices. The envisioned modeling framework incorporates (1) a kinetic neutral particle model, (2) a kinetic ion model, (3) a fluid electron model, and (4) an RF power deposition model. The models are loosely coupled and iterated until convergence to steady-state. Of the four required solvers, the kinetic ion and neutral particle simulation can now be done within the SSUBPIC code. Recent SSUBPIC modifications include implementation and testing of a Coulomb collision model (Lemons et al., JCP, 228(5), pp. 1391-1403) allowing efficient coupling of kineticly-treated ions to fluid electrons, and implementation of a neutral particle tracking mode with charge-exchange and electron impact ionization physics. These new simulation capabilities are demonstrated working independently and coupled to ``dummy'' profiles for RF power deposition to converge on steady-state plasma and neutral profiles. The geometry and conditions considered are similar to those of the MARIA experiment at UW-Madison. Initial results qualitatively show the expected neutral gas depletion effect in which neutrals in the plasma core are not replenished at a sufficient rate to sustain a higher plasma density. This work is funded by the NSF CAREER award PHY-1455210 and NSF Grant PHY-1206421.

Separative analyses of a chromatographic column packed with a core-shell adsorbent for lithium isotope separation

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

Sugiyama, T.; Sugura, K.; Enokida, Y.

2015-03-15

Lithium-6 is used as a blanket material for sufficient tritium production in DT fueled fusion reactors. A core-shell type adsorbent was proposed for lithium isotope separation by chromatography. The mass transfer model in a chromatographic column consisted of 4 steps, such as convection and dispersion in the column, transfer through liquid films, intra-particle diffusion and and adsorption or desorption at the local adsorption sites. A model was developed and concentration profiles and time variation in the column were numerically simulated. It became clear that core-shell type adsorbents with thin porous shell were saturated rapidly relatively to fully porous one andmore » established a sharp edge of adsorption band. This is very important feature because lithium isotope separation requires long-distance development of adsorption band. The values of HETP (Height Equivalent of a Theoretical Plate) for core-shell adsorbent packed column were estimated by statistical moments of the step response curve. The value of HETP decreased with the thickness of the porous shell. A core-shell type adsorbent is, then, useful for lithium isotope separation. (authors)« less

Simulation and Modeling of charge particles transport using SIMION for our Time of Flight Positron Annihilation Induce Auger Electron Spectroscopy systems

NASA Astrophysics Data System (ADS)

Joglekar, Prasad; Shastry, K.; Satyal, Suman; Weiss, Alexander

2012-02-01

Time of flight Positron Annihilation Induced Auger Electron Spectroscopy system, a highly surface selective analytical technique using time of flight of auger electron resulting from the annihilation of core electrons by trapped incident positron in image potential well. We simulated and modeled the trajectories of the charge particles in TOF-PAES using SIMION for the development of new high resolution system at U T Arlington and current TOFPAES system. This poster presents the SIMION simulations results, Time of flight calculations and larmor radius calculations for current system as well as new system.

Algebraic perturbation theory for dense liquids with discrete potentials

NASA Astrophysics Data System (ADS)

Adib, Artur B.

2007-06-01

A simple theory for the leading-order correction g1(r) to the structure of a hard-sphere liquid with discrete (e.g., square-well) potential perturbations is proposed. The theory makes use of a general approximation that effectively eliminates four-particle correlations from g1(r) with good accuracy at high densities. For the particular case of discrete perturbations, the remaining three-particle correlations can be modeled with a simple volume-exclusion argument, resulting in an algebraic and surprisingly accurate expression for g1(r) . The structure of a discrete “core-softened” model for liquids with anomalous thermodynamic properties is reproduced as an application.

Incorporation of deoxyribonucleotides and ribonucleotides by a dNTP-binding cleft mutated reverse transcriptase in hepatitis B virus core particles

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

Kim, Hee-Young; Kim, Hye-Young; Jung, Jaesung

2008-01-05

Our recent observation that hepatitis B virus (HBV) DNA polymerase (P) might initiate minus-strand DNA synthesis without primer [Kim et al., (2004) Virology 322, 22-30], raised a possibility that HBV P protein may have the potential to function as an RNA polymerase. Thus, we mutated Phe 436, a bulky amino acid with aromatic side chain, at the putative dNTP-binding cleft in reverse transcriptase (RT) domain of P protein to smaller amino acids (Gly or Val), and examined RNA polymerase activity. HBV core particles containing RT dNTP-binding cleft mutant P protein were able to incorporate {sup 32}P-ribonucleotides, but not HBV coremore » particles containing wild type (wt), priming-deficient mutant, or RT-deficient mutant P proteins. Since all the experiments were conducted with core particles isolated from transfected cells, our results indicate that the HBV RT mutant core particles containing RT dNTP-binding cleft mutant P protein could incorporate both deoxyribonucleotides and ribonucleotides in replicating systems.« less

Rapid determination of parabens in seafood sauces by high-performance liquid chromatography: A practical comparison of core-shell particles and sub-2 μm fully porous particles.

PubMed

Ye, Jing; Cao, Xiaoji; Cheng, Zhuo; Qin, Ye; Lu, Yanbin

2015-12-01

In this work, the chromatographic performance of superficially porous particles (Halo core-shell C18 column, 50 mm × 2.1 mm, 2.7 μm) was compared with that of sub-2 μm fully porous particles (Acquity BEH C18 , 50 mm × 2.1 mm, 1.7 μm). Four parabens, methylparaben, ethylparaben, propylparaben, and butylparaben, were used as representative compounds for calculating the plate heights in a wide flow rate range and analyzed on the basis of the Van Deemter and Knox equations. Theoretical Poppe plots were constructed for each column to compare their kinetic performance. Both phases gave similar minimum plate heights when using nonreduced coordinates. Meanwhile, the flat C-term of the core-shell column provided the possibilities for applying high flow rates without significant loss in efficiency. The low backpressure of core-shell particles allowed this kind of column, especially compatible with conventional high-performance liquid chromatography systems. Based on these factors, a simple high-performance liquid chromatography method was established and validated for the determination of parabens in various seafood sauces using the Halo core-shell C18 column for separation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatial connectivity in a highly heterogeneous aquifer: From cores to preferential flow paths

USGS Publications Warehouse

Bianchi, M.; Zheng, C.; Wilson, C.; Tick, G.R.; Liu, Gaisheng; Gorelick, S.M.

2011-01-01

This study investigates connectivity in a small portion of the extremely heterogeneous aquifer at the Macrodispersion Experiment (MADE) site in Columbus, Mississippi. A total of 19 fully penetrating soil cores were collected from a rectangular grid of 4 m by 4 m. Detailed grain size analysis was performed on 5 cm segments of each core, yielding 1740 hydraulic conductivity (K) estimates. Three different geostatistical simulation methods were used to generate 3-D conditional realizations of the K field for the sampled block. Particle tracking calculations showed that the fastest particles, as represented by the first 5% to arrive, converge along preferential flow paths and exit the model domain within preferred areas. These 5% fastest flow paths accounted for about 40% of the flow. The distribution of preferential flow paths and particle exit locations is clearly influenced by the occurrence of clusters formed by interconnected cells with K equal to or greater than the 0.9 decile of the data distribution (10% of the volume). The fraction of particle paths within the high-K clusters ranges from 43% to 69%. In variogram-based K fields, some of the fastest paths are through media with lower K values, suggesting that transport connectivity may not require fully connected zones of relatively homogenous K. The high degree of flow and transport connectivity was confirmed by the values of two groups of connectivity indicators. In particular, the ratio between effective and geometric mean K (on average, about 2) and the ratio between the average arrival time and the arrival time of the fastest particles (on average, about 9) are consistent with flow and advective transport behavior characterized by channeling along preferential flow paths. ?? 2011 by the American Geophysical Union.

Two-proton capture on the 68Se nucleus with a new self-consistent cluster model

NASA Astrophysics Data System (ADS)

Hove, D.; Garrido, E.; Jensen, A. S.; Sarriguren, P.; Fynbo, H. O. U.; Fedorov, D. V.; Zinner, N. T.

2018-07-01

We investigate the two-proton capture reaction of the prominent rapid proton capture waiting point nucleus, 68Se, that produces the borromean nucleus 70Kr (68Se + p + p). We apply a recently formulated general model where the core nucleus, 68Se, is treated in the mean-field approximation and the three-body problem of the two valence protons and the core is solved exactly. We compare using two popular Skyrme interactions, SLy4 and SkM*. We calculate E2 electromagnetic two-proton dissociation and capture cross sections, and derive the temperature dependent capture rates. We vary the unknown 2+ resonance energy without changing any of the structures computed self-consistently for both core and valence particles. We find rates increasing quickly with temperature below 2-4 GK after which we find rates varying by about a factor of two independent of 2+ resonance energy. The capture mechanism is sequential through the f5/2 proton-core resonance, but the continuum background contributes significantly.

Magnetic space-based field measurements

NASA Technical Reports Server (NTRS)

Langel, R. A.

1981-01-01

Because the near Earth magnetic field is a complex combination of fields from outside the Earth of fields from its core and of fields from its crust, measurements from space prove to be the only practical way to obtain timely, global surveys. Due to difficulty in making accurate vector measurements, early satellites such as Sputnik and Vanguard measured only the magnitude survey. The attitude accuracy was 20 arc sec. Both the Earth's core fields and the fields arising from its crust were mapped from satellite data. The standard model of the core consists of a scalar potential represented by a spherical harmonics series. Models of the crustal field are relatively new. Mathematical representation is achieved in localized areas by arrays of dipoles appropriately located in the Earth's crust. Measurements of the Earth's field are used in navigation, to map charged particles in the magnetosphere, to study fluid properties in the Earth's core, to infer conductivity of the upper mantels, and to delineate regional scale geological features.

Bose-Einstein condensate & degenerate Fermi cored dark matter halos

NASA Astrophysics Data System (ADS)

Chung, W.-J.; Nelson, L. A.

2018-06-01

There has been considerable interest in the last several years in support of the idea that galaxies and clusters could have highly condensed cores of dark matter (DM) within their central regions. In particular, it has been suggested that dark matter could form Bose-Einstein condensates (BECs) or degenerate Fermi cores. We examine these possibilities under the assumption that the core consists of highly condensed DM (either bosons or fermions) that is embedded in a diffuse envelope (e.g., isothermal sphere). The novelty of our approach is that we invoke composite polytropes to model spherical collisionless structures in a way that is physically intuitive and can be generalized to include other equations of state (EOSs). Our model is very amenable to the analysis of BEC cores (composed of ultra-light bosons) that have been proposed to resolve small-scale CDM anomalies. We show that the analysis can readily be applied to bosons with or without small repulsive self-interactions. With respect to degenerate Fermi cores, we confirm that fermionic particle masses between 1—1000 keV are not excluded by the observations. Finally, we note that this approach can be extended to include a wide range of EOSs in addition to multi-component collisionless systems.

Multiple Interfacial Fe3O4@BaTiO3/P(VDF-HFP) Core-Shell-Matrix Films with Internal Barrier Layer Capacitor (IBLC) Effects and High Energy Storage Density.

PubMed

Zhou, Ling; Fu, Qiuyun; Xue, Fei; Tang, Xiahui; Zhou, Dongxiang; Tian, Yahui; Wang, Geng; Wang, Chaohong; Gou, Haibo; Xu, Lei

2017-11-22

Flexible nanocomposites composed of high dielectric constant fillers and polymer matrix have shown great potential for electrostatic capacitors and energy storage applications. To obtain the composited material with high dielectric constant and high breakdown strength, multi-interfacial composited particles, which composed of conductive cores and insulating shells and possessed the internal barrier layer capacitor (IBLC) effect, were adopted as fillers. Thus, Fe 3 O 4 @BaTiO 3 core-shell particles were prepared and loaded into the poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) polymer matrix. As the mass fraction of core-shell fillers increased from 2.5 wt % to 30 wt %, the dielectric constant of the films increased, while the loss tangent remained at a low level (<0.05 at 1 kHz). Both high electric displacement and high electric breakdown strength were achieved in the films with 10 wt % core-shell fillers loaded. The maximum energy storage density of 7.018 J/cm 3 was measured at 2350 kV/cm, which shows significant enhancement than those of the pure P(VDF-HFP) films and analogous composited films with converse insulating-conductive core-shell fillers. A Maxwell-Wagner capacitor model was also adopted to interpret the efficiency of IBLC effects on the suppressed loss tangent and the superior breakdown strength. This work explored an effective approach to prepare dielectric nanocomposites for energy storage applications experimentally and theoretically.

Size-exclusion chromatography using core-shell particles.

PubMed

Pirok, Bob W J; Breuer, Pascal; Hoppe, Serafine J M; Chitty, Mike; Welch, Emmet; Farkas, Tivadar; van der Wal, Sjoerd; Peters, Ron; Schoenmakers, Peter J

2017-02-24

Size-exclusion chromatography (SEC) is an indispensable technique for the separation of high-molecular-weight analytes and for determining molar-mass distributions. The potential application of SEC as second-dimension separation in comprehensive two-dimensional liquid chromatography demands very short analysis times. Liquid chromatography benefits from the advent of highly efficient core-shell packing materials, but because of the reduced total pore volume these materials have so far not been explored in SEC. The feasibility of using core-shell particles in SEC has been investigated and contemporary core-shell materials were compared with conventional packing materials for SEC. Columns packed with very small core-shell particles showed excellent resolution in specific molar-mass ranges, depending on the pore size. The analysis times were about an order of magnitude shorter than what could be achieved using conventional SEC columns. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis, microstructure and magnetic properties of Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite core

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

Wang, Jian, E-mail: snove418562@163.com; Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081; Fan, Xi’an, E-mail: groupfxa@163.com

2015-11-15

Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite core have been synthesized via a modified stöber method combined with following high temperature sintering process. Most of conductive Fe{sub 3}Si{sub 0.7}Al{sub 0.3} particles could be uniformly coated by insulating SiO{sub 2} using the modified stöber method. The Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles exhibited good soft magnetic properties with low coercivity and high saturation magnetization. The reaction 4Al+3SiO{sub 2}=2α-Al{sub 2}O{sub 3}+3Si took place during the sintering process. As a result the new Fe{sub 3}Si/Al{sub 2}O{sub 3} composite was formed. The Fe{sub 3}Si/Al{sub 2}O{submore » 3} composite core displayed more excellent soft magnetic properties, better frequency stability at high frequencies, much higher electrical resistivity and lower core loss than the pure Fe{sub 3}Si{sub 0.7}Al{sub 0.3} core. The method of introducing insulating layers surrounding magnetic particles provides a promising route to develop new and high compact soft magnetic materials with good magnetic and electric properties. - Graphical abstract: In Fe{sub 3}Si/Al{sub 2}O{sub 3} composite, Fe{sub 3}Si phases are separated by Al{sub 2}O{sub 3} layers and the eddy currents are confined in Fe{sub 3}Si phases, thus increasing resistivity and reducing core loss. - Highlights: • Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} cores were prepared. • Fe{sub 3}Si{sub 0.7}Al{sub 0.3} particles could be uniformly coated by nano-sized SiO{sub 2} clusters. • Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} cores showed good soft magnetic properties. • Fe{sub 3}Si/Al{sub 2}O{sub 3} had lower core loss and better frequency stability than Fe{sub 3}Si{sub 0.7}Al{sub 0.3} cores.« less

Condensed-phase biogenic-anthropogenic interactions with implications for cold cloud formation.

PubMed

Charnawskas, Joseph C; Alpert, Peter A; Lambe, Andrew T; Berkemeier, Thomas; O'Brien, Rachel E; Massoli, Paola; Onasch, Timothy B; Shiraiwa, Manabu; Moffet, Ryan C; Gilles, Mary K; Davidovits, Paul; Worsnop, Douglas R; Knopf, Daniel A

2017-08-24

Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil fuel combustion can acquire a coating of SOA. We investigate SOA-soot biogenic-anthropogenic interactions and their impact on ice nucleation in relation to the particles' organic phase state. SOA particles were generated from the OH oxidation of naphthalene, α-pinene, longifolene, or isoprene, with or without the presence of sulfate or soot particles. Corresponding particle glass transition (T g ) and full deliquescence relative humidity (FDRH) were estimated using a numerical diffusion model. Longifolene SOA particles are solid-like and all biogenic SOA sulfate mixtures exhibit a core-shell configuration (i.e. a sulfate-rich core coated with SOA). Biogenic SOA with or without sulfate formed ice at conditions expected for homogeneous ice nucleation, in agreement with respective T g and FDRH. α-pinene SOA coated soot particles nucleated ice above the homogeneous freezing temperature with soot acting as ice nuclei (IN). At lower temperatures the α-pinene SOA coating can be semisolid, inducing ice nucleation. Naphthalene SOA coated soot particles acted as ice nuclei above and below the homogeneous freezing limit, which can be explained by the presence of a highly viscous SOA phase. Our results suggest that biogenic SOA does not play a significant role in mixed-phase cloud formation and the presence of sulfate renders this even less likely. However, anthropogenic SOA may have an enhancing effect on cloud glaciation under mixed-phase and cirrus cloud conditions compared to biogenic SOA that dominate during pre-industrial times or in pristine areas.

Hybrid particles and associated methods

DOEpatents

Fox, Robert V; Rodriguez, Rene; Pak, Joshua J; Sun, Chivin

2015-02-10

Hybrid particles that comprise a coating surrounding a chalcopyrite material, the coating comprising a metal, a semiconductive material, or a polymer; a core comprising a chalcopyrite material and a shell comprising a functionalized chalcopyrite material, the shell enveloping the core; or a reaction product of a chalcopyrite material and at least one of a reagent, heat, and radiation. Methods of forming the hybrid particles are also disclosed.

Approximate symmetries in atomic nuclei from a large-scale shell-model perspective

NASA Astrophysics Data System (ADS)

Launey, K. D.; Draayer, J. P.; Dytrych, T.; Sun, G.-H.; Dong, S.-H.

2015-05-01

In this paper, we review recent developments that aim to achieve further understanding of the structure of atomic nuclei, by capitalizing on exact symmetries as well as approximate symmetries found to dominate low-lying nuclear states. The findings confirm the essential role played by the Sp(3, ℝ) symplectic symmetry to inform the interaction and the relevant model spaces in nuclear modeling. The significance of the Sp(3, ℝ) symmetry for a description of a quantum system of strongly interacting particles naturally emerges from the physical relevance of its generators, which directly relate to particle momentum and position coordinates, and represent important observables, such as, the many-particle kinetic energy, the monopole operator, the quadrupole moment and the angular momentum. We show that it is imperative that shell-model spaces be expanded well beyond the current limits to accommodate particle excitations that appear critical to enhanced collectivity in heavier systems and to highly-deformed spatial structures, exemplified by the second 0+ state in 12C (the challenging Hoyle state) and 8Be. While such states are presently inaccessible by large-scale no-core shell models, symmetry-based considerations are found to be essential.

Effects of pore topology and iron oxide core on doxorubicin loading and release from mesoporous silica nanoparticles

NASA Astrophysics Data System (ADS)

Ronhovde, Cicily J.; Baer, John; Larsen, Sarah C.

2017-06-01

Mesoporous silica nanoparticles (MSNs) have a network of pores that give rise to extremely high specific surface areas, making them attractive materials for applications such as adsorption and drug delivery. The pore topology can be readily tuned to achieve a variety of structures such as the hexagonally ordered Mobil Crystalline Material 41 (MCM-41) and the disordered "wormhole" (WO) mesoporous silica (MS) structure. In this work, the effects of pore topology and iron oxide core on doxorubicin loading and release were investigated using MSNs with pore diameters of approximately 3 nm and sub-100 nm particle diameters. The nanoparticles were loaded with doxorubicin, and the drug release into phosphate-buffered saline (PBS, 10 mM, pH 7.4) at 37 °C was monitored by fluorescence spectroscopy. The release profiles were fit using the Peppas model. The results indicated diffusion-controlled release for all samples. Statistically significant differences were observed in the kinetic host-guest parameters for each sample due to the different pore topologies and the inclusion of an iron oxide core. Applying a static magnetic field to the iron oxide core WO-MS shell materials did not have a significant impact on the doxorubicin release. This is the first time that the effects of pore topology and iron oxide core have been isolated from pore diameter and particle size for these materials.

Defined polymer shells on nanoparticles via a continuous aerosol-based process

NASA Astrophysics Data System (ADS)

Sigmund, Stephanie; Akgün, Ertan; Meyer, Jörg; Hubbuch, Jürgen; Wörner, Michael; Kasper, Gerhard

2014-08-01

A continuous aerosol-based process is described for the encapsulation of nanoparticles with a thin polymer shell. The process is essentially based on directed binary collisions between gas-borne core particles and liquid monomer droplets carrying opposite electrical charges, followed by photo-initiated polymerization. Once the two streams are mixed together, the process runs to completion on a time scale of about 2 min or less, required for coagulation and polymerization. Gold, silica, and sodium chloride nanoparticles were successfully coated by this technique with PHDDA [poly(hexanediol diacrylate)] and/or crosslinked PMMA [poly(methyl methacrylate)]. It was found that all core materials as well as agglomerates were wettable at room temperature and that the spreading kinetics of the monomer were fast enough to cover the core particles uniformly within the time scale provided for coagulation. The shell thickness depends on the volume ratio between core particles and monomer droplets. This was demonstrated for a combination of monodisperse silica spheres ( d = 241 nm) and polydisperse methyl methacrylate droplets, resulting in a theoretical shell thickness of 18 nm. There was very good agreement between measurements by TEM and electrical mobility spectroscopy. The results revealed that about 90 % or more of the core-shell structures were formed from 1:1 collisions between a core particle and a single monomer droplet.

Magnetic nanofibers with core (Fe 3O 4 nanoparticle suspension)/sheath (poly ethylene terephthalate) structure fabricated by coaxial electrospinning

NASA Astrophysics Data System (ADS)

Sung, Yun Kyung; Ahn, Byung Wook; Kang, Tae Jin

2012-03-01

One-dimensional magnetic nanostructures have recently attracted much attention because of their intriguing properties that are not realized by their bulk or particle form. These nanostructures are potentially useful for the application to ultrahigh-density data storages, sensors and bulletproof vest. The magnetic particles in magnetic nanofibers of blend types cannot fully align along the external magnetic field because magnetic particles are arrested in solid polymer matrix. To improve the mobility of magnetic particles, we used magneto-rheological fluid (MRF), which has the good mobility and dispersibility. Superparamagnetic core/sheath composite nanofibers were obtained with MRF and poly (ethylene terephthalate) (PET) solution via a coaxial electrospinning technique. Coaxial electrospinning is suited for fabricating core/sheath nanofibers encapsulating MRF materials within a polymer sheath. The magnetic nanoparticles in MRF were dispersed within core part of the nanofibers. The core/sheath magnetic composite nanofibers exhibited superparamagnetic behavior at room temperature and the magnetic nanoparticles in MRF well responded to an applied magnetic field. Also, the mechanical properties of the nanofiber were improved in the magnetic field. This study aimed to fabricate core/sheath magnetic composite nanofibers using coaxial electrospinning and characterize the magnetic as well as mechanical properties of composite nanofibers.

Particle distributions in approximately 10(13) - 10(16) eV air shower cores at mountain altitude and comparison with Monte Carlo simulations

NASA Technical Reports Server (NTRS)

Ash, A. G.

1985-01-01

Photographs of 521 shower cores in an array of current-limited spark (discharge) chambers at Sacramento Peak (2900m above sea level, 730 g /sq cm.), New Mexico, U.S.A., have been analyzed and the results compared with similar data from Leeds (80m above sea level, 1020 g sq cm.). It was found that the central density differential spectrum is consistent with a power law index of -2 up to approx. 1500/sq m where it steepens, and that shower cores become flatter on average with increasing size. Scaling model predictions for proton primaries with a approx E sup -2.71 energy spectrum account well for the altitude dependence of the data at lower densities. However, deviations at higher densities indicate a change in hadron interaction characteristics between approx few x 10 to the 14th power and 10 to the 15th power eV primary energy causing particles close to the shower axis to be spread further out.

The mutable nature of particle-core excitations with spin in the one-valence-proton nucleus 133Sb

NASA Astrophysics Data System (ADS)

Bocchi, G.; Leoni, S.; Fornal, B.; Colò, G.; Bortignon, P. F.; Bottoni, S.; Bracco, A.; Michelagnoli, C.; Bazzacco, D.; Blanc, A.; de France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Régis, J.-M.; Simpson, G.; Soldner, T.; Ur, C. A.; Urban, W.; Fraile, L. M.; Lozeva, R.; Belvito, B.; Benzoni, G.; Bruce, A.; Carroll, R.; Cieplicka-Oryǹczak, N.; Crespi, F. C. L.; Didierjean, F.; Jolie, J.; Korten, W.; Kröll, T.; Lalkovski, S.; Mach, H.; Mărginean, N.; Melon, B.; Mengoni, D.; Million, B.; Nannini, A.; Napoli, D.; Olaizola, B.; Paziy, V.; Podolyák, Zs.; Regan, P. H.; Saed-Samii, N.; Szpak, B.; Vedia, V.

2016-09-01

The γ-ray decay of excited states of the one-valence-proton nucleus 133Sb has been studied using cold-neutron induced fission of 235U and 241Pu targets, during the EXILL campaign at the ILL reactor in Grenoble. By using a highly efficient HPGe array, coincidences between γ-rays prompt with the fission event and those delayed up to several tens of microseconds were investigated, allowing to observe, for the first time, high-spin excited states above the 16.6 μs isomer. Lifetimes analysis, performed by fast-timing techniques with LaBr3(Ce) scintillators, revealed a difference of almost two orders of magnitude in B(M1) strength for transitions between positive-parity medium-spin yrast states. The data are interpreted by a newly developed microscopic model which takes into account couplings between core excitations (both collective and non-collective) of the doubly magic nucleus 132Sn and the valence proton, using the Skyrme effective interaction in a consistent way. The results point to a fast change in the nature of particle-core excitations with increasing spin.

Plasma coating of nanoparticles in the presence of an external electric field

NASA Astrophysics Data System (ADS)

Ebadi, Zahra; Pourali, Nima; Mohammadzadeh, Hosein

2018-04-01

Film deposition onto nanoparticles by low-pressure plasma in the presence of an external electric field is studied numerically. The plasma discharge fluid model along with surface deposition and heating models for nanoparticles, as well as a dynamics model considering the motion of nanoparticles, are employed for this study. The results of the simulation show that applying external field during the process increases the uniformity of the film deposited onto nanoparticles and leads to that nanoparticles grow in a spherical shape. Increase in film uniformity and particles sphericity is related to particle dynamics that is controlled by parameters of the external field like frequency and amplitude. The results of this work can be helpful to produce spherical core-shell nanoparticles in nanomaterial industry.

A parallel Discrete Element Method to model collisions between non-convex particles

NASA Astrophysics Data System (ADS)

Rakotonirina, Andriarimina Daniel; Delenne, Jean-Yves; Wachs, Anthony

2017-06-01

In many dry granular and suspension flow configurations, particles can be highly non-spherical. It is now well established in the literature that particle shape affects the flow dynamics or the microstructure of the particles assembly in assorted ways as e.g. compacity of packed bed or heap, dilation under shear, resistance to shear, momentum transfer between translational and angular motions, ability to form arches and block the flow. In this talk, we suggest an accurate and efficient way to model collisions between particles of (almost) arbitrary shape. For that purpose, we develop a Discrete Element Method (DEM) combined with a soft particle contact model. The collision detection algorithm handles contacts between bodies of various shape and size. For nonconvex bodies, our strategy is based on decomposing a non-convex body into a set of convex ones. Therefore, our novel method can be called "glued-convex method" (in the sense clumping convex bodies together), as an extension of the popular "glued-spheres" method, and is implemented in our own granular dynamics code Grains3D. Since the whole problem is solved explicitly, our fully-MPI parallelized code Grains3D exhibits a very high scalability when dynamic load balancing is not required. In particular, simulations on up to a few thousands cores in configurations involving up to a few tens of millions of particles can readily be performed. We apply our enhanced numerical model to (i) the collapse of a granular column made of convex particles and (i) the microstructure of a heap of non-convex particles in a cylindrical reactor.

Co-firing straw with coal in a swirl-stabilized dual-feed burner: modelling and experimental validation.

PubMed

Yin, Chungen; Kaer, Søren K; Rosendahl, Lasse; Hvid, Søren L

2010-06-01

This paper presents a comprehensive computational fluid dynamics (CFD) modelling study of co-firing wheat straw with coal in a 150kW swirl-stabilized dual-feed burner flow reactor, in which the pulverized straw particles (mean diameter of 451microm) and coal particles (mean diameter of 110.4microm) are independently fed into the burner through two concentric injection tubes, i.e., the centre and annular tubes, respectively. Multiple simulations are performed, using three meshes, two global reaction mechanisms for homogeneous combustion, two turbulent combustion models, and two models for fuel particle conversion. It is found that for pulverized biomass particles of a few hundred microns in diameter the intra-particle heat and mass transfer is a secondary issue at most in their conversion, and the global four-step mechanism of Jones and Lindstedt may be better used in modelling volatiles combustion. The baseline CFD models show a good agreement with the measured maps of main species in the reactor. The straw particles, less affected by the swirling secondary air jet due to the large fuel/air jet momentum and large particle response time, travels in a nearly straight line and penetrate through the oxygen-lean core zone; whilst the coal particles are significantly affected by secondary air jet and swirled into the oxygen-rich outer radius with increased residence time (in average, 8.1s for coal particles vs. 5.2s for straw particles in the 3m high reactor). Therefore, a remarkable difference in the overall burnout of the two fuels is predicted: about 93% for coal char vs. 73% for straw char. As the conclusion, a reliable modelling methodology for pulverized biomass/coal co-firing and some useful co-firing design considerations are suggested. Copyright 2010 Elsevier Ltd. All rights reserved.

Quadrupole magnetic field-flow fractionation: A novel technique for the characterization of magnetic particles

NASA Astrophysics Data System (ADS)

Carpino, Francesca

In the last few decades, the development and use of nanotechnology has become of increasing importance. Magnetic nanoparticles, because of their unique properties, have been employed in many different areas of application. They are generally made of a core of magnetic material coated with some other material to stabilize them and to help disperse them in suspension. The unique feature of magnetic nanoparticles is their response to a magnetic field. They are generally superparamagnetic, in which case they become magnetized only in a magnetic field and lose their magnetization when the field is removed. It is this feature that makes them so useful for drug targeting, hyperthermia and bioseparation. For many of these applications, the synthesis of uniformly sized magnetic nanoparticles is of key importance because their magnetic properties depend strongly on their dimensions. Because of the difficulty of synthesizing monodisperse particulate materials, a technique capable of characterizing the magnetic properties of polydisperse samples is of great importance. Quadrupole magnetic field-flow fractionation (MgFFF) is a technique capable of fractionating magnetic particles based on their content of magnetite or other magnetic material. In MgFFF, the interplay of hydrodynamic and magnetic forces separates the particles as they are carried along a separation channel. Since the magnetic field and the gradient in magnetic field acting on the particles during their migration are known, it is possible to calculate the quantity of magnetic material in the particles according to their time of emergence at the channel outlet. Knowing the magnetic properties of the core material, MgFFF can be used to determine both the size distribution and the mean size of the magnetic cores of polydisperse samples. When magnetic material is distributed throughout the volume of the particles, the derived data corresponds to a distribution in equivalent spherical diameters of magnetic material in the particles. MgFFF is unique in its ability to characterize the distribution in magnetic properties of a particulate sample. This knowledge is not only of importance to the optimization and quality control of particle preparation. It is also of great importance in modeling magnetic cell separation, drug targeting, hyperthermia, and other areas of application.

Spectroscopic properties of 130Sb, 132Te and 134I nuclei in 100-132Sn magic cores

NASA Astrophysics Data System (ADS)

Benrachi, Fatima; Khiter, Meriem; Laouet, Nadjet

2017-09-01

We have performed shell model calculations by means of Oxbash nuclear structure code using recent experimental single particle (spes) and single hole (shes) energies with valence space models above the 100sn and 132sn doubly magic cores. The two-body matrix elements (tbme) of original CD-Bonn realistic interaction are introduced after have been modified taking into account the three-body forces. We have focused our study on spectroscopic properties evaluation of 130Sb, 132Te and 134I nuclei, in particular their energy spectra, transition probabilities and moments have been determined. The getting spectra are in reasonable agreement with the experimental data.

Dissipative hidden sector dark matter

NASA Astrophysics Data System (ADS)

Foot, R.; Vagnozzi, S.

2015-01-01

A simple way of explaining dark matter without modifying known Standard Model physics is to require the existence of a hidden (dark) sector, which interacts with the visible one predominantly via gravity. We consider a hidden sector containing two stable particles charged under an unbroken U (1 )' gauge symmetry, hence featuring dissipative interactions. The massless gauge field associated with this symmetry, the dark photon, can interact via kinetic mixing with the ordinary photon. In fact, such an interaction of strength ε ˜10-9 appears to be necessary in order to explain galactic structure. We calculate the effect of this new physics on big bang nucleosynthesis and its contribution to the relativistic energy density at hydrogen recombination. We then examine the process of dark recombination, during which neutral dark states are formed, which is important for large-scale structure formation. Galactic structure is considered next, focusing on spiral and irregular galaxies. For these galaxies we modeled the dark matter halo (at the current epoch) as a dissipative plasma of dark matter particles, where the energy lost due to dissipation is compensated by the energy produced from ordinary supernovae (the core-collapse energy is transferred to the hidden sector via kinetic mixing induced processes in the supernova core). We find that such a dynamical halo model can reproduce several observed features of disk galaxies, including the cored density profile and the Tully-Fisher relation. We also discuss how elliptical and dwarf spheroidal galaxies could fit into this picture. Finally, these analyses are combined to set bounds on the parameter space of our model, which can serve as a guideline for future experimental searches.

Visualization assisted by parallel processing

NASA Astrophysics Data System (ADS)

Lange, B.; Rey, H.; Vasques, X.; Puech, W.; Rodriguez, N.

2011-01-01

This paper discusses the experimental results of our visualization model for data extracted from sensors. The objective of this paper is to find a computationally efficient method to produce a real time rendering visualization for a large amount of data. We develop visualization method to monitor temperature variance of a data center. Sensors are placed on three layers and do not cover all the room. We use particle paradigm to interpolate data sensors. Particles model the "space" of the room. In this work we use a partition of the particle set, using two mathematical methods: Delaunay triangulation and Voronoý cells. Avis and Bhattacharya present these two algorithms in. Particles provide information on the room temperature at different coordinates over time. To locate and update particles data we define a computational cost function. To solve this function in an efficient way, we use a client server paradigm. Server computes data and client display this data on different kind of hardware. This paper is organized as follows. The first part presents related algorithm used to visualize large flow of data. The second part presents different platforms and methods used, which was evaluated in order to determine the better solution for the task proposed. The benchmark use the computational cost of our algorithm that formed based on located particles compared to sensors and on update of particles value. The benchmark was done on a personal computer using CPU, multi core programming, GPU programming and hybrid GPU/CPU. GPU programming method is growing in the research field; this method allows getting a real time rendering instates of a precompute rendering. For improving our results, we compute our algorithm on a High Performance Computing (HPC), this benchmark was used to improve multi-core method. HPC is commonly used in data visualization (astronomy, physic, etc) for improving the rendering and getting real-time.

Fabrication of Cu-Ag core-shell bimetallic superfine powders by eco-friendly reagents and structures characterization

NASA Astrophysics Data System (ADS)

Zhao, Jun; Zhang, Dongming; Zhao, Jie

2011-09-01

Superfine bimetallic Cu-Ag core-shell powders were synthesized by reduction of copper sulfate pentahydrate and silver nitrate with eco-friendly ascorbic acid as a reducing agent and cyclodextrins as a protective agent in an aqueous system. The influence of Ag/Cu ratio on coatings was investigated. Ag was homogeneously distributed on the surface of Cu particles at a mole ratio of Ag/Cu=1. FE-SEM showed an uniformity of Ag coatings on Cu particles. Antioxidation of Cu particles was improved by increasing Ag/Cu ratio. TEM-EDX and UV-vis spectra also revealed that Cu cores were covered by Ag nanoshells on the whole. The surface composition analysis by XPS indicated that only small parts of Cu atoms in the surface were oxidized. It was noted that the hindrance of cyclodextrins chemisorbed on particles plays an important role in forming high quality and good dispersity Cu-Ag (Cu@Ag) core-shell powders.

Development of novel magnetic nanoparticles for hyperthermia cancer therapy

NASA Astrophysics Data System (ADS)

Cassim, Shiraz M.; Giustini, Andrew J.; Baker, Ian; Hoopes, P. Jack

2011-03-01

Advances in magnetic nanoparticle hyperthermia are opening new doors in cancer therapy. As a standalone or adjuvant therapy this new modality has the opportunity significantly advance thermal medicine. Major advantages of using magnetic magnetite (Fe3O4) nanoparticles are their highly localized power deposition and the fact that the alternating magnetic fields (AMF) used to excite them can penetrate deeply into the body without harmful effect. One limitation, however, which hinders the technology, is the problem of inductive heating of normal tissue by the AMF if the frequency and fields strength are not appropriately matched to the tissue. Restricting AMF amplitude and frequency limits the heat dose which can be selectively applied to cancerous tissue via the magnetic nanoparticle, thus lowering therapeutic effect. In an effort to address this problem, particles with optimized magnetic properties must be developed. Using particles with higher saturation magnetizations and coercivity will enhance hysteresis heating increasing particle power density at milder AMF strengths and frequencies. In this study we used oil in water microemulsions to develop nanoparticles with zero-valent Fe cores and magnetite shells. The superior magnetic properties of zero-valent Fe give these particles the potential for improved SAR over pure magnetite particles. Silane and subsequently dextran have been attached to the particle surface in order to provide a biocompatible surfactant coating. The heating capability of the particles was tested in-vivo using a mouse tumor model. Although we determined that the final stage of synthesis, purification of the dextran coated particles, permits significant corrosion/oxidation of the iron core to hematite, the particles can effectively heat tumor tissue. Improving the purification procedure will allow the generation Fe/Fe3O4 with superior SAR values.

Development and validation of a critical gradient energetic particle driven Alfven eigenmode transport model for DIII-D tilted neutral beam experiments

NASA Astrophysics Data System (ADS)

Waltz, R. E.; Bass, E. M.; Heidbrink, W. W.; VanZeeland, M. A.

2015-11-01

Recent experiments with the DIII-D tilted neutral beam injection (NBI) varying the beam energetic particle (EP) source profiles have provided strong evidence that unstable Alfven eigenmodes (AE) drive stiff EP transport at a critical EP density gradient [Heidbrink et al 2013 Nucl. Fusion 53 093006]. Here the critical gradient is identified by the local AE growth rate being equal to the local ITG/TEM growth rate at the same low toroidal mode number. The growth rates are taken from the gyrokinetic code GYRO. Simulation show that the slowing down beam-like EP distribution has a slightly lower critical gradient than the Maxwellian. The ALPHA EP density transport code [Waltz and Bass 2014 Nucl. Fusion 54 104006], used to validate the model, combines the low-n stiff EP critical density gradient AE mid-core transport with the Angioni et al (2009 Nucl. Fusion 49 055013) energy independent high-n ITG/TEM density transport model controling the central core EP density profile. For the on-axis NBI heated DIII-D shot 146102, while the net loss to the edge is small, about half the birth fast ions are transported from the central core r/a  <  0.5 and the central density is about half the slowing down density. These results are in good agreement with experimental fast ion pressure profiles inferred from MSE constrained EFIT equilibria.

Morphology and orientational behavior of silica-coated spindle-type hematite particles in a magnetic field probed by small-angle X-ray scattering.

PubMed

Reufer, Mathias; Dietsch, Hervé; Gasser, Urs; Hirt, Ann; Menzel, Andreas; Schurtenberger, Peter

2010-04-15

Form factor and magnetic properties of silica-coated spindle-type hematite nanoparticles are determined from SAXS measurements with applied magnetic field and magnetometry measurements. The particle size, polydispersity and porosity are determined using a core-shell model for the form factor. The particles are found to align with their long axis perpendicular to the applied field. The orientational order is determined from the SAXS data and compared to the orientational order obtained from magnetometry. The direct access to both, the orientational order of the particles, and the magnetic moments allow one to determine the magnetic properties of the individual spindle-type hematite particles. We study the influence of the silica coating on the magnetic properties and find a fundamentally different behavior of silica-coated particles. The silica coating reduces the effective magnetic moment of the particles. This effect is enhanced with field strength and can be explained by superparamagnetic relaxation in the highly porous particles.

A nano-disperse ferritin-core mimetic that efficiently corrects anemia without luminal iron redox activity

PubMed Central

Powell, Jonathan J.; Bruggraber, Sylvaine F.A.; Faria, Nuno; Poots, Lynsey K.; Hondow, Nicole; Pennycook, Timothy J.; Latunde-Dada, Gladys O.; Simpson, Robert J.; Brown, Andy P.; Pereira, Dora I.A.

2014-01-01

The 2-5 nm Fe(III) oxo-hydroxide core of ferritin is less ordered and readily bioavailable compared to its pure synthetic analogue, ferrihydrite. We report the facile synthesis of tartrate-modified, nano-disperse ferrihydrite of small primary particle size, but with enlarged or strained lattice structure (~ 2.7 Å for the main Bragg peak versus 2.6 Å for synthetic ferrihydrite). Analysis indicated that co-precipitation conditions can be achieved for tartrate inclusion into the developing ferrihydrite particles, retarding both growth and crystallization and favoring stabilization of the cross-linked polymeric structure. In murine models, gastrointestinal uptake was independent of luminal Fe(III) reduction to Fe(II) and, yet, absorption was equivalent to that of ferrous sulphate, efficiently correcting the induced anemia. This process may model dietary Fe(III) absorption and potentially provide a side effect-free form of cheap supplemental iron. From the Clinical Editor Small size tartrate-modified, nano-disperse ferrihydrite was used for efficient gastrointestinal delivery of soluble Fe(III) without the risk for free radical generation in murine models. This method may provide a potentially side effect-free form iron supplementation. PMID:24394211

Diffraction data of core-shell nanoparticles from an X-ray free electron laser

DOE PAGES

Li, Xuanxuan; Chiu, Chun -Ya; Wang, Hsiang -Ju; ...

2017-04-11

X-ray free-electron lasers provide novel opportunities to conduct single particle analysis on nanoscale particles. Coherent diffractive imaging experiments were performed at the Linac Coherent Light Source (LCLS), SLAC National Laboratory, exposing single inorganic core-shell nanoparticles to femtosecond hard-X-ray pulses. Each facetted nanoparticle consisted of a crystalline gold core and a differently shaped palladium shell. Scattered intensities were observed up to about 7 nm resolution. Analysis of the scattering patterns revealed the size distribution of the samples, which is consistent with that obtained from direct real-space imaging by electron microscopy. Furthermore, scattering patterns resulting from single particles were selected and compiledmore » into a dataset which can be valuable for algorithm developments in single particle scattering research.« less

Design and synthesis of magnetic nanoparticles with gold shells for single particle optical tracking

NASA Astrophysics Data System (ADS)

Lim, Jitkang

The design, synthesis, and characterization of iron oxide core, gold shell nanoparticles are studied in this thesis. Firstly, nanoparticles with 18 +/- 1.7 nm diameter iron oxide cores with ˜5 nm thick gold shells were synthesized via a new seed-mediated electroless deposition method. The nanoparticles were superparamagnetic at room temperature and could be reversibly collected by a permanent magnet. These nanoparticles displayed a sharp localized surface plasmon resonance peak at 605 nm, as predicted by scattering theory, and their large scattering cross-section allowed them to be individually resolved in darkfield optical microscopy while undergoing Brownian motion in aqueous suspension. Later, commercially available 38 +/- 3.8 nm diameter spherical iron oxide nanoparticles (from Ocean Nanotech, Inc) were employed to make core-shell particles. These particles were decorated with cationic poly(diallyldimethylammonium chloride) (PDDA) which further promotes the attachment of small gold clusters. After gold seeding, the average hydrodynamic diameter of the core-shell particles is 172 +/- 65.9 nm. The magnetophoretic motion of these particles was guided by a piece of magnetized mu-metal. Individual particle trajectories were observed by darkfield optical microscopy. The typical magnetophoretic velocity achieved was within the range of 1--10 mum/sec. Random walk analysis performed on these particles while undergoing Brownian motion confirmed that individual particles were indeed being imaged. The particle size variation within the observed sample obtained through random walk analysis was within the size distribution obtained by dynamic light scattering. When the current to the solenoid used to magnetize the mu-metal was turned off, all the collected core-shell particles were readily redispersed by diffusion back into the surrounding environment. A Peclet number analysis was performed to probe the convective motion of nanospheres and nanorods under the influence of magnetophoresis and diffusion. Under most circumstances, magnetophoretic behavior dominates diffusion for nanorods, as the magnetic field lines tend to align the magnetic moment along the rod axis. The synthesis and dispersion of fluorophore-tagged nanorods are described. Fluorescence microscopy was employed to image the nanorod motion in a magnetic field gradient. The preliminary experimental data are consistent with the Peclet number analysis. Lastly, the colloidal stability of iron oxide core, gold shell nanoparticles in high ionic strength media was investigated. Such particles are sufficiently charged to be stable against flocculation without modification in low ionic strength media, but they require surface modification to be stably dispersed in elevated ionic strength media that are appropriate for biotechnological applications. Dynamic light scattering and ultraviolet-visible spectrophotometry were used to monitor the colloidal stability of core-shell particles in pH 7.4, 150 mM ionic strength phosphate buffered saline (PBS). While uncoated particles flocculated immediately upon being introduced into PBS, core-shell particles with adsorbed layers of bovine serum albumin or the amphiphilic triblock copolymers Pluronic F127 and Pluronic F68 resist flocculation after more than five days in PBS. Adsorbed dextran allowed flocculation that was limited to the formation of small clusters, while poly(ethylene glycol) homopolymers ranging in molecular weight from 6,000 to 100,000 were ineffective steric stabilizers. The effectiveness of adsorbed Pluronic copolymers as steric stabilizers was interpreted in terms of the measured adsorbed layer thickness and extended DLVO theory predictions of the interparticle interactions.

Chemical association in simple models of molecular and ionic fluids. III. The cavity function

NASA Astrophysics Data System (ADS)

Zhou, Yaoqi; Stell, George

1992-01-01

Exact equations which relate the cavity function to excess solvation free energies and equilibrium association constants are rederived by using a thermodynamic cycle. A zeroth-order approximation, derived previously by us as a simple interpolation scheme, is found to be very accurate if the associative bonding occurs on or near the surface of the repulsive core of the interaction potential. If the bonding radius is substantially less than the core radius, the approximation overestimates the association degree and the association constant. For binary association, the zeroth-order approximation is equivalent to the first-order thermodynamic perturbation theory (TPT) of Wertheim. For n-particle association, the combination of the zeroth-order approximation with a ``linear'' approximation (for n-particle distribution functions in terms of the two-particle function) yields the first-order TPT result. Using our exact equations to go beyond TPT, near-exact analytic results for binary hard-sphere association are obtained. Solvent effects on binary hard-sphere association and ionic association are also investigated. A new rule which generalizes Le Chatelier's principle is used to describe the three distinct forms of behaviors involving solvent effects that we find. The replacement of the dielectric-continuum solvent model by a dipolar hard-sphere model leads to improved agreement with an experimental observation. Finally, equation of state for an n-particle flexible linear-chain fluid is derived on the basis of a one-parameter approximation that interpolates between the generalized Kirkwood superposition approximation and the linear approximation. A value of the parameter that appears to be near optimal in the context of this application is obtained from comparison with computer-simulation data.

NEUTRONIC REACTOR SYSTEM

DOEpatents

Daniels, F.

1957-10-15

Gas-cooled solid-moderator type reactors wherein the fissionable fuel and moderator materials are each in the form of solid pebbles, or discrete particles, and are substantially homogeneously mixed in the proper proportion and placed within the core of the reactor are described. The shape of these discrete particles must be such that voids are present between them when mixed together. Helium enters the bottom of the core and passes through the voids between the fuel and moderator particles to absorb the heat generated by the chain reaction. The hot helium gas is drawn off the top of the core and may be passed through a heat exchanger to produce steam.

Synthesis and characterization of monodispersed polymer/polydiacetylene nanocrystal composite particles.

PubMed

Wei, Zhong; Ujiiye-Ishii, Kento; Masuhara, Akito; Kasai, Hitoshi; Okada, Shuji; Matsune, Hideki; Asahi, Tsuyoshi; Masuhara, Hiroshi; Nakanishi, Hachiro

2005-06-01

Monodispersed polymer/polydiacetylenecomposite particles were synthesized by soap-free seeded emulsion polymerization of styrene andmethyl methacrylate; the products were characterized by XRD, SEM, TEM, UV-visible spectroscopy, and single particle scattering spectroscopy. In the synthesis process, polydiacetylene nanocrystals were found to act as inhibitor, and consequently a relatively low concentration was necessary. Different monomers lead to the differences in reaction condition and particle morphology; the PMMA composite particles were simpler in preparation than polystyrene particles, but the latter havebetter spherical morphology. The composite particles were composed of polymer shells and polydiacetylene cores, which kept their crystal structure and optical properties. A high percentage of cored particles could be achieved with optimized reaction conditions where the amount of seed was sufficient and the oily oligomer by-product was suppressed.

Results of a Neutronic Simulation of HTR-Proteus Core 4.2 using PEBBED and other INL Reactor Physics Tools: FY-09 Report

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

Hans D. Gougar

The Idaho National Laboratory’s deterministic neutronics analysis codes and methods were applied to the computation of the core multiplication factor of the HTR-Proteus pebble bed reactor critical facility. A combination of unit cell calculations (COMBINE-PEBDAN), 1-D discrete ordinates transport (SCAMP), and nodal diffusion calculations (PEBBED) were employed to yield keff and flux profiles. Preliminary results indicate that these tools, as currently configured and used, do not yield satisfactory estimates of keff. If control rods are not modeled, these methods can deliver much better agreement with experimental core eigenvalues which suggests that development efforts should focus on modeling control rod andmore » other absorber regions. Under some assumptions and in 1D subcore analyses, diffusion theory agrees well with transport. This suggests that developments in specific areas can produce a viable core simulation approach. Some corrections have been identified and can be further developed, specifically: treatment of the upper void region, treatment of inter-pebble streaming, and explicit (multiscale) transport modeling of TRISO fuel particles as a first step in cross section generation. Until corrections are made that yield better agreement with experiment, conclusions from core design and burnup analyses should be regarded as qualitative and not benchmark quality.« less

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

Pavlou, A. T.; Betzler, B. R.; Burke, T. P.

Uncertainties in the composition and fabrication of fuel compacts for the Fort St. Vrain (FSV) high temperature gas reactor have been studied by performing eigenvalue sensitivity studies that represent the key uncertainties for the FSV neutronic analysis. The uncertainties for the TRISO fuel kernels were addressed by developing a suite of models for an 'average' FSV fuel compact that models the fuel as (1) a mixture of two different TRISO fuel particles representing fissile and fertile kernels, (2) a mixture of four different TRISO fuel particles representing small and large fissile kernels and small and large fertile kernels and (3)more » a stochastic mixture of the four types of fuel particles where every kernel has its diameter sampled from a continuous probability density function. All of the discrete diameter and continuous diameter fuel models were constrained to have the same fuel loadings and packing fractions. For the non-stochastic discrete diameter cases, the MCNP compact model arranged the TRISO fuel particles on a hexagonal honeycomb lattice. This lattice-based fuel compact was compared to a stochastic compact where the locations (and kernel diameters for the continuous diameter cases) of the fuel particles were randomly sampled. Partial core configurations were modeled by stacking compacts into fuel columns containing graphite. The differences in eigenvalues between the lattice-based and stochastic models were small but the runtime of the lattice-based fuel model was roughly 20 times shorter than with the stochastic-based fuel model. (authors)« less

Core-shell structured SiO2@YVO4:Dy3+/Sm3+ phosphor particles: sol-gel preparation and characterization.

PubMed

Wang, H; Yu, M; Lin, C K; Lin, J

2006-08-01

Spherical SiO(2) particles have been coated with YVO(4):Dy(3+)/Sm(3+) phosphor layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO(2)@YVO(4):Dy(3+)/Sm(3+) particles. X-ray diffraction (XRD), Fourier-transform IR spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting SiO(2)@YVO(4):Dy(3+)/Sm(3+) core-shell phosphors. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 300 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (20 nm for one deposition cycle). The core-shell particles show strong characteristic emission from Dy(3+) for SiO(2)@YVO(4):Dy(3+) and from Sm(3+) for SiO(2)@YVO(4):Sm(3+) due to an efficient energy transfer from YVO(4) host to them. The PL intensity of Dy(3+) and Sm(3+) increases with raising the annealing temperature and the number of coating cycles.

JPRS Report, Science & Technology, China: Energy

DTIC Science & Technology

1988-06-29

capacity. There are currently two types of HTGR reactor designs: the particle-bed core , which uses spherical fuel elements, and the rod type core , in...and trial operating experience with the HTGR reactor. Its main design features are as follows. 1. A particle-bed core , continuous fueling and...Favorable for Development of Small-Scale HTGR (Xu Jiming; HE DONGLI GONGCHENG, Feb 88) 47 ERRATUM: In JPRS-CEN-88-003 of 25 April 1988 in article

Correlative cellular ptychography with functionalized nanoparticles at the Fe L-edge

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

Gallagher-Jones, Marcus; Dias, Carlos Sato Baraldi; Pryor, Alan

Precise localization of nanoparticles within a cell is crucial to the understanding of cell-particle interactions and has broad applications in nanomedicine. Here in this paper, we report a proof-of-principle experiment for imaging individual functionalized nanoparticles within a mammalian cell by correlative microscopy. Using a chemically-fixed HeLa cell labeled with fluorescent core-shell nanoparticles as a model system, we implemented a graphene-oxide layer as a substrate to significantly reduce background scattering. We identified cellular features of interest by fluorescence microscopy, followed by scanning transmission X-ray tomography to localize the particles in 3D, and ptychographic coherent diffractive imaging of the fine features inmore » the region at high resolution. By tuning the X-ray energy to the Fe L-edge, we demonstrated sensitive detection of nanoparticles composed of a 22 nm magnetic Fe 3O 4 core encased by a 25-nm-thick fluorescent silica (SiO 2) shell. These fluorescent core-shell nanoparticles act as landmarks and offer clarity in a cellular context. Our correlative microscopy results confirmed a subset of particles to be fully internalized, and high-contrast ptychographic images showed two oxidation states of individual nanoparticles with a resolution of ~16.5 nm. The ability to precisely localize individual fluorescent nanoparticles within mammalian cells will expand our understanding of the structure/function relationships for functionalized nanoparticles.« less

Correlative cellular ptychography with functionalized nanoparticles at the Fe L-edge

DOE PAGES

Gallagher-Jones, Marcus; Dias, Carlos Sato Baraldi; Pryor, Alan; ...

2017-07-06

Precise localization of nanoparticles within a cell is crucial to the understanding of cell-particle interactions and has broad applications in nanomedicine. Here in this paper, we report a proof-of-principle experiment for imaging individual functionalized nanoparticles within a mammalian cell by correlative microscopy. Using a chemically-fixed HeLa cell labeled with fluorescent core-shell nanoparticles as a model system, we implemented a graphene-oxide layer as a substrate to significantly reduce background scattering. We identified cellular features of interest by fluorescence microscopy, followed by scanning transmission X-ray tomography to localize the particles in 3D, and ptychographic coherent diffractive imaging of the fine features inmore » the region at high resolution. By tuning the X-ray energy to the Fe L-edge, we demonstrated sensitive detection of nanoparticles composed of a 22 nm magnetic Fe 3O 4 core encased by a 25-nm-thick fluorescent silica (SiO 2) shell. These fluorescent core-shell nanoparticles act as landmarks and offer clarity in a cellular context. Our correlative microscopy results confirmed a subset of particles to be fully internalized, and high-contrast ptychographic images showed two oxidation states of individual nanoparticles with a resolution of ~16.5 nm. The ability to precisely localize individual fluorescent nanoparticles within mammalian cells will expand our understanding of the structure/function relationships for functionalized nanoparticles.« less

GPU COMPUTING FOR PARTICLE TRACKING

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

Nishimura, Hiroshi; Song, Kai; Muriki, Krishna

2011-03-25

This is a feasibility study of using a modern Graphics Processing Unit (GPU) to parallelize the accelerator particle tracking code. To demonstrate the massive parallelization features provided by GPU computing, a simplified TracyGPU program is developed for dynamic aperture calculation. Performances, issues, and challenges from introducing GPU are also discussed. General purpose Computation on Graphics Processing Units (GPGPU) bring massive parallel computing capabilities to numerical calculation. However, the unique architecture of GPU requires a comprehensive understanding of the hardware and programming model to be able to well optimize existing applications. In the field of accelerator physics, the dynamic aperture calculationmore » of a storage ring, which is often the most time consuming part of the accelerator modeling and simulation, can benefit from GPU due to its embarrassingly parallel feature, which fits well with the GPU programming model. In this paper, we use the Tesla C2050 GPU which consists of 14 multi-processois (MP) with 32 cores on each MP, therefore a total of 448 cores, to host thousands ot threads dynamically. Thread is a logical execution unit of the program on GPU. In the GPU programming model, threads are grouped into a collection of blocks Within each block, multiple threads share the same code, and up to 48 KB of shared memory. Multiple thread blocks form a grid, which is executed as a GPU kernel. A simplified code that is a subset of Tracy++ [2] is developed to demonstrate the possibility of using GPU to speed up the dynamic aperture calculation by having each thread track a particle.« less

Tailored Core Shell Cathode Powders for Solid Oxide Fuel Cells

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

Swartz, Scott

2015-03-23

In this Phase I SBIR project, a “core-shell” composite cathode approach was evaluated for improving SOFC performance and reducing degradation of lanthanum strontium cobalt ferrite (LSCF) cathode materials, following previous successful demonstrations of infiltration approaches for achieving the same goals. The intent was to establish core-shell cathode powders that enabled high performance to be obtained with “drop-in” process capability for SOFC manufacturing (i.e., rather than adding an infiltration step to the SOFC manufacturing process). Milling, precipitation and hetero-coagulation methods were evaluated for making core-shell composite cathode powders comprised of coarse LSCF “core” particles and nanoscale “shell” particles of lanthanum strontiummore » manganite (LSM) or praseodymium strontium manganite (PSM). Precipitation and hetero-coagulation methods were successful for obtaining the targeted core-shell morphology, although perfect coverage of the LSCF core particles by the LSM and PSM particles was not obtained. Electrochemical characterization of core-shell cathode powders and conventional (baseline) cathode powders was performed via electrochemical impedance spectroscopy (EIS) half-cell measurements and single-cell SOFC testing. Reliable EIS testing methods were established, which enabled comparative area-specific resistance measurements to be obtained. A single-cell SOFC testing approach also was established that enabled cathode resistance to be separated from overall cell resistance, and for cathode degradation to be separated from overall cell degradation. The results of these EIS and SOFC tests conclusively determined that the core-shell cathode powders resulted in significant lowering of performance, compared to the baseline cathodes. Based on the results of this project, it was concluded that the core-shell cathode approach did not warrant further investigation.« less

Cusps in the center of galaxies: a real conflict with observations or a numerical artefact of cosmological simulations?

NASA Astrophysics Data System (ADS)

Baushev, A. N.; del Valle, L.; Campusano, L. E.; Escala, A.; Muñoz, R. R.; Palma, G. A.

2017-05-01

Galaxy observations and N-body cosmological simulations produce conflicting dark matter halo density profiles for galaxy central regions. While simulations suggest a cuspy and universal density profile (UDP) of this region, the majority of observations favor variable profiles with a core in the center. In this paper, we investigate the convergency of standard N-body simulations, especially in the cusp region, following the approach proposed by [1]. We simulate the well known Hernquist model using the SPH code Gadget-3 and consider the full array of dynamical parameters of the particles. We find that, although the cuspy profile is stable, all integrals of motion characterizing individual particles suffer strong unphysical variations along the whole halo, revealing an effective interaction between the test bodies. This result casts doubts on the reliability of the velocity distribution function obtained in the simulations. Moreover, we find unphysical Fokker-Planck streams of particles in the cusp region. The same streams should appear in cosmological N-body simulations, being strong enough to change the shape of the cusp or even to create it. Our analysis, based on the Hernquist model and the standard SPH code, strongly suggests that the UDPs generally found by the cosmological N-body simulations may be a consequence of numerical effects. A much better understanding of the N-body simulation convergency is necessary before a `core-cusp problem' can properly be used to question the validity of the CDM model.

Cusps in the center of galaxies: a real conflict with observations or a numerical artefact of cosmological simulations?

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

Baushev, A.N.; Valle, L. del; Campusano, L.E.

2017-05-01

Galaxy observations and N-body cosmological simulations produce conflicting dark matter halo density profiles for galaxy central regions. While simulations suggest a cuspy and universal density profile (UDP) of this region, the majority of observations favor variable profiles with a core in the center. In this paper, we investigate the convergency of standard N-body simulations, especially in the cusp region, following the approach proposed by [1]. We simulate the well known Hernquist model using the SPH code Gadget-3 and consider the full array of dynamical parameters of the particles. We find that, although the cuspy profile is stable, all integrals ofmore » motion characterizing individual particles suffer strong unphysical variations along the whole halo, revealing an effective interaction between the test bodies. This result casts doubts on the reliability of the velocity distribution function obtained in the simulations. Moreover, we find unphysical Fokker-Planck streams of particles in the cusp region. The same streams should appear in cosmological N-body simulations, being strong enough to change the shape of the cusp or even to create it. Our analysis, based on the Hernquist model and the standard SPH code, strongly suggests that the UDPs generally found by the cosmological N-body simulations may be a consequence of numerical effects. A much better understanding of the N-body simulation convergency is necessary before a 'core-cusp problem' can properly be used to question the validity of the CDM model.« less

Cluster-model calculations of exotic decays from heavy nuclei

NASA Astrophysics Data System (ADS)

Buck, B.; Merchant, A. C.

1989-05-01

A cluster model employing a local, effective cluster-core potential is used to investigate exotic decay from heavy nuclei as a quantum tunneling phenomenon within a semiclassical approximation. Excellent agreement with all reported experimental measurements of the decay widths for 14C and 24Ne emission is obtained. As an added bonus, the width for alpha particle emission from 212Po is also calculated in good agreement with experiment.

Energy Transport Effects in Flaring Atmospheres Heated by Mixed Particle Beams

NASA Astrophysics Data System (ADS)

Zharkova, Valentina; Zharkov, Sergei; Macrae, Connor; Druett, Malcolm; Scullion, Eamon

2016-07-01

We investigate energy and particle transport in the whole flaring atmosphere from the corona to the photosphere and interior for the flaring events on the 1st July 2012, 6 and 7 September 2011 by using the RHESSI and SDO instruments as well as high-resolution observations from the Swedish 1-metre Solar Telescope (SST3) CRISP4 (CRisp Imaging Spectro-polarimeter). The observations include hard and soft X-ray emission, chromospheric emission in both H-alpha 656.3 nm core and continuum, as well as, in the near infra-red triplet Ca II 854.2 nm core and continuum channels and local helioseismic responses (sunquakes). The observations are compared with the simulations of hard X-ray emission and tested by hydrodynamic simulations of flaring atmospheres of the Sun heated by mixed particle beams. The temperature, density and macro-velocity variations of the ambient atmospheres are calculated for heating by mixed beams and the seismic response of the solar interior to generation of supersonic shocks moving into the solar interior. We investigate the termination depths of these shocks beneath the quiet photosphere levels and compare them with the parameters of seismic responses in the interior, or sunquakes (Zharkova and Zharkov, 2015). We also present an investigation of radiative conditions modelled in a full non-LTE approach for hydrogen during flare onsets with particular focus on Balmer and Paschen emission in the visible, near UV and near IR ranges and compare them with observations. The links between different observational features derived from HXR, optical and seismic emission are interpreted by different particle transport models that will allow independent evaluation of the particle transport scenarios.

Viscous organic aerosol particles in the upper troposphere: diffusivity-controlled water uptake and ice nucleation?

DOE PAGES

Lienhard, D. M.; Huisman, A. J.; Krieger, U. K.; ...

2015-01-01

New measurements of water diffusion in secondary organic aerosol (SOA) material produced by oxidation of α-pinene and in a number of organic/inorganic model mixtures (3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA), levoglucosan, levoglucosan/NH 4HSO 4, raffinose) are presented. These indicate that water diffusion coefficients are determined by several properties of the aerosol substance and cannot be inferred from the glass transition temperature or bouncing properties. Our results suggest that water diffusion in SOA particles is faster than often assumed and imposes no significant kinetic limitation on water uptake and release at temperatures above 220 K. The fast diffusion of water suggests that heterogeneous icemore » nucleation on a glassy core is very unlikely in these systems. At temperatures below 220 K, model simulations of SOA particles suggest that heterogeneous ice nucleation may occur in the immersion mode on glassy cores which remain embedded in a liquid shell when experiencing fast updraft velocities. The particles absorb significant quantities of water during these updrafts which plasticize their outer layers such that these layers equilibrate readily with the gas phase humidity before the homogeneous ice nucleation threshold is reached. Glass formation is thus unlikely to restrict homogeneous ice nucleation. Only under most extreme conditions near the very high tropical tropopause may the homogeneous ice nucleation rate coefficient be reduced as a consequence of slow condensed-phase water diffusion. Since the differences between the behavior limited or non limited by diffusion are small even at the very high tropical tropopause, condensed-phase water diffusivity is unlikely to have significant consequences on the direct climatic effects of SOA particles under tropospheric conditions.« less

Development of a novel drug release system, time-controlled explosion system (TES). I. Concept and design.

PubMed

Ueda, S; Hata, T; Asakura, S; Yamaguchi, H; Kotani, M; Ueda, Y

1994-01-01

A novel controlled drug release system. Time-Controlled Explosion System (TES) has been developed. TES has a four-layered spherical structure, which consists of core, drug, swelling agent and water insoluble polymer membrane. TES is characterized by a rapid drug release with a precisely programmed lag time; i.e. expansion of the swelling agent by water penetrating through the outer membrane, destruction of the membrane by stress due to swelling force and subsequent rapid drug release. For establishing the concept and development strategy, TES was designed using metoprolol and polystyrene balls (size: 3.2 mm in diameter) as a model drug and core particles. Among the polymers screened, low-substituted hydroxypropylcellulose (L-HPC) and ethylcellulose (EC) were selected for a swelling agent and an outer water insoluble membrane, respectively. The release profiles of metoprolol from the system were not affected by the pH of the dissolution media. Lag time was controlled by the thickness of the outer EC membrane; thus, a combination of TES particles possessing different lag times could offer any desired release profile of the model compound, metoprolol.

Redistribution of fast ions during sawtooth reconnection

NASA Astrophysics Data System (ADS)

Jaulmes, F.; Westerhof, E.; de Blank, H. J.

2014-10-01

In a tokamak-based fusion power plant, possible scenarios may include regulated sawtooth oscillations to remove thermalized helium from the core of the plasma. During a sawtooth crash, the helium ash and other impurities trapped in the core are driven by the instability to an outer region. However, in a fusion plasma, high energy ions will represent a significant population. We thus study the behaviour of these energetic particles during a sawtooth. This paper presents the modelling of the redistribution of fast ions during a sawtooth reconnection event in a tokamak plasma. Along the lines of the model for the evolution of the flux surfaces during a sawtooth collapse described in Ya.I. Kolesnichenko and Yu.V. Yakovenko 1996 Nucl. Fusion 36 159, we have built a time-dependent electromagnetic model of a sawtooth reconnection. The trajectories of the ions are described by a complete gyro-orbit integration. The fast particles were evolved from specific initial parameters (given energy and uniform spread in pitch) or distributed initially according to a slowing-down distribution created by fusion reactions. Our modelling is used to understand the main equilibrium parameters driving the motions during the collapse and to determine the evolution of the distribution function of energetic ions when different geometries of reconnection are considered.

Capsule-Like Safe Genetic Vectors - Cell-Penetrating Core-Shell Particles Selectively Release Functional Small RNA and Entrap its Encoding DNA.

PubMed

Yu, Han; Pan, Houwen Matthew; Evalin, Fnu; Trau, Dieter Wilhelm; Patzel, Volker

2018-06-05

The breakthrough of genetic therapy is set back by the lack of suitable genetic vector systems. We present the development of permeability-tunable, capsule-like, polymeric, micron-sized, core-shell particles for delivery of recombinant nucleic acids into target cells. These particles were demonstrated to effectively release rod-shaped small hairpin RNA and to selectively retain the RNA-encoding DNA template which was designed to form a bulky tripartite structure. Thus, they can serve as delivery vectors preloaded with cargo RNA or alternatively as RNA producing micro-bioreactors. The internalization of particles by human tissue culture cells inversely correlated with particle size and with the cell to particle ratio, though at a higher than stoichiometric excess of particles over cells, cell viability was impaired. Among primary human peripheral blood mononuclear cells, up to 50% of the monocytes displayed positive uptake of particles. Finally, these particles efficiently delivered siRNA into HEK293T cells triggering functional knockdown of the target gene lamin A/C. Particle-mediated knockdown was superior to that observed after conventional siRNA delivery via lipofection. Core-shell particles protect encapsulated nucleic acids from degradation and target cell genomes from direct contact with recombinant DNA, thus representing a promising delivery vector system that can be explored for genetic therapy and vaccination.

Parallel Algorithms for Monte Carlo Particle Transport Simulation on Exascale Computing Architectures

NASA Astrophysics Data System (ADS)

Romano, Paul Kollath

Monte Carlo particle transport methods are being considered as a viable option for high-fidelity simulation of nuclear reactors. While Monte Carlo methods offer several potential advantages over deterministic methods, there are a number of algorithmic shortcomings that would prevent their immediate adoption for full-core analyses. In this thesis, algorithms are proposed both to ameliorate the degradation in parallel efficiency typically observed for large numbers of processors and to offer a means of decomposing large tally data that will be needed for reactor analysis. A nearest-neighbor fission bank algorithm was proposed and subsequently implemented in the OpenMC Monte Carlo code. A theoretical analysis of the communication pattern shows that the expected cost is O( N ) whereas traditional fission bank algorithms are O(N) at best. The algorithm was tested on two supercomputers, the Intrepid Blue Gene/P and the Titan Cray XK7, and demonstrated nearly linear parallel scaling up to 163,840 processor cores on a full-core benchmark problem. An algorithm for reducing network communication arising from tally reduction was analyzed and implemented in OpenMC. The proposed algorithm groups only particle histories on a single processor into batches for tally purposes---in doing so it prevents all network communication for tallies until the very end of the simulation. The algorithm was tested, again on a full-core benchmark, and shown to reduce network communication substantially. A model was developed to predict the impact of load imbalances on the performance of domain decomposed simulations. The analysis demonstrated that load imbalances in domain decomposed simulations arise from two distinct phenomena: non-uniform particle densities and non-uniform spatial leakage. The dominant performance penalty for domain decomposition was shown to come from these physical effects rather than insufficient network bandwidth or high latency. The model predictions were verified with measured data from simulations in OpenMC on a full-core benchmark problem. Finally, a novel algorithm for decomposing large tally data was proposed, analyzed, and implemented/tested in OpenMC. The algorithm relies on disjoint sets of compute processes and tally servers. The analysis showed that for a range of parameters relevant to LWR analysis, the tally server algorithm should perform with minimal overhead. Tests were performed on Intrepid and Titan and demonstrated that the algorithm did indeed perform well over a wide range of parameters. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs mit.edu)

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

Sherman, Andrew J

A heterogeneous body having ceramic rich cermet regions in a more ductile metal matrix. The heterogeneous bodies are formed by thermal spray operations on metal substrates. The thermal spray operations apply heat to a cermet powder and project it onto a solid substrate. The cermet powder is composed of complex composite particles in which a complex ceramic-metallic core particle is coated with a matrix precursor. The cermet regions are generally comprised of complex ceramic-metallic composites that correspond approximately to the core particles. The cermet regions are approximately lenticular shaped with an average width that is at least approximately twice themore » average thickness. The cermet regions are imbedded within the matrix phase and generally isolated from one another. They have obverse and reverse surfaces. The matrix phase is formed from the matrix precursor coating on the core particles. The amount of heat applied during the formation of the heterogeneous body is controlled so that the core particles soften but do not become so fluid that they disperse throughout the matrix phase. The force of the impact on the surface of the substrate tends to flatten them. The flattened cermet regions tend to be approximately aligned with one another in the body.« less

The sustained-release behavior and in vitro and in vivo transfection of pEGFP-loaded core-shell-structured chitosan-based composite particles

PubMed Central

Wang, Yun; Lin, Fu-xing; Zhao, Yu; Wang, Mo-zhen; Ge, Xue-wu; Gong, Zheng-xing; Bao, Dan-dan; Gu, Yu-fang

2014-01-01

Novel submicron core-shell-structured chitosan-based composite particles encapsulated with enhanced green fluorescent protein plasmids (pEGFP) were prepared by complex coacervation method. The core was pEGFP-loaded thiolated N-alkylated chitosan (TACS) and the shell was pH- and temperature-responsive hydroxybutyl chitosan (HBC). pEGFP-loaded TACS-HBC composite particles were spherical, and had a mean diameter of approximately 120 nm, as measured by transmission electron microscopy and particle size analyzer. pEGFP showed sustained release in vitro for >15 days. Furthermore, in vitro transfection in human embryonic kidney 293T and human cervix epithelial cells, and in vivo transfection in mice skeletal muscle of loaded pEGFP, were investigated. Results showed that the expression of loaded pEGFP, both in vitro and in vivo, was slow but could be sustained over a long period. pEGFP expression in mice skeletal muscle was sustained for >60 days. This work indicates that these submicron core-shell-structured chitosan-based composite particles could potentially be used as a gene vector for in vivo controlled gene transfection. PMID:25364253

The sustained-release behavior and in vitro and in vivo transfection of pEGFP-loaded core-shell-structured chitosan-based composite particles.

PubMed

Wang, Yun; Lin, Fu-xing; Zhao, Yu; Wang, Mo-zhen; Ge, Xue-wu; Gong, Zheng-xing; Bao, Dan-dan; Gu, Yu-fang

2014-01-01

Novel submicron core-shell-structured chitosan-based composite particles encapsulated with enhanced green fluorescent protein plasmids (pEGFP) were prepared by complex coacervation method. The core was pEGFP-loaded thiolated N-alkylated chitosan (TACS) and the shell was pH- and temperature-responsive hydroxybutyl chitosan (HBC). pEGFP-loaded TACS-HBC composite particles were spherical, and had a mean diameter of approximately 120 nm, as measured by transmission electron microscopy and particle size analyzer. pEGFP showed sustained release in vitro for >15 days. Furthermore, in vitro transfection in human embryonic kidney 293T and human cervix epithelial cells, and in vivo transfection in mice skeletal muscle of loaded pEGFP, were investigated. Results showed that the expression of loaded pEGFP, both in vitro and in vivo, was slow but could be sustained over a long period. pEGFP expression in mice skeletal muscle was sustained for >60 days. This work indicates that these submicron core-shell-structured chitosan-based composite particles could potentially be used as a gene vector for in vivo controlled gene transfection.

Influence of arc current and pressure on non-chemical equilibrium air arc behavior

NASA Astrophysics Data System (ADS)

Yi, WU; Yufei, CUI; Jiawei, DUAN; Hao, SUN; Chunlin, WANG; Chunping, NIU

2018-01-01

The influence of arc current and pressure on the non-chemical equilibrium (non-CE) air arc behavior of a nozzle structure was investigated based on the self-consistent non-chemical equilibrium model. The arc behavior during both the arc burning and arc decay phases were discussed at different currents and different pressures. We also devised the concept of a non-equilibrium parameter for a better understanding of non-CE effects. During the arc burning phase, the increasing current leads to a decrease of the non-equilibrium parameter of the particles in the arc core, while the increasing pressure leads to an increase of the non-equilibrium parameter of the particles in the arc core. During the arc decay phase, the non-CE effect will decrease by increasing the arc burning current and the nozzle pressure. Three factors together—convection, diffusion and chemical reactions—influence non-CE behavior.

Planetesimal and Protoplanet Dynamics in a Turbulent Protoplanetary Disk

NASA Astrophysics Data System (ADS)

Yang, Chao-Chin; Mac Low, M.; Menou, K.

2010-01-01

In core accretion scenario of planet formation, kilometer-sized planetesimals are the building blocks toward planetary cores. Their dynamics, however, are strongly influenced by their natal protoplanetary gas disks. It is generally believed that these disks are turbulent, most likely due to magnetorotational instability. The resulting density perturbations in the gas render the movement of the particles a random process. Depending on its strength, this process might cause several interesting consequences in the course of planet formation, specifically the survivability of objects under rapid inward type-I migration and/or collisional destruction. Using the local-shearing-box approximation, we conduct numerical simulations of planetesimals moving in a turbulent, magnetized gas disk, either unstratified or vertically stratified. We produce a fiducial disk model with turbulent accretion of Shakura-Sunyaev alpha about 10-2 and root-mean-square density perturbation of about 10% and statistically characterize the evolution of the orbital properties of the particles moving in the disk. These measurements result in accurate calibration of the random process of particle orbital change, indicating noticeably smaller magnitudes than predicted by global simulations, although the results may depend on the size of the shearing box. We apply these results to revisit the survivability of planetesimals under collisional destruction or protoplanets under type-I migration. Planetesimals are probably secure from collisional destruction, except for kilometer-sized objects situated in the outer regions of a young protoplanetary disk. On the other hand, we confirm earlier studies of local models in that type-I migration probably dominates diffusive migration due to stochastic torques for most planetary cores and terrestrial planets. Discrepancies in the derived magnitude of turbulence between local and global simulations of magnetorotationally unstable disks remains an open issue, with important consequences for planet formation scenarios.

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

Stampfl, Sibylle; Stampfl, Ulrike; Bellemann, Nadine

The objective of this study was to evaluate inflammatory response and recanalization after embolization with a new spherical embolic agent based on a core and shell design with a hydrogel core of polymethylmethacrylate (PMMA) and a Polyzene-F nanoscale coating in a porcine kidney model. Thirty-six minipigs were enrolled for superselective renal embolization. Polyzene-F-coated PMMA particles and uncoated PMMA particles with a diameter of 300-600 {mu}m were used. Either 4 or 12 weeks post-embolization, arteriography of the embolized kidneys was performed and then compared with pre- and immediate post-embolization arteriograms using a specific recanalization score to determine the extent of recanalization.more » Using a microscopic inflammation score (Banff classification), the embolized organs were examined for local inflammatory effects which occurred in response to the embolic agent. In Polyzene-F-coated particles, the Banff classification showed an average inflammation score of 0.26 {+-} 0.58 at 4 weeks and of 0.08 {+-} 0.28 at 12 weeks. In uncoated particles, the Banff score measured 0.37 {+-} 0.6 at 4 weeks, which was higher, but without a statistically significant difference. According to the recanalization score used in this study, mild angiographic recanalization was evident in all groups, without statistically significant differences (3.0 {+-} 0.71 in coated particles, 3.09 {+-} 0.81 in uncoated particles; p = 0.74). We conclude that both uncoated hydrogel particles and Polyzene-F-coated embolic agents triggered virtually no inflammatory response and effectively occluded target arteries. This study demonstrates good biocompatibility of the new embolic material. As in other spherical embolic agents, recanalization can occur to some degree.« less

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

Charnawskas, Joseph C.; Alpert, Peter A.; Lambe, Andrew

Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil-fuel combustion can acquire a coating of SOA. We investigate SOA-soot biogenic-anthropogenic interactions and their impact on ice nucleation in relation to the particles’ organic phase state. SOA particles were generated from the OH oxidation of naphthalene, α-pinene, longifolene, or isoprene, with or without presence of sulfate or soot particles. Corresponding particle glass transition (T g) and full deliquescence relative humidity (FDRH) were estimated by a numerical diffusion model. Longifolene SOA particles are solid-like and all biogenic SOA sulfate mixtures exhibitmore » a core-shell configuration (i.e. a sulfate-rich core coated with SOA). Biogenic SOA with or without sulfate formed ice at conditions expected for homogeneous ice nucleation in agreement with respective T g and FDRH. α-pinene SOA coated soot particles nucleated ice above the homogeneous freezing temperature with soot acting as ice nuclei (IN). At lower temperatures the α-pinene SOA coating can be semisolid inducing ice nucleation. Naphthalene SOA coated soot particles acted as IN above and below the homogeneous freezing limit, which can be explained by the presence of a highly viscous SOA phase. Our results suggest that biogenic SOA does not play a significant role in mixed-phase cloud formation and the presence of sulfate further renders this even less likely. Furthermore, anthropogenic SOA may have an enhancing effect on cloud glaciation under mixed-phase and cirrus cloud conditions compared to biogenic SOA that dominate during preindustrial times or in pristine areas.« less

Condensed-phase biogenic-anthropogenic interactions with implications for cold cloud formation

DOE PAGES

Charnawskas, Joseph C.; Alpert, Peter A.; Lambe, Andrew; ...

2017-01-24

Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil-fuel combustion can acquire a coating of SOA. We investigate SOA-soot biogenic-anthropogenic interactions and their impact on ice nucleation in relation to the particles’ organic phase state. SOA particles were generated from the OH oxidation of naphthalene, α-pinene, longifolene, or isoprene, with or without presence of sulfate or soot particles. Corresponding particle glass transition (T g) and full deliquescence relative humidity (FDRH) were estimated by a numerical diffusion model. Longifolene SOA particles are solid-like and all biogenic SOA sulfate mixtures exhibitmore » a core-shell configuration (i.e. a sulfate-rich core coated with SOA). Biogenic SOA with or without sulfate formed ice at conditions expected for homogeneous ice nucleation in agreement with respective T g and FDRH. α-pinene SOA coated soot particles nucleated ice above the homogeneous freezing temperature with soot acting as ice nuclei (IN). At lower temperatures the α-pinene SOA coating can be semisolid inducing ice nucleation. Naphthalene SOA coated soot particles acted as IN above and below the homogeneous freezing limit, which can be explained by the presence of a highly viscous SOA phase. Our results suggest that biogenic SOA does not play a significant role in mixed-phase cloud formation and the presence of sulfate further renders this even less likely. Furthermore, anthropogenic SOA may have an enhancing effect on cloud glaciation under mixed-phase and cirrus cloud conditions compared to biogenic SOA that dominate during preindustrial times or in pristine areas.« less

Influence of extrusion rate and magma rheology on the growth of lava domes: Insights from particle-dynamics modeling

NASA Astrophysics Data System (ADS)

Husain, Taha; Elsworth, Derek; Voight, Barry; Mattioli, Glen; Jansma, Pamela

2014-09-01

Lava domes are structures that grow by the extrusion of viscous silicic or intermediate composition magma from a central volcanic conduit. Repeated cycles of growth are punctuated by collapse, as the structure becomes oversized for the strength of the composite magma that rheologically stiffens and strengthens at its surface. Here we explore lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional carapace that caps a ductile magma core. Extrusion rate and magma rheology together with crystallization temperature and volatile content govern the distribution of strength in the composite structure. This new model is calibrated against existing observational models of lava dome growth. Results show that the shape and extent of the ductile core and the overall structure of the lava dome are strongly controlled by the infusion rate. The effects of extrusion rate on magma rheology are sensitive to material stiffness, which in turn is a function of volatile content and crystallinity. Material stiffness and material strength are key model parameters which govern magma rheology and subsequently the morphological character of the lava dome and in turn stability. Degassing induced crystallization causes material stiffening and enhances material strength reflected in non-Newtonian magma behavior. The increase in stiffness and strength of the injected magma causes a transition in the style of dome growth, from endogenous expansion of a ductile core, to stiffer and stronger intruding material capable of punching through the overlying material and resulting in the development of a spine or possibly inducing dome collapse. Simulation results mimic development of a megaspine upon the influx of fresh magma which leads to the re-direction of magma flow, creating a new shear zone and the switching of dome growth from one side to the other. Our model shows similar dome growth dynamics as observed at Soufriere Hills Volcano, Montserrat, indicating a strong correlation between extrusion rate and its subsequent effect on mechanical properties and variations in magma rheology.

The attachment of α -synuclein to a fiber: A coarse-grain approach

NASA Astrophysics Data System (ADS)

Ilie, Ioana M.; den Otter, Wouter K.; Briels, Wim J.

2017-03-01

We present simulations of the amyloidogenic core of α-synuclein, the protein causing Parkinson's disease, as a short chain of coarse-grain patchy particles. Each particle represents a sequence of about a dozen amino acids. The fluctuating secondary structure of this intrinsically disordered protein is modelled by dynamic variations of the shape and interaction characteristics of the patchy particles, ranging from spherical with weak isotropic attractions for the disordered state to spherocylindrical with strong directional interactions for a β-sheet. Flexible linkers between the particles enable sampling of the tertiary structure. This novel model is applied here to study the growth of an amyloid fibril, by calculating the free energy profile of a protein attaching to the end of a fibril. The simulation results suggest that the attaching protein readily becomes trapped in a mis-folded state, thereby inhibiting further growth of the fibril until the protein has readjusted to conform to the fibril structure, in line with experimental findings and previous simulations on small fragments of other proteins.

Structure of 29F in the rotation-aligned coupling scheme of the particle-rotor model

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

Macchiavelli, A. O.; Crawford, H. L.; Fallon, P.

Recent results from RIKEN/RIBF on the low-lying level structure of 29F are interpreted within the Particle-Rotor Model. We show that the experimental data can be understood in the Rotation-aligned Coupling Scheme, with the 5/2 + ground state as the bandhead of a decoupled band. In this picture, the energy of the observed 1/2more » $$+\\atop{1}$$ state correlates strongly with the rotational energy of the core and provides an estimate of the 2 + energy in 28O. Our analysis suggests a moderate deformation, ϵ 2 ~ 0.16, and places the 2 + in 28O at ~ 2.5 MeV.« less

Structure of 29F in the rotation-aligned coupling scheme of the particle-rotor model

DOE PAGES

Macchiavelli, A. O.; Crawford, H. L.; Fallon, P.; ...

2017-10-23

Recent results from RIKEN/RIBF on the low-lying level structure of 29F are interpreted within the Particle-Rotor Model. We show that the experimental data can be understood in the Rotation-aligned Coupling Scheme, with the 5/2 + ground state as the bandhead of a decoupled band. In this picture, the energy of the observed 1/2more » $$+\\atop{1}$$ state correlates strongly with the rotational energy of the core and provides an estimate of the 2 + energy in 28O. Our analysis suggests a moderate deformation, ϵ 2 ~ 0.16, and places the 2 + in 28O at ~ 2.5 MeV.« less

Effects of nuclear structure in the spin-dependent scattering of weakly interacting massive particles

NASA Astrophysics Data System (ADS)

Nikolaev, M. A.; Klapdor-Kleingrothaus, H. V.

1993-06-01

We present calculations of the nuclear from factors for spin-dependent elastic scattering of dark matter WIMPs from123Te and131Xe isotopes, proposed to be used for dark matter detection. A method based on the theory of finite Fermi systems was used to describe the reduction of the single-particle spin-dependent matrix elements in the nuclear medium. Nucleon single-particle states were calculated in a realistic shell model potential; pairing effects were treated within the BCS model. The coupling of the lowest single-particle levels in123Te to collective 2+ excitations of the core was taken into account phenomenologically. The calculated nuclear form factors are considerably less then the single-particle ones for low momentum transfer. At high momentum transfer some dynamical amplification takes place due to the pion exchange term in the effective nuclear interaction. But as the momentum transfer increases, the difference disappears, the momentum transfer increases and the quenching effect disappears. The shape of the nuclear form factor for the131Xe isotope differs from the one obtained using an oscillator basis.

A model of energetic ion effects on pressure driven tearing modes in tokamaks

DOE PAGES

Halfmoon, M. R.; Brennan, D. P.

2017-06-05

Here, the effects that energetic trapped ions have on linear resistive magnetohydrodynamic (MHD) instabilities are studied in a reduced model that captures the essential physics driving or damping the modes through variations in the magnetic shear. The drift-kinetic orbital interaction of a slowing down distribution of trapped energetic ions with a resistive MHD instability is integrated to a scalar contribution to the perturbed pressure, and entered into an asymptotic matching formalism for the resistive MHD dispersion relation. Toroidal magnetic field line curvature is included to model trapping in the particle distribution, in an otherwise cylindrical model. The focus is onmore » a configuration that is driven unstable to the m/n = 2/1 mode by increasing pressure, where m is the poloidal mode number and n is the toroidal. The particles and pressure can affect the mode both in the core region where there can be low and reversed shear and outside the resonant surface in significant positive shear. The results show that the energetic ions damp and stabilize the mode when orbiting in significant positive shear, increasing the marginal stability boundary. However, the inner core region contribution with low and reversed shear can drive the mode unstable. This effect of shear on the energetic ion pressure contribution is found to be consistent with the literature. These results explain the observation that the 2/1 mode was found to be damped and stabilized by energetic ions in delta δf-MHD simulations of tokamak experiments with positive shear throughout, while the 2/1 mode was found to be driven unstable in simulations of experiments with weakly reversed shear in the core. This is also found to be consistent with related experimental observations of the stability of the 2/1 mode changing significantly with core shear.« less

A model of energetic ion effects on pressure driven tearing modes in tokamaks

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

Halfmoon, M. R.; Brennan, D. P.

Here, the effects that energetic trapped ions have on linear resistive magnetohydrodynamic (MHD) instabilities are studied in a reduced model that captures the essential physics driving or damping the modes through variations in the magnetic shear. The drift-kinetic orbital interaction of a slowing down distribution of trapped energetic ions with a resistive MHD instability is integrated to a scalar contribution to the perturbed pressure, and entered into an asymptotic matching formalism for the resistive MHD dispersion relation. Toroidal magnetic field line curvature is included to model trapping in the particle distribution, in an otherwise cylindrical model. The focus is onmore » a configuration that is driven unstable to the m/n = 2/1 mode by increasing pressure, where m is the poloidal mode number and n is the toroidal. The particles and pressure can affect the mode both in the core region where there can be low and reversed shear and outside the resonant surface in significant positive shear. The results show that the energetic ions damp and stabilize the mode when orbiting in significant positive shear, increasing the marginal stability boundary. However, the inner core region contribution with low and reversed shear can drive the mode unstable. This effect of shear on the energetic ion pressure contribution is found to be consistent with the literature. These results explain the observation that the 2/1 mode was found to be damped and stabilized by energetic ions in delta δf-MHD simulations of tokamak experiments with positive shear throughout, while the 2/1 mode was found to be driven unstable in simulations of experiments with weakly reversed shear in the core. This is also found to be consistent with related experimental observations of the stability of the 2/1 mode changing significantly with core shear.« less

Fluorescence-based remote irradiation sensor in liquid-filled hollow-core photonic crystal fiber

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

Zeltner, R.; Russell, P. St.J.; Department of Physics, University of Erlangen-Nuremberg, Guenther-Scharowsky-Str. 1, 91058 Erlangen

2016-06-06

We report an irradiation sensor based on a fluorescent “flying particle” that is optically trapped and propelled inside the core of a water-filled hollow-core photonic crystal fiber. When the moving particle passes through an irradiated region, its emitted fluorescence is captured by guided modes of the fiber core and so can be monitored using a filtered photodiode placed at the fiber end. The particle speed and position can be precisely monitored using in-fiber Doppler velocimetry, allowing the irradiation profile to be measured to a spatial resolution of ∼10 μm. The spectral response can be readily adjusted by appropriate choice of particlemore » material. Using dye-doped polystyrene particles, we demonstrate detection of green (532 nm) and ultraviolet (340 nm) light.« less

Nanocrystalline p-hydroxyacetanilide (paracetamol) and gold core-shell structure as a model drug deliverable organic-inorganic hybrid nanostructure

NASA Astrophysics Data System (ADS)

Das, Subhojit; Paul, Anumita; Chattopadhyay, Arun

2013-09-01

We report on the generation of core-shell nanoparticles (NPs) having an organic nanocrystal (NC) core coated with an inorganic metallic shell, being dispersed in aqueous medium. First, NCs of p-hydroxyacetanilide (pHA)--known also as paracetamol--were generated in an aqueous medium. Transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) evidenced the formation of pHA NCs and of their crystalline nature. The NCs were then coated with Au to form pHA@Au core-shell NPs, where the thickness of the Au shell was on the order of nanometers. The formation of Au nanoshell--surrounding pHA NC--was confirmed from its surface plasmon resonance (SPR) band in the UV/Vis spectrum and by TEM measurements. Further, on treatment of the core-shell particles with a solution comprising NaCl and HCl (pH < 3), the Au shell could be dissolved, subsequently releasing pHA molecules. The dissolution of Au shell was marked by a gradual diminishing of its SPR band, while the release of pHA molecules in the solution was confirmed from TEM and FTIR studies. The findings suggest that the core-shell NP could be hypothesized to be a model for encapsulating drug molecules, in their crystalline forms, for slow as well as targeted release.We report on the generation of core-shell nanoparticles (NPs) having an organic nanocrystal (NC) core coated with an inorganic metallic shell, being dispersed in aqueous medium. First, NCs of p-hydroxyacetanilide (pHA)--known also as paracetamol--were generated in an aqueous medium. Transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) evidenced the formation of pHA NCs and of their crystalline nature. The NCs were then coated with Au to form pHA@Au core-shell NPs, where the thickness of the Au shell was on the order of nanometers. The formation of Au nanoshell--surrounding pHA NC--was confirmed from its surface plasmon resonance (SPR) band in the UV/Vis spectrum and by TEM measurements. Further, on treatment of the core-shell particles with a solution comprising NaCl and HCl (pH < 3), the Au shell could be dissolved, subsequently releasing pHA molecules. The dissolution of Au shell was marked by a gradual diminishing of its SPR band, while the release of pHA molecules in the solution was confirmed from TEM and FTIR studies. The findings suggest that the core-shell NP could be hypothesized to be a model for encapsulating drug molecules, in their crystalline forms, for slow as well as targeted release. Electronic supplementary information (ESI) available: See DOI: 10.1039/c3nr03566b

Morphology and Optical Properties of Mixed Aerosol Particles

NASA Astrophysics Data System (ADS)

Fard, Mehrnoush M.; Krieger, Ulrich; Rudich, Yinon; Marcolli, Claudia; Peter, Thomas

2016-04-01

Experiments and modeling studies have shown that deliquesced aerosols can exist not only as one-phase system containing organics, inorganic salts and water, but often as two-phase systems consisting of a predominantly organic and a predominantly inorganic aqueous phase (1,2). Recent laboratory studies conducted with model mixtures representing tropospheric aerosols (1,2,3), secondary organic aerosol (SOA) from smog chamber experiments (4), and field measurements (5) suggest that liquid-liquid phase separations (LLPS) is indeed a common phenomenon in mixed organic/ inorganic particles. During LLPS, particles may adopt different morphologies mainly core-shell and partially engulfed. A core-shell configuration will have consequences for heterogeneous chemistry and hygroscopicity and as a result will alter the optical properties of the particles in particular for organic phases containing absorbing molecules, e.g. brown carbon. The primary objective of this project is to establish a method for investigating the morphology of mixed inorganic and absorbing organic compounds of atmospheric relevance and study their radiative properties before, during, and after phase transitions mainly during LLPS. This will be the first study looking into the radiative effect of LLPS in detail. Our ternary model system consist of ammonium sulfate (AS)/ Polyethylene Glycol (PEG)/ and water (H2O). Carminic acid (CA) was added as a proxy for an absorbing organic compound to the system. The behavior of single droplets of above ternary mixture was monitored during relative humidity (RH) cycles using optical microscopy. The same ternary mixture particle was levitated in an electrodynamic balance (EDB) and the change in its absorption properties was measured at varying RH. In addition, Mie-code modeling is used to predict the absorption efficiency of the same ternary system and the result will be compared with the data obtained from EDB experiment. We also intend to determine the occurrence of LLPS in accumulation-sized particles and the change in their absorption using a cavity ring down aerosol spectrometer. If LLPS alters the absorptive properties of the suggested model aerosols significantly, absorption measurements of accumulation mode particles of the same composition would allow proving that LLPS indeed occurs in particles of accumulation mode size. Up to now LLPS has not been studied for particles in this size range. References: 1. Bertram, et al. Atmos. Chem & Phys, 11(21), 10995-11006, 2011.
 2. Krieger, et al. Chemical Society Reviews, 41(19), 6631-6662, 2012 
3. Song, M. et al. Geophys Res Lett, 39(19), 2012b 4. Smith et al. Atmos Chem & Phys, 12(20), 9613- 9628, 2012.
 5. You, Y. et al. Proceedings of the National Academy of Sciences, 109(33), 13188-13193, 2012.

Diffusion of multiple species with excluded-volume effects.

PubMed

Bruna, Maria; Chapman, S Jonathan

2012-11-28

Stochastic models of diffusion with excluded-volume effects are used to model many biological and physical systems at a discrete level. The average properties of the population may be described by a continuum model based on partial differential equations. In this paper we consider multiple interacting subpopulations/species and study how the inter-species competition emerges at the population level. Each individual is described as a finite-size hard core interacting particle undergoing brownian motion. The link between the discrete stochastic equations of motion and the continuum model is considered systematically using the method of matched asymptotic expansions. The system for two species leads to a nonlinear cross-diffusion system for each subpopulation, which captures the enhancement of the effective diffusion rate due to excluded-volume interactions between particles of the same species, and the diminishment due to particles of the other species. This model can explain two alternative notions of the diffusion coefficient that are often confounded, namely collective diffusion and self-diffusion. Simulations of the discrete system show good agreement with the analytic results.

Modeling Dust in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Zonca, Alberto; Casu, Silvia; Mulas, Giacomo; Aresu, Giambattista; Cecchi-Pestellini, Cesare

2015-09-01

We model the extinction profiles observed in the Small and Large Magellanic clouds with a synthetic population of dust grains consisting of core-mantle particles and a collection of free-flying polycyclic aromatic hydrocarbons (PAHs). All different flavors of the extinction curves observed in the Magellanic Clouds (MCs) can be described by the present model, which has been previously (successfully) applied to a large sample of diffuse and translucent lines of sight in the Milky Way. We find that in the MCs the extinction produced by classical grains is generally larger than absorption by PAHs. Within this model, the nonlinear far-UV rise is accounted for by PAHs, whose presence in turn is always associated with a gap in the size distribution of classical particles. This hints either at a physical connection between (e.g., a common cause for) PAHs and the absence of middle-sized dust particles or the need for an additional component in the model that can account for the nonlinear far-UV rise without contributing to the UV bump at ∼217 nm such as, e.g., nanodiamonds.

Effect of fuel injection pressure on a heavy-duty diesel engine nonvolatile particle emission.

PubMed

Lähde, Tero; Rönkkö, Topi; Happonen, Matti; Söderström, Christer; Virtanen, Annele; Solla, Anu; Kytö, Matti; Rothe, Dieter; Keskinen, Jorma

2011-03-15

The effects of the fuel injection pressure on a heavy-duty diesel engine exhaust particle emissions were studied. Nonvolatile particle size distributions and gaseous emissions were measured at steady-state engine conditions while the fuel injection pressure was changed. An increase in the injection pressure resulted in an increase in the nonvolatile nucleation mode (core) emission at medium and at high loads. At low loads, the core was not detected. Simultaneously, a decrease in soot mode number concentration and size and an increase in the soot mode distribution width were detected at all loads. Interestingly, the emission of the core was independent of the soot mode concentration at load conditions below 50%. Depending on engine load conditions, growth of the geometric mean diameter of the core mode was also detected with increasing injection pressure. The core mode emission and also the size of the mode increased with increasing NOx emission while the soot mode size and emission decreased simultaneously.

Morphology and Optical Properties of Mixed Aerosol Particles

NASA Astrophysics Data System (ADS)

Fard, Mehrnoush M.; Krieger, Ulrich; Rudich, Yinon; Marcolli, Claudia; Peter, Thomas

2015-04-01

Experiments and modeling studies have shown that deliquesced aerosols can be present not only as one-phase system containing organics, inorganic salts and water, but often as two-phase systems consisting of a predominantly organic and a predominantly inorganic aqueous phase 1,2. Recent laboratory studies conducted with model mixtures representing tropospheric aerosols1,2,3, secondary organic aerosol (SOA) from smog chamber experiments4, and field measurements5 suggest that liquid- liquid phase separations (LLPS) is indeed a common phenomenon in mixed organic/ ammonium sulfate (AS) particles. During LLPS, particles may adopt different morphologies mainly core- shell and partially engulfed. A core- shell configuration will have consequences for heterogeneous chemistry and hygroscopicity and as a result will alter the optical properties of the particles since the aqueous inorganic-rich phase will be totally enclosed by a probably highly viscous organic coating with low diffusivity for reactants and water. The primary objective of this project is to establish a method for investigating the morphology of mixed inorganic and absorbing organic compounds of atmospheric relevance and study their radiative properties before, during, and after phase transitions mainly during LLPS. This will be the first study looking into the radiative effect of LLPS in detail. In this first experiment, the behavior of single droplets of carminic acid (CA)/ AS/ H2O mixture was monitored during relative humidity (RH) cycles using optical microscopy. The same mixture particle was levitated in an electrodynamic balance (EDB) and the change in its absorption properties was measured at varying RH. We also intend to determine the occurrence of LLPS in accumulation- sized particles and the change in their absorption using a cavity ring down aerosol spectrometer. If LLPS alters the absorptive properties of the suggested model aerosols significantly, absorption measurements of accumulation mode particles of the same composition would allow proving that LLPS indeed occurs in particles of atmospheric relevant size ranges. Up to now this prove is missing. References: 1. Bertram, et al. Atmos. Chem & Phys, 11(21), 10995-11006, 2011. 2. Krieger, et al. Chemical Society Reviews, 41(19), 6631-6662, 2012 3. Song, M. et al. Geophys Res Lett, 39(19), 2012b 4. Smith et al. Atmos Chem & Phys, 12(20), 9613- 9628, 2012. 5. You, Y. et al. Proceedings of the National Academy of Sciences, 109(33), 13188-13193, 2012.

Effects of tablet formulation and subsequent film coating on the supersaturated dissolution behavior of amorphous solid dispersions.

PubMed

Sakai, Toshiro; Hirai, Daiki; Kimura, Shin-Ichiro; Iwao, Yasunori; Itai, Shigeru

2018-04-05

The effects of tablet preparation and subsequent film coating with amorphous solid dispersion (ASD) particles that were composed of a drug with poor water solubility and hydrophilic polymers were investigated. ASD particles were prepared with a drug and vinylpyrrolidone-vinyl acetate copolymer (PVPVA) or polyvinylpyrrolidone (PVP) at a weight ratio of 1:1 or 1:2 using a melt extrusion technique. Tablets were prepared by conventional direct compression followed by pan coating. A mathematical model based on the Noyes-Whitney equation assuming that stable crystals precipitated at the changeable surface area of the solid-liquid interface used to estimate drug dissolution kinetics in a non-sink dissolution condition. All the ASD particles showed a maximum dissolution concentration approximately ten times higher than that of the crystalline drug. The ASD particles with PVPVA showed higher precipitation rate with lower polymer ratio, while PVP did not precipitate within 960 min regardless of the polymer ratio, suggesting the ASD particles of 1:1 drug:PVPVA (ASD-1) were the most unstable among the ASD particles considered. The dissolution of a core tablet with ASD-1 showed less supersaturation and a much higher precipitation rate than those of ASD-1 particles. However, a film-coated tablet or core tablet with a trace amount of hydroxypropylmethylcellulose (HPMC) showed a similar dissolution profile to that of the ASD-1 particles, indicating HPMC had a remarkable precipitation inhibition effect. Overall, these results suggest that tablet preparation with ASD may adversely affect the maintenance of supersaturation; however, this effect can be mitigated by adding an appropriate precipitation inhibitor to the formulation. Copyright © 2018 Elsevier B.V. All rights reserved.

A novel dressing for the combined delivery of platelet lysate and vancomycin hydrochloride to chronic skin ulcers: Hyaluronic acid particles in alginate matrices.

PubMed

Rossi, S; Mori, M; Vigani, B; Bonferoni, M C; Sandri, G; Riva, F; Caramella, C; Ferrari, F

2018-06-15

The aim of the present work was to develop a medication allowing for the combined delivery of platelet lysate (PL) and an anti-infective model drug, vancomycin hydrochloride (VCM), to chronic skin ulcers. A simple method was set up for the preparation of hyaluronic acid (HA) core-shell particles, loaded with PL and coated with calcium alginate, embedded in a VCM containing alginate matrix. Two different CaCl 2 concentrations were investigated to allow for HA/PL core-shell particle formation. The resulting dressings were characterized for mechanical and hydration properties and tested in vitro (on fibroblasts) and ex-vivo (on skin biopsies) for biological activity. They were found of sufficient mechanical strength to withstand packaging and handling stress and able to absorb a high amount of wound exudate and to form a protective gel on the lesion area. The CaCl 2 concentration used for shell formation did not affect VCM release from the alginate matrix, but strongly modified the release of PGFAB (chosen as representative of growth factors present in PL) from HA particles. In vitro and ex vivo tests provided sufficient proof of concept of the ability of dressings to improve skin ulcers healing. Copyright © 2018 Elsevier B.V. All rights reserved.

Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2.

PubMed

Aaboud, M; Aad, G; Abbott, B; Abdallah, J; Abdinov, O; Abeloos, B; Abidi, S H; AbouZeid, O S; Abraham, N L; Abramowicz, H; Abreu, H; Abreu, R; Abulaiti, Y; Acharya, B S; Adachi, S; Adamczyk, L; Adelman, J; Adersberger, M; Adye, T; Affolder, A A; Agatonovic-Jovin, T; Agheorghiesei, C; Aguilar-Saavedra, J A; Ahlen, S P; Ahmadov, F; Aielli, G; Akatsuka, S; Akerstedt, H; Åkesson, T P A; Akimov, A V; Alberghi, G L; Albert, J; Albicocco, P; Alconada Verzini, M J; Aleksa, M; Aleksandrov, I N; Alexa, C; Alexander, G; Alexopoulos, T; Alhroob, M; Ali, B; Aliev, M; Alimonti, G; Alison, J; Alkire, S P; Allbrooke, B M M; Allen, B W; Allport, P P; Aloisio, A; Alonso, A; Alonso, F; Alpigiani, C; Alshehri, A A; Alstaty, M; Alvarez Gonzalez, B; Álvarez Piqueras, D; Alviggi, M G; Amadio, B T; Amaral Coutinho, Y; Amelung, C; Amidei, D; Santos, S P Amor Dos; Amorim, A; Amoroso, S; Amundsen, G; Anastopoulos, C; Ancu, L S; Andari, N; Andeen, T; Anders, C F; Anders, J K; Anderson, K J; Andreazza, A; Andrei, V; Angelidakis, S; Angelozzi, I; Angerami, A; Anisenkov, A V; Anjos, N; Annovi, A; Antel, C; Antonelli, M; Antonov, A; Antrim, D J; Anulli, F; Aoki, M; Aperio Bella, L; Arabidze, G; Arai, Y; Araque, J P; Araujo Ferraz, V; Arce, A T H; Ardell, R E; Arduh, F A; Arguin, J-F; Argyropoulos, S; Arik, M; Armbruster, A J; Armitage, L J; Arnaez, O; Arnold, H; Arratia, M; Arslan, O; Artamonov, A; Artoni, G; Artz, S; Asai, S; Asbah, N; Ashkenazi, A; Asquith, L; Assamagan, K; Astalos, R; Atkinson, M; Atlay, N B; Augsten, K; Avolio, G; Axen, B; Ayoub, M K; Azuelos, G; Baas, A E; Baca, M J; Bachacou, H; Bachas, K; Backes, M; Backhaus, M; Bagnaia, P; Bahrasemani, H; Baines, J T; Bajic, M; Baker, O K; Baldin, E M; Balek, P; Balli, F; Balunas, W K; Banas, E; Banerjee, Sw; Bannoura, A A E; Barak, L; Barberio, E L; Barberis, D; Barbero, M; Barillari, T; Barisits, M-S; Barklow, T; Barlow, N; Barnes, S L; Barnett, B M; Barnett, R M; Barnovska-Blenessy, Z; Baroncelli, A; Barone, G; Barr, A J; Barranco Navarro, L; Barreiro, F; Barreiro Guimarães da Costa, J; Bartoldus, R; Barton, A E; Bartos, P; Basalaev, A; Bassalat, A; Bates, R L; Batista, S J; Batley, J R; Battaglia, M; Bauce, M; Bauer, F; Bawa, H S; Beacham, J B; Beattie, M D; Beau, T; Beauchemin, P H; Bechtle, P; Beck, H P; Becker, K; Becker, M; Beckingham, M; Becot, C; Beddall, A J; Beddall, A; Bednyakov, V A; Bedognetti, M; Bee, C P; Beermann, T A; Begalli, M; Begel, M; Behr, J K; Bell, A S; Bella, G; Bellagamba, L; Bellerive, A; Bellomo, M; Belotskiy, K; Beltramello, O; Belyaev, N L; Benary, O; Benchekroun, D; Bender, M; Bendtz, K; Benekos, N; Benhammou, Y; Benhar Noccioli, E; Benitez, J; Benjamin, D P; Benoit, M; Bensinger, J R; Bentvelsen, S; Beresford, L; Beretta, M; Berge, D; Bergeaas Kuutmann, E; Berger, N; Beringer, J; Berlendis, S; Bernard, N R; Bernardi, G; Bernius, C; Bernlochner, F U; Berry, T; Berta, P; Bertella, C; Bertoli, G; Bertolucci, F; Bertram, I A; Bertsche, C; Bertsche, D; Besjes, G J; Bessidskaia Bylund, O; Bessner, M; Besson, N; Betancourt, C; Bethani, A; Bethke, S; Bevan, A J; Beyer, J; Bianchi, R M; Biebel, O; Biedermann, D; Bielski, R; Biesuz, N V; Biglietti, M; Billoud, T R V; Bilokon, H; Bindi, M; Bingul, A; Bini, C; Biondi, S; Bisanz, T; Bittrich, C; Bjergaard, D M; Black, C W; Black, J E; Black, K M; Blair, R E; Blazek, T; Bloch, I; Blocker, C; Blue, A; Blum, W; Blumenschein, U; Blunier, S; Bobbink, G J; Bobrovnikov, V S; Bocchetta, S S; Bocci, A; Bock, C; Boehler, M; Boerner, D; Bogavac, D; Bogdanchikov, A G; Bohm, C; Boisvert, V; Bokan, P; Bold, T; Boldyrev, A S; Bolz, A E; Bomben, M; Bona, M; Boonekamp, M; Borisov, A; Borissov, G; Bortfeldt, J; Bortoletto, D; Bortolotto, V; Boscherini, D; Bosman, M; Bossio Sola, J D; Boudreau, J; Bouffard, J; Bouhova-Thacker, E V; Boumediene, D; Bourdarios, C; Boutle, S K; Boveia, A; Boyd, J; Boyko, I R; Bracinik, J; Brandt, A; Brandt, G; Brandt, O; Bratzler, U; Brau, B; Brau, J E; Breaden Madden, W D; Brendlinger, K; Brennan, A J; Brenner, L; Brenner, R; Bressler, S; Briglin, D L; Bristow, T M; Britton, D; Britzger, D; Brochu, F M; Brock, I; Brock, R; Brooijmans, G; Brooks, T; Brooks, W K; Brosamer, J; Brost, E; Broughton, J H; de Renstrom, P A Bruckman; Bruncko, D; Bruni, A; Bruni, G; Bruni, L S; Brunt, B H; Bruschi, M; Bruscino, N; Bryant, P; Bryngemark, L; Buanes, T; Buat, Q; Buchholz, P; Buckley, A G; Budagov, I A; Buehrer, F; Bugge, M K; Bulekov, O; Bullock, D; Burch, T J; Burckhart, H; Burdin, S; Burgard, C D; Burger, A M; Burghgrave, B; Burka, K; Burke, S; Burmeister, I; Burr, J T P; Busato, E; Büscher, D; Büscher, V; Bussey, P; Butler, J M; Buttar, C M; Butterworth, J M; Butti, P; Buttinger, W; Buzatu, A; Buzykaev, A R; Cabrera Urbán, S; Caforio, D; Cairo, V M; Cakir, O; Calace, N; Calafiura, P; Calandri, A; Calderini, G; Calfayan, P; Callea, G; Caloba, L P; Calvente Lopez, S; Calvet, D; Calvet, S; Calvet, T P; Camacho Toro, R; Camarda, S; Camarri, P; Cameron, D; Caminal Armadans, R; Camincher, C; Campana, S; Campanelli, M; Camplani, A; 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2017-01-01

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 [Formula: see text] for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb[Formula: see text] of data collected by the ATLAS experiment and simulation of proton-proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 [Formula: see text]. The impact of charged-particle separations and multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 [Formula: see text] is quantified using a novel, data-driven, method. The method uses the energy loss, [Formula: see text], to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is [Formula: see text] and [Formula: see text] for jet transverse momenta of 200-400 [Formula: see text] and 1400-1600 [Formula: see text], respectively.

Modelling component evaporation and composition change of traffic-induced ultrafine particles during travel from street canyon to urban background.

PubMed

Nikolova, Irina; MacKenzie, A Rob; Cai, Xiaoming; Alam, Mohammed S; Harrison, Roy M

2016-07-18

We developed a model (CiTTy-Street-UFP) of traffic-related particle behaviour in a street canyon and in the nearby downwind urban background that accounts for aerosol dynamics and the variable vapour pressure of component organics. The model simulates the evolution and fate of traffic generated multicomponent ultrafine particles (UFP) composed of a non-volatile core and 17 Semi-Volatile Organic Compounds (SVOC, modelled as n-alkane proxies). A two-stage modelling approach is adopted: (1) a steady state simulation inside the street canyon is achieved, in which there exists a balance between traffic emissions, condensation/evaporation, deposition, coagulation and exchange with the air above roof-level; and (2) a continuing simulation of the above-roof air parcel advected to the nearby urban park during which evaporation is dominant. We evaluate the component evaporation and associated composition changes of multicomponent organic particles in realistic atmospheric conditions and compare our results with observations from London (UK) in a street canyon and an urban park. With plausible input conditions and parameter settings, the model can reproduce, with reasonable fidelity, size distributions in central London in 2007. The modelled nucleation-mode peak diameter, which is 23 nm in the steady-state street canyon, decreases to 9 nm in a travel time of just 120 s. All modelled SVOC in the sub-10 nm particle size range have evaporated leaving behind only non-volatile material, whereas modelled particle composition in the Aitken mode contains SVOC between C26H54 and C32H66. No data on particle composition are available in the study used for validation, or elsewhere. Measurements addressing in detail the size resolved composition of the traffic emitted UFP in the atmosphere are a high priority for future research. Such data would improve the representation of these particles in dispersion models and provide the data essential for model validation. Enhanced knowledge of the chemical composition of nucleation-mode particles from diesel engine exhaust is needed to predict both their atmospheric behaviour and their implications for human health.

Waterlike anomalies in a two-dimensional core-softened potential

NASA Astrophysics Data System (ADS)

Bordin, José Rafael; Barbosa, Marcia C.

2018-02-01

We investigate the structural, thermodynamic, and dynamic behavior of a two-dimensional (2D) core-corona system using Langevin dynamics simulations. The particles are modeled by employing a core-softened potential which exhibits waterlike anomalies in three dimensions. In previous studies in a quasi-2D system a new region in the pressure versus temperature phase diagram of structural anomalies was observed. Here we show that for the two-dimensional case two regions in the pressure versus temperature phase diagram with structural, density, and diffusion anomalies are observed. Our findings indicate that, while the anomalous region at lower densities is due the competition between the two length scales in the potential at higher densities, the anomalous region is related to the reentrance of the melting line.

A Lagrangian parcel based mixing plane method for calculating water based mixed phase particle flows in turbo-machinery

NASA Astrophysics Data System (ADS)

Bidwell, Colin S.

2015-05-01

A method for calculating particle transport through turbo-machinery using the mixing plane analogy was developed and used to analyze the energy efficient engine . This method allows the prediction of temperature and phase change of water based particles along their path and the impingement efficiency and particle impact property data on various components in the engine. This methodology was incorporated into the LEWICE3D V3.5 software. The method was used to predict particle transport in the low pressure compressor of the . The was developed by NASA and GE in the early 1980s as a technology demonstrator and is representative of a modern high bypass turbofan engine. The flow field was calculated using the NASA Glenn ADPAC turbo-machinery flow solver. Computations were performed for a Mach 0.8 cruise condition at 11,887 m assuming a standard warm day for ice particle sizes of 5, 20 and 100 microns and a free stream particle concentration of . The impingement efficiency results showed that as particle size increased average impingement efficiencies and scoop factors increased for the various components. The particle analysis also showed that the amount of mass entering the inner core decreased with increased particle size because the larger particles were less able to negotiate the turn into the inner core due to particle inertia. The particle phase change analysis results showed that the larger particles warmed less as they were transported through the low pressure compressor. Only the smallest 5 micron particles were warmed enough to produce melting with a maximum average melting fraction of 0.18. The results also showed an appreciable amount of particle sublimation and evaporation for the 5 micron particles entering the engine core (22.6 %).

Internal stresses in pre-stressed micron-scale aluminum core-shell particles and their improved reactivity

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

Levitas, Valery I., E-mail: vlevitas@iastate.edu; McCollum, Jena; Pantoya, Michelle L.

2015-09-07

Dilatation of aluminum (Al) core for micron-scale particles covered by alumina (Al{sub 2}O{sub 3}) shell was measured utilizing x-ray diffraction with synchrotron radiation for untreated particles and particles after annealing at 573 K and fast quenching at 0.46 K/s. Such a treatment led to the increase in flame rate for Al + CuO composite by 32% and is consistent with theoretical predictions based on the melt-dispersion mechanism of reaction for Al particles. Experimental results confirmed theoretical estimates and proved that the improvement of Al reactivity is due to internal stresses. This opens new ways of controlling particle reactivity through creating and monitoringmore » internal stresses.« less

A laboratory model for solidification of Earth's core

NASA Astrophysics Data System (ADS)

Bergman, Michael I.; Macleod-Silberstein, Marget; Haskel, Michael; Chandler, Benjamin; Akpan, Nsikan

2005-11-01

To better understand the influence of rotating convection in the outer core on the solidification of the inner core we have constructed a laboratory model for solidification of Earth's core. The model consists of a 15 cm radius hemispherical acrylic tank concentric with a 5 cm radius hemispherical aluminum heat exchanger that serves as the incipient inner core onto which we freeze ice from salt water. Long exposure photographs of neutrally buoyant particles in illuminated planes suggest reduction of flow parallel to the rotation axis. Thermistors in the tank near the heat exchanger show that in experiments with rotation the temperature near the pole is lower than near the equator, unlike for control experiments without rotation or with a polymer that increases the fluid viscosity. The photographs and thermistors suggest that our observation that ice grows faster near the pole than near the equator for experiments with rotation is a result of colder water not readily convecting away from the pole. Because of the reversal of the thermal gradient, we expect faster equatorial solidification in the Earth's core. Such anisotropy in solidification has been suggested as a cause of inner core elastic (and attenuation) anisotropy, though the plausibility of this suggestion will depend on the core Nusselt number and the slope of the liquidus, and the effects of post-solidification deformation. Previous experiments on hexagonal close-packed alloys such as sea ice and zinc-tin have shown that fluid flow in the melt can result in a solidification texture transverse to the solidification direction, with the texture depending on the nature of the flow. A comparison of the visualized flow and the texture of columnar ice crystals in thin sections from these experiments confirms flow-induced transverse textures. This suggests that the convective pattern at the base of the outer core is recorded in the texture of the inner core, and that outer core convection might contribute to the complexity in the seismically inferred pattern of anisotropy in the Earth's inner core.

Volcanic ash ingestion by a large gas turbine aeroengine: fan-particle interaction

NASA Astrophysics Data System (ADS)

Vogel, Andreas; Clarkson, Rory; Durant, Adam; Cassiani, Massimo; Stohl, Andreas

2016-04-01

Airborne particles from explosive volcanic eruptions are a major safety threat for aviation operations. The fine fraction of the emitted particles (<63 microns diameter) may remain in the atmosphere for days, or even weeks, and can affect commercial air traffic routes. Over the past century, there have been a considerable number of aircraft encounters with drifting volcanic ash clouds. Particles ingested into the engine cause erosion of upstream surfaces of compressor fan blades and rotor-path components, and can also cause contamination or blockage of electrical systems and the fuel system such as fuel nozzles and air bleed filters. Ash particles that enter the hot-section of the engine (combustor and turbine stages; temperature between 1400-1800°C) are rapidly heated above the glass transition temperature (about 650-1000°C) and become soft (or form a melt) and can stick as re-solidified deposits on nozzle guide vanes. The glass deposits change the internal aerodynamic airflow in the engine and can affect the cooling capability of the different components by clogging the cooling inlets/outlets, which can lead to a loss of power or flame-out. The nature of volcanic ash ingestion is primarily influenced by the fan at the front of the engine which produces the thrust that drives the aircraft. The ingested air is split between the core (compressor/combustor/turbine) and bypass (thrust) at a ratio of typically between, 1:5-10 on modern engines. Consequently, the ash particles are fractionated between the core and bypass by the geometry and dynamics of the fan blades. This study uses computational fluid dynamics (CFD) simulations of particle-laden airflows into a turbofan engine under different atmospheric and engine operation conditions. The main aim was to investigate the possible centrifugal effect of the fan blades as a function of particle size, and to relate this to the core intake concentration. We generated a generic 3D axial high-bypass turbofan engine using realistic dimensions of the turbofan, engine intake and other aerodynamically relevant parts. The CFD experiments include three scenarios of aircraft performance (climb, cruise and descent) and for two different typical altitude ranges (10000 and 39000 ft). The fluid dynamics simulations were carried out using a commercial code (CD Adapco STAR-CCM+ with an implicit coupled flow and energy algorithm) for compressible high-speed flows including a Lagrangian particle-tracking model for the simulation of the particle behaviour for typical atmospheric particle size ranges between 1 and 100 μm. The simulations indicate that the predominant proportion of larger particles (> 20 microns) tend to be transported into the bypass duct of the engine (by the centrifugal effect of the fan), whereas the smaller particles follow the fluid flow streamlines and are distributed homogenously in the engine (bypass ducts and core region). This result is significant as it indicates that the absolute ash mass that causes issues for aeroengine operation is a fraction of the ambient (observed or forecast) ash quantity.

No nitrate spikes detectable in several polar ice cores following the largest known solar events

NASA Astrophysics Data System (ADS)

Mekhaldi, Florian; McConnell, Joseph R.; Adolphi, Florian; Arienzo, Monica; Chellman, Nathan J.; Maselli, Olivia; Sigl, Michael; Muscheler, Raimund

2017-04-01

Solar energetic particle (SEP) events are a genuine and recognized threat to our modern society which is increasingly relying on satellites and technological infrastructures. However, knowledge on the frequency and on the upper limit of the intensity of major solar storms is largely limited by the relatively short direct observation period. In an effort to extend the observation period and because atmospheric ionization induced by solar particles can lead to the production of odd nitrogen, spikes in the nitrate content of ice cores have been tentatively used to reconstruct both the occurrence and intensity of past SEP events. Yet the reliability of its use as such a proxy has been long debated. This is partly due to differing chemistry-climate model outputs, equivocal detection of nitrate spikes in single ice cores for single events, and possible alternative sources to explain nitrate spikes in ice cores. Here we present nitrate measurements from several Antarctic and Greenland ice cores for time periods covering the largest known solar events. More specifically, we use new highly-resolved nitrate and biomass burning proxy species data (e.g. black carbon) from continuous flow analysis following the largest known solar events from the paleo record - the SEP events of 775 and 994 AD. We also consider the historical Carrington event of 1859 as well as contemporary events from the past 60 years which were observed by satellites. Doing so we show that i) there are no reproducible nitrate spikes in Greenland and Antarctic ice cores following any of these major events and that ii) most nitrate spikes found in ice cores are related to biomass burning plumes. Our analysis thus suggests that ice-core nitrate data is not a reliable proxy for atmospheric ionization by SEP events. In light of our results, we advocate that nitrate spikes so far identified from single ice cores should not be used to assess the intensity and occurrence rate of extreme solar events.

Software package for modeling spin-orbit motion in storage rings

NASA Astrophysics Data System (ADS)

Zyuzin, D. V.

2015-12-01

A software package providing a graphical user interface for computer experiments on the motion of charged particle beams in accelerators, as well as analysis of obtained data, is presented. The software package was tested in the framework of the international project on electric dipole moment measurement JEDI (Jülich Electric Dipole moment Investigations). The specific features of particle spin motion imply the requirement to use a cyclic accelerator (storage ring) consisting of electrostatic elements, which makes it possible to preserve horizontal polarization for a long time. Computer experiments study the dynamics of 106-109 particles in a beam during 109 turns in an accelerator (about 1012-1015 integration steps for the equations of motion). For designing an optimal accelerator structure, a large number of computer experiments on polarized beam dynamics are required. The numerical core of the package is COSY Infinity, a program for modeling spin-orbit dynamics.

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

Lienhard, D. M.; Huisman, A. J.; Krieger, U. K.

New measurements of water diffusion in secondary organic aerosol (SOA) material produced by oxidation of α-pinene and in a number of organic/inorganic model mixtures (3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA), levoglucosan, levoglucosan/NH 4HSO 4, raffinose) are presented. These indicate that water diffusion coefficients are determined by several properties of the aerosol substance and cannot be inferred from the glass transition temperature or bouncing properties. Our results suggest that water diffusion in SOA particles is faster than often assumed and imposes no significant kinetic limitation on water uptake and release at temperatures above 220 K. The fast diffusion of water suggests that heterogeneous icemore » nucleation on a glassy core is very unlikely in these systems. At temperatures below 220 K, model simulations of SOA particles suggest that heterogeneous ice nucleation may occur in the immersion mode on glassy cores which remain embedded in a liquid shell when experiencing fast updraft velocities. The particles absorb significant quantities of water during these updrafts which plasticize their outer layers such that these layers equilibrate readily with the gas phase humidity before the homogeneous ice nucleation threshold is reached. Glass formation is thus unlikely to restrict homogeneous ice nucleation. Only under most extreme conditions near the very high tropical tropopause may the homogeneous ice nucleation rate coefficient be reduced as a consequence of slow condensed-phase water diffusion. Since the differences between the behavior limited or non limited by diffusion are small even at the very high tropical tropopause, condensed-phase water diffusivity is unlikely to have significant consequences on the direct climatic effects of SOA particles under tropospheric conditions.« less

Oil sorption by lignocellulosic fibers

Treesearch

Beom-Goo Lee; James S. Han; Roger M. Rowell

1999-01-01

The oil sorption capacities of cotton fiber, kenaf bast fiber, kenaf core fiber, and moss fiber were compared after refining, extraction, and reduction in particle sizes. The tests were conducted on diesel oil in a pure form. Cotton fiber showed the highest capacity, followed by kenaf core and bast fibers. Wetting, extraction, and reduction in particle size all...

Nucleosome Core Particle

NASA Technical Reports Server (NTRS)

1997-01-01

Nucleosome Core Particle grown on STS-81. The fundamental structural unit of chromatin and is the basis for organization within the genome by compaction of DNA within the nucleus of the cell and by making selected regions of chromosomes available for transcription and replication. Principal Investigator's are Dr. Dan Carter and Dr. Gerard Bunick of New Century Pharmaceuticals.

Multi-photon excited luminescence of magnetic FePt core-shell nanoparticles.

PubMed

Seemann, K M; Kuhn, B

2014-07-01

We present magnetic FePt nanoparticles with a hydrophilic, inert, and biocompatible silico-tungsten oxide shell. The particles can be functionalized, optically detected, and optically manipulated. To show the functionalization the fluorescent dye NOPS was bound to the FePt core-shell nanoparticles with propyl-triethoxy-silane linkers and fluorescence of the labeled particles were observed in ethanol (EtOH). In aqueous dispersion the NOPS fluorescence is quenched making them invisible using 1-photon excitation. However, we observe bright luminescence of labeled and even unlabeled magnetic core-shell nanoparticles with multi-photon excitation. Luminescence can be detected in the near ultraviolet and the full visible spectral range by near infrared multi-photon excitation. For optical manipulation, we were able to drag clusters of particles, and maybe also single particles, by a focused laser beam that acts as optical tweezers by inducing an electric dipole in the insulated metal nanoparticles. In a first application, we show that the luminescence of the core-shell nanoparticles is bright enough for in vivo multi-photon imaging in the mouse neocortex down to cortical layer 5.

Colloidal crystal beads composed of core-shell particles for multiplex bioassay.

PubMed

Xu, Hua; Zhu, Cun; Zhao, Yuanjin; Zhao, Xiangwei; Hu, Jing; Gu, Zhongze

2009-04-01

A convenient method was developed to fabricate colloidal crystal beads (CCBs) with tough mechanical strength, which was used as encoded carriers for multiplex bioassay. The latex particles used for the construction of the CCBs were designed with a rigid core PS and a elastomeric shell poly(MMA/EA/MAA), and were prepared via one-step soap-free emulsion polymerization. The as-above-prepared CCBs were thermo-treated to drive the elastomeric shells of adjacent latex particles joining together. It was found that the coalescence of latex particles can greatly improve the mechanical strength of the CCBs for multiplex bioassay.

Submicron magnetic core conducting polypyrrole polymer shell: Preparation and characterization.

PubMed

Tenório-Neto, Ernandes Taveira; Baraket, Abdoullatif; Kabbaj, Dounia; Zine, Nadia; Errachid, Abdelhamid; Fessi, Hatem; Kunita, Marcos Hiroiuqui; Elaissari, Abdelhamid

2016-04-01

Magnetic particles are of great interest in various biomedical applications, such as, sample preparation, in vitro biomedical diagnosis, and both in vivo diagnosis and therapy. For in vitro applications and especially in labs-on-a-chip, microfluidics, microsystems, or biosensors, the needed magnetic dispersion should answer various criteria, for instance, submicron size in order to avoid a rapid sedimentation rate, fast separations under an applied magnetic field, and appreciable colloidal stability (stable dispersion under shearing process). Then, the aim of this work was to prepare highly magnetic particles with a magnetic core and conducting polymer shell particles in order to be used not only as a carrier, but also for the in vitro detection step. The prepared magnetic seed dispersions were functionalized using pyrrole and pyrrole-2-carboxylic acid. The obtained core-shell particles were characterized in terms of particle size, size distribution, magnetization properties, FTIR analysis, surface morphology, chemical composition, and finally, the conducting property of those particles were evaluated by cyclic voltammetry. The obtained functional submicron highly magnetic particles are found to be conducting material bearing function carboxylic group on the surface. These promising conducting magnetic particles can be used for both transport and lab-on-a-chip detection. Copyright © 2015. Published by Elsevier B.V.

Radiation quality and tissue-specific microenvironments following exposure to 1 GeV/amu Fe

NASA Technical Reports Server (NTRS)

Costes, S.; Barcellos-Hoff, M. H.

2002-01-01

This paper summarizes quantitative in vivo laminin immunofluorescence analysis of mammary glands and skin epithelial structures from mice exposed to 1 GeV/amu Fe ions. Digital confocal microscopic images were quantified and linked to the rough "core-penumbra" Fe track physical description. Comparison to gamma-ray sparsely ionizing radiation suggested the core of the Fe track being responsible for a biological response only seen with energetic Fe particles. Conclusions for modeling in vivo responses to radiation were then implied. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Temperature Sensitivity of Water-Soluble CdTe and CdSe/ZnS Quantum Dots Incorporated into Biopolymer Submicron Particles

NASA Astrophysics Data System (ADS)

Slyusarenko, N. V.; Gerasimova, M. A.; Slabko, V. V.; Slyusareva, E. A.

2017-07-01

Polymer particles with sizes 0.3-0.4 μm are synthesized based on chitosan and chondroitin sulfate with incorporated CdTe (core) and CdSe/ZnS (core-shell) quantum dots. Their morphological and spectral properties are investigated by the methods of dynamic scattering, electron microscopy, and absorption and luminescence spectroscopy at temperatures from 10 to 80°C. Spectral effects associated with a change in temperature (a red shift and a decrease in the amplitude of the photoluminescence spectrum) can be explained by the temperature expansion of the quantum dots and activation of surface traps. It is shown that the temperature sensitivity of spectra of the quantum dots incorporated into the biopolymer particles is not less than in water. To develop an optical temperature sensor, the core quantum dots are more preferable than the core-shell quantum dots.

Monodisperse core-shell particles composed of magnetite and dye-functionalized mesoporous silica

NASA Astrophysics Data System (ADS)

Eurov, D. A.; Kurdyukov, D. A.; Medvedev, A. V.; Kirilenko, D. A.; Yakovlev, D. R.; Golubev, V. G.

2017-08-01

Hybrid particles with a core-shell structure have been obtained in the form of monodisperse spherical mesoporous silica particles filled with magnetite and covered with a mesoporous silica shell functionalized with a luminescent dye. The particles have a small root-mean-square size deviation (at most 10%), possess a specific surface area and specific pore volume of up to 250 m2/g and 0.15 cm3/g, respectively, and exhibit visible luminescence peaked at a wavelength of 530 nm. The particles can be used in diagnostics of cancerous diseases, serving simultaneously for therapeutic (magnetic hyperthermia and targeted drug delivery) and diagnostic (contrast agent for magnetic-resonance tomography and luminescent marker) purposes.

Three Dimensional Characterization of Typical Urban and Desert Particles: Implications to Particle Optics

NASA Astrophysics Data System (ADS)

Goel, V.; Mishra, S.; Ahlawat, A. S.; Sharma, C.; Kotnala, R. K.

2017-12-01

Aerosol particles are generally considered as chemically homogeneous spheres in the retrieval techniques of ground and space borne observations which is not accurate approach and can lead to erroneous observations. For better simulation of optical and radiative properties of aerosols, a good knowledge of aerosol's morphology, chemical composition and internal structure is essential. Till date, many studies have reported the morphology and chemical composition of particles but very few of them provide internal structure and spatial distribution of different chemical species within the particle. The research on the effect of particle internal structure and its contribution to particle optics is extremely limited. In present work, we characterize the PM10 particles collected form typical arid (the Thar Desert, Rajasthan, India) and typical urban (New Delhi, India) environment using microscopic techniques. The particles were milled several times to investigate their internal structure. The EDS (Energy Dispersive X-ray Spectroscopy) spectra were recorded after each milling to check the variation in the chemical composition. In arid environment, Fe, Ca, C, Al, and Mg rich shell was observed over a Si rich particle whereas in urban environment, shell of Hg, Ag, C and N was observed over a Cu rich particle. Based on the observations, different model shapes [homogenous sphere and spheroid; heterogeneous sphere and spheroid; core shell] have been considered for assessing the associated uncertainties with the routine modeling of optical properties where volume equivalent homogeneous sphere approximation is considered. The details will be discussed during presentation.

Multistage Core Formation in Planetesimals Revealed by Numerical Modeling and Hf-W Chronometry of Iron Meteorites

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

Neumann, W.; Kruijer, T. S.; Breuer, D.

Iron meteorites provide some of the most direct insights into the processes and timescales of core formation in planetesimals. Of these, group IVB irons stand out by having one of the youngest 182Hf- 182W model ages for metal segregation (2.9 ± 0.6 Ma after solar system formation), as well as the lowest bulk sulfur content and hence highest liquidus temperature. Here in this paper, using a new model for the internal evolution of the IVB parent body, we show that a single stage of metal-silicate separation cannot account for the complete melting of pure Fe metal at the relatively latemore » time given by the Hf-W model age. Instead, a complex metal-silicate separation scenario is required that includes migration of partial silicate melts, formation of a shallow magma ocean, and core formation in two distinct stages of metal segregation. In the first stage, a protocore formed at ≈1.5 Ma via settling of metal particles in a mantle magma ocean, followed by metal segregation from a shallow magma ocean at ≈5.4 Ma. As these stages of metal segregation occurred at different times, the two metal fractions had different 182W compositions. Consequently, the final 182W composition of the IVB core does not correspond to a single differentiation event, but represents the average composition of early- and late-segregated core fractions. Our best fit model indicates an ≈100 km radius for the IVB parent body and provides an accretion age of ≈0.1–0.5 Ma after solar system formation. The computed solidification time is, furthermore, consistent with the Re-Os age for crystallization of the IVB core.« less

Multistage Core Formation in Planetesimals Revealed by Numerical Modeling and Hf-W Chronometry of Iron Meteorites

DOE PAGES

Neumann, W.; Kruijer, T. S.; Breuer, D.; ...

2018-02-01

Iron meteorites provide some of the most direct insights into the processes and timescales of core formation in planetesimals. Of these, group IVB irons stand out by having one of the youngest 182Hf- 182W model ages for metal segregation (2.9 ± 0.6 Ma after solar system formation), as well as the lowest bulk sulfur content and hence highest liquidus temperature. Here in this paper, using a new model for the internal evolution of the IVB parent body, we show that a single stage of metal-silicate separation cannot account for the complete melting of pure Fe metal at the relatively latemore » time given by the Hf-W model age. Instead, a complex metal-silicate separation scenario is required that includes migration of partial silicate melts, formation of a shallow magma ocean, and core formation in two distinct stages of metal segregation. In the first stage, a protocore formed at ≈1.5 Ma via settling of metal particles in a mantle magma ocean, followed by metal segregation from a shallow magma ocean at ≈5.4 Ma. As these stages of metal segregation occurred at different times, the two metal fractions had different 182W compositions. Consequently, the final 182W composition of the IVB core does not correspond to a single differentiation event, but represents the average composition of early- and late-segregated core fractions. Our best fit model indicates an ≈100 km radius for the IVB parent body and provides an accretion age of ≈0.1–0.5 Ma after solar system formation. The computed solidification time is, furthermore, consistent with the Re-Os age for crystallization of the IVB core.« less

Multistage Core Formation in Planetesimals Revealed by Numerical Modeling and Hf-W Chronometry of Iron Meteorites

NASA Astrophysics Data System (ADS)

Neumann, W.; Kruijer, T. S.; Breuer, D.; Kleine, T.

2018-02-01

Iron meteorites provide some of the most direct insights into the processes and timescales of core formation in planetesimals. Of these, group IVB irons stand out by having one of the youngest 182Hf-182W model ages for metal segregation (2.9 ± 0.6 Ma after solar system formation), as well as the lowest bulk sulfur content and hence highest liquidus temperature. Here, using a new model for the internal evolution of the IVB parent body, we show that a single stage of metal-silicate separation cannot account for the complete melting of pure Fe metal at the relatively late time given by the Hf-W model age. Instead, a complex metal-silicate separation scenario is required that includes migration of partial silicate melts, formation of a shallow magma ocean, and core formation in two distinct stages of metal segregation. In the first stage, a protocore formed at ≈1.5 Ma via settling of metal particles in a mantle magma ocean, followed by metal segregation from a shallow magma ocean at ≈5.4 Ma. As these stages of metal segregation occurred at different times, the two metal fractions had different 182W compositions. Consequently, the final 182W composition of the IVB core does not correspond to a single differentiation event, but represents the average composition of early- and late-segregated core fractions. Our best fit model indicates an ≈100 km radius for the IVB parent body and provides an accretion age of ≈0.1-0.5 Ma after solar system formation. The computed solidification time is, furthermore, consistent with the Re-Os age for crystallization of the IVB core.

Recombinant Expression of Tandem-HBc Virus-Like Particles (VLPs).

PubMed

Stephen, Sam L; Beales, Lucy; Peyret, Hadrien; Roe, Amy; Stonehouse, Nicola J; Rowlands, David J

2018-01-01

The hepatitis B virus (HBV) core protein (HBc) has formed the building block for virus-like particle (VLP) production for more than 30 years. The ease of production of the protein, the robust ability of the core monomers to dimerize and assemble into intact core particles, and the strong immune responses they elicit when presenting antigenic epitopes all demonstrate its promise for vaccine development (reviewed in Pumpens and Grens (Intervirology 44: 98-114, 2001)). HBc has been modified in a number of ways in attempts to expand its potential as a novel vaccine platform. The HBc protein is predominantly α-helical in structure and folds to form an L-shaped molecule. The structural subunit of the HBc particle is a dimer of monomeric HBc proteins which together form an inverted T-shaped structure. In the assembled HBc particle the four-helix bundle formed at each dimer interface appears at the surface as a prominent "spike." The tips of the "spikes" are the preferred sites for the insertion of foreign sequences for vaccine purposes as they are the most highly exposed regions of the assembled particles. In the tandem-core modification two copies of the HBc protein are covalently linked by a flexible amino acid sequence which allows the fused dimer to fold correctly and assemble into HBc particles. The advantage of the modified structure is that the assembly of the dimeric subunits is defined and not formed by random association. This facilitates the introduction of single, larger sequences at the tip of each surface "spike," thus overcoming the conformational clashes contingent on insertion of large structures into monomeric HBc proteins.Differences in inserted sequences influence the assembly characteristics of the modified proteins, and it is important to optimize the design of each novel construct to maximize efficiency of assembly into regular VLPs. In addition to optimization of the construct, the expression system used can also influence the ability of recombinant structures to assemble into regular isometric particles. Here, we describe the production of recombinant tandem-core particles in bacterial, yeast and plant expression systems.

Nonthermal emission from clusters of galaxies

NASA Astrophysics Data System (ADS)

Kushnir, Doron; Waxman, Eli

2009-08-01

We show that the spectral and radial distribution of the nonthermal emission of massive, M gtrsim 1014.5Msun, galaxy clusters may be approximately described by simple analytic expressions, which depend on the cluster thermal X-ray properties and on two model parameter, βcore and ηe. βcore is the ratio of the cosmic-ray (CR) energy density (within a logarithmic CR energy interval) and the thermal energy density at the cluster core, and ηe(p) is the fraction of the thermal energy generated in strong collisionless shocks, which is deposited in CR electrons (protons). Using a simple analytic model for the evolution of intra-cluster medium CRs, which are produced by accretion shocks, we find that βcore simeq ηp/200, nearly independent of cluster mass and with a scatter Δln βcore simeq 1 between clusters of given mass. We show that the hard X-ray (HXR) and γ-ray luminosities produced by inverse Compton scattering of CMB photons by electrons accelerated in accretion shocks (primary electrons) exceed the luminosities produced by secondary particles (generated in hadronic interactions within the cluster) by factors simeq 500(ηe/ηp)(T/10 keV)-1/2 and simeq 150(ηe/ηp)(T/10 keV)-1/2 respectively, where T is the cluster temperature. Secondary particle emission may dominate at the radio and very high energy (gtrsim 1 TeV) γ-ray bands. Our model predicts, in contrast with some earlier work, that the HXR and γ-ray emission from clusters of galaxies are extended, since the emission is dominated at these energies by primary (rather than by secondary) electrons. Our predictions are consistent with the observed nonthermal emission of the Coma cluster for ηp ~ ηe ~ 0.1. The implications of our predictions to future HXR observations (e.g. by NuStar, Simbol-X) and to (space/ground based) γ-ray observations (e.g. by Fermi, HESS, MAGIC, VERITAS) are discussed. In particular, we identify the clusters which are the best candidates for detection in γ-rays. Finally, we show that our model's results agree with results of detailed numerical calculations, and that discrepancies between the results of various numerical simulations (and between such results and our model) are due to inaccuracies in the numerical calculations.

Core-Shell Particles as Building Blocks for Systems with High Duality Symmetry

NASA Astrophysics Data System (ADS)

Rahimzadegan, Aso; Rockstuhl, Carsten; Fernandez-Corbaton, Ivan

2018-05-01

Material electromagnetic duality symmetry requires a system to have equal electric and magnetic responses. Intrinsically dual materials that meet the duality conditions at the level of the constitutive relations do not exist in many frequency bands. Nevertheless, discrete objects like metallic helices and homogeneous dielectric spheres can be engineered to approximate the dual behavior. We exploit the extra degrees of freedom of a core-shell dielectric sphere in a particle optimization procedure. The duality symmetry of the resulting particle is more than 1 order of magnitude better than previously reported nonmagnetic objects. We use T -matrix-based multiscattering techniques to show that the improvement is transferred onto the duality symmetry of composite objects when the core-shell particle is used as a building block instead of homogeneous spheres. These results are relevant for the fashioning of systems with high duality symmetry, which are required for some technologically important effects.

Numerical models for fluid-grains interactions: opportunities and limitations

NASA Astrophysics Data System (ADS)

Esteghamatian, Amir; Rahmani, Mona; Wachs, Anthony

2017-06-01

In the framework of a multi-scale approach, we develop numerical models for suspension flows. At the micro scale level, we perform particle-resolved numerical simulations using a Distributed Lagrange Multiplier/Fictitious Domain approach. At the meso scale level, we use a two-way Euler/Lagrange approach with a Gaussian filtering kernel to model fluid-solid momentum transfer. At both the micro and meso scale levels, particles are individually tracked in a Lagrangian way and all inter-particle collisions are computed by a Discrete Element/Soft-sphere method. The previous numerical models have been extended to handle particles of arbitrary shape (non-spherical, angular and even non-convex) as well as to treat heat and mass transfer. All simulation tools are fully-MPI parallel with standard domain decomposition and run on supercomputers with a satisfactory scalability on up to a few thousands of cores. The main asset of multi scale analysis is the ability to extend our comprehension of the dynamics of suspension flows based on the knowledge acquired from the high-fidelity micro scale simulations and to use that knowledge to improve the meso scale model. We illustrate how we can benefit from this strategy for a fluidized bed, where we introduce a stochastic drag force model derived from micro-scale simulations to recover the proper level of particle fluctuations. Conversely, we discuss the limitations of such modelling tools such as their limited ability to capture lubrication forces and boundary layers in highly inertial flows. We suggest ways to overcome these limitations in order to enhance further the capabilities of the numerical models.

Hydrodynamic metamaterials: Microfabricated arrays to steer, refract, and focus streams of biomaterials

PubMed Central

Morton, Keith J.; Loutherback, Kevin; Inglis, David W.; Tsui, Ophelia K.; Sturm, James C.; Chou, Stephen Y.; Austin, Robert H.

2008-01-01

We show that it is possible to direct particles entrained in a fluid along trajectories much like rays of light in classical optics. A microstructured, asymmetric post array forms the core hydrodynamic element and is used as a building block to construct microfluidic metamaterials and to demonstrate refractive, focusing, and dispersive pathways for flowing beads and cells. The core element is based on the concept of deterministic lateral displacement where particles choose different paths through the asymmetric array based on their size: Particles larger than a critical size are displaced laterally at each row by a post and move along the asymmetric axis at an angle to the flow, while smaller particles move along streamline paths. We create compound elements with complex particle handling modes by tiling this core element using multiple transformation operations; we show that particle trajectories can be bent at an interface between two elements and that particles can be focused into hydrodynamic jets by using a single inlet port. Although particles propagate through these elements in a way that strongly resembles light rays propagating through optical elements, there are unique differences in the paths of our particles as compared with photons. The unusual aspects of these modular, microfluidic metamaterials form a rich design toolkit for mixing, separating, and analyzing cells and functional beads on-chip. PMID:18495920

Optical trapping of core-shell magnetic microparticles by cylindrical vector beams

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

Zhong, Min-Cheng; Gong, Lei; Li, Di

2014-11-03

Optical trapping of core-shell magnetic microparticles is experimentally demonstrated by using cylindrical vector beams. Second, we investigate the optical trapping efficiencies. The results show that radially and azimuthally polarized beams exhibit higher axial trapping efficiencies than the Gaussian beam. Finally, a trapped particle is manipulated to kill a cancer cell. The results make possible utilizing magnetic particles for optical manipulation, which is an important advantage for magnetic particles as labeling agent in targeted medicine and biological analysis.

Stretchable inductor with liquid magnetic core

NASA Astrophysics Data System (ADS)

Lazarus, N.; Meyer, C. D.

2016-03-01

Adding magnetic materials is a well-established method for improving performance of inductors. However, traditional magnetic cores are rigid and poorly suited for the emerging field of stretchable electronics, where highly deformable inductors are used to wirelessly couple power and data signals. In this work, stretchable inductors are demonstrated based on the use of ferrofluids, magnetic liquids based on distributed magnetic particles, to create a compliant magnetic core. Using a silicone molding technique to create multi-layer fluidic channels, a liquid metal solenoid is fabricated around a ferrofluid channel. An analytical model is developed for the effects of mechanical strain, followed by experimental verification using two different ferrofluids with different permeabilities. Adding ferrofluid was found to increase the unstrained inductance by up to 280% relative to a similar inductor with a non-magnetic silicone core, while retaining the ability to survive uniaxial strains up to 100%.

DNA-tagged Microparticles for Tracing Water Flows and Travel Times in Natural Systems: The First results from Controlled Laboratory Experiments

NASA Astrophysics Data System (ADS)

Bogaard, T.; Bandyopadhyay, S.; Foppen, J. W.

2017-12-01

Societal demand for water safety is continuously increasing, being it resilient against flood/droughts, clean water for ecosystems, recreation or safe drinking water. Robust methods to measure temporal and spatial patterns of water and contaminant pathways are still lacking. Our research project aims to develop and apply (1) innovative, robust, and environmental-friendly silica-protected iron oxide micro-particles tagged with artificial DNA to trace contaminant movement and travel times of water in natural systems and (2) an innovative coupled model approach to capture dynamics in hydrological pathways and their effects on water quality. The exceptional property of DNA-tagging is the infinite number of unique tracers that can be produced and their detectability at extreme low concentrations. The advantage of the iron-core of the particle is the magnetic harvesting of the particles from water-samples. Such tracers are thought to give the water sector a unique tool for in-situ mapping of transport of contaminants and pathogenic microorganisms in water systems. However, the characteristics of the particle like magnetic property of the iron-core and surface potential of the silica layer, are of key importance for the behaviour of the particle in surface water and in soils. Furthermore, the application of such micro-particles requires strict protocols for the experiment, sampling and laboratory handling which are currently not available. We used two different types of silica-protected DNA-tagged micro-particles. We performed batch, column and flow experiments to assess the behaviour of the particles. We will present the first results of the controlled laboratory experiments for hydrological tracing. We will discuss the results and link it to the differences in particles design. Furthermore, we will draw conclusions and discuss knowledge gaps for future application of silica-protected DNA-tagged micro-particles in hydrological research.

The WAIS Melt Monitor: An automated ice core melting system for meltwater sample handling and the collection of high resolution microparticle size distribution data

NASA Astrophysics Data System (ADS)

Breton, D. J.; Koffman, B. G.; Kreutz, K. J.; Hamilton, G. S.

2010-12-01

Paleoclimate data are often extracted from ice cores by careful geochemical analysis of meltwater samples. The analysis of the microparticles found in ice cores can also yield unique clues about atmospheric dust loading and transport, dust provenance and past environmental conditions. Determination of microparticle concentration, size distribution and chemical makeup as a function of depth is especially difficult because the particle size measurement either consumes or contaminates the meltwater, preventing further geochemical analysis. Here we describe a microcontroller-based ice core melting system which allows the collection of separate microparticle and chemistry samples from the same depth intervals in the ice core, while logging and accurately depth-tagging real-time electrical conductivity and particle size distribution data. This system was designed specifically to support microparticle analysis of the WAIS Divide WDC06A deep ice core, but many of the subsystems are applicable to more general ice core melting operations. Major system components include: a rotary encoder to measure ice core melt displacement with 0.1 millimeter accuracy, a meltwater tracking system to assign core depths to conductivity, particle and sample vial data, an optical debubbler level control system to protect the Abakus laser particle counter from damage due to air bubbles, a Rabbit 3700 microcontroller which communicates with a host PC, collects encoder and optical sensor data and autonomously operates Gilson peristaltic pumps and fraction collectors to provide automatic sample handling, melt monitor control software operating on a standard PC allowing the user to control and view the status of the system, data logging software operating on the same PC to collect data from the melting, electrical conductivity and microparticle measurement systems. Because microparticle samples can easily be contaminated, we use optical air bubble sensors and high resolution ice core density profiles to guide the melting process. The combination of these data allow us to analyze melt head performance, minimize outer-to-inner fraction contamination and avoid melt head flooding. The WAIS Melt Monitor system allows the collection of real-time, sub-annual microparticle and electrical conductivity data while producing and storing enough sample for traditional Coulter-Counter particle measurements as well long term acid leaching of bioactive metals (e.g., Fe, Co, Cd, Cu, Zn) prior to chemical analysis.

Directed Magnetic Particle Transport above Artificial Magnetic Domains Due to Dynamic Magnetic Potential Energy Landscape Transformation.

PubMed

Holzinger, Dennis; Koch, Iris; Burgard, Stefan; Ehresmann, Arno

2015-07-28

An approach for a remotely controllable transport of magnetic micro- and/or nanoparticles above a topographically flat exchange-bias (EB) thin film system, magnetically patterned into parallel stripe domains, is presented where the particle manipulation is achieved by sub-mT external magnetic field pulses. Superparamagnetic core-shell particles are moved stepwise by the dynamic transformation of the particles' magnetic potential energy landscape due to the external magnetic field pulses without affecting the magnetic state of the thin film system. The magnetic particle velocity is adjustable in the range of 1-100 μm/s by the design of the substrate's magnetic field landscape (MFL), the particle-substrate distance, and the magnitude of the applied external magnetic field pulses. The agglomeration of magnetic particles is avoided by the intrinsic magnetostatic repulsion of particles due to the parallel alignment of the particles' magnetic moments perpendicular to the transport direction and parallel to the surface normal of the substrate during the particle motion. The transport mechanism is modeled by a quantitative theory based on the precise knowledge of the sample's MFL and the particle-substrate distance.

An Application of X-Ray Fluorescence as Process Analytical Technology (PAT) to Monitor Particle Coating Processes.

PubMed

Nakano, Yoshio; Katakuse, Yoshimitsu; Azechi, Yasutaka

2018-06-01

An attempt to apply X-Ray Fluorescence (XRF) analysis to evaluate small particle coating process as a Process Analytical Technologies (PAT) was made. The XRF analysis was used to monitor coating level in small particle coating process with at-line manner. The small particle coating process usually consists of multiple coating processes. This study was conducted by a simple coating particles prepared by first coating of a model compound (DL-methionine) and second coating by talc on spherical microcrystalline cellulose cores. The particles with two layered coating are enough to demonstrate the small particle coating process. From the result by the small particle coating process, it was found that the XRF signal played different roles, resulting that XRF signals by first coating (layering) and second coating (mask coating) could demonstrate the extent with different mechanisms for the coating process. Furthermore, the particle coating of the different particle size has also been investigated to evaluate size effect of these coating processes. From these results, it was concluded that the XRF could be used as a PAT in monitoring particle coating processes and become powerful tool in pharmaceutical manufacturing.

Stellar evolution of high mass based on the Ledoux criterion for convection

NASA Technical Reports Server (NTRS)

Stothers, R.; Chin, C.

1972-01-01

Theoretical evolutionary sequences of models for stars of 15 and 30 solar masses were computed from the zero-age main sequence to the end of core helium burning. During the earliest stages of core helium depletion, the envelope rapidly expands into the red-supergiant configuration. At 15 solar mass, a blue loop on the H-R diagram ensues if the initial metals abundance, initial helium abundance, or C-12 + alpha particle reaction rate is sufficiently large, or if the 3-alpha reaction rate is sufficiently small. These quantities affect the opacity of the base of the outer convection zone, the mass of the core, and the thermal properties of the core. The blue loop occurs abruptly and fully developed when the critical value of any of these quantities is exceeded, and the effective temperature range and fraction of the lifetime of core helium burning during the slow phase of the blue loop vary surprisingly little. At 30 solar mass no blue loop occurs for any reasonable set of input parameters.

The effects of particle recycling on the divertor plasma: A particle-in-cell with Monte Carlo collision simulation

NASA Astrophysics Data System (ADS)

Chang, Mingyu; Sang, Chaofeng; Sun, Zhenyue; Hu, Wanpeng; Wang, Dezhen

2018-05-01

A Particle-In-Cell (PIC) with Monte Carlo Collision (MCC) model is applied to study the effects of particle recycling on divertor plasma in the present work. The simulation domain is the scrape-off layer of the tokamak in one-dimension along the magnetic field line. At the divertor plate, the reflected deuterium atoms (D) and thermally released deuterium molecules (D2) are considered. The collisions between the plasma particles (e and D+) and recycled neutral particles (D and D2) are described by the MCC method. It is found that the recycled neutral particles have a great impact on divertor plasma. The effects of different collisions on the plasma are simulated and discussed. Moreover, the impacts of target materials on the plasma are simulated by comparing the divertor with Carbon (C) and Tungsten (W) targets. The simulation results show that the energy and momentum losses of the C target are larger than those of the W target in the divertor region even without considering the impurity particles, whereas the W target has a more remarkable influence on the core plasma.

N -tag probability law of the symmetric exclusion process

NASA Astrophysics Data System (ADS)

Poncet, Alexis; Bénichou, Olivier; Démery, Vincent; Oshanin, Gleb

2018-06-01

The symmetric exclusion process (SEP), in which particles hop symmetrically on a discrete line with hard-core constraints, is a paradigmatic model of subdiffusion in confined systems. This anomalous behavior is a direct consequence of strong spatial correlations induced by the requirement that the particles cannot overtake each other. Even if this fact has been recognized qualitatively for a long time, up to now there has been no full quantitative determination of these correlations. Here we study the joint probability distribution of an arbitrary number of tagged particles in the SEP. We determine analytically its large-time limit for an arbitrary density of particles, and its full dynamics in the high-density limit. In this limit, we obtain the time-dependent large deviation function of the problem and unveil a universal scaling form shared by the cumulants.

Modeling Core Collapse Supernovae

NASA Astrophysics Data System (ADS)

Mezzacappa, Anthony

2017-01-01

Core collapse supernovae, or the death throes of massive stars, are general relativistic, neutrino-magneto-hydrodynamic events. The core collapse supernova mechanism is still not in hand, though key components have been illuminated, and the potential for multiple mechanisms for different progenitors exists. Core collapse supernovae are the single most important source of elements in the Universe, and serve other critical roles in galactic chemical and thermal evolution, the birth of neutron stars, pulsars, and stellar mass black holes, the production of a subclass of gamma-ray bursts, and as potential cosmic laboratories for fundamental nuclear and particle physics. Given this, the so called ``supernova problem'' is one of the most important unsolved problems in astrophysics. It has been fifty years since the first numerical simulations of core collapse supernovae were performed. Progress in the past decade, and especially within the past five years, has been exponential, yet much work remains. Spherically symmetric simulations over nearly four decades laid the foundation for this progress. Two-dimensional modeling that assumes axial symmetry is maturing. And three-dimensional modeling, while in its infancy, has begun in earnest. I will present some of the recent work from the ``Oak Ridge'' group, and will discuss this work in the context of the broader work by other researchers in the field. I will then point to future requirements and challenges. Connections with other experimental, observational, and theoretical efforts will be discussed, as well.

Fabricating core (Au)-shell (different stimuli-responsive polymers) nanoparticles via inverse emulsion polymerization: Comparing DOX release behavior in dark room and under NIR lighting.

PubMed

Mazloomi-Rezvani, Mahsa; Salami-Kalajahi, Mehdi; Roghani-Mamaqani, Hossein

2018-06-01

Different core-shell nanoparticles with Au as core and stimuli-responsive polymers such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), poly(N-isopropylacrylamide) (PNIPAAm), poly(N,N'-methylenebis(acrylamide)) (PMBA), poly(2-hydroxyethyl methacrylate) (PHEMA) and poly((2-dimethylamino)ethyl methacrylate) (PDMAEMA) as shells were fabricated via inverse emulsion polymerization. Dynamic light scattering (DLS) was used to investigate particles sizes and particle size distributions and transmission electron microscopy (TEM) was applied to observe the core-shell structure of Au-polymer nanoparticles. Also, surface charge of all samples was studied by measurement of zeta potentials. Synthesized core-shell nanoparticles were utilized as nanocarriers of DOX as anti-cancer drug and drug release behaviors were investigated in dark room and under irradiation of near-infrared (NIR) light. Results showed that all core-shell samples have particle sizes less than 100 nm with narrow particle size distributions. Moreover, amount of drug loading decreased by increasing zeta potential. In dark room, lower pH resulted in higher cumulative drug release due to better solubility of DOX in acidic media. Also, NIR lighting on DOX-loaded samples led to increasing cumulative drug release significantly. However, DOX-loaded Au-PAA and Au-PMAA showed higher drug release at pH = 7.4 compared to 5.3 under NIR lighting. Copyright © 2018 Elsevier B.V. All rights reserved.

Iron Oxide Nanoparticles: Tunable Size Synthesis and Analysis in Terms of the Core-Shell Structure and Mixed Coercive Model

NASA Astrophysics Data System (ADS)

Phong, P. T.; Oanh, V. T. K.; Lam, T. D.; Phuc, N. X.; Tung, L. D.; Thanh, Nguyen T. K.; Manh, D. H.

2017-04-01

Iron oxide nanoparticles (NPs) are currently a very active research field. To date, a comprehensive study of iron oxide NPs is still lacking not only on the size dependence of structural phases but also in the use of an appropriate model. Herein, we report on a systematic study of the structural and magnetic properties of iron oxide NPs prepared by a co-precipitation method followed by hydrothermal treatment. X-ray diffraction and transmission electron microscopy reveal that the NPs have an inverse spinel structure of iron oxide phase (Fe3O4) with average crystallite sizes ( D XRD) of 6-19 nm, while grain sizes ( D TEM) are of 7-23 nm. In addition, the larger the particle size, the closer the experimental lattice constant value is to that of the magnetite structure. Magnetic field-dependent magnetization data and analysis show that the effective anisotropy constants of the Fe3O4 NPs are about five times larger than that of their bulk counterpart. Particle size ( D) dependence of the magnetization and the non-saturating behavior observed in applied fields up to 50 kOe are discussed using the core-shell structure model. We find that with decreasing D, while the calculated thickness of the shell of disordered spins ( t ˜ 0.3 nm) remains almost unchanged, the specific surface areas S a increases significantly, thus reducing the magnetization of the NPs. We also probe the coercivity of the NPs by using the mixed coercive Kneller and Luborsky model. The calculated results indicate that the coercivity rises monotonously with the particle size, and are well matched with the experimental ones.

Fast gradient screening of pharmaceuticals with 5 cm long, narrow bore reversed-phase columns packed with sub-3 μm core-shell and sub-2 μm totally porous particles.

PubMed

Fekete, Szabolcs; Fekete, Jeno

2011-04-15

The performance of 5 cm long narrow-bore columns packed with 2.6-2.7 μm core-shell particles and a column packed with 1.7 μm totally porous particles was compared in very fast gradient separations of polar neutral active pharmaceutical compounds. Peak capacities as a function of flow-rate and gradient time were measured. Peak capacities around 160-170 could be achieved within 25 min with these 5 cm long columns. The highest peak capacity was obtained with the Kinetex column however it was found that as the flow-rate increases, the peak capacity of the new Poroshell-120 column is getting closer to that obtained with the Kinetex column. Considering the column permeability, peak capacity per unit time and per unit pressure was also calculated. In this comparison the advantage of sub-3 μm core-shell particles is more significant compared to sub-2 μm totally porous particles. Moreover it was found that the very similar sized (d(p)=2.7 μm) and structured (ρ=0.63) new Poroshell-120 and the earlier introduced Ascentis Express particles showed different efficiency. Results obtained showed that the 5 cm long narrow bore columns packed with sub-3 μm core-shell particles offer the chance of very fast and efficient gradient separations, thus these columns can be applied for fast screening measurements of routine pharmaceutical analysis such as cleaning validation. Copyright © 2011 Elsevier B.V. All rights reserved.

Coring: a potential problem in eye surgery.

PubMed

Stein, H A; Vu, B L

1994-03-01

Any needle passing through a rubber stopper can aspirate a core of rubber. This rubber may then be injected into the eye or into the retrobulbar or peribulbar space. Aspirates from a number of syringes were spun down in a centrifuge and examined for microscopic particles. All specimens contained microscopic particles even from half-used bottles of Xylocaine.

Portable apparatus for surface evaluation of furniture panels

Treesearch

B. G. Heebink

1963-01-01

In 1959, a new technique was devised at the Forest Products Laboratory that provided a means of examining, evaluating, and recording the show- through pattern (often called telegraphing) of panels made with particle board cores. Although the technique was devised as a working tool to evaluate show-through characteristics of particle board cores, it can be used equally...

Response Surface Methodology for Design of Porous Hollow Sphere Thermal Insulator

NASA Astrophysics Data System (ADS)

Shohani, Nazanin; Pourmahdian, Saeed; Shirkavand Hadavand, Behzad

2017-11-01

In this study, response surface method is used for synthesizing polystyrene (PS) as sacrificial templates and optimizing the particle size. Three factors of initiator, stabilizer concentration and also stirring rate were selected as variable factors. Then, three different concentration of tetraethyl orthosilicate (TEOS) added to reaction media and core-shell structure with PS core and silica shell was developed. Finally, core-shell structure was changed to hollow silica sphere for using as thermal insulator. We observed that increased initiator concentration caused to larger PS particles, increase the stirring rate caused the smaller PS and also with increased the stabilizer concentration obtained that particle size decrease then after 2.5% began to increase. Also the optimum amount of TEOS was found.

Preparation of pH-Responsive Hollow Capsules via Layer-by-Layer Assembly of Exfoliated Layered Double Hydroxide Nanosheets and Polyelectrolytes.

PubMed

Katagiri, Kiyofumi; Shishijima, Yoshinori; Koumoto, Kunihito; Inumaru, Kei

2018-01-01

pH-Responsive smart capsules were developed by the layer-by-layer assembly with a colloidtemplating technique. Polystyrene (PS) particles were employed as core templates. Acid-soluble inorganic nanosheets were prepared from Mg-Al layered double hydroxide (LDH) by an exfoliation technique. LDH nanosheets and anionic polyelectrolytes were alternatively deposited on PS core particles by the layer-by-layer assembly using electrostatic interaction. Hollow capsules were obtained by the removal of the PS core particles. The hollow capsules obtained thus were collapsed at acidic conditions by dissolution of LDH nanosheets in the hollow shells. The dissolution rate, i.e., the responsiveness of capsule, is tunable according to the strength of acids.

Topological Defects in a Living Nematic Ensnare Swimming Bacteria

NASA Astrophysics Data System (ADS)

Genkin, Mikhail M.; Sokolov, Andrey; Lavrentovich, Oleg D.; Aranson, Igor S.

2017-01-01

Active matter exemplified by suspensions of motile bacteria or synthetic self-propelled particles exhibits a remarkable propensity to self-organization and collective motion. The local input of energy and simple particle interactions often lead to complex emergent behavior manifested by the formation of macroscopic vortices and coherent structures with long-range order. A realization of an active system has been conceived by combining swimming bacteria and a lyotropic liquid crystal. Here, by coupling the well-established and validated model of nematic liquid crystals with the bacterial dynamics, we develop a computational model describing intricate properties of such a living nematic. In faithful agreement with the experiment, the model reproduces the onset of periodic undulation of the director and consequent proliferation of topological defects with the increase in bacterial concentration. It yields a testable prediction on the accumulation of bacteria in the cores of +1 /2 topological defects and depletion of bacteria in the cores of -1 /2 defects. Our dedicated experiment on motile bacteria suspended in a freestanding liquid crystalline film fully confirms this prediction. Our findings suggest novel approaches for trapping and transport of bacteria and synthetic swimmers in anisotropic liquids and extend a scope of tools to control and manipulate microscopic objects in active matter.

The contribution of phosphate–phosphate repulsions to the free energy of DNA bending

PubMed Central

Range, Kevin; Mayaan, Evelyn; Maher, L. J.; York, Darrin M.

2005-01-01

DNA bending is important for the packaging of genetic material, regulation of gene expression and interaction of nucleic acids with proteins. Consequently, it is of considerable interest to quantify the energetic factors that must be overcome to induce bending of DNA, such as base stacking and phosphate–phosphate repulsions. In the present work, the electrostatic contribution of phosphate–phosphate repulsions to the free energy of bending DNA is examined for 71 bp linear and bent-form model structures. The bent DNA model was based on the crystallographic structure of a full turn of DNA in a nucleosome core particle. A Green's function approach based on a linear-scaling smooth conductor-like screening model was applied to ascertain the contribution of individual phosphate–phosphate repulsions and overall electrostatic stabilization in aqueous solution. The effect of charge neutralization by site-bound ions was considered using Monte Carlo simulation to characterize the distribution of ion occupations and contribution of phosphate repulsions to the free energy of bending as a function of counterion load. The calculations predict that the phosphate–phosphate repulsions account for ∼30% of the total free energy required to bend DNA from canonical linear B-form into the conformation found in the nucleosome core particle. PMID:15741179

Irradiation effect of low-energy ion on polyurethane nanocoating containing metal oxide nanoparticles

NASA Astrophysics Data System (ADS)

Verma, Jaya; Nigam, Subhasha; Sinha, Surbhi; Sikarwar, B. S.; Bhattacharya, Arpita

2017-12-01

Irradiation effect of low-energy ion beam has been investigated on nanocoating developed with silica, titania and silica-titania core-shell nanoparticles embedded in an organic binder for nanopaint application. In this work, we have taken polyurethane as a model organic binder. Silica nanoparticles have been prepared through sol-gel synthesis with a particle size of 85 nm. Titania and core-shell nanoparticles have been prepared through both sol-gel and peptization process. Particle sizes obtained were 107 nm for titania and 240 nm for core-shell nanoparticles prepared through sol-gel process and 75 nm for TiO2 and 144 nm for core-shell nanoparticles prepared through peptization process. The coating formulations were developed with the above nanoparticles individually and nanoparticle concentration was varied from 1 to 6 wt% and the best performance in terms of hydrophobicity was obtained with 4 wt % of the nanoparticles in polyurethane coating formulation. All the coating formulations prepared were applied on a glass substrate and dried at 100°C. The dry film thickness obtained was around 100 µm in each case. These films dried on glass substrate were irradiated by nitrogen and argon ion beam with energy of 26 keV at fluences of 1014 to 1016 ions/cm2. The anti-algal property of the irradiated samples was improved and hydrophobicity was reduced.

Are annual layers preserved in NorthGRIP Eemian ice?

NASA Astrophysics Data System (ADS)

Kettner, E.; Bigler, M.; Nielsen, M. E.; Steffensen, J. P.; Svensson, A.

2009-04-01

A newly developed setup for continuous flow analysis (CFA) of ice cores in Copenhagen is optimized for high resolution analysis of four components: Soluble sodium (mainly deriving from sea salt), soluble ammonium (related to biological processes and biomass burning events), insoluble dust particles (basically transported from Asian deserts to Greenland), and the electrolytic melt water conductivity (which is a bulk signal for all ionic constituents). Furthermore, we are for the first time implementing a flow cytometer to obtain high quality dust concentration and size distribution profiles based on individual dust particle measurements. Preliminary measurements show that the setup is able to resolve annual layers of 1 cm thickness. Ice flow models predict that annual layers in the Eemian section of the Greenland NorthGRIP ice core (130-115 ka BP) have a thickness of around 1 cm. However, the visual stratigraphy of the ice core indicates that the annual layering in the Eemian section may be disturbed by micro folds and rapid crystal growth. In this case study we will measure the impurity content of an Eemian segment of the NorthGRIP ice core with the new CFA setup. This will allow for a comparison to well-known impurity levels of the Holocene in both Greenland and Antarctic ice and we will attempt to determine if annual layers are still present in the ice.

Photophysical Properties of II-VI Semiconductor Nanocrystals

NASA Astrophysics Data System (ADS)

Gong, Ke

As it is well known, semiconductor nanocrystals (also called quantum dots, QDs) are being actively pursued for use in many different types of luminescent optical materials. These materials include the active media for luminescence downconversion in artificial lighting, lasers, luminescent solar concentrators and many other applications. Chapter 1 gives general introduction of QDs, which describe the basic physical properties and optical properties. Based on the experimental spectroscopic study, a semiquantitative method-effective mass model is employed to give theoretical prediction and guide. The following chapters will talks about several topics respectively. A predictive understanding of the radiative lifetimes is therefore a starting point for the understanding of the use of QDs for these applications. Absorption intensities and radiative lifetimes are fundamental properties of any luminescent material. Meantime, achievement of high efficiency with high working temperature and heterostructure fabrication with manipulation of lattice strain are not easy and need systematic investigation. To make accurate connections between extinction coefficients and radiative recombination rates, chapter 2 will consider three closely related aspects of the size dependent spectroscopy of II-VI QDs. First, it will consider the existing literature on cadmium selenide (CdSe) QD absorption spectra and extinction coefficients. From these results and fine structure considerations Boltzmann weighted radiative lifetimes are calculated. These lifetimes are compared to values measured on very high quality CdSe and CdSe coated with zinc selenide (ZnSe) shells. Second, analogous literature data are analyzed for cadmium telluride (CdTe) nanocrystals and compared to lifetimes measured for very high quality QDs. Furthermore, studies of the absorption and excitation spectra and measured radiative lifetimes for CdTe/CdSe Type-II core/shell QDs are reported. These results are also analyzed in terms of a Boltzmann population of exciton sublevels and calculated electron and hole wave functions. Much of the absorption data and fine structure calculations are already in the literature. These results are combined with new measurements of radiative lifetimes and electron-hole overlap calculations to produce an integrated picture of the II-VI QD spectroscopic fundamentals. Finally, we adopt recent synthetic advances to make very monodisperse zincblende CdSe/CdS quantum dots having near-unity photoluminescence quantum yields (PLQYs). Due the absence of nonradiative decay pathways, accurate values of the radiative lifetimes can be obtained from time resolved PL measurements. Radiative lifetimes can also be obtained from the Einstein relations, using the static absorption spectra and the relative thermal populations in the angular momentum sublevels. One of the inputs into these calculations is the shell thickness, and it is useful to be able to determine shell thickness from spectroscopic measurements. We use an empirically corrected effective mass model to produce a "map" of exciton wavelength as a function of core size and shell thickness. These calculations use an elastic continuum model and the known lattice and elastic constants to include the effect of lattice strain on the band gap energy. Radiative lifetimes calculated both experimentally and theoretically are checked and the size dependence is compared to previous studied Type-I, II and single component particles. However, it is not enough to just understanding these basic photophysics of absorption and emission. The emission intensities (related to QYs) also change with changes of the temperature. The temperature dependent PLs of II-VI QDs is extensively studied, but most of this work is at low temperatures. Temperatures well above ambient are of interest to lighting applications and in this regime both the reversible and irreversible loss of quantum yield (thermal quenching) are serious impediments to the implementation of QDs in commercial devices. Chapter 3 will elucidate the mechanism of static thermal quenching, in which the reduction of QYs does not affect the PL decay kinetics, on CdSe, CdTe and CdSe/ZnSe QDs as a function of particle sizes/shapes, surface composition and surface ligands. Through systematic experiments, this part of the dissertation discusses several possible mechanisms (e.g. structural, activated excited state, and electronic charging) and examines which the dominant cause for loss of QY at high temperature is. The more practical step is to develop the synthetic method of highly luminescent and stable core/shell QDs with minimum thermal quenching, which greatly enhance the energy efficiency of light emitting and photovoltaic devices. As the nonradiative Auger processed are induced by surface charging described in chapter 3, static and time-resolved fluorescence and high and low power transient absorption results on CdSe/CdS and CdSe/ZnSe core/shell particles are presented in chapter 4. Two CdS shell thicknesses were examined and all of the particles had either octadecylamine (ODA) and tributylphosphine (TBP) or just ODA ligands. The results can be understood in terms of a mechanism in which there is a thermal equilibrium between electrons being in the valence band or in chalcogenide localized surface states. Thermal promotion of a valence band electron to a surface state leaves the particle core positively charged. Photon absorption when the particle is in this state results in a positive trion, which undergoes a fast Auger recombination, making the particle nonluminescent. A lack of TBP ligands results in more empty surface orbitals and therefore shifts the equilibrium toward surface trapped electrons and hence trion formation. Low- and high-power transient absorption measurements give the trion and biexciton lifetimes and the ratio of the trion to biexciton Auger lifetimes are examined and compared to the degeneracies of Auger pathways. We also study the shell thickness and composition dependence of Auger times, which is compared to the scaling factors of effective volume and electron-hole overlap considerations. Core/shell QDs often exhibit much higher luminescence quantum yields (QYs), more stability, and are depicted as having a nearly spherical core and a shell of very nearly uniform thickness, which results in a very simple picture of surface passivation. The uniformity of the shell is crucial in obtaining QDs with well passivated surfaces. However, transmission electron microscope (TEM) images disprove the ideal situation. Defects and thickness inhomogeneity in shell materials are treated qualitatively as an analog to film thickness inhomogeneity in epitaxially grown thin films. More quantitatively, the extent to which the shell thickness of core/shell particles is constant can be determined by time-resolved PL studies that measure the dynamics of hole tunneling to acceptors that are adsorbed on the shell surface due that tunneling rates varies strongly with core-acceptor separation. Careful analysis of the hole transfer kinetics reveals the extent of shell thickness inhomogeneity, however, it may be complicated by the distribution of numbers of adsorbed acceptors. All the considerations can be incorporated into a model we establish in Chapter 5for the distribution of measured hole tunneling rates. From this analysis the distribution of shell thicknesses can be extracted from the luminescence kinetic results. This approach is therefore a sensitive measure of the distribution of tunneling distances. Thus, any defects or structural irregularities that allow the hole acceptors to adsorb closer to the particle core increases the hole tunneling rate and can be detected and quantified. A quantitative treatment of the lattice strain energy in determining the shell morphology of CdSe/CdS core/shell nanoparticles is presented in chapter 5. We use the inhomogeneity in hole tunneling rates through the shell to adsorbed hole acceptors to quantify the extent of shell thickness inhomogeneity. The results can be understood in terms of a model based on elastic continuum calculations, which indicate that the lattice strain energy depends on both core size and shell thickness. This model assumes thermodynamic equilibrium, i.e., that the shell morphology corresponds to a minimum total (lattice strain plus surface) energy. Comparison with the experimental results indicates that CdSe/CdS nanoparticles undergo an abrupt transition from smooth to rough shells when the total lattice strain energy exceeds about 27eV or the strain energy density exceeds 0.59 eV/nm2. The predictions of this model are not followed for CdSe/CdS nanoparticles when the shell is deposited at very low temperature and therefore equilibrium is not established. The effects of lattice strain on the spectroscopy and photoluminescence quantum yields of zincblende CdSe/CdS core/shell quantum dots are examined. The quantum yields are measured as a function of core size and shell thickness. High quantum yields are achieved as long as the lattice strain energy density is below ~0.85 eV/nm2, which is considerably greater than the limiting value of 0.59 eV/nm2 for thermodynamicstability of a smooth, defect free shell, as previously reported in chapter 5. Thus, core/shell quantum dots having strain energy densities between 0.59 and 0.85 eV/nm2 can have very high PL QYs, but are metastable with respect to surface defect formation. Such metastable core/shell QDs can be produced by shell deposition at comparatively low temperatures (< 140 °C). Annealing of these particles causes partial loss of core pressure, and a red shift of the spectrum.

The influence of different black carbon and sulfate mixing methods on their optical and radiative properties

NASA Astrophysics Data System (ADS)

Zhang, Hua; Zhou, Chen; Wang, Zhili; Zhao, Shuyun; Li, Jiangnan

2015-08-01

Three different internal mixing methods (Core-Shell, Maxwell-Garnett, and Bruggeman) and one external mixing method are used to study the impact of mixing methods of black carbon (BC) with sulfate aerosol on their optical properties, radiative flux, and heating rate. The optical properties of a mixture of BC and sulfate aerosol particles are considered for three typical bands. The results show that mixing methods, the volume ratio of BC to sulfate, and relative humidity have a strong influence on the optical properties of mixed aerosols. Compared to internal mixing, external mixing underestimates the particle mass absorption coefficient by 20-70% and the particle mass scattering coefficient by up to 50%, whereas it overestimates the particle single scattering albedo by 20-50% in most cases. However, the asymmetry parameter is strongly sensitive to the equivalent particle radius, but is only weakly sensitive to the different mixing methods. Of the internal methods, there is less than 2% difference in all optical properties between the Maxwell-Garnett and Bruggeman methods in all bands; however, the differences between the Core-Shell and Maxwell-Garnett/Bruggeman methods are usually larger than 15% in the ultraviolet and visible bands. A sensitivity test is conducted with the Beijing Climate Center Radiation transfer model (BCC-RAD) using a simulated BC concentration that is typical of east-central China and a sulfate volume ratio of 75%. The results show that the internal mixing methods could reduce the radiative flux more effectively because they produce a higher absorption. The annual mean instantaneous radiative force due to BC-sulfate aerosol is about -3.18 W/m2 for the external method and -6.91 W/m2 for the internal methods at the surface, and -3.03/-1.56/-1.85 W/m2 for the external/Core-Shell/(Maxwell-Garnett/Bruggeman) methods, respectively, at the tropopause.

Accelerating Pseudo-Random Number Generator for MCNP on GPU

NASA Astrophysics Data System (ADS)

Gong, Chunye; Liu, Jie; Chi, Lihua; Hu, Qingfeng; Deng, Li; Gong, Zhenghu

2010-09-01

Pseudo-random number generators (PRNG) are intensively used in many stochastic algorithms in particle simulations, artificial neural networks and other scientific computation. The PRNG in Monte Carlo N-Particle Transport Code (MCNP) requires long period, high quality, flexible jump and fast enough. In this paper, we implement such a PRNG for MCNP on NVIDIA's GTX200 Graphics Processor Units (GPU) using CUDA programming model. Results shows that 3.80 to 8.10 times speedup are achieved compared with 4 to 6 cores CPUs and more than 679.18 million double precision random numbers can be generated per second on GPU.

Nucleon matter equation of state, particle number fluctuations, and shear viscosity within UrQMD box calculations

NASA Astrophysics Data System (ADS)

Motornenko, A.; Bravina, L.; Gorenstein, M. I.; Magner, A. G.; Zabrodin, E.

2018-03-01

Properties of equilibrated nucleon system are studied within the ultra-relativistic quantum molecular dynamics (UrQMD) transport model. The UrQMD calculations are done within a finite box with periodic boundary conditions. The system achieves thermal equilibrium due to nucleon-nucleon elastic scattering. For the UrQMD-equilibrium state, nucleon energy spectra, equation of state, particle number fluctuations, and shear viscosity η are calculated. The UrQMD results are compared with both, statistical mechanics and Chapman-Enskog kinetic theory, for a classical system of nucleons with hard-core repulsion.

Chlorophyll Proteins of Photosystem I 1

PubMed Central

Mullet, John E.; Burke, John J.; Arntzen, Charles J.

1980-01-01

Data are presented which suggest the existence of a light-harvesting pigment-protein complex which is functionally and structurally associated with photosystem I (PSI) reaction centers. These observations are based on techniques which allow isolation of PSI using minimal concentrations of Triton X-100. Properties of density and self aggregation allowed purification of a “native” PSI complex. The isolated PSI particles appear as 106 Å spherical subunits when viewed by freeze fracture microscopy. When incorporated into phosphatidyl choline vesicles, the particles lose self-aggregation properties and disperse uniformly within the lipid membrane. The isolated PSI preparation contains 100 ± 10 chlorophylls/P700 (Chl a/b ratio greater than 18); this represents a recovery of 27% of the original chloroplast membrane Chl. These particles were enriched in Chl a forms absorbing at 701 to 710 nm. Chl fluorescence at room temperature exhibited a maximum at 690 nm with a pronounced shoulder at 710 nm. At 77 K, peak fluorescence emission was at 736 nm; in the presence of dithionite an additional fluorescence maximum at 695 nm was obtained at 77 K. This dual fluorescence emission peak for the PSI particles is evidence for at least two Chl populations within the PSI membrane subunit. The fluorescence emission observed at 695 nm was identified as arising from the core of PSI which contains 40 Chl/P700 (PSI-40). This core complex, derived from native PSI particles, was enriched in Chl a absorbing at 680 and 690 nm and fluorescing with maximal emission at 694 nm at 77 K. PSI particles consisting of the PSI core complex plus 20 to 25 Chl antennae (65 Chl/P700) could also be derived from native PSI complexes. These preparations were enriched in Chl a forms absorbing at 697 nm and exhibited a 77 K fluorescence emission maximum at 722 nm. A comparison of native PSI particles which contain 110 Chl/P700 (PSI-110) and PSI particles containing 65 Chl/P700 (PSI-65) provides evidence for the existence of a peripheral Chl-protein complex tightly associated in the native PSI complex. The native PSI subunits contain polypeptides of 22,500 to 24,500 daltons which are not found in the PSI-65 or PSI-40 subfractions. It is suggested that these polypeptides function to bind 40 to 45 Chl per structural complex, including the Chl which emits fluorescence at 736 nm. A model for the organization of Chl forms is presented in which the native PSI membrane subunit consists of a reaction center core complex plus two regions of associated light-harvesting antennae. The presence of energy “sinks” within the antennae is discussed. Images PMID:16661288

Neutron-gamma flux and dose calculations in a Pressurized Water Reactor (PWR)

NASA Astrophysics Data System (ADS)

Brovchenko, Mariya; Dechenaux, Benjamin; Burn, Kenneth W.; Console Camprini, Patrizio; Duhamel, Isabelle; Peron, Arthur

2017-09-01

The present work deals with Monte Carlo simulations, aiming to determine the neutron and gamma responses outside the vessel and in the basemat of a Pressurized Water Reactor (PWR). The model is based on the Tihange-I Belgian nuclear reactor. With a large set of information and measurements available, this reactor has the advantage to be easily modelled and allows validation based on the experimental measurements. Power distribution calculations were therefore performed with the MCNP code at IRSN and compared to the available in-core measurements. Results showed a good agreement between calculated and measured values over the whole core. In this paper, the methods and hypotheses used for the particle transport simulation from the fission distribution in the core to the detectors outside the vessel of the reactor are also summarized. The results of the simulations are presented including the neutron and gamma doses and flux energy spectra. MCNP6 computational results comparing JEFF3.1 and ENDF-B/VII.1 nuclear data evaluations and sensitivity of the results to some model parameters are presented.

Characterization of the stability and folding of H2A.Z chromatin particles: implications for transcriptional activation.

PubMed

Abbott, D W; Ivanova, V S; Wang, X; Bonner, W M; Ausió, J

2001-11-09

H2A.Z and H2A.1 nucleosome core particles and oligonucleosome arrays were obtained using recombinant versions of these histones and a native histone H2B/H3/H4 complement reconstituted onto appropriate DNA templates. Analysis of the reconstituted nucleosome core particles using native polyacrylamide gel electrophoresis and DNase I footprinting showed that H2A.Z nucleosome core particles were almost structurally indistinguishable from its H2A.1 or native chicken erythrocyte counterparts. While this result is in good agreement with the recently published crystallographic structure of the H2A.Z nucleosome core particle (Suto, R. K., Clarkson, M J., Tremethick, D. J., and Luger, K. (2000) Nat. Struct. Biol. 7, 1121-1124), the ionic strength dependence of the sedimentation coefficient of these particles exhibits a substantial destabilization, which is most likely the result of the histone H2A.Z-H2B dimer binding less tightly to the nucleosome. Analytical ultracentrifuge analysis of the H2A.Z 208-12, a DNA template consisting of 12 tandem repeats of a 208-base pair sequence derived from the sea urchin Lytechinus variegatus 5 S rRNA gene, reconstituted oligonucleosome complexes in the absence of histone H1 shows that their NaCl-dependent folding ability is significantly reduced. These results support the notion that the histone H2A.Z variant may play a chromatin-destabilizing role, which may be important for transcriptional activation.

Annually resolved Holocene record of dust deposition and size distribution from the South Pole

NASA Astrophysics Data System (ADS)

Chesler, A.; Koffman, B. G.; Kreutz, K. J.; Osterberg, E. C.; Winski, D.; Ferris, D. G.; Cole-Dai, J.; Wells, M. L.; Handley, M.

2017-12-01

Ice cores offer insights into past changes in atmospheric composition and circulation at high temporal resolution. Dust particles preserved in ice cores provide information regarding the atmospheric burden of dust and associated trace elements, changes in atmospheric circulation, and variations in the climates of dust-producing regions. Well resolved ice core dust records, therefore, can be used to gain a better understanding of the dynamics affecting ocean overturning circulation, to constrain atmospheric nutrient deposition to ocean ecosystems, and to assess atmospheric albedo variations. Existing Antarctic ice core dust records are generally either low-resolution and long-duration (glacial/interglacial timescale), or high-resolution and short-duration (past 2400 years), but high-resolution and long-duration records are rare. Here we present a continuous high-resolution record of dust deposition, including particle size distribution (PSD) and concentration, from the South Pole Ice (SPICE) Core, the first Holocene dust record from this location. The SPICE core was drilled during 2014-2016, reaching a depth of 1751 m. Cores were melted and analyzed for particles (1.0-12 µm diameter) using a continuous-flow Abakus laser particle sensor at Dartmouth College. The current SPICE Core chronology is based on: 1) visual stratigraphy from 0-10.2 ka and 2) correlations to the IceCube dust log calibration beyond 10.2 ka. Annual layer counts of Mg, dust (1.0 µm and 2.4 µm), Na, and SO4 demonstrate that the dust record is annually resolved through most of the Holocene ( 10.3 ka), allowing us to assess dust/climate relationships at high temporal resolution. We use meteorological and reanalysis data to understand modern drivers of observed variability in particle concentration and size distribution, and compare the new SPICE dust record to available Antarctic dust records including from EPICA Dome C, WAIS Divide, Taylor Dome, Taylor Glacier, Talos Dome, Siple Dome, and EPICA Dronning Maud Land. Interpretations of the SPICE dust record will be used to improve understanding of dust emissions, transport and deposition processes, and dust/climate relationships, through the Holocene.

Topological defects in a living nematic ensnare swimming bacteria [Linking bacterial motility and liquid crystallinity in a model of living nematic

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

Genkin, Mikhail Mikhailovich; Sokolov, Andrey; Lavrentovich, Oleg D.

Active matter exemplified by suspensions of motile bacteria or synthetic self-propelled particles exhibits a remarkable propensity to self-organization and collective motion. The local input of energy and simple particle interactions often lead to complex emergent behavior manifested by the formation of macroscopic vortices and coherent structures with long-range order. A realization of an active system has been conceived by combining swimming bacteria and a lyotropic liquid crystal. Here, by coupling the well-established and validated model of nematic liquid crystals with the bacterial dynamics, we develop a computational model describing intricate properties of such a living nematic. In faithful agreement withmore » the experiment, the model reproduces the onset of periodic undulation of the director and consequent proliferation of topological defects with the increase in bacterial concentration. It yields a testable prediction on the accumulation of bacteria in the cores of +1/2 topological defects and depletion of bacteria in the cores of -1/2 defects. Our dedicated experiment on motile bacteria suspended in a freestanding liquid crystalline film fully confirms this prediction. Lastly, our findings suggest novel approaches for trapping and transport of bacteria and synthetic swimmers in anisotropic liquids and extend a scope of tools to control and manipulate microscopic objects in active matter.« less

Topological defects in a living nematic ensnare swimming bacteria [Linking bacterial motility and liquid crystallinity in a model of living nematic

DOE PAGES

Genkin, Mikhail Mikhailovich; Sokolov, Andrey; Lavrentovich, Oleg D.; ...

2017-03-08

Active matter exemplified by suspensions of motile bacteria or synthetic self-propelled particles exhibits a remarkable propensity to self-organization and collective motion. The local input of energy and simple particle interactions often lead to complex emergent behavior manifested by the formation of macroscopic vortices and coherent structures with long-range order. A realization of an active system has been conceived by combining swimming bacteria and a lyotropic liquid crystal. Here, by coupling the well-established and validated model of nematic liquid crystals with the bacterial dynamics, we develop a computational model describing intricate properties of such a living nematic. In faithful agreement withmore » the experiment, the model reproduces the onset of periodic undulation of the director and consequent proliferation of topological defects with the increase in bacterial concentration. It yields a testable prediction on the accumulation of bacteria in the cores of +1/2 topological defects and depletion of bacteria in the cores of -1/2 defects. Our dedicated experiment on motile bacteria suspended in a freestanding liquid crystalline film fully confirms this prediction. Lastly, our findings suggest novel approaches for trapping and transport of bacteria and synthetic swimmers in anisotropic liquids and extend a scope of tools to control and manipulate microscopic objects in active matter.« less

Manipulation of metal-dielectric core-shell particles in optical fields

NASA Astrophysics Data System (ADS)

Chvátal, Lukáš; Šiler, Martin; Zemánek, Pavel

2014-12-01

Metal-dielectric core-shell particles represent promising tools in nanoplasmonics. In combination with optical tweezers they can be manipulated in a contactless way through fluid and their plasmonic properties can be used to probe or modify the local environment. We perform a numerical parametric study to find the particle geometry and material parameters under which such particle can be stably confined in optical tweezers. We use the theory based on Mie scattering in the focal field of an ideal water immersion objective of numerical aperture NA=1.2. For very thin metal layers we find that strong trapping on the optical axis can be achieved.

On the Internal Structure of Bacteriophage Lambda

PubMed Central

Kaiser, A. D.

1966-01-01

The structure of bacteriophage lambda has been studied by electron microscopy of negatively stained particles. The phage particles will eject their DNA if they are heated or dialyzed against a chelating agent. The ghost particles, so formed, have a channel running down their tails. Since the channel is not visible in normal particles, the channel may be filled with part of the DNA molecule. Up to 30% of the ghosts contain round objects about half the internal diameter of the head. The round objects, called "cores," have the same buoyant density as the coat protein. The core may be a protein spool about which the phage DNA is wound. PMID:5967429

Chemical compositions of black carbon particle cores and coatings via soot particle aerosol mass spectrometry with photoionization and electron ionization.

PubMed

Canagaratna, Manjula R; Massoli, Paola; Browne, Eleanor C; Franklin, Jonathan P; Wilson, Kevin R; Onasch, Timothy B; Kirchstetter, Thomas W; Fortner, Edward C; Kolb, Charles E; Jayne, John T; Kroll, Jesse H; Worsnop, Douglas R

2015-05-14

Black carbon is an important constituent of atmospheric aerosol particle matter (PM) with significant effects on the global radiation budget and on human health. The soot particle aerosol mass spectrometer (SP-AMS) has been developed and deployed for real-time ambient measurements of refractory carbon particles. In the SP-AMS, black carbon or metallic particles are vaporized through absorption of 1064 nm light from a CW Nd:YAG laser. This scheme allows for continuous "soft" vaporization of both core and coating materials. The main focus of this work is to characterize the extent to which this vaporization scheme provides enhanced chemical composition information about aerosol particles. This information is difficult to extract from standard SP-AMS mass spectra because they are complicated by extensive fragmentation from the harsh 70 eV EI ionization scheme that is typically used in these instruments. Thus, in this work synchotron-generated vacuum ultraviolet (VUV) light in the 8-14 eV range is used to measure VUV-SP-AMS spectra with minimal fragmentation. VUV-SP-AMS spectra of commercially available carbon black, fullerene black, and laboratory generated flame soots were obtained. Small carbon cluster cations (C(+)-C5(+)) were found to dominate the VUV-SP-AMS spectra of all the samples, indicating that the corresponding neutral clusters are key products of the SP vaporization process. Intercomparisons of carbon cluster ratios observed in VUV-SP-AMS and SP-AMS spectra are used to confirm spectral features that could be used to distinguish between different types of refractory carbon particles. VUV-SP-AMS spectra of oxidized organic species adsorbed on absorbing cores are also examined and found to display less thermally induced decomposition and fragmentation than spectra obtained with thermal vaporization at 200 °C (the minimum temperature needed to quantitatively vaporize ambient oxidized organic aerosol with a continuously heated surface). The particle cores tested in these studies include black carbon, silver, gold, and platinum nanoparticles. These results demonstrate that SP vaporization is capable of providing enhanced organic chemical composition information for a wide range of organic coating materials and IR absorbing particle cores. The potential of using this technique to study organic species of interest in seeded laboratory chamber or flow reactor studies is discussed.

Results of the Simulation of the HTR-Proteus Core 4.2 Using PEBBED-COMBINE: FY10 Report

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

Hans Gougar

2010-07-01

ABSTRACT The Idaho National Laboratory’s deterministic neutronics analysis codes and methods were applied to the computation of the core multiplication factor of the HTR-Proteus pebble bed reactor critical facility. This report is a follow-on to INL/EXT-09-16620 in which the same calculation was performed but using earlier versions of the codes and less developed methods. In that report, results indicated that the cross sections generated using COMBINE-7.0 did not yield satisfactory estimates of keff. It was concluded in the report that the modeling of control rods was not satisfactory. In the past year, improvements to the homogenization capability in COMBINE havemore » enabled the explicit modeling of TRIS particles, pebbles, and heterogeneous core zones including control rod regions using a new multi-scale version of COMBINE in which the 1-dimensional discrete ordinate transport code ANISN has been integrated. The new COMBINE is shown to yield benchmark quality results for pebble unit cell models, the first step in preparing few-group diffusion parameters for core simulations. In this report, the full critical core is modeled once again but with cross sections generated using the capabilities and physics of the improved COMBINE code. The new PEBBED-COMBINE model enables the exact modeling of the pebbles and control rod region along with better approximation to structures in the reflector. Initial results for the core multiplication factor indicate significant improvement in the INL’s tools for modeling the neutronic properties of a pebble bed reactor. Errors on the order of 1.6-2.5% in keff are obtained; a significant improvement over the 5-6% error observed in the earlier This is acceptable for a code system and model in the early stages of development but still too high for a production code. Analysis of a simpler core model indicates an over-prediction of the flux in the low end of the thermal spectrum. Causes of this discrepancy are under investigation. New homogenization techniques and assumptions were used in this analysis and as such, they require further confirmation and validation. Further refinement and review of the complex Proteus core model are likely to reduce the errors even further.« less

Proton-hole and core-excited states in the semi-magic nucleus 131In82

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

Taprogge, J.; Jungclaus, A.; Grawe, H.

2016-11-01

The decay of the N = 83 nucleus Cd-131 has been studied at the RIBF facility at the RIKEN Nishina Center. The main purpose of the study was to identify the position of the and proton-hole states and the energies of core-excited configurations in the semi-magic nucleus In-131. From the radiation emitted following the decay, a level scheme of In-131 was established and the feeding to each excited state determined. Similarities between the single-particle transitions observed in the decays of the N = 83 isotones In-132 and Cd-131 are discussed. Finally the excitation energies of several core-excited configurations in In-131more » are compared to QRPA and shell-model calculations.« less

A Melting Layer Model for Passive/Active Microwave Remote Sensing Applications. Part 1; Model Formulation and Comparison with Observations

NASA Technical Reports Server (NTRS)

Olson, William S.; Bauer, Peter; Viltard, Nicolas F.; Johnson, Daniel E.; Tao, Wei-Kuo

2000-01-01

In this study, a 1-D steady-state microphysical model which describes the vertical distribution of melting precipitation particles is developed. The model is driven by the ice-phase precipitation distributions just above the freezing level at applicable gridpoints of "parent" 3-D cloud-resolving model (CRM) simulations. It extends these simulations by providing the number density and meltwater fraction of each particle in finely separated size categories through the melting layer. The depth of the modeled melting layer is primarily determined by the initial material density of the ice-phase precipitation. The radiative properties of melting precipitation at microwave frequencies are calculated based upon different methods for describing the dielectric properties of mixed phase particles. Particle absorption and scattering efficiencies at the Tropical Rainfall Measuring Mission Microwave Imager frequencies (10.65 to 85.5 GHz) are enhanced greatly for relatively small (approx. 0.1) meltwater fractions. The relatively large number of partially-melted particles just below the freezing level in stratiform regions leads to significant microwave absorption, well-exceeding the absorption by rain at the base of the melting layer. Calculated precipitation backscatter efficiencies at the Precipitation Radar frequency (13.8 GHz) increase in proportion to the particle meltwater fraction, leading to a "bright-band" of enhanced radar reflectivities in agreement with previous studies. The radiative properties of the melting layer are determined by the choice of dielectric models and the initial water contents and material densities of the "seeding" ice-phase precipitation particles. Simulated melting layer profiles based upon snow described by the Fabry-Szyrmer core-shell dielectric model and graupel described by the Maxwell-Garnett water matrix dielectric model lead to reasonable agreement with radar-derived melting layer optical depth distributions. Moreover, control profiles that do not contain mixed-phase precipitation particles yield optical depths that are systematically lower than those observed. Therefore, the use of the melting layer model to extend 3-D CRM simulations appears justified, at least until more realistic spectral methods for describing melting precipitation in high-resolution, 3-D CRM's are implemented.

Superficially Porous Particles with 1000 Å Pores for Large Biomolecule High Performance Liquid Chromatography and Polymer Size Exclusion Chromatography

PubMed Central

Wagner, Brian M.; Schuster, Stephanie A.; Boyes, Barry E.; Shields, Taylor J.; Miles, William L.; Haynes, Mark J.; Moran, Robert E.; Kirkland, Joseph J.; Schure, Mark R.

2017-01-01

To facilitate mass transport and column efficiency, solutes must have free access to particle pores to facilitate interactions with the stationary phase. To ensure this feature, particles should be used for HPLC separations which have pores sufficiently large to accommodate the solute without restricted diffusion. This paper describes the design and properties of superficially porous (also called Fused-Core®, core shell or porous shell) particles with very large (1000 Å) pores specifically developed for separating very large biomolecules and polymers. Separations of DNA fragments, monoclonal antibodies, large proteins and large polystyrene standards are used to illustrate the utility of these particles for efficient, high-resolution applications. PMID:28213987

Superficially porous particles with 1000Å pores for large biomolecule high performance liquid chromatography and polymer size exclusion chromatography.

PubMed

Wagner, Brian M; Schuster, Stephanie A; Boyes, Barry E; Shields, Taylor J; Miles, William L; Haynes, Mark J; Moran, Robert E; Kirkland, Joseph J; Schure, Mark R

2017-03-17

To facilitate mass transport and column efficiency, solutes must have free access to particle pores to facilitate interactions with the stationary phase. To ensure this feature, particles should be used for HPLC separations which have pores sufficiently large to accommodate the solute without restricted diffusion. This paper describes the design and properties of superficially porous (also called Fused-Core ® , core shell or porous shell) particles with very large (1000Å) pores specifically developed for separating very large biomolecules and polymers. Separations of DNA fragments, monoclonal antibodies, large proteins and large polystyrene standards are used to illustrate the utility of these particles for efficient, high-resolution applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Changes in particle transport as a result of resonant magnetic perturbations in DIII-D

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

Mordijck, S.; Doyle, E. J.; Rhodes, T. L.

2012-05-15

In this paper, we introduce the first direct perturbed particle transport measurements in resonant magnetic perturbation (RMP) H-mode plasmas. The perturbed particle transport increases as a result of application of RMP deep into the core. In the core, a large reduction in E Multiplication-Sign B shear to a value below the linear growth rate, in conjunction with increasing density fluctuations, is consistent with an increase in turbulent particle transport. In the edge, the changes in turbulent particle transport are less obvious. There is a clear correlation between the linear growth rates and the density fluctuations measured at different scales, butmore » it is uncertain which is the cause and which is the consequence.« less

Changes in particle transport as a result of resonant magnetic perturbations in DIII-D

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

Mordijck, S.; Doyle, E. J.; McKee, G. R.

2012-01-01

In this paper, we introduce the first direct perturbed particle transport measurements in resonant magnetic perturbation (RMP) H-mode plasmas. The perturbed particle transport increases as a result of application of RMP deep into the core. In the core, a large reduction in E x B shear to a value below the linear growth rate, in conjunction with increasing density fluctuations, is consistent with an increase in turbulent particle transport. In the edge, the changes in turbulent particle transport are less obvious. There is a clear correlation between the linear growth rates and the density fluctuations measured at different scales, butmore » it is uncertain which is the cause and which is the consequence.« less

Repetitive heterocoagulation of oppositely charged particles for enhancement of magnetic nanoparticle loading into monodisperse silica particles.

PubMed

Matsumoto, Hideki; Nagao, Daisuke; Konno, Mikio

2010-03-16

Oppositely charged particles were repetitively heterocoagulated to fabricate highly monodisperse magnetic silica particles with high loading of magnetic nanoparticles. Positively charged magnetic nanoparticles prepared by surface modification with N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TSA) were used to heterocoagulate with silica particles under basic conditions to give rise to negative silica surface charge and prevent the oxidation of the magnetic nanoparticles. The resultant particles of silica core homogeneously coated with the magnetic nanoparticles were further coated with thin silica layer with sodium silicate in order to enhance colloidal stability and avoid desorption of the magnetic nanoparticles from the silica cores. Five repetitions of the heterocoagulation and the silica coating could increase saturation magnetization of the magnetic silica particles to 27.7 emu/g, keeping the coefficient of variation of particle sizes (C(V)) less than 6.5%. Highly homogeneous loading of the magnetic component was confirmed by measuring Fe-to-Si atomic ratios of individual particles with energy dispersive X-ray spectroscopy.

Structure of Immune Stimulating Complex Matrices and Immune Stimulating Complexes in Suspension Determined by Small-Angle X-Ray Scattering

PubMed Central

Pedersen, Jan Skov; Oliveira, Cristiano L.P.; Hübschmann, Henriette Baun; Arleth, Lise; Manniche, Søren; Kirkby, Nicolai; Nielsen, Hanne Mørck

2012-01-01

Immune stimulating complex (ISCOM) particles consisting of a mixture of Quil-A, cholesterol, and phospholipids were structurally characterized by small-angle x-ray scattering (SAXS). The ISCOM particles are perforated vesicles of very well-defined structures. We developed and implemented a novel (to our knowledge) modeling method based on Monte Carlo simulation integrations to describe the SAXS data. This approach is similar to the traditional modeling of SAXS data, in which a structure is assumed, the scattering intensity is calculated, and structural parameters are optimized by weighted least-squares methods when the model scattering intensity is fitted to the experimental data. SAXS data from plain ISCOM matrix particles in aqueous suspension, as well as those from complete ISCOMs (i.e., with an antigen (tetanus toxoid) incorporated) can be modeled as a polydisperse distribution of perforated bilayer vesicles with icosahedral, football, or tennis ball structures. The dominating structure is the tennis ball structure, with an outer diameter of 40 nm and with 20 holes 5–6 nm in diameter. The lipid bilayer membrane is 4.6 nm thick, with a low-electron-density, 2.0-nm-thick hydrocarbon core. Surprisingly, in the ISCOMs, the tetanus toxoid is located just below the membrane inside the particles. PMID:22677391

Highly temperature responsive core-shell magnetic particles: synthesis, characterization and colloidal properties.

PubMed

Rahman, Md Mahbubor; Chehimi, Mohamed M; Fessi, Hatem; Elaissari, Abdelhamid

2011-08-15

Temperature responsive magnetic polymer submicron particles were prepared by two step seed emulsion polymerization process. First, magnetic seed polymer particles were obtained by emulsion polymerization of styrene using potassium persulfate (KPS) as an initiator and divinylbenzne (DVB) as a cross-linker in the presence of oil-in-water magnetic emulsion (organic ferrofluid droplets). Thereafter, DVB cross-linked magnetic polymer particles were used as seed in the precipitation polymerization of N-isopropylacrylamide (NIPAM) to induce thermosensitive PNIPAM shell onto the hydrophobic polymer surface of the cross-linked magnetic polymer particles. To impart cationic functional groups in the thermosensitive PNIPAM backbone, the functional monomer aminoethylmethacrylate hydrochloride (AEMH) was used to polymerize with NIPAM while N,N'-methylenebisacrylamide (MBA) and 2, 2'-azobis (2-methylpropionamidine) dihydrochloride (V-50) were used as a cross-linker and as an initiator respectively. The effect of seed to monomer (w/w) ratio along with seed nature on the final particle morphology was investigated. Dynamic light scattering (DLS) results demonstrated particles swelling at below volume phase transition temperature (VPTT) and deswelling above the VPTT. The perfect core (magnetic) shell (polymer) structure of the particles prepared was confirmed by Transmission Electron Microscopy (TEM). The chemical composition of the particles were determined by thermogravimetric analysis (TGA). The effect of temperature, pH, ionic strength on the colloidal properties such as size and zeta potential of the micron sized thermo-sensitive magnetic particles were also studied. In addition, a short mechanistic discussion on the formation of core-shell morphology of magnetic polymer particles has also been discussed. Copyright © 2011 Elsevier Inc. All rights reserved.

Phreatomagmatic eruptions under the West Antarctic Ice Sheet: potential hazard for ice sheet stability

NASA Astrophysics Data System (ADS)

Iverson, N. A.; Dunbar, N. W.; Lieb-Lappen, R.; Kim, E. J.; Golden, E. J.; Obbard, R. W.

2014-12-01

Volcanic tephra layers have been seen in most ice cores in Antarctica. These tephra layers are deposited almost instantaneously across wide areas of ice sheets, creating horizons that can provide "pinning points" to adjust ice time scales that may otherwise be lacking detailed chronology. A combination of traditional particle morphology characterization by SEM with new non-destructive X-ray micro-computed tomography (Micro-CT) has been used to analyze selected coarse grained tephra in the West Antarctica Ice Sheet (WAIS) Divide WDC06A ice core. Micro-CT has the ability to image particles as small as 50µm in length (15µm resolution), quantifying both particle shape and size. The WDC06A contains hundreds of dusty layers of which 36 have so far been identified as primary tephra layers. Two of these tephra layers have been characterized as phreatomagmatic eruptions based on SEM imagery and are blocky and platy in nature, with rare magmatic particles. These layers are strikingly different in composition from the typical phonolitic and trachytic tephra produced from West Antarctic volcanoes. These two layers are coarser in grain size, with many particles (including feldspar crystals) exceeding 100µm in length. One tephra layer found at 3149.138m deep in the ice core is a coarse ~1mm thick basanitic tephra layer with a WDC06-7 ice core age of 45,381±2000yrs. The second layer is a ~1.3 cm thick zoned trachyandesite to trachydacite tephra found at 2569.205m deep with an ice core age 22,470±835yrs. Micro-CT analysis shows that WDC06A-3149.138 has normal grading with the largest particles at the bottom of the sample (~160μm). WDC06A-2569.205 has a bimodal distribution of particles with large particles at the top and bottom of the layer. These large particles are more spherical in shape at the base and become more irregular and finer grained higher in the layer, likely showing changes in eruption dynamics. The distinct chemistry as well as the blocky and large grain size of the two tephra lead us to believe that these eruptions are from volcanoes proximal to WAIS Divide and did not transport far because neither tephra was observed in the Byrd core (<100km away). It is likely that these tephra are sourced from volcanoes beneath the WAIS and have since been buried and if they were to erupt again, may contribute to ice sheet instability.

Unmelted meteoritic debris in the Late Pliocene iridium anomaly - Evidence for the ocean impact of a nonchondritic asteroid

NASA Technical Reports Server (NTRS)

Kyte, F. T.; Brownlee, D. E.

1985-01-01

Ir-bearing particles have been recovered from two piston cores in the Antarctic Basin in the southeastern Pacific. In core E13-3, the particles closely correspond to the Late Pliocene Ir anomaly and have a fluence of about 100 mg/cm sq. In core E13-4, 120 km to the southwest, the particle fluence is about 4 mg/cm sq. Particles with diameters from 0.5 to 4 mm contain at least 35 percent of the Ir in this horizon. Three types of particles have been identified: (1) vesicular, (2) basaltic, and (3) metal. The vesicular particles appear to be shock-melted debris derived from the oceanic impact of a howarditic asteroid containing a minor metal component. These particles have recrystallized from a melt and impact into the ocean has resulted in the incorporation of Na, K, Cl, and radiogenic Sr from the ocean water target. The basaltic clasts appear to be unmelted fragments of the original asteroid which may have separated from the main body prior to impact. Combined vesicular and basaltic particles are believed to have formed by collisions in the debris cloud. Estimates of the diameter of the projectile range from 100 to 500 m. By many orders of magnitude, this is the most massive achondrite sampled by a single meteorite fall.

Adsorption of Small Cationic Nanoparticles onto Large Anionic Particles from Aqueous Solution: A Model System for Understanding Pigment Dispersion and the Problem of Effective Particle Density.

PubMed

North, S M; Jones, E R; Smith, G N; Mykhaylyk, O O; Annable, T; Armes, S P

2017-02-07

The present study focuses on the use of copolymer nanoparticles as a dispersant for a model pigment (silica). Reversible addition-fragmentation chain transfer (RAFT) alcoholic dispersion polymerization was used to synthesize sterically stabilized diblock copolymer nanoparticles. The steric stabilizer block was poly(2-(dimethylamino)ethyl methacrylate) (PDMA) and the core-forming block was poly(benzyl methacrylate) (PBzMA). The mean degrees of polymerization for the PDMA and PBzMA blocks were 71 and 100, respectively. Transmission electron microscopy (TEM) studies confirmed a near-monodisperse spherical morphology, while dynamic light scattering (DLS) studies indicated an intensity-average diameter of 30 nm. Small-angle X-ray scattering (SAXS) reported a volume-average diameter of 29 ± 0.5 nm and a mean aggregation number of 154. Aqueous electrophoresis measurements confirmed that these PDMA 71 -PBzMA 100 nanoparticles acquired cationic character when transferred from ethanol to water as a result of protonation of the weakly basic PDMA chains. Electrostatic adsorption of these nanoparticles from aqueous solution onto 470 nm silica particles led to either flocculation at submonolayer coverage or steric stabilization at or above monolayer coverage, as judged by DLS. This technique indicated that saturation coverage was achieved on addition of approximately 465 copolymer nanoparticles per silica particle, which corresponds to a fractional surface coverage of around 0.42. These adsorption data were corroborated using thermogravimetry, UV spectroscopy and X-ray photoelectron spectroscopy. TEM studies indicated that the cationic nanoparticles remained intact on the silica surface after electrostatic adsorption, while aqueous electrophoresis confirmed that surface charge reversal occurred below pH 7. The relatively thick layer of adsorbed nanoparticles led to a significant reduction in the effective particle density of the silica particles from 1.99 g cm -3 to approximately 1.74 g cm -3 , as judged by disk centrifuge photosedimentometry (DCP). Combining the DCP and SAXS data suggests that essentially no deformation of the PBzMA cores occurs during nanoparticle adsorption onto the silica particles.

Shape-Controlled Synthesis of Magnetic Iron Oxide@SiO₂-Au@C Particles with Core-Shell Nanostructures.

PubMed

Li, Mo; Li, Xiangcun; Qi, Xinhong; Luo, Fan; He, Gaohong

2015-05-12

The preparation of nonspherical magnetic core-shell nanostructures with uniform sizes still remains a challenge. In this study, magnetic iron oxide@SiO2-Au@C particles with different shapes, such as pseduocube, ellipsoid, and peanut, were synthesized using hematite as templates and precursors of magnetic iron oxide. The as-obtained magnetic particles demonstrated uniform sizes, shapes, and well-designed core-shell nanostructures. Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) analysis showed that the Au nanoparticles (AuNPs) of ∼6 nm were uniformly distributed between the silica and carbon layers. The embedding of the metal nanocrystals into the two different layers prevented the aggregation and reduced the loss of the metal nanocrystals during recycling. Catalytic performance of the peanut-like particles kept almost unchanged without a noticeable decrease in the reduction of 4-nitrophenol (4-NP) in 8 min even after 7 cycles, indicating excellent reusability of the particles. Moreover, the catalyst could be readily recycled magnetically after each reduction by an external magnetic field.

Separation of natural product using columns packed with Fused-Core particles.

PubMed

Yang, Peilin; Litwinski, George R; Pursch, Matthias; McCabe, Terry; Kuppannan, Krishna

2009-06-01

Three HPLC columns packed with 3 microm, sub-2 microm, and 2.7 microm Fused-Core (superficially porous) particles were compared in separation performance using two natural product mixtures containing 15 structurally related components. The Ascentis Express C18 column packed with Fused-Core particles showed an 18% increase in column efficiency (theoretical plates), a 76% increase in plate number per meter, a 65% enhancement in separation speed and a 19% increase in back pressure compared to the Atlantis T3 C18 column packed with 3 microm particles. Column lot-to-lot variability for critical pairs in the natural product mixture was observed with both columns, with the Atlantis T3 column exhibiting a higher degree of variability. The Ascentis Express column was also compared with the Acquity BEH column packed with sub-2 microm particles. Although the peak efficiencies obtained by the Ascentis Express column were only about 74% of those obtained by the Acquity BEH column, the 50% lower back pressure and comparable separation speed allowed high-efficiency and high-speed separation to be performed using conventional HPLC instrumentation.

Comprehensive evaluation of the linear stability of Alfvén eigenmodes driven by alpha particles in an ITER baseline scenario

NASA Astrophysics Data System (ADS)

Figueiredo, A. C. A.; Rodrigues, P.; Borba, D.; Coelho, R.; Fazendeiro, L.; Ferreira, J.; Loureiro, N. F.; Nabais, F.; Pinches, S. D.; Polevoi, A. R.; Sharapov, S. E.

2016-07-01

The linear stability of Alfvén eigenmodes in the presence of fusion-born alpha particles is thoroughly assessed for two variants of an ITER baseline scenario, which differ significantly in their core and pedestal temperatures. A systematic approach based on CASTOR-K (Borba and Kerner 1999 J. Comput. Phys. 153 101; Nabais et al 2015 Plasma Sci. Technol. 17 89) is used that considers all possible eigenmodes for a given magnetic equilibrium and determines their growth rates due to alpha-particle drive and Landau damping on fuel ions, helium ashes and electrons. It is found that the fastest growing instabilities in the aforementioned ITER scenario are core-localized, low-shear toroidal Alfvén eigenmodes. The largest growth-rates occur in the scenario variant with higher core temperatures, which has the highest alpha-particle density and density gradient, for eigenmodes with toroidal mode numbers n≈ 30 . Although these eigenmodes suffer significant radiative damping, which is also evaluated, their growth rates remain larger than those of the most unstable eigenmodes found in the variant of the ITER baseline scenario with lower core temperatures, which have n≈ 15 and are not affected by radiative damping.

Effect of attractive interactions on the water-like anomalies of a core-softened model potential.

PubMed

Pant, Shashank; Gera, Tarun; Choudhury, Niharendu

2013-12-28

It is now well established that water-like anomalies can be reproduced by a spherically symmetric potential with two length scales, popularly known as core-softened potential. In the present study we aim to investigate the effect of attractive interactions among the particles in a model fluid interacting with core-softened potential on the existence and location of various water-like anomalies in the temperature-pressure plane. We employ extensive molecular dynamic simulations to study anomalous nature of various order parameters and properties under isothermal compression. Order map analyses have also been done for all the potentials. We observe that all the systems with varying depth of attractive wells show structural, dynamic, and thermodynamic anomalies. As many of the previous studies involving model water and a class of core softened potentials have concluded that the structural anomaly region encloses the diffusion anomaly region, which in turn, encloses the density anomaly region, the same pattern has also been observed in the present study for the systems with less depth of attractive well. For the systems with deeper attractive well, we observe that the diffusion anomaly region shifts toward higher densities and is not always enclosed by the structural anomaly region. Also, density anomaly region is not completely enclosed by diffusion anomaly region in this case.

Synthesis of basalt fiber@Zn1-xMgxO core/shell nanostructures for selective photoreduction of CO2 to CO

NASA Astrophysics Data System (ADS)

Kwak, Byeong Sub; Kim, Kang Min; Park, Sun-Min; Kang, Misook

2017-06-01

This study focused on the development of a catalyst for converting carbon dioxide, the main cause of global warming, into a beneficial energy source. Core@shell structured particles, BF@ZnO and BF@Zn1-xMgxO, are synthesized in order to selectively obtain CO gas from the photoreduction of CO2. A modified sol-gel process is used to synthesize the core@shell structures with a three-dimensional microstructure, which are subsequently characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDAX), ultraviolet (UV)-vis absorption, photoluminescence (PL), and photocurrent density analysis. The CO2 adsorption abilities of the core@shell particles are estimated through CO2-temperature programmed desorption (TPD). The core@shell structured BF@Zn1-xMgxO particles including the Mg ingredient significantly increased the adsorption of CO2 gas at the microfiber/nanoparticle interface. Both the BF@ZnO and BF@Zn1-xMgxO particles selectively reduce the carbon dioxide to carbon monoxide, with almost no other reduced products being observed. These results are attributed to the effective adsorption of CO2 gas and inhibited recombination of the photogenerated electron-hole pairs. BF@Zn0.75Mg0.25O exhibited superior photocatalytic behavior and selectively produced 5.0 μmolgcat-1 L-1 of CO gas after 8 h of reaction.

On fast solid-body rotation of the solar core and differential (liquid-like) rotation of the solar surface

NASA Astrophysics Data System (ADS)

Pashitskii, E. A.

2017-07-01

On the basis of a two-component (two-fluid) hydrodynamic model, it is shown that the probable phenomenon of solar core rotation with a velocity higher than the average velocity of global rotation of the Sun, discovered by the SOHO mission, can be related to fast solid-body rotation of the light hydrogen component of the solar plasma, which is caused by thermonuclear fusion of hydrogen into helium inside the hot dense solar core. Thermonuclear fusion of four protons into a helium nucleus (α-particle) creates a large free specific volume per unit particle due to the large difference between the densities of the solar plasma and nuclear matter. As a result, an efficient volumetric sink of one of the components of the solar substance—hydrogen—forms inside the solar core. Therefore, a steady-state radial proton flux converging to the center should exist inside the Sun, which maintains a constant concentration of hydrogen as it burns out in the solar core. It is demonstrated that such a converging flux of hydrogen plasma with the radial velocity v r ( r) = -β r creates a convective, v r ∂ v φ/∂ r, and a local Coriolis, v r v φ/ r,φ nonlinear hydrodynamic forces in the solar plasma, rotating with the azimuthal velocity v φ. In the absence of dissipation, these forces should cause an exponential growth of the solid-body rotation velocity of the hydrogen component inside the solar core. However, friction between the hydrogen and helium components of the solar plasma due to Coulomb collisions of protons with α-particles results in a steady-state regime of rotation of the hydrogen component in the solar core with an angular velocity substantially exceeding the global rotational velocity of the Sun. It is suggested that the observed differential (liquid-like) rotation of the visible surface of the Sun (photosphere) with the maximum angular velocity at the equator is caused by sold-body rotation of the solar plasma in the radiation zone and strong turbulence in the tachocline layer, where the turbulent viscosity reaches its maximum value at the equator. There, the tachocline layer exerts the most efficient drag on the less dense outer layers of the solar plasma, which are slowed down due to the interaction with the ambient space plasma (solar wind).

Parallelization of a Monte Carlo particle transport simulation code

NASA Astrophysics Data System (ADS)

Hadjidoukas, P.; Bousis, C.; Emfietzoglou, D.

2010-05-01

We have developed a high performance version of the Monte Carlo particle transport simulation code MC4. The original application code, developed in Visual Basic for Applications (VBA) for Microsoft Excel, was first rewritten in the C programming language for improving code portability. Several pseudo-random number generators have been also integrated and studied. The new MC4 version was then parallelized for shared and distributed-memory multiprocessor systems using the Message Passing Interface. Two parallel pseudo-random number generator libraries (SPRNG and DCMT) have been seamlessly integrated. The performance speedup of parallel MC4 has been studied on a variety of parallel computing architectures including an Intel Xeon server with 4 dual-core processors, a Sun cluster consisting of 16 nodes of 2 dual-core AMD Opteron processors and a 200 dual-processor HP cluster. For large problem size, which is limited only by the physical memory of the multiprocessor server, the speedup results are almost linear on all systems. We have validated the parallel implementation against the serial VBA and C implementations using the same random number generator. Our experimental results on the transport and energy loss of electrons in a water medium show that the serial and parallel codes are equivalent in accuracy. The present improvements allow for studying of higher particle energies with the use of more accurate physical models, and improve statistics as more particles tracks can be simulated in low response time.

Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2

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

Aaboud, M.; Aad, G.; Abbott, B.

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 TeV for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb -1 of data collected by the ATLAS experiment and simulation of proton–proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 TeV. The impact of charged-particle separations andmore » multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 GeV is quantified using a novel, data-driven, method. The method uses the energy loss, dE/dx, to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is 0.061±0.006 (stat.)±0.014 (syst.) and 0.093±0.017 (stat.)±0.021 (syst.) for jet transverse momenta of 200–400 GeV and 1400–1600 GeV, respectively.« less

Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2

DOE PAGES

Aaboud, M.; Aad, G.; Abbott, B.; ...

2017-10-11

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 TeV for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb -1 of data collected by the ATLAS experiment and simulation of proton–proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 TeV. The impact of charged-particle separations andmore » multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 GeV is quantified using a novel, data-driven, method. The method uses the energy loss, dE/dx, to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is 0.061±0.006 (stat.)±0.014 (syst.) and 0.093±0.017 (stat.)±0.021 (syst.) for jet transverse momenta of 200–400 GeV and 1400–1600 GeV, respectively.« less

From Dot to Ring: The Role of Friction in the Deposition Pattern of a Drying Colloidal Suspension Droplet.

PubMed

Xie, Qingguang; Harting, Jens

2018-05-08

The deposition of particles on a substrate by drying a colloidal suspension droplet is at the core of applications ranging from traditional printing on paper to printable electronics or photovoltaic devices. The self-pinning induced by the accumulation of particles at the contact line plays an important role in the formation of a deposit. In this article, we investigate, both numerically and theoretically, the effect of friction between the particles and the substrate on the deposition pattern. Without friction, the contact line shows a stick-slip behavior and a dotlike deposit is left after the droplet is evaporated. By increasing the friction force, we observe a transition from a dotlike to a ringlike deposit. We propose a theoretical model to predict the effective radius of the particle deposit as a function of the friction force. Our theoretical model predicts a critical friction force when self-pinning happens and the effective radius of deposit increases with increasing friction force, confirmed by our simulation results. Our results can find implications for developing active control strategies for the deposition of drying droplets.

New Mechanism of Extractive Electrospray Ionization Mass Spectrometry for Heterogeneous Solid Particles.

PubMed

Kumbhani, S; Longin, T; Wingen, L M; Kidd, C; Perraud, V; Finlayson-Pitts, B J

2018-02-06

Real-time in situ mass spectrometry analysis of airborne particles is important in several applications, including exposure studies in ambient air, industrial settings, and assessing impacts on visibility and climate. However, obtaining molecular and 3D structural information is more challenging, especially for heterogeneous solid or semisolid particles. We report a study of extractive electrospray ionization mass spectrometry (EESI-MS) for the analysis of solid particles with an organic coating. The goal is to elucidate how much of the overall particle content is sampled, and determine the sensitivity of this technique to the surface layers. It is shown that, for NaNO 3 particles coated with glutaric acid (GA), very little of the solid NaNO 3 core is sampled compared to the GA coating, whereas for GA particles coated with malonic acid (MA), significant signals from both the MA coating and the GA core are observed. However, conventional ESI-MS of the same samples collected on a Teflon filter (and then extracted) detects much more core material compared to EESI-MS in both cases. These results show that, for the experimental conditions used here, EESI-MS does not sample the entire particle but, instead, is more sensitive to surface layers. Separate experiments on single-component particles of NaNO 3 , GA, or citric acid show that there must be a kinetics limitation to dissolution that is important in determining EESI-MS sensitivity. We propose a new mechanism of EESI solvent droplet interaction with solid particles that is consistent with the experimental observations. In conjunction with previous EESI-MS studies of organic particles, these results suggest that EESI does not necessarily sample the entire particle when solid, and that not only solubility but also surface energies and the kinetics of dissolution play an important role.

Probing velocity dependent self-interacting dark matter with neutrino telescopes

NASA Astrophysics Data System (ADS)

Robertson, Denis S.; Albuquerque, Ivone F. M.

2018-02-01

Self-interacting dark matter models constitute an attractive solution to problems in structure formation on small scales. A simple realization of these models considers the dark force mediated by a light particle which can couple to the Standard Model through mixings with the photon or the Z boson. Within this scenario we investigate the sensitivity of the IceCube-DeepCore and PINGU neutrino telescopes to the associated muon neutrino flux produced by dark matter annihilations in the Sun. Despite the model's simplicity, several effects naturally appear: momentum suppressed capture by nuclei, velocity dependent dark matter self-capture, Sommerfeld enhanced annihilation, as well as the enhancement on the neutrino flux due to mediator late decays. Taking all these effects into account, we find that most of the model relevant parameter space can be tested by the three years of data already collected by the IceCube-DeepCore. We show that indirect detection through neutrinos can compete with the strong existing limits from direct detection experiments, specially in the case of isospin violation.

Preliminary Assessment of the Impact on Reactor Vessel dpa Rates Due to Installation of a Proposed Low Enriched Uranium (LEU) Core in the High Flux Isotope Reactor (HFIR)

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

Daily, Charles R.

2015-10-01

An assessment of the impact on the High Flux Isotope Reactor (HFIR) reactor vessel (RV) displacements-per-atom (dpa) rates due to operations with the proposed low enriched uranium (LEU) core described by Ilas and Primm has been performed and is presented herein. The analyses documented herein support the conclusion that conversion of HFIR to low-enriched uranium (LEU) core operations using the LEU core design of Ilas and Primm will have no negative impact on HFIR RV dpa rates. Since its inception, HFIR has been operated with highly enriched uranium (HEU) cores. As part of an effort sponsored by the National Nuclearmore » Security Administration (NNSA), conversion to LEU cores is being considered for future HFIR operations. The HFIR LEU configurations analyzed are consistent with the LEU core models used by Ilas and Primm and the HEU balance-of-plant models used by Risner and Blakeman in the latest analyses performed to support the HFIR materials surveillance program. The Risner and Blakeman analyses, as well as the studies documented herein, are the first to apply the hybrid transport methods available in the Automated Variance reduction Generator (ADVANTG) code to HFIR RV dpa rate calculations. These calculations have been performed on the Oak Ridge National Laboratory (ORNL) Institutional Cluster (OIC) with version 1.60 of the Monte Carlo N-Particle 5 (MCNP5) computer code.« less

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

Ovchinnikov, Mikhail; Ackerman, Andrew; Avramov, Alex

Large-eddy simulations of mixed-phase Arctic clouds by 11 different models are analyzed with the goal of improving understanding and model representation of processes controlling the evolution of these clouds. In a case based on observations from the Indirect and Semi-Direct Aerosol Campaign (ISDAC), it is found that ice number concentration, Ni, exerts significant influence on the cloud structure. Increasing Ni leads to a substantial reduction in liquid water path (LWP) and potential cloud dissipation, in agreement with earlier studies. By comparing simulations with the same microphysics coupled to different dynamical cores as well as the same dynamics coupled to differentmore » microphysics schemes, it is found that the ice water path (IWP) is mainly controlled by ice microphysics, while the inter-model differences in LWP are largely driven by physics and numerics of the dynamical cores. In contrast to previous intercomparisons, all models here use the same ice particle properties (i.e., mass-size, mass-fall speed, and mass-capacitance relationships) and a common radiation parameterization. The constrained setup exposes the importance of ice particle size distributions (PSD) in influencing cloud evolution. A clear separation in LWP and IWP predicted by models with bin and bulk microphysical treatments is documented and attributed primarily to the assumed shape of ice PSD used in bulk schemes. Compared to the bin schemes that explicitly predict the PSD, schemes assuming exponential ice PSD underestimate ice growth by vapor deposition and overestimate mass-weighted fall speed leading to an underprediction of IWP by a factor of two in the considered case.« less

Global Modeling of Nebulae with Particle Growth, Drift, and Evaporation Fronts. I. Methodology and Typical Results

NASA Astrophysics Data System (ADS)

Estrada, Paul R.; Cuzzi, Jeffrey N.; Morgan, Demitri A.

2016-02-01

We model particle growth in a turbulent, viscously evolving protoplanetary nebula, incorporating sticking, bouncing, fragmentation, and mass transfer at high speeds. We treat small particles using a moments method and large particles using a traditional histogram binning, including a probability distribution function of collisional velocities. The fragmentation strength of the particles depends on their composition (icy aggregates are stronger than silicate aggregates). The particle opacity, which controls the nebula thermal structure, evolves as particles grow and mass redistributes. While growing, particles drift radially due to nebula headwind drag. Particles of different compositions evaporate at “evaporation fronts” (EFs) where the midplane temperature exceeds their respective evaporation temperatures. We track the vapor and solid phases of each component, accounting for advection and radial and vertical diffusion. We present characteristic results in evolutions lasting 2 × 105 years. In general, (1) mass is transferred from the outer to the inner nebula in significant amounts, creating radial concentrations of solids at EFs; (2) particle sizes are limited by a combination of fragmentation, bouncing, and drift; (3) “lucky” large particles never represent a significant amount of mass; and (4) restricted radial zones just outside each EF become compositionally enriched in the associated volatiles. We point out implications for millimeter to submillimeter SEDs and the inference of nebula mass, radial banding, the role of opacity on new mechanisms for generating turbulence, the enrichment of meteorites in heavy oxygen isotopes, variable and nonsolar redox conditions, the primary accretion of silicate and icy planetesimals, and the makeup of Jupiter’s core.

Solution on the Bethe lattice of a hard core athermal gas with two kinds of particles.

PubMed

Oliveira, Tiago J; Stilck, Jürgen F

2011-11-14

Athermal lattice gases of particles with first neighbor exclusion have been studied for a long time as simple models exhibiting a fluid-solid transition. At low concentration the particles occupy randomly both sublattices, but as the concentration is increased one of the sublattices is occupied preferentially. Here, we study a mixed lattice gas with excluded volume interactions only in the grand-canonical formalism with two kinds of particles: small ones, which occupy a single lattice site and large ones, which, when placed on a site, do not allow other particles to occupy its first neighbors also. We solve the model on a Bethe lattice of arbitrary coordination number q. In the parameter space defined by the activities of both particles, at low values of the activity of small particles (z(1)) we find a continuous transition from the fluid to the solid phase as the activity of large particles (z(2)) is increased. At higher values of z(1) the transition becomes discontinuous, both regimes are separated by a tricritical point. The critical line has a negative slope at z(1) = 0 and displays a minimum before reaching the tricritical point, so that a re-entrant behavior is observed for constant values of z(2) in the region of low density of small particles. The isobaric curves of the total density of particles as a function of the density or the activity of small particles show a minimum in the fluid phase. © 2011 American Institute of Physics

Pasta phases in core-collapse supernova matter

NASA Astrophysics Data System (ADS)

Pais, Helena; Chiacchiera, Silvia; Providência, Constança

2016-04-01

The pasta phase in core-collapse supernova matter (finite temperatures and fixed proton fractions) is studied within relativistic mean field models. Three different calculations are used for comparison, the Thomas-Fermi (TF), the Coexisting Phases (CP) and the Compressible Liquid Drop (CLD) approximations. The effects of including light clusters in nuclear matter and the densities at which the transitions between pasta configurations and to uniform matter occur are also investigated. The free energy and pressure, in the space of particle number densities and temperatures expected to cover the pasta region, are calculated. Finally, a comparison with a finite temperature Skyrme-Hartree-Fock calculation is drawn.

SUPRATHERMAL SOLAR WIND ELECTRONS AND LANGMUIR TURBULENCE

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

Kim, Sunjung; Yoon, Peter H.; Choe, G. S.

2016-09-01

The steady-state model recently put forth for the solar wind electron velocity distribution function during quiet time conditions, was originally composed of three population electrons (core, halo, and superhalo) with the core remaining nonresonant with any plasma waves while the halo and superhalo separately maintained steady-state resonance with whistler- and Langmuir-frequency range fluctuations, respectively. However, a recent paper demonstrates that whistler-range fluctuations in fact have no significant contribution. The present paper represents a consummation of the model in that a self-consistent model of the suprathermal electron population, which encompasses both the halo and the superhalo, is constructed solely on themore » basis of the Langmuir fluctuation spectrum. Numerical solutions to steady-state particle and wave kinetic equations are obtained on the basis of an initial trial electron distribution and Langmuir wave spectrum. Such a finding offers a self-consistent explanation for the observed steady-state electron distribution in the solar wind.« less

Low-Temperature Crystal Structures of the Hard Core Square Shoulder Model.

PubMed

Gabriëlse, Alexander; Löwen, Hartmut; Smallenburg, Frank

2017-11-07

In many cases, the stability of complex structures in colloidal systems is enhanced by a competition between different length scales. Inspired by recent experiments on nanoparticles coated with polymers, we use Monte Carlo simulations to explore the types of crystal structures that can form in a simple hard-core square shoulder model that explicitly incorporates two favored distances between the particles. To this end, we combine Monte Carlo-based crystal structure finding algorithms with free energies obtained using a mean-field cell theory approach, and draw phase diagrams for two different values of the square shoulder width as a function of the density and temperature. Moreover, we map out the zero-temperature phase diagram for a broad range of shoulder widths. Our results show the stability of a rich variety of crystal phases, such as body-centered orthogonal (BCO) lattices not previously considered for the square shoulder model.

Scaling relations of halo cores for self-interacting dark matter

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

Lin, Henry W.; Loeb, Abraham, E-mail: henrylin@college.harvard.edu, E-mail: aloeb@cfa.harvard.edu

2016-03-01

Using a simple analytic formalism, we demonstrate that significant dark matter self-interactions produce halo cores that obey scaling relations nearly independent of the underlying particle physics parameters such as the annihilation cross section and the mass of the dark matter particle. For dwarf galaxies, we predict that the core density ρ{sub c} and the core radius r{sub c} should obey ρ{sub c} r{sub c} ≈ 41 M{sub ⊙} pc{sup −2} with a weak mass dependence ∼ M{sup 0.2}. Remarkably, such a scaling relation has recently been empirically inferred. Scaling relations involving core mass, core radius, and core velocity dispersion are predicted and agree well with observationalmore » data. By calibrating against numerical simulations, we predict the scatter in these relations and find them to be in excellent agreement with existing data. Future observations can test our predictions for different halo masses and redshifts.« less

Product layer development during sulfation and sulfidation of uncalcined limestone particles at elevated pressures

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

Zevenhoven, C.A.P.; Yrjas, K.P.; Hupa, M.M.

1998-07-01

Fluidized bed combustion or gasification allows for in-bed sulfur capture with a calcium-based sorbent such as limestone or dolomite. Sorbent particle size, porosity, internal surface, and their variation during conversion have great influence on the conversion of the sorbent. The uptake of SO{sub 2} and H{sub 2}S by five physically different limestones is discussed, for typical pressurized fluidized bed combustor or gasifier conditions: 850/950 C, 15/20 bar. Tests were done in a pressurized thermogravimetric apparatus (P-TGA), the size of the limestone particles was 250--300 {micro}m. It is stressed that the limestones remain uncalcined. A changing internal structure (CIS) model ismore » presented in which reaction kinetics and product layer diffusion are related to the intraparticle surface of reaction, instead of the outer particle surface as in unreacted shrinking core (USC)-type models. The random pore model was used for describing the changing internal pore and reaction surfaces. Rate parameters were extracted for all five limestones using the CIS model and a USC model with variable effective diffusivity. Differences in the sulfur capture performance of the limestones were evaluated. Plots of the CaSO{sub 4} or CaS product layer thickness as a function of conversion are given, and the relative importance of limestone porosity and internal surface is discussed.« less

Formation of an Anti-Core–Shell Structure in Layered Oxide Cathodes for Li-Ion Batteries

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

Zhang, Hanlei; Omenya, Fredrick; Whittingham, M. Stanley

The layered → rock-salt phase transformation in the layered dioxide cathodes for Li-ion batteries is believed to result in a “core-shell” structure of the primary particles, in which the core region maintains as the layered phase while the surface region undergoes the phase transformation to the rock-salt phase. Using transmission electron microscopy, here we demonstrate the formation of an “anti-core-shell” structure in cycled primary particles with a formula of LiNi0.80Co0.15Al0.05O2, in which the surface and subsurface regions remain as the layered structure while the rock-salt phase forms as domains in the bulk with a thin layer of the spinel phasemore » between the rock-salt core and the skin of the layered phase. Formation of this anti-core-shell structure is attributed to the oxygen loss at the surface that drives the migration of oxygen from the bulk to the surface, thereby resulting in localized areas of significantly reduced oxygen levels in the bulk of the particle, which subsequently undergoes the phase transformation to the rock-salt domains. The formation of the anti-core-shell rock-salt domains is responsible for the reduced capacity, discharge voltage and ionic conductivity in cycled cathode.« less

Characterization of the structural collapse undergone by an unstable system of ultrasoft particles

NASA Astrophysics Data System (ADS)

Prestipino, Santi; Malescio, Gianpietro

2016-09-01

The effective repulsion between macromolecules such as polymer chains or dendrimers is everywhere finite, implying that interaction centers can even coincide. If, in addition, the large-distance attraction is sufficiently strong, then the system is driven unstable. An unstable system lacks a conventional thermodynamics since, in the infinite-size limit, it eventually collapses to a finite-size cluster (for instance, a polymer dispersion undergoes irreversible coagulation when increasing the amount of dissolved salt beyond a certain limit). Using a double-Gaussian (DG) potential for demonstration, we study the phase behavior of a system of ultrasoft particles as a function of the attraction strength η. Above a critical threshold ηc, the DG system is unstable but its collective behavior is far from trivial since two separate regions of the thermodynamic plane can be identified, based on the value taken by the average waiting time for collapse: this is finite and small on one side of the boundary, while presumably infinite in the other region. In order to make sense of this evidence, we consider a stable system of particles interacting through a DG potential augmented with a hard core (stabilized DG, or SDG potential). We provide arguments supporting the view that the boundary line of the unstable DG model is the remnant of the spinodal line of a fluid-fluid phase transition occurring in the SDG model when the hard-core diameter is sent to zero.

Validation of a coupled core-transport, pedestal-structure, current-profile and equilibrium model

NASA Astrophysics Data System (ADS)

Meneghini, O.

2015-11-01

The first workflow capable of predicting the self-consistent solution to the coupled core-transport, pedestal structure, and equilibrium problems from first-principles and its experimental tests are presented. Validation with DIII-D discharges in high confinement regimes shows that the workflow is capable of robustly predicting the kinetic profiles from on axis to the separatrix and matching the experimental measurements to within their uncertainty, with no prior knowledge of the pedestal height nor of any measurement of the temperature or pressure. Self-consistent coupling has proven to be essential to match the experimental results, and capture the non-linear physics that governs the core and pedestal solutions. In particular, clear stabilization of the pedestal peeling ballooning instabilities by the global Shafranov shift and destabilization by additional edge bootstrap current, and subsequent effect on the core plasma profiles, have been clearly observed and documented. In our model, self-consistency is achieved by iterating between the TGYRO core transport solver (with NEO and TGLF for neoclassical and turbulent flux), and the pedestal structure predicted by the EPED model. A self-consistent equilibrium is calculated by EFIT, while the ONETWO transport package evolves the current profile and calculates the particle and energy sources. The capabilities of such workflow are shown to be critical for the design of future experiments such as ITER and FNSF, which operate in a regime where the equilibrium, the pedestal, and the core transport problems are strongly coupled, and for which none of these quantities can be assumed to be known. Self-consistent core-pedestal predictions for ITER, as well as initial optimizations, will be presented. Supported by the US Department of Energy under DE-FC02-04ER54698, DE-SC0012652.

Numerical Modeling of Reactive Multiphase Flow for FCC and Hot Gas Desulfurization Circulating Fluidized Beds

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

Miller, Aubrey L.

2005-07-01

This work was carried out to understand the behavior of the solid and gas phases in a CFB riser. Only the riser is modeled as a straight pipe. A model with linear algebraic approximation to solids viscosity of the form, {musubs} = 5.34{epsisubs}, ({espisubs} is the solids volume fraction) with an appropriate boundary condition at the wall obtained by approximate momentum balance solution at the wall to acount for the solids recirculation is tested against experimental results. The work done was to predict the flow patterns in the CFB risers from available experimental data, including data from a 7.5-cm-ID CFBmore » riser at the Illinois Institute of Technology and data from a 20.0-cm-ID CFB riser at the Particulate Solid Research, Inc., facility. This research aims at modeling the removal of hydrogen sulfide from hot coal gas using zinc oxide as the sorbent in a circulating fluidized bed and in the process indentifying the parameters that affect the performance of the sulfidation reactor. Two different gas-solid reaction models, the unreacted shrinking core (USC) and the grain model were applied to take into account chemical reaction resistances. Also two different approaches were used to affect the hydrodynamics of the process streams. The first model takes into account the effect of micro-scale particle clustering by adjusting the gas-particle drag law and the second one assumes a turbulent core with pseudo-steady state boundary condition at the wall. A comparison is made with experimental results.« less

Measurements and Modeling of Aerosol Absorption and Single Scattering Albedo at Ambient Relative Hum

NASA Technical Reports Server (NTRS)

Redemann, J.; Russell, P. B.; Hamill, P.

2000-01-01

Uncertainties in the aerosol single scattering albedo have been identified to be an important source of errors in current large-scale model estimates of the direct aerosol radiative forcing of climate. A number of investigators have obtained estimates of the single scattering albedo from a variety of remote sensing and in situ measurements during aerosol field experiments. During the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX, 1996) for example, estimates of the aerosol single scattering albedo were obtained (1) as a best-fit parameter in comparing radiative flux changes measured by airborne pyranometer to those computed from independently measured aerosol properties; (2) from estimates of the aerosol complex index of refraction derived using a combination of airborne sunphotometer, lidar backscatter and in situ size distribution measurements; and (3) from airborne measurements of aerosol scattering and absorption using nephelometers and absorption photometers. In this paper, we briefly compare the results of the latter two methods for two TARFOX case studies, since those techniques provide height-resolved information about the aerosol single scattering albedo. Estimates of the aerosol single scattering albedo from nephelometer and absorption photometer measurements require knowledge of the scattering and absorption humidification (i.e., the increase in these properties in response to an increase in ambient relative humidity), since both measurements are usually carried out at a relative humidity different from the ambient atmosphere. In principle, the scattering humidification factor can be measured, but there is currently no technique widely available to measure the absorption of an aerosol sample as a function of relative humidity. Frequently, for lack of better knowledge, the absorption humidification is assumed to be unity (meaning that there is no change in aerosol absorption due to an increase in ambient relative humidity). This assumption then enters the estimate of the single scattering albedo at ambient relative humidity. To investigate the validity of this assumption we have carried out modeling studies of the absorption humidification factor, assuming that the aerosols contain an insoluble soot core and a coating which determines its hygroscopic growth behavior. The aerosol optical properties are then computed on the basis of the shell/core particle morphology using a Mie-code for concentric shells. From basic physical principles, it is conceivable that aerosol absorption increases when an atmospheric aerosol particle collects a non-absorbing shell, since the soot core is then exposed to an increased (focused) electric field strength. Indeed, our preliminary modeling studies show that the absorption of an atmospheric aerosol particle composed of a soot core and an aqueous sulfuric acid shell may increase by a factor of 50% due to a change in ambient relative humidity from 30 to 95%. We will show how this increased absorption is a function of the initial particle size and soot mass fraction.

SR-BI selective lipid uptake: subsequent metabolism of acute phase HDL.

PubMed

de Beer, Maria C; Webb, Nancy R; Whitaker, Nathan L; Wroblewski, Joanne M; Jahangiri, Anisa; van der Westhuyzen, Deneys R; de Beer, Frederick C

2009-09-01

The purpose of this study was to investigate the interaction of SAA and SR-BI in remodeling of acute phase HDL (AP HDL). We used SAA and SR-BI adenoviral vector expression models to study the interaction between these entities. SR-BI processing of mouse AP HDL generated progressively smaller discreet HDL particles with distinct apolipoprotein compositions. SR-BI actions segregated apolipoproteins with the smallest particles containing only apoA-I. Larger remnants contained apoA-I, apoA-II, and SAA. Small apoA-I only particles failed to associate with preformed HDL, whereas larger remnants readily did. The presence of SAA on SR-BI-processed HDL particles propelled apoA-I to a small lipid-poor form and accelerated apoA-I catabolism. Data indicate that after core and surface HDL lipid perturbation by SR-BI, SAA propels apoA-I to a small lipid-poor form while accelerating HDL metabolism.

SR-BI Selective Lipid Uptake: Subsequent Metabolism of Acute Phase HDL

PubMed Central

de Beer, Maria C.; Webb, Nancy R.; Whitaker, Nathan L.; Wroblewski, Joanne M.; Jahangiri, Anisa; van der Westhuyzen, Deneys R.; de Beer, Frederick C.

2009-01-01

Objective To investigate the interaction of SAA and SR-BI in remodeling of acute phase HDL (AP HDL). Methods and Results We used SAA and SR-BI adenoviral vector expression models to study the interaction between these entities. SR-BI processing of mouse AP HDL generated progressively smaller discreet HDL particles with distinct apolipoprotein compositions. SR-BI actions segregated apolipoproteins with the smallest particles containing only apoA-I. Larger remnants contained apoA-I, apoA-II and SAA. Small apoA-I only particles failed to associate with preformed HDL whereas larger remnants readily did. The presence of SAA on SR-BI processed HDL particles propelled apoA-I to a small lipid-poor form and accelerated apoA-I catabolism. Conclusions Data indicate that after core and surface HDL lipid perturbation by SR-BI, SAA propels apoA-I to a small lipid-poor form while accelerating HDL metabolism. PMID:19304574

Modeling Secondary Organic Aerosols over Europe: Impact of Activity Coefficients and Viscosity

NASA Astrophysics Data System (ADS)

Kim, Y.; Sartelet, K.; Couvidat, F.

2014-12-01

Semi-volatile organic species (SVOC) can condense on suspended particulate materials (PM) in the atmosphere. The modeling of condensation/evaporation of SVOC often assumes that gas-phase and particle-phase concentrations are at equilibrium. However, recent studies show that secondary organic aerosols (SOA) may not be accurately represented by an equilibrium approach between the gas and particle phases, because organic aerosols in the particle phase may be very viscous. The condensation in the viscous liquid phase is limited by the diffusion from the surface of PM to its core. Using a surrogate approach to represent SVOC, depending on the user's choice, the secondary organic aerosol processor (SOAP) may assume equilibrium or model dynamically the condensation/evaporation between the gas and particle phases to take into account the viscosity of organic aerosols. The model is implemented in the three-dimensional chemistry-transport model of POLYPHEMUS. In SOAP, activity coefficients for organic mixtures can be computed using UNIFAC for short-range interactions between molecules and AIOMFAC to also take into account the effect of inorganic species on activity coefficients. Simulations over Europe are performed and POLYPHEMUS/SOAP is compared to POLYPHEMUS/H2O, which was previously used to model SOA using the equilibrium approach with activity coefficients from UNIFAC. Impacts of the dynamic approach on modeling SOA over Europe are evaluated. The concentrations of SOA using the dynamic approach are compared with those using the equilibrium approach. The increase of computational cost is also evaluated.

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer

PubMed Central

2013-01-01

Bifunctional monodispersed Fe3O4 particles coated with an ultrathin Y2O3:Tb3+ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe3O4 core and outer Y2O3:Tb3+ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging. PMID:23962025

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer

NASA Astrophysics Data System (ADS)

Atabaev, Timur Sh; Kim, Hyung-Kook; Hwang, Yoon-Hwae

2013-08-01

Bifunctional monodispersed Fe3O4 particles coated with an ultrathin Y2O3:Tb3+ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe3O4 core and outer Y2O3:Tb3+ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging.

Design and calculation of low infrared transmittance and low emissivity coatings for heat radiative applications

NASA Astrophysics Data System (ADS)

Wang, Guang-Hai; Zhang, Yue; Zhang, Da-Hai; Fan, Jin-Peng

2012-02-01

The infrared transmittance and emissivity of heat-insulating coatings pigmented with various structural particles were studied using Kubelka-Munk theory and Mie theory. The primary design purpose was to obtain the low transmittance and low emissivity coatings to reduce the heat transfer by thermal radiation for high-temperature applications. In the case of silica coating layers constituted with various structural titania particles (solid, hollow, and core-shell spherical), the dependence of transmittance and emissivity of the coating layer on the particle structure and the layer thickness was investigated and optimized. The results indicate that the coating pigmented with core-shell titania particles exhibits a lower infrared transmittance and a lower emissivity value than that with other structural particles and is suitable to radiative heat-insulating applications.

Importance of pH-regulated charge density on the electrophoresis of soft particles

NASA Astrophysics Data System (ADS)

Gopmandal, Partha P.; Ohshima, H.

2017-02-01

The present study deals with the electrophoresis of spherical soft particles consisting of an ion and liquid-penetrable but liquid-flow-impenetrable inner core surrounded by an ion and fluid-penetrable polyelectrolyte layer. The inner core is considered to be dielectric and bearing basic functional group coated with polyelectrolyte layer containing acidic functional group. An approximate expression for the electrophoretic mobility of such a particle is obtained under a low potential limit. The electrophoretic behaviour of the undertaken particle is investigated for a wide range of bulk pH values and electrolyte concentrations. Our study also indicates some remarkable features of the electrophoresis e.g., occurrence of zero mobility, mobility reversal etc.

Classification of Magnetic Nanoparticle Systems—Synthesis, Standardization and Analysis Methods in the NanoMag Project

PubMed Central

Bogren, Sara; Fornara, Andrea; Ludwig, Frank; del Puerto Morales, Maria; Steinhoff, Uwe; Fougt Hansen, Mikkel; Kazakova, Olga; Johansson, Christer

2015-01-01

This study presents classification of different magnetic single- and multi-core particle systems using their measured dynamic magnetic properties together with their nanocrystal and particle sizes. The dynamic magnetic properties are measured with AC (dynamical) susceptometry and magnetorelaxometry and the size parameters are determined from electron microscopy and dynamic light scattering. Using these methods, we also show that the nanocrystal size and particle morphology determines the dynamic magnetic properties for both single- and multi-core particles. The presented results are obtained from the four year EU NMP FP7 project, NanoMag, which is focused on standardization of analysis methods for magnetic nanoparticles. PMID:26343639

Interface control in BaTiO3 based supercapacitors

NASA Astrophysics Data System (ADS)

Maglione, Mario; Elissalde, Catherine; Chung, U.-Chan

2010-03-01

Core shell BaTiO3 based particles sintered using advanced processes provide a high control of grain boundaries in bulk composites. As a result, supercapacitor behavior was evidenced which came from the balance between inner grain conductivity and grain boundary dielectric barrier. Thanks to the core-shell structure of the starting particles, improved control of the effective dielectric parameters can be achieved.

Structural heterogeneity of milk casein micelles: a SANS contrast variation study.

PubMed

Bouchoux, Antoine; Ventureira, Jorge; Gésan-Guiziou, Geneviève; Garnier-Lambrouin, Fabienne; Qu, Peng; Pasquier, Coralie; Pézennec, Stéphane; Schweins, Ralf; Cabane, Bernard

2015-01-14

We examine the internal structure of milk casein micelles using the contrast variation method in Small-Angle Neutron Scattering (SANS). Experiments were performed with casein dispersions of different origins (i.e., milk powder or fresh milk) and extended to very low q-values (∼9 × 10(-4) Å(-1)), thus making it possible to precisely determine the apparent gyration radius Rg at each contrast. From the variation of I(q → 0) with contrast, we determine the distribution of composition of all the particles in the dispersions. As expected, most of these particles are micelles, made of casein and calcium phosphate, with a narrow distribution in compositions. These micelles always coexist with a very small fraction of fat droplets, with sizes in the range of 20-400 nm. For the dispersions prepared from fresh milk, which were purified under particularly stringent conditions, the number ratio of fat droplets to casein micelles is as low as 1 to 10(6). In that case, we are able to subtract from the total intensity the contribution of the fat droplets and in this way obtain the contribution of the micelles only. We then analyze the variation of this contribution with contrast using the approach pioneered by H. B. Stuhrmann. We model the casein micelle as a core-shell spherical object, in which the local scattering length density is determined by the ratio of calcium phosphate nanoclusters to proteins. We find that models in which the shell has a lower concentration of calcium phosphate than the core give a better agreement than models in which the shell has a higher density than the core.

Nuclear chirality, a model and the data

NASA Astrophysics Data System (ADS)

Starosta, K.; Koike, T.

2017-09-01

In the last decade, the manifestation of chirality in atomic nuclei has become the subject of numerous experimental and theoretical studies. The common feature of current model calculations is that the chiral geometry of angular momentum coupling is extracted from expectation values of orientation operators, rather than being a starting point in construction of a model. However, using the particle-hole coupling model for triaxial odd-odd nuclei it is possible to construct a basis which contains right-handed, left-handed and planar states of angular momentum coupling. If this basis is used, the chirality is an explicit rather than an extracted feature as in any other models with non-chiral bases. The time-reversal symmetry, which relates the basis states of opposite handedness, can be used to reduce the dimension of matrices for diagonalization of the model Hamiltonian, proving the effectiveness of this approach. Moreover, the final model eigenstate wave functions show a concentration of amplitudes among a relatively small number (˜1%) of components compared to the full model space. In that sense, the ‘chiral’ basis provides a useful tool to examine model predictions providing direct insight into the structure of doublet states. In this work, similarities and differences between the rotational behaviour of an axial and triaxial body provide a starting point for derivation of the basis optimal for valence nucleon coupling to an axial and a triaxial core. The derived ‘chiral’ basis is optimal for coupling of a valence particle and hole to the triaxial core. Model predictions are presented and discussed. A comprehensive review of current experimental data on observed chiral band candidates is also provided.

Hydrogen sulfide capture by limestone and dolomite at elevated pressure. 2: Sorbent particle conversion modeling

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

Zevenhoven, C.A.P.; Yrjas, K.P.; Hupa, M.M.

1996-03-01

The physical structure of a limestone or dolomite to be used in in-bed sulfur capture in fluidized bed gasifiers has a great impact on the efficiency of sulfur capture and sorbent use. In this study an unreacted shrinking core model with variable effective diffusivity is applied to sulfidation test data from a pressurized thermogravimetric apparatus (P-TGA) for a set of physically and chemically different limestone and dolomite samples. The particle size was 250--300 {micro}m for all sorbents, which were characterized by chemical composition analysis, particle density measurement, mercury porosimetry, and BET internal surface measurement. Tests were done under typical conditionsmore » for a pressurized fluidized-bed gasifier, i.e., 20% CO{sub 2}, 950 C, 20 bar. At these conditions the limestone remains uncalcined, while the dolomite is half-calcined. Additional tests were done at low CO{sub 2} partial pressures, yielding calcined limestone and fully calcined dolomite. The generalized model allows for determination of values for the initial reaction rate and product layer diffusivity.« less

Finding consistency between different views of the absorption enhancement of black carbon: An observationally constrained hybrid model to support a transition in optical properties with mass fraction

NASA Astrophysics Data System (ADS)

Coe, H.; Allan, J. D.; Whitehead, J.; Alfarra, M. R. R.; Villegas, E.; Kong, S.; Williams, P. I.; Ting, Y. C.; Haslett, S.; Taylor, J.; Morgan, W.; McFiggans, G.; Spracklen, D. V.; Reddington, C.

2015-12-01

The mixing state of black carbon is uncertain yet has a significant influence on the efficiency with which a particle absorbs light. In turn, this may make a significant contribution to the uncertainty in global model predictions of the black carbon radiative budget. Previous modelling studies that have represented this mixing state using a core-shell approach have shown that aged black carbon particles may be considerably enhanced compared to freshly emitted black carbon due to the addition of co-emitted, weakly absorbing species. However, recent field results have demonstrated that any enhancement of absorption is minor in the ambient atmosphere. Resolving these differences in absorption efficiency is important as they will have a major impact on the extent to which black carbon heats the atmospheric column. We have made morphology-independent measurements of refractory black carbon mass and associated weakly absorbing material in single particles from laboratory-generated diesel soot and black carbon particles in ambient air influenced by traffic and wood burning sources and related these to the optical properties of the particles. We compared our calculated optical properties with optical models that use varying mixing state assumptions and by characterising the behaviour in terms of the relative amounts of weakly absorbing material and black carbon in a particle we show a sharp transition in mixing occurs. We show that the majority of black carbon particles from traffic-dominated sources can be treated as externally mixed and show no absorption enhancement, whereas models assuming internal mixing tend to give the best estimate of the absorption enhancement of thickly coated black carbon particles from biofuel or biomass burning. This approach reconciles the differences in absorption enhancement previously observed and offers a systematic way of treating the differences in behaviour observed.

ACCELERATION OF COMPACT RADIO JETS ON SUB-PARSEC SCALES

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

Lee, Sang-Sung; Lobanov, Andrei P.; Krichbaum, Thomas P.

2016-08-01

Jets of compact radio sources are highly relativistic and Doppler boosted, making studies of their intrinsic properties difficult. Observed brightness temperatures can be used to study the intrinsic physical properties of relativistic jets, and constrain models of jet formation in the inner jet region. We aim to observationally test such inner jet models. The very long baseline interferometry (VLBI) cores of compact radio sources are optically thick at a given frequency. The distance of the core from the central engine is inversely proportional to the frequency. Under the equipartition condition between the magnetic field energy and particle energy densities, themore » absolute distance of the VLBI core can be predicted. We compiled the brightness temperatures of VLBI cores at various radio frequencies of 2, 8, 15, and 86 GHz. We derive the brightness temperature on sub-parsec scales in the rest frame of the compact radio sources. We find that the brightness temperature increases with increasing distance from the central engine, indicating that the intrinsic jet speed (the Lorentz factor) increases along the jet. This implies that the jets are accelerated in the (sub-)parsec regions from the central engine.« less

Characteristics of Dust Deposition at High Elevation Sites in Caucasus Over the Past 190 years Recorded in Ice Cores.

NASA Astrophysics Data System (ADS)

Kutuzov, Stanislav; Ginot, Patrick; Mikhaenko, Vladimir; Krupskaya, Victoria; Legrand, Michel; Preunkert, Suzanne; Polukhov, Alexey; Khairedinova, Alexandra

2017-04-01

The nature and extent of both radiative and geochemical impacts of mineral dust on snow pack and glaciers depend on physical and chemical properties of dust particles and its deposition rates. Ice cores can provide information about amount of dust particles in the atmosphere and its characteristic and also give insights on strengths of the dust sources and its changes in the past. A series of shallow ice cores have been obtained in Caucasus mountains, Russia in 2004 - 2015. A 182 meter ice core has been recovered at the Western Plateau of Mt. Elbrus (5115 m a.s.l.) in 2009. The ice cores have been dated using stable isotopes, NH4+ and succinic acid data with the seasonal resolution. Samples were analysed for chemistry, concentrations of dust and black carbon, and particle size distributions. Dust mineralogy was assessed by XRD. Individual dust particles were analysed using SEM. Dust particle number concentration was measured using the Markus Klotz GmbH (Abakus) implemented into the CFA system. Abakus data were calibrated with Coulter Counter multisizer 4. Back trajectory cluster analysis was used to assess main dust source areas. It was shown that Caucasus region experiencing influx of mineral dust from the Sahara and deserts of the Middle East. Mineralogy of dust particles of desert origin was significantly different from the local debris material and contained large proportion of calcite and clay minerals (kaolinite, illite, palygorskite) associated with material of desert origin. Annual dust flux in the Caucasus Mountains was estimated as 300 µg/cm2 a-1. Particle size distribution depends on individual characteristics of dust deposition event and also on the elevation of the drilling site. The contribution of desert dust deposition was estimated as 35-40 % of the total dust flux. Average annual Ca2+ concentration over the period from 1824 to 2013 was of 150 ppb while some of the strong dust deposition events led to the Ca2+ concentrations reaching 4400 ppb. An increase of dust and Ca2+ concentration was registered since the beginning of XX century. The ice core record depicts also a prominent increase of dust concentration in 1980's which may be related to the increase of dust sources strength in North Africa.

Intravenous hemostats: challenges in translation to patients

NASA Astrophysics Data System (ADS)

Lashof-Sullivan, Margaret; Shoffstall, Andrew; Lavik, Erin

2013-10-01

Excessive bleeding and the resulting complications are a leading killer of young people globally. There are many successful methods to halt bleeding in the extremities, including compression, tourniquets, and dressings. However, current treatments for internal hemorrhage (including from head or truncal injuries), termed non-compressible bleeding, are inadequate. For these non-compressible injuries, blood transfusions are the current treatment standard. However, they must be refrigerated, may potentially transfer disease, and are of limited supply. In addition, time is of the essence for halting hemorrhage, since more than a third of civilian deaths due to hemorrhage from trauma occur before the patient even reaches the hospital. As a result, particles that can cross-link activated platelets through the glycoprotein IIb/IIIa receptor expressed on activated platelets are being investigated as an alternative treatment for non-compressible bleeding. Ideally, these particles would interact specifically with platelets to stabilize the platelet plug. Initial designs used biologically derived microparticles with red blood cell fragment or albumin cores decorated with RGD or fibrinogen, which bind to GPIIb/IIIa. More recently there has been research into the use of fully synthetic nanoparticles with liposomal or polymer cores that crosslink platelets through a targeting peptide bound to the surface. Some of the challenges for the development of these particles include appropriate sizing to prevent blocking the capillaries of the lungs, immune system evasion to prevent strong reactions and increase circulation time, and storage and resuspension so that first responders can easily use the particles. In addition, the effectiveness of the variety of animal bleeding models in predicting outcomes must be examined before test results can be fully understood. Progress has been made in the development of particles to combat hemorrhage, but issues of immune sensitivity and storage must be resolved before these types of particles can be translated for human use.

Water column and bed-sediment core samples collected from Brownlee Reservoir near Oxbow, Oregon, 2012

USGS Publications Warehouse

Fosness, Ryan L.; Naymik, Jesse; Hopkins, Candice B.; DeWild, John F.

2013-01-01

The U.S. Geological Survey, in cooperation with Idaho Power Company, collected water-column and bed-sediment core samples from eight sites in Brownlee Reservoir near Oxbow, Oregon, during May 5–7, 2012. Water-column and bed-sediment core samples were collected at each of the eight sites and analyzed for total mercury and methylmercury. Additional bed-sediment core samples, collected from three of the eight sites, were analyzed for pesticides and other organic compounds, trace metals, and physical characteristics, such as particle size. Total mercury and methylmercury were detected in each of the water column and bed-sediment core samples. Only 17 of the 417 unique pesticide and organic compounds were detected in bed-sediment core samples. Concentrations of most organic wastewater compounds detected in bed sediment were less than the reporting level. Trace metals detected were greater than the reporting level in all the bed-sediment core samples submitted for analysis. The particle size distribution of bed-sediment core samples was predominantly clay mixed with silt.

Key Role of Nitrate in Phase Transitions of Urban Particles: Implications of Important Reactive Surfaces for Secondary Aerosol Formation

NASA Astrophysics Data System (ADS)

Sun, Jiaxing; Liu, Lei; Xu, Liang; Wang, Yuanyuan; Wu, Zhijun; Hu, Min; Shi, Zongbo; Li, Yongjie; Zhang, Xiaoye; Chen, Jianmin; Li, Weijun

2018-01-01

Ammonium sulfate (AS) and ammonium nitrate (AN) are key components of urban fine particles. Both field and model studies showed that heterogeneous reactions of SO2, NO2, and NH3 on wet aerosols accelerated the haze formation in northern China. However, little is known on phase transitions of AS-AN containing haze particles. Here hygroscopic properties of laboratory-generated AS-AN particles and individual particles collected during haze events in an urban site were investigated using an individual particle hygroscopicity system. AS-AN particles showed a two-stage deliquescence at mutual deliquescence relative humidity (MDRH) and full deliquescence relative humidity (DRH) and three physical states: solid before MDRH, solid-aqueous between MDRH and DRH, and aqueous after DRH. During hydration, urban haze particles displayed a solid core and aqueous shell at RH = 60-80% and aqueous phase at RH > 80%. Most particles were in aqueous phase at RH > 50% during dehydration. Our results show that AS content in individual particles determines their DRH and AN content determines their MDRH. AN content increase can reduce MDRH, which indicates occurrence of aqueous shell at lower RH. The humidity-dependent phase transitions of nitrate-abundant urban particles are important to provide reactive surfaces of secondary aerosol formation in the polluted air.

Implementing microscopic charcoal in a global climate-aerosol model

NASA Astrophysics Data System (ADS)

Gilgen, Anina; Lohmann, Ulrike; Brügger, Sandra; Adolf, Carole; Ickes, Luisa

2017-04-01

Information about past fire activity is crucial to validate fire models and to better understand their deficiencies. Several paleofire records exist, among them ice cores and sediments, which preserve fire tracers like levoglucosan, vanillic acid, or charcoal particles. In this work, we implement microscopic charcoal particles (maximum dimension 10-100 μm) into the global climate-aerosol model ECHAM6.3HAM2.3. Since we are not aware of any reliable estimates of microscopic charcoal emissions, we scaled black carbon emissions from GFAS to capture the charcoal fluxes from a calibration dataset. After that, model results were compared with a validation dataset. The coarse model resolution (T63L31; 1.9°x1.9°) impedes the model to capture local variability of charcoal fluxes. However, variability on the global scale is pronounced due to highly-variable fire emissions. In future, we plan to model charcoal fluxes in the past 1-2 centuries using fire emissions provided from fire models. Furthermore, we intend to compare modelled charcoal fluxes from prescribed fire emissions with those calculated by an interactive fire model.

Characterization of Two Unique Cholesterol-Rich Lipid Particles Isolated from Human Atherosclerotic Lesions

PubMed Central

Chao, Fei-Fei; Blanchette-Mackie, E. Joan; Chen, Ya-Jun; Dickens, Benjamin F.; Berlin, Elliott; Amende, Lynn M.; Skarlatos, Sonia I.; Gamble, Wilbert; Resau, James H.; Mergner, Wolfgang T.; Kruth, Howard S.

1990-01-01

The authors' laboratory, using histochemicalmethods, previously identified two types of cholesterol-containing lipid particles in the extracellular spaces of human atherosclerotic lesions, one particle enriched in esterified cholesterol and the other particle enriched in unesterified cholesterol. The authors isolated and characterized these lipid particles. The esterified cholesterol-rich lipid particle was a small lipid droplet and differed from intracellular lipid dropletsfound in foam cells with respect to size and chemical composition. It had an esterified cholesterol core surrounded by aphospholipidunesterified cholesterol monolayer. Some aqueous spaces were seen within the particle core. Unesterified cholesterol-rich lipid particles were multilamellated, solid structures and vesicles comprised of single or multiple lamellas. The esterified cholesterol-rich particle had a density <1.01 g/ml, whereas the unesterified cholesterol-rich particle had a density between 1.03 and 1.05 g/ml. Both particles were similar in size fraction, whereas palmitate, stearate, oleate, and linoleate were predominant in the phospholipid fraction. The origins and the role of these two unusual lipid particles in vessel wall cholesterol metabolism remain to be determined. ImagesFigure 1Figure 3Figure 4Figure 5 PMID:2297045

Plasmonic Library Based on Substrate-Supported Gradiential Plasmonic Arrays

PubMed Central

2014-01-01

We present a versatile approach to produce macroscopic, substrate-supported arrays of plasmonic nanoparticles with well-defined interparticle spacing and a continuous particle size gradient. The arrays thus present a “plasmonic library” of locally noncoupling plasmonic particles of different sizes, which can serve as a platform for future combinatorial screening of size effects. The structures were prepared by substrate assembly of gold-core/poly(N-isopropylacrylamide)-shell particles and subsequent post-modification. Coupling of the localized surface plasmon resonance (LSPR) could be avoided since the polymer shell separates the encapsulated gold cores. To produce a particle array with a broad range of well-defined but laterally distinguishable particle sizes, the substrate was dip-coated in a growth solution, which resulted in an overgrowth of the gold cores controlled by the local exposure time. The kinetics was quantitatively analyzed and found to be diffusion rate controlled, allowing for precise tuning of particle size by adjusting the withdrawal speed. We determined the kinetics of the overgrowth process, investigated the LSPRs along the gradient by UV–vis extinction spectroscopy, and compared the spectroscopic results to the predictions from Mie theory, indicating the absence of local interparticle coupling. We finally discuss potential applications of these substrate-supported plasmonic particle libraries and perspectives toward extending the concept from size to composition variation and screening of plasmonic coupling effects. PMID:25137554

Physical properties of macromolecule-metal oxide nanoparticle complexes: Magnetophoretic mobility, sizes, and interparticle potentials

NASA Astrophysics Data System (ADS)

Mefford, Olin Thompson, IV

Magnetic nanoparticles coated with polymers hold great promise as materials for applications in biotechnology. In this body of work, magnetic fluids for the treatment of retinal detachment are examined closely in three regimes; motion of ferrofluid droplets in aqueous media, size analysis of the polymer-iron oxide nanoparticles, and calculation of interparticle potentials as a means for predicting fluid stability. The macromolecular ferrofluids investigated herein are comprised of magnetite nanoparticles coated with tricarboxylate-functional polydimethylsiloxane (PDMS) oligomers. The nanoparticles were formed by reacting stoichiometric concentrations of iron chloride salts with base. After the magnetite particles were prepared, the functional PDMS oligomers were adsorbed onto the nanoparticle surfaces. The motion of ferrofluid droplets in aqueous media was studied using both theoretical modeling and experimental verification. Droplets (˜1-2 mm in diameter) of ferrofluid were moved through a viscous aqueous medium by an external magnet of measured field and field gradient. Theoretical calculations were made to approximate the forces on the droplet. Using the force calculations, the times required for the droplet to travel across particular distances were estimated. These estimated times were within close approximation of experimental values. Characterization of the sizes of the nanoparticles was particularly important, since the size of the magnetite core affects the magnetic properties of the system, as well as the long-term stability of the nanoparticles against flocculation. Transmission electron microscopy (TEM) was used to measure the sizes and size distributions of the magnetite cores. Image analyses were conducted on the TEM micrographs to measure the sizes of approximately 6000 particles per sample. Distributions of the diameters of the magnetite cores were determined from this data. A method for calculating the total particle size, including the magnetite core and the adsorbed polymer, in organic dispersions was established. These estimated values were compared to measurements of the entire complex utilizing dynamic light scattering (DLS). Better agreement was found for narrow particle size distributions as opposed to broader distribution. The stability against flocculation of the complexes over time in organic media were examined via modified Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations. DLVO theory allows for predicting the total particle-particle interaction potentials, which include steric and electrostatic repulsions as well as van der Waals and magnetic attractions. The interparticle potentials can be determined as a function of separation of the particle surfaces. At a constant molecular weight of the polymer dispersion stabilizer, these calculations indicated that dispersions of smaller PDMS-magnetite particles should be more stable than those containing larger particles. The rheological characteristics of neat magnetite-PDMS complexes (i.e., no solvent or carrier fluid were present) were measured over time in the absence of an applied magnetic field to probe the expected properties upon storage. The viscosity of a neat ferrofluid increased over the course of a month, indicating that some aggregation occurred. However, this effect could be removed by shearing the fluids at a high rate. This suggests that the particles do not irreversibly flocculate under these conditions.

Dynamics of the one-dimensional Anderson insulator coupled to various bosonic baths

NASA Astrophysics Data System (ADS)

Bonča, Janez; Trugman, Stuart A.; Mierzejewski, Marcin

2018-05-01

We study a particle which propagates in a one-dimensional strong random potential and is coupled to a bosonic bath. We independently test various properties of bosons (hopping term, hard-core effects, and generic boson-boson interaction) and show that bosonic itineracy is the essential ingredient governing the dynamics of the particle. Coupling of the particle to itinerant phonons or hard-core bosons alike leads to delocalization of the particle by virtue of a subdiffusive (or diffusive) spread from the initially localized state. Delocalization remains in effect even when the boson frequency and the bandwidth of itinerant bosons remain an order of magnitude smaller than the magnitude of the random potential. When the particle is coupled to localized bosons, its spread remains logarithmic or even sublogarithmic. The latter result together with the survival probability shows that the particle remains localized despite being coupled to bosons.

Analysis of Alfvén eigenmode destabilization by energetic particles in Large Helical Device using a Landau-closure model

DOE PAGES

Varela, Jacobo Rodriguez; Spong, D. A.; Garcia, L.

2017-03-06

Here, energetic particle populations in nuclear fusion experiments can destabilize the Alfvén Eigenmodes through inverse Landau damping and couplings with gap modes in the shear Alfvén continua. We use the reduced MHD equations to describe the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system, coupled with equations of density and parallel velocity moments for the energetic particles. We add the Landau damping and resonant destabilization effects using a closure relation. We apply the model to study the Alfvén mode stability in the inward-shifted configurations of the Large Helical Device (LHD), performing a parametric analysis of the energetic particle β (more » $${{\\beta}_{f}}$$ ) in a range of realistic values, the ratios of the energetic particle thermal/Alfvén velocities ($${{V}_{\\text{th}}}/{{V}_{A0}}$$ ), the magnetic Lundquist numbers (S) and the toroidal modes (n). The n = 1 and n = 2 TAEs are destabilized, although the n = 3 and n = 4 TAEs are weakly perturbed. The most unstable configurations are associated with the density gradients of energetic particles in the plasma core: the TAEs are destabilized, even for small energetic particle populations, if their thermal velocity is lower than 0.4 times the Alfvén velocity. The frequency range of MHD bursts measured in the LHD are 50–70 kHz for the n = 1 and 60–80 kHz for the n = 2 TAE, which is consistent with the model predictions.« less

Effects of NO(y) aging on the dehydration dynamics of model sea spray aerosol.

PubMed

Woods, Ephraim; Heylman, Kevin D; Gibson, Amanda K; Ashwell, Adam P; Rossi, Sean R

2013-05-23

The reactions of NO(y) species in the atmosphere with sea spray aerosol replace halogen anions with nitrate. These experiments show the effect of increasing the nitrate content of model sea spray aerosol particles on the morphology changes and the phase transitions driven by changes in relative humidity (RH). The components of the model particles include H2O, Na+, Mg2+, Cl-, NO3-, and SO4(2-). Tandem differential mobility analyzer (TDMA) measurements yield the water content and efflorescence relative humidity (ERH) of these particles, and probe molecule spectroscopic measurements reveal subsequent phase transitions and partially characterize the salt composition on the surface of dry particles. The results show three effects of increasing the nitrate composition: decreasing the EFH (46 to 29%), production of a metastable aqueous layer on the surface of effloresced particles, and decreasing the sulfate content near the surface of dry particles. For the mixtures studied here, the initial crystallization event forms a core of NaCl. For particles that contain a substantial metastable aqueous layer following efflorescence, probe molecule spectroscopy shows a second crystallization at a lower RH. This subsequent phase transition is likely the formation of Na2SO4. Homogeneous nucleation theory (HNT) using a semiempirical formulation predicts the ERH of all mixtures within 2.0% RH, with a mean absolute deviation of 1.0%. The calculations suggest that structures associated with highly concentrated or supersaturated magnesium ions strongly affect the interfacial tension between the NaCl crystal nucleus and the droplet from which it forms.

Charge-based characterization of nanometric cationic bifunctional maghemite/silica core/shell particles by capillary zone electrophoresis.

PubMed

d'Orlyé, Fanny; Varenne, Anne; Georgelin, Thomas; Siaugue, Jean-Michel; Teste, Bruno; Descroix, Stéphanie; Gareil, Pierre

2009-07-01

In view of employing functionalized nanoparticles (NPs) in the context of an immunodiagnostic, aminated maghemite/silica core/shell particles were synthesized so as to be further coated with an antibody or an antigen via the amino groups at their surface. Different functionalization rates were obtained by coating these maghemite/silica core/shell particles with 3-(aminopropyl)triethoxysilane and 2-[methoxy(polyethyleneoxy)propyl]-trimethoxysilane at different molar ratios. Adequate analytical performances with CE coupled with UV-visible detection were obtained through semi-permanent capillary coating with didodecyldimethyl-ammonium bromide, thus preventing particle adsorption. First, the influence of experimental conditions such as electric field strength, injected particle amount as well as electrolyte ionic strength and pH, was evaluated. A charge-dependent electrophoretic mobility was evidenced and the separation selectivity was tuned according to electrolyte ionic strength and pH. The best resolutions were obtained at pH 8.0, high ionic strength (ca. 100 mM), and low total particle volume fraction (ca. 0.055%), thus eliminating interference effects between different particle populations in mixtures. A protocol derived from Kaiser's original description was performed for quantitation of the primary amino groups attached onto the NP surface. Thereafter a correlation between particle electrophoretic mobility and the density of amino groups at their surface was established. Eventually, CE proved to be an easy, fast, and reliable method for the determination of NP effective surface charge density.

Software package for modeling spin–orbit motion in storage rings

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

Zyuzin, D. V., E-mail: d.zyuzin@fz-juelich.de

2015-12-15

A software package providing a graphical user interface for computer experiments on the motion of charged particle beams in accelerators, as well as analysis of obtained data, is presented. The software package was tested in the framework of the international project on electric dipole moment measurement JEDI (Jülich Electric Dipole moment Investigations). The specific features of particle spin motion imply the requirement to use a cyclic accelerator (storage ring) consisting of electrostatic elements, which makes it possible to preserve horizontal polarization for a long time. Computer experiments study the dynamics of 10{sup 6}–10{sup 9} particles in a beam during 10{supmore » 9} turns in an accelerator (about 10{sup 12}–10{sup 15} integration steps for the equations of motion). For designing an optimal accelerator structure, a large number of computer experiments on polarized beam dynamics are required. The numerical core of the package is COSY Infinity, a program for modeling spin–orbit dynamics.« less

Numerical simulation on the powder propellant pickup characteristics of feeding system at high pressure

NASA Astrophysics Data System (ADS)

Sun, Haijun; Hu, Chunbo; Zhu, Xiaofei

2017-10-01

A numerical study of powder propellant pickup progress at high pressure was presented in this paper by using two-fluid model with kinetic theory of granular flow in the computational fluid dynamics software package ANSYS/Fluent. Simulations were conducted to evaluate the effects of initial pressure, initial powder packing rate and mean particle diameter on the flow characteristics in terms of velocity vector distribution, granular temperature, pressure drop, particle velocity and volume. The numerical results of pressure drop were also compared with experiments to verify the TFM model. The simulated results show that the pressure drop value increases as the initial pressure increases, and the granular temperature under the conditions of different initial pressures and packing rates is almost the same in the area of throttling orifice plate. While there is an appropriate value for particle size and packing rate to form a ;core-annulus; structure in powder box, and the time-averaged velocity vector distribution of solid phase is inordinate.

Integrated tokamak modeling: when physics informs engineering and research planning

NASA Astrophysics Data System (ADS)

Poli, Francesca

2017-10-01

Simulations that integrate virtually all the relevant engineering and physics aspects of a real tokamak experiment are a power tool for experimental interpretation, model validation and planning for both present and future devices. This tutorial will guide through the building blocks of an ``integrated'' tokamak simulation, such as magnetic flux diffusion, thermal, momentum and particle transport, external heating and current drive sources, wall particle sources and sinks. Emphasis is given to the connection and interplay between external actuators and plasma response, between the slow time scales of the current diffusion and the fast time scales of transport, and how reduced and high-fidelity models can contribute to simulate a whole device. To illustrate the potential and limitations of integrated tokamak modeling for discharge prediction, a helium plasma scenario for the ITER pre-nuclear phase is taken as an example. This scenario presents challenges because it requires core-edge integration and advanced models for interaction between waves and fast-ions, which are subject to a limited experimental database for validation and guidance. Starting from a scenario obtained by re-scaling parameters from the demonstration inductive ``ITER baseline'', it is shown how self-consistent simulations that encompass both core and edge plasma regions, as well as high-fidelity heating and current drive source models are needed to set constraints on the density, magnetic field and heating scheme. This tutorial aims at demonstrating how integrated modeling, when used with adequate level of criticism, can not only support design of operational scenarios, but also help to asses the limitations and gaps in the available models, thus indicating where improved modeling tools are required and how present experiments can help their validation and inform research planning. Work supported by DOE under DE-AC02-09CH1146.

Flow instability in particle-bed nuclear reactors

NASA Astrophysics Data System (ADS)

Kerrebrock, Jack L.

The particle-bed core offers mitigation of some of the problems of solid-core nuclear rocket reactors. Dividing the fuel elements into small spherical particles contained in a cylindrical bed through which the propellant flows radially, may reduce the thermal stress in the fuel elements, allowing higher propellant temperatures to be reached. The high temperature regions of the reactor are confined to the interior of cylindrical fuel assemblies, so most of the reactor can be relatively cool. This enables the use of structural and moderating materials which reduce the minimum critical size and mass of the reactor. One of the unresolved questions about this concept is whether the flow through the particle-bed will be well behaved, or will be subject to destructive flow instabilities. Most of the recent analyses of the stability of the particle-bed reactor have been extensions of the approach of Bussard and Delauer, where the bed is essentially treated as an array of parallel passages, so that the mass flow is continuous from inlet to outlet through any one passage. A more general three dimensional model of the bed is adopted, in which the fluid has mobility in three dimensions. Comparison of results of the earlier approach to the present one shows that the former does not accurately represent the stability at low Re. The more complete model presented should be capable of meeting this deficiency while accurately representing the effects of the cold and hot frits, and of heat conduction and radiation in the particle-bed. It can be extended to apply to the cylindrical geometry of particle-bed reactors without difficulty. From the exemplary calculations which were carried out, it can be concluded that a particle-bed without a cold frit would be subject to instability if operated at the high temperatures desired for nuclear rockets, and at power densities below about 4 megawatts per liter. Since the desired power density is about 40 megawatts per liter, it can be concluded that operation at design exit temperature but at reduced power could be hazardous for such a reactor. But the calculations also show that an appropriate cold frit could very likely cure the instability. More definite conclusions must await calculations for specific designs.

Flow instability in particle-bed nuclear reactors

NASA Technical Reports Server (NTRS)

Kerrebrock, Jack L.

1993-01-01

The particle-bed core offers mitigation of some of the problems of solid-core nuclear rocket reactors. Dividing the fuel elements into small spherical particles contained in a cylindrical bed through which the propellant flows radially, may reduce the thermal stress in the fuel elements, allowing higher propellant temperatures to be reached. The high temperature regions of the reactor are confined to the interior of cylindrical fuel assemblies, so most of the reactor can be relatively cool. This enables the use of structural and moderating materials which reduce the minimum critical size and mass of the reactor. One of the unresolved questions about this concept is whether the flow through the particle-bed will be well behaved, or will be subject to destructive flow instabilities. Most of the recent analyses of the stability of the particle-bed reactor have been extensions of the approach of Bussard and Delauer, where the bed is essentially treated as an array of parallel passages, so that the mass flow is continuous from inlet to outlet through any one passage. A more general three dimensional model of the bed is adopted, in which the fluid has mobility in three dimensions. Comparison of results of the earlier approach to the present one shows that the former does not accurately represent the stability at low Re. The more complete model presented should be capable of meeting this deficiency while accurately representing the effects of the cold and hot frits, and of heat conduction and radiation in the particle-bed. It can be extended to apply to the cylindrical geometry of particle-bed reactors without difficulty. From the exemplary calculations which were carried out, it can be concluded that a particle-bed without a cold frit would be subject to instability if operated at the high temperatures desired for nuclear rockets, and at power densities below about 4 megawatts per liter. Since the desired power density is about 40 megawatts per liter, it can be concluded that operation at design exit temperature but at reduced power could be hazardous for such a reactor. But the calculations also show that an appropriate cold frit could very likely cure the instability. More definite conclusions must await calculations for specific designs.

Attitude stability of spinning flexible spacecraft

NASA Technical Reports Server (NTRS)

Likins, P. W.; Barbera, F. J.

1971-01-01

The stability of spinning flexible satellites in a force-free environment was analyzed. The satellite was modeled as a rigid core having attached to it a flexible appendage idealized as a collection of particles (point masses) interconnected by springs. Both Liapunov and Routh-Hurwitz stability procedures are used. In the former, the Hamiltonian of the system, constrained through the angular momentum integral so as to admit complete damping, is used as a testing function. Equations of motion are written using the hybrid coordinate formulation, which readily accepts a modal coordinate transformation ultimately allowing truncation to a level amenable to literal stability analysis. Closed form stability criteria are generated for the first mode of a restricted appendage model lying in a plane containing the system center of mass and orthogonal to the spin axis. The effects of spin on flexible bodies are discussed by considering a very elementary particle model. Control of passively unstable spacecraft is briefly considered.

Aerosol-Cloud Interactions during Tropical Deep Convection: Evidence for the Importance of Free Tropospheric Aerosols

NASA Technical Reports Server (NTRS)

Ackerman, A.; Jensen, E.; Stevens, D.; Wang, D.; Heymsfield, A.; Miloshevich, L.; Twohy, C.; Poellot, M.; VanReken, T.; Fridland, Ann

2003-01-01

NASA's 2002 CRYSTAL-FACE field experiment focused on the formation and evolution of tropical cirrus cloud systems in southern Florida. Multiple aircraft extensively sampled cumulonimbus dynamical and microphysical properties, as well as characterizing ambient aerosol populations both inside and outside the full depth of the convective column. On July 18, unique measurements were taken when a powerful updraft was traversed directly by aircraft, providing a window into the primary source region of cumulonimbus anvil crystals. Observations of the updraft, entered at approximately l0 km altitude and -34 C, indicated more than 200 cloud particles per mL at vertical velocities exceeding 20 m/s and the presence of significant condensation nuclei and liquid water within the core. In this work, aerosol and cloud phase observations are integrated by simulating the updraft conditions using a large-eddy resolving model with 3 explicit multiphase microphysics, including treatment of size-resolved aerosol fields, aerosol activation and freezing, and evaporation of cloud particles back to the aerosol phase. Simulations were initialized with observed thermodynamic and aerosol size distributions profiles and convection was driven by surface fluxes assimilated from the ARPS forecast model. Model results are consistent with the conclusions that most crystals are homogeneously frozen droplets and that entrained free tropospheric aerosols may contribute a significant fraction of the crystals. Thus most anvil crystals appear to be formed aloft in updraft cores, well above cloud base. These conclusions are supported by observations of hydrometeor size distribution made while traversing the dore, as well as aerosol and cloud particle size distributions generally observed by aircraft below 4km and crystal properties generally observed by aircraft above 12km.

Parallel particle filters for online identification of mechanistic mathematical models of physiology from monitoring data: performance and real-time scalability in simulation scenarios.

PubMed

Zenker, Sven

2010-08-01

Combining mechanistic mathematical models of physiology with quantitative observations using probabilistic inference may offer advantages over established approaches to computerized decision support in acute care medicine. Particle filters (PF) can perform such inference successively as data becomes available. The potential of PF for real-time state estimation (SE) for a model of cardiovascular physiology is explored using parallel computers and the ability to achieve joint state and parameter estimation (JSPE) given minimal prior knowledge tested. A parallelized sequential importance sampling/resampling algorithm was implemented and its scalability for the pure SE problem for a non-linear five-dimensional ODE model of the cardiovascular system evaluated on a Cray XT3 using up to 1,024 cores. JSPE was implemented using a state augmentation approach with artificial stochastic evolution of the parameters. Its performance when simultaneously estimating the 5 states and 18 unknown parameters when given observations only of arterial pressure, central venous pressure, heart rate, and, optionally, cardiac output, was evaluated in a simulated bleeding/resuscitation scenario. SE was successful and scaled up to 1,024 cores with appropriate algorithm parametrization, with real-time equivalent performance for up to 10 million particles. JSPE in the described underdetermined scenario achieved excellent reproduction of observables and qualitative tracking of enddiastolic ventricular volumes and sympathetic nervous activity. However, only a subset of the posterior distributions of parameters concentrated around the true values for parts of the estimated trajectories. Parallelized PF's performance makes their application to complex mathematical models of physiology for the purpose of clinical data interpretation, prediction, and therapy optimization appear promising. JSPE in the described extremely underdetermined scenario nevertheless extracted information of potential clinical relevance from the data in this simulation setting. However, fully satisfactory resolution of this problem when minimal prior knowledge about parameter values is available will require further methodological improvements, which are discussed.

Variations in soil detachment rates after wildfire as a function of soil depth, flow properties, and root properties

USGS Publications Warehouse

Moody, John A.; Nyman, Peter

2013-01-01

Wildfire affects hillslope erosion through increased surface runoff and increased sediment availability, both of which contribute to large post-fire erosion events. Relations between soil detachment rate, soil depth, flow and root properties, and fire impacts are poorly understood and not represented explicitly in commonly used post-fire erosion models. Detachment rates were measured on intact soil cores using a modified tilting flume. The cores were mounted flush with the flume-bed and a measurement was made on the surface of the core. The core was extruded upward, cut off, and another measurement was repeated at a different depth below the original surface of the core. Intact cores were collected from one site burned by the 2010 Fourmile Canyon (FMC) fire in Colorado and from one site burned by the 2010 Pozo fire in California. Each site contained contrasting vegetation and soil types. Additional soil samples were collected alongside the intact cores and were analyzed in the laboratory for soil properties (organic matter, bulk density, particle-size distribution) and for root properties (root density and root-length density). Particle-size distribution and root properties were different between sites, but sites were similar in terms of bulk density and organic matter. Soil detachment rates had similar relations with non-uniform shear stress and non-uniform unit stream power. Detachment rates within single sampling units displayed a relatively weak and inconsistent relation to flow variables. When averaged across all clusters, the detachment rate displayed a linear relation to shear stress, but variability in soil properties meant that the shear stress accounted for only a small proportion of the overall variability in detachment rates (R2 = 0.23; R2 is the coefficient of determination). Detachment rate was related to root-length density in some clusters (R2 values up to 0.91) and unrelated in others (R2 values 2 value improved and the range of exponents became narrower by applying a multivariate regression model where boundary shear stress and root-length density were included as explanatory variables. This suggests that an erodibility parameter which incorporates the effects of both flow and root properties on detachment could improve the representation of sediment availability after wildfire.

The South Atlantic Anomaly throughout the solar cycle

NASA Astrophysics Data System (ADS)

Domingos, João; Jault, Dominique; Pais, Maria Alexandra; Mandea, Mioara

2017-09-01

The Sun-Earth's interaction is characterized by a highly dynamic electromagnetic environment, in which the magnetic field produced in the Earth's core plays an important role. One of the striking characteristics of the present geomagnetic field is denoted the South Atlantic Anomaly (SAA) where the total field intensity is unusually low and the flux of charged particles, trapped in the inner Van Allen radiation belts, is maximum. Here, we use, on one hand, a recent geomagnetic field model, CHAOS-6, and on the other hand, data provided by different platforms (satellites orbiting the Earth - POES NOAA for 1998-2014 and CALIPSO for 2006-2014). Evolution of the SAA particle flux can be seen as the result of two main effects, the secular variation of the Earth's core magnetic field and the modulation of the density of the inner radiation belts during the solar cycle, as a function of the L value that characterises the drift shell, where charged particles are trapped. To study the evolution of the particle flux anomaly, we rely on a Principal Component Analysis (PCA) of either POES particle flux or CALIOP dark noise. Analysed data are distributed on a geographical grid at satellite altitude, based on a L-shell reference frame constructed from the moving eccentric dipole. Changes in the main magnetic field are responsible for the observed westward drift. Three PCA modes account for the time evolution related to solar effects. Both the first and second modes have a good correlation with the thermospheric density, which varies in response to the solar cycle. The first mode represents the total intensity variation of the particle flux in the SAA, and the second the movement of the anomaly between different L-shells. The proposed analysis allows us to well recover the westward drift rate, as well as the latitudinal and longitudinal solar cycle oscillations, although the analysed data do not cover a complete (Hale) magnetic solar cycle (around 22 yr). Moreover, the developments made here would enable us to forecast the impact of the South Atlantic Anomaly on space weather. A model of the evolution of the eccentric dipole field (magnitude, offset and tilt) would suffice, together with a model for the solar cycle evolution.

An integrated, cross-disciplinary study of soil hydrophobicity at atomic, molecular, core and landscape scales

NASA Astrophysics Data System (ADS)

Matthews, G. Peter; Doerr, Stefan; Van Keulen, Geertje; Dudley, Ed; Francis, Lewis; Whalley, Richard; Gazze, Andrea; Hallin, Ingrid; Quinn, Gerry; Sinclair, Kat; Ashton, Rhys

2017-04-01

Soil hydrophobicity can lead to reduced soil fertility and heightened flood risk caused by increased run-off. Soil hydrophobicity is a well-known phenomenon when induced by natural events such as wildfires and anthropogenic causes including adding organic wastes or hydrocarbon contaminants. This presentation concerns a much more subtle effect - the naturally occurring changes between hydrophilic and hydrophobic states caused by periods of wetness and drought. Although subtle, they nevertheless affect vast areas of soil, and so their effects can be very significant, and are predicted to increase under climate change conditions. To understand the effect, a major interdisciplinary study has been commissioned by the UK's Natural Environment Research Council (NERC) to investigate soil hydrophobicity over length scales ranging from atomic through molecular, core and landscape scale. We present the key findings from the many publications currently in preparation. The programme is predicated on the hypothesis that changes in soil protein abundance and localization, induced by variations in soil moisture and temperature, are crucial driving forces for transitions between hydrophobic and hydrophilic conditions at soil particle surfaces, and that these effects can be meaningfully upscaled from molecular to landscape scale. Three soils were chosen based on the severity of hydrophobicity that can be achieved in the field: severe to extreme (natural rough pasture, Wales), intermediate to severe (pasture, Wales), and subcritical (managed research grassland, Rothamsted Research, England). The latter is already highly characterised so was also used as a control. Hydrophobic/ hydrophilic transitions were determined from water droplet penetration times. Scientific advances in the following five areas will be described: (i) the identification of these soil proteins by proteomic methods, using novel separation methods which reduces interference by humic acids, and allows identification by ESI and MALDI TOF mass spectrometry and database searches, (ii) the examination of such proteins, which form ordered hydrophobic ridges, and measurement of their elasticity, stickiness and hydrophobicity at nano- to microscale using atomic force microscopy adapted for the rough surfaces of soil particles, (iii) the novel use of a picoliter goniometer to show hydrophobic effects at a 1 micron diameter droplet level, which avoids the averaging over soil cores and particles evident in microliter goniometry, with which the results are compared, (iv) measurements at core scale using water retention and wicking experiments, and (v) the modelling and upscaling of the results from molecular to core scale using the PoreXpert void network model of dynamic wetting and Haines jumps. An explanation will also be given as to how the results will be further upscaled by incorporation into the JULES hydrological model of the UK Meteorological Office, used to predict flooding for different soil types and usage.

Investigation of Flow Structures Downstream of SAPIEN 3, CoreValve, and PERIMOUNT Magna Using Particle Image Velocimetry

NASA Astrophysics Data System (ADS)

Barakat, Mohammed; Lengsfeld, Corinne; Dvir, Danny; Azadani, Ali

2017-11-01

Transcatheter aortic valves provide superior systolic hemodynamic performance in terms of valvular pressure gradient and effective orifice area compared with equivalent size surgical bioprostheses. However, in depth investigation of the flow field structures is of interest to examine the flow field characteristics and provide experimental evidence necessary for validation of computational models. The goal of this study was to compare flow field characteristics of the three most commonly used transcatheter and surgical valves using phase-locked particle image velocimetry (PIV). 26mm SAPIEN 3, 26mm CoreValve, and 25mm PERIMOUNT Magna were examined in a pulse duplicator with input parameters matching ISO-5840. A 2D PIV system was used to obtain the velocity fields. Flow velocity and shear stress were obtained during the entire cardiac cycle. In-vitro testing showed that mean gradient was lowest for SAPIEN 3, followed by CoreValve and PERIMOUNT Magna. In all the valves, the peak jet velocity and maximum viscous shear stress were 2 m/s and 2 MPa, respectively. In conclusion, PIV was used to investigate flow field downstream of the three bioprostheses. Viscous shear stress was low and consequently shear-induced thrombotic trauma or shear-induced damage to red blood cells is unlikely.

Hepatitis Virus Capsid Polymorphs Respond Differently to Changes in Encapsulated Cargo Size

PubMed Central

He, Li; Porterfield, J. Zachary; van der Schoot, Paul; Zlotnick, Adam; Dragnea, Bogdan

2017-01-01

A templated assembly approach for Hepatitis B virus-like particles was employed to determine how the T = 3 and T = 4 polymorphs of the Hepatitis B virus (HBV) icosahedral cores respond to a systematic, gradual change in the encapsulated cargo size. It was found that assembly into complete virus-like particles occurs cooperatively around a variety of core diameters, albeit the degree of cooperativity varies. Among these virus-like particles, it was found that those of an outer diameter similar to T = 4 are able to accommodate the widest range of cargo sizes. PMID:24010404

Correction coil cable

DOEpatents

Wang, S.T.

1994-11-01

A wire cable assembly adapted for the winding of electrical coils is taught. A primary intended use is for use in particle tube assemblies for the Superconducting Super Collider. The correction coil cables have wires collected in wire array with a center rib sandwiched therebetween to form a core assembly. The core assembly is surrounded by an assembly housing having an inner spiral wrap and a counter wound outer spiral wrap. An alternate embodiment of the invention is rolled into a keystoned shape to improve radial alignment of the correction coil cable on a particle tube in a particle tube assembly. 7 figs.

Morphology and electronic structure of the oxide shell on the surface of iron nanoparticles.

PubMed

Wang, Chongmin; Baer, Donald R; Amonette, James E; Engelhard, Mark H; Antony, Jiji; Qiang, You

2009-07-01

An iron (Fe) nanoparticle exposed to air at room temperature will be instantly covered by an oxide shell that is typically approximately 3 nm thick. The nature of this native oxide shell, in combination with the underlying Fe(0) core, determines the physical and chemical behavior of the core-shell nanoparticle. One of the challenges of characterizing core-shell nanoparticles is determining the structure of the oxide shell, that is, whether it is FeO, Fe(3)O(4), gamma-Fe(2)O(3), alpha-Fe(2)O(3), or something else. The results of prior characterization efforts, which have mostly used X-ray diffraction and spectroscopy, electron diffraction, and transmission electron microscopic imaging, have been framed in terms of one of the known Fe-oxide structures, although it is not necessarily true that the thin layer of Fe oxide is a known Fe oxide. In this Article, we probe the structure of the oxide shell on Fe nanoparticles using electron energy loss spectroscopy (EELS) at the oxygen (O) K-edge with a spatial resolution of several nanometers (i.e., less than that of an individual particle). We studied two types of representative particles: small particles that are fully oxidized (no Fe(0) core) and larger core-shell particles that possess an Fe core. We found that O K-edge spectra collected for the oxide shell in nanoparticles show distinct differences from those of known Fe oxides. Typically, the prepeak of the spectra collected on both the core-shell and the fully oxidized particles is weaker than that collected on standard Fe(3)O(4). Given the fact that the origin of this prepeak corresponds to the transition of the O 1s electron to the unoccupied state of O 2p hybridized with Fe 3d, a weak pre-edge peak indicates a combination of the following four factors: a higher degree of occupancy of the Fe 3d orbital; a longer Fe-O bond length; a decreased covalency of the Fe-O bond; and a measure of cation vacancies. These results suggest that the coordination configuration in the oxide shell on Fe nanoparticles is defective as compared to that of their bulk counterparts. Implications of these defective structural characteristics on the properties of core-shell structured iron nanoparticles are discussed.

Optical trapping of nanoshells

NASA Astrophysics Data System (ADS)

Hester, Brooke C.; Crawford, Alice; Kishore, Rani B.; Helmerson, Kristian; Halas, Naomi J.; Levin, Carly

2007-09-01

We investigate near-resonant trapping of Rayleigh particles in optical tweezers. Although optical forces due to a near-resonant laser beam have been extensively studied for atoms, the situation for larger particles is that the laser wavelength is far from any absorption resonance. Theory predicts, however, that the trapping force exerted on a Rayleigh particle is enhanced, and may be three to fifty times larger for frequencies near resonance than for frequencies far off resonance. The ability to selectively trap only particles with a given absorption peak may have many practical applications. In order to investigate near-resonant trapping we are using nanoshells, particles with a dielectric core and metallic coating that can exhibit plasmon resonances. The resonances of the nanoshells can be tuned by adjusting the ratio of the radius of the dielectric core, r I, to the overall radius, r II, which includes the thickness of the metallic coating. Our nanoshells, fabricated at Rice University, consist of a silica core with a gold coating. Using back focal plane detection, we measure the trap stiffness of a single focus optical trap (optical tweezers), from a diode laser at 853 nm for nanoshells with several different r I/r II ratios.

MATCHED-INDEX-OF-REFRACTION FLOW FACILITY FOR FUNDAMENTAL AND APPLIED RESEARCH

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

Piyush Sabharwall; Carl Stoots; Donald M. McEligot

2014-11-01

Significant challenges face reactor designers with regard to thermal hydraulic design and associated modeling for advanced reactor concepts. Computational thermal hydraulic codes solve only a piece of the core. There is a need for a whole core dynamics system code with local resolution to investigate and understand flow behavior with all the relevant physics and thermo-mechanics. The matched index of refraction (MIR) flow facility at Idaho National Laboratory (INL) has a unique capability to contribute to the development of validated computational fluid dynamics (CFD) codes through the use of state-of-the-art optical measurement techniques, such as Laser Doppler Velocimetry (LDV) andmore » Particle Image Velocimetry (PIV). PIV is a non-intrusive velocity measurement technique that tracks flow by imaging the movement of small tracer particles within a fluid. At the heart of a PIV calculation is the cross correlation algorithm, which is used to estimate the displacement of particles in some small part of the image over the time span between two images. Generally, the displacement is indicated by the location of the largest peak. To quantify these measurements accurately, sophisticated processing algorithms correlate the locations of particles within the image to estimate the velocity (Ref. 1). Prior to use with reactor deign, the CFD codes have to be experimentally validated, which requires rigorous experimental measurements to produce high quality, multi-dimensional flow field data with error quantification methodologies. Computational thermal hydraulic codes solve only a piece of the core. There is a need for a whole core dynamics system code with local resolution to investigate and understand flow behavior with all the relevant physics and thermo-mechanics. Computational techniques with supporting test data may be needed to address the heat transfer from the fuel to the coolant during the transition from turbulent to laminar flow, including the possibility of an early laminarization of the flow (Refs. 2 and 3) (laminarization is caused when the coolant velocity is theoretically in the turbulent regime, but the heat transfer properties are indicative of the coolant velocity being in the laminar regime). Such studies are complicated enough that computational fluid dynamics (CFD) models may not converge to the same conclusion. Thus, experimentally scaled thermal hydraulic data with uncertainties should be developed to support modeling and simulation for verification and validation activities. The fluid/solid index of refraction matching technique allows optical access in and around geometries that would otherwise be impossible while the large test section of the INL system provides better spatial and temporal resolution than comparable facilities. Benchmark data for assessing computational fluid dynamics can be acquired for external flows, internal flows, and coupled internal/external flows for better understanding of physical phenomena of interest. The core objective of this study is to describe MIR and its capabilities, and mention current development areas for uncertainty quantification, mainly the uncertainty surface method and cross-correlation method. Using these methods, it is anticipated to establish a suitable approach to quantify PIV uncertainty for experiments performed in the MIR.« less

Size distribution and mixing state of black carbon particles during a heavy air pollution episode in Shanghai

NASA Astrophysics Data System (ADS)

Gong, Xianda; Zhang, Ci; Chen, Hong; Nizkorodov, Sergey A.; Chen, Jianmin; Yang, Xin

2016-04-01

A Single Particle Aerosol Mass Spectrometer (SPAMS), a Single Particle Soot Photometer (SP2) and various meteorological instruments were employed to investigate the chemical and physical properties of black carbon (BC) aerosols during a regional air pollution episode in urban Shanghai over a 5-day period in December 2013. The refractory black carbon (rBC) mass concentrations measured by SP2 averaged 3.2 µg m-3, with the peak value of 12.1 µg m-3 at 04:26 LT on 7 December. The number of BC-containing particles captured by SPAMS in the size range 200-1200 nm agreed very well with that detected by SP2 (R2 = 0.87). A cluster analysis of the single particle mass spectra allowed for the separation of BC-containing particles into five major classes: (1) Pure BC; (2) BC attributed to biomass burning (BBBC); (3) K-rich BC-containing (KBC); (4) BC internally mixed with OC and ammonium sulfate (BCOC-SOx); (5) BC internally mixed with OC and ammonium nitrate (BCOC-NOx). The size distribution of internally mixed BC particles was bimodal. Detected by SP2, the condensation mode peaked around ˜ 230 nm and droplet mode peaked around ˜ 380 nm, with a clear valley in the size distribution around ˜ 320 nm. The condensation mode mainly consisted of traffic emissions, with particles featuring a small rBC core (˜ 60-80 nm) and a relatively thin absolute coating thickness (ACT, ˜ 50-130 nm). The droplet mode included highly aged traffic emission particles and biomass burning particles. The biomass burning particles had a larger rBC core (˜ 80-130 nm) and a thick ACT (˜ 110-300 nm). The highly aged traffic emissions had a smaller core (˜ 60-80 nm) and a very thick ACT (˜ 130-300 nm), which is larger than reported in any previous literature. A fast growth rate (˜ 20 nm h-1) of rBC with small core sizes was observed during the experiment. High concentrations pollutants like NO2 likely accelerated the aging process and resulted in a continuous size growth of rBC-containing particles from traffic emission.

Radial heterogeneity of some analytical columns used in high-performance liquid chromatography.

PubMed

Abia, Jude A; Mriziq, Khaled S; Guiochon, Georges A

2009-04-10

An on-column electrochemical microdetector was used to determine accurately the radial distribution of the mobile phase velocity and of the column efficiency at the exit of three common analytical columns, namely a 100 mm x 4.6mm C18 bonded silica-based monolithic column, a 150 mm x 4.6mm column packed with 2.7 microm porous shell particles of C18 bonded silica (HALO), and a 150 mm x 4.6mm column packed with 3 microm fully porous C18 bonded silica particles (LUNA). The results obtained demonstrate that all three columns are not radially homogeneous. In all three cases, the efficiency was found to be lower in the wall region of the column than in its core region (the central core with a radius of 1/3 the column inner radius). The decrease in local efficiency from the core to the wall regions was lower in the case of the monolith (ca. 25%) than in that of the two particle-packed columns (ca. 35-50%). The mobile phase velocity was found to be ca. 1.5% higher in the wall than in the core region of the monolithic column while, in contrast, it was ca. 2.5-4.0% lower in the wall region for the two particle-packed columns.

Core-shell monodisperse spherical mSiO2/Gd2O3:Eu3+@mSiO2 particles as potential multifunctional theranostic agents

NASA Astrophysics Data System (ADS)

Eurov, Daniil A.; Kurdyukov, Dmitry A.; Kirilenko, Demid A.; Kukushkina, Julia A.; Nashchekin, Alexei V.; Smirnov, Alexander N.; Golubev, Valery G.

2015-02-01

Core-shell nanoparticles with diameters in the range 100-500 nm have been synthesized as monodisperse spherical mesoporous (pore diameter 3 nm) silica particles with size deviation of less than 4 %, filled with gadolinium and europium oxides and coated with a mesoporous silica shell. It is shown that the melt technique developed for filling with gadolinium and europium oxides provides a nearly maximum filling of mesopores in a single-run impregnation, with gadolinium and europium uniformly distributed within the particles and forming no bulk oxides on their surface. The coating with a shell does not impair the monodispersity and causes no coagulation. The coating technique enables controlled variation of the shell thickness within the range 5-100 % relative to the core diameter. The thus produced nanoparticles are easily dispersed in water, have large specific surface area (300 m2 g-1) and pore volume (0.3 cm3 g-1), and are bright solid phosphor with superior stability in aqueous media. The core-shell structured particles can be potentially used for cancer treatment as a therapeutic agent (gadolinium neutron-capture therapy and drug delivery system) and, simultaneously, as a multimodal diagnostic tool (fluorescence and magnetic resonance imaging), thereby serving as a multifunctional theranostic agent.

Evaluation of damage progression and mechanical behavior under compression of bone cements containing core-shell nanoparticles by using acoustic emission technique.

PubMed

Pacheco-Salazar, O F; Wakayama, Shuichi; Sakai, Takenobu; Cauich-Rodríguez, J V; Ríos-Soberanis, C R; Cervantes-Uc, J M

2015-06-01

In this work, the effect of the incorporation of core-shell particles on the fracture mechanisms of the acrylic bone cements by using acoustic emission (AE) technique during the quasi-static compression mechanical test was investigated. Core-shell particles were composed of a poly(butyl acrylate) (PBA) rubbery core and a methyl methacrylate/styrene copolymer (P(MMA-co-St)) outer glassy shell. Nanoparticles were prepared with different core-shell ratio (20/80, 30/70, 40/60 and 50/50) and were incorporated into the solid phase of bone cement at several percentages (5, 10 and 15 wt%). It was observed that the particles exhibited a spherical morphology averaging ca. 125 nm in diameter, and the dynamic mechanical analysis (DMA) thermograms revealed the desired structuring pattern of phases associated with core-shell structures. A fracture mechanism was proposed taking into account the detected AE signals and the scanning electron microscopy (SEM) micrographs. In this regard, core-shell nanoparticles can act as both additional nucleation sites for microcracks (and crazes) and to hinder the microcrack propagation acting as a barrier to its growth; this behavior was presented by all formulations. Cement samples containing 15 wt% of core-shell nanoparticles, either 40/60 or 50/50, were fractured at 40% deformation. This fact seems related to the coalescence of microcracks after they surround the agglomerates of core-shell nanoparticles to continue growing up. This work also demonstrated the potential of the AE technique to be used as an accurate and reliable detection tool for quasi-static compression test in acrylic bone cements. Copyright © 2015 Elsevier Ltd. All rights reserved.

Maxwell-Stefan diffusion: a framework for predicting condensed phase diffusion and phase separation in atmospheric aerosol

NASA Astrophysics Data System (ADS)

Fowler, Kathryn; Connolly, Paul J.; Topping, David O.; O'Meara, Simon

2018-02-01

The composition of atmospheric aerosol particles has been found to influence their micro-physical properties and their interaction with water vapour in the atmosphere. Core-shell models have been used to investigate the relationship between composition, viscosity and equilibration timescales. These models have traditionally relied on the Fickian laws of diffusion with no explicit account of non-ideal interactions. We introduce the Maxwell-Stefan diffusion framework as an alternative method, which explicitly accounts for non-ideal interactions through activity coefficients. e-folding time is the time it takes for the difference in surface and bulk concentration to change by an exponential factor and was used to investigate the interplay between viscosity and solubility and the effect this has on equilibration timescales within individual aerosol particles. The e-folding time was estimated after instantaneous increases in relative humidity to binary systems of water and an organic component. At low water mole fractions, viscous effects were found to dominate mixing. However, at high water mole fractions, equilibration times were more sensitive to a range in solubility, shown through the greater variation in e-folding times. This is the first time the Maxwell-Stefan framework has been applied to an atmospheric aerosol core-shell model and shows that there is a complex interplay between the viscous and solubility effects on aerosol composition that requires further investigation.

Observations and Modeling of the Green Ocean Amazon 2014/15: Transmission Electron Microscopy Analysis of Aerosol Particles Field Campaign Report

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

Buseck, Peter

2016-03-01

During two Intensive Operational Periods (IOP), we collected samples at 3-hour intervals for transmission electron microscopy analysis. The resulting transmission electron microscopy images and compositions were analyzed for the samples of interest. Further analysis will be done especially for the plume of interest. We found solid spherical organic particles from rebounded samples collected with Professor Scot Martin’s group (Harvard University). Approximately 30% of the rebounded particles at 95% relative humidity were spherical organic particles. Their sources and formation process are not known, but such spherical particles could be solid and will have heterogeneous chemical reactions. We observed many organic particlesmore » that are internally mixed with inorganic elements such as potassium and nitrogen. They are either homogeneously mixed or have inorganic cores with organic aerosol coatings. Samples collected from the Manaus, Brazil, pollution plume included many nano-size soot particles mixed with organic material and sulfate. Aerosol particles from clean periods included organic aerosol particles, sulfate, sea salt, dust, and primary biogenic aerosol particles. There was more dust, primary biogenic aerosol, and tar balls in samples taken during IOP1 than those taken during IOP2. Many dust particles were found between March 2 and 3.« less

A new class of g-modes in neutron stars

NASA Technical Reports Server (NTRS)

Reisenegger, Andreas; Goldreich, Peter

1992-01-01

Because a neutron star is born hot, its internal composition is close to chemical equilibrium. In the fluid core, this implies that the ratio of the number densities of charged particles (protons and electrons) to neutrons is an increasing function of the mass density. This composition gradient stably stratifies the matter giving rise to a Brunt-Vaisala frequency N of about 500/s. Consequently, a neutron star core provides a cavity that supports gravity modes (g-modes). These g-modes are distinct from those previously identified with the thermal stratification of the surface layers and the chemical stratification of the crust. We compute the lowest-order, quadrupolar, g-modes for cold, Newtonian, neutron star models with M/solar M = 0.581 and M/solar M = 1.405, and show that the crustal and core g-modes have similar periods. We also discuss damping mechanisms and estimate damping rates for the core g-modes. Particular attention is paid to damping due to the emission of gravitational radiation.