Toxoplasma gondii: Biochemical and biophysical characterization of recombinant soluble dense granule proteins GRA2 and GRA6

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

Bittame, Amina; Université Grenoble Alpes, 38042 Grenoble; Effantin, Grégory

2015-03-27

The most prominent structural feature of the parasitophorous vacuole (PV) in which the intracellular parasite Toxoplasma gondii proliferates is a membranous nanotubular network (MNN), which interconnects the parasites and the PV membrane. The MNN function remains unclear. The GRA2 and GRA6 proteins secreted from the parasite dense granules into the PV have been implicated in the MNN biogenesis. Amphipathic alpha-helices (AAHs) predicted in GRA2 and an alpha-helical hydrophobic domain predicted in GRA6 have been proposed to be responsible for their membrane association, thereby potentially molding the MMN in its structure. Here we report an analysis of the recombinant proteins (expressedmore » in detergent-free conditions) by circular dichroism, which showed that full length GRA2 displays an alpha-helical secondary structure while recombinant GRA6 and GRA2 truncated of its AAHs are mainly random coiled. Dynamic light scattering and transmission electron microscopy showed that recombinant GRA6 and truncated GRA2 constitute a homogenous population of small particles (6–8 nm in diameter) while recombinant GRA2 corresponds to 2 populations of particles (∼8–15 nm and up to 40 nm in diameter, respectively). The unusual properties of GRA2 due to its AAHs are discussed. - Highlights: • Toxoplasma gondii: soluble GRA2 forms 2 populations of particles. • T. gondii: the dense granule protein GRA2 folds intrinsically as an alpha-helix. • T. gondii: monomeric soluble GRA6 forms particles of 6–8 nm in diameter. • T. gondii: monomeric soluble GRA6 is random coiled. • Unusual biophysical properties of the dense granule protein GRA2 from T. gondii.« less

High-temperature, flexible, thermal barrier seal

NASA Technical Reports Server (NTRS)

Sirocky, Paul J. (Inventor); Steinetz, Bruce M. (Inventor)

1991-01-01

This device seals the sliding interfaces between structural panels that are roughly perpendicular to each other or whose edges are butted against one another. The nonuniformity of the gap between the panels requires significant flexibility along the seal length. The seal is mounted in a rectangular groove in a movable structural panel. A plurality of particles or balls is densely packed in an outer sheathing. The balls are laterally preloaded to maintain sealing contact with the adjacent wall using a pressurized linear bellows. Distortions in the adjacent panel are accommodated by rearrangement of the particles within the outer sheathing. Leakage through the seal is minimized by densely compacting the internal particles and by maintaining positive preload along the back side of the seal. The braid architecture of the outer sheathing is selected to minimize leakage through the seal and to resist mechanical abrasion.

Direct observation of impact propagation and absorption in dense colloidal monolayers

NASA Astrophysics Data System (ADS)

Buttinoni, Ivo; Cha, Jinwoong; Lin, Wei-Hsun; Job, Stéphane; Daraio, Chiara; Isa, Lucio

2017-11-01

Dense colloidal suspensions can propagate and absorb large mechanical stresses, including impacts and shocks. The wave transport stems from the delicate interplay between the spatial arrangement of the structural units and solvent-mediated effects. For dynamic microscopic systems, elastic deformations of the colloids are usually disregarded due to the damping imposed by the surrounding fluid. Here, we study the propagation of localized mechanical pulses in aqueous monolayers of micron-sized particles of controlled microstructure. We generate extreme localized deformation rates by exciting a target particle via pulsed-laser ablation. In crystalline monolayers, stress propagation fronts take place, where fast-moving particles (V approximately a few meters per second) are aligned along the symmetry axes of the lattice. Conversely, more viscous solvents and disordered structures lead to faster and isotropic energy absorption. Our results demonstrate the accessibility of a regime where elastic collisions also become relevant for suspensions of microscopic particles, behaving as “billiard balls” in a liquid, in analogy with regular packings of macroscopic spheres. We furthermore quantify the scattering of an impact as a function of the local structural disorder.

Direct observation of impact propagation and absorption in dense colloidal monolayers

PubMed Central

Cha, Jinwoong; Lin, Wei-Hsun; Job, Stéphane; Daraio, Chiara

2017-01-01

Dense colloidal suspensions can propagate and absorb large mechanical stresses, including impacts and shocks. The wave transport stems from the delicate interplay between the spatial arrangement of the structural units and solvent-mediated effects. For dynamic microscopic systems, elastic deformations of the colloids are usually disregarded due to the damping imposed by the surrounding fluid. Here, we study the propagation of localized mechanical pulses in aqueous monolayers of micron-sized particles of controlled microstructure. We generate extreme localized deformation rates by exciting a target particle via pulsed-laser ablation. In crystalline monolayers, stress propagation fronts take place, where fast-moving particles (V approximately a few meters per second) are aligned along the symmetry axes of the lattice. Conversely, more viscous solvents and disordered structures lead to faster and isotropic energy absorption. Our results demonstrate the accessibility of a regime where elastic collisions also become relevant for suspensions of microscopic particles, behaving as “billiard balls” in a liquid, in analogy with regular packings of macroscopic spheres. We furthermore quantify the scattering of an impact as a function of the local structural disorder. PMID:29087329

Maximally dense packings of two-dimensional convex and concave noncircular particles.

PubMed

Atkinson, Steven; Jiao, Yang; Torquato, Salvatore

2012-09-01

Dense packings of hard particles have important applications in many fields, including condensed matter physics, discrete geometry, and cell biology. In this paper, we employ a stochastic search implementation of the Torquato-Jiao adaptive-shrinking-cell (ASC) optimization scheme [Nature (London) 460, 876 (2009)] to find maximally dense particle packings in d-dimensional Euclidean space R(d). While the original implementation was designed to study spheres and convex polyhedra in d≥3, our implementation focuses on d=2 and extends the algorithm to include both concave polygons and certain complex convex or concave nonpolygonal particle shapes. We verify the robustness of this packing protocol by successfully reproducing the known putative optimal packings of congruent copies of regular pentagons and octagons, then employ it to suggest dense packing arrangements of congruent copies of certain families of concave crosses, convex and concave curved triangles (incorporating shapes resembling the Mercedes-Benz logo), and "moonlike" shapes. Analytical constructions are determined subsequently to obtain the densest known packings of these particle shapes. For the examples considered, we find that the densest packings of both convex and concave particles with central symmetry are achieved by their corresponding optimal Bravais lattice packings; for particles lacking central symmetry, the densest packings obtained are nonlattice periodic packings, which are consistent with recently-proposed general organizing principles for hard particles. Moreover, we find that the densest known packings of certain curved triangles are periodic with a four-particle basis, and we find that the densest known periodic packings of certain moonlike shapes possess no inherent symmetries. Our work adds to the growing evidence that particle shape can be used as a tuning parameter to achieve a diversity of packing structures.

Maximally dense packings of two-dimensional convex and concave noncircular particles

NASA Astrophysics Data System (ADS)

Atkinson, Steven; Jiao, Yang; Torquato, Salvatore

2012-09-01

Dense packings of hard particles have important applications in many fields, including condensed matter physics, discrete geometry, and cell biology. In this paper, we employ a stochastic search implementation of the Torquato-Jiao adaptive-shrinking-cell (ASC) optimization scheme [Nature (London)NATUAS0028-083610.1038/nature08239 460, 876 (2009)] to find maximally dense particle packings in d-dimensional Euclidean space Rd. While the original implementation was designed to study spheres and convex polyhedra in d≥3, our implementation focuses on d=2 and extends the algorithm to include both concave polygons and certain complex convex or concave nonpolygonal particle shapes. We verify the robustness of this packing protocol by successfully reproducing the known putative optimal packings of congruent copies of regular pentagons and octagons, then employ it to suggest dense packing arrangements of congruent copies of certain families of concave crosses, convex and concave curved triangles (incorporating shapes resembling the Mercedes-Benz logo), and “moonlike” shapes. Analytical constructions are determined subsequently to obtain the densest known packings of these particle shapes. For the examples considered, we find that the densest packings of both convex and concave particles with central symmetry are achieved by their corresponding optimal Bravais lattice packings; for particles lacking central symmetry, the densest packings obtained are nonlattice periodic packings, which are consistent with recently-proposed general organizing principles for hard particles. Moreover, we find that the densest known packings of certain curved triangles are periodic with a four-particle basis, and we find that the densest known periodic packings of certain moonlike shapes possess no inherent symmetries. Our work adds to the growing evidence that particle shape can be used as a tuning parameter to achieve a diversity of packing structures.

INTRACELLULAR FORMS OF POX VIRUSES AS SHOWN BY THE ELECTRON MICROSCOPE (VACCINIA, ECTROMELIA, MOLLUSCUM CONTAGIOSUM)

PubMed Central

Gaylord, William H.; Melnick, Joseph L.

1953-01-01

The intracellular development of three pox viruses has been studied with the electron microscope using thin sections of infected tissue. Cells infected with vaccinia, ectromelia, and molluscum contagiosum viruses all form developmental bodies preliminary to the production of mature virus. Developmental bodies, believed to be virus precursors, are round to oval, slightly larger than mature virus particles, less dense to electrons, and have a more varied morphology. It is suggested as a working hypothesis that the process of maturation of a virus particle takes place as follows. In the earliest form the developmental bodies appear as hollow spheres, imbedded in a very dense cytoplasmic mass constituting an inclusion body, or in a less dense matrix near the nucleus in cells without typical inclusion bodies. The spheres become filled with a homogeneous material of low electron density. A small, dense granule appears in each developmental body and grows in size at the expense of the low density material. Following growth of the granule, particles are found with the dimensions of mature virus and having complex internal structure resembling bars or dumbells. Mature virus is ovoid and very dense to electrons. An "empty" interior may be found within its thick walls. PMID:13069658

FCC-HCP coexistence in dense thermo-responsive microgel crystals

NASA Astrophysics Data System (ADS)

Karthickeyan, D.; Joshi, R. G.; Tata, B. V. R.

2017-06-01

Analogous to hard-sphere suspensions, monodisperse thermo-responsive poly (N-isopropyl acrylamide) (PNIPAM) microgel particles beyond a volume fraction (ϕ) of 0.5 freeze into face centered cubic (FCC)-hexagonal close packed (HCP) coexistence under as prepared conditions and into an FCC structure upon annealing. We report here FCC-HCP coexistence to be stable in dense PNIPAM microgel crystals (ϕ > 0.74) with particles in their deswollen state (referred to as osmotically compressed microgel crystals) and the FCC structure with particles in their swollen state by performing annealing studies with different cooling rates. The structure of PNIPAM microgel crystals is characterized using static light scattering technique and UV-Visible spectroscopy and dynamics by dynamic light scattering (DLS). DLS studies reveal that the particle motion is diffusive at short times in crystals with ϕ < 0.74 and sub-diffusive at short times in PNIPAM crystals with ϕ > 0.74. The observed sub-diffusive behavior at short times is due to the overlap (interpenetration) of the dangling polymer chains between the shells of neighbouring PNIPAM microgel particles. Overlap is found to disappear upon heating the crystals well above their melting temperature, Tm due to reduction in the particle size. Annealing studies confirm that the overlap of dangling polymer chains between the shells of neighbouring PNIPAM spheres is responsible for the stability of FCC-HCP coexistence observed in osmotically compressed PNIPAM microgel crystals. Results are discussed in the light of recent reports of stabilizing the HCP structure in hard sphere crystals by adding interacting polymer chains.

X-ray (image)

MedlinePlus

X-rays are a form of electromagnetic radiation, just like visible light. Structures that are dense (such as bone) will block most of the x-ray particles, and will appear white. Metal and contrast media ( ...

Exploring the Early Structure of a Rapidly Decompressed Particle Bed

NASA Astrophysics Data System (ADS)

Zunino, Heather; Adrian, R. J.; Clarke, Amanda; Johnson, Blair; Arizona State University Collaboration

2017-11-01

Rapid expansion of dense, pressurized beds of fine particles subjected to rapid reduction of the external pressure is studied in a vertical shock tube. A near-sonic expansion wave impinges on the particle bed-gas interface and rapidly unloads the particle bed. A high-speed video camera captures events occurring during bed expansion. The particle bed does not expand homogeneously, but breaks down into horizontal slabs and then transforms into a cellular-type structure. There are several key parameters that affect the particle bed evolution, including particle size and initial bed height. Analyses of this bed structure evolution from experiments with varying particle sizes and initial bed heights is presented. This work is supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science and Academic Alliance Program, under Contract No. DE-NA0002378.

Fine structure of the vapor field in evaporating dense sprays

NASA Astrophysics Data System (ADS)

Villermaux, Emmanuel; Moutte, Alexandre; Amielh, Muriel; Meunier, Patrice

2017-11-01

Making use of an original technique which permits the simultaneous measurement of both the displacement field of evaporating droplets in a spray, and of their vapor, we investigate the relevance of a scenario introduced earlier to describe the evaporation dynamics of dense sprays. A plume of dense acetone droplets evaporating in air is studied, for which the stirring field is measured by particle image velocimetry of the droplets, and the vapor field is imaged quantitatively by laser-induced fluorescence. We show, thanks to these unique in situ measurements, that the spray boundary with the diluting environment is slaved to the dynamics of its saturating vapor concentration field, whose structure is analyzed for different well defined local flow topologies.

Shell-corona microgels from double interpenetrating networks.

PubMed

Rudyak, Vladimir Yu; Gavrilov, Alexey A; Kozhunova, Elena Yu; Chertovich, Alexander V

2018-04-18

Polymer microgels with a dense outer shell offer outstanding features as universal carriers for different guest molecules. In this paper, microgels formed by an interpenetrating network comprised of collapsed and swollen subnetworks are investigated using dissipative particle dynamics (DPD) computer simulations, and it is found that such systems can form classical core-corona structures, shell-corona structures, and core-shell-corona structures, depending on the subchain length and molecular mass of the system. The core-corona structures consisting of a dense core and soft corona are formed at small microgel sizes when the subnetworks are able to effectively separate in space. The most interesting shell-corona structures consist of a soft cavity in a dense shell surrounded with a loose corona, and are found at intermediate gel sizes; the area of their existence depends on the subchain length and the corresponding mesh size. At larger molecular masses the collapsing network forms additional cores inside the soft cavity, leading to the core-shell-corona structure.

Modeling shear-induced particle ordering and deformation in a dense soft particle suspension

NASA Astrophysics Data System (ADS)

Liao, Chih-Tang; Wu, Yi-Fan; Chien, Wei; Huang, Jung-Ren; Chen, Yeng-Long

2017-11-01

We apply the lattice Boltzmann method and the bead-spring network model of deformable particles (DPs) to study shear-induced particle ordering and deformation and the corresponding rheological behavior for dense DP suspensions confined in a narrow gap under steady external shear. The particle configuration is characterized with small-angle scattering intensity, the real-space 2D local order parameter, and the particle shape factors including deformation, stretching and tilt angles. We investigate how particle ordering and deformation vary with the particle volume fraction ϕ (=0.45-0.65) and the external shear rate characterized with the capillary number Ca (=0.003-0.191). The degree of particle deformation increases mildly with ϕ but significantly with Ca. Under moderate shear rate (Ca  =  0.105), the inter-particle structure evolves from string-like ordering to layered hexagonal close packing (HCP) as ϕ increases. A long wavelength particle slithering motion emerges for sufficiently large ϕ. For ϕ  =  0.61, the structure maintains layered HCP for Ca  =  0.031-0.143 but gradually becomes disordered for larger and smaller Ca. The correlation in particle zigzag movements depends sensitively on ϕ and particle ordering. Layer-by-layer analysis reveals how the non-slippery hard walls affect particle ordering and deformation. The shear-induced reconfiguration of DPs observed in the simulation agrees qualitatively with experimental results of sheared uniform emulsions. The apparent suspension viscosity increases with ϕ but exhibits much weaker dependence compared to hard-sphere suspensions, indicating that particle deformation and unjamming under shear can significantly reduce the viscous stress. Furthermore, the suspension shear-thins, corresponding to increased inter-DP ordering and particle deformation with Ca. This work provides useful insights into the microstructure-rheology relationship of concentrated deformable particle suspensions.

Modeling shear-induced particle ordering and deformation in a dense soft particle suspension.

PubMed

Liao, Chih-Tang; Wu, Yi-Fan; Chien, Wei; Huang, Jung-Ren; Chen, Yeng-Long

2017-11-01

We apply the lattice Boltzmann method and the bead-spring network model of deformable particles (DPs) to study shear-induced particle ordering and deformation and the corresponding rheological behavior for dense DP suspensions confined in a narrow gap under steady external shear. The particle configuration is characterized with small-angle scattering intensity, the real-space 2D local order parameter, and the particle shape factors including deformation, stretching and tilt angles. We investigate how particle ordering and deformation vary with the particle volume fraction ϕ (=0.45-0.65) and the external shear rate characterized with the capillary number Ca (=0.003-0.191). The degree of particle deformation increases mildly with ϕ but significantly with Ca. Under moderate shear rate (Ca  =  0.105), the inter-particle structure evolves from string-like ordering to layered hexagonal close packing (HCP) as ϕ increases. A long wavelength particle slithering motion emerges for sufficiently large ϕ. For ϕ  =  0.61, the structure maintains layered HCP for Ca  =  0.031-0.143 but gradually becomes disordered for larger and smaller Ca. The correlation in particle zigzag movements depends sensitively on ϕ and particle ordering. Layer-by-layer analysis reveals how the non-slippery hard walls affect particle ordering and deformation. The shear-induced reconfiguration of DPs observed in the simulation agrees qualitatively with experimental results of sheared uniform emulsions. The apparent suspension viscosity increases with ϕ but exhibits much weaker dependence compared to hard-sphere suspensions, indicating that particle deformation and unjamming under shear can significantly reduce the viscous stress. Furthermore, the suspension shear-thins, corresponding to increased inter-DP ordering and particle deformation with Ca. This work provides useful insights into the microstructure-rheology relationship of concentrated deformable particle suspensions.

Nonlinear microrheology of dense colloidal suspensions: A mode-coupling theory

NASA Astrophysics Data System (ADS)

Gazuz, I.; Fuchs, M.

2013-03-01

A mode-coupling theory for the motion of a strongly forced probe particle in a dense colloidal suspension is presented. Starting point is the Smoluchowski equation for N bath and a single probe particle. The probe performs Brownian motion under the influence of a strong constant and uniform external force Fex. It is immersed in a dense homogeneous bath of (different) particles also performing Brownian motion. Fluid and glass states are considered; solvent flow effects are neglected. Based on a formally exact generalized Green-Kubo relation, mode coupling approximations are performed and an integration through transients approach applied. A microscopic theory for the nonlinear velocity-force relations of the probe particle in a dense fluid and for the (de-) localized probe in a glass is obtained. It extends the mode coupling theory of the glass transition to strongly forced tracer motion and describes active microrheology experiments. A force threshold is identified which needs to be overcome to pull the probe particle free in a glass. For the model of hard sphere particles, the microscopic equations for the threshold force and the probability density of the localized probe are solved numerically. Neglecting the spatial structure of the theory, a schematic model is derived which contains two types of bifurcation, the glass transition and the force-induced delocalization, and which allows for analytical and numerical solutions. We discuss its phase diagram, forcing effects on the time-dependent correlation functions, and the friction increment. The model was successfully applied to simulations and experiments on colloidal hard sphere systems [Gazuz , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.248302 102, 248302 (2009)], while we provide detailed information on its derivation and general properties.

Wet formation and structural characterization of quasi-hexagonal monolayers.

PubMed

Batys, Piotr; Weroński, Paweł; Nosek, Magdalena

2016-01-01

We have presented a simple and efficient method for producing dense particle monolayers with controlled surface coverage. The method is based on particle sedimentation, manipulation of the particle-substrate electrostatic interaction, and gentle mechanical vibration of the system. It allows for obtaining quasi-hexagonal structures under wet conditions. Using this method, we have produced a monolayer of 3 μm silica particles on a glassy carbon substrate. By optical microscopy, we have determined the coordinates of the particles and surface coverage of the obtained structure to be 0.82. We have characterized the monolayer structure by means of the pair-correlation function and power spectrum. We have also compared the results with those for a 2D hexagonal monolayer and monolayer generated by random sequential adsorption at the coverage 0.50. We have found the surface fractal dimension to be 2.5, independently of the monolayer surface coverage. Copyright © 2015 Elsevier Inc. All rights reserved.

Ultrastructural and x-ray microanalytical observations of minocycline-related hyperpigmentation of the skin

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

Sato, S.; Murphy, G.F.; Bernhard, J.D.

1981-09-01

In order to elucidate the nature and distribution of the pigment responsible for the circumscribed blue-black cutaneous hyperpigmentation occurring after administration of minocycline hydrochloride, transmission electron microscopy and energy-dispersive electron x-ray microanalysis were performed on lesional skin. Ultrastructural observations demonstrated electron-dense iron-containing particles either incorporated into a variety of siderosomes, within dermal histiocytes, free within the cytoplasm, or, rarely, scattered among dermal collagen fibers. Electron x-ray microanalysis confirmed iron content present within these particles. Although siderosomal inclusions contained occasional melanosome complexes, the degree of deposition of electron-dense iron-containing particles in dermal histiocytes seemed to be primarily responsible for the blue-blackmore » discoloration of the skin. The present study is an investigation of the structure and composition of the pigment responsible for minocycline-related cutaneous hyperpigmentation.« less

Effect of particle size distribution on the hydrodynamics of dense CFB risers

NASA Astrophysics Data System (ADS)

Bakshi, Akhilesh; Khanna, Samir; Venuturumilli, Raj; Altantzis, Christos; Ghoniem, Ahmed

2015-11-01

Circulating Fluidized Beds (CFB) are favorable in the energy and chemical industries, due to their high efficiency. While accurate hydrodynamic modeling is essential for optimizing performance, most CFB riser simulations are performed assuming equally-sized solid particles, owing to limited computational resources. Even though this approach yields reasonable predictions, it neglects commonly observed experimental findings suggesting the strong effect of particle size distribution (psd) on the hydrodynamics and chemical conversion. Thus, this study is focused on the inclusion of discrete particle sizes to represent the psd and its effect on fluidization via 2D numerical simulations. The particle sizes and corresponding mass fluxes are obtained using experimental data in dense CFB riser while the modeling framework is described in Bakshi et al 2015. Simulations are conducted at two scales: (a) fine grid to resolve heterogeneous structures and (b) coarse grid using EMMS sub-grid modifications. Using suitable metrics which capture bed dynamics, this study provides insights into segregation and mixing of particles as well as highlights need for improved sub-grid models.

Longitudinal domain wall formation in elongated assemblies of ferromagnetic nanoparticles

PubMed Central

Varón, Miriam; Beleggia, Marco; Jordanovic, Jelena; Schiøtz, Jakob; Kasama, Takeshi; Puntes, Victor F.; Frandsen, Cathrine

2015-01-01

Through evaporation of dense colloids of ferromagnetic ~13 nm ε-Co particles onto carbon substrates, anisotropic magnetic dipolar interactions can support formation of elongated particle structures with aggregate thicknesses of 100–400 nm and lengths of up to some hundred microns. Lorenz microscopy and electron holography reveal collective magnetic ordering in these structures. However, in contrast to continuous ferromagnetic thin films of comparable dimensions, domain walls appear preferentially as longitudinal, i.e., oriented parallel to the long axis of the nanoparticle assemblies. We explain this unusual domain structure as the result of dipolar interactions and shape anisotropy, in the absence of inter-particle exchange coupling. PMID:26416297

Method of bonding a conductive layer on an electrode of an electrochemical cell

DOEpatents

Bowker, J.C.; Singh, P.

1989-08-29

A dense, electronically conductive interconnection layer is bonded onto a porous, tubular, electronically conductive air electrode structure, optionally supported by a ceramic support, by (A) providing an air electrode surface, (B) forming on a selected portion of the electrode surface, without the use of pressure, particles of LaCrO[sub 3] doped with an element selected from the group consisting of Sr, Mg, Ca, Ba, Co, and mixtures thereof, where the particles have a deposit on their surface comprising calcium oxide and chromium oxide; (C) heating the particles with the oxide surface deposit in an oxidizing atmosphere at from 1,300 C to 1,550 C, without the application of pressure, to provide a dense, sintered, interconnection material bonded to the air electrode, where calcium and chromium from the surface deposit are incorporated into the structure of the LaCrO[sub 3]. A solid electrolyte layer can be applied to the uncovered portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell. 4 figs.

Method of bonding a conductive layer on an electrode of an electrochemical cell

DOEpatents

Bowker, Jeffrey C.; Singh, Prabhakar

1989-01-01

A dense, electronically conductive interconnection layer 26 is bonded onto a porous, tubular, electronically conductive air electrode structure 16, optionally supported by a ceramic support 22, by (A) providing an air electrode surface, (B) forming on a selected portion of the electrode surface 24, without the use of pressure, particles of LaCrO.sub.3 doped with an element selected from the group consisting of Sr, Mg, Ca, Ba, Co, and mixtures thereof, where the particles have a deposit on their surface comprising calcium oxide and chromium oxide; (C) heating the particles with the oxide surface deposit in an oxidizing atmosphere at from 1,300.degree. C. to 1,550.degree. C., without the application of pressure, to provide a dense, sintered, interconnection material 26 bonded to the air electrode 16, where calcium and chromium from the surface deposit are incorporated into the structure of the LaCrO.sub.3. A solid electrolyte layer 18 can be applied to the uncovered portion of the air electrode, and a fuel electrode 20 can be applied to the solid electrolyte, to provide an electrochemical cell 10.

The Million-Body Problem: Particle Simulations in Astrophysics

ScienceCinema

Rasio, Fred

2018-05-21

Computer simulations using particles play a key role in astrophysics. They are widely used to study problems across the entire range of astrophysical scales, from the dynamics of stars, gaseous nebulae, and galaxies, to the formation of the largest-scale structures in the universe. The 'particles' can be anything from elementary particles to macroscopic fluid elements, entire stars, or even entire galaxies. Using particle simulations as a common thread, this talk will present an overview of computational astrophysics research currently done in our theory group at Northwestern. Topics will include stellar collisions and the gravothermal catastrophe in dense star clusters.

Shear Induced Structural Relaxation in a Supercooled Colloidal Liquid

NASA Astrophysics Data System (ADS)

Chen, Dandan; Semwogerere, Denis; Weeks, Eric R.

2009-11-01

Amorphous materials include many common products we use everyday, such as window glass, moisturizer, shaving cream and peanut butter. These materials have liquid-like disordered structure, but keep their shapes like a solid. The rheology of dense amorphous materials under large shear strain is not fully understood, partly due to the difficulty of directly viewing the microscopic details of such materials. We use a colloidal suspension to simulate amorphous materials, and study the shear- induced structural relaxation with fast confocal microscopy. We quantify the plastic rearrangements of the particles using standard analysis techniques based on the motion of the particles.

The effects of particle loading on turbulence structure and modelling

NASA Technical Reports Server (NTRS)

Squires, Kyle D.; Eaton, J. K.

1989-01-01

The objective of the present research was to extend the Direct Numerical Simulation (DNS) approach to particle-laden turbulent flows using a simple model of particle/flow interaction. The program addressed the simplest type of flow, homogeneous, isotropic turbulence, and examined interactions between the particles and gas phase turbulence. The specific range of problems examined include those in which the particle is much smaller than the smallest length scales of the turbulence yet heavy enough to slip relative to the flow. The particle mass loading is large enough to have a significant impact on the turbulence, while the volume loading was small enough such that particle-particle interactions could be neglected. Therefore, these simulations are relevant to practical problems involving small, dense particles conveyed by turbulent gas flows at moderate loadings. A sample of the results illustrating modifications of the particle concentration field caused by the turbulence structure is presented and attenuation of turbulence by the particle cloud is also illustrated.

Fine coal cleaning via the micro-mag process

DOEpatents

Klima, Mark S.; Maronde, Carl P.; Killmeyer, Richard P.

1991-01-01

A method of cleaning particulate coal which is fed with a dense medium slurry as an inlet feed to a cyclone separator. The coal particle size distribution is in the range of from about 37 microns to about 600 microns. The dense medium comprises water and ferromagnetic particles that have a relative density in the range of from about 4.0 to about 7.0. The ferromagnetic particles of the dense medium have particle sizes of less than about 15 microns and at least a majority of the particle sizes are less than about 5 microns. In the cyclone, the particulate coal and dense-medium slurry is separated into a low gravity product stream and a high gravity produce stream wherein the differential in relative density between the two streams is not greater than about 0.2. The low gravity and high gravity streams are treated to recover the ferromagnetic particles therefrom.

Influence of a depletion interaction on dynamical heterogeneity in a dense quasi-two-dimensional colloid liquid.

PubMed

Ho, Hau My; Cui, Bianxiao; Repel, Stephen; Lin, Binhua; Rice, Stuart A

2004-11-01

We report the results of digital video microscopy studies of the large particle displacements in a quasi-two-dimensional binary mixture of large (L) and small (S) colloid particles with diameter ratio sigma(L)/sigma(S)=4.65, as a function of the large and small colloid particle densities. As in the case of the one-component quasi-two-dimensional colloid system, the binary mixtures exhibit structural and dynamical heterogeneity. The distribution of large particle displacements over the time scale examined provides evidence for (at least) two different mechanisms of motion, one associated with particles in locally ordered regions and the other associated with particles in locally disordered regions. When rhoL*=Npisigma(L) (2)/4A< or =0.35, the addition of small colloid particles leads to a monotonic decrease in the large particle diffusion coefficient with increasing small particle volume fraction. When rhoL* > or =0.35 the addition of small colloid particles to a dense system of large colloid particles at first leads to an increase in the large particle diffusion coefficient, which is then followed by the expected decrease of the large particle diffusion coefficient with increasing small colloid particle volume fraction. The mode coupling theory of the ideal glass transition in three-dimensional systems makes a qualitative prediction that agrees with the initial increase in the large particle diffusion coefficient with increasing small particle density. Nevertheless, because the structural and dynamical heterogeneities of the quasi-two-dimensional colloid liquid occur within the field of equilibrium states, and the fluctuations generate locally ordered domains rather than just disordered regions of higher and lower density, it is suggested that mode coupling theory does not account for all classes of relevant fluctuations in a quasi-two-dimensional liquid. (c) 2004 American Institute of Physics.

Dependent scattering and absorption by densely packed discrete spherical particles: Effects of complex refractive index

NASA Astrophysics Data System (ADS)

Ma, L. X.; Tan, J. Y.; Zhao, J. M.; Wang, F. Q.; Wang, C. A.; Wang, Y. Y.

2017-07-01

Due to the dependent scattering and absorption effects, the radiative transfer equation (RTE) may not be suitable for dealing with radiative transfer in dense discrete random media. This paper continues previous research on multiple and dependent scattering in densely packed discrete particle systems, and puts emphasis on the effects of particle complex refractive index. The Mueller matrix elements of the scattering system with different complex refractive indexes are obtained by both electromagnetic method and radiative transfer method. The Maxwell equations are directly solved based on the superposition T-matrix method, while the RTE is solved by the Monte Carlo method combined with the hard sphere model in the Percus-Yevick approximation (HSPYA) to consider the dependent scattering effects. The results show that for densely packed discrete random media composed of medium size parameter particles (equals 6.964 in this study), the demarcation line between independent and dependent scattering has remarkable connections with the particle complex refractive index. With the particle volume fraction increase to a certain value, densely packed discrete particles with higher refractive index contrasts between the particles and host medium and higher particle absorption indexes are more likely to show stronger dependent characteristics. Due to the failure of the extended Rayleigh-Debye scattering condition, the HSPYA has weak effect on the dependent scattering correction at large phase shift parameters.

Spherical Nucleic Acids: A New Form of DNA

NASA Astrophysics Data System (ADS)

Cutler, Joshua Isaac

Spherical Nucleic Acids (SNAs) are a new class of nucleic acid-based nanomaterials that exhibit unique properties currently being explored in the contexts of gene-based cancer therapies and in the design of programmable nanoparticle-based materials. The properties of SNAs differ from canonical, linear nucleic acids by virtue of their dense packing into an oriented 3-dimensional array. SNAs can be synthesized from a number of useful nanoparticle templates, such as plasmonic gold and silver, magnetic oxides, luminescent semi-conductor quantum dots, and silica. In addition, by crosslinking the oligonucleotides and dissolving the core, they can be made in a hollow form as well. This dissertation describes the evolution of SNAs from initial studies of inorganic nanoparticle-based materials densely functionalized with oligonucleotides to the proving of a hypothesis that their unique properties can be observed in a core-less structure if the nucleic acids are densely packed and highly oriented. Chapter two describes the synthesis of densely functionalized polyvalent oligonucleotide superparamagnetic iron oxide nanoparticles using the copper-catalyzed azide-alkyne cycloaddition reaction. These particles are shown to exhibit cooperative binding in a density- and salt concentration-dependent fashion, with nearly identical behaviors to those of SNA-functionalized gold nanoparticles. Importantly, these particles are the first non-gold particles shown to be capable of entering cells in high numbers via the SNA-mediated cellular uptake pathway, and provided the first evidence that SNA-mediated cellular uptake is core-independent. In the third chapter, a gold nanoparticle catalyzed alkyne cross-linking reaction is described that is capable of forming hollow organic nanoparticles using polymers with alkyne-functionalized backbones. With this method, the alkyne-modified polymers adsorb to the particle surfaces, cross-link on the surface, allowing the gold nanoparticle to be subsequently dissolved oxidatively with KCN or Iodine. The reaction pathway is analyzed through characterization of the reaction progression and resulting products, and a mechanistic pathway is proposed. This is the first report of a gold nanoparticle catalyzed reaction involving the conversion of propargyl ethers to terminal alcohols, which can subsequently cross-link if densely arranged on a gold nanoparticle surface. Importantly, these structures can be synthesized using gold nanoparticles of a range of sizes, thereby providing control over the size and properties of the resulting crosslinked particle. Chapter four returns to the topic of SNAs and builds upon the chemistry of chapter three culminating in the synthesis of cross-linked hollow SNA nanoparticles. These structures are formed by the cross-linking of synthetically modified alkyne-bearing oligonucleotides through the pathway described in chapter three. When the gold core is dissolved, the resulting hollow SNAs exhibit nearly identical binding, nuclease resistance, cellular uptake, and gene regulation properties of SNA-gold nanoparticle conjugates. Indeed, this chapter demonstrates that the unique properties of SNA-nanoparticle conjugates are core-independent and stem solely from the dense ensemble of oligonucleotides arranged on their surfaces. The fifth chapter further asserts the synthetic achievements made in chapter four by showing how hollow SNAs can be substituted for SNA-gold nanoparticles in the context of DNA-programmable assembly. In this case, they can be used as building blocks within binary synthetic schemes to synthesize unique nanoparticle superlattices. It bolsters the design rules of DNA-programmable assembly by showing that the predicted structures form based on the behavior of SNA hybridization, and are universal for any SNA-functionalized nanoparticle.

A high-speed tracking algorithm for dense granular media

NASA Astrophysics Data System (ADS)

Cerda, Mauricio; Navarro, Cristóbal A.; Silva, Juan; Waitukaitis, Scott R.; Mujica, Nicolás; Hitschfeld, Nancy

2018-06-01

Many fields of study, including medical imaging, granular physics, colloidal physics, and active matter, require the precise identification and tracking of particle-like objects in images. While many algorithms exist to track particles in diffuse conditions, these often perform poorly when particles are densely packed together-as in, for example, solid-like systems of granular materials. Incorrect particle identification can have significant effects on the calculation of physical quantities, which makes the development of more precise and faster tracking algorithms a worthwhile endeavor. In this work, we present a new tracking algorithm to identify particles in dense systems that is both highly accurate and fast. We demonstrate the efficacy of our approach by analyzing images of dense, solid-state granular media, where we achieve an identification error of 5% in the worst evaluated cases. Going further, we propose a parallelization strategy for our algorithm using a GPU, which results in a speedup of up to 10 × when compared to a sequential CPU implementation in C and up to 40 × when compared to the reference MATLAB library widely used for particle tracking. Our results extend the capabilities of state-of-the-art particle tracking methods by allowing fast, high-fidelity detection in dense media at high resolutions.

Dynamics and Emergent Structures in Active Fluids

NASA Astrophysics Data System (ADS)

Baskaran, Aparna

2014-03-01

In this talk, we consider an active fluid of colloidal sized particles, with the primary manifestation of activity being a self-replenishing velocity along one body axis of the particle. This is a minimal model for varied systems such as bacterial colonies, cytoskeletal filament motility assays vibrated granular particles and self propelled diffusophoretic colloids, depending on the nature of interaction among the particles. Using microscopic Brownian dynamics simulations, coarse-graining using the tools of non-equilibrium statistical mechanics and analysis of macroscopic hydrodynamic theories, we characterize emergent structures seen in these systems, which are determined by the symmetry of the interactions among the active units, such as propagating density waves, dense stationary bands, asters and phase separated isotropic clusters. We identify a universal mechanism, termed ``self-regulation,'' as the underlying physics that leads to these structures in diverse systems. Support from NSF through DMR-1149266 and DMR-0820492.

ELECTRON MICROSCOPY OF HELA CELLS INFECTED WITH ADENOVIRUSES

PubMed Central

Harford, Carl G.; Hamlin, Alice; Parker, Esther; van Ravenswaay, Theodore

1956-01-01

HeLa cells were infected with adenoviruses (types 1–4) and sectioned for electron microscopy after intervals of 20 to 48 hours. Clusters of virus-like particles were found within the nuclei of infected cultures but not in those of uninfected controls. The particles were often arranged in rows as if in crystalline formation. Maximal diameter of particles was approximately 65 mµ, and internal bodies were demonstrated. Lesions of infected cells included target-like structures of the nuclear membrane, large nuclear vacuoles (type 2), and increased numbers of large irregular electron-dense granules in the cytoplasm 48 hours after infection. Examination of infected cultures by light microscopy, using the Feulgen reaction, showed intranuclear inclusion bodies and a cytopathogenic effect consisting of clumping of cells without pyknosis of nuclei. A lipide stain showed numerous cytoplasmic granules that were not identical with the large, irregular, electron-dense granules of the cytoplasm. Practically all the cells showed the viral cytopathogenic effect, but only a minority of cells were found to contain virus-like particles or intranuclear inclusion bodies. PMID:13357696

Invited Article: Refractive index matched scanning of dense granular materials

NASA Astrophysics Data System (ADS)

Dijksman, Joshua A.; Rietz, Frank; Lőrincz, Kinga A.; van Hecke, Martin; Losert, Wolfgang

2012-01-01

We review an experimental method that allows to probe the time-dependent structure of fully three-dimensional densely packed granular materials and suspensions by means of particle recognition. The method relies on submersing a granular medium in a refractive index matched fluid. This makes the resulting suspension transparent. The granular medium is then visualized by exciting, layer by layer, the fluorescent dye in the fluid phase. We collect references and unreported experimental know-how to provide a solid background for future development of the technique, both for new and experienced users.

Restrike Particle Beam Experiments on a Dense Plasma Focus. Opening Switch Research on a Dense Plasma Focus.

DTIC Science & Technology

1985-06-01

Research on this grant has focused on plasma focus experiments in the areas of particle beam generation and as a potential repetitive opening switch...as were scaling laws for the increase of electron energy and current with input energy. The potential of the plasma focus as an opening switch was...delay line technique. The observed frequencies were most consistent with the lower hybrid frequency. Keywords include: Dense Plasma Focus , Particle Beam Generation, Opening Switch, Load Experiments, Pulsed Power.

The small, dense LDL phenotype and the risk of coronary heart disease: epidemiology, patho-physiology and therapeutic aspects.

PubMed

Lamarche, B; Lemieux, I; Després, J P

1999-09-01

More than decade ago, several cross-sectional studies have reported differences in LDL particle size, density and composition between coronary heart disease (CHD) patients and healthy controls. Three recent prospective, nested case-control studies have since confirmed that the presence of small, dense LDL particles was associated with more than a three-fold increase in the risk of CHD. The small, dense LDL phenotype rarely occurs as an isolated disorder. It is most frequently accompanied by hypertriglyceridemia, reduced HDL cholesterol levels, abdominal obesity, insulin resistance and by a series of other metabolic alterations predictive of an impaired endothelial function and increased susceptibility to thrombosis. Whether or not the small, dense LDL phenotype should be considered an independent CHD risk factor remains to be clearly established. The cluster of metabolic abnormalities associated with small, dense LDL particles has been referred to as the insulin resistance-dyslipidemic phenotype of abdominal obesity. Results from the Québec Cardiovascular Study have indicated that individuals displaying three of the numerous features of insulin resistance (elevated plasma insulin and apolipoprotein B concentrations and small, dense LDL particles) showed a remarkable increase in CHD risk. Our data suggest that the increased risk of CHD associated with having small, dense LDL particles may be modulated to a significant extent by the presence/absence of insulin resistance, abdominal obesity and increased LDL particle concentration. We suggest that the complex interactions among the metabolic alterations of the insulin resistance syndrome should be considered when evaluating the risk of CHD associated with the small, dense LDL phenotype. From a therapeutic standpoint, the treatment of this condition should not only aim at reducing plasma triglyceride levels, but also at improving all features of the insulin resistance syndrome, for which body weight loss and mobilization of abdominal fat appear as key elements. Finally, interventions leading to reduction in fasting triglyceride levels will increase LDL particle size and contribute to reduce CHD risk, particularly if plasma apolipoprotein B concentration (as a surrogate of the number of atherogenic particles) is also reduced.

Coagulation of grains in static and collapsing protostellar clouds

NASA Technical Reports Server (NTRS)

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

1994-01-01

We simulate collisional evolution of grains in dense turbulent molecular cloud cores (or Bok globules) in static equilibrium and free-fall collapse, assuming spherical symmetry. Relative velocities are due to thermal motions, differential settling, and turbulence, with the latter dominant for sonic turbulence with an assumed Kolmogorov spectrum. Realistic criteria are used to determine outcomes of collisions (coagulation vs. destruction) as functions of particle size and velocity. Results are presented for a variety of cloud parameters (radial density profile, turbulent velocity) and particle properties (density, impact strength). Results are sensitive to the assumed mechanical properties (density and impact strength) of grain aggregates. Particle growth is enhanced if aggregates have low density or fractal structures. On a timescale of a few Myr, an initial population of 0.1 micrometers grains may produce dense compact particles approximately 1 micrometer in size, or fluffy aggregates approximately 100 micrometers. For impact strengths less than or equal to 10(exp 6) ergs/g, a steady state is reached between coagulation of small grains and collisional disruption of larger aggregates. Formation of macroscopic aggregates requires high mechanical strengths and low aggregate densities. We assume sonic turbulence during collapse, with varied eddy size scales determining the dissipation rate or turbulence strength. The degree of collisional evolution during collapse is sensitive to the assumed small-scale structure (inner sc ale) of the turbulence. Weak turbulence results in few collisions and preserves the precollapse particle size distribution with little change. Strong turbulence tends to produce net destruction, rather than particle growth, during infall, unless inpact strengths are greater than 10(exp 6)ergs/g.

Microstructured Electrolyte Membranes to Improve Fuel Cell Performance

NASA Astrophysics Data System (ADS)

Wei, Xue

Fuel cells, with the advantages of high efficiency, low greenhouse gas emission, and long lifetime are a promising technology for both portable power and stationary power sources. The development of efficient electrolyte membranes with high ionic conductivity, good mechanical durability and dense structure at low cost remains a challenge to the commercialization of fuel cells. This thesis focuses on exploring novel composite polymer membranes and ceramic electrolytes with the microstructure engineered to improve performance in direct methanol fuel cells (DMFCs) and solid oxide fuel cells (SOFCs), respectively. Polymer/particle composite membranes hold promise to meet the demands of DMFCs at lower cost. The structure of composite membranes was controlled by aligning proton conducting particles across the membrane thickness under an applied electric field. The field-induced structural changes caused the membranes to display an enhanced water uptake, proton conductivity, and methanol permeability in comparison to membranes prepared without an applied field. Although both methanol permeability and proton conductivity are enhanced by the applied field, the permeability increase is relatively lower than the proton conductivity improvement, which results in enhanced proton/methanol selectivity and improved DMFC performance. Apatite ceramics are a new class of fast ion conductors being studied as alternative SOFC electrolytes in the intermediate temperature range. An electrochemical/hydrothermal deposition method was developed to grow fully dense apatite membranes containing well-developed crystals with c-axis alignment to promote ion conductivity. Hydroxyapatite seed crystals were first deposited onto a metal substrate electrochemically. Subsequent ion substitution during the hydrothermal growth process promoted the formation of dense, fully crystalline films with microstructure optimal for ion transport. The deposition parameters were systematically investigated, such as reactant type, reagent concentration, solution pH, and reaction time. Dense apatite films were formed on palladium substrates that can serve as intermediate temperature fuel cell anodes. The novel apatite membrane structure is promising for fuel cell applications, as well as in improving the biocompatibility of orthopedic implants when coated on stainless steel or titanium substrates.

Not just fractal surfaces, but surface fractal aggregates: Derivation of the expression for the structure factor and its applications

NASA Astrophysics Data System (ADS)

Besselink, R.; Stawski, T. M.; Van Driessche, A. E. S.; Benning, L. G.

2016-12-01

Densely packed surface fractal aggregates form in systems with high local volume fractions of particles with very short diffusion lengths, which effectively means that particles have little space to move. However, there are no prior mathematical models, which would describe scattering from such surface fractal aggregates and which would allow the subdivision between inter- and intraparticle interferences of such aggregates. Here, we show that by including a form factor function of the primary particles building the aggregate, a finite size of the surface fractal interfacial sub-surfaces can be derived from a structure factor term. This formalism allows us to define both a finite specific surface area for fractal aggregates and the fraction of particle interfacial sub-surfaces at the perimeter of an aggregate. The derived surface fractal model is validated by comparing it with an ab initio approach that involves the generation of a "brick-in-a-wall" von Koch type contour fractals. Moreover, we show that this approach explains observed scattering intensities from in situ experiments that followed gypsum (CaSO4 ṡ 2H2O) precipitation from highly supersaturated solutions. Our model of densely packed "brick-in-a-wall" surface fractal aggregates may well be the key precursor step in the formation of several types of mosaic- and meso-crystals.

An incompressible two-dimensional multiphase particle-in-cell model for dense particle flows

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

Snider, D.M.; O`Rourke, P.J.; Andrews, M.J.

1997-06-01

A two-dimensional, incompressible, multiphase particle-in-cell (MP-PIC) method is presented for dense particle flows. The numerical technique solves the governing equations of the fluid phase using a continuum model and those of the particle phase using a Lagrangian model. Difficulties associated with calculating interparticle interactions for dense particle flows with volume fractions above 5% have been eliminated by mapping particle properties to a Eulerian grid and then mapping back computed stress tensors to particle positions. This approach utilizes the best of Eulerian/Eulerian continuum models and Eulerian/Lagrangian discrete models. The solution scheme allows for distributions of types, sizes, and density of particles,more » with no numerical diffusion from the Lagrangian particle calculations. The computational method is implicit with respect to pressure, velocity, and volume fraction in the continuum solution thus avoiding courant limits on computational time advancement. MP-PIC simulations are compared with one-dimensional problems that have analytical solutions and with two-dimensional problems for which there are experimental data.« less

Direct Numerical Simulation of dense particle-laden turbulent flows using immersed boundaries

NASA Astrophysics Data System (ADS)

Wang, Fan; Desjardins, Olivier

2009-11-01

Dense particle-laden turbulent flows play an important role in many engineering applications, ranging from pharmaceutical coating and chemical synthesis to fluidized bed reactors. Because of the complexity of the physics involved in these flows, current computational models for gas-particle processes, such as drag and heat transfer, rely on empirical correlations and have been shown to lack accuracy. In this work, direct numerical simulations (DNS) of dense particle-laden flows are conducted, using immersed boundaries (IB) to resolve the flow around each particle. First, the accuracy of the proposed approach is tested on a range of 2D and 3D flows at various Reynolds numbers, and resolution requirements are discussed. Then, various particle arrangements and number densities are simulated, the impact on particle wake interaction is assessed, and existing drag models are evaluated in the case of fixed particles. In addition, the impact of the particles on turbulence dissipation is investigated. Finally, a strategy for handling moving and colliding particles is discussed.

A comment on the position dependent diffusion coefficient representation of structural heterogeneity

NASA Astrophysics Data System (ADS)

Wolfson, Molly; Liepold, Christopher; Lin, Binhua; Rice, Stuart A.

2018-05-01

Experimental studies of the variation of the mean square displacement (MSD) of a particle in a confined colloid suspension that exhibits density variations on the scale length of the particle diameter are not in agreement with the prediction that the spatial variation in MSD should mimic the spatial variation in density. The predicted behavior is derived from the expectation that the MSD of a particle depends on the system density and the assumption that the force acting on a particle is a point function of position. The experimental data are obtained from studies of the MSDs of particles in narrow ribbon channels and between narrowly spaced parallel plates and from new data, reported herein, of the radial and azimuthal MSDs of a colloid particle in a dense colloid suspension confined to a small circular cavity. In each of these geometries, a dense colloid suspension exhibits pronounced density oscillations with spacing of a particle diameter. We remove the discrepancy between prediction and experiment using the Fisher-Methfessel interpretation of how local equilibrium in an inhomogeneous system is maintained to argue that the force acting on a particle is delocalized over a volume with radius equal to a particle diameter. Our interpretation has relevance to the relationship between the scale of inhomogeneity and the utility of translation of the particle MSD into a position dependent diffusion coefficient and to the use of a spatially dependent diffusion coefficient to describe mass transport in a heterogeneous system.

Gravity and the cell: Intracellular structures and Stokes sedimentation

NASA Technical Reports Server (NTRS)

Todd, P.

1977-01-01

Plant and certain animal embryos appear to be responsive to the gravity vector during early stages of development. The convection of particle sedimentation as the basis for the sensing of gravity is investigated using the cells of wheat seedlings, amphibian embryos, and mammals. Exploration of the mammalian cell for sedimenting particles reveals that their existence is unlikely, especially in the presence of a network of microtubules and microfilaments considered to be responsible for intracellular organization. Destruction of these structures renders the cell susceptible to accelerations several times g. Large dense particles, such as chromosomes, nucleoli, and cytoplasmic organelles are acted upon by forces much larger than that due to gravity, and their positions in the cell appear to be insensitive to gravity.

Weak correlations between local density and dynamics near the glass transition.

PubMed

Conrad, J C; Starr, F W; Weitz, D A

2005-11-17

We perform experiments on two different dense colloidal suspensions with confocal microscopy to probe the relationship between local structure and dynamics near the glass transition. We calculate the Voronoi volume for our particles and show that this quantity is not a universal probe of glassy structure for all colloidal suspensions. We correlate the Voronoi volume to displacement and find that these quantities are only weakly correlated. We observe qualitatively similar results in a simulation of a polymer melt. These results suggest that the Voronoi volume does not predict dynamical behavior in experimental colloidal suspensions; a purely structural approach based on local single particle volume likely cannot describe the colloidal glass transition.

The structure of mononuclear phagocytes differentiating in vivo. III. The effect of particulate foreign substances.

PubMed

Goldner, R D; Adams, D O

1977-11-01

The response of mononuclear phagocytes to three inert particles--barium sulfate, talc, and thorium dioxide--was studied by correlated light and electron microscopy. All three particles induced maturation of the mononuclear phagocytes, which proceeded to the stage of the mature macrophage and required 7 to 9 days. Once established, maturation persisted as long as 45 days, as did the inert particles. The resultant lesions, dense aggregates of mature macrophages, were termed mature granulomas. The resultant maturation differed from that produced by digestible bacteria in tempo and extent but not in pattern.

Enhanced Mobility in Concentrated Pyroclastic Density Currents: An Examination of a Self-Fluidization Mechanism

NASA Astrophysics Data System (ADS)

Breard, Eric C. P.; Dufek, Josef; Lube, Gert

2018-01-01

Pyroclastic density currents (PDCs) are a significant volcanic hazard. However, their dominant transport mechanisms remain poorly understood, in part because of the large variability of PDC types and deposits. Here we combine field data with experimental and numerical simulations to illuminate the twofold fate of particles settling from an ash cloud to form the dense PDC basal flow. At solid fractions >1 vol %, heterogeneous drag leads to formation of mesoscale particle clusters that favor rapid particle settling and result in a mobile dense layer with significant bed weight support. Conversely, at lower concentrations the absence of particle clusters typically leads to formation of poorly mobile dense beds that deposit massive layers. Based on this transport dichotomy, we present a numerical dense-dilute parameter that allows a PDC's dominant transport mechanism to be determined directly from the deposit geometry and grainsize characteristics.

A non-local structural derivative model for characterization of ultraslow diffusion in dense colloids

NASA Astrophysics Data System (ADS)

Liang, Yingjie; Chen, Wen

2018-03-01

Ultraslow diffusion has been observed in numerous complicated systems. Its mean squared displacement (MSD) is not a power law function of time, but instead a logarithmic function, and in some cases grows even more slowly than the logarithmic rate. The distributed-order fractional diffusion equation model simply does not work for the general ultraslow diffusion. Recent study has used the local structural derivative to describe ultraslow diffusion dynamics by using the inverse Mittag-Leffler function as the structural function, in which the MSD is a function of inverse Mittag-Leffler function. In this study, a new stretched logarithmic diffusion law and its underlying non-local structural derivative diffusion model are proposed to characterize the ultraslow diffusion in aging dense colloidal glass at both the short and long waiting times. It is observed that the aging dynamics of dense colloids is a class of the stretched logarithmic ultraslow diffusion processes. Compared with the power, the logarithmic, and the inverse Mittag-Leffler diffusion laws, the stretched logarithmic diffusion law has better precision in fitting the MSD of the colloidal particles at high densities. The corresponding non-local structural derivative diffusion equation manifests clear physical mechanism, and its structural function is equivalent to the first-order derivative of the MSD.

Synthesis of Platelike {100} SrTiO3 Particles by Topochemical Microcrystal Conversion and Fabrication of Grain-Oriented Ceramics

NASA Astrophysics Data System (ADS)

Saito, Yasuyoshi; Takao, Hisaaki

2006-09-01

Platelike SrTiO3 particles with a cubic perovskite structure were synthesized by topochemical microcrystal conversion (TMC) from platelike precursor particles of layer-structured SrBi4Ti4O15 at 950 °C. SrTiO3 particles preserved the shape of precursor particles, and had a thickness of approximately 0.5 μm and a width of 5-10 μm. X-ray diffraction analysis revealed that in the TMC reaction, the crystallographic {001} plane of SrBi4Ti4O15 is converted into the {100} plane of SrTiO3. Using the platelike SrTiO3 particles as a template in templated grain growth method, dense {100} grain-oriented SrTiO3 ceramics having a {100} orientation degree (Lotgering’s factor) higher than 91% could be fabricated at sintering temperatures between 1350 and 1550 °C. The maximum orientation factor reached 99.3%.

Structure and organization of paramyxovirus particles.

PubMed

Cox, Robert M; Plemper, Richard K

2017-06-01

The paramyxovirus family comprises major human and animal pathogens such as measles virus (MeV), mumps virus (MuV), the parainfluenzaviruses, Newcastle disease virus (NDV), and the highly pathogenic zoonotic hendra (HeV) and nipah (NiV) viruses. Paramyxovirus particles are pleomorphic, with a lipid envelope, nonsegmented RNA genomes of negative polarity, and densely packed glycoproteins on the virion surface. A number of crystal structures of different paramyxovirus proteins and protein fragments were solved, but the available information concerning overall virion organization remains limited. However, recent studies have reported cryo-electron tomography-based reconstructions of Sendai virus (SeV), MeV, NDV, and human parainfluenza virus type 3 (HPIV3) particles and a surface assessment of NiV-derived virus-like particles (VLPs), which have yielded innovative hypotheses concerning paramyxovirus particle assembly, budding, and organization. Following a summary of the current insight into paramyxovirus virion morphology, this review will focus on discussing the implications of these particle reconstructions on the present models of paramyxovirus assembly and infection. Copyright © 2017 Elsevier B.V. All rights reserved.

Massive shelf dense water flow influences plankton community structure and particle transport over long distance.

PubMed

Bernardi Aubry, Fabrizio; Falcieri, Francesco Marcello; Chiggiato, Jacopo; Boldrin, Alfredo; Luna, Gian Marco; Finotto, Stefania; Camatti, Elisa; Acri, Francesco; Sclavo, Mauro; Carniel, Sandro; Bongiorni, Lucia

2018-03-14

Dense waters (DW) formation in shelf areas and their cascading off the shelf break play a major role in ventilating deep waters, thus potentially affecting ecosystem functioning and biogeochemical cycles. However, whether DW flow across shelves may affect the composition and structure of plankton communities down to the seafloor and the particles transport over long distances has not been fully investigated. Following the 2012 north Adriatic Sea cold outbreak, DW masses were intercepted at ca. 460 km south the area of origin and compared to resident ones in term of plankton biomass partitioning (pico to micro size) and phytoplankton species composition. Results indicated a relatively higher contribution of heterotrophs in DW than in deep resident water masses, probably as result of DW-mediated advection of fresh organic matter available to consumers. DWs showed unusual high abundances of Skeletonema sp., a diatom that bloomed in the north Adriatic during DW formation. The Lagrangian numerical model set up on this diatom confirmed that DW flow could be an important mechanism for plankton/particles export to deep waters. We conclude that the predicted climate-induced variability in DW formation events could have the potential to affect the ecosystem functioning of the deeper part of the Mediterranean basin, even at significant distance from generation sites.

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.

Relating quantum discord with the quantum dense coding capacity

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

Wang, Xin; Qiu, Liang, E-mail: lqiu@cumt.edu.cn; Li, Song

2015-01-15

We establish the relations between quantum discord and the quantum dense coding capacity in (n + 1)-particle quantum states. A necessary condition for the vanishing discord monogamy score is given. We also find that the loss of quantum dense coding capacity due to decoherence is bounded below by the sum of quantum discord. When these results are restricted to three-particle quantum states, some complementarity relations are obtained.

Stripes instability of an oscillating non-Brownian iso-dense suspension of spheres

NASA Astrophysics Data System (ADS)

Roht, Y. L.; Ippolito, I.; Hulin, J. P.; Salin, D.; Gauthier, G.

2018-03-01

We analyze experimentally the behavior of a non-Brownian, iso-dense suspension of spheres submitted to periodic square wave oscillations of the flow in a Hele-Shaw cell of gap H. We do observe an instability of the initially homogeneous concentration in the form of concentration variation stripes transverse to the flow. The wavelength of these regular spatial structures scales roughly as the gap of the cell and is independent of the particle concentration and of the period of oscillation. This instability requires large enough particle volume fractions φ≥ 0.25 and a gap large enough compared to the sphere diameter (H/d ≥ 8) . Mapping the domain of the existence of this instability in the space of the control parameters shows that it occurs only in a limited range of amplitudes of the fluid displacement. The analysis of the concentration distribution across the gap supports a scenario of particle migration towards the wall followed by an instability due to a particle concentration gradient with a larger concentration at the walls. In order to account for the main features of this stripes instability, we use the theory of longitudinal instability due to normal stresses difference and recent observations of a dependence of the first normal stresses difference on the particle concentration.

Gelation under shear

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

Butler, B.D.; Hanley, H.J.M.; Straty, G.C.

An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying tomore » interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.« less

Generation of dense granular deposits for porosity analysis: assessment and application of large-scale non-smooth granular dynamics

NASA Astrophysics Data System (ADS)

Schruff, T.; Liang, R.; Rüde, U.; Schüttrumpf, H.; Frings, R. M.

2018-01-01

The knowledge of structural properties of granular materials such as porosity is highly important in many application-oriented and scientific fields. In this paper we present new results of computer-based packing simulations where we use the non-smooth granular dynamics (NSGD) method to simulate gravitational random dense packing of spherical particles with various particle size distributions and two types of depositional conditions. A bin packing scenario was used to compare simulation results to laboratory porosity measurements and to quantify the sensitivity of the NSGD regarding critical simulation parameters such as time step size. The results of the bin packing simulations agree well with laboratory measurements across all particle size distributions with all absolute errors below 1%. A large-scale packing scenario with periodic side walls was used to simulate the packing of up to 855,600 spherical particles with various particle size distributions (PSD). Simulation outcomes are used to quantify the effect of particle-domain-size ratio on the packing compaction. A simple correction model, based on the coordination number, is employed to compensate for this effect on the porosity and to determine the relationship between PSD and porosity. Promising accuracy and stability results paired with excellent computational performance recommend the application of NSGD for large-scale packing simulations, e.g. to further enhance the generation of representative granular deposits.

Plastic scintillators in coincidence for the study of multi-particle production of sea level cosmic rays in dense medium

NASA Technical Reports Server (NTRS)

Chuang, L. S.; Chan, K. W.; Wada, M.

1985-01-01

Cosmic ray particles at sea level penetrate a thick layer of dense medium without appreciable interaction. These penetrating particles are identified with muons. The only appreciable interaction of muons are by knock on processes. A muon may have single, double or any number of knock on with atoms of the material so that one, two, three or more particles will come out from the medium in which the knock on processes occur. The probability of multiparticle production is expected to decrease with the increase of multiplicity. Measurements of the single, double, and triple particles generated in a dense medium (Fe and Al) by sea level cosmic rays at 22.42 N. Lat. and 114.20 E. Long. (Hong Kong) are presented using a detector composed of two plastic scintillators connected in coincidence.

Method of forming a leak proof plasma sprayed interconnection layer on an electrode of an electrochemical cell

DOEpatents

Kuo, Lewis J. H.; Vora, Shailesh D.

1995-01-01

A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an electrode structure of an electrochemical cell by: (A) providing an electrode structure; (B) forming on a selected portion of the electrode surface, an interconnection layer having the general formula La.sub.1-x M.sub.x Cr.sub.1-y N.sub.y O.sub.3, where M is a dopant selected from the group of Ca, Sr, Ba, and mixtures thereof, and where N is a dopant selected from the group of Mg, Co, Ni, Al, and mixtures thereof, and where x and y are each independently about 0.075-0.25, by thermally spraying, preferably plasma arc spraying, a flux added interconnection spray powder, preferably agglomerated, the flux added powder comprising flux particles, preferably including dopant, preferably (CaO).sub.12. (Al.sub.2 O.sub.3).sub.7 flux particles including Ca and Al dopant, and LaCrO.sub.3 interconnection particles, preferably undoped LaCrO.sub.3, to form a dense and substantially gas-tight interconnection material bonded to the electrode structure by a single plasma spraying step; and, (C) heat treating the interconnection layer at from about 1200.degree. to 1350.degree. C. to further densify and heal the micro-cracks and macro-cracks of the thermally sprayed interconnection layer. The result is a substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode structure. The electrode structure can be an air electrode, and a solid electrolyte layer can be applied to the unselected portion of the air electrode, and further a fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell for generation of electrical power.

Method of forming a leak proof plasma sprayed interconnection layer on an electrode of an electrochemical cell

DOEpatents

Kuo, L.J.H.; Vora, S.D.

1995-02-21

A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an electrode structure of an electrochemical cell by: (A) providing an electrode structure; (B) forming on a selected portion of the electrode surface, an interconnection layer having the general formula La{sub 1{minus}x}M{sub x}Cr{sub 1{minus}y}N{sub y}O{sub 3}, where M is a dopant selected from the group of Ca, Sr, Ba, and mixtures thereof, and where N is a dopant selected from the group of Mg, Co, Ni, Al, and mixtures thereof, and where x and y are each independently about 0.075--0.25, by thermally spraying, preferably plasma arc spraying, a flux added interconnection spray powder, preferably agglomerated, the flux added powder comprising flux particles, preferably including dopant, preferably (CaO){sub 12}(Al{sub 2}O{sub 3}){sub 7} flux particles including Ca and Al dopant, and LaCrO{sub 3} interconnection particles, preferably undoped LaCrO{sub 3}, to form a dense and substantially gas-tight interconnection material bonded to the electrode structure by a single plasma spraying step; and (C) heat treating the interconnection layer at from about 1,200 to 1,350 C to further densify and heal the micro-cracks and macro-cracks of the thermally sprayed interconnection layer. The result is a substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode structure. The electrode structure can be an air electrode, and a solid electrolyte layer can be applied to the unselected portion of the air electrode, and further a fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell for generation of electrical power. 4 figs.

Microwave Signatures of Melting/Refreezing Snow: Observations and Modeling Using Dense Medium Radiative Transfer Theory

NASA Technical Reports Server (NTRS)

Tedesco, Marco; Kim, Edward J.; England, Anthony; deRoo, Roger; Hardy, Janet

2005-01-01

Microwave brightness temperatures of snow covered terrains can be modeled by means of the Dense Radiative Transfer Medium Theory (DMRT). In a dense medium, such as snow, the assumption of independent scattering is no longer valid and the scattering of correlated scatterers must be considered. In the DMRT, this is done considering a pair distribution function of the particles position. In the electromagnetic model, the snowpack is simulated as a homogeneous layer having effective permittivity and albedo calculated through the DMRT. In order to account for clustering of snow crystals, a model of cohesive particles can be applied, where the cohesion between the particles is described by means of a dimensionless parameters called stickiness (z), representing a measure of the inversion of the attraction of the particles. The lower the z the higher the stickiness. In this study, microwave signatures of melting and refreezing cycles of seasonal snowpacks at high altitudes are studied by means of both experimental and modeling tools. Radiometric data were collected 24 hours per day by the University of Michigan Tower Mounted Radiometer System (TMRS). The brightness temperatures collected by means of the TMRS are simulated by means of a multi-layer electromagnetic model based on the dense medium theory with the inputs to the model derived from the data collected at the snow pits and from the meteorological station. The paper is structured as follows: in the first Section the temperature profiles recorded by the meteorological station and the snow pit data are presented and analyzed; in the second Section, the characteristics of the radiometric system used to collect the brightness temperatures are reported together with the temporal behavior of the recorded brightness temperatures; in the successive Section the multi-layer DMRT-based electromagnetic model is described; in the fourth Section the comparison between modeled and measured brightness temperatures is discussed. We dedicate the last Section to the conclusions and future works.

Light-field camera-based 3D volumetric particle image velocimetry with dense ray tracing reconstruction technique

NASA Astrophysics Data System (ADS)

Shi, Shengxian; Ding, Junfei; New, T. H.; Soria, Julio

2017-07-01

This paper presents a dense ray tracing reconstruction technique for a single light-field camera-based particle image velocimetry. The new approach pre-determines the location of a particle through inverse dense ray tracing and reconstructs the voxel value using multiplicative algebraic reconstruction technique (MART). Simulation studies were undertaken to identify the effects of iteration number, relaxation factor, particle density, voxel-pixel ratio and the effect of the velocity gradient on the performance of the proposed dense ray tracing-based MART method (DRT-MART). The results demonstrate that the DRT-MART method achieves higher reconstruction resolution at significantly better computational efficiency than the MART method (4-50 times faster). Both DRT-MART and MART approaches were applied to measure the velocity field of a low speed jet flow which revealed that for the same computational cost, the DRT-MART method accurately resolves the jet velocity field with improved precision, especially for the velocity component along the depth direction.

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids.

PubMed

Dahlberg, Jerry; Tkacik, Peter T; Mullany, Brigid; Fleischhauer, Eric; Shahinian, Hossein; Azimi, Farzad; Navare, Jayesh; Owen, Spencer; Bisel, Tucker; Martin, Tony; Sholar, Jodie; Keanini, Russell G

2017-12-04

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a standard fluid dynamic diagnostic, particle image velocimetry (PIV), to measure: i) velocities of individual particles (grains), extant on short, grain-collision time-scales, ii) velocities of systems of particles, on both short collision-time- and long, continuum-flow-time-scales, iii) collective hydrodynamic modes known to exist in dense molecular fluids, and iv) short- and long-time-scale velocity autocorrelation functions, central to understanding particle-scale dynamics in strongly interacting, dense fluid systems. The basic system is composed of an imaging system, light source, vibrational sensors, vibrational system with a known media, and PIV and analysis software. Required experimental measurements and an outline of the theoretical tools needed when using the analog technique to study molecular-scale hydrodynamic processes are highlighted. The proposed technique provides a relatively straightforward alternative to photonic and neutron beam scattering methods traditionally used in molecular hydrodynamic studies.

Dense CO2 as a Solute, Co-Solute or Co-Solvent in Particle Formation Processes: A Review

PubMed Central

Nunes, Ana V. M.; Duarte, Catarina M. M.

2011-01-01

The application of dense gases in particle formation processes has attracted great attention due to documented advantages over conventional technologies. In particular, the use of dense CO2 in the process has been subject of many works and explored in a variety of different techniques. This article presents a review of the current available techniques in use in particle formation processes, focusing exclusively on those employing dense CO2 as a solute, co-solute or co-solvent during the process, such as PGSS (Particles from gas-saturated solutions®), CPF (Concentrated Powder Form®), CPCSP (Continuous Powder Coating Spraying Process), CAN-BD (Carbon dioxide Assisted Nebulization with a Bubble Dryer®), SEA (Supercritical Enhanced Atomization), SAA (Supercritical Fluid-Assisted Atomization), PGSS-Drying and DELOS (Depressurization of an Expanded Liquid Organic Solution). Special emphasis is given to modifications introduced in the different techniques, as well as the limitations that have been overcome. PMID:28824121

The effect of calcium on the composition and physical properties of whey protein particles prepared using emulsification.

PubMed

Westerik, Nieke; Scholten, Elke; Corredig, Milena

2015-06-15

Protein microparticles were formed through emulsification of 25% (w/w) whey protein isolate (WPI) solutions containing various concentrations of calcium (0.0-400.0mM) in an oil phase stabilized by polyglycerol polyricinoleate (PGPR). The emulsions were heated (at 80°C) and the microparticles subsequently re-dispersed in an aqueous phase. Light microscopy and scanning electron microscopy (SEM) images revealed that control particles and those prepared with 7.4mM calcium were spherical and smooth. Particles prepared with 15.0mM calcium gained an irregular, cauliflower-like structure, and at concentrations larger than 30.0mM, shells formed and the particles were no longer spherical. These results describe, for the first time, the potential of modulating the properties of dense whey protein particles by using calcium, and may be used as structuring agents for the design of functional food matrices with increased protein and calcium content. Copyright © 2015. Published by Elsevier Ltd.

Tuning structure and mobility of solvation shells surrounding tracer additives

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

Carmer, James; Jain, Avni; Bollinger, Jonathan A.

2015-03-28

Molecular dynamics simulations and a stochastic Fokker-Planck equation based approach are used to illuminate how position-dependent solvent mobility near one or more tracer particle(s) is affected when tracer-solvent interactions are rationally modified to affect corresponding solvation structure. For tracers in a dense hard-sphere fluid, we compare two types of tracer-solvent interactions: (1) a hard-sphere-like interaction, and (2) a soft repulsion extending beyond the hard core designed via statistical mechanical theory to enhance tracer mobility at infinite dilution by suppressing coordination-shell structure [Carmer et al., Soft Matter 8, 4083–4089 (2012)]. For the latter case, we show that the mobility of surroundingmore » solvent particles is also increased by addition of the soft repulsive interaction, which helps to rationalize the mechanism underlying the tracer’s enhanced diffusivity. However, if multiple tracer surfaces are in closer proximity (as at higher tracer concentrations), similar interactions that disrupt local solvation structure instead suppress the position-dependent solvent dynamics.« less

Tuning structure and mobility of solvation shells surrounding tracer additives.

PubMed

Carmer, James; Jain, Avni; Bollinger, Jonathan A; van Swol, Frank; Truskett, Thomas M

2015-03-28

Molecular dynamics simulations and a stochastic Fokker-Planck equation based approach are used to illuminate how position-dependent solvent mobility near one or more tracer particle(s) is affected when tracer-solvent interactions are rationally modified to affect corresponding solvation structure. For tracers in a dense hard-sphere fluid, we compare two types of tracer-solvent interactions: (1) a hard-sphere-like interaction, and (2) a soft repulsion extending beyond the hard core designed via statistical mechanical theory to enhance tracer mobility at infinite dilution by suppressing coordination-shell structure [Carmer et al., Soft Matter 8, 4083-4089 (2012)]. For the latter case, we show that the mobility of surrounding solvent particles is also increased by addition of the soft repulsive interaction, which helps to rationalize the mechanism underlying the tracer's enhanced diffusivity. However, if multiple tracer surfaces are in closer proximity (as at higher tracer concentrations), similar interactions that disrupt local solvation structure instead suppress the position-dependent solvent dynamics.

Turbulent dusty boundary layer in an ANFO surface-burst explosion

NASA Astrophysics Data System (ADS)

Kuhl, A. L.; Ferguson, R. E.; Chien, K. Y.; Collins, J. P.

1992-01-01

This paper describes the results of numerical simulations of the dusty, turbulent boundary layer created by a surface burst explosion. The blast wave was generated by the detonation of a 600-T hemisphere of ANFO, similar to those used in large-scale field tests. The surface was assumed to be ideally noncratering but contained an initial loose layer of dust. The dust-air mixture in this fluidized bed was modeled as a dense gas (i.e., an equilibrium model, valid for very small-diameter dust particles). The evolution of the flow was calculated by a high-order Godunov code that solves the nonsteady conservation laws. Shock interactions with dense layer generated vorticity near the wall, a result that is similar to viscous, no-slip effects found in clean flows. The resulting wall shear layer was unstable, and rolled up into large-scale rotational structures. These structures entrained dense material from the wall layer and created a chaotically striated flow. The boundary layer grew due to merging of the large-scale structures and due to local entrainment of the dense material from the fluidized bed. The chaotic flow was averaged along similarity lines (i.e., lines of constant values of x = r/Rs and y = z/Rs where R(sub s) = ct(exp alpha)) to establish the mean-flow profiles and the r.m.s. fluctuating-flow profiles of the boundary layer.

Two-way coupled SPH and particle level set fluid simulation.

PubMed

Losasso, Frank; Talton, Jerry; Kwatra, Nipun; Fedkiw, Ronald

2008-01-01

Grid-based methods have difficulty resolving features on or below the scale of the underlying grid. Although adaptive methods (e.g. RLE, octrees) can alleviate this to some degree, separate techniques are still required for simulating small-scale phenomena such as spray and foam, especially since these more diffuse materials typically behave quite differently than their denser counterparts. In this paper, we propose a two-way coupled simulation framework that uses the particle level set method to efficiently model dense liquid volumes and a smoothed particle hydrodynamics (SPH) method to simulate diffuse regions such as sprays. Our novel SPH method allows us to simulate both dense and diffuse water volumes, fully incorporates the particles that are automatically generated by the particle level set method in under-resolved regions, and allows for two way mixing between dense SPH volumes and grid-based liquid representations.

Method of bonding an interconnection layer on an electrode of an electrochemical cell

DOEpatents

Pal, U.B.; Isenberg, A.O.; Folser, G.R.

1992-01-14

An electrochemical cell containing an air electrode, contacting electrolyte and electronically conductive interconnection layer, and a fuel electrode, has the interconnection layer attached by: (A) applying a thin, closely packed, discrete layer of LaCrO[sub 3] particles, doped with an element selected from the group consisting of Ca, Sr, Co, Ba, Mg and their mixtures on a portion of the air electrode, and then (B) electrochemical vapor depositing a dense skeletal structure between and around the doped LaCrO[sub 3] particles. 2 figs.

The Origin and Fate of Annulate Lamellae in Maturing Sand Dollar Eggs

PubMed Central

Merriam, R. W.

1959-01-01

Electron micrograph evidence is presented that the nuclear envelope of the mature ovum of Dendraster excentricus is implicated in a proliferation of what appear as nuclear envelope replicas in the cytoplasm. The proliferation is associated with intranuclear vesicles which apparently coalesce to form comparatively simple replicas of the nuclear envelope closely applied to the inside of the nuclear envelope. The envelope itself may become disorganized at the time when fully formed annulate lamellae appear on the cytoplasmic side and parallel with it. The concept of interconvertibility of general cytoplasmic vesicles with most of the membrane systems of the cytoplasm is presented. The structure of the annuli in the annulate lamellae is shown to include small spheres or vesicles of variable size embedded in a dense matrix. Dense particles which are about 150 A in diameter are often found closely associated with annulate lamellae in the cytoplasm. Similar structures in other echinoderm eggs are basophilic. In this species, unlike other published examples, the association apparently takes place in the cytoplasm only after the lamellae have separated from the nucleus. If 150 A particles are synthesized by annulate lamellae, as their close physical relationship suggests, then in this species at least the necessary synthetic mechanisms and specificity must reside in the structure of annulate lamellae. PMID:13630942

Toxoplasma gondii: biochemical and biophysical characterization of recombinant soluble dense granule proteins GRA2 and GRA6.

PubMed

Bittame, Amina; Effantin, Grégory; Pètre, Graciane; Ruffiot, Pauline; Travier, Laetitia; Schoehn, Guy; Weissenhorn, Winfried; Cesbron-Delauw, Marie-France; Gagnon, Jean; Mercier, Corinne

2015-03-27

The most prominent structural feature of the parasitophorous vacuole (PV) in which the intracellular parasite Toxoplasma gondii proliferates is a membranous nanotubular network (MNN), which interconnects the parasites and the PV membrane. The MNN function remains unclear. The GRA2 and GRA6 proteins secreted from the parasite dense granules into the PV have been implicated in the MNN biogenesis. Amphipathic alpha-helices (AAHs) predicted in GRA2 and an alpha-helical hydrophobic domain predicted in GRA6 have been proposed to be responsible for their membrane association, thereby potentially molding the MMN in its structure. Here we report an analysis of the recombinant proteins (expressed in detergent-free conditions) by circular dichroism, which showed that full length GRA2 displays an alpha-helical secondary structure while recombinant GRA6 and GRA2 truncated of its AAHs are mainly random coiled. Dynamic light scattering and transmission electron microscopy showed that recombinant GRA6 and truncated GRA2 constitute a homogenous population of small particles (6-8 nm in diameter) while recombinant GRA2 corresponds to 2 populations of particles (∼8-15 nm and up to 40 nm in diameter, respectively). The unusual properties of GRA2 due to its AAHs are discussed. Copyright © 2015 Elsevier Inc. All rights reserved.

Bottom-up photonic crystal approach with top-down defect and heterostructure fine-tuning.

PubMed

Ding, Tao; Song, Kai; Clays, Koen; Tung, Chen-Ho

2010-03-16

We combine the most efficient (chemical) approach toward three-dimensional photonic crystals with the most convenient (physical) technique for creating non-close-packed crystalline structures. Self-assembly of colloidal particles in artificial opals is followed by a carefully tuned plasma etching treatment. By covering the resulting top layer of more open structure with original dense opal, embedded defect layers and heterostructures can be conveniently designed for advanced photonic band gap and band edge engineering.

Deposit Structure for Particle-laden Droplets Targeted by Electrospray

NASA Astrophysics Data System (ADS)

Ghafouri, Aref; Singler, Timothy; Yong, Xin; Chiarot, Paul

2017-11-01

A hybrid printing technique that combines electrospray atomization with inkjet printing provides unique capabilities for exploring transport creating nanoparticle deposits with controlled structures. In this research, we use electrospray to deliver dry nanoparticles to the interface of particle-laden sessile droplets. Upon evaporation of the target sessile droplet, the particles at the interface are mapped to the underlying substrate. Particle locations in the final deposit were observed separately by tagging the particles dispersed inside the droplet and at its interface with different fluorophores. As expected, surfactant-free particles inside the target droplet were transported to its (pinned) contact line, creating a ``coffee ring'' morphology in the final deposit. The transport and final location of the interfacial particles was highly dependent on the presence of surfactant in the electrosprayed solution. If surfactant was present, the interfacial particles were transported to the apex of the target droplet, forming a dense region at the center of the final deposit. If the electrosprayed solution was surfactant-free, the transport of the interfacial particles was arrested and they were distributed uniformly across the final deposit. Similar deposit morphologies were found when experimenting with various surfactants, including Tween and sodium dodecyl sulfate. These results highlight the important of Marangoni flow in governing the final deposit structure for hybrid printing. This research supported by the National Science Foundation (Award 1538090).

Competitive Heterogeneous Nucleation Between Zr and MgO Particles in Commercial Purity Magnesium

NASA Astrophysics Data System (ADS)

Peng, G. S.; Wang, Y.; Fan, Z.

2018-04-01

Grain refining of commercial purity (CP) Mg by Zr addition with intensive melt shearing prior to solidification has been investigated. Experimental results showed that, when intensive melt shearing is imposed prior to solidification, the grain structure of CP Mg exhibits a complex changing pattern with increasing Zr addition. This complex behavior can be attributed to the change of nucleating particles in terms of their crystal structure, size, and number density with varied Zr additions. Naturally occurring MgO particles are found to be {100} faceted with a cubic morphology and 50 to 300 nm in size. Such MgO particles are usually populated densely in a liquid film (usually referred as oxide film) and can be effectively dispersed by intensive melt shearing. It has been confirmed that the dispersed MgO particles can act as nucleating substrates resulting in a significant grain refinement of CP Mg when no other more potent particles are present in the melt. However, Zr particles in the Mg-Zr alloys are more potent than MgO particles for nucleation of Mg due to their same crystal structure and similar lattice parameters with Mg. With the addition of Zr, Zr and the MgO particles co-exist in the melt. Grain refining efficiency is closely related to the competition for heterogeneous nucleation between Zr and the MgO particles. The final solidified microstructure is mainly determined by the interplay of three factors: nucleation potency (measured by lattice misfit), particle size, and particle number density.

Competitive Heterogeneous Nucleation Between Zr and MgO Particles in Commercial Purity Magnesium

NASA Astrophysics Data System (ADS)

Peng, G. S.; Wang, Y.; Fan, Z.

2018-06-01

Grain refining of commercial purity (CP) Mg by Zr addition with intensive melt shearing prior to solidification has been investigated. Experimental results showed that, when intensive melt shearing is imposed prior to solidification, the grain structure of CP Mg exhibits a complex changing pattern with increasing Zr addition. This complex behavior can be attributed to the change of nucleating particles in terms of their crystal structure, size, and number density with varied Zr additions. Naturally occurring MgO particles are found to be {100} faceted with a cubic morphology and 50 to 300 nm in size. Such MgO particles are usually populated densely in a liquid film (usually referred as oxide film) and can be effectively dispersed by intensive melt shearing. It has been confirmed that the dispersed MgO particles can act as nucleating substrates resulting in a significant grain refinement of CP Mg when no other more potent particles are present in the melt. However, Zr particles in the Mg-Zr alloys are more potent than MgO particles for nucleation of Mg due to their same crystal structure and similar lattice parameters with Mg. With the addition of Zr, Zr and the MgO particles co-exist in the melt. Grain refining efficiency is closely related to the competition for heterogeneous nucleation between Zr and the MgO particles. The final solidified microstructure is mainly determined by the interplay of three factors: nucleation potency (measured by lattice misfit), particle size, and particle number density.

Processes for making dense, spherical active materials for lithium-ion cells

DOEpatents

Kang, Sun-Ho [Naperville, IL; Amine, Khalil [Downers Grove, IL

2011-11-22

Processes are provided for making dense, spherical mixed-metal carbonate or phosphate precursors that are particularly well suited for the production of active materials for electrochemical devices such as lithium ion secondary batteries. Exemplified methods include precipitating dense, spherical particles of metal carbonates or metal phosphates from a combined aqueous solution using a precipitating agent such as ammonium hydrogen carbonate, sodium hydrogen carbonate, or a mixture that includes sodium hydrogen carbonate. Other exemplified methods include precipitating dense, spherical particles of metal phosphates using a precipitating agent such as ammonium hydrogen phosphate, ammonium dihydrogen phosphate, sodium phosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate, or a mixture of any two or more thereof. Further provided are compositions of and methods of making dense, spherical metal oxides and metal phosphates using the dense, spherical metal precursors. Still further provided are electrodes and batteries using the same.

Structure of Saturn's Rings from Cassini Diametric Radio Occultations

NASA Astrophysics Data System (ADS)

Marouf, E.; French, R.; Rappaport, N.; Kliore, A.; Flasar, M.; Nagy, A.; McGhee, C.; Schinder, P.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D.; Goltz, G.; Johnston, D.; Rochblatt, D.; Thomson, F.; Wong, K.

2005-08-01

Cassini orbits around Saturn were designed to provide eight optimized radio occultation observations of Saturn's rings during summer, 2005. Three monochromatic radio signals (0.94, 3.6, and 13 cm-wavelength) were transmitted by Cassini through the rings and observed at multiple stations of the NASA Deep Space Network. A rich data set has been collected. Detailed structure of Ring B is revealed for the first time, including multi-feature dense ''core'' ˜ 6,000 km wide of normal optical depth > 4.3, a ˜ 5,500 km region of oscillations in optical depth ( ˜ 1.7 to ˜ 3.4) over characteristic radial scales of few hundred kilometers interior to the core, and a ˜ 5,000 km region exterior to the core of similar nature but smaller optical depth fluctuation ( ˜ 2.2 to ˜ 3.3). The innermost ˜ 7,000 km region is the thinnest (mean optical depth ˜ 1.2), and includes two unusually uniform regions and a prominent density wave. With few exceptions, the structure is nearly identical for the three radio signals (when detectable), indicating that Ring B is relatively devoid of centimeters and smaller size particles. The structure is largely circularly symmetric, except for radius > ˜ 116,600 km. In Ring A, numerous (> 40) density waves are clearly observed at multiple longitudes, different average background optical depth is observed among different occultations suggesting that the azimuthal asymmetry extends over most Ring A, and strong dependence of the observed structure on wavelength implies increase in the abundance of centimeter and smaller size particles with increasing radius. Multiple longitude observations of Ring C and the Cassini Division structure reveal remarkable variability of gaps and their embedded narrow eccentric ringlets, and a wake/wave like feature interior to the gap at ˜ 118,200 km (embedded moonlet?). Wavelength dependent structure of Ring C implies abundance of centimeter size particles everywhere and sorting by size within dense embedded features.

Measurement of dispersion of nanoparticles in a dense suspension by high-sensitivity low-coherence dynamic light scattering

NASA Astrophysics Data System (ADS)

Ishii, Katsuhiro; Nakamura, Sohichiro; Sato, Yuki

2014-08-01

High-sensitivity low-coherence DLS apply to measurement of particle size distribution of pigments suspended in a ink. This method can be apply to extremely dense and turbid media without dilution. We show the temporal variation of particle size distribution of thixotropy and sedimentary pigments due to aggregation, agglomerate, and sedimentation. Moreover, we demonstrate the influence of dilution of ink to particle size distribution.

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.

Material exchange and food web of seagrass beds in the Sylt-Rømø Bight: how significant are community changes at the ecosystem level?

NASA Astrophysics Data System (ADS)

Asmus, H.; Asmus, R.

2000-07-01

Material exchange, biodiversity and trophic transfer within the food web were investigated in two different types of intertidal seagrass beds: a sheltered, dense Zostera marina bed and a more exposed, sparse Z. noltii bed, in the Northern Wadden Sea. Both types of Zostera beds show a seasonal development of above-ground biomass, and therefore measurements were carried out during the vegetation period in summer. The exchange of particles and nutrients between seagrass beds and the overlying water was measured directly using an in situ flume. Particle sedimentation [carbon (C), nitrogen (N) and phosphorus (P) constituents] from the water column prevailed in dense seagrass beds. In the sheltered, dense seagrass bed, a net particle uptake was found even on windy days (7-8 Beaufort). Dissolved inorganic N and orthophosphate were mainly taken up by the dense seagrass bed. At times of strong winds, nutrients were released from the benthic community to tidal waters. In a budget calculation of total N and total P, the dense seagrass beds were characterised as a material sink. The seagrass beds with sparse Z. noltii were a source of particles even during calm weather. The uptake of dissolved inorganic N in the sparse seagrass bed was low but significant, while the uptake of inorganic phosphate and silicate by seagrasses and their epiphytes was exceeded by release processes from the sediment into the overlying water. Estimates at the ecosystem level showed that material fluxes of seagrass beds in the Sylt-Rømø Bight are dominated by the dense type of Zostera beds. Therefore, seagrass beds act as a sink for particles and for dissolved inorganic nutrients. During storms, seagrass beds are distinct sources for inorganic nutrients. The total intertidal area of the Sylt-Rømø Bight could be described as a sink for particles and a source for dissolved nutrients. This balance of the material budget was estimated by either including or excluding seagrass beds. Including the subtidal part, the function of the ecosystem as a source for particles increased, supposing that all seagrass beds were lost from the area. During the vegetation period, seagrass beds act as a storage compartment for material accumulated in the living biomass of the community. There was great biodiversity among the plant and animal groups found in intertidal seagrass beds of the Sylt-Rømø Bay, representing 50-86% of the total number of species investigated, depending on the particular group. Since most species are not exclusively seagrass residents, the loss of intertidal seagrass beds would be of minor importance for biodiversity at the ecosystem level. Food web structure in seagrass beds is different from other intertidal communities. Primary production and detritus input is high, but secondary production is similar to that of unvegetated areas, although the relative importance of the trophic guilds is different. The loss of seagrass beds leads to profound alterations in the food web of the total ecosystem. Historical as well as recent changes in material fluxes and energy flow due to man-made alterations to the ecosystem are discussed.

Implementation and Re nement of a Comprehensive Model for Dense Granular Flows

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

Sundaresan, Sankaran

2015-09-30

Dense granular ows are ubiquitous in both natural and industrial processes. They manifest three di erent ow regimes, each exhibiting its own dependence on solids volume fraction, shear rate, and particle-level properties. This research project sought to develop continuum rheological models for dense granular ows that bridges multiple regimes of ow, implement them in open-source platforms for gas-particle ows and perform test simulations. The rst phase of the research covered in this project involved implementation of a steady- shear rheological model that bridges quasi-static, intermediate and inertial regimes of ow into MFIX (Multiphase Flow with Interphase eXchanges - a generalmore » purpose computer code developed at the National Energy Technology Laboratory). MFIX simulations of dense granular ows in hourglass-shaped hopper were then performed as test examples. The second phase focused on formulation of a modi ed kinetic theory for frictional particles that can be used over a wider range of particle volume fractions and also apply for dynamic, multi- dimensional ow conditions. To guide this work, simulations of simple shear ows of identical mono-disperse spheres were also performed using the discrete element method. The third phase of this project sought to develop and implement a more rigorous treatment of boundary e ects. Towards this end, simulations of simple shear ows of identical mono-disperse spheres con ned between parallel plates were performed and analyzed to formulate compact wall boundary conditions that can be used for dense frictional ows at at frictional boundaries. The fourth phase explored the role of modest levels of cohesive interactions between particles on the dense phase rheology. The nal phase of this project focused on implementation and testing of the modi ed kinetic theory in MFIX and running bin-discharge simulations as test examples.« less

X-ray Emission from the Interaction of a Macroscopic Particle with a Dense Plasma Focus.

DTIC Science & Technology

1976-10-01

Recently the interest in dense plasma focus has greatly increased because of the possibility of developing the device into an intense, pulsed...using a macroscopic particle to interact with a plasma focus . A theoretical study was carried out to predict the relative amount of X-ray increase

Rheology of dense suspensions of non colloidal particles

NASA Astrophysics Data System (ADS)

Guazzelli, Élisabeth

2017-06-01

Dense suspensions are materials with broad applications both in industrial processes (e.g. waste disposal, concrete, drilling muds, metalworking chip transport, and food processing) and in natural phenomena (e.g. flows of slurries, debris, and lava). Despite its long research history and its practical relevance, the mechanics of dense suspensions remain poorly understood. The major difficulty is that the grains interact both by hydrodynamic interactions through the liquid and by mechanical contact. These systems thus belong to an intermediate regime between pure suspensions and granular flows. We show that we can unify suspension and granular rheology under a common framework by transferring the frictional approach of dry granular media to wet suspensions of spherical particles. We also discuss non-Newtonian behavior such as normal-stress differences and shear-induced migration. Beyond the classical problem of dense suspension of hard spheres which is far from being completely resolved, there are also entirely novel avenues of study concerning more complex mixtures of particles and fluids such as those involving other types of particles (e.g. fibers) or non-Newtonian fluids that we will also address.

Competition between excluded-volume and electrostatic interactions for nanogel swelling: effects of the counterion valence and nanogel charge.

PubMed

Adroher-Benítez, Irene; Martín-Molina, Alberto; Ahualli, Silvia; Quesada-Pérez, Manuel; Odriozola, Gerardo; Moncho-Jordá, Arturo

2017-03-01

In this work the equilibrium distribution of ions around a thermo-responsive charged nanogel particle in an electrolyte aqueous suspension is explored using coarse-grained Monte Carlo computer simulations and the Ornstein-Zernike integral equation theory. We explicitly consider the ionic size in both methods and study the interplay between electrostatic and excluded-volume effects for swollen and shrunken nanogels, monovalent and trivalent counterions, and for two different nanogel charges. We find good quantitative agreement between the ionic density profiles obtained using both methods when the excluded repulsive force exerted by the cross-linked polymer network is taken into account. For the shrunken conformation, the electrostatic repulsion between the charged groups provokes a heterogeneous polymer density profile, leading to a nanogel structure with an internal low density hole surrounded by a dense corona. The results show that the excluded-volume repulsion strongly hinders the ion permeation for shrunken nanogels, where volume exclusion is able to significantly reduce the concentration of counterions in the more dense regions of the nanogel. In general, we demonstrate that the thermosensitive behaviour of nanogels, as well as their internal structure, is strongly influenced by the valence of the counterions and also by the charge of the particles. On the one hand, an increase of the counterion valence moves the swelling transition to lower temperatures, and induces a major structuring of the charged monomers into internal and external layers around the crown for shrunken nanogels. On the other hand, increasing the particle charge shifts the swelling curve to larger values of the effective radius of the nanogel.

Effective density and mixing state of aerosol particles in a near-traffic urban environment.

PubMed

Rissler, Jenny; Nordin, Erik Z; Eriksson, Axel C; Nilsson, Patrik T; Frosch, Mia; Sporre, Moa K; Wierzbicka, Aneta; Svenningsson, Birgitta; Löndahl, Jakob; Messing, Maria E; Sjogren, Staffan; Hemmingsen, Jette G; Loft, Steffen; Pagels, Joakim H; Swietlicki, Erik

2014-06-03

In urban environments, airborne particles are continuously emitted, followed by atmospheric aging. Also, particles emitted elsewhere, transported by winds, contribute to the urban aerosol. We studied the effective density (mass-mobility relationship) and mixing state with respect to the density of particles in central Copenhagen, in wintertime. The results are related to particle origin, morphology, and aging. Using a differential mobility analyzer-aerosol particle mass analyzer (DMA-APM), we determined that particles in the diameter range of 50-400 nm were of two groups: porous soot aggregates and more dense particles. Both groups were present at each size in varying proportions. Two types of temporal variability in the relative number fraction of the two groups were found: soot correlated with intense traffic in a diel pattern and dense particles increased during episodes with long-range transport from polluted continental areas. The effective density of each group was relatively stable over time, especially of the soot aggregates, which had effective densities similar to those observed in laboratory studies of fresh diesel exhaust emissions. When heated to 300 °C, the soot aggregate volatile mass fraction was ∼10%. For the dense particles, the volatile mass fraction varied from ∼80% to nearly 100%.

Flash X-Ray measurements on the shock-induced dispersal of a dense particle curtain

DOE PAGES

Wagner, Justin L.; Kearney, Sean P.; Beresh, Steven J.; ...

2015-11-23

The interaction of a Mach 1.67 shock wave with a dense particle curtain is quantified using flash radiography. These new data provide a view of particle transport inside a compressible, dense gas–solid flow of high optical opacity. The curtain, composed of 115-µm glass spheres, initially spans 87 % of the test section width and has a streamwise thickness of about 2 mm. Radiograph intensities are converted to particle volume fraction distributions using the Beer–Lambert law. The mass in the particle curtain, as determined from the X-ray data, is in reasonable agreement with that given from a simpler method using amore » load cell and particle imaging. Following shock impingement, the curtain propagates downstream and the peak volume fraction decreases from about 23 to about 4 % over a time of 340 µs. The propagation occurs asymmetrically, with the downstream side of the particle curtain experiencing a greater volume fraction gradient than the upstream side, attributable to the dependence of particle drag on volume fraction. Bulk particle transport is quantified from the time-dependent center of mass of the curtain. Furthermore, the bulk acceleration of the curtain is shown to be greater than that predicted for a single 115-µm particle in a Mach 1.67 shock-induced flow.« less

Flash X-Ray measurements on the shock-induced dispersal of a dense particle curtain

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

Wagner, Justin L.; Kearney, Sean P.; Beresh, Steven J.

The interaction of a Mach 1.67 shock wave with a dense particle curtain is quantified using flash radiography. These new data provide a view of particle transport inside a compressible, dense gas–solid flow of high optical opacity. The curtain, composed of 115-µm glass spheres, initially spans 87 % of the test section width and has a streamwise thickness of about 2 mm. Radiograph intensities are converted to particle volume fraction distributions using the Beer–Lambert law. The mass in the particle curtain, as determined from the X-ray data, is in reasonable agreement with that given from a simpler method using amore » load cell and particle imaging. Following shock impingement, the curtain propagates downstream and the peak volume fraction decreases from about 23 to about 4 % over a time of 340 µs. The propagation occurs asymmetrically, with the downstream side of the particle curtain experiencing a greater volume fraction gradient than the upstream side, attributable to the dependence of particle drag on volume fraction. Bulk particle transport is quantified from the time-dependent center of mass of the curtain. Furthermore, the bulk acceleration of the curtain is shown to be greater than that predicted for a single 115-µm particle in a Mach 1.67 shock-induced flow.« less

Flash X-ray measurements on the shock-induced dispersal of a dense particle curtain

NASA Astrophysics Data System (ADS)

Wagner, Justin L.; Kearney, Sean P.; Beresh, Steven J.; DeMauro, Edward P.; Pruett, Brian O.

2015-12-01

The interaction of a Mach 1.67 shock wave with a dense particle curtain is quantified using flash radiography. These new data provide a view of particle transport inside a compressible, dense gas-solid flow of high optical opacity. The curtain, composed of 115-µm glass spheres, initially spans 87 % of the test section width and has a streamwise thickness of about 2 mm. Radiograph intensities are converted to particle volume fraction distributions using the Beer-Lambert law. The mass in the particle curtain, as determined from the X-ray data, is in reasonable agreement with that given from a simpler method using a load cell and particle imaging. Following shock impingement, the curtain propagates downstream and the peak volume fraction decreases from about 23 to about 4 % over a time of 340 µs. The propagation occurs asymmetrically, with the downstream side of the particle curtain experiencing a greater volume fraction gradient than the upstream side, attributable to the dependence of particle drag on volume fraction. Bulk particle transport is quantified from the time-dependent center of mass of the curtain. The bulk acceleration of the curtain is shown to be greater than that predicted for a single 115-µm particle in a Mach 1.67 shock-induced flow.

Improved understanding of the acoustophoretic focusing of dense suspensions in a microchannel

NASA Astrophysics Data System (ADS)

Karthick, S.; Sen, A. K.

2017-11-01

We provide improved understanding of acoustophoretic focusing of a dense suspension (volume fraction φ >10 % ) in a microchannel subjected to an acoustic standing wave using a proposed theoretical model and experiments. The model is based on the theory of interacting continua and utilizes a momentum transport equation for the mixture, continuity equation, and transport equation for the solid phase. The model demonstrates the interplay between acoustic radiation and shear-induced diffusion (SID) forces that is critical in the focusing of dense suspensions. The shear-induced particle migration model of Leighton and Acrivos, coupled with the acoustic radiation force, is employed to simulate the continuum behavior of particles. In the literature, various closures for the diffusion coefficient Dφ* are available for rigid spheres at high concentrations and nonspherical deformable particles [e.g., red blood cells (RBCs)] at low concentrations. Here we propose a closure for Dφ* for dense suspension of RBCs and validate the proposed model with experimental data. While the available closures for Dφ* fail to predict the acoustic focusing of a dense suspension of nonspherical deformable particles like RBCs, the predictions of the proposed model match experimental data within 15%. Both the model and experiments reveal a competition between acoustic radiation and SID forces that gives rise to an equilibrium width w* of a focused stream of particles at some distance Leq* along the flow direction. Using different shear rates, acoustic energy densities, and particle concentrations, we show that the equilibrium width is governed by Péclet number Pe and Strouhal number Stas w*=1.4(PeSt) -0.5 while the length required to obtain the equilibrium-focused width depends on St as Leq*=3.8 /(St)0.6 . The proposed model and correlations would find significance in the design of microchannels for acoustic focusing of dense suspensions such as undiluted blood.

Effect of Nozzle Geometry on the Microstructure and Properties of HVAF-Sprayed WC-10Co4Cr and Cr3C2-25NiCr Coatings

NASA Astrophysics Data System (ADS)

Matikainen, V.; Koivuluoto, H.; Vuoristo, P.; Schubert, J.; Houdková, Š.

2018-04-01

Thermally sprayed hard metal coatings are the industrial standard solution for numerous demanding applications to improve wear resistance. In the aim of improving coating quality by utilising finer particle size distributions, several approaches have been studied to control the spray temperature. The most viable solution is to use the modern high velocity air-fuel (HVAF) spray process, which has already proven to produce high-quality coatings with dense structures. In HVAF spray process, the particle heating and acceleration can be efficiently controlled by changing the nozzle geometry. In this study, fine WC-10Co4Cr and Cr3C2-25NiCr powders were sprayed with three nozzle geometries to investigate their effect on the particle temperature, velocity and coating microstructure. The study demonstrates that the particle melting and resulting carbide dissolution can be efficiently controlled by changing the nozzle geometry from cylindrical to convergent-divergent. Moreover, the average particle velocity was increased from 780 to over 900 m/s. The increase in particle velocity significantly improved the coating structure and density. Further evaluation was carried out to resolve the effect of particle in-flight parameters on coating structure and cavitation erosion resistance, which was significantly improved in the case of WC-10Co4Cr coatings with the increasing average particle velocity.

Effect of particle-size dynamics on properties of dense spongy-particle systems: Approach towards equilibrium.

PubMed

Zakhari, Monica E A; Anderson, Patrick D; Hütter, Markus

2017-07-01

Open-porous deformable particles, often envisaged as sponges, are ubiquitous in biological and industrial systems (e.g., casein micelles in dairy products and microgels in cosmetics). The rich behavior of these suspensions is owing to the elasticity of the supporting network of the particle, and the viscosity of permeating solvent. Therefore, the rate-dependent size change of these particles depends on their structure, i.e., the permeability. This work aims at investigating the effect of the particle-size dynamics and the underlying particle structure, i.e., the particle permeability, on the transient and long-time behavior of suspensions of spongy particles in the absence of applied deformation, using the dynamic two-scale model developed by Hütter et al. [Farad. Discuss. 158, 407 (2012)1359-664010.1039/c2fd20025b]. In the high-density limit, the transient behavior is found to be accelerated by the particle-size dynamics, even at average size changes as small as 1%. The accelerated dynamics is evidenced by (i) the higher short-time diffusion coefficient as compared to elastic-particle systems and (ii) the accelerated formation of the stable fcc crystal structure. Furthermore, after long times, the particle-size dynamics of spongy particles is shown to result in lower stationary values of the energy and normal stresses as compared to elastic-particle systems. This dependence of the long-time behavior of these systems on the permeability, that essentially is a transport coefficient and hence must not affect the equilibrium properties, confirms that full equilibration has not been reached.

Effect of particle-size dynamics on properties of dense spongy-particle systems: Approach towards equilibrium

NASA Astrophysics Data System (ADS)

Zakhari, Monica E. A.; Anderson, Patrick D.; Hütter, Markus

2017-07-01

Open-porous deformable particles, often envisaged as sponges, are ubiquitous in biological and industrial systems (e.g., casein micelles in dairy products and microgels in cosmetics). The rich behavior of these suspensions is owing to the elasticity of the supporting network of the particle, and the viscosity of permeating solvent. Therefore, the rate-dependent size change of these particles depends on their structure, i.e., the permeability. This work aims at investigating the effect of the particle-size dynamics and the underlying particle structure, i.e., the particle permeability, on the transient and long-time behavior of suspensions of spongy particles in the absence of applied deformation, using the dynamic two-scale model developed by Hütter et al. [Farad. Discuss. 158, 407 (2012), 10.1039/c2fd20025b]. In the high-density limit, the transient behavior is found to be accelerated by the particle-size dynamics, even at average size changes as small as 1 % . The accelerated dynamics is evidenced by (i) the higher short-time diffusion coefficient as compared to elastic-particle systems and (ii) the accelerated formation of the stable fcc crystal structure. Furthermore, after long times, the particle-size dynamics of spongy particles is shown to result in lower stationary values of the energy and normal stresses as compared to elastic-particle systems. This dependence of the long-time behavior of these systems on the permeability, that essentially is a transport coefficient and hence must not affect the equilibrium properties, confirms that full equilibration has not been reached.

Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode

DOEpatents

Richards, Von L.; Singhal, Subhash C.; Pal, Uday B.

1992-01-01

A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro.sub.3 particles; (2) dispersing doped LaCrO.sub.3 particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then electrochemical vapor depositing a dense skeletal LaCrO.sub.3 structure, between and around the doped LaCrO.sub.3 particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell.

Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode

DOEpatents

Richards, V.L.; Singhal, S.C.; Pal, U.B.

1992-07-21

A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro[sub 3] particles; (2) dispersing doped LaCrO[sub 3] particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then a dense skeletal LaCrO[sub 3] structure is electrochemically vapor deposited between and around the doped LaCrO[sub 3] particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell. 4 figs.

Dense Suspension Splash

NASA Astrophysics Data System (ADS)

Zhang, Wendy; Dodge, Kevin M.; Peters, Ivo R.; Ellowitz, Jake; Klein Schaarsberg, Martin H.; Jaeger, Heinrich M.

2014-03-01

Upon impact onto a solid surface at several meters-per-second, a dense suspension plug splashes by ejecting liquid-coated particles. We study the mechanism for splash formation using experiments and a numerical model. In the model, the dense suspension is idealized as a collection of cohesionless, rigid grains with finite surface roughness. The grains also experience lubrication drag as they approach, collide inelastically and rebound away from each other. Simulations using this model reproduce the measured momentum distribution of ejected particles. They also provide direct evidence supporting the conclusion from earlier experiments that inelastic collisions, rather than viscous drag, dominate when the suspension contains macroscopic particles immersed in a low-viscosity solvent such as water. Finally, the simulations reveal two distinct routes for splash formation: a particle can be ejected by a single high momentum-change collision. More surprisingly, a succession of small momentum-change collisions can accumulate to eject a particle outwards. Supported by NSF through its MRSEC program (DMR-0820054) and fluid dynamics program (CBET-1336489).

AN ELECTRON MICROSCOPE STUDY OF NERVES INFECTED WITH HUMAN POLIOMYELITIS VIRUS

PubMed Central

De Robertis, E.; Schmitt, F. O

1949-01-01

Sciatic nerves of rhesus monkeys infected with CAM and Wis. '45 strains of human poliomyelitis virus were fixed in formalin, sectioned, fragmented, and examined in the electron microscope. Most of the neurotubules of nerves infected with the CAM strain have normal appearance but a very small number show the presence of dense particles irregularly aligned within the edges of the neurotubules. The diameters of the particles range between 160 and 500 Å, the mean being 330 Å. The particles were found in regions along the nerve which varied with the time after infection, indicating a central movement of the morphological alteration of the order of 2 mm. per hour. Relatively abundant dense particulate material was found in nerves infected with Wis. '45 strain virus and the particles were chiefly attached to the edges of the neurotubules and in the adjacent areas of the field. The dense particles appear to be associated with the virus infection but no further characterization is possible at this time. PMID:18140661

Micro-structure and motion of two-dimensional dense short spherocylinder liquids

NASA Astrophysics Data System (ADS)

Wang, Wen; Lin, Jyun-Ting; Su, Yen-Shuo; I, Lin

2018-03-01

We numerically investigate the micro-structure and motion of 2D liquids composed of dense short spherocylinders, by reducing the shape aspect ratio from 3. It is found that reducing shape aspect ratio from 3 causes a smooth transition from heterogeneous structures composed of crystalline ordered domains with good tetratic alignment order to those with good hexagonal bond-orientational order at an aspect ratio equaling 1.35. In the intermediate regime, both structural orders are strongly deteriorated, and the translational hopping rate reaches a maximum due to the poor particle interlocking of the disordered structure. Shortening rod length allows easier rotation, induces monotonic increase of rotational hopping rates, and resumes the separation of rotational and translational hopping time scales at the small aspect ratio end, after the crossover of their rates in the intermediate regime. At the large shape aspect ratio end, the poor local tetratic order has the same positive effects on facilitating local rotational and translational hopping. In contrast, at the small shape aspect ratio end, the poor local bond orientational order has the opposite effects on facilitating local rotational and translational hopping.

Crystal-structure prediction via the Floppy-Box Monte Carlo algorithm: Method and application to hard (non)convex particles

NASA Astrophysics Data System (ADS)

de Graaf, Joost; Filion, Laura; Marechal, Matthieu; van Roij, René; Dijkstra, Marjolein

2012-12-01

In this paper, we describe the way to set up the floppy-box Monte Carlo (FBMC) method [L. Filion, M. Marechal, B. van Oorschot, D. Pelt, F. Smallenburg, and M. Dijkstra, Phys. Rev. Lett. 103, 188302 (2009), 10.1103/PhysRevLett.103.188302] to predict crystal-structure candidates for colloidal particles. The algorithm is explained in detail to ensure that it can be straightforwardly implemented on the basis of this text. The handling of hard-particle interactions in the FBMC algorithm is given special attention, as (soft) short-range and semi-long-range interactions can be treated in an analogous way. We also discuss two types of algorithms for checking for overlaps between polyhedra, the method of separating axes and a triangular-tessellation based technique. These can be combined with the FBMC method to enable crystal-structure prediction for systems composed of highly shape-anisotropic particles. Moreover, we present the results for the dense crystal structures predicted using the FBMC method for 159 (non)convex faceted particles, on which the findings in [J. de Graaf, R. van Roij, and M. Dijkstra, Phys. Rev. Lett. 107, 155501 (2011), 10.1103/PhysRevLett.107.155501] were based. Finally, we comment on the process of crystal-structure prediction itself and the choices that can be made in these simulations.

A New Self-Consistent Field Model of Polymer/Nanoparticle Mixture

NASA Astrophysics Data System (ADS)

Chen, Kang; Li, Hui-Shu; Zhang, Bo-Kai; Li, Jian; Tian, Wen-De

2016-02-01

Field-theoretical method is efficient in predicting assembling structures of polymeric systems. However, it’s challenging to generalize this method to study the polymer/nanoparticle mixture due to its multi-scale nature. Here, we develop a new field-based model which unifies the nanoparticle description with the polymer field within the self-consistent field theory. Instead of being “ensemble-averaged” continuous distribution, the particle density in the final morphology can represent individual particles located at preferred positions. The discreteness of particle density allows our model to properly address the polymer-particle interface and the excluded-volume interaction. We use this model to study the simplest system of nanoparticles immersed in the dense homopolymer solution. The flexibility of tuning the interfacial details allows our model to capture the rich phenomena such as bridging aggregation and depletion attraction. Insights are obtained on the enthalpic and/or entropic origin of the structural variation due to the competition between depletion and interfacial interaction. This approach is readily extendable to the study of more complex polymer-based nanocomposites or biology-related systems, such as dendrimer/drug encapsulation and membrane/particle assembly.

Method of bonding an interconnection layer on an electrode of an electrochemical cell

DOEpatents

Pal, Uday B.; Isenberg, Arnold O.; Folser, George R.

1992-01-01

An electrochemical cell containing an air electrode (16), contacting electrolyte and electronically conductive interconnection layer (26), and a fuel electrode, has the interconnection layer (26) attached by: (A) applying a thin, closely packed, discrete layer of LaCrO.sub.3 particles (30), doped with an element selected from the group consisting of Ca, Sr, Co, Ba, Mg and their mixtures on a portion of the air electrode, and then (B) electrochemical vapor depositing a dense skeletal structure (32) between and around the doped LaCrO.sub.3 particles (30).

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.

How to form planetesimals from mm-sized chondrules and chondrule aggregates

NASA Astrophysics Data System (ADS)

Carrera, Daniel; Johansen, Anders; Davies, Melvyn B.

2015-07-01

The size distribution of asteroids and Kuiper belt objects in the solar system is difficult to reconcile with a bottom-up formation scenario due to the observed scarcity of objects smaller than ~100 km in size. Instead, planetesimals appear to form top-down, with large 100-1000 km bodies forming from the rapid gravitational collapse of dense clumps of small solid particles. In this paper we investigate the conditions under which solid particles can form dense clumps in a protoplanetary disk. We used a hydrodynamic code to model the interaction between solid particles and the gas inside a shearing box inside the disk, considering particle sizes from submillimeter-sized chondrules to meter-sized rocks. We found that particles down to millimeter sizes can form dense particle clouds through the run-away convergence of radial drift known as the streaming instability. We made a map of the range of conditions (strength of turbulence, particle mass-loading, disk mass, and distance to the star) that are prone to producing dense particle clumps. Finally, we estimate the distribution of collision speeds between mm-sized particles. We calculated the rate of sticking collisions and obtain a robust upper limit on the particle growth timescale of ~105 years. This means that mm-sized chondrule aggregates can grow on a timescale much smaller than the disk accretion timescale (~106-107 years). Our results suggest a pathway from the mm-sized grains found in primitive meteorites to fully formed asteroids. We speculate that asteroids may form from a positive feedback loop in which coagualation leads to particle clumping driven by the streaming instability. This clumping, in turn, reduces collision speeds and enhances coagulation. Future simulations should model coagulation and the streaming instability together to explore this feedback loop further. Appendices are available in electronic form at http://www.aanda.org

Shear thickening regimes of dense non-Brownian suspensions.

PubMed

Ness, Christopher; Sun, Jin

2016-01-21

We propose a unifying rheological framework for dense suspensions of non-Brownian spheres, predicting the onsets of particle friction and particle inertia as distinct shear thickening mechanisms, while capturing quasistatic and soft particle rheology at high volume fractions and shear rates respectively. Discrete element method simulations that take suitable account of hydrodynamic and particle-contact interactions corroborate the model predictions, demonstrating both mechanisms of shear thickening, and showing that they can occur concurrently with carefully selected particle surface properties under certain flow conditions. Microstructural transitions associated with frictional shear thickening are presented. We find very distinctive divergences of both microstructural and dynamic variables with respect to volume fraction in the thickened and non-thickened states.

An optimized surface plasmon photovoltaic structure using energy transfer between discrete nano-particles.

PubMed

Lin, Albert; Fu, Sze-Ming; Chung, Yen-Kai; Lai, Shih-Yun; Tseng, Chi-Wei

2013-01-14

Surface plasmon enhancement has been proposed as a way to achieve higher absorption for thin-film photovoltaics, where surface plasmon polariton(SPP) and localized surface plasmon (LSP) are shown to provide dense near field and far field light scattering. Here it is shown that controlled far-field light scattering can be achieved using successive coupling between surface plasmonic (SP) nano-particles. Through genetic algorithm (GA) optimization, energy transfer between discrete nano-particles (ETDNP) is identified, which enhances solar cell efficiency. The optimized energy transfer structure acts like lumped-element transmission line and can properly alter the direction of photon flow. Increased in-plane component of wavevector is thus achieved and photon path length is extended. In addition, Wood-Rayleigh anomaly, at which transmission minimum occurs, is avoided through GA optimization. Optimized energy transfer structure provides 46.95% improvement over baseline planar cell. It achieves larger angular scattering capability compared to conventional surface plasmon polariton back reflector structure and index-guided structure due to SP energy transfer through mode coupling. Via SP mediated energy transfer, an alternative way to control the light flow inside thin-film is proposed, which can be more efficient than conventional index-guided mode using total internal reflection (TIR).

Dibaryons in neutron stars

NASA Technical Reports Server (NTRS)

Olinto, Angela V.; Haensel, Pawel; Frieman, Joshua A.

1991-01-01

The effects are studied of H-dibaryons on the structure of neutron stars. It was found that H particles could be present in neutron stars for a wide range of dibaryon masses. The appearance of dibaryons softens the equations of state, lowers the maximum neutron star mass, and affects the transport properties of dense matter. The parameter space is constrained for dibaryons by requiring that a 1.44 solar mass neutron star be gravitationally stable.

Multi-object model-based multi-atlas segmentation for rodent brains using dense discrete correspondences

NASA Astrophysics Data System (ADS)

Lee, Joohwi; Kim, Sun Hyung; Styner, Martin

2016-03-01

The delineation of rodent brain structures is challenging due to low-contrast multiple cortical and subcortical organs that are closely interfacing to each other. Atlas-based segmentation has been widely employed due to its ability to delineate multiple organs at the same time via image registration. The use of multiple atlases and subsequent label fusion techniques has further improved the robustness and accuracy of atlas-based segmentation. However, the accuracy of atlas-based segmentation is still prone to registration errors; for example, the segmentation of in vivo MR images can be less accurate and robust against image artifacts than the segmentation of post mortem images. In order to improve the accuracy and robustness of atlas-based segmentation, we propose a multi-object, model-based, multi-atlas segmentation method. We first establish spatial correspondences across atlases using a set of dense pseudo-landmark particles. We build a multi-object point distribution model using those particles in order to capture inter- and intra- subject variation among brain structures. The segmentation is obtained by fitting the model into a subject image, followed by label fusion process. Our result shows that the proposed method resulted in greater accuracy than comparable segmentation methods, including a widely used ANTs registration tool.

Preparation and characterization of calcium phosphate ceramics and composites as bone substitutes

NASA Astrophysics Data System (ADS)

Zhang, Xing

Marine CaCO3 skeletons have tailored architectures created by nature, which give them structural support and other functions. For example, seashells have dense lamellar structures, while coral, cuttlebone and sea urchin spines have interconnected porous structures. In our experiments, seashells, coral and cuttlebone were hydrothermally converted to hydroxyapatite (HAP), and sea urchin spines were converted to Mg-substituted tricalcium phosphate (beta-TCMP), while maintaining their original structures. Partially converted shell samples have mechanical strength, which is close to that of compact human bone. After implantation of converted shell and spine samples in rat femoral defects for 6 weeks, there was newly formed bone growth up to and around the implants. Some new bone was found to migrate through the pores of converted spine samples and grow inward. These results show good bioactivity and osteoconductivity of the implants, indicating the converted shell and spine samples can be used as bone defect fillers. Calcium phosphate powders were prepared through different synthesis methods. Micro-size HAP rods were synthesized by hydrothermal method through a nucleation-growth mechanism. On the other hand, HAP particles, which have good crystallinity, were prepared by wet precipitation with further hydrothermal treatment. beta-TCP or beta-TCMP powders were prepared by a two-step process: wet precipitation of apatitic tricalcium phosphate ('precursor') and calcination of the precursor at 800°C for 3 hours. beta-TCMP or beta-TCP powders were also prepared by solid-state reactions from CaHPO4 and CaCO 3 with/without MgO. Biphasic calcium phosphate, which is mixture of HAP and beta-TCP, can be prepared though mechanical mixing of HAP and beta-TCP powders synthesized as above. Dense beta-TCP and beta-TCMP ceramics can be produced by pressing green bodies at 100MPa and further sintering above 1100°C for 2 hours. beta-TCMP ceramics ˜99.4% relative dense were prepared by this method. Dense beta-TCP ceramics have average strength up to 540MPa. Macroporous beta-TCMP ceramics were produced with sucrose as the porogen following a two-step pressing method. Porous beta-TCMP ceramics were also prepared by replication of polyurethane sponge. beta-TCMP ceramics with porous structures in the center surrounded by dense structures were created. The outside dense structures give the scaffold mechanical strength, while the central porous structures enable cells migration and vascular infiltration, and finally in-growth of new bone into the scaffold.

Structure-function relationship of biological gels revealed by multiple-particle tracking and differential interference contrast microscopy: The case of human lamin networks

NASA Astrophysics Data System (ADS)

Panorchan, Porntula; Wirtz, Denis; Tseng, Yiider

2004-10-01

Lamin B1 filaments organize into a thin dense meshwork underlying the nucleoplasmic side of the nuclear envelope. Recent experiments in vivo suggest that lamin B1 plays a key structural role in the nuclear envelope, but the intrinsic mechanical properties of lamin B1 networks remain unknown. To assess the potential mechanical contribution of lamin B1 in maintaining the integrity and providing structural support to the nucleus, we measured the micromechanical properties and examined the ultrastructural distribution of lamin B1 networks in vitro using particle tracking methods and differential interference contrast (DIC) microscopy. We exploit various surface chemistries of the probe microspheres (carboxylated, polyethylene glycol-coated, and amine-modified) to differentiate lamin-rich from lamin-poor regions and to rigorously extract local viscoelastic moduli from the mean-squared displacements of noninteracting particles. Our results show that human lamin B1 can, even in the absence of auxiliary proteins, form stiff and yet extremely porous networks that are well suited to provide structural strength to the nuclear lamina. Combining DIC microscopy and particle tracking allows us to relate directly the local organization of a material to its local mechanical properties, a general methodology that can be extended to living cells.

Radial particle-size segregation during packing of particulates into cylindrical containers

USGS Publications Warehouse

Ripple, C.D.; James, R.V.; Rubin, J.

1973-01-01

In a series of experiments, soil materials were placed in long cylindrical containers, using various packing procedures. Soil columns produced by deposition and simultaneous vibratory compaction were dense and axially uniform, but showed significant radial segregation of particle sizes. Similar results were obtained with deposition and simultaneous impact-type compaction when the impacts resulted in significant container "bouncing". The latter procedure, modified to minimize "bouncing" produced dense, uniform soil columns, showing little radial particle-size segregation. Other procedures tested (deposition alone and deposition followed by compaction) did not result in radial segregation, but produced columns showing either relatively low or axially nonuniform densities. Current data suggest that radial particle-size segregation is mainly due to vibration-induced particle circulation in which particles of various sizes have different circulation rates and paths. ?? 1973.

Optimization of In-Situ Shot-Peening-Assisted Cold Spraying Parameters for Full Corrosion Protection of Mg Alloy by Fully Dense Al-Based Alloy Coating

NASA Astrophysics Data System (ADS)

Wei, Ying-Kang; Luo, Xiao-Tao; Li, Cheng-Xin; Li, Chang-Jiu

2017-01-01

Magnesium-based alloys have excellent physical and mechanical properties for a lot of applications. However, due to high chemical reactivity, magnesium and its alloys are highly susceptible to corrosion. In this study, Al6061 coating was deposited on AZ31B magnesium by cold spray with a commercial Al6061 powder blended with large-sized stainless steel particles (in-situ shot-peening particles) using nitrogen gas. Microstructure and corrosion behavior of the sprayed coating was investigated as a function of shot-peening particle content in the feedstock. It is found that by introducing the in-situ tamping effect using shot-peening (SP) particles, the plastic deformation of deposited particles is significantly enhanced, thereby resulting in a fully dense Al6061 coating. SEM observations reveal that no SP particle is deposited into Al6061 coating at the optimization spraying parameters. Porosity of the coating significantly decreases from 10.7 to 0.4% as the SP particle content increases from 20 to 60 vol.%. The electrochemical corrosion experiments reveal that this novel in-situ SP-assisted cold spraying is effective to deposit fully dense Al6061 coating through which aqueous solution is not permeable and thus can provide exceptional protection of the magnesium-based materials from corrosion.

Improving the efficiency of quantum hash function by dense coding of coin operators in discrete-time quantum walk

NASA Astrophysics Data System (ADS)

Yang, YuGuang; Zhang, YuChen; Xu, Gang; Chen, XiuBo; Zhou, Yi-Hua; Shi, WeiMin

2018-03-01

Li et al. first proposed a quantum hash function (QHF) in a quantum-walk architecture. In their scheme, two two-particle interactions, i.e., I interaction and π-phase interaction are introduced and the choice of I or π-phase interactions at each iteration depends on a message bit. In this paper, we propose an efficient QHF by dense coding of coin operators in discrete-time quantum walk. Compared with existing QHFs, our protocol has the following advantages: the efficiency of the QHF can be doubled and even more; only one particle is enough and two-particle interactions are unnecessary so that quantum resources are saved. It is a clue to apply the dense coding technique to quantum cryptographic protocols, especially to the applications with restricted quantum resources.

Formation of Heterogeneous Toroidal-Spiral Particles -- by Drop Sedimentation and Interaction

NASA Astrophysics Data System (ADS)

Liu, Ying; Nitsche, Ludwig; Gemeinhart, Richard; Sharma, Vishal; Szymusiak, Magdalena; Shen, Hao

2013-03-01

We describe self-assembly of polymeric particles, whereby competitive kinetics of viscous sedimentation, diffusion, and cross-linking yield a controllable toroidal-spiral (TS) structure. Precursor polymeric droplets are splashed through the surface of a less dense, miscible solution, after which viscous forces entrain the surrounding bulk solution into the sedimenting polymer drop to form TS channels. The intricate structure forms because low interfacial tension between the two miscible solutions is dominated by viscous forces. The biocompatible polymer, poly(ethylene glycol) diacrylate (PEG-DA), is used to demonstrate the solidification of the TS shapes at various configurational stages by UV-triggered cross-linking. The dimensions of the channels are controlled by Weber number during impact on the surface, and Reynolds number and viscosity ratio during subsequent sedimentation. Within the critical separation distance, interaction of multiple drops generates similar structure with more flexibility. Furthermore, the understanding of multiple drop interaction is essential for mass production of TS particles by using parallel and sequential arrays of drops. This work was supported by NSF CBET Grant CBET-1039531.

Evidence for Universality in the Initial Planetesimal Mass Function

NASA Astrophysics Data System (ADS)

Simon, Jacob B.; Armitage, Philip J.; Youdin, Andrew N.; Li, Rixin

2017-10-01

Planetesimals may form from the gravitational collapse of dense particle clumps initiated by the streaming instability. We use simulations of aerodynamically coupled gas-particle mixtures to investigate whether the properties of planetesimals formed in this way depend upon the sizes of the particles that participate in the instability. Based on three high-resolution simulations that span a range of dimensionless stopping times 6× {10}-3≤slant τ ≤slant 2, no statistically significant differences in the initial planetesimal mass function are found. The mass functions are fit by a power law, {dN}/{{dM}}p\\propto {M}p-p, with p = 1.5-1.7 and errors of {{Δ }}p≈ 0.1. Comparing the particle density fields prior to collapse, we find that the high-wavenumber power spectra are similarly indistinguishable, though the large-scale geometry of structures induced via the streaming instability is significantly different between all three cases. We interpret the results as evidence for a near-universal slope to the mass function, arising from the small-scale structure of streaming-induced turbulence.

Mesons from Laser-Induced Processes in Ultra-Dense Hydrogen H(0)

PubMed Central

2017-01-01

Large signals of charged light mesons are observed in the laser-induced particle flux from ultra-dense hydrogen H(0) layers. The mesons are formed in such layers on metal surfaces using < 200 mJ laser pulse-energy. The time variation of the signal to metal foil collectors and the magnetic deflection to a movable pin collector are now studied. Relativistic charged particles with velocity up to 500 MeV u-1 thus 0.75 c are observed. Characteristic decay time constants for meson decay are observed, for charged and neutral kaons and also for charged pions. Magnetic deflections agree with charged pions and kaons. Theoretical predictions of the decay chains from kaons to muons in the particle beam agree with the results. Muons are detected separately by standard scintillation detectors in laser-induced processes in ultra-dense hydrogen H(0) as published previously. The muons formed do not decay appreciably within the flight distances used here. Most of the laser-ejected particle flux with MeV energy is not deflected by the magnetic fields and is thus neutral, either being neutral kaons or the ultra-dense HN(0) precursor clusters. Photons give only a minor part of the detected signals. PACS: 67.63.Gh, 14.40.-n, 79.20.Ds, 52.57.-z. PMID:28081199

Encapsidated Host Factors in Alphavirus Particles Influence Midgut Infection of Aedes aegypti.

PubMed

Mackenzie-Liu, David; Sokoloski, Kevin J; Purdy, Sarah; Hardy, Richard W

2018-05-16

Transmission of mosquito-borne viruses requires the efficient infection of both a permissive vertebrate host and a competent mosquito vector. The infectivity of Sindbis virus (SINV), the type species of the Alphavirus genus, is influenced by both the original and new host cell. We have shown that infection of vertebrate cells by SINV, chikungunya virus (CHIKV), and Ross River virus (RRV) produces two subpopulations of virus particles separable based on density. In contrast, a single population of viral particles is produced by mosquito cells. Previous studies demonstrated that the denser vertebrate-derived particles and the mosquito-derived particles contain components of the small subunit of the host cell ribosome, whereas the less dense vertebrate-derived particles do not. Infection of mice with RRV showed that both particle subpopulations are produced in an infected vertebrate, but in a tissue specific manner with serum containing only the less dense version of the virus particles. Previous infectivity studies using SINV particles have shown that the denser particles (SINV Heavy ) and mosquito derived particles SINV C6/36 are significantly more infectious in vertebrate cells than the less dense vertebrate derived particles (SINV Light ). The current study shows that SINV Light particles, initiate the infection of the mosquito midgut more efficiently than SINV Heavy particles and that this enhanced infectivity is associated with an exacerbated immune response to SINV Light infection in midgut tissues. The enhanced infection of SINV Light is specific to the midgut as intrathoracically injected virus do not exhibit the same fitness advantage. Together, our data indicate a biologically significant role for the SINV Light subpopulation in the efficient transmission from infected vertebrates to the mosquito vector.

Formation of polymeric toroidal-spiral particles.

PubMed

Sharma, Vishal; Szymusiak, Magdalena; Shen, Hao; Nitsche, Ludwig C; Liu, Ying

2012-01-10

Compared to spherical matrices, particles with well-defined internal structure provide large surface to volume ratio and predictable release kinetics for the encapsulated payloads. We describe self-assembly of polymeric particles, whereby competitive kinetics of viscous sedimentation, diffusion, and cross-linking yield a controllable toroidal-spiral (T-S) structure. Precursor polymeric droplets are splashed through the surface of a less dense, miscible solution, after which viscous forces entrain the surrounding bulk solution into the sedimenting polymer drop to form T-S channels. The intricate structure forms because low interfacial tension between the two miscible solutions is dominated by viscous forces. The biocompatible polymer, poly(ethylene glycol) diacrylate (PEG-DA), is used to demonstrate the solidification of the T-S shapes at various configurational stages by UV-triggered cross-linking. The dimensions of the channels are controlled by Weber number during impact on the surface, and Reynolds number and viscosity ratio during subsequent sedimentation. We anticipate applications of the T-S particle in drug delivery, wherein diffusion through these T-S channels and the polymer matrix would offer parallel release pathways for molecules of different sizes. Polyphosphate, as a model macromolecule, is entrained in T-S particles during their formation. The in vitro release kinetics of polyphosphate from the T-S particles with various channel length and width is reported. In addition, self-assembly of T-S particles occurs in a single step under benign conditions for delicate macromolecules, and appears conducive to scaleup.

The nonchromatin substructures of the nucleus: the ribonucleoprotein (RNP)-containing and RNP-depleted matrices analyzed by sequential fractionation and resinless section electron microscopy

PubMed Central

1986-01-01

The nonchromatin structure or matrix of the nucleus has been studied using an improved fractionation in concert with resinless section electron microscopy. The resinless sections show the nucleus of the intact cell to be filled with a dense network or lattice composed of soluble proteins and chromatin in addition to the structural nuclear constituents. In the first fractionation step, soluble proteins are removed by extraction with Triton X-100, and the dense nuclear lattice largely disappears. Chromatin and nonchromatin nuclear fibers are now sharply imaged. Nuclear constituents are further separated into three well-defined, distinct protein fractions. Chromatin proteins are those that require intact DNA for their association with the nucleus and are released by 0.25 M ammonium sulfate after internucleosomal DNA is cut with DNAase I. The resulting structure retains most heterogeneous nuclear ribonucleoprotein (hnRNP) and is designated the RNP-containing nuclear matrix. The proteins of hnRNP are those associated with the nucleus only if RNA is intact. These are released when nuclear RNA is briefly digested with RNAase A. Ribonuclease digestion releases 97% of the hnRNA and its associated proteins. These proteins correspond to the hnRNP described by Pederson (Pederson, T., 1974, J. Mol. Biol., 83:163- 184) and are distinct from the proteins that remain in the ribonucleoprotein (RNP)-depleted nuclear matrix. The RNP-depleted nuclear matrix is a core structure that retains lamins A and C, the intermediate filaments, and a unique set of nuclear matrix proteins (Fey, E. G., K. M. Wan, and S. Penman, 1984, J. Cell Biol. 98:1973- 1984). This core had been previously designated the nuclear matrix- intermediate filament scaffold and its proteins are a third, distinct, and nonoverlapping subset of the nuclear nonhistone proteins. Visualizing the nuclear matrix using resinless sections shows that nuclear RNA plays an important role in matrix organization. Conventional Epon-embedded electron microscopy sections show comparatively little of the RNP-containing and RNP-depleted nuclear matrix structure. In contrast, resinless sections show matrix interior to be a three-dimensional network of thick filaments bounded by the nuclear lamina. The filaments are covered with 20-30-nm electron dense particles which may contain the hnRNA. The large electron dense bodies, enmeshed in the interior matrix fibers, have the characteristic morphology of nucleoli. Treatment of the nuclear matrix with RNAase results in the aggregation of the interior fibers and the extensive loss of the 20-30-nm particles.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3700470

Theoretical model of x-ray scattering as a dense matter probe.

PubMed

Gregori, G; Glenzer, S H; Rozmus, W; Lee, R W; Landen, O L

2003-02-01

We present analytical expressions for the dynamic structure factor, or form factor S(k,omega), which is the quantity describing the x-ray cross section from a dense plasma or a simple liquid. Our results, based on the random phase approximation for the treatment on the charged particle coupling, can be applied to describe scattering from either weakly coupled classical plasmas or degenerate electron liquids. Our form factor correctly reproduces the Compton energy down-shift and the known Fermi-Dirac electron velocity distribution for S(k,omega) in the case of a cold degenerate plasma. The usual concept of scattering parameter is also reinterpreted for the degenerate case in order to include the effect of the Thomas-Fermi screening. The results shown in this work can be applied to interpreting x-ray scattering in warm dense plasmas occurring in inertial confinement fusion experiments or for the modeling of solid density matter found in the interior of planets.

The effect of char structure on burnout during pulverized coal combustion at pressure

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

Liu, G.; Wu, H.; Benfell, K.E.

An Australian bituminous coal sample was burnt in a drop tube furnace (DTF) at 1 atm and a pressurized drop tube furnace (PDTF) at 15 atm. The char samples were collected at different burnout levels, and a scanning electron microscope was used to examine the structures of chars. A model was developed to predict the burnout of char particles with different structures. The model accounts for combustion of the thin-walled structure of cenospheric char and its fragmentation during burnout. The effect of pressure on reaction rate was also considered in the model. As a result, approximately 40% and 70% cenosphericmore » char particles were observed in the char samples collected after coal pyrolysis in the DTF and PDTF respectively. A large number of fine particles (< 30 mm) were observed in the 1 atm char samples at burnout levels between 30% and 50%, which suggests that significant fragmentation occurred during early combustion. Ash particle size distributions show that a large number of small ash particles formed during burnout at high pressure. The time needed for 70% char burnout at 15 atm is approximately 1.6 times that at 1 atm under the same temperature and gas environment conditions, which is attributed to the different pressures as well as char structures. The overall reaction rate for cenospheric char was predicted to be approximately 2 times that of the dense chars, which is consistent with previous experimental results. The predicted char burnout including char structures agrees reasonably well with the experimental measurements that were obtained at 1 atm and 15 atm pressures.« less

Effect of pH on film structure and electrical property of PMMA-Au composite particles prepared by redox transmetalation

NASA Astrophysics Data System (ADS)

Wu, Hong-Mao; Lin, Kuan-Ju; Yu, Yi-Hsiuan; Ho, Chan-Yuan; Wei, Ming-Hsiung; Lu, Fu-Hsing; Tseng, Wenjea J.

2014-01-01

Surface-selective deposition of gold (Au) on electroless plated poly(methyl methacrylate)-nickel (PMMA-Ni) beads was prepared chemically by a facile redox-transmetalation route in which the Ni atoms on the PMMA surface were reacted with Au precursors, i.e., chloroauric acid (HAuCl4), in water to form predominately core-shell PMMA-Au composite particles without the need of reducing agent. The Ni layer acted as a sacrificial template to facilitate the selective transmetalation deposition of a metallic Au film. When pH of the precursor solution was adjusted from 6 to 9, morphology of the Au film changed from a uniform particulate film consisting of assemblies of Au nanoparticles, to densely packed, continuous film with platelet Au crystals, and finally to isolated Au islands on the PMMA surface with a raspberry-like core-shell morphology. Uniformly dense Au coating with a thickness of about 200 nm was formed on the PMMA beads at pH of 7 to 8, which gave rise to an electrical resistivity as low as 3 × 10-2 Ω cm.

Review on urban vegetation and particle air pollution - Deposition and dispersion

NASA Astrophysics Data System (ADS)

Janhäll, Sara

2015-03-01

Urban vegetation affects air quality through influencing pollutant deposition and dispersion. Both processes are described by many existing models and experiments, on-site and in wind tunnels, focussing e.g. on urban street canyons and crossings or vegetation barriers adjacent to traffic sources. There is an urgent need for well-structured experimental data, including detailed empirical descriptions of parameters that are not the explicit focus of the study. This review revealed that design and choice of urban vegetation is crucial when using vegetation as an ecosystem service for air quality improvements. The reduced mixing in trafficked street canyons on adding large trees increases local air pollution levels, while low vegetation close to sources can improve air quality by increasing deposition. Filtration vegetation barriers have to be dense enough to offer large deposition surface area and porous enough to allow penetration, instead of deflection of the air stream above the barrier. The choice between tall or short and dense or sparse vegetation determines the effect on air pollution from different sources and different particle sizes.

Kinetic Monte Carlo simulation of nanoparticle film formation via nanocolloid drying

NASA Astrophysics Data System (ADS)

Kameya, Yuki

2017-06-01

A kinetic Monte Carlo simulation of nanoparticle film formation via nanocolloid drying is presented. The proposed two-dimensional model addresses the dynamics of nanoparticles in the vertical plane of a drying nanocolloid film. The gas-liquid interface movement due to solvent evaporation was controlled by a time-dependent chemical potential, and the resultant particle dynamics including Brownian diffusion and aggregate growth were calculated. Simulations were performed at various Peclet numbers defined based on the rate ratio of solvent evaporation and nanoparticle diffusion. At high Peclet numbers, nanoparticles accumulated at the top layer of the liquid film and eventually formed a skin layer, causing the formation of a particulate film with a densely packed structure. At low Peclet numbers, enhanced particle diffusion led to significant particle aggregation in the bulk colloid, and the resulting film structure became highly porous. The simulated results showed some typical characteristics of a drying nanocolloid that had been reported experimentally. Finally, the potential of the model as well as the remaining challenges are discussed.

Assembly of Ultra-Dense Nanowire-Based Computing Systems

DTIC Science & Technology

2006-06-30

34* characterized basic device element properties and statistics "* demonstrated product of sums (POS) validating assembled 2-bit adder structures " Demonstrated...linear region (Vds= 10 mV) from the peak g = 3 jiS at IVg -VTI= 0.13 V using the charge control model, representsmore than a factor of 10 improvement over...disrupted by ionizing particles or thermal fluctuation. Further, when working with such small charges, it is statistically possible that logic

Time-resolved large-scale volumetric pressure fields of an impinging jet from dense Lagrangian particle tracking

NASA Astrophysics Data System (ADS)

Huhn, F.; Schanz, D.; Manovski, P.; Gesemann, S.; Schröder, A.

2018-05-01

Time-resolved volumetric pressure fields are reconstructed from Lagrangian particle tracking with high seeding concentration using the Shake-The-Box algorithm in a perpendicular impinging jet flow with exit velocity U=4 m/s (Re˜ 36,000) and nozzle-plate spacing H/D=5. Helium-filled soap bubbles are used as tracer particles which are illuminated with pulsed LED arrays. A large measurement volume has been covered (cloud of tracked particles in a volume of 54 L, ˜ 180,000 particles). The reconstructed pressure field has been validated against microphone recordings at the wall with high correlation coefficients up to 0.88. In a reduced measurement volume (13 L), dense Lagrangian particle tracking is shown to be feasable up to the maximal possible jet velocity of U=16 m/s.

The dynamics of particle disks. III - Dense and spinning particle disks. [development of kinetic theory for planetary rings

NASA Technical Reports Server (NTRS)

Araki, Suguru

1991-01-01

The kinetic theory of planetary rings developed by Araki and Tremaine (1986) and Araki (1988) is extended and refined, with a focus on the implications of finite particle size: (1) nonlocal collisions and (2) finite filling factors. Consideration is given to the derivation of the equations for the local steady state, the low-optical-depth limit, and the steady state at finite filling factors (including the effects of collision inelasticity, spin degrees of freedom, and self-gravity). Numerical results are presented in extensive graphs and characterized in detail. The importance of distinguishing effects (1) and (2) at low optical depths is stressed, and the existence of vertical density profiles with layered structures at high filling factors is demonstrated.

Microstructures of Randall's plaques and their interfaces with calcium oxalate monohydrate kidney stones reflect underlying mineral precipitation mechanisms.

PubMed

Sethmann, Ingo; Wendt-Nordahl, Gunnar; Knoll, Thomas; Enzmann, Frieder; Simon, Ludwig; Kleebe, Hans-Joachim

2017-06-01

Randall's plaques (RP) are preferred sites for the formation of calcium oxalate monohydrate (COM) kidney stones. However, although processes of interstitial calcium phosphate (CaP) plaque formation are not well understood, the potential of plaque microstructures as indicators of CaP precipitation conditions received only limited attention. We investigated RP-associated COM stones for structural details of the calcified tissues and microstructural features of plaque-stone interfaces as indicators of the initial processes of stone formation. Significantly increased CaP supersaturation can be expected for interstitial fluid, if reabsorbed ions from the tubular system continuously diffuse into the collagenous connective tissue. Densely packed, fine-grained CaP particles were found in dense textures of basement membranes while larger, laminated particles were scattered in coarse-meshed interstitial tissue, which we propose to be due to differential spatial confinements and restrictions of ion diffusion. Particle morphologies suggest an initial precipitation as metastable amorphous calcium phosphate (ACP). Morphologies and arrangements of first COM crystals at the RP-stone interface ranged from stacked euhedral platelets to skeletal morphologies and even porous, dendritic structures, indicating, in this order, increasing levels of COM supersaturation. Furthermore, these first COM crystals were often coated with CaP. On this basis, we propose that ions from CaP-supersaturated interstitial fluid may diffuse through porous RP into the urine, where a resulting local increase in COM supersaturation could trigger crystal nucleation and, hence, initiate stone formation. Ion-depleted fluid in persistent pores of initial COM layers may get replenished from interstitial fluid, leading to CaP precipitation in porous COM.

Improving particle filters in rainfall-runoff models: application of the resample-move step and development of the ensemble Gaussian particle filter

NASA Astrophysics Data System (ADS)

Plaza Guingla, D. A.; Pauwels, V. R.; De Lannoy, G. J.; Matgen, P.; Giustarini, L.; De Keyser, R.

2012-12-01

The objective of this work is to analyze the improvement in the performance of the particle filter by including a resample-move step or by using a modified Gaussian particle filter. Specifically, the standard particle filter structure is altered by the inclusion of the Markov chain Monte Carlo move step. The second choice adopted in this study uses the moments of an ensemble Kalman filter analysis to define the importance density function within the Gaussian particle filter structure. Both variants of the standard particle filter are used in the assimilation of densely sampled discharge records into a conceptual rainfall-runoff model. In order to quantify the obtained improvement, discharge root mean square errors are compared for different particle filters, as well as for the ensemble Kalman filter. First, a synthetic experiment is carried out. The results indicate that the performance of the standard particle filter can be improved by the inclusion of the resample-move step, but its effectiveness is limited to situations with limited particle impoverishment. The results also show that the modified Gaussian particle filter outperforms the rest of the filters. Second, a real experiment is carried out in order to validate the findings from the synthetic experiment. The addition of the resample-move step does not show a considerable improvement due to performance limitations in the standard particle filter with real data. On the other hand, when an optimal importance density function is used in the Gaussian particle filter, the results show a considerably improved performance of the particle filter.

Leptons from decay of mesons in the laser-induced particle pulse from ultra-dense protium p(0)

NASA Astrophysics Data System (ADS)

Holmlid, Leif

2016-10-01

Kaons and pions are observed by their characteristic decay times of 12, 52 and 26 ns after impact of relatively weak ns-long laser pulses on ultra-dense hydrogen H(0), as reported previously. The signal using an ultra-dense protium p(0) generator with natural hydrogen is now studied. Deflection in a weak magnetic field or penetration through metal foils cannot distinguish between the types of decaying mesons. The signals observed are thus not caused by the decaying mesons themselves, but by the fast particles often at >50MeV u-1 formed in their decay. The fast particles are concluded to be mainly muons from their relatively small magnetic deflection and strong penetration. This is further supported by published studies on the direct observation of the beta decay of muons in scintillators and solid converters using the same type of p(0) generator.

Catalyst containing oxygen transport membrane

DOEpatents

Lane, Jonathan A.; Wilson, Jamie R.; Christie, Gervase Maxwell; Petigny, Nathalie; Sarantopoulos, Christos

2017-02-07

A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a microstructure exhibiting substantially uniform pore size distribution as a result of using PMMA pore forming materials or a bi-modal particle size distribution of the porous support layer materials. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

Local order and crystallization of dense polydisperse hard spheres

NASA Astrophysics Data System (ADS)

Coslovich, Daniele; Ozawa, Misaki; Berthier, Ludovic

2018-04-01

Computer simulations give precious insight into the microscopic behavior of supercooled liquids and glasses, but their typical time scales are orders of magnitude shorter than the experimentally relevant ones. We recently closed this gap for a class of models of size polydisperse fluids, which we successfully equilibrate beyond laboratory time scales by means of the swap Monte Carlo algorithm. In this contribution, we study the interplay between compositional and geometric local orders in a model of polydisperse hard spheres equilibrated with this algorithm. Local compositional order has a weak state dependence, while local geometric order associated to icosahedral arrangements grows more markedly but only at very high density. We quantify the correlation lengths and the degree of sphericity associated to icosahedral structures and compare these results to those for the Wahnström Lennard-Jones mixture. Finally, we analyze the structure of very dense samples that partially crystallized following a pattern incompatible with conventional fractionation scenarios. The crystal structure has the symmetry of aluminum diboride and involves a subset of small and large particles with size ratio approximately equal to 0.5.

Contributions and mechanisms of action of graphite nanomaterials in ultra high performance concrete

NASA Astrophysics Data System (ADS)

Sbia, Libya Ahmed

Ultra-high performance concrete (UHPC) reaches high strength and impermeability levels by using a relatively large volume fraction of a dense binder with fine microstructure in combination with high-quality aggregates of relatively small particle size, and reinforcing fibers. The dense microstructure of the cementitions binder is achieved by raising the packing density of the particulate matter, which covers sizes ranging from few hundred nanometers to few millimeters. The fine microstructure of binder in UHPC is realized by effective use of pozzolans to largely eliminate the coarse crystalline particles which exist among cement hydrates. UHPC incorporates (steel) fibers to overcome the brittleness of its dense, finely structured cementitious binder. The main thrust of this research is to evaluate the benefits of nanmaterials in UHPC. The dense, finely structure cementitious binder as well as the large volume fraction of the binder in UHPC benefit the dispersion of nanomaterials, and their interfacial interactions. The relatively close spacing of nanomaterials within the cementitious binder of UHPC enables them to render local reinforcement effects in critically stressed regions such as those in the vicinity of steel reinforcement and prestressing strands as well as fibers. Nanomaterials can also raise the density of the binder in UHPC by extending the particle size distribution down to the few nanometers range. Comprehensive experimental studies supported by theoretical investigations were undertake in order to optimize the use of nanomaterials in UHPC, identity the UHPC (mechanical) properties which benefit from the introduction of nanomaterials, and define the mechanisms of action of nanomaterials in UHPC. Carbon nanofiber was the primary nanomaterial used in this investigation. Some work was also conducted with graphite nanoplates. The key hypotheses of the project were as follows: (i) nanomaterials can make important contributions to the packing density of the particulate matter in UHPC by extending the particle size distribution down to the few nanometers range; (ii) there are synergistic reinforcing actions of steel fibers and graphite nanomaterials in UHPC, which can be explained by their complementary spacing and also the benefit of nanomaterials to the interfacial bonding and pullout behavior of steel fibers; and (iii) nanomaterials make important contributions to the bonding and pullout behavior of prestressing strands and deformed bars in concrete, which can be attributed to the close spacing of nanomaterials within the highly stressed interfacial regions occurring in the vicinity of strands and reinforcing bars; steel fibers are loss effective in this regard due to the disturbance of their distribution and orientation in the vicinity of strands and bars. These hypotheses were successfully verified through the experimental and theoretical investigations conducted in this research.

Method for producing ceramic particles and agglomerates

DOEpatents

Phillips, Jonathan; Gleiman, Seth S.; Chen, Chun-Ku

2001-01-01

A method for generating spherical and irregularly shaped dense particles of ceramic oxides having a controlled particle size and particle size distribution. An aerosol containing precursor particles of oxide ceramics is directed into a plasma. As the particles flow through the hot zone of the plasma, they melt, collide, and join to form larger particles. If these larger particles remain in the hot zone, they continue melting and acquire a spherical shape that is retained after they exit the hot zone, cool down, and solidify. If they exit the hot zone before melting completely, their irregular shape persists and agglomerates are produced. The size and size distribution of the dense product particles can be controlled by adjusting several parameters, the most important in the case of powder precursors appears to be the density of powder in the aerosol stream that enters the plasma hot zone. This suggests that particle collision rate is responsible for determining ultimate size of the resulting sphere or agglomerate. Other parameters, particularly the gas flow rates and the microwave power, are also adjusted to control the particle size distribution.

Complex dynamics induced by strong confinement - From tracer diffusion in strongly heterogeneous media to glassy relaxation of dense fluids in narrow slits

NASA Astrophysics Data System (ADS)

Mandal, Suvendu; Spanner-Denzer, Markus; Leitmann, Sebastian; Franosch, Thomas

2017-08-01

We provide an overview of recent advances of the complex dynamics of particles in strong confinements. The first paradigm is the Lorentz model where tracers explore a quenched disordered host structure. Such systems naturally occur as limiting cases of binary glass-forming systems if the dynamics of one component is much faster than the other. For a certain critical density of the host structure the tracers undergo a localization transition which constitutes a critical phenomenon. A series of predictions in the vicinity of the transition have been elaborated and tested versus computer simulations. Analytical progress is achieved for small obstacle densities. The second paradigm is a dense strongly interacting liquid confined to a narrow slab. Then the glass transition depends nonmonotonically on the separation of the plates due to an interplay of local packing and layering. Very small slab widths allow to address certain features of the statics and dynamics analytically.

Viewing inside Pyroclastic Flows - Large-scale Experiments on hot pyroclast-gas mixture flows

NASA Astrophysics Data System (ADS)

Breard, E. C.; Lube, G.; Cronin, S. J.; Jones, J.

2014-12-01

Pyroclastic density currents are the largest threat from volcanoes. Direct observations of natural flows are persistently prevented because of their violence and remain limited to broad estimates of bulk flow behaviour. The Pyroclastic Flow Generator - a large-scale experimental facility to synthesize hot gas-particle mixture flows scaled to pyroclastic flows and surges - allows investigating the physical processes behind PDC behaviour in safety. The ability to simulate natural eruption conditions and to view and measure inside the hot flows allows deriving validation and calibration data sets for existing numerical models, and to improve the constitutive relationships necessary for their effective use as powerful tools in hazard assessment. We here report on a systematic series of large-scale experiments on up to 30 ms-1 fast, 2-4.5 m thick, 20-35 m long flows of natural pyroclastic material and gas. We will show high-speed movies and non-invasive sensor data that detail the internal structure of the analogue pyroclastic flows. The experimental PDCs are synthesized by the controlled 'eruption column collapse' of variably diluted suspensions into an instrumented channel. Experiments show four flow phases: mixture acceleration and dilution during free fall; impact and lateral blasting; PDC runout; and co-ignimbrite cloud formation. The fully turbulent flows reach Reynolds number up to 107 and depositional facies similar to natural deposits. In the PDC runout phase, the shear flows develop a four-partite structure from top to base: a fully turbulent, strongly density-stratified ash cloud with average particle concentrations <<1vol%; a transient, turbulent dense suspension region with particle concentrations between 1 and 10 vol%; a non-turbulent, aerated and highly mobile dense underflows with particle concentrations between 40 and 50 vol%; and a vertically aggrading bed of static material. We characterise these regions and the exchanges of energy and momentum through their interfaces via vertical time-series profiles of velocity, particle concentration, gas and particle transport directionality and turbulent eddy characteristics. We highlight the importance of each region for the PDC runout dynamics and introduce a new transport and sedimentation model for downslope evolving pyroclastic flows.

The simulation and experimental validation on gas-solid two phase flow in the riser of a dense fluidized bed

NASA Astrophysics Data System (ADS)

Wang, Xue-Yao; Jiang, Fan; Xu, Xiang; Wang, Sheng-Dian; Fan, Bao-Guo; Xiao, Yun-Han

2009-06-01

Gas-solid flow in dense CFB (circulating fluidized bed)) riser under the operating condition, superficial gas 15.5 m/s and solid flux 140 kg/m2s using Geldart B particles (sand) was investigated by experiments and CFD (computational fluid dynamics) simulation. The overall and local flow characteristics are determined using the axial pressure profiles and solid concentration profiles. The cold experimental results indicate that the axial solid concentration distribution contains a dilute region towards the up-middle zone and a dense region near the bottom and the top exit zones. The typical core-annulus structure and the back-mixing phenomenon near the wall of the riser can be observed. In addition, owing to the key role of the drag force of gas-solid phase, a revised drag force coefficient, based on the EMMS (energy-minimization multi-scale) model which can depict the heterogeneous character of gas-solid two phase flow, was proposed and coupled into the CFD control equations. In order to find an appropriate drag force model for the simulation of dense CFB riser, not only the revised drag force model but some other kinds of drag force model were used in the CFD. The flow structure, solid concentration, clusters phenomenon, fluctuation of two phases and axial pressure drop were analyzed. By comparing the experiment with the simulation, the results predicted by the EMMS drag model showed a better agreement with the experimental axial average pressure drop and apparent solid volume fraction, which proves that the revised drag force based on the EMMS model is an appropriate model for the dense CFB simulation.

A numerical framework for the direct simulation of dense particulate flow under explosive dispersal

NASA Astrophysics Data System (ADS)

Mo, H.; Lien, F.-S.; Zhang, F.; Cronin, D. S.

2018-05-01

In this paper, we present a Cartesian grid-based numerical framework for the direct simulation of dense particulate flow under explosive dispersal. This numerical framework is established through the integration of the following numerical techniques: (1) operator splitting for partitioned fluid-solid interaction in the time domain, (2) the second-order SSP Runge-Kutta method and third-order WENO scheme for temporal and spatial discretization of governing equations, (3) the front-tracking method for evolving phase interfaces, (4) a field function proposed for low-memory-cost multimaterial mesh generation and fast collision detection, (5) an immersed boundary method developed for treating arbitrarily irregular and changing boundaries, and (6) a deterministic multibody contact and collision model. Employing the developed framework, this paper further studies particle jet formation under explosive dispersal by considering the effects of particle properties, particulate payload morphologies, and burster pressures. By the simulation of the dispersal processes of dense particle systems driven by pressurized gas, in which the driver pressure reaches 1.01325× 10^{10} Pa (10^5 times the ambient pressure) and particles are impulsively accelerated from stationary to a speed that is more than 12000 m/s within 15 μ s, it is demonstrated that the presented framework is able to effectively resolve coupled shock-shock, shock-particle, and particle-particle interactions in complex fluid-solid systems with shocked flow conditions, arbitrarily irregular particle shapes, and realistic multibody collisions.

Influence of galactic arm scale dynamics on the molecular composition of the cold and dense ISM. I. Observed abundance gradients in dense clouds

NASA Astrophysics Data System (ADS)

Ruaud, M.; Wakelam, V.; Gratier, P.; Bonnell, I. A.

2018-04-01

Aim. We study the effect of large scale dynamics on the molecular composition of the dense interstellar medium during the transition between diffuse to dense clouds. Methods: We followed the formation of dense clouds (on sub-parsec scales) through the dynamics of the interstellar medium at galactic scales. We used results from smoothed particle hydrodynamics (SPH) simulations from which we extracted physical parameters that are used as inputs for our full gas-grain chemical model. In these simulations, the evolution of the interstellar matter is followed for 50 Myr. The warm low-density interstellar medium gas flows into spiral arms where orbit crowding produces the shock formation of dense clouds, which are held together temporarily by the external pressure. Results: We show that depending on the physical history of each SPH particle, the molecular composition of the modeled dense clouds presents a high dispersion in the computed abundances even if the local physical properties are similar. We find that carbon chains are the most affected species and show that these differences are directly connected to differences in (1) the electronic fraction, (2) the C/O ratio, and (3) the local physical conditions. We argue that differences in the dynamical evolution of the gas that formed dense clouds could account for the molecular diversity observed between and within these clouds. Conclusions: This study shows the importance of past physical conditions in establishing the chemical composition of the dense medium.

Transmission electron microscopy for archaeo-materials research: Nanoparticles in glazes and red/yellow glass and inorganic pigments in painted context

NASA Astrophysics Data System (ADS)

Fredrickx, Peggy

2004-10-01

This dissertation addresses the application of Transmission Electron Microscopy (TEM) to historic objects, concentrating on colour-causing nanoparticles in vitreous materials and pigments with the focus on substrates in lake pigments used in thin glaze layers, and on manuscript illustrations. TEM is well suited for archaeometry: it gives chemical elemental information, imaging and diffraction information and the amount of material needed is minimal. Sample preparation techniques suitable for historic materials are discussed. Nanoparticles can be incorporated in glass through staining. Yellow coloured glass plates contain Ag particles. Baking temperatures and different Ag-salts determine the density of the nanoparticles. Dense layers cause more saturated colours. Red glass plates can be obtained by staining with Cu-salts. Metallic Cu particles have a diameter of about 24 nm. Comparison with XRF results suggests that often a combination of Cu and Ag was used for warmer colours. Red glass can be "flashed" to the substrate glass. Then, the colour is also caused by metallic Cu particles. The red layer often displays a band structure of stacked red and transparent bands. In the transparent bands, no nanoparticles have been found. In lustre-ware, Ag and metallic Cu occur. Their distribution throughout the material determines the colour of the fragment. In both there is a dense top layer with particles of sizes smaller than 15 nm. If this top layer consists of Ag particles, the resulting colour is golden. In one sample, under this top layer the amount of Cu particles increases. This underlying layer causes the colour to redden. Particles are mainly between 5 and 15 nm in diameter. Using reconstructions, it has been demonstrated that TEM can detect and identify a stacking of thin layers in parchment decorations. A pink powder sample from Pompeii consists of a basis of allophane type clay. The lake substrates consist of Al, O, S and their amorphous structure does not seem to be noticeably changed by the addition of organic colourants. Hydrocerussite crystals (i.e. the main component of lead white) have been added to some historic glaze layers. Further it was confirmed that sometimes crystalline CaSO4 particles were added to lakes.

A combined model for pseudo-rapidity distributions in Cu-Cu collisions at BNL-RHIC energies

NASA Astrophysics Data System (ADS)

Jiang, Z. J.; Wang, J.; Huang, Y.

2016-04-01

The charged particles produced in nucleus-nucleus collisions come from leading particles and those frozen out from the hot and dense matter created in collisions. The leading particles are conventionally supposed having Gaussian rapidity distributions normalized to the number of participants. The hot and dense matter is assumed to expand according to the unified hydrodynamics, a hydro model which unifies the features of Landau and Hwa-Bjorken model, and freeze out into charged particles from a time-like hypersurface with a proper time of τFO. The rapidity distribution of this part of charged particles can be derived analytically. The combined contribution from both leading particles and unified hydrodynamics is then compared against the experimental data performed by BNL-RHIC-PHOBOS Collaboration in different centrality Cu-Cu collisions at sNN = 200 and 62.4GeV, respectively. The model predictions are consistent with experimental measurements.

The plasma membrane of myxosporidian valve cells: freeze fracture data.

PubMed

Desportes-Livage, I; Nicolas, G

1990-01-01

Freeze fracturing of Myxosporidian spores reveals the occurrence of a continuous layer of transmembrane particles all over the surface area of the valve cells which form the spore envelope. These particles are densely packed all over the P face membrane. Due to their polygonal outline, their diameter (6-7 nm) and their central core, they resemble the particles forming the connections of gap junctions which metabolically couple the neighboring cells in animal tissues. In the present report, the role of the transmembrane particles is still hypothetical. However, they might represent a membrane structural specialization of the spores which are submitted to osmotic variations of the fluid external medium. Furthermore similar transmembrane particles are observed at the level of the septate junction which seals the valve cells. In this occurrence, they are arranged in a series of 40 double rows parallel to the suture of the spore envelope. These findings support the view that Myxosporidia are Metazoa and raise the problem of their origin.

Shear-induced organization of forces in dense suspensions: signatures of discontinuous shear thickening

NASA Astrophysics Data System (ADS)

Sarkar, Sumantra; Shatoff, Elan; Ramola, Kabir; Mari, Romain; Morris, Jeffrey; Chakraborty, Bulbul

2017-06-01

Dense suspensions can exhibit an abrupt change in their viscosity in response to increasing shear rate. The origin of this discontinuous shear thickening (DST) has been ascribed to the transformation of lubricated contacts to frictional, particle-on-particle contacts. Recent research on the flowing and jamming behavior of dense suspensions has explored the intersection of ideas from granular physics and Stokesian fluid dynamics to better understand this transition from lubricated to frictional rheology. DST is reminiscent of classical phase transitions, and a key question is how interactions between the microscopic constituents give rise to a macroscopic transition. In this paper, we extend a formalism that has proven to be successful in understanding shear jamming of dry grains to dense suspensions. Quantitative analysis of the collective evolution of the contactforce network accompanying the DST transition demonstrates clear changes in the distribution of microscopic variables, and leads to the identification of an "order parameter" characterizing DST.

Jammed Clusters and Non-locality in Dense Granular Flows

NASA Astrophysics Data System (ADS)

Kharel, Prashidha; Rognon, Pierre

We investigate the micro-mechanisms underpinning dense granular flow behaviour from a series of DEM simulations of pure shear flows of dry grains. We observe the development of transient clusters of jammed particles within the flow. Typical size of such clusters is found to scale with the inertial number with a power law that is similar to the scaling of shear-rate profile relaxation lengths observed previously. Based on the simple argument that transient clusters of size l exist in the dense flow regime, the formulation of steady state condition for non-homogeneous shear flow results in a general non-local relation, which is similar in form to the non-local relation conjectured for soft glassy flows. These findings suggest the formation of jammed clusters to be the key micro-mechanism underpinning non-local behaviour in dense granular flows. Particles and Grains Laboratory, School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia.

Geometrical optics of dense aerosols: forming dense plasma slabs.

PubMed

Hay, Michael J; Valeo, Ernest J; Fisch, Nathaniel J

2013-11-01

Assembling a freestanding, sharp-edged slab of homogeneous material that is much denser than gas, but much more rarefied than a solid, is an outstanding technological challenge. The solution may lie in focusing a dense aerosol to assume this geometry. However, whereas the geometrical optics of dilute aerosols is a well-developed field, the dense aerosol limit is mostly unexplored. Yet controlling the geometrical optics of dense aerosols is necessary in preparing such a material slab. Focusing dense aerosols is shown here to be possible, but the finite particle density reduces the effective Stokes number of the flow, a critical result for controlled focusing.

The Influence of Spray Parameters on the Characteristics of Hydroxyapatite In-Flight Particles, Splats and Coatings by Micro-plasma Spraying

NASA Astrophysics Data System (ADS)

Liu, Xiao-mei; He, Ding-yong; Wang, Yi-ming; Zhou, Zheng; Wang, Guo-hong; Tan, Zhen; Wang, Zeng-jie

2018-04-01

Hydroxyapatite (HA) is one of the most important bioceramic materials used in medical implants. The structure of HA coatings is closely related to their manufacturing process. In the present study, HA coatings were deposited on Ti-6Al-4V substrate by micro-plasma spraying. Results show that three distinct HA coatings could be obtained by changing the spraying power from 0.5 to 1.0 kW and spraying stand-off distance from 60 to 110 mm: (1) high crystallinity (93.3%) coatings with porous structure, (2) high crystallinity coatings (86%) with columnar structure, (3) higher amorphous calcium phosphate (ACP, 50%) coatings with dense structure. The in-flight particles melting state and splat topography was analyzed to better understand the formation mechanism of three distinct HA coatings. Results show that HA coatings sprayed at low spraying power and short stand-off distance exhibit high crystallinity and porosity is attributed to the presence of partially melted particles. High crystallinity HA coatings with (002) crystallographic texture could be deposited due to the complete melting of the in-flight particles and low cooling rate of the disk shape splats under higher spraying power and shorter SOD. However, splashed shape splats with relative high cooling can be provided by increasing SOD, which leads to the formation of ACP.

The influence of different processing stages on particle size, microstructure, and appearance of dark chocolate.

PubMed

Glicerina, Virginia; Balestra, Federica; Dalla Rosa, Marco; Bergenhstål, Bjorn; Tornberg, Eva; Romani, Santina

2014-07-01

The effect of different process stages on microstructural and visual properties of dark chocolate was studied. Samples were obtained at each phase of the manufacture process: mixing, prerefining, refining, conching, and tempering. A laser light diffraction technique and environmental scanning electron microscopy (ESEM) were used to study the particle size distribution (PSD) and to analyze modifications in the network structure. Moreover, colorimetric analyses (L*, h°, and C*) were performed on all samples. Each stage influenced in stronger way the microstructural characteristic of products and above all the PSD. Sauter diameter (D [3.2]) decreased from 5.44 μm of mixed chocolate sample to 3.83 μm, of the refined one. ESEM analysis also revealed wide variations in the network structure of samples during the process, with an increase of the aggregation and contact point between particles from mixing to refining stage. Samples obtained from the conching and tempering were characterized by small PS, and a less dense aggregate structure. From color results, samples with the finest particles, having larger specific surface area and the smallest diameter, appeared lighter and more saturated than those with coarse particles. Final quality of food dispersions is affected by network and particles characteristics. The deep knowledge of the influence of single processing stage on chocolate microstructural properties is useful in order to improve or modify final product characteristics. ESEM and laser diffraction are suitable techniques to study changes in chocolate microstructure. © 2014 Institute of Food Technologists®

Experimental study of droplet formation of dense suspensions

NASA Astrophysics Data System (ADS)

Martensson, Gustaf; Carson, Fabian

2017-11-01

As with the jet printing of dyes and other low-viscosity fluids, the jetting of dense fluid suspensions is dependent on the repeatable break-off of the fluid filament into well-formed droplets. It is well known that the break-off of dense suspensions is dependent on the volume fraction of the solid phase, particle size and morphology, fluid phase viscosity et cetera, see for example van Deen et al. (2013). The purpose of this study is to establish a deeper understanding of the formation process of droplets of dense suspensions. Previous experiments have utilised a filament break-off device (FilBO) developed in-house. These experiments utilise an ejection device based on rapid volumetric displacement of the fluid through a conical nozzle. The suspension samples consist of a resin-based flux and spherical particles with diameters of dp = 5 - 25 μ m. A droplet of of the suspension with a volume of Vdrop = 2 - 50 nl is ejected from the nozzle. Correlations between droplet speed and the temporal development of the volumetric displacement will be presented. Further results relating break-off length and rate versus particle diameter, volume fraction and probe speed will be presented.

A multiple scattering theory for EM wave propagation in a dense random medium

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.; Wong, K. W.

1985-01-01

For a dense medium of randomly distributed scatterers an integral formulation for the total coherent field has been developed. This formulation accounts for the multiple scattering of electromagnetic waves including both the twoand three-particle terms. It is shown that under the Markovian assumption the total coherent field and the effective field have the same effective wave number. As an illustration of this theory, the effective wave number and the extinction coefficient are derived in terms of the polarizability tensor and the pair distribution function for randomly distributed small spherical scatterers. It is found that the contribution of the three-particle term increases with the particle size, the volume fraction, the frequency and the permittivity of the particle. This increase is more significant with frequency and particle size than with other parameters.

WE-H-BRA-08: A Monte Carlo Cell Nucleus Model for Assessing Cell Survival Probability Based On Particle Track Structure Analysis

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

Lee, B; Georgia Institute of Technology, Atlanta, GA; Wang, C

Purpose: To correlate the damage produced by particles of different types and qualities to cell survival on the basis of nanodosimetric analysis and advanced DNA structures in the cell nucleus. Methods: A Monte Carlo code was developed to simulate subnuclear DNA chromatin fibers (CFs) of 30nm utilizing a mean-free-path approach common to radiation transport. The cell nucleus was modeled as a spherical region containing 6000 chromatin-dense domains (CDs) of 400nm diameter, with additional CFs modeled in a sparser interchromatin region. The Geant4-DNA code was utilized to produce a particle track database representing various particles at different energies and dose quantities.more » These tracks were used to stochastically position the DNA structures based on their mean free path to interaction with CFs. Excitation and ionization events intersecting CFs were analyzed using the DBSCAN clustering algorithm for assessment of the likelihood of producing DSBs. Simulated DSBs were then assessed based on their proximity to one another for a probability of inducing cell death. Results: Variations in energy deposition to chromatin fibers match expectations based on differences in particle track structure. The quality of damage to CFs based on different particle types indicate more severe damage by high-LET radiation than low-LET radiation of identical particles. In addition, the model indicates more severe damage by protons than of alpha particles of same LET, which is consistent with differences in their track structure. Cell survival curves have been produced showing the L-Q behavior of sparsely ionizing radiation. Conclusion: Initial results indicate the feasibility of producing cell survival curves based on the Monte Carlo cell nucleus method. Accurate correlation between simulated DNA damage to cell survival on the basis of nanodosimetric analysis can provide insight into the biological responses to various radiation types. Current efforts are directed at producing cell survival curves for high-LET radiation.« less

Extreme dust storm over the eastern Mediterranean in September 2015: satellite, lidar, and surface observations in the Cyprus region

NASA Astrophysics Data System (ADS)

Mamouri, Rodanthi-Elisavet; Ansmann, Albert; Nisantzi, Argyro; Solomos, Stavros; Kallos, George; Hadjimitsis, Diofantos G.

2016-11-01

A record-breaking dust storm originating from desert regions in northern Syria and Iraq occurred over the eastern Mediterranean in September 2015. In this contribution of a series of two articles (part 1, observations; part 2, atmospheric modeling), we provide a comprehensive overview of the aerosol conditions during this extreme dust outbreak in the Cyprus region. These observations are based on satellite observations (MODIS, moderate resolution imaging spectroradiometer) of aerosol optical thickness (AOT) and Ångström exponent, surface particle mass (PM10) concentrations measured at four sites in Cyprus, visibility observations at three airports in southern Cyprus and corresponding conversion products (particle extinction coefficient, dust mass concentrations), EARLINET (European Aerosol Research Lidar Network) lidar observations of dust vertical layering over Limassol, particle optical properties (backscatter, extinction, lidar ratio, linear depolarization ratio), and derived profiles of dust mass concentrations. Maximum 550 nm AOT exceeded values of 5.0, according to MODIS, and the mass loads were correspondingly > 10 g m-2 over Larnaca and Limassol during the passage of an extremely dense dust front on 8 September 2015. Hourly mean PM10 values were close to 8000 µg m-3 and the observed meteorological optical range (visibility) was reduced to 300-750 m at Larnaca and Limassol. The visibility observations suggest peak values of the near-surface total suspended particle (TSP) extinction coefficients of 6000 Mm-1 and thus TSP mass concentrations of 10 000 µg m-3. The Raman polarization lidar observations mainly indicated a double layer structure of the dust plumes (reaching to about 4 km height), pointing to at least two different dust source regions. Dust particle extinction coefficients (532 nm) already exceeded 1000 Mm-1 and the mass concentrations reached 2000 µg m-3 in the elevated dust layers on 7 September, more than 12 h before the peak dust front on 8 September reached the Limassol lidar station around local noon. Typical Middle Eastern dust lidar ratios around 40 sr were observed in the dense dust plumes. The particle depolarization ratio decreased from around 0.3 in the lofted dense dust layers to 0.2 at the end of the dust period (11 September), indicating an increasing impact of anthropogenic haze.

Large-Scale Chaos and Fluctuations in Active Nematics

NASA Astrophysics Data System (ADS)

Ngo, Sandrine; Peshkov, Anton; Aranson, Igor S.; Bertin, Eric; Ginelli, Francesco; Chaté, Hugues

2014-07-01

We show that dry active nematics, e.g., collections of shaken elongated granular particles, exhibit large-scale spatiotemporal chaos made of interacting dense, ordered, bandlike structures in a parameter region including the linear onset of nematic order. These results are obtained from the study of both the well-known (deterministic) hydrodynamic equations describing these systems and of the self-propelled particle model they were derived from. We prove, in particular, that the chaos stems from the generic instability of the band solution of the hydrodynamic equations. Revisiting the status of the strong fluctuations and long-range correlations in the particle model, we show that the giant number fluctuations observed in the chaotic phase are a trivial consequence of density segregation. However anomalous, curvature-driven number fluctuations are present in the homogeneous quasiordered nematic phase and characterized by a nontrivial scaling exponent.

Theory of nonlinear elasticity, stress-induced relaxation, and dynamic yielding in dense fluids of hard nonspherical colloids

NASA Astrophysics Data System (ADS)

Zhang, Rui; Schweizer, Kenneth S.

2012-04-01

We generalize the microscopic naïve mode coupling and nonlinear Langevin equation theories of the coupled translation-rotation dynamics of dense suspensions of uniaxial colloids to treat the effect of applied stress on shear elasticity, cooperative cage escape, structural relaxation, and dynamic and static yielding. The key concept is a stress-dependent dynamic free energy surface that quantifies the center-of-mass force and torque on a moving colloid. The consequences of variable particle aspect ratio and volume fraction, and the role of plastic versus double glasses, are established in the context of dense, glass-forming suspensions of hard-core dicolloids. For low aspect ratios, the theory provides a microscopic basis for the recently observed phenomenon of double yielding as a consequence of stress-driven sequential unlocking of caging constraints via reduction of the distinct entropic barriers associated with the rotational and translational degrees of freedom. The existence, and breadth in volume fraction, of the double yielding phenomena is predicted to generally depend on both the degree of particle anisotropy and experimental probing frequency, and as a consequence typically occurs only over a window of (high) volume fractions where there is strong decoupling of rotational and translational activated relaxation. At high enough concentrations, a return to single yielding is predicted. For large aspect ratio dicolloids, rotation and translation are always strongly coupled in the activated barrier hopping event, and hence for all stresses only a single yielding process is predicted.

Suppressing turbulence of self-propelling rods by strongly coupled passive particles.

PubMed

Su, Yen-Shuo; Wang, Hao-Chen; I, Lin

2015-03-01

The strong turbulence suppression, mainly for large-scale modes, of two-dimensional self-propelling rods, by increasing the long-range coupling strength Γ of low-concentration passive particles, is numerically demonstrated. It is found that large-scale collective rod motion in forms of swirls or jets is mainly contributed from well-aligned dense patches, which can push small poorly aligned rod patches and uncoupled passive particles. The more efficient momentum transfer and dissipation through increasing passive particle coupling leads to the formation of a more ordered and slowed down network of passive particles, which competes with coherent dense active rod clusters. The frustration of active rod alignment ordering and coherent motion by the passive particle network, which interrupt the inverse cascading of forming large-scale swirls, is the key for suppressing collective rod motion with scales beyond the interpassive distance, even in the liquid phase of passive particles. The loosely packed active rods are weakly affected by increasing passive particle coupling due to the weak rod-particle interaction. They mainly contribute to the small-scale modes and high-speed motion.

Effects of radiation type and delivery mode on a radioresistant eukaryote Cryptococcus neoformans

PubMed Central

Shuryak, Igor; Bryan, Ruth A.; Broitman, Jack; Marino, Stephen A.; Morgenstern, Alfred; Apostolidis, Christos; Dadachova, Ekaterina

2015-01-01

Introduction Most research on radioresistant fungi, particularly on human pathogens such as Cryptococcus neoformans, involves sparsely-ionizing radiation. Consequently, fungal responses to densely-ionizing radiation, which can be harnessed to treat life-threatening fungal infections, remain incompletely understood. Methods We addressed this issue by quantifying and comparing the effects of densely-ionizing α-particles (delivered either by external beam or by 213Bi-labeled monoclonal antibodies), and sparsely-ionizing 137Cs γ-rays, on Cryptococus neoformans. Results The best-fit linear-quadratic parameters for clonogenic survival were the following: α=0.24×10−2 Gy−1 for γ-rays and 1.07×10−2 Gy−1 for external-beam α-particles, and β=1.44×10−5 Gy−2 for both radiation types. Fungal cell killing by radiolabeled antibodies was consistent with predictions based on the α-particle dose to the cell nucleus and the linear-quadratic parameters for external-beam α-particles. The estimated RBE (for α-particles vs γ-rays) at low doses was 4.47 for the initial portion of the α-particle track, and 7.66 for the Bragg peak. Non-radiological antibody effects accounted for up to 23% of cell death. Conclusions These results quantify the degree of C. neoformans resistance to densely-ionizing radiations, and show how this resistance can be overcome with fungus-specific radiolabeled antibodies. PMID:25800676

Measurement of charged-particle stopping in warm-dense plasma

DOE PAGES

Zylstra, A.  B.; Frenje, J.  A.; Grabowski, P. E.; ...

2015-05-27

We measured the stopping of energetic protons in an isochorically-heated solid-density Be plasma with an electron temperature of ~32 eV, corresponding to moderately-coupled [(e²/a/(k BT e + E F ) ~ 0.3] and moderately-degenerate [k BT e/E F ~2] 'warm dense matter' (WDM) conditions. We present the first high-accuracy measurements of charged-particle energy loss through dense plasma, which shows an increased loss relative to cold matter, consistent with a reduced mean ionization potential. The data agree with stopping models based on an ad-hoc treatment of free and bound electrons, as well as the average-atom local-density approximation; this work is themore » first test of these theories in WDM plasma.« less

Anisotropic magnetic particles in a magnetic field

PubMed Central

Martchenko, Ilya; Mihut, Adriana M.; Bialik, Erik; Hirt, Ann M.; Rufier, Chantal; Menzel, Andreas; Dietsch, Hervé; Linse, Per

2016-01-01

We characterize the structural properties of magnetic ellipsoidal hematite colloids with an aspect ratio ρ ≈ 2.3 using a combination of small-angle X-ray scattering and computer simulations. The evolution of the phase diagram with packing fraction φ and the strength of an applied magnetic field B is described, and the coupling between orientational order of magnetic ellipsoids and the bulk magnetic behavior of their suspension addressed. We establish quantitative structural criteria for the different phase and arrest transitions and map distinct isotropic, polarized non-nematic, and nematic phases over an extended range in the φ–B coordinates. We show that upon a rotational arrest of the ellipsoids around φ = 0.59, the bulk magnetic behavior of their suspension switches from superparamagnetic to ordered weakly ferromagnetic. If densely packed and arrested, these magnetic particles thus provide persisting remanent magnetization of the suspension. By exploring structural and magnetic properties together, we extend the often used colloid-atom analogy to the case of magnetic spins. PMID:27722439

Intracellular localisation of dengue-2 RNA in mosquito cell culture using electron microscopic in situ hybridisation.

PubMed

Grief, C; Galler, R; Côrtes, L M; Barth, O M

1997-01-01

Non-isotopic in situ hybridisation was used at the electron microscope level to determine the localisation of viral RNA in dengue-2 infected mosquito cells at 14, 24, 48 and 72 h post-infection. In situ hybridisation was carried out on sections of dengue-2 infected mosquito cells using a digoxigenin-labelled DNA probe to the envelope protein gene sequence of the virus. Viral RNA was consistently localised over the rough endoplasmic reticulum and the virus-induced smooth membrane structures which form within the endoplasmic reticulum. During the later stages of infection electron-dense areas were observed to develop in close proximity to the smooth membrane structures. Electron microscopic in situ hybridisation showed that these denser areas contained both viral RNA and virus particles. Our results show that in dengue-2 infected mosquito cells the smooth membrane structures are an important site for the concentration of dengue viral RNA and its possible subsequent encapsidation into virus particles.

Dynamic properties of polydisperse colloidal particles in the presence of thermal gradient studied by a modified Brownian dynamic model

NASA Astrophysics Data System (ADS)

Song, Dongxing; Jin, Hui; Jing, Dengwei; Wang, Xin

2018-03-01

Aggregation and migration of colloidal particles under the thermal gradient widely exists in nature and many industrial processes. In this study, dynamic properties of polydisperse colloidal particles in the presence of thermal gradient were studied by a modified Brownian dynamic model. Other than the traditional forces on colloidal particles, including Brownian force, hydrodynamic force, and electrostatic force from other particles, the electrostatic force from the asymmetric ionic diffusion layer under a thermal gradient has been considered and introduced into the Brownian dynamic model. The aggregation ratio of particles (R A), the balance time (t B) indicating the time threshold when {{R}A} becomes constant, the porosity ({{P}BA} ), fractal dimension (D f) and distributions of concentration (DISC) and aggregation (DISA) for the aggregated particles were discussed based on this model. The aggregated structures formed by polydisperse particles are less dense and the particles therein are loosely bonded. Also it showed a quite large compressibility as the increases of concentration and interparticle potential can significantly increase the fractal dimension. The thermal gradient can induce two competitive factors leading to a two-stage migration of particles. When t<{{t}B} , the unsynchronized aggregation is dominant and the particles slightly migrate along the thermal gradient. When t>{{t}B} , the thermophoresis becomes dominant thus the migrations of particles are against the thermal gradient. The effect of thermophoresis on the aggregate structures was found to be similar to the effect of increasing particle concentration. This study demonstrates how the thermal gradient affects the aggregation of monodisperse and polydisperse particles and can be a guide for the biomimetics and precise control of colloid system under the thermal gradient. Moreover, our model can be easily extended to other more complex colloidal systems considering shear, temperature fluctuation, surfactant, etc.

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

Kononchik, Joseph P.; Vancini, Ricardo; Brown, Dennis T., E-mail: dennis_brown@ncsu.edu

Sindbis Virus (SV), the prototype alphavirus in the family togaviridae, infects both mammalian and insect cells. The ability of SV to infect cells possessing significantly different biochemical environments suggests that there may be a common mode of entry into each cell type. Previous studies show that up to 4 h post infection cells are permeable to small ions and alpha sarcin suggesting that the plasma membrane is compromised as infection takes place. Thin-section electron microscopy has also shown SV to bind to the plasma membrane and lose its electron dense core through a pore like structure developed upon interaction ofmore » the virus with the cell surface. Using freeze-fracture replicas, thin-sections and antibody labeling the data presented herein show virus associated with intramembrane particles on mosquito cells. These data suggest that the intramembrane particles associated with SV may be part of the pore structure consisting of virus proteins and cell receptor.« less

Enhanced hydrolysis of cellulose hydrogels by morphological modification.

PubMed

Alfassi, Gilad; Rein, Dmitry M; Cohen, Yachin

2017-11-01

Cellulose is one of the most abundant bio-renewable materials on earth, yet the potential of cellulosic bio-fuels is not fully exploited, primarily due to the high costs of conversion. Hydrogel particles of regenerated cellulose constitute a useful substrate for enzymatic hydrolysis, due to their porous and amorphous structure. This article describes the influence of several structural aspects of the cellulose hydrogel on its hydrolysis. The hydrogel density was shown to be directly proportional to the cellulose concentration in the initial solution, thus affecting its hydrolysis rate. Using high-resolution scanning electron microscopy, we show that the hydrogel particles in aqueous suspension exhibit a dense external surface layer and a more porous internal network. Elimination of the external surface layer accelerated the hydrolysis rate by up to sixfold and rendered the process nearly independent of cellulose concentration. These findings may be of practical relevance to saccharification processing costs, by reducing required solvent quantities and enzyme load.

AFM imaging of milk casein micelles: evidence for structural rearrangement upon acidification.

PubMed

Ouanezar, Mustapha; Guyomarc'h, Fanny; Bouchoux, Antoine

2012-03-20

Milk casein micelles are natural association colloids that we all encounter in everyday life, yet we still lack an accurate description of their internal structure and the interactions that stabilize it. In this letter, we provide for the first time detailed images of intact casein micelles as obtained through atomic force microscopy under liquid conditions close to physiological. The micelles appear as heterogeneous raspberry-like particles, which is consistent with a hierarchical/spongelike structure made of connected 10-40 nm dense casein regions. Upon in situ acidification to pH 5, the micelles decrease in size and lose their surface heterogeneities, indicating that this structure is highly sensitive to variations in mineral content and caseins net charge.

Entropic depletion in colloidal suspensions and polymer liquids: Role of nanoparticle surface topography

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

Banerjee, Debapriya; Yang, Jian; Schweizer, Kenneth S.

2015-01-01

Here, we employ a hybrid Monte Carlo plus integral equation theory approach to study how dense fluids of small nanoparticles or polymer chains mediate entropic depletion interactions between topographically rough particles where all interaction potentials are hard core repulsion. The corrugated particle surfaces are composed of densely packed beads which present variable degrees of controlled topographic roughness and free volume associated with their geometric crevices. This pure entropy problem is characterized by competing ideal translational and (favorable and unfavorable) excess entropic contributions. Surface roughness generically reduces particle depletion aggregation relative to the smooth hard sphere case. However, the competition betweenmore » ideal and excess packing entropy effects in the bulk, near the particle surface and in the crevices, results in a non-monotonic variation of the particle-monomer packing correlation function as a function of the two dimensionless length scale ratios that quantify the effective surface roughness. As a result, the inter-particle potential of mean force (PMF), second virial coefficient, and spinodal miscibility volume fraction vary non-monotonically with the surface bead to monomer diameter and particle core to surface bead diameter ratios. A miscibility window is predicted corresponding to an optimum degree of surface roughness that completely destroys depletion attraction resulting in a repulsive PMF. Variation of the (dense) matrix packing fraction can enhance or suppress particle miscibility depending upon the amount of surface roughness. Connecting the monomers into polymer chains destabilizes the system via enhanced contact depletion attraction, but the non-monotonic variations with surface roughness metrics persist.« less

Method for non-contact particle manipulation and control of particle spacing along an axis

DOEpatents

Goddard, Gregory Russ; Kaduchak, Gregory; Jett, James Hubert; Graves, Steven Wayde

2013-09-10

One or more of the embodiments of the present invention provide for a method of non-contact particle manipulation and control of particle spacing along an axis which includes axial and radial acoustic standing wave fields. Particles are suspended in an aqueous solution, and this solution then flows into the cylindrical flow channel. While the solution flows through the flow channel, the outer structure of the flow channel is vibrated at a resonant frequency, causing a radial acoustic standing wave field to form inside the flow channel in the solution. These radial acoustic standing waves focus the particles suspended in the solution to the center axis of the cylindrical flow channel. At the same time, a transducer is used to create an axial acoustic standing wave field in the flow channel parallel to the axis of the flow channel. This drives the particles, which are already being focused to the center axis of the flow channel, to nodes or anti-nodes of the axial standing wave at half-wavelength intervals, depending on whether the particles are more or less dense and more or less compressible than the surrounding fluid.

Driving morphological changes in magnetic nanoparticle structures through the application of acoustic waves and magnetic fields

NASA Astrophysics Data System (ADS)

Huang, Ann; Miansari, Morteza; Friend, James

The growing interest in acoustic manipulation of particles in micro to nanofluidics using surface acoustic waves (SAW), together with the many applications of magnetic nanoparticles-whether individual or in arrays-underpins our discovery of how these forces can be used to rapidly, easily, and irreversibly form 1D chains and 2D films. These films and chains are currently difficult to produce yet offer many advantages over individual nanoparticles in suspension. Making use of the scale of the structures formed, 10-9 to 10-5 m, and by taking a balance of the relevant external and interparticle forces, the underlying mechanisms responsible for the phenomena become apparent. For 1D chains, the magnetic field alone is sufficient, though applying an acoustic field drives a topology change from loosely connected chains to loops of 10 -100 particles. Adding the acoustic field drives a transition from these looped structures to dense 2D arrays via interparticle Bjerknes forces. Inter-particle drainage of the surrounding fluid leaves these structures intact after removal of the externally applied forces. Clear morphology transitions are present and depend on the relative amplitude of the incident Brownian, Bjerknes, and magnetic forces. UCSD: Frontiers of Innovation Scholars Program (U-1024).

Separating twin images and locating the center of a microparticle in dense suspensions using correlations among reconstructed fields of two parallel holograms.

PubMed

Ling, Hangjian; Katz, Joseph

2014-09-20

This paper deals with two issues affecting the application of digital holographic microscopy (DHM) for measuring the spatial distribution of particles in a dense suspension, namely discriminating between real and virtual images and accurate detection of the particle center. Previous methods to separate real and virtual fields have involved applications of multiple phase-shifted holograms, combining reconstructed fields of multiple axially displaced holograms, and analysis of intensity distributions of weakly scattering objects. Here, we introduce a simple approach based on simultaneously recording two in-line holograms, whose planes are separated by a short distance from each other. This distance is chosen to be longer than the elongated trace of the particle. During reconstruction, the real images overlap, whereas the virtual images are displaced by twice the distance between hologram planes. Data analysis is based on correlating the spatial intensity distributions of the two reconstructed fields to measure displacement between traces. This method has been implemented for both synthetic particles and a dense suspension of 2 μm particles. The correlation analysis readily discriminates between real and virtual images of a sample containing more than 1300 particles. Consequently, we can now implement DHM for three-dimensional tracking of particles when the hologram plane is located inside the sample volume. Spatial correlations within the same reconstructed field are also used to improve the detection of the axial location of the particle center, extending previously introduced procedures to suspensions of microscopic particles. For each cross section within a particle trace, we sum the correlations among intensity distributions in all planes located symmetrically on both sides of the section. This cumulative correlation has a sharp peak at the particle center. Using both synthetic and recorded particle fields, we show that the uncertainty in localizing the axial location of the center is reduced to about one particle's diameter.

Pore-scale Modeling of CO2 Local Trapping in Heterogeneous Porous Media with Inter-granular Cements

NASA Astrophysics Data System (ADS)

Wang, D.; Li, Y.

2017-12-01

Based on pore-scale modeling of CO2/brine multiphase flow in heterogeneous porous media with inter-granular cements, we numerically analyze the effects of cement-modified pore structure on CO2 local trapping. Results indicate: 1) small pore throat is the main reason for causing CO2 local trapping in front of low-porosity layers (namely dense layers) formed by inter-granular cements; 2) in the case of the same pore throat size, the smaller particle size can increase the number of flow paths for CO2 plume and equivalently enhances local permeability, which may counteract the impediment of high capillary pressure on CO2 migration to some extent and consequently disables CO2 local capillary trapping; 3) the isolated pores by inter-granular cements can lead to dramatic reduction of CO2 saturation inside the dense layers, whereas the change of connectivity of some pores due to the cements can increase CO2 accumulation in front of the dense layers by lowering the displacement area of CO2 plume.

Packing and self-assembly of truncated triangular bipyramids

NASA Astrophysics Data System (ADS)

Haji-Akbari, Amir; Chen, Elizabeth R.; Engel, Michael; Glotzer, Sharon C.

2013-07-01

Motivated by breakthroughs in the synthesis of faceted nano- and colloidal particles, as well as theoretical and computational studies of their packings, we investigate a family of truncated triangular bipyramids. We report dense periodic packings with small unit cells that were obtained via numerical and analytical optimization. The maximal packing fraction ϕmax changes continuously with the truncation parameter t. Eight distinct packings are identified based on discontinuities in the first and second derivatives of ϕmax(t). These packings differ in the number of particles in the fundamental domain (unit cell) and the type of contacts between the particles. In particular, we report two packings with four particles in the unit cell for which both ϕmax(t) and ϕmax'(t) are continuous and the discontinuity occurs in the second derivative only. In the self-assembly simulations that we perform for larger boxes with 2048 particles, only one out of eight packings is found to assemble. In addition, the degenerate quasicrystal reported previously for triangular bipyramids without truncation [Haji-Akbari , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.215702 107, 215702 (2011)] assembles for truncations as high as 0.45. The self-assembly propensities for the structures formed in the thermodynamic limit are explained using the isoperimetric quotient of the particles and the coordination number in the disordered fluid and in the assembled structure.

Surface Modification of Zirconia Substrate by Calcium Phosphate Particles Using Sol-Gel Method.

PubMed

Jin, So Dam; Um, Sang Cheol; Lee, Jong Kook

2015-08-01

Surface modification with a biphasic composition of hydroxyapatite (HA) and tricalcium phosphate (TCP) was performed on a zirconia substrate using a sol-gel method. An initial calcium phosphate sol was prepared by mixing a solution of Ca(NO3)2 · 4H20 and (C2H5O)3P(O), while both porous and dense zirconia were used as substrates. The sol-gel coating was performed using a spin coater. The coated porous zirconia substrate was re-sintered at 1350 °C 2 h, while coated dense zirconia substrate was heat-treated at 750 °C 1 h. The microstructure of the resultant HA/TCP coatings was found to be dependent on the type of zirconia substrate used. With porous zirconia as a starting substrate, numerous isolated calcium phosphate particles (TCP and HA) were uniformly dispersed on the surface, and the particle size and covered area were dependent on the viscosity of the calcium phosphate sol. Conversely, when dense zirconia was used as a starting substrate, a thick film of nano-sized HA particles was obtained after heat treatment, however, substantial agglomeration and cracking was also observed.

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

Zardecki, A.

The effect of multiple scattering on the validity of the Beer-Lambert law is discussed for a wide range of particle-size parameters and optical depths. To predict the amount of received radiant power, appropriate correction terms are introduced. For particles larger than or comparable to the wavelength of radiation, the small-angle approximation is adequate; whereas for small densely packed particles, the diffusion theory is advantageously employed. These two approaches are used in the context of the problem of laser-beam propagation in a dense aerosol medium. In addition, preliminary results obtained by using a two-dimensional finite-element discrete-ordinates transport code are described. Multiple-scatteringmore » effects for laser propagation in fog, cloud, rain, and aerosol cloud are modeled.« less

Intragranular cracking as a critical barrier for high-voltage usage of layer-structured cathode for lithium-ion batteries

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

Yan, Pengfei; Zheng, Jianming; Gu, Meng

LiNi 1/3Mn 1/3Co 1/3O 2 (NMC333) layered cathode is often fabricated as secondary particles of consisting of densely packed primary particles, which offers advantage of high energy density and alleviation of cathode side reactions/corrosions, but introduces other drawbacks, such as intergranular cracking. Here, we report unexpected observations on the nucleation and growth of intragranular cracks in the commercial NMC333 layered cathode by using advanced S/TEM. We found that the formation of the intragranular cracks is directly associated with high voltage cycling, which is an electrochemically driven and diffusion controlled process. The intragranular cracks were noticed to be characteristically initiated frommore » grain interior, a consequence of dislocation based crack incubation mechanism. This observation is in sharp contrast with the general theoretical models, predicting the initiation of intragranular cracks from grain boundaries or particle surface. As a result, our study indicates that maintain a structural stability is the key step toward high voltage operation of layered cathode materials.« less

Intragranular cracking as a critical barrier for high-voltage usage of layer-structured cathode for lithium-ion batteries

DOE PAGES

Yan, Pengfei; Zheng, Jianming; Gu, Meng; ...

2017-01-16

LiNi 1/3Mn 1/3Co 1/3O 2 (NMC333) layered cathode is often fabricated as secondary particles of consisting of densely packed primary particles, which offers advantage of high energy density and alleviation of cathode side reactions/corrosions, but introduces other drawbacks, such as intergranular cracking. Here, we report unexpected observations on the nucleation and growth of intragranular cracks in the commercial NMC333 layered cathode by using advanced S/TEM. We found that the formation of the intragranular cracks is directly associated with high voltage cycling, which is an electrochemically driven and diffusion controlled process. The intragranular cracks were noticed to be characteristically initiated frommore » grain interior, a consequence of dislocation based crack incubation mechanism. This observation is in sharp contrast with the general theoretical models, predicting the initiation of intragranular cracks from grain boundaries or particle surface. As a result, our study indicates that maintain a structural stability is the key step toward high voltage operation of layered cathode materials.« less

Geometrical Optics of Dense Aerosols

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

Hay, Michael J.; Valeo, Ernest J.; Fisch, Nathaniel J.

2013-04-24

Assembling a free-standing, sharp-edged slab of homogeneous material that is much denser than gas, but much more rare ed than a solid, is an outstanding technological challenge. The solution may lie in focusing a dense aerosol to assume this geometry. However, whereas the geometrical optics of dilute aerosols is a well-developed fi eld, the dense aerosol limit is mostly unexplored. Yet controlling the geometrical optics of dense aerosols is necessary in preparing such a material slab. Focusing dense aerosols is shown here to be possible, but the nite particle density reduces the eff ective Stokes number of the flow, amore » critical result for controlled focusing. __________________________________________________« less

System-spanning dynamically jammed region in response to impact of cornstarch and water suspensions

NASA Astrophysics Data System (ADS)

Allen, Benjamin; Sokol, Benjamin; Mukhopadhyay, Shomeek; Maharjan, Rijan; Brown, Eric

2018-05-01

We experimentally characterize the structure of concentrated suspensions of cornstarch and water in response to impact. Using surface imaging and particle tracking at the boundary opposite the impactor, we observed that a visible structure and particle flow at the boundary occur with a delay after impact. We show the delay time is about the same time as the strong stress response, confirming that the strong stress response results from deformation of the dynamically jammed structure once it spans between the impactor and a solid boundary. A characterization of this strong stress response is reported in a companion paper [Maharjan, Mukhopadhyay, Allen, Storz, and Brown, Phys. Rev. E 97, 052602 (2018), 10.1103/PhysRevE.97.052602]. We observed particle flow in the outer part of the dynamically jammed region at the bottom boundary, with a net transverse displacement of up to about 5% of the impactor displacement, indicating shear at the boundary. Direct imaging of the surface of the outer part of the dynamically jammed region reveals a change in surface structure that appears the same as the result of dilation in other cornstarch suspensions. Imaging also reveals cracks, like a brittle solid. These observations suggest the dynamically jammed structure can temporarily support stress according to an effective modulus, like a soil or dense granular material, along a network of frictional contacts between the impactor and solid boundary.

Charactrisation of particle assemblies by 3D cross correlation light scattering and diffusing wave spectroscopy

NASA Astrophysics Data System (ADS)

Scheffold, Frank

2014-08-01

To characterize the structural and dynamic properties of soft materials and small particles, information on the relevant mesoscopic length scales is required. Such information is often obtained from traditional static and dynamic light scattering (SLS/DLS) experiments in the single scattering regime. In many dense systems, however, these powerful techniques frequently fail due to strong multiple scattering of light. Here I will discuss some experimental innovations that have emerged over the last decade. New methods such as 3D static and dynamic light scattering (3D LS) as well as diffusing wave spectroscopy (DWS) can cover a much extended range of experimental parameters ranging from dilute polymer solutions, colloidal suspensions to extremely opaque viscoelastic emulsions.

Two types of amorphous protein particles facilitate crystal nucleation.

PubMed

Yamazaki, Tomoya; Kimura, Yuki; Vekilov, Peter G; Furukawa, Erika; Shirai, Manabu; Matsumoto, Hiroaki; Van Driessche, Alexander E S; Tsukamoto, Katsuo

2017-02-28

Nucleation, the primary step in crystallization, dictates the number of crystals, the distribution of their sizes, the polymorph selection, and other crucial properties of the crystal population. We used time-resolved liquid-cell transmission electron microscopy (TEM) to perform an in situ examination of the nucleation of lysozyme crystals. Our TEM images revealed that mesoscopic clusters, which are similar to those previously assumed to consist of a dense liquid and serve as nucleation precursors, are actually amorphous solid particles (ASPs) and act only as heterogeneous nucleation sites. Crystalline phases never form inside them. We demonstrate that a crystal appears within a noncrystalline particle assembling lysozyme on an ASP or a container wall, highlighting the role of heterogeneous nucleation. These findings represent a significant departure from the existing formulation of the two-step nucleation mechanism while reaffirming the role of noncrystalline particles. The insights gained may have significant implications in areas that rely on the production of protein crystals, such as structural biology, pharmacy, and biophysics, and for the fundamental understanding of crystallization mechanisms.

Discontinuous contact line motion of evaporating particle-laden droplet on superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Yamada, Yutaka; Horibe, Akihiko

2018-04-01

The three-phase contact line motion on a superhydrophobic surface through particle-laden sessile droplet evaporation was investigated. Sample surfaces with micro- and nanoscale structures were generated by various durations of chemical treatment and Si O2 spherical particles with different sizes were used as additives of test liquid. The contact angle and contact radius profiles were studied, and the discontinuous motion of those profiles on micro- and nanostructured hierarchical surfaces was observed, while it was not observed on a nanostructured superhydrophobic surface. Suspensions with low particle concentration induced a relatively large contact radius jump compared to the high-concentrated condition; in contrast, the previous report showed the opposite trend for flat surfaces. In order to explain this result, a simple explanation was provided—that the stacked particles at the contact line region suppressed to the deformation of the liquid-vapor interface near the contact line. This is confirmed by side-view images of the deposition results because the contact line region after evaporation of the dense suspension showed a large contact angle compared to that of the diluted suspension. In addition, deposition at the contact line region was observed by scanning electron microscopy to discuss the effect of the characteristic length scale of the surface structure and particles on the contact line motion. We believe that these results will help one to understand the deposition phenomenon during particle-laden droplet evaporation on the superhydrophobic surface and its applications such as evaporation-driven materials deposition.

Simulating the Smallest Ring World of Chariklo

NASA Astrophysics Data System (ADS)

Michikoshi, Shugo; Kokubo, Eiichiro

2017-03-01

A ring system consisting of two dense narrow rings has been discovered around Centaur Chariklo. The existence of these rings around a small object poses various questions about their origin, stability, and lifetime. In order to understand the nature of Chariklo’s rings, we perform global N-body simulations of the self-gravitating collisional particle rings for the first time. We find that Chariklo should be denser than the ring material in order to avoid the rapid diffusion of the rings. If Chariklo is denser than the ring material, fine spiral structures called self-gravity wakes occur in the inner ring. These wakes accelerate the viscous spreading of the ring significantly and typically occur on timescales of about 100 {years} for m-sized ring particles, which is considerably shorter than the timescales suggested in previous studies. The existence of these narrow rings implies smaller ring particles or the existence of shepherding satellites.

Investigation of unsteadiness in Shock-particle cloud interaction: Fully resolved two-dimensional simulation and one-dimensional modeling

NASA Astrophysics Data System (ADS)

Hosseinzadeh-Nik, Zahra; Regele, Jonathan D.

2015-11-01

Dense compressible particle-laden flow, which has a complex nature, exists in various engineering applications. Shock waves impacting a particle cloud is a canonical problem to investigate this type of flow. It has been demonstrated that large flow unsteadiness is generated inside the particle cloud from the flow induced by the shock passage. It is desirable to develop models for the Reynolds stress to capture the energy contained in vortical structures so that volume-averaged models with point particles can be simulated accurately. However, the previous work used Euler equations, which makes the prediction of vorticity generation and propagation innacurate. In this work, a fully resolved two dimensional (2D) simulation using the compressible Navier-Stokes equations with a volume penalization method to model the particles has been performed with the parallel adaptive wavelet-collocation method. The results still show large unsteadiness inside and downstream of the particle cloud. A 1D model is created for the unclosed terms based upon these 2D results. The 1D model uses a two-phase simple low dissipation AUSM scheme (TSLAU) developed by coupled with the compressible two phase kinetic energy equation.

Structural transitions and hysteresis in clump- and stripe-forming systems under dynamic compression.

PubMed

McDermott, Danielle; Olson Reichhardt, Cynthia J; Reichhardt, Charles

2016-11-28

Using numerical simulations, we study the dynamical evolution of particles interacting via competing long-range repulsion and short-range attraction in two dimensions. The particles are compressed using a time-dependent quasi-one dimensional trough potential that controls the local density, causing the system to undergo a series of structural phase transitions from a low density clump lattice to stripes, voids, and a high density uniform state. The compression proceeds via slow elastic motion that is interrupted with avalanche-like bursts of activity as the system collapses to progressively higher densities via plastic rearrangements. The plastic events vary in magnitude from small rearrangements of particles, including the formation of quadrupole-like defects, to large-scale vorticity and structural phase transitions. In the dense uniform phase, the system compresses through row reduction transitions mediated by a disorder-order process. We characterize the rearrangement events by measuring changes in the potential energy, the fraction of sixfold coordinated particles, the local density, and the velocity distribution. At high confinements, we find power law scaling of the velocity distribution during row reduction transitions. We observe hysteresis under a reversal of the compression when relatively few plastic rearrangements occur. The decompressing system exhibits distinct phase morphologies, and the phase transitions occur at lower compression forces as the system expands compared to when it is compressed.

Recent results from PHOBOS on particle production at high p T

NASA Astrophysics Data System (ADS)

Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Busza, W.; Carroll, A.; Chai, Z.; Chetluru, V.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Halliwell, C.; Hamblen, J.; Harnarine, I.; Hauer, M.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Khan, N.; Kulinich, P.; Kuo, C. M.; Li, W.; Lin, W. T.; Loizides, C.; Manly, S.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Reed, C.; Richardson, E.; Roland, C.; Roland, G.; Sagerer, J.; Seals, H.; Sedykh, I.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Szostak, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Walters, P.; Wenger, E.; Willhelm, D.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wyngaardt, S.; Wysłouch, B.

2009-06-01

A selection of experimental results from the PHOBOS Collaboration relevant for probing high-energy nuclear collisions with high transverse momentum particles is presented. The inclusive yields of charged particles and comparisons between nuclear and elementary collisions already reveal a large amount of parton energy loss in the hot and dense medium created in heavy ion collisions. Remarkable scaling and factorization features are observed, unifying the data taken at various collision energies, centralities and nuclear sizes. To further analyze the nature of the energy loss, a measurement of pseudorapidity (Δ η) and azimuthal angle (Δ φ) correlations between high transverse momentum charged hadrons ( p T >2.5 GeV/ c) and all associated charged particles is presented at both short-range (small Δ η) and long-range (large Δ η) over a continuous detector acceptance covering -4<Δ η<2. Various near- and away-side features of the correlation structure are discussed as a function of centrality in Au + Au collisions at sqrt{s_{NN}}=200 GeV. The results provide new information about the longitudinal (Δ η) extent of the near-side ‘ridge’ structure, first observed by the STAR Collaboration over a narrower η range. In central Au + Au collisions the ridge structure extends to at least Δ η=4, and its strength completely diminishes as collisions become more peripheral.

Structural transitions and hysteresis in clump- and stripe-forming systems under dynamic compression

DOE PAGES

McDermott, Danielle; Olson Reichhardt, Cynthia J.; Reichhardt, Charles

2016-11-11

In using numerical simulations, we study the dynamical evolution of particles interacting via competing long-range repulsion and short-range attraction in two dimensions. The particles are compressed using a time-dependent quasi-one dimensional trough potential that controls the local density, causing the system to undergo a series of structural phase transitions from a low density clump lattice to stripes, voids, and a high density uniform state. The compression proceeds via slow elastic motion that is interrupted with avalanche-like bursts of activity as the system collapses to progressively higher densities via plastic rearrangements. The plastic events vary in magnitude from small rearrangements ofmore » particles, including the formation of quadrupole-like defects, to large-scale vorticity and structural phase transitions. In the dense uniform phase, the system compresses through row reduction transitions mediated by a disorder-order process. We also characterize the rearrangement events by measuring changes in the potential energy, the fraction of sixfold coordinated particles, the local density, and the velocity distribution. At high confinements, we find power law scaling of the velocity distribution during row reduction transitions. We observe hysteresis under a reversal of the compression when relatively few plastic rearrangements occur. The decompressing system exhibits distinct phase morphologies, and the phase transitions occur at lower compression forces as the system expands compared to when it is compressed.« less

The Self- and Directed Assembly of Nanowires

NASA Astrophysics Data System (ADS)

Smith, Benjamin David

This thesis explores the self- and directed assembly of nanowires. Specifically, we examine the driving forces behind nanowire self-assembly and the macro-structures that are formed. Particle-dense, oriented nanowire structures show promise in the fields of photonics, energy, sensing, catalysis, and electronics. Arrays of spherical particles have already found uses in electronic inks, sensing arrays, and many other commercial applications; but, it is a challenge to create specific arrays of morphologically and/or compositionally anisotropic particles. The following chapters illuminate the interactions that drive the assembly of anisotropic particles in high density solutions in the absence of applied fields or solution drying. Special emphasis is placed on the structures that are formed. The properties of micro- and nanoparticles and their assembly are introduced in Chapter 1. In particular, the properties of shape and material anisotropic particles are highlighted, while challenges in producing desired arrays are discussed. In this thesis, metallic nanowires of increasing complexity were used to examine the self-assembly behavior of both shape and material anisotropic particles. Nanowires were synthesized through templated electrodeposition. In this process, porous alumina membranes served as a template in which metal salts were reduced to form particles. Upon template dissolution, billions of nominally identical particles were released. We specifically focused on segmented, metallic nanowires 2-13 mum in length and 180 to 350 nm in diameter. Since these particles have strong van der Waals (VDWs) attractions, an electrostatically repulsive coating was necessary to prevent aggregation; we used small molecule, DNA, or amorphous silica coatings. Nanowires and their coatings were characterized by electron microscopy. In order to study self-assembly behavior, particle-dense aqueous suspensions were placed within an assembly chamber defined by a silicone spacer. The nanowires rapidly sedimented due to gravity onto a glass cover slip to concentrate and form a dense film. Particles and assemblies were imaged using inverted optical microscopy. We quantitatively analyzed the images and movies captured in order to track and classify particles and classify the overall arrays formed. We then correlated how particle characteristics, e.g., materials, size, segmentation, etc. changed the ordering and alignment observed. With that knowledge, we hope to be able to form new and interesting structures. We began our studies by examining the assembly of single component nanowires. Chapter 2 describes this work, in which solid Au nanowires measuring 2-7 mum in length and 290 nm in diameter self-assembled into smectic rows. By both experiment and theory, we determined that these rows formed due to a balance of electrostatic repulsions and van der Waals attractions. Final assemblies were stable for at least several days. Monte Carlo methods were used to simulate assemblies and showed structures that mirrored those experimentally observed. Simulations indicated that the smectic phase was preferred over others, i.e., nematic, when an additional small charge was added to the ends of the nanowires. Our particles have rough tips, which might create these additional electrostatic repulsions. To increase the particle and array complexity, two-component, metallic nanowire assembly was explored in Chapter 3. We examined numerous types of nanowires by changing the segment length, ratio, and material, the nanowire length, the surface coating, and the presence of small third segments. These segmented nanowires were generally Au-Ag and also ordered into smectic rows. Segmented wires arranged in rows, however, can be aligned in two possible ways with respect to a neighboring particle. The Au segments on neighboring particles can be oriented in the same direction or opposed to each other. Orientation was quantified in terms of an order parameter that took into account alignment with respect to nearest neighbor particles. All experiments showed order parameters indicating a slight preference for orientational ordering that was relatively insensitive to segment size, nanowire size, and nanowire coating. Monte Carlo simulations pointed towards this alignment as a consequence of small differences in the van der Waals attractions between the segments. Experimentally, ordering might to be limited by the large size of the nanowires, which results in kinetically trapped structures. In an attempt to obtain better ordering within rows, silica coated nanowires with partial Au cores were made. The synthesis involved silica-coating the nanowires and selectively etching a Ag segment. These particles have extremely different VDWs attractions between their segments, as the Au cores are much more attractive than the solvent-filled etched ends. The assembly of these partially etched nanowires (PENs) is detailed in Chapters 4, 5, and 6. When allowed to self-assemble, we observed the formation of either vertically or horizontally oriented arrays depending on PEN composition. The formation of vertically oriented arrays of anisotropic particles is important, since not many methods to produce these structures are currently available for particles of this size. We examined the effects of PEN length, PEN diameter, and the size, number, and location of the core segments. Our findings showed a large etched segment at one end (which resulted in a large offset in the center of mass and concentrated the VDWs attractions to one end of the particle) resulted in the best columnar assemblies. These vertically orientated arrays formed in a two part process. First, after PENs sedimented, they fell flat and oriented parallel to the surface. These PENs then sampled many orientations, including rotating out of the surface plane. When higher surface concentrations of particles built as more PENs fell to the surface of the cover slip, neighboring particles stabilized vertical orientations. Second, particles fell oriented vertically and when the surface concentrations were high, they retained this orientation upon reaching the substrate. Since vertically aligned PENs supported each other, assembly into vertical arrays was highly dependent on the surface concentration. But, oriented arrays could be easily formed on larger or smaller substrates, provided a particle concentration scaled to the substrate were used. The mixing of these particles to form heterogeneous arrays was examined. The overall array structure favored that of particles which sedimented more quickly and/or were present in higher amounts. The semi-automated counting of PENs in images by software is used heavily in Chapters 4 and 5. Appendix A describes the use, development, and validation of macros within Image-Pro. The structure, syntax, and use are specifically examined for three nanowire counting macros. The counting results; including: number of particles in an image, number of horizontally vs. vertically oriented PENs, and PENs in microwells; are compared with manual hand counts. Chapter 7 examines the overall conclusions and future directions for this research. By combining our assembly techniques with known directing forces (e.g., electric or magnetic fields) more specific alignment and/or positioning could be achieved. We have also begun to explore directing assembly through lithographic microwells. Further work needs to explore the integration of arrays into devices and the use of functional materials. Then, high density, oriented arrays could be created for photonic, energy, sensing, catalytic, and electronic applications.

Prediction of a Densely Loaded Particle-Laden Jet using a Euler-Lagrange Dense Spray Model

NASA Astrophysics Data System (ADS)

Pakseresht, Pedram; Apte, Sourabh V.

2017-11-01

Modeling of a dense spray regime using an Euler-Lagrange discrete-element approach is challenging because of local high volume loading. A subgrid cluster of droplets can lead to locally high void fractions for the disperse phase. Under these conditions, spatio-temporal changes in the carrier phase volume fractions, which are commonly neglected in spray simulations in an Euler-Lagrange two-way coupling model, could become important. Accounting for the carrier phase volume fraction variations, leads to zero-Mach number, variable density governing equations. Using pressure-based solvers, this gives rise to a source term in the pressure Poisson equation and a non-divergence free velocity field. To test the validity and predictive capability of such an approach, a round jet laden with solid particles is investigated using Direct Numerical Simulation and compared with available experimental data for different loadings. Various volume fractions spanning from dilute to dense regimes are investigated with and without taking into account the volume displacement effects. The predictions of the two approaches are compared and analyzed to investigate the effectiveness of the dense spray model. Financial support was provided by National Aeronautics and Space Administration (NASA).

The effect of micro-structure on upconversion luminescence of Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glass-ceramics

NASA Astrophysics Data System (ADS)

Zhang, Minghui; Wen, Haiqin; Pan, Xiuhong; Yu, Jianding; Jiang, Meng; Yu, Huimei; Tang, Meibo; Gai, Lijun; Ai, Fei

2018-03-01

Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glasses have been prepared by aerodynamic levitation method. The glasses show high refractive index of 2.28 and Abbe number of 18.3. Glass-ceramics heated at 880 °C for 50 min perform the strongest upconversion luminescence. X-ray diffraction patterns of glass-ceramics with different depths indicate that rare earth ions restrain crystallization. Body crystallization mechanism mixed with surface crystallization is confirmed in the heat treatment. Surface crystals achieve priority to grow, resulting in important effects on upconversion luminescence. The results of atomic force microscope and scanning electron microscope indicate that crystal particles with uniform size distribute densely and homogenously on the surface and large amount of glass matrix exists in the glass ceramics heated at 880 °C for 50 min. Crystals in the glass-ceramics present dense structure and strong boundaries, which can reduce the mutual nonradiative relaxation rate among rare earth ions and then improve upconversion luminescence effectively. Based on micro-structural study, the mechanism that upconversion luminescence can be improved by heat treatment has been revealed. The results of micro-structural analysis agree well with the spectra.

Spherical shock-wave propagation in three-dimensional granular packings.

PubMed

Xue, Kun; Bai, Chun-Hua

2011-02-01

We investigate numerically the spherical shock-wave propagation in an open dense granular packing perturbed by the sudden expansion of a spherical intruder in the interior of the pack, focusing on the correlation between geometrical fabrics and propagating properties. The measurements of the temporal and spatial variations in a variety of propagating properties define a consistent serrated wave substructure with characteristic length on the orders of particle diameters. Further inspection of particle packing reveals a well-defined particle layering that persists several particle diameters away from the intruder, although its dominant effects are only within one to two diameters. This interface-induced layering not only exactly coincides with the serrated wave profile, but also highlights the competition between two energy transmission mechanisms involving distinct transport speeds. The alternating dominances between these two mechanisms contribute to the nonlinear wave propagation on the particle scale. Moreover, the proliferation of intricate three-dimensional contact force networks suggests the anisotropic stress transmission, which is found to also arise from the localized packing structure in the vicinity of the intruder.

Acceptance Test Data for BWXT Coated Particle Batch 93164A Defective IPyC Fraction and Pyrocarbon Anisotropy

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

Helmreich, Grant W.; Hunn, John D.; Skitt, Darren J.

2017-02-01

Coated particle fuel batch J52O-16-93164 was produced by Babcock and Wilcox Technologies (BWXT) for possible selection as fuel for the Advanced Gas Reactor Fuel Development and Qualification (AGR) Program’s AGR-5/6/7 irradiation test in the Idaho National Laboratory (INL) Advanced Test Reactor (ATR), or may be used as demonstration production-scale coated particle fuel for other experiments. The tristructural-isotropic (TRISO) coatings were deposited in a 150-mm-diameter production-scale fluidizedbed chemical vapor deposition (CVD) furnace onto 425-μm-nominal-diameter spherical kernels from BWXT lot J52L-16-69316. Each kernel contained a mixture of 15.5%-enriched uranium carbide and uranium oxide (UCO) and was coated with four consecutive CVD layers:more » a ~50% dense carbon buffer layer with 100-μm-nominal thickness, a dense inner pyrolytic carbon (IPyC) layer with 40-μm-nominal thickness, a silicon carbide (SiC) layer with 35-μm-nominal thickness, and a dense outer pyrolytic carbon (OPyC) layer with 40-μm-nominal thickness. The TRISO-coated particle batch was sieved to upgrade the particles by removing over-sized and under-sized material, and the upgraded batch was designated by appending the letter A to the end of the batch number (i.e., 93164A).« less

On the high fidelity simulation of chemical explosions and their interaction with solid particle clouds

NASA Astrophysics Data System (ADS)

Balakrishnan, Kaushik

The flow field behind chemical explosions in multiphase environments is investigated using a robust, state-of-the-art simulation strategy that accounts for the thermodynamics, gas dynamics and fluid mechanics of relevance to the problem. Focus is laid on the investigation of blast wave propagation, growth of hydrodynamic instabilities behind explosive blasts, the mixing aspects behind explosions, the effects of afterburn and its quantification, and the role played by solid particles in these phenomena. In particular, the confluence and interplay of these different physical phenomena are explored from a fundamental perspective, and applied to the problem of chemical explosions. A solid phase solver suited for the study of high-speed, two-phase flows has been developed and validated. This solver accounts for the inter-phase mass, momentum and energy transfer through empirical laws, and ensures two-way coupling between the two phases, viz. solid particles and gas. For dense flow fields, i.e., when the solid volume fraction becomes non-negligible (˜60%), the finite volume method with a Godunov type shock-capturing scheme requires modifications to account for volume fraction gradients during the computation of cell interface gas fluxes. To this end, the simulation methodology is extended with the formulation of an Eulerian gas, Lagrangian solid approach, thereby ensuring that the so developed two-phase simulation strategy can be applied for both flow conditions, dilute and dense alike. Moreover, under dense loading conditions the solid particles inevitably collide, which is accounted for in the current research effort with the use of an empirical collision/contact model from literature. Furthermore, the post-detonation flow field consists of gases under extreme temperature and pressure conditions, necessitating the use of real gas equations of state in the multiphase model. This overall simulation strategy is then extended to the investigation of chemical explosions in multiphase environments, with emphasis on the study of hydrodynamic instability growth, mixing, afterburn effects ensuing from the process, particle ignition and combustion (if reactive), dispersion, and their interaction with the vortices in the mixing layer. The post-detonation behavior of heterogeneous explosives is addressed by using three parts to the investigation. In the first part, only one-dimensional effects are considered, with the goal to assess the presently developed dense two-phase formulation. The total deliverable impulsive loading from heterogeneous explosive charges containing inert steel particles is estimated for a suite of operating parameters and compared, and it is demonstrated that heterogeneous explosive charges deliver a higher near-field impulse than homogeneous explosive charges containing the same mass of the high explosive. In the second part, three-dimensional effects such as hydrodynamic instabilities are accounted for, with the focus on characterizing the mixing layer ensuing from the detonation of heterogeneous explosive charges containing inert steel particles. It is shown that particles introduce significant amounts of hydrodynamic instabilities in the mixing layer, resulting in additional physical phenomena that play a prominent role in the flow features. In particular, the fluctuation intensities, fireball size and growth rates are augmented for heterogeneous explosions vis-a-vis homogeneous explosions, thereby demonstrating that solid particles enhance the perturbation intensities in the flow. In the third part of the investigation of heterogeneous explosions, dense, aluminized explosions are considered, and the particles are observed to burn in two phases, with an initial quenching due to the rarefaction wave, and a final quenching outside the fireball. Due to faster response time scales, smaller particles are observed to heat and accelerate more during early times, and also cool and decelerate more at late times, compared to counterpart larger particle sizes. Furthermore, the average particle velocities at late times are observed to be independent of the initial solid volume fraction in the explosive charge, as the particles eventually reach an equilibrium with the local gas. These studies have provided some crucial insights to the flow physics of dense, aluminized explosives. (Abstract shortened by UMI.)

Fusion and erosion of cell walls during confugation in the fussion yeast (Schizosaccharomyces pombe).

PubMed

Calleja, G B; Yoo, B Y; Johnson, B F

1977-06-01

Conjugation in Schizosaccharomyces pombe was studied by transmission electron microscopy. Mural and nuclear events were scored from induction, the initial event, to meiosis I, the start of sporulation. These morphogenic markers were separately identifiable as flocculation, copulation, conjugation-tube formation, cross-wall formation, cross-wall erosion, conjugation-tube expansion, cytoplasmic fusion, de-differentiation of site of union, nuclear migration and karyogamy. The following were identified as new structural elements: sex hairs, which presumably mediate hydrogen bonding between cells during flocculation; crimp at the site of union; dark patch, which presumably serves as a leak-proof seal at the time of cross-wall erosion; suture, an electron-dense seam formed by the union of a copulant pair; and small electron-dense particles close to the site of wall erosion. No special structures on the cell wall could be identified as indicative of specific sites for potential copulatory activity. The discontinuity of the 2 cell walls at the site of union became so de-differentiated after fusion and erosion that it was no longer possible to pinpoint the site of union.

Self-assembled nanoparticle arrays as nanomasks for pattern transfer

NASA Astrophysics Data System (ADS)

Sachan, M.; Bonnoit, C.; Hogg, C.; Evarts, E.; Bain, J. A.; Majetich, S. A.; Park, J.-H.; Zhu, J.-G.

2008-07-01

Argon ion milling was used to transfer the pattern of sparse 12 nm iron oxide nanoparticles into underlying thin films of Pt and magnetic tunnel junction stacks and quantify their etching rates and morphological evolution. Under typical milling conditions, Pt milled at 10 nm min-1, while the isolated particles of iron oxide used for the mask milled at 5 nm min-1. Dilute dispersions of nanoparticles were used to produce the sparse nanomasks, and high resolution scanning electron microscopy (SEM) and atomic force microscopy were used to monitor the evolution of etched structures as a function of milling time. SEM measurements indicate an apparent 20% increase in feature diameter before the features began to diminish under additional milling, suggesting redeposition as a limiting feature in the milling of dense arrays. Simulations of the milling process in nanoparticle arrays that include redeposition are consistent with this observation. These simulations predict that an edge-to-edge spacing of 3 nm in a dense array is feasible, but that redeposition reduces the final structure aspect ratio from that of the masking array by as much as a factor of two.

Formation of a disordered solid via a shock-induced transition in a dense particle suspension

NASA Astrophysics Data System (ADS)

Petel, Oren E.; Frost, David L.; Higgins, Andrew J.; Ouellet, Simon

2012-02-01

Shock wave propagation in multiphase media is typically dominated by the relative compressibility of the two components of the mixture. The difference in the compressibility of the components results in a shock-induced variation in the effective volume fraction of the suspension tending toward the random-close-packing limit for the system, and a disordered solid can take form within the suspension. The present study uses a Hugoniot-based model to demonstrate this variation in the volume fraction of the solid phase as well as a simple hard-sphere model to investigate the formation of disordered structures within uniaxially compressed model suspensions. Both models are discussed in terms of available experimental plate impact data in dense suspensions. Through coordination number statistics of the mesoscopic hard-sphere model, comparisons are made with the trends of the experimental pressure-volume fraction relationship to illustrate the role of these disordered structures in the bulk properties of the suspensions. A criterion for the dynamic stiffening of suspensions under high-rate dynamic loading is suggested as an analog to quasi-static jamming based on the results of the simulations.

A Green Method for Processing Polymers using Dense Gas Technology

PubMed Central

Yoganathan, Roshan B.; Mammucari, Raffaella; Foster, Neil R.

2010-01-01

Dense CO2 can be used as an environmentally-benign polymer processing medium because of its liquid-like densities and gas-like mass transfer properties.In this work, polymer bio-blends of polycarbonate (PC), a biocompatible polymer, and polycaprolactone (PCL), a biodegradable polymer were prepared. Dense CO2 was used as a reaction medium for the melt-phase PC polymerization in the presence of dense CO2-swollen PCL particles and this method was used to prepare porous PC/PCL blends. To extend the applicability of dense CO2 to the biomedical industry and polymer blend processing, the impregnation of ibuprofen into the blend was conducted and subsequent dissolution characteristics were observed.

Biomimetic whisker-shaped apatite coating of titanium powder.

PubMed

Sim, Young Uk; Kim, Jong Hee; Yang, Tae Young; Yoon, Seog Young; Park, Hong Chae

2010-05-01

Biomimetic apatite coatings on chemically modified titanium powder have been processed and the resulting coating layers evaluated in terms of morphology, composition and structure, using TF-XRD, XPS, SEM, TEM and FTIR analysis. After 7 days immersion in a simulated body fluid (SBF), nanometer-sized fine precipitates with an amorphous whisker-like phase and a Ca/P atomic ratio of 1.94 were obtained on the external surface of the titanium particles. When the immersion time in SBF was extended to 16 days, the coating layer consisted of the whisker-like nanostructured crystals of carbonated hydroxyapatite with a atomic ratio of 3; in such a case, a double coating layer was developed. The double layer could be divided into two regions and could be clearly distinguished: an inner dense region (approximately 200 nm in thickness) which may include hard agglomerated crystals and an outer less dense region (> 500 nm in thickness) in which crystals are loosely distributed.

Beam-driven acceleration in ultra-dense plasma media

DOE PAGES

Shin, Young-Min

2014-09-15

Accelerating parameters of beam-driven wakefield acceleration in an extremely dense plasma column has been analyzed with the dynamic framed particle-in-cell plasma simulator, and compared with analytic calculations. In the model, a witness beam undergoes a TeV/m scale alternating potential gradient excited by a micro-bunched drive beam in a 10 25 m -3 and 1.6 x 10 28 m -3 plasma column. The acceleration gradient, energy gain, and transformer ratio have been extensively studied in quasi-linear, linear-, and blowout-regimes. The simulation analysis indicated that in the beam-driven acceleration system a hollow plasma channel offers 20 % higher acceleration gradient by enlargingmore » the channel radius (r) from 0.2 Ap to 0.6 .Ap in a blowout regime. This paper suggests a feasibility of TeV/m scale acceleration with a hollow crystalline structure (e.g. nanotubes) of high electron plasma density.« less

Catalyst containing oxygen transport membrane

DOEpatents

Christie, Gervase Maxwell; Wilson, Jamie Robyn; van Hassel, Bart Antonie

2012-12-04

A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a high average pore diameter and the intermediate porous layer has a lower permeability and lower pore diameter than the porous support layer. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

Propagation of monochromatic light in a hot and dense medium

NASA Astrophysics Data System (ADS)

Masood, Samina S.

2017-12-01

Photons, as quanta of electromagnetic fields, determine the electromagnetic properties of an extremely hot and dense medium. Considering the properties of the photons in the interacting medium of charged particles, we explicitly calculate the electromagnetic properties such as the electric permittivity, magnetic permeability, refractive index and the propagation speed of electromagnetic signals in an extremely hot and dense background. Photons acquire a dynamically generated mass in such a medium. The screening mass of the photon, the Debye shielding length and the plasma frequency are calculated as functions of the statistical parameters of the medium. We study the properties of the propagating particles in astrophysical systems of distinct statistical conditions. The modifications in the properties of the medium lead to the equation of state of the system. We mainly calculate all these parameters for extremely high temperatures of the early universe.

Effects of particle fracturing and moisture content on fire behaviour in masticated fuelbeds burned in a laboratory

Treesearch

Jesse K. Kreye; J. Morgan Varner; Eric E. Knapp

2011-01-01

Mechanical mastication is a fuels treatment that converts shrubs and small trees into dense fuelbeds composed of fractured woody particles. Although compaction is thought to reduce fireline intensity, the added particle surface area due to fracturing could also influence fire behavior. We evaluated effects of particle fracturing and moisture content (ranging from 2.5...

Saha equation, single and two particle states

NASA Technical Reports Server (NTRS)

Kraeft, W. D.; Girardeau, M. D.; Strege, B.

1990-01-01

Single- and two-particle properties in a dense plasma are discussed in connection with their role in the mass action law for a partially ionized plasma. The two-particle-bound states are nearly density independent, while the continuum is essentially shifted. The single-particle states are damped, and their energy has a negative shift and a parabolic behavior for small momenta.

Influence of Particle Morphology on 3D Kinematic Behavior and Strain Localization of Sheared Sand

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

Alshibli, Khalid A.; Jarrar, Maha F.; Druckrey, Andrew M.

The constitutive behavior of sheared sand is highly influenced by particle morphology, gradation, mineralogy, specimen density, loading condition, stress path, and boundary conditions. The current literature lacks a three-dimensional (3D) systematic experimental study that investigates the influence of particle morphology, confining pressure, and specimen density on the failure mode of sheared sand. In this paper, surface texture, roundness, and sphericity of three uniform sands and glass beads with similar grain size were quantified by using 3D images of particles. In situ nondestructive 3D synchrotron microcomputed tomography (SMT) was used to monitor the deformation of medium-dense and very dense dry sandmore » specimens that were tested under axisymmetric triaxial loading condition at 15 and 400 kPa confining pressures. The particles were identified and tracked in 3D as shearing progressed within the specimens, and maps of incremental particle translation and rotation were developed and used to uncover the relationship between particle morphology, specimen density, and confining pressure on the deformation and failure mode of sheared sand. This paper discusses the relationship between the failure mode and particle morphology, specimen density, and confining pressure.« less

Rheology of dense granular flows for elongated particles

NASA Astrophysics Data System (ADS)

Nagy, Dániel B.; Claudin, Philippe; Börzsönyi, Tamás; Somfai, Ellák

2017-12-01

We study the rheology of dense granular flows for frictionless spherocylinders by means of 3D numerical simulations. As in the case of spherical particles, the effective friction μ is an increasing function of the inertial number I , and we systematically investigate the dependence of μ on the particle aspect ratio Q , as well as that of the normal stress differences, the volume fraction, and the coordination number. We show in particular that the quasistatic friction coefficient is nonmonotonic with Q : from the spherical case Q =1 , it first sharply increases, reaches a maximum around Q ≃1.05 , and then gently decreases until Q =3 , passing its initial value at Q ≃2 . We provide a microscopic interpretation for this unexpected behavior through the analysis of the distribution of dissipative contacts around the particles: as compared to spheres, slightly elongated grains enhance contacts in their central cylindrical band, whereas at larger aspect ratios particles tend to align and dissipate by preferential contacts at their hemispherical caps.

A description of the pseudorapidity distributions in heavy ion collisions at RHIC and LHC energies

NASA Astrophysics Data System (ADS)

Jiang, Z. J.; Zhang, Y.; Zhang, H. L.; Deng, H. P.

2015-09-01

The charged particles produced in nucleus-nucleus collisions are classified into two parts: One is from the hot and dense matter created in collisions. The other is from leading particles. The hot and dense matter is assumed to expand and generate particles according to BJP hydrodynamics, a theory put forward by A. Bialas, R.A. Janik and R. Peschanski. The leading particles are argued to possess a Gaussian rapidity distribution with the normalization constant equaling the number of participants. A comparison is made between the theoretical results and the experimental measurements performed by BRAHMS and PHOBOS Collaborations at BNL-RHIC in Au-Au and Cu-Cu collisions at √{sNN} = 200 GeV and by ALICE Collaboration at CERN-LHC in Pb-Pb collisions at √{sNN} = 2.76 TeV. The theoretical results are well consistent with experimental data.

Universal Scaling Laws for Dense Particle Suspensions in Turbulent Wall-Bounded Flows.

PubMed

Costa, Pedro; Picano, Francesco; Brandt, Luca; Breugem, Wim-Paul

2016-09-23

The macroscopic behavior of dense suspensions of neutrally buoyant spheres in turbulent plane channel flow is examined. We show that particles larger than the smallest turbulence scales cause the suspension to deviate from the continuum limit in which its dynamics is well described by an effective suspension viscosity. This deviation is caused by the formation of a particle layer close to the wall with significant slip velocity. By assuming two distinct transport mechanisms in the near-wall layer and the turbulence in the bulk, we define an effective wall location such that the flow in the bulk can still be accurately described by an effective suspension viscosity. We thus propose scaling laws for the mean velocity profile of the suspension flow, together with a master equation able to predict the increase in drag as a function of the particle size and volume fraction.

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

Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLs

NASA Technical Reports Server (NTRS)

Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Gelger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)

2006-01-01

A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water, The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles.

Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLS

NASA Technical Reports Server (NTRS)

Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Geiger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)

2003-01-01

A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water. The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles

Regulation of low-density lipoprotein subfractions by carbohydrates.

PubMed

Gerber, Philipp A; Berneis, Kaspar

2012-07-01

This article aims at reviewing the recent findings that have been made concerning the crosstalk of carbohydrate metabolism with the generation of small, dense low-density lipoprotein (LDL) particles, which are known to be associated with an adverse cardiovascular risk profile. Studies conducted during the past few years have quite unanimously shown that the quantity of carbohydrates ingested is associated with a decrease of LDL particle size and an increase in its density. Conversely, diets that aim at a reduction of carbohydrate intake are able to improve LDL quality. Furthermore, a reduction of the glycaemic index without changing the amount of carbohydrates ingested has similar effects. Diseases with altered carbohydrate metabolism, for example, type 2 diabetes, are associated with small, dense LDL particles. Finally, even the kind of monosaccharide the carbohydrate intake consists of is important concerning LDL particle size: fructose has been shown to alter the LDL particle subclass profile more adversely than glucose in many recent studies. LDL particle quality, rather than its quantity, is affected by carbohydrate metabolism, which is of clinical importance, in particular, in the light of increased carbohydrate consumption in today's world.

Efficient energy absorption of intense ps-laser pulse into nanowire target

NASA Astrophysics Data System (ADS)

Habara, H.; Honda, S.; Katayama, M.; Sakagami, H.; Nagai, K.; Tanaka, K. A.

2016-06-01

The interaction between ultra-intense laser light and vertically aligned carbon nanotubes is investigated to demonstrate efficient laser-energy absorption in the ps laser-pulse regime. Results indicate a clear enhancement of the energy conversion from laser to energetic electrons and a simultaneously small plasma expansion on the surface of the target. A two-dimensional plasma particle calculation exhibits a high absorption through laser propagation deep into the nanotube array, even for a dense array whose structure is much smaller than the laser wavelength. The propagation leads to the radial expansion of plasma perpendicular to the nanotubes rather than to the front side. These features may contribute to fast ignition in inertial confinement fusion and laser particle acceleration, both of which require high current and small surface plasma simultaneously.

Stability diagram for dense suspensions of model colloidal Al2O3 particles in shear flow.

PubMed

Hecht, Martin; Harting, Jens; Herrmann, Hans J

2007-05-01

In Al2O3 suspensions, depending on the experimental conditions, very different microstructures can be found, comprising fluidlike suspensions, a repulsive structure, and a clustered microstructure. For technical processing in ceramics, the knowledge of the microstructure is of importance, since it essentially determines the stability of a workpiece to be produced. To enlighten this topic, we investigate these suspensions under shear by means of simulations. We observe cluster formation on two different length scales: the distance of nearest neighbors and on the length scale of the system size. We find that the clustering behavior does not depend on the length scale of observation. If interparticle interactions are not attractive the particles form layers in the shear flow. The results are summarized in a stability diagram.

Explosive desorption of icy grain mantles in dense clouds

NASA Technical Reports Server (NTRS)

Schutte, W. A.; Greenberg, J. M.

1991-01-01

The cycling of the condensible material in dense clouds between the gas phase and the icy grain mantles is investigated. In the model studied, desorption of the ice occurs due to grain mantle explosions when photochemically stored energy is released after transient heating by a cosmic ray particle. It is shown that, depending on the grain size distribution in dense clouds, explosive desorption can maintain up to about eight percent of the carbon in the form of CO in the gas phase at typical cloud densities.

Model of the vertical structure of the optical parameters of the Neptune atmosphere.

NASA Astrophysics Data System (ADS)

Morozhenko, A. V.

Analyzes the wavelength dependence of the geometric albedo of Neptune's disk and estimates some parameters of the planet's atmosphere by the method based on the determination of deviations of the vertical structure of the cloud layer from the homogeneity condition. The ratio between the methane and gas scale heights is found to be about 0.4. For the upper atmosphere, components of methane, aerosol, the mean geometric radius of particles, the turbulent mixing coefficient are determined. Two solutions were found for deeper atmospheric layers. The first one suggests a rather dense cloud; in the second solution the lower cloud layer is an extension of the upper aerosol layer.

Organizing principles for dense packings of nonspherical hard particles: Not all shapes are created equal

NASA Astrophysics Data System (ADS)

Torquato, Salvatore; Jiao, Yang

2012-07-01

We have recently devised organizing principles to obtain maximally dense packings of the Platonic and Archimedean solids and certain smoothly shaped convex nonspherical particles [Torquato and Jiao, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.81.041310 81, 041310 (2010)]. Here we generalize them in order to guide one to ascertain the densest packings of other convex nonspherical particles as well as concave shapes. Our generalized organizing principles are explicitly stated as four distinct propositions. All of our organizing principles are applied to and tested against the most comprehensive set of both convex and concave particle shapes examined to date, including Catalan solids, prisms, antiprisms, cylinders, dimers of spheres, and various concave polyhedra. We demonstrate that all of the densest known packings associated with this wide spectrum of nonspherical particles are consistent with our propositions. Among other applications, our general organizing principles enable us to construct analytically the densest known packings of certain convex nonspherical particles, including spherocylinders, “lens-shaped” particles, square pyramids, and rhombic pyramids. Moreover, we show how to apply these principles to infer the high-density equilibrium crystalline phases of hard convex and concave particles. We also discuss the unique packing attributes of maximally random jammed packings of nonspherical particles.

Nano-sized structured layered positive electrode materials to enable high energy density and high rate capability lithium batteries

DOEpatents

Deng, Haixia; Belharouak, Ilias; Amine, Khalil

2012-10-02

Nano-sized structured dense and spherical layered positive active materials provide high energy density and high rate capability electrodes in lithium-ion batteries. Such materials are spherical second particles made from agglomerated primary particles that are Li.sub.1+.alpha.(Ni.sub.xCo.sub.yMn.sub.z).sub.1-tM.sub.tO.sub.2-dR.sub.d- , where M is selected from can be Al, Mg, Fe, Cu, Zn, Cr, Ag, Ca, Na, K, In, Ga, Ge, V, Mo, Nb, Si, Ti, Zr, or a mixture of any two or more thereof, R is selected from F, Cl, Br, I, H, S, N, or a mixture of any two or more thereof, and 0.ltoreq..alpha..ltoreq.0.50; 0

Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

DOEpatents

Singh, Prabhakar; Ruka, Roswell J.

1995-01-01

A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO.sub.3 particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr.sub.2 O.sub.3 on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO.sub.3 layer coated with CaO and Cr.sub.2 O.sub.3 surface deposit at from about 1000.degree. C. to 1200.degree. C. to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO.sub.3 layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power.

Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

DOEpatents

Singh, P.; Ruka, R.J.

1995-02-14

A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO{sub 3} particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr{sub 2}O{sub 3} on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO{sub 3} layer coated with CaO and Cr{sub 2}O{sub 3} surface deposit at from about 1,000 C to 1,200 C to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO{sub 3} layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power. 5 figs.

Dense plasma focus (DPF) accelerated non radio isotopic radiological source

DOEpatents

Rusnak, Brian; Tang, Vincent

2017-01-31

A non-radio-isotopic radiological source using a dense plasma focus (DPF) to produce an intense z-pinch plasma from a gas, such as helium, and which accelerates charged particles, such as generated from the gas or injected from an external source, into a target positioned along an acceleration axis and of a type known to emit ionizing radiation when impinged by the type of accelerated charged particles. In a preferred embodiment, helium gas is used to produce a DPF-accelerated He2+ ion beam to a beryllium target, to produce neutron emission having a similar energy spectrum as a radio-isotopic AmBe neutron source. Furthermore, multiple DPFs may be stacked to provide staged acceleration of charged particles for enhancing energy, tunability, and control of the source.

Neutrino Oscillations in Dense Matter

NASA Astrophysics Data System (ADS)

Lobanov, A. E.

2017-03-01

A modification of the electroweak theory, where the fermions with the same electroweak quantum numbers are combined in multiplets and are treated as different quantum states of a single particle, is proposed. In this model, mixing and oscillations of particles arise as a direct consequence of the general principles of quantum field theory. The developed approach enables one to calculate the probabilities of the processes taking place in the detector at long distances from the particle source. Calculations of higher-order processes, including computation of the contributions due to radiative corrections, can be performed in the framework of the perturbation theory using the regular diagram technique. As a result, the analog to the Dirac-Schwinger equation of quantum electrodynamics describing neutrino oscillations and its spin rotation in dense matter can be obtained.

Acceptance Test Data for Candidate AGR-5/6/7 TRISO Particle Batches BWXT Coater Batches 93165 93172 Defective IPyC Fraction and Pyrocarbon Anisotropy

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

Helmreich, Grant W.; Hunn, John D.; Skitt, Darren J.

2017-03-01

Coated particle fuel batches J52O-16-93165, 93166, 93168, 93169, 93170, and 93172 were produced by Babcock and Wilcox Technologies (BWXT) for possible selection as fuel for the Advanced Gas Reactor Fuel Development and Qualification (AGR) Program’s AGR-5/6/7 irradiation test in the Idaho National Laboratory (INL) Advanced Test Reactor (ATR). Some of these batches may alternately be used as demonstration coated particle fuel for other experiments. Each batch was coated in a 150-mm-diameter production-scale fluidized-bed chemical vapor deposition (CVD) furnace. Tristructural isotropic (TRISO) coatings were deposited on 425-μm-nominal-diameter spherical kernels from BWXT lot J52R-16-69317 containing a mixture of 15.5%-enriched uranium carbide andmore » uranium oxide (UCO). The TRISO coatings consisted of four consecutive CVD layers: a ~50% dense carbon buffer layer with 100-μm-nominal thickness, a dense inner pyrolytic carbon (IPyC) layer with 40-μm-nominal thickness, a silicon carbide (SiC) layer with 35-μm-nominal thickness, and a dense outer pyrolytic carbon (OPyC) layer with 40-μmnominal thickness. The TRISO-coated particle batches were sieved to upgrade the particles by removing over-sized and under-sized material, and the upgraded batches were designated by appending the letter A to the end of the batch number (e.g., 93165A).« less

Electrostatic forces in planetary rings

NASA Technical Reports Server (NTRS)

Goertz, C. K.; Shan, Linhua; Havnes, O.

1988-01-01

The average charge on a particle in a particle-plasma cloud, the plasma potential inside the cloud, and the Coulomb force acting on the particle are calculated. The net repulsive electrostatic force on a particle depends on the plasma density, temperature, density of particles, particle size, and the gradient of the particle density. In a uniformly dense ring the electrostatic repulsion is zero. It is also shown that the electrostatic force acts like a pressure force, that even a collisionless ring can be stable against gravitational collapse, and that a finite ring thickness does not necessarily imply a finite velocity dispersion. A simple criterion for the importance of electrostatic forces in planetary rings is derived which involves the calculation of the vertical ring thickness which would result if only electrostatic repulsion were responsible for the finite ring thickness. Electrostatic forces are entirely negligible in the main rings of Saturn and the E and G rings. They may also be negligible in the F ring. However, the Uranian rings and Jupiter's ring seem to be very much influenced by electrostatic repulsion. In fact, electrostatic forces could support a Jovian ring which is an order of magnitude more dense than observed.

Small-angle neutron scattering study of the short-range organization of dispersed CsNi[Cr(CN){sub 6}] nanoparticles

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

Ridier, Karl; Gillon, Béatrice; André, Gilles

2015-09-21

Prussian blue analogues magnetic nanoparticles (of radius R{sub 0} = 2.4–8.6 nm) embedded in PVP (polyvinylpyrrolidone) or CTA{sup +} (cetyltrimethylammonium) matrices have been studied using neutron diffraction and small angle neutron scattering (SANS) at several concentrations. For the most diluted particles in neutral PVP, the SANS signal is fully accounted for by a “single-particle” spherical form factor with no structural correlations between the nanoparticles and with radii comparable to those inferred from neutron diffraction. For higher concentration in PVP, structural correlations modify the SANS signal with the appearance of a structure factor peak, which is described using an effective “mean-field” model. A newmore » length scale R{sup * }≈ 3R{sub 0}, corresponding to an effective repulsive interaction radius, is evidenced in PVP samples. In CTA{sup +}, electrostatic interactions play a crucial role and lead to a dense layer of CTA{sup +} around the nanoparticles, which considerably alter the SANS patterns as compared to PVP. The SANS data of nanoparticles in CTA{sup +} are best described by a core-shell model without visible inter-particle structure factor.« less

Tri-track: free software for large-scale particle tracking.

PubMed

Vallotton, Pascal; Olivier, Sandra

2013-04-01

The ability to correctly track objects in time-lapse sequences is important in many applications of microscopy. Individual object motions typically display a level of dynamic regularity reflecting the existence of an underlying physics or biology. Best results are obtained when this local information is exploited. Additionally, if the particle number is known to be approximately constant, a large number of tracking scenarios may be rejected on the basis that they are not compatible with a known maximum particle velocity. This represents information of a global nature, which should ideally be exploited too. Some time ago, we devised an efficient algorithm that exploited both types of information. The tracking task was reduced to a max-flow min-cost problem instance through a novel graph structure that comprised vertices representing objects from three consecutive image frames. The algorithm is explained here for the first time. A user-friendly implementation is provided, and the specific relaxation mechanism responsible for the method's effectiveness is uncovered. The software is particularly competitive for complex dynamics such as dense antiparallel flows, or in situations where object displacements are considerable. As an application, we characterize a remarkable vortex structure formed by bacteria engaged in interstitial motility.

Synthesis and Performance Evaluation of Pulse Electrodeposited Ni-AlN Nanocomposite Coatings

PubMed Central

Ali, Kamran; Narayana, Sivaprasad; Okonkwo, Paul C.; Yusuf, Moinuddin M.; Alashraf, Abdullah

2018-01-01

This research work presents the microscopic analysis of pulse electrodeposited Ni-AlN nanocomposite coatings using SEM and AFM techniques and their performance evaluation (mechanical and electrochemical) by employing nanoindentation and electrochemical methods. The Ni-AlN nanocomposite coatings were developed by pulse electrodeposition. The nickel matrix was reinforced with various amounts of AlN nanoparticles (3, 6, and 9 g/L) to develop Ni-AlN nanocomposite coatings. The effect of reinforcement concentration on structure, surface morphology, and mechanical and anticorrosion properties was studied. SEM and AFM analyses indicate that Ni-AlN nanocomposite coatings have dense, homogenous, and well-defined pyramid structure containing uniformly distributed AlN particles. A decent improvement in the corrosion protection performance is also observed by the addition of AlN particles to the nickel matrix. Corrosion current was reduced from 2.15 to 1.29 μA cm−2 by increasing the AlN particles concentration from 3 to 9 g/L. It has been observed that the properties of Ni-AlN nanocomposite coating are sensitive to the concentration of AlN nanoparticles used as reinforcement. PMID:29619143

Small Angle Neutron-Scattering Studies of the Core Structure of Intact Neurosecretory Vesicles.

NASA Astrophysics Data System (ADS)

Krueger, Susan Takacs

Small angle neutron scattering (SANS) was used to study the state of the dense cores within intact neurosecretory vesicles. These vesicles transport the neurophysin proteins, along with their associated hormones, oxytocin or vasopressin, from the posterior pituitary gland to the bloodstream, where the entire vesicle contents are released. Knowledge of the vesicle core structure is important in developing an understanding of this release mechanism. Since the core constituents exist in a dense state at concentrations which cannot be reproduced (in solution) in the laboratory, a new method was developed to determine the core structure from SANS experiments performed on intact neurosecretory vesicles. These studies were complemented by biochemical assays performed to determine the role, if any, played by phospholipids in the interactions between the core constituents. H_2O/D_2 O ratio in the solvent can be adjusted, using the method of contrast variation, such that the scattering due to the vesicle membranes is minimized, thus emphasizing the scattering originating from the cores. The applicability of this method for examining the interior of biological vesicles was tested by performing an initial study on human red blood cells, which are similar in structure to other biological vesicles. Changes in intermolecular hemoglobin interactions, occurring when the ionic strength of the solvent was varied or when the cells were deoxygenated, were examined. The results agreed with those expected for dense protein solutions, indicating that the method developed was suitable for the study of hemoglobin within the cells. Similar SANS studies were then performed on intact neurosecretory vesicles. The experimental results were inconsistent with model calculations which assumed that the cores consisted of small, densely-packed particles or large, globular aggregates. Although a unique model could not be determined, the data suggest that the core constituents form long aggregates of varying cross-sectional diameters. The biochemical experiments not only confirmed the ability of the core constituents to form large aggregates but also established that phospholipids do not play a role in this aggregate formation.

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

Ishige, Ryohei; Williams, Gregory A.; Higaki, Yuji

A molded film of single-component polymer-grafted nanoparticles (SPNP), consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated byin situultra-small-angle X-ray scattering (USAXS) measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c.) lattice structure with the [11-1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis ofin situUSAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction inmore » proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress–strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles.« less

In-Situ Analysis of the Chemical Vapor Synthesis of Nanocrystalline Silicon Carbide by Aerosol Mass Spectrometry

DTIC Science & Technology

2001-11-01

ultrafine particles with a narrow size distribution and high purity. Chemical Vapor Synthesis (CVS) is a method to generate particles in the size range...high temperatures due to strong covalent bonds. Ultrafine particles of SiC are promising for the production of dense bulk solids due to the small grain

The Role of Citric Acid in the Stabilization of Nanoparticles and Colloidal Particles in the Environment: Measurement of Surface Forces between Hafnium Oxide Surfaces in the Presence of Citric Acid.

PubMed

Shinohara, Shuhei; Eom, Namsoon; Teh, E-Jen; Tamada, Kaoru; Parsons, Drew; Craig, Vincent S J

2018-02-27

The interactions between colloidal particles and nanoparticles determine solution stability and the structures formed when the particles are unstable to flocculation. Therefore, knowledge of the interparticle interactions is important for understanding the transport, dissolution, and fate of particles in the environment. The interactions between particles are governed by the surface properties of the particles, which are altered when species adsorb to the surface. The important interactions in the environment are almost never those between the bare particles but rather those between particles that have been modified by the adsorption of natural organic materials. Citric acid is important in this regard not only because it is present in soil but also as a model of humic and fulvic acids. Here we have studied the surface forces between the model metal oxide surface hafnia in the presence of citric acid in order to understand the stability of colloidal particles and nanoparticles. We find that citric acid stabilizes the particles over a wide range of pH at low to moderate ionic strength. At high ionic strength, colloidal particles will flocculate due to a secondary minimum, resulting in aggregates that are dense and easily redispersed. In contrast, nanoparticles stabilized by citric acid remain stable at high ionic strengths and therefore exist in solution as individual particles; this will contribute to their dispersion in the environment and the uptake of nanoparticles by mammalian cells.

Synthesis of low-size flower-like AlOOH structures

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

Bakina, Olga V., E-mail: ovbakina@ispms.tsc.ru, E-mail: eagl@ispms.tsc.ru; Glazkova, Elena A., E-mail: ovbakina@ispms.tsc.ru, E-mail: eagl@ispms.tsc.ru; Lozhkomoev, Aleksandr S., E-mail: asl@ispms.tsc.ru

Al/Cu, Al/Zn, and Al/Fe bimetallic nanoparticles have been obtained using the method of simultaneous electrical explosion of metal pairs in an argon atmosphere. The nanoparticles are chemically active and interact with water at 60°C forming flower-like hierarchical porous structures with a high specific surface area. As the Al/Cu nanopowder is oxidized with water, flower-like pseudoboehmite composite structures are formed with the size of under 1.0 μm; structurally heterogeneous electron-dense spherical inclusions of unreacted metal copper and intermetallides are identified inside them. Al/Fe product transformations are presented by the flower-like pseudoboehmite surrounded by lamellar structures enriched with ferric oxides. Al/Zn nanoparticlesmore » react with water, forming the flower-like pseudoboehmite and mainly hexagonal zinc oxide laminae. The composite particles obtained can be used as antibacterial agents in manufacturing medical supplies.« less

Chevrons, filaments, spinning clusters and phase coexistence: emergent dynamics of 2- and 3-d particle suspensions driven by multiaxial magnetic fields

DOE PAGES

Solis, Kyle J.; Martin, James E.

2017-07-06

In recent years a rich variety of emergent phenomena have been observed when suspensions of magnetic particles are subjected to alternating magnetic fields. These particle assemblies often exhibit vigorous dynamics due to the injection of energy from the field. These include surface and interface phenomena, such as highly organized, segmented “snakes” that can be induced to swim by structural symmetry breaking, and “asters” and “anti-asters,” particle assemblies that can be manipulated to capture and transport cargo. In bulk suspensions of magnetic platelets subjected to multiaxial alternating fields, advection lattices and even vortex lattices have been created, and a variety ofmore » biomimetic dynamics – serpents, bees and amoebas – have been discovered in magnetic fluids suspended in an immiscible liquid. In this paper several new driven phases are presented, including flying chevrons, dense spinning clusters, filaments, and examples of phase coexistence in driven phases. These observations broaden the growing field of driven magnetic suspensions and present new challenges to those interested in simulating the dynamics of these complex systems.« less

Virus-like particles in cystic mammary adenoma of a snow leopard.

PubMed

Chandra, S; Laughlin, D C

1975-11-01

Virus-like particles were observed in the giant cells of a mammary adenoma of a snow leopard kept in captivity. Particles that measured 115 to 125 nm in diameter budded from the lamella of endoplasmic reticulum and were studded on their inner surfaces with dense granules (approximately 12 nm) that gave them their unique ultrastructural morphology. Such particles were not observed extracellularly. Type B or type C particles were not seen in the tumor tissue.

Restrike Particle Beam Experiments on a Dense Plasma Focus.

DTIC Science & Technology

1981-11-30

particle beams generated in a plasma focus with the current flowing in the circuit just before the radial collapse of the pinch, IMB. The results show...the implications for the application of the plasma focus as an opening switch are discussed. (Author)

Obseration of flow regime transition in CFB riser using an LDV

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

Yue, Paul C.; Mei, Joseph S.; Shadle, Lawrence J.

2011-01-01

The solids flow in a circulating fluidized bed (CFB) riser is often described to have a core-annular structure. For a given superficial gas velocity, at the initial introduction of solids into a riser a flow structure of dilute upflow regime exists. Continuing to increase the solids flow in the riser transitions the flow structure to the core-annular flow regime. However, with further increase of solids flow a condition is reached, depending on the superficial gas velocity, where all the solids across the riser cross section flow upwards, even those at the wall. When the solids flux, solids fraction and gasmore » velocity are relatively high, such a condition is described as the dense phase suspense upflow (DSU) regime. In this paper we report our observations of these flow regime transitions by using a laser Doppler velocimeter (LDV) to monitor the upward and downward particle flow velocities at and near the riser wall of the National Energy Technology Laboratory’s 30.4 centimeters diameter CFB cold flow model. The particles were high density polyethylene (PPE) spheres with a Sauter mean diameter of 861 micron and a density of 800 kg/m3. Three superficial gas velocities of 6.55 m/s, 10.67 m/s and 13.72 m/s were used in this study. For the case of superficial gas velocity 6.55 m/s, the experimental data show that the transition from dilute upflow to core-annular flow occurred when the solids flux was about 7 kg/m{sup 2}-s and the transition from core-annular flow to dense suspension upflow was about 147 kg/m{sup 2}-s. As the superficial gas velocity was increased to 10.67 m/s the corresponding flow regime transitions were at 34 kg/m{sup 2}-s and 205 kg/m{sup 2}-s, respectively. For the case of superficial gas velocity of 13.72 m/s the data showed no distinct transition of flow regimes. The particles were all upflow for the range of solids fluxes from 10 kg/m{sup 2}-s to 286 kg/m{sup 2}-s.« less

Dense plasma chemistry of hydrocarbons at conditions relevant to planetary interiors and inertial confinement fusion

NASA Astrophysics Data System (ADS)

Kraus, Dominik

2017-10-01

Carbon-hydrogen demixing and subsequent diamond precipitation has been predicted to strongly participate in shaping the internal structure and evolution of icy giant planets like Neptune and Uranus. The very same dense plasma chemistry is also a potential concern for CH plastic ablator materials in inertial confinement fusion (ICF) experiments where similar conditions are present during the first compression stage of the imploding capsule. Here, carbon-hydrogen demixing may enhance the hydrodynamic instabilities occurring in the following compression stages. First experiments applying dynamic compression and ultrafast in situ X-ray diffraction at SLAC's Linac Coherent Light Source demonstrated diamond formation from polystyrene (CH) at 150 GPa and 5000 K. Very recent experiments have now investigated the influence of oxygen, which is highly abundant in icy giant planets on the phase separation process. Compressing PET (C5H4O2) and PMMA(C5H8O2), we find again diamond formation at pressures above 150 GPa and temperatures of several thousand kelvins, showing no strong effect due to the presence of oxygen. Thus, diamond precipitation deep inside icy giant planets seems very likely. Moreover, small-angle X-ray scattering (SAXS) was added to the platform, which determines an upper limit for the diamond particle size, while the width of the diffraction features provides a lower limit. We find that diamond particles of several nanometers in size are formed on a nanosecond timescale. Finally, spectrally resolved X-ray scattering is used to scale amorphous diffraction signals and allows for determining the amount of carbon-hydrogen demixing inside the compressed samples even if no crystalline diamond is formed. This whole set of diagnostics provides unprecedented insights into the nanosecond kinetics of dense plasma chemistry.

Contact-aware simulations of particulate Stokesian suspensions

NASA Astrophysics Data System (ADS)

Lu, Libin; Rahimian, Abtin; Zorin, Denis

2017-10-01

We present an efficient, accurate, and robust method for simulation of dense suspensions of deformable and rigid particles immersed in Stokesian fluid in two dimensions. We use a well-established boundary integral formulation for the problem as the foundation of our approach. This type of formulation, with a high-order spatial discretization and an implicit and adaptive time discretization, have been shown to be able to handle complex interactions between particles with high accuracy. Yet, for dense suspensions, very small time-steps or expensive implicit solves as well as a large number of discretization points are required to avoid non-physical contact and intersections between particles, leading to infinite forces and numerical instability. Our method maintains the accuracy of previous methods at a significantly lower cost for dense suspensions. The key idea is to ensure interference-free configuration by introducing explicit contact constraints into the system. While such constraints are unnecessary in the formulation, in the discrete form of the problem, they make it possible to eliminate catastrophic loss of accuracy by preventing contact explicitly. Introducing contact constraints results in a significant increase in stable time-step size for explicit time-stepping, and a reduction in the number of points adequate for stability.

Numerically Exact Computer Simulations of Light Scattering by Densely Packed, Random Particulate Media

NASA Technical Reports Server (NTRS)

Dlugach, Janna M.; Mishchenko, Michael I.; Liu, Li; Mackowski, Daniel W.

2011-01-01

Direct computer simulations of electromagnetic scattering by discrete random media have become an active area of research. In this progress review, we summarize and analyze our main results obtained by means of numerically exact computer solutions of the macroscopic Maxwell equations. We consider finite scattering volumes with size parameters in the range, composed of varying numbers of randomly distributed particles with different refractive indices. The main objective of our analysis is to examine whether all backscattering effects predicted by the low-density theory of coherent backscattering (CB) also take place in the case of densely packed media. Based on our extensive numerical data we arrive at the following conclusions: (i) all backscattering effects predicted by the asymptotic theory of CB can also take place in the case of densely packed media; (ii) in the case of very large particle packing density, scattering characteristics of discrete random media can exhibit behavior not predicted by the low-density theories of CB and radiative transfer; (iii) increasing the absorptivity of the constituent particles can either enhance or suppress typical manifestations of CB depending on the particle packing density and the real part of the refractive index. Our numerical data strongly suggest that spectacular backscattering effects identified in laboratory experiments and observed for a class of high-albedo Solar System objects are caused by CB.

Numerical modeling for dilute and dense sprays

NASA Technical Reports Server (NTRS)

Chen, C. P.; Kim, Y. M.; Shang, H. M.; Ziebarth, J. P.; Wang, T. S.

1992-01-01

We have successfully implemented a numerical model for spray-combustion calculations. In this model, the governing gas-phase equations in Eulerian coordinate are solved by a time-marching multiple pressure correction procedure based on the operator-splitting technique. The droplet-phase equations in Lagrangian coordinate are solved by a stochastic discrete particle technique. In order to simplify the calculation procedure for the circulating droplets, the effective conductivity model is utilized. The k-epsilon models are utilized to characterize the time and length scales of the gas phase in conjunction with turbulent modulation by droplets and droplet dispersion by turbulence. This method entails random sampling of instantaneous gas flow properties and the stochastic process requires a large number of computational parcels to produce the satisfactory dispersion distributions even for rather dilute sprays. Two major improvements in spray combustion modelings were made. Firstly, we have developed a probability density function approach in multidimensional space to represent a specific computational particle. Secondly, we incorporate the Taylor Analogy Breakup (TAB) model for handling the dense spray effects. This breakup model is based on the reasonable assumption that atomization and drop breakup are indistinguishable processes within a dense spray near the nozzle exit. Accordingly, atomization is prescribed by injecting drops which have a characteristic size equal to the nozzle exit diameter. Example problems include the nearly homogeneous and inhomogeneous turbulent particle dispersion, and the non-evaporating, evaporating, and burning dense sprays. Comparison with experimental data will be discussed in detail.

Toroidal-spiral particles for codelivery of anti-VEGFR-2 antibody and irinotecan: a potential implant to hinder recurrence of glioblastoma multiforme.

PubMed

Sharma, Vishal; Köllmer, Melanie; Szymusiak, Magdalena; Nitsche, Ludwig C; Gemeinhart, Richard A; Liu, Ying

2014-03-10

Heterogeneous toroidal-spiral particles (TSPs) were generated by polymer droplet sedimentation, interaction, and cross-linking. TSPs provide a platform for encapsulation and release of multiple compounds of different sizes and physicochemical properties. As a model system, we demonstrate the encapsulation and independently controlled release of an anti-VEGFR-2 antibody and irinotecan for the treatment of glioblastoma multiforme. The anti-VEGFR-2 antibody was released from the TS channels and its binding to HUVECs was confirmed by confocal microscopy and flow cytometry, suggesting active antibody encapsulation and release. Irinotecan, a small molecule drug, was released from the dense polymer matrix of poly(ethylene glycol) diacrylate (MW ~ 700 g/mol; PEGDA 700). Released irinotecan inhibited the proliferation of U251 malignant glioma cells. Since the therapeutic compounds are released through different pathways, specifically diffusion through the polymer matrix versus TS channels, the release rate can be controlled independently through the design of the structure and material of particle components.

Theory of molecular crowding in Brownian hard-sphere liquids.

PubMed

Zaccone, Alessio; Terentjev, Eugene M

2012-06-01

We derive an analytical pair potential of mean force for Brownian molecules in the liquid state. Our approach accounts for many-particle correlations of crowding particles of the liquid and for diffusive transport across the spatially modulated local density of crowders in the dense environment. Focusing on the limit of equal-size particles, we show that this diffusive transport leads to additional density- and structure-dependent terms in the interaction potential and to a much stronger attraction (by a factor of ≈4 at average volume fraction of crowders φ{0}=0.25) than in the standard depletion interaction where the diffusive effects are neglected. As an illustration of the theory, we use it to study the size of a polymer chain in a solution of inert crowders. Even in the case of an athermal background solvent, when a classical chain should be fully swollen, we find a sharp coil-globule transition of the ideal chain collapsing at a critical value of the crowder volume fraction φ{c}≈0.145.

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

Solis, Kyle J.; Martin, James E.

In recent years a rich variety of emergent phenomena have been observed when suspensions of magnetic particles are subjected to alternating magnetic fields. These particle assemblies often exhibit vigorous dynamics due to the injection of energy from the field. These include surface and interface phenomena, such as highly organized, segmented “snakes” that can be induced to swim by structural symmetry breaking, and “asters” and “anti-asters,” particle assemblies that can be manipulated to capture and transport cargo. In bulk suspensions of magnetic platelets subjected to multiaxial alternating fields, advection lattices and even vortex lattices have been created, and a variety ofmore » biomimetic dynamics – serpents, bees and amoebas – have been discovered in magnetic fluids suspended in an immiscible liquid. In this paper several new driven phases are presented, including flying chevrons, dense spinning clusters, filaments, and examples of phase coexistence in driven phases. These observations broaden the growing field of driven magnetic suspensions and present new challenges to those interested in simulating the dynamics of these complex systems.« less

Droplet formation and scaling in dense suspensions

PubMed Central

Miskin, Marc Z.; Jaeger, Heinrich M.

2012-01-01

When a dense suspension is squeezed from a nozzle, droplet detachment can occur similar to that of pure liquids. While in pure liquids the process of droplet detachment is well characterized through self-similar profiles and known scaling laws, we show here the simple presence of particles causes suspensions to break up in a new fashion. Using high-speed imaging, we find that detachment of a suspension drop is described by a power law; specifically we find the neck minimum radius, rm, scales like near breakup at time τ = 0. We demonstrate data collapse in a variety of particle/liquid combinations, packing fractions, solvent viscosities, and initial conditions. We argue that this scaling is a consequence of particles deforming the neck surface, thereby creating a pressure that is balanced by inertia, and show how it emerges from topological constraints that relate particle configurations with macroscopic Gaussian curvature. This new type of scaling, uniquely enforced by geometry and regulated by the particles, displays memory of its initial conditions, fails to be self-similar, and has implications for the pressure given at generic suspension interfaces. PMID:22392979

Topical application of nanoparticles: prospects and safety aspects (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lademann, Jürgen M.; Richter, Heike; Jung, Sora; Meinke, Martina C.; Rühl, Eckart; Alexiev, Ulrike; Calderon, Marcelo; Patzelt, Alexa

2016-03-01

The requirements on nanoparticles for cosmetic and medical applications are very different. While nanoparticles applied in sunscreens shall remain on the skin surface or in the upper cell layers of the stratum corneum, nanoparticles for medical drug delivery shall penetrate through the skin barrier to the target structures in the living cells. Under the Collaborative Research Project 1112 various methods are used at the CCP to investigate the cutaneous penetration and storage of nanoparticles, hair follicles being in the focus of attention. Human hair follicles are ideal target structures for drug delivery. Hosting both the stem and dendritic cells, they are surrounded by a dense network of blood vessels. Investigating nanoparticles of different size and materials, particles of approximately 600 nm in diameter were found to penetrate best into the hair follicles, where they can be stored for maximally 10 days. Their retention time in the hair follicles exceeds that in the stratum corneum by almost one order of magnitude. Particles penetrate more efficiently into the hair follicles than non-particulate substances. For particles from 40 nm-1 µm in diameter, however, no follicular penetration has been detectable if the skin barrier was intact. This is plausible as the hair follicle has its own barrier. It will be demonstrated that the best way for drug delivery is the application of drug-loaded particulate carrier systems. In the hair follicles the particles may either dissolve and release the drug, or an external signal must trigger the drug release from the particle.

Volcanic explosion clouds - Density, temperature, and particle content estimates from cloud motion

NASA Technical Reports Server (NTRS)

Wilson, L.; Self, S.

1980-01-01

Photographic records of 10 vulcanian eruption clouds produced during the 1978 eruption of Fuego Volcano in Guatemala have been analyzed to determine cloud velocity and acceleration at successive stages of expansion. Cloud motion is controlled by air drag (dominant during early, high-speed motion) and buoyancy (dominant during late motion when the cloud is convecting slowly). Cloud densities in the range 0.6 to 1.2 times that of the surrounding atmosphere were obtained by fitting equations of motion for two common cloud shapes (spheres and vertical cylinders) to the observed motions. Analysis of the heat budget of a cloud permits an estimate of cloud temperature and particle weight fraction to be made from the density. Model results suggest that clouds generally reached temperatures within 10 K of that of the surrounding air within 10 seconds of formation and that dense particle weight fractions were less than 2% by this time. The maximum sizes of dense particles supported by motion in the convecting clouds range from 140 to 1700 microns.

Hypernuclei and the hyperon problem in neutron stars

DOE PAGES

Bedaque, Paulo F.; Steiner, Andrew W.

2015-08-17

The likely presence ofmore » $$\\Lambda$$ baryons in dense hadronic matter tends to soften the equation of state to an extend that the observed heaviest neutron stars are difficult to explain. Here we analyze this "hyperon problem" with a phenomenological approach. First, we review what can be learned about the interaction of $$\\Lambda$$ particle with dense matter from the observed hypernuclei and extend this phenomenological analysis to asymmetric matter. We add to this the current knowledge on non-strange dense matter, including its uncertainties, to conclude that the interaction between $$\\Lambda$$s and dense matter has to become repulsive at densities below three times the nuclear saturation density.« less

Dust Charging in Saturn's Rings: Observations and Theory

NASA Astrophysics Data System (ADS)

Horanyi, M.

2008-12-01

Saturn's rings show a variety of dusty plasma processes. The electrostatic charging and subsequent orbital dynamics of small grains can establish their size and spatial distributions, for example. Simultaneously, dust can alter the composition, density and temperature of the plasma surrounding it. The dynamics of charged dust particles can be surprisingly complex and fundamentally different from the well understood limits of gravitationally dominated motions of neutral particles or the adiabatic motion of electrons and ions in electromagnetic fields that dominate gravity. This talk will focus on recent Cassini observations at Saturn that are best explained by theories describing the effects of the magnetospheric fields and plasmas on the rings. As our best examples, we will discuss the physics describing the large-scale structure of the E-ring, and the formation of 'spokes' over the dense rings of Saturn.

Following in Real Time the Two-Step Assembly of Nanoparticles into Mesocrystals in Levitating Drops.

PubMed

Agthe, Michael; Plivelic, Tomás S; Labrador, Ana; Bergström, Lennart; Salazar-Alvarez, German

2016-11-09

Mesocrystals composed of crystallographically aligned nanocrystals are present in biominerals and assembled materials which show strongly directional properties of importance for mechanical protection and functional devices. Mesocrystals are commonly formed by complex biomineralization processes and can also be generated by assembly of anisotropic nanocrystals. Here, we follow the evaporation-induced assembly of maghemite nanocubes into mesocrystals in real time in levitating drops. Analysis of time-resolved small-angle X-ray scattering data and ex situ scanning electron microscopy together with interparticle potential calculations show that the substrate-free, particle-mediated crystallization process proceeds in two stages involving the formation and rapid transformation of a dense, structurally disordered phase into ordered mesocrystals. Controlling and tailoring the particle-mediated formation of mesocrystals could be utilized to assemble designed nanoparticles into new materials with unique functions.

A charging model for three-axis stabilized spacecraft

NASA Technical Reports Server (NTRS)

Massaro, M. J.; Green, T.; Ling, D.

1977-01-01

A charging model was developed for geosynchronous, three-axis stabilized spacecraft when under the influence of a geomagnetic substorm. The differential charging potentials between the thermally coated or blanketed outer surfaces and metallic structure of a spacecraft were determined when the spacecraft was immersed in a dense plasma cloud of energetic particles. The spacecraft-to-environment interaction was determined by representing the charged particle environment by equivalent current source forcing functions and by representing the spacecraft by its electrically equivalent circuit with respect to the plasma charging phenomenon. The charging model included a sun/earth/spacecraft orbit model that simulated the sum illumination conditions of the spacecraft outer surfaces throughout the orbital flight on a diurnal as well as a seasonal basis. Transient and steady-state numerical results for a three-axis stabilized spacecraft are presented.

Efficient energy absorption of intense ps-laser pulse into nanowire target

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

Habara, H.; Honda, S.; Katayama, M.

The interaction between ultra-intense laser light and vertically aligned carbon nanotubes is investigated to demonstrate efficient laser-energy absorption in the ps laser-pulse regime. Results indicate a clear enhancement of the energy conversion from laser to energetic electrons and a simultaneously small plasma expansion on the surface of the target. A two-dimensional plasma particle calculation exhibits a high absorption through laser propagation deep into the nanotube array, even for a dense array whose structure is much smaller than the laser wavelength. The propagation leads to the radial expansion of plasma perpendicular to the nanotubes rather than to the front side. Thesemore » features may contribute to fast ignition in inertial confinement fusion and laser particle acceleration, both of which require high current and small surface plasma simultaneously.« less

Scientific program and abstracts

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

Gerich, C.

1983-01-01

The Fifth International Conference on High-Power Particle Beams is organized jointly by the Lawrence Livermore National Laboratory and Physics International Company. As in the previous conferences in this series, the program includes the following topics: high-power, electron- and ion-beam acceleration and transport; diode physics; high-power particle beam interaction with plasmas and dense targets; particle beam fusion (inertial confinement); collective ion acceleration; particle beam heating of magnetically confined plasmas; and generation of microwave/free-electron lasers.

Measurements of the principal Hugoniots of dense gaseous deuterium-helium mixtures: Combined multi-channel optical pyrometry, velocity interferometry, and streak optical pyrometry measurements

NASA Astrophysics Data System (ADS)

Li, Zhi-Guo; Chen, Qi-Feng; Gu, Yun-Jun; Zheng, Jun; Chen, Xiang-Rong

2016-10-01

The accurate hydrodynamic description of an event or system that addresses the equations of state, phase transitions, dissociations, ionizations, and compressions, determines how materials respond to a wide range of physical environments. To understand dense matter behavior in extreme conditions requires the continual development of diagnostic methods for accurate measurements of the physical parameters. Here, we present a comprehensive diagnostic technique that comprises optical pyrometry, velocity interferometry, and time-resolved spectroscopy. This technique was applied to shock compression experiments of dense gaseous deuterium-helium mixtures driven via a two-stage light gas gun. The advantage of this approach lies in providing measurements of multiple physical parameters in a single experiment, such as light radiation histories, particle velocity profiles, and time-resolved spectra, which enables simultaneous measurements of shock velocity, particle velocity, pressure, density, and temperature and expands understanding of dense high pressure shock situations. The combination of multiple diagnostics also allows different experimental observables to be measured and cross-checked. Additionally, it implements an accurate measurement of the principal Hugoniots of deuterium-helium mixtures, which provides a benchmark for the impedance matching measurement technique.

Fluid-Driven Deformation of a Soft Granular Material

NASA Astrophysics Data System (ADS)

MacMinn, Christopher W.; Dufresne, Eric R.; Wettlaufer, John S.

2015-01-01

Compressing a porous, fluid-filled material drives the interstitial fluid out of the pore space, as when squeezing water out of a kitchen sponge. Inversely, injecting fluid into a porous material can deform the solid structure, as when fracturing a shale for natural gas recovery. These poromechanical interactions play an important role in geological and biological systems across a wide range of scales, from the propagation of magma through Earth's mantle to the transport of fluid through living cells and tissues. The theory of poroelasticity has been largely successful in modeling poromechanical behavior in relatively simple systems, but this continuum theory is fundamentally limited by our understanding of the pore-scale interactions between the fluid and the solid, and these problems are notoriously difficult to study in a laboratory setting. Here, we present a high-resolution measurement of injection-driven poromechanical deformation in a system with granular microsctructure: We inject fluid into a dense, confined monolayer of soft particles and use particle tracking to reveal the dynamics of the multiscale deformation field. We find that a continuum model based on poroelasticity theory captures certain macroscopic features of the deformation, but the particle-scale deformation field exhibits dramatic departures from smooth, continuum behavior. We observe particle-scale rearrangement and hysteresis, as well as petal-like mesoscale structures that are connected to material failure through spiral shear banding.

Constrained Sintering in Fabrication of Solid Oxide Fuel Cells

PubMed Central

Lee, Hae-Weon; Park, Mansoo; Hong, Jongsup; Kim, Hyoungchul; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook

2016-01-01

Solid oxide fuel cells (SOFCs) are inevitably affected by the tensile stress field imposed by the rigid substrate during constrained sintering, which strongly affects microstructural evolution and flaw generation in the fabrication process and subsequent operation. In the case of sintering a composite cathode, one component acts as a continuous matrix phase while the other acts as a dispersed phase depending upon the initial composition and packing structure. The clustering of dispersed particles in the matrix has significant effects on the final microstructure, and strong rigidity of the clusters covering the entire cathode volume is desirable to obtain stable pore structure. The local constraints developed around the dispersed particles and their clusters effectively suppress generation of major process flaws, and microstructural features such as triple phase boundary and porosity could be readily controlled by adjusting the content and size of the dispersed particles. However, in the fabrication of the dense electrolyte layer via the chemical solution deposition route using slow-sintering nanoparticles dispersed in a sol matrix, the rigidity of the cluster should be minimized for the fine matrix to continuously densify, and special care should be taken in selecting the size of the dispersed particles to optimize the thermodynamic stability criteria of the grain size and film thickness. The principles of constrained sintering presented in this paper could be used as basic guidelines for realizing the ideal microstructure of SOFCs. PMID:28773795

Multiscale structure, interfacial cohesion, adsorbed layers, miscibility and properties in dense polymer-particle mixtures

NASA Astrophysics Data System (ADS)

Schweizer, Ken

2012-02-01

A major goal in polymer nanocomposite research is to understand and predict how the chemical and physical nature of individual polymers and nanoparticles, and thermodynamic state (temperature, composition, solvent dilution, filler loading), determine bulk assembly, miscibility and properties. Microscopic PRISM theory provides a route to this goal for equilibrium disordered mixtures. A major prediction is that by manipulating the net polymer-particle interfacial attraction, miscibility is realizable via the formation of thin thermodynamically stable adsorbed layers, which, however, are destroyed by entropic depletion and bridging attraction effects if interface cohesion is too weak or strong, respectively. This and related issues are quantitatively explored for miscible mixtures of hydrocarbon polymers, silica nanospheres, and solvent using x-ray scattering, neutron scattering and rheology. Under melt conditions, quantitative agreement between theory and silica scattering experiments is achieved under both steric stabilization and weak depletion conditions. Using contrast matching neutron scattering to characterize the collective structure factors of polymers, particles and their interface, the existence and size of adsorbed polymer layers, and their consequences on microstructure, is determined. Failure of the incompressible RPA, accuracy of PRISM theory, the nm thickness of adsorbed layers, and qualitative sensitivity of the bulk modulus to interfacial cohesion and particle size are demonstrated for concentrated PEO-silica-ethanol nanocomposites. Temperature-dependent complexity is discovered when water is the solvent, and nonequilibrium effects emerge for adsorbing entangled polymers that strongly impact structure. By varying polymer chemistry, the effect of polymer-particle attraction on the intrinsic viscosity is explored with striking non-classical effects observed. This work was performed in collaboration with S.Y.Kim, L.M.Hall, C.Zukoski and B.Anderson.

Inner Edges of Compact Debris Disks around Metal-rich White Dwarfs

NASA Astrophysics Data System (ADS)

Rafikov, Roman R.; Garmilla, José A.

2012-12-01

A number of metal-rich white dwarfs (WDs) are known to host compact, dense particle disks, which are thought to be responsible for metal pollution of these stars. In many such systems, the inner radii of disks inferred from their spectra are so close to the WD that particles directly exposed to starlight must be heated above 1500 K and are expected to be unstable against sublimation. To reconcile this expectation with observations, we explore particle sublimation in H-poor debris disks around WDs. We show that because of the high metal vapor pressure the characteristic sublimation temperature in these disks is 300-400 K higher than in their protoplanetary analogs, allowing particles to survive at higher temperatures. We then look at the structure of the inner edges of debris disks and show that they should generically feature superheated inner rims directly exposed to starlight with temperatures reaching 2500-3500 K. Particles migrating through the rim toward the WD (and rapidly sublimating) shield the disk behind them from strong stellar heating, making the survival of solids possible close to the WD. Our model agrees well with observations of WD+disk systems provided that disk particles are composed of Si-rich material such as olivine, and have sizes in the range ~0.03-30 cm.

Warm spraying—a novel coating process based on high-velocity impact of solid particles

PubMed Central

Kuroda, Seiji; Kawakita, Jin; Watanabe, Makoto; Katanoda, Hiroshi

2008-01-01

In recent years, coating processes based on the impact of high-velocity solid particles such as cold spraying and aerosol deposition have been developed and attracting much industrial attention. A novel coating process called ‘warm spraying’ has been developed, in which coatings are formed by the high-velocity impact of solid powder particles heated to appropriate temperatures below the melting point of the powder material. The advantages of such process are as follows: (1) the critical velocity needed to form a coating can be significantly lowered by heating, (2) the degradation of feedstock powder such as oxidation can be significantly controlled compared with conventional thermal spraying where powder is molten, and (3) various coating structures can be realized from porous to dense ones by controlling the temperature and velocity of the particles. The principles and characteristics of this new process are discussed in light of other existing spray processes such as high-velocity oxy-fuel spraying and cold spraying. The gas dynamics of particle heating and acceleration by the spraying apparatus as well as the high-velocity impact phenomena of powder particles are discussed in detail. Several examples of depositing heat sensitive materials such as titanium, metallic glass, WC–Co cermet and polymers are described with potential industrial applications. PMID:27877996

Warm spraying-a novel coating process based on high-velocity impact of solid particles.

PubMed

Kuroda, Seiji; Kawakita, Jin; Watanabe, Makoto; Katanoda, Hiroshi

2008-07-01

In recent years, coating processes based on the impact of high-velocity solid particles such as cold spraying and aerosol deposition have been developed and attracting much industrial attention. A novel coating process called 'warm spraying' has been developed, in which coatings are formed by the high-velocity impact of solid powder particles heated to appropriate temperatures below the melting point of the powder material. The advantages of such process are as follows: (1) the critical velocity needed to form a coating can be significantly lowered by heating, (2) the degradation of feedstock powder such as oxidation can be significantly controlled compared with conventional thermal spraying where powder is molten, and (3) various coating structures can be realized from porous to dense ones by controlling the temperature and velocity of the particles. The principles and characteristics of this new process are discussed in light of other existing spray processes such as high-velocity oxy-fuel spraying and cold spraying. The gas dynamics of particle heating and acceleration by the spraying apparatus as well as the high-velocity impact phenomena of powder particles are discussed in detail. Several examples of depositing heat sensitive materials such as titanium, metallic glass, WC-Co cermet and polymers are described with potential industrial applications.

Heuristic rule for binary superlattice coassembly: mixed plastic mesophases of hard polyhedral nanoparticles.

PubMed

Khadilkar, Mihir R; Escobedo, Fernando A

2014-10-17

Sought-after ordered structures of mixtures of hard anisotropic nanoparticles can often be thermodynamically unfavorable due to the components' geometric incompatibility to densely pack into regular lattices. A simple compatibilization rule is identified wherein the particle sizes are chosen such that the order-disorder transition pressures of the pure components match (and the entropies of the ordered phases are similar). Using this rule with representative polyhedra from the truncated-cube family that form pure-component plastic crystals, Monte Carlo simulations show the formation of plastic-solid solutions for all compositions and for a wide range of volume fractions.

Thermoelectric Properties Studies on n-type Bi2Te3-xSex

NASA Astrophysics Data System (ADS)

Yang, Jian; Yan, Xiao; Ma, Yi; Poudel, Bed; Lan, Yucheng; Wang, D. Z.; Ren, Z. F.; Hao, Q.; Chen, G.

2008-03-01

Bi2Te3-xSex is a classic room temperature n-type thermoelectric material. In spite of the long history of research, its ZT is still below 1. By directly making nano sized particles using mechanical alloy from element, then pressing the nanoparticles into 100% dense bulk sample with nano-structures by hot press, we expect to decrease the thermal conductivity by the increased grain boundary scattering of phonons so to improve the ZT above 1. The ratio of Te/Se was varied systematically to investigate its effect on thermal conductivity.

Study of the Anatomy of the X-Ray and Neutron Production Scaling Laws in the Plasma Focus.

DTIC Science & Technology

1980-05-15

plasma focus discharge in deuterium as an extension of our previous work on scaling laws of x-ray and neutron production. The structure of dense plasmoids which emit MeV ions has been recorded by ion imaging with pinhole camera and contact print techniques. The plasmoids are generated in the same region in which particle beams, neutron and x-ray emission reach a maximum of intensity. Sharply defined boundaries of the ion-beam source and of plasmoids have been obtained by ion track etching on plastic material

Complex patchy colloids shaped from deformable seed particles through capillary interactions.

PubMed

Meester, V; Kraft, D J

2018-02-14

We investigate the mechanisms underlying the reconfiguration of random aggregates of spheres through capillary interactions, the so-called "colloidal recycling" method, to fabricate a wide variety of patchy particles. We explore the influence of capillary forces on clusters of deformable seed particles by systematically varying the crosslink density of the spherical seeds. Spheres with a poorly crosslinked polymer network strongly deform due to capillary forces and merge into large spheres. With increasing crosslink density and therefore rigidity, the shape of the spheres is increasingly preserved during reconfiguration, yielding patchy particles of well-defined shape for up to five spheres. In particular, we find that the aspect ratio between the length and width of dumbbells, L/W, increases with the crosslink density (cd) as L/W = B - A·exp(-cd/C). For clusters consisting of more than five spheres, the particle deformability furthermore determines the patch arrangement of the resulting particles. The reconfiguration pathway of clusters of six densely or poorly crosslinked seeds leads to octahedral and polytetrahedral shaped patchy particles, respectively. For seven particles several geometries were obtained with a preference for pentagonal dipyramids by the rigid spheres, while the soft spheres do rarely arrive in these structures. Even larger clusters of over 15 particles form non-uniform often aspherical shapes. We discuss that the reconfiguration pathway is largely influenced by confinement and geometric constraints. The key factor which dominates during reconfiguration depends on the deformability of the spherical seed particles.

A Bottle-around-a-Ship Method To Generate Hollow Thin-Shelled Particles Containing Encapsulated Iron Species with Application to the Environmental Decontamination of Chlorinated Compounds.

PubMed

Su, Yang; Wang, Yingqing; Owoseni, Olasehinde; Zhang, Yueheng; Gamliel, David Pierce; Valla, Julia A; McPherson, Gary L; John, Vijay T

2018-04-25

Thin-shelled hollow silica particles are synthesized using an aerosol-based process where the concentration of a silica precursor tetraethyl orthosilicate (TEOS) determines the shell thickness. The synthesis involves a novel concept of the salt bridging of an iron salt, FeCl 3 , to a cationic surfactant, cetyltrimethylammonium bromide (CTAB), which modulates the templating effect of the surfactant on silica porosity. The salt bridging leads to a sequestration of the surfactant in the interior of the droplet with the formation of a dense silica shell around the organic material. Subsequent calcination consistently results in hollow particles with encapsulated iron oxides. Control of the TEOS levels leads to the generation of ultrathin-shelled (∼10 nm) particles which become susceptible to rupture upon exposure to ultrasound. The dense silica shell that is formed is impervious to entry of chemical species. Mesoporosity is restored to the shell through desilication and reassembly, again using CTAB as a template. The mesoporous-shelled hollow particles show good reactivity toward the reductive dichlorination of trichloroethylene (TCE), indicating access of TCE to the particle interior. The ordered mesoporous thin-shelled particles containing active iron species are viable systems for chemical reaction and catalysis.

Dry-growth of silver single-crystal nanowires from porous Ag structure

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

Chen, Chuantong, E-mail: chenchuantong@sanken.osaka-u.ac.jp; Nagao, Shijo; Jiu, Jinting

A fabrication method of single crystal Ag nanowires in large scale is introduced without any chemical synthesis in wet processes, which usually generates fivefold twinned nanowires of fcc metals. Dense single-crystal nanowires grow on a mechanically polished surface of micro-porous Ag structure, which is created from Ag micro-particles. The diameter and the length of the nanowires can be controlled simply by changing the temperature and the time of the heating during the nanowire growth in air. Unique growth mechanism is described in detail, based on stress-induced migration accelerated by the micro-porous structure where the origin of Ag nanowires growth ismore » incubated. Transmission electron microscopy analysis on the single crystal nanowires is also presented. This simple method offered an alternative preparation for metallic nanowires, especially with the single crystal structure in numerous applications.« less

Meteor research program

NASA Technical Reports Server (NTRS)

Southworth, R. B.; Mccrosky, R. E.

1970-01-01

An overview of research on radio and radar meteors accomplished during the past decade is presented, and the work of the past year is highlighted. Velocity distribution and mass flux data are obtained for meteors in the range 10 to 0.0001 g, the size believed to be the principal hazard to space missions. The physical characteristics of mass, structure and density, luminosity, and ablation are briefly described, and the formulation of a theory for interactions of ionization and excitation during collision of atomic particles is mentioned. Five classes of meteoroids are identified, including the two of iron and stone meteorites. Stream meteors associated with known comets are Classes A or C, and parent comets of Class B streams are not observed. Class A meteoroids are identified with the core of a cometary nucleus, Class C with less dense surface of the nucleus after sublimation of ices, and Class B with less dense cores of smaller cometary nuclei. Atmospheric meteor phenomena associated with winds and gravity waves, density and temperature, atomic oxygen, and meteor rate changes are mentioned.

Method of forming a plasma sprayed interconnection layer on an electrode of an electrochemical cell

DOEpatents

Spengler, Charles J.; Folser, George R.; Vora, Shailesh D.; Kuo, Lewis; Richards, Von L.

1995-01-01

A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by plasma spraying doped LaCrO.sub.3 powder, preferably compensated with chromium as Cr.sub.2 O.sub.3 and/or dopant element, preferably by plasma arc spraying; and, (C) heating the doped and compensated LaCrO.sub.3 layer to about 1100.degree. C. to 1300.degree. C. to provide a dense, substantially gas-tight, substantially hydration-free, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the unselected portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell.

Method of forming a plasma sprayed interconnection layer on an electrode of an electrochemical cell

DOEpatents

Spengler, C.J.; Folser, G.R.; Vora, S.D.; Kuo, L.; Richards, V.L.

1995-06-20

A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by plasma spraying doped LaCrO{sub 3} powder, preferably compensated with chromium as Cr{sub 2}O{sub 3} and/or dopant element, preferably by plasma arc spraying; and, (C) heating the doped and compensated LaCrO{sub 3} layer to about 1100 C to 1300 C to provide a dense, substantially gas-tight, substantially hydration-free, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the unselected portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell. 6 figs.

Nanoengineering of bioactive glasses: hollow and dense nanospheres

NASA Astrophysics Data System (ADS)

Luz, Gisela M.; Mano, João F.

2013-02-01

The possibility of engineering bioactive glass (BG) nanoparticles into suitable sizes and shapes represents a significant achievement regarding the development of new osteoconductive biomaterials for therapeutic strategies to replace or regenerate damaged mineralised tissues. Herein we report the structural and chemical evolution of sol-gel derived BG nanoparticles for both the binary (SiO2:CaO (mol%) = 70:30) and ternary (SiO2:CaO:P2O5 (mol%) = 55:40:5) formulations, in order to understand how the particles formation can be directed. Hollow BG nanospheres were obtained through Ostwald ripening. The presence of a non ionic surfactant, poly(ethylene glycol) (PEG), allowed the formation of dense BG nanospheres with controllable diameters depending on the molecular weight of PEG. A deep insight into the genesis of BG nanoparticles formation is essential to design BG based materials with controlled compositions, morphologies and sizes at the nanoscale, in order to improve their performance in orthopaedic applications including bone tissue engineering.

ALEGRA-HEDP simulations of the dense plasma focus.

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

Flicker, Dawn G.; Kueny, Christopher S.; Rose, David V.

We have carried out 2D simulations of three dense plasma focus (DPF) devices using the ALEGRA-HEDP code and validated the results against experiments. The three devices included two Mather-type machines described by Bernard et. al. and the Tallboy device currently in operation at NSTec in North Las Vegas. We present simulation results and compare to detailed plasma measurements for one Bernard device and to current and neutron yields for all three. We also describe a new ALEGRA capability to import data from particle-in-cell calculations of initial gas breakdown, which will allow the first ever simulations of DPF operation from themore » beginning of the voltage discharge to the pinch phase for arbitrary operating conditions and without assumptions about the early sheath structure. The next step in understanding DPF pinch physics must be three-dimensional modeling of conditions going into the pinch, and we have just launched our first 3D simulation of the best-diagnosed Bernard device.« less

Simulating immersed particle collisions: the Devil's in the details

NASA Astrophysics Data System (ADS)

Biegert, Edward; Vowinckel, Bernhard; Meiburg, Eckart

2015-11-01

Simulating densely-packed particle-laden flows with any degree of confidence requires accurate modeling of particle-particle collisions. To this end, we investigate a few collision models from the fluids and granular flow communities using sphere-wall collisions, which have been studied by a number of experimental groups. These collisions involve enough complexities--gravity, particle-wall lubrication forces, particle-wall contact stresses, particle-wake interactions--to challenge any collision model. Evaluating the successes and shortcomings of the collision models, we seek improvements in order to obtain more consistent results. We will highlight several implementation details that are crucial for obtaining accurate results.

Additional flux of particles and albedo-electrons in upper atmosphere

NASA Technical Reports Server (NTRS)

Aitbaev, F. B.; Dyuisembaev, B. M.; Kolomeets, E. V.

1985-01-01

The results are presented of the Monte Carlo simulation of albedo flux from the dense layers of the Earth's atmosphere and the dependence of angular distribution on the rigidity of geomagnetic cut off and additional flux of particles at the depth in the atmosphere 15-20 g/sq sm. Influence of geomagnetic field on the propagation of charged particles was not taken into account.

A granular flow model for dense planetary rings

NASA Technical Reports Server (NTRS)

Borderies, N.; Goldreich, P.; Tremaine, S.

1985-01-01

In the present study of the viscosity of a differentially rotating particle disk, in the limiting case where the particles are densely packed and their collective behavior resembles that of a liquid, the pressure tensor is derived from both the equations of hydrodynamics and a simple kinetic model of collisions due to Haff (1983). Density waves and narrow circular rings are unstable if the liquid approximation applies, and the consequent nonlinear perturbations may generate 'splashing' of the ring material in the vertical direction. These results are pertinent to the origin of the ellipticities of ringlets, the nonaxisymmetric features near the outer edge of the Saturn B ring, and unexplained residuals in kinematic models of the Saturn and Uranus rings.

The role of collective self-gravity in the nonlinear evolution of viscous overstability in Saturn's rings

NASA Astrophysics Data System (ADS)

Lehmann, M.; Schmidt, J.; Salo, H.

2017-09-01

Observational evidence for the presence of axisymmetric periodic micro-structure on length scales of 100m - 200m in Saturn's A and B rings was revealed by several instruments onboard the Cassini mission to Saturn. The structure was seen in radio occultations performed by the Radio Science Subsystem (RSS) (Thomson et al. (2007)) and stellar occultations carried out with the Ultraviolet Imaging Spectrograph (UVIS) (Colwell et al. (2007)), and the Visual and Infrared Mapping Spectrometer (VIMS) (Hedman et al. (2014)). Up to date, this micro-structure is best explained by the viscous overstability, which arises as a spontaneous oscillatory instability in a dense ring, if certain conditions are met, leading to the formation of axisymmetric density waves with wavelengths on the order of 100m. We investigate the influence of collective self-gravity forces on the nonlinear, large scale evolution of the viscous overstability in Saturn's rings. To this end we numerically solve the nonlinear hydrodynamic model equations for a dense ring, including radial self-gravity and employing values for the transport coefficients (such as the ring's viscosity and heat conductivity) derived by salo et al. (2001). We concentrate on ring optical depths of order unity, which are appropriate to model Saturn's dense rings. Furthermore, local N-body simulations, incorporating vertical and radial collective self-gravity forces are performed. Direct particle-particle forces are omitted, which prevents small scale gravitational instabilities (self-gravity wakes) from forming, an approximation that allows us to study long radial scales of some 10 kilometers and to compare directly the hydrodynamic model and the N-body simulations. Our hydrodynamic model results, in the limit of vanishing self-gravity, compare very well with the studies of Latter & Ogilvie (2010) and Rein & Latter (2013). In contrast, for rings with non-vanishing radial self-gravity we find that the wavelengths of saturated overstable wave trains tend to settle close to the frequency minimum of the nonlinear dispersion relation, i.e. the saturation wavelengths decrease with increasing surface mass density of the ring. Good agreement between hydrodynamics and N-body simulations is found for disks with strong radial self-gravity, while the largest deviations occur in the limit of weak self-gravity. The resulting saturation wavelengths of the viscous overstability for moderate and strong radial self-gravity (100m-300m) agree reasonably well with the length scale of the axisymmetric periodic micro structure in Saturn's inner A ring and the B ring, as found by Cassini.

Directed self-assembly into low-density colloidal liquid crystal phases

NASA Astrophysics Data System (ADS)

Gao, Yongxiang; Romano, Flavio; Dullens, Roel P. A.; Doye, Jonathan K.; Aarts, Dirk G. A. L.

2018-01-01

Alignment of anisometric particles into liquid crystals (LCs) often results from an entropic competition between their rotational and translational degrees of freedom at dense packings. Here we show that by selectively functionalizing the heads of colloidal rods with magnetic nanoparticles this tendency can be broken to direct the particles into novel, low-density LC phases. Under an external magnetic field, the magnetic heads line up in columns whereas the nonmagnetic tails point out randomly in a plane perpendicular to the columns, forming bottle-brush-like objects; laterally, the bottle brushes are entropically stabilized against coalescence. Experiments and simulations show that upon increasing the particle density the system goes from a dilute gas to a dense two-dimensional liquid of bottle brushes with a density well below the zero-field nematic phase. Our findings offer a strategy for self-assembly into three-dimensional open phases that may find applications in switchable photonics, filtration, and light-weight materials.

Carbon nanotubes synthesized by Ni-assisted atmospheric pressure thermal chemical vapor deposition

NASA Astrophysics Data System (ADS)

Choi, G. S.; Cho, Y. S.; Hong, S. Y.; Park, J. B.; Son, K. H.; Kim, D. J.

2002-03-01

A detailed systematic study on the growth morphology of carbon nanotubes (CNTs) on Si in atmospheric pressure thermal chemical vapor deposition was undertaken. The role of NH3 for vertical alignment of CNTs was investigated. The direct cause for the alignment was a dense distribution of the catalytic metal particles, but that the particles are maintained catalytically active under amorphous carbon deposits was established by NH3. It allows a dense nucleation of the CNTs, and consequently, assists vertical alignment through entanglement and mechanical leaning among the tubes. The CNTs grew in a base growth mode. Since Ni is consumed both by silicide reaction and by capture into the growing tube, the growth stops when Ni is totally depleted. It occurs earlier for smaller particles, and thus a long time of growth results in a thin bottom with poor adhesion.

Isothermal Oxidation of Magnetite to Hematite in Air and Cyclic Reduction/Oxidation Under Carbon Looping Combustion Conditions

NASA Astrophysics Data System (ADS)

Simmonds, Tegan; Hayes, Peter C.

2017-12-01

In the carbon looping combustion process the oxygen carrier is regenerated through oxidation in air; this process has been simulated by the oxidation of dense synthetic magnetite for selected temperatures and times. The oxidation of magnetite in air is shown to occur through the formation of dense hematite layers on the particle surface. This dense hematite forms through lath type shear transformations or solid-state diffusion through the product layer. Cyclic reduction in CO-CO2/oxidation in air of hematite single crystals has been carried out under controlled laboratory conditions at 1173 K (900 °C). It has been shown that the initial reduction step is critical to determining the product microstructure, which consists of gas pore dendrites in the magnetite matrix with blocky hematite formed on the pore surfaces. The progressive growth of the magnetite layer with the application of subsequent cycles appears to continue until no original hematite remains, after which physical disintegration of the particles takes place.

"Reticular" and "Areticular" Nissl Bodies in Sympathetic Neurons of a Lizard

PubMed Central

Smith, Stuart W.

1959-01-01

Sympathetic ganglia of the horned lizard, Phrynosoma cornutum, were fixed in OsO4 and imbedded in methacrylate. Thin sections were cut for electron microscopy. Some adjacent thick sections were cut for light microscopy and were stained in acidified, dilute thionine both before and after digestion by RNase. In the light microscope two types of Nissl bodies are found, both removable by RNase: (1) a deep, diffuse, indistinctly bounded, metachromatic variety, and (2) a superficial, dense, sharply delimited, orthochromatic sort. Electron microscopically, the former ("reticular" Nissl bodies) corresponds to the granulated endoplasmic reticular structure of Nissl material previously described by others, whereas the latter ("areticular" Nissl bodies) comprises compact masses of particles of varying internal density and devoid of elements of endoplasmic reticulum. The constituent particles of the areticular Nissl material are 4 to 8 x the diameter of single ribonucleoprotein granules of the reticular Nissl substance and seem, near zones of junction with the reticular type, to arise by clustering of such granules with subsequent partial dispersion of the substance of the granules into an added, less dense material. It is suggested that the observed orthochromasia of the areticular Nissl substance is due to accumulation of a large amount of protein bound to RNA and, further, that these Nissl bodies may represent storage depots of RNA and protein. PMID:13673051

Influence of Impact Conditions on Feedstock Deposition Behavior of Cold-Sprayed Fe-Based Metallic Glass

NASA Astrophysics Data System (ADS)

Ziemian, Constance W.; Wright, Wendelin J.; Cipoletti, David E.

2018-05-01

Cold spray is a promising method by which to deposit dense Fe-based metallic glass coatings on conventional metal substrates. Relatively low process temperatures offer the potential to prevent the crystallization of amorphous feedstock powders while still providing adequate particle softening for bonding and coating formation. In this study, Fe48Mo14Cr15Y2C15B6 powder was sprayed onto a mild steel substrate, using a variety of process conditions, to investigate the feasibility of forming well-bonded amorphous Fe-based coatings. Particle splat adhesion was examined relative to impact conditions, and the limiting values of temperature and velocity associated with successful softening and adhesion were empirically established. Variability of particle sizes, impact temperatures, and impact velocities resulted in splat morphologies ranging from well-adhered deformed particles to substrate craters formed by rebounded particles and a variety of particle/substrate interface conditions. Transmission electron microscopy studies revealed the presence of a thin oxide layer between well-adhered particles and the substrate, suggesting that bonding is feasible even with an increased oxygen content at the interface. Results indicate that the proper optimization of cold spray process parameters supports the formation of Fe-based metallic glass coatings that successfully retain their amorphous structure, as well as the superior corrosion and wear-resistant properties of the feedstock powder.

DNA Packaging Mutant: Repression of the Vaccinia Virus A32 Gene Results in Noninfectious, DNA-Deficient, Spherical, Enveloped Particles

PubMed Central

Cassetti, Maria Cristina; Merchlinsky, Michael; Wolffe, Elizabeth J.; Weisberg, Andrea S.; Moss, Bernard

1998-01-01

The vaccinia virus A32 open reading frame was predicted to encode a protein with a nucleoside triphosphate-binding motif and a mass of 34 kDa. To investigate the role of this protein, we constructed a mutant in which the original A32 gene was replaced by an inducible copy. The recombinant virus, vA32i, has a conditional lethal phenotype: infectious virus formation was dependent on isopropyl-β-d-thiogalactopyranoside (IPTG). Under nonpermissive conditions, the mutant synthesized early- and late-stage viral proteins, as well as viral DNA that was processed into unit-length genomes. Electron microscopy of cells infected in the absence of IPTG revealed normal-appearing crescents and immature virus particles but very few with nucleoids. Instead of brick-shaped mature particles with defined core structures, there were numerous electron-dense, spherical particles. Some of these spherical particles were wrapped with cisternal membranes, analogous to intracellular and extracellular enveloped virions. Mutant viral particles, purified by sucrose density gradient centrifugation, had low infectivity and transcriptional activity, and the majority were spherical and lacked DNA. Nevertheless, the particle preparation contained representative membrane proteins, cleaved and uncleaved core proteins, the viral RNA polymerase, the early transcription factor and several enzymes, suggesting that incorporation of these components is not strictly coupled to DNA packaging. PMID:9621036

Research on acting mechanism and behavior of a gas bubble in the air dense medium fluidized bed

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

Tao, X.; Chen, Q.; Yang, Y.

1996-12-31

Coal dry beneficiation with air-dense medium fluidized bed has now been established as a high efficiency dry separation technology, it is the application of fluidization technology to the coal preparation field. The tiny particle media forms an uniform and stable fluidized bed with a density acted by airflow, which is used to separate 80{micro}m to {approximately}6mm size coal. This technology has achieved satisfied industrialization results, and attracted the expert`s attention in the field. In fluidized bed, the interaction between gas and solid was mainly decided by the existence state of heavy media particles mass (position and distance) relative velocity ofmore » gas-solid two phase, as well turbulent action. A change of vertical gas-solid fluidizing state essentially is the one of a energy transforming process. For a coal separating process with air-dense medium fluidized bed, the gas bubble, producing a turbulent and stirring action in the bed, leads to two effects. It can promote a uniform distribution of heavy media particles, and a uniform and stability of a bed density. Otherwise it will decrease effective contacts between gas-solids two phases, producing a bigger gas bubble. Therefore controlling a gas bubble size in bed should be optimized. This paper analyzes mutual movement between gas-solid, and studies the gas bubble behavior in the bed. A mechanic mode and a separating process of coal in the bed is discussed. It aims to research the coal separating mechanism with air-dense fluidized bed.« less

Energy transfer dynamics in strongly inhomogeneous hot-dense-matter systems

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

Stillman, C. R.; Nilson, P. M.; Sefkow, A. B.

Direct measurements of energy transfer across steep density and temperature gradients in a hot-dense-matter system are presented. Hot dense plasma conditions were generated by high-intensity laser irradiation of a thin-foil target containing a buried metal layer. Energy transfer to the layer was measured using picosecond time-resolved x-ray emission spectroscopy. Here, the data show two x-ray flashes in time. Fully explicit, coupled particle-in-cell and collisional-radiative atomic kinetics model predictions reproduce these observations, connecting the two x-ray flashes with staged radial energy transfer within the target.

Energy transfer dynamics in strongly inhomogeneous hot-dense-matter systems

DOE PAGES

Stillman, C. R.; Nilson, P. M.; Sefkow, A. B.; ...

2018-06-25

Direct measurements of energy transfer across steep density and temperature gradients in a hot-dense-matter system are presented. Hot dense plasma conditions were generated by high-intensity laser irradiation of a thin-foil target containing a buried metal layer. Energy transfer to the layer was measured using picosecond time-resolved x-ray emission spectroscopy. Here, the data show two x-ray flashes in time. Fully explicit, coupled particle-in-cell and collisional-radiative atomic kinetics model predictions reproduce these observations, connecting the two x-ray flashes with staged radial energy transfer within the target.

A two-phase flow model for submarine granular flows: With an application to collapse of deeply-submerged granular columns

NASA Astrophysics Data System (ADS)

Lee, Cheng-Hsien; Huang, Zhenhua

2018-05-01

The collapse process of a submerged granular column is strongly affected by its initial packing. Previous models for particle response time, which is used to quantify the drag force between the solid and liquid phases in rheology-based two-phase flow models, have difficulty in simulating the collapse process of granular columns with different initial concentrations (initial packing conditions). This study introduces a new model for particle response time, which enables us to satisfactorily model the drag force between the two phases for a wide range of volume concentration. The present model can give satisfactory results for both loose and dense packing conditions. The numerical results have shown that (i) the initial packing affects the occurrence of contractancy/diltancy behavior during the collapse process, (ii) the general buoyancy and drag force are strongly affected by the initial packing through contractancy and diltancy, and (iii) the general buoyancy and drag force can destabilize the granular material in loose packing condition but stabilize the granular material in dense packing condition. The results have shown that the collapse process of a densely-packed granular column is more sensitive to particle response time than that of a loosely-packed granular column.

Glider monitoring of shelf suspended particle dynamics and transport during storm and flooding conditions

NASA Astrophysics Data System (ADS)

Bourrin, François; Many, Gaël; Durrieu de Madron, Xavier; Martín, Jacobo; Puig, Pere; Houpert, Loic; Testor, Pierre; Kunesch, Stéphane; Mahiouz, Karim; Béguery, Laurent

2015-10-01

Transfers of particulate matter on continental margins primarily occur during energetic events. As part of the CASCADE (CAscading, Storm, Convection, Advection and Downwelling Events) experiment, a glider equipped with optical sensors was deployed in the coastal area of the Gulf of Lions, NW Mediterranean in March 2011 to assess the spatio-temporal variability of hydrology, suspended particles properties and fluxes during energetic conditions. This deployment complemented a larger observational effort, a part of the MOOSE (Mediterranean Ocean Observing System of the Environment) network, composed of a coastal benthic station, a surface buoy and moorings on the continental slope. This set of observations permitted to measure the impact of three consecutive storms and a flood event across the entire continental shelf. Glider data showed that the sediment resuspension and transport observed at the coastal station during the largest storm (Hs>4 m) was effective down to a water depth of 80 m. The mid-shelf mud belt, located between 40 and 90 m depth, appears as the zone where the along-shelf flux of suspended sediment is maximum. Besides, the across-shelf flux of suspended sediment converges towards the outer limit of the mid-shelf mud belt, where deposition of suspended particles probably occurs and contributes to the nourishment of this area. Hydrological structures, suspended particles transport and properties changed drastically during stormy periods and the following flood event. Prior to the storms, the shelf waters were weakly stratified due in particular to the presence of cold dense water on the inner- and mid-shelf. The storms rapidly swept away this dense water, as well as the resuspended sediments, along the shelf and towards a downstream submarine canyon. The buoyant river plumes that spread along the shelf after the flooding period provoked a restratification of the water column on the inner- and mid-shelf. The analysis of glider's optical data at different wavelengths suggests that the coastal area and the bottom nepheloid layer during the largest storm are primarily composed of coarse particles, probably macroflocs, and that the size of particles decreases further offshore. A similar trend, albeit less contrasted, is observed after the flooding. This work provided a unique synoptic view across the entire shelf of the impact of a typical Mediterranean storm on bottom sediment erosion and particulate fluxes. Repeated glider transects across the south-western part of the Gulf of Lions shelf permitted for the first time to measure continuously the thermo-haline structures, the suspended particles concentrations and size, the current speed, and to estimate the particulate transport before, during and after typical Mediterranean storm events. Glider data complement and compare well with concomitant high frequency time series at fixed stations along the coast and in a downstream submarine canyon.

In situ ultra-small-angle X-ray scattering study under uniaxial stretching of colloidal crystals prepared by silica nanoparticles bearing hydrogen-bonding polymer grafts

DOE PAGES

Ishige, Ryohei; Williams, Gregory A.; Higaki, Yuji; ...

2016-04-19

A molded film of single-component polymer-grafted nanoparticles (SPNP), consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated byin situultra-small-angle X-ray scattering (USAXS) measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c.) lattice structure with the [11-1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis ofin situUSAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction inmore » proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress–strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles.« less

Magnetic nanoparticles through organometallic synthesis: evolution of the magnetic properties from isolated nanoparticles to organised nanostructures.

PubMed

Dumestre, Fréderic; Martinez, Susana; Zitoun, David; Fromen, Marie-Claire; Casanove, Marie-José; Lecante, Pierre; Respaud, Marc; Serres, Arnaud; Benfield, Robert E; Amiens, Catherine; Chaudret, Bruno

2004-01-01

Co and NiFe nanoparticles (2.7 to 3.3 nm mean diameter) of narrow size distribution have been obtained through the decomposition of organometallic precursors in organic solutions of long alkyl chain ligands, namely oleic acid and hexadecylamine. Materials of various volume fractions were produced. The particles have been structurally characterised by WAXS. Both adopt the bulk structure: HCP in the case of cobalt; a mixture of FCC and BCC for NiFe. Their aptitude to self-assemble either on flat supports or in bulk solid state has been investigated by means of TEM and SAXS. This study suggests the crystallisation of the nanoparticles upon solvent evaporation, especially a local FCC arrangement was observed for the NiFe material. Magnetic measurements (SQUID) confirm this tendency. The blocking temperature depends on the metal volume fraction, i.e. on the anisotropy generated by the dipolar couplings (Ki). We show that, for dense samples, the particles of high intrinsic anisotropy, Ku, (Co) still display an individual behaviour while the soft ones (NiFe) display a collective behaviour.

Multiple scattering in planetary regoliths using first-order incoherent interactions

NASA Astrophysics Data System (ADS)

Muinonen, Karri; Markkanen, Johannes; Väisänen, Timo; Penttilä, Antti

2017-10-01

We consider scattering of light by a planetary regolith modeled using discrete random media of spherical particles. The size of the random medium can range from microscopic sizes of a few wavelengths to macroscopic sizes approaching infinity. The size of the particles is assumed to be of the order of the wavelength. We extend the numerical Monte Carlo method of radiative transfer and coherent backscattering (RT-CB) to the case of dense packing of particles. We adopt the ensemble-averaged first-order incoherent extinction, scattering, and absorption characteristics of a volume element of particles as input for the RT-CB. The volume element must be larger than the wavelength but smaller than the mean free path length of incoherent extinction. In the radiative transfer part, at each absorption and scattering process, we account for absorption with the help of the single-scattering albedo and peel off the Stokes parameters of radiation emerging from the medium in predefined scattering angles. We then generate a new scattering direction using the joint probability density for the local polar and azimuthal scattering angles. In the coherent backscattering part, we utilize amplitude scattering matrices along the radiative-transfer path and the reciprocal path, and utilize the reciprocity of electromagnetic waves to verify the computation. We illustrate the incoherent volume-element scattering characteristics and compare the dense-medium RT-CB to asymptotically exact results computed using the Superposition T-matrix method (STMM). We show that the dense-medium RT-CB compares favorably to the STMM results for the current cases of sparse and dense discrete random media studied. The novel method can be applied in modeling light scattering by the surfaces of asteroids and other airless solar system objects, including UV-Vis-NIR spectroscopy, photometry, polarimetry, and radar scattering problems.Acknowledgments. Research supported by European Research Council with Advanced Grant No. 320773 SAEMPL, Scattering and Absorption of ElectroMagnetic waves in ParticuLate media. Computational resources provided by CSC - IT Centre for Science Ltd, Finland.

Surrogate Lipid Markers for Small Dense Low-Density Lipoprotein Particles in Overweight Youth

PubMed Central

Burns, Stephen F.; Lee, So Jung; Arslanian, Silva A.

2013-01-01

Objectives To determine if the ratio of triglycerides to high-density lipoprotein cholesterol (TG/HDL) and non–HDL cholesterol concentration could identify youth with small dense low-density lipoprotein (LDL). Study design One hundred forty-one (75 black and 66 white) overweight adolescents (9 to <18 years) had a fasting measurement of plasma lipids and LDL particle concentrations and size. Receiver operating characteristic curves were used to indicate the ability of different TG/HDL ratios and non–HDL cholesterol concentrations to identify overweight youth with atherogenic LDL concentration and size. Results Youth with a TG/HDL ratio of ≥3 vs <3 had higher concentrations of small dense LDL (1279.5 ± 60.1 vs 841.8 ± 24.2 nmol/L, P < .001) and smaller LDL particle size (20.3 ± 0.1 vs 21.2 ± 0.1 nm, P < .001). In receiver operating characteristic analyses a TG/HDL cut-point of 3 best predicted LDL concentration in white youth, and 2.5 in black youth. Non-HDL cholesterol cut-point of 120 mg/dL and 145 mg/dL predicted LDL particle concentration in white and in black youth, respectively. TG/HDL ratio with body mass index or waist circumference explained 71% and 79% of the variance, respectively, in total small LDL. Conclusions TG/HDL ratio and non-HDL cholesterol can identify overweight youth with atherogenic LDL particles. These easily obtained clinical lipid markers, in combination with body mass index and waist circumference, could be cost effective, in observational or interventional studies, for screening and follow-up of youth at heightened risk for atherogenic LDL. PMID:22809659

Surrogate lipid markers for small dense low-density lipoprotein particles in overweight youth.

PubMed

Burns, Stephen F; Lee, So Jung; Arslanian, Silva A

2012-12-01

To determine if the ratio of triglycerides to high-density lipoprotein cholesterol (TG/HDL) and non-HDL cholesterol concentration could identify youth with small dense low-density lipoprotein (LDL). One hundred forty-one (75 black and 66 white) overweight adolescents (9 to <18 years) had a fasting measurement of plasma lipids and LDL particle concentrations and size. Receiver operating characteristic curves were used to indicate the ability of different TG/HDL ratios and non-HDL cholesterol concentrations to identify overweight youth with atherogenic LDL concentration and size. Youth with a TG/HDL ratio of ≥3 vs <3 had higher concentrations of small dense LDL (1279.5 ± 60.1 vs 841.8 ± 24.2 nmol/L, P < .001) and smaller LDL particle size (20.3 ± 0.1 vs 21.2 ± 0.1 nm, P < .001). In receiver operating characteristic analyses a TG/HDL cut-point of 3 best predicted LDL concentration in white youth, and 2.5 in black youth. Non-HDL cholesterol cut-point of 120 mg/dL and 145 mg/dL predicted LDL particle concentration in white and in black youth, respectively. TG/HDL ratio with body mass index or waist circumference explained 71% and 79% of the variance, respectively, in total small LDL. TG/HDL ratio and non-HDL cholesterol can identify overweight youth with atherogenic LDL particles. These easily obtained clinical lipid markers, in combination with body mass index and waist circumference, could be cost effective, in observational or interventional studies, for screening and follow-up of youth at heightened risk for atherogenic LDL. Copyright © 2012 Mosby, Inc. All rights reserved.

A semi-Lagrangian transport method for kinetic problems with application to dense-to-dilute polydisperse reacting spray flows

NASA Astrophysics Data System (ADS)

Doisneau, François; Arienti, Marco; Oefelein, Joseph C.

2017-01-01

For sprays, as described by a kinetic disperse phase model strongly coupled to the Navier-Stokes equations, the resolution strategy is constrained by accuracy objectives, robustness needs, and the computing architecture. In order to leverage the good properties of the Eulerian formalism, we introduce a deterministic particle-based numerical method to solve transport in physical space, which is simple to adapt to the many types of closures and moment systems. The method is inspired by the semi-Lagrangian schemes, developed for Gas Dynamics. We show how semi-Lagrangian formulations are relevant for a disperse phase far from equilibrium and where the particle-particle coupling barely influences the transport; i.e., when particle pressure is negligible. The particle behavior is indeed close to free streaming. The new method uses the assumption of parcel transport and avoids to compute fluxes and their limiters, which makes it robust. It is a deterministic resolution method so that it does not require efforts on statistical convergence, noise control, or post-processing. All couplings are done among data under the form of Eulerian fields, which allows one to use efficient algorithms and to anticipate the computational load. This makes the method both accurate and efficient in the context of parallel computing. After a complete verification of the new transport method on various academic test cases, we demonstrate the overall strategy's ability to solve a strongly-coupled liquid jet with fine spatial resolution and we apply it to the case of high-fidelity Large Eddy Simulation of a dense spray flow. A fuel spray is simulated after atomization at Diesel engine combustion chamber conditions. The large, parallel, strongly coupled computation proves the efficiency of the method for dense, polydisperse, reacting spray flows.

New challenges in high-energy particle radiobiology

PubMed Central

2014-01-01

Densely ionizing radiation has always been a main topic in radiobiology. In fact, α-particles and neutrons are sources of radiation exposure for the general population and workers in nuclear power plants. More recently, high-energy protons and heavy ions attracted a large interest for two applications: hadrontherapy in oncology and space radiation protection in manned space missions. For many years, studies concentrated on measurements of the relative biological effectiveness (RBE) of the energetic particles for different end points, especially cell killing (for radiotherapy) and carcinogenesis (for late effects). Although more recently, it has been shown that densely ionizing radiation elicits signalling pathways quite distinct from those involved in the cell and tissue response to photons. The response of the microenvironment to charged particles is therefore under scrutiny, and both the damage in the target and non-target tissues are relevant. The role of individual susceptibility in therapy and risk is obviously a major topic in radiation research in general, and for ion radiobiology as well. Particle radiobiology is therefore now entering into a new phase, where beyond RBE, the tissue response is considered. These results may open new applications for both cancer therapy and protection in deep space. PMID:24198199

A Spectroscopic Study On Two Glasses With Different Vesicularity From The Astroni Tephra (phlegraean Fields, Italy): Implications On Bubble Expansion

NASA Astrophysics Data System (ADS)

Slejko, F. F.; Petrini, R.

Bubble growth in ascending viscous magmas by volatile exsolution from the melt structure is important in causing the magma fragmentation which determines the trans- form from a lava flow to a pyroclastic explosion. Volatile solubility and speciation in the melt vary during pressure and temperature changes. The pressure drop which oc- curs as a magma rises towards the surface in a volcanic conduit, causes the release of the volatiles dissolved in the melt and the progressive growth in the size of bubbles against the retarding forces to expansion generated by the polymeric interconnections in the silicate melt structure. At some critical growth rate with respect to the relax- ation time of the melt structure, the disruption of the interbubbles walls in the melt marks the fragmentation threshold, with the transition from a viscous bubbly liquid to a fast-uprising gas carrying on fragments of vesiculated magma. Highly polymer- ized, silica-rich melts are characterised by relaxation times which may be long com- pared to the quick growth and deformation of bubbles during rapid magma decom- pression and cooling, and the glassy pumices which form may retain informations on the vesiculation and degassing processes which occurred close to the fragmentation depth. Furthermore, the formation of vesicles during the cooling and decompression of an ascending volatile-supersaturated high-silica magma is strongly favoured by the occurrence of bubble nucleating sites in the melt. In order to investigate the influ- ence of the structure and iron speciation on bubble growth during explosive volcan- ism, a dense glass and a vesiculated pumice glass coexisting in the same pyroclastic unit of the Astroni volcano tephra in the Phlegraean Fields Caldera (4.1-3.8 ka BP) were investigated by 29Si 2D phase adjusted spinning sidebands (PASS) NMR, 1H MAS NMR, electron spin resonance (ESR) and Mössbauer spectroscopy. 29Si 2D PASS spectra show that silicon copolymerizes in the structure dominantly by Q3 and Q4 groups, with partly overlapping chemical shift. Spectrum fittings indicate that the dense glass is characterised by a larger abundance of Q3 species compared to the vesiculated pumice, suggesting a less polymerized structure. 1H MAS spectra reveal a larger amount of hydrogen concentration in the dense glass, partly attributable to structural hydroxyl groups possibly in Q3-OH terminations depolymerizing the glass structure. The less polymerized structure of the dense glass could have allowed an easier volatile exsolution, preventing the bubble formation. The EPR spectra indicate that the Fe3+ has similar surroundings in both samples, suggesting that Fe3+ is likely to occur in both network forming and modifying sites. Nevertheless, the vesiculated glass is characterised by a significantly higher amount of magnetite particles, which could have enhanced the bubble nucleation. Mössbauer spectra show four doublets attributable to ferric iron in both tetrahedral and octahedral sites and ferrous iron only in octahedral coordination. The oxidation of Fe2+ to Fe3+ observed in the vesicu- lated glass with respect to the dense glass could be an evidence of pressure drop with consequent bubble expansion.

Preparation of polymeric Janus particles by directional UV-induced reactions.

PubMed

Liu, Lianying; Ren, Mingwei; Yang, Wantai

2009-09-15

Polymeric Janus particles are obtained by UV-induced selective surface grafting polymerizations and coupling reactions, in virtue of the light-absorption of photoreactive materials such as the immobilized photoinitiator and spread photoinitiator solution on the surfaces exposed to UV light and the sheltering of densely arrayed immovable particles from light. Varying the monomers or macromolecules applied in photografting polymerization or coupling reaction, and choosing diverse polymeric particles of various size, bicolor and amphiphilic Janus particles could be successfully achieved. Observations by fluorescence microscope, scanning electron microscope ,and transmission electron microscope confirmed the asymmetrical morphology of the resultant Janus particles.

Characteristics of storm runoff and sediment dispersal in the San Pedro Channel, southern California.

PubMed

Ahn, J H; Grant, S B

2007-01-01

In-site measurements of particle size spectra were obtained from three offshore cruises to evaluate the physical consequences of increased sediment transport and deposition offshore which was caused by episodic storm runoff water from the Santa Ana River watershed, a highly urbanised coastal watershed in southern California. Of the total annual runoff discharge to the coastal ocean, 89.2% occurred in the 2003/2004 winter season, and 0.22 Mt of sediment mass was transported during the storm events. The runoff plume at surface taken offshore by cross-shore currents progressed rapid aggregation and sedimentation, while the initially high concentration of suspended sediment discharged from the river outlet was dominated by small particles. Vertical profiles of particle size spectra revealed two separated plumes near the river outlet and turbidity plume along the bottom consisted of an abundance of very fine and dense particles. It would appear to support the theory that even if the storm runoff does not carry a high concentration of sediment being capable of generating negative buoyancy, sediment deposition on the shelf might mobilise in dense, fluid mud transported offshore by gravity. In a coastal pollution context, sediment particle size spectra information may offer potentially useful means of characterising particle-associated pollutants for purposes of source tracking and environmental interpretation.

Ion-ion dynamic structure factor of warm dense mixtures

DOE PAGES

Gill, N. M.; Heinonen, R. A.; Starrett, C. E.; ...

2015-06-25

In this study, the ion-ion dynamic structure factor of warm dense matter is determined using the recently developed pseudoatom molecular dynamics method [Starrett et al., Phys. Rev. E 91, 013104 (2015)]. The method uses density functional theory to determine ion-ion pair interaction potentials that have no free parameters. These potentials are used in classical molecular dynamics simulations. This constitutes a computationally efficient and realistic model of dense plasmas. Comparison with recently published simulations of the ion-ion dynamic structure factor and sound speed of warm dense aluminum finds good to reasonable agreement. Using this method, we make predictions of the ion-ionmore » dynamical structure factor and sound speed of a warm dense mixture—equimolar carbon-hydrogen. This material is commonly used as an ablator in inertial confinement fusion capsules, and our results are amenable to direct experimental measurement.« less

A new class of tunable hypersonic phononic crystals based on polymer-tethered colloids.

PubMed

Alonso-Redondo, E; Schmitt, M; Urbach, Z; Hui, C M; Sainidou, R; Rembert, P; Matyjaszewski, K; Bockstaller, M R; Fytas, G

2015-09-22

The design and engineering of hybrid materials exhibiting tailored phononic band gaps are fundamentally relevant to innovative material technologies in areas ranging from acoustics to thermo-optic devices. Phononic hybridization gaps, originating from the anti-crossing between local resonant and propagating modes, have attracted particular interest because of their relative robustness to structural disorder and the associated benefit to 'manufacturability'. Although hybridization gap materials are well known, their economic fabrication and efficient control of the gap frequency have remained elusive because of the limited property variability and expensive fabrication methodologies. Here we report a new strategy to realize hybridization gap materials by harnessing the 'anisotropic elasticity' across the particle-polymer interface in densely polymer-tethered colloidal particles. Theoretical and Brillouin scattering analysis confirm both the robustness to disorder and the tunability of the resulting hybridization gap and provide guidelines for the economic synthesis of new materials with deliberately controlled gap position and width frequencies.

Introduction to Big Bang nucleosynthesis - Open and closed models, anisotropies

NASA Astrophysics Data System (ADS)

Tayler, R. J.

1982-10-01

A variety of observations suggest that the universe had a hot dense origin and that the pregalactic composition of the universe was determined by nuclear reactions that occurred in the first few minutes. There is no unique hot Big Bang theory, but the simplest version produces a primeval chemical composition that is in good qualitative agreement with the abundances deduced from observation. Whether or not any Big Bang theory will provide quantitative agreement with observations depends on a variety of factors in elementary particle physics (number and masses of stable or long-lived particles, half-life of neutron, structure of grand unified theories) and from observational astronomy (present mean baryon density of the universe, the Hubble constant and deceleration parameter). The influence of these factors on the abundances is discussed, as is the effect of departures from homogeneity and isotropy in the early universe.

A high-density lipoprotein-mediated drug delivery system.

PubMed

Mo, Zhong-Cheng; Ren, Kun; Liu, Xing; Tang, Zhen-Li; Yi, Guang-Hui

2016-11-15

High-density lipoprotein (HDL) is a comparatively dense and small lipoprotein that can carry lipids as a multifunctional aggregate in plasma. Several studies have shown that increasing the levels or improving the functionality of HDL is a promising target for treating a wide variety of diseases. Among lipoproteins, HDL particles possess unique physicochemical properties, including naturally synthesized physiological components, amphipathic apolipoproteins, lipid-loading and hydrophobic agent-incorporating characteristics, specific protein-protein interactions, heterogeneity, nanoparticles, and smaller size. Recently, the feasibility and superiority of using HDL particles as drug delivery vehicles have been of great interest. In this review, we summarize the structure, constituents, biogenesis, remodeling, and reconstitution of HDL drug delivery systems, focusing on their delivery capability, characteristics, applications, manufacturing, and drug-loading and drug-targeting characteristics. Finally, the future prospects are presented regarding the clinical application and challenges of using HDL as a pharmacodelivery carrier. Copyright © 2016 Elsevier B.V. All rights reserved.

Molecular dynamics study of the structure and interparticle interactions of polyethylene glycol-conjugated PAMAM dendrimers.

PubMed

Lee, Hwankyu; Larson, Ronald G

2009-10-08

We performed molecular dynamics (MD) simulations of one or two copies of polyethylene glycol of molecular weight 550 (PEG550) and 5000 (PEG5000) daltons, conjugated to generation 3 (G3) to 5 (G5) polyamidoamine (PAMAM) dendrimers with explicit water using a coarse-grained model. We found the radii of gyration of these dendrimer-PEG molecules to be close to those measured in experiments by Hedden and Bauer (Hedden , R. C. ; Bauer , B. J. Macromolecules 2003 , 36 , 1829.). Densely grafted PEG ligands (>50% of the dendrimer surface) extend like brushes, with layer thickness in agreement with theory for starlike polymers. Two dendrimer-PEG complexes in the box drift away from each other, indicating that no aggregation is induced by either short or long PEG chains, conflicting with a recent view that the cytotoxicity of some PEGylated particles might be due to particle aggregation for long PEG lengths.

Structure of corneal layers, collagen fibrils, and proteoglycans of tree shrew cornea.

PubMed

Almubrad, Turki; Akhtar, Saeed

2011-01-01

The stroma is the major part of the cornea, in which collagen fibrils and proteoglycans are distributed uniformly. We describe the ultrastructure of corneal layers, collagen fibrils (CF), and proteoglycans (PGs) in the tree shrew cornea. Tree shrew corneas (5, 6, and 10 week old animals) and normal human corneas (24, 25, and 54 years old) were fixed in 2.5% glutaraldehyde containing cuprolinic blue in a sodium acetate buffer. The tissue was processed for electron microscopy. The 'iTEM Olympus Soft Imaging Solutions GmbH' program was used to measure the corneal layers, collagen fibril diameters and proteoglycan areas. The tree shrew cornea consists of 5 layers: the epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. The epithelium was composed of squamous cells, wing cells and basal cells. The Bowman's layer was 5.5±1.0 µm thick and very similar to a normal human Bowman's layer. The stroma was 258±7.00 µm thick and consisted of collagen fibril lamellae. The lamellae were interlaced with one another in the anterior stroma, but ran parallel to one another in the middle and posterior stroma. Collagen fibrils were decorated with proteoglycan filaments with an area size of 390 ±438 nm(2). The collagen fibril had a minimum diameter of 39±4.25 nm. The interfibrillar spacing was 52.91±6.07 nm. Within the collagen fibrils, very small electron-dense particles were present. The structure of the tree shrew cornea is very similar to that of the normal human cornea. As is the case with the human cornea, the tree shrew cornea had a Bowman's layer, lamellar interlacing in the anterior stroma and electron-dense particles within the collagen fibrils. The similarities of the tree shrew cornea with the human cornea suggest that it could be a good structural model to use when studying changes in collagen fibrils and proteoglycans in non-genetic corneal diseases, such as ectasia caused after LASIK (laser-assisted in situ keratomileusis).

An Electron Microscope Study of the Rat Ovum

PubMed Central

Sotelo, J. Roberto; Porter, Keith R.

1959-01-01

This paper reports on the fine structure of rat oocytes at stages before ovulation, during maturation, fertilization, and early cleavage. The study includes parallel observations on light and electron microscope preparations with attempted correlations. The follicular cells of the ovarian egg are described as sending long processes through the zona pellucida to the egg surface where they mingle with thin projections from the egg itself. No open communication between follicle cell cytoplasm and egg cytoplasm was observed. During maturation and fertilization both types of processes are withdrawn from the zona. The germinal vesicle and later the pronuclei of the fertilized egg are characterized by numerous large nucleoli. These have the form of thick walled vesicles with diameters as great as 8 to 10 µ. The wall is dense in the EM image and appears to consist in part of small granules. The cytoplasm shows several inclusions including mitochondria of usual form and a Golgi component which has the typical fine structure and the distribution described by earlier light studies. Small dense particles, presumably RNP particles, are distributed throughout the cytoplasmic matrix and show no preference for membranes. The endoplasmic reticulum of the oocyte is represented by a scattering only of vesicles, but begins a more extensive and elaborate development with the onset of segmentation. One inclusion of the ooplasm, similar in size to mitochondria, receives special attention. It is a vesicular structure, containing a large number of small vesicles (10 to 50 mµ in diameter) and frequently a central density or nucleoid. They are referred to as multivesicular bodies. Such bodies are found in small number in the ovarian egg, but increase greatly in number during maturation and fertilization. It appears from the micrographs of eggs in these latter stages that these vesicular bodies break down and liberate their content of small vesicles to the surrounding ooplasm. Comments are provided on the apparent significance of the various observations. PMID:13654454

Mass production of polymer nano-wires filled with metal nano-particles.

PubMed

Lomadze, Nino; Kopyshev, Alexey; Bargheer, Matias; Wollgarten, Markus; Santer, Svetlana

2017-08-17

Despite the ongoing progress in nanotechnology and its applications, the development of strategies for connecting nano-scale systems to micro- or macroscale elements is hampered by the lack of structural components that have both, nano- and macroscale dimensions. The production of nano-scale wires with macroscale length is one of the most interesting challenges here. There are a lot of strategies to fabricate long nanoscopic stripes made of metals, polymers or ceramics but none is suitable for mass production of ordered and dense arrangements of wires at large numbers. In this paper, we report on a technique for producing arrays of ordered, flexible and free-standing polymer nano-wires filled with different types of nano-particles. The process utilizes the strong response of photosensitive polymer brushes to irradiation with UV-interference patterns, resulting in a substantial mass redistribution of the polymer material along with local rupturing of polymer chains. The chains can wind up in wires of nano-scale thickness and a length of up to several centimeters. When dispersing nano-particles within the film, the final arrangement is similar to a core-shell geometry with mainly nano-particles found in the core region and the polymer forming a dielectric jacket.

Modified kinetic theory applied to the shear flows of granular materials

DOE PAGES

Duan, Yifei; Feng, Zhi -Gang; Michaelides, Efstathios E.; ...

2017-04-11

Here, granular materials are characterized by large collections of discrete particles, where the particle-particle interactions are significantly more important than the particle-fluid interactions. The current kinetic theory captures fairly accurately the granular flow behavior in the dilute case, when only binary interactions are significant, but is not accurate at all in the dense flow regime, where multi-particle interactions and contacts must be modeled. To improve the kinetic theory results for granular flows in the dense flow regime, we propose a Modified Kinetic Theory (MKT) model that utilizes the contact duration or cut-off time to account for the complex particle-particle interactionsmore » in the dense regime. The contact duration model, also called TC model, is originally proposed by Luding and McNamara to solve the inelastic collapse issue existing in the Inelastic Hard Sphere (IHS) model. This model defines a cut-off time t c such that dissipation is not counted if the time between two consecutive contacts is less than t c. As shown in their study, the use of a cut-off time t c can also reduce the dissipation during multi-particle contacts. In this paper we relate the TC model with the Discrete Element Method (DEM) by choosing the cut-off time t c to be the duration of contact calculated from the linear-spring-dashpot soft-sphere model of the DEM. We examine two types of granular flows: simple shear flow and the plane shear flow, and compare the results of the classical Kinetic Theory (KT) model, the present MKT model, and the DEM model. Here, we show that the MKT model entails a significant improvement over the KT model for simple shear flows at inertial regimes. With the MKT model the calculations are close to the DEM results at solid fractions as high as 0.57. Even for the plane shear flows, where shear rate and solid fraction are inhomogeneous, the results of the MKT model agree very well with the DEM results.« less

Modified kinetic theory applied to the shear flows of granular materials

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

Duan, Yifei; Feng, Zhi -Gang; Michaelides, Efstathios E.

Here, granular materials are characterized by large collections of discrete particles, where the particle-particle interactions are significantly more important than the particle-fluid interactions. The current kinetic theory captures fairly accurately the granular flow behavior in the dilute case, when only binary interactions are significant, but is not accurate at all in the dense flow regime, where multi-particle interactions and contacts must be modeled. To improve the kinetic theory results for granular flows in the dense flow regime, we propose a Modified Kinetic Theory (MKT) model that utilizes the contact duration or cut-off time to account for the complex particle-particle interactionsmore » in the dense regime. The contact duration model, also called TC model, is originally proposed by Luding and McNamara to solve the inelastic collapse issue existing in the Inelastic Hard Sphere (IHS) model. This model defines a cut-off time t c such that dissipation is not counted if the time between two consecutive contacts is less than t c. As shown in their study, the use of a cut-off time t c can also reduce the dissipation during multi-particle contacts. In this paper we relate the TC model with the Discrete Element Method (DEM) by choosing the cut-off time t c to be the duration of contact calculated from the linear-spring-dashpot soft-sphere model of the DEM. We examine two types of granular flows: simple shear flow and the plane shear flow, and compare the results of the classical Kinetic Theory (KT) model, the present MKT model, and the DEM model. Here, we show that the MKT model entails a significant improvement over the KT model for simple shear flows at inertial regimes. With the MKT model the calculations are close to the DEM results at solid fractions as high as 0.57. Even for the plane shear flows, where shear rate and solid fraction are inhomogeneous, the results of the MKT model agree very well with the DEM results.« less

Synchrotron x-ray microtomography of the interior microstructure of chocolate

NASA Astrophysics Data System (ADS)

Lügger, Svenja K.; Wilde, Fabian; Dülger, Nihan; Reinke, Lennart M.; Kozhar, Sergii; Beckmann, Felix; Greving, Imke; Vieira, Josélio; Heinrich, Stefan; Palzer, Stefan

2016-10-01

The structure of chocolate, a multicomponent food product, was analyzed using microtomography. Chocolate consists of a semi-solid cocoa butter matrix and a dense network of suspended particles. A detailed analysis of the microstructure is needed to understand mass transport phenomena. Transport of lipids from e.g. a filling or liquid cocoa butter is responsible for major problems in the confectionery industry such as formation of chocolate bloom, which is the formation of visible white spots or a grayish haze on the chocolate surface and leads to consumer rejections and thus large sales losses for the confectionery industry. In this study it was possible to visualize the inner structure of chocolate and clearly distinguish the particles from the continuous phase by taking advantage of the high density contrast of synchrotron radiation. Consequently, particle arrangement and cracks within the sample were made visible. The cracks are several micrometers thick and propagate throughout the entire sample. Images of pure cocoa butter, chocolate without any particles, did not show any cracks and thus confirmed that cracks are a result of embedded particles. They arise during the manufacturing process. Thus, the solidification process, a critical manufacturing step, was simulated with finite element methods in order to understand crack formation during this step. The simulation showed that cracks arise because of significant contraction of cocoa butter, the matrix phase, without any major change of volume of the suspended particles. Tempering of the chocolate mass prior to solidification is another critical step for a good product quality. We found that samples which solidified in an uncontrolled manner are less homogeneous than tempered samples. In summary, our study visualized for the first time the inner microstructure of tempered and untempered cocoa butter as well as chocolate without sample destruction and revealed cracks, which might act as transport pathways.

Peculiarities of gamma-quanta distribution at 20 TeV energy

NASA Technical Reports Server (NTRS)

Ermakov, P. M.; Loktionov, A. A.; Lukin, Y. T.; Sadykov, T. K.

1985-01-01

The angular distribution of protons from the fragmentational region is analyzed. The gamma-quanta families are generated in a dense target by cosmic ray particles at 20 Tev energy. Families were found which had dense groups (spikes) of gamma-quanta where the rapidity/density is 3 times more than the average value determined for all registered families. The experimental data is compared with the results of artificial families simulation.

Modeling of non-stationary local response on impurity penetration in plasma

NASA Astrophysics Data System (ADS)

Tokar, M. Z.; Koltunov, M.

2012-04-01

In fusion devices, strongly localized intensive sources of impurities may arise unexpectedly, e.g., if the wall is excessively demolished by hot plasma particles, or can be created deliberately through impurity seeding. The spreading of impurities from such sources both along and perpendicular to the magnetic field is affected by coulomb collisions with background particles, ionization, acceleration by electric field, etc. Simultaneously, the plasma itself can be significantly disturbed by these interactions. To describe self-consistently the impurity spreading process and the plasma response, three-dimensional fluid equations for the particle, parallel momentum, and energy balances of various plasma components are solved by reducing them to ordinary differential equations for the time evolution of several parameters characterizing the solutions in principal details: the maximum densities of impurity ions of different charges, the dimensions both along and across the magnetic field of the shells occupied by these particles, the characteristic temperatures of all plasma components, and the densities of the main ions and electrons in different shells. The results of modeling for penetration of lithium singly charged particles in tokamak edge plasma are presented. A new mechanism for the condensation phenomenon and formation of cold dense plasma structures, implying an outstanding role of coulomb collisions between main and impurity ions, is proposed.

Energy loss of α-particle moving in warm dense deuterium plasma: Role of local field corrections

NASA Astrophysics Data System (ADS)

Fu, Zhen-Guo; Wang, Zhigang; Zhang, Ping

2017-11-01

We theoretically study the energy loss of α-particles traveling in the warm dense plasma (WDP) of deuterium (D) with temperatures from 10 to 100 eV and electron number densities from 1023 to 1024 cm-3. Beyond the random phase approximation (RPA) model, the extended Mermin dielectric function (MDF) model including the static and dynamic local field corrections (LFC) is employed in the calculations. Compared with the static LFC, the dynamic LFC introduced in the extended MDF model gives rise to a more significant departure from the RPA result. For the plasma conditions focused in this work, the departure induced by dynamic LFC reaches almost ˜ 30 % , which may be detected in the inertial confinement fusion (ICF) related experiment. Moreover, we find that the effect of static e-e collision may be of importance (unimportance) for the WDP of D with a temperature of tens (hundreds) of eV. Our findings may be important for ICF ignition since the uncertainty induced by the correlation effects between plasma component particles is crucial for the prediction of α-particle heating in fusion plasmas.

Limiting diffusion current at rotating disk electrode with dense particle layer.

PubMed

Weroński, P; Nosek, M; Batys, P

2013-09-28

Exploiting the concept of diffusion permeability of multilayer gel membrane and porous multilayer we have derived a simple analytical equation for the limiting diffusion current at rotating disk electrode (RDE) covered by a thin layer with variable tortuosity and porosity, under the assumption of negligible convection in the porous film. The variation of limiting diffusion current with the porosity and tortuosity of the film can be described in terms of the equivalent thickness of stagnant solution layer, i.e., the average ratio of squared tortuosity to porosity. In case of monolayer of monodisperse spherical particles, the equivalent layer thickness is an algebraic function of the surface coverage. Thus, by means of cyclic voltammetry of RDE with a deposited particle monolayer we can determine the monolayer surface coverage. The effect of particle layer adsorbed on the surface of RDE increases non-linearly with surface coverage. We have tested our theoretical results experimentally by means of cyclic voltammetry measurements of limiting diffusion current at the glassy carbon RDE covered with a monolayer of 3 μm silica particles. The theoretical and experimental results are in a good agreement at the surface coverage higher than 0.7. This result suggests that convection in a monolayer of 3 μm monodisperse spherical particles is negligibly small, in the context of the coverage determination, in the range of very dense particle layers.

Effect of particle stiffness on contact dynamics and rheology in a dense granular flow

NASA Astrophysics Data System (ADS)

Bharathraj, S.; Kumaran, V.

2018-01-01

Dense granular flows have been well described by the Bagnold rheology, even when the particles are in the multibody contact regime and the coordination number is greater than 1. This is surprising, because the Bagnold law should be applicable only in the instantaneous collision regime, where the time between collisions is much larger than the period of a collision. Here, the effect of particle stiffness on rheology is examined. It is found that there is a rheological threshold between a particle stiffness of 104-105 for the linear contact model and 105-106 for the Hertzian contact model above which Bagnold rheology (stress proportional to square of the strain rate) is valid and below which there is a power-law rheology, where all components of the stress and the granular temperature are proportional to a power of the strain rate that is less then 2. The system is in the multibody contact regime at the rheological threshold. However, the contact energy per particle is less than the kinetic energy per particle above the rheological threshold, and it becomes larger than the kinetic energy per particle below the rheological threshold. The distribution functions for the interparticle forces and contact energies are also analyzed. The distribution functions are invariant with height, but they do depend on the contact model. The contact energy distribution functions are well fitted by Gamma distributions. There is a transition in the shape of the distribution function as the particle stiffness is decreased from 107 to 106 for the linear model and 108 to 107 for the Hertzian model, when the contact number exceeds 1. Thus, the transition in the distribution function correlates to the contact regime threshold from the binary to multibody contact regime, and is clearly different from the rheological threshold. An order-disorder transition has recently been reported in dense granular flows. The Bagnold rheology applies for both the ordered and disordered states, even though the rheological constants differ by orders of magnitude. The effect of particle stiffness on the order-disorder transition is examined here. It is found that when the particle stiffness is above the rheological threshold, there is an order-disorder transition as the base roughness is increased. The order-disorder transition disappears after the crossover to the soft-particle regime when the particle stiffness is decreased below the rheological threshold, indicating that the transition is a hard-particle phenomenon.

Effect of particle stiffness on contact dynamics and rheology in a dense granular flow.

PubMed

Bharathraj, S; Kumaran, V

2018-01-01

Dense granular flows have been well described by the Bagnold rheology, even when the particles are in the multibody contact regime and the coordination number is greater than 1. This is surprising, because the Bagnold law should be applicable only in the instantaneous collision regime, where the time between collisions is much larger than the period of a collision. Here, the effect of particle stiffness on rheology is examined. It is found that there is a rheological threshold between a particle stiffness of 10^{4}-10^{5} for the linear contact model and 10^{5}-10^{6} for the Hertzian contact model above which Bagnold rheology (stress proportional to square of the strain rate) is valid and below which there is a power-law rheology, where all components of the stress and the granular temperature are proportional to a power of the strain rate that is less then 2. The system is in the multibody contact regime at the rheological threshold. However, the contact energy per particle is less than the kinetic energy per particle above the rheological threshold, and it becomes larger than the kinetic energy per particle below the rheological threshold. The distribution functions for the interparticle forces and contact energies are also analyzed. The distribution functions are invariant with height, but they do depend on the contact model. The contact energy distribution functions are well fitted by Gamma distributions. There is a transition in the shape of the distribution function as the particle stiffness is decreased from 10^{7} to 10^{6} for the linear model and 10^{8} to 10^{7} for the Hertzian model, when the contact number exceeds 1. Thus, the transition in the distribution function correlates to the contact regime threshold from the binary to multibody contact regime, and is clearly different from the rheological threshold. An order-disorder transition has recently been reported in dense granular flows. The Bagnold rheology applies for both the ordered and disordered states, even though the rheological constants differ by orders of magnitude. The effect of particle stiffness on the order-disorder transition is examined here. It is found that when the particle stiffness is above the rheological threshold, there is an order-disorder transition as the base roughness is increased. The order-disorder transition disappears after the crossover to the soft-particle regime when the particle stiffness is decreased below the rheological threshold, indicating that the transition is a hard-particle phenomenon.

Epithelial stem cells are formed by small-particles released from particle-producing cells

PubMed Central

Kong, Wuyi; Zhu, Xiao Ping; Han, Xiu Juan; Nuo, Mu; Wang, Hong

2017-01-01

Recent spatiotemporal report demonstrated that epidermal stem cells have equal potential to divide or differentiate, with no asymmetric cell division observed. Therefore, how epithelial stem cells maintain lifelong stem-cell support still needs to be elucidated. In mouse blood and bone marrow, we found a group of large cells stained strongly for eosin and containing coiled-tubing-like structures. Many were tightly attached to each other to form large cellular clumps. After sectioning, these large cell-clumps were composed of not cells but numerous small particles, however with few small “naked” nuclei. The small particles were about 2 to 3 μm in diameter and stained dense red for eosin, so they may be rich in proteins. Besides the clumps composed of small particles, we identified clumps formed by fusion of the small particles and clumps of newly formed nucleated cells. These observations suggest that these small particles further fused and underwent cellularization. E-cadherin was expressed in particle-fusion areas, some “naked” nuclei and the newly formed nucleated cells, which suggests that these particles can form epithelial cells via fusion and nuclear remodeling. In addition, we observed similar-particle fusion before epithelial cellularization in mouse kidney ducts after kidney ischemia, which suggests that these particles can be released in the blood and carried to the target tissues for epithelial-cell regeneration. Oct4 and E-cadherin expressed in the cytoplasmic areas in cells that were rich in protein and mainly located in the center of the cellular clumps, suggesting that these newly formed cells have become tissue-specific epithelial stem cells. Our data provide evidence that these large particle-producing cells are the origin of epithelial stem cells. The epithelial stem cells are newly formed by particle fusion. PMID:28253358

Structure-property relationships of a biological mesocrystal in the adult sea urchin spine

PubMed Central

Seto, Jong; Ma, Yurong; Davis, Sean A.; Meldrum, Fiona; Gourrier, Aurelien; Kim, Yi-Yeoun; Schilde, Uwe; Sztucki, Michael; Burghammer, Manfred; Maltsev, Sergey; Jäger, Christian; Cölfen, Helmut

2012-01-01

Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature’s demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials. PMID:22343283

Structure-property relationships of a biological mesocrystal in the adult sea urchin spine.

PubMed

Seto, Jong; Ma, Yurong; Davis, Sean A; Meldrum, Fiona; Gourrier, Aurelien; Kim, Yi-Yeoun; Schilde, Uwe; Sztucki, Michael; Burghammer, Manfred; Maltsev, Sergey; Jäger, Christian; Cölfen, Helmut

2012-03-06

Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature's demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials.

Light scattering and absorption by space weathered planetary bodies: Novel numerical solution

NASA Astrophysics Data System (ADS)

Markkanen, Johannes; Väisänen, Timo; Penttilä, Antti; Muinonen, Karri

2017-10-01

Airless planetary bodies are exposed to space weathering, i.e., energetic electromagnetic and particle radiation, implantation and sputtering from solar wind particles, and micrometeorite bombardment.Space weathering is known to alter the physical and chemical composition of the surface of an airless body (C. Pieters et al., J. Geophys. Res. Planets, 121, 2016). From the light scattering perspective, one of the key effects is the production of nanophase iron (npFe0) near the exposed surfaces (B. Hapke, J. Geophys. Res., 106, E5, 2001). At visible and ultraviolet wavelengths these particles have a strong electromagnetic response which has a major impact on scattering and absorption features. Thus, to interpret the spectroscopic observations of space-weathered asteroids, the model should treat the contributions of the npFe0 particles rigorously.Our numerical approach is based on the hierarchical geometric optics (GO) and radiative transfer (RT). The modelled asteroid is assumed to consist of densely packed silicate grains with npFe0 inclusions. We employ our recently developed RT method for dense random media (K. Muinonen, et al., Radio Science, submitted, 2017) to compute the contributions of the npFe0 particles embedded in silicate grains. The dense media RT method requires computing interactions of the npFe0 particles in the volume element for which we use the exact fast superposition T-matrix method (J. Markkanen, and A.J. Yuffa, JQSRT 189, 2017). Reflections and refractions on the grain surface and propagation in the grain are addressed by the GO. Finally, the standard RT is applied to compute scattering by the entire asteroid.Our numerical method allows for a quantitative interpretation of the spectroscopic observations of space-weathered asteroids. In addition, it may be an important step towards more rigorous a thermophysical model of asteroids when coupled with the radiative and conductive heat transfer techniques.Acknowledgments. Research supported by European Research Council with Advanced Grant No. 320773 SAEMPL. Computational resources provided by CSC- IT Centre for Science Ltd, Finland.

Acceptance Test Data for BWXT Coated Particle Batches 93172B and 93173B—Defective IPyC and Pyrocarbon Anisotropy

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

Hunn, John D.; Helmreich, Grant W.; Dyer, John A.

Coated particle batches J52O-16-93172B and J52O-16-93173B were produced by Babcock and Wilcox Technologies (BWXT) as part of the production campaign for the Advanced Gas Reactor Fuel Development and Qualification (AGR) Program’s AGR-5/6/7 irradiation test in the Idaho National Laboratory (INL) Advanced Test Reactor (ATR), but were not used in the final fuel composite. However, these batches may be used as demonstration production-scale coated particle fuel for other experiments. Each batch was coated in a 150-mm-diameter production-scale fluidized-bed chemical vapor deposition (CVD) furnace. Tristructural isotropic (TRISO) coatings were deposited on 425-μm-nominal-diameter spherical kernels from BWXT lot J52R-16-69317 containing a mixture ofmore » 15.5%-enriched uranium carbide and uranium oxide (UCO). The TRISO coatings consisted of four consecutive CVD layers: a ~50% dense carbon buffer layer with 100-μm-nominal thickness, a dense inner pyrolytic carbon (IPyC) layer with 40-μm-nominal thickness, a silicon carbide (SiC) layer with 35-μm-nominal thickness, and a dense outer pyrolytic carbon (OPyC) layer with 40-μm-nominal thickness. The TRISO-coated particle batches were sieved to upgrade the particles by removing over-sized and under-sized material, and the upgraded batches were designated by appending the letter A to the end of the batch number (e.g., 93172A). Secondary upgrading by sieving was performed on the A-designated batches to remove particles with missing or very-thin buffer layers that were identified during previous analysis of the individual batches for defective IPyC, as reported in the acceptance test data report for the AGR-5/6/7 production batches [Hunn et al. 2017b]. The additionally-upgraded batches were designated by appending the letter B to the end of the batch number (e.g., 93172B).« less

Deconstructing Temperature Gradients across Fluid Interfaces: The Structural Origin of the Thermal Resistance of Liquid-Vapor Interfaces

NASA Astrophysics Data System (ADS)

Muscatello, Jordan; Chacón, Enrique; Tarazona, Pedro; Bresme, Fernando

2017-07-01

The interfacial thermal resistance determines condensation-evaporation processes and thermal transport across material-fluid interfaces. Despite its importance in transport processes, the interfacial structure responsible for the thermal resistance is still unknown. By combining nonequilibrium molecular dynamics simulations and interfacial analyses that remove the interfacial thermal fluctuations we show that the thermal resistance of liquid-vapor interfaces is connected to a low density fluid layer that is adsorbed at the liquid surface. This thermal resistance layer (TRL) defines the boundary where the thermal transport mechanism changes from that of gases (ballistic) to that characteristic of dense liquids, dominated by frequent particle collisions involving very short mean free paths. We show that the thermal conductance is proportional to the number of atoms adsorbed in the TRL, and hence we explain the structural origin of the thermal resistance in liquid-vapor interfaces.

Lateral Structure Formation in Polyelectrolyte Brushes Induced by Multivalent Ions

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

Brettmann, Blair; Pincus, Philip; Tirrell, Matthew

2017-01-13

We provide a theoretical model for the collapse of polyelectrolyte brushes in the presence of multivalent ions, focusing on the formation of lateral inhomogeneties in the collapsed state. Polyelectrolyte brushes are important in a variety of applications, including stabilizing colloidal particles and lubricating surfaces. Many uses rely on the extension of the densely grafted polymer chains from the surface in the extended brush morphology. In the presence Extended Brush of multivalent ions, brushes are significantly shorter than in monovalent ionic solutions, which greatly affects their properties. We base our theoretical analysis on an analogous collapse of polyelectrolyte brushes in amore » poor solvent, providing an energy balance representation for pinned micelles and cylindrical bundles. The equilibrium brush heights predicted for these structures are of a similar magnitude to those measured experimentally. The formation of lateral structures can open new avenues for stimuli-responsive applications that rely on nanoscale pattern formation on surfaces.« less

Transformation of the ordered internal structures during the acceleration of fast charged particles in a dense plasma focus

NASA Astrophysics Data System (ADS)

Kubes, P.; Paduch, M.; Cikhardt, J.; Cikhardtova, B.; Klir, D.; Kravarik, J.; Rezac, K.; Zielinska, E.; Sadowski, M. J.; Szymaszek, A.; Tomaszewski, K.; Zaloga, D.

2017-07-01

The paper concerns important differences in the evolution of plasma column structures during the production of fusion neutrons in the first and subsequent neutron pulses, as observed for plasma-focus discharges performed with the deuterium filling. The first neutron pulse, of a more isotropic distribution, is usually produced during the formation of the first big plasmoid. The next neutron pulses can be generated by the fast deuterons moving dominantly in the downstream direction, at the instants of a disruption of the pinch constriction, when other plasmoids are formed during the constriction evolution. In both cases, the fusion neutrons are produced by a beam-target mechanism, and the acceleration of fast electron- and deuteron-beams can be interpreted by transformation and decay of the magnetic field associated with a filamentary structure of the current flow in the plasmoid.

Study and Fabrication of Super Low-Cost Solar Cell (SLC-SC) Based on Counter Electrode from Animal’s Bone

NASA Astrophysics Data System (ADS)

Fadlilah, D. R.; Fajar, M. N.; Aini, A. N.; Haqqiqi, R. I.; Wirawan, P. R.; Endarko

2018-04-01

The synthesized carbon from bones of chicken, cow, and fish with the calcination temperature at 450 and 600°C have been successfully fabricated for counter electrode in the Super Low-Cost Solar Cell (SLC-LC) based the structure of Dye-Sensitized Solar Cells (DSSC). The main proposed study was to fabricate SLC-SC and investigate the influence of the synthesized carbon from animal’s bone for counter electrode towards to photovoltaic performance of SLC-SC. X-Ray Diffraction and UV-Vis was used to characterize the phase and the optical properties of TiO2 as photoanode in SLC-SC. Meanwhile, the morphology and particle size distribution of the synthesized carbon in counter electrodes were investigated by Scanning Electron Microscopy (SEM) and Particle Size Analyzer (PSA). The results showed that the TiO2 has anatase phase with the absorption wavelength of 300 to 550 nm. The calcination temperature for synthesizing of carbon could affect morphology and particle size distribution. The increasing temperature gave the effect more dense in morphology and increased the particle size of carbon in the counter electrode. Changes in morphology and particle size of carbon give effect to the performance of the SLC-SC where the increased morphology’s compact and particle size make decreased in the performance of the SLC-SC.

Active micromachines: Microfluidics powered by mesoscale turbulence

PubMed Central

Thampi, Sumesh P.; Doostmohammadi, Amin; Shendruk, Tyler N.; Golestanian, Ramin; Yeomans, Julia M.

2016-01-01

Dense active matter, from bacterial suspensions and microtubule bundles driven by motor proteins to cellular monolayers and synthetic Janus particles, is characterized by mesoscale turbulence, which is the emergence of chaotic flow structures. By immersing an ordered array of symmetric rotors in an active fluid, we introduce a microfluidic system that exploits spontaneous symmetry breaking in mesoscale turbulence to generate work. The lattice of rotors self-organizes into a spin state where neighboring discs continuously rotate in permanent alternating directions due to combined hydrodynamic and elastic effects. Our virtual prototype demonstrates a new research direction for the design of micromachines powered by the nematohydrodynamic properties of active turbulence. PMID:27419229

On the characterization of inhomogeneity of the density distribution in supercritical fluids via molecular dynamics simulation and data mining analysis.

PubMed

Idrissi, Abdenacer; Vyalov, Ivan; Georgi, Nikolaj; Kiselev, Michael

2013-10-10

We combined molecular dynamics simulation and DBSCAN algorithm (Density Based Spatial Clustering of Application with Noise) in order to characterize the local density inhomogeneity distribution in supercritical fluids. The DBSCAN is an algorithm that is capable of finding arbitrarily shaped density domains, where domains are defined as dense regions separated by low-density regions. The inhomogeneity of density domain distributions of Ar system in sub- and supercritical conditions along the 50 bar isobar is associated with the occurrence of a maximum in the fluctuation of number of particles of the density domains. This maximum coincides with the temperature, Tα, at which the thermal expansion occurs. Furthermore, using Voronoi polyhedral analysis, we characterized the structure of the density domains. The results show that with increasing temperature below Tα, the increase of the inhomogeneity is mainly associated with the density fluctuation of the border particles of the density domains, while with increasing temperature above Tα, the decrease of the inhomogeneity is associated with the core particles.

Direct measurement of the ballistic motion of a freely floating colloid in Newtonian and viscoelastic fluids.

PubMed

Hammond, Andrew P; Corwin, Eric I

2017-10-01

A thermal colloid suspended in a liquid will transition from a short-time ballistic motion to a long-time diffusive motion. However, the transition between ballistic and diffusive motion is highly dependent on the properties and structure of the particular liquid. We directly observe a free floating tracer particle's ballistic motion and its transition to the long-time regime in both a Newtonian fluid and a viscoelastic Maxwell fluid. We examine the motion of the free particle in a Newtonian fluid and demonstrate a high degree of agreement with the accepted Clercx-Schram model for motion in a dense fluid. Measurements of the functional form of the ballistic-to-diffusive transition provide direct measurements of the temperature, viscosity, and tracer radius. We likewise measure the motion in a viscoelastic Maxwell fluid and find a significant disagreement between the theoretical asymptotic behavior and our measured values of the microscopic properties of the fluid. We observe a greatly increased effective mass for a freely moving particle and a decreased plateau modulus.

Direct Visualization of Conformation and Dense Packing of DNA-Based Soft Colloids

NASA Astrophysics Data System (ADS)

Zhang, Jing; Lettinga, Paul M.; Dhont, Jan K. G.; Stiakakis, Emmanuel

2014-12-01

Soft colloids—such as polymer-coated particles, star polymers, block-copolymer micelles, microgels—constitute a broad class of materials where microscopic properties such as deformability and penetrability of the particle play a key role in tailoring their macroscopic properties which is of interest in many technological areas. The ability to access these microscopic properties is not yet demonstrated despite its great importance. Here we introduce novel DNA-coated colloids with star-shaped architecture that allows accessing the above local structural information by directly visualizing their intramolecular monomer density profile and arm's free-end locations with confocal fluorescent microscopy. Compression experiments on a two-dimensional hexagonal lattice formed by these macromolecular assemblies reveal an exceptional resistance to mutual interpenetration of their charged corona at pressures approaching the MPa range. Furthermore, we find that this lattice, in a close packing configuration, is surprisingly tolerant to particle size variation. We anticipate that these stimuli-responsive materials could aid to get deeper insight in a wide range of problems in soft matter, including the study and design of biomimetic lubricated surfaces.

Two-dimensional positive column structure with dust cloud: Experiment and nonlocal kinetic simulation

NASA Astrophysics Data System (ADS)

Zobnin, A. V.; Usachev, A. D.; Petrov, O. F.; Fortov, V. E.; Thoma, M. H.; Fink, M. A.

2018-03-01

The influence of a dust cloud on the structure of the positive column of a direct current gas discharge in a cylindrical glass tube under milligravity conditions has been studied both experimentally and numerically. The discharge was produced in neon at 60 Pa in a glass tube with a diameter of 30 mm at a discharge current 1 mA. Spherical monodisperse melamine formaldehyde dust particles with a diameter of 6.86 μm were injected into the positive column and formed there a uniform dust cloud with a maximum diameter of 14.4 mm. The shape of the cloud and the dust particle number density were measured. The cloud was stationary in the radial direction and slowly drifted in the axial direction. It was found that in the presence of the dust cloud, the intensity of the neon spectral line with a wavelength by 585.25 nm emitted by the discharge plasma increased by 2.3 times and 2 striations appeared on the anode side of the cloud. A numerical simulation of the discharge was performed using the 2D (quasi-3D) nonlocal self-consistent kinetic model of a longitudinally inhomogeneous axially symmetric positive column [Zobnin et al., Phys. Plasmas 21, 113503 (2014)], which was supplemented by a program module performing a self-consistent calculation of dust particle charges, the plasma recombination rate on dust particles, and ion scattering on dust particles. A new approach to the calculation of particle charges and the screening radius in dense dust clouds is proposed. The results of the simulation are presented, compared with experimental data and discussed. It is demonstrated that for the best agreement between simulated and experimental data, it is necessary to take into account the reflection of electrons from the dust particle surface in order to correctly describe the recombination rate in the cloud, its radial stability, and the dust particle charges.

Dense crystalline packings of ellipsoids

NASA Astrophysics Data System (ADS)

Jin, Weiwei; Jiao, Yang; Liu, Lufeng; Yuan, Ye; Li, Shuixiang

2017-03-01

An ellipsoid, the simplest nonspherical shape, has been extensively used as a model for elongated building blocks for a wide spectrum of molecular, colloidal, and granular systems. Yet the densest packing of congruent hard ellipsoids, which is intimately related to the high-density phase of many condensed matter systems, is still an open problem. We discover an unusual family of dense crystalline packings of self-dual ellipsoids (ratios of the semiaxes α : √{α }:1 ), containing 24 particles with a quasi-square-triangular (SQ-TR) tiling arrangement in the fundamental cell. The associated packing density ϕ exceeds that of the densest known SM2 crystal [ A. Donev et al., Phys. Rev. Lett. 92, 255506 (2004), 10.1103/PhysRevLett.92.255506] for aspect ratios α in (1.365, 1.5625), attaining a maximal ϕ ≈0.758 06 ... at α = 93 /64 . We show that the SQ-TR phase derived from these dense packings is thermodynamically stable at high densities over the aforementioned α range and report a phase diagram for self-dual ellipsoids. The discovery of the SQ-TR crystal suggests organizing principles for nonspherical particles and self-assembly of colloidal systems.

Development and utilization of new diagnostics for dense-phase pneumatic transport. Quarterly technical progress report, October 1-December 31, 1989

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

Louge, M. Y.; Jenkins, J. T.

The main objective of this work is to develop probes for local measurements of solid velocity and holdup in dense gas-solid flows. In particular, capacitance probes are designed to measure local, time-dependent particle concentrations. In addition, a new optical fiber probe based on laser-induced-phosphorescence is developed to measure particle velocities. The principles for the capacitance and optical diagnostics were given in our first and second quarterly reports. In this reporting period, we have demonstrated with success the feasibility of the optical fiber probe. Another objective of this work is to develop a model of dense-phase conveying and to test thismore » model in a setup that incorporates our diagnostics. In this period, as a prelude to these modeling efforts scheduled for the third year of the contract, we have carried out additional computer simulations of rapid granular flows to verify the theories of Jenkins and Richman (1988) on the anisotropy of the second moment in simple shear. 2 refs., 5 figs.« less

Development and utilization of new diagnostics for dense-phase pneumatic transport

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

Louge, M.Y.; Jenkins, J.T.

Dense-phase pneumatic transport is an attractive means of conveying solids. Unfortunately, because of the high solid concentrations, this transport method is a difficult regime in which to carry out detailed measurements. Hence most details of the flow are unknown. In this context, the main objective of this work is to develop probes for local measurements of solid velocity and holdup in dense gas-solid flows. In particular, the authors have designed capacitance probes to measure local, time-dependent particle concentrations, and a new optical fiber probe based on laser-induced-phosphorescence to measure particle velocities. The principles for the capacitance and optical diagnostics weremore » given in the first and second quarterly reports. A final version of the optical fiber probe was designed in the previous reporting period. Because granular flows depends strongly on the nature of their interaction with a boundary, the authors have sought in the present reporting period to verify the boundary conditions recently calculated by Jenkins (J. Appl. Mech., in press (1991)) using computer simulations. 2 refs., 2 figs.« less

Microstructure and Mechanical Properties of Ti-6Al-4V Fabricated by Selective Laser Melting of Powder Produced by Granulation-Sintering-Deoxygenation Method

NASA Astrophysics Data System (ADS)

Sun, Pei; Fang, Z. Zak; Zhang, Ying; Xia, Yang

2017-12-01

Commercial spherical Ti powders for additive manufacturing applications are produced today by melt-atomization methods at relatively high costs. A meltless production method, called granulation-sintering-deoxygenation (GSD), was developed recently to produce spherical Ti alloy powder at a significantly reduced cost. In this new process, fine hydrogenated Ti particles are agglomerated to form spherical granules, which are then sintered to dense spherical particles. After sintering, the solid fully dense spherical Ti alloy particles are deoxygenated using novel low-temperature deoxygenation processes with either Mg or Ca. This technical communication presents results of 3D printing using GSD powder and the selective laser melting (SLM) technique. The results showed that tensile properties of parts fabricated from spherical GSD Ti-6Al-4V powder by SLM are comparable with typical mill-annealed Ti-6Al-4V. The characteristics of 3D printed Ti-6Al-4V from GSD powder are also compared with that of commercial materials.

Detection of banned meat and bone meal in feedstuffs by near-infrared microscopic analysis of the dense sediment fraction.

PubMed

Baeten, Vincent; von Holst, Christoph; Garrido, Ana; Vancutsem, Jeroen; Michotte Renier, Antoine; Dardenne, Pierre

2005-05-01

In this paper we present an alternative method for detection of meat and bone meal (MBM) in feedstuffs by near-infrared microscopic (NIRM) analysis of the particles in the sediment fraction (dense fraction (d >1.62) from dichloroethylene) of compound feeds. To apply this method the particles of the sediment fraction are spread on a sample holder and presented to the NIR microscope. By using the pointer of the microscope the infrared beam is focussed on each particle and the NIR spectrum (1112-2500 nm) is collected. This method can be used to detect the presence of MBM at concentrations as low as 0.05% mass fraction. When results from the NIRM method were compared with the classical microscopic method, a coefficient of determination (R2) of 0.87 was obtained. The results of this study demonstrated that this method could be proposed as a complementary tool for the detection of banned MBM in feedstuffs by reinforcement of the monitoring of feeds.

Cytochemical localization of cellulases in decayed and nondecayed wood

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

Murmanis, L.; Highley, T.L.; Palmer, J.G.

1987-01-01

Sawdust from undecayed western hemlock wood and from wood previously decayed by the brown-rot fungus Poria placenta or by the white-rot fungus Ganoderma applanatum was incubated with commercial cellulase from Trichoderma viride. Samples were treated cytochemically to locate cellulase activity and examined by TEM. Results showed that cellulase degraded undecayed wood extensively, with the attack starting on the outer border of a cell wall and progressing inside. Wood decayed by P. placenta, with or without cellulase incubation, and treated by the cytochemical test showed uniform distribution of electron dense particles throughout the cell walls. In wood decayed by G. applanatum,more » cellulase degradation was similar to that in undecayed wood. From measurements of particle diameter it is suggested that electron dense particles are cellulase. It is concluded that brown-rot and white-rot fungi have different effects on the microstructure of wood. The brown-rot fungus appears to open the wood microstructure so that cellulase can diffuse throughout the degraded tracheid wall.« less

Characterizing dense suspensions: two case studies from the pharmaceutical industry

NASA Astrophysics Data System (ADS)

Goldfarb, David J.; Khawaja, Nazia; Kazakevich, Irina; Bhattacharjee, Himanshu; Heslinga, Michael; Dalton, Chad

2015-11-01

Liquid suspensions of Active Pharmaceutical Ingredient powders are present as pharmaceutical dosage forms in the form of oral suspensions and injectables. We present two case studies, both dense (~ 30-40%) suspensions, in which the physical characterization of the product, specifically, particle size & shape and rheology were key to understanding the key product attributes as pertaining to the manufacturing process and to patient administration. For the one case study, an oral suspension, identifying variations in particle morphology during the wet milling of the product was key to the product understanding necessary to modify the milling process. Rheological measurements were applied as well. For the second case study, an injectable, results from different particle size measurement techniques and rheological measurements indicated the possibility of flocculation in a formulation. Additionally, measurements were obtained to assess the ``injectability'' of the product via rheometer and texture analyzer measurements and Poiseuille flow modeling. As a result, the relevant shear rate regime for this drug product administration was identified.

Voidage correction algorithm for unresolved Euler-Lagrange simulations

NASA Astrophysics Data System (ADS)

Askarishahi, Maryam; Salehi, Mohammad-Sadegh; Radl, Stefan

2018-04-01

The effect of grid coarsening on the predicted total drag force and heat exchange rate in dense gas-particle flows is investigated using Euler-Lagrange (EL) approach. We demonstrate that grid coarsening may reduce the predicted total drag force and exchange rate. Surprisingly, exchange coefficients predicted by the EL approach deviate more significantly from the exact value compared to results of Euler-Euler (EE)-based calculations. The voidage gradient is identified as the root cause of this peculiar behavior. Consequently, we propose a correction algorithm based on a sigmoidal function to predict the voidage experienced by individual particles. Our correction algorithm can significantly improve the prediction of exchange coefficients in EL models, which is tested for simulations involving Euler grid cell sizes between 2d_p and 12d_p . It is most relevant in simulations of dense polydisperse particle suspensions featuring steep voidage profiles. For these suspensions, classical approaches may result in an error of the total exchange rate of up to 30%.

Histopathological observation of lymphocystis disease and lymphocystis disease virus (LCDV) detection in cultured diseased Sebastes schlegeli

NASA Astrophysics Data System (ADS)

Sheng, Xiuzhen; Zhan, Wenbin; Xu, Songjuan; Cheng, Shunfeng

2007-10-01

Lymphocystis nodules occurring in the cultured sting fish Sebastes schlegeli were observed under light and electron microscope. Lymphocystis disease virus (LCDV) in the tissues of diseased fish was detected with indirect immunofluorescence test (IFAT). Results showed that lymphocystis cells had overly irregular nuclei, basophilic intracytoplasmic inclusion bodies with virions budding from the surface, and hyaline capsules outside the cell membrane. Numerous virus particles about 200 nm in diameter scattered in the cytoplasm, electron-dense particles 70 80 nm in diameter filled in perinuclear cisterna, and membrane-enveloped particles with electron-dense core of 70 80 nm appeared around cellular nucleus. IFAT using monoclonal antibody against LCDV from Paralichthys olivaceus revealed that specific green fluorescence was present in the cytoplasm of lymphocystis cells, epithelium of stomach, gill lamellae, and muscular fibers under epidermis of S. schlegeli, just as that in the cytoplasm of lymphocystis cells of P. olivaceus, suggesting the presence of LCDV in these tissues.

Dense, gravity-driven granular-liquid flows down steep channels

NASA Astrophysics Data System (ADS)

Armanini, A.; Larcher, M.; Nucci, E.

2011-12-01

Debris flows are complex natural phenomena, characterized by a mixture of poorly sorted sediments and water driven by gravity. Depending on the size distribution, on the volume concentration of sediments and on the geometry and topography of the channel, flow conditions may be very different, ranging from very fast flows, dominated by granular collisions and by the turbulence on the liquid phase, to very slow and dense flows, dominated by the frictional contacts among the grains. To investigate the basic physics of debris flows, it is very useful to analyze the flow of a mixture of identical spherical particles saturated by water and driven by gravity down a steep channel in steady flow condition (Armanini et al. 2005). The flow presents three regions: an external one, near to the free surface, dominated by nearly instantaneous contacts among the particles (collisional regime), an internal region dominated by prolonged contacts among the particles (frictional regime) and a static bed in which the particles are immobile. The detailed vertical structure of this kind of flows was obtained by means of experiments carried out by Armanini et al. (2005) and Larcher et al. (2007). Armanini et al. (2009) analysed the stratification of rheological mechanisms inside the flow, focusing on the coexistence of frictional and collisional regimes, on the stress transmission inside the flow and on particles kinematics. In particular, it was observed that debris flows may show locally a typical intermittence of the flow regime, switching alternatively from frictional to collisional. While the rheology of the collisional layers is well described by the dense gas analogy (kinetic theory), a persuasive theoretical description of the frictional regime does not yet exist. A Coulombian scheme is often assumed, but this hypothesis is rather limitative because it requires a constant concentration or a distribution of particles concentration known a priori. An interesting scheme of this kind was recently proposed by GDR-Midi (2004), but this model does not contain a suitable formulation for the granular pressure (equation of state of the mixture). Following Armanini (2010), we propose a reinterpretation of the model, as weighted average of a pure Coulombian stress (dependent on the static friction angle at the static bed level) and of a dynamic stress, represented by a dynamic friction angle. Besides, a state relation is introduced for the granular pressure and the dynamic friction angle is derived from the kinetic theory. The proposed relations are finally successfully compared with the experimental data introduced above. REFERENCES A. Armanini, H. Capart, L. Fraccarollo, M. Larcher, 2005, J.F.M., 532, 269-319. A. Armanini, M. Larcher, L. Fraccarollo, Ph. Rev. E, 2009, 79, 051306. A. Armanini, 2010, Palermo, Proc. XXXII Conv. Naz. di Idr. e C.I. (in Italian) GDR MiDi, 2004. Eur. Phys. J. E, 14, 341-365 M. Larcher, L. Fraccarollo, A. Armanini, H. Capart, 2007, Journal Hydr. Res., 45, 59-71.

Dynamics of dense granular flows of small-and-large-grain mixtures in an ambient fluid.

PubMed

Meruane, C; Tamburrino, A; Roche, O

2012-08-01

Dense grain flows in nature consist of a mixture of solid constituents that are immersed in an ambient fluid. In order to obtain a good representation of these flows, the interaction mechanisms between the different constituents of the mixture should be considered. In this article, we study the dynamics of a dense granular flow composed of a binary mixture of small and large grains immersed in an ambient fluid. In this context, we extend the two-phase approach proposed by Meruane et al. [J. Fluid Mech. 648, 381 (2010)] to the case of flowing dense binary mixtures of solid particles, by including in the momentum equations a constitutive relation that describes the interaction mechanisms between the solid constituents in a dense regime. These coupled equations are solved numerically and validated by comparing the numerical results with experimental measurements of the front speed of gravitational granular flows resulting from the collapse, in ambient air or water, of two-dimensional granular columns that consisted of mixtures of small and large spherical particles of equal mass density. Our results suggest that the model equations include the essential features that describe the dynamics of grains flows of binary mixtures in an ambient fluid. In particular, it is shown that segregation of small and large grains can increase the front speed because of the volumetric expansion of the flow. This increase in flow speed is damped by the interaction forces with the ambient fluid, and this behavior is more pronounced in water than in air.

Instability-induced ordering, universal unfolding and the role of gravity in granular Couette flow

NASA Astrophysics Data System (ADS)

Alam, Meheboob; Arakeri, V. H.; Nott, P. R.; Goddard, J. D.; Herrmann, H. J.

2005-01-01

Linear stability theory and bifurcation analysis are used to investigate the role of gravity in shear-band formation in granular Couette flow, considering a kinetic-theory rheological model. We show that the only possible state, at low shear rates, corresponds to a "plug" near the bottom wall, in which the particles are densely packed and the shear rate is close to zero, and a uniformly sheared dilute region above it. The origin of such plugged states is shown to be tied to the spontaneous symmetry-breaking instabilities of the gravity-free uniform shear flow, leading to the formation of ordered bands of alternating dilute and dense regions in the transverse direction, via an infinite hierarchy of pitchfork bifurcations. Gravity plays the role of an "imperfection", thus destroying the "perfect" bifurcation structure of uniform shear. The present bifurcation problem admits universal unfolding of pitchfork bifurcations which subsequently leads to the formation of a sequence of a countably infinite number of "isolas", with the solution structures being a modulated version of their gravity-free counterpart. While the solution with a plug near the bottom wall looks remarkably similar to the shear-banding phenomenon in dense slow granular Couette flows, a "floating" plug near the top wall is also a solution of these equations at high shear rates. A two-dimensional linear stability analysis suggests that these floating plugged states are unstable to long-wave travelling disturbances.The unique solution having a bottom plug can also be unstable to long waves, but remains stable at sufficiently low shear rates. The implications and realizability of the present results are discussed in the light of shear-cell experiments under "microgravity" conditions.

Activated dynamics in dense fluids of attractive nonspherical particles. II. Elasticity, barriers, relaxation, fragility, and self-diffusion

NASA Astrophysics Data System (ADS)

Tripathy, Mukta; Schweizer, Kenneth S.

2011-04-01

In paper II of this series we apply the center-of-mass version of Nonlinear Langevin Equation theory to study how short-range attractive interactions influence the elastic shear modulus, transient localization length, activated dynamics, and kinetic arrest of a variety of nonspherical particle dense fluids (and the spherical analog) as a function of volume fraction and attraction strength. The activation barrier (roughly the natural logarithm of the dimensionless relaxation time) is predicted to be a rich function of particle shape, volume fraction, and attraction strength, and the dynamic fragility varies significantly with particle shape. At fixed volume fraction, the barrier grows in a parabolic manner with inverse temperature nondimensionalized by an onset value, analogous to what has been established for thermal glass-forming liquids. Kinetic arrest boundaries lie at significantly higher volume fractions and attraction strengths relative to their dynamic crossover analogs, but their particle shape dependence remains the same. A limited universality of barrier heights is found based on the concept of an effective mean-square confining force. The mean hopping time and self-diffusion constant in the attractive glass region of the nonequilibrium phase diagram is predicted to vary nonmonotonically with attraction strength or inverse temperature, qualitatively consistent with recent computer simulations and colloid experiments.

Assembling oppositely charged lock and key responsive colloids: A mesoscale analog of adaptive chemistry

PubMed Central

Mihut, Adriana M.; Stenqvist, Björn; Lund, Mikael; Schurtenberger, Peter; Crassous, Jérôme J.

2017-01-01

We have seen a considerable effort in colloid sciences to copy Nature’s successful strategies to fabricate complex functional structures through self-assembly. This includes attempts to design colloidal building blocks and their intermolecular interactions, such as creating the colloidal analogs of directional molecular interactions, molecular recognition, host-guest systems, and specific binding. We show that we can use oppositely charged thermoresponsive particles with complementary shapes, such as spherical and bowl-shaped particles, to implement an externally controllable lock-and-key self-assembly mechanism. The use of tunable electrostatic interactions combined with the temperature-dependent size and shape and van der Waals interactions of these building blocks provides an exquisite control over the selectivity and specificity of the interactions and self-assembly process. The dynamic nature of the mechanism allows for reversibly cycling through various structures that range from weakly structured dense liquids to well-defined molecule-shaped clusters with different configurations through variations in temperature and ionic strength. We link this complex and dynamic self-assembly behavior to the relevant molecular interactions, such as screened Coulomb and van der Waals forces and the geometrical complementarity of the two building blocks, and discuss our findings in the context of the concepts of adaptive chemistry recently introduced to molecular systems. PMID:28929133

Nonequilibrium Fluctuations and Enhanced Diffusion of a Driven Particle in a Dense Environment

NASA Astrophysics Data System (ADS)

Illien, Pierre; Bénichou, Olivier; Oshanin, Gleb; Sarracino, Alessandro; Voituriez, Raphaël

2018-05-01

We study the diffusion of a tracer particle driven out of equilibrium by an external force and traveling in a dense environment of arbitrary density. The system evolves on a discrete lattice and its stochastic dynamics is described by a master equation. Relying on a decoupling approximation that goes beyond the naive mean-field treatment of the problem, we calculate the fluctuations of the position of the tracer around its mean value on a lattice of arbitrary dimension, and with different boundary conditions. We reveal intrinsically nonequilibrium effects, such as enhanced diffusivity of the tracer induced by both the crowding interactions and the external driving. We finally consider the high-density and low-density limits of the model and show that our approximation scheme becomes exact in these limits.

Model of Fluidized Bed Containing Reacting Solids and Gases

NASA Technical Reports Server (NTRS)

Bellan, Josette; Lathouwers, Danny

2003-01-01

A mathematical model has been developed for describing the thermofluid dynamics of a dense, chemically reacting mixture of solid particles and gases. As used here, "dense" signifies having a large volume fraction of particles, as for example in a bubbling fluidized bed. The model is intended especially for application to fluidized beds that contain mixtures of carrier gases, biomass undergoing pyrolysis, and sand. So far, the design of fluidized beds and other gas/solid industrial processing equipment has been based on empirical correlations derived from laboratory- and pilot-scale units. The present mathematical model is a product of continuing efforts to develop a computational capability for optimizing the designs of fluidized beds and related equipment on the basis of first principles. Such a capability could eliminate the need for expensive, time-consuming predesign testing.

High velocity collisions of nanoparticles

NASA Astrophysics Data System (ADS)

Johnson, Donald F.; Mattson, William D.

2017-01-01

Nanoparticles (NPs) are a unique class of material with highly functionalizable surfaces and exciting applications. With a large surface-to-volume ratio and potentially high surface tension, shocked nanoparticles might display unique materials behavior. Using density functional theory, we have simulated high-velocity NP collisions under a variety of conditions. NPs composed of diamond-C, cubic-BN, and diamond-Si were considered with particle sizes up to 3.5 nm diameter. Additional simulations involved NPs that were destabilized by incorporating internal strain. The initial spherical NP structures were carved out of bulk crystals while the NPs with internal strain were constructed as a dense core (compressive strain) encompassed by a thin shell (tensile strain). Both on-axis and off-axis collisions were simulated at 10 km/s relative velocity. The amount of internal strain was artificially increased by creating a dense inner core with bond lengths compressed up to 8%. Collision dynamics, shock propagation, and fragmentation will be analyzed, but the simulation are ongoing and results are not finalized. The effect of material properties, internal strain, and collision velocity will be discussed.

Processing and properties of magnesium containing a dense uniform dispersion of nanoparticles.

PubMed

Chen, Lian-Yi; Xu, Jia-Quan; Choi, Hongseok; Pozuelo, Marta; Ma, Xiaolong; Bhowmick, Sanjit; Yang, Jenn-Ming; Mathaudhu, Suveen; Li, Xiao-Chun

2015-12-24

Magnesium is a light metal, with a density two-thirds that of aluminium, is abundant on Earth and is biocompatible; it thus has the potential to improve energy efficiency and system performance in aerospace, automobile, defence, mobile electronics and biomedical applications. However, conventional synthesis and processing methods (alloying and thermomechanical processing) have reached certain limits in further improving the properties of magnesium and other metals. Ceramic particles have been introduced into metal matrices to improve the strength of the metals, but unfortunately, ceramic microparticles severely degrade the plasticity and machinability of metals, and nanoparticles, although they have the potential to improve strength while maintaining or even improving the plasticity of metals, are difficult to disperse uniformly in metal matrices. Here we show that a dense uniform dispersion of silicon carbide nanoparticles (14 per cent by volume) in magnesium can be achieved through a nanoparticle self-stabilization mechanism in molten metal. An enhancement of strength, stiffness, plasticity and high-temperature stability is simultaneously achieved, delivering a higher specific yield strength and higher specific modulus than almost all structural metals.

Furthering the investigation of eruption styles through quantitative shape analyses of volcanic ash particles

NASA Astrophysics Data System (ADS)

Nurfiani, D.; Bouvet de Maisonneuve, C.

2018-04-01

Volcanic ash morphology has been quantitatively investigated for various aims such as studying the settling velocity of ash for modelling purposes and understanding the fragmentation processes at the origin of explosive eruptions. In an attempt to investigate the usefulness of ash morphometry for monitoring purposes, we analyzed the shape of volcanic ash particles through a combination of (1) traditional shape descriptors such as solidity, convexity, axial ratio and form factor and (2) fractal analysis using the Euclidean Distance transform (EDT) method. We compare ash samples from the hydrothermal eruptions of Iwodake (Japan) in 2013, Tangkuban Perahu (Indonesia) in 2013 and Marapi (Sumatra, Indonesia) in 2015, the dome explosions of Merapi (Java, Indonesia) in 2013, the Vulcanian eruptions of Merapi in 2010 and Tavurvur (Rabaul, Papaua New Guinea) in 2014, and the Plinian eruption of Kelud (Indonesia) in 2014. Particle size and shape measurements were acquired from a Particle Size Analyzer with a microscope camera attached to the instrument. Clear differences between dense/blocky particles from hydrothermal or dome explosions and vesicular particles produced by the fragmentation of gas-bearing molten magma are well highlighted by conventional shape descriptors and the fractal method. In addition, subtle differences between dense/blocky particles produced by hydrothermal explosions, dome explosions, or quench granulation during phreatomagmatic eruptions can be evidenced with the fractal method. The combination of shape descriptors and fractal analysis is therefore potentially able to distinguish between juvenile and non-juvenile magma, which is of importance for eruption monitoring.

Characterization of a new Hencken burner with a transition from a reducing-to-oxidizing environment for fundamental coal studies

NASA Astrophysics Data System (ADS)

Adeosun, Adewale; Huang, Qian; Li, Tianxiang; Gopan, Akshay; Wang, Xuebin; Li, Shuiqing; Axelbaum, Richard L.

2018-02-01

In pulverized coal burners, coal particles usually transition from a locally reducing environment to an oxidizing environment. The locally reducing environment in the near-burner region is due to a dense region of coal particles undergoing devolatilization. Following this region, the particles move into an oxidizing environment. This "reducing-to-oxidizing" transition can influence combustion processes such as ignition, particulate formation, and char burnout. To understand these processes at a fundamental level, a system is required that mimics such a transition. Hence, we have developed and characterized a two-stage Hencken burner to evaluate the effect of the reducing-to-oxidizing transition and particle-to-particle interaction (which characterizes dense region of coal particles) on ignition and ultrafine aerosol formation. The two-stage Hencken burner allows coal particles to experience a reducing environment followed by a transition to an oxidizing environment. This work presents the results of the design and characterization of the new two-stage Hencken burner and its new coal feeder. In a unique approach to the operation of the flat-flame of the Hencken burner, the flame configurations are operated as either a normal flame or inverse flame. Gas temperatures and oxygen concentrations for the Hencken burner are measured in reducing-to-oxidizing and oxidizing environments. The results show that stable flames with well-controlled conditions, relatively uniform temperatures, and species concentrations can be achieved in both flame configurations. This new Hencken burner provides an effective system for evaluating the effect of the reducing-to-oxidizing transition and particle-to-particle interaction on early-stage processes of coal combustion such as ignition and ultrafine particle formation.

Kinematic Model of Transient Shape-Induced Anisotropy in Dense Granular Flow

NASA Astrophysics Data System (ADS)

Nadler, B.; Guillard, F.; Einav, I.

2018-05-01

Nonspherical particles are ubiquitous in nature and industry, yet previous theoretical models of granular media are mostly limited to systems of spherical particles. The problem is that in systems of nonspherical anisotropic particles, dynamic particle alignment critically affects their mechanical response. To study the tendency of such particles to align, we propose a simple kinematic model that relates the flow to the evolution of particle alignment with respect to each other. The validity of the proposed model is supported by comparison with particle-based simulations for various particle shapes ranging from elongated rice-like (prolate) to flattened lentil-like (oblate) particles. The model shows good agreement with the simulations for both steady-state and transient responses, and advances the development of comprehensive constitutive models for shape-anisotropic particles.

Resolving electrical conductivities from collisionally damped plasmons in isochorically heated warm dense aluminum

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

Sperling, P.; Fletcher, L. B.; Chung, H. -K.

2016-03-29

We measure the highly-resolved inelastic x-ray scattering spectrum of isochorically ultrafast heated aluminum. In the x-ray forward scattering spectra the electron temperature could be measured from the down- and upshifted plasmon, where the electron density of ne = 1:8 1023 cm 3 is known a priori. We have studied the plasmon damping by applying electron-particle collision models beyond the Born approximation determining the electrical conductivity of warm dense aluminum.

Evidence for chiral symmetry restoration in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Moreau, P.; Palmese, A.; Cassing, W.; Seifert, E.; Steinert, T.; Bratkovskaya, E. L.

2017-11-01

We study the effect of the chiral symmetry restoration (CSR) on heavy-ion collisions observables in the energy range √{sNN} = 3- 20GeV within the Parton-Hadron-String Dynamics (PHSD) transport approach. The PHSD includes the deconfinement phase transition as well as essential aspects of CSR in the dense and hot hadronic medium, which are incorporated in the Schwinger mechanism for particle production. Our systematic studies show that chiral symmetry restoration plays a crucial role in the description of heavy-ion collisions at √{sNN} = 3- 20GeV, realizing an increase of the hadronic particle production in the strangeness sector with respect to the non-strange one. Our results provide a microscopic explanation for the horn structure in the excitation function of the K+ /π+ ratio: the CSR in the hadronic phase produces the steep increase of this particle ratio up to √{sNN} ≈ 7GeV, while the drop at higher energies is associated to the appearance of a deconfined partonic medium. Furthermore, the appearance/disappearance of the horn structure is investigated as a function of the system size. We additionally present an analysis of strangeness production in the (T ,μB)-plane (as extracted from the PHSD for central Au+Au collisions) and discuss the perspectives to identify a possible critical point in the phase diagram.

Continuum simulation of heat transfer and solidification behavior of AlSi10Mg in Direct Metal Laser Sintering Process

NASA Astrophysics Data System (ADS)

Ojha, Akash; Samantaray, Mihir; Nath Thatoi, Dhirendra; Sahoo, Seshadev

2018-03-01

Direct Metal Laser Sintering (DMLS) process is a laser based additive manufacturing process, which built complex structures from powder materials. Using high intensity laser beam, the process melts and fuse the powder particles makes dense structures. In this process, the laser beam in terms of heat flux strikes the powder bed and instantaneously melts and joins the powder particles. The partial solidification and temperature distribution on the powder bed endows a high cooling rate and rapid solidification which affects the microstructure of the build part. During the interaction of the laser beam with the powder bed, multiple modes of heat transfer takes place in this process, that make the process very complex. In the present research, a comprehensive heat transfer and solidification model of AlSi10Mg in direct metal laser sintering process has been developed on ANSYS 17.1.0 platform. The model helps to understand the flow phenomena, temperature distribution and densification mechanism on the powder bed. The numerical model takes into account the flow, heat transfer and solidification phenomena. Simulations were carried out for sintering of AlSi10Mg powders in the powder bed having dimension 3 mm × 1 mm × 0.08 mm. The solidification phenomena are incorporated by using enthalpy-porosity approach. The simulation results give the fundamental understanding of the densification of powder particles in DMLS process.

Single-shot mega-electronvolt ultrafast electron diffraction for structure dynamic studies of warm dense matter

NASA Astrophysics Data System (ADS)

Mo, M. Z.; Shen, X.; Chen, Z.; Li, R. K.; Dunning, M.; Sokolowski-Tinten, K.; Zheng, Q.; Weathersby, S. P.; Reid, A. H.; Coffee, R.; Makasyuk, I.; Edstrom, S.; McCormick, D.; Jobe, K.; Hast, C.; Glenzer, S. H.; Wang, X.

2016-11-01

We have developed a single-shot mega-electronvolt ultrafast-electron-diffraction system to measure the structural dynamics of warm dense matter. The electron probe in this system is featured by a kinetic energy of 3.2 MeV and a total charge of 20 fC, with the FWHM pulse duration and spot size at sample of 350 fs and 120 μm respectively. We demonstrate its unique capability by visualizing the atomic structural changes of warm dense gold formed from a laser-excited 35-nm freestanding single-crystal gold foil. The temporal evolution of the Bragg peak intensity and of the liquid signal during solid-liquid phase transition are quantitatively determined. This experimental capability opens up an exciting opportunity to unravel the atomic dynamics of structural phase transitions in warm dense matter regime.

Communication and Collective Consensus Making in Animal Groups via Mechanical Interactions

NASA Astrophysics Data System (ADS)

Várkonyi, Péter L.

2011-06-01

Mechanical constraints have a strong influence on the dynamics and structure of granular aggregations. The contact forces within dense suspensions of active particles may give rise to intriguing phenomena, including anomalous density fluctuations, long-range orientational ordering, and spontaneous pattern formation. Various authors have proposed that these physical phenomena contribute to the ability of animal groups to move coherently. Our systematic numerical simulations confirm that spontaneous interactions of elongated individuals can trigger oriented motion in small groups. They are, however, insufficient in larger ones, despite their significant imprint on the group's internal structure. It is also demonstrated that preferred directions of motion of a minority of group members can be communicated to others solely by mechanical interactions. These findings strengthen the link between pattern formation in active nematics and the collective decision making of social animals.

Mutation induction by heavy ions

NASA Astrophysics Data System (ADS)

Kiefer, J.; Stoll, U.; Schneider, E.

1994-10-01

Mutation induction by heavy ions is compared in yeast and mammalian cells. Since mutants can only be recovered in survivors the influence of inactivation cross sections has to be taken into account. It is shown that both the size of the sensitive cellular site as well as track structure play an important role. Another parameter which influences the probability of mutation induction is repair: Contrary to naive assumptions primary radiation damage does not directly lead to mutations but requires modification to reconstitute the genetic machinery so that mutants can survive. The molecular structure of mutations was analyzed after exposure to deuterons by amplification with the aid of polymerase chain reaction. The results-although preliminary-demonstrate that even with densely ionizing particles a large fraction does not carry big deletions which suggests that point mutations may also be induced by heavy ions.

Ultrastructural identification of peripheral myelin proteins by a pre-embedding immunogold labeling method.

PubMed

Canron, Marie-Hélène; Bouillot, Sandrine; Favereaux, Alexandre; Petry, Klaus G; Vital, Anne

2003-03-01

Ultrastructural immunolabeling of peripheral nervous system components is an important tool to study the relation between structure and function. Owing to the scarcity of certain antigens and the dense structure of the peripheral nerve, a pre-embedding technique is likely appropriate. After several investigations on procedures for pre-embedding immunolabeling, we propose a method that offers a good compromise between detection of antigenic sites and preservation of morphology at the ultrastructural level, and that is easy to use and suitable for investigations on peripheral nerve biopsies from humans. Pre-fixation by immersion in paraformaldehyde/glutaraldehyde is necessary to stabilize the ultrastructure. Then, ultrasmall gold particles with silver enhancement are advised. Antibodies against myelin protein zero and myelin basic protein were chosen for demonstration. The same technique was applied to localize a 35 kDa myelin protein.

Effects of porous films on the light reflectivity of pigmentary titanium dioxide particles

NASA Astrophysics Data System (ADS)

Liang, Yong; Qiao, Bing; Wang, Tig-Jie; Gao, Han; Yu, Keyi

2016-11-01

The light reflectivity of the film-coated titanium dioxide particles (TiO2) as a function of the film refractive index was derived and calculated using a plane film model. For the refractive index in the range of 1.00-2.15, the lower the film refractive index is, the higher is the light reflectivity of the film. It is inferred that the lower apparent refractive index of the porous film resulted in the higher reflectivity of light, i.e., the higher hiding power of the titanium dioxide particles. A dense film coating on TiO2 particles with different types of oxides, i.e., SiO2, Al2O3, MgO, ZnO, ZrO2, TiO2, corresponding to different refractive indices of the film from 1.46 to 2.50, was achieved, and the effects of refractive index on the hiding power from the model prediction were confirmed. Porous film coating of TiO2 particles was achieved by adding the organic template agent triethanolamine (TEA). The hiding power of the coated TiO2 particles was increased from 88.3 to 90.8 by adding the TEA template to the film coating (5-20 wt%). In other words, the amount of titanium dioxide needed was reduced by approximately 10% without a change in the hiding power. It is concluded that the film structure coated on TiO2 particle surface affects the light reflectivity significantly, namely, the porous film exhibits excellent performance for pigmentary titanium dioxide particles with high hiding power.

Unscrambling the Omlette: a New Bubble and Crystal Clustering Mechanism in Chaotically Mixed Magma Flows

NASA Astrophysics Data System (ADS)

Robertson, J.; Metcalfe, G.; Wang, S.; Barnes, S. J.

2014-12-01

The concentration of bubbles, crystals or droplets into small volumes of magma is a key trigger for many interesting magmatic processes. For example, gas slugs driving Strombolian eruptions form from the coalesence of exsolved bubbles within a volcanic conduit, while Ni-Cu-PGE magmatic sulfide deposits require a concentration of dense sulfide droplets from a large volume of magma to form a massive ore body. However the physical mechanism for this clustering remains unresolved - especially since small particles in active magma flows are expected to mostly track flow streamlines rather than clustering. We have uncovered a previously unreported clustering mechanism which is applicable to magmatic flows. This mechanism involves the interaction of particles with two kinds of chaotic flow structure: (a) high-strain regions within the well-mixed chaotic zones of the flow, and (b) unmixed islands of stability within the chaotic flow, known as Kolmogorov-Arnold-Moser (KAM) regions. The first figure shows the difference between chaotic and KAM regions in a chaotic laminar pipe flow. Trapping occurs when particles are scattered from high-strain regions in the chaotic zones and become trapped in the KAM regions, leading to a rapid concentration of particles relative to their original distribution (shown in the second series of figures). Using a combination of these analogue experiments and theoretical analysis we outline the conditions under which this clustering process can occur. We examine the onset of secondary density-related instabilities and the effects of increased particle-particle interaction within the clustered particles, and highlight the impact of particle clustering on the dynamics of magma ascent and emplacement.

Ultrastructural organisation of HCV from the bloodstream of infected patients revealed by electron microscopy after specific immunocapture.

PubMed

Piver, Eric; Boyer, Audrey; Gaillard, Julien; Bull, Anne; Beaumont, Elodie; Roingeard, Philippe; Meunier, Jean-Christophe

2017-08-01

HCV particles are associated with very low-density lipoprotein components in chronically infected patients. These hybrid particles, or 'lipo-viro particles' (LVPs), are rich in triglycerides, and contain the viral RNA, the capsid protein, E1E2 envelope glycoproteins and apolipoproteins B and E. However, their specific ultrastructural organisation has yet to be determined. We developed a strategy for the preparation of any viral sample that preserves the native structure of the LVPs, facilitating their precise morphological characterisation. Using a strategy based on the direct specific immunocapture of particles on transmission electron microscopy (TEM) grids, we characterised the precise morphology of the viral particle by TEM. The LVP consists of a broad nucleocapsid surrounding an electron-dense centre, presumably containing the HCV genome. The nucleocapsid is surrounded by an irregular, detergent-sensitive crescent probably composed of lipids. Lipid content may determine particle size. These particles carry HCV E1E2, ApoB and ApoE, as shown in our immuno-EM analysis. Our results also suggest that these putative LVPs circulate in the serum of patients as part of a mixed population, including lipoprotein-like particles and complete viral particles. Twenty-five years after the discovery of HCV, this study finally provides information about the precise morphological organisation of viral particles. It is truly remarkable that our TEM images fully confirm the ultrastructure of LVPs predicted by several authors, almost exclusively from the results of molecular biology studies. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Investigating the Impacts of Particle Size and Wind Speed on Brownout

DTIC Science & Technology

2015-03-26

mixture of sand, silt, clay , and organic material, classified based on its size and texture. Sand is the largest of the particle materials, with...smallest soil component is clay , with particle sizes less than 0.002 mm. Ultra-fine in texture, clay feels sticky when wet, is extremely cohesive, and does...not allow air to move through it easily. Clay makes a soil dense and is hard as concrete when dry. Loam is a nearly even mixture of sand and silt

Thermophoretic separation of aerosol particles from a sampled gas stream

DOEpatents

Postma, A.K.

1984-09-07

This disclosure relates to separation of aerosol particles from gas samples withdrawn from within a contained atmosphere, such as containment vessels for nuclear reactors or other process equipment where remote gaseous sampling is required. It is specifically directed to separation of dense aerosols including particles of any size and at high mass loadings and high corrosivity. The United States Government has rights in this invention pursuant to Contract DE-AC06-76FF02170 between the US Department of Energy and Westinghouse Electric Corporation.

A semi-Lagrangian transport method for kinetic problems with application to dense-to-dilute polydisperse reacting spray flows

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

Doisneau, François, E-mail: fdoisne@sandia.gov; Arienti, Marco, E-mail: marient@sandia.gov; Oefelein, Joseph C., E-mail: oefelei@sandia.gov

For sprays, as described by a kinetic disperse phase model strongly coupled to the Navier–Stokes equations, the resolution strategy is constrained by accuracy objectives, robustness needs, and the computing architecture. In order to leverage the good properties of the Eulerian formalism, we introduce a deterministic particle-based numerical method to solve transport in physical space, which is simple to adapt to the many types of closures and moment systems. The method is inspired by the semi-Lagrangian schemes, developed for Gas Dynamics. We show how semi-Lagrangian formulations are relevant for a disperse phase far from equilibrium and where the particle–particle coupling barelymore » influences the transport; i.e., when particle pressure is negligible. The particle behavior is indeed close to free streaming. The new method uses the assumption of parcel transport and avoids to compute fluxes and their limiters, which makes it robust. It is a deterministic resolution method so that it does not require efforts on statistical convergence, noise control, or post-processing. All couplings are done among data under the form of Eulerian fields, which allows one to use efficient algorithms and to anticipate the computational load. This makes the method both accurate and efficient in the context of parallel computing. After a complete verification of the new transport method on various academic test cases, we demonstrate the overall strategy's ability to solve a strongly-coupled liquid jet with fine spatial resolution and we apply it to the case of high-fidelity Large Eddy Simulation of a dense spray flow. A fuel spray is simulated after atomization at Diesel engine combustion chamber conditions. The large, parallel, strongly coupled computation proves the efficiency of the method for dense, polydisperse, reacting spray flows.« less

Periodic organosilica hollow nanospheres as anode materials for lithium ion rechargeable batteries

NASA Astrophysics Data System (ADS)

Sasidharan, Manickam; Nakashima, Kenichi; Gunawardhana, Nanda; Yokoi, Toshiyuki; Ito, Masanori; Inoue, Masamichi; Yusa, Shin-Ichi; Yoshio, Masaki; Tatsumi, Takashi

2011-11-01

Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and dipropyldisulfide bridging functionalities using poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) micelles. These hollow particles were thoroughly characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TG/DTA), Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), magic angle spinning-nuclear magnetic resonance (29Si MAS NMR and 13CP-MAS NMR), Raman spectroscopy, and nitrogen adsorption/desorption analyses. The benzene-silica hollow nanospheres with molecular scale periodicity in the shell domain exhibit higher cycling performance of up to 300 cycles in lithium ion rechargeable batteries compared with micron-sized dense benzene-silica particles.Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and dipropyldisulfide bridging functionalities using poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) micelles. These hollow particles were thoroughly characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TG/DTA), Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), magic angle spinning-nuclear magnetic resonance (29Si MAS NMR and 13CP-MAS NMR), Raman spectroscopy, and nitrogen adsorption/desorption analyses. The benzene-silica hollow nanospheres with molecular scale periodicity in the shell domain exhibit higher cycling performance of up to 300 cycles in lithium ion rechargeable batteries compared with micron-sized dense benzene-silica particles. Electronic supplementary information (ESI) available: FTIR, Raman spectral data, additional TEM pictures, N2 adsorption and physical characteristics of hollow particles data, and cycling performance of dense silica particles. See DOI: 10.1039/c1nr10804b

Transformation Characteristics of Ferrite/Carbide Aggregate in Continuously Cooled, Low Carbon-Manganese Steels

NASA Astrophysics Data System (ADS)

Di Martino, S. F.; Thewlis, G.

2014-02-01

Transformation characteristics and morphological features of ferrite/carbide aggregate (FCA) in low carbon-manganese steels have been investigated. Work shows that FCA has neither the lamellae structure of pearlite nor the lath structure of bainite and martensite. It consists of a fine dispersion of cementite particles in a smooth ferrite matrix. Carbide morphologies range from arrays of globular particles or short fibers to extended, branched, and densely interconnected fibers. Work demonstrates that FCA forms over similar cooling rate ranges to Widmanstätten ferrite. Rapid transformation of both phases occurs at temperatures between 798 K and 973 K (525 °C and 700 °C). FCA reaction is not simultaneous with Widmanstätten ferrite but occurs at temperatures intermediate between Widmanstätten ferrite and bainite. Austenite carbon content calculations verify that cementite precipitation is thermodynamically possible at FCA reaction temperatures without bainite formation. The pattern of precipitation is confirmed to be discontinuous. CCT diagrams have been constructed that incorporate FCA. At low steel manganese content, Widmanstätten ferrite and bainite bay sizes are significantly reduced so that large amounts of FCA are formed over a wide range of cooling rates.

Testing the paradigms of the glass transition in colloids

NASA Astrophysics Data System (ADS)

Zia, Roseanna; Wang, Jialun; Peng, Xiaoguang; Li, Qi; McKenna, Gregory

2017-11-01

Many molecular liquids freeze upon fast enough cooling. This so-called glass state is path dependent and out of equilibrium, as measured by the Kovacs signature experiments, i.e. intrinsic isotherms, asymmetry of approach and memory effect. The reasons for this path- and time-dependence are not fully understood, due to fast molecular relaxations. Colloids provide a natural way to model such behavior, owing to disparity in colloidal versus solvent time scales that can slow dynamics. To shed light on the ambiguity of glass transition, we study via large-scale dynamic simulation of hard-sphere colloidal glass after volume-fraction jumps, where particle size increases at fixed system volume followed by protocols of the McKenna-Kovacs signature experiments. During and following each jump, the positions, velocities, and particle-phase stress are tracked and utilized to characterize relaxation time scales. The impact of both quench depth and quench rate on arrested dynamics and ``state'' variables is explored. In addition, we expand our view to various structural signatures, and rearrangement mechanism is proposed. The results provide insight into not only the existence of an ``ideal'' glass transition, but also the role of structure in such a dense amorphous system.

3D Reconnection and SEP Considerations in the CME-Flare Problem

NASA Astrophysics Data System (ADS)

Moschou, S. P.; Cohen, O.; Drake, J. J.; Sokolov, I.; Borovikov, D.; Alvarado Gomez, J. D.; Garraffo, C.

2017-12-01

Reconnection is known to play a major role in particle acceleration in both solar and astrophysical regimes, yet little is known about its connection with the global scales and its comparative contribution in the generation of SEPs with respect to other acceleration mechanisms, such as the shock at a fast CME front, in the presence of a global structure such as a CME. Coupling efforts, combining both particle and global scales, are necessary to answer questions about the fundamentals of the energetic processes evolved. We present such a coupling modeling effort that looks into particle acceleration through reconnection in a self-consistent CME-flare model in both particle and fluid regimes. Of special interest is the supra-thermal component of the acceleration due to the reconnection that will at a later time interact colliding with the solar atmospheric material of the more dense chromospheric layer and radiate in hard X- and γ-rays for super-thermal electrons and protons respectively. Two cutting edge computational codes are used to capture the global CME and flare dynamics, specifically a two fluid MHD code and a 3D PIC code for the flare scales. Finally, we are connecting the simulations with current observations in different wavelengths in an effort to shed light to the unified CME-flare picture.

The small dense LDL particle/large buoyant LDL particle ratio is associated with glucose metabolic status in pregnancy.

PubMed

Chen, Yanmin; Du, Mengkai; Xu, Jianyun; Chen, Danqing

2017-12-14

The lipoprotein subfraction particle profile can be used to improve clinical assessments of cardiovascular disease risk and contribute to early detection of atherogenic dyslipidemia. Lipid alterations in gestational diabetes have been extensively studied, but the results have been inconsistent. Here, we investigated serum lipoprotein subfraction particle levels and their association with glucose metabolic status in pregnancy. Twenty-eight pregnant women with gestational diabetes and 56 pregnant women with normal glucose tolerance matched for body mass index were enrolled in this study. We assessed fasting serum lipid concentrations and lipoprotein subfraction particle levels in participants between 24 and 28 weeks of gestation. The level of low-density lipoprotein (LDL) cholesterol was significantly lower in women with gestational diabetes than in those with normal glucose tolerance, but the triglyceride and high-density lipoprotein (HDL) cholesterol levels of the two groups were similar. Lipoprotein particle analysis showed that very-low-density lipoprotein (VLDL) particle number and the small dense LDL particle/large buoyant LDL particle (sdLDL-P/lbLDL-P) ratio were significantly higher in women with gestational diabetes than in those with normal glucose tolerance (P = 0.013 and P = 0.015, respectively). In multivariate analysis, fasting glucose was independently and positively associated with sdLDL-P/lbLDL-P ratio even after adjustment for maternal age, gestational weight gain, BMI and LDL cholesterol (standardized Beta = 0.214, P = 0.029). The sdLDL-P/lbLDL-P ratio is higher in GDM compared with non-diabetic pregnant women, and positively and independently associated with fasting glucose in pregnant women.

Method of forming and assembly of parts

DOEpatents

Ripley, Edward B.

2010-12-28

A method of assembling two or more parts together that may be metal, ceramic, metal and ceramic parts, or parts that have different CTE. Individual parts are formed and sintered from particles that leave a network of interconnecting porosity in each sintered part. The separate parts are assembled together and then a fill material is infiltrated into the assembled, sintered parts using a method such as capillary action, gravity, and/or pressure. The assembly is then cured to yield a bonded and fully or near-fully dense part that has the desired physical and mechanical properties for the part's intended purpose. Structural strength may be added to the parts by the inclusion of fibrous materials.

Alfven's critical ionization velocity observed in high power impulse magnetron sputtering discharges

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

Brenning, N.; Lundin, D.

2012-09-15

Azimuthally rotating dense plasma structures, spokes, have recently been detected in several high power impulse magnetron sputtering (HiPIMS) devices used for thin film deposition and surface treatment, and are thought to be important for plasma buildup, energizing of electrons, as well as cross-B transport of charged particles. In this work, the drift velocities of these spokes are shown to be strongly correlated with the critical ionization velocity, CIV, proposed by Alfven. It is proposed as the most promising approach in combining the CIV and HiPIMS research fields is to focus on the role of spokes in the process of electronmore » energization.« less

Universal scaling laws of diffusion in two-dimensional granular liquids.

PubMed

Wang, Chen-Hung; Yu, Szu-Hsuan; Chen, Peilong

2015-06-01

We find, in a two-dimensional air table granular system, that the reduced diffusion constant D* and excess entropy S(2) follow two distinct scaling laws: D*∼e(S(2)*) for dense liquids and D∼e(3S(2)*) for dilute ones. The scaling for dense liquids is very similar to that for three-dimensional liquids proposed previously [M. Dzugutov, Nature (London) 381, 137 (1996); A. Samanta et al., Phys. Rev. Lett. 92, 145901 (2004)]. In the dilute regime, a power law [Y. Rosenfeld, J. Phys.: Condens. Matter 11, 5415 (1999)] also fits our data reasonably well. In our system, particles experience low air drag dissipation and interact with each others through embedded magnets. These near-conservative many-body interactions are responsible for the measured Gaussian velocity distribution functions and the scaling laws. The dominance of cage relaxations in dense liquids leads to the different scaling laws for dense and dilute regimes.

Electron injection and acceleration in the plasma bubble regime driven by an ultraintense laser pulse combined with using dense-plasma wall and block

NASA Astrophysics Data System (ADS)

Zhao, Xue-Yan; Xie, Bai-Song; Wu, Hai-Cheng; Zhang, Shan; Hong, Xue-Ren; Aimidula, Aimierding

2012-03-01

An optimizing and alternative scheme for electron injection and acceleration in the wake bubble driven by an ultraintense laser pulse is presented. In this scheme, the dense-plasma wall with an inner diameter matching the expected bubble size is placed along laser propagation direction. Meanwhile, a dense-plasma block dense-plasma is adhered inward transversely at some certain position of the wall. Particle-in-cell simulations are performed, which demonstrate that the block plays an important role in the first electron injection and acceleration. The result shows that a collimated electron bunch with a total number of about 4.04×108μm-1 can be generated and accelerated stably to 1.61 GeV peak energy with 2.6% energy spread. The block contributes about 50% to the accelerated electron injection bunch by tracing and sorting statistically the source.

Physical and Chemical Characterization of Therapeutic Iron Containing Materials: A Study of Several Superparamagnetic Drug Formulations with the β-FeOOH or Ferrihydrite Structure

NASA Astrophysics Data System (ADS)

Funk, Felix; Long, Gary J.; Hautot, Dimitri; Büchi, Ruth; Christl, Iso; Weidler, Peter G.

2001-03-01

The effectiveness of therapeutically used iron compounds is related to their physical and chemical properties. Four different iron compounds used in oral, intravenous, and intramuscular therapy have been examined by X-ray powder diffraction, iron-57 Mössbauer spectroscopy, transmission electron microscopy, BET surface area measurement, potentiometric titration and studied through dissolution kinetics determinations using acid, reducing and chelating agents. All compounds are nanosized with particle diameters, as determined by X-ray diffraction, ranging from 1 to 4.1 nm. The superparamagnetic blocking temperatures, as determined by Mössbauer spectroscopy, indicate that the relative diameters of the aggregates range from 2.5 to 4.1 nm. Three of the iron compounds have an akaganeite-like structure, whereas one has a ferrihydrite-like structure. As powders the particles form large and dense aggregates which have a very low surface area on the order of 1 m2 g-1. There is evidence, however, that in a colloidal solution the surface area is increased by two to three orders of magnitude, presumably as a result of the break up of the aggregates. Iron release kinetics by acid, chelating and reducing agents reflect the high surface area, the size and crystallinity of the particles, and the presence of the protective carbohydrate layer coating the iron compound. Within a physiologically relevant time period, the iron release produced by acid or large chelating ligands is small. In contrast, iron is rapidly mobilized by small organic chelating agents, such as oxalate, or by chelate-forming reductants, such as thioglycolate.

Laboratory light scattering measurements on "natural" particles with the PROGRA2 experiment: an overview

NASA Astrophysics Data System (ADS)

Hadamcik, E.; Rrenard, J.; Levasseur-Regourd, A. C.; Worms, J. C.

Polarimetric phase curves were obtained with the PROGRA2 instrument for different particles: glass beads, polyhedral solids, rough particles, dense aggregates and aggregates with porosity higher than 90 %. The main purpose of these measurements is to build a large database, which allows interpreting remote sensing observations of solar system bodies. For some samples numerical or experimental models (i.e. DDA, stochastically built particles, microwave analogue) and laboratory experiments are compared to better disentangle the involved physical properties. This paper gives some main results of the experiment, and their applications to Earth atmosphere, comets and asteroids.

Single-shot mega-electronvolt ultrafast electron diffraction for structure dynamic studies of warm dense matter

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

Mo, M. Z., E-mail: mmo09@slac.stanford.edu; Shen, X.; Chen, Z.

We have developed a single-shot mega-electronvolt ultrafast-electron-diffraction system to measure the structural dynamics of warm dense matter. The electron probe in this system is featured by a kinetic energy of 3.2 MeV and a total charge of 20 fC, with the FWHM pulse duration and spot size at sample of 350 fs and 120 μm respectively. We demonstrate its unique capability by visualizing the atomic structural changes of warm dense gold formed from a laser-excited 35-nm freestanding single-crystal gold foil. The temporal evolution of the Bragg peak intensity and of the liquid signal during solid-liquid phase transition are quantitatively determined.more » This experimental capability opens up an exciting opportunity to unravel the atomic dynamics of structural phase transitions in warm dense matter regime.« less

Single-shot mega-electronvolt ultrafast electron diffraction for structure dynamic studies of warm dense matter

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

Mo, M. Z.; Shen, X.; Chen, Z.

We have developed a single-shot mega-electronvolt ultrafast-electron-diffraction system to measure the structural dynamics of warm dense matter. The electron probe in this system is featured by a kinetic energy of 3.2 MeV and a total charge of 20 fC, with the FWHM pulse duration and spot size at sample of 350 fs and 120 µm respectively. We demonstrate its unique capability by visualizing the atomic structural changes of warm dense gold formed from a laser-excited 35-nm freestanding single-crystal gold foil. The temporal evolution of the Bragg peak intensity and of the liquid signal during solid-liquid phase transition are quantitatively determined.more » This experimental capability opens up an exciting opportunity to unravel the atomic dynamics of structural phase transitions in warm dense matter regime« less

Single-shot mega-electronvolt ultrafast electron diffraction for structure dynamic studies of warm dense matter

DOE PAGES

Mo, M. Z.; Shen, X.; Chen, Z.; ...

2016-08-04

We have developed a single-shot mega-electronvolt ultrafast-electron-diffraction system to measure the structural dynamics of warm dense matter. The electron probe in this system is featured by a kinetic energy of 3.2 MeV and a total charge of 20 fC, with the FWHM pulse duration and spot size at sample of 350 fs and 120 µm respectively. We demonstrate its unique capability by visualizing the atomic structural changes of warm dense gold formed from a laser-excited 35-nm freestanding single-crystal gold foil. The temporal evolution of the Bragg peak intensity and of the liquid signal during solid-liquid phase transition are quantitatively determined.more » This experimental capability opens up an exciting opportunity to unravel the atomic dynamics of structural phase transitions in warm dense matter regime« less

Propeller, Light and Dark

NASA Image and Video Library

2013-06-24

NASA Cassini spacecraft has been monitoring propeller features such as Bleriot since their discovery. The bright dash-like features are regions where a small moonlet has caused ring particles to cluster together more densely than normal.

Radiographic and histological evaluation of ectopic application of deproteinized bovine bone matrix.

PubMed

da Silva, Rodrigo Carlos; Crivellaro, Viviane Rozeira; Giovanini, Allan Fernando; Scariot, Rafaela; Gonzaga, Carla Castiglia; Zielak, João César

2016-01-01

To evaluate, through radiographic and histological analysis, the tissue reaction induced by a biomaterial based on deproteinized bovine bone matrix (DBBM) in the muscle of sheep. Sixteen sheep were used. The animals underwent surgery to insert polyethylene tubes containing the biomaterial in the muscle of the lower back (ectopic site) and were euthanized after 3 and 6 months. Each sheep received three tubes: Group 1 - sham group (negative control - tube without biomaterial), Group 2 - particulate autogenous bone (positive control), and Group 3 - DBBM biomaterial (GenOx Inorg). The material removed was evaluated by radiographic, macroscopic, and microscopic analysis, descriptively. Macroscopic analysis showed that Group 3 had a greater tissue volume maintenance. Microscopic analysis indicated that Group 1 had a higher concentration of dense, thin collagen fibers (3 and 6 months); in Group 2, there was a decrease in the inflammatory process and the deposition of dense, thin collagen fibers (3 and 6 months); in Group 3, the presence of a dense connective tissue was noted, in which the DBBM particles (3 months) were found. On the periphery of these particles, a deposition of basophilic material was found, indicating the formation of mineral particles and the formation of tissues with osteoid characteristics (6 months). Based on the results obtained, it can be concluded that the biomaterial based on DBBM led to the formation of tissue with similar characteristics to an osteoid matrix in a postoperative period of 6 months. However, none of the groups evaluated showed ectopic bone neoformation.

Constitutive model development for flows of granular materials

NASA Astrophysics Data System (ADS)

Chialvo, Sebastian

Granular flows are ubiquitous in both natural and industrial processes. When com- posed of dry, noncohesive particles, they manifest three different flow regimes---commonly referred to as the quasistatic, inertial, and intermediate regimes---each of which exhibits its own dependences on solids volume fraction, shear rate, and particle-level properties. The differences in these regimes can be attributed to microscale phenomena, with quasistatic flows being dominated by enduring, frictional contacts between grains, inertial flows by grain collisions, and intermediate flows by a combination of the two. Existing constitutive models for the solids-phase stress tend to focus on one or two regimes at a time, with a limited degree of success; the same is true of models for wall-boundary conditions for granular flows. Moreover, these models tend not to be based on detailed particle-level flow data, either from experiment or simulation. Clearly, a comprehensive modeling framework is lacking. The work in this thesis aims to address these issues by proposing continuum models constructed on the basis of discrete element method (DEM) simulations of granular shear flows. Specifically, we propose (a) a constitutive stress model that bridges the three dense flow regimes, (b) an modified kinetic-theory model that covers both the dense and dilute ends of the inertial regime, and (c) a boundary-condition model for dense, wall-bounded flows. These models facilitate the modeling of a wide range of flow systems of practical interest and provide ideas for further model development and refinement.

Steady flow of smooth, inelastic particles on a bumpy inclined plane: Hard and soft particle simulations

NASA Astrophysics Data System (ADS)

Tripathi, Anurag; Khakhar, D. V.

2010-04-01

We study smooth, slightly inelastic particles flowing under gravity on a bumpy inclined plane using event-driven and discrete-element simulations. Shallow layers (ten particle diameters) are used to enable simulation using the event-driven method within reasonable computational times. Steady flows are obtained in a narrow range of angles (13°-14.5°) ; lower angles result in stopping of the flow and higher angles in continuous acceleration. The flow is relatively dense with the solid volume fraction, ν≈0.5 , and significant layering of particles is observed. We derive expressions for the stress, heat flux, and dissipation for the hard and soft particle models from first principles. The computed mean velocity, temperature, stress, dissipation, and heat flux profiles of hard particles are compared to soft particle results for different values of stiffness constant (k) . The value of stiffness constant for which results for hard and soft particles are identical is found to be k≥2×106mg/d , where m is the mass of a particle, g is the acceleration due to gravity, and d is the particle diameter. We compare the simulation results to constitutive relations obtained from the kinetic theory of Jenkins and Richman [J. T. Jenkins and M. W. Richman, Arch. Ration. Mech. Anal. 87, 355 (1985)] for pressure, dissipation, viscosity, and thermal conductivity. We find that all the quantities are very well predicted by kinetic theory for volume fractions ν<0.5 . At higher densities, obtained for thicker layers ( H=15d and H=20d ), the kinetic theory does not give accurate prediction. Deviations of the kinetic theory predictions from simulation results are relatively small for dissipation and heat flux and most significant deviations are observed for shear viscosity and pressure. The results indicate the range of applicability of soft particle simulations and kinetic theory for dense flows.

Effects of the finite particle size in turbulent wall-bounded flows of dense suspensions

NASA Astrophysics Data System (ADS)

Costa, Pedro; Picano, Francesco; Brandt, Luca; Breugem, Wim-Paul

2018-05-01

We use interface-resolved simulations to study finite-size effects in turbulent channel flow of neutrally-buoyant spheres. Two cases with particle sizes differing by a factor of 2, at the same solid volume fraction of 20% and bulk Reynolds number are considered. These are complemented with two reference single-phase flows: the unladen case, and the flow of a Newtonian fluid with the effective suspension viscosity of the same mixture in the laminar regime. As recently highlighted in Costa et al. (PRL 117, 134501), a particle-wall layer is responsible for deviations of the statistics from what is observed in the continuum limit where the suspension is modeled as a Newtonian fluid with an effective viscosity. Here we investigate the fluid and particle dynamics in this layer and in the bulk. In the particle-wall layer, the near wall inhomogeneity has an influence on the suspension micro-structure over a distance proportional to the particle size. In this layer, particles have a significant (apparent) slip velocity that is reflected in the distribution of wall shear stresses. This is characterized by extreme events (both much higher and much lower than the mean). Based on these observations we provide a scaling for the particle-to-fluid apparent slip velocity as a function of the flow parameters. We also extend the flow scaling laws in to second-order Eulerian statistics in the homogeneous suspension region away from the wall. Finite-size effects in the bulk of the channel become important for larger particles, while negligible for lower-order statistics and smaller particles. Finally, we study the particle dynamics along the wall-normal direction. Our results suggest that 1-point dispersion is dominated by particle-turbulence (and not particle-particle) interactions, while differences in 2-point dispersion and collisional dynamics are consistent with a picture of shear-driven interactions.

X-ray Analysis of Defects and Anomalies in AGR-5/6/7 TRISO Particles

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

Helmreich, Grant W.; Hunn, John D.; Skitt, Darren J.

2017-06-01

Coated particle fuel batches J52O-16-93164, 93165, 93166, 93168, 93169, 93170, and 93172 were produced by Babcock and Wilcox Technologies (BWXT) for possible selection as fuel for the Advanced Gas Reactor Fuel Development and Qualification (AGR) Program’s AGR-5/6/7 irradiation test in the Idaho National Laboratory (INL) Advanced Test Reactor (ATR), or may be used for other tests. Each batch was coated in a 150-mm-diameter production-scale fluidized-bed chemical vapor deposition (CVD) furnace. Tristructural isotropic (TRISO) coatings were deposited on 425-μm-nominal-diameter spherical kernels from BWXT lot J52R-16-69317 containing a mixture of 15.4%-enriched uranium carbide and uranium oxide (UCO), with the exception of Batchmore » 93164, which used similar kernels from BWXT lot J52L-16-69316. The TRISO-coatings consisted of a ~50% dense carbon buffer layer with 100-μmnominal thickness, a dense inner pyrolytic carbon (IPyC) layer with 40-μm-nominal thickness, a silicon carbide (SiC) layer with 35-μm-nominal thickness, and a dense outer pyrolytic carbon (OPyC) layer with 40-μm-nominal thickness. Each coated particle batch was sieved to upgrade the particles by removing over-sized and under-sized material, and the upgraded batch was designated by appending the letter A to the end of the batch number (e.g., 93164A). Secondary upgrading by sieving was performed on the upgraded batches to remove specific anomalies identified during analysis for Defective IPyC, and the upgraded batches were designated by appending the letter B to the end of the batch number (e.g., 93165B). Following this secondary upgrading, coated particle composite J52R-16-98005 was produced by BWXT as fuel for the AGR Program’s AGR-5/6/7 irradiation test in the INL ATR. This composite was comprised of coated particle fuel batches J52O-16-93165B, 93168B, 93169B, and 93170B.« less

Methylsilane derived silicon carbide particle coatings produced by fluid-bed chemical vapor deposition

NASA Astrophysics Data System (ADS)

Miller, James Henry

This report describes the research effort that was undertaken to develop and understand processing techniques for the deposition of both low and high density SiC coatings from a non-halide precursor, in support of the Generation IV Gas-Cooled Fast Reactor (GFR) fuel development program. The research was conducted in two phases. In the first phase, the feasibility of producing both porous SiC coatings and dense SiC coatings on surrogate fuel particles by fluidized bed chemical vapor deposition (FBCVD) using gas mixtures of methylsilane and argon was demonstrated. In the second phase, a combined experimental and modeling effort was carried out in order to gain an understanding of the deposition mechanisms that result in either porous or dense SiC coatings, depending on the coating conditions. For this second phase effort, a simplified (compared to the fluid bed) single-substrate chemical vapor deposition (CVD) system was employed. Based on the experimental and modeling results, the deposition of SiC from methylsilane is controlled by the extent of gas-phase reaction, and is therefore highly sensitive to temperature. The results show that all SiC coatings are due to the surface adsorption of species that result from gas-phase reactions. The model terms these gas-borne species embryos, and while the model does not include a prediction of coating morphology, a comparison of the model and experimental results indicates that the morphology of the coatings is controlled by the nucleation and growth of the embryos. The coating that results from small embryos (embryos with only two Si-C pairs) appears relatively dense and continuous, while the coating that results from larger embryos becomes less continuous and more nodular as embryo size increases. At some point in the growth of embryos they cease to behave as molecular species and instead behave as particles that grow by either agglomeration or by incorporation of molecular species on their surface. As these particles adhere to the substrate surface and become fixed in place by surface deposition in the interstices between adjacent particles, a low density coating consisting of these particles results.

Generation of 3-D hydrostratigraphic zones from dense airborne electromagnetic data to assess groundwater model prediction error

USGS Publications Warehouse

Christensen, Nikolaj K; Minsley, Burke J.; Christensen, Steen

2017-01-01

We present a new methodology to combine spatially dense high-resolution airborne electromagnetic (AEM) data and sparse borehole information to construct multiple plausible geological structures using a stochastic approach. The method developed allows for quantification of the performance of groundwater models built from different geological realizations of structure. Multiple structural realizations are generated using geostatistical Monte Carlo simulations that treat sparse borehole lithological observations as hard data and dense geophysically derived structural probabilities as soft data. Each structural model is used to define 3-D hydrostratigraphical zones of a groundwater model, and the hydraulic parameter values of the zones are estimated by using nonlinear regression to fit hydrological data (hydraulic head and river discharge measurements). Use of the methodology is demonstrated for a synthetic domain having structures of categorical deposits consisting of sand, silt, or clay. It is shown that using dense AEM data with the methodology can significantly improve the estimated accuracy of the sediment distribution as compared to when borehole data are used alone. It is also shown that this use of AEM data can improve the predictive capability of a calibrated groundwater model that uses the geological structures as zones. However, such structural models will always contain errors because even with dense AEM data it is not possible to perfectly resolve the structures of a groundwater system. It is shown that when using such erroneous structures in a groundwater model, they can lead to biased parameter estimates and biased model predictions, therefore impairing the model's predictive capability.

Generation of 3-D hydrostratigraphic zones from dense airborne electromagnetic data to assess groundwater model prediction error

NASA Astrophysics Data System (ADS)

Christensen, N. K.; Minsley, B. J.; Christensen, S.

2017-02-01

We present a new methodology to combine spatially dense high-resolution airborne electromagnetic (AEM) data and sparse borehole information to construct multiple plausible geological structures using a stochastic approach. The method developed allows for quantification of the performance of groundwater models built from different geological realizations of structure. Multiple structural realizations are generated using geostatistical Monte Carlo simulations that treat sparse borehole lithological observations as hard data and dense geophysically derived structural probabilities as soft data. Each structural model is used to define 3-D hydrostratigraphical zones of a groundwater model, and the hydraulic parameter values of the zones are estimated by using nonlinear regression to fit hydrological data (hydraulic head and river discharge measurements). Use of the methodology is demonstrated for a synthetic domain having structures of categorical deposits consisting of sand, silt, or clay. It is shown that using dense AEM data with the methodology can significantly improve the estimated accuracy of the sediment distribution as compared to when borehole data are used alone. It is also shown that this use of AEM data can improve the predictive capability of a calibrated groundwater model that uses the geological structures as zones. However, such structural models will always contain errors because even with dense AEM data it is not possible to perfectly resolve the structures of a groundwater system. It is shown that when using such erroneous structures in a groundwater model, they can lead to biased parameter estimates and biased model predictions, therefore impairing the model's predictive capability.

Fabrication and Microstructure of Hydroxyapatite Coatings on Zirconia by Room Temperature Spray Process.

PubMed

Seo, Dong Seok; Chae, Hak Cheol; Lee, Jong Kook

2015-08-01

Hydroxyapatite coatings were fabricated on zirconia substrates by a room temperature spray process and were investigated with regards to their microstructure, composition and dissolution in water. An initial hydroxyapatite powder was prepared by heat treatment of bovine-bone derived powder at 1100 °C for 2 h, while dense zirconia substrates were fabricated by pressing 3Y-TZP powder and sintering it at 1350 °C for 2 h. Room temperature spray coating was performed using a slit nozzle in a low pressure-chamber with a controlled coating time. The phase composition of the resultant hydroxyapatite coatings was similar to that of the starting powder, however, the grain size of the hydroxyapatite particles was reduced to about 100 nm due to their formation by particle impaction and fracture. All areas of the coating had a similar morphology, consisting of reticulated structure with a high surface roughness. The hydroxyapatite coating layer exhibited biostability in a stimulated body fluid, with no severe dissolution being observed during in vitro experimentation.

Two-dimensional particle-in-cell plasma source ion implantation of a prolate spheroid target

NASA Astrophysics Data System (ADS)

Liu, Cheng-Sen; Han, Hong-Ying; Peng, Xiao-Qing; Chang, Ye; Wang, De-Zhen

2010-03-01

A two-dimensional particle-in-cell simulation is used to study the time-dependent evolution of the sheath surrounding a prolate spheroid target during a high voltage pulse in plasma source ion implantation. Our study shows that the potential contour lines pack more closely in the plasma sheath near the vertex of the major axis, i.e. where a thinner sheath is formed, and a non-uniform total ion dose distribution is incident along the surface of the prolate spheroid target due to the focusing of ions by the potential structure. Ion focusing takes place not only at the vertex of the major axis, where dense potential contour lines exist, but also at the vertex of the minor axis, where sparse contour lines exist. This results in two peaks of the received ion dose, locating at the vertices of the major and minor axes of the prolate spheroid target, and an ion dose valley, staying always between the vertices, rather than at the vertex of the minor axis.

An investigation on characterizing dense coal-water slurry with ultrasound: theoretical and experimental method

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

Xue, M.H.; Su, M.X.; Dong, L.L.

2010-07-01

Particle size distribution and concentration in particulate two-phase flow are important parameters in a wide variety of industrial areas. For the purpose of online characterization in dense coal-water slurries, ultrasonic methods have many advantages such as avoiding dilution, the capability for being used in real time, and noninvasive testing, while light-based techniques are not capable of providing information because optical methods often require the slurry to be diluted. In this article, the modified Urick equation including temperature modification, which can be used to determine the concentration by means of the measurement of ultrasonic velocity in a coal-water slurry, is evaluatedmore » on the basis of theoretical analysis and experimental study. A combination of the coupled-phase model and the Bouguer-Lambert-Beer law is employed in this work, and the attenuation spectrum is measured within the frequency region from 3 to 12 MHz. Particle size distributions of the coal-water slurry at different volume fractions are obtained with the optimum regularization technique. Therefore, the ultrasonic technique presented in this work brings the possibility of using ultrasound for online measurements of dense slurries.« less

Nuclear quantum dynamics in dense hydrogen

PubMed Central

Kang, Dongdong; Sun, Huayang; Dai, Jiayu; Chen, Wenbo; Zhao, Zengxiu; Hou, Yong; Zeng, Jiaolong; Yuan, Jianmin

2014-01-01

Nuclear dynamics in dense hydrogen, which is determined by the key physics of large-angle scattering or many-body collisions between particles, is crucial for the dynamics of planet's evolution and hydrodynamical processes in inertial confinement confusion. Here, using improved ab initio path-integral molecular dynamics simulations, we investigated the nuclear quantum dynamics regarding transport behaviors of dense hydrogen up to the temperatures of 1 eV. With the inclusion of nuclear quantum effects (NQEs), the ionic diffusions are largely higher than the classical treatment by the magnitude from 20% to 146% as the temperature is decreased from 1 eV to 0.3 eV at 10 g/cm3, meanwhile, electrical and thermal conductivities are significantly lowered. In particular, the ionic diffusion is found much larger than that without NQEs even when both the ionic distributions are the same at 1 eV. The significant quantum delocalization of ions introduces remarkably different scattering cross section between protons compared with classical particle treatments, which explains the large difference of transport properties induced by NQEs. The Stokes-Einstein relation, Wiedemann-Franz law, and isotope effects are re-examined, showing different behaviors in nuclear quantum dynamics. PMID:24968754

1.9 μm superficially porous packing material with radially oriented pores and tailored pore size for ultra-fast separation of small molecules and biomolecules.

PubMed

Min, Yi; Jiang, Bo; Wu, Ci; Xia, Simin; Zhang, Xiaodan; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

2014-08-22

In this work, 1.9 μm reversed-phase packing materials with superficially porous structure were prepared to achieve the rapid and high efficient separation of peptides and proteins. The silica particles were synthesized via three steps, nonporous silica particle preparation by a modified seeded growth method, mesoporous shell formation by a one pot templated dissolution and redeposition strategy, and pore size expansion via acid-refluxing. By such a method, 1.9 μm superficially porous materials with 0.18 μm shell thickness and tailored pore diameter (10 nm, 15 nm) were obtained. After pore enlargement, the formerly dense arrays of mesoporous structure changed, the radially oriented pores dominated the superficially porous structure. The chromatographic performance of such particles was investigated after C18 derivatization. For packing materials with 1.9 μm diameter and 10 nm pore size, the column efficiency could reach 211,300 plates per m for naphthalene. To achieve the high resolution separation of peptides and proteins, particles with pore diameter of 15 nm were tailored, by which the baseline separation of 5 peptides and 5 intact proteins could be respectively achieved within 1 min, demonstrating the superiority in the high efficiency and high throughput analysis of biomolecules. Furthermore, BSA digests were well separated with peak capacity of 120 in 30 min on a 15 cm-long column. Finally, we compared our columns with a 1.7 μm Kinetex C18 column under the same conditions, our particles with 10nm pore size demonstrated similar performance for separation of the large intact proteins. Moreover, the particles with 15 nm pore size showed more symmetrical peaks for the separation of large proteins (BSA, OVA and IgG) and provided rapid separation of protein extracts from Escherichia coli in 5 min. All these results indicated that the synthesized 1.9 μm superficially porous silica packing materials would be promising in the ultra-fast and high-resolution separation of biomolecules. Copyright © 2014 Elsevier B.V. All rights reserved.

Spermatological characters of the pseudophyllidean cestode Bothriocephalus scorpii (Müller, 1776).

PubMed

Levron, Céline; Brunanská, Magdaléna; Poddubnaya, Larisa G

2006-06-01

Spermiogenesis of Bothriocephalus scorpii (Cestoda, Pseudophyllidea) includes an orthogonal development of two flagella, followed by a flagellar rotation and a proximo-distal fusion with the median cytoplasmic process. The fusion occurs at the level of four attachment zones. The presence of dense material in the apical region of the differentiation zone in the early stage of spermiogenesis appears to be a characteristic feature for the Pseudophyllidea. The mature spermatozoon possesses two axonemes of 9+"1" pattern of the Trepaxonemata, nucleus, cortical microtubules, electron-dense granules and crested body. The anterior part of the gamete exhibits a centriole surrounded by electron-dense tubular structures arranged as incomplete spiral. When the crested body disappears, the electron-dense tubular structures are arranged into a ring encircling the axoneme. The electron-dense tubular structures and their arrangement appear to be a specific feature for the clade "Bothriocephalidea". The organization of the posterior extremity of the gamete with the nucleus is described for the first time in the Pseudophyllidea.

A prospective, randomized controlled preclinical trial to evaluate different formulations of biphasic calcium phosphate in combination with a hydroxyapatite collagen membrane to reconstruct deficient alveolar ridges.

PubMed

Nevins, Myron; Nevins, Marc L; Schupbach, Peter; Kim, Soo-Woo; Lin, Zhao; Kim, David M

2013-04-01

Many patients and clinicians would prefer a synthetic particulate bone replacement graft, but most available alloplastic biomaterials have limited osteogenic potential. An alloplast with increased regenerative capacity would be advantageous for the treatment of localized alveolar ridge defects. This prospective, randomized controlled preclinical trial utilized 6 female foxhounds to analyze the osteogenic impact of different formulations of biphasic calcium phosphate (BCP) in combination with an hydroxyapatite-collagen membrane and their ability to reconstruct deficient alveolar ridges for future implant placement. The grafted sites were allowed to heal 3 months, and then trephine biopsies were obtained to perform light microscopic and histomorphometric analyses. All treated sites healed well with no early membrane exposure or adverse soft tissue responses during the healing period. The grafted sites exhibited greater radiopacity than the surrounding native bone with BCP particles seen as radiopaque granules. The graft particles appeared to be well-integrated and no areas of loose particles were observed. Histologic evaluation demonstrated BCP particles embedded in woven bone with dense connective tissue/marrow space. New bone growth was observed around the graft particles as well as within the structure of the graft particulate. There was intimate contact between the graft particles and newly formed bone, and graft particles were bridged by the newly formed bone in all biopsies from the tested groups. The present study results support the potential of these BCP graft particulates to stimulate new bone formation. Clinical studies are recommended to confirm these preclinical findings.

PIV measurement of internal structure of diesel fuel spray

NASA Astrophysics Data System (ADS)

Cao, Z.-M.; Nishino, K.; Mizuno, S.; Torii, K.

2000-12-01

This paper reports particle image velocimetry (PIV) measurements of diesel fuel spray injected from a single-hole nozzle at injection pressures ranging from 30 to 70MPa, which are comparable to partial-load operating conditions of commercial diesel engines. The fuel is injected into a non-combusting environment pressurized up to 2.0MPa. A laser-induced fluorescent (LIF) technique is utilized to visualize internal structures of fuel sprays formed by densely-distributing droplets. A specially designed synchronization system is developed to acquire double-frame spray images at an arbitrary time delay after injection. A direct cross-correlation PIV technique is applied to measure instantaneous droplet velocity distribution. Unique large-scale structures in droplet concentration, called `branch-like structures' by Azetsu etal. (1990), are observed and shown to be associated with active vortical motions, which appear to be responsible for the mixing between droplets and the surrounding gas. It is found that the droplets tend to move out of the vortical structures and accumulate in the regions of low vorticity. Some other interesting features concerning droplet velocity fields are also presented.

PIV measurement of internal structure of diesel fuel spray

NASA Astrophysics Data System (ADS)

Cao, Z.-M.; Nishino, K.; Mizuno, S.; Torii, K.

This paper reports particle image velocimetry (PIV) measurements of diesel fuel spray injected from a single-hole nozzle at injection pressures ranging from 30 to 70MPa, which are comparable to partial-load operating conditions of commercial diesel engines. The fuel is injected into a non-combusting environment pressurized up to 2.0MPa. A laser-induced fluorescent (LIF) technique is utilized to visualize internal structures of fuel sprays formed by densely-distributing droplets. A specially designed synchronization system is developed to acquire double-frame spray images at an arbitrary time delay after injection. A direct cross-correlation PIV technique is applied to measure instantaneous droplet velocity distribution. Unique large-scale structures in droplet concentration, called `branch-like structures' by Azetsu etal. (1990), are observed and shown to be associated with active vortical motions, which appear to be responsible for the mixing between droplets and the surrounding gas. It is found that the droplets tend to move out of the vortical structures and accumulate in the regions of low vorticity. Some other interesting features concerning droplet velocity fields are also presented.

Depinning and heterogeneous dynamics of colloidal crystal layers under shear flow

NASA Astrophysics Data System (ADS)

Gerloff, Sascha; Klapp, Sabine H. L.

2016-12-01

Using Brownian dynamics (BD) simulations and an analytical approach we investigate the shear-induced, nonequilibrium dynamics of dense colloidal suspensions confined to a narrow slit-pore. Focusing on situations where the colloids arrange in well-defined layers with solidlike in-plane structure, the confined films display complex, nonlinear behavior such as collective depinning and local transport via density excitations. These phenomena are reminiscent of colloidal monolayers driven over a periodic substrate potential. In order to deepen this connection, we present an effective model that maps the dynamics of the shear-driven colloidal layers to the motion of a single particle driven over an effective substrate potential. This model allows us to estimate the critical shear rate of the depinning transition based on the equilibrium configuration, revealing the impact of important parameters, such as the slit-pore width and the interaction strength. We then turn to heterogeneous systems where a layer of small colloids is sheared with respect to bottom layers of large particles. For these incommensurate systems we find that the particle transport is dominated by density excitations resembling the so-called "kink" solutions of the Frenkel-Kontorova (FK) model. In contrast to the FK model, however, the corresponding "antikinks" do not move.

Application of a Dense Gas Technique for Sterilizing Soft Biomaterials

PubMed Central

Karajanagi, Sandeep S.; Yoganathan, Roshan; Mammucari, Raffaella; Park, Hyoungshin; Cox, Julian; Zeitels, Steven M.; Langer, Robert; Foster, Neil R.

2017-01-01

Sterilization of soft biomaterials such as hydrogels is challenging because existing methods such as gamma irradiation, steam sterilization, or ethylene oxide sterilization, while effective at achieving high sterility assurance levels (SAL), may compromise their physicochemical properties and biocompatibility. New methods that effectively sterilize soft biomaterials without compromising their properties are therefore required. In this report, a dense-carbon dioxide (CO2)-based technique was used to sterilize soft polyethylene glycol (PEG)-based hydrogels while retaining their structure and physicochemical properties. Conventional sterilization methods such as gamma irradiation and steam sterilization severely compromised the structure of the hydrogels. PEG hydrogels with high water content and low elastic shear modulus (a measure of stiffness) were deliberately inoculated with bacteria and spores and then subjected to dense CO2. The dense CO2-based methods effectively sterilized the hydrogels achieving a SAL of 10−7 without compromising the viscoelastic properties, pH, water-content, and structure of the gels. Furthermore, dense CO2-treated gels were biocompatible and non-toxic when implanted subcutaneously in ferrets. The application of novel dense CO2-based methods to sterilize soft biomaterials has implications in developing safe sterilization methods for soft biomedical implants such as dermal fillers and viscosupplements. PMID:21337339

Developing Cost-Effective Dense Continuous SDC Barrier Layers for SOFCs

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

Nguyen, Hoang Viet P.; Hardy, John S.; Coyle, Christopher A.

Significantly improved performance during electrochemical testing of a cell with a dense continuous pulsed laser deposited (PLD) samarium doped ceria (SDC) layer spurred investigations into the fabrication of dense continuous SDC barrier layers by means of cost-effective deposition using screen printing which is amenable to industrial production of SOFCs. Many approaches to improve the SDC density have been explored including the use of powder with reduced particle sizes, inks with increased solids loading, and doping with sintering aids (1). In terms of sintering aids, dopants like Mo or binary systems of Mo+Cu or Fe+Co greatly enhance SDC sinterability. In fact,more » adding dopants to a screen printed, prefired, porous SDC layer made it possible to achieve a dense continuous barrier layer atop the YSZ electrolyte without sintering above 1200°C. Although the objective of fabricating a dense continuous layer was achieved, additional studies have been initiated to improve the cell performance. Underlying issues with constrained sintering and dopant-enhanced ceria-zirconia solid solubility are also addressed in this paper.« less

The D-material universe

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

Elghozi, Thomas; Mavromatos, Nick E.; Sakellariadou, Mairi

In a previous publication by some of the authors (N.E.M., M.S. and M.F.Y.), we have argued that the ''D-material universe'', that is a model of a brane world propagating in a higher-dimensional bulk populated by collections of D-particle stringy defects, provides a model for the growth of large-scale structure in the universe via the vector field in its spectrum. The latter corresponds to D-particle recoil velocity excitations as a result of the interactions of the defects with stringy matter and radiation on the brane world. In this article, we first elaborate further on the results of the previous study onmore » the galactic growth era and analyse the circumstances under which the D-particle recoil velocity fluid may ''mimic'' dark matter in galaxies. A lensing phenomenology is also presented for some samples of galaxies, which previously were known to provide tension for modified gravity (TeVeS) models. The current model is found in agreement with these lensing data. Then we discuss a cosmic evolution for the D-material universe by analysing the conditions under which the late eras of this universe associated with large-scale structure are connected to early epochs, where inflation takes place. It is shown that inflation is induced by dense populations of D-particles in the early universe, with the rôle of the inflaton field played by the condensate of the D-particle recoil-velocity fields under their interaction with relativistic stringy matter, only for sufficiently large brane tensions and low string mass scales compared to the Hubble scale. On the other hand, for large string scales, where the recoil-velocity condensate fields are weak, inflation cannot be driven by the D-particle defects alone. In such cases inflation may be driven by dilaton (or other moduli) fields in the underlying string theory.« less

Structure of corneal layers, collagen fibrils, and proteoglycans of tree shrew cornea

PubMed Central

Almubrad, Turki

2011-01-01

Purpose The stroma is the major part of the cornea, in which collagen fibrils and proteoglycans are distributed uniformly. We describe the ultrastructure of corneal layers, collagen fibrils (CF), and proteoglycans (PGs) in the tree shrew cornea. Methods Tree shrew corneas (5, 6, and 10 week old animals) and normal human corneas (24, 25, and 54 years old) were fixed in 2.5% glutaraldehyde containing cuprolinic blue in a sodium acetate buffer. The tissue was processed for electron microscopy. The ‘iTEM Olympus Soft Imaging Solutions GmbH’ program was used to measure the corneal layers, collagen fibril diameters and proteoglycan areas. Results The tree shrew cornea consists of 5 layers: the epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium. The epithelium was composed of squamous cells, wing cells and basal cells. The Bowman’s layer was 5.5±1.0 µm thick and very similar to a normal human Bowman’s layer. The stroma was 258±7.00 µm thick and consisted of collagen fibril lamellae. The lamellae were interlaced with one another in the anterior stroma, but ran parallel to one another in the middle and posterior stroma. Collagen fibrils were decorated with proteoglycan filaments with an area size of 390 ±438 nm2. The collagen fibril had a minimum diameter of 39±4.25 nm. The interfibrillar spacing was 52.91±6.07 nm. Within the collagen fibrils, very small electron-dense particles were present. Conclusions The structure of the tree shrew cornea is very similar to that of the normal human cornea. As is the case with the human cornea, the tree shrew cornea had a Bowman's layer, lamellar interlacing in the anterior stroma and electron-dense particles within the collagen fibrils. The similarities of the tree shrew cornea with the human cornea suggest that it could be a good structural model to use when studying changes in collagen fibrils and proteoglycans in non-genetic corneal diseases, such as ectasia caused after LASIK (laser-assisted in situ keratomileusis). PMID:21921979

Fabrication of Controllable Pore and Particle Size of Mesoporous Silica Nanoparticles via a Liquid-phase Synthesis Method and Its Absorption Characteristics

NASA Astrophysics Data System (ADS)

Nandiyanto, Asep Bayu Dani; Iskandar, Ferry; Okuyama, Kikuo

2011-12-01

Monodisperse spherical mesoporous silica nanoparticles were successfully synthesized using a liquid-phase synthesis method. The result showed particles with controllable pore size from several to tens nanometers with outer diameter of several tens nanometers. The ability in the control of pore size and outer diameter was altered by adjusting the precursor solution ratios. In addition, we have conducted the adsorption ability of the prepared particles. The result showed that large organic molecules were well-absorbed to the prepared silica porous particles, in which this result was not obtained when using commercial dense silica particle and/or hollow silica particle. With this result, the prepared mesoporous silica particles may be used efficiently in various applications, such as sensors, pharmaceuticals, environmentally sensitive pursuits, etc.

Hybrid metal organic scintillator materials system and particle detector

DOEpatents

Bauer, Christina A.; Allendorf, Mark D.; Doty, F. Patrick; Simmons, Blake A.

2011-07-26

We describe the preparation and characterization of two zinc hybrid luminescent structures based on the flexible and emissive linker molecule, trans-(4-R,4'-R') stilbene, where R and R' are mono- or poly-coordinating groups, which retain their luminescence within these solid materials. For example, reaction of trans-4,4'-stilbenedicarboxylic acid and zinc nitrate in the solvent dimethylformamide (DMF) yielded a dense 2-D network featuring zinc in both octahedral and tetrahedral coordination environments connected by trans-stilbene links. Similar reaction in diethylformamide (DEF) at higher temperatures resulted in a porous, 3-D framework structure consisting of two interpenetrating cubic lattices, each featuring basic to zinc carboxylate vertices joined by trans-stilbene, analogous to the isoreticular MOF (IRMOF) series. We demonstrate that the optical properties of both embodiments correlate directly with the local ligand environments observed in the crystal structures. We further demonstrate that these materials produce high luminescent response to proton radiation and high radiation tolerance relative to prior scintillators. These features can be used to create sophisticated scintillating detection sensors.

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

Ma, Xiang; Zhang, Shuai; Jiao, Fang

Two-step nucleation pathways in which disordered, amorphous, or dense liquid states precede appearance of crystalline phases have been reported for a wide range of materials, but the dynamics of such pathways are poorly understood. Moreover, whether these pathways are general features of crystallizing systems or a consequence of system-specific structural details that select for direct vs two-step processes is unknown. Using atomic force microscopy to directly observe crystallization of sequence-defined polymers, we show that crystallization pathways are indeed sequence dependent. When a short hydrophobic region is added to a sequence that directly forms crystalline particles, crystallization instead follows a two-stepmore » pathway that begins with creation of disordered clusters of 10-20 molecules and is characterized by highly non-linear crystallization kinetics in which clusters transform into ordered structures that then enter the growth phase. The results shed new light on non-classical crystallization mechanisms and have implications for design of self-assembling polymer systems.« less

Performance of μ-RWELL detector vs resistivity of the resistive stage

NASA Astrophysics Data System (ADS)

Bencivenni, G.; De Oliveira, R.; Felici, G.; Gatta, M.; Morello, G.; Ochi, A.; Lener, M. Poli; Tskhadadze, E.

2018-04-01

The μ-RWELL is a compact spark-protected single amplification stage Micro-Pattern-Gaseous-Detector (MPGD). The detector amplification stage is realized with a polyimide structure, micro-patterned with a dense matrix of blind-holes, integrated into the readout structure. The anode is formed by a thin Diamond Like Carbon (DLC) resistive layer separated by an insulating glue layer from the readout strips. The introduction of the resistive layer strongly suppressing the transition from streamer to spark gives the possibility to achieve large gains (> 104), without significantly affecting the capability to be efficiently operated in high particle fluxes. In this work we present the results of a systematic study of the μ-RWELL performance as a function of the DLC resistivity. The tests have been performed either with collimated 5.9 keV X-rays or with pion and muon beams at the SPS Secondary Beamline H4 and H8 at CERN.

Electrokinetic Aggregation of Colloidal Particles on Electrodes

NASA Astrophysics Data System (ADS)

Anderson, John L.; Solomentsev, Yuri E.; Guelcher, Scott A.

1999-11-01

Colloidal particles deposited on an electrode have been observed to attract each other and form clusters in the presence of an applied electric field. This aggregation is important to the formation of dense monolayer films during electrophoretic depositon processes. Under dc fields two particles attract each other over a length scale comparable to the particle size, and the velocity of approach between two particles is proportional to the applied electric field and the particles' zeta potential. We have developed a theory for particle aggregation based on electroosmotic flow about each deposited particle. Experimental results for the relative motion of two particles are in good quantitative agreement with the theory. Our recent experiments with ac fields also show attraction between particles that is roughly proportional to the rms electric field but inversely proportional to the frequency. We discuss here a model based on electrokinetic processes that can account for some of the observations in ac fields.

Dense Regions in Supersonic Isothermal Turbulence

NASA Astrophysics Data System (ADS)

Robertson, Brant; Goldreich, Peter

2018-02-01

The properties of supersonic isothermal turbulence influence a variety of astrophysical phenomena, including the structure and evolution of star-forming clouds. This work presents a simple model for the structure of dense regions in turbulence in which the density distribution behind isothermal shocks originates from rough hydrostatic balance between the pressure gradient behind the shock and its deceleration from ram pressure applied by the background fluid. Using simulations of supersonic isothermal turbulence and idealized waves moving through a background medium, we show that the structural properties of dense, shocked regions broadly agree with our analytical model. Our work provides a new conceptual picture for describing the dense regions, which complements theoretical efforts to understand the bulk statistical properties of turbulence and attempts to model the more complex features of star-forming clouds like magnetic fields, self-gravity, or radiative properties.

Application of dense gas techniques for the production of fine particles.

PubMed

Foster, Neil R; Dehghani, Fariba; Charoenchaitrakoo, Kiang M; Warwick, Barry

2003-01-01

The feasibility of using dense gas techniques such as rapid expansion of supercritical solutions (RESS) and aerosol solvent extraction system (ASES) for micronization of pharmaceutical compounds is demonstrated. The chiral nonsteroidal anti-inflammatory racemic ibuprofen is soluble in carbon dioxide at 35 degrees C and pressures above 90 bar. The particle size decreased to less than 2 microm while the degree of crystallinity was slightly decreased when processed by RESS. The dissolution rate of the ibuprofen (a poorly water-soluble compound) was significantly enhanced after processing by RESS. The nonsteroidal anti-inflammatory drug Cu2(indomethacin)4L2(Cu-Indo); (L = dimethylformamide [DMF]), which possessed very low solubility in supercritical CO2, was successfully micronized by ASES at 25 degrees C and 68.9 bar using DMF as the solvent and CO2 as the antisolvent. The concentration of solute dramatically influenced the precipitate characteristics. The particles obtained from the ASES process were changed from bipyramidal to spherical, with particle size less than 5 microm, as the concentration increased from 5 to 100 mg/g. A further increase in solute concentration to 200 mg/g resulted in large porous spheres, between 20 and 50 micron, when processing Cu-Indo by the ASES method. The dissolution rate of the micronized Cu-Indo was significantly higher than the commercial product.

Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2.

PubMed

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Chernyatin, V; Cheu, E; Chevalier, L; Chiarella, V; Chiarelli, G; Chiodini, G; Chisholm, A S; Chitan, A; Chiu, Y H; Chizhov, M V; Choi, K; Chomont, A R; Chouridou, S; Christodoulou, V; Chromek-Burckhart, D; Chu, M C; Chudoba, J; Chuinard, A J; Chwastowski, J J; Chytka, L; Ciftci, A K; Cinca, D; Cindro, V; Cioara, I A; Ciocca, C; Ciocio, A; Cirotto, F; Citron, Z H; Citterio, M; Ciubancan, M; Clark, A; Clark, B L; Clark, M R; Clark, P J; Clarke, R N; Clement, C; Coadou, Y; Cobal, M; Coccaro, A; Cochran, J; Colasurdo, L; Cole, B; Colijn, A P; Collot, J; Colombo, T; Conde Muiño, P; Coniavitis, E; Connell, S H; Connelly, I A; Constantinescu, S; Conti, G; Conventi, F; Cooke, M; Cooper-Sarkar, A M; Cormier, F; Cormier, K J R; Corradi, M; Corriveau, F; Cortes-Gonzalez, A; Cortiana, G; Costa, G; Costa, M J; Costanzo, D; Cottin, G; Cowan, G; Cox, B E; Cranmer, K; Crawley, S J; Creager, R A; Cree, G; Crépé-Renaudin, S; Crescioli, F; Cribbs, W A; Cristinziani, M; Croft, V; Crosetti, G; Cueto, A; Cuhadar Donszelmann, T; Cukierman, A R; Cummings, J; Curatolo, M; Cúth, J; Czirr, H; Czodrowski, P; D'amen, G; D'Auria, S; D'eramo, L; D'Onofrio, M; Da Cunha Sargedas De Sousa, M J; Via, C Da; Dabrowski, W; Dado, T; Dai, T; Dale, O; Dallaire, F; Dallapiccola, C; Dam, M; Dandoy, J R; Daneri, M F; Dang, N P; Daniells, A C; Dann, N S; Danninger, M; Hoffmann, M Dano; Dao, V; Darbo, G; Darmora, S; Dassoulas, J; Dattagupta, A; Daubney, T; Davey, W; David, C; Davidek, T; Davies, M; Davis, D R; Davison, P; Dawe, E; Dawson, I; De, K; de Asmundis, R; De Benedetti, A; De Castro, S; De Cecco, S; De Groot, N; de Jong, P; De la Torre, H; De Lorenzi, F; De Maria, A; De Pedis, D; De Salvo, A; De Sanctis, U; De Santo, A; De Vasconcelos Corga, K; De Vivie De Regie, J B; Dearnaley, W J; Debbe, R; Debenedetti, C; Dedovich, D V; Dehghanian, N; Deigaard, I; Del Gaudio, M; Del Peso, J; Prete, T Del; Delgove, D; Deliot, F; Delitzsch, C M; Dell'Acqua, A; Dell'Asta, L; Dell'Orso, M; Della Pietra, M; Della Volpe, D; Delmastro, M; Delporte, C; 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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.

Revealing the Evolution of Non-thermal Electrons in Solar Flares Using 3D Modeling

NASA Astrophysics Data System (ADS)

Fleishman, Gregory D.; Nita, Gelu M.; Kuroda, Natsuha; Jia, Sabina; Tong, Kevin; Wen, Richard R.; Zhizhuo, Zhou

2018-05-01

Understanding non-thermal particle generation, transport, and escape in solar flares requires detailed quantification of the particle evolution in the realistic 3D domain where the flare takes place. Rather surprisingly, apart from the standard flare scenario and integral characteristics of non-thermal electrons, not much is known about the actual evolution of non-thermal electrons in the 3D spatial domain. This paper attempts to begin to remedy this situation by creating sets of evolving 3D models, the synthesized emission from which matches the evolving observed emission. Here, we investigate two contrasting flares: a dense, “coronal-thick-target” flare SOL2002-04-12T17:42, that contained a single flare loop observed in both microwaves and X-rays, and a more complex flare, SOL2015-06-22T17:50, that contained at least four distinct flaring loops needed to consistently reproduce the microwave and X-ray emission. Our analysis reveals differing evolution patterns for the non-thermal electrons in the dense and tenuous loops; however, both patterns suggest that resonant wave–particle interactions with turbulence play a central role. These results offer new constraints for theory and models of the particle acceleration and transport in solar flares.

Simulation of concentration distribution of urban particles under wind

NASA Astrophysics Data System (ADS)

Chen, Yanghou; Yang, Hangsheng

2018-02-01

The concentration of particulate matter in the air is too high, which seriously affects people’s health. The concentration of particles in densely populated towns is also high. Understanding the distribution of particles in the air helps to remove them passively. The concentration distribution of particles in urban streets is simulated by using the FLUENT software. The simulation analysis based on Discrete Phase Modelling (DPM) of FLUENT. Simulation results show that the distribution of the particles is caused by different layout of buildings. And it is pointed out that in the windward area of the building and the leeward sides of the high-rise building are the areas with high concentration of particles. Understanding the concentration of particles in different areas is also helpful for people to avoid and reduce the concentration of particles in high concentration areas.

The Impact of Microstructure on an Accurate Snow Scattering Parameterization at Microwave Wavelengths

NASA Astrophysics Data System (ADS)

Honeyager, Ryan

High frequency microwave instruments are increasingly used to observe ice clouds and snow. These instruments are significantly more sensitive than conventional precipitation radar. This is ideal for analyzing ice-bearing clouds, for ice particles are tenuously distributed and have effective densities that are far less than liquid water. However, at shorter wavelengths, the electromagnetic response of ice particles is no longer solely dependent on particle mass. The shape of the ice particles also plays a significant role. Thus, in order to understand the observations of high frequency microwave radars and radiometers, it is essential to model the scattering properties of snowflakes correctly. Several research groups have proposed detailed models of snow aggregation. These particle models are coupled with computer codes that determine the particles' electromagnetic properties. However, there is a discrepancy between the particle model outputs and the requirements of the electromagnetic models. Snowflakes have countless variations in structure, but we also know that physically similar snowflakes scatter light in much the same manner. Structurally exact electromagnetic models, such as the discrete dipole approximation (DDA), require a high degree of structural resolution. Such methods are slow, spending considerable time processing redundant (i.e. useless) information. Conversely, when using techniques that incorporate too little structural information, the resultant radiative properties are not physically realistic. Then, we ask the question, what features are most important in determining scattering? This dissertation develops a general technique that can quickly parameterize the important structural aspects that determine the scattering of many diverse snowflake morphologies. A Voronoi bounding neighbor algorithm is first employed to decompose aggregates into well-defined interior and surface regions. The sensitivity of scattering to interior randomization is then examined. The loss of interior structure is found to have a negligible impact on scattering cross sections, and backscatter is lowered by approximately five percent. This establishes that detailed knowledge of interior structure is not necessary when modeling scattering behavior, and it also provides support for using an effective medium approximation to describe the interiors of snow aggregates. The Voronoi diagram-based technique enables the almost trivial determination of the effective density of this medium. A bounding neighbor algorithm is then used to establish a greatly improved approximation of scattering by equivalent spheroids. This algorithm is then used to posit a Voronoi diagram-based definition of effective density approach, which is used in concert with the T-matrix method to determine single-scattering cross sections. The resulting backscatters are found to reasonably match those of the DDA over frequencies from 10.65 to 183.31 GHz and particle sizes from a few hundred micrometers to nine millimeters in length. Integrated error in backscatter versus DDA is found to be within 25% at 94 GHz. Errors in scattering cross-sections and asymmetry parameters are likewise small. The observed cross-sectional errors are much smaller than the differences observed among different particle models. This represents a significant improvement over established techniques, and it demonstrates that the radiative properties of dense aggregate snowflakes may be adequately represented by equal-mass homogeneous spheroids. The present results can be used to supplement retrieval algorithms used by CloudSat, EarthCARE, Galileo, GPM and SWACR radars. The ability to predict the full range of scattering properties is potentially also useful for other particle regimes where a compact particle approximation is applicable.

Effect of grain size on optical transmittance of birefringent polycrystalline ceramics

NASA Astrophysics Data System (ADS)

Wen, Tzu-Chien

Polycrystalline ceramics are increasingly used for fabricating windows and domes for the mid infra-red regime (3-5 mum) due to their superior durability as compared to glass and the lower cost of their fabrication and finishing relative to single crystals without significant compromise in optical properties. Due to the noncubic structure, MgF2 and Al2O3 are birefringent ceramics. Birefringence causes scatter of light at the grain boundaries and diminishes in-line transmittance and optical performance. This dissertation presents experimental results and analyses of the grain-size and wavelength dependence of the in-line transmittance of polycrystalline MgF2 and Al2O3. Chapter 2 presents experimental results and analyses of light transmission in polycrystalline MgF2 as a function of the mean grain size at different wavelengths. The scattering coefficient of polycrystalline MgF 2 increased linearly with the mean grain size and inversely with the square of the wavelength of light. These trends are consistent with theoretical models based on both a limiting form of the Raleigh-Gans-Debye theory of particle scattering and light retardation theories that take refractive-index variations along the light path. Chapter 3 investigates the applicability of particle light scattering theories to light attenuation in birefringent polycrystalline ceramics by measuring light transmittance in a model two-phase system. The system consisted of microspheres of silica dispersed in a solution of glycerol in water. It was found that RGD theory showed the systematic deviation for higher particle volume fraction (φ > 0.2) and larger particle size (d p > 1 mum). This result suggested that light scattering models based on single particle scattering are unlikely to provide viable physical explanation for the effect of grain size on light transmittance in birefringent polycrystalline ceramics due to the high volume fraction in dense polycrystalline ceramics. Chapter 4 analyses light transmission properties of polycrystalline Al 2O3 using theories of wave propagation in random media. Fully dense polycrystalline Al2O3 was fabricated using a pressure filtration method. By obtaining the Delta n2 measured from EBSD, the wave retardation theories of Raman and Viswanathan and Kahan et al. provided upper and lower bounds for the theoretical predictions of light transmittance as a function of mean intercept length.

Stimulated Desorption from Icy Aerosol Particles: A Possible Relevance To Titan's Ionospheric Conditions

NASA Astrophysics Data System (ADS)

Bordalo, Vinicius; Mejia, Christian; da Silveira, Enio F.; Seperuelo Duarte, Eduardo; Pilling, Sergio

Saturn's largest moon, Titan, has a dense atmosphere primarily composed of molecular nitro-gen (N2 , 96%) and methane (CH4 , 4%). Its atmospheric structure has been intensively studied recently due to the large amount of data obtained in situ by the Huygens probe during its de-cent to the surface on 14 January 2005. The probe could diagnose the composition of the haze particles made up organic chains containing H, C and N. Hydrocarbons and nitriles produced by photolysis of CH4 at high altitudes (˜ 2,000 km) act as embryos of aerosols of Titan as they fall to the surface. It is expected that CH4 condenses on these particles forming a layer of ice by adsorption or nucleation. Due to the high abundance of these aerosols throughout the atmo-sphere of Titan, their presence are relevant for the ionic balance of the atmosphere, especially the lower ionosphere promoted mainly by the flux of galactic cosmic rays (GCR). We have investigated the production of ions by electronic sputtering process due to the bombardment of the surfaces of aerosols by heavy ions. Time-of-flight (TOF) technique was used to obtain ion sputtering yields. An ice layer of CH4 was grown by condensation over a pre-condensed N2 ice in high vacuum chamber (1 × 10-7 mbar) at cryogenic temperature (10 K). Relative sputtering yields due to fast projectiles (252 Cf fission fragment ˜ 65 MeV) on the ice surfaces were measured. The bombardment was continued during the successive growth of both con-densed layers; the negative and positive sputtered ions were identified by TOF. Hybrid species including NH+ (17 u), HCN+ (27 u) and CN- (26 u) were formed, as well as the acetonitrile 3 ion (CH3 CN+ , 41 u). We argue that a similar process of continued ion replenishment into the gas phase by sputtering in aerosols ubiquitous in the lower ionosphere of Titan may occur and should be further investigated.

Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures

PubMed Central

Conrad, Jacinta C.

2014-01-01

The behavior of confined colloidal suspensions with attractive interparticle interactions is critical to the rational design of materials for directed assembly1-3, drug delivery4, improved hydrocarbon recovery5-7, and flowable electrodes for energy storage8. Suspensions containing fluorescent colloids and non-adsorbing polymers are appealing model systems, as the ratio of the polymer radius of gyration to the particle radius and concentration of polymer control the range and strength of the interparticle attraction, respectively. By tuning the polymer properties and the volume fraction of the colloids, colloid fluids, fluids of clusters, gels, crystals, and glasses can be obtained9. Confocal microscopy, a variant of fluorescence microscopy, allows an optically transparent and fluorescent sample to be imaged with high spatial and temporal resolution in three dimensions. In this technique, a small pinhole or slit blocks the emitted fluorescent light from regions of the sample that are outside the focal volume of the microscope optical system. As a result, only a thin section of the sample in the focal plane is imaged. This technique is particularly well suited to probe the structure and dynamics in dense colloidal suspensions at the single-particle scale: the particles are large enough to be resolved using visible light and diffuse slowly enough to be captured at typical scan speeds of commercial confocal systems10. Improvements in scan speeds and analysis algorithms have also enabled quantitative confocal imaging of flowing suspensions11-16,37. In this paper, we demonstrate confocal microscopy experiments to probe the confined phase behavior and flow properties of colloid-polymer mixtures. We first prepare colloid-polymer mixtures that are density- and refractive-index matched. Next, we report a standard protocol for imaging quiescent dense colloid-polymer mixtures under varying confinement in thin wedge-shaped cells. Finally, we demonstrate a protocol for imaging colloid-polymer mixtures during microchannel flow. PMID:24894062

Quantum Control of Open Systems and Dense Atomic Ensembles

NASA Astrophysics Data System (ADS)

DiLoreto, Christopher

Controlling the dynamics of open quantum systems; i.e. quantum systems that decohere because of interactions with the environment, is an active area of research with many applications in quantum optics and quantum computation. My thesis expands the scope of this inquiry by seeking to control open systems in proximity to an additional system. The latter could be a classical system such as metal nanoparticles, or a quantum system such as a cluster of similar atoms. By modelling the interactions between the systems, we are able to expand the accessible state space of the quantum system in question. For a single, three-level quantum system, I examine isolated systems that have only normal spontaneous emission. I then show that intensity-intensity correlation spectra, which depend directly on the density matrix of the system, can be used detect whether transitions share a common energy level. This detection is possible due to the presence of quantum interference effects between two transitions if they are connected. This effect allows one to asses energy level structure diagrams in complex atoms/molecules. By placing an open quantum system near a nanoparticle dimer, I show that the spontaneous emission rate of the system can be changed "on demand" by changing the polarization of an incident, driving field. In a three-level, Lambda system, this allows a qubit to both retain high qubit fidelity when it is operating, and to be rapidly initialized to a pure state once it is rendered unusable by decoherence. This type of behaviour is not possible in a single open quantum system; therefore adding a classical system nearby extends the overall control space of the quantum system. An open quantum system near identical neighbours in a dense ensemble is another example of how the accessible state space can be expanded. I show that a dense ensemble of atoms rapidly becomes disordered with states that are not directly excited by an incident field becoming significantly populated. This effect motivates the need for using multi-directional basis sets in theoretical analysis of dense quantum systems. My results demonstrate the shortcomings of short-pulse techniques used in many recent studies. Based on my numerical studies, I hypothesize that the dense ensemble can be modelled by an effective single quantum system that has a decoherence rate that changes over time. My effective single particle model provides a way in which computational time can be reduced, and also a model in which the underlying physical processes involved in the system's evolution are much easier to understand. I then use this model to provide an elegant theoretical explanation for an unusual experimental result called "transverse optical magnetism''. My effective single particle model's predictions match very well with experimental data.

The Green Bank Ammonia Survey: Observations of Hierarchical Dense Gas Structures in Cepheus-L1251

NASA Astrophysics Data System (ADS)

Keown, Jared; Di Francesco, James; Kirk, Helen; Friesen, Rachel K.; Pineda, Jaime E.; Rosolowsky, Erik; Ginsburg, Adam; Offner, Stella S. R.; Caselli, Paola; Alves, Felipe; Chacón-Tanarro, Ana; Punanova, Anna; Redaelli, Elena; Seo, Young Min; Matzner, Christopher D.; Chun-Yuan Chen, Michael; Goodman, Alyssa A.; Chen, How-Huan; Shirley, Yancy; Singh, Ayushi; Arce, Hector G.; Martin, Peter; Myers, Philip C.

2017-11-01

We use Green Bank Ammonia Survey observations of NH3 (1, 1) and (2, 2) emission with 32″ FWHM resolution from a ˜10 pc2 portion of the Cepheus-L1251 molecular cloud to identify hierarchical dense gas structures. Our dendrogram analysis of the NH3 data results in 22 top-level structures, which reside within 13 lower-level parent structures. The structures are compact (0.01 {pc}≲ {R}{eff}≲ 0.1 {pc}) and are spatially correlated with the highest H2 column density portions of the cloud. We also compare the ammonia data to a catalog of dense cores identified by higher-resolution (18.″2 FWHM) Herschel Space Observatory observations of dust continuum emission from Cepheus-L1251. Maps of kinetic gas temperature, velocity dispersion, and NH3 column density, derived from detailed modeling of the NH3 data, are used to investigate the stability and chemistry of the ammonia-identified and Herschel-identified structures. We show that the dust and dense gas in the structures have similar temperatures, with median T dust and T K measurements of 11.7 ± 1.1 K and 10.3 ± 2.0 K, respectively. Based on a virial analysis, we find that the ammonia-identified structures are gravitationally dominated, yet may be in or near a state of virial equilibrium. Meanwhile, the majority of the Herschel-identified dense cores appear to be not bound by their own gravity and instead confined by external pressure. CCS (20 - 10) and HC5N (9-8) emission from the region reveal broader line widths and centroid velocity offsets when compared to the NH3 (1, 1) emission in some cases, likely due to these carbon-based molecules tracing the turbulent outer layers of the dense cores.

Method for producing dense lithium lanthanum tantalate lithium-ion conducting ceramics

DOEpatents

Brown-Shaklee, Harlan James; Ihlefeld, Jon; Spoerke, Erik David; Blea-Kirby, Mia Angelica

2018-05-08

A method to produce high density, uniform lithium lanthanum tantalate lithium-ion conducting ceramics uses small particles that are sintered in a pressureless crucible that limits loss of Li₂O.

Assembly of Colloidal Aggregates by Electrohydrodynamic Flow: Kinetic Experiments and Scaling Analysis

NASA Technical Reports Server (NTRS)

Ristenpart, W. D.; Aksay, I. A.; Saville, D. A.

2004-01-01

Electric fields generate transverse flows near electrodes that sweep colloidal particles into densely packed assemblies. We interpret this behavior in terms of electrohydrodynamic motion stemming from distortions of the field by the particles that alter the body force distribution in the electrode charge polarization layer. A scaling analysis shows how the action of the applied electric field generates fluid motion that carries particles toward one another. The resulting fluid velocity is proportional to the square of the applied field and decreases inversely with frequency. Experimental measurements of the particle aggregation rate accord with the electrohydrodynamic theory over a wide range of voltages and frequencies.

Shearing Low-frictional 3D Granular Materials

NASA Astrophysics Data System (ADS)

Chen, David; Zheng, Hu; Behringer, Robert

Shear jamming occurs in frictional particles over a range of packing fractions, from random loose to random dense. Simulations show shear jamming for frictionless spheres, but over a vanishing range as the system size grows. We use packings of submerged and diffractive index-matched hydrogel particles to determine the shear-induced microscopic response of 3D, low-frictional granular systems near jamming, bridging the gap between frictionless and low friction packings. We visualize the particles by a laser scanning technique, and we track particle motion along with their interparticle contact forces from its 3D-reconstructions. NSF-DMF-1206351, NASA NNX15AD38G, William M. Keck Foundation, and DARPA.

Hydrodynamic interactions in dense active suspensions: From polar order to dynamical clusters

NASA Astrophysics Data System (ADS)

Yoshinaga, Natsuhiko; Liverpool, Tanniemola B.

2017-08-01

We study the role of hydrodynamic interactions in the collective behavior of collections of microscopic active particles suspended in a fluid. We introduce a calculational framework that allows us to separate the different contributions to their collective dynamics from hydrodynamic interactions on different length scales. Hence we are able to systematically show that lubrication forces when the particles are very close to each other play as important a role as long-range hydrodynamic interactions in determining their many-body behavior. We find that motility-induced phase separation is suppressed by near-field interactions, leading to open gel-like clusters rather than dense clusters. Interestingly, we find a globally polar ordered phase appears for neutral swimmers with no force dipole that is enhanced by near-field lubrication forces in which the collision process rather than long-range interaction dominates the alignment mechanism.

Transverse momentum dependence of spectra of cumulative particles produced from droplets of dense nuclear matter

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

Vechernin, Vladimir

2016-01-22

The transverse momentum dependence of the yields of particles produced from the clusters of dense cold nuclear matter in nuclei is calculated in the approach based on perturbative QCD calculations of the corresponding quark diagrams near the thresholds. It is shown that the transverse momentum dependence of the pion and proton spectra at different values of the Feynman variable x in the cumulative region, x > 1, can be described by the only parameter - the constituent quark mass, taken to be equal 300 MeV. It is found that the cumulative protons are formed predominantly via a coherent coalescence of threemore » fast cluster quarks, whereas the production of cumulative pions is dominated by one fast cluster quark hadronization. This enabled to explain the experimentally observed more slow increase of the mean transverse momentum of cumulative protons with the increase of the cumulative variable x, compared to pions.« less

Nuclear Fusion Within Extremely Dense Plasma Enhanced by Quantum Particle Waves

NASA Astrophysics Data System (ADS)

Miao, Feng; Zheng, Xianjun; Deng, Baiquan

2015-05-01

Quantum effects play an enhancement role in p-p chain reactions occurring within stars. Such an enhancement is quantified by a wave penetration factor that is proportional to the density of the participating fuel particles. This leads to an innovative theory for dense plasma, and its result shows good agreement with independent data derived from the solar energy output. An analysis of the first Z-pinch machine in mankind's history exhibiting neutron emission leads to a derived deuterium plasma beam density greater than that of water, with plasma velocities exceeding 10000 km/s. Fusion power could be achieved by the intersection of four such pinched plasma beams with powerful head-on collisions in their common focal region due to the beam and target enhanced reaction. supported by the Fund for the Construction of Graduate Degree of China (No. 2014XWD-S0805)

Volume fraction instability in an oscillating non-Brownian iso-dense suspension.

NASA Astrophysics Data System (ADS)

Roht, Y. L.; Gauthier, G.; Hulin, J. P.; Salin, D.; Chertcoff, R.; Auradou, H.; Ippolito, I.

2017-06-01

The instability of an iso-dense non-Brownian suspension of polystyrene beads of diameter 40 μm dispersed in a water-glycerol mixture submitted to a periodic square wave oscillating flow in a Hele-Shaw cell is studied experimentally. The instability gives rise to stationary bead concentration waves transverse to the flow. It has been observed for average particle volume fractions between 0.25 and 0.4, for periods of the square wave flow variation between 0.4 and 10 s and in finite intervals of the amplitude of the fluid displacement. The study shows that the wavelength λ increases roughly linearly with the amplitude of the oscillatory flow; on the other hand, λ is independent of the particle concentration and of the period of oscillation of the flow although the minimum threshold amplitude for observing the instability increases with the period.

Analysis of photoelectron effect on the antenna impedance via Particle-In-Cell simulation

NASA Astrophysics Data System (ADS)

Miyake, Y.; Usui, H.

2008-08-01

We present photoelectron effects on the impedance of electric field antennas used for plasma wave investigations. To illustrate the photoelectron effects, we applied electromagnetic Particle-In-Cell simulation to the self-consistent antenna impedance analysis. We confirmed the formation of a dense photoelectron region around the sunlit surfaces of the antenna and the spacecraft. The dense photoelectrons enhance the real part, and decrease the absolute value of the imaginary part, of antenna impedance at low frequencies. We also showed that the antenna conductance can be analytically calculated from simulation results of the electron current flowing into or out of the antenna. The antenna impedance in the photoelectron environment is represented by a parallel equivalent circuit consisting of a capacitance and a resistance, which is consistent with empirical knowledge. The results also imply that the impedance varies with the spin of the spacecraft, which causes the variation of the photoelectron density around the antenna.

Phase behavior of a simple dipolar fluid under shear flow in an electric field.

PubMed

McWhirter, J Liam

2008-01-21

Nonequilibrium molecular dynamics simulations are performed on a dense simple dipolar fluid under a planar Couette shear flow. Shear generates heat, which is removed by thermostatting terms added to the equations of motion of the fluid particles. The spatial structure of simple fluids at high shear rates is known to depend strongly on the thermostatting mechanism chosen. Kinetic thermostats are either biased or unbiased: biased thermostats neglect the existence of secondary flows that appear at high shear rates superimposed upon the linear velocity profile of the fluid. Simulations that employ a biased thermostat produce a string phase where particles align in strings with hexagonal symmetry along the direction of the flow. This phase is known to be a simulation artifact of biased thermostatting, and has not been observed by experiments on colloidal suspensions under shear flow. In this paper, we investigate the possibility of using a suitably directed electric field, which is coupled to the dipole moments of the fluid particles, to stabilize the string phase. We explore several thermostatting mechanisms where either the kinetic or configurational fluid degrees of freedom are thermostated. Some of these mechanisms do not yield a string phase, but rather a shear-thickening phase; in this case, we find the influence of the dipolar interactions and external field on the packing structure, and in turn their influence on the shear viscosity at the onset of this shear-thickening regime.

Preparation of a dense, polycrystalline ceramic structure

DOEpatents

Cooley, Jason; Chen, Ching-Fong; Alexander, David

2010-12-07

Ceramic nanopowder was sealed inside a metal container under a vacuum. The sealed evacuated container was forced through a severe deformation channel at an elevated temperature below the melting point of the ceramic nanopowder. The result was a dense nanocrystalline ceramic structure inside the metal container.

Highly parallel sparse Cholesky factorization

NASA Technical Reports Server (NTRS)

Gilbert, John R.; Schreiber, Robert

1990-01-01

Several fine grained parallel algorithms were developed and compared to compute the Cholesky factorization of a sparse matrix. The experimental implementations are on the Connection Machine, a distributed memory SIMD machine whose programming model conceptually supplies one processor per data element. In contrast to special purpose algorithms in which the matrix structure conforms to the connection structure of the machine, the focus is on matrices with arbitrary sparsity structure. The most promising algorithm is one whose inner loop performs several dense factorizations simultaneously on a 2-D grid of processors. Virtually any massively parallel dense factorization algorithm can be used as the key subroutine. The sparse code attains execution rates comparable to those of the dense subroutine. Although at present architectural limitations prevent the dense factorization from realizing its potential efficiency, it is concluded that a regular data parallel architecture can be used efficiently to solve arbitrarily structured sparse problems. A performance model is also presented and it is used to analyze the algorithms.

Quantum molecular dynamics study on the structures and dc conductivity of warm dense silane

NASA Astrophysics Data System (ADS)

Sun, Huayang; Kang, Dongdong; Dai, Jiayu; Zeng, Jiaolong; Yuan, Jianmin

2014-02-01

The ionic and electronic structures of warm dense silane at the densities of 1.795, 2.260, 3.382, and 3.844 g/cm3 have been studied with temperatures from 1000 K to 3 eV using quantum molecular dynamics simulations. At all densities, the structures are melted above 1000 K. The matter states are characterized as polymeric from 1000 to 4000 K and become dense plasma states with further increasing temperature to 1 eV. At two lower densities of 1.795 and 2.260 g/cm3, silane first dissociates and then becomes the polymeric state via a chain state from the initial crystalline structure. At higher densities, however, no dissociation stage was found. These findings can help us understand how the warm dense matter forms. A rise is found for the direct current electric conductivity at T ˜1000 K, indicating the nonmetal-to-metal transition. The conductivity decreases slightly with the increase of temperature, which is due to the more disordered structures at higher temperatures.

Modeling multi-layer effects in passive microwave remote sensing of dry snow using Dense Media Radiative Transfer Theory (DMRT) based on quasicrystalline approximation

USGS Publications Warehouse

Liang, D.; Xu, X.; Tsang, L.; Andreadis, K.M.; Josberger, E.G.

2008-01-01

The Dense Media Radiative Transfer theory (DMRT) of Quasicrystalline Approximation of Mie scattering by sticky particles is used to study the multiple scattering effects in layered snow in microwave remote sensing. Results are illustrated for various snow profile characteristics. Polarization differences and frequency dependences of multilayer snow model are significantly different from that of the single-layer snow model. Comparisons are also made with CLPX data using snow parameters as given by the VIC model. ?? 2007 IEEE.

Air Parcel Residence Times within Tropical Forest Canopies and Implications for Reactive Gases

NASA Astrophysics Data System (ADS)

Gerken, T.; Chamecki, M.; Fuentes, J. D.

2014-12-01

The Amazon rainforest is the world's largest natural emitter of reactive trace gases. Due to its dense vegetation (leaf area index > 4), turbulence fluctuations are highly attenuated deep inside the canopy. However, strong coherent eddies that penetrate the upper portion of the canopy can be very effective in transporting gases. Sweeps and ejections act in the order of seconds and transport air parcels into or out of the canopy. The effects of coherent structures on the air parcel residence times and associated chemical processing of reactive gases remain largely unquantified in tropical forests. We combine canopy resolving Large-Eddy Simulation (LES) and field observations in the Brazilian Amazon to study residence times of air parcels in the rainforest as a function of canopy structure and height (h). Good agreement is obtained between simulated and observed turbulence statistics within and above the forest. Coherent structure properties obtained from quadrant analysis are also well reproduced. A Lagrangian particle tracking algorithm is used to quantify the distribution of residence times of air parcels "released" at different heights. Canopy residence times were determined from the particle trajectories. The resulting probability density function (PDF) strongly depended on the particle release height (z). For particles released in the upper canopy (at z/h=0.75) the most frequent residence times were in the order of 30s, with 50% of all particles ejected from the canopy after ~2 minutes. The mean residence time was close to 5 minutes, indicating a very skewed PDF. At z/h=0.25 the PDF was more evenly distributed with its median and mean in the order of ~10 minutes. Due to sweeps, both simulations had a non- negligible fraction of particles transported deep into the canopy, thus increasing greatly their residence times. As the reaction timescales of many biogenic volatile organic compounds (BVOC) are in the order of seconds to minutes, significant chemical processing can take place before particles are transported out of the canopy. This result highlights the importance of coherent motions on the capability of BVOC to escape the canopy space. Hence, it is important to consider the real distribution of residence times, highlighting the need for accurate canopy representation in LES models.

Physical conditions near red giant and supergiant stars - An interpretation of SiO VLBI maps

NASA Technical Reports Server (NTRS)

Alcock, Charles; Ross, Randy R.

1986-01-01

Understanding the dynamical structure of circumstellar envelopes around cool giant and supergiant stars depends critically on the knowledge of what happens in the 'near zone' of the envelope, within a few stellar radii of the star. One probe with adequate angular resolution to study the near zone is VLBI observation of the SiO masers. It is shown that VLBI maps of VX Sgr establish that the particle density in the SiO masers is very high (about 10 to the 12th/cu cm), indicating that the masers form in dense cloudlets and not in a spherically expanding wind. The implications of these results for the mechanism of mass loss are discussed.

The physics of neutron stars.

PubMed

Lattimer, J M; Prakash, M

2004-04-23

Neutron stars are some of the densest manifestations of massive objects in the universe. They are ideal astrophysical laboratories for testing theories of dense matter physics and provide connections among nuclear physics, particle physics, and astrophysics. Neutron stars may exhibit conditions and phenomena not observed elsewhere, such as hyperon-dominated matter, deconfined quark matter, superfluidity and superconductivity with critical temperatures near 10(10) kelvin, opaqueness to neutrinos, and magnetic fields in excess of 10(13) Gauss. Here, we describe the formation, structure, internal composition, and evolution of neutron stars. Observations that include studies of pulsars in binary systems, thermal emission from isolated neutron stars, glitches from pulsars, and quasi-periodic oscillations from accreting neutron stars provide information about neutron star masses, radii, temperatures, ages, and internal compositions.

The Resolvent Algebra of Non-relativistic Bose Fields: Observables, Dynamics and States

NASA Astrophysics Data System (ADS)

Buchholz, Detlev

2018-05-01

The structure of the gauge invariant (particle number preserving) C*-algebra generated by the resolvents of a non-relativistic Bose field is analyzed. It is shown to form a dense subalgebra of the bounded inverse limit of a directed system of approximately finite dimensional C*-algebras. Based on this observation, it is proven that the closure of the gauge invariant algebra is stable under the dynamics induced by Hamiltonians involving pair potentials. These facts allow to proceed to a description of interacting Bosons in terms of C*-dynamical systems. It is outlined how the present approach leads to simplifications in the construction of infinite bosonic states and sheds new light on topics in many body theory.

Method of forming and assembly of metal and ceramic parts

DOEpatents

Ripley, Edward B

2014-04-22

A method of forming and assembling at least two parts together that may be metal, ceramic, or a combination of metal and ceramic parts. Such parts may have different CTE. Individual parts that are formed and sintered from particles leave a network of interconnecting porosity in each sintered part. The separate parts are assembled together and then a fill material is infiltrated into the assembled parts using a method such as capillary action, gravity, and/or pressure. The assembly is then cured to yield a bonded and fully or near-fully dense part that has the desired physical and mechanical properties for the part's intended purpose. Structural strength may be added to the parts by the inclusion of fibrous materials.

Method of forming and assembly of metal parts and ceramic parts

DOEpatents

Ripley, Edward B [Knoxville, TN

2011-11-22

A method of forming and assembling at least two parts together that may be metal, ceramic, or a combination of metal and ceramic parts. Such parts may have different CTE. Individual parts that are formed and sintered from particles leave a network of interconnecting porosity in each sintered part. The separate parts are assembled together and then a fill material is infiltrated into the assembled parts using a method such as capillary action, gravity, and/or pressure. The assembly is then cured to yield a bonded and fully or near-fully dense part that has the desired physical and mechanical properties for the part's intended purpose. Structural strength may be added to the parts by the inclusion of fibrous materials.

Phase separation of a Lennard-Jones fluid interacting with a long, condensed polymer chain: implications for the nuclear body formation near chromosomes.

PubMed

Oh, Inrok; Choi, Saehyun; Jung, YounJoon; Kim, Jun Soo

2015-08-28

Phase separation in a biological cell nucleus occurs in a heterogeneous environment filled with a high density of chromatins and thus it is inevitably influenced by interactions with chromatins. As a model system of nuclear body formation in a cell nucleus filled with chromatins, we simulate the phase separation of a low-density Lennard-Jones (LJ) fluid interacting with a long, condensed polymer chain. The influence of the density variation of LJ particles above and below the phase boundary and the role of attractive interactions between LJ particles and polymer segments are investigated at a fixed value of strong self-interaction between LJ particles. For a density of LJ particles above the phase boundary, phase separation occurs and a dense domain of LJ particles forms irrespective of interactions with the condensed polymer chain whereas its localization relative to the polymer chain is determined by the LJ-polymer attraction strength. Especially, in the case of moderately weak attractions, the domain forms separately from the polymer chain and subsequently associates with the polymer chain. When the density is below the phase boundary, however, the formation of a dense domain is possible only when the LJ-polymer attraction is strong enough, for which the domain grows in direct contact with the interacting polymer chain. In this work, different growth behaviors of LJ particles result from the differences in the density of LJ particles and in the LJ-polymer interaction, and this work suggests that the distinct formation of activity-dependent and activity-independent nuclear bodies (NBs) in a cell nucleus may originate from the differences in the concentrations of body-specific NB components and in their interaction with chromatins.

Spray‐Dried Sodium Zirconate: A Rapid Absorption Powder for CO2 Capture with Enhanced Cyclic Stability

PubMed Central

Bamiduro, Faith; Ji, Guozhao; Brown, Andy P.; Dupont, Valerie A.

2017-01-01

Abstract Improved powders for capturing CO2 at high temperatures are required for H2 production using sorption‐enhanced steam reforming. Here, we examine the relationship between particle structure and carbonation rate for two types of Na2ZrO3 powders. Hollow spray‐dried microgranules with a wall thickness of 100–300 nm corresponding to the dimensions of the primary acetate‐derived particles gave about 75 wt % theoretical CO2 conversion after a process‐relevant 5 min exposure to 15 vol % CO2. A conventional powder prepared by solid‐state reaction carbonated more slowly, achieving only 50 % conversion owing to a greater proportion of the reaction requiring bulk diffusion through the densely agglomerated particles. The hollow granular structure of the spray‐dried powder was retained postcarbonation but chemical segregation resulted in islands of an amorphous Na‐rich phase (Na2CO3) within a crystalline ZrO2 particle matrix. Despite this phase separation, the reverse reaction to re‐form Na2ZrO3 could be achieved by heating each powder to 900 °C in N2 (no dwell time). This resulted in a very stable multicycle performance in 40 cycle tests using thermogravimetric analysis for both powders. Kinetic analysis of thermogravimetric data showed the carbonation process fits an Avrami–Erofeyev 2 D nucleation and nuclei growth model, consistent with microstructural evidence of a surface‐driven transformation. Thus, we demonstrate that spray drying is a viable processing route to enhance the carbon capture performance of Na2ZrO3 powder. PMID:28371521

Structure factor of blends of solvent-free nanoparticle-organic hybrid materials: density-functional theory and small angle X-ray scattering.

PubMed

Yu, Hsiu-Yu; Srivastava, Samanvaya; Archer, Lynden A; Koch, Donald L

2014-12-07

We investigate the static structure factor S(q) of solvent-free nanoparticle-organic hybrid materials consisting of silica nanocores and space-filling polyethylene glycol coronas using a density-functional theory and small angle X-ray scattering measurements. The theory considers a bidisperse suspension of hard spheres with different radii and tethered bead-spring oligomers with different grafting densities to approximate the polydispersity effects in experiments. The experimental systems studied include pure samples with different silica core volume fractions and the associated mean corona grafting densities, and blends with different mixing ratios of the pure samples, in order to introduce varying polydispersity of corona grafting density. Our scattering experiments and theory show that, compared to the hard-sphere suspension with the same core volume fraction, S(q) for pure samples exhibit both substantially smaller values at small q and stronger particle correlations corresponding to a larger effective hard core at large q, indicating that the tethered incompressible oligomers enforce a more uniform particle distribution, and the densely grafted brush gives rise to an additional exclusionary effect between the nanoparticles. According to the theory, polydispersity in the oligomer grafting density controls the deviation of S(q) from the monodisperse system at smaller q, and the interplay of the enhanced effective core size and the entropic attraction among the particles is responsible for complex variations in the particle correlations at larger q. The successful comparison between the predictions and the measurements for the blends further suggests that S(q) can be used to assess the uniformity of grafting density in polymer-grafted nanoparticle materials.

Positron emission particle tracking and its application to granular media

NASA Astrophysics Data System (ADS)

Parker, D. J.

2017-05-01

Positron emission particle tracking (PEPT) is a technique for tracking a single radioactively labelled particle. Accurate 3D tracking is possible even when the particle is moving at high speed inside a dense opaque system. In many cases, tracking a single particle within a granular system provides sufficient information to determine the time-averaged behaviour of the entire granular system. After a general introduction, this paper describes the detector systems (PET scanners and positron cameras) used to record PEPT data, the techniques used to label particles, and the algorithms used to process the data. This paper concentrates on the use of PEPT for studying granular systems: the focus is mainly on work at Birmingham, but reference is also made to work from other centres, and options for wider diversification are suggested.

Realizing the potential of the Actinium-225 radionuclide generator in targeted alpha-particle therapy applications

PubMed Central

Miederer, Matthias; Scheinberg, David A.; McDevitt, Michael R.

2013-01-01

Alpha particle-emitting isotopes have been proposed as novel cytotoxic agents for augmenting targeted therapy. Properties of alpha particle radiation such as their limited range in tissue of a few cell diameters and their high linear energy transfer leading to dense radiation damage along each alpha track are promising in the treatment of cancer, especially when single cells or clusters of tumor cells are targeted. Actinium-225 (225Ac) is an alpha particle-emitting radionuclide that generates 4 net alpha particle isotopes in a short decay chain to stable 209Bi, and as such can be described as an alpha particle nanogenerator. This article reviews the literature pertaining to the research, development, and utilization of targeted 225Ac to potently and specifically affect cancer. PMID:18514364

Filtered cathodic arc deposition apparatus and method

DOEpatents

Krauss, Alan R.

1999-01-01

A filtered cathodic arc deposition method and apparatus for the production of highly dense, wear resistant coatings which are free from macro particles. The filtered cathodic arc deposition apparatus includes a cross shaped vacuum chamber which houses a cathode target having an evaporable surface comprised of the coating material, means for generating a stream of plasma, means for generating a transverse magnetic field, and a macro particle deflector. The transverse magnetic field bends the generated stream of plasma in the direction of a substrate. Macro particles are effectively filtered from the stream of plasma by traveling, unaffected by the transverse magnetic field, along the initial path of the plasma stream to a macro particle deflector. The macro particle deflector has a preformed surface which deflects macro particles away from the substrate.

Dense colloidal mixtures in an external sinusoidal potential

NASA Astrophysics Data System (ADS)

Capellmann, R. F.; Khisameeva, A.; Platten, F.; Egelhaaf, S. U.

2018-03-01

Concentrated binary colloidal mixtures containing particles with a size ratio 1:2.4 were exposed to a periodic potential that was realized using a light field, namely, two crossed laser beams creating a fringe pattern. The arrangement of the particles was recorded using optical microscopy and characterized in terms of the pair distribution function along the minima, the occupation probability perpendicular to the minima, the angular bond distribution, and the average potential energy per particle. The particle arrangement was investigated in dependence of the importance of particle-potential and particle-particle interactions by changing the potential amplitude and particle concentration, respectively. An increase in the potential amplitude leads to a stronger localization, especially of the large particles, but also results in an increasing fraction of small particles being located closer to the potential maxima, which also occurs upon increasing the particle density. Furthermore, increasing the potential amplitude induces a local demixing of the two particle species, whereas an increase in the total packing fraction favors a more homogeneous arrangement.

Lower sintering temperature of nanostructured dense ceramics compacted from dry nanopowders using powerful ultrasonic action

NASA Astrophysics Data System (ADS)

Khasanov, O.; Reichel, U.; Dvilis, E.; Khasanov, A.

2011-10-01

Nanostructured high dense zirconia ceramics have been sintered from dry nanopowders compacted by uniaxial pressing with simultaneous powerful ultrasonic action (PUA). Powerful ultrasound with frequency of 21 kHz was supplied from ultrasonic generator to the mold, which was the ultrasonic wave-guide. Previously the mold was filled by non-agglomerated zirconia nanopowder having average particle size of 40 nm. Any binders or plasticizers were excluded at nanopowder processing. Compaction pressure was 240 MPa, power of ultrasonic generator at PUA was 1 kW and 3 kW. The fully dense zirconia ceramics has been sintered at 1345°C and high-dense ceramics with a density of 99.1%, the most grains of which had the sizes Dgr <= 200 nm, has been sintered at low sintering temperature (1325°C). Applied approach prevents essential grain growth owing to uniform packing of nanoparticles under vibrating PU-action at pressing, which provides the friction forces control during dry nanopowder compaction without contaminating binders or plasticizers.

Porous Architecture of SPS Thick YSZ Coatings Structured at the Nanometer Scale (~50 nm)

NASA Astrophysics Data System (ADS)

Bacciochini, Antoine; Montavon, Ghislain; Ilavsky, Jan; Denoirjean, Alain; Fauchais, Pierre

2010-01-01

Suspension plasma spraying (SPS) is a fairly recent technology that is able to process sub-micrometer-sized or nanometer-sized feedstock particles and permits the deposition of coatings thinner (from 20 to 100 μm) than those resulting from conventional atmospheric plasma spraying (APS). SPS consists of mechanically injecting within the plasma flow a liquid suspension of particles of average diameter varying between 0.02 and 1 μm. Due to the large volume fraction of the internal interfaces and reduced size of stacking defects, thick nanometer- or sub-micrometer-sized coatings exhibit better properties than conventional micrometer-sized ones (e.g., higher coefficients of thermal expansion, lower thermal diffusivity, higher hardness and toughness, better wear resistance, among other coating characteristics and functional properties). They could hence offer pertinent solutions to numerous emerging applications, particularly for energy production, energy saving, etc. Coatings structured at the nanometer scale exhibit nanometer-sized voids. Depending upon the selection of operating parameters, among which plasma power parameters (operating mode, enthalpy, spray distance, etc.), suspension properties (particle size distribution, powder mass percentage, viscosity, etc.), and substrate characteristics (topology, temperature, etc.), different coating architectures can be manufactured, from dense to porous layers, from connected to non-connected network. Nevertheless, the discrimination of porosity in different classes of criteria such as size, shape, orientation, specific surface area, etc., is essential to describe the coating architecture. Moreover, the primary steps of the coating manufacturing process affect significantly the coating porous architecture. These steps need to be further understood. Different types of imaging experiments were performed to understand, describe and quantify the pore level of thick finely structured ceramics coatings.

Filter Bed of Packed Spheres

NASA Technical Reports Server (NTRS)

Elleman, D. D.; Wang, T. G.

1986-01-01

Spheres sized and treated for desired sieve properties. Filter constructed from densely packed spheres restrained by screens. Hollow gas-filled plastic or metal spheres normally used. Manufactured within one percent or better diameter tolerance. Normally, all spheres in filter of same nominal diameter. Filter used as sieve to pass only particles smaller than given size or to retain particles larger than that size. Options available under filter concept make it easy to design for specific applications.

Order - disorder transitions in granular sphere packings

NASA Astrophysics Data System (ADS)

Panaitescu, Andreea M.

Granular materials are ubiquitous in many industrial and natural processes, yet their complex behaviors characterized by unusual static and dynamic properties are still poorly understood. In this dissertation we investigate both the geometrical structure and the dynamical properties (the response to shear deformations, disorder-order transition and crystallization) of packings of mono-sized spheres as a function of the packing volume fraction. Different average packing fractions were obtained by submitting a dense granular material to periodic shear deformations and by epitaxy. Using advanced imaging techniques including the refractive index matched imaging (RIM) and X-ray computed tomography (CT) enables us to determine the three dimensional particles position inside the packing. From positions we obtain the Voronoi tessellation corresponding to the particles in the bulk and calculate the radial distribution and the bond-order metric. These two parameters are widely used to quantify the structure of the spherical particle systems. A granular packing undergoing periodic shear deformations is observed to slowly evolve towards crystallization and the packing fraction is correspondingly observed to increase smoothly from loose packing fraction, 0.59, well above the random close packing fraction, 0.637. Tracking the particles over several shear cycles allows us to obtain the probability distributions of particle displacements and the mean-square displacements and to compute the components of the diffusion tensor. We find that in a shear flow, the initial self-diffusion of the particles is anisotropic with diffusion greater in the flow direction compared with the velocity gradient direction which in turn is greater than in the vorticity direction. We further find that the granular matter under cyclic shear shows reversible as well as irreversible or plastic response for small enough strain amplitude. The appearance and the propagation of the crystalline order were studied using the orientational order metric. By following the evolution of the nucleating crystallites, we identified critical nuclei, determined their size and symmetry, and measured the average surface free energy. The structure of the nuclei was found to be random hexagonal close-packed, their average shape was non-spherical and they were oriented preferentially along the shear axis. When the packing volume fraction approaches a value close to the random close packing, crystallites with face centered cubic (fcc) order are observed with increasing probability, and ordered domains grow rapidly. A polycrystalline phase with domains of fcc and hcp order is obtained after hundreds of thousands of shear cycles. Depositing spheres on a substrate under the influence of gravity gives rise to a wide range of volume fractions and packing structures by simply controlling the nature of the substrate, the deposition rate and the energy of the particles. We analyzed the structures formed and investigate the development of the disordered phases as a function of the deposition rate. Furthermore, by comparing these structures with packings obtained by cyclic shear we showed that the structure of a granular packing depends strongly on the protocol used.

Object-Based Dense Matching Method for Maintaining Structure Characteristics of Linear Buildings

PubMed Central

Yan, Yiming; Qiu, Mingjie; Zhao, Chunhui; Wang, Liguo

2018-01-01

In this paper, we proposed a novel object-based dense matching method specially for the high-precision disparity map of building objects in urban areas, which can maintain accurate object structure characteristics. The proposed framework mainly includes three stages. Firstly, an improved edge line extraction method is proposed for the edge segments to fit closely to building outlines. Secondly, a fusion method is proposed for the outlines under the constraint of straight lines, which can maintain the building structural attribute with parallel or vertical edges, which is very useful for the dense matching method. Finally, we proposed an edge constraint and outline compensation (ECAOC) dense matching method to maintain building object structural characteristics in the disparity map. In the proposed method, the improved edge lines are used to optimize matching search scope and matching template window, and the high-precision building outlines are used to compensate the shape feature of building objects. Our method can greatly increase the matching accuracy of building objects in urban areas, especially at building edges. For the outline extraction experiments, our fusion method verifies the superiority and robustness on panchromatic images of different satellites and different resolutions. For the dense matching experiments, our ECOAC method shows great advantages for matching accuracy of building objects in urban areas compared with three other methods. PMID:29596393

Dense-body aggregates as plastic structures supporting tension in smooth muscle cells.

PubMed

Zhang, Jie; Herrera, Ana M; Paré, Peter D; Seow, Chun Y

2010-11-01

The wall of hollow organs of vertebrates is a unique structure able to generate active tension and maintain a nearly constant passive stiffness over a large volume range. These properties are predominantly attributable to the smooth muscle cells that line the organ wall. Although smooth muscle is known to possess plasticity (i.e., the ability to adapt to large changes in cell length through structural remodeling of contractile apparatus and cytoskeleton), the detailed structural basis for the plasticity is largely unknown. Dense bodies, one of the most prominent structures in smooth muscle cells, have been regarded as the anchoring sites for actin filaments, similar to the Z-disks in striated muscle. Here, we show that the dense bodies and intermediate filaments formed cable-like structures inside airway smooth muscle cells and were able to adjust the cable length according to cell length and tension. Stretching the muscle cell bundle in the relaxed state caused the cables to straighten, indicating that these intracellular structures were connected to the extracellular matrix and could support passive tension. These plastic structures may be responsible for the ability of smooth muscle to maintain a nearly constant tensile stiffness over a large length range. The finding suggests that the structural plasticity of hollow organs may originate from the dense-body cables within the smooth muscle cells.

A Distributed-Memory Package for Dense Hierarchically Semi-Separable Matrix Computations Using Randomization

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

Rouet, François-Henry; Li, Xiaoye S.; Ghysels, Pieter

In this paper, we present a distributed-memory library for computations with dense structured matrices. A matrix is considered structured if its off-diagonal blocks can be approximated by a rank-deficient matrix with low numerical rank. Here, we use Hierarchically Semi-Separable (HSS) representations. Such matrices appear in many applications, for example, finite-element methods, boundary element methods, and so on. Exploiting this structure allows for fast solution of linear systems and/or fast computation of matrix-vector products, which are the two main building blocks of matrix computations. The compression algorithm that we use, that computes the HSS form of an input dense matrix, reliesmore » on randomized sampling with a novel adaptive sampling mechanism. We discuss the parallelization of this algorithm and also present the parallelization of structured matrix-vector product, structured factorization, and solution routines. The efficiency of the approach is demonstrated on large problems from different academic and industrial applications, on up to 8,000 cores. Finally, this work is part of a more global effort, the STRUctured Matrices PACKage (STRUMPACK) software package for computations with sparse and dense structured matrices. Hence, although useful on their own right, the routines also represent a step in the direction of a distributed-memory sparse solver.« less

A Distributed-Memory Package for Dense Hierarchically Semi-Separable Matrix Computations Using Randomization

DOE PAGES

Rouet, François-Henry; Li, Xiaoye S.; Ghysels, Pieter; ...

2016-06-30

In this paper, we present a distributed-memory library for computations with dense structured matrices. A matrix is considered structured if its off-diagonal blocks can be approximated by a rank-deficient matrix with low numerical rank. Here, we use Hierarchically Semi-Separable (HSS) representations. Such matrices appear in many applications, for example, finite-element methods, boundary element methods, and so on. Exploiting this structure allows for fast solution of linear systems and/or fast computation of matrix-vector products, which are the two main building blocks of matrix computations. The compression algorithm that we use, that computes the HSS form of an input dense matrix, reliesmore » on randomized sampling with a novel adaptive sampling mechanism. We discuss the parallelization of this algorithm and also present the parallelization of structured matrix-vector product, structured factorization, and solution routines. The efficiency of the approach is demonstrated on large problems from different academic and industrial applications, on up to 8,000 cores. Finally, this work is part of a more global effort, the STRUctured Matrices PACKage (STRUMPACK) software package for computations with sparse and dense structured matrices. Hence, although useful on their own right, the routines also represent a step in the direction of a distributed-memory sparse solver.« less

Digital holographic microscope for measuring three-dimensional particle distributions and motions.

PubMed

Sheng, Jian; Malkiel, Edwin; Katz, Joseph

2006-06-01

Better understanding of particle-particle and particle-fluid interactions requires accurate 3D measurements of particle distributions and motions. We introduce the application of in-line digital holographic microscopy as a viable tool for measuring distributions of dense micrometer (3.2 microm) and submicrometer (0.75 microm) particles in a liquid solution with large depths of 1-10 mm. By recording a magnified hologram, we obtain a depth of field of approximately 1000 times the object diameter and a reduced depth of focus of approximately 10 particle diameters, both representing substantial improvements compared to a conventional microscope and in-line holography. Quantitative information on depth of field, depth of focus, and axial resolution is provided. We demonstrate that digital holographic microscopy can resolve the locations of several thousand particles and can measure their motions and trajectories using cinematographic holography. A sample trajectory and detailed morphological information of a free-swimming copepod nauplius are presented.

Replication-guided nucleosome packing and nucleosome breathing expedite the formation of dense arrays

PubMed Central

Osberg, Brendan; Nuebler, Johannes; Korber, Philipp; Gerland, Ulrich

2014-01-01

The first level of genome packaging in eukaryotic cells involves the formation of dense nucleosome arrays, with DNA coverage near 90% in yeasts. How cells achieve such high coverage within a short time, e.g. after DNA replication, remains poorly understood. It is known that random sequential adsorption of impenetrable particles on a line reaches high density extremely slowly, due to a jamming phenomenon. The nucleosome-shifting action of remodeling enzymes has been proposed as a mechanism to resolve such jams. Here, we suggest two biophysical mechanisms which assist rapid filling of DNA with nucleosomes, and we quantitatively characterize these mechanisms within mathematical models. First, we show that the ‘softness’ of nucleosomes, due to nucleosome breathing and stepwise nucleosome assembly, significantly alters the filling behavior, speeding up the process relative to ‘hard’ particles with fixed, mutually exclusive DNA footprints. Second, we explore model scenarios in which the progression of the replication fork could eliminate nucleosome jamming, either by rapid filling in its wake or via memory of the parental nucleosome positions. Taken together, our results suggest that biophysical effects promote rapid nucleosome filling, making the reassembly of densely packed nucleosomes after DNA replication a simpler task for cells than was previously thought. PMID:25428353

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

Modelling compressible dense and dilute two-phase flows

NASA Astrophysics Data System (ADS)

Saurel, Richard; Chinnayya, Ashwin; Carmouze, Quentin

2017-06-01

Many two-phase flow situations, from engineering science to astrophysics, deal with transition from dense (high concentration of the condensed phase) to dilute concentration (low concentration of the same phase), covering the entire range of volume fractions. Some models are now well accepted at the two limits, but none are able to cover accurately the entire range, in particular regarding waves propagation. In the present work, an alternative to the Baer and Nunziato (BN) model [Baer, M. R. and Nunziato, J. W., "A two-phase mixture theory for the deflagration-to-detonation transition (DDT) in reactive granular materials," Int. J. Multiphase Flow 12(6), 861 (1986)], initially designed for dense flows, is built. The corresponding model is hyperbolic and thermodynamically consistent. Contrarily to the BN model that involves 6 wave speeds, the new formulation involves 4 waves only, in agreement with the Marble model [Marble, F. E., "Dynamics of a gas containing small solid particles," Combustion and Propulsion (5th AGARD Colloquium) (Pergamon Press, 1963), Vol. 175] based on pressureless Euler equations for the dispersed phase, a well-accepted model for low particle volume concentrations. In the new model, the presence of pressure in the momentum equation of the particles and consideration of volume fractions in the two phases render the model valid for large particle concentrations. A symmetric version of the new model is derived as well for liquids containing gas bubbles. This model version involves 4 characteristic wave speeds as well, but with different velocities. Last, the two sub-models with 4 waves are combined in a unique formulation, valid for the full range of volume fractions. It involves the same 6 wave speeds as the BN model, but at a given point of space, 4 waves only emerge, depending on the local volume fractions. The non-linear pressure waves propagate only in the phase with dominant volume fraction. The new model is tested numerically on various test problems ranging from separated phases in a shock tube to shock-particle cloud interaction. Its predictions are compared to BN and Marble models as well as against experimental data showing clear improvements.

Acceptance Test Data for the AGR-5/6/7 Irradiation Test Fuel Composite Defective IPyC Fraction and Pyrocarbon Anisotropy

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

Helmreich, Grant W.; Hunn, John D.; Skitt, Darren J.

Coated particle composite J52R-16-98005 was produced by Babcock and Wilcox Technologies (BWXT) as fuel for the Advanced Gas Reactor Fuel Development and Qualification (AGR) Program’s AGR-5/6/7 irradiation test in the Idaho National Laboratory (INL) Advanced Test Reactor (ATR). This composite was comprised of four coated particle fuel batches J52O-16-93165B (26%), 93168B (26%), 93169B (24%), and 93170B (24%), chosen based on the Quality Control (QC) data acquired for each individual candidate AGR-5/6/7 batch. Each batch was coated in a 150-mm-diameter production-scale fluidized-bed chemical vapor deposition (CVD) furnace. Tristructural isotropic (TRISO) coatings were deposited on 425-μm-nominal-diameter spherical kernels from BWXT Lot J52R-16-69317more » containing a mixture of 15.5%-enriched uranium carbide and uranium oxide (UCO). The TRISO coatings consisted of four consecutive CVD layers: a ~50% dense carbon buffer layer with 100-μm-nominal thickness, a dense inner pyrolytic carbon (IPyC) layer with 40-μm-nominal thickness, a silicon carbide (SiC) layer with 35-μm-nominal thickness, and a dense outer pyrolytic carbon (OPyC) layer with 40-μm-nominal thickness. The TRISO-coated particle batches were sieved to upgrade the particles by removing over-sized and under-sized material, and the upgraded batches were designated by appending the letter A to the end of the batch number (e.g., 93165A). Secondary upgrading by sieving was performed on the A-designated batches to remove particles with missing or very-thin buffer layers that were identified during previous analysis of the individual batches for defective IPyC, as reported in the acceptance test data report for the AGR-5/6/7 production batches [Hunn et al. 2017]. The additionally-upgraded batches were designated by appending the letter B to the end of the batch number (e.g., 93165B).« less

Testing of a new dense gas approach in the Lagrangian Dispersion Model SPRAY.

NASA Astrophysics Data System (ADS)

Mortarini, Luca; Alessandrini, Stefano; Ferrero, Enrico; Anfossi, Domenico; Manfrin, Massimiliano

2013-04-01

A new original method for the dispersion of a positively and negatively buoyant plume is proposed. The buoyant pollutant movement is treated introducing a fictitious scalar inside the Lagrangian Stochastic Particle Model SPRAY. The method is based on the same idea of Alessandrini and Ferrero (Phys. A 388:1375-1387, 2009) for the treatment of a background substance entrainment into the plume. In this application, the fictitious scalar is the density and momentum difference between the plume portions and the environment air that naturally takes into account the interaction between the plume and the environment. As a consequence, no more particles than those inside the plume have to be released to simulate the entrainment of the background air temperature. In this way the entrainment is properly simulated and the plume sink is calculated from the local property of the flow. This new approach is wholly Lagrangian in the sense that the Eulerian grid is only used to compute the propriety of a portion of the plume from the particles contained in every cell. No equation of the bulk plume is solved on a fixed grid. To thoroughly test the turbulent velocity field calculated by the model, the latter is compared with a water tank experiment carried out in the TURLAB laboratory in Turin (Italy). A vertical density driven current was created releasing a saline solution (salt and water) in a water tank with no mean flow. The experiment reproduces in physical similarity, based on the density Froud number, the release of a dense gas in the planetary boundary layer and the Particle Image Velocimetry technique has been used to analyze the buoyancy generated velocity field. The high temporal and spatial resolution of the measurements gives a deep insight to the problems of the bouncing of the dense gas and of the creation of the outflow velocity at the ground.

New generation nuclear fuel structures: Dense particles in selectively soluble matrix

NASA Astrophysics Data System (ADS)

Devlin, Dave; Jarvinen, Gordon; Patterson, Brian; Pattillo, Steve; Valdez, James; Liu, X.-Y.; Phillips, Jonathan

2009-11-01

We have developed a technology for dispersing sub-millimeter sized fuel particles within a bulk matrix that can be selectively dissolved. This may enable the generation of advanced nuclear fuels with easy separation of actinides and fission products. The large kinetic energy of the fission products results in most of them escaping from the sub-millimeter sized fuel particles and depositing in the matrix during burning of the fuel in the reactor. After the fuel is used and allowed to cool for a period of time, the matrix can be dissolved and the fission products removed for disposal while the fuel particles are collected by filtration for recycle. The success of such an approach would meet a major goal of the GNEP program to provide advanced recycle technology for nuclear energy production. The benefits of such an approach include (1) greatly reduced cost of the actinide/fission product separation process, (2) ease of recycle of the fuel particles, and (3) a radiation barrier to prevent theft or diversion of the recycled fuel particles during the time they are re-fabricated into new fuel. In this study we describe a method to make surrogate nuclear fuels of micrometer scale W (shell)/Mo (core) or HfO 2 particles embedded in an MgO matrix that allows easy separation of the fission products and their embedded particles. In brief, the method consists of physically mixing W-Mo or hafnia particles with an MgO precursor. Heating the mixture, in air or argon, without agitation, to a temperature is required for complete decomposition of the precursor. The resulting material was examined using chemical analysis, scanning electron microscopy, X-ray diffraction and micro X-ray computed tomography and found to consist of evenly dispersed particles in an MgO + matrix. We believe this methodology can be extended to actinides and other matrix materials.

Self-Diffusiophoresis of Janus Particles in Near-Critical Mixtures.

PubMed

Würger, Alois

2015-10-30

We theoretically study the self-propulsion of a laser-heated Janus particle in a near-critical water-lutidine mixture, and we relate its velocity v_{p} and squirmer parameter β to the wetting properties of its two hemispheres. For nonionic surface forces, the particle moves the active cap at the front, whereas a charged hydrophilic cap leads to backward motion, in agreement with the experiment. Both v_{p} and β show nonmonotonic dependencies on the heating power, and they may even change sign. The variation of β is expected to strongly affect the collective behavior of dense squirmer systems.

Unifying Suspension and Granular flows near Jamming

NASA Astrophysics Data System (ADS)

DeGiuli, Eric; Wyart, Matthieu

2017-06-01

Rheological properties of dense flows of hard particles are singular as one approaches the jamming threshold where flow ceases, both for granular flows dominated by inertia, and for over-damped suspensions. Concomitantly, the lengthscale characterizing velocity correlations appears to diverge at jamming. Here we review a theoretical framework that gives a scaling description of stationary flows of frictionless particles. Our analysis applies both to suspensions and inertial flows of hard particles. We report numerical results in support of the theory, and show the phase diagram that results when friction is added, delineating the regime of validity of the frictionless theory.

Centrosome structure and function is altered by chloral hydrate and diazepam during the first reproductive cell cycles in sea urchin eggs

NASA Technical Reports Server (NTRS)

Schatten, H.; Chakrabarti, A.

1998-01-01

This paper explores the mode of action of the tranquillizers chloral hydrate and diazepam during fertilization and mitosis of the first reproductive cell cycles in sea urchin eggs. Most striking effects of these drugs are the alteration of centrosomal material and the abnormal microtubule configurations during exposure and after recovery from the drugs. This finding is utilized to study the mechanisms of centrosome compaction and decompaction and the dynamic configurational changes of centrosomal material and its interactions with microtubules. When 0.1% chloral hydrate or 350-750 microM diazepam is applied at specific phases during the first cell cycle of sea urchin eggs, expanded centrosomal material compacts at distinct regions and super-compacts into dense spheres while microtubules disassemble. When eggs are treated before pronuclear fusion, centrosomal material aggregates around each of the two pronuclei while microtubules disappear. Upon recovery, atypical asters oftentimes with multiple foci are formed from centrosomal material surrounding the pronuclei which indicates that the drugs have affected centrosomal material and prevent it from functioning normally. Electron microscopy and immunofluorescence studies with antibodies that routinely stain centrosomes in sea urchin eggs (4D2; and Ah-6) depict centrosomal material that is altered when compared to control cells. This centrosomal material is not able to reform normal microtubule patterns upon recovery but will form multiple asters around the two pronuclei. When cells are treated with 0.1% chloral hydrate or 350-750 microM diazepam during mitosis, the bipolar centrosomal material becomes compacted and aggregates into multiple dense spheres while spindle and polar microtubules disassemble. With increased incubation time, the smaller dense centrosome particles aggregate into bigger and fewer spheres. Upon recovery, unusual irregular microtubule configurations are formed from centrosomes that have lost their ability to reform normal mitotic figures. These results indicate that chloral hydrate and diazepam affect centrosome structure which results in the inability to reform normal microtubule formations and causes abnormal fertilization and mitosis.

Kinetic theory of shear thickening for a moderately dense gas-solid suspension: From discontinuous thickening to continuous thickening

NASA Astrophysics Data System (ADS)

Hayakawa, Hisao; Takada, Satoshi; Garzó, Vicente

2017-10-01

The Enskog kinetic theory for moderately dense gas-solid suspensions under simple shear flow is considered as a model to analyze the rheological properties of the system. The influence of the environmental fluid on solid particles is modeled via a viscous drag force plus a stochastic Langevin-like term. The Enskog equation is solved by means of two independent but complementary routes: (i) Grad's moment method and (ii) event-driven Langevin simulation of hard spheres. Both approaches clearly show that the flow curve (stress-strain rate relation) depends significantly on the volume fraction of the solid particles. In particular, as the density increases, there is a transition from the discontinuous shear thickening (observed in dilute gases) to the continuous shear thickening for denser systems. The comparison between theory and simulations indicates that while the theoretical predictions for the kinetic temperature agree well with simulations for densities φ ≲0.5 , the agreement for the other rheological quantities (the viscosity, the stress ratio, and the normal stress differences) is limited to more moderate densities (φ ≲0.3 ) if the inelasticity during collisions between particles is not large.

Monte Carlo simulations of ionization potential depression in dense plasmas

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

Stransky, M., E-mail: stransky@fzu.cz

A particle-particle grand canonical Monte Carlo model with Coulomb pair potential interaction was used to simulate modification of ionization potentials by electrostatic microfields. The Barnes-Hut tree algorithm [J. Barnes and P. Hut, Nature 324, 446 (1986)] was used to speed up calculations of electric potential. Atomic levels were approximated to be independent of the microfields as was assumed in the original paper by Ecker and Kröll [Phys. Fluids 6, 62 (1963)]; however, the available levels were limited by the corresponding mean inter-particle distance. The code was tested on hydrogen and dense aluminum plasmas. The amount of depression was up tomore » 50% higher in the Debye-Hückel regime for hydrogen plasmas, in the high density limit, reasonable agreement was found with the Ecker-Kröll model for hydrogen plasmas and with the Stewart-Pyatt model [J. Stewart and K. Pyatt, Jr., Astrophys. J. 144, 1203 (1966)] for aluminum plasmas. Our 3D code is an improvement over the spherically symmetric simplifications of the Ecker-Kröll and Stewart-Pyatt models and is also not limited to high atomic numbers as is the underlying Thomas-Fermi model used in the Stewart-Pyatt model.« less

Enhanced laser-energy coupling to dense plasmas driven by recirculating electron currents

NASA Astrophysics Data System (ADS)

Gray, R. J.; Wilson, R.; King, M.; Williamson, S. D. R.; Dance, R. J.; Armstrong, C.; Brabetz, C.; Wagner, F.; Zielbauer, B.; Bagnoud, V.; Neely, D.; McKenna, P.

2018-03-01

The absorption of laser energy and dynamics of energetic electrons in dense plasma is fundamental to a range of intense laser-driven particle and radiation generation mechanisms. We measure the total reflected and scattered laser energy as a function of intensity, distinguishing between the influence of pulse energy and focal spot size on total energy absorption, in the interaction with thin foils. We confirm a previously published scaling of absorption with intensity by variation of laser pulse energy, but find a slower scaling when changing the focal spot size. 2D particle-in-cell simulations show that the measured differences arise due to energetic electrons recirculating within the target and undergoing multiple interactions with the laser pulse, which enhances absorption in the case of large focal spots. This effect is also shown to be dependent on the laser pulse duration, the target thickness and the electron beam divergence. The parameter space over which this absorption enhancement occurs is explored via an analytical model. The results impact our understanding of the fundamental physics of laser energy absorption in solids and thus the development of particle and radiation sources driven by intense laser–solid interactions.

Kinetic theory of shear thickening for a moderately dense gas-solid suspension: From discontinuous thickening to continuous thickening.

PubMed

Hayakawa, Hisao; Takada, Satoshi; Garzó, Vicente

2017-10-01

The Enskog kinetic theory for moderately dense gas-solid suspensions under simple shear flow is considered as a model to analyze the rheological properties of the system. The influence of the environmental fluid on solid particles is modeled via a viscous drag force plus a stochastic Langevin-like term. The Enskog equation is solved by means of two independent but complementary routes: (i) Grad's moment method and (ii) event-driven Langevin simulation of hard spheres. Both approaches clearly show that the flow curve (stress-strain rate relation) depends significantly on the volume fraction of the solid particles. In particular, as the density increases, there is a transition from the discontinuous shear thickening (observed in dilute gases) to the continuous shear thickening for denser systems. The comparison between theory and simulations indicates that while the theoretical predictions for the kinetic temperature agree well with simulations for densities φ≲0.5, the agreement for the other rheological quantities (the viscosity, the stress ratio, and the normal stress differences) is limited to more moderate densities (φ≲0.3) if the inelasticity during collisions between particles is not large.

Actinium-225 in targeted alpha-particle therapeutic applications

PubMed Central

Scheinberg, David A.; McDevit, Michael R.

2017-01-01

Alpha particle-emitting isotopes are being investigated in radioimmunotherapeutic applications because of their unparalleled cytotoxicity when targeted to cancer and their relative lack of toxicity towards untargeted normal tissue. Actinium-225 has been developed into potent targeting drug constructs and is in clinical use against acute myelogenous leukemia. The key properties of the alpha particles generated by 225Ac are the following: i) limited range in tissue of a few cell diameters; ii) high linear energy transfer leading to dense radiation damage along each alpha track; iii) a 10 day half-life; and iv) four net alpha particles emitted per decay. Targeting 225Ac-drug constructs have potential in the treatment of cancer. PMID:22202153

Influence des traitements thermiques et de la microstructure sur les phénomènes de découplage dans les composés au bismuth

NASA Astrophysics Data System (ADS)

Nicolas, M.; Guyen van Huong, C. N.; Burger, J. P.; Dubon, A.; Fitoussi, J. P.; Laval, J. Y.

1991-11-01

a.c. susceptibility measurements and 3D electronic microscopy observation were carried out on three Bi-compounds (2212 and 2223). Depending on the annealing conditions, one observes lamellar-type materials organized either in a more or less dense structure of fine particles or in very large slabs. The a.c. susceptibility signals allow to separate the intergranular from the intragranular effects. The combined results obtained by both techniques lead us to conclude that the intergranular and the intragranular decoupling, induced by magnetic fields are of same nature, i.e. occur at the (BiO)2 slab. Nous avons couplé des mesures de susceptibilité altemative et d'observation au microscope électronique en 3D sur trois échantillons supraconducteurs au bismuth (2212 et 2223). Selon les conditions de recuit, on observe des matériaux de type lamellaire, organisés soit en une structure plus ou moins dense de fines particules, soit en larges plaquettes. L'étude des signaux de susceptibilité alternative χ' et χ'' permet de séparer les effets intergranulaires des effets intragranulaires. les résultats combinés des deux techniques nous ont conduit à conclure que les deux types de découplage (inter et intragranulaires), induits par les champs magnétiques sont de même nature, c'est-à-dire se produisent au niveau des bicouches (BiO)2.

Numerical Study of Particle Damping Mechanism in Piston Vibration System via Particle Dynamics Simulation

NASA Astrophysics Data System (ADS)

Bai, Xian-Ming; Shah, Binoy; Keer, Leon; Wang, Jane; Snurr, Randall

2008-03-01

Mechanical damping systems with granular particles as the damping media have promising applications in extreme temperature conditions. In particle-based damping systems, the mechanical energy is dissipated through the inelastic collision and friction of particles. In the past, many experiments have been performed to investigate the particle damping problems. However, the detailed energy dissipation mechanism is still unclear due to the complex collision and flow behavior of dense particles. In this work, we use 3-D particle dynamics simulation to investigate the damping mechanism of an oscillating cylinder piston immerged in millimeter-size steel particles. The time evolution of the energy dissipation through the friction and inelastic collision is accurately monitored during the damping process. The contribution from the particle-particle interaction and particle-wall interaction is also separated for investigation. The effects of moisture, surface roughness, and density of particles are carefully investigated in the simulation. The comparison between the numerical simulation and experiment is also performed. The simulation results can help us understand the particle damping mechanism and design the new generation of particle damping devices.

Nuclear quantum effects on structure and transport properties of dense liquid helium

NASA Astrophysics Data System (ADS)

Kang, Dongdong; Dai, Jiayu; Yuan, Jianmin

2015-11-01

Transport properties of dense liquid helium under the conditions of planet's core and cool atmosphere of white dwarfs are important for determining the structure and evolution of these astrophysical objects. We have investigated these properties of dense liquid helium by using the improved centroid path-integral simulations combined with density functional theory. The results show that with the inclusion of nuclear quantum effects (NQEs), the self-diffusion is largely higher while the shear viscosity is notably lower than the results of without the inclusion of NQEs due to the lower collision cross sections even when the NQEs have little effects on the static structures. The potential surface of helium atom along the simulation trajectory is quite different between MD and PIMD simulations. We have shown that the quantum nuclear character induces complex behaviors for ionic transport properties of dense liquid helium. NQEs bring more fluctuations of local electronic density of states than the classical treatment. Therefore, in order to construct more reasonable structure and evolution model for the planets and WDs, NQEs must be reconsidered when calculating the transport properties at certain temperature and density conditions.

Kinetic theory molecular dynamics and hot dense matter: theoretical foundations.

PubMed

Graziani, F R; Bauer, J D; Murillo, M S

2014-09-01

Electrons are weakly coupled in hot, dense matter that is created in high-energy-density experiments. They are also mildly quantum mechanical and the ions associated with them are classical and may be strongly coupled. In addition, the dynamical evolution of plasmas under these hot, dense matter conditions involve a variety of transport and energy exchange processes. Quantum kinetic theory is an ideal tool for treating the electrons but it is not adequate for treating the ions. Molecular dynamics is perfectly suited to describe the classical, strongly coupled ions but not the electrons. We develop a method that combines a Wigner kinetic treatment of the electrons with classical molecular dynamics for the ions. We refer to this hybrid method as "kinetic theory molecular dynamics," or KTMD. The purpose of this paper is to derive KTMD from first principles and place it on a firm theoretical foundation. The framework that KTMD provides for simulating plasmas in the hot, dense regime is particularly useful since current computational methods are generally limited by their inability to treat the dynamical quantum evolution of the electronic component. Using the N-body von Neumann equation for the electron-proton plasma, three variations of KTMD are obtained. Each variant is determined by the physical state of the plasma (e.g., collisional versus collisionless). The first variant of KTMD yields a closed set of equations consisting of a mean-field quantum kinetic equation for the electron one-particle distribution function coupled to a classical Liouville equation for the protons. The latter equation includes both proton-proton Coulombic interactions and an effective electron-proton interaction that involves the convolution of the electron density with the electron-proton Coulomb potential. The mean-field approach is then extended to incorporate equilibrium electron-proton correlations through the Singwi-Tosi-Land-Sjolander (STLS) ansatz. This is the second variant of KTMD. The STLS contribution produces an effective electron-proton interaction that involves the electron-proton structure factor, thereby extending the usual mean-field theory to correlated but near equilibrium systems. Finally, a third variant of KTMD is derived. It includes dynamical electrons and their correlations coupled to a MD description for the ions. A set of coupled equations for the one-particle electron Wigner function and the electron-electron and electron-proton correlation functions are coupled to a classical Liouville equation for the protons. This latter variation has both time and momentum dependent correlations.

A continuous stochastic model for non-equilibrium dense gases

NASA Astrophysics Data System (ADS)

Sadr, M.; Gorji, M. H.

2017-12-01

While accurate simulations of dense gas flows far from the equilibrium can be achieved by direct simulation adapted to the Enskog equation, the significant computational demand required for collisions appears as a major constraint. In order to cope with that, an efficient yet accurate solution algorithm based on the Fokker-Planck approximation of the Enskog equation is devised in this paper; the approximation is very much associated with the Fokker-Planck model derived from the Boltzmann equation by Jenny et al. ["A solution algorithm for the fluid dynamic equations based on a stochastic model for molecular motion," J. Comput. Phys. 229, 1077-1098 (2010)] and Gorji et al. ["Fokker-Planck model for computational studies of monatomic rarefied gas flows," J. Fluid Mech. 680, 574-601 (2011)]. The idea behind these Fokker-Planck descriptions is to project the dynamics of discrete collisions implied by the molecular encounters into a set of continuous Markovian processes subject to the drift and diffusion. Thereby, the evolution of particles representing the governing stochastic process becomes independent from each other and thus very efficient numerical schemes can be constructed. By close inspection of the Enskog operator, it is observed that the dense gas effects contribute further to the advection of molecular quantities. That motivates a modelling approach where the dense gas corrections can be cast in the extra advection of particles. Therefore, the corresponding Fokker-Planck approximation is derived such that the evolution in the physical space accounts for the dense effects present in the pressure, stress tensor, and heat fluxes. Hence the consistency between the devised Fokker-Planck approximation and the Enskog operator is shown for the velocity moments up to the heat fluxes. For validation studies, a homogeneous gas inside a box besides Fourier, Couette, and lid-driven cavity flow setups is considered. The results based on the Fokker-Planck model are compared with respect to benchmark simulations, where good agreement is found for the flow field along with the transport properties.

Particle morphology dependent superhydrophobicity in treated diatomaceous earth/polystyrene coatings

NASA Astrophysics Data System (ADS)

Sedai, Bhishma R.; Alavi, S. Habib; Harimkar, Sandip P.; McCollum, Mark; Donoghue, Joseph F.; Blum, Frank D.

2017-09-01

Superhydrophobic surfaces have been prepared from three different types of diatomaceous earth (DE) particles treated with 3-(heptafluoroisopropoxy)propyltrimethoxysilane (HFIP-TMS) and low molecular mass polystyrene. The untreated particles, consisting of CelTix DE (disk shape), DiaFil DE (rod shape) and EcoFlat DE (irregular), were studied using particle size analysis, bulk density, pore volume and surface area analysis (via Brunauer-Emmett-Teller, BET, methods). The treated particles were characterized with thermogravimetric analysis (TGA), contact angles, scanning electron microscopy, profilometry, and FTIR spectroscopy. The minimum amount of silane coupling agent on the DE surfaces required to obtain superhydrophobicity of the particles was determined and found to be dependent on the particle morphology. In the coatings made from different particles with 2.4 wt% HFIP-TMS, the minimum amounts of treated particles (loadings) for superhydrophobicity was determined with the less dense CelTix DE requiring about 30 wt%, DiaFil DE requiring about 40 wt%, and EcoFlat DE each requiring about 60 wt% loading of treated particles.

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

An innovative architectural design to enhance the electrochemical performance of La2NiO4+δ cathodes for solid oxide fuel cell applications

NASA Astrophysics Data System (ADS)

Sharma, Rakesh K.; Burriel, Mónica; Dessemond, Laurent; Martin, Vincent; Bassat, Jean-Marc; Djurado, Elisabeth

2016-06-01

An architectural design of the cathode microstructure based on combining electrostatic spray deposition (ESD) and screen-printing (SP) techniques has demonstrated to be an innovative strategy to enhance the electrochemical properties of La2NiO4+δ (LNO) as oxygen electrode on Ce0.9Gd0.1O2-δ (CGO) electrolyte for solid oxide fuel cells. For this purpose, the influence of the ESD process parameters on the microstructure has been systematically investigated. Electrochemical performances of four selected cathode microstructures are investigated: (i) 3-D coral nanocrystalline (average particle size ∼ 100 nm) LNO film grown by ESD; (ii) 3-D coral nanocrystalline film (average particle size ∼ 150 nm) grown by ESD with a continuous nanometric dense interface; (iii) porous screen-printed LNO film (average particle size ∼ 400 nm); and (iv) 3-D coral nanocrystalline film (average particle size ∼ 150 nm) with a continuous nanometric dense interface prepared by ESD topped by a LNO current collector prepared by SP. A significant reduction in the polarization resistance (Rpol) is obtained (0.08 Ω cm2 at 700 °C) for 3-D coral topped by the SP layer. Moreover LNO is found to be stable and compatible with CGO up to 800 °C for only 10 days duration in air, making it potentially suitable for SOFCs cathode application.

Dynamic properties of the energy loss of multi-MeV charged particles traveling in two-component warm dense plasmas.

PubMed

Fu, Zhen-Guo; Wang, Zhigang; Li, Meng-Lei; Li, Da-Fang; Kang, Wei; Zhang, Ping

2016-12-01

The energy loss of multi-MeV charged particles moving in two-component warm dense plasmas (WDPs) is studied theoretically beyond the random-phase approximation. The short-range correlations between particles are taken into account via dynamic local field corrections (DLFC) in a Mermin dielectric function for two-component plasmas. The mean ionization states are obtained by employing the detailed configuration accounting model. The Yukawa-type effective potential is used to derive the DLFC. Numerically, the DLFC are obtained via self-consistent iterative operations. We find that the DLFC are significant around the maximum of the stopping power. Furthermore, by using the two-component extended Mermin dielectric function model including the DLFC, the energy loss of a proton with an initial energy of ∼15 MeV passing through a WDP of beryllium with an electronic density around the solid value n_{e}≈3×10^{23}cm^{-3} and with temperature around ∼40 eV is estimated numerically. The numerical result is reasonably consistent with the experimental observations [A. B. Zylsta et al., Phys. Rev. Lett. 111, 215002 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.215002]. Our results show that the partial ionization and the dynamic properties should be of importance for the stopping of charged particles moving in the WDP.

Importance of intrinsic properties of dense caseinate dispersions for structure formation.

PubMed

Manski, Julita M; van Riemsdijk, Lieke E; van der Goot, Atze J; Boom, Remko M

2007-11-01

Rheological measurements of dense calcium caseinate and sodium caseinate dispersions (> or =15%) provided insight into the factors determining shear-induced structure formation in caseinates. Calcium caseinate at a sufficiently high concentration (30%) was shown to form highly anisotropic structures during shearing and concurrent enzymatic cross-linking. In contrast, sodium caseinate formed isotropic structures using similar processing conditions. The main difference between the two types of caseinates is the counterion present, and as a consequence, the size of structural elements and their interactions. The rheological behavior of calcium caseinate and sodium caseinate reflected these differences, yielding non-monotonic and shear thinning flow behavior for calcium caseinate whereas sodium caseinate behaved only slightly shear thinning. It appears that the intrinsic properties of the dense caseinate dispersions, which are reflected in their rheological behavior, affect the structure formation that was found after applying shear. Therefore, rheological measurements are useful to obtain an indication of the structure formation potential of caseinate dispersions.

The Transition from Diffuse to Dense Gas in Herschel Dust Emission Maps

NASA Astrophysics Data System (ADS)

Goldsmith, Paul

Dense cores in dark clouds are the sites where young stars form. These regions manifest as relatively small (<0.1pc) pockets of cold and dense gas. If we wish to understand the star formation process, we have to understand the physical conditions in dense cores. This has been a main aim of star formation research in the past decade. Today, we do indeed possess a good knowledge of the density and velocity structure of cores, as well as their chemical evolution and physical lifetime. However, we do not understand well how dense cores form out of the diffuse gas clouds surrounding them. It is crucial that we constrain the relationship between dense cores and their environment: if we only understand dense cores, we may be able to understand how individual stars form --- but we would not know how the star forming dense cores themselves come into existence. We therefore propose to obtain data sets that reveal both dense cores and the clouds containing them in the same map. Based on these maps, we will study how dense cores form out of their natal clouds. Since cores form stars, this knowledge is crucial for the development of a complete theoretical and observational understanding of the formation of stars and their planets, as envisioned in NASA's Strategic Science Plan. Fortunately, existing archival data allow to derive exactly the sort of maps we need for our analysis. Here, we describe a program that exclusively builds on PACS and SPIRE dust emission imaging data from the NASA-supported Herschel mission. The degree-sized wide-field Herschel maps of the nearby (<260pc) Polaris Flare and Aquila Rift clouds are ideal for our work. They permit to resolve dense cores (<0.1pc), while the maps also reveal large-scale cloud structure (5pc and larger). We will generate column density maps from these dust emission maps and then run a tree-based hierarchical multi-scale structure analysis on them. Only this procedure permits to exploit the full potential of the maps: we will characterize cloud structure over a vast range of spatial scales. This work has many advantages over previous studies, where information about dense cores and their environment was pieced together using a variety of methods an instruments. Now, the Herschel maps permit for the first time to characterize both molecular clouds and their cores in one shot in a single data set. We use these data to answer a variety of simple yet very important questions. First, we study whether dense cores have sharp boundaries. If such boundaries exist, they would indicate that dense cores have an individual identity well-separate from the near-fractal cloud structure on larger spatial scales. Second, we will --- in very approximate sense --- derive global density gradients for molecular clouds from radii <0.1pc to 5pc and larger. These "synoptic" density gradients provide a useful quantitative description of the relation between cloud material at very different spatial scales. Also, these measurements can be compared to synoptic density gradients derived in the same fashion for theoretical cloud models. Third, we study how dense cores are nested into the "clumps" forming molecular clouds, i.e., we study whether the most massive dense cores in a cloud (<0.1pc) reside in the most massive regions identified on lager spatial scale (1pc and larger). This will show how the properties of dense cores are influenced by their environment. Our study will derive unique constraints to cloud structure. But our small sample forbids to make strong statements. This pilot study does thus prepare future larger efforts. Our entire project builds on data reduction and analysis methods which our team has used in the past. This guarantees a swift completion of the project with predictable efficiency. We present pilot studies that demonstrate that the data and analysis methods are suited to tackle the science goals. This project is thus guaranteed to return significant results.

Effects of absorption on multiple scattering by random particulate media: exact results.

PubMed

Mishchenko, Michael I; Liu, Li; Hovenier, Joop W

2007-10-01

We employ the numerically exact superposition T-matrix method to perform extensive computations of elec nottromagnetic scattering by a volume of discrete random medium densely filled with increasingly absorbing as well as non-absorbing particles. Our numerical data demonstrate that increasing absorption diminishes and nearly extinguishes certain optical effects such as depolarization and coherent backscattering and increases the angular width of coherent backscattering patterns. This result corroborates the multiple-scattering origin of such effects and further demonstrates the heuristic value of the concept of multiple scattering even in application to densely packed particulate media.

SIZE DISTRIBUTIONS OF ELEMENTAL CARBON IN ATMOSPHERIC AEROSOLS

EPA Science Inventory

Environmental problems caused by atmospheric aerosols are well documented in the specialized literature. Studies reporting on the role of dense clouds of soil particles in past mass extinctions of life on Earth and, more recently (Turco et al., 1983), on calculations of potential...

EFFECT OF ACTIVE ACCUMULATION OF CALCIUM AND PHOSPHATE IONS ON THE STRUCTURE OF RAT LIVER MITOCHONDRIA

PubMed Central

Greenawalt, John W.; Rossi, Carlo S.; Lehninger, Albert L.

1964-01-01

Rat liver mitochondria allowed to accumulate maximal amounts of Ca++ and HPO4 = ions from the suspending medium in vitro during respiration have a considerably higher specific gravity than normal mitochondria and may be easily separated from the latter by isopycnic centrifugation in density gradients of sucrose or cesium chloride. When the mitochondria are allowed to accumulate less than maximal amounts of Ca++ and HPO4 = from the medium, they have intermediate specific gravities which are roughly proportional to their content of calcium phosphate. Maximally "loaded" mitochondria are relatively homogeneous with respect to specific gravity. Correlated biochemical and electron microscopic studies show that Ca++-loaded mitochondria contain numerous dense granules, of which some 85 per cent are over 500 A in diameter. These granules are electron-opaque not only following fixation and staining with heavy metal reagents, but also following fixation with formaldehyde, demonstrating that the characteristic granules in Ca++-loaded mitochondria have intrinsic electron-opacity. The dense granules are almost always located within the inner compartment of the mitochondria and not in the space between the inner and outer membranes. They are frequently located at or near the cristae and they often show electron-transparent "cores." Such granules appear to be made up of clusters of smaller dense particles, but preliminary x-ray diffraction analysis and electron diffraction studies have revealed no evidence of crystallinity in the deposits. The electron-opaque granules decrease in number when the Ca++-loaded mitochondria are incubated with 2,4-dinitrophenol; simultaneously there is discharge of Ca++ and phosphate from the mitochondria into the medium. PMID:14228516

Pathogenesis of developmental anomalies of the central nervous system induced by congenital cytomegalovirus infection.

PubMed

Kawasaki, Hideya; Kosugi, Isao; Meguro, Shiori; Iwashita, Toshihide

2017-02-01

In humans, the herpes virus family member cytomegalovirus (CMV) is the most prevalent mediator of intrauterine infection-induced congenital defect. Central nervous system (CNS) dysfunction is a distinguishing symptom of CMV infection, and characterized by ventriculoencephalitis and microglial nodular encephalitis. Reports on the initial distribution of CMV particles and its receptors on the blood brain barrier (BBB) are rare. Nevertheless, several factors are suggested to affect CMV etiology. Viral particle size is the primary factor in determining the pattern of CNS infections, followed by the expression of integrin β1 in endothelial cells, pericytes, meninges, choroid plexus, and neural stem progenitor cells (NSPCs), which are the primary targets of CMV infection. After initial infection, CMV disrupts BBB structural integrity to facilitate the spread of viral particles into parenchyma. Then, the initial meningitis and vasculitis eventually reaches NSPC-dense areas such as ventricular zone and subventricular zone, where viral infection inhibits NSPC proliferation and differentiation and results in neuronal cell loss. These cellular events clinically manifest as brain malformations such as a microcephaly. The purpose of this review is to clearly delineate the pathophysiological basis of congenital CNS anomalies caused by CMV. © 2017 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.

Microstructure characteristics of Ni/WC composite cladding coatings

NASA Astrophysics Data System (ADS)

Yang, Gui-rong; Huang, Chao-peng; Song, Wen-ming; Li, Jian; Lu, Jin-jun; Ma, Ying; Hao, Yuan

2016-02-01

A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr7C3/Cr23C6, CrB, and Ni+Ni3Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.

Brine assemblages of ultrasmall microbial cells within the ice cover of Lake Vida, Antarctica.

PubMed

Kuhn, Emanuele; Ichimura, Andrew S; Peng, Vivian; Fritsen, Christian H; Trubl, Gareth; Doran, Peter T; Murray, Alison E

2014-06-01

The anoxic and freezing brine that permeates Lake Vida's perennial ice below 16 m contains an abundance of very small (≤0.2-μm) particles mixed with a less abundant population of microbial cells ranging from >0.2 to 1.5 μm in length. Fluorescent DNA staining, electron microscopy (EM) observations, elemental analysis, and extraction of high-molecular-weight genomic DNA indicated that a significant portion of these ultrasmall particles are cells. A continuous electron-dense layer surrounding a less electron-dense region was observed by EM, indicating the presence of a biological membrane surrounding a cytoplasm. The ultrasmall cells are 0.192 ± 0.065 μm, with morphology characteristic of coccoid and diplococcic bacterial cells, often surrounded by iron-rich capsular structures. EM observations also detected the presence of smaller unidentified nanoparticles of 0.020 to 0.140 μm among the brine cells. A 16S rRNA gene clone library from the brine 0.1- to 0.2-μm-size fraction revealed a relatively low-diversity assemblage of Bacteria sequences distinct from the previously reported >0.2-μm-cell-size Lake Vida brine assemblage. The brine 0.1- to 0.2-μm-size fraction was dominated by the Proteobacteria-affiliated genera Herbaspirillum, Pseudoalteromonas, and Marinobacter. Cultivation efforts of the 0.1- to 0.2-μm-size fraction led to the isolation of Actinobacteria-affiliated genera Microbacterium and Kocuria. Based on phylogenetic relatedness and microscopic observations, we hypothesize that the ultrasmall cells in Lake Vida brine are ultramicrocells that are likely in a reduced size state as a result of environmental stress or life cycle-related conditions.

Brine Assemblages of Ultrasmall Microbial Cells within the Ice Cover of Lake Vida, Antarctica

PubMed Central

Kuhn, Emanuele; Ichimura, Andrew S.; Peng, Vivian; Fritsen, Christian H.; Trubl, Gareth; Doran, Peter T.

2014-01-01

The anoxic and freezing brine that permeates Lake Vida's perennial ice below 16 m contains an abundance of very small (≤0.2-μm) particles mixed with a less abundant population of microbial cells ranging from >0.2 to 1.5 μm in length. Fluorescent DNA staining, electron microscopy (EM) observations, elemental analysis, and extraction of high-molecular-weight genomic DNA indicated that a significant portion of these ultrasmall particles are cells. A continuous electron-dense layer surrounding a less electron-dense region was observed by EM, indicating the presence of a biological membrane surrounding a cytoplasm. The ultrasmall cells are 0.192 ± 0.065 μm, with morphology characteristic of coccoid and diplococcic bacterial cells, often surrounded by iron-rich capsular structures. EM observations also detected the presence of smaller unidentified nanoparticles of 0.020 to 0.140 μm among the brine cells. A 16S rRNA gene clone library from the brine 0.1- to 0.2-μm-size fraction revealed a relatively low-diversity assemblage of Bacteria sequences distinct from the previously reported >0.2-μm-cell-size Lake Vida brine assemblage. The brine 0.1- to 0.2-μm-size fraction was dominated by the Proteobacteria-affiliated genera Herbaspirillum, Pseudoalteromonas, and Marinobacter. Cultivation efforts of the 0.1- to 0.2-μm-size fraction led to the isolation of Actinobacteria-affiliated genera Microbacterium and Kocuria. Based on phylogenetic relatedness and microscopic observations, we hypothesize that the ultrasmall cells in Lake Vida brine are ultramicrocells that are likely in a reduced size state as a result of environmental stress or life cycle-related conditions. PMID:24727273

Seeing the Forest Through the Trees: The Distribution and Properties of Dense Molecular Gas in the Milky Way Galaxy

NASA Astrophysics Data System (ADS)

Ellsworth-Bowers, Timothy P.

The Milky Way Galaxy serves as a vast laboratory for studying the dynamics and evolution of the dense interstellar medium and the processes of and surrounding massive star formation. From our vantage point within the Galactic plane, however, it has been extremely difficult to construct a coherent picture of Galactic structure; we cannot see the forest for the trees. The principal difficulties in studying the structure of the Galactic disk have been obscuration by the ubiquitous dust and molecular gas and confusion between objects along a line of sight. Recent technological advances have led to large-scale blind surveys of the Galactic plane at (sub-)millimeter wavelengths, where Galactic dust is generally optically thin, and have opened a new avenue for studying the forest. The Bolocam Galactic Plane Survey (BGPS) observed over 190 deg 2 of the Galactic plane in dust continuum emission near lambda = 1.1 mm, producing a catalog of over 8,000 dense molecular cloud structures across a wide swath of the Galactic disk. Deriving the spatial distribution and physical properties of these objects requires knowledge of distance, a component lacking in the data themselves. This thesis presents a generalized Bayesian probabilistic distance estimation method for dense molecular cloud structures, and demonstrates it with the BGPS data set. Distance probability density functions (DPDFs) are computed from kinematic distance likelihoods (which may be double- peaked for objects in the inner Galaxy) and an expandable suite of prior information to produce a comprehensive tally of our knowledge (and ignorance) of the distances to dense molecular cloud structures. As part of the DPDF formalism, this thesis derives several prior DPDFs for resolving the kinematic distance ambiguity in the inner Galaxy. From the collection of posterior DPDFs, a set of objects with well-constrained distance estimates is produced for deriving Galactic structure and the physical properties of dense molecular cloud structures. This distance catalog of 1,802 objects across the Galactic plane represents the first large-scale analysis of clump-scale objects in a variety of Galactic environments. The Galactocentric positions of these objects begin to trace out the spiral structure of the Milky Way, and suggest that dense molecular gas settles nearer the Galactic midplane than tracers of less-dense gas such as CO. Physical properties computed from the DPDFs reveal that BGPS objects trace a continuum of scales within giant molecular clouds, and extend the scaling relationships known as Larson's Laws to lower-mass substructures. The results presented here represent the first step on the road to seeing the molecular content of the Milky Way as a forest rather than individual nearby trees.

Microstructure and Mechanical Properties of Zn-Ni-Al₂O₃ Composite Coatings.

PubMed

Bai, Yang; Wang, Zhenhua; Li, Xiangbo; Huang, Guosheng; Li, Caixia; Li, Yan

2018-05-21

Zn-Ni-Al₂O₃ composite coatings with different Ni contents were fabricated by low-pressure cold spray (LPCS) technology. The effects of the Ni content on the microstructural and mechanical properties of the coatings were investigated. According to X-ray diffraction patterns, the composite coatings were primarily composed of metallic-phase Zn and Ni and ceramic-phase Al₂O₃. The energy-dispersive spectroscopy results show that the Al₂O₃ content of the composite coatings gradually decreased with increasing of Ni content. The cross-sectional morphology revealed thick, dense coatings with a wave-like stacking structure. The process of depositing Zn and Ni particles and Al₂O₃ particles by the LPCS method was examined, and the deposition mechanism was demonstrated to be mechanical interlocking. The bond strength, micro hardness and friction coefficient of the coatings did not obviously change when the Ni content varied. The presence of Al₂O₃ and Ni increased the wear resistance of the composite coatings, which was higher than that of pure Zn coatings, and the wear mechanism was abrasive and adhesive wear.

Communication: Hypothetical ultralow-density ice polymorphs

NASA Astrophysics Data System (ADS)

Matsui, Takahiro; Hirata, Masanori; Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2017-09-01

More than 300 kinds of porous ice structures derived from zeolite frameworks and space fullerenes are examined using classical molecular dynamics simulations. It is found that a hypothetical zeolitic ice phase is less dense and more stable than the sparse ice structures reported by Huang et al. [Chem. Phys. Lett. 671, 186 (2017)]. In association with the zeolitic ice structure, even less dense structures, "aeroices," are proposed. It is found that aeroices are the most stable solid phases of water near the absolute zero temperature under negative pressure.

An Instability in Narrow Planetary Rings

NASA Astrophysics Data System (ADS)

Weiss, J. W.; Stewart, G. R.

2003-08-01

We will present our work investigating the behavior of narrow planetary rings with low dispersion velocities. Such narrow a ring will be initially unstable to self-gravitational collapse. After the collapse, the ring is collisionally very dense. At this stage, it is subject to a new instability. Waves appear on the inner and outer edges of the ring within half of an orbital period. The ring then breaks apart radially, taking approximately a quarter of an orbital period of do so. As clumps of ring particles expand radially away from the dense ring, Kepler shear causes these clumps to stretch out azimuthally, and eventually collapse into a new set of dense rings. Small-scale repetitions of the original instability in these new rings eventually leads to a stabilized broad ring with higher dispersion velocities than the initial ring. Preliminary results indicate that this instability may be operating on small scales in broad rings in the wake-like features seen by Salo and others. Some intriguing properties have been observed during this instability. The most significant is a coherence in the epicyclic phases of the particles. Both self-gravity and collisions in the ring operated to create and enforce this coherence. The coherence might also be responsible for the instability to radial expansion. We also observe that guiding centers of the particles do not migrate to the center of the ring during the collapse phase of the ring. In fact, guiding centers move radially away from the core of the ring during this phase, consistent with global conservation of angular momentum. We will show the results of our simulations to date, including movies of the evolution of various parameters. (Audiences members wanting popcorn are advised to bring their own.) This work is supported by a NASA Graduate Student Research Program grant and by the Cassini mission.

Recent Advances in the Development and Application of Power Plate Transducers in Dense Gas Extraction and Aerosol Agglomeration Processes

NASA Astrophysics Data System (ADS)

Riera, E.; Cardoni, A.; Gallego-Juárez, J. A.; Acosta, V. M.; Blanco, A.; Rodríguez, G.; Blasco, M.; Herranz, L. E.

Power ultrasound (PU) is an emerging, innovative, energy saving and environmental friendly technology that is generating a great interest in sectors such as food and pharmaceutical industries, green chemistry, environmental pollution, and other processes, where sustainable and energy efficient methods are required to improve and/or produce specific effects. Two typical effects of PU are the enhancement of mass transfer in gases and liquids, and the induction of particle agglomeration in aerosols. These effects are activated by a variety of mechanisms associated to the nonlinear propagation of high amplitude ultrasonic waves such as diffusion, agitation, entrainment, turbulence, etc. During the last years a great effort has been jointly made by the Spanish National Research Council (CSIC) and the company Pusonics towards introducing novel processes into the market based on airborne ultrasonic plate transducers. This technology was specifically developed for the treatment of gas and multiphasic media characterized by low specific acoustic impedance and high acoustic absorption. Different strategies have been developed to mitigate the effects of the nonlinear dynamic behavior of such ultrasonic piezoelectric transducers in order to enhance and stabilize their response at operational power conditions. This work deals with the latter advances in the mitigation of nonlinear problems found in power transducers; besides it describes two applications assisted by ultrasound developed at semi-industrial and laboratory scales and consisting in extraction via dense gases and particle agglomeration. Dense Gas Extraction (DGE) assisted by PU is a new process with a potential to enhance the extraction kinetics with supercritical CO2. Acoustic agglomeration of fine aerosol particles has a great potential for the treatment of air pollution problems generated by particulate materials. Experimental and numerical results in both processes will be shown and discussed.

First-principles calculations of K-shell X-ray absorption spectra for warm dense nitrogen

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

Li, Zi; Zhang, Shen; Kang, Wei

2016-05-15

X-ray absorption spectrum is a powerful tool for atomic structure detection on warm dense matter. Here, we perform first-principles molecular dynamics and X-ray absorption spectrum calculations on warm dense nitrogen along a Hugoniot curve. From the molecular dynamics trajectory, the detailed atomic structures are examined for each thermodynamical condition. The K-shell X-ray absorption spectrum is calculated, and its changes with temperature and pressure along the Hugoniot curve are discussed. The warm dense nitrogen systems may contain isolated nitrogen atoms, N{sub 2} molecules, and nitrogen clusters, which show quite different contributions to the total X-ray spectrum due to their different electronmore » density of states. The changes of X-ray spectrum along the Hugoniot curve are caused by the different nitrogen structures induced by the temperature and the pressure. Some clear signatures on X-ray spectrum for different thermodynamical conditions are pointed out, which may provide useful data for future X-ray experiments.« less

Concluding Remarks: Connecting Relativistic Heavy Ion Collisions and Neutron Star Mergers by the Equation of State of Dense Hadron- and Quark Matter as signalled by Gravitational Waves

NASA Astrophysics Data System (ADS)

Hanauske, Matthias; Steinheimer, Jan; Bovard, Luke; Mukherjee, Ayon; Schramm, Stefan; Takami, Kentaro; Papenfort, Jens; Wechselberger, Natascha; Rezzolla, Luciano; Stöcker, Horst

2017-07-01

The underlying open questions in the fields of general relativistic astrophysics and elementary particle and nuclear physics are strongly connected and their results are interdependent. Although the physical systems are quite different, the 4D-simulation of a merger of a binary system of two neutron stars and the properties of the hot and dense matter created in high energy heavy ion collisions, strongly depend on the equation of state of fundamental elementary matter. Neutron star mergers represent optimal astrophysical laboratories to investigate the QCD phase structure using a spectrogram of the post-merger phase of the emitted gravitational waves. These studies can be supplemented by observations from heavy ion collisions to possibly reach a conclusive picture on the QCD phase structure at high density and temperature. As gravitational waves (GWs) emitted from merging neutron star binaries are on the verge of their first detection, it is important to understand the main characteristics of the underlying merging system in order to predict the expected GW signal. Based on numerical-relativity simulations of merging neutron star binaries, the emitted GW and the interior structure of the generated hypermassive neutron stars (HMNS) have been analyzed in detail. This article will focus on the internal and rotational HMNS properties and their connection with the emitted GW signal. Especially, the appearance of the hadon-quark phase transition in the interior region of the HMNS and its conjunction with the spectral properties of the emitted GW will be addressed and confronted with the simulation results of high energy heavy ion collisions.

Elemental analysis of sunflower cataract in Wilson's disease: a study using scanning transmission electron microscopy and energy dispersive spectroscopy.

PubMed

Jang, Hyo Ju; Kim, Joon Mo; Choi, Chul Young

2014-04-01

Signature ophthalmic characteristics of Wilson's disease (WD) are regarded as diagnostically important manifestations of the disease. Previous studies have proved the common occurrence of copper accumulation in the liver of patients with WD. However, in the case of sunflower cataracts, one of the rare diagnostic signs of WD, no study has demonstrated copper accumulation in the lens capsules of sunflower cataracts in WD patients. To investigate the nanostructure and elemental composition of sunflower cataracts in WD, transmission electron microscopy (TEM) was done on the capsulorhexised anterior lens capsule of sunflower cataracts in WD in order to evaluate anatomical variation and elemental changes. We utilized energy dispersive X-ray spectroscopy (EDS) to investigate the elemental composition of the lens capsule using both point and mapping spectroscopy. Quantitative analysis was performed for relative comparison of the elements. TEM showed the presence of granular deposits of varying size (20-350 nm), appearing mainly in the posterior one third of the anterior capsule. The deposits appeared in linear patterns with scattered dots. There were no electron-dense particles in the epithelial cell layer of the lens. Copper and sulfur peaks were consistently revealed in electron-dense granular deposits. In contrast, copper and sulfur peaks were absent in other tissues, including granule-free lens capsules and epithelial tissue. Most copper was exclusively located in clusters of electron-dense particles, and the copper distribution overlapped with sulfur on mapping spectroscopy. Quantitative analysis presented inconsistent ratios of copper to sulfur in each electron-dense granule. The mean ratio of copper to sulfur was about 3.25 (with a range of 2.39-3.78). This is the first elemental analysis of single electron particles in sunflower cataracts using EDS in the ophthalmic area. Sunflower cataracts with WD are assumed to be the result of accumulation of heterogeneous compounds composed of several materials, including copper, sulfur, and/or copper-binding proteins. Linear patterns of copper and sulfur deposition were detected in various sizes and composition ratios with these elements in cases of WD. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cytochemical features common to nucleoli and cytoplasmic nucleoloids of Olea europaea meiocytes: detection of rRNA by in situ hybridization.

PubMed

Alché, J D; Fernández, M C; Rodríguez-García, M I

1994-02-01

We used light and electron microscopic techniques to study the composition of cytoplasmic nucleoloids during meiotic division in Olea europaea. Nucleoloids were found in two clearly distinguishable morphological varieties: one similar in morphology to the nucleolus, and composed mainly of dense fibrillar component, and another surrounded by many ribosome-like particles. Cytochemical and immunocytochemical techniques showed similar reactivities in nucleoloids and the nucleolus: both are ribonucleoproteic in nature, and possess argyrophillic, argentaffinic and highly phosphorylated proteins. Immunohistochemical techniques failed to detect DNA in either structure. In situ hybridization to a 18 S rRNA probe demonstrated the presence of ribosomal transcripts in both the nucleolus and nucleoloids. These similarities in morphology and composition may reflect similar functionalities.