Photon structure functions with heavy particle mass effects

Energy Technology Data Exchange (ETDEWEB)

Uematsu, Tsuneo, E-mail: uematsu@scphys.kyoto-u.jp [Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto, 606-8502 (Japan); Maskawa Institute for Science and Culture, Kyoto Sangyo University, Kamigamo, Kita-ku, Kyoto 603-8555 (Japan)

2013-01-15

In the framework of the perturbative QCD we investigate heavy particle mass effects on the unpolarized and polarized photon structure functions, F{sub 2}{sup γ} and g{sub 1}{sup γ}, respectively. We present our basic formalism to treat heavy particle mass effects to NLO in perturbative QCD. We also study heavy quark effects on the QCD sum rule for the first moment of g{sub 1}{sup γ}, which is related to axial anomaly. The photon structure function in supersymmetric QCD is also briefly discussed.

Relativistic Collisions of Structured Atomic Particles

CERN Document Server

Voitkiv, Alexander

2008-01-01

The book reviews the progress achieved over the last decade in the study of collisions between an ion and an atom in which both the atomic particles carry electrons and can undergo transitions between their internal states -- including continua. It presents the detailed considerations of different theoretical approaches, that can be used to describe collisions of structured atomic particles for the very broad interval of impact energies ranging from 0.5--1 MeV/u till extreme relativistic energies where the collision velocity very closely approaches the speed of light.

Exploring the Early Structure of a Rapidly Decompressed Particle Bed

Science.gov (United States)

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.

Structure and dynamics of particle-accumulation in thermocapillary liquid bridges

International Nuclear Information System (INIS)

Kuhlmann, Hendrik C; Mukin, Roman V; Sano, Tomoaki; Ueno, Ichiro

2014-01-01

The accumulation of small mono-disperse heavy particles in thermocapillary liquid bridges is investigated experimentally and numerically. We consider particle accumulation near the center of the toroidal vortex, the so-called toroidal core of particles (COP), and the particle-depletion zone near the axis of the liquid bridge. Based on the acceleration and deceleration of the tangential flow along the thermocapillary free surface it is argued that the interaction of the particles with the free surface is of key importance for the fast particle accumulation within a few characteristic momentum diffusion times. The experimentally determined particle-accumulation times are compared with time-scale estimates for accumulation due to either particle free-surface interaction or due to inertia of particles which are heavier than the liquid. We show that the experimental accumulation times are compatible with the accumulation times predicted by the particle–free-surface interaction (PSI) while the time-scale estimates based on the inertia of the particles are too large to explain the fast de-mixing observed in experiments. The shape of the COP resembles certain KAM tori of the incompressible flow of a hydrothermal wave. Two scenarios are proposed to explain the structure and the dynamics of the COP depending on the existence or non-existence of suitable KAM structures. The shape of the experimental particle-depletion zone agrees well with the release surface which is defined by the particle–free-surface interaction process. The favorable comparison of the dynamics and structure of experimental and numerical accumulation patterns provides strong evidence for the existence and relevance of the PSI as the most rapid physical accumulation mechanism. (paper)

Structural transformations in PbSe films irradiated by α-particles

International Nuclear Information System (INIS)

Freik, D.M.; Ostapchuk, A.I.; Ogorodnik, Ya.V.; Shkol'nyj, A.K.; Mezhilovskaya, L.I.

1990-01-01

Structural changes in PbSe epitaxial layers irradiated by 5 MeV alpha-particles in integral flux of 2x10 12 cm -2 are investigated. It is ascertained that irradiation by alpha-particles can be successfully used as a technological factor dfor directed change of lead selenide properties. Radiation treatment by alpha-particle of epitaxial layers by the doses of ∼ 10 12 cm -2 results in the dispersion of their structure up to polycrystal phase formation. Irradiation by alpha-particles causes donor effect leading to a decrease in hole concentration and to the growth of electronic constituent of conductivity and to the conductivity inversion from p- for n-type

Structure of magnetic particles studied by small angle neutron scattering. [Magnetic colloid particles in stable liquid dispersion

Energy Technology Data Exchange (ETDEWEB)

Cebula, D J; Charles, S W; Popplewell, J

1981-03-01

The purpose of this note is to show how the use of small angle neutron scattering (SANS) can provide fundamental information on the structure of magnetic colloid particles in stable liquid dispersion. A more detailed account elaborating the use of the technique to provide fundamental information on interactions will appear later. This contribution contains some principal results on particle structure. The technique of SANS provides a very sensitive means of measuring particle size by measuring the scattered neutron intensity, I(Q), as a function of scattered wave vector, Q.

Weakly interacting massive particles and stellar structure

International Nuclear Information System (INIS)

Bouquet, A.

1988-01-01

The existence of weakly interacting massive particles (WIMPs) may solve both the dark matter problem and the solar neutrino problem. Such particles affect the energy transport in the stellar cores and change the stellar structure. We present the results of an analytic approximation to compute these effects in a self-consistent way. These results can be applied to many different stars, but we focus on the decrease of the 8 B neutrino flux in the case of the Sun

Self-assembly of three-dimensional open structures using patchy colloidal particles.

Science.gov (United States)

Rocklin, D Zeb; Mao, Xiaoming

2014-10-14

Open structures can display a number of unusual properties, including a negative Poisson's ratio, negative thermal expansion, and holographic elasticity, and have many interesting applications in engineering. However, it is a grand challenge to self-assemble open structures at the colloidal scale, where short-range interactions and low coordination number can leave them mechanically unstable. In this paper we discuss the self-assembly of three-dimensional open structures using triblock Janus particles, which have two large attractive patches that can form multiple bonds, separated by a band with purely hard-sphere repulsion. Such surface patterning leads to open structures that are stabilized by orientational entropy (in an order-by-disorder effect) and selected over close-packed structures by vibrational entropy. For different patch sizes the particles can form into either tetrahedral or octahedral structural motifs which then compose open lattices, including the pyrochlore, the hexagonal tetrastack and the perovskite lattices. Using an analytic theory, we examine the phase diagrams of these possible open and close-packed structures for triblock Janus particles and characterize the mechanical properties of these structures. Our theory leads to rational designs of particles for the self-assembly of three-dimensional colloidal structures that are possible using current experimental techniques.

Fundamental Particle Structure in the Cosmological Dark Matter

Science.gov (United States)

Khlopov, Maxim

2013-11-01

The nonbaryonic dark matter of the universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro-world and mechanisms of its symmetry breaking. Particle candidates for cosmological dark matter are lightest particles that bear new conserved quantum numbers. Dark matter particles may represent ideal gas of noninteracting particles. Self-interacting dark matter weakly or superweakly coupled to ordinary matter is also possible, reflecting nontrivial pattern of particle symmetry in the hidden sector of particle theory. In the early universe the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which macroscopic cosmological defects or primordial nonlinear structures can be originated. Primordial black holes (PBHs) can be not only a candidate for dark matter, but also represent a universal probe for superhigh energy physics in the early universe. Evaporating PBHs turn to be a source of even superweakly interacting particles, while clouds of massive PBHs can serve as nonlinear seeds for galaxy formation. The observed broken symmetry of the three known families may provide a simultaneous solution for the problems of the mass of neutrino and strong CP-violation in the unique framework of models of horizontal unification. Dark matter candidates can also appear in the new families of quarks and leptons and the existence of new stable charged leptons and quarks is possible, hidden in elusive "dark atoms." Such possibility, strongly restricted by the constraints on anomalous isotopes of light elements, is not excluded in scenarios that predict stable double charged particles. The excessive -2 charged particles are bound in these scenarios with primordial helium in O-helium "atoms," maintaining specific nuclear-interacting form of the dark matter, which may provide an interesting solution for the puzzles of the direct dark matter searches. In the context of cosmoparticle physics, studying

Evolution of single-particle structure of silicon isotopes

Science.gov (United States)

Bespalova, O. V.; Fedorov, N. A.; Klimochkina, A. A.; Markova, M. L.; Spasskaya, T. I.; Tretyakova, T. Yu.

2018-01-01

New data on proton and neutron single-particle energies E_{nlj} of Si isotopes with neutron number N from 12 to 28 as well as occupation probabilities N_{nlj} of single-particle states of stable isotopes 28, 30Si near the Fermi energy were obtained by the joint evaluation of the stripping and pick-up reaction data and excited state decay schemes of neighboring nuclei. The evaluated data indicate the following features of single-particle structure evolution: persistence of Z = 14 subshell closure with N increase, the new magicity of the number N = 16, and the conservation of the magic properties of the number N = 20 in Si isotopic chain. The features were described by the dispersive optical model. The calculation also predicts the weakening of N = 28 shell closure and demonstrates evolution of a bubble-like structure of the proton density distributions in neutron-rich Si isotopes.

Virtual Field and Internal Structure of Half-Dressed Extended Particles

International Nuclear Information System (INIS)

Compagno, G.; Persico, F.

1988-01-01

A new method is proposed to investigate the internal geometrical structure of an extended particle surrounded by an incomplete virtual dressing field. This method involves analysing the time-dependent virtual field at large distances from the particle, without any direct interaction with the latter. As an example, the pulselike, time-dependent virtual field of an extended QED source is investigated using a model which has a well-known counterpart in meson theory. In the framework of nonrelativistic QED it is shown that, contrary to the case of a point source, the pulse has finite width and height. For the case of a spherically symmetric source, it is explicitly shown that the width and shape of the pulse at distance r from the particle depend on the parameters determining the space structure of the source. It is concluded that the study of the field of half-dressed particles may provide a new method to investigate their internal structure

The effect of particle structure on apparent density of electrolytic copper powder

Directory of Open Access Journals (Sweden)

K. I. POPOV

2001-12-01

Full Text Available The quantitative microstructural analysis and the sieve analysis of copper powder as well as the scanning electron microscopy analysis of the copper powders particles were performed. It was found that the structure of the copper powder particles determines the apparent density of copper powder. The powder particles from the same fractions of different powders occupy approximately the same volume, but the structure of metallic copper is very different. This causes the difference in apparent densities of copper powder obtained under different conditions. The more dendritic is the structure of powder particles the smaller is the apparent density of copper powder.

Evolution of single-particle structure of silicon isotopes

Energy Technology Data Exchange (ETDEWEB)

Bespalova, O.V.; Klimochkina, A.A.; Spasskaya, T.I.; Tretyakova, T.Yu. [Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow (Russian Federation); Fedorov, N.A.; Markova, M.L. [Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation)

2018-01-15

New data on proton and neutron single-particle energies E{sub nlj} of Si isotopes with neutron number N from 12 to 28 as well as occupation probabilities N{sub nlj} of single-particle states of stable isotopes {sup 28,30}Si near the Fermi energy were obtained by the joint evaluation of the stripping and pick-up reaction data and excited state decay schemes of neighboring nuclei. The evaluated data indicate the following features of single-particle structure evolution: persistence of Z = 14 subshell closure with N increase, the new magicity of the number N = 16, and the conservation of the magic properties of the number N = 20 in Si isotopic chain. The features were described by the dispersive optical model. The calculation also predicts the weakening of N = 28 shell closure and demonstrates evolution of a bubble-like structure of the proton density distributions in neutron-rich Si isotopes. (orig.)

Effect of milling time on the structure, particle size, and morphology of montmorillonite

International Nuclear Information System (INIS)

Abareshi, M.

2017-01-01

In the current research, effect of milling on the structure, particle size and morphology of montmorillonite was investigated. For this purpose, the montmorillonite was analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Then the montmorillonite was milled using high energy planetary ball mill at different milling times (1-60 hours). After that, the structure, particle size and morphology of all samples were investigated by XRD, FTIR, SEM, and transmission electron microscopy. Results showed that the ball milling causes the particle size reduction of clay and separation of the clay layers. Moreover, ball milling increases the overall structural disorder and transforms the crystalline structure into an amorphous phase. Also, the morphology of clay particle changes from layered to aggregates of almost rounded particles after 60 hours of milling.

Current oscillations in avalanche particle detectors with PNIPN-structure

International Nuclear Information System (INIS)

Lukin, K.A.

1995-08-01

The model of an avalanche high energy particle detector consisting of two pn-junctions, connected through an intrinsic semiconductor with a reverse biased voltage applied. This detector is able to generate the oscillatory response on the single particle passage through the structure. The possibility of oscillations leading to chaotic behaviour is pointed out

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

Science.gov (United States)

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

2017-04-18

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

Second class current and structure of elementary particles

Energy Technology Data Exchange (ETDEWEB)

Senju, H [Nagoya Municipal Women' s Junior Coll. (Japan); Matsushima, T

1976-10-01

We examine what is required for the structure of elementary particles by the second class nucleonic currents which was recently discovered by Sugimoto et al. The experiment strongly suggests that the quark has a radius of a few tenth of fermi and the partons are constituents of quarks. We discuss briefly a possible internal structure of the quark.

Single-particle electron microscopy in the study of membrane protein structure.

Science.gov (United States)

De Zorzi, Rita; Mi, Wei; Liao, Maofu; Walz, Thomas

2016-02-01

Single-particle electron microscopy (EM) provides the great advantage that protein structure can be studied without the need to grow crystals. However, due to technical limitations, this approach played only a minor role in the study of membrane protein structure. This situation has recently changed dramatically with the introduction of direct electron detection device cameras, which allow images of unprecedented quality to be recorded, also making software algorithms, such as three-dimensional classification and structure refinement, much more powerful. The enhanced potential of single-particle EM was impressively demonstrated by delivering the first long-sought atomic model of a member of the biomedically important transient receptor potential channel family. Structures of several more membrane proteins followed in short order. This review recounts the history of single-particle EM in the study of membrane proteins, describes the technical advances that now allow this approach to generate atomic models of membrane proteins and provides a brief overview of some of the membrane protein structures that have been studied by single-particle EM to date. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Computer simulation of structures and distributions of particles in MAGIC fluid

International Nuclear Information System (INIS)

Zhu Yongsheng; Umehara, Noritsugu; Ido, Yasushi; Sato, Atsushi

2006-01-01

MAGIC (MAG-netic Intelligent Compound) is a solidified magnetic ferrofluid (MF) containing both magnetic particles (MPs) and abrasive particles (APs, nonmagnetic) of micron size. The distribution of APs in MAGIC can be controlled by applying a magnetic field during cooling process of MAGIC fluid. In this paper, the influences of magnetic field, size and concentration of particles on the final structures of MPs and the distributions of APs in MAGIC fluid are preliminarily investigated using Stokesian dynamic (SD) simulation method. Simulation results show that MPs prefer to form strip-like structures in MAGIC fluid, the reason for this phenomenon is mainly attributed to the strong dipolar interactions between them. It is also found that MPs prefer to form big agglomerations in weak magnetic field while chains and strip-like structures in strong magnetic field; no long chains or strip-like structures of MPs are observed in low-concentration MAGIC fluid; and for big-size MPs, pure wall-like structures are formed. Evaluation on the distribution of APs with uniformity coefficient shows that strong magnetic field, high concentration and small-size particles can induce more uniform distribution of APs in MAGIC fluid, the uniformity of APs in MAGIC is about 10% higher than that in normal grinding tools

Energy group structure determination using particle swarm optimization

International Nuclear Information System (INIS)

Yi, Ce; Sjoden, Glenn

2013-01-01

Highlights: ► Particle swarm optimization is applied to determine broad group structure. ► A graph representation of the broad group structure problem is introduced. ► The approach is tested on a fuel-pin model. - Abstract: Multi-group theory is widely applied for the energy domain discretization when solving the Linear Boltzmann Equation. To reduce the computational cost, fine group cross libraries are often down-sampled into broad group cross section libraries. Cross section data collapsing generally involves two steps: Firstly, the broad group structure has to be determined; secondly, a weighting scheme is used to evaluate the broad cross section library based on the fine group cross section data and the broad group structure. A common scheme is to average the fine group cross section weighted by the fine group flux. Cross section collapsing techniques have been intensively researched. However, most studies use a pre-determined group structure, open based on experience, to divide the neutron energy spectrum into thermal, epi-thermal, fast, etc. energy range. In this paper, a swarm intelligence algorithm, particle swarm optimization (PSO), is applied to optimize the broad group structure. A graph representation of the broad group structure determination problem is introduced. And the swarm intelligence algorithm is used to solve the graph model. The effectiveness of the approach is demonstrated using a fuel-pin model

Dengue Virus Non-structural Protein 1 Modulates Infectious Particle Production via Interaction with the Structural Proteins.

Directory of Open Access Journals (Sweden)

Pietro Scaturro

Full Text Available Non-structural protein 1 (NS1 is one of the most enigmatic proteins of the Dengue virus (DENV, playing distinct functions in immune evasion, pathogenesis and viral replication. The recently reported crystal structure of DENV NS1 revealed its peculiar three-dimensional fold; however, detailed information on NS1 function at different steps of the viral replication cycle is still missing. By using the recently reported crystal structure, as well as amino acid sequence conservation, as a guide for a comprehensive site-directed mutagenesis study, we discovered that in addition to being essential for RNA replication, DENV NS1 is also critically required for the production of infectious virus particles. Taking advantage of a trans-complementation approach based on fully functional epitope-tagged NS1 variants, we identified previously unreported interactions between NS1 and the structural proteins Envelope (E and precursor Membrane (prM. Interestingly, coimmunoprecipitation revealed an additional association with capsid, arguing that NS1 interacts via the structural glycoproteins with DENV particles. Results obtained with mutations residing either in the NS1 Wing domain or in the β-ladder domain suggest that NS1 might have two distinct functions in the assembly of DENV particles. By using a trans-complementation approach with a C-terminally KDEL-tagged ER-resident NS1, we demonstrate that the secretion of NS1 is dispensable for both RNA replication and infectious particle production. In conclusion, our results provide an extensive genetic map of NS1 determinants essential for viral RNA replication and identify a novel role of NS1 in virion production that is mediated via interaction with the structural proteins. These studies extend the list of NS1 functions and argue for a central role in coordinating replication and assembly/release of infectious DENV particles.

Inflation, large scale structure and particle physics

Indian Academy of Sciences (India)

Logo of the Indian Academy of Sciences ... Hybrid inflation; Higgs scalar field; structure formation; curvation. ... We then discuss a particle physics model of supersymmetric hybrid inflation at the intermediate scale in which ... May 2018. Home · Volumes & Issues · Special Issues · Forthcoming Articles · Search · Editorial Board ...

Helical structures in vertically aligned dust particle chains in a complex plasma

Science.gov (United States)

Hyde, Truell W.; Kong, Jie; Matthews, Lorin S.

2013-05-01

Self-assembly of structures from vertically aligned, charged dust particle bundles within a glass box placed on the lower, powered electrode of a Gaseous Electronics Conference rf reference cell were produced and examined experimentally. Self-organized formation of one-dimensional vertical chains, two-dimensional zigzag structures, and three-dimensional helical structures of triangular, quadrangular, pentagonal, hexagonal, and heptagonal symmetries are shown to occur. System evolution is shown to progress from a one-dimensional chain structure, through a zigzag transition to a two-dimensional, spindlelike structure, and then to various three-dimensional, helical structures exhibiting multiple symmetries. Stable configurations are found to be dependent upon the system confinement, γ2=ω0h/ω0v2 (where ω0h,v are the horizontal and vertical dust resonance frequencies), the total number of particles within a bundle, and the rf power. For clusters having fixed numbers of particles, the rf power at which structural phase transitions occur is repeatable and exhibits no observable hysteresis. The critical conditions for these structural phase transitions as well as the basic symmetry exhibited by the one-, two-, and three-dimensional structures that subsequently develop are in good agreement with the theoretically predicted configurations of minimum energy determined employing molecular dynamics simulations for charged dust particles confined in a prolate, spheroidal potential as presented theoretically by Kamimura and Ishihara [Kamimura and Ishihara, Phys. Rev. EPLEEE81063-651X10.1103/PhysRevE.85.016406 85, 016406 (2012)].

Hierarchical structures of ZnO spherical particles synthesized solvothermally

Science.gov (United States)

Saito, Noriko; Haneda, Hajime

2011-12-01

We review the solvothermal synthesis, using a mixture of ethylene glycol (EG) and water as the solvent, of zinc oxide (ZnO) particles having spherical and flower-like shapes and hierarchical nanostructures. The preparation conditions of the ZnO particles and the microscopic characterization of the morphology are summarized. We found the following three effects of the ratio of EG to water on the formation of hierarchical structures: (i) EG restricts the growth of ZnO microcrystals, (ii) EG promotes the self-assembly of small crystallites into spheroidal particles and (iii) the high water content of EG results in hollow spheres.

Selected aspects in the structure of beta-delayed particle spectra

International Nuclear Information System (INIS)

Honkanen, J.; Aeystoe, J.; Eskola, K.

1986-01-01

Some weak beta-delayed particle emitters in the T z =-3/2, -1, -1/2, +1/2 and +5/2 series are reviewed. Selected features of the delayed particle emission are discussed in terms of experimental delayed particle data and (p,γ), (p,p') and (p,n) reaction data. Experimental beta transition strengths are compared with the existing complete shell-model calculations for the sd-shell nuclei. The effect of the Gamow-Teller giant resonance on the structure of the delayed particle spectra is considered. The correlation between the widths of two decay channels, protons and alpha particles, and the preceeding beta decay is studied in the case of the 40 Sc decay. (orig.)

Preparation of porous carbon particle with shell/core structure

Directory of Open Access Journals (Sweden)

2007-05-01

Full Text Available Porous carbon particles with a shell/core structure have been prepared successfully by controlled precipitation of the polymer from droplets of oil-in-water emulsion, followed by curing and carbonization. The droplets of the oil phase are composed of phenolic resin (PFR, a good solvent (ethyl acetate and porogen (Poly(methyl methacrylate, PMMA. The microstructure was characterized in detail by scanning electron microscopy (SEM, transmission electron microscopy (TEM, nitrogen adsorption, and thermo gravimetric analysis (TGA. The obtained carbon particles have a capsular structure with a microporous carbon shell and a mesoporous carbon core. The BET surface area and porous volume are calculated to be 499 m2g-1 and 0.56 cm3g-1, respectively. The effects of the amount of porogen (PMMA, co-solvent (acetone and surfactant on the resultant structure were studied in detail.

Particle reacceleration and apparent radio source structure

International Nuclear Information System (INIS)

Eilek, J.A.

1982-01-01

The radio galaxy model which uses magnetohydrodynamic turbulence generated by surface instabilities to reaccelerate the radiating electrons has striking consequences for apparent source structure. Strong wave damping in the plasma results in a narrow turbulent edge. Particles accelerated in this edge must diffuse across field lines into the radio source; this predicts strong limb brightening in some cases. The structure of this edge and diffusion into the source are described. The relevance of this model to jets, radio tails, and standard double sources is discussed

Energy spectrum structure and ''trap'' effects in a three-particle system

International Nuclear Information System (INIS)

Simenog, I.V.; Sitnichenko, A.I.

1982-01-01

Investigation is made of the threshold energy spectrum structure in a system of three spinless particles depending on the form of two-particle interaction. The correlation dependence of the spectrum and low-energy scattering parameters are shown. A new phenomenon of ''traps'' for the spectrum in a three-particle system with interaction involving components of considerably different ranges is established

Particle-scale structure in frozen colloidal suspensions from small-angle x-ray scattering

KAUST Repository

Spannuth, Melissa

2011-02-01

During directional solidification of the solvent in a colloidal suspension, the colloidal particles segregate from the growing solid, forming high-particle-density regions with structure on a hierarchy of length scales ranging from that of the particle-scale packing to the large-scale spacing between these regions. Previous work has concentrated mostly on the medium- to large-length scale structure, as it is the most accessible and thought to be more technologically relevant. However, the packing of the colloids at the particle scale is an important component not only in theoretical descriptions of the segregation process, but also to the utility of freeze-cast materials for new applications. Here we present the results of experiments in which we investigated this structure across a wide range of length scales using a combination of small-angle x-ray scattering and direct optical imaging. As expected, during freezing the particles were concentrated into regions between ice dendrites forming a microscopic pattern of high- and low-particle-density regions. X-ray scattering indicates that the particles in the high-density regions were so closely packed as to be touching. However, the arrangement of the particles does not conform to that predicted by standard interparticle pair potentials, suggesting that the particle packing induced by freezing differs from that formed during equilibrium densification processes. © 2011 American Physical Society.

Particle-scale structure in frozen colloidal suspensions from small-angle x-ray scattering

KAUST Repository

Spannuth, Melissa; Mochrie, S. G. J.; Peppin, S. S. L.; Wettlaufer, J. S.

2011-01-01

During directional solidification of the solvent in a colloidal suspension, the colloidal particles segregate from the growing solid, forming high-particle-density regions with structure on a hierarchy of length scales ranging from that of the particle-scale packing to the large-scale spacing between these regions. Previous work has concentrated mostly on the medium- to large-length scale structure, as it is the most accessible and thought to be more technologically relevant. However, the packing of the colloids at the particle scale is an important component not only in theoretical descriptions of the segregation process, but also to the utility of freeze-cast materials for new applications. Here we present the results of experiments in which we investigated this structure across a wide range of length scales using a combination of small-angle x-ray scattering and direct optical imaging. As expected, during freezing the particles were concentrated into regions between ice dendrites forming a microscopic pattern of high- and low-particle-density regions. X-ray scattering indicates that the particles in the high-density regions were so closely packed as to be touching. However, the arrangement of the particles does not conform to that predicted by standard interparticle pair potentials, suggesting that the particle packing induced by freezing differs from that formed during equilibrium densification processes. © 2011 American Physical Society.

Mode structure symmetry breaking of energetic particle driven beta-induced Alfvén eigenmode

Science.gov (United States)

Lu, Z. X.; Wang, X.; Lauber, Ph.; Zonca, F.

2018-01-01

The mode structure symmetry breaking of energetic particle driven Beta-induced Alfvén Eigenmode (BAE) is studied based on global theory and simulation. The weak coupling formula gives a reasonable estimate of the local eigenvalue compared with global hybrid simulation using XHMGC. The non-perturbative effect of energetic particles on global mode structure symmetry breaking in radial and parallel (along B) directions is demonstrated. With the contribution from energetic particles, two dimensional (radial and poloidal) BAE mode structures with symmetric/asymmetric tails are produced using an analytical model. It is demonstrated that the symmetry breaking in radial and parallel directions is intimately connected. The effects of mode structure symmetry breaking on nonlinear physics, energetic particle transport, and the possible insight for experimental studies are discussed.

Determining Complex Structures using Docking Method with Single Particle Scattering Data

Directory of Open Access Journals (Sweden)

Haiguang Liu

2017-04-01

Full Text Available Protein complexes are critical for many molecular functions. Due to intrinsic flexibility and dynamics of complexes, their structures are more difficult to determine using conventional experimental methods, in contrast to individual subunits. One of the major challenges is the crystallization of protein complexes. Using X-ray free electron lasers (XFELs, it is possible to collect scattering signals from non-crystalline protein complexes, but data interpretation is more difficult because of unknown orientations. Here, we propose a hybrid approach to determine protein complex structures by combining XFEL single particle scattering data with computational docking methods. Using simulations data, we demonstrate that a small set of single particle scattering data collected at random orientations can be used to distinguish the native complex structure from the decoys generated using docking algorithms. The results also indicate that a small set of single particle scattering data is superior to spherically averaged intensity profile in distinguishing complex structures. Given the fact that XFEL experimental data are difficult to acquire and at low abundance, this hybrid approach should find wide applications in data interpretations.

Influence of PEG Stoichiometry on Structure-Tuned Formation of Self-Assembled Submicron Nickel Particles

Directory of Open Access Journals (Sweden)

Bingxue Pu

2018-01-01

Full Text Available Self-assembled submicron nickel particles were successfully synthesized via the one-step surfactant-assisted solvothermal method. The impact of surfactant and reducing agent stoichiometry is investigated in this manuscript. Different morphologies and structures of Ni particles, including flower-like nanoflakes, hydrangea-like structures, chain structures, sphere-like structures, and hollow structures were prepared through different processing conditions with two parameters such as temperature and time. Based on scanning electron microscopy (SEM, X-ray diffraction (XRD, thermal gravimetric analysis (TGA and vibrating sample magnetometry (VSM, the submicron nickel particles show good saturation magnetization and excellent thermal stabilities with a possible growth mechanism for the variety of the structure-tuned formation. Importantly, the microwave absorption properties of the submicron nickel particles were studied. The lowest reflection loss of Ni-P9/T200/H15 with a thin layer thickness of 1.7 mm can reach −42.6 dB at 17.3 GHz.

Thermomechanical interactions of particle bed-structural wall in a layered configuration. Pt. 1. Effect of particle bed thermal expansions

International Nuclear Information System (INIS)

Tehranian, F.

1995-01-01

Materials in the form of particle beds have been considered for shielding and tritium breeding as well as neutron multiplication in many of the conceptual reactor design studies. As the level of effort of the fusion blanket community in the area of out-of-pile and in-pile (ITER) testing of integrated test modules increases, so does the need for modelling capability for predicting the thermomechanical responses of the test modules under reactor environment.In this study, the thermomechanical responses of a particle bed-structural wall system in a layered configuration, subjected to bed temperature rise and/or external coolant pressure, were considered. Equations were derived which represent the dependence of the particle-to-particle and particle-to-wall contact forces and areas on the structural wall deformations and in turn on the thermomechanical loads. Using the derived equations, parametric analyses were performed to study the variations in the thermomechanical response quantities of a beryllium particle bed-stainless steel structural wall when subjected to thermomechanical loads. The results are presented in two parts. In Part I, presented in this paper, the derivation of the analytical equations and the effects of bed temperature rise are discussed. In Part II of this study, also presented in this symposium, the effects of external coolant pressure as well as the combined effects of bed temperature rise and coolant pressure on the thermomechanical responses are given.It is shown that, depending on the stiffness of the structural walls, uniform bed temperature rises in the range 100-400 C result in non-uniform effective thermal properties through the prticle bed and could increase the bed effective thermal conductivity by a factor of 2-5 and the bed-wall interface thermal conductance by even a larger factor. (orig.)

Channel flow structure measurements using particle image velocimetry

International Nuclear Information System (INIS)

Norazizi Mohamed; Noraeini Mokhtar; Aziz Ibrahim; Ramli Abu Hassan

1996-01-01

Two different flow structures in a laboratory channel were examined using a flow visualization technique, known as Particle Image Velocimetry (PIV). The first channel flow structure was that of a steady flow over a horizontal channel bottom. Photographs of particle displacements were taken in the boundary layer in a plane parallel to the flow. These photographs were analyzed to give simultaneous measurements of two components of the velocity at hundreds of points in the plane. Averaging these photographs gave the velocity profile a few millimeters from the bottom of the channel to the water surface. The results gave good agreement with the known boundary layer theory. This technique is extended to the study of the structure under a progressive wave in the channel. A wavelength of the propagating wave is divided into sections by photographing it continously for a number of frames. Each frame is analyzed and a velocity field under this wave at various phase points were produced with their respective directions. The results show that velocity vectors in a plane under the wave could be achieved instantaneously and in good agreement with the small amplitude wave theory

SoAx: A generic C++ Structure of Arrays for handling particles in HPC codes

Science.gov (United States)

Homann, Holger; Laenen, Francois

2018-03-01

The numerical study of physical problems often require integrating the dynamics of a large number of particles evolving according to a given set of equations. Particles are characterized by the information they are carrying such as an identity, a position other. There are generally speaking two different possibilities for handling particles in high performance computing (HPC) codes. The concept of an Array of Structures (AoS) is in the spirit of the object-oriented programming (OOP) paradigm in that the particle information is implemented as a structure. Here, an object (realization of the structure) represents one particle and a set of many particles is stored in an array. In contrast, using the concept of a Structure of Arrays (SoA), a single structure holds several arrays each representing one property (such as the identity) of the whole set of particles. The AoS approach is often implemented in HPC codes due to its handiness and flexibility. For a class of problems, however, it is known that the performance of SoA is much better than that of AoS. We confirm this observation for our particle problem. Using a benchmark we show that on modern Intel Xeon processors the SoA implementation is typically several times faster than the AoS one. On Intel's MIC co-processors the performance gap even attains a factor of ten. The same is true for GPU computing, using both computational and multi-purpose GPUs. Combining performance and handiness, we present the library SoAx that has optimal performance (on CPUs, MICs, and GPUs) while providing the same handiness as AoS. For this, SoAx uses modern C++ design techniques such template meta programming that allows to automatically generate code for user defined heterogeneous data structures.

The structure of particle gels as studied with confocal microscopy and computer simulations

NARCIS (Netherlands)

Bos, M.T.A.

1997-01-01

This thesis contains the results of a PhD-study on the structure of particle gels. Part of it is directed at a quantification of this structure from measured data, part of it at modelling the aggregation processes that lead to particle gels. Chapter 1 of this thesis is a general

Effect of long-range repulsive Coulomb interactions on packing structure of adhesive particles.

Science.gov (United States)

Chen, Sheng; Li, Shuiqing; Liu, Wenwei; Makse, Hernán A

2016-02-14

The packing of charged micron-sized particles is investigated using discrete element simulations based on adhesive contact dynamic model. The formation process and the final obtained structures of ballistic packings are studied to show the effect of interparticle Coulomb force. It is found that increasing the charge on particles causes a remarkable decrease of the packing volume fraction ϕ and the average coordination number 〈Z〉, indicating a looser and chainlike structure. Force-scaling analysis shows that the long-range Coulomb interaction changes packing structures through its influence on particle inertia before they are bonded into the force networks. Once contact networks are formed, the expansion effect caused by repulsive Coulomb forces are dominated by short-range adhesion. Based on abundant results from simulations, a dimensionless adhesion parameter Ad*, which combines the effects of the particle inertia, the short-range adhesion and the long-range Coulomb interaction, is proposed and successfully scales the packing results for micron-sized particles within the latest derived adhesive loose packing (ALP) regime. The structural properties of our packings follow well the recent theoretical prediction which is described by an ensemble approach based on a coarse-grained volume function, indicating some kind of universality in the low packing density regime of the phase diagram regardless of adhesion or particle charge. Based on the comprehensive consideration of the complicated inter-particle interactions, our findings provide insight into the roles of short-range adhesion and repulsive Coulomb force during packing formation and should be useful for further design of packings.

Spacetime structure of massive Majorana particles and massive gravitino

CERN Document Server

Ahluwalia, D V

2003-01-01

The profound difference between Dirac and Majorana particles is traced back to the possibility of having physically different constructs in the (1/2, 0) 0 (0,1/2) representation space. Contrary to Dirac particles, Majorana-particle propagators are shown to differ from the simple linear gamma mu p submu, structure. Furthermore, neither Majorana particles, nor their antiparticles can be associated with a well defined arrow of time. The inevitable consequence of this peculiarity is the particle-antiparticle metamorphosis giving rise to neutrinoless double beta decay, on the one side, and enabling spin-1/2 fields to act as gauge fields, gauginos, on the other side. The second part of the lecture notes is devoted to massive gravitino. We argue that a spin measurement in the rest frame for an unpolarized ensemble of massive gravitino, associated with the spinor-vector [(1/2, 0) 0 (0,1/2)] 0 (1/2,1/2) representation space, would yield the results 3/2 with probability one half, and 1/2 with probability one half. The ...

Structural optimization of Au–Pd bimetallic nanoparticles with improved particle swarm optimization method

International Nuclear Information System (INIS)

Shao Gui-Fang; Zhu Meng; Shangguan Ya-Li; Li Wen-Ran; Zhang Can; Wang Wei-Wei; Li Ling

2017-01-01

Due to the dependence of the chemical and physical properties of the bimetallic nanoparticles (NPs) on their structures, a fundamental understanding of their structural characteristics is crucial for their syntheses and wide applications. In this article, a systematical atomic-level investigation of Au–Pd bimetallic NPs is conducted by using the improved particle swarm optimization (IPSO) with quantum correction Sutton–Chen potentials (Q-SC) at different Au/Pd ratios and different sizes. In the IPSO, the simulated annealing is introduced into the classical particle swarm optimization (PSO) to improve the effectiveness and reliability. In addition, the influences of initial structure, particle size and composition on structural stability and structural features are also studied. The simulation results reveal that the initial structures have little effects on the stable structures, but influence the converging rate greatly, and the convergence rate of the mixing initial structure is clearly faster than those of the core-shell and phase structures. We find that the Au–Pd NPs prefer the structures with Au-rich in the outer layers while Pd-rich in the inner ones. Especially, when the Au/Pd ratio is 6:4, the structure of the nanoparticle (NP) presents a standardized Pd core Au shell structure. (paper)

Structure modification of particle track membranes

International Nuclear Information System (INIS)

Lueck, H.B.; Gemende, B.; Heinrich, B.

1991-01-01

Three different structure modifications were studied in order to improve the flux and dirt loading capacity of particle track membranes without affecting their retention characteristic. Divergent irradiation is a very effective tool for decreasing the number of multiple pores and increasing the porosity up to 20 per cent. The technique leads to a remarkable but not efficient enhancement of the surface porosity. Improved surface porosity produced by a double irradiation technique turns out to be very effective with respect to the filtration performance. (author)

Internal Structure of Charged Particles in a GRT Gravitational Model

Science.gov (United States)

Khlestkov, Yu. A.; Sukhanova, L. A.

2018-05-01

With the help of an exact solution of the Einstein and Maxwell equations, the internal structure of a multiply connected space of wormhole type with two unclosed static throats leading out of it into two parallel vacuum spaces or into one space is investigated in GRT for a free electric field and dust-like matter. The given geometry is considered as a particle-antiparticle pair with fundamental constants arising in the form of first integrals in the solution of the Cauchy problem - electric charges ±e of opposite sign in the throats and rest mass m0 - the total gravitational mass of the inner world of the particle in the throat. With the help of the energy conservation law, the unremovable rotation of the internal structure is included and the projection of the angular momentum of which onto the rotation axis is identified with the z-projection of the spin of the charged particle. The radius of 2-Gaussian curvature of the throat R* is identified with the charge radius of the particle, and the z-projection of the magnetic moment and the g-factor are found. The feasibility of the given gravitational model is confirmed by the found condition of independence of the spin quantum number of the electron and the proton s = 1/2 of the charge radius R* and the relativistic rest mass m* of the rotating throat, which is reliably confirmed experimentally, and also by the coincidence with high accuracy of the proton radius calculated in the model R*p = 0.8412·10-13 cm with the value of the proton charge radius obtained experimentally by measuring the Lamb shift on muonic hydrogen. The electron in the given model also turns out to be a structured particle with radius R*e = 3.8617·10-11 cm.

Magnetic assembly of nonmagnetic particles into photonic crystal structures.

Science.gov (United States)

He, Le; Hu, Yongxing; Kim, Hyoki; Ge, Jianping; Kwon, Sunghoon; Yin, Yadong

2010-11-10

We report the rapid formation of photonic crystal structures by assembly of uniform nonmagnetic colloidal particles in ferrofluids using external magnetic fields. Magnetic manipulation of nonmagnetic particles with size down to a few hundred nanometers, suitable building blocks for producing photonic crystals with band gaps located in the visible regime, has been difficult due to their weak magnetic dipole moment. Increasing the dipole moment of magnetic holes has been limited by the instability of ferrofluids toward aggregation at high concentration or under strong magnetic field. By taking advantage of the superior stability of highly surface-charged magnetite nanocrystal-based ferrofluids, in this paper we have been able to successfully assemble 185 nm nonmagnetic polymer beads into photonic crystal structures, from 1D chains to 3D assemblies as determined by the interplay of magnetic dipole force and packing force. In a strong magnetic field with large field gradient, 3D photonic crystals with high reflectance (83%) in the visible range can be rapidly produced within several minutes, making this general strategy promising for fast creation of large-area photonic crystals using nonmagnetic particles as building blocks.

Dependence of the Internal Structure on Water/Particle Volume Ratio in an Amphiphilic Janus Particle-Water-Oil Ternary System: From Micelle-like Clusters to Emulsions of Spherical Droplets.

Science.gov (United States)

Noguchi, Tomohiro G; Iwashita, Yasutaka; Kimura, Yasuyuki

2017-01-31

Amphiphilic Janus particles (AJP), composed of hydrophilic and hydrophobic hemispheres, are one of the simplest anisotropic colloids, and they exhibit higher surface activities than particles with homogeneous surface properties. Consequently, a ternary system of AJP, water, and oil can form extremely stable Pickering emulsions, with internal structures that depend on the Janus structure of the particles and the system composition. However, the detail of these structures has not been fully explored, especially for the composition range where the amount of the minority liquid phase and AJP are comparable, where one would expect the Janus characteristics to be directly reflected. In this study, we varied the volume ratio of the particles and the minority liquid phase, water, by 2 orders of magnitude around the comparable composition range, and observed the resultant structures at the resolution of the individual particle dimensions by optical microscopy. When the volume ratio of water is smaller than that of the Janus particles, capillary interactions between the hydrophilic hemispheres of the particles induce micelle-like clusters in which the hydrophilic sides of the particles face inward. With increasing water content, these clusters grow into a rodlike morphology. When the water volume exceeds that of the particles, the structure transforms into an emulsion state composed of spherical droplets, colloidosomes, because of the surface activity of particles at the liquid-liquid interface. Thus, we found that a change in volume fraction alters the mechanism of structure formation in the ternary system, and large resulting morphological changes in the self-assembled structures reflect the anisotropy of the particles. The self-assembly shows essential commonalities with that in microemulsions of surfactant molecules, however the AJP system is stabilized only kinetically. Analysis of the dependence of the emulsion droplet size on composition shows that almost all the

An absorbing phase transition from a structured active particle phase

Energy Technology Data Exchange (ETDEWEB)

Lopez, Cristobal [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain); Ramos, Francisco [Departamento de Electromagnetismo y Fisica de la Materia and Instituto de Fisica Teorica y Computacional Carlos I, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain); Hernandez-GarcIa, Emilio [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain)

2007-02-14

In this work we study the absorbing state phase transition of a recently introduced model for interacting particles with neighbourhood-dependent reproduction rates. The novelty of the transition is that as soon as the active phase is reached by increasing a control parameter a periodically arranged structure of particle clusters appears. A numerical study in one and two dimensions shows that the system falls into the directed percolation universality class.

Spacetime structure of massive Majorana particles and massive gravitino

Energy Technology Data Exchange (ETDEWEB)

Ahluwalia, D.V.; Kirchbach, M. [Theoretical Physics Group, Facultad de Fisica, Universidad Autonoma de Zacatecas, A.P. 600, 98062 Zacatecas (Mexico)

2003-07-01

The profound difference between Dirac and Majorana particles is traced back to the possibility of having physically different constructs in the (1/2, 0) 0 (0,1/2) representation space. Contrary to Dirac particles, Majorana-particle propagators are shown to differ from the simple linear {gamma} {mu} p{sub {mu}}, structure. Furthermore, neither Majorana particles, nor their antiparticles can be associated with a well defined arrow of time. The inevitable consequence of this peculiarity is the particle-antiparticle metamorphosis giving rise to neutrinoless double beta decay, on the one side, and enabling spin-1/2 fields to act as gauge fields, gauginos, on the other side. The second part of the lecture notes is devoted to massive gravitino. We argue that a spin measurement in the rest frame for an unpolarized ensemble of massive gravitino, associated with the spinor-vector [(1/2, 0) 0 (0,1/2)] 0 (1/2,1/2) representation space, would yield the results 3/2 with probability one half, and 1/2 with probability one half. The latter is distributed uniformly, i.e. as 1/4, among the two spin-1/2+ and spin-1/2- states of opposite parities. From that we draw the conclusion that the massive gravitino should be interpreted as a particle of multiple spin. (Author)

Effect of Turbulence Internal Structure on Diffusion of Heavy Inertial Particles

Directory of Open Access Journals (Sweden)

I. V. Derevich

2015-01-01

Full Text Available Based on the spectral expansion of Euler correlation of the carrier medium the a closed system of functional equations for the Lagrange spectra of heavy inertial particles and the velocity fluctuations of the carrier medium on the particle trajectory have been obtained. To split the fourth moments the approximation of quasinormality and velocity fluctuations of particles is performed by a random Gaussian process. The approximate self-consistent method is proposed for solving the resulting system of functional equations. The influence of the particle inertia, the velocity of the averaged slip and microstructure of velocity fluctuations of the medium on the parameters of the chaotic motion of an impurity has been studied. It is shown that the difference in integral time scales of Eulerian and Lagrangian correlations is associated with the spatial microstructure of velocity fluctuations of the medium. It is established that in the absence of mass forces, the coefficient of the stationary diffusion of inertial particles is always greater than the diffusion coefficient of inertialess impurity. The dependence of the turbulent diffusion coefficient of particles impurity on the structural parameter of turbulence has been illustrated. The spectrum of Euler correlations of medium velocity fluctuations is modeled by Karman distributions. The influence of the particle inertia, the velocity of the averaged slip and microstructure of velocity fluctuations of the medium on the parameters of the chaotic motion of an impurity has been studied. It is shown that the difference in integral time scales of Eulerian and Lagrangian correlations is associated with the spatial microstructure of velocity fluctuations of the medium. It is established that in the absence of mass forces, the coefficient of the stationary diffusion of inertial particles is always larger than the diffusion coefficient of inertialess impurity. The dependence of the turbulent diffusion

High frequency single mode traveling wave structure for particle acceleration

Energy Technology Data Exchange (ETDEWEB)

Ivanyan, M.I.; Danielyan, V.A.; Grigoryan, B.A.; Grigoryan, A.H. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Tsakanian, A.V. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Technische Universität Darmstadt, Institut TEMF, 64289 Darmstadt (Germany); Tsakanov, V.M., E-mail: tsakanov@asls.candle.am [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Vardanyan, A.S.; Zakaryan, S.V. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia)

2016-09-01

The development of the new high frequency slow traveling wave structures is one of the promising directions in accomplishment of charged particles high acceleration gradient. The disc and dielectric loaded structures are the most known structures with slowly propagating modes. In this paper a large aperture high frequency metallic two-layer accelerating structure is studied. The electrodynamical properties of the slowly propagating TM{sub 01} mode in a metallic tube with internally coated low conductive thin layer are examined.

Interaction of particles with complex electrostatic structures and 3D clusters

International Nuclear Information System (INIS)

Antonova, Tetyana

2007-01-01

Particles of micrometer size externally introduced in plasmas usually find their positions of levitation in the plasma sheath, where the gravity force is compensated by the strong electric field. Here due to electrostatic interaction they form different structures, which are interesting objects for the investigation of strongly coupled systems and critical phenomena. Because of the low damping (e.g. in comparison to colloidal suspension) it is possible to measure the dynamics up to the relevant highest frequency (e.g. Einstein frequency) at the most elementary level of single particle motion. The task of this work was to analyze the three dimensional structure, dynamical processes and the limit of the cooperative behavior in small plasma crystals. In addition to the study of the systems formed, the immersed particles themselves may be used for diagnostics of the plasma environment: estimation of parameters or monitoring of the processes inside plasma. The laboratory experiments are performed in two radio-frequency (RF) plasma reactors with parallel plate electrodes, where the lower electrode is a so-called ''adaptive electrode''. This electrode is segmented into 57 small ''pixels'' independently driven in DC (direct current) and/or RF voltage. When RF voltage is applied to one of these pixels, a bright localized glow, ''secondary plasma ball'', appears above. Three dimensional dust crystals with less than 100 particles are formed inside this ''plasma ball'' - the ideal conditions for the investigation of the transition from cluster systems to collective systems. The investigation of the particle interactions in crystals is performed with an optical diagnostic, which allows determination of all three particle coordinates simultaneously with time resolution of 0.04 sec. The experimental results are: 1. The binary interaction among particles in addition to the repelling Coulomb force exhibits also an attractive part, which is experimentally determined for the first

Interaction of particles with complex electrostatic structures and 3D clusters

Energy Technology Data Exchange (ETDEWEB)

Antonova, Tetyana

2007-10-16

Particles of micrometer size externally introduced in plasmas usually find their positions of levitation in the plasma sheath, where the gravity force is compensated by the strong electric field. Here due to electrostatic interaction they form different structures, which are interesting objects for the investigation of strongly coupled systems and critical phenomena. Because of the low damping (e.g. in comparison to colloidal suspension) it is possible to measure the dynamics up to the relevant highest frequency (e.g. Einstein frequency) at the most elementary level of single particle motion. The task of this work was to analyze the three dimensional structure, dynamical processes and the limit of the cooperative behavior in small plasma crystals. In addition to the study of the systems formed, the immersed particles themselves may be used for diagnostics of the plasma environment: estimation of parameters or monitoring of the processes inside plasma. The laboratory experiments are performed in two radio-frequency (RF) plasma reactors with parallel plate electrodes, where the lower electrode is a so-called 'adaptive electrode'. This electrode is segmented into 57 small 'pixels' independently driven in DC (direct current) and/or RF voltage. When RF voltage is applied to one of these pixels, a bright localized glow, 'secondary plasma ball', appears above. Three dimensional dust crystals with less than 100 particles are formed inside this 'plasma ball' - the ideal conditions for the investigation of the transition from cluster systems to collective systems. The investigation of the particle interactions in crystals is performed with an optical diagnostic, which allows determination of all three particle coordinates simultaneously with time resolution of 0.04 sec. The experimental results are: 1. The binary interaction among particles in addition to the repelling Coulomb force exhibits also an attractive part, which is

Self-assembled structures of Gaussian nematic particles.

Science.gov (United States)

Nikoubashman, Arash; Likos, Christos N

2010-03-17

We investigate the stable crystalline configurations of a nematic liquid crystal made of soft parallel ellipsoidal particles interacting via a repulsive, anisotropic Gaussian potential. For this purpose, we use genetic algorithms (GA) in order to predict all relevant and possible solid phase candidates into which this fluid can freeze. Subsequently we present and discuss the emerging novel structures and the resulting zero-temperature phase diagram of this system. The latter features a variety of crystalline arrangements, in which the elongated Gaussian particles in general do not align with any one of the high-symmetry crystallographic directions, a compromise arising from the interplay and competition between anisotropic repulsions and crystal ordering. Only at very strong degrees of elongation does a tendency of the Gaussian nematics to align with the longest axis of the elementary unit cell emerge.

Two-particle approach to the electronic structure of solids

International Nuclear Information System (INIS)

Gonis, A.

2007-01-01

Based on an extension of Hubbard's treatment of the electronic structure of correlated electrons in matter we propose a methodology that incorporates the scattering off the Coulomb interaction through the determination of a two-particle propagator. The Green function equations of motion are then used to obtain single-particle Green functions and related properties such as densities of states. The solutions of the equations of motion in two- and single-particle spaces are accomplished through applications of the coherent potential approximation. The formalism is illustrated by means of calculations for a single-band model system representing a linear arrangement of sites with nearest neighbor hopping and an one-site repulsion when two electrons of opposite spin occupy the same site in the lattice in the manner described by the so-called Hubbard Hamiltonian

Charged particle reflection by a planar artificially structured boundary with electrostatic plugging

Directory of Open Access Journals (Sweden)

R. M. Hedlof

2017-11-01

Full Text Available A classical trajectory Monte Carlo simulation is used to investigate an artificially structured boundary for confinement and control of charged particles. The artificially structured boundary considered here incorporates a planar sequence of conducting wires, where adjacent wires carry current in opposite directions. Such a configuration creates a sequence of magnetic cusps and was studied previously [C. A. Ordonez, J. Appl. Phys. 106, 024905 (2009]. The effect of introducing a sequence of electrodes for electrostatic plugging of the cusps is investigated. The results of the simulations are used to identify regions of parameter space in which particle losses through the cusps may be negligible in the single particle limit. A trap based on a cylindrical generalization of the artificially structured boundary presented here may lead to a method for confining non-neutral and partially neutralized plasmas along the edge, such that the bulk of a confined plasma is effectively free of externally applied electromagnetic fields.

Unstable structure of ribosomal particles synthesized in. gamma. -irradiated Escherichia coli

Energy Technology Data Exchange (ETDEWEB)

Fujita, H; Morita, K [National Inst. of Radiological Sciences, Chiba (Japan)

1975-06-01

Stability of Escherichia coli ribosomes newly synthesized after ..gamma..-irradiation was compared with that of normal ribosomes. The ribosomal particles around 70-S synthesized in irradiated cells were more sensitive to digestion by pancreatic ribonuclease A. A larger number of the salt-unstable '50-S' precursor particles existed in the extract from irradiated cells than in the extract from unirradiated cells. These facts suggest that ribosomal particles, synthesized during an earlier stage in irradiated cells, maintain an incomplete structure even though they are not distinguishable from normal ribosomes by means of sucrose density-gradient centrifugation.

Structure evolution of gelatin particles induced by pH and ionic strength.

Science.gov (United States)

Xu, Jing; Li, Tianduo; Tao, Furong; Cui, Yuezhi; Xia, Yongmei

2013-03-01

Microstructure of gelatin particles played a key role in determining the physicochemical properties of gelatin. Ionic strength and pH as systematic manners were considered to affect gelatin particles structure on the micrometer scale. Scanning electron microscopy was used for depicting the morphologies of gelatin particles. Increasing pH to 10.0 or decreasing pH to 4.0, spherical, spindle, and irregular aggregates of gelatin particles at 2, 6, 10, and 14% solution (w/w) were all transformed to spindle aggregates. When NaCl was added to the system, the molecular chains of gelatin possibly rearranged themselves in a stretched state, and the ribbon aggregates was observed. The structural transitions of gelatin aggregates were strongly depended on the electrostatic repulsion. In the gelatin-sodium dodecyl sulfate (SDS) case, the micrometer scale of aggregates was larger and the different degrees of cross-links were induced through hydrophobic interaction and electrostatic repulsion. Copyright © 2012 Wiley Periodicals, Inc.

Simulation study on the structural properties of colloidal particles with offset dipoles.

Science.gov (United States)

Rutkowski, David M; Velev, Orlin D; Klapp, Sabine H L; Hall, Carol K

2017-05-03

A major research theme in materials science is determining how the self-assembly of new generations of colloidal particles of complex shape and surface charge is guided by their interparticle interactions. In this paper, we describe results from quasi-2D Monte Carlo simulations of systems of colloidal particles with offset transversely-oriented extended dipole-like charge distributions interacting via an intermediate-ranged Yukawa potential. The systems are cooled slowly through an annealing procedure during which the temperature is lowered in discrete steps, allowing the system to equilibrate. We perform ground state calculations for two, three and four particles at several shifts of the dipole vector from the particle center. We create state diagrams in the plane spanned by the temperature and the area fraction outlining the boundaries between fluid, string-fluid and percolated states at various values of the shift. Remarkably we find that the effective cooling rate in our simulations has an impact on the structures formed, with chains being more prevalent if the system is cooled quickly and cyclic structures more prevalent if the system is cooled slowly. As the dipole is further shifted from the center, there is an increased tendency to assemble into small cyclic structures at intermediate temperatures. These systems further self-assemble into open lattice-like arrangements at very low temperatures. The novel structures identified might be useful for photonic applications, new types of porous media for filtration and catalysis, and gel matrices with unusual properties.

Transition from the mechanics of material points to the mechanics of structured particles

Science.gov (United States)

Somsikov, V. M.

2016-01-01

In this paper, necessity of creation of mechanics of structured particles is discussed. The way to create this mechanics within the laws of classical mechanics with the use of energy equation is shown. The occurrence of breaking of time symmetry within the mechanics of structured particles is shown, as well as the introduction of concept of entropy in the framework of classical mechanics. The way to create the mechanics of non-equilibrium systems in the thermodynamic approach is shown. It is also shown that the use of hypothesis of holonomic constraints while deriving the canonical Lagrange equation made it impossible to describe irreversible dynamics. The difference between the mechanics of structured particles and the mechanics of material points is discussed. It is also shown that the matter is infinitely divisible according to the laws of classical mechanics.

Synthesis, structural and magnetic characterization of soft magnetic nanocrystalline ternary FeNiCo particles

Energy Technology Data Exchange (ETDEWEB)

Toparli, Cigdem [Department of Metallurgical & Materials Eng., Istanbul Technical University, 34469 Istanbul (Turkey); Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf (Germany); Ebin, Burçak [Department of Metallurgical & Materials Eng., Istanbul Technical University, 34469 Istanbul (Turkey); Nuclear Chemistry and Industrial Material Recycling, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, S-412 96 Gothenburg (Sweden); Gürmen, Sebahattin, E-mail: gurmen@itu.edu.tr [Department of Metallurgical & Materials Eng., Istanbul Technical University, 34469 Istanbul (Turkey)

2017-02-01

The present study focuses on the synthesis, microstructural and magnetic properties of ternary FeNiCo nanoparticles. Nanocrystalline ternary FeNiCo particles were synthesized via hydrogen reduction assisted ultrasonic spray pyrolysis method in single step. The effect of precursor concentration on the morphology and the size of particles was investigated. The syntheses were performed at 800 °C. Structure, morphology and magnetic properties of the as-prepared products were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) studies. Scherer calculation revealed that crystallite size of the ternary particles ranged between 36 and 60 nm. SEM and TEM investigations showed that the particle size was strongly influenced by the precursor concentration and Fe, Ni, Co elemental composition of individual particles was homogeneous. Finally, the soft magnetic properties of the particles were observed to be a function of their size. - Highlights: • Ternary FeNiCo alloy nanocrystalline particles were synthesized in a single step. • Cubic crystalline structure and spherical morphology was observed by XRD, SEM and TEM investigations. • The analysis of magnetic properties indicates the soft magnetic features of particles.

DYNECHARM++: a toolkit to simulate coherent interactions of high-energy charged particles in complex structures

Science.gov (United States)

Bagli, Enrico; Guidi, Vincenzo

2013-08-01

A toolkit for the simulation of coherent interactions between high-energy charged particles and complex crystal structures, called DYNECHARM++ has been developed. The code has been written in C++ language taking advantage of this object-oriented programing method. The code is capable to evaluating the electrical characteristics of complex atomic structures and to simulate and track the particle trajectory within them. Calculation method of electrical characteristics based on their expansion in Fourier series has been adopted. Two different approaches to simulate the interaction have been adopted, relying on the full integration of particle trajectories under the continuum potential approximation and on the definition of cross-sections of coherent processes. Finally, the code has proved to reproduce experimental results and to simulate interaction of charged particles with complex structures.

Analysis of Soil Structure Turnover with Garnet Particles and X-Ray Microtomography.

Directory of Open Access Journals (Sweden)

Steffen Schlüter

Full Text Available Matter turnover in soil is tightly linked to soil structure which governs the heterogeneous distribution of habitats, reaction sites and pathways in soil. Thereby, the temporal dynamics of soil structure alteration is deemed to be important for essential ecosystem functions of soil but very little is known about it. A major reason for this knowledge gap is the lack of methods to study soil structure turnover directly at microscopic scales. Here we devise a conceptual approach and an image processing workflow to study soil structure turnover by labeling some initial state of soil structure with small garnet particles and tracking their fate with X-ray microtomography. The particles adhere to aggregate boundaries at the beginning of the experiment but gradually change their position relative to the nearest pore as structure formation progresses and pores are destructed or newly formed. A new metric based on the contact distances between particles and pores is proposed that allows for a direct quantification of soil structure turnover rates. The methodology is tested for a case study about soil compaction of a silty loam soil during stepwise increase of bulk density (ρ = {1.1, 1.3, 1.5} g/cm3. We demonstrate that the analysis of mean contact distances provides genuinely new insights about changing diffusion pathways that cannot be inferred neither from conventional pore space attributes (porosity, mean pore size, pore connectivity nor from deformation analysis with digital image correlation. This structure labeling approach to quantify soil structure turnover provides a direct analogy to stable isotope labeling for the analysis of matter turnover and can be readily combined with each other.

Analysis of Soil Structure Turnover with Garnet Particles and X-Ray Microtomography.

Science.gov (United States)

Schlüter, Steffen; Vogel, Hans-Jörg

2016-01-01

Matter turnover in soil is tightly linked to soil structure which governs the heterogeneous distribution of habitats, reaction sites and pathways in soil. Thereby, the temporal dynamics of soil structure alteration is deemed to be important for essential ecosystem functions of soil but very little is known about it. A major reason for this knowledge gap is the lack of methods to study soil structure turnover directly at microscopic scales. Here we devise a conceptual approach and an image processing workflow to study soil structure turnover by labeling some initial state of soil structure with small garnet particles and tracking their fate with X-ray microtomography. The particles adhere to aggregate boundaries at the beginning of the experiment but gradually change their position relative to the nearest pore as structure formation progresses and pores are destructed or newly formed. A new metric based on the contact distances between particles and pores is proposed that allows for a direct quantification of soil structure turnover rates. The methodology is tested for a case study about soil compaction of a silty loam soil during stepwise increase of bulk density (ρ = {1.1, 1.3, 1.5} g/cm3). We demonstrate that the analysis of mean contact distances provides genuinely new insights about changing diffusion pathways that cannot be inferred neither from conventional pore space attributes (porosity, mean pore size, pore connectivity) nor from deformation analysis with digital image correlation. This structure labeling approach to quantify soil structure turnover provides a direct analogy to stable isotope labeling for the analysis of matter turnover and can be readily combined with each other.

Prototype models for particle structure in gauge supersymmetry

International Nuclear Information System (INIS)

Nath, P.; Arnowitt, R.

1981-01-01

Particle content in prototype models of gauge supersymmetry is examined. The properties of the prototype models which are in common with those of gauge supersymmetries are the initial non-diagonality of the quadratic part of the action, global supersymmetry invariance and the existence of a mass parameter in the quadratic part of the action. The analysis exhibits the particle content of prototype models to consist of normal poles and sets of complex conjugate poles on the physical sheet. Diagonalization of the hamiltonian can be carried out for such systems (in contrast to the prototype model of conformal supergravity where dipole ghosts arose). Essentially the pole structure observed in the prototype models of gauge supersymmetry is the supersymmetric analogue of the Lee-Wick phenomenon where the normal and the complex conjugate poles form global multiplets. (orig.)

Mobility particle size spectrometers: harmonization of technical standards and data structure to facilitate high quality long-term observations of atmospheric particle number size distributions

Directory of Open Access Journals (Sweden)

A. Wiedensohler

2012-03-01

Full Text Available Mobility particle size spectrometers often referred to as DMPS (Differential Mobility Particle Sizers or SMPS (Scanning Mobility Particle Sizers have found a wide range of applications in atmospheric aerosol research. However, comparability of measurements conducted world-wide is hampered by lack of generally accepted technical standards and guidelines with respect to the instrumental set-up, measurement mode, data evaluation as well as quality control. Technical standards were developed for a minimum requirement of mobility size spectrometry to perform long-term atmospheric aerosol measurements. Technical recommendations include continuous monitoring of flow rates, temperature, pressure, and relative humidity for the sheath and sample air in the differential mobility analyzer.

We compared commercial and custom-made inversion routines to calculate the particle number size distributions from the measured electrical mobility distribution. All inversion routines are comparable within few per cent uncertainty for a given set of raw data.

Furthermore, this work summarizes the results from several instrument intercomparison workshops conducted within the European infrastructure project EUSAAR (European Supersites for Atmospheric Aerosol Research and ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network to determine present uncertainties especially of custom-built mobility particle size spectrometers. Under controlled laboratory conditions, the particle number size distributions from 20 to 200 nm determined by mobility particle size spectrometers of different design are within an uncertainty range of around ±10% after correcting internal particle losses, while below and above this size range the discrepancies increased. For particles larger than 200 nm, the uncertainty range increased to 30%, which could not be explained. The network reference mobility spectrometers with identical design agreed within ±4% in the

Preparation of gluten-free bread using a meso-structured whey protein particle system

NARCIS (Netherlands)

Riemsdijk, van L.E.; Goot, van der A.J.; Hamer, R.J.; Boom, R.M.

2011-01-01

This article presents a novel method for making gluten-free bread using mesoscopically structured whey protein. The use of the meso-structured protein is based on the hypothesis that the gluten structure present in a developed wheat dough features a particle structure on a mesoscopic length scale

Influence of silicon on local structure and morphology of γ-FeOOH and α-FeOOH particles

International Nuclear Information System (INIS)

Kwon, Sang-Koo; Shinoda, Kozo; Suzuki, Shigeru; Waseda, Yoshio

2007-01-01

The extended X-ray absorption fine structure (EXAFS) method was used for investigating the local structures of lepidocrocite and goethite with and without silicon. The structure and morphology of these particles were investigated using X-ray diffraction and transmission electron microscopy, respectively. The bonding structure was examined by Fourier transform infrared spectroscopy (FT-IR). When silicon species was added, the structure and morphology changed while the linkage of FeO 6 octahedral units was distorted. The FT-IR spectra revealed the formation of the Fe-O-Si bond in particles containing silicate ions, and the characteristic bond affects the local structure and morphology of the particles

The effect of Co particle structures on the mechanical properties and microstructure of TiCN-based cermets

International Nuclear Information System (INIS)

Deng, Y.; Jiang, X.Q.; Zhang, Y.H.; Chen, H.; Tu, M.J.; Deng, L.; Zou, J.P.

2016-01-01

Ti(C,N) based cermets are composite materials composed of a hard phase and a binder phase structure. Cubic-structured Co particles are the best choice for the binder phase of Ti(C,N) based cermets due to their excellent toughness performance. However, the application of β-Co particles in cermets has not been reported in the literature so far. In this pioneer study, ultrafine Ti(C,N) based cermet samples were prepared by separately using Co particles of different structures as the binder phase, and the effect of the Co particle structures on the mechanical properties and microstructure of the cermets were studied: First, the Empirical Electron Theory was used to calculate the difference in the interface density (∆ρ) for different crystals, and the interface combined strength between the hard phase of different structures containing Co particles were evaluated. Second, we systematically investigated the evolution of the microstructures of the two cermets during the sintering process, and evaluated the characteristics of the microstructure (which determines the properties of the cermets). Finally, the mechanical properties of the samples were tested, and the performances of the Co structures were evaluated. The results show that β-Co particles can optimize the cermet microstructure, which leads to excellent mechanical performance.

The effect of Co particle structures on the mechanical properties and microstructure of TiCN-based cermets

Energy Technology Data Exchange (ETDEWEB)

Deng, Y. [Chongqing University of Arts and Science, Chongqing 402160 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Jiang, X.Q. [Southwest University, Chongqing Academy Science and Technology, Chongqing 4100715 (China); Zhang, Y.H.; Chen, H.; Tu, M.J. [Chongqing University of Arts and Science, Chongqing 402160 (China); Deng, L., E-mail: dengying.163@163.com [Chengdu Chengliang Tool Group Co., Ltd., Chengdu 610056 (China); Zou, J.P., E-mail: 1042551842@qq.com [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China)

2016-10-15

Ti(C,N) based cermets are composite materials composed of a hard phase and a binder phase structure. Cubic-structured Co particles are the best choice for the binder phase of Ti(C,N) based cermets due to their excellent toughness performance. However, the application of β-Co particles in cermets has not been reported in the literature so far. In this pioneer study, ultrafine Ti(C,N) based cermet samples were prepared by separately using Co particles of different structures as the binder phase, and the effect of the Co particle structures on the mechanical properties and microstructure of the cermets were studied: First, the Empirical Electron Theory was used to calculate the difference in the interface density (∆ρ) for different crystals, and the interface combined strength between the hard phase of different structures containing Co particles were evaluated. Second, we systematically investigated the evolution of the microstructures of the two cermets during the sintering process, and evaluated the characteristics of the microstructure (which determines the properties of the cermets). Finally, the mechanical properties of the samples were tested, and the performances of the Co structures were evaluated. The results show that β-Co particles can optimize the cermet microstructure, which leads to excellent mechanical performance.

Probing the partonic structure of exotic particles in hard electroproduction

International Nuclear Information System (INIS)

Anikin, I.V.; Pire, B.; Szymanowski, L.; Teryaev, O.V.; Wallon, S.

2005-01-01

We argue that the electroproduction of exotic particles is a useful tool for study of their partonic structure. In the case of hybrid mesons, the magnitude of their cross sections shows that they are accessible for measurements in existing electroproduction experiments

Heavy particle track structure parameters for biophysical modelling

International Nuclear Information System (INIS)

Watt, D.E.

1994-01-01

Averaged values of physical track structure parameters are important in radiobiology and radiological protection for the expression of damage mechanisms and for quantifying radiation effects. To provide a ready reference, tables of relevant quantities have been compiled for heavy charged particles in liquid water. The full tables will be published elsewhere but here illustrative examples are given of the trends for the most important quantities. In the tables, data are given for 74 types of heavy charged particle ranging from protons to uranium ions at specific energies between 0.1 keV/u and 1 GeV/u. Aggregate effects in liquid water are taken into account implicitly in the calculations. Results are presented for instantaneous particle energies and for averages over the charged particle equilibrium spectrum. The latter are of special relevance to radiation dosimetry. Quality parameters calculated are: β 2 ; z 2 /β 2 ; linear primary ionisation and the mean free path between ionisations; LET; track and dose-restricted LET with 100 eV cut-off; relative variances; delta-ray energies and ranges; ion energies and ranges and kerma factors. Here, the procedures used in the calculations are indicated. Representative results are shown in graphical form. The role of the physical track properties is discussed with regard to optimisation of the design of experiments intended to elucidate biological damage mechanisms in mammalian cells and their relevance to radiological protection. ((orig.))

Quantitative structure-activity relationships for green algae growth inhibition by polymer particles.

NARCIS (Netherlands)

Nolte, Tom M; Peijnenburg, Willie J G M; Hendriks, A Jan; van de Meent, Dik

After use and disposal of chemical products, many types of polymer particles end up in the aquatic environment with potential toxic effects to primary producers like green algae. In this study, we have developed Quantitative Structure-Activity Relationships (QSARs) for a set of highly structural

Discrete particle swarm optimization for identifying community structures in signed social networks.

Science.gov (United States)

Cai, Qing; Gong, Maoguo; Shen, Bo; Ma, Lijia; Jiao, Licheng

2014-10-01

Modern science of networks has facilitated us with enormous convenience to the understanding of complex systems. Community structure is believed to be one of the notable features of complex networks representing real complicated systems. Very often, uncovering community structures in networks can be regarded as an optimization problem, thus, many evolutionary algorithms based approaches have been put forward. Particle swarm optimization (PSO) is an artificial intelligent algorithm originated from social behavior such as birds flocking and fish schooling. PSO has been proved to be an effective optimization technique. However, PSO was originally designed for continuous optimization which confounds its applications to discrete contexts. In this paper, a novel discrete PSO algorithm is suggested for identifying community structures in signed networks. In the suggested method, particles' status has been redesigned in discrete form so as to make PSO proper for discrete scenarios, and particles' updating rules have been reformulated by making use of the topology of the signed network. Extensive experiments compared with three state-of-the-art approaches on both synthetic and real-world signed networks demonstrate that the proposed method is effective and promising. Copyright © 2014 Elsevier Ltd. All rights reserved.

The 3.2 Angstrom Resolution Structure of the Polymorphic Cowpea Chlorotic Mottle Virus Ribonucleoprotein Particle

Science.gov (United States)

Speir, Jeffrey Alan

Structural studies of the polymorphic cowpea chlorotic mottle virus have resulted in high resolution structures for two distinct icosahedral ribonucleoprotein particle conformations dependent upon whether acidic or basic pH conditions prevail. CCMV is stable below pH 6.5, however metal-free particles maintain a 10% increase in hydrodynamic volume at pH >=q 7.5. Identification of this swollen' form of CCMV, which can easily be disrupted with 1M NaCl, led to the first reassembly of an icosahedral virus in vitro from purified viral protein and RNA to form infectious particles, and its assembly has been the subject of biochemical and biophysical investigations for over twenty-five years. Under well defined conditions of pH, ionic strength and divalent metal ion concentration, CCMV capsid protein or capsid protein and RNA will reassemble to form icosahedral particles of various sizes, sheets, tubes, rosettes, and a variety of laminar structures which resemble virion structures from non-related virus families. Analysis of native particles at 3.2A resolution and swollen particles at 28A resolution has suggested that the chemical basis for the formation of polymorphic icosahedral and anisometric structures is: (i) hexamers formed of beta-barrel subunits stabilized by an unusual hexameric parallel beta structure made up of their N-termini, (ii) the location of protein-RNA interactions, (iii) divalent metal cation binding sites that regulate quasi-symmetrical subunit associations, (iv) charge repulsion across the same interfaces when lacking divalent metal ions at basic pH, which induces the formation of sixty 20A diameter portals for RNA release, and (v) a novel, C-terminal-based, subunit dimer assembly unit. The use of C- and N-terminal arms in CCMV has not been observed in other icosahedral RNA virus structures determined at near atomic resolution, however, their detailed interactions and roles in stabilizing the quaternary organization of CCMV are related to that found

Structural evaluation of a DTHR bundle divertor particle collector

International Nuclear Information System (INIS)

Prevenslik, T.V.

1980-09-01

The purpose of this report is to present a structural evaluation of the current bundle divertor particle collector BDPC design under a peak heat flux in relation to criteria that protect against coolant leakage into the plasma over replacement schedules planned during DTHR operation. In addition, an assessment of the BDPC structural integrity at higher heat fluxes is presented. Further, recommendations for modifications in the current BDPC design that would improve design reliability to be considered in future design studies are described. Finally, experimental test programs directed to establishing materials data necessary in providing greater confidence in subsequent structural evaluations of BDPC designs in relation to coolant leakage over planned replacement schedules are identified

Structural changes in microferrogels cross-linked by magnetically anisotropic particles

Energy Technology Data Exchange (ETDEWEB)

Ryzhkov, A.V., E-mail: ryzhkov.a@icmm.ru [Perm National Research Polytechnic University, Perm 614990 (Russian Federation); Institute of Continuous Media Mechanics, Russian Academy of Sciences, Ural Branch, Perm 614013 (Russian Federation); Raikher, Yu. L. [Institute of Continuous Media Mechanics, Russian Academy of Sciences, Ural Branch, Perm 614013 (Russian Federation)

2017-06-01

Chaining of magnetic nanoparticles in a microscopic ferrogel (MFG) due to interparticle interaction and external field is analyzed by the coarse-grained molecular dynamics. The embedded nanoparticles, unlike existing conventional models, are assumed to possess uniaxial magnetic anisotropy. By that, the consideration is brought closer to reality. Evolution of particle chains, both in length and straightness, is handled with the aid of “axial” radial distribution function that is sensitive to orientation of the aggregates. The effect of the particle magnetic anisotropy on the structural alterations as well as on volume changes of MFGs is demonstrated.

Nanocomposite YSZ-NiO Particles with Tailored Structure Synthesized in a Two-Stage Continuous Hydrothermal Flow Reactor

DEFF Research Database (Denmark)

Zielke, Philipp; Xu, Yu; Kiebach, Wolff-Ragnar

2016-01-01

core-shell structures or surface decorated particles could exhibit better performance compared with single phase materials. To obtain such advanced structures is the aim of the ProEco project (www.proeco.dk). In this project, a two-stage continuous reactor is built and used to synthesize such nano...... the performance of energy storage and conversion devices such as fuel cells, electrolyzers and batteries is important. One promising approach to further improve these devices is the use of carefully structured nanosized materials. Nano-composite particles combining different materials in advanced geometries like......-of-the-art solid oxide fuel and electrolysis cells. The prepared particles were characterized by X-ray powder diffraction, (high resolution) transmission electron microscopy, scanning tunnel transmission microscopy and Raman spectroscopy in order to determine crystal structure, particle size, surface morphology...

Synthesis and textural evolution of alumina particles with mesoporous structures

Science.gov (United States)

Liu, Xun; Peng, Tianyou; Yao, Jinchun; Lv, Hongjin; Huang, Cheng

2010-06-01

Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous γ-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl - in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into γ-Al 2O 3 particles with mesostructures after further calcination at 1173 K, whereas coexisting SO 42- can promote above morphology evolution and then transformed into γ-Al 2O 3 nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m 2 g -1 even after calcinations at 1173 K.

Determination of Particle Size and Distribution through Image-Based Macroscopic Analysis of the Structure of Biomass Briquettes

Directory of Open Access Journals (Sweden)

Veronika Chaloupková

2018-02-01

Full Text Available Via image-based macroscopic, analysis of a briquettes’ surface structure, particle size, and distribution was determined to better understand the behavioural pattern of input material during agglomeration in the pressing chamber of a briquetting machine. The briquettes, made of miscanthus, industrial hemp and pine sawdust were produced by a hydraulic piston press. Their structure was visualized by a stereomicroscope equipped with a digital camera and software for image analysis and data measurements. In total, 90 images of surface structure were obtained and quantitatively analysed. Using Nikon Instruments Software (NIS-Elements software, the length and area of 900 particles were measured and statistically tested to compare the size of the particles at different surface locations. Results showed statistically significant differences in particles’ size distribution: larger particles were generally on the front side of briquettes and vice versa, smaller particles were on the rear side. As well, larger particles were centred in the middle of cross sections and the smaller particles were centred on the bottom of the briquette.

Structural Transformations Versus Hard Particles Motion in the Brass Ingots

Directory of Open Access Journals (Sweden)

Wołczyński W.

2017-12-01

Full Text Available A mathematical method for the forecast of the type of structure in the steel static ingot has been recently developed. Currently, the method has been applied to structural zones prediction in the brass ingots obtained by the continuous casting. Both the temperature field and thermal gradient field have been calculated in order to predict mathematically the existence of some structural zones in the solidifying brass ingot. Particularly, the velocity of the liquidus isotherm movement and thermal gradient behavior versus solidification time have been considered. The analysis of the mentioned velocity allows the conclusion that the brass ingots can evince: chilled columnar grains-, (CC, fine columnar grains-, (FC, columnar grains-, (C, equiaxed grains zone, (E, and even the single crystal, (SC, situated axially. The role of the mentioned morphologies is analyzed to decide whether the hard particles existing in the brass ingots can be swallowed or rejected by the solid / liquid (s/l interface of a given type of the growing grains. It is suggested that the columnar grains push the hard particles to the end of a brass ingot during its continuous casting.

Effect of Seeding Particles on the Shock Structure of a Supersonic Jet

Science.gov (United States)

Porta, David; Echeverría, Carlos; Stern, Catalina

2012-11-01

The original goal of our work was to measure. With PIV, the velocity field of a supersonic flow produced by the discharge of air through a 4mm cylindrical nozzle. The results were superposed to a shadowgraph and combined with previous density measurements made with a Rayleigh scattering technique. The idea was to see if there were any changes in the flow field, close to the high density areas near the shocks. Shadowgraphs were made with and without seeding particles, (spheres of titanium dioxide). Surprisingly, it was observed that the flow structure with particles was shifted in the direction opposite to the flow with respect to the flow structure obtained without seeds. This result might contradict the belief that the seeding particles do not affect the flow and that the speed of the seeds correspond to the local speed of the flow. We acknowledge support from DGAPA UNAM through project IN117712 and from Facultad de Ciencias UNAM.

Structure of zinc particles formed by condensation for transportation to an analytic device

Energy Technology Data Exchange (ETDEWEB)

Barone, T.; Wochele, J.; Ludwig, C.; Schuler, A.J.; Ketterer, B.

2002-03-01

Aerosol containing small particles with homogeneous structural characteristics are desired for analysis in Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). To investigate heavy metal evaporation behaviour during thermal treatment a laboratory on-line elemental analyzer has been developed. The analyzer consists of a Condensation Interface (CI) for the generation of aerosols and an ICP-OES as detector. The settings at the CI can strongly influence the particle formation, and therefore the quality of the measurements. To improve the method preliminary experiments were conducted to investigate the characteristics of zinc particles formed in the evaporation/condensation process. System conditions, such as vaporization temperature, carrier gas, and flow rate, were varied to investigate their influence on particle size, homogeneity and shape. The experiments suggest that particles vary most with temperature, lower vaporization temperatures resulted in the formation of smaller particles. (author)

Structural Characterization of Silica Particles Extracted from Grass Stenotaphrum secundatum: Biotransformation via Annelids

Directory of Open Access Journals (Sweden)

A. Espíndola-Gonzalez

2014-01-01

Full Text Available This study shows the structural characterization of silica particles extracted from Stenotaphrum secundatum (St. Augustine grass using an annelid-based biotransformation process. This bioprocess starts when St. Augustine grass is turned into humus by vermicompost, and then goes through calcination and acid treatment to obtain silica particles. To determine the effect of the bioprocess, silica particles without biotransformation were extracted directly from the sample of grass. The characterization of the silica particles was performed using Infrared (FTIR and Raman spectroscopy, Transmission Electron Microscopy (TEM, X-ray Diffraction (XRD, Dynamic Light Scattering (DLS, and Energy Dispersion Spectroscopy (EDS. Both types of particles showed differences in morphology and size. The particles without biotransformation were essentially amorphous while those obtained via annelids showed specific crystalline phases. The biological relationship between the metabolisms of worms and microorganisms and the organic-mineral matter causes changes to the particles' properties. The results of this study are important because they will allow synthesis of silica in cheaper and more ecofriendly ways.

Cross-Sectional Information on Pore Structure and Element Distribution of Sediment Particles by SEM and EDS

Directory of Open Access Journals (Sweden)

Minghong Chen

2017-01-01

Full Text Available The interaction between pollutants and sediment particles often occurs on the particle surface, so surface properties directly affect surface reaction. The physical and chemical processes occurring on sediment particle surfaces are microscopic processes and as such need to be studied from a microscopic perspective. In this study, field emission scanning electron microscopy (SEM and energy dispersive X-ray spectrometer (EDS were adopted to observe and analyze the pore structure and element distribution of sediment particles. In particular, a special method of sample preparation was used to achieve the corresponding cross-sectional information of sediment particles. Clear images of a particle profile and pore microstructure were obtained by high-resolution SEM, while element distribution maps of sediment particles were obtained by EDS. The results provide an intuitive understanding of the internal microenvironment and external behavior of sediment particles, in addition to revealing a significant role of pore microstructure in the adsorption and desorption of pollutants. Thus, a combination of different experimental instruments and observation methods can provide real images and information on microscopic pore structure and element distribution of sediment particles. These results should help to improve our understanding of sediment dynamics and its environmental effects.

Structural and magnetic characterization of YIG particles prepared using microemulsions

International Nuclear Information System (INIS)

Teijeiro, A.G.; Baldomir, D.; Rivas, J.; Paz, S.; Vaqueiro, P.; Lopez Quintela, A.

1995-01-01

Yttrium-iron-garnet (YIG) particles have been synthesized using the microemulsion technique. A comparison of ferrite powders obtained by this method and those prepared by sol-gel and solid state reactions is reported. We have studied both the magnetic and structural properties and have found a dependence on annealing temperatures. ((orig.))

Simulation of diffusion-induced stress using reconstructed electrodes particle structures generated by micro/nano-CT

International Nuclear Information System (INIS)

Lim, Cheolwoong; Yan Bo; Yin Leilei; Zhu Likun

2012-01-01

Highlights: ► The microstructure of LIB electrodes was obtained by X-ray micro/nano-CT. ► We studied diffusion-induced stresses based on realistic 3D microstructures. ► Stresses depend on geometric characteristics of electrode particle. ► Stresses in a real particle are much higher than those in a spherical particle. - Abstract: Lithium ion batteries experience diffusion-induced stresses during charge and discharge processes which can cause electrode failure in the form of fracture. Previous diffusion-induced stress models and simulations are mainly based on simple active material particle structures, such as spheres and ellipsoids. However, the simple structure model cannot reveal the stress development in a real complex lithium ion battery electrode. In this paper, we studied the diffusion-induced stresses numerically based on a realistic morphology of reconstructed particles during the lithium ion intercalation process. The morphology of negative and positive active materials of a lithium ion battery was determined using X-ray micro/nano computed tomography technology. Diffusion-induced stresses were simulated at different C rates under galvonostatic conditions and compared with spherical particles. The simulation results show that the intercalation stresses of particles depend on their geometric characteristics. The highest von Mises stress and Tresca stress in a real particle are several times higher than the stresses in a spherical particle with the same volume.

A cloud/particle model of the interstellar medium - Galactic spiral structure

Science.gov (United States)

Levinson, F. H.; Roberts, W. W., Jr.

1981-01-01

A cloud/particle model for gas flow in galaxies is developed that incorporates cloud-cloud collisions and supernovae as dominant local processes. Cloud-cloud collisions are the main means of dissipation. To counter this dissipation and maintain local dispersion, supernova explosions in the medium administer radial snowplow pushes to all nearby clouds. The causal link between these processes is that cloud-cloud collisions will form stars and that these stars will rapidly become supernovae. The cloud/particle model is tested and used to investigate the gas dynamics and spiral structures in galaxies where these assumptions may be reasonable. Particular attention is given to whether large-scale galactic shock waves, which are thought to underlie the regular well-delineated spiral structure in some galaxies, form and persist in a cloud-supernova dominated interstellar medium; this question is answered in the affirmative.

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

Science.gov (United States)

Gritti, Fabrice; Horvath, Krisztian; Guiochon, Georges

2012-11-09

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

Scaling relations between structure and rheology of ageing casein particle gels

NARCIS (Netherlands)

Mellema, M.

2000-01-01

Mellema, M. (Michel), Scaling relations between structure and rheology of ageing casein particle gels , PhD Thesis, Wageningen University, 150 + 10 pages, references by chapter, English and Dutch summaries (2000).

The relation between (colloidal)

Influence of the Hydrophobicity of Polyelectrolytes on Polyelectrolyte Complex Formation and Complex Particle Structure and Shape

Directory of Open Access Journals (Sweden)

Gudrun Petzold

2011-08-01

Full Text Available Polyelectrolyte complexes (PECs were prepared by structural uniform and strongly charged cationic and anionic modified alternating maleic anhydride copolymers. The hydrophobicity of the polyelectrolytes was changed by the comonomers (ethylene, isobutylene and styrene. Additionally, the n−/n+ ratio of the molar charges of the polyelectrolytes and the procedure of formation were varied. The colloidal stability of the systems and the size, shape, and structure of the PEC particles were investigated by turbidimetry, dynamic light scattering (DLS and atomic force microscopy (AFM. Dynamic light scattering indicates that beside large PEC particle aggregates distinct smaller particles were formed by the copolymers which have the highest hydrophobicity (styrene. These findings could be proved by AFM. Fractal dimension (D, root mean square (RMS roughness and the surface profiles of the PEC particles adsorbed on mica allow the following conclusions: the higher the hydrophobicity of the polyelectrolytes, the broader is the particle size distribution and the minor is the swelling of the PEC particles. Hence, the most compact particles are formed with the very hydrophobic copolymer.

Studies of the neutron single-particle structure of exotic nuclei at the HRIBF

International Nuclear Information System (INIS)

Thomas, J.S.; Bardayan, D.W.; Blackmon, J.C.; Cizewski, J.A.; Greife, U.; Gross, C.J.; Johnson, M.S.; Jones, K.L.; Kozub, R.L.; Liang, J.F.; Livesay, R.J.; Ma, Z.; Moazen, B.H.; Nesaraja, C.D.; Shapira, D.; Smith, M.S.

2004-01-01

The study of neutron single-particle strengths in neutron-rich nuclei is of interest for nuclear structure and nuclear astrophysics. The distribution of single-particle strengths constrains the effective Hamiltonian and pairing interactions and determines neutron interaction rates that are crucial for understanding the synthesis of heavy nuclei in supernovae via the rapid neutron capture process. Particularly important are the neutron single-particle levels in nuclei near closed neutron shells. Radioactive ion beams from the Holifield Radioactive Ion Beam Facility have been used to study (d,p) reactions in inverse kinematics in order to probe neutron single-particle states in exotic nuclei. The results of a measurement with a 82 Ge beam will be presented

Noise bias in the refinement of structures derived from single particles

International Nuclear Information System (INIS)

Stewart, Alex; Grigorieff, Nikolaus

2004-01-01

One of the main goals in the determination of three-dimensional macromolecular structures from electron microscope images of individual molecules and complexes (single particles) is a sufficiently high spatial resolution, about 4 A, at which the interpretation with an atomic model becomes possible. To reach high resolution, an iterative refinement procedure using an expectation maximization algorithm is often used that leads to a more accurate alignment of the positional and orientational parameters for each particle. We show here the results of refinement algorithms that use a phase residual, a linear correlation coefficient, or a weighted correlation coefficient to align individual particles. The algorithms were applied to computer-generated data sets that contained projections from model structures, as well as noise. The algorithms show different degrees of over-fitting, especially at high resolution where the signal is weak. We demonstrate that the degree of over-fitting is reduced with a weighting scheme that depends on the signal-to-noise ratio in the data. The weighting also improves the accuracy of resolution measurement by the commonly used Fourier shell correlation. The performance of the refinement algorithms is compared to that using a maximum likelihood approach. The weighted correlation coefficient was implemented in the computer program FREALIGN

Smoothed particle hydrodynamics modelling in continuum mechanics: fluid-structure interaction

Directory of Open Access Journals (Sweden)

Groenenboom P. H. L.

2009-06-01

Full Text Available Within this study, the implementation of the smoothed particle hydrodynamics (SPH method solving the complex problem of interaction between a quasi-incompressible fluid involving a free surface and an elastic structure is outlined. A brief description of the SPH model for both the quasi-incompressible fluid and the isotropic elastic solid is presented. The interaction between the fluid and the elastic structure is realised through the contact algorithm. The results of numerical computations are confronted with the experimental as well as computational data published in the literature.

From quantum fields to fractal structures: intermittency in particle physics

International Nuclear Information System (INIS)

Peschanski, R.

1991-01-01

Some features and theoretical interpretations of the intermittency phenomenon observed in high-energy multi-particle production are recalled. One develops on the various connections found with fractal structuration of fluctuations in turbulence, spin-glass physics and aggregation phenomena described by the non-linear Smoluchowski equation. This may lead to a new approach to quantum field properties

Particle swarm optimization of the stable structure of tetrahexahedral Pt-based bimetallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Liu, Tun-Dong; Fan, Tian-E [Center for Cloud Computing and Big Data, Department of Automation, Xiamen University, Xiamen 361005 (China); Shao, Gui-Fang, E-mail: gfshao@xmu.edu.cn [Center for Cloud Computing and Big Data, Department of Automation, Xiamen University, Xiamen 361005 (China); Zheng, Ji-Wen [Center for Cloud Computing and Big Data, Department of Automation, Xiamen University, Xiamen 361005 (China); Wen, Yu-Hua [Institute of Theoretical Physics and Astrophysics, Department of Physics, Xiamen University, Xiamen 361005 (China)

2014-08-14

Bimetallic nanoparticles, enclosed by high-index facets, have great catalytic activity and selectivity owing to the synergy effects of high-index facets and the electronic structures of alloy. In this paper, a discrete particle swarm optimization algorithm was employed to systematically investigate the structural stability and features of tetrahexahedral Pt-based bimetallic nanoparticles with high-index facets. Different Pt/Ag, Pt/Cu, Pt/Pd atom ratios and particle sizes were considered in this work. The simulation results reveal that these alloy nanoparticles exhibit considerably different structural characteristics. Pt–Ag nanoparticles tend to form Pt–Ag core–shell structure. Pt–Cu nanoparticles are preferred to take multi-shell structure with Cu on the outer surface while Pt–Pd nanoparticles present a mixing structure in the interior and Pd-dominated surface. Atomic distribution and bonding characteristics were applied to further characterize the structural features of Pt-based nanoparticles. This study provides an important insight into the structural stability and features of Pt-based nanoparticles with different alloys. - Highlights: • We explore the structural stability of Pt-based alloy NPs by a discrete PSO. • Our study discovers the different structural characteristics for Pt-based NPs. • Alloy composition and size have important effects on the surface segregation. • Our work shows strong phase separation for Pt–Ag NPs while weak for Pt–Pd NPs.

Particle swarm optimization of the stable structure of tetrahexahedral Pt-based bimetallic nanoparticles

International Nuclear Information System (INIS)

Liu, Tun-Dong; Fan, Tian-E; Shao, Gui-Fang; Zheng, Ji-Wen; Wen, Yu-Hua

2014-01-01

Bimetallic nanoparticles, enclosed by high-index facets, have great catalytic activity and selectivity owing to the synergy effects of high-index facets and the electronic structures of alloy. In this paper, a discrete particle swarm optimization algorithm was employed to systematically investigate the structural stability and features of tetrahexahedral Pt-based bimetallic nanoparticles with high-index facets. Different Pt/Ag, Pt/Cu, Pt/Pd atom ratios and particle sizes were considered in this work. The simulation results reveal that these alloy nanoparticles exhibit considerably different structural characteristics. Pt–Ag nanoparticles tend to form Pt–Ag core–shell structure. Pt–Cu nanoparticles are preferred to take multi-shell structure with Cu on the outer surface while Pt–Pd nanoparticles present a mixing structure in the interior and Pd-dominated surface. Atomic distribution and bonding characteristics were applied to further characterize the structural features of Pt-based nanoparticles. This study provides an important insight into the structural stability and features of Pt-based nanoparticles with different alloys. - Highlights: • We explore the structural stability of Pt-based alloy NPs by a discrete PSO. • Our study discovers the different structural characteristics for Pt-based NPs. • Alloy composition and size have important effects on the surface segregation. • Our work shows strong phase separation for Pt–Ag NPs while weak for Pt–Pd NPs

Synthesis and textural evolution of alumina particles with mesoporous structures

International Nuclear Information System (INIS)

Liu Xun; Peng Tianyou; Yao Jinchun; Lv Hongjin; Huang Cheng

2010-01-01

Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous γ-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl - in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into γ-Al 2 O 3 particles with mesostructures after further calcination at 1173 K, whereas coexisting SO 4 2- can promote above morphology evolution and then transformed into γ-Al 2 O 3 nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m 2 g -1 even after calcinations at 1173 K. - Graphical abstract: Co-existing Cl - is beneficial for the formation of γ-alumina nanoparticles with mesostructures during the precipitation process. Interparticle and intraparticle mesopores can be derived from acidic solution and near neutral solution, respectively.

Quasi-discrete particle motion in an externally imposed, ordered structure in a dusty plasma at high magnetic field

Energy Technology Data Exchange (ETDEWEB)

Thomas, Edward, E-mail: etjr@auburn.edu; Konopka, Uwe; Lynch, Brian; Adams, Stephen; LeBlanc, Spencer [Physics Department, Auburn University, Auburn, Alabama 36849 (United States); Merlino, Robert L. [Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242 (United States); Rosenberg, Marlene [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States)

2015-11-15

Dusty plasmas have been studied in argon, radio frequency (rf) glow discharge plasmas at magnetic fields up to 2.5 T where the electrons and ions are strongly magnetized. Plasmas are generated between two parallel plate electrodes where the lower, powered electrode is solid and the upper electrode supports a dual mesh consisting of #24 brass and #30 aluminum wire cloth. In this experiment, we study the formation of imposed ordered structures and particle dynamics as a function of magnetic field. Through observations of trapped particles and the quasi-discrete (i.e., “hopping”) motion of particles between the trapping locations, it is possible to make a preliminary estimate of the potential structure that confines the particles to a grid structure in the plasma. This information is used to gain insight into the formation of the imposed grid pattern of the dust particles in the plasma.

Aqueous Lubrication, Structure and Rheological Properties of Whey Protein Microgel Particles.

Science.gov (United States)

Sarkar, Anwesha; Kanti, Farah; Gulotta, Alessandro; Murray, Brent S; Zhang, Shuying

2017-12-26

Aqueous lubrication has emerged as an active research area in recent years due to its prevalence in nature in biotribological contacts and its enormous technological soft-matter applications. In this study, we designed aqueous dispersions of biocompatible whey-protein microgel particles (WPM) (10-80 vol %) cross-linked via disulfide bonding and focused on understanding their rheological, structural and biotribological properties (smooth polydimethylsiloxane (PDMS) contacts, R a ball bearings", the latter supported by negligible change in size and microstructure of the WPM particles after tribology. An ultralow boundary friction coefficient, μ ≤ 0.03 was achieved using WPM between O 2 plasma-treated hydrophilic PDMS contacts coated with bovine submaxillary mucin (water contact angle 47°), and electron micrographs revealed that the WPM particles spread effectively as a layer of particles even at low ϕ∼ 10%, forming a lubricating load-bearing film that prevented the two surfaces from true adhesive contact. However, above an optimum volume fraction, μ increased in HL+BSM surfaces due to the interpenetration of particles that possibly impeded effective rolling, explaining the slight increase in friction. These effects are reflected in the highly shear thinning nature of the WPM dispersions themselves plus the tendency for the apparent viscosity to fall as dispersions are forced to very high volume fractions. The present work demonstrates a novel approach for providing ultralow friction in soft polymeric surfaces using proteinaceous microgel particles that satisfy both load bearing and kinematic requirements. These findings hold great potential for designing biocompatible particles for aqueous lubrication in numerous soft matter applications.

Tunnel current through virus particles between columnar structures in mesoporous silicon

Energy Technology Data Exchange (ETDEWEB)

Vashpanov, Yuriy; Jung, Jae-Il; Dal Kwack, Kae [Electrical Engineering and Computer Science Division of Hanyang Institute of Technology, Hanyang University, 17 Haengdang-dong, Seongdong-gu, 133-791 Seoul (Korea, Republic of)

2011-07-15

Earlier we reported on a tunnel charge transport mechanism in mesoporous silicon with columnar structures under adsorption of plant nematode-transmitted polyhedral (NEPO) viruses at room temperature. Additional experiments are performed in this paper to establish that this observed tunnel current is connected to a conduction path through virus particles. The plant NEPO viruses have an orbicular shape with a diameter of around 25-30 nm. This size is matched well to the porous size distribution in manufactured samples. The tunnel charge transport in semiconductor structures was not observed on loading protein macromolecules of smaller sizes. A physical mechanism of the observed phenomena can be interpreted to be the result of a shunting effect through virus particles between the two closely located columnar silicon structures. This effect is likely to result from double points at virus adsorption under the condition of matching of pore and virus sizes. The magnitudes of the tunnel barrier heights depend on the type of loaded plant viruses. The investigated columnar structures of mesoporous silicon can be used for research on the electrical properties of different viruses with corresponding sizes in the range of 20-30 nm. The existence of a tunnel current between columnar structures in mesoporous silicon under virus adsorption can be used as a simple method for their detection in the environment. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Structure and acidity of individual Fluid Catalytic Cracking catalyst particles studied by synchrotron-based infrared micro-spectroscopy

NARCIS (Netherlands)

Buurmans, I.L.C.; Soulimani, F.; Ruiz Martinez, J.; van der Bij, H.E.; Weckhuysen, B.M.

2013-01-01

A synchrotron-based infrared micro-spectroscopy study has been conducted to investigate the structure as well as the Brønsted and Lewis acidity of Fluid Catalytic Cracking (FCC) catalyst particles at the individual particle level. Both fresh and laboratory-deactivated catalyst particles have been

Particle roughness in magnetorheology: effect on the strength of the field-induced structures

International Nuclear Information System (INIS)

Vereda, F; Segovia-Gutiérrez, J P; De Vicente, J; Hidalgo-Alvarez, R

2015-01-01

We report a study on the effect of particle roughness on the strength of the field-induced structures of magnetorheological (MR) fluids in the quasi-static regime. We prepared one set of MR fluids with carbonyl iron particles and another set with magnetite particles, and in both sets we had particles with different degrees of surface roughness. Small amplitude oscillatory shear (SAOS) magnetosweeps and steady shear (SS) tests were carried out on the suspensions to measure their elastic modulus (G′) and static yield stress (τ static ). Results for both the iron and the magnetite sets of suspensions were consistent: for the MR fluids prepared with rougher particles, G′ increased at smaller fields and τ static was ca. 20% larger than for the suspensions prepared with relatively smooth particles. In addition to the experimental study, we carried out finite element method calculations to assess the effect of particle roughness on the magnetic interaction between particles. These calculations showed that roughness can facilitate the magnetization of the particles, thus increasing the magnetic energy of the system for a given field, but that this effect depends on the concrete morphology of the surface. For our real systems, no major differences were observed between the magnetization cycles of the MR fluids prepared with particles with different degree of roughness, which implied that the effect of roughness on the measured G′ and τ static was due mainly to friction between the solid surfaces of adjacent particles. (paper)

Structure and properties of carbon black particles

Science.gov (United States)

Xu, Wei

Structure and properties of carbon black particles were investigated using atomic force microscopy, gas adsorption, Raman spectroscopy, and X-ray diffraction. Supplementary information was obtained using TEM and neutron scattering. The AFM imaging of carbon black aggregates provided qualitative visual information on their morphology, complementary to that obtained by 3-D modeling based on TEM images. Our studies showed that carbon black aggregates were relatively flat. The surface of all untreated carbon black particles was found to be rough and its fractal dimension was 2.2. Heating reduced the roughness and fractal dimension for all samples heat treated at above 1300 K to 2.0. Once the samples were heat treated rapid cooling did not affect the surface roughness. However, rapid cooling reduced crystallite sizes, and different Raman spectra were obtained for carbon blacks of various history of heat treatment. By analyzing the Raman spectra we determined the crystallite sizes and identified amorphous carbon. The concentration of amorphous carbon depends on hydrogen content. Once hydrogen was liberated at increased temperature, the concentration of amorphous carbon was reduced and crystallites started to grow. Properties of carbon blacks at high pressure were also studied. Hydrostatic pressure did not affect the size of the crystallites in carbon black particles. The pressure induced shift in Raman frequency of the graphitic component was a result of increased intermolecular forces and not smaller crystallites. Two methods of determining the fractal dimension, the FHH model and the yardstick technique based on the BET theory were used in the literature. Our study proved that the FHH model is sensitive to numerous assumptions and leads to wrong conclusions. On the other hand the yardstick method gave correct results, which agreed with the AFM results.

Estimation of effective permeability for magnetoactive composites containing multi-chain-structured particles based on the generalized Mori–Tanaka approach

International Nuclear Information System (INIS)

Zhang, Haiyu; Wang, Xingzhe

2014-01-01

We present an analytic approach to evaluate the effective permeability of multi-chain-structured magnetic particle-filled composites which is formulated by a microstructure-based double-inclusion magnetic model with the generalized Mori–Tanaka theorem. The local magnetic field in a representative volume element (RVE) containing multi-chain-structured particles is derived by using a modified Green’s function. The average fields in the particles, in a matrix coated by particles, and in an effective medium far away from particles are rendered by homogenization of the local magnetic distributions. By means of the relation between the average magnetic field and induction, the effective magnetic permeability of magnetoactive composites is explicitly derived; it exhibits anisotropic and universal behavior. The proposed model has been compared with the available experimental data and other microstructure-based models in the literature; it shows good agreement and gives reliable predictions for magnetic particle-filled composites, especially in terms of capturing the magnetic anisotropic characteristics with respect to the multi-chain-structured particle distribution. (paper)

Smoothed Particle Hydrodynamics Simulations of Dam-Break Flows Around Movable Structures

OpenAIRE

Jian, Wei; Liang, Dongfang; Shao, Songdong; Chen, Ridong; Yang, Kejun

2015-01-01

In this paper, 3D weakly compressible and incompressible Smoothed Particle Hydrodynamics (WCSPH & ISPH) models are used to study dam-break flows impacting on either a fixed or a movable structure. First, the two models’ performances are compared in terms of CPU time efficiency and numerical accuracy, as well as the water surface shapes and pressure fields. Then, they are applied to investigate dam-break flow interactions with structures placed in the path of the flood. The study found that th...

Quasi-particle excitations and dynamical structure function of trapped Bose-condensates in the WKB approximation

OpenAIRE

Csordás, András; Graham, Robert; Szépfalusy, Péter

1997-01-01

The Bogoliubov equations of the quasi-particle excitations in a weakly interacting trapped Bose-condensate are solved in the WKB approximation in an isotropic harmonic trap, determining the discrete quasi-particle energies and wave functions by torus (Bohr-Sommerfeld) quantization of the integrable classical quasi-particle dynamics. The results are used to calculate the position and strengths of the peaks in the dynamic structure function which can be observed by off-resonance inelastic light...

Structure functions and particle production in the cumulative region: two different exponentials

International Nuclear Information System (INIS)

Braun, M.; Vechernin, V.

1997-01-01

In the framework of the recently proposed (QCD-based parton model for the cumulative phenomena in the interactions with nuclei two mechanisms for particle production, direct and spectator ones, are analyzed. It is shown that due to final-state interactions the leading terms of the direct mechanism contribution are cancelled and the spectator mechanism is the dominant one. It leads to a smaller slope of the cumulative particle production rates compared to the slope of the nuclear structure function in the cumulative region x ≥ 1, in agreement with the recent experimental data

Optimization of mechanical structures using particle swarm optimization

International Nuclear Information System (INIS)

Leite, Victor C.; Schirru, Roberto

2015-01-01

Several optimization problems are dealed with the particle swarm optimization (PSO) algorithm, there is a wide kind of optimization problems, it may be applications related to logistics or the reload of nuclear reactors. This paper discusses the use of the PSO in the treatment of problems related to mechanical structure optimization. The geometry and material characteristics of mechanical components are important for the proper functioning and performance of the systems were they are applied, particularly to the nuclear field. Calculations related to mechanical aspects are all made using ANSYS, while the PSO is programed in MATLAB. (author)

Optimization of mechanical structures using particle swarm optimization

Energy Technology Data Exchange (ETDEWEB)

Leite, Victor C.; Schirru, Roberto, E-mail: victor.coppo.leite@lmp.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (LMP/PEN/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Lab. de Monitoracao de Processos

2015-07-01

Several optimization problems are dealed with the particle swarm optimization (PSO) algorithm, there is a wide kind of optimization problems, it may be applications related to logistics or the reload of nuclear reactors. This paper discusses the use of the PSO in the treatment of problems related to mechanical structure optimization. The geometry and material characteristics of mechanical components are important for the proper functioning and performance of the systems were they are applied, particularly to the nuclear field. Calculations related to mechanical aspects are all made using ANSYS, while the PSO is programed in MATLAB. (author)

A new rf structure for intermediate-velocity particles

International Nuclear Information System (INIS)

Billen, J.H.; Krawczyk, F.L.; Wood, R.L.; Young, L.M.

1994-01-01

This paper describes an rf structure with high shunt impedance and good field stability for particle velocities o.1 ≤ β ≤ 0.5. Traditionally, the drift-tube linac (DTL) has been the structure of choice for this velocity range. The new structure, called a coupled-cavity drift-tube linac (CCDTL), combines features of the Alvarez DTL and the π-mode coupled-cavity linac (CCL). Each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between gaps is γλ. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a π/2 structure mode so the coupling cavities are nominally unexcited. We will discuss 2-D and 3-D electromagnetic code calculations, and some initial measurements on a low-power model of a CCDTL. We will compare shunt impedance calculations for DTL, CCL, and CCDTL structures. The CCDTL has potential application for a wide range of ion linacs. For example, high-intensity proton linacs could use the CCDTL instead of a DTL up to an energy of about 200 MeV. Another example is a stand-alone, low-duty, low-current, very high gradient, proton, cancer therapy machine. The advantage for this application would be a saving in the cost of the machine because the linac would be short

Possibilities of the particle finite element method for fluid-soil-structure interaction problems

Science.gov (United States)

Oñate, Eugenio; Celigueta, Miguel Angel; Idelsohn, Sergio R.; Salazar, Fernando; Suárez, Benjamín

2011-09-01

We present some developments in the particle finite element method (PFEM) for analysis of complex coupled problems in mechanics involving fluid-soil-structure interaction (FSSI). The PFEM uses an updated Lagrangian description to model the motion of nodes (particles) in both the fluid and the solid domains (the later including soil/rock and structures). A mesh connects the particles (nodes) defining the discretized domain where the governing equations for each of the constituent materials are solved as in the standard FEM. The stabilization for dealing with an incompressibility continuum is introduced via the finite calculus method. An incremental iterative scheme for the solution of the non linear transient coupled FSSI problem is described. The procedure to model frictional contact conditions and material erosion at fluid-solid and solid-solid interfaces is described. We present several examples of application of the PFEM to solve FSSI problems such as the motion of rocks by water streams, the erosion of a river bed adjacent to a bridge foundation, the stability of breakwaters and constructions sea waves and the study of landslides.

Bond particle model for semiconductor melts and its application to liquid structure germanium

International Nuclear Information System (INIS)

Ferrante, A.; Tosi, M.P.

1988-08-01

A simple type of liquid state model is proposed to describe on a primitive level the melt of an elemental group IV semiconductor as a mixture of atoms and bond particles. The latter, on increase of a coupling strength parameter becomes increasingly localized between pairs of atoms up to local tetrahedral coordination of atoms by bond particles. Angular interatomic correlations are built into the model as bond particle localization grows, even though the bare interactions between the components of the liquid are formally described solely in terms of central pair potentials. The model is solved for liquid structure by standard integral equation techniques of liquid state theory and by Monte Carlo simulation, for values of the parameters which are appropriate to liquid germanium down to strongly supercooled states. The calculated liquid structure is compared with the results of diffraction experiments on liquid germanium near freezing and discussed in relation to diffraction data on amorphous germanium. The model suggests simple melting criteria for elemental and polar semiconductors, which are empirically verified. (author). 25 refs, 9 figs, 3 tabs

Particle versus field structure in conformal quantum field theories

International Nuclear Information System (INIS)

Schroer, Bert

2000-06-01

I show that a particle structure in conformal field theory is incompatible with interactions. As a substitute one has particle-like excitations whose interpolating fields have in addition to their canonical dimension an anomalous contribution. The spectra of anomalous dimension is given in terms of the Lorentz invariant quadratic invariant (compact mass operator) of a conformal generator R μ with pure discrete spectrum. The perturbative reading of R o as a Hamiltonian in its own right, associated with an action in a functional integral setting naturally leads to the Ad S formulation. The formal service role of Ad S in order to access C QFT by a standard perturbative formalism (without being forced to understand first massive theories and then taking their scale-invariant limit) vastly increases the realm of conventionally accessible 4-dim. C QFT beyond those for which one had to use Lagrangians with supersymmetry in order to have a vanishing Beta-function. (author)

Structure organization and magnetic properties of microscale ferrogels: The effect of particle magnetic anisotropy

Science.gov (United States)

Ryzhkov, Aleksandr V.; Melenev, Petr V.; Balasoiu, Maria; Raikher, Yuriy L.

2016-08-01

The equilibrium structure and magnetic properties of a ferrogel object of small size (microferrogel(MFG)) are investigated by coarse-grained molecular dynamics. As a generic model of a microferrogel (MFG), a sample with a lattice-like mesh is taken. The solid phase of the MFG consists of magnetic (e.g., ferrite) nanoparticles which are mechanically linked to the mesh making some part of its nodes. Unlike previous models, the finite uniaxial magnetic anisotropy of the particles, as it is the case for real ferrogels, is taken into account. For comparison, two types of MFGs are considered: MFG-1, which dwells in virtually non-aggregated state independently of the presence of an external magnetic field, and MFG-2, which displays aggregation yet under zero field. The structure states of the samples are analyzed with the aid of angle-resolved radial distribution functions and cluster counts. The results reveal the crucial role of the matrix elasticity on the structure organization as well as on magnetization of both MFGs. The particle anisotropy, which plays insignificant role in MFG-1 (moderate interparticle magnetodipole interaction), becomes an important factor in MFG-2 (strong interaction). There, the restrictions imposed on the particle angular freedom by the elastic matrix result in notable diminution of the particle chain lengths as well as the magnetization of the sample. The approach proposed enables one to investigate a large variety of MFGs, including those of capsule type and to purposefully choose the combination of their magnetoelastic parameters.

Particle filtering based structural assessment with acoustic emission sensing

Science.gov (United States)

Yan, Wuzhao; Abdelrahman, Marwa; Zhang, Bin; Ziehl, Paul

2017-02-01

Nuclear structures are designed to withstand severe loading events under various stresses. Over time, aging of structural systems constructed with concrete and steel will occur. This deterioration may reduce service life of nuclear facilities and/or lead to unnecessary or untimely repairs. Therefore, online monitoring of structures in nuclear power plants and waste storage has drawn significant attention in recent years. Of many existing non-destructive evaluation and structural monitoring approaches, acoustic emission is promising for assessment of structural damage because it is non-intrusive and is sensitive to corrosion and crack growth in reinforced concrete elements. To provide a rapid, actionable, and graphical means for interpretation Intensity Analysis plots have been developed. This approach provides a means for classification of damage. Since the acoustic emission measurement is only an indirect indicator of structural damage, potentially corrupted by non-genuine data, it is more suitable to estimate the states of corrosion and cracking in a Bayesian estimation framework. In this paper, we will utilize the accelerated corrosion data from a specimen at the University of South Carolina to develop a particle filtering-based diagnosis and prognosis algorithm. Promising features of the proposed algorithm are described in terms of corrosion state estimation and prediction of degradation over time to a predefined threshold.

Accelerator structure for a charged particle linear accelerator working in standing wave mode

International Nuclear Information System (INIS)

Tran, D.T.; Tronc, Dominique.

1977-01-01

Charged particle accelerators generally include a pre-grouping or pre-accelerating structure associated with the accelerator structure itself. But pre-grouping or pre-accelerating structures of known type (Patent application No. 70 39261 for example) present electric and dimensional characteristics that rule them out for accelerators working at high frequencies (C or X bands for example), since the distance separating the interaction spaces becomes very small in this case. The accelerator structure mentioned in this invention can be used to advantage for such accelerators [fr

Slow wave structures using twisted waveguides for charged particle applications

Science.gov (United States)

Kang, Yoon W.; Fathy, Aly E.; Wilson, Joshua L.

2012-12-11

A rapidly twisted electromagnetic accelerating structure includes a waveguide body having a central axis, one or more helical channels defined by the body and disposed around a substantially linear central axial channel, with central portions of the helical channels merging with the linear central axial channel. The structure propagates electromagnetic waves in the helical channels which support particle beam acceleration in the central axial channel at a phase velocity equal to or slower than the speed of light in free space. Since there is no variation in the shape of the transversal cross-section along the axis of the structure, inexpensive mechanical fabrication processes can be used to form the structure, such as extrusion, casting or injection molding. Also, because the field and frequency of the resonant mode depend on the whole structure rather than on dimensional tolerances of individual cells, no tuning of individual cells is needed. Accordingly, the overall operating frequency may be varied with a tuning/phase shifting device located outside the resonant waveguide structure.

Plasma and energetic particle structure of a collisionless quasi-parallel shock

Science.gov (United States)

Kennel, C. F.; Scarf, F. L.; Coroniti, F. V.; Russell, C. T.; Smith, E. J.; Wenzel, K. P.; Reinhard, R.; Sanderson, T. R.; Feldman, W. C.; Parks, G. K.

1983-01-01

The quasi-parallel interplanetary shock of November 11-12, 1978 from both the collisionless shock and energetic particle points of view were studied using measurements of the interplanetary magnetic and electric fields, solar wind electrons, plasma and MHD waves, and intermediate and high energy ions obtained on ISEE-1, -2, and -3. The interplanetary environment through which the shock was propagating when it encountered the three spacecraft was characterized; the observations of this shock are documented and current theories of quasi-parallel shock structure and particle acceleration are tested. These observations tend to confirm present self consistent theories of first order Fermi acceleration by shocks and of collisionless shock dissipation involving firehouse instability.

Computed and experimental interactions between eddy structure and dispersed particles in developing free shear layers

International Nuclear Information System (INIS)

Buckingham, A.C.; Siekhaus, W.J.; Keller, J.O.; Ellzey, J.; Hubbard, G.; Daily, J.W.

1982-01-01

We are investigating the interactive process between turbulent flow and dispersed phase particles. We are focusing on the mechanisms that appear to result in a reduction of local turbulent intensity and a corresponding reduction in wall heat transfer and subsequent wall erosion in turbulent solid propellant combustion flow. We apply computational simulations and physical experiments specialized to a developing free shear layer over a rearward facing step and over a parallel splitter plate. The flow configuration evolves in a two-dimensional, steady, combustion and non-combustion turbulent free shear mixing region, with and without particle additives. The computational simulations combine three basic components: gas phase Navier-Stokes solutions, Lagrange particle field solutions and a Monte Carlo technique for the random encounters, forces and accelerations between the two fields. We concentrate here on relatively large sized additive particles (of the order of tens of microns to 100 microns mean diameter). We examine their apparent influence in breaking up the larger, energy bearing eddy structures into smaller structures which are more readily dissipated

Magnetic structure evolution in mechanically milled nanostructured ZnFe2O4 particles

DEFF Research Database (Denmark)

Jiang, Jianzhong; Wynn, P.; Mørup, Steen

1999-01-01

Nanostructured partially-inverted ZnFe2O4 particles have been prepared from bulk ZnFe2O4 by high-energy ball milling in an open container. The grain size reduction, cation site distributions, and the evolution of magnetic structures have been studied by x-ray diffraction with Rietveld structure...... refinements, transmission electron microscopy, and Mossbauer spectroscopy. It is found that a change of magnetic structure from an antiferromagnetic to a ferrimagnetic (or ferromagnetic) structure occurs in the milled samples. This change is correlated with the redistribution of the cations, Zn and Fe...

Controllable dielectric and electrical performance of polymer composites with novel core/shell-structured conductive particles through biomimetic method

International Nuclear Information System (INIS)

Yang, Dan; Tian, Ming; Wang, Wencai; Li, Dongdong; Li, Runyuan; Liu, Haoliang; Zhang, Liqun

2013-01-01

Highlights: ► Conductive core/shell-structured particles were synthesized by biomimetic method. ► These particles with silica/poly(dopamine)/silver core and poly(dopamine) shell. ► Dielectric composites were prepared with resulted particles and silicone elastomer. ► The dielectric properties of the composites can be controlled by shell thickness. ► This biomimetic method is simple, nontoxic, efficient and easy to control. - Abstract: Novel silica/poly(dopamine)/silver (from inner to outer) (denoted as SiO 2 /PDA/Ag) conductive micro-particles were first synthesized by biomimetic poly(dopamine) coating. These micro-particles were then coated with a poly(dopamine) layer to form core/shell-structured particles, with silica/poly(dopamine)/silver core and poly(dopamine) shell (denoted as SiO 2 /PDA/Ag/PDA). This multilayer core/shell micro-particles were confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscope. Polymer composites were then prepared by mechanical blending of poly(dimethyl siloxane) and the core/shell-structured particles. It was found that the silver layer and the poly(dopamine) shell had good adhesion with substrate and they kept intact even under violent shearing stress during mechanical mixing. The effect of the thickness of outermost poly(dopamine) shell as well as the loading amount of this filler on the dielectric and electrical properties of the composites was further studied. The results showed that the dielectric constant, dielectric loss, and conductivity of the composites decreased with increasing shell thickness (10–53 nm) at the same loading level. And the maximal dielectric constant of composites was achieved in the composites filled with SiO 2 /PDA/Ag/PDA (with 10–15 nm PDA shell) particles, which was much larger than that of the composite filled with SiO 2 /PDA/Ag particles without insulative PDA shell. At the same time, the composites can change

Investigation of the single Particle Structure of the neutron-rich Sodium Isotopes $^{27-31}\\!$Na

CERN Document Server

2002-01-01

We propose to study the single particle structure of the neutron-rich isotopes $^{27-31}\\!$Na. These isotopes will be investigated via neutron pickup reactions in inverse kinematics on a deuterium and a beryllium target. Scattered beam particles and transfer products are detected in a position sensitive detector located around 0$^\\circ$. De-excitation $\\gamma$-rays emitted after an excited state has been populated will be registered by the MINIBALL Germanium array. The results will shed new light on the structure of the neutron-rich sodium isotopes and especially on the region of strong deformation around the N=20 nucleus $^{31}\\!$Na.

Emulsification in binary liquids containing colloidal particles: a structure-factor analysis

International Nuclear Information System (INIS)

Thijssen, Job H J; Clegg, Paul S

2010-01-01

We present a quantitative confocal-microscopy study of the transient and final microstructure of particle-stabilized emulsions formed via demixing in a binary liquid. To this end, we have developed an image-analysis method that relies on structure factors obtained from discrete Fourier transforms of individual frames in confocal image sequences. Radially averaging the squared modulus of these Fourier transforms before peak fitting allows extraction of dominant length scales over the entire temperature range of the quench. Our procedure even yields information just after droplet nucleation, when the (fluorescence) contrast between the two separating phases is scarcely discernible in the images. We find that our emulsions are stabilized on experimental timescales by interfacial particles and that they are likely to have bimodal droplet-size distributions. We attribute the latter to coalescence together with creaming being the main coarsening mechanism during the late stages of emulsification and we support this claim with (direct) confocal-microscopy observations. In addition, our results imply that the observed droplets emerge from particle-promoted nucleation, possibly followed by a free-growth regime. Finally, we argue that creaming strongly affects droplet growth during the early stages of emulsification. Future investigations could clarify the link between quench conditions and resulting microstructure, paving the way for tailor-made particle-stabilized emulsions from binary liquids.

Study of nanoscale structural biology using advanced particle beam microscopy

Science.gov (United States)

Boseman, Adam J.

This work investigates developmental and structural biology at the nanoscale using current advancements in particle beam microscopy. Typically the examination of micro- and nanoscale features is performed using scanning electron microscopy (SEM), but in order to decrease surface charging, and increase resolution, an obscuring conductive layer is applied to the sample surface. As magnification increases, this layer begins to limit the ability to identify nanoscale surface structures. A new technology, Helium Ion Microscopy (HIM), is used to examine uncoated surface structures on the cuticle of wild type and mutant fruit flies. Corneal nanostructures observed with HIM are further investigated by FIB/SEM to provide detailed three dimensional information about internal events occurring during early structural development. These techniques are also used to reconstruct a mosquito germarium in order to characterize unknown events in early oogenesis. Findings from these studies, and many more like them, will soon unravel many of the mysteries surrounding the world of developmental biology.

Particle transport across a circular shear layer with coherent structures

International Nuclear Information System (INIS)

Nielsen, A.H.; Lynov, J.P.; Juul Rasmussen, J.

1998-01-01

In the study of the dynamics of coherent structures, forced circular shear flows offer many desirable features. The inherent quantisation of circular geometries due to the periodic boundary conditions makes it possible to design experiments in which the spatial and temporal complexity of the coherent structures can be accurately controlled. Experiments on circular shear flows demonstrating the formation of coherent structures have been performed in different physical systems, including quasi-neutral plasmas, non-neutral plasmas and rotating fluids. In this paper we investigate the evolution of such coherent structures by solving the forced incompressible Navier-Stokes equations numerically using a spectral code. The model is formulated in the context of a rotating fluid but apply equally well to low frequency electrostatic oscillations in a homogeneous magnetized plasma. In order to reveal the Lagrangian properties of the flow and in particular to investigate the transport capacity in the shear layer, passive particles are traced by the velocity field. (orig.)

Modeling the fusion of cylindrical bioink particles in post bioprinting structure formation

Science.gov (United States)

McCune, Matt; Shafiee, Ashkan; Forgacs, Gabor; Kosztin, Ioan

2015-03-01

Cellular Particle Dynamics (CPD) is an effective computational method to describe the shape evolution and biomechanical relaxation processes in multicellular systems. Thus, CPD is a useful tool to predict the outcome of post-printing structure formation in bioprinting. The predictive power of CPD has been demonstrated for multicellular systems composed of spherical bioink units. Experiments and computer simulations were related through an independently developed theoretical formalism based on continuum mechanics. Here we generalize the CPD formalism to (i) include cylindrical bioink particles often used in specific bioprinting applications, (ii) describe the more realistic experimental situation in which both the length and the volume of the cylindrical bioink units decrease during post-printing structure formation, and (iii) directly connect CPD simulations to the corresponding experiments without the need of the intermediate continuum theory inherently based on simplifying assumptions. Work supported by NSF [PHY-0957914]. Computer time provided by the University of Missouri Bioinformatics Consortium.

Morphology and nano-structure analysis of soot particles sampled from high pressure diesel jet flames under diesel-like conditions

Science.gov (United States)

Jiang, Hao; Li, Tie; Wang, Yifeng; He, Pengfei

2018-04-01

Soot particles emitted from diesel engines have a significant impact on the atmospheric environment. Detailed understanding of soot formation and oxidation processes is helpful for reducing the pollution of soot particles, which requires information such as the size and nano-structure parameters of the soot primary particles sampled in a high-temperature and high-pressure diesel jet flame. Based on the thermophoretic principle, a novel sampling probe minimally disturbing the diesel jet flame in a constant volume combustion vessel is developed for analysing soot particles. The injected quantity of diesel fuel is less than 10 mg, and the soot particles sampled by carriers with a transmission electron microscope (TEM) grid and lacey TEM grid can be used to analyse the morphologies of soot aggregates and the nano-structure of the soot primary particles, respectively. When the quantity of diesel fuel is more than 10 mg, in order to avoid burning-off of the carriers in higher temperature and pressure conditions, single-crystal silicon chips are employed. Ultrasonic oscillations and alcohol extraction are then implemented to obtain high quality soot samples for observation using a high-resolution transmission electron microscope. An in-house Matlab-based code is developed to extract the nano-structure parameters of the soot particles. A complete sampling and analysis procedure of the soot particles is provided to study the formation and oxidation mechanism of soot.

Incremental discovery of hidden structure: Applications in theory of elementary particles

International Nuclear Information System (INIS)

Zytkow, J.M.; Fischer, P.J.

1996-01-01

Discovering hidden structure is a challenging, universal research task in Physics, Chemistry, Biology, and other disciplines. Not only must the elements of hidden structure be postulated by the discoverer, but they can only be verified by indirect evidence, at the level of observable objects. In this paper we describe a framework for hidden structure discovery, built on a constructive definition of hidden structure. This definition leads to operators that build models of hidden structure step by step, postulating hidden objects, their combinations and properties, reactions described in terms of hidden objects, and mapping between the hidden and the observed structure. We introduce the operator dependency diagram, which shows the order of operator application and model evaluation. Different observational knowledge supports different evaluation criteria, which lead to different search systems with verifiable sequences of operator applications. Isomorph-free structure generation is another issue critical for efficiency of search. We apply our framework in the system GELL-MANN, that hypothesizes hidden structure for elementary particles and we present the results of a large scale search for quark models

CONDENSED MATTER: STRUCTURE, THERMAL AND MECHANICAL PROPERTIES: Pair interaction of bilayer-coated nanoscopic particles

Science.gov (United States)

Zhang, Qi-Yi

2009-02-01

The pair interaction between bilayer membrane-coated nanosized particles has been explored by using the self-consistent field (SCF) theory. The bilayer membranes are composed of amphiphilic polymers. For different system parameters, the pair-interaction free energies are obtained. Particular emphasis is placed on the analysis of a sequence of structural transformations of bilayers on spherical particles, which occur during their approaching processes. For different head fractions of amphiphiles, the asymmetrical morphologies between bilayers on two particles and the inverted micellar intermediates have been found in the membrane fusion pathway. These results can benefit the fabrication of vesicles as encapsulation vectors for drug and gene delivery.

Layer-by-layer assembly of patchy particles as a route to nontrivial structures

Science.gov (United States)

Patra, Niladri; Tkachenko, Alexei V.

2017-08-01

We propose a strategy for robust high-quality self-assembly of nontrivial periodic structures out of patchy particles and investigate it with Brownian dynamics simulations. Its first element is the use of specific patch-patch and shell-shell interactions between the particles, which can be implemented through differential functionalization of patched and shell regions with specific DNA strands. The other key element of our approach is the use of a layer-by-layer protocol that allows one to avoid the formation of undesired random aggregates. As an example, we design and self-assemble in silico a version of a double diamond lattice in which four particle types are arranged into bcc crystal made of four fcc sublattices. The lattice can be further converted to cubic diamond by selective removal of the particles of certain types. Our results demonstrate that by combining the directionality, selectivity of interactions, and the layer-by-layer protocol, a high-quality robust self-assembly can be achieved.

Structure and phase transition of BiFeO3 cubic micro-particles prepared by hydrothermal method

International Nuclear Information System (INIS)

Zhou, Jian-Ping; Yang, Ruo-Lin; Xiao, Rui-Juan; Chen, Xiao-Ming; Deng, Chao-Yong

2012-01-01

Graphical abstract: Bismuth ferrite (BiFeO 3 ) cubic micro-particles with smooth surfaces were synthesized. BiFeO 3 has a hexagonal perovskite structure with a space group R3c below 370 °C and rhombohedral perovskite structure with a space group R3m below 755 °C, undergoes a phase transition in the temperature range of 755–817 °C to a cubic structure, then decompose to liquid and Fe 2 O 3 above 939 °C. Highlights: ► BiFeO 3 micro-particles with smooth surface were synthesized by hydrothermal method. ► BiFeO 3 enjoys hexagonal structure with well element ratio and chemical valence. ► BiFeO 3 transition from rhombohedral phase to cubic phase lasts 60 °C. -- Abstract: Single-phase bismuth ferrite (BiFeO 3 ) powders were synthesized with a hydrothermal method by controlling the experimental conditions carefully. The powder structure, morphology and composition were characterized by using X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscope, Raman measurement and X-ray photoelectron spectroscopy. The particles change from irregular agglomerations to regular cubes with increasing KOH concentration. The large BiFeO 3 cubic particles enjoy much smooth surfaces with well-matched element ratio (Bi:Fe:O = 1:1:3) and chemical valence (Bi 3+ , Fe 3+ and O 2− ). The high temperature XRD and differential scanning calorimetry show that BiFeO 3 powders have a hexagonal perovskite structure with a space group R3c below 370 °C and a rhombohedral structure with a space group R3m below 755 °C. BiFeO 3 undergoes a phase transition in the temperature range of 755–817 °C from rhombohedral structure to a cubic phase, then decomposes to liquid and Fe 2 O 3 above 939 °C.

Geochemically structural characteristics of municipal solid waste incineration fly ash particles and mineralogical surface conversions by chelate treatment.

Science.gov (United States)

Kitamura, Hiroki; Sawada, Takaya; Shimaoka, Takayuki; Takahashi, Fumitake

2016-01-01

Leaching behaviors of heavy metals contained in municipal solid waste incineration (MSWI) fly ash have been studied well. However, micro-characteristics of MSWI fly ash particles are still uncertain and might be non-negligible to describe their leaching behaviors. Therefore, this study investigated micro-characteristics of MSWI fly ash particles, especially their structural properties and impacts of chelate treatment on surface characteristics. According to SEM observations, raw fly ash particles could be categorized into four types based on their shapes. Because chelate treatment changed the surface of fly ash particles dramatically owing to secondary mineral formations like ettringite, two more types could be categorized for chelate-treated fly ash particles. Acid extraction experiments suggest that fly ash particles, tested in this study, consist of Si-base insoluble core structure, Al/Ca/Si-base semi-soluble matrices inside the body, and KCl/NaCl-base soluble aggregates on the surface. Scanning electron microscope (SEM) observations of the same fly ash particles during twice moistening treatments showed that KCl/NaCl moved under wet condition and concentrated at different places on the particle surface. However, element mobility depended on secondary mineral formations. When insoluble mineral like gypsum was generated and covered the particle surface, it inhibited element transfer under wet condition. Surface characteristics including secondary mineral formation of MSWI fly ash particles are likely non-negligible to describe trace element leaching behaviors.

Micrometer-sized Water Ice Particles for Planetary Science Experiments: Influence of Surface Structure on Collisional Properties

Science.gov (United States)

Gaertner, Sabrina; Gundlach, Bastian; Headen, Thomas F.; Ratte, Judy; Oesert, Joachim; Gorb, Stanislav N.; Youngs, Tristan G. A.; Bowron, Daniel T.; Blum, Jürgen; Fraser, Helen

2018-06-01

Models and observations suggest that particle aggregation at and beyond the snowline is aided by water ice. As icy particles play such a crucial role in the earliest stages of planet formation, many laboratory studies have exploited their collisional properties across a wide range of parameters (particle size, impact velocity, temperature T, and pressure P).However, not all of these parameters have always been varied systematically, leading to apparently contradictory results on collision outcomes. Previous experiments only agreed that a temperature dependence set in above ≈210 K. Open questions remain as to what extent the structural properties of the particles themselves dictate collision outcomes. The P–T gradients in protoplanetary disks mean that the ices are constantly processed, undergoing phase changes between different solid phases and the gas phase. To understand how effectively collision experiments reproduce protoplanetary disk conditions, environmental impacts on particle structure need to be investigated.We characterized the bulk and surface structure of icy particles used in collision experiments, exploiting the unique capabilities of the NIMROD neutron scattering instrument. Varying temperature at a constant pressure of around 30 mbar, we studied structural alterations to determine which of the observed properties matches the temperature dependencies observed in collisional behaviour.Our icy grains are formed under liquid nitrogen and heated from 103 to 247 K. As a result, they undergo changes in the crystalline ice-phase, sublimation, sintering and surface pre-melting. An increase in the thickness of the diffuse surface layer from ≈10 to ≈30 Å (≈2.5 to 12 bilayers) suggests increased molecular mobility at temperatures above ≈210 K.Because none of the other changes ties in with the temperature trends in collisional outcomes, we conclude that the diffuse interface plays a key role in collision experiments at these temperatures

The research of structural features of astralens - nanodimensional carbon particles of fulleroid type

International Nuclear Information System (INIS)

Ponomarev, A.N.; Nikitin, V.A.; Rybalko, V.V.

2006-01-01

The article is focused on the research of structural features of astralens - nanodimensional carbonic particles of fulleroid type. Astralens are perspective nanomodificators of properties of materials of different types. The potentials os astralens as modificators depend on their characteristic structural features, and in the first place, on the distribution of nanoparticles by sizes. The typical dimensions of astralens are determined to be within the range of 15-75 nm [ru

Flocculation - Formation and structure of aggregates composed of polyelectrolyte chains and clay colloidal particles

OpenAIRE

Sakhawoth , Yasine

2017-01-01

Flocculation is a key process in numerous environmental and industrial technologies such as purification of waste-water or paper making. It is necessary to understand the formation and structure of the aggregates to control and optimize such a process. Most of the studies on flocculation involve spherical particles, but there is a clear need to understand the flocculation of anisotropic particles such as clay colloids, which are platelets. I studied the flocculation of montmorillonite clay su...

Nuclear structure near the particle drip-lines and explosive nucleosynthesis processes

International Nuclear Information System (INIS)

Kratz, K.L.; Pfeiffer, B.; Moeller, P.; Thielemann, F.K.; Wiescher, M.

1999-01-01

In this paper, we discuss the nuclear physics input for a selected set of explosive nucleosynthesis scenarios leading to rapid proton-- and neutron--capture processes. Observables (like e.g. luminosity curves or elemental abundance distributions) witness the interplay between nuclear structure aspects near the particle drip-lines and the appropriate astrophysical environments, and can give guidance to and constraints on stellar conditions and the associated nucleosynthesis. (authors)

Morphology of Nano and Micro Fiber Structures in Ultrafine Particles Filtration

International Nuclear Information System (INIS)

Kimmer, Dusan; Vincent, Ivo; Fenyk, Jan; Petras, David; Zatloukal, Martin; Sambaer, Wannes; Zdimal, Vladimir

2011-01-01

Selected procedures permitting to prepare homogeneous nanofibre structures of the desired morphology by employing a suitable combination of variables during the electrospinning process are presented. A comparison (at the same pressure drop) was made of filtration capabilities of planar polyurethane nanostructures formed exclusively by nanofibres, space polycarbonate nanostructures having bead spacers, structures formed by a combination of polymethyl methacrylate micro- and nanofibres and polypropylene meltblown microstructures, through which ultrafine particles of ammonium sulphate 20-400 nm in size were filtered. The structures studied were described using a new digital image analysis technique based on black and white images obtained by scanning electron microscopy. More voluminous structures modified with distance microspheres and having a greater thickness and mass per square area of the material, i.e. structures possessing better mechanical properties, demanded so much in nanostructures, enable preparation of filters having approximately the same free volume fraction as flat nanofibre filters but an increased effective fibre surface area, changed pore size morphology and, consequently, a higher filter quality.

Advances in computational dynamics of particles, materials and structures a unified approach

CERN Document Server

Har, Jason

2012-01-01

Computational methods for the modeling and simulation of the dynamic response and behavior of particles, materials and structural systems have had a profound influence on science, engineering and technology. Complex science and engineering applications dealing with complicated structural geometries and materials that would be very difficult to treat using analytical methods have been successfully simulated using computational tools. With the incorporation of quantum, molecular and biological mechanics into new models, these methods are poised to play an even bigger role in the future. Ad

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

Science.gov (United States)

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).

Synthesis, structural characterization and in vitro testing of dysprosium containing silica particles as potential MRI contrast enhancing agents

International Nuclear Information System (INIS)

Chiriac, L.B.; Trandafir, D.L.; Turcu, R.V.F.; Todea, M.; Simon, S.

2016-01-01

Highlights: • Dysprosium containing silica microparticles obtained by freeze and spray drying. • Higher structural units interconnection achieved in freeze vs. spray dried samples. • Dy occurance on the outermost layer of the microparticles evidenced by XPS. • Enhanced MRI contrast observed for freeze dried samples with 5% mol Dy_2O_3. - Abstract: The work is focused on synthesis and structural characterization of novel dysprosium-doped silica particles which could be considered as MRI contrast agents. Sol-gel derived silica rich particles obtained via freeze-drying and spray-drying processing methods were structurally characterized by XRD, "2"9Si MAS-NMR and XPS methods. The occurrence of dysprosium on the outermost layer of dysprosium containing silica particles was investigated by XPS analysis. The MRI contrast agent characteristics have been tested using RARE-T_1 and RARE-T_2 protocols. The contrast of MRI images delivered by the investigated samples was correlated with their local structure. Dysprosium disposal on microparticles with surface structure characterised by decreased connectivity of the silicate network units favours dark T_2-weighted MRI contrast properties.

Predictive modeling of multicellular structure formation by using Cellular Particle Dynamics simulations

Science.gov (United States)

McCune, Matthew; Shafiee, Ashkan; Forgacs, Gabor; Kosztin, Ioan

2014-03-01

Cellular Particle Dynamics (CPD) is an effective computational method for describing and predicting the time evolution of biomechanical relaxation processes of multicellular systems. A typical example is the fusion of spheroidal bioink particles during post bioprinting structure formation. In CPD cells are modeled as an ensemble of cellular particles (CPs) that interact via short-range contact interactions, characterized by an attractive (adhesive interaction) and a repulsive (excluded volume interaction) component. The time evolution of the spatial conformation of the multicellular system is determined by following the trajectories of all CPs through integration of their equations of motion. CPD was successfully applied to describe and predict the fusion of 3D tissue construct involving identical spherical aggregates. Here, we demonstrate that CPD can also predict tissue formation involving uneven spherical aggregates whose volumes decrease during the fusion process. Work supported by NSF [PHY-0957914]. Computer time provided by the University of Missouri Bioinformatics Consortium.

General structure of a two-body operator for spin-(1/2) particles

International Nuclear Information System (INIS)

Ershov, S.N.

2004-01-01

A direct derivation of the operator structure for two spin-(1/2) particles is presented subject to invariance under basic symmetries and Galilean frame transformation. The partial wave decomposition for coefficient functions, valid on- and off-shell, is explicitly deduced. The momentum transfer representation and angular momentum decomposition for general spin-dependent potentials are obtained

Horizon structure of rotating Bardeen black hole and particle acceleration

International Nuclear Information System (INIS)

Ghosh, Sushant G.; Amir, Muhammed

2015-01-01

We investigate the horizon structure and ergosphere in a rotating Bardeen regular black hole, which has an additional parameter (g) due to the magnetic charge, apart from the mass (M) and the rotation parameter (a). Interestingly, for each value of the parameter g, there exists a critical rotation parameter (a = a E ), which corresponds to an extremal black hole with degenerate horizons, while for a < a E it describes a non-extremal black hole with two horizons, and no black hole for a > a E . We find that the extremal value a E is also influenced by the parameter g, and so is the ergosphere. While the value of a E remarkably decreases when compared with the Kerr black hole, the ergosphere becomes thicker with the increase in g.We also study the collision of two equal mass particles near the horizon of this black hole, and explicitly show the effect of the parameter g. The center-of-mass energy (E CM ) not only depend on the rotation parameter a, but also on the parameter g. It is demonstrated that the E CM could be arbitrarily high in the extremal cases when one of the colliding particles has a critical angular momentum, thereby suggesting that the rotating Bardeen regular black hole can act as a particle accelerator. (orig.)

Structure and phase transition of BiFeO{sub 3} cubic micro-particles prepared by hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Zhou, Jian-Ping, E-mail: zhoujp@snnu.edu.cn [College of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062 (China); Yang, Ruo-Lin; Xiao, Rui-Juan; Chen, Xiao-Ming [College of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062 (China); Deng, Chao-Yong [Department of Electronic Science, Guizhou University, Guizhou Guiyang 550025 (China)

2012-11-15

Graphical abstract: Bismuth ferrite (BiFeO{sub 3}) cubic micro-particles with smooth surfaces were synthesized. BiFeO{sub 3} has a hexagonal perovskite structure with a space group R3c below 370 °C and rhombohedral perovskite structure with a space group R3m below 755 °C, undergoes a phase transition in the temperature range of 755–817 °C to a cubic structure, then decompose to liquid and Fe{sub 2}O{sub 3} above 939 °C. Highlights: ► BiFeO{sub 3} micro-particles with smooth surface were synthesized by hydrothermal method. ► BiFeO{sub 3} enjoys hexagonal structure with well element ratio and chemical valence. ► BiFeO{sub 3} transition from rhombohedral phase to cubic phase lasts 60 °C. -- Abstract: Single-phase bismuth ferrite (BiFeO{sub 3}) powders were synthesized with a hydrothermal method by controlling the experimental conditions carefully. The powder structure, morphology and composition were characterized by using X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscope, Raman measurement and X-ray photoelectron spectroscopy. The particles change from irregular agglomerations to regular cubes with increasing KOH concentration. The large BiFeO{sub 3} cubic particles enjoy much smooth surfaces with well-matched element ratio (Bi:Fe:O = 1:1:3) and chemical valence (Bi{sup 3+}, Fe{sup 3+} and O{sup 2−}). The high temperature XRD and differential scanning calorimetry show that BiFeO{sub 3} powders have a hexagonal perovskite structure with a space group R3c below 370 °C and a rhombohedral structure with a space group R3m below 755 °C. BiFeO{sub 3} undergoes a phase transition in the temperature range of 755–817 °C from rhombohedral structure to a cubic phase, then decomposes to liquid and Fe{sub 2}O{sub 3} above 939 °C.

Sintering of Spherical Particles of Equal and Different Size Arranged in a Body Centered Cubic Structure

DEFF Research Database (Denmark)

Redanz, Pia; McMeeking, R. M.

2003-01-01

Solid-state sintering of a bcc structure of spherical particles has been studied numerically by use of simple shape parameters to describe the state of the unit cell. Both free and pressure-assisted sintering of particles of equal and different sizes for various ratios of boundary and surface dif......, different dihedral angles and the evolution of relative density and sintering stresses are studied....

The effect of the electronic structure, phase transition, and localized dynamics of atoms in the formation of tiny particles of gold

Energy Technology Data Exchange (ETDEWEB)

Ali, Mubarak, E-mail: mubarak74@comsats.edu.pk, E-mail: mubarak74@mail.com [COMSATS Institute of Information Technology, Department of Physics (Pakistan); Lin, I-Nan [Tamkang University, Department of Physics (China)

2017-01-15

In addition to self-governing properties, tiny-sized particles of metallic colloids are the building blocks of large-sized particles; thus, their study has been the subject of a large number of publications. In the present work, it has been discussed that geometry structure of tiny particle made through atom-to-atom amalgamation depends on attained dynamics of gold atoms along with protruded orientations. The localized process conditions direct two-dimensional structure of a tiny particle at atomically flat air-solution interface while heating locally dynamically approached atoms, thus, negate the role of van der Waals interactions. At electronphoton-solution interface, impinging electrons stretch or deform atoms of tiny particles depending on the mechanism of impingement. In addition, to strike regular grid of electrons ejected on split of atoms not executing excitations and de-excitations of their electrons, atoms of tiny particles also deform or stretch while occupying various sites depending on the process of synergy. Under suitable impinging electron streams, those tiny particles in monolayer two-dimensional structure electron states of their atoms are diffused in the direction of transferred energy, thus, coincide to the next adjacent atoms in each one-dimensional array dealing the same sort of behavior. Instantaneously, photons of adequate energy propagate on the surfaces of such electronic structures and modify those into smooth elements, thus, disregard the phenomenon of localized surface plasmons. This study highlights the fundamental process of formation of tiny particles where the role of localized dynamics of atoms and their electronic structure along with interaction to light are discussed. Such a tool of processing materials, in nonequilibrium pulse-based process, opens a number of possibilities to develop engineered materials with specific chemical, optical, and electronic properties.

Synthesis, structural characterization and in vitro testing of dysprosium containing silica particles as potential MRI contrast enhancing agents

Energy Technology Data Exchange (ETDEWEB)

Chiriac, L.B.; Trandafir, D.L. [Faculty of Physics & National Magnetic Resonance Center, Babeş-Bolyai University, Cluj-Napoca, RO-400084 (Romania); Interdisciplinary Research Institute on Bio-Nano-Sciences & Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca, RO-400084 (Romania); Turcu, R.V.F. [Faculty of Physics & National Magnetic Resonance Center, Babeş-Bolyai University, Cluj-Napoca, RO-400084 (Romania); Todea, M. [Interdisciplinary Research Institute on Bio-Nano-Sciences & Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca, RO-400084 (Romania); Simon, S., E-mail: simons@phys.ubbcluj.ro [Faculty of Physics & National Magnetic Resonance Center, Babeş-Bolyai University, Cluj-Napoca, RO-400084 (Romania); Interdisciplinary Research Institute on Bio-Nano-Sciences & Faculty of Physics, Babeş-Bolyai University, Cluj-Napoca, RO-400084 (Romania)

2016-11-01

Highlights: • Dysprosium containing silica microparticles obtained by freeze and spray drying. • Higher structural units interconnection achieved in freeze vs. spray dried samples. • Dy occurance on the outermost layer of the microparticles evidenced by XPS. • Enhanced MRI contrast observed for freeze dried samples with 5% mol Dy{sub 2}O{sub 3}. - Abstract: The work is focused on synthesis and structural characterization of novel dysprosium-doped silica particles which could be considered as MRI contrast agents. Sol-gel derived silica rich particles obtained via freeze-drying and spray-drying processing methods were structurally characterized by XRD, {sup 29}Si MAS-NMR and XPS methods. The occurrence of dysprosium on the outermost layer of dysprosium containing silica particles was investigated by XPS analysis. The MRI contrast agent characteristics have been tested using RARE-T{sub 1} and RARE-T{sub 2} protocols. The contrast of MRI images delivered by the investigated samples was correlated with their local structure. Dysprosium disposal on microparticles with surface structure characterised by decreased connectivity of the silicate network units favours dark T{sub 2}-weighted MRI contrast properties.

Space-time structure of particle production in high-energy heavy-ion collisions

Energy Technology Data Exchange (ETDEWEB)

Ohtsuka, Naohiko; Ohnishi, Akira [Hokkaido Univ., Sapporo (Japan); Nara, Yasushi; Maruyama, Tomoyuki

1998-07-01

Space-Time structure of freeze-out of produced particles in relativistic nucleus-nucleus collisions are studied in the framework of two different cascade models, either with or without higher baryonic resonances. While higher excited baryonic resonances do not influence the spatial source size of freeze-out point, the freeze-out time distribution is shifted to be later by these resonances. (author)

Three Dimensional Characterization of Typical Urban and Desert Particles: Implications to Particle Optics

Science.gov (United States)

Goel, V.; Mishra, S.; Ahlawat, A. S.; Sharma, C.; Kotnala, R. K.

2017-12-01

Aerosol particles are generally considered as chemically homogeneous spheres in the retrieval techniques of ground and space borne observations which is not accurate approach and can lead to erroneous observations. For better simulation of optical and radiative properties of aerosols, a good knowledge of aerosol's morphology, chemical composition and internal structure is essential. Till date, many studies have reported the morphology and chemical composition of particles but very few of them provide internal structure and spatial distribution of different chemical species within the particle. The research on the effect of particle internal structure and its contribution to particle optics is extremely limited. In present work, we characterize the PM10 particles collected form typical arid (the Thar Desert, Rajasthan, India) and typical urban (New Delhi, India) environment using microscopic techniques. The particles were milled several times to investigate their internal structure. The EDS (Energy Dispersive X-ray Spectroscopy) spectra were recorded after each milling to check the variation in the chemical composition. In arid environment, Fe, Ca, C, Al, and Mg rich shell was observed over a Si rich particle whereas in urban environment, shell of Hg, Ag, C and N was observed over a Cu rich particle. Based on the observations, different model shapes [homogenous sphere and spheroid; heterogeneous sphere and spheroid; core shell] have been considered for assessing the associated uncertainties with the routine modeling of optical properties where volume equivalent homogeneous sphere approximation is considered. The details will be discussed during presentation.

Structural Changes and Material Transport in Al2O3-Supported Cu/Fe Spinel Particles in a Simulated Chemical Looping Combustion Environment

Science.gov (United States)

Nealley, W. H. Harrison; Nakano, Anna; Nakano, Jinichiro; Bennett, James P.

2018-05-01

Alumina-supported Cu/Fe spinel particles were exposed to oxidation/reduction atmospheres at 800°C. Structural changes of the particles subjected to gas cycles between air and 10 vol.% CO-90 vol.% Ar were studied from physical data and real-time images collected using a confocal scanning laser microscope equipped with a heating chamber. Overall particle volume slowly expanded with cycles while surface roughness decreased. Cross-sections of the exposed particles showed segregation of Cu and Fe to the edges of inner grains, which may have acted as oxygen carriers during the exposures. The particles remained whole during the cyclic exposures without any noticeable structural breakdown.

Structural characterizaiton and gas reactions of small metal particles by high-resolution, in-situ TEM and TED

Science.gov (United States)

1984-01-01

The existing in-situ transmission electron microscopy (TEM) facility was improved by adding a separately pumped mini-specimen chamber. The chamber contains wire-evaporation sources for three metals and a specimen heater for moderate substrate temperatures. A sample introduction device was constructed, installed, and tested, facilitating rapid introduction of a specimen into the mini-chamber while maintaining the background pressure in that chamber in the 10(-9) millibar range. Small particles and clusters of Pd, grown by deposition from the vapor phase in an in-situ TEM facility on amorphous and crystalline support films of alumina and on ultra-thin carbon films, were analyzed by conventional high-resolution TEM and image analysis in terms of detectability, number density, and size distribution. The smallest particles that could be detected and counted contained no more than 6 atoms; size determinations could be made for particles 1 nm in diameter. The influence of various oxygen plasma treatments, annealing treatments, and of increasing the substrate temperature during deposition was investigated. The TEM technique was employed to demonstrate that under otherwise identica l conditions the lattice parameter of Pd particles in the 1 to 2 nm size range and supported in random orientation on ex-situ prepared mica films is expanded by some 3% when compared to 5 nm size particles. It is believed that this expansion is neither a small-particle diffraction effect nor due to pseudomorphism, but that it is due to a annealing-induced transformation of the small as-deposited particles with predominantly composite crystal structures into larger particles with true f.c.c. structure and thus inherently smaller lattice parameter.

Charge neutrality of fine particle (dusty) plasmas and fine particle cloud under gravity

Energy Technology Data Exchange (ETDEWEB)

Totsuji, Hiroo, E-mail: totsuji-09@t.okadai.jp

2017-03-11

The enhancement of the charge neutrality due to the existence of fine particles is shown to occur generally under microgravity and in one-dimensional structures under gravity. As an application of the latter, the size and position of fine particle clouds relative to surrounding plasmas are determined under gravity. - Highlights: • In fine particle (dusty) plasmas, the charge neutrality is much enhanced by the existence of fine particles. • The enhancement of charge neutrality generally occurs under microgravity and gravity. • Structure of fine particle clouds under gravity is determined by applying the enhanced charge neutrality.

PART 2: LARGE PARTICLE MODELLING Simulation of particle filtration processes in deformable media

Directory of Open Access Journals (Sweden)

Gernot Boiger

2008-06-01

Full Text Available In filtration processes it is necessary to consider both, the interaction of thefluid with the solid parts as well as the effect of particles carried in the fluidand accumulated on the solid. While part 1 of this paper deals with themodelling of fluid structure interaction effects, the accumulation of dirtparticles will be addressed in this paper. A closer look is taken on theimplementation of a spherical, LAGRANGIAN particle model suitable forsmall and large particles. As dirt accumulates in the fluid stream, it interactswith the surrounding filter fibre structure and over time causes modificationsof the filter characteristics. The calculation of particle force interactioneffects is necessary for an adequate simulation of this situation. A detailedDiscrete Phase Lagrange Model was developed to take into account thetwo-way coupling of the fluid and accumulated particles. The simulation oflarge particles and the fluid-structure interaction is realised in a single finitevolume flow solver on the basis of the OpenSource software OpenFoam.

Test-particle motion in Einstein's unified field theory. III. Magnetic monopoles and charged particles

International Nuclear Information System (INIS)

Johnson, C.R.

1986-01-01

In a previous paper (paper I), we developed a method for finding the exact equations of structure and motion of multipole test particles in Einstein's unified field theory: the theory of the nonsymmetric field. In that paper we also applied the method and found in Einstein's unified field theory the equations of structure and motion of neutral pole-dipole test particles possessing no electromagnetic multipole moments. In a second paper (paper II), we applied the method and found in Einstein's unified field theory the exact equations of structure and motion of charged test particles possessing no magnetic monopole moments. In the present paper (paper III), we apply the method and find in Einstein's unified field theory the exact equations of structure and motion of charged test particles possessing magnetic monopole moments. It follows from the form of these equations of structure and motion that in general in Einstein's unified field theory a test particle possessing a magnetic monopole moment in a background electromagnetic field must also possess spin

Quantitative structure-activity relationships for green algae growth inhibition by polymer particles.

Science.gov (United States)

Nolte, Tom M; Peijnenburg, Willie J G M; Hendriks, A Jan; van de Meent, Dik

2017-07-01

After use and disposal of chemical products, many types of polymer particles end up in the aquatic environment with potential toxic effects to primary producers like green algae. In this study, we have developed Quantitative Structure-Activity Relationships (QSARs) for a set of highly structural diverse polymers which are capable to estimate green algae growth inhibition (EC50). The model (N = 43, R 2  = 0.73, RMSE = 0.28) is a regression-based decision tree using one structural descriptor for each of three polymer classes separated based on charge. The QSAR is applicable to linear homo polymers as well as copolymers and does not require information on the size of the polymer particle or underlying core material. Highly branched polymers, non-nitrogen cationic polymers and polymeric surfactants are not included in the model and thus cannot be evaluated. The model works best for cationic and non-ionic polymers for which cellular adsorption, disruption of the cell wall and photosynthesis inhibition were the mechanisms of action. For anionic polymers, specific properties of the polymer and test characteristics need to be known for detailed assessment. The data and QSAR results for anionic polymers, when combined with molecular dynamics simulations indicated that nutrient depletion is likely the dominant mode of toxicity. Nutrient depletion in turn, is determined by the non-linear interplay between polymer charge density and backbone flexibility. Copyright © 2017 Elsevier Ltd. All rights reserved.

Calculated high-pressure structural properties, lattice dynamics and quasi particle band structures of perovskite fluorides KZnF3, CsCaF3 and BaLiF3.

Science.gov (United States)

Vaitheeswaran, G; Kanchana, V; Zhang, Xinxin; Ma, Yanming; Svane, A; Christensen, N E

2016-08-10

A detailed study of the high-pressure structural properties, lattice dynamics and band structures of perovskite structured fluorides KZnF3, CsCaF3 and BaLiF3 has been carried out by means of density functional theory. The calculated structural properties including elastic constants and equation of state agree well with available experimental information. The phonon dispersion curves are in good agreement with available experimental inelastic neutron scattering data. The electronic structures of these fluorides have been calculated using the quasi particle self-consistent [Formula: see text] approximation. The [Formula: see text] calculations reveal that all the fluorides studied are wide band gap insulators, and the band gaps are significantly larger than those obtained by the standard local density approximation, thus emphasizing the importance of quasi particle corrections in perovskite fluorides.

Alpha-particle irradiation induced defects in SiO2 films of Si-SiO2 structures

International Nuclear Information System (INIS)

Koman, B.P.; Gal'chynskyy, O.V.; Kovalyuk, R.O.; Shkol'nyy, A.K.

1996-01-01

The aim of the work was to investigate alpha-particle irradiation induced defects in Si-SiO 2 structures by means of the thermostimulated discharge currents (TSDC) analysis. The object of investigation were (p-Si)-SiO 2 structures formed by a combined oxidation of the industrial p-Si wafers in dry and wet oxygen at temperature of 1150 C. The TSD currents were investigated in the temperature range between 90 and 500 K under linear heating rate. Pu 238 isotopes were the source of alpha-particles with an energy of 4-5 MeV and a density of 5.10 7 s -1 cm -2 . The TSD current curves show two peculiar maxima at about 370 and 480 K. Alpha-particle irradiation doesn't affect the general shape of the TSDC curves but leads to a shift of the maximum at 370 K and reduces the total electret charge which is accumulated in the Si-SiO 2 structures during polarization. The energy distribution function of the defects which are involved in SiO 2 polarization has been calculated. It showes that defects with activation energies of about 0.8 and 1.0 eV take part in forming the electret state, and these activation energies have certain energy distributions. It has been found that the TSDC maximum at 370 K has space charge nature and is caused by migration of hydrogen ions. In irradiated samples hydrogen and natrium ions localize on deeper trapping centres induced by alpha-particle irradiation. (orig.)

Budded baculovirus particle structure revisited

NARCIS (Netherlands)

Wang, Qiushi; Bosch, Berend-Jan; Vlak, Just M; van Oers, Monique M; Rottier, Peter J; van Lent, Jan W M

2015-01-01

Baculoviruses are a group of enveloped, double-stranded DNA insect viruses with budded (BV) and occlusion-derived (ODV) virions produced during their infection cycle. BVs are commonly described as rod shaped particles with a high apical density of protein extensions (spikes) on the lipid envelope

Novel fabrication techniques for low-mass composite structures in silicon particle detectors

Energy Technology Data Exchange (ETDEWEB)

Hartman, Neal, E-mail: neal.hartman@cern.ch; Silber, Joseph; Anderssen, Eric; Garcia-Sciveres, Maurice; Gilchriese, Murdock; Johnson, Thomas; Cepeda, Mario

2013-12-21

The structural design of silicon-based particle detectors is governed by competing demands of reducing mass while maximizing stability and accuracy. These demands can only be met by fiber reinforced composite laminates (CFRP). As detecting sensors and electronics become lower mass, the motivation to reduce structure as a proportion of overall mass pushes modern detector structures to the lower limits of composite ply thickness, while demanding maximum stiffness. However, classical approaches to composite laminate design require symmetric laminates and flat structures, in order to minimize warping during fabrication. This constraint of symmetry in laminate design, and a “flat plate” approach to fabrication, results in more massive structures. This study presents an approach to fabricating stable and accurate, geometrically complex composite structures by bonding warped, asymmetric, but ultra-thin component laminates together in an accurate tool, achieving final overall precision normally associated with planar structures. This technique has been used to fabricate a prototype “I-beam” that supports two layers of detecting elements, while being up to 20 times stiffer and up to 30% lower mass than comparable, independent planar structures (typically known as “staves”)

X-ray structure analyses of biological molecules and particles in Japan. A brief history and future prospect

International Nuclear Information System (INIS)

Nakasako, Masayoshi; Yamamoto, Masaki

2015-01-01

In Japan, X-ray structure analyses of molecules and particles from biology started in the 1970s. The structure analysis methods have been developed through the innovation of various techniques in advance, and have contributed for understanding the elementary and microscopic processes in life. Here we summarize briefly the history of X-ray structure analyses for structural biology in Japan and think about the prospect. (author)

Nonlocal transformation of the internal quantum particle structure

Directory of Open Access Journals (Sweden)

Alexey Yu. Samarin

2016-09-01

Full Text Available The analysis of the integral wave equation, having path integral kernel, has resulted, that collapse phenomenon is based on the nonlocal transformation of the internal structure of a quantum particle, considering in the form of the matter fields collection. This nonlocality allows to escape the contradiction between the reduction quantum mechanics postulate and special relativity. It is shown, that the wave function transformation, corresponding to von Neumann's reduction, has the deterministic nature and the quantum mechanics stochasticity is a consequence of a macroscopic measurer presence in the measuring process. Besides it is demonstrated, that the decogerence phenomenon has the same mechanism of the wave function transformation. EPR-type experiment is described in detail and the possibility of the faster-then light communication is proved, as well the possible rules of thumb of this communication are proposed.

Particle Shape Effect on Macroscopic Behaviour of Underground Structures: Numerical and Experimental Study

Directory of Open Access Journals (Sweden)

Szarf Krzysztof

2015-02-01

Full Text Available The mechanical performance of underground flexible structures such as buried pipes or culverts made of plastics depend not only on the properties of the structure, but also on the material surrounding it. Flexible drains can deflect by 30% with the joints staying tight, or even invert. Large deformations of the structure are difficult to model in the framework of Finite Element Method, but straightforward in Discrete Element Methods. Moreover, Discrete Element approach is able to provide information about the grain-grain and grain-structure interactions at the microscale. This paper presents numerical and experimental investigations of flexible buried pipe behaviour with focus placed on load transfer above the buried structure. Numerical modeling was able to reproduce the experimental results. Load repartition was observed, being affected by a number of factors such as particle shape, pipe friction and pipe stiffness.

Structural-Phase States of Fe-Cu and Fe-Ag Bimetallic Particles Produced by Electric Explosion of Two Wires

Science.gov (United States)

Lerner, M. I.; Bakina, O. V.; Pervikov, A. V.; Glazkova, E. A.; Lozhkomoev, A. S.; Vorozhtsov, A. B.

2018-05-01

X-ray phase analysis, transmission electron microscopy, and X-ray microanalysis were used to examine the structural-phase states of Fe-Cu and Fe-Ag bimetallic nanoparticles. The nanoparticles were obtained by the electric explosion of two twisted metal wires in argon atmosphere. It was demonstrated that the nanoparticles have the structure of Janus particles. Presence of the Janus particle structure in the samples indicates formation of binary melt under conditions of combined electric explosion of two wires. Phases based on supersaturated solid solutions were not found in the examined samples. The data obtained allow arguing that it is possible to achieve uniform mixing of the two-wire explosion products under the described experiment conditions.

Budded baculovirus particle structure revisited

NARCIS (Netherlands)

Wang, Qiushi; Bosch, Berend Jan; Vlak, J.M.; Oers, van M.M.; Rottier, P.J.; Lent, van J.W.M.

2016-01-01

Baculoviruses are a group of enveloped, double-stranded DNA insect viruses with budded (BV) and occlusion-derived (ODV) virions produced during their infection cycle. BVs are commonly described as rod shaped particles with a high apical density of protein extensions (spikes) on the lipid envelope

SIMULATIONS OF LATERAL TRANSPORT AND DROPOUT STRUCTURE OF ENERGETIC PARTICLES FROM IMPULSIVE SOLAR FLARES

Energy Technology Data Exchange (ETDEWEB)

Tooprakai, P. [Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Seripienlert, A.; Ruffolo, D.; Chuychai, P. [Thailand Center of Excellence in Physics, CHE, Ministry of Education, Bangkok 10400 (Thailand); Matthaeus, W. H., E-mail: david.ruf@mahidol.ac.th [Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

2016-11-10

We simulate trajectories of energetic particles from impulsive solar flares for 2D+slab models of magnetic turbulence in spherical geometry to study dropout features, i.e., sharp, repeated changes in the particle density. Among random-phase realizations of two-dimensional (2D) turbulence, a spherical harmonic expansion can generate homogeneous turbulence over a sphere, but a 2D fast Fourier transform (FFT) locally mapped onto the lateral coordinates in the region of interest is much faster computationally, and we show that the results are qualitatively similar. We then use the 2D FFT field as input to a 2D MHD simulation, which dynamically generates realistic features of turbulence such as coherent structures. The magnetic field lines and particles spread non-diffusively (ballistically) to a patchy distribution reaching up to 25° from the injection longitude and latitude at r ∼ 1 au. This dropout pattern in field line trajectories has sharper features in the case of the more realistic 2D MHD model, in better qualitative agreement with observations. The initial dropout pattern in particle trajectories is relatively insensitive to particle energy, though the energy affects the pattern’s evolution with time. We make predictions for future observations of solar particles near the Sun (e.g., at 0.25 au), for which we expect a sharp pulse of outgoing particles along the dropout pattern, followed by backscattering that first remains close to the dropout pattern and later exhibits cross-field transport to a distribution that is more diffusive, yet mostly contained within the dropout pattern found at greater distances.

SIMULATIONS OF LATERAL TRANSPORT AND DROPOUT STRUCTURE OF ENERGETIC PARTICLES FROM IMPULSIVE SOLAR FLARES

International Nuclear Information System (INIS)

Tooprakai, P.; Seripienlert, A.; Ruffolo, D.; Chuychai, P.; Matthaeus, W. H.

2016-01-01

We simulate trajectories of energetic particles from impulsive solar flares for 2D+slab models of magnetic turbulence in spherical geometry to study dropout features, i.e., sharp, repeated changes in the particle density. Among random-phase realizations of two-dimensional (2D) turbulence, a spherical harmonic expansion can generate homogeneous turbulence over a sphere, but a 2D fast Fourier transform (FFT) locally mapped onto the lateral coordinates in the region of interest is much faster computationally, and we show that the results are qualitatively similar. We then use the 2D FFT field as input to a 2D MHD simulation, which dynamically generates realistic features of turbulence such as coherent structures. The magnetic field lines and particles spread non-diffusively (ballistically) to a patchy distribution reaching up to 25° from the injection longitude and latitude at r ∼ 1 au. This dropout pattern in field line trajectories has sharper features in the case of the more realistic 2D MHD model, in better qualitative agreement with observations. The initial dropout pattern in particle trajectories is relatively insensitive to particle energy, though the energy affects the pattern’s evolution with time. We make predictions for future observations of solar particles near the Sun (e.g., at 0.25 au), for which we expect a sharp pulse of outgoing particles along the dropout pattern, followed by backscattering that first remains close to the dropout pattern and later exhibits cross-field transport to a distribution that is more diffusive, yet mostly contained within the dropout pattern found at greater distances.

Spatiotemporal Structure of Aeolian Particle Transport on Flat Surface

Science.gov (United States)

Niiya, Hirofumi; Nishimura, Kouichi

2017-05-01

We conduct numerical simulations based on a model of blowing snow to reveal the long-term properties and equilibrium state of aeolian particle transport from 10-5 to 10 m above the flat surface. The numerical results are as follows. (i) Time-series data of particle transport are divided into development, relaxation, and equilibrium phases, which are formed by rapid wind response below 10 cm and gradual wind response above 10 cm. (ii) The particle transport rate at equilibrium is expressed as a power function of friction velocity, and the index of 2.35 implies that most particles are transported by saltation. (iii) The friction velocity below 100 µm remains roughly constant and lower than the fluid threshold at equilibrium. (iv) The mean particle speed above 300 µm is less than the wind speed, whereas that below 300 µm exceeds the wind speed because of descending particles. (v) The particle diameter increases with height in the saltation layer, and the relationship is expressed as a power function. Through comparisons with the previously reported random-flight model, we find a crucial problem that empirical splash functions cannot reproduce particle dynamics at a relatively high wind speed.

Synergistic structures from magnetic freeze casting with surface magnetized alumina particles and platelets.

Science.gov (United States)

Frank, Michael B; Hei Siu, Sze; Karandikar, Keyur; Liu, Chin-Hung; Naleway, Steven E; Porter, Michael M; Graeve, Olivia A; McKittrick, Joanna

2017-12-01

Magnetic freeze casting utilizes the freezing of water, a low magnetic field and surface magnetized materials to make multi-axis strengthened porous scaffolds. A much greater magnetic moment was measured for larger magnetized alumina platelets compared with smaller particles, which indicated that more platelet aggregation occurred within slurries. This led to more lamellar wall alignment along the magnetic field direction during magnetic freeze casting at 75 mT. Slurries with varying ratios of magnetized particles to platelets (0:1, 1:3, 1:1, 3:1, 7:1, 1:0) produced porous scaffolds with different structural features and degrees of lamellar wall alignment. The greatest mechanical enhancement in the magnetic field direction was identified in the synergistic condition with the highest particle to platelet ratio (7:1). Magnetic freeze casting with varying ratios of magnetized anisotropic and isotropic alumina provided insights about how heterogeneous morphologies aggregate within lamellar walls that impact mechanical properties. Fabrication of strengthened scaffolds with multi-axis aligned porosity was achieved without introducing different solid materials, freezing agents or additives. Resemblance of 7:1 particle to platelet scaffold microstructure to wood light-frame house construction is framed in the context of assembly inspiration being derived from both natural and synthetic sources. Copyright © 2017 Elsevier Ltd. All rights reserved.

Plasma and energetic particle structure upstream of a quasi-parallel interplanetary shock

Science.gov (United States)

Kennel, C. F.; Scarf, F. L.; Coroniti, F. V.; Russell, C. T.; Wenzel, K.-P.; Sanderson, T. R.; Van Nes, P.; Smith, E. J.; Tsurutani, B. T.; Scudder, J. D.

1984-01-01

ISEE 1, 2 and 3 data from 1978 on interplanetary magnetic fields, shock waves and particle energetics are examined to characterize a quasi-parallel shock. The intense shock studied exhibited a 640 km/sec velocity. The data covered 1-147 keV protons and electrons and ions with energies exceeding 30 keV in regions both upstream and downstream of the shock, and also the magnitudes of ion-acoustic and MHD waves. The energetic particles and MHD waves began being detected 5 hr before the shock. Intense halo electron fluxes appeared ahead of the shock. A closed magnetic field structure was produced with a front end 700 earth radii from the shock. The energetic protons were cut off from the interior of the magnetic bubble, which contained a markedly increased density of 2-6 keV protons as well as the shock itself.

Assembly and luminescence properties of lanthanide-polyoxometalates/polyethyleneimine/SiO{sub 2} particles with core–shell structure

Energy Technology Data Exchange (ETDEWEB)

Wang, Jun, E-mail: junwang924@yahoo.com.cn; Fan, Shaohua; Zhao, Weiqian; Zhang, Hongyan

2013-01-01

In this paper, two lanthanide-polyoxometalate (LnW{sub 10}) complexes were bonded on the surface of the polyethyleneimine (PEI)-modified silica nanoparticles with different sizes, resulting in the formation of LnW{sub 10}/PEI/SiO{sub 2} particles. The hybrid core–shell particles were characterized by infrared, luminescent spectra, scanning electronic microscope, and transmission electronic microscope. The particles obtained exhibit the fine spherical core–shell structure and the excellent luminescence properties. The luminescence spectra studies revealed that the formation of LnW{sub 10}/PEI/SiO{sub 2} particles and the size of particle have an influence on the luminescence properties of lanthanide ions. - Highlights: ► SiO{sub 2}/polyethyleneimine (PEI) shows the chemisorption for Ln-polyoxometalates (LnW{sub 10}). ► The core-shell LnW{sub 10}/PEI/SiO{sub 2} nanoparticles with different sizes were fabricated. ► The hybrid particles exhibit the excellent luminescence properties. ► The sizes of particles affect the luminescence properties of lanthanide ions.

When size matters: differences in demineralized bone matrix particles affect collagen structure, mesenchymal stem cell behavior, and osteogenic potential.

Science.gov (United States)

Dozza, B; Lesci, I G; Duchi, S; Della Bella, E; Martini, L; Salamanna, F; Falconi, M; Cinotti, S; Fini, M; Lucarelli, E; Donati, D

2017-04-01

Demineralized bone matrix (DBM) is a natural, collagen-based, osteoinductive biomaterial. Nevertheless, there are conflicting reports on the efficacy of this product. The purpose of this study was to evaluate whether DBM collagen structure is affected by particle size and can influence DBM cytocompatibility and osteoinductivity. Sheep cortical bone was ground and particles were divided in three fractions with different sizes, defined as large (L, 1-2 mm), medium (M, 0.5-1 mm), and small (S, structure, with DBM-M being altered but not as much as DBM-S. DBM-M displayed a preferable trend in almost all biological characteristics tested, although all DBM particles revealed an optimal cytocompatibility. Subcutaneous implantation of DBM particles into immunocompromised mice resulted in bone induction only for DBM-M. When sheep MSC were seeded onto particles before implantation, all DBM particles were able to induce new bone formation with the best incidence for DBM-M and DBM-S. In conclusion, the collagen alteration in DBM-M is likely the best condition to promote bone induction in vivo. Furthermore, the choice of 0.5-1 mm particles may enable to obtain more efficient and consistent results among different research groups in bone tissue-engineering applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1019-1033, 2017. © 2017 Wiley Periodicals, Inc.

In-situ synthesis of SiC particles by the structural evolution of TiCx in Al–Si melt

International Nuclear Information System (INIS)

Nie, Jinfeng; Li, Dakui; Wang, Enzhao; Liu, Xiangfa

2014-01-01

Highlights: • A facile method to in-situ synthesize SiC was developed utilizing the structural evolution of TiC x in Al–Si melt. • The SiC particles have the size range from 2.5 to 7.5 μm and a block-like morphology. • The SiC particles and (SiC + TiB 2 ) hybrid-particles reinforced Al–18Si composite were prepared. • The wear resistance effect of SiC on the based alloy was investigated. - Abstract: A facile method has been developed to in-situ synthesize SiC particles utilizing the structural instability and evolution of TiC x in Al–Si melt. It is considered that the synthesis of SiC particles occurs via the gradual reaction between TiC x and Si atoms, whilst Si content plays the crucial role in this approach. If the Si content in the melt is above 30%, TiC x directly reacts with Si and Al to form SiC, but the needle-like TiAl x Si y phase formed simultaneously will do harm to the mechanical properties of the composites. Thus, it is proposed to add B element in the melt to transform the TiAl x Si y into TiB 2 particles. Therefore, the SiC and (SiC + TiB 2 ) hybrid-particles reinforced Al–18Si composites were successfully prepared using the method. In the composites, the SiC particles have the size range from 2.5 to 7.5 μm and a block-like morphology. Furthermore, the mechanical properties of base alloy, including the wear resistance and macro-hardness, have been obviously improved by the in-situ SiC particles. Besides, the relevant underlying mechanisms are also discussed

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

Science.gov (United States)

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.

Elementary particles

International Nuclear Information System (INIS)

Prasad, R.

1984-01-01

Two previous monographs report on investigations into the extent to which a unified field theory can satisfactorily describe physical reality. The first, Unified field Theory, showed that the paths within a non-Riemannian space are governed by eigenvalue equations. The second, Fundamental Constants, show that the field tensors satisfy sets of differential equations with solutions which represent the evolution of the fields along the paths of the space. The results from the first two monographs are used in this one to make progress on the theory of elementary particles. The five chapters are as follows - Quantum mechanics, gravitation and electromagnetism are aspects of the Unified theory; the fields inside the particle; the quadratic and linear theories; the calculation of the eigenvalues and elementary particles as stable configurations of interacting fields. It is shown that it is possible to construct an internal structure theory for elementary particles. The theory lies within the framework of Einstein's programme-to identify physical reality with a specified geometrical structure. (U.K.)

Two-dimensional Monte Carlo simulations of structures of a suspension comprised of magnetic and nonmagnetic particles in uniform magnetic fields

International Nuclear Information System (INIS)

Peng Xiaoling; Min Yong; Ma Tianyu; Luo Wei; Yan Mi

2009-01-01

The structures of suspensions comprised of magnetic and nonmagnetic particles in magnetic fields are studied using two-dimensional Monte Carlo simulations. The magnetic interaction among magnetic particles, magnetic field strength, and concentrations of both magnetic and nonmagnetic particles are considered as key influencing factors in the present work. The results show that chain-like clusters of magnetic particles are formed along the field direction. The size of the clusters increases with increasing magnetic interaction between magnetic particles, while it keeps nearly unchanged as the field strength increases. As the concentration of magnetic particles increases, both the number and size of the clusters increase. Moreover, nonmagnetic particles are found to hinder the migration of magnetic ones. As the concentration of nonmagnetic particles increases, the hindrance on migration of magnetic particles is enhanced

Framework to model neutral particle flux in convex high aspect ratio structures using one-dimensional radiosity

Science.gov (United States)

Manstetten, Paul; Filipovic, Lado; Hössinger, Andreas; Weinbub, Josef; Selberherr, Siegfried

2017-02-01

We present a computationally efficient framework to compute the neutral flux in high aspect ratio structures during three-dimensional plasma etching simulations. The framework is based on a one-dimensional radiosity approach and is applicable to simulations of convex rotationally symmetric holes and convex symmetric trenches with a constant cross-section. The framework is intended to replace the full three-dimensional simulation step required to calculate the neutral flux during plasma etching simulations. Especially for high aspect ratio structures, the computational effort, required to perform the full three-dimensional simulation of the neutral flux at the desired spatial resolution, conflicts with practical simulation time constraints. Our results are in agreement with those obtained by three-dimensional Monte Carlo based ray tracing simulations for various aspect ratios and convex geometries. With this framework we present a comprehensive analysis of the influence of the geometrical properties of high aspect ratio structures as well as of the particle sticking probability on the neutral particle flux.

Effects of WC Particle Size and Co Content on the Graded Structure in Functionally Gradient WC-Co Composites

Directory of Open Access Journals (Sweden)

Yuan Yigao

2016-01-01

Full Text Available Functionally gradient WC-Co composites having a Co depleted surface zone and not comprising the h phase can be manufactured via carburizing process. During carburizing, besides carburizing process parameters, the microstructural parameters of WC-Co materials, such as WC grain size and Co content, also have significant influences on the formation of Co gradient structure. In this study, the effects of WC particle size and Co content on the gradient structure within gradient hardmetals have been studied, based on a series of carburizing experiments of WC-Co materials with different WC particle sizes and cobalt contents. The results show that both the thickness and the amplitude of the gradients within gradient WC-Co materials increase with increasing initial WC particle size and Co content of WC-Co alloys. The reason for this finding is discussed.

Coagulation-agglomeration of fractal-like particles: structure and self-preserving size distribution.

Science.gov (United States)

Goudeli, Eirini; Eggersdorfer, Maximilian L; Pratsinis, Sotiris E

2015-02-03

Agglomeration occurs in environmental and industrial processes, especially at low temperatures where particle sintering or coalescence is rather slow. Here, the growth and structure of particles undergoing agglomeration (coagulation in the absence of coalescence, condensation, or surface growth) are investigated from the free molecular to the continuum regime by discrete element modeling (DEM). Particles coagulating in the free molecular regime follow ballistic trajectories described by an event-driven method, whereas in the near-continuum (gas-slip) and continuum regimes, Langevin dynamics describe their diffusive motion. Agglomerates containing about 10-30 primary particles, on the average, attain their asymptotic fractal dimension, D(f), of 1.91 or 1.78 by ballistic or diffusion-limited cluster-cluster agglomeration, corresponding to coagulation in the free molecular or continuum regimes, respectively. A correlation is proposed for the asymptotic evolution of agglomerate D(f) as a function of the average number of constituent primary particles, n̅(p). Agglomerates exhibit considerably broader self-preserving size distribution (SPSD) by coagulation than spherical particles: the number-based geometric standard deviations of the SPSD agglomerate radius of gyration in the free molecular and continuum regimes are 2.27 and 1.95, respectively, compared to ∼1.45 for spheres. In the transition regime, agglomerates exhibit a quasi-SPSD whose geometric standard deviation passes through a minimum at Knudsen number Kn ≈ 0.2. In contrast, the asymptotic D(f) shifts linearly from 1.91 in the free molecular regime to 1.78 in the continuum regime. Population balance models using the radius of gyration as collision radius underestimate (up to about 80%) the small tail of the SPSD and slightly overpredict the overall agglomerate coagulation rate, as they do not account for cluster interpenetration during coagulation. In the continuum regime, when a recently developed

In Vitro-Assembled Alphavirus Core-Like Particles Maintain a Structure Similar to That of Nucleocapsid Cores in Mature Virus

OpenAIRE

Mukhopadhyay, Suchetana; Chipman, Paul R.; Hong, Eunmee M.; Kuhn, Richard J.; Rossmann, Michael G.

2002-01-01

In vitro-assembled core-like particles produced from alphavirus capsid protein and nucleic acid were studied by cryoelectron microscopy. These particles were found to have a diameter of 420 Å with 240 copies of the capsid protein arranged in a T=4 icosahedral surface lattice, similar to the nucleocapsid core in mature virions. However, when the particles were subjected to gentle purification procedures, they were damaged, preventing generation of reliable structural information. Similarly, pu...

Structure, Immunogenicity, and Protective Mechanism of an Engineered Enterovirus 71-Like Particle Vaccine Mimicking 80S Empty Capsid.

Science.gov (United States)

Wang, Xiaoli; Ku, Zhiqiang; Zhang, Xiang; Ye, Xiaohua; Chen, Jinhuan; Liu, Qingwei; Zhang, Wei; Zhang, Chao; Fu, Zhenglin; Jin, Xia; Cong, Yao; Huang, Zhong

2018-01-01

Enterovirus 71 (EV71) is the major causative agent of severe hand, foot, and mouth disease, which affects millions of young children in the Asia-Pacific region annually. In this study, we engineered a novel EV71 virus-like particle (VLP) that lacks VP4 (therefore designated VLP ΔVP4 ) and investigated its structure, antigenicity, and vaccine potential. The cryo-electron microscopy (cryo-EM) structure of VLP ΔVP4 was reconstructed to 3.71-Å resolution. Results from structural and biochemical analyses revealed that VLP ΔVP4 resembles the end product of the viral uncoating process, the 80S empty capsid. VLP ΔVP4 is able to elicit high-titer neutralizing antibodies and to fully protect mice against lethal viral challenge. Mechanistic studies showed that, at the cellular level, the anti-VLP ΔVP4 sera exert neutralization effects at both pre- and postattachment stages by inhibiting both virus attachment and internalization, and at the molecular level, the antisera can block multiple interactions between EV71 and its key receptors. Our study gives a better understanding of EV71 capsid assembly and provides important information for the design and development of new-generation vaccines for EV71, and perhaps for other enteroviruses, as well. IMPORTANCE Enterovirus 71 (EV71) infection may lead to severe hand, foot, and mouth disease, with significant morbidity and mortality. Knowledge regarding EV71 particle assembly remains limited. Here, we report the generation and characterization of a novel EV71 virus-like particle that lacks the VP4 capsid subunit protein. This particle, termed VLP ΔVP4 , structurally mimics the 80S empty capsid, which is the end stage of EV71 uncoating. We further show that VLP ΔVP4 exhibits desirable immunogenicity and protective efficacy in proof-of-concept studies. In addition, the inhibitory mechanisms of the VLP ΔVP4 -induced antibodies are unraveled at both the cellular and molecular levels. Our work provides the first evidence of

Structural composition of organic matter in particle-size fractions of soils along a climo-biosequence in the main range of Peninsular Malaysia

Science.gov (United States)

Jafarzadeh-Haghighi, Amir Hossein; Shamshuddin, Jusop; Hamdan, Jol; Zainuddin, Norhazlin

2016-09-01

Information on structural composition of organic matter (OM) in particle-size fractions of soils along a climo-biosequence is sparse. The objective of this study was to examine structural composition and morphological characteristics of OM in particle-size fractions of soils along a climo-biosequence in order to better understand the factors and processes affecting structural composition of soil organic matter. To explore changes in structural composition of OM in soils with different pedogenesis, the A-horizon was considered for further analyses including particle-size fractionation, solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscopy (SEM). Due to the increase in the thickness of organic layer with increasing elevation, the A-horizon was situated at greater depth in soils of higher elevation. The relationship between relative abundances of carbon (C) structures and particle-size fractions was examined using principal component analysis (PCA). It was found that alkyl C (20.1-73.4%) and O-alkyl C (16.8-67.7%) dominated particle-size fractions. The proportion of alkyl C increased with increasing elevation, while O-alkyl C showed an opposite trend. Results of PCA confirmed this finding and showed the relative enrichment of alkyl C in soils of higher elevation. Increase in the proportion of alkyl C in 250-2000 μm fraction is linked to selective preservation of aliphatic compounds derived from root litter. SEM results showed an increase in root contribution to the 250-2000 μm fraction with increasing elevation. For the changes in structural composition of OM in particle-size fractions of soils along the studied climo-biosequence are attributed to site-specific differences in pedogenesis as a function of climate and vegetation.

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

Energy Technology Data Exchange (ETDEWEB)

Lee, B [Northwestern Memorial Hospital, Chicago, IL (United States); Georgia Institute of Technology, Atlanta, GA (Georgia); Wang, C [Georgia Institute of Technology, Atlanta, GA (Georgia)

2016-06-15

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. 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

Polyhydroxy surfactants for the formulation of lipid nanoparticles (SLN and NLC): effects on size, physical stability and particle matrix structure.

Science.gov (United States)

Kovacevic, A; Savic, S; Vuleta, G; Müller, R H; Keck, C M

2011-03-15

The two polyhydroxy surfactants polyglycerol 6-distearate (Plurol(®)Stearique WL1009 - (PS)) and caprylyl/capryl glucoside (Plantacare(®) 810 - (PL)) are a class of PEG-free stabilizers, made from renewable resources. They were investigated for stabilization of aqueous solid lipid nanoparticle (SLN) and nanostructured lipid carrier (NLC) dispersions. Production was performed by high pressure homogenization, analysis by photon correlation spectroscopy (PCS), laser diffraction (LD), zeta potential measurements and differential scanning calorimetry (DSC). Particles were made from Cutina CP as solid lipid only (SLN) and its blends with Miglyol 812 (NLC, the blends containing increasing amounts of oil from 20% to 60%). The obtained particle sizes were identical for both surfactants, about 200 nm with polydispersity indices below 0.20 (PCS), and unimodal size distribution (LD). All dispersions with both surfactants were physically stable for 3 months at room temperature, but Plantacare (PL) showing a superior stability. The melting behaviour and crystallinity of bulk lipids/lipid blends were compared to the nanoparticles. Both were lower for the nanoparticles. The crystallinity of dispersions stabilized with PS was higher, the zeta potential decreased with storage time associated with this higher crystallinity, and leading to a few, but negligible larger particles. The lower crystallinity particles stabilized with PL remained unchanged in zeta potential (about -50 mV) and in size. These data show that surfactants have a distinct influence on the particle matrix structure (and related stability and drug loading), to which too little attention was given by now. Despite being from the same surfactant class, the differences on the structure are pronounced. They are attributed to the hydrophobic-lipophilic tail structure with one-point anchoring in the interface (PL), and the loop conformation of PS with two hydrophobic anchor points, i.e. their molecular structure and its

Structures of the particles of the condensed dispersed phase in solid fuel combustion products plasma

International Nuclear Information System (INIS)

Samaryan, A.A.; Chernyshev, A.V.; Nefedov, A.P.; Petrov, O.F.; Fortov, V.E.; Mikhailov, Yu.M.; Mintsev, V.B.

2000-01-01

The results of experimental investigations of a type of dusty plasma which has been least studied--the plasma of solid fuel combustion products--were presented. Experiments to determine the parameters of the plasma of the combustion products of synthetic solid fuels with various compositions together with simultaneous diagnostics of the degree of ordering of the structures of the particles of the dispersed condensed phase were performed. The measurements showed that the charge composition of the plasma of the solid fuels combustion products depends strongly on the easily ionized alkali-metal impurities which are always present in synthetic fuel in one or another amount. An ordered arrangement of the particles of a condensed dispersed phase in structures that form in a boundary region between the high-temperature and condensation zones was observed for samples of aluminum-coated solid fuels with a low content of alkali-metal impurities

Field assessment of the impacts of landscape structure on different-sized airborne particles in residential areas of Beijing, China

Science.gov (United States)

Fan, Shuxin; Li, Xiaopeng; Han, Jing; Cao, Yu; Dong, Li

2017-10-01

In high-density metropolis, residential areas are important human living environments. Aimed at investigating the impacts of landscape structure on the levels of different-sized airborne particle in residential areas, we conducted field monitoring of the levels of TSP, PM10, PM2.5 and PM1 using mobile traverses in 18 residential areas during the daytime in winter (Dec. 2015-Feb. 2016) and summer (Jun.-Aug. 2016) in Beijing, China. The net concentration differences (d) of the four-sized particles (dTSP, dPM10, dPM2.5 and dPM1) between residential environments and nearby corresponding urban backgrounds, which can be regarded as the reduction of particle concentration in residential environments, were calculated. The effects and relative contributions of different landscape structure parameters on these net concentration differences were further investigated. Results showed that the distribution of particle concentrations has great spatial variation in urban environments. Within the residential environment, there were overall lower concentrations of the four-sized particles compared with the nearby urban background. The net concentration differences of the four-sized particles were all significantly different among the 18 studied residential areas. The average dTSP, dPM10, dPM2.5 and dPM1 reached 18.92, 12.28, 2.01 and 0.53 μg/m3 in summer, and 9.91, 7.81, 1.39 and 0.38 μg/m3 in winter, respectively. The impacts and relative contribution of different landscape structure parameters on the reductions of TSP, PM10, PM2.5 and PM1 in residential environments differed and showed seasonal variation. Percentage of vegetation cover (PerVC) and building cover (PerBC) had the greatest impact. A 10% increase in PerVC would increase about 5.03, 8.15, 2.16 and 0.20 μg/m3 of dTSP, dPM10, dPM2.5 and dPM1 in summer, and a 10% increase in PerBC would decreased about 41.37, 16.54, 2.47 and 0.95 μg/m3 of them in winter. Increased vegetation coverage and decreased building

Structural, magnetic, and electrical properties of Gd-doped BiFeO3 nanoparticles with reduced particle size

International Nuclear Information System (INIS)

Lotey, Gurmeet Singh; Verma, N. K.

2012-01-01

Pure and Gd-doped BiFeO 3 nanoparticles have been synthesized by sol–gel method. The significant effects of size and Gd-doping on structural, electrical, and magnetic properties have been investigated. X-ray diffraction study reveals that the pure BiFeO 3 nanoparticles possess rhombohedral structure, but with 10% Gd-doping complete structural transformation from rhombohedral to orthorhombic has been observed. The particle size of pure and Gd-doped BiFeO 3 nanoparticles, calculated using Transmission electron microscopy, has been found to be in the range 25–15 nm. Pure and Gd-doped BiFeO 3 nanoparticles show ferromagnetic character, and the magnetization increases with decrease in particle size and increase in doping concentration. Scanning electron microscopy study reveals that grain size decreases with increase in Gd concentration. Well-saturated polarization versus electric field loop is observed for the doped samples. Leakage current density decreases by four orders by doping Gd in BiFeO 3 . The incorporation of Gd in BiFeO 3 enhances spin as well as electric polarization at room temperature. The possible origin of enhancement in these properties has been explained on the basis of dopant and its concentration, phase purity, small particle, and grain size.

Impact of the track structure of heavy charged particles on cytogenetic damage in human blood lymphocytes

Science.gov (United States)

Lee, Ryonfa; Nasonova, Elena; Sommer, Sylwetster; Hartel, Carola; Durante, Marco; Ritter, Sylvia

In space, astronauts are unavoidably exposed to charged particles from protons to irons. For a better estimate of the health risks of astronauts, further knowledge on the biological effects of charged particles, in particular the induction of cytogenetic damage is required. One im-portant factor that determines the biological response is the track structure of particles, i.e. their microscopic dose deposition in cells. The aim of the present study was to assess the influence of track structure of heavy ions on the yield and the quality of cytogenetic damage in human peripheral blood lymphocytes representing normal tissue. Cells were irradiated with 9.5 MeV/u C-ions or 990 MeV/u Fe-ions which have a comparable LET (175 keV/µm and 155 keV/µm, respectively) but a different track radius (2.3 and 6200 µm, respectively). When aberrations were analyzed in first cycle metaphases collected at different post-irradiation times (48-84 h) following fluorescence plus Giemsa staining, an increase in the aberration yield with sampling time was observed for both radiation qualities reflecting a damage dependent cell cycle progression delay to mitosis. The pronounced differences in the aberration frequency per cell are attributable to the stochastic distribution of particle traversals per cell nucleus (radius: 2.8 µm). Following C-ion exposure we found a high fraction of non-aberrant cells in samples collected at 48 h which represent cells not directly hit by a particle and slightly damaged cells that successfully repaired the induced lesions. In addition, at higher C-ion fluences the aberra-tion yield saturated, suggesting that a fraction of lymphocytes receiving multiple particle hits is not able to reach mitosis. On the other hand, at 48 h after Fe-ion exposure the proportion of non-aberrant cells is lower than after C-ion irradiation clearly reflecting the track structure of high energy particles (i.e. more homogeneous dose deposition compared to low energy C

Particle structure function and subbarrier fusion in hot nuclei

International Nuclear Information System (INIS)

Moretto, L.G.; Jing, K.X.; Phair, L.; Wozniak, G.J.

1997-02-01

The study of particle evaporation spectra can provide information about shape polarization phenomena induced by the nascent particle on the residual nucleus, and about optical modulations felt by the particle as it is preformed inside the nucleus. These aspects can be studied as a function temperature. Preliminary experimental evidence about these features has been obtained

Investigating the settling dynamics of cohesive silt particles with particle-resolving simulations

Science.gov (United States)

Sun, Rui; Xiao, Heng; Sun, Honglei

2018-01-01

The settling of cohesive sediment is ubiquitous in aquatic environments, and the study of the settling process is important for both engineering and environmental reasons. In the settling process, the silt particles show behaviors that are different from non-cohesive particles due to the influence of inter-particle cohesive force. For instance, the flocs formed in the settling process of cohesive silt can loosen the packing, and thus the structural densities of cohesive silt beds are much smaller than that of non-cohesive sand beds. While there is a consensus that cohesive behaviors depend on the characteristics of sediment particles (e.g., Bond number, particle size distribution), little is known about the exact influence of these characteristics on the cohesive behaviors. In addition, since the cohesive behaviors of the silt are caused by the inter-particle cohesive forces, the motions of and the contacts among silt particles should be resolved to study these cohesive behaviors in the settling process. However, studies of the cohesive behaviors of silt particles in the settling process based on particle-resolving approach are still lacking. In the present work, three-dimensional settling process is investigated numerically by using CFD-DEM (Computational Fluid Dynamics-Discrete Element Method). The inter-particle collision force, the van der Waals force, and the fluid-particle interaction forces are considered. The numerical model is used to simulate the hindered settling process of silt based on the experimental setup in the literature. The results obtained in the simulations, including the structural densities of the beds, the characteristic lines, and the particle terminal velocity, are in good agreement with the experimental observations in the literature. To the authors' knowledge, this is the first time that the influences of non-dimensional Bond number and particle polydispersity on the structural densities of silt beds have been investigated separately

Structures in the K-shell delta electron spectrum near threshold for ionization by fast charged particles

International Nuclear Information System (INIS)

Amundsen, P.A.; Aashamar, K.

Results of calculations of the delta electron spectrum for K-shell ionization of atoms by fast charged particles for target charges in the range 6 2 <=40 are presented. Appreciable structure is found in the spectrum near the ionization threshold, in particular for fast projectiles and heavy target elements. The structure can be quite sensitive to the details of the effective atomic potentials. (Auth.)

Hopf algebra structures in particle physics

International Nuclear Information System (INIS)

Weinzierl, Stefan

2004-01-01

In the recent years, Hopf algebras have been introduced to describe certain combinatorial properties of quantum field theories. I give a basic introduction to these algebras and review some occurrences in particle physics. (orig.)

An Empirical Method for Particle Damping Design

Directory of Open Access Journals (Sweden)

Zhi Wei Xu

2004-01-01

Full Text Available Particle damping is an effective vibration suppression method. The purpose of this paper is to develop an empirical method for particle damping design based on extensive experiments on three structural objects – steel beam, bond arm and bond head stand. The relationships among several key parameters of structure/particles are obtained. Then the procedures with the use of particle damping are proposed to provide guidelines for practical applications. It is believed that the results presented in this paper would be helpful to effectively implement the particle damping for various structural systems for the purpose of vibration suppression.

Structure determination of feline calicivirus virus-like particles in the context of a pseudo-octahedral arrangement.

Directory of Open Access Journals (Sweden)

Wim P Burmeister

Full Text Available The vesivirus feline calicivirus (FCV is a positive strand RNA virus encapsidated by an icosahedral T=3 shell formed by the viral VP1 protein. Upon its expression in the insect cell - baculovirus system in the context of vaccine development, two types of virus-like particles (VLPs were formed, a majority built of 60 subunits (T=1 and a minority probably built of 180 subunits (T=3. The structure of the small particles was determined by x-ray crystallography at 0.8 nm resolution helped by cryo-electron microscopy in order to understand their formation. Cubic crystals belonged to space group P213. Their self-rotation function showed the presence of an octahedral pseudo-symmetry similar to the one described previously by Agerbandje and co-workers for human parvovirus VLPs. The crystal structure could be solved starting from the published VP1 structure in the context of the T=3 viral capsid. In contrast to viral capsids, where the capsomers are interlocked by the exchange of the N-terminal arm (NTA domain, this domain is disordered in the T=1 capsid of the VLPs. Furthermore it is prone to proteolytic cleavage. The relative orientation of P (protrusion and S (shell domains is alerted so as to fit VP1 to the smaller T=1 particle whereas the intermolecular contacts around 2-fold, 3-fold and 5-fold axes are conserved. By consequence the surface of the VLP is very similar compared to the viral capsid and suggests a similar antigenicity. The knowledge of the structure of the VLPs will help to improve their stability, in respect to a use for vaccination.

The effects of surface-charged submicron polystyrene particles on the structure and performance of PSF forward osmosis membrane

Science.gov (United States)

Zuo, Hao-Ran; Fu, Jia-Bei; Cao, Gui-Ping; Hu, Nian; Lu, Hui; Liu, Hui-Qing; Chen, Peng-Peng; Yu, Jie

2018-04-01

Monodisperse surface-charged submicron polystyrene particles were designed, synthesized, and blended into polysulfone (PSF) support layer to prepare forward osmosis (FO) membrane with high performance. The membrane incorporated with particles were characterized with respect to morphology, porosity, and internal osmotic pressure (IOP). Results showed that the polymer particles not only increased the hydrophilicity and porosity of support layer, but also generated considerable IOP, which helped markedly decreasing the structure parameter from 1550 to 670 μm. The measured mass transfer parameters further confirmed the beneficial effects of the surface-charged submicron polymer particles on the performance of FO membrane. For instance, the water permeability coefficient (5.37 L m-2 h-1 bar-1) and water flux (49.7 L m-2 h-1) of the FO membrane incorporated with 5 wt% particles were almost twice as much as that of FO membrane without incorporation. This study suggests that monodisperse surface-charged submicron polymer particles are potential modifiers for improving the performance of FO membranes.

Composite of ceramic-coated magnetic alloy particles

Science.gov (United States)

Moorhead, Arthur J.; Kim, Hyoun-Ee

2000-01-01

A composite structure and method for manufacturing same, the composite structure being comprised of metal particles and an inorganic bonding media. The method comprises the steps of coating particles of a metal powder with a thin layer of an inorganic bonding media selected from the group of powders consisting of a ceramic, glass, and glass-ceramic. The particles are assembled in a cavity and heat, with or without the addition of pressure, is thereafter applied to the particles until the layer of inorganic bonding media forms a strong bond with the particles and with the layer of inorganic bonding media on adjacent particles. The resulting composite structure is strong and remains cohesive at high temperatures.

Structure of events with a particle at large transverse momentum in proton-proton collisions at the CERN ISR

International Nuclear Information System (INIS)

Herr, W.F.

1985-01-01

The structure of events with a particle with large transverse momentum has been studied for proton-proton collisions at a centre-of-mass energy of √s=62.2 GeV. The experiment was performed with the Split-Field-Magnet detector at the CERN Intersecting Storage Rings and events were recorded with high-psub(T) particles with psub(T)>2 GeV/c produced at polar angles around 45 0 and 20 0 . The distributions of charged particles in the jet recoiling against the high-psub(T) particle have been measured as a function of the fragmentation variable xsub(E)=psub(T)/psub(T)sup(tri). The production of high-psub(T) particles is usually interpreted in the quark parton model as the hard collision of proton constituents. The asymmetry and charge composition of the recoil jet and their correlation with the flavour of the high-psub(T) particle supports this qualitative picture. Model calculations using first order Quantum Chromodynamics (QCD) and phenomenological fragmentation model cannot explain the particle distribution in the recoil jet. (orig.) [de

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

Science.gov (United States)

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.

Impact of functionalized particle structure on roll compaction/dry granulation and tableting of calcium carbonate.

Science.gov (United States)

Grote, Simon; Kleinebudde, Peter

2018-06-10

The influence of a functionalized raw material particle structure on the granulation behavior and tabletabilty of calcium carbonate (CaCO 3 ) was investigated. Therefore, a milled grade of CaCO 3 was compared to different binary mixtures of milled and functionalized CaCO 3 . Relevant properties of raw materials, ribbons and granules were measured. The starting materials and two fractions of dry granules were compressed to tablets. The tabletability of granules was compared to that of the powders and the influence of specific compaction force and granule size on tablet tensile strength was evaluated. Adding functionalized particles drastically influenced the granulation and tableting behavior of CaCO 3 . Increasing proportions increased the ribbon porosity and granule size. Tensile strength of tablets from powder mixtures and granules was increased as well. Nevertheless, adding functionalized CaCO 3 led to a loss in tabletability induced by a previous compaction step to an extent depending on its proportion in the formulation. A clear influence of the particle morphology on granulation and tableting behavior was demonstrated by the study. The functionalized structure showed aspects of a more plastic deformation behavior. Adding functionalized CaCO 3 to a mixture, even in small amounts, seemed to be beneficial to increase granule size and tablet strength. Copyright © 2018 Elsevier B.V. All rights reserved.

Non-Born-Oppenheimer electronic and nuclear densities for a Hooke-Calogero three-particle model: non-uniqueness of density-derived molecular structure.

Science.gov (United States)

Ludeña, E V; Echevarría, L; Lopez, X; Ugalde, J M

2012-02-28

We consider the calculation of non-Born-Oppenheimer, nBO, one-particle densities for both electrons and nuclei. We show that the nBO one-particle densities evaluated in terms of translationally invariant coordinates are independent of the wavefunction describing the motion of center of mass of the whole system. We show that they depend, however, on an arbitrary reference point from which the positions of the vectors labeling the particles are determined. We examine the effect that this arbitrary choice has on the topology of the one-particle density by selecting the Hooke-Calogero model of a three-body system for which expressions for the one-particle densities can be readily obtained in analytic form. We extend this analysis to the one-particle densities obtained from full Coulomb interaction wavefunctions for three-body systems. We conclude, in view of the fact that there is a close link between the choice of the reference point and the topology of one-particle densities that the molecular structure inferred from the topology of these densities is not unique. We analyze the behavior of one-particle densities for the Hooke-Calogero Born-Oppenheimer, BO, wavefunction and show that topological transitions are also present in this case for a particular mass value of the light particles even though in the BO regime the nuclear masses are infinite. In this vein, we argue that the change in topology caused by variation of the mass ratio between light and heavy particles does not constitute a true indication in the nBO regime of the emergence of molecular structure.

Nano-structured Fabry–Pérot resonators in neutron optics and tunneling of neutron wave-particles

International Nuclear Information System (INIS)

Maaza, M.; Hamidi, D.

2012-01-01

Correlated to the quantum mechanics wave-particle duality, the optical analogy between electromagnetic waves and cold neutrons manifests itself through several interference phenomena particularly the so called Frustrated Total Reflection i.e., the tunneling process in Fabry–Pérot nano-structured cavities. Prominent resonant situations offered by this configuration allow the attainment of numerous fundamental investigations and surface-interface studies as well as to devise new kinds of neutron optics devices. This review contribution reports such possibilities in addition to the recently observed peculiar Goos–Hänchen longitudinal shift of neutron wave-particles which was predicted by Sir Isaac Newton as early as 1730.

Investigation of doping and particle size effect on structural, magnetic and magnetoresistance properties of manganites

Directory of Open Access Journals (Sweden)

M. Hakimi

2008-06-01

Full Text Available  In this paper after introduction of manganites, we have studied the effect of particle size and doping on structural, magnetic and magnetoresistance of LSMO manganite samples. The magnetoresistance measurements show that, by decreasing the particle size LFMR increases. Also the results show that the LFMR increases at low doping levels and decreases at high doping levels. The spin dependent tunneling and scattering at the grain boundaries is the origin of increasing the LFMR at low doping levels. Also the substitution of impurity ions at Mn sites and subsequently weaking of double exchange is responsible for decreasing of LFMR at high doping level.

Structural and fluorescence properties of Ni:MgO-SiO2 particles synthesized by flame spray pyrolysis

International Nuclear Information System (INIS)

Suzuki, Takenobu; Ohishi, Yasutake; Tani, Takao

2006-01-01

Structural and fluorescence properties of flame spray-synthesized Ni 1 mol%-doped MgO-SiO 2 nano-particles (MgO:SiO 2 = 100:0, 50:50, 25:75 and 0:100 in mol%) were investigated as a first step to prepare transparent materials containing Ni:MgO for optical gain media. Polyhedral aggregates of primary particles with diameters of 8-19 nm were obtained for all compositions. The 100MgO particles were single crystalline and showed the fluorescences (centered at 1260 and 1320 nm) and lifetime (3.8 ms) similar to those of solid state-synthesized Ni:MgO polycrystalline powder under laser excitation at 976 nm, suggesting Ni ions incorporated in MgO

Diffusion of oriented particles in porous media

Energy Technology Data Exchange (ETDEWEB)

Haber, René [Institut für Physik, Technische Universität Chemnitz, D-09107 Chemnitz (Germany); Centre for Nonlinear Studies, Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn (Estonia); Prehl, Janett [Institut für Physik, Technische Universität Chemnitz, D-09107 Chemnitz (Germany); Herrmann, Heiko [Centre for Nonlinear Studies, Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn (Estonia); Hoffmann, Karl Heinz, E-mail: hoffmann@physik.tu-chemnitz.de [Institut für Physik, Technische Universität Chemnitz, D-09107 Chemnitz (Germany)

2013-11-29

Diffusion of particles in porous media often shows subdiffusive behavior. Here, we analyze the dynamics of particles exhibiting an orientation. The features we focus on are geometrical restrictions and the dynamical consequences of the interactions between the local surrounding structure and the particle orientation. This interaction can lead to particles getting temporarily stuck in parts of the structure. Modeling this interaction by a particular random walk dynamics on fractal structures we find that the random walk dimension is not affected while the diffusion constant shows a variety of interesting and surprising features.

Diffusion of oriented particles in porous media

International Nuclear Information System (INIS)

Haber, René; Prehl, Janett; Herrmann, Heiko; Hoffmann, Karl Heinz

2013-01-01

Diffusion of particles in porous media often shows subdiffusive behavior. Here, we analyze the dynamics of particles exhibiting an orientation. The features we focus on are geometrical restrictions and the dynamical consequences of the interactions between the local surrounding structure and the particle orientation. This interaction can lead to particles getting temporarily stuck in parts of the structure. Modeling this interaction by a particular random walk dynamics on fractal structures we find that the random walk dimension is not affected while the diffusion constant shows a variety of interesting and surprising features.

Data needs for the track structure of alpha particles and electrons in water

International Nuclear Information System (INIS)

Pagnamenta, A.

1983-01-01

We have made calculations of the ionization spectra for alpha particle and electron tracks in water. We have also computed the number of ions created per micrometre of track length, the energy distribution of the secondaries, and the energy expended per ion pair created. Our aim is less toward theoretical derivations than to obtain a numerically accurate description of the track structure at all energies in a form suitable for biomedical applications. 13 references

Investigating fundamental properties of wind turbine wake structure using particle image velocimetry

Energy Technology Data Exchange (ETDEWEB)

Whale, J. [Univ. of Edinburgh, Dept. of Mechanical Engineering, Edinburgh (United Kingdom)

1997-08-01

Low Reynolds number flow visualization tests are often used for showing the flow pattern changes associated with changes in lift-coefficients at a higher Reynolds number. In wind turbine studies, analysis of measured wake structures at small scale may reveal fundamental properties of the wake which will offer wake modellers a more complete understanding of rotor flows. Measurements are presented from experiments on a model wind turbine rig conducted in a water channel. The laser-optics technique of Particle Image Velocimetry (PIV) is used to make simultaneous multi-point measurements of the wake flow behind small-scale rotors. Analysis of the PIV data shows trends in velocity and vorticity structure in the wake. Study of the flow close to the rotor plane reveals information on stalled flow and blade performance. (au)

Particle correlations in the recombination model associated with modified Kuti-Weisskopf structure functions

International Nuclear Information System (INIS)

Takasugi, E.; Tata, X.

1982-01-01

The recombination model associated with modified Kuti-Weisskopf multiquark structure functions is used to analyze particle production by hadronic collisions. The justification of the use of the impulse approximation in these processes and the universal nature of the recombination process are discussed. Single-meson inclusive production in the fragmentation domains of the proton, the pion, and the kaon is used as an input to determine the primitive structure functions. Our parameter-free predictions for low-p/sub T/ multimeson and associated meson-baryon inclusive production are found to be in good agreement with a large amount of recently obtained correlation data. It is pointed out, however, that reactions involving multivalence recombination fall outside the scope of present considerations

Hadron production in high energy muon scattering. [Quark-parton model, 225 GeV, structure functions, particle ratios

Energy Technology Data Exchange (ETDEWEB)

Hicks, R.G.

1978-01-01

An experiment was performed to study muon-proton scattering at an incident energy of 225 GeV and a total effective flux of 4.3 x 10/sup 10/ muons. This experiment is able to detect charged particles in coincidence with the scattered muon in the forward hemisphere, and results are reported for the neutral strange particles K/sub s//sup 0/ and ..lambda../sup 0/ decaying into two charged particles. Within experimental limits the masses and lifetimes of these particles are consistent with previous measurements. The distribution of hadrons produced in muon scattering is determined, measuring momentum components parallel and transverse to the virtual photon direction, and these distributions are compared to other high energy experiments involving the scattering of pions, protons, and neutrinos from protons. Structure functions for hadron production and particle ratios are calculated. No azimuthal dependence is observed, and lambda production does not appear to be polarized. The physical significance of the results is discussed within the framework of the quark-parton model. 29 references.

Analysis of the structure, particle morphology and photoluminescent properties of ZnS:Mn2+ nanoparticulate phosphors

CSIR Research Space (South Africa)

Raleaooa, PV

2018-01-01

Full Text Available stream_source_info Raleaooa_20160_2018.pdf.txt stream_content_type text/plain stream_size 1286 Content-Encoding UTF-8 stream_name Raleaooa_20160_2018.pdf.txt Content-Type text/plain; charset=UTF-8 Optik - International... journal for Light and Electron Optics Analysis of the structure, particle morphology and photoluminescent properties of ZnS:Mn2+ nanoparticulate phosphors Raleaooa PV Roodt A Mhlongo GH Motaung DE Ntwaeaborwa OM ABSTRACT: The structure...

Development of a Laser-Powered Dielectric Structure-Based Accelerator as a Stand-Alone Particle Source

International Nuclear Information System (INIS)

Yoder, R. B.; Travish, G.; Arab, E. R.; Fong, D.; Hoyer, Z.; Lacroix, U. H.; Vartanian, N.; Rosenzweig, J. B.

2010-01-01

An experimental program to develop and build a dielectric-based slab-symmetric structure (the micro-accelerator platform, or MAP) for generating and accelerating low-energy electrons is underway at UCLA and Manhattanville College. This optical acceleration structure is effectively a resonant cavity powered by a side-coupled laser, and has applications as a radiation source for medicine or industry. We present recent experimental and computational results on the accelerator, and progress toward its incorporation into a self-contained particle source. Such a particle source would incorporate a micron-scale electron emitter and a non-relativistic capture region to enable self-injection into the synchronous field within the accelerator. A prototype of the accelerator itself has been constructed from candidate dielectric materials using micromanufacturing techniques; the current status of the testing program is described. A novel electron emitter incorporating pyroelectric crystals with field-enhancing tips has been demonstrated to produce steady currents; the results are dependent on tip geometry, and appear suitable for injection into a microstructure. Extension of the MAP concept to non-relativistic velocities, as in the stand-alone source, requires a tapered structure that gives rise to numerous complications including beam defocusing and manufacturing challenges; approaches for addressing these complications are mentioned.

Structural state diagram of concentrated suspensions of jammed soft particles in oscillatory shear flow

Science.gov (United States)

Khabaz, Fardin; Cloitre, Michel; Bonnecaze, Roger T.

2018-03-01

In a recent study [Khabaz et al., Phys. Rev. Fluids 2, 093301 (2017), 10.1103/PhysRevFluids.2.093301], we showed that jammed soft particle glasses (SPGs) crystallize and order in steady shear flow. Here we investigate the rheology and microstructures of these suspensions in oscillatory shear flow using particle-dynamics simulations. The microstructures in both types of flows are similar, but their evolutions are very different. In both cases the monodisperse and polydisperse suspensions form crystalline and layered structures, respectively, at high shear rates. The crystals obtained in the oscillatory shear flow show fewer defects compared to those in the steady shear. SPGs remain glassy for maximum oscillatory strains less than about the yield strain of the material. For maximum strains greater than the yield strain, microstructural and rheological transitions occur for SPGs. Polydisperse SPGs rearrange into a layered structure parallel to the flow-vorticity plane for sufficiently high maximum shear rates and maximum strains about 10 times greater than the yield strain. Monodisperse suspensions form a face-centered cubic (FCC) structure when the maximum shear rate is low and hexagonal close-packed (HCP) structure when the maximum shear rate is high. In steady shear, the transition from a glassy state to a layered one for polydisperse suspensions included a significant induction strain before the transformation. In oscillatory shear, the transformation begins to occur immediately and with different microstructural changes. A state diagram for suspensions in large amplitude oscillatory shear flow is found to be in close but not exact agreement with the state diagram for steady shear flow. For more modest amplitudes of around one to five times the yield strain, there is a transition from a glassy structure to FCC and HCP crystals, at low and high frequencies, respectively, for monodisperse suspensions. At moderate frequencies, the transition is from glassy to HCP via

Rotating structures in low temperature magnetized plasmas - Insight from particle simulations

Directory of Open Access Journals (Sweden)

Jean-Pierre eBoeuf

2014-12-01

Full Text Available The EXB configuration of various low temperature plasma devices is often responsible for the formation of rotating structures and instabilities leading to anomalous electron transport across the magnetic field. In these devices, electrons are strongly magnetized while ions are weakly or not magnetized and this leads to specific physical phenomena that are not present in fusion plasmas where both electrons and ions are strongly magnetized. In this paper we describe basic phenomena involving rotating plasma structures in simple configurations of low temperature EXB plasma devices on the basis of PIC-MCC (Particle-In-Cell Monte Carlo Collisions simulations. We focus on three examples: rotating electron vortices and rotating spokes in cylindrical magnetrons, and azimuthal electron-cyclotron drift instability in Hall thrusters. The simulations are not intended to give definite answers to the many physics issues related to low temperature EXB plasma devices but are used to illustrate and discuss some of the basic questions that need further studies.

Transverse-structure electrostatic charged particle beam lens

Science.gov (United States)

Moran, M.J.

1998-10-13

Electrostatic particle-beam lenses using a concentric co-planar array of independently biased rings can be advantageous for some applications. Traditional electrostatic lenses often consist of axial series of biased rings, apertures, or tubes. The science of lens design has devoted much attention to finding axial arrangements that compensate for the substantial optical aberrations of the individual elements. Thus, as with multi-element lenses for light, a multi-element charged-particle lens can have optical behavior that is far superior to that of the individual elements. Transverse multiple-concentric-ring lenses achieve high performance, while also having advantages in terms of compactness and optical versatility. 7 figs.

Structure of proton-proton events at high center-of-mass energy with an identified particle of large transverse momentum

International Nuclear Information System (INIS)

Hanke, P.

1977-01-01

At the CERN-ISR events of pp-collisions, in which particles of large transverse momentum psub(T) are produced, were studied at √S = 52 GeV center-of-mass energy, using the 'Split-Field'-magnetspectrometer. The lorentz-invariant production cross-section of positive particles with high psub(T) was measured in the fragmentation region (average* approximately 20 0 ). In the same kinematical region the pion-fraction of produced particles for both charges was determined. In these events the effect of 'strangeness'-conservation on the dynamics of additionally produced particles was investigated. The comparison of events with negative pions and events with heavier particles - mainly kaons - at high psub(T) indicates, that the compensation of transverse momentum does not depend on the 'strangeness' of the particle at high psub(T). The quantum-number conservation rather influences the particle-content from the hadronic rest inside longitudinal phase-space. This was shown by reconstruction of decay-vertices of neutral kaons. The results obtained can be interpreted by 'constituent'-models of the proton-structure. (orig.) [de

Particle and particle systems characterization small-angle scattering (SAS) applications

CERN Document Server

Gille, Wilfried

2016-01-01

Small-angle scattering (SAS) is the premier technique for the characterization of disordered nanoscale particle ensembles. SAS is produced by the particle as a whole and does not depend in any way on the internal crystal structure of the particle. Since the first applications of X-ray scattering in the 1930s, SAS has developed into a standard method in the field of materials science. SAS is a non-destructive method and can be directly applied for solid and liquid samples. Particle and Particle Systems Characterization: Small-Angle Scattering (SAS) Applications is geared to any scientist who might want to apply SAS to study tightly packed particle ensembles using elements of stochastic geometry. After completing the book, the reader should be able to demonstrate detailed knowledge of the application of SAS for the characterization of physical and chemical materials.

Targeted Drug Delivery and Treatment of Endoparasites with Biocompatible Particles of pH-Responsive Structure.

Science.gov (United States)

Mathews, Patrick D; Fernandes Patta, Ana C M; Gonçalves, Joao V; Gama, Gabriella Dos Santos; Garcia, Irene Teresinha Santos; Mertins, Omar

2018-02-12

Biomaterials conceived for vectorization of bioactives are currently considered for biomedical, biological, and environmental applications. We have produced a pH-sensitive biomaterial composed of natural source alginate and chitosan polysaccharides for application as a drug delivery system via oral administration. The composite particle preparation was in situ monitored by means of isothermal titration calorimetry. The strong interaction established between the macromolecules during particle assembly led to 0.60 alginate/chitosan effective binding sites with an intense exothermic effect and negative enthalpy variation on the order of a thousand kcal/mol. In the presence of model drugs mebendazole and ivermectin, with relatively small and large structures, respectively, mebendazole reduced the amount of chitosan monomers available to interact with alginate by 27%, which was not observed for ivermectin. Nevertheless, a state of intense negative Gibbs energy and large entropic decrease was achieved, providing evidence that formation of particles is thermodynamically driven and favored. Small-angle X-ray scattering provided further evidence of similar surface aspects independent of the presence of drug. The physical responses of the particles to pH variation comprise partial hydration, swelling, and the predominance of positive surface charge in strong acid medium, whereas ionization followed by deprotonation leads to compaction and charge reversal rather than new swelling in mild and slightly acidic mediums, respectively. In vivo performance was evaluated in the treatment of endoparasites in Corydoras fish. Systematically with a daily base oral administration, particles significantly reduced the infections over 15 days of treatment. The experiments provide evidence that utilizing particles granted and boosted the action of the antiparasitic drugs, leading to substantial reduction or elimination of infection. Hence, the pH-responsive particles represent a biomaterial

Multi-particle structure in the Zn-chiral Potts models

International Nuclear Information System (INIS)

Gehlen, G. von; Honecker, A.

1992-10-01

We calculate the lowest translationally invariant levels of the Z 3 - and Z 4 -symmetrical chiral Potts quantum chains, using numerical diagonalization of the hamiltonian for N≤12 and N≤10 sites, respectively, and extrapolating N→∞. In the high-temperature massive phase we find that the pattern of the low-lying zero momentum levels can be explained assuming the existence of n-1 particles carrying Z n -charges Q=1, ..., n-1 (mass m Q ), and their scattering states. In the superintegrable case the masses of the n-1 particles become proportional to their respective charges: m Q =Qm 1 . Exponential convergence in N is observed for the single particle gaps, while power convergence is seen for the scattering levels. We also verify that qualitatively the same pattern appears for the self-dual and integrable cases. For general Z n we show that the energy-momentum relations of the particles show a parity non-conservation asymmetry which for very high temperatures is exclusive due to the presence of a macroscopic momentum P m =(1-2Q/n)Φ, where Φ is the chiral angle and Q is the Z n -charge of the respective particle. (orig.)

Particulate morphology mathematics applied to particle assemblies

CERN Document Server

Gotoh, Keishi

2012-01-01

Encompassing over fifty years of research, Professor Gotoh addresses the correlation function of spatial structures and the statistical geometry of random particle assemblies. In this book morphological study is formed into random particle assemblies to which various mathematics are applied such as correlation function, radial distribution function and statistical geometry. This leads to the general comparison between the thermodynamic state such as gases and liquids and the random particle assemblies. Although structures of molecular configurations change at every moment due to thermal vibration, liquids can be regarded as random packing of particles. Similarly, gaseous states correspond to particle dispersion. If physical and chemical properties are taken away from the subject, the remainder is the structure itself. Hence, the structural study is ubiquitous and of fundamental importance. This book will prove useful to chemical engineers working on powder technology as well as mathematicians interested in le...

Dynamical phases of attractive particles sliding on a structured surface

International Nuclear Information System (INIS)

Hasnain, J; Jungblut, S; Dellago, C

2015-01-01

Inspired by experiments on quartz crystal microbalance setups, we study the mobility of a monolayer of Lennard-Jones particles driven over a hexagonal external potential. We pay special attention to the changes in the dynamical phases that arise when the lattice constant of the external substrate potential and the Lennard-Jones interaction are mismatched. We find that if the average particle separation is such that the particles repel each other, or interact harmonically, the qualitative behavior of the system is akin to that of a monolayer of purely repulsive Yukawa particles. On the other hand, if the particles typically attract each other, the ensuing dynamical states are determined entirely by the relative strength of the Lennard-Jones interaction with respect to that of the external potential. (paper)

Propagation of localized structures in relativistic magnetized electron-positron plasmas using particle-in-cell simulations

Energy Technology Data Exchange (ETDEWEB)

López, Rodrigo A. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción 4070386 (Chile); Muñoz, Víctor [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Viñas, Adolfo F. [Geospace Physics Laboratory, Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Valdivia, Juan A. [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnología (CEDENNA), Santiago 9170124 (Chile)

2015-09-15

We use a particle-in-cell simulation to study the propagation of localized structures in a magnetized electron-positron plasma with relativistic finite temperature. We use as initial condition for the simulation an envelope soliton solution of the nonlinear Schrödinger equation, derived from the relativistic two fluid equations in the strongly magnetized limit. This envelope soliton turns out not to be a stable solution for the simulation and splits in two localized structures propagating in opposite directions. However, these two localized structures exhibit a soliton-like behavior, as they keep their profile after they collide with each other due to the periodic boundary conditions. We also observe the formation of localized structures in the evolution of a spatially uniform circularly polarized Alfvén wave. In both cases, the localized structures propagate with an amplitude independent velocity.

Propagation of localized structures in relativistic magnetized electron-positron plasmas using particle-in-cell simulations

International Nuclear Information System (INIS)

López, Rodrigo A.; Muñoz, Víctor; Viñas, Adolfo F.; Valdivia, Juan A.

2015-01-01

We use a particle-in-cell simulation to study the propagation of localized structures in a magnetized electron-positron plasma with relativistic finite temperature. We use as initial condition for the simulation an envelope soliton solution of the nonlinear Schrödinger equation, derived from the relativistic two fluid equations in the strongly magnetized limit. This envelope soliton turns out not to be a stable solution for the simulation and splits in two localized structures propagating in opposite directions. However, these two localized structures exhibit a soliton-like behavior, as they keep their profile after they collide with each other due to the periodic boundary conditions. We also observe the formation of localized structures in the evolution of a spatially uniform circularly polarized Alfvén wave. In both cases, the localized structures propagate with an amplitude independent velocity

Particle supply and recovery device

International Nuclear Information System (INIS)

Yamada, Kimio; Okazaki, Takashi.

1988-01-01

This invention concerns a particle supply and recovery device suitable to the supply of fuels and exhaustion of reaction products in a tokamak device. The divertor chamber is divided into an inner side and an outer side, in which only the outer side is constituted as a tightly closed structure. Particles are supplied from the inside of main plasmas and exhausted from the outer side of the divertor chamber. In the divertor equilibrium arrangement, particles escaping from the main plasmas are conveyed mainly passing through the outer side scrape-off layer to the divertor chamber. The particle density is higher at the outer side and lower at the inner side of the scrape-off layer. By making the outer side as a tightly closed structure, the pressure is increased and the particle exhaustion efficiency is improved. Since the particle density is low in the inner scrape-layer, the particle supply efficiency to the main plasma is increased by supplying the particles from the inside. Further, particles ionized in the inner scrape-off layer are returned to the main plasma chamber and then supplied again since the inner divertor chamber is not closed. Accordingly, the particle supply efficiency can further be improved. (K.M.)

Particle accelerator

International Nuclear Information System (INIS)

Ress, R.I.

1976-01-01

Charged particles are entrained in a predetermined direction, independent of their polarity, in a circular orbit by a magnetic field rotating at high speed about an axis in a closed cylindrical or toroidal vessel. The field may be generated by a cylindrical laser structure, whose beam is polygonally reflected from the walls of an excited cavity centered on the axis, or by high-frequency energization of a set of electromagnets perpendicular to the axis. In the latter case, a separate magnetostatic axial field limits the orbital radius of the particles. These rotating and stationary magnetic fields may be generated centrally or by individual magnets peripherally spaced along its circular orbit. Chemical or nuclear reactions can be induced by collisions between the orbiting particles and an injected reactant, or by diverting high-speed particles from one doughnut into the path of counterrotating particles in an adjoining doughnut

Tailoring the synthesis of supported Pd catalysts towards desired structure and size of metal particles.

Science.gov (United States)

Suresh, Gatla; Radnik, Jörg; Kalevaru, Venkata Narayana; Pohl, Marga-Martina; Schneider, Matthias; Lücke, Bernhard; Martin, Andreas; Madaan, Neetika; Brückner, Angelika

2010-05-14

In a systematic study, the influence of different preparation parameters on phase composition and size of metal crystallites and particles in Pd-Cu/TiO(2) and Pd-Sb/TiO(2) catalyst materials has been explored. Temperature and atmosphere of thermal pretreatment (pure He or 10% H(2)/He), nature of metal precursors (chlorides, nitrates or acetates) as well as of ammonium additives (ammonium sulfate, nitrate, carbonate) and urea were varied with the aim of tailoring the synthesis procedure for the preferential formation of metal particles with similar size and structure as observed recently in active catalysts after long-term equilibration under catalytic reaction conditions in acetoxylation of toluene to benzylacetate. Among the metal precursors and additives, the chloride metal precursors and (NH(4))(2)SO(4) were most suitable. Upon thermal pretreatment of Pd-Sb or Pd-Cu precursors, chloroamine complexes of Pd and Cu are formed, which decompose above 220 degrees C to metallic phases independent of the atmosphere. In He, metallic Pd particles were formed with both the co-components. In H(2)/He flow, Pd-Cu precursors were converted to core-shell particles with a Cu shell and a Pd core, while Sb(1)Pd(1) and Sb(7)Pd(20) alloy phases were formed in the presence of Sb. Metal crystallites of about 40 nm agglomerate to particles of up to 150 nm in He and to even larger size in H(2)/He.

Regime of aggregate structures and magneto-rheological characteristics of a magnetic rod-like particle suspension: Monte Carlo and Brownian dynamics simulations

Energy Technology Data Exchange (ETDEWEB)

Okada, Kazuya [School of Akita Prefectural University, Yurihonjo (Japan); Satoh, Akira, E-mail: asatoh@akita-pu.ac.jp [Department of Machine Intelligence and System Engineering, Akita Prefectural University, Yurihonjo (Japan)

2017-09-01

Highlights: • Monte Carlo simulations have been employed for the aggregate structures. • Brownian dynamics simulations have been employed for the magneto-rheology. • Even a weak shear flow induces a significant regime change in the aggregates. • A strong external magnetic field drastically changes the aggregates. • The dependence of the viscosity on these factors is governed in a complex manner. - Abstract: In the present study, we address a suspension composed ferromagnetic rod-like particles to elucidate a regime change in the aggregate structures and the magneto-rheological characteristics. Monte Carlo simulations have been employed for investigating the aggregate structures in thermodynamic equilibrium, and Brownian dynamics simulations for magneto-rheological features in a simple shear flow. The main results obtained here are summarized as follows. For the case of thermodynamic equilibrium, the rod-like particles aggregate to form thick chain-like clusters and the neighboring clusters incline in opposite directions. If the external magnetic field is increased, the thick chain-like clusters in the magnetic field direction grow thicker by adsorbing the neighboring clusters that incline in the opposite direction. Hence, a significant phase change in the particle aggregates is not induced by an increase in the magnetic field strength. For the case of a simple shear flow, even a weak shear flow induces a significant regime change from the thick chain-like clusters of thermodynamic equilibrium into wall-like aggregates composed of short raft-like clusters. A strong external magnetic field drastically changes these aggregates into wall-like aggregates composed of thick chain-like clusters rather than the short raft-like clusters. The internal structure of these aggregates is not strongly influenced by a shear flow, and the formation of the short raft-like clusters is maintained inside the aggregates. The main contribution to the net viscosity is the

Structural, mechanical, and tribological characterization of sol-gel layers with inbedded anorganic fullerene-like tungsten-disulphide particles

International Nuclear Information System (INIS)

Hattermann, Hilke

2010-01-01

The preparation of composite coatings consisting of different materials with improved properties has been an intensively studied area of thin film technology in recent years. One method to prepare such composite coatings is the incorporation of nano or micro particles into a matrix of a different material. In this thesis, such composite coatings are investigated which have been prepared via a sol-gel route und contain up to about 30 wt.-% tungsten disulfide particles. These inorganic fullerenes have typical particle sizes of about 100 nm to 200 nm. Two different types of composite coatings with a thickness of up to a few micrometers and with embedded tungsten disulfide particles are prepared: First, coatings with a relatively stiff alumina matrix, and second, coatings with a matrix made of organically modified silica. Different analytical methods are used for the structural characterization of the coatings. The crystal structure and the chemical composition of the coatings are determined via X-ray diffraction and X-ray fluorescence measurements and via energy-dispersive X-ray spectroscopy. Through scanning and transmission electron microscopy the incorporation and the distribution of the tungsten disulfide particles in the respective matrix are analysed. Furthermore, the roughness and the adhesion of the coatings on the substrate are investigated. The influence of the embedded particles and of the temperature of the final heat treatment during the sample preparation on the mechanical properties, like elastic modulus and hardness, of the composite coatings are measured through nanoindentation testing. These experimental results are compared with theoretical values determined via different analytical models for effective materials. Finally, the tribological behavior of the composite coatings is investigated in comparison to pure coatings made of alumina or organically modified silica. With ball-on-disc tests the coefficient of friction of the coatings is measured

Analysis of ultra-relativistic charged particle beam and stretched wire measurement interactions with cylindrically symmetric structures

International Nuclear Information System (INIS)

Deibele, C.E.

1996-01-01

The beam impedance and wakefield are quantities which describe the stability of charged particles in their trajectory within an accelerator. The stretched wire measurement technique is a method which estimates the beam impedance and wakefield. Definitions for the beam impedance, the wakefield, and the stretched wire measurement are presented. A pillbox resonator with circular beampipes is studied for its relatively simple profile and mode structure. Theoretical predictions and measurement data are presented for the interaction of various charged particle beams and center conductor geometries between the cavity and beampipe. Time domain predictions for the stretched wire measurement and wakefield are presented and are shown to be a linear interaction

Surface structure and oxidation reactivity of oil sand coke particles

Energy Technology Data Exchange (ETDEWEB)

Fairbridge, C.; Palmer, A.D.; Ng, S.H.; Furimsky, E.

1987-05-01

Fractions of particles of varying mean diameter were isolated from coke obtained from the fluid coking of Athabasca bitumen. Correlations were established between the rate of oxygen sorption and the apparent surface area as measured by carbon dioxide adsorption. The rate of oxygen sorption, r/sub o/, could be related to particle radius, R, by r/sub o/ varying with R/sup D/ T over a range of particle size where D is the fractal dimension of the coke. The existence of such correlations may be related to the iterative processes which form the particles. 14 refs., 5 figs., 2 tabs.

Understanding of the mechanical and structural changes induced by alpha particles and heavy ions in the French simulated nuclear waste glass

International Nuclear Information System (INIS)

Karakurt, G.; Abdelouas, A.; Guin, J.-P.; Nivard, M.; Sauvage, T.; Paris, M.; Bardeau, J.-F.

2016-01-01

Borosilicate glasses are considered for the long-term confinement of high-level nuclear wastes. External irradiations with 1 MeV He + ions and 7 MeV Au 5+ ions were performed to simulate effects produced by alpha particles and by recoil nuclei in the simulated SON68 nuclear waste glass. To better understand the structural modifications, irradiations were also carried out on a 6-oxides borosilicate glass, a simplified version of the SON68 glass (ISG glass). The mechanical and macroscopic properties of the glasses were studied as function of the deposited electronic and nuclear energies. Alpha particles and gold ions induced a volume change up to −0.7% and −2.7%, respectively, depending on the glass composition. Nano-indentations tests were used to determine the mechanical properties of the irradiated glasses. A decrease of about −22% to −38% of the hardness and a decrease of the reduced Young's modulus by −8% were measured after irradiations. The evolution of the glass structure was studied by Raman spectroscopy, and also 11 B and 27 Al Nuclear Magnetic Resonance (MAS-NMR) on a 20 MeV Kr irradiated ISG glass powder. A decrease of the silica network connectivity after irradiation with alpha particles and gold ions is deduced from the structural changes observations. NMR spectra revealed a partial conversion of BO 4 to BO 3 units but also a formation of AlO 5 and AlO 6 species after irradiation with Kr ions. The relationships between the mechanical and structural changes are also discussed. - Highlights: • Mechanical and structural properties of two borosilicate glass compositions irradiated with alpha particles and heavy ions were investigated. • Both kinds of particles induced a decrease of the hardness, reduced Young's modulus and density. • Electronic and nuclear interactions are responsible for the changes observed. • The evolution of the mechanical properties under irradiation is linked to the changes occured in the

ON THE STRUCTURE OF ELEMENTARY PARTICLES IN CLASSICAL ELECTRODYNAMICS

Energy Technology Data Exchange (ETDEWEB)

Prigogine, I.; Henin, F.

1963-06-15

For particles that can be characterized by three scalars bare mass, electromagnetic mass, and electric charge), it is noted that there can be constructed a theory that is finite, relativistic, strictly causal, and that permits the definition of an energy tensor for the particle. (T.F.H.)

Random walks of oriented particles on fractals

International Nuclear Information System (INIS)

Haber, René; Prehl, Janett; Hoffmann, Karl Heinz; Herrmann, Heiko

2014-01-01

Random walks of point particles on fractals exhibit subdiffusive behavior, where the anomalous diffusion exponent is smaller than one, and the corresponding random walk dimension is larger than two. This is due to the limited space available in fractal structures. Here, we endow the particles with an orientation and analyze their dynamics on fractal structures. In particular, we focus on the dynamical consequences of the interactions between the local surrounding fractal structure and the particle orientation, which are modeled using an appropriate move class. These interactions can lead to particles becoming temporarily or permanently stuck in parts of the structure. A surprising finding is that the random walk dimension is not affected by the orientation while the diffusion constant shows a variety of interesting and surprising features. (paper)

An Electron is the God Particle

Science.gov (United States)

Wolff, Milo

2001-04-01

Philosophers, Clifford, Mach, Einstein, Wyle, Dirac & Schroedinger, believed that only a wave structure of particles could satisfy experiment and fulfill reality. A quantum Wave Structure of Matter is described here. It predicts the natural laws more accurately and completely than classic laws. Einstein reasoned that the universe depends on particles which are "spherically, spatially extended in space." and "Hence a discrete material particle has no place as a fundamental concept in a field theory." Thus the discrete point particle was wrong. He deduced the true electron is primal because its force range is infinite. Now, it is found the electron's wave structure contains the laws of Nature that rule the universe. The electron plays the role of creator - the God particle. Electron structure is a pair of spherical outward/inward quantum waves, convergent to a center in 3D space. This wave pair creates a h/4pi quantum spin when the in-wave spherically rotates to become the out-wave. Both waves form a spinor satisfying the Dirac Equation. Thus, the universe is binary like a computer. Reference: http://members.tripod.com/mwolff

Particles, contacts, bulk behavior

NARCIS (Netherlands)

Luding, Stefan; Tomas, J.

2014-01-01

Granular matter consists of discrete “particles”. These can be separate sand-grains, agglomerates (made of many primary particles), or solid materials like rock, composites, or metal-alloys—all with particulate inhomogeneous, possibly anisotropic micro-structure. Particles can be as small as

Particle exhaust with vented structures: application to the ergodic divertor of Tore Supra

International Nuclear Information System (INIS)

Azeroual, A.

2000-01-01

In a thermonuclear reactor, one must continuously fuel the discharge and extract the ashes resulting from fusion reactions. To avoid the risk of discharge poisoning, α-particle concentration is limited to ∼ 10 %. To allow for steady-state conditions requires then to extract ≥2 % of the helium out flux. In Tore Supra, the ergodic divertor is the main component managing the heat and particle fluxes at the edge. Its principle consists in generating a resonant perturbation able to destroy magnetic surfaces at the plasma periphery. In this region, the field lines are open and connected at both ends to neutralizers which are wetted by the major part of the heat and particle fluxes and are the structures through which a part of the plasma out flux is pumped for maintaining the discharge in steady-state conditions. This work describes the neutral recirculation around the ergodic divertor and is based on a data base of 56 discharges. One discuss the two processes allowing for particle exhaust: the ballistic collection of ions and that of neutrals backscattered by atomic reactions. These two processes are modelled accounting for a realistic description of the divertor geometry. A comparison between simulations and experiments is presented for measurements characterising the three main actors of plasma-wall interaction: the edge plasma, the D α light emission and the neutral pressure in the divertor plenum. Last, one question how such a system can be extrapolated to next step machines, for which one must account for technical constraints linked to the presence of the shield protecting the coils from the high neutron flux. (author)

Structural and fractal properties of particles emitted from spark ignition engines.

Science.gov (United States)

Chakrabarty, Rajan K; Moosmüller, Hans; Arnott, W Patrick; Garro, Mark A; Walker, John

2006-11-01

Size, morphology, and microstructure of particles emitted from one light-duty passenger vehicle (Buick Century; model year 1990; PM (particulate matter) mass emission rate 3.1 mg/km) and two light-duty trucks (Chevrolet C2; model year 1973; PM mass emission rate 282 mg/km, and Chevrolet El Camino; model year 1976; PM mass emission rate 31 mg/km), running California's unified driving cycles (UDC) on a chassis dynamometer, were studied using scanning electron microscopy (SEM). SEM images yielded particle properties including three-dimensional density fractal dimensions, monomer and agglomerate number size distributions, and three different shape descriptors, namely aspect ratio, root form factor, and roundness. The density fractal dimension of the particles was between 1.7 and 1.78, while the number size distribution of the particles placed the majority of the particles in the accumulation mode (0.1-0.3 microm). The shape descriptors were found to decrease with increasing particle size. Partial melting of particles, a rare and previously unreported phenomenon, was observed upon exposure of particles emitted during phase 2 of the UDC to the low accelerating voltage electron beam of the SEM. The rate of melting was quantified for individual particles, establishing a near linear relationship between the melting rate and the organic carbon 1 to elemental carbon ratio.

Test-particle motion in Einstein's unified field theory. I. General theory and application to neutral test particles

International Nuclear Information System (INIS)

Johnson, C.R.

1985-01-01

We develop a method for finding the exact equations of structure and motion of multipole test particles in Einstein's unified field theory: the theory of the nonsymmetric field. The method is also applicable to Einstein's gravitational theory. Particles are represented by singularities in the field. The method is covariant at each step of the analysis. We also apply the method and find both in Einstein's unified field theory and in Einstein's gravitational theory the equations of structure and motion of neutral pole-dipole test particles possessing no electromagnetic multipole moments. In the case of Einstein's gravitational theory the results are the well-known equations of structure and motion of a neutral pole-dipole test particle in a given background gravitational field. In the case of Einstein's unified field theory the results are the same, providing we identify a certain symmetric second-rank tensor field appearing in Einstein's theory with the metric and gravitational field. We therefore discover not only the equations of structure and motion of a neutral test particle in Einstein's unified field theory, but we also discover what field in Einstein's theory plays the role of metric and gravitational field

Soft template synthesis of yolk/silica shell particles.

Science.gov (United States)

Wu, Xue-Jun; Xu, Dongsheng

2010-04-06

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

When is a particle

International Nuclear Information System (INIS)

Drell, S.D.

1978-01-01

The concept of elementary constituents or ultimate building blocks of nature in recent years is reviewed. The quark hypothesis, neutrinos, color, hard collisions, psi and other recent resonances, flavor, quantum chromodynamics, the tau particle, and particle structure are among the ideas considered. 22 references

Microchip Coulter particle counter

DEFF Research Database (Denmark)

Larsen, Ulrik Darling; Blankenstein, Gert; Branebjerg, J.

1997-01-01

This paper presents a micro device employing the Coulter principle for counting and sizing of living cells and particles in liquid suspension. The microchip Coulter particle counter (μCPC) has been employed in a planar silicon structure covered with glass, which enables detailed observation during...

Spinning self-dual particles

International Nuclear Information System (INIS)

Gamboa, J.; Rivelles, V.O.

1989-02-01

We study spinning self-dual particles in two dimensions. They are obtained from the chiral bosonic particle through the square root technique. We show that the resulting field theory can be either fermionic or bosonic and that the associated self-dual field reveals its Lorentz tensor structure which remains hidden in the usual formulations. We also calculate the spinning self-dual particle propagators using the BFV formalism. (author) [pt

Tuning the structure of platinum particles on ceria in situ for enhancing the catalytic performance of exhaust gas catalysts

International Nuclear Information System (INIS)

Gaenzler, Andreas M.; Casapu, Maria; Grunwaldt, Jan-Dierk; Vernoux, Philippe; Loridant, Stephane; Cadete Santos Aires, Francisco J.; Epicier, Thierry; Betz, Benjamin; Hoyer, Ruediger

2017-01-01

A dynamic structural behavior of Pt nanoparticles on the ceria surface under reducing/oxidizing conditions was found at moderate temperatures (<500 C) and exploited to enhance the catalytic activity of Pt/CeO 2 -based exhaust gas catalysts. Redispersion of platinum in an oxidizing atmosphere already occurred at 400 C. A protocol with reducing pulses at 250-400 C was applied in a subsequent step for controlled Pt-particle formation. Operando X-ray absorption spectroscopy unraveled the different extent of reduction and sintering of Pt particles: The choice of the reductant allowed the tuning of the reduction degree/particle size and thus the catalytic activity (CO>H 2 >C 3 H 6 ). This dynamic nature of Pt on ceria at such low temperatures (250-500 C) was additionally confirmed by in situ environmental transmission electron microscopy. A general concept is proposed to adjust the noble metal dispersion (size, structure), for example, during operation of an exhaust gas catalyst. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Tuning the structure of platinum particles on ceria in situ for enhancing the catalytic performance of exhaust gas catalysts

Energy Technology Data Exchange (ETDEWEB)

Gaenzler, Andreas M.; Casapu, Maria; Grunwaldt, Jan-Dierk [Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany); Vernoux, Philippe; Loridant, Stephane; Cadete Santos Aires, Francisco J. [Institut de Recherches sur la Catalyse et l' Environnement de Lyon, UMR 5256, CNRS, Universite Claude Bernard Lyon 1, Universite de Lyon, Villeurbanne (France); Epicier, Thierry [Materiaux, Ingenierie et Science, UMR 5510, CNRS, INSA de Lyon, Universite de Lyon, Villeurbanne (France); Betz, Benjamin [Umicore AG and Co. KG, Hanau (Germany); Ernst-Berl Institut, Technische Universitaet Darmstadt (Germany); Hoyer, Ruediger [Umicore AG and Co. KG, Hanau (Germany)

2017-10-09

A dynamic structural behavior of Pt nanoparticles on the ceria surface under reducing/oxidizing conditions was found at moderate temperatures (<500 C) and exploited to enhance the catalytic activity of Pt/CeO{sub 2}-based exhaust gas catalysts. Redispersion of platinum in an oxidizing atmosphere already occurred at 400 C. A protocol with reducing pulses at 250-400 C was applied in a subsequent step for controlled Pt-particle formation. Operando X-ray absorption spectroscopy unraveled the different extent of reduction and sintering of Pt particles: The choice of the reductant allowed the tuning of the reduction degree/particle size and thus the catalytic activity (CO>H{sub 2}>C{sub 3}H{sub 6}). This dynamic nature of Pt on ceria at such low temperatures (250-500 C) was additionally confirmed by in situ environmental transmission electron microscopy. A general concept is proposed to adjust the noble metal dispersion (size, structure), for example, during operation of an exhaust gas catalyst. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Particle morphology and mineral structure of heavy metal-contaminated kaolin soil before and after electrokinetic remediation.

Science.gov (United States)

Roach, Nicole; Reddy, Krishna R; Al-Hamdan, Ashraf Z

2009-06-15

This study aims to characterize the physical distribution of heavy metals in kaolin soil and the chemical and structural changes in kaolinite minerals that result from electrokinetic remediation. Three bench-scale electrokinetic experiments were conducted on kaolin that was spiked with Cr(VI) alone, Ni (II) alone, and a combination of Cr(VI), Ni(II) and Cd(II) under a constant electric potential of 1VDC/cm for a total duration of 4 days. Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analyses were performed on the soil samples before and after electrokinetic remediation. Results showed that the heavy metal contaminant distribution in the soil samples was not observable using TEM and EDX. EDX detected nickel and chromium on some kaolinite particles and titanium-rich, high-contrast particles, but no separate phases containing the metal contaminants were detected. Small amounts of heavy metal contaminants that were detected by EDX in the absence of a visible phase suggest that ions are adsorbed to kaolinite particle surfaces as a thin coating. There was also no clear correlation between semiquantitative analysis of EDX spectra and measured total metal concentrations, which may be attributed to low heavy metal concentrations and small size of samples used. X-ray diffraction analyses were aimed to detect any structural changes in kaolinite minerals resulting from EK. The diffraction patterns showed a decrease in peak height with decreasing soil pH value, which indicates possible dissolution of kaolinite minerals during electrokinetic remediation. Overall this study showed that the changes in particle morphology were found to be insignificant, but a relationship was found between the crystallinity of kaolin and the pH changes induced by the applied electric potential.

Particle morphology and mineral structure of heavy metal-contaminated kaolin soil before and after electrokinetic remediation

International Nuclear Information System (INIS)

Roach, Nicole; Reddy, Krishna R.; Al-Hamdan, Ashraf Z.

2009-01-01

This study aims to characterize the physical distribution of heavy metals in kaolin soil and the chemical and structural changes in kaolinite minerals that result from electrokinetic remediation. Three bench-scale electrokinetic experiments were conducted on kaolin that was spiked with Cr(VI) alone, Ni (II) alone, and a combination of Cr(VI), Ni(II) and Cd(II) under a constant electric potential of 1 VDC/cm for a total duration of 4 days. Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analyses were performed on the soil samples before and after electrokinetic remediation. Results showed that the heavy metal contaminant distribution in the soil samples was not observable using TEM and EDX. EDX detected nickel and chromium on some kaolinite particles and titanium-rich, high-contrast particles, but no separate phases containing the metal contaminants were detected. Small amounts of heavy metal contaminants that were detected by EDX in the absence of a visible phase suggest that ions are adsorbed to kaolinite particle surfaces as a thin coating. There was also no clear correlation between semiquantitative analysis of EDX spectra and measured total metal concentrations, which may be attributed to low heavy metal concentrations and small size of samples used. X-ray diffraction analyses were aimed to detect any structural changes in kaolinite minerals resulting from EK. The diffraction patterns showed a decrease in peak height with decreasing soil pH value, which indicates possible dissolution of kaolinite minerals during electrokinetic remediation. Overall this study showed that the changes in particle morphology were found to be insignificant, but a relationship was found between the crystallinity of kaolin and the pH changes induced by the applied electric potential.

Laws of motion for interacting Yang-Mills particles

International Nuclear Information System (INIS)

Fuchs, H.

1988-01-01

Our recent Lagrangian approach to the equations of motion for test particles with internal structure can be enlarged to the laws of motion for interacting particles, at least in principle. As an example we consider the interaction of point particles endowed with a pole-dipole structure of the non-abelian charge. (author)

Extended two-particle Green close-quote s functions and optical potentials for two particle scattering by by many-body targets

International Nuclear Information System (INIS)

Brand, J.; Cederbaum, L.S.

1996-01-01

An extension of the fermionic particle-particle propagator is presented that possesses similar algebraic properties to the single-particle Green close-quote s function. In particular, this extended two-particle Green close-quote s function satisfies Dyson close-quote s equation and its self energy has the same analytic structure as the self energy of the single-particle Green close-quote s function. For the case of a system interacting with one-particle potentials only, the two-particle self energy takes on a particularly simple form, just like the common self energy does. The new two-particle self energy also serves as a well behaved optical potential for the elastic scattering of a two-particle projectile by a many-body target. Due to its analytic structure, the two-particle self energy avoids divergences that appear with effective potentials derived by other means. Copyright copyright 1996 Academic Press, Inc

Synthesis of Polyhydroxybutyrate Particles with Micro-to-Nanosized Structures and Application as Protective Coating for Packaging Papers

Directory of Open Access Journals (Sweden)

Vibhore Kumar Rastogi

2016-12-01

Full Text Available This study reports on the development of bio-based hydrophobic coatings for packaging papers through deposition of polyhydroxybutyrate (PHB particles in combination with nanofibrillated cellulose (NFC and plant wax. In the first approach, PHB particles in the micrometer range (PHB-MP were prepared through a phase-separation technique providing internally-nanosized structures. The particles were transferred as a coating by dip-coating filter papers in the particle suspension, followed by sizing with a carnauba wax solution. This approach allowed partial to almost full surface coverage of PHB-MP over the paper surface, resulting in static water contact angles of 105°–122° and 129°–144° after additional wax coating. In the second approach, PHB particles with submicron sizes (PHB-SP were synthesized by an oil-in-water emulsion (o/w solvent evaporation method and mixed in aqueous suspensions with 0–7 wt % NFC. After dip-coating filter papers in PHB-SP/NFC suspensions and sizing with a carnauba wax solution, static water contact angles of 112°–152° were obtained. The intrinsic properties of the particles were analyzed by scanning electron microscopy, thermal analysis and infrared spectroscopy, indicating higher crystallinity for PHB-SP than PHB-MP. The chemical interactions between the more amorphous PHB-MP particles and paper fibers were identified as an esterification reaction, while the morphology of the NFC fibrillar network was playing a key role as the binding agent in the retention of more crystalline PHB-SP at the paper surface, hence contributing to higher hydrophobicity.

Synthesis of Polyhydroxybutyrate Particles with Micro-to-Nanosized Structures and Application as Protective Coating for Packaging Papers.

Science.gov (United States)

Rastogi, Vibhore Kumar; Samyn, Pieter

2016-12-30

This study reports on the development of bio-based hydrophobic coatings for packaging papers through deposition of polyhydroxybutyrate (PHB) particles in combination with nanofibrillated cellulose (NFC) and plant wax. In the first approach, PHB particles in the micrometer range (PHB-MP) were prepared through a phase-separation technique providing internally-nanosized structures. The particles were transferred as a coating by dip-coating filter papers in the particle suspension, followed by sizing with a carnauba wax solution. This approach allowed partial to almost full surface coverage of PHB-MP over the paper surface, resulting in static water contact angles of 105°-122° and 129°-144° after additional wax coating. In the second approach, PHB particles with submicron sizes (PHB-SP) were synthesized by an oil-in-water emulsion (o/w) solvent evaporation method and mixed in aqueous suspensions with 0-7 wt % NFC. After dip-coating filter papers in PHB-SP/NFC suspensions and sizing with a carnauba wax solution, static water contact angles of 112°-152° were obtained. The intrinsic properties of the particles were analyzed by scanning electron microscopy, thermal analysis and infrared spectroscopy, indicating higher crystallinity for PHB-SP than PHB-MP. The chemical interactions between the more amorphous PHB-MP particles and paper fibers were identified as an esterification reaction, while the morphology of the NFC fibrillar network was playing a key role as the binding agent in the retention of more crystalline PHB-SP at the paper surface, hence contributing to higher hydrophobicity.

Synthesis of Polyhydroxybutyrate Particles with Micro-to-Nanosized Structures and Application as Protective Coating for Packaging Papers

Science.gov (United States)

Rastogi, Vibhore Kumar; Samyn, Pieter

2016-01-01

This study reports on the development of bio-based hydrophobic coatings for packaging papers through deposition of polyhydroxybutyrate (PHB) particles in combination with nanofibrillated cellulose (NFC) and plant wax. In the first approach, PHB particles in the micrometer range (PHB-MP) were prepared through a phase-separation technique providing internally-nanosized structures. The particles were transferred as a coating by dip-coating filter papers in the particle suspension, followed by sizing with a carnauba wax solution. This approach allowed partial to almost full surface coverage of PHB-MP over the paper surface, resulting in static water contact angles of 105°–122° and 129°–144° after additional wax coating. In the second approach, PHB particles with submicron sizes (PHB-SP) were synthesized by an oil-in-water emulsion (o/w) solvent evaporation method and mixed in aqueous suspensions with 0–7 wt % NFC. After dip-coating filter papers in PHB-SP/NFC suspensions and sizing with a carnauba wax solution, static water contact angles of 112°–152° were obtained. The intrinsic properties of the particles were analyzed by scanning electron microscopy, thermal analysis and infrared spectroscopy, indicating higher crystallinity for PHB-SP than PHB-MP. The chemical interactions between the more amorphous PHB-MP particles and paper fibers were identified as an esterification reaction, while the morphology of the NFC fibrillar network was playing a key role as the binding agent in the retention of more crystalline PHB-SP at the paper surface, hence contributing to higher hydrophobicity. PMID:28336839

Shell structure of natural rubber particles: evidence of chemical stratification by electrokinetics and cryo-TEM.

Science.gov (United States)

Rochette, Christophe N; Crassous, Jérôme J; Drechsler, Markus; Gaboriaud, Fabien; Eloy, Marie; de Gaudemaris, Benoît; Duval, Jérôme F L

2013-11-26

The interfacial structure of natural rubber (NR) colloids is investigated by means of cryogenic transmission electron microscopy (cryo-TEM) and electrokinetics over a broad range of KNO3 electrolyte concentrations (4-300 mM) and pH values (1-8). The asymptotic plateau value reached by NR electrophoretic mobility (μ) in the thin double layer limit supports the presence of a soft (ion- and water-permeable) polyelectrolytic type of layer located at the periphery of the NR particles. This property is confirmed by the analysis of the electron density profile obtained from cryo-TEM that evidences a ∼2-4 nm thick corona surrounding the NR polyisoprene core. The dependence of μ on pH and salt concentration is further marked by a dramatic decrease of the point of zero electrophoretic mobility (PZM) from 3.6 to 0.8 with increasing electrolyte concentration in the range 4-300 mM. Using a recent theory for electrohydrodynamics of soft multilayered particles, this "anomalous" dependence of the PZM on electrolyte concentration is shown to be consistent with a radial organization of anionic and cationic groups across the peripheral NR structure. The NR electrokinetic response in the pH range 1-8 is indeed found to be equivalent to that of particles surrounded by a positively charged ∼3.5 nm thick layer (mean dissociation pK ∼ 4.2) supporting a thin and negatively charged outermost layer (0.6 nm in thickness, pK ∼ 0.7). Altogether, the strong dependence of the PZM on electrolyte concentration suggests that the electrostatic properties of the outer peripheral region of the NR shell are mediated by lipidic residues protruding from a shell containing a significant amount of protein-like charges. This proposed NR shell interfacial structure questions previously reported NR representations according to which the shell consists of either a fully mixed lipid-protein layer, or a layer of phospholipids residing exclusively beneath an outer proteic film.

Simulations of DSB Yields and Radiation-induced Chromosomal Aberrations in Human Cells Based on the Stochastic Track Structure Induced by HZE Particles

Science.gov (United States)

Ponomarev, Artem; Plante, Ianik; George, Kerry; Wu, Honglu

2014-01-01

The formation of double-strand breaks (DSBs) and chromosomal aberrations (CAs) is of great importance in radiation research and, specifically, in space applications. We are presenting a new particle track and DNA damage model, in which the particle stochastic track structure is combined with the random walk (RW) structure of chromosomes in a cell nucleus. The motivation for this effort stems from the fact that the model with the RW chromosomes, NASARTI (NASA radiation track image) previously relied on amorphous track structure, while the stochastic track structure model RITRACKS (Relativistic Ion Tracks) was focused on more microscopic targets than the entire genome. We have combined chromosomes simulated by RWs with stochastic track structure, which uses nanoscopic dose calculations performed with the Monte-Carlo simulation by RITRACKS in a voxelized space. The new simulations produce the number of DSBs as function of dose and particle fluence for high-energy particles, including iron, carbon and protons, using voxels of 20 nm dimension. The combined model also calculates yields of radiation-induced CAs and unrejoined chromosome breaks in normal and repair deficient cells. The joined computational model is calibrated using the relative frequencies and distributions of chromosomal aberrations reported in the literature. The model considers fractionated deposition of energy to approximate dose rates of the space flight environment. The joined model also predicts of the yields and sizes of translocations, dicentrics, rings, and more complex-type aberrations formed in the G0/G1 cell cycle phase during the first cell division after irradiation. We found that the main advantage of the joined model is our ability to simulate small doses: 0.05-0.5 Gy. At such low doses, the stochastic track structure proved to be indispensable, as the action of individual delta-rays becomes more important.

Slowing the Starch Digestion by Structural Modification through Preparing Zein/Pectin Particle Stabilized Water-in-Water Emulsion.

Science.gov (United States)

Chen, Jia-Feng; Guo, Jian; Zhang, Tao; Wan, Zhi-Li; Yang, Juan; Yang, Xiao-Quan

2018-04-25

Slowing the digestion of starch is one of the dominant concerns in the food industry. A colloidal structural modification strategy for solving this problem was proposed in this work. Due to thermodynamic incompatibility between two biopolymers, water/water emulsion of waxy corn starch (WCS) droplets dispersed in a continuous aqueous guar gum (GG) was prepared, and zein particles (ZPs), obtained by antisolvent precipitation and pectin modification, were used as stabilizer. As the ratio of zein to pectin in the particles was 1:1, their wetting properties in the two polysaccharides were similar, which made them accumulate at the interface and cover the WCS-rich droplets. The analysis of digestibility curves indicated that a rapid (rate constant k 1 : 0.145 min -1 ) and a slow phase ( k 2 : 0.022 min -1 ) existed during WCS digestion. However, only one slow phase ( k 2 : 0.019 min -1 ) was found in the WCS/GG emulsion, suggesting that this structure was effective in slowing starch digestion.

Systematic UHV-AFM experiments on Na nano-particles and nano-structures in NaCl

OpenAIRE

Sugonyako, A.V.; Turkin, A.A.; Gaynutdinov, R.; Vainshtein, D.I.; Hartog, H.W. den; Bukharaev, A.A.

2005-01-01

Results of systematic AFM (atomic force microscopy) experiments on heavily and moderatly irradiated NaCl samples are presented. The sodium nanoparticles and structures of nanoparticles are poduced in sodium chloride during irradiation. The AFM images of the nanoparticles have been obtained in ultra high vacuum (UHV) in the non-contact mode with an Omicron UHV AFM/STM system. The sizes and arrangements of the observed particles depend on the irradiation conditions. The melting behaviour of the...

Particle physics

International Nuclear Information System (INIS)

Kamal, Anwar

2014-01-01

Provides step-by-step derivations. Contains numerous tables and diagrams. Supports learning and teaching with numerous worked examples, questions and problems with answers. Sketches also the historical development of the subject. This textbook teaches particle physics very didactically. It supports learning and teaching with numerous worked examples, questions and problems with answers. Numerous tables and diagrams lead to a better understanding of the explanations. The content of the book covers all important topics of particle physics: Elementary particles are classified from the point of view of the four fundamental interactions. The nomenclature used in particle physics is explained. The discoveries and properties of known elementary particles and resonances are given. The particles considered are positrons, muon, pions, anti-protons, strange particles, neutrino and hadrons. The conservation laws governing the interactions of elementary particles are given. The concepts of parity, spin, charge conjugation, time reversal and gauge invariance are explained. The quark theory is introduced to explain the hadron structure and strong interactions. The solar neutrino problem is considered. Weak interactions are classified into various types, and the selection rules are stated. Non-conservation of parity and the universality of the weak interactions are discussed. Neutral and charged currents, discovery of W and Z bosons and the early universe form important topics of the electroweak interactions. The principles of high energy accelerators including colliders are elaborately explained. Additionally, in the book detectors used in nuclear and particle physics are described. This book is on the upper undergraduate level.

Capillary interactions in nano-particle suspensions

International Nuclear Information System (INIS)

Bossev, D.P.; Warren, G.

2009-01-01

We have investigated the structures formed by colloidal particles suspended in solvents at volume fractions below 10% and interacting through capillary bridges. Such systems resemble colloidal gas of sticky nano-spheres that form pearl-necklace like chains that, in turn, induce strong viscoelasticity due to the formation of 3-D fractal network. The capillary force dominates the electrostatic and Van der Waals forces in solutions and can bridge multiple particles depending of the volume of the capillary bridge. We have investigated the morphology of the structures formed at different fractions of the bridging fluid. Small-angle neutron scattering (SANS) is used to study nanoparticles with an average diameter of 10 nm in polar and non-polar organic solvents at ambient temperatures. SANS intensity as a function of the scattering vector is analyzed as a product of a form factor, that depends on the particle shape, and a structure factor, that characterizes the interparticle inter reactions. The interaction of particles in polar solvents is considered to be through electrostatic repulsion and the data is successfully fitted by Hayter-Penfold mean spherical approximation (HPMSA). Computer simulations of a pearl necklace-like chain of spheres is conducted to explain the structure factor when capillary bridges are present. Alternatively, we have analyzed the slope of the intensity at low scattering vector in a double logarithmic plot to determine the dimension of the fractal structures formed by the particles at different volume fraction of the bridging fluid. We have also studied the properties of the capillary bridge between a pair of particles. The significance of this study is to explore the possibility of using capillary force as a tool to engineer new colloidal structures and materials in solutions and to optimize their viscoelastic properties. (author)

General particle transport equation. Final report

International Nuclear Information System (INIS)

Lafi, A.Y.; Reyes, J.N. Jr.

1994-12-01

The general objectives of this research are as follows: (1) To develop fundamental models for fluid particle coalescence and breakage rates for incorporation into statistically based (Population Balance Approach or Monte Carlo Approach) two-phase thermal hydraulics codes. (2) To develop fundamental models for flow structure transitions based on stability theory and fluid particle interaction rates. This report details the derivation of the mass, momentum and energy conservation equations for a distribution of spherical, chemically non-reacting fluid particles of variable size and velocity. To study the effects of fluid particle interactions on interfacial transfer and flow structure requires detailed particulate flow conservation equations. The equations are derived using a particle continuity equation analogous to Boltzmann's transport equation. When coupled with the appropriate closure equations, the conservation equations can be used to model nonequilibrium, two-phase, dispersed, fluid flow behavior. Unlike the Eulerian volume and time averaged conservation equations, the statistically averaged conservation equations contain additional terms that take into account the change due to fluid particle interfacial acceleration and fluid particle dynamics. Two types of particle dynamics are considered; coalescence and breakage. Therefore, the rate of change due to particle dynamics will consider the gain and loss involved in these processes and implement phenomenological models for fluid particle breakage and coalescence

Particle Swarm Optimization

Science.gov (United States)

Venter, Gerhard; Sobieszczanski-Sobieski Jaroslaw

2002-01-01

The purpose of this paper is to show how the search algorithm known as particle swarm optimization performs. Here, particle swarm optimization is applied to structural design problems, but the method has a much wider range of possible applications. The paper's new contributions are improvements to the particle swarm optimization algorithm and conclusions and recommendations as to the utility of the algorithm, Results of numerical experiments for both continuous and discrete applications are presented in the paper. The results indicate that the particle swarm optimization algorithm does locate the constrained minimum design in continuous applications with very good precision, albeit at a much higher computational cost than that of a typical gradient based optimizer. However, the true potential of particle swarm optimization is primarily in applications with discrete and/or discontinuous functions and variables. Additionally, particle swarm optimization has the potential of efficient computation with very large numbers of concurrently operating processors.

Understanding of the mechanical and structural changes induced by alpha particles and heavy ions in the French simulated nuclear waste glass

Energy Technology Data Exchange (ETDEWEB)

Karakurt, G., E-mail: karakurt_gokhan@yahoo.fr [SUBATECH, UMR 6457CNRS-IN2P3, Ecole des Mines de Nantes, 4 rue Alfred Kastler, 44307 Nantes (France); Abdelouas, A. [SUBATECH, UMR 6457CNRS-IN2P3, Ecole des Mines de Nantes, 4 rue Alfred Kastler, 44307 Nantes (France); Guin, J.-P.; Nivard, M. [Institut de Physique de Rennes, Université de Rennes 1 – UMR 62051 IPR, 263 avenue du Général Leclerc, 35042 Rennes (France); Sauvage, T. [Laboratoire CEMHTI (Conditions Extrêmes et Matériaux: Haute Température et Irradiation), CNRS UPR, 3079 Orléans (France); Paris, M. [Institut des Matériaux Jean ROUXEL, Université de Nantes, UMR 6502 CNRS, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 03 (France); Bardeau, J.-F. [Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, avenue Olivier Messiaen, 72085 Le Mans (France)

2016-07-15

Borosilicate glasses are considered for the long-term confinement of high-level nuclear wastes. External irradiations with 1 MeV He{sup +} ions and 7 MeV Au{sup 5+} ions were performed to simulate effects produced by alpha particles and by recoil nuclei in the simulated SON68 nuclear waste glass. To better understand the structural modifications, irradiations were also carried out on a 6-oxides borosilicate glass, a simplified version of the SON68 glass (ISG glass). The mechanical and macroscopic properties of the glasses were studied as function of the deposited electronic and nuclear energies. Alpha particles and gold ions induced a volume change up to −0.7% and −2.7%, respectively, depending on the glass composition. Nano-indentations tests were used to determine the mechanical properties of the irradiated glasses. A decrease of about −22% to −38% of the hardness and a decrease of the reduced Young's modulus by −8% were measured after irradiations. The evolution of the glass structure was studied by Raman spectroscopy, and also {sup 11}B and {sup 27}Al Nuclear Magnetic Resonance (MAS-NMR) on a 20 MeV Kr irradiated ISG glass powder. A decrease of the silica network connectivity after irradiation with alpha particles and gold ions is deduced from the structural changes observations. NMR spectra revealed a partial conversion of BO{sub 4} to BO{sub 3} units but also a formation of AlO{sub 5} and AlO{sub 6} species after irradiation with Kr ions. The relationships between the mechanical and structural changes are also discussed. - Highlights: • Mechanical and structural properties of two borosilicate glass compositions irradiated with alpha particles and heavy ions were investigated. • Both kinds of particles induced a decrease of the hardness, reduced Young's modulus and density. • Electronic and nuclear interactions are responsible for the changes observed. • The evolution of the mechanical properties under irradiation is linked

Microdroplet engineering for microbioassay and synthesis of functional structured porous particles

Science.gov (United States)

Rastogi, Vinayak

We present methods where sessile or suspended microdroplets are used to develop applications in the areas of bio-detection, photonics, drug delivery and catalysis. The first technique we report is for droplet-on-a-chip microbioassays. The assays are performed in droplet micro-containers suspended on the surface of high density fluorinated oil and are based on the process of agglutination of antibody-coated particles. Droplet microbioassays for the detection of Ricin were designed and their performance was compared to the standard handheld field assays. These droplet microbioassays were found to be 10 times more sensitive in terms of analyte concentration while requiring 100 times smaller volumes. We developed a model for the agglutination kinetics and mass transfer processes inside the droplets, which correlates well with the experimental data. The second technique that we developed uses droplet templates dispensed on superhydrophobic substrates for the fabrication of a new class of three dimensional hierarchical microsphere assemblies. The technique is termed Dry Self Assembly (DSA) since the fabricated supraparticles are easily detached from the substrate and collected unlike methods where assembled structures are suspended in liquid environment. The sessile droplet templates cast the final supraparticles into light diffracting near-spherical assemblies. When illuminated with a collimated beam of light, the structures exhibit unique ring shaped color diffraction patterns on their surface. The experimental observations for the angular position and wavelength corresponding to a spot on the rings are interpreted using a surface diffraction grating model. We also tailored the DSA method to produce both shape-anisotropic and composition-anisotropic supraparticles. The shape anisotropy was demonstrated by fabricating "doughnut" assemblies using droplets of both pure silica suspensions and silica mixed with gold nanoparticles. The composition anisotropy was realized by

Particles and nuclei, letters

International Nuclear Information System (INIS)

2000-01-01

The present collection of letters from JINR, Dubna, contains seven separate records on the integral representation for structure functions and target mass effects, multiscale properties of DNA primary structure including cross-scale correlations, dissipative evolution of the elementary act, the fine structure of the M T =1 Gamow-Teller resonance in 147g Tb→ 147 Gd β + /EC decay, the behaviour of the TVO temperature sensors in the magnetic fields, a fast method for searching for tracks in multilayer drift chambers of HADES spectrometer, a novel approach to particle track etching including surfactant enhanced control of pore morphology, azimuthal correlations of secondary particles in 32 S induced interactions with Ag(Br) nuclei at 4.5 GeV/ c/ nucleon

Electrokinetically driven continuous-flow enrichment of colloidal particles by Joule heating induced temperature gradient focusing in a convergent-divergent microfluidic structure.

Science.gov (United States)

Zhao, Cunlu; Ge, Zhengwei; Song, Yongxin; Yang, Chun

2017-09-07

Enrichment of colloidal particles in continuous flow has not only numerous applications but also poses a great challenge in controlling physical forces that are required for achieving particle enrichment. Here, we for the first time experimentally demonstrate the electrokinetically-driven continuous-flow enrichment of colloidal particles with Joule heating induced temperature gradient focusing (TGF) in a microfluidic convergent-divergent structure. We consider four mechanisms of particle transport, i.e., advection due to electroosmosis, electrophoresis, dielectrophoresis and, and further clarify their roles in the particle enrichment. It is experimentally determined and numerically verified that the particle thermophoresis plays dominant roles in enrichment of all particle sizes considered in this study and the combined effect of electroosmosis-induced advection and electrophoresis is mainly to transport particles to the zone of enrichment. Specifically, the enrichment of particles is achieved with combined DC and AC voltages rather than a sole DC or AC voltage. A numerical model is formulated with consideration of the abovementioned four mechanisms, and the model can rationalize the experimental observations. Particularly, our analysis of numerical and experimental results indicates that thermophoresis which is usually an overlooked mechanism of material transport is crucial for the successful electrokinetic enrichment of particles with Joule heating induced TGF.

Structural basis for substrate placement by an archaeal box C/D ribonucleoprotein particle.

Science.gov (United States)

Xue, Song; Wang, Ruiying; Yang, Fangping; Terns, Rebecca M; Terns, Michael P; Zhang, Xinxin; Maxwell, E Stuart; Li, Hong

2010-09-24

Box C/D small nucleolar and Cajal body ribonucleoprotein particles (sno/scaRNPs) direct site-specific 2'-O-methylation of ribosomal and spliceosomal RNAs and are critical for gene expression. Here we report crystal structures of an archaeal box C/D RNP containing three core proteins (fibrillarin, Nop56/58, and L7Ae) and a half-mer box C/D guide RNA paired with a substrate RNA. The structure reveals a guide-substrate RNA duplex orientation imposed by a composite protein surface and the conserved GAEK motif of Nop56/58. Molecular modeling supports a dual C/D RNP structure that closely mimics that recently visualized by electron microscopy. The substrate-bound dual RNP model predicts an asymmetric protein distribution between the RNP that binds and methylates the substrate RNA. The predicted asymmetric nature of the holoenzyme is consistent with previous biochemical data on RNP assembly and provides a simple solution for accommodating base-pairing between the C/D guide RNA and large ribosomal and spliceosomal substrate RNAs. Copyright © 2010 Elsevier Inc. All rights reserved.

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

Science.gov (United States)

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

2014-01-01

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

Simulation of the time structure of Extensive Air Showers with CORSIKA initiated by various primary particles at Alborz-I observatory level

Science.gov (United States)

Bahmanabadi, Mahmud; Moghaddam, Saba Mortazavi

2018-05-01

A detailed simulation of showers with various zenith angles in atmosphere produced by different primary particles including gamma, proton, carbon, and iron at Alborz-I observatory level (35∘43‧N, 51∘20‧E, 1200 m a.s.l= 890 gcm-2), in the energy range 3 × 1013 eV-3 × 1015 eV, has been performed by means of the CORSIKA Monte Carlo code. The aim of this study is to examine the time structure of secondary particles in Extensive Air Showers (EAS) produced by the different primary particles. For each primary particle, the distribution of the mean values of the time delays of secondary particles relative to the first particle hitting the ground level in each EAS, = , and the distribution of their mean standard deviations, in terms of distance from the shower core are obtained. The mean thickness and profile of showers as a function of their energy, primary mass, and zenith angle is described.

Structural characterization and gas reactions of small metal particles by high resolution in-situ TEM (Transmission Electron Microscopy) and TED (Transmission Electron Diffraction)

Science.gov (United States)

Heinemann, K.

1987-01-01

The detection and size analysis of small metal particles supported on amorphous substrates becomes increasingly difficult when the particle size approaches that of the phase contrast background structures of the support. An approach of digital image analysis, involving Fourier transformation of the original image, filtering, and image reconstruction was studied with respect to the likelihood of unambiguously detecting particles of less than 1 nm diameter on amorphous substrates from a single electron micrograph.

Effect of Particle Damping on an Acoustically Excited Curved Vehicle Panel Structure with varied Equipment Assemblies

Science.gov (United States)

Parsons, David; Smith, Andrew; Knight, Brent; Hunt, Ron; LaVerde, Bruce; Craigmyle, Ben

2012-01-01

Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from trials to determine how effective use of these dampers might be for equipment mounted to a curved orthogrid vehicle panel. Trends for damping are examined for variations in damper fill level, component mass, and excitation energy. A significant response reduction at the component level would suggest that comparatively small, thoughtfully placed, particle dampers might be advantageously used in vehicle design. The results of this test will be compared with baseline acoustic response tests and other follow-on testing involving a range of isolation and damping methods. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results.

[Adsorption of Cu on Core-shell Structured Magnetic Particles: Relationship Between Adsorption Performance and Surface Properties].

Science.gov (United States)

Li, Qiu-mei; Chen, Jing; Li, Hai-ning; Zhang, Xiao-lei; Zhang, Gao-sheng

2015-12-01

In order to reveal the relationship between the adsorption performance of adsorbents and their compositions, structure, and surface properties, the core-shell structured Fe₃O₄/MnO2 and Fe-Mn/Mn₂2 magnetic particles were systematically characterized using multiple techniques and their Cu adsorption behaviors as well as mechanism were also investigated in details. It was found that both Fe₃O4 and Fe-Mn had spinel structure and no obvious crystalline phase change was observed after coating with MnO₂. The introduction of Mn might improve the affinity between the core and the shell, and therefore enhanced the amount and distribution uniformity of the MnO₂ coated. Consequently, Fe-Mn/MnO₂ exhibited a higher BET specific surface area and a lower isoelectric point. The results of sorption experiments showed that Fe-Mn had a higher maximal Cu adsorption capacity of 33.7 mg · g⁻¹ at pH 5.5, compared with 17.5 mg · g⁻¹ of Fe₃O4. After coating, the maximal adsorption capacity of Fe-Mn/MnO₂ was increased to 58.2 mg · g⁻¹, which was 2.6 times as high as that of Fe₃O₄/MnO₂ and outperformed the majority of magnetic adsorbents reported in literature. In addition, a specific adsorption of Cu occurred at the surface of Fe₃O₄/MnO₂ or Fe-Mn/MnO₂ through the formation of inner-sphere complexes. In conclusion, the adsorption performance of the magnetic particles was positively related to their compositions, structure, and surface properties.

Particle acceleration in modified shocks

Energy Technology Data Exchange (ETDEWEB)

Drury, L.O' C. (Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany, F.R.)); Axford, W.I. (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany, F.R.)); Summers, D. (Memorial Univ. of Newfoundland, St. John' s (Canada))

1982-03-01

Efficient particle acceleration in shocks must modify the shock structure with consequent changes in the particle acceleration. This effect is studied and analytic solutions are found describing the diffusive acceleration of particles with momentum independent diffusion coefficients in hyperbolic tangent type velocity transitions. If the input particle spectrum is a delta function, the shock smoothing replaces the truncated power-law downstream particle spectrum by a more complicated form, but one which has a power-law tail at high momenta. For a cold plasma this solution can be made completely self-consistent. Some problems associated with momentum dependent diffusion coefficients are discussed.

Particle acceleration in modified shocks

International Nuclear Information System (INIS)

Drury, L.O'C.; Axford, W.I.; Summers, D.

1982-01-01

Efficient particle acceleration in shocks must modify the shock structure with consequent changes in the particle acceleration. This effect is studied and analytic solutions are found describing the diffusive acceleration of particles with momentum independent diffusion coefficients in hyperbolic tangent type velocity transitions. If the input particle spectrum is a delta function, the shock smoothing replaces the truncated power-law downstream particle spectrum by a more complicated form, but one which has a power-law tail at high momenta. For a cold plasma this solution can be made completely self-consistent. Some problems associated with momentum dependent diffusion coefficients are discussed. (author)

D term and the structure of pointlike and composed spin-0 particles

Science.gov (United States)

Hudson, Jonathan; Schweitzer, Peter

2017-12-01

This work deals with form factors of the energy-momentum tensor (EMT) of spin-0 particles and the unknown particle property D term related to the EMT, and it is divided into three parts. The first part explores free, weakly and strongly interacting theories to study EMT form factors with the following findings. (i) The free Klein-Gordon theory predicts for the D term D =-1 . (ii) Even infinitesimally small interactions can drastically impact D . (iii) In strongly interacting theories one can encounter large negative D though notable exceptions exist, which include Goldstone bosons of chiral symmetry breaking. (iv) Contrary to common belief one cannot arbitrarily add "total derivatives" to the EMT. Rather the EMT must be defined in an unambiguous way. The second part deals with the interpretation of the information content of EMT form factors in terms of 3D densities with the following results. (i) The 3D-density formalism is internally consistent. (ii) The description is subject to relativistic corrections but those are acceptably small in phenomenologically relevant situations including nucleons and nuclei. (iii) The free-field result D =-1 persists when a spin-0 boson is not pointlike but "heuristically given some internal structure." The third part investigates the question of whether such "giving of an extended structure" can be implemented dynamically, and it has the following insights. (i) We construct a consistent microscopic theory which, in a certain parametric limit, interpolates between extended and pointlike solutions. (ii) This theory is exactly solvable which is rare in 3 +1 dimensions, admits nontopological solitons of Q -ball type, and has a Gaussian field amplitude. (iii) The interaction of this theory belongs to a class of logarithmic potentials which were discussed in the literature, albeit in different contexts including beyond-standard-model phenomenology, cosmology, and Higgs physics.

Micrometer-sized Water Ice Particles for Planetary Science Experiments: Influence of Surface Structure on Collisional Properties

Energy Technology Data Exchange (ETDEWEB)

Gärtner, S.; Fraser, H. J. [School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Gundlach, B.; Ratte, J.; Blum, J. [Institut für Geophysik und extraterrestrische Physik, TU Braunschweig, Mendelssohnstr. 3, D-38106 Braunschweig (Germany); Headen, T. F.; Youngs, T. G. A.; Bowron, D. T. [ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX (United Kingdom); Oesert, J.; Gorb, S. N., E-mail: sabrina.gaertner@stfc.ac.uk, E-mail: helen.fraser@open.ac.uk [Zoologisches Institut, Christian-Albrechts-Universität zu Kiel, Am Botanischen Garten 1-9, D-24118 Kiel (Germany)

2017-10-20

Models and observations suggest that ice-particle aggregation at and beyond the snowline dominates the earliest stages of planet formation, which therefore is subject to many laboratory studies. However, the pressure–temperature gradients in protoplanetary disks mean that the ices are constantly processed, undergoing phase changes between different solid phases and the gas phase. Open questions remain as to whether the properties of the icy particles themselves dictate collision outcomes and therefore how effectively collision experiments reproduce conditions in protoplanetary environments. Previous experiments often yielded apparently contradictory results on collision outcomes, only agreeing in a temperature dependence setting in above ≈210 K. By exploiting the unique capabilities of the NIMROD neutron scattering instrument, we characterized the bulk and surface structure of icy particles used in collision experiments, and studied how these structures alter as a function of temperature at a constant pressure of around 30 mbar. Our icy grains, formed under liquid nitrogen, undergo changes in the crystalline ice-phase, sublimation, sintering and surface pre-melting as they are heated from 103 to 247 K. An increase in the thickness of the diffuse surface layer from ≈10 to ≈30 Å (≈2.5 to 12 bilayers) proves increased molecular mobility at temperatures above ≈210 K. Because none of the other changes tie-in with the temperature trends in collisional outcomes, we conclude that the surface pre-melting phenomenon plays a key role in collision experiments at these temperatures. Consequently, the pressure–temperature environment, may have a larger influence on collision outcomes than previously thought.

Bethe-Salpeter kernels and particle structure in the Yukawa2 quantum field theory

International Nuclear Information System (INIS)

Cooper, A.S.

1981-01-01

The author discusses the extension to the (weakly coupled) Yukawa quantum field theory in two space-time dimensions (Y 2 ), with equal bare masses, of some techniques used in the analysis of particle structure for weakly coupled even P(PHI) 2 . In particular he considers existence, regularity, and decay properties for the inverse two point functions and various Bethe-Salpeter kernels of the theory. These properties suffice to ensure that in the +-2 fermion sectors the mass spectrum is discrete below 2m 0 and the S-matrix is unitary up to 2m 0 + epsilon. (Auth.)

Simulations of DSB Yields and Radiation-induced Chromosomal Aberrations in Human Cells Based on the Stochastic Track Structure iIduced by HZE Particles

Science.gov (United States)

Ponomarev, Artem; Plante, Ianik; George, Kerry; Wu, Honglu

2014-01-01

The formation of double-strand breaks (DSBs) and chromosomal aberrations (CAs) is of great importance in radiation research and, specifically, in space applications. We are presenting a new particle track and DNA damage model, in which the particle stochastic track structure is combined with the random walk (RW) structure of chromosomes in a cell nucleus. The motivation for this effort stems from the fact that the model with the RW chromosomes, NASARTI (NASA radiation track image) previously relied on amorphous track structure, while the stochastic track structure model RITRACKS (Relativistic Ion Tracks) was focused on more microscopic targets than the entire genome. We have combined chromosomes simulated by RWs with stochastic track structure, which uses nanoscopic dose calculations performed with the Monte-Carlo simulation by RITRACKS in a voxelized space. The new simulations produce the number of DSBs as function of dose and particle fluence for high-energy particles, including iron, carbon and protons, using voxels of 20 nm dimension. The combined model also calculates yields of radiation-induced CAs and unrejoined chromosome breaks in normal and repair deficient cells. The joined computational model is calibrated using the relative frequencies and distributions of chromosomal aberrations reported in the literature. The model considers fractionated deposition of energy to approximate dose rates of the space flight environment. The joined model also predicts of the yields and sizes of translocations, dicentrics, rings, and more complex-type aberrations formed in the G0/G1 cell cycle phase during the first cell division after irradiation. We found that the main advantage of the joined model is our ability to simulate small doses: 0.05-0.5 Gy. At such low doses, the stochastic track structure proved to be indispensable, as the action of individual delta-rays becomes more important.

Delivery of single accelerated particles

International Nuclear Information System (INIS)

McNulty, P.J.; Pease, V.P.; Bond, V.P.; Schimmerling, W.; Vosburgh, K.G.; Crebbin, K.; Everette, W.; Howard, J.

1978-01-01

It is desirable for certain experiments involving accelerators to have the capability of delivering just a single beam particle to the target area. The essential features of such a one-at-a-time facility are discussed. Two such facilities are described which were implemented at high-energy heavy ion accelerators without having to make major structural changes in the existing beam lines or substantially interfering with other accelerator uses. Two accelerator facilities are described which had the capability of delivering a single beam particle to the target area. This feature is necessary in certain experiments investigating visual phenomena induced by charged particles, other single particle interactions in biology, and other experiments in which the low intensities of cosmic rays need to be simulated. Both facilities were implemented without having to make structural changes in the existing beam lines or substantially interfering with other accelerator uses. (Auth.)

Plasma particle accelerators

International Nuclear Information System (INIS)

Dawson, J.M.

1988-01-01

The Superconducting Supercollider (SSC) will require an 87-kilometer accelerator ring to boost particles to 40 TeV. The SSC's size is due in part to the fact that its operating principle is the same one that has dominated accelerator design for 50 years: it guides particles by means of magnetic fields and propels them by strong electric fields. If one were to build an equally powerful but smaller accelerator, one would need to increase the strength of the guiding and propelling fields. Actually, however, conventional technology may not be able to provide significant increases in field strength. There are two reasons. First, the forces from magnetic fields are becoming greater than the structural forces that hold a magnetic material together; the magnets that produce these fields would themselves be torn apart. Second, the energy from electric fields is reaching the energies that bind electrons to atoms; it would tear electrons from nuclei in the accelerator's support structures. It is the electric field problem that plasma accelerators can overcome. Plasma particle accelerators are based on the principle that particles can be accelerated by the electric fields generated within a plasma. Because the plasma has already been ionized, plasma particle accelerators are not susceptible to electron dissociation. They can in theory sustain accelerating fields thousands of times stronger that conventional technologies. So far two methods for creating plasma waves for accelerators have been proposed and tested: the wakefield and the beat wave. Although promising electric fields have been produced, more research is necessary to determine whether plasma particle accelerators can compete with the existing accelerators. 7 figs

NiCo2O4 particles with diamond-shaped hexahedron structure for high-performance supercapacitors

Science.gov (United States)

Li, Yanfang; Hou, Xiaojuan; Zhang, Zengxing; Hai, Zhenyin; Xu, Hongyan; Cui, Danfeng; Zhuiykov, Serge; Xue, Chenyang

2018-04-01

Nickel cobalt oxide (NiCo2O4) particles with a diamond-shaped hexahedral porous sheet structure are successfully synthesized by a facile hydrothermal method, followed by calcination in one step. NiCo2O4-I and NiCo2O4-II particles are prepared using the same method with different contents of urea (CO(NH2)2) and ammonium fluoride (NH4F). The different morphologies of the NiCo2O4-I and NiCo2O4-II particles illustrate that CO(NH2)2 and NH4F play an important role in crystal growth. To verify the influence of NH4F and CO(NH2)2 on the morphology of the NiCo2O4 particles, the theory of crystal growth morphology is analyzed. The electrochemical measurements show that NiCo2O4 particles exhibit a high specific capacitance. At a current density of 1.0 mA cm-2, the mass specific capacitances of the NiCo2O4-I and NiCo2O4-II electrodes are 690.75 and 1710.9 F g-1, respectively, in a 6 M KOH aqueous electrolyte. The specific capacitances of the NiCo2O4-I and NiCo2O4-II electrodes remain ∼95.95% and ∼70.58% of the initial capacitance values after 5000 cycles, respectively. According to the two-electrode test, the NiCo2O4-II//AC asymmetric electrodes exhibited an ultrahigh energy density of 64.67 Wh kg-1 at the power density of 12 kW kg-1, demonstrating its excellent application potential as an electrode material for supercapacitors.

Synthesis, structural, dielectric and magnetic properties of polyol assisted copper ferrite nano particles

Energy Technology Data Exchange (ETDEWEB)

Pavithradevi, S. [Assistant Professor, Department of Physics, Park College of Engineering and Technology, Coimbatore (India); Suriyanarayanan, N., E-mail: madurasuri2210@yahoo.com [Prof & Head, Department of Physics, Government College of Technology, Coimbatore (India); Boobalan, T. [Lecturer, Department of Physics, PSG Polytechnic College, Coimbatore (India)

2017-03-15

Nanocrystalline copper ferrite CuFe{sub 2}O{sub 4} is synthesized by co-precipitation method in ethylene glycol as chelating agent, using sodium Hydroxide as precipitator at pH 8. The as synthesized CuFe{sub 2}O{sub 4} is annealed at temperatures of 350 °C, 700 °C, and 1050 °C for 2 h respectively. The thermal analysis of the synthesized sample is done by TG technique. It is shown that at 260 °C ethylene glycol has evaporated completely and after 715 °C, spinel ferrite is formed with a cubic structure. The calculated lattice parameters are in agreement with the reported values. FTIR spectra of CuFe{sub 2}O{sub 4} nano particles are as synthesized and annealed at 1050 °C and recorded between 400 cm{sup −1} and 4000 cm{sup −1}. It shows that when the temperature increases ethylene glycol gradually evaporates. Finally, nano crystalline single phase spinel ferrite is obtained. X-ray diffraction (XRD) and electron diffraction (EDS) studies show that the sample is indexed as the face centered cubic spinel structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the particles are flaky and spherical with the crystallite size in the range of 25–34 nm. From the dielectric studies, the dielectric constant decreases as the frequency increases. Low value of dielectric loss at higher frequencies suggests that the material is suitable for high frequency applications. AC conductivity increases with frequency. The magnetic properties of the samples are measured using a vibrating sample magnetometer (VSM) at room temperature, which shows that the sample exhibited a typical super paramagnetic behavior at low temperature. The saturation magnetization, remanant magnetism, and coercivity increases with applied field. - Highlights: • Complete removal of hematite phase along with ethylene glycol at 1050 °C. • Large decrease in particle sizes noticed along with ethylene glycol. • Ethylene glycol improves purity of the

Laser and Particle Guiding Micro-Elements for Particle Accelerators

CERN Document Server

Plettner, Tomas; Spencer, James; Wisdom, Jeffrey

2005-01-01

Laser driven particle accelerators based on the current generation of lasers will require sub-micron control of the laser field as well as precise beam guiding. Hence the fabrication techniques that allow integrating both elements into an accelerator-on-chip format become critical for the success of such particle accelerators. Micromachining technology for silicon has been shown to be one such feasible technology in PAC2003 but with a variety of complications on the laser side. Fortunately, in recent years the fabrication of transparent ceramics has become an interesting technology that could be applied for laser-particle accelerators in several ways. We discuss this area, its advantages such as the range of materials it provides and various ways to implement it followed by some different test examples that have been considered. One important goal of this approach is an integrated system that could avoid the necessity of having to inject either laser or particle pulses into these structures.

Modulation of mesenchymal stem cell behavior by nano- and micro-sized β-tricalcium phosphate particles in suspension and composite structures

Science.gov (United States)

Smoak, Mollie; Hogan, Katie; Kriegh, Lisa; Chen, Cong; Terrell, LeKeith B.; Qureshi, Ammar T.; Todd Monroe, W.; Gimble, Jeffrey M.; Hayes, Daniel J.

2015-04-01

Interest has grown in the use of microparticles and nanoparticles for modifying the mechanical and biological properties of synthetic bone composite structures. Micro- and nano-sized calcium phosphates are of interest for their osteoinductive behavior. Engineered composites incorporating polymers and ceramics, such as poly-l-lactic acid (PLLA) and beta-tricalcium phosphate (β-TCP), for bone tissue regeneration have been well investigated for their proliferative and osteoinductive abilities. Only limited research has been done to investigate the effects of different sizes of β-TCP particles on human mesenchymal stromal cell behavior. As such, the aim of this study was to investigate the modulations of human adipose-derived stem cell (hASCs) behavior within cell/particle and cell/composite systems as functions of particle size, concentration, and exposure time. The incorporation of nanoscale calcium phosphate resulted in improved mechanical properties and osteogenic behavior within the scaffold compared to the microscale calcium phosphate additives. Particle exposure results indicate that cytotoxicity on hASCs correlates inversely with particle size and increases with the increasing exposure time and particle concentration. Composites with increasing β-TCP content, whether microparticles or nanoparticles, were less toxic than colloidal micro- and nano-sized β-TCP particles directly supplied to hASCs. The difference in viability observed as a result of varying exposure route is likely related to the increased cell-particle interactions in the direct exposure compared to the particles becoming trapped within the scaffold/polymer matrix.

Modulation of mesenchymal stem cell behavior by nano- and micro-sized β-tricalcium phosphate particles in suspension and composite structures

Energy Technology Data Exchange (ETDEWEB)

Smoak, Mollie; Hogan, Katie; Kriegh, Lisa; Chen, Cong, E-mail: cchen19@tigers.lsu.edu; Terrell, LeKeith B.; Qureshi, Ammar T.; Todd Monroe, W. [Louisiana State University and LSU AgCenter, Department of Biological and Agricultural Engineering (United States); Gimble, Jeffrey M., E-mail: Jeffrey.Gimble@pbrc.edu [Tulane University School of Medicine, Center for Stem Cell Research & Regenerative Medicine (United States); Hayes, Daniel J., E-mail: danielhayes@lsu.edu [Louisiana State University and LSU AgCenter, Department of Biological and Agricultural Engineering (United States)

2015-04-15

Interest has grown in the use of microparticles and nanoparticles for modifying the mechanical and biological properties of synthetic bone composite structures. Micro- and nano-sized calcium phosphates are of interest for their osteoinductive behavior. Engineered composites incorporating polymers and ceramics, such as poly-l-lactic acid (PLLA) and beta-tricalcium phosphate (β-TCP), for bone tissue regeneration have been well investigated for their proliferative and osteoinductive abilities. Only limited research has been done to investigate the effects of different sizes of β-TCP particles on human mesenchymal stromal cell behavior. As such, the aim of this study was to investigate the modulations of human adipose-derived stem cell (hASCs) behavior within cell/particle and cell/composite systems as functions of particle size, concentration, and exposure time. The incorporation of nanoscale calcium phosphate resulted in improved mechanical properties and osteogenic behavior within the scaffold compared to the microscale calcium phosphate additives. Particle exposure results indicate that cytotoxicity on hASCs correlates inversely with particle size and increases with the increasing exposure time and particle concentration. Composites with increasing β-TCP content, whether microparticles or nanoparticles, were less toxic than colloidal micro- and nano-sized β-TCP particles directly supplied to hASCs. The difference in viability observed as a result of varying exposure route is likely related to the increased cell–particle interactions in the direct exposure compared to the particles becoming trapped within the scaffold/polymer matrix.

Patchy particles made by colloidal fusion

Science.gov (United States)

Gong, Zhe; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

2017-10-01

Patches on the surfaces of colloidal particles provide directional information that enables the self-assembly of the particles into higher-order structures. Although computational tools can make quantitative predictions and can generate design rules that link the patch motif of a particle to its internal microstructure and to the emergent properties of the self-assembled materials, the experimental realization of model systems of particles with surface patches (or `patchy' particles) remains a challenge. Synthetic patchy colloidal particles are often poor geometric approximations of the digital building blocks used in simulations and can only rarely be manufactured in sufficiently high yields to be routinely used as experimental model systems. Here we introduce a method, which we refer to as colloidal fusion, for fabricating functional patchy particles in a tunable and scalable manner. Using coordination dynamics and wetting forces, we engineer hybrid liquid-solid clusters that evolve into particles with a range of patchy surface morphologies on addition of a plasticizer. We are able to predict and control the evolutionary pathway by considering surface-energy minimization, leading to two main branches of product: first, spherical particles with liquid surface patches, capable of forming curable bonds with neighbouring particles to assemble robust supracolloidal structures; and second, particles with a faceted liquid compartment, which can be cured and purified to yield colloidal polyhedra. These findings outline a scalable strategy for the synthesis of patchy particles, first by designing their surface patterns by computer simulation, and then by recreating them in the laboratory with high fidelity.

Airflow structures and nano-particle deposition in a human upper airway model

Science.gov (United States)

Zhang, Z.; Kleinstreuer, C.

2004-07-01

Considering a human upper airway model, or equivalently complex internal flow conduits, the transport and deposition of nano-particles in the 1-150 nm diameter range are simulated and analyzed for cyclic and steady flow conditions. Specifically, using a commercial finite-volume software with user-supplied programs as a solver, the Euler-Euler approach for the fluid-particle dynamics is employed with a low-Reynolds-number k- ω model for laminar-to-turbulent airflow and the mass transfer equation for dispersion of nano-particles or vapors. Presently, the upper respiratory system consists of two connected segments of a simplified human cast replica, i.e., the oral airways from the mouth to the trachea (Generation G0) and an upper tracheobronchial tree model of G0-G3. Experimentally validated computational fluid-particle dynamics results show the following: (i) transient effects in the oral airways appear most prominently during the decelerating phase of the inspiratory cycle; (ii) selecting matching flow rates, total deposition fractions of nano-size particles for cyclic inspiratory flow are not significantly different from those for steady flow; (iii) turbulent fluctuations which occur after the throat can persist downstream to at least Generation G3 at medium and high inspiratory flow rates (i.e., Qin⩾30 l/min) due to the enhancement of flow instabilities just upstream of the flow dividers; however, the effects of turbulent fluctuations on nano-particle deposition are quite minor in the human upper airways; (iv) deposition of nano-particles occurs to a relatively greater extent around the carinal ridges when compared to the straight tubular segments in the bronchial airways; (v) deposition distributions of nano-particles vary with airway segment, particle size, and inhalation flow rate, where the local deposition is more uniformly distributed for large-size particles (say, dp=100 nm) than for small-size particles (say, dp=1 nm); (vi) dilute 1 nm particle

Polarized particle levitation in hexapole field

International Nuclear Information System (INIS)

Jones, T.B.; Kallio, G.A.; Robinson, K.S.

1976-06-01

Proposed here is a novel electrostatic levitation scheme which uses the force exerted by a non-uniform electric field on a polarized particle. The scheme differs from conventional quadrupole levitation devices principally in that the levitated particle is uncharged. In order to provide the proper force required to achieve dynamic stabilization, a very intense non-uniform time-varying electric field produced by a three-dimensional hexapole electrode structure is utilized. The primary advantage of this levitation scheme might accrue in target fabrication operations where particle charge is undesirable or where reproducible charging of the particles themselves is difficult, due to high resistivity. The disadvantages of this scheme, as compared to charged particle levitation, are (i) a more complex electrode structure and (ii) significantly higher voltages. The scheme has possible application to molecular mass spectrometry, in situations where un-ionized but strongly polar or polarizable molecules are to be trapped or confined for analysis

Internal structure analysis of particle-double network gels used in a gel organ replica

Science.gov (United States)

Abe, Mei; Arai, Masanori; Saito, Azusa; Sakai, Kazuyuki; Kawakami, Masaru; Furukawa, Hidemitsu

2016-04-01

In recent years, the fabrication of patient organ replicas using 3D printers has been attracting a great deal of attention in medical fields. However, the cost of these organ replicas is very high as it is necessary to employ very expensive 3D printers and printing materials. Here we present a new gel organ replica, of human kidney, fabricated with a conventional molding technique, using a particle-double network hydrogel (P-DN gel). The replica is transparent and has the feel of a real kidney. It is expected that gel organ replicas produced this way will be a useful tool for the education of trainee surgeons and clinical ultrasonography technologists. In addition to developing a gel organ replica, the internal structure of the P-DN gel used is also discussed. Because the P-DN gel has a complex structure comprised of two different types of network, it has not been possible to investigate them internally in detail. Gels have an inhomogeneous network structure. If it is able to get a more uniform structure, it is considered that this would lead to higher strength in the gel. In the present study we investigate the structure of P-DN gel, using the gel organ replica. We investigated the internal structure of P-DN gel using Scanning Microscopic Light Scattering (SMILS), a non-contacting and non-destructive.

Single-particle motion in large-amplitude quadrupole shape transition

International Nuclear Information System (INIS)

Yamada, Kazuya

1991-01-01

The microscopic structure of the single-particle motion for the spherical-deformed transitional nuclei is analysed by using the self-consistent collective-coordinate method (SCC method). The single-particle motion in the moving-frame of reference called the collective vibrating coordinate frame is introduced by the generalized Bogoliubov transformation depending on the collective coordinate. The numerical calculations of the single-particle (quasi-particle) energy level diagrams and their occupation probabilities for the static deformation are carried out for the Sm isotopes. A clear change of the single-particle distribution structure appears in the course of deformation. (author)

Structures of Adenovirus Incomplete Particles Clarify Capsid Architecture and Show Maturation Changes of Packaging Protein L1 52/55k.

Science.gov (United States)

Condezo, Gabriela N; Marabini, Roberto; Ayora, Silvia; Carazo, José M; Alba, Raúl; Chillón, Miguel; San Martín, Carmen

2015-09-01

Adenovirus is one of the most complex icosahedral, nonenveloped viruses. Even after its structure was solved at near-atomic resolution by both cryo-electron microscopy and X-ray crystallography, the location of minor coat proteins is still a subject of debate. The elaborated capsid architecture is the product of a correspondingly complex assembly process, about which many aspects remain unknown. Genome encapsidation involves the concerted action of five virus proteins, and proteolytic processing by the virus protease is needed to prime the virion for sequential uncoating. Protein L1 52/55k is required for packaging, and multiple cleavages by the maturation protease facilitate its release from the nascent virion. Light-density particles are routinely produced in adenovirus infections and are thought to represent assembly intermediates. Here, we present the molecular and structural characterization of two different types of human adenovirus light particles produced by a mutant with delayed packaging. We show that these particles lack core polypeptide V but do not lack the density corresponding to this protein in the X-ray structure, thereby adding support to the adenovirus cryo-electron microscopy model. The two types of light particles present different degrees of proteolytic processing. Their structures provide the first glimpse of the organization of L1 52/55k protein inside the capsid shell and of how this organization changes upon partial maturation. Immature, full-length L1 52/55k is poised beneath the vertices to engage the virus genome. Upon proteolytic processing, L1 52/55k disengages from the capsid shell, facilitating genome release during uncoating. Adenoviruses have been extensively characterized as experimental systems in molecular biology, as human pathogens, and as therapeutic vectors. However, a clear picture of many aspects of their basic biology is still lacking. Two of these aspects are the location of minor coat proteins in the capsid and the

Formation of polymeric toroidal-spiral particles.

Science.gov (United States)

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.

Suspensions of colloidal particles and aggregates

CERN Document Server

Babick, Frank

2016-01-01

This book addresses the properties of particles in colloidal suspensions. It has a focus on particle aggregates and the dependency of their physical behaviour on morphological parameters. For this purpose, relevant theories and methodological tools are reviewed and applied to selected examples. The book is divided into four main chapters. The first of them introduces important measurement techniques for the determination of particle size and interfacial properties in colloidal suspensions. A further chapter is devoted to the physico-chemical properties of colloidal particles—highlighting the interfacial phenomena and the corresponding interactions between particles. The book’s central chapter examines the structure-property relations of colloidal aggregates. This comprises concepts to quantify size and structure of aggregates, models and numerical tools for calculating the (light) scattering and hydrodynamic properties of aggregates, and a discussion on van-der-Waals and double layer interactions between ...

Tailoring particle size and morphology of colloidal Ag particles via chemical precipitation for Ag-BSCCO composites

International Nuclear Information System (INIS)

Medendorp, N.W. Jr.; Bowman, K.J.; Trumble, K.P.

1996-01-01

The chemical precipitation of silver particles is an effective method for tailoring the particle size and morphology. This article investigates a chemical precipitation method for producing silver colloids, and how processing parameters affected particle size, morphology and adherence. Decreasing the silver nitrate concentration during precipitation with sodium borohydride decreased the colloidal silver particle size. Decreasing the addition rate of the reducing agent produced faceted particles. Reversing the reactant addition order also changed the particle size and the morphology. Precipitated colloids demonstrated a difference between the growth-dominated and the equilibrium structures. Co-dispersing Bi-based superconducting platelets during precipitation allowed Ag colloids to preferentially nucleate on the platelets and to remain adhered even after the additional processing. (orig.)

SiO2-supported Pt particles studied by electron microscopy

International Nuclear Information System (INIS)

Wang, D.; Penner, S.; Su, D.S.; Rupprechter, G.; Hayek, K.; Schloegl, R.

2003-01-01

Regularly grown Pt particles supported by amorphous SiO 2 were heated in hydrogen at 873 K after an oxidising treatment. The morphological and structural changes were studied by electron microscopy. Platinum silicides Pt 3 Si with L1 2 (Cu 3 Au) structure, monoclinic Pt 3 Si and tetragonal Pt 12 Si 5 were identified after the treatment. The mechanisms of coalescence of the particles and the formation of irregular large particles are suggested. A topotactic structural transformation accompanied with the migration of Si from the substrate to the particles are suggested to take place during Pt 3 Si formation

Quasi-three-dimensional particle imaging with digital holography.

Science.gov (United States)

Kemppinen, Osku; Heinson, Yuli; Berg, Matthew

2017-05-01

In this work, approximate three-dimensional structures of microparticles are generated with digital holography using an automated focus method. This is done by stacking a collection of silhouette-like images of a particle reconstructed from a single in-line hologram. The method enables estimation of the particle size in the longitudinal and transverse dimensions. Using the discrete dipole approximation, the method is tested computationally by simulating holograms for a variety of particles and attempting to reconstruct the known three-dimensional structure. It is found that poor longitudinal resolution strongly perturbs the reconstructed structure, yet the method does provide an approximate sense for the structure's longitudinal dimension. The method is then applied to laboratory measurements of holograms of single microparticles and their scattering patterns.

Morphological Evolution of Block Copolymer Particles: Effect of Solvent Evaporation Rate on Particle Shape and Morphology.

Science.gov (United States)

Shin, Jae Man; Kim, YongJoo; Yun, Hongseok; Yi, Gi-Ra; Kim, Bumjoon J

2017-02-28

Shape and morphology of polymeric particles are of great importance in controlling their optical properties or self-assembly into unusual superstructures. Confinement of block copolymers (BCPs) in evaporative emulsions affords particles with diverse structures, including prolate ellipsoids, onion-like spheres, oblate ellipsoids, and others. Herein, we report that the evaporation rate of solvent from emulsions encapsulating symmetric polystyrene-b-polybutadiene (PS-b-PB) determines the shape and internal nanostructure of micron-sized BCP particles. A distinct morphological transition from the ellipsoids with striped lamellae to the onion-like spheres was observed with decreasing evaporation rate. Experiments and dissipative particle dynamics (DPD) simulations showed that the evaporation rate affected the organization of BCPs at the particle surface, which determined the final shape and internal nanostructure of the particles. Differences in the solvent diffusion rates in PS and PB at rapid evaporation rates induced alignment of both domains perpendicular to the particle surface, resulting in ellipsoids with axial lamellar stripes. Slower evaporation rates provided sufficient time for BCP organization into onion-like structures with PB as the outermost layer, owing to the preferential interaction of PB with the surroundings. BCP molecular weight was found to influence the critical evaporation rate corresponding to the morphological transition from ellipsoid to onion-like particles, as well as the ellipsoid aspect ratio. DPD simulations produced morphologies similar to those obtained from experiments and thus elucidated the mechanism and driving forces responsible for the evaporation-induced assembly of BCPs into particles with well-defined shapes and morphologies.

Particles, particle labels, and quanta: The toll of unacknowledged metaphysics

International Nuclear Information System (INIS)

Redhead, M.; Teller, P.

1991-01-01

The practice of describing multiparticle quantum systems in terms of labeled particles indicates that the authors think of quantum entities as individuatable. The labels, together with particle indistinguishability, create the need for symmetrization or antisymmetrization (or, in principle, higher-order symmetries), which in turn results in 'surplus formal structure' in the formalism, formal structure which corresponds to nothing in the real world. The authors argue that these facts show quanta to be unindividuatable entities, things in principle incapable of supporting labels, and so things which support no factual difference if two of them are thought of as being switched. When thinking of the metaphysics of quanta, one should eschew the misleading labels of the tensor product Hilbert space formalism and prefer the ontologically more faithful description of the Fock space formalism. This conception eliminates puzzles about the quantum statistics of bosons

Enzymatic Inverse Opal Hydrogel Particles for Biocatalyst.

Science.gov (United States)

Wang, Huan; Gu, Hongcheng; Chen, Zhuoyue; Shang, Luoran; Zhao, Ze; Gu, Zhongze; Zhao, Yuanjin

2017-04-19

Enzymatic carriers have a demonstrated value for chemical reactions and industrial applications. Here, we present a novel kind of inverse opal hydrogel particles as the enzymatic carriers. The particles were negatively replicated from spherical colloidal crystal templates by using magnetic nanoparticles tagged acrylamide hydrogel. Thus, they were endowed with the features of monodispersity, small volume, complete penetrating structure, and controllable motion, which are all beneficial for improving the efficiency of biocatalysis. In addition, due to the ordered porous nanostructure, the inverse opal hydrogel particles were imparted with unique photonic band gaps (PBGs) and vivid structural colors for encoding varieties of immobilized enzymes and for constructing a multienzymes biocatalysis system. These features of the inverse opal hydrogel particles indicate that they are ideal enzymatic carriers for biocatalysis.

Synthesis method of asymmetric gold particles.

Science.gov (United States)

Jun, Bong-Hyun; Murata, Michael; Hahm, Eunil; Lee, Luke P

2017-06-07

Asymmetric particles can exhibit unique properties. However, reported synthesis methods for asymmetric particles hinder their application because these methods have a limited scale and lack the ability to afford particles of varied shapes. Herein, we report a novel synthetic method which has the potential to produce large quantities of asymmetric particles. Asymmetric rose-shaped gold particles were fabricated as a proof of concept experiment. First, silica nanoparticles (NPs) were bound to a hydrophobic micro-sized polymer containing 2-chlorotritylchloride linkers (2-CTC resin). Then, half-planar gold particles with rose-shaped and polyhedral structures were prepared on the silica particles on the 2-CTC resin. Particle size was controlled by the concentration of the gold source. The asymmetric particles were easily cleaved from the resin without aggregation. We confirmed that gold was grown on the silica NPs. This facile method for synthesizing asymmetric particles has great potential for materials science.

Local atomic structure of Pd and Ag in the SiC containment layer of TRISO fuel particles fissioned to 20% burn-up

Science.gov (United States)

Seibert, Rachel L.; Terrani, Kurt A.; Velázquez, Daniel; Hunn, John D.; Baldwin, Charles A.; Montgomery, Fred C.; Terry, Jeff

2018-03-01

The structure and speciation of fission products within the SiC barrier layer of tristructural-isotropic (TRISO) fuel particles irradiated to 19.6% fissions per initial metal atom (FIMA) burnup in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) was investigated. As-irradiated fuel particles, as well as those subjected to simulated accident scenarios, were examined. The TRISO particles were characterized using synchrotron X-ray absorption fine-structure spectroscopy (XAFS) at the Materials Research Collaborative Access Team (MRCAT) beamline at the Advanced Photon Source. The TRISO particles were produced at Oak Ridge National Laboratory under the Advanced Gas Reactor Fuel Development and Qualification Program and sent to the ATR for irradiation. XAFS measurements on the palladium and silver K-edges were collected using the MRCAT undulator beamline. Analysis of the Pd edge indicated the formation of palladium silicides of the form PdxSi (2 ≤ x ≤ 3). In contrast, Ag was found to be metallic within the SiC shell safety tested to 1700 °C. To the best of our knowledge, this is the first result demonstrating metallic bonding of silver from fissioned samples. Knowledge of these reaction pathways will allow for better simulations of radionuclide transport in the various coating layers of TRISO fuels for next generation nuclear reactors. They may also suggest different ways to modify TRISO particles to improve their fuel performance and to mitigate potential fission product release under both normal operation and accident conditions.

Accelerating universes driven by bulk particles

International Nuclear Information System (INIS)

Brito, F.A.; Cruz, F.F.; Oliveira, J.F.N.

2005-01-01

We consider our universe as a 3d domain wall embedded in a 5d dimensional Minkowski space-time. We address the problem of inflation and late time acceleration driven by bulk particles colliding with the 3d domain wall. The expansion of our universe is mainly related to these bulk particles. Since our universe tends to be permeated by a large number of isolated structures, as temperature diminishes with the expansion, we model our universe with a 3d domain wall with increasing internal structures. These structures could be unstable 2d domain walls evolving to fermi-balls which are candidates to cold dark matter. The momentum transfer of bulk particles colliding with the 3d domain wall is related to the reflection coefficient. We show a nontrivial dependence of the reflection coefficient with the number of internal dark matter structures inside the 3d domain wall. As the population of such structures increases the velocity of the domain wall expansion also increases. The expansion is exponential at early times and polynomial at late times. We connect this picture with string/M-theory by considering BPS 3d domain walls with structures which can appear through the bosonic sector of a five-dimensional supergravity theory

Particle-in-cell simulations of asymmetric guide-field reconnection: quadrupolar structure of Hall magnetic field

Science.gov (United States)

Schmitz, R. G.; Alves, M. V.; Barbosa, M. V. G.

2017-12-01

One of the most important processes that occurs in Earth's magnetosphere is known as magnetic reconnection (MR). This process can be symmetric or asymmetric, depending basically on the plasma density and magnetic field in both sides of the current sheet. A good example of symmetric reconnection in terrestrial magnetosphere occurs in the magnetotail, where these quantities are similar on the north and south lobes. In the dayside magnetopause MR is asymmetric, since the plasma regimes and magnetic fields of magnetosheath and magnetosphere are quite different. Symmetric reconnection has some unique signatures. For example, the formation of a quadrupolar structure of Hall magnetic field and a bipolar Hall electric field that points to the center of the current sheet. The different particle motions in the presence of asymmetries change these signatures, causing the quadrupolar pattern to be distorted and forming a bipolar structure. Also, the bipolar Hall electric field is modified and gives rise to a single peak pointing toward the magnetosheat, considering an example of magnetopause reconnection. The presence of a guide-field can also distort the quadrupolar pattern, by giving a shear angle across the current sheet and altering the symmetric patterns, according to previous simulations and observations. Recently, a quadrupolar structure was observed in an asymmetric guide-field MR event using MMS (Magnetospheric Multiscale) mission data [Peng et al., JGR, 2017]. This event shows clearly that the density asymmetry and the guide-field were not sufficient to form signatures of asymmetric reconnection. Using the particle-in-cell code iPIC3D [Markidis et al, Mathematics and Computers in Simulation, 2010] with the MMS data from this event used to define input parameters, we found a quadrupolar structure of Hall magnetic field and a bipolar pattern of Hall electric field in ion scales, showing that our results are in an excellent agreement with the MMS observations. To our

Study of the structural and magnetic properties of metallic iron-hematite particles for use in magnetorheological fluids

Energy Technology Data Exchange (ETDEWEB)

Osorio Ospina, Diana Marcela; Castro Navas, Irvin Jadway [Universidad del Valle, Escuela de Ingenieria de Materiales (Colombia); Perez Alcazar, German Antonio; Tabares, Jesus Anselmo, E-mail: jesus_tabares_8@hotmail.com [Universidad del Valle, Departamento de Fisica (Colombia)

2012-03-15

Magnetorheological (MR) fluids are new iron-based materials, whose applications include brakes, dampers, clutches, shock absorbers systems and polishing of optical surfaces (lens and mirrors). They are dependent on the size and shape of particles as the magnetic properties. Interested in the possibility of using iron-rich powders, commonly used in nondestructive testing, ranging in size from a few {mu}m to about 200 {mu}m and lower cost than those commercially used for MR fluids, a study of the structural and magnetic properties of iron-rich metallic particles by X-ray diffraction (XRD) and Moessbauer spectroscopy (MS) at room temperature has been done. Powders, as received, were separated into particle sizes smaller than 20 {mu}m (sample A) and in the range of 20-38 {mu}m (sample B) because these are the sizes generally required for applications in MR fluids. The particles whose sizes exceed the above values were ground in a high energy planetary mill for 3 h, using different values of rotational speed/time: 200 rpm for one hour, a pause of 10 s, 140 rpm for one hour, pause 10 s and then 175 rpm during the last hour. These powders were sieved to obtain particles smaller than 20 {mu}m (sample C). According XRD results, in all samples, only {alpha}-Fe (lattice parameter a = 2,867(2) Angstrom-Sign ) and Fe{sub 2}O{sub 3} (lattice parameter a 5,037(1) Angstrom-Sign and c = 13,755(8) Angstrom-Sign ) were present. The Moessbauer spectra were fitted with two sextets. The hyperfine parameters values allowed us to assign the highest relative area spectrum (sextet) corresponding to {alpha}-Fe and the second one to Fe{sub 2}O{sub 3} in accord to the XRD results. Thus, the preparation method using mechanical milling for diminishing the size of the metallic particles allowed us to get particles with size and magnetic properties that could lead to potentially MR fluids applications.

Study of the structural and magnetic properties of metallic iron-hematite particles for use in magnetorheological fluids

International Nuclear Information System (INIS)

Osorio Ospina, Diana Marcela; Castro Navas, Irvin Jadway; Pérez Alcázar, German Antonio; Tabares, Jesus Anselmo

2012-01-01

Magnetorheological (MR) fluids are new iron-based materials, whose applications include brakes, dampers, clutches, shock absorbers systems and polishing of optical surfaces (lens and mirrors). They are dependent on the size and shape of particles as the magnetic properties. Interested in the possibility of using iron-rich powders, commonly used in nondestructive testing, ranging in size from a few μm to about 200 μm and lower cost than those commercially used for MR fluids, a study of the structural and magnetic properties of iron-rich metallic particles by X-ray diffraction (XRD) and Mössbauer spectroscopy (MS) at room temperature has been done. Powders, as received, were separated into particle sizes smaller than 20 μm (sample A) and in the range of 20–38 μm (sample B) because these are the sizes generally required for applications in MR fluids. The particles whose sizes exceed the above values were ground in a high energy planetary mill for 3 h, using different values of rotational speed/time: 200 rpm for one hour, a pause of 10 s, 140 rpm for one hour, pause 10 s and then 175 rpm during the last hour. These powders were sieved to obtain particles smaller than 20 μm (sample C). According XRD results, in all samples, only α-Fe (lattice parameter a = 2,867(2) Å) and Fe 2 O 3 (lattice parameter a 5,037(1) Å and c = 13,755(8) Å) were present. The Mössbauer spectra were fitted with two sextets. The hyperfine parameters values allowed us to assign the highest relative area spectrum (sextet) corresponding to α-Fe and the second one to Fe 2 O 3 in accord to the XRD results. Thus, the preparation method using mechanical milling for diminishing the size of the metallic particles allowed us to get particles with size and magnetic properties that could lead to potentially MR fluids applications.

Particle physics and cosmology

International Nuclear Information System (INIS)

Turner, M.S.; Schramm, D.N.

1985-01-01

During the past year, the research of the members of our group has spanned virtually all the topics at the interface of cosmology and particle physics: inflationary Universe scenarios, astrophysical and cosmological constraints on particle properties, ultra-high energy cosmic ray physics, quantum field theory in curved space-time, cosmology with extra dimensions, superstring cosmology, neutrino astronomy with large, underground detectors, and the formation of structure in the Universe

r-particle irreducible kernels, asymptotic completeness and analyticity properties of several particle collision amplitudes

International Nuclear Information System (INIS)

Bros, J.

1984-01-01

An account is given of the present status of many-particle structure analysis in the general framework of massive quantum field theory. Two main questions are discussed, namely: i) the equivalence between the asymptotic completeness of a field and the r-particle irreducibility of associated Bether-Salpeter type kernels; ii) the derivation of extended analyticity properties of the Green functions and multiparticle collision amplitudes around the corresponding physical regions. Substantial results concerning the 3→3 particle processes are described. An analogous multiparticle version of these results yields a partial understanding of the general case

Particle physics

CERN Document Server

Martin, Brian R

2017-01-01

An accessible and carefully structured introduction to Particle Physics, including important coverage of the Higgs Boson and recent progress in neutrino physics. Fourth edition of this successful title in the Manchester Physics series. Includes information on recent key discoveries including : An account of the discovery of exotic hadrons, beyond the simple quark model; Expanded treatments of neutrino physics and CP violation in B-decays; An updated account of ‘physics beyond the standard model’, including the interaction of particle physics with cosmology; Additional problems in all chapters, with solutions to selected problems available on the book’s website; Advanced material appears in optional starred sections.

Analytic properties of many-particle amplitudes

Energy Technology Data Exchange (ETDEWEB)

Medvedev, B V; Pavlov, V P; Polivanov, M K; Sukhanov, A D [Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Moscow. Inst. Teoreticheskoj i Ehksperimental' noj Fiziki; AN SSSR, Moscow. Matematicheskij Inst.)

1982-08-01

In the framework of N. N. Bogolyubov axiomatic approach the complete proof of the existence of an analytic function the boundary values of which are the amplitudes of any channel of n-particle process is given. The one-particle structure of this function is described.

Particle physics and cosmology, Task C

International Nuclear Information System (INIS)

Turner, M.S.

1993-05-01

The research has spanned many topics at the boundary of particle physics and cosmology. The major focus has been in the general areas of inflationary cosmology, cosmological phase transitions, astrophysical constraints to particle physics theories, and dark matter/structure formation as it relates to particle physics. Some attention is given to axion physics. Narrative summaries of the research of the individual group members are given, followed by a list of publications

Near-ground tornado-like vortex structure resolved by particle image velocimetry (PIV)

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wei [Iowa State University, Aerospace Engineering Department, Ames, IA (United States); University of Minnesota, Saint Anthony Falls Laboratory, Minneapolis, MN (United States); Sarkar, Partha P. [Iowa State University, Aerospace Engineering Department, Ames, IA (United States)

2012-02-15

The near-ground flow structure of tornadoes is of utmost interest because it determines how and to what extent civil structures could get damaged in tornado events. We simulated tornado-like vortex flow at the swirl ratios of S = 0.03-0.3 (vane angle {theta}{sub v} = 15 -60 ), using a laboratory tornado simulator and investigated the near-ground-vortex structure by particle imaging velocimetry. Complicated near-ground flow was measured in two orthogonal views: horizontal planes at various elevations (z = 11, 26 and 53 mm above the ground) and the meridian plane. We observed two distinct vortex structures: a single-celled vortex at the lowest swirl ratio (S = 0.03, {theta}{sub v} = 15 ) and multiple suction vortices rotating around the primary vortex (two-celled vortex) at higher swirl ratios (S = 0.1-0.3, {theta}{sub v} = 30 -60 ). We quantified the effects of vortex wandering on the mean flow and found that vortex wandering was important and should be taken into account in the low swirl ratio case. The tangential velocity, as the dominant velocity component, has the peak value about three times that of the maximum radial velocity regardless of the swirl ratio. The maximum velocity variance is about twice at the high swirl ratio ({theta}{sub v} = 45 ) that at the low swirl ratio ({theta}{sub v} = 15 ), which is contributed significantly by the multiple small-scale secondary vortices. Here, the results show that not only the intensified mean flow but greatly enhanced turbulence occurs near the surface in the tornado-like vortex flow. The intensified mean flow and enhanced turbulence at the ground level, correlated with the ground-vortex interaction, may cause dramatic damage of the civil structures in tornadoes. This work provides detailed characterization of the tornado-like vortex structure, which has not been fully revealed in previous field studies and laboratory simulations. It would be helpful in improving the understanding of the interaction between the

Synthesis of flower-like BaTiO3/Fe3O4 hierarchically structured particles and their electrorheological and magnetic properties.

Science.gov (United States)

Wang, Baoxiang; Yin, Yichao; Liu, Chenjie; Yu, Shoushan; Chen, Kezheng

2013-07-21

Flower-like BaTiO3/Fe3O4 hierarchically structured particles composed of nano-scale structures on micro-scale materials were synthesized by a simple solvothermal approach and characterized by the means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), magnetic testing and rotary viscometer. The influences on the morphology and structure of solvothermal times, type and amount of surfactant, EG : H2O ratio, etc. were studied. Magnetic testing results show that the samples have strong magnetism and they exhibit superparamagnetic behavior, as evidenced by no coercivity and the remanence at room temperature, due to their very small sizes, observed on the M-H loop. The saturation magnetization (M(s)) value can achieve 18.3 emu g(-1). The electrorheological (ER) effect was investigated using a suspension of the flower-like BaTiO3/Fe3O4 hierarchically structured particles dispersed in silicone oil. We can observe a slight shear-thinning behavior of shear viscosity at a low shear rate region even at zero applied electric field and a Newtonian fluid behavior at high shear rate regions.

Synthesis Structural and Optical Properties Of (Co, Al) co-doped ZnO Nano Particles

Science.gov (United States)

Swapna, P.; Venkatramana Reddy, S.

2018-02-01

We prepared (Co, Al) co-doped ZnO nanostructures using the method chemical co-precipitation successfully, at room temperature using PEG (Poly ethylene glycol) as stabilizing agent. Samples are prepared with different concentrations by keeping aluminium at 5 mol percent constant and varying the concentration of cobalt from 1 to 5 mol percent. After the preparation all the samples are carefully subjected to characterizations such as XRD, SEM with EDS, TEM, PL and UV-VIS-NIR. XRD pattern shows that all the samples possess hexagonal wurtzite crystal structure having no secondary phases pertaining to Al or cobalt, which shows successful dissolution of the dopents. TEM results shows the accurate size of particles and is confirmed the XRD data. SEM images of all the samples shows that particles are in nearly spherical shape, EDS spectrum reveals that incorporation of cobalt and aluminum in host lattice. PL spectrum shows that all the samples containing two prominent peaks centered at 420 nm and 446 nm. UV-VIS-NIR spectra has shown three absorptions peaks in the range of wavelength 550 nm to 700 nm, which are ascribed as typical d-d transitions of cobalt ions.

Influence of coated particle structure in thermal neutron spectrum energy range

Energy Technology Data Exchange (ETDEWEB)

Hansen, U; Teuchert, E

1971-02-15

The heterogenity due to lumping the fuel in coated particles affects the thermal neutron spectrum. A calculation model is discussed which, apart from some simplifying assumptions about the statistical distribution, allows a rigorous computation of effective cross sections for all nuclides of the heterogeneous medium. It is based on an exact computation of the neutron penetration probability through coating and kernel. The model is incorporated in a THERMOS-code providing a double heterogeneous cell calculation, which can be repeated automatically at different time steps in the depletion code system MAFIA-V.S.O.P.. A discussion of the effects of the coated particle structure is given by a comparison of calculations for heterogeneous and homogeneous fuel zones in pebble bed reactor elements. This is performed for enriched UO{sub 2} fuel and for a ThO{sub 2}-PuO{sub 2} mixture in the grains. Depending on the energy dependent total sigmas in the kernels the changes of the cross sections are ranging from 0.1% up to 45%. The influence on the spectrum averaged sigmas of the nuclides in the fresh UO{sub 2} fuel is lower than 1%. For the emerging {sup 240}Pu it increases up to 3.3% during irradiation. For the ThO{sub 2}-PuO{sub 2} fuel the averaged sigmas of the isotopes vary from 0.5% to 5.7% depending on the state of irradiation. Correspondingly there is an influence on the plutonium isotopic composition, on breeding ratios, and on the tilt of k{sub eff} during burnup which will be discussed in detail.

Fletcher-Reeves based Particle Swarm Optimization for prediction of molecular structure.

Science.gov (United States)

Agrawal, Shikha; Silakari, Sanjay

2014-04-01

The determination of the most stable conformers of a molecule can be formulated as a global optimization problem. Knowing the stable conformers of a molecule is important because it allows us to understand its properties and behavior based on its structure. The most stable conformation is that involving the global minimum of potential energy. The problem of finding this global minimum is highly complex, and is computationally difficult because of the number of local minima, which grows exponentially with molecular size. In this paper, we propose a hybrid approach combining Particle Swarm Optimization (PSO) and the Fletcher-Reeves algorithm to minimize the potential energy function. The proposed hybrid algorithm is applied to a simplified molecular potential energy function in problems with up to 100 degrees of freedom and also to a realistic potential energy function modeling a pseudoethane molecule. The computational results for both the cases show that the proposed method performs significantly better than the other algorithms. Copyright © 2014 Elsevier Inc. All rights reserved.

Acquiring Structural Information on Virus Particles with Charge Detection Mass Spectrometry

Science.gov (United States)

Keifer, David Z.; Motwani, Tina; Teschke, Carolyn M.; Jarrold, Martin F.

2016-06-01

Charge detection mass spectrometry (CDMS) is a single-molecule technique particularly well-suited to measuring the mass and charge distributions of heterogeneous, MDa-sized ions. In this work, CDMS has been used to analyze the assembly products of two coat protein variants of bacteriophage P22. The assembly products show broad mass distributions extending from 5 to 15 MDa for A285Y and 5 to 25 MDa for A285T coat protein variants. Because the charge of large ions generated by electrospray ionization depends on their size, the charge can be used to distinguish hollow shells from more compact structures. A285T was found to form T = 4 and T = 7 procapsids, and A285Y makes a small number of T = 3 and T = 4 procapsids. Owing to the decreased stability of the A285Y and A285T particles, chemical cross-linking was required to stabilize them for electrospray CDMS. Graphical Abstract[Figure not available: see fulltext.

Parking simulation of three-dimensional multi-sized star-shaped particles

International Nuclear Information System (INIS)

Zhu, Zhigang; Chen, Huisu; Xu, Wenxiang; Liu, Lin

2014-01-01

The shape and size of particles may have a great impact on the microstructure as well as the physico-properties of particulate composites. However, it is challenging to configure a parking system of particles to a geometrical shape that is close to realistic grains in particulate composites. In this work, with the assistance of x-ray tomography and a spherical harmonic series, we present a star-shaped particle that is close to realistic arbitrary-shaped grains. To realize such a hard particle parking structure, an inter-particle overlapping detection algorithm is introduced. A serial sectioning approach is employed to visualize the particle parking structure for the purpose of justifying the reliability of the overlapping detection algorithm. Furthermore, the validity of the area and perimeter of solids in any arbitrary section of a plane calculated using a numerical method is verified by comparison with those obtained using an image analysis approach. This contribution is helpful to further understand the dependence of the micro-structure and physico-properties of star-shaped particles on the realistic geometrical shape. (paper)

Interpretation of quarks having fractional quantum numbers as structural quasi-particles by means of the composite model with integral quantum numbers

International Nuclear Information System (INIS)

Tyapkin, A.A.

1976-01-01

The problem is raised on the interpretation of quarks having fractional quantum numbers as structural quasi-particles. A new composite model is proposed on the basis of the fundamental triplet representation of fermions having integral quantum numbers

Dense particles and slow sedimenting particles produced by ultraviolet irradiation of poliovirus

International Nuclear Information System (INIS)

Wetz, K.; Zeichhardt, H.; Willingmann, P.; Habermehl, K.-O.

1983-01-01

Low doses of u.v. radiation rapidly inactivate poliovirus, the virus progressively converting into dense particles (DPs) of buoyant density 1.44 g/ml in CsCl. The DPs are structurally and antigenically related to standard virus (N-antigen), i.e. indistinguishable from virus in their RNA and protein content and in sedimentation properties. Furthermore, there is no difference in reactivity of the structural proteins of virus and DPs with the monofunctional reagent [ 3 H]N-succinimidyl propionate ( 3 H-NSP). However, DPs differ from virus in that their capsids are permeable to several ions, and they can be degraded by RNase and protease. Increasing the radiation dose causes a successive transformation of DPs into 105S slow-sedimenting particles (SSPs), antigenically related to 76S artificial empty capsids (AECs) or H-antigen, but differing physically and structurally. The SSPs have a higher S value than AECs and contain all the capsid proteins, including VP4, and the RNA, both of these macromolecules being absent from AECs. It is concluded, therefore, that transformation from N- to H- antigenicity by u.v. radiation does not require release of RNA and VP4. Conversion of virus particles to SSPs correlates with altered reactivity of VP2 and to a lesser extent VP1 and VP3, with the monofunctional reagent 3 H-NSP. (author)

Dense particles and slow sedimenting particles produced by ultraviolet irradiation of poliovirus

Energy Technology Data Exchange (ETDEWEB)

Wetz, K.; Zeichhardt, H.; Willingmann, P.; Habermehl, K.O. (Freie Univ. Berlin (Germany, F.R.))

1983-06-01

Low doses of u.v. radiation rapidly inactivate poliovirus, the virus progressively converting into dense particles (DPs) of buoyant density 1.44 g/ml in CsCl. The DPs are structurally and antigenically related to standard virus (N-antigen), i.e. indistinguishable from virus in their RNA and protein content and in sedimentation properties. Furthermore, there is no difference in reactivity of the structural proteins of virus and DPs with the monofunctional reagent (/sup 3/H)N-succinimidyl propionate (/sup 3/H-NSP). However, DPs differ from virus in that their capsids are permeable to several ions, and they can be degraded by RNase and protease. Increasing the radiation dose causes a successive transformation of DPs into 105S slow-sedimenting particles (SSPs), antigenically related to 76S artificial empty capsids (AECs) or H-antigen, but differing physically and structurally. The SSPs have a higher S value than AECs and contain all the capsid proteins, including VP4, and the RNA, both of these macromolecules being absent from AECs. It is concluded, therefore, that transformation from N- to H- antigenicity by u.v. radiation does not require release of RNA and VP4. Conversion of virus particles to SSPs correlates with altered reactivity of VP2 and to a lesser extent VP1 and VP3, with the monofunctional reagent /sup 3/H-NSP.

3-dimensional free standing micro-structures by proton beam writing of Su 8-silver nanoParticle polymeric composite

Science.gov (United States)

Igbenehi, H.; Jiguet, S.

2012-09-01

Proton beam lithography a maskless direct-write lithographic technique (well suited for producing 3-Dimensional microstructures in a range of resist and semiconductor materials) is demonstrated as an effective tool in the creation of electrically conductive freestanding micro-structures in an Su 8 + Nano Silver polymer composite. The structures produced show non-ohmic conductivity and fit the percolation theory conduction model of tunneling of separated nanoparticles. Measurements show threshold switching and a change in conductivity of at least 4 orders of magnitude. The predictable range of protons in materials at a given energy is exploited in the creation of high aspect ratio, free standing micro-structures, made from a commercially available SU8 Silver nano-composite (GMC3060 form Gersteltec Inc. a negative tone photo-epoxy with added metallic nano-particles(Silver)) to create films with enhanced electrical properties when exposed and cured. Nano-composite films are directly written on with a finely focused MeV accelerated Proton particle beam. The energy loss of the incident proton beams in the target polymer nano- composite film is concentrated at the end of its range, where damage occurs; changing the chemistry of the nano-composite film via an acid initiated polymerization - creating conduction paths. Changing the energy of the incident beams provide exposed regions with different penetration and damage depth - exploited in the demonstrated cantilever microstructure.

Dynamic self-organization in particle-laden channel flow

NARCIS (Netherlands)

Geurts, Bernardus J.; Vreman, A.W.

2006-01-01

We study dynamic flow-structuring and mean-flow properties of turbulent particle-laden riser-flow at significant particle volume fractions of about 1.5%. We include particle–particle as well as particle–fluid interactions through inelastic collisions and drag forces, in a so-called four-way coupled

Modulation of Cyclodextrin Particle Amphiphilic Properties to Stabilize Pickering Emulsion.

Science.gov (United States)

Xi, Yongkang; Luo, Zhigang; Lu, Xuanxuan; Peng, Xichun

2018-01-10

Cyclodextrins have been proven to form complexes with linear oil molecules and stabilize emulsions. Amphiphilic properties of cyclodextrin particles were modulated through esterification reaction between β-cyclodextrin (β-CD) and octadecenyl succinic anhydride (ODSA) under alkaline conditions. ODS-β-CD particles with degree of substitution (DS) of 0.003, 0.011, and 0.019 were obtained. The introduced hydrophobic long chain that was linked within β-CD cavity led to the change of ODS-β-CD in terms of morphological structure, surface charge density, size, and contact angle, upon which the properties and stability of the emulsions stabilized by ODS-β-CD were highly dependent. The average diameter of ODS-β-CD particles ranged from 449 to 1484 nm. With the DS increased from 0.003 to 0.019, the contact angle and absolute zeta potential value of these ODS-β-CD particles improved from 25.7° to 47.3° and 48.1 to 62.8 mV, respectively. The cage structure of β-CD crystals was transformed to channel structure, then further to amorphous structure after introduction of the octadecenyl succinylation chain. ODS-β-CD particles exhibited higher emulsifying ability compared to β-CD. The resulting Pickering emulsions formed by ODS-β-CD particles were more stable during storage. This study investigates the ability of these ODS-β-CD particles to stabilize oil-in-water emulsions with respect to their amphiphilic character and structural properties.

Mechanical Properties and Structures of Pyrolytic Carbon Coating Layer in HTR Coated Particle Fuel

International Nuclear Information System (INIS)

Lee, Young Woo; Kim, Young Min; Kim, Woong Ki; Cho, Moon Sung

2009-01-01

The TRISO(tri-isotropic)-coated fuel particle for a HTR(High Temperature gas-cooled Reactor) has a diameter of about 1 mm, composed of a nuclear fuel kernel and four different outer coating layers, consisting of a buffer PyC (pyrolytic carbon) layer, inner PyC layer, SiC layer, and outer PyC layer with different coating thicknesses following a specific fuel design. While the fuel kernel is a source for a heat generation by a nuclear fission of fissile uranium, each of the four coating layers acts as a different role in view of retaining the generated fission products and the other interactions during an in-reactor service. Among these coating layers, PyC properties are scarcely in agreement among various investigators and the dependency of their changes upon the deposition condition is comparatively large due to their additional anisotropic properties. Although a recent review work has contributed to an establishment of relationship between the material properties and QC measurements, the data on the mechanical properties and structural parameters of PyC coating layers remain still unclearly evaluated. A review work on dimensional changes of PyC by neutron irradiation was one of re-evaluative works recently attempted by the authors. In this work, an attempt was made to analyze and re-evaluate the existing data of the experimental results of the mechanical properties, i.e., Young's modulus and fracture stress, in relation with the coating conditions, density and the BAF (Bacon Anisotropy Factor), an important structural parameter, of PyC coating layers obtained from various experiments performed in the early periods of the HTR coated particle development

Chemical Structure, Ensemble and Single-Particle Spectroscopy of Thick-Shell InP-ZnSe Quantum Dots.

Science.gov (United States)

Reid, Kemar R; McBride, James R; Freymeyer, Nathaniel J; Thal, Lucas B; Rosenthal, Sandra J

2018-02-14

Thick-shell (>5 nm) InP-ZnSe colloidal quantum dots (QDs) grown by a continuous-injection shell growth process are reported. The growth of a thick crystalline shell is attributed to the high temperature of the growth process and the relatively low lattice mismatch between the InP core and ZnSe shell. In addition to a narrow ensemble photoluminescence (PL) line-width (∼40 nm), ensemble and single-particle emission dynamics measurements indicate that blinking and Auger recombination are reduced in these heterostructures. More specifically, high single-dot ON-times (>95%) were obtained for the core-shell QDs, and measured ensemble biexciton lifetimes, τ 2x ∼ 540 ps, represent a 7-fold increase compared to InP-ZnS QDs. Further, high-resolution energy dispersive X-ray (EDX) chemical maps directly show for the first time significant incorporation of indium into the shell of the InP-ZnSe QDs. Examination of the atomic structure of the thick-shell QDs by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) reveals structural defects in subpopulations of particles that may mitigate PL efficiencies (∼40% in ensemble), providing insight toward further synthetic refinement. These InP-ZnSe heterostructures represent progress toward fully cadmium-free QDs with superior photophysical properties important in biological labeling and other emission-based technologies.

Durable Lotus-effect surfaces with hierarchical structure using micro- and nanosized hydrophobic silica particles.

Science.gov (United States)

Ebert, Daniel; Bhushan, Bharat

2012-02-15

Surfaces with a very high apparent water contact angle (CA) and low water contact angle hysteresis (CAH) exhibit many useful characteristics, among them extreme water repellency, low drag for fluid flow, and a self-cleaning effect. The leaf of the Lotus plant (Nelumbo nucifera) achieves these properties using a hierarchical structure with roughness on both the micro- and nanoscale. It is of great interest to create durable surfaces with the so-called "Lotus effect" for many important applications. In this study, hierarchically structured surfaces with Lotus-effect properties were fabricated using micro- and nanosized hydrophobic silica particles and a simple spray method. In addition, hierarchically structured surfaces were prepared by spraying a nanoparticulate coating over a micropatterned surface. To examine the similarities between surfaces using microparticles versus a uniform micropattern as the microstructure, CA and CAH were compared across a range of pitch values for the two types of microstructures. Wear experiments were performed using an atomic force microscope (AFM), a ball-on-flat tribometer, and a water jet apparatus to verify multiscale wear resistance. These surfaces have potential uses in engineering applications requiring Lotus-effect properties and high durability. Copyright © 2011 Elsevier Inc. All rights reserved.

Synthesis and characterization of chemically ordered FePt magnetic nano-particles

Energy Technology Data Exchange (ETDEWEB)

Srinivasa Rao, K. [Centre for Materials for Electronics Technology (C-MET), IDA phase-III, Cherlapally, Hyderabad 500 051 (India); Balaji, T., E-mail: theerthambalaji@yahoo.co [Centre for Materials for Electronics Technology (C-MET), IDA phase-III, Cherlapally, Hyderabad 500 051 (India); Lingappa, Y. [Department of Chemistry, Sri Venkateswara University, Tirupati 517 502 (India); Reddy, M.R.P.; Kumar, Arbind; Prakash, T.L. [Centre for Materials for Electronics Technology (C-MET), IDA phase-III, Cherlapally, Hyderabad 500 051 (India)

2010-08-15

Monodispersed FePt alloy magnetic nano-particles are prepared by reduction of platinum acetyl acetonate and iron acetyl acetonate salts together in the presence of oleic acid and oleyl amine stabilizers by polyol process. The particle size of FePt is in the range of 2-3 nm confirmed by transmission electron microscopy (TEM). As-synthesized FePt nano-particles are chemically disordered with face centre cubic (fcc) structure where as after vacuum annealing these particles changed to face centre tetragonal (fct) ordered structure confirmed by the X-ray diffraction technique. Magnetic coercivity of 5.247 KOe was observed for fct structure.

Particles in flows

CERN Document Server

Galdi, Giovanni; Nečasová, Šárka

2017-01-01

This book aims to face particles in flows from many different, but essentially interconnected sides and points of view. Thus the selection of authors and topics represented in the chapters, ranges from deep mathematical analysis of the associated models, through the techniques of their numerical solution, towards real applications and physical implications. The scope and structure of the book as well as the selection of authors was motivated by the very successful summer course and workshop "Particles in Flows'' that was held in Prague in the August of 2014. This meeting revealed the need for a book dealing with this specific and challenging multidisciplinary subject, i.e. particles in industrial, environmental and biomedical flows and the combination of fluid mechanics, solid body mechanics with various aspects of specific applications.

Diffraction of radiation from channelled charged particles

International Nuclear Information System (INIS)

Baryshevskij, V.G.; Grubich, A.O.; Dubovskaya, I.Ya.

1978-01-01

An explicit expression for cross-section and radiation spectrum at diffraction is calculated. It is shown that photons emitted by channelled particles form a typical diffraction pattern which contains information about the crystal structure. It is also shown that the change of the longitudinal energy of the particle caused by the radiation braking becomes important when the particle energy is increased. (author)

Collective motion of active Brownian particles with polar alignment.

Science.gov (United States)

Martín-Gómez, Aitor; Levis, Demian; Díaz-Guilera, Albert; Pagonabarraga, Ignacio

2018-04-04

We present a comprehensive computational study of the collective behavior emerging from the competition between self-propulsion, excluded volume interactions and velocity-alignment in a two-dimensional model of active particles. We consider an extension of the active brownian particles model where the self-propulsion direction of the particles aligns with the one of their neighbors. We analyze the onset of collective motion (flocking) in a low-density regime (10% surface area) and show that it is mainly controlled by the strength of velocity-alignment interactions: the competition between self-propulsion and crowding effects plays a minor role in the emergence of flocking. However, above the flocking threshold, the system presents a richer pattern formation scenario than analogous models without alignment interactions (active brownian particles) or excluded volume effects (Vicsek-like models). Depending on the parameter regime, the structure of the system is characterized by either a broad distribution of finite-sized polar clusters or the presence of an amorphous, highly fluctuating, large-scale traveling structure which can take a lane-like or band-like form (and usually a hybrid structure which is halfway in between both). We establish a phase diagram that summarizes collective behavior of polar active brownian particles and propose a generic mechanism to describe the complexity of the large-scale structures observed in systems of repulsive self-propelled particles.

Particle Control in Phase Space by Global K-Means Clustering

DEFF Research Database (Denmark)

Frederiksen, Jacob Trier; Lapenta, G.; Pessah, M. E.

2015-01-01

We devise and explore an iterative optimization procedure for controlling particle populations in particle-in-cell (PIC) codes via merging and splitting of computational macro-particles. Our approach, is to compute an optimal representation of the global particle phase space structure while decre...

Anisotropic magnetism in field-structured composites

International Nuclear Information System (INIS)

Martin, James E.; Venturini, Eugene; Odinek, Judy; Anderson, Robert A.

2000-01-01

Magnetic field-structured composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g., rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chainlike particle structures, and a biaxial field produces sheetlike particle structures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCs of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material. (c) 2000 The American Physical Society

The influence of final state interaction on two-particle correlations in multiple production of particles and resonances

International Nuclear Information System (INIS)

Lednicky, R.; Lyuboshitz, V.L.

1996-01-01

The structure of pair correlations of interacting particles moving with nearby velocities is analysed. A general formalism of the two-particle space-time density matrix, taking into account the space-time coherence of the production process, is developed. The influence of strong final state interaction on two-particle correlations in the case of the production of a system resonance + particle is investigated in detail. It is shown that in the limit of small distances between the resonance and particle production points the effect of final state interaction is enhanced due to logarithmic singularity of the triangle diagram. Numerical estimates indicate that, in this limit, the effect of strong final state interaction becomes important even for two-pion correlations. (author)

Structural properties of silver nanoparticle agglomerates based on transmission electron microscopy: relationship to particle mobility analysis

International Nuclear Information System (INIS)

Shin, Weon Gyu; Wang Jing; Mertler, Michael; Sachweh, Bernd; Fissan, Heinz; Pui, David Y. H.

2009-01-01

In this work, the structural properties of silver nanoparticle agglomerates generated using condensation and evaporation method in an electric tube furnace followed by a coagulation process are analyzed using Transmission Electron Microscopy (TEM). Agglomerates with mobility diameters of 80, 120, and 150 nm are sampled using the electrostatic method and then imaged by TEM. The primary particle diameter of silver agglomerates was 13.8 nm with a standard deviation of 2.5 nm. We obtained the relationship between the projected area equivalent diameter (d pa ) and the mobility diameter (d m ), i.e., d pa = 0.92 ± 0.03 d m for particles from 80 to 150 nm. We obtained fractal dimensions of silver agglomerates using three different methods: (1) D f = 1.84 ± 0.03, 1.75 ± 0.06, and 1.74 ± 0.03 for d m = 80, 120, and 150 nm, respectively from projected TEM images using a box counting algorithm; (2) fractal dimension (D fL ) = 1.47 based on maximum projected length from projected TEM images using an empirical equation proposed by Koylu et al. (1995) Combust Flame 100:621-633; and (3) mass fractal-like dimension (D fm ) = 1.71 theoretically derived from the mobility analysis proposed by Lall and Friedlander (2006) J Aerosol Sci 37:260-271. We also compared the number of primary particles in agglomerate and found that the number of primary particles obtained from the projected surface area using an empirical equation proposed by Koylu et al. (1995) Combust Flame 100:621-633 is larger than that from using the relationship, d pa = 0.92 ± 0.03 d m or from using the mobility analysis.

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

Science.gov (United States)

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

2018-06-20

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

Non-relativistic model of two-particle decay

International Nuclear Information System (INIS)

Dittrich, J.; Exner, P.

1986-01-01

A simple non-relativistic model of a spinless particle decaying into two lighter particles is treated in detail. It is similar to the Lee-model description of V-particle decay. Galilean covariance is formulated properly, by means of a unitary projective representation acting on the state space of the model. After separating the centre-of-mass motion the meromorphic structure of the reduced resolvent is deduced

Pair interaction of bilayer-coated nanoscopic particles

International Nuclear Information System (INIS)

Qi-Yi, Zhang

2009-01-01

The pair interaction between bilayer membrane-coated nanosized particles has been explored by using the self-consistent field (SCF) theory. The bilayer membranes are composed of amphiphilic polymers. For different system parameters, the pair-interaction free energies are obtained. Particular emphasis is placed on the analysis of a sequence of structural transformations of bilayers on spherical particles, which occur during their approaching processes. For different head fractions of amphiphiles, the asymmetrical morphologies between bilayers on two particles and the inverted micellar intermediates have been found in the membrane fusion pathway. These results can benefit the fabrication of vesicles as encapsulation vectors for drug and gene delivery. (condensed matter: structure, thermal and mechanical properties)

Single particle train ordering in microchannel based on inertial and vortex effects

Science.gov (United States)

Fan, Liang-Liang; Yan, Qing; Zhe, Jiang; Zhao, Liang

2018-06-01

A new microfluidic device for microparticle focusing and ordering in a single particle train is reported. The particle focusing and ordering are based on inertial and vortex effects in a microchannel with a series of suddenly contracted and widely expanded structures on one side. In the suddenly contracted regions, particles located near the contracted structures are subjected to a strong wall-effect lift force and momentum-change-induced inertial force due to the highly curved trajectory, migrating to the straight wall. A horizontal vortex is generated downstream of the contracted structure, which prevents the particle from getting close to the wall. In the widely expanded regions, the streamline is curved and no vortex is generated. The shear-gradient lift force and the momentum-change-induced inertial force are dominant for particle lateral migration, driving particles towards the wall of the expanded structures. Eventually, particles are focused and ordered in a single particle train by the combination effects of the inertial forces and the vortex. In comparison with other single-stream particle focusing methods, this device requires no sheath flow, is easy for fabrication and operation, and can work over a wide range of Reynolds numbers from 19.1–142.9. The highly ordered particle chain could be potentially utilized in a variety of lab-chip applications, including micro-flow cytometer, imaging and droplet-based cell entrapment.

Effect of the structure of Pt-Ru/C particles on COad monolayer vibrational properties and electrooxidation kinetics

International Nuclear Information System (INIS)

Maillard, Frederic; Bonnefont, Antoine; Chatenet, Marian; Guetaz, Laure; Doisneau-Cottignies, Beatrice; Roussel, Herve; Stimming, Ulrich

2007-01-01

In this paper, we combined FTIR spectroscopy and CO ad stripping voltammetry to investigate CO ad adsorption and electrooxidation on Pt-Ru/C nanoparticles. The Pt:Ru elemental composition and the metal loading were determined by ICP-AES. The X-ray diffraction patterns of the Pt-Ru/C indicated formation of a Pt-Ru (fcc) alloy. HREM images revealed an increase in the fraction of agglomerated Pt-Ru/C particles with increasing the metal loading and showed that agglomerated Pt-Ru/C nanoparticles present structural defects such as twins or grain boundaries. In addition, isolated Pt-Ru/C nanoparticles have similar mean particle size (ca. 2.5 nm) and particle size distributions whatever the metal loading. Therefore, we could determine precisely the effect of particle agglomeration on the CO ad vibrational properties and electrooxidation kinetics. FTIR measurements revealed a main CO ad stretching band at ca. ν-bar CO L =2030cm -1 , which we ascribed to a-top CO ad on Pt domains electronically modified by the presence of Ru. As the metal loading increased, the position of this band was blue shifted by ca. 5 cm -1 and a shoulder around 2005 cm -1 developed, which was ascribed to a-top CO ad on Ru domains. The reason for this was suggested to be the increasing size of Ru domains on agglomerated Pt-Ru/C particles, which lifts dipole-dipole coupling and allows two vibrational features to be observed (CO ad /Ru, CO ad /Pt). This is evidence that FTIR spectroscopy can be used to probe small chemical fluctuations of the Pt-Ru/C surface. Finally, we comment on the CO ad electrooxidation kinetics. We observed that CO ad was converted more easily into CO 2 as the metal loading, i.e. the fraction of agglomerated Pt-Ru/C nanoparticles, increased

Directional Freezing of Nanocellulose Dispersions Aligns the Rod-Like Particles and Produces Low-Density and Robust Particle Networks.

Science.gov (United States)

Munier, Pierre; Gordeyeva, Korneliya; Bergström, Lennart; Fall, Andreas B

2016-05-09

We show that unidirectional freezing of nanocellulose dispersions produces cellular foams with high alignment of the rod-like nanoparticles in the freezing direction. Quantification of the alignment in the long direction of the tubular pores with X-ray diffraction shows high orientation of cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) at particle concentrations above 0.2 wt % (CNC) and 0.08 wt % (CNF). Aggregation of CNF by pH decrease or addition of salt significantly reduces the particle orientation; in contrast, exceeding the concentration where particles gel by mobility constraints had a relatively small effect on the orientation. The dense nanocellulose network formed by directional freezing was sufficiently strong to resist melting. The formed hydrogels were birefringent and displayed anisotropic laser diffraction patterns, suggesting preserved nanocellulose alignment and cellular structure. Nondirectional freezing of the hydrogels followed by sublimation generates foams with a pore structure and nanocellulose alignment resembling the structure of the initial directional freezing.

Determination of band structure parameters and the quasi-particle gap of CdSe quantum dots by cyclic voltammetry.

Science.gov (United States)

Inamdar, Shaukatali N; Ingole, Pravin P; Haram, Santosh K

2008-12-01

Band structure parameters such as the conduction band edge, the valence band edge and the quasi-particle gap of diffusing CdSe quantum dots (Q-dots) of various sizes were determined using cyclic voltammetry. These parameters are strongly dependent on the size of the Q-dots. The results obtained from voltammetric measurements are compared to spectroscopic and theoretical data. The fit obtained to the reported calculations based on the semi-empirical pseudopotential method (SEPM)-especially in the strong size-confinement region, is the best reported so far, according to our knowledge. For the smallest CdSe Q-dots, the difference between the quasi-particle gap and the optical band gap gives the electron-hole Coulombic interaction energy (J(e1,h1)). Interband states seen in the photoluminescence spectra were verified with cyclic voltammetry measurements.

Simulations of flame generated particles

KAUST Repository

Patterson, Robert

2016-01-01

The nonlinear structure of the equations describing the evolution of a population of coagulating particles in a flame make the use of stochastic particle methods attractive for numerical purposes. I will present an analysis of the stochastic fluctuations inherent in these numerical methods leading to an efficient sampling technique for steady-state problems. I will also give some examples where stochastic particle methods have been used to explore the effect of uncertain parameters in soot formation models. In conclusion I will try to indicate some of the issues in optimising these methods for the study of uncertain model parameters.

Simulations of flame generated particles

KAUST Repository

Patterson, Robert

2016-01-05

The nonlinear structure of the equations describing the evolution of a population of coagulating particles in a flame make the use of stochastic particle methods attractive for numerical purposes. I will present an analysis of the stochastic fluctuations inherent in these numerical methods leading to an efficient sampling technique for steady-state problems. I will also give some examples where stochastic particle methods have been used to explore the effect of uncertain parameters in soot formation models. In conclusion I will try to indicate some of the issues in optimising these methods for the study of uncertain model parameters.

Fractals control in particle's velocity

International Nuclear Information System (INIS)

Zhang Yongping; Liu Shutang; Shen Shulan

2009-01-01

Julia set, a fractal set of the literature of nonlinear physics, has significance for the engineering applications. For example, the fractal structure characteristics of the generalized M-J set could visually reflect the change rule of particle's velocity. According to the real world requirement, the system need show various particle's velocity in some cases. Thus, the control of the nonlinear behavior, i.e., Julia set, has attracted broad attention. In this work, an auxiliary feedback control is introduced to effectively control the Julia set that visually reflects the change rule of particle's velocity. It satisfies the performance requirement of the real world problems.

Lunar Regolith Particle Shape Analysis

Science.gov (United States)

Kiekhaefer, Rebecca; Hardy, Sandra; Rickman, Douglas; Edmunson, Jennifer

2013-01-01

Future engineering of structures and equipment on the lunar surface requires significant understanding of particle characteristics of the lunar regolith. Nearly all sediment characteristics are influenced by particle shape; therefore a method of quantifying particle shape is useful both in lunar and terrestrial applications. We have created a method to quantify particle shape, specifically for lunar regolith, using image processing. Photomicrographs of thin sections of lunar core material were obtained under reflected light. Three photomicrographs were analyzed using ImageJ and MATLAB. From the image analysis measurements for area, perimeter, Feret diameter, orthogonal Feret diameter, Heywood factor, aspect ratio, sieve diameter, and sieve number were recorded. Probability distribution functions were created from the measurements of Heywood factor and aspect ratio.

Transistor-based particle detection systems and methods

Science.gov (United States)

Jain, Ankit; Nair, Pradeep R.; Alam, Muhammad Ashraful

2015-06-09

Transistor-based particle detection systems and methods may be configured to detect charged and non-charged particles. Such systems may include a supporting structure contacting a gate of a transistor and separating the gate from a dielectric of the transistor, and the transistor may have a near pull-in bias and a sub-threshold region bias to facilitate particle detection. The transistor may be configured to change current flow through the transistor in response to a change in stiffness of the gate caused by securing of a particle to the gate, and the transistor-based particle detection system may configured to detect the non-charged particle at least from the change in current flow.

Interplanetary Magnetic Field Guiding Relativistic Particles

Science.gov (United States)

Masson, S.; Demoulin, P.; Dasso, S.; Klein, K. L.

2011-01-01

The origin and the propagation of relativistic solar particles (0.5 to few Ge V) in the interplanetary medium remains a debated topic. These relativistic particles, detected at the Earth by neutron monitors have been previously accelerated close to the Sun and are guided by the interplanetary magnetic field (IMF) lines, connecting the acceleration site and the Earth. Usually, the nominal Parker spiral is considered for ensuring the magnetic connection to the Earth. However, in most GLEs the IMF is highly disturbed, and the active regions associated to the GLEs are not always located close to the solar footprint of the nominal Parker spiral. A possible explanation is that relativistic particles are propagating in transient magnetic structures, such as Interplanetary Coronal Mass Ejections (ICMEs). In order to check this interpretation, we studied in detail the interplanetary medium where the particles propagate for 10 GLEs of the last solar cycle. Using the magnetic field and the plasma parameter measurements (ACE/MAG and ACE/SWEPAM), we found widely different IMF configurations. In an independent approach we develop and apply an improved method of the velocity dispersion analysis to energetic protons measured by SoHO/ERNE. We determined the effective path length and the solar release time of protons from these data and also combined them with the neutron monitor data. We found that in most of the GLEs, protons propagate in transient magnetic structures. Moreover, the comparison between the interplanetary magnetic structure and the interplanetary length suggest that the timing of particle arrival at Earth is dominantly determined by the type of IMF in which high energetic particles are propagating. Finally we find that these energetic protons are not significantly scattered during their transport to Earth.

Transient Liquid Phase Behavior of Sn-Coated Cu Particles and Chip Bonding using Paste Containing the Particles

Directory of Open Access Journals (Sweden)

Hwang Jun Ho

2017-06-01

Full Text Available Sn-coated Cu particles were prepared as a filler material for transient liquid phase (TLP bonding. The thickness of Sn coating was controlled by controlling the number of plating cycles. The Sn-coated Cu particles best suited for TLP bonding were fabricated by Sn plating thrice, and the particles showed a pronounced endothermic peak at 232°C. The heating of the particles for just 10 s at 250°C destroyed the initial core-shell structure and encouraged the formation of Cu-Sn intermetallic compounds. Further, die bonding was also successfully performed at 250°C under a slight bonding pressure of around 0.1 MPa using a paste containing the particles. The bonding time of 30 s facilitated the bonding of Sn-coated Cu particles to the Au surface and also increased the probability of network formation between particles.

Experimental techniques in nuclear and particle physics

CERN Document Server

Tavernier, Stefaan

2009-01-01

The book is based on a course in nuclear and particle physics that the author has taught over many years to physics students, students in nuclear engineering and students in biomedical engineering. It provides the basic understanding that any student or researcher using such instruments and techniques should have about the subject. After an introduction to the structure of matter at the subatomic scale, it covers the experimental aspects of nuclear and particle physics. Ideally complementing a theoretically-oriented textbook on nuclear physics and/or particle physics, it introduces the reader to the different techniques used in nuclear and particle physics to accelerate particles and to measurement techniques (detectors) in nuclear and particle physics. The main subjects treated are: interactions of subatomic particles in matter; particle accelerators; basics of different types of detectors; and nuclear electronics. The book will be of interest to undergraduates, graduates and researchers in both particle and...

Theory and simulation of epitaxial rotation. Light particles adsorbed on graphite

DEFF Research Database (Denmark)

Vives, E.; Lindgård, P.-A.

1993-01-01

We present a theory and Monte Carlo simulations of adsorbed particles on a corrugated substrate. We have focused on the case of rare gases and light molecules, H-2 and D2, adsorbed on graphite. The competition between the particle-particle and particle-substrate interactions gives rise to frustra...... found a modulated 4 x 4 structure. Energy, structure-factor intensities, peak positions, and epitaxial rotation angles as a function of temperature and coverage have been determined from the simulations. Good agreement with theory and experimental data is found.......We present a theory and Monte Carlo simulations of adsorbed particles on a corrugated substrate. We have focused on the case of rare gases and light molecules, H-2 and D2, adsorbed on graphite. The competition between the particle-particle and particle-substrate interactions gives rise...... between the commensurate and incommensurate phase for the adsorbed systems. From our simulations and our theory, we are, able to understand the gamma phase of D2 as an ordered phase stabilized by disorder. It can be described as a 2q-modulated structure. In agreement with the experiments, we have also...

Structural and morphological changes in pseudobarrier films of anodic aluminum oxide caused by irradiation with high-energy particles

International Nuclear Information System (INIS)

Chernykh, M.A.; Belov, V.T.

1988-01-01

We have studied the structural and morphological changes, occurring under the electron beam in pseudobarrier films of anodic aluminum oxide, prepared in seven different solutions and irradiated beforehand by protons of x-rays, with the aim of elucidating the structure of anodic aluminum oxides. An increased stability of the pseudobarrier films of anodic aluminum oxide has been observed towards the action of the electron beam of an UEMV-100K microscope at standard working regimes (75 keV) as a result of irradiation with protons or x-rays. A difference has been found to exist between structural and morphological changes of anodic aluminum oxide films, prepared in different solutions, when irradiated with high-energy particles. A structural and phase inhomogeneity of amorphous pseudobarrier films of anodic aluminum oxide has been detected and its influence on the character of solid-phase transformations under the maximum-intensity electron beam

How to Determine the Core-Shell Nature in Bimetallic Catalyst Particles?

Directory of Open Access Journals (Sweden)

Emma Westsson

2014-11-01

Full Text Available Nanometer-sized materials have significantly different chemical and physical properties compared to bulk material. However, these properties do not only depend on the elemental composition but also on the structure, shape, size and arrangement. Hence, it is not only of great importance to develop synthesis routes that enable control over the final structure but also characterization strategies that verify the exact nature of the nanoparticles obtained. Here, we consider the verification of contemporary synthesis strategies for the preparation of bimetallic core-shell particles in particular in relation to potential particle structures, such as partial absence of core, alloying and raspberry-like surface. It is discussed what properties must be investigated in order to fully confirm a covering, pin-hole free shell and which characterization techniques can provide such information. Not uncommonly, characterization strategies of core-shell particles rely heavily on visual imaging like transmission electron microscopy. The strengths and weaknesses of various techniques based on scattering, diffraction, transmission and absorption for investigating core-shell particles are discussed and, in particular, cases where structural ambiguities still remain will be highlighted. Our main conclusion is that for particles with extremely thin or mono-layered shells—i.e., structures outside the limitation of most imaging techniques—other strategies, not involving spectroscopy or imaging, are to be employed. We will provide a specific example of Fe-Pt core-shell particles prepared in bicontinuous microemulsion and point out the difficulties that arise in the characterization process of such particles.

The strange story of god particle

International Nuclear Information System (INIS)

Sengupta, Soumitra

2015-01-01

Discoveries of new fundamental particles are not new in the history of search of elementary structures of the material world around us. However the discovery of Higgs boson created sensation in the entire science community and is considered as a rare milestone among all scientific achievements. In this talk I shall try to explain why the moment of this discovery is so special in our understanding of this Universe and what is the God-like power associated with this very special particle Higgs boson - which popularly became famous as God Particle. I shall also describe the spectacular technological marvel which finally helped to discover this particle. (author)

The Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage: Track Structure Effects and Cytogenetic Signatures of High-LET Exposure

Science.gov (United States)

George, K.; Hada, M.; Chappell, L.; Cucinotta, F. A.

2012-01-01

Track structure models predict that at a fixed value of LET, particles with lower charge number, Z will have a higher biological effectiveness compared to particles with a higher Z. In this report we investigated how track structure effects induction of chromosomal aberration in human cells. Human lymphocytes were irradiated in vitro with various energies of accelerated iron, silicon, neon, or titanium ions and chromosome damage was assessed in using three color FISH chromosome painting in chemically induced PCC samples collected a first cell division post irradiation. The LET values for these ions ranged from 30 to 195 keV/micrometers. Of the particles studied, Neon ions have the highest biological effectiveness for induction of total chromosome damage, which is consistent with track structure model predictions. For complex-type exchanges 64 MeV/ u Neon and 450 MeV/u Iron were equally effective and induced the most complex damage. In addition we present data on chromosomes exchanges induced by six different energies of protons (5 MeV/u to 2.5 GeV/u). The linear dose response term was similar for all energies of protons suggesting that the effect of the higher LET at low proton energies is balanced by the production of nuclear secondaries from the high energy protons. All energies of protons have a much higher percentage of complex-type chromosome exchanges than gamma rays, signifying a cytogenetic signature for proton exposures.

Soft radiation in heavy-particle pair production: All-order colour structure and two-loop anomalous dimension

International Nuclear Information System (INIS)

Beneke, M.; Falgari, P.; Schwinn, C.

2010-01-01

We consider the total production cross section of heavy coloured particle pairs in hadronic collisions at the production threshold. We construct a basis in colour space that diagonalizes to all orders in perturbation theory the soft function, which appears in a new factorization formula for the combined resummation of soft gluon and Coulomb gluon effects. This extends recent results on the structure of soft anomalous dimensions and allows us to determine an analytic expression for the two-loop soft anomalous dimension at threshold for all production processes of interest.

Structural-morphological variations in pseudo-barrier films of anode aluminium oxide under irradiation with high-energy particles

International Nuclear Information System (INIS)

Chernykh, M.A.; Belov, V.T.

1988-01-01

Comparative study of structural-morphological variations under electron beam effect in pseudo-barrier films of anode aluminium oxide, obtained in seven different solutions and proton or X-rays pre-irradiated to determine structure peculiarities of anode aluminium oxides, is presented. Such study is a matter of interest from the solid-phase transformation theory point of view and for anode aluminium films application under radiation. Stability increase of pseudo-barrier films of anode aluminium oxide to the effect of UEhMV-100 K microscope electron beam at standard modes of operation (75 kV) due to proton or X-rays irradiation is found. Difference in structural-monorphological variations obtained in different solutions of anode aluminium films under high-energy particles irradiation is determined. Strucural-phase microinhomogeneity of amorphous pseudo-barrier films of anode aluminium oxide and its influence on solid-phase transformations character under electron bean of maximal intensity are detected

Stacking faults in Zr(Fe, Cr)2 Laves structured secondary phase particle in Zircaloy-4 alloy.

Science.gov (United States)

Liu, Chengze; Li, Geping; Yuan, Fusen; Han, Fuzhou; Zhang, Yingdong; Gu, Hengfei

2018-02-01

Stacking faults (SFs) in secondary phase particles (SPPs), which generally crystallize in the Laves phase in Zircaloy-4 (Zr-4) alloy, have been frequently observed by researchers. However, few investigations on the nano-scale structure of SFs have been carried out. In the present study, an SF containing C14 structured SPP, which located at grain boundaries (GBs) in the α-Zr matrix, was chosen to be investigated, for its particular substructure as well as location, aiming to reveal the nature of the SFs in the SPPs in Zr-4 alloy. It was indicated that the SFs in the C14 structured SPP actually existed in the local C36 structured Laves phase, for their similarities in crystallography. The C14 → C36 phase transformation, which was driven by synchroshearing among the (0001) basal planes, was the formation mechanism of the SFs in the SPPs. By analyzing the strained regions near the SPP, a model for understanding the driving force of the synchroshear was proposed: the interaction between SPP and GB resulted in the Zener pinning effect, leading to the shearing parallel to the (0001) basal planes of the C14 structured SPP, and the synchroshear was therefore activated.

Effect of alpha particles on Toroidal Alfven Eigenmodes

International Nuclear Information System (INIS)

Berk, H.L.

1992-11-01

An overview is given of the analytic structure for the linear theory of the Toroidal Alfven Eigenmode (TAE), where multiple gap structures occur. A discussion is given of the alpha particle drive and the various dissipation mechanisms that can stabilize the system. A self-consistent calculation of the TAE mode, for a low-beta high-aspect-ratio plasma, indicates that though the alpha particle drive is comparable to the dissipation mechanisms, overall stability is still achieved for ignited ITER-like plasma. A brief discussion is given of the nonlinear theory for the TAE mode and how nonlinear alpha particle dynamics can be treated by mapping methods

Particles trajectories in magnetic filaments

Energy Technology Data Exchange (ETDEWEB)

Bret, A. [ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain); Instituto de Investigaciones Energéticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real (Spain)

2015-07-15

The motion of a particle in a spatially harmonic magnetic field is a basic problem involved, for example, in the mechanism of formation of a collisionless shock. In such settings, it is generally reasoned that particles entering a Weibel generated turbulence are trapped inside it, provided their Larmor radius in the peak field is smaller than the field coherence length. The goal of this work is to put this heuristic conclusion on firm ground by studying, both analytically and numerically, such motion. A toy model is analyzed, consisting of a relativistic particle entering a region of space occupied by a spatially harmonic field. The particle penetrates the magnetic structure in a direction aligned with the magnetic filaments. Although the conclusions are not trivial, the main result is confirmed.

Particles trajectories in magnetic filaments

International Nuclear Information System (INIS)

Bret, A.

2015-01-01

The motion of a particle in a spatially harmonic magnetic field is a basic problem involved, for example, in the mechanism of formation of a collisionless shock. In such settings, it is generally reasoned that particles entering a Weibel generated turbulence are trapped inside it, provided their Larmor radius in the peak field is smaller than the field coherence length. The goal of this work is to put this heuristic conclusion on firm ground by studying, both analytically and numerically, such motion. A toy model is analyzed, consisting of a relativistic particle entering a region of space occupied by a spatially harmonic field. The particle penetrates the magnetic structure in a direction aligned with the magnetic filaments. Although the conclusions are not trivial, the main result is confirmed

Particles trajectories in magnetic filaments

Science.gov (United States)

Bret, A.

2015-07-01

The motion of a particle in a spatially harmonic magnetic field is a basic problem involved, for example, in the mechanism of formation of a collisionless shock. In such settings, it is generally reasoned that particles entering a Weibel generated turbulence are trapped inside it, provided their Larmor radius in the peak field is smaller than the field coherence length. The goal of this work is to put this heuristic conclusion on firm ground by studying, both analytically and numerically, such motion. A toy model is analyzed, consisting of a relativistic particle entering a region of space occupied by a spatially harmonic field. The particle penetrates the magnetic structure in a direction aligned with the magnetic filaments. Although the conclusions are not trivial, the main result is confirmed.

Preparation and Characterization of Stable α-Synuclein Lipoprotein Particles.

Science.gov (United States)

Eichmann, Cédric; Campioni, Silvia; Kowal, Julia; Maslennikov, Innokentiy; Gerez, Juan; Liu, Xiaoxia; Verasdonck, Joeri; Nespovitaya, Nadezhda; Choe, Senyon; Meier, Beat H; Picotti, Paola; Rizo, Josep; Stahlberg, Henning; Riek, Roland

2016-04-15

Multiple neurodegenerative diseases are caused by the aggregation of the human α-Synuclein (α-Syn) protein. α-Syn possesses high structural plasticity and the capability of interacting with membranes. Both features are not only essential for its physiological function but also play a role in the aggregation process. Recently it has been proposed that α-Syn is able to form lipid-protein particles reminiscent of high-density lipoproteins. Here, we present a method to obtain a stable and homogeneous population of nanometer-sized particles composed of α-Syn and anionic phospholipids. These particles are called α-Syn lipoprotein (nano)particles to indicate their relationship to high-density lipoproteins formed by human apolipoproteins in vivo and of in vitro self-assembling phospholipid bilayer nanodiscs. Structural investigations of the α-Syn lipoprotein particles by circular dichroism (CD) and magic angle solid-state nuclear magnetic resonance (MAS SS-NMR) spectroscopy establish that α-Syn adopts a helical secondary structure within these particles. Based on cryo-electron microscopy (cryo-EM) and dynamic light scattering (DLS) α-Syn lipoprotein particles have a defined size with a diameter of ∼23 nm. Chemical cross-linking in combination with solution-state NMR and multiangle static light scattering (MALS) of α-Syn particles reveal a high-order protein-lipid entity composed of ∼8-10 α-Syn molecules. The close resemblance in size between cross-linked in vitro-derived α-Syn lipoprotein particles and a cross-linked species of endogenous α-Syn from SH-SY5Y human neuroblastoma cells indicates a potential functional relevance of α-Syn lipoprotein nanoparticles. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Composite particles and symplectic (Semi-) groups

International Nuclear Information System (INIS)

Kramer, P.

1978-01-01

Nuclear composits particle dynamics is intimately related to the fermion character of nucleons. This property is implemented via the permutational structure of nuclear states, leading to the concept of exchange and to the quantum number of the orbital partition. We review Weyl operators and representations of linear canonical transformations in Bargmann Hilbert space. In section 4 we use canonical transformations to describe the general n-body dynamics. In section 5 we derive the composite particle dynamics and discuss an algorithm to obtain the interaction of composite particles whose constituents are assumed to be in harmonic oscillator states. As a first example we treat in section 6 composite particles with unexcited internal oscillator states. In section 7 we deal with composite particles of internal oscillator shell configurations. (orig.) [de

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

Science.gov (United States)

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

2016-04-21

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

Optimal Sensor Placement for Latticed Shell Structure Based on an Improved Particle Swarm Optimization Algorithm

Directory of Open Access Journals (Sweden)

Xun Zhang

2014-01-01

Full Text Available Optimal sensor placement is a key issue in the structural health monitoring of large-scale structures. However, some aspects in existing approaches require improvement, such as the empirical and unreliable selection of mode and sensor numbers and time-consuming computation. A novel improved particle swarm optimization (IPSO algorithm is proposed to address these problems. The approach firstly employs the cumulative effective modal mass participation ratio to select mode number. Three strategies are then adopted to improve the PSO algorithm. Finally, the IPSO algorithm is utilized to determine the optimal sensors number and configurations. A case study of a latticed shell model is implemented to verify the feasibility of the proposed algorithm and four different PSO algorithms. The effective independence method is also taken as a contrast experiment. The comparison results show that the optimal placement schemes obtained by the PSO algorithms are valid, and the proposed IPSO algorithm has better enhancement in convergence speed and precision.

Numerical Simulation of Flow and Heat Transfer in Structured Packed Beds with Smooth or Dimpled Spheres at Low Channel to Particle Diameter Ratio

Directory of Open Access Journals (Sweden)

Shiyang Li

2018-04-01

Full Text Available Packed beds are widely used in catalytic reactors or nuclear reactors. Reducing the pressure drop and improving the heat transfer performance of a packed bed is a common research aim. The dimpled structure has a complex influence on the flow and heat transfer characteristics. In the present study, the flow and heat transfer characteristics in structured packed beds with smooth or dimpled spheres are numerically investigated, where two different low channel to particle diameter ratios (N = 1.00 and N = 1.15 are considered. The pressure drop and the Nusselt number are obtained. The results show that, for N = 1.00, compared with the structured packed bed with smooth spheres, the structured packed bed with dimpled spheres has a lower pressure drop and little higher Nusselt number at 1500 < ReH < 14,000, exhibiting an improved overall heat transfer performance. However, for N = 1.15, the structured packed bed with dimpled spheres shows a much higher pressure drop, which dominantly affects the overall heat transfer performance, causing it to be weaker. Comparing the different channel to particle diameter ratios, we find that different configurations can result in: (i completely different drag reduction effect; and (ii relatively less influence on heat transfer enhancement.

Molecular and structural properties of polymer composites filled with activated charcoal particles

Energy Technology Data Exchange (ETDEWEB)

Tahir, Dahlang, E-mail: dtahir@fmipa.unhas.ac.id; Bakri, Fahrul [Department of Physics, Hasanuddin University, Makassar 90245 Indonesia (Indonesia); Liong, Syarifuddin [Department of Chemistry, Hasanuddin University, Makassar 90245 Indonesia (Indonesia)

2016-03-11

We have studied the molecular properties, structural properties, and chemical composition of composites by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, and X-ray fluorescence (XRF) spectroscopy, respectively. FTIR spectra shows absorption band of hydroxyl group (-OH), methyl group (-CH{sub 3}) and aromatic group (C-C). The absorption band for aromatic group (C-C) shows the formation of carbonaceous in composites. XRF shows chemical composition of composites, which the main chemicals are SO{sub 3}, Cl, and ZnO. The loss on ignition value (LOI) of activated charcoal indicates high carbonaceous matter. The crystallite size for diffraction pattern from hydrogel polymer is about 17 nm and for activated charcoal are about 19 nm. The crystallite size of the polymer is lower than that of activated charcoal, which make possible of the particle from filler in contact with each other to form continuous conducting polymer through polymer matrix.

Modeling and characterization of dielectrophoretically structured piezoelectric composites using piezoceramic particle inclusions with high aspect ratios

Science.gov (United States)

van den Ende, D. A.; Maier, R. A.; van Neer, P. L. M. J.; van der Zwaag, S.; Randall, C. A.; Groen, W. A.

2013-01-01

In this work, the piezoelectric properties at high electric fields of dielectrophoretically aligned PZT—polymer composites containing high aspect ratio particles (such as short fibers) are presented. Polarization and strain as a function of electric field are evaluated. The properties of the composites are compared to those of PZT-polymer composites with equiaxed particles, continuous PZT fiber-polymer composites, and bulk PZT ceramics. From high-field polarization and strain measurements, the effective field dependent permittivity and piezoelectric charge constant in the poling direction are determined for dielectrophoresis structured PZT-polymer composites, continuous PZT fiber-polymer composites, and bulk PZT ceramics. The changes in dielectric properties of the inclusions and the matrix at high fields influence the dielectric and piezoelectric properties of the composites. It is found that the permittivity and piezoelectric charge constants increase towards a maximum at an applied field of around 2.5-5 kV/mm. The electric field at which the maximum occurs depends on the aspect ratio and degree of alignment of the inclusions. Experimental values of d33 at low and high applied fields are compared to a model describing the composites as a continuous polymer matrix containing PZT particles of various aspect ratios arranged into chains. Thickness mode coupling factors were determined from measured impedance data using fitted equivalent circuit model simulations. The relatively high piezoelectric strain constants, voltage constants, and thickness coupling factors indicate that such aligned short fiber composites could be useful as flexible large area transducers.

Oscillatory regime of avalanche particle detectors

International Nuclear Information System (INIS)

Lukin, K.A.; Cerdeira, H.A.; Colavita, A.A.

1995-06-01

We describe the model of an avalanche high energy particle detector consisting of two pn-junctions, connected through an intrinsic semiconductor with a reverse biased voltage applied. We show that this detector is able to generate the oscillatory response on the single particle passage through the structure. The possibility of oscillations leading to chaotic behaviour is pointed out. (author). 15 refs, 7 figs

Fast particle tracking with wake fields

Energy Technology Data Exchange (ETDEWEB)

Dohlus, M.; Floettmann, K.; Henning, C.

2012-01-15

Tracking calculations of charged particles in electromagnetic fields require in principle the simultaneous solution of the equation of motion and of Maxwell's equations. In many tracking codes a simpler and more efficient approach is used: external fields like that of the accelerating structures are provided as field maps, generated in separate computations and for the calculation of self fields the model of a particle bunch in uniform motion is used. We describe how an externally computed wake function can be approximated by a table of Taylor coefficients and how the wake field kick can be calculated for the particle distribution in a tracking calculation. The integrated kick, representing the effect of a distributed structure, is applied at a discrete time. As an example, we use our approach to calculate the emittance growth of a bunch in an undulator beam pipe due to resistive wall wake field effects. (orig.)

Determination of charge on vertically aligned particles in a complex plasma using laser excitations

CERN Document Server

Prior, N J; Samarian, A A

2003-01-01

Experimental studies on vertical oscillations of few particle vertical structures are described. One and two particle strings were subjected to two types of vertically driven oscillations. The first was electrode driven, which excites the structure as a whole, while the second was laser driven, which excites one particle in the structure only. The latter experiments are highly original, enabling us to excite two vertical resonances in our two particle structures. From the close agreement between our experimental data and theoretical model, several important physical parameters have been estimated, including the charge ratio and the Debye length.

Probing fine magnetic particles with neutron scattering

International Nuclear Information System (INIS)

Pynn, R.

1991-01-01

Because thermal neutrons are scattered both by nuclei and by unpaired electrons, they provide an ideal probe for studying the atomic and magnetic structures of fine-grained magnetic materials, including nanocrystalline solids, thin epitaxial layers, and colloidal suspensions of magnetic particles, known as ferrofluids. Diffraction, surface reflection, and small angle neutron scattering (SANS) are the techniques used. With the exception of surface reflection, these methods are described in this article. The combination of SANS with refractive-index matching and neutron polarisation analysis is particularly powerful because it allows the magnetic and atomic structures to be determined independently. This technique has been used to study both dilute and concentrated ferrofluid suspensions of relatively monodisperse cobalt particles, subjected to a series of applied magnetic fields. The size of the cobalt particle core and the surrounding surfactant layer were determined. The measured interparticle structure factor agrees well with a recent theory that allows correlations in binary mixtures of magnetic particles to be calculated in the case of complete magnetic alignment. When one of the species in such a binary mixture is a nonmagnetic, cyclindrical macromolecule, application of a magnetic field leads to some degree of alignment of the nonmagnetic species. This result has been demonstrated with tobacco mosaic virus suspended in a water-based ferrofluid

Insight into particle production mechanisms from angular correlations of identified particles in pp collisions measured by ALICE

CERN Multimedia

CERN. Geneva

2017-01-01

Two-particle angular correlations are a robust tool which provide access to the underlying physics phenomena of particle production in collisions of both protons and heavy ions by studying distributions of particles in pseudorapidity and azimuthal angle difference. The correlation measurement is sensitive to several phenomena, including mini-jets, elliptic flow, Bose-Einstein correlations, resonance decays, conservation laws, which can be separated by selections of momentum, particle type and by analysing the shapes of the correlation structures. In this talk, we report measurements of the correlations of identified particles and their antiparticles (for pions, kaons, protons, and lambdas) at low transverse momenta in pp collisions at sqrt(s) = 7 TeV, recently submitted for publication by the ALICE Collaboration [arXiv:1612.08975]. The analysis reveals differences in particle production between baryons and mesons. The correlation functions for mesons exhibit the expected peak dominated by effects of mini-jet...

SOLAR ENERGETIC PARTICLE MODULATIONS ASSOCIATED WITH COHERENT MAGNETIC STRUCTURES

International Nuclear Information System (INIS)

Trenchi, L.; Bruno, R.; D'amicis, R.; Marcucci, M. F.; Telloni, D.; Zurbuchen, T. H.; Weberg, M.

2013-01-01

In situ observations of solar energetic particles (SEPs) often show rapid variations of their intensity profile, affecting all energies simultaneously, without time dispersion. A previously proposed interpretation suggests that these modulations are directly related to the presence of magnetic structures with a different magnetic topology. However, no compelling evidence of local changes in magnetic field or in plasma parameters during SEP modulations has been reported. In this paper, we performed a detailed analysis of SEP events and we found several signatures in the local magnetic field and/or plasma parameters associated with SEP modulations. The study of magnetic helicity allowed us to identify magnetic boundaries, associated with variations of plasma parameters, which are thought to represent the borders between adjacent magnetic flux tubes. It is found that SEP dispersionless modulations are generally associated with such magnetic boundaries. Consequently, we support the idea that SEP modulations are observed when the spacecraft passes through magnetic flux tubes, filled or devoid of SEPs, which are alternatively connected and not connected with the flare site. In other cases, we found SEP dropouts associated with large-scale magnetic holes. A possible generation mechanism suggests that these holes are formed in the high solar corona as a consequence of magnetic reconnection. This reconnection process modifies the magnetic field topology, and therefore, these holes can be magnetically isolated from the surrounding plasma and could also explain their association with SEP dropouts.

Twistor theory a particle-physicist attitude

International Nuclear Information System (INIS)

Perjes, Z.

1979-07-01

Particle models in twistor theory are reviewed, starting with an introduction into the kinematical-twistor formalism which describes massive particles in Minkowski space-time. The internal transformations of constituent twistors are then discussed. The quantization rules available from a study of twistor scattering situations are used to construct quantum models of fundamental particles. The theory allows the introduction of an internal space with a Kaehlerian metric where hadron structure is described by ''spherical'' states of bound constituents. It is conjectured that the spectrum of successive families of hadrons might approach an accumulation point in energy. Above this threshold energy, the Kaehlerian analog of ionization could occur wherein the zero-mass constituents (twistors) of the particle break free. (author)

Collisionless shocks in space plasmas structure and accelerated particles

CERN Document Server

Burgess, David

2015-01-01

Shock waves are an important feature of solar system plasmas, from the solar corona out to the edge of the heliosphere. This engaging introduction to collisionless shocks in space plasmas presents a comprehensive review of the physics governing different types of shocks and processes of particle acceleration, from fundamental principles to current research. Motivated by observations of planetary bow shocks, interplanetary shocks and the solar wind termination shock, it emphasises the physical theory underlying these shock waves. Readers will develop an understanding of the complex interplay between particle dynamics and the electric and magnetic fields that explains the observations of in situ spacecraft. Written by renowned experts in the field, this up-to-date text is the ideal companion for both graduate students new to heliospheric physics and researchers in astrophysics who wish to apply the lessons of solar system shocks to different astrophysical environments.

From the Yukawa Particle to the QGCW

CERN Document Server

Zichichi, A

2008-01-01

The remarkable consequences of the Yukawa particle, theoretically proposed in 1935, are reviewed. The production, the decay and the intrinsic structure of the Yukawa particle opened new frontiers with laws and regularities which brought us to the discovery of subnuclear physics and now to the Quark-Gluon-Coloured-World (QGCW).

Particle Interferometry for Relativistic Heavy-Ion Collisions

CERN Document Server

Wiedemann, Urs Achim; Wiedemann, Urs Achim; Heinz, Ulrich

1999-01-01

In this report we give a detailed account on Hanbury Brown/Twiss (HBT) particle interferometric methods for relativistic heavy-ion collisions. These exploit identical two-particle correlations to gain access to the space-time geometry and dynamics of the final freeze-out stage. The connection between the measured correlations in momentum space and the phase-space structure of the particle emitter is established, both with and without final state interactions. Suitable Gaussian parametrizations for the two-particle correlation function are derived and the physical interpretation of their parameters is explained. After reviewing various model studies, we show how a combined analysis of single- and two-particle spectra allows to reconstruct the final state of relativistic heavy-ion collisions.

Irreversible adsorption of particles on heterogeneous surfaces.

Science.gov (United States)

Adamczyk, Zbigniew; Jaszczółt, Katarzyna; Michna, Aneta; Siwek, Barbara; Szyk-Warszyńska, Lilianna; Zembala, Maria

2005-12-30

Methods of theoretical and experimental evaluation of irreversible adsorption of particles, e.g., colloids and globular proteins at heterogeneous surfaces were reviewed. The theoretical models were based on the generalized random sequential adsorption (RSA) approach. Within the scope of these models, localized adsorption of particles occurring as a result of short-ranged attractive interactions with discrete adsorption sites was analyzed. Monte-Carlo type simulations performed according to this model enabled one to determine the initial flux, adsorption kinetics, jamming coverage and the structure of the particle monolayer as a function of the site coverage and the particle/site size ratio, denoted by lambda. It was revealed that the initial flux increased significantly with the site coverage theta(s) and the lambda parameter. This behavior was quantitatively interpreted in terms of the scaled particle theory. It also was demonstrated that particle adsorption kinetics and the jamming coverage increased significantly, at fixed site coverage, when the lambda parameter increased. Practically, for alpha = lambda2theta(s) > 1 the jamming coverage at the heterogeneous surfaces attained the value pertinent to continuous surfaces. The results obtained prove unequivocally that spherically shaped sites were more efficient in binding particles in comparison with disk-shaped sites. It also was predicted that for particle size ratio lambda charge. Particle deposition occurred under diffusion-controlled transport conditions and their coverage was evaluated by direct particle counting using the optical and electron microscopy. Adsorption kinetics was quantitatively interpreted in terms of numerical solutions of the governing diffusion equation with the non-linear boundary condition derived from Monte-Carlo simulations. It was proven that for site coverage as low as a few percent the initial flux at heterogeneous surfaces attained the maximum value pertinent to homogeneous

Rotation of hard particles in a soft matrix

Science.gov (United States)

Yang, Weizhu; Liu, Qingchang; Yue, Zhufeng; Li, Xiaodong; Xu, Baoxing

Soft-hard materials integration is ubiquitous in biological materials and structures in nature and has also attracted growing attention in the bio-inspired design of advanced functional materials, structures and devices. Due to the distinct difference in their mechanical properties, the rotation of hard phases in soft matrixes upon deformation has been acknowledged, yet is lack of theory in mechanics. In this work, we propose a theoretical mechanics framework that can describe the rotation of hard particles in a soft matrix. The rotation of multiple arbitrarily shaped, located and oriented particles with perfectly bonded interfaces in an elastic soft matrix subjected to a far-field tensile loading is established and analytical solutions are derived by using complex potentials and conformal mapping methods. Strong couplings and competitions of the rotation of hard particles among each other are discussed by investigating numbers, relative locations and orientations of particles in the matrix at different loading directions. Extensive finite element analyses are performed to validate theoretical solutions and good agreement of both rotation and stress field between them are achieved. Possible extensions of the present theory to non-rigid particles, viscoelastic matrix and imperfect bonding are also discussed. Finally, by taking advantage of the rotation of hard particles, we exemplify an application in a conceptual design of soft-hard material integrated phononic crystal and demonstrate that phononic band gaps can be successfully tuned with a high accuracy through the mechanical tension-induced rotation of hard particles. The present theory established herein is expected to be of immediate interests to the design of soft-hard materials integration based functional materials, structures and devices with tunable performance via mechanical rotation of hard phases.

Morphology and ultrastructure of retrovirus particles

Directory of Open Access Journals (Sweden)

Wei Zhang

2015-08-01

Full Text Available Retrovirus morphogenesis entails assembly of Gag proteins and the viral genome on the host plasma membrane, acquisition of the viral membrane and envelope proteins through budding, and formation of the core through the maturation process. Although in both immature and mature retroviruses, Gag and capsid proteins are organized as paracrystalline structures, the curvatures of these protein arrays are evidently not uniform within one or among all virus particles. The heterogeneity of retroviruses poses significant challenges to studying the protein contacts within the Gag and capsid lattices. This review focuses on current understanding of the molecular organization of retroviruses derived from the sub-nanometer structures of immature virus particles, helical capsid protein assemblies and soluble envelope protein complexes. These studies provide insight into the molecular elements that maintain the stability, flexibility and infectivity of virus particles. Also reviewed are morphological studies of retrovirus budding, maturation, infection and cell-cell transmission, which inform the structural transformation of the viruses and the cells during infection and viral transmission, and lead to better understanding of the interplay between the functioning viral proteins and the host cell.

Proton resonance elastic scattering of $^{30}$Mg for single particle structure of $^{31}$Mg

CERN Multimedia

The single particle structure of $^{31}$Mg, which is located in the so-called “island of inversion”, will be studied through measuring Isobaric Analog Resonances (IARs) of bound states of $^{31}$Mg. They are located in the high excitation energy of $^{31}$Al. We are going to determine the spectroscopic factors and angular momenta of the parent states by measuring the excitation function of the proton resonance elastic scattering around 0 degrees in the laboratory frame with around 3 MeV/nucleon $^{30}$Mg beam. The present study will reveal the shell evolution around $^{32}$Mg. In addition, the spectroscopic factor of the (7/2)$^{−}$ state which was not yet determined experimentally, may allow one to study the shape coexistence in this nucleus.

Visualizing Ebolavirus Particles Using Single-Particle Interferometric Reflectance Imaging Sensor (SP-IRIS).

Science.gov (United States)

Carter, Erik P; Seymour, Elif Ç; Scherr, Steven M; Daaboul, George G; Freedman, David S; Selim Ünlü, M; Connor, John H

2017-01-01

This chapter describes an approach for the label-free imaging and quantification of intact Ebola virus (EBOV) and EBOV viruslike particles (VLPs) using a light microscopy technique. In this technique, individual virus particles are captured onto a silicon chip that has been printed with spots of virus-specific capture antibodies. These captured virions are then detected using an optical approach called interference reflectance imaging. This approach allows for the detection of each virus particle that is captured on an antibody spot and can resolve the filamentous structure of EBOV VLPs without the need for electron microscopy. Capture of VLPs and virions can be done from a variety of sample types ranging from tissue culture medium to blood. The technique also allows automated quantitative analysis of the number of virions captured. This can be used to identify the virus concentration in an unknown sample. In addition, this technique offers the opportunity to easily image virions captured from native solutions without the need for additional labeling approaches while offering a means of assessing the range of particle sizes and morphologies in a quantitative manner.

Layer structured Na{sub 2}Ni(MoO{sub 4}){sub 2} particles as a visible-light-driven photocatalyst for degradation of methylene blue

Energy Technology Data Exchange (ETDEWEB)

Lu, Yuting; Chen, Luyang; Huang, Yanlin [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Chen, Cuili; Kim, Sun Il [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

2015-03-15

Highlights: • Na{sub 2}Ni(MoO{sub 4}){sub 2} nanoparticles were developed by Pechini method. • The nanoparticles show high absorption in UV–vis wavelength region. • Na{sub 2}Ni(MoO{sub 4}){sub 2} has high activity in the MB dye degradation under visible light. • Hexagonal layers with heavily distorted NiO{sub 6} were superiority for photocatalysis. - Abstract: A new visible-light-driven photocatalyst of Na{sub 2}Ni(MoO{sub 4}){sub 2} particle was prepared by the modified Pechini method. The crystal structure was measured by X-ray diffraction (XRD) and the structural refinement. The sample was investigated by scanning electron microscope (SEM), transmission electron microscopy (TEM), and UV–vis absorption spectrum measurements. The average size of Na{sub 2}Ni(MoO{sub 4}){sub 2} particle is about 180 nm. Na{sub 2}Ni(MoO{sub 4}){sub 2} particle have an efficient optical absorption in the UV–visible light wavelength region with a direct allowed electronic transition of 2.06 eV. The effective photodegradation of methylene blue (MB) dye was demonstrated, which benefits from the special crystal structure of Na{sub 2}Ni(MoO{sub 4}){sub 2} particle. This crystal lattice has two infinite chains formed by (Ni,Na)O{sub 6} and MoO{sub 4} polyhedra standing in lines alone with the inner wall of the hexagonal tunnels. This results in the efficient optical absorption and provides more chances for electron–hole separations, which can further react with dye molecules to oxidize the dye pollutant into non-toxic products.

Towards the directed evolution of virus-like particles derived from polyomaviruses

NARCIS (Netherlands)

Teunissen, E.A.

2014-01-01

Virus-like particles (VLPs) are assemblies of viral structural proteins. These particles resemble the native viral capsid in structure, tropism, and transduction efficiency, but do not contain any viral genetic material. This makes them a safer alternative to viral vectors for gene therapy, and

Structural, morphological and luminescence properties of nanocrystalline up-converting Y{sub 1.89}Yb{sub 0.1}Er{sub 0.01}O{sub 3} phosphor particles synthesized through aerosol route

Energy Technology Data Exchange (ETDEWEB)

Lojpur, V.; Mancic, L. [Institute of Technical Sciences of the Serbian Academy of Sciences and Arts, K. Mihailova 35/IV, 11000 Belgrade (Serbia); Rabanal, M.E. [University Carlos III of Madrid, Avd. Universidad 30, 28911 Leganes, Madrid (Spain); Dramicanin, M.D. [Vinca Institute of Nuclear Science, University of Belgrade, P.O. Box 522, Belgrade (Serbia); Tan, Z.; Hashishin, T.; Ohara, S. [JWRI, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Milosevic, O., E-mail: olivera.milosevic@itn.sanu.ac.rs [Institute of Technical Sciences of the Serbian Academy of Sciences and Arts, K. Mihailova 35/IV, 11000 Belgrade (Serbia)

2013-12-15

Highlights: •The Y{sub 1.89}Yb{sub 0.1}Er{sub 0.01}O{sub 3} phosphor particles are synthesized via aerosol route. •We report influence of process parameters on the particle structure and morphology. •Spherical, submicronic size and nano-crystalline particle morphology are confirmed. •The particles show improved luminescence properties and decay time. •Synthesized powders exhibit the temperature dependant up-conversion emission. -- Abstract: Nanocrystalline up-converting Y{sub 2}O{sub 3}:Yb{sup 3+}, Er{sup 3+} phosphor particles were processed in a dispersed system-aerosol, generated ultrasonically at 1.3 MHz from common nitrate precursor solution having fixed ytterbium-to-erbium concentration ratio. The appropriate process parameters: residence time 21 s, carrier gas (air) flow rate 1.6 dm{sup 3}/min, synthesis temperature 900 °C, led to the formation of un-agglomerated spherical nanostructured secondary particles, having mean particle size of approx 450 nm, composed of primary nanoscaled (20 nm) subunits. In order to reach targeting phase crystallinity, the as-prepared particles were additionally annealed at 1100 °C in air for 12, 24 and 48 h, respectively. Particle structure, morphology and purity were analyzed by X-ray powder diffraction (XRPD), scanning electron microscopy (FESEM/SEM), analytical and high resolution transmission electron microscopy (TEM/HRTEM) in combination with energy dispersive X-ray analysis and Fourier Transform Infrared Spectroscopy (FTIR). All samples crystallized in a cubic bixbyte-structure, space group Ia-3. The crystallite size changed with annealing time from 30 nm in as-prepared sample to 135 nm in sample annealed for 48 h, respectively. Emission spectra were assigned to the following trivalent erbium f–f electronic transitions: {sup 2}H{sub 9/2} → {sup 4}I{sub 15/2} (blue: 407–420 nm), ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) → {sup 4}I{sub 15/2} (green: 510–590 nm), and {sup 4}F{sub 9/2} → {sup 4}I{sub 15

High-resolution noise substitution to measure overfitting and validate resolution in 3D structure determination by single particle electron cryomicroscopy

International Nuclear Information System (INIS)

Chen, Shaoxia; McMullan, Greg; Faruqi, Abdul R.; Murshudov, Garib N.; Short, Judith M.; Scheres, Sjors H.W.; Henderson, Richard

2013-01-01

Three-dimensional (3D) structure determination by single particle electron cryomicroscopy (cryoEM) involves the calculation of an initial 3D model, followed by extensive iterative improvement of the orientation determination of the individual particle images and the resulting 3D map. Because there is much more noise than signal at high resolution in the images, this creates the possibility of noise reinforcement in the 3D map, which can give a false impression of the resolution attained. The balance between signal and noise in the final map at its limiting resolution depends on the image processing procedure and is not easily predicted. There is a growing awareness in the cryoEM community of how to avoid such over-fitting and over-estimation of resolution. Equally, there has been a reluctance to use the two principal methods of avoidance because they give lower resolution estimates, which some people believe are too pessimistic. Here we describe a simple test that is compatible with any image processing protocol. The test allows measurement of the amount of signal and the amount of noise from overfitting that is present in the final 3D map. We have applied the method to two different sets of cryoEM images of the enzyme beta-galactosidase using several image processing packages. Our procedure involves substituting the Fourier components of the initial particle image stack beyond a chosen resolution by either the Fourier components from an adjacent area of background, or by simple randomisation of the phases of the particle structure factors. This substituted noise thus has the same spectral power distribution as the original data. Comparison of the Fourier Shell Correlation (FSC) plots from the 3D map obtained using the experimental data with that from the same data with high-resolution noise (HR-noise) substituted allows an unambiguous measurement of the amount of overfitting and an accompanying resolution assessment. A simple formula can be used to calculate an

High-resolution noise substitution to measure overfitting and validate resolution in 3D structure determination by single particle electron cryomicroscopy

Energy Technology Data Exchange (ETDEWEB)

Chen, Shaoxia; McMullan, Greg; Faruqi, Abdul R.; Murshudov, Garib N.; Short, Judith M.; Scheres, Sjors H.W.; Henderson, Richard, E-mail: rh15@mrc-lmb.cam.ac.uk

2013-12-15

Three-dimensional (3D) structure determination by single particle electron cryomicroscopy (cryoEM) involves the calculation of an initial 3D model, followed by extensive iterative improvement of the orientation determination of the individual particle images and the resulting 3D map. Because there is much more noise than signal at high resolution in the images, this creates the possibility of noise reinforcement in the 3D map, which can give a false impression of the resolution attained. The balance between signal and noise in the final map at its limiting resolution depends on the image processing procedure and is not easily predicted. There is a growing awareness in the cryoEM community of how to avoid such over-fitting and over-estimation of resolution. Equally, there has been a reluctance to use the two principal methods of avoidance because they give lower resolution estimates, which some people believe are too pessimistic. Here we describe a simple test that is compatible with any image processing protocol. The test allows measurement of the amount of signal and the amount of noise from overfitting that is present in the final 3D map. We have applied the method to two different sets of cryoEM images of the enzyme beta-galactosidase using several image processing packages. Our procedure involves substituting the Fourier components of the initial particle image stack beyond a chosen resolution by either the Fourier components from an adjacent area of background, or by simple randomisation of the phases of the particle structure factors. This substituted noise thus has the same spectral power distribution as the original data. Comparison of the Fourier Shell Correlation (FSC) plots from the 3D map obtained using the experimental data with that from the same data with high-resolution noise (HR-noise) substituted allows an unambiguous measurement of the amount of overfitting and an accompanying resolution assessment. A simple formula can be used to calculate an

Surface Modification of α-Fe Metal Particles by Chemical Surface Coating

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

The structure of α-Fe metal magnetic recording particles coated with silane coupling agents have been studied by TEM, FT-IR, EXAFS, Mossbauer. The results show that a close, uniform, firm and ultra thin layer, which is beneficial to the magnetic and chemical stability, has been formed by the cross-linked chemical bond Si-O-Si. And the organic molecule has chemically bonded to the particle surface, which has greatly affected the surface Fe atom electronic structure. Furthermore, the covalent bond between metal particle surface and organic molecule has obvious effect on the near edge structure of the surface Fe atoms.

Modulation in magnetic exchange interaction, core shell structure and Hopkinson's peak with chromium substitution into Ni0.75Co0.25Fe2O4 nano particles

Science.gov (United States)

Uday Bhasker, S.; Choudary, G. S. V. R. K.; Reddy, M. V. Ramana

2018-05-01

The ever growing applications and ever evolving challenges of magnetic nano particles has been motivating the researchers from various disciplines towards this area of magnetic nano particles. Cation substitutional effect on the magnetic structure of the nanoparticles forms a crucial aspect in their applications. Here the environmentally benign auto combustion method was employed to synthesize chromium substituted nickel cobalt ferrite (Ni0.75Co0.25Fe2-xCrxO4; x = 0, 0.10, 0.15) nano particles, from aqueous metal nitrate solutions. Chromium substitution has shown its effect on the structural, magnetic and electrical properties of Ni0.75Co0.25Fe2O4. Structural and phase analysis of the prepared samples show increased phase purity of ferrite sample with increasing Cr substitution. The TEM (Transmission Electron Microscope) image confirms the nano size of the particles, EDS (Energy dispersive X-ray Spectroscopy) has supported the stoichiometry of the prepared samples and FTIR (Fourier-transform infrared spectroscopic) analysis confirms the spinel structure and also suggests cation redistributions with chromium substitution. VSM (Vibrational Sample Magnetometer) is used to study the magnetic properties through magnetic hysteresis (M-H) loop and magnetic Hopkinson effect. All samples show hysteresis and show reduction in magnetic properties with increase in chromium content. The thermo magnetic study shows Hopkinson peak(s) in the magnetization vs. temperature (M-T) graph and also shows variation in the nature of Hopkinson peak with chromium substitution. Possible reasons for the changes in the nature of the peak are discussed.

Seasonal cycle and modal structure of particle number size distribution at Dome C, Antarctica

Directory of Open Access Journals (Sweden)

E. Järvinen

2013-08-01

Full Text Available We studied new particle formation and modal behavior of ultrafine aerosol particles on the high East Antarctic plateau at the Concordia station, Dome C (75°06' S, 123°23' E. Aerosol particle number size distributions were measured in the size range 10–600 nm from 14 December 2007 to 7 November 2009. We used an automatic algorithm for fitting up to three modes to the size distribution data. The total particle number concentration was low with the median of 109 cm−3. There was a clear seasonal cycle in the total particle number and the volume concentrations. The concentrations were at their highest during the austral summer with the median values of 260 cm−3 and 0.086 μm3 cm−3, and at their lowest during the austral winter with corresponding values of 15 cm−3 and 0.009 μm3 cm−3. New particle formation events were determined from the size distribution data. During the measurement period, natural new particle formation was observed on 60 days and for 15 of these days the particle growth rates from 10 to 25 nm in size could be determined. The median particle growth rate during all these events was 2.5 nm h−1 and the median formation rate of 10 nm particles was 0.023 cm−3 s−1. Most of the events were similar to those observed at other continental locations, yet also some variability in event types was observed. Exceptional features in Dome C were the winter events that occurred during dark periods, as well as the events for which the growth could be followed during several consecutive days. We called these latter events slowly growing events. This paper is the first one to analyze long-term size distribution data from Dome C, and also the first paper to show that new particle formation events occur in central Antarctica.

Single particle inclusive spectra resulting from the collision of relativistic protons, deuterons, alpha particles, and carbon ions with nuclei

International Nuclear Information System (INIS)

Papp, J.

1975-05-01

The yields of positive and negative particles resulting from the collision of 1.05 GeV/nucleon and 2.1 GeV/nucleon protons, deuterons, alpha particles, and 1.05 GeV/nucleon carbon nuclei with various targets have been measured. Single particle inclusive cross sections for production of π + , π - , p, d, 3 H, 3 He, and 4 He at 2.5 0 (lab) were obtained. How the results bear on the concepts of limiting fragmentation and scaling, the structure of the alpha particle and deuteron, and the possibility of ''coherent'' production of pions by heavy ions are discussed. (U.S.)

Single-particle dispersion in compressible turbulence

Science.gov (United States)

Zhang, Qingqing; Xiao, Zuoli

2018-04-01

Single-particle dispersion statistics in compressible box turbulence are studied using direct numerical simulation. Focus is placed on the detailed discussion of effects of the particle Stokes number and turbulent Mach number, as well as the forcing type. When solenoidal forcing is adopted, it is found that the single-particle dispersion undergoes a transition from the ballistic regime at short times to the diffusive regime at long times, in agreement with Taylor's particle dispersion argument. The strongest dispersion of heavy particles is announced when the Stokes number is of order 1, which is similar to the scenario in incompressible turbulence. The dispersion tends to be suppressed as the Mach number increases. When hybrid solenoidal and compressive forcing at a ratio of 1/2 is employed, the flow field shows apparent anisotropic property, characterized by the appearance of large shock wave structures. Accordingly, the single-particle dispersion shows extremely different behavior from the solenoidal forcing case.

Correlation between morphology and magnetic properties of electrochemically produced cobalt powder particles

Directory of Open Access Journals (Sweden)

Maksimović Vesna M.

2015-01-01

Full Text Available Cobalt 3D powder particles were successfully prepared by the galvanostatic electrodeposition. Electrodeposited cobalt powder were characterized by X-ray diffraction (XRD, scanning electron microscope (SEM, Energy Dispersive Spectroscopy (EDS analysis and SQUID magnetometry. It has been shown that morphology, structure and magnetic properties of cobalt particles are closely associated and can be easily controlled by adjusting process parameters of electrodeposition. Morphology of cobalt powder particles is strongly affected by hydrogen evolution reaction as a parallel reaction to cobalt electrodeposition. Depending on the applied current density, the two types of powder particles were formed: dendrites at lower and spongy-like particles at higher current densities. Morphologies and structures of powder particles are correlated with their magnetic properties, and compared with those of the bulk cobalt. In comparison with the properties of bulk cobalt, the obtained 3D structures exhibited a decreased saturation magnetization (MS, but an enhanced coercivity (HC which is explained by their peculiar morphology. [Projekat Ministarstva nauke Republike Srbije, br. III 45012

Core–shell composite particles composed of biodegradable polymer particles and magnetic iron oxide nanoparticles for targeted drug delivery

Energy Technology Data Exchange (ETDEWEB)

Oka, Chiemi; Ushimaru, Kazunori [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Horiishi, Nanao [Bengala Techno Laboratory, 9-5-1006, 1-1 Kodai, Miyamae-ku, Kawasaki 216-0007 (Japan); Tsuge, Takeharu [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Kitamoto, Yoshitaka, E-mail: kitamoto.y.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan)

2015-05-01

Core–shell composite particles with biodegradability and superparamagnetic behavior were prepared using a Pickering emulsion for targeted drug delivery based on magnetic guidance. The composite particles were composed of a core of biodegradable polymer and a shell of assembled magnetic iron oxide nanoparticles. It was found that the dispersibility of the nanoparticles is crucial for controlling the core–shell structure. The addition of a small amount of dispersant into the nanoparticle's suspension could improve the dispersibility and led to the formation of composite particles with a thin magnetic shell covering a polymeric core. The composite particles were also fabricated with a model drug loaded into the core, which was released via hydrolysis of the core under strong alkaline conditions. Because the core can also be biodegraded by lipase, this result suggests that the slow release of the drug from the composite particles should occur inside the body. - Highlights: • Core−shell composites with biodegradability and magnetism are prepared. • O/W emulsion stabilized by iron oxide nanoparticles is utilized for the preparation. • The nanoparticle's dispersibility is crucial for controlling the composite structure. • Composites loading a model drug are also prepared. • The model drug is released with decomposition of the composites.

Dynamic Hydrogen Production from Methanol/Water Photo-Splitting Using Core@Shell-Structured CuS@TiO2 Catalyst Wrapped by High Concentrated TiO2 Particles

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Younghwan Im

2013-01-01

Full Text Available This study focused on the dynamic hydrogen production ability of a core@shell-structured CuS@TiO2 photocatalyst coated with a high concentration of TiO2 particles. The rectangular-shaped CuS particles, 100 nm in length and 60 nm in width, were surrounded by a high concentration of anatase TiO2 particles (>4~5 mol. The synthesized core@shell-structured CuS@TiO2 particles absorbed a long wavelength (a short band gap above 700 nm compared to that pure TiO2, which at approximately 300 nm, leading to easier electronic transitions, even at low energy. Hydrogen evolution from methanol/water photo-splitting over the core@shell-structured CuS@TiO2 photocatalyst increased approximately 10-fold compared to that over pure CuS. In particular, 1.9 mmol of hydrogen gas was produced after 10 hours when 0.5 g of 1CuS@4TiO2 was used at pH = 7. This level of production was increased to more than 4-fold at higher pH. Cyclic voltammetry and UV-visible absorption spectroscopy confirmed that the CuS in CuS@TiO2 strongly withdraws the excited electrons from the valence band in TiO2 because of the higher reduction potential than TiO2, resulting in a slower recombination rate between the electrons and holes and higher photoactivity.

Direct numerical simulations of agglomeration of circular colloidal particles in two-dimensional shear flow

International Nuclear Information System (INIS)

Choi, Young Joon; Djilali, Ned

2016-01-01

Colloidal agglomeration of nanoparticles in shear flow is investigated by solving the fluid-particle and particle-particle interactions in a 2D system. We use an extended finite element method in which the dynamics of the particles is solved in a fully coupled manner with the flow, allowing an accurate description of the fluid-particle interfaces without the need of boundary-fitted meshes or of empirical correlations to account for the hydrodynamic interactions between the particles. Adaptive local mesh refinement using a grid deformation method is incorporated with the fluid-structure interaction algorithm, and the particle-particle interaction at the microscopic level is modeled using the Lennard-Jones potential. Motivated by the process used in fabricating fuel cell catalysts from a colloidal ink, the model is applied to investigate agglomeration of colloidal particles under external shear flow in a sliding bi-periodic Lees-Edwards frame with varying shear rates and particle fraction ratios. Both external shear and particle fraction are found to have a crucial impact on the structure formation of colloidal particles in a suspension. Segregation intensity and graph theory are used to analyze the underlying agglomeration patterns and structures, and three agglomeration regimes are identified

Dynamics of magnetic nano-particle assembly

International Nuclear Information System (INIS)

Kondratyev, V N

2010-01-01

Ferromagnetically coupled nano-particle assembly is analyzed accounting for inter- and intra- particle electronic structures within the randomly jumping interacting moments model including quantum fluctuations due to the discrete levels and disorder. At the magnetic jump anomalies caused by quantization the magnetic state equation and phase diagram are found to indicate an existence of spinodal regions and critical points. Arrays of magnetized nano-particles with multiple magnetic response anomalies are predicted to display some specific features. In a case of weak coupling such arrays exhibit the well-separated instability regions surrounding the anomaly positions. With increasing coupling we observe further structure modification, plausibly, of bifurcation type. At strong coupling the dynamical instability region become wide while the stable regime arises as a narrow islands at small disorders. It is shown that exploring correlations of magnetic noise amplitudes represents convenient analytical tool for quantitative definition, description and study of supermagnetism, as well as self-organized criticality.

Test Particle Energization and the Anisotropic Effects of Dynamical MHD Turbulence

Science.gov (United States)

González, C. A.; Dmitruk, P.; Mininni, P. D.; Matthaeus, W. H.

2017-11-01

In this paper, we analyze the effect of dynamical three-dimensional magnetohydrodynamic (MHD) turbulence on test particle acceleration and compare how this evolving system affects particle energization by current sheet interaction, as opposed to frozen-in-time fields. To do this, we analyze the ensemble particle acceleration for static electromagnetic fields extracted from direct numerical simulations of the MHD equations, and compare it with the dynamical fields. We show that a reduction in particle acceleration in the dynamical model results from particle trapping in field lines, which forces the particles to be advected by the flow and suppresses long exposures to the strong electric field gradients that take place between structures and generate (among other effects) an efficient particle acceleration in the static case. In addition, we analyze the effect of anisotropy caused by the mean magnetic field. It is well known that for sufficiently strong external fields, the system experiences a transition toward a two-dimensional flow. This causes an increment in the size of the coherent structures, resulting in a magnetized state of the particles and a reduction in particle energization.

Improved graphite matrix for coated-particle fuel

International Nuclear Information System (INIS)

Schell, D.H.; Davidson, K.V.

1978-10-01

An experimental process was developed to incorporate coated fuel particles in an extruded graphite matrix. This structure, containing 41 vol% particles, had a high matrix density, >1.6 g/cm 3 , and a matrix conductivity three to four times that of a pitch-injected fuel rod at 1775 K. Experiments were conducted to determine the uniformity of particle loadings in extrusions. Irradiation specimens were supplied for five tests in the High-Fluence Isotope Reactor at the Oak Ridge National Laboratory

Structure, single-particle and many-particle coefficients of Lennard ...