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Sample records for ii core particles

  1. Interaction of RNA polymerase II with acetylated nucleosomal core particles

    SciTech Connect

    Pineiro, M.; Gonzalez, P.J.; Hernandez, F.; Palacian, E. )

    1991-05-31

    Chemical acetylation of nucleosomal cores is accompanied by an increase in their efficiency as in vitro transcription templates. Low amounts of acetic anhydride cause preferential modification of the amino-terminal tails of core histones. Modification of these domains, which causes moderate structural effects, is apparently correlated with the observed stimulation of RNA synthesis. In contrast, extensive modification of the globular regions of core histones, which is accompanied by a large structural relaxation of the particle, causes little additional effect on transcription. Acetylation of the amino-terminal domains of histones might stimulate transcription by changing the interaction of the histone tails with components of the transcriptional machinery.

  2. Nucleosome Core Particle

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Nucleosome Core Particle grown on STS-81. The fundamental structural unit of chromatin and is the basis for organization within the genome by compaction of DNA within the nucleus of the cell and by making selected regions of chromosomes available for transcription and replication. Principal Investigator's are Dr. Dan Carter and Dr. Gerard Bunick of New Century Pharmaceuticals.

  3. Vortex Cores of Inertial Particles.

    PubMed

    Günther, Tobias; Theisel, Holger

    2014-12-01

    The cores of massless, swirling particle motion are an indicator for vortex-like behavior in vector fields and to this end, a number of coreline extractors have been proposed in the literature. Though, many practical applications go beyond the study of the vector field. Instead, engineers seek to understand the behavior of inertial particles moving therein, for instance in sediment transport, helicopter brownout and pulverized coal combustion. In this paper, we present two strategies for the extraction of the corelines that inertial particles swirl around, which depend on particle density, particle diameter, fluid viscosity and gravity. The first is to deduce the local swirling behavior from the autonomous inertial motion ODE, which eventually reduces to a parallel vectors operation. For the second strategy, we use a particle density estimation to locate inertial attractors. With this, we are able to extract the cores of swirling inertial particle motion for both steady and unsteady 3D vector fields. We demonstrate our techniques in a number of benchmark data sets, and elaborate on the relation to traditional massless corelines. PMID:26356967

  4. Effective particle magnetic moment of multi-core particles

    NASA Astrophysics Data System (ADS)

    Ahrentorp, Fredrik; Astalan, Andrea; Blomgren, Jakob; Jonasson, Christian; Wetterskog, Erik; Svedlindh, Peter; Lak, Aidin; Ludwig, Frank; van IJzendoorn, Leo J.; Westphal, Fritz; Grüttner, Cordula; Gehrke, Nicole; Gustafsson, Stefan; Olsson, Eva; Johansson, Christer

    2015-04-01

    In this study we investigate the magnetic behavior of magnetic multi-core particles and the differences in the magnetic properties of multi-core and single-core nanoparticles and correlate the results with the nanostructure of the different particles as determined from transmission electron microscopy (TEM). We also investigate how the effective particle magnetic moment is coupled to the individual moments of the single-domain nanocrystals by using different measurement techniques: DC magnetometry, AC susceptometry, dynamic light scattering and TEM. We have studied two magnetic multi-core particle systems - BNF Starch from Micromod with a median particle diameter of 100 nm and FeraSpin R from nanoPET with a median particle diameter of 70 nm - and one single-core particle system - SHP25 from Ocean NanoTech with a median particle core diameter of 25 nm.

  5. Improved Thermoplastic/Iron-Particle Transformer Cores

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    A method of fabricating improved transformer cores from composites of thermoplastic matrices and iron-particles has been invented. Relative to commercially available laminated-iron-alloy transformer cores, the cores fabricated by this method weigh less and are less expensive. Relative to prior polymer-matrix/ iron-particle composite-material transformer cores, the cores fabricated by this method can be made mechanically stronger and more magnetically permeable. In addition, whereas some prior cores have exhibited significant eddy-current losses, the cores fabricated by this method exhibit very small eddy-current losses. The cores made by this method can be expected to be attractive for use in diverse applications, including high-signal-to-noise transformers, stepping motors, and high-frequency ignition coils. The present method is a product of an experimental study of the relationships among fabrication conditions, final densities of iron particles, and mechanical and electromagnetic properties of fabricated cores. Among the fabrication conditions investigated were molding pressures (83, 104, and 131 MPa), and molding temperatures (250, 300, and 350 C). Each block of core material was made by uniaxial-compression molding, at the applicable pressure/temperature combination, of a mixture of 2 weight percent of LaRC (or equivalent high-temperature soluble thermoplastic adhesive) with 98 weight percent of approximately spherical iron particles having diameters in the micron range. Each molded block was cut into square cross-section rods that were used as core specimens in mechanical and electromagnetic tests. Some of the core specimens were annealed at 900 C and cooled slowly before testing. For comparison, a low-carbon-steel core was also tested. The results of the tests showed that density, hardness, and rupture strength generally increased with molding pressure and temperature, though the correlation was rather weak. The weakness of the correlation was attributed to

  6. Analytical analysis of particle-core dynamics

    SciTech Connect

    Batygin, Yuri K

    2010-01-01

    Particle-core interaction is a well-developed model of halo formation in high-intensity beams. In this paper, we present an analytical solution for averaged, single particle dynamics, around a uniformly charged beam. The problem is analyzed through a sequence of canonical transformations of the Hamiltonian, which describes nonlinear particle oscillations. A closed form expression for maximum particle deviation from the axis is obtained. The results of this study are in good agreement with numerical simulations and with previously obtained data.

  7. Core-shell diodes for particle detectors

    NASA Astrophysics Data System (ADS)

    Jia, Guobin; Plentz, Jonathan; Höger, Ingmar; Dellith, Jan; Dellith, Andrea; Falk, Fritz

    2016-02-01

    High performance particle detectors are needed for fundamental research in high energy physics in the exploration of the Higgs boson, dark matter, anti-matter, gravitational waves and proof of the standard model, which will extend the understanding of our Universe. Future particle detectors should have ultrahigh radiation hardness, low power consumption, high spatial resolution and fast signal response. Unfortunately, some of these properties are counter-influencing for the conventional silicon drift detectors (SDDs), so that they cannot be optimized simultaneously. In this paper, the main issues of conventional SDDs have been analyzed, and a novel core-shell detector design based on micro- and nano-structures etched into Si-wafers is proposed. It is expected to simultaneously reach ultrahigh radiation hardness, low power consumption, fast signal response and high spatial resolution down to the sub-micrometer range, which will probably meet the requirements for the most powerful particle accelerators in the near future. A prototype core-shell detector was fabricated using modern silicon nanotechnology and the functionality was tested using electron-beam-induced current measurements. Such a high performance detector will open many new applications in extreme radiation environments such as high energy physics, astrophysics, high resolution (bio-) imaging and crystallography, which will push these fields beyond their current boundaries.

  8. Multiscale modelling of nucleosome core particle aggregation

    NASA Astrophysics Data System (ADS)

    Lyubartsev, Alexander P.; Korolev, Nikolay; Fan, Yanping; Nordenskiöld, Lars

    2015-02-01

    The nucleosome core particle (NCP) is the basic building block of chromatin. Under the influence of multivalent cations, isolated mononucleosomes exhibit a rich phase behaviour forming various columnar phases with characteristic NCP-NCP stacking. NCP stacking is also a regular element of chromatin structure in vivo. Understanding the mechanism of nucleosome stacking and the conditions leading to self-assembly of NCPs is still incomplete. Due to the complexity of the system and the need to describe electrostatics properly by including the explicit mobile ions, novel modelling approaches based on coarse-grained (CG) methods at the multiscale level becomes a necessity. In this work we present a multiscale CG computer simulation approach to modelling interactions and self-assembly of solutions of NCPs induced by the presence of multivalent cations. Starting from continuum simulations including explicit three-valent cobalt(III)hexammine (CoHex3+) counterions and 20 NCPs, based on a previously developed advanced CG NCP model with one bead per amino acid and five beads per two DNA base pair unit (Fan et al 2013 PLoS One 8 e54228), we use the inverse Monte Carlo method to calculate effective interaction potentials for a ‘super-CG’ NCP model consisting of seven beads for each NCP. These interaction potentials are used in large-scale simulations of up to 5000 NCPs, modelling self-assembly induced by CoHex3+. The systems of ‘super-CG’ NCPs form a single large cluster of stacked NCPs without long-range order in agreement with experimental data for NCPs precipitated by the three-valent polyamine, spermidine3+.

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

    PubMed

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

    2016-08-01

    Water-soluble chitosan-based core-shell particles that contained changeable cores were successfully applied to anchor carbon dioxide. The entrapment capacity of the particles for carbon dioxide (EC) depended on the cores. It was found that EC of the particles contained aqueous cores was higher than that of the beads with water-soluble chitosan gel cores, which was confirmed with thermogravimetric analysis. In addition, calcium ions and sodium hydroxide were introduced within the particles to examine their effect on the entrapment. EC of the particles was enhanced with sodium hydroxide when the cores were WSC gel. The incorporation of calcium ions was helpful for stabilizing carbon dioxide through the formation of calcium carbonate, which was verified with Fourier transform infrared spectra and scanning electron microscopy/energy-dispersive spectrometry. This phenomenon meant the role of calcium ions for fixating carbon dioxide was significant. PMID:27174910

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

    PubMed

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

    2014-08-01

    Abstract The applicability of porous spherical silica (PSS) was evaluated as core particles for pharmaceutical products by comparing it with commercial core particles such as mannitol (NP-108), sucrose and microcrystalline cellulose spheres. We investigated the physical properties of core particles, such as particle size distribution, flow properties, crushing strength, plastic limit, drying rate, hygroscopic property and aggregation degree. It was found that PSS was a core particle of small particle size, low friability, high water adsorption capacity, rapid drying rate and lower occurrence of particle aggregation, although wettability is a factor to be carefully considered. The aggregation and taste-masking ability using PSS and NP-108 as core particles were evaluated at a fluidized-bed coating process. The functional coating under the excess spray rate shows different aggregation trends and dissolution profiles between PSS and NP-108; thereby, exhibiting the formation of uniform coating under the excess spray rate in the case of PSS. This expands the range of the acceptable spray feed rates to coat fine particles, and indicates the possibility of decreasing the coating time. The results obtained in this study suggested that the core particle, which has a property like that of PSS, was useful in overcoming such disadvantages as large particle size, which feels gritty in oral cavity; particle aggregation; and the long coating time of the particle coating process. These results will enable the practical fine particle coating method by increasing the range of optimum coating conditions and decreasing the coating time in fluidized bed technology. PMID:23781858

  11. One-step synthesis of gold polyaniline core shell particles

    NASA Astrophysics Data System (ADS)

    Wang, Zhijuan; Yuan, Junhua; Han, Dongxue; Niu, Li; Ivaska, Ari

    2007-03-01

    A one-step method has been developed for synthesizing gold-polyaniline (Au@PANI) core-shell particles by using chlorauric acid (HAuCl4) to oxidize aniline in the presence of acetic acid and Tween 40 at room temperature. SEM images indicated that the resulting core-shell particles were composed of submicrometre-scale Au particles and PANI shells with an average thickness of 25 nm. Furthermore, a possible mechanism concerning the growth of Au@PANI particles was also proposed based on the results of control experiments.

  12. Histone hyperacetylation can induce unfolding of the nucleosome core particle.

    PubMed Central

    Oliva, R; Bazett-Jones, D P; Locklear, L; Dixon, G H

    1990-01-01

    A direct correlation exists between the level of histone H4 hyperacetylation induced by sodium butyrate and the extent to which nucleosomes lose their compact shape and become elongated (62.0% of the particles have a length/width ratio over 1.6; overall mean in the length/width ratio = 1.83 +/- 0.48) when bound to electron microscope specimen grids at low ionic strength (1mM EDTA, 10mM Tris, pH 8.0). A marked proportion of elongated core particles is also observed in the naturally occurring hyperacetylated chicken testis chromatin undergoing spermatogenesis when analyzed at low ionic strength (36.8% of the particles have a length/width ratio over 1.6). Core particles of elongated shape (length/width ratio over 1.6) generated under low ionic strength conditions are absent in the hypoacetylated chicken erythrocyte chromatin and represent only 2.3% of the untreated Hela S3 cell core particles containing a low proportion of hyperacetylated histones. The marked differences between control and hyperacetylated core particles are absent if the particles are bound to the carbon support film in the presence of 0.2 M NaCl, 6mM MgCl2 and 10mM Tris pH 8.0, conditions known to stabilize nucleosomes. A survey of the published work on histone hyperacetylation together with the present results indicate that histone hyperacetylation does not produce any marked disruption of the core particle 'per se', but that it decreases intranucleosomal stabilizing forces as judged by the lowered stability of the hyperacetylated core particle under conditions of shearing stress such as cationic competition by the carbon support film of the EM grid for DNA binding. Images PMID:2339060

  13. Spherical core-shell magnetic particles constructed by main-chain palladium N-heterocyclic carbenes

    NASA Astrophysics Data System (ADS)

    Zhao, Huaixia; Li, Liuyi; Wang, Jinyun; Wang, Ruihu

    2015-02-01

    The encapsulation of the functional species on magnetic core is a facile approach for the synthesis of core-shell magnetic materials, and surface encapsulating matrices play crucial roles in regulating their properties and applications. In this study, two core-shell palladium N-heterocyclic carbene (NHC) particles (Fe3O4@PNP1 and Fe3O4@PNP2) were prepared by a one-pot reaction of semi-rigid tripodal imidazolium salts and palladium acetate in the presence of magnetite nanoparticles. The magnetite nanoparticles are encapsulated inside the main-chain palladium, which act as cores. The conjugated effects of triphenyltriazine and triphenylbenzene in the imidazolium salts have important influence on their physical properties and catalytic performances. Fe3O4@PNP2 shows better recyclability than Fe3O4@PNP1. Unexpectedly, Pd(ii) is well maintained after six consecutive catalytic runs in Fe3O4@PNP2, and Pd(0) and Pd(ii) coexist in Fe3O4@PNP1 under the same conditions; moreover, the morphologies of these spherical core-shell particles show no significant variation after six consecutive catalytic runs.The encapsulation of the functional species on magnetic core is a facile approach for the synthesis of core-shell magnetic materials, and surface encapsulating matrices play crucial roles in regulating their properties and applications. In this study, two core-shell palladium N-heterocyclic carbene (NHC) particles (Fe3O4@PNP1 and Fe3O4@PNP2) were prepared by a one-pot reaction of semi-rigid tripodal imidazolium salts and palladium acetate in the presence of magnetite nanoparticles. The magnetite nanoparticles are encapsulated inside the main-chain palladium, which act as cores. The conjugated effects of triphenyltriazine and triphenylbenzene in the imidazolium salts have important influence on their physical properties and catalytic performances. Fe3O4@PNP2 shows better recyclability than Fe3O4@PNP1. Unexpectedly, Pd(ii) is well maintained after six consecutive catalytic runs in

  14. Modeling the Arm II core in MicroCap IV

    SciTech Connect

    Dalton, A.C.

    1996-11-01

    This paper reports on how an electrical model for the core of the Arm II machine was created and how to use this model. We wanted to get a model for the electrical characteristics of the ARM II core, in order to simulate this machine and to assist in the design of a future machine. We wanted this model to be able to simulate saturation, variable loss, and reset. Using the Hodgdon model and the circuit analysis program MicroCap IV, this was accomplished. This paper is written in such a way as to allow someone not familiar with the project to understand it.

  15. Chromatin core particle unfolding induced by tryptic cleavage of histones.

    PubMed Central

    Lilley, D M; Tatchell, K

    1977-01-01

    Chromatin 'core particles' have been digested with trypsin to varying extents. The resulting particles are homogeneous by the criterion of ultracentrifuge boundary analysis. Sedimentation coefficients are lowered as cleavages are introduced into the histones, showing that an unfolding of the core particle occurs. This unfolding is further characterised by a lower melting temperature together with a premelting phase, higher molar ellipticity in the circular dichroism spectra at 280 nm and increased kinetics of digestion by both micrococcal nuclease and DNase I. Differences are also observed in the products of nuclease digestion. The most consistent interpretation of the data involves an unfolding process whereby free rods of DNA are released to extend from a nucleoprotein core. Images PMID:896484

  16. PMMA/PMMA core-shell particles with ellipsoidal, fluorescent cores: accessing rotational dynamics.

    PubMed

    Klein, Matthias K; Klinkenberg, Nele; Schuetter, Stefan; Saenger, Nicolai; Pfleiderer, Patrick; Zumbusch, Andreas

    2015-03-10

    For several decades, nonaqueous dispersions of PMMA particles have played an important role in colloid research. They have found application as colloidal model systems, which are used to probe glassy dynamics or to explore crystal nucleation. To date, most research has focused on spherical particles, in which only translational motion can be investigated. Recently, however, there has been a surge of interest in analyzing also rotational dynamics. In this contribution, we introduce a new class of core-shell particles, which can be used as rotational probes. The colloids described herein are composed of shape anisotropic, fluorescent cores covered with nonfluorescent PMMA shells. The core-shell particles are built up in four steps. In a first step, we produce fluorescent and photo-cross-linkable PMMA colloids. In the second step, these particles are thermomechanically elongated and fixed in defined ellipsoidal shapes by photo-cross-linking. Subsequently, we cover the cross-linked, fluorescent core with a nonfluorescent PMMA shell. The shape of the resulting core-shell colloids is tunable between the initial anisotropic and perfect spherical shape. For shaping, we apply a simple solvent swelling procedure. As one option, this method yields perfect PMMA spheres with ellipsoidal, fluorescent centers. We also report morphological particle characterization using various fluorescence microscopy techniques. Finally, we demonstrate that the rotational dynamics of individual colloids can be tracked and analyzed. PMID:25654438

  17. Optimization of nanoparticle core size for magnetic particle imaging

    SciTech Connect

    Ferguson, Matthew R.; Minard, Kevin R.; Krishnan, Kannan M.

    2009-05-01

    Magnetic Particle Imaging (MPI) is a powerful new diagnostic visualization platform designed for measuring the amount and location of superparamagnetic nanoscale molecular probes (NMPs) in biological tissues. Promising initial results indicate that MPI can be extremely sensitive and fast, with good spatial resolution for imaging human patients or live animals. Here, we present modeling results that show how MPI sensitivity and spatial resolution both depend on NMP-core physical properties, and how MPI performance can be effectively optimized through rational core design. Monodisperse magnetite cores are attractive since they are readily produced with a biocompatible coating and controllable size that facilitates quantitative imaging.

  18. Optical properties of core-mantle spheroidal particles

    NASA Astrophysics Data System (ADS)

    Somsikov, Vadim V.; Farafonov, Victor G.

    1994-12-01

    The new solution of the problem of light scattering by coated spheroids was used to calculate the optical properties of prolate and oblate particles. The solution was obtained by the method of separation of variables for confocal spheroids. We consider the silicate core ice mantle particles and present the extinction cross-sections for prolate and oblate spheroids with the refractive indices mcore equals 1.7 + Oi, 1.7 + 0.1i and mmantle equals 1.3, the aspect ratio (a/b)mantle equals 2 and various volume ratios Vcore/Vtotal. The results are plotted for different size parameters xv equals 2(pi) rv/(lambda) , where rv is the radius of equivolume sphere and (lambda) is the wavelength of incident radiation. The main conclusions are: (a) if Vcore/Vtotal equals 0.5, the optical properties of a core-mantle particle are determined mainly by its core: for prolate non-absorbing spheroids when xv 10, for oblate absorbing and non-absorbing spheroids when xv particles with xv equals 1 and 2. (c) the non-linear increase of cross- sections is obtained for oblate particles with size parameters xv equals 1 - 5. (d) the small imaginary part of the core refractive index m [Im(m) < 0.01] practically does not change the optical properties of an inhomogeneous particle. When the imaginary part reaches 0.1, the noticeable changes of cross-sections may be detected.

  19. Hollow-core waveguide characterization by optically induced particle transport.

    PubMed

    Measor, Philip; Kühn, Sergei; Lunt, Evan J; Phillips, Brian S; Hawkins, Aaron R; Schmidt, Holger

    2008-04-01

    We introduce a method for optical characterization of hollow-core optical waveguides. Radiation pressure exerted by the waveguide modes on dielectric microspheres is used to analyze salient properties such as propagation loss and waveguide mode profiles. These quantities were measured for quasi-single-mode and multimode propagation in on-chip liquid-filled hollow-core antiresonant reflecting optical waveguides. Excellent agreement with analytical and numerical models is found, demonstrating that optically induced particle transport provides a simple, inexpensive, and nondestructive alternative to other characterization methods. PMID:18382513

  20. Flying particle sensors in hollow-core photonic crystal fibre

    NASA Astrophysics Data System (ADS)

    Bykov, D. S.; Schmidt, O. A.; Euser, T. G.; Russell, P. St. J.

    2015-07-01

    Optical fibre sensors make use of diverse physical effects to measure parameters such as strain, temperature and electric field. Here we introduce a new class of reconfigurable fibre sensor, based on a ‘flying-particle’ optically trapped inside a hollow-core photonic crystal fibre and illustrate its use in electric field and temperature sensing with high spatial resolution. The electric field distribution near the surface of a multi-element electrode is measured with a resolution of ∼100 μm by monitoring changes in the transmitted light signal due to the transverse displacement of a charged silica microparticle trapped within the hollow core. Doppler-based velocity measurements are used to map the gas viscosity, and thus the temperature, along a hollow-core photonic crystal fibre. The flying-particle approach represents a new paradigm in fibre sensors, potentially allowing multiple physical quantities to be mapped with high positional accuracy over kilometre-scale distances.

  1. Hollow-Core Photonic Band Gap Fibers for Particle Acceleration

    SciTech Connect

    Noble, Robert J.; Spencer, James E.; Kuhlmey, Boris T.; /Sydney U.

    2011-08-19

    Photonic band gap (PBG) dielectric fibers with hollow cores are being studied both theoretically and experimentally for use as laser driven accelerator structures. The hollow core functions as both a longitudinal waveguide for the transverse-magnetic (TM) accelerating fields and a channel for the charged particles. The dielectric surrounding the core is permeated by a periodic array of smaller holes to confine the mode, forming a photonic crystal fiber in which modes exist in frequency pass-bands, separated by band gaps. The hollow core acts as a defect which breaks the crystal symmetry, and so-called defect, or trapped modes having frequencies in the band gap will only propagate near the defect. We describe the design of 2-D hollow-core PBG fibers to support TM defect modes with high longitudinal fields and high characteristic impedance. Using as-built dimensions of industrially-made fibers, we perform a simulation analysis of the first prototype PBG fibers specifically designed to support speed-of-light TM modes.

  2. Teaching Elementary Particle Physics, Part II

    ERIC Educational Resources Information Center

    Hobson, Art

    2011-01-01

    In order to explain certain features of radioactive beta decay, Wolfgang Pauli suggested in 1930 that the nucleus emitted, in addition to a beta particle, another particle of an entirely new type. The hypothesized particle, dubbed the neutrino, would not be discovered experimentally for another 25 years. It's not easy to detect neutrinos, because…

  3. New particle searches at Tevatron (II)

    SciTech Connect

    Kamon, T.; CDF and D0 Collaborations

    1996-05-01

    Various recent results of new particle searches at the Fermilab Tevatron are presented. No evidence is found for supersymmetric particles (chargino, gluino), leptoquark bosons and heavy gauge bosons in {ital p{anti P}} collisions at {radical}s = 1.8 TeV. Excluded mass regions for each particle are determined.

  4. Therapeutic activity of modified U1 core spliceosomal particles

    PubMed Central

    Rogalska, Malgorzata Ewa; Tajnik, Mojca; Licastro, Danilo; Bussani, Erica; Camparini, Luca; Mattioli, Chiara; Pagani, Franco

    2016-01-01

    Modified U1 snRNAs bound to intronic sequences downstream of the 5′ splice site correct exon skipping caused by different types of mutations. Here we evaluate the therapeutic activity and structural requirements of these exon-specific U1 snRNA (ExSpeU1) particles. In a severe spinal muscular atrophy, mouse model, ExSpeU1, introduced by germline transgenesis, increases SMN2 exon 7 inclusion, SMN protein production and extends life span. In vitro, RNA mutant analysis and silencing experiments show that while U1A protein is dispensable, the 70K and stem loop IV elements mediate most of the splicing rescue activity through improvement of exon and intron definition. Our findings indicate that precise engineering of the U1 core spliceosomal RNA particle has therapeutic potential in pathologies associated with exon-skipping mutations. PMID:27041075

  5. Therapeutic activity of modified U1 core spliceosomal particles.

    PubMed

    Rogalska, Malgorzata Ewa; Tajnik, Mojca; Licastro, Danilo; Bussani, Erica; Camparini, Luca; Mattioli, Chiara; Pagani, Franco

    2016-01-01

    Modified U1 snRNAs bound to intronic sequences downstream of the 5' splice site correct exon skipping caused by different types of mutations. Here we evaluate the therapeutic activity and structural requirements of these exon-specific U1 snRNA (ExSpeU1) particles. In a severe spinal muscular atrophy, mouse model, ExSpeU1, introduced by germline transgenesis, increases SMN2 exon 7 inclusion, SMN protein production and extends life span. In vitro, RNA mutant analysis and silencing experiments show that while U1A protein is dispensable, the 70K and stem loop IV elements mediate most of the splicing rescue activity through improvement of exon and intron definition. Our findings indicate that precise engineering of the U1 core spliceosomal RNA particle has therapeutic potential in pathologies associated with exon-skipping mutations. PMID:27041075

  6. Core-shell composite particles composed of biodegradable polymer particles and magnetic iron oxide nanoparticles for targeted drug delivery

    NASA Astrophysics Data System (ADS)

    Oka, Chiemi; Ushimaru, Kazunori; Horiishi, Nanao; Tsuge, Takeharu; Kitamoto, Yoshitaka

    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.

  7. Teaching Elementary Particle Physics, Part II

    NASA Astrophysics Data System (ADS)

    Hobson, Art

    2011-03-01

    In order to explain certain features of radioactive beta decay, Wolfgang Pauli suggested in 1930 that the nucleus emitted, in addition to a beta particle, another particle of an entirely new type. The hypothesized particle, dubbed the neutrino, would not be discovered experimentally for another 25 years. It's not easy to detect neutrinos, because they respond to neither the EM force nor the strong force. For example, the mean free path (average penetration distance before it interacts) of a typical beta-decay neutrino moving through solid lead is about 1.5 light years! Enrico Fermi argued that neutrinos indicated a new force was at work. During the 1930s, he quickly adapted ideas from the developing new theory of QED to this new force, dubbed the weak force. Fermi's theory was able to predict the half-lives of beta-emitting nuclei and the range of energies of the emitted beta particles.

  8. OBSERVED CORE OF A GRADUAL SOLAR ENERGETIC PARTICLE EVENT

    SciTech Connect

    Kocharov, L.; Valtonen, E.; Reiner, M. J.; Thompson, B. J.; Klassen, A.

    2010-12-20

    Using space-borne particle and EUV detection and radio spectrograms from both ground-based and space-borne instruments, we study the first phase of the major solar energetic particle (SEP) event associated with the western solar flare and fast and wide coronal mass ejection (CME) on 2000 April 4. The SEP event being observed at the magnetic connection to the eruption's center starts with deka-MeV nucl{sup -1} helium- and relativistic electron-rich production from coronal sources identified with the electromagnetic diagnostics and the SEP event modeling. The broadband observations and modeling of the initial phase of the 'well-connected' major SEP event support the idea that acceleration of SEPs starts in the helium-rich plasma of the eruption's core in association with coronal shocks and magnetic reconnections caused by the CME liftoff, and that the coronal component dominates during the first hour of the SEP event considered, not yet being shielded by the CME bow shock in the solar wind. The first phase of the SEP event is followed by a second phase of SEP production associated with a decelerating CME-driven shock wave in the solar wind, which accelerates ions from a distinct, helium-poor seed particle population that may originate from the CME interaction with a coronal streamer.

  9. Experimental Breeder Reactor II (EBR-II): Instrumentation for core surveillance

    SciTech Connect

    Christensen, L.J.

    1989-01-01

    EBR-II has operated for 25 years in support of several major programs. During this time period, several of the original, non-replaceable, flow sensors, RDT sensors and thermocouples have failed in the primary system. This has led to the development of new sensors and the use of calculated values using computer models of the plant. It is important for the next generation of LMR reactors to minimize or eliminate the use of non-replaceable sensors. EBR-II is perhaps the best modeled reactor in the world, thanks to a dedicated T-H analysis program. The success of this program relied on excellent measurements of temperature and flow in subassemblies in the core. The instrumented subassemblies of the XX series provided that measurement capability. From this test series, EBR-II calculations showed that the core could withstand a loss-of-flow without scram accident and a loss-of-heat sink without scram accident from full reactor power without core damage. From this, reactor designers can now design with confidence, inherently safe reactors. 11 refs., 8 figs.

  10. Naked singularities as particle accelerators. II

    SciTech Connect

    Patil, Mandar; Joshi, Pankaj S.; Malafarina, Daniele

    2011-03-15

    We generalize here our earlier results on particle acceleration by naked singularities. We showed recently [M. Patil and P. S. Joshi, Phys. Rev. D 82, 104049 (2010).] that the naked singularities that form due to the gravitational collapse of massive stars provide a suitable environment where particles could get accelerated and collide at arbitrarily high center-of-mass energies. However, we focused there only on the spherically symmetric gravitational collapse models, which were also assumed to be self-similar. In this paper, we broaden and generalize the result to all gravitational collapse models leading to the formation of a naked singularity as the final state of collapse, evolving from a regular initial data, without making any prior restrictive assumptions about the spacetime symmetries such as above. We show that, when the particles interact and collide near the Cauchy horizon, the energy of collision in the center-of-mass frame will be arbitrarily high, thus offering a window to the Planck scale physics. We also consider the issue of various possible physical mechanisms of generation of such very high-energy particles from the vicinity of naked singularity. We then construct a model of gravitational collapse to a timelike naked singularity to demonstrate the working of these ideas, where the pressure is allowed to be negative, but the energy conditions are respected. We show that a finite amount of mass-energy density has to be necessarily radiated away from the vicinity of the naked singularity as the collapse evolves. Therefore, the nature of naked singularities, both at the classical and quantum level, could play an important role in the process of particle acceleration, explaining the occurrence of highly energetic outgoing particles in the vicinity of the Cauchy horizon that participate in extreme high-energy collisions.

  11. FINDING THE FIRST COSMIC EXPLOSIONS. II. CORE-COLLAPSE SUPERNOVAE

    SciTech Connect

    Whalen, Daniel J.; Joggerst, Candace C.; Fryer, Chris L.; Stiavelli, Massimo; Heger, Alexander; Holz, Daniel E.

    2013-05-01

    Understanding the properties of Population III (Pop III) stars is prerequisite to elucidating the nature of primeval galaxies, the chemical enrichment and reionization of the early intergalactic medium, and the origin of supermassive black holes. While the primordial initial mass function (IMF) remains unknown, recent evidence from numerical simulations and stellar archaeology suggests that some Pop III stars may have had lower masses than previously thought, 15-50 M{sub Sun} in addition to 50-500 M{sub Sun }. The detection of Pop III supernovae (SNe) by JWST, WFIRST, or the TMT could directly probe the primordial IMF for the first time. We present numerical simulations of 15-40 M{sub Sun} Pop III core-collapse SNe performed with the Los Alamos radiation hydrodynamics code RAGE. We find that they will be visible in the earliest galaxies out to z {approx} 10-15, tracing their star formation rates and in some cases revealing their positions on the sky. Since the central engines of Pop III and solar-metallicity core-collapse SNe are quite similar, future detection of any Type II SNe by next-generation NIR instruments will in general be limited to this epoch.

  12. Polystyrene-Core-Silica-Shell Hybrid Particles Containing Gold and Magnetic Nanoparticles.

    PubMed

    Tian, Jia; Vana, Philipp

    2016-02-18

    Polystyrene-core-silica-shell hybrid particles were synthesized by combining the self-assembly of nanoparticles and the polymer with a silica coating strategy. The core-shell hybrid particles are composed of gold-nanoparticle-decorated polystyrene (PS-AuNP) colloids as the core and silica particles as the shell. PS-AuNP colloids were generated by the self-assembly of the PS-grafted AuNPs. The silica coating improved the thermal stability and dispersibility of the AuNPs. By removing the "free" PS of the core, hollow particles with a hydrophobic cage having a AuNP corona and an inert silica shell were obtained. Also, Fe3O4 nanoparticles were encapsulated in the core, which resulted in magnetic core-shell hybrid particles by the same strategy. These particles have potential applications in biomolecular separation and high-temperature catalysis and as nanoreactors. PMID:26639677

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

    SciTech Connect

    Lee, Hee Uk; Song, Yoon Seok; Park, Chulhwan; Kim, Seung Wook

    2012-12-15

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

  14. Environmentally responsive core/shell particles via electrohydrodynamic co-jetting of fully miscible polymer solutions.

    PubMed

    Kazemi, Abbass; Lahann, Joerg

    2008-10-01

    Herein it is demonstrated that electrohydrodynamic co-jetting is not limited to Janus-type particles, but can also be used for the preparation of core/shell particles. Using side-by-side flow of miscible polymer solutions, electrohydrodynamic co-jetting offers an elegant and scalable route towards preparation of core/shell particles with otherwise difficult-to-prepare particle architectures, including particles with hydrophilic shell and core. Throughout this study, electrohydrodynamic co-jetting of aqueous solutions consisting of a mixture of PAAm-co-AA and PAA is used, and a range of different types of particles with distinct compartments are observed. Transition from Janus particles to core/shell particles appears to be caused by changes in the relative conductivity of the two jetting solutions. After crosslinking, the core/shell particles are stable in aqueous solution and exhibit reproducible swelling behavior while maintaining the original core/shell geometry. In addition, the pH-responsiveness of the particles is demonstrated by repeatedly switching the environmental pH between 1.3 and 12. Moreover, the core/shell particles show surprising uptake selectivity. For instance, a 450% increase in uptake of 6-carboxyfluorescein over rhodamine B base is found. PMID:18819137

  15. Search for dark particles at Belle (II)

    NASA Astrophysics Data System (ADS)

    Jaegle, Igal; Belle (II) Collaboration

    2015-04-01

    We will present a search for the dark photon, A', and the dark Higgs boson, h', in the so-called Higgs-strahlung channel, e+e- -->A'h' , with h' -->A'A' . We investigated ten exclusive final-states with A' -->e+e- , μ+μ- , or π+π- , in the mass ranges 0 . 1 GeV/c2 II.

  16. SAGE II aerosol validation - Selected altitude measurements, including particle micromeasurements

    NASA Technical Reports Server (NTRS)

    Oberbeck, Verne R.; Russell, Philip B.; Pueschel, Rudolf F.; Snetsinger, Kenneth G.; Ferry, Guy V.; Livingston, John M.; Rosen, James N.; Osborn, Mary T.; Kritz, Mark A.

    1989-01-01

    The validity of particulate extinction coefficients derived from limb path solar radiance measurements obtained during the Stratospheric Aerosol and Gas Experiment (SAGE) II is tested. The SAGE II measurements are compared with correlative aerosol measurements taken during January 1985, August 1985, and July 1986 with impactors, laser spectrometers, and filter samplers on a U-2 aircraft, an upward pointing lidar on a P-3 aircraft, and balloon-borne optical particle counters. The data for July 29, 1986 are discussed in detail. The aerosol measurements taken on this day at an altitude of 20.5 km produce particulate extinction values which validate the SAGE II values for similar wavelengths.

  17. Core shell particles consisting of cobalt ferrite and silica as model ferrofluids [CoFe 2O 4-SiO 2 core shell particles

    NASA Astrophysics Data System (ADS)

    Wagner, Joachim; Autenrieth, Tina; Hempelmann, Rolf

    2002-11-01

    Nearly monodisperse core shell particles consisting of a magnetic core of cobalt ferrite (CoFe 2O 4) and a shell of silica (SiO 2) are prepared via a modified Stöber synthesis. The core shell structure is confirmed by TEM, the size distribution of the whole particles was determined by means of photon correlation spectroscopy and small angle X-ray scattering. Due to charged surface groups of the silica shells and the magnetic moments of the cores, these particles interact both via a screened Coulomb potential and via a magnetic dipole potential. If stray ions are removed in the presence of a mixed bed ion exchanger, the electrostatic repulsion induces colloidal crystallisation. The lattice constant is influenced by the interaction with a magnetic field gradient, indicated by a blue shift of the Laue spots towards increasing field gradient.

  18. Tunable core-shell particles generated from smart water-soluble chitosan seeds.

    PubMed

    Xiao, Congming; You, Rongrui; Dong, Yanrui; Zhang, Zhongxin

    2016-05-20

    A chain-like route was presented to create various core-shell particles with soft, aqueous or inorganic cores respectively. Water-soluble chitosan (WSC) gel particles were obtained through gelating the aqueous WSC solution of 0.02g/mL at its isoelectric point. Then, polyelectrolyte complexes were formed and surrounded on the outer surfaces of WSC gel particles by immersing the particles in 2wt% aqueous sodium alginate. Soft WSC cores in these core-shell particles disappeared after maintaining the particles in 1M HCl for 6h. The cores of obtained particles at this step became aqueous, and could be further transformed into inorganic ones via contacting the particles with copper sulfate and sodium sulfide aqueous solutions successively. The composition of the shell was verified with Fourier transform infrared spectroscopy. The formation of various core-shell particles was confirmed with digital photographic observation, thermogravimetric and fluorescence analyses. The whole process was a chain-like one and was able to stop at any stage to harvest a corresponding target. PMID:26917373

  19. Particle-core study of halo dynamics in periodic-focusing channels

    SciTech Connect

    Wang, Tai-Sen F.

    2000-01-01

    This paper reports on an approach to investigate the dynamics of halo particles in mismatched charged-particle beams propagating through periodic-focusing channels using the particle-core model. The proposed method employs canonical transformations to minimize, in new phase-space variables, the flutter due to the periodic focusing to allow making stroboscopic plots. Applying this method, we find that in periodic-focusing systems, certain particles initially not in the halo region can be brought into resonance with the core oscillation to become halo particles. (c) 2000 The American Physical Society.

  20. Gold nanoparticle localization at the core surface by using thermosensitive core-shell particles as a template.

    PubMed

    Suzuki, Daisuke; Kawaguchi, Haruma

    2005-12-01

    We report novel thermosensitive hybrid core-shell particles via in situ gold nanoparticle formation using thermosensitive core-shell particles as a template. This method for the in situ synthesis of gold nanoparticles with microgel interiors offers the advantage of eliminating or significantly reducing particle aggregation. In addition, by using thermosensitive microgel structures in which the shell has thermosensitive and gel properties in water--whereas the core itself is a water-insoluble polymer--we were able to synthesize the gold nanoparticles only at the surface of the core, which had reactive sites to bind metal ions. After the gold nanoparticles were synthesized, electroless gold plating was carried out to control the thickness of the gold nanoshells. The dispersions of the obtained hybrid particles were characterized by dynamic light scattering and UV-vis absorption spectroscopy, and the dried particles were also observed by electron microscopy. Adaptation of the technique shown here will create a number of applications as optical, electronic, and biomedical functional materials. PMID:16316147

  1. Effective medium theory expressions for the effective diffusion in chromatographic beds filled with porous, non-porous and porous-shell particles and cylinders. Part II: Numerical verification and quantitative effect of solid core on expected B-term band broadening.

    PubMed

    Deridder, Sander; Desmet, Gert

    2011-01-01

    The results of a numerical simulation study of the diffusion and retention in fully porous spheres and cylinders are compared with some of the high order accuracy analytical solutions for the effective diffusion coefficient that have been derived from the effective medium theory (EMT) theory in part I of the present study. A variety of different ordered (spheres and cylinders) and disordered (cylinders) packings arrangements has been considered. The agreement between simulations and theory was always excellent, lying within the (very tight) accuracy limits of the simulations over the full range of retention factor and diffusion constant values that is practically relevant for most LC applications. Subsequently filling up the spheres and cylinders with a central solid core, while keeping the same packing geometry and the same mobile phase (same thermodynamic retention equilibrium), it was found that the core induces an additional obstruction which reduces the effective intra-particle diffusion coefficient exactly with a factor γ(part)=2/(2+ρ³) for spherical particles and γ(part)=1/(1+ρ²) for cylinders (ρ is the ratio of the core to the particle diameter, ρ=d(core)/d(part)). These expressions hold independently of the packing geometry, the value of the diffusion coefficients and the equilibrium constant or the size of the core. The expressions also imply that, if considering equal mobile phase conditions, the presence of the solid core will never reduce the particle contribution to the B-term band broadening with more than 33% (50% in case of cylindrical pillars). PMID:21122871

  2. Importin β Can Bind Hepatitis B Virus Core Protein and Empty Core-Like Particles and Induce Structural Changes.

    PubMed

    Chen, Chao; Wang, Joseph Che-Yen; Pierson, Elizabeth E; Keifer, David Z; Delaleau, Mildred; Gallucci, Lara; Cazenave, Christian; Kann, Michael; Jarrold, Martin F; Zlotnick, Adam

    2016-08-01

    Hepatitis B virus (HBV) capsids are found in many forms: immature single-stranded RNA-filled cores, single-stranded DNA-filled replication intermediates, mature cores with relaxed circular double-stranded DNA, and empty capsids. A capsid, the protein shell of the core, is a complex of 240 copies of core protein. Mature cores are transported to the nucleus by a complex that includes both importin α and importin β (Impα and Impβ), which bind to the core protein's C-terminal domains (CTDs). Here we have investigated the interactions of HBV core protein with importins in vitro. Strikingly, empty capsids and free core protein can bind Impβ without Impα. Cryo-EM image reconstructions show that the CTDs, which are located inside the capsid, can extrude through the capsid to be bound by Impβ. Impβ density localized on the capsid exterior near the quasi-sixfold vertices, suggested a maximum of 30 Impβ per capsid. However, examination of complexes using single molecule charge-detection mass spectrometry indicate that some complexes include over 90 Impβ molecules. Cryo-EM of capsids incubated with excess Impβ shows a population of damaged particles and a population of "dark" particles with internal density, suggesting that Impβ is effectively swallowed by the capsids, which implies that the capsids transiently open and close and can be destabilized by Impβ. Though the in vitro complexes with great excess of Impβ are not biological, these results have implications for trafficking of empty capsids and free core protein; activities that affect the basis of chronic HBV infection. PMID:27518410

  3. Importin β Can Bind Hepatitis B Virus Core Protein and Empty Core-Like Particles and Induce Structural Changes

    PubMed Central

    Pierson, Elizabeth E.; Keifer, David Z.; Delaleau, Mildred; Gallucci, Lara; Cazenave, Christian; Kann, Michael; Jarrold, Martin F.; Zlotnick, Adam

    2016-01-01

    Hepatitis B virus (HBV) capsids are found in many forms: immature single-stranded RNA-filled cores, single-stranded DNA-filled replication intermediates, mature cores with relaxed circular double-stranded DNA, and empty capsids. A capsid, the protein shell of the core, is a complex of 240 copies of core protein. Mature cores are transported to the nucleus by a complex that includes both importin α and importin β (Impα and Impβ), which bind to the core protein’s C-terminal domains (CTDs). Here we have investigated the interactions of HBV core protein with importins in vitro. Strikingly, empty capsids and free core protein can bind Impβ without Impα. Cryo-EM image reconstructions show that the CTDs, which are located inside the capsid, can extrude through the capsid to be bound by Impβ. Impβ density localized on the capsid exterior near the quasi-sixfold vertices, suggested a maximum of 30 Impβ per capsid. However, examination of complexes using single molecule charge-detection mass spectrometry indicate that some complexes include over 90 Impβ molecules. Cryo-EM of capsids incubated with excess Impβ shows a population of damaged particles and a population of “dark” particles with internal density, suggesting that Impβ is effectively swallowed by the capsids, which implies that the capsids transiently open and close and can be destabilized by Impβ. Though the in vitro complexes with great excess of Impβ are not biological, these results have implications for trafficking of empty capsids and free core protein; activities that affect the basis of chronic HBV infection. PMID:27518410

  4. A Core-Particle Model for Periodically Focused Ion Beams with Intense Space-Charge

    SciTech Connect

    Lund, S M; Barnard, J J; Bukh, B; Chawla, S R; Chilton, S H

    2006-08-02

    A core-particle model is derived to analyze transverse orbits of test particles evolving in the presence of a core ion beam described by the KV distribution. The core beam has uniform density within an elliptical cross-section and can be applied to model both quadrupole and solenoidal focused beams in periodic or aperiodic lattices. Efficient analytical descriptions of electrostatic space-charge fields external to the beam core are derived to simplify model equations. Image charge effects are analyzed for an elliptical beam centered in a round, conducting pipe to estimate model corrections resulting from image charge nonlinearities. Transformations are employed to remove coherent utter motion associated with oscillations of the ion beam core due to rapidly varying, linear applied focusing forces. Diagnostics for particle trajectories, Poincare phase-space projections, and single-particle emittances based on these transformations better illustrate the effects of nonlinear forces acting on particles evolving outside the core. A numerical code has been written based on this model. Example applications illustrate model characteristics. The core-particle model described has recently been applied to identify physical processes leading to space-charge transport limits for an rms matched beam in a periodic quadrupole focusing channel [Lund and Chawla, Nuc. Instr. and Meth. A 561, 203 (2006)]. Further characteristics of these processes are presented here.

  5. ESC-EEC-EPC code system for plasma core and edge equilibrium and particle orbits

    NASA Astrophysics Data System (ADS)

    Li, Xujing

    2013-10-01

    A new Edge Equilibrium Code (EEC), which is a new solver of the Grad-Shafranov equation complementing the existing ESC code (based on Fourier representation) is presented. EEC, being developed specifically for the near edge region with an arbitrary shape of the plasma boundary, uses adaptive flux coordinates with Hermite finite element representation. A special routine for fast solving the sparse matrix equations was created for EEC. The edge solution of EEC is matched with the core solution from ESC through a virtual boundary and the two codes communicate as two parallel processes. This approach addresses the future needs in enhancing functionality of EEC without conflicting with the interface of both codes. The code was complemented by Edge Particle Code (EPC) for massive calculation of collisional particle orbits using GPU. The resulting ESC-EEC-EPC code system acquired unmatched ability (a) in fast free and fixed boundary equilibrium calculations for arbitrary plasma shapes, (b) in using both r - z and different flux coordinates, (c) in choosing different combinations of input profiles, (d) in performing equilibrium reconstruction together with variances analysis, and (e) in assessing the diagnostics used for equilibrium reconstruction. Chinese National Magnetic Confinement Fusion Science Program 2011GB105003, US DOE SBIR grant # 94307S10-II.

  6. Amino-functionalized core-shell magnetic mesoporous composite microspheres for Pb(II) and Cd(II) removal.

    PubMed

    Tang, Yulin; Liang, Song; Wang, Juntao; Yu, Shuili; Wang, Yilong

    2013-04-01

    Amino-functionalized Fe3O4@mesoporous SiO2 core-shell composite microspheres NH2-MS in created in multiple synthesis steps have been investigated for Pb(II) and Cd(II) adsorption. The microspheres were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), N2 adsorption-desorption, zeta potential measurements and vibrating sample magnetometer. Batch adsorption tests indicated that NH2-MS exhibited higher adsorption affinity toward Pb(II) and Cd(II) than MS did. The Langmuir model could fit the adsorption isotherm very well with maximum adsorption capacity of 128.21 and 51.81 mg/g for Pb(II) and Cd(II), respectively, implying that adsorption processes involved monolayer adsorption. Pb(II) and Cd(II) adsorption could be well described by the pseudo second-order kinetics model, and was found to be strongly dependent on pH and humic acid. The Pb(II)- and Cd(II)-loaded microspheres were effectively desorbed using 0.01 mol/L HCl or EDTA solution. NH2-MS have promise for use as adsorbents in the removal of Pb(II) and Cd(II) in wastewater treatment processes. PMID:23923794

  7. A core-particle model for periodically focused ion beams withintense space-charge

    SciTech Connect

    Lund, Steven M.; Barnard, John J.; Bukh, Boris; Chawla, SurgreevR.; Chilton, Sven H.

    2006-08-28

    A core-particle model is derived to analyze transverse orbits of test particles evolving in the presence of a core ion beam that has uniform density within an elliptical cross-section. The model can be applied to both quadrupole and solenoidal focused beams in periodic or aperiodic lattices. Efficient analytical descriptions of electrostatic space-charge fields external to the beam core are derived to simplify model equations. Image charge effects are analyzed for an elliptical beam centered in a round, conducting pipe to estimate model corrections resulting from image charge nonlinearities. Transformations are employed to remove coherent flutter motion associated with oscillations of the ion beam core due to rapidly varying, linear applied focusing forces. Diagnostics for particle trajectories, Poincare phase-space projections, and single-particle emittances based on these transformations better illustrate the effects of nonlinear forces acting on particles evolving outside the core. A numerical code has been written based on this model. Example applications illustrate model characteristics. The core-particle model described has recently been applied to identify physical processes leading to space-charge transport limits for an rms matched beam in a periodic quadrupole focusing channel. Further characteristics of these processes are presented here.

  8. Kansas Vocational Agriculture Education. Basic Core Curriculum Project, Horticulture II.

    ERIC Educational Resources Information Center

    Albracht, James, Ed.

    This second horticulture guide is one of a set of three designated as the basic core of instruction for horticulture programs in Kansas. Units of instruction are presented in eight sections: (1) Leadership, (2) Supervised Occupational Experience, (3) Plant Propagation, (4) Soil and Plant Growth Media, (5) Fertilizers, (6) Greenhouse, (7) Plant…

  9. Theory of longitudinal beam halo in RF linacs: I. core/test-particle formulation

    SciTech Connect

    Barnard, J.J.; Lund, S.M.

    1997-05-01

    For intense beams, the analysis of tenuous halo components of the particle distribution that surround the main core of the distribution can be challenging. So-called core/test particle models in which a test particle is evolved in the applied and space-charge forces of the beam core have been instrumental in understanding the structure and extent of transverse beam halo produced by resonant particle interactions with the oscillating space-charge forces of a mismatched beam core. Here we present a core/test particle model developed for the analysis of longitudinal beam halo in intense, ion-beam rf linacs. Equations of motion are derived for a test particle moving interior to, and exterior to, a uniform density ellipsoidal beam bunch. Coupled transverse-longitudinal mismatch modes of the ellipsoidal beam envelope are analyzed. Typical parameters suggest the possibility of a low-order resonant interaction between longitudinal particle oscillations and a low-frequency envelope mode. Properties of this resonance are in an accompanying paper by the authors in these proceedings.

  10. Neutronic and thermal-hydraulic analysis of new irradiation channels inside the Moroccan TRIGA Mark II research reactor core.

    PubMed

    Chham, E; El Bardouni, T; Benaalilou, K; Boukhal, H; El Bakkari, B; Boulaich, Y; El Younoussi, C; Nacir, B

    2016-10-01

    This study was conducted to improve the capacity of radioisotope production in the Moroccan TRIGA Mark II research reactor, which is considered as one of the most important applications of research reactors. The aim of this study is to enhance the utilization of TRIGA core in the field of neutron activation and ensure an economic use of the fuel. The main idea was to create an additional irradiation channel (IC) inside the core. For this purpose, three new core configurations are proposed, which differ according to the IC position in the core. Thermal neutron flux distribution and other neutronic safety parameters such as power peaking factors, excess reactivity, and control rods worth reactivity were calculated using the Monte Carlo N-Particle Transport (MCNP) code and neutron cross-section library based on ENDF/B-VII evaluation. The calculated thermal flux in the central thimble (CT) and in the added IC for the reconfigured core is compared with the thermal flux in the CT of the existing core, which is taken as a reference. The results show that all the obtained fluxes in CTs are very close to the reference value, while a remarkable difference is observed between the fluxes in the new ICs and reference. This difference depends on the position of IC in the reactor core. To demonstrate that the Moroccan TRIGA reactor could safely operate at 2MW, with new configurations based on new ICs, different safety-related thermal-hydraulic parameters were investigated. The PARET model was used in this study to verify whether the safety margins are met despite the new modifications of the core. The results show that it is possible to introduce new ICs safely in the reactor core, because the obtained values of the parameters are largely far from compromising the safety of the reactor. PMID:27552124

  11. TOP counter for particle identification at the Belle II experiment

    NASA Astrophysics Data System (ADS)

    Inami, Kenji

    2014-12-01

    Ring imaging Cherenkov counter, named TOP counter, utilizing precise photon detection timing has been developed as a particle identification detector for the Belle II experiment. The real size prototype has been produced and tested with 2 GeV positrons at Spring-8 LEPS beam line. The quartz radiator production and assembling with microchannel plate photomultipliers was successfully carried out. The beam test data shows good agreement with full Monte-Carlo simulation results in the ring image and the distribution of number of detected photons and timing information.

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

    PubMed

    Colin, Jérôme

    2012-03-01

    The morphological evolution by surface diffusion of a core-shell spherical particle has been investigated theoretically under hydrostatic pressure when the shear modulii of the core and shell are different. A linear stability analysis has demonstrated that depending on the pressure, shear modulii, and radii of both phases, the free surface of the composite particle may be unstable with respect to a shape perturbation. A stability diagram finally emphasizes that the roughness development is favored in the case of a hard shell with a soft core. PMID:22587137

  13. A Probabilistic Foundation of Elementary Particle Statistics. Part II.

    NASA Astrophysics Data System (ADS)

    Costantini, Domenico; Garibaldi, Ubaldo

    The long history of ergodic and quasi-ergodic hypotheses provides the best example of the attempt to supply non-probabilistic justifications for the use of statistical mechanics in describing mechanical systems. In this paper we reverse the terms of the problem. We aim to show that accepting a probabilistic foundation of elementary particle statistics dispenses with the need to resort to ambiguous non-probabilistic notions like that of (in)distinguishability. In the quantum case, starting from suitable probability conditions, it is possible to deduce elementary particle statistics in a unified way. Following our approach Maxwell-Boltzmann statistics can also be deduced, and this deduction clarifies its status. Thus our primary aim in this paper is to give a mathematically rigorous deduction of the probability of a state with given energy for a perfect gas in statistical equilibrium; that is, a deduction of the equilibrium distributions for a perfect gas. A crucial step in this deduction is the statement of a unified statistical theory based on clearly formulated probability conditions from which the particle statistics follows. We believe that such a deduction represents an important improvement in elementary particle statistics, and a step towards a probabilistic foundation of statistical mechanics. The present Part II is devoted to this deduction. Part I presented the necessary tools. After the deduction of the probability of a state with given energy for a system in statistical equilibrium, we will propose in the last section a simple model giving an ergodic interpretation of the equilibrium distributions.

  14. Self-Assembly of Nucleocapsid-Like Particles from Recombinant Hepatitis C Virus Core Protein

    PubMed Central

    Kunkel, Meghan; Lorinczi, Marta; Rijnbrand, René; Lemon, Stanley M.; Watowich, Stanley J.

    2001-01-01

    Little is known about the assembly pathway and structure of hepatitis C virus (HCV) since insufficient quantities of purified virus are available for detailed biophysical and structural studies. Here, we show that bacterially expressed HCV core proteins can efficiently self-assemble in vitro into nucleocapsid-like particles. These particles have a regular, spherical morphology with a modal distribution of diameters of approximately 60 nm. Self-assembly of nucleocapsid-like particles requires structured RNA molecules. The 124 N-terminal residues of the core protein are sufficient for self-assembly into nucleocapsid-like particles. Inclusion of the carboxy-terminal domain of the core protein modifies the core assembly pathway such that the resultant particles have an irregular outline. However, these particles are similar in size and shape to those assembled from the 124 N-terminal residues of the core protein. These results provide novel opportunities to delineate protein-protein and protein-RNA interactions critical for HCV assembly, to study the molecular details of HCV assembly, and for performing high-throughput screening of assembly inhibitors. PMID:11160716

  15. Hydrothermal synthesis of high-quality type-II CdTe/CdSe core/shell quantum dots with dark red emission.

    PubMed

    Liu, Ning; Yang, Ping

    2014-08-01

    A hydrothermal method was used to synthesize type-II CdTe/CdSe core/shell quantum dots (QDs) using the thilglycolic acid (TGA) capped CdTe QDs as cores, which show a number of advantages. Because of the spatial separation of carriers the low excited states of CdTe/CdSe QDs, they exhibit many novel properties that are fundamentally different from the type-I QDs. On the other hand, our experiment results show that the wave function of the hole of the exciton in the CdTe core extends well into the CdSe shell. The results also reveal that a thick shell can confine the electrons inside the particles and thereby improve the PL efficiency and prolong the lifetime of the core/shell QDs. We use the UV-vis absorption and fluorescence spectrum measurements on growing particles in detail. We found that the fluorescence of the CdTe/CdSe QDs was strongly dependent on the thick of the shell and size of the core as well as the unique type-II heterostructure, which make the type-II core/shell QDs more suitable in photovoltaic or photoconduction applications. PMID:25936008

  16. Enhanced Electrorheological Properties of Elastomers Containing TiO₂/Urea Core-Shell Particles.

    PubMed

    Niu, Chenguang; Dong, Xufeng; Qi, Min

    2015-11-11

    Polar molecule-coated core-shell particles have been used to prepare electrorheological (ER) fluids with high performance. Inspired by those studies, TiO2/urea core-shell structured particles were fabricated and used to prepare novel ER elastomers, whose properties were compared with the ER elastomers with bare TiO2 particles. Particles characterization results illustrate the TiO2/urea particles present little change in size, morphology and crystal structure with respect to the bare amorphous TiO2 particles, while clear core-shell structure is observed. Compared with the bare TiO2 particles filled elastomer, the TiO2/urea particles filled elastomer presents higher dielectric constant, indicating enhanced polarization. The viscoelastic properties of the two elastomers under different strain amplitude, frequency and electric field were tested. The results indicate that the TiO2/urea particles filled elastomer shows higher storage modulus G' and higher relative ER effect within the low field strength region from 0 to 2 kV/mm. Coating polar molecules is an effective method to improve the ER performance for ER elastomers. PMID:26492099

  17. Synthesis and Characterization of Polyvinylpyrrolidone Silica Core-Shell Nanocomposite Particles.

    PubMed

    Chen, Lian-Xi; Li, Jie; Li, Xi; Zhang, Zhong-Min; Jiao, Cai-Bin

    2015-03-01

    In this work, a novel and facile strategy for making a new type of polymer/silica nanocomposte particle was proposed. Colloidally stable polyvinypyrrolidone (PVP)/silica core-shell nanocomposite particles have been successfully synthesized using an azo initiator via seed polymerization of N-vinyl-2-pyrrolidone (NVP) and VFSs (VFSs) that were derived from vinyl triethoxysilane (VTES). It was suggested from the FTIR and TGA analysis that the copolymerization reaction of NVP with VFSs has been thoroughly carried out. In addition, SEM images showed that PVP/silica nanocomposite particles have relatively rough surface due to surface polymerization in comparison with VFSs. Furthermore, TEM results proved that the size of VFSs had considerable effects on the appearance of PVP/silica nanocomposite particles. Generally, it presented that several silica nanoparticle cores with an average size of 78 nm mainly pack together within each nanocomposite particle after seed polymerization. Interestingly, the average shell thickness was 59 nm for most PVP/silica nanocomposite particles with cores about 242 nm. However, when the core size was large enough to about 504 nm, a series of PVP/silica nanocomposite particles with a relative thin shell were observed. PMID:26413650

  18. Particle Simulations of DARHT-II Transport System

    SciTech Connect

    Poole, B; Chen, Y J

    2001-06-11

    The DARHT-II beam line utilizes a fast stripline kicker to temporally chop a high current electron beam from a single induction LINAC and deliver multiple temporal electron beam pulses to an x-ray converter target. High beam quality needs to be maintained throughout the transport line from the end of the accelerator through the final focus lens to the x-ray converter target to produce a high quality radiographic image. Issues that will affect beam quality such as spot size and emittance at the converter target include dynamic effects associated with the stripline kicker as well as emittance growth due to the nonlinear forces associated with the kicker and various focusing elements in the transport line. In addition, dynamic effects associated with transverse resistive wall instability as well as gas focusing will affect the beam transport. A particle-in-cell code is utilized to evaluate beam transport in the downstream transport line in DARHT-II. External focusing forces are included utilizing either analytic expressions or field maps. Models for wakefields from the beam kicker, transverse resistive wall instability, and gas focusing are included in the simulation to provide a more complete picture of beam transport in DARHT-II. From these simulations, for various initial beam loads based on expected accelerator performance the temporally integrated target spot size and emittance can be estimated.

  19. Evaluation of storing Shippingport Core II spent blanket fuel assemblies in the T Plant PWR Core II fuel pool without active cooling

    SciTech Connect

    Gilbert, E.R.; Lanning, D.D.; Dana, C.M.; Hedengren, D.C.

    1994-10-01

    PWR Core II fuel pool chiller-off test was conducted because it appeared possible that acceptable pool-water temperatures could be maintained without operating the chillers, thus saving hundreds of thousands of dollars in maintenance and replacement costs. Test results showed that the water-cooling capability is no longer needed to maintain pool temperature below 38{degrees}C (100{degrees}F).

  20. A core-particle model for periodically focused ion beams with intense space-charge

    NASA Astrophysics Data System (ADS)

    Lund, Steven M.; Barnard, John J.; Bukh, Boris; Chawla, Sugreev R.; Chilton, Sven H.

    2007-07-01

    A core-particle (CP) model is derived to analyze transverse orbits of test-particles evolving in the presence of a core ion beam that has uniform density within an elliptical cross-section. The model can be applied to both quadrupole and solenoidal focused beams in periodic or aperiodic lattices. Efficient analytical descriptions of electrostatic space-charge fields external to the beam core are derived to simplify model equations. Image-charge effects are analyzed for an elliptical beam centered in a round, conducting pipe to estimate model corrections resulting from image-charge nonlinearities. Transformations are employed in diagnostics to remove coherent flutter motion associated with oscillations of the ion beam core due to rapidly varying, linear applied-focusing forces. Diagnostics for particle trajectories, Poincaré phase-space projections, and single-particle emittances based on these transformations better illustrate the effects of nonlinear forces acting on particles evolving outside the core. A numerical code has been written based on this model. Example applications illustrate model characteristics. The CP model described has recently been applied to identify physical processes leading to space-charge transport limits for an rms-envelope matched beam in a periodic quadrupole focusing-channel [S.M. Lund, S.R. Chawla, Nucl. Instr. and Meth. A 561 (2006) 203]. Further characteristics of these processes are presented here.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  3. [Scattering properties of core-shell structure of mist wrapped dust particles].

    PubMed

    Feng, Shi-qi; Song, Wei; Wang, Yan; Miao, Xin-hui; Xu, Li-jun; Liu, Yu; Li, Cheng; Li Wen-long; Wang, Yi-ran; Cai, Hong-xing

    2014-12-01

    The authors have investigated the optical properties of core-shell structure of mist wrapped dust particles based on the method of discrete dipole approximation (DDA). The influence on the thickness of the elliptical core-shell structure were calculated which the ratio of long axis and short axis is 2:1, and the change of scattering angle for scattering characteristics. The results shows that the thickness of outer layer increase from 1.2 to 4.8 μm with the scattering and extinction coefficient of double core-shell layers particles decrease from 3.4 and 3.43 to 2.543 and 2.545, when the size of inner core isn't change. And scattering relative strength also increased obviously. The thickness of inner core increase from 0.6 to 2.4 μm with the of scattering and extinction coefficient change from 2.59 and 2.88 to 2.6 and 2.76 when thickness of outer remain constant. Effect of the thickness of visible outer layer on the scattering characteristics of double core-shell layers particles is greater, because of the interaction between scattering light and outer materials. The scattering relative intensity decrease with wavelength increased, while increased with the scale of core-shell structure increase. The results make a promotion on the study of the transportation characteristics of laser and scattering characteristics when the atmospheric aerosol and water mist interact together. PMID:25881412

  4. Importance of core electrostatic properties on the electrophoresis of a soft particle.

    PubMed

    De, Simanta; Bhattacharyya, Somnath; Gopmandal, Partha P

    2016-08-01

    The impact of the volumetric charged density of the dielectric rigid core on the electrophoresis of a soft particle is analyzed numerically. The volume charge density of the inner core of a soft particle can arise for a dendrimer structure or bacteriophage MS2. We consider the electrokinetic model based on the conservation principles, thus no conditions for Debye length or applied electric field is imposed. The fluid flow equations are coupled with the ion transport equations and the equation for the electric field. The occurrence of the induced nonuniform surface charge density on the outer surface of the inner core leads to a situation different from the existing analysis of a soft particle electrophoresis. The impact of this induced surface charge density together with the double-layer polarization and relaxation due to ion convection and electromigration is analyzed. The dielectric permittivity and the charge density of the core have a significant impact on the particle electrophoresis when the Debye length is in the order of the particle size. We find that by varying the ionic concentration of the electrolyte, the particle can exhibit reversal in its electrophoretic velocity. The role of the polymer layer softness parameter is addressed in the present analysis. PMID:27627364

  5. Fast isolation of highly active photosystem II core complexes from spinach.

    PubMed

    Wang, Zhao-Gai; Xu, Tian-Hua; Liu, Cheng; Yang, Chun-Hong

    2010-09-01

    Purification of photosystem II (PSII) core complexes is a time-consuming and low-efficiency process. In order to isolate pure and active PSII core complexes in large amounts, we have developed a fast method to isolate highly active monomeric and dimeric PSII core complexes from spinach leaves by using sucrose gradient ultracentrifugation. By using a vertical rotor the process was completed significantly faster compared with a swing-out rotor. In order to keep the core complexes in high activity, the whole isolation procedure was performed in the presence of glycine betain and pH at 6.3. The isolated pigment-protein complexes were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, absorption spectroscopy, 77 K fluorescence spectroscopy and high performance liquid chromatography. Our results show that this method is a better choice for quick and efficient isolation of functionally active PSII core complexes. PMID:20738723

  6. Interfacial strain effect on type-I and type-II core/shell quantum dots

    NASA Astrophysics Data System (ADS)

    Gheshlaghi, Negar; Pisheh, Hadi Sedaghat; Karim, M. Rezaul; Malkoc, Derya; Ünlü, Hilmi

    2016-09-01

    A comparative experimental and theoretical study on the calculation of capped core diameter in ZnSe/ZnS, CdSe/Cd(Zn)S type-I and ZnSe/CdS type-II core/shell nanocrystals is presented. The lattice mismatch induced interface strain between core and shell was calculated from continuum elastic theory and applied in effective mass approximation method to obtain the corresponding capped core diameter. The calculated results were compared with diameter of bare cores (CdSe and ZnSe) from transmission electron microscopy images to obtain the amount of the stretched or squeezed core after deposition of tensile or compressive shells. The result of the study showed that the core is squeezed in ZnSe/ZnS and CdSe/Cd(Zn)S after compressive shell and stretched in ZnSe/CdS after tensile shell deposition. The stretched and squeezed amount of the capped core found to be in proportion with lattice mismatch amount in the core/shell structure.

  7. Optofluidic immobility of particles trapped in liquid-filled hollow-core photonic crystal fiber.

    PubMed

    Garbos, M K; Euser, T G; Russell, P St J

    2011-09-26

    We study the conditions under which a particle, laser-guided in a vertically-oriented hollow-core photonic crystal fiber filled with liquid, can be kept stationary against a microfluidic counter-flow. An immobility parameter-the fluid flow rate required to immobilize a particle against the radiation force produced by unit guided optical power-is introduced to quantify the conditions under which this occurs, including radiation, viscous and gravity forces. Measurements show that this parameter depends strongly on the ratio of particle radius a to core radius R, peaking at an intermediate value of a/R. The results follow fairly well the theoretical estimates of the optical (calculated approximately using a ray optics approach) and numerically simulated drag forces. We suggest that the system has potential applications in, e.g., measurement of the diameter, refractive index and density of particles, synthesis and biomedical research. PMID:21996905

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

    DOE PAGESBeta

    Jiang, Xingmao; Jiang, Ying-Bing; Liu, Nanguo; Xu, Huifang; Rathod, Shailendra; Shah, Pratik; Brinker, C. Jeffrey

    2011-01-01

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

  9. Chemical compositions of black carbon particle cores and coatings via soot particle aerosol mass spectrometry with photoionization and electron ionization.

    PubMed

    Canagaratna, Manjula R; Massoli, Paola; Browne, Eleanor C; Franklin, Jonathan P; Wilson, Kevin R; Onasch, Timothy B; Kirchstetter, Thomas W; Fortner, Edward C; Kolb, Charles E; Jayne, John T; Kroll, Jesse H; Worsnop, Douglas R

    2015-05-14

    Black carbon is an important constituent of atmospheric aerosol particle matter (PM) with significant effects on the global radiation budget and on human health. The soot particle aerosol mass spectrometer (SP-AMS) has been developed and deployed for real-time ambient measurements of refractory carbon particles. In the SP-AMS, black carbon or metallic particles are vaporized through absorption of 1064 nm light from a CW Nd:YAG laser. This scheme allows for continuous "soft" vaporization of both core and coating materials. The main focus of this work is to characterize the extent to which this vaporization scheme provides enhanced chemical composition information about aerosol particles. This information is difficult to extract from standard SP-AMS mass spectra because they are complicated by extensive fragmentation from the harsh 70 eV EI ionization scheme that is typically used in these instruments. Thus, in this work synchotron-generated vacuum ultraviolet (VUV) light in the 8-14 eV range is used to measure VUV-SP-AMS spectra with minimal fragmentation. VUV-SP-AMS spectra of commercially available carbon black, fullerene black, and laboratory generated flame soots were obtained. Small carbon cluster cations (C(+)-C5(+)) were found to dominate the VUV-SP-AMS spectra of all the samples, indicating that the corresponding neutral clusters are key products of the SP vaporization process. Intercomparisons of carbon cluster ratios observed in VUV-SP-AMS and SP-AMS spectra are used to confirm spectral features that could be used to distinguish between different types of refractory carbon particles. VUV-SP-AMS spectra of oxidized organic species adsorbed on absorbing cores are also examined and found to display less thermally induced decomposition and fragmentation than spectra obtained with thermal vaporization at 200 °C (the minimum temperature needed to quantitatively vaporize ambient oxidized organic aerosol with a continuously heated surface). The particle cores

  10. Determining the size distribution of core-shell spheres and other complex particles by laser diffraction.

    PubMed

    Lagasse, R R; Richards, D Wayne

    2003-11-01

    The goal of this work is to determine the size distribution of hollow glass spheres by laser diffraction, an experiment which involves measuring angle-dependent scattering of light from particles dispersed in a liquid. The proprietary software supplied with commercial instruments is not strictly applicable to our two-layer, glass-shell, hollow-core spheres because it requires that the particles have spatially homogeneous properties. We therefore developed Fortran code to compute the scattering from core-shell spherical particles. The results show that the scattering from representative hollow glass particles diverges from homogeneous sphere scattering when the radius decreases from 10 to 3 microm. Additionally, scattering measurements on two core-shell hollow glass powders were analyzed using the exact core-shell optical model and homogeneous sphere approximations. In both cases, the size distribution determined using the exact core-shell model differs from that determined using the homogeneous-sphere approximation when the distribution covers radii smaller than about 10 microm, as expected. The size distribution based on the exact core-shell optical model was determined using a new algorithm. Although the basic equations used in the algorithm have been published previously, they are developed here in a different form, which can be implemented using Fortran and MatLab routines available commercially and in the public domain. This algorithm could be used to determine the size distribution of other kinds of particles, such as cylindrical rods, as long as their angle-dependent scattering could be computed. PMID:14554168

  11. Career Ladders and Core Curriculum in Human Services. Phase II Final Report.

    ERIC Educational Resources Information Center

    Soong, Robert K.

    This portion of Phase II of the Social Service Aide Project, a program of exemplary education for the career development of paraprofessionals in social and/or human services, represented an attempt to broaden the career ladders developed during Phase I and to extend the core curriculum above and below the Associate in Arts degree. The scheme of…

  12. Electron Cryotomography Studies of Maturing HIV-1 Particles Reveal the Assembly Pathway of the Viral Core

    PubMed Central

    Woodward, Cora L.; Cheng, Sarah N.

    2014-01-01

    ABSTRACT To better characterize the assembly of the HIV-1 core, we have used electron cryotomography (ECT) to image infected cells and the viral particles cryopreserved next to them. We observed progressive stages of virus assembly and egress, including flower-like flat Gag lattice assemblies, hemispherical budding profiles, and virus buds linked to the plasma membrane via a thin membrane neck. The population of budded viral particles contains immature, maturation-intermediate, and mature core morphologies. Structural characteristics of the maturation intermediates suggest that the core assembly pathway involves the formation of a CA sheet that associates with the condensed ribonucleoprotein (RNP) complex. Our analysis also reveals a correlation between RNP localization within the viral particle and the formation of conical cores, suggesting that the RNP helps drive conical core assembly. Our findings support an assembly pathway for the HIV-1 core that begins with a small CA sheet that associates with the RNP to form the core base, followed by polymerization of the CA sheet along one side of the conical core toward the tip, and then closure around the body of the cone. IMPORTANCE During HIV-1 assembly and release, the Gag polyprotein is organized into a signature hexagonal lattice, termed the immature lattice. To become infectious, the newly budded virus must disassemble the immature lattice by proteolyzing Gag and then reassemble the key proteolytic product, the structural protein p24 (CA), into a distinct, mature hexagonal lattice during a process termed maturation. The mature HIV-1 virus contains a conical capsid that encloses the condensed viral genome at its wide base. Mutations or small molecules that interfere with viral maturation also disrupt viral infectivity. Little is known about the assembly pathway that results in the conical core and genome encapsidation. Here, we have used electron cryotomography to structurally characterize HIV-1 particles that are

  13. Pb(II) ion-imprinted micro-porous particles for the selective separation of Pb(II) ions.

    PubMed

    Jiang, Yang; Kim, Dukjoon

    2014-11-01

    Pb(II) ion-imprinted micro-porous particles were prepared from the ionic complexes formed between vinyl pyridine functional monomers and template Pb(II) ions. The self-assembled Pb(II)/monomer complex was suspension polymerized in the presence of divinylbenzene cross-linker. The prepared micro-particles were 400-600 μm in size. Their chemical and physical structures, morphologies, and adsorption capacity were analyzed by energy dispersive X-ray spectrometry (EDX) Brunauer-Emmett-Teller (BET) analysis, scanningelectron microscopy (SEM), and atomic adsorption spectroscopy (AAS). The adsorption capacity of the imprinted polymer for the Pb(II) template ions was significantly affected by the initial concentration and the pH of the feed solution. Adsorptionis rapid in the first 1 h, after which it slowly increases to equilibrium. The imprinted particles showed high selectivity for lead ions; the adsorption capacity for the Pb(II) ions, 28 mg g(-1) polymer, was much higher than those for other metal ions such as Ni(II)Zn(II), Fe(II), or Cd(II). The imprinted particles maintain high standards of their adsorption ability after 10 repeated uses. PMID:25958566

  14. Design of Gas-phase Synthesis of Core-Shell Particles by Computational Fluid - Aerosol Dynamics.

    PubMed

    Buesser, B; Pratsinis, S E

    2011-11-01

    Core-shell particles preserve the bulk properties (e.g. magnetic, optical) of the core while its surface is modified by a shell material. Continuous aerosol coating of core TiO2 nanoparticles with nanothin silicon dioxide shells by jet injection of hexamethyldisiloxane precursor vapor downstream of titania particle formation is elucidated by combining computational fluid and aerosol dynamics. The effect of inlet coating vapor concentration and mixing intensity on product shell thickness distribution is presented. Rapid mixing of the core aerosol with the shell precursor vapor facilitates efficient synthesis of hermetically coated core-shell nanoparticles. The predicted extent of hermetic coating shells is compared to the measured photocatalytic oxidation of isopropanol by such particles as hermetic SiO2 shells prevent the photocatalytic activity of titania. Finally the performance of a simpler, plug-flow coating model is assessed by comparisons to the present detailed CFD model in terms of coating efficiency and silica average shell thickness and texture. PMID:23729817

  15. Trajectories of microsecond molecular dynamics simulations of nucleosomes and nucleosome core particles.

    PubMed

    Shaytan, Alexey K; Armeev, Grigoriy A; Goncearenco, Alexander; Zhurkin, Victor B; Landsman, David; Panchenko, Anna R

    2016-06-01

    We present here raw trajectories of molecular dynamics simulations for nucleosome with linker DNA strands as well as minimalistic nucleosome core particle model. The simulations were done in explicit solvent using CHARMM36 force field. We used this data in the research article Shaytan et al., 2016 [1]. The trajectory files are supplemented by TCL scripts providing advanced visualization capabilities. PMID:27222871

  16. Resonant optical propulsion of a particle inside a hollow-core photonic crystal fiber.

    PubMed

    Maslov, A V

    2016-07-01

    Resonant propulsion of small nonresonant particles inside metal waveguides due to the formation of resonant states by the guided modes below their cutoffs has been predicted in the past. Here it is shown that stable resonant propulsion exists in hollow-core photonic crystal fibers, which are all-dielectric structures and are a major platform for various photonic applications. Specific features of the resonant propulsion are discussed together with the fiber design issues. The results may enable power-efficient transport of particles over long distances, particle sorting, and sensitive detection. PMID:27367102

  17. Microfluidic conceived pH sensitive core-shell particles for dual drug delivery.

    PubMed

    Khan, Ikram Ullah; Stolch, Lukas; Serra, Christophe A; Anton, Nicolas; Akasov, Roman; Vandamme, Thierry F

    2015-01-15

    In current study, we report on the synthesis of core-shell microparticles for dual drug delivery by means of a two co-axial microfluidic device and online UV assisted free radical polymerization. Before developing pH-sensitive particles, ketoprofen loaded poly(methyl acrylate) core-ranitidine HCl loaded poly(acrylamide) shell particles were produced. Influence of inner and outer phases flow rates on particle size, shape, core diameter, shell thickness, and drug release properties was studied. All the particles were monodispersed with coefficient of variation below 5%. Furthermore, their diameter ranged from 100 to 151 μm by increasing continuous (Qc) to middle (Qm) phase flow rate ratio (Qc/Qm). Core diameter varied from 58 to 115 μm by decreasing middle (Qm) to inner (Qi) phase flow rate ratio (Qm/Qi) at constant continuous phase flow rate as confirmed by SEM images. It was observed that an optimum concentration of acrylamide (30 wt%) and an appropriate combination of surfactants were necessary to get core-shell particles otherwise Janus structure was obtained. FTIR confirmed the complete polymerization of core and shell phases. MTT assay showed variation in viability of cells under non-contact and contact conditions with less cytotoxicity for the former. Under non-contact conditions LD50 was 3.1mg/mL. Release studies in USP phosphate buffer solution showed simultaneously release of ketoprofen and ranitidine HCl for non pH-sensitive particles. However, release rates of ranitidine HCl and ketoprofen were higher at low and high pH respectively. To develop pH-sensitive particles for colon targeting, the previous shell phase was admixed with few weight percentage of pH sensitive carboxyethyl acrylate monomer. Core and shell contained the same hydrophobic and hydrophilic model drugs as in previous case. The pH-sensitive shell prevented the release of the two entrapped molecules at low pH while increasing significantly their release rate at higher pH with a maximum

  18. Core Fueling and Edge Particle Flux Analysis in Ohmically and Auxiliary Heated NSTX Plasmas

    SciTech Connect

    V.A. Soukhanovskii; R. Maingi; R. Raman; H.W. Kugel; B.P. LeBlanc; L. Roquemore; C.H. Skinner; NSTX Research Team

    2002-06-12

    The Boundary Physics program of the National Spherical Torus Experiment (NSTX) is focusing on optimization of the edge power and particle flows in b * 25% L- and H-mode plasmas of t {approx} 0.8 s duration heated by up to 6 MW of high harmonic fast wave and up to 5 MW of neutral beam injection. Particle balance and core fueling efficiencies of low and high field side gas fueling of L-mode homic and NBI heated plasmas have been compared using an analytical zero dimensional particle balance model and measured ion and neutral fluxes. Gas fueling efficiencies are in the range of 0.05-0.20 and do not depend on discharge magnetic configuration, density or poloidal location of the injector. The particle balance modeling indicates that the addition of HFS fueling results in a reversal of the wall loading rate and higher wall inventories. Initial particle source estimates obtained from neutral pressure and spectroscopic measurements indicate that ion flux into the divertor greatly exceeds midplane ion flux from the main plasma, suggesting that the scrape-off cross-field transport plays a minor role in diverted plasmas. Present analysis provides the basis for detailed fluid modeling of core and edge particle flows and particle confinement properties of NSTX plasmas. This research was supported by the U.S. Department of Energy under contracts No. DE-AC02-76CH03073, DE-AC05-00OR22725, and W-7405-ENG-36.

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

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  1. Biodegradable and magnetic core-shell composite particle prepared by emulsion solvent diffusion method

    NASA Astrophysics Data System (ADS)

    Oka, Chiemi; Ushimaru, Kazunori; Horiishi, Nanao; Tsuge, Takeharu; Kitamoto, Yoshitaka

    2016-02-01

    The present paper describes optimization of preparation conditions of a core-shell composite particle, and its heat generation by alternating magnetic fields. The composite particles are prepared with a modified emulsion solvent diffusion method, which is combined with Pickering emulsion stabilized by magnetic nanoparticles. In this method, the magnetic nanoparticles act as an emulsifier, and its amount and size are crucial to morphology of the composite particles. The magnetic nanoparticles of 8-9 nm would be strongly adsorbed at a liquid-liquid interface rather than the larger nanoparticles. At the optimized concentration of the magnetic nanoparticle’s suspension for the preparation, small and uniform composite particles are obtained since the amount of the nanoparticles is enough to prevent coalescence of droplets during the formation of the composites. The heat generation by alternating magnetic fields emerged certainly. This result suggests the composite particles have a property as a heat-generating carrier for hyperthermia treatment.

  2. Structure of RCC1 chromatin factor bound to the nucleosome core particle

    SciTech Connect

    Makde, Ravindra D.; England, Joseph R.; Yennawar, Hemant P.; Tan, Song

    2010-11-11

    The small GTPase Ran enzyme regulates critical eukaryotic cellular functions including nuclear transport and mitosis through the creation of a RanGTP gradient around the chromosomes. This concentration gradient is created by the chromatin-bound RCC1 (regulator of chromosome condensation) protein, which recruits Ran to nucleosomes and activates Ran's nucleotide exchange activity. Although RCC1 has been shown to bind directly with the nucleosome, the molecular details of this interaction were not known. Here we determine the crystal structure of a complex of Drosophila RCC1 and the nucleosome core particle at 2.9 {angstrom} resolution, providing an atomic view of how a chromatin protein interacts with the histone and DNA components of the nucleosome. Our structure also suggests that the Widom 601 DNA positioning sequence present in the nucleosomes forms a 145-base-pair nucleosome core particle, not the expected canonical 147-base-pair particle.

  3. Synthesis of poly(aminopropyl/methyl)silsesquioxane particles as effective Cu(II) and Pb(II) adsorbents.

    PubMed

    Lu, Xin; Yin, Qiangfeng; Xin, Zhong; Li, Yang; Han, Ting

    2011-11-30

    Poly(aminopropyl/methyl)silsesquioxane (PAMSQ) particles have been synthesized by a one-step hydrolytic co-condensation process using 3-aminopropyltriethoxysilane (APTES) and methyltrimethoxysilane (MTMS) as precursors in the presence of base catalyst in aqueous medium. The amino functionalities of the particles could be controlled by adjusting the organosilanes feed ratio. The compositions of the amino-functionalized polysilsesquioxanes were confirmed by FT-IR spectroscopy, solid-state (29)Si NMR spectroscopy, and elemental analysis. The strong adsorbability of Cu(II) and Pb(II) ions onto PAMSQ particles was systematically examined. The effect of adsorption time, initial metal ions concentration and pH of solutions was studied to optimize the metal ions adsorbability of PAMSQ particles. The kinetic studies indicated that the adsorption process well fits the pseudo-second-order kinetics. Adsorption phenomena appeared to follow Langmuir isotherm. The PAMSQ particles demonstrate the highest Cu(II) and Pb(II) adsorption capacity of 2.29 mmol/g and 1.31 mmol/g at an initial metal ions concentration of 20mM, respectively. The PAMSQ particles demonstrate a promising application in the removal of Cu(II) and Pb(II) ions from aqueous solutions. PMID:21945683

  4. Vocational Agriculture II Curriculum Guide, 10th Grade. Kansas Vocational Agriculture Education: Basic Core Curriculum II.

    ERIC Educational Resources Information Center

    Pittsburg State Univ., KS. Kansas Vocational Curriculum and Research Center.

    This basic core curriculum for vocational agriculture education contains 35 units of instruction in five content areas: agricultural chemicals (1 unit), leadership (2 units), farm management (5 units), plant and soil science (10 units), animal science (8 units), and farm mechanics (9 units). Each unit follows a typical format that includes…

  5. Water-soluble core/shell nanoparticles for proton therapy through particle-induced radiation

    NASA Astrophysics Data System (ADS)

    Park, Jeong Chan; Jung, Myung-Hwan; Kim, Maeng Jun; Kim, Kye-Ryung

    2015-02-01

    Metallic nanoparticles have been used in biomedical applications such as magnetic resonance imaging (MRI), therapy, and drug delivery systems. Metallic nanoparticles as therapeutic tools have been demonstrated using radio-frequency magnetic fields or near-infrared light. Recently, therapeutic applications of metallic nanomaterials combined with proton beams have been reported. Particle-induced radiation from metallic nanoparticles, which can enhance the therapeutic effects of proton therapy, was released when the nanoparticles were bombarded by a high-energy proton beam. Core/shell nanoparticles, especially Au-coated magnetic nanoparticles, have drawn attention in biological applications due to their attractive characteristics. However, studies on the phase transfer of organic-ligand-based core/shell nanoparticles into water are limited. Herein, we demonstrated that hydrophobic core/shell structured nanomaterials could be successfully dispersed in water through chloroform/surfactant mixtures. The effects of the core/shell nanomaterials and the proton irradiation on Escherichia coli (E. coli) were also explored.

  6. Highly temperature responsive core-shell magnetic particles: synthesis, characterization and colloidal properties.

    PubMed

    Rahman, Md Mahbubor; Chehimi, Mohamed M; Fessi, Hatem; Elaissari, Abdelhamid

    2011-08-15

    Temperature responsive magnetic polymer submicron particles were prepared by two step seed emulsion polymerization process. First, magnetic seed polymer particles were obtained by emulsion polymerization of styrene using potassium persulfate (KPS) as an initiator and divinylbenzne (DVB) as a cross-linker in the presence of oil-in-water magnetic emulsion (organic ferrofluid droplets). Thereafter, DVB cross-linked magnetic polymer particles were used as seed in the precipitation polymerization of N-isopropylacrylamide (NIPAM) to induce thermosensitive PNIPAM shell onto the hydrophobic polymer surface of the cross-linked magnetic polymer particles. To impart cationic functional groups in the thermosensitive PNIPAM backbone, the functional monomer aminoethylmethacrylate hydrochloride (AEMH) was used to polymerize with NIPAM while N,N'-methylenebisacrylamide (MBA) and 2, 2'-azobis (2-methylpropionamidine) dihydrochloride (V-50) were used as a cross-linker and as an initiator respectively. The effect of seed to monomer (w/w) ratio along with seed nature on the final particle morphology was investigated. Dynamic light scattering (DLS) results demonstrated particles swelling at below volume phase transition temperature (VPTT) and deswelling above the VPTT. The perfect core (magnetic) shell (polymer) structure of the particles prepared was confirmed by Transmission Electron Microscopy (TEM). The chemical composition of the particles were determined by thermogravimetric analysis (TGA). The effect of temperature, pH, ionic strength on the colloidal properties such as size and zeta potential of the micron sized thermo-sensitive magnetic particles were also studied. In addition, a short mechanistic discussion on the formation of core-shell morphology of magnetic polymer particles has also been discussed. PMID:21570083

  7. A theoretical study on the advantage of core-shell particles with radially-oriented mesopores.

    PubMed

    Deridder, Sander; Catani, Martina; Cavazzini, Alberto; Desmet, Gert

    2016-07-22

    We report on a first-principles numerical study explaining the potential advantage of core-shell particles with strictly radially-oriented mesopores. Comparing the efficiency of these particles with fully porous and core-shell particles with a conventional (i.e., randomly oriented) mesopore network, the present numerical study shows a similar strong reduction in minimal reduced plate height (hmin) as was very recently observed in an experimental study by Wei et al. (respectively a hmin-reduction on the order of about 1 and 0.5 reduced plate height-units). As such, the present work provides a theoretical basis to understand and confirm their experimental findings and quantifies the general advantage of "radial-diffusion-only" particles. Determining the effective longitudinal diffusion (B-term contribution) in a series of dedicated, independent simulations, it was found that this contribution can be described by a very simple, yet fully exact mathematical expression for the case of "radial- diffusion-only" particles. Using this expression, the significant increase in efficiency of these particles can be fully attributed to their much smaller B-term band broadening, while their C-term band broadening (representing the mass transfer resistance) remains unaffected. PMID:27317003

  8. In-Situ Characterization of Cloud Condensation Nuclei, Interstitial, and background Particles using Single Particle Mass Spectrometer, SPLAT II

    SciTech Connect

    Zelenyuk, Alla; Imre, D.; Earle, Michael; Easter, Richard C.; Korolev, Alexei; Leaitch, W. R.; Liu, Peter; Macdonald, A. M.; Ovchinnikov, Mikhail; Strapp, Walter

    2010-10-01

    Aerosol indirect effect remains the most uncertain aspect of climate change modeling because proper test requires knowledge of individual particles sizes and compositions with high spatial and temporal resolution. We present the first deployment of a single particle mass spectrometer (SPLAT II) that is operated in a dual data acquisition mode to measure all the required individual particle properties with sufficient temporal resolution to definitively resolve the aerosol-cloud interaction in this exemplary case. We measured particle number concentrations, asphericity, and individual particle size, composition, and density with better than 60 seconds resolution. SPLAT II measured particle number concentrations between 70 particles cm-3and 300 particles cm-3, an average particle density of 1.4 g cm-3. Found that most particles are composed of oxygenated organics, many of which are mixed with sulfates. Biomass burn particles some with sulfates were prevalent, particularly at higher altitudes, and processed sea-salt was observed over the ocean. Analysis of cloud residuals shows that with time cloud droplets acquire sulfate by the reaction of peroxide with SO2. Based on the particle mass spectra and densities we find that the compositions of cloud condensation nuclei are similar to those of background aerosol but, contain on average ~7% more sulfate, and do not include dust and metallic particles. A comparison between the size distributions of background, activated, and interstitial particles shows that while nearly none of the activated particles is smaller than 115 nm, more than 80% of interstitial particles are smaller than 115 nm. We conclude that for this cloud the most important difference between CCN and background aerosol is particle size although having more sulfate also helps.

  9. Novel nucleosomal particles containing core histones and linker DNA but no histone H1

    PubMed Central

    Cole, Hope A.; Cui, Feng; Ocampo, Josefina; Burke, Tara L.; Nikitina, Tatiana; Nagarajavel, V.; Kotomura, Naoe; Zhurkin, Victor B.; Clark, David J.

    2016-01-01

    Eukaryotic chromosomal DNA is assembled into regularly spaced nucleosomes, which play a central role in gene regulation by determining accessibility of control regions. The nucleosome contains ∼147 bp of DNA wrapped ∼1.7 times around a central core histone octamer. The linker histone, H1, binds both to the nucleosome, sealing the DNA coils, and to the linker DNA between nucleosomes, directing chromatin folding. Micrococcal nuclease (MNase) digests the linker to yield the chromatosome, containing H1 and ∼160 bp, and then converts it to a core particle, containing ∼147 bp and no H1. Sequencing of nucleosomal DNA obtained after MNase digestion (MNase-seq) generates genome-wide nucleosome maps that are important for understanding gene regulation. We present an improved MNase-seq method involving simultaneous digestion with exonuclease III, which removes linker DNA. Remarkably, we discovered two novel intermediate particles containing 154 or 161 bp, corresponding to 7 bp protruding from one or both sides of the nucleosome core. These particles are detected in yeast lacking H1 and in H1-depleted mouse chromatin. They can be reconstituted in vitro using purified core histones and DNA. We propose that these ‘proto-chromatosomes’ are fundamental chromatin subunits, which include the H1 binding site and influence nucleosome spacing independently of H1. PMID:26400169

  10. LDL particle core enrichment in cholesteryl oleate increases proteoglycan binding and promotes atherosclerosis[S

    PubMed Central

    Melchior, John T.; Sawyer, Janet K.; Kelley, Kathryn L.; Shah, Ramesh; Wilson, Martha D.; Hantgan, Roy R.; Rudel, Lawrence L.

    2013-01-01

    Several studies in humans and animals suggest that LDL particle core enrichment in cholesteryl oleate (CO) is associated with increased atherosclerosis. Diet enrichment with MUFAs enhances LDL CO content. Steroyl O-acyltransferase 2 (SOAT2) is the enzyme that catalyzes the synthesis of much of the CO found in LDL, and gene deletion of SOAT2 minimizes CO in LDL and protects against atherosclerosis. The purpose of this study was to test the hypothesis that the increased atherosclerosis associated with LDL core enrichment in CO results from an increased affinity of the LDL particle for arterial proteoglycans. ApoB-100-only Ldlr−/− mice with and without Soat2 gene deletions were fed diets enriched in either cis-MUFA or n-3 PUFA, and LDL particles were isolated. LDL:proteogylcan binding was measured using surface plasmon resonance. Particles with higher CO content consistently bound with higher affinity to human biglycan and the amount of binding was shown to be proportional to the extent of atherosclerosis of the LDL donor mice. The data strongly support the thesis that atherosclerosis was induced through enhanced proteoglycan binding of LDL resulting from LDL core CO enrichment. PMID:23804810

  11. The core collapse supernova rate from the SDSS-II supernova survey

    SciTech Connect

    Taylor, Matt; Cinabro, David; Dilday, Ben; Galbany, Lluis; Gupta, Ravi R.; Kessler, R.; Marriner, John; Nichol, Robert C.; Richmond, Michael; Schneider, Donald P.; Sollerman, Jesper

    2014-09-10

    We use the Sloan Digital Sky Survey II Supernova Survey (SDSS-II SNS) data to measure the volumetric core collapse supernova (CCSN) rate in the redshift range (0.03 < z < 0.09). Using a sample of 89 CCSN, we find a volume-averaged rate of 1.06 ± 0.19 × 10{sup –4}((h/0.7){sup 3}/(yr Mpc{sup 3})) at a mean redshift of 0.072 ± 0.009. We measure the CCSN luminosity function from the data and consider the implications on the star formation history.

  12. Coherent coexistence of nanodiamonds and carbon onions in icosahedral core-shell particles

    SciTech Connect

    Shevchenko, Vladimir Ya. Madison, Alexey E.; Mackay, Alan L.

    2007-03-01

    In icosahedral carbon nanoparticles, the diamond-like core can undergo a reversible topological transition into and coexist coherently with the onion shells. The general approach for describing and designing complex hierarchical icosahedral structures is discussed. Structural models of icosahedral carbon nanoparticles in which the local arrangement of atoms is virtually identical to that in diamond are derived. It is shown that icosahedral diamond-like particles can be transformed into onion-like shell structures (and vice versa) by the consecutive smoothing (puckering) of atomic networks without disturbance of their topological integrity. The possibility of coherent coexistence of icosahedral diamond-like core with onion shells is shown.

  13. Investigation of the EAS Lateral Particle Density at 500 m Distance from Shower Core

    SciTech Connect

    Toma, G.

    2008-01-24

    For the experimental conditions of the KASCADE-Grande experiment, the density of EAS charged particles at the distance of about 500 m from the shower core S(500) has been shown by detailed simulation studies to be an approximate energy estimator, being nearly independent of the mass of the primary particle. This report presents some experimentally observed features of the S(500) observable registered with the KASCADE-Grande array installed at the Forschungszentrum Karlsruhe, Germany The measured energy deposits of particles in the 37 scintillation detector stations have been used to reconstruct the lateral charged particle distributions that are described by a Linsley parameterization (LDF). Among other features, the S(500) dependence from the EAS angle of incidence has been studied.

  14. Code System to Calculate Mixed Cores in TRIGA Mark II Research Reactor.

    Energy Science and Technology Software Center (ESTSC)

    2001-08-29

    Version 00 TRIGLAV is a computer program for reactor calculations of mixed cores in a TRIGA Mark II research reactor. It can be applied for fuel element burn-up calculations, for power and flux distributions calculations and for reactivity predictions. The TRIGLAV program requires the WIMS-D4 program with the original WIMS cross-section library extended for TRIGA reactor specific nuclides. This package includes the code TRIGAC, which is a new version of TRIGAP.

  15. Alternative designs for construction of the class II transfer RNA tertiary core.

    PubMed Central

    Nissan, T A; Perona, J J

    2000-01-01

    The structural requirements for assembly of functional class II transfer RNA core regions have been examined by sequence analysis and tested by reconstruction of alternative folds into the tertiary domain of Escherichia coli tRNA(2)Gln. At least four distinct designs have been identified that permit stable folding and efficient synthetase recognition, as assessed by thermal melting profiles and glutaminylation kinetics. Although most large variable-arm tRNAs found in nature possess an enlarged D-loop, lack of this feature can be compensated for by insertion of nucleotides either 3' to the variable loop or within the short acceptor/D-stem connector region. Rare pyrimidines at nt 9 in the core region can be accommodated in the class II framework, but only if specific nucleotides are present either in the D-loop or 3' to the variable arm. Glutaminyl-tRNA synthetase requires one or two unpaired uridines 3' to the variable arm to efficiently aminoacylate several of the class II frameworks. Because there are no specific enzyme contacts in the tRNAGln core region, these data suggest that tRNA discrimination by GlnRS depends in part on indirect readout of RNA sequence information. PMID:11105758

  16. Containment performance for the core melt accidents in BWRs with Mark I and Mark II containments

    SciTech Connect

    Perkins, K.R.; Yang, J.W.; Greene, G.A.; Pratt, W.T.; Hofmayer, C.

    1985-01-01

    Most previous risk assessment studies have assumed catastrophic failure of containments for severe accidents which are predicted to exceed the containment yield stress. This investigation analyzes the progression of a severe accident in order to develop realistic containment temperature and pressure loading, utilizes models for containment leakage estimates for the various loading histories, and assesses the expected failure modes and timing of releases for core melt accidents in Boiling Water Reactors (BWRs) with Mark I and Mark II containments. The results of the investigation indicate that leakage through the seal on the drywell head may be sufficient to prevent catastrophic failure of the containments for a wide range of hypothetical core melt scenarios. In addition, the investigation has indicated the potential for a previously inidentified failure mode (containment liner meltthrough) for Mark I containments in which a large fraction of the core is released from the vessel in a molten state. 14 refs.

  17. Surface mode hybridization in the optical response of core-shell particles

    NASA Astrophysics Data System (ADS)

    Thiessen, E.; Heinisch, R. L.; Bronold, F. X.; Fehske, H.

    2016-03-01

    We present an exact rewriting of the Mie coefficients describing the scattering of light by a spherical core-shell particle which enables their interpretation in terms of a hybridization of the two surface modes arising, respectively, at the core-shell and the shell-medium interface. For this particular case, we thus obtain from the Mie theory—analytically for all multipole orders and hence for arbitrarily sized particles—the hybridization scenario, which so far has been employed primarily for small particles in the electrostatic approximation. To demonstrate the strength of the rewriting approach, we also extract the hybridization scenario for a stratified sphere directly from the expansion coefficients for the electromagnetic fields.

  18. Epoxy-acrylic core-shell particles by seeded emulsion polymerization.

    PubMed

    Chen, Liang; Hong, Liang; Lin, Jui-Ching; Meyers, Greg; Harris, Joseph; Radler, Michael

    2016-07-01

    We developed a novel method for synthesizing epoxy-acrylic hybrid latexes. We first prepared an aqueous dispersion of high molecular weight solid epoxy prepolymers using a mechanical dispersion process at elevated temperatures, and we subsequently used the epoxy dispersion as a seed in the emulsion polymerization of acrylic monomers comprising methyl methacrylate (MMA) and methacrylic acid (MAA). Advanced analytical techniques, such as scanning transmission X-ray microscopy (STXM) and peak force tapping atomic force microscopy (PFT-AFM), have elucidated a unique core-shell morphology of the epoxy-acrylic hybrid particles. Moreover, the formation of the core-shell morphology in the seeded emulsion polymerization process is primarily attributed to kinetic trapping of the acrylic phase at the exterior of the epoxy particles. By this new method, we are able to design the epoxy and acrylic polymers in two separate steps, and we can potentially synthesize epoxy-acrylic hybrid latexes with a broad range of compositions. PMID:27078740

  19. EFFECTS OF TUMORS ON INHALED PHARMACOLOGIC DRUGS: II. PARTICLE MOTION

    EPA Science Inventory

    ABSTRACT

    Computer simulations were conducted to describe drug particle motion in human lung bifurcations with tumors. The computations used FIDAP with a Cray T90 supercomputer. The objective was to better understand particle behavior as affected by particle characteristics...

  20. Crystallography of decahedral and icosahedral particles. II - High symmetry orientations

    NASA Technical Reports Server (NTRS)

    Yang, C. Y.; Yacaman, M. J.; Heinemann, K.

    1979-01-01

    Based on the exact crystal structure of decahedral and icosahedral particles, high energy electron diffraction patterns and image profiles have been derived for various high symmetry orientations of the particles with respect to the incident beam. These results form a basis for the identification of small metal particle structures with advanced methods of transmission electron microscopy.

  1. A Bioinspired Molecular Polyoxometalate Catalyst with Two Cobalt(II) Oxide Cores for Photocatalytic Water Oxidation.

    PubMed

    Wei, Jie; Feng, Yingying; Zhou, Panpan; Liu, Yan; Xu, Jingyin; Xiang, Rui; Ding, Yong; Zhao, Chongchao; Fan, Linyuan; Hu, Changwen

    2015-08-24

    To overcome the bottleneck of water splitting, the exploration of efficient, selective, and stable water oxidation catalysts (WOCs) is crucial. We report an all-inorganic, oxidatively and hydrolytically stable WOC based on a polyoxometalate [(A-α-SiW9 O34)2Co8(OH)6(H2O)2(CO3)3](16-) (Co8 POM). As a cobalt(II)-based cubane water oxidation catalyst, Co8POM embeds double Co(II)4O3 cores. The self-assembled catalyst is similar to the oxygen evolving complex (OEC) of photosystem II (PS II). Using [Ru(bpy)3](2+) as a photosensitizer and persulfate as a sacrificial electron acceptor, Co8POM exhibits excellent water oxidation activity with a turnover number (TON) of 1436, currently the highest among bioinspired catalysts with a cubical core, and a high initial turnover frequency (TOF). Investigation by several spectroscopy, spectrometry, and other techniques confirm that Co8POM is a stable and efficient catalyst for visible light-driven water oxidation. The results offer a useful insight into the design of water oxidation catalysts. PMID:26130568

  2. Synthesis of zirconium tungstate-zirconia core-shell composite particles

    SciTech Connect

    Khazeni, Nasser; Mavis, Bora; Guenduez, Guengoer; Colak, Uner

    2011-11-15

    Highlights: {yields} ZrW{sub 2}O{sub 8}-ZrO{sub 2} core-shell particles to offer solutions for sintering problems. {yields} Core synthesis by a precursor based on tungstic acid and zirconium acetate. {yields} Shell phase by urea hydrolysis in the presence of zirconium ions. {yields} [Urea]/[ZrOCl{sub 2}] ratio controls the rate of shell precursor precipitation. -- Abstract: In this work, ZrW{sub 2}O{sub 8}-ZrO{sub 2} core-shell composite particles were synthesized. ZrW{sub 2}O{sub 8} that was used in the core is a material with negative coefficient of thermal expansion, and it was synthesized from a high-pH precursor based on use of tungstic acid and zirconium acetate. Shell layer was composed of ZrO{sub 2} nanocrystallites and precipitated from an aqueous solution by urea hydrolysis. While volume of the shell was effectively controlled by the initial zirconium ion concentration in the solutions, the rate of precipitation was a function of the ratio of initial concentrations of urea to zirconium ions. It is hypothesized that isolation of the ZrW{sub 2}O{sub 8} within a layer of ZrO{sub 2}, will be a key element in solving problems associated with reactivity of ZrW{sub 2}O{sub 8} towards other components in sintering of ceramic-ceramic composites with tuned or zero thermal expansion coefficient.

  3. Low loss Sendust powder cores comprised of particles coated by sodium salt insulating layer

    NASA Astrophysics Data System (ADS)

    Wei, Ding; Wang, Xian; Nie, Yan; Feng, Zekun; Gong, Rongzhou; Chen, Yajie; Harris, V. G.

    2015-05-01

    Toroid-shaped Sendust powder cores were prepared from cold pressing mechanically pulverized Fe-Si-Al powder that had been coated using an inorganic insulating layer. The present work focuses on the effect of the sodium salt-coated Sendust particles upon the high frequency magnetic properties. Sendust powders, having a particle size range of ˜125 μm, exhibit a high saturation magnetization of 118.9 A.m2/kg and a low coercivity of 56 A/m. The experiments indicate that the sodium-based glass insulating layer synthesized from sodium metaphosphate and sodium metaborate can effectively reduce the change in permeability with frequency or DC bias field, yielding high effective permeability (μe) of ˜113 over a wide frequency range from 10 kHz-1 MHz. Furthermore, the effective permeability is measured at ˜27 at H = 7854 A/m, indicating stable and high effective permeability under a DC bias field. The measurements of permeability under DC bias field indicate a peak in the quality factor (Q) values corresponding to a DC-bias field of 1.5-6 (kA/m) at frequencies from 50 to 200 kHz: The effective permeability remains at ˜74. The sodium salt-coated granular cores demonstrate a core loss of 68 mW/cm3 at Bm = 50 mT and f = 50 kHz: These values compare favorably to those of silicone coated Sendust particles.

  4. Particle transport after pellet injection in the TJ-II stellarator

    NASA Astrophysics Data System (ADS)

    Velasco, J. L.; McCarthy, K. J.; Panadero, N.; Satake, S.; López-Bruna, D.; Alonso, A.; Calvo, I.; Dinklage, A.; Estrada, T.; Fontdecaba, J. M.; Hernández, J.; García, R.; Medina, F.; Ochando, M.; Pastor, I.; Perfilov, S.; Sánchez, E.; Soleto, A.; Van Milligen, B. Ph; Zhezhera, A.; the TJ-II Team

    2016-08-01

    We study radial particle transport in stellarator plasmas using cryogenic pellet injection. By means of perturbative experiments, we estimate the experimental particle flux and compare it with neoclassical simulations. Experimental evidence is obtained of the fact that core depletion in helical devices can be slowed-down even by pellets that do not reach the core region. This phenomenon is well captured by neoclassical predictions with DKES and FORTEC-3D.

  5. Synthesis, molecular docking and evaluation of antifungal activity of Ni(II),Co(II) and Cu(II) complexes of porphyrin core macromolecular ligand.

    PubMed

    Singh, Urvashi; Malla, Ali Mohammad; Bhat, Imtiyaz Ahmad; Ahmad, Ajaz; Bukhari, Mohd Nadeem; Bhat, Sneha; Anayutullah, Syed; Hashmi, Athar Adil

    2016-04-01

    Porphyrin core dendrimeric ligand (L) was synthesized by Rothemund synthetic route in which p-hydroxy benzaldehyde and pyrrole were fused together. The prepared ligand was complexed with Ni(II), Cu(II) and Co(II) ions, separately. Both the ligand and its complexes were characterized by elemental analysis and spectroscopic studies (FT-IR, UV-Vis, (1)HNMR). Square planar geometries were proposed for Cu(II), Ni(II) and Co(II) ions in cobalt, Nickel and copper complexes, respectively on the basis of UV-Vis spectroscopic data. The ligand and its complex were screened on Candida albicans (ATCC 10231), Aspergillus fumigatus (ATCC 1022), Trichophyton mentagrophytes (ATCC 9533) and Pencillium marneffei by determining MICs and inhibition zones. The activity of the ligand and its complexes was found to be in the order: CuL ˃ CoL ≈ NiL ˃ L. Detection of DNA damage at the level of the individual eukaryotic cell was observed by commet assay. Molecular docking technique was used to understand the ligand-DNA interactions. From docking experiment, we conclude that copper complex interacts more strongly than rest two. PMID:26911647

  6. Controllable fabrication and characterization of biocompatible core-shell particles and hollow capsules as drug carrier

    NASA Astrophysics Data System (ADS)

    Hao, Lingyun; Gong, Xinglong; Xuan, Shouhu; Zhang, Hong; Gong, Xiuqing; Jiang, Wanquan; Chen, Zuyao

    2006-10-01

    SiO 2@CdSe core-shell particles were fabricated by controllable deposition CdSe nanoparticles on silica colloidal spheres. Step-wise coating process was tracked by the TEM and XRD measurements. In addition, SiO 2@CdSe/polypyrrole(PPy) multi-composite particles were synthesized based on the as-prepared SiO 2@CdSe particles by cationic polymerization. The direct electrochemistry of myoglobin (Mb) could be performed by immobilizing Mb on the surface of SiO 2@CdSe particles. Immobilized with Mb, SiO 2@CdSe/PPy-Mb also displayed good bioelectrochemical activity. It confirmed the good biocompatible property of the materials with protein. CdSe hollow capsules were further obtained as the removal of the cores of SiO 2@CdSe spheres. Hollow and porous character of CdSe sub-meter size capsules made them becoming hopeful candidates as drug carriers. Doxorubicin, a typical an antineoplastic drug, was introduced into the capsules. A good sustained drug release behavior of the loading capsules was discovered via performing a release test in the PBS buffer (pH 7.4) solution at 310 k. Furthermore, SiO 2@CdSe/PPy could be converted to various smart hollow capsules via selectively removal of their relevant components.

  7. Ni(II) affects ubiquitination of core histones H2B and H2A

    SciTech Connect

    Karaczyn, Aldona A.; Golebiowski, Filip; Kasprzak, Kazimierz S. . E-mail: kasprkaz@mail.ncifcrf.gov

    2006-10-15

    The molecular mechanisms of nickel-induced malignant cell transformation include effects altering the structure and covalent modifications of core histones. Previously, we found that exposure of cells to Ni(II) resulted in truncation of histones H2A and H2B and thus elimination of some modification sites. Here, we investigated the effect of Ni(II) on one such modification, ubiquitination, of histones H2B and H2A in nuclei of cultured 1HAEo- and HPL1D human lung cells. After 1-5 days of exposure, Ni(II) up to 0.25 mM stimulated mono-ubiquitination of both histones, while at higher concentrations a suppression was found. Di-ubiquitination of H2A was not affected except for a drop after 5 days at 0.5 mM Ni(II). The decrease in mono-ubiquitination coincided with the appearance of truncated H2B that lacks the K120 ubiquitination site. However, prevention of truncation did not avert the decrease of H2B ubiquitination, indicating mechanistic independence of these effects. The changes in H2B ubiquitination did not fully coincide with concurrent changes in the nuclear levels of the ubiquitin-conjugating enzymes Rad6 and UbcH6. Overall, our results suggest that dysregulation of H2B ubiquitination is a part of Ni(II) adverse effects on gene expression and DNA repair which may assist in cell transformation.

  8. Continuous syntheses of Pd@Pt and Cu@Ag core-shell nanoparticles using microwave-assisted core particle formation coupled with galvanic metal displacement.

    PubMed

    Miyakawa, Masato; Hiyoshi, Norihito; Nishioka, Masateru; Koda, Hidekazu; Sato, Koichi; Miyazawa, Akira; Suzuki, Toshishige M

    2014-08-01

    Continuous synthesis of Pd@Pt and Cu@Ag core-shell nanoparticles was performed using flow processes including microwave-assisted Pd (or Cu) core-nanoparticle formation followed by galvanic displacement with a Pt (or Ag) shell. The core-shell structure and the nanoparticle size were confirmed using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) observation and EDS elemental mapping. The Pd@Pt nanoparticles with a particle size of 6.5 ± 0.6 nm and a Pt shell thickness of ca. 0.25 nm were synthesized with appreciably high Pd concentration (Pd 100 mM). This shell thickness corresponds to one atomic layer thickness of Pt encapsulating the Pd core metal. The particle size of core Pd was controlled by tuning the initial concentrations of Na2[PdCl4] and PVP. Core-shell Cu@Ag nanoparticles with a particle size of 90 ± 35 nm and an Ag shell thickness of ca. 3.5 nm were obtained using similar sequential reactions. Oxidation of the Cu core was suppressed by the coating of Cu nanoparticles with the Ag shell. PMID:24948122

  9. Comparisons of MgII core-wing data with Ground-Based Ca K-line

    NASA Astrophysics Data System (ADS)

    Chapman, G. A.; Preminger, D.

    2011-12-01

    Magnesium_II core-wing ratio data will be compared with ground-based K-line photometry for most of cycle 22 and 23. The ground-based data is the photmetric sum computed from the composite K-line obtained from the San Fernando Observatory. We will examine several MgII core-wing composites. This work is partially supported by grants NNX11AB51G from NASA and ATM-0848518 from NSF.

  10. Classical relativistic constituent particles and composite states. II

    NASA Astrophysics Data System (ADS)

    King, Marcia J.

    1985-05-01

    A classical theory of interacting relativistic constituent and composite particles is developed further. The Lorentz-invariant Lagrangian, a function of the single unmeasurable evolution parameter s, is considered for attractive and repulsive harmonic-oscillator forces acting pairwise between constituent particles. Nonrelativistic Newtonian equations of motion can be derived by letting c-->∞ in ``equal-time'' solutions, but, in general, there is a ``surplus'' of solutions which have no nonrelativistic counterpart. These solutions are used to construct classical models of strongly interacting composite particles. Asymptotic selection rules and constituent confinement are postulated and lead to space-time conservation laws for systems of scattering composite particles. Constituent four-vectors are linear combinations of ``kinematic'' terms and ``intrinsic'' normal modes. The latter are identified with internal symmetries of the composite particles, which are labeled by sets of ``intrinsic numbers'' analogous to additive quantum numbers. Formation of two- and three-body composite particles follows an exact analogy to the color quark model, in which the meson is composed of a quark and an antiquark of the same color, and the baryon is formed from three quarks of three different colors. Scattering examples are given analogous to MM-->MM, MB-->MB, and BB-->BB. The reactions take place through constituent exchange, and total intrinsic numbers are conserved. There are other similarities to quantum field theory, such as particle-antiparticle pair creation and annihilation, fixed relative values of internal angular momenta, fixed orbital angular momentum, and many-particle systems characterized by a vacuum state (lowest energy state) and the existence of virtual composite particles as well as physically observable composite particles.

  11. Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering.

    PubMed

    Çınar, Simge; Tevis, Ian D; Chen, Jiahao; Thuo, Martin

    2016-01-01

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate ('/' = physisorbed, '-' = chemisorbed), from molten Field's metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity. PMID:26902483

  12. Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering

    NASA Astrophysics Data System (ADS)

    Çınar, Simge; Tevis, Ian D.; Chen, Jiahao; Thuo, Martin

    2016-02-01

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate (‘/’ = physisorbed, ‘-’ = chemisorbed), from molten Field’s metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity.

  13. Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering

    PubMed Central

    Çınar, Simge; Tevis, Ian D.; Chen, Jiahao; Thuo, Martin

    2016-01-01

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate (‘/’ = physisorbed, ‘-’ = chemisorbed), from molten Field’s metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity. PMID:26902483

  14. Core/shell silicon/polyaniline particles via in-flight plasma-induced polymerization

    NASA Astrophysics Data System (ADS)

    Yasar-Inceoglu, Ozgul; Zhong, Lanlan; Mangolini, Lorenzo

    2015-08-01

    Although silicon nanoparticles have potential applications in many relevant fields, there is often the need for post-processing steps to tune the property of the nanomaterial and to optimize it for targeted applications. In particular surface modification is generally necessary to both tune dispersibility of the particles in desired solvents to achieve optimal coating conditions, and to interface the particles with other materials to realize functional heterostructures. In this contribution we discuss the realization of core/shell silicon/polymer nanoparticles realized using a plasma-initiated in-flight polymerization process. Silicon particles are produced in a non-thermal plasma reactor using silane as a precursor. After synthesis they are aerodynamically injected into a second plasma reactor into which aniline vapor is introduced. The second plasma initiates the polymerization reactor leading to the formation of a 3-4 nm thick polymer shell surrounding the silicon core. The role of processing conditions on the properties of the polymeric shell is discussed. Preliminary results on the testing of this material as an anode for lithium ion batteries are presented.

  15. Nanostructured core-shell Ni deposition on SiC particles by alkaline electroless coating

    NASA Astrophysics Data System (ADS)

    Uysal, M.; Karslioğlu, R.; Alp, A.; Akbulut, H.

    2011-10-01

    In this study, core-shell nanostructured nickel formation on silicon carbide (SiC) ceramic powders was achieved through the electroless deposition method using alkaline solutions. To produce a nano core-shell Ni deposition on the SiC surfaces, process parameters such as pH values, the type of reducer material, deposition temperature, stirring rate and activation procedure among others were determined. Full coverage of core-shell nickel structures on SiC surfaces was achieved with a grain size of between 100 and 300 nm, which was approximately the same deposition thickness on the SiC surfaces. The surface morphology of the coated SiC particles showed a homogenous distribution of nanostructured nickel grains characterized by scanning electron microscopy and X-ray diffraction techniques. The nanostructures of the crystalline Ni coatings were observed to be attractive for achieving both good bonding and dense structure. The thin core shell-structure of Ni on the SiC surfaces was assessed as a beneficial reinforcement for possible metal matrix composite manufacturing.

  16. Experimental challenge to nucleosynthesis in core-collapse supernovae - Very early epoch of type II SNe -

    NASA Astrophysics Data System (ADS)

    Kubono, S.; Binh, Dam N.; Hayakawa, S.; Hashimoto, T.; Kahl, D. M.; Yamaguchi, H.; Wakabayashi, Y.; Teranishi, T.; Iwasa, N.; Komatsubara, T.; Kato, S.; Chen, A.; Cherubini, S.; Choi, S. H.; Hahn, I. S.; He, J. J.; Khiem, Le H.; Lee, C. S.; Kwon, Y. K.; Wanajo, S.; Janka, H.-T.

    2013-05-01

    Nucleosynthesis is one of the keys in studying the mechanism of core-collapse supernovae, which is an interesting challenge for modern science. The νp-process, which is similar to an explosive hydrogen burning process, has been proposed as the most probable process in the very early epoch of type II supernovae. Here, we discuss our experimental efforts for the νp-process, the first extensive direct measurements of the (α,p) reactions on bottle-neck proto-rich nuclei in light mass regions. Other challenges for the νp-process study are also discussed.

  17. An assessment of the Arctic Ocean in a suite of interannual CORE-II simulations. Part II: Liquid freshwater

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Ilicak, Mehmet; Gerdes, Rüdiger; Drange, Helge; Aksenov, Yevgeny; Bailey, David A.; Bentsen, Mats; Biastoch, Arne; Bozec, Alexandra; Böning, Claus; Cassou, Christophe; Chassignet, Eric; Coward, Andrew C.; Curry, Beth; Danabasoglu, Gokhan; Danilov, Sergey; Fernandez, Elodie; Fogli, Pier Giuseppe; Fujii, Yosuke; Griffies, Stephen M.; Iovino, Doroteaciro; Jahn, Alexandra; Jung, Thomas; Large, William G.; Lee, Craig; Lique, Camille; Lu, Jianhua; Masina, Simona; Nurser, A. J. George; Rabe, Benjamin; Roth, Christina; Salas y Mélia, David; Samuels, Bonita L.; Spence, Paul; Tsujino, Hiroyuki; Valcke, Sophie; Voldoire, Aurore; Wang, Xuezhu; Yeager, Steve G.

    2016-03-01

    The Arctic Ocean simulated in 14 global ocean-sea ice models in the framework of the Coordinated Ocean-ice Reference Experiments, phase II (CORE-II) is analyzed in this study. The focus is on the Arctic liquid freshwater (FW) sources and freshwater content (FWC). The models agree on the interannual variability of liquid FW transport at the gateways where the ocean volume transport determines the FW transport variability. The variation of liquid FWC is induced by both the surface FW flux (associated with sea ice production) and lateral liquid FW transport, which are in phase when averaged on decadal time scales. The liquid FWC shows an increase starting from the mid-1990s, caused by the reduction of both sea ice formation and liquid FW export, with the former being more significant in most of the models. The mean state of the FW budget is less consistently simulated than the temporal variability. The model ensemble means of liquid FW transport through the Arctic gateways compare well with observations. On average, the models have too high mean FWC, weaker upward trends of FWC in the recent decade than the observation, and low consistency in the temporal variation of FWC spatial distribution, which needs to be further explored for the purpose of model development.

  18. Papain digestion of crude Trichoderma reesei cellulase: Purification and properties of cellobiohydrolase I and II core proteins

    SciTech Connect

    Woodward, J.; Brown, J.P.; Evans, B.R.; Affholter, K.A.

    1992-01-01

    Papain digestion of a crude Trichoderma reesei cellulose preparation followed by gel filtration on a Superdex column resulted in the separation of cellobiohydrolase (CBH) I and II core proteins (cp). They were further purified to apparent homogeneity by chromatofocusing. N-terminal protein sequencing of the CBH II cp preparation confirmed its identity. A comparison of the catalytic activity and cellulose-binding ability of these core proteins was made. The major differences between them were the findings that CBH II cp possessed a sixfold higher specific activity toward p-nitrophenylcellobioside than the native CBH II preparation and still bound to microcrystalline cellulose, unlike CBH I cp. Neither CBH I cp nor CBH II cp had activity toward carboxymethylcellulose, but both were able to hydrolyze barley b-glucan. These data suggest that removal of the cellulose-binding domain and hinge region from CBH I and II have different effects on their properties.

  19. Charge separation and energy transfer in the photosystem II core complex studied by femtosecond midinfrared spectroscopy.

    PubMed

    Pawlowicz, N P; Groot, M-L; van Stokkum, I H M; Breton, J; van Grondelle, R

    2007-10-15

    The core of photosystem II (PSII) of green plants contains the reaction center (RC) proteins D1D2-cytb559 and two core antennas CP43 and CP47. We have used time-resolved visible pump/midinfrared probe spectroscopy in the region between 1600 and 1800 cm(-1) to study the energy transfer and charge separation events within PSII cores. The absorption difference spectra in the region of the keto and ester chlorophyll modes show spectral evolution with time constants of 3 ps, 27 ps, 200 ps, and 2 ns. Comparison of infrared (IR) difference spectra obtained for the isolated antennas CP43 and CP47 and the D1D2-RC with those measured for the PSII core allowed us to identify the features specific for each of the PSII core components. From the presence of the CP43 and CP47 specific features in the spectra up to time delays of 20-30 ps, we conclude that the main part of the energy transfer from the antennas to the RC occurs on this timescale. Direct excitation of the pigments in the RC evolution associated difference spectra to radical pair formation of PD1+PheoD1- on the same timescale as multi-excitation annihilation and excited state equilibration within the antennas CP43 and CP47, which occur within approximately 1-3 ps. The formation of the earlier radical pair ChlD1+PheoD1-, as identified in isolated D1D2 complexes with time-resolved mid-IR spectroscopy is not observed in the current data, probably because of its relatively low concentration. Relaxation of the state PD1+PheoD1-, caused by a drop in free energy, occurs in 200 ps in closed cores. We conclude that the kinetic model proposed earlier for the energy and electron transfer dynamics within the D1D2-RC, plus two slowly energy-transferring antennas C43 and CP47 explain the complex excited state and charge separation dynamics in the PSII core very well. We further show that the time-resolved IR-difference spectrum of PD1+PheoD1- as observed in PSII cores is virtually identical to that observed in the isolated D1D2-RC

  20. Electronic excitation transport in core antennae of enriched photosystem I particles from spinach chloroplasts

    SciTech Connect

    Causgrove, T.P.; Yang, S.; Struve, W.S.

    1988-10-20

    The polarized photobleaching recovery of PSI-60 particles enriched in iron-sulfur protein and P700 was monitored with approx. 2-ps resolution at 665, 670, 675, and 681 nm. Considerable residual anisotropy appears at long times, proving that local ordering exists in the Chl a-protein core antenna of PSI-60. At these four wavelengths, the polarization decays with mean lifetimes between 2.9 and 6.6 ps. This slow time scale suggests that the depolarization accompanies electronic excitation transport between clusters of Chl a chromophores rather than between individual nearest-neighbor chromophores.

  1. Exchange coupled SrFe12O19/Fe-Co core/shell particles with different shell thickness

    NASA Astrophysics Data System (ADS)

    Xu, Xia; Hong, Yang-Ki; Park, Jihoon; Lee, Woncheol; Lane, Alan M.

    2015-11-01

    SrFe12O19/Fe-Co core/shell particles with different shell thickness were synthesized by polyol reduction of Fe and Co ions at 180°C with SrFe12O19 particles dispersed in solvent. The core/shell structure is formed by magnetic self-assembly due to the remanent magnetization of SrFe12O19 particles. Within a limited concentration range, the shell thickness could be controlled by regulating the concentration of Fe and Co ions. Core/shell structured SrFe12O19/Fe-Co particles showed more effective exchange coupling effects between hard and soft phases than physically mixed SrFe12O19 and Fe-Co particles. [Figure not available: see fulltext.

  2. Influence of rigid core permittivity and double layer polarization on the electrophoresis of a soft particle: A numerical study

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, S.; De, Simanta

    2016-01-01

    The nonlinear electrophoresis of a soft particle with a polarizable uncharged rigid core coated with a polyelectrolyte layer is studied. Due to the coupled nature of the governing electrokinetic equations, a numerical approach is adopted. Our numerical solutions are in good agreement with the existing experimental and theoretical results for a particle with a non-polarizable core when the impacts of the nonlinear effects are low. The induced surface potential of the dielectric rigid core has an impact on the soft particle electrophoresis. The combined effects of the solid polarization of the core and double layer polarization have not been addressed previously in the context of soft particle electrophoresis. We have found that both these effects create retardation on the electrophoresis and are significant when the applied electric field is not weak. The double layer polarization is significant when the Debye length is in the order of the particle size. The range of the applied electric field for which the electrophoretic velocity of a soft particle with a non-polarizable core varies linearly with the applied electric field may create a nonlinear variation in electrophoretic velocity when the core is considered to be polarizable.

  3. Site-specific aflatoxin B sub 1 adduction of sequence-positioned nucleosome core particles

    SciTech Connect

    Moyer, R.A.

    1988-01-01

    The question of how the presence of nucleosomal packing of DNA modifies carcinogen interaction at specific sites cannot be answered by studies on whole chromatin or bulk nucleosomes because of the heterogeneity of DNA sequences in the particles. This problem was circumvented by constructing nucleosomes that are homogenous in DNA-histone contact points. A cloned DNA fragment, containing a sea urchin 5S gene which precisely positions a histone octamer was employed. By using {sup 32}P end-labeled DNA and genotoxins that allow cleavage at sites of attack, the frequency of adduction at every susceptible nucleotide can be determined on sequencing gels. The small methylating agent dimethyl sulfate (DMS) and the bulky alkylating agent afatoxin B{sub 1}-dichloride (AFB{sub 1}-Cl{sub 2}) were used to probe the influence of DNA-histone interactions on DNA alkylation patterns in sequence-positioned core particles.

  4. Fluorescence studies of cyanobacterial phycobiliproteins: I. Spectroscopy of allophycocyanin core complexes. II. Spectroscopy of two phycobilisome core insertion mutants

    SciTech Connect

    Maxson, P.

    1988-10-01

    The work described here relates to the mechanisms governing energy transfer in the core polypeptides of the cyanobacterial phycobilisome. Two approaches are represented: measurements were made on isolated core components for which a great deal of structural information is available; and the fluorescence properties were characterized for the whole phycobilisome from two phycobilisome core insertion mutants. 130 refs.

  5. Sorption selectivity of birnessite particle edges: a d-PDF analysis of Cd(ii) and Pb(ii) sorption by δ-MnO2 and ferrihydrite.

    PubMed

    van Genuchten, Case M; Peña, Jasquelin

    2016-08-10

    Birnessite minerals (layer-type MnO2), which bear both internal (cation vacancies) and external (particle edges) metal sorption sites, are important sinks of contaminants in soils and sediments. Although the particle edges of birnessite minerals often dominate the total reactive surface area, especially in the case of nanoscale crystallites, the metal sorption reactivity of birnessite particle edges remains elusive. In this study, we investigated the sorption selectivity of birnessite particle edges by combining Cd(ii) and Pb(ii) adsorption isotherms at pH 5.5 with surface structural characterization by differential pair distribution function (d-PDF) analysis. We compared the sorption reactivity of δ-MnO2 to that of the nanomineral, 2-line ferrihydrite, which exhibits only external surface sites. Our results show that, whereas Cd(ii) and Pb(ii) both bind to birnessite layer vacancies, only Pb(ii) binds extensively to birnessite particle edges. For ferrihydrite, significant Pb(ii) adsorption to external sites was observed (roughly 20 mol%), whereas Cd(ii) sorption was negligible. These results are supported by bond valence calculations that show comparable degrees of saturation of oxygen atoms on birnessite and ferrihydrite particle edges. Therefore, we propose that the sorption selectivity of birnessite edges follows the same order of that reported previously for ferrihydrite: Ca(ii) < Cd(ii) < Ni(ii) < Zn(ii) < Cu(ii) < Pb(ii). PMID:27183472

  6. The treatment of mixing in core helium burning models - II. Constraints from cluster star counts

    NASA Astrophysics Data System (ADS)

    Constantino, Thomas; Campbell, Simon W.; Lattanzio, John C.; van Duijneveldt, Adam

    2016-03-01

    The treatment of convective boundaries during core helium burning is a fundamental problem in stellar evolution calculations. In the first paper of this series, we showed that new asteroseismic observations of these stars imply they have either very large convective cores or semiconvection/partially mixed zones that trap g modes. We probe this mixing by inferring the relative lifetimes of asymptotic giant branch (AGB) and horizontal branch (HB) from R2, the observed ratio of these stars in recent HST photometry of 48 Galactic globular clusters. Our new determinations of R2 are more self-consistent than those of previous studies and our overall calculation of R2 = 0.117 ± 0.005 is the most statistically robust now available. We also establish that the luminosity difference between the HB and the AGB clump is Δ log {L}_HB^AGB = 0.455 ± 0.012. Our results accord with earlier findings that standard models predict a lower R2 than is observed. We demonstrate that the dominant sources of uncertainty in models are the prescription for mixing and the stochastic effects that can result from its numerical treatment. The luminosity probability density functions that we derive from observations feature a sharp peak near the AGB clump. This constitutes a strong new argument against core breathing pulses, which broaden the predicted width of the peak. We conclude that the two mixing schemes that can match the asteroseismology are capable of matching globular cluster observations, but only if (i) core breathing pulses are avoided in models with a semiconvection/partially mixed zone, or (ii) that models with large convective cores have a particular depth of mixing beneath the Schwarzschild boundary during subsequent early-AGB `gravonuclear' convection.

  7. Cu-Ni nano-alloy: mixed, core-shell or Janus nano-particle?

    NASA Astrophysics Data System (ADS)

    Guisbiers, Grégory; Khanal, Subarna; Ruiz-Zepeda, Francisco; Roque de La Puente, Jorge; José-Yacaman, Miguel

    2014-11-01

    Bimetallic nanoparticles like Cu-Ni are particularly attractive due to their magnetic and catalytic properties; however, their properties depend strongly on the structure of the alloy i.e. mixed, core-shell or Janus. To predict the alloy structure, this paper investigates the size and shape effects as well as the surface segregation effect on the Cu-Ni phase diagram. Phase maps have been plotted to determine the mixing/demixing behavior of this alloy according the particle shape. Cu-Ni nanoalloy can form a mixed particle or a Janus one depending on the synthesis temperature. Surface segregation is also considered and reveals a nickel surface-enrichment. Finally, this paper provides a useful roadmap for experimentalists.Bimetallic nanoparticles like Cu-Ni are particularly attractive due to their magnetic and catalytic properties; however, their properties depend strongly on the structure of the alloy i.e. mixed, core-shell or Janus. To predict the alloy structure, this paper investigates the size and shape effects as well as the surface segregation effect on the Cu-Ni phase diagram. Phase maps have been plotted to determine the mixing/demixing behavior of this alloy according the particle shape. Cu-Ni nanoalloy can form a mixed particle or a Janus one depending on the synthesis temperature. Surface segregation is also considered and reveals a nickel surface-enrichment. Finally, this paper provides a useful roadmap for experimentalists. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05739b

  8. Basics of particle therapy II: relative biological effectiveness

    PubMed Central

    Choi, Jinhyun

    2012-01-01

    In the previous review, the physical aspect of heavy particles, with a focus on the carbon beam was introduced. Particle beam therapy has many potential advantages for cancer treatment without increasing severe side effects in normal tissue, these kinds of radiation have different biologic characteristics and have advantages over using conventional photon beam radiation during treatment. The relative biological effectiveness (RBE) is used for many biological, clinical endpoints among different radiation types and is the only convenient way to transfer the clinical experience in radiotherapy with photons to another type of radiation therapy. However, the RBE varies dependent on the energy of the beam, the fractionation, cell types, oxygenation status, and the biological endpoint studied. Thus this review describes the concerns about RBE related to particle beam to increase interests of the Korean radiation oncologists' society. PMID:23120738

  9. A core-shell structured inorganic-organic hybrid nanocomposite for Hg(II) sensing and removal.

    PubMed

    Jiqu, Han; Qixia, Yang

    2015-10-01

    In the present paper, a core-shell structured inorganic-organic hybrid nanocomposite for Hg(II) sensing and removal was designed and fabricated, where the core was composed of superparamagnetic Fe3O4 and the shell consisted of molecular silica sieve MCM-41. A rhodamine derived probe was grafted onto the backbone of MCM-41 through a silane coupling reagent to control its loading content. This probe functionalized core-shell structure was confirmed and characterized by XRD analysis, electron microscopy images, IR spectra, thermogravimetry and N2 adsorption/desorption isotherms. It was found that the emission of this composite increased with increasing Hg(II) concentrations but was immune to other metal ions, showing good selectivity and high sensitivity towards Hg(II) ions. A linear Stern-Volmer curve was observed with short response time. In addition, this composite possessed good Hg(II)-removing and recycling performance. PMID:25978016

  10. One-piece micropumps from liquid crystalline core-shell particles

    NASA Astrophysics Data System (ADS)

    Fleischmann, Eva-Kristina; Liang, Hsin-Ling; Kapernaum, Nadia; Giesselmann, Frank; Lagerwall, Jan; Zentel, Rudolf

    2012-11-01

    Responsive polymers are low-cost, light weight and flexible, and thus an attractive class of materials for the integration into micromechanical and lab-on-chip systems. Triggered by external stimuli, liquid crystalline elastomers are able to perform mechanical motion and can be utilized as microactuators. Here we present the fabrication of one-piece micropumps from liquid crystalline core-shell elastomer particles via a microfluidic double-emulsion process, the continuous nature of which enables a low-cost and rapid production. The liquid crystalline elastomer shell contains a liquid core, which is reversibly pumped into and out of the particle by actuation of the liquid crystalline shell in a jellyfish-like motion. The liquid crystalline elastomer shells have the potential to be integrated into a microfluidic system as micropumps that do not require additional components, except passive channel connectors and a trigger for actuation. This renders elaborate and high-cost micromachining techniques, which are otherwise required for obtaining microstructures with pump function, unnecessary.

  11. Strategies for crystallizing a chromatin protein in complex with the nucleosome core particle

    PubMed Central

    Makde, Ravindra D.; Tan, Song

    2013-01-01

    The molecular details for how chromatin factors and enzymes interact with the nucleosome are critical to understand fundamental genetic processes including cell division and gene regulation. A structural understanding of such processes has been hindered by the difficulty producing diffraction quality crystals of chromatin proteins in complex with the nucleosome. We describe here the steps used to grow crystals of the 300 kDa RCC1 chromatin factor/nucleosome core particle complex which diffract to 2.9 Å resolution. These steps included both pre- and post-crystallization strategies potentially useful to other complexes. We screened multiple variant RCC1-nucleosome core particle complexes assembled using different RCC1 homologs and deletion variants, and nucleosomes containing nucleosomal DNA with different sequences and lengths as well as histone deletion variants. We found that using RCC1 from different species produced different crystal forms of the RCC1-nucleosome complex consistent with key crystal packing interactions mediated by RCC1. Optimization of post-crystallization soaks to dehydrate the crystals dramatically improved the diffraction quality of the RCC1/nucleosome crystal from 5.0 to 2.9 Å resolution. PMID:23928047

  12. Construction of a Ca II Core-to-Wing Ratio Image

    NASA Astrophysics Data System (ADS)

    Roberts, H.

    2015-12-01

    To understand Earth's climate, we must first understand the Sun. However, there are still significant uncertainties associated with both the fundamental mechanisms of solar variability and how they enter into the Earth's climate system. An important method to study the causes of solar variability can be found through the analysis of solar images. The Precision Solar Photometric Telescope (PSPT) located at the Mauna Loa Solar Observatory (MLSO) acquires images of the Sun in three different photometric bands to monitor the evolution of solar surface features that change over the course of a solar cycle. These images provide a complete knowledge about the Sun by targeting different layers of the solar atmosphere. Though raw images are meaningful and important, precision image processing is required to remove instrumental artifacts and false features that may appear in these images prior to usage for scientific purposes. A scientific application of the high precision solar images is investigated by analyzing a set of narrow band of Calcium II K core and wing images. The Core and Wing images are processed to remove the influence of the center-to-limb variation; the resultant core-to-wing ratio image enhances the appearance of network structures on the entire solar disk along with the more obvious facula and plage brightening associated with the passage of active regions.

  13. Purification of infective bluetongue virus particles by immuno-affinity chromatography using anti-core antibody.

    PubMed

    Chand, Karam; Biswas, Sanchay K; Mondal, Bimalendu

    2016-03-01

    An immuno-affinity chromatography technique for purification of infective bluetongue virus (BTV) has been descried using anti-core antibodies. BTV anti-core antibodies (prepared in guinea pig) were mixed with cell culture-grown BTV-1 and then the mixture was added to the cyanogens bromide-activated protein-A Sepharose column. Protein A binds to the antibody which in turn binds to the antigen (i.e. BTV). After thorough washing, antigen-antibody and antibody-protein A couplings were dissociated with 4M MgCl2, pH6.5. Antibody molecules were removed by dialysis and virus particles were concentrated by spin column ultrafiltration. Dialyzed and concentrated material was tested positive for BTV antigen by a sandwich ELISA and the infectivity of the chromatography-purified virus was demonstrated in cell culture. This method was applied for selective capture of BTV from a mixture of other viruses. As group-specific antibodies (against BTV core) were used to capture the virus, it is expected that virus of all BTV serotypes could be purified by this method. This method will be helpful for selective capture and enrichment of BTV from concurrently infected blood or tissue samples for efficient isolation in cell culture. Further, this method can be used for small scale purification of BTV avoiding ultracentrifugation. PMID:26925450

  14. Water masers embedded in ultracompact H II regions: The W 75N cloud core

    NASA Astrophysics Data System (ADS)

    Hunter, T. R.; Taylor, G. B.; Felli, M.; Tofani, G.

    1994-04-01

    We present radio observations of the W 75N star forming region consisting of:(1) high-resolution Very Large Array (VLA) radio continuum and H2O maser maps, (2) CSO molecular maps in the CS and CO lines, (3) results from a six-year monitoring campaign of the H2O maser emission with the 32-m Medicina telescope. Using the VLA in A-configuration, we find that the 22 GHz H2O maser spots in W 75N spatially coincide with very weak, small diameter (less than 1 sec) radio continuum sources at the center of the dense molecular cloud core. The very high optical obscuration (Ar greater than or equal 90 mag), the high total luminosity of the source and the high electron density suggest that in W 75N we are witnessing the first appearance of an ultracompact H II region (UCH II) produced by an early type star still deeply embedded in the progenitor molecular cloud. The H2O maser - UCH II association may last only for the short time (approximately 103 y) needed by the H II to expand out to the distance where masers are formed. Both the H2O and OH masers as well as the continuum sources extend a few seconds of arc along a roughly N-S line, matching the extension of the core evident in the CS J = 7 goes to 6 map and nearly perpendicular to the axis of the molecular outflow. As traced by the CO J = 3 goes to 2 transition, the origin of the outflow lies at the position of the UCH IIs, suggesting that they are associated with the powering source. The H2O spectrum extends over approximately 30 km/s, with many distinct velocity components, part of which can be unambiguously identified with individual spatial components of the VLA H2O map. The variability of the H2O emission of each velocity component is very high, with time scales of the order of a few years and dynamic range almost up to two orders of magnitude. For the bluest velocity component, well isolated in the velocity and space domains, there is evidence of a continuous velocity drift of approximately 4 km/s over 2 years. The

  15. Sialic Acid-Imprinted Fluorescent Core-Shell Particles for Selective Labeling of Cell Surface Glycans.

    PubMed

    Shinde, Sudhirkumar; El-Schich, Zahra; Malakpour, Atena; Wan, Wei; Dizeyi, Nishtman; Mohammadi, Reza; Rurack, Knut; Gjörloff Wingren, Anette; Sellergren, Börje

    2015-11-01

    The expression of cell surface glycans terminating with sialic acid (SA) residues has been found to correlate with various disease states there among cancer. We here report a novel strategy for specific fluorescence labeling of such motifs. This is based on sialic acid-imprinted core-shell nanoparticles equipped with nitrobenzoxadiazole (NBD) fluorescent reporter groups allowing environmentally sensitive fluorescence detection at convenient excitation and emission wavelengths. Imprinting was achieved exploiting a hybrid approach combining reversible boronate ester formation between p-vinylphenylboronic acid and SA, the introduction of cationic amine functionalities, and the use of an NBD-appended urea-monomer as a binary hydrogen-bond donor targeting the SA carboxylic acid and OH functionalities. The monomers were grafted from 200 nm RAFT-modified silica core particles using ethylene glycol dimethacrylate (EGDMA) as cross-linker resulting in a shell thickness of ca. 10 nm. The particles displayed strong affinity for SA in methanol/water mixtures (K = 6.6 × 10(5) M(-1) in 2% water, 5.9 × 10(3) M(-1) in 98% water, B(max) ≈ 10 μmol g(-1)), whereas binding of the competitor glucuronic acid (GA) and other monosaccharides was considerably weaker (K (GA) = 1.8 × 10(3) M(-1) in 98% water). In cell imaging experiments, the particles selectively stained different cell lines in correlation with the SA expression level. This was further verified by enzymatic cleavage of SA and by staining using a FITC labeled SA selective lectin. PMID:26414878

  16. Theory of longitudinal beam halo in RF linacs: II. envelope-particle resonances

    SciTech Connect

    Lund, S.M.; Barnard, J.J.

    1997-05-01

    Using the core/test-particle model described in a companion paper in these proceedings (``Theory of Longitudinal Halo in rf Linacs: I. Core/Test Particle Formulation,`` by J. J. Barnard and S. M. Lund), we analyze longitudinal beam halo produced by resonant self-field interactions in intense, ion-beam rf linacs. It is shown that particles moving in the presence of the space-charge forces of an oscillating, mismatched ellipsoidal beam bunch can be resonantly driven to large longitudinal amplitude. This resonantly produced halo is first analyzed in a limit where it is most simply understood, with particles moving purely longitudinally and with linear rf focusing. Then modifications of the resonance induced by nonlinear rf and transverse-longitudinal coupling are explored.

  17. Long-rising Type II supernovae from Palomar Transient Factory and Caltech Core-Collapse Project

    NASA Astrophysics Data System (ADS)

    Taddia, F.; Sollerman, J.; Fremling, C.; Migotto, K.; Gal-Yam, A.; Armen, S.; Duggan, G.; Ergon, M.; Filippenko, A. V.; Fransson, C.; Hosseinzadeh, G.; Kasliwal, M. M.; Laher, R. R.; Leloudas, G.; Leonard, D. C.; Lunnan, R.; Masci, F. J.; Moon, D.-S.; Silverman, J. M.; Wozniak, P. R.

    2016-04-01

    Context. Supernova (SN) 1987A was a peculiar hydrogen-rich event with a long-rising (~84 d) light curve, stemming from the explosion of a compact blue supergiant star. Only a few similar events have been presented in the literature in recent decades. Aims: We present new data for a sample of six long-rising Type II SNe (SNe II), three of which were discovered and observed by the Palomar Transient Factory (PTF) and three observed by the Caltech Core-Collapse Project (CCCP). Our aim is to enlarge this small family of long-rising SNe II, characterizing their differences in terms of progenitor and explosion parameters. We also study the metallicity of their environments. Methods: Optical light curves, spectra, and host-galaxy properties of these SNe are presented and analyzed. Detailed comparisons with known SN 1987A-like events in the literature are shown, with particular emphasis on the absolute magnitudes, colors, expansion velocities, and host-galaxy metallicities. Bolometric properties are derived from the multiband light curves. By modeling the early-time emission with scaling relations derived from the SuperNova Explosion Code (SNEC) models of MESA progenitor stars, we estimate the progenitor radii of these transients. The modeling of the bolometric light curves also allows us to estimate other progenitor and explosion parameters, such as the ejected 56Ni mass, the explosion energy, and the ejecta mass. Results: We present PTF12kso, a long-rising SN II that is estimated to have the largest amount of ejected 56Ni mass measured for this class. PTF09gpn and PTF12kso are found at the lowest host metallicities observed for this SN group. The variety of early light-curve luminosities depends on the wide range of progenitor radii of these SNe, from a few tens of R⊙ (SN 2005ci) up to thousands (SN 2004ek) with some intermediate cases between 100 R⊙ (PTF09gpn) and 300 R⊙ (SN 2004em). Conclusions: We confirm that long-rising SNe II with light-curve shapes closely

  18. Type II solar radio bursts, interplanetary shocks, and energetic particle events

    NASA Technical Reports Server (NTRS)

    Cane, H. V.; Stone, R. G.

    1984-01-01

    Using the ISEE-3 radio astronomy experiment data 37 interplanetary (IP) type II bursts have been identified in the period September 1978 to December 1981. These events and the associated phenomena are listed. The events are preceded by intense, soft X ray events with long decay times (LDEs) and type II and/or type IV bursts at meter wavelengths. The meter wavelength type II bursts are usually intense and exhibit herringbone structure. The extension of the herringbone structure into the kilometer wavelength range results in the occurrence of a shock accelerated (SA) event. The majority of the interplanetary type II bursts are associated with energetic particle events. These results support other studies awhich indicate that energetic solar particles detected at 1 A.U. are generated by shock acceleration. From a preliminary analysis of the available data there appears to be a high correlation with white light coronal transients.

  19. H II REGIONS, EMBEDDED PROTOSTARS, AND STARLESS CORES IN SHARPLESS 2-157

    SciTech Connect

    Chen, Chian-Chou; Williams, Jonathan P.; Pandian, Jagadheep D. E-mail: jpw@ifa.hawaii.edu

    2012-06-20

    We present arcsecond resolution 1.4 mm observations of the high-mass star-forming region, Sharpless 2-157, that reveal the cool dust associated with the first stages of star formation. These data are compared with archival images at optical, infrared, and radio wavelengths, and complemented with new arcsecond resolution mid-infrared data. We identify a dusty young H II region, numerous infrared sources within the cluster envelope, and four starless condensations. Three of the cores lie in a line to the south of the cluster peak, but the most massive one is right at the center and associated with a jumble of bright radio and infrared sources. This presents an interesting juxtaposition of high- and low-mass star formation within the same cluster which we compare with similar observations of other high-mass star-forming regions and discuss in the context of cluster formation theory.

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

    PubMed

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

    2016-04-13

    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. PMID:26948023

  1. The structure of nucleosomal core particles within transcribed and repressed gene regions.

    PubMed Central

    Studitsky, V M; Belyavsky, A V; Melnikova, A F; Mirzabekov, A D

    1988-01-01

    The arrangement of histones along DNA in nucleosomal core particles within transcribed heat shock gene (hsp 70) region and repressed insertion within ribosomal genes of Drosophila was analysed by using protein-DNA crosslinking methods combined with hybridization tests. In addition, two-dimensional gel electrophoresis was employed to compare the overall nucleosomal shape and the nucleosomal DNA size. The arrangement of histones along DNA and general compactness of nucleosomes were shown to be rather similar in transcriptionally active and inactive genomic regions. On the other hand, nucleosomes within transcriptionally active chromatin are characterized by a larger size of nucleosomal DNA produced by micrococcal nuclease digestion and some peculiarity in electrophoretic mobility. Images PMID:3144704

  2. Assembly Pathway of Hepatitis B Core Virus-like Particles from Genetically Fused Dimers*

    PubMed Central

    Holmes, Kris; Shepherd, Dale A.; Ashcroft, Alison E.; Whelan, Mike; Rowlands, David J.; Stonehouse, Nicola J.

    2015-01-01

    Macromolecular complexes are responsible for many key biological processes. However, in most cases details of the assembly/disassembly of such complexes are unknown at the molecular level, as the low abundance and transient nature of assembly intermediates make analysis challenging. The assembly of virus capsids is an example of such a process. The hepatitis B virus capsid (core) can be composed of either 90 or 120 dimers of coat protein. Previous studies have proposed a trimer of dimers as an important intermediate species in assembly, acting to nucleate further assembly by dimer addition. Using novel genetically-fused coat protein dimers, we have been able to trap higher-order assembly intermediates and to demonstrate for the first time that both dimeric and trimeric complexes are on pathway to virus-like particle (capsid) formation. PMID:25953902

  3. Comprehensive computer model for magnetron sputtering. II. Charged particle transport

    SciTech Connect

    Jimenez, Francisco J. Dew, Steven K.; Field, David J.

    2014-11-01

    Discharges for magnetron sputter thin film deposition systems involve complex plasmas that are sensitively dependent on magnetic field configuration and strength, working gas species and pressure, chamber geometry, and discharge power. The authors present a numerical formulation for the general solution of these plasmas as a component of a comprehensive simulation capability for planar magnetron sputtering. This is an extensible, fully three-dimensional model supporting realistic magnetic fields and is self-consistently solvable on a desktop computer. The plasma model features a hybrid approach involving a Monte Carlo treatment of energetic electrons and ions, along with a coupled fluid model for thermalized particles. Validation against a well-known one-dimensional system is presented. Various strategies for improving numerical stability are investigated as is the sensitivity of the solution to various model and process parameters. In particular, the effect of magnetic field, argon gas pressure, and discharge power are studied.

  4. Particle-core coupling in 37S

    NASA Astrophysics Data System (ADS)

    Chapman, R.; Wang, Z. M.; Bouhelal, M.; Haas, F.; Liang, X.; Azaiez, F.; Behera, B. R.; Burns, M.; Caurier, E.; Corradi, L.; Curien, D.; Deacon, A. N.; Dombrádi, Zs.; Farnea, E.; Fioretto, E.; Gadea, A.; Hodsdon, A.; Ibrahim, F.; Jungclaus, A.; Keyes, K.; Kumar, V.; Lunardi, S.; Mǎrginean, N.; Montagnoli, G.; Napoli, D. R.; Nowacki, F.; Ollier, J.; O'Donnell, D.; Papenberg, A.; Pollarolo, G.; Salsac, M.-D.; Scarlassara, F.; Simpson, G.; Smith, J. F.; Spohr, K. M.; Stanoiu, M.; Stefanini, A. M.; Szilner, S.; Trotta, M.; Verney, D.

    2016-04-01

    Excited states of the neutron-rich N =21 37S nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of 36S ions with a thin 208Pb target. The magnetic spectrometer, PRISMA, and the γ -ray array, CLARA, were used in the measurements. The level scheme of 37S was established to an excitation energy of 4196 keV and a number of new transitions were observed, in particular that corresponding to the decay of the proposed Jπ=(11 /2 -) level at an excitation energy of 2776 keV. The structure of the state is discussed within the context of state-of-the-art shell-model calculations using the SDPF-U effective interaction; the main component of the wave function corresponds to the coupling of the odd 1 f7 /2 neutron to the first 2+ state of the 36S core. The electromagnetic decay properties of the state are discussed within the context of a particle-core coupling model and the shell model. The other members of the multiplet of states are also discussed.

  5. Topoisomerase I activity associated with human immunodeficiency virus (HIV) particles and equine infectious anemia virus core.

    PubMed Central

    Priel, E; Showalter, S D; Roberts, M; Oroszlan, S; Segal, S; Aboud, M; Blair, D G

    1990-01-01

    In the present study, we found a topoisomerase I (topo I) activity in two strains of human immunodeficiency virus type 1 (HIV-1) and equine infectious anemia virus (EIAV) particles. The topo I activity was located in the EIAV cores and differed from the cellular topo I in its ionic requirements and response to ATP, indicating that these were two distinct forms of this enzyme. Topo I activity was removed from the viral lysates and viral cores by anti-topo I antiserum. The only protein recognized by this antiserum was an 11.5 kd protein in HIV lysate and 11 kd in EIAV lysate. We showed that the 11 kd protein recognized by the anti-topo I antiserum is the EIAV p11 nucleocapsid protein. Furthermore, purified topo I protein blocked the binding of the antibodies to the p11 protein and vice versa, purified p11 protein blocked the binding of these antibodies to the cellular topo I. These results suggest that the EIAV p11 nucleocapsid protein and the cellular topo I share similar epitopes. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. Fig. 7. PMID:2174357

  6. Multiparticle Production in Particle and Nuclear Collisions. II

    NASA Astrophysics Data System (ADS)

    Kanki, T.; Kinoshita, K.; Sumiyoshi, H.; Takagi, F.

    The dominant phenomenon in high-energy particle and nuclear collisions is multiple production of hadrons. This had attracted may physicists in 1950's, the period of the first remarkable development of particle physics. Multiparticle production was already observed in cosmic-ray experiments and expected to be explained as a natural consequence of the strong Yukawa interaction. Statistical and hydrodynamical models were then proposed by Fermi, Landau and others. These theories are still surviving even today as a prototype of modern ``fire-ball'' models. After twenty years, a golden age came in this field of physics. It was closely related to the rapid development of accelerator facilities, especially, the invention of colliding-beam machines which yield high enough center-of-mass energies for studying reactions with high multiplicity. Abundant data on final states of multiparticle production have been accumulated mainly by measuring inclusive cross sections and multiplicity distributions. In super high-energy bar{p}p collisions at CERN S pmacr pS Collider, we confirmed the increasing total cross section and found violations of many scaling laws which seemed to be valid at lower energies. This suggests a fundamental complexity of the multiparticle phenomena and offers new materials for further development of theoretical investigations. In the same period, studies of constituent (quark-gluon) structure of hadrons had also been develped. Nowadays, pysicists believe that the quantum chromodynamics (QCD) is the fundamental law of the hadronic world. Multiparticle dynamics should also be described by QCD. We have known that the hard-jet phenomena are well explained by the perturbative QCD. On the other hand, the soft processes are considered to be non-perturbative phenomena which have not yet been solved, and related to the mechanism of the color confinement and formation of strings or color-flux tubes. Multiparticle production would offer useful information on this

  7. Synthetic observations of first hydrostatic cores in collapsing low-mass dense cores. II. Simulated ALMA dust emission maps

    NASA Astrophysics Data System (ADS)

    Commerçon, B.; Levrier, F.; Maury, A. J.; Henning, Th.; Launhardt, R.

    2012-12-01

    Context. First hydrostatic cores are predicted by theories of star formation, but their existence has never been demonstrated convincingly by (sub)millimeter observations. Furthermore, the multiplicity in the early phases of the star formation process is poorly constrained. Aims: The purpose of this paper is twofold. First, we seek to provide predictions for ALMA dust continuum emission maps from early Class 0 objects. Second, we show to what extent ALMA will be able to probe the fragmentation scale in these objects. Methods: Following our companion paper, we post-processed three state-of-the-art radiation-magneto-hydrodynamic 3D adaptive mesh refinement calculations to compute the emanating dust emission maps. We then produced synthetic ALMA observations of the dust thermal continuum from first hydrostatic cores. Results: We present the first synthetic ALMA observations of dust continuum emission from the first hydrostatic cores. We analyze the results given by the different bands and configurations and we discuss for which combinations of the two the first hydrostatic cores would most likely be observed. We also show that observing dust continuum emission with ALMA will help in identifying the physical processes occurring within collapsing dense cores. If the magnetic field is playing a role, the emission pattern will show evidence of a pseudo-disk and even of a magnetically driven outflow, which pure hydrodynamical calculations cannot reproduce. Conclusions: The capabilities of ALMA will enable us to make significant progress towards understanding the fragmentation at the early Class 0 stage and discovering first hydrostatic cores.

  8. Self-assembled dicopper(II) diethanolaminate cores for mild aerobic and peroxidative oxidation of alcohols.

    PubMed

    Figiel, Paweł J; Kirillov, Alexander M; Guedes da Silva, M Fátima C; Lasri, Jamal; Pombeiro, Armando J L

    2010-11-01

    The new dicopper(ii) complexes [Cu(2)(μ-Hmdea)(2)(NCS)(2)] (1) and [Cu(2)(μ-Hedea)(2)(N(3))(2)]·(H(2)O)(0.25) (2) with the {Cu(2)(μ-O)(2)} diethanolaminate cores have been easily generated by aqueous medium self-assembly reactions of copper(ii) nitrate with N-methyl- or N-ethyldiethanolamine (H(2)mdea or H(2)edea, respectively), in the presence of sodium thiocyanate (for 1) or sodium azide (for 2) as ancillary ligands sources. They have been isolated as air-stable crystalline solids and fully characterized by IR and UV-vis spectroscopies, ESI-MS(+), elemental and single-crystal X-ray diffraction analyses. The latter complex also features a fourfold linkage of neighbouring dimeric units via strong intermolecular O-HO hydrogen bonds, giving rise to the formation of tetracopper aggregates. The catalytic activity of compounds 1 and 2 has been studied for the mild (50-80 °C) and selective oxidations of alcohols, namely for (i) the aerobic aqueous medium oxidation of benzyl alcohols to benzaldehydes, mediated by TEMPO radical, and for (ii) the solvent-free oxidation of secondary alcohols to ketones by t-BuOOH under microwave (MW) irradiation. Complex 2 shows the highest efficiency in both oxidation systems, resulting in up to 99% molar yields (based on the alcohol substrate) of products. In addition, remarkably high values of TON (1020) and TOF (4080 h(-1)) have been achieved in the MW-assisted peroxidative oxidation of 1-phenylethanol to acetophenone (model reaction). Attractive green features of these catalytic systems include the operation in aqueous or solvent-free reaction medium, under mild conditions and with high yields and selectivities, using Cu catalyst precursors that are readily available by self-assembly in water of simple chemicals. PMID:20844801

  9. Chloramphenicol Mediates Superoxide Production in Photosystem II and Enhances Its Photodamage in Isolated Membrane Particles

    PubMed Central

    Rehman, Ateeq Ur; Kodru, Sandeesha; Vass, Imre

    2016-01-01

    Chloramphenicol (CAP) is an inhibitor of protein synthesis, which is frequently used to decouple photodamage and protein synthesis dependent repair of Photosystem II during the process of photoinhibition. It has been reported earlier that CAP is able to mediate superoxide production by transferring electrons from the acceptor side of Photosystem I to oxygen. Here we investigated the interaction of CAP with Photosystem II electron transport processes by oxygen uptake and variable chlorophyll fluorescence measurements. Our data show that CAP can accept electrons at the acceptor side of Photosystem II, most likely from Pheophytin, and deliver them to molecular oxygen leading to superoxide production. In addition, the presence of CAP enhances photodamage of Photosystem II electron transport in isolated membrane particles, which effect is reversible by superoxide dismutase. It is concluded that CAP acts as electron acceptor in Photosystem II and mediates its superoxide dependent photodamage. This effect has potential implications for the application of CAP in photoinhibitory studies in intact systems. PMID:27092170

  10. Starvation Induces Proteasome Autophagy with Different Pathways for Core and Regulatory Particles*

    PubMed Central

    Waite, Kenrick A.; Mota-Peynado, Alina De-La; Vontz, Gabrielle; Roelofs, Jeroen

    2016-01-01

    The proteasome is responsible for the degradation of many cellular proteins. If and how this abundant and normally stable complex is degraded by cells is largely unknown. Here we show that in yeast, upon nitrogen starvation, proteasomes are targeted for vacuolar degradation through autophagy. Using GFP-tagged proteasome subunits, we observed that autophagy of a core particle (CP) subunit depends on the deubiquitinating enzyme Ubp3, although a regulatory particle (RP) subunit does not. Furthermore, upon blocking of autophagy, RP remained largely nuclear, although CP largely localized to the cytosol as well as granular structures within the cytosol. In all, our data reveal a regulated process for the removal of proteasomes upon nitrogen starvation. This process involves CP and RP dissociation, nuclear export, and independent vacuolar targeting of CP and RP. Thus, in addition to the well characterized transcriptional up-regulation of genes encoding proteasome subunits, cells are also capable of down-regulating cellular levels of proteasomes through proteaphagy. PMID:26670610

  11. Fast determination of biogenic amines in beverages by a core-shell particle column.

    PubMed

    Preti, Raffaella; Antonelli, Marta Letizia; Bernacchia, Roberta; Vinci, Giuliana

    2015-11-15

    A fast and reliable HPLC method for the determination of 11 biogenic amines in beverages has been performed. After pre-column derivatization with dansyl-chloride a Kinetex C18 core-shell particle column (100 mm × 4.6 mm, 2.6 μm particle size) has been employed and the biogenic amines were identified and quantified in a total run time of 13 min with ultraviolet (UV) or fluorescence detection (FLD). Chromatographic conditions such as column temperature (kept at 50 °C), gradient elution and flow rate have been optimized and the method has been tested on red wine and fruit nectar. The proposed method is enhanced in terms of reduced analysis time and eluent consumption with respect of classical HPLC method as to be comparable to UHPLC methods. Green and cost-effective, this method can be used as a quality-control tool for routine quantitative analysis of biogenic amines in beverages for the average laboratory. PMID:25977063

  12. Magnetically self-assembled SrFe12O19/Fe-Co core/shell particles

    SciTech Connect

    Xu, X; Park, J; Hong, YK; Lane, AM

    2015-02-15

    Epitaxial growth to synthesize core/shell-structured materials is limited because large lattice mismatches are common between materials. Magnetically hard/soft, core/shell-structured materials can be potentially used for rare-earth free permanent magnets, but their synthesis presents a challenge. We report a wet chemistry method to synthesize core/shell structured particles consisting of a magnetically hard SrFe12O19 core and a soft Fe-Co shell, with a lattice mismatch of similar to 100%, which cannot be achieved by conventional epitaxial growth or other alternative methods. When decreasing the size of the magnetically soft Fe-Co nanoclusters to below 5 nm, we show that they can be magnetically attracted by the hard SrFe12O19 to form core/shell structured particles. An AC demagnetization experiment demonstrates the formation mechanism of the core/shell particles, and their magnetic hysteresis loop shows potential for use as rare-earth free permanent magnets. Published by Elsevier B.V.

  13. Advantages of core-shell particle columns in Sequential Injection Chromatography for determination of phenolic acids.

    PubMed

    Chocholouš, Petr; Vacková, Jana; Srámková, Ivana; Satínský, Dalibor; Solich, Petr

    2013-01-15

    Currently, for Sequential Injection Chromatography (SIC), only reversed phase C18 columns have been used for chromatographic separations. This article presents the first use of three different stationary phases: three core-shell particle-packed reversed phase columns in flow systems. The aim of this work was to extend the chromatographic capabilities of the SIC system. Despite the particle-packed columns reaching system pressures of ≤ 610 PSI, their conditions matched those of a commercially produced and optimised SIC system (SIChrom™ (FIAlab(®), USA)) with a 8-port high-pressure selection valve and medium-pressure Sapphire™ syringe pump with a 4 mL reservoir and maximum system pressure of ≤ 1000 PSI. The selectivity of each of the tested columns, Ascentis(®) Express RP-Amide, Ascentis(®) Express Phenyl-Hexyl and Ascentis(®) Express C18 (30 mm × 4.6mm, core-shell particle size 2.7 μm), was compared by their ability to separate seven phenolic acids that are secondary metabolite substances widely distributed in plants. The separations of all of the components were performed by isocratic elution using binary mobile phases composed of acetonitrile and 0.065% phosphoric acid at pH 2.4 (a specific ratio was used for each column) at a flow-rate of 0.60 mL/min. The volume of the mobile phase was 3.8 mL for each separation. The injection volume of the sample was 10 μL for each separation. The UV detection wavelengths were set to 250, 280 and 325 nm. The RP-Amide column provided the highest chromatographic resolution and allowed for complete baseline separation of protocatechuic, syringic, vanillic, ferulic, sinapinic, p-coumaric and o-coumaric acids. The Phenyl-Hexyl and C18 columns were unable to completely separate the tested mixture, syringic and vanillic acid and ferulic and sinapinic acids could not be separated from one another. The analytical parameters were a LOD of 0.3 mg L(-1), a LOQ of 1.0 mg L(-1), a calibration range of 1.0-50.0 (100.0) mg L(-1

  14. Charged-particle mutagenesis II. Mutagenic effects of high energy charged particles in normal human fibroblasts

    NASA Technical Reports Server (NTRS)

    Chen, D. J.; Tsuboi, K.; Nguyen, T.; Yang, T. C.

    1994-01-01

    The biological effects of high LET charged particles are a subject of great concern with regard to the prediction of radiation risk in space. In this report, mutagenic effects of high LET charged particles are quantitatively measured using primary cultures of human skin fibroblasts, and the spectrum of induced mutations are analyzed. The LET of the charged particles ranged from 25 KeV/micrometer to 975 KeV/micrometer with particle energy (on the cells) between 94-603 MeV/u. The X-chromosome linked hypoxanthine guanine phosphoribosyl transferase (hprt) locus was used as the target gene. Exposure to these high LET charged particles resulted in exponential survival curves; whereas, mutation induction was fitted by a linear model. The Relative Biological Effect (RBE) for cell-killing ranged from 3.73 to 1.25, while that for mutant induction ranged from 5.74 to 0.48. Maximum RBE values were obtained at the LET of 150 keV/micrometer. The inactivation cross-section (alpha i) and the action cross-section for mutant induction (alpha m) ranged from 2.2 to 92.0 micrometer2 and 0.09 to 5.56 x 10(-3) micrometer2, respectively. The maximum values were obtained by 56Fe with an LET of 200 keV/micrometer. The mutagenicity (alpha m/alpha i) ranged from 2.05 to 7.99 x 10(-5) with the maximum value at 150 keV/micrometer. Furthermore, molecular analysis of mutants induced by charged particles indicates that higher LET beams are more likely to cause larger deletions in the hprt locus.

  15. Charged-particle mutagenesis II. Mutagenic effects of high energy charged particles in normal human fibroblasts

    NASA Astrophysics Data System (ADS)

    Chen, D. J.; Tsuboi, K.; Nguyen, T.; Yang, T. C.

    1994-10-01

    The biological effects of high LET charged particles are a subject of great concern with regard to the prediction of radiation risk in space. In this report, mutagenic effects of high LET charged particles are quantitatively measured using primary cultures of human skin fibroblasts, and the spectrum of induced mutations are analyzed. The LET of the charged particles ranged from 25 KeV/μm to 975 KeV/gmm with particle energy (on the cells) between 94 - 603 MeV/u. The X-chromosome linked hypoxanthine guanine phosphoribosyl transferase (hprt) locus was used as the target gene. Exposure to these high LET charged particles resulted in exponential survival curves; whereas, mutation induction was fitted by a linear model. The Relative Biological Effect (RBE) for cell-killing ranged from 3.73 to 1.25, while that for mutant induction ranged from 5.74 to 0.48. Maximum RBE values were obtained at the LET of 150 keV/μm. The inactivation cross-section (αi) and the action-section for mutant induction (αm) ranged from 2.2 to 92.0 μm2 and 0.09 to 5.56 × 10-3 μm2, respectively. The maximum values were obtained by 56Fe with an LET of 200 keV/μm. The mutagenicity (αm/αi) ranged from 2.05 to 7.99 × 10-5 with the maximum value at 150 keV/μm. Furthermore, molecular analysis of mutants induced by charged particles indicates that higher LET beams are more likely to cause larger deletions in the hprt locus.

  16. Core-shell-structured silica/polyacrylate particles prepared by Pickering emulsion: influence of the nucleation model on particle interfacial organization and emulsion stability

    PubMed Central

    2014-01-01

    This work reports a new evidence of the versatility of silica sol as a stabilizer for Pickering emulsions. The organization of silica particles at the oil-water interface is a function of the nucleation model. The present results show that nucleation model, together with monomer hydrophobicity, can be used as a trigger to modify the packing density of silica particles at the oil-water interface: Less hydrophobic methylmethacrylate, more wettable with silica particles, favors the formation of core-shell-structured composite when the composite particles are prepared by miniemulsion polymerization in which monomers are fed in batch (droplet nucleation). By contrast, hydrophobic butylacrylate promotes the encapsulating efficiency of silica when monomers are fed dropwise (homogeneous nucleation). The morphologies of polyacrylate-nano-SiO2 composites prepared from different feed ratio of methylmethacrylate/butylacrylate (with different hydrophobicity) and by different feed processes are characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. The results from SEM and TEM show that the morphologies of the as-prepared polyacrylate/nano-SiO2 composite can be a core-shell structure or a bare acrylic sphere. The stability of resulting emulsions composed of these composite particles is strongly dependent on the surface coverage of silica particles. The emulsion stability is improved by densely silica-packed composite particles. PMID:25313299

  17. Replacement of tyrosine D with phenylalanine affects the normal proton transfer pathways for the reduction of P680+ in oxygen-evolving photosystem II particles from Chlamydomonas.

    PubMed

    Jeans, C; Schilstra, M J; Ray, N; Husain, S; Minagawa, J; Nugent, J H A; Klug, D R

    2002-12-31

    We have probed the electrostatics of P680(+) reduction in oxygenic photosynthesis using histidine-tagged and histidine-tagged Y(D)-less Photosystem II cores. We make two main observations: (i) that His-tagged Chlamydomonas cores show kinetics which are essentially identical to those of Photosystem II enriched thylakoid membranes from spinach; (ii) that the microsecond kinetics, previously shown to be proton/hydrogen transfer limited [Schilstra et al. (1998) Biochemistry 37, 3974-3981], are significantly different in Y(D)-less Chlamydomonas particles when compared with both the His-tagged Chlamydomonas particles and the spinach membranes. The oscillatory nature of the kinetics in both Chlamydomonas samples is normal, indicating that S-state cycling is unaffected by either the histidine-tagging or the replacement of tyrosine D with phenylalanine. We propose that the effects on the proton-coupled electron transfers of P680(+) reduction in the absence of Y(D) are likely to be due to pK shifts of residues in a hydrogen-bonded network of amino acids in the vicinity of Y(Z). Tyrosine D is 35 A from Y(Z) and yet has a significant influence on proton-coupled electron transfer events in the vicinity of Y(Z). This finding emphasizes the delicacy of the proton balance that Photosystem II has to achieve during the water splitting process. PMID:12501204

  18. Physical Investigations of Small Particles: (I) Aerosol Particle Charging and Flux Enhancement and (II) Whispering Gallery Mode Sensing

    NASA Astrophysics Data System (ADS)

    Lopez-Yglesias, Xerxes

    of the molecule and the electromagnetic interaction between the molecule and particle, especially for the neutral particle case, are completely ignored, or, as is often the case for a permanent dipole vapor species, strongly underestimated. Comparing our model to these classical models we determine an "enhancement factor" to characterize how important the addition of these physical parameters and processes is to the understanding of particle nucleation and growth. Part II: Whispering gallery mode (WGM) optical biosensors are capable of extraordinarily sensitive specific and non-specific detection of species suspended in a gas or fluid. Recent experimental results suggest that these devices may attain single-molecule sensitivity to protein solutions in the form of stepwise shifts in their resonance wavelength, lambdaR, but present sensor models predict much smaller steps than were reported. This study examines the physical interaction between a WGM sensor and a molecule adsorbed to its surface, exploring assumptions made in previous efforts to model WGM sensor behavior, and describing computational schemes that model the experiments for which single protein sensitivity was reported. The resulting model is used to simulate sensor performance, within constraints imposed by the limited material property data. On this basis, we conclude that nonlinear optical effects would be needed to attain the reported sensitivity, and that, in the experiments for which extreme sensitivity was reported, a bound protein experiences optical energy fluxes too high for such effects to be ignored.

  19. A Catalog of Low-mass Star-forming Cores Observed with SHARC-II at 350 μm

    NASA Astrophysics Data System (ADS)

    Suresh, Akshaya; Dunham, Michael M.; Arce, Héctor G.; Evans, Neal J., II; Bourke, Tyler L.; Merello, Manuel; Wu, Jingwen

    2016-08-01

    We present a catalog of low-mass dense cores observed with the SHARC-II instrument at 350 μm. Our observations have an effective angular resolution of 10″, approximately 2.5 times higher than observations at the same wavelength obtained with the Herschel Space Observatory, albeit with lower sensitivity, especially to extended emission. The catalog includes 81 maps covering a total of 164 detected sources. For each detected source, we tabulate basic source properties including position, peak intensity, flux density in fixed apertures, and radius. We examine the uncertainties in the pointing model applied to all SHARC-II data and conservatively find that the model corrections are good to within ∼3″, approximately 1/3 of the SHARC-II beam. We examine the differences between two array scan modes and find that the instrument calibration, beam size, and beam shape are similar between the two modes. We also show that the same flux densities are measured when sources are observed in the two different modes, indicating that there are no systematic effects introduced into our catalog by utilizing two different scan patterns during the course of taking observations. We find a detection rate of 95% for protostellar cores but only 45% for starless cores, and demonstrate the existence of a SHARC-II detection bias against all but the most massive and compact starless cores. Finally, we discuss the improvements in protostellar classification enabled by these 350 μm observations.

  20. Characterization of a purified photosystem II-phycobilisome particle preparation from Porphyridium cruentum

    SciTech Connect

    Chereskin, B.M.; Clement-Metral, J.D.; Gantt, E.

    1985-01-01

    Detergent preparations isolated from thylakoids of the red alga Porphyridium cruentum, in a sucrose, phosphate, citrate, magnesium chloride medium consist of phycobilisomes and possess high rates of photosystem II activity. Characterization of these particles shows that the O/sub 2/-evolving activity is stable for several hours and the pH optimum is about 6.5 to 7.2. Response of the system to light, electron donors and acceptors, and inhibitors verify that the observed activity, measured both as O/sub 2/ evolution and 2,6-dichlorophenol-indophenol reduction, is due to photosystem II. Furthermore, photosystem II is functionally coupled to the phycobilisome in this preparation since green light, absorbed by phycobilisomes of P. cruentum, is effective in promoting both O/sub 2/ evolution and 2,6-dichlorophenol-indophenol reduction. Photosystem II activity declines when light with wavelengths shorter than 665 nm is removed. Both 3-(3,4-dichlorophenyl)-1,1-dimethylurea and atrazine inhibit photosystem II activity in this preparation, indicating that the herbicide binding site is a component of the photosystem II-phycobilisome particle. 24 references, 4 figures, 2 tables.

  1. North and equatorial Pacific Ocean circulation in the CORE-II hindcast simulations

    NASA Astrophysics Data System (ADS)

    Tseng, Yu-heng; Lin, Hongyang; Chen, Han-ching; Thompson, Keith; Bentsen, Mats; Böning, Claus W.; Bozec, Alexandra; Cassou, Christophe; Chassignet, Eric; Chow, Chun Hoe; Danabasoglu, Gokhan; Danilov, Sergey; Farneti, Riccardo; Fogli, Pier Giuseppe; Fujii, Yosuke; Griffies, Stephen M.; Ilicak, Mehmet; Jung, Thomas; Masina, Simona; Navarra, Antonio; Patara, Lavinia; Samuels, Bonita L.; Scheinert, Markus; Sidorenko, Dmitry; Sui, Chung-Hsiung; Tsujino, Hiroyuki; Valcke, Sophie; Voldoire, Aurore; Wang, Qiang; Yeager, Steve G.

    2016-08-01

    We evaluate the mean circulation patterns, water mass distributions, and tropical dynamics of the North and Equatorial Pacific Ocean based on a suite of global ocean-sea ice simulations driven by the CORE-II atmospheric forcing from 1963-2007. The first three moments (mean, standard deviation and skewness) of sea surface height and surface temperature variability are assessed against observations. Large discrepancies are found in the variance and skewness of sea surface height and in the skewness of sea surface temperature. Comparing with the observation, most models underestimate the Kuroshio transport in the Asian Marginal seas due to the missing influence of the unresolved western boundary current and meso-scale eddies. In terms of the Mixed Layer Depths (MLDs) in the North Pacific, the two observed maxima associated with Subtropical Mode Water and Central Mode Water formation coalesce into a large pool of deep MLDs in all participating models, but another local maximum associated with the formation of Eastern Subtropical Mode Water can be found in all models with different magnitudes. The main model bias of deep MLDs results from excessive Subtropical Mode Water formation due to inaccurate representation of the Kuroshio separation and of the associated excessively warm and salty Kuroshio water. Further water mass analysis shows that the North Pacific Intermediate Water can penetrate southward in most models, but its distribution greatly varies among models depending not only on grid resolution and vertical coordinate but also on the model dynamics. All simulations show overall similar large scale tropical current system, but with differences in the structures of the Equatorial Undercurrent. We also confirm the key role of the meridional gradient of the wind stress curl in driving the equatorial transport, leading to a generally weak North Equatorial Counter Current in all models due to inaccurate CORE-II equatorial wind fields. Most models show a larger

  2. PDMAEMA-grafted core-shell-corona particles for nonviral gene delivery and magnetic cell separation.

    PubMed

    Majewski, Alexander P; Stahlschmidt, Ullrich; Jérôme, Valérie; Freitag, Ruth; Müller, Axel H E; Schmalz, Holger

    2013-09-01

    Monodisperse, magnetic nanoparticles as vectors for gene delivery were successfully synthesized via the grafting-from approach. First, oleic acid stabilized maghemite nanoparticles (γ-Fe2O3) were encapsulated with silica utilizing a reverse microemulsion process with simultaneous functionalization with initiating sites for atom transfer radical polymerization (ATRP). Polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) from the core-shell nanoparticles led to core-shell-corona hybrid nanoparticles (γ-Fe2O3@silica@PDMAEMA) with an average grafting density of 91 polymer chains of DP(n) = 540 (PDMAEMA540) per particle. The permanent attachment of the arms was verified by field-flow fractionation. The dual-responsive behavior (pH and temperature) was confirmed by dynamic light scattering (DLS) and turbidity measurements. The interaction of the hybrid nanoparticles with plasmid DNA at various N/P ratios (polymer nitrogen/DNA phosphorus) was investigated by DLS and zeta-potential measurements, indicating that for N/P ≥ 7.5 the complexes bear a positive net charge and do not undergo secondary aggregation. The hybrids were tested as transfection agents under standard conditions in CHO-K1 and L929 cells, revealing transfection efficiencies >50% and low cytotoxicity at N/P ratios of 10 and 15, respectively. Due to the magnetic properties of the hybrid gene vector, it is possible to collect most of the cells that have incorporated a sufficient amount of magnetic material by using a magnetic activated cell sorting system (MACS). Afterward, cells were further cultivated and displayed a transfection efficiency of ca. 60% together with a high viability. PMID:23889326

  3. Design of Gas-phase Synthesis of Core-Shell Particles by Computational Fluid – Aerosol Dynamics

    PubMed Central

    Buesser, B.; Pratsinis, S.E.

    2013-01-01

    Core-shell particles preserve the bulk properties (e.g. magnetic, optical) of the core while its surface is modified by a shell material. Continuous aerosol coating of core TiO2 nanoparticles with nanothin silicon dioxide shells by jet injection of hexamethyldisiloxane precursor vapor downstream of titania particle formation is elucidated by combining computational fluid and aerosol dynamics. The effect of inlet coating vapor concentration and mixing intensity on product shell thickness distribution is presented. Rapid mixing of the core aerosol with the shell precursor vapor facilitates efficient synthesis of hermetically coated core-shell nanoparticles. The predicted extent of hermetic coating shells is compared to the measured photocatalytic oxidation of isopropanol by such particles as hermetic SiO2 shells prevent the photocatalytic activity of titania. Finally the performance of a simpler, plug-flow coating model is assessed by comparisons to the present detailed CFD model in terms of coating efficiency and silica average shell thickness and texture. PMID:23729817

  4. Thermosensitive core-shell particles as model systems for studying the flow behavior of concentrated colloidal dispersions.

    PubMed

    Crassous, J J; Siebenbürger, M; Ballauff, M; Drechsler, M; Henrich, O; Fuchs, M

    2006-11-28

    We report on a comprehensive investigation of the flow behavior of colloidal thermosensitive core-shell particles at high densities. The particles consist of a solid core of poly(styrene) onto which a network of cross-linked poly(N-isopropylacrylamide) is affixed. Immersed in water the shell of these particles will swell if the temperature is low. Raising the temperature above 32 degrees C leads to a volume transition within this shell which leads to a marked shrinking of the shell. The particles have well-defined core-shell structure and a narrow size distribution. The remaining electrostatic interactions due to a small number of charges affixed to the core particles can be screened by adding 0.05M KCl to the suspensions. Below the lower critical solution temperature at 32 degrees C the particles are purely repulsive. Above this transition, a thermoreversible coagulation takes place. Lowering the temperature again leads to full dissociation of the aggregates formed by this process. The particles crystallize for effective volume fractions between 0.48 and 0.55. The crystallites can be molten by shear in order to reach a fluid sample again. The reduced shear stress measured in this metastable disordered state was found to be a unique function of the shear rate and the effective volume fraction. These reduced flow curves thus obtained can be described quantitatively by the theory of Fuchs and Cates [Phys. Rev. Lett. 89, 248304 (2002)] which is based on the mode-coupling theory of the glass transition. PMID:17144739

  5. Monodisperse and core-shell-structured SiO2@YBO3:Eu3+ spherical particles: synthesis and characterization.

    PubMed

    Lin, Cuikun; Kong, Deyan; Liu, Xiaoming; Wang, Huan; Yu, Min; Lin, Jun

    2007-04-01

    Y0.9Eu0.1BO3 phosphor layers were deposited on monodisperse SiO2 particles of different sizes (300, 570, 900, and 1200 nm) via a sol-gel process, resulting in the formation of core-shell-structured SiO2@Y0.9Eu0.1BO3 particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as lifetimes were employed to characterize the resulting composite particles. The results of XRD, FE-SEM, and TEM indicate that the 800 degrees C annealed sample consists of crystalline YBO3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. Under UV (240 nm) and VUV (172 nm) light or electron beam (1-6 kV) excitation, these particles show the characteristic 5D0-7F1-4 orange-red emission lines of Eu3+ with a quantum yield ranging from 36% (one-layer Y0.9Eu0.1BO3 on SiO2) to 54% (four-layer Y0.9Eu0.1BO3 on SiO2). The luminescence properties (emission intensity and color coordinates) of Eu3+ ions in the core-shell particles can be tuned by the coating number of Y0.9Eu0.1BO3 layers and SiO2 core particle size to some extent, pointing out the great potential for these particles applied in displaying and lightening fields. PMID:17338518

  6. Zn(II) and Cu(II) adsorption and retention onto iron oxyhydroxide nanoparticles: effects of particle aggregation and salinity

    PubMed Central

    2014-01-01

    Background Iron oxyhydroxides are commonly found in natural aqueous systems as nanoscale particles, where they can act as effective sorbents for dissolved metals due to their natural surface reactivity, small size and high surface area. These properties make nanoscale iron oxyhydroxides a relevant option for the remediation of water supplies contaminated with dissolved metals. However, natural geochemical processes, such as changes in ionic strength, pH, and temperature, can cause these particles to aggregate, thus affecting their sorption capabilities and remediation potential. Other environmental parameters such as increasing salinity may also impact metal retention, e.g. when particles are transported from freshwater to seawater. Results After using synthetic iron oxyhydroxide nanoparticles and nanoparticle aggregates in batch Zn(II) adsorption experiments, the addition of increasing concentrations of chloride (from 0.1 M to 0.6 M) appears to initially reduce Zn(II) retention, likely due to the desorption of outer-sphere zinc surface complexes and subsequent formation of aqueous Zn-Cl complexes, before then promoting Zn(II) retention, possibly through the formation of ternary surface complexes (supported by EXAFS spectroscopy) which stabilize zinc on the surface of the nanoparticles/aggregates. In batch Cu(II) adsorption experiments, Cu(II) retention reaches a maximum at 0.4 M chloride. Copper-chloride surface complexes are not indicated by EXAFS spectroscopy, but there is an increase in the formation of stable aqueous copper-chloride complexes as chloride concentration rises (with CuCl+ becoming dominant in solution at ~0.5 M chloride) that would potentially inhibit further sorption or encourage desorption. Instead, the presence of bidentate edge-sharing and monodentate corner-sharing complexes is supported by EXAFS spectroscopy. Increasing chloride concentration has more of an impact on zinc retention than the mechanism of nanoparticle aggregation, whereas

  7. Linker histone protects linker DNA on only one side of the core particle and in a sequence-dependent manner

    PubMed Central

    An, Woojin; Leuba, Sanford H.; van Holde, Kensal; Zlatanova, Jordanka

    1998-01-01

    The protection against micrococcal nuclease digestion afforded to chromatosomal DNA by the presence of a linker histone (H1o) has been quantitatively measured in two reconstituted systems. We have used chromatosomes reconstituted at two distinct positions on a DNA fragment containing the 5S rRNA gene from Lytechinus variegatus and at a specific position on a sequence containing Gal4- and USF-binding sites. In all cases, we find asymmetric protection, with ≈20 bp protected on one side of the core particle and no protection on the other. We demonstrated through crosslinking experiments that the result is not due to any sliding of the histone core caused by either linker histone addition or micrococcal nuclease cleavage. Because the core particle is itself a symmetric object, the preferred asymmetric location of a linker histone must be dictated by unknown elements in the DNA sequence. PMID:9520377

  8. Glass-NiP-CoFeP triplex-shell particles with hollow cores and tunable magnetic properties.

    PubMed

    An, Zhenguo; Zhang, Jingjie

    2013-02-01

    Low density (0.55-0.92g/mL, depending on the shell thickness and composition) glass-metal-metal triplex-shell hollow particles (TSHP) were prepared by a three-step route. First, micrometer-sized silicate glass particles with hollow cores, uniform shells, and high sphericity were prepared through spray drying and subsequent melting. NiP shell was uniformly assembled to the previously obtained glass hollow particles by silver seed induced chemical reduction of Ni(2+) by sodium hypophosphite, and glass-NiP double-shell hollow particles (DSHP) with compact and uniform shells were formed. The as-formed NiP particles further acted as the seeds for the directed formation and assembly of the CoFeP shell on the NiP shell to form the final glass-NiP-CoFeP triplex-shell hollow particles (TSHP). The influences of the component of the reaction system on the composition, structure, and magnetic properties of the hollow particles were studied. The multishell hollow particles thus obtained may have some promising applications in the fields of low-density magnetic materials, conduction, microwave absorbers, catalysis, etc. This work provides an additional strategy to fabricate multishell structured hollow particles with tailored shell composition and magnetic properties, which can be extended to the controlled preparation of multishell composite particles with the shells consisting of metal, oxides, or other compounds. PMID:23281871

  9. Investigation of high velocity separator for particle removal in coal gasification plants. Phase II report

    SciTech Connect

    Linhardt, H.D.

    1980-01-15

    This report summarizes the results of Phase II of the High Velocity Particle Separator Program performed under Contract EF-77-C-01-2709. This high velocity wedge separator has the potential to reduce equipment size and cost of high temperature and pressurized particulate removal equipment for coal derived gases. Phase II has been directed toward testing and detailed conceptual design of an element suitable for a commercial scale high temperature, high pressure particle separator (HTPS). Concurrently, Phase IA has been conducted, which utilized the ambient analog method (AAM) for aerodynamic and collection performance investigation of each HTPS configuration prior and during hot testing. This report summarizes the results of Phase IA and II. The AAM effort established correlation of theoretical analysis and experiment for HTPS pressure drop, purge flow ratio and collection efficiency potential. Task I defined the initial test conditions to be the contract design point of 1800/sup 0/F and 350 psia. The 1800/sup 0/F, 350 psia testing represents the main high temperature testing with coal-derived particulates in the 2 to 10 micron range. Phase IA and Phase II have demonstrated efficient particle collection with acceptable pressure drop. In view of these encouraging results, it is reasonable to apply the developed technology toward future hot gas particulate cleanup requirements.

  10. Substrate water exchange in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae.

    PubMed

    Nilsson, Håkan; Krupnik, Tomasz; Kargul, Joanna; Messinger, Johannes

    2014-08-01

    The binding affinity of the two substrate-water molecules to the water-oxidizing Mn₄CaO₅ catalyst in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae was studied in the S₂ and S₃ states by the exchange of bound ¹⁶O-substrate against ¹⁸O-labeled water. The rate of this exchange was detected via the membrane-inlet mass spectrometric analysis of flash-induced oxygen evolution. For both redox states a fast and slow phase of water-exchange was resolved at the mixed labeled m/z 34 mass peak: kf=52 ± 8s⁻¹ and ks=1.9 ± 0.3s⁻¹ in the S₂ state, and kf=42 ± 2s⁻¹ and kslow=1.2 ± 0.3s⁻¹ in S₃, respectively. Overall these exchange rates are similar to those observed previously with preparations of other organisms. The most remarkable finding is a significantly slower exchange at the fast substrate-water site in the S₂ state, which confirms beyond doubt that both substrate-water molecules are already bound in the S2 state. This leads to a very small change of the affinity for both the fast and the slowly exchanging substrates during the S₂→S₃ transition. Implications for recent models for water-oxidation are briefly discussed. PMID:24726350

  11. A zeaxanthin-independent nonphotochemical quenching mechanism localized in the photosystem II core complex.

    PubMed

    Finazzi, Giovanni; Johnson, Giles N; Dall'Osto, Luca; Dallosto, Luca; Joliot, Pierre; Wollman, Francis-André; Bassi, Roberto

    2004-08-17

    Illumination of dark-adapted barley plants with low light transiently induced a large nonphotochemical quenching of chlorophyll fluorescence. This reaction was identified as a form of high-energy-state quenching. Its appearance was not accompanied by zeaxanthin synthesis but was associated with a reversible inactivation of a fraction of photosystem II (PSII) centers. Both the fluorescence quenching and PSII inactivation relaxed in parallel with the activation of the Calvin cycle. We interpret the induction of this phenomenon as due to the generation of a quenched state in the PSII core complex. This reaction is probably caused by the transient overacidification of the thylakoid lumen, whereas its dissipation results from the relaxation of both the pH gradient across the thylakoid membrane and redox pressure upon activation of carbon fixation. At saturating light intensities, inactivation of PSII was still observed at the onset of illumination, although its recovery did not result in dissipation of high-energy quenching, which presents typical characteristics of an antenna-associated quenching at steady state. Reaction-center quenching seems therefore to be a common transient feature during illumination, being replaced by other phenomena (photochemical or antenna quenching and photoinhibition), depending on the balance between light and carbon fixation fluxes. PMID:15304641

  12. Fabrication and characterization of flaky core-shell particles by magnetron sputtering silver onto diatomite

    NASA Astrophysics Data System (ADS)

    Wang, Yuanyuan; Zhang, Deyuan; Cai, Jun

    2016-02-01

    Diatomite has delicate porous structures and various shapes, making them ideal templates for microscopic core-shell particles fabrication. In this study, a new process of magnetron sputtering assisted with photoresist positioning was proposed to fabricate lightweight silver coated porous diatomite with superior coating quality and performance. The diatomite has been treated with different sputtering time to investigate the silver film growing process on the surface. The morphologies, constituents, phase structures and surface roughness of the silver coated diatomite were analyzed with SEM, EDS, XRD and AFM respectively. The results showed that the optimized magnetron sputtering time was 8-16 min, under which the diatomite templates were successfully coated with uniform silver film, which exhibits face centered cubic (fcc) structure, and the initial porous structures were kept. Moreover, this silver coating has lower surface roughness (RMS 4.513 ± 0.2 nm) than that obtained by electroless plating (RMS 15.692 ± 0.5 nm). And the infrared emissivity of coatings made with magnetron sputtering and electroless plating silver coated diatomite can reach to the lowest value of 0.528 and 0.716 respectively.

  13. Use of novel phenyl-hexyl core-shell particles in nano-LC.

    PubMed

    Fanali, Salvatore; Rocchi, Silvia; Chankvetadze, Bezhan

    2013-06-01

    This paper reports the use of novel phenyl-hexyl core-shell particles packed into fused silica capillaries in nano-LC. Capillary columns of different id of 25, 50, 75, 100, and 150 μm were packed employing the slurry packing method. The columns were used for the separation of a model mixture containing five aromatic hydrocarbons. Benzene, toluene, ethylbenzene, n-propylbenzene, and n-butylbenzene were separated utilizing an isocratic elution mode. Mixtures of water/ACN at different ratio were studied to find optimal experimental conditions for baseline separation of all sample components. As expected with this novel stationary phase, an RP chromatographic mechanism was observed. A mixture of water/ACN, 30:70, v/v allowed the complete resolution of the studied analytes. Efficiency increased by decreasing the capillary id recording the highest number of plates per meter with capillaries of 25 μm id. The decrease of the column id also resulted in a flatter dependence of the plate numbers on the linear flow rate of the mobile phase allowing the increase of the flow rate of the mobile phase without significant decrease of efficiency. PMID:23423853

  14. Internal stresses in pre-stressed micron-scale aluminum core-shell particles and their improved reactivity

    SciTech Connect

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

    2015-09-07

    Dilatation of aluminum (Al) core for micron-scale particles covered by alumina (Al{sub 2}O{sub 3}) shell was measured utilizing x-ray diffraction with synchrotron radiation for untreated particles and particles after annealing at 573 K and fast quenching at 0.46 K/s. Such a treatment led to the increase in flame rate for Al + CuO composite by 32% and is consistent with theoretical predictions based on the melt-dispersion mechanism of reaction for Al particles. Experimental results confirmed theoretical estimates and proved that the improvement of Al reactivity is due to internal stresses. This opens new ways of controlling particle reactivity through creating and monitoring internal stresses.

  15. Light ion sources and target results on PBFA II (Particle Beam Fusion Accelerator II)

    SciTech Connect

    Cook, D.L.; Bailey, J.E.; Bieg, K.W.; Bloomquist, D.D.; Coats, R.S.; Chandler, G.C.; Cuneo, M.E.; Derzon, M.S.; Desjarlais, M.P.; Dreike, P.L.; Dukart, R.J.; Gerber, R.A.; Johnson, D.J.; Leeper, R.J.; Lockner, T.R.; McDaniel, D.H.; Maenchen, J.E.; Matzen, M.K.; Mehlhorn, T.A.; Mix, L.P.; Moats, A.R.; Nelson, W.E.; Pointon, T.D.; Pregenzer, A.L.; Quintenz, J.P.; Renk, T.J.; Rosenthal, S.E.; Ruiz, C.L.; Slutz, S.A.; Stinnett, R

    1990-01-01

    Advances in ion beam theory, diagnostics, and experiments in the past two years have enabled efficient generation of intense proton beams on PBFA II, and focusing of the beam power to 5.4 TW/cm{sup 2} on a 6-mm-diameter target. Target experiments have been started with the intense proton beams, since the range of protons at 4--5 MeV is equivalent to that of lithium at 30 MeV. Three series of experiments have been conducted using planar, conical, and cylindrical targets. These tests have provided information on ion beam power density, uniformity, and energy deposition. In order to increase the power density substantially for target implosion experiments, we are now concentrating on development of high voltage lithium ion beams. 10 refs., 13 figs.

  16. Fission product retention in TRISCO coated UO sub 2 particle fuels subjected to HTR simulated core heating tests

    SciTech Connect

    Baldwin, C.A.; Kania, M.J.

    1990-11-01

    Results of the examination and analysis of 25,730 individual microspheres from spherical fuel elements HFR-K3/1 and HFR-K3/3 are reported. The parent spheres were irradiated in excess of end-of-life exposure and subsequently subjected to simulated core heating tests in a special high-temperature furnace at Forschungszentrum, Juelich, GmbH (KFA). Following the heating tests, the spheres were electrolytically deconsolidated to obtain unbonded fuel particles for Irradiated Microsphere Gamma Analyzer (IMGA) analysis. For sphere HFR-K3/1, which was heated for 500 h at 1600{degree}C, only four particles were identified as having released fission products. The remaining particles from the sphere showed no statistical evidence of fission product release. Scanning Electron Microscopy (SEM) examination showed that three of the defect particles had large sections of the TRISO coating missing, while the fourth appeared normal. For sphere HFR-K3/3, which was heated for 100 h at 1800{degree}C, the IMGA data revealed that fission product release (cesium) from individual particles was significant and that there was large particle-to-particle variation in retention capabilities. Individual particle release (cesium) averaged ten times the KFA-measured integral spherical fuel element release value. In addition, the bimodal distribution of the individual particle data indicated that two distinct modes of failure at fuel temperatures of 1800{degree}C and above may exist. 6 refs., 6 figs., 4 tabs.

  17. The {alpha}-particle imaging of a compressed core of microtargets in a pinhole camera with a regular multi-pinhole diaphragm

    SciTech Connect

    Suslov, N A

    2000-08-31

    The {alpha}-particle imaging of a compressed core of microtargets using a multi-pinhole regular diaphragm is proposed. The image reconstruction technique is described. The results of the {alpha}-particle imaging of a compressed core of microtargets obtained at the 'Iskra-4' laser facility are reported. (interaction of laser radiation with matter. laser plasma)

  18. Fabrication of quantum dot/silica core-shell particles immobilizing Au nanoparticles and their dual imaging functions

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yoshio; Matsudo, Hiromu; Li, Ting-ting; Shibuya, Kyosuke; Kubota, Yohsuke; Oikawa, Takahiro; Nakagawa, Tomohiko; Gonda, Kohsuke

    2016-03-01

    The present work proposes preparation methods for quantum dot/silica (QD/SiO2) core-shell particles that immobilize Au nanoparticles (QD/SiO2/Au). A colloid solution of QD/SiO2 core-shell particles with an average size of 47.0 ± 6.1 nm was prepared by a sol-gel reaction of tetraethyl orthosilicate in the presence of the QDs with an average size of 10.3 ± 2.1 nm. A colloid solution of Au nanoparticles with an average size of 17.9 ± 1.3 nm was prepared by reducing Au3+ ions with sodium citrate in water at 80 °C. Introduction of amino groups to QD/SiO2 particle surfaces was performed using (3-aminopropyl)-triethoxysilane (QD/SiO2-NH2). The QD/SiO2/Au particles were fabricated by mixing the Au particle colloid solution and the QD/SiO2-NH2 particle colloid solution. Values of radiant efficiency and computed tomography for the QD/SiO2/Au particle colloid solution were 2.23 × 107 (p/s/cm2/sr)/(μW/cm2) at a QD concentration of 8 × 10-7 M and 1180 ± 314 Hounsfield units and an Au concentration of 5.4 × 10-2 M. The QD/SiO2/Au particle colloid solution was injected into a mouse chest wall. Fluorescence emitted from the colloid solution could be detected on the skin covering the chest wall. The colloid solution could also be X-ray-imaged in the chest wall. Consequently, the QD/SiO2/Au particle colloid solution was found to have dual functions, i.e., fluorescence emission and X-ray absorption in vivo, which makes the colloid solution suitable to function as a contrast agent for dual imaging processes.

  19. Host cellular annexin II is associated with cytomegalovirus particles isolated from cultured human fibroblasts.

    PubMed Central

    Wright, J F; Kurosky, A; Pryzdial, E L; Wasi, S

    1995-01-01

    A significant amount of host cellular annexin II was found to be associated with human cytomegalovirus isolated from cultured human fibroblasts (approximately 1,160 molecules per virion). This composition was established by four different analytical approaches that included (i) Western blot (immunoblot) analysis of gradient-purified virions with a monoclonal antibody specific for annexin II, (ii) peptide mapping and sequence analysis of virus-associated proteins and proteins dissociated from virus following EDTA treatment, (iii) electron microscopic immunocytochemistry of gradient-purified virions, and (iv) labeling of virus-associated proteins by lactoperoxidase-catalyzed radioiodination. These results indicated that annexin II was primarily localized to the viral surface, where it bound in a divalent cation-dependent manner. In functional experiments, a rabbit antiserum raised against annexin II inhibited cytomegalovirus plaque formation in human foreskin fibroblast monolayers in a concentration-dependent manner. Cumulatively, these studies demonstrate an association of host annexin II with cytomegalovirus particles and provide evidence for the involvement of this cellular protein in virus infectivity. PMID:7609045

  20. Self-Assembly of an Alphavirus Core-like Particle Is Distinguished by Strong Intersubunit Association Energy and Structural Defects.

    PubMed

    Wang, Joseph Che-Yen; Chen, Chao; Rayaprolu, Vamseedhar; Mukhopadhyay, Suchetana; Zlotnick, Adam

    2015-09-22

    Weak association energy can lead to uniform nanostructures: defects can anneal due to subunit lability. What happens when strong association energy leads to particles where defects are trapped? Alphaviruses are enveloped viruses whose icosahedral nucleocapsid core can assemble independently. We used a simplest case system to study Ross River virus (RRV) core-like particle (CLP) self-assembly using purified capsid protein and a short DNA oligomer. We find that capsid protein binds the oligomer with high affinity to form an assembly competent unit (U). Subsequently, U assembles with concentration dependence into CLPs. We determined that U-U pairwise interactions are very strong (ca. -6 kcal/mol) compared to other virus assembly systems. Assembled RRV CLPs appeared morphologically uniform and cryo-EM image reconstruction with imposed icosahedral symmetry yielded a T = 4 structure. However, 2D class averages of the CLPs show that virtually every class had disordered regions. These results suggested that irregular cores may be present in RRV virions. To test this hypothesis, we determined 2D class averages of RRV virions using authentic virions or only the core from intact virions isolated by computational masking. Virion-based class averages were symmetrical, geometric, and corresponded well to projections of image reconstructions. In core-based class averages, cores and envelope proteins in many classes were disordered. These results suggest that partly disordered components are common even in ostensibly well-ordered viruses, a biological realization of a patchy particle. Biological advantages of partly disordered complexes may arise from their ease of dissociation and asymmetry. PMID:26275088

  1. Modeling Lost-Particle Backgrounds in PEP-II Using LPTURTLE

    SciTech Connect

    Fieguth, T.; Barlow, R.; Kozanecki, W.; /DAPNIA, Saclay

    2005-05-17

    Background studies during the design, construction, commissioning, operation and improvement of BaBar and PEP-II have been greatly influenced by results from a program referred to as LPTURTLE (Lost Particle TURTLE) which was originally conceived for the purpose of studying gas background for SLC. This venerable program is still in use today. We describe its use, capabilities and improvements and refer to current results now being applied to BaBar.

  2. Coagulation of quartz particles in aqueous solutions of copper(II)

    SciTech Connect

    Larson, I.; Pugh, R.J.

    1998-12-15

    The colloidal stability of quartz suspension was determined over a wide range of pH in aqueous copper nitrate where the state of Cu(II) is changed from mainly aqua ions and monohydroxyl complexes in the acid and neutral pH to polynuclear hydroxo complexes and colloidal precipitated copper hydroxide at higher pH. Two regions of instability were observed and in both cases the particles were shown to have low electrophoretic mobility. In the neutral pH region, the uptake of Cu(II) was sufficient to reduce the mobility of the particles to zero, while in the high-pH region evidence suggested coagulation between precipitated Cu(OH){sub 2} and the quartz particles. It was shown that in all cases the coagulation was reversible and that the uptake of Cu(II) was dependent on the uncharged surface hydroxyl density. Studies of the coagulation kinetics showed that extended time scales were involved (several minutes in the neutral pH region to tens of minutes at high pH).

  3. Collapse and fragmentation of magnetic molecular cloud cores with the Enzo AMR MHD code. II. Prolate and oblate cores

    SciTech Connect

    Boss, Alan P.; Keiser, Sandra A.

    2014-10-10

    We present the results of a large suite of three-dimensional models of the collapse of magnetic molecular cloud cores using the adaptive mesh refinement code Enzo2.2 in the ideal magnetohydrodynamics approximation. The cloud cores are initially either prolate or oblate, centrally condensed clouds with masses of 1.73 or 2.73 M {sub ☉}, respectively. The radial density profiles are Gaussian, with central densities 20 times higher than boundary densities. A barotropic equation of state is used to represent the transition from low density isothermal phases, to high density optically thick phases. The initial magnetic field strength ranges from 6.3 to 100 μG, corresponding to clouds that are strongly to marginally supercritical, respectively, in terms of the mass to magnetic flux ratio. The magnetic field is initially uniform and aligned with the clouds' rotation axes, with initial ratios of rotational to gravitational energy ranging from 10{sup –4} to 0.1. Two significantly different outcomes for collapse result: (1) formation of single protostars with spiral arms, and (2) fragmentation into multiple protostar systems. The transition between these two outcomes depends primarily on the initial magnetic field strength, with fragmentation occurring for mass to flux ratios greater than about 14 times the critical ratio for prolate clouds. Oblate clouds typically fragment into several times more clumps than prolate clouds. Multiple, rather than binary, system formation is the general rule in either case, suggesting that binary stars are primarily the result of the orbital dissolution of multiple protostar systems.

  4. Rheological properties of magnetorheological suspensions based on core-shell structured polyaniline-coated carbonyl iron particles

    NASA Astrophysics Data System (ADS)

    Sedlačík, M.; Pavlínek, V.; Sáha, P.; Švrčinová, P.; Filip, P.; Stejskal, J.

    2010-11-01

    The sedimentation caused by the high density of suspended particles used in magnetorheological fluids is a significant obstacle for their wider application. In the present paper, core-shell structured carbonyl iron-polyaniline particles in silicone oil were used as a magnetorheological suspension with enhanced dispersion stability. Bare carbonyl iron particles were suspended in silicone oil to create model magnetorheological suspensions of different loading. For a magnetorheological suspension of polyaniline-coated particles the results show a decrease in the base viscosity. Moreover, the polyaniline coating has a negligible influence on the MR properties under an external magnetic field B. The change in the viscoelastic properties of magnetorheological suspensions in the small-strain oscillatory shear flow as a function of the strain amplitude, the frequency and the magnetic flux density was also investigated.

  5. Synthesis and Characterization of Monodisperse Metallodielectric SiO2@Pt@SiO2 Core-Shell-Shell Particles.

    PubMed

    Petrov, Alexey; Lehmann, Hauke; Finsel, Maik; Klinke, Christian; Weller, Horst; Vossmeyer, Tobias

    2016-01-26

    Metallodielectric nanostructured core-shell-shell particles are particularly desirable for enabling novel types of optical components, including narrow-band absorbers, narrow-band photodetectors, and thermal emitters, as well as new types of sensors and catalysts. Here, we present a facile approach for the preparation of submicron SiO2@Pt@SiO2 core-shell-shell particles. As shown by transmission and scanning electron microscopy, the first steps of this approach allow for the deposition of closed and almost perfectly smooth platinum shells onto silica cores via a seeded growth mechanism. By choosing appropriate conditions, the shell thickness could be adjusted precisely, ranging from ∼3 to ∼32 nm. As determined by X-ray diffraction, the crystalline domain sizes of the polycrystalline metal shells were ∼4 nm, regardless of the shell thickness. The platinum content of the particles was determined by atomic absorption spectroscopy and for thin shells consistent with a dense metal layer of the TEM-measured thickness. In addition, we show that the roughness of the platinum shell strongly depends on the storage time of the gold seeds used to initiate reductive platinum deposition. Further, using polyvinylpyrrolidone as adhesion layer, it was possible to coat the metallic shells with very homogeneous and smooth insulating silica shells of well-controlled thicknesses between ∼2 and ∼43 nm. After depositing the particles onto silicon substrates equipped with interdigitated electrode structures, the metallic character of the SiO2@Pt particles and the insulating character of the SiO2 shells of the SiO2@Pt@SiO2 particles were successfully demonstrated by charge transport measurements at variable temperatures. PMID:26731341

  6. Self-assembled HCV core virus-like particles targeted and inhibited tumor cell migration and invasion

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Xu, Xuehe; Jin, Aihui; Jia, Qunying; Zhou, Huaibin; Kang, Shuai; Lou, Yongliang; Gao, Jimin; Lu, Jianxin

    2013-09-01

    We used a baculovirus expression system to express fusion proteins of HCV core, RGD (Arg-Gly-Asp) peptide, and IFN-α2a fragments in Sf9 cells. Western blotting and electron microscopy demonstrate that HCV core, peptides RGD, and IFN-α2a fusion proteins assemble into 30 to 40 nm nano-particles (virus-like particles, VLPs). Xenograft assays show that VLPs greatly reduced tumor volume and weight with regard to a nontreated xenograft. Migration and invasion results show that VLPs can inhibit the migration and invasion of the breast cancer cells MDA-MB231. This study will provide theoretical and experimental basis for the establishment of safe and effective tumor-targeted drug delivery systems and clinical application of VLPs carrying cell interacting cargo.

  7. Kinetic evaluation of new generation of column packed with 1.3 μm core-shell particles.

    PubMed

    Fekete, Szabolcs; Guillarme, Davy

    2013-09-20

    The goal of this study was to critically evaluate a new generation of columns packed with 1.3 μm core-shell particles. The practical possibilities and limitations of this column technology were assessed and performance was compared with other reference columns packed with 1.7, 2.6 and 5 μm core-shell particles. The column efficiency achieved with 1.3 μm core-shell particles was indeed impressive, Hmin value of only 1.95 μm was achieved, this would correspond to an efficiency of more than 500,000 plates/m. The separation impedance of this column was particularly low, Emin=2000, mostly due to a reduced plate height, h of 1.50. Comparing the kinetic performance of 1.3 μm core-shell particles to that of other particle dimensions tested in this study revealed that the 1.3 μm material could provide systematically the shortest analysis time in a range of below 30,000 theoretical plates (N<30,000).Despite its excellent chromatographic performance, it was evident that this column suffers from the limitations of current instrumentation in terms of upper pressure limit and extra-column band broadening: (1) even at 1,200 bar, it was not possible to reach an optimal linear velocity showing minimal plate height value, due to the low permeability of this column (Kv=1.7×10(-11)cm(2)), and (2) for these short narrow bore columns packed with 1.3 μm core shell particles, which is mandatory for performing fast-analysis and preventing the influence of frictional heat on column performance in UHPLC, it was observed that the extra-column band broadening could have a major impact on the apparent kinetic performance. In the present work, significant plate count loss was noticed for retention factors of less than 5, even with the best system on the market (σ(2)ec=2 μL(2)). PMID:23953620

  8. Synthesis of TiO{sub 2} core/RuO{sub 2} shell particles using multistep ultrasonic spray pyrolysis

    SciTech Connect

    Stopic, Srecko; Friedrich, Bernd; Schroeder, Michael; Weirich, Thomas E.

    2013-09-01

    Graphical abstract: - Highlights: • TiO{sub 2} core/RuO{sub 2} shell submicron-particles were prepared via a sequential spray pyrolysis. • Spherical particles have the mean particle diameters between 200 and 400 nm. • This method is promising for synthesis of core–shell and core–multishell materials. - Abstract: Spherical submicron-particles with TiO{sub 2} core–RuO{sub 2} shell structure have been synthesized by employing sequential ultrasonic spray pyrolysis. The particles have been investigated by X-ray powder diffraction, scanning electron microscopy and different transmission electron microscopy techniques. The quality of the core–shell structure of the particles has been confirmed by comparison of the experimental data with those generated on the basis of a hard sphere core–shell model. It has been found that the mixing of the Ru-containing aerosol with the TiO{sub 2} particle stream has a significant impact on the core–shell formation. The method introduced in this study can probably be applied for preparation of core–shell and core–multishell materials that are difficult to synthesize in a single step spray pyrolysis process.

  9. Young Starless Cores Embedded in the Magnetically Dominated Pipe Nebula. II. Extended Data Set

    NASA Astrophysics Data System (ADS)

    Frau, P.; Girart, J. M.; Beltrán, M. T.; Padovani, M.; Busquet, G.; Morata, O.; Masqué, J. M.; Alves, F. O.; Sánchez-Monge, Á.; Franco, G. A. P.; Estalella, R.

    2012-11-01

    The Pipe nebula is a massive, nearby, filamentary dark molecular cloud with a low star formation efficiency threaded by a uniform magnetic field perpendicular to its main axis. It harbors more than a hundred, mostly quiescent, very chemically young starless cores. The cloud is therefore a good laboratory to study the earliest stages of the star formation process. We aim to investigate the primordial conditions and the relation among physical, chemical, and magnetic properties in the evolution of low-mass starless cores. We used the IRAM 30 m telescope to map the 1.2 mm dust continuum emission of five new starless cores, which are in good agreement with previous visual extinction maps. For the sample of nine cores, which includes the four cores studied in a previous work, we derived an A V to N_H_2 factor of (1.27 ± 0.12) × 10-21 mag cm2 and a background visual extinction of ~6.7 mag possibly arising from the cloud material. We derived an average core diameter of ~0.08 pc, density of ~105 cm-3, and mass of ~1.7 M ⊙. Several trends seem to exist related to increasing core density: (1) the diameter seems to shrink, (2) the mass seems to increase, and (3) the chemistry tends to be richer. No correlation is found between the direction of the surrounding diffuse medium magnetic field and the projected orientation of the cores, suggesting that large-scale magnetic fields seem to play a secondary role in shaping the cores. We also used the IRAM 30 m telescope to extend the previous molecular survey at 1 and 3 mm of early- and late-time molecules toward the same five new Pipe nebula starless cores, and analyzed the normalized intensities of the detected molecular transitions. We confirmed the chemical differentiation toward the sample and increased the number of molecular transitions of the "diffuse" (e.g., the "ubiquitous" CO, C2H, and CS), "oxo-sulfurated" (e.g., SO and CH3OH), and "deuterated" (e.g., N2H+, CN, and HCN) starless core groups. The chemically defined

  10. YOUNG STARLESS CORES EMBEDDED IN THE MAGNETICALLY DOMINATED PIPE NEBULA. II. EXTENDED DATA SET

    SciTech Connect

    Frau, P.; Girart, J. M.; Padovani, M.; Beltran, M. T.; Sanchez-Monge, A.; Busquet, G.; Morata, O.; Masque, J. M.; Estalella, R.; Alves, F. O.; Franco, G. A. P.

    2012-11-01

    The Pipe nebula is a massive, nearby, filamentary dark molecular cloud with a low star formation efficiency threaded by a uniform magnetic field perpendicular to its main axis. It harbors more than a hundred, mostly quiescent, very chemically young starless cores. The cloud is therefore a good laboratory to study the earliest stages of the star formation process. We aim to investigate the primordial conditions and the relation among physical, chemical, and magnetic properties in the evolution of low-mass starless cores. We used the IRAM 30 m telescope to map the 1.2 mm dust continuum emission of five new starless cores, which are in good agreement with previous visual extinction maps. For the sample of nine cores, which includes the four cores studied in a previous work, we derived an A {sub V} to N{sub H{sub 2}} factor of (1.27 {+-} 0.12) Multiplication-Sign 10{sup -21} mag cm{sup 2} and a background visual extinction of {approx}6.7 mag possibly arising from the cloud material. We derived an average core diameter of {approx}0.08 pc, density of {approx}10{sup 5} cm{sup -3}, and mass of {approx}1.7 M {sub Sun }. Several trends seem to exist related to increasing core density: (1) the diameter seems to shrink, (2) the mass seems to increase, and (3) the chemistry tends to be richer. No correlation is found between the direction of the surrounding diffuse medium magnetic field and the projected orientation of the cores, suggesting that large-scale magnetic fields seem to play a secondary role in shaping the cores. We also used the IRAM 30 m telescope to extend the previous molecular survey at 1 and 3 mm of early- and late-time molecules toward the same five new Pipe nebula starless cores, and analyzed the normalized intensities of the detected molecular transitions. We confirmed the chemical differentiation toward the sample and increased the number of molecular transitions of the 'diffuse' (e.g., the 'ubiquitous' CO, C{sub 2}H, and CS), 'oxo-sulfurated' (e.g., SO and

  11. Production of rotavirus core-like particles in Sf9 cells using recombinase-mediated cassette exchange.

    PubMed

    Fernandes, Fabiana; Dias, Mafalda M; Vidigal, João; Sousa, Marcos F Q; Patrone, Marco; Teixeira, Ana P; Alves, Paula M

    2014-02-10

    A flexible Sf9 insect cell line was recently developed leveraging the recombinase-mediated cassette exchange (RMCE) technology, which competes with the popular baculovirus expression vector system (BEVS) in terms of speed to produce new proteins. Herein, the ability of this cell platform to produce complex proteins, such as rotavirus core-like particles, was evaluated. A gene construct coding for a VP2-GFP fusion protein was targeted to a pre-characterized high recombination efficiency locus flanked by flipase (Flp) recognition target sites and, after three weeks in selection, an isogenic cell population was obtained. Despite the lower cell specific productivities with respect to those obtained by baculovirus infection, the titers of VP2-GFP reached in shake flask batch cultures were comparable as a result of higher cell densities. To further improve the VP2-GFP levels from stable expression, analysis of exhausted medium was undertaken to design feeding strategies enabling higher cell densities as well as increased culture duration. The implementation of the best strategy allowed reaching 20 million cells per ml in bioreactor cultures; the integrity of the rotavirus core-like particles could be confirmed by electron microscopy. Overall, we show that this Sf9-Flp cell platform represents a valuable alternative to the BEVS for producing complex recombinant proteins, such as rotavirus core-like particles. PMID:24333128

  12. Detection of DNA polymerase activities associated with purified duck hepatitis B virus core particles by using an activity gel assay.

    PubMed Central

    Oberhaus, S M; Newbold, J E

    1993-01-01

    Replication of hepadnaviruses involves reverse transcription of an intermediate RNA molecule. It is generally accepted that this replication scheme is carried out by a virally encoded, multifunctional polymerase which has DNA-dependent DNA polymerase, reverse transcriptase, and RNase H activities. Biochemical studies of the polymerase protein(s) have been limited by the inability to purify useful quantities of functional enzyme from virus particles and, until recently, to express enzymatically active polymerase proteins in heterologous systems. An activity gel assay which detects in situ catalytic activities of DNA polymerases after electrophoresis in partially denaturing polyacrylamide gels was used by M.R. Bavand and O. Laub (J. Virol. 62:626-628, 1988) to show the presence of DNA- and RNA-dependent DNA polymerase activities associated with hepatitis B virus particles produced in vitro. This assay has provided the only means by which hepadnavirus polymerase proteins have been detected in association with enzymatic activities. Since conventional methods have not allowed purification of useful quantities of enzymatically active polymerase protein(s), we have devised a protocol for purifying large quantities of duck hepatitis B virus (DHBV) core particles to near homogeneity. These immature virus particles contain DNA- and RNA-dependent DNA polymerase activities, as shown in the endogenous DNA polymerase assay. We have used the activity gel assay to detect multiple DNA- and RNA-dependent DNA polymerase proteins associated with these purified DHBV core particles. These enzymatically active proteins appear larger than, approximately the same size as, and smaller than an unmodified DHBV polymerase protein predicted from the polymerase open reading frame. This is the first report of the detection of active hepadnavirus core-associated DNA polymerase proteins derived from a natural host. Images PMID:8411359

  13. Development of polymer-biomolecule core-shell particles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Suthiwangcharoen, Nisaraporn

    Developing efficient strategies to introduce biomolecules around polymeric nanoparticles (NPs) is critical for targeted delivery of therapeutic or diagnostic agents. Although polymeric NPs have been well established, problems such as toxicity, stability, and immunoresistance remain potential concerns. The first part of this dissertation focuses on the development of nanosized targeted drug delivery vehicle in cancer chemotherapy. The vehicle was created by the self-assembly of folate-grafted filamentous bacteriophage M13 with poly(caprolactone- b-2-vinylpyridine) while doxorubicin, the antitumor drugs, was successfully loaded in the interior of the vehicles. These particles offer unique properties of being able to selectively target tumor cells while appearing to be safe and non-toxic to normal cells. Although they have shown great prospects in many biomedical applications, less is known about the interactions between biomolecules and polymers. The next part of the dissertation focuses on the self-assembly of proteins and polymers to create polymer-protein core-shell nanoparticles (PPCS-NPs). Several proteins with different isoelectric points and molecular weights were employed to demonstrate a versatility of our assembly method while a series of esterified derivatives of poly(2-hydroxyethyl methacrylate) (pHEMA) were synthesized to evaluate the interaction between proteins and polymers. Our data indicated that the polymers containing pyridine residues can successfully assemble with proteins, and the mechanism is mainly governed by hydrogen bonding and the hydrophobic/hydrophilic interactions. This in turn helps retaining proteins' folding conformation and functionality, which are also demonstrated in the in vitro/in vivo cellular uptake of the PPCS-NPs in endothelial cells. The last part of the dissertation focuses on the self-assembly of the bienzyme-polymer NPs. Glucose oxidase (GOX) together with horseradish peroxidase (HRP) were employed to construct bienzyme

  14. Extended-soft-core baryon-baryon model. II. Hyperon-nucleon interaction

    SciTech Connect

    Rijken, Th.A.; Yamamoto, Y.

    2006-04-15

    The YN results are presented from the extended soft-core (ESC) interactions. They consist of local and nonlocal potentials because of (i) one-boson exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial mesons; (ii) diffractive exchanges; (iii) two-pseudoscalar exchange; and (iv) meson-pair exchange (MPE). Both the OBE and pair vertices are regulated by Gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the baryon-baryon-meson (BBM) vertices is dependent on the SU(3) classification of the exchanged mesons for OBE and a similar scheme for MPE. The particular version of the ESC model, called ESC04 [T. A. Rijken, Phys. Rev. C 73, 044007 (2006)], describes nucleon-nucleon (NN) and hyperon-nucleon (YN) interactions in a unified way using broken SU(3) symmetry. Novel ingredients are the inclusion of (i) the axial-vector meson potentials and (ii) a zero in the scalar- and axial-vector meson form factors. These innovations made it possible for the first time to keep the parameters of the model close to the predictions of the {sup 3}P{sub 0} quark-antiquark creation model. This is also the case for the F/(F+D) ratios. Furthermore, the introduction of the zero helped to avoid the occurrence of unwanted bound states. Broken SU(3) symmetry serves to connect the NN and the YN channels, which leaves after fitting NN only a few free parameters for the determination of the YN interactions. In particular, the meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the NN analysis as input. Here, as a novel feature, medium-strong flavor-symmetry breaking (FSB) of the coupling constants was allowed, using the {sup 3}P{sub 0} model with a Gell-Mann-Okubo hypercharge breaking for the BBM coupling. Very good fits for ESC model with and without FSB were obtained. The charge-symmetry breaking in the {lambda}p and {lambda}n channels, which is an SU(2

  15. Extended-soft-core baryon-baryon model. II. Hyperon-nucleon interaction

    NASA Astrophysics Data System (ADS)

    Rijken, Th. A.; Yamamoto, Y.

    2006-04-01

    The YN results are presented from the extended soft-core (ESC) interactions. They consist of local and nonlocal potentials because of (i) one-boson exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial mesons; (ii) diffractive exchanges; (iii) two-pseudoscalar exchange; and (iv) meson-pair exchange (MPE). Both the OBE and pair vertices are regulated by Gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the baryon-baryon-meson (BBM) vertices is dependent on the SU(3) classification of the exchanged mesons for OBE and a similar scheme for MPE. The particular version of the ESC model, called ESC04 [T. A. Rijken, Phys. Rev. C 73, 044007 (2006)], describes nucleon-nucleon (NN) and hyperon-nucleon (YN) interactions in a unified way using broken SU(3) symmetry. Novel ingredients are the inclusion of (i) the axial-vector meson potentials and (ii) a zero in the scalar- and axial-vector meson form factors. These innovations made it possible for the first time to keep the parameters of the model close to the predictions of the 3P0 quark-antiquark creation model. This is also the case for the F/(F+D) ratios. Furthermore, the introduction of the zero helped to avoid the occurrence of unwanted bound states. Broken SU(3) symmetry serves to connect the NN and the YN channels, which leaves after fitting NN only a few free parameters for the determination of the YN interactions. In particular, the meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the NN analysis as input. Here, as a novel feature, medium-strong flavor-symmetry breaking (FSB) of the coupling constants was allowed, using the 3P0 model with a Gell-Mann-Okubo hypercharge breaking for the BBM coupling. Very good fits for ESC model with and without FSB were obtained. The charge-symmetry breaking in the Λp and Λn channels, which is an SU(2) isospin breaking, is included in the

  16. Iron(ii)-triazole core-shell nanocomposites: toward multistep spin crossover materials.

    PubMed

    Wang, Yu-Xia; Qiu, Dan; Xi, Sai-Fei; Ding, Zheng-Dong; Li, Zaijun; Li, Yunxing; Ren, Xuehong; Gu, Zhi-Guo

    2016-06-28

    The first SCO@SCO core-shell nanomaterials have been synthesized by the step-by-step microemulsion method. The observed gyroscopic core-shell nanocomposites exhibit three-step spin crossover behaviour with thermal hysteresis at around room temperature. This offers an efficient and novel strategy for the development of multistable SCO materials. PMID:27263855

  17. An assessment of the Arctic Ocean in a suite of interannual CORE-II simulations: Hydrography and fluxes

    NASA Astrophysics Data System (ADS)

    Ilicak, Mehmet; Drange, Helge

    2016-04-01

    We compare the simulated Arctic Ocean in fifteen global ocean-sea ice models in the framework of the Coordinated Ocean-ice Reference Experiments, phase II (CORE-II). Most of these models are the ocean and sea-ice components of the coupled climate models used in the Coupled Model Intercomparison Project Phase 5 (CMIP5) experiments. We mainly focus on the hydrography of the Arctic interior, the state of Atlantic Water layer and heat and volume transports at the gateways of the Davis Strait, the Bering Strait, the Fram Strait and the Barents Sea Opening. We found that there is a large spread in temperature in the Arctic Ocean between the models, and generally large differences compared to the observed temperature at intermediate depths. Warm bias models have a strong temperature anomaly of inflow of the Atlantic Water entering the Arctic Ocean through the Fram Strait. Another process that is not represented accurately in the CORE-II models is the formation of cold and dense water, originating on the eastern shelves. In the cold bias models, excessive cold water forms in the Barents Sea and spreads into the Arctic Ocean through the St. Anna Through. There is a large spread in the simulated mean heat and volume transports through the Fram Strait and the Barents Sea Opening. The models agree more on the decadal variability, to a large degree dictated by the common atmospheric forcing. We conclude that the CORE-II model study helps us to understand the crucial biases in the Arctic Ocean. The current coarse resolution state-of-the-art ocean models need to be improved in accurate representation of the Atlantic Water inflow into the Arctic and density currents coming from the shelves.

  18. An unusual chemical reactivity of Sm site adenosines strongly correlates with proper assembly of core U snRNP particles.

    PubMed

    Hartmuth, K; Raker, V A; Huber, J; Branlant, C; Lührmann, R

    1999-01-01

    The small nuclear ribonucleoprotein particles (snRNP) U1, U2, U4, and U5 contain a common set of eight Sm proteins that bind to the conserved single-stranded 5'-PuAU3-6GPu-3' (Sm binding site) region of their constituent U snRNA (small nuclear RNA), forming the Sm core RNP. Using native and in vitro reconstituted U1 snRNPs, accessibility of the RNA within the Sm core RNP to chemical structure probes was analyzed. Hydroxyl radical footprinting of in vitro reconstituted U1 snRNP demonstrated that riboses within a large continuous RNA region, including the Sm binding site, were protected. This protection was dependent on the binding of the Sm proteins. In contrast with the riboses, the phosphate groups within the Sm core site were accessible to modifying reagents. The invariant adenosine residue at the 5' end, as well as an adenosine two nucleotides downstream of the Sm binding site, showed an unexpected reactivity with dimethyl sulfate. This novel reactivity could be attributed to N7-methylation of the adenosine and was not observed in naked RNA, indicating that it is an intrinsic property of the RNA- protein interactions within the Sm core RNP. Further, this reactivity was observed concomitantly with formation of the Sm subcore intermediate during Sm core RNP assembly. As the Sm subcore can be viewed as the commitment complex in this assembly pathway, these results suggest that the peculiar reactivity of the Sm site adenosine bases may be diagnostic for proper assembly of the Sm core RNP. Consistent with this idea, a strong correlation was found between the unusual N7-A methylation sensitivity of the Sm core RNP and its ability to be imported into the nucleus of Xenopus laevis oocytes. PMID:9878394

  19. A novel concept of QUADRISO particles : Part II Utilization for excess reactivity control.

    SciTech Connect

    Talamo, A.

    2011-01-01

    In high temperature reactors, burnable absorbers are utilized to manage the excess reactivity at the early stage of the fuel cycle. In this paper QUADRISO particles are proposed to manage the initial excess reactivity of high temperature reactors. The QUADRISO concept synergistically couples the decrease of the burnable poison with the decrease of the fissile materials at the fuel particle level. This mechanism is set up by introducing a burnable poison layer around the fuel kernel in ordinary TRISO particles or by mixing the burnable poison with any of the TRISO coated layers. At the beginning of life, the initial excess reactivity is small because some neutrons are absorbed in the burnable poison and they are prevented from entering the fuel kernel. At the end of life, when the absorber is almost depleted, more neutrons stream into the fuel kernel of QUADRISO particles causing fission reactions. The mechanism has been applied to a prismatic high temperature reactor with europium or erbium burnable absorbers, showing a significant reduction in the initial excess reactivity of the core.

  20. A novel concept of QUADRISO particles. Part II: Utilization for excess reactivity control.

    SciTech Connect

    Talamo, A.

    2010-07-01

    In high temperature reactors, burnable absorbers are utilized to manage the excess reactivity at the early stage of the fuel cycle. In this paper QUADRISO particles are proposed to manage the initial excess reactivity of high temperature reactors. The QUADRISO concept synergistically couples the decrease of the burnable poison with the decrease of the fissile materials at the fuel particle level. This mechanism is set up by introducing a burnable poison layer around the fuel kernel in ordinary TRISO particles or by mixing the burnable poison with any of the TRISO coated layers. At the beginning of life, the initial excess reactivity is small because some neutrons are absorbed in the burnable poison and they are prevented from entering the fuel kernel. At the end of life, when the absorber is almost depleted, more neutrons stream into the fuel kernel of QUADRISO particles causing fission reactions. The mechanism has been applied to a prismatic high temperature reactor with europium or erbium burnable absorbers, showing a significant reduction in the initial excess reactivity of the core.

  1. Fe(I)-mediated reductive cleavage and coupling of CO2: An FeII(μ-O,μ -CO)FeII core

    PubMed Central

    Lu, Connie C.; Saouma, Caroline T.; Day, Michael W.; Peters, Jonas C.

    2008-01-01

    THF solutions of a new iron(I) source, “[PhBPCH2Cy3]Fe” ([PhBPCH2Cy3] = [PhBP(CH2P(CH2Cy)2)3]−), effect the reductive cleavage of CO2 via O-atom transfer at ambient temperature. The dominant reaction pathway is bimetallic and leads to the formation of a structurally unprecedented diiron FeII(μ-O)(μ-CO)FeII core. X-ray data are also available to suggest that bimetallic reductive CO2 coupling to generate oxalate occurs as a minor reaction pathway. These initial observations forecast a diverse reaction landscape between CO2 and iron (I) synthons. PMID:17199260

  2. Association of Coronal Mass Ejections and Type II Radio Bursts with Impulsive Solar Energetic Particle Events

    NASA Astrophysics Data System (ADS)

    Yashiro, S.; Gopalswamy, N.; Cliver, E. W.; Reames, D. V.; Kaiser, M. L.; Howard, R. A.

    2004-12-01

    We report the association of impulsive solar energetic particle (SEP) events with coronal mass ejections (CMEs) and metric type II radio bursts. We identified 38 impulsive SEP events using the WIND/EPACT instrument and their CME association was investigated using white light data from SOHO/LASCO. We found that (1) at least ˜ 28--39 % of impulsive SEP events were associated with CMEs, (2) only 8--13 % were associated with metric type II radio bursts. The statistical properties of the associated CMEs were investigated and compared with those of general CMEs and CMEs associated with large gradual SEP events. The CMEs associated with impulsive SEP events were significantly slower (median speed of 613 kmps) and narrower (49 deg) than those of CMEs associated with large gradual SEP events (1336 kmps, 360 deg), but faster than the general CMEs (408 kmps).

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

    PubMed

    Sarma, Dominik; Gawlitza, Kornelia; Rurack, Knut

    2016-04-19

    The need for rapid and high-throughput screening in analytical laboratories has led to significant growth in interest in suspension array technologies (SATs), especially with regard to cytometric assays targeting a low to medium number of analytes. Such SAT or bead-based assays rely on spherical objects that constitute the analytical platform. Usually, functionalized polymer or silica (SiO2) microbeads are used which each have distinct advantages and drawbacks. In this paper, we present a straightforward synthetic route to highly monodisperse SiO2-coated polystyrene core-shell (CS) beads for SAT with controllable architectures from smooth to raspberry- and multilayer-like shells by varying the molecular weight of poly(vinylpyrrolidone) (PVP), which was used as the stabilizer of the cores. The combination of both organic polymer core and a structurally controlled inorganic SiO2 shell in one hybrid particle holds great promises for flexible next-generation design of the spherical platform. The particles were characterized by electron microscopy (SEM, T-SEM, and TEM), thermogravimetry, flow cytometry, and nitrogen adsorption/desorption, offering comprehensive information on the composition, size, structure, and surface area. All particles show ideal cytometric detection patterns and facile handling due to the hybrid structure. The beads are endowed with straightforward modification possibilities through the defined SiO2 shells. We successfully implemented the particles in fluorometric SAT model assays, illustrating the benefits of tailored surface area which is readily available for small-molecule anchoring. Very promising assay performance was shown for DNA hybridization assays with quantification limits down to 8 fmol. PMID:27018430

  4. Ion beam generation and focusing on PBFA (Particle Beam Fusion Accelerator) II

    SciTech Connect

    Stinnett, R.W.; Bailey, J.E.; Bieg, K.W.; Coats, R.S.; Chandler, G.; Derzon, M.S.; Desjarlais, M.P.; Dreike, P.L.; Gerber, R.A.; Johnson, D.J.; Leeper, R.J.; Lockner, T.R.; Maenchen, J.; Mehlhorn, T.A.; Pregenzer, A.L.; Quintenz, J.P.; Renk, T.J.; Rosenthal, S.E.; Ruiz, C.L.; Slutz, S.A.; Stygar, W.A.; Tisone, G.C.; Woodworth, J.R. ); Maron, Y. (Weizmann Inst. of Science, R

    1990-01-01

    During the past year we have succeeded in obtaining a 5 TW/cm{sup 2} proton focus on Sandia National Laboratories' Particle Beam Fusion Accelerator (PBFA) II. This has allowed us to shift our experimental emphasis to the implementation of an improved ion diode geometry for higher voltage operation, full azimuthal beam characterization, and especially lithium ion source experiments. We have made significant progress in each of these areas during the past year, demonstrating 10 MV diode operation, {plus minus}10% azimuthal beam symmetry, and promising initial results from lithium ion source experiments. 8 refs., 6 figs.

  5. Particle identification using dE/dx in the Mark II detector at the SLC

    SciTech Connect

    Boyarski, A.; Coupal, D.P.; Feldman, G.J.; Hanson, G.; Nash, J.; O'Shaughnessy, K.F.; Rankin, P.; Van Kooten, R.

    1989-04-01

    The central drift chamber in the Mark II detector at the SLAC Linear Collider has been instrumented with 100-MHz Flash-ADCs. Pulse digitization provides particle identification through the measurement of average ionization loss in the chamber. We present the results of a study of system performance and outline the systematic corrections that optimize resolution. The data used are from a short test run at PEP with one-third of the FADCs installed and an extensive cosmic ray sample with the fully instrumented chamber. 11 refs., 9 figs.

  6. Correlating Type II and III Radio Bursts with Solar Energetic Particle Events

    NASA Astrophysics Data System (ADS)

    Ledbetter, K.; Winter, L. M.; Quinn, R. A.

    2013-12-01

    Solar energetic particles (SEPs) are high-energy particles, such as protons, which are accelerated at the Sun and speed outward into the solar system. If they reach Earth, they can be harmful to satellites, ionospheric communications, and humans in space or on polar airline routes. NOAA defines an SEP event as an occasion when the flux of protons with energies higher than 10 MeV exceeds 10 pfu (particle flux units) as measured by the GOES satellites in geosynchronous orbit. The most intense SEP events are associated with shocks, driven by coronal mass ejections (CMEs), which accelerate particles as they move through the corona. However, very few CMEs result in SEP events. To determine what factors are most important in distinguishing the shock waves that will result in SEP acceleration toward Earth, we take into account several variables and perform a principal component analysis (PCA) to examine their correlations. First, we examine Type II radio bursts, which are caused by electrons accelerating in the same CME-driven shocks that can accelerate SEPs. Using data from the WAVES instrument on the WIND satellite, these Type II radio bursts, as well as the Type III bursts that often accompany them, can be characterized by slope in 1/f space and by intensity. In addition, local Langmuir waves detected by WIND, which are caused by electrons speeding through the plasma surrounding the satellite, can be an indicator of the magnetic connectivity between the active region and Earth. Finally, X-ray flares directly preceding the Type II burst are also taken into consideration in the PCA analysis. The accompanying figure illustrates an example of the WAVES solar radio bursts along with the GOES solar proton flux >= 10 MeV during the SEP event on April 11, 2013. Using PCA to determine which of these factors are most relevant to the onset, intensity, and duration of SEP events will be valuable in future work to predict such events. In total, we present the analysis of all type

  7. Tailoring Sandwich Face/Core Interfaces for Improved Damage Tolerance—Part II: Experiments

    NASA Astrophysics Data System (ADS)

    Lundsgaard-Larsen, Christian; Berggreen, Christian; Carlsson, Leif A.

    2010-12-01

    A face/core debond in a sandwich structure may propagate in the interface or kink into either the face or core. It is found that certain modifications of the face/core interface region influence the kinking behavior, which is studied experimentally in the present paper. A sandwich double cantilever beam specimen loaded by uneven bending moments (DCB-UBM) allows for accurate measurements of the J integral as the crack propagates under large scale fibre bridging. By altering the mode-mixity of the loading, the crack path changes and deflects from the interface into the adjacent face or core. The transition points where the crack kinks are identified and the influence of four various interface design modifications on the propagation path and fracture resistance are investigated.

  8. A new tetranuclear copper(II) Schiff base complex containing Cu 4O 4 cubane core: Structural and spectral characterizations

    NASA Astrophysics Data System (ADS)

    Shit, Shyamapada; Rosair, Georgina; Mitra, Samiran

    2011-04-01

    A new tetra-nuclear coordination complex [Cu 4(HL) 4] ( 1) containing Cu 4O 4 cubane core has been synthesized by using Schiff base ligand [(OH)C 6H 4CH dbnd N sbnd C(CH 3)(CH 2OH) 2] (H 3L), obtained by the 1:1 condensation of 2-amino-2-methyl-1,3-propanediol with salicylaldehyde and thoroughly characterized by micro-analytical, FT-IR, UV-Vis, thermal and room temperature magnetic susceptibility measurements. Structural characterization of the complex has been done by single crystal X-ray diffraction analysis. Structural elucidation reveals versatile coordination modes for two identical alkoxo oxygen atoms of the Schiff base ligand; one in its deprotonated form exhibits μ 3-bridging to bind three similar copper(II) centers whilst the protonated one remains as monodentate or non-coordinating. Structural analysis also shows that the Cu 4O 4 cubane core in 1 consists of four μ 3-alkoxo oxygen bridged copper(II) atoms giving an approximately cubic array of alternating oxygen atoms and copper(II) atoms where the metal centers display both distorted square pyramidal and distorted octahedral geometries.

  9. Mobilization and preferential transport of soil particles during infiltration: A core-scale modeling approach

    NASA Astrophysics Data System (ADS)

    Majdalani, Samer; Michel, Eric; di Pietro, Liliana; Angulo-Jaramillo, Rafael; Rousseau, Marine

    2007-05-01

    Understanding particle movement in soils is a major concern for both geotechnics and soil physics with regard to environmental protection and water resources management. This paper describes a model for mobilization and preferential transport of soil particles through structured soils. The approach combines a kinematic-dispersive wave model for preferential water flow with a convective-dispersive equation subject to a source/sink term for particle transport and mobilization. Particle detachment from macropore walls is considered during both the steady and transient water flow regimes. It is assumed to follow first-order kinetics with a varying detachment efficiency, which depends on the history of the detachment process. Estimates of model parameters are obtained by comparing simulations with experimental particle breakthrough curves obtained during infiltrations through undisturbed soil columns. Both water flux and particle concentrations are satisfactorily simulated by the model. Particle mobilization parameters favoring both attachment and detachment of particles are related to the incoming solution ionic strength by a Fermi-type function.

  10. Preparation and characterization of core-shell structured TiO 2-BaCO 3 particles

    NASA Astrophysics Data System (ADS)

    Gablenz, Silvio; Damm, Cornelia; Müller, Franz Werner; Israel, Gunter; Rössel, Michael; Röder, Andreas; Abicht, Hans-Peter

    2001-03-01

    Preparation of core-shell structured TiO 2-BaCO 3 particles as precursor of BaTiO 3 genesis, proceeds using a two step procedure, by first coating the TiO 2 core by Ba(OH) 2 shell followed by conversion of the shell region with CO 2 gas by the formation of BaCO 3. Straightforward experimental results reveal environmental scanning electron microscopy (ESEM) and scanning transmission electron microscopy (STEM) as suitable methods for analytical characterization of the core and shell regions from individual TiO 2-BaCO 3 grains. Evidence of coating the whole ensemble of TiO 2 particles is possible using Photo Electro Motive Force (Photo EMF, PEMF) measurements. This method is able to indicate very sensitively changes of surface properties of TiO 2 after coating with Ba(OH) 2 and BaCO 3, respectively. PEMF measurements were used for the first time with concern to this topic.

  11. TRIGGERING COLLAPSE OF THE PRESOLAR DENSE CLOUD CORE AND INJECTING SHORT-LIVED RADIOISOTOPES WITH A SHOCK WAVE. II. VARIED SHOCK WAVE AND CLOUD CORE PARAMETERS

    SciTech Connect

    Boss, Alan P.; Keiser, Sandra A. E-mail: keiser@dtm.ciw.edu

    2013-06-10

    A variety of stellar sources have been proposed for the origin of the short-lived radioisotopes that existed at the time of the formation of the earliest solar system solids, including Type II supernovae (SNe), asymptotic giant branch (AGB) and super-AGB stars, and Wolf-Rayet star winds. Our previous adaptive mesh hydrodynamics models with the FLASH2.5 code have shown which combinations of shock wave parameters are able to simultaneously trigger the gravitational collapse of a target dense cloud core and inject significant amounts of shock wave gas and dust, showing that thin SN shocks may be uniquely suited for the task. However, recent meteoritical studies have weakened the case for a direct SN injection to the presolar cloud, motivating us to re-examine a wider range of shock wave and cloud core parameters, including rotation, in order to better estimate the injection efficiencies for a variety of stellar sources. We find that SN shocks remain as the most promising stellar source, though planetary nebulae resulting from AGB star evolution cannot be conclusively ruled out. Wolf-Rayet (WR) star winds, however, are likely to lead to cloud core shredding, rather than to collapse. Injection efficiencies can be increased when the cloud is rotating about an axis aligned with the direction of the shock wave, by as much as a factor of {approx}10. The amount of gas and dust accreted from the post-shock wind can exceed that injected from the shock wave, with implications for the isotopic abundances expected for a SN source.

  12. Influence of core size on the upconversion luminescence properties of spherical Gd{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+}@SiO{sub 2} particles with core-shell structures

    SciTech Connect

    Zheng, Kezhi; Liu, Zhenyu; Liu, Ye; Song, Weiye; Qin, Weiping

    2013-11-14

    Spherical SiO{sub 2} particles with different sizes (30, 80, 120, and 180 nm) have been coated with Gd{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} layers by a heterogeneous precipitation method, leading to the formation of core-shell structural Gd{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+}@SiO{sub 2} particles. The samples were characterized by using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, upconversion (UC) emission spectra, and fluorescent dynamical analysis. The obtained core-shell particles have perfect spherical shape with narrow size distribution. Under the excitation of 980 nm diode laser, the core-shell samples showed size-dependent upconversion luminescence (UCL) properties. The inner SiO{sub 2} cores in core-shell samples were proved to have limited effect on the total UCL intensities of Er{sup 3+} ions. The UCL intensities of core-shell particles were demonstrated much higher than the values obtained in pure Gd{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} with the same phosphor volume. The dependence of the specific area of a UCL shell on the size of its inner SiO{sub 2} particle was calculated and analyzed for the first time. It was confirmed that the surface effect came from the outer surfaces of emitting shells is dominant in influencing the UCL property in the core-shell samples. Three-photon UC processes for the green emissions were observed in the samples with small sizes of SiO{sub 2} cores. The results of dynamical analysis illustrated that more nonradiative relaxation occurred in the core-shell samples with smaller SiO{sub 2} core sizes.

  13. Influence of core size on the upconversion luminescence properties of spherical Gd2O3:Yb3+/Er3+@SiO2 particles with core-shell structures

    NASA Astrophysics Data System (ADS)

    Zheng, Kezhi; Liu, Zhenyu; Liu, Ye; Song, Weiye; Qin, Weiping

    2013-11-01

    Spherical SiO2 particles with different sizes (30, 80, 120, and 180 nm) have been coated with Gd2O3:Yb3+/Er3+ layers by a heterogeneous precipitation method, leading to the formation of core-shell structural Gd2O3:Yb3+/Er3+@SiO2 particles. The samples were characterized by using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, upconversion (UC) emission spectra, and fluorescent dynamical analysis. The obtained core-shell particles have perfect spherical shape with narrow size distribution. Under the excitation of 980 nm diode laser, the core-shell samples showed size-dependent upconversion luminescence (UCL) properties. The inner SiO2 cores in core-shell samples were proved to have limited effect on the total UCL intensities of Er3+ ions. The UCL intensities of core-shell particles were demonstrated much higher than the values obtained in pure Gd2O3:Yb3+/Er3+ with the same phosphor volume. The dependence of the specific area of a UCL shell on the size of its inner SiO2 particle was calculated and analyzed for the first time. It was confirmed that the surface effect came from the outer surfaces of emitting shells is dominant in influencing the UCL property in the core-shell samples. Three-photon UC processes for the green emissions were observed in the samples with small sizes of SiO2 cores. The results of dynamical analysis illustrated that more nonradiative relaxation occurred in the core-shell samples with smaller SiO2 core sizes.

  14. Models of molecular cloud cores. II. Multitransition study of CS-34

    SciTech Connect

    Mundy, L.G.; Evans, N.J.,II; Snell, R.L.; Goldsmith, P.F.; Bally, J.

    1986-07-01

    The dense cores embedded in the M17, S140 and NGC 2024 molecular clouds are mapped in the J = 5-4, J = 3-2, and J = 2-1 transitions of CS-34, and these lines are found to be a factor of 3-4 weaker, and 25 percent narrower, than the CS lines mapped in these cores by Snell et al. (1984). The data are well fitted by spherical LGV models for the excitation, and the excellent correlation between the CS-34 and CS column densities corroborates the absence of a systematic increase in the gas density with decreasing core radius found by Snell et al. Though the CS/CS-34 column density ratio is 9-17, rather than the terrestrial value of 22.5, the column density relationship is linear. The data support of a clump model in which the column density distribution in the core is determined by the volume filling factor of clumps with high, fairly uniform gas density, and it is suggested that the dense gas in the data represents the dominant component of the core gas. 22 references.

  15. NON-EQUILIBRIUM CHEMISTRY OF DYNAMICALLY EVOLVING PRESTELLAR CORES. II. IONIZATION AND MAGNETIC FIELD

    SciTech Connect

    Tassis, Konstantinos; Willacy, Karen; Yorke, Harold W.; Turner, Neal J.

    2012-07-20

    We study the effect that non-equilibrium chemistry in dynamical models of collapsing molecular cloud cores has on measurements of the magnetic field in these cores, the degree of ionization, and the mean molecular weight of ions. We find that OH and CN, usually used in Zeeman observations of the line-of-sight magnetic field, have an abundance that decreases toward the center of the core much faster than the density increases. As a result, Zeeman observations tend to sample the outer layers of the core and consistently underestimate the core magnetic field. The degree of ionization follows a complicated dependence on the number density at central densities up to 10{sup 5} cm{sup -3} for magnetic models and 10{sup 6} cm{sup -3} in non-magnetic models. At higher central densities, the scaling approaches a power law with a slope of -0.6 and a normalization which depends on the cosmic-ray ionization rate {zeta} and the temperature T as ({zeta}T){sup 1/2}. The mean molecular weight of ions is systematically lower than the usually assumed value of 20-30, and, at high densities, approaches a value of 3 due to the asymptotic dominance of the H{sup +}{sub 3} ion. This significantly lower value implies that ambipolar diffusion operates faster.

  16. High angular resolution far-infrared and submillimeter mapping survey of the dust cores associated with ultracompact H II regions

    NASA Technical Reports Server (NTRS)

    Phillips, T. G.

    1995-01-01

    The primary objective of the research funded under this grant has been to perform a high angular resolution mapping survey of the far-infrared and submillimeter continuum emission from the dust cocoons surrounding young, deeply embedded massive stars and the ultracompact H II regions they create. The high infrared, submillimeter, and radio luminosity makes the ultracompact H II regions ideal tracers of current high-mass star formation. Detailed investigations of their structure, evolution, and interaction with their parent molecular clouds are thus important for understanding the early evolutionary phases of massive main sequence stars, the nature of the dense molecular cores in which they form, and the relationship to coeval low-mass star formation.

  17. A unified N-body and statistical treatment of stellar dynamics. I - The hybrid code. II - Applications to globular cluster cores

    NASA Technical Reports Server (NTRS)

    Mcmillan, S. L. W.; Lightman, A. P.

    1984-01-01

    A unified N-body and statistical treatment of stellar dynamics is developed and applied to the late stages of core collapse and early stages of post collapse evolution in globular clusters. A 'hybrid' computer code is joined to a direct N-body code which is used to calculate exactly the behavior of particles in the inner spatial region, and the combination is used to follow particles statistically in the outer spatial region. A transition zone allows the exchange of particles and energy between the two regions. The main application results include: formation of a hard central binary system, reversal of core collapse and expansion due to the heat input from this binary, ejection of the binary from the core, and recollapse of the core; density profiles that form a one-parameter sequence during the core oscillations; and indications that these oscillations will eventually cease.

  18. Nonlinear behavior of solar gravity modes driven by He-3 in the core. II - Numerical simulations

    NASA Astrophysics Data System (ADS)

    Merryfield, William J.; Gough, Douglas; Toomre, Juri

    1991-02-01

    The nonlinear behavior of gravity-mode oscillations driven by He-3-destroying reactions in the solar core has been examined by numerically integrating equations describing a very simplified model. The results of a previous bifurcation analysis, which suggest that such oscillations are unlikely to attain amplitudes sufficient to trigger core convection, are verified. These results are extended to models whose nuclear reaction rates and thermal stratification represent the core somewhat more accurately. Nonlinear processes give rise to a preference for the oscillations to develop as standing waves rather than traveling waves, thus breaking the degeneracy between these two types of motion which exists in linearized theory. Study of the large-amplitude behavior of the oscillations is hindered by a tendency for the model to become thermally unstable.

  19. Theory of self-resonance after inflation. II. Quantum mechanics and particle-antiparticle asymmetry

    NASA Astrophysics Data System (ADS)

    Hertzberg, Mark P.; Karouby, Johanna; Spitzer, William G.; Becerra, Juana C.; Li, Lanqing

    2014-12-01

    We further develop a theory of self-resonance after inflation in a large class of models involving multiple scalar fields. We concentrate on inflaton potentials that carry an internal symmetry, but also analyze weak breaking of this symmetry. This is the second part of a two-part series of papers. Here in Part 2 we develop an understanding of the resonance structure from the underlying many-particle quantum mechanics. We begin with a small-amplitude analysis, which obtains the central resonant wave numbers, and relate it to perturbative processes. We show that the dominant resonance structure is determined by (i) the nonrelativistic scattering of many quantum particles and (ii) the application of Bose-Einstein statistics to the adiabatic and isocurvature modes, as introduced in Part 1 [M. P. Hertzberg et al., Phys. Rev. D 90, 123528 (2014)]. Other resonance structures are understood in terms of annihilations and decays. We set up Bunch-Davies vacuum initial conditions during inflation and track the evolution of modes including Hubble expansion. In the case of a complex inflaton carrying an internal U(1) symmetry, we show that when the isocurvature instability is active, the inflaton fragments into separate regions of ϕ -particles and anti-ϕ -particles. We then introduce a weak breaking of the U(1) symmetry; this can lead to baryogenesis, as shown by some of us recently [M. P. Hertzberg and J. Karouby, Phys. Lett. B 737, 34 (2014); Phys. Rev. D 89, 063523 (2014)]. Then using our results, we compute corrections to the particle-antiparticle asymmetry from this preheating era.

  20. Particle identification performance of the prototype aerogel RICH counter for the Belle II experiment

    NASA Astrophysics Data System (ADS)

    Iwata, S.; Adachi, I.; Hara, K.; Iijima, T.; Ikeda, H.; Kakuno, H.; Kawai, H.; Kawasaki, T.; Korpar, S.; Križan, P.; Kumita, T.; Nishida, S.; Ogawa, S.; Pestotnik, R.; Šantelj, L.; Seljak, A.; Sumiyoshi, T.; Tabata, M.; Tahirovic, E.; Yusa, Y.

    2016-03-01

    We have developed a new type of particle identification device, called an aerogel ring imaging Cherenkov (ARICH) counter, for the Belle II experiment. It uses silica aerogel tiles as Cherenkov radiators. For detection of Cherenkov photons, hybrid avalanche photo-detectors (HAPDs) are used. The designed HAPD has a high sensitivity to single photons under a strong magnetic field. We have confirmed that the HAPD provides high efficiency for single-photon detection even after exposure to neutron and γ -ray radiation that exceeds the levels expected in the 10-year Belle II operation. In order to confirm the basic performance of the ARICH counter system, we carried out a beam test at the using a prototype of the ARICH counter with six HAPD modules. The results are in agreement with our expectations and confirm the suitability of the ARICH counter for the Belle II experiment. Based on the in-beam performance of the device, we expect that the identification efficiency at 3.5 GeV/c is 97.4% and 4.9% for pions and kaons, respectively. This paper summarizes the development of the HAPD for the ARICH and the evaluation of the performance of the prototype ARICH counter built with the final design components.

  1. Hollow-core photonic crystal fiber based multifunctional optical system for trapping, position sensing, and detection of fluorescent particles.

    PubMed

    Shinoj, V K; Murukeshan, V M

    2012-05-15

    We demonstrate a novel multifunctional optical system that is capable of trapping, imaging, position sensing, and fluorescence detection of micrometer-sized fluorescent test particles using hollow-core photonic crystal fiber (HC-PCF). This multifunctional optical system for trapping, position sensing, and fluorescent detection is designed such that a near-IR laser light is used to create an optical trap across a liquid-filled HC-PCF, and a 473 nm laser is employed as a source for fluorescence excitation. This proposed system and the obtained results are expected to significantly enable an efficient integrated trapping platform employing HC-PCF for diagnostic biomedical applications. PMID:22627511

  2. High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer’s disease

    PubMed Central

    Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F.; Arellano-Jiménez, M. Josefina; Zhu, Xiongwei; Rogers, Jack T.; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

    2016-01-01

    Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles. PMID:27121137

  3. High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer's disease.

    PubMed

    Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F; Arellano-Jiménez, M Josefina; Zhu, Xiongwei; Rogers, Jack T; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

    2016-01-01

    Abnormal accumulation of brain metals is a key feature of Alzheimer's disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles. PMID:27121137

  4. An atomic model AAA-ATPase/20S core particle sub-complex of the 26S proteasome

    SciTech Connect

    Foerster, Friedrich; Lasker, Keren; Beck, Florian; Nickell, Stephan; Sali, Andrej; Baumeister, Wolfgang

    2009-10-16

    The 26S proteasome is the most downstream element of the ubiquitin-proteasome pathway of protein degradation. It is composed of the 20S core particle (CP) and the 19S regulatory particle (RP). The RP consists of 6 AAA-ATPases and at least 13 non-ATPase subunits. Based on a cryo-EM map of the 26S proteasome, structures of homologs, and physical protein-protein interactions we derive an atomic model of the AAA-ATPase-CP sub-complex. The ATPase order in our model (Rpt1/Rpt2/Rpt6/Rpt3/Rpt4/Rpt5) is in excellent agreement with the recently identified base-precursor complexes formed during the assembly of the RP. Furthermore, the atomic CP-AAA-ATPase model suggests that the assembly chaperone Nas6 facilitates CP-RP association by enhancing the shape complementarity between Rpt3 and its binding CP alpha subunits partners.

  5. High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer’s disease

    NASA Astrophysics Data System (ADS)

    Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F.; Arellano-Jiménez, M. Josefina; Zhu, Xiongwei; Rogers, Jack T.; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

    2016-04-01

    Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles.

  6. An atomic model AAA-ATPase/20S core particle sub-complex of the 26S proteasome.

    PubMed

    Förster, Friedrich; Lasker, Keren; Beck, Florian; Nickell, Stephan; Sali, Andrej; Baumeister, Wolfgang

    2009-10-16

    The 26S proteasome is the most downstream element of the ubiquitin-proteasome pathway of protein degradation. It is composed of the 20S core particle (CP) and the 19S regulatory particle (RP). The RP consists of 6 AAA-ATPases and at least 13 non-ATPase subunits. Based on a cryo-EM map of the 26S proteasome, structures of homologs, and physical protein-protein interactions we derive an atomic model of the AAA-ATPase-CP sub-complex. The ATPase order in our model (Rpt1/Rpt2/Rpt6/Rpt3/Rpt4/Rpt5) is in excellent agreement with the recently identified base-precursor complexes formed during the assembly of the RP. Furthermore, the atomic CP-AAA-ATPase model suggests that the assembly chaperone Nas6 facilitates CP-RP association by enhancing the shape complementarity between Rpt3 and its binding CP alpha subunits partners. PMID:19653995

  7. Core II Materials for Metropolitan Agriculture/Horticulture Programs. Units G-L.

    ERIC Educational Resources Information Center

    Biondo, Ron; And Others

    This second volume of a 2-volume curriculum guide contains 12 problem areas selected as suggested areas of study to be included in a core curriculum for 10th-grade or second-year students enrolled in a metropolitan agriculture program. The 12 problem areas are divided into 5 units: Growing and Managing Horticultural Crops (4 problem areas),…

  8. Core II Materials for Rural Agriculture Programs. Units E-H.

    ERIC Educational Resources Information Center

    Biondo, Ron; And Others

    This curriculum guide includes teaching packets for 21 problem areas to be included in a core curriculum for 10th grade students enrolled in a rural agricultural program. Covered in the four units included in this volume are crop science (harvesting farm crops and growing small grains); soil science and conservation of natural resources…

  9. Core II Materials for Rural Agricultural Programs. Units A-D.

    ERIC Educational Resources Information Center

    Biondo, Ron; And Others

    This curriculum guide includes teaching packets for 21 problem areas to be included in a core curriculum for 10th-grade students enrolled in a rural agricultural program. Covered in the four units included in this volume are orientation to agricultural occupations (orientation to vocational agricultural course and developing effective study…

  10. Synthesis of polystyrene/polysilsesquioxane core/shell composite particles via emulsion polymerization in the existence of poly(γ-methacryloxypropyl trimethoxysilane) sol.

    PubMed

    Yang, Shenglin; Song, Chunfeng; Qiu, Teng; Guo, Longhai; Li, Xiaoyu

    2013-01-01

    Here, we synthesized the polystyrene/polysilsesquioxane (PS/PSQ) core/shell latex particles via emulsion polymerization, which behave as an amusing morphology. First, the nanosized PSQ particles were prepared by the hydrolysis-condensation reaction of γ-methacryloxypropyl trimethoxysilane (MPTS) in ethanol medium. Subsequently, the as-obtained methacryloxypropylene functionalized PSQ (PMPTS) sol was directly added into the emulsion system of styrene (St) monomer, and PS/PSQ composite particles with core/shell structure were obtained through emulsion polymerization. We found that the structure of the composite particles can be affected by the synthesis parameters such as reaction time, content of PMPTS added in the reaction, amount of coemulsifier, and the pH value of emulsion system, which were systemically explored by transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and thermogravimetric analysis (TGA) in this work. These results indicate that the PMPTS particles in the size of about 5 nm could first absorb onto the surface of PS latex particles so as to assemble in a strawberry-like morphology. The further coalescence among the PMPTS particles would result in a continuous PMPTS shell around the PS core. Moreover, the hollow PSQ capsules were prepared after extraction of the PS core by organic solvent, further confirming the core/shell structure of the as-synthesized PS/PMPTS particles. Meanwhile, we also explored the application of the PS/PSQ core/shell particles as a new kind of Pickering emulsifier in the emulsion polymerization of St, and composite particles with complex patchy morphologies have been obtained finally under different ratios of styrene monomer to PS/PMPTS colloidal emulsifier. PMID:23231420

  11. Highly efficient near-infrared light-emitting diodes by using type-II CdTe/CdSe core/shell quantum dots as a phosphor.

    PubMed

    Shen, Huaibin; Zheng, Ying; Wang, Hongzhe; Xu, Weiwei; Qian, Lei; Yang, Yixing; Titov, Alexandre; Hyvonen, Jake; Li, Lin Song

    2013-11-29

    In this paper, we present an innovative method for the synthesis of CdTe/CdSe type-II core/shell structure quantum dots (QDs) using 'greener' chemicals. The PL of CdTe/CdSe type-II core/shell structure QDs ranges from 600 to 820 nm, and the as-synthesized core/shell structures show narrow size distributions and stable and high quantum yields (50–75%). Highly efficient near-infrared light-emitting diodes (LEDs) have been demonstrated by employing the CdTe/CdSe type-II core/shell QDs as emitters. The devices fabricated based on these type-II core/shell QDs show color-saturated near-infrared emission from the QD layers, a low turn-on voltage of 1.55 V, an external quantum efficiency (EQE) of 1.59%, and a current density and maximum radiant emittance of 2.1 × 10(3) mA cm−2 and 17.7 mW cm−2 at 8 V; it is the first report to use type-II core/shell QDs as near-infrared emitters and these results may offer a practicable platform for the realization of near-infrared QD-based light-emitting diodes, night-vision-readable displays, and friend/foe identification system. PMID:24192490

  12. Highly efficient near-infrared light-emitting diodes by using type-II CdTe/CdSe core/shell quantum dots as a phosphor

    NASA Astrophysics Data System (ADS)

    Shen, Huaibin; Zheng, Ying; Wang, Hongzhe; Xu, Weiwei; Qian, Lei; Yang, Yixing; Titov, Alexandre; Hyvonen, Jake; Li, Lin Song

    2013-11-01

    In this paper, we present an innovative method for the synthesis of CdTe/CdSe type-II core/shell structure quantum dots (QDs) using ‘greener’ chemicals. The PL of CdTe/CdSe type-II core/shell structure QDs ranges from 600 to 820 nm, and the as-synthesized core/shell structures show narrow size distributions and stable and high quantum yields (50-75%). Highly efficient near-infrared light-emitting diodes (LEDs) have been demonstrated by employing the CdTe/CdSe type-II core/shell QDs as emitters. The devices fabricated based on these type-II core/shell QDs show color-saturated near-infrared emission from the QD layers, a low turn-on voltage of 1.55 V, an external quantum efficiency (EQE) of 1.59%, and a current density and maximum radiant emittance of 2.1 × 103 mA cm-2 and 17.7 mW cm-2 at 8 V it is the first report to use type-II core/shell QDs as near-infrared emitters and these results may offer a practicable platform for the realization of near-infrared QD-based light-emitting diodes, night-vision-readable displays, and friend/foe identification system.

  13. Core and grain boundary sensitivity of tungsten-oxide sensor devices by molecular beam assisted particle deposition

    NASA Astrophysics Data System (ADS)

    Huelser, T. P.; Lorke, A.; Ifeacho, P.; Wiggers, H.; Schulz, C.

    2007-12-01

    In this study, we investigate the synthesis of WO3 and WOx (2.6≥x≤2.8) by adding different concentrations of tungsten hexafluoride (WF6) into a H2/O2/Ar premixed flame within a low-pressure reactor equipped with a particle-mass spectrometer (PMS). The PMS results show that mean particle diameters dp between 5 and 9 nm of the as-synthesized metal-oxides can be obtained by varying the residence time and precursor concentration in the reactor. This result is further validated by N2 adsorption measurements on the particle surface, which yielded a 91 m2/g surface area, corresponding to a spherical particle diameter of 9 nm (Brunauer-Emmett-Teller technique). H2/O2 ratios of 1.6 and 0.63 are selected to influence the stoichiometry of the powders, resulting in blue-colored WOx and white WO3 respectively. X-ray diffraction (XRD) analysis of the as-synthesized materials indicates that the powders are mostly amorphous, and the observed broad reflexes can be attributed to the orthorhombic structure of β-WO3. Thermal annealing at 973 K for 3 h in air resulted in crystalline WO3 comprised of both monoclinic and orthorhombic phases. The transmission electron microscope micrograph analysis shows that the particles exhibit spherical morphology with some degree of agglomeration. Impedance spectroscopy is used for the electrical characterization of tungsten-oxide thin films with a thickness of 50 nm. Furthermore, the temperature-dependent gas-sensing properties of the material deposited on interdigital capacitors are investigated. Sensitivity experiments reveal two contributions to the overall sensitivity, which result from the surface and the core of each particle.

  14. Characterization of polymer-silica nanocomposite particles with core-shell morphologies using Monte Carlo simulations and small angle X-ray scattering.

    PubMed

    Balmer, Jennifer A; Mykhaylyk, Oleksandr O; Schmid, Andreas; Armes, Steven P; Fairclough, J Patrick A; Ryan, Anthony J

    2011-07-01

    A two-population model based on standard small-angle X-ray scattering (SAXS) equations is verified for the analysis of core-shell structures comprising spherical colloidal particles with particulate shells. First, Monte Carlo simulations of core-shell structures are performed to demonstrate the applicability of the model. Three possible shell packings are considered: ordered silica shells due to either charge-dependent repulsive or size-dependent Lennard-Jones interactions or randomly arranged silica particles. In most cases, the two-population model produces an excellent fit to calculated SAXS patterns for the simulated core-shell structures, together with a good correlation between the fitting parameters and structural parameters used for the simulation. The limits of application are discussed, and then, this two-population model is applied to the analysis of well-defined core-shell vinyl polymer/silica nanocomposite particles, where the shell comprises a monolayer of spherical silica nanoparticles. Comprehensive SAXS analysis of a series of poly(styrene-co-n-butyl acrylate)/silica colloidal nanocomposite particles (prepared by the in situ emulsion copolymerization of styrene and n-butyl acrylate in the presence of a glycerol-functionalized silica sol) allows the overall core-shell particle diameter, the copolymer latex core diameter and polydispersity, the mean silica shell thickness, the mean silica diameter and polydispersity, the volume fractions of the two components, the silica packing density, and the silica shell structure to be obtained. These experimental SAXS results are consistent with electron microscopy, dynamic light scattering, thermogravimetry, helium pycnometry, and BET surface area studies. The high electron density contrast between the (co)polymer and the silica components, together with the relatively low polydispersity of these core-shell nanocomposite particles, makes SAXS ideally suited for the characterization of this system. Moreover

  15. Hollow and Core-Shell Microgels at Oil-Water Interfaces: Spreading of Soft Particles Reduces the Compressibility of the Monolayer.

    PubMed

    Geisel, Karen; Rudov, Andrey A; Potemkin, Igor I; Richtering, Walter

    2015-12-01

    We investigate the influence of a solid core and of the cross-link density on the compression of microgel particles at oil-water interfaces by means of compression isotherms and computer simulations. We investigate particles with different morphology, namely core-shell particles containing a solid silica core surrounded by a cross-linked polymer shell of poly(N-isopropylacrylamide), and the corresponding hollow microgels where the core was dissolved. The polymer shell contains different amounts of cross-linker. The compression isotherms show that the removal of the core leads to an increase of the surface pressure at low compression, and the same effect can be observed when the polymer cross-link density is decreased. Low cross-link density and a missing core thus facilitate spreading of the polymer chains at the interface and, at high compression, hinder the transition to close hexagonal packing. Furthermore, the compression modulus only depends on the cross-link density at low compression, and no difference can be observed between the core-shell particles and the corresponding hollow microgels. It is especially remarkable that a low cross-link density leads to a high compression modulus at low compression, while this behavior is reversed at high compression. Thus, the core does not influence the particle behavior until the polymer shell is highly compressed and the core is directly exposed to the pressure. This is related to an enhanced spreading of polymer chains at the interface and thus high adsorption energy. These conclusions are fully supported by computer simulations which show that the cross-link density of the polymer shell defines the degree of deformation at the interface. Additionally, the core restricts the spreading of polymer chains at the interface. These results illustrate the special behavior of soft microgels at liquid interfaces. PMID:26575794

  16. Smoothed particle hydrodynamics simulations of the core-degenerate scenario for Type Ia supernovae

    NASA Astrophysics Data System (ADS)

    Aznar-Siguán, G.; García-Berro, E.; Lorén-Aguilar, P.; Soker, N.; Kashi, A.

    2015-07-01

    The core-degenerate scenario for Type Ia supernovae involves the merger of the hot core of an asymptotic giant branch star and a white dwarf, and might contribute a non-negligible fraction of all thermonuclear supernovae. Despite its potential interest, very few studies, and based on only crude simplifications, have been devoted to investigate this possible scenario, compared with the large efforts invested to study some other scenarios. Here we perform the first three-dimensional simulations of the merger phase, and find that this process can lead to the formation of a massive white dwarf, as required by this scenario. We consider two situations, according to the mass of the circumbinary disc formed around the system during the final stages of the common envelope phase. If the disc is massive enough, the stars merge on a highly eccentric orbit. Otherwise, the merger occurs after the circumbinary disc has been ejected and gravitational wave radiation has brought the stars close enough for the secondary to overflow its Roche lobe radius. Not surprisingly, the overall characteristics of the merger remnants are similar to those found for the double-degenerate scenario, independently of the very different core temperature and of the orbits of the merging stars. They consist of a central massive white dwarf, surrounded by a hot, rapidly rotating corona and a thick debris region.

  17. Relations between the photospheric magnetic field and the emission from the outer atmospheres of cool stars. I - The solar Ca II K line core emission

    NASA Technical Reports Server (NTRS)

    Schrijver, C. J.; Cote, J.; Zwaan, C.; Saar, S. H.

    1989-01-01

    Observations of a solar active region complex and its surroundings are used to establish a quantitative relation between the Ca II K line core intensity and magnetic flux density. The Ca II K line core intensity is transformed to a Ca II H + K line core flux density to facilitate a comparison of solar and stellar data. A new absolute calibration for the Mount Wilson Ca II H + K fluxes for G-type dwarfs is derived. The minimum Ca II K flux, found in the centers of supergranulation cells in quiet regions on the sun, is identical to the minimum flux that is observed for solar-type stars. An expression is presented for the nonlinear trend between the Ca II H + K line core excess flux density and the absolute value of the magnetic flux density. Models that explain the nonlinearity of the mean trend and the large intrinsic scatter about it are discussed. The solar data define a relation that is similar to the relation between stellar hemisphere-average magnetic flux densities and Ca II H + K excess flux densities.

  18. Enhanced group II intron retrohoming in magnesium-deficient Escherichia coli via selection of mutations in the ribozyme core

    PubMed Central

    Truong, David M.; Sidote, David J.; Russell, Rick; Lambowitz, Alan M.

    2013-01-01

    Mobile group II introns are bacterial retrotransposons thought to be evolutionary ancestors of spliceosomal introns and retroelements in eukaryotes. They consist of a catalytically active intron RNA (“ribozyme”) and an intron-encoded reverse transcriptase, which function together to promote RNA splicing and intron mobility via reverse splicing of the intron RNA into new DNA sites (“retrohoming”). Although group II introns are active in bacteria, their natural hosts, they function inefficiently in eukaryotes, where lower free Mg2+ concentrations decrease their ribozyme activity and constitute a natural barrier to group II intron proliferation within nuclear genomes. Here, we show that retrohoming of the Ll.LtrB group II intron is strongly inhibited in an Escherichia coli mutant lacking the Mg2+ transporter MgtA, and we use this system to select mutations in catalytic core domain V (DV) that partially rescue retrohoming at low Mg2+ concentrations. We thus identified mutations in the distal stem of DV that increase retrohoming efficiency in the MgtA mutant up to 22-fold. Biochemical assays of splicing and reverse splicing indicate that the mutations increase the fraction of intron RNA that folds into an active conformation at low Mg2+ concentrations, and terbium-cleavage assays suggest that this increase is due to enhanced Mg2+ binding to the distal stem of DV. Our findings indicate that DV is involved in a critical Mg2+-dependent RNA folding step in group II introns and demonstrate the feasibility of selecting intron variants that function more efficiently at low Mg2+ concentrations, with implications for evolution and potential applications in gene targeting. PMID:24043808

  19. Topological invariants for interacting topological insulators. II. Breakdown of single-particle Green's function formalism

    NASA Astrophysics Data System (ADS)

    He, Yuan-Yao; Wu, Han-Qing; Meng, Zi Yang; Lu, Zhong-Yi

    2016-05-01

    Topological phase transitions in free fermion systems can be characterized by the closing of single-particle gap and the change in topological invariants. However, in the presence of electronic interactions, topological phase transitions can be more complicated. In paper I of this series [Phys. Rev. B 93, 195163 (2016), 10.1103/PhysRevB.93.195163], we have proposed an efficient scheme to evaluate the topological invariants based on the single-particle Green's function formalism. Here, in paper II, we demonstrate several interaction-driven topological phase transitions (TPTs) in two-dimensional (2D) interacting topological insulators (TIs) via large-scale quantum Monte Carlo (QMC) simulations, based on the scheme of evaluating topological invariants presented in paper I. Across these transitions, the defining symmetries of the TIs have been neither explicitly nor spontaneously broken. In the first two models, the topological invariants calculated from the Green's function formalism succeed in characterizing the topologically distinct phases and identifying interaction-driven TPTs. However, in the other two models, we find that the single-particle gap does not close and the topological invariants constructed from the single-particle Green's function acquire no change across the TPTs. Unexpected breakdown of the Green's function formalism in constructing the topological invariants is thus discovered. We thence classify the topological phase transitions in interacting TIs into two categories in practical computation: Those that have noninteracting correspondence can be characterized successfully by the topological invariants constructed from the Green's functions, while for the others that do not have noninteracting correspondence, the Green's function formalism experiences a breakdown, but more interesting and exciting phenomena, such as emergent collective critical modes at the transition, arise. Discussion on the success and breakdown of topological invariants

  20. Synthesis, microstructure and magnetic properties of Fe3Si0.7Al0.3@SiO2 core-shell particles and Fe3Si/Al2O3 soft magnetic composite core

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Fan, Xi'an; Wu, Zhaoyang; Li, Guangqiang

    2015-11-01

    Fe3Si0.7Al0.3@SiO2 core-shell particles and Fe3Si/Al2O3 soft magnetic composite core have been synthesized via a modified stöber method combined with following high temperature sintering process. Most of conductive Fe3Si0.7Al0.3 particles could be uniformly coated by insulating SiO2 using the modified stöber method. The Fe3Si0.7Al0.3@SiO2 core-shell particles exhibited good soft magnetic properties with low coercivity and high saturation magnetization. The reaction 4Al+3SiO2=2α-Al2O3+3Si took place during the sintering process. As a result the new Fe3Si/Al2O3 composite was formed. The Fe3Si/Al2O3 composite core displayed more excellent soft magnetic properties, better frequency stability at high frequencies, much higher electrical resistivity and lower core loss than the pure Fe3Si0.7Al0.3 core. The method of introducing insulating layers surrounding magnetic particles provides a promising route to develop new and high compact soft magnetic materials with good magnetic and electric properties.

  1. Refactoring the Six-Gene Photosystem II Core in the Chloroplast of the Green Algae Chlamydomonas reinhardtii.

    PubMed

    Gimpel, Javier A; Nour-Eldin, Hussam H; Scranton, Melissa A; Li, Daphne; Mayfield, Stephen P

    2016-07-15

    Oxygenic photosynthesis provides the energy to produce all food and most of the fuel on this planet. Photosystem II (PSII) is an essential and rate-limiting component of this process. Understanding and modifying PSII function could provide an opportunity for optimizing photosynthetic biomass production, particularly under specific environmental conditions. PSII is a complex multisubunit enzyme with strong interdependence among its components. In this work, we have deleted the six core genes of PSII in the eukaryotic alga Chlamydomonas reinhardtii and refactored them in a single DNA construct. Complementation of the knockout strain with the core PSII synthetic module from three different green algae resulted in reconstitution of photosynthetic activity to 85, 55, and 53% of that of the wild-type, demonstrating that the PSII core can be exchanged between algae species and retain function. The strains, synthetic cassettes, and refactoring strategy developed for this study demonstrate the potential of synthetic biology approaches for tailoring oxygenic photosynthesis and provide a powerful tool for unraveling PSII structure-function relationships. PMID:26214707

  2. Synthesis and electrochemical performance of surface-modified nano-sized core/shell tin particles for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Schmuelling, Guido; Oehl, Nikolas; Knipper, Martin; Kolny-Olesiak, Joanna; Plaggenborg, Thorsten; Meyer, Hinrich-Wilhelm; Placke, Tobias; Parisi, Jürgen; Winter, Martin

    2014-09-01

    Tin is able to lithiate and delithiate reversibly with a high theoretical specific capacity, which makes it a promising candidate to supersede graphite as the state-of-the-art negative electrode material in lithium ion battery technology. Nevertheless, it still suffers from poor cycling stability and high irreversible capacities. In this contribution, we show the synthesis of three different nano-sized core/shell-type particles with crystalline tin cores and different amorphous surface shells consisting of SnOx and organic polymers. The spherical size and the surface shell can be tailored by adjusting the synthesis temperature and the polymer reagents in the synthesis, respectively. We determine the influence of the surface modifications with respect to the electrochemical performance and characterize the morphology, structure, and thermal properties of the nano-sized tin particles by means of high-resolution transmission electron microscopy, x-ray diffraction, and thermogravimetric analysis. The electrochemical performance is investigated by constant current charge/discharge cycling as well as cyclic voltammetry.

  3. FROM PRESTELLAR TO PROTOSTELLAR CORES. II. TIME DEPENDENCE AND DEUTERIUM FRACTIONATION

    SciTech Connect

    Aikawa, Y.; Wakelam, V.; Hersant, F.; Garrod, R. T.; Herbst, E.

    2012-11-20

    We investigate the molecular evolution and D/H abundance ratios that develop as star formation proceeds from a dense molecular cloud core to a protostellar core, by solving a gas-grain reaction network applied to a one-dimensional radiative hydrodynamic model with infalling fluid parcels. Spatial distributions of gas and ice-mantle species are calculated at the first-core stage, and at times after the birth of a protostar. Gas-phase methanol and methane are more abundant than CO at radii r {approx}< 100 AU in the first-core stage, but gradually decrease with time, while abundances of larger organic species increase. The warm-up phase, when complex organic molecules are efficiently formed, is longer-lived for those fluid parcels infalling at later stages. The formation of unsaturated carbon chains (warm carbon-chain chemistry) is also more effective in later stages; C{sup +}, which reacts with CH{sub 4} to form carbon chains, increases in abundance as the envelope density decreases. The large organic molecules and carbon chains are strongly deuterated, mainly due to high D/H ratios in the parent molecules, determined in the cold phase. We also extend our model to simulate simply the chemistry in circumstellar disks, by suspending the one-dimensional infall of a fluid parcel at constant disk radii. The species CH{sub 3}OCH{sub 3} and HCOOCH{sub 3} increase in abundance in 10{sup 4}-10{sup 5} yr at the fixed warm temperature; both also have high D/H ratios.

  4. The core helium flash revisited. II. Two and three-dimensional hydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Mocák, M.; Müller, E.; Weiss, A.; Kifonidis, K.

    2009-07-01

    Context: We study turbulent convection during the core helium flash close to its peak by comparing the results of two and three-dimensional hydrodynamic simulations. Aims: In a previous study we found that the temporal evolution and the properties of the convection inferred from two-dimensional hydrodynamic studies are similar to those predicted by quasi-hydrostatic stellar evolutionary calculations. However, as vorticity is conserved in axisymmetric flows, two-dimensional simulations of convection are characterized by incorrect dominant spatial scales and exaggerated velocities. Here, we present three-dimensional simulations that eliminate the restrictions and flaws of two-dimensional models and that provide a geometrically unbiased insight into the hydrodynamics of the core helium flash. In particular, we study whether the assumptions and predictions of stellar evolutionary calculations based on the mixing-length theory can be confirmed by hydrodynamic simulations. Methods: We used a multidimensional Eulerian hydrodynamics code based on state-of-the-art numerical techniques to simulate the evolution of the helium core of a 1.25 M⊙ Pop I star. Results: Our three-dimensional hydrodynamic simulations of the evolution of a star during the peak of the core helium flash do not show any explosive behavior. The convective flow patterns developing in the three-dimensional models are structurally different from those of the corresponding two-dimensional models, and the typical convective velocities are lower than those found in their two-dimensional counterparts. Three-dimensional models also tend to agree more closely with the predictions of mixing length theory. Our hydrodynamic simulations show the turbulent entrainment that leads to a growth of the convection zone on a dynamic time scale. In contrast to mixing length theory, the outer part of the convection zone is characterized by a subadiabatic temperature gradient.

  5. The formation of entropy cores in non-radiative galaxy cluster simulations: smoothed particle hydrodynamics versus adaptive mesh refinement

    NASA Astrophysics Data System (ADS)

    Power, C.; Read, J. I.; Hobbs, A.

    2014-06-01

    We simulate cosmological galaxy cluster formation using three different approaches to solving the equations of non-radiative hydrodynamics - classic smoothed particle hydrodynamics (SPH), novel SPH with a higher order dissipation switch (SPHS), and an adaptive mesh refinement (AMR) method. Comparing spherically averaged entropy profiles, we find that SPHS and AMR approaches result in a well-defined entropy core that converges rapidly with increasing mass and force resolution. In contrast, the central entropy profile in the SPH approach is sensitive to the cluster's assembly history and shows poor numerical convergence. We trace this disagreement to the known artificial surface tension in SPH that appears at phase boundaries. Varying systematically numerical dissipation in SPHS, we study the contributions of numerical and physical dissipation to the entropy core and argue that numerical dissipation is required to ensure single-valued fluid quantities in converging flows. However, provided it occurs only at the resolution limit and does not propagate errors to larger scales, its effect is benign - there is no requirement to build `sub-grid' models of unresolved turbulence for galaxy cluster simulations. We conclude that entropy cores in non-radiative galaxy cluster simulations are physical, resulting from entropy generation in shocked gas during cluster assembly.

  6. Construction and Immunological Evaluation of Multivalent Hepatitis B Virus (HBV) Core Virus-Like Particles Carrying HBV and HCV Epitopes▿

    PubMed Central

    Sominskaya, Irina; Skrastina, Dace; Dislers, Andris; Vasiljev, Denis; Mihailova, Marija; Ose, Velta; Dreilina, Dzidra; Pumpens, Paul

    2010-01-01

    A multivalent vaccine candidate against hepatitis B virus (HBV) and hepatitis C virus (HCV) infections was constructed on the basis of HBV core (HBc) virus-like particles (VLPs) as carriers. Chimeric VLPs that carried a virus-neutralizing HBV pre-S1 epitope corresponding to amino acids (aa) 20 to 47 in the major immunodominant region (MIR) and a highly conserved N-terminal HCV core epitope corresponding to aa 1 to 60 at the C terminus of the truncated HBcΔ protein (N-terminal aa 1 to 144 of full-length HBc) were produced in Escherichia coli cells and examined for their antigenicity and immunogenicity. The presence of two different foreign epitopes within the HBc molecule did not interfere with its VLP-forming ability, with the HBV pre-S1 epitope exposed on the surface and the HCV core epitope buried within the VLPs. After immunization of BALB/c mice, specific T-cell activation by both foreign epitopes and a high-titer antibody response against the pre-S1 epitope were found, whereas an antibody response against the HBc carrier was notably suppressed. Both inserted epitopes also induced a specific cytotoxic-T-lymphocyte (CTL) response, as shown by the gamma interferon (IFN-γ) production profile. PMID:20410327

  7. Core-shell designs of photoluminescent nanodiamonds with porous silica coatings for bioimaging and drug delivery II: application

    NASA Astrophysics Data System (ADS)

    Prabhakar, Neeraj; Näreoja, Tuomas; von Haartman, Eva; Karaman, Didem Şen; Jiang, Hua; Koho, Sami; Dolenko, Tatiana A.; Hänninen, Pekka E.; Vlasov, Denis I.; Ralchenko, Victor G.; Hosomi, Satoru; Vlasov, Igor I.; Sahlgren, Cecilia; Rosenholm, Jessica M.

    2013-04-01

    Recent advances within materials science and its interdisciplinary applications in biomedicine have emphasized the potential of using a single multifunctional composite material for concurrent drug delivery and biomedical imaging. Here we present a novel composite material consisting of a photoluminescent nanodiamond (ND) core with a porous silica (SiO2) shell. This novel multifunctional probe serves as an alternative nanomaterial to address the existing problems with delivery and subsequent tracing of the particles. Whereas the unique optical properties of ND allows for long-term live cell imaging and tracking of cellular processes, mesoporous silica nanoparticles (MSNs) have proven to be efficient drug carriers. The advantages of both ND and MSNs were hereby integrated in the new composite material, ND@MSN. The optical properties provided by the ND core rendered the nanocomposite suitable for microscopy imaging in fluorescence and reflectance mode, as well as super-resolution microscopy as a STED label; whereas the porous silica coating provided efficient intracellular delivery capacity, especially in surface-functionalized form. This study serves as a demonstration how this novel nanomaterial can be exploited for both bioimaging and drug delivery for future theranostic applications.Recent advances within materials science and its interdisciplinary applications in biomedicine have emphasized the potential of using a single multifunctional composite material for concurrent drug delivery and biomedical imaging. Here we present a novel composite material consisting of a photoluminescent nanodiamond (ND) core with a porous silica (SiO2) shell. This novel multifunctional probe serves as an alternative nanomaterial to address the existing problems with delivery and subsequent tracing of the particles. Whereas the unique optical properties of ND allows for long-term live cell imaging and tracking of cellular processes, mesoporous silica nanoparticles (MSNs) have proven

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

    PubMed Central

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

    2015-01-01

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

  9. Loss-of-function of OsSTN8 suppresses the photosystem II core protein phosphorylation and interferes with the photosystem II repair mechanism in rice (Oryza sativa).

    PubMed

    Nath, Krishna; Poudyal, Roshan Sharma; Eom, Joon-Seob; Park, Yu Shin; Zulfugarov, Ismayil S; Mishra, Sujata R; Tovuu, Altanzaya; Ryoo, Nayeoon; Yoon, Ho-Sung; Nam, Hong Gil; An, Gynheung; Jeon, Jong-Seong; Lee, Choon-Hwan

    2013-11-01

    STN8 kinase is involved in photosystem II (PSII) core protein phosphorylation (PCPP). To examine the role of PCPP in PSII repair during high light (HL) illumination, we characterized a T-DNA insertional knockout mutant of the rice (Oryza sativa) STN8 gene. In this osstn8 mutant, PCPP was significantly suppressed, and the grana were thin and elongated. Upon HL illumination, PSII was strongly inactivated in the mutants, but the D1 protein was degraded more slowly than in wild-type, and mobilization of the PSII supercomplexes from the grana to the stromal lamellae for repair was also suppressed. In addition, higher accumulation of reactive oxygen species and preferential oxidation of PSII reaction center core proteins in thylakoid membranes were observed in the mutants during HL illumination. Taken together, our current data show that the absence of STN8 is sufficient to abolish PCPP in osstn8 mutants and to produce all of the phenotypes observed in the double mutant of Arabidopsis, indicating the essential role of STN8-mediated PCPP in PSII repair. PMID:24103067

  10. Nanoscale Au-In alloy-oxide core-shell particles as electrocatalysts for efficient hydroquinone detection

    SciTech Connect

    Sutter, E.; Tong, X.; Medina-Plaza, C.; Rodriguez-Mendez, M. L.; Sutter, P.

    2015-10-09

    The presence of hydroquinone (HQ), a phenol ubiquitous in nature and widely used in industry, needs to be monitored because of its toxicity to the environment. Here we demonstrate efficient detection of HQ using simple, fast, and noninvasive electrochemical measurements on indium tin oxide (ITO) electrodes modified with nanoparticles comprising bimetallic Au–In cores and mixed Au–In oxide shells. Whereas bare ITO electrodes show very low activity for the detection of HQ, their modification with Au–In core–shell nanoparticles induces a pronounced shift of the oxidation peak to lower potentials, i.e., facilitated oxidation. The response of the different electrodes was correlated with the initial composition of the bimetallic nanoparticle cores, which in turn determined the amount of Au and In stabilized on the surface of the amorphous Au–In oxide shells available for the electrochemical reaction. While adding core–shell nanostructures with different compositions of the alloy core facilitates the electrocatalytic (reduction-) oxidation of HQ, the activity is highest for particles with AuIn cores (i.e., a Au:In ratio of 1). This optimal system is found to follow a single pathway, the two-electron oxidation of the quinone–hydroquinone couple, which gives rise to high oxidation peaks and is most effective in facilitating the electrode-to-analyte charge transfer and thus detection. The limits of detection (LOD) decreased when increasing the amount of Au exposed on the surface of the amorphous Au–In oxide shells. As a result the LODs were in the range of 10–5 – 10–6 M and were lower than those obtained using bulk Au.