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Sample records for glassy matrices effets

  1. Photoluminescence of silver in glassy matrices

    SciTech Connect

    Garcia, M.A.; Garcia-Heras, M.; Cano, E.; Bastidas, J.M.; Villegas, M.A.; Montero, E.; Llopis, J.; Sada, C.; Marchi, G. de; Battaglin, G.; Mazzoldi, P.

    2004-10-01

    This work studies the behavior of Ag{sup +} ions incorporated in different silica-based glassy matrices. To this end, Ag-doped silica coatings, prepared via sol-gel and deposited on pure silica and soda-lime glasses, are investigated by means of structural and optical spectroscopy techniques. Silver tends to segregate towards the interface during the annealing process, but in the case of soda-lime glassy substrates the exchange process favors its diffusion into the substrate. The environment of Ag{sup +} ions during the annealing process determines their final oxidation state. In the pure silica matrix, Ag{sup +} ions are found to be unstable and tend to reduce to Ag{sup 0}, with the subsequent formation of metallic nanoparticles. However, the presence of network formers and modifiers gives rise to the appearance of nonbridging oxygen, which allows the stabilization of Ag{sup +} ions in the matrix.

  2. Caracterisation de l'effet du vieillissement en milieu aqueux sur les proprietes mecaniques de composites a matrice elastomere

    NASA Astrophysics Data System (ADS)

    Favre, Audrey

    Rubber composites are widely used in several engineering fields, such as automotive, and more recently for inflatable dams and other innovative underwater applications. These rubber materials are composed by an elastomeric matrix while the reinforcing phase is a synthetic fabric. Since these components are expected to operate several years in water environment, their durability must be guaranteed. The use of rubber materials immersed in water is not new, in fact, these materials have been studied for almost one century. However, the knowledge on reinforced rubber composites immersed several years in water is still limited. In this work, investigations on reinforced rubbers were carried out in the framework of a research project in partnership with Alstom and Hydro-Quebec. The objective of this study was to identify rubber composites that could be used under water for long periods. Various rubber composites with ethylene-propylene-diene monomer (EPDM), silicone, EPDM/silicone and polychloroprene (Neoprene) matrices reinforced with E-glass fabric were studied. Thus, these materials were exposed to an accelerated ageing at 85 °C underwater for periods varying from 14 to 365 days. For comparison purposes, they were also immersed and aged one year at room temperature (21 °C). The impact of accelerated aging was estimated through three different characterization methods. Scanning electron microscopy (SEM) was first used to assess the quality of fiber-matrix interface. Then, water absorption tests were performed to quantify the rate of water absorption during immersion. Finally the evolution of the mechanical properties was followed by the determination of Young's modulus (E) and ultimate stress (sigmau) using a dedicated traction test. This analysis allowed to point out that the quality of the fiber-matrix interface was the main factor influencing the drop of the mechanical properties and their durability. Moreover, it was noticed that this interface could be improved

  3. Protein/ionic liquid/glassy carbon sensors following analyte focusing by ionic liquid micelle collapse for simultaneous determination of water soluble vitamins in plasma matrices.

    PubMed

    Abd El-Hady, D; Albishri, H M

    2015-07-01

    Two novel sensors based on human serum albumin (HSA)-ionic liquid (IL) and bovine serum albumin (BSA)-ionic liquid (IL) composites modified glassy carbon electrode (GCE) were produced for simultaneous determination of water soluble vitamins B2, B6 and C in human plasma following analytes focusing by IL micelles collapse (AFILMC). For selective and efficient extraction, vitamins were dissolved in 3.0molL(-1) micellar solution of 1-octyl-3-methyl imidazolium bromide IL. The extracted vitamins were hydrodynamically injected by 25mbar for 20s into a running buffer of 12.5mmolL(-1) phosphate at pH 6.0 followed by electrochemical detection (ECD) on protein/1-octyl-3-methyl imidazolium hexafluorophosphate IL/GC sensors. The chemical stability of proposed sensors was achieved up to 7 days without any decomposition of PF6-based IL/protein and adsorption of interfering ions. In the current work, the sensitivity enhancement factor (SEF) up to 5000-fold was achieved using the AFILMC/ECD setup compared to conventional CE/UV. Under optimal conditions, linear calibration graphs were obtained from 0.5, 0.5 and 1.0 to 1500.0µgmL(-1) of vitamins B2, B6 and C, respectively. Detection limits of analytes were ranged from 180.0 to 520.0ngmL(-1). The proposed AFILMC/ECD setup was successfully applied to the assay of trace level quantification of vitamins in human plasma samples and also their binding constants with HSA and BSA were determined. The concurrent use of IL micelles for the proposed separation and detection processes exhibited some advantages, such as, a reduction of use toxic solvents, an efficient extraction and a direct injection of samples with a short-single run. Furthermore, IL micelles, having variable possibility of interactions, facilitated the successful achievements of AFILMC/ECD setup for the quantification of vitamins in plasma matrices.

  4. Spin-lattice relaxation and ODMR linenarrowing of the photoexcited triplet state of pyrene in polycrystalline Shpol'skii hosts and glassy matrices

    NASA Astrophysics Data System (ADS)

    Tringali, Arthur E.; Brenner, Henry C.

    1998-01-01

    Phosphorescence and ODMR linewidths, and spin-lattice relaxation (SLR) rates were measured at pumped helium temperatures for the triplet excited state of pyrene doped in several n-alkane polycrystalline hosts as well as in 3-methylpentane (3-MP) glass, in order to test the expectation that the optimum Shpol'skii matrix for pyrene should lead to the slowest SLR rates. Among the series of n-alkanes, n-hexane showed the best Shpol'skii effect for pyrene in terms of the narrowest phosphorescence and weakest guest-host phonon coupling. The 2| E| and | D+ E| ODMR linewidths for pyrene were minimized in n-hexane as well. Microwave saturated phosphorescence decay and fast passage methods were used to measure the SLR rates in the range 1.75-4.2 K. SLR appeared to be slowest in n-octane rather than n-hexane, but was significantly faster in n-decane and 3-MP. A marked anisotropy was observed in all hosts, in which the in-plane ( x ⇄  y) relaxation rate was 20-40 times the other rates. While this was suggestive of a mechanism in which SLR occurs by means of thermal promotion to a local phonon state with rotated spin axes, the observed activation energy was too small (2-3 cm -1) to be consistent with such a mechanism. In n-hexane, the relaxation appears to proceed by means of a direct process (rate αT1) in this temperature range. In the 3-MP glass, relaxation was faster than in the polycrystalline hosts, and followed a power law temperature dependence with an exponent of 2.4±0.2, in agreement with earlier studies of naphthalene derivatives in the same host, indicating that a direct two-level-system phonon mechanism is important in this glassy host.

  5. Glassy correlations in nematic elastomers

    NASA Astrophysics Data System (ADS)

    Lu, Bing; Goldbart, Paul; Mao, Xiaoming

    2009-03-01

    We address the physical properties of an isotropic melt or solution of nematogenic polymers that is then cross-linked beyond the vulcanization point. To do this, we construct a replica Landau theory involving a coupled pair of order- parameter fields: one describing vulcanization, the other describing local nematic order. Thermal nematic fluctuations, present at the time of cross-linking, are trapped by cross- linking into the vulcanized network. The resulting glassy nematic fluctuations are analyzed in the Gaussian approximation in two regimes. When the localization length is shorter than the thermal nematic correlation length, the nematic correlations are well captured as glassy correlations. In the opposite regime, fluctuations in the positions of the localized polymers partially wash out the glassy nematic correlations.

  6. Glassy composition for hermetic seals

    DOEpatents

    Wilder, Jr., James A.

    1980-01-01

    The invention relates to a glassy composition adaptable for sealing to aluminum-based alloys to form a hermetically-sealed insulator body. The composition may either be employed as a glass or, after devitrifying heat treatment, as a glass-ceramic.

  7. Microscopic origin of the non-Gaussian behavior of dynamic structure factors of glassy matter

    NASA Astrophysics Data System (ADS)

    Cabrillo, C.; González, M. A.; Cuello, G. J.; Bermejo, F. J.; Saboungi, M. L.; Price, D. L.

    2004-04-01

    We consider the Lamb-Mössbauer factors corresponding to the structure factors of a material (ethyl alcohol) showing two glassy phases, one of those being an orientationally disordered crystal. The deviations from the idealized Gaussian behavior expected for an isotropic-harmonic vibrator within the amorphous phase and disordered crystal are found to be remarkably close. Such proximity enables us to take advantage of the crystal symmetry to gain access to specific details of the effective interparticle potential. Once this is done the treatment is extended to include the fully amorphous material. The results depict atomic motions within the glassy matrices as significantly anisotropic and highly anharmonic and thus provide a way to understand the microscopic origin of phenomena considered as fingerprints of glassy dynamics.

  8. Glassy features of crystal plasticity

    NASA Astrophysics Data System (ADS)

    Lehtinen, Arttu; Costantini, Giulio; Alava, Mikko J.; Zapperi, Stefano; Laurson, Lasse

    2016-08-01

    Crystal plasticity occurs by deformation bursts due to the avalanchelike motion of dislocations. Here we perform extensive numerical simulations of a three-dimensional dislocation dynamics model under quasistatic stress-controlled loading. Our results show that avalanches are power-law distributed and display peculiar stress and sample size dependence: The average avalanche size grows exponentially with the applied stress, and the amount of slip increases with the system size. These results suggest that intermittent deformation processes in crystalline materials exhibit an extended critical-like phase in analogy to glassy systems instead of originating from a nonequilibrium phase transition critical point.

  9. Structural order in glassy water.

    PubMed

    Giovambattista, Nicolas; Debenedetti, Pablo G; Sciortino, Francesco; Stanley, H Eugene

    2005-06-01

    We investigate structural order in glassy water by performing classical molecular dynamics simulations using the extended simple point charge (SPC/E) model of water. We perform isochoric cooling simulations across the glass transition temperature at different cooling rates and densities. We quantify structural order by orientational and translational order metrics. Upon cooling the liquid into the glassy state, both the orientational order parameter Q and translational order parameter tau increase. At T=0 K, the glasses fall on a line in the Q-tau plane or order map. The position of this line depends only on density and coincides with the location in the order map of the inherent structures (IS) sampled upon cooling. We evaluate the energy of the IS, eIS(T), and find that both order parameters for the IS are proportional to eIS. We also study the structural order during the transformation of low-density amorphous ice (LDA) to high-density amorphous ice (HDA) upon isothermal compression and are able to identify distinct regions in the order map corresponding to these glasses. Comparison of the order parameters for LDA and HDA with those obtained upon isochoric cooling indicates major structural differences between glasses obtained by cooling and glasses obtained by compression. These structural differences are only weakly reflected in the pair correlation function. We also characterize the evolution of structural order upon isobaric annealing, leading at high pressure to very-high density amorphous ice (VHDA). PMID:16089741

  10. Ending Aging in Super Glassy Polymer Membranes

    SciTech Connect

    Lau, CH; Nguyen, PT; Hill, MR; Thornton, AW; Konstas, K; Doherty, CM; Mulder, RJ; Bourgeois, L; Liu, ACY; Sprouster, DJ; Sullivan, JP; Bastow, TJ; Hill, AJ; Gin, DL; Noble, RD

    2014-04-16

    Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4-methyl-2-pentyne) (PMP), and polymers with intrinsic microporosity (PIM-1) reduces gas permeabilities and limits their application as gas-separation membranes. While super glassy polymers are initially very porous, and ultra-permeable, they quickly pack into a denser phase becoming less porous and permeable. This age-old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N-2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.

  11. Random antagonistic matrices

    NASA Astrophysics Data System (ADS)

    Cicuta, Giovanni M.; Molinari, Luca Guido

    2016-09-01

    The ensemble of antagonistic matrices is introduced and studied. In antagonistic matrices the entries {{ A }}i,j and {{ A }}j,i are real and have opposite signs, or are both zero, and the diagonal is zero. This generalization of antisymmetric matrices is suggested by the linearized dynamics of competitive species in ecology.

  12. Cooperative strings and glassy interfaces.

    PubMed

    Salez, Thomas; Salez, Justin; Dalnoki-Veress, Kari; Raphaël, Elie; Forrest, James A

    2015-07-01

    We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer. PMID:26100908

  13. Cooperative strings and glassy interfaces.

    PubMed

    Salez, Thomas; Salez, Justin; Dalnoki-Veress, Kari; Raphaël, Elie; Forrest, James A

    2015-07-01

    We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer.

  14. Random bistochastic matrices

    NASA Astrophysics Data System (ADS)

    Cappellini, Valerio; Sommers, Hans-Jürgen; Bruzda, Wojciech; Życzkowski, Karol

    2009-09-01

    Ensembles of random stochastic and bistochastic matrices are investigated. While all columns of a random stochastic matrix can be chosen independently, the rows and columns of a bistochastic matrix have to be correlated. We evaluate the probability measure induced into the Birkhoff polytope of bistochastic matrices by applying the Sinkhorn algorithm to a given ensemble of random stochastic matrices. For matrices of order N = 2 we derive explicit formulae for the probability distributions induced by random stochastic matrices with columns distributed according to the Dirichlet distribution. For arbitrary N we construct an initial ensemble of stochastic matrices which allows one to generate random bistochastic matrices according to a distribution locally flat at the center of the Birkhoff polytope. The value of the probability density at this point enables us to obtain an estimation of the volume of the Birkhoff polytope, consistent with recent asymptotic results.

  15. Molecular mobility in glassy dispersions.

    PubMed

    Mehta, Mehak; McKenna, Gregory B; Suryanarayanan, Raj

    2016-05-28

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF-PV P>NIF-HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  16. Molecular mobility in glassy dispersions

    NASA Astrophysics Data System (ADS)

    Mehta, Mehak; McKenna, Gregory B.; Suryanarayanan, Raj

    2016-05-01

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF-PV P>NIF-HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  17. On the Marginal Stability of Glassy Systems

    NASA Astrophysics Data System (ADS)

    Yan, Le; Baity-Jesi, Marco; Müller, Markus; Wyart, Matthieu

    2015-03-01

    In various glassy systems that are out of equilibrium, like spin glasses and granular packings, the dynamics appears to be critical: avalanches involving almost the whole system could happen. A recent conceptual breakthrough argues that such glassy systems sample the ensemble of marginal stable states, which inevitably results into critical dynamics. However, it is unclear how the marginal stability is dynamically guaranteed. We investigate this marginal stability assumption by studying specifically the critical athermal dynamics of the Sherrington-Kirkpatrick model. We discuss how a pseudo-gap in the density distribution of local fields characterizing the marginal stability arises dynamically.

  18. Active cage model of glassy dynamics.

    PubMed

    Fodor, Étienne; Hayakawa, Hisao; Visco, Paolo; van Wijland, Frédéric

    2016-07-01

    We build up a phenomenological picture in terms of the effective dynamics of a tracer confined in a cage experiencing random hops to capture some characteristics of glassy systems. This minimal description exhibits scale invariance properties for the small-displacement distribution that echo experimental observations. We predict the existence of exponential tails as a crossover between two Gaussian regimes. Moreover, we demonstrate that the onset of glassy behavior is controlled only by two dimensionless numbers: the number of hops occurring during the relaxation of the particle within a local cage and the ratio of the hopping length to the cage size. PMID:27575182

  19. Active cage model of glassy dynamics

    NASA Astrophysics Data System (ADS)

    Fodor, Étienne; Hayakawa, Hisao; Visco, Paolo; van Wijland, Frédéric

    2016-07-01

    We build up a phenomenological picture in terms of the effective dynamics of a tracer confined in a cage experiencing random hops to capture some characteristics of glassy systems. This minimal description exhibits scale invariance properties for the small-displacement distribution that echo experimental observations. We predict the existence of exponential tails as a crossover between two Gaussian regimes. Moreover, we demonstrate that the onset of glassy behavior is controlled only by two dimensionless numbers: the number of hops occurring during the relaxation of the particle within a local cage and the ratio of the hopping length to the cage size.

  20. Deformation and Fracture Behavior of Metallic Glassy Alloys and Glassy-Crystal Composites

    NASA Astrophysics Data System (ADS)

    Louzguine-Luzgin, D. V.; Vinogradov, A.; Li, S.; Kawashima, A.; Xie, G.; Yavari, A. R.; Inoue, A.

    2011-06-01

    The present work demonstrates the deformation behavior of Zr-Cu-Ni-Al bulk glassy alloys and Zr-Ni-Cu-Al-Pd glassy foils as well as Ni-Cu-Ti-Zr bulk crystal-glassy composites. Fracture of Zr60Cu16Ni14Al10 and Zr64.13Ni10.12Cu15.75Al10 bulk glassy alloys is featured by nearly equal fraction areas of cleavage-like and vein-type relief. The observed pattern of alternating cleavage-like and vein-type patterns illustrates a result of dynamically self-organizing shear propagation at the final catastrophic stage. The deformation behavior of Zr64.13Ni10.12Cu15.75Al10 alloy has also been tested at LN2 temperature. The strength of the sample decreases with temperature, and no clear serrated flow typical for bulk glassy samples tested at room temperature is observed in the case of the samples tested at LN2 temperature. We also studied the deformation behavior of Zr-Ni-Cu-Al-Pd glassy foils thinned to electron transparency in situ in tension in a transmission electron microscope. We also present a Ni-Cu-Ti-Zr crystal-glassy composite material having a superior strength paired with a considerable ductility exceeding 10 pct. The metastable cP2 crystalline phase promotes a strain-induced martensitic transformation leading to pseudoelastic behavior as well as enhanced plasticity at room temperature. Underlying mechanisms of plastic deformation are discussed in terms of the interplay between the dislocation slip in the crystalline phase and the shear deformation in the glassy matrix.

  1. Effets perturbateurs endocriniens des pesticides organochlores.

    PubMed

    Charlier, C; Plomteux, G

    2002-01-01

    Xenoestrogens such organochlorine pesticides are known to induce changes in reproductive development, function or behaviour in wildlife. Because these compounds are able to modify the estrogens metabolism, or to compete with estradiol for binding to the estrogen receptor, it may be possible that these products affect the risk of developing impaired fertility, precocious puberty or some kinds of cancer in man. Le plus ancien récit de lutte contre la pollution remonte à une légende indienne racontant que la divinité Sing-bonga était incommodée par les émanations des fours dans lesquels les Asuras fondaient leurs métaux (1). Evidemment depuis, la problématique n-a cessé de s-accroître et la contamination de la Terre par de nombreux polluants est devenue aujourd-hui un problème majeur de notre Société. La protection de notre environnement est une question capitale qui doit être respectée malgré la pression économique actuelle et qui ne cessera de croître au cours des prochaines années même si l-identification objective et indiscutable de ce qui est essentiel - donc devant être prioritairement garanti sur la planète - est difficile à cerner (2). « Un oiseau en mauvais état ne pond pas de bons oeufs » disait un proverbe grec. Mais ce n-est qu-à partir de la seconde moitié du XXème siècle que les toxicologues ont commencé à identifier les effets qu-avaient entraînés à l-échelle mondiale les pollutions émises aux XIXème siècle sur la faune sauvage et sur le cheptel (3). L-histoire contemporaine des pesticides industriels commence vers 1874 (synthèse des organochlorés) et se poursuit tout au long de ces 2 siècles en passant par la synthèse des organophosphorés (1950), des carbamates (1970) et des pyréthroïdes (1975) (4). Le dichlorodiphényltrichloroéthane (DDT) a été synthétisé pour la première fois par un étudiant en cours de préparation de sa thèse de doctorat : Othmer Zeidler. La production, reprise par les

  2. Random cyclic matrices.

    PubMed

    Jain, Sudhir R; Srivastava, Shashi C L

    2008-09-01

    We present a Gaussian ensemble of random cyclic matrices on the real field and study their spectral fluctuations. These cyclic matrices are shown to be pseudosymmetric with respect to generalized parity. We calculate the joint probability distribution function of eigenvalues and the spacing distributions analytically and numerically. For small spacings, the level spacing distribution exhibits either a Gaussian or a linear form. Furthermore, for the general case of two arbitrary complex eigenvalues, leaving out the spacings among real eigenvalues, and, among complex conjugate pairs, we find that the spacing distribution agrees completely with the Wigner distribution for a Poisson process on a plane. The cyclic matrices occur in a wide variety of physical situations, including disordered linear atomic chains and the Ising model in two dimensions. These exact results are also relevant to two-dimensional statistical mechanics and nu -parametrized quantum chromodynamics. PMID:18851127

  3. Plastic flow modeling in glassy polymers

    SciTech Connect

    Clements, Brad

    2010-12-13

    Glassy amorphous and semi-crystalline polymers exhibit strong rate, temperature, and pressure dependent polymeric yield. As a rule of thumb, in uniaxial compression experiments the yield stress increases with the loading rate and applied pressure, and decreases as the temperature increases. Moreover, by varying the loading state itself complex yield behavior can be observed. One example that illustrates this complexity is that most polymers in their glassy regimes (i.e., when the temperature is below their characteristic glass transition temperature) exhibit very pronounced yield in their uniaxial stress stress-strain response but very nebulous yield in their uniaxial strain response. In uniaxial compression, a prototypical glassy-polymer stress-strain curve has a stress plateau, often followed by softening, and upon further straining, a hardening response. Uniaxial compression experiments of this type are typically done from rates of 10{sup -5} s{sup -1} up to about 1 s{sup -1}. At still higher rates, say at several thousands per second as determined from Split Hopkinson Pressure Bar experiments, the yield can again be measured and is consistent with the above rule of thumb. One might expect that that these two sets of experiments should allow for a successful extrapolation to yet higher rates. A standard means to probe high rates (on the order of 105-107 S-I) is to use a uniaxial strain plate impact experiment. It is well known that in plate impact experiments on metals that the yield stress is manifested in a well-defined Hugoniot Elastic Limit (HEL). In contrast however, when plate impact experiments are done on glassy polymers, the HEL is arguably not observed, let alone observed at the stress estimated by extrapolating from the lower strain rate experiments. One might argue that polymer yield is still active but somehow masked by the experiment. After reviewing relevant experiments, we attempt to address this issue. We begin by first presenting our recently

  4. Depolarizing differential Mueller matrices.

    PubMed

    Ortega-Quijano, Noé; Arce-Diego, José Luis

    2011-07-01

    The evolution of a polarized beam can be described by the differential formulation of Mueller calculus. The nondepolarizing differential Mueller matrices are well known. However, they only account for 7 out of the 16 independent parameters that are necessary to model a general anisotropic depolarizing medium. In this work we present the nine differential Mueller matrices for general depolarizing media, highlighting the physical implications of each of them. Group theory is applied to establish the relationship between the differential matrix and the set of transformation generators in the Minkowski space, of which Lorentz generators constitute a particular subgroup. PMID:21725434

  5. Wafer-level microstructuring of glassy carbon

    NASA Astrophysics Data System (ADS)

    Hans, Loïc. E.; Prater, Karin; Kilchoer, Cédric; Scharf, Toralf; Herzig, Hans Peter; Hermerschmidt, Andreas

    2014-03-01

    Glassy carbon is used nowadays for a variety of applications because of its mechanical strength, thermal stability and non-sticking adhesion properties. One application is glass molding that allows to realize high resolution diffractive optical elements on large areas and at affordable price appropriate for mass production. We study glassy carbon microstructuring for future precision compression molding of low and high glass-transition temperature. For applications in optics the uniformity, surface roughness, edge definition and lateral resolution are very important parameters for a stamp and the final product. We study different methods of microstructuring of glassy carbon by etching and milling. Reactive ion etching with different protection layers such as photoresists, aluminium and titanium hard masks have been performed and will be compare with Ion beam etching. We comment on the quality of the structure definition and give process details as well as drawbacks for the different methods. In our fabrications we were able to realize optically flat diffractive structures with slope angles of 80° at typical feature sizes of 5 micron and 700 nm depth qualified for high precision glass molding.

  6. Destructive Clustering of Metal Nanoparticles in Chalcogenide and Oxide Glassy Matrices.

    PubMed

    Shpotyuk, M V; Shpotyuk, O I; Cebulski, J; Kozyukhin, S

    2016-12-01

    The energetic χ-criterion is developed to parameterize difference in the origin of high-order optical non-linearity associated with metallic atoms (Cu, Ag, Au) embedded destructively in oxide- and chalcogenide glasses. Within this approach, it is unambiguously proved that covalent-bonded networks of soft semiconductor chalcogenides exemplified by binary As(Ge)-S(Se) glasses differ essentially from those typical for hard dielectric oxides like vitreous silica by impossibility to accommodate pure agglomerates of metallic nanoparticles. In an excellence according to known experimental data, it is suggested that destructive clustering of nanoparticles is possible in Cu-, Ag-, and Au-ion-implanted dielectric oxide glass media, possessing a strongly negative χ-criterion. Some recent speculations trying to ascribe equally this ability to soft chalcogenide glasses despite an obvious difference in the corresponding bond dissociation energies have been disclosed and criticized as inconclusive.

  7. Destructive Clustering of Metal Nanoparticles in Chalcogenide and Oxide Glassy Matrices

    NASA Astrophysics Data System (ADS)

    Shpotyuk, M. V.; Shpotyuk, O. I.; Cebulski, J.; Kozyukhin, S.

    2016-01-01

    The energetic χ-criterion is developed to parameterize difference in the origin of high-order optical non-linearity associated with metallic atoms (Cu, Ag, Au) embedded destructively in oxide- and chalcogenide glasses. Within this approach, it is unambiguously proved that covalent-bonded networks of soft semiconductor chalcogenides exemplified by binary As(Ge)-S(Se) glasses differ essentially from those typical for hard dielectric oxides like vitreous silica by impossibility to accommodate pure agglomerates of metallic nanoparticles. In an excellence according to known experimental data, it is suggested that destructive clustering of nanoparticles is possible in Cu-, Ag-, and Au-ion-implanted dielectric oxide glass media, possessing a strongly negative χ-criterion. Some recent speculations trying to ascribe equally this ability to soft chalcogenide glasses despite an obvious difference in the corresponding bond dissociation energies have been disclosed and criticized as inconclusive.

  8. Etude des effets du martelage repetitif sur les contraintes residuelles

    NASA Astrophysics Data System (ADS)

    Hacini, Lyes

    L'assemblage par soudage peut engendrer des contraintes residuelles. Ces contraintes provoquent des fissurations prematurees et un raccourcissement de la duree de vie des composants. Dans ce contexte, le martelage robotise est utilise pour relaxer ces contraintes residuelles. Trois volets sont presentes: le premier est l'evaluation des effets des impacts unitaires repetes sur le champ de contraintes developpe dans des plaques d'acier inoxydable austenitique 304L vierges ou contenant des contraintes residuelles initiales. Dans la deuxieme partie de ce projet, le martelage est applique grace au robot SCOMPI. Les contraintes residuelles induites et relaxees par martelage sont ensuite mesurees par la methode des contours, qui a ete adaptee a cet effet. Dans la troisieme partie, le martelage est modelise par la methode des elements finis. Un modele axisymetrique developpe grace au logiciel ANSYS permet de simuler des impacts repetes d'un marteau elastique sur une plaque ayant un comportement elastoplastique.

  9. Singular Mueller matrices.

    PubMed

    Gil, José J; Ossikovski, Razvigor; José, Ignacio San

    2016-04-01

    Singular Mueller matrices play an important role in polarization algebra and have peculiar properties that stem from the fact that either the medium exhibits maximum diattenuation and/or polarizance or because its associated canonical depolarizer has the property of fully randomizing the circular component (at least) of the states of polarization of light incident on it. The formal reasons for which the Mueller matrix M of a given medium is singular are systematically investigated, analyzed, and interpreted in the framework of the serial decompositions and the characteristic ellipsoids of M. The analysis allows for a general classification and geometric representation of singular Mueller matrices, which are of potential usefulness to experimentalists dealing with such media. PMID:27140769

  10. Singular Mueller matrices.

    PubMed

    Gil, José J; Ossikovski, Razvigor; José, Ignacio San

    2016-04-01

    Singular Mueller matrices play an important role in polarization algebra and have peculiar properties that stem from the fact that either the medium exhibits maximum diattenuation and/or polarizance or because its associated canonical depolarizer has the property of fully randomizing the circular component (at least) of the states of polarization of light incident on it. The formal reasons for which the Mueller matrix M of a given medium is singular are systematically investigated, analyzed, and interpreted in the framework of the serial decompositions and the characteristic ellipsoids of M. The analysis allows for a general classification and geometric representation of singular Mueller matrices, which are of potential usefulness to experimentalists dealing with such media.

  11. Stable lepton mass matrices

    NASA Astrophysics Data System (ADS)

    Domcke, Valerie; Romanino, Andrea

    2016-06-01

    We study natural lepton mass matrices, obtained assuming the stability of physical flavour observables with respect to the variations of individual matrix elements. We identify all four possible stable neutrino textures from algebraic conditions on their entries. Two of them turn out to be uniquely associated to specific neutrino mass patterns. We then concentrate on the semi-degenerate pattern, corresponding to an overall neutrino mass scale within the reach of future experiments. In this context we show that i) the neutrino and charged lepton mixings and mass matrices are largely constrained by the requirement of stability, ii) naturalness considerations give a mild preference for the Majorana phase most relevant for neutrinoless double- β decay, α ˜ π/2, and iii) SU(5) unification allows to extend the implications of stability to the down quark sector. The above considerations would benefit from an experimental determination of the PMNS ratio | U 32 /U 31|, i.e. of the Dirac phase δ.

  12. Glassy aerosols heterogeneously nucleate cirrus ice particles

    NASA Astrophysics Data System (ADS)

    Wilson, Theodore W.; Murray, Benjamin J.; Dobbie, Steven; Cui, Zhiqiang; Al-Jumur, Sardar M. R. K.; Möhler, Ottmar; Schnaiter, Martin; Wagner, Robert; Benz, Stefan; Niemand, Monika; Saathoff, Harald; Ebert, Volker; Wagner, Steven; Kärcher, Bernd

    2010-05-01

    Ice clouds in the tropical tropopause layer (TTL, ~12-18 km, ~180-200 K) play a key role in dehydrating air entering the stratosphere. However, in-situ measurements show that air within these clouds is unexpectedly supersaturated(1); normally the growth of ice crystals rapidly quenches any supersaturation. A number of explanations for high in-cloud humidity have been put forward, but recent research suggests high humidity may be related to the low numbers of ice crystals found within these clouds(1). Low ice number densities can be produced through selective nucleation by a small subset of aerosol particles. This is inconsistent with homogeneous nucleation of ice in liquid aerosols. However, droplets rich in organic material, ubiquitous in the TTL, are known to become glassy (amorphous, non-crystalline solid) under TTL conditions(2,3). Here we show, using a large cloud simulation chamber, that glassy solution droplets nucleate ice heterogeneously at low supersaturations. Using a one-dimensional cirrus model we also show that nucleation by glassy aerosol in the TTL may explain low TTL ice number densities and high in-cloud humidity. Recent measurements of the composition of TTL cirrus residues are consistent with our findings(4). (1) Krämer, M. et al. Ice supersaturations and cirrus cloud crystal numbers. Atm. Chem. Phys. 9, 3505-3522 (2009). (2) Murray, B. J. Inhibition of ice crystallisation in highly viscous aqueous organic acid droplets. Atm. Chem. Phys. 8, 5423-5433 (2008). (3) Zobrist, B., Marcolli, C., Pedernera, D. A. & Koop, T. Do atmospheric aerosols form glasses? Atm. Chem. Phys. 8, 5221-5244 (2008). (4) Froyd, K. D., Murphy, D. M., Lawson, P., Baumgardner, D. & Herman, R. L. Aerosols that form subvisible cirrus at the tropical tropopause. Atmos. Chem. Phys. 10, 209-218 (2010).

  13. Water sorption and diffusion in glassy polymers

    NASA Astrophysics Data System (ADS)

    Davis, Eric Mikel

    Water sorption and diffusion in glassy polymers is important in many fields, including drug delivery, desalination, energy storage and delivery, and packaging. Accurately measuring and understanding the underlying transport mechanisms of water in these glassy polymers is often complex due to both the nonequilibrium state of the polymer and the self-associating nature of water (e.g., hydrogen bonding). In this work, water sorption and diffusion in a number of glassy polymers were measured using gravimetric and spectroscopic techniques, including quartz spring microbalance, quartz crystal microbalance, and in situ time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian diffusion was observed in all polymers studied, indicated by an initial stage of water uptake, followed by a second stage of continuous, gradual uptake of water at later experimental times. These phenomena were attributed to diffusion driven by a concentration gradient, as well as diffusion driven by slow polymer relaxation resulting in additional water ingress over time. In order to gain additional insight into these phenomena, which are a product of nonequilibrium state of the polymers, diffusion-relaxation models were developed and employed to determine the time scales for both diffusion and polymer relaxation, where the ratio of these values (Deborah number) confirmed the observed non-Fickian water diffusion. In addition, the solubility of water in these polymers was predicted using two nonequilibrium thermodynamic models: the nonequilibrium lattice fluid (NELF) model and the nonequilibrium statistical associating fluid theory (NE-SAFT), where excellent agreement between the NE-SAFT predictions and experimental data was obtained over the entire water vapor activity range explored. Furthermore, the states of water were analyzed using the Zimm-Lundberg clustering theory, as well as in situ FTIR-ATR spectroscopy, where the latter technique provides a

  14. How Glassy States Affect Brown Carbon Production?

    NASA Astrophysics Data System (ADS)

    Liu, P.; Li, Y.; Wang, Y.; Bateman, A. P.; Zhang, Y.; Gong, Z.; Gilles, M. K.; Martin, S. T.

    2015-12-01

    Secondary organic material (SOM) can become light-absorbing (i.e. brown carbon) via multiphase reactions with nitrogen-containing species such as ammonia and amines. The physical states of SOM, however, potentially slow the diffusion of reactant molecules in organic matrix under conditions that semisolids or solids prevail, thus inhibiting the browning reaction pathways. In this study, the physical states and the in-particle diffusivity were investigated by measuring the evaporation kinetics of both water and organics from aromatic-derived SOMs using a quartz-crystal-microbalance (QCM). The results indicate that the SOMs derived from aromatic precursors toluene and m-xylene became solid (glassy) and the in particle diffusion was significantly impeded for sufficiently low relative humidity ( < 20% RH) at 293 K. Optical properties and the AMS spectra were measured for toluene-derived SOM after ammonia exposure at varied RHs. The results suggest that the production of light-absorbing nitrogen-containing compounds from multiphase reactions with ammonia was kinetically limited in the glassy organic matrix, which otherwise produce brown carbon. The results of this study have significant implications for production and optical properties of brown carbon in urban atmospheres that ultimately influence the climate and tropospheric photochemistry.

  15. Deformation and failure of glassy materials

    NASA Astrophysics Data System (ADS)

    Rottler, Joerg Gerhard

    Elastoplastic deformation of disordered solids and the formation of polymer crazes in amorphous polymer glasses are studied using large-scale molecular dynamics simulations. It is shown that the pressure-modified von Mises criterion accurately describes the maximum shear yield stress under general loading conditions. The pressure coefficient is insensitive to most model parameters, but is related to the bead geometry in analogy to friction coefficients. The yield stress decreases linearly with rising temperature and the strain rate dependence can be described by a power-law, or in a limited range, by a logarithm. The rate dependence does not vary with temperature, which is inconsistent with simple rate-state models of thermal activation such as the Eyring model. An analysis of the dynamics of the local stress distribution as well as modern phenomenological theories of rheology of glassy materials are discussed in light of these findings. We then present a comprehensive investigation of the deformation of glassy polymeric systems into a dense load-bearing network of fibrils and voids called a craze at large strains. This expansion takes place in the form of a drawing process, where the strain rate is strongly localized in a narrow interface region between dense polymer and craze. The expansion is controlled by some polymer chain segments between entanglements that are stretched taut during crazing. We also find that the distribution of tension in the craze develops an exponential force tail in close analogy to compressed jammed systems such as granular media. This highly anisotropic stress distribution and the localization of large forces on relatively few chains indicate that earlier models of the crazing process that treat the polymer as a viscous fluid with hydrodynamic interactions are incorrect. Simulations and simple scaling arguments are presented that describe craze breakdown through disentanglement or chain scission. Glassy polymers exhibit an unusually

  16. Active fluidization in dense glassy systems.

    PubMed

    Mandal, Rituparno; Bhuyan, Pranab Jyoti; Rao, Madan; Dasgupta, Chandan

    2016-07-20

    Dense soft glasses show strong collective caging behavior at sufficiently low temperatures. Using molecular dynamics simulations of a model glass former, we show that the incorporation of activity or self-propulsion, f0, can induce cage breaking and fluidization, resulting in the disappearance of the glassy phase beyond a critical f0. The diffusion coefficient crosses over from being strongly to weakly temperature dependent as f0 is increased. In addition, we demonstrate that activity induces a crossover from a fragile to a strong glass and a tendency of active particles to cluster. Our results are of direct relevance to the collective dynamics of dense active colloidal glasses and to recent experiments on tagged particle diffusion in living cells. PMID:27380935

  17. NRA of hydrogen in glassy polymeric carbon

    NASA Astrophysics Data System (ADS)

    Zimmerman, R. L.; Ila, D.; Jenkins, G. M.; Hirvonen, J. K.; Maleki, H.

    1997-02-01

    Glassy Polymeric Carbon (GPC) is prepared from a precursor resin by careful heat treatment. Heat Treatment Temperatures (HTT) above 1500 °C are believed to expel all hydrogen and oxygen from the grafene structure of GPC. However, we have shown that significant amounts of oxygen remain sequestered in the pores of GPC even at HTT's above 1500 °C. In the present study we report the detection of similar amounts of hydrogen for various heat treatment temperatures up to 2500 °C. A Nuclear Reaction Analysis (NRA) method with the 1H(15N,αγ)12C reaction and a specifically designed coincidence array is used to detect the 4.43 MeV gamma ray whose yield is proportional to the hydrogen content in the GPC. The H:C atomic ratio decreases with increasing HTT and we show that it exceeds 1:100 even for a HTT of 2500 °C.

  18. Glassy Behavior in a Micellar Polyelectrolyte System

    NASA Astrophysics Data System (ADS)

    Bhatia, Surita; Crichton, Mark; Mourchid, Ahmed

    2003-03-01

    We present SANS and rheology for micellar solutions of polystyrene-poly(acrylic acid) block copolymers that can be regarded as attractive colloids. These systems form gels at high effective micellar volume fractions that are suggestive of disordered colloidal glasses. At the gel point, the solution rheology follows the scaling predicted by classical percolation theory. We argue that this scaling could be due either to formation of a percolated network or a pre-transitional glassy phase. The addition of cationic and anionic surfactants (DTAB and SDS) can be used to modify the intermicellar interactions and solution rheology. Addition of an anionic surfactant acts to screen attractive interactions and causes a monotonic decrease in the elastic modulus. However, the addition of a cationic surfactant appears to initially induce a stronger intermicellar attraction, leading to gels with a higher elastic modulus. At higher surfactant concentrations, the cationic surfactant begins to screen intermicellar association, leading to a decrease in elasticity.

  19. Plastic and glassy crystal states of caffeine.

    PubMed

    Descamps, Marc; Correia, Natalia T; Derollez, Patrick; Danede, Florence; Capet, Frédéric

    2005-08-25

    The present paper focuses on the high temperature form I of caffeine and on its low temperature metastable form. Structural, dynamic, and kinetic information has been obtained by X-ray, dielectric, and calorimetric investigations. This study shows the following features: (1) The high temperature phase (I) of caffeine is in a state of dynamically orientationally disordered crystalline state (so-called "plastic, or rotator, phase"). (2) This high-symmetry hexagonal phase can be maintained at low temperature in a metastable situation. (3) Under deep undercooling of form I a glass transition occurs in the disordered crystalline state near room temperature. It is associated with the orientational freezing in of the molecular motions. Otherwise stated, the metastable state I enters into a nonergodic unstable state, so-called "glassy crystal" state. These findings rationalize the difficulties seen with caffeine in pharmaceutical science.

  20. Biaxial stress relaxation in glassy polymers - Polymethylmethacrylate.

    NASA Technical Reports Server (NTRS)

    Sternstein, S. S.; Ho, T. C.

    1972-01-01

    Biaxial stress relaxation studies were performed on glassy polymethylmethacrylate in combined torsion-tension strain fields using a specially designed apparatus with exceptionally high stiffness and low cross talk between the torsional and tensile load measuring transducers. It was found that at low strain levels uniaxial tension relaxation is slower than pure torsion relaxation; tensile-component relaxation rates are unaffected by the level of torsional strain; torsional-component relaxation rates decrease as tensile strain is increased; uniaxial tension relaxation rates approach the pure torsion rates at higher strains (about 2%). A phenomenological treatment is presented which shows that relaxation rates can be coupled to the strain fields in which they are observed and yet be consistent with the concepts of linear viscoelasticity and the Boltzmann superposition integral.

  1. Glassy Dynamics, Cell Mechanics and Endothelial Permeability

    PubMed Central

    Hardin, Corey; Rajendran, Kavitha; Manomohan, Greeshma; Tambe, Dhananjay T.; Butler, James P.; Fredberg, Jeffrey J.; Martinelli, Roberta; Carman, Christopher V.; Krishnan, Ramaswamy

    2013-01-01

    A key feature of all inflammatory processes is disruption of the vascular endothelial barrier. Such disruption is initiated in part through active contraction of the cytoskeleton of the endothelial cell (EC). Because contractile forces are propagated from cell to cell across a great many cell-cell junctions, this contractile process is strongly cooperative and highly nonlocal. We show here that the characteristic length scale of propagation is modulated by agonists and antagonists that impact permeability of the endothelial barrier. In the presence of agonists including thrombin, histamine, and H202, force correlation length increases, whereas in the presence of antagonists including sphingosine-1-phosphate, hepatocyte growth factor, and the rho kinase inhibitor, Y27632, force correlation length decreases. Intercellular force chains and force clusters are also evident, both of which are reminiscent of soft glassy materials approaching a glass transition. PMID:23638866

  2. Generating random density matrices

    NASA Astrophysics Data System (ADS)

    Życzkowski, Karol; Penson, Karol A.; Nechita, Ion; Collins, Benoît

    2011-06-01

    We study various methods to generate ensembles of random density matrices of a fixed size N, obtained by partial trace of pure states on composite systems. Structured ensembles of random pure states, invariant with respect to local unitary transformations are introduced. To analyze statistical properties of quantum entanglement in bi-partite systems we analyze the distribution of Schmidt coefficients of random pure states. Such a distribution is derived in the case of a superposition of k random maximally entangled states. For another ensemble, obtained by performing selective measurements in a maximally entangled basis on a multi-partite system, we show that this distribution is given by the Fuss-Catalan law and find the average entanglement entropy. A more general class of structured ensembles proposed, containing also the case of Bures, forms an extension of the standard ensemble of structureless random pure states, described asymptotically, as N → ∞, by the Marchenko-Pastur distribution.

  3. Shock-wave studies of anomalous compressibility of glassy carbon

    NASA Astrophysics Data System (ADS)

    Molodets, A. M.; Golyshev, A. A.; Savinykh, A. S.; Kim, V. V.

    2016-02-01

    The physico-mechanical properties of amorphous glassy carbon are investigated under shock compression up to 10 GPa. Experiments are carried out on the continuous recording of the mass velocity of compression pulses propagating in glassy carbon samples with initial densities of 1.502(5) g/cm3 and 1.55(2) g/cm3. It is shown that, in both cases, a compression wave in glassy carbon contains a leading precursor with amplitude of 0.135(5) GPa. It is established that, in the range of pressures up to 2 GPa, a shock discontinuity in glassy carbon is transformed into a broadened compression wave, and shock waves are formed in the release wave, which generally means the anomalous compressibility of the material in both the compression and release waves. It is shown that, at pressure higher than 3 GPa, anomalous behavior turns into normal behavior, accompanied by the formation of a shock compression wave. In the investigated area of pressure, possible structural changes in glassy carbon under shock compression have a reversible character. A physico-mechanical model of glassy carbon is proposed that involves the equation of state and a constitutive relation for Poisson's ratio and allows the numerical simulation of physico-mechanical and thermophysical properties of glassy carbon of different densities in the region of its anomalous compressibility.

  4. High temperature annealing studies of strontium ion implanted glassy carbon

    NASA Astrophysics Data System (ADS)

    Odutemowo, O. S.; Malherbe, J. B.; Prinsloo, L.; Langa, D. F.; Wendler, E.

    2016-03-01

    Glassy carbon samples were implanted with 200 keV strontium ions to a fluence of 2 × 1016 ions/cm2 at room temperature. Analysis with Raman spectroscopy showed that ion bombardment amorphises the glassy carbon structure. Partial recovery of the glassy carbon structure was achieved after the implanted sample was vacuum annealed at 900 °C for 1 h. Annealing the strontium ion bombarded sample at 2000 °C for 5 h resulted in recovery of the glassy carbon substrate with the intensity of the D peak becoming lower than that of the pristine glassy carbon. Rutherford backscattering spectroscopy (RBS) showed that the implanted strontium diffused towards the surface of the glassy carbon after annealing the sample at 900 °C. This diffusion was also accompanied by loss of the implanted strontium. Comparison between the as-implanted and 900 °C depth profiles showed that less than 30% of the strontium was retained in the glassy carbon after heat treatment at 900 °C. The RBS profile after annealing at 2000 °C indicated that no strontium ions were retained after heat treatment at this temperature.

  5. Enhancing Understanding of Transformation Matrices

    ERIC Educational Resources Information Center

    Dick, Jonathan; Childrey, Maria

    2012-01-01

    With the Common Core State Standards' emphasis on transformations, teachers need a variety of approaches to increase student understanding. Teaching matrix transformations by focusing on row vectors gives students tools to create matrices to perform transformations. This empowerment opens many doors: Students are able to create the matrices for…

  6. Anodic electrosynthesis of some peroxy compounds on glassy carbon electrodes

    SciTech Connect

    Khomutov, N.E.; Zakhodyakina, N.A.; Svirida, L.V.; Nesvat, N.V.

    1987-11-10

    The authors present the results of a study of the anodic electrosynthesis of hydrogen peroxide and its derivatives on glassy carbon in solutions of sodium carbonate and sodium carbonate with sodium borate. We studied the kinetics of anodic processes on glassy carbon with the aid of polarization measurements and a method for determining the concentrations of active oxygen in the anolyte and the current efficiency. The current efficiencies with respect to active oxygen obtained on glassy carbon in the mixed solution of sodium borate and sodium carbonate are close to the current efficiencies which are observed on platinum anodes in the industrial electrosynthesis of perborates.

  7. Parametrisation D'effets Non-Standard EN Phenomenologie Electrofaible

    NASA Astrophysics Data System (ADS)

    Maksymyk, Ivan

    Cette these pat articles porte sur la parametrisation d'effets non standard en physique electrofaible. Dans chaque analyse, nous avons ajoute plusieurs operateurs non standard au lagrangien du modele standard electrofaible. Les operateurs non standard decrivent les nouveaux effets decoulant d'un modele sous-jacent non-specefie. D'emblee, le nombre d'operateurs non standard que l'on peut inclure dans une telle analyse est illimite. Mais pour une classe specifique de modeles sous-jacents, les effets non standard peuvent etre decrits par un nombre raisonnable d'operateurs. Dans chaque analyse nous avons developpe des expressions pour des observables electrofaibles, en fonction des coefficients des operateurs nouveaux. En effectuant un "fit" statistique sur un ensemble de donnees experimentales precises, nous avons obtenu des contraintes phenomenologiques sur ces coefficients. Dans "Model-Independent Global Constraints on New Physics", nous avons adopte des hypotheses tres peu contraignantes relatives aux modeles sous-jacents. Nous avons tronque le lagrangien effectif a la dimension cinq (inclusivement). Visant la plus grande generalite possible, nous avons admis des interactions qui ne respectent pas les symetries discretes (soit C, P et CP) ainsi que des interactions qui ne conservent pas la saveur. Le lagrangien effectif contient une quarantaine d'operateurs nouveaux. Nous avons determine que, pour la plupart des coefficients des nouveaux operateurs, les contraintes sont assez serrees (2 ou 3%), mais il y a des exceptions interessantes. Dans "Bounding Anomalous Three-Gauge-Boson Couplings", nous avons determine des contraintes phenomenologiques sur les deviations des couplages a trois bosons de jauge par rapport aux interactions prescrites par le modele standard. Pour ce faire, nous avons calcule les contributions indirectes des CTBJ non standard aux observables de basse energie. Puisque le lagrangien effectif est non-renormalisable, certaines difficultes techniques

  8. On Some Properties of Gamma Matrices

    ERIC Educational Resources Information Center

    Dumais, Jean-Francois

    1977-01-01

    Discusses the problem of the order, reducibility, and equivalence of systems of Dirac gamma matrices. Gives a simple systematic method for finding the matrices connecting different systems of 4 x 4 gamma matrices. (MLH)

  9. Covalent modification of glassy carbon spheres through ball milling under solvent free conditions: A novel electrochemical interface for mercury(II) quantification.

    PubMed

    Kempegowda, Raghu G; Malingappa, Pandurangappa

    2014-08-01

    A simple and green chemistry protocol has been proposed based on the covalent anchoring of benzamide molecule on glassy carbon spheres through ball milling under solvent free condition. The modification proceeds through the formation of an amide bond between carboxylic group of glassy carbon spheres and the amino group of modifier molecule. The formation of covalent bond was ascertained using X-ray photoelectron spectroscopy. Scanning electron microscopy was used to study the surface morphology of milled glassy carbon spheres. The aqueous colloidal solution of modified glassy carbon spheres was used in the preparation of thin film electrodes and subsequently used as a novel electrochemical interface in the quantification of mercury at trace level using a differential pulse anodic stripping voltammetric technique. The modified electrode showed good sensitivity and selectivity towards mercury with a detection limit of 1nM with least interference from most of the ions. The analytical utility of the proposed electrode has been validated by determining the mercury levels in number of sample matrices. PMID:24881534

  10. Singular-potential random-matrix model arising in mean-field glassy systems

    NASA Astrophysics Data System (ADS)

    Akemann, Gernot; Villamaina, Dario; Vivo, Pierpaolo

    2014-06-01

    We consider an invariant random matrix ensemble where the standard Gaussian potential is distorted by an additional single pole of arbitrary fixed order. Potentials with first- and second-order poles have been considered previously and found applications in quantum chaos and number theory. Here we present an application to mean-field glassy systems. We derive and solve the loop equation in the planar limit for the corresponding class of potentials. We find that the resulting mean or macroscopic spectral density is generally supported on two disconnected intervals lying on the two sides of the repulsive pole, whose edge points can be completely determined imposing the additional constraint of traceless matrices on average. For an unbounded potential with an attractive pole, we also find a possible one-cut solution for certain values of the couplings, which is ruled out when the traceless condition is imposed. Motivated by the calculation of the distribution of the spin-glass susceptibility in the Sherrington-Kirkpatrick spin-glass model, we consider in detail a second-order pole for a zero-trace model and provide the most explicit solution in this case. In the limit of a vanishing pole, we recover the standard semicircle. Working in the planar limit, our results apply to matrices with orthogonal, unitary, and symplectic invariance. Numerical simulations and an independent analytical Coulomb fluid calculation for symmetric potentials provide an excellent confirmation of our results.

  11. Singular-potential random-matrix model arising in mean-field glassy systems.

    PubMed

    Akemann, Gernot; Villamaina, Dario; Vivo, Pierpaolo

    2014-06-01

    We consider an invariant random matrix ensemble where the standard Gaussian potential is distorted by an additional single pole of arbitrary fixed order. Potentials with first- and second-order poles have been considered previously and found applications in quantum chaos and number theory. Here we present an application to mean-field glassy systems. We derive and solve the loop equation in the planar limit for the corresponding class of potentials. We find that the resulting mean or macroscopic spectral density is generally supported on two disconnected intervals lying on the two sides of the repulsive pole, whose edge points can be completely determined imposing the additional constraint of traceless matrices on average. For an unbounded potential with an attractive pole, we also find a possible one-cut solution for certain values of the couplings, which is ruled out when the traceless condition is imposed. Motivated by the calculation of the distribution of the spin-glass susceptibility in the Sherrington-Kirkpatrick spin-glass model, we consider in detail a second-order pole for a zero-trace model and provide the most explicit solution in this case. In the limit of a vanishing pole, we recover the standard semicircle. Working in the planar limit, our results apply to matrices with orthogonal, unitary, and symplectic invariance. Numerical simulations and an independent analytical Coulomb fluid calculation for symmetric potentials provide an excellent confirmation of our results.

  12. A structural approach to relaxation in glassy liquids

    NASA Astrophysics Data System (ADS)

    Schoenholz, S. S.; Cubuk, E. D.; Sussman, D. M.; Kaxiras, E.; Liu, A. J.

    2016-05-01

    In contrast with crystallization, there is no noticeable structural change at the glass transition. Characteristic features of glassy dynamics that appear below an onset temperature, T0 (refs ,,), are qualitatively captured by mean field theory, which assumes uniform local structure. Studies of more realistic systems have found only weak correlations between structure and dynamics. This raises the question: is structure important to glassy dynamics in three dimensions? We answer this question affirmatively, using machine learning to identify a new field, `softness' which characterizes local structure and is strongly correlated with dynamics. We find that the onset of glassy dynamics at T0 corresponds to the onset of correlations between softness (that is, structure) and dynamics. Moreover, we construct a simple model of relaxation that agrees well with our simulation results, showing that a theory of the evolution of softness in time would constitute a theory of glassy dynamics.

  13. Ductile mode electrochemical oxidation assisted micromachining for glassy carbon

    NASA Astrophysics Data System (ADS)

    Nam, Eunseok; Lee, Chan-Young; Jun, Martin B. G.; Min, Byung-Kwon

    2015-04-01

    Recently, a new mechanical machining process using electrochemical oxidation was reported. Electrochemical oxidation assisted micromachining was applied to the machining of glassy carbon. The material removal process of the electrochemical oxidation assisted micromachining consists of repeated cycles of oxidation followed by removal of the oxide layer. In this paper, we experimentally investigate and compare the critical chip thickness for ductile mode cutting in mechanical machining and electrochemical oxidation assisted micromachining of glassy carbon. The theoretical critical chip thickness is calculated for mechanical machining of glassy carbon and experimentally verified. The effect of electrochemical oxidation on the critical chip thickness for ductile mode micromachining is also studied for glassy carbon. It is found that the critical chip thickness is increased for the electrochemical oxidation assisted micromachining.

  14. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-08-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/sqrt{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/sqrt{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example, we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  15. Adhesion in hydrogels and model glassy polymers

    NASA Astrophysics Data System (ADS)

    Guvendiren, Murat

    Two main topics are addressed in this dissertation: (1) adhesion in hydrogels; (2) interfacial interactions between model glassy polymers. A self-assembly technique for the formation of hydrogels from acrylic triblock copolymer solutions was developed, based on vapor phase solvent exchange. Structure formation in the gels was characterized by small angle X-ray scattering, and swelling was measured in controlled pH buffer solutions. Strong gels are formed with polymer weight fractions between 0.01 and 0.15, and with shear moduli between 0.6 kPa and 3.5 kPa. Adhesive functionality, based on 3,4-dihydroxy-L-phenylalanine (DOPA) was also incorporated into the triblock copolymers. The effect of DOPA concentration on gel formation and swelling was investigated in detail. The adhesive properties of DOPA-functionalized hydrogels on TiO2 were investigated with an axisymmetric adhesion method. It was shown that the presence of DOPA enhances the adhesive properties of the hydrogels, but that the effect is minimized at pH values below 10, where the DOPA groups are hydrophobic. Thin film membranes were produced in order to study the specific interactions between DOPA and TiO2 and DOPA and tissue, using a membrane inflation method. The presence of DOPA in the membranes enhances the adhesion on TiO 2 and tissue, although adhesion to tissue requires that the DOPA groups be oxidized while in contact with the tissue of interest. Porous hydrogel scaffolds for tissue engineering applications were formed by adding salt crystals to the triblock copolymer solution prior to solvent exchange. Salt was then leached out by immersing the gel into water. Structures of the porous hydrogels were characterized by confocal laser scanning microscopy. These hydrogels were shown to be suitable for tissue regeneration and drug delivery applications. Diffusion-mediated adhesion between two component miscible polymer systems having very different glassy temperatures was also investigated. Axisymmetric

  16. Synthesis and characterization of novel glassy liquid crystals

    NASA Astrophysics Data System (ADS)

    Chen, Huang-Ming Philip

    As an emerging class of photonic and electronic materials, glassy liquid crystals are capable of preserving in the solid state molecular order characteristic of liquid crystals. Because of superior chemical purity and favorable rheological properties, glassy liquid crystals can be readily processed into large-area monodomain films. This thesis aimed at deterministic synthesis of glassy chiral nematics, photochromic glassy nematics, and glassy discotics. The most significant contributions are recapitulated as follows: (1) Through deterministic synthesis of multifunctional materials via enzymatic and chemical approaches, enantiomeric glassy chiral nematics were prepared efficiently and shown to possess a glass transition temperature over 60°C and a cholesteric fluid temperature range wider than 100°C. Device concepts were also demonstrated for high-performance circular polarizers, notch filters and reflectors in the ultraviolet, across the visible, and to the infrared region. (2) The first photochromic glassy nematic liquid crystal was successfully designed, synthesized and characterized to possess a glass transition temperature over 100°C and a clearing point over 200°C. A large-area solid film was prepared through melt processing to demonstrate high-speed switching of anisotropic refractive indices and optical birefringence as a novel approach to rewritable optical memory and photonic switching in solid films. (3) Glassy discotic liquid crystals were synthesized and characterized by x-ray diffraction, polarizing optical microscopy, differential scanning calorimetry, and dynamic mechanical analysis to reveal sub-freezing glass transition temperatures. However, the absence of recrystallization at room temperature over a period of over four years was a manifestation of morphological stability of the discotics.

  17. No inherent glassiness in a Penrose tiling quasicrystal

    SciTech Connect

    Strandburg, K.J.; Dressel, P.R.

    1988-11-01

    Consideration of the structure of the Penrose pattern has led to speculation that a system with a Penrose tiling ground state might be subject to inherent glassy behavior. Monte Carol simulations show, using a simple model of the energetics, that there is no inherent glassiness in the Penrose tiling. Thermodynamic quantities measured are completely reversible, displaying no observable hysterisis, and the system may be easily cooled from a highly disordered configuration into its lowest energy state. 11 refs., 7 figs.

  18. Structural Properties of Defects in Glassy Liquids.

    PubMed

    Cubuk, Ekin D; Schoenholz, Samuel S; Kaxiras, Efthimios; Liu, Andrea J

    2016-07-01

    At zero temperature a disordered solid corresponds to a local minimum in the energy landscape. As the temperature is raised or the system is driven with a mechanical load, the system explores different minima via dynamical events in which particles rearrange their relative positions. We have shown recently that the dynamics of particle rearrangements are strongly correlated with a structural quantity associated with each particle, "softness", which we can identify using supervised machine learning. Particles of a given softness have a well-defined energy scale that governs local rearrangements; because of this property, softness greatly simplifies our understanding of glassy dynamics. Here we investigate the correlation of softness with other commonly used structural quantities, such as coordination number and local potential energy. We show that although softness strongly correlates with these properties, its predictive power for rearrangement dynamics is much higher. We introduce a useful metric for quantifying the quality of structural quantities as predictors of dynamics. We hope that, in the future, authors introducing new structural measures of dynamics will compare their proposals quantitatively to softness using this metric. We also show how softness correlations give insight into rearrangements. Finally, we explore the physical meaning of softness using unsupervised dimensionality reduction and reduced curve-fitting models, and show that softness can be recast in a form that is amenable to analytical treatment.

  19. Lithium ion diffusion through glassy carbon plate

    SciTech Connect

    Inaba, M.; Nohmi, S.; Funabiki, A.; Abe, T.; Ogumi, Z.

    1998-07-01

    The electrochemical permeation method was applied to the determination of the diffusion coefficient of Li{sup +} ion (D{sub Li{sup +}}) in a glassy carbon (GC) plate. The cell was composed of two compartments, which were separated by the GC plate. Li{sup +} ions were inserted electrochemically from one face, and extracted from the other. The flux of the permeated Li{sup +} ions was monitored as an oxidation current at the latter face. The diffusion coefficient was determined by fitting the transient current curve with a theoretical one derived from Fick's law. When the potential was stepped between two potentials in the range of 0 to 0.5 V, transient curves were well fitted with the theoretical one, which gave D{sub Li{sup +}} values on the order of 10{sup {minus}8} cm{sup {minus}2} s{sup {minus}1}. In contrast, when the potential was stepped between two potentials across 0.5 V, significant deviation was observed. The deviation indicated the presence of trap sites as well as diffusion sites for Li{sup +} ions, the former of which is the origin of the irreversible capacity of GC.

  20. Effect of additives on physicochemical properties in amorphous starch matrices.

    PubMed

    Liang, Jun; Wang, Simon; Ludescher, Richard D

    2015-03-15

    The effect of the addition of non-reducing sugars or methylcellulose on the matrix physical properties and rate of non-enzymatic browning (NBR) between exogenous glucose+lysine in a starch-based glassy matrix were studied, using the methods of luminescence and FTIR. Amorphous starch-based matrices were formulated by rapidly dehydrating potato starch gel mixed with additives at weight ratios of 7:93 (additive:starch). Data on the phosphorescence emission energy and lifetime from erythrosin B dispersed in the matrices indicated that sugars decreased starch matrix mobility in a Tg-dependent manner, except for trehalose that interacted with starch in a unique mode, while methylcellulose, the additive with the highest Tg, increased the molecular mobility. Using FTIR, we found that methylcellulose decreased the strength of hydrogen bond network and sugars enhanced the hydrogen bond strength in the order: trehalose>maltitol>sucrose. Comparing those changes with the rate of NBR between exogenous glucose+lysine, we suggest that NBR rates are primarily influenced by matrix mobility, which is modulated by the hydrogen bond network, and interactions among components. PMID:25308673

  1. Computer-Access-Code Matrices

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.

    1990-01-01

    Authorized users respond to changing challenges with changing passwords. Scheme for controlling access to computers defeats eavesdroppers and "hackers". Based on password system of challenge and password or sign, challenge, and countersign correlated with random alphanumeric codes in matrices of two or more dimensions. Codes stored on floppy disk or plug-in card and changed frequently. For even higher security, matrices of four or more dimensions used, just as cubes compounded into hypercubes in concurrent processing.

  2. Shear banding in soft glassy materials

    NASA Astrophysics Data System (ADS)

    Fielding, S. M.

    2014-10-01

    Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic ‘glassy’ features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.

  3. Probing Properties of Glassy Water and Other Liquids with Site Selective Spectroscopies

    SciTech Connect

    Dang, Nhan Chuong

    2005-01-01

    The standard non-photochemical hole burning (NPHB) mechanism, which involves phonon-assisted tunneling in the electronically excited state, was originally proposed to explain the light-induced frequency change of chemically stable molecules in glassy solids at liquid helium temperatures by this research group more than two decades ago. The NPHB mechanism was then further elucidated and the concept of intrinsic to glass configurational relaxation processes as pre-mediating step to the hole burning process was introduced. The latter provided the theoretical basis for NPHB to evolve into a powerful tool probing the dynamics and nature of amorphous media, which aside from ''simple'' inorganic glasses may include also ''complex'' biological systems such as living cells and cancerous/normal tissues. Presented in this dissertation are the experimental and theoretical results of hole burning properties of aluminum phthalocyanine tetrasulphonate (APT) in several different matrices: (1) hyperquenched glassy water (HGW); (2) cubic ice (Ic); and (3) water confined into poly(2-hydroxyethylmethacrylate) (poly-HEMA). In addition, results of photochemical hole burning (PHB) studies obtained for phthalocyanine tetrasulphonate (PcT) in HGW and free base phthalocyanine (Pc) in ortho-dichlorobenzene (DCB) glass are reported. The goal of this dissertation was to provide further evidence supporting the NPHB mechanism and to provide more insight that leads to a better understanding of the kinetic events (dynamics) in glasses, and various dynamical processes of different fluorescent chromorphores in various amorphous solids and the liquid that exist above the glass transition temperature (Tg). The following issues are addressed in detail: (1) time evolution of hole being burned under different conditions and in different hole burning systems; (2) temperature dependent hole profile; and (3) the structure/dynamics of water in confined space, which

  4. Thermal Barrier Coatings Resistant to Glassy Deposits

    NASA Astrophysics Data System (ADS)

    Drexler, Julie Marie

    Engineering of alloys has for years allowed aircraft turbine engines to become more efficient and operate at higher temperatures. As advancements in these alloy systems have become more difficult, ceramic thermal barrier coatings (TBCs), often yttria (7 wt %) stabilized zirconia (7YSZ), have been utilized for thermal protection. TBCs have allowed for higher engine operating temperatures and better fuel efficiency but have also created new engineering problems. Specifically, silica based particles such as sand and volcanic ash that enter the engine during operation form glassy deposits on the TBCs. These deposits can cause the current industrial 7YSZ thermal barrier coatings to fail since the glass formed penetrates and chemically interacts with the TBC. When this occurs, coating failure may occur due to a loss of strain tolerance, which can lead to fracture, and phase changes of the TBC material. There have been several approaches used to stop calcium-magnesium aluminio-silcate (CMAS) glasses (molten sand) from destroying the entire TBC, but overall there is still limited knowledge. In this thesis, 7YSZ and new TBC materials will be examined for thermochemical and thermomechanical performance in the presence of molten CMAS and volcanic ash. Two air plasma sprayed TBCs will be shown to be resistant to volcanic ash and CMAS. The first type of coating is a modified 7YSZ coating with 20 mol% Al2O3 and 5 mol% TiO2 in solid solution (YSZ+20Al+5Ti). The second TBC is made of gadolinium zirconate. These novel TBCs impede CMAS and ash penetration by interacting with the molten CMAS or ash and drastically changing the chemistry. The chemically modified CMAS or ash will crystallize into an apatite or anorthite phase, blocking the CMAS or ash from further destroying the coating. A presented mechanism study will show these coatings are effective due to the large amount of solute (Gd, Al) in the zirconia structure, which is the key to creating the crystalline apatite or

  5. Optical speckles of blood proteins embedded in porous glassy substrate

    NASA Astrophysics Data System (ADS)

    Holden, T.; Dehipawala, S.; Kokkinos, D.; Berisha, A.; Cheung, E.; Nguyen, A.; Golebiewska, U.; Schneider, P.; Tremberger, G., Jr.; Lieberman, D.; Cheung, T.

    2012-03-01

    Blood protein molecules could be embedded in porous glassy substrate with 10-nm pores. The embedding principle is based on blood cell dehydration with the destruction of the cell membrane, and reconstitution and centrifuge could yield a suitable solution for doping into a porous glassy medium. The doped glassy substrate speckle pattern under laser illumination could be used to characterize the protein size distribution. Calibration with known protein embedded samples would result in an optical procedure for the characterization of a blood sample. Samples embedded with larger kilo-Dalton protein molecule show more variation in the speckle patterns, consistent with protein folding interaction inside a pore cavity. A regression model has been used to correlate the protein molecule sizes with speckle sizes. The use of diffusion mean free path information to study protein folding in the embedding process is briefly discussed.

  6. Truncations of random orthogonal matrices.

    PubMed

    Khoruzhenko, Boris A; Sommers, Hans-Jürgen; Życzkowski, Karol

    2010-10-01

    Statistical properties of nonsymmetric real random matrices of size M, obtained as truncations of random orthogonal N×N matrices, are investigated. We derive an exact formula for the density of eigenvalues which consists of two components: finite fraction of eigenvalues are real, while the remaining part of the spectrum is located inside the unit disk symmetrically with respect to the real axis. In the case of strong nonorthogonality, M/N=const, the behavior typical to real Ginibre ensemble is found. In the case M=N-L with fixed L, a universal distribution of resonance widths is recovered.

  7. Truncations of random orthogonal matrices

    NASA Astrophysics Data System (ADS)

    Khoruzhenko, Boris A.; Sommers, Hans-Jürgen; Życzkowski, Karol

    2010-10-01

    Statistical properties of nonsymmetric real random matrices of size M , obtained as truncations of random orthogonal N×N matrices, are investigated. We derive an exact formula for the density of eigenvalues which consists of two components: finite fraction of eigenvalues are real, while the remaining part of the spectrum is located inside the unit disk symmetrically with respect to the real axis. In the case of strong nonorthogonality, M/N=const , the behavior typical to real Ginibre ensemble is found. In the case M=N-L with fixed L , a universal distribution of resonance widths is recovered.

  8. Iterative methods for Toeplitz-like matrices

    SciTech Connect

    Huckle, T.

    1994-12-31

    In this paper the author will give a survey on iterative methods for solving linear equations with Toeplitz matrices, Block Toeplitz matrices, Toeplitz plus Hankel matrices, and matrices with low displacement rank. He will treat the following subjects: (1) optimal (w)-circulant preconditioners is a generalization of circulant preconditioners; (2) Optimal implementation of circulant-like preconditioners in the complex and real case; (3) preconditioning of near-singular matrices; what kind of preconditioners can be used in this case; (4) circulant preconditioning for more general classes of Toeplitz matrices; what can be said about matrices with coefficients that are not l{sub 1}-sequences; (5) preconditioners for Toeplitz least squares problems, for block Toeplitz matrices, and for Toeplitz plus Hankel matrices.

  9. The Erevan howardite: Petrology of glassy clasts and mineral chemistry

    NASA Technical Reports Server (NTRS)

    Nazarov, M. A.; Ariskin, A. A.

    1993-01-01

    The Erevan howardite is a polymict regolith breccia containing xenoliths of carbonaceous chondrites. In this work, we studied glassy clasts, which could be considered as primary quenched melts, and mineral chemistry of the breccia. The study reveals that the Erevan howardite consists of common rocks of the HED suite. However, unique glassy clasts, which are present in some eucritic melts, were identified. The mineral chemistry and the simulation of crystallization of the melts suggest that the compositions of the melts reflect those of some primary lithologies of EPB.

  10. Making almost commuting matrices commute

    SciTech Connect

    Hastings, Matthew B

    2008-01-01

    Suppose two Hermitian matrices A, B almost commute ({parallel}[A,B]{parallel} {<=} {delta}). Are they close to a commuting pair of Hermitian matrices, A', B', with {parallel}A-A'{parallel},{parallel}B-B'{parallel} {<=} {epsilon}? A theorem of H. Lin shows that this is uniformly true, in that for every {epsilon} > 0 there exists a {delta} > 0, independent of the size N of the matrices, for which almost commuting implies being close to a commuting pair. However, this theorem does not specifiy how {delta} depends on {epsilon}. We give uniform bounds relating {delta} and {epsilon}. The proof is constructive, giving an explicit algorithm to construct A' and B'. We provide tighter bounds in the case of block tridiagonal and tridiagnonal matrices. Within the context of quantum measurement, this implies an algorithm to construct a basis in which we can make a projective measurement that approximately measures two approximately commuting operators simultaneously. Finally, we comment briefly on the case of approximately measuring three or more approximately commuting operators using POVMs (positive operator-valued measures) instead of projective measurements.

  11. Fibonacci Identities, Matrices, and Graphs

    ERIC Educational Resources Information Center

    Huang, Danrun

    2005-01-01

    General strategies used to help discover, prove, and generalize identities for Fibonacci numbers are described along with some properties about the determinants of square matrices. A matrix proof for identity (2) that has received immense attention from many branches of mathematics, like linear algebra, dynamical systems, graph theory and others…

  12. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    PubMed Central

    Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T.; Evoy, Stephane

    2016-01-01

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors. PMID:26985910

  13. The nonequilibrium glassy dynamics of self-propelled particles.

    PubMed

    Flenner, Elijah; Szamel, Grzegorz; Berthier, Ludovic

    2016-09-14

    We study the glassy dynamics taking place in dense assemblies of athermal active particles that are driven solely by a nonequilibrium self-propulsion mechanism. Active forces are modeled as an Ornstein-Uhlenbeck stochastic process, characterized by a persistence time and an effective temperature, and particles interact via a Lennard-Jones potential that yields well-studied glassy behavior in the Brownian limit, which is obtained as the persistence time vanishes. By increasing the persistence time, the system departs more strongly from thermal equilibrium and we provide a comprehensive numerical analysis of the structure and dynamics of the resulting active fluid. Finite persistence times profoundly affect the static structure of the fluid and give rise to nonequilibrium velocity correlations that are absent in thermal systems. Despite these nonequilibrium features, for any value of the persistence time we observe a nonequilibrium glass transition as the effective temperature is decreased. Surprisingly, increasing departure from thermal equilibrium is found to promote (rather than suppress) the glassy dynamics. Overall, our results suggest that with increasing persistence time, microscopic properties of the active fluid change quantitatively, but the general features of the nonequilibrium glassy dynamics observed with decreasing the effective temperature remain qualitatively similar to those of thermal glass-formers. PMID:27499055

  14. Introduction to the Glassy State in the Undergraduate Curriculum

    ERIC Educational Resources Information Center

    Johari, Gyan P.

    1974-01-01

    Presents fundamentals of the glassy state which can serve as an introductory, phenomenological, and nonmathematical exposure to undergraduates in at most two lectures. Suggests the use of the material following students' acquisition of an elementary knowledge of thermodynamics, liquids, and the crystalline state. (CC)

  15. Virial expansion for almost diagonal random matrices

    NASA Astrophysics Data System (ADS)

    Yevtushenko, Oleg; Kravtsov, Vladimir E.

    2003-08-01

    Energy level statistics of Hermitian random matrices hat H with Gaussian independent random entries Higeqj is studied for a generic ensemble of almost diagonal random matrices with langle|Hii|2rangle ~ 1 and langle|Hi\

  16. Pressure-induced transformations in computer simulations of glassy water.

    PubMed

    Chiu, Janet; Starr, Francis W; Giovambattista, Nicolas

    2013-11-14

    Glassy water occurs in at least two broad categories: low-density amorphous (LDA) and high-density amorphous (HDA) solid water. We perform out-of-equilibrium molecular dynamics simulations to study the transformations of glassy water using the ST2 model. Specifically, we study the known (i) compression-induced LDA-to-HDA, (ii) decompression-induced HDA-to-LDA, and (iii) compression-induced hexagonal ice-to-HDA transformations. We study each transformation for a broad range of compression/decompression temperatures, enabling us to construct a "P-T phase diagram" for glassy water. The resulting phase diagram shows the same qualitative features reported from experiments. While many simulations have probed the liquid-state phase behavior, comparatively little work has examined the transitions of glassy water. We examine how the glass transformations relate to the (first-order) liquid-liquid phase transition previously reported for this model. Specifically, our results support the hypothesis that the liquid-liquid spinodal lines, between a low-density and high-density liquid, are extensions of the LDA-HDA transformation lines in the limit of slow compression. Extending decompression runs to negative pressures, we locate the sublimation lines for both LDA and hyperquenched glassy water (HGW), and find that HGW is relatively more stable to the vapor. Additionally, we observe spontaneous crystallization of HDA at high pressure to ice VII. Experiments have also seen crystallization of HDA, but to ice XII. Finally, we contrast the structure of LDA and HDA for the ST2 model with experiments. We find that while the radial distribution functions (RDFs) of LDA are similar to those observed in experiments, considerable differences exist between the HDA RDFs of ST2 water and experiment. The differences in HDA structure, as well as the formation of ice VII (a tetrahedral crystal), are a consequence of ST2 overemphasizing the tetrahedral character of water. PMID:24320281

  17. 2H NMR studies of glycerol dynamics in protein matrices.

    PubMed

    Herbers, C R; Sauer, D; Vogel, M

    2012-03-28

    We use (2)H NMR spectroscopy to investigate the rotational motion of glycerol molecules in matrices provided by the connective tissue proteins elastin and collagen. Analyzing spin-lattice relaxation, line-shape properties, and stimulated-echo decays, we determine the rates and geometries of the motion as a function of temperature and composition. It is found that embedding glycerol in an elastin matrix leads to a mild slowdown of glycerol reorientation at low temperatures and glycerol concentrations, while the effect vanishes at ambient temperatures or high solvent content. Furthermore, it is observed that the nonexponential character of the rotational correlation functions is much more prominent in the elastin matrix than in the bulk liquid. Results from spin-lattice relaxation and line shape measurements indicate that, in the mixed systems, the strong nonexponentiality is in large part due to the existence of distributions of correlation times, which are broader on the long-time flank and, hence, more symmetric than in the neat system. Stimulated-echo analysis of slow glycerol dynamics reveals that, when elastin is added, the mechanism for the reorientation crosses over from small-angle jump dynamics to large-angle jump dynamics and the geometry of the motion changes from isotropic to anisotropic. The results are discussed against the background of present and previous findings for glycerol and water dynamics in various protein matrices and compared with observations for other dynamically highly asymmetric mixtures so as to ascertain in which way the viscous freezing of a fast component in the matrix of a slow component differs from the glassy slowdown in neat supercooled liquids. PMID:22462878

  18. 2H NMR studies of glycerol dynamics in protein matrices

    NASA Astrophysics Data System (ADS)

    Herbers, C. R.; Sauer, D.; Vogel, M.

    2012-03-01

    We use 2H NMR spectroscopy to investigate the rotational motion of glycerol molecules in matrices provided by the connective tissue proteins elastin and collagen. Analyzing spin-lattice relaxation, line-shape properties, and stimulated-echo decays, we determine the rates and geometries of the motion as a function of temperature and composition. It is found that embedding glycerol in an elastin matrix leads to a mild slowdown of glycerol reorientation at low temperatures and glycerol concentrations, while the effect vanishes at ambient temperatures or high solvent content. Furthermore, it is observed that the nonexponential character of the rotational correlation functions is much more prominent in the elastin matrix than in the bulk liquid. Results from spin-lattice relaxation and line shape measurements indicate that, in the mixed systems, the strong nonexponentiality is in large part due to the existence of distributions of correlation times, which are broader on the long-time flank and, hence, more symmetric than in the neat system. Stimulated-echo analysis of slow glycerol dynamics reveals that, when elastin is added, the mechanism for the reorientation crosses over from small-angle jump dynamics to large-angle jump dynamics and the geometry of the motion changes from isotropic to anisotropic. The results are discussed against the background of present and previous findings for glycerol and water dynamics in various protein matrices and compared with observations for other dynamically highly asymmetric mixtures so as to ascertain in which way the viscous freezing of a fast component in the matrix of a slow component differs from the glassy slowdown in neat supercooled liquids.

  19. S-matrices and integrability

    NASA Astrophysics Data System (ADS)

    Bombardelli, Diego

    2016-08-01

    In these notes we review the S-matrix theory in (1+1)-dimensional integrable models, focusing mainly on the relativistic case. Once the main definitions and physical properties are introduced, we discuss the factorization of scattering processes due to integrability. We then focus on the analytic properties of the two-particle scattering amplitude and illustrate the derivation of the S-matrices for all the possible bound states using the so-called bootstrap principle. General algebraic structures underlying the S-matrix theory and its relation with the form factors axioms are briefly mentioned. Finally, we discuss the S-matrices of sine-Gordon and SU(2), SU(3) chiral Gross–Neveu models. In loving memory of Lilia Grandi.

  20. S-matrices and integrability

    NASA Astrophysics Data System (ADS)

    Bombardelli, Diego

    2016-08-01

    In these notes we review the S-matrix theory in (1+1)-dimensional integrable models, focusing mainly on the relativistic case. Once the main definitions and physical properties are introduced, we discuss the factorization of scattering processes due to integrability. We then focus on the analytic properties of the two-particle scattering amplitude and illustrate the derivation of the S-matrices for all the possible bound states using the so-called bootstrap principle. General algebraic structures underlying the S-matrix theory and its relation with the form factors axioms are briefly mentioned. Finally, we discuss the S-matrices of sine-Gordon and SU(2), SU(3) chiral Gross-Neveu models. In loving memory of Lilia Grandi.

  1. Threaded Operations on Sparse Matrices

    SciTech Connect

    Sneed, Brett

    2015-09-01

    We investigate the use of sparse matrices and OpenMP multi-threading on linear algebra operations involving them. Several sparse matrix data structures are presented. Implementation of the multi- threading primarily occurs in the level one and two BLAS functions used within the four algorithms investigated{the Power Method, Conjugate Gradient, Biconjugate Gradient, and Jacobi's Method. The bene ts of launching threads once per high level algorithm are explored.

  2. Rotationally invariant ensembles of integrable matrices

    NASA Astrophysics Data System (ADS)

    Yuzbashyan, Emil A.; Shastry, B. Sriram; Scaramazza, Jasen A.

    2016-05-01

    We construct ensembles of random integrable matrices with any prescribed number of nontrivial integrals and formulate integrable matrix theory (IMT)—a counterpart of random matrix theory (RMT) for quantum integrable models. A type-M family of integrable matrices consists of exactly N -M independent commuting N ×N matrices linear in a real parameter. We first develop a rotationally invariant parametrization of such matrices, previously only constructed in a preferred basis. For example, an arbitrary choice of a vector and two commuting Hermitian matrices defines a type-1 family and vice versa. Higher types similarly involve a random vector and two matrices. The basis-independent formulation allows us to derive the joint probability density for integrable matrices, similar to the construction of Gaussian ensembles in the RMT.

  3. Loss of halogens from crystallized and glassy silicic volcanic rocks

    USGS Publications Warehouse

    Noble, D.C.; Smith, V.C.; Peck, L.C.

    1967-01-01

    One hundred and sixty-four F and Cl analyses of silicic welded tuffs and lavas and glass separates are presented. Comparison of the F and Cl contents of crystallized rocks with those of nonhydrated glass and hydrated glassy rocks from the same rock units shows that most of the halogens originally present were lost on crystallization. An average of about half of the F and four-fifths of the Cl originally present was lost. Analyses of hydrated natural glasses and of glassy rocks indicate that in some cases significant amounts of halogens may be removed from or added to hydrated glass through prolonged contact with ground water. The data show that the original halogen contents of the groundmass of a silicic volcanic rock can be reliably determined only from nonhydrated glass. ?? 1967.

  4. Glassy correlations and thermal fluctuations in nematic elastomers

    NASA Astrophysics Data System (ADS)

    Lu, Bing; Xing, Xiangjun; Ye, Fangfu; Goldbart, Paul

    2010-03-01

    By means of the vulcanization theory framework we address the properties of nematic elastomers prepared in the isotropic liquid state and subsequently randomly cross-linked beyond the gelation point. We base our analysis on a model replica Landau free energy, in which the vulcanization order parameter is coupled to the order parameter describing the local degree of nematic ordering, retaining fluctuation terms to the Gaussian level. We explore how the cross-linking renormalizes the thermal correlations of the local nematic order, and also results in frozen-in, glassy nematic correlations. We examine these thermal and glassy correlations for two different preparation histories of the system: in the first, the cross-linking is done at temperatures close to the isotropic-nematic transition; in the other, the cross-linking is done at higher temperatures, but the system is subsequently cooled to near this transition temperature.

  5. Understanding soft glassy materials using an energy landscape approach

    NASA Astrophysics Data System (ADS)

    Hwang, Hyun Joo; Riggleman, Robert A.; Crocker, John C.

    2016-09-01

    Many seemingly different soft materials--such as soap foams, mayonnaise, toothpaste and living cells--display strikingly similar viscoelastic behaviour. A fundamental physical understanding of such soft glassy rheology and how it can manifest in such diverse materials, however, remains unknown. Here, by using a model soap foam consisting of compressible spherical bubbles, whose sizes slowly evolve and whose collective motion is simply dictated by energy minimization, we study the foam's dynamics as it corresponds to downhill motion on an energy landscape function spanning a high-dimensional configuration space. We find that these downhill paths, when viewed in this configuration space, are, surprisingly, fractal. The complex behaviour of our model, including power-law rheology and non-diffusive bubble motion and avalanches, stems directly from the fractal dimension and energy function of these paths. Our results suggest that ubiquitous soft glassy rheology may be a consequence of emergent fractal geometry in the energy landscapes of many complex fluids.

  6. 2H NMR studies of supercooled and glassy aspirin

    NASA Astrophysics Data System (ADS)

    Nath, R.; Nowaczyk, A.; Geil, B.; Bohmer, R.

    2007-11-01

    Acetyl salicylic acid, deuterated at the methyl group, was investigated using 2H-NMR in its supercooled and glassy states. Just above the glass transition temperature the molecular reorientations were studied using stimulated-echo spectroscopy and demonstrated a large degree of similarity with other glass formers. Deep in the glassy phase the NMR spectra look similar to those reported for the crystal [A. Detken, P. Focke, H. Zimmermann, U. Haeberlen, Z. Olejniczak, Z. T. Lalowicz, Z. Naturforsch. A 50 (1995) 95] and below 20 K they are indicative for rotational tunneling with a relatively large tunneling frequency. Measurements of the spin-lattice relaxation times for temperatures below 150 K reveal a broad distribution of correlation times in the glass. The dominant energy barrier characterizing the slow-down of the methyl group is significantly smaller than the well defined barrier in the crystal.

  7. Understanding soft glassy materials using an energy landscape approach.

    PubMed

    Hwang, Hyun Joo; Riggleman, Robert A; Crocker, John C

    2016-09-01

    Many seemingly different soft materials-such as soap foams, mayonnaise, toothpaste and living cells-display strikingly similar viscoelastic behaviour. A fundamental physical understanding of such soft glassy rheology and how it can manifest in such diverse materials, however, remains unknown. Here, by using a model soap foam consisting of compressible spherical bubbles, whose sizes slowly evolve and whose collective motion is simply dictated by energy minimization, we study the foam's dynamics as it corresponds to downhill motion on an energy landscape function spanning a high-dimensional configuration space. We find that these downhill paths, when viewed in this configuration space, are, surprisingly, fractal. The complex behaviour of our model, including power-law rheology and non-diffusive bubble motion and avalanches, stems directly from the fractal dimension and energy function of these paths. Our results suggest that ubiquitous soft glassy rheology may be a consequence of emergent fractal geometry in the energy landscapes of many complex fluids. PMID:27322823

  8. Glassy states in fermionic systems with strong disorder and interactions

    NASA Astrophysics Data System (ADS)

    Schwab, David J.; Chakravarty, Sudip

    2009-03-01

    We study the competition between interactions and disorder in two dimensions. Whereas a noninteracting system is always Anderson localized by disorder in two dimensions, a pure system can develop a Mott gap for sufficiently strong interactions. Within a simple model, with short-ranged repulsive interactions, we show that, even in the limit of strong interaction, the Mott gap is completely washed out by disorder for an infinite system for dimensions D≤2 , leading to a glassy state. Moreover, the Mott insulator cannot maintain a broken symmetry in the presence of disorder. We then show that the probability of a nonzero gap as a function of system size falls onto a universal curve, reflecting the glassy dynamics. An analytic calculation is also presented in one dimension that provides further insight into the nature of slow dynamics.

  9. Effets des electrons secondaires sur l'ADN

    NASA Astrophysics Data System (ADS)

    Boudaiffa, Badia

    Les interactions des electrons de basse energie (EBE) representent un element important en sciences des radiations, particulierement, les sequences se produisant immediatement apres l'interaction de la radiation ionisante avec le milieu biologique. Il est bien connu que lorsque ces radiations deposent leur energie dans la cellule, elles produisent un grand nombre d'electrons secondaires (4 x 104/MeV), qui sont crees le long de la trace avec des energies cinetiques initiales bien inferieures a 20 eV. Cependant, il n'y a jamais eu de mesures directes demontrant l'interaction de ces electrons de tres basse energie avec l'ADN, du principalement aux difficultes experimentales imposees par la complexite du milieu biologique. Dans notre laboratoire, les dernieres annees ont ete consacrees a l'etude des phenomenes fondamentaux induits par impact des EBE sur differentes molecules simples (e.g., N2, CO, O2, H2O, NO, C2H 4, C6H6, C2H12) et quelques molecules complexes dans leur phase solide. D'autres travaux effectues recemment sur des bases de l'ADN et des oligonucleotides ont montre que les EBE produisent des bris moleculaires sur les biomolecules. Ces travaux nous ont permis d'elaborer des techniques pour mettre en evidence et comprendre les interactions fondamentales des EBE avec des molecules d'interet biologique, afin d'atteindre notre objectif majeur d'etudier l'effet direct de ces particules sur la molecule d'ADN. Les techniques de sciences des surfaces developpees et utilisees dans les etudes precitees peuvent etre etendues et combinees avec des methodes classiques de biologie pour etudier les dommages de l'ADN induits par l'impact des EBE. Nos experiences ont montre l'efficacite des electrons de 3--20 eV a induire des coupures simple et double brins dans l'ADN. Pour des energies inferieures a 15 eV, ces coupures sont induites par la localisation temporaire d'un electron sur une unite moleculaire de l'ADN, ce qui engendre la formation d'un ion negatif transitoire

  10. Localization and Glassy Dynamics in the Immune System

    NASA Astrophysics Data System (ADS)

    Sun, Jun; Earl, David J.; Deem, Michael W.

    We discuss use of the generalized NK model to examine evolutionary dynamics within the immune system. We describe how randomness and diversity play key roles in the immune response and how their effects are captured by this hierarchical spin glass model. We discuss analytical aspects of the model as well as practical applications to design of the annual influenza vaccine. We discuss the subtle role that the glassy evolutionary dynamics plays in suppressing autoimmune disease.

  11. Yield Stress Enhancement in Glassy-Polyethylene Block Copolymers

    NASA Astrophysics Data System (ADS)

    Mulhearn, William; Register, Richard

    Polyethylene (PE) has the highest annual production volume of all synthetic polymers worldwide, and is valuable across many applications due to its low cost, toughness, processability, and chemical resistance. However, PE is not well suited to certain applications due to its modest yield stress and Young's modulus (approximately 30 MPa and 1 GPa, respectively for linear, high-density PE). Irreversible deformation of PE results from dislocation of crystal stems and eventual crystal fragmentation under applied stress. The liquid-like amorphous fraction provides no useful mechanical support to the crystal fold surface in a PE homopolymer, so the only method to enhance the force required for crystal slip, and hence the yield stress, is crystal thickening via thermal treatment. An alternative route towards modifying the mechanical properties of PE involves copolymerization of a minority high-glass transition temperature block into a majority-PE block copolymer. In this work, we investigate a system of glassy/linear-PE block copolymers prepared via ring-opening metathesis polymerization of cyclopentene and substituted norbornene monomers followed by hydrogenation. We demonstrate that a large change in mechanical properties can be achieved with the addition of a short glassy block (e.g. a doubling of the yield stress and Young's modulus versus PE homopolymer with the addition of 25 percent glassy block). Furthermore, owing to the low interaction energy between PE and the substituted polynorbornene blocks employed, these high-yield PE block copolymers can exhibit single-phase melts for ease of processability.

  12. Non-Equilibrium Water-Glassy Polymer Dynamics

    NASA Astrophysics Data System (ADS)

    Davis, Eric; Minelli, Matteo; Baschetti, Marco; Sarti, Giulio; Elabd, Yossef

    2012-02-01

    For many applications (e.g., medical implants, packaging), an accurate assessment and fundamental understanding of the dynamics of water-glassy polymer interactions is of great interest. In this study, sorption and diffusion of pure water in several glassy polymers films, such as poly(styrene) (PS), poly(methyl methacrylate) (PMMA), poly(lactide) (PLA), were measured over a wide range of vapor activities and temperatures using several experimental techniques, including quartz spring microbalance (QSM), quartz crystal microbalance (QCM), and time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian behavior (diffusion-relaxation phenomena) was observed by all three techniques, while FTIR-ATR spectroscopy also provides information about the distribution of the states of water and water transport mechanisms on a molecular-level. Specifically, the states of water are significantly different in PS compared to PMMA and PLA. Additionally, a purely predictive non-equilibrium lattice fluid (NELF) model was applied to predict the sorption isotherms of water in these glassy polymers.

  13. Exploration for facultative endosymbionts of glassy-wingedsharpshooter (Hemiptera: Cicadellidae)

    SciTech Connect

    Montllor-Curley, C.; Brodie, E.L.; Lechner, M.G.; Purcell, A.H.

    2006-07-01

    Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae),glassy-winged sharpshooter, was collected in California and severalstates in the southeastern United States in 2002 and 2003 and analyzedfor endosymbiotic bacteria. Hemolymph, eggs, and bacteriomes wereexamined for the presence of bacteria by polymerase chain reaction. Asubset of hemolymph and egg samples had their 16S rRNA gene ampliconscloned and sequenced or analyzed by restriction digest patterns ofsamples compared with known bacterial DNA. Baumannia cicadellinicola, oneof the primary symbionts of glassy-winged sharpshooter, was found in themajority of hemolymph samples, although it has been considered until nowto reside primarily inside the specialized host bacteriocytes. Wolbachiasp., a common secondary symbiont in many insect taxa investigated todate, was the second most frequently detected bacterium in hemolymphsamples. In addition, we detected bacteria that were most closely related(by 16S rRNA gene sequence) to Pseudomonas, Stenotrophomonas, andAcinetobacter in hemolymph samples of one and/or two glassy-wingedsharpshooters, but their origin is uncertain.

  14. Thermodynamics of Water Sorption in High Performance Glassy Thermoplastic Polymers

    NASA Astrophysics Data System (ADS)

    Mensitieri, Giuseppe; Scherillo, Giuseppe; Petretta, Mauro; Galizia, Michele; La Manna, Pietro; Musto, Pellegrino

    2014-05-01

    Sorption thermodynamics of water in two glassy polymers, polyetherimide (PEI) and polyetheretherketone (PEEK), is investigated by coupling gravimetry and on line FTIR spectroscopy in order to gather information on the total amount of sorbed water as well as on the different species of water molecules absorbed within the polymers, addressing the issue of cross- and self-interactions occurring in the polymer/water systems. Water sorption isotherms have been determined at temperatures ranging fro 30 to 70°C while FTIR spectroscopy has been performed only at 30°C. The experimental analysis provided information on the groups present on the polymer backbones involved in hydrogen bonding interactions with absorbed water molecules. Moreover, it also supplied qualitative indications about the different’populations’ of water molecules present within the PEEK and a quantitative assessment of these ‘populations’ in the case of PEI.The results of the experimental analysis have been interpreted using an equation of state theory based on a compressible lattice fluid model for the Gibbs energy of the polymer-water mixture, developed by extending to the case of out of equilibrium glassy polymers a previous model intended for equilibrium rubbery polymers. The model accounts for the non equilibrium nature of glassy poymers as well as for mean field and for hydrogen bonding interactions, providing a satisfactory quantitative interpretation of the experimental data.

  15. Quantifying glassy and crystalline basalt partitioning in the oceanic crust

    NASA Astrophysics Data System (ADS)

    Moore, Rachael; Ménez, Bénédicte

    2016-04-01

    The upper layers of the oceanic crust are predominately basaltic rock, some of which hosts microbial life. Current studies of microbial life within the ocean crust mainly focus on the sedimentary rock fraction, or those organisms found within glassy basalts while the potential habitability of crystalline basalts are poorly explored. Recently, there has been recognition that microbial life develops within fractures and grain boundaries of crystalline basalts, therefore estimations of total biomass within the oceanic crust may be largely under evaluated. A deeper understanding of the bulk composition and fractionation of rocks within the oceanic crust is required before more accurate estimations of biomass can be made. To augment our understanding of glassy and crystalline basalts within the oceanic crust we created two end-member models describing basalt fractionation: a pillow basalt with massive, or sheet, flows crust and a pillow basalt with sheeted dike crust. Using known measurements of massive flow thickness, dike thickness, chilled margin thickness, pillow lava size, and pillow lava glass thickness, we have calculated the percentage of glassy versus crystalline basalts within the oceanic crust for each model. These models aid our understanding of textural fractionation within the oceanic crust, and can be applied with bioenergetics models to better constrain deep biomass estimates.

  16. Fast algorithms for glassy materials: methods and explorations

    NASA Astrophysics Data System (ADS)

    Middleton, A. Alan

    2014-03-01

    Glassy materials with frozen disorder, including random magnets such as spin glasses and interfaces in disordered materials, exhibit striking non-equilibrium behavior such as the ability to store a history of external parameters (memory). Precisely due to their glassy nature, direct simulation of models of these materials is very slow. In some fortunate cases, however, algorithms exist that exactly compute thermodynamic quantities. Such cases include spin glasses in two dimensions and interfaces and random field magnets in arbitrary dimensions at zero temperature. Using algorithms built using ideas developed by computer scientists and mathematicians, one can even directly sample equilibrium configurations in very large systems, as if one picked the configurations out of a ``hat'' of all configurations weighted by their Boltzmann factors. This talk will provide some of the background for these methods and discuss the connections between physics and computer science, as used by a number of groups. Recent applications of these methods to investigating phase transitions in glassy materials and to answering qualitative questions about the free energy landscape and memory effects will be discussed. This work was supported in part by NSF grant DMR-1006731. Creighton Thomas and David Huse also contributed to much of the work to be presented.

  17. Three-dimensional jamming and flows of soft glassy materials.

    PubMed

    Ovarlez, G; Barral, Q; Coussot, P

    2010-02-01

    Various disordered dense systems, such as foams, gels, emulsions and colloidal suspensions, undergo a jamming transition from a liquid state (they flow) to a solid state below a yield stress. Their structure, which has been thoroughly studied with powerful means of three-dimensional characterization, shows some analogy with that of glasses, which led to them being named soft glassy materials. However, despite its importance for geophysical and industrial applications, their rheological behaviour, and its microscopic origin, is still poorly known, in particular because of its nonlinear nature. Here we show from two original experiments that a simple three-dimensional continuum description of the behaviour of soft glassy materials can be built. We first show that when a flow is imposed in some direction there is no yield resistance to a secondary flow: these systems are always unjammed simultaneously in all directions of space. The three-dimensional jamming criterion seems to be the plasticity criterion encountered in most solids. We also find that they behave as simple liquids in the direction orthogonal to that of the main flow; their viscosity is inversely proportional to the main flow shear rate, as a signature of shear-induced structural relaxation, in close similarity to the structural relaxations driven by temperature and density in other glassy systems. PMID:20062046

  18. Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon

    SciTech Connect

    Baker, D.F.

    1983-02-01

    These properties of glassy carbon heat treated for three hours between 1200 and 2700/sup 0/C were measured from 3 to 300/sup 0/K in magnetic fields up to 5 tesla. The magnetoresistance was generally negative and saturated with reciprocal temperature, but still increased as a function of magnetic field. The maximum negative magnetoresistance measured was 2.2% for 2700/sup 0/C material. Several models based on the negative magnetoresistance being proportional to the square of the magnetic moment were attempted; the best fit was obtained for the simplest model combining Curie and Pauli paramagnetism for heat treatments above 1600/sup 0/C. Positive magnetoresistance was found only in less than 1600/sup 0/C treated glassy carbon. The electrical conductivity, of the order of 200 (ohm-cm)/sup -1/ at room temperature, can be empirically written as sigma = A + Bexp(-CT/sup -1/4) - DT/sup -1/2. The Hall coefficient was independent of magnetic field, insensitive to temperature, but was a strong function of heat treatment temperature, crossing over from negative to positive at about 1700/sup 0/C and ranging from -0.048 to 0.126 cm/sup 3//coul. The idea of one-dimensional filaments in glassy carbon suggested by the electrical conductivity is compatible with the present consensus view of the microstructure.

  19. Effets de la formation sur la violence conjugale

    PubMed Central

    Zaher, Eman; Keogh, Kelly; Ratnapalan, Savithiri

    2014-01-01

    Résumé Objectif Décrire et évaluer l’efficacité de la formation concernant la violence conjugale pour améliorer les connaissances et permettre la reconnaissance et la prise en charge par les médecins des femmes victimes de violence. Sources des données On a fait une recension dans la base de données des révisions systématiques de Cochrane, MEDLINE, PubMed, PsycINFO, ERIC et EMBASE pour trouver des articles publiés entre le 1e janvier 2000 et le 1e novembre 2012. Des recherches manuelles ont complété cette recension pour cerner des articles pertinents à l’aide d’une stratégie de recherche combinant des textes, mots et expressions MeSH. Sélection des études On a choisi des études randomisées contrôlées qui portaient sur des interventions éducatives à l’intention des médecins et fournissaient des données sur les effets des interventions. Synthèse On a inclus 9 études randomisées contrôlées qui décrivaient différentes approches pédagogiques et diverses mesures des résultats. Trois études examinaient les effets d’interventions éducatives pour des médecins en formation postdoctorale et ont constaté une augmentation des connaissances, mais il n’y a eu aucun changement dans le comportement en ce qui a trait à l’identification des victimes de violence conjugale. Six études portaient sur des interventions éducatives pour des médecins en pratique active. Trois d’entre elles utilisaient une approche à multiples facettes pour les médecins, qui combinait une formation ainsi que des interventions de soutien de la part du système pour changer les comportements des médecins, comme une sensibilisation générale accrue à la violence conjugale au moyen de brochures et d’affiches, des aide-mémoire pour rappeler aux médecins comment identifier les victimes, des moyens pour faciliter l’accès des médecins à des services de soutien pour les victimes, la réalisation d’audits et la fourniture de rétroaction. Les

  20. Investigation of glassy state molecular motions in thermoset polymers

    NASA Astrophysics Data System (ADS)

    Tu, Jianwei

    This dissertation presents the investigation of the glassy state molecular motions in isomeric thermoset epoxies by means of solid-state deuterium (2H) NMR spectroscopy technique. The network structure of crosslinked epoxies was altered through monomer isomerism; specifically, diglycidyl ether of bisphenol A (DGEBA) was cured with isomeric amine curatives, i.e., the meta-substituted diaminodiphenylsulfone (33DDS) and para-substituted diaminodiphenylsulfone (44DDS). The use of structural isomerism provided a path way for altering macroscopic material properties while maintaining identical chemical composition within the crosslinked networks. The effects of structural isomerism on the glassy state molecular motions were studied using solid-state 2H NMR spectroscopy, which offers unrivaled power to monitor site-specific molecular motions. Three distinctive molecular groups on each isomeric network, i.e., the phenylene rings in the bisphenol A structure (BPA), the phenylene rings in the diaminodiphenylsulfone structure (DDS), and the hydroxypropoyl ether group (HPE) have been selectively deuterated for a comprehensive study of the structure-dynamics- property relationships in thermoset epoxies. Quadrupolar echo experiments and line shape simulations were employed as the main research approach to gain both qualitative and quantitative motional information of the epoxy networks in the glassy state. Quantitative information on the geometry and rate of the molecular motions allows the elucidation of the relationship between molecular motions and macro physical properties and the role of these motions in the mechanical relaxation. Specifically, it is revealed that both the BPA and HPE moieties in the isomeric networks have almost identical behaviors in the deep glassy state, which indicates that the molecular motions in the glassy state are localized, and the correlation length of the motions does not exceed the length of the DGEBA repeat unit. BPA ring motions contribute

  1. Local Eigenvalue Density for General MANOVA Matrices

    NASA Astrophysics Data System (ADS)

    Erdős, László; Farrell, Brendan

    2013-09-01

    We consider random n× n matrices of the form where X and Y have independent entries with zero mean and variance one. These matrices are the natural generalization of the Gaussian case, which are known as MANOVA matrices and which have joint eigenvalue density given by the third classical ensemble, the Jacobi ensemble. We show that, away from the spectral edge, the eigenvalue density converges to the limiting density of the Jacobi ensemble even on the shortest possible scales of order 1/ n (up to log n factors). This result is the analogue of the local Wigner semicircle law and the local Marchenko-Pastur law for general MANOVA matrices.

  2. Crystallization of the glassy grain boundary phase in silicon nitride ceramics

    NASA Technical Reports Server (NTRS)

    Drummond, Charles H., III

    1991-01-01

    The role was studied of the intergranular glassy phase in silicon nitride as-processed with yttria as a sintering aid. The microstructure, crystallization, and viscosity of the glassy phase were areas studied. Crystallization of the intergranular glassy phase to more refractory crystalline phases should improve the high temperature mechanical properties of the silicon nitride. The addition of a nucleating agent will increase the rate of crystallization. The measurement of the viscosity of the glassy phase will permit the estimation of the high temperature deformation of the silicon nitride.

  3. Some Recent Developments in Structure and Glassy Behavior of Proteins

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun

    2012-02-01

    We have used ARVO developed by us to find that the ratio of volume and surface area of proteins in Protein Data Bank distributed in a very narrow region [1]. Such result is useful for the determination of protein 3D structures. It has been widely known that a spin glass model can be used to understand the slow relaxation behavior of a glass at low temperatures [2]. We have used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that polymer chains with neighboring monomers connected by rigid bonds can relax very slowly and show glassy behavior [3]. We have also found that native collagen fibrils show glassy behavior at room temperatures [4]. The results of [3] and [4] about the glassy behavior of polymers or proteins are useful for understanding the mechanism for a biological system to maintain in a non-equilibrium state, including the ancient seed [5], which can maintain in a non-equilibrium state for a very long time. (1) M.-C. Wu, M. S. Li, W.-J. Ma, M. Kouza, and C.-K. Hu, EPL, in press (2011); (2) C. Dasgupta, S.-K. Ma, and C.-K. Hu. Phys. Rev. B 20, 3837-3849 (1979); (3) W.-J. Ma and C.-K. Hu, J. Phys. Soc. Japan 79, 024005, 024006, 054001, and 104002 (2010), C.-K. Hu and W.-J. Ma, Prog. Theor. Phys. Supp. 184, 369 (2010); S. G. Gevorkian, A. E. Allahverdyan, D. S. Gevorgyan and C.-K. Hu, EPL 95, 23001 (2011); S. Sallon, et al. Science 320, 1464 (2008).

  4. Biocompatibility of Experimental Polymeric Tracheal Matrices.

    PubMed

    Kiselevskii, M V; Chikileva, I O; Vlasenko, R Ya; Sitdikova, S M; Tenchurin, T Kh; Mamagulashvili, V G; Shepelev, A D; Grigoriev, T A; Chvalun, S N

    2016-08-01

    Biocompatibility of a new tracheal matrix is studied. The new matrix is based on polymeric ultra-fiber material colonized by mesenchymal multipotent stromal cells. The experiments demonstrate cytoconductivity of the synthetic matrices and no signs of their degradation within 2 months after their implantation to recipient mice. These data suggest further studies of the synthetic tracheal matrices on large laboratory animals. PMID:27591876

  5. Proper Values of Matrices and Some Applications.

    ERIC Educational Resources Information Center

    Amir-Moez, Ali R.

    1992-01-01

    Presents a short study of proper values of two-by-two matrices with real entries. Gives examples of symmetric matrices and applications to systems of linear equations of perpendicular lines intersecting at the origin and central conics rotated about the origin to eliminate the xy term from its equation. (MDH)

  6. Evidence for a glassy state in strongly driven carbon.

    PubMed

    Brown, C R D; Gericke, D O; Cammarata, M; Cho, B I; Döppner, T; Engelhorn, K; Förster, E; Fortmann, C; Fritz, D; Galtier, E; Glenzer, S H; Harmand, M; Heimann, P; Kugland, N L; Lamb, D Q; Lee, H J; Lee, R W; Lemke, H; Makita, M; Moinard, A; Murphy, C D; Nagler, B; Neumayer, P; Plagemann, K-U; Redmer, R; Riley, D; Rosmej, F B; Sperling, P; Toleikis, S; Vinko, S M; Vorberger, J; White, S; White, T G; Wünsch, K; Zastrau, U; Zhu, D; Tschentscher, T; Gregori, G

    2014-01-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

  7. Microscale rheology of a soft glassy material close to yielding.

    PubMed

    Jop, Pierre; Mansard, Vincent; Chaudhuri, Pinaki; Bocquet, Lydéric; Colin, Annie

    2012-04-01

    Using confocal microscopy, we study the flow of a model soft glassy material: a concentrated emulsion. We demonstrate the micro-macro link between in situ measured movements of droplets during the flow and the macroscopic rheological response of a concentrated emulsion, in the form of scaling relationships connecting the rheological "fluidity" with local standard deviation of the strain-rate tensor. Furthermore, we measure correlations between these local fluctuations, thereby extracting a correlation length which increases while approaching the yielding transition, in accordance with recent theoretical predictions.

  8. Positronics of radiation-induced effects in chalcogenide glassy semiconductors

    SciTech Connect

    Shpotyuk, O.; Kozyukhin, S. A.; Shpotyuk, M.; Ingram, A.; Szatanik, R.

    2015-03-15

    Using As{sub 2}S{sub 3} and AsS{sub 2} glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.

  9. Anomalous glassy relaxation near the isotropic-nematic phase transition

    NASA Astrophysics Data System (ADS)

    Jose, Prasanth P.; Chakrabarti, Dwaipayan; Bagchi, Biman

    2005-03-01

    Dynamical heterogeneity in a system of Gay-Berne ellipsoids near its isotropic-nematic (I-N) transition, and also in an equimolar mixture of Lennard-Jones spheres and Gay-Berne ellipsoids in deeply supercooled regime, is probed by the time evolution of non-Gaussian parameters (NGP). The appearance of a dominant second peak in the rotational NGP near the I-N transition signals the growth of pseudonematic domains. Surprisingly, such a second peak is instead observed in the translational NGP for the glassy binary mixture. Localization of orientational motion near the I-N transition is found to be responsible for the observed anomalous orientational relaxation.

  10. Evidence for a glassy state in strongly driven carbon

    SciTech Connect

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Gwangju Inst. of Science and Technology, Gwangju; Inst. for Basic Science, Gwangju ; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; Glenzer, S. H.; Harmand, M.; Heimann, P.; Kugland, N. L.; Lamb, D. Q.; Lee, H. J.; Lee, R. W.; Lemke, H.; Makita, M.; Moinard, A.; Murphy, C. D.; Nagler, B.; Neumayer, P.; Plagemann, K. -U.; Redmer, R.; Riley, D.; Rosmej, F. B.; Sperling, P.; Toleikis, S.; Vinko, S. M.; Vorberger, J.; White, S.; White, T. G.; Wünsch, K.; Zastrau, U.; Zhu, D.; Tschentscher, T.; Gregori, G.

    2014-06-09

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

  11. Products of Independent Elliptic Random Matrices

    NASA Astrophysics Data System (ADS)

    O'Rourke, Sean; Renfrew, David; Soshnikov, Alexander; Vu, Van

    2015-07-01

    For fixed , we study the product of independent elliptic random matrices as tends to infinity. Our main result shows that the empirical spectral distribution of the product converges, with probability , to the -th power of the circular law, regardless of the joint distribution of the mirror entries in each matrix. This leads to a new kind of universality phenomenon: the limit law for the product of independent random matrices is independent of the limit laws for the individual matrices themselves. Our result also generalizes earlier results of Götze-Tikhomirov (On the asymptotic spectrum of products of independent random matrices, available at http://arxiv.org/abs/1012.2710) and O'Rourke-Soshnikov (J Probab 16(81):2219-2245, 2011) concerning the product of independent iid random matrices.

  12. Deformation in Thin Glassy Polymer Films from Surface towards Interior

    NASA Astrophysics Data System (ADS)

    Chowdhury, Mithun; de Silva, Johann P.; Cross, Graham L. W.

    Polymer thin glassy films occupy an important place in last two decades of condensed matter research, concerning its surprising surface mobility and spatially dependent structural relaxation. However, ranges of cleverly designed indirect measurements on confined polymer glassy films already probed its mechanical properties; it is still a challenging task to directly probe such small confined volume through conventional mechanical testing. We have designed confined layer compression testing with a precisely designed and aligned flat probe during nanoindentation, which was further accompanied with atomic force microscopy. Due to natural confinement from the surrounding material, we show that a state of `uniaxial strain' is created beneath the probe under small axial strains. By this methodology we are able to directly probe uniaxial flows under both anelastic and plastic conditions while doing controlled creep studies at different positions in the film starting from surface towards interior. Depending on the extent of deformation, we found ranges of effects, such as densification, anelastic yield, and plastic yield. Enhanced creep rate upon deformation supports the idea of `deformation induced mobility'. Work performed at Trinity College Dublin.

  13. Electrical studies on silver based fast ion conducting glassy materials

    SciTech Connect

    Rao, B. Appa Kumar, E. Ramesh Kumari, K. Rajani Bhikshamaiah, G.

    2014-04-24

    Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI−Ag{sub 2}O−[(1−x)B{sub 2}O{sub 3}−xTeO{sub 2}] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz–3MHz by Impedance Analyzer in the temperature range 303–423K. The DC conductivity measurements were also carried out in the temperature range 300–523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO{sub 2} as well as with temperature. The conductivity of the present glass system is found to be of the order of 10{sup −2} S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.

  14. Dynamics of caged ions in glassy ionic conductors.

    PubMed

    Habasaki, J; Ngai, K L; Hiwatari, Y

    2004-05-01

    At sufficiently high frequency and low temperature, the dielectric responses of glassy, crystalline, and molten ionic conductors all invariably exhibit nearly constant loss. This ubiquitous characteristic occurs in the short-time regime when the ions are still caged, indicating that it could be a determining factor of the mobility of the ions in conduction at longer times. An improved understanding of its origin should benefit the research of ion conducting materials for portable energy source as well as the resolution of the fundamental problem of the dynamics of ions. We perform molecular dynamics simulations of glassy lithium metasilicate (Li2SiO3) and find that the length scales of the caged Li+ ions motions are distributed according to a Levy distribution that has a long tail. These results suggest that the nearly constant loss originates from "dynamic anharmonicity" experienced by the moving but caged Li+ ions and provided by the surrounding matrix atoms executing correlated movements. The results pave the way for rigorous treatments of caged ion dynamics by nonlinear Hamiltonian dynamics.

  15. Effects of glassy-winged sharpshooter feeding, size, and lipid content on egg maturation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (Homalodisca vitripennis) is synovigenic and must feed during the adult stage to produce eggs. While glassy-winged sharpshooter egg production is related to adult feeding, rates of egg production are variable. In this study, effects of lipid allocation to eggs and fema...

  16. Use of glassy carbon as a working electrode in controlled potential coulometry.

    PubMed

    Plock, C E; Vasquez, J

    1969-11-01

    Glassy carbon has been used as the working electrode in controlled potential coulometry. The results of coulometric investigations of chromium, copper, iron, uranium and neptunium are compared with results obtained with platinum or mercury working electrodes. The accuracy of results with the glassy carbon electrode compares favourably with the results obtainable with the other electrodes, but the precision is poorer.

  17. Use of glassy carbon as a working electrode in controlled potential coulometry.

    PubMed

    Plock, C E; Vasquez, J

    1969-11-01

    Glassy carbon has been used as the working electrode in controlled potential coulometry. The results of coulometric investigations of chromium, copper, iron, uranium and neptunium are compared with results obtained with platinum or mercury working electrodes. The accuracy of results with the glassy carbon electrode compares favourably with the results obtainable with the other electrodes, but the precision is poorer. PMID:18960665

  18. Silicon-tin oxynitride glassy composition and use as anode for lithium-ion battery

    DOEpatents

    Neudecker, Bernd J.; Bates, John B.

    2001-01-01

    Disclosed are silicon-tin oxynitride glassy compositions which are especially useful in the construction of anode material for thin-film electrochemical devices including rechargeable lithium-ion batteries, electrochromic mirrors, electrochromic windows, and actuators. Additional applications of silicon-tin oxynitride glassy compositions include optical fibers and optical waveguides.

  19. Evaluation of grapevine as a host for the glassy-winged sharpshooter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grapevine was evaluated as a feeding and oviposition host for the glassy-winged sharpshooter. Two sets of experiments were conducted. The first set compared performance and preference of glassy-winged sharpshooter females for grapevine (cv. Chardonnay) versus cowpea (Vigna unguiculata cultivar black...

  20. Effect of glassy modes on electron spin-lattice relaxation in solid ethanol

    NASA Astrophysics Data System (ADS)

    Merunka, Dalibor; Kveder, Marina; Jokić, Milan; Rakvin, Boris

    2013-03-01

    Electron spin-lattice relaxation (SLR) of TEMPO radical was measured in the crystalline and glassy states of deuterated ethanol in the temperature range 5-80 K using X-band electron paramagnetic resonance (EPR). The measured SLR rates are higher in the glassy than in crystalline state and the excess SLR rate in glassy state is much lower than in ethanol. This result suggests that extra modes in glassy state, i.e. glassy modes, produce the excess SLR rate via the electron-nuclear dipolar (END) interaction between the electron spin of radical and the matrix protons or deuterons. Using the soft-potential model and assuming the END interaction between the electron spin and the matrix protons, the contributions to SLR rate of various mechanisms of glassy modes were theoretically analyzed. The evaluations of SLR rates in glassy ethanol indicate two main mechanisms of glassy modes: thermally activated relaxation of double-well systems and phonon-induced relaxation of quasi-harmonic local modes. The SLR rates induced by these mechanisms correlate well with the experimental data.

  1. Gels from soft hairy nanoparticles in polymeric matrices

    NASA Astrophysics Data System (ADS)

    Vlassopoulos, Dimitris

    2013-03-01

    Hairy particles represent a huge class of soft colloids with tunable interactions and properties. Advances in synthetic chemistry have enabled obtaining well-characterized such systems for specific needs. In this talk we present two model hairy soft particles with diameters of the order of tens of nanometers, star polymers and polymerically grafted spherical particles. In particular, we discuss design strategies for dispersing them in polymeric matrices and eventually creating and breaking gels. Control parameters are the matrix molar mass, the grafting density (or functionality) and the size of the grafts (or arms). The linear viscoelastic properties and slow time evolution of the gels are examined in view of the existing knowledge from colloidal gels consisting of micron-sized particles, and compared. In the case of stars we start from a concentrated glassy suspension in molecular solvent and add homopolymer at increasing concentration, and as a result of the induced osmotic pressure the stars shrink and a depletion gel is formed. For the grafted colloidal particles, they are added at low concentration to a polymer matrix, and it has been shown that under certain conditions the anisotropy of interactions gives rise to network formation. We then focus on the nonlinear rheological response and in particular the effect of shear flow in inducing a solid to liquid transition. Our studies show that the yielding process is gradual and shares many common features with that of flocculated colloidal suspensions, irrespectively of the shape of the building block of the gel. Whereas shear can melt such a gel, it cannot break it into its constituent blocks and hence fully disperse the hairy nanoparticles. On the other hand, the hairy particles are intrinsically hybrid. We show how this important feature is reflected on the heating of the gels. In that case, the mismatch of thermal expansion coefficients of core and shell appears to play a role on the particle response as it

  2. Community Detection for Correlation Matrices

    NASA Astrophysics Data System (ADS)

    MacMahon, Mel; Garlaschelli, Diego

    2015-04-01

    A challenging problem in the study of complex systems is that of resolving, without prior information, the emergent, mesoscopic organization determined by groups of units whose dynamical activity is more strongly correlated internally than with the rest of the system. The existing techniques to filter correlations are not explicitly oriented towards identifying such modules and can suffer from an unavoidable information loss. A promising alternative is that of employing community detection techniques developed in network theory. Unfortunately, this approach has focused predominantly on replacing network data with correlation matrices, a procedure that we show to be intrinsically biased because of its inconsistency with the null hypotheses underlying the existing algorithms. Here, we introduce, via a consistent redefinition of null models based on random matrix theory, the appropriate correlation-based counterparts of the most popular community detection techniques. Our methods can filter out both unit-specific noise and system-wide dependencies, and the resulting communities are internally correlated and mutually anticorrelated. We also implement multiresolution and multifrequency approaches revealing hierarchically nested subcommunities with "hard" cores and "soft" peripheries. We apply our techniques to several financial time series and identify mesoscopic groups of stocks which are irreducible to a standard, sectorial taxonomy; detect "soft stocks" that alternate between communities; and discuss implications for portfolio optimization and risk management.

  3. Kerov's interlacing sequences and random matrices

    SciTech Connect

    Bufetov, Alexey

    2013-11-15

    To a N × N real symmetric matrix Kerov assigns a piecewise linear function whose local minima are the eigenvalues of this matrix and whose local maxima are the eigenvalues of its (N − 1) × (N − 1) submatrix. We study the scaling limit of Kerov's piecewise linear functions for Wigner and Wishart matrices. For Wigner matrices the scaling limit is given by the Verhik-Kerov-Logan-Shepp curve which is known from asymptotic representation theory. For Wishart matrices the scaling limit is also explicitly found, and we explain its relation to the Marchenko-Pastur limit spectral law.

  4. ESTIMATION OF FUNCTIONALS OF SPARSE COVARIANCE MATRICES

    PubMed Central

    Fan, Jianqing; Rigollet, Philippe; Wang, Weichen

    2016-01-01

    High-dimensional statistical tests often ignore correlations to gain simplicity and stability leading to null distributions that depend on functionals of correlation matrices such as their Frobenius norm and other ℓr norms. Motivated by the computation of critical values of such tests, we investigate the difficulty of estimation the functionals of sparse correlation matrices. Specifically, we show that simple plug-in procedures based on thresholded estimators of correlation matrices are sparsity-adaptive and minimax optimal over a large class of correlation matrices. Akin to previous results on functional estimation, the minimax rates exhibit an elbow phenomenon. Our results are further illustrated in simulated data as well as an empirical study of data arising in financial econometrics. PMID:26806986

  5. Synchronous correlation matrices and Connes' embedding conjecture

    NASA Astrophysics Data System (ADS)

    Dykema, Kenneth J.; Paulsen, Vern

    2016-01-01

    In the work of Paulsen et al. [J. Funct. Anal. (in press); preprint arXiv:1407.6918], the concept of synchronous quantum correlation matrices was introduced and these were shown to correspond to traces on certain C*-algebras. In particular, synchronous correlation matrices arose in their study of various versions of quantum chromatic numbers of graphs and other quantum versions of graph theoretic parameters. In this paper, we develop these ideas further, focusing on the relations between synchronous correlation matrices and microstates. We prove that Connes' embedding conjecture is equivalent to the equality of two families of synchronous quantum correlation matrices. We prove that if Connes' embedding conjecture has a positive answer, then the tracial rank and projective rank are equal for every graph. We then apply these results to more general non-local games.

  6. A Computer Program for Clustering Large Matrices

    ERIC Educational Resources Information Center

    Koch, Valerie L.

    1976-01-01

    A Fortran V program is described derived for the Univac 1100 Series Computer for clustering into hierarchical structures large matrices, up to 1000 x 1000 and larger, of interassociations between objects. (RC)

  7. Surface treatment of Glassy Polymeric Carbon artifacts for medical applications

    SciTech Connect

    Rodrigues, M. G.; Zimmerman, R. L.; Rezende, M. C.

    1999-06-10

    Glassy Polymeric Carbon (GPC) has been used for mechanical cardiac valves. GCP valves are chemically biocompatible and durable, but less thromboresistant than biological valves. Enhanced thromboresistance of mechanical cardiac components with porous surface has been demonstrated. The endothelialized tissue blood-contacting surface adheres to the porous prosthetic component and decreases the formation of thrombus. Our experience has shown that the porosity of GPC can be increased and controlled by MeV ion bombardment. We report here that the surface roughness of heat-treated GPC bombarded with C, O, Si and Au is also enhanced. The surface roughness of the ion-bombarded samples is on a smaller scale than those roughened by sand blasting (measurements made with Perthomete S and P). The roughness decreases slightly after heat treatment, in linear proportion to the shrinkage of the test piece. Possible beneficial effects of the imbedded ions on tissue adherence and thromboresistance must be determined by in vivo animal experiments.

  8. Anomalous glassy relaxation near the isotropic-nematic phase transition.

    PubMed

    Jose, Prasanth P; Chakrabarti, Dwaipayan; Bagchi, Biman

    2005-03-01

    Dynamical heterogeneity in a system of Gay-Berne ellipsoids near its isotropic-nematic (I-N) transition, and also in an equimolar mixture of Lennard-Jones spheres and Gay-Berne ellipsoids in deeply supercooled regime, is probed by the time evolution of non-Gaussian parameters (NGP). The appearance of a dominant second peak in the rotational NGP near the I-N transition signals the growth of pseudonematic domains. Surprisingly, such a second peak is instead observed in the translational NGP for the glassy binary mixture. Localization of orientational motion near the I-N transition is found to be responsible for the observed anomalous orientational relaxation. PMID:15903399

  9. Manufacturing of glassy thin shell for adaptive optics: results achieved

    NASA Astrophysics Data System (ADS)

    Poutriquet, F.; Rinchet, A.; Carel, J.-L.; Leplan, H.; Ruch, E.; Geyl, R.; Marque, G.

    2012-07-01

    Glassy thin shells are key components for the development of adaptive optics and are part of future & innovative projects such as ELT. However, manufacturing thin shells is a real challenge. Even though optical requirements for the front face - or optical face - are relaxed compared to conventional passive mirrors, requirements concerning thickness uniformity are difficult to achieve. In addition, process has to be completely re-defined as thin mirror generates new manufacturing issues. In particular, scratches and digs requirement is more difficult as this could weaken the shell, handling is also an important issue due to the fragility of the mirror. Sagem, through REOSC program, has recently manufactured different types of thin shells in the frame of European projects: E-ELT M4 prototypes and VLT Deformable Secondary Mirror (VLT DSM).

  10. Determination of Fracture Patterns in Glass and Glassy Polymers.

    PubMed

    Baca, Allison C; Thornton, John I; Tulleners, Frederic A

    2016-01-01

    The study of fractures of glass, glassy-type materials, and plastic has long been of interest to the forensic community. The focus of this interest has been the use of glass and polymer fractures to associate items of evidence under the assumption that each fracture is different. Generally, it is well-accepted that deviations exist; however, the emphasis has been on classifying and predicting fracture rather than determining that each fracture is different. This study documented the controlled fracture patterns of 60 glass panes, 60 glass bottles, and 60 plastic tail light lens covers using both dynamic impact and static pressure methods under closely controlled conditions. Each pattern was intercompared, and based on the limited specimens tested in this study, the results illustrate that the fracture patterns are different. Further repetitive studies, under controlled conditions, will be needed to provide more statistical significance to the theory that each fracture forms a nonreproducible fracture pattern. PMID:26524485

  11. Evidence for a glassy state in strongly driven carbon

    DOE PAGES

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; et al

    2014-06-09

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen closemore » to their original positions in the fluid.« less

  12. Evidence for a glassy state in strongly driven carbon

    PubMed Central

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; Glenzer, S. H.; Harmand, M.; Heimann, P.; Kugland, N. L.; Lamb, D. Q.; Lee, H. J.; Lee, R. W.; Lemke, H.; Makita, M.; Moinard, A.; Murphy, C. D.; Nagler, B.; Neumayer, P.; Plagemann, K.-U.; Redmer, R.; Riley, D.; Rosmej, F. B.; Sperling, P.; Toleikis, S.; Vinko, S. M.; Vorberger, J.; White, S.; White, T. G.; Wünsch, K.; Zastrau, U.; Zhu, D.; Tschentscher, T.; Gregori, G.

    2014-01-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid. PMID:24909903

  13. Electroanalytical study of nifedipine using activated glassy carbon electrode.

    PubMed

    Sentürk, Z; Ozkan, S A; Ozkan, Y

    1998-01-01

    The electrochemical properties of nifedipine have been investigated in aqueous solution by linear sweep and cyclic voltammetry. The method is based both on the reduction and on the oxidation of the drug at a glassy carbon electrode activated by applying a new pre-treatment. The voltammograms of nifedipine on pH, concentration and scan rate have been carefully examined. Both the electroreduction and electrooxidation of nifedipine allow its determination at pH 1.5 in the concentration range of 2 x 10(-5)-6 x 10(-4) M and 8 x 10(-5)-1 x 10(-3) M, respectively. The method has been applied to commercial samples (tablets and capsules).

  14. Development of an Automatic Fabrication System for Cast Glassy Alloys

    NASA Astrophysics Data System (ADS)

    Yokoyama, Yoshihiko

    2015-04-01

    The developed automatic fabrication system comprised three component functions: weighing, alloying, and casting. The measurement error of automatic weighing specimen was about less 1 pct for Zr-based master alloys (approximately 30 g). Especially, sufficient stirrer effect of arc-melting ingot for homogeneity can be achieved by the development of sinusoidal arcing and applying magnetic field. In order to achieve superior homogeneity of the glass structure with no secondary phase ( i.e., an intermetallic compound with a high melting temperature), a prealloying process should be advisable. In this study, high reliability of the density and mechanical properties of automatic processed cast glassy alloys (CGAs) was successfully obtained. The developed automatic fabrication process has a potential to accelerate the industrial application of CGAs in the near future.

  15. Point-to-set lengths, local structure, and glassiness

    NASA Astrophysics Data System (ADS)

    Yaida, Sho; Berthier, Ludovic; Charbonneau, Patrick; Tarjus, Gilles

    2016-09-01

    The growing sluggishness of glass-forming liquids is thought to be accompanied by growing structural order. The nature of such order, however, remains hotly debated. A decade ago, point-to-set (PTS) correlation lengths were proposed as measures of amorphous order in glass formers, but recent results raise doubts as to their generality. Here, we extend the definition of PTS correlations to agnostically capture any type of growing order in liquids, be it local or amorphous. This advance enables the formulation of a clear distinction between slowing down due to conventional critical ordering and that due to glassiness, and provides a unified framework to assess the relative importance of specific local order and generic amorphous order in glass formation.

  16. Evidence for a glassy state in strongly driven carbon.

    PubMed

    Brown, C R D; Gericke, D O; Cammarata, M; Cho, B I; Döppner, T; Engelhorn, K; Förster, E; Fortmann, C; Fritz, D; Galtier, E; Glenzer, S H; Harmand, M; Heimann, P; Kugland, N L; Lamb, D Q; Lee, H J; Lee, R W; Lemke, H; Makita, M; Moinard, A; Murphy, C D; Nagler, B; Neumayer, P; Plagemann, K-U; Redmer, R; Riley, D; Rosmej, F B; Sperling, P; Toleikis, S; Vinko, S M; Vorberger, J; White, S; White, T G; Wünsch, K; Zastrau, U; Zhu, D; Tschentscher, T; Gregori, G

    2014-01-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid. PMID:24909903

  17. Poly(4-vinylpyridine)-coated glassy carbon flow detectors

    SciTech Connect

    Wang, J.; Golden, T.; Tuzhi, P.

    1987-03-01

    The performance of a thin-layer flow detector with a glassy carbon electrode coated with a film of protonated poly(4-vinylpyridine) is described. Substantial improvement in the selectivity of amperometric detection for liquid chromatography and flow injection systems is observed as a result of excluding cationic species from the surface. The detector response was evaluated with respect to flow rate, solute concentration, coating scheme, film-to-film reproducibility, and other variables. Despite the increase in diffusional resistance, low detection limits of ca. 0.04 and 0.10 ng of ascorbic acid and uric acid, respectively, are maintained. Protection from organic surfactants can be coupled to the charge exclusion effect by using a bilayer coating, with a cellulose acetate film atop the poly(4-vinylpyridine) layer. Applicability to urine sample is demonstrated.

  18. Electroanalysis of trimethoprim on metalloporphyrin incorporated glassy carbon electrode.

    PubMed

    Rajith, Leena; Kumar, Krishnapillai Girish

    2010-09-01

    Trimethoprim (TMP) is a bacteriostatic antibiotic mainly used in the prophylaxis and treatment of urinary tract infections. It belongs to the class of chemotherapeutic agents known as dihydrofolate reductase inhibitors. Its use is associated with idiosyncratic reactions, including liver toxicity and agranulocytosis. In order to determine TMP electrochemically, a metalloporphyrin modified glassy carbon electrode was prepared by coating [5,10,15,20- tetrakis(4-methoxyphenyl) porphyrinato]Mn (III)chloride (TMOPPMn(III)Cl) solution on the surface of the electrode. The electrochemical behaviour of TMP in Phosphate buffer solution (PBS) on TMOPPMn(III)Cl modified glassy carbon electrode (TMOPPMn(III)Cl/GCE) was explored using differential pulse voltammetry (DPV). The voltammograms showed enhanced oxidation response at the TMOPPMn (III)Cl/GCE with respect to the bare GCE for TMP, attributable to the electrocatalytic activity of TMOPPMn(III)Cl. Electrochemical parameters of the oxidation of TMP on the modified electrode were analyzed. The electro-oxidation of TMP was found to be irreversible, pH dependent and adsorption controlled on the modified electrode. It is found that the oxidation peak current is proportional to the concentration of TMP over the range 6 × 10⁻⁸ - 1 × 10⁻⁶ M with a very low detection limit of 3 × 10⁻⁹ M at 2 min open circuit accumulation. The repeatability expressed as relative standard deviation (RSD) for n = 9 was 3.2% and the operational stability was found to be 20 days. Another striking feature is that equimolar concentration of sulfamethoxazole did not interfere in the determination of TMP. Applicability to assay the drug in urine and tablet samples has also been studied.

  19. A Brief Historical Introduction to Matrices and Their Applications

    ERIC Educational Resources Information Center

    Debnath, L.

    2014-01-01

    This paper deals with the ancient origin of matrices, and the system of linear equations. Included are algebraic properties of matrices, determinants, linear transformations, and Cramer's Rule for solving the system of algebraic equations. Special attention is given to some special matrices, including matrices in graph theory and electrical…

  20. Polymorphism in glassy silicon: Inherited from liquid-liquid phase transition in supercooled liquid

    NASA Astrophysics Data System (ADS)

    Zhang, Shiliang; Wang, Li-Min; Zhang, Xinyu; Qi, Li; Zhang, Suhong; Ma, Mingzhen; Liu, Riping

    2015-02-01

    Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014 K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL).

  1. Condition number estimation of preconditioned matrices.

    PubMed

    Kushida, Noriyuki

    2015-01-01

    The present paper introduces a condition number estimation method for preconditioned matrices. The newly developed method provides reasonable results, while the conventional method which is based on the Lanczos connection gives meaningless results. The Lanczos connection based method provides the condition numbers of coefficient matrices of systems of linear equations with information obtained through the preconditioned conjugate gradient method. Estimating the condition number of preconditioned matrices is sometimes important when describing the effectiveness of new preconditionerers or selecting adequate preconditioners. Operating a preconditioner on a coefficient matrix is the simplest method of estimation. However, this is not possible for large-scale computing, especially if computation is performed on distributed memory parallel computers. This is because, the preconditioned matrices become dense, even if the original matrices are sparse. Although the Lanczos connection method can be used to calculate the condition number of preconditioned matrices, it is not considered to be applicable to large-scale problems because of its weakness with respect to numerical errors. Therefore, we have developed a robust and parallelizable method based on Hager's method. The feasibility studies are curried out for the diagonal scaling preconditioner and the SSOR preconditioner with a diagonal matrix, a tri-daigonal matrix and Pei's matrix. As a result, the Lanczos connection method contains around 10% error in the results even with a simple problem. On the other hand, the new method contains negligible errors. In addition, the newly developed method returns reasonable solutions when the Lanczos connection method fails with Pei's matrix, and matrices generated with the finite element method.

  2. Modelisations des effets de surface sur les jets horizontaux subsoniques d'hydrogene et de methane

    NASA Astrophysics Data System (ADS)

    Gomez, Luis Fernando

    Le developpement des codes et de normes bases sur une methodologie scientifique requiert la capacite de predire l'etendue inflammable de deversements gazeux d'hydrogene sous differentes conditions. Des etudes anterieures ont deja etabli des modeles bases sur les lois de conservation de la mecanique des fluides basees sur des correlations experimentales qui permettent de predire la decroissance de la concentration et de la vitesse d'un gaz le long de l'axe d'un jet libre vertical. Cette etude s'interesse aux effets de proximite a une surface horizontale parallele sur un jet turbulent. Nous nous interessons a son impact sur l'etendue du champ de la concentration et sur l'enveloppe inflammable en particulier. Cette etude est comparative : l'hydrogene est compare au methane. Ceci permet de degager l'influence des effets de difference de la densite sur le comportement du jet, et de comparer le comportement de l'hydrogene aux correlations experimentales, qui ont ete essentiellement etablies pour le methane. Un modele decrivant l'evolution spatio-temporelle du champ de concentration du gaz dilue est propose, base sur la mecanique des fluides computationnelle. Cette approche permet de varier systematiquement les conditions aux frontieres (proximite du jet a la surface, par exemple) et de connaitre en detail les proprietes de l'ecoulement. Le modele est implemente dans le code de simulations par volumes finis de FLUENT. Les resultats des simulations sont compares avec les lois de similitudes decoulant de la theorie des jets d'ecoulements turbulents libres ainsi qu'avec les resultats experimentaux disponibles. L'effet de la difference des masses molaires des constituantes du jet et des constituantes du milieu de dispersion est egalement etudie dans le contexte du comportement d'echelle de la region developpee du jet.

  3. Bayesian Nonparametric Clustering for Positive Definite Matrices.

    PubMed

    Cherian, Anoop; Morellas, Vassilios; Papanikolopoulos, Nikolaos

    2016-05-01

    Symmetric Positive Definite (SPD) matrices emerge as data descriptors in several applications of computer vision such as object tracking, texture recognition, and diffusion tensor imaging. Clustering these data matrices forms an integral part of these applications, for which soft-clustering algorithms (K-Means, expectation maximization, etc.) are generally used. As is well-known, these algorithms need the number of clusters to be specified, which is difficult when the dataset scales. To address this issue, we resort to the classical nonparametric Bayesian framework by modeling the data as a mixture model using the Dirichlet process (DP) prior. Since these matrices do not conform to the Euclidean geometry, rather belongs to a curved Riemannian manifold,existing DP models cannot be directly applied. Thus, in this paper, we propose a novel DP mixture model framework for SPD matrices. Using the log-determinant divergence as the underlying dissimilarity measure to compare these matrices, and further using the connection between this measure and the Wishart distribution, we derive a novel DPM model based on the Wishart-Inverse-Wishart conjugate pair. We apply this model to several applications in computer vision. Our experiments demonstrate that our model is scalable to the dataset size and at the same time achieves superior accuracy compared to several state-of-the-art parametric and nonparametric clustering algorithms. PMID:27046838

  4. Advanced incomplete factorization algorithms for Stiltijes matrices

    SciTech Connect

    Il`in, V.P.

    1996-12-31

    The modern numerical methods for solving the linear algebraic systems Au = f with high order sparse matrices A, which arise in grid approximations of multidimensional boundary value problems, are based mainly on accelerated iterative processes with easily invertible preconditioning matrices presented in the form of approximate (incomplete) factorization of the original matrix A. We consider some recent algorithmic approaches, theoretical foundations, experimental data and open questions for incomplete factorization of Stiltijes matrices which are {open_quotes}the best{close_quotes} ones in the sense that they have the most advanced results. Special attention is given to solving the elliptic differential equations with strongly variable coefficients, singular perturbated diffusion-convection and parabolic equations.

  5. Origin of symmetric PMNS and CKM matrices

    NASA Astrophysics Data System (ADS)

    Rodejohann, Werner; Xu, Xun-Jie

    2015-03-01

    The Pontecorvo-Maki-Nakagawa-Sakata and Cabibbo-Kobayashi-Maskawa matrices are phenomenologically close to symmetric, and a symmetric form could be used as zeroth-order approximation for both matrices. We study the possible theoretical origin of this feature in flavor symmetry models. We identify necessary geometric properties of discrete flavor symmetry groups that can lead to symmetric mixing matrices. Those properties are actually very common in discrete groups such as A4 , S4 , or Δ (96 ) . As an application of our theorem, we generate a symmetric lepton mixing scheme with θ12=θ23=36.21 ° ; θ13=12.20 ° , and δ =0 , realized with the group Δ (96 ) .

  6. Surface micro-structuring of glassy carbon for precision glass molding of diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Hermerschmidt, Andreas

    2014-09-01

    Glassy carbon is used nowadays for a variety of applications because of its mechanical strength, thermal stability and non-sticking adhesion properties. This makes it also a suitable candidate as mold material for precision compression molding of low and high glass-transition temperature materials. To fabricate molds for diffractive optics a highresolution structuring technique is needed. We introduce a process that allows the micro-structuring of glassy carbon by reactive ion etching. Key parameters such as uniformity, surface roughness, edge definition and lateral resolution are discussed. They are the most relevant parameters for a stamp in optical applications. The use of titanium as a hard mask makes it possible to achieve a reasonable selectivity of 4:1, which has so far been one of the main problems in microstructuring of glassy carbon. We investigate the titanium surface structure with its 5-10 nm thick layer of TiO2 grains and its influence on the shape of the hard mask. In our fabrication procedure we were able to realize optically flat diffractive structures with slope angles of more than 80° at typical feature sizes of 5 μm and at 700 nm depth. The fabricated glassy carbon molds were applied to thermal imprinting onto different glasses. Glassy carbon molds with 1 mm thickness were tested with binary optical structures. Our experiments show the suitability of glassy carbon as molds for cost efficient mass production with a high quality.

  7. Sparse Matrices in MATLAB: Design and Implementation

    NASA Technical Reports Server (NTRS)

    Gilbert, John R.; Moler, Cleve; Schreiber, Robert

    1992-01-01

    The matrix computation language and environment MATLAB is extended to include sparse matrix storage and operations. The only change to the outward appearance of the MATLAB language is a pair of commands to create full or sparse matrices. Nearly all the operations of MATLAB now apply equally to full or sparse matrices, without any explicit action by the user. The sparse data structure represents a matrix in space proportional to the number of nonzero entries, and most of the operations compute sparse results in time proportional to the number of arithmetic operations on nonzeros.

  8. Spectral properties of ghost Neumann matrices

    SciTech Connect

    Bonora, L.; Santos, R. J. Scherer; Tolla, D. D.

    2008-05-15

    We continue the analysis of the ghost wedge states in the oscillator formalism by studying the spectral properties of the ghost matrices of Neumann coefficients. We show that the traditional spectral representation is not valid for these matrices and propose a new heuristic formula that allows one to reconstruct them from the knowledge of their eigenvalues and eigenvectors. It turns out that additional data, which we call boundary data, are needed in order to actually implement the reconstruction. In particular our result lends support to the conjecture that there exists a ghost three strings vertex with properties parallel to those of the matter three strings vertex.

  9. Factorization Of Positive Definite, Banded Hermitian Matrices

    NASA Technical Reports Server (NTRS)

    Salama, Moktar A.; Utku, Senol; Melosh, Robert

    1989-01-01

    Report discusses application of Cholesky factorization algorithm to positive definite, banded Hermitian matrices. Begins by extending Cholesky factorization algorithm to cover uniformly-partitioned, banded, positive definite matrices of rank n that is real symmetric or Hermitian. Then two stratagems given for use of algorithm in concurrent-processing system in which N less than it has to be to enable factorization of matrix in as few serial steps as possible and where uniformly high efficiency expected from all processing elements. One of major purposes of this and related studies to maximize speedup and efficiency in system of concurrent-data-processing elements.

  10. Terbium induced glassy magnetism in La,Ca-based cobaltites

    SciTech Connect

    Maryško, M. Hejtmánek, J.; Jirák, Z.; Kaman, O.; Knížek, K.

    2014-05-07

    The La{sub 0.8–x}Tb{sub x}Ca{sub 0.2}CoO{sub 3} cobaltites of orthoperovskite Pbnm structure were investigated by the X-ray and neutron diffraction, specific heat, and magnetization measurements. The terbium doping has two important effects, it increases the size disorder on perovskite A-sites and influences the magnetic properties due to large Ising-type moments (∼8.9 Bohr magnetons per Tb). The compounds show a bulk magnetic moment below T{sub C} = 82 K, 53 K, and 30 K for x = 0.1, 0.2, and 0.3, respectively. The neutron diffraction evidences a long-range ferromagnetic arrangement of cobalt moments, combined below ∼20 K with ordering of terbium moments in a canted arrangement. A homogeneous magnetic phase is proved for the x = 0.1 sample, while x = 0.2 and 0.3 are in an intrinsically non-homogeneous magnetic state with long-range ordering only comprising 55% and 30% of the sample volumes. The ac susceptibility experiments prove a glassy character of the terbium doped samples and provide arguments for the short-range ordering above T{sub C} and wide distribution of relaxation times.

  11. Mechanics of particulate composites with glassy polymer binders in compression

    PubMed Central

    Jordan, J. L.; Spowart, J. E.; Kendall, M. J.; Woodworth, B.; Siviour, C. R.

    2014-01-01

    Whether used as structural components in design or matrix materials for composites, the mechanical properties of polymers are increasingly important. The compressive response of extruded polymethyl methacrylate (PMMA) rod with aligned polymer chains and Al–Ni–PMMA particulate composites are investigated across a range of strain rates and temperatures. The particulate composites were prepared using an injection-moulding technique resulting in highly anisotropic microstructures. The mechanics of these materials are discussed in the light of theories of deformation for glassy polymers. The experimental data from this study are compared with PMMA results from the literature as well as epoxy-based composites with identical particulates. The PMMA exhibited the expected strain rate and temperature dependence and brittle failure was observed at the highest strain rates and lowest temperatures. The Al–Ni–PMMA composites were found to have similar stress–strain response to the PMMA with reduced strain softening after yield. Increasing volume fraction of particulates in the composite resulted in decreased strength. PMID:24711495

  12. Glassy state and cryopreservation of mint shoot tips.

    PubMed

    Teixeira, Aline S; González-Benito, M Elena; Molina-García, Antonio D

    2013-01-01

    Vitrification refers to the physical process by which a liquid supercools to very low temperatures and finally solidifies into a metastable glass, without undergoing crystallization at a practical cooling rate. Thus, vitrification is an effective freeze-avoidance mechanism and living tissue cryopreservation is, in most cases, relying on it. As a glass is exceedingly viscous and stops all chemical reactions that require molecular diffusion, its formation leads to metabolic inactivity and stability over time. To investigate glassy state in cryopreserved plant material, mint shoot tips were submitted to the different stages of a frequently used cryopreservation protocol (droplet-vitrification) and evaluated for water content reduction and sucrose content, as determined by ion chromatography, frozen water fraction and glass transitions occurrence by differential scanning calorimetry, and investigated by low-temperature scanning electron microscopy, as a way to ascertain if their cellular content was vitrified. Results show how tissues at intermediate treatment steps develop ice crystals during liquid nitrogen cooling, while specimens whose treatment was completed become vitrified, with no evidence of ice formation. The agreement between calorimetric and microscopic observations was perfect. Besides finding a higher sucrose concentration in tissues at the more advanced protocol steps, this level was also higher in plants precultured at 25/-1°C than in plants cultivated at 25°C.

  13. Dielectric studies of molecular motions in glassy and liquid nicotine

    NASA Astrophysics Data System (ADS)

    Kaminski, K.; Paluch, M.; Ziolo, J.; Ngai, K. L.

    2006-06-01

    The dielectric permittivity and loss spectra of glassy and liquid states of nicotine have been measured over the frequency range 10-2-109 Hz. The relaxation spectra are similar to common small molecular glass-forming substances, showing the structural α-relaxation and its precursor, the Johari-Goldstein β-relaxation. The α-relaxation is well described by the Fourier transform of the Kohlrausch-Williams-Watts stretched exponential function with an approximately constant stretch exponent that is equal to 0.70 as the glass transition temperature is approached. The dielectric α-relaxation time measured over 11 orders of magnitude cannot be described by a single Vogel-Fulcher-Tamman-Hesse equation. The most probable Johari-Goldstein β-relaxation time determined from the dielectric spectra is in good agreement with the primitive relaxation time of the coupling model calculated from parameters of the structural α-relaxation. The shape of the dielectric spectra of nicotine is compared with that of other glass-formers having about the same stretch exponent, and they are shown to be nearly isomorphic. The results indicate that the molecular dynamics of nicotine conform to the general pattern found in other glass-formers, and the presence of the universal Johari-Goldstein secondary relaxation, which plays a role in the crystallization of amorphous pharmaceuticals.

  14. Glassy cell carcinoma of the cervix: a literature review.

    PubMed

    Zolciak-Siwinska, A; Jonska-Gmyrek, J

    2014-08-01

    Glassy cell carcinoma (GCC) is a histologically aggressive subtype of cervical cancer with rapid growth and early metastases. The prognosis for patients with GCC is poor. This article reviews the literature pertinent to the epidemiology, cytology, pathology, immunohistochemistry, treatment and prognosis of GCC. MEDLINE (PubMed) was searched for all articles or abstracts on patients diagnosed with GCC published (in English) since the original definition by Glucksmann and Cherry, Cancer 1956;9:971. Accurate diagnosis of GCC enables implementation of the correct treatment strategy. Early-stage GCC should be treated with hysterectomy and pelvic lymph node dissection, with adjuvant radiochemotherapy if at least one intermediate or high risk factor for cervical cancer is present. Advanced GCC should be treated with neoadjuvant radiochemotherapy or chemotherapy with the aim of making the disease operable. There is a need for retrospective evaluation of GCC treatment from several centres to explore knowledge about this rare entity. Future studies should explore the role of targeted therapies and the most efficient chemotherapy regimen for the management of GCC.

  15. Mathematical modeling of glassy-winged sharpshooter population.

    PubMed

    Yoon, Jeong-Mi; Hrynkiv, Volodymyr; Morano, Lisa; Nguyen, Anh Tuan; Wilder, Sara; Mitchell, Forrest

    2014-06-01

    Pierce's disease (PD) is a fatal disease of grapevines which results from an infection by the plant pathogen Xyllela fastidiosa. This bacterium grows in the xylem (water-conducting) vessels of the plant blocking movement of water. PD can kill vines in one year and poses a serious threat to both the California and the expanding Texas wine industries. Bacteria are vectored from one vine to the next by a number of xylem feeding insect species. Of these, the Glassy-winged Sharpshooter (GWSS) is considered to be the primary xylem feeding insect in Texas vineyards. An extensive database of the xylem-feeding population frequencies was collected by USDA-APHIS for Texas vineyards over multiple years. This project focused on a subset of data, GWSS frequencies within 25 vineyards in Edwards Plateau located in central Texas. The proposed model investigates the natural population dynamics and the decline in GWSS, likely the result of pest management campaigns on the insects within the region. The model is a delay Gompertz differential equation with harvesting and immigration terms, and we use the data to estimate the model parameters.

  16. Mathematical modeling of glassy-winged sharpshooter population.

    PubMed

    Yoon, Jeong-Mi; Hrynkiv, Volodymyr; Morano, Lisa; Nguyen, Anh Tuan; Wilder, Sara; Mitchell, Forrest

    2014-06-01

    Pierce's disease (PD) is a fatal disease of grapevines which results from an infection by the plant pathogen Xyllela fastidiosa. This bacterium grows in the xylem (water-conducting) vessels of the plant blocking movement of water. PD can kill vines in one year and poses a serious threat to both the California and the expanding Texas wine industries. Bacteria are vectored from one vine to the next by a number of xylem feeding insect species. Of these, the Glassy-winged Sharpshooter (GWSS) is considered to be the primary xylem feeding insect in Texas vineyards. An extensive database of the xylem-feeding population frequencies was collected by USDA-APHIS for Texas vineyards over multiple years. This project focused on a subset of data, GWSS frequencies within 25 vineyards in Edwards Plateau located in central Texas. The proposed model investigates the natural population dynamics and the decline in GWSS, likely the result of pest management campaigns on the insects within the region. The model is a delay Gompertz differential equation with harvesting and immigration terms, and we use the data to estimate the model parameters. PMID:24506556

  17. Structural origin of low temperature glassy relaxation in magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Laha, Suvra; Regmi, Rajesh; Lawes, Gavin

    2013-03-01

    Magnetic nanoparticles often exhibit glass-like relaxation features at low temperatures. Here we discuss the effects of doping boron, cobalt, gadolinium and lanthanum on the low temperature magnetic properties of Fe3O4 nanoparticles. We investigated the structure of the nanoparticles using both X-ray diffraction and Raman studies, and find evidence for secondary phase formation in certain samples. We acquired Transmission Electron Microscopic images to give direct information on the morphology and microstructure of these doped nanoparticles. We measured the ac out-of-phase susceptibility (χ//) vs temperature (T) to parameterize the low temperature glassy magnetic relaxation. All samples show low temperature magnetic relaxation, but the amplitude of the signal increases dramatically for certain dopants. We attribute these low temperature frequency-dependent magnetic relaxation features to structural defects, which are enhanced in some of the doped Fe3O4 nanoparticles. These studies also confirm that the low temperature relaxation in nanoparticles arises from single particle effects and are not associated with interparticle interactions.

  18. Surface temperatures and glassy state investigations in tribology, part 1

    NASA Technical Reports Server (NTRS)

    Winer, W. O.; Sanborn, D. M.

    1978-01-01

    The research in this report is divided into two categories: (1) lubricant rheological behavior, and (2) thermal behavior of a simulated elastohydrodynamic contact. The studies of the lubricant rheological behavior consists of high pressure, low shear rate viscosity measurements, viscoelastic transition measurements, by volume dilatometry, dielectric transitions at atmospheric pressure and light scattering transitions. Lubricant shear stress-strain behavior in the amorphous glassy state was measured on several fluids. It appears clear from these investigations that many lubricants undergo viscoplastic transitions in typical EHD contacts and that the lubricant has a limiting maximum shear stress it can support which in turn will determine the traction in the contact except in cases of very low slide-roll ratio. Surface temperature measurements were made for a naphthenic mineral oil and a polyphenyl ether. The maximum surface temperature in these experiments was approximately symmetrical about the zero slide-roll ration except for absolute values of slide-roll ratio greater than about 0.9. Additional surface temperature measurements were made in contacts with rough surfaces where the composite surface roughness was approximately equal to the EHD film thickness. A regression analysis was done to obtain a predictive equation for surface temperatures as a function of pressure, sliding speed, and surface roughness. A correction factor for surface roughness effects to the typical flash temperature analysis was found.

  19. Comparaison des effets des irradiations γ, X et UV dans les fibres optiques

    NASA Astrophysics Data System (ADS)

    Girard, S.; Ouerdane, Y.; Baggio, J.; Boukenter, A.; Meunier, J.-P.; Leray, J.-L.

    2005-06-01

    Les fibres optiques présentent de nombreux avantages incitant à les intégrer dans des applications devant résister aux environnements radiatifs associés aux domaines civil, spatial ou militaire. Cependant, leur exposition à un rayonnement entraîne la création de défauts ponctuels dans la silice amorphe pure ou dopée qui constitue les différentes parties de la fibre optique. Ces défauts causent, en particulier, une augmentation transitoire de l'atténuation linéique des fibres optiques responsable de la dégradation voire de la perte du signal propagé dans celles-ci. Dans cet article, nous comparons les effets de deux types d'irradiation: une impulsion X et une dose γ cumulée. Les effets de ces irradiations sont ensuite comparés avec ceux induits par une insolation ultraviolette (244 nm) sur les propriétés d'absorption des fibres optiques. Nous montrons qu'il existe des similitudes entre ces différentes excitations et qu'il est possible, sous certaines conditions, d'utiliser celles-ci afin d'évaluer la capacité de certaines fibres optiques à fonctionner dans un environnement nucléaire donné.

  20. Malware analysis using visualized image matrices.

    PubMed

    Han, KyoungSoo; Kang, BooJoong; Im, Eul Gyu

    2014-01-01

    This paper proposes a novel malware visual analysis method that contains not only a visualization method to convert binary files into images, but also a similarity calculation method between these images. The proposed method generates RGB-colored pixels on image matrices using the opcode sequences extracted from malware samples and calculates the similarities for the image matrices. Particularly, our proposed methods are available for packed malware samples by applying them to the execution traces extracted through dynamic analysis. When the images are generated, we can reduce the overheads by extracting the opcode sequences only from the blocks that include the instructions related to staple behaviors such as functions and application programming interface (API) calls. In addition, we propose a technique that generates a representative image for each malware family in order to reduce the number of comparisons for the classification of unknown samples and the colored pixel information in the image matrices is used to calculate the similarities between the images. Our experimental results show that the image matrices of malware can effectively be used to classify malware families both statically and dynamically with accuracy of 0.9896 and 0.9732, respectively. PMID:25133202

  1. Tsirelson's problem and asymptotically commuting unitary matrices

    SciTech Connect

    Ozawa, Narutaka

    2013-03-15

    In this paper, we consider quantum correlations of bipartite systems having a slight interaction, and reinterpret Tsirelson's problem (and hence Kirchberg's and Connes's conjectures) in terms of finite-dimensional asymptotically commuting positive operator valued measures. We also consider the systems of asymptotically commuting unitary matrices and formulate the Stronger Kirchberg Conjecture.

  2. SPECIATION OF ARSENIC IN EXPOSURE ASSESSMENT MATRICES

    EPA Science Inventory

    The speciaton of arsenic in water, food and urine are analytical capabilities which are an essential part in arsenic risk assessment. The cancer risk associated with arsenic has been the driving force in generating the analytical research in each of these matrices. This presentat...

  3. Noisy covariance matrices and portfolio optimization

    NASA Astrophysics Data System (ADS)

    Pafka, S.; Kondor, I.

    2002-05-01

    According to recent findings [#!bouchaud!#,#!stanley!#], empirical covariance matrices deduced from financial return series contain such a high amount of noise that, apart from a few large eigenvalues and the corresponding eigenvectors, their structure can essentially be regarded as random. In [#!bouchaud!#], e.g., it is reported that about 94% of the spectrum of these matrices can be fitted by that of a random matrix drawn from an appropriately chosen ensemble. In view of the fundamental role of covariance matrices in the theory of portfolio optimization as well as in industry-wide risk management practices, we analyze the possible implications of this effect. Simulation experiments with matrices having a structure such as described in [#!bouchaud!#,#!stanley!#] lead us to the conclusion that in the context of the classical portfolio problem (minimizing the portfolio variance under linear constraints) noise has relatively little effect. To leading order the solutions are determined by the stable, large eigenvalues, and the displacement of the solution (measured in variance) due to noise is rather small: depending on the size of the portfolio and on the length of the time series, it is of the order of 5 to 15%. The picture is completely different, however, if we attempt to minimize the variance under non-linear constraints, like those that arise e.g. in the problem of margin accounts or in international capital adequacy regulation. In these problems the presence of noise leads to a serious instability and a high degree of degeneracy of the solutions.

  4. Spectral averaging techniques for Jacobi matrices

    SciTech Connect

    Rio, Rafael del; Martinez, Carmen; Schulz-Baldes, Hermann

    2008-02-15

    Spectral averaging techniques for one-dimensional discrete Schroedinger operators are revisited and extended. In particular, simultaneous averaging over several parameters is discussed. Special focus is put on proving lower bounds on the density of the averaged spectral measures. These Wegner-type estimates are used to analyze stability properties for the spectral types of Jacobi matrices under local perturbations.

  5. Malware Analysis Using Visualized Image Matrices

    PubMed Central

    Im, Eul Gyu

    2014-01-01

    This paper proposes a novel malware visual analysis method that contains not only a visualization method to convert binary files into images, but also a similarity calculation method between these images. The proposed method generates RGB-colored pixels on image matrices using the opcode sequences extracted from malware samples and calculates the similarities for the image matrices. Particularly, our proposed methods are available for packed malware samples by applying them to the execution traces extracted through dynamic analysis. When the images are generated, we can reduce the overheads by extracting the opcode sequences only from the blocks that include the instructions related to staple behaviors such as functions and application programming interface (API) calls. In addition, we propose a technique that generates a representative image for each malware family in order to reduce the number of comparisons for the classification of unknown samples and the colored pixel information in the image matrices is used to calculate the similarities between the images. Our experimental results show that the image matrices of malware can effectively be used to classify malware families both statically and dynamically with accuracy of 0.9896 and 0.9732, respectively. PMID:25133202

  6. Malware analysis using visualized image matrices.

    PubMed

    Han, KyoungSoo; Kang, BooJoong; Im, Eul Gyu

    2014-01-01

    This paper proposes a novel malware visual analysis method that contains not only a visualization method to convert binary files into images, but also a similarity calculation method between these images. The proposed method generates RGB-colored pixels on image matrices using the opcode sequences extracted from malware samples and calculates the similarities for the image matrices. Particularly, our proposed methods are available for packed malware samples by applying them to the execution traces extracted through dynamic analysis. When the images are generated, we can reduce the overheads by extracting the opcode sequences only from the blocks that include the instructions related to staple behaviors such as functions and application programming interface (API) calls. In addition, we propose a technique that generates a representative image for each malware family in order to reduce the number of comparisons for the classification of unknown samples and the colored pixel information in the image matrices is used to calculate the similarities between the images. Our experimental results show that the image matrices of malware can effectively be used to classify malware families both statically and dynamically with accuracy of 0.9896 and 0.9732, respectively.

  7. The Rank of Reduced Dispersion Matrices.

    ERIC Educational Resources Information Center

    Bekker, Paul A.; de Leeuw, Jan

    1987-01-01

    Psychometricians working in factor analysis and econometricians working in regression with measurement error in all variables are both interested in the rank of dispersion matrices under variation of diagonal elements. This paper reviews both fields; points out various small errors; and presents a methodological comparision of factor analysis and…

  8. Development of the glassy state of benzophenone and effect of heating rate from the glassy state on solidification

    SciTech Connect

    Thoma, P.E.; Boehm, J.J.

    1997-12-31

    Benzophenone supercools to a glass when cooled to {minus}100 C. In fact, it is difficult to freeze benzophenone on cooling. In this investigation, the effect of cooling rate and the minimum cooling rate to obtain benzophenone as a glass is determined. From the glassy state, the influence of heating rate on the solidification temperature of benzophenone is determined. When heated at 3 C/min., solidification starts at about {minus}29 C. Upon additional heating, melting usually starts at about +24 C, which is 23 C lower than the solid equilibrium structure melting temperature of 47 C. Occasionally the solid that forms at about {minus}29 C undergoes a solid state phase transformation at about +22 C, when heated at 3 C/min. If this solid state phase transformation occurs, then the solid benzophenone starts to melt at 47 C. When solid benzophenone with the equilibrium structure is cooled to {minus}100 C, no solid state phase transformation occurs. It appears that the structure that solidified at {minus}29 C is metastable.

  9. Immobilization of DNA at Glassy Ccarbon Electrodes: A Critical Study of Adsorbed Layer

    PubMed Central

    Pedano, M. L.; Rivas, G. A.

    2005-01-01

    In this work we present a critical study of the nucleic acid layer immobilized at glassy carbon electrodes. Different studies were performed in order to assess the nature of the interaction between DNA and the electrode surface. The adsorption and electrooxidation of DNA demonstrated to be highly dependent on the surface and nature of the glassy carbon electrode. The DNA layer immobilized at a freshly polished glassy carbon electrode was very stable even after applying highly negative potentials. The electron transfer of potassium ferricyanide, catechol and dopamine at glassy carbon surfaces modified with thin (obtained by adsorption under controlled potential conditions) and thick (obtained by casting the glassy carbon surface with highly concentrated DNA solutions) DNA layers was slower than that at the bare glassy carbon electrode, although this effect was dependent on the thickness of the layer and was not charge selective. Raman experiments showed an important decrease of the vibrational modes assigned to the nucleobases residues, suggesting a strong interaction of these residues with the electrode surface. The hybridization of oligo(dG)21 and oligo(dC)21 was evaluated from the guanine oxidation signal and the reduction of the redox indicator Co(phen)33+. In both cases the chronopotentiometric response indicated that the compromise of the bases in the interaction of DNA with the electrode surface is too strong, preventing further hybridization. In summary, glassy carbon is a useful electrode material to detect DNA in a direct and very sensitive way, but not to be used for the preparation of biorecognition layers by direct adsorption of the probe sequence on the electrode surface for detecting the hybridization event.

  10. How important are glassy SOA ice nuclei for the formation of cirrus clouds?

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Penner, J. E.; Lin, G.; Liu, X.; Wang, M.

    2014-12-01

    Extremely low ice numbers (i.e. 5 - 100 / L) have been observed in the tropical troposphere layer (TTL) in a variety of field campaigns. Various mechanisms have been proposed to explain these low numbers, including the effect of glassy secondary organic aerosol acting as heterogeneous ice nuclei (IN). In this study, we explored these effects using the CAM5.3 model. SOA fields were provided by an offline version of the University of Michigan-IMPACT model, which has a detailed process-based mechanism that describes aerosol microphysics and SOA formation through both gas phase and multiphase reactions. The transition criterion of SOA to glassy heterogeneous IN follows the parameterization developed by Wang et al. 2012. With this parameterization, glassy SOA IN form mainly when the temperature (T) is lower than 210K. In the default CAM5.3 set-up in which only the fraction of Aitken mode sulfate aerosols with diameter larger than 100nm participate in the ice nucleation (Liu and Penner 2005 parameterization), glassy SOA IN are shown to decrease the ice number (Ni) by suppressing some of the homogeneous freezing at low temperatures thereby leading to an improved representation of the relationship between Ni and T compared to the observations summarized by Kramer et al. 2009. However, when we allow the total number of the Aitken mode sulfate particles to participate in homogeneous freezing, glassy SOA IN have only a small impact on the relationship between Ni and T. If the subgrid updraft velocity is decreased to 0.1 m/s (compared to 0.2 m/s in the default set-up), there is a large decrease of Ni, since homogeneous freezing is more easily suppressed by glassy SOA IN at these updrafts. We also present the effects of glassy SOA IN using an alternative ice nucleation scheme (Barahona and Nenes, 2009).

  11. How fast is water uptake on glassy and amorphous aerosol?

    NASA Astrophysics Data System (ADS)

    Bones, D. L.; Lienhard, D. M.; Krieger, U.; Reid, J. P.

    2011-12-01

    Atmospheric aerosol particles are typically complex mixtures of organic and inorganic species with correspondingly complex behaviour in their response to changes in humidity. Indeed, it has been recently recognised that many aerosols exist as highly viscous solutions or as amorphous glasses, rather than a crystalline state, over a wide range of relative humidities (Virtanen, et al. 2010). In this work, we investigate the formation of glassy or highly viscous phases in aqueous sugar aerosols such as sucrose and levoglucosan and aerosols of mixtures of sugars and inorganic compounds, reporting the timescale for the mass transfer of water between the particle and the gas phase with variation in water activity. Optical tweezers are used to trap single aerosol particles and examine the time-dependent response in their size to stepwise changes in RH, which result in the evaporation or condensation of water. The evolving particle size and homogeneity in composition are estimated from the wavelengths of specific resonance modes of the cavity enhanced Raman scattering spectra, deducing size changes with an accuracy of better than 1 nm. The experimental data is compared with a kinetic model of diffusional limited size change (Zobrist, et al. 2011), in which the diffusion of water within the particle bulk limits the rate of water transport between the gas and condensed phases. We report measurements in which ternary mixtures, with varying mole ratios of sucrose and sodium chloride, have allowed us to examine the water transport and response time in particle size over a wide range of bulk viscosities. Changes in size are dramatically hindered at low RH, with time scales approaching 10000s, for both increasing and decreasing RH regimes (Tong, et al. 2011). We also observe a marked relative shift in resonance modes, suggesting initial formation of a layer of water on the surface of the glassy particle and subsequent establishment of a steep concentration gradient within the

  12. Charge transport and glassy dynamics in ionic liquids.

    PubMed

    Sangoro, Joshua R; Kremer, Friedrich

    2012-04-17

    Ionic liquids (ILs) exhibit unique features such as low melting points, low vapor pressures, wide liquidus temperature ranges, high thermal stability, high ionic conductivity, and wide electrochemical windows. As a result, they show promise for use in variety of applications: as reaction media, in batteries and supercapacitors, in solar and fuel cells, for electrochemical deposition of metals and semiconductors, for protein extraction and crystallization, and many others. Because of the ease with which they can be supercooled, ionic liquids offer new opportunities to investigate long-standing questions regarding the nature of the dynamic glass transition and its possible link to charge transport. Despite the significant steps achieved from experimental and theoretical studies, no generally accepted quantitative theory of dynamic glass transition to date has been capable of reproducing all the experimentally observed features. In this Account, we discuss recent studies of the interplay between charge transport and glassy dynamics in ionic liquids as investigated by a combination of several experimental techniques including broadband dielectric spectroscopy, pulsed field gradient nuclear magnetic resonance, dynamic mechanical spectroscopy, and differential scanning calorimetry. Based on Einstein-Smoluchowski relations, we use dielectric spectra of ionic liquids to determine diffusion coefficients in quantitative agreement with independent pulsed field gradient nuclear magnetic resonance measurements, but spanning a broader range of more than 10 orders of magnitude. This approach provides a novel opportunity to determine the electrical mobility and effective number density of charge carriers as well as their types of thermal activation from the measured dc conductivity separately. We also unravel the origin of the remarkable universality of charge transport in different classes of glass-forming ionic liquids.

  13. Charge Transport and Glassy Dynamics in Ionic Liquids

    SciTech Connect

    Sangoro, Joshua R; Kremer, Friedrich

    2012-01-01

    Ionic liquids (ILs) exhibit unique features such as low melting points, low vapor pressures, wide liquidus temperature ranges, high thermal stability, high ionic conductivity, and wide electrochemical windows. As a result, they show promise for use in variety of applications: as reaction media, in batteries and supercapacitors, in solar and fuel cells, for electrochemical deposition of metals and semiconductors, for protein extraction and crystallization, and many others. Because of the ease with which they can be supercooled, ionic liquids offer new opportunities to investigate long-standing questions regarding the nature of the dynamic glass transition and its possible link to charge transport. Despite the significant steps achieved from experimental and theoretical studies, no generally accepted quantitative theory of dynamic glass transition to date has been capable of reproducing all the experimentally observed features. In this Account, we discuss recent studies of the interplay between charge transport and glassy dynamics in ionic liquids as investigated by a combination of several experimental techniques including broadband dielectric spectroscopy, pulsed field gradient nuclear magnetic resonance, dynamic mechanical spectroscopy, and differential scanning calorimetry. Based on EinsteinSmoluchowski relations, we use dielectric spectra of ionic liquids to determine diffusion coefficients in quantitative agreement with independent pulsed field gradient nuclear magnetic resonance measurements, but spanning a broader range of more than 10 orders of magnitude. This approach provides a novel opportunity to determine the electrical mobility and effective number density of charge carriers as well as their types of thermal activation from the measured dc conductivity separately. We also unravel the origin of the remarkable universality of charge transport in different classes of glass-forming ionic liquids.

  14. Modeling mechanophore activation within a crosslinked glassy matrix

    NASA Astrophysics Data System (ADS)

    Silberstein, Meredith N.; Min, Kyoungmin; Cremar, Lee D.; Degen, Cassandra M.; Martinez, Todd J.; Aluru, Narayana R.; White, Scott R.; Sottos, Nancy R.

    2013-07-01

    Mechanically induced reactivity is a promising means for designing self-reporting materials. Mechanically sensitive chemical groups called mechanophores are covalently linked into polymers in order to trigger specific chemical reactions upon mechanical loading. These mechanophores can be linked either within the backbone or as crosslinks between backbone segments. Mechanophore response is sensitive to both the matrix properties and placement within the matrix, providing two avenues for material design. A model framework is developed to describe reactivity of mechanophores located as crosslinks in a glassy polymer matrix. Simulations are conducted at the molecular and macromolecular scales in order to develop macroscale constitutive relations. The model is developed specifically for the case of spiropyran (SP) in lightly crosslinked polymethylmethacrylate (PMMA). This optically trackable mechanophore (fluorescent when activated) allows the model to be assessed in terms of observed experimental behavior. The force modified potential energy surface (FMPES) framework is used in conjunction with ab initio steered molecular dynamics (MD) simulations of SP to determine the mechanophore kinetics. MD simulations of the crosslinked PMMA structure under shear deformation are used to determine the relationship between macroscale stress and local force on the crosslinks. A continuum model implemented in a finite element framework synthesizes these mechanochemical relations with the mechanical behavior. The continuum model with parameters taken directly from the FMPES and MD analyses under predicts stress-driven activation relative to experimental data. The continuum model, with the physically motivated modification of force fluctuations, provides an accurate prediction for monotonic loading across three decades of strain rate and creep loading, suggesting that the fundamental physics are captured.

  15. Bulk glassy and nonequilibrium crystalline alloys by stabilization of supercooled liquid: fabrication, functional properties and applications (Part 2)

    NASA Astrophysics Data System (ADS)

    Inoue, A.

    The novel stabilization phenomenon of supercooled liquid in special multi-component metallic alloys that follow the three component rules has enabled us to fabricate a number of bulk glassy and nonequilibrium crystalline alloys exhibiting useful characteristics. Following the previous review (Part 1; Proc. Jpn. Acad. Ser. B 81, 156-171), this paper (Part 2) reviews our recent results on the physical, chemical, mechanical and magnetic properties of the resulting bulk nonequilibrium materials including glassy single phase alloys, nanocrystal-, nanoquasicrystal- and dendritic crystal-dispersed glassy alloys and nanocrystalline alloys. Finally, the application potential of bulk glassy alloys is addressed, taking account of their novel engineering properties and production processes.

  16. A brief historical introduction to matrices and their applications

    NASA Astrophysics Data System (ADS)

    Debnath, L.

    2014-04-01

    This paper deals with the ancient origin of matrices, and the system of linear equations. Included are algebraic properties of matrices, determinants, linear transformations, and Cramer's Rule for solving the system of algebraic equations. Special attention is given to some special matrices, including matrices in graph theory and electrical networks. It contains a wide variety of important materials accessible to college and even high school students and teachers at all levels.

  17. Stiffness and mass matrices for shells of revolution (SAMMSOR II)

    NASA Technical Reports Server (NTRS)

    Tillerson, J. R.; Haisler, W. E.

    1974-01-01

    Utilizing element properties, structural stiffness and mass matrices are generated for as many as twenty harmonics and stored on magnetic tape. Matrices generated constitute input data to be used by other stiffness of revolution programs. Variety of boundary and loading conditions can be employed without having to create new mass and stiffness matrices for each case.

  18. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301,...

  19. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301,...

  20. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301,...

  1. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301,...

  2. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301,...

  3. Improved Separability Criteria Based on Bloch Representation of Density Matrices

    PubMed Central

    Shen, Shu-Qian; Yu, Juan; Li, Ming; Fei, Shao-Ming

    2016-01-01

    The correlation matrices or tensors in the Bloch representation of density matrices are encoded with entanglement properties. In this paper, based on the Bloch representation of density matrices, we give some new separability criteria for bipartite and multipartite quantum states. Theoretical analysis and some examples show that the proposed criteria can be more efficient than the previous related criteria. PMID:27350031

  4. Universality of the glassy transitions in the two-dimensional ±J Ising model.

    PubMed

    Parisen Toldin, Francesco; Pelissetto, Andrea; Vicari, Ettore

    2010-08-01

    We investigate the zero-temperature glassy transitions in the square-lattice ±J Ising model, with bond distribution P(J{xy})=pδ(J{xy}-J)+(1-p)δ(J{xy}+J) ; p=1 and p=1/2 correspond to the pure Ising model and to the Ising spin glass with symmetric bimodal distribution, respectively. We present finite-temperature Monte Carlo simulations at p=4/5 , which is close to the low-temperature paramagnetic-ferromagnetic transition line located at p≈0.89 , and at p=1/2 . Their comparison provides a strong evidence that the glassy critical behavior that occurs for 1-p{0}glassy and magnetic modes are not coupled at the multicritical zero-temperature point where the paramagnetic-ferromagnetic transition line and the T=0 glassy transition line meet. On the theoretical side we discuss the validity of finite-size scaling in glassy systems with a zero-temperature transition and a discrete Hamiltonian spectrum. Because of a freezing phenomenon which occurs in a finite volume at sufficiently low temperatures, the standard finite-size scaling limit in terms of TL(1/ν) does not exist; the renormalization-group invariant quantity ξ/L should be used instead as basic variable.

  5. Cure kinetics, morphologies, and mechanical properties of thermoplastic/MWCNT modified multifunctional glassy epoxies prepared via continuous reaction methods

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaole

    The primary goal of this dissertation is to develop a novel continuous reactor method to prepare partially cured epoxy prepolymers for aerospace prepreg applications with the aim of replacing traditional batch reactors. Compared to batch reactors, the continuous reactor is capable of solubilizing and dispersing a broad range of additives including thermoplastic tougheners, stabilizers, nanoparticles and curatives and advancing epoxy molecular weights and viscosities while reducing energy consumption. In order to prove this concept, polyethersulfone (PES) modified 4, 4'-diaminodiphenylsulfone (44DDS)/tetraglycidyl-4, 4'-diaminodiphenylmethane (TGDDM) epoxy prepolymers were firstly prepared using both continuous reactor and batch reactor methods. Kinetic studies confirmed the chain extension reaction in the continuous reactor is similar to the batch reactor, and the molecular weights and viscosities of prepolymers were readily controlled through reaction kinetics. Atomic force microscopy (AFM) confirmed similar cured network morphologies for formulations prepared from batch and continuous reactors. Additionally tensile strength, tensile modulus and fracture toughness analyses concluded mechanical properties of cured epoxy matrices produced from both reactors were equivalent. Effects of multifunctional epoxy compositions on thermoplastics phase-separated morphologies were systematically studied using a combination of AFM with nanomechanical mapping, spectroscopic and calorimetric techniques to provide new insights to tailor cured reaction induced phase separation (CRIPS) in multifunctional epoxy blend networks. Furthermore, how resultant crosslinked glassy polymer network and phase-separated morphologies correlated with mechanical properties are discussed in detail. Multiwall carbon nanotube (MWCNT)/TGDDM epoxy prepolymers were further prepared by combining the successful strategies for advancing epoxy chemistries and dispersing nanotubes using the continuous reactor

  6. Bruit thermique et effets quantiques dans une cavité optique de grande finesse

    NASA Astrophysics Data System (ADS)

    Caniard, T.; Briant, T.; Heidmann, A.; Pinard, M.

    2006-10-01

    Nous nous intéressons aux bruits dans les mesures optiques de très grande sensibilité et aux limites associées. Une des limitations fondamentales des mesures interférométriques, telles que les détections d'ondes gravitationnelles, est liée aux fluctuations de la pression de radiation exercée par la lumière sur les miroirs. Celle-ci induit des corrélations quantiques entre la position des miroirs et les fluctuations de la lumière. L'observation de ces effets quantiques ouvrirait de nombreuses perspectives: étude de la limite quantique standard, production d'états comprimés, réalisation d'une mesure quantique non destructive ldots

  7. L'effet Casimir : théorie et expériences

    NASA Astrophysics Data System (ADS)

    Lambrecht, A.; Genet, C.; Intravaia, F.; Reynaud, S.

    2004-11-01

    L'existence de fluctuations irréductibles de champ dans le vide est une prédiction importante de la théorie quantique. Ces fluctuations ont de nombreuses conséquences observables comme l'effet Casimir, qui est maintenant mesuré avec une bonne précision et un bon accord avec la théorie, pourvu que celle-ci tienne compte des différences entre les expériences rélles et la situation idéale considérée par H.G.B. Casimir. Nous présenterons quelqu'unes des expériences récentes et discuterons les principales corrections à la force de Casimir liées à la situation expérimentale.

  8. Effet Bauschinger lors de la plasticité cyclique de l'aluminium pur monocristallin

    NASA Astrophysics Data System (ADS)

    Alhamany, A.; Chicois, J.; Fougères, R.; Hamel, A.

    1992-08-01

    This paper is concerned with the study of microscopic mechanisms which control the cyclic deformation of pure aluminium and especially with the analysis of the Bauschinger effect which appears in aluminium single crystals deformed by cyclic straining. Fatigue tests are performed on Al single crystals with the crystal axis parallel to [ overline{1}23] at room temperature, at plastic shear strain amplitudes in the range from 10^{-4} to 3× 10^{-3}. Mechanical saturation is not obtained at any strain level. Instead, a hardening-softening-secondary hardening sequence is found. The magnitude of the Bauschinger effect as the difference between yield stresses in traction and in compression, changes all along the fatigue loop and during the fatigue test. The Bauschinger effect disappears at two points of the fatigue loop, one in the traction part, the other in the compression one. At these points, the Bauschinger effect is inverted. Dislocation arrangement evolutions with fatigue conditions can explain the cyclic behaviour of Al single crystals. An heterogeneous dislocation distribution can be observed in the cyclically strained metal : dislocation tangles, long dislocation walls and dislocation cell walls, separated by dislocation poor channels appear in the material as a function of the cycle number. The long range internal stress necessary to ensure the compatibility of deformation between the hard and soft regions controls the observed Bauschinger effect. Ce travail s'inscrit dans le cadre de l'étude des mécanismes microsocopiques intervenant lors de la déformation cyclique de l'aluminium pur et concerne en particulier l'analyse de l'effet Bauschinger apparaissant au cours de la solliciation cyclique des monocristaux. L'étude a été menée à température ambiante sur des monocristaux d'aluminium pur orientés pour un glissement simple (axe [ overline{1}23] ), à des amplitudes de déformation plastique comprise entre 10^{-4} et quelques 10^{-3}. Nous n'avons pas

  9. L’effet du yoga chez les patients atteints de cancer

    PubMed Central

    Côté, Andréanne; Daneault, Serge

    2012-01-01

    Résumé Objectif Déterminer si le yoga thérapeutique améliore la qualité de vie de patients atteints de cancer. Sources des données Recherche effectuée avec la base de données MEDLINE (1950–2010) en utilisant les mots-clés yoga, cancer et quality of life. Sélection des études Priorité accordée aux études cliniques randomisées contrôlées évaluant l’effet du yoga sur différents symptômes susceptibles de se présenter chez des patients atteints de cancer en Amérique du Nord. Synthèse Quatre études cliniques randomisées contrôlées ont d’abord été analysées, puis 2 études sans groupe-contrôle. Trois études réalisées en Inde et au Proche-Orient ont également apporté des éléments intéressants au plan méthodologique. Les interventions proposées comprenaient des séances de yoga d’une durée et d’une fréquence variables. Les paramètres mesurés variaient également d’une étude à l’autre. Plusieurs symptômes ont connu des améliorations significatives avec le yoga (meilleure qualité du sommeil, diminution des symptômes anxieux ou dépressifs, amélioration du bien-être spirituel, etc.). Il a aussi semblé que la qualité de vie, dans sa globalité ou dans certaines de ses composantes spécifiques, s’améliorait. Conclusion La variété des effets bénéfiques produits, l’absence d’effet secondaire et le rapport coût-bénéfice avantageux du yoga thérapeutique en fait une intervention intéressante à suggérer par les médecins de famille aux patients atteints de cancer. Certaines lacunes méthodologiques ont pu diminuer la puissance statistique des études présentées, à commencer par la taille restreinte des échantillons et par l’assiduité variable des patients soumis à l’intervention. Il est également possible que les échelles de mesure utilisées ne convenaient pas à ce type de situation et de clientèle pour qu’en soit dégagé un effet significatif. Toutefois, les commentaires

  10. Approximate inverse preconditioners for general sparse matrices

    SciTech Connect

    Chow, E.; Saad, Y.

    1994-12-31

    Preconditioned Krylov subspace methods are often very efficient in solving sparse linear matrices that arise from the discretization of elliptic partial differential equations. However, for general sparse indifinite matrices, the usual ILU preconditioners fail, often because of the fact that the resulting factors L and U give rise to unstable forward and backward sweeps. In such cases, alternative preconditioners based on approximate inverses may be attractive. We are currently developing a number of such preconditioners based on iterating on each column to get the approximate inverse. For this approach to be efficient, the iteration must be done in sparse mode, i.e., we must use sparse-matrix by sparse-vector type operatoins. We will discuss a few options and compare their performance on standard problems from the Harwell-Boeing collection.

  11. Characteristic Matrices for Spherical Shell Photonic Systems

    NASA Technical Reports Server (NTRS)

    Fuller, Kirk A.; Smith, David D.

    2004-01-01

    We establish a parallel between the transfer matrix used in the study of plane-parallel photonic structures and the matrix characterizing transfer of partial waves in concentric spheres. We derive explicit expressions for the elements of the transfer matrix for concentric spherical layers, and from those expressions derive the scattering coefficients of a multilayered sphere. The transfer matrices are 4x4 block diagonal with only four independent elements. Matrix elements for the case of TM waves are related to those for the case of TE waves through simple interchange and multiplicative constants. In analogy with plane parallel layers, the transfer matrix for concentric multilayers is simply the product of the transfer matrices of the individual layers.

  12. Evolutionary Games with Randomly Changing Payoff Matrices

    NASA Astrophysics Data System (ADS)

    Yakushkina, Tatiana; Saakian, David B.; Bratus, Alexander; Hu, Chin-Kun

    2015-06-01

    Evolutionary games are used in various fields stretching from economics to biology. In most of these games a constant payoff matrix is assumed, although some works also consider dynamic payoff matrices. In this article we assume a possibility of switching the system between two regimes with different sets of payoff matrices. Potentially such a model can qualitatively describe the development of bacterial or cancer cells with a mutator gene present. A finite population evolutionary game is studied. The model describes the simplest version of annealed disorder in the payoff matrix and is exactly solvable at the large population limit. We analyze the dynamics of the model, and derive the equations for both the maximum and the variance of the distribution using the Hamilton-Jacobi equation formalism.

  13. Some physical applications of random hierarchical matrices

    SciTech Connect

    Avetisov, V. A.; Bikulov, A. Kh.; Vasilyev, O. A.; Nechaev, S. K.; Chertovich, A. V.

    2009-09-15

    The investigation of spectral properties of random block-hierarchical matrices as applied to dynamic and structural characteristics of complex hierarchical systems with disorder is proposed for the first time. Peculiarities of dynamics on random ultrametric energy landscapes are discussed and the statistical properties of scale-free and polyscale (depending on the topological characteristics under investigation) random hierarchical networks (graphs) obtained by multiple mapping are considered.

  14. Analysis of thematic map classification error matrices.

    USGS Publications Warehouse

    Rosenfield, G.H.

    1986-01-01

    The classification error matrix expresses the counts of agreement and disagreement between the classified categories and their verification. Thematic mapping experiments compare variables such as multiple photointerpretation or scales of mapping, and produce one or more classification error matrices. This paper presents a tutorial to implement a typical problem of a remotely sensed data experiment for solution by the linear model method.-from Author

  15. Temporal disconnectivity of the energy landscape in glassy systems

    NASA Astrophysics Data System (ADS)

    Lempesis, Nikolaos; Boulougouris, Georgios C.; Theodorou, Doros N.

    2013-03-01

    An alternative graphical representation of the potential energy landscape (PEL) has been developed and applied to a binary Lennard-Jones glassy system, providing insight into the unique topology of the system's potential energy hypersurface. With the help of this representation one is able to monitor the different explored basins of the PEL, as well as how - and mainly when - subsets of basins communicate with each other via transitions in such a way that details of the prior temporal history have been erased, i.e., local equilibration between the basins in each subset has been achieved. In this way, apart from detailed information about the structure of the PEL, the system's temporal evolution on the PEL is described. In order to gather all necessary information about the identities of two or more basins that are connected with each other, we consider two different approaches. The first one is based on consideration of the time needed for two basins to mutually equilibrate their populations according to the transition rate between them, in the absence of any effect induced by the rest of the landscape. The second approach is based on an analytical solution of the master equation that explicitly takes into account the entire explored landscape. It is shown that both approaches lead to the same result concerning the topology of the PEL and dynamical evolution on it. Moreover, a "temporal disconnectivity graph" is introduced to represent a lumped system stemming from the initial one. The lumped system is obtained via a specially designed algorithm [N. Lempesis, D. G. Tsalikis, G. C. Boulougouris, and D. N. Theodorou, J. Chem. Phys. 135, 204507 (2011), 10.1063/1.3663207]. The temporal disconnectivity graph provides useful information about both the lumped and the initial systems, including the definition of "metabasins" as collections of basins that communicate with each other via transitions that are fast relative to the observation time. Finally, the two examined

  16. Evidence for the Powdered, Glassy Nature of the Mercurian Surface

    NASA Astrophysics Data System (ADS)

    Cooper, B. L.; Potter, A. E., Jr.; Killen, R. M.; Morgan, T. H.

    1998-09-01

    We have developed a technique to obtain thermal IR spectra of Mercury in the 8-13 micron region in daylight [1]. We observed a smooth spectral curve for Mercury, with the exception of minor features near 9.6 microns and 12.7 microns. There was no evidence of a Christiansen feature down to the 8-micron limit of our spectra. This is in general agreement with Mercury spectra reported by [2], who found Christiansen peaks just at, or slightly below, 8 microns. Features near 9.6 microns are due to incomplete compensation of the ozone absorption band. There appears to be a shallow dip in the spectrum around 12.7 microns. This may represent a transparency peak in emission. Features in the Mercury spectrum have been reported at this wavelength [2], but as a shallow elevation instead of a dip. Most acidic silicates have a feature at around 12.2 microns, whereas mafic minerals (such as hypersthene and olivine) show this feature at longer wavelengths--12.7 to 13.2 microns [3]. The 12.7 micron feature could be evidence for mafic material on the Mercurian surface. However, the lack of a Christiansen feature at 8.5 - 9.0 microns (typical of hypersthene or olivine) makes this doubtful. The smoothness of the spectra suggests that the spectral contrast of the reststrahlen bands from the Mercury surface is below the signal-to-noise level of our data. The spectral contrast of reststrahlen features is greatly reduced in powdered minerals under vacuum, requiring S/N ratios of the order of 1000 to be detected [4]. Glass formation further reduces spectral contrast by disordering the crystal lattice. Consequently, our results imply that the surface of Mercury is covered by a fine powder, which is probably also glassy as a result of intense meteoroid bombardment [5]. References [1] Cooper et al. (1998) EOS, 79, no. 24, W59 [abstract] [2] Sprague and Roush (1998) Icarus, 133, 174. [3] Salisbury et al. (1988) USGS Open-File Report 88-686, Reston, Virginia. [4] Salisbury et al. (1997) Icarus

  17. Effect of entanglements on mechanical properties of glassy polymers

    NASA Astrophysics Data System (ADS)

    Hoy, Robert Scott

    Glass forming polymers are of great industrial importance and scientific interest because of their unique mechanical properties, which arise from the connectivity and random-walk-like structure of the constituent chains. In this thesis I study the relation of entanglements to the mechanical properties of model polymer glasses and brushes using molecular dynamics simulations. We perform extensive studies of glassy strain hardening, which stabilizes polymers against strain localization and fracture. Fundamental inconsistencies in existing entropic models of strain hardening imply that our understanding of its microscopic origins is far from complete. The dependence of stress on strain and entanglement density is consistent with experiment and entropic models. However, many of the assumptions of these models are totally inconsistent with our simulation results. The dependence on temperature, rate and interaction strength can be understood as reflecting changes in the plastic flow stress rather than a network entropy. A substantial energetic contribution to the stress rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic arrangements. The deformation of the entanglement network is not affine to the macroscopic stretch. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain. The entropic back stress responsible for shape recovery arises from chain orientation rather than entanglement. We also present some other results unrelated to strain hardening. We analyze the entanglement of polymer brushes embedded in long-chain melts and in implicit good and theta solvents. The melt-embedded brushes are more self-entangled than those in the solvents. The degree of self-entanglement of the brushes in the solvents follows a simple

  18. Direct Imaging of Dynamic Glassy Behavior in a Strained Manganite Film.

    PubMed

    Kundhikanjana, Worasom; Sheng, Zhigao; Yang, Yongliang; Lai, Keji; Ma, Eric Yue; Cui, Yong-Tao; Kelly, Michael A; Nakamura, Masao; Kawasaki, Masashi; Tokura, Yoshinori; Tang, Qiaochu; Zhang, Kun; Li, Xinxin; Shen, Zhi-Xun

    2015-12-31

    Complex many-body interaction in perovskite manganites gives rise to a strong competition between ferromagnetic metallic and charge-ordered phases with nanoscale electronic inhomogeneity and glassy behaviors. Investigating this glassy state requires high-resolution imaging techniques with sufficient sensitivity and stability. Here, we present the results of a near-field microwave microscope imaging on the strain-driven glassy state in a manganite film. The high contrast between the two electrically distinct phases allows direct visualization of the phase separation. The low-temperature microscopic configurations differ upon cooling with different thermal histories. At sufficiently high temperatures, we observe switching between the two phases in either direction. The dynamic switching, however, stops below the glass transition temperature. Compared with the magnetization data, the phase separation was microscopically frozen, while spin relaxation was found in a short period of time. PMID:26765006

  19. Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants

    NASA Astrophysics Data System (ADS)

    Chen, Huang-Ming Philip; Tsai, Yun-Yen; Lin, Chi-Wen; Shieh, Han-Ping David

    2006-08-01

    A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 °C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 μm pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.

  20. InP synthesis by the synthesis, solute diffusion (SSD) method using glassy-carbon crucibles

    SciTech Connect

    Miskys, C.R.; Oliveira, C.E.M. de; Carvalho, M.M.G. de

    1996-12-31

    An Indium Phosphide (InP) Synthesis system by the Synthesis, Solute Diffusion (SSD) method has been built. It provides high purity InP charges with low carrier densities (3 {times} 10{sup 14} to 2 {times} 10{sup 15} cm{sup {minus}3}) to be used as starting material for InP single-crystal Liquid Encapsulated Czochralski (LEC) growth. Glassy-carbon is a refractory material with low vapor pressure that can be moulded in various forms and sizes. Indeed the glassy-carbon crucible is reusable after the synthesis because InP does not stick to its walls. Preliminary electrical characteristics measurements showed residual carrier concentration below 3 {times} 10{sup 15} cm{sup {minus}3}. These results are comparable with those achieved utilizing quartz crucibles. The features denoted makes glassy-carbon an interesting alternative in comparison with quartz and PBN crucibles.

  1. Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials

    NASA Astrophysics Data System (ADS)

    Kojima, Seiji; Shibata, Tomohiko; Igawa, Hikaru; Mori, Tatsuya

    2014-03-01

    Low-energy IR active modes of glassy and crystalline drug materials were studied by the broadband Terahertz Time Domain Spectroscopy (THz-TDS) in the frequency range from 0.5 to 6.5 THz using a Cherenkov type THz generator. In order to determine the real and imaginary parts of complex dielectric constant, all samples were measured by the transmission using a pure pellet without mixing polyethylene. For glassy indomethacine, the broadband THz spectrum of real part of dielectric constant shows step-wise decrease with the increase of frequency, while the imaginary part shows a broad peak at about 3 THz reflecting quenched glassy disordered structure. The observed spectra of crystalline racemic ketoprofen show the noncoincidence of peak frequencies between low-frequency Raman scattering and THz absorbance spectra. It can be attributed to the fact that the mutual exclusion principle between Raman and IR activities holds below 6 THz.

  2. Glassiness and exotic entropy scaling induced by quantum fluctuations in a disorder-free frustrated magnet

    PubMed Central

    Klich, I.; Lee, S.-H.; Iida, K.

    2014-01-01

    When spins are arranged in a lattice of triangular motif, the phenomenon of frustration leads to numerous energetically equivalent ground states, and results in exotic states such as spin liquid and spin ice. Here we report an alternative situation: a system, classically a liquid, freezes in the clean limit into a glassy state induced by quantum fluctuations. We call such glassy state a spin jam. The case in point is a frustrated magnet, where spins are arranged in a triangular network of bipyramids. Quantum corrections break the classical degeneracy into a set of aperiodic spin configurations forming local minima in a rugged energy landscape. This is established by mapping the problem into tiling with hexagonal tiles. The number of tessellations scales with the boundary length rather than its volume, showing the absence of local zero-energy modes. Low-temperature thermodynamics is discussed to compare it with other glassy materials. PMID:24686398

  3. A magnetic glassy phase in Fe(1+y)Se(x)Te(1-x) single crystals.

    PubMed

    Lamura, G; Shiroka, T; Bonfà, P; Sanna, S; Bernardini, F; De Renzi, R; Viennois, R; Giannini, E; Piriou, A; Emery, N; Cimberle, M R; Putti, M

    2013-04-17

    The evolution of magnetic order in Fe1+ySexTe1-x crystals as a function of Se content was investigated by means of ac/dc magnetometry and muon-spin spectroscopy. Experimental results and self-consistent density functional theory calculations both indicate that muons are implanted in vacant iron-excess sites, where they probe a local field mainly of dipolar origin, resulting from an antiferromagnetic (AFM) bicollinear arrangement of iron spins. This long-range AFM phase becomes progressively disordered with increasing Se content. At the same time all the tested samples manifest a marked glassy character that vanishes for high Se contents. The presence of local electronic/compositional inhomogeneities most likely favours the growth of clusters whose magnetic moment 'freezes' at low temperature. This glassy magnetic phase justifies both the coherent muon precession seen at short times in the asymmetry data, as well as the glassy behaviour evidenced by both dc and ac magnetometry.

  4. Direct Imaging of Dynamic Glassy Behavior in a Strained Manganite Film

    NASA Astrophysics Data System (ADS)

    Kundhikanjana, Worasom; Sheng, Zhigao; Yang, Yongliang; Lai, Keji; Ma, Eric Yue; Cui, Yong-Tao; Kelly, Michael A.; Nakamura, Masao; Kawasaki, Masashi; Tokura, Yoshinori; Tang, Qiaochu; Zhang, Kun; Li, Xinxin; Shen, Zhi-Xun

    2015-12-01

    Complex many-body interaction in perovskite manganites gives rise to a strong competition between ferromagnetic metallic and charge-ordered phases with nanoscale electronic inhomogeneity and glassy behaviors. Investigating this glassy state requires high-resolution imaging techniques with sufficient sensitivity and stability. Here, we present the results of a near-field microwave microscope imaging on the strain-driven glassy state in a manganite film. The high contrast between the two electrically distinct phases allows direct visualization of the phase separation. The low-temperature microscopic configurations differ upon cooling with different thermal histories. At sufficiently high temperatures, we observe switching between the two phases in either direction. The dynamic switching, however, stops below the glass transition temperature. Compared with the magnetization data, the phase separation was microscopically frozen, while spin relaxation was found in a short period of time.

  5. Deterministic matrices matching the compressed sensing phase transitions of Gaussian random matrices

    PubMed Central

    Monajemi, Hatef; Jafarpour, Sina; Gavish, Matan; Donoho, David L.; Ambikasaran, Sivaram; Bacallado, Sergio; Bharadia, Dinesh; Chen, Yuxin; Choi, Young; Chowdhury, Mainak; Chowdhury, Soham; Damle, Anil; Fithian, Will; Goetz, Georges; Grosenick, Logan; Gross, Sam; Hills, Gage; Hornstein, Michael; Lakkam, Milinda; Lee, Jason; Li, Jian; Liu, Linxi; Sing-Long, Carlos; Marx, Mike; Mittal, Akshay; Monajemi, Hatef; No, Albert; Omrani, Reza; Pekelis, Leonid; Qin, Junjie; Raines, Kevin; Ryu, Ernest; Saxe, Andrew; Shi, Dai; Siilats, Keith; Strauss, David; Tang, Gary; Wang, Chaojun; Zhou, Zoey; Zhu, Zhen

    2013-01-01

    In compressed sensing, one takes samples of an N-dimensional vector using an matrix A, obtaining undersampled measurements . For random matrices with independent standard Gaussian entries, it is known that, when is k-sparse, there is a precisely determined phase transition: for a certain region in the (,)-phase diagram, convex optimization typically finds the sparsest solution, whereas outside that region, it typically fails. It has been shown empirically that the same property—with the same phase transition location—holds for a wide range of non-Gaussian random matrix ensembles. We report extensive experiments showing that the Gaussian phase transition also describes numerous deterministic matrices, including Spikes and Sines, Spikes and Noiselets, Paley Frames, Delsarte-Goethals Frames, Chirp Sensing Matrices, and Grassmannian Frames. Namely, for each of these deterministic matrices in turn, for a typical k-sparse object, we observe that convex optimization is successful over a region of the phase diagram that coincides with the region known for Gaussian random matrices. Our experiments considered coefficients constrained to for four different sets , and the results establish our finding for each of the four associated phase transitions. PMID:23277588

  6. Deterministic sensing matrices in compressive sensing: a survey.

    PubMed

    Nguyen, Thu L N; Shin, Yoan

    2013-01-01

    Compressive sensing is a sampling method which provides a new approach to efficient signal compression and recovery by exploiting the fact that a sparse signal can be suitably reconstructed from very few measurements. One of the most concerns in compressive sensing is the construction of the sensing matrices. While random sensing matrices have been widely studied, only a few deterministic sensing matrices have been considered. These matrices are highly desirable on structure which allows fast implementation with reduced storage requirements. In this paper, a survey of deterministic sensing matrices for compressive sensing is presented. We introduce a basic problem in compressive sensing and some disadvantage of the random sensing matrices. Some recent results on construction of the deterministic sensing matrices are discussed.

  7. Random Coulomb antiferromagnets: From diluted spin liquids to Euclidean random matrices

    NASA Astrophysics Data System (ADS)

    Rehn, J.; Sen, Arnab; Andreanov, A.; Damle, Kedar; Moessner, R.; Scardicchio, A.

    2015-08-01

    We study a disordered classical Heisenberg magnet with uniformly antiferromagnetic interactions which are frustrated on account of their long-range Coulomb form, i.e., J (r )˜-A lnr in d =2 and J (r )˜A /r in d =3 . This arises naturally as the T →0 limit of the emergent interactions between vacancy-induced degrees of freedom in a class of diluted Coulomb spin liquids (including the classical Heisenberg antiferromagnets in checkerboard, SCGO, and pyrochlore lattices) and presents a novel variant of a disordered long-range spin Hamiltonian. Using detailed analytical and numerical studies we establish that this model exhibits a very broad paramagnetic regime that extends to very large values of A in both d =2 and d =3 . In d =2 , using the lattice-Green-function-based finite-size regularization of the Coulomb potential (which corresponds naturally to the underlying low-temperature limit of the emergent interactions between orphans), we find evidence that freezing into a glassy state occurs only in the limit of strong coupling, A =∞ , while no such transition seems to exist in d =3 . We also demonstrate the presence and importance of screening for such a magnet. We analyze the spectrum of the Euclidean random matrices describing a Gaussian version of this problem and identify a corresponding quantum mechanical scattering problem.

  8. Self-Induced Glassiness and Pattern Formation in Spin Systems Subject to Long-Range Interactions

    NASA Astrophysics Data System (ADS)

    Principi, Alessandro; Katsnelson, Mikhail I.

    2016-09-01

    We study the glass formation in two- and three-dimensional Ising and Heisenberg spin systems subject to competing interactions and uniaxial anisotropy with a mean-field approach. In three dimensions, for sufficiently strong anisotropy the systems always modulate in a striped phase. Below a critical strength of the anisotropy, a glassy phase exists in a finite range of temperature, and it becomes more stable as the system becomes more isotropic. In two dimensions the criticality is always avoided and the glassy phase always exists.

  9. Electrochemical assembling of methionine-gold nanoparticles and catalysis on the surface of glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Song, Y. Z.; Wang, J. H.; Zhang, X. M.; Cao, W.; Ge, A.; Zhou, L.

    2014-12-01

    In this paper cyclic voltammetry was used for the synthesis of linear array spherical gold nanoparticles on the surface of glassy carbon electrode using methionine as a stable reagent. The methionine-gold nanoparticles on the surface of glassy electrode were obtained. The methionine-gold nanoparticles were characterized by cyclic voltammetry, scanning electron microscopy, energy dispersive spectrometry and powder X-ray diffraction. Electrochemical behavior of methionine at methionine-gold nanoparticle modified electrode was investigated. It was demonstrated that the methionine-gold nanoparticles can catalyze electrochemical transformations of methionine.

  10. A Thermodynamic Theory of Solid Viscoelasticity. Part 3: Nonlinear Glassy Viscoelasticity, Stability Constraints, Specifications

    NASA Technical Reports Server (NTRS)

    Freed, Alan; Leonov, Arkady I.

    2002-01-01

    This paper, the last in the series, continues developing the nonlinear constitutive relations for non-isothermal, compressible, solid viscoelasticity. We initially discuss a single integral approach, more suitable for the glassy state of rubber-like materials, with basic functionals involved in the thermodynamic description for this type of viscoelasticity. Then we switch our attention to analyzing stability constraints, imposed on the general formulation of the nonlinear theory of solid viscoelasticity. Finally, we discuss specific (known from the literature or new) expressions for material functions that are involved in the constitutive formulations of both the rubber-like and glassy-like, complementary parts of the theory.

  11. Elastic properties of aspirin in its crystalline and glassy phases studied by micro-Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Ko, Jae-Hyeon; Lee, Kwang-Sei; Ike, Yuji; Kojima, Seiji

    2008-11-01

    The acoustic waves propagating along the direction perpendicular to the (1 0 0) cleavage plane of aspirin crystal were investigated using micro-Brillouin spectroscopy from which C11, C55 and C66 were obtained. The temperature dependence of the longitudinal acoustic waves could be explained by normal anharmonic lattice models, while the transverse acoustic waves showed an abnormal increase in the hypersonic attenuation at low temperatures indicating their coupling to local remnant dynamics. The sound velocity as well as the attenuation of the longitudinal acoustic waves of glassy aspirin showed a substantial change at ˜235 K confirming a transition from glassy to supercooled liquid state in vitreous aspirin.

  12. Fabrication of Glassy and Crystalline Ferroelectric Oxide by Containerless Processing

    NASA Astrophysics Data System (ADS)

    Yoda, Shinichi

    1. Instruction Much effort has been devoted to forming bulk glass from the melt of ferroelectric crystalline materials without adding any network-forming oxides such as SiO2 due to the potential for producing transparent glass ceramics with high dielectric constant and enhanced piezoelectric, pyroelectric and electro-optic effects. However, they require a higher cooling rate than glass formed by conventional techniques. Therefore, only amorphous thin-films have been formed, using rapid quenching with a cooling rate >105 K/s. The containerless processing is an attractive synthesis technique as it can prevent melt contamination, minimize heterogeneous nucleation, and allow melt to achieve deep undercooling for forming metastable phase and glassy material. Recently a new ferroelectric materiel, monoclinic BaTi2 O5 , with Currie temperature as 747 K was reported. In this study, we fabricated a bulk BaTi2 O5 glass from melt using containerless processing to study the phase relations and ferroelectric properties of BaTi2 O5 . To our knowledge, this was the first time that a bulk glass of ferroelectric material was fabricated from melt without adding any network-forming oxide. 2. Experiments BaTi2 O5 sphere glass with 2mm diameter was fabricated using containerless processing in an Aerodynamic Levitation Furnace (ALF). The containerless processing allowed the melt to achieve deep undercooling for glass forming. High purity commercial BaTiO3 and TiO2 powders were mixed with a mole ratio of 1:1 and compressed into rods and then sintered at 1427 K for 10 h. Bulk samples with a mass of about 20 mg were cut from the rod, levitated with the ALF, and then melted by a CO2 laser beam. After quenching with a cooling rate of about 1000 K/s, 2 mm diameter sphere glass could be obtained. To analyze the glass structure, a high-energy x-ray diffraction experiment was performed using an incident photon energy of 113.5 keV at the high-energy x-ray diffraction beamline BL04B2 of SPring-8

  13. Effets Seebeck et Nernst dans les cuprates: Etude de la reconstruction de la surface de Fermi sous champ magnetique intense

    NASA Astrophysics Data System (ADS)

    Laliberte, Francis

    2010-06-01

    Ce memoire presente des mesures de transport thermoelectrique, les effets Seebeck et Nernst, dans une serie d'echantillons de supraconducteurs a haute temperature critique. Des resultats obtenus recemment au Laboratoire National des Champs Magnetiques Intenses a Grenoble sur La1.7Eu0.2Sr0.1 CuO4, La1.675Eu0.2Sr0.125CuO 4, La1.64Eu0.2Sr0.16CuO4, La1.74Eu0.1Sr0.16CuO4 et La 1.4Nd0.4Sr0.2CuO4 sont analyses. Une attention particuliere est accordee aux equations de la theorie semi-classique du transport et leur validite est verifiee. La procedure experimentale et les materiaux utilises pour concevoir les montages de mesures sont expliques en detail. Enfin, un chapitre est dedie a l'explication et l'interpretation des resultats de transport thermoelectrique sur YBa2Cu3O6+delta publies au cours de l'hiver 2010 dans les revues Nature et Physical Review Letters. Les donnees d'effet Seebeck dans les echantillons de La 1.8-x,Eu0.2SrxCuO 4, ou un changement de signe est observe, permettent de conclure a la presence d'une poche d'electrons dans la surface de Fermi qui domine le transport a basse temperature dans la region sous-dopee du diagramme de phase. Cette conclusion est similaire a celle obtenue par des mesures d'effet Hall dans YBa 2Cu3O6+delta et elle cadre bien dans un scenario de reconstruction de la surface de Fermi. Les donnees d'effet Nernst recueillies indiquent que la contribution des fluctuations supraconductrices est limitee a un modeste intervalle de temperature au-dessus de la temperature critique.

  14. Decontamination of matrices containing actinide oxides

    SciTech Connect

    Villarreal, Robert

    1997-12-01

    There is provided a method for removing actinides and actinide oxides, particularly fired actinides, from soil and other contaminated matrices, comprising: (a) contacting a contaminated material with a solution of at least one inhibited fluoride and an acid to form a mixture; (b) heating the mixture of contaminated material and solution to a temperature in the range from about 30 C to about 90 C while stirring; (c) separating the solution from any undissolved matrix material in the mixture; (d) washing the undissolved matrix material to remove any residual materials; and (e) drying and returning the treated matrix material to the environment.

  15. Generalized Jones matrices for anisotropic media.

    PubMed

    Ortega-Quijano, Noé; Arce-Diego, José Luis

    2013-03-25

    The interaction of arbitrary three-dimensional light beams with optical elements is described by the generalized Jones calculus, which has been formally proposed recently [Azzam, J. Opt. Soc. Am. A 28, 2279 (2011)]. In this work we obtain the parametric expression of the 3×3 differential generalized Jones matrix (dGJM) for arbitrary optical media assuming transverse light waves. The dGJM is intimately connected to the Gell-Mann matrices, and we show that it provides a versatile method for obtaining the macroscopic GJM of media with either sequential or simultaneous anisotropic effects. Explicit parametric expressions of the GJM for some relevant optical elements are provided.

  16. Parallel mergs sort using comparison matrices. I

    SciTech Connect

    Romm, Y.E.

    1995-05-01

    The topics discussed in this paper are connected with internal merge sorting by a key (in short, M-sorting or M-sort). Originally developed by von Neumann, this is one of the first sorting methods. It still remains one of the fastest, involving Nlog{sub 2}N comparisons. The purpose of our article is to demonstrate the use of comparison matrices (CMs) for merging in M-sort. While preserving the known advantages of the sequential implementation of M-sort. CMs ensure more efficient use of main memory (one of the known weaknesses of M-sort is its large memory requirements) and effective parallelizability.

  17. Glassy-winged sharpshooter can use a mechanical mechanism to inoculate Xylella fastidiosa into grapevines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Xylem-feeding leafhoppers such as the glassy-winged sharpshooter, Homalodisca vitripennis (Cicadellidae: Cicadellinae), are thought to inoculate the bacterium Xylella fastidiosa (Xf) from colonies bound to cuticle of the sharpshooter’s functional foregut (precibarium and cibarium). The mechanism of ...

  18. Glassy-winged sharpshooter oviposition effects on foliar grapevine and red-tipped photinia terpenoid levels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is an important vector of Xylella fastidiosa, the bacterium that causes Pierce's disease of grapevine and is a threat to grape production throughout the United States. Female GWSS deposit egg masses be...

  19. Substrate-borne vibrational signals in intraspecific communication of glassy-winged sharpshooters (GWSS)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Exploitation of vibrational signals for suppressing glassy-winged sharpshooter (GWSS) populations could prove to be a useful tool. However, existing knowledge on GWSS vibrational communication is insufficient to implement a management program for this pest in California. Therefore, the objective of ...

  20. Effects of feeding on glassy-winged sharpshooter lipid content and egg production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Glassy-winged sharpshooter females emerge without mature eggs, and females must feed to produce mature eggs. As a result, allocation of incoming resources must be balanced between egg production and maintenance of other critical biological functions. Central to this process is allocation of lipids s...

  1. Glassy-winged sharpshooter oviposition effects on photinia volatile chemistry with implications on egg parasitoid effectiveness

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An effective way to limit incidence of Pierce’s disease of grapevine is to reduce populations of glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), which transmit the causal bacterium, Xylella fastidiosa. One strategy is to utilize egg parasitoids such as ...

  2. Columbia River Basalt Chemistry, Degassing, and Eruption Dynamics: Insights From Quenched Glassy Lapilli and Tuffs

    NASA Astrophysics Data System (ADS)

    Davis, K.; Wolff, J.; Rowe, M. C.; Neill, O. K.

    2015-12-01

    Primary eruptive vent areas for several lavas in the Imnaha and Grande Ronde Formations of the Columbia River Basalt exhibit phreatomagmatic character, due to the interaction of rising flood basalt magma with groundwater and/or surface water. Vent constructional forms range from extensive (>1 km) maar complexes with abundant basement lithics to small (<<1 km), lithic-poor low-angle cones. Phreatomagmatic tephra is lithified and variably palagonitized, but glassy basaltic lapilli can be recovered from many locations. Many lapilli have experienced variable degrees of Na leaching but preserve magmatic abundances of most other elements; nonetheless in many cases pristine, unmodified glass is amenable to analysis. In addition, phenocrysts in lapilli have fully glassy melt inclusions. Glassy lapilli have highly variable S contents between ~100 and ~1300 ppm. This is consistent with quenching before degassing was complete, a common feature of phreatomagmatic eruptions. Melt inclusions have ≤2900 ppm S, ≤3400 ppm CO2 and ≤2.6 wt% H2O, allowing estimates of atmospheric input from the main phase of Columbia River volcanism. In addition, the lithophile trace element contents, and petrogenetically significant ratios such as Ba/Nb, of glassy lapilli exhibit differ from those in the equivalent 'stony' lava flows by up to a factor of 2. This suggests that processes in the flow and crystallization of lava serve to modify trace element abundances, and may place limits on the petrogenetic significance of trace element data from crystalline lava samples.

  3. Brittle metallic glass deforms plastically at room temperature in glassy multilayers

    NASA Astrophysics Data System (ADS)

    Sharma, Parmanand; Yubuta, Kunio; Kimura, Hisamichi; Inoue, Akihisa

    2009-07-01

    Bulk metallic glasses are emerging as a new class of materials that can have applications ranging from structural materials to materials for future nanotechnology. However, catastrophic mechanical failure is a serious issue hindering the use of these materials in engineering applications. Here we introduce an approach to understanding and solving the problem of brittleness of metallic glasses. We have shown that even a very brittle metallic glass (La based) can be forced to deform plastically at room temperature if it is made in the form of multilayers involving other metallic glasses, i.e., a two-phase glass. The mechanically soft glassy layer (La based) having a lower critical shear stress acts as a nucleation or an initiation site for shear bands and the mechanically hard glassy layer (Zr based) acts as an obstacle to the propagation of shear bands. This process results in the multiplication of shear bands. Since the shear bands are associated with a local rise in temperature, a large number of shear bands can raise the overall temperature of the soft layer and eventually can drive it to the supercooled liquid state, where deformation of metallic glass is very large and homogeneous. The results reported here not only clarify the mechanism of large plastic deformation in two-phase glassy alloys but also suggest the possibility of a different kind of two-phase bulk glassy alloys exhibiting large plastic deformation at room temperature.

  4. THE ROLE OF GLASSY-WINGED SHARPSHOOTER SALIVARY ENZYMES IN INFECTION AND MOVEMENT OF X. FASTIDIOSA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The purpose of this project is to determine whether a vector’s enzymatic saliva aids the establishment of the few ‘pioneer’ Xylella fastidiosa (Xf) cells that are inoculated into a plant; thus the bacteria would co-localize with the saliva. Previous work showed that watery saliva of glassy-winged ...

  5. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-04-01

    The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA), levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition) before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosols that have re-vitrified in contact with the

  6. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-09-01

    The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA), levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition) before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosol particles that have re-vitrified in contact

  7. Effets de la pollution de l’air sur la santé

    PubMed Central

    Abelsohn, Alan; Stieb, Dave M.

    2011-01-01

    Résumé Objectif Faire connaître aux médecins de famille les effets de la pollution atmosphérique sur la santé et indiquer quels conseils donner aux patients vulnérables pour qu’ils soient moins exposés. Sources de l’information On a consulté MEDLINE à l’aide des termes relatifs à la pollution atmosphérique et à ses effets indésirables. On a révisé les articles en anglais publiés entre janvier 2008 et décembre 2009. La plupart des études contenaient des preuves de niveau II. Principal message Au Canada, la pollution de l’air extérieur cause une morbidité et une mortalité importantes. Elle peut affecter le système respiratoire (exacerbation de l’asthme et de la maladie pulmonaire obstructive chronique) et le système cardiovasculaire (déclencher l’arythmie, l’insuffisance cardiaque et les AVC). La cote air santé (CAS) est un nouvel outil de communication mis au point par Santé Canada et Environnement Canada qui indique sur une échelle de 1 à 10, le risque pour la santé causé par la pollution atmosphérique. La CAS est largement diffusée dans les médias et cet outil pourrait être utile au médecin de famille pour inciter les patients à haut risque (comme ceux qui souffrent d’asthme, de maladie pulmonaire obstructive chronique ou d’insuffisance cardiaque) à réduire leur exposition à la pollution atmosphérique. Conclusion Le médecin de famille peut se servir de la CAS et de ses messages sur la santé pour enseigner aux asthmatiques et aux autres patients à risque élevé la façon de réduire les risques pour la santé causés par la pollution atmosphérique.

  8. Effet getter dans des plaquettes de silicium multicristallin par diffusion de phosphore

    NASA Astrophysics Data System (ADS)

    Perichaud, I.; Martinuzzi, S.

    1992-03-01

    The external gettering effect by phosphorus diffusion is used to improve the electrical properties of multicrystalline silicon wafers. After diffusion at 900 °C for 4 h it was found that the effective diffusion lengths L_n of minority carriers achieve or overpass the thickness of the wafers. After diffusion at 850 °C for 4 h the improvements are less marked and hydrogenation is needed to obtain the same increase of L_n. SIMS analysis indicates that the gettered impurities are essentially iron, copper and nickel. Some restricted regions of the wafers are only poorly improved. It was found after chemical etching that these regions contain a high density of subgrain boundaries. The mechanism of the gettering effect used in this work is proposed, taking in account dissolved impurities in the grains and impurities segregated by dislocations. The additivity of the hydrogenation effect might be understood by the neutralisation of the recombination centers related to oxygen atoms segregated by the dislocations. L'effet getter externe par diffusion de phosphore est utilisé pour améliorer les propriétés électriques de plaquettes de silicium multicristallin. Après 4h à 900°C les longueurs de diffusion des porteurs minoritaires atteignent ou dépassent l'épaisseur des plaquettes. Après 4h à 850°C, les augmentations sont moins spectaculaires et une hydrogénation du matériau est nécessaire pour obtenir un résultat comparable au précédent. Les analyses SIMS indiquent que les impuretés extraites sont surtout du fer, du cuivre et du nickel. Certaines régions du matériau, d'extension limitée, sont toutefois peu améliorées. Elles sont caractérisées par la présence d'un réseau très dense de sous-joints. Une interprétation du mécanisme de l'effet getter observé est proposée faisant intervenir les impuretés métalliques dissoutes et celles ségrégées par les dislocations. L'additivité de l'action de l'hydrogène s'expliquerait par la neutralisation

  9. The Approximation of Two-Mode Proximity Matrices by Sums of Order-Constrained Matrices.

    ERIC Educational Resources Information Center

    Hubert, Lawrence; Arabie, Phipps

    1995-01-01

    A least-squares strategy is proposed for representing a two-mode proximity matrix as an approximate sum of a small number of matrices that satisfy certain simple order constraints on their entries. The primary class of constraints considered defines Q-forms for particular conditions in a two-mode matrix. (SLD)

  10. Frequency filtering decompositions for unsymmetric matrices and matrices with strongly varying coefficients

    SciTech Connect

    Wagner, C.

    1996-12-31

    In 1992, Wittum introduced the frequency filtering decompositions (FFD), which yield a fast method for the iterative solution of large systems of linear equations. Based on this method, the tangential frequency filtering decompositions (TFFD) have been developed. The TFFD allow the robust and efficient treatment of matrices with strongly varying coefficients. The existence and the convergence of the TFFD can be shown for symmetric and positive definite matrices. For a large class of matrices, it is possible to prove that the convergence rate of the TFFD and of the FFD is independent of the number of unknowns. For both methods, schemes for the construction of frequency filtering decompositions for unsymmetric matrices have been developed. Since, in contrast to Wittums`s FFD, the TFFD needs only one test vector, an adaptive test vector can be used. The TFFD with respect to the adaptive test vector can be combined with other iterative methods, e.g. multi-grid methods, in order to improve the robustness of these methods. The frequency filtering decompositions have been successfully applied to the problem of the decontamination of a heterogeneous porous medium by flushing.

  11. Median Approximations for Genomes Modeled as Matrices.

    PubMed

    Zanetti, Joao Paulo Pereira; Biller, Priscila; Meidanis, Joao

    2016-04-01

    The genome median problem is an important problem in phylogenetic reconstruction under rearrangement models. It can be stated as follows: Given three genomes, find a fourth that minimizes the sum of the pairwise rearrangement distances between it and the three input genomes. In this paper, we model genomes as matrices and study the matrix median problem using the rank distance. It is known that, for any metric distance, at least one of the corners is a [Formula: see text]-approximation of the median. Our results allow us to compute up to three additional matrix median candidates, all of them with approximation ratios at least as good as the best corner, when the input matrices come from genomes. We also show a class of instances where our candidates are optimal. From the application point of view, it is usually more interesting to locate medians farther from the corners, and therefore, these new candidates are potentially more useful. In addition to the approximation algorithm, we suggest a heuristic to get a genome from an arbitrary square matrix. This is useful to translate the results of our median approximation algorithm back to genomes, and it has good results in our tests. To assess the relevance of our approach in the biological context, we ran simulated evolution tests and compared our solutions to those of an exact DCJ median solver. The results show that our method is capable of producing very good candidates. PMID:27072561

  12. Hydrodynamical spectral evolution for random matrices

    NASA Astrophysics Data System (ADS)

    Forrester, Peter J.; Grela, Jacek

    2016-02-01

    The eigenvalues of the matrix structure X+{X}(0), where X is a random Gaussian Hermitian matrix and {X}(0) is non-random or random independent of X, are closely related to Dyson Brownian motion. Previous works have shown how an infinite hierarchy of equations satisfied by the dynamical correlations become triangular in the infinite density limit, and give rise to the complex Burgers equation for the Green’s function of the corresponding one-point density function. We show how this and analogous partial differential equations, for chiral, circular and Jacobi versions of Dyson Brownian motion follow from a macroscopic hydrodynamical description involving the current density and continuity equation. The method of characteristics gives a systematic approach to solving the PDEs, and in the chiral case we show how this efficiently reclaims the characterization of the global eigenvalue density for non-central Wishart matrices due to Dozier and Silverstein. Collective variables provide another approach to deriving the complex Burgers equation in the Gaussian case, and we show that this approach applies equally as well to chiral matrices. We relate both the Gaussian and chiral cases to the asymptotics of matrix integrals.

  13. Generalized Eigenvalues for pairs on heritian matrices

    NASA Technical Reports Server (NTRS)

    Rublein, George

    1988-01-01

    A study was made of certain special cases of a generalized eigenvalue problem. Let A and B be nxn matrics. One may construct a certain polynomial, P(A,B, lambda) which specializes to the characteristic polynomial of B when A equals I. In particular, when B is hermitian, that characteristic polynomial, P(I,B, lambda) has real roots, and one can ask: are the roots of P(A,B, lambda) real when B is hermitian. We consider the case where A is positive definite and show that when N equals 3, the roots are indeed real. The basic tools needed in the proof are Shur's theorem on majorization for eigenvalues of hermitian matrices and the interlacing theorem for the eigenvalues of a positive definite hermitian matrix and one of its principal (n-1)x(n-1) minors. The method of proof first reduces the general problem to one where the diagonal of B has a certain structure: either diag (B) = diag (1,1,1) or diag (1,1,-1), or else the 2 x 2 principal minors of B are all 1. According as B has one of these three structures, we use an appropriate method to replace A by a positive diagonal matrix. Since it can be easily verified that P(D,B, lambda) has real roots, the result follows. For other configurations of B, a scaling and a continuity argument are used to prove the result in general.

  14. Fabrication of reconfigurable protein matrices by cracking

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoyue; Mills, Kristen L.; Peters, Portia R.; Bahng, Joong Hwan; Liu, Elizabeth Ho; Shim, Jeongsup; Naruse, Keiji; Csete, Marie E.; Thouless, M. D.; Takayama, Shuichi

    2005-05-01

    The interface between extracellular matrices and cells is a dynamic environment that is crucial for regulating important cellular processes such as signal transduction, growth, differentiation, motility and apoptosis. In vitro cellular studies and the development of new biomaterials would benefit from matrices that allow reversible modulation of the cell adhesive signals at a scale that is commensurate with individual adhesion complexes. Here, we describe the fabrication of substrates containing arrays of cracks in which cell-adhesive proteins are selectively adsorbed. The widths of the cracks (120-3,200 nm) are similar in size to individual adhesion complexes (typically 500-3,000 nm) and can be modulated by adjusting the mechanical strain applied to the substrate. Morphology of cells can be reversibly manipulated multiple times through in situ adjustment of crack widths and hence the amount of the cell-adhesive proteins accessible to the cell. These substrates provide a new tool for assessing cellular responses associated with exposure to matrix proteins.

  15. Bromination of selected pharmaceuticals in water matrices.

    PubMed

    Benitez, F Javier; Acero, Juan L; Real, Francisco J; Roldan, Gloria; Casas, Francisco

    2011-11-01

    The bromination of five selected pharmaceuticals (metoprolol, naproxen, amoxicillin, phenacetin, and hydrochlorothiazide) was studied with these compounds individually dissolved in ultra-pure water. The apparent rate constants for the bromination reaction were determined as a function of the pH, obtaining the sequence amoxicillin>naproxen>hydrochlorothiazide≈phenacetin≈metoprolol. A kinetic mechanism specifying the dissociation reactions and the species formed for each compound according to its pK(a) value and the pH allowed the intrinsic rate constants to be determined for each elementary reaction. There was fairly good agreement between the experimental and calculated values of the apparent rate constants, confirming the goodness of the proposed reaction mechanism. In a second stage, the bromination of the selected pharmaceuticals simultaneously dissolved in three water matrices (a groundwater, a surface water from a public reservoir, and a secondary effluent from a WWTP) was investigated. The pharmaceutical elimination trend agreed with the previously determined rate constants. The influence of the main operating conditions (pH, initial bromine dose, and characteristics of the water matrix) on the degradation of the pharmaceuticals was established. An elimination concentration profile for each pharmaceutical in the water matrices was proposed based on the use of the previously evaluated apparent rate constants, and the theoretical results agreed satisfactorily with experiment. Finally, chlorination experiments performed in the presence of bromide showed that low bromide concentrations slightly accelerate the oxidation of the selected pharmaceuticals during chlorine disinfection.

  16. Median Approximations for Genomes Modeled as Matrices.

    PubMed

    Zanetti, Joao Paulo Pereira; Biller, Priscila; Meidanis, Joao

    2016-04-01

    The genome median problem is an important problem in phylogenetic reconstruction under rearrangement models. It can be stated as follows: Given three genomes, find a fourth that minimizes the sum of the pairwise rearrangement distances between it and the three input genomes. In this paper, we model genomes as matrices and study the matrix median problem using the rank distance. It is known that, for any metric distance, at least one of the corners is a [Formula: see text]-approximation of the median. Our results allow us to compute up to three additional matrix median candidates, all of them with approximation ratios at least as good as the best corner, when the input matrices come from genomes. We also show a class of instances where our candidates are optimal. From the application point of view, it is usually more interesting to locate medians farther from the corners, and therefore, these new candidates are potentially more useful. In addition to the approximation algorithm, we suggest a heuristic to get a genome from an arbitrary square matrix. This is useful to translate the results of our median approximation algorithm back to genomes, and it has good results in our tests. To assess the relevance of our approach in the biological context, we ran simulated evolution tests and compared our solutions to those of an exact DCJ median solver. The results show that our method is capable of producing very good candidates.

  17. Tensor Dictionary Learning for Positive Definite Matrices.

    PubMed

    Sivalingam, Ravishankar; Boley, Daniel; Morellas, Vassilios; Papanikolopoulos, Nikolaos

    2015-11-01

    Sparse models have proven to be extremely successful in image processing and computer vision. However, a majority of the effort has been focused on sparse representation of vectors and low-rank models for general matrices. The success of sparse modeling, along with popularity of region covariances, has inspired the development of sparse coding approaches for these positive definite descriptors. While in earlier work, the dictionary was formed from all, or a random subset of, the training signals, it is clearly advantageous to learn a concise dictionary from the entire training set. In this paper, we propose a novel approach for dictionary learning over positive definite matrices. The dictionary is learned by alternating minimization between sparse coding and dictionary update stages, and different atom update methods are described. A discriminative version of the dictionary learning approach is also proposed, which simultaneously learns dictionaries for different classes in classification or clustering. Experimental results demonstrate the advantage of learning dictionaries from data both from reconstruction and classification viewpoints. Finally, a software library is presented comprising C++ binaries for all the positive definite sparse coding and dictionary learning approaches presented here.

  18. Glassy slags for minimum additive waste stabilization. Interim progress report, May 1993--February 1994

    SciTech Connect

    Feng, X.; Wronkiewicz, D.J.; Bates, J.K.; Brown, N.R.; Buck, E.C.; Dietz, N.L.; Gong, M.; Emery, J.W.

    1994-05-01

    Glassy slag waste forms are being developed to complement glass waste forms in implementing Minimum Additive Waste Stabilization (MAWS) for supporting DOE`s environmental restoration efforts. The glassy slag waste form is composed of various crystalline and metal oxide phases embedded in a silicate glass phase. The MAWS approach was adopted by blending multiple waste streams to achieve up to 100% waste loadings. The crystalline phases, such as spinels, are very durable and contain hazardous and radioactive elements in their lattice structures. These crystalline phases may account for up to 80% of the total volume of slags having over 80% metal loading. The structural bond strength model was used to quantify the correlation between glassy slag composition and chemical durability so that optimized slag compositions were obtained with limited crucible melting and testing. Slag compositions developed through crucible melts were also successfully generated in a pilot-scale Retech plasma centrifugal furnace at Ukiah, California. Utilization of glassy slag waste forms allows the MAWS approach to be applied to a much wider range of waste streams than glass waste forms. The initial work at ANL has indicated that glassy slags are good final waste forms because of (1) their high chemical durability; (2) their ability to incorporate large amounts of metal oxides; (3) their ability to incorporate waste streams having low contents of flux components; (4) their less stringent requirements on processing parameters, compared to glass waste forms; and (5) their low requirements for purchased additives, which means greater waste volume reduction and treatment cost savings.

  19. Quantum circuits employing roots of the Pauli matrices

    NASA Astrophysics Data System (ADS)

    Soeken, Mathias; Miller, D. Michael; Drechsler, Rolf

    2013-10-01

    The Pauli matrices are a set of three 2×2 complex Hermitian unitary matrices. In this article, we investigate the relationships between certain roots of the Pauli matrices and how gates implementing those roots are used in quantum circuits. Techniques for simplifying such circuits are given. In particular, we show how those techniques can be used to find a circuit of Clifford+T gates starting from a circuit composed of gates from the well-studied NOT, CNOT, V library.

  20. Solid-State Li-Ion Batteries Using Fast, Stable, Glassy Nanocomposite Electrolytes for Good Safety and Long Cycle-Life.

    PubMed

    Tan, Guoqiang; Wu, Feng; Zhan, Chun; Wang, Jing; Mu, Daobin; Lu, Jun; Amine, Khalil

    2016-03-01

    The development of safe, stable, and long-life Li-ion batteries is being intensively pursued to enable the electrification of transportation and intelligent grid applications. Here, we report a new solid-state Li-ion battery technology, using a solid nanocomposite electrolyte composed of porous silica matrices with in situ immobilizing Li(+)-conducting ionic liquid, anode material of MCMB, and cathode material of LiCoO2, LiNi1/3Co1/3Mn1/3O2, or LiFePO4. An injection printing method is used for the electrode/electrolyte preparation. Solid nanocomposite electrolytes exhibit superior performance to the conventional organic electrolytes with regard to safety and cycle-life. They also have a transparent glassy structure with high ionic conductivity and good mechanical strength. Solid-state full cells tested with the various cathodes exhibited high specific capacities, long cycling stability, and excellent high temperature performance. This solid-state battery technology will provide new avenues for the rational engineering of advanced Li-ion batteries and other electrochemical devices. PMID:26862941

  1. Racah matrices and hidden integrability in evolution of knots

    NASA Astrophysics Data System (ADS)

    Mironov, A.; Morozov, A.; Morozov, An.; Sleptsov, A.

    2016-09-01

    We construct a general procedure to extract the exclusive Racah matrices S and S bar from the inclusive 3-strand mixing matrices by the evolution method and apply it to the first simple representations R = [ 1 ], [2], [3] and [ 2 , 2 ]. The matrices S and S bar relate respectively the maps (R ⊗ R) ⊗ R bar ⟶ R with R ⊗ (R ⊗ R bar) ⟶ R and (R ⊗ R bar) ⊗ R ⟶ R with R ⊗ (R bar ⊗ R) ⟶ R. They are building blocks for the colored HOMFLY polynomials of arbitrary arborescent (double fat) knots. Remarkably, the calculation realizes an unexpected integrability property underlying the evolution matrices.

  2. Development and validation of a dynamic vapor sorption-fast gas chromatography-flame ionization detection method for rapid analysis of volatile release from glassy matrices.

    PubMed

    Bohn, Dawn M; Cadwallader, Keith R; Schmidt, Shelly J

    2005-04-20

    Historically, saturated salt solutions in desiccators have been used to investigate the effects of increasing relative humidity and temperature on the volatile retention efficiency of amorphous glasses. Obtaining data using desiccators is a static process that gives the researcher discrete data points with which to draw conclusions. Dynamic vapor sorption (DVS; SMS, London, U.K.) is a humidification system that creates specific relative humidity and temperature environments within a chamber that contains the material being investigated. This study had two specific aims: (1) to develop a DVS-fast GC-FID method that dynamically evaluates the effects of humidification and temperature increases on volatile release from amorphous carbohydrate glasses and (2) to evaluate the validity of the DVS-fast GC-FID method. Artificial cherry Durarome (Firmenich, Plainsboro, NJ) was used as the model system. The DVS-fast GC-FID method proved to be an innovative, accurate, and precise technique that can be used to conduct humidification/temperature-volatile release studies. PMID:15826072

  3. Association of scattering matrices in quantum networks

    SciTech Connect

    Almeida, F.A.G.; Macêdo, A.M.S.

    2013-06-15

    Algorithms based on operations that associate scattering matrices in series or in parallel (analogous to impedance association in a classical circuit) are developed here. We exemplify their application by calculating the total scattering matrix of several types of quantum networks, such as star graphs and a chain of chaotic quantum dots, obtaining results with good agreement with the literature. Through a computational-time analysis we compare the efficiency of two algorithms for the simulation of a chain of chaotic quantum dots based on series association operations of (i) two-by-two centers and (ii) three-by-three ones. Empirical results point out that the algorithm (ii) is more efficient than (i) for small number of open scattering channels. A direct counting of floating point operations justifies quantitatively the superiority of the algorithm (i) for large number of open scattering channels.

  4. Carbon nanomaterials in silica aerogel matrices

    SciTech Connect

    Hamilton, Christopher E; Chavez, Manuel E; Duque, Juan G; Gupta, Gautam; Doorn, Stephen K; Dattelbaum, Andrew M; Obrey, Kimberly A D

    2010-01-01

    Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWCNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWCNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWCNTs and graphene-based materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications.

  5. Investigation of degradation mechanisms in composite matrices

    NASA Technical Reports Server (NTRS)

    Giori, C.; Yamauchi, T.

    1982-01-01

    Degradation mechanisms were investigated for graphite/polysulfone and graphite/epoxy laminates exposed to ultraviolet and high-energy electron radiations in vacuum up to 960 equivalent sun hours and 10 to the ninth power rads respectively. Based on GC and combined GC/MS analysis of volatile by-products evolved during irradiation, several free radical mechanisms of composite degradation were identified. The radiation resistance of different matrices was compared in terms of G values and quantum yields for gas formation. All the composite materials evaluated show high electron radiation stability and relatively low ultraviolet stability as indicated by low G values and high quantum for gas formation. Mechanical property measurements of irradiated samples did not reveal significant changes, with the possible exception of UV exposed polysulfone laminates. Hydrogen and methane were identified as the main by-products of irradiation, along with unexpectedly high levels of CO and CO2.

  6. Robust Generalized Low Rank Approximations of Matrices.

    PubMed

    Shi, Jiarong; Yang, Wei; Zheng, Xiuyun

    2015-01-01

    In recent years, the intrinsic low rank structure of some datasets has been extensively exploited to reduce dimensionality, remove noise and complete the missing entries. As a well-known technique for dimensionality reduction and data compression, Generalized Low Rank Approximations of Matrices (GLRAM) claims its superiority on computation time and compression ratio over the SVD. However, GLRAM is very sensitive to sparse large noise or outliers and its robust version does not have been explored or solved yet. To address this problem, this paper proposes a robust method for GLRAM, named Robust GLRAM (RGLRAM). We first formulate RGLRAM as an l1-norm optimization problem which minimizes the l1-norm of the approximation errors. Secondly, we apply the technique of Augmented Lagrange Multipliers (ALM) to solve this l1-norm minimization problem and derive a corresponding iterative scheme. Then the weak convergence of the proposed algorithm is discussed under mild conditions. Next, we investigate a special case of RGLRAM and extend RGLRAM to a general tensor case. Finally, the extensive experiments on synthetic data show that it is possible for RGLRAM to exactly recover both the low rank and the sparse components while it may be difficult for previous state-of-the-art algorithms. We also discuss three issues on RGLRAM: the sensitivity to initialization, the generalization ability and the relationship between the running time and the size/number of matrices. Moreover, the experimental results on images of faces with large corruptions illustrate that RGLRAM obtains the best denoising and compression performance than other methods. PMID:26367116

  7. Dirac matrices for Chern-Simons gravity

    SciTech Connect

    Izaurieta, Fernando; Ramirez, Ricardo; Rodriguez, Eduardo

    2012-10-06

    A genuine gauge theory for the Poincare, de Sitter or anti-de Sitter algebras can be constructed in (2n- 1)-dimensional spacetime by means of the Chern-Simons form, yielding a gravitational theory that differs from General Relativity but shares many of its properties, such as second order field equations for the metric. The particular form of the Lagrangian is determined by a rank n, symmetric tensor invariant under the relevant algebra. In practice, the calculation of this invariant tensor can be reduced to the computation of the trace of the symmetrized product of n Dirac Gamma matrices {Gamma}{sub ab} in 2n-dimensional spacetime. While straightforward in principle, this calculation can become extremely cumbersome in practice. For large enough n, existing computer algebra packages take an inordinate long time to produce the answer or plainly fail having used up all available memory. In this talk we show that the general formula for the trace of the symmetrized product of 2n Gamma matrices {Gamma}{sub ab} can be written as a certain sum over the integer partitions s of n, with every term being multiplied by a numerical cofficient {alpha}{sub s}. We then give a general algorithm that computes the {alpha}-coefficients as the solution of a linear system of equations generated by evaluating the general formula for different sets of tensors B{sup ab} with random numerical entries. A recurrence relation between different coefficients is shown to hold and is used in a second, 'minimal' algorithm to greatly speed up the computations. Runtime of the minimal algorithm stays below 1 min on a typical desktop computer for up to n = 25, which easily covers all foreseeable applications of the trace formula.

  8. Novel Factor-loaded Polyphosphazene Matrices

    PubMed Central

    Oredein-McCoy, Olugbemisola; Krogman, Nicholas R.; Weikel, Arlin L.; Hindenlang, Mark D.; Allcock, Harry R.; Laurencin, Cato T.

    2009-01-01

    Currently employed bone tissue engineered scaffolds often lack the potential for vascularization, which may be enhanced through the incorporation of and regulated release of angiogenic factors. For this reason, our objective was to fabricate and characterize protein-loaded amino acid ester polyphosphazene (Pphos)-based scaffolds and evaluate the novel sintering method used for protein incorporation, a method which will ultimately allow for the incorporation of proangiogenic agents. To test the hypothesis, Pphos and their composite microspheres with nanocrystalline hydroxyapatite (Pphos-HAp) were fabricated via the emulsion solvent evaporation method. Next, bovine serum albumin (BSA)-containing microsphere matrices were created using a novel solvent-non solvent approach for protein loading. The resulting protein (BSA) loaded-circular porous microsphere based scaffolds were characterized for morphology, porosity, protein structure, protein distribution, and subsequent protein release pattern. Scanning electron microscopy revealed porous microsphere scaffolds with a smooth surface and sufficient level of sintering, illustrated by fusion of adjacent microspheres. The porosity measured for the PNPhGly and PNPhGly-HAp scaffolds were 23 +/- 0.11% and 18+/- 4.02%, respectively, and within the range of trabecular bone. Circular dichroism confirmed an intact secondary protein structure for BSA following the solvent sintering method used for loading, and confocal microscopy verified that FITC-BSA was successfully entrapped both between adjacent microspheres and within the surface of the microspheres while sintering. For both Pphos and their composite microsphere scaffolds, BSA was released at a steady rate over a 21day time period, following a zero order release profile. HAp particles in the composite scaffolds served to improve the release profile pattern, underscoring the potential of HAp for growth factor delivery. Moreover, the results of this work suggests that the

  9. Robust Generalized Low Rank Approximations of Matrices

    PubMed Central

    Shi, Jiarong; Yang, Wei; Zheng, Xiuyun

    2015-01-01

    In recent years, the intrinsic low rank structure of some datasets has been extensively exploited to reduce dimensionality, remove noise and complete the missing entries. As a well-known technique for dimensionality reduction and data compression, Generalized Low Rank Approximations of Matrices (GLRAM) claims its superiority on computation time and compression ratio over the SVD. However, GLRAM is very sensitive to sparse large noise or outliers and its robust version does not have been explored or solved yet. To address this problem, this paper proposes a robust method for GLRAM, named Robust GLRAM (RGLRAM). We first formulate RGLRAM as an l1-norm optimization problem which minimizes the l1-norm of the approximation errors. Secondly, we apply the technique of Augmented Lagrange Multipliers (ALM) to solve this l1-norm minimization problem and derive a corresponding iterative scheme. Then the weak convergence of the proposed algorithm is discussed under mild conditions. Next, we investigate a special case of RGLRAM and extend RGLRAM to a general tensor case. Finally, the extensive experiments on synthetic data show that it is possible for RGLRAM to exactly recover both the low rank and the sparse components while it may be difficult for previous state-of-the-art algorithms. We also discuss three issues on RGLRAM: the sensitivity to initialization, the generalization ability and the relationship between the running time and the size/number of matrices. Moreover, the experimental results on images of faces with large corruptions illustrate that RGLRAM obtains the best denoising and compression performance than other methods. PMID:26367116

  10. Photoisomerization of azobenzenes isolated in cryogenic matrices.

    PubMed

    Duarte, Luís; Khriachtchev, Leonid; Fausto, Rui; Reva, Igor

    2016-06-22

    2,2'-Dihydroxyazobenzene (DAB), 2,2'-azotoluene (AT) and azobenzene (AB) were isolated in argon and xenon matrices and their molecular structures and photochemical transformations were characterized by infrared spectroscopy and theoretical calculations. All these compounds can adopt the E and Z isomeric forms around the central CNNC moiety, which can be enriched by several conformational and tautomeric modifications for DAB and AT. A number of DAB and AT isomeric forms were identified for the first time. For DAB, the E azo-enol isomer with two intramolecular six-membered quasi-rings formed via OHN hydrogen bonds was found after deposition. Irradiation with UV light generated a different E azo-enol form with two intramolecular H-bonded five-membered quasi-rings. Phototransformation was shown to be reversible and the forms could be interconverted by irradiation at different wavelengths. The isomerization between these two forms constitutes a direct experimental observation of an E → E isomerization in azobenzene-type molecules. Further irradiation generated a form(s) bearing both OH and NH groups. For AT, two E isomers with the CH3 groups forming five-membered and five/six-membered quasi-rings with the azo group were observed in the as-deposited matrices. Irradiation of AT with UV light generated a Z form that can be converted back to the E form at different irradiation wavelengths. E-AB was deposited in a xenon matrix and both E → Z and Z → E phototransformations were observed (contrary to what was previously reported in an argon matrix where only the Z → E conversion occurred). AB photoisomerization becomes more pronounced at elevated temperatures, thus indicating that the matrix effects responsible for hindering the AB photoisomerization are essentially due to steric restrictions. The different photoisomerization channels observed for these compounds are discussed in terms of a small-amplitude pedal motion. PMID:27279432

  11. Effects of molecular architecture on fluid ingress behavior of glassy polymer networks

    NASA Astrophysics Data System (ADS)

    Jaskson, Matthew Blaine

    This manuscript demonstrates the synthesis of glassy polymer network isomers to control morphological variations and study solvent ingress behavior independent of chemical affinity. Well-controlled network architectures with varying free volume average hole-sizes have been shown to substantially influence solvent ingress within glassy polymer networks. Bisphenol-A diglycidyl ether (DGEBA), bisphenol-F diglycidyl ether (DGEBF), Triglycidyl p-aminophenol (pAP, MY0510), Triglycidyl maminophenol (mAP, MY0610), and tetraglydicyl-4,4'-diamino-diphenyl methane (TGDDM, MY721) were cured with 3,3'- and 4,4'-diaminodiphenyl sulfone (DDS) at a stoichiometric ratio of 1:1 oxirane to amine active hydrogen to generate a series of network architectures with an average free volume hole-size (Vh) ranging between 54-82 A3. Polymer networks were exposed to water and a broad range of organic solvents ranging in van der Waals (vdW) volumes from 18-88 A3 for up to 10,000h time. A clear relationship between glassy polymer network Vh and fluid penetration has been established. As penetrant vdW volume approached Vh, uptake kinetics significantly decreased, and as penetrant vdW volume exceeded Vh, a blocking mechanism dominated ingress and prevented penetrant transport. These results suggest that reducing the free volume hole-size is a reasonable approach to control solvent properties for glassy polymer networks. New techniques to monitor and predict the diffusion behavior of liquids through glassy networks are also presented. Digital Image Correlation (DIC) was employed to accurately measure the strain developed during case II diffusion. This technique also presented a new theory for a relationship between sample topology and irreversible macroscopic brittle failure induced by solvent absorption. A new modeling technique has been developed which can accurately predict the chemical and physical interactions a solvent may have with a glassy network. This new model can be used as a

  12. Some Interesting Characteristics of Markov Chain Transition Matrices.

    ERIC Educational Resources Information Center

    Egelston, Richard L.

    A Monte Carlo investigation of Markov chain matrices was conducted to create empirical distributions for two statistics created from the transition matrices. Curve fitting techniques developed by Karl Pearson were used to deduce if theoretical equations could be fit to the two sets of distributions. The set of distributions which describe the…

  13. Efficient quantum circuits for Toeplitz and Hankel matrices

    NASA Astrophysics Data System (ADS)

    Mahasinghe, A.; Wang, J. B.

    2016-07-01

    Toeplitz and Hankel matrices have been a subject of intense interest in a wide range of science and engineering related applications. In this paper, we show that quantum circuits can efficiently implement sparse or Fourier-sparse Toeplitz and Hankel matrices. This provides an essential ingredient for solving many physical problems with Toeplitz or Hankel symmetry in the quantum setting with deterministic queries.

  14. The Modern Origin of Matrices and Their Applications

    ERIC Educational Resources Information Center

    Debnath, L.

    2014-01-01

    This paper deals with the modern development of matrices, linear transformations, quadratic forms and their applications to geometry and mechanics, eigenvalues, eigenvectors and characteristic equations with applications. Included are the representations of real and complex numbers, and quaternions by matrices, and isomorphism in order to show…

  15. Matric Potential of Several Plant Tissues and Biocolloids 1

    PubMed Central

    Wiebe, Herman H.

    1966-01-01

    The pressure membrane apparatus was used to study the matric potential (imbibition pressure or moisture tension) of plant tissues and of several organic colloidal preparations. The moisture release curves of aqueous 2% agar, 12% gelatin, and filter paper were smooth parabolic curves between matric potentials of −0.1 and −15 bars. When logarithms of the matric potentials were plotted against logarithms of the moisture content, the data yielded straight lines for agar and filter paper. Slices of fresh tissue lost little water after 2 days in the apparatus at maximum pressure of 15 bars. Osmotic forces in conjunction with cell membranes are able to retain moisture against pressure of this magnitude. After the cells were disrupted by freezing and thawing, up to 90% of the original moisture was removed by a 15 bar pressure, with lesser amounts removed at lower pressures. The results gave a parabolic relationship, and straight lines could be fitted to log—log plots of data from potato tuber and young asparagus stem slices. Sections from the tips of asparagus stems held less moisture at all matric potentials than more basal sections. The method permits the study of the matric potential of tissues independently of the osmotic potential. As measured, however, the matric potential is a composite of matric potentials of colloidal substances in the protoplasm and cell walls after disruption of cells by freezing and mixing of the contents. The value is therefore only an approximation of the matric potentials occurring in the living tissues. PMID:16656421

  16. Component Identification and Item Difficulty of Raven's Matrices Items.

    ERIC Educational Resources Information Center

    Green, Kathy E.; Kluever, Raymond C.

    Item components that might contribute to the difficulty of items on the Raven Colored Progressive Matrices (CPM) and the Standard Progressive Matrices (SPM) were studied. Subjects providing responses to CPM items were 269 children aged 2 years 9 months to 11 years 8 months, most of whom were referred for testing as potentially gifted. A second…

  17. Host plant effects on development and reproduction of the glassy-winged sharpshooter, Homalodisca vitripennis (Homoptera: Cicadellidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Development, survivorship, longevity, reproduction and life table parameters of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar), were examined in the laboratory using three host plants, sunflower (Helianthus annuus L.), Chrysanthemum morifolium L. and euonymus (Euonymus japonica Thu...

  18. Time series, correlation matrices and random matrix models

    SciTech Connect

    Vinayak; Seligman, Thomas H.

    2014-01-08

    In this set of five lectures the authors have presented techniques to analyze open classical and quantum systems using correlation matrices. For diverse reasons we shall see that random matrices play an important role to describe a null hypothesis or a minimum information hypothesis for the description of a quantum system or subsystem. In the former case various forms of correlation matrices of time series associated with the classical observables of some system. The fact that such series are necessarily finite, inevitably introduces noise and this finite time influence lead to a random or stochastic component in these time series. By consequence random correlation matrices have a random component, and corresponding ensembles are used. In the latter we use random matrices to describe high temperature environment or uncontrolled perturbations, ensembles of differing chaotic systems etc. The common theme of the lectures is thus the importance of random matrix theory in a wide range of fields in and around physics.

  19. Elastic Properties of 4-6 nm-thick Glassy Carbon Thin Films

    NASA Astrophysics Data System (ADS)

    Manoharan, M. P.; Lee, H.; Rajagopalan, R.; Foley, H. C.; Haque, M. A.

    2010-01-01

    Glassy carbon is a disordered, nanoporous form of carbon with superior thermal and chemical stability in extreme environments. Freestanding glassy carbon specimens with 4-6 nm thickness and 0.5 nm average pore size were synthesized and fabricated from polyfurfuryl alcohol precursors. Elastic properties of the specimens were measured in situ inside a scanning electron microscope using a custom-built micro-electro-mechanical system. The Young’s modulus, fracture stress and strain values were measured to be about 62 GPa, 870 MPa and 1.3%, respectively; showing strong size effects compared to a modulus value of 30 GPa at the bulk scale. This size effect is explained on the basis of the increased significance of surface elastic properties at the nanometer length-scale.

  20. Age-dependent modes of extensional necking instability in soft glassy materials.

    PubMed

    Hoyle, David M; Fielding, Suzanne M

    2015-04-17

    We study the instability to necking of an initially cylindrical filament of soft glassy material subject to extensional stretching. By numerical simulation of the soft glassy rheology model and a simplified fluidity model, and by analytical predictions within a highly generic toy description, we show that the mode of instability is set by the age of the sample relative to the inverse of the applied extensional strain rate. Young samples neck gradually via a liquidlike mode, the onset of which is determined by both the elastic loading and plastic relaxation terms in the stress constitutive equation. Older samples fail at smaller draw ratios via a more rapid mode, the onset of which is determined only by the solidlike elastic loading terms (though plastic effects arise later, once appreciable necking develops). We show this solidlike mode to be the counterpart, for elastoplastic materials, of the Considère mode of necking in strain-rate-independent solids. PMID:25933343

  1. Relaxation of enthalpy fluctuations during sub-T(g) annealing of glassy selenium.

    PubMed

    Gulbiten, Ozgur; Mauro, John C; Lucas, Pierre

    2013-06-28

    The relaxation behavior of glass is influenced by the presence of dynamical heterogeneities, which lead to an intrinsically non-monotonic decay of fluctuations in density and enthalpy during isothermal annealing. This is apparently a universal feature of fragile glass forming systems associated with localized spatial variations in relaxation time. Here we present direct experimental observation of the nonmonotonic evolution of enthalpy fluctuations in glassy selenium annealed near room temperature. The nonmonotonic change in the distribution of enthalpy fluctuations measured by heat capacity spectroscopy offers direct evidence for the presence of dynamical heterogeneity in this glass. An enthalpy landscape model of selenium is then used to simulate annealing under identical conditions. The simulation results closely follow the evolution of enthalpy fluctuations observed experimentally. The close match between model and experiment demonstrate that enthalpy and density fluctuations are sources of dynamical heterogeneities in glassy materials.

  2. Mechanical properties of thin glassy polymer films filled with spherical polymer-grafted nanoparticles.

    PubMed

    Maillard, Damien; Kumar, Sanat K; Fragneaud, Benjamin; Kysar, Jeffrey W; Rungta, Atri; Benicewicz, Brian C; Deng, Hua; Brinson, L Cate; Douglas, Jack F

    2012-08-01

    It is commonly accepted that the addition of spherical nanoparticles (NPs) cannot simultaneously improve the elastic modulus, the yield stress, and the ductility of an amorphous glassy polymer matrix. In contrast to this conventional wisdom, we show that ductility can be substantially increased, while maintaining gains in the elastic modulus and yield stress, in glassy nanocomposite films composed of spherical silica NPs grafted with polystyrene (PS) chains in a PS matrix. The key to these improvements are (i) uniform NP spatial dispersion and (ii) strong interfacial binding between NPs and the matrix, by making the grafted chains sufficiently long relative to the matrix. Strikingly, the optimal conditions for the mechanical reinforcement of the same nanocomposite material in the melt state is completely different, requiring the presence of spatially extended NP clusters. Evidently, NP spatial dispersions that optimize material properties are crucially sensitive to the state (melt versus glass) of the polymeric material.

  3. Glassy states and super-relaxation in populations of coupled phase oscillators.

    PubMed

    Iatsenko, D; McClintock, P V E; Stefanovska, A

    2014-01-01

    Large networks of coupled oscillators appear in many branches of science, so that the kinds of phenomena they exhibit are not only of intrinsic interest but also of very wide importance. In 1975, Kuramoto proposed an analytically tractable model to describe these systems, which has since been successfully applied in many contexts and remains a subject of intensive research. Some related problems, however, remain unclarified for decades, such as the existence and properties of the oscillator glass state. Here we present a detailed analysis of a very general form of the Kuramoto model. In particular, we find the conditions when it can exhibit glassy behaviour, which represents a kind of synchronous disorder in the present case. Furthermore, we discover a new and intriguing phenomenon that we refer to as super-relaxation where the oscillators feel no interaction at all while relaxing to incoherence. Our findings offer the possibility of creating glassy states and observing super-relaxation in real systems.

  4. Low substrate temperature deposition of diamond coatings derived from glassy carbon

    DOEpatents

    Holcombe, C.E. Jr.; Seals, R.D.

    1995-09-26

    A process is disclosed for depositing a diamond coating on a substrate at temperatures less than about 550 C. A powder mixture of glassy carbon and diamond particles is passed through a high velocity oxy-flame apparatus whereupon the powders are heated prior to impingement at high velocity against the substrate. The powder mixture contains between 5 and 50 powder volume percent of the diamond particles, and preferably between 5 and 15 powder volume percent. The particles have a size from about 5 to about 100 micrometers, with the diamond particles being about 5 to about 30 micrometers. The flame of the apparatus provides a velocity of about 350 to about 1000 meters per second, with the result that upon impingement upon the substrate, the glassy carbon is phase transformed to diamond as coaxed by the diamond content of the powder mixture. 2 figs.

  5. High-resolution images of Pd particles supported on highly oriented pyrolytic graphite and glassy carbon

    SciTech Connect

    Murakami, Yasushi; Naoi, Katsuo; Yahikozawa, Kiyochika; Takasu, Yoshio . Dept. of Fine Materials Engineering)

    1994-09-01

    Ultrafine metal particles dispersed on supporting materials have been developed as catalysts for the oxidation of automobile exhaust gas, the hydrogenation of carbon monoxide, and electrodes of fuel cells. Both activities and selectivities of these reactions depend on the morphology of the dispersed metal. The morphology of palladium particles supported on both highly oriented pyrolytic graphite (HOPG) and glassy carbon was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The particles on the HOPG were linked with neighboring particles to agglomerate, while the particles on the glassy carbon were circular. AFM data with tapping mode for the palladium particles on HOPG were consistent with the high-resolution SEM image. Although the lateral resolution of the AFM image was lower than that for the high-resolution SEM data, the AFM image clearly indicated the height distribution of the agglomerates.

  6. Low substrate temperature deposition of diamond coatings derived from glassy carbon

    DOEpatents

    Holcombe, Jr., Cressie E.; Seals, Roland D.

    1995-01-01

    A process for depositing a diamond coating on a substrate at temperatures less than about 550.degree. C. A powder mixture of glassy carbon and diamond particles is passed through a high velocity oxy-flame apparatus whereupon the powders are heated prior to impingement at high velocity against the substrate. The powder mixture contains between 5 and 50 powder volume percent of the diamond particles, and preferably between 5 and 15 powder volume percent. The particles have a size from about 5 to about 100 micrometers, with the diamond particles being about 5 to about 30 micrometers. The flame of the apparatus provides a velocity of about 350 to about 1000 meters per second, with the result that upon impingement upon the substrate, the glassy carbon is phase transformed to diamond as coaxed by the diamond content of the powder mixture.

  7. Unraveling the Mechanism of Nanoscale Mechanical Reinforcement in Glassy Polymer Nanocomposites

    DOE PAGES

    Cheng, Shiwang; Bocharova, Vera; Belianinov, Alex; Xiong, Shaomin; Kisliuk, Alexander; Somnath, Suhas; Holt, Adam P.; Ovchinnikova, Olga S.; Jesse, Stephen; Martin, Halie J.; et al

    2016-05-20

    The mechanical reinforcement of polymer nanocomposites (PNCs) above the glass transition temperature, Tg, has been extensively researched. However, not much is known about the origin of this effect below Tg. In this paper, we unravel the mechanism of PNC reinforcement within the glassy state by directly probing nanoscale mechanical properties with atomic force microscopy and macroscopic properties with Brillouin light scattering. Our results unambiguously show that the "glassy" Young's modulus in the interfacial polymer layer of PNCs is two-times higher than in the bulk polymer, which results in significant reinforcement below Tg. We ascribe this phenomenon to a high stretchingmore » of the chains within the interfacial layer. Since the interfacial chain packing is essentially temperature independent, these findings provide a new insight into the mechanical reinforcement of PNCs also above Tg.« less

  8. Connection between NMR and electrical conductivity in glassy chalcogenide fast ionic conductors

    SciTech Connect

    Kim, K.H.

    1995-11-01

    The work documented in this thesis follows the traditional order. In this chapter a general discussion of ionic conduction and of glassy materials are followed by a brief outline of the experimental techniques for the investigation of fast ionic conduction in glassy materials, including NMR and impedance spectroscopy techniques. A summary of the previous and present studies is presented in the last section of this introductory chapter. The details of the background theory and models are found in the Chapter II, followed by the description of the experimental details in Chapter III. Chapter IV of the thesis describes the experimental results and the analysis of the experimental observations followed by the conclusions in chapter V.

  9. Growth of InP single crystals by liquid encapsulated Czochralski (LEC) using glassy-carbon crucibles

    SciTech Connect

    Oliveira, C.E.M. de; Miskys, C.R.; Carvalho, M.M.G. de

    1996-12-31

    Using a high pressure puller and Glassy-Carbon crucibles, undoped InP single crystals weighing 100g and with 25 mm diameter were grown in the <100> direction. The residual carrier concentration of samples, measure by the Van der Pauw method at 300K, was about 5 {times} 10{sup 15}cm{sup {minus}3}, result as good as those obtained with Quartz crucibles with the advantage that Glassy-Carbon crucibles are fully reusable.

  10. L'effet des deformations plastiques severes sur les proprietes d'hydruration du magnesium

    NASA Astrophysics Data System (ADS)

    Lang, Julien

    Le travail de recherche effectue durant mon projet de maitrise en physique a l'Universite du Quebec a Trois-Rivieres dans les laboratoires de l'Institut de Recherche sur l'Hydrogene etait de comparer l'effet du laminage a froid de la poudre de MgH2 avec celui du broyage mecanique. Nous avons etudie cette nouvelle technique en utilisant un laminoir vertical concu specialement pour laminer de la poudre. Nous avons lamine la poudre de MgH2 5, 25, 50 et 100 fois. La comparaison de la morphologie de la poudre de MgH 2 telle que recu du manufacturier et broye mecaniquement pendant 30 minutes avec celle de la poudre laminee ete faite a l'aide d'un microscope electronique a balayage. Nous avons par la suite mesure les proprietes de sorption d'hydrogene grace un appareil PCT de type Sievert. Nous avons aussi determine la structure cristalline par diffraction de rayons X. A partir de ces resultats, nous avons constate que le nombre optimal de laminages est de cinq et a les caracteristiques d'absorption/desorption d'hydrogene similaires a un broyage mecanique de 30 minutes. Nous avons aussi utilise les courbes de cinetiques d'absorption et de desorption d'hydrogene pour calculer l'etape limitative dans les reactions de sorption des echantillons lamines. Comme cinq laminages se font en environ 10 secondes, on voit que le laminage a froid est une technique plus interessante industriellement que le broyage mecanique a cause de l'important gain en temps et en energie.

  11. Glassy Objects (Microtektites?) from Deep-Sea Sediments near the Ivory Coast.

    PubMed

    Glass, B P

    1968-08-30

    Glassy objects of spherical, oval, dumbbell, teardrop, and irregular shapes have been found in a deep-sea sediment core taken off the Ivory Coast. They occur in a layer of sediment that was apparently deposited about 800,000 years ago. Their geographic location, appearance, and physical properties suggest that they are microtektites and that they are related to the tektite-strewn field of the Ivory Coast.

  12. Solute induced relaxation in glassy polymers: Experimental measurements and nonequilibrium thermodynamic model

    SciTech Connect

    Minelli, Matteo; Doghieri, Ferruccio

    2014-05-15

    Data for kinetics of mass uptake from vapor sorption experiments in thin glassy polymer samples are here interpreted in terms of relaxation times for volume dilation. To this result, both models from non-equilibrium thermodynamics and from mechanics of volume relaxation contribute. Different kind of sorption experiments have been considered in order to facilitate the direct comparison between kinetics of solute induced volume dilation and corresponding data from process driven by pressure or temperature jumps.

  13. The Influence of Ion Implantation on cell Attachment to Glassy Polymeric Carbon

    SciTech Connect

    Zimmerman, R.; Ila, D.; Gurhan, I.; Ozdal-Kurt, F.; Sen, B. H.; Rodrigues, M.

    2006-11-13

    In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that near surface implantation of silver in Glassy Polymeric Carbon (GPC) can completely inhibit cell attachment on implanted areas while leaving adjacent areas unaffected. Patterned ion implantation permits precise control of tissue growth on medical applications of GPC. We have shown that silver ion implantation or argon ion assisted surface deposition of silver inhibits cell growth on GPC, a desirable improvement of current cardiac implants.

  14. Crystallization of the glassy phase of grain boundaries in silicon nitride

    NASA Technical Reports Server (NTRS)

    Jefferson, D. A.; Thomas, J. M.; Wen, S.

    1984-01-01

    Three types of hot-pressed silicon nitride specimens (containing 5wt% Y2O3 and 2wt% Al2O3 additives) which were subjected to different temperature heat treatments were studied by X-ray diffraction, X-ray microanalysis and high resolution electron microscopy. The results indicated that there were phase changes in the grain boundaries after heat treatment and the glassy phase at the grain boundaries was crystallized by heat treatment.

  15. Highly Selective Membranes For The Separation Of Organic Vapors Using Super-Glassy Polymers

    DOEpatents

    Pinnau, Ingo; Lokhandwala, Kaaeid; Nguyen, Phuong; Segelke, Scott

    1997-11-18

    A process for separating hydrocarbon gases of low boiling point, particularly methane, ethane and ethylene, from nitrogen. The process is performed using a membrane made from a super-glassy material. The gases to be separated are mixed with a condensable gas, such as a C.sub.3+ hydrocarbon. In the presence of the condensable gas, improved selectivity for the low-boiling-point hydrocarbon gas over nitrogen is achieved.

  16. Radiation-induced intermediates in irradiated glassy ionic liquids at low temperature

    NASA Astrophysics Data System (ADS)

    Saenko, Elizaveta V.; Lukianova, Mariia A.; Shiryaeva, Ekaterina S.; Takahashi, Kenji; Feldman, Vladimir I.

    2016-07-01

    The primary radiation-induced processes in irradiated low-temperature pyrrolidinium- and piperidinium-type ionic liquids were investigated by EPR and optical absorption spectroscopy. A narrow singlet signal in the EPR spectra of irradiated ionic liquids was attributed to the physically stabilized electron. Broad absorption band in visible region was ascribed to "hole" species. Aromatic scavengers react with "hole" species in glassy irradiated ionic liquids at 77 K.

  17. A Novel Method for Electroplating Ultra-High-Strength Glassy Metals

    NASA Technical Reports Server (NTRS)

    Ramsey, Brian; Engelhaupt, Darell; Six, N. Frank (Technical Monitor)

    2002-01-01

    A novel method for electroplating ultra-high-strength glassy metals, nickel-phosphorous and nickel-cobalt-phosphorous, has been developed at NASA Marshall Space Flight Center, cooperatively with the University of Alabama in Huntsville. Traditionally, thin coatings of these metals are achieved via electroless deposition. Benefits of the new electrolytic process include thick, low-stress deposits, free standing shapes, lower plating temperature, low maintenance, and safer operation with substantially lower cost.

  18. Glassy Objects (Microtektites?) from Deep-Sea Sediments near the Ivory Coast.

    PubMed

    Glass, B P

    1968-08-30

    Glassy objects of spherical, oval, dumbbell, teardrop, and irregular shapes have been found in a deep-sea sediment core taken off the Ivory Coast. They occur in a layer of sediment that was apparently deposited about 800,000 years ago. Their geographic location, appearance, and physical properties suggest that they are microtektites and that they are related to the tektite-strewn field of the Ivory Coast. PMID:17812117

  19. Effete, an E2 ubiquitin-conjugating enzyme with multiple roles in Drosophila development and chromatin organization

    PubMed Central

    Cipressa, Francesca; Cenci, Giovanni

    2013-01-01

    The Drosophila effete gene encodes an extremely conserved class I E2 ubiquitin-conjugating enzyme. Growing evidence indicates that Eff is involved in many cellular processes including eye development, maintenance of female germline stem cells, and regulation of apoptosis. Eff is also a major component of Drosophila chromatin and it is particularly enriched in chromatin with repressive properties. In addition, Eff is required for telomere protection and to prevent telomere fusion. Consistent with its multiple roles in chromatin maintenance, Eff is also one of the rare factors that modulate both telomere-induced and heterochromatin-induced position effect variegation. PMID:24088712

  20. Spectroscopic ellipsometric and Raman spectroscopic investigations of pulsed laser treated glassy carbon surfaces

    NASA Astrophysics Data System (ADS)

    Csontos, J.; Pápa, Z.; Gárdián, A.; Füle, M.; Budai, J.; Toth, Z.

    2015-05-01

    In this study spectroscopic ellipsometry (SE) and Raman spectroscopy are applied to study structural modification of glassy carbon, due to high intensity laser ablation. Two KrF lasers with different pulse durations (480 fs and 18 ns), an ArF (20 ns), and a frequency doubled Nd:YAG laser (8 ns) were applied to irradiate the surface of glassy carbon targets. The main characteristics of the different laser treatments are compared by introducing the volumetric fluence which takes into account the different absorption values at different wavelengths. SE showed the appearance of a modified layer on the ablated surfaces. In the case of the ns lasers the thickness of this layer was in the range of 10-60 nm, while in the case of fs laser it was less than 20 nm. In all cases the average refractive index (n) of the modified layers slightly decreased compared to the refractive index of glassy carbon. Increase in extinction coefficient (k) was observed in the cases of ArF and fs KrF laser treatment, while the k values decreased significantly in the cases of nanosecond pulse duration KrF and Nd:YAG laser treatments. In the Raman spectra of the ablated areas the characteristic D and G peaks were widened due to appearance of an amorphous phase. Both Raman spectroscopy and SE indicate that the irradiated areas show carbon nanoparticle formation in all cases.

  1. Modelling multi-scale deformation of amorphous glassy polymers with experimentally motivated evolution of the microstructure

    NASA Astrophysics Data System (ADS)

    Engqvist, Jonas; Wallin, Mathias; Ristinmaa, Matti; Hall, Stephen A.; Plivelic, Tomás S.

    2016-11-01

    Novel experimental data, obtained recently using advanced multi-scale experiments, have been used to develop a micro-mechanically motivated constitutive model for amorphous glassy polymers. Taking advantage of the experiments, the model makes use of a microstructural deformation gradient to incorporate the experimentally obtained deformation of the microstructure, as well as its evolving orientation. By comparing results from the model to experimental data, it is shown that the proposed approach is able to accurately predict glassy polymer deformation over a wide range of length-scales, from the macroscopic response (mm range) down to the deformation of the microstructure (nm range). The proposed model is evaluated by comparing the numerical response to experimental results on multiple scales from an inhomogeneous cold drawing experiment of glassy polycarbonate. Besides the macroscopic force-displacement response, a qualitative comparison of the deformation field at the surface of the specimen is performed. Furthermore, the predicted evolution of the fabric orientation is compared to experimental results obtained from X-ray scattering experiments. The model shows very good agreement with the experimental data over a wide range of length scales.

  2. Protection of nuclear graphite toward fluoride molten salt by glassy carbon deposit

    NASA Astrophysics Data System (ADS)

    Bernardet, V.; Gomes, S.; Delpeux, S.; Dubois, M.; Guérin, K.; Avignant, D.; Renaudin, G.; Duclaux, L.

    2009-02-01

    Molten salt reactor represents one of the promising future Generation IV nuclear reactors families where the fuel, a liquid molten fluoride salt, is circulating through the graphite reactor core. The interactions between nuclear graphite and fluoride molten salt and also the graphite surface protection were investigated in this paper by powder X-ray diffraction, micro-Raman spectroscopy and scanning electron microscopy coupled with X-ray microanalysis. Nuclear graphite discs were covered by two kinds of protection deposit: a glassy carbon coating and a double coating of pyrolitic carbon/glassy carbon. Different behaviours have been highlighted according to the presence and the nature of the coated protection film. Intercalation of molten salt between the graphite layers did not occur. Nevertheless the molten salt adhered more or less to the surface of the graphite disc, filled more or less the graphite surface porosity and perturbed more or less the graphite stacking order at the disc surface. The behaviour of unprotected graphite was far to be satisfactory after two days of immersion of graphite in molten salt at 500 °C. The best protection of the graphite disc surface, with the maximum of inertness towards molten salt, has been obtained with the double coating of pyrolitic carbon/glassy carbon.

  3. Microwave enhanced electroanalysis of formulations: processes in micellar media at glassy carbon and at platinum electrodes.

    PubMed

    Ghanem, Mohamed A; Compton, Richard G; Coles, Barry A; Canals, Antonio; Marken, Frank

    2005-10-01

    The direct electroanalysis of complex formulations containing alpha-tocopherol (vitamin E) is possible in micellar solution and employing microwave-enhanced voltammetry. In the presence of microwave radiation substantial heating and current enhancement effects have been observed at 330 microm diameter glassy carbon electrodes placed into a micellar aqueous solution and both hydrophilic and highly hydrophobic redox systems are detected. For the water soluble Fe(CN)(6)(3-/4-) redox system in micellar aqueous solutions of 0.1 M NaCl and 0.1 M sodium dodecylsulfate (SDS) at low to intermediate microwave power, thermal effects and convection effects are observed. At higher microwave power, thermal cavitation is induced and dominates the mass transport at the electrode surface. For the micelle-soluble redox systems tert-butylferrocene and 2,5-di-tert-butyl-1,4-benzoquinone, strong and concentration dependent current responses are observed only in the presence of microwave radiation. For the oxidation of micelle-soluble alpha-tocopherol current responses at glassy carbon electrodes are affected by adsorption and desorption processes whereas at platinum electrodes, analytical limiting currents are obtained over a wide range of alpha-tocopherol concentrations. However, for the determination of alpha-tocopherol in a commercial formulation interference from proteins is observed at platinum electrodes and direct measurements are possible only over a limited concentration range and at glassy carbon electrodes.

  4. Graphene oxide-mediated electrochemistry of glucose oxidase on glassy carbon electrodes.

    PubMed

    Castrignanò, Silvia; Valetti, Francesca; Gilardi, Gianfranco; Sadeghi, Sheila J

    2016-01-01

    Glucose oxidase (GOD) was immobilized on glassy carbon electrodes in the presence of graphene oxide (GO) as a model system for the interaction between GO and biological molecules. Lyotropic properties of didodecyldimethylammonium bromide (DDAB) were used to stabilize the enzymatic layer on the electrode surface resulting in a markedly improved electrochemical response of the immobilized GOD. Transmission electron microscopy images of the GO with DDAB confirmed the distribution of the GO in a two-dimensional manner as a foil-like material. Although it is known that glassy carbon surfaces are not ideal for hydrogen peroxide detection, successful chronoamperometric titrations of the GOD in the presence of GO with β-d-glucose were performed on glassy carbon electrodes, whereas no current response was detected upon β-d-glucose addition in the absence of GO. The GOD-DDAB-GO system displayed a high turnover efficiency and substrate affinity as a glucose biosensor. The simplicity and ease of the electrode preparation procedure of this GO/DDAB system make it a good candidate for immobilizing other biomolecules for fabrication of amperometric biosensors. PMID:25939764

  5. A magnetic glassy phase in Fe1+ySexTe1-x single crystals

    NASA Astrophysics Data System (ADS)

    Lamura, G.; Shiroka, T.; Bonfà, P.; Sanna, S.; Bernardini, F.; De Renzi, R.; Viennois, R.; Giannini, E.; Piriou, A.; Emery, N.; Cimberle, M. R.; Putti, M.

    2013-04-01

    The evolution of magnetic order in Fe1+ySexTe1-x crystals as a function of Se content was investigated by means of ac/dc magnetometry and muon-spin spectroscopy. Experimental results and self-consistent density functional theory calculations both indicate that muons are implanted in vacant iron-excess sites, where they probe a local field mainly of dipolar origin, resulting from an antiferromagnetic (AFM) bicollinear arrangement of iron spins. This long-range AFM phase becomes progressively disordered with increasing Se content. At the same time all the tested samples manifest a marked glassy character that vanishes for high Se contents. The presence of local electronic/compositional inhomogeneities most likely favours the growth of clusters whose magnetic moment ‘freezes’ at low temperature. This glassy magnetic phase justifies both the coherent muon precession seen at short times in the asymmetry data, as well as the glassy behaviour evidenced by both dc and ac magnetometry.

  6. Glassy slags as novel waste forms for remediating mixed wastes with high metal contents

    SciTech Connect

    Feng, X.; Wronkiewicz, D.J.; Bates, J.K.; Brown, N.R.; Buck, E.C.; Gong, M.; Ebert, W.L.

    1994-03-01

    Argonne National Laboratory (ANL) is developing a glassy slag final waste form for the remediation of low-level radioactive and mixed wastes with high metal contents. This waste form is composed of various crystalline and metal oxide phases embedded in a silicate glass phase. This work indicates that glassy slag shows promise as final waste form because (1) it has similar or better chemical durability than high-level nuclear waste (HLW) glasses, (2) it can incorporate large amounts of metal wastes, (3) it can incorporate waste streams having low contents of flux components (boron and alkalis), (4) it has less stringent processing requirements (e.g., viscosity and electric conductivity) than glass waste forms, (5) its production can require little or no purchased additives, which can result in greater reduction in waste volume and overall treatment costs. By using glassy slag waste forms, minimum additive waste stabilization approach can be applied to a much wider range of waste streams than those amenable only to glass waste forms.

  7. Glassy carbon as an absolute intensity calibration standard for small-angle scattering.

    SciTech Connect

    Zhang, F.; Ilavsky, J.; Long, G.; Allen, A.; Quintana, J.; Jemian, P.; NIST

    2010-05-01

    Absolute calibration of small-angle scattering (SAS) intensity data (measured in terms of the differential scattering cross section per unit sample volume per unit solid angle) is essential for many important aspects of quantitative SAS analysis, such as obtaining the number density, volume fraction, and specific surface area of the scatterers. It also enables scattering data from different instruments (light, X-ray, or neutron scattering) to be combined, and it can even be useful to detect the existence of artifacts in the experimental data. Different primary or secondary calibration methods are available. In the latter case, absolute intensity calibration requires a stable artifact with the necessary scattering profile. Glassy carbon has sometimes been selected as this intensity calibration standard. Here we review the spatial homogeneity and temporal stability of one type of commercially available glassy carbon that is being used as an intensity calibration standard at a number of SAS facilities. We demonstrate that glassy carbon is sufficiently homogeneous and stable during routine use to be relied upon as a suitable standard for absolute intensity calibration of SAS data.

  8. Generation of fine hydromagmatic ash by growth and disintegration of glassy rinds

    USGS Publications Warehouse

    Mastin, L.G.

    2007-01-01

    The deposits of mafic hydromagmatic eruptions are more fine grained and variable in vesicularity than dry magmatic deposits. Blocky, equant shapes of many hydromagmatic clasts also contrast with droplet, thread, and bubble wall morphology of dry magmatic fragments. Small (glassy rinds on pyroclast surfaces as they deform within turbulent flows. This process, termed "turbulent shedding", may occur during the expansion phase of vapor explosions or during turbulent but nonexplosive mixing of magma with water, steam, or water sprays. The occurrence of turbulent shedding and the resulting fragment sizes depend on the timescale for rind growth and the timescale between disturbances that remove or disintegrate glassy rinds. Turbulent shedding is directly observable in some small littoral jets at Kilauea. Calculations suggest that, in the presence of liquid water or water sprays, glassy rinds having a thickness of microns to millimeters should form in milliseconds to seconds. This is similar to the timescale between turbulent velocity fluctuations that can shred lava globules and remove such rinds. The fraction of a deposit consisting of fine ash should increase with the duration of this process: Large-scale Surtseyan jets generate hundreds or thousands of shedding events; bubble bursts or tephra jets at Kilauea's coast may produce only a few.

  9. Microscopic theory of the glassy dynamics of passive and active network materials.

    PubMed

    Wang, Shenshen; Wolynes, Peter G

    2013-03-28

    Signatures of glassy dynamics have been identified experimentally for a rich variety of materials in which molecular networks provide rigidity. Here we present a theoretical framework to study the glassy behavior of both passive and active network materials. We construct a general microscopic network model that incorporates nonlinear elasticity of individual filaments and steric constraints due to crowding. Based on constructive analogies between structural glass forming liquids and random field Ising magnets implemented using a heterogeneous self-consistent phonon method, our scheme provides a microscopic approach to determine the mismatch surface tension and the configurational entropy, which compete in determining the barrier for structural rearrangements within the random first order transition theory of escape from a local energy minimum. The influence of crosslinking on the fragility of inorganic network glass formers is recapitulated by the model. For active network materials, the mapping, which correlates the glassy characteristics to the network architecture and properties of nonequilibrium motor processes, is shown to capture several key experimental observations on the cytoskeleton of living cells: Highly connected tense networks behave as strong glass formers; intense motor action promotes reconfiguration. The fact that our model assuming a negative motor susceptibility predicts the latter suggests that on average the motorized processes in living cells do resist the imposed mechanical load. Our calculations also identify a spinodal point where simultaneously the mismatch penalty vanishes and the mechanical stability of amorphous packing disappears.

  10. Minimum Contradiction Matrices in Whole Genome Phylogenies

    PubMed Central

    Thuillard, Marc

    2008-01-01

    Minimum contradiction matrices are a useful complement to distance-based phylogenies. A minimum contradiction matrix represents phylogenetic information under the form of an ordered distance matrix Yi, jn. A matrix element corresponds to the distance from a reference vertex n to the path (i, j). For an X-tree or a split network, the minimum contradiction matrix is a Robinson matrix. It therefore fulfills all the inequalities defining perfect order: Yi, jn ≥ Yi,kn, Yk jn ≥ Yk, In, i ≤ j ≤ k < n. In real phylogenetic data, some taxa may contradict the inequalities for perfect order. Contradictions to perfect order correspond to deviations from a tree or from a split network topology. Efficient algorithms that search for the best order are presented and tested on whole genome phylogenies with 184 taxa including many Bacteria, Archaea and Eukaryota. After optimization, taxa are classified in their correct domain and phyla. Several significant deviations from perfect order correspond to well-documented evolutionary events. PMID:19204821

  11. On polynomial preconditioning for indefinite Hermitian matrices

    NASA Technical Reports Server (NTRS)

    Freund, Roland W.

    1989-01-01

    The minimal residual method is studied combined with polynomial preconditioning for solving large linear systems (Ax = b) with indefinite Hermitian coefficient matrices (A). The standard approach for choosing the polynomial preconditioners leads to preconditioned systems which are positive definite. Here, a different strategy is studied which leaves the preconditioned coefficient matrix indefinite. More precisely, the polynomial preconditioner is designed to cluster the positive, resp. negative eigenvalues of A around 1, resp. around some negative constant. In particular, it is shown that such indefinite polynomial preconditioners can be obtained as the optimal solutions of a certain two parameter family of Chebyshev approximation problems. Some basic results are established for these approximation problems and a Remez type algorithm is sketched for their numerical solution. The problem of selecting the parameters such that the resulting indefinite polynomial preconditioners speeds up the convergence of minimal residual method optimally is also addressed. An approach is proposed based on the concept of asymptotic convergence factors. Finally, some numerical examples of indefinite polynomial preconditioners are given.

  12. Photochemistry of glycolaldehyde in cryogenic matrices

    SciTech Connect

    Chin, W. Chevalier, M.; Thon, R.; Crépin, C.; Pollet, R.

    2014-06-14

    The photochemistry of glycolaldehyde (GA) upon irradiation at 266 nm is investigated in argon, nitrogen, neon, and para-hydrogen matrices by IR spectroscopy. Isomerization and fragmentation processes are found to compete. The hydrogen-bonded Cis-Cis form of GA is transformed mainly to the open Trans-Trans conformer and to CO and CH{sub 3}OH fragments and their mixed complexes. Different photo-induced behaviours appear depending on the matrix. In nitrogen, small amounts of Trans-Gauche and Trans-Trans conformers are detected after deposition and grow together upon irradiation. The Trans-Gauche conformer is characterized for the first time. In para-hydrogen due to a weaker cage effect additional H{sub 2}CO and HCO fragments are seen. Calculations of the potential energy surfaces of S{sub 0}, S{sub 1}, and T{sub 1} states – to analyse the torsional deformations which are involved in the isomerization process – and a kinetic analysis are presented to investigate the different relaxation pathways of GA. Fragmentation of GA under UV irradiation through the CO+CH{sub 3}OH molecular channel is a minor process, as in the gas phase.

  13. Osteogenic signaling on silk-based matrices.

    PubMed

    Midha, Swati; Murab, Sumit; Ghosh, Sourabh

    2016-08-01

    Bone tissue engineering has mainly focused on generating 3D grafts to repair bone defects. However, the underlying signaling mechanisms responsible for development of such 3D bone equivalents have largely been ignored. Here we describe the crucial aspects of embryonic osteogenesis and bone development including cell sources and general signaling cascades that guide mesenchymal progenitors towards osteogenic lineage. Drawing from the knowledge of developmental biology, we then review how silk biomaterial can regulate osteogenic signaling by focusing on the expression of cell surface markers, functional genomic information (mRNA) of stem cells cultured on silk matrices. In an attempt to recapitulate exact in vivo microenvironment of osteogenesis, role of scaffold architecture and material chemistry in regulating cellular differentiation is elaborated. The generated knowledge will not only improve our understanding of cell-material interactions but reveal newer strategies beyond a conventional tissue engineering paradigm and open new prospects for developing silk-based therapies against clinically relevant bone disorders. PMID:27163625

  14. Generalized graph states based on Hadamard matrices

    SciTech Connect

    Cui, Shawn X.; Yu, Nengkun; Zeng, Bei

    2015-07-15

    Graph states are widely used in quantum information theory, including entanglement theory, quantum error correction, and one-way quantum computing. Graph states have a nice structure related to a certain graph, which is given by either a stabilizer group or an encoding circuit, both can be directly given by the graph. To generalize graph states, whose stabilizer groups are abelian subgroups of the Pauli group, one approach taken is to study non-abelian stabilizers. In this work, we propose to generalize graph states based on the encoding circuit, which is completely determined by the graph and a Hadamard matrix. We study the entanglement structures of these generalized graph states and show that they are all maximally mixed locally. We also explore the relationship between the equivalence of Hadamard matrices and local equivalence of the corresponding generalized graph states. This leads to a natural generalization of the Pauli (X, Z) pairs, which characterizes the local symmetries of these generalized graph states. Our approach is also naturally generalized to construct graph quantum codes which are beyond stabilizer codes.

  15. Occam's razor in quark mass matrices

    NASA Astrophysics Data System (ADS)

    Tanimoto, Morimitsu; Yanagida, Tsutomu T.

    2016-04-01

    From the standpoint of the Occam's razor approach, we consider the minimum number of parameters in the quark mass matrices needed for successful CKM mixing and CP violation. We impose three zeros in the down-quark mass matrix while taking the diagonal up-quark mass matrix to reduce the number of free parameters. The three zeros are maximal zeros in order to have a CP-violating phase in the quark mass matrix. Then, there remain six real parameters and one CP-violating phase, which is the minimal number needed to reproduce the observed data of the down-quark masses and the CKM parameters. Twenty textures with three zeros are examined. Among these, thirteen textures are viable for the down-quark mass matrix. As a representative of these textures, we discuss a texture Md^{(1)} in detail. By using the experimental data on sin 2β , θ _{13}, and θ _{23}, together with the observed quark masses, the Cabibbo angle is predicted to be close to the experimental data. It is found that this surprising result remains unchanged in all other viable textures. We also investigate the correlations between |V_{ub}/V_{cb}|, sin 2β , and J_CP. For all textures, the maximal value of the ratio |V_{ub}/V_{cb}| is 0.09, which is smaller than the upper bound of the experimental data, 0.094. We hope that this prediction will be tested in future experiments.

  16. Decellularized matrices for cardiovascular tissue engineering.

    PubMed

    Moroni, Francesco; Mirabella, Teodelinda

    2014-01-01

    Cardiovascular disease (CVD) is one of the leading causes of death in the Western world. The replacement of damaged vessels and valves has been practiced since the 1950's. Synthetic grafts, usually made of bio-inert materials, are long-lasting and mechanically relevant, but fail when it comes to "biointegration". Decellularized matrices, instead, can be considered biological grafts capable of stimulating in vivo migration and proliferation of endothelial cells (ECs), recruitment and differentiation of mural cells, finally, culminating in the formation of a biointegrated tissue. Decellularization protocols employ osmotic shock, ionic and non-ionic detergents, proteolitic digestions and DNase/RNase treatments; most of them effectively eliminate the cellular component, but show limitations in preserving the native structure of the extracellular matrix (ECM). In this review, we examine the current state of the art relative to decellularization techniques and biological performance of decellularized heart, valves and big vessels. Furthermore, we focus on the relevance of ECM components, native and resulting from decellularization, in mediating in vivo host response and determining repair and regeneration, as opposed to graft corruption.

  17. Partitioning sparse matrices with eigenvectors of graphs

    NASA Technical Reports Server (NTRS)

    Pothen, Alex; Simon, Horst D.; Liou, Kang-Pu

    1990-01-01

    The problem of computing a small vertex separator in a graph arises in the context of computing a good ordering for the parallel factorization of sparse, symmetric matrices. An algebraic approach for computing vertex separators is considered in this paper. It is shown that lower bounds on separator sizes can be obtained in terms of the eigenvalues of the Laplacian matrix associated with a graph. The Laplacian eigenvectors of grid graphs can be computed from Kronecker products involving the eigenvectors of path graphs, and these eigenvectors can be used to compute good separators in grid graphs. A heuristic algorithm is designed to compute a vertex separator in a general graph by first computing an edge separator in the graph from an eigenvector of the Laplacian matrix, and then using a maximum matching in a subgraph to compute the vertex separator. Results on the quality of the separators computed by the spectral algorithm are presented, and these are compared with separators obtained from other algorithms for computing separators. Finally, the time required to compute the Laplacian eigenvector is reported, and the accuracy with which the eigenvector must be computed to obtain good separators is considered. The spectral algorithm has the advantage that it can be implemented on a medium-size multiprocessor in a straightforward manner.

  18. Substituted amylose matrices for oral drug delivery

    NASA Astrophysics Data System (ADS)

    Moghadam, S. H.; Wang, H. W.; Saddar El-Leithy, E.; Chebli, C.; Cartilier, L.

    2007-03-01

    High amylose corn starch was used to obtain substituted amylose (SA) polymers by chemically modifying hydroxyl groups by an etherification process using 1,2-epoxypropanol. Tablets for drug-controlled release were prepared by direct compression and their release properties assessed by an in vitro dissolution test (USP XXIII no 2). The polymer swelling was characterized by measuring gravimetrically the water uptake ability of polymer tablets. SA hydrophilic matrix tablets present sequentially a burst effect, typical of hydrophilic matrices, and a near constant release, typical of reservoir systems. After the burst effect, surface pores disappear progressively by molecular association of amylose chains; this allows the creation of a polymer layer acting as a diffusion barrier and explains the peculiar behaviour of SA polymers. Several formulation parameters such as compression force, drug loading, tablet weight and insoluble diluent concentration were investigated. On the other hand, tablet thickness, scanning electron microscope analysis and mercury intrusion porosimetry showed that the high crushing strength values observed for SA tablets were due to an unusual melting process occurring during tabletting although the tablet external layer went only through densification, deformation and partial melting. In contrast, HPMC tablets did not show any traces of a melting process.

  19. Decellularized matrices for cardiovascular tissue engineering

    PubMed Central

    Moroni, Francesco; Mirabella, Teodelinda

    2014-01-01

    Cardiovascular disease (CVD) is one of the leading causes of death in the Western world. The replacement of damaged vessels and valves has been practiced since the 1950’s. Synthetic grafts, usually made of bio-inert materials, are long-lasting and mechanically relevant, but fail when it comes to “biointegration”. Decellularized matrices, instead, can be considered biological grafts capable of stimulating in vivo migration and proliferation of endothelial cells (ECs), recruitment and differentiation of mural cells, finally, culminating in the formation of a biointegrated tissue. Decellularization protocols employ osmotic shock, ionic and non-ionic detergents, proteolitic digestions and DNase/RNase treatments; most of them effectively eliminate the cellular component, but show limitations in preserving the native structure of the extracellular matrix (ECM). In this review, we examine the current state of the art relative to decellularization techniques and biological performance of decellularized heart, valves and big vessels. Furthermore, we focus on the relevance of ECM components, native and resulting from decellularization, in mediating in vivo host response and determining repair and regeneration, as opposed to graft corruption. PMID:24660110

  20. Random matrices as models for the statistics of quantum mechanics

    NASA Astrophysics Data System (ADS)

    Casati, Giulio; Guarneri, Italo; Mantica, Giorgio

    1986-05-01

    Random matrices from the Gaussian unitary ensemble generate in a natural way unitary groups of evolution in finite-dimensional spaces. The statistical properties of this time evolution can be investigated by studying the time autocorrelation functions of dynamical variables. We prove general results on the decay properties of such autocorrelation functions in the limit of infinite-dimensional matrices. We discuss the relevance of random matrices as models for the dynamics of quantum systems that are chaotic in the classical limit. Permanent address: Dipartimento di Fisica, Via Celoria 16, 20133 Milano, Italy.

  1. UV-laser ablation of ionic liquid matrices.

    PubMed

    Hellwig, Nils; Thrun, Alexander; Muskat, Tassilo; Grotemeyer, Jürgen

    2009-12-01

    Ionic liquid matrices are a new class of matrices used in MALDI mass spectrometry. The ablation process of several ionic liquid matrices was studied by determining the velocity distribution of ablated neutral matrix molecules. This was done by a postionization approach, where the neutrals were ionized in the ablation plume by a second laser pulse. It was found that a second, time-delayed ablation event occurs consisting completely of neutral molecules. To explain this, the reflected-shockwave model is used, which assumes that the shockwave emerging from the laser ablation is reflected at the sample holder surface. When the shockwave arrives at the sample surface it causes a second ablation.

  2. Birkhoff's Polytope and Unistochastic Matrices, N = 3 and N = 4

    NASA Astrophysics Data System (ADS)

    Bengtsson, Ingemar; Ericsson, Åsa; Kuś, Marek; Tadej, Wojciech; Życzkowski, Karol

    2005-10-01

    The set of bistochastic or doubly stochastic N×N matrices is a convex set called Birkhoff’s polytope, which we describe in some detail. Our problem is to characterize the set of unistochastic matrices as a subset of Birkhoff’s polytope. For N=3 we present fairly complete results. For N=4 partial results are obtained. An interesting difference between the two cases is that there is a ball of unistochastic matrices around the van der Waerden matrix for N=3, while this is not the case for N=4.

  3. Bunch-Kaufman factorization for real symmetric indefinite banded matrices

    NASA Technical Reports Server (NTRS)

    Jones, Mark T.; Patrick, Merrell L.

    1989-01-01

    The Bunch-Kaufman algorithm for factoring symmetric indefinite matrices was rejected for banded matrices because it destroys the banded structure of the matrix. Herein, it is shown that for a subclass of real symmetric matrices which arise in solving the generalized eigenvalue problem using Lanczos's method, the Bunch-Kaufman algorithm does not result in major destruction of the bandwidth. Space time complexities of the algorithm are given and used to show that the Bunch-Kaufman algorithm is a significant improvement over LU factorization.

  4. Effet galvanique et spectroscopie d'ionisation multiphotonique à large bande : application à l'uranium

    NASA Astrophysics Data System (ADS)

    Gagné, Jean-Marie; Babin, François

    1992-04-01

    The uranium single colour multiphoton ionization spectrum, with high laser bandwidth excitation, was measured, in the spectral range of R6G, using the fast pulsed (sim 10^{-9} s) optogalvanic signal generated by photoionization in the dark space of a hollow cathode discharge. Results indicate that this spectrum is dense in the 570 to 610 nm spectral range. A list of the 74 most intense lines is given. The results of a try at explaining these lines by a three photon resonant or quasi-resonant scheme, using know levels of uranium, are presented. The multiphoton ionization line at 591.54 nm is a special case which is discussed more thoroughly. Grâce à l'effet optogalvanique pulsé rapide (sim 10^{-9} s) généré par la photoionisation dans l'espace sombre d'une décharge en régime cathode creuse, le spectre d'ionisation multiphotonique à large bande de l'uranium, dans le domaine spectral de la rhodamine 6G, a été mesuré. Les résultats indiquent que pour cette bande spectrale du laser, comprise entre 570 et 610 nm, ce spectre optogalvanique d'ionisation multiphotonique est très riche. Une liste de 74 raies photoioniques les plus significatives est présentée. Les résultats préliminaires d'une étude pour expliquer la présence de ces raies, en utilisant des schémas d'ionisation à trois photons résonnants ou quasi-résonnants, à partir d'une liste de niveaux publiés, sont également présentés. La raie d'ionisation associée à la longueur d'oride 591,54 nm est un cas spécial qui est discuté plus longuement.

  5. P03-based precession-nutation matrices

    NASA Astrophysics Data System (ADS)

    Wallace, P.; Capitaine, N.

    2006-10-01

    The IAU WG on precession and the ecliptic has recommended the adoption of the P03 models of Capitaine et al. (2003). We discuss methods for generating the rotation matrices that transform celestial to terrestrial coordinates, taking into account frame bias (B), P03 precession (P), P03-adjusted IAU 2000A nutation (N) and Earth rotation. The NPB portion can refer either to the equinox or the celestial intermediate origin (CIO), requiring either the Greenwich sidereal time (GST) or the Earth rotation angle (ERA) as the measure of Earth rotation. The equinox based NPB transformation can be formed using various sequences of rotations, while the CIO based transformation can be formed using series for the X, Y coordinates of the celestial intermediate pole (CIP) and for the CIO locator s; also, either matrix can be computing using series for the x, y, z components of the "rotation vector". Common to both methods is the CIP, which forms the bottom row of the transformation matrix. In the case of the CIO based transformation, the CIO is the top row of the NPB matrix, whereas in the equinox based case it enters via the GST formulation in the form of the equation of the origins (EO). The EO is the difference between ERA and GST and equivalently the distance between the CIO and equinox. The choice of method is dictated by considerations of internal consistency, flexibility and ease of use; the different ways agree at the level of a few microarcseconds over several centuries, and consume similar computing resources.

  6. Comparison of eigensolvers for symmetric band matrices

    PubMed Central

    Moldaschl, Michael; Gansterer, Wilfried N.

    2014-01-01

    We compare different algorithms for computing eigenvalues and eigenvectors of a symmetric band matrix across a wide range of synthetic test problems. Of particular interest is a comparison of state-of-the-art tridiagonalization-based methods as implemented in Lapack or Plasma on the one hand, and the block divide-and-conquer (BD&C) algorithm as well as the block twisted factorization (BTF) method on the other hand. The BD&C algorithm does not require tridiagonalization of the original band matrix at all, and the current version of the BTF method tridiagonalizes the original band matrix only for computing the eigenvalues. Avoiding the tridiagonalization process sidesteps the cost of backtransformation of the eigenvectors. Beyond that, we discovered another disadvantage of the backtransformation process for band matrices: In several scenarios, a lot of gradual underflow is observed in the (optional) accumulation of the transformation matrix and in the (obligatory) backtransformation step. According to the IEEE 754 standard for floating-point arithmetic, this implies many operations with subnormal (denormalized) numbers, which causes severe slowdowns compared to the other algorithms without backtransformation of the eigenvectors. We illustrate that in these cases the performance of existing methods from Lapack and Plasma reaches a competitive level only if subnormal numbers are disabled (and thus the IEEE standard is violated). Overall, our performance studies illustrate that if the problem size is large enough relative to the bandwidth, BD&C tends to achieve the highest performance of all methods if the spectrum to be computed is clustered. For test problems with well separated eigenvalues, the BTF method tends to become the fastest algorithm with growing problem size. PMID:26594079

  7. Invariant functions for the Lyapunov exponents of random matrices

    SciTech Connect

    Protasov, Vladimir Yu

    2011-01-31

    A new approach to the study of Lyapunov exponents of random matrices is presented. We prove that any family of nonnegative (dxd)-matrices has a continuous concave invariant functional on R{sup d}{sub +}. Under some standard assumptions on the matrices, this functional is strictly positive, and the coefficient corresponding to it is equal to the largest Lyapunov exponent. As a corollary we obtain asymptotics for the expected value of the logarithm of norms of matrix products and of their spectral radii. Another corollary gives new upper and lower bounds for the Lyapunov exponent, and an algorithm for computing it for families of nonnegative matrices. We consider possible extensions of our results to general nonnegative matrix families and present several applications and examples. Bibliography: 29 titles.

  8. Performance Properties of Graphite Reinforced Composites with Advanced Resin Matrices

    NASA Technical Reports Server (NTRS)

    Kourtides, Demetrius A.

    1980-01-01

    This article looks at the effect of different resin matrices on thermal and mechanical properties of graphite composites, and relates the thermal and flammability properties to the anaerobic char yield of the resins. The processing parameters of graphite composites utilizing graphite fabric and epoxy or other advanced resins as matrices are presented. Thermoset resin matrices studied were: aminecured polyfunctional glycidyl aminetype epoxy (baseline), phenolicnovolac resin based on condensation of dihydroxymethyl-xylene and phenol cured with hexamine, two types of polydismaleimide resins, phenolic resin, and benzyl resin. The thermoplastic matrices studied were polyethersulfone and polyphenylenesulfone. Properties evaluated in the study included anaerobic char yield, limiting oxygen index, smoke evolution, moisture absorption, and mechanical properties at elevated temperatures including tensile, compressive, and short-beam shear strengths. Generally, it was determined that graphite composites with the highest char yield exhibited optimum fire-resistant properties.

  9. Synbiotic matrices derived from plant oligosaccharides and polysaccharides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A porous synbiotic matrix was prepared by lyophilization of alginate and pectin or fructan oligosaccharides and polysaccharides cross-linked with calcium. These synbiotic matrices were excellent physical structures to support the growth of Lactobacillus acidophilus (1426) and Lactobacillus reuteri (...

  10. Portal frame inertia and stiffness matrices by substructure synthesis

    NASA Astrophysics Data System (ADS)

    Morales, C. A.

    2005-05-01

    Generic expressions of mass and stiffness matrices of the portal frame are presented. These are derived by means of the substructure synthesis method. This method is exceptionally characterised by low-order eigenvalue problems and highly accurate eigensolutions.

  11. Systems of Differential Equations with Skew-Symmetric, Orthogonal Matrices

    ERIC Educational Resources Information Center

    Glaister, P.

    2008-01-01

    The solution of a system of linear, inhomogeneous differential equations is discussed. The particular class considered is where the coefficient matrix is skew-symmetric and orthogonal, and where the forcing terms are sinusoidal. More general matrices are also considered.

  12. ALGORITHM FOR THE EVALUATION OF REDUCED WIGNER MATRICES

    SciTech Connect

    Prezeau, G.; Reinecke, M.

    2010-10-15

    Algorithms for the fast and exact computation of Wigner matrices are described and their application to a fast and massively parallel 4{pi} convolution code between a beam and a sky is also presented.

  13. Separation of traces of metal ions from sodium matrices

    NASA Technical Reports Server (NTRS)

    Korkisch, J.; Orlandini, K. A.

    1969-01-01

    Method for isolating metal ion traces from sodium matrices consists of two extractions and an ion exchange step. Extraction is accomplished by using 2-thenoyltrifluoracetone and dithizone followed by cation exchange.

  14. Plasticizing effect of ibuprofen induced an alteration of drug released from Kollidon SR matrices produced by direct compression.

    PubMed

    Wiranidchapong, Chutima; Ruangpayungsak, Nuchnan; Suwattanasuk, Pattaraporn; Shuwisitkul, Duangratana; Tanvichien, Sujimon

    2015-06-01

    The objectives of this study were to investigate the effect of storage temperature on drug release from matrices containing 10, 40 and 70% w/w ibuprofen in Kollidon® SR (KSR). The matrix tablets were produced by direct compression and then kept at 30 and 45 °C for 3 months. Drug release from the matrix tablets was examined after storage for 0, 1, 4 and 12 weeks. Scanning electron microscope was used to reveal physical appearance of the tablet surface at the respective time intervals. In addition, differential scanning calorimeter was used to investigate glass transition temperature (Tg) of ibuprofen in KSR at 0-100% w/w based on the principle of Gordon-Taylor equation. At 45 °C, the dissolution of ibuprofen in KSR as well as the coalescence of polymer particles were observed to be higher than those of storage at 30 °C. The physical state of ibuprofen dispersed in the polymeric matrix and degree of polymer coalescence led to the variation of drug release. The coalescence of polymer particles was a result of the polymer transition from glassy to rubbery state according to water absorption of KSR and plasticizing effect of ibuprofen. The reduction of the Tg of ibuprofen blended with KSR could be better described by the Kwei equation, a modified version of Gordon-Taylor equation.

  15. Estimating soil matric potential in Owens Valley, California

    USGS Publications Warehouse

    Sorenson, Stephen K.; Miller, R.F.; Welch, M.R.; Groeneveld, D.P.; Branson, F.A.

    1988-01-01

    Much of the floor of the Owens Valley, California, is covered with alkaline scrub and alkaline meadow plant communities, whose existence is dependent partly on precipitation and partly on water infiltrated into the rooting zone from the shallow water table. The extent to which these plant communities are capable of adapting to and surviving fluctuations in the water table depends on physiological adaptations of the plants and on the water content, matric potential characteristics of the soils. Two methods were used to estimate soil matric potential in test sites in Owens Valley. The first was the filter-paper method, which uses water content of filter papers equilibrated to water content of soil samples taken with a hand auger. The other method of estimating soil matric potential was a modeling approach based on data from this and previous investigations. These data indicate that the base 10 logarithm of soil matric potential is a linear function of gravimetric soil water content for a particular soil. Estimates of soil water characteristic curves were made at two sites by averaging the gravimetric soil water content and soil matric potential values from multiple samples at 0.1 m depths derived by using the hand auger and filter paper method and entering these values in the soil water model. The characteristic curves then were used to estimate soil matric potential from estimates of volumetric soil water content derived from neutron-probe readings. Evaluation of the modeling technique at two study sites indicated that estimates of soil matric potential within 0.5 pF units of the soil matric potential value derived by using the filter paper method could be obtained 90 to 95% of the time in soils where water content was less than field capacity. The greatest errors occurred at depths where there was a distinct transition between soils of different textures. (Lantz-PTT)

  16. Boundary transfer matrices and boundary quantum KZ equations

    SciTech Connect

    Vlaar, Bart

    2015-07-15

    A simple relation between inhomogeneous transfer matrices and boundary quantum Knizhnik-Zamolodchikov (KZ) equations is exhibited for quantum integrable systems with reflecting boundary conditions, analogous to an observation by Gaudin for periodic systems. Thus, the boundary quantum KZ equations receive a new motivation. We also derive the commutativity of Sklyanin’s boundary transfer matrices by merely imposing appropriate reflection equations, in particular without using the conditions of crossing symmetry and unitarity of the R-matrix.

  17. On Fluctuations of Eigenvalues of Random Band Matrices

    NASA Astrophysics Data System (ADS)

    Shcherbina, M.

    2015-10-01

    We consider the fluctuations of linear eigenvalue statistics of random band matrices whose entries have the form with i.i.d. possessing the th moment, where the function u has a finite support , so that M has only nonzero diagonals. The parameter b (called the bandwidth) is assumed to grow with n in a way such that . Without any additional assumptions on the growth of b we prove CLT for linear eigenvalue statistics for a rather wide class of test functions. Thus we improve and generalize the results of the previous papers (Jana et al., arXiv:1412.2445; Li et al. Random Matrices 2:04, 2013), where CLT was proven under the assumption . Moreover, we develop a method which allows to prove automatically the CLT for linear eigenvalue statistics of the smooth test functions for almost all classical models of random matrix theory: deformed Wigner and sample covariance matrices, sparse matrices, diluted random matrices, matrices with heavy tales etc.

  18. Effet de la composition des materiaux composites sur la caracterisation et detection par ondes de Lamb

    NASA Astrophysics Data System (ADS)

    Ostiguy, Pierre-Claude

    Les matériaux composites sont de plus en plus utilisés en aéronautique. Leurs excellentes propriétés mécaniques et leur faible poids leur procurent un avantage certain par rapport aux matériaux métalliques. Ceux-ci étant soumis à diverses conditions de chargement et environnementales, ils sont suceptibles de subir plusieurs types d'endommagements, compromettant leur intégrité. Des méthodes fiables d'inspection sont donc nécessaires pour évaluer leur intégrité. Néanmoins, peu d'approches non destructives, embarquées et efficaces sont présentement utilisées. Ce travail de recherche se penche sur l'étude de l'effet de la composition des matériaux composites sur la détection et la caractérisation par ondes guidées. L'objectif du projet est de développer une approche de caractérisation mécanique embarquée permettant d'améliorer la performance d'une approche d'imagerie par antenne piézoélectriques sur des structures composite et métalliques. La contribution de ce projet est de proposer une approche embarquée de caractérisation mécanique par ultrasons qui ne requiert pas une mesure sur une multitude d'échantillons et qui est non destructive. Ce mémoire par articles est divisé en quatre parties, dont les parties deux A quatre présentant les articles publiés et soumis. La première partie présente l'état des connaissances dans la matière nécessaires à l'acomplissement de ce projet de maîtrise. Les principaux sujets traités portent sur les matériaux composites, propagation d'ondes, la modélisation des ondes guidées, la caractérisation par ondes guidées et la surveillance embarquée des structures. La deuxième partie présente une étude de l'effet des propriétés mécaniques sur la performance de l'algorithme d'imagerie Excitelet. L'étude est faite sur une structure isotrope. Les résultats ont démontré que l'algorithme est sensible à l'exactitude des propriétés mécaniques utilisées dans le modèle. Cette

  19. Laser micromilling of convex microfluidic channels onto glassy carbon for glass molding dies

    NASA Astrophysics Data System (ADS)

    Tseng, Shih-Feng; Chen, Ming-Fei; Hsiao, Wen-Tse; Huang, Chien-Yao; Yang, Chung-Heng; Chen, Yu-Sheng

    2014-06-01

    This study reports the fabrication of convex microfluidic channels on glassy carbon using an ultraviolet laser processing system to produce glass molding dies. The laser processing parameters, including various laser fluences and scanning speeds of galvanometers, were adjusted to mill a convex microchannel on a glassy carbon substrate to identify the effects of material removal. The machined glassy carbon substrate was then applied as a glass molding die to fabricate a glass-based microfluidic biochip. The surface morphology, milled width and depth, and surface roughness of the microchannel die after laser micromilling were examined using a three-dimensional confocal laser scanning microscope. This study also investigates the transcription rate of microchannels after the glass molding process. To produce a 180 μm high microchannel on the GC substrate, the optimal number of milled cycles, laser fluence, and scanning speed were 25, 4.9 J/cm2, and 200 mm/s, respectively. The width, height, and surface roughness of milled convex microchannels were 119.6±0.217 μm, 180.26±0.01 μm, and 0.672±0.08 μm, respectively. These measured values were close to the predicted values and suitable for a glass molding die. After the glass molding process, a typical glass-based microchannel chip was formed at a molding temperature of 660 °C and the molding force of 0.45 kN. The transcription rates of the microchannel width and depth were 100% and 99.6%, respectively. Thus, the proposed approach is suitable for performing in chemical, biochemical, or medical reactions.

  20. Methyl group dynamics in glassy, polycrystalline, and liquid coenzyme Q10 studied by quasielastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Smuda, Christoph; Busch, Sebastian; Wagner, Bernd; Unruh, Tobias

    2008-08-01

    The methyl group rotation of coenzyme Q10 confined in nanosized droplets was studied using quasielastic neutron scattering (QENS). Q10 as an oligoisoprene derivative with ten isoprene units can easily be supercooled in nanodroplets. Fixed window scans and QENS spectra at several temperatures of glassy Q10 were recorded to study the methyl group rotation which can be described by a logarithmic Gaussian distribution of hopping rates for temperatures below the glass transition temperature (Tg~200 K). A mean activation energy of 4.8 kJ/mol with a distribution width of 2.1 kJ/mol was obtained from the evaluation of the QENS spectra. A corresponding analysis of a fixed window scan yielded an average activation energy of 5.1 kJ/mol with a distribution width of 1.8 kJ/mol. The results are compared and discussed with those of chain deuterated polyisoprene-d5. For polycrystalline Q10, the QENS spectra could be described by the same model yielding a similar average activation energy as found for glassy Q10. However, no temperature dependence of the distribution width was observed. Based on the performed low-temperature measurements, the correlation times for the methyl group rotation were extrapolated to temperatures of liquid Q10. The complex dynamics of liquid Q10 could be described by a model yielding an apparent diffusion coefficient, the jump rate of the methyl groups, as well as an overall molecular rotational diffusion coefficient. The correlation times of the methyl group rotation in liquid Q10 at a given temperature T0 coincide with values determined in the glassy phase and extrapolated to T0.

  1. Inorganic Nanoparticle Nucleation on Polymer Matrices

    NASA Astrophysics Data System (ADS)

    Kosteleski, Adrian John

    dressing applications. PAA's ability to nucleate nanoparticles in a solid matrix was displayed. Interestingly enough PAA retains its ability to nucleate nanoparticle even when its reactive functional groups are used in the crosslinking process. Silver nanoparticle composition and size on the solid polymer matrices was controlled by varying the composition of PAA. PAA and silver nanoparticles effect on the mechanical properties of the calcium alginate hydrogels were also studied. Physically crosslinking PAA with calcium alginate gels enables the development of intricate gel structures that are decorated with nucleated silver; yielding a composite biomaterial with improved and enhanced antimicrobial properties.

  2. Crystalline Colloidal Arrays in Polymer Matrices

    NASA Technical Reports Server (NTRS)

    Sunkara, Hari B.; Penn, B. G.; Frazier, D. O.; Ramachandran, N.

    1997-01-01

    matrices, the factors which affect the optical diffraction qualities of resulting polymer films, and methods to improve the efficiencies of solid optical filters. Before this, we also present the experimental demonstration, of controlling the optical diffraction intensities from aqueous CCA dispersions by varying the temperature, which establishes the feasibility of fabricating all-optical switching devices with nonlinear periodic array structures.

  3. Estimated correlation matrices and portfolio optimization

    NASA Astrophysics Data System (ADS)

    Pafka, Szilárd; Kondor, Imre

    2004-11-01

    Correlations of returns on various assets play a central role in financial theory and also in many practical applications. From a theoretical point of view, the main interest lies in the proper description of the structure and dynamics of correlations, whereas for the practitioner the emphasis is on the ability of the models to provide adequate inputs for the numerous portfolio and risk management procedures used in the financial industry. The theory of portfolios, initiated by Markowitz, has suffered from the “curse of dimensions” from the very outset. Over the past decades a large number of different techniques have been developed to tackle this problem and reduce the effective dimension of large bank portfolios, but the efficiency and reliability of these procedures are extremely hard to assess or compare. In this paper, we propose a model (simulation)-based approach which can be used for the systematical testing of all these dimensional reduction techniques. To illustrate the usefulness of our framework, we develop several toy models that display some of the main characteristic features of empirical correlations and generate artificial time series from them. Then, we regard these time series as empirical data and reconstruct the corresponding correlation matrices which will inevitably contain a certain amount of noise, due to the finiteness of the time series. Next, we apply several correlation matrix estimators and dimension reduction techniques introduced in the literature and/or applied in practice. As in our artificial world the only source of error is the finite length of the time series and, in addition, the “true” model, hence also the “true” correlation matrix, are precisely known, therefore in sharp contrast with empirical studies, we can precisely compare the performance of the various noise reduction techniques. One of our recurrent observations is that the recently introduced filtering technique based on random matrix theory performs

  4. Permanent photoalignment of liquid crystals on nanostructured chalcogenide glassy thin films

    SciTech Connect

    Gelbaor, Miri; Abdulhalim, I.; Klebanov, Matvey; Lyubin, Victor

    2011-02-14

    Photoalignment of nematic liquid crystals is obtained on the chalcogenide glassy thin film of As{sub 2}S{sub 3} using irradiation with polarized blue light. A uniform homogeneously aligned device is obtained with high contrast and strong anchoring. The device alignment quality is permanent as checked by following its functionality over a period of few months. The origin of the observed photoalignment is attributed to the photoinduced anisotropy in chalcogenide glasses. No differences between the different As{sub 2}S{sub 3} film thicknesses observed, thus supporting the proposition that some orientational order is photoinduced on the surface of the glass and responsible for the photoalignment.

  5. A study on oxidized glassy carbon sheets for bipolar supercapacitor electrodes

    SciTech Connect

    Braun, A.; Baertsch, M.; Geiger, F.

    2000-07-01

    Electrochemical Double Layer Capacitors (EDLC) for high energy and power density applications, based on glassy carbon (GC) electrodes, are being developed in this laboratory. In the context of this project, GC sheets were oxidized and investigated with Small Angle X-ray Scattering (SAXS), Electrochemical Impedance Spectroscopy (EIS) and Nitrogen Gas Adsorption (BET). During oxidation on active film with open pores is built on the surface of the GC. Upon oxidation, the internal volumetric surface area of the active film decreases, whereas the volumetric electrochemical double layer capacitance increases. The authors show that this effect is correlated with the opening, the growth and the coalescence of the pores.

  6. Simple Model for the Deformation-Induced Relaxation of Glassy Polymers

    NASA Astrophysics Data System (ADS)

    Fielding, S. M.; Larson, R. G.; Cates, M. E.

    2012-01-01

    Glassy polymers show “strain hardening”: at constant extensional load, their flow first accelerates, then arrests. Recent experiments have found this to be accompanied by a striking and unexplained dip in the segmental relaxation time. Here we explain such behavior by combining a minimal model of flow-induced liquefaction of a glass with a description of the stress carried by strained polymers, creating a nonfactorable interplay between aging and strain-induced rejuvenation. Under constant load, liquefaction of segmental motion permits strong flow that creates polymer-borne stress. This slows the deformation enough for the segmental modes to revitrify, causing strain hardening.

  7. High-frequency collective excitations in molten and glassy Te studied by inelastic neutron scattering

    SciTech Connect

    Ruiz-Martin, M. D.; Jimenez-Ruiz, M.; Bermejo, F. J.

    2006-03-01

    The spectra of collective excitations of liquid and glassy tellurium have been studied by means of inelastic neutron scattering. Here we report on the dynamics of liquid Te as measured at two different temperatures, just above melting (T{sub m}=723 K) and at {approx}1000 K as well as the glass that is studied at room temperature. Estimates for the velocity of propagating excitations for both temperatures have been obtained from the experimental data, and a contrasting behavior is found with respect to anomalies shown by the adiabatic sound velocity measured by ultrasound methods. The origin of such differences is finally discussed.

  8. Non-Gaussian nature of glassy dynamics by cage to cage motion

    SciTech Connect

    Vorselaars, Bart; Lyulin, Alexey V.; Michels, M. A. J.; Karatasos, K.

    2007-01-15

    A model based on a single Brownian particle moving in a periodic effective field is used to understand the non-Gaussian dynamics in glassy systems of cage escape and subsequent recaging, often thought to be caused by a heterogeneous glass structure. The results are compared to molecular-dynamics simulations of systems with varying complexity: quasi-two-dimensional colloidlike particles, atactic polystyrene, and a dendritic glass. The model nicely describes generic features of all three topologically different systems, in particular around the maximum of the non-Gaussian parameter. This maximum is a measure for the average distance between cages.

  9. Transmission of phage by glassy-winged sharpshooters, a vector of Xylella fastidiosa

    PubMed Central

    Bhowmick, Tushar Suvra; Das, Mayukh; Heinz, Kevin M.; Krauter, Peter C.; Gonzalez, Carlos F.

    2016-01-01

    ABSTRACT Xylella fastidiosa subsp. fastidiosa (Xff) is the causal agent of Pierce's Disease (PD) of grapevines and is vectored by the glassy-winged sharpshooter (GWSS, Homalodisca vitripennis). Previously we have reported the development of a bacteriophage (phage) based biocontrol system for PD, but no information on insect transmission of phages has been reported. Here we communicate that laboratory reared GWSSs fed on cowpea plants (Vigna unguiculata subsp. unguiculata) harboring the virulent phage Paz were able to uptake of phage efficiently when the phage was present in high concentration, but were inefficient in transfer to plants. PMID:27738554

  10. Dielectric relaxation studies in Se90Cd8Sb2 glassy alloy

    NASA Astrophysics Data System (ADS)

    Shukla, Nitesh; Rao, Vandita; Dwivedi, D. K.

    2016-05-01

    Se90Cd8Sb2 chalcogenide semiconducting alloy was prepared by melt quench technique. The prepared glassy alloy has been characterized by techniques such as scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX).Dielectric properties of Se90Cd8Sb2 chalcogenide semiconductor have been studied using impedance spectroscopic technique in the frequency range 5×102Hz - 1×105Hz and in temperature range 303-318K. It is found that dielectric constant ɛ' and dielectric loss factor ɛ″ are dependent on frequency and temperature.

  11. Geographic distribution and relative abundance of the invasive glassy-winged sharpshooter: effects of temperature and egg parasitoids.

    PubMed

    Gutierrez, Andrew Paul; Ponti, Luigi; Hoddle, Mark; Almeida, Rodrigo P P; Irvin, Nicola A

    2011-08-01

    The capacity to predict the geographic distribution and relative abundance of invasive species is pivotal to developing policy for eradication or control and management. Commonly used methods fall under the ambit of ecological niche models (ENMs). These methods were reviewed and shortcomings identified. Weather-driven physiologically based demographic models (PBDMs) are proposed that resolve many of the deficiencies of ENMs. The PBDM approach is used to analyze the invasiveness of the polyphagous glassy-winged sharpshooter (Homalodisca vitripennis [Germar]), a pest native to the southeastern United States and northeastern Mexico that extended its range into California in 1989. Glassy-winged sharpshooter vectors the pathogenic bacterium, Xylella fastidiosa (Wells) that causes Pierce's disease in grape and scorch-like diseases in other plants. PBDMs for glassy-winged sharpshooter and its egg parasitoids (Gonatocerus ashmeadi Girault and G. triguttatus Girault) were developed and linked to a PBDM for grape published by Wermelinger et al. (1991). Daily weather data from 108 locations across California for the period 1995-2006 were used to drive the PBDM system, and GRASS GIS was used to map the simulation results. The geographic distribution of glassy-winged sharpshooter, as observed, is predicted to be largely restricted to the warm areas of southern California, with the action of the two egg parasitoids reducing its abundance >90%. The average indispensable mortality contributed by G. triguttatus is <1%. A temperature-dependent developmental rate model for X. fastidiosa was developed that suggests its geographic range is also limited to the warm inland areas of southern California. Biological control of glassy-winged sharpshooter further decreases the pathogen's relative range. Climate warming scenarios of +2°C and +3°C suggest that the distribution and severity of glassy-winged sharpshooter and X. fastidiosa will increase in the agriculturally rich central valley

  12. Définir les choix à risque: l'éthique et les effets des décisions organisationnelles.

    PubMed

    Warren, Marika

    2016-07-01

    Les choix de vivre « à risque » sont complexes et difficiles. Ils peuvent être structurés par les politiques organisationnelles. Certaines personnes veulent vraiment vivre dans des situations à haut risque ou perçues comme telles parce qu'elles en tirent un avantage important. Cependant, il est probable que ces choix dépendent en grande partie du contexte et qu'ils ne se soient pas posés dans une autre situation. L'article plaide pour la responsabilité d'être attentif aux effets des décisions organisationnelles sur les choix de vivre à risque et sur la répartition globale du risque.

  13. Randomized Algorithms for Matrices and Data

    NASA Astrophysics Data System (ADS)

    Mahoney, Michael W.

    2012-03-01

    This chapter reviews recent work on randomized matrix algorithms. By “randomized matrix algorithms,” we refer to a class of recently developed random sampling and random projection algorithms for ubiquitous linear algebra problems such as least-squares (LS) regression and low-rank matrix approximation. These developments have been driven by applications in large-scale data analysis—applications which place very different demands on matrices than traditional scientific computing applications. Thus, in this review, we will focus on highlighting the simplicity and generality of several core ideas that underlie the usefulness of these randomized algorithms in scientific applications such as genetics (where these algorithms have already been applied) and astronomy (where, hopefully, in part due to this review they will soon be applied). The work we will review here had its origins within theoretical computer science (TCS). An important feature in the use of randomized algorithms in TCS more generally is that one must identify and then algorithmically deal with relevant “nonuniformity structure” in the data. For the randomized matrix algorithms to be reviewed here and that have proven useful recently in numerical linear algebra (NLA) and large-scale data analysis applications, the relevant nonuniformity structure is defined by the so-called statistical leverage scores. Defined more precisely below, these leverage scores are basically the diagonal elements of the projection matrix onto the dominant part of the spectrum of the input matrix. As such, they have a long history in statistical data analysis, where they have been used for outlier detection in regression diagnostics. More generally, these scores often have a very natural interpretation in terms of the data and processes generating the data. For example, they can be interpreted in terms of the leverage or influence that a given data point has on, say, the best low-rank matrix approximation; and this

  14. Estimating soil matric potential in Owens Valley, California

    USGS Publications Warehouse

    Sorenson, Stephen K.; Miller, Reuben F.; Welch, Michael R.; Groeneveld, David P.; Branson, Farrel A.

    1989-01-01

    Much of the floor of Owens Valley, California, is covered with alkaline scrub and alkaline meadow plant communities, whose existence is dependent partly on precipitation and partly on water infiltrated into the rooting zone from the shallow water table. The extent to which these plant communities are capable of adapting to and surviving fluctuations in the water table depends on physiological adaptations of the plants and on the water content, matric potential characteristics of the soils. Two methods were used to estimate soil matric potential in test sites in Owens Valley. The first, the filter-paper method, uses water content of filter papers equilibrated to water content of soil samples taken with a hand auger. The previously published calibration relations used to estimate soil matric potential from the water content of the filter papers were modified on the basis of current laboratory data. The other method of estimating soil matric potential was a modeling approach based on data from this and previous investigations. These data indicate that the base-10 logarithm of soil matric potential is a linear function of gravimetric soil water content for a particular soil. The slope and intercepts of this function vary with the texture and saturation capacity of the soil. Estimates of soil water characteristic curves were made at two sites by averaging the gravimetric soil water content and soil matric potential values from multiple samples at 0.1-m depth intervals derived by using the hand auger and filter-paper method and entering these values in the soil water model. The characteristic curves then were used to estimate soil matric potential from estimates of volumetric soil water content derived from neutron-probe readings. Evaluation of the modeling technique at two study sites indicated that estimates of soil matric potential within 0.5 pF units of the soil matric potential value derived by using the filter-paper method could be obtained 90 to 95 percent of the

  15. Diazonium Chemistry for the Bio-Functionalization of Glassy Nanostring Resonator Arrays

    PubMed Central

    Zheng, Wei; Du, Rongbing; Cao, Yong; Mohammad, Mohammad A.; Dew, Steven K.; McDermott, Mark T.; Evoy, Stephane

    2015-01-01

    Resonant glassy nanostrings have been employed for the detection of biomolecules. These devices offer high sensitivity and amenability to large array integration and multiplexed assays. Such a concept has however been impaired by the lack of stable and biocompatible linker chemistries. Diazonium salt reduction-induced aryl grafting is an aqueous-based process providing strong chemical adhesion. In this work, diazonium-based linker chemistry was performed for the first time on glassy nanostrings, which enabled the bio-functionalization of such devices. Large arrays of nanostrings with ultra-narrow widths down to 10 nm were fabricated employing electron beam lithography. Diazonium modification was first developed on SiCN surfaces and validated by X-ray photoelectron spectroscopy. Similarly modified nanostrings were then covalently functionalized with anti-rabbit IgG as a molecular probe. Specific enumeration of rabbit IgG was successfully performed through observation of downshifts of resonant frequencies. The specificity of this enumeration was confirmed through proper negative control experiments. Helium ion microscopy further verified the successful functionalization of nanostrings. PMID:26263989

  16. Comparing the mechanism of water condensation and evaporation in glassy aerosol

    PubMed Central

    Bones, David L.; Reid, Jonathan P.; Lienhard, Daniel M.; Krieger, Ulrich K.

    2012-01-01

    Atmospheric models generally assume that aerosol particles are in equilibrium with the surrounding gas phase. However, recent observations that secondary organic aerosols can exist in a glassy state have highlighted the need to more fully understand the kinetic limitations that may control water partitioning in ambient particles. Here, we explore the influence of slow water diffusion in the condensed aerosol phase on the rates of both condensation and evaporation, demonstrating that significant inhibition in mass transfer occurs for ultraviscous aerosol, not just for glassy aerosol. Using coarse mode (3–4 um radius) ternary sucrose/sodium chloride/aqueous droplets as a proxy for multicomponent ambient aerosol, we demonstrate that the timescale for particle equilibration correlates with bulk viscosity and can be ≫103 s. Extrapolation of these timescales to particle sizes in the accumulation mode (e.g., approximately 100 nm) by applying the Stokes-Einstein equation suggests that the kinetic limitations imposed on mass transfer of water by slow bulk phase diffusion must be more fully investigated for atmospheric aerosol. Measurements have been made on particles covering a range in dynamic viscosity from < 0.1 to > 1013 Pa s. We also retrieve the radial inhomogeneities apparent in particle composition during condensation and evaporation and contrast the dynamics of slow dissolution of a viscous core into a labile shell during condensation with the slow percolation of water during evaporation through a more homogeneous viscous particle bulk. PMID:22753520

  17. Molecular dynamics simulation of rupture in glassy polymer bridges within filler aggregates

    NASA Astrophysics Data System (ADS)

    Froltsov, Vladimir A.; Klüppel, Manfred; Raos, Guido

    2012-10-01

    We present a series of nonequilibrium molecular dynamics simulations, investigating the rupture mechanisms in glassy polymer films confined between two solid surfaces. Such systems provide a useful model for the strong nonlinear reinforcement of rubber by colloidal filler particles. Depending on the degree of confinement three qualitatively different rupture modes have been found, which originate from the interplay of internal (polymer-polymer) and external (polymer-wall) interactions. In very thin films we observe the formation and stretching of many single-chain bridges between the confining surfaces. Progressing to thicker samples we observe fewer bridges, consisting of bundled polymer chains, and eventually just one large bridge in thick specimens. The yield stress and the elongational modulus of the polymer films have been calculated from the stress-strain curves at various temperatures and confinements and their behavior has been analyzed in terms of polymer-polymer and polymer-surface interaction energies. The thinnest films (5 monomer diameters) are always glassy in our simulations, while the others display a glass transition temperature around 0.50-0.55 (in units ɛ0/kB of the Lennard-Jones interaction energy), depending on their thickness. This range of values, which has been determined using both the nonequilibrium tensile simulations and equilibrium diffusion data, agrees with the transition temperature previously found by shear simulations [Baljon and Robbins, ScienceSCIEAS0036-807510.1126/science.271.5248.482 271, 482 (1996)].

  18. Analyzing aging under oscillatory strain field through the soft glassy rheology model.

    PubMed

    Kaushal, Manish; Joshi, Yogesh M

    2016-06-28

    In this work, we solve the Soft Glassy Rheology (SGR) model under application of oscillatory deformation field with varying magnitudes of strain as well as frequency for different noise temperatures. In the glassy domain, the SGR model undergoes time evolution of elastic modulus. Increase in strain magnitude beyond the linear regime is observed to enhance the rate of aging as manifested by a faster evolution of elastic modulus with increase in strain amplitude due to overaging. However at higher strain magnitudes, the rejuvenation effect starts dominating over the aging, thereby reducing the rate at which elastic modulus evolves. We also plot the aging phase diagram describing an occurrence of the linear, the overaging, and the rejuvenation regimes as a function of strain and frequency for different noise temperatures. The aging phase diagram suggests that while the linear regime remains unaffected by the changes in frequency and noise temperature, the width of the overaging regime increases with increase in frequency and noise temperature. We also study the time evolution of the shapes of relaxation time spectra as a function of strain amplitude, which renders further insight into the overaging and the rejuvenation behavior. While the phenomenon of overaging is observed to be an inherent character of the SGR model, experimentally not all the materials demonstrate overaging. Such a discrepancy suggests that the energy well depths before and after a yielding event may not be completely uncorrelated as assumed in the SGR formalism. PMID:27369524

  19. Multilevel micro-structuring of glassy carbon for precision glass molding of diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Plöger, Sven; Hermerschmidt, Andreas

    2015-03-01

    A consumer market for diffractive optical elements in glass can only be created if high efficient elements are available at affordable prices. In diffractive optics the efficiency and optical properties increases with the number of levels used, but in the same way the costs are multiplied by the number if fabrication steps. Replication of multilevel diffractive optical elements in glass would allow cost efficient fabrication but a suitable mold material is needed. Glassy carbon shows a high mechanical strength, thermal stability and non-sticking adhesion properties, which makes it an excellent candidate as mold material for precision compression molding of low and high glass-transition temperature materials. We introduce an 8 level micro structuring process for glassy carbon molds with standard photolithography and a Ti layer as hard mask for reactive ion etching. The molds were applied to thermal imprinting onto low and high transition temperature glass. Optical performance was tested for the molded samples with different designs for laser beamsplitters. The results show a good agreement to the design specification. Our result allow us to show limitations of our fabrication technique and we discussed the suitability of precision glass molding for cost efficient mass production with a high quality.

  20. Gas-to-liquid permeation in silicon-containing, crosslinked, glassy copolymers of methyl methacrylate.

    PubMed

    Yang, W M; Peppas, N A

    1983-10-01

    Copolymers of methyl methacrylate with disiloxane derivatives have been proposed as biomaterials for contact lens applications. Although glassy, these copolymers exhibit high oxygen permeability and adequate wettability so that they can be used for manufacture of hard, extended wear lenses. Crosslinked copolymers of poly(methylmethacrylate-co-1,3-bis(methacryloxymethyl) -1,1,3,3-tetramethyl-disiloxane), P(MMA-co-BMTDS), containing from 0.085 to 0.53 mole fraction of BMTDS were prepared and tested for oxygen permeation using a novel apparatus which simulates the atmosphere/lens/cornea conditions. The gas-to-liquid dissolved oxygen permeability, P gd1 was determined and it was found to increase with BMTDS content. Permeability values for P(MMA-co-BMTDS) at 34 degrees C were significantly higher than for pure homopolymer PMMA, although these copolymers were glassy at this temperature. The increased oxygen permeation was attributed to increased oxygen solubility in the copolymers due to the presence of the -Si-O-bonds. PMID:6640054

  1. Structural characterization and aging of glassy pharmaceuticals made using acoustic levitation.

    PubMed

    Benmore, Chris J; Weber, J K R; Tailor, Amit N; Cherry, Brian R; Yarger, Jeffery L; Mou, Qiushi; Weber, Warner; Neuefeind, Joerg; Byrn, Stephen R

    2013-04-01

    Here, we report the structural characterization of several amorphous drugs made using the method of quenching molten droplets suspended in an acoustic levitator. (13) C NMR, X-ray, and neutron diffraction results are discussed for glassy cinnarizine, carbamazepine, miconazole nitrate, probucol, and clotrimazole. The (13) C NMR results did not find any change in chemical bonding induced by the amorphization process. High-energy X-ray diffraction results were used to characterize the ratio of crystalline to amorphous material present in the glasses over a period of 8 months. All the glasses were stable for at least 6 months except carbamazepine, which has a strong tendency to crystallize within a few months. Neutron and X-ray pair distribution function analyses were applied to the glassy materials, and the results were compared with their crystalline counterparts. The two diffraction techniques yielded similar results in most cases and identified distinct intramolecular and intermolecular correlations. The intramolecular scattering was calculated based on the crystal structure and fit to the measured X-ray structure factor. The resulting intermolecular pair distribution functions revealed broad-nearest and next-nearest neighbor molecule-molecule correlations. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1290-1300, 2013. PMID:23381910

  2. Electrochemical behavior of triflusal, aspirin and their metabolites at glassy carbon and boron doped diamond electrodes.

    PubMed

    Enache, Teodor Adrian; Fatibello-Filho, Orlando; Oliveira-Brett, Ana Maria

    2010-08-01

    The electrochemical behavior of triflusal (TRF) and aspirin (ASA), before and after hydrolysis in water and in alkaline medium using two different electrode surfaces, glassy carbon and boron doped diamond, was study by differential pulse voltammetry over a wide pH range. The hydrolysis products are 2-(hydroxyl)-4-(trifluoromethyl)-benzoic acid (HTB) for triflusal and salicylic acid (SA) for aspirin, which in vivo represent their main metabolites. The hydrolysis processes were also followed by spectrophotometry. The UV results showed complete hydrolysis after one hour for TRF and after two hours for ASA in alkaline solution. The glassy carbon electrode enables only indirect determination of TRF and ASA through the electrochemical detection of their hydrolysis products HTB and SA, respectively. The oxidation processes of HTB and SA are pH dependent and involve different numbers of electrons and protons. Moreover, the difference between the oxidation peak potential of SA and HTB was equal to 100 mV in the studied pH range from 1 to 8 due to the CF3 of the aromatic ring of HTB molecule. Due to its wider oxidation potential range, the boron doped diamond electrode was used to study the direct oxidation of TRF and ASA, as well as of their respective metabolites HTB and SA.

  3. Separating the ferromagnetic and glassy behavior within the metal-organic magnet Ni (TCNQ) 2

    NASA Astrophysics Data System (ADS)

    Berlie, Adam; Terry, Ian; Szablewski, Marek; Giblin, Sean R.

    2015-11-01

    An in-depth study of the metal-organic magnet Ni (TCNQ) 2 was conducted where the deuterated form was synthesised both to attempt to alter the magnetic properties of the material and to be advantageous in techniques such as neutron scattering and muon spectroscopy. Deuteration saw a 3 K increase in TC with magnetization and heat capacity measurements demonstrating a spin wave contribution at low temperatures confirming the 3D nature of the ferromagnetic state shown by Ni (TCNQ-D4)2 . AC susceptibility results suggest there is a glassy component associated with the magnetically ordered state, though muon spectroscopy measurements did not support the presence of a spin glass state. Instead muon spectroscopy at zero magnetic field indicated the presence of two magnetic transitions, one at 20 K and another below 6 K; the latter is likely due to the system entering a quasistatic regime, similar to what one might expect of a superspin or cluster glass. Neutron diffraction measurements further supported this by revealing very weak magnetic Bragg peaks suggesting that the magnetism may have a short coherence length and be confined to small grains or clusters. The separation of the ferromagnetic and glassy magnetic components of the material's properties suggest that this system may show promise as a metal-organic magnet which is easily modified to change its magnetic properties, providing larger grain sizes can be synthesized.

  4. A neutron-X-ray, NMR and calorimetric study of glassy Probucol synthesized using containerless techniques

    NASA Astrophysics Data System (ADS)

    Weber, J. K. R.; Benmore, C. J.; Tailor, A. N.; Tumber, S. K.; Neuefeind, J.; Cherry, B.; Yarger, J. L.; Mou, Q.; Weber, W.; Byrn, S. R.

    2013-10-01

    Acoustic levitation was used to trap 1-3 mm diameter drops of Probucol and other pharmaceutical materials in containerless conditions. Samples were studied in situ using X-ray diffraction and ex situ using neutron diffraction, NMR and DSC techniques. The materials were brought into non-equilibrium states by supersaturating solutions or by supercooling melts. The glass transition and crystallization temperatures of glassy Probucol were 29 ± 1 and 71 ± 1 °C respectively. The glassy form was stable with a shelf life of at least 8 months. A neutron/X-ray difference function of the glass showed that while molecular sub-groups remain rigid, many of the hydrogen correlations observed in the crystal become smeared out in the disordered material. The glass is principally comprised of slightly distorted Form I Probucol molecules with disordered packing rather than large changes in the individual molecular structure. Avoiding surface contact-induced nucleation provided access to highly non-equilibrium phases and enabled synthesis of phase-pure glasses.

  5. Electrochemical behavior of triflusal, aspirin and their metabolites at glassy carbon and boron doped diamond electrodes.

    PubMed

    Enache, Teodor Adrian; Fatibello-Filho, Orlando; Oliveira-Brett, Ana Maria

    2010-08-01

    The electrochemical behavior of triflusal (TRF) and aspirin (ASA), before and after hydrolysis in water and in alkaline medium using two different electrode surfaces, glassy carbon and boron doped diamond, was study by differential pulse voltammetry over a wide pH range. The hydrolysis products are 2-(hydroxyl)-4-(trifluoromethyl)-benzoic acid (HTB) for triflusal and salicylic acid (SA) for aspirin, which in vivo represent their main metabolites. The hydrolysis processes were also followed by spectrophotometry. The UV results showed complete hydrolysis after one hour for TRF and after two hours for ASA in alkaline solution. The glassy carbon electrode enables only indirect determination of TRF and ASA through the electrochemical detection of their hydrolysis products HTB and SA, respectively. The oxidation processes of HTB and SA are pH dependent and involve different numbers of electrons and protons. Moreover, the difference between the oxidation peak potential of SA and HTB was equal to 100 mV in the studied pH range from 1 to 8 due to the CF3 of the aromatic ring of HTB molecule. Due to its wider oxidation potential range, the boron doped diamond electrode was used to study the direct oxidation of TRF and ASA, as well as of their respective metabolites HTB and SA. PMID:20402644

  6. Mediatorless solar energy conversion by covalently bonded thylakoid monolayer on the glassy carbon electrode.

    PubMed

    Lee, Jinhwan; Im, Jaekyun; Kim, Sunghyun

    2016-04-01

    Light reactions of photosynthesis that take place in thylakoid membranes found in plants or cyanobacteria are among the most effective ways of utilizing light. Unlike most researches that use photosystem I or photosystem II as conversion units for converting light to electricity, we have developed a simple method in which the thylakoid monolayer was covalently immobilized on the glassy carbon electrode surface. The activity of isolated thylakoid membrane was confirmed by measuring evolving oxygen under illumination. Glassy carbon surfaces were first modified with partial or full monolayers of carboxyphenyl groups by reductive C-C coupling using 4-aminobenzoic acid and aniline and then thylakoid membrane was bioconjugated through the peptide bond between amine residues of thylakoid and carboxyl groups on the surface. Surface properties of modified surfaces were characterized by cyclic voltammetry, contact angle measurements, and electrochemical impedance spectroscopy. Photocurrent of 230 nA cm(-2) was observed when the thylakoid monolayer was formed on the mixed monolayer of 4-carboxylpheny and benzene at applied potential of 0.4V vs. Ag/AgCl. A small photocurrent resulted when the 4-carboxyphenyl full monolayer was used. This work shows the possibility of solar energy conversion by directly employing the whole thylakoid membrane through simple surface modification.

  7. Effect of water polyamorphism on the molecular vibrations of glycerol in its glassy aqueous solutions

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoshiharu; Mishima, Osamu

    2016-07-01

    A glassy dilute glycerol-water solution undergoes a mutual polyamorphic transition relating to the transition between high- and low-density amorphous ices of solvent water. The polyamorphic transition behavior depends on the glycerol concentration, indicating that the glycerol affects the water polyamorphism. Here, we used the glassy dilute glycerol-water solution of the solute molar fraction of 0.07 and examined the effect of the polyamorphic change in solvent water on the molecular vibrations of glycerol via Raman spectroscopy. It is found that the molecular vibration of glycerol in high-density liquid like solvent water is different from that in the low-density liquid like solvent water and that the change in the molecular vibration of glycerol is synchronized with the polyamorphic transition of solvent water. The dynamical change of the solute molecule relates to the polyamorphic state of solvent water. This result suggests that the polyamorphic fluctuation of water structure emanated from the presumed liquid-liquid critical point plays an important role for the function of aqueous solution under an ambient condition such as the conformational stability of solute, the functional expression of solute, and so on.

  8. Effect of chemical substituents on the structure of glassy diphenyl polycarbonates.

    PubMed

    Sulatha, M S; Natarajan, Upendra

    2011-02-24

    Polycarbonates offer a wide variety of physical property behavior that is difficult to predict due to complexities at the molecular scale. Here, the physical structure of amorphous glassy polycarbonates having aliphatic and cycloaliphatic chemical groups is explored through atomistic simulations. The influence of chemical structure on solubility parameter, torsion distributions, radial distribution function, scattering structure factor, orientation distributions of phenylene rings and carbonate groups, and free volume distributions, leading to interchain packing effects, are shown. The effect of the cyclohexyl ring at the isopropylidene carbon as compared to the effect of the methyl groups positioned on the phenylene rings results in a larger reduction in the solubility parameter (δ). The interchain distance estimated for polycarbonates in this work is in the range of 5-5.8 Å. The o-methyl groups on the phenylene rings, as compared to a cyclohexyl ring, lead to higher interchain distances. The highest interchain distance is observed with a trimethylcyclohexylidene group at the isopropylidene carbon. Atomistic simulations reveal two different types of packing arrangement of nearest-neighbor chains in the glassy state, one type of which agrees with the NMR experimental data. The fundamental insights provided here can be utilized for design of chemical structures for tailored macroscopic properties.

  9. Molecular dynamics simulation of rupture in glassy polymer bridges within filler aggregates.

    PubMed

    Froltsov, Vladimir A; Klüppel, Manfred; Raos, Guido

    2012-10-01

    We present a series of nonequilibrium molecular dynamics simulations, investigating the rupture mechanisms in glassy polymer films confined between two solid surfaces. Such systems provide a useful model for the strong nonlinear reinforcement of rubber by colloidal filler particles. Depending on the degree of confinement three qualitatively different rupture modes have been found, which originate from the interplay of internal (polymer-polymer) and external (polymer-wall) interactions. In very thin films we observe the formation and stretching of many single-chain bridges between the confining surfaces. Progressing to thicker samples we observe fewer bridges, consisting of bundled polymer chains, and eventually just one large bridge in thick specimens. The yield stress and the elongational modulus of the polymer films have been calculated from the stress-strain curves at various temperatures and confinements and their behavior has been analyzed in terms of polymer-polymer and polymer-surface interaction energies. The thinnest films (5 monomer diameters) are always glassy in our simulations, while the others display a glass transition temperature around 0.50-0.55 (in units ε(0)/k(B) of the Lennard-Jones interaction energy), depending on their thickness. This range of values, which has been determined using both the nonequilibrium tensile simulations and equilibrium diffusion data, agrees with the transition temperature previously found by shear simulations [Baljon and Robbins, Science 271, 482 (1996)]. PMID:23214604

  10. Determination of trace amounts of lead and cadmium using a bismuth/glassy carbon composite electrode.

    PubMed

    Hwang, Gil-Ho; Han, Won-Kyu; Hong, Seok-Jun; Park, Joon-Shik; Kang, Sung-Goon

    2009-02-15

    We examined the use of a bismuth-glassy carbon (Bi/C) composite electrode for the determination of trace amounts of lead and cadmium. Incorporated bismuth powder in the composite electrode was electrochemically dissolved in 0.1M acetate buffer (pH 4.5) where nanosized bismuth particles were deposited on the glassy carbon at the reduction potential. The anodic stripping voltammetry on the Bi/C composite electrode exhibited well-defined, sharp and undistorted peaks with a favorable resolution for lead and cadmium. Comparing a non-oxidized Bi/C composite electrode with an in-situ plated bismuth film electrode, the Bi/C composite electrode exhibited superior performance due to its much larger surface area. The limit of detection was 0.41 microg/L for lead and 0.49 microg/L for cadmium. Based on this study, we are able to conclude that various types of composite electrodes for electroanalytical applications can be developed with a prudent combination of electrode materials.

  11. Incoherent chimera and glassy states in coupled oscillators with frustrated interactions

    NASA Astrophysics Data System (ADS)

    Choe, Chol-Ung; Ri, Ji-Song; Kim, Ryong-Son

    2016-09-01

    We suggest a site disorder model that describes the population of identical oscillators with quenched random interactions for both the coupling strength and coupling phase. We obtain the reduced equations for the suborder parameters, on the basis of Ott-Antonsen ansatz theory, and present a complete bifurcation analysis of the reduced system. New effects include the appearance of the incoherent chimera and glassy state, both of which are caused by heterogeneity of the coupling phases. In the incoherent chimera state, the system displays an exotic symmetry-breaking behavior in spite of the apparent structural symmetry where the oscillators for both of the two subpopulations are in a frustrated state, while the phase distribution for each subpopulation approaches a steady state that differs from each other. When the incoherent chimera undergoes Hopf bifurcation, the system displays a breathing incoherent chimera. The glassy state that occurs on a surface of three-dimensional parameter space exhibits a continuum of metastable states with zero value of the global order parameter. Explicit formulas are derived for the system's Hopf, saddle-node, and transcritical bifurcation curves, as well as the codimension-2 crossing points, including the Takens-Bogdanov point.

  12. Mediatorless solar energy conversion by covalently bonded thylakoid monolayer on the glassy carbon electrode.

    PubMed

    Lee, Jinhwan; Im, Jaekyun; Kim, Sunghyun

    2016-04-01

    Light reactions of photosynthesis that take place in thylakoid membranes found in plants or cyanobacteria are among the most effective ways of utilizing light. Unlike most researches that use photosystem I or photosystem II as conversion units for converting light to electricity, we have developed a simple method in which the thylakoid monolayer was covalently immobilized on the glassy carbon electrode surface. The activity of isolated thylakoid membrane was confirmed by measuring evolving oxygen under illumination. Glassy carbon surfaces were first modified with partial or full monolayers of carboxyphenyl groups by reductive C-C coupling using 4-aminobenzoic acid and aniline and then thylakoid membrane was bioconjugated through the peptide bond between amine residues of thylakoid and carboxyl groups on the surface. Surface properties of modified surfaces were characterized by cyclic voltammetry, contact angle measurements, and electrochemical impedance spectroscopy. Photocurrent of 230 nA cm(-2) was observed when the thylakoid monolayer was formed on the mixed monolayer of 4-carboxylpheny and benzene at applied potential of 0.4V vs. Ag/AgCl. A small photocurrent resulted when the 4-carboxyphenyl full monolayer was used. This work shows the possibility of solar energy conversion by directly employing the whole thylakoid membrane through simple surface modification. PMID:26625272

  13. Sensitive Electrochemical Detection of Enzymatically-generated Thiocholine at Carbon Nanotube Modified Glassy Carbon Electrode

    SciTech Connect

    Liu, Guodong; Riechers, Shawn L.; Mellen, Maria C.; Lin, Yuehe

    2005-11-01

    A carbon nanotube modified glassy-carbon (CNT/GC) electrode was used for enhancing the sensitivity of electrochemical measurements of enzymatically-generated thiocholine. Cyclic voltammetric and amperometric characteristics of thiocholine at CNT/GC, glassy carbon, carbon paste, and gold electrodes were compared. The CNT layer leads to a greatly improved anodic detection of enzymatically generated thiocholine product including lower oxidation overpotential (0.15 V) and higher sensitivity because of its electrocatalytic activity, fast electron transfer and large surface area. The sensor performance was optimized with respect to the operating conditions. Under the optimal batch conditions, a detection limit of 5 ?10 -6 mol/L was obtained with good precision (RSD = 5.2%, n=10). Furthermore, the attractive response of thiocholine on a CNT/GC electrode has allowed it to be used for constant-potential flow injection analysis. The detection limit was greatly improved to 0.3 ?10-6 mol/L. The high sensitivity electrochemical detection of enzymatically generated thiocholine with a CNT sensing platform holds great promise to prepare an acetylcholinesterase biosensor for monitoring organophosphate pesticides and nerve agents.

  14. Mechanistic study of carvacrol processing and stabilization as glassy solid solution and microcapsule.

    PubMed

    Tackenberg, Markus W; Geisthövel, Carola; Marmann, Andreas; Schuchmann, Heike P; Kleinebudde, Peter; Thommes, Markus

    2015-01-30

    Essential oils and other liquid active pharmaceutical ingredients (APIs) are frequently microencapsulated to improve shelf life, handling, and for tailoring release. A glassy solid solution (GSS), a single-phase system, where the excipient is plasticized by the API, could be an alternative formulation system. Thus this study focuses on the investigation of two formulation strategies using carvacrol as a model compound, namely a microcapsule (MC) and a glassy solid solution (GSS). Applying the solubility parameter approach, polyvinylpyrrolidone (PVP) was chosen as a suitable matrix material for a GSS system, whereas maltodextrin and sucrose served as excipients for a microcapsule (MC) system. Differential scanning calorimetry (DSC) measurements of the excipients' glass transition temperatures and the melting point of carvacrol verified plasticizing properties of carvacrol on PVP. Batch mixing processes, as preliminary experiments for future extrusion processes, were performed to prepare GSSs and MCs with various amounts of carvacrol, followed by crushing and sieving. Maximally 4.5% carvacrol was encapsulated in the carbohydrate material, whereas up to 16.3% were stabilized as GSS, which is an outstanding amount. However, grinding of the samples led to a loss of up to 30% of carvacrol.

  15. Diazonium Chemistry for the Bio-Functionalization of Glassy Nanostring Resonator Arrays.

    PubMed

    Zheng, Wei; Du, Rongbing; Cao, Yong; Mohammad, Mohammad A; Dew, Steven K; McDermott, Mark T; Evoy, Stephane

    2015-01-01

    Resonant glassy nanostrings have been employed for the detection of biomolecules. These devices offer high sensitivity and amenability to large array integration and multiplexed assays. Such a concept has however been impaired by the lack of stable and biocompatible linker chemistries. Diazonium salt reduction-induced aryl grafting is an aqueous-based process providing strong chemical adhesion. In this work, diazonium-based linker chemistry was performed for the first time on glassy nanostrings, which enabled the bio-functionalization of such devices. Large arrays of nanostrings with ultra-narrow widths down to 10 nm were fabricated employing electron beam lithography. Diazonium modification was first developed on SiCN surfaces and validated by X-ray photoelectron spectroscopy. Similarly modified nanostrings were then covalently functionalized with anti-rabbit IgG as a molecular probe. Specific enumeration of rabbit IgG was successfully performed through observation of downshifts of resonant frequencies. The specificity of this enumeration was confirmed through proper negative control experiments. Helium ion microscopy further verified the successful functionalization of nanostrings. PMID:26263989

  16. Room-temperature nonlinear transport phenomena in low-dimensional Ni-Nb-Zr-H glassy alloys and its device

    SciTech Connect

    Fukuhara, Mikio; Yoshida, Hajime

    2014-05-15

    We report the room-temperature switching and Coulomb blockade effects in three–terminal glassy alloy field effect transistor (GAFET), using the millimeter sized glassy alloy. By applying dc and ac voltages to a gate electrode, GAFET can be switched from a metallic conducting state to an insulating state with Coulomb oscillation at a period of 14 μV at room temperature. The transistor showed the three-dimensional Coulomb diamond structure. The fabrication of a low-energy controllable device throws a new light on cluster electronics without wiring.

  17. Relaxation phenomena in supercooled liquid and glassy acetaminophen studied by dielectric, photon correlation and Brillouin light scattering spectroscopies

    NASA Astrophysics Data System (ADS)

    Kwon, Hyun-Joung; Kim, Tae Hyun; Ko, Jae-Hyeon; Hwang, Yoon-Hwae

    2013-01-01

    Relaxation phenomena and acoustic properties of acetaminophen in the glassy and supercooled liquid phase were studied by dielectric, photon correlation and Brillouin spectroscopies. Dielectric and photon correlation studies revealed the structural relaxation process while a new relaxation process was found by dielectric measurement in a much lower frequency range. The acoustic anomalies clearly indicated a glass transition at 293 K and some remnant localized motions in the glassy phase that contributed to the acoustic damping. Partial crystallization in the supercooled liquid phase was signified at temperatures above 318 K by drastic changes in the Brillouin spectrum and decrease in the dielectric strength.

  18. Nucleation and growth of thin films of the organic conductor TTF-iodide over glassy carbon. Electrochemical and spectroelectrochemical study.

    PubMed

    Gómez, L; Rodríguez-Amaro, R

    2009-04-21

    On the basis of the electrochemical and spectroelectrochemical behavior of thin films of TTF over a glassy carbon electrode in iodide media, a new, more complete mechanism for the electrode processes involved is proposed. The voltammetric and chronoamperometric results for the films can be explained in light of a recently developed nucleation-growth model involving a layer-by-layer mechanism. Also, their in situ UV-vis spectral data expand the available knowledge about the overall mechanism and the nature of the compound formed over the glassy carbon electrode. PMID:19366229

  19. Nucleation and growth of thin films of the organic conductor TTF-iodide over glassy carbon. Electrochemical and spectroelectrochemical study.

    PubMed

    Gómez, L; Rodríguez-Amaro, R

    2009-04-21

    On the basis of the electrochemical and spectroelectrochemical behavior of thin films of TTF over a glassy carbon electrode in iodide media, a new, more complete mechanism for the electrode processes involved is proposed. The voltammetric and chronoamperometric results for the films can be explained in light of a recently developed nucleation-growth model involving a layer-by-layer mechanism. Also, their in situ UV-vis spectral data expand the available knowledge about the overall mechanism and the nature of the compound formed over the glassy carbon electrode.

  20. Electrochemical study of functionalization on the surface of a chitin/platinum-modified glassy carbon paste electrode.

    PubMed

    Sugawara, Kazuharu; Yugami, Asako; Terui, Norifumi; Kuramitz, Hideki

    2009-11-01

    To functionalize chitin surfaces using proteins, we developed a glucose oxidase (GOD)-chitin/platinum-modified glassy carbon paste electrode (GCPE) as a model. In a weakly acidic solution, negatively charged GOD were immobilized by the protonated acetylamide groups on chitin. When the electrode was immersed in a solution containing GOD, the enzyme was readily immobilized due to the electrostatic interaction. In addition, measurements were performed using electrodes made with powders of different sizes because sensor performance depends on the particle sizes of glassy carbon powder. PMID:19907096

  1. Recombinant spider silk matrices for neural stem cell cultures.

    PubMed

    Lewicka, Michalina; Hermanson, Ola; Rising, Anna U

    2012-11-01

    Neural stem cells (NSCs) have the capacity to differentiate into neurons, astrocytes, and oligodendrocytes. Accordingly, NSCs hold great promise in drug screening and treatment of several common diseases. However, a major obstacle in applied stem cell research is the limitation of synthetic matrices for culturing stem cells. The objective of this study was to evaluate the suitability of recombinant spider silk (4RepCT) matrices for growth of NSCs. NSCs isolated from the cerebral cortices of mid-gestation rat embryos were cultured on either 4RepCT matrices or conventional poly-L-ornithine and fibronectin (P + F) coated polystyrene plates. From 48 h of culture, no significant differences in cell proliferation or viability were detected in NSC cultures on 4RepCT compared to control matrices (polystyrene plates coated with P + F). The NSCs retained an undifferentiated state, displaying low or no staining for markers of differentiated cells. Upon stimulation NSCs grown on 4RepCT differentiated efficiently into neuronal and astrocytic cells to virtually the same degree as control cultures, but a slightly less efficient oligodendrocyte differentiation was noted. We suggest that recombinant spider silk matrices provide a functional microenvironment and represent a useful tool for the development of new strategies in neural stem cell research. PMID:22863380

  2. Calibration and temperature correction of heat dissipation matric potential sensors

    USGS Publications Warehouse

    Flint, A.L.; Campbell, G.S.; Ellett, K.M.; Calissendorff, C.

    2002-01-01

    This paper describes how heat dissipation sensors, used to measure soil water matric potential, were analyzed to develop a normalized calibration equation and a temperature correction method. Inference of soil matric potential depends on a correlation between the variable thermal conductance of the sensor's porous ceramic and matric poten-tial. Although this correlation varies among sensors, we demonstrate a normalizing procedure that produces a single calibration relationship. Using sensors from three sources and different calibration methods, the normalized calibration resulted in a mean absolute error of 23% over a matric potential range of -0.01 to -35 MPa. Because the thermal conductivity of variably saturated porous media is temperature dependent, a temperature correction is required for application of heat dissipation sensors in field soils. A temperature correction procedure is outlined that reduces temperature dependent errors by 10 times, which reduces the matric potential measurement errors by more than 30%. The temperature dependence is well described by a thermal conductivity model that allows for the correction of measurements at any temperature to measurements at the calibration temperature.

  3. Efficient computer algebra algorithms for polynomial matrices in control design

    NASA Technical Reports Server (NTRS)

    Baras, J. S.; Macenany, D. C.; Munach, R.

    1989-01-01

    The theory of polynomial matrices plays a key role in the design and analysis of multi-input multi-output control and communications systems using frequency domain methods. Examples include coprime factorizations of transfer functions, cannonical realizations from matrix fraction descriptions, and the transfer function design of feedback compensators. Typically, such problems abstract in a natural way to the need to solve systems of Diophantine equations or systems of linear equations over polynomials. These and other problems involving polynomial matrices can in turn be reduced to polynomial matrix triangularization procedures, a result which is not surprising given the importance of matrix triangularization techniques in numerical linear algebra. Matrices with entries from a field and Gaussian elimination play a fundamental role in understanding the triangularization process. In the case of polynomial matrices, matrices with entries from a ring for which Gaussian elimination is not defined and triangularization is accomplished by what is quite properly called Euclidean elimination. Unfortunately, the numerical stability and sensitivity issues which accompany floating point approaches to Euclidean elimination are not very well understood. New algorithms are presented which circumvent entirely such numerical issues through the use of exact, symbolic methods in computer algebra. The use of such error-free algorithms guarantees that the results are accurate to within the precision of the model data--the best that can be hoped for. Care must be taken in the design of such algorithms due to the phenomenon of intermediate expressions swell.

  4. Mechanochemical investigation of a glassy epoxy-amine thermoset subjected to fatigue

    NASA Astrophysics Data System (ADS)

    Foster, Stephen Finley

    Covalent bonds in organic molecules can be produced, altered, and broken through various sources of energy and processes. These include photochemical, thermochemical, chemical, and mechanochemical processes. Polymeric materials derive their physical properties from the time scale of motion, summation of intermolecular forces, and number of chain entanglements and crosslinks. Glassy thermoset polymers experience mechanical fatigue during dynamic stress loading and properties diminish with inevitable material failure at stress levels below the ultimate tensile strength (UTS). Damage modeling has been successful in predicting the number of cycles required to induce failure in a specimen due to stress. However, it does not directly provide an explanation of the origin of fatigue in polymers. It is hypothesized herein that mechanical failure at stress levels below the ultimate strength property is due to the accumulation of mechanically induced homolytic chain scission events throughout the glassy thermoset network. The goal of this research will be to quantify homolytic chain scission events with fatigue cycles with the ultimate goal of correlating mechanical property loss with degradation of covalent network structure. To accomplish this goal, stable free nitroxyl radicals were incorporated into an epoxy-amine matrix to detect homolytic chain scission resulting from fatigue. Chapter II discusses a successful synthesis and characterization of the nitroxyl radical molecule, a product of 4-hydroxy-2,2,5,5-tetramethylpiperdin-1-yl-oxyl (TEMPO) and isophorone diisocyanate designated as BT-IPDI. In Chapter III, the epoxy-amine reaction was determined to be unaffected by incorporation of up to 5 wt% of BT-IPDI. Although 50% UTS fatigue studies produced property degradation and fatigue failure as shown in Chapter IV, analysis of BT-IPDI through EPR did not detect homolytic chain scission. Chapter V reveals that mechano-radicals were produced from cryo-grinding the glassy

  5. Induced Ginibre ensemble of random matrices and quantum operations

    NASA Astrophysics Data System (ADS)

    Fischmann, Jonit; Bruzda, Wojciech; Khoruzhenko, Boris A.; Sommers, Hans-Jürgen; Życzkowski, Karol

    2012-02-01

    A generalization of the Ginibre ensemble of non-Hermitian random square matrices is introduced. The corresponding probability measure is induced by the ensemble of rectangular Gaussian matrices via a quadratization procedure. We derive the joint probability density of eigenvalues for such an induced Ginibre ensemble and study various spectral correlation functions for complex and real matrices, and analyse universal behaviour in the limit of large dimensions. In this limit, the eigenvalues of the induced Ginibre ensemble cover uniformly a ring in the complex plane. The real induced Ginibre ensemble is shown to be useful to describe the statistical properties of evolution operators associated with random quantum operations for which the dimensions of the input state and the output state do differ.

  6. Light activated cell migration in synthetic extracellular matrices.

    PubMed

    Guo, Qiongyu; Wang, Xiaobo; Tibbitt, Mark W; Anseth, Kristi S; Montell, Denise J; Elisseeff, Jennifer H

    2012-11-01

    Synthetic extracellular matrices provide a framework in which cells can be exposed to defined physical and biological cues. However no method exists to manipulate single cells within these matrices. It is desirable to develop such methods in order to understand fundamental principles of cell migration and define conditions that support or inhibit cell movement within these matrices. Here, we present a strategy for manipulating individual mammalian stem cells in defined synthetic hydrogels through selective optical activation of Rac, which is an intracellular signaling protein that plays a key role in cell migration. Photoactivated cell migration in synthetic hydrogels depended on mechanical and biological cues in the biomaterial. Real-time hydrogel photodegradation was employed to create geometrically defined channels and spaces in which cells could be photoactivated to migrate. Cell migration speed was significantly higher in the photo-etched channels and cells could easily change direction of movement compared to the bulk hydrogels.

  7. Further thoughts on the utility of risk matrices.

    PubMed

    Ball, David J; Watt, John

    2013-11-01

    Risk matrices are commonly encountered devices for rating hazards in numerous areas of risk management. Part of their popularity is predicated on their apparent simplicity and transparency. Recent research, however, has identified serious mathematical defects and inconsistencies. This article further examines the reliability and utility of risk matrices for ranking hazards, specifically in the context of public leisure activities including travel. We find that (1) different risk assessors may assign vastly different ratings to the same hazard, (2) even following lengthy reflection and learning scatter remains high, and (3) the underlying drivers of disparate ratings relate to fundamentally different worldviews, beliefs, and a panoply of psychosocial factors that are seldom explicitly acknowledged. It appears that risk matrices when used in this context may be creating no more than an artificial and even untrustworthy picture of the relative importance of hazards, which may be of little or no benefit to those trying to manage risk effectively and rationally.

  8. Parikh matrices of words under a generalized Thue morphism

    NASA Astrophysics Data System (ADS)

    Subramanian, K. G.; Isawasan, Pradeep; Venkat, Ibrahim; Khader, Ahamad Tajudin

    2013-10-01

    Parikh matrix of a word w, which is a sequence of symbols from an alphabet, was introduced by Mateescu et al. (2001) to count certain subwords in the word w. Subsequently, several investigations on various properties of Parikh matrices have been done. Parikh matrices of words that involve certain weak ratio-property are investigated by Subramanian et al (2009). On the other hand a morphism f is a mapping on words u,v whose images f(u), f(v) are also words with the property that f(uv) = f(u)f(v). Thue morphism on a binary alphabet is a special kind of morphism. Here we consider a generalization of Thue morphism, introduced by Seebold (2003) but restricting it to three symbols. We obtain certain properties of images of binary words under this generalized Thue morphism and also of their Parikh matrices, in the context of the weak ratio-property.

  9. Asymmetric correlation matrices: an analysis of financial data

    NASA Astrophysics Data System (ADS)

    Livan, G.; Rebecchi, L.

    2012-06-01

    We analyse the spectral properties of correlation matrices between distinct statistical systems. Such matrices are intrinsically non-symmetric, and lend themselves to extend the spectral analyses usually performed on standard Pearson correlation matrices to the realm of complex eigenvalues. We employ some recent random matrix theory results on the average eigenvalue density of this type of matrix to distinguish between noise and non-trivial correlation structures, and we focus on financial data as a case study. Namely, we employ daily prices of stocks belonging to the American and British stock exchanges, and look for the emergence of correlations between two such markets in the eigenvalue spectrum of their non-symmetric correlation matrix. We find several non trivial results when considering time-lagged correlations over short lags, and we corroborate our findings by additionally studying the asymmetric correlation matrix of the principal components of our datasets.

  10. Stable viscosity matrices for systems of conservation laws

    NASA Astrophysics Data System (ADS)

    Majda, Andrew; Pego, Robert L.

    A natural class of appropriate viscosity matrices for strictly hyperbolic systems of conservation laws in one space dimension, u1 + f( u) x = 0, uɛRm, is studied. These matrices are admissible in the sense that small-amplitude shock wave solutions of the hyperbolic system are shown to be limits of smooth traveling wave solutions of the parabolic system ut + f( u) x = v( Dux) x as ifv → 0 if D is in this class. The class is determined by a linearized stability requirement: The Cauchy problem for the equation u1 + f'( u0) ux = vDuxx should be well posed in L2 uniformly in v as v → 0. Previous examples of inadmissible viscosity matrices are accounted for through violation of the stability criterion.

  11. Large N matrices from a nonlocal spin system

    NASA Astrophysics Data System (ADS)

    Anninos, Dionysios; Hartnoll, Sean A.; Huijse, Liza; Martin, Victoria L.

    2015-10-01

    Large N matrices underpin the best understood models of emergent spacetime. We suggest that large N matrices can themselves be emergent from simple quantum mechanical spin models with finite dimensional Hilbert spaces. We exhibit the emergence of large N matrices in a nonlocal statistical physics model of order N2 Ising spins. The spin partition function is shown to admit a large N saddle described by a matrix integral, which we solve. The matrix saddle is dominant at high temperatures, metastable at intermediate temperatures and ceases to exist below a critical order one temperature. The matrix saddle is disordered in a sense we make precise and competes with ordered low energy states. We verify our analytic results by Monte Carlo simulation of the spin system.

  12. Nano-Fiber Reinforced Enhancements in Composite Polymer Matrices

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2009-01-01

    Nano-fibers are used to reinforce polymer matrices to enhance the matrix dependent properties that are subsequently used in conventional structural composites. A quasi isotropic configuration is used in arranging like nano-fibers through the thickness to ascertain equiaxial enhanced matrix behavior. The nano-fiber volume ratios are used to obtain the enhanced matrix strength properties for 0.01,0.03, and 0.05 nano-fiber volume rates. These enhanced nano-fiber matrices are used with conventional fiber volume ratios of 0.3 and 0.5 to obtain the composite properties. Results show that nano-fiber enhanced matrices of higher than 0.3 nano-fiber volume ratio are degrading the composite properties.

  13. Evaluation of matrices for the sorption and biodegradation of phenanthrene.

    PubMed

    Leglize, Pierre; Saada, Alain; Berthelin, Jacques; Leyval, Corinne

    2006-07-01

    Permeable reactive barriers (PRBs), a new cost effective technology for the remediation of contaminated groundwater, have rarely been considered for PAH contamination. We evaluated three candidate matrices (activated carbon (AC), pouzzolana coated (PzF) or not (Pz) with heavy fuel oil) for phenanthrene (PHE) sorption capacity and the biodegradation of adsorbed PHE. Adsorption-desorption batch experiments showed higher sorption capacity of AC than PzF (60 fold) and Pz (1,500 fold). Sorption isotherms were not linear for all matrices as described by a Freundlich model. Phenanthrene desorption from AC and PzF within 48 h was limited (1-3%). Mineralization of (14)C-PHE by a PAH-degrading bacterial strain increased in the presence of AC and Pz (+16 and +12%). Among the three matrices, AC may be a good candidate for PRBs due to high adsorption, low desorption and increased PHE degradation.

  14. Commutative law for products of infinitely large isotropic random matrices

    NASA Astrophysics Data System (ADS)

    Burda, Zdzislaw; Livan, Giacomo; Swiech, Artur

    2013-08-01

    Ensembles of isotropic random matrices are defined by the invariance of the probability measure under the left (and right) multiplication by an arbitrary unitary matrix. We show that the multiplication of large isotropic random matrices is spectrally commutative and self-averaging in the limit of infinite matrix size N→∞. The notion of spectral commutativity means that the eigenvalue density of a product ABC... of such matrices is independent of the order of matrix multiplication, for example, the matrix ABCD has the same eigenvalue density as ADCB. In turn, the notion of self-averaging means that the product of n independent but identically distributed random matrices, which we symbolically denote by AAA..., has the same eigenvalue density as the corresponding power An of a single matrix drawn from the underlying matrix ensemble. For example, the eigenvalue density of ABCCABC is the same as that of A2B2C3. We also discuss the singular behavior of the eigenvalue and singular value densities of isotropic matrices and their products for small eigenvalues λ→0. We show that the singularities at the origin of the eigenvalue density and of the singular value density are in one-to-one correspondence in the limit N→∞: The eigenvalue density of an isotropic random matrix has a power-law singularity at the origin ˜|λ|-s with a power s∈(0,2) when and only when the density of its singular values has a power-law singularity ˜λ-σ with a power σ=s/(4-s). These results are obtained analytically in the limit N→∞. We supplement these results with numerical simulations for large but finite N and discuss finite-size effects for the most common ensembles of isotropic random matrices.

  15. Random reverse-cyclic matrices and screened harmonic oscillator.

    PubMed

    Srivastava, Shashi C L; Jain, Sudhir R

    2012-04-01

    We have calculated the joint probability distribution function for random reverse-cyclic matrices and shown that it is related to an N-body exactly solvable model. We refer to this well-known model potential as a screened harmonic oscillator. The connection enables us to obtain all the correlations among the particle positions moving in a screened harmonic potential. The density of nontrivial eigenvalues of this ensemble is found to be of the Wigner form and admits a hole at the origin, in contrast to the semicircle law of the Gaussian orthogonal ensemble of random matrices. The spacing distributions assume different forms ranging from Gaussian-like to Wigner. PMID:22680453

  16. SAXS study on myoglobin embedded in amorphous saccharide matrices.

    PubMed

    Giuffrida, S; Panzica, M; Giordano, F M; Longo, A

    2011-09-01

    We report on Small Angle X-ray Scattering (SAXS) measurements performed on samples of carboxy-myoglobin and met-myoglobin embedded in low hydrated matrices of four different saccharides (trehalose, sucrose, maltose and lactose). Results confirm the already reported occurrence of inhomogeneities, which are not peculiar of trehalose samples, but appear also in maltose and lactose, and in some cases also sucrose, being dependent on the sample hydration and on the presence of sodium dithionite. This behaviour confirms our previous interpretation about the nature of the inhomogeneities, and prompt it as a possible general behaviour for highly concentrated sugar matrices. PMID:21938613

  17. In vitro characterization of polycaprolactone matrices generated in aqueous media

    PubMed Central

    Pok, Seok Won; Wallace, Kristin N.; Madihally, Sundararajan V.

    2010-01-01

    In this study, a novel process of dissolving polycaprolactone (PCL) matrices in glacial acetic acid was explored in which matrices spontaneously formed upon contact with water. Scanning electron microscopy analysis showed rough architecture and holes on the self-assembled matrix relative to matrices formed after dissolving in chloroform. Immersion in the gelatin solution reduced its roughness and number of micropores. Atomic force microscopy (AFM) analysis confirmed the increased roughness of the self-assembled matrices. The roughness of the matrices decreased after incubation in 1 N NaOH for 10 min. AFM analysis also revealed that the self-assembled matrix had a net positive surface charge, whereas chloroform–cast matrix had a negative surface charge. The surface charge of self-assembled matrix after immersion in gelatin changed to negative. However, incubation in NaOH did not affect the surface charge. The tensile properties were tested in both the dry state (25 °C) and the wet state (37 °C) by immersion in phosphate-buffered saline. Self-assembled matrix had lower elastic modulus, break stress and break strain than chloroform–cast matrix in both states. The elastic modulus in the wet condition was reduced by half in self-assembled matrix but tensile strain increased. Samples were further analyzed by ramp-hold test for assessing stress relaxation behavior. Both self-assembled and chloroform–cast matrices had similar trends in stress relaxation behavior. However, stress accumulation in self-assembled matrix was half that of chloroform–cast matrix. In vitro cell cultures were conducted using human foreskin fibroblast (HFF-1) in serum-free medium. Cytoskeletal actin staining showed cell adhesion and spreading on all matrices. Cell retention was significantly increased in self-assembled matrix compared to chloroform–cast matrix. Addition of gelatin improved the retention of seeded cells on the surface. In summary, PCL matrices generated using this novel

  18. Glassy-winged sharpshooter Microbiota explored using deep 16S rRNA sequencing from individual insects

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce’s disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of sharpshooters, where ...

  19. Exploring glassy-winged sharpshooter microbiota using deep 16S rRNA sequencing from individual insects

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce’s disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of sharpshooters, where ...

  20. The Role of Olfactory Cues in Host-Plant Selection by the Glassy-Winged Sharpshooter, Homalodisca coagulata

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS) is a highly polyphagous and mobile vector of Pierce's disease of grapes. Trap captures in a multi-crop agricultural landscape under constant deficit irrigation suggest that adult GWSS movement is tied to irrigation schedules. To understand the observed patterns...

  1. Electrografting of 3-Aminopropyltriethoxysilane on a Glassy Carbon Electrode for the Improved Adhesion of Vertically Oriented Mesoporous Silica Thin Films.

    PubMed

    Nasir, Tauqir; Zhang, Lin; Vilà, Neus; Herzog, Grégoire; Walcarius, Alain

    2016-05-01

    Vertically oriented mesoporous silica has proven to be of interest for applications in a variety of fields (e.g., electroanalysis, energy, and nanotechnology). Although glassy carbon is widely used as an electrode material, the adherence of silica deposits is rather poor, causing mechanical instability. A solution to improve the adhesion of mesoporous silica films onto glassy carbon electrodes without compromising the vertical orientation and the order of the mesopores will greatly contribute to the use of this kind of modified carbon electrode. We propose here the electrografting of 3-aminopropyltriethoxysilane on glassy carbon as a molecular glue to improve the mechanical stability of the silica film on the electrode surface without disturbing the vertical orientation and the order of the mesoporous silica obtained by electrochemically assisted self-assembly. These findings are supported by a series of surface chemistry techniques such as X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and cyclic voltammetry. Finally, methylviologen was used as a model redox probe to investigate the cathodic potential region of both glassy carbon and indium tin oxide electrodes modified with mesoporous silica in order to demonstrate further the interest in the approach developed here. PMID:27065214

  2. Composition dependence of dielectric properties in Se{sub 100-x}Cu{sub x} glassy alloys

    SciTech Connect

    Sharma, J.; Shrotriya, D.; Kumar, S.

    2015-06-24

    In this paper we report the composition dependent of dielectric properties in Se{sub 100-x}Cu{sub x} (x = 0, 2, 4 and 6) glassy alloys. The temperature and frequency dependence of the dielectric constants and the dielectric losses in the above glassy systems in the frequency range (1k Hz-5 M Hz) and temperature range (300 K–350 K) have been measured. It has been found that dielectric constant and the dielectric loss both are highly dependent on frequency and temperature and also found to increase with increasing concentration of Cu in pure amorphous Se. The role of Cu, as an impurity in the pure a-Se glassy alloy, is also discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system. Apart from this, the results have been also correlated in terms of a dipolar model which considers the hopping of charge carriers over a potential barrier between charged defect states.

  3. Effect of host plant fertilization on the developmental biology and feeding preference of the glassy-winged sharpshooter.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The main objective of this research was to evaluate the effect of host plant fertilization on the survival, immature development, adult fecundity, and the feeding of the glassy-winged sharpshooter (GWSS), a primary vector of Xylella fastidiosa (Xf). The development biology of GWSS was studied on co...

  4. Salivary Secretions of the Glassy-winged Sharpshooter, Homalodisca vitripennis: Novel Method of Collection and Protein Profile

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter, Homalodisca vitripennis Takiya (Hemiptera: Cicadellidae) is a xylophagous leafhopper that efficiently transmits Xylella fastidiosa, causative agent of a variety of scorch diseases such as Pierce’s Disease of grapes. The transmission mechanism of X. fastidiosa by the ...

  5. Evaluation of a method to quantify glassy-winged sharpshooter (Hemiptera: Cicadellidae) egg maturation during a feeding assay

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Methods to improve an assay relating adult feeding to egg maturation by the glassy-winged sharpshooter (Hemiptera: Cicadellidae) were evaluated. The assay consisted of confining adult females to cowpea stems in parafilm enclosures and quantifying adult feeding and egg maturation. Adult feeding was...

  6. EXPERIMENTAL ANALYSIS OF BIOLOGICAL PARAMETERS AND VECTOR ABILITY OF GLASSY-WINGED SHARPSHOOTERS FROM ALLOPATRIC POPULATIONS IN CALIFORNIA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar), is native to the southeastern United States and northeastern Mexico. It was detected in southern California in the late 1980s and in the San Joaquin Valley in 1999, where it transmits the bacterium Xylella fastidiosa to grapev...

  7. Role of Cu additive on the dielectric relaxation of Se75Te25 and Se85Te15 glassy alloys

    NASA Astrophysics Data System (ADS)

    Sharma, J.; Kumar, S.

    2010-07-01

    The effect of Cu additive on the dielectric relaxation of two binary Se-Te glassy systems, comparing the properties of a-Se75Te25, a-Se85Te15 and a-Se75Te15Cu10 alloys has been reported. The temperature and frequency dependence of dielectric parameters in Glassy Se75Te25, Se85Te15 and Se75Te15Cu10 alloys are studied by measuring capacitance and dissipation factor in the frequency range (1 kHz-5 MHz) and temperature range (300-350 K). A Debye like relaxation of dielectric behavior has been observed. A comprehensive study on the relaxation mechanism revealed that the presence of grains and grain boundaries across the pallet thickness is the basic relaxation process. A detailed analysis shows that the observed dielectric loss is in agreement with the Guintini's theory of dielectric dispersion based on two electron hopping over a potential barrier and is applicable in the present case. Dielectric constant (ɛ’), dielectric loss (ɛ”), loss tangent (δ) and capacitive reactance (Xc) are found highly frequency and temperature dependent. Dependence of these dielectric parameters over the metallic impurity Cu, has also been found in the present glassy system and has been discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system.

  8. "G.P.S Matrices" programme: A method to improve the mastery level of social science students in matrices operations

    NASA Astrophysics Data System (ADS)

    Lee, Ken Voon

    2013-04-01

    The purpose of this action research was to increase the mastery level of Form Five Social Science students in Tawau II National Secondary School in the operations of addition, subtraction and multiplication of matrices in Mathematics. A total of 30 students were involved. Preliminary findings through the analysis of pre-test results and questionnaire had identified the main problem faced in which the students felt confused with the application of principles of the operations of matrices when performing these operations. Therefore, an action research was conducted using an intervention programme called "G.P.S Matrices" to overcome the problem. This programme was divided into three phases. 'Gift of Matrices' phase aimed at forming matrix teaching aids. The second and third phases were 'Positioning the Elements of Matrices' and 'Strenghtening the Concept of Matrices'. These two phases were aimed at increasing the level of understanding and memory of the students towards the principles of matrix operations. Besides, this third phase was also aimed at creating an interesting learning environment. A comparison between the results of pre-test and post-test had shown a remarkable improvement in students' performances after implementing the programme. In addition, the analysis of interview findings also indicated a positive feedback on the changes in students' attitude, particularly in the aspect of students' understanding level. Moreover, the level of students' memory also increased following the use of the concrete matrix teaching aids created in phase one. Besides, teachers felt encouraging when conducive learning environment was created through students' presentation activity held in third phase. Furthermore, students were voluntarily involved in these student-centred activities. In conclusion, this research findings showed an increase in the mastery level of students in these three matrix operations and thus the objective of the research had been achieved.

  9. Polymorphic ethyl alcohol as a model system for the quantitative study of glassy behavior

    NASA Astrophysics Data System (ADS)

    Fischer, H. E.; Bermejo, F. J.; Fayos, R.; Dawidowski, J.; Ramos, M. A.; Vieira, S.; Schober, H.; González, M. A.

    1997-02-01

    We have performed neutron diffraction experiments as well as neutron time-of-flight (TOF) and low-temperature specific heat ( Cp) measurements, on both hydrogenated and deuterated ethanol as functions of temperature. Ethanol appears to be unique in its ability to form a rotator-phase crystal and an orientational glass in the same temperature range where the amorphous phase can be produced. We find that these two orientationally disordered crystal phases have structures and dynamics which are very similar to those of the amorphous phase at the same temperature. These are therefore glassy systems which, due to the presence of an underlying lattice and a stoichiometry identical to the amorphous phase, are ideal for quantitative study.

  10. Characterization of anomalous movements of spherical living cells on a silicon dioxide glassy substrate

    PubMed Central

    Son, Myeonggu; Lee, Gyudo; Son, Jongsang; Choi, Seungyeop; Kim, Youngho; Lee, Sei-Young; Yoon, Young-Ro; Yoon, Dae Sung; Lee, Sang Woo

    2015-01-01

    The random walk of spherical living cells on a silicon dioxide glassy substrate was studied experimentally and numerically. This random walk trajectory exhibited erratic dancing, which seemingly obeyed anomalous diffusion (i.e., Lévy-like walk) rather than normal diffusion. Moreover, the angular distribution (−π to π) of the cells' trajectory followed a “U-shaped pattern” in comparison to the uniform distribution seen in the movements of negatively charged polystyrene microspheres. These effects could be attributable to the homeostasis-driven structural resilient character of cells and physical interactions derived from temporarily retained nonspecific binding due to weak forces between the cells and substrates. Our results provide new insights into the stochastic behavior of mesoscopic biological particles with respect to structural properties and physical interactions. PMID:25610514

  11. Understanding glass-forming ability through sluggish crystallization of atomically thin metallic glassy films

    SciTech Connect

    Sun, Y. T.; Cao, C. R.; Huang, K. Q.; Zhao, N. J.; Gu, L. E-mail: dzheng@iphy.ac.cn Zheng, D. N. E-mail: dzheng@iphy.ac.cn Wang, W. H. E-mail: dzheng@iphy.ac.cn

    2014-08-04

    The glass-forming ability (GFA) of an alloy, closely related to its ability to resist crystallization, is a crucial issue in condensed matter physics. So far, the studies on GFA are mostly statistical and empirical guides. Benefiting from the ultrahigh thermal stability of ultrathin metallic glassy film and high resolution spherical aberration-corrected transmission electron microscope, the crystallization of atomically thin ZrCu and its microalloyed ZrCuAl glasses with markedly different GFA was investigated at the atomic scale. We find the Zr diffusivity estimated from the density of nuclei is dramatically decreased by adding of Al, which is the major reason for the much better GFA of the ZrCuAl metallic glass.

  12. Amperometric biosensor based on glassy carbon electrode modified with long-length carbon nanotube and enzyme

    NASA Astrophysics Data System (ADS)

    Furutaka, Hajime; Nemoto, Kentaro; Inoue, Yuki; Hidaka, Hiroki; Muguruma, Hitoshi; Inoue, Hitoshi; Ohsawa, Tatsuya

    2016-05-01

    An amperometric biosensor based on a glassy carbon electrode modified with long-length multiwalled carbon nanotubes (MWCNTs) and enzyme nicotinamide-adenine-dinucleotide-dependent glucose dehydrogenase (GDH) is presented. We demonstrate the effect of the MWCNT length on the amperometric response of the enzyme biosensor. The long length of MWCNT is 200 µm (average), whereas the normal length of MWCNT is 1 µm (average). The response of the long MWCNT–GDH electrode is 2 times more sensitive than that of the normal-length MWCNT–GDH electrode in the concentration range from 0.25–35 mM. The result of electrochemical impedance spectroscopy measurements suggest that the long-length MWCNT–GDH electrode formed a better electron transfer network than the normal-length one.

  13. Voltammetric Determination of Flunixin on Molecularly Imprinted Polypyrrole Modified Glassy Carbon Electrode

    PubMed Central

    Radi, Abd-Elgawad; Abd El-Ghany, Nadia; Wahdan, Tarek

    2016-01-01

    A novel electrochemical sensing approach, based on electropolymerization of a molecularly imprinted polypyrrole (MIPpy) film onto a glassy carbon electrode (GCE) surface, was developed for the detection of flunixin (FXN). The sensing conditions and the performance of the constructed sensor were assessed by cyclic, differential pulse and (DPV) square wave voltammetry (SWV). The sensor exhibited high sensitivity, with linear responses in the range of 5.0 to 50.0 µM with detection limits of 1.5 and 1.0 µM for DPV and SWV, respectively. In addition, the sensor showed high selectivity towards FXN in comparison to other interferents. The sensor was successfully utilized for the direct determination of FXN in buffalo raw milk samples. PMID:27242945

  14. Electrocatalytic determination of paraquat using a nafion film coated glassy carbon electrode.

    PubMed

    Lu, T H; Sun, I W

    2000-11-01

    A nafion film coated glassy carbon electrode (NFGCE) was employed for the determination of paraquat. Paraquat was accumulated onto NFGCE by the cation-exchange feature of nafion at open circuit potential in basic medium followed by cathodic differential pulse voltammetric (CDPV) determination in a medium containing permanganate ions. The sensitivity for the determination of paraquat was improved through the electrocatalytic reduction of permanganate by the reduced paraquat. With 3-min accumulation, the analytical signal versus concentration dependence was linear from 1.0 to 100 ppb with a detection limit of 0.5 ppb. The interference from common metal ions was minimized by addition of ethylenediaminetetraacetate (EDTA) into the sample solution. The use of nafion also improves the resistance to interference from surfactants.

  15. Oxygen determination in organic fluorine compounds by means of a glassy-carbon pyrolysis tube.

    PubMed

    Imaeda, K; Kuriki, T; Ohsawa, K

    1977-07-01

    A conventional apparatus for determination of oxygen in organic compounds has been improved for application to organic fluorine compounds. A feature of the apparatus is the use of a pyrolysis tube made of glassy carbon instead of quartz, which eliminates effects due to hydrogen fluoride produced in pyrolysis of the sample. Ten analyses of dexamethasone with the apparatus gave a mean value of 20.44% for oxygen (theory, 20.38%), with a standard deviation of 0.16%. Oxygen in 9 organic fluorine compounds was accurately determined by using the apparatus, with an average error of +0.1%. One analysis by a gravimetric or a coulometric method took about 40 or 25 min, respectively.

  16. Synthesis of One-Dimensional SiC Nanostructures from a Glassy Buckypaper

    SciTech Connect

    Ding, Mengning; Star, Alexander

    2013-02-21

    A simple and scalable synthetic strategy was developed for the fabrication of one-dimensional SiC nanostructures - nanorods and nanowires. Thin sheets of single-walled carbon nanotubes (SWNTs) were prepared by vacuum filtration and were washed repeatedly with sodium silicate (Na₂SiO₃) solution. The resulting “glassy buckypaper” was heated at 1300 - 1500 °C under Ar/H₂ to allow a solid state reaction between C and Si precursors to form a variety of SiC nanostructures. The morphology and crystal structures of SiC nanorods and nanowires were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive xray spectroscopy (EDX), electron diffraction (ED) and x-ray diffraction (XRD) techniques. Furthermore, electrical conductance measurements were performed on SiC nanorods, demonstrating their potential applications in high-temperature sensors and control systems.

  17. Amperometric biosensor based on glassy carbon electrode modified with long-length carbon nanotube and enzyme

    NASA Astrophysics Data System (ADS)

    Furutaka, Hajime; Nemoto, Kentaro; Inoue, Yuki; Hidaka, Hiroki; Muguruma, Hitoshi; Inoue, Hitoshi; Ohsawa, Tatsuya

    2016-05-01

    An amperometric biosensor based on a glassy carbon electrode modified with long-length multiwalled carbon nanotubes (MWCNTs) and enzyme nicotinamide-adenine-dinucleotide-dependent glucose dehydrogenase (GDH) is presented. We demonstrate the effect of the MWCNT length on the amperometric response of the enzyme biosensor. The long length of MWCNT is 200 µm (average), whereas the normal length of MWCNT is 1 µm (average). The response of the long MWCNT-GDH electrode is 2 times more sensitive than that of the normal-length MWCNT-GDH electrode in the concentration range from 0.25-35 mM. The result of electrochemical impedance spectroscopy measurements suggest that the long-length MWCNT-GDH electrode formed a better electron transfer network than the normal-length one.

  18. Energy barriers, entropy barriers, and non-Arrhenius behavior in a minimal glassy model.

    PubMed

    Du, Xin; Weeks, Eric R

    2016-06-01

    We study glassy dynamics using a simulation of three soft Brownian particles confined to a two-dimensional circular region. If the circular region is large, the disks freely rearrange, but rearrangements are rarer for smaller system sizes. We directly measure a one-dimensional free-energy landscape characterizing the dynamics. This landscape has two local minima corresponding to the two distinct disk configurations, separated by a free-energy barrier that governs the rearrangement rate. We study several different interaction potentials and demonstrate that the free-energy barrier is composed of a potential-energy barrier and an entropic barrier. The heights of both of these barriers depend on temperature and system size, demonstrating how non-Arrhenius behavior can arise close to the glass transition. PMID:27415326

  19. Toward the Control of the Creation of Mixed Monolayers on Glassy Carbon Surfaces by Amine Oxidation.

    PubMed

    Groppi, Jessica; Bartlett, Philip N; Kilburn, Jeremy D

    2016-01-18

    A versatile and simple methodology for the creation of mixed monolayers on glassy carbon (GC) surfaces was developed, using an osmium-bipyridyl complex and anthraquinone as model redox probes. The work consisted in the electrochemical grafting on GC of a mixture of mono-protected diamine linkers in varying ratios which, after attachment to the surface, allowed orthogonal deprotection. After optimisation of the deprotection conditions, it was possible to remove one of the protecting groups selectively, couple a suitable osmium complex and cap the residual free amines. The removal of the second protecting group allowed the coupling of anthraquinone. The characterisation of the resulting surfaces by cyclic voltammetry showed the variation of the surface coverage of the two redox centres in relation to the initial ratio of the linking amine in solution.

  20. Electrochemistry of raloxifene on glassy carbon electrode and its determination in pharmaceutical formulations and human plasma.

    PubMed

    Bagheri, Akbar; Hosseini, Hadi

    2012-12-01

    The electrochemical behavior of raloxifene (RLX) on the surface of a glassy carbon electrode (GCE) has been studied by cyclic voltammetry (CV). The CV studies were performed in various supporting electrolytes, wide range of potential scan rates, and pHs. The results showed an adsorption-controlled and quasi-reversible process for the electrochemical reaction of RLX, and a probable redox mechanism was suggested. Under the optimum conditions, differential pulse voltammetry (DPV) was applied for quantitative determination of the RLX in pharmaceutical formulations. The DPV measurements showed that the anodic peak current of the RLX was linear to its concentration in the range of 0.2-50.0μM with a detection limit of 0.0750μM, relative standard deviation (RSD %) below 3.0%, and a good sensitivity. The proposed method was successfully applied for determination of the RLX in pharmaceutical and human plasma samples with a good selectivity and suitable recovery.

  1. Glassy phases and driven response of the phase-field-crystal model with random pinning.

    PubMed

    Granato, E; Ramos, J A P; Achim, C V; Lehikoinen, J; Ying, S C; Ala-Nissila, T; Elder, K R

    2011-09-01

    We study the structural correlations and the nonlinear response to a driving force of a two-dimensional phase-field-crystal model with random pinning. The model provides an effective continuous description of lattice systems in the presence of disordered external pinning centers, allowing for both elastic and plastic deformations. We find that the phase-field crystal with disorder assumes an amorphous glassy ground state, with only short-ranged positional and orientational correlations, even in the limit of weak disorder. Under increasing driving force, the pinned amorphous-glass phase evolves into a moving plastic-flow phase and then, finally, a moving smectic phase. The transverse response of the moving smectic phase shows a vanishing transverse critical force for increasing system sizes. PMID:22060323

  2. NMR evidence for inhomogeneous glassy behavior driven by nematic fluctuations in iron arsenide superconductors

    DOE PAGES

    Dioguardi, A. P.; Lawson, M. M.; Bush, B. T.; Crocker, J.; Shirer, K. R.; Nisson, D. M.; Kissikov, T.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.; et al

    2015-10-16

    We present 75As nuclear magnetic resonance spin-lattice and spin-spin relaxation rate data in Ba(Fe1–xCox)2As2 and Ba(Fe1–xCux)2As2 as a function of temperature, doping, and magnetic field. The relaxation curves exhibit a broad distribution of relaxation rates, consistent with inhomogeneous glassy behavior up to 100 K. The doping and temperature response of the width of the dynamical heterogeneity is similar to that of the nematic susceptibility measured by elastoresistance measurements. In this study, we argue that quenched random fields which couple to the nematic order give rise to a nematic glass that is reflected in the spin dynamics.

  3. NMR evidence for inhomogeneous glassy behavior driven by nematic fluctuations in iron arsenide superconductors

    SciTech Connect

    Dioguardi, A. P.; Lawson, M. M.; Bush, B. T.; Crocker, J.; Shirer, K. R.; Nisson, D. M.; Kissikov, T.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.; Yuan, S.; Kuhns, P. L.; Reyes, A. P.; Grafe, H. -J.; Curro, N. J.

    2015-10-16

    We present 75As nuclear magnetic resonance spin-lattice and spin-spin relaxation rate data in Ba(Fe1–xCox)2As2 and Ba(Fe1–xCux)2As2 as a function of temperature, doping, and magnetic field. The relaxation curves exhibit a broad distribution of relaxation rates, consistent with inhomogeneous glassy behavior up to 100 K. The doping and temperature response of the width of the dynamical heterogeneity is similar to that of the nematic susceptibility measured by elastoresistance measurements. In this study, we argue that quenched random fields which couple to the nematic order give rise to a nematic glass that is reflected in the spin dynamics.

  4. Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects

    NASA Astrophysics Data System (ADS)

    Eisenbach, A.; Havdala, T.; Delahaye, J.; Grenet, T.; Amir, A.; Frydman, A.

    2016-09-01

    Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibrium contains information on the sample's excitation history, an effect often refer to as "aging." We demonstrate that under the right conditions a glass can also possess a different type of memory. We study the conductance relaxation of electron glasses that are fabricated at low temperatures. Remarkably, the dynamics are found to depend not only on the ambient measurement temperature but also on the maximum temperature to which the system was exposed. Hence the system "remembers" its highest temperature. This effect may be qualitatively understood in terms of energy barriers and local minima in configuration space and therefore may be a general property of the glass state.

  5. Amperometric sensing of hydrogen peroxide using glassy carbon electrode modified with copper nanoparticles

    SciTech Connect

    Sophia, J.; Muralidharan, G.

    2015-10-15

    In this paper, fabrication of glassy carbon electrode (GCE) modified with nano copper particles is discussed. The modified electrode has been tested for the non-enzymatic electrochemical detection of hydrogen peroxide (H{sub 2}O{sub 2}). The copper nanoparticles (Cu NPs) were prepared employing a simple chemical reduction method. The presence of Cu NPs was confirmed through UV–visible (UV–vis) absorption spectroscopy and X-ray diffraction (XRD) analysis. The size and morphology of the particles were investigated using transmission electron microscopy (TEM). The electrochemical properties of the fabricated sensor were studied via cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The electrochemical sensor displayed excellent performance features towards H{sub 2}O{sub 2} detection exhibiting wide linear range, low detection limit, swift response time, good reproducibility and stability.

  6. Thermomechanical processing of metallic glasses: extending the range of the glassy state

    NASA Astrophysics Data System (ADS)

    Sun, Yonghao; Concustell, Amadeu; Greer, A. Lindsay

    2016-09-01

    For crystalline metals, the science, technology and application of thermomechanical processing are established, but this is not true for glasses. Metallic glasses — because they can be plastically deformed — offer a unique opportunity to study the effects of thermomechanical treatments on the structure and properties of glasses. Depending on the rate of cooling, various glassy states can form from a liquid. Slower cooling gives states of lower enthalpy and smaller volume; such states might also be reached by annealing, which induces structural ‘relaxation’. A reduction in the degree of relaxation, or ‘rejuvenation’, is achievable through processes such as irradiation and mechanical deformation. In this Review, we explore the extent of relaxation and rejuvenation induced by thermomechanical processing (that is, elastic and plastic deformation, including cold and hot working, and cyclic loading). The issues that remain to be investigated and the prospects for further progress are discussed.

  7. Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects.

    PubMed

    Eisenbach, A; Havdala, T; Delahaye, J; Grenet, T; Amir, A; Frydman, A

    2016-09-01

    Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibrium contains information on the sample's excitation history, an effect often refer to as "aging." We demonstrate that under the right conditions a glass can also possess a different type of memory. We study the conductance relaxation of electron glasses that are fabricated at low temperatures. Remarkably, the dynamics are found to depend not only on the ambient measurement temperature but also on the maximum temperature to which the system was exposed. Hence the system "remembers" its highest temperature. This effect may be qualitatively understood in terms of energy barriers and local minima in configuration space and therefore may be a general property of the glass state. PMID:27661707

  8. Molecular motions in supercooled and glassy ibuprofen: deuteron magnetic resonance and high-resolution rheology study.

    PubMed

    Bauer, S; Storek, M; Gainaru, C; Zimmermann, H; Böhmer, R

    2015-04-16

    Using deuteron nuclear magnetic resonance, the molecular motions of specifically isotope-labeled ibuprofen were probed at the carboxylic group and at the methin group next to it. Spin relaxometry revealed slight differences between the molecular motions of the two isotopomers that are rationalized with reference to the hydrogen bonding of the COOH moiety. In the glassy state, a small-angle jump process among about four sites, related to the so-called γ-process, was identified using stimulated-echo spectroscopy. Indications for a Debye-like process, previously found to leave a weak signature in the dielectric loss, could not unambiguously be detected in magnetic resonance or shear mechanical experiments carried out for supercooled liquid ibuprofen.

  9. Determination of trimebutine in pharmaceuticals by differential pulse voltammetry at a glassy carbon electrode.

    PubMed

    Adhoum, Nafaâ; Monser, Lotfi

    2005-07-15

    The differential pulse voltammetric (DPV) determination of trimebutine (TMB) was achieved at a glassy carbon electrode in acetonitrile/0.1 M LiClO4. Trimebutine gave two irreversible, diffusion controlled peaks at 740 and 1318 mV versus Ag/AgCl reference electrode, respectively. The second oxidation peak was used to determine trimebutine concentrations in the range 1-50 microg ml(-1) with a detection limit (3sigmam) of 0.3 microg ml(-1). Precision of the method (RSD, n=6) within- and between-days obtained from six determinations at 5 microg ml(-1) was found to be 0.7 and 1.1%, respectively. The method was successfully applied to the quantitation of TMB in granule dosage form (Debridat) and recoveries between 98.4 and 101% were obtained. Excipients did not interfere with the assay and the results agreed well with those determined by previously established HPLC method. PMID:15967289

  10. Glassy behavior in a one-dimensional continuous-wave erbium-doped random fiber laser

    NASA Astrophysics Data System (ADS)

    Gomes, Anderson S. L.; Lima, Bismarck C.; Pincheira, Pablo I. R.; Moura, André L.; Gagné, Mathieu; Raposo, Ernesto P.; de Araújo, Cid B.; Kashyap, Raman

    2016-07-01

    The photonic analog of the paramagnetic to spin-glass phase transition in disordered magnetic systems, signaled by the phenomenon of replica symmetry breaking, has been reported using random lasers as the photonic platform. We report here a demonstration of replica symmetry breaking in a one-dimensional photonic system consisting of an erbium-doped random fiber laser operating in the continuous-wave regime. The system is based on a unique random fiber grating system which plays the role of random scattering, providing the disordered feedback mechanism. The clear transition from a photonic paramagnetic to a photonic spin-glass phase, characterized by the Parisi overlap parameter, was verified and indicates the glassy random-fiber-laser behavior.

  11. Toward the Control of the Creation of Mixed Monolayers on Glassy Carbon Surfaces by Amine Oxidation.

    PubMed

    Groppi, Jessica; Bartlett, Philip N; Kilburn, Jeremy D

    2016-01-18

    A versatile and simple methodology for the creation of mixed monolayers on glassy carbon (GC) surfaces was developed, using an osmium-bipyridyl complex and anthraquinone as model redox probes. The work consisted in the electrochemical grafting on GC of a mixture of mono-protected diamine linkers in varying ratios which, after attachment to the surface, allowed orthogonal deprotection. After optimisation of the deprotection conditions, it was possible to remove one of the protecting groups selectively, couple a suitable osmium complex and cap the residual free amines. The removal of the second protecting group allowed the coupling of anthraquinone. The characterisation of the resulting surfaces by cyclic voltammetry showed the variation of the surface coverage of the two redox centres in relation to the initial ratio of the linking amine in solution. PMID:26637108

  12. Survival of Staphylococcus aureus and enterotoxin A in glassy and rubbery states of gelatin.

    PubMed

    Bolton, K J; Dodd, C E; Gould, G W; Waites, W M

    1996-08-01

    About 1% of Staphylococcus aureus cells survived the production of gelatin sheets containing nutrient broth. Those cells which survived showed no evidence of injury. Growth occurred in rubbery state gelatin with a(w) values of 0.98 and 0.93 ; viability decreased during storage at a(w) values of 0.89, 0.62 and 0.36 but there was little loss of viability in gelatin at an aw of 0.25 over 27 d storage at 26 degrees C. Assays for enterotoxin A detected no synthesis of new toxin but no loss in pre-formed toxin. The results suggest that high levels of Staph. aureus and its toxins should be excluded from glassy and rubbery state food products in order to prevent illness. PMID:8760328

  13. Can Stress Relaxation Experiments be Used to Assess Deformation Induced Mobility in Glassy Polymers?

    NASA Astrophysics Data System (ADS)

    Kropka, Jamie; Long, Kevin

    The observance of an increase in glassy polymer relaxation rates under a mechanical deformation is often referred to as deformation induced mobility (DIM). It has been argued that stress relaxation experiments can provide indirect evidence of this phenomenon. Recently, stress relaxation experiments have been interpreted as demonstrating a mobility decrease with increased deformation when very slow strain rates, 1.2 x 10-5 s-1, are used to apply the deformation. This would suggest against generality of DIM and would have significant implications to constitutive models founded on this principle. Here, a mathematical exercise is performed to evaluate the implications of DIM on stress relaxation response. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  14. Electrochemical Determination of Glycoalkaloids Using a Carbon Nanotubes-Phenylboronic Acid Modified Glassy Carbon Electrode

    PubMed Central

    Wang, Huiying; Liu, Mingyue; Hu, Xinxi; Li, Mei; Xiong, Xingyao

    2013-01-01

    A versatile strategy for electrochemical determination of glycoalkaloids (GAs) was developed by using a carbon nanotubes-phenylboronic acid (CNTs-PBA) modified glassy carbon electrode. PBA reacts with α-solanine and α-chaconine to form a cyclic ester, which could be utilized to detect GAs. This method allowed GA detection from 1 μM to 28 μM and the detection limit was 0.3 μM. Affinity interaction of GAs and immobilized PBA caused an essential change of the peak current. The CNT-PBA modified electrodes were sensitive for detection of GAs, and the peak current values were in quite good agreement with those measured by the sensors. PMID:24287539

  15. Glassy phases and driven response of the phase-field-crystal model with random pinning.

    PubMed

    Granato, E; Ramos, J A P; Achim, C V; Lehikoinen, J; Ying, S C; Ala-Nissila, T; Elder, K R

    2011-09-01

    We study the structural correlations and the nonlinear response to a driving force of a two-dimensional phase-field-crystal model with random pinning. The model provides an effective continuous description of lattice systems in the presence of disordered external pinning centers, allowing for both elastic and plastic deformations. We find that the phase-field crystal with disorder assumes an amorphous glassy ground state, with only short-ranged positional and orientational correlations, even in the limit of weak disorder. Under increasing driving force, the pinned amorphous-glass phase evolves into a moving plastic-flow phase and then, finally, a moving smectic phase. The transverse response of the moving smectic phase shows a vanishing transverse critical force for increasing system sizes.

  16. Glassy and Metastable Crystalline BaTi2O5 by Containerless Processing

    NASA Astrophysics Data System (ADS)

    Yoda, Shinichi; Kentei Yu, Yu; Kumar, Vijaya; Kameko, Masashi

    Many efforts have been devoted to forming bulk glass from the melt of ferroelectric crystalline materials without adding any network-forming oxides such as SiO2 due to the potential for producing transparent glass ceramics with high dielectric constant and enhanced piezoelectric, pyroelectric and electro-optic use. The containerless processing is an attractive synthesis tech-nique as it can prevent melt contamination, minimize heterogeneous nucleation, and allow melt to achieve deep undercooling for forming metastable and glassy materials. We have fabricated a new ferroelectric materiel BaTi2 O5 [1] as bulk glass from melt by us-ing containerless processing and studied the phase relationship between microstructure and ferroelectric properties of BaTi2 O5 [2]. The structures of glassy and metastable crystalline BaTi2 O5 fabricated by the containerless pro-cessing were comprehensively investigated by combined X-ray and neutron diffractions, XANES analyses and computer simulations [3]. The 3-dimensional atomic structure of glassy BaTi2 O5 (g-BaTi2 O5 ), simulated by Reverse Monte Carlo (RMC) modelling on diffraction data, shows that extremely distorted TiO5 polyhedra interconnected with both corner-and edge-shared oxy-gen, formed a higher packing density structure than that of conventional silicate glass linked with only corner-sharing of SiO4 polyhedra. In addition, XANES measurement reveales that five-coordinated TiO5 polyhedra were formable in the crystallized metastable a-and b-BaTi2 O5 phases. The structure of metastable b-BaTi2 O5 was solved by ab initio calculation, and refined by Rietveld refinement as group Pnma with unit lattices a = 10.23784 ˚, b = 3.92715 ˚, c A A = 10.92757 A ˚. Our results show that the glass-forming ability enhanced by containerless pro-cessing, not by `strong glass former', fabricated new bulk oxide glasses with peculiar structures and properties. The intermediate-range structure of g-BaTi2 O5 and the crystalline structure of

  17. Thermal expansion of a glassy alloy studied using a real-space pair distribution function

    SciTech Connect

    Louzguine-Luzgin, Dmitri V.; Inoue, Akihisa; Yavari, Alain R.; Vaughan, Gavin

    2006-03-20

    Thermal expansion of a glassy Cu{sub 55}Hf{sub 25}Ti{sub 15}Pd{sub 5} alloy studied by using reciprocal space functions is verified using a real-space pair distribution function. The experimental results obtained by real-time diffraction during heating in a synchrotron beam and their Fourier transformation processing to derive radial distribution functions indicate that both reciprocal and real-space distribution functions give good agreement in the calculation of thermal expansion data. In addition to providing structural information, these findings indicate that the change in the average atomic nearest-neighbor distance evaluated from the variation of the position of the main broad diffraction maximum can provide good thermal expansion data for metallic glasses.

  18. On the notion of ``1/f noise'' and data analysis for glassy water

    NASA Astrophysics Data System (ADS)

    Johari, G. P.

    2005-07-01

    It is argued that the measured dielectric loss is the sum of a background loss and a dipolar relaxation loss, and both should be considered in a dielectric spectrum analysis. The background loss can be determined by fitting a relaxation function to the spectral peak region. It is also shown that the dielectric loss tangent tanδ of glassy water, which has been rejected as "1/f noise" [A. Minoguchi, R. Richert, and C. A. Angell, Phys. Rev. Lett.93, 215703 (2004)], contains a large contribution from dipole relaxation loss, and its tanδ neither remains constant with change in f nor varies as 1/f. The incorrect attribution of water's tanδ of Minoguchi et al. puts into question the basis of their analysis.

  19. Amperometric determination of phenazopyridine hydrochloride in a flowing stream at the glassy carbon electrode.

    PubMed

    Belal, F

    1985-01-01

    A flow-injection method is described for the determination of phenazopyridine hydrochloride, based on electrochemical oxidation at the glassy carbon electrode. The suggested method is highly specific and can be used to determine phenazopyridine HCl in the presence of most drugs commonly found in pharmaceutical dosage forms or administered therapeutically. Applying a constant potential of +950 mV vs Ag/AgCl/3.5M KCl reference electrode, the calibration curve was linear in the 1-30 micrograms/mL range, with minimum detectability of 0.2 ng (signal-to-noise ratio 2). Good accuracy and precision were obtained when the method was applied to some dosage forms containing phenazopyridine HCl. Although automation was not used in this study, an automated system could be incorporated because the method uses the technique of continuous analysis in a flowing stream.

  20. Characterization of anomalous movements of spherical living cells on a silicon dioxide glassy substrate.

    PubMed

    Son, Myeonggu; Lee, Gyudo; Son, Jongsang; Choi, Seungyeop; Kim, Youngho; Lee, Sei-Young; Yoon, Young-Ro; Yoon, Dae Sung; Lee, Sang Woo

    2015-01-01

    The random walk of spherical living cells on a silicon dioxide glassy substrate was studied experimentally and numerically. This random walk trajectory exhibited erratic dancing, which seemingly obeyed anomalous diffusion (i.e., Lévy-like walk) rather than normal diffusion. Moreover, the angular distribution (-π to π) of the cells' trajectory followed a "U-shaped pattern" in comparison to the uniform distribution seen in the movements of negatively charged polystyrene microspheres. These effects could be attributable to the homeostasis-driven structural resilient character of cells and physical interactions derived from temporarily retained nonspecific binding due to weak forces between the cells and substrates. Our results provide new insights into the stochastic behavior of mesoscopic biological particles with respect to structural properties and physical interactions. PMID:25610514

  1. Inverse of polynomial matrices in the irreducible form

    NASA Technical Reports Server (NTRS)

    Chang, Fan R.; Shieh, Leang S.; Mcinnis, Bayliss C.

    1987-01-01

    An algorithm is developed for finding the inverse of polynomial matrices in the irreducible form. The computational method involves the use of the left (right) matrix division method and the determination of linearly dependent vectors of the remainders. The obtained transfer function matrix has no nontrivial common factor between the elements of the numerator polynomial matrix and the denominator polynomial.

  2. Analyzing Multivariate Repeated Measures Designs When Covariance Matrices Are Heterogeneous.

    ERIC Educational Resources Information Center

    Lix, Lisa M.; And Others

    Methods for the analysis of within-subjects effects in multivariate groups by trials repeated measures designs are considered in the presence of heteroscedasticity of the group variance-covariance matrices and multivariate nonnormality. Under a doubly multivariate model approach to hypothesis testing, within-subjects main and interaction effect…

  3. Soft matrices on soft multisets in an optimal decision process

    NASA Astrophysics Data System (ADS)

    Coskun, Arzu Erdem; Aras, Cigdem Gunduz; Cakalli, Huseyin; Sonmez, Ayse

    2016-08-01

    In this paper, we introduce a concept of a soft matrix on a soft multiset, and investigate how to use soft matrices to solve decision making problems. An algorithm for a multiple choose selection problem is also provided. Finally, we demonstrate an illustrative example to show the decision making steps.

  4. Simplified symmetric quark mass matrices and flavor mixing

    SciTech Connect

    Frampton, P.H. ); Okada, Y. )

    1991-07-30

    In this paper a formula relating flavor mixing and quark masses is derived from an ansatz for mass matrices. In particular, given m{sub u}, m{sub c} and {vert bar}V{sub cb}{vert bar} the formula relates the top mass m{sub t} to {vert bar}V{sub ub}{vert bar}.

  5. Cluster Matrices for Health Occupations. Education for Employment Task Lists.

    ERIC Educational Resources Information Center

    Lathrop, Janice

    These cluster matrices provide duties and tasks that form the basis of instructional content for secondary, postsecondary, and adult training programs for health occupations. The eight clusters (and the job titles included in each cluster) are as follows: (1) dental assisting (dental assistant); (2) dental laboratory technology (dental laboratory…

  6. Automorphisms of semigroups of invertible matrices with nonnegative integer elements

    SciTech Connect

    Semenov, Pavel P

    2012-09-30

    Let G{sub n}(Z) be the subsemigroup of GL{sub n}(Z) consisting of the matrices with nonnegative integer coefficients. In the paper, the automorphisms of this semigroup are described for n{>=}2. Bibliography: 5 titles.

  7. Current technologies for detection of ricin in different matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ricin is a convenient, potent, and available toxin for terrorist acts. The importance of detecting it in various matrices is obvious. This chapter reviews methods for ricin detection based on the mechanisms used for assay development. Five detection approaches are reviewed: 1. Antibody-based metho...

  8. Axisymmetric analytical stiffness matrices with Green-Lagrange strains

    NASA Astrophysics Data System (ADS)

    Pedersen, P.

    2005-02-01

    Stiffness matrices based on the non-linear Green-Lagrange definition seem complicated, but for the case of a linear displacement ring-element with triangular cross-section, closed form final results are listed, directly suited for coding in a finite element program. These analytical secant and tangent element stiffness matrices are obtained by separating the dependence on the material constitutive parameters and on the stress/strain state from the dependence on the initial geometry and the displacement assumption. As an example of application, numerical results for a circular plate problem show the indirect severe errors that may result from a linear strain model. It is difficult to predict the indirect errors that follow from the erroneous displacement field, and the explanations behind such predictions are attempted. The nodal positions of an element and the displacement assumption give six basic matrices that do not depend on material and stress strain state, and thus are unchanged during the necessary iterations for obtaining a solution based on Green-Lagrange strain measure. The presented resulting stiffness matrices are especially useful in design optimization, because analytical sensitivity analysis can then be performed.

  9. Controlled growth factor release from synthetic extracellular matrices

    NASA Astrophysics Data System (ADS)

    Lee, Kuen Yong; Peters, Martin C.; Anderson, Kenneth W.; Mooney, David J.

    2000-12-01

    Polymeric matrices can be used to grow new tissues and organs, and the delivery of growth factors from these matrices is one method to regenerate tissues. A problem with engineering tissues that exist in a mechanically dynamic environment, such as bone, muscle and blood vessels, is that most drug delivery systems have been designed to operate under static conditions. We thought that polymeric matrices, which release growth factors in response to mechanical signals, might provide a new approach to guide tissue formation in mechanically stressed environments. Critical design features for this type of system include the ability to undergo repeated deformation, and a reversible binding of the protein growth factors to polymeric matrices to allow for responses to repeated stimuli. Here we report a model delivery system that can respond to mechanical signalling and upregulate the release of a growth factor to promote blood vessel formation. This approach may find a number of applications, including regeneration and engineering of new tissues and more general drug-delivery applications.

  10. Dimensionality of Data Matrices with Applications to Gene Expression Profiles

    ERIC Educational Resources Information Center

    Feng, Xingdong

    2009-01-01

    Probe-level microarray data are usually stored in matrices. Take a given probe set (gene), for example, each row of the matrix corresponds to an array, and each column corresponds to a probe. Often, people summarize each array by the gene expression level. Is one number sufficient to summarize a whole probe set for a specific gene in an array?…

  11. Variation in Raven's Progressive Matrices Scores across Time and Place

    ERIC Educational Resources Information Center

    Brouwers, Symen A.; Van de Vijver, Fons J. R.; Van Hemert, Dianne A.

    2009-01-01

    The paper describes a cross-cultural and historical meta-analysis of Raven's Progressive Matrices. Data were analyzed of 798 samples from 45 countries (N = 244,316), which were published between 1944 and 2003. Country-level indicators of educational permeation (which involves a broad set of interrelated educational input and output factors that…

  12. Extremal Positive Maps on M3(ℂ) and Idempotent Matrices

    NASA Astrophysics Data System (ADS)

    Miller, Marek; Olkiewicz, Robert

    2016-03-01

    A new method of analysing positive bistochastic maps on the algebra of complex matrices M3 has been proposed. By identifying the set of such maps with a convex set of linear operators on ℝ8, one can employ techniques from the theory of compact semigroups to obtain results concerning asymptotic properties of positive maps. It turns out that the idempotent elements play a crucial role in classifying the convex set into subsets, in which representations of extremal positive maps are to be found. It has been shown that all positive bistochastic maps, extremal in the set of all positive maps of M3, that are not Jordan isomorphisms of M3 are represented by matrices that fall into two possible categories, determined by the simplest idempotent matrices: one by the zero matrix, and the other by a one-dimensional orthogonal projection. Some norm conditions for matrices representing possible extremal maps have been specified and examples of maps from both categories have been brought up, based on the results published previously.

  13. Quantitative mass spectrometry of unconventional human biological matrices.

    PubMed

    Dutkiewicz, Ewelina P; Urban, Pawel L

    2016-10-28

    The development of sensitive and versatile mass spectrometric methodology has fuelled interest in the analysis of metabolites and drugs in unconventional biological specimens. Here, we discuss the analysis of eight human matrices-hair, nail, breath, saliva, tears, meibum, nasal mucus and skin excretions (including sweat)-by mass spectrometry (MS). The use of such specimens brings a number of advantages, the most important being non-invasive sampling, the limited risk of adulteration and the ability to obtain information that complements blood and urine tests. The most often studied matrices are hair, breath and saliva. This review primarily focuses on endogenous (e.g. potential biomarkers, hormones) and exogenous (e.g. drugs, environmental contaminants) small molecules. The majority of analytical methods used chromatographic separation prior to MS; however, such a hyphenated methodology greatly limits analytical throughput. On the other hand, the mass spectrometric methods that exclude chromatographic separation are fast but suffer from matrix interferences. To enable development of quantitative assays for unconventional matrices, it is desirable to standardize the protocols for the analysis of each specimen and create appropriate certified reference materials. Overcoming these challenges will make analysis of unconventional human biological matrices more common in a clinical setting.This article is part of the themed issue 'Quantitative mass spectrometry'. PMID:27644966

  14. A Role for M-Matrices in Modelling Population Growth

    ERIC Educational Resources Information Center

    James, Glyn; Rumchev, Ventsi

    2006-01-01

    Adopting a discrete-time cohort-type model to represent the dynamics of a population, the problem of achieving a desired total size of the population under a balanced growth (contraction) and the problem of maintaining the desired size, once achieved, are studied. Properties of positive-time systems and M-matrices are used to develop the results,…

  15. R-Matrices and the Tensor Product Graph Method

    NASA Astrophysics Data System (ADS)

    Gould, Mark D.; Zhang, Yao-Zhong

    2002-11-01

    A systematic method for constructing trigonometric R-matrices corresponding to the (multiplicity-free) tensor product of any two affinizable representations of a quantum algebra or superalgebra has been developed by the Brisbane group and its collaborators. This method has been referred to as the Tensor Product Graph Method. Here we describe applications of this method to untwisted and twisted quantum affine superalgebras.

  16. R-Matrices and the Tensor Product Graph Method

    NASA Astrophysics Data System (ADS)

    Gould, Mark D.; Zhang, Yao-Zhong

    A systematic method for constructing trigonometric R-matrices corresponding to the (multiplicity-free) tensor product of any two affinizable representations of a quantum algebra or superalgebra has been developed by the Brisbane group and its collaborators. This method has been referred to as the Tensor Product Graph Method. Here we describe applications of this method to untwisted and twisted quantum affine superalgebras.

  17. Technologies for detecting botulinum neurotoxins in biological and environmental matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biomonitoring of food and environmental matrices is critical for the rapid and sensitive diagnosis, treatment, and prevention of diseases caused by toxins. The United States Centers for Disease Control and Prevention (CDC) has noted that toxins from bacteria, fungi, algae, and plants present an ongo...

  18. Quantitative mass spectrometry of unconventional human biological matrices

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, Ewelina P.; Urban, Pawel L.

    2016-10-01

    The development of sensitive and versatile mass spectrometric methodology has fuelled interest in the analysis of metabolites and drugs in unconventional biological specimens. Here, we discuss the analysis of eight human matrices-hair, nail, breath, saliva, tears, meibum, nasal mucus and skin excretions (including sweat)-by mass spectrometry (MS). The use of such specimens brings a number of advantages, the most important being non-invasive sampling, the limited risk of adulteration and the ability to obtain information that complements blood and urine tests. The most often studied matrices are hair, breath and saliva. This review primarily focuses on endogenous (e.g. potential biomarkers, hormones) and exogenous (e.g. drugs, environmental contaminants) small molecules. The majority of analytical methods used chromatographic separation prior to MS; however, such a hyphenated methodology greatly limits analytical throughput. On the other hand, the mass spectrometric methods that exclude chromatographic separation are fast but suffer from matrix interferences. To enable development of quantitative assays for unconventional matrices, it is desirable to standardize the protocols for the analysis of each specimen and create appropriate certified reference materials. Overcoming these challenges will make analysis of unconventional human biological matrices more common in a clinical setting. This article is part of the themed issue 'Quantitative mass spectrometry'.

  19. Effect of an Interactive Courseware in the Learning of Matrices

    ERIC Educational Resources Information Center

    Hoon, Teoh Sian; Chong, Toh Seong; Binti Ngah, Nor Azilah

    2010-01-01

    The main aim of this study is to integrate cooperative learning strategies, mastery learning and interactive multimedia to improve students' performance in Mathematics, specifically in the topic of matrices. It involved a quasi-experimental design with gain scores and time-on-task as dependent variables. The independent variables were three…

  20. "Non-equilibrium" block copolymer micelles with glassy cores: a predictive approach based on theory of equilibrium micelles.

    PubMed

    Nagarajan, Ramanathan

    2015-07-01

    Micelles generated in water from most amphiphilic block copolymers are widely recognized to be non-equilibrium structures. Typically, the micelles are prepared by a kinetic process, first allowing molecular scale dissolution of the block copolymer in a common solvent that likes both the blocks and then gradually replacing the common solvent by water to promote the hydrophobic blocks to aggregate and create the micelles. The non-equilibrium nature of the micelle originates from the fact that dynamic exchange between the block copolymer molecules in the micelle and the singly dispersed block copolymer molecules in water is suppressed, because of the glassy nature of the core forming polymer block and/or its very large hydrophobicity. Although most amphiphilic block copolymers generate such non-equilibrium micelles, no theoretical approach to a priori predict the micelle characteristics currently exists. In this work, we propose a predictive approach for non-equilibrium micelles with glassy cores by applying the equilibrium theory of micelles in two steps. In the first, we calculate the properties of micelles formed in the mixed solvent while true equilibrium prevails, until the micelle core becomes glassy. In the second step, we freeze the micelle aggregation number at this glassy state and calculate the corona dimension from the equilibrium theory of micelles. The condition when the micelle core becomes glassy is independently determined from a statistical thermodynamic treatment of diluent effect on polymer glass transition temperature. The predictions based on this "non-equilibrium" model compare reasonably well with experimental data for polystyrene-polyethylene oxide diblock copolymer, which is the most extensively studied system in the literature. In contrast, the application of the equilibrium model to describe such a system significantly overpredicts the micelle core and corona dimensions and the aggregation number. The non-equilibrium model suggests ways to

  1. Effects of Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Feeding, Size, and Lipid Content on Egg Maturation.

    PubMed

    Sisterson, Mark S; Wallis, Christopher M; Stenger, Drake C

    2015-06-01

    The glassy-winged sharpshooter (Homalodisca vitripennis) is synovigenic and must feed as an adult to produce eggs. Egg maturation rates depend on the host plant species provided to the adult female for feeding and are variable for females provided with the same host plant species. Here, the contribution of female size and lipid content to variation in egg maturation rates among females held on the same host plant species was assessed. To assess effects of female size and lipid content on egg maturation, feeding assays followed by measurements of egg load, female size, and lipid content were conducted. To accomplish this, females were field collected and held on cowpea until producing approximately 0, 12, 25, or 50 ml of excreta. After reaching prescribed excreta thresholds, females were dissected to determine egg load, hind tibia length, and head capsule width. Mature eggs were removed from the abdomen and dry weight of eggs and bodies (head, thorax, and abdomen) were obtained. Lipid content of eggs and bodies were determined using a quantitative colorimetric assay. Rates of body weight gain and body lipid gain were rapid with low levels of feeding (12 ml of excreta) but decelerated with additional feeding (>12 ml of excreta). In contrast, low levels of feeding (12 ml of excreta) resulted in little egg production, with rates of egg production accelerating with additional feeding (>12 ml of excreta). Accordingly, egg production was preceded by an increase in body dry weight and body lipid content. In agreement, probability that a female carried eggs increased with body lipid content in the 0-, 12-, and 25-ml feeding treatments. Across treatments, larger females carried more eggs than smaller females. Collectively, results suggest that variation in glassy-winged sharpshooter egg maturation rates partially may be explained by availability of lipid reserves at the start of a feeding bout and female size. PMID:26470224

  2. Permeability of Rubbery and Glassy Membranes of Ionic Liquid Filled Polymersome Nanoreactors in Water.

    PubMed

    So, Soonyong; Yao, Letitia J; Lodge, Timothy P

    2015-12-01

    Nanoemulsion-like polymer vesicles (polymersomes) having ionic liquid interiors dispersed in water are attractive for nanoreactor applications. In a previous study, we demonstrated that small molecules could pass through rubbery polybutadiene membranes on a time scale of seconds, which is practical for chemical transformations. It is of interest to determine how sensitive the rate of transport is to temperature, particularly for membranes in the vicinity of the glass transition (Tg). In this work, the molecular exchange rate of 1-butylimidazole through glassy polystyrene (PS) bilayer membranes is investigated via pulsed field gradient nuclear magnetic resonance (PFG-NMR) over the temperature range from 25 to 70 °C. The vesicles were prepared by the cosolvent method in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([EMIM][TFSI]), and four different polystyrene-b-poly(ethylene oxide) (PS-PEO) diblock polymers with varying PS molecular weights were examined. The vesicles were transferred from the ionic liquid to water at room temperature to form nanoemulsion solutions of polymer vesicles in water. The exchange rate of 1-butylimidazole added to the aqueous solutions was observed under equilibrium conditions at each temperature. The exchange rate decreased as the membrane thickness increased, and the exchange rate through the glassy membranes was three to four times slower than through the rubbery polybutadiene membranes under the same experimental conditions. These results demonstrate that the permeability through nanosized membranes depends on both the dimension and chemistry of membrane-forming blocks. Furthermore, the exchange rate was investigated as a function of temperature in the vicinity of the Tg of PS-PEO membranes. The exchange rate, however, is not a strong function of the temperature in the vicinity of the membrane Tg, due to a combination of the nanoscopic dimension of the membrane, and some degree of solvent

  3. Multilevel micro-structuring of glassy carbon molds for precision glass molding

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Plöger, Sven; Hermerschmidt, Andreas

    2015-09-01

    Replication techniques for diffractive optical elements (DOEs) in soft materials such as plastic injection molding are state of the art. For precision glass molding in glasses with high transition temperatures, molds with extreme thermal resistivity, low chemical reactivity and high mechanical strength are needed. Glassy Carbon can be operated up to 2000°C making it possible to mold almost all glasses including Fused Silica with a transition temperatures above 1060°C. For the structuring of Glassy Carbon wafers photolithography and a RIE process is used. We have developed a process using Si as a hard mask material. If the flow rates of the etching gases O2 and SF6 are chosen properly, high selectivity of GC to Si 19:1 can be achieved, which provides excellent conditions to realize high resolution elements with feature size down to 1 micron and fulfills requirements for optical applications. We fabricated several multilevel GC molds with 8 levels of structuring. Two different optical functionalities were implemented: 6x6 array beamsplitter and 1x4 linear beamsplitter. The molds were applied for precision glass molding of a low Tg glass L-BAL 42 (from Ohara) with a transition temperature of 565°C. Their optical performance was measured. A more detailed analysis of the impact of mold fabrication defects on optical performance is done. Rigorous coupled wave analysis simulations are performed, where we included fabrication constrains such as duty cycle, edge depth errors, wall verticality and misalignment errors. We will compare the results with the design specifications and discuss the influence of fabrication errors introduced during the different process steps.

  4. Permeability of Rubbery and Glassy Membranes of Ionic Liquid Filled Polymersome Nanoreactors in Water.

    PubMed

    So, Soonyong; Yao, Letitia J; Lodge, Timothy P

    2015-12-01

    Nanoemulsion-like polymer vesicles (polymersomes) having ionic liquid interiors dispersed in water are attractive for nanoreactor applications. In a previous study, we demonstrated that small molecules could pass through rubbery polybutadiene membranes on a time scale of seconds, which is practical for chemical transformations. It is of interest to determine how sensitive the rate of transport is to temperature, particularly for membranes in the vicinity of the glass transition (Tg). In this work, the molecular exchange rate of 1-butylimidazole through glassy polystyrene (PS) bilayer membranes is investigated via pulsed field gradient nuclear magnetic resonance (PFG-NMR) over the temperature range from 25 to 70 °C. The vesicles were prepared by the cosolvent method in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([EMIM][TFSI]), and four different polystyrene-b-poly(ethylene oxide) (PS-PEO) diblock polymers with varying PS molecular weights were examined. The vesicles were transferred from the ionic liquid to water at room temperature to form nanoemulsion solutions of polymer vesicles in water. The exchange rate of 1-butylimidazole added to the aqueous solutions was observed under equilibrium conditions at each temperature. The exchange rate decreased as the membrane thickness increased, and the exchange rate through the glassy membranes was three to four times slower than through the rubbery polybutadiene membranes under the same experimental conditions. These results demonstrate that the permeability through nanosized membranes depends on both the dimension and chemistry of membrane-forming blocks. Furthermore, the exchange rate was investigated as a function of temperature in the vicinity of the Tg of PS-PEO membranes. The exchange rate, however, is not a strong function of the temperature in the vicinity of the membrane Tg, due to a combination of the nanoscopic dimension of the membrane, and some degree of solvent

  5. Effects of Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Feeding, Size, and Lipid Content on Egg Maturation.

    PubMed

    Sisterson, Mark S; Wallis, Christopher M; Stenger, Drake C

    2015-06-01

    The glassy-winged sharpshooter (Homalodisca vitripennis) is synovigenic and must feed as an adult to produce eggs. Egg maturation rates depend on the host plant species provided to the adult female for feeding and are variable for females provided with the same host plant species. Here, the contribution of female size and lipid content to variation in egg maturation rates among females held on the same host plant species was assessed. To assess effects of female size and lipid content on egg maturation, feeding assays followed by measurements of egg load, female size, and lipid content were conducted. To accomplish this, females were field collected and held on cowpea until producing approximately 0, 12, 25, or 50 ml of excreta. After reaching prescribed excreta thresholds, females were dissected to determine egg load, hind tibia length, and head capsule width. Mature eggs were removed from the abdomen and dry weight of eggs and bodies (head, thorax, and abdomen) were obtained. Lipid content of eggs and bodies were determined using a quantitative colorimetric assay. Rates of body weight gain and body lipid gain were rapid with low levels of feeding (12 ml of excreta) but decelerated with additional feeding (>12 ml of excreta). In contrast, low levels of feeding (12 ml of excreta) resulted in little egg production, with rates of egg production accelerating with additional feeding (>12 ml of excreta). Accordingly, egg production was preceded by an increase in body dry weight and body lipid content. In agreement, probability that a female carried eggs increased with body lipid content in the 0-, 12-, and 25-ml feeding treatments. Across treatments, larger females carried more eggs than smaller females. Collectively, results suggest that variation in glassy-winged sharpshooter egg maturation rates partially may be explained by availability of lipid reserves at the start of a feeding bout and female size.

  6. Selective electrochemical detection of 2,4,6-trinitrotoluene (TNT) in water based on poly(styrene-co-acrylic acid) PSA/SiO2/Fe3O4/AuNPs/lignin-modified glassy carbon electrode.

    PubMed

    Mahmoud, Khaled A; Abdel-Wahab, Ahmed; Zourob, Mohammed

    2015-01-01

    A new versatile electrochemical sensor based on poly(styrene-co-acrylic acid) PSA/SiO2/Fe3O4/AuNPs/lignin (L-MMS) modified glassy carbon electrode (GCE) was developed for the selective detection of trace trinitrotoluene (TNT) from aqueous media with high sensitivity. The fabricated magnetic microspheres were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). L-MMS films were cast on the GCE surface to fabricate the TNT sensing electrode. The limit of detection (LOD) of TNT determined by the amperometric i-t curve reached 35 pM. The lignin film and well packed Fe3O4/AuNPs facilitated the pre-concentration of trace TNT on the electrode surface resulting in a fast amperometric response of 3 seconds near the detection limit. The high sensitivity and excellent catalytic activity of the modified electrode could be attributed to the lignin layer and highly packed Fe3O4/AuNPs on the electrode surface. The total recovery of TNT from tapwater and seawater matrices was 98% and 96%, respectively. The electrode film was highly stable after five repeated adsorption/desorption cycles. The new electrochemical sensing scheme provides a highly selective, sensitive and versatile assay for the in-situ detection of TNT in complex water media.

  7. Selective electrochemical detection of 2,4,6-trinitrotoluene (TNT) in water based on poly(styrene-co-acrylic acid) PSA/SiO2/Fe3O4/AuNPs/lignin-modified glassy carbon electrode.

    PubMed

    Mahmoud, Khaled A; Abdel-Wahab, Ahmed; Zourob, Mohammed

    2015-01-01

    A new versatile electrochemical sensor based on poly(styrene-co-acrylic acid) PSA/SiO2/Fe3O4/AuNPs/lignin (L-MMS) modified glassy carbon electrode (GCE) was developed for the selective detection of trace trinitrotoluene (TNT) from aqueous media with high sensitivity. The fabricated magnetic microspheres were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). L-MMS films were cast on the GCE surface to fabricate the TNT sensing electrode. The limit of detection (LOD) of TNT determined by the amperometric i-t curve reached 35 pM. The lignin film and well packed Fe3O4/AuNPs facilitated the pre-concentration of trace TNT on the electrode surface resulting in a fast amperometric response of 3 seconds near the detection limit. The high sensitivity and excellent catalytic activity of the modified electrode could be attributed to the lignin layer and highly packed Fe3O4/AuNPs on the electrode surface. The total recovery of TNT from tapwater and seawater matrices was 98% and 96%, respectively. The electrode film was highly stable after five repeated adsorption/desorption cycles. The new electrochemical sensing scheme provides a highly selective, sensitive and versatile assay for the in-situ detection of TNT in complex water media. PMID:26540539

  8. Effet de l'interaction coulombienne sur la localisation d'Anderson dans le gaz bidimensionnel d'électrons

    NASA Astrophysics Data System (ADS)

    Fleury, G.

    2010-09-01

    Nous étudions l’effet des interactions coulombiennes sur la localisation d’Anderson dans le gaz bidimensionnel d’électrons désordonné. L’objectif est de statuer sur la question de l’existence de métaux à deux dimensions. En l’absence d’interaction, la théorie d’échelle de la localisation prédit qu’un désordre infinitésimal suffit à localiser la fonction d’onde électronique et donc à rendre le système isolant à température nulle (Abrahams et al., 1979). Dans certaines limites extrêmes, les interactions peuvent être prises en compte et l’on aboutit également à un état isolant. Cependant, aucune théorie analytique ne permet de traiter le régime quantique non-perturbatif où désordre et interaction sont intermédiaires. Expérimentalement, il est possible de l’explorer dans des échantillons de haute mobilité et basse densité. Depuis 1994, des comportements métalliques inexpliqués y ont été observés (Kravchenko et al., 1994). Nous avons mis au point une méthode numérique permettant d’étudier le problème couplé de la localisation d’Anderson en présence d’interaction. Cette méthode mêle Monte Carlo quantique à température nulle et théorie d’échelle pour la conductance de Thouless. Nous trouvons que la théorie d’échelle de la localisation est préservée en présence d’interaction et donc que le gaz bidimensionnel, même corrélé, est isolant à température nulle. Nos résultats montrent de plus que les interactions délocalisent le gaz bidimensionnel et que cet effet de délocalisation est accru en présence de dégénérescence de vallées. Ils nous permettent de proposer un mécanisme simple rendant compte des principales caractéristiques des comportements métalliques observés expérimentalement.

  9. Efficient linear algebra routines for symmetric matrices stored in packed form.

    PubMed

    Ahlrichs, Reinhart; Tsereteli, Kakha

    2002-01-30

    Quantum chemistry methods require various linear algebra routines for symmetric matrices, for example, diagonalization or Cholesky decomposition for positive matrices. We present a small set of these basic routines that are efficient and minimize memory requirements.

  10. Effete, a Drosophila Chromatin-Associated Ubiquitin-Conjugating Enzyme That Affects Telomeric and Heterochromatic Position Effect Variegation

    PubMed Central

    Cipressa, Francesca; Romano, Sabrina; Centonze, Silvia; zur Lage, Petra I.; Vernì, Fiammetta; Dimitri, Patrizio; Gatti, Maurizio; Cenci, Giovanni

    2013-01-01

    Drosophila telomeres are elongated by the transposition of telomere-specific retrotransposons rather than telomerase activity. Proximal to the terminal transposon array, Drosophila chromosomes contain several kilobases of a complex satellite DNA termed telomere-associated sequences (TASs). Reporter genes inserted into or next to the TAS are silenced through a mechanism called telomere position effect (TPE). TPE is reminiscent of the position effect variegation (PEV) induced by Drosophila constitutive heterochromatin. However, most genes that modulate PEV have no effect on TPE, and systematic searches for TPE modifiers have so far identified only a few dominant suppressors. Surprisingly, only a few of the genes required to prevent telomere fusion have been tested for their effect on TPE. Here, we show that with the exception of the effete (eff; also called UbcD1) mutant alleles, none of the tested mutations at the other telomere fusion genes affects TPE. We also found that mutations in eff, which encodes a class I ubiquitin-conjugating enzyme, act as suppressors of PEV. Thus, eff is one of the rare genes that can modulate both TPE and PEV. Immunolocalization experiments showed that Eff is a major constituent of polytene chromosomes. Eff is enriched at several euchromatic bands and interbands, the TAS regions, and the chromocenter. Our results suggest that Eff associates with different types of chromatin affecting their abilities to regulate gene expression. PMID:23821599

  11. Spectral density of generalized Wishart matrices and free multiplicative convolution

    NASA Astrophysics Data System (ADS)

    Młotkowski, Wojciech; Nowak, Maciej A.; Penson, Karol A.; Życzkowski, Karol

    2015-07-01

    We investigate the level density for several ensembles of positive random matrices of a Wishart-like structure, W =X X† , where X stands for a non-Hermitian random matrix. In particular, making use of the Cauchy transform, we study the free multiplicative powers of the Marchenko-Pastur (MP) distribution, MP⊠s, which for an integer s yield Fuss-Catalan distributions corresponding to a product of s -independent square random matrices, X =X1⋯Xs . New formulas for the level densities are derived for s =3 and s =1 /3 . Moreover, the level density corresponding to the generalized Bures distribution, given by the free convolution of arcsine and MP distributions, is obtained. We also explain the reason of such a curious convolution. The technique proposed here allows for the derivation of the level densities for several other cases.

  12. Spectral density of generalized Wishart matrices and free multiplicative convolution.

    PubMed

    Młotkowski, Wojciech; Nowak, Maciej A; Penson, Karol A; Życzkowski, Karol

    2015-07-01

    We investigate the level density for several ensembles of positive random matrices of a Wishart-like structure, W=XX(†), where X stands for a non-Hermitian random matrix. In particular, making use of the Cauchy transform, we study the free multiplicative powers of the Marchenko-Pastur (MP) distribution, MP(⊠s), which for an integer s yield Fuss-Catalan distributions corresponding to a product of s-independent square random matrices, X=X(1)⋯X(s). New formulas for the level densities are derived for s=3 and s=1/3. Moreover, the level density corresponding to the generalized Bures distribution, given by the free convolution of arcsine and MP distributions, is obtained. We also explain the reason of such a curious convolution. The technique proposed here allows for the derivation of the level densities for several other cases.

  13. Mutually unbiased bases and Hadamard matrices of order six

    NASA Astrophysics Data System (ADS)

    Bengtsson, Ingemar; Bruzda, Wojciech; Ericsson, A.˚Sa; Larsson, Jan-A.˚Ke; Tadej, Wojciech; Życzkowski, Karol

    2007-05-01

    We report on a search for mutually unbiased bases (MUBs) in six dimensions. We find only triplets of MUBs, and thus do not come close to the theoretical upper bound 7. However, we point out that the natural habitat for sets of MUBs is the set of all complex Hadamard matrices of the given order, and we introduce a natural notion of distance between bases in Hilbert space. This allows us to draw a detailed map of where in the landscape the MUB triplets are situated. We use available tools, such as the theory of the discrete Fourier transform, to organize our results. Finally, we present some evidence for the conjecture that there exists a four dimensional family of complex Hadamard matrices of order 6. If this conjecture is true the landscape in which one may search for MUBs is much larger than previously thought.

  14. Crystalline matrices for immobilization of actinides: Corrosion resistance in water

    NASA Astrophysics Data System (ADS)

    Yudintsev, S. V.; Aleksandrova, E. V.; Livshits, T. S.; Mal'kovskii, V. I.; Bychkova, Ya. V.; Tagirov, B. R.

    2014-10-01

    The rate of leaching of actinide-simulating rare-earth elements from two types of crystalline matrices consisting of titanate and titanozirconate phases was examined. The experiments were carried out at 95°C in distilled water. The rates of REE leaching from the samples were below 10-3 g/m2 day, which satisfied the requirements for the characteristics of matrices for immobilization of actinides. After passing the treated solutions through filters of 450 to 25 nm pore sizes, the REE content was changed slightly or not at all. This fact points to the minor role or to the absence of the colloidal form of REE in the solutions after the experiments.

  15. A new method for estimating growth transition matrices.

    PubMed

    Hillary, R M

    2011-03-01

    The vast majority of population models work using age or stage not length but there are many cases where animals cannot be aged sensibly or accurately. For these cases length-based models form the logical alternative but there has been little work done to develop and compare different methods of estimating growth transition matrices to be used in such models. This article demonstrates how a consistent Bayesian framework for estimating growth parameters and a novel method for constructing length transition matrices accounts for variation in growth in a clear and consistent manner and avoids potential subjective choices required using more established methods. The inclusion of the resultant growth uncertainty in population assessment models and the potential impact on management decisions is also addressed.

  16. Optical detection of parasitic protozoa in sol-gel matrices

    NASA Astrophysics Data System (ADS)

    Livage, Jacques; Barreau, J. Y.; Da Costa, J. M.; Desportes, I.

    1994-10-01

    Whole cell parasitic protozoa have been entrapped within sol-gel porous silica matrices. Stationary phase promastigote cells of Leishmania donovani infantum are mixed with a silica sol before gelation occurs. They remain trapped within the growing oxide network and their cellular organization appears to be well preserved. Moreover protozoa retain their antigenic properties in the porous gel. They are still able to detect parasite specific antibodies in serum samples from infected patients via an enzyme linked immunosorbent assay (ELISA). Antigen- antibody associations occurring in the gel are optically detected via the reactions of a peroxidase conjugate with ortho-phenylenediamine leading to the formation of a yellow coloration. A clear-cut difference in optical density is measured between positive and negative sera. Such an entrapment of antigenic species into porous sol-gel matrices avoids the main problems due to non specific binding and could be advantageously used in diagnostic kits.

  17. Optimal Estimation and Rank Detection for Sparse Spiked Covariance Matrices

    PubMed Central

    Cai, Tony; Ma, Zongming; Wu, Yihong

    2014-01-01

    This paper considers a sparse spiked covariancematrix model in the high-dimensional setting and studies the minimax estimation of the covariance matrix and the principal subspace as well as the minimax rank detection. The optimal rate of convergence for estimating the spiked covariance matrix under the spectral norm is established, which requires significantly different techniques from those for estimating other structured covariance matrices such as bandable or sparse covariance matrices. We also establish the minimax rate under the spectral norm for estimating the principal subspace, the primary object of interest in principal component analysis. In addition, the optimal rate for the rank detection boundary is obtained. This result also resolves the gap in a recent paper by Berthet and Rigollet [2] where the special case of rank one is considered. PMID:26257453

  18. Pseudounitary symmetry and the Gaussian pseudounitary ensemble of random matrices.

    PubMed

    Ahmed, Zafar; Jain, Sudhir R

    2003-04-01

    Employing the currently discussed notion of pseudo-Hermiticity, we define a pseudounitary group. Further, we develop a random matrix theory that is invariant under such a group and call this ensemble of pseudo-Hermitian random matrices the pseudounitary ensemble. We obtain exact results for the nearest-neighbor level-spacing distribution for (2 x 2) PT-invariant Hamiltonian matrices that have forms, approximately Sln(1/S) near zero spacing for three independent elements and approximately S for four independent elements. This shows a level repulsion in a marked distinction with an algebraic form S(beta) in the Wigner surmise. We believe that this paves the way for a description of varied phenomena in two-dimensional statistical mechanics, quantum chromodynamics, and so on. PMID:12786422

  19. Transformation matrices between non-linear and linear differential equations

    NASA Technical Reports Server (NTRS)

    Sartain, R. L.

    1983-01-01

    In the linearization of systems of non-linear differential equations, those systems which can be exactly transformed into the second order linear differential equation Y"-AY'-BY=0 where Y, Y', and Y" are n x 1 vectors and A and B are constant n x n matrices of real numbers were considered. The 2n x 2n matrix was used to transform the above matrix equation into the first order matrix equation X' = MX. Specially the matrix M and the conditions which will diagonalize or triangularize M were studied. Transformation matrices P and P sub -1 were used to accomplish this diagonalization or triangularization to return to the solution of the second order matrix differential equation system from the first order system.

  20. Chemical stability of titanium diboride reinforcement in nickel aluminide matrices

    NASA Technical Reports Server (NTRS)

    Rigney, J. D.; Lewandowski, J. J.

    1993-01-01

    Chemical stability of TiB2 reinforcement in NiAl (45 at percent Al) and Ni3Al (24 at percent Al) matrices has been theoretically and experimentally investigated. Calculations were made using thermodynamic properties of the systems to predict behavior at temperatures between 1173 and 1573 K. Experimental investigation of hot-press consolidated TiB2 particulate/prealloyed matrix powder blends were conducted using energy dispersive X-ray analysis, XRD, AES, and TEM. The theoretical and experimental analyses suggest that TiB2 is chemically stable in both matrices up to 1573 K; however, TiB2 was found to be less active in NiAl than in Ni3Al due to lower nickel activity in NiAl.

  1. Glassy ferromagnetism and magnetic phase separation in La1-xSrxCoO3

    NASA Astrophysics Data System (ADS)

    Wu, J.; Leighton, C.

    2003-05-01

    We present the results of a comprehensive investigation of the dc magnetization, ac susceptibility, and magnetotransport properties of the glassy ferromagnet La1-xSrxCoO3. The compositions studied span the range from the end-member LaCoO3 (x=0.0) through to x=0.7. These materials have attracted attention recently, primarily due to the spin-state transition phenomena in LaCoO3 and the unusual nature of the magnetic ground state for finite x. In this paper we present a consistent picture of the magnetic behavior of La1-xSrxCoO3 in terms of short-range ferromagnetic ordering and intrinsic phase separation. At high Sr doping (x>0.2) the system exhibits unconventional ferromagnetism (with a Curie temperature up to 250 K), which is interpreted in terms of the coalescence of short-range-ordered ferromagnetic clusters. Brillouin function fits to the temperature dependence of the magnetization as well as high-temperature Curie-Weiss behavior suggest that the Co3+ and Co4+ ions are both in the intermediate spin state. At lower Sr doping (x<0.18) the system enters a mixed phase that displays the characteristics of both a spin glass and a ferromagnet. A cusp in the zero-field-cooled dc magnetization, a frequency-dependent peak in the ac susceptibility and time-dependent effects in both dc and ac magnetic properties all point towards glassy behavior. On the other hand, field cooling results in a relatively large ferromagneticlike moment, with zero-field-cooled and field-cooled magnetizations bifurcating at an irreversibility point. Even in the region above x=0.2 the out-of-phase component of the ac susceptibility shows frequency-dependent peaks below the Curie temperature (indicative of glassy behavior) which have previously been interpreted in terms of the freezing of clusters. All of the results are consistent with the existence of a strong tendency towards magnetic phase separation in this material, a conclusion which is further reinforced by consideration of the electronic

  2. Solution of the determinantal assignment problem using the Grassmann matrices

    NASA Astrophysics Data System (ADS)

    Karcanias, Nicos; Leventides, John

    2016-02-01

    The paper provides a direct solution to the determinantal assignment problem (DAP) which unifies all frequency assignment problems of the linear control theory. The current approach is based on the solvability of the exterior equation ? where ? is an n -dimensional vector space over ? which is an integral part of the solution of DAP. New criteria for existence of solution and their computation based on the properties of structured matrices are referred to as Grassmann matrices. The solvability of this exterior equation is referred to as decomposability of ?, and it is in turn characterised by the set of quadratic Plücker relations (QPRs) describing the Grassmann variety of the corresponding projective space. Alternative new tests for decomposability of the multi-vector ? are given in terms of the rank properties of the Grassmann matrix, ? of the vector ?, which is constructed by the coordinates of ?. It is shown that the exterior equation is solvable (? is decomposable), if and only if ? where ?; the solution space for a decomposable ?, is the space ?. This provides an alternative linear algebra characterisation of the decomposability problem and of the Grassmann variety to that defined by the QPRs. Further properties of the Grassmann matrices are explored by defining the Hodge-Grassmann matrix as the dual of the Grassmann matrix. The connections of the Hodge-Grassmann matrix to the solution of exterior equations are examined, and an alternative new characterisation of decomposability is given in terms of the dimension of its image space. The framework based on the Grassmann matrices provides the means for the development of a new computational method for the solutions of the exact DAP (when such solutions exist), as well as computing approximate solutions, when exact solutions do not exist.

  3. Supercritical Fluid Infusion of Iron Additives in Polymeric Matrices

    NASA Technical Reports Server (NTRS)

    Nazem, Negin; Taylor, Larry T.

    1999-01-01

    The objective of this project was the experimentation to measure preparation of iron nanophases within polymeric matrices via supercritical fluid infusion of iron precursors followed by thermal reduction. Another objective was to determine if supercritical CO2 could infuse into the polymer. The experiment is described along with the materials, and the supercritical fluid infusion and cure procedures. X-ray photoelectron spectra and transmission electron micrographs were obtained. The results are summarized in charts, and tables.

  4. Ideal amino acid exchange forms for approximating substitution matrices.

    PubMed

    Pokarowski, Piotr; Kloczkowski, Andrzej; Nowakowski, Szymon; Pokarowska, Maria; Jernigan, Robert L; Kolinski, Andrzej

    2007-11-01

    We have analyzed 29 published substitution matrices (SMs) and five statistical protein contact potentials (CPs) for comparison. We find that popular, 'classical' SMs obtained mainly from sequence alignments of globular proteins are mostly correlated by at least a value of 0.9. The BLOSUM62 is the central element of this group. A second group includes SMs derived from alignments of remote homologs or transmembrane proteins. These matrices correlate better with classical SMs (0.8) than among themselves (0.7). A third group consists of intermediate links between SMs and CPs - matrices and potentials that exhibit mutual correlations of at least 0.8. Next, we show that SMs can be approximated with a correlation of 0.9 by expressions c(0) + x(i)x(j) + y(i)y(j) + z(i)z(j), 1matrices, and the highly significant dependence of classical SMs on coil preferences are new findings.

  5. Higher order matrix differential equations with singular coefficient matrices

    SciTech Connect

    Fragkoulis, V. C.; Kougioumtzoglou, I. A.; Pantelous, A. A.; Pirrotta, A.

    2015-03-10

    In this article, the class of higher order linear matrix differential equations with constant coefficient matrices and stochastic process terms is studied. The coefficient of the highest order is considered to be singular; thus, rendering the response determination of such systems in a straightforward manner a difficult task. In this regard, the notion of the generalized inverse of a singular matrix is used for determining response statistics. Further, an application relevant to engineering dynamics problems is included.

  6. Challenges of Detecting Bioterrorism Agents in Complex Matrices

    NASA Astrophysics Data System (ADS)

    Hartmann, Erica M.; Halden, Rolf U.

    This chapter offers an overview of the shift from the use of mass ­spectrometry for studying purified bioterrorism agents to the development of methods for rapid detection thereof in environmental and clinical samples. We discuss the difficulties of working with such complex matrices and present methods for quickly and effectively reducing complexity through sample preparation. Finally, we examine a success story wherein the common pathogen and potential bioterrorism agent norovirus is detected at clinically relevant levels in human stool.

  7. Probing quark mass matrices with [ital CP] violation

    SciTech Connect

    Belanger, G. ); Boridy, E.; Hamzaoui, C.; Jakimow, G. )

    1993-11-01

    Mass matrices are discussed in the standard model, taking into account the small observed value of [ital CP] violation, in order to disclose possible patterns. A particular mass pattern emerges in the limit of small [ital CP] violation. We obtain the following relations between the Kobayashi-Maskawa matrix elements and the quark masses: [vert bar][ital V][sub [ital u][ital b

  8. Trace inequalities for products of positive definite matrices

    NASA Astrophysics Data System (ADS)

    Bhatia, Rajendra

    2014-01-01

    It is shown that for positive definite matrices A and B the inequality ||ApBq + BpAq||2 ⩽ ||ApBq + AqBp||2 holds for all positive real number p and q for which p/(p + q) is in [1/4, 3/4]. This is a significant improvement on a recent result of Hayajneh and Kittaneh ["Lieb-Thirring trace inequalities and a question of Bourin," J. Math. Phys. 54, 033504 (2013)].

  9. Partitioning Rectangular and Structurally Nonsymmetric Sparse Matrices for Parallel Processing

    SciTech Connect

    B. Hendrickson; T.G. Kolda

    1998-09-01

    A common operation in scientific computing is the multiplication of a sparse, rectangular or structurally nonsymmetric matrix and a vector. In many applications the matrix- transpose-vector product is also required. This paper addresses the efficient parallelization of these operations. We show that the problem can be expressed in terms of partitioning bipartite graphs. We then introduce several algorithms for this partitioning problem and compare their performance on a set of test matrices.

  10. The Reliability and Validity of the MATRICS Functional Assessment Battery

    PubMed Central

    Velligan, Dawn I.; Fredrick, Megan; Mintz, Jim; Li, Xueying; Rubin, Maureen; Dube, Sanjay; Deshpande, Smita N.; Trivedi, Jitendra K.; Gautam, Shiv; Avasthi, Ajit; Kern, Robert S.; Marder, Stephen R.

    2014-01-01

    Objectives: The Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) initiative was designed to encourage the development of cognitive enhancing agents for schizophrenia. For a medication to receive this indication, regulatory agencies require evidence of improvement in both cognition and functional outcome. Functional capacity measures typically used in clinical trials as intermediate measures of functional outcome must be adapted to fit different cultural contexts for use internationally. We examined the psychometric properties of the MATRICS Functional Assessment Battery (MFAB), comprised of 2 subtests from the UCSD Performance-based Skills Assessment (UPSA) and one from the Test of Adaptive Behavior in Schizophrenia (TABS) that were rated by experts in a previous study to be the most appropriate functional capacity assessments across different cultural contexts. Method: Four sites in India administered the MFAB, a brief version of the UPSA, the MATRICS Cognitive Consensus Battery, measures of symptomatology, and a measure of global functional outcome to 141 individuals with schizophrenia at a baseline assessment and at 4 weeks later. Results: Test-retest reliability based on the intraclass correlation coefficient was significantly better for the UCSD Performance-Based Skills Assessment-Brief (UPSA-B). Pearson correlation coefficients over time were not significantly different for the 2 measures. Only the MFAB was significantly correlated with functional outcome as measured by the Specific Levels of Functioning Scale. Conclusions: The psychometric properties of the MFAB and UPSA-B were similar. The MATRICS scientific board chose to translate the MFAB into multiple languages for potential use in studies of novel medications seeking an indication for improving cognition in schizophrenia. PMID:24214931

  11. Shuttle Program. Euler angles, quaternions, and transformation matrices working relationships

    NASA Technical Reports Server (NTRS)

    Henderson, D. M.

    1977-01-01

    A brief mathematical development of the relationship between the Euler angles and the transformation matrix, the quaternion and the transformation matrix, and the Euler angles and the quaternion is presented. The analysis and equations presented apply directly to current space shuttle problems. The twelve three-axis Euler transformation matrices are given as functions of the Euler angles, the equations for the quaternion as a funtion of the Euler angles, and the Euler angles as a function of the transformation matrix elements.

  12. On the Assessment of Psychometric Adequacy in Correlation Matrices.

    ERIC Educational Resources Information Center

    Dziuban, Charles D.; Shirkey, Edwin C.

    Three techniques for assessing the adequacy of correlation matrices for factor analysis were applied to four examples from the literature. The methods compared were: (1) inspection of the off diagonal elements of the anti-image covariance matrix S(to the 2nd) R(to the -1) and S(to the 2nd); (2) the Measure of Sampling Adequacy (M.S.A.), and (3)…

  13. Random density matrices versus random evolution of open system

    NASA Astrophysics Data System (ADS)

    Pineda, Carlos; Seligman, Thomas H.

    2015-10-01

    We present and compare two families of ensembles of random density matrices. The first, static ensemble, is obtained foliating an unbiased ensemble of density matrices. As criterion we use fixed purity as the simplest example of a useful convex function. The second, dynamic ensemble, is inspired in random matrix models for decoherence where one evolves a separable pure state with a random Hamiltonian until a given value of purity in the central system is achieved. Several families of Hamiltonians, adequate for different physical situations, are studied. We focus on a two qubit central system, and obtain exact expressions for the static case. The ensemble displays a peak around Werner-like states, modulated by nodes on the degeneracies of the density matrices. For moderate and strong interactions good agreement between the static and the dynamic ensembles is found. Even in a model where one qubit does not interact with the environment excellent agreement is found, but only if there is maximal entanglement with the interacting one. The discussion is started recalling similar considerations for scattering theory. At the end, we comment on the reach of the results for other convex functions of the density matrix, and exemplify the situation with the von Neumann entropy.

  14. Reproducible quantitative proteotype data matrices for systems biology

    PubMed Central

    Röst, Hannes L.; Malmström, Lars; Aebersold, Ruedi

    2015-01-01

    Historically, many mass spectrometry–based proteomic studies have aimed at compiling an inventory of protein compounds present in a biological sample, with the long-term objective of creating a proteome map of a species. However, to answer fundamental questions about the behavior of biological systems at the protein level, accurate and unbiased quantitative data are required in addition to a list of all protein components. Fueled by advances in mass spectrometry, the proteomics field has thus recently shifted focus toward the reproducible quantification of proteins across a large number of biological samples. This provides the foundation to move away from pure enumeration of identified proteins toward quantitative matrices of many proteins measured across multiple samples. It is argued here that data matrices consisting of highly reproducible, quantitative, and unbiased proteomic measurements across a high number of conditions, referred to here as quantitative proteotype maps, will become the fundamental currency in the field and provide the starting point for downstream biological analysis. Such proteotype data matrices, for example, are generated by the measurement of large patient cohorts, time series, or multiple experimental perturbations. They are expected to have a large effect on systems biology and personalized medicine approaches that investigate the dynamic behavior of biological systems across multiple perturbations, time points, and individuals. PMID:26543201

  15. Damage detection using experimentally measured mass and stiffness matrices

    NASA Technical Reports Server (NTRS)

    Peterson, L. D.; Alvin, K. F.; Doebling, S. W.; Park, K. C.

    1993-01-01

    A method is presented for locating physical damage or change in a structure using experimentally measured mass and stiffness matrices. The approach uses a recently developed algorithm for transforming a state-space realization into a second order structural model with physical displacements as the generalized coordinates. This is accomplished by first rotating a state-space model of the identified structural dynamics into modal coordinates and approximating the mass normalized modal vectors for the output measurement set. Next, the physical mass, damping and stiffness matrices are synthesized directly from the measured modal parameters. This yields experimental mass and stiffness matrices for the structure without the use of a finite element model or a numerical search. The computed mass and stiffness are asymptotically equivalent to a static condensation of the global physical coordinate model. Techniques for solving the inverse connectivity problem are then developed whereby it is possible to assess the stiffness in a region of the structure bounded by several sensors. Applications to both simulated data and experimental data are used to discuss the effectiveness of the approach.

  16. Damage detection using experimentally measured mass and stiffness matrices

    NASA Astrophysics Data System (ADS)

    Peterson, L. D.; Alvin, K. F.; Doebling, S. W.; Park, K. C.

    1993-04-01

    A method is presented for locating physical damage or change in a structure using experimentally measured mass and stiffness matrices. The approach uses a recently developed algorithm for transforming a state-space realization into a second order structural model with physical displacements as the generalized coordinates. This is accomplished by first rotating a state-space model of the identified structural dynamics into modal coordinates and approximating the mass normalized modal vectors for the output measurement set. Next, the physical mass, damping and stiffness matrices are synthesized directly from the measured modal parameters. This yields experimental mass and stiffness matrices for the structure without the use of a finite element model or a numerical search. The computed mass and stiffness are asymptotically equivalent to a static condensation of the global physical coordinate model. Techniques for solving the inverse connectivity problem are then developed whereby it is possible to assess the stiffness in a region of the structure bounded by several sensors. Applications to both simulated data and experimental data are used to discuss the effectiveness of the approach.

  17. Visualization of newt aragonitic otoconial matrices using transmission electron microscopy

    NASA Technical Reports Server (NTRS)

    Steyger, P. S.; Wiederhold, M. L.

    1995-01-01

    Otoconia are calcified protein matrices within the gravity-sensing organs of the vertebrate vestibular system. These protein matrices are thought to originate from the supporting or hair cells in the macula during development. Previous studies of mammalian calcitic, barrel-shaped otoconia revealed an organized protein matrix consisting of a thin peripheral layer, a well-defined organic core and a flocculent matrix inbetween. No studies have reported the microscopic organization of the aragonitic otoconial matrix, despite its protein characterization. Pote et al. (1993b) used densitometric methods and inferred that prismatic (aragonitic) otoconia have a peripheral protein distribution, compared to that described for the barrel-shaped, calcitic otoconia of birds, mammals, and the amphibian utricle. By using tannic acid as a negative stain, we observed three kinds of organic matrices in preparations of fixed, decalcified saccular otoconia from the adult newt: (1) fusiform shapes with a homogenous electron-dense matrix; (2) singular and multiple strands of matrix; and (3) more significantly, prismatic shapes outlined by a peripheral organic matrix. These prismatic shapes remain following removal of the gelatinous matrix, revealing an internal array of organic matter. We conclude that prismatic otoconia have a largely peripheral otoconial matrix, as inferred by densitometry.

  18. Threshold partitioning of sparse matrices and applications to Markov chains

    SciTech Connect

    Choi, Hwajeong; Szyld, D.B.

    1996-12-31

    It is well known that the order of the variables and equations of a large, sparse linear system influences the performance of classical iterative methods. In particular if, after a symmetric permutation, the blocks in the diagonal have more nonzeros, classical block methods have a faster asymptotic rate of convergence. In this paper, different ordering and partitioning algorithms for sparse matrices are presented. They are modifications of PABLO. In the new algorithms, in addition to the location of the nonzeros, the values of the entries are taken into account. The matrix resulting after the symmetric permutation has dense blocks along the diagonal, and small entries in the off-diagonal blocks. Parameters can be easily adjusted to obtain, for example, denser blocks, or blocks with elements of larger magnitude. In particular, when the matrices represent Markov chains, the permuted matrices are well suited for block iterative methods that find the corresponding probability distribution. Applications to three types of methods are explored: (1) Classical block methods, such as Block Gauss Seidel. (2) Preconditioned GMRES, where a block diagonal preconditioner is used. (3) Iterative aggregation method (also called aggregation/disaggregation) where the partition obtained from the ordering algorithm with certain parameters is used as an aggregation scheme. In all three cases, experiments are presented which illustrate the performance of the methods with the new orderings. The complexity of the new algorithms is linear in the number of nonzeros and the order of the matrix, and thus adding little computational effort to the overall solution.

  19. Reproducible quantitative proteotype data matrices for systems biology.

    PubMed

    Röst, Hannes L; Malmström, Lars; Aebersold, Ruedi

    2015-11-01

    Historically, many mass spectrometry-based proteomic studies have aimed at compiling an inventory of protein compounds present in a biological sample, with the long-term objective of creating a proteome map of a species. However, to answer fundamental questions about the behavior of biological systems at the protein level, accurate and unbiased quantitative data are required in addition to a list of all protein components. Fueled by advances in mass spectrometry, the proteomics field has thus recently shifted focus toward the reproducible quantification of proteins across a large number of biological samples. This provides the foundation to move away from pure enumeration of identified proteins toward quantitative matrices of many proteins measured across multiple samples. It is argued here that data matrices consisting of highly reproducible, quantitative, and unbiased proteomic measurements across a high number of conditions, referred to here as quantitative proteotype maps, will become the fundamental currency in the field and provide the starting point for downstream biological analysis. Such proteotype data matrices, for example, are generated by the measurement of large patient cohorts, time series, or multiple experimental perturbations. They are expected to have a large effect on systems biology and personalized medicine approaches that investigate the dynamic behavior of biological systems across multiple perturbations, time points, and individuals.

  20. Visual optimization of DCT quantization matrices for individual images

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.

    1993-01-01

    Many image compression standards (JPEG, MPEG, H.261) are based on the Discrete Cosine Transform (DCT). However, these standards do not specify the actual DCT quantization matrix. We have previously provided mathematical formulae to compute a perceptually lossless quantization matrix. Here I show how to compute a matrix that is optimized for a particular image. The method treats each DCT coefficient as an approximation to the local response of a visual 'channel'. For a given quantization matrix, the DCT quantization errors are adjusted by contrast sensitivity, light adaptation, and contrast masking, and are pooled non-linearly over the blocks of the image. This yields an 8x8 'perceptual error matrix'. A second non-linear pooling over the perceptual error matrix yields total perceptual error. With this model we may estimate the quantization matrix for a particular image that yields minimum bit rate for a given total perceptual error, or minimum perceptual error for a given bit rate. Custom matrices for a number of images show clear improvement over image-independent matrices. Custom matrices are compatible with the JPEG standard, which requires transmission of the quantization matrix.

  1. Raven's matrices and working memory: a dual-task approach.

    PubMed

    Rao, K Venkata; Baddeley, Alan

    2013-01-01

    Raven's Matrices Test was developed as a "pure" measure of Spearman's concept of general intelligence, g. Subsequent research has attempted to specify the processes underpinning performance, some relating it to the concept of working memory and proposing a crucial role for the central executive, with the nature of other components currently unclear. Up to this point, virtually all work has been based on correlational analysis of number of correct solutions, sometimes related to possible strategies. We explore the application to this problem of the concurrent task methodology used widely in developing the concept of multicomponent working memory. Participants attempted to solve problems from the matrices under baseline conditions, or accompanied by backward counting or verbal repetition tasks, assumed to disrupt the central executive and phonological loop components of working memory, respectively. As in other uses of this method, number of items correct showed little effect, while solution time measures gave very clear evidence of an important role for the central executive, but no evidence for phonological loop involvement. We conclude that this and related concurrent task techniques hold considerable promise for the analysis of Raven's matrices and potentially for other established psychometric tests.

  2. Stabilization and solidification of Pb in cement matrices.

    PubMed

    Gollmann, Maria A C; da Silva, Márcia M; Masuero, Angela B; dos Santos, João Henrique Z

    2010-07-15

    Pb was incorporated to a series of cement matrices, which were submitted to different testes of solidified/stabilized product. The leaching behaviors of aqueous solution were monitored by graphite furnace atomic absorption spectroscopy (GF-AAS). The mechanical strengths were evaluated by unconfined compressive strength (UCS) at 7 and 28 ages. Data are discussed in terms of metal mobility along the cement block monitored by X-ray fluorescence (XRF) spectrometry. Complementary techniques, namely, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), thermal gravimetric analysis (TGA), small angle X-ray scattering (SAXS) and X-ray diffraction spectroscopy (XRD) were employed in the characterization of the modified matrices. The Pb incorporated matrices have shown that a long cure time is more suitable for avoiding metal leaching. At pH 8 lower Pb leaching took place both for both short and long cure time. For a longer cure period there is a decreasing in the compressive strength. TGA and DRIFTS analyses show that the resistance fall observed in the UCS tests in the sample with Pb are not caused by hydration excess. XRF analyses show that there is a lower Ca concentration in the matrix in which Pb was added.

  3. IUPAC-NIST Solubility Data Series 70. The Solubility of Gases in Glassy Polymers

    NASA Astrophysics Data System (ADS)

    Paterson, Russell; Yampol'Skii, Yuri P.; Fogg, Peter G. T.; Bokarev, Alexandre; Bondar, Valerii; Ilinich, Oleg; Shishatskii, Sergey

    1999-09-01

    Solubility of gases in polymers is an important property of polymeric materials relevant to many practical applications. Sorption of small molecules in polymers is a fundamental concern in such areas as food packaging, beverage storage, and polymer processing. However, by far the main interest in the solubility of gases in polymers, and especially in glassy polymers, is related to development of novel advanced materials for gas separation membranes. This is because the concentration gradient of a dissolved gas is the driving force of membrane processes. Development of these novel separation methods resulted in a rapid accumulation, in the recent literature, of thermodynamic data related to the solubility of gases in polymers at different temperatures and pressures. Polymers can be regarded as special cases of media intermediate between liquids and solids. As a consequence, modeling of gas sorption in polymers is very difficult and presents a permanent challenge to theoreticians and experimenters. The collection and critical evaluation of solubility data for various gas-polymer systems is relevant to both practical aspects of polymer applications and to fundamental studies of polymer behavior. This volume of the IUPAC-NIST Solubility Data Series summarizes the compilations and critical evaluations of the data on solubility of gases in glassy polymers. It is implied in this edition that "gases" are the components that are either permanent gases (supercitical fluids) or have saturated vapor pressure more than 1 atm at ambient conditions (298 K). The polymeric components of compilations and critical evaluations are primarily high molecular mass, amorphous, linear (noncross-linked) compounds that have the glass transition temperatures above ambient temperature. The data for each gas-polymer system have been evaluated, if the results of at least three independent and reliable studies have been reported. Where the data of sufficient accuracy and reliability are available

  4. Multiscale simulations of PS-SiO2 nanocomposites: from melt to glassy state.

    PubMed

    Mathioudakis, I G; Vogiatzis, G G; Tzoumanekas, C; Theodorou, D N

    2016-09-28

    The interaction energetics, molecular packing, entanglement network properties, segmental dynamics, and elastic constants of atactic polystyrene-amorphous silica nanocomposites in the molten and the glassy state are studied via molecular simulations using two interconnected levels of representation: (a) a coarse-grained one, wherein each polystyrene repeat unit is mapped onto a single "superatom" and the silica nanoparticle is viewed as a solid sphere. Equilibration at all length scales at this level is achieved via connectivity-altering Monte Carlo simulations. (b) A united-atom (UA) level, wherein the polymer chains are represented in terms of a united-atom forcefield and the silica nanoparticle is represented in terms of a simplified, fully atomistic model. Initial configurations for UA molecular dynamics (MD) simulations are obtained by reverse mapping well-equilibrated coarse-grained configurations. By analysing microcanonical UA MD trajectories, the polymer density profile is studied and the polymer is found to exhibit layering in the vicinity of the nanoparticle surface. An estimate of the enthalpy of mixing between polymer and nanoparticles, derived from the UA simulations, compares favourably against available experimental values. The dynamical behaviour of polystyrene (in neat and filled melt systems) is characterized in terms of bond orientation and dihedral angle time autocorrelation functions. At low concentration in the molten polymer matrix, silica nanoparticles are found to cause a slight deceleration of the segmental dynamics close to their surface compared to the bulk polymer. Well-equilibrated coarse-grained long-chain configurations are reduced to entanglement networks via topological analysis with the CReTA algorithm, yielding a slightly lower density of entanglements in the filled than in the neat systems. UA melt configurations are glassified by MD cooling. The elastic moduli of the resulting glassy nanocomposites are computed through an

  5. Voltammetric oxidation and determination of cinnarizine at glassy carbon electrode modified with multi-walled carbon nanotubes.

    PubMed

    Hegde, Rajesh N; Hosamani, Ragunatharaddi R; Nandibewoor, Sharanappa T

    2009-09-01

    The voltammetric oxidation of cinnarizine was investigated. In pH 2.5 Britton-Robinson buffer, cinnarizine shows an irreversible oxidation peak at about 1.20 V at a multi-walled carbon nanotube (MWCNT)-modified glassy carbon electrode. The cyclic voltammetric results indicate that MWCNT-modified glassy carbon electrode can remarkably enhance electrocatalytic activity towards the oxidation of cinnarizine. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the cinnarizine determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit are 9.0x10(-8) to 6.0x10(-6) M and 2.58x10(-9) M, respectively for cinnarizine. The proposed method was successfully applied to cinnarizine determination in pharmaceutical samples. The analytical performance of this sensor has been evaluated for the detection of analyte in urine as a real sample. PMID:19446444

  6. Glass Forming Ability of Hard Magnetic Nd55Al20Fe25 Bulk Glassy Alloy with Distinct Glass Transition

    NASA Astrophysics Data System (ADS)

    Xia, L.; Jo, C. L.; Dong, Y. D.

    Nd55Al20Fe25 bulk sample was prepared in the shape of rods 3 mm in diameter by suction casting. The sample exhibits typical amorphous characters in XRD pattern, distinct glass transition in DSC traces and hard magnetic properties. The distinct glass transition, which is invisible in DSC traces of previously reported Nd—Al—Fe ternary BMGs, allows us to investigate the glass forming ability (GFA) of Nd55Al20Fe25 alloy using the reduced glass transition temperature Trg and the recently defined parameter γ. However, it is found that the obtained diameter of the Nd55Al20Fe25 glassy rod is much larger than the critical section thickness of the BMG predicted by either Trg or γ. The microstructure of Nd55Al20 Fe25 as-cast rod was studied and the apparent GFA of the alloy was supposed to be enhanced by the metastable nano-precipitates dispersed within the glassy matrix.

  7. Prediction of physical aging in controlled-release coatings: the application of the relaxation coupling model to glassy cellulose acetate.

    PubMed

    Sinko, C M; Yee, A F; Amidon, G L

    1991-06-01

    The effect of physical aging on both the water transport properties and the mechanical properties of glassy cellulose acetate was investigated. Results indicate a reduction in the mechanical rate of relaxation as well as a reduction in the water permeability as the glass ages. A model which describes the low-frequency relaxation behavior of condensed, amorphous systems is used to quantitate the mechanical relaxation data. Systematic changes in key parameters from this model signify alterations in the microscopic or short-range structure as the glass physically ages. Predictions from this model correlate quite closely with the observed water permeability reductions and thus indicate that the transport properties of glassy polymers are dependent on the structure of the glass. This approach may provide further insight into the effects of nonequilibrium behavior on pharmaceutically important properties and may serve as a basis for predicting aging and permeability changes in controlled-release dosage forms.

  8. Some thoughts on positive definiteness in the consideration of nuclear data covariance matrices

    SciTech Connect

    Geraldo, L.P.; Smith, D.L.

    1988-01-01

    Some basic mathematical features of covariance matrices are reviewed, particularly as they relate to the property of positive difiniteness. Physical implications of positive definiteness are also discussed. Consideration is given to an examination of the origins of non-positive definite matrices, to procedures which encourage the generation of positive definite matrices and to the testing of covariance matrices for positive definiteness. Attention is also given to certain problems associated with the construction of covariance matrices using information which is obtained from evaluated data files recorded in the ENDF format. Examples are provided to illustrate key points pertaining to each of the topic areas covered.

  9. Etude Par Spectroscopie Infrarouge des Oxydes Moleculaires Superoxyde de Potassium, Peroxyde de Potassium et Trioxyde de Silicium Isoles EN Matrice D'argon

    NASA Astrophysics Data System (ADS)

    Tremblay, Benoit

    1995-01-01

    A l'aide de la spectroscopie d'absorption infrarouge et de la technique d'isolation en matrice d'argon, nous avons repris l'etude des differents oxydes moleculaires qui se forment lorsque l'oxygene moleculaire se trouve dans des agregats avec du potassium, du silicium et de l'oxyde de silicium SiO. Le choix des oxydes moleculaires KO_2 et K_2O_2 a ete motive par le fait qu'ils ont souvent ete mis en evidence dans tres travaux en physique des surfaces lors de letude du systeme O_2/K/Si. Ces oxydes avaient deja ete identifies par spectroscopie infrarouge en matrice d'argon au debut des annees soixante-dix. Pour KO_2, l'observation des modes nu_2 et nu_3 pour de nombreuses especes isotopiques nous a permis de deduire la longueur de la liaison K-O et de l'angle O-K-O. En effet, la construction d'un champ de force harmonique nous a permis de determiner sa structure et des constantes de force qui reprodusient tres bien les frequences experimentales observees. L'etude de l'oxyde K_2O _2 s'est averee interessante car avant notre travail, seule une vibration avait ete mise en evidence. Nous avons reussi a observer deux nouvelles vibrations fondamentales: une bande infrarouge faible a 185 cm^{-1}, avec les isotopes ^{16}O _2, ^{18}O _2 et ^{16} O^{18}O de l'oxygene, et une autre, activee en infrarouge avec l'isotope ^{16}O^{18 }O a 405 cm^{-1}. Les donnees experimentales etant insuffisantes pour deduire la structure de la molecule, des calculs theoriques avec la methode de la fonctionnelle de la densite ont donne le structure et les vibrations non observees du K _2O_2. Ces donnees supplementaires sont venues completer les resultats experimentaux et nous ont permis de construire un champ de force harmonique avec <=uel nous avons trouve des constantes de force qui reproduisent tres bien les frequences observees. Les calculs theoriques ont monte que K_2O _2 doit etre de structure C_ {rm 2v}, bien que la structure D _{rm 2h} ne puisse pas etre rejetee, puisque qu'il y a un

  10. Behavior of nuclear waste elements during hydrothermal alteration of glassy rhyolite in an active geothermal system: Yellowstone National Park, Wyoming

    SciTech Connect

    Sturchio, N.C.; Seitz, M.G.

    1984-12-31

    The behavior of a group of nuclear waste elements (U, Th, Sr, Zr, Sb, Cs, Ba, and Sm) during hydrothermal alteration of glassy rhyolite is investigated through detailed geochemical analyses of whole rocks, glass and mineral separates, and thermal waters. Significant mobility of U, Sr, Sb, Cs, and Ba is found, and the role of sorption processes in their observed behavior is identified. Th, Zr, and Sm are relatively immobile, except on a microscopic scale. 9 references, 2 figures, 2 tables.

  11. Scanning Electron Microscopy and Petrography of Glassy Particles Produced by Lava Fountain Eruptions. Ph.D. Thesis - Final Report

    NASA Technical Reports Server (NTRS)

    Ladle, G. H.

    1978-01-01

    A conceptual model of a lava fountain consists of a vent, spatter ramparts, fountain column, downwind plume and associated pumice deposits. Glassy particles produced by lava fountain eruptions consist primarily of sideromelane glass and minor to moderate amounts of vesicles and crystals. Particles are classified on the basis of morphology as: (1) spherical, (2) elongate, (3) glass-coated mineral grain, (4) shard, (5) reticulite, (6) composite particle, and (7) lithic fragment.

  12. Attachment of gold nanoparticles to glassy carbon electrode and its application for the direct electrochemistry and electrocatalytic behavior of hemoglobin.

    PubMed

    Zhang, Lei; Jiang, Xiue; Wang, Erkang; Dong, Shaojun

    2005-08-15

    Gold nanoparticles have been attached onto glassy carbon electrode surface through sulfhydryl-terminated monolayer and characterized by X-ray photoelectron spectroscopy, atomic force microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The gold nanoparticles-attached glassy carbon electrodes have been applied to the immobilization/adsorption of hemoglobin, with a monolayer surface coverage of about 2.1 x 10(-10) mol cm(-2), and consequently obtained the direct electrochemistry of hemoglobin. Gold nanoparticles, acting as a bridge of electron transfer, can greatly promote the direct electron transfer between hemoglobin and the modified glassy carbon electrode without the aid of any electron mediator. In phosphate buffer solution with pH 6.8, hemoglobin shows a pair of well-defined redox waves with formal potential (E0') of about -0.085 V (versus Ag/AgCl/saturated KCl). The immobilized hemoglobin maintained its biological activity, showing a surface controlled electrode process with the apparent heterogeneous electron transfer rate constant (ks) of 1.05 s(-1) and charge-transfer coefficient (a) of 0.46, and displays the features of a peroxidase in the electrocatalytic reduction of hydrogen peroxide. A potential application of the hemoglobin-immobilized gold nanoparticles modified glassy carbon electrode as a biosensor to monitor hydrogen peroxide has been investigated. The steady-state current response increases linearly with hydrogen peroxide concentration from 2.0 x 10(-6) to 2.4 x 10(-4) M. The detection limit (3sigma) for hydrogen peroxide is 9.1 x 10(-7) M.

  13. Isolation of long-lived technetium-99 in confinement matrices

    NASA Astrophysics Data System (ADS)

    Laverov, N. P.; Yudintsev, S. V.; Omel'Yanenko, B. I.

    2009-08-01

    Amongst fission products formed in atomic reactors, 99Tc is the most hazardous for the environment because of its long half-life (213000 yr), high content in spent nuclear fuel (SNF) (0.8-1.0 kg per ton of SNF), low sorption ability, and high mobility under aerobic conditions. The bulk of 99Tc (˜200 t) is incorporated into SNF. In the course of SNF reprocessing, this radioisotope is released as a separate fraction or along with actinides. More than 60 t of highly concentrated 99Tc have been accumulated to date. It is evident that isolation of 99Tc from the environment is a matter of great urgency. The immobilization of technetium in a highly stable and poorly soluble matrix is a necessary element in settling this problem. Ceramics composed of titanates with pyrochlore, perovskite, and rutile structures are proposed as matrices able to retain technetium along with actinides. The high chemical stability of these compounds has been corroborated by experiments. The difficulties in production of such matrices are related to the fugacity of Tc and the necessity of converting it into Tc(IV). To overcome this obstacle, self-propagating high-temperature synthesis (SHS), characterized by reductive conditions and a high reaction rate, is proposed. The charge for matrix synthesis consists of reducing agents (metallic powders with a strong affinity to oxygen, e.g., Ti and Zr), oxidants (MoO3, Fe2O3, CuO), and additives (TiO2, ZrO2, Y2O3, CaO, etc.), which taken together with other elements form target phases. Instead of Tc, Mo, close in chemical properties, is used in matrix synthesis as a simulator. Samples of Mo-bearing matrices have been synthesized with SHS; their phase compositions and Mo distribution therein are characterized. It has been shown that up to 40 wt % Mo can be incorporated into the synthesized matrices in the form of metal or structural admixtures in titanates. The titanate-zirconate pyrochlore-based matrices are the most appropriate for the joint

  14. Production and characterization of cornstarch/cellulose acetate/silver sulfadiazine extrudate matrices.

    PubMed

    Zepon, Karine Modolon; Petronilho, Fabricia; Soldi, Valdir; Salmoria, Gean Vitor; Kanis, Luiz Alberto

    2014-11-01

    The production and evaluation of cornstarch/cellulose acetate/silver sulfadiazine extrudate matrices are reported herein. The matrices were melt extruded under nine different conditions, altering the temperature and the screw speed values. The surface morphology of the matrices was examined by scanning electron microscopy. The micrographs revealed the presence of non-melted silver sulfadiazine microparticles in the matrices extruded at lower temperature and screw speed values. The thermal properties were evaluated and the results for both the biopolymer and the drug indicated no thermal degradation during the melt extrusion process. The differential scanning analysis of the extrudate matrices showed a shift to lower temperatures for the silver sulfadiazine melting point compared with the non-extruded drug. The starch/cellulose acetate matrices containing silver sulfadiazine demonstrated significant inhibition of the growth of Pseudomonas aeruginosa and Staphylococcus aureus. In vivo inflammatory response tests showed that the extrudate matrices, with or without silver sulfadiazine, did not trigger chronic inflammatory processes.

  15. N.Q.R measurements of low energy Chiral structures in powdered glassy As2Se3

    NASA Astrophysics Data System (ADS)

    Nelson, Chris

    2012-02-01

    Experimental and theoretical work on the As-chalcogen glasses have shown that in the glassy state the local cylindrical symmetry associated with the elemental pyramidal unit is preserved. Here we introduce a local paracrystalline model of glassy As2Se3. This model is based on a tight binding calculation of the electric field gradient (EFG) at the core of an As atom located at the apex of the pyramidal structure. This EFG is shown to be hyper sensitive to the bond angles and bond lengths the As atom forms with the chalcogen nearest neighbors, as well as the hybrid angle formed with second neighbor As atoms. A continuous variation of the bonding parameters produces a unique set of these pyramidal units which are shown to fit the NQR data for powdered glassy samples. The best fit to the NQR data indicates that the pyramidal units organize themselves into Chiral structures in the glass. A plot of the electronic energy per molecular site shows that the chiral structures have on average a lower electronic energy than a random configuration.

  16. FTIR and Mössbauer spectroscopic study of sodium-aluminum-iron phosphate glassy materials for high level waste immobilization

    NASA Astrophysics Data System (ADS)

    Stefanovsky, S. V.; Stefanovsky, O. I.; Remizov, M. B.; Belanova, E. A.; Kozlov, P. V.; Glazkova, Ya. S.; Sobolev, A. V.; Presniakov, I. A.; Kalmykov, S. N.; Myasoedov, B. F.

    2015-11-01

    Complex sodium-aluminum-iron phosphate glassy materials with various Al2O3 to Fe2O3 ratio containing high level waste (HLW) surrogate were characterized by X-ray diffraction and scanning electron microscopy and studied in details by Fourier transform infrared (FTIR) spectroscopy. The samples with high Al2O3 content and not containing Fe2O3 were predominantly amorphous but subjected to devitrification under annealing. Addition of B2O3 and partial Fe2O3 substitution for Al2O3 in the materials increases their resistance to devitrification whereas further substitution and NiO incorporation significantly increase the tendency to devitrification. FTIR spectra demonstrate changes in the structure of glassy materials caused by both structural variations in the anionic motif and occurrence of crystalline phases in the materials. According to Mössbauer spectroscopy data, iron in the glassy samples is present as octahedrally coordinated Fe3+ ions while in the partly devitrified samples iron is partitioned among vitreous and crystalline phases entering the vitreous phase mainly as Fe3+O6 units and crystalline phases as major Fe3+ and minor Fe2+ ions in a magnetically ordered state and participating in a "fast" electronic exchange.

  17. Chondrule Glass Alteration in Type IIA Chondrules in the CR2 Chondrites EET 87770 and EET 92105: Insights into Elemental Exchange Between Chondrules and Matrices

    NASA Technical Reports Server (NTRS)

    Burger, Paul V.; Brearley, Adrian J.

    2004-01-01

    CR2 carbonaceous chondrites are a primitive group of meteorites that preserve evidence of a variety of processes that occurred in the solar nebula as well as on asteroidal parent bodies. CR2 chondrites are distinct from other carbonaceous chondrites by (among other properties) their relatively high abundance of chondrules (50-60 vol. %) and Fe,Ni metal (5-8 vol. %) [1]. Like the CM2 chondrites, the CRs have been affected by aqueous alteration and according to [2] show a range of degrees of alteration. In weakly- altered CR chondrites, fine-grained matrices and chondrule rims have been partially altered and chondrule mesostases show evidence of incipient aqueous alteration. In these meteorites, glassy mesostasis is still common. However, some CR chondrites, (e.g. Renazzo and Al Rais) show evidence of much more extensive alteration with complete replacement of chondrule mesostasis [2] by chlorite and serpentine. Although the general characteristics of alteration of the CR chondrites have been described, the details of alteration reactions in these meteorites remain unclear. In addition, the setting for aqueous alteration is poorly understood: both asteroidal and preaccretionary alteration scenarios have been proposed [2].

  18. Investigations into crazing in glassy amorphous polymers through molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Venkatesan, Sudarkodi; Basu, Sumit

    2015-04-01

    In many glassy amorphous polymers, localisation of deformation during loading leads to crazes. Crazes are crack like features whose faces are bridged either by fibrils or a cellular network of voids and fibrils. While formation of crazes is aided by the presence of surface imperfections and embedded dust particles, in this work, we focus on intrinsic crazes that form spontaneously in the volume of the material. We perform carefully designed molecular dynamics simulations on well equilibrated samples of a model polymer with a view to gaining insights into certain incompletely understood aspects of the crazing process. These include genesis of the early nanovoids leading to craze nucleation, mechanisms of stabilising the cellular or fibrillar structure and the competition between chain scission and chain disentanglement in causing the final breakdown of the craze. Additionally, we identify and enumerate clusters of entanglement points with high functionality as effective topological constraints on macromolecular chains. We show that regions with low density of entanglement clusters serve as sites for nanovoid nucleation under high mean stress. Growth occurs by the repeated triggering of cavitation instabilities above a growing void. The growth of the void is aided by disentanglement in and flow of entanglements away from the cavitating region. Finally, for the chain lengths chosen, scission serves to supply short chains to the growing craze but breakdown occurs by complete disentanglement of the chains. In fact, most of the energy supplied to the material seems to be used in causing disentanglements and very little energy is required to create a stable fibril.

  19. Bucky-gel coated glassy carbon electrodes, for voltammetric detection of femtomolar leveled lead ions.

    PubMed

    Wan, Qijin; Yu, Fen; Zhu, Lina; Wang, Xiaoxia; Yang, Nianjun

    2010-10-15

    Femtomolar (fM) leveled lead ions were electrochemically detected using a bucky-gel coated glassy carbon electrode and differential pulse anodic stripping voltammetry. The bucky-gel was composed of dithizone, ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate), and multi-walled carbon nanotubes (MWCNTs). The fabrication of the bucky-gel coated electrode was optimized. The modified electrode was characterized with voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. After the accumulation of lead ions into the bucky-gel modified electrode at -1.2V vs. saturated calomel electrode (SCE) for 5 min in a pH 4.4 sodium acetate-acetate acid buffer solution, differential pulse anodic stripping voltammograms of the accumulated lead show an anodic wave at -0.58 V. The anodic peak current is detectable for lead ions in the concentration range from 1.0 μM down to 500 fM. The detection limit is calculated to be 100 fM. The proposed method was successfully applied for the detection of lead ions in lake water. PMID:20875583

  20. Au nanoparticles/poly(caffeic acid) composite modified glassy carbon electrode for voltammetric determination of acetaminophen.

    PubMed

    Li, Tianbao; Xu, Juan; Zhao, Lei; Shen, Shaofei; Yuan, Maosen; Liu, Wenming; Tu, Qin; Yu, Ruijin; Wang, Jinyi

    2016-10-01

    An Au nanoparticles/poly(caffeic acid) (AuNPs/PCA) composite modified glassy carbon (GC) electrode was prepared by successively potentiostatic technique in pH 7.4 phosphate buffer solution containing 0.02mM caffeic acid and 1.0mM HAuCl4. Electrochemical characterization of the AuNPs/PCA-GC electrode was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior of acetaminophen (AP) at the AuNPs/PCA-GC electrode was also studied by cyclic voltammetry. Compared with bare GC and poly(caffeic acid) modified GC electrode, the AuNPs/PCA-GC electrode was exhibited excellent electrocatalytic activity toward the oxidation of AP. The plot of catalytic current versus AP concentration showed two linear segments in the concentration ranges 0.2-20µM and 50-1000µM. The detection limit of 14 nM was obtained by using the first range of the calibration plot. The AuNPs/PCA-GC electrode has been successfully applied and validated by analyzing AP in blood, urine and pharmaceutical samples. PMID:27474318