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Sample records for glassy matrices effets

  1. Structural and thermodynamic aspects of plasticization and antiplasticization in glassy encapsulation and biostabilization matrices.

    PubMed

    Ubbink, Job

    2016-05-01

    The structural and thermodynamic properties of glassy carbohydrate matrices for the encapsulation and biostabilization of sensitive bioactive compounds, such as pharmaceutically active proteins and oxidation-sensitive compounds, are reviewed in the context of the plasticization and antiplasticization of glassy carbohydrates of intermediate and high molecular weight by low molecular weight diluents. Plasticization and antiplasticization may be monitored either by dynamic measures or by structural and thermodynamic features of the glassy matrices. Specifically, it is demonstrated that the decrease in size of the molecular free volume holes with increasing diluent content, as determined by positron annihilation lifetime spectroscopy (PALS), is related to the antiplasticization of glassy carbohydrate matrices, resulting in increased barrier properties of the glassy matrix. As far as could be ascertained from the available data, the regimes as identified by PALS map on those detected by neutron scattering and dielectric spectroscopy for glassy matrices consisting of trehalose and the diluent glycerol. The review is concluded by a survey of the published results on the stability of bioactive compounds encapsulated in carbohydrate glasses and an overview of outstanding questions. PMID:26748258

  2. Glassy state and thermal inactivation of invertase and lactase in dried amorphous matrices.

    PubMed

    Schebor, C; Burin, L; Buera, M P; Aguilera, J M; Chirife, J

    1997-01-01

    The thermal stability of enzymes lactase and invertase in dried, amorphous matrices of sugars (trehalose, maltose, lactose, sucrose, raffinose) and some other selected systems (casein, PVP, milk) was studied. The glass transition temperature (Tg) was limited as a threshold parameter for predicting enzyme inactivation because (a) enzyme inactivation was observed in glassy matrices, (b) a specific effect of enzyme stabilization by certain matrices particularly trehalose was observed, and (c) enzyme stability appeared to depend on heating temperature (T) "per se" rather than (T-Tg). For these reasons, a protective mechanism by sugars related to the maintenance of the tertiary structure of the enzyme was favored. A rapid loss of enzyme (lactase) activity was observed in heated sucrose systems at T > Tg, and this was attributed to sucrose crystallization since it is known that upon crystallization the protective effect of sugars is lost. Thus, the stabilizing effect could be indirectly affected by the Tg of the matrix, since crystallization of sugars only occurs above Tg. Trehalose model systems (with added invertase) showed an exceptional stability toward "darkening" (e.g., non-enzymatic browning) when heated in the dried state to elevated temperatures and for long periods of time. PMID:9413144

  3. Studies on the transients generated in the γ radiolysis of benzoyl-1,1,1-trifluoroacetone in glassy matrices: The radiolytically induced ketonization

    NASA Astrophysics Data System (ADS)

    Shou-te, Lian C. T.; Mittal, Jai P.

    The transients generated in the γ radiolysis of deaerated solutions of benzoyl-1,1,1-trifluoroacetone (BTA) are stabilized at 77 K and studied by their absorption spectra in the glassy matrices of isopropyl alcohol and methanol-11 mol % H 2O. The transients identified are BTA ∸enol, BTA ∸keto, BTAH rad ketyl, [BTA 2∸enolate] unrelax, and [BTA 2∸enolate] rela x. BTA ∸enol isomerizes to BTA ∸keto, apparently suggesting that anion radical formation stabilizes the keto form. BTA 2∸enolate undergoes configurational relaxation from an initially unstable to a final stable relaxed configuration. Both BTA ∸enol and BTA ∸keto react with protons produced on γ radiolysis to give BTAH rad ketyl.

  4. 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

  5. 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. PMID:25882421

  6. Solubility of gases and liquids in glassy polymers.

    PubMed

    De Angelis, Maria Grazia; Sarti, Giulio C

    2011-01-01

    This review discusses a macroscopic thermodynamic procedure to calculate the solubility of gases, vapors, and liquids in glassy polymers that is based on the general procedure provided by the nonequilibrium thermodynamics for glassy polymers (NET-GP) method. Several examples are presented using various nonequilibrium (NE) models including lattice fluid (NELF), statistical associating fluid theory (NE-SAFT), and perturbed hard sphere chain (NE-PHSC). Particular applications illustrate the calculation of infinite-dilution solubility coefficients in different glassy polymers and the prediction of solubility isotherms for different gases and vapors in pure polymers as well as in polymer blends. The determination of model parameters is discussed, and the predictive abilities of the models are illustrated. Attention is also given to the solubility of gas mixtures and solubility isotherms in nanocomposite mixed matrices. The fractional free volume determined from solubility data can be used to correlate solute diffusivities in mixed matrices. PMID:22432612

  7. The glassy wormlike chain

    NASA Astrophysics Data System (ADS)

    Kroy, Klaus; Glaser, Jens

    2007-11-01

    We introduce a new model for the dynamics of a wormlike chain (WLC) in an environment that gives rise to a rough free energy landscape, which we name the glassy WLC. It is obtained from the common WLC by an exponential stretching of the relaxation spectrum of its long-wavelength eigenmodes, controlled by a single parameter \\boldsymbol{\\cal E} . Predictions for pertinent observables such as the dynamic structure factor and the microrheological susceptibility exhibit the characteristics of soft glassy rheology and compare favourably with experimental data for reconstituted cytoskeletal networks and live cells. We speculate about the possible microscopic origin of the stretching, implications for the nonlinear rheology, and the potential physiological significance of our results.

  8. Compound matrices

    NASA Astrophysics Data System (ADS)

    Kravvaritis, Christos; Mitrouli, Marilena

    2009-02-01

    This paper studies the possibility to calculate efficiently compounds of real matrices which have a special form or structure. The usefulness of such an effort lies in the fact that the computation of compound matrices, which is generally noneffective due to its high complexity, is encountered in several applications. A new approach for computing the Singular Value Decompositions (SVD's) of the compounds of a matrix is proposed by establishing the equality (up to a permutation) between the compounds of the SVD of a matrix and the SVD's of the compounds of the matrix. The superiority of the new idea over the standard method is demonstrated. Similar approaches with some limitations can be adopted for other matrix factorizations, too. Furthermore, formulas for the n - 1 compounds of Hadamard matrices are derived, which dodge the strenuous computations of the respective numerous large determinants. Finally, a combinatorial counting technique for finding the compounds of diagonal matrices is illustrated.

  9. Formation mechanism of silver nanoparticles stabilized in glassy matrices.

    PubMed

    Simo, Anne; Polte, Jörg; Pfänder, Norbert; Vainio, Ulla; Emmerling, Franziska; Rademann, Klaus

    2012-11-14

    In any given matrix control over the final particle size distribution requires a constitutive understanding of the mechanisms and kinetics of the particle evolution. In this contribution we report on the formation mechanism of silver nanoparticles embedded in a soda-lime silicate glass matrix. For the silver ion-exchanged glass it is shown that at temperatures below 410 °C only molecular clusters (diameter <1 nm) are forming which are most likely silver dimers. These clusters grow to nanoparticles (diameter >1 nm) by annealing above this threshold temperature of 410 °C. It is evidenced that the growth and thus the final silver nanoparticle size are determined by matrix-assisted reduction mechanisms. As a consequence, particle growth proceeds after the initial formation of stable clusters by addition of silver monomers which diffuse from the glass matrix. This is in contrast to the widely accepted concept of particle growth in metal-glass systems, in which it is assumed that the nanoparticle formation is predominantly governed by Ostwald ripening processes. PMID:23098252

  10. 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.

  11. 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.

  12. Oxidation Behavior of Glassy Alloys

    NASA Technical Reports Server (NTRS)

    Yurek, G.

    1985-01-01

    The oxidation behavior of high temperature glassy alloys produced by rapid solidification processing is investigated and the effects of processing and composition on oxidation behavior is studied. Glassy Ta-44.5at%Ir, Ta-40at%Ir-10at%B and Nb-45at%Ir oxidized rapidly at 700 to 800 C at an oxygen partial pressure of .001 atm. The alloys were embrittled during the oxidation process. No apparent oxidation or embrittlement of the Ta-Ir alloy occurred after oxidation for 4h at 500 C at an oxygen partial pressure of .001 atm. Embrittlement occurred, however, after 100h of exposure under the latter conditions. Alloy embrittlement is associated with the partial or full conversion of the metallic glass to a mixture of crystalline beta-Ta2O5 and metallic iridium. Hot compaction of glassy alloys of this type must be limited to relatively low temperatures (approx. 500 C) and short times at the low temperatures unless extremely low oxygen partial pressures can be achieved during the compaction process.

  13. Multifunctional Glassy Liquid Crystal for Photonics

    SciTech Connect

    Chen,S.H.

    2004-11-05

    As an emerging class of photonic materials, morphologically stable glassy liquid crystals, were developed following a versatile molecular design approach. Glassy cholesteric liquid crystals with elevated phase-transition temperatures and capability for selective-wavelength reflection and circular polarization were synthesized via determinstic synthesis strategies. Potential applications of glassy cholesteric liquid crystals include high-performance polarizers, optical notch filters and reflectors, and circularly polarized photoluminescence. A glassy nematic liquid crystal comprising a dithienylethene core was also synthesized for the demonstration of nondestructive rewritable optical memory and photonic switching in the sollid state.

  14. 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.

  15. 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

  16. 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.

  17. 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

  18. Cooperative strings and glassy interfaces

    PubMed Central

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

    2015-01-01

    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

  19. Higher dimensional Hadamard matrices

    NASA Technical Reports Server (NTRS)

    Schlichta, P. J.

    1979-01-01

    The paper defines higher dimensional Hadamard matrices and enumerates on some of the simplest three-, four-, and five-dimensional cases and procedures for generating them. Special emphasis is given to proper matrices that have a dimensional hierarchy of orthogonalities. It is determined that this property lends itself primarily to the application of higher dimensional Hadamard matrices to error-correcting codes. A list of derived statements for n-dimensional Hadamard matrices are given, as well as a definition of Hadamard matrix families, such as minimal, Petrie polygon, antipodal (n-2)-dimensional sections, and double proximity shells.

  20. 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. PMID:27250315

  1. 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.

  2. Crazing in Glassy Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Young; Zhang, Qingling; Emrick, Todd; Crosby, Alfred

    2006-03-01

    Crazing is a polymer deformation process in which dense arrays of nanoscale fibrils grow prior to the propagation of a crack. Here, we discuss experimental results on the impact of two nanostructured materials on the crazing process: 1) ordered glassy block copolymers and 2) homopolymer/nanoparticle composites. We not only find that an ordered lamellar microstructure leads a lower craze growth rate compared with polystyrene homopolymer, but also nanoscale, surface terraces significantly decrease the failure strain of these advanced materials. For homopolymer/nanoparticle composites, we discover significant alterations in the crazing process. Specifically, nanoparticles in the presence of a craze undergo three stages of rearrangement: 1) Alignment along the precraze (fluid-like region), 2) Expulsion from nanoscale craze fibrils, and 3) Assembly into clusters trapped between craze fibrils. Although nanoparticles have no effect on the initiation strain, fibril breakdown strain, and craze growth rate, the composite failure strain can be increased significantly by nearly 100% compared to neat homopolymer films. These results provide direct evidence for the physical mechanisms that control the mechanical properties of polymer nanocomposites.

  3. 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

  4. Absorption Of Gases By Glassy Polymers

    NASA Technical Reports Server (NTRS)

    Fedors, Robert F.

    1990-01-01

    Report discusses solubility of gas in glassy polymer, both above and below glass-transition temperature (Tg). Thermodynamic arguments brought to bear on previously-developed mathematical models, result being new model that enables calculation of infinite-dilution partial molar volume of solvent in glass or liquid solvent from data on pressure, volume, and temperature of solute in equilibrium with solvent.

  5. On the cytoskeleton and soft glassy rheology.

    PubMed

    Mandadapu, Kranthi K; Govindjee, Sanjay; Mofrad, Mohammad R K

    2008-01-01

    The cytoskeleton is a complex structure within the cellular corpus that is responsible for the main structural properties and motilities of cells. A wide range of models have been utilized to understand cytoskeletal rheology and mechanics (see e.g. [Mofrad, M., Kamm, R., 2006. Cytoskeletal Mechanics: Models and Measurements. Cambridge University Press, Cambridge]). From this large collection of proposed models, the soft glassy rheological model (originally developed for inert soft glassy materials) has gained a certain traction in the literature due to the close resemblance of its predictions to certain mechanical data measured on cell cultures [Fabry, B., Maksym, G., Butler, J., Glogauer, M., Navajas, D., Fredberg, J., 2001. Scaling the microrheology of living cells. Physical Review Letters 87, 14102]. We first review classical linear rheological theory in a concise fashion followed by an examination of the soft glassy rheological theory. With this background we discuss the observed behavior of the cytoskeleton and the inherent limitations of classical rheological models for the cytoskeleton. This then leads into a discussion of the advantages and disadvantages presented to us by the soft glassy rheological model. We close with some comments of caution and recommendations on future avenues of exploration. PMID:18402964

  6. 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

  7. The superconducting state parameters of glassy superconductors

    NASA Astrophysics Data System (ADS)

    Vora, Aditya M.

    2011-11-01

    We present theoretical investigations of the superconducting state parameters (SSPs), i.e. the electron-phonon coupling strength, λ, Coulomb pseudopotential, μ*, transition temperature, Tc, isotope effect exponent, α, and effective interaction strength, N0V, of glassy superconductors by employing Ashcroft's well know empty core model potential for the first time using five screening functions proposed by Hartree (H), Taylor, Ichimaru-Utsumi (IU), Farid et al and Sarkar et al. The Tc obtained from the H and IU screening functions is found to be in excellent agreement with available experimental data. Also, the present results confirm the superconducting phase in bulk metallic glass superconductors. A strong dependency of the SSPs of the glassy superconductors on the 'Z' valence is found.

  8. Glassy Spin Dynamics in Buckled Colloidal Crystal

    NASA Astrophysics Data System (ADS)

    Zhou, Di; Wang, Feng; Han, Yilong

    Geometric frustration arises when lattice structure prevents simultaneous minimization of local interaction energies. It leads to highly degenerate ground states and complex behaviors in frustrated magnetic materials. Here we experimentally studied buckled 1.5-layer colloidal NIPA microgel crystals confined between parallel plates. Spheres buckled up and down are analogous to antiferromagnetic Ising spins. These spins on the distorted triangular lattice exhibit glassy dynamics at low temperatures. In particular, a spin only has 13 nearest-neighbor configurations, which enables to reveal the correlation between structures and dynamical heterogeneity. Soft modes also localize at high-energy regions. Further, we compared the colloidal spin system with kinetic constrained models (KCMs) and observed dynamical facilitation behaviors including excitations lines in space-time. Similar structures and glassy dynamics are also observed in our simulation of Coulomb charges on a triangular lattice. The work was supported by Grant RGC-GRF601613.

  9. The viscoelastic behavior of notched glassy polymers

    NASA Technical Reports Server (NTRS)

    Crook, R. A.; Letton, Alan

    1993-01-01

    In the bulk, glassy polymers exhibit a nonlinear viscoelastic response during deformation. Stress or strain induced damage (i.e. crazing, microshear banding) results in the production of nonrecoverable work and observed nonlinearity. Stress or strain dependent shift factors have been used to mathematically model the mechanical behavior of these polymers. Glassy polymers that have been notched, may exhibit very different load displacement response compared to the same material under bulk deformation. If a sharp notch is introduced into the body then loaded, the load displacement trace may appear to be single-valued in the absence of viscoelasticity and crack growth. This suggests the volume of damaged material is small compared to the overall dimensions of the specimen. The ability to produce a single-valued load-load-line displacement trace through the use of the Correspondence Principle may prove to be useful for fracture of viscoelastic materials.

  10. Vapor Condensed and Supercooled Glassy Nanoclusters.

    PubMed

    Qi, Weikai; Bowles, Richard K

    2016-03-22

    We use molecular simulation to study the structural and dynamic properties of glassy nanoclusters formed both through the direct condensation of the vapor below the glass transition temperature, without the presence of a substrate, and via the slow supercooling of unsupported liquid nanodroplets. An analysis of local structure using Voronoi polyhedra shows that the energetic stability of the clusters is characterized by a large, increasing fraction of bicapped square antiprism motifs. We also show that nanoclusters with similar inherent structure energies are structurally similar, independent of their history, which suggests the supercooled clusters access the same low energy regions of the potential energy landscape as the vapor condensed clusters despite their different methods of formation. By measuring the intermediate scattering function at different radii from the cluster center, we find that the relaxation dynamics of the clusters are inhomogeneous, with the core becoming glassy above the glass transition temperature while the surface remains mobile at low temperatures. This helps the clusters sample the highly stable, low energy structures on the potential energy surface. Our work suggests the nanocluster systems are structurally more stable than the ultrastable glassy thin films, formed through vapor deposition onto a cold substrate, but the nanoclusters do not exhibit the superheating effects characteristic of the ultrastable glass states. PMID:26866858

  11. 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.

  12. Singular Mueller matrices

    NASA Astrophysics Data System (ADS)

    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, of potential usefulness to experimentalists dealing with such media.

  13. 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

  14. 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.

  15. 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. PMID:26787053

  16. 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.

  17. 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

  18. Intermittency and random matrices

    NASA Astrophysics Data System (ADS)

    Sokoloff, Dmitry; Illarionov, E. A.

    2015-08-01

    A spectacular phenomenon of intermittency, i.e. a progressive growth of higher statistical moments of a physical field excited by an instability in a random medium, attracted the attention of Zeldovich in the last years of his life. At that time, the mathematical aspects underlying the physical description of this phenomenon were still under development and relations between various findings in the field remained obscure. Contemporary results from the theory of the product of independent random matrices (the Furstenberg theory) allowed the elaboration of the phenomenon of intermittency in a systematic way. We consider applications of the Furstenberg theory to some problems in cosmology and dynamo theory.

  19. 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.

  20. Glassy dislocation dynamics in colloidal dimer crystals

    NASA Astrophysics Data System (ADS)

    Gerbode, Sharon

    2012-02-01

    Dislocation mobility is central to both the mechanical response and the relaxation mechanisms of crystalline materials. Recent experiments have explored the role of novel particle anisotropies in affecting the rules of defect motion in crystals. ``Peanut-shaped'' colloidal dimer particles consisting of two connected spherical lobes form densely packed crystals in 2D. In these ``degenerate crystals,'' the particle lobes occupy triangular lattice sites while the particle axes are randomly oriented among the three crystalline directions. One consequence of the random orientations of the dimers is that dislocation glide is severely limited by certain particle arrangements in the degenerate crystals. Using optical tweezers to manipulate single lobe-sized spherical intruder particles, we locally deform the crystal, creating defects. During subsequent relaxation, the dislocations formed during the deformation leave the crystal grain, either via annihilation with other dislocations or by moving to a grain boundary. Interestingly, in large crystalline grains this dislocation relaxation occurs through a two-stage process reminiscent of slow relaxations in glassy systems, suggesting the novel concept that glassy phenomena may be introduced to certain kinds of colloidal crystals via simple anisotropic constituents.

  1. Approaching theoretical strength in glassy carbon nanolattices

    NASA Astrophysics Data System (ADS)

    Bauer, J.; Schroer, A.; Schwaiger, R.; Kraft, O.

    2016-04-01

    The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced--achieved by an 80% shrinkage of the polymer during pyrolysis--and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm-3 are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio.

  2. 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

  3. 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…

  4. Ubiquitous ``glassy'' relaxation in catalytic reaction networks

    NASA Astrophysics Data System (ADS)

    Awazu, Akinori; Kaneko, Kunihiko

    2009-10-01

    Study of reversible catalytic reaction networks is important not only as an issue for chemical thermodynamics but also for protocells. From extensive numerical simulations and theoretical analysis, slow relaxation dynamics to sustain nonequlibrium states are commonly observed. These dynamics show two types of salient behaviors that are reminiscent of glassy behavior: slow relaxation along with the logarithmic time dependence of the correlation function and the emergence of plateaus in the relaxation-time course. The former behavior is explained by the eigenvalue distribution of a Jacobian matrix around the equilibrium state that depends on the distribution of kinetic coefficients of reactions. The latter behavior is associated with kinetic constraints rather than metastable states and is due to the absence of catalysts for chemicals in excess and the negative correlation between two chemical species. Examples are given and generality is discussed with relevance to bottleneck-type dynamics in biochemical reactions as well.

  5. Glassy dynamics of driven elastic manifolds

    SciTech Connect

    Vinokur, V.M.

    1996-12-31

    We study the low-temperature dynamics of an elastic manifold driven through a random medium. For driving forces well below the zero- temperature depinning force, the manifold advances via thermally activated hops over the energy barriers separating favorable metastable states. We develop a scaling theory of the thermally activated dynamics (creep) and find a nonlinear glassy response for the driven manifold, {upsilon}{approximately}exp(-const{times}F{sup - {mu}}). We consider an exactly solvable 1-D model for random driven dynamics which exhibits a creep-like velocity-force characteristic. We discuss a microscopic mechanism for the creep motion and show that the distribution of waiting times for the hopping processes scales as a power law. This power-law distribution naturally yields an exponential response for the creep of the manifold.

  6. 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

  7. Shear banding in soft glassy materials.

    PubMed

    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. PMID:25303030

  8. 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.

  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. 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.

  11. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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/√{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/√{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.

  12. 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/√{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/√{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.

  13. Numerical inversion of finite Toeplitz matrices and vector Toeplitz matrices

    NASA Technical Reports Server (NTRS)

    Bareiss, E. H.

    1969-01-01

    Numerical technique increases the efficiencies of the numerical methods involving Toeplitz matrices by reducing the number of multiplications required by an N-order Toeplitz matrix from N-cubed to N-squared multiplications. Some efficient algorithms are given.

  14. Metagenomics of Glassy-Winged Sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A Metagenomics approach was used to identify unknown organisms which live in association with the glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae). Metagenomics combines molecular biology and genetics to identify, and characterize genetic material from unique biological ...

  15. Glassy dislocation dynamics in 2D colloidal dimer crystals.

    PubMed

    Gerbode, Sharon J; Agarwal, Umang; Ong, Desmond C; Liddell, Chekesha M; Escobedo, Fernando; Cohen, Itai

    2010-08-13

    Although glassy relaxation is typically associated with disorder, here we report on a new type of glassy dynamics relating to dislocations within 2D crystals of colloidal dimers. Previous studies have demonstrated that dislocation motion in dimer crystals is restricted by certain particle orientations. Here, we drag an optically trapped particle through such dimer crystals, creating dislocations. We find a two-stage relaxation response where initially dislocations glide until encountering particles that cage their motion. Subsequent relaxation occurs logarithmically slowly through a second process where dislocations hop between caged configurations. Finally, in simulations of sheared dimer crystals, the dislocation mean squared displacement displays a caging plateau typical of glassy dynamics. Together, these results reveal a novel glassy system within a colloidal crystal. PMID:20868079

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. What's wrong with risk matrices?

    PubMed

    Cox, Louis Anthony

    2008-04-01

    Risk matrices-tables mapping "frequency" and "severity" ratings to corresponding risk priority levels-are popular in applications as diverse as terrorism risk analysis, highway construction project management, office building risk analysis, climate change risk management, and enterprise risk management (ERM). National and international standards (e.g., Military Standard 882C and AS/NZS 4360:1999) have stimulated adoption of risk matrices by many organizations and risk consultants. However, little research rigorously validates their performance in actually improving risk management decisions. This article examines some mathematical properties of risk matrices and shows that they have the following limitations. (a) Poor Resolution. Typical risk matrices can correctly and unambiguously compare only a small fraction (e.g., less than 10%) of randomly selected pairs of hazards. They can assign identical ratings to quantitatively very different risks ("range compression"). (b) Errors. Risk matrices can mistakenly assign higher qualitative ratings to quantitatively smaller risks. For risks with negatively correlated frequencies and severities, they can be "worse than useless," leading to worse-than-random decisions. (c) Suboptimal Resource Allocation. Effective allocation of resources to risk-reducing countermeasures cannot be based on the categories provided by risk matrices. (d) Ambiguous Inputs and Outputs. Categorizations of severity cannot be made objectively for uncertain consequences. Inputs to risk matrices (e.g., frequency and severity categorizations) and resulting outputs (i.e., risk ratings) require subjective interpretation, and different users may obtain opposite ratings of the same quantitative risks. These limitations suggest that risk matrices should be used with caution, and only with careful explanations of embedded judgments. PMID:18419665

  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. 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.

  3. 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. PMID:27092716

  4. Constructions of Factorizable Multilevel Hadamard Matrices

    NASA Astrophysics Data System (ADS)

    Matsufuji, Shinya; Fan, Pingzhi

    Factorization of Hadamard matrices can provide fast algorithm and facilitate efficient hardware realization. In this letter, constructions of factorizable multilevel Hadamard matrices, which can be considered as special case of unitary matrices, are inverstigated. In particular, a class of ternary Hadamard matrices, together with its application, is presented.

  5. 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.

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

    SciTech Connect

    Nhan Chuong Dang

    2005-08-12

    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 (I{sub c}); 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 (T{sub g}). 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 has been studied, in part

  7. 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.

  8. Dynamical Heterogeneity of the Glassy State

    NASA Astrophysics Data System (ADS)

    Wisitsorasak, Apiwat

    The understanding and the complete description of the glass transition are impeded by the complexity of nature of the glass. Parts of this complexity come from the emergence of long-lived inherent structures of a liquid at a temperature below which the activated reconfiguration events play a dominant role. Molecules in a glass change their locations through the activated process at a rate which varies throughout the glass owing to these local and aperiodic structures. Motions in one location also cause or relieve constrains, thereby altering the rate of transitions of neighboring regions. The key to understanding this problem is the interplay between the activated events that generate mobility and the transport of mobility. In the following we explore fluctuating mobility generation and transport in glasses to understand the dynamics of the glassy state within the framework of the random first order transition theory of glass. Fluctuating mobility generation and transport in the glass that arise from there being a distribution of local stability and thus effective temperature are treated by numerically solving stochastic continuum equations for mobility and fictive temperature fields. Fluctuating spatiotemporal structures in aging and rejuvenating glasses lead to dynamical heterogeneity in glasses with characteristics that are distinct from those found in the equilibrium liquid. We illustrate in this thesis how the heterogeneity in glasses gives rises of a non-Gaussian distribution of activation free energies, the stretching exponent, and the growth of characteristic lengths. These are studied along with the four-point dynamic correlation function. Asymmetric thermodynamic responses upon heating and cooling are also predicted to be the results of the heterogeneity and the out-of-equilibrium behavior of glasses below the glass transition temperature. Moreover the dynamical heterogeneity can lead to a growth front of mobility in rejuvenating glasses that emanates

  9. Thermodynamics of Supercooled and Glassy Water

    NASA Astrophysics Data System (ADS)

    Debenedetti, Pablo G.

    1998-03-01

    The behavior of metastable water at low temperatures is unusual. The isothermal compressibility, the isobaric heat capacity, and the magnitude of the thermal expansion coefficient increase sharply upon supercooling, and structural relaxation becomes extremely sluggish at temperatures far above the glass transition(Angell, C.A., Annu. Rev. Phys. Chem., 34, 593, 1983)(Debenedetti, P.G., Metastable Liquids. Concepts and Principles, Princeton University Press, 1996). Water has two distinct glassy phases, low- and high-density amorphous ice (LDA, HDA). The transition between LDA and HDA is accompanied by sharp volume and enthalpy changes, and appears to be first-order(Mishima, O., L.D.Calvert, and E. Whalley, Nature, 314, 76, 1985)(Mishima, O., J. Chem. Phys., 100, 5910, 1994). The understanding of these observations in terms of an underlying global phase behavior remains incomplete(Speedy, R.J., J. Phys. Chem., 86, 982, 1982)(Poole, P.H., F. Sciortino, U. Essman, and H.E. Stanley, Nature, 360, 324, 1992)(Sastry, S., P.G. Debenedetti, F. Sciortino, and H.E. Stanley, Phys. Rev. E, 53, 6144, 1996)(Tanaka, H., Nature, 380, 328, 1996)(Xie, Y., K.F. Ludwig, G. Morales, D.E. Hare, and C.M. Sorensen, Phys. Rev. Lett., 71, 2050, 1993). Microscopic theories and computer simulations suggest several scenarios that can reproduce some experimental observations. Interesting and novel ideas have resulted from this body of theoretical work, such as the possibility of liquid-liquid immiscibility in a pure substance(Poole, P.H., F.Sciortino, T.Grande, H.E. Stanley, and C.A. Angell, Phys. Rev. Lett., 73, 1632, 1994)(Roberts, C.J., and P.G. Debenedetti, J. Chem. Phys., 105, 658, 1996)(Roberts, C.J., P.G. Debenedetti, and A.Z. Panagiotopoulos, Phys. Rev. Lett., 77, 4386, 1996)(Harrington, S., R. Zhang, P.H. Poole, F. Sciortino, and H.E. Stanley, Phys. Rev. Lett., 78, 2409, 1997). In this talk I will review the experimental facts, discuss their theoretical interpretation, and identify key

  10. 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.

  11. 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.

  12. 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.

  13. Outstanding properties of bistochastic matrices

    NASA Astrophysics Data System (ADS)

    Brugia, O.; Wolfowicz, W.

    1981-10-01

    The statistical properties of many devices used in communication systems, such as scramblers and line coding and decoding devices, are described by mathematical models in which the transition probability matrix is bistochastic. To facilitate the analysis of systems response, the specific properties of the bistochastic matrices are described in six theorems which are demonstrated.

  14. 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…

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

    PubMed

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

    2016-03-01

    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

  16. 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

  17. 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

  18. MODELING GLASSY-WINGED SHARPSHOOTER PHENOLOGY AND PIERCE'S DISEASE INCIDENCE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Insect, plant, and bacterial growth are all regulated by environmental factors, such as temperature. Consequently, climate plays an important role in the: 1) ability of glassy winged sharpshooter (GWSS) to survive the winter, 2) development of GWSS populations throughout the year, and 3) propensity...

  19. A method to quantify glassy-winged sharpshooter egg maturation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To identify factors affecting glassy-winged sharpshooter egg production, a method to accurately estimate the number of mature eggs produced during a short-term assay is needed. Egg production is typically quantified by determining the number of eggs deposited during the assay plus the number of matu...

  20. Immunological detection of glassy-winged sharpshooter saliva in grapevine

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is a major vector for transmission of Xylella fastidiosa (Xf), the causative agent of Pierce’s Disease in grapevine. During the feeding process of stylet penetration and xylem fluid ingestion, GWSS inject saliva into the plant. Inoculation...

  1. Fabrication of Bulk Glassy Alloy Foams by High Pressure Hydrogen

    NASA Astrophysics Data System (ADS)

    Wada, Takeshi; Inoue, Akihisa

    Porous Pd42.5Cu30Ni7.5P20 bulk glassy alloy rods with porosities of up to 70% were successfully prepared by high pressure hydrogen of 15 MPa. The melt of Pd42.5Cu30Ni7.5P20 alloy kept under high pressure hydrogen absorbs hydrogen and subsequent water quenching of the melt causes the homogeneous dispersion of hydrogen bubbles, which was resulted from the decrease of hydrogen solubility with decrease of pressure. Annealing the hydrogen bubble containing sample at a supercooled liquid state under vacuum, the bubbles are allowed to expand due to the decrease of viscosity of metallic glass matrix. Pores expansion continues until glassy matrix crystallizes or the equilibration among pressure of the pores, pressure of the atmosphere and surface tension is achieved. By utilizing these phenomena, pores up to 80 m in diameters are homogeneously distributed over the whole cross-sectional area of a fully glassy matrix. Under compressive deformation, the porous alloys with porosities exceeding 40% did not show macroscopic fracture in a wide compressive strain range up to 0.6 whereas the non-porous alloy fractures instantly after elastic limit of about 0.02. Porous bulk glassy alloys exhibit higher plateau stress, lower Young‧s modulus and higher energy absorption capacity compared with the conventional crystalline metal foams.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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.

  3. 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

  4. 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.

  5. 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.

  6. Householder factorizations of unitary matrices

    NASA Astrophysics Data System (ADS)

    Urías, Jesús

    2010-07-01

    A method to construct all representations of finite dimensional unitary matrices as the product of Householder reflections is given. By arbitrarily severing the state space into orthogonal subspaces, the method may, e.g., identify the entangling and single-component quantum operations that are required in the engineering of quantum states of composite (multipartite) systems. Earlier constructions are shown to be extreme cases of the unifying scheme that is presented here.

  7. Compliance matrices for cracked bodies

    NASA Technical Reports Server (NTRS)

    Ballarini, R.

    1986-01-01

    An algorithm is presented which can be used to develop compliance matrices for cracked bodies. The method relies on the numerical solution of singular integral equations with Cauchy-type kernels and provides an efficient and accurate procedure for relating applied loadings to crack opening displacements. The algorithm should be of interest to those performing repetitive calculations in the analysis of experimental results obtained from fracture specimens.

  8. 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.

  9. Effet Hall et Magnetisme des Alliages Amorphes Nickel-Zirconium Fabriques Par Pulverisation

    NASA Astrophysics Data System (ADS)

    Morel, Robert

    Cette these se situe dans le cadre d'une etude des proprietes electroniques et structurales des alliages metalliques amorphes, en cours depuis quelques annees a l'Universite de Montreal. Ce programme nous a entre autres amene a caracteriser la magnetoresistivite et l'effet Hall d'alliages FeZr, CoZr et NiZr, ce qui a permis de mettre en evidence deux caracteristiques de l'effet Hall: Dans les alliages amorphes ferromagnetiques, la resistivite elevee engendre un effet Hall extraordinaire beaucoup plus important que celui enregistre dans les metaux cristallins. La polarisation des spins entrai ne une asymetrie de la diffusion qui, tant dans les phases cristalline et amorphe, est tenue responsable de cette contribution. L'autre particularite du comportement de Hall de ces systemes est le renversement de signe du coefficient de Hall ordinaire, qui passe du negatif au positif dans les echantillons plus riches en zirconium. Dans les metaux cristallins, un modele d'electrons libres predit un signe negatif a moins que la conduction ne soit dominee par les trous. Or, dans un milieu desordonne les memes concepts sont difficilement applicables et de nouvelles theories ont du etre elaborees pour expliquer ce phenomene. Jusqu'a maintenant, l'etude des alliages amorphes nickel-zirconium s'est faite surtout a partir d'echantillons fabriques par trempe sur roue. Malheureusement cette technique ne permet pas la fabrication d'alliages contenant plus de 70% de nickel, a l'exception du seul compose Ni _{90}Zr_{10 }. Pour pallier a cette lacune et etendre nos connaissance a l'ensemble de la gamme de compositions, nous avons fabrique par pulverisation cathodique des echantillons NiZr amorphes--et quelques alliages cristallins tres riches en nickel--couvrant une bonne partie de la gamme interdite par la technique de trempe sur roue. Dans un premier temps, par comparaison avec les resultats connus nous avons mis en evidence les similitudes et les differences entre les alliages obtenus par

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Nanoparticle Alignment and Repulsion During Failure of Glassy Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Crosby, Alfred; Lee, Jong-Young; Zhang, Qingling; Emrick, Todd

    2007-03-01

    We investigate crazing and failure in a model nanocomposite of surface modified nanoparticles (cadmium selenide, diameter is 5 nm) blended into polystyrene. We demonstrate that nanoparticles undergo three stages of rearrangement during craze formation and propagation in glassy polymer nanocomposites: 1) Alignment along the precraze, 2) Expulsion from craze fibrils, and 3) Assembly into clusters entrapped between craze fibrils. At an optimal volume fraction of nanoparticles, the failure strain of the nanocomposite is increased by nearly 100% relative to unfilled polystyrene. This optimal volume fraction is related to the balance of two mechanisms: 1) the decrease in cross-tie fibril density for craze structures, and 2) the decrease in the probability of craze widening at higher tensile strain by decreasing the number of polymer entanglements at small interparticle lengths. These results offer a clear and detailed understanding of failure mechanism of glassy polymer-nanoparticle composites, and provide predictions for the future design of nanoparticle-based materials.

  15. Superalgebraic representation of Dirac matrices

    NASA Astrophysics Data System (ADS)

    Monakhov, V. V.

    2016-01-01

    We consider a Clifford extension of the Grassmann algebra in which operators are constructed from products of Grassmann variables and derivatives with respect to them. We show that this algebra contains a subalgebra isomorphic to a matrix algebra and that it additionally contains operators of a generalized matrix algebra that mix states with different numbers of Grassmann variables. We show that these operators are extensions of spin-tensors to the case of superspace. We construct a representation of Dirac matrices in the form of operators of a generalized matrix algebra.

  16. 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.

  17. The Nature of the Glassy Phase in 4He Crystals

    NASA Astrophysics Data System (ADS)

    Antsygina, T. N.; Poltavskaya, M. I.; Chishko, K. A.

    2015-08-01

    A model of a close-packed polytype with a random stacking fault structure is used to interpret the anomalies of the thermodynamic properties of the disordered (glassy) phase in solid HCP 4He in the so-called supersolid state. The temperature dependence of the phonon pressure is calculated theoretically, and compared to experimental data. A quantitative agreement between the theory and the experiment is achieved.

  18. Molecular mechanisms of deformation and failure in glassy materials

    NASA Astrophysics Data System (ADS)

    Rottler, Joerg

    2004-03-01

    Understanding the molecular origins of macroscopic mechanical properties is a fundamental scientific challenge. Fracture of both amorphous and crystalline materials involves many length scales reaching from the continuum to atomic level processes near a crack tip. Using molecular simulations of simple models for amorphous glassy materials, we first study elastoplastic deformation and discuss the nature of the shear yield stress and its dependence on loading conditions, strain rate and temperature. We then focus on the deformation of glassy polymeric systems into crazes at large strains. In the craze, polymers ( 0.5 nm diameter) are bundled into an intricate network of 10 nm diameter fibrils that extends 10 micrometers on either side of a mm crack tip. Analysis of local geometry and stresses provide insight into the real-space nature of the entanglements that control craze formation as well as melt dynamics. Crazes are also shown to share many features with jammed systems such as granular media and foams, but are unique in jamming under a tensile load. This allows explanations for the exponential force distribution in jammed systems to be tested. The force distribution strongly influences the ultimate breakdown of the craze fibrils either through disentanglement or chain scission. We conclude by quantifying the contribution of crazing to the unusually large fracture energy of glassy polymers.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. Liquid and Glassy Water: Two Materials of Interdisciplinary Interest

    NASA Astrophysics Data System (ADS)

    Eugene Stanley, H.

    We can superheat water above its boiling temperature and supercool it below its freezing temperature, down to approximately — 40°C, below which water inevitably crystallizes. In this deeply supercooled region, strange things happen: response functions and transport functions appear as if they might diverge to infinity at a temperature of about-45 °C. These experiments were pioneered by Angell and co-workers over the past 30 years [1-4]. Down in the glassy region of water, additional strange things happen, e.g., there is not just one glassy phase [1]. Rather, just as there is more than one polymorph of crystalline water, so also there appears to be more than one polyamorph of glassy water. The first clear indication of this was a discovery of Mishima in 1985: at low pressure there is one form, called low-density amorphous (LDA) ice [5], while at high pressure Mishima discovered a new form, called highdensity amorphous (HDA) ice [6]. The volume discontinuity separating these two phases is comparable to the volume discontinuity separating low-density and high-density polymorphs of crystalline ice, 25-35 percent [7, 8].

  4. Thermodynamics of water sorption in high performance glassy thermoplastic polymers

    PubMed Central

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

    2014-01-01

    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 from 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 polymers as well as for mean field and for hydrogen bonding interactions, providing a satisfactory quantitative interpretation of the experimental data. PMID:24860802

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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

  11. Investigation of network architecture development and properties in thermoset matrices

    NASA Astrophysics Data System (ADS)

    Swanson, Jeremy Owen

    Matrices employed in composite materials directly influence overall composite properties. In all thermoset materials, molecular level interactions and transformations during cure result in heterogeneous architecture. Variability in connectivity results from the often dramatic spatial and topological changes that occur during the crosslinking process. Compatibility (fillers, pigments, additives), temperature gradients and reactivity differences in the precursors only serve to increase the complexity of network formation. The objective of the research herein is to characterize and understand the relationships between cure conditions, conversion, connectivity, network architecture and properties in glassy thermosetting matrix resins. In this research, epoxy and vinyl ester resins (VERs) were characterized to identify controlling factors in the development of network architecture and understand how they affect the mechanical properties. VERs cure under low temperature conditions (< 50°C) via redox catalysis resulted in vitrification limiting conversion with resulting glass transition temperatures (Tgs) approximately 15°C above the cure temperature. Subsequently, in situ ligand exchange altered the activity of the metal catalyst, and the reduced connectivity of the resulting networks translated into a 30% reduction in stiffness above Tg. Network architecture was further manipulated by changing the chemical composition of the backbone. Incorporation of POSS nanoparticles into VERs resulted in changes to initial network development, with higher levels of conversion prior to vitrification. 3,3'-DDS was cured with a variety of epoxies and examined for conversion, connectivity and mechanical properties. Comparison with 4,4'-DDS revealed significant correlations between molecular level structure and properties. The research established relationships between cure conditions, conversion, connectivity and properties in glassy thermosetting matrix resins. Specifically, the

  12. Quasiperiodic tilings generated by matrices

    NASA Astrophysics Data System (ADS)

    Rao, Nagaraja S.; Suryanarayan, E. R.

    1994-02-01

    Using the inflation method, Watanabe, Ito and Soma [3], Clark and Suryanarayan [4] and Balagurusamy, Ramesh and Gopal [5] have obtained nonperiodic tilings of the plane with n-fold rotational symmetry, n = 2, 3, 4, 5, 8, using two unit prototiles. Fortunately, there is an easier way to generate a more general class of nonperiodic tilings which contains the above-mentioned tilings as special cases. We do this by specifying two matrices of order two which define the two classes of tilings; thus, our approach uses the basic techniques from linear algebra in the study of quasiperiodic tilings and the method can be generalized to obtain tilings that have more than two prototiles. The tilings generated are fractals and their dimensions and the rate of growth are determined.

  13. 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.

  14. Shrinkage estimators for covariance matrices.

    PubMed

    Daniels, M J; Kass, R E

    2001-12-01

    Estimation of covariance matrices in small samples has been studied by many authors. Standard estimators, like the unstructured maximum likelihood estimator (ML) or restricted maximum likelihood (REML) estimator, can be very unstable with the smallest estimated eigenvalues being too small and the largest too big. A standard approach to more stably estimating the matrix in small samples is to compute the ML or REML estimator under some simple structure that involves estimation of fewer parameters, such as compound symmetry or independence. However, these estimators will not be consistent unless the hypothesized structure is correct. If interest focuses on estimation of regression coefficients with correlated (or longitudinal) data, a sandwich estimator of the covariance matrix may be used to provide standard errors for the estimated coefficients that are robust in the sense that they remain consistent under misspecification of the covariance structure. With large matrices, however, the inefficiency of the sandwich estimator becomes worrisome. We consider here two general shrinkage approaches to estimating the covariance matrix and regression coefficients. The first involves shrinking the eigenvalues of the unstructured ML or REML estimator. The second involves shrinking an unstructured estimator toward a structured estimator. For both cases, the data determine the amount of shrinkage. These estimators are consistent and give consistent and asymptotically efficient estimates for regression coefficients. Simulations show the improved operating characteristics of the shrinkage estimators of the covariance matrix and the regression coefficients in finite samples. The final estimator chosen includes a combination of both shrinkage approaches, i.e., shrinking the eigenvalues and then shrinking toward structure. We illustrate our approach on a sleep EEG study that requires estimation of a 24 x 24 covariance matrix and for which inferences on mean parameters critically

  15. 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

  16. 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)

  17. Harmonic balance calculations by using matrices

    NASA Astrophysics Data System (ADS)

    Fergusson, N. J.; Leung, A. Y. T.

    1995-05-01

    The computation of the total and tangential stiffness matrices associated with the harmonic balance method for non-linear ordinary differential equations requires some complicated calculations involving double sums. Some matrix results are presented here that ease the associated book-keeping and allow the matrices to be programmed easily.

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  2. Linear Response Theory for Hard and Soft Glassy Materials

    SciTech Connect

    Langer, J.; Bouchbinder, Eran

    2011-01-01

    Despite qualitative differences in their underlying physics, both hard and soft glassy materials exhibit almost identical linear rheological behaviors. We show that these nearly universal properties emerge naturally in a shear-transformation-zone (STZ) theory of amorphous plasticity, extended to include a broad distribution of internal thermal-activation barriers. The principal features of this barrier distribution are predicted by nonequilibrium, effective-temperature thermodynamics. Our theoretical loss modulus G{double_prime}({omega}) has a peak at the {alpha} relaxation rate, and a power law decay of the form {omega}{sup -{zeta}} for higher frequencies, in quantitative agreement with experimental data.

  3. Nonequilibrium thermodynamics of the soft glassy rheology model.

    PubMed

    Fuereder, Ingo; Ilg, Patrick

    2013-10-01

    The soft glassy rheology (SGR) model is a mesoscopic framework which proved to be very successful in describing flow and deformation of various amorphous materials phenomenologically (e.g., pastes, slurries, foams, etc.). In this paper, we cast SGR in a general, model-independent framework for nonequilibrium thermodynamics called general equation for the nonequilibrium reversible-irreversible coupling. This leads to a formulation of SGR which clarifies how it can properly be coupled to hydrodynamic fields, resulting in a thermodynamically consistent, local, continuum version of SGR. Additionally, we find that compliance with thermodynamics imposes the existence of a modification to the stress tensor as predicted by SGR. PMID:24229142

  4. 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.

  5. 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

  6. Rotationally invariant ensembles of integrable matrices

    NASA Astrophysics Data System (ADS)

    Scaramazza, Jasen; Yuzbashyan, Emil; Shastry, Sriram

    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 parameterization 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, in a manner similar to the construction of Gaussian ensembles in the RMT. This work was supported in part by the David and Lucille Packard Foundation. The work at UCSC was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award # FG02-06ER46319.

  7. 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.

  8. Zeolitization of glassy Topopah Spring tuff under hydrothermal conditions

    SciTech Connect

    Knauss, K.G.

    1987-01-01

    In support of the Nevada Nuclear Waste Storage Investigations Project experiments were conducted to study the effects of heat generated by a nuclear waste repository in densely welded, devitrified tuff on the underlying, compositionally-equivalent glassy tuff at Yucca Mtn. Solid wafers of glassy tuff were reacted with a dilute ground water for several months at 150{sup 0}C and 250{sup 0}C at 100 bars pressure in Dickson-type, gold-bag rocking autoclaves. The in-situ chemistry of the hydrothermal fluids was modeled and the chemical affinities for all possible mineral precipitation reactions were calculated using the EQ3/6 program. In the 250{sup 0}C experiment the calculations suggest that a zeolite mineral would be expected to form. Analyses of the run products showed that not only had the wafer been extensively corroded and the glass shards replaced by clinoptilolite, but pure clinoptilolite had precipitated directly from solution. In the 150{sup 0}C experiment, although clay minerals were thermodynamically favored to form in the first half of the experiment, by the end of the run a zeolite mineral was predicted to form. Analyses of the run products showed no well-formed secondary minerals (clays or zeolites) had formed. At the lower temperature the effects of precipitation kinetics may preclude the formation of the zeolite within the time span of this experiment. In general the observations are in relatively good agreement with the geochemical model calculations.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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-Ag2O-[(1-x)B2O3-xTeO2] (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 TeO2 as well as with temperature. The conductivity of the present glass system is found to be of the order of 10-2 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.

  10. 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.

  11. Confined glassy dynamics at grain boundaries in colloidal crystals

    PubMed Central

    Nagamanasa, K. Hima; Gokhale, Shreyas; Ganapathy, Rajesh; Sood, A. K.

    2011-01-01

    Grain boundary (GB) microstructure and dynamics dictate the macroscopic properties of polycrystalline materials. Although GBs have been investigated extensively in conventional materials, it is only recently that molecular dynamics simulations have shown that GBs exhibit features similar to those of glass-forming liquids. However, current simulation techniques to probe GBs are limited to temperatures and driving forces much higher than those typically encountered in atomic experiments. Further, the short spatial and temporal scales in atomic systems preclude direct experimental access to GB dynamics. Here, we have used confocal microscopy to investigate the dynamics of high misorientation angle GBs in a three-dimensional colloidal polycrystal, with single-particle resolution, in the zero-driving force limit. We show quantitatively that glassy behavior is inherent to GBs as exemplified by the slowing down of particle dynamics due to transient cages formed by their nearest neighbors, non-Gaussian probability distribution of particle displacements and string-like cooperative rearrangements of particles. Remarkably, geometric confinement of the GB region by adjacent crystallites decreases with the misorientation angle and results in an increase in the size of cooperatively rearranging regions and hence the fragility of the glassy GBs. PMID:21705662

  12. Approaching theoretical strength in glassy carbon nanolattices.

    PubMed

    Bauer, J; Schroer, A; Schwaiger, R; Kraft, O

    2016-04-01

    The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced--achieved by an 80% shrinkage of the polymer during pyrolysis--and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm(-3) are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio. PMID:26828314

  13. TOPICAL REVIEW: Fracture in glassy polymers: a molecular modeling perspective

    NASA Astrophysics Data System (ADS)

    Rottler, Jörg

    2009-11-01

    Over the past 25 years, molecular modeling and simulations have provided important insights into the physics of deformation and fracture of glassy polymers. This review presents an overview of key results discussed in the context of experimentally observed polymer behavior. Both atomistic and coarse-grained polymer models have been used in different deformation protocols to study elastic properties, shear yielding, creep, physical aging, strain hardening and crazing. Simulations reproduce most of the macroscopic features of plasticity in polymer glasses such as stress-strain relations and creep response, and reveal information about the underlying atomistic processes. Trends of the shear yield stress with loading conditions, temperature and strain rate, and the atomistic dynamics under load have been systematically explored. Most polymers undergo physical aging, which leads to a history-dependent mechanical response. Simulations of strain hardening and crazing demonstrate the nature of polymer entanglements in the glassy state and the role of local plasticity and provide insight into the origin of fracture toughness of amorphous polymers.

  14. Fracture in glassy polymers: a molecular modeling perspective.

    PubMed

    Rottler, Jörg

    2009-11-18

    Over the past 25 years, molecular modeling and simulations have provided important insights into the physics of deformation and fracture of glassy polymers. This review presents an overview of key results discussed in the context of experimentally observed polymer behavior. Both atomistic and coarse-grained polymer models have been used in different deformation protocols to study elastic properties, shear yielding, creep, physical aging, strain hardening and crazing. Simulations reproduce most of the macroscopic features of plasticity in polymer glasses such as stress-strain relations and creep response, and reveal information about the underlying atomistic processes. Trends of the shear yield stress with loading conditions, temperature and strain rate, and the atomistic dynamics under load have been systematically explored. Most polymers undergo physical aging, which leads to a history-dependent mechanical response. Simulations of strain hardening and crazing demonstrate the nature of polymer entanglements in the glassy state and the role of local plasticity and provide insight into the origin of fracture toughness of amorphous polymers. PMID:21715863

  15. Modeling VOC Sorption and Transport in Glassy Polymeric Membranes

    NASA Astrophysics Data System (ADS)

    De Angelis, Maria Grazia; Olivieri, Luca; Sarti, G. C.

    2010-06-01

    In this work we evaluated the sorption, diffusion and permeation of a series of volatile organic compounds (VOCs) (acetone, n-butane, n-pentane, n-hexane, ethanol, methanol, chloroform and toluene) into glassy polymers of increasing fractional free volume (FFV): Polycarbonate (PC), Amorphous Teflon AF1600 and AF2400, poly-trimethylsilyl norbornene (PTMSN) and poly[1-(trimethylsilyl)-1-propyne] (PTMSP). Based on some experimental data of sorption and diffusion, and on theoretical and empirical models for the solubility and diffusion coefficients, the permeability for vapor/N2 mixtures was evaluated. These parameters are useful for the membrane separation processes and for other applications such as chemical sensors. The ideal separation factors of glassy polymeric membranes versus mixtures of VOCs and N2 were estimated at various pressures and compositions and at 25° C. The selectivity vs. permeability maps for the mixtures considered were plotted, showing that some of these materials show potentially the same selective ability of rubbery polymeric films. In particular it is shown that, the higher the FFV, the better the vapor/gas selectivity.

  16. 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.

  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. 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...

  19. Glassy-winged sharpshooter excreta production and egg maturation on grapevines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To better understand glassy-winged sharpshooter movement and reproduction in vineyards, studies evaluating glassy-winged sharpshooter feeding (as measured by excreta production) and egg maturation on grapevines were conducted. In 2010, studies compared excreta production and egg maturation of femal...

  20. 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.

  1. 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...

  2. Kerov's interlacing sequences and random matrices

    NASA Astrophysics Data System (ADS)

    Bufetov, Alexey

    2013-11-01

    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.

  3. LU decompositions of generalized diagonally dominant matrices

    SciTech Connect

    Funderlic, R.E.; Neumann, M.; Plemmons, R.J.

    1982-02-01

    Using the simple vehicle of M-matrices, the existence and stability of LU decompositions of matrices A which can be scaled to diagonally dominant (possibly singular) matrices are investigated. Bounds on the growth factor for Gaussian elimination on A are derived. Motivation for this study is provided in part by applications to solving homogeneous systems of linear equations Ax = 0, arising in Markov queuing networks, input-output models in economics and compartmental systems, where A or -A is an irreducible, singular M-matrix.

  4. 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.

  5. Heterogeneous nucleation of ice particles on glassy aerosols modifies TTL cirrus

    NASA Astrophysics Data System (ADS)

    Wilson, T. W.; Murray, B. J.; Dobbie, S.; Al-Jumur, S. M.; Cui, Z.; Wagner, R.; Moehler, O.; Schnaiter, M.; Benz, S.; Niemand, M.; Saathoff, H.; Skrotzki, J.; Ebert, V.; Wagner, S.; Karcher, B.

    2010-12-01

    Experiments at the AIDA chamber, Karlsruhe Institute of Technology, have shown that glassy aqueous citric acid aerosol can nucleate ice at temperatures relevant to the tropical tropopause layer (TTL)(1). Modelling suggests this new route to the formation of TTL cirrus can provide an explanation for the very low ice particle number density observed in cirrus clouds in this region and may lead to high in-cloud supersaturations(1). Nucleation of ice on glassy aerosol is consistent with the absence of traditional ice nuclei in sampled TTL cirrus residue(2). In addition, we will present new data from experiments performed in July 2010 at the AIDA chamber using glassy aerosols composed of other atmospherically relevant compounds (levoglucosan, raffinose) and an internal mixture of five dicarboxylic acids and ammonium sulphate (raffinose/M5AS)(3). All four systems tested nucleate ice when in a glassy state. This indicates that heterogeneous ice nucleation is a general property of glassy aerosols and that natural aerosols which are composed of similar molecules will also nucleate ice if glassy. Glassy aqueous levoglucosan and raffinose/M5AS aerosol nucleated ice at temperatures similar to those found for glassy aqueous citric acid aerosol (<202 K). Whereas raffinose, which forms a glass at much higher temperatures, nucleated ice heterogeneously at up to ~220 K. This activity at higher temperatures suggests that ice nucleation by glassy aerosol may also play a role in the formation of warmer ice clouds. (1)B. J. Murray et al., Heterogeneous nucleation of ice particles on glassy aerosols under cirrus conditions, Nature Geosci, 2010, 3, 233-237. (2)K. D. Froyd et al., Aerosols that form subvisible cirrus at the tropical tropopause, Atmos. Chem. Phys., 2010, 10, 209-218. (3)B. Zobrist et al., Do atmospheric aerosols form glasses?, Atmos. Chem. Phys., 2008, 8, 5221-5244.

  6. 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.

  7. 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

  8. 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)

  9. Mechanisms of diphylline release from dual-solute loaded poly(vinyl alcohol) matrices.

    PubMed

    Hasimi, Albana; Papadokostaki, Kyriaki G; Sanopoulou, Merope

    2014-01-01

    The release kinetics of the model hydrophilic drug, diphylline (DPL), from physically crosslinked poly(vinyl alcohol) (PVA) matrices, is studied in relation to the drug load and the presence of a second solute incorporated in the matrix. The second solute, a gadolinium (III) complex (Gd-DTPA), is a commonly used MRI contrast agent. The water uptake kinetics by the glassy PVA matrix was found to deviate from t(1/2) law and to occur on time scales comparable to those of diphylline release. The corresponding rate of diphylline release was found to be substantially stabilized as compared to a purely diffusion-controlled release process, in line with theoretical predictions under conditions of relaxation-controlled water uptake kinetics. The release rate of DPL was found (i) to increase with increasing DPL load and (ii) for a particular DPL load, to increase in the presence of Gd-DTPA, incorporated in the matrix. The results were interpreted on the basis of the diphylline-induced plasticization of the polymer (evidenced by the depression of Tg) and of the excess hydration of the matrix at high solute loads. The latter effect was found to be additive in the case of dual-solute loaded matrices. PMID:24268271

  10. Fermion masses from SO(10) Hermitian matrices

    SciTech Connect

    Moorhouse, R. G.

    2008-03-01

    Masses of fermions in the SO(10) 16-plet are constructed using only the 10, 120, and 126 scalar multiplets. The mass matrices are restricted to be Hermitian and the theory is constructed to have certain assumed quark masses, charged lepton masses, and Cabibbo-Kobayashi-Maskawa (CKM) matrix in accord with data. The remaining free parameters are found by fitting to light neutrino masses and Maki-Nakagawa-Sakata (MNS) matrices result as predictions.

  11. Fermion masses from SO(10) Hermitian matrices

    NASA Astrophysics Data System (ADS)

    Moorhouse, R. G.

    2008-03-01

    Masses of fermions in the SO(10) 16-plet are constructed using only the 10, 120, and 126¯ scalar multiplets. The mass matrices are restricted to be Hermitian and the theory is constructed to have certain assumed quark masses, charged lepton masses, and Cabibbo-Kobayashi-Maskawa (CKM) matrix in accord with data. The remaining free parameters are found by fitting to light neutrino masses and Maki-Nakagawa-Sakata (MNS) matrices result as predictions.

  12. Optimization of an absolute sensitivity in a glassy matrix during DNP-enhanced multidimensional solid-state NMR experiments.

    PubMed

    Takahashi, Hiroki; Fernández-de-Alba, Carlos; Lee, Daniel; Maurel, Vincent; Gambarelli, Serge; Bardet, Michel; Hediger, Sabine; Barra, Anne-Laure; De Paëpe, Gaël

    2014-02-01

    Thanks to instrumental and theoretical development, notably the access to high-power and high-frequency microwave sources, high-field dynamic nuclear polarization (DNP) on solid-state NMR currently appears as a promising solution to enhance nuclear magnetization in many different types of systems. In magic-angle-spinning DNP experiments, systems of interest are usually dissolved or suspended in glass-forming matrices doped with polarizing agents and measured at low temperature (down to ∼100K). In this work, we discuss the influence of sample conditions (radical concentration, sample temperature, etc.) on DNP enhancements and various nuclear relaxation times which affect the absolute sensitivity of DNP spectra, especially in multidimensional experiments. Furthermore, DNP-enhanced solid-state NMR experiments performed at 9.4 T are complemented by high-field CW EPR measurements performed at the same magnetic field. Microwave absorption by the DNP glassy matrix is observed even below the glass transition temperature caused by softening of the glass. Shortening of electron relaxation times due to glass softening and its impact in terms of DNP sensitivity is discussed. PMID:24480716

  13. Optimization of an absolute sensitivity in a glassy matrix during DNP-enhanced multidimensional solid-state NMR experiments

    NASA Astrophysics Data System (ADS)

    Takahashi, Hiroki; Fernández-de-Alba, Carlos; Lee, Daniel; Maurel, Vincent; Gambarelli, Serge; Bardet, Michel; Hediger, Sabine; Barra, Anne-Laure; De Paëpe, Gaël

    2014-02-01

    Thanks to instrumental and theoretical development, notably the access to high-power and high-frequency microwave sources, high-field dynamic nuclear polarization (DNP) on solid-state NMR currently appears as a promising solution to enhance nuclear magnetization in many different types of systems. In magic-angle-spinning DNP experiments, systems of interest are usually dissolved or suspended in glass-forming matrices doped with polarizing agents and measured at low temperature (down to ∼100 K). In this work, we discuss the influence of sample conditions (radical concentration, sample temperature, etc.) on DNP enhancements and various nuclear relaxation times which affect the absolute sensitivity of DNP spectra, especially in multidimensional experiments. Furthermore, DNP-enhanced solid-state NMR experiments performed at 9.4 T are complemented by high-field CW EPR measurements performed at the same magnetic field. Microwave absorption by the DNP glassy matrix is observed even below the glass transition temperature caused by softening of the glass. Shortening of electron relaxation times due to glass softening and its impact in terms of DNP sensitivity is discussed.

  14. 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…

  15. Developmental Differences in Strategies for Solving Figural Matrices.

    ERIC Educational Resources Information Center

    Foorman, Barbara R.; And Others

    In order to study children's strategies for solving geometric matrices similar to those in the Raven's Progressive Matrices, ninety 7-, 10-, and 13-year-old boys and girls were administered tests of auditory and visual memory, the Raven's, and geometric matrices. The matrices varied in number of elements (1 to 3) and number of transformations (0…

  16. 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.

  17. 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).

  18. 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

  19. 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

  20. Evidence for a glassy state in strongly driven carbon

    DOE PAGESBeta

    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

  1. 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

  2. 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

  3. 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.

  4. 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. PMID:25816331

  5. Condition Number Estimation of Preconditioned Matrices

    PubMed Central

    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. PMID:25816331

  6. 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).

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

    PubMed Central

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

    2015-01-01

    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). PMID:25716054

  8. Au nanoparticles and graphene quantum dots co-modified glassy carbon electrode for catechol sensing

    NASA Astrophysics Data System (ADS)

    Zhao, Xuan; He, Dawei; Wang, Yongsheng; Hu, Yin; Fu, Chen

    2016-03-01

    In this letter, the gold nanoparticles and graphene quantum dots were applied to the modification of glassy carbon electrode for the detection of catechol. The synergist cooperation between gold nanoparticles and graphene quantum dots can increase specific surface area and enhance electronic and catalytic properties of glassy carbon electrode. The detection limit of catechol is 0.869 μmol/L, demonstrating the superior detection efficiency of the gold nanoparticles and graphene quantum dots co-modified glassy carbon electrode as a new sensing platform.

  9. 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

  10. Octonion generalization of Pauli and Dirac matrices

    NASA Astrophysics Data System (ADS)

    Chanyal, B. C.

    2015-10-01

    Starting with octonion algebra and its 4 × 4 matrix representation, we have made an attempt to write the extension of Pauli's matrices in terms of division algebra (octonion). The octonion generalization of Pauli's matrices shows the counterpart of Pauli's spin and isospin matrices. In this paper, we also have obtained the relationship between Clifford algebras and the division algebras, i.e. a relation between octonion basis elements with Dirac (gamma), Weyl and Majorana representations. The division algebra structure leads to nice representations of the corresponding Clifford algebras. We have made an attempt to investigate the octonion formulation of Dirac wave equations, conserved current and weak isospin in simple, compact, consistent and manifestly covariant manner.

  11. 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 ) .

  12. 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.

  13. 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.

  14. Jump in the electrical conductivity of shock-compressed glassy carbon

    NASA Astrophysics Data System (ADS)

    Molodets, A. M.; Golyshev, A. A.; Emel'yanov, A. N.; Shul'ga, Yu. M.; Fortov, V. E.

    2014-04-01

    The effect of high dynamic pressures on the electrical conductivity of the amorphous conducting carbon phase (glassy carbon) has been studied. The electrical conductivity of glassy carbon samples has been measured under the condition of shock compression and subsequent release wave. The history of the shock loading of glassy carbon has been calculated with the developed semiempirical equations of state. It has been shown the electrical conductivity of glassy carbon samples in the compression phase at a pressure of 45(5) GPa decreases abruptly by two orders of magnitude. In the relief phase, partially reversible change in the electrical conductivity of an amorphous carbon sample occurs. The recorded effect has been treated as a result of a partially reversible physicochemical transformation of shock-compressed amorphous carbon.

  15. Sub-nanoscale nanoimprint fabrication of atomically stepped glassy substrates of silicate glass and acryl polymer

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Mamoru

    2015-11-01

    In the nanoimprint process, the resolution limit of patterning has attracted much attention from both scientific and industrial aspects. In this article, we briefly review the main achievements of our research group on sub-nanoscale nanoimprint fabrication of atomically patterned glassy substrates of oxide glass and polymer. By applying the sapphire (α-Al2O3 single crystal) wafers with self-organized nanopatterns of atomic steps as thermal nanoimprinting molds, we successfully transferred their nanoscale patterns onto the surfaces of glassy substrates such as soda-lime silicate glasses and poly(methyl methacrylate) polymers. The surfaces of nanoimprinted glassy materials exhibited regularly arrayed atomic stairs with 0.2-0.3 nm step height, which were in good agreement with the sub-nanopatterns of sapphire molds. These atomically stepped morphologies on the glassy substrates were found to be stable for about 1 year.

  16. Fast transforms: Banded matrices with banded inverses

    PubMed Central

    Strang, Gilbert

    2010-01-01

    It is unusual for both A and A-1 to be banded—but this can be a valuable property in applications. Block-diagonal matrices F are the simplest examples; wavelet transforms are more subtle. We show that every example can be factored into A = F1…FN where N is controlled by the bandwidths of A and A-1 (but not by their size, so this extends to infinite matrices and leads to new matrix groups). PMID:20615937

  17. 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.

  18. 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.

  19. Robust organic lasers comprising glassy-cholesteric pentafluorene doped with a red-emitting oligofluorene

    NASA Astrophysics Data System (ADS)

    Wei, Simon K. H.; Chen, Shaw H.; Dolgaleva, Ksenia; Lukishova, Svetlana G.; Boyd, Robert W.

    2009-01-01

    Doped with a red-emitting oligofluorene, fluid and glassy cholesteric liquid crystal (CLC) films are characterized by similar lasing thresholds and efficiencies. With picosecond excitations the output from a glassy CLC laser is temporally stable, but that from a fluid CLC laser decays with time. The difference in stability is attributable to external perturbations on supramolecular structure in the fluid but not the solid state, such as heating through optical pumping, light-induced pitch dilation, and laser-induced flow.

  20. Controlled release of drugs from cellulose acetate matrices produced from sugarcane bagasse: monitoring by square-wave voltammetry.

    PubMed

    Rodrigues Filho, Guimes; Almeida, Flávia; Ribeiro, Sabrina D; Tormin, Thiago F; Muñoz, Rodrigo A A; Assunção, Rosana M N; Barud, Hernane

    2016-07-01

    In this paper, cellulose triacetate (CTA) was produced from sugarcane bagasse and used as matrices for controlled release of paracetamol. Symmetric and asymmetric membranes were obtained by formulations of CTA/dichloromethane/drug and CTA/dichloromethane/water/drug, respectively, and they were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Different morphologies of membranes were observed by SEM, and the incorporation of paracetamol was confirmed by lowering of the glass transition temperature (Tg) in the DSC curves. This indicates the existence of interactions between the matrix and the drug. The evaluation of drug release was based on the electrochemical monitoring of paracetamol through its oxidation at a glassy carbon electrode surface using square-wave voltammetry (SWV), which provides fast, precise and accurate in situ measurements. The studies showed a content release of 27% and 45% by the symmetric and asymmetric membranes, respectively, during 8 h. PMID:26596497

  1. 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.

  2. Glassy Dynamics versus Thermodynamics: The Case of 2-Adamantanone.

    PubMed

    Szewczyk, D; Jeżowski, A; Vdovichenko, G A; Krivchikov, A I; Bermejo, F J; Tamarit, J Ll; Pardo, L C; Taylor, J W

    2015-07-01

    The heat capacity and thermal conductivity of the monoclinic and the fully ordered orthorhombic phases of 2-adamantanone (C10H14O) have been measured for temperatures between 2 and 150 K. The heat capacities for both phases are shown to be strikingly close regardless of the site disorder present in the monoclinic crystal which arises from the occupancy of three nonequivalent sites for the oxygen atom. The heat capacity curves are also well accounted for by an evaluation carried out within the harmonic approximation in terms of the g(ω) vibrational frequency distributions measured by means of inelastic neutron scattering. Such spectral functions show however a significant excess of low frequency modes for the crystal showing statistical disorder. In contrast, large differences are found for the thermal conductivity which contrary to what could be expected, shows the substitutionally disordered crystal to exhibit better heat transport properties than the fully ordered orthorhombic phase. Such an anomalous behavior is understood from examination of the crystalline structure of the orthorhombic phase which leads to very strong scattering of heat-carrying phonons due to grain boundary effects able to yield a largely reduced value of the conductivity as well as to a plateau-like feature at intermediate temperatures which contrasts with a bell-shaped maximum shown by data pertaining the disordered crystal. The relevance of the present findings within the context of glassy dynamics of the orientational glass state is finally discussed. PMID:26073682

  3. Electrochemical determination of mesotrione at organoclay modified glassy carbon electrodes.

    PubMed

    Kamga Wagheu, Josephine; Forano, Claude; Besse-Hoggan, Pascale; Tonle, Ignas K; Ngameni, Emmanuel; Mousty, Christine

    2013-01-15

    A natural Cameroonian smectite-type clay (SaNa) was exchanged with cationic surfactants, namely cetyltrimethylammonium (CTA) and didodecyldimethyl ammonium (DDA) modifying its physico-chemical properties. The resulting organoclays that have higher adsorption capacity for mesotrione than the pristine SaNa clay, have been used as modifiers of glassy carbon electrode for the electrochemical detection of this herbicide by square wave voltammetry. The stripping performances of SaNa, SaCTA and SaDDA modified electrodes were therefore evaluated and the experimental parameters were optimized. SaDDA gives the best results in deoxygenated acetate buffer solution (pH 6.0) after 2 min accumulation under open circuit conditions. Under optimal conditions, the reduction current is proportional to mesotrione concentration in the range from 0.25 to 2.5 μM with a detection limit of 0.26 μM. The fabricated electrode was also applied for the commercial formulation CALLISTO, used in European maize market. PMID:23200396

  4. Frequency-dependent conductivity in bismuth-vanadate glassy semiconductors

    NASA Astrophysics Data System (ADS)

    Ghosh, Aswini

    1990-01-01

    The first measurements are reported for the frequency-dependent (ac) conductivity (real as well as imaginary parts) for various compositions of the bismuth-vanadate glassy semiconductors in the frequency range 102-105 Hz and in the temperature range 77-420 K. The behavior of the ac conductivity is broadly similar to what has been observed previously in many other types of amorphous semiconductors, namely, nearly linear frequency dependence and weak temperature dependence. The experimental results are analyzed with reference to various theoretical models based on quantum-mechanical tunneling and classical hopping over barriers. The analysis shows that the temperature dependence of the ac conductivity is consistent with the simple quantum-mechanical tunneling model at low temperatures; however, this model completely fails to predict the observed temperature dependence of the frequency exponent. The overlapping-large-polaron tunneling model can explain the temperature dependence of the frequency exponent at low temperatures. Fitting of this model to the low-temperature data yields a reasonable value of the wave-function decay constant. However, this model predicts the temperature dependence of the ac conductivity much higher than what actual data showed. The correlated barrier hopping model is consistent with the temperature dependence of both the ac conductivity and its frequency exponent. This model provides reasonable values of the maximum barrier heights but higher values of characteristic relaxation times.

  5. Real-time nonequilibrium dynamics of quantum glassy systems

    NASA Astrophysics Data System (ADS)

    Cugliandolo, Leticia F.; Lozano, Gustavo

    1999-01-01

    We develop a systematic analytic approach to aging effects in quantum disordered systems in contact with an environment. Within the closed-time path-integral formalism we include dissipation by coupling the system to a set of independent harmonic oscillators that mimic a quantum thermal bath. After integrating over the bath variables and averaging over disorder we obtain an effective action that determines the real-time dynamics of the system. The classical limit yields the Martin-Siggia-Rose generating functional associated to a colored noise. We apply this general formalism to a prototype model related to the p spin glass. We show that the model has a dynamic phase transition separating the paramagnetic from the spin-glass phase and that quantum fluctuations depress the transition temperature until a quantum critical point is reached. We show that the dynamics in the paramagnetic phase is stationary but presents an interesting crossover from a region controlled by the classical critical point to another one controlled by the quantum critical point. The most characteristic property of the dynamics in a glassy phase, namely, aging, survives the quantum fluctuations. In the subcritical region the quantum fluctuation-dissipation theorem is modified in a way that is consistent with the notion of effective temperatures introduced for the classical case. We discuss these results in connection with recent experiments in dipolar quantum spin glasses and the relevance of the effective temperatures with respect to the understanding of the low-temperature dynamics.

  6. 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.

  7. Growth, microstructure, and failure of crazes in glassy polymers

    NASA Astrophysics Data System (ADS)

    Rottler, Jörg; Robbins, Mark O.

    2003-07-01

    We report on an extensive study of craze formation in glassy polymers. Molecular dynamics simulations of a coarse-grained bead-spring model were employed to investigate the molecular level processes during craze nucleation, widening, and breakdown for a wide range of temperature, polymer chain length N, entanglement length Ne, and strength of adhesive interactions between polymer chains. Craze widening proceeds via a fibril-drawing process at constant drawing stress. The extension ratio is determined by the entanglement length, and the characteristic length of stretched chain segments in the polymer craze is Ne/3. In the craze, tension is mostly carried by the covalent backbone bonds, and the force distribution develops an exponential tail at large tensile forces. The failure mode of crazes changes from disentanglement to scission for N/Ne˜10, and breakdown through scission is governed by large stress fluctuations. The simulations also reveal inconsistencies with previous theoretical models of craze widening, which were based on continuum level hydrodynamics.

  8. Gamma ray attenuation in a developed borate glassy system

    NASA Astrophysics Data System (ADS)

    Saeed, Aly; El shazly, R. M.; Elbashar, Y. H.; Abou El-azm, A. M.; El-Okr, M. M.; Comsan, M. N. H.; Osman, A. M.; Abdal-monem, A. M.; El-Sersy, A. R.

    2014-09-01

    Measurements and calculations of gamma ray attenuation coefficients in glass barriers of xBaO-5ZnO-5MgO-14Na2O--1Li2O-(75-x)B2O3, previously prepared by the melt-quenching technique [1], were performed for γ-ray of energies 121.8, 244.7, 344.14, 661.66, 778.7, 974, 1086.7, 1173.24, 1332.5, and 1407.9 keV; which emitted from 152Eu, 137Cs, and 60Co radioactive gamma ray sources. The transmitted γ-rays were detected by 3″×3″ and 5″×5″ NaI (Tl) scintillation γ-ray spectrometers, and a highly calibrated survey meter. The mass attenuation coefficients of γ-rays (σ(E) were deduced from the attenuation curves, while the WinXCom computer program (version 3.1) was used to calculate the mass attenuation coefficients of γ-rays for such energies at different barium concentrations of a glassy system. A good agreement between both experimental and theoretical results was achieved as well as results obtained by other workers in similar field.

  9. CO2 reduction catalyzed by mercaptopteridine on glassy carbon.

    PubMed

    Xiang, Dongmei; Magana, Donny; Dyer, R Brian

    2014-10-01

    The catalytic reduction of CO2 is of great current interest because of its role in climate change and the energy cycle. We report a pterin electrocatalyst, 6,7-dimethyl-4-hydroxy-2-mercaptopteridine (PTE), that catalyzes the reduction of CO2 and formic acid on a glassy carbon electrode. Pterins are natural cofactors for a wide range of enzymes, functioning as redox mediators and C1 carriers, but they have not been exploited as electrocatalysts. Bulk electrolysis of a saturated CO2 solution in the presence of the PTE catalyst produces methanol, as confirmed by gas chromatography and (13)C NMR spectroscopy, with a Faradaic efficiency of 10-23%. FTIR spectroelectrochemistry detected a progression of two-electron reduction products during bulk electrolysis, including formate, aqueous formaldehyde, and methanol. A transient intermediate was also detected by FTIR and tentatively assigned as a PTE carbamate. The results demonstrate that PTE catalyzes the reduction of CO2 at low overpotential and without the involvement of any metal. PMID:25259884

  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. 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.

  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. Evolution of Entanglements During Crazing of Glassy Polymers

    NASA Astrophysics Data System (ADS)

    Ge, Ting; Robbins, Mark O.; Hoy, Robert; Anogiannakis, Stefanos; Tzoumanekas, Christos; Theodorou, Doros

    2011-03-01

    Craze formation increases the fracture energy of glassy polymers by orders of magnitude. The polymer volume expands by an extension ratio which is assumed to be determined by the entanglement network. We test this assumption with molecular simulations that use the Contour Reduction Topological Analysis (CReTA) algorithm to follow topological constraints (TCs) associated with the entanglement network. The TCs are identified with contacts between chains after applying CReTA. Within systematic errors, crazing does not change the number of TCs or the distribution of chemical distances between them. Moreover, about 75% of the contacts remain between the same chains at nearly the same location. The 25% of contacts that change do not reflect a comparable loss of entanglements. Instead, small displacements within the tube change which chains contact after CReTA. This interpretation is tested by adding fixed crosslinks to a sparse entanglement network and crazing preoriented samples. This material is based upon work supported by NSF Grant DMR 108474.

  15. Entanglements and the Mechanical Properties of Glassy Polymers

    NASA Astrophysics Data System (ADS)

    Robbins, Mark

    2011-03-01

    The response of glassy polymers to shear or tensile strain is strongly influenced by the entanglement network that is inherited from the melt. Molecular dynamics simulations are used to probe the microscopic origins of stress-strain curves and their connection to entanglements. The latter are identified in real space by examining topological constraints along the primitive path. The first part of the talk will consider the process of craze formation, where the entanglement density is correlated to the volume increase during crazing. Simulations show that entanglements are preserved during crazing, but the craze density does not correspond to pulling chains taut between entanglements. The second part of the talk will examine the effect of entanglements on strain hardening under uniaxial strain. The stress is directly associated with the degree of orientational order along the strain axis, and nearly independent of order along perpendicular directions. Studies with mixtures of short and long chains show that the degree of order is independent of the surrounding chains. The final part of the talk will examine the strength of welds formed by diffusion across polymer interfaces. The shear stress follows the bulk response until chains are pulled taut on the scale of the length of segments that have diffused across the interface. When this length is several times the entanglement length, the maximum shear stress saturates at the bulk value and chains fail through scission. Similar trends are found for the fracture energy in tensile loading. This material is based upon work supported by NSF Grant DMR 108474.

  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. 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.

  18. Multifunctional matrices for oral peptide delivery.

    PubMed

    Bernkop-Schnürch, A; Walker, G

    2001-01-01

    The oral administration of peptide drugs represents one of the greatest challenges in pharmaceutical technology. To gain a sufficient bioavailability of these therapeutic agents, various barriers including the mucus-layer barrier, the enzymatic barrier, and the membrane barrier have to be overcome. A promising strategy for achieving this goal is the use of multifunctional matrices. These matrices are based on polymers that display mucoadhesive properties, a permeation-enhancing effect, enzyme-inhibiting properties, and/or a high buffer capacity. Moreover, a sustained or delayed drug release can be provided by delivery systems that contain such polymers. Among them, polyacrylates, cellulose derivatives, and chitosan are promising excipients that can also be customized by chemical modification to improve certain properties. For example, the covalent attachment of thiol moieties on these polymers leads to improved mucoadhesive and permeation-enhancing properties, and the conjugation of enzyme inhibitors enables the matrices to provide protection for peptide drugs against enzymatic degradation. The efficacy of multifunctional matrices in oral peptide delivery has been verified by various in vivo studies that could pave the way for the development of commercially viable formulations. PMID:11763498

  19. 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...

  20. Parameterized BLOSUM Matrices for Protein Alignment.

    PubMed

    Song, Dandan; Chen, Jiaxing; Chen, Guang; Li, Ning; Li, Jin; Fan, Jun; Bu, Dongbo; Li, Shuai Cheng

    2015-01-01

    Protein alignment is a basic step for many molecular biology researches. The BLOSUM matrices, especially BLOSUM62, are the de facto standard matrices for protein alignments. However, after widely utilization of the matrices for 15 years, programming errors were surprisingly found in the initial version of source codes for their generation. And amazingly, after bug correction, the "intended" BLOSUM62 matrix performs consistently worse than the "miscalculated" one. In this paper, we find linear relationships among the eigenvalues of the matrices and propose an algorithm to find optimal unified eigenvectors. With them, we can parameterize matrix BLOSUMx for any given variable x that could change continuously. We compare the effectiveness of our parameterized isentropic matrix with BLOSUM62. Furthermore, an iterative alignment and matrix selection process is proposed to adaptively find the best parameter and globally align two sequences. Experiments are conducted on aligning 13,667 families of Pfam database and on clustering MHC II protein sequences, whose improved accuracy demonstrates the effectiveness of our proposed method. PMID:26357279

  1. 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

  2. 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

  3. 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.

  4. On reduced density matrices for disjoint subsystems

    NASA Astrophysics Data System (ADS)

    Iglói, F.; Peschel, I.

    2010-02-01

    We show that spin and fermion representations for solvable quantum chains lead in general to different reduced density matrices if the subsystem is not singly connected. We study the effect for two sites in XX and XY chains as well as for sublattices in XX and transverse Ising chains.

  5. Constructing random matrices to represent real ecosystems.

    PubMed

    James, Alex; Plank, Michael J; Rossberg, Axel G; Beecham, Jonathan; Emmerson, Mark; Pitchford, Jonathan W

    2015-05-01

    Models of complex systems with n components typically have order n(2) parameters because each component can potentially interact with every other. When it is impractical to measure these parameters, one may choose random parameter values and study the emergent statistical properties at the system level. Many influential results in theoretical ecology have been derived from two key assumptions: that species interact with random partners at random intensities and that intraspecific competition is comparable between species. Under these assumptions, community dynamics can be described by a community matrix that is often amenable to mathematical analysis. We combine empirical data with mathematical theory to show that both of these assumptions lead to results that must be interpreted with caution. We examine 21 empirically derived community matrices constructed using three established, independent methods. The empirically derived systems are more stable by orders of magnitude than results from random matrices. This consistent disparity is not explained by existing results on predator-prey interactions. We investigate the key properties of empirical community matrices that distinguish them from random matrices. We show that network topology is less important than the relationship between a species' trophic position within the food web and its interaction strengths. We identify key features of empirical networks that must be preserved if random matrix models are to capture the features of real ecosystems. PMID:25905510

  6. 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.

  7. 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.

  8. 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).

  9. 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

  10. 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

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

    PubMed

    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

  12. 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.

  13. 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,...

  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. Electrochemical oxidation of butein at glassy carbon electrodes.

    PubMed

    Tesio, Alvaro Yamil; Robledo, Sebastián Noel; Fernández, Héctor; Zon, María Alicia

    2013-06-01

    The electrochemical oxidation of flavonoid butein is studied at glassy carbon electrodes in phosphate and citrate buffer solutions of different pH values, and 1M perchloric acid aqueous solutions by cyclic and square wave voltammetries. The oxidation peak corresponds to the 2e(-), 2H(+) oxidation of the 3,4-dihydroxy group in B ring of butein, given the corresponding quinone species. The overall electrode process shows a quasi-reversible behavior and an adsorption/diffusion mixed control at high butein bulk concentrations. At low butein concentrations, the electrode process shows mainly an adsorption control. Butein surface concentration values were obtained from the charge associated with the adsorbed butein oxidation peaks, which are in agreement with those values expected for the formation of a monolayer of adsorbate in the concentration range from 1 to 5μM. Square wave voltammetry was used to perform a full thermodynamic and kinetics characterization of the butein surface redox couple. Therefore, from the combination of the "quasi-reversible maximum" and the "splitting of the net square wave voltammetric peak" methods, values of (0.386±0.003) V, (0.46±0.04), and 2.7×10(2)s(-1) were calculated for the formal potential, the anodic transfer coefficient, and the formal rate constant, respectively, of the butein overall surface redox process in pH4.00 citrate buffer solutions. These results will be then used to study the interaction of butein, and other flavonoids with the deoxyribonucleic acid, in order to better understand the potential therapeutic applications of these compounds. PMID:23434740

  16. 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.

  17. 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. PMID:22082024

  18. 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

  19. 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.

  20. Bioisosteric matrices for ligands of serotonin receptors.

    PubMed

    Warszycki, Dawid; Mordalski, Stefan; Staroń, Jakub; Bojarski, Andrzej J

    2015-04-01

    The concept of bioisosteric replacement matrices is applied to explore the chemical space of serotonin receptor ligands, aiming to determine the most efficient ways of manipulating the affinity for all 5-HT receptor subtypes. Analysis of a collection of over 1 million bioisosteres of compounds with measured activity towards serotonin receptors revealed that an average of 31 % of the ligands for each target are mutual bioisosteres. In addition, the collected dataset allowed the development of bioisosteric matrices-qualitative and quantitative descriptions of the biological effects of each predefined type of bioisosteric substitution, providing favored paths of modifying the compounds. The concept exemplified here for serotonin receptor ligands can likely be more broadly applied to other target classes, thus representing a useful guide for medicinal chemists designing novel ligands. PMID:25772514

  1. 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.

  2. Relaxation dynamics and crystallization study of sildenafil in the liquid and glassy states.

    PubMed

    Kolodziejczyk, K; Paluch, M; Grzybowska, K; Grzybowski, A; Wojnarowska, Z; Hawelek, L; Ziolo, J D

    2013-06-01

    In this paper, the physical stability and molecular dynamics of amorphous sildenafil are investigated in both the liquid and glassy states. We have established that the amorphous sildenafil is resistant to recrystallization at temperatures below the glass transition temperature Tg during the experimental period of its storage (i.e., above 6 months), however, it easily undergoes cold crystallization at T > Tg. To determine the crystallization mechanism, the isothermal and non-isothermal studies of the cold crystallization kinetics of the drug are performed by using the broadband dielectric spectroscopy (BDS) and the differential scanning calorimetry (DSC), respectively. The cold crystallization mechanism has been found to be similar in both the isothermal and non-isothermal cases. This mechanism has been analyzed from the point of view of the molecular mobility of sildenafil investigated in the supercooled liquid and glassy states by using the BDS measurements in the wide temperature range. This analysis has been enriched with a new approach based on a recently reported measure of dynamic heterogeneity given by a four-point dynamic susceptibility function. No tendency to recrystallization of glassy sildenafil at T < Tg is also discussed in relation to molecular dynamics of sildenafil in the glassy state. The relatively small molecular mobility reflected in one secondary relaxation as well as the predicted large time scale of structural relaxation of glassy sildenafil suggests that amorphous sildenafil should not recrystallize during its long-term storage at room temperature. PMID:23594226

  3. Sorption of water by bidisperse mixtures of carbohydrates in glassy and rubbery states.

    PubMed

    Ubbink, Job; Giardiello, Maria-Isabelle; Limbach, Hans-Jörg

    2007-09-01

    Water sorption by bidisperse carbohydrate mixtures consisting of varying ratios of a narrow-molecular-weight distribution maltopolymer and the disaccharide maltose is investigated to establish a quantitative relation between the composition of the carbohydrate system and the water sorption isotherm. The sorption of water is approached from two limiting cases: the glassy state at low water content and the dilute aqueous carbohydrate solution. In the glassy state, the water content at a given water activity decreases with increasing maltose content of the matrix, whereas in the rubbery state it increases with increasing maltose content. The water sorption behavior in the glassy state is quantified using a variety of models, including the often-utilized but physically poorly founded Guggenheim-Anderson-de Boer model, several variants of the free-volume theory of sorption by glassy polymers, and a two-state sorption model introduced in the present paper. It is demonstrated that both the free-volume models and the two-state sorption model, which all encompass the Flory-Huggins theory for the rubbery-state sorption but which differ in their modeling of the glassy-state sorption, provide a physically consistent foundation for the analysis of water sorption by the carbohydrate matrixes. PMID:17691841

  4. Understanding the Physical Aging Behavior of Glassy Polystyrene Layers in Close Contact with Rubbery Domains

    NASA Astrophysics Data System (ADS)

    Roth, Connie; Rauscher, Phil; Pye, Justin; Baglay, Roman

    2014-03-01

    Recent advances in synthesis strategies and processing methods have led to new nanostructured polymer blend and block-copolymer materials containing domain sizes less than 100 nm with glassy and rubbery domains in close proximity. Given the outsized role interfacial perturbations have played in causing large changes in the glass transition temperature Tg and physical aging of ultrathin single-layer films, we are interested in studying how the presence of glassy-rubbery interfaces between neighboring polymer domains may alter the local stability and physical aging of confined glassy layers. Using a polystyrene (PS) / poly(n-butyl methacrylate) (PnBMA) weakly immiscible system with 7 nm interfacial width, we demonstrate how ellipsometry can be used to isolate the physical aging rate of thin PS layers atop rubbery PnBMA layers. Despite a 25-30 K reduction in the average Tg of 84 nm thick PS layers atop PnBMA as measured by fluorescence, we observe no change in the PS aging rate relative to bulk. These results are in contrast with previous works on single-layer polymer films that have found the local aging rate to often be correlated with local Tg changes. This appears not to be the case for glassy PS layers atop rubbery PnBMA suggesting some additional factor is affecting the structural relaxation occurring near the glassy-rubbery interface.

  5. Mechanisms of crazing in glassy polymers revealed by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Mahajan, Dhiraj K.; Hartmaier, Alexander

    2012-08-01

    Mechanisms leading to initiation of crazing type failure in a glassy polymer are not clearly understood. This is mainly due to the difficulty in characterizing the stress state and polymer configuration sufficiently locally at the craze initiation site. Using molecular dynamics simulations, we have now been able to access this information and have shown that the local heterogeneous deformation leads to craze initiation in glassy polymers. We found that zones of high plastic activity are constrained by their neighborhood and become unstable, initiating crazing from these sites. Furthermore, based on the constant flow stresses observed in the unstable zones, we conclude that microcavitation is the essential local deformation mode to trigger crazing in glassy polymers. Our results demonstrate the basic difference in the local deformation mode as well as the conditions that lead to either shear-yielding or crazing type failures in glassy polymers. We anticipate our paper to help in devising a new criterion for craze initiation that not only considers the stress state, but also considers local deformation heterogeneities that form the necessary condition for crazing in glassy polymers.

  6. Mechanisms of crazing in glassy polymers revealed by molecular dynamics simulations.

    PubMed

    Mahajan, Dhiraj K; Hartmaier, Alexander

    2012-08-01

    Mechanisms leading to initiation of crazing type failure in a glassy polymer are not clearly understood. This is mainly due to the difficulty in characterizing the stress state and polymer configuration sufficiently locally at the craze initiation site. Using molecular dynamics simulations, we have now been able to access this information and have shown that the local heterogeneous deformation leads to craze initiation in glassy polymers. We found that zones of high plastic activity are constrained by their neighborhood and become unstable, initiating crazing from these sites. Furthermore, based on the constant flow stresses observed in the unstable zones, we conclude that microcavitation is the essential local deformation mode to trigger crazing in glassy polymers. Our results demonstrate the basic difference in the local deformation mode as well as the conditions that lead to either shear-yielding or crazing type failures in glassy polymers. We anticipate our paper to help in devising a new criterion for craze initiation that not only considers the stress state, but also considers local deformation heterogeneities that form the necessary condition for crazing in glassy polymers. PMID:23005778

  7. 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

  8. Photochromic Behavior of Spiropyran in Polymer Matrices

    NASA Astrophysics Data System (ADS)

    Tork, Amir; Boudreault, Francois; Roberge, Mathieu; Ritcey, Anna M.; Lessard, Roger A.; Galstian, Tigran V.

    2001-03-01

    The photoexcitation, relaxation, and optical erasure regimes of spiropyran- (SP-) doped polymer films were studied. Cellulose acetate, poly(vinyl acetate), and poly(methyl methacrylate) (PMMA) were used as host polymer matrices. We studied the character of the photoreaction for both coloring and bleaching processes. Reversible holographic recording in SP -PMMA films and the origin of the photochemical fatigue was studied upon repeated UV -visible irradiation cycles.

  9. 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.

  10. Preconditioning matrices for Chebyshev derivative operators

    NASA Technical Reports Server (NTRS)

    Rothman, Ernest E.

    1986-01-01

    The problem of preconditioning the matrices arising from pseudo-spectral Chebyshev approximations of first order operators is considered in both one and two dimensions. In one dimension a preconditioner represented by a full matrix which leads to preconditioned eigenvalues that are real, positive, and lie between 1 and pi/2, is already available. Since there are cases in which it is not computationally convenient to work with such a preconditioner, a large number of preconditioners were studied which were more sparse (in particular three and four diagonal matrices). The eigenvalues of such preconditioned matrices are compared. The results were applied to the problem of finding the steady state solution to an equation of the type u sub t = u sub x + f, where the Chebyshev collocation is used for the spatial variable and time discretization is performed by the Richardson method. In two dimensions different preconditioners are proposed for the matrix which arises from the pseudo-spectral discretization of the steady state problem. Results are given for the CPU time and the number of iterations using a Richardson iteration method for the unpreconditioned and preconditioned cases.

  11. Quark flavor mixings from hierarchical mass matrices

    NASA Astrophysics Data System (ADS)

    Verma, Rohit; Zhou, Shun

    2016-05-01

    In this paper, we extend the Fritzsch ansatz of quark mass matrices while retaining their hierarchical structures and show that the main features of the Cabibbo-Kobayashi-Maskawa (CKM) matrix V, including |V^{}_{us}| ˜eq |V^{}_{cd}|, |V^{}_{cb}| ˜eq |V^{}_{ts}| and |V^{}_{ub}|/|V^{}_{cb}| < |V^{}_{td}|/|V^{}_{ts}|, can be well understood. This agreement is observed especially when the mass matrices have non-vanishing (1, 3) and (3, 1) off-diagonal elements. The phenomenological consequences of these for the allowed texture content and gross structural features of `hierarchical' quark mass matrices are addressed from a model-independent prospective under the assumption of factorizable phases in these. The approximate and analytical expressions of the CKM matrix elements are derived and a detailed analysis reveals that such structures are in good agreement with the observed quark flavor mixing angles and the CP-violating phase at the 1σ level and call upon a further investigation of the realization of these structures from a top-down prospective.

  12. Special paraunitary matrices, Cayley transform, and multidimensional orthogonal filter banks.

    PubMed

    Zhou, Jianping; Do, Minh N; Kovaĉević, Jelena

    2006-02-01

    We characterize and design multidimensional (MD) orthogonal filter banks using special paraunitary matrices and the Cayley transform. Orthogonal filter banks are represented by paraunitary matrices in the polyphase domain. We define special paraunitary matrices as paraunitary matrices with unit determinant. We show that every paraunitary matrix can be characterized by a special paraunitary matrix and a phase factor. Therefore, the design of paraunitary matrices (and thus of orthogonal filter banks) becomes the design of special paraunitary matrices, which requires a smaller set of nonlinear equations. Moreover, we provide a complete characterization of special paraunitary matrices in the Cayley domain, which converts nonlinear constraints into linear constraints. Our method greatly simplifies the design of MD orthogonal filter banks and leads to complete characterizations of such filter banks. PMID:16479821

  13. 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

  14. 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.

  15. 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

  16. 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

  17. Controlling the Protein Dynamical Transition with Sugar-Based Bioprotectant Matrices: A Neutron Scattering Study

    PubMed Central

    Cornicchi, E.; Marconi, M.; Onori, G.; Paciaroni, A.

    2006-01-01

    Through elastic neutron scattering we measured the mean-square displacements of the hydrogen atoms of lysozyme embedded in a glucose-water glassy matrix as a function of the temperature and at various water contents. The elastic intensity of all the samples has been interpreted in terms of the double-well model in the whole temperature range. The dry sample shows an onset of anharmonicity at ∼100 K, which can be attributed to the activation of methyl group reorientations. Such a protein intrinsic dynamics is decoupled from the external environment on the whole investigated temperature range. In the hydrated samples an additional and larger anharmonic contribution is provided by the protein dynamical transition, which appears at a higher temperature Td. As hydration increases the coupling between the protein internal dynamics and the surrounding matrix relaxations becomes more effective. The behavior of Td that, as a function of the water content, diminishes by ∼60 K, supports the picture of the protein dynamics as driven by solvent relaxations. A possible connection between the protein dynamical response versus T and the thermal stability in glucose-water bioprotectant matrices is proposed. PMID:16617083

  18. 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.

  19. 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

  20. Pattern formation in polymer via electrohydrodynamic instabilities and glassy fracture

    NASA Astrophysics Data System (ADS)

    Pease, Leonard Franklin, III

    Fabrication of micro and nano structures from polymeric materials has attracted significant attention due to their promise of inexpensive, fast throughput and ease of integration into existing fabrication processes. This dissertation describes our contributions to two such processes. In the first process, electrohydrodynamic flow drives a thin polymer film sandwiched between electrodes with an intervening gap into multidomained, hexagonally packed pillars or concentric rings. We model the initial stages of formation by performing a linear stability analysis under the lubrication approximation. We find the presence of free charge at the free interface both decreases the pillar-to-pillars spacing and increases the growth rate. We examined the possible sources of electrostatic field in the absence of an applied voltage to find static charge to be the most likely candidate. In practice, however, the lubrication approximation may not strictly apply in the situations of greatest interest. Accordingly, we contrasted results of the linear stability analysis with and without the lubrication approximation to show that the approximation fails where surface tension is small and electric fields are large, typical of experiments with a polymer/organic liquid instead of air in the gap---precisely the conditions that predict the smallest pillar arrays. Motivated by the discovery of concentric rings, we adapted the form of the perturbation from sinusoids to Bessel functions to predict constant ring-to-ring spacings, constant annular widths and growth rates in agreement with experiment. In the second patterning technique, a thin film sandwiched between two substrates fractures into periodic ridges upon insertion of a razor blade. We investigated the conditions that selected for the presence or absence of the gratings, their fractional coverage, their period, and their alignment. Our key findings indicated that the gratings form from all glassy materials tested with periods of

  1. 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

  2. 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.

  3. 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

  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. 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.

  6. 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.

  7. Nature of ThF bonding in crystalline and glassy states using EXAFS and XANES

    NASA Astrophysics Data System (ADS)

    Rao, K. J.; Wong, J.; Shafer, M. W.

    1984-11-01

    A binary glass of thorium and hafnium tetrafluorides (with dopant concentrations of LaF 3) has been investigated using EXAFS and XANES analysis of the L Ill edge spectra of thorium. Results of EXAFS analysis indicate that there is no change in the number of nearest neighbors of thorium ions. However, the intensity of the white line in XANES is significantly higher in the glass. This increase in intensity has been explained semiquantitatively in terms of enhanced covalency of ThF bonding. Since the coordination number of Th 4+ remains constant in both crystalline and glassy states, covalency enhancement seems to be a general characteristic of glassy state of ionic materials.

  8. Characterization of molecular mobility within the glassy matrix of dry seeds using mechanical properties: pea cotyledon as a test study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seed glasses form during maturation drying and regulate seed longevity. Seeds continue to age within the glassy state and, even during cryogenic storage, viability eventually declines. Inevitability of aging suggests some level of molecular motion within the glassy matrix and quantifying these “rel...

  9. Soft magnetic properties of bulk FeCoMoPCBSi glassy core prepared by copper mold casting

    NASA Astrophysics Data System (ADS)

    Zhang, Mingxiao; Kong, Fanli; Wang, Anding; Chang, Chuntao; Shen, Baolong

    2012-04-01

    Bulk Fe66Co10Mo3.5P10C4B4Si2.5 glassy core of 10 mm in outer diameter, 6 mm in inner diameter, and 1 mm in thickness was successfully prepared by copper mold casting. The effects of annealing treatments on magnetic properties and microstructure of these cores were investigated. After an optimum annealing treatment, the resulting bulk glassy core exhibits good magnetic properties, i.e., high saturation magnetic flux density of 1.23 T, low coercive force of 1.0 A/m, high maximum permeability of 450 000, respectively. In addition, the glassy core also shows low core loss of 0.4 W/kg at 50 Hz and at maximum magnetic flux density of 1 T. The synthesis of bulk glassy core with excellent magnetic properties is encouraging for enlarging the application field of ferromagnetic bulk glassy alloys.

  10. 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.