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Sample records for network glass transition

  1. Depression of Glass Transition Temperatures of Polymer Networks by Diluents

    NARCIS (Netherlands)

    Brinke, Gerrit ten; Karasz, Frank E.; Ellis, Thomas S.

    1983-01-01

    A classical thermodynamic theory is used to derive expressions for the depression of the glass transition temperature Tg of a polymer network by a diluent. The enhanced sensitivity of Tg in cross-linked systems to small amounts of diluent is explained. Predictions of the theory are in satisfactory

  2. Glass-Glass Transitions by Means of an Acceptor-Donor Percolating Electric-Dipole Network

    Science.gov (United States)

    Zhang, Le; Lou, Xiaojie; Wang, Dong; Zhou, Yan; Yang, Yang; Kuball, Martin; Carpenter, Michael A.; Ren, Xiaobing

    2017-11-01

    We report the ferroelectric glass-glass transitions in KN (K+/Nb5 +) -doped BaTiO3 ferroelectric ceramics, which have been proved by x-ray diffraction profile and Raman spectra data. The formation of glass-glass transitions can be attributed to the existence of cubic (C )-tetragonal (T )-orthorhombic (O )-rhombohedral (R ) ferroelectric transitions in short-range order. These abnormal glass-glass transitions can perform very small thermal hysteresis (approximately 1.0 K ) with a large dielectric constant (approximately 3000), small remanent polarization Pr , and relative high maximum polarization Pm remaining over a wide temperature range (220-350 K) under an electrical stimulus, indicating the potential applications in dielectric recoverable energy-storage devices with high thermal reliability. Further phase field simulations suggest that these glass-glass transitions are induced by the formation of a percolating electric defect-dipole network (PEDN). This proper PEDN breaks the long-range ordered ferroelectric domain pattern and results in the local phase transitions at the nanoscale. Our work may further stimulate the fundamental physical theory and accelerate the development of dielectric energy-storing devices.

  3. Effects of chemical composition and mean coordination number on glass transitions in Ge-Sb-Se glasses

    Science.gov (United States)

    Wei, Wen-Hou

    2017-12-01

    Glass transitions in the Ge-Sb-Se glasses were investigated by means of differential scanning calorimetry (DSC) under non-isothermal conditions. The glass transition temperature (Tg), activation energy of glass transition (Et), and fragility index as functions of the mean coordination number (MCN) and atomic percent of Ge were examined. The maximum value of Tg in each group of the glasses occurred at the chemically stoichiometric composition, suggesting a glass transition threshold. The Et and fragility index were calculated from the heating rate dependence of Tg. Both Et and fragility index show the minima at MCN = 2.4 which can be attributed to the structural phase transition of a covalently glassy network at MCN = 2.4. The analysis of the experimental results suggests that both the chemical composition and MCN have significant effects on the glass transitions in Ge-Sb-Se glasses.

  4. Phase transitions and glass transition in a hyperquenched silica–alumina glass

    DEFF Research Database (Denmark)

    Zhang, Y.F.; Zhao, D.H.; Yue, Yuanzheng

    2017-01-01

    We investigate phase transitions, glass transition, and dynamic behavior in the hyperquenched 69SiO2–31Al2O3 (mol%) glass (SA glass). Upon reheating, the SA glass exhibits a series of thermal responses. Subsequent to the sub-Tg enthalpy release, the glass undergoes a large jump in isobaric heat...... capacity (ΔCp) during glass transition, implying the fragile nature of the SA glass. The mullite starts to form before the end of glass transition, indicating that the SA glass is extremely unstable against crystallization. After the mullite formation, the remaining glass phase exhibits an increased Tg...... and a suppressed ΔCp. The formation of cristobalite at 1553 K indicates the dominance of silica in the remaining glass matrix. The cristobalite gradually re-melts as the isothermal heat-treatment temperature is raised from 1823 to 1853 K, which is well below the melting point of cristobalite, while the amount...

  5. Paramagnetic and glass transitions in sudoku

    Science.gov (United States)

    Williams, A.; Ackland, G. J.

    2012-09-01

    We study the statistical mechanics of a model glassy system based on sudoku, a familiar and popular mathematical puzzle. Sudoku puzzles provide a very rare example of a class of frustrated systems with a unique ground state without symmetry. Here, the puzzle is recast as a thermodynamic system where the number of violated rules defines the energy. We use Monte Carlo simulation to show that the “sudoku Hamiltonian” exhibits two transitions as a function of temperature, a paramagnetic, and a glass transition. Of these, the intermediate condensed phase is the only one that visits the ground state (i.e., it solves the puzzle, though this is not the purpose of the study). Both transitions are associated with an entropy change, paramagnetism measured from the dynamics of the Monte Carlo run, showing a peak in specific heat, while the residual glass entropy is determined by finding multiple instances of the glass by repeated annealing. There are relatively few such simple models for frustrated or glassy systems that exhibit both ordering and glass transitions; sudoku puzzles are unique for the ease with which they can be obtained, with the proof of the existence of a unique ground state via the satisfiability of all constraints. Simulations suggest that in the glass phase there is an increase in information entropy with lowering temperature. In fact, we have shown that sudoku puzzles have the type of rugged energy landscape with multiple minima that typifies glasses in many physical systems. This puzzling result is a manifestation of the paradox of the residual glass entropy. These readily available puzzles can now be used as solvable model Hamiltonian systems for studying the glass transition.

  6. Glass Transition, Crystallization of Glass-Forming Melts, and Entropy

    Directory of Open Access Journals (Sweden)

    Jürn W. P. Schmelzer

    2018-02-01

    Full Text Available A critical analysis of possible (including some newly proposed definitions of the vitreous state and the glass transition is performed and an overview of kinetic criteria of vitrification is presented. On the basis of these results, recent controversial discussions on the possible values of the residual entropy of glasses are reviewed. Our conclusion is that the treatment of vitrification as a process of continuously breaking ergodicity with entropy loss and a residual entropy tending to zero in the limit of zero absolute temperature is in disagreement with the absolute majority of experimental and theoretical investigations of this process and the nature of the vitreous state. This conclusion is illustrated by model computations. In addition to the main conclusion derived from these computations, they are employed as a test for several suggestions concerning the behavior of thermodynamic coefficients in the glass transition range. Further, a brief review is given on possible ways of resolving the Kauzmann paradox and its implications with respect to the validity of the third law of thermodynamics. It is shown that neither in its primary formulations nor in its consequences does the Kauzmann paradox result in contradictions with any basic laws of nature. Such contradictions are excluded by either crystallization (not associated with a pseudospinodal as suggested by Kauzmann or a conventional (and not an ideal glass transition. Some further so far widely unexplored directions of research on the interplay between crystallization and glass transition are anticipated, in which entropy may play—beyond the topics widely discussed and reviewed here—a major role.

  7. On relaxation nature of glass transition in amorphous materials

    Science.gov (United States)

    Sanditov, Damba S.; Ojovan, Michael I.

    2017-10-01

    A short review on relaxation theories of glass transition is presented. The main attention is paid to modern aspects of the glass transition equation qτg = C, suggested by Bartenev in 1951 (q - cooling rate of the melt, τg - structural relaxation time at the glass transition temperature Tg). This equation represents a criterion of structural relaxation at transition from liquid to glass at T = Tg (analogous to the condition of mechanical relaxation ωτ = 1, where the maximum of mechanical loss is observed). The empirical parameter С = δTg has the meaning of temperature range δTg that characterizes the liquid-glass transition. Different approaches of δTg calculation are reviewed. In the framework of the model of delocalized atoms a modified kinetic criterion of glass transition is proposed (q/Tg)τg = Cg, where Cg ≅ 7·10-3 is a practically universal dimensionless constant. It depends on fraction of fluctuation volume fg, which is frozen at the glass transition temperature Cg = fg/ln(1/fg). The value of fg is approximately constant fg ≅ 0.025. At Tg the process of atom delocalization, i.e. its displacement from the equilibrium position, is frozen. In silicate glasses atom delocalization is reduced to critical displacement of bridge oxygen atom in Si-O-Si bridge necessary to switch a valence bond according to Muller and Nemilov. An equation is derived for the temperature dependence of viscosity of glass-forming liquids in the wide temperature range, including the liquid-glass transition and the region of higher temperatures. Notion of (bridge) atom delocalization is developed, which is related to necessity of local low activation deformation of structural network for realization of elementary act of viscous flow - activated switch of a valence (bridge) bond. Without atom delocalization (;trigger mechanism;) a switch of the valence bond is impossible and, consequently, the viscous flow. Thus the freezing of atom delocalization process at low temperatures

  8. Superconducting Metallic Glass Transition-Edge-Sensors

    Science.gov (United States)

    Hays, Charles C. (Inventor)

    2013-01-01

    A superconducting metallic glass transition-edge sensor (MGTES) and a method for fabricating the MGTES are provided. A single-layer superconducting amorphous metal alloy is deposited on a substrate. The single-layer superconducting amorphous metal alloy is an absorber for the MGTES and is electrically connected to a circuit configured for readout and biasing to sense electromagnetic radiation.

  9. Models of agglomeration and glass transition

    CERN Document Server

    Kerner, Richard

    2007-01-01

    This book is for any physicist interested in new vistas in the domain of non-crystalline condensed matter, aperiodic and quasi-crystalline networks and especially glass physics and chemistry. Students with an elementary background in thermodynamics and statistical physics will find the book accessible. The physics of glasses is extensively covered, focusing on their thermal and mechanical properties, as well as various models leading to the formation of the glassy states of matter from overcooled liquids. The models of agglomeration and growth are also applied to describe the formation of quasicrystals, fullerenes and, in biology, to describe virus assembly pathways.

  10. Structure-Property Relationships and the Mixed Network Former Effect in Boroaluminosilicate Glasses

    DEFF Research Database (Denmark)

    Zheng, Qiuju; Potuzak, Marcel; Mauro, John C.

    Boroaluminosilicate glasses are important materials for various applications, e.g., liquid crystal display substrates, glass fibers for reinforcement, and thermal shock-resistant glass containers. The complicated structural speciation in these glasses leads to a mixed network former effect yielding...... compositions by substituting Al2O3 for SiO2. We also investigate the various roles of sodium in the glasses including charge compensation of tetrahedral aluminum and boron atoms and formation of non-bridging oxygen. We find that mechanical properties (density, elastic moduli, and hardness), glass transition...... the effect of iron on the measured properties by doping these glasses with ~1 mol% of iron oxide....

  11. Glass Transition Temperature- and Specific Volume- Composition Models for Tellurite Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Brian J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Vienna, John D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-09-01

    This report provides models for predicting composition-properties for tellurite glasses, namely specific gravity and glass transition temperature. Included are the partial specific coefficients for each model, the component validity ranges, and model fit parameters.

  12. Ising model of a glass transition.

    Science.gov (United States)

    Langer, J S

    2013-07-01

    Numerical simulations by Tanaka and co-workers indicate that glass-forming systems of moderately polydisperse hard-core particles, in both two and three dimensions, exhibit diverging correlation lengths. These correlations are described by Ising-like critical exponents, and are associated with diverging, Vogel-Fulcher-Tamann, structural relaxation times. Related simulations of thermalized hard disks indicate that the curves of pressure versus packing fraction for different polydispersities exhibit a sequence of transition points, starting with a liquid-hexatic transition for the monodisperse case, and crossing over with increasing polydispersity to glassy, Ising-like critical points. I propose to explain these observations by assuming that glass-forming fluids contain twofold degenerate, locally ordered clusters of particles, similar to the two-state systems that have been invoked to explain other glassy phenomena. This paper starts with a brief statistical derivation of the thermodynamics of thermalized, hard-core particles. It then discusses how a two-state, Ising-like model can be described within that framework in terms of a small number of statistically relevant, internal state variables. The resulting theory agrees accurately with the simulation data. I also propose a rationale for the observed relation between the Ising-like correlation lengths and the Vogel-Fulcher-Tamann formula.

  13. How active forces influence nonequilibrium glass transitions

    Science.gov (United States)

    Berthier, Ludovic; Flenner, Elijah; Szamel, Grzegorz

    2017-12-01

    Dense assemblies of self-propelled particles undergo a nonequilibrium form of glassy dynamics. Physical intuition suggests that increasing departure from equilibrium due to active forces fluidifies a glassy system. We falsify this belief by devising a model of self-propelled particles where increasing departure from equilibrium can both enhance or depress glassy dynamics, depending on the chosen state point. We analyze a number of static and dynamic observables and suggest that the location of the nonequilibrium glass transition is primarily controlled by the evolution of two-point static density correlations due to active forces. The dependence of the density correlations on the active forces varies non-trivially with the details of the system, and is difficult to predict theoretically. Our results emphasize the need to develop an accurate liquid state theory for nonequilibrium systems.

  14. Glass transition temperature and its relevance in food processing.

    Science.gov (United States)

    Roos, Yrjö H

    2010-01-01

    Amorphous, noncrystalline solids are typical of low water content and frozen foods. Solids in these foods, e.g., confectionary, dehydrated foods, cereal foods, and frozen foods, often form nonequilibrium glass-like structures. The glassy state of the solids forms during food processing in a reversible glass transition. Vitrification can occur in numerous glassy states that exhibit various relaxations around the glass transition. The success of freeze drying, spray drying, and extrusion and the stability of dehydrated foods against flow, collapse, and crystallization is based on the control of the glassy state during the dehydration process and storage. Encapsulation processes often use glass-forming materials to entrap dispersed components or improve retention of volatiles. Plasticization of the noncrystalline structures by temperature or water reduce relaxation times exponentially above the glass transition, which results in rapid deterioration. Critical values for water activity and water content express the level of water plasticization leading to glass transition in food storage.

  15. Resolution of conflicting views on thermodynamics of glass transition

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Classical description of thermodynamic properties during glass transition has been questioned by the entropy-loss model. The uncompensated loss of entropy at the glass transition temperature and zero residual entropy is at the heart of the controversy. Both the models are critically reviewed. A unified model is.

  16. Echoes of the Glass Transition in Athermal Soft Spheres

    Science.gov (United States)

    Morse, Peter K.; Corwin, Eric I.

    2017-09-01

    Recent theoretical advances have led to the creation of a unified phase diagram for the thermal glass and athermal jamming transitions. This diagram makes clear that, while related, the mode-coupling—or dynamic—glass transition is distinct from the jamming transition, occurring at a finite temperature and significantly lower density than the jamming transition. Nonetheless, we demonstrate a prejamming transition in athermal frictionless spheres which occurs at the same density as the mode-coupling transition and is marked by percolating clusters of locally rigid particles. At this density in both the thermal and athermal systems, individual motions of an extensive number of particles become constrained, such that only collective motion is possible. This transition, which is well below jamming, exactly matches the definition of collective behavior at the dynamical transition of glasses. Thus, we reveal that the genesis of rigidity in both thermal and athermal systems is governed by the same underlying topological transition in their shared configuration space.

  17. The glass transition in high-density amorphous ice.

    Science.gov (United States)

    Loerting, Thomas; Fuentes-Landete, Violeta; Handle, Philip H; Seidl, Markus; Amann-Winkel, Katrin; Gainaru, Catalin; Böhmer, Roland

    2015-01-01

    There has been a long controversy regarding the glass transition in low-density amorphous ice (LDA). The central question is whether or not it transforms to an ultraviscous liquid state above 136 K at ambient pressure prior to crystallization. Currently, the most widespread interpretation of the experimental findings is in terms of a transformation to a superstrong liquid above 136 K. In the last decade some work has also been devoted to the study of the glass transition in high-density amorphous ice (HDA) which is in the focus of the present review. At ambient pressure HDA is metastable against both ice I and LDA, whereas at > 0.2 GPa HDA is no longer metastable against LDA, but merely against high-pressure forms of crystalline ice. The first experimental observation interpreted as the glass transition of HDA was made using in situ methods by Mishima, who reported a glass transition temperature Tg of 160 K at 0.40 GPa. Soon thereafter Andersson and Inaba reported a much lower glass transition temperature of 122 K at 1.0 GPa. Based on the pressure dependence of HDA's Tg measured in Innsbruck, we suggest that they were in fact probing the distinct glass transition of very high-density amorphous ice (VHDA). Very recently the glass transition in HDA was also observed at ambient pressure at 116 K. That is, LDA and HDA show two distinct glass transitions, clearly separated by about 20 K at ambient pressure. In summary, this suggests that three glass transition lines can be defined in the p-T plane for LDA, HDA, and VHDA.

  18. Liquid-liquid phase transition and glass transition in a monoatomic model system.

    Science.gov (United States)

    Xu, Limei; Buldyrev, Sergey V; Giovambattista, Nicolas; Stanley, H Eugene

    2010-01-01

    We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses.

  19. Citrate increases glass transition temperature of vitrified sucrose preparations

    NARCIS (Netherlands)

    Kets, E.P.W.; Lipelaar, P.J.; Hoekstra, F.A.; Vromans, H.

    2004-01-01

    The aim of this study was to investigate the effect of sodium citrate on the properties of dried amorphous sucrose glasses. Addition of sodium citrate to a sucrose solution followed by freeze-drying or convective drying resulted in a glass transition temperature (T-g) that was higher than the

  20. Glass transitions and viscoelastic properties of carbopol and noveon compacts.

    Science.gov (United States)

    Gómez-Carracedo, A; Alvarez-Lorenzo, C; Gómez-Amoza, J L; Concheiro, A

    2004-04-15

    Glass transitions of five varieties of Carbopol (acrylic acid polymers cross-linked with allyl sucrose or allyl pentaerythritol) and two varieties of Noveon (calcium salts of acrylic acid polymer cross-linked with divinylglycol) differing in cross-linking density and nature and content in residual solvents, were analysed (as compressed probes) by differential scanning calorimetry (DSC), modulated temperature differential scanning calorimetry (MTDSC), and oscillatory rheometry. All carbopol compacts showed a main glass transition, at a temperature between 130 and 140 degrees C, Tg, independently of their cross-linking degree and molecular weight. Additionally two batches of Carbopol 971P, which had greater contents in residual solvents, also presented a secondary transition at 65-70 degrees C. Sorption of water during storage of carbopol compacts at different relative humidity environments caused the Tg to strongly decrease. Compacts stored at 97.5% relative humidity have Tg below 0 degrees C and behave, at room temperature, as flexible hydrogels. The Gordon-Taylor/Kelley-Bueche equation only fit the dependence of Tg on water content well for carbopol compacts containing less than 15% water. The plasticizing effect of water was clearly evidenced in the considerable decrease in the storage and loss moduli of the compacts. Although the energy associated to the glass transitions of carbopol polymers, 0.40-0.50 Jg(-1) degrees C(-1), is high enough to be clearly detected by DSC, in some cases the evaporation of residual solvents may make it difficult to observe the Tg. This inconvenience is overcome using MTDSC or oscillatory rheometry. The decrease in Tg of carbopol caused by water sorption when compacts were stored at 97.5% R.H. explains why their loss (G") and storage (G') moduli at room temperature decreased four orders of magnitude. In contrast, in noveon varieties, calcium ions act as ionic cross-linkers of the carboxylic groups, providing rigid networks with much

  1. [Glass transition of Chinese medicine extract powder and its application].

    Science.gov (United States)

    Luo, Xiao-Jian; Liu, Hui; Liang, Hong-Bo; Xiong, Lei; Rao, Xiao-Yong; Xie, Yin; He, Yan

    2017-01-01

    Glass transition theory is an important theory in polymer science, which is used to characterize the physical properties. It refers to the transition of amorphous polymer from the glassy state to the rubber state due to heating or the transition from rubber state to glassy state due to cooling. In this paper, the glassy state and glass transition of food and the similar relationship between the composition of Chinese medicine extract powder and food ingredients were described; the determination method for glass transition temperature (Tg) of Chinese medicine extract powder was established and its main influencing factors were analyzed. Meanwhile, the problems in drying process, granulation process and Chinese medicine extract powder and solid preparation storage were analyzed and investigated based on Tg, and then the control strategy was put forward to provide guidance for the research and production of Chinese medicine solid preparation. Copyright© by the Chinese Pharmaceutical Association.

  2. Hydrogen-bond network formation of water molecules and its effects on the glass transitions in the ethylene glycol aqueous solutions: failure of the Gordon-Taylor law in the water-rich range and absence of the T(g) = 115 K rearrangement process in bulk pure water.

    Science.gov (United States)

    Nagoe, Atsushi; Oguni, Masaharu

    2010-08-18

    Enthalpy relaxation processes proceeding in ethylene glycol (EG) aqueous solutions [(EG)(x)(H(2)O)(1 - x)] within silica-gel nanopores were studied by adiabatic calorimetry. While the x = 0.25 solution within pores with diameter of 52 nm showed a glass transition at T(g) = 139 K, ageing of the solution at 160 K caused a phase separation to reveal glass transitions at T(g) = 145 and 160 K for EG-rich and water-rich regions, respectively: the water molecules are understood to form a more developed hydrogen-bond network, and consequently force the EG molecules in between the water-rich regions. The T(g) = 160 K is in good agreement with the T(g) value of the internal (not interfacial) water confined within pores with thickness of 1.1 nm. The ageing further remarkably diminished the T(g) = 115 K glass transition. This indicates that, while the molecules responsible for the glass transition are the mobile water ones forming a lower number of hydrogen bonds than four, the fraction of such water molecules is reduced in association with the development of the network and the glass transition is absent in bulk pure water. When the same x = 0.25 solution was confined within 1.1- and 12 nm pores, the water molecules developed a hydrogen-bond network in the pore centre due to the presence of the pore wall and pushed the EG molecules onto the pore surface even at higher temperatures: the water-rich region gave T(g) = 155 K close to 160 K. It is concluded that the hydrogen-bond network inherent to water structure is developed/collapsed remarkably in the range near x = 0; consequently, the composition dependence of T(g) in the bulk system deviates sharply in the range from the Gordon-Taylor empirical law followed for large x > 0.2.

  3. Glass transition of repulsive charged rods (fd-viruses).

    Science.gov (United States)

    Kang, Kyongok

    2014-05-14

    It has recently been shown that suspensions of long and thin charged fibrous viruses (fd) form a glass at low ionic strengths. The corresponding thick electric double layers give rise to long-ranged repulsive electrostatic interactions, which lead to caging and structural arrest at concentrations far above the isotropic-nematic coexistence region. Structural arrest and freezing of the orientational texture are found to occur at the same concentration. In addition, various types of orientational textures are equilibrated below the glass transition concentration, ranging from a chiral-nematic texture with a large pitch (of about 100 μm), an X-pattern, and a tightly packed domain texture, consisting of helical domains with a relatively small pitch (of about 10 μm) and twisted boundaries. The dynamics of both particles as well as the texture are discussed, below and above the glass transition. Dynamic light scattering correlation functions exhibit two dynamical modes, where the slow mode is attributed to the elasticity of helical domains. On approach of the glass-transition concentration, the slow mode increases in amplitude, while as the amplitudes of the fast and slow mode become equal at the glass transition. Finally, interesting features of the "transient" behaviors of charged fd-rod glass are shown as the initial caging due to structural arrest, the propagation of flow originating from stress release, and the transition to the final metastable glass state. In addition to the intensity correlation function, power spectra are presented as a function of the waiting time, at the zero-frequency limit that may access to the thermal anomalities in a charged system.

  4. Glass transition and heavy oil dynamics at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Abivin, P.; Indo, K.; Cheng, Y.; Freed, D.; Taylor, S. D. [Schlumberger (Canada)], email: PAbivin@slb.com

    2011-07-01

    In the oil industry, the viscosity of crude oils is a key factor as it affects market value, field developments and the design of production strategies. In heavy oils, a glass transition occurs and previous work related this to oil's temperature-viscosity behavior. This study aimed at better characterizing heavy oil dynamics and the temperature dependency of viscosity. Experiments were conducted with differential scanning calorimetry and shear rate sweeps on heavy oils from Asia, South America and North America over a wide range of temperatures to measure their viscosities and characterize their glass transition. The glass transition was observed at around 210K and results showed that the Arrhenius model does not fit the experimental data at low temperatures but the WLF model does. This research provided a better understanding of heavy oil dynamics but further work is required to explain the viscosity-temperature behavior of heavy oils at low temperatures.

  5. Thermal and fragility aspects of microwave synthesized glasses containing transition metal ions and heavy metal ions

    Science.gov (United States)

    Renuka, C.; Viswanatha, R.; Reddy, C. Narayana

    2017-02-01

    A simple, clean and energy efficient microwave heating route is used to prepare glasses in the systems xMnO-33(0.09PbCl2:0.91PbO)-(67-x) NaPO3 and xPbCl2-33PbO-(67-x) NaPO3 where 0.1 ≤ x ≤ 4 (mol%). Thermal data extracted from differential scanning calorimetry (DSC) thermograms are used to study the composition dependence of glass transition temperature (Tg), heat capacity, thermal stability and fragility. The decrease in glass transition temperature with modifier oxide (Na2O + MnO) content can be ascribed to network degradation and the volume increasing effect caused by PbCl2. The change in heat capacity of MnPb glass being greater than that of PbNP glass, suggests that MnPb glasses are more covalent than PbNP glasses. DSC thermograms taken at different heating rates (φ) reveal the dependence of Tg on φ, and the thermal stability of the glass increases due to MnO addition. Fragility aspects have also been studied by calculating the fragility functions ( {{Δ {{C}}_{{p}} }/{{{C}_{{pl}} }}{{and}}{[ {{NBO}} ]}/{{{V}_{{m}}3 {{T}}_{{g}} }}} ). Results obtained from both the fragility functions compare well and reveal the dependence of fragility functions on modifier content and PbCl2 mol%. Further, the decrease in Tg and Hv are suggested to be due to the increase in the number of non-bridging oxygens, which results in the lowering of stiffness and rigidity of the glass network. Analysis of the infrared spectra confirms that the glassy matrix is composed of P-O-P, P-O-Pb, P=O and P-O- bonding.

  6. Inward Cationic Diffusion and Percolation Transition in Glass-Ceramics

    DEFF Research Database (Denmark)

    Smedsklaer, Morten Mattrup; Yue, Yuanzheng; Mørup, Steen

    2010-01-01

    We show the quantitative correlation between the degree of crystallization and the cationic diffusion extent in iron-containing diopside glass–ceramics at the glass transition temperature. We find a critical degree of crystallization, above which the diffusion extent sharply drops with the degree...... of crystallization. Below the critical value, the diffusion extent decreases only slightly with the degree of crystallization. No cationic diffusion is observed in the fully crystalline materials. The critical value might be associated with a percolation transition from an interconnected to a disconnected glass...

  7. Fluorinated epoxy resins with high glass transition temperatures

    Science.gov (United States)

    Griffith, James R.

    1991-01-01

    Easily processed liquid resins of low dielectric constants and high glass transition temperatures are useful for the manufacture of certain composite electronic boards. That combination of properties is difficult to acquire when dielectric constants are below 2.5, glass transition temperatures are above 200 C and processability is of conventional practicality. A recently issued patent (US 4,981,941 of 1 Jan. 1991) teaches practical materials and is the culmination of 23 years of research and effort and 15 patents owned by the Navy in the field of fluorinated resins of several classes. In addition to high fluorine content, practical utility was emphasized.

  8. Review: Pressure-Induced Densification of Oxide Glasses at the Glass Transition

    Science.gov (United States)

    Kapoor, Saurabh; Wondraczek, Lothar; Smedskjaer, Morten M.

    2017-02-01

    Densification of oxide glasses at the glass transition offers a novel route to develop bulk glasses with tailored properties for emerging applications. Such densification can be achieved in the technologically relevant pressure regime of up to 1GPa. However, the present understanding of the composition-structure-property relationships governing these glasses is limited, with key questions, e.g., related to densification mechanism, remaining largely unanswered. Recent advances in structural characterization tools and high-pressure apparatuses have prompted new research efforts. Here, we review this recent progress and the insights gained in the understanding of the influence of isostatic compression at elevated temperature (so-called hot compression) on the composition-structure-property relationships of oxide glasses. We focus on compression at temperatures at or around the glass transition temperature (Tg), with relevant comparisons made to glasses prepared by pressure quenching and cold compression. We show that permanent densification at 1 GPa sets-in at temperatures above 0.7Tg and the degree of densification increases with increasing compression temperature and time, until attaining an approximately constant value for temperatures above Tg. For glasses compressed at the same temperature/pressure conditions, we demonstrate direct relations between the degree of volume densification and the pressure-induced change in micro-mechanical properties such as hardness, elastic moduli, and extent of the indentation size effect across a variety of glass families. Furthermore, we summarize the results on relaxation behavior of hot compressed glasses. All the pressure-induced changes in the structure and properties exhibit strong composition dependence. The experimental results highlight new opportunities for future investigation and identify research challenges that need to be overcome to advance the field.

  9. Size effect on dynamics and glass transition in metallic liquids and glasses

    Science.gov (United States)

    Li, Y. Z.; Sun, Y. T.; Lu, Z.; Li, M. Z.; Bai, H. Y.; Wang, W. H.

    2017-06-01

    The relaxation dynamics and glass transition in finite-sized metallic liquid droplets were investigated via molecular dynamic simulations in model monoatomic Ta and binary Cu50Zr50 metallic liquids. We find that the droplet size has a significant impact on liquid dynamics and glass transition. Glass transition temperature and structural relaxation time exhibit strong size dependence and decrease drastically as the droplet is smaller than a certain size. It is revealed that this results from a liquid-like surface layer (˜1 nm thick) of droplets, in which the dynamics is much faster than the interior of droplets. A proposed scaling relationship can well describe the size dependent behavior of the glass transition temperature in metallic liquid droplets. These findings provide insight into the dynamics of metallic liquid droplets and plausible understanding of recent novel experimental observations. Apart from temperature and pressure, size may be another important parameter for potentially tuning the properties of metallic liquids and glasses in nanometer scale.

  10. Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System

    Directory of Open Access Journals (Sweden)

    Nicolas Giovambattista

    2010-12-01

    Full Text Available We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses.

  11. Deformation, Stress Relaxation, and Crystallization of Lithium Silicate Glass Fibers Below the Glass Transition Temperature

    Science.gov (United States)

    Ray, Chandra S.; Brow, Richard K.; Kim, Cheol W.; Reis, Signo T.

    2004-01-01

    The deformation and crystallization of Li(sub 2)O (center dot) 2SiO2 and Li(sub 2)O (center dot) 1.6SiO2 glass fibers subjected to a bending stress were measured as a function of time over the temperature range -50 to -150 C below the glass transition temperature (Tg). The glass fibers can be permanently deformed at temperatures about 100 C below T (sub)g, and they crystallize significantly at temperatures close to, but below T,, about 150 C lower than the onset temperature for crystallization for these glasses in the no-stress condition. The crystallization was found to occur only on the surface of the glass fibers with no detectable difference in the extent of crystallization in tensile and compressive stress regions. The relaxation mechanism for fiber deformation can be best described by a stretched exponential (Kohlrausch-Williams-Watt (KWW) approximation), rather than a single exponential model.The activation energy for stress relaxation, Es, for the glass fibers ranges between 175 and 195 kJ/mol, which is considerably smaller than the activation energy for viscous flow, E, (about 400 kJ/mol) near T, for these glasses at normal, stress-free condition. It is suspected that a viscosity relaxation mechanism could be responsible for permanent deformation and crystallization of the glass fibers below T,

  12. Does a Growing Static Length Scale Control the Glass Transition?

    Science.gov (United States)

    Wyart, Matthieu; Cates, Michael E.

    2017-11-01

    Several theories of the glass transition propose that the structural relaxation time τα is controlled by a growing static length scale ξ that is determined by the free energy landscape but not by the local dynamic rules governing its exploration. We argue, based on recent simulations using particle-radius-swap dynamics, that only a modest factor in the increase in τα on approach to the glass transition may stem from the growth of a static length, with a vastly larger contribution attributable, instead, to a slowdown of local dynamics. This reinforces arguments that we base on the observed strong coupling of particle diffusion and density fluctuations in real glasses.

  13. Beta relaxation of nonpolymeric liquids close to the glass transition

    DEFF Research Database (Denmark)

    Olsen, Niels Boye; Christensen, Tage Emil; Dyre, Jeppe

    2000-01-01

    Dielectric beta relaxation in a pyridine-toluene solution is studied close to the glass transition. Loss peak frequency and maximum loss both exhibit thermal hysteresis. An annealing-state-independent parameter involving loss and loss peak frequency is identified. This parameter has a simple...

  14. Application of Kissinger analysis to glass transition and study of ...

    Indian Academy of Sciences (India)

    Mater. Sci., Vol. 35, No. 4, August 2012, pp. 657–664. c Indian Academy of Sciences. Application of Kissinger analysis to glass transition and study of thermal degradation kinetics of phenolic–acrylic IPNs. S GOSWAMI. ∗ and K KIRAN. Department of Polymer Engineering, Birla Institute of Technology, Ranchi 835 215, India.

  15. Theoretical approaches to the glass transition in simple liquids

    Indian Academy of Sciences (India)

    Abstract. Theoretical approaches to the development of an understanding of the be- haviour of simple supercooled liquids near the structural glass transition are reviewed and our work on this problem, based on the density functional theory of freezing and replicated liquid state theory, are summarized in this context.

  16. Theoretical approaches to the glass transition in simple liquids

    Indian Academy of Sciences (India)

    Theoretical approaches to the development of an understanding of the behaviour of simple supercooled liquids near the structural glass transition are reviewed and our work on this problem, based on the ... Department of Physics, Centre for Condensed Matter Theory, Indian Institute of Science, Bangalore 560 012, India ...

  17. Glass transition near the free surface studied by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sikorski, M.

    2008-06-15

    A comprehensive picture of the glass transition near the liquid/vapor interface of the model organic glass former dibutyl phthalate is presented in this work. Several surface-sensitive techniques using x-ray synchrotron radiation were applied to investigate the static and dynamic aspects of the formation of the glassy state from the supercooled liquid. The amorphous nature of dibutyl phthalate close to the free surface was confirmed by grazing incidence X-ray diffraction studies. Results from X-ray reflectivity measurements indicate a uniform electron density distribution close to the interface excluding the possibility of surface freezing down to 175 K. Dynamics on sub-{mu}m length-scales at the surface was studied with coherent synchrotron radiation via x-ray photon correlation spectroscopy. From the analysis of the dispersion relation of the surface modes, viscoelastic properties of the dibutyl phthalate are deduced. The Kelvin-Voigt model of viscoelastic media was found to describe well the properties of the liquid/vapor interface below room temperature. The data show that the viscosity at the interface matches the values reported for bulk dibutyl phthalate. The scaled relaxation rate at the surface agrees with the bulk data above 210 K. Upon approaching the glass transition temperature the free surface was observed to relax considerably faster close to the liquid/vapor interface than in bulk. The concept of higher relaxation rate at the free surface is also supported by the results of the quasielastic nuclear forward scattering experiment, during which dynamics on molecular length scales around the calorimetric glass transition temperature is studied. The data were analyzed using mode-coupling theory of the glass transition and the model of the liquid(glass)/vapor interface, predicting inhomogeneous dynamics near the surface. The quasielastic nuclear forward scattering data can be explained when the molecular mobility is assumed to decrease with the increasing

  18. Spectroscopic and ultrasonic investigations on structural characterization of borate glass specimen doped with transition metal ions.

    Science.gov (United States)

    Sathish, K; Thirumaran, S

    2015-08-05

    The present work describes the glass samples of composition (x% V₂O₅-(80-x)% B₂O₃-20% Na₂CO₃) VBS glass system and (x%MnO₂-(80-x)% B₂O₃-20% Na₂CO₃) in MBS glass system with mol% ranging from x=3, 6, 9, 12, 15 and 18 in steps of 3 mol% are prepared by melt quenching technique. For these prepared glass systems, sound velocity (longitudinal and shear velocities) and density have been measured. The sound velocity (longitudinal and shear) was measured by using pulse-echo technique at 5 MHz. The XRD study was carried to out to ascertain the amorphous nature of the glass specimen. Using these measured values, the elastic moduli, Poisson's ratio, Debye temperature, acoustic impedance and thermal expansion coefficient of the two glass systems were evaluated. The elastic and mechanical properties of the prepared glass systems are analyzed from ultrasonic study and the structural characterization from spectroscopic study. The effects due to the doping of transition metal ions with borate have been discussed. In the V₂O₅ doped glass system,(VBS glass system) the sound velocity, density and elastic moduli, steeply increases after 12 mol% comparatively with MnO₂ doped glass system (VBS glass system). The present study critically observes the doping of V₂O₅ with borate enhances the strengthening of network linkage and hardening of the glassy network structure than MnO₂. The IR spectral analysis reveals depolymerization of the borate network and conversion of BO₃ or BO4 units with the formation of non-bridging oxygen. The FTIR spectral studies confirm the presence of various functional groups of the sample. FTIR spectrum of sample exhibits broad absorption bands indicating the wide distribution of borate structural units. The effect of Na₂CO₃, V₂O₅ and MnO₂ contents on the structures of borate glass is evaluated from the FTIR spectra. The topological aspects of the prepared glass samples are exhaustively reported from SEM micrographs

  19. Spectroscopic and ultrasonic investigations on structural characterization of borate glass specimen doped with transition metal ions

    Science.gov (United States)

    Sathish, K.; Thirumaran, S.

    2015-08-01

    The present work describes the glass samples of composition (x% V2O5-(80-x)% B2O3-20% Na2CO3) VBS glass system and (x% MnO2-(80-x)% B2O3-20% Na2CO3) in MBS glass system with mol% ranging from x = 3, 6, 9, 12, 15 and 18 in steps of 3 mol% are prepared by melt quenching technique. For these prepared glass systems, sound velocity (longitudinal and shear velocities) and density have been measured. The sound velocity (longitudinal and shear) was measured by using pulse-echo technique at 5 MHz. The XRD study was carried to out to ascertain the amorphous nature of the glass specimen. Using these measured values, the elastic moduli, Poisson's ratio, Debye temperature, acoustic impedance and thermal expansion coefficient of the two glass systems were evaluated. The elastic and mechanical properties of the prepared glass systems are analyzed from ultrasonic study and the structural characterization from spectroscopic study. The effects due to the doping of transition metal ions with borate have been discussed. In the V2O5 doped glass system, (VBS glass system) the sound velocity, density and elastic moduli, steeply increases after 12 mol% comparatively with MnO2 doped glass system (VBS glass system). The present study critically observes the doping of V2O5 with borate enhances the strengthening of network linkage and hardening of the glassy network structure than MnO2. The IR spectral analysis reveals depolymerization of the borate network and conversion of BO3 or BO4 units with the formation of non-bridging oxygen. The FTIR spectral studies confirm the presence of various functional groups of the sample. FTIR spectrum of sample exhibits broad absorption bands indicating the wide distribution of borate structural units. The effect of Na2CO3, V2O5 and MnO2 contents on the structures of borate glass is evaluated from the FTIR spectra. The topological aspects of the prepared glass samples are exhaustively reported from SEM micrographs.

  20. Glass heat capacity and its abrupt change in glass transition region

    DEFF Research Database (Denmark)

    Yue, Yuanzheng; Smedskjær, Morten Mattrup; Mauro, John C.

    Glass transition (GT) has been a fascinating, but challenging subject in the condensed matter science over decades. Despite progress in understanding GT, many crucial problems still need to be clarified. One of the problems deals with the microscopic origin of abrupt change of heat capacity (Cp) ...

  1. Multiple glass transitions and freezing events of aqueous citric acid.

    Science.gov (United States)

    Bogdan, Anatoli; Molina, Mario J; Tenhu, Heikki; Loerting, Thomas

    2015-05-14

    Calorimetric and optical cryo-microscope measurements of 10-64 wt % citric acid (CA) solutions subjected to moderate (3 K/min) and slow (0.5 and 0.1 K/min) cooling/warming rates and also to quenching/moderate warming between 320 and 133 K are presented. Depending on solution concentration and cooling rate, the obtained thermograms show one freezing event and from one to three liquid-glass transitions upon cooling and from one to six liquid-glass and reverse glass-liquid transitions, one or two freezing events, and one melting event upon warming of frozen/glassy CA/H2O. The multiple freezing events and glass transitions pertain to the mother CA/H2O solution itself and two freeze-concentrated solution regions, FCS1 and FCS2, of different concentrations. The FCS1 and FCS2 (or FCS22) are formed during the freezing of CA/H2O upon cooling and/or during the freezing upon warming of partly glassy or entirely glassy mother CA/H2O. The formation of two FCS1 and FCS22 regions during the freezing upon warming to our best knowledge has never been reported before. Using an optical cryo-microscope, we are able to observe the formation of a continuous ice framework (IF) and its morphology and reciprocal distribution of IF/(FCS1 + FCS2). Our results provide a new look at the freezing and glass transition behavior of aqueous solutions and can be used for the optimization of lyophilization and freezing of foods and biopharmaceutical formulations, among many other applications where freezing plays a crucial role.

  2. The glass and jamming transitions in dense granular matter

    Science.gov (United States)

    Coulais, Corentin; Candelier, Raphaël; Dauchot, Olivier

    2013-06-01

    Everyday life tells us that matter acquires rigidity either when it cools down, like lava flows which turn into solid rocks, or when it is compacted, like tablets simply formed by powder compression. As suggested by these examples, solidification is not the sole privilege of crystals but also happens for disordered media such as glass formers, granular media, foams, emulsions and colloidal suspensions. Fifteen years ago the "Jamming paradigm" emerged to encompass in a unique framework the glass transition and the emergence of yield stress, two challenging issues in modern condensed matter physics. One must realize how bold this proposal was, given that the glass transition is a finite temperature transition governing the dynamical properties of supercooled liquids, while Jamming is essentially a zero temperature, zero external stress and purely geometric transition which occurs when a given packing of particles reaches the maximum compression state above which particles start to overlap. More recently, the observation of remarkable scaling properties on the approach to jamming led to the conjecture that this zero temperature "critical point" could determine the properties of dense particle systems within a region of the parameter space to be determined, which in principle could include thermal and stressed systems. Fifteen years of intense theoretical and experimental work later, what have we learned about Jamming and glassy dynamics? In this paper, we discuss these issues in the light of the experiments we have been conducting with vibrated grains.

  3. Trust Transitivity in Social Networks

    Science.gov (United States)

    Richters, Oliver; Peixoto, Tiago P.

    2011-01-01

    Non-centralized recommendation-based decision making is a central feature of several social and technological processes, such as market dynamics, peer-to-peer file-sharing and the web of trust of digital certification. We investigate the properties of trust propagation on networks, based on a simple metric of trust transitivity. We investigate analytically the percolation properties of trust transitivity in random networks with arbitrary in/out-degree distributions, and compare with numerical realizations. We find that the existence of a non-zero fraction of absolute trust (i.e. entirely confident trust) is a requirement for the viability of global trust propagation in large systems: The average pair-wise trust is marked by a discontinuous transition at a specific fraction of absolute trust, below which it vanishes. Furthermore, we perform an extensive analysis of the Pretty Good Privacy (PGP) web of trust, in view of the concepts introduced. We compare different scenarios of trust distribution: community- and authority-centered. We find that these scenarios lead to sharply different patterns of trust propagation, due to the segregation of authority hubs and densely-connected communities. While the authority-centered scenario is more efficient, and leads to higher average trust values, it favours weakly-connected “fringe” nodes, which are directly trusted by authorities. The community-centered scheme, on the other hand, favours nodes with intermediate in/out-degrees, in detriment of the authorities and its “fringe” peers. PMID:21483683

  4. Trust transitivity in social networks.

    Directory of Open Access Journals (Sweden)

    Oliver Richters

    Full Text Available Non-centralized recommendation-based decision making is a central feature of several social and technological processes, such as market dynamics, peer-to-peer file-sharing and the web of trust of digital certification. We investigate the properties of trust propagation on networks, based on a simple metric of trust transitivity. We investigate analytically the percolation properties of trust transitivity in random networks with arbitrary in/out-degree distributions, and compare with numerical realizations. We find that the existence of a non-zero fraction of absolute trust (i.e. entirely confident trust is a requirement for the viability of global trust propagation in large systems: The average pair-wise trust is marked by a discontinuous transition at a specific fraction of absolute trust, below which it vanishes. Furthermore, we perform an extensive analysis of the Pretty Good Privacy (PGP web of trust, in view of the concepts introduced. We compare different scenarios of trust distribution: community- and authority-centered. We find that these scenarios lead to sharply different patterns of trust propagation, due to the segregation of authority hubs and densely-connected communities. While the authority-centered scenario is more efficient, and leads to higher average trust values, it favours weakly-connected "fringe" nodes, which are directly trusted by authorities. The community-centered scheme, on the other hand, favours nodes with intermediate in/out-degrees, in detriment of the authorities and its "fringe" peers.

  5. Multiple Glass Transitions and Freezing Events of Aqueous Citric Acid

    Science.gov (United States)

    2014-01-01

    Calorimetric and optical cryo-microscope measurements of 10–64 wt % citric acid (CA) solutions subjected to moderate (3 K/min) and slow (0.5 and 0.1 K/min) cooling/warming rates and also to quenching/moderate warming between 320 and 133 K are presented. Depending on solution concentration and cooling rate, the obtained thermograms show one freezing event and from one to three liquid–glass transitions upon cooling and from one to six liquid–glass and reverse glass–liquid transitions, one or two freezing events, and one melting event upon warming of frozen/glassy CA/H2O. The multiple freezing events and glass transitions pertain to the mother CA/H2O solution itself and two freeze-concentrated solution regions, FCS1 and FCS2, of different concentrations. The FCS1 and FCS2 (or FCS22) are formed during the freezing of CA/H2O upon cooling and/or during the freezing upon warming of partly glassy or entirely glassy mother CA/H2O. The formation of two FCS1 and FCS22 regions during the freezing upon warming to our best knowledge has never been reported before. Using an optical cryo-microscope, we are able to observe the formation of a continuous ice framework (IF) and its morphology and reciprocal distribution of IF/(FCS1 + FCS2). Our results provide a new look at the freezing and glass transition behavior of aqueous solutions and can be used for the optimization of lyophilization and freezing of foods and biopharmaceutical formulations, among many other applications where freezing plays a crucial role. PMID:25482069

  6. Motility-Driven Glass and Jamming Transitions in Biological Tissues

    Science.gov (United States)

    Bi, Dapeng; Yang, Xingbo; Marchetti, M. Cristina; Manning, M. Lisa

    2016-04-01

    Cell motion inside dense tissues governs many biological processes, including embryonic development and cancer metastasis, and recent experiments suggest that these tissues exhibit collective glassy behavior. To make quantitative predictions about glass transitions in tissues, we study a self-propelled Voronoi model that simultaneously captures polarized cell motility and multibody cell-cell interactions in a confluent tissue, where there are no gaps between cells. We demonstrate that the model exhibits a jamming transition from a solidlike state to a fluidlike state that is controlled by three parameters: the single-cell motile speed, the persistence time of single-cell tracks, and a target shape index that characterizes the competition between cell-cell adhesion and cortical tension. In contrast to traditional particulate glasses, we are able to identify an experimentally accessible structural order parameter that specifies the entire jamming surface as a function of model parameters. We demonstrate that a continuum soft glassy rheology model precisely captures this transition in the limit of small persistence times and explain how it fails in the limit of large persistence times. These results provide a framework for understanding the collective solid-to-liquid transitions that have been observed in embryonic development and cancer progression, which may be associated with epithelial-to-mesenchymal transition in these tissues.

  7. Self-organization and stress in network glasses

    Science.gov (United States)

    Wang, Fei

    Raman pressure measurements on GexSe1-x glasses using Diamond Anvil Cells show onset of a steady increase in the frequency of modes of corner-sharing GeSe4 tetrahedra when the external pressure P exceeds a threshold value (Pc). The threshold pressure Pc(x) decreases with x to nearly zero for 0.20 glasses observed in this same composition range. Chalcohalide Ge25Se75-yIy glasses were synthesized over a wide range (0 glasses show that one-fold coordinated atoms play an important role in determining the onset of rigidity. Raman scattering on Ge-Se-I glasses permits a quantitative measurement of mixed tetrahedral Ge(Se1/2)4-mIm units. The results show the concentration of the iostatically rigid m = 1 units to display a step-like variation in the range 15.5% glasses at y 16.4% floppy. The observed molecular structural rearrangement (populating the m = 1 units) observed in the intermediate phase provides a means to release network stress. Results on ternary Ge-S-I glasses did not show such a step, we suppose because network stress did not build up because of atomic size mismatch. These results show that there is an intrinsic difference in network stress distribution between ternary Ge-Se-I and Ge-S-I glasses. The stress induced by oversized iodine alloying is much greater in Ge-Se-I glasses than in Ge-S-I glasses because of the bigger size of Se atoms in relation to S atoms. Plus, because of the size and mass mismatch in the Ge-S based glass, iodine alloying induced stress is locally dissipated; on the other hand, in the equi-sized and equi-massed base glass Ge-Se, stress due to the iodine alloying is found to propagate globally. Pronounced photo-polymerization effects are observed in floppy (partially polymerized) Ge25Se75-yIy (y > 30%) glasses and floppy GexS1-x (x glasses. In the former glasses, GeI4 monomers are decoupled from the backbone can be opened and alloyed in the base glass network upon near-band-gap radiation. In the latter glasses S8 crowns decouple from

  8. Dynamic and thermodynamic characteristics associated with the glass transition of amorphous trehalose-water mixtures.

    Science.gov (United States)

    Weng, Lindong; Elliott, Gloria D

    2014-06-21

    The glass transition temperature Tg of biopreservative formulations is important for predicting the long-term storage of biological specimens. As a complementary tool to thermal analysis techniques, which are the mainstay for determining Tg, molecular dynamics simulations have been successfully applied to predict the Tg of several protectants and their mixtures with water. These molecular analyses, however, rarely focused on the glass transition behavior of aqueous trehalose solutions, a subject that has attracted wide scientific attention via experimental approaches. Important behavior, such as hydrogen-bonding dynamics and self-aggregation has yet to be explored in detail, particularly below, or in the vicinity of, Tg. Using molecular dynamics simulations of several dynamic and thermodynamic properties, this study reproduced the supplemented phase diagram of trehalose-water mixtures (i.e., Tg as a function of the solution composition) based on experimental data. The structure and dynamics of the hydrogen-bonding network in the trehalose-water systems were also analyzed. The hydrogen-bonding lifetime was determined to be an order of magnitude higher in the glassy state than in the liquid state, while the constitution of the hydrogen-bonding network exhibited no noticeable change through the glass transition. It was also found that trehalose molecules preferred to form small, scattered clusters above Tg, but self-aggregation was substantially increased below Tg. The average cluster size in the glassy state was observed to be dependent on the trehalose concentration. Our findings provided insights into the glass transition characteristics of aqueous trehalose solutions as they relate to biopreservation.

  9. Structural Transitions and Strengths of Mg-Silicate Glasses to 80 GPa

    Science.gov (United States)

    Grocholski, B.; Catalli, K.; Shim, S.

    2008-12-01

    Early Earth's mantle may be molten to its deep interior. Therefore, physical processes in the magma ocean determine the initial conditions for the structure of the mantle. Seismologic studies have shown that the present-day mantle has melts atop the transition zone and the core-mantle boundary. Therefore, the properties of silicate melts are important for understanding the evolution of the Earth's mantle. We measured Raman scattering of silicate glasses, frozen forms of melts, with mantle related compositions, MgSiO3, Mg2SiO4, and CaSiO3, in the diamond-anvil cell up to 80 GPa. In MgSiO3 glass, Raman spectra show a structural transition associated with increases in the coordination number at 19-38 GPa and another transition likely related to changes in the Si-O polyhedral connectivity at 65-70 GPa. However, in CaSiO3 and Mg2SiO4 glasses, the former transition occurs at higher pressures (P) by 5-10 GPa and the latter transition does not occur to our maximum P, indicating that a less polymerized Si-O network increases the transition P. The compositional sensitivity of the transition P in silicate melts would result in dense MgSiO3 melt in a high-P structure and less dense Mg2SiO4 and CaSiO3 melts in low-P structures at mid-mantle depths. This density contrast will make Si-rich melts negatively buoyant but Si-poor melts postively buoyant, resulting in the Si-enriched deeper mantle. Therefore, the early magma ocean may be compositionally stratified and therefore contribute to the formation of "hidden geochemical reservoir". Our findings provide a physical mechanism for the early differentiation suggested from geochemical observations of short-lived 142Nd (Boyet and Carlson, 2005). We also measured the yield strength of MgSiO3, Mg2SiO4, and SiO2 glasses to 55 GPa in the diamond cell through the pressure gradients in the samples. The change in thickness with P was monitored visually by measuring the change in focal point from both sides of the sample. Yield strength does

  10. The old problems of glass and the glass transition, and the many new twists.

    Science.gov (United States)

    Angell, C A

    1995-07-18

    In this paper I review the ways in which the glassy state is obtained both in nature and in materials science and highlight a "new twist"--the recent recognition of polymorphism within the glassy state. The formation of glass by continuous cooling (viscous slowdown) is then examined, the strong/fragile liquids classification is reviewed, and a new twist-the possibility that the slowdown is a result of an avoided critical point-is noted. The three canonical characteristics of relaxing liquids are correlated through the fragility. As a further new twist, the conversion of strong liquids to fragile liquids by pressure-induced coordination number increases is demonstrated. It is then shown that, for comparable systems, it is possible to have the same conversion accomplished via a first-order transition within the liquid state during quenching. This occurs in the systems in which "polyamorphism" (polymorphism in the glassy state) is observed, and the whole phenomenology is accounted for by Poole's bond-modified van der Waals model. The sudden loss of some liquid degrees of freedom through such weak first-order transitions is then related to the polyamorphic transition between native and denatured hydrated proteins, since the latter are also glass-forming systems--water-plasticized, hydrogen bond-cross-linked chain polymers (and single molecule glass formers). The circle is closed with a final new twist by noting that a short time scale phenomenon much studied by protein physicists-namely, the onset of a sharp change in d/dT ( is the Debye-Waller factor)--is general for glass-forming liquids, including computer-simulated strong and fragile ionic liquids, and is closely correlated with the experimental glass transition temperature. The latter thus originates in strong anharmonicity in certain components of the vibrational density of states, which permits the system to access the multiple minima of its configuration space. The connection between the anharmonicity in these

  11. Dynamic thermal expansivity of liquids near the glass transition

    DEFF Research Database (Denmark)

    Niss, Kristine; Gundermann, Ditte; Christensen, Tage Emil

    2012-01-01

    ) in the ultraviscous regime. Compared to the method of Bauer et al., the dynamical range has been extended by making time-domain experiments and by making very small and fast temperature steps. The modeling of the experiment presented in this paper includes the situation in which the capacitor is not full because......Based on previous works on polymers by Bauer et al. [ Phys. Rev. E 61 1755 (2000)], this paper describes a capacitative method for measuring the dynamical expansion coefficient of a viscous liquid. Data are presented for the glass-forming liquid tetramethyl tetraphenyl trisiloxane (DC704...... the liquid contracts when cooling from room temperature down to around the glass-transition temperature, which is relevant when measuring on a molecular liquid rather than a polymer....

  12. Structural influence of mixed transition metal ions on lithium bismuth borate glasses

    Science.gov (United States)

    Yadav, Arti; Dahiya, Manjeet S.; Hooda, A.; Chand, Prem; Khasa, S.

    2017-08-01

    Lithium bismuth borate glasses containing mixed transition metals having composition 7CoO·23Li2O·20Bi2O3·50B2O3 (CLBB), 7V2O5·23Li2O·20Bi2O3·50B2O3 (VLBB) and x(2CoO·V2O5)·(30 - x)Li2O·20Bi2O3·50B2O3 (x = 0.0 (LBB) and x = 2.0, 5.0, 7.0, 10.0 mol% (CVLBB1-4)) are synthesized via melt quench route. The synthesized compositions are investigated for their physical properties using density (D) and molar volume (Vm), thermal properties by analyzing DSC/TG thermo-graphs, structural properties using IR absorption spectra in the mid-IR range and optical properties using UV-Vis-NIR spectroscopy. The Electron Paramagnetic Resonance (EPR) spectra of vanadyl and cobalt ion have been analyzed to study compositional effects on spin-Hamiltonian parameters. The non linear variations in physical properties depict a strong structural influence of Co/V- oxides on the glassy matrix. The compositional variations in characteristic temperatures (glass transition temperature Tg, glass crystallization temperature Tp and glass melting temperature Tm) reveals that Tg for glass samples CLBB is relatively less than that of pure lithium bismuth borate (LBB) glass sample wherein Tg for sample VLBB is higher than that of LBB. The increase in Tg (as compared with LBB) with an enhanced substitution of mixed transition metal oxides (2CoO·V2O5) shows a progressive structure modification of bismuth borate matrix. These predictions are very well corroborated by corresponding compositional trends of Tp and Tm. FTIR studies reveal that Co2+& VO2+ ions lead to structural rearrangements through the conversion of three-coordinated boron into four coordinated boron and thereby reducing number of non-bridging oxygen atoms. Bismuth is found to exist in [BiO6] octahedral units only, whereas boroxol rings are not present in the glass network. The theoretical values of optical basicity (Λth) and corresponding oxide ion polarizability (αo2-) have also been calculated to investigate oxygen covalency of

  13. Effects of fragility and reduced glass transition temperature on the glass formation ability of amorphous alloys

    Science.gov (United States)

    Xu, Xiao-Jin; Long, Zhi-Lin; Liu, Wei; Liao, Guang-Kai

    2017-11-01

    In this paper, based on the reduced glass transition temperature ({{T}rg} ) proposed by Turnbull and the relation between the glass-forming ability (GFA) and the short-range bond ordering of liquids demonstrated by Tanaka, a detailed analysis on the specific roles of {{T}rg} and fragility of the glass forming liquid (m) in characterizing the GFA has been conducted, and then a novel GFA parameter α [=2/3× (100{{T}rg}{)}-(16/100)× m=67{{T}rg}-0.16m] was put forward. This new GFA parameter α , which increases with a decrease in the critical cooling rate (R c) for glass formation, is a complex function of {{T}rg} and m. The relationship between R c and the parameter α was identified and verified using available literature data for broad range of amorphous alloys with widely varying GFA. The correlation coefficient (R 2) of 0.9 clearly shows an excellent correlation between GFA and the parameter α and that α is a more superior indicator compared to currently reported similar GFA parameters.

  14. A phenomenological molecular model for yielding and brittle-ductile transition of polymer glasses

    Science.gov (United States)

    Wang, Shi-Qing; Cheng, Shiwang; Lin, Panpan; Li, Xiaoxiao

    2014-09-01

    This work formulates, at a molecular level, a phenomenological theoretical description of the brittle-ductile transition (BDT) in tensile extension, exhibited by all polymeric glasses of high molecular weight (MW). The starting point is our perception of a polymer glass (under large deformation) as a structural hybrid, consisting of a primary structure due to the van der Waals bonding and a chain network whose junctions are made of pairs of hairpins and function like chemical crosslinks due to the intermolecular uncrossability. During extension, load-bearing strands (LBSs) emerge between the junctions in the affinely strained chain network. Above the BDT, i.e., at "warmer" temperatures where the glass is less vitreous, the influence of the chain network reaches out everywhere by activating all segments populated transversely between LBSs, starting from those adjacent to LBSs. It is the chain network that drives the primary structure to undergo yielding and plastic flow. Below the BDT, the glassy state is too vitreous to yield before the chain network suffers a structural breakdown. Thus, brittle failure becomes inevitable. For any given polymer glass of high MW, there is one temperature TBD or a very narrow range of temperature where the yielding of the glass barely takes place as the chain network also reaches the point of a structural failure. This is the point of the BDT. A theoretical analysis of the available experimental data reveals that (a) chain pullout occurs at the BDT when the chain tension builds up to reach a critical value fcp during tensile extension; (b) the limiting value of fcp, extrapolated to far below the glass transition temperature Tg, is of a universal magnitude around 0.2-0.3 nN, for all eight polymers examined in this work; (c) pressurization, which is known [K. Matsushige, S. V. Radcliffe, and E. Baer, J. Appl. Polym. Sci. 20, 1853 (1976)] to make brittle polystyrene (PS) and poly(methyl methacrylate) (PMMA) ductile at room temperature

  15. Routing strategies in traffic network and phase transition in network ...

    Indian Academy of Sciences (India)

    Routing strategy; network traffic flow; hysteretic loop; phase transition from free flow state to congestion state; scale-free network; bi-stable state; traffic dynamics. PACS Nos 89.75.Hc; 89.20.Hh; 05.10.-a; 89.75.Fb. 1. Traffic dynamics based on local routing strategy on scale-free networks. Communication networks such as ...

  16. Influence of processing conditions on the glass-crystal transition into borosilicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Deschanels, X.; Cachia, J.N.; Lopez, C.; Peuget, S. [CEA Marcoule, BP 17171, 30207 Bagnols sur Ceze (France)

    2008-07-01

    The precipitation of a crystalline phase in glass is observed when one element exceeds its loading limit (i.e.: solubility limit). In this work we have studied the solubility of different actinides and surrogates (lanthanides and hafnium) in borosilicate glass used for the immobilization of the high-level nuclear waste (HLW glasses). The results obtained show an increase of the solubility limits of these elements with the processing temperature and the redox potential of the melt. The elements at the oxidation state (III) exhibit a higher solubility than the element at oxidation state (IV). In this framework, cerium is an interesting element because its oxidation state tunes from (IV) to (III) as a function of the processing conditions. It is shown that the solubility of cerium can be multiplied by a factor of 20 at 1100 C. degrees. In order to have a better understanding of the mechanisms that underline the evolution of the solubility, XAFS and NMR investigation has been undertaken. Trivalent elements present the characteristics of network-modified cations while tetravalent elements look like network-former cations.

  17. Transition and post-transition metal ions in borate glasses: Borate ligand speciation, cluster formation, and their effect on glass transition and mechanical properties

    Science.gov (United States)

    Möncke, D.; Kamitsos, E. I.; Palles, D.; Limbach, R.; Winterstein-Beckmann, A.; Honma, T.; Yao, Z.; Rouxel, T.; Wondraczek, L.

    2016-09-01

    A series of transition and post-transition metal ion (Mn, Cu, Zn, Pb, Bi) binary borate glasses was studied with special consideration of the cations impact on the borate structure, the cations cross-linking capacity, and more generally, structure-property correlations. Infrared (IR) and Raman spectroscopies were used for the structural characterization. These complementary techniques are sensitive to the short-range order as in the differentiation of tetrahedral and trigonal borate units or regarding the number of non-bridging oxygen ions per unit. Moreover, vibrational spectroscopy is also sensitive to the intermediate-range order and to the presence of superstructural units, such as rings and chains, or the combination of rings. In order to clarify band assignments for the various borate entities, examples are given from pure vitreous B2O3 to meta-, pyro-, ortho-, and even overmodified borate glass compositions. For binary metaborate glasses, the impact of the modifier cation on the borate speciation is shown. High field strength cations such as Zn2+ enhance the disproportionation of metaborate to polyborate and pyroborate units. Pb2+ and Bi3+ induce cluster formation, resulting in PbOn- and BiOn-pseudophases. Both lead and bismuth borate glasses show also a tendency to stabilize very large superstructural units in the form of diborate polyanions. Far-IR spectra reflect on the bonding states of modifier cations in glasses. The frequency of the measured cation-site vibration band was used to obtain the average force constant for the metal-oxygen bonding, FM-O. A linear correlation between glass transition temperature (Tg) and FM-O was shown for the metaborate glass series. The mechanical properties of the glasses also correlate with the force constant FM-O, though for cations of similar force constant the fraction of tetrahedral borate units (N4) strongly affects the thermal and mechanical properties. For paramagnetic Cu- and Mn-borate glasses, N4 was determined

  18. Quantum Phase Transitions: A Network Approach

    Science.gov (United States)

    Vargas, David L.; Larue, David M.; Carr, Lincoln D.

    2014-03-01

    Understanding the network structure of complex systems has opened up new avenues of research in sociology, biology, technology, and physics. In this talk we present evidence that complex network measures are able to identify the phases in two well known models. We distinguish the ferromagnetic and paramagnetic phases of the transverse Ising Hamiltonian. We also identify the Mott-insulator to superfluid transition of the Bose-Hubbard Hamiltonian. The network approach to the analysis of quantum phase transitions provides us with a new set of tools to explore the many body physics of quantum phase transitions. Supported by NSF and AFOSR.

  19. Glass transition, crystallization kinetics and pressure effect on crystallization of ZrNbCuNiBe bulk metallic glass

    DEFF Research Database (Denmark)

    Xing, P.F.; Zhuang, Yanxin; Wang, W.H.

    2002-01-01

    The glass transition behavior and crystallization kinetics of Zr48Nb8Cu14Ni12Be18 bulk metallic glass have been investigated by differential scanning calorimetry and x-ray powder diffraction (XRD). The activation energies of both glass transition and crystallization events have been obtained using...... the Kissinger method. Results indicate that this glass crystallizes by a three-stage reaction: (1) phase separation and primary crystallization of glass, (2) formation of intermetallic compounds, and (3) decomposition of intermetallic compounds and crystallization of residual amorphous phase. The pressure...... effect on crystallization is studied by in situ high-pressure and high-temperature XRD using synchrotron radiation. Two crystallization temperatures, observed by in-situ XRD, behave differently with varying pressure. The onset crystallization temperature increases with pressure with a slope of 9.5 K...

  20. The vortex glass to liquid transition in Bi2212 whisker

    Science.gov (United States)

    Zheng, P.; Zhou, Y. Q.; Chen, Z. J.; Luo, S.; Wang, W. H.; He, Y. S.; Duo, J.

    1999-05-01

    Through scaling the dc I- V isotherms of Bi2212 whisker in magnetic field H‖ c, the vortex glass-liquid transition is found in Bi2212 whisker whereas it does not appear in Bi2212 crystal slab [R. Behr, J. Kotzler, G. Nakielski, M. Baumann, M. Kaufmann, J. Kowalewski, Physica C 235 (1994) 2669]. The critical exponents are ν=0.5, z=4.0. We found that the critical exponents are influenced by the planar defects of the sample. The result was compared to those of single crystals and films [Behr et al., 1994; H. Yamasaki, K. Endo, S. Kosaka, M. Umeda, S. Yoshida, K. Kajimura, Phys. Rev. B 50 (17) (1994) 12959].

  1. Local elastic response measured near the colloidal glass transition

    Science.gov (United States)

    Anderson, D.; Schaar, D.; Hentschel, H. G. E.; Hay, J.; Habdas, Piotr; Weeks, Eric R.

    2013-03-01

    We examine the response of a dense colloidal suspension to a local force applied by a small magnetic bead. For small forces, we find a linear relationship between the force and the displacement, suggesting the medium is elastic, even though our colloidal samples macroscopically behave as fluids. We interpret this as a measure of the strength of colloidal caging, reflecting the proximity of the samples' volume fractions to the colloidal glass transition. The strain field of the colloidal particles surrounding the magnetic probe appears similar to that of an isotropic homogeneous elastic medium. When the applied force is removed, the strain relaxes as a stretched exponential in time. We introduce a model that suggests this behavior is due to the diffusive relaxation of strain in the colloidal sample.

  2. The glass transition process in humid biopolymers. DSC study

    Energy Technology Data Exchange (ETDEWEB)

    Grunina, N A; Belopolskaya, T V; Tsereteli, G I [V.A. Fock Research Institute for Physics of Saint-Petersburg State University, 198504, Petrodvorets (Russian Federation)

    2006-05-15

    Thermal properties of native and denatured biopolymers with quite different chemical and steric structure (globular and fibrillar proteins, DNA, starches) were studied by means of differential scanning calorimetry in a wide range of temperatures and concentrations of water. It was shown that both native and denatured humid biopolymers are glassy systems. The glass transition temperature of these systems strongly depends on percentage of water, with water being simultaneously an intrinsic element of systems' ordered structure and a plasticizer of its amorphous state. On the base of the absolute values of heat capacities for biopolymer-water systems as a whole, heat capacities for biopolymers themselves were calculated as functions on water concentration at fixed temperatures. The S-shaped change of heat capacity observed on diagrams of state both for native and denatured biopolymers is the manifestation of biopolymers' passing through the vitrification region, as it occurs for denatured samples at heating.

  3. Quantum spin-glass transition in the two-dimensional electron gas

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 2 ... Spin glasses; quantum phase transition; ferromagnetism; electron gas. ... We argue that a quantum transition involving the destruction of the spin-glass order in an applied in-plane magnetic field offers a natural explanation of some features of recent ...

  4. Shear banding of colloidal glasses: Observation of a dynamic first order transition

    NARCIS (Netherlands)

    Chikkadi, V.; Miedema, D.M.; Dang, M.T.; Nienhuis, B.; Schall, P.

    2014-01-01

    We demonstrate that application of an increasing shear field on a glass leads to an intriguing dynamic first-order transition in analogy with equilibrium transitions. By following the particle dynamics as a function of the driving field in a colloidal glass, we identify a critical shear rate upon

  5. Direct investigations of deformation and yield induced structure transitions in polyamide 6 below glass transition temperature with WAXS and SAXS

    DEFF Research Database (Denmark)

    Guo, Huilong; Wang, Jiayi; Zhou, Chengbo

    2015-01-01

    Deformation and yield induced structure transitions of polyamide 6 (PA6) were detected with the combination of the wide- and small-angle X-ray scattering (WAXS and SAXS) at 30 degrees C below glass transition temperature (T-g) of PA6. During deformation, gamma-alpha phase transition was found...

  6. glasses

    Indian Academy of Sciences (India)

    several applications. Some of the possible applications are optical amplifiers in telecommunication,7 phosphorescence materials and electrochemical batteries.8 Rare earth metal ions when added to borate act as network modifiers and change the properties of glasses .... where R is the universal gas constant. 3.3 Electrical ...

  7. Observability transition in real networks

    Science.gov (United States)

    Yang, Yang; Radicchi, Filippo

    2016-09-01

    We consider the observability model in networks with arbitrary topologies. We introduce a system of coupled nonlinear equations, valid under the locally treelike ansatz, to describe the size of the largest observable cluster as a function of the fraction of directly observable nodes present in the network. We perform a systematic analysis on 95 real-world graphs and compare our theoretical predictions with numerical simulations of the observability model. Our method provides almost perfect predictions in the majority of the cases, even for networks with very large values of the clustering coefficient. Potential applications of our theory include the development of efficient and scalable algorithms for real-time surveillance of social networks, and monitoring of technological networks.

  8. The glass transition in a nutshell: a source of inspiration to describe the subcritical transition to turbulence.

    Science.gov (United States)

    Dauchot, Olivier; Bertin, Eric

    2014-04-01

    The starting point of the present work is the observation of possible analogies, both at the phenomenological and at the methodological level, between the subcritical transition to turbulence and the glass transition. Having recalled the phenomenology of the subcritical transition to turbulence, we review the theories of the glass transition at a very basic level, focusing on the history of their development as well as on the concepts they have elaborated. Doing so, we aim at attracting the attention on the above-mentioned analogies, which we believe could inspire new developments in the theory of the subcritical transition to turbulence. We then briefly describe a model inspired by one of the simplest and most inspiring models of the glass transition, the so-called Random Energy Model, as a first step in that direction.

  9. Analysis of early medieval glass beads - Glass in the transition period

    Energy Technology Data Exchange (ETDEWEB)

    Smit, Ziga, E-mail: ziga.smit@ijs.si [Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana (Slovenia); Jozef Stefan Institute, Jamova 39, P.O.B. 3000, SI-1001 Ljubljana (Slovenia); Knific, Timotej [National Museum of Slovenia, Presernova 20, SI-1000 Ljubljana (Slovenia); Jezersek, David [Jozef Stefan Institute, Jamova 39, P.O.B. 3000, SI-1001 Ljubljana (Slovenia); Istenic, Janka [National Museum of Slovenia, Presernova 20, SI-1000 Ljubljana (Slovenia)

    2012-05-01

    Glass beads from graves excavated in Slovenia and dated archaeologically to the 7th-10th century AD were analysed by the combined PIXE-PIGE method. The results indicate two groups of glass; natron glass made in the Roman tradition and glass made with alkalis from the ash of halophytic plants, which gradually replaced natron glass after c. 800 AD. The alkalis used in the second group of glass seem to be in close relation to a variant of the Venetian white glass that appeared several centuries later. The origin of this glass may be traced to glass production in Mesopotamia and around the Aral Sea. All the mosaic beads with eye decoration, as well as most of the drawn-segmented and drawn-cut beads analysed, are of plant-ash glass, which confirms their supposed oriental origin.

  10. Effects of adding LiBF4 on the glass-transition kinetics of 1,2-propanediol

    Science.gov (United States)

    Terashima, Yukio; Takeda, Kiyoshi

    2017-11-01

    By applying an isoconversional method to differential-scanning calorimetry (DSC) data, we have discovered that the addition of LiBF4 significantly affects the activation energy Eα of the glass transition of 1,2-propanediol. Depending upon its concentration, the dynamics of the glass transition are affected more by adding LiBF4 at an early stage of the glass-to-liquid transition rather than at later stages. As the mole fraction x of LiBF4 increases, the value of Eα initially increases, but it decreases dramatically during the glass transition. The abrupt decline in Eα suggests that the addition of LiBF4 breaks cooperative rearranging motions into smaller parts. The expansion of cooperativity, and its fragmentation with increasing temperature, can be explained in terms of competition between the hydrogen-bond networks of the alcohol solvent and the ionic interactions due to the added salt. The variability of Eα with temperature is found to correlate exponentially with the dynamic fragility.

  11. Exploring the Origin of Fragile-to-Strong Transition in Some Glass-Forming Liquids

    DEFF Research Database (Denmark)

    Yue, Yuanzheng; Hu, L. N.

    2014-01-01

    , topological and thermodynamic changes causing this transition. The theory for describing the transition has not been fully established. In this paper, we summarize our current understanding of the fragile-to-strong transition in some glass-forming liquids basedon our two published papers and recent...

  12. X-ray tomography of feed-to-glass transition of simulated borosilicate waste glasses

    Czech Academy of Sciences Publication Activity Database

    Harris, W.H.; Guillen, D.P.; Kloužek, Jaroslav; Pokorný, P.; Yano, T.; Lee, S.; Schweiger, M. J.; Hrma, P.

    2017-01-01

    Roč. 100, č. 9 (2017), s. 3883-3894 ISSN 0002-7820 Institutional support: RVO:67985891 Keywords : borosilicate glass * computed tomography * glass melting * morphology * nuclear waste * X-ray Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.841, year: 2016

  13. Strain Hardening in Polymer Glasses: Limitations of Network Models

    OpenAIRE

    Hoy, Robert S.; Robbins, Mark O.

    2007-01-01

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of l...

  14. African Transitional Justice Research Network | IDRC - International ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    ... the creation and sustainable expansion of an electronically-based research network on options and lessons learned pertaining to transitional justice. A second objective is to build the capacity of 75 African human rights researchers to produce locally based research and carry out evidence-based human rights advocacy.

  15. A Model of Mental State Transition Network

    Science.gov (United States)

    Xiang, Hua; Jiang, Peilin; Xiao, Shuang; Ren, Fuji; Kuroiwa, Shingo

    Emotion is one of the most essential and basic attributes of human intelligence. Current AI (Artificial Intelligence) research is concentrating on physical components of emotion, rarely is it carried out from the view of psychology directly(1). Study on the model of artificial psychology is the first step in the development of human-computer interaction. As affective computing remains unpredictable, creating a reasonable mental model becomes the primary task for building a hybrid system. A pragmatic mental model is also the fundament of some key topics such as recognition and synthesis of emotions. In this paper a Mental State Transition Network Model(2) is proposed to detect human emotions. By a series of psychological experiments, we present a new way to predict coming human's emotions depending on the various current emotional states under various stimuli. Besides, people in different genders and characters are taken into consideration in our investigation. According to the psychological experiments data derived from 200 questionnaires, a Mental State Transition Network Model for describing the transitions in distribution among the emotions and relationships between internal mental situations and external are concluded. Further more the coefficients of the mental transition network model were achieved. Comparing seven relative evaluating experiments, an average precision rate of 0.843 is achieved using a set of samples for the proposed model.

  16. Mode-coupling glass transition in a fluid confined by a periodic potential.

    Science.gov (United States)

    Nandi, Saroj Kumar; Bhattacharyya, Sarika Maitra; Ramaswamy, Sriram

    2011-12-01

    We show that a fluid under strong spatially periodic confinement displays a glass transition within mode-coupling theory at a much lower density than the corresponding bulk system. We use fluctuating hydrodynamics, with confinement imposed through a periodic potential whose wavelength plays an important role in our treatment. To make the calculation tractable we implement a detailed calculation in one dimension. Although we do not expect simple 1d fluids to show a glass transition, our results are indicative of the behavior expected in higher dimensions. In a certain region of parameter space we observe a three-step relaxation reported recently in computer simulations [S. H. Krishnan, Ph.D. thesis, Indian Institute of Science (2005); Kim et al., Eur. Phys. J. Special Topics 189, 135 (2010)] and a glass-glass transition. We compare our results to those of Krakoviack [Phys. Rev. E 75, 031503 (2007)] and Lang et al. [Phys. Rev. Lett. 105, 125701 (2010)].

  17. Pressure effect of glass transition temperature in Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk metallic glass

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Roseker, W.; Sikorski, M.

    2004-01-01

    Pressure effects on glass transition temperature and supercooled liquid region of a Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass have been investigated by performing in situ high-temperature and high-pressure x-ray powder diffraction measurements using synchrotron radiation. The glass transition was det...... range of 0-2.2 GPa. This method opens a possibility to study the pressure effect of glass transition process in glassy systems under high pressures (>1 GPa). (C) 2004 American Institute of Physics....

  18. A Calorimetric Study of the Glass Transition Behaviors in Axes of Bean Seeds with Relevance to Storage Stability.

    Science.gov (United States)

    Leprince, O.; Walters-Vertucci, C.

    1995-12-01

    Although the presence of intracellular aqueous glasses has been established in seeds, their physiological role in storage stability is still conjectural. Therefore, we examined, using differential scanning calorimetry, the thermal behavior of glass transitions in axes of bean (Phaseolus vulgaris L.) with water contents (WC) between 0 and 1 g H2O/g dry weight (g/g) and temperatures between -120 and +120[deg]C. Three types of thermal behaviors associated with the glass transition were observed. The appearance, the glass -> liquid transition temperature, and the amount of energy released during these transitions were dependent on the tissue WC. No glass transitions were observed at WC lower than 0.03 and higher than 0.45 g/g. A brief exposure to 100[deg]C altered the glass properties of tissues with WC between 0.03 and 0.08 g/g but did not affect the thermal behavior of glasses with higher WC, demonstrating that thermal history is important to the intracellular glass behavior at lower WC. Correspondence of data from bean to models predicting the effects of glass components on the glass -> liquid transition temperature suggests that the intracellular glasses are composed of a highly complex sugar matrix, in which sugar and water molecules interact together and influence the glass properties. Our data provide evidence that additional glass properties must be characterized to understand the implications of a glassy state in storage stability of seeds.

  19. Phase transitions in Pareto optimal complex networks.

    Science.gov (United States)

    Seoane, Luís F; Solé, Ricard

    2015-09-01

    The organization of interactions in complex systems can be described by networks connecting different units. These graphs are useful representations of the local and global complexity of the underlying systems. The origin of their topological structure can be diverse, resulting from different mechanisms including multiplicative processes and optimization. In spatial networks or in graphs where cost constraints are at work, as it occurs in a plethora of situations from power grids to the wiring of neurons in the brain, optimization plays an important part in shaping their organization. In this paper we study network designs resulting from a Pareto optimization process, where different simultaneous constraints are the targets of selection. We analyze three variations on a problem, finding phase transitions of different kinds. Distinct phases are associated with different arrangements of the connections, but the need of drastic topological changes does not determine the presence or the nature of the phase transitions encountered. Instead, the functions under optimization do play a determinant role. This reinforces the view that phase transitions do not arise from intrinsic properties of a system alone, but from the interplay of that system with its external constraints.

  20. Strain hardening in polymer glasses: limitations of network models.

    Science.gov (United States)

    Hoy, Robert S; Robbins, Mark O

    2007-09-14

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic rearrangements. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain.

  1. Topological Origin of the Network Dilation Anomaly in Ion-Exchanged Glasses

    Science.gov (United States)

    Wang, Mengyi; Smedskjaer, Morten M.; Mauro, John C.; Sant, Gaurav; Bauchy, Mathieu

    2017-11-01

    Ion exchange is commonly used to strengthen oxide glasses. However, the resulting stuffed glasses usually do not reach the molar volume of as-melted glasses of similar composition—a phenomenon known as the network dilation anomaly. This behavior seriously limits the potential for the chemical strengthening of glasses and its origin remains one of the mysteries of glass science. Here, based on molecular dynamics simulations of sodium silicate glasses coupled with topological constraint theory, we show that the topology of the atomic network controls the extent of ion-exchange-induced dilation. We demonstrate that isostatic glasses do not show any network dilation anomaly. This is found to arise from the combined absence of floppy modes of deformation and internal eigenstress in isostatic atomic networks.

  2. Fabrication of transparent superhydrophobic glass with fibered-silica network

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Feng [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China); Shi, Zhenwu, E-mail: zwshi@suda.edu.cn [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China); Jiang, Yingjie; Xu, Chengyun; Wu, Zhuhui; Wang, Yanyan [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China); Peng, Changsi, E-mail: changsipeng@suda.edu.cn [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China)

    2017-06-15

    Highlights: • Superhydrophobic fibred-silica film with water contact angle of 166° and sliding angle of 1° was efficiently prepared using soot as template by CVD. • The film showed transmittance of 88% in visible range. • The superhydrophobic film possesses excellent mechanical robustness, chemical corrosion resistance, and thermal stability. • The superhydrophobic film showed outstanding self-cleaning behavior. - Abstract: In this paper, silica was deposited on the soot film pre-coated glass via chemical vapor deposition. Through calcination at 500 °C with the assistance of O{sub 2} airflow, the soot film was removed and a novel robust fibered-silica network film was then decorated onto the glass substrate. After modification with fluorosilane, the surface water contact angle (WCA) was 166° and sliding angle (SA) was 1° which behaves a good self-cleaning for the as-prepared glass. And its average transmittance was still over 88% in visible wavelength. Moreover, this fibered-silica coating showed a strong tolerance for heavy water droplets, acid/alkali corrosion, salt solution immersion and thermal treatment.

  3. Glass transition-related thermorheological complexity in polystyrene melts

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Y-H [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan (China)

    2007-11-21

    The relaxation-modulus G(t) functional forms covering the whole time range are given by incorporating a stretched exponential for the structural- (glassy-) relaxation process into the extended reptation theory (ERT; for entangled systems) or the Rouse theory (for entanglement-free systems). The creep compliance J(t) curves of two entangled (A and B) and one entanglement-free (C) polystyrene samples (Plazek) as well as the viscoelastic spectra G*({omega}) of four entanglement-free polystyrene samples (Inoue et al) have been quantitatively analyzed in terms of the given G(t) functional forms. In such quantitatively successful analyses, the ERT or the Rouse theory works as the frame of reference in both the line shape and timescale. The thermorheological complexity in the J(t) curves is explained naturally and precisely by the temperature dependence of the energetic-interaction-derived structural relaxation being stronger than that of the entropic ERT or Rouse dynamics in a simple way. Structural-relaxation times {tau}{sub S} (= 18s{sup '}K{sup '}) of all the studied samples are equally well separated into two decoupled quantities: the structural-growth parameter s{sup '} and the frictional factor K{sup '} (for the Rouse-Mooney or Rouse modes of motion). The separation is fundamentally a clean-cut process: s{sup '} is determined entirely by the line shape of J(t) or G*({omega}) while K{sup '} is calculated from the timescale shifting factor obtained from the superposition of the calculated curves onto the measured. The glassy-relaxation strength A{sub G}{sup f} and the stretching parameter {beta} extracted from the J(t) and G*({omega}) results over the glassy-relaxation region are in good agreement. The glass-transition temperature T{sub g} is defined as corresponding to {tau}{sub S} 1000 s for all the studied samples. The {tau}{sub S}, s{sup '} and K{sup '} data points of samples A, B and C extracted from their J(t) curves

  4. Polymeric nanoparticles - Influence of the glass transition temperature on drug release.

    Science.gov (United States)

    Lappe, Svenja; Mulac, Dennis; Langer, Klaus

    2017-01-30

    The physico-chemical characterisation of nanoparticles is often lacking the determination of the glass transition temperature, a well-known parameter for the pure polymer carrier. In the present study the influence of water on the glass transition temperature of poly (DL-lactic-co-glycolic acid) nanoparticles was assessed. In addition, flurbiprofen and mTHPP as model drugs were incorporated in poly (DL-lactic-co-glycolic acid), poly (DL-lactic acid), and poly (L-lactic acid) nanoparticles. For flurbiprofen-loaded nanoparticles a decrease in the glass transition temperature was observed while mTHPP exerted no influence on this parameter. Based on this observation, the release behaviour of the drug-loaded nanoparticles was investigated at different temperatures. For all preparations an initial burst release was measured that could be attributed to the drug adsorbed to the large nanoparticle surface. At temperatures above the glass transition temperature an instant drug release of the nanoparticles was observed, while at lower temperatures less drug was released. It could be shown that the glass transition temperature of drug loaded nanoparticles in suspension more than the corresponding temperature of the pure polymer is the pivotal parameter when characterising a nanostructured drug delivery system. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. The glass transition in cured epoxy thermosets: A comparative molecular dynamics study in coarse-grained and atomistic resolution

    Energy Technology Data Exchange (ETDEWEB)

    Langeloth, Michael; Böhm, Michael C.; Müller-Plathe, Florian [Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich Weiss Straße 4, D-64287 Darmstadt (Germany); Sugii, Taisuke, E-mail: taisuke.sugii.zs@hitachi.com [Center for Technology Innovation – Mechanical Engineering, Research & Development Group, Hitachi, Ltd., 832-2, Horiguchi, Hitachinaka, Ibaraki 312-0034 (Japan)

    2015-12-28

    We investigate the volumetric glass transition temperature T{sub g} in epoxy thermosets by means of molecular dynamics simulations. The epoxy thermosets consist of the resin bisphenol A diglycidyl ether and the hardener diethylenetriamine. A structure based coarse-grained (CG) force field has been derived using iterative Boltzmann inversion in order to facilitate simulations of larger length scales. We observe that T{sub g} increases clearly with the degree of cross-linking for all-atomistic (AA) and CG simulations. The transition T{sub g} in CG simulations of uncured mixtures is much lower than in AA-simulations due to the soft nature of the CG potentials, but increases all the more with the formation of rigid cross-links. Additional simulations of the CG mixtures in contact with a surface show the existence of an interphase region of about 3 nm thickness in which the network properties deviate significantly from the bulk. In accordance to experimental studies, we observe that T{sub g} is reduced in this interphase region and gradually increases to its bulk value with distance from the surface. The present study shows that the glass transition is a local phenomenon that depends on the network structure in the immediate environment.

  6. Size-Dependent Brittle-to-Ductile Transition in Silica Glass Nanofibers.

    Science.gov (United States)

    Luo, Junhang; Wang, Jiangwei; Bitzek, Erik; Huang, Jian Yu; Zheng, He; Tong, Limin; Yang, Qing; Li, Ju; Mao, Scott X

    2016-01-13

    Silica (SiO2) glass, an essential material in human civilization, possesses excellent formability near its glass-transition temperature (Tg > 1100 °C). However, bulk SiO2 glass is very brittle at room temperature. Here we show a surprising brittle-to-ductile transition of SiO2 glass nanofibers at room temperature as its diameter reduces below 18 nm, accompanied by ultrahigh fracture strength. Large tensile plastic elongation up to 18% can be achieved at low strain rate. The unexpected ductility is due to a free surface affected zone in the nanofibers, with enhanced ionic mobility compared to the bulk that improves ductility by producing more bond-switching events per irreversible bond loss under tensile stress. Our discovery is fundamentally important for understanding the damage tolerance of small-scale amorphous structures.

  7. Shear Banding of Colloidal Glasses: Observation of a Dynamic First-Order Transition

    Science.gov (United States)

    Chikkadi, V.; Miedema, D. M.; Dang, M. T.; Nienhuis, B.; Schall, P.

    2014-11-01

    We demonstrate that application of an increasing shear field on a glass leads to an intriguing dynamic first-order transition in analogy with equilibrium transitions. By following the particle dynamics as a function of the driving field in a colloidal glass, we identify a critical shear rate upon which the diffusion time scale of the glass exhibits a sudden discontinuity. Using a new dynamic order parameter, we show that this discontinuity is analogous to a first-order transition, in which the applied stress acts as the conjugate field on the system's dynamic evolution. These results offer new perspectives to comprehend the generic shear-banding instability of a wide range of amorphous materials.

  8. Structure and properties of transition metal-metalloid glasses based on refractory metals

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, W.L.; Williams, A.R.

    1979-01-01

    The structure and properties of several new transition metal-metalloid (TM/sub 1-x/M/sub x/) metallic glasses based on refractory transition metals (e.g. Mo, W, Ru etc.) have been systemically investigated as a function of composition. The structure of the alloys has been investigated by x-ray diffraction methods and measurements of superconducting properties, electrical resistivity, density, hardness, and mechanical behavior were made. These data are used in developing a novel description of the structure of TM/sub 1-x/M/sub x/ glasses. The experimental evidence suggests that an ideal amorphous phase forms at a specific composition x/sub c/ and that this phase has a well defined atomic short range order. For metallic glasses having x < x/sub c/ (metalloid poor glasses) vacancy-like defects form, which are characterized by the excess volume which they contribute to the glass. Another, as yet unspecified defect appears to form in glasses with x > x/sub c/. This novel picture can explain the variation of many properties of these glasses with metalloid concentration.

  9. Glass transition. A new approach based on cluster model of glasses*

    Indian Academy of Sciences (India)

    Abstract. The structure of real glasses has been considered to be microheterogeneous, composed of clusters and'connective tissue. Particles in the cluster are assumed to be highly. Correlated in positions. The tissue is considered to have a truly amorphous structure with its particles vibrating in highly anharmonic potentials ...

  10. Glass transition in the spin-density wave phase of (TMTSF)2PF6

    DEFF Research Database (Denmark)

    Lasjaunias, J.C.; Biljakovic, K.; Nad, F.

    1994-01-01

    We present the results of low frequency dielectric measurements and a detailed kinetic investigation of the specific heat anomaly in the spin-density wave phase of (TMTSF)(2)PF6 in the temperature range between 2 and 4 K. The dielectric relaxation shows a critical slowing down towards a ''static......'' glass transition around 2 K. The jump in the specific heat in different controlled kinetic conditions shows all the characteristics of freezing in supercooled liquids. Both effects give direct evidence of a glass transition in the spin-density wave ground state....

  11. Glass transition behavior of ternary disaccharide-ethylene glycol-water solutions

    Science.gov (United States)

    Yu, Tongxu; Zhao, Lishan; Wang, Qiang; Cao, Zexian

    2017-06-01

    Glass transition behavior of ternary disaccharide-ethylene glycol-water solutions, in reference to that of the binary combinations, has been investigated towards a better understanding of their cryoprotective ability. In water-deficient solutions, the disaccharides, including trehalose, sucrose and maltose, can associate with more than 100 ethylene glycol molecules to form amorphous complex, one order of magnitude larger than the corresponding hydration numbers. In water-rich solutions, a second glass transition emerges with increasing molar fraction of ethylene glycol, indicating the possible synergy of disaccharides and ethylene glycol in vitrification of the ternary aqueous solution.

  12. Glass transition of poly (methyl methacrylate) filled with nanosilica and core-shell structured silica

    DEFF Research Database (Denmark)

    Song, Yihu; Bu, Jing; Zuo, Min

    2017-01-01

    Core-shell (CS) nanocomposite particles with 53.4 wt% cross-linked poly (methyl methacrylate) (PMMA) shell of 11.6 nm in thickness were fabricated via miniemulsion polymerization of methyl methacrylate in the presence of modified nanosilica. The influence of nanosilica and CS nanoparticles on glass...... transition and segmental dynamics of PMMA in the nanocomposites prepared via solution casting was compared. The remarkable depression (≥10 °C) of glass transition temperature (Tg) induced by the incorporation of SiO2 and CS was both observed at low loadings. Here, different mechanisms were responsible...

  13. Critical Transitions in Social Network Activity

    DEFF Research Database (Denmark)

    Kuehn, Christian; Martens, Erik Andreas; Romero, Daniel M

    2014-01-01

    for a priori unknown events in society are present in social networks is an exciting open problem, to which at present only highly speculative answers can be given. Here, we instead provide a first step towards tackling a simpler question by focusing on a priori known events and analyse a social media data set...... with a focus on classical variance and autocorrelation warning signs. Our results thus pertain to one absolutely fundamental question: Can the stochastic warning signs known from other areas also be detected in large-scale social media data? We answer this question affirmatively as we find that several...... a priori known events are preceded by variance and autocorrelation growth. Our findings thus clearly establish the necessary starting point to further investigate the relationship between abstract mathematical theory and various classes of critical transitions in social networks....

  14. The Homogeneity Research of Urban Rail Transit Network Performance

    Directory of Open Access Journals (Sweden)

    Wang Fu-jian

    2016-01-01

    Full Text Available Urban Rail Transit is an important part of the public transit, it is necessary to carry out the corresponding network function analysis. Previous studies mainly about network performance analysis of a single city rail transit, lacking of horizontal comparison between the multi-city, it is difficult to find inner unity of different Urban Rail Transit network functions. Taking into account the Urban Rail Transit network is a typical complex networks, so this paper proposes the application of complex network theory to research the homogeneity of Urban Rail Transit network performance. This paper selects rail networks of Beijing, Shanghai, Guangzhou as calculation case, gave them a complex network mapping through the L, P Space method and had a static topological analysis using complex network theory, Network characteristics in three cities were calculated and analyzed form node degree distribution and node connection preference. Finally, this paper studied the network efficiency changes of Urban Rail Transit system under different attack mode. The results showed that, although rail transport network size, model construction and construction planning of the three cities are different, but their network performance in many aspects showed high homogeneity.

  15. Anomalous Crystallization as a Signature of the Fragile-to-Strong Transition in Metallic Glass-Forming Liquids

    DEFF Research Database (Denmark)

    Yang, X.N.; Zhou, C.; Sun, Q.J.

    2014-01-01

    We study the fragile-to-strong (F−S) transition of metallic glass-forming liquids (MGFLs) by measuring the thermal response during annealing and dynamic heating of La55Al25Ni5Cu15 glass ribbons fabricated at different cooling rates. We find that the glasses fabricated in the intermediate regime...

  16. Transition Communities and the Glass Ceiling of Environmental Sustainability Policies at Three Universities

    Science.gov (United States)

    Pardellas Santiago, Miguel; Meira Cartea, Pablo; Iglesias da Cunha, Lucía

    2017-01-01

    Purpose: This paper deals with the experiences of three European universities that have implemented transition initiatives, using the Transition Network's methodology to promote their sustainability plans. The Transition Communities' model for change is presented from a socio-educational perspective as an effective methodology for encouraging…

  17. Transcriptional networks in epithelial-mesenchymal transition.

    Directory of Open Access Journals (Sweden)

    Christo Venkov

    Full Text Available Epithelial-mesenchymal transition (EMT changes polarized epithelial cells into migratory phenotypes associated with loss of cell-cell adhesion molecules and cytoskeletal rearrangements. This form of plasticity is seen in mesodermal development, fibroblast formation, and cancer metastasis.Here we identify prominent transcriptional networks active during three time points of this transitional process, as epithelial cells become fibroblasts. DNA microarray in cultured epithelia undergoing EMT, validated in vivo, were used to detect various patterns of gene expression. In particular, the promoter sequences of differentially expressed genes and their transcription factors were analyzed to identify potential binding sites and partners. The four most frequent cis-regulatory elements (CREs in up-regulated genes were SRY, FTS-1, Evi-1, and GC-Box, and RNA inhibition of the four transcription factors, Atf2, Klf10, Sox11, and SP1, most frequently binding these CREs, establish their importance in the initiation and propagation of EMT. Oligonucleotides that block the most frequent CREs restrain EMT at early and intermediate stages through apoptosis of the cells.Our results identify new transcriptional interactions with high frequency CREs that modulate the stability of cellular plasticity, and may serve as targets for modulating these transitional states in fibroblasts.

  18. Using combined computational techniques to predict the glass transition temperatures of aromatic polybenzoxazines.

    Directory of Open Access Journals (Sweden)

    Phumzile Mhlanga

    Full Text Available The Molecular Operating Environment software (MOE is used to construct a series of benzoxazine monomers for which a variety of parameters relating to the structures (e.g. water accessible surface area, negative van der Waals surface area, hydrophobic volume and the sum of atomic polarizabilities, etc. are obtained and quantitative structure property relationships (QSPR models are formulated. Three QSPR models (formulated using up to 5 descriptors are first used to make predictions for the initiator data set (n = 9 and compared to published thermal data; in all of the QSPR models there is a high level of agreement between the actual data and the predicted data (within 0.63-1.86 K of the entire dataset. The water accessible surface area is found to be the most important descriptor in the prediction of T(g. Molecular modelling simulations of the benzoxazine polymer (minus initiator carried out at the same time using the Materials Studio software suite provide an independent prediction of T(g. Predicted T(g values from molecular modelling fall in the middle of the range of the experimentally determined T(g values, indicating that the structure of the network is influenced by the nature of the initiator used. Hence both techniques can provide predictions of glass transition temperatures and provide complementary data for polymer design.

  19. Stability-to-instability transition in the structure of large-scale networks.

    Science.gov (United States)

    Hu, Dandan; Ronhovde, Peter; Nussinov, Zohar

    2012-12-01

    We examine phase transitions between the "easy," "hard," and "unsolvable" phases when attempting to identify structure in large complex networks ("community detection") in the presence of disorder induced by network "noise" (spurious links that obscure structure), heat bath temperature T, and system size N. The partition of a graph into q optimally disjoint subgraphs or "communities" inherently requires Potts-type variables. In earlier work [Philos. Mag. 92, 406 (2012)], when examining power law and other networks (and general associated Potts models), we illustrated that transitions in the computational complexity of the community detection problem typically correspond to spin-glass-type transitions (and transitions to chaotic dynamics in mechanical analogs) at both high and low temperatures and/or noise. The computationally "hard" phase exhibits spin-glass type behavior including memory effects. The region over which the hard phase extends in the noise and temperature phase diagram decreases as N increases while holding the average number of nodes per community fixed. This suggests that in the thermodynamic limit a direct sharp transition may occur between the easy and unsolvable phases. When present, transitions at low temperature or low noise correspond to entropy driven (or "order by disorder") annealing effects, wherein stability may initially increase as temperature or noise is increased before becoming unsolvable at sufficiently high temperature or noise. Additional transitions between contending viable solutions (such as those at different natural scales) are also possible. Identifying community structure via a dynamical approach where "chaotic-type" transitions were found earlier. The correspondence between the spin-glass-type complexity transitions and transitions into chaos in dynamical analogs might extend to other hard computational problems. In this work, we examine large networks (with a power law distribution in cluster size) that have a large

  20. Thermalization calorimetry: A simple method for investigating glass transition and crystallization of supercooled liquids

    DEFF Research Database (Denmark)

    Jakobsen, Bo; Sanz, Alejandro; Niss, Kristine

    2016-01-01

    We present a simple method for fast and cheap thermal analysis on supercooled glass-forming liquids. This “Thermalization Calorimetry” technique is based on monitoring the temperature and its rate of change during heating or cooling of a sample for which the thermal power input comes from heat...... conduction through an insulating material, i.e., is proportional to the temperature difference between sample and surroundings. The monitored signal reflects the sample’s specific heat and is sensitive to exo- and endothermic processes. The technique is useful for studying supercooled liquids...... and their crystallization, e.g., for locating the glass transition and melting point(s), as well as for investigating the stability against crystallization and estimating the relative change in specific heat between the solid and liquid phases at the glass transition...

  1. Thermalization calorimetry: A simple method for investigating glass transition and crystallization of supercooled liquids

    Directory of Open Access Journals (Sweden)

    Bo Jakobsen

    2016-05-01

    Full Text Available We present a simple method for fast and cheap thermal analysis on supercooled glass-forming liquids. This “Thermalization Calorimetry” technique is based on monitoring the temperature and its rate of change during heating or cooling of a sample for which the thermal power input comes from heat conduction through an insulating material, i.e., is proportional to the temperature difference between sample and surroundings. The monitored signal reflects the sample’s specific heat and is sensitive to exo- and endothermic processes. The technique is useful for studying supercooled liquids and their crystallization, e.g., for locating the glass transition and melting point(s, as well as for investigating the stability against crystallization and estimating the relative change in specific heat between the solid and liquid phases at the glass transition.

  2. The Relationships Between Polymers and Glass Transition Temperatures. Part 3.

    Science.gov (United States)

    1967-09-01

    eicosane . A good fit was obtained with C I = 768 cal/mole for the energy difference between trans and gauche states, and gauche rotations of opposite...transition temperatures for the n-alkanes, hexane to eicosane . A good fit was obtained with E1 =768 cal/molf for the energy difference between trans and

  3. Glass transitions of barley starch and protein in the endosperm and isolated form

    NARCIS (Netherlands)

    Donkelaar, van L.H.G.; Martinez, J.T.; Frijters, H.; Noordman, T.R.; Boom, R.M.; Goot, van der A.J.

    2015-01-01

    When studying the glass-to-rubber transition inside natural materials, it is important to take into account not only the moisture content but also the moisture distribution over the components in the material. We measured the Tg of protein and starch isolated from barley at different moisture

  4. Studying the Adhesion Force and Glass Transition of Thin Polystyrene Films by Atomic Force Microscopy

    DEFF Research Database (Denmark)

    Kang, Hua; Qian, Xiaoqin; Guan, Li

    2018-01-01

    microscopy (AFM)-based forcedistance curve to study the relaxation dynamics and the film thickness dependence of glass transition temperature (T-g) for normal thin polystyrene (PS) films supported on silicon substrate. The adhesion force (F-ad) between AFM tip and normal thin PS film surfaces...

  5. Physical stability of drugs after storage above and below the glass transition temperature: Relationship to glass-forming ability.

    Science.gov (United States)

    Alhalaweh, Amjad; Alzghoul, Ahmad; Mahlin, Denny; Bergström, Christel A S

    2015-11-10

    Amorphous materials are inherently unstable and tend to crystallize upon storage. In this study, we investigated the extent to which the physical stability and inherent crystallization tendency of drugs are related to their glass-forming ability (GFA), the glass transition temperature (Tg) and thermodynamic factors. Differential scanning calorimetry was used to produce the amorphous state of 52 drugs [18 compounds crystallized upon heating (Class II) and 34 remained in the amorphous state (Class III)] and to perform in situ storage for the amorphous material for 12h at temperatures 20°C above or below the Tg. A computational model based on the support vector machine (SVM) algorithm was developed to predict the structure-property relationships. All drugs maintained their Class when stored at 20°C below the Tg. Fourteen of the Class II compounds crystallized when stored above the Tg whereas all except one of the Class III compounds remained amorphous. These results were only related to the glass-forming ability and no relationship to e.g. thermodynamic factors was found. The experimental data were used for computational modeling and a classification model was developed that correctly predicted the physical stability above the Tg. The use of a large dataset revealed that molecular features related to aromaticity and π-π interactions reduce the inherent physical stability of amorphous drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Deuteron NMR (Nuclear Magnetic Resonance) in relation to the glass transition in polymers

    Science.gov (United States)

    Roessler, E.; Sillescu, H.; Spiess, H. W.; Wallwitz, R.

    1983-01-01

    H-2NMR is introduced as a tool for investigating slow molecular motion in the glass transition region of amorphous polymers. In particular, we compare H-2 spin alignment echo spectra of chain deuterated polystyrene with model calculations for restricted rotational Brownian motion. Molecular motion in the polyztyrene-toluene system has been investigated by analyzing H-2NMR of partially deuterated polystyrene and toluene, respectively. The diluent mobility in the mixed glass has been decomposed into solid and liquid components where the respective average correlation times differ by more than 5 decades.

  7. Photoswitching of glass transition temperatures of azobenzene-containing polymers induces reversible solid-to-liquid transitions

    Science.gov (United States)

    Zhou, Hongwei; Xue, Changguo; Weis, Philipp; Suzuki, Yasuhito; Huang, Shilin; Koynov, Kaloian; Auernhammer, Günter K.; Berger, Rüdiger; Butt, Hans-Jürgen; Wu, Si

    2017-02-01

    The development of polymers with switchable glass transition temperatures (Tg) can address scientific challenges such as the healing of cracks in high-Tg polymers and the processing of hard polymers at room temperature without using plasticizing solvents. Here, we demonstrate that light can switch the Tg of azobenzene-containing polymers (azopolymers) and induce reversible solid-to-liquid transitions of the polymers. The azobenzene groups in the polymers exhibit reversible cis-trans photoisomerization abilities. Trans azopolymers are solids with Tg above room temperature, whereas cis azopolymers are liquids with Tg below room temperature. Because of the photoinduced solid-to-liquid transitions of these polymers, light can reduce the surface roughness of azopolymer films by almost 600%, repeatedly heal cracks in azopolymers, and control the adhesion of azopolymers for transfer printing. The photoswitching of Tg provides a new strategy for designing healable polymers with high Tg and allows for control over the mechanical properties of polymers with high spatiotemporal resolution.

  8. Common behaviors associated with the glass transitions of water-like models

    Science.gov (United States)

    Horstmann, R.; Vogel, M.

    2017-07-01

    We perform molecular dynamics simulations to ascertain effects of the molecular polarity on structural and dynamical properties of water-like systems, in particular, on their glassy slowdown. To systematically vary the molecular dipole moments, we scale the partial charges of the established SPC/E and TIP4P/2005 models. In broad ranges of the molecular polarity, the studied SPC/E and TIP4P/2005 descendants show a density anomaly, which can be attributed to the removal of water molecules interstitial between the first and the second neighbor shells upon cooling. While all considered modified water models behave as typical glass formers, the structural relaxation time τ heavily depends on the molecular dipole moment. This large dynamical diversity is exploited to systematically ascertain characteristic properties of glass-forming liquids. For all studied water-like systems, we observe a close relation between the activation energy E∞ describing the Arrhenius behavior of the regular liquid and the glass transition temperature Tg characterizing the supercooled liquid, explicitly, E∞/Tg≈10 . Moreover, decomposing the activation energy of the structural relaxation according to E (T ) =E∞+Ec(T ) , we show that the glassy slowdown of all modified water molecules can fully be traced back to an exponential temperature dependence of the contribution Ec(T) related to cooperative dynamics. Extrapolation of this behavior suggests a common value at the glass transition temperature, Ec(Tg ) /Tg≈25 . Finally, we discuss links between the structural relaxation and the vibrational displacement, as proposed in various theoretical approaches to the glass transition.

  9. Anomalous glass transition behavior of SBR-Al2O3 nanocomposites at small filler concentrations

    Science.gov (United States)

    Sushko, Rymma; Filimon, Marlena; Dannert, Rick; Elens, Patrick; Sanctuary, Roland; Baller, Jörg

    2014-10-01

    Elastomers filled with hard nanoparticles are of great technical importance for the rubber industry. In general, fillers improve mechanical properties of polymer materials, e.g. elastic moduli, tensile strength etc. The smaller the size of the particles, the larger is the interface where interactions between polymer molecules and fillers can generate new properties. Using temperature-modulated differential scanning calorimetry and dynamic mechanical analysis, we investigated the properties of pure styrene-butadiene rubber (SBR) and SBR/alumina nanoparticles. Beside a reinforcement effect seen in the complex elastic moduli, small amounts of nanoparticles of about 2 wt% interestingly lead to an acceleration of the relaxation modes responsible for the thermal glass transition. This leads to a minimum in the glass transition temperature as a function of nanoparticle content in the vicinity of this critical concentration. The frequency dependent elastic moduli are used to discuss the possible reduction of the entanglement of rubber molecules as one cause for this unexpected behavior.

  10. Understanding ductile-to-brittle transition of metallic glasses from shear transformation zone dilatation

    Directory of Open Access Journals (Sweden)

    M.Q. Jiang

    2015-08-01

    Full Text Available A theoretical model that takes into account the free-volume aided cooperative shearing of shear transformation zones (STZs is developed to quantitatively understand the ductile-to-brittle transition (DBT of metallic glasses. The STZ dilatational strain is defined as the ratio of STZ-activated free volume to STZ volume itself. The model demonstrates that the STZ dilatational strain will increase drastically and exceed the characteristic shear strain of STZ as temperature decreases below a critical value. This critical temperature is in good agreement with the experimentally measured DBT temperature. Our results suggest that the DBT of metallic glasses is underpinned by the transition of atomic-cluster motions from STZ-type rearrangements to dilatational processes (termed tension transformation zones (TTZs.

  11. Anomalous glass transition behavior of SBR-Al₂O₃ nanocomposites at small filler concentrations.

    Science.gov (United States)

    Sushko, Rymma; Filimon, Marlena; Dannert, Rick; Elens, Patrick; Sanctuary, Roland; Baller, Jörg

    2014-10-24

    Elastomers filled with hard nanoparticles are of great technical importance for the rubber industry. In general, fillers improve mechanical properties of polymer materials, e.g. elastic moduli, tensile strength etc. The smaller the size of the particles, the larger is the interface where interactions between polymer molecules and fillers can generate new properties. Using temperature-modulated differential scanning calorimetry and dynamic mechanical analysis, we investigated the properties of pure styrene-butadiene rubber (SBR) and SBR/alumina nanoparticles. Beside a reinforcement effect seen in the complex elastic moduli, small amounts of nanoparticles of about 2 wt% interestingly lead to an acceleration of the relaxation modes responsible for the thermal glass transition. This leads to a minimum in the glass transition temperature as a function of nanoparticle content in the vicinity of this critical concentration. The frequency dependent elastic moduli are used to discuss the possible reduction of the entanglement of rubber molecules as one cause for this unexpected behavior.

  12. Mathematical modeling of photoinitiated coating degradation: Effects of coating glass transition temperature and light stabilizers

    DEFF Research Database (Denmark)

    Kiil, Søren; G.de With, R.A.T.M.Van Benthem

    2013-01-01

    A mathematical model, describing coating degradation mechanisms of thermoset coatings exposed to ultraviolet radiation and humidity at constant temperature, was extended to simulate the behavior of a coating with a low glass transition temperature. The effects of adding light stabilizers (a UV......, and simulates the transient development of an oxidation zone. Simulations are in good agreement with experimental data for a fast degrading epoxy-amine coating with a glass transition temperature of −50°C. It was found that the degradation rate of the non-stabilized coating was influenced significantly...... by the diffusion rate of oxygen in the oxidation zone, whereas light absorption by the photoproducts formed was only a secondary effect. On the other hand, the degradation rate of the stabilized coating was mainly influenced by the light absorption capability of the coating and in this case there was no oxygen...

  13. Transition to Glass: Pilot Training for High-Technology Transport Aircraft

    Science.gov (United States)

    Wiener, Earl L.; Chute, Rebecca D.; Moses, John H.

    1999-01-01

    This report examines the activities of a major commercial air carrier between 1993 and late 1996 as it acquired an advanced fleet of high-technology aircraft (Boeing 757). Previously, the airline's fleet consisted of traditional (non-glass) aircraft, and this report examines the transition from a traditional fleet to a glass one. A total of 150 pilots who were entering the B-757 transition training volunteered for the study, which consisted of three query phases: (1) first day of transition training, (2) 3 to 4 months after transition training, and (3) 12 to 14 months after initial operating experience. Of these initial 150 pilots, 99 completed all three phases of the study, with each phase consisting of probes on attitudes and experiences associated with their training and eventual transition to flying the line. In addition to the three questionnaires, 20 in-depth interviews were conducted. Although the primary focus of this study was on the flight training program, additional factors such as technical support, documentation, and training aids were investigated as well. The findings generally indicate that the pilot volunteers were highly motivated and very enthusiastic about their training program. In addition, the group had low levels of apprehension toward automation and expressed a high degree of satisfaction toward their training. However, there were some concerns expressed regarding the deficiencies in some of the training aids and lack of a free-play flight management system training device.

  14. Glasses

    DEFF Research Database (Denmark)

    Dyre, Jeppe

    2004-01-01

    The temperature dependence of the viscosity of most glassforming liquids is known to depart significantly from the classical Arrhenius behaviour of simple fluids. The discovery of an unexpected correlation between the extent of this departure and the Poisson ratio of the resulting glass could lead...... to new understanding of glass ageing and viscous liquid dynamics....

  15. SEM Analysis of the Interfacial Transition Zone between Cement-Glass Powder Paste and Aggregate of Mortar under Microwave Curing

    National Research Council Canada - National Science Library

    Kong, Yaning; Wang, Peiming; Liu, Shuhua; Zhao, Guorong; Peng, Yu

    2016-01-01

      In order to investigate the effects of microwave curing on the microstructure of the interfacial transition zone of mortar prepared with a composite binder containing glass powder and to explain...

  16. Glass transition-related changes in molecular mobility below glass transition temperature of freeze-dried formulations, as measured by dielectric spectroscopy and solid state nuclear magnetic resonance.

    Science.gov (United States)

    Yoshioka, Sumie; Aso, Yukio

    2005-02-01

    The purpose of this study was to explore why changes in the molecular mobility associated with glass transition, the timescale of which is on the order of 100 s, can be detected by measuring the nuclear magnetic resonance relaxation times that reflect molecular motions on the order of 10 kHz and 1 MHz. The molecular motions in freeze-dried dextran 40k, dextran 1k, isomaltotriose (IMT), and alpha-glucose comprising a common unit but with different glass transition temperatures, were investigated by dielectric spectroscopy (DES) in the frequency range of 0.01 Hz to 100 kHz and in the temperature range of -20 degrees to 200 degrees C, in order to compare with the molecular motions reflected in nuclear magnetic resonance relaxation times. The alpha-relaxation process for freeze-dried alpha-glucose was visualized by DES, whereas those for freeze-dried dextran 40k, dextran 1k, and IMT were too slow to be visualized by DES. The latter freeze-dried cakes exhibited quasi-dc polarization because of proton-hopping-like motion rather than alpha-relaxation process. The correlation time (tau(c)) for the backbone carbon of dextran 40k and IMT, calculated from the measured value of spin-lattice relaxation time in the rotating frame, was found to be close to the relaxation time of proton-hopping-like motion determined by DES (tau(DES)) at temperatures around glass transition temperature. The timescales of molecular motions reflected in the tau(c) and tau(DES) were significantly smaller than that of motions leading to molecular rearrangement (molecular rearrangement motions), which correspond to alpha-relaxation. However, the shapes of temperature dependence for the tau(c) and tau(DES) were similar to that of the calorimetrically determined relaxation time of molecular rearrangement motions. Results suggest that the molecular motions reflected in the tau(c) and tau(DES) are linked to molecular rearrangement motions, such that enhancement of molecular rearrangement motions enhances

  17. The peculiar behavior of the glass transition temperature of amorphous drug-polymer films coated on inert sugar spheres.

    Science.gov (United States)

    Dereymaker, Aswin; Van Den Mooter, Guy

    2015-05-01

    Fluid bed coating has been proposed in the past as an alternative technology for manufacturing of drug-polymer amorphous solid dispersions, or so-called glass solutions. It has the advantage of being a one-step process, and thus omitting separate drying steps, addition of excipients, or manipulation of the dosage form. In search of an adequate sample preparation method for modulated differential scanning calorimetry analysis of beads coated with glass solutions, glass transition broadening and decrease of the glass transition temperature (Tg ) were observed with increasing particle size of crushed coated beads and crushed isolated films of indomethacin (INDO) and polyvinylpyrrolidone (PVP). Substituting INDO with naproxen gave comparable results. When ketoconazole was probed or the solvent in INDO-PVP films was switched to dichloromethane (DCM) or a methanol-DCM mixture, two distinct Tg regions were observed. Small particle sizes had a glass transition in the high Tg region, and large particle sizes had a glass transition in the low Tg region. This particle size-dependent glass transition was ascribed to different residual solvent amounts in the bulk and at the surface of the particles. A correlation was observed between the deviation of the Tg from that calculated from the Gordon-Taylor equation and the amount of residual solvent at the Tg of particles with different sizes. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  18. Correlating the Network Topology of Oxide Glasses with their Chemical Durability.

    Science.gov (United States)

    Mascaraque, Nerea; Bauchy, Mathieu; Smedskjaer, Morten M

    2017-02-09

    Glasses gradually dissolve and corrode when they are exposed to aqueous solutions, and for many applications it is necessary to understand and predict the kinetics of the glass dissolution. Despite the recent progress in understanding the impact of chemical composition on the dissolution rate, a detailed understanding of the structural and topological origin of chemical durability in solutions of different pH is still largely lacking. Such knowledge would enable the tailoring of glass dissolution kinetics as a function of chemical composition. In a recent study focusing on silicate minerals and glasses, a direct relation was demonstrated between the dissolution rate at high pH and the number of chemical topological constraints per atom (nc) acting within the molecular network [Pignatelli, I.; Kumar, A.; Bauchy, M.; Sant, G. Langmuir 2016, 32, 4434-4439]. Here, we extend this work by studying the bulk dissolution rate (Dr) of a wider range of oxide glasses in various acidic, neutral, and basic solutions. The glass compositions have been selected to obtain a wide range of chemistries and values of nc, from flexible phosphate glasses to stressed-rigid aluminosilicate glasses. We show that, in flexible glasses, the internal modes of deformation facilitate the hydration of the network, whereas, in stressed-rigid glasses, the high number of constraints largely inhibits hydration in basic, neutral, and acidic solutions. Our study of chemical dissolution also allows establishing the kinetic mechanisms, which is controlled through an effective activation energy and depends on pH and glass topology. The energy barrier that needs to be overcome to break a unit atomic constraint is approximately constant for pH > 2, but then decreases at lower pH, indicating a change in dissolution mechanism from hydrolysis to ion exchange at low pH. Thus, with this research and existing topological models, the atomistic design of new oxide glasses with a specific chemical durability for a

  19. Complex quantum network geometries: Evolution and phase transitions

    Science.gov (United States)

    Bianconi, Ginestra; Rahmede, Christoph; Wu, Zhihao

    2015-08-01

    Networks are topological and geometric structures used to describe systems as different as the Internet, the brain, or the quantum structure of space-time. Here we define complex quantum network geometries, describing the underlying structure of growing simplicial 2-complexes, i.e., simplicial complexes formed by triangles. These networks are geometric networks with energies of the links that grow according to a nonequilibrium dynamics. The evolution in time of the geometric networks is a classical evolution describing a given path of a path integral defining the evolution of quantum network states. The quantum network states are characterized by quantum occupation numbers that can be mapped, respectively, to the nodes, links, and triangles incident to each link of the network. We call the geometric networks describing the evolution of quantum network states the quantum geometric networks. The quantum geometric networks have many properties common to complex networks, including small-world property, high clustering coefficient, high modularity, and scale-free degree distribution. Moreover, they can be distinguished between the Fermi-Dirac network and the Bose-Einstein network obeying, respectively, the Fermi-Dirac and Bose-Einstein statistics. We show that these networks can undergo structural phase transitions where the geometrical properties of the networks change drastically. Finally, we comment on the relation between quantum complex network geometries, spin networks, and triangulations.

  20. Study of Glass-Transition Kinetics of Pb-Modified SeIn System by Using Non-isothermal Differential Scanning Calorimetry

    Science.gov (United States)

    Ram, Indra Sen; Singh, Kedar

    2014-01-01

    Glass-transition kinetics of ( 0, 5, 10, and 15) chalcogenide glasses have been carried out at different heating rates by using differential scanning calorimeter (DSC) under the non-isothermal condition. The glass-transition temperature and peak glass-transition temperature have been determined from DSC thermograms. The reduced glass temperature , total relaxation time thermal-stability parameters and , the activation energy of glass transition , the fragility index , and the average coordination number have been calculated on the basis of the experimental results. The temperature differences , and are found to be maxima for glass. This indicates that glass has the highest thermal stability and glass-forming ability in the investigated compositional range. These results could be explained on the basis of modification of the chemical bond formation due to incorporation of Pb in the Se-In glassy matrix.

  1. Correlation between floppy to rigid transitions and non-Arrhenius conductivity in glasses.

    Science.gov (United States)

    Malki, M; Micoulaut, M; Chaimbault, F; Vaills, Y

    2006-04-14

    Non-Arrhenius behavior is observed for a number of virgin potassium silicate glasses (1-x)SiO2-xK2O with a potassium oxide concentration larger than a certain value x = x(c). Recovering of Arrhenius behavior is provided by the annealing that enhances densification. These various results are the manifestation of the floppy or rigid nature of the network. Compositional effects and saturation with temperature can be analyzed with a combination of constraint theory and a point defect model. They underscore the key role played by network rigidity for the understanding of conduction and saturation effects in glassy electrolytes.

  2. Transition Towards An Integrated Network Organisation

    DEFF Research Database (Denmark)

    Mykhaylenko, Alona; Wæhrens, Brian Vejrum

    2016-01-01

    Management of internationally dispersed and networked operations has been in the focus of research attention. However, the existing studies underestimate the incrementality of changes shaping such organisations. This work investigates how organisations evolve into network structures, with particu......Management of internationally dispersed and networked operations has been in the focus of research attention. However, the existing studies underestimate the incrementality of changes shaping such organisations. This work investigates how organisations evolve into network structures...

  3. Interaction network based early-warning indicators of vegetation transitions

    NARCIS (Netherlands)

    Tirabassi, Giulio; Viebahn, Jan; Dakos, V.; Dijkstra, Hendrik; Masoller, C.; Rietkerk, Max; Dekker, Stefan

    2014-01-01

    Changes in vegetation patterns in semi-arid regions can precede the abrupt transition to bare soil. Here, complex network techniques are used to develop novel early-warning indicators for these desertification transitions. These indicators are applied to results from a local positive feedback

  4. Neurodynamics of up and down Transitions in Network Model

    OpenAIRE

    Xuying Xu; Rubin Wang

    2013-01-01

    This paper focuses on the neurodynamical research of a small neural network that consists of 25 neurons. We study the periodic spontaneous activity and transitions between up and down states without synaptic input. The results demonstrate that these transitions are bidirectional or unidirectional with the parameters changing, which not only reveals the function of the cortex, but also cohere with the experiment results.

  5. On the glass transition of the one-component metallic melts

    Science.gov (United States)

    Fedorchenko, A. I.

    2017-10-01

    In this paper, the conditions for one-component metallic melts vitrification by quenching from a liquid state were formulated. It is shown that the tendency to the glass formation drastically increases with the temperature of melting. The maximum glass layer thickness and the associated cooling rates along with the vitrification temperatures was determined for Al, Cu, and Ni melts deposited on the Cu substrate. The results are in agreement with the available experimental data. Based on analytical solution of the impinging droplet solidification, the numerical value of the early-introduced asymptotic Ω criterion, which separates equilibrium and non-equilibrium phase transitions, was determined. Good agreement between the calculated and experimental values of the thickness of the splats shows that Ω criterion indeed predicts a priori a scenario of solidification.

  6. Glass Transitions in Monodisperse Cluster-Forming Ensembles: Vortex Matter in Type-1.5 Superconductors

    Science.gov (United States)

    Díaz-Méndez, Rogelio; Mezzacapo, Fabio; Lechner, Wolfgang; Cinti, Fabio; Babaev, Egor; Pupillo, Guido

    2017-02-01

    At low enough temperatures and high densities, the equilibrium configuration of an ensemble of ultrasoft particles is a self-assembled, ordered, cluster crystal. In the present Letter, we explore the out-of-equilibrium dynamics for a two-dimensional realization, which is relevant to superconducting materials with multiscale intervortex forces. We find that, for small temperatures following a quench, the suppression of the thermally activated particle hopping hinders the ordering. This results in a glass transition for a monodispersed ensemble, for which we derive a microscopic explanation in terms of an "effective polydispersity" induced by multiscale interactions. This demonstrates that a vortex glass can form in clean systems of thin films of "type-1.5" superconductors. An additional setup to study this physics can be layered superconducting systems, where the shape of the effective vortex-vortex interactions can be engineered.

  7. The major transitions of life from a network perspective

    Directory of Open Access Journals (Sweden)

    Bela eSuki

    2012-04-01

    Full Text Available Many attempts have been made to understand the origin of life and biological complexity both at the experimental and theoretical levels but neither is fully explained. In an influential work, Maynard Smith and Szatmáry(The major transitions in evolution. Oxford; New York: W.H. Freeman Spektrum, 1995 argued that the majority of the increase in complexity is not gradual, but it is associated with a few so called major transitions along the way of the evolution of life. For each major transition, they identified specific mechanisms that could account for the change in complexity related to information transmission across generations. In this work, I propose that the sudden and unexpected improvement in the functionality of an organism that followed a major transition was enabled by a phase transition in the network structure associated with that function. The increase in complexity following a major transition is therefore directly linked to the emergence of a novel structure-function relation which altered the course of evolution. As a consequence, emergent phenomena arising from these network phase transitions can serve as a common organizing principle for understanding the major transitions. As specific examples, I analyze the emergence of life, the emergence of the genetic apparatus, the rise of the eukaryotic cells, the evolution of movement and mechanosensitivity and the emergence of consciousness. Finally, I discuss the implications of network associated phase transitions to issues that bear relevance to the history, the immediate present and perhaps the future, of life.

  8. Fuel Pellets from Wheat Straw: The Effect of Lignin Glass Transition and Surface Waxes on Pelletizing Properties

    DEFF Research Database (Denmark)

    Stelte, Wolfgang; Clemons, Craig; Holm, Jens K.

    2012-01-01

    are investigated by comparing wheat straw before and after organic solvent extraction. The lignin glass transition temperature for wheat straw and extracted wheat straw is determined by dynamic mechanical thermal analysis. At a moisture content of 8%, transitions are identified at 53°C and 63°C, respectively...

  9. Glass transition of polymers in bulk, confined geometries, and near interfaces

    Science.gov (United States)

    Napolitano, Simone; Glynos, Emmanouil; Tito, Nicholas B.

    2017-03-01

    When cooled or pressurized, polymer melts exhibit a tremendous reduction in molecular mobility. If the process is performed at a constant rate, the structural relaxation time of the liquid eventually exceeds the time allowed for equilibration. This brings the system out of equilibrium, and the liquid is operationally defined as a glass—a solid lacking long-range order. Despite almost 100 years of research on the (liquid/)glass transition, it is not yet clear which molecular mechanisms are responsible for the unique slow-down in molecular dynamics. In this review, we first introduce the reader to experimental methodologies, theories, and simulations of glassy polymer dynamics and vitrification. We then analyse the impact of connectivity, structure, and chain environment on molecular motion at the length scale of a few monomers, as well as how macromolecular architecture affects the glass transition of non-linear polymers. We then discuss a revised picture of nanoconfinement, going beyond a simple picture based on interfacial interactions and surface/volume ratio. Analysis of a large body of experimental evidence, results from molecular simulations, and predictions from theory supports, instead, a more complex framework where other parameters are relevant. We focus discussion specifically on local order, free volume, irreversible chain adsorption, the Debye-Waller factor of confined and confining media, chain rigidity, and the absolute value of the vitrification temperature. We end by highlighting the molecular origin of distributions in relaxation times and glass transition temperatures which exceed, by far, the size of a chain. Fast relaxation modes, almost universally present at the free surface between polymer and air, are also remarked upon. These modes relax at rates far larger than those characteristic of glassy dynamics in bulk. We speculate on how these may be a signature of unique relaxation processes occurring in confined or heterogeneous polymeric

  10. Ferroic glasses

    Science.gov (United States)

    Ji, Yuanchao; Wang, Dong; Wang, Yu; Zhou, Yumei; Xue, Dezhen; Otsuka, Kazuhiro; Wang, Yunzhi; Ren, Xiaobing

    2017-10-01

    Ferroic glasses (strain glass, relaxor and cluster spin glass) refer to frozen disordered states in ferroic systems; they are conjugate states to the long-range ordered ferroic states—the ferroic crystals. Ferroic glasses exhibit unusual properties that are absent in ferroic crystals, such as slim hysteresis and gradual property changes over a wide temperature range. In addition to ferroic glasses and ferroic crystals, a third ferroic state, a glass-ferroic (i.e., a composite of ferroic glass and ferroic crystal), can be produced by the crystallization transition of ferroic glasses. It can have a superior property not possessed by its two components. These three classes of ferroic materials (ferroic crystal, ferroic glass and glass-ferroic) correspond to three transitions (ferroic phase transition, ferroic glass transition and crystallization transition of ferroic glass, respectively), as demonstrated in a generic temperature vs. defect-concentration phase diagram. Moreover, through constructing a phase field model, the microstructure evolution of three transitions and the phase diagram can be reproduced, which reveals the important role of point defects in the formation of ferroic glass and glass-ferroic. The phase diagram can be used to design various ferroic glasses and glass-ferroics that may exhibit unusual properties.

  11. Analysis of a Polystyrene-Toluene System through "Dynamic" Sorption Tests: Glass Transitions and Retrograde Vitrification.

    Science.gov (United States)

    Pierleoni, Davide; Minelli, Matteo; Scherillo, Giuseppe; Mensitieri, Giuseppe; Loianno, Valerio; Bonavolontà, Francesco; Doghieri, Ferruccio

    2017-10-26

    Exposing a glassy polymer to a fluid phase (in gaseous or liquid state) containing a low molecular weight compound results in the sorption of the latter within the polymer, inducing, among other effects, the plasticization of the material which also promotes a change in the glass transition temperature. The amount of sorbed penetrant is often related in a complex fashion to the temperature and pressure of the fluid, thus determining that the locus of glass transition, when represented in pressure-temperature coordinates, may display as well rather complex patterns. This is an issue of particular importance in several applications of glassy polymers. In particular, we investigated the behavior of polystyrene in contact with toluene vapor by performing several modes of dynamic sorption experiments, in which the rate of change of the temperature of the system and/or of the pressure of the vapor phase are controlled with high accuracy, with the aim of creating a map of rubbery and glassy states of the polymer as a function of temperature and pressure of the toluene vapor. Isothermal tests were performed by changing the pressure at a controlled rate, isobaric tests were performed by changing the temperature at a controlled rate, and isoactivity tests were performed by concurrently changing, in a proper way, both temperature and pressure. A relevant feature resulting from these experiments is the presence of a discontinuity in the slope of the mass of toluene sorbed within polystyrene reported as a function of temperature and/or pressure. This discontinuity has been interpreted as the indication of the occurrence of a glass transition. The elaboration of the experimental results allowed identification of the pressure/temperature conditions at which rubbery or glassy states of the polymer mixture are established. Quite interestingly, the system displays the so- called "retrograde vitrification" phenomenon, which consists of the occurrence of a rubbery-to-glassy state

  12. Glass-transition temperature gradient in nanocomposites: evidence from nuclear magnetic resonance and differential scanning calorimetry.

    Science.gov (United States)

    Papon, Aurélie; Montes, Hélène; Hanafi, Mohamed; Lequeux, François; Guy, Laurent; Saalwächter, Kay

    2012-02-10

    The slowing-down of the dynamics of a polymer chain near a surface has been observed for many years now. Here we show that the behavior of model nanocomposites can be quantitatively described with a gradient of glass-transition temperature. We describe with a single parameter-the range of this gradient-the temperature and solvent effect on the spin relaxation dynamics. Moreover, this parameter allows a quantitative description of the nanocomposite calorimetric response from the one of the bulk polymer.

  13. Brillouin light scattering from shear waves in an epoxy resin through the glass transition

    Science.gov (United States)

    Comez, L.; Fioretto, D.; Verdini, L.; Rolla, P. A.

    1997-05-01

    The temperature dependences of the characteristic frequency and lifetime of hypersonic transverse acoustic waves in the epoxy system EPON 828 have been probed by means of the Brillouin light scattering technique. Evidence has been found of a very broad dispersion region, together with a discontinuity close to the glass transition temperature 0953-8984/9/19/016/img7. For temperatures higher than 0953-8984/9/19/016/img7, the shear loss data obtained from Brillouin spectra are in quantitative agreement with dielectric data for the same system. For lower temperatures, the Brillouin data deviate from the dielectric ones, the former being more sensitive to the secondary relaxation processes.

  14. Predicting the glass transition temperature as function of crosslink density and polymer interactions in rubber compounds

    Science.gov (United States)

    D'Escamard, Gabriella; De Rosa, Claudio; Auriemma, Finizia

    2016-05-01

    Crosslink sulfur density in rubber compounds and interactions in polymer blends are two of the composition elements that affect the rubber compound properties and glass transition temperature (Tg), which is a marker of polymer properties related to its applications. Natural rubber (NR), butadiene rubber (BR) and styrene-butadiene rubber (SBR) compounds were investigated using calorimetry (DSC) and dynamic mechanical analysis (DMA). The results indicate that the Di Marzio's and Schneider's Models predict with accuracy the dependence of Tg on crosslink density and composition in miscible blends, respectively, and that the two model may represent the base to study the relevant "in service" properties of real rubber compounds.

  15. Molecular dynamics simulations of disordered materials from network glasses to phase-change memory alloys

    CERN Document Server

    Massobrio, Carlo; Bernasconi, Marco; Salmon, Philip S

    2015-01-01

    This book is a unique reference work in the area of atomic-scale simulation of glasses. For the first time, a highly selected panel of about 20 researchers provides, in a single book, their views, methodologies and applications on the use of molecular dynamics as a tool to describe glassy materials. The book covers a wide range of systems covering ""traditional"" network glasses, such as chalcogenides and oxides, as well as glasses for applications in the area of phase change materials. The novelty of this work is the interplay between molecular dynamics methods (both at the classical and firs

  16. Transitions in Smokers' Social Networks After Quit Attempts: A Latent Transition Analysis.

    Science.gov (United States)

    Bray, Bethany C; Smith, Rachel A; Piper, Megan E; Roberts, Linda J; Baker, Timothy B

    2016-12-01

    Smokers' social networks vary in size, composition, and amount of exposure to smoking. The extent to which smokers' social networks change after a quit attempt is unknown, as is the relation between quitting success and later network changes. Unique types of social networks for 691 smokers enrolled in a smoking-cessation trial were identified based on network size, new network members, members' smoking habits, within network smoking, smoking buddies, and romantic partners' smoking. Latent transition analysis was used to identify the network classes and to predict transitions in class membership across 3 years from biochemically assessed smoking abstinence. Five network classes were identified: Immersed (large network, extensive smoking exposure including smoking buddies), Low Smoking Exposure (large network, minimal smoking exposure), Smoking Partner (small network, smoking exposure primarily from partner), Isolated (small network, minimal smoking exposure), and Distant Smoking Exposure (small network, considerable nonpartner smoking exposure). Abstinence at years 1 and 2 was associated with shifts in participants' social networks to less contact with smokers and larger networks in years 2 and 3. In the years following a smoking-cessation attempt, smokers' social networks changed, and abstinence status predicted these changes. Networks defined by high levels of exposure to smokers were especially associated with continued smoking. Abstinence, however, predicted transitions to larger social networks comprising less smoking exposure. These results support treatments that aim to reduce exposure to smoking cues and smokers, including partners who smoke. Prior research has shown that social network features predict the likelihood of subsequent smoking cessation. The current research illustrates how successful quitting predicts social network change over 3 years following a quit attempt. Specifically, abstinence predicts transitions to networks that are larger and afford

  17. The major transitions of life from a network perspective.

    Science.gov (United States)

    Suki, Béla

    2012-01-01

    Many attempts have been made to understand the origin of life and biological complexity both at the experimental and theoretical levels but neither is fully explained. In an influential work, Maynard Smith and Szathmáry (1995) argued that the majority of the increase in complexity is not gradual, but it is associated with a few so-called major transitions along the way of the evolution of life. For each major transition, they identified specific mechanisms that could account for the change in complexity related to information transmission across generations. In this work, I propose that the sudden and unexpected improvement in the functionality of an organism that followed a major transition was enabled by a phase transition in the network structure associated with that function. The increase in complexity following a major transition is therefore directly linked to the emergence of a novel structure-function relation which altered the course of evolution. As a consequence, emergent phenomena arising from these network phase transitions can serve as a common organizing principle for understanding the major transitions. As specific examples, I analyze the emergence of life, the emergence of the genetic apparatus, the rise of the eukaryotic cells, the evolution of movement and mechanosensitivity, and the emergence of consciousness. Finally, I discuss the implications of network associated phase transitions to issues that bear relevance to the history, the immediate present and perhaps the future, of life.

  18. An all-glass microfluidic network with integrated amorphous silicon photosensors for on-chip monitoring of enzymatic biochemical assay

    NARCIS (Netherlands)

    Costantini, Francesca; Tiggelaar, Roald M.; Salvio, Riccardo; Nardecchia, Marco; Schlautmann, Stefan; Manetti, Cesare; Gardeniers, Han J.G.E.; de Cesare, Giampiero; Caputo, Domenico; Nascetti, Augusto

    2017-01-01

    A lab-on-chip system, integrating an all-glass microfluidics and on-chip optical detection, was developed and tested. The microfluidic network is etched in a glass substrate, which is then sealed with a glass cover by direct bonding. Thin film amorphous silicon photosensors have been fabricated on

  19. Weak- versus strong-disorder superfluid—Bose glass transition in one dimension

    Science.gov (United States)

    Doggen, Elmer V. H.; Lemarié, Gabriel; Capponi, Sylvain; Laflorencie, Nicolas

    2017-11-01

    Using large-scale simulations based on matrix product state and quantum Monte Carlo techniques, we study the superfluid to Bose glass transition for one-dimensional attractive hard-core bosons at zero temperature, across the full regime from weak to strong disorder. As a function of interaction and disorder strength, we identify a Berezinskii-Kosterlitz-Thouless critical line with two different regimes. At small attraction where critical disorder is weak compared to the bandwidth, the critical Luttinger parameter Kc takes its universal Giamarchi-Schulz value Kc=3 /2 . Conversely, a nonuniversal Kc>3 /2 emerges for stronger attraction where weak-link physics is relevant. In this strong-disorder regime, the transition is characterized by self-similar power-law-distributed weak links with a continuously varying characteristic exponent α .

  20. Vanadium dioxide thin film with low phase transition temperature deposited on borosilicate glass substrate

    Energy Technology Data Exchange (ETDEWEB)

    Huang Zhangli; Chen Sihai, E-mail: cshai99@mail.hust.edu.cn; Wang Boqing; Huang Ying; Liu Nengfu; Xu Jin; Lai Jianjun

    2011-04-29

    A nanostructured vanadium dioxide (VO{sub 2}) thin film showing a low metal-insulator transition temperature of 30 {sup o}C has been fabricated through reactive ion beam sputtering followed by thermal annealing. The thin film was grown on borosilicate glass substrate at the temperature of 280 {sup o}C with a Si{sub 3}N{sub 4} buffer layer. Both scanning electron microscopy and atomic force microscopy images have been taken to investigate the configuration of VO{sub 2} thin film. The average height of the crystallite is 20 nm and the grain size ranges from 40 nm to 100 nm. The transmittance measured from low to high temperatures also reveals that the film possesses excellent switching property in infrared light at critical transition temperature, with switching efficiency of 52% at 2600 nm. This experiment paves the way of VO{sub 2} thin film's application in smart windows.

  1. Transition to Chaos in Random Neuronal Networks

    National Research Council Canada - National Science Library

    Jonathan Kadmon; Haim Sompolinsky

    2015-01-01

    .... Indeed, simplified rate-based neuronal networks with synaptic connections drawn from Gaussian distribution and sigmoidal nonlinearity are known to exhibit chaotic dynamics when the synaptic gain (i.e...

  2. Understanding the physical stability of freeze dried dosage forms from the glass transition temperature of the amorphous components.

    Science.gov (United States)

    Fitzpatrick, Shaun; Saklatvala, Robert

    2003-12-01

    Modulated differential scanning calorimetry has been applied to understanding the long-term physical stability of freeze-dried units. It is known that these units are liable to contract on exposure to elevated temperature or humidity. The contraction occurs when the storage temperature is above the glass transition temperature of the amorphous components in the system. The effect of moisture content on the glass transition temperature of the amorphous components in the system has been studied. By combining this information with the moisture sorption isotherm it has been demonstrated that it is possible to predict the temperature and humidity conditions that will induce contraction of the unit. The magnitude of the glass transition temperature is composed of the contribution of each of the amorphous components in the system. It is proposed that it should be possible to develop a more robust system by the rational selection of excipients that increase the glass transition temperature or by modification of the processing conditions to promote crystallization of components that would otherwise depress the glass transition temperature. Copyright 2003 Wiley-Liss, Inc.

  3. Correlation between floppy to rigid transitions and non-Arrhenius conductivity in glasses

    OpenAIRE

    Malki, M.; Micoulaut, M; Chaimbault, F.; Vaills, Y.

    2005-01-01

    Non-Arrhenius behaviour and fast increase of the ionic conductivity is observed for a number of potassium silicate glasses $(1-x)SiO_2-xK_2O$ with potassium oxide concentration larger than a certain value $x=x_c=0.14$. Recovering of Arrhenius behaviour is provided by the annealing that enhances densification. Conductivity furthermore obeys a percolation law with the same critical concentration $x_c$. These various results are the manifestation of the floppy or rigid nature of the network and ...

  4. Network Inoculation: Heteroclinics and phase transitions in an epidemic model

    CERN Document Server

    Yang, Hui; Gross, Thilo

    2016-01-01

    In epidemiological modelling, dynamics on networks, and in particular adaptive and heterogeneous networks have recently received much interest. Here we present a detailed analysis of a previously proposed model that combines heterogeneity in the individuals with adaptive rewiring of the network structure in response to a disease. We show that in this model qualitative changes in the dynamics occur in two phase transitions. In a macroscopic description one of these corresponds to a local bifurcation whereas the other one corresponds to a non-local heteroclinic bifurcation. This model thus provides a rare example of a system where a phase transition is caused by a non-local bifurcation, while both micro- and macro-level dynamics are accessible to mathematical analysis. The bifurcation points mark the onset of a behaviour that we call network inoculation. In the respective parameter region exposure of the system to a pathogen will lead to an outbreak that collapses, but leaves the network in a configuration wher...

  5. Phase transitions for information diffusion in random clustered networks

    Science.gov (United States)

    Lim, Sungsu; Shin, Joongbo; Kwak, Namju; Jung, Kyomin

    2016-09-01

    We study the conditions for the phase transitions of information diffusion in complex networks. Using the random clustered network model, a generalisation of the Chung-Lu random network model incorporating clustering, we examine the effect of clustering under the Susceptible-Infected-Recovered (SIR) epidemic diffusion model with heterogeneous contact rates. For this purpose, we exploit the branching process to analyse information diffusion in random unclustered networks with arbitrary contact rates, and provide novel iterative algorithms for estimating the conditions and sizes of global cascades, respectively. Showing that a random clustered network can be mapped into a factor graph, which is a locally tree-like structure, we successfully extend our analysis to random clustered networks with heterogeneous contact rates. We then identify the conditions for phase transitions of information diffusion using our method. Interestingly, for various contact rates, we prove that random clustered networks with higher clustering coefficients have strictly lower phase transition points for any given degree sequence. Finally, we confirm our analytical results with numerical simulations of both synthetically-generated and real-world networks.

  6. Determination of the Glass Transition Temperature of Freestanding and Supported Azo-Polymer Thin Films by Thermal Assisted Atomic Force Microscopy

    Science.gov (United States)

    Chernykh, Elena; Kharintsev, Sergey; Fishman, Alexandr; Alekseev, Alexander; Salakhov, Myakzuym

    2017-03-01

    In this paper we introduce and apply the method for determination of the glass transition temperature of the sub-100 nm thick freestanding and supported polymer films based on thermally assisted atomic force microscopy (AFM). In proposed approach changes of the phase of an oscillating AFM cantilever are used to determine glass transition temperature. An anomalous decrease of the glass transition temperature for both free-standing and supported azobenzene-functionalized polymer thin films is shown.

  7. Effect of sodium chloride on the glass transition of condensed starch systems.

    Science.gov (United States)

    Chuang, Lillian; Panyoyai, Naksit; Shanks, Robert; Kasapis, Stefan

    2015-10-01

    The present investigation deals with the structural properties of condensed potato starch-sodium chloride systems undergoing a thermally induced glass transition. Sample preparation included hot pressing at 120°C for 7 min to produce extensive starch gelatinisation. Materials covered a range of moisture contents from 3.6% to 18.8%, which corresponded to relative humidity values of 11% and 75%. Salt addition was up to 6.0% in formulations. Instrumental work was carried out with dynamic mechanical analysis in tension, modulated differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy and wide angle X-ray diffraction. Experimental conditions ensured the development of amorphous matrices that exhibited thermally reversible glassy consistency. Both moisture content and addition of sodium chloride affected the mechanical strength and glass transition temperature of polymeric systems. Sodium ions interact with chemical moieties of the polysaccharide chain to alter considerably structural properties, as compared to the starch-water matrix. Copyright © 2015. Published by Elsevier Ltd.

  8. Relaxation transition in glass-forming polybutadiene as revealed by nuclear resonance X-ray scattering.

    Science.gov (United States)

    Kanaya, Toshiji; Inoue, Rintaro; Saito, Makina; Seto, Makoto; Yoda, Yoshitaka

    2014-04-14

    We investigated the arrest mechanism of molecular motions in a glass forming polybutadiene near the glass transition using a new nuclear resonance synchrotron X-ray scattering technique to cover a wide time range (10(-9) to 10(-5) s) and a scattering vector Q range (9.6-40 nm(-1)), which have never been accessed by other methods. Owing to the wide time and Q ranges it was found for the first time that a transition of the α-process to the slow β-process (or the Johari-Goldstein process) was observed in a Q range higher than the first peak in the structure factor S(Q) at the critical temperature T(c) in the mode coupling theory. The results suggest the important roles of hopping motions below T(c), which was predicted by the recent extended mode coupling theory and the cooperative motions due to the strong correlation at the first peak in S(Q) in the arrest mechanism.

  9. Impact of caramelization on the glass transition temperature of several caramelized sugars. Part I: Chemical analyses.

    Science.gov (United States)

    Jiang, Bin; Liu, Yeting; Bhandari, Bhesh; Zhou, Weibiao

    2008-07-09

    This study aims to investigate the relationship between caramelization of several sugars including fructose, glucose, and sucrose and their glass transition temperature (Tg). Differential scanning calorimetry (DSC) was used for creating caramelized sugar samples as well as determining their glass transition temperature, which was found to decrease first and then increase as the holding time at the highest temperature increased. The extent of caramelization was quantified by UV-vis absorbance measurement and high-performance liquid chromatography analysis. Results showed that the amount of small molecules from the degradation of sugar increased very fast at the beginning of heating, and this increase slowed down in the later stage of caramelization. On the other hand, there was a lag phase in the formation of large molecules from the degradation of sugar at the beginning of heating, followed by a fast increase in the later stage of caramelization. The obtained results clearly indicate the impact of melting condition on the T g of sugars through formation of intermediates and end products of caramelization. Generally, when the heating condition is relatively mild, small molecules are formed first by decomposition of the sugar, which leads to a decrease of the overall Tg, and as the heating time becomes longer and/or the heating condition becomes more severe, polymerization takes over and more large molecules are formed, which results in an increase of the overall Tg. Mathematical modeling of the relationship will be presented as part II of the study in a separate paper.

  10. Impact of caramelization on the glass transition temperature of several caramelized sugars. Part II: Mathematical modeling.

    Science.gov (United States)

    Jiang, Bin; Liu, Yeting; Bhandari, Bhesh; Zhou, Weibiao

    2008-07-09

    Further to part I of this study, this paper discusses mathematical modeling of the relationship between caramelization of several sugars including fructose, glucose, and sucrose and their glass transition temperatures ( T g). Differential scanning calorimetry (DSC) was used for creating caramelized sugar samples and determining their glass transition temperatures ( T g). UV-vis absorbance measurement and high-performance liquid chromatography (HPLC) analysis were used for quantifying the extent of caramelization. Specifically, absorbances at 284 and 420 nm were obtained from UV-vis measurement, and the contents of sucrose, glucose, fructose, and 5-hydroxymethyl-furfural (HMF) in the caramelized sugars were obtained from HPLC measurements. Results from the UV and HPLC measurements were correlated with the Tg values measured by DSC. By using both linear and nonlinear regressions, two sets of mathematical models were developed for the prediction of Tg values of sugar caramels. The first set utilized information obtained from both UV-vis measurement and HPLC analysis, while the second set utilized only information from the UV-vis measurement, which is much easier to perform in practice. As a caramelization process is typically characterized by two stages, separate models were developed for each of the stages within a set. Furthermore, a third set of nonlinear equations were developed, serving as criteria to decide at which stage a caramelized sample is. The models were evaluated through a validation process.

  11. Structure and dynamical intra-molecular heterogeneity of star polymer melts above glass transition temperature

    Science.gov (United States)

    Chremos, Alexandros; Glynos, Emmanouil; Green, Peter F.

    2015-01-01

    Structural and dynamical properties of star melts have been investigated with molecular dynamics simulations of a bead-spring model. Star polymers are known to be heterogeneous, but a systematic simulation study of their properties in melt conditions near the glass transition temperature was lacking. To probe their properties, we have expanded from linear to star polymers the applicability of Dobkowski's chain-length dependence correlation function [Z. Dobkowski, Eur. Polym. J. 18, 563 (1982)]. The density and the isokinetic temperature, based on the canonical definition of the laboratory glass-transition, can be described well by the correlation function and a subtle behavior manifests as the architecture becomes more complex. For linear polymer chains and low functionality star polymers, we find that an increase of the arm length would result in an increase of the density and the isokinetic temperature, but high functionality star polymers have the opposite behavior. The effect between low and high functionalities is more pronounced for short arm lengths. Complementary results such as the specific volume and number of neighbors in contact provide further insights on the subtle relation between structure and dynamics. The findings would be valuable to polymer, colloidal, and nanocomposites fields for the design of materials in absence of solution with the desired properties.

  12. Treatments of intrinsic viscosity and glass transition temperature data of poly(2,6-dimethylphenylmethacrylate)

    Energy Technology Data Exchange (ETDEWEB)

    Hamidi, Nasrollah; Massoudi, Ruhullah

    2003-03-05

    A useful relationship, ln(T{sub g})=ln(T{sub g,{infinity}})-m[{eta}]{sup -{nu}}, between intrinsic viscosity and glass transition temperature for a series of homologous polymers was obtained by combining the Mark-Houwink-Kuhn-Sakurada (MHKS) relation for intrinsic viscosity and molecular mass, and the Fox-Flory equation for glass transition temperature and number-average molecular mass. This relationship was applied to poly(2,6-dimethylphenylmethacrylate) (PDMPh) in a variety of solvents (ideal to good) such as toluene, tetrahydrofuran/water, tetrahydrofuran, and chlorobenzene systems. The parameter {alpha} estimated by this procedure in toluene, tetrahydrofuran/water, tetrahydrofuran, and chlorobenzene systems are 0.50{sub 6}, 0.51{sub 1}, 0.56{sub 7}, and 0.67{sub 3}, respectively which are in agreement with those of Mark-Houwink-Kuhn-Sakurada values by less than 5% differences. The T{sub g,{infinity}} quantity estimated from this equation also is within the standard deviation of that obtained from the Fox-Flory method. The m quantity is increasing as the thermodynamic quality of the solvent improves, therefore, m may be considered as an indicator of coil conformations in a given solvent.

  13. Thermodynamic Properties, Sorption Isotherms and Glass Transition Temperature of Cape Gooseberry (Physalis peruviana L.

    Directory of Open Access Journals (Sweden)

    Jessica López

    2014-01-01

    Full Text Available Adsorption and desorption isotherms of fresh and dried Cape gooseberry (Physalis peruviana L. were determined at three temperatures (20, 40 and 60 °C using a gravimetric technique. The data obtained were fitted to several models including Guggenheim-Anderson- De Boer (GAB, Brunauer-Emmett-Teller (BET, Henderson, Caurie, Smith, Oswin, Halsey and Iglesias-Chirife. A non-linear least square regression analysis was used to evaluate the models. The Iglesias-Chirife model fitted best the experimental data. Isosteric heat of sorption was also determined from the equilibrium sorption data using the Clausius-Clapeyron equation and was found to decrease exponentially with increasing moisture content. The enthalpy-entropy compensation theory was applied to the sorption isotherms and indicated an enthalpy-controlled sorption process. Glass transition temperature (Tg of Cape gooseberry was also determined by differential scanning calorimetry and modelled as a function of moisture content with the Gordon-Taylor, the Roos and the Khalloufi models, which proved to be excellent tools for predicting glass transition of Cape gooseberry.

  14. Critical current properties and vortex-glass-liquid transition in Ag-sheathed Bi-2223 tapes

    Science.gov (United States)

    Mawatari, Y.; Yamasaki, H.; Kosaka, S.; Umeda, M.

    The magnetic field and temperature dependence of the critical current density Jc and the voltage-current characteristics of a Bi-2223 tape in a magnetic field parallel to the c-axis are studied. The critical current density decreases with increasing field in a power-law manner at low magnetic fields, and decreases exponentially at high fields. These field dependences suggest the validity of the brick-wall model proposed by Malozemoff, in which the critical current density is limited by the grain boundaries perpendicular to the c-axis. The magnetic field dependence of the macroscopic pinning force density, Fp = JcB, shows clear scaling behaviour for different temperatures. Furthermore, we investigated the temperature dependence of the voltage-current characteristics precisely, and a critical scaling analysis demonstrates the existence of a quasi-two-dimensional vortex-glass-liquid transition, which has been observed recently in Bi-2223 epitaxial films. The observed glass-liquid transition temperatures Tg were found to be much higher than those in the epitaxial films.

  15. On the theoretical determination of the Prigogine-Defay ratio in glass transition.

    Science.gov (United States)

    Tropin, Timur V; Schmelzer, Jürn W P; Gutzow, Ivan; Schick, Christoph

    2012-03-28

    In a recent analysis [J. W. P. Schmelzer and I. Gutzow, J. Chem. Phys. 125, 184511 (2006)] it was shown for the first time that--in contrast to earlier belief arising from the works of Prigogine and Defay [Chemical Thermodynamics (Longman, London, 1954), Chap. 19; The first French edition of this book was published in 1950] and Davies and Jones [Adv. Phys. 2, 370 (1953); and Proc. R. Soc. London, Ser. A 217, 26 (1953)]--a satisfactory theoretical interpretation of the experimentally observed values of the so-called Prigogine-Defay ratio Π, being a combination of jumps of thermodynamic coefficients at glass transition, can be given employing only one structural order parameter. According to this analysis, this ratio has to be, in full agreement with experimental findings, larger than one (Π > 1). Its particular value depends both on the thermodynamic properties of the system under consideration and on cooling and heating rates. Based on above-mentioned analysis, latter dependence on cooling rates has been studied in detail in another own preceding paper [T. V. Tropin, J. W. P. Schmelzer, and C. Schick, J. Non-Cryst. Solids 357, 1303 (2011)]. In the present analysis, an alternative general method of determination of the Prigogine-Defay ratio is outlined, allowing one to determine this ratio having at ones disposal the generalized equation of state of the glass-forming melts under consideration and, in particular, the knowledge of the equilibrium properties of the melts in the glass transformation range. Employing, as an illustration of the method, a particular model for the description of glass-forming melts, theoretical estimates are given for this ratio being, again, in good agreement with experimental data.

  16. Meissner Effects, Vortex Core States, and the Vortex Glass Phase Transition.

    Science.gov (United States)

    Huang, Ming

    This thesis covers three topics involving Meissner effects and the resulting defect structures. The first is a study of Meissner effects in superconductivity and in systems with broken translational symmetry. The Meissner effect in superconductors is a rigidity against external magnetic field caused by the breaking of the gauge symmetry. Other condensed matter systems also exhibit rigidities like this: The breaking of the translational symmetry in a cubic-liquid -crystal causes the system to expel twist deformations and the breaking of the translational symmetry in a nematic liquid crystal gives it a tendency to expel twist and bend deformations. In this thesis, we study these generalized Meissner effects in detail. The second is a study of the quasiparticle states bound to the vortex defect in superconductors. Scanning -tunneling-microscope measurements by Harald Hess et al. of the local density of states in a vortex core show a pronounced peak at small bias. These measurements contradict with previous theoretical calculations. Here, we solve the Bogoliubov equations to obtain the local density of states in the core and satisfactorily explain the experimental observations. We also predicted additional structure in the local density of states which were later observed in experiments. The third is a study of vortex dynamics in the precense of disorder. A mean field theory is developed for the recently proposed normal to superconducting vortex glass transition. Using techniques developed to study the critical dynamics of spin glasses, we calculate the mean field vortex glass phase boundary and the critical exponents. We also explain the experimentally observed magnetic field induced transition broadening.

  17. Brittle to ductile transition of metallic glasses induced by embedding spherical nanovoids

    Science.gov (United States)

    Zhu, Bida; Huang, Minsheng; Li, Zhenhuan

    2017-12-01

    The lack of global plasticity at low temperature seriously limits the application of metallic glasses (MGs) as structural materials. An approach to enhance the MG-ductility by dispersed spherical nanovoids is suggested and validated by molecular dynamics in the present paper. By introducing these nanovoids, a deformation mode transition from localized shear banding to homogeneous flow occurs. The ratio of void-surface area to MG volume λ is revealed to be the dominant factor controlling this brittle-to-ductile transition. Generally, for a given void volume fraction, smaller nanovoids with larger λ have better toughening effects. It is also discovered that the ductile responses of porous MGs with embedded nanovoids remain unchanged, even after several cycles of tensile-compressive loads. The intrinsic mechanism may be the transition of energetic void-surface atoms into internal atoms with lower potential energy. This process induces many uniformly distributed potential nucleation sites for shear transformation zones or embryonic shear bands (SBs), and thus provides another homogenous way to release the stored strain energy in MGs rather than by the formation of a single dominant SB. As a consequence, the highly localized deformation mode of classical MGs can be avoided. In addition, the effect of free and periodical boundary conditions and random distribution of nanovoids on the brittle-to-ductile transition are also discussed. The results may shed a light on the fabrication of better ductile MG materials.

  18. Bellanet Network Transition Period | IDRC - International ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Since its creation in 1995, Bellanet has built a sound reputation helping international development organizations use information technology to communicate and collaborate. Since then, the centre of gravity of this virtual network of knowledge management practitioners has shifted southward. What began as a multi-donor ...

  19. Feature to prototype transition in neural networks

    Science.gov (United States)

    Krotov, Dmitry; Hopfield, John

    Models of associative memory with higher order (higher than quadratic) interactions, and their relationship to neural networks used in deep learning are discussed. Associative memory is conventionally described by recurrent neural networks with dynamical convergence to stable points. Deep learning typically uses feedforward neural nets without dynamics. However, a simple duality relates these two different views when applied to problems of pattern classification. From the perspective of associative memory such models deserve attention because they make it possible to store a much larger number of memories, compared to the quadratic case. In the dual description, these models correspond to feedforward neural networks with one hidden layer and unusual activation functions transmitting the activities of the visible neurons to the hidden layer. These activation functions are rectified polynomials of a higher degree rather than the rectified linear functions used in deep learning. The network learns representations of the data in terms of features for rectified linear functions, but as the power in the activation function is increased there is a gradual shift to a prototype-based representation, the two extreme regimes of pattern recognition known in cognitive psychology. Simons Center for Systems Biology.

  20. Modeling Network Transition Constraints with Hypergraphs

    DEFF Research Database (Denmark)

    Harrod, Steven

    2011-01-01

    values. A directed hypergraph formulation is derived to address railway network sequencing constraints, and an experimental problem sample solved to estimate the magnitude of objective inflation when interaction effects are ignored. The model is used to demonstrate the value of advance scheduling...

  1. Pressure Induced Liquid-to-Liquid Transition in Zr-based Supercooled Melts and Pressure Quenched Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Dmowski, W.; Gierlotka, S.; Wang, Z.; Yokoyama, Y.; Palosz, B.; Egami, T.

    2017-07-26

    Through high-energy x-ray diffraction and atomic pair density function analysis we find that Zr-based metallic alloy, heated to the supercooled liquid state under hydrostatic pressure and then quenched to room temperature, exhibits a distinct glassy structure. The PDF indicates that the Zr-Zr distances in this glass are significantly reduced compared to those quenched without pressure. Annealing at the glass transition temperature at ambient pressure reverses structural changes and the initial glassy state is recovered. This result suggests that pressure causes a liquid-to-liquid phase transition in this metallic alloy supercooled melt. Such a pressure induced transition is known for covalent liquids, but has not been observed for metallic liquids. The High Pressure Quenched glasses are stable in ambient conditions after decompression.

  2. Weighted Complex Network Analysis of Shanghai Rail Transit System

    Directory of Open Access Journals (Sweden)

    Yingying Xing

    2016-01-01

    Full Text Available With increasing passenger flows and construction scale, Shanghai rail transit system (RTS has entered a new era of networking operation. In addition, the structure and properties of the RTS network have great implications for urban traffic planning, design, and management. Thus, it is necessary to acquire their network properties and impacts. In this paper, the Shanghai RTS, as well as passenger flows, will be investigated by using complex network theory. Both the topological and dynamic properties of the RTS network are analyzed and the largest connected cluster is introduced to assess the reliability and robustness of the RTS network. Simulation results show that the distribution of nodes strength exhibits a power-law behavior and Shanghai RTS network shows a strong weighted rich-club effect. This study also indicates that the intentional attacks are more detrimental to the RTS network than to the random weighted network, but the random attacks can cause slightly more damage to the random weighted network than to the RTS network. Our results provide a richer view of complex weighted networks in real world and possibilities of risk analysis and policy decisions for the RTS operation department.

  3. Neurodynamics of up and down Transitions in Network Model

    Directory of Open Access Journals (Sweden)

    Xuying Xu

    2013-01-01

    Full Text Available This paper focuses on the neurodynamical research of a small neural network that consists of 25 neurons. We study the periodic spontaneous activity and transitions between up and down states without synaptic input. The results demonstrate that these transitions are bidirectional or unidirectional with the parameters changing, which not only reveals the function of the cortex, but also cohere with the experiment results.

  4. SU-F-T-17: A Feasibility Study for the Transit Dosimetry with a Glass Dosimeter in Brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Moon, S; Yoon, M [Korea University, Seoul (Korea, Republic of); Chung, W; Chung, M; Kim, D [Kyung Hee University Hospital at Gangdong, Gangdonggu, Seoul (Korea, Republic of)

    2016-06-15

    Purpose: Confirming the dose delivered to a patient is important to make sure the treatment quality and safety of the radiotherapy. Measuring a transit dose of the patient during the radiotherapy could be an interesting way to confirm the patient dose. In this study, we evaluated the feasibility of the transit dosimetry with a glass dosimeter in brachytherapy. Methods: We made a phantom that inserted the glass dosimeters and placed under patient lying on a couch for cervix cancer brachytherapy. The 18 glass dosimeters were placed in the phantom arranged 6 per row. A point putting 1cm vertically from the source was prescribed as 500.00 cGy. Solid phantoms of 0, 2, 4, 6, 8, 10 cm were placed between the source and the glass dosimeter. The transit dose was measured each thickness using the glass dosimeters and compared with a treatment planning system (TPS). Results: When the transit dose was smaller than 10 cGy, the average of the differences between measured values and calculated values by TPS was 0.50 cGy and the standard deviation was 0.69 cGy. If the transit dose was smaller than 100 cGy, the average of the error was 1.67 ± 4.01 cGy. The error to a point near the prescription point was −14.02 cGy per 500.00 cGy of the prescription dose. Conclusion: The distances from the sources to skin of the patient generally are within 10 cm for cervix cancer cases in brachytherapy. The results of this preliminary study showed the probability of the glass dosimeter as the transit dosimeter in brachytherapy.

  5. Executable Code Recognition in Network Flows Using Instruction Transition Probabilities

    Science.gov (United States)

    Kim, Ikkyun; Kang, Koohong; Choi, Yangseo; Kim, Daewon; Oh, Jintae; Jang, Jongsoo; Han, Kijun

    The ability to recognize quickly inside network flows to be executable is prerequisite for malware detection. For this purpose, we introduce an instruction transition probability matrix (ITPX) which is comprised of the IA-32 instruction sets and reveals the characteristics of executable code's instruction transition patterns. And then, we propose a simple algorithm to detect executable code inside network flows using a reference ITPX which is learned from the known Windows Portable Executable files. We have tested the algorithm with more than thousands of executable and non-executable codes. The results show that it is very promising enough to use in real world.

  6. Spectral estimation of the percolation transition in clustered networks

    Science.gov (United States)

    Zhang, Pan

    2017-10-01

    There have been several spectral bounds for the percolation transition in networks, using spectrum of matrices associated with the network such as the adjacency matrix and the nonbacktracking matrix. However, they are far from being tight when the network is sparse and displays clustering or transitivity, which is represented by existence of short loops, e.g., triangles. In this paper, for the bond percolation, we first propose a message-passing algorithm for calculating size of percolating clusters considering effects of triangles, then relate the percolation transition to the leading eigenvalue of a matrix that we name the triangle-nonbacktracking matrix, by analyzing stability of the message-passing equations. We establish that our method gives a tighter lower bound to the bond percolation transition than previous spectral bounds, and it becomes exact for an infinite network with no loops longer than 3. We evaluate numerically our methods on synthetic and real-world networks, and discuss further generalizations of our approach to include higher-order substructures.

  7. Conducting-insulating transition in adiabatic memristive networks

    Science.gov (United States)

    Sheldon, Forrest C.; Di Ventra, Massimiliano

    2017-01-01

    The development of neuromorphic systems based on memristive elements—resistors with memory—requires a fundamental understanding of their collective dynamics when organized in networks. Here, we study an experimentally inspired model of two-dimensional disordered memristive networks subject to a slowly ramped voltage and show that they undergo a discontinuous transition in the conductivity for sufficiently high values of memory, as quantified by the memristive ON-OFF ratio. We investigate the consequences of this transition for the memristive current-voltage characteristics both through simulation and theory, and demonstrate the role of current-voltage duality in relating forward and reverse switching processes. Our work sheds considerable light on the statistical properties of memristive networks that are presently studied both for unconventional computing and as models of neural networks.

  8. Communication: Analysing kinetic transition networks for rare events

    Science.gov (United States)

    Stevenson, Jacob D.; Wales, David J.

    2014-07-01

    The graph transformation approach is a recently proposed method for computing mean first passage times, rates, and committor probabilities for kinetic transition networks. Here we compare the performance to existing linear algebra methods, focusing on large, sparse networks. We show that graph transformation provides a much more robust framework, succeeding when numerical precision issues cause the other methods to fail completely. These are precisely the situations that correspond to rare event dynamics for which the graph transformation was introduced.

  9. Properties of kinetic transition networks for atomic clusters and glassy solids.

    Science.gov (United States)

    Morgan, John W R; Mehta, Dhagash; Wales, David J

    2017-09-27

    A database of minima and transition states corresponds to a network where the minima represent nodes and the transition states correspond to edges between the pairs of minima they connect via steepest-descent paths. Here we construct networks for small clusters bound by the Morse potential for a selection of physically relevant parameters, in two and three dimensions. The properties of these unweighted and undirected networks are analysed to examine two features: whether they are small-world, where the shortest path between nodes involves only a small number or edges; and whether they are scale-free, having a degree distribution that follows a power law. Small-world character is present, but statistical tests show that a power law is not a good fit, so the networks are not scale-free. These results for clusters are compared with the corresponding properties for the molecular and atomic structural glass formers ortho-terphenyl and binary Lennard-Jones. These glassy systems do not show small-world properties, suggesting that such behaviour is linked to the structure-seeking landscapes of the Morse clusters.

  10. A model for phosphate glass topology considering the modifying ion sub-network

    DEFF Research Database (Denmark)

    Hermansen, Christian; Mauro, J.C.; Yue, Yuanzheng

    2014-01-01

    In the present paper we establish a temperature dependent constraint model of alkali phosphate glasses considering the structural and topological role of the modifying ion sub-network constituted by alkali ions and their non-bonding oxygen coordination spheres. The model is consistent with availa...

  11. Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay

    Science.gov (United States)

    Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mârtensson, Lena; Swenson, Jan

    2014-07-01

    The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the

  12. Types of social networks and the transition to parenthood

    Directory of Open Access Journals (Sweden)

    Daniel Lois

    2016-04-01

    Full Text Available Background: A growing body of literature acknowledges the importance of social interaction and ideational factors for generative behavior. Building on this research, the present study identifies specific types of social network and gauges their value for predicting fertility behavior. Methods: Based on data from the German Family Panel (N = 3,104 respondents aged 20 to 42, four types of ego-centric social networks were identified using cluster analyses. Clusters were used to prospectively predict the transition to parenthood using a discrete-time event history analysis. Results: In the event history analyses, the highest propensity to start a family was found for 'family-centered' social networks, which were characterized primarily by a high share of persons with young children, a high amount of network support in case of parenthood, and a high proportion of strong ties to members of the nuclear family. By contrast, respondents who were embedded in 'family-remote' networks had the lowest transition rate to parenthood. Family-remote networks were characterized by a high share of friends and acquaintances, a high proportion of weak ties, and a low amount of social support and social pressure. Regarding selection effects, a comparison of cluster affiliation over time does not consistently confirm that persons who start a family select themselves into 'fertility-promoting' network types. In sum, the results enhance our understanding of how mechanisms of social influence and structural features of ego-centric social networks are interlinked.

  13. Double Percolation Phase Transition in Clustered Complex Networks

    Directory of Open Access Journals (Sweden)

    Pol Colomer-de-Simón

    2014-10-01

    Full Text Available The internal organization of complex networks often has striking consequences on either their response to external perturbations or on their dynamical properties. In addition to small-world and scale-free properties, clustering is the most common topological characteristic observed in many real networked systems. In this paper, we report an extensive numerical study on the effects of clustering on the structural properties of complex networks. Strong clustering in heterogeneous networks induces the emergence of a core-periphery organization that has a critical effect on the percolation properties of the networks. We observe a novel double phase transition with an intermediate phase in which only the core of the network is percolated and a final phase in which the periphery percolates regardless of the core. This result implies breaking of the same symmetry at two different values of the control parameter, in stark contrast to the modern theory of continuous phase transitions. Inspired by this core-periphery organization, we introduce a simple model that allows us to analytically prove that such an anomalous phase transition is, in fact, possible.

  14. Recurrence networks to study dynamical transitions in a turbulent combustor

    Science.gov (United States)

    Godavarthi, V.; Unni, V. R.; Gopalakrishnan, E. A.; Sujith, R. I.

    2017-06-01

    Thermoacoustic instability and lean blowout are the major challenges faced when a gas turbine combustor is operated under fuel lean conditions. The dynamics of thermoacoustic system is the result of complex nonlinear interactions between the subsystems—turbulent reactive flow and the acoustic field of the combustor. In order to study the transitions between the dynamical regimes in such a complex system, the time series corresponding to one of the dynamic variables is transformed to an ɛ-recurrence network. The topology of the recurrence network resembles the structure of the attractor representing the dynamics of the system. The transitions in the thermoacoustic system are then captured as the variation in the topological characteristics of the network. We show the presence of power law degree distribution in the recurrence networks constructed from time series acquired during the occurrence of combustion noise and during the low amplitude aperiodic oscillations prior to lean blowout. We also show the absence of power law degree distribution in the recurrence networks constructed from time series acquired during the occurrence of thermoacoustic instability and during the occurrence of intermittency. We demonstrate that the measures derived from recurrence network can be used as tools to capture the transitions in the turbulent combustor and also as early warning measures for predicting impending thermoacoustic instability and blowout.

  15. Routing strategies in traffic network and phase transition in network ...

    Indian Academy of Sciences (India)

    The dynamics of information traffic over scale-free networks has been investigated systematically. A series of routing strategies of data packets have been proposed, including the local routing strategy, the next-nearest-neighbour routing strategy, and the mixed routing strategy based on local static and dynamic information.

  16. A spinning thermometer to monitor microwave heating and glass transitions in dynamic nuclear polarization.

    Science.gov (United States)

    Miéville, Pascal; Vitzthum, Veronika; Caporini, Marc A; Jannin, Sami; Gerber-Lemaire, Sandrine; Bodenhausen, Geoffrey

    2011-11-01

    As previously demonstrated by Thurber and Tycko, the peak position of (79)Br in potassium bromide (KBr) allows one to determine the temperature of a spinning sample. We propose to adapt the original design by using a compact KBr tablet placed at the bottom of the magic angle spinning rotor, separated from the sample under investigation by a thin disk made of polytetrafluoroethylene (or 'Teflon'®). This design allows spinning the sample up to at least 16 kHz. The KBr tablet can remain in the rotor when changing the sample under investigation. Calibration in the range of 98 nuclear polarization enhancement decreases with increasing temperature, in particular when a frozen glassy sample undergoes a glass transition. Copyright © 2011 John Wiley & Sons, Ltd.

  17. Structural evolution during fragile-to-strong transition in CuZr(Al) glass-forming liquids

    DEFF Research Database (Denmark)

    Zhou, C.; Hu, L.N.; Sun, Q.J.

    2015-01-01

    In the present work, we show experimental evidence for the dynamic fragile-to-strong (F-S) transition in a series of CuZr(Al) glass-forming liquids (GFLs). A detailed analysis of the dynamics of 98 glass-forming liquids indicates that the F-S transition occurs around Tf-s ≈ 1.36 Tg. Using...... the hyperquenching-annealing-x-ray scattering approach, we have observed a three-stage evolution pattern of medium-range ordering (MRO) structures during the F-S transition, indicating a dramatic change of the MRO clusters around Tf-s upon cooling. The F-S transition in CuZr(Al) GFLs is attributed to the competition...... among the MRO clusters composed of different locally ordering configurations. A phenomenological scenario has been proposed to explain the structural evolution from the fragile to the strong phase in the CuZr(Al) GFLs....

  18. Evolution of weighted complex bus transit networks with flow

    Science.gov (United States)

    Huang, Ailing; Xiong, Jie; Shen, Jinsheng; Guan, Wei

    2016-02-01

    Study on the intrinsic properties and evolutional mechanism of urban public transit networks (PTNs) has great significance for transit planning and control, particularly considering passengers’ dynamic behaviors. This paper presents an empirical analysis for exploring the complex properties of Beijing’s weighted bus transit network (BTN) based on passenger flow in L-space, and proposes a bi-level evolution model to simulate the development of transit routes from the view of complex network. The model is an iterative process that is driven by passengers’ travel demands and dual-controlled interest mechanism, which is composed of passengers’ spatio-temporal requirements and cost constraint of transit agencies. Also, the flow’s dynamic behaviors, including the evolutions of travel demand, sectional flow attracted by a new link and flow perturbation triggered in nearby routes, are taken into consideration in the evolutional process. We present the numerical experiment to validate the model, where the main parameters are estimated by using distribution functions that are deduced from real-world data. The results obtained have proven that our model can generate a BTN with complex properties, such as the scale-free behavior or small-world phenomenon, which shows an agreement with our empirical results. Our study’s results can be exploited to optimize the real BTN’s structure and improve the network’s robustness.

  19. African Transitional Justice Research Network - Phase II | IDRC ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    The African Transitional Justice Research Network (ATJRN) aims to strengthen the capacity of African researchers and civil society institutions to conduct effective human rights advocacy through the production of high-quality, locally based and targeted empirical research. Phase I of the project (102862) focused on creating ...

  20. African Transitional Justice Research Network - Phase II | CRDI ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    The African Transitional Justice Research Network (ATJRN) aims to strengthen the capacity of African researchers and civil society institutions to conduct effective human rights advocacy through the production of high-quality, locally based and targeted empirical research. Phase I of the project (102862) focused on creating ...

  1. Sub-critical crack growth in silicate glasses: Role of network topology

    Science.gov (United States)

    Smedskjaer, Morten M.; Bauchy, Mathieu

    2015-10-01

    The presence of water in the surrounding atmosphere can cause sub-critical crack growth (SCCG) in glasses, a phenomenon known as fatigue or stress corrosion. Here, to facilitate the compositional design of more fatigue-resistant glasses, we investigate the composition dependence of SCCG by studying fourteen silicate glasses. The fatigue curves (V-KI) have been obtained by indentation experiments through measurements of the crack length as a function of post-indentation fatigue duration. Interestingly, we find that the fatigue resistance parameter N is generally improved by increasing the alumina content and is thereby found to exhibit a fairly linear dependence on the measured Vickers hardness HV for a wide range of N and HV values. This finding highlights the important role of network topology in governing the SCCG in silicate glasses, since hardness has been shown to scale linearly with the number of atomic constraints. Our results therefore suggest that glasses showing under-constrained flexible networks, which feature floppy internal modes of deformation, are more readily attacked by water molecules, thus promoting stress corrosion and reducing the fatigue resistance.

  2. The glass transition and interfacial dynamics of single strand fibers of polymers.

    Science.gov (United States)

    Cho, Hyun Woo; Sung, Bong June

    2017-02-08

    We investigate the glass transition and interfacial dynamics of single strand fibers of flexible polymers by employing molecular dynamics (MD) simulations along with a coarse grained model. While the polymer fiber has drawn significant attention due to its applicability in tissue engineering and stretchable electronics, its dynamic properties, especially the glass transition temperature (Tg), are yet to be understood at the molecular level. For example, there has been a controversy on the effect of the polymer fiber radius (R) on Tg: Tg decreased with a decrease in R for some polymer fibers, whereas Tg of other polymer fibers was not sensitive to R. In this article, we estimate the bond relaxation time of polymers and evaluate both Tg and fragility (m) as a function of R. We illustrate that Tg of the polymer fiber decreased with a decrease in R monotonically and also that the values of Tg follow faithfully the empirical equation proposed by Keddie et al. as a function of R, which was successfully employed to fit the values of Tg of both polyvinyl alcohol (PVA) fibers and polyethylene (PE) fibers. We also find that the dynamics of polymers at the interface between a polymer fiber and air is faster than that of polymers at the center. By employing Adam-Gibbs theory, we show that the fast interface dynamics of polymer fibers should influence the cooperative motion of monomers, which should be responsible for the decrease in Tg for smaller values of R. Near the interface there are more mobile monomers that participate in the cooperative motions of polymers. Interesting is that due to the curved surface (unlike flat polymer films) the cooperative motion of monomers is anisotropic in polymer fibers.

  3. Complexity and state-transitions in social dependence networks

    Directory of Open Access Journals (Sweden)

    Giuliano Pistolesi

    2001-01-01

    Full Text Available Computation of complexity in Social Dependence Networks is an interesting research domain to understand evolution processes and group exchange dynamics in natural and artificial intelligent Multi-Agent Systems. We perform an agent-based simulation by NET-PLEX (Conte and Pistolesi, 2000, a new software system able both to build interdependence networks tipically emerging in Multi-Agent System scenarios and to investigate complexity phenomena, i.e., unstability and state-transitions like Hopf bifurcation (Nowak and Lewenstein, 1994, and to describe social self organization phenomena emerging in these artificial social systems by means of complexity measures similar to those introduced by Hubermann and Hogg (1986. By performing analysis of complexity in these kind of artificial societies we observed interesting phenomena in emerging organizations that suggest state-transitions induced by critical configurations of parameters describing the social system similar to those observed in many studies on state-transitions in bifurcation chaos (Schuster, 1988; Ruelle, 1989.

  4. Fractal Topology of Gene Promoter Networks at Phase Transitions

    Directory of Open Access Journals (Sweden)

    Preston R. Aldrich

    2010-07-01

    Full Text Available Much is known regarding the structure and logic of genetic regulatory networks. Less understood is the contextual organization of promoter signals used during transcription initiation, the most pivotal stage during gene expression. Here we show that promoter networks organize spontaneously at a dimension between the 1-dimension of the DNA and 3-dimension of the cell. Network methods were used to visualize the global structure of E. coli sigma (σ recognition footprints using published promoter sequences (RegulonDB. Footprints were rendered as networks with weighted edges representing bp-sharing between promoters (nodes. Serial thresholding revealed phase transitions at positions predicted by percolation theory, and nuclei denoting short steps through promoter space with geometrically constrained linkages. The network nuclei are fractals, a power-law organization not yet described for promoters. Genome-wide promoter abundance also scaled as a power-law. We propose a general model for the development of a fractal nucleus in a transcriptional grammar.

  5. Concurrency-Induced Transitions in Epidemic Dynamics on Temporal Networks

    Science.gov (United States)

    Onaga, Tomokatsu; Gleeson, James P.; Masuda, Naoki

    2017-09-01

    Social contact networks underlying epidemic processes in humans and animals are highly dynamic. The spreading of infections on such temporal networks can differ dramatically from spreading on static networks. We theoretically investigate the effects of concurrency, the number of neighbors that a node has at a given time point, on the epidemic threshold in the stochastic susceptible-infected-susceptible dynamics on temporal network models. We show that network dynamics can suppress epidemics (i.e., yield a higher epidemic threshold) when the node's concurrency is low, but can also enhance epidemics when the concurrency is high. We analytically determine different phases of this concurrency-induced transition, and confirm our results with numerical simulations.

  6. Competition policy and optimal retail network development in transitional economies

    Directory of Open Access Journals (Sweden)

    Lovreta Stipe

    2013-01-01

    Full Text Available The choice of retail store location is a very complex process, with many different stakeholders having interests in both the micro and macro locations. The goal of this work is to contribute to the better understanding of the different interests of corporative and public policies in choosing retail store locations, in order to enable more efficient and effective trade network development. After having slowed down as a consequence of the global economic crisis, the retail sector is experiencing strong expansion in the markets of transitional countries. Insufficient engagement of public policy in planning trade networks can violate market competition. An active government role in carrying out the policy of retail network development in transitional countries is necessary to maintain the level of competition and prevent big market players abusing their dominant position.

  7. Effect of lithium halide on glass network structure and upconversion luminescence in Er3+ co-doped oxyfluoride glass ceramics containing NaGdF4 nanocrystals

    Science.gov (United States)

    Ren, Peng; Yang, Yong; Zhou, Dacheng; Li, Zhencai; Qiu, Jianbei

    2017-10-01

    LiR(R = Br, Cl, F) co-doped oxyfluoride glass ceramics containing NaGdF4 nanocrystals were prepared. The effect on glass network structure by dopants was investigated through the Raman spectra. The crystallization temperature and integrity of the glass network structure was gradually reduced by introducing halogen ions. The types and distribution of nanocrystals were determined by X-ray diffraction and transmission electron microscope. The size of nanocrystals were shown in column type distribution map. The mean size of nanocrystals was bigger from SABr to SAF. The upconversion luminescence of Er3+ in SABr, SACl and SAF were study. The intensity ratio of red and green light was reduced in glass ceramics when the content from LiBr turn to LiF.

  8. Effect of molecular weight and glass transition on relaxation and release behaviour of poly(DL-lactic acid) tablets

    NARCIS (Netherlands)

    Steendam, R.; Van Steenbergen, M.J.; Hennink, W.E.; Frijlink, H.W.; Lerk, C.F.

    2001-01-01

    Different molecular weight grades of poly(DL-lactic acid) were applied as release controlling excipients in tablets for oral drug administration. The role of molecular weight and glass transition in the mechanism of water-induced volume expansion and drug release of PDLA tablets was investigated.

  9. Effect of molecular weight and glass transition on relaxation and release behaviour of poly(DL-lactic acid) tablets.

    Science.gov (United States)

    Steendam, R; van Steenbergen, M J; Hennink, W E; Frijlink, H W; Lerk, C F

    2001-01-29

    Different molecular weight grades of poly(DL-lactic acid) were applied as release controlling excipients in tablets for oral drug administration. The role of molecular weight and glass transition in the mechanism of water-induced volume expansion and drug release of PDLA tablets was investigated. Modulated differential scanning calorimetry (MDSC) was used to determine the glass transition temperature of both dry and hydrated PDLA samples. The absorption rate and total amounts of sorbed water by the polymer were determined by dynamic vapour sorption (DVS). Expansion behaviour of PDLA tablets was measured using thermal mechanical analysis (TMA). At 95% relative humidity all molecular weight grades of PDLA sorbed 1.1-1.3% w/w water, as was determined with DVS. MDSC showed glass transition temperature reductions of 10-11 degrees C for all molecular weight grades of PDLA in water. Volume expansion studies using TMA showed that the molecular relaxation time and equilibrium porosity of the tablets increased with molecular weight. The mean relaxation time increased exponentially with the temperature interval T(g)-T. The onset temperature of shape recovery of hydrated tablets was approximately 8 degrees C lower than for dry samples. Drug release was only slightly affected by molecular weight. It is concluded that volume expansion of compressed PDLA tablets is related to the glass transition behaviour, originates from water-induced and thermally stimulated shape memory behaviour and is therefore highly dependent on the molecular weight of PDLA.

  10. Waveguides and nonlinear index of refraction of borate glass doped with transition metals

    Science.gov (United States)

    Almeida, Juliana M. P.; Fonseca, Ruben D.; De Boni, Leonardo; Diniz, Andre Rosa S.; Hernandes, Antonio C.; Ferreira, Paulo H. D.; Mendonca, Cleber R.

    2015-04-01

    The ability to write 3D waveguides by femtosecond laser micromachining and the nonlinear refractive index (n2) spectrum of a new borate glass matrix, containing zinc and lead oxides - (BZP) have been investigated. The transparent matrix was doped with transition metals (CdCl2, Fe2O3, MnO2 and CoO) in order to introduce electronic transitions in visible spectrum, aiming to evaluate their influence on the waveguides and n2 spectrum. We observed that n2 is approximately constant from 600 to 1500 nm, exhibiting an average value of 4.5 × 10-20 m2/W, which is about twice larger than the one for fused silica. The waveguide profile is influenced by the self-focusing effect of the matrix owing to its positive nonlinear index of refraction in the wavelength used for micromachining. A decrease in the waveguide loss of approximately four times was observed for the sample doped with Fe in comparison to the other ones, which may be associated with the change in the optical gap energy.

  11. Thermal analysis of ice and glass transitions in insects that do and do not survive freezing.

    Science.gov (United States)

    Rozsypal, Jan; Moos, Martin; Šimek, Petr; Koštál, Vladimír

    2018-03-01

    Some insects rely on the strategy of freeze tolerance for winter survival. During freezing, extracellular body water transitions from the liquid to solid phase and cells undergo freeze-induced dehydration. Here we present results of a thermal analysis (from differential scanning calorimetry) of ice fraction dynamics during gradual cooling after inoculative freezing in variously acclimated larvae of two drosophilid flies, Drosophila melanogaster and Chymomyza costata. Although the species and variants ranged broadly between 0 and close to 100% survival of freezing, there were relatively small differences in ice fraction dynamics. For instance, the maximum ice fraction (IF max ) ranged between 67.9 and 77.7% total body water (TBW). The C. costata larvae showed statistically significant phenotypic shifts in parameters of ice fraction dynamics (melting point and IF max ) upon entry into diapause, cold-acclimation, and feeding on a proline-augmented diet. These differences were mostly driven by colligative effects of accumulated proline (ranging between 6 and 487 mmol.kg -1 TBW) and other metabolites. Our data suggest that these colligative effects per se do not represent a sufficient mechanistic explanation for high freeze tolerance observed in diapausing, cold-acclimated C. costata larvae. Instead, we hypothesize that accumulated proline exerts its protective role via a combination of mechanisms. Specifically, we found a tight association between proline-induced stimulation of glass transition in partially-frozen body liquids (vitrification) and survival of cryopreservation in liquid nitrogen. © 2018. Published by The Company of Biologists Ltd.

  12. Spin-glass and antiferromagnetic transitions in Ru2-xFexCrSi

    Science.gov (United States)

    Hiroi, Masahiko; Ko, Haku; Nakashima, Shingo; Shigeta, Iduru; Ito, Masakazu; Manaka, Hirotaka; Terada, Norio

    2012-12-01

    In this study the properties of the Heusler compounds Ru2-xFexCrSi (0CrSi was revealed to exhibit two anomalies in the temperature dependence of magnetization M(T); one is a peak in M(T) at T*N ~ 30 K and the other is strong irreversibility in M(T) below T*N, the onset of which is defined as Tg. M(T) and specific heat CP(T) of Ru2CrSi are measured. A clear peak is observed in both M(T) and CP(T). This is in quite contrast to the case for Ru1.9Fe0.1CrSi, where no anomaly in CP(T) was observed at T*N or at any other temperatures. These indicate that an antiferromagnetic transition occurs at TN = 14 K in Ru2CrSi. For x = 0.02 the characteristic two anomalies in M(T) are also found at various magnetic fields, and their field dependence is basically the same as that for x = 0.1. These two anomalies are suggestive of successive spin-glass transitions. As for the dependence of the two anomalies on x, Tg does not change with x, whereas T*N decreases with decreasing x and seems to approach Tg at zero field.

  13. Detection of phase transition via convolutional neural network

    CERN Document Server

    Tanaka, Akinori

    2016-01-01

    We design a Convolutional Neural Network (CNN) which studies correlation between discretized inverse temperature and spin configuration of 2D Ising model and show that it can find a feature of the phase transition without teaching any a priori information for it. We also define a new order parameter via the CNN and show that it provides well approximated critical inverse temperature. In addition, we compare the activation functions for convolution layer and find that the Rectified Linear Unit (ReLU) is important to detect the phase transition of 2D Ising model.

  14. fastBMA: scalable network inference and transitive reduction.

    Science.gov (United States)

    Hung, Ling-Hong; Shi, Kaiyuan; Wu, Migao; Young, William Chad; Raftery, Adrian E; Yeung, Ka Yee

    2017-10-01

    Inferring genetic networks from genome-wide expression data is extremely demanding computationally. We have developed fastBMA, a distributed, parallel, and scalable implementation of Bayesian model averaging (BMA) for this purpose. fastBMA also includes a computationally efficient module for eliminating redundant indirect edges in the network by mapping the transitive reduction to an easily solved shortest-path problem. We evaluated the performance of fastBMA on synthetic data and experimental genome-wide time series yeast and human datasets. When using a single CPU core, fastBMA is up to 100 times faster than the next fastest method, LASSO, with increased accuracy. It is a memory-efficient, parallel, and distributed application that scales to human genome-wide expression data. A 10 000-gene regulation network can be obtained in a matter of hours using a 32-core cloud cluster (2 nodes of 16 cores). fastBMA is a significant improvement over its predecessor ScanBMA. It is more accurate and orders of magnitude faster than other fast network inference methods such as the 1 based on LASSO. The improved scalability allows it to calculate networks from genome scale data in a reasonable time frame. The transitive reduction method can improve accuracy in denser networks. fastBMA is available as code (M.I.T. license) from GitHub (https://github.com/lhhunghimself/fastBMA), as part of the updated networkBMA Bioconductor package (https://www.bioconductor.org/packages/release/bioc/html/networkBMA.html) and as ready-to-deploy Docker images (https://hub.docker.com/r/biodepot/fastbma/). © The Authors 2017. Published by Oxford University Press.

  15. Crystallization study of Te–Bi–Se glasses

    Indian Academy of Sciences (India)

    Unknown

    The glass transition temperature, Tg, increases slightly with the variation of Bi content. From the heating rate dependence of Tg, the activation energy for glass transition (Et) has been evaluated. The results are discussed on the basis of Kissinger's approach and are interpreted using the chemically ordered network model.

  16. Detection of Phase Transition via Convolutional Neural Networks

    Science.gov (United States)

    Tanaka, Akinori; Tomiya, Akio

    2017-06-01

    A convolutional neural network (CNN) is designed to study correlation between the temperature and the spin configuration of the two-dimensional Ising model. Our CNN is able to find the characteristic feature of the phase transition without prior knowledge. Also a novel order parameter on the basis of the CNN is introduced to identify the location of the critical temperature; the result is found to be consistent with the exact value.

  17. Three-dimensional optical sensing network written in fused silica glass with femtosecond laser.

    Science.gov (United States)

    Zhang, Haibin; Ho, Stephen; Eaton, Shane M; Li, Jianzhao; Herman, Peter R

    2008-09-01

    A single-step fast-writing method of burst ultrafast laser modification was applied to form a mesh network of multi-wavelength Bragg grating waveguides in bulk fused silica glass. Strain-optic and thermo-optic responses of the laser-written internal sensors are reported for the first time. A dual planar layout provided independent temperature- and strain-compensated characterization of temperature and strain distribution with coarse spatial resolution. The grating responses were thermally stable to 500 masculineC. To our best knowledge, the grating network represents the first demonstration of 3D distributed optical sensing network in a bulk transparent medium. Such 3D grating networks open new directions for strain and temperature sensing in optical circuits, optofluidic, MEMS or lab-on-a-chip microsystems, actuators, and windows and other large display or civil structures.

  18. Pathways for diffusion in the potential energy landscape of the network glass former SiO2

    Science.gov (United States)

    Niblett, S. P.; Biedermann, M.; Wales, D. J.; de Souza, V. K.

    2017-10-01

    We study the dynamical behaviour of a computer model for viscous silica, the archetypal strong glass former, and compare its diffusion mechanism with earlier studies of a fragile binary Lennard-Jones liquid. Three different methods of analysis are employed. First, the temperature and time scale dependence of the diffusion constant is analysed. Negative correlation of particle displacements influences transport properties in silica as well as in fragile liquids. We suggest that the difference between Arrhenius and super-Arrhenius diffusive behaviour results from competition between the correlation time scale and the caging time scale. Second, we analyse the dynamics using a geometrical definition of cage-breaking transitions that was proposed previously for fragile glass formers. We find that this definition accurately captures the bond rearrangement mechanisms that control transport in open network liquids, and reproduces the diffusion constants accurately at low temperatures. As the same method is applicable to both strong and fragile glass formers, we can compare correlation time scales in these two types of systems. We compare the time spent in chains of correlated cage breaks with the characteristic caging time and find that correlations in the fragile binary Lennard-Jones system persist for an order of magnitude longer than those in the strong silica system. We investigate the origin of the correlation behaviour by sampling the potential energy landscape for silica and comparing it with the binary Lennard-Jones model. We find no qualitative difference between the landscapes, but several metrics suggest that the landscape of the fragile liquid is rougher and more frustrated. Metabasins in silica are smaller than those in binary Lennard-Jones and contain fewer high-barrier processes. This difference probably leads to the observed separation of correlation and caging time scales.

  19. Impact of the glass transition on exciton dynamics in polymer thin films

    Science.gov (United States)

    Ehrenreich, Philipp; Proepper, Daniel; Graf, Alexander; Jores, Stefan; Boris, Alexander V.; Schmidt-Mende, Lukas

    2017-11-01

    In the development of organic electronics, unlimited design possibilities of conjugated polymers offer a wide variety of mechanical and electronic properties. Thereby, it is crucially important to reveal universal physical characteristics that allow efficient and forward developments of new chemical compounds. In particular for organic solar cells, a deeper understanding of exciton dynamics in polymer films can help to improve the charge generation process further. For this purpose, poly(3-hexylthiophene) (P3HT) is commonly used as a model system, although exciton decay kinetics have found different interpretations. Using temperature-dependent time-resolved photoluminescence spectroscopy in combination with low-temperature spectroscopic ellipsometry, we can show that P3HT is indeed a model system in which excitons follow a simple diffusion/hopping model. Based on our results we can exclude the relevance of hot-exciton emission as well as a dynamic torsional relaxation upon photoexcitation on a ps time scale. Instead, we depict the glass transition temperature of polymers to strongly affect exciton dynamics.

  20. Molecular relaxation behavior and isothermal crystallization above glass transition temperature of amorphous hesperetin.

    Science.gov (United States)

    Shete, Ganesh; Khomane, Kailas S; Bansal, Arvind Kumar

    2014-01-01

    The purpose of this paper was to investigate the relaxation behavior of amorphous hesperetin (HRN), using dielectric spectroscopy, and assessment of its crystallization kinetics above glass transition temperature (Tg ). Amorphous HRN exhibited both local (β-) and global (α-) relaxations. β-Relaxation was observed below Tg , whereas α-relaxation prominently emerged above Tg . β-Relaxation was found to be of Johari-Goldstein type and was correlated with α-process by coupling model. Secondly, isothermal crystallization experiments were performed at 363 K (Tg + 16.5 K), 373 K (Tg + 26.5 K), and 383 K (Tg + 36.5 K). The kinetics of crystallization, obtained from the normalized dielectric strength, was modeled using the Avrami model. Havriliak-Negami (HN) shape parameters, αHN and αHN .βHN , were analyzed during the course of crystallization to understand the dynamics of amorphous phase during the emergence of crystallites. HN shape parameters indicated that long range (α-like) were motions affected to a greater extent than short range (β-like) motions during isothermal crystallization studies at all temperature conditions. The variable behavior of α-like motions at different isothermal crystallization temperatures was attributed to evolving crystallites with time and increase in electrical conductivity with temperature. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

  1. Glass transition dynamics and charge carrier mobility in conjugated polyfluorene thin films

    Science.gov (United States)

    Qin, Hui; Liu, Dan; Wang, Tao

    Conjugated polymers are commonly used in organic optoelectronic devices, e.g. organic photovoltaics (OPVs), light-emitting diodes (LEDs) and field effect transistors (FETs). In these devices, the conjugated polymers are prepared as thin films with thicknesses in the range of tens to hundreds of nanometers, and are interfaced with different function layers made from organic or inorganic materials. We have studied the glass transition temperature (Tg) of poly(9, 9-dioctylfluorene)-co-N-(1, 4-butylphenyl)diphenylamine) (TFB) thin films supported on different substrates, as well as their SCLC charge carrier mobility in photodiodes. Both Monotonic and non-monotonic Tg deviations are observed in TFB thin films supported on Si/SiOx and PEDOT:PSS, respectively. With low to moderate thermal crosslinking, the thickness dependent Tg deviation still exists, which diminishes in TFB films with a high crosslinking degree. The vertical charge carrier mobility of TFB thin films extracted from the SCLC measurements is found increase with film thickness, a value increases from 1 to 50 x 10-6 cm2 V-1 s-1 in the thickness range from 15 to 180 nm. Crosslinking was found to reduce the carrier mobility in TFB thin films. The Tg deviations are also discussed using the classic layered models in the literature. Our results provide a precise guide for the fabrication and design of high performance optoelectronic devices.

  2. Glass transition and degree of conversion of a light-cured orthodontic composite

    Directory of Open Access Journals (Sweden)

    Michela M. D. S. Sostena

    2009-12-01

    Full Text Available OBJECTIVE: This study evaluated the glass transition temperature (Tg and degree of conversion (DC of a light-cured (Fill Magic versus a chemically cured (Concise orthodontic composite. MATERIAL AND METHODS: Anelastic relaxation spectroscopy was used for the first time to determine the Tg of a dental composite, while the DC was evaluated by infrared spectroscopy. The light-cured composite specimens were irradiated with a commercial LED light-curing unit using different exposure times (40, 90 and 120 s. RESULTS: Fill Magic presented lower Tg than Concise (35-84ºC versus 135ºC, but reached a higher DC. CONCLUSIONS: The results of this study suggest that Fill Magic has lower Tg than Concise due to its higher organic phase content, and that when this light-cured composite is used to bond orthodontic brackets, a minimum energy density of 7.8 J/cm² is necessary to reach adequate conversion level and obtain satisfactory adhesion.

  3. Hydrogen bond induced nonmonotonic composition behavior of the glass transition in aqueous binary mixtures.

    Science.gov (United States)

    Sjöström, Johan; Mattsson, Johan; Bergman, Rikard; Swenson, Jan

    2011-08-25

    The glass transition temperature, T(g), of a binary mixture commonly varies monotonically between the T(g)s of its two components. However, mixtures of strongly associating liquids can instead exhibit a nonmonotonic T(g) variation. The origins of such nonideal mixing behavior have often been correlated with composition dependent structural variations. For binary mixtures between a hydrogen- (H-) bonded liquid and water, however, such behavior is generally not well understood. The ubiquity and importance of aqueous mixtures both in nature and in man-made applications stresses the needed for a better understanding. We here demonstrate nonmonotonic T(g) variations in binary mixtures of n-propylene glycol monomethyl ethers (nPGMEs) and water, where the composition dependent T(g) show maxima within an intermediate composition range. We show that these T(g) maxima correspond to crossovers in the composition dependence of the step amplitude in the isobaric heat capacity at T(g). We further demonstrate that the observed effects are caused by H-bond interactions involving the nPGME hydroxyl group. We can account for our obervations using a simple model based on two effects due to the added water: (i) an H-bond induced formation of effective relaxing entities and (ii) a plasticizing effect at high water contents. © 2011 American Chemical Society

  4. Application of biopolymers for improving the glass transition temperature of hairtail fish meat.

    Science.gov (United States)

    Yu, Haixia; Yang, Shuibing; Yuan, Chunhong; Hu, Qinglan; Li, Yuan; Chen, Shiguo; Hu, Yaqin

    2017-08-04

    Glass transition temperature (Tg ) and food moisture content are closely related, especially in foods with a high moisture content, such as surimi products. In order to improve storage condition and maintain food quality, the influence of six biopolymers on the Tg of hairtail fish meat paste was investigated by differential scanning colorimetry. Samples were stored at -8 °C (>Tg ), -14 °C (Tg ) and -18 °C (

  5. CO2 Induced Foaming Behavior of Polystyrene near the Glass Transition

    Directory of Open Access Journals (Sweden)

    Salah Al-Enezi

    2017-01-01

    Full Text Available This paper examines the effect of high-pressure carbon dioxide on the foaming process in polystyrene near the glass transition temperature and the foaming was studied using cylindrical high-pressure view cell with two optical windows. This technique has potential applications in the shape foaming of polymers at lower temperatures, dye impregnation, and the foaming of polystyrene. Three sets of experiments were carried out at operating temperatures of 50, 70, and 100°C, each over a range of pressures from 24 to 120 bar. Foaming was not observed when the polymer was initially at conditions below Tg but was observed above Tg. The nucleation appeared to occur randomly leading to subsequent bubble growth from these sites, with maximum radius of 0.02–0.83 mm. Three models were applied on the foaming experimental data. Variable diffusivity and viscosity model (Model C was applied to assess the experimental data with the WLF equation. The model shows very good agreement by using realistic parameter values. The expansion occurs by diffusion of a dissolved gas from the supersaturated polymer envelope into the bubble.

  6. Ionic liquids and their bases: Striking differences in the dynamic heterogeneity near the glass transition.

    Science.gov (United States)

    Grzybowska, K; Grzybowski, A; Wojnarowska, Z; Knapik, J; Paluch, M

    2015-11-19

    Ionic liquids (ILs) constitute an active field of research due to their important applications. A challenge for these investigations is to explore properties of ILs near the glass transition temperature Tg, which still require our better understanding. To shed a new light on the issues, we measured ILs and their base counterparts using the temperature modulated calorimetry. We performed a comparative analysis of the dynamic heterogeneity at Tg for bases and their salts with a simple monoatomic anion (Cl(-)). Each pair of ionic and non-ionic liquids is characterized by nearly the same chemical structure but their intermolecular interactions are completely different. We found that the size of the dynamic heterogeneity of ILs near Tg is considerably smaller than that established for their dipolar counterparts. Further results obtained for several other ILs near Tg additionally strengthen the conclusion about the relatively small size of the dynamic heterogeneity of molecular systems dominated by electrostatic interactions. Our finding opens up new perspectives on designing different material properties depending on intermolecular interaction types.

  7. Chemical Structure And Glass Transition Temperature Of Ricinodendron Heudelotii Wood For Its Pulp Production Potential

    Directory of Open Access Journals (Sweden)

    Bolade M. Ogunleye

    2017-02-01

    Full Text Available The chemical structure and glass transition temperature of Ricinodendron heudelotii wood were studied using Attenuated total reflectance Fourier transform infrared FTIR spectroscopy and dynamic mechanical analysis DMA respectively. The thermal characteristic of R. heudelotii was conducted on N-methyl-2-pyrolidone saturated specimens while submerged under the same solvent at a temperature range from 130 to 0C at 3Cmin multi-frequencies of 0.1-10 Hz using DMA. Ratios of syringyl to guaiacyl associated bands along the longitudinal and radial positions of the wood differ significantly. Higher syringylguaiacyl ratio of the corewood than middlewood correlate well with lowering softening temperature. The findings in this research reveals that more chemical would be required to pulp R. heudelotii wood obtained from the base 10 of the merchantable height and outerwood because of the presence of high lignin content compared to the other longitudinal and radial positions respectively where wood were collected. Also outerwood favour pulp production compared to middlewood and corewood because of the high holocellulose content.

  8. Confinement effects on glass transition temperature, transition breadth, and linear expansivity: an ultraslow X-ray reflectivity study on supported ultrathin polystyrene films.

    Science.gov (United States)

    Yang, Chunming; Onitsuka, Rena; Takahashi, Isao

    2013-06-01

    X-ray reflectivity measurements of the glass transition in thin polystyrene films supported on Si substrates were performed at slow cooling rates ranging from 0.62 to 0.01 (°)C/min. At a cooling rate of 0.14 (°)C/min, a depression in the glass transition temperature Tg was clearly observed with decreasing thickness. However, at a cooling rate of 0.62 (°)C/min, only a slight decrease in Tg for a 12-nm-thick film was observed, while at an ultraslow cooling rate of 0.01 °C/min, a significant reduction in the Tg of ultrathin films (12 and 6 nm) was observed. As the thickness decreased, a broadening in the width of the glass transition, w, was found at higher cooling rates (0.62 °C/min and 0.14 °C/min), while narrowing of w was observed at ultraslow cooling rates of 0.01 °C/min and 0.04 °C/min. A narrow distribution of relaxation time in the ultrathin films indicates that most segments are able to relax under the ultraslow cooling process, thus showing an inherent reduction in the Tg of the confined thin polymer films.

  9. The question of high- or low-temperature glass transition in frozen fish. Construction of the supplemented state diagram for tuna muscle by differential scanning calorimetry.

    Science.gov (United States)

    Orlien, Vibeke; Risbo, Jens; Andersen, Mogens L; Skibsted, Leif H

    2003-01-01

    The thermal behavior of fresh tuna muscle, rehydrated freeze-dried tuna muscle, and tuna sarcoplasmic protein fraction was studied by three types of differential scanning calorimetry (DSC): conventional DSC, alternating DSC, and sensitive micro-DSC. The relationship between glass transition temperature, T(g), and water content was established. Only a low-temperature glass transition was detected for fresh tuna and freeze-dried tuna rehydrated to high water contents, whereas for sarcoplasmic protein fraction both a low-temperature and an apparent high-temperature glass transition were detected for samples of high water content. Construction of the supplemented state diagrams for whole tuna muscle and for tuna sarcoplasmic protein fraction confirmed the low-temperature transition to be glass transition of the maximally freeze-dehydrated phase. The apparent upper transition of sarcoplasmic protein fraction was shown not to be a glass transition but rather to originate from the onset of melting of ice, and the temperature of this event should be denoted T(m)'. The glass transition temperature and the concentration of the maximally freeze dehydrated tuna muscle are -74 degrees C and 79% (w/w), respectively.

  10. Molecular simulation and mathematical modelling of glass transition temperature depression induced by CO2 plasticization in Polysulfone membranes

    Science.gov (United States)

    Lock, S. S. M.; Lau, K. K.; Lock Sow Mei, Irene; Shariff, A. M.; Yeong, Y. F.; Bustam, A. M.

    2017-08-01

    A sequence of molecular modelling procedure has been proposed to simulate experimentally validated membrane structure characterizing the effect of CO2 plasticization, whereby it can be subsequently employed to elucidate the depression in glass transition temperature (Tg ). Based on the above motivation, unswollen and swollen Polysulfone membrane structures with different CO2 loadings have been constructed, whereby the accuracy has been validated through good compliance with experimentally measured physical properties. It is found that the presence of CO2 constitutes to enhancement in polymeric chain relaxation, which consequently promotes the enlargement of molecular spacing and causes dilation in the membrane matrix. A series of glass transition temperature treatment has been conducted on the verified molecular structure to elucidate the effect of CO2 loadings to the depression in Tg induced by plasticization. Subsequently, a modified Michealis-Menten (M-M) function has been implemented to quantify the effect of CO2 loading attributed to plasticization towards Tg .

  11. Molecular origin of aging of pure Se glass: Growth of inter-chain structural correlations, network compaction, and partial ordering

    Science.gov (United States)

    Dash, S.; Chen, P.; Boolchand, P.

    2017-06-01

    Glass transition width W of pure Se narrows from 7.1(3) °C to 1.5(2) °C and the non-reversing enthalpy of relaxation (Δ Hnr) at Tg increases from 0.23(5) cal/g to 0.90(5) cal/g upon room temperature aging for 4 months in the dark as examined in modulated differential scanning colorimetry (MDSC) at low scan rates. In Raman scattering, such aging leads the A1 mode of Sen-chains (near 250 cm-1) to narrow by 26% and its scattering strength to decrease as the strength of modes of correlated chains (near 235 cm-1) and of Se8 rings (near 264 cm-1) systematically grows. These calorimetric and Raman scattering results are consistent with the "molecular" chains of Sen, predominant in the fresh glass, reconstructing with each other to compact and partially order the network. Consequences of the aging induced reconstruction of the long super-flexible and uncorrelated Sen-chains are also manifested upon alloying up to 4 mol. % of Ge as revealed by a qualitative narrowing (by 25%) of the Raman vibrational mode of the corner-sharing GeSe4 tetrahedra and a blue-shift of the said mode by nearly 1 cm-1 in 194 cm-1. But, at higher Ge content (x > 6%), as the length of Sen chain-segments across Ge cross-links decreases qualitatively (⟨n ⟩ 10% to acquire values observed earlier as alloying concentration approaches 20% and networks become spontaneously rigid.

  12. Effect of 3d-transition metal doping on the shielding behavior of barium borate glasses: a spectroscopic study.

    Science.gov (United States)

    ElBatal, H A; Abdelghany, A M; Ghoneim, N A; ElBatal, F H

    2014-12-10

    UV-visible and FT infrared spectra were measured for prepared samples before and after gamma irradiation. Base undoped barium borate glass of the basic composition (BaO 40%-B2O3 60mol.%) reveals strong charge transfer UV absorption bands which are related to unavoidable trace iron impurities (Fe(3+)) within the chemical raw materials. 3d transition metal (TM)-doped glasses exhibit extra characteristic absorption bands due to each TM in its specific valence or coordinate state. The optical spectra show that TM ions favor generally the presence in the high valence or tetrahedral coordination state in barium borate host glass. Infrared absorption bands of all prepared glasses reveal the appearance of both triangular BO3 units and tetrahedral BO4 units within their characteristic vibrational modes and the TM-ions cause minor effects because of the low doping level introduced (0.2%). Gamma irradiation of the undoped barium borate glass increases the intensity of the UV absorption together with the generation of an induced broad visible band at about 580nm. These changes are correlated with suggested photochemical reactions of trace iron impurities together with the generation of positive hole center (BHC or OHC) within the visible region through generated electrons and positive holes during the irradiation process. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Observation of exchanging role of gold and silver nanoparticles in bimetallic thin film upon annealing above the glass transition temperature

    Science.gov (United States)

    Htet Kyaw, Htet; Tay Zar Myint, Myo; Hamood Al-Harthi, Salim; Maekawa, Toru; Yanagisawa, Keiichi; Sellai, Azzouz; Dutta, Joydeep

    2017-08-01

    The exchange role of gold (Au) and silver (Ag) in bimetallic films co-evaporated onto soda-lime glass substrates with Au-Ag volume ratios of 1:2, 1:1 and 2:1 have been demonstrated. Annealing of the films above the glass transition temperature in air led to non-alloying nature of the films, silver neutrals (Ag0) and gold nanoparticles (AuNPs) on the surface, along with silver nanoparticles (AgNPs) inside the glass matrix. Moreover, the size distribution and interparticle spacing of the AuNPs on the surface were governed by the Ag content in the deposited film. In contrast, the content of Au in the film played an opposite role leading to the migration of Ag ions (i.e. Ag0 being transformed to Ag ions after annealing in oxygen ambient) to form AgNPs inside the glass matrix. The higher the Au content in the film is, the more likely Ag0 to stay on the surface and impacts on the size distribution of AuNPs and consequently on the refractive index sensitivity measurements. Experimental realisation of this fact was reflected from the best performance for localized surface plasmon resonance (LSPR) sensitivity test achieved with Au-Ag ratio of 1:2. The Au/Ag/glass bimetallic dynamic results of this study can be pertinent to sensor applications integrated with optical devices.

  14. Bonding at Compatible and Incompatible Amorphous Interfaces of Polystyrene and Poly(Methyl Methacrylate) Below the Glass Transition Temperature

    DEFF Research Database (Denmark)

    Boiko, Yuri M.; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    Films of high-molecular-weight amorphous polystyrene (PS, M-w = 225 kg/mol, M-w/M-n = 3, T-g-bulk = 97degreesC, where T-g-bulk is the glass transition temperature of the bulk sample) and poly(methyl methacrylate) (PMMA, M-w = 87 kg/mol, M-w/M-n = 2, Tg-bulk = 109degreesC) were brought into contact...

  15. Evaluating the mechanical properties of E-Glass fiber/carbon fiber reinforced interpenetrating polymer networks

    Directory of Open Access Journals (Sweden)

    G. Suresh

    2015-02-01

    Full Text Available A series of vinyl ester and polyurethane interpenetrating polymer networks were prepared by changing the component ratios of VER (Vinyl ester and PU (Polyurethane and the polymerization process was confirmed with Fourier Transform infrared spectroscopy. IPN (Inter Penetrating Polymer Network - VER/PU reinforced Glass and carbon fiber composite laminates were made using the Hand lay up technique. The Mechanical properties of the E-glass and carbon fiber specimens were compared from tests including Tensile, Compressive, Flexural, ILSS (Inter Laminar Shear Strength, Impact & Head Deflection Test (HDT. The IPN Reinforced Carbon fiber specimen showed better results in all the tests than E-Glass fibre reinforced IPN laminate with same thickness of the specimen, according to ASTM standards. It was found that the combination of 60%VER and 40%PU IPN exhibits better impact strength and maximum elongation at break, but at the slight expense of mechanical properties such as tensile, compressive, flexural, ILSS properties. The morphology of the unreinforced and reinforced composites was analyzed with help of scanning electron microscopy.

  16. Glass-Transition Temperature Profile Measured in a Wood Cell Wall Using Scanning Thermal Expansion Microscope (SThEM)

    Science.gov (United States)

    Antoniow, J. S.; Maigret, J.-E.; Jensen, C.; Trannoy, N.; Chirtoc, M.; Beaugrand, J.

    2012-11-01

    This study aims to assess the in situ spatial distribution of glass-transition temperatures ( T g) of the main lignocellulosic biopolymers of plant cell walls. Studies are conducted using scanning thermal expansion microscopy to analyze the cross-section of the cell wall of poplar. The surface topography is mapped over a range of probe-tip temperatures to capture the change of thermal expansion on the sample surface versus temperature. For different temperature values chosen between 20 °C and 250 °C, several quantitative mappings were made to show the spatial variation of the thermal expansion. As the glass transition affects the thermal expansion coefficient and elastic modulus considerably, the same data line of each topography image was extracted to identify specific thermal events in their topographic evolution as a function of temperature. In particular, it is shown that the thermal expansion of the contact surface is not uniform across the cell wall and a profile of the glass-transition temperature could thus be evidenced and quantified corresponding to the mobility of lignocellulosic polymers having a role in the organization of the cell wall structures.

  17. SEM Analysis of the Interfacial Transition Zone between Cement-Glass Powder Paste and Aggregate of Mortar under Microwave Curing.

    Science.gov (United States)

    Kong, Yaning; Wang, Peiming; Liu, Shuhua; Zhao, Guorong; Peng, Yu

    2016-08-27

    In order to investigate the effects of microwave curing on the microstructure of the interfacial transition zone of mortar prepared with a composite binder containing glass powder and to explain the mechanism of microwave curing on the improvement of compressive strength, in this study, the compressive strength of mortar under microwave curing was compared against mortar cured using (a) normal curing at 20 ± 1 °C with relative humidity (RH) > 90%; (b) steam curing at 40 °C for 10 h; and (c) steam curing at 80 °C for 4 h. The microstructure of the interfacial transition zone of mortar under the four curing regimes was analyzed by Scanning electron microscopy (SEM). The results showed that the improvement of the compressive strength of mortar under microwave curing can be attributed to the amelioration of the microstructure of the interfacial transition zone. The hydration degree of cement is accelerated by the thermal effect of microwave curing and Na⁺ partially dissolved from the fine glass powder to form more reticular calcium silicate hydrate, which connects the aggregate, calcium hydroxide, and non-hydrated cement and glass powder into a denser integral structure. In addition, a more stable triangular structure of calcium hydroxide contributes to the improvement of compressive strength.

  18. Roles of water and solids composition in the control of glass transition and stickiness of milk powders.

    Science.gov (United States)

    Silalai, Nattiga; Roos, Yrjö H

    2010-06-01

    Plasticization and glass transition of amorphous components in food powders often result in stickiness and caking. The glass transition temperature (T(g)) of milk powders was measured by differential scanning calorimetry (DSC) and a viscometer method was used to determine sticky-point temperatures. Water sorption isotherms were established for varying solids compositions. Lactose contents were analyzed by high-performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) and proteins were identified using SDS-PAGE gel electrophoresis. Solids composition and water affected both the T(g) and stickiness behavior. Stickiness was governed by carbohydrates and water plasticization. At low protein contents, precrystallization of lactose decreased the sticky point temperature, but increasing protein content in all milk powders decreased stickiness at all water activities. The results showed that glass transition can be used to describe time-dependent stickiness and crystallization phenomena, and it can be used as a parameter to control and reduce stickiness of dairy solids with various compositions.

  19. Glass Transitions, Semiconductor-Metal Transitions, and Fragilities in Ge -V -Te (V =As , Sb) Liquid Alloys: The Difference One Element Can Make

    Science.gov (United States)

    Wei, Shuai; Coleman, Garrett J.; Lucas, Pierre; Angell, C. Austen

    2017-03-01

    Glass-transition temperatures (Tg ) and liquid fragilities are measured along a line of constant Ge content in the system Ge-As-Te, and contrasted with the lack of glass-forming ability in the twin system Ge-Sb-Te at the same Ge content. The one composition established as free of crystal contamination in the latter system shows a behavior opposite to that of a more covalent system. The comparison of Tg vs bond density in the three systems Ge-As-chalcogen differing in chalcogen, i.e., S, Se, or Te, shows that as the chalcogen becomes more metallic, i.e., in the order S effect on Tg becomes systematically weaker, with a crossover at ⟨r ⟩=2.3 . When the more metallic Sb replaces As at ⟨r ⟩ greater than 2.3, incipient metallicity rather than directional bond covalency apparently gains control of the physics. This observation leads us to an examination of the electronic conductivity and then semiconductor-to-metal (SC-M ) transitions, with their associated thermodynamic manifestations in relevant liquid alloys. The thermodynamic components, as seen previously, control liquid fragility and cause fragile-to-strong transitions during cooling. We tentatively conclude that liquid-state behavior in phase-change materials is controlled by liquid-liquid (LL) and SC-M transitions that have become submerged below the liquidus surface. In the case of the Ge-Te binary, a crude extrapolation to GeTe stoichiometry indicates that the SC-M transition lies about 20% below the melting point, suggesting a parallel with the intensely researched "hidden liquid-liquid transition" in supercooled water. In the water case, superfast crystallization initiates in the high-fragility domain some 4% above the LL transition temperature (TLL ) which is located at approximately 15% below the (ambient pressure) melting point.

  20. Untangling complex networks: risk minimization in financial markets through accessible spin glass ground states.

    Science.gov (United States)

    Lisewski, Andreas Martin; Lichtarge, Olivier

    2010-08-15

    Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the relative margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network's Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.

  1. Searching for planetary transits around M dwarfs with telescope networks

    Directory of Open Access Journals (Sweden)

    Casal Estefanía

    2013-04-01

    Full Text Available As of today, hundreds of extrasolar planets have been discoverd, and thousands of candidates are waiting for confirmation. Although we already have discovered dozens of the least massive planets (the so called super-Earths, only a few have been found to be orbiting low mass stars, and only one that actually transist a bright M star. Here, we propose to carry out a photometric search for transiting super-Earths in the Habitable Zone of a large sample of very low-mass stars (M < 0.3 M⊙. These planets have a higher transit detection probability, shorter orbital periods and produce larger radial velocity amplitudes than those orbiting Solar type stars. The observing strategy proposed for such a search would require a robotic network of 1-m class telescopes, such as the LCOGT will provide.

  2. Effect of sugar addition on glass transition temperatures of cassava starch with low to intermediate moisture contents.

    Science.gov (United States)

    Figueroa, Yetzury; Guevara, Marvilan; Pérez, Adriana; Cova, Aura; Sandoval, Aleida J; Müller, Alejandro J

    2016-08-01

    This work studies how sucrose (S) addition modifies the thermal properties of cassava starch (CS). Neat CS and CS-S blends with 4, 6 and 8% sugar contents (CS-S-4%, CS-S-6% and CS-S-8%) were prepared and analyzed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), in a wide range of moisture levels (2-20%). In equilibrated samples with moisture contents lower than 10%, twoendothermic steps were observed during first DSC heating scans and two corresponding relaxation maxima in tan δ were detected by DMTA. The first transition, detected at around 45-55°C by both DSC and DMTA, is frequently found in starchy foods, while the second observed at higher temperatures is associated to the glass transition temperature of the blends. At higher moisture contents, only one thermal transition was observed. Samples analyzed immediately after cooling from the melt (i.e., after erasing their thermal history), exhibited a single glass transition temperature, regardless of their moisture content. Addition of sugar promotes water plasticization of CS only at high moisture contents. In the low moisture content range, anti-plasticization was observed for both neat and sugar-added CS samples. Addition of sugar decreases the moisture content needed to achieve the maximum value of the glass transition temperature before plasticization starts. The results of this work may be valuable for the study of texture establishment in low moisture content extruded food products. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Computational modelling of large deformations in layered-silicate/PET nanocomposites near the glass transition

    Science.gov (United States)

    Figiel, Łukasz; Dunne, Fionn P. E.; Buckley, C. Paul

    2010-01-01

    Layered-silicate nanoparticles offer a cost-effective reinforcement for thermoplastics. Computational modelling has been employed to study large deformations in layered-silicate/poly(ethylene terephthalate) (PET) nanocomposites near the glass transition, as would be experienced during industrial forming processes such as thermoforming or injection stretch blow moulding. Non-linear numerical modelling was applied, to predict the macroscopic large deformation behaviour, with morphology evolution and deformation occurring at the microscopic level, using the representative volume element (RVE) approach. A physically based elasto-viscoplastic constitutive model, describing the behaviour of the PET matrix within the RVE, was numerically implemented into a finite element solver (ABAQUS) using an UMAT subroutine. The implementation was designed to be robust, for accommodating large rotations and stretches of the matrix local to, and between, the nanoparticles. The nanocomposite morphology was reconstructed at the RVE level using a Monte-Carlo-based algorithm that placed straight, high-aspect ratio particles according to the specified orientation and volume fraction, with the assumption of periodicity. Computational experiments using this methodology enabled prediction of the strain-stiffening behaviour of the nanocomposite, observed experimentally, as functions of strain, strain rate, temperature and particle volume fraction. These results revealed the probable origins of the enhanced strain stiffening observed: (a) evolution of the morphology (through particle re-orientation) and (b) early onset of stress-induced pre-crystallization (and hence lock-up of viscous flow), triggered by the presence of particles. The computational model enabled prediction of the effects of process parameters (strain rate, temperature) on evolution of the morphology, and hence on the end-use properties.

  4. Network topology for the formation of solvated electrons in binary CaO–Al2O3 composition glasses

    Science.gov (United States)

    Akola, Jaakko; Kohara, Shinji; Ohara, Koji; Fujiwara, Akihiko; Watanabe, Yasuhiro; Masuno, Atsunobu; Usuki, Takeshi; Kubo, Takashi; Nakahira, Atsushi; Nitta, Kiyofumi; Uruga, Tomoya; Weber, J. K. Richard; Benmore, Chris J.

    2013-01-01

    Glass formation in the CaO–Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO–Al2O3 glasses using combined density functional theory–reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O–Ca and O–Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al–O is stronger than that of Ca–O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71–74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass. PMID:23723350

  5. Network topology for the formation of solvated electrons in binary CaO-Al2O3 composition glasses.

    Science.gov (United States)

    Akola, Jaakko; Kohara, Shinji; Ohara, Koji; Fujiwara, Akihiko; Watanabe, Yasuhiro; Masuno, Atsunobu; Usuki, Takeshi; Kubo, Takashi; Nakahira, Atsushi; Nitta, Kiyofumi; Uruga, Tomoya; Weber, J K Richard; Benmore, Chris J

    2013-06-18

    Glass formation in the CaO-Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO-Al2O3 glasses using combined density functional theory-reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O-Ca and O-Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al-O is stronger than that of Ca-O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71-74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass.

  6. Complex Network Theory Applied to the Growth of Kuala Lumpur's Public Urban Rail Transit Network.

    Directory of Open Access Journals (Sweden)

    Rui Ding

    Full Text Available Recently, the number of studies involving complex network applications in transportation has increased steadily as scholars from various fields analyze traffic networks. Nonetheless, research on rail network growth is relatively rare. This research examines the evolution of the Public Urban Rail Transit Networks of Kuala Lumpur (PURTNoKL based on complex network theory and covers both the topological structure of the rail system and future trends in network growth. In addition, network performance when facing different attack strategies is also assessed. Three topological network characteristics are considered: connections, clustering and centrality. In PURTNoKL, we found that the total number of nodes and edges exhibit a linear relationship and that the average degree stays within the interval [2.0488, 2.6774] with heavy-tailed distributions. The evolutionary process shows that the cumulative probability distribution (CPD of degree and the average shortest path length show good fit with exponential distribution and normal distribution, respectively. Moreover, PURTNoKL exhibits clear cluster characteristics; most of the nodes have a 2-core value, and the CPDs of the centrality's closeness and betweenness follow a normal distribution function and an exponential distribution, respectively. Finally, we discuss four different types of network growth styles and the line extension process, which reveal that the rail network's growth is likely based on the nodes with the biggest lengths of the shortest path and that network protection should emphasize those nodes with the largest degrees and the highest betweenness values. This research may enhance the networkability of the rail system and better shape the future growth of public rail networks.

  7. Quantum spin-glass transition in the two-dimensional electron gas

    Indian Academy of Sciences (India)

    Abstract. We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides in the plane orthogonal to the ferromagnetic moment.

  8. Rounding of abrupt phase transitions in brain networks

    Science.gov (United States)

    Villa Martín, Paula; Moretti, Paolo; Muñoz, Miguel A.

    2015-01-01

    The observation of critical-like behavior in cortical networks represents a major step forward in elucidating how the brain manages information. Understanding the origin and functionality of critical-like dynamics, as well as its robustness, is a major challenge in contemporary neuroscience. Here, we present an extensive numerical study of a family of simple dynamical models, which describe activity propagation in brain networks through the integration of different neighboring spiking potentials, mimicking basic neural interactions. The requirement of signal integration may lead to discontinuous phase transitions in networks that are well described by the mean-field approximation, thus preventing the emergence of critical points in such systems. Brain networks, however, are finite dimensional and exhibit a heterogeneous hierarchical structure that cannot be encoded in mean-field models. Here we propose that, as a consequence of the presence of such a heterogeneous substrate with its concomitant structural disorder, critical-like features may emerge even in the presence of integration. These conclusions may prove significant in explaining the observation of traits of critical behavior in large-scale measurements of brain activity.

  9. Kinetics of a bioactive compound (caffeine) mobility at the vicinity of the mechanical glass transition temperature induced by gelling polysaccharide.

    Science.gov (United States)

    Jiang, Bin; Kasapis, Stefan

    2011-11-09

    An investigation of the diffusional mobility of a bioactive compound (caffeine) within the high-solid (80.0% w/w) matrices of glucose syrup and κ-carrageenan plus glucose syrup exhibiting distinct mechanical glass transition properties is reported. The experimental temperature range was from 20 to -60 °C, and the techniques of modulated differential scanning calorimetry, small deformation dynamic oscillation in shear, and UV spectrometry were employed. Calorimetric and mechanical measurements were complementary in recording the relaxation dynamics of high-solid matrices upon controlled heating. Predictions of the reaction rate theory and the combined WLF/free volume framework were further utilized to pinpoint the glass transition temperature (T(g)) of the two matrices in the softening dispersion. Independent of composition, calorimetry yielded similar T(g) predictions for both matrices at this level of solids. Mechanical experimentation, however, was able to detect the effect of adding gelling polysaccharide to glucose syrup as an accelerated pattern of vitrification leading to a higher value of T(g). Kinetic rates of caffeine diffusion within the experimental temperature range were taken with UV spectroscopy. These demonstrated the pronounced effect of the gelling κ-carrageenan/glucose syrup mixture to retard diffusion of the bioactive compound near the mechanical T(g). Modeling of the diffusional mobility of caffeine produced activation energy and fractional free-volume estimates, which were distinct from those of the carbohydrate matrix within the glass transition region. This result emphasizes the importance of molecular interactions between macromolecular matrix and small bioactive compound in glass-related relaxation phenomena.

  10. The network modifier and former role of the bismuth ions in the bismuth-lead-germanate glasses.

    Science.gov (United States)

    Rada, M; Rus, L; Rada, S; Culea, E; Rusu, T

    2014-11-11

    The present work is focused on the enhancement of network former environment in lead-germanate glasses by bismuth ions doping. A series of bismuth-lead-germanate glasses with the xBi2O3·(100-x)[7GeO2·3PbO] composition glass where 0≤x≤30 mol% Bi2O3 were synthesized by melt-quenching method. The FTIR, UV-VIS spectroscopy and cyclic voltammetry were conducted on these samples to evaluate the doping effect of structure of the host matrix network. Our results indicate that direct incorporation of Bi2O3 into the lead-germanate network modifies the lead-germanate network and the internal structure of glass network is rearranged. The structural flexibility of the lead-germanate network is possible due to its incapacity to accommodate with the excess of oxygen atoms and the creation of bridging oxygen ions. Optical gap energy and refractive index were obtained as a function of Bi2O3 content. Gap energy values decrease as Bi2O3 content increased from 0 to 10 mol%. Further increase of Bi2O3 concentration beyond 10 mol% increased the gap energy values. These behaviors of the glass system can be explained by two mechanisms: (i) for x≤10 mol% Bi2O3--increase of degree of disorder of the host matrix because Bi2O3 is network modifier and (ii) for x>10 mol%--Bi2O3 acts as a network former. Cyclic voltammetry measurements using the glass system with 10Bi2O3·90[7GeO2·3PbO] composition as working electrode show the mobility of the lead ions, in agreement with UV-VIS data. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Chaotic state to self-organized critical state transition of serrated flow dynamics during brittle-to-ductile transition in metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.; Wang, W. H.; Bai, H. Y., E-mail: hybai@aphy.iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, B. A. [Centre for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon Tong, Kowloon (Hong Kong)

    2016-02-07

    We study serrated flow dynamics during brittle-to-ductile transition induced by tuning the sample aspect ratio in a Zr-based metallic glass. The statistical analysis reveals that the serrated flow dynamics transforms from a chaotic state characterized by Gaussian-distribution serrations corresponding to stick-slip motion of randomly generated and uncorrelated single shear band and brittle behavior, into a self-organized critical state featured by intermittent scale-free distribution of shear avalanches corresponding to a collective motion of multiple shear bands and ductile behavior. The correlation found between serrated flow dynamics and plastic deformation might shed light on the plastic deformation dynamic and mechanism in metallic glasses.

  12. Superconductor-insulator transition on annealed complex networks

    Science.gov (United States)

    Bianconi, Ginestra

    2012-06-01

    Cuprates show multiphase and multiscale complexity that has hindered physicists search for the mechanism of high Tc for many years. Recently the interest has been addressed to a possible optimum inhomogeneity of dopants, defects, and interstitials, and the structural scale invariance of dopants detected by scanning micro-x-ray diffraction has been reported to promote the critical temperature. In order to shed light on critical phenomena on granular materials, here we propose a stylized model capturing the essential characteristics of the superconducting-insulator transition of a highly dynamical, heterogeneous granular material: the random transverse Ising model (RTIM) on annealed complex network. We show that when the networks encode for high heterogeneity of the expected degrees described by a power-law distribution, the critical temperature for the onset of the superconducting phase diverges to infinity as the power-law exponent γ of the expected degree distribution is less than 3, i.e., γelectronic background is triggered by an external parameter g that determines an exponential cutoff in the power-law expected degree distribution characterized by an exponent γ. We find that for g=gc the critical temperature for the superconducting-insulator transition has a maximum if γ>3 and diverges if γ<3.

  13. Water-dependent interfacial transition zone in resin-modified glass-ionomer cement/dentin interfaces.

    Science.gov (United States)

    Tay, F R; Sidhu, S K; Watson, T F; Pashley, D H

    2004-08-01

    The function of the interfacial transition zone (absorption layer) in resin-modified glass-ionomer cements bonded to deep dentin remains obscure. This study tested the hypotheses that the absorption layer is formed only in the presence of water derived from hydrated dentin and allows for better bonding of resin-modified glass-ionomer cements to dentin. Ten percent polyacrylic acid-conditioned, hydrated, and dehydrated deep dentin specimens were bonded with 2 resin-modified glass-ionomer cements and sealed with resins to prevent environmental water gain or loss. A non-particulate absorption layer was identified over hydrated dentin only, and was clearly discernible from the hybrid layer when bonded interfaces were examined with transmission electron microscopy. This layer was relatively more resistant to dehydration stresses, and remained intact over the dentin surface after tensile testing. The absorption layer mediates better bonding of resin-modified glass-ionomer cements to deep dentin, and functions as a stress-relieving layer to reduce stresses induced by desiccation and shrinkage.

  14. Heat capacities and volumetric changes in the glass transition range: a constitutive approach based on the standard linear solid

    Science.gov (United States)

    Lion, Alexander; Mittermeier, Christoph; Johlitz, Michael

    2017-09-01

    A novel approach to represent the glass transition is proposed. It is based on a physically motivated extension of the linear viscoelastic Poynting-Thomson model. In addition to a temperature-dependent damping element and two linear springs, two thermal strain elements are introduced. In order to take the process dependence of the specific heat into account and to model its characteristic behaviour below and above the glass transition, the Helmholtz free energy contains an additional contribution which depends on the temperature history and on the current temperature. The model describes the process-dependent volumetric and caloric behaviour of glass-forming materials, and defines a functional relationship between pressure, volumetric strain, and temperature. If a model for the isochoric part of the material behaviour is already available, for example a model of finite viscoelasticity, the caloric and volumetric behaviour can be represented with the current approach. The proposed model allows computing the isobaric and isochoric heat capacities in closed form. The difference c_p -c_v is process-dependent and tends towards the classical expression in the glassy and equilibrium ranges. Simulations and theoretical studies demonstrate the physical significance of the model.

  15. Transitioning glass-ceramic scintillators for diagnostic x-ray imaging from the laboratory to commercial scale

    Science.gov (United States)

    Beckert, M. Brooke; Gallego, Sabrina; Elder, Eric; Nadler, Jason

    2016-10-01

    This study sought to mitigate risk in transitioning newly developed glass-ceramic scintillator technology from a laboratory concept to commercial product by identifying the most significant hurdles to increased scale. These included selection of cost effective raw material sources, investigation of process parameters with the most significant impact on performance, and synthesis steps that could see the greatest benefit from participation of an industry partner that specializes in glass or optical component manufacturing. Efforts focused on enhancing the performance of glass-ceramic nanocomposite scintillators developed specifically for medical imaging via composition and process modifications that ensured efficient capture of incident X-ray energy and emission of scintillation light. The use of cost effective raw materials and existing manufacturing methods demonstrated proof-of-concept for economical viable alternatives to existing benchmark materials, as well as possible disruptive applications afforded by novel geometries and comparatively lower cost per volume. The authors now seek the expertise of industry to effectively navigate the transition from laboratory demonstrations to pilot scale production and testing to evince the industry of the viability and usefulness of composite-based scintillators.

  16. Identification of Conserved Moieties in Metabolic Networks by Graph Theoretical Analysis of Atom Transition Networks

    Science.gov (United States)

    Haraldsdóttir, Hulda S.; Fleming, Ronan M. T.

    2016-01-01

    Conserved moieties are groups of atoms that remain intact in all reactions of a metabolic network. Identification of conserved moieties gives insight into the structure and function of metabolic networks and facilitates metabolic modelling. All moiety conservation relations can be represented as nonnegative integer vectors in the left null space of the stoichiometric matrix corresponding to a biochemical network. Algorithms exist to compute such vectors based only on reaction stoichiometry but their computational complexity has limited their application to relatively small metabolic networks. Moreover, the vectors returned by existing algorithms do not, in general, represent conservation of a specific moiety with a defined atomic structure. Here, we show that identification of conserved moieties requires data on reaction atom mappings in addition to stoichiometry. We present a novel method to identify conserved moieties in metabolic networks by graph theoretical analysis of their underlying atom transition networks. Our method returns the exact group of atoms belonging to each conserved moiety as well as the corresponding vector in the left null space of the stoichiometric matrix. It can be implemented as a pipeline of polynomial time algorithms. Our implementation completes in under five minutes on a metabolic network with more than 4,000 mass balanced reactions. The scalability of the method enables extension of existing applications for moiety conservation relations to genome-scale metabolic networks. We also give examples of new applications made possible by elucidating the atomic structure of conserved moieties. PMID:27870845

  17. Untangling complex networks: Risk minimization in financial markets through accessible spin glass ground states

    Science.gov (United States)

    Lisewski, Andreas Martin; Lichtarge, Olivier

    2010-08-01

    Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network’s Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.

  18. The order parameter of glass transition: Spontaneously delocalized nanoscale solitary wave with transverse ripplon-like soft wave

    Directory of Open Access Journals (Sweden)

    Jia Lin Wu

    2013-06-01

    Full Text Available In macromolecular self-avoiding random walk, movement of each chain-particle accompanies an instantaneous spin system with de Gennes n = 0 that provides extra energy, extra vacancy volume and relaxation time needed for chain-particles co-movement. Using these additional and instantaneous spin systems not only directly yields the same Brownian motion mode in glass transition (GT and reptation-tube model, but also proves that the entangled chain length corresponding to the Reynolds number in hydrodynamics and the inherent diffusion - delocalization mode of entangled chains, from frozen glass state to melt liquid state, is a chain-size solitary wave with transverse ripplon-like soft wave. Thus, the order parameter of GT is found. The various currently available GT theories, such as Static Replica, Random First-Order Transition, Potential Energy Landscape, Mode-Coupling and Nanoscale Heterogeneity, can be unified using the additional and instantaneous spin system. GT served as an inspiration and continues to serve as the paradigm in the universal random delocalization transitions from disorder to more disorder until turbulence.

  19. The order parameter of glass transition: Spontaneously delocalized nanoscale solitary wave with transverse ripplon-like soft wave

    Science.gov (United States)

    Wu, Jia Lin

    2013-06-01

    In macromolecular self-avoiding random walk, movement of each chain-particle accompanies an instantaneous spin system with de Gennes n = 0 that provides extra energy, extra vacancy volume and relaxation time needed for chain-particles co-movement. Using these additional and instantaneous spin systems not only directly yields the same Brownian motion mode in glass transition (GT) and reptation-tube model, but also proves that the entangled chain length corresponding to the Reynolds number in hydrodynamics and the inherent diffusion - delocalization mode of entangled chains, from frozen glass state to melt liquid state, is a chain-size solitary wave with transverse ripplon-like soft wave. Thus, the order parameter of GT is found. The various currently available GT theories, such as Static Replica, Random First-Order Transition, Potential Energy Landscape, Mode-Coupling and Nanoscale Heterogeneity, can be unified using the additional and instantaneous spin system. GT served as an inspiration and continues to serve as the paradigm in the universal random delocalization transitions from disorder to more disorder until turbulence.

  20. Origin of the strain glass transition in Ti{sub 50}(Ni{sub 50−x} D{sub x}) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xu [School of Materials Science and Engineering, Beihang University, Beijing, 100191 (China); Shang, Jia-Xiang, E-mail: shangjx@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing, 100191 (China); Wang, Fu-He [Department of Physics, Capital Normal University, Beijing, 100048 (China); Chen, Yue, E-mail: yuechen@hku.hk [Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR (China)

    2016-09-05

    Direct evidence was recently discovered for the unique strain glass (STG) transition, which breaks the local symmetries (PRL 112, 025701 (2014)). To understand the origin of the STG transition, the effects of doping point defects on Ti{sub 50}(Ni{sub 50−x} D{sub x}) are investigated using first-principle calculations. The experimental observation that STG only exists in a limited range of chemical composition x is successfully rationalized. The mechanisms that correspond to the division of a system into domains with distinctly different compositions are found to be directly related to a dip in the defect formation energy. - Highlights: • The strain glass transition phenomenon in Ti−Ni-based alloys is rationalized. • The electronic-structure origins of the strain glass transition are uncovered. • The separation of domains with different compositions is explained.

  1. Coherent Network Optimizing of Rail-Based Urban Mass Transit

    Directory of Open Access Journals (Sweden)

    Ying Zhang

    2012-01-01

    Full Text Available An efficient public transport is more than ever a crucial factor when it comes to the quality of life and competitiveness of many cities and regions in Asia. In recent years, the rail-based urban mass transit has been regarded as one of the key means to overcoming the great challenges in Chinese megacities. The purpose of this study is going to develop a coherent network optimizing for rail-based urban mass transit to find the best alternatives for the user and to demonstrate how to meet sustainable development needs and to match the enormous capacity requirements simultaneously. This paper presents an introduction to the current situation of the important lines, and transfer points in the metro system Shanghai. The insufficient aspects are analyzed and evaluated; while the optimizing ideas and measurements are developed and concreted. A group of examples are used to illustrate the approach. The whole study could be used for the latest reference for other megacities which have to be confronted with the similar situations and processes with enormous dynamic travel and transport demands.

  2. Multicolor emission based on amorphous-to-crystalline phase transitions in nanostructured Mn-doped glass

    Science.gov (United States)

    Hoshino, Yoshinobu; Takahashi, Yoshihiro; Terakado, Nobuaki; Fujiwara, Takumi

    2017-12-01

    We fabricated glass-ceramics composed of emissive nanocrystals that show variation in photoluminescence coloration. The change in emission color is based on the amorphous-to-crystalline phase transformation in a Mn-containing zincogermanate glass. The transformation occurred at a 50 °C temperature range (538–588 °C), resulting in a change in photoluminescence color from orange to white to green. The color change is attributed to the co-crystallization of emissive nanophases and a change in the coordination state of Mn2+. Using laser-induced crystallization, we also achieved the space-selective arrangement of the different photoluminescence colors, indicating that photoluminescence coloration can be tuned in this Mn-doped glass.

  3. Highly sensitive pseudo-differential ac-nanocalorimeter for the study of the glass transition

    Energy Technology Data Exchange (ETDEWEB)

    Laarraj, Mohcine [Institut NÉEL, CNRS, 25 Avenue des Martyrs, F-38042 Grenoble (France); University Grenoble Alpes, Institut NEEL, F-38042 Grenoble (France); Laboratoire d’Ingénierie et des Matériaux (LIMAT), Université Hassan II de Casablanca, Faculté des Sciences Ben M’Sik, Casablanca Maroc (Morocco); Adhiri, Rahma; Moussetad, Mohamed [Laboratoire d’Ingénierie et des Matériaux (LIMAT), Université Hassan II de Casablanca, Faculté des Sciences Ben M’Sik, Casablanca Maroc (Morocco); Ouaskit, Said [Laboratoire de Physique de la Matière Condensée (LPMC), Université Hassan II de Casablanca, Faculté des Sciences Ben M’Sik, Casablanca Maroc (Morocco); Guttin, Christophe; Richard, Jacques; Garden, Jean-Luc [Institut NÉEL, CNRS, 25 Avenue des Martyrs, F-38042 Grenoble (France); University Grenoble Alpes, Institut NEEL, F-38042 Grenoble (France)

    2015-11-15

    We present a nanocalorimeter designed for the measurement of the dynamic heat capacity of thin films. The microfabricated sensor, the thermal conditioning of the sensor, as well as the highly stable and low noise electronic chain allow measurements of the real and imaginary parts of the complex specific heat with a resolution Δ C/C of about 10{sup −5}. The performances of this quasi-differential nanocalorimeter were tested on a model of polymeric glass-former, the polyvinyl acetate (PVAc). The high stability and low noise of the device are essential for accurate studies on non-equilibrium slow relaxing systems such as glasses.

  4. Influence of chain topology and bond potential on the glass transition of polymer chains simulated with the bond fluctuation model

    Energy Technology Data Exchange (ETDEWEB)

    Freire, J J [Departamento de Ciencias y Tecnicas FisicoquImicas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia (UNED), Senda del Rey 9, 28040 Madrid (Spain)], E-mail: jfreire@invi.uned.es

    2008-07-16

    The bond fluctuation model with a bond potential has been applied to investigation of the glass transition of linear chains and chains with a regular disposition of small branches. Cooling and subsequent heating curves are obtained for the chain energies and also for the mean acceptance probability of a bead jump. In order to mimic different trends to vitrification, a factor B gauging the strength of the bond potential with respect to the long-range potential (i.e. the intramolecular or intermolecular potential between indirectly bonded beads) has been introduced. (A higher value of B leads to a preference for the highest bond lengths and a higher total energy, implying a greater tendency to vitrify.) Different cases have been considered for linear chains: no long-range potential, no bond potential and several choices for B. Furthermore, two distinct values of B have been considered for alternate bonds in linear chains. In the case of the branched chains, mixed models with different values of B for bonds in the main chain and in the branches have also been investigated. The possible presence of ordering or crystallization has been characterized by calculating the collective light scattering function of the different samples after annealing at a convenient temperature below the onset of the abrupt change in the curves associated with a thermodynamic transition. It is concluded that ordering is inherited more efficiently in the systems with branched chains and also for higher values of B. The branched molecules with the highest B values in the main chain bonds exhibit two distinct transitions in the heating curves, which may be associated with two glass transitions. This behavior has been detected experimentally for chains with relatively long flexible branches.

  5. Dynamical transition in molecular glasses and proteins observed by spin relaxation of nitroxide spin probes and labels

    Science.gov (United States)

    Golysheva, Elena A.; Shevelev, Georgiy Yu.; Dzuba, Sergei A.

    2017-08-01

    In glassy substances and biological media, dynamical transitions are observed in neutron scattering that manifests itself as deviations of the translational mean-squared displacement, , of hydrogen atoms from harmonic dynamics. In biological media, the deviation occurs at two temperature intervals, at ˜100-150 K and at ˜170-230 K, and it is attributed to the motion of methyl groups in the former case and to the transition from harmonic to anharmonic or diffusive motions in the latter case. In this work, electron spin echo (ESE) spectroscopy—a pulsed version of electron paramagnetic resonance—is applied to study the spin relaxation of nitroxide spin probes and labels introduced in molecular glass former o-terphenyl and in protein lysozyme. The anisotropic contribution to the rate of the two-pulse ESE decay, ΔW, is induced by spin relaxation appearing because of restricted orientational stochastic molecular motion; it is proportional to τc, where is the mean-squared angle of reorientation of the nitroxide molecule around the equilibrium position and τc is the correlation time of reorientation. The ESE time window allows us to study motions with τc τc temperature dependence shows a transition near 240 K, which is in agreement with the literature data on . For spin probes of essentially different size, the obtained data were found to be close, which evidences that motion is cooperative, involving a nanocluster of several neighboring molecules. For the dry lysozyme, the τc values below 260 K were found to linearly depend on the temperature in the same way as it was observed in neutron scattering for . As spin relaxation is influenced only by stochastic motion, the harmonic motions seen in ESE must be overdamped. In the hydrated lysozyme, ESE data show transitions near 130 K for all nitroxides, near 160 K for the probe located in the hydration layer, and near 180 K for the label in the protein interior. For this system, the two latter transitions are not

  6. Role of Sulfur as a Reducing Agent for the Transition Metals Incorporated into Lithium Silicate Glass

    Directory of Open Access Journals (Sweden)

    M. Y. Hassaan

    2015-12-01

    Full Text Available Li2O·0.25Fe2O3·0.25NiO·1.5SiO2 glass was prepared with and without 5 wt % sulfur (S while melting the mixture of the starting materials at 1350 °C for 1 h in air. A part of the as-prepared glass was heat treated for 1 h near its crystallization temperature (Tc as determined from differential thermal analysis. Each glass was also investigated by means of Mössbauer spectroscopy, X-ray diffraction, FTIR, and DC conductivity. The Mössbauer spectra showed ionic Fe2+ and Fe3+ species in the glass as well as in the precipitated phase obtained after heat treatment. XRD patterns demonstrated the glassy phase formation in the as-quenched samples irrespective of the presence of sulfur. The heat treated samples showed different precipitated phases containing iron particles of nanometer size. The electric conductivity measurements showed that sulfur-doped samples had high values of (σ probably because of small polaron hopping between Fe2+ and Fe3+.

  7. On the Frequency Correction in Temperature-Modulated Differential Scanning Calorimetry of Glass Transition

    DEFF Research Database (Denmark)

    Guo, Xiaoju; Mauro, J.C.; Allan, D.C.

    2012-01-01

    Temperature-modulated differential scanning calorimetry (TMDSC) is based on conventional DSC but with a sinusoidally modulated temperature path. Simulations of TMDSC signals were performed for Corning EAGLE XG® glass over a wide range of modulation frequencies. Our results reveal that the frequency...

  8. Unraveling protein stabilization mechanisms : Vitrification and water replacement in a glass transition temperature controlled system

    NARCIS (Netherlands)

    Grasmeijer, N; Stankovic, M; de Waard, H; Frijlink, H W; Hinrichs, W L J

    2013-01-01

    The aim of this study was to elucidate the role of the two main mechanisms used to explain the stabilization of proteins by sugar glasses during drying and subsequent storage: the vitrification and the water replacement theory. Although in literature protein stability is often attributed to either

  9. EFFECTS OF TRITIUM GAS EXPOSURE ON THE GLASS TRANSITION TEMPERATURE OF EPDM ELASTOMER AND ON THE CONDUCTIVITY OF POLYANILINE

    Energy Technology Data Exchange (ETDEWEB)

    Clark, E; Marie Kane, M

    2008-12-12

    Four formulations of EPDM (ethylene-propylene diene monomer) elastomer were exposed to tritium gas initially at one atmosphere and ambient temperature for between three and four months in closed containers. Material properties that were characterized include density, volume, mass, appearance, flexibility, and dynamic mechanical properties. The glass transition temperature was determined by analysis of the dynamic mechanical property data per ASTM standards. EPDM samples released significant amounts of gas when exposed to tritium, and the glass transition temperature increased by about 3 C. during the exposure. Effects of ultraviolet and gamma irradiation on the surface electrical conductivity of two types of polyaniline films are also documented as complementary results to planned tritium exposures. Future work will determine the effects of tritium gas exposure on the electrical conductivity of polyaniline films, to demonstrate whether such films can be used as a sensor to detect tritium. Surface conductivity was significantly reduced by irradiation with both gamma rays and ultraviolet light. The results of the gamma and UV experiments will be correlated with the tritium exposure results.

  10. An Analysis of Public Transit Connectivity Index in Tehran. The Case Study: Tehran Multi-Modal Transit Network

    Directory of Open Access Journals (Sweden)

    Amir Reza Mamdoohi

    2016-10-01

    Full Text Available Public transit is a major priority in modern management of large cities and metropolitan areas in particular. Public transit systems in such cities consist of a large number of nodes and lines which are represented by a complex network. A station for public transit is a bridge between the people and public transit network, based on which, the concept of input and output power for each station can be defined. The objective of this study is the application of the transit connectivity indices to the multimodal transit network in the city of Tehran. The public transit network data employed in this study is taken from Tehran Traffic Control Company, and Tehran Urban and Suburban Railway Operation Company. The methodology for measuring transit connectivity consists of three measures: Node connectivity, Line connectivity and Regional connectivity, where activity density is applied to these measures. The results of node connectivity analysis shows that most of the node connectivity in concentrated in the city center with many nodes in the center along routes going north and south. The line connectivity analysis shows that there is a concentration of highly connected lines that are near Tehran municipality region 12 and 16. Finally, we find that areas with more metro and bus facilities with respect to the other areas, have a better regional connectivity. One of these areas includes Sadeghiyeh Metro Station which is the junction of Tehran Metro Line 2 and Tehran Metro Line 5 which have a high connectivity power. Results of this study can be used to suggest some ideas on how future investments in rail and bus should be prioritized. Particularly in Transit Oriented Development (TOD and sustainble development projects, urban planners can design transit stations with high performance to access the crucial services in poor areas.

  11. Customer-Driven Supply Chains From Glass Pipelines to Open Innovation Networks

    CERN Document Server

    Lyons, Andrew C; Piller, Frank; Poler, Raúl

    2012-01-01

    In recent years, the supply chain has become a key element to the survival and prosperity of organisations in different industry sectors. Organisations dealing in dynamic business environments demand supply chains that support the satisfaction of customer needs. The principles of lean thinking that once permeated standalone organisations have now been transferred to the supply chain, making imperative the development of innovative approaches to supply chain management.    Customer-Driven Supply Chains: From Glass Pipelines to Open Innovation Networks reviews the concept of lean thinking and its relationship to other key initiatives associated with supply chain management. Detailed industrial case studies based on the authors’ experience illustrate the principles behind lean supply chains. Moreover, a series of diagrams are used to illustrate critical concepts and supply chain architectures. Special emphasis is placed on the importance of transferring lean principles from the organisational level to the s...

  12. Looking at learning communities with the appropriate glasses: hints and ideas from network sciences

    Directory of Open Access Journals (Sweden)

    Fabio Nascimbeni

    2013-02-01

    Full Text Available 0 0 1 229 1263 USAL 10 2 1490 14.0 Normal 0 21 false false false ES JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-ansi-language:ES; mso-fareast-language:EN-US;} The level of network thinking within education – intended as the capacity to look at learning systems and communities by focussing on the relations among the involved actors (primarily teachers and learners and not only on the actors characteristics – is growing, with different speeds depending on the educational sector, but not at the pace needed to keep up with the increasingly network nature of our societies. We claim that educational research and practices should increase their capacity to look at learning communities through appropriate “networking-sensitive” glasses, and get equipped with tools and methods – such as Social network Analysis - to properly understand and support these networks. The application of Social Network Analysis to education, especially in the case of distance learning, can allow understanding the patterns of interactions between teachers and learners, and can facilitate the consolidation of new approaches to understand collaboration mechanisms. The paper presents and discusses - from a learning viewpoint - a brief overview of the main theoretical and practical contributions coming from Social Network Analysis – such as the “random graphs”, the “small-worlds” or the “weak-ties” theories – together with some general

  13. The influence of some transition metal ions in lead- and calcium-phosphate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Vedeanu, N.S. [Iuliu Hatieganu University of Medicine and Pharmacy, Department of Physics-Biophysics, RO-400023 Cluj-Napoca (Romania); Magdas, D.A., E-mail: amagdas@itim-cj.ro [National Institute for Research and Development for Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania)

    2012-09-05

    Highlights: Black-Right-Pointing-Pointer Preparation of phosphate glasses dopped with: CuO, V{sub 2}O{sub 5}, Fe{sub 2}O{sub 3}, MoO{sub 3.} Black-Right-Pointing-Pointer EPR investigation on x(CuO{center_dot}V{sub 2}O{sub 5})(100-x)[P{sub 2}O{sub 5}{center_dot}CaO] glass system, x Less-Than-Or-Slanted-Equal-To 50 mol%. Black-Right-Pointing-Pointer EPR investigation on x(Fe{sub 2}O{sub 3}MoO{sub 3}) (1-x)[2P{sub 2}O{sub 5}PbO] glass system, x Less-Than-Or-Slanted-Equal-To 50 mol%. - Abstract: Phosphate glasses, despite of their poor chemical durability have many biomedical and technological applications. Phosphate materials containing calcium oxide are intensely studied because they may have bioactive potential. Such materials with calcium oxide can be produced to have similar bone structure or to be used as microstructures for active implant. On the other hand phosphate materials containing lead oxide are used in the nuclear technique as nuclear waste encapsulation. The present work is a structural study on some phosphate glasses containing vanadium, copper, molybdenum and iron ions. The following two glass systems were investigated by EPR method: x(CuO{center_dot}V{sub 2}O{sub 5})(100-x)[P{sub 2}O{sub 5}{center_dot}CaO] and x(Fe{sub 2}O{sub 3}MoO{sub 3}) (1-x)[2P{sub 2}O{sub 5}PbO] with 0.5 Less-Than-Or-Slanted-Equal-To x Less-Than-Or-Slanted-Equal-To 50 mol%. In both systems, EPR spectra evidenced the hyperfine structure of vanadium and molybdenum ions. EPR parameters indicate the presence of V{sup 4+} ions in C{sub 4V} symmetry until 7 mol%. After this concentration the hyperfine structure of vanadium disappears due to the clusters formation. Hyperfine structure of copper was not evidenced in x(CuO{center_dot}V{sub 2}O{sub 5})(100-x)[P{sub 2}O{sub 5}{center_dot}CaO] system. EPR spectra for xFe{sub 2}O{sub 3}MoO{sub 3} (1-x)[2P{sub 2}O{sub 5}PbO] evidence the presence of molybdenum ions in a C{sub 4v} symmetry, but for iron ions weak signals at g Almost

  14. Social network based dynamic transit service through the OMITS system.

    Science.gov (United States)

    2014-02-01

    The Open Mode Integrated Transportation System (OMITS) forms a sustainable information infrastructure for communication within and between the mobile/Internet network, the roadway : network, and the users social network. It manipulates the speed g...

  15. Phase transitions in Ising models on directed networks.

    Science.gov (United States)

    Lipowski, Adam; Ferreira, António Luis; Lipowska, Dorota; Gontarek, Krzysztof

    2015-11-01

    We examine Ising models with heat-bath dynamics on directed networks. Our simulations show that Ising models on directed triangular and simple cubic lattices undergo a phase transition that most likely belongs to the Ising universality class. On the directed square lattice the model remains paramagnetic at any positive temperature as already reported in some previous studies. We also examine random directed graphs and show that contrary to undirected ones, percolation of directed bonds does not guarantee ferromagnetic ordering. Only above a certain threshold can a random directed graph support finite-temperature ferromagnetic ordering. Such behavior is found also for out-homogeneous random graphs, but in this case the analysis of magnetic and percolative properties can be done exactly. Directed random graphs also differ from undirected ones with respect to zero-temperature freezing. Only at low connectivity do they remain trapped in a disordered configuration. Above a certain threshold, however, the zero-temperature dynamics quickly drives the model toward a broken symmetry (magnetized) state. Only above this threshold, which is almost twice as large as the percolation threshold, do we expect the Ising model to have a positive critical temperature. With a very good accuracy, the behavior on directed random graphs is reproduced within a certain approximate scheme.

  16. Stability of anthocyanins in frozen and freeze-dried raspberries during long-term storage: in relation to glass transition.

    Science.gov (United States)

    Syamaladevi, Roopesh M; Sablani, Shyam S; Tang, Juming; Powers, Joseph; Swanson, Barry G

    2011-08-01

    Anthocyanins, natural plant pigments in the flavonoid group, are responsible for the red color and some of the nutraceutical benefits of raspberries. This study explores anthocyanin degradation in frozen and freeze-dried raspberries during storage in relation to glass transition temperatures. Frozen raspberries were stored at -80, -35, and -20 °C, while freeze-dried raspberries were stored at selected water activity (a(w)) values ranging from 0.05 to 0.75 at room temperature (23 °C) for more than a year. The characteristic glass transition temperatures (T'(g)) of raspberries with high water content and glass transition temperature (T(g)) of raspberries with small water content were determined using a differential scanning calorimeter. The pH differential method was used to determine the quantity of anthocyanins in frozen and freeze-dried raspberries at selected time intervals. The total anthocyanins in raspberries fluctuated during 378 d of storage at -20 and -35, and -80 °C. Anthocyanin degradation in freeze-dried raspberries ranged from 27% to 32% and 78% to 89% at a(w) values of 0.05 to 0.07 and 0.11 to 0.43, respectively, after 1 y. Anthocyanins were not detectable in freeze-dried raspberries stored at a(w) values of 0.53 to 0.75 after 270 d. First order and Weibull equations were used to fit the anthocyanin degradation in freeze-dried raspberries. The 1(st)-order rate constant (k) of anthocyanin degradation ranged from 0.003 to 0.023 days⁻¹ at the selected water activities. Significant anthocyanin degradation occurred in both the glassy and rubbery states of freeze-dried raspberries during long-term storage. However, the rate of anthocyanin degradation in freeze-dried raspberries stored in the glassy state was significantly smaller than the rate of anthocyanin degradation in the rubbery state. © 2011 Institute of Food Technologists®

  17. Hour-Glass Neural Network Based Daily Money Flow Estimation for Automatic Teller Machines

    Science.gov (United States)

    Karungaru, Stephen; Akashi, Takuya; Nakano, Miyoko; Fukumi, Minoru

    Monetary transactions using Automated Teller Machines (ATMs) have become a normal part of our daily lives. At ATMs, one can withdraw, send or debit money and even update passbooks among many other possible functions. ATMs are turning the banking sector into a ubiquitous service. However, while the advantages for the ATM users (financial institution customers) are many, the financial institution side faces an uphill task in management and maintaining the cash flow in the ATMs. On one hand, too much money in a rarely used ATM is wasteful, while on the other, insufficient amounts would adversely affect the customers and may result in a lost business opportunity for the financial institution. Therefore, in this paper, we propose a daily cash flow estimation system using neural networks that enables better daily forecasting of the money required at the ATMs. The neural network used in this work is a five layered hour glass shaped structure that achieves fast learning, even for the time series data for which seasonality and trend feature extraction is difficult. Feature extraction is carried out using the Akamatsu Integral and Differential transforms. This work achieves an average estimation accuracy of 92.6%.

  18. Magnetic susceptibility studies of the spin-glass and Verwey transitions in magnetite nanoparticles

    OpenAIRE

    Lopez Maldonado, K. L.; Presa Muñoz del Toro, Patricia de la; Flores Tavizon, E.; Farias Mancilla, J: R:; Matutes Aquino, J. A.; Hernando Grande, Antonio; Elizalde Galindo, J. T.

    2013-01-01

    Magnetite nanostructured powder samples were synthesized by aging chemical method. Phase, structural, and magnetic properties were characterized. X-ray diffraction patterns showed cubic magnetite pure phase, with average crystallite size, , equal to 40 nm. Susceptibility measurements showed the well-known Verwey transition at a temperature of 90 K. The decrease of Verwey transition temperature, with respect to the one reported in literature (125 K) was attributed to the low average cryst...

  19. Transition from glass to digital slide microscopy in the teaching of oral pathology in a Brazilian dental school.

    Science.gov (United States)

    Fonseca, Felipe-Paiva; Santos-Silva, Alan-Roger; Lopes, Márcio-Ajudarte; Almeida, Oslei-Paes de; Vargas, Pablo-Agustin

    2015-01-01

    Several medical and dental schools have described their experience in the transition from conventional to digital microscopy in the teaching of general pathology and histology disciplines; however, this transitional process has scarcely been reported in the teaching of oral pathology. Therefore, the objective of the current study is to report the transition from conventional glass slide to virtual microscopy in oral pathology teaching, a unique experience in Latin America. An Aperio ScanScope® scanner was used to digitalize histological slides used in practical lectures of oral pathology. The challenges and benefits observed by the group of Professors from the Piracicaba Dental School (Brazil) are described and a questionnaire to evaluate the students' compliance to this new methodology was applied. An improvement in the classes was described by the Professors who mainly dealt with questions related to pathological changes instead of technical problems; also, a higher interaction with the students was described. The simplicity of the software used and the high quality of the virtual slides, requiring a smaller time to identify microscopic structures, were considered important for a better teaching process. Virtual microscopy used to teach oral pathology represents a useful educational methodology, with an excellent compliance of the dental students.

  20. Transition from glass to digital slide microscopy in the teaching of oral pathology in a Brazilian dental school

    Science.gov (United States)

    Fonseca, Felipe-Paiva; Santos-Silva, Alan-Roger; Lopes, Márcio-Ajudarte; de Almeida, Oslei-Paes

    2015-01-01

    Objectives: Several medical and dental schools have described their experience in the transition from conventional to digital microscopy in the teaching of general pathology and histology disciplines; however, this transitional process has scarcely been reported in the teaching of oral pathology. Therefore, the objective of the current study is to report the transition from conventional glass slide to virtual microscopy in oral pathology teaching, a unique experience in Latin America. Study Design: An Aperio ScanScope® scanner was used to digitalize histological slides used in practical lectures of oral pathology. The challenges and benefits observed by the group of Professors from the Piracicaba Dental School (Brazil) are described and a questionnaire to evaluate the students’ compliance to this new methodology was applied. Results: An improvement in the classes was described by the Professors who mainly dealt with questions related to pathological changes instead of technical problems; also, a higher interaction with the students was described. The simplicity of the software used and the high quality of the virtual slides, requiring a smaller time to identify microscopic structures, were considered important for a better teaching process. Conclusions: Virtual microscopy used to teach oral pathology represents a useful educational methodology, with an excellent compliance of the dental students. Key words:Digital microscopy, virtual microscopy, dental education, virtual slides, oral pathology. PMID:25129250

  1. Structural and topological aspects of borophosphate glasses and their relation to physical properties

    DEFF Research Database (Denmark)

    Hermansen, Christian; Youngman, R.E.; Wang, J.

    2015-01-01

    We establish a topological model of alkali borophosphate and calcium borophosphate glasses that describes both the effect of the network formers and network modifiers on physical properties. We show that the glass transition temperature (Tg), Vickers hardness (HV), liquid fragility (m) and isobaric...... heat capacity jump at Tg (ΔCp) of these glasses are related to the network topology, which is determined by structure of the glass. Therefore, we also demonstrate that the temperature dependent constraint theory can quantitatively explain the mixed network former effect (MNFE) in borophosphate glasses....... The origin of the effect of the type of network modifying oxide on Tg, HV, m and ΔCp of calcium borophosphate glasses is revealed in terms of the modifying ion sub-network. The same topological principles quantitatively explain the significant differences in physical properties between the alkali...

  2. Compositional dependence of up-conversion emission and optical transition in Yb3+-Ho3+ co-doped tellurite-phosphate glasses

    Science.gov (United States)

    Yang, Yanmin; Zhang, Wei; Guo, Shuqing; Yang, Zhiping

    2010-07-01

    Optical absorption and photoluminescence properties of Yb3+-Ho3+ co-doped tellurite-phosphate glasses have been investigated. Up-conversion emissions have been observed at 540nm (green) and 650nm (red) at room temperature. The effect of host composition on up-conversion luminescence has been studied by analyzing the phenomenological Judd-Ofelt parameters Ωλ (λ = 2,4,6) as well as radiative transition probability and emission cross sections of 5F4 (5S2) and 5F5 levels in these glasses samples. Obtained data indicated that the green transition rapidly decreased relative to the red transition with increasing phosphate concentration, which can be attributed to increasing population of 5F4 (5S2) and 5F5 levels due to increasing host phonon energy. So, the color of up-conversion emission can be modulated by changed host composition. The effect of Ho3+ concentration on up-conversion emission was also studied in Yb3+-Ho3+ co-doped tellurite glasses. The red transition rapidly decreased relative to the green transition with increasing Ho3+ concentration. We attributed it to the lower phonon energy of tellurite glass host.

  3. Spin-Glass Transition and Giant Paramagnetism in Heavily Hole-Doped Bi2Sr2Co2Oy

    Science.gov (United States)

    Hsu, Hung Chang; Lee, Wei-Li; Lin, Jiunn-Yuan; Young, Ben-Li; Kung, Hsiang-Hsi; Huang, Jian; Chou, Fang Cheng

    2014-02-01

    Hole-doped single crystals of misfit-layered cobaltate Bi2-xPbxSr2-zCo2Oy (x = 0-0.61, y = 8.28-8.62, and z = 0.01-0.22) have been successfully grown using the optical floating-zone method. Heavier hole doping has been achieved through both Pb substitution in the Bi site and the more effective Sr vacancy formation. The Co4+ : Co3+ ratio can be raised significantly from its original ˜1 : 1 to 4.5 : 1, as confirmed by iodometric titration. A spin-glass transition temperature of Tg ˜ 70 K is confirmed by ac susceptibility measurement when the Co4+ : Co3+ ratio becomes higher than 2 : 1, presumably owing to the significantly increased probability of triangular geometrical frustration among antiferromagnetically coupled localized Co4+ spins.

  4. Freeze-Drying Above the Glass Transition Temperature in Amorphous Protein Formulations While Maintaining Product Quality and Improving Process Efficiency.

    Science.gov (United States)

    Depaz, Roberto A; Pansare, Swapnil; Patel, Sajal Manubhai

    2016-01-01

    This study explored the ability to conduct primary drying during lyophilization at product temperatures above the glass transition temperature of the maximally freeze-concentrated solution (Tg′) in amorphous formulations for four proteins from three different classes. Drying above Tg′ resulted in significant reductions in lyophilization cycle time. At higher protein concentrations, formulations freeze dried above Tg′ but below the collapse temperature yielded pharmaceutically acceptable cakes. However, using an immunoglobulin G type 4 monoclonal antibody as an example, we found that as protein concentration decreased, minor extents of collapse were observed in formulations dried at higher temperatures. No other impacts to product quality, physical stability, or chemical stability were observed in this study among the different drying conditions for the different proteins. Drying amorphous formulations above Tg′, particularly high protein concentration formulations, is a viable means to achieve significant time and cost savings in freeze-drying processes.

  5. Spin-glass transition in Ni carbide single crystal nanoparticles with Ni3C − type structure

    Directory of Open Access Journals (Sweden)

    S. Fujieda

    2016-05-01

    Full Text Available Hexagonal shaped nanoparticles about 60 nm in size were successfully synthesized in tetraethylene glycol solution containing polyvinylpyrrolidone. By the analysis of the electron diffraction pattern, these were identified as a single crystal of Ni carbide with Ni3C − type structure. Their magnetization curve at 5 K was not completely saturated under a magnetic field of 5 T. The thermomagnetization curves after zero-field cooling and after field cooling exhibited the magnetic cooling effect at low temperatures. Furthermore, the 2nd order nonlinear term of AC magnetic susceptibility exhibited a negative divergence at about 17 K. It is concluded that Ni carbide single crystal nanoparticles with the Ni3C − type structure exhibit spin-glass transition at low temperatures.

  6. Will electrical cyber-physical interdependent networks undergo first-order transition under random attacks?

    Science.gov (United States)

    Ji, Xingpei; Wang, Bo; Liu, Dichen; Dong, Zhaoyang; Chen, Guo; Zhu, Zhenshan; Zhu, Xuedong; Wang, Xunting

    2016-10-01

    Whether the realistic electrical cyber-physical interdependent networks will undergo first-order transition under random failures still remains a question. To reflect the reality of Chinese electrical cyber-physical system, the "partial one-to-one correspondence" interdependent networks model is proposed and the connectivity vulnerabilities of three realistic electrical cyber-physical interdependent networks are analyzed. The simulation results show that due to the service demands of power system the topologies of power grid and its cyber network are highly inter-similar which can effectively avoid the first-order transition. By comparing the vulnerability curves between electrical cyber-physical interdependent networks and its single-layer network, we find that complex network theory is still useful in the vulnerability analysis of electrical cyber-physical interdependent networks.

  7. Thermodynamics of open networks: Ordering and entropy in NaAlSiO4 glass, liquid, and polymorphs

    Science.gov (United States)

    Richet, P.; Robie, R.A.; Rogez, J.; Hemingway, B.S.; Courtial, P.; Tequi, C.

    1990-01-01

    The thermodynamic properties of carnegieite and NaAlSiO4 glass and liquid have been investigated through Cp determinations from 10 to 1800 K and solution-calorimetry measurements. The relative entropies S298-S0 of carnegieite and NaAlSiO4 glass are 118.7 and 124.8 J/mol K, respectively. The low-high carnegieite transition has been observed at 966 K with an enthalpy of transition of 8.1??0.3 kJ/mol, and the enthalpy of fusion of carnegieite at the congruent melting point of 1799 K is 21.7??3 kJ/mol. These results are consistent with the reported temperature of the nepheline-carnegieite transition and available thermodynamic data for nepheline. The entropy of quenched NaAlSiO4 glass at 0 K is 9.7??2 J/mol K and indicates considerable ordering among AlO4 and SiO4 tetrahedra. In the liquid state, progressive, temperature-induced Si, Al disordering could account for the high configurational heat capacity. Finally, the differences between the entropies and heat capacities of nepheline and carnegieite do not seem to conform to current polyhedral modeling of these properties ?? 1990 Springer-Verlag.

  8. Molecular Dynamic Simulations of Glass Transition Temperature and Mechanical Properties in the Amorphous Region of Oil-Immersed Transformer Insulation Paper

    Science.gov (United States)

    Wang, You-Yuan; Yang, Tao; Liao, Rui-Jin

    2012-07-01

    The glass transition temperature (Tg) in the amorphous region of an insulation paper is one of the most important characteristics for thermal stability. Molecular dynamic simulations have been performed on three micro-structural models, namely, amorphous pure cellulose, amorphous cellulose with water and amorphous cellulose with oil, to study the microscopic mechanism of the glass transition process for oil-immersed transformer insulation paper. Using the method of specific volume versus temperature curve, the Tg of amorphous pure cellulose, cellulose with water, and cellulose with oil was determined as 448, 418 and 440 K, respectively. The current study may provide some information for thermal aging. The simulation results show that during the glass transition process, both the chain motion and mechanical properties of cellulose changes significantly. Relative to the oil molecules, water molecules immersed in the amorphous region of insulation paper can disrupt hydrogen bonds between cellulose chains. This phenomenon results in a significant reduction in the glass transition temperature and affects the thermal stability of the insulation paper.

  9. Dynamic cooperative behavior of constituting species at the glass transition vicinity: Inspirational links to Bořivoj Hlaváček (1941-2014) legacy

    Czech Academy of Sciences Publication Activity Database

    Šesták, Jaroslav

    2015-01-01

    Roč. 120, č. 1 (2015), s. 167-173 ISSN 1388-6150 Institutional support: RVO:68378271 Keywords : glass transition temperature * crossover and void temperature * linear and nonlinear oscillations * viscoelasticity * shear viscosity Subject RIV: BJ - Thermodynamics Impact factor: 1.781, year: 2015

  10. Comment on ``The effect of charged impurities on a glass transition in a polar medium'' [J. Chem. Phys. 104, 664 (1996)

    Science.gov (United States)

    Miller, Danforth P.; de Pablo, Juan J.; Corti, Horacio R.

    1996-11-01

    Dakhnovskii and Lubchenko have recently presented a theory to predict the effect of charged impurities on the glass transition temperature (Tg) in a polar medium. We present and cite more extensive sets of experimental results that show that the electrolyte concentration required to induce a 10 K increase in Tg is nearly three orders of magnitude greater than that predicted from their theory.

  11. Bond orientational order in liquids: Towards a unified description of water-like anomalies, liquid-liquid transition, glass transition, and crystallization: Bond orientational order in liquids.

    Science.gov (United States)

    Tanaka, Hajime

    2012-10-01

    There are at least three fundamental states of matter, depending upon temperature and pressure: gas, liquid, and solid (crystal). These states are separated by first-order phase transitions between them. In both gas and liquid phases a complete translational and rotational symmetry exist, whereas in a solid phase both symmetries are broken. In intermediate phases between liquid and solid, which include liquid crystal and plastic crystal phases, only one of the two symmetries is preserved. Among the fundamental states of matter, the liquid state is the most poorly understood. We argue that it is crucial for a better understanding of liquids to recognize that a liquid generally has the tendency to have a local structural order and its presence is intrinsic and universal to any liquid. Such structural ordering is a consequence of many-body correlations, more specifically, bond angle correlations, which we believe are crucial for the description of the liquid state. We show that this physical picture may naturally explain difficult unsolved problems associated with the liquid state, such as anomalies of water-type liquids (water, Si, Ge, ...), liquid-liquid transition, liquid-glass transition, crystallization and quasicrystal formation, in a unified manner. In other words, we need a new order parameter representing a low local free-energy configuration, which is a bond orientational order parameter in many cases, in addition to a density order parameter for the physical description of these phenomena. Here we review our two-order-parameter model of liquid and consider how transient local structural ordering is linked to all of the above-mentioned phenomena. The relationship between these phenomena is also discussed.

  12. A model of choice a public transit network by data envelopment analysis

    Directory of Open Access Journals (Sweden)

    Nikolić Miloš Lj.

    2015-01-01

    Full Text Available The problem of public transit network design belongs to the class of NP hard combinatorial optimization problem. Since optimal solution of this problem is difficult to discover, many heuristic algorithms have been proposed in the literature. By applying various heuristic algorithms to one problem instance, various solutions could be generated. We assume, in this paper, that decisions related to public transit network choice should be made in the presence of trade-offs between two or more conflicting objectives (usually, the passengers' and operator's interests are in conflict. In this paper, we propose the model for public transit network choice. The proposed model is based on the Data Envelopment Analysis (DEA. The proposed model is tested on the one of the best known benchmark examples for the transit network design problem.

  13. Optimizing Bus Frequencies under Uncertain Demand: Case Study of the Transit Network in a Developing City

    OpenAIRE

    Huang, Zhengfeng; Ren, Gang; Liu, Haixu

    2013-01-01

    Various factors can make predicting bus passenger demand uncertain. In this study, a bilevel programming model for optimizing bus frequencies based on uncertain bus passenger demand is formulated. There are two terms constituting the upper-level objective. The first is transit network cost, consisting of the passengers’ expected travel time and operating costs, and the second is transit network robustness performance, indicated by the variance in passenger travel time. The second term reflect...

  14. Information Technology Management: Transition From the Automatic Digital Network to the Defense Message System

    Science.gov (United States)

    2003-04-08

    Information Technology Management Department of Defense Office of the Inspector General April 8, 2003 AccountabilityIntegrityQuality Transition From...Dates Covered (from... to) - Title and Subtitle Information Technology Management : Transition From the Automatic Digital Network to the Defense Message

  15. An All-Glass Microfluidic Network with Integrated Amorphous Silicon Photosensors for on-Chip Monitoring of Enzymatic Biochemical Assay.

    Science.gov (United States)

    Costantini, Francesca; Tiggelaar, Roald M; Salvio, Riccardo; Nardecchia, Marco; Schlautmann, Stefan; Manetti, Cesare; Gardeniers, Han J G E; de Cesare, Giampiero; Caputo, Domenico; Nascetti, Augusto

    2017-12-05

    A lab-on-chip system, integrating an all-glass microfluidics and on-chip optical detection, was developed and tested. The microfluidic network is etched in a glass substrate, which is then sealed with a glass cover by direct bonding. Thin film amorphous silicon photosensors have been fabricated on the sealed microfluidic substrate preventing the contamination of the micro-channels. The microfluidic network is then made accessible by opening inlets and outlets just prior to the use, ensuring the sterility of the device. The entire fabrication process relies on conventional photolithographic microfabrication techniques and is suitable for low-cost mass production of the device. The lab-on-chip system has been tested by implementing a chemiluminescent biochemical reaction. The inner channel walls of the microfluidic network are chemically functionalized with a layer of polymer brushes and horseradish peroxidase is immobilized into the coated channel. The results demonstrate the successful on-chip detection of hydrogen peroxide down to 18 μM by using luminol and 4-iodophenol as enhancer agent.

  16. Phase-glass scaling near the coherence transition in granular HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Roa-Rojas, J.; Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, A. A. 14490, Bogota DC (Colombia); Prieto, P. [Grupo de Peliculas Delgadas, Departamento de Fisica, Universidad del Valle, A. A. 25360, Cali (Colombia)

    2005-07-01

    Systematic measurements of electrical magnetoconductivity near the coherence transition of granular HoBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films are reported. Experiments performed in magnetic fields ranging from 0 to 2500 Oe reveal that close to the coherence transition temperature T{sub c0}(H), the correlation length scales as a power law of temperature with a thermal-dependent critical exponent, {nu}. In low external fields the corresponding value of {nu} is consistent with the two-dimensional phase-glass model, which is in the same dynamical universality class of the so-called vortex-glass model. At applied fields H > 1000 Oe, the vortex dynamics becomes stronger and the coherence transition is not observed. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. On the glass transition of the one-component metallic melts

    Czech Academy of Sciences Publication Activity Database

    Fedorchenko, Alexander I.

    2017-01-01

    Roč. 475, October (2017), s. 362-367 ISSN 0022-0248 Institutional support: RVO:61388998 Keywords : equilibrium and non-equilibrium solidification * criterion of the phase transition scenario * one-component metal melts Subject RIV: BJ - Thermodynamics Impact factor: 1.751, year: 2016 http://ac.els-cdn.com/S0022024817304281/1-s2.0-S0022024817304281-main.pdf?_tid=a12ba97e-873b-11e7-b6be-00000aacb35e&acdnat=1503407763_5cdbcdb15d504baf5f8dfb94886b3100

  18. Tuning the glass transition of asphalt binder based on viscosity criteria under zero shear rates

    Science.gov (United States)

    Kwang-Hua, Chu Rainer

    2017-05-01

    With the theory of absolute reaction rate or transition-state approach together with the boundary perturbation method we calculate the possible temperature-dependent viscosity of bitumen or asphalt binder via tuning of activation volume as well as activation energy for the first time under zero shear rates. Before we present our novel approach and numerical results we firstly verify our calculations with both ambient temperature and high temperature viscosity measurements for bitumen conducted previously. Our tuning activation volume of bitumen will be useful to the current needs of intelligent compaction and application of nanotechnology to easily handling or processing asphalt binder.

  19. Analysis of network-wide transit passenger flows based on principal component analysis

    NARCIS (Netherlands)

    Luo, D.; Cats, O.; van Lint, J.W.C.

    2017-01-01

    Transit networks are complex systems in which the passenger flow dynamics are difficult to capture and understand. While there is a growing ability to monitor and record travelers' behavior in the past decade, knowledge on network-wide passenger flows, which are essentially high-dimensional

  20. Vulnerability Analysis of Urban Rail Transit Networks: A Case Study of Shanghai, China

    Directory of Open Access Journals (Sweden)

    Daniel (Jian Sun

    2015-05-01

    Full Text Available Rail transit is developing rapidly in major cities of China and has become a key component of urban transport. Nevertheless, the security and reliability in operation are significant issues that cannot be neglected. In this paper, the network and station vulnerabilities of the urban rail transit system were analyzed based on complex network and graph theories. A vulnerability evaluation model was proposed by accounting metro interchange and passenger flow and further validated by a case study of Shanghai Metro with full-scale network and real-world traffic data. It is identified that the urban rail transit network is rather robust to random attacks, but is vulnerable to the largest degree node-based attacks and the highest betweenness node-based attacks. Metro stations with a large node degree are more important in maintaining the network size, while stations with a high node betweenness are critical to network efficiency and origin-destination (OD connectivity. The most crucial stations in maintaining network serviceability do not necessarily have the highest passenger throughput or the largest structural connectivity. A comprehensive evaluation model as proposed is therefore essential to assess station vulnerability, so that attention can be placed on appropriate nodes within the metro system. The findings of this research are of both theoretical and practical significance for urban rail transit network design and performance evaluation.

  1. Channel noise-induced temporal coherence transitions and synchronization transitions in adaptive neuronal networks with time delay

    Science.gov (United States)

    Gong, Yubing; Xie, Huijuan

    2017-09-01

    Using spike-timing-dependent plasticity (STDP), we study the effect of channel noise on temporal coherence and synchronization of adaptive scale-free Hodgkin-Huxley neuronal networks with time delay. It is found that the spiking regularity and spatial synchronization of the neurons intermittently increase and decrease as channel noise intensity is varied, exhibiting transitions of temporal coherence and synchronization. Moreover, this phenomenon depends on time delay, STDP, and network average degree. As time delay increases, the phenomenon is weakened, however, there are optimal STDP and network average degree by which the phenomenon becomes strongest. These results show that channel noise can intermittently enhance the temporal coherence and synchronization of the delayed adaptive neuronal networks. These findings provide a new insight into channel noise for the information processing and transmission in neural systems.

  2. Stochastic User Equilibrium Assignment in Schedule-Based Transit Networks with Capacity Constraints

    Directory of Open Access Journals (Sweden)

    Wangtu Xu

    2012-01-01

    Full Text Available This paper proposes a stochastic user equilibrium (SUE assignment model for a schedule-based transit network with capacity constraint. We consider a situation in which passengers do not have the full knowledge about the condition of the network and select paths that minimize a generalized cost function encompassing five components: (1 ride time, which is composed of in-vehicle and waiting times, (2 overload delay, (3 fare, (4 transfer constraints, and (5 departure time difference. We split passenger demands among connections which are the space-time paths between OD pairs of the network. All transit vehicles have a fixed capacity and operate according to some preset timetables. When the capacity constraint of the transit line segment is reached, we show that the Lagrange multipliers of the mathematical programming problem are equivalent to the equilibrium passenger overload delay in the congested transit network. The proposed model can simultaneously predict how passengers choose their transit vehicles to minimize their travel costs and estimate the associated costs in a schedule-based congested transit network. A numerical example is used to illustrate the performance of the proposed model.

  3. Sustainable transition of socio-technological systems: How can Governance Network Research and Transition Theory contribute to the transition to biofuel for transportation?

    DEFF Research Database (Denmark)

    Hansen, Ole Erik; Stærdahl, Jens; Søndergård, Bent

    and policymaking for sustainability has to work with issues of understanding how actors and networks configure, requirements to effective networks and metagovernance of governance networks. Research within innovation systems, transition management and technology systems combined with planning and experimental...... activities provides both a theoretical and empirical body of knowledge of such governance processes. The paper presents these approaches and demonstrates how they can be used in relation to the process of developing bio-fuel systems for transportation.......The paper suggests that the challenge of sustainability demands a shift of the attention of environmental planning and policy to the transition of socio-technological systems. Deliberate planning for sustainability then becomes a question of addressing governance structures of socio...

  4. Precise calculation of a bond percolation transition and survival rates of nodes in a complex network.

    Science.gov (United States)

    Kawamoto, Hirokazu; Takayasu, Hideki; Jensen, Henrik Jeldtoft; Takayasu, Misako

    2015-01-01

    Through precise numerical analysis, we reveal a new type of universal loopless percolation transition in randomly removed complex networks. As an example of a real-world network, we apply our analysis to a business relation network consisting of approximately 3,000,000 links among 300,000 firms and observe the transition with critical exponents close to the mean-field values taking into account the finite size effect. We focus on the largest cluster at the critical point, and introduce survival probability as a new measure characterizing the robustness of each node. We also discuss the relation between survival probability and k-shell decomposition.

  5. Dynamic State Transitions in the Nervous System: From Ion Channels to Neurons to Networks

    Science.gov (United States)

    Århem, Peter; Braun, Hans A.; Huber, Martin T.; Liljenström, Hans

    The following sections are included: * Introduction * Ion channels: The microscopic scale * The variety of ion channels * Channel kinetics * Neurons: The mesoscopic scale * The feedback loops between membrane potential and ion currents * Neuron models: Concepts and examples * Impulse pattern modulation by ion channel densities * Oscillatory patterns * Irregular patterns * Impulse pattern modulation by subthreshold oscillations * The cold receptor model * Deterministic patterns and noise induced state-transitions on temperature scaling * Neuronal networks: The oscopic scale * Random channel events cause network state transitions * A hippocampal neural network model * Simulating noise-induced state transitions * Functional significance of oscopic neurodynamics * Conclusions * Appendix A: Computation of the neuron models * Hippocampal neuron model * The cold receptor model * Appendix B: Neural network model * References

  6. A microfluidic investigation of gas exsolution in glass and shale fracture networks

    Science.gov (United States)

    Porter, M. L.; Jimenez-Martinez, J.; Harrison, A.; Currier, R.; Viswanathan, H. S.

    2016-12-01

    Microfluidic investigations of pore-scale fluid flow and transport phenomena has steadily increased in recent years. In these investigations fluid flow is restricted to two-dimensions allowing for real-time visualization and quantification of complex flow and reactive transport behavior, which is difficult to obtain in other experimental systems. In this work, we describe a unique high pressure (up to 10.3 MPa) and temperature (up to 80 °C) microfluidics experimental system that allows us to investigate fluid flow and transport in geo-material (e.g., shale, Portland cement, etc.) micromodels. The use of geo-material micromodels allows us to better represent fluid-rock interactions including wettability, chemical reactivity, and nano-scale porosity at conditions representative of natural subsurface environments. Here, we present experimental results in fracture systems with applications to hydrocarbon mobility in fractured rocks. Complex fracture network patterns are derived from 3D x-ray tomography images of actual fractures created in shale rock cores. We use both shale and glass micromodels, allowing for a detailed comparison between flow phenomena in the different materials. We discuss results from two-phase gas (CO2 and N2) injection experiments designed to enhance oil recovery. In these experiments gas was injected into micromodels saturated with oil and allowed to soak for approximately 12 hours at elevated pressures. The pressure in the system was then decreased to atmospheric, causing the gas to expand and/or dissolve out of solution, subsequently mobilizing the oil. In addition to the experimental results, we present a relatively simple model designed to quantify the amount of oil mobilized as a function of decreasing system pressure. We will show comparisons between the experiments and model, and discuss the potential use of the model in field-scale reservoir simulations.

  7. Synchronous transitions of up and down states in a network model based on stimulations.

    Science.gov (United States)

    Xu, Xuying; Ni, Li; Wang, Rubin

    2017-01-07

    The phenomenon of spontaneous periodic up and down transitions is considered to be a significant characteristic of slow oscillations. Our previous theoretical studies have shown that the single neuron and network model can both exhibit spontaneous up and down transitions. Another characteristic of up and down dynamics is the synchronicity. So in this paper, we focused on the synchronized characteristic of up and down transitions in the network based on stimulations. Spontaneous activities showed no synchronous transitions between neurons. However, the external stimulation, mainly the stimulation frequency and the number of neurons stimulated on were related to the synchronous transitions of up and down states. The simulation results suggested that simultaneous high frequency excitation or firing of neurons in the network was responsible for the generation of synchronous transitions of up and down states. Through the observation and analysis of the findings, we have tried to explain the reason for synchronous up and down transitions and to lay the foundation for further work on the role of these synchronized transitions in cortex activity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Viscosity and Softening Behavior of Alkali Zinc Sulfophosphate Glasses

    DEFF Research Database (Denmark)

    Da, Ning; Krolikowski, Sebastian; Nielsen, Karsten Hansgaard

    2010-01-01

    We report on the softening properties and viscosity of glasses from the system ZnO-Na2O-SO3-P2O5 for low-temperature sealing applications. Up to a ratio of network-forming ions PO(4)3-:SO(4)2- of about 2:1, a gradual substitution of P2O5 by SO3 results in decreasing glass transition and softening...... the macroscopic glass transition temperature, which is interpreted as a result of the formation of an increasingly interconnected assembly of SO(4)2- and PO(4)3- units with increasing SO3 content....

  9. Communicability reveals a transition to coordinated behavior in multiplex networks

    Science.gov (United States)

    Estrada, Ernesto; Gómez-Gardeñes, Jesús

    2014-04-01

    We analyze the flow of information in multiplex networks by means of the communicability function. First, we generalize this measure from its definition from simple graphs to multiplex networks. Then, we study its relevance for the analysis of real-world systems by studying a social multiplex where information flows using formal-informal channels and an air transportation system where the layers represent different air companies. Accordingly, the communicability, which is essential for the good performance of these complex systems, emerges at a systemic operation point in the multiplex where the performance of the layers operates in a coordinated way very differently from the state represented by a collection of unconnected networks.

  10. Contrasting dynamics of fragile and non-fragile polyalcohols through the glass, and dynamical, transitions: A comparison of neutron scattering and dielectric relaxation data for sorbitol and glycerol.

    Science.gov (United States)

    Migliardo, F; Angell, C A; Magazù, S

    2017-01-01

    Glycerol and sorbitol are glass-forming hydrogen-bonded systems characterized by intriguing properties which make these systems very interesting also from the applications point of view. The goal of this work is to relate the hydrogen-bonded features, relaxation dynamics, glass transition properties and fragility of these systems, in particular to seek insight into their very different liquid fragilities. The comparison between glycerol and sorbitol is carried out by collecting the elastic incoherent neutron scattering (EINS) intensity as a function of temperature and of the instrumental energy resolution. Intensity data vs temperature and resolution are analyzed in terms of thermal restraint and Resolution Elastic Neutron Scattering (RENS) approaches. The number of OH groups, which are related to the connecting sites, is a significant parameter both in the glass transition and in the dynamical transition. On the other hand, the disordered nature of sorbitol is confirmed by the existence of different relaxation processes. From the applications point of view, glycerol and sorbitol have remarkable bioprotectant properties which make these systems useful in different technological and industrial fields. Furthermore, polyols are rich in glassforming liquid phenomenology and highly deserving of study in their own right. The comparison of EINS and calorimetric data on glycerol and sorbitol helps provide a connection between structural relaxation, dynamical transition, glass transition, and fragility. The evaluation of the inflection point in the elastic intensity behavior as a function of temperature and instrumental energy resolution provides a confirmation of the validity of the RENS approach. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo. Copyright © 2016. Published by Elsevier B.V.

  11. Reformulation of time-convolutionless mode-coupling theory near the glass transition

    Science.gov (United States)

    Tokuyama, Michio

    2017-10-01

    The time-convolutionless mode-coupling theory (TMCT) recently proposed is reformulated under the condition that one of two approximations, which have been used to formulate the original TMCT in addition to the MCT approximations done on a derivation of nonlinear memory function in terms of the intermediate-scattering function, is not employed because it causes unphysical results for intermediate times. The improved TMCT equation is then derived consistently under another approximation. It is first checked that the ergodic to non-ergodic transition obtained by a new equation is exactly the same as that obtained by an old one because the long-time dynamics of both equations coincides with each other. However, it is emphasized that a difference between them appears in the intermediate-time dynamics of physical quantities. Such a difference is explored numerically in the dynamics of a non-Gaussian parameter by employing the Percus-Yevick static structure factor to calculate the nonlinear memory function.

  12. Effects of relative humidity and ionic liquids on the water content and glass transition of plasticized starch.

    Science.gov (United States)

    Bendaoud, Amine; Chalamet, Yvan

    2013-09-12

    The purpose of the present work was to investigate the relationship between the glass transition temperature of the materials produced by the melting method and the water content, as well as the nature and concentration of the plasticizer used. Native starch was successfully treated with ionic liquid to obtain thermoplastic starch (TPS). Ionic liquids have shown a better plasticization, and low absorption of water compared to glycerol, which means a better interaction of starch with ionic liquids. The water binding properties of TPS were studied by commenting the water absorption for the plasticized starch at different % RH and with different ratios of plasticizers. An amount of 22.5 wt% AMIMCl is the maximum that can act as a plasticizer. Above this composition, an increase in the wt% water and wt% AMIMCl induces a phase separation. This value corresponds to a chemical interpretation, which corresponds to a ratio of 1:3 AMIMCl/anhydro-glucose. A schematic representation of the different binding between starch, plasticizer and water has been proposed. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Synthesis and Characterization of Fluorescently Labeled Diblock Copolymers for Location-Specific Measurements of The Glass Transition Temperature

    Science.gov (United States)

    Christie, Dane; Register, Richard; Priestley, Rodney

    Interfaces play a determinant role in the size dependence of the glass transition temperature (Tg) of polymers confined to nanometric length scales. Interfaces are intrinsic in diblock copolymers, which, depending on their molecular weight and composition, are periodically nanostructured in the bulk. As a result diblock copolymers are model systems for characterizing the effect of interfaces on Tg in bulk nanostructured materials. Investigating the effect of intrinsic interfaces on Tg in diblock copolymers has remained unexplored due to their small periodic length scale. By selectively incorporating trace amounts of a fluorescent probe into a diblock copolymer, Tg can be characterized relative to the diblock copolymer's intrinsic interface using fluorescence spectroscopy. Here, pyrene is selectively incorporated into the poly(methyl methacrylate) (PMMA) block of lamellar forming diblock copolymers of poly(butyl- b-methyl methacrylate) (PBMA-PMMA). Preliminary results show a correlation of Tg as measured by fluorescence with the onset of Tg as measured by calorimetry in labeled homopolymers of PMMA. This result is consistent with previous characterizations of Tg using fluorescence spectroscopy. In selectively labeled diblock copolymers Tg is found to vary systematically depending on the distance of the probe from the PBMA-PMMA interface. We acknowledge funding from the Princeton Center for Complex Materials, a MRSEC supported by NSF Grant DMR 1420541.

  14. Effect of borojo (Borojoa patinoi Cuatrecasas) three-phase composition and gum arabic on the glass transition temperature.

    Science.gov (United States)

    Rodríguez-Bernal, Jenny M; Tello, Edisson; Flores-Andrade, Enrique; Perea-Flores, Maria de Jesús; Vallejo-Cardona, Alba A; Gutiérrez-López, Gustavo F; Quintanilla-Carvajal, Maria X

    2016-02-01

    The search for natural, novel, high-quality, stable food ingredients is an ongoing practice in the food industry. Pulp of borojo (Borojoa patinoi Cuatrecasas), which is a fruit of the Colombian Pacific region, can be separated into three phases: liquid (LP), medium (MP) and solid (SP) phases. The objective of this work was to evaluate the effect of the three-phase composition and gum arabic on their glass transitions temperatures (T(g)). The best mixture, LP-MP, MP-SP and LP-SP and gum arabic (GA) was identified by response surface methodology. When adding GA to SP borojo phase in a 1:1 proportion, the resulting T(g) of the mixture was 132.27 °C whereas Tg for GA and SP-phase were 154.89 °C and 79.86 °C respectively, which supported this combination as attractive from a processing perspective and supports an industrial advantage of using borojo as food ingredient. Phases were characterized by high-performance liquid chromatography, Fourier transform infrared spectroscopy, confocal laser scanning microscopy and mass spectrometry. Low molecular weight compounds such as fructose for MP lowered T(g) whereas the presence of lignin increased T(g) of the mixtures as with the SP. The addition of GA significantly increased T(g) of borojo phases so leading to propose them as novel food processing materials. © 2015 Society of Chemical Industry.

  15. Impact of hydrogenated starch hydrolysate on glass transition, hygroscopic behavior and crystallization of isomalt-based systems

    Directory of Open Access Journals (Sweden)

    Kanitha Tananuwong

    2017-02-01

    Full Text Available Glass transition behavior, adsorption isotherm and crystallization of isomalt-hydrogenated starch hydrolysate (HSH mixtures (0-20% HSH and pure HSH were investigated. At similar solid content, Tg decreased as HSH concentration increased. Tg data at different solid contents were well-fitted with Gordon-Taylor equation (gR2≥0.97. Adsorption isotherm showed that systems with greater HSH concentration became more hygroscopic. Accelerated storage test (30°C, 84% RH of modeled hard candy containing 10% HSH and pure isomalt formula was done. HSH enhanced water uptake and crystallization of polyols in hard candy during aging without packaging; however, those effects were lessen for the samples aged in polyethylene terephthalate/cast polypropylene (PET/CPP pouches, and were negligible after the application of superior moisture barrier, oriented polypropylene/metalized cast polypropylene (OPP/MCPP film. Although HSH adversely affected storage stability of sugarless hard candies, it could be add into the formulation together with the application of packaging having a good moisture barrier.

  16. Influence of manufacturing factors on physical stability and solubility of solid dispersions containing a low glass transition temperature drug.

    Science.gov (United States)

    Sakurai, Atsushi; Sako, Kazuhiro; Maitani, Yoshie

    2012-01-01

    In this study, we investigated the effect of manufacturing factors such as particle size, water content and manufacturing method on the physical stability and solubility of solid dispersion formulations of a low-glass-transition-temperature (T(g)) drug. Solid dispersions were prepared from polyvinylpyrrolidone (PVP) and hydroxypropylmethylcellulose (HPMC) by hot melt extrusion or spray drying. Water content of solid dispersions prepared by hot melt extrusion determined by dynamic moisture sorption measurement was increased drastically with relative humidity below a certain level of particle size. The blends with a lower water content (0.8%) prepared by hot melt extrusion during storage were more stable than those with a higher water content (3.5%) prepared by spray drying, which caused rapid recrystallization. Physical stability in the hot melt blends may be attributed to reduced molecular mobility due to a higher T(g). Dissolution study revealed that solid dispersions prepared by hot melt extrusion with the smallest particle size showed decreased solubility, attributed to reduced wetting properties (surface energy), which is not predictable by the Noyes-Whitney equation. Taken together, these results indicate that the control of particle size concerned in water content or wetting properties is critical to ensuring the physical stability or enhancing solubility of low-T(g) drugs. Further, hot melt extrusion, which can reduce water content, is a suitable manufacturing method for solid dispersions of low-T(g) drugs.

  17. Protein brownian rotation at the glass transition temperature of a freeze-concentrated buffer probed by superparamagnetic nanoparticles.

    Science.gov (United States)

    Eloi, J-C; Okuda, M; Jones, S E Ward; Schwarzacher, W

    2013-06-18

    For applications from food science to the freeze-thawing of proteins it is important to understand the often complex freezing behavior of solutions of biomolecules. Here we use a magnetic method to monitor the Brownian rotation of a quasi-spherical cage-shaped protein, apoferritin, approaching the glass transition Tg in a freeze-concentrated buffer (Tris-HCl). The protein incorporates a synthetic magnetic nanoparticle (Co-doped Fe3O4 (magnetite)). We use the magnetic signal from the nanoparticles to monitor the protein orientation. As T decreases toward Tg of the buffer solution the protein's rotational relaxation time increases exponentially, taking values in the range from a few seconds up to thousands of seconds, i.e., orders of magnitude greater than usually accessed, e.g., by NMR. The longest relaxation times measured correspond to estimated viscosities >2 MPa s. As well as being a means to study low-temperature, high-viscosity environments, our method provides evidence that, for the cooling protocol used, the following applies: 1), the concentration of the freeze-concentrated buffer at Tg is independent of its initial concentration; 2), little protein adsorption takes place at the interface between ice and buffer; and 3), the protein is free to rotate even at temperatures as low as 207 K. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  18. Sorption isotherms, thermodynamic properties and glass transition temperature of mucilage extracted from chia seeds (Salvia hispanica L.).

    Science.gov (United States)

    Velázquez-Gutiérrez, Sandra Karina; Figueira, Ana Cristina; Rodríguez-Huezo, María Eva; Román-Guerrero, Angélica; Carrillo-Navas, Hector; Pérez-Alonso, César

    2015-05-05

    Freeze-dried chia mucilage adsorption isotherms were determined at 25, 35 and 40°C and fitted with the Guggenheim-Anderson-de Boer model. The integral thermodynamic properties (enthalpy and entropy) were estimated with the Clausius-Clapeyron equation. Pore radius of the mucilage, calculated with the Kelvin equation, varied from 0.87 to 6.44 nm in the temperature range studied. The point of maximum stability (minimum integral entropy) ranged between 7.56 and 7.63kg H2O per 100 kg of dry solids (d.s.) (water activity of 0.34-0.53). Enthalpy-entropy compensation for the mucilage showed two isokinetic temperatures: (i) one occurring at low moisture contents (0-7.56 kg H2O per 100 kg d.s.), controlled by changes in water entropy; and (ii) another happening in the moisture interval of 7.56-24 kg H2O per 100 kg d.s. and was enthalpy driven. The glass transition temperature Tg of the mucilage fluctuated between 42.93 and 57.93°C. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. The glass transition and sub-T(g)-relaxation in pharmaceutical powders and dried proteins by thermally stimulated current.

    Science.gov (United States)

    Reddy, Renuka; Chang, Liuquan ' Lucy '; Luthra, Suman; Collins, George; Lopez, Ciro; Shamblin, Sheri L; Pikal, Michael J; Gatlin, Larry A; Shalaev, Evgenyi Y

    2009-01-01

    The main goal of the study was to evaluate the applicability of thermally stimulated current (TSC) as a measure of molecular mobility in dried globular proteins. Three proteins, porcine somatotropin, bovine serum albumin, and immunoglobulin, as well as materials with a strong calorimetric glass transition (T(g)), that is, indomethacin and poly(vinypyrrolidone) (PVP), were studied by both TSC and differential scanning calorimetry (DSC). Protein/sugar colyophilized mixtures were also studied by DSC, to estimate calorimetric T(g) for proteins using extrapolation procedure. In the majority of cases, TSC detected relaxation events that were not observed by DSC. For example, a sub-T(g) TSC event (beta-relaxation) was observed for PVP at approximately 120 degrees C, which was not detected by the DSC. Similarly, DSC did not detect events in any of the three proteins below the thermal denaturation temperature whereas a dipole relaxation was detected by TSC in the range of 90-140 degrees C depending on the protein studied. The TSC signal in proteins was tentatively assigned as localized mobility of protein segments, which is different from a large-scale cooperative motions usually associated with calorimetric T(g). TSC is a promising method to study the molecular mobility in proteins and other materials with weak calorimetric T(g). (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

  20. Freezing and glass transitions upon cooling and warming and ice/freeze-concentration-solution morphology of emulsified aqueous citric acid.

    Science.gov (United States)

    Bogdan, Anatoli; Molina, Mario J; Tenhu, Heikki

    2016-12-01

    Although freeze-induced phase separation and the ice/FCS (freeze-concentration solution) morphology of aqueous solutions play an important role in fields ranging from life sciences and biotechnology to geophysics and high-altitude ice clouds, their understanding is far from complete. Herein, using differential scanning calorimetry (DSC) and optical cryo-microscope (OC-M), we have studied the freezing and glass transition behavior and the ice/FCS morphology of emulsified 10-60wt% CA (citric acid) solutions in the temperature region of ∼308and153K. We have obtained a lot of new result which are understandable and unclear. The most essential understandable results are as follows: (i) similar to bulk CA/H2O, emulsified CA/H2O also freezes upon cooling and warming and (ii) the ice/FCS morphology of frozen drops smaller than ∼3-4μm is less ramified than that of frozen bulk solutions. Unclear results, among others, are as follows: (i) in contrast to bulk solutions, which produce one freezing event, emulsified CA/H2O produces two freezing events and (ii) in emulsions, drop concentration is not uniform. Our results demonstrate that DSC thermograms and OC-M images/movies are mutually supplementary and allow us to extract important information which cannot be gained when DSC and OC-M techniques are used alone. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Doping influence by some transition elements on the irradiation effects in nuclear waste glasses; Influence du dopage par certains elements de transition sur les effets d'irradiation dans des verres d'interet nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Florent, Olivier

    2006-06-15

    High-level waste glasses are submitted to auto-irradiation. Modelling it using external irradiations on simple glasses revealed defects production and non negligible structural changes. This thesis aims at determining the impact of a more complex composition on these effects, especially the influence of adding polyvalent transition metals. Silicate, soda-lime and alumino-borosilicate glasses are doped with different iron, chromium and manganese concentrations then {beta} irradiated at different doses up to 10{sup 9} Gy. Non doped glasses show an increase of their density and polymerisation coupled with a molecular oxygen and point defects production. Adding 0.16 mol% Fe decreases the amount of defects by 85 % and all irradiation effects. A Fe{sup 3+} reduction is also observed by EPR, optical absorption and indirectly by Raman spectroscopy. A higher than 0.32 mol% Fe concentration causes complete blockage of the evolution of polymerisation, density and defect production. The same results are obtained on chromium or manganese doped glasses. An original in situ optical absorption device shows the quick decrease of Fe{sup 3+} amount to a 25 % lower level during irradiation. Stopping irradiation causes a lower decrease of 65 %, suggesting a dynamic (h{sup 0}/e-) consuming equilibrium. He{sup +} and Kr{sup 3+} ions and {gamma} irradiated glasses tend to confirm these phenomena for all kind of irradiation with electronic excitations. (author)

  2. The Cognitive Social Network in Dreams: Transitivity, Assortativity, and Giant Component Proportion Are Monotonic.

    Science.gov (United States)

    Han, Hye Joo; Schweickert, Richard; Xi, Zhuangzhuang; Viau-Quesnel, Charles

    2016-04-01

    For five individuals, a social network was constructed from a series of his or her dreams. Three important network measures were calculated for each network: transitivity, assortativity, and giant component proportion. These were monotonically related; over the five networks as transitivity increased, assortativity increased and giant component proportion decreased. The relations indicate that characters appear in dreams systematically. Systematicity likely arises from the dreamer's memory of people and their relations, which is from the dreamer's cognitive social network. But the dream social network is not a copy of the cognitive social network. Waking life social networks tend to have positive assortativity; that is, people tend to be connected to others with similar connectivity. Instead, in our sample of dream social networks assortativity is more often negative or near 0, as in online social networks. We show that if characters appear via a random walk, negative assortativity can result, particularly if the random walk is biased as suggested by remote associations. Copyright © 2015 Cognitive Science Society, Inc.

  3. Optimizing Bus Frequencies under Uncertain Demand: Case Study of the Transit Network in a Developing City

    Directory of Open Access Journals (Sweden)

    Zhengfeng Huang

    2013-01-01

    Full Text Available Various factors can make predicting bus passenger demand uncertain. In this study, a bilevel programming model for optimizing bus frequencies based on uncertain bus passenger demand is formulated. There are two terms constituting the upper-level objective. The first is transit network cost, consisting of the passengers’ expected travel time and operating costs, and the second is transit network robustness performance, indicated by the variance in passenger travel time. The second term reflects the risk aversion of decision maker, and it can make the most uncertain demand be met by the bus operation with the optimal transit frequency. With transit link’s proportional flow eigenvalues (mean and covariance obtained from the lower-level model, the upper-level objective is formulated by the analytical method. In the lower-level model, the above two eigenvalues are calculated by analyzing the propagation of mean transit trips and their variation in the optimal strategy transit assignment process. The genetic algorithm (GA used to solve the model is tested in an example network. Finally, the model is applied to determining optimal bus frequencies in the city of Liupanshui, China. The total cost of the transit system in Liupanshui can be reduced by about 6% via this method.

  4. Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with g-Alumina Nanoparticles

    Directory of Open Access Journals (Sweden)

    Sergio Diez-Berart

    2015-06-01

    Full Text Available In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy-ω-(1-pyrenimine-benzylidene-4′-oxy undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations.

  5. Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with γ-Alumina Nanoparticles

    Science.gov (United States)

    Diez-Berart, Sergio; López, David O.; Salud, Josep; Diego, José Antonio; Sellarès, Jordi; Robles-Hernández, Beatriz; de la Fuente, María Rosario; Ros, María Blanca

    2015-01-01

    In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy)-ω-(1-pyrenimine-benzylidene-4′-oxy) undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations.

  6. Modifier constraint in alkali borophosphate glasses using topological constraint theory

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiang [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zeng, Huidan, E-mail: hdzeng@ecust.edu.cn [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Jiang, Qi [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zhao, Donghui [Unifrax Corporation, Niagara Falls, NY 14305 (United States); Chen, Guorong [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Wang, Zhaofeng; Sun, Luyi [Department of Chemical & Biomolecular Engineering and Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, CT 06269 (United States); Chen, Jianding [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2016-12-01

    In recent years, composition-dependent properties of glasses have been successfully predicted using the topological constraint theory. The constraints of the glass network are derived from two main parts: network formers and network modifiers. The constraints of the network formers can be calculated on the basis of the topological structure of the glass. However, the latter cannot be accurately calculated in this way, because of the existing of ionic bonds. In this paper, the constraints of the modifier ions in phosphate glasses were thoroughly investigated using the topological constraint theory. The results show that the constraints of the modifier ions are gradually increased with the addition of alkali oxides. Furthermore, an improved topological constraint theory for borophosphate glasses is proposed by taking the composition-dependent constraints of the network modifiers into consideration. The proposed theory is subsequently evaluated by analyzing the composition dependence of the glass transition temperature in alkali borophosphate glasses. This method is supposed to be extended to other similar glass systems containing alkali ions.

  7. Unique sodium phosphosilicate glasses designed through extended topological constraint theory.

    Science.gov (United States)

    Zeng, Huidan; Jiang, Qi; Liu, Zhao; Li, Xiang; Ren, Jing; Chen, Guorong; Liu, Fude; Peng, Shou

    2014-05-15

    Sodium phosphosilicate glasses exhibit unique properties with mixed network formers, and have various potential applications. However, proper understanding on the network structures and property-oriented methodology based on compositional changes are lacking. In this study, we have developed an extended topological constraint theory and applied it successfully to analyze the composition dependence of glass transition temperature (Tg) and hardness of sodium phosphosilicate glasses. It was found that the hardness and Tg of glasses do not always increase with the content of SiO2, and there exist maximum hardness and Tg at a certain content of SiO2. In particular, a unique glass (20Na2O-17SiO2-63P2O5) exhibits a low glass transition temperature (589 K) but still has relatively high hardness (4.42 GPa) mainly due to the high fraction of highly coordinated network former Si((6)). Because of its convenient forming and manufacturing, such kind of phosphosilicate glasses has a lot of valuable applications in optical fibers, optical amplifiers, biomaterials, and fuel cells. Also, such methodology can be applied to other types of phosphosilicate glasses with similar structures.

  8. Local glass transition temperature Tg(z) of polystyrene next to different polymers: Hard vs. soft confinement

    Science.gov (United States)

    Baglay, Roman R.; Roth, Connie B.

    2017-05-01

    The depth to which the local glass transition temperature Tg and alpha-relaxations are perturbed near a boundary is believed to be related to the characteristic length scales associated with cooperative dynamics in dynamically heterogeneous glasses. Following our recent work [R. R. Baglay and C. R. Roth, J. Chem. Phys. 143, 111101 (2015)] that measured a very broad 350-400 nm local Tg(z) profile across a glassy-rubbery interface of polystyrene (PS)/poly(n-butyl methacrylate) (PnBMA), we compare here how the Tg(z) profile in PS varies when changing the neighboring polymer from a lower Tg material to a higher Tg material. Here we report local Tg(z) profiles for PS when in contact with polysulfone (PSF), poly(methyl methacrylate) (PMMA), and poly(isobutyl methacrylate) (PiBMA). We find that the distance from the interface before bulk Tg of PS (Tgbulk=101 °C) is recovered depends on whether PS forms the high-Tg glassy component experiencing so-called soft confinement, z ≈ 225-250 nm for PS next to PiBMA (Tgbulk=62°C) and PnBMA (Tgbulk=21 °C), or PS forms the low-Tg rubbery component experiencing hard confinement, z ≈ 100-125 nm for PS next to PSF (Tgbulk=186°C) and PMMA (Tgbulk=120 °C). The depth to which these Tg(z) perturbations persist and the magnitude of the local Tg perturbation at the interface are independent of the difference in Tgbulk between the two polymers, the interaction parameter, and the chemical structure. We demonstrate that these broad, extended Tg(z) length scales appear to be universal across these different systems but show that the strong dynamical coupling across the dissimilar polymer-polymer interface only occurs when this interface has been annealed to equilibrium. We consider why dissimilar polymer-polymer interfaces exhibit continuous local dynamics across the interface in contrast to polymer-free surface, polymer-substrate, or polymer-liquid interfaces that show discontinuous local dynamics.

  9. Metallic glasses

    NARCIS (Netherlands)

    Schaafsma, Arjen Sybren

    1981-01-01

    It is shown in section 7.1. that the influence of topological disorder on the range of magnetic interactions in ferromagnetic transition metal-metalloid (TM-M) glasses, is much less than often assumed. This is demonstrated via a study of the temperature dependence of the average iron hyperfine field

  10. Bellanet Network Transition Period | CRDI - Centre de recherches ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Since its creation in 1995, Bellanet has built a sound reputation helping international development organizations use information technology to communicate and collaborate. Since then, the centre of gravity of this virtual network of knowledge management practitioners has shifted southward. What began as a multi-donor ...

  11. Multiple phase transitions of the susceptible-infected-susceptible epidemic model on complex networks

    CERN Document Server

    Mata, Angélica S

    2014-01-01

    We show that the susceptible-infected-susceptible (SIS) epidemic dynamics running on the top of networks with a power law degree distribution can exhibit multiple phase transitions. Three main transitions involving different mechanisms responsible by sustaining the epidemics are identified: A short-term epidemics concentrated around the most connected vertex; a long-term (asymptotically stable) localized epidemics with a vanishing threshold; and an endemic phase occurring at a finite threshold. The different transitions are suited through different mean-field approaches. We finally show that the multiple transitions are due to the activations of different domains of the network that are observed in rapid (singular) variations of both stationary density of infected vertices and the participation ratio against the infection rate.

  12. Setting Access Permission through Transitive Relationship in Web-based Social Networks

    Science.gov (United States)

    Hong, Dan; Shen, Vincent Y.

    The rising popularity of various social networking websites has created a huge problem on Internet privacy. Although it is easy to post photos, comments, opinions on some events, etc. on the Web, some of these data (such as a person’s location at a particular time, criticisms of a politician, etc.) are private and should not be accessed by unauthorized users. Although social networks facilitate sharing, the fear of sending sensitive data to a third party without knowledge or permission of the data owners discourages people from taking full advantage of some social networking applications. We exploit the existing relationships on social networks and build a ‘‘trust network’’ with transitive relationship to allow controlled data sharing so that the privacy and preferences of data owners are respected. The trust network linking private data owners, private data requesters, and intermediary users is a directed weighted graph. The permission value for each private data requester can be automatically assigned in this network based on the transitive relationship. Experiments were conducted to confirm the feasibility of constructing the trust network from existing social networks, and to assess the validity of permission value assignments in the query process. Since the data owners only need to define the access rights of their closest contacts once, this privacy scheme can make private data sharing easily manageable by social network participants.

  13. The influence of passenger flow on the topology characteristics of urban rail transit networks

    Science.gov (United States)

    Hu, Yingyue; Chen, Feng; Chen, Peiwen; Tan, Yurong

    2017-05-01

    Current researches on the network characteristics of metro networks are generally carried out on topology networks without passenger flows running on it, thus more complex features of the networks with ridership loaded on it cannot be captured. In this study, we incorporated the load of metro networks, passenger volume, into the exploration of network features. Thus, the network can be examined in the context of operation, which is the ultimate purpose of the existence of a metro network. To this end, section load was selected as an edge weight to demonstrate the influence of ridership on the network, and a weighted calculation method for complex network indicators and robustness were proposed to capture the unique behaviors of a metro network with passengers flowing in it. The proposed method was applied on Beijing Subway. Firstly, the passenger volume in terms of daily origin and destination matrix was extracted from exhausted transit smart card data. Using the established approach and the matrix as weighting, common indicators of complex network including clustering coefficient, betweenness and degree were calculated, and network robustness were evaluated under potential attacks. The results were further compared to that of unweighted networks, and it suggests indicators of the network with consideration of passenger volumes differ from that without ridership to some extent, and networks tend to be more vulnerable than that without load on it. The significance sequence for the stations can be changed. By introducing passenger flow weighting, actual operation status of the network can be reflected more accurately. It is beneficial to determine the crucial stations and make precautionary measures for the entire network’s operation security.

  14. Critical phenomena and noise-induced phase transitions in neuronal networks

    Science.gov (United States)

    Lee, K.-E.; Lopes, M. A.; Mendes, J. F. F.; Goltsev, A. V.

    2014-01-01

    We study numerically and analytically first- and second-order phase transitions in neuronal networks stimulated by shot noise (a flow of random spikes bombarding neurons). Using an exactly solvable cortical model of neuronal networks on classical random networks, we find critical phenomena accompanying the transitions and their dependence on the shot noise intensity. We show that a pattern of spontaneous neuronal activity near a critical point of a phase transition is a characteristic property that can be used to identify the bifurcation mechanism of the transition. We demonstrate that bursts and avalanches are precursors of a first-order phase transition, paroxysmal-like spikes of activity precede a second-order phase transition caused by a saddle-node bifurcation, while irregular spindle oscillations represent spontaneous activity near a second-order phase transition caused by a supercritical Hopf bifurcation. Our most interesting result is the observation of the paroxysmal-like spikes. We show that a paroxysmal-like spike is a single nonlinear event that appears instantly from a low background activity with a rapid onset, reaches a large amplitude, and ends up with an abrupt return to lower activity. These spikes are similar to single paroxysmal spikes and sharp waves observed in electroencephalographic (EEG) measurements. Our analysis shows that above the saddle-node bifurcation, sustained network oscillations appear with a large amplitude but a small frequency in contrast to network oscillations near the Hopf bifurcation that have a small amplitude but a large frequency. We discuss an amazing similarity between excitability of the cortical model stimulated by shot noise and excitability of the Morris-Lecar neuron stimulated by an applied current.

  15. Critical phenomena and noise-induced phase transitions in neuronal networks.

    Science.gov (United States)

    Lee, K-E; Lopes, M A; Mendes, J F F; Goltsev, A V

    2014-01-01

    We study numerically and analytically first- and second-order phase transitions in neuronal networks stimulated by shot noise (a flow of random spikes bombarding neurons). Using an exactly solvable cortical model of neuronal networks on classical random networks, we find critical phenomena accompanying the transitions and their dependence on the shot noise intensity. We show that a pattern of spontaneous neuronal activity near a critical point of a phase transition is a characteristic property that can be used to identify the bifurcation mechanism of the transition. We demonstrate that bursts and avalanches are precursors of a first-order phase transition, paroxysmal-like spikes of activity precede a second-order phase transition caused by a saddle-node bifurcation, while irregular spindle oscillations represent spontaneous activity near a second-order phase transition caused by a supercritical Hopf bifurcation. Our most interesting result is the observation of the paroxysmal-like spikes. We show that a paroxysmal-like spike is a single nonlinear event that appears instantly from a low background activity with a rapid onset, reaches a large amplitude, and ends up with an abrupt return to lower activity. These spikes are similar to single paroxysmal spikes and sharp waves observed in electroencephalographic (EEG) measurements. Our analysis shows that above the saddle-node bifurcation, sustained network oscillations appear with a large amplitude but a small frequency in contrast to network oscillations near the Hopf bifurcation that have a small amplitude but a large frequency. We discuss an amazing similarity between excitability of the cortical model stimulated by shot noise and excitability of the Morris-Lecar neuron stimulated by an applied current.

  16. Mixed alkali effect in glasses containing MnO2

    Science.gov (United States)

    Reddy, M. Sudhakara; Rajiv, Asha; Veeranna Gowda, V. C.; Chakradhar, R. P. S.; Reddy, C. Narayana

    2013-02-01

    Glass systems of the composition xLi2O-(25-x)K2O-70(0.4ZnO+0.6P2O5)+5MnO2 (x = 4,8,12,16 and 20 mol %) have been prepared by melt quenching technique. The thermal and mechanical properties of the glasses have been evaluated as a function of mixed alkali content. Glass transition temperature and Vickers's hardness of the glasses show a pronounced deviation from linearity at 12 mol% Li2O. Theoretically estimated elastic moduli of the glasses show small positive deviations from linearity. MAE in these properties has been attributed to the localized changes in the glass network. The absorption spectra of Mn2+ ions in these glasses showed strong broad absorption band at 514 nm corresponding to the transition 6A1g(S)→4T1g(G), characteristic of manganese ions in octahedral symmetry. The fundamental absorption edge in UV region is used to study the optical transitions and electronic band structure. From UV absorption edge, optical band gap energies have been evaluated. Band gap energies of the glasses have exhibited MAE and shows minimum value for 12 mol% Li2O glass.

  17. Relationship of Topology, Multiscale Phase Synchronization, and State Transitions in Human Brain Networks

    Directory of Open Access Journals (Sweden)

    Minkyung Kim

    2017-06-01

    Full Text Available How the brain reconstitutes consciousness and cognition after a major perturbation like general anesthesia is an important question with significant neuroscientific and clinical implications. Recent empirical studies in animals and humans suggest that the recovery of consciousness after anesthesia is not random but ordered. Emergence patterns have been classified as progressive and abrupt transitions from anesthesia to consciousness, with associated differences in duration and electroencephalogram (EEG properties. We hypothesized that the progressive and abrupt emergence patterns from the unconscious state are associated with, respectively, continuous and discontinuous synchronization transitions in functional brain networks. The discontinuous transition is explainable with the concept of explosive synchronization, which has been studied almost exclusively in network science. We used the Kuramato model, a simple oscillatory network model, to simulate progressive and abrupt transitions in anatomical human brain networks acquired from diffusion tensor imaging (DTI of 82 brain regions. To facilitate explosive synchronization, distinct frequencies for hub nodes with a large frequency disassortativity (i.e., higher frequency nodes linking with lower frequency nodes, or vice versa were applied to the brain network. In this simulation study, we demonstrated that both progressive and abrupt transitions follow distinct synchronization processes at the individual node, cluster, and global network levels. The characteristic synchronization patterns of brain regions that are “progressive and earlier” or “abrupt but delayed” account for previously reported behavioral responses of gradual and abrupt emergence from the unconscious state. The characteristic network synchronization processes observed at different scales provide new insights into how regional brain functions are reconstituted during progressive and abrupt emergence from the unconscious

  18. Topological phase transition of a fractal spin system: The relevance of the network complexity

    Directory of Open Access Journals (Sweden)

    Felipe Torres

    2016-05-01

    Full Text Available A new type of collective excitations, due to the topology of a complex random network that can be characterized by a fractal dimension DF, is investigated. We show analytically that these excitations generate phase transitions due to the non-periodic topology of the DF > 1 complex network. An Ising system, with long range interactions, is studied in detail to support the claim. The analytic treatment is possible because the evaluation of the partition function can be decomposed into closed factor loops, in spite of the architectural complexity. The removal of the infrared divergences leads to an unconventional phase transition, with spin correlations that are robust against thermal fluctuations.

  19. A Matheuristic for the Liner Shipping Network Design Problem with Transit Time Restrictions

    DEFF Research Database (Denmark)

    Brouer, Berit Dangaard; Desaulniers, Guy; Karsten, Christian Vad

    2015-01-01

    We present a mathematical model for the liner shipping network design problem with transit time restrictions on the cargo flow. We extend an existing matheuristic for the liner shipping network design problem to consider transit time restrictions. The matheuristic is an improvement heuristic, where...... an integer program is solved iteratively as a move operator in a large-scale neighborhood search. To assess the effects of insertions/removals of port calls, flow and revenue changes are estimated for relevant commodities along with an estimation of the change in the vessel cost. Computational results...

  20. Transitions across place and space – Spatial transitions in an Actor Network perspective

    DEFF Research Database (Denmark)

    Kerndrup, Søren; Mosgaard, Mette

    2012-01-01

    in a simple one dimensional framework based on geographical distance overlooking the social, economic and institutional dimensions. (Latour 2005, Boshma 2005, Knoben 2008) Therefore the aim of this paper is to combine the transitions framework with a relational geographic perspective influenced by the actor...

  1. Selecting polymers for two-phase partitioning bioreactors (TPPBs): Consideration of thermodynamic affinity, crystallinity, and glass transition temperature.

    Science.gov (United States)

    Bacon, Stuart L; Peterson, Eric C; Daugulis, Andrew J; Parent, J Scott

    2015-01-01

    Two-phase partitioning bioreactor technology involves the use of a secondary immiscible phase to lower the concentration of cytotoxic solutes in the fermentation broth to subinhibitory levels. Although polymeric absorbents have attracted recent interest due to their low cost and biocompatibility, material selection requires the consideration of properties beyond those of small molecule absorbents (i.e., immiscible organic solvents). These include a polymer's (1) thermodynamic affinity for the target compound, (2) degree of crystallinity (wc ), and (3) glass transition temperature (Tg ). We have examined the capability of three thermodynamic models to predict the partition coefficient (PC) for n-butyric acid, a fermentation product, in 15 polymers. Whereas PC predictions for amorphous materials had an average absolute deviation (AAD) of ≥16%, predictions for semicrystalline polymers were less accurate (AAD ≥ 30%). Prediction errors were associated with uncertainties in determining the degree of crystallinity within a polymer and the effect of absorbed water on n-butyric acid partitioning. Further complications were found to arise for semicrystalline polymers, wherein strongly interacting solutes increased the polymer's absorptive capacity by actually dissolving the crystalline fraction. Finally, we determined that diffusion limitations may occur for polymers operating near their Tg , and that the Tg can be reduced by plasticization by water and/or solute. This study has demonstrated the impact of basic material properties that affects the performance of polymers as sequestering phases in TPPBs, and reflects the additional complexity of polymers that must be taken into account in material selection. © 2015 American Institute of Chemical Engineers.

  2. Some properties of asymmetric Hopfield neural networks with finite time of transition between states

    Science.gov (United States)

    Suleimenov, Ibragim; Mun, Grigoriy; Panchenko, Sergey; Pak, Ivan

    2016-11-01

    There were implemented samples of asymmetric Hopfield neural networks which have finite time of transition from one state to another. It was shown that in such systems, various oscillation modes could occur. It was revealed that the oscillation of the output signal of certain neuron could be treated as extra logical variable, which describes the state of the neuron. Asymmetric Hopfield neural networks are described in terms of ternary logic. Such logic may be employed in image recognition procedure.

  3. Spike-timing-dependent plasticity enhanced synchronization transitions induced by autapses in adaptive Newman-Watts neuronal networks.

    Science.gov (United States)

    Gong, Yubing; Wang, Baoying; Xie, Huijuan

    2016-12-01

    In this paper, we numerically study the effect of spike-timing-dependent plasticity (STDP) on synchronization transitions induced by autaptic activity in adaptive Newman-Watts Hodgkin-Huxley neuron networks. It is found that synchronization transitions induced by autaptic delay vary with the adjusting rate Ap of STDP and become strongest at a certain Ap value, and the Ap value increases when network randomness or network size increases. It is also found that the synchronization transitions induced by autaptic delay become strongest at a certain network randomness and network size, and the values increase and related synchronization transitions are enhanced when Ap increases. These results show that there is optimal STDP that can enhance the synchronization transitions induced by autaptic delay in the adaptive neuronal networks. These findings provide a new insight into the roles of STDP and autapses for the information transmission in neural systems. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  4. Cell transmission model of dynamic assignment for urban rail transit networks.

    Directory of Open Access Journals (Sweden)

    Guangming Xu

    Full Text Available For urban rail transit network, the space-time flow distribution can play an important role in evaluating and optimizing the space-time resource allocation. For obtaining the space-time flow distribution without the restriction of schedules, a dynamic assignment problem is proposed based on the concept of continuous transmission. To solve the dynamic assignment problem, the cell transmission model is built for urban rail transit networks. The priority principle, queuing process, capacity constraints and congestion effects are considered in the cell transmission mechanism. Then an efficient method is designed to solve the shortest path for an urban rail network, which decreases the computing cost for solving the cell transmission model. The instantaneous dynamic user optimal state can be reached with the method of successive average. Many evaluation indexes of passenger flow can be generated, to provide effective support for the optimization of train schedules and the capacity evaluation for urban rail transit network. Finally, the model and its potential application are demonstrated via two numerical experiments using a small-scale network and the Beijing Metro network.

  5. The dynamic and geometric phase transition in the cellular network of pancreatic islet

    Science.gov (United States)

    Wang, Xujing

    2013-03-01

    The pancreatic islet is a micro-organ that contains several thousands of endocrine cells, majority of which being the insulin releasing β - cells . - cellsareexcitablecells , andarecoupledtoeachother through gap junctional channels. Here, using percolation theory, we investigate the role of network structure in determining the dynamics of the β-cell network. We show that the β-cell synchronization depends on network connectivity. More specifically, as the site occupancy is reducing, initially the β-cell synchronization is barely affected, until it reaches around a critical value, where the synchronization exhibit a sudden rapid decline, followed by an slow exponential tail. This critical value coincides with the critical site open probability for percolation transition. The dependence over bond strength is similar, exhibiting critical-behavior like dependence around a certain value of bond strength. These results suggest that the β-cell network undergoes a dynamic phase transition when the network is percolated. We further apply the findings to study diabetes. During the development of diabetes, the β - cellnetworkconnectivitydecreases . Siteoccupancyreducesfromthe reducing β-cell mass, and the bond strength is increasingly impaired from β-cell stress and chronic hyperglycemia. We demonstrate that the network dynamics around the percolation transition explain the disease dynamics around onset, including a long time mystery in diabetes, the honeymoon phenomenon.

  6. Transit clairvoyance: enhancing TESS follow-up using artificial neural networks

    Science.gov (United States)

    Kipping, David M.; Lam, Christopher

    2017-03-01

    The upcoming Transiting Exoplanet Survey Satellite (TESS) mission is expected to find thousands of transiting planets around bright stars, yet for three-quarters of the fields observed the temporal coverage will limit discoveries to planets with orbital periods below 13.7 d. From the Kepler catalogue, the mean probability of these short-period transiting planets having additional longer period transiters (which would be missed by TESS) is 18 per cent, a value 10 times higher than the average star. In this work, we show how this probability is not uniform but functionally dependent upon the properties of the observed short-period transiters, ranging from less than 1 per cent up to over 50 per cent. Using artificial neural networks (ANNs) trained on the Kepler catalogue and making careful feature selection to account for the differing sensitivity of TESS, we are able to predict the most likely short-period transiters to be accompanied by additional transiters. Through cross-validation, we predict that a targeted, optimized TESS transit and/or radial velocity follow-up programme using our trained ANN would have a discovery yield improved by a factor of 2. Our work enables a near-optimal follow-up strategy for surveys following TESS targets for additional planets, improving the science yield derived from TESS and particularly beneficial in the search for habitable-zone transiting worlds.

  7. Transition from Arrhenius to non-Arrhenius temperature dependence of structural relaxation time in glass-forming liquids: continuous versus discontinuous scenario.

    Science.gov (United States)

    Popova, V A; Surovtsev, N V

    2014-09-01

    The temperature dependences of α relaxation time τ(α)(T) of three glass-forming liquids (salol, o-terphenyl, and α-picoline) were investigated by a depolarized light scattering technique. A detailed description of τ(α)(T) near T(A), the temperature of the transition from the Arrhenius law at high temperatures to a non-Arrhenius behavior of τ(α)(T) at lower temperatures, was done. It was found that this transition is quite sharp. If the transition is described as switching from the Arrhenius law to the Vogel-Fulcher-Tammann law, it occurs within the temperature range of about 15 K or less. Most of the known expressions for τ(α)(T) cannot describe this sharp transition. Our analysis revealed that this transition can be described either as a discontinuous transition in the spirit of the frustration-limited domain theory [D. Kivelson, G. Tarjus, X. Zhao, and S. A. Kivelson, Phys. Rev. E 53, 751 (1996)], implying a phase transition, or by a phenomenological expression recently suggested [B. Schmidtke, N. Petzold, R. Kahlau, M. Hofmann, and E. A. Rössler, Phys. Rev. E 86, 041507 (2012)], where the activation energy includes the term depending exponentially on temperature.

  8. Localization transition of biased random walks on random networks.

    Science.gov (United States)

    Sood, Vishal; Grassberger, Peter

    2007-08-31

    We study random walks on large random graphs that are biased towards a randomly chosen but fixed target node. We show that a critical bias strength bc exists such that most walks find the target within a finite time when b > bc. For b infinity before hitting the target. The phase transition at b=bc is a critical point in the sense that quantities such as the return probability P(t) show power laws, but finite-size behavior is complex and does not obey the usual finite-size scaling ansatz. By extending rigorous results for biased walks on Galton-Watson trees, we give the exact analytical value for bc and verify it by large scale simulations.

  9. Infrared spectroscopy of network and cation dynamics in binary and mixed alkali borate glasses

    NARCIS (Netherlands)

    Verhoef, A.H; Hartog, H.W.den

    Infrared reflectance spectra of twenty different glasses of the type (B2O3)(1-x-y)(Li2O)(x)(Cs2O)(y) have been measured in the frequency range of 10-5000 cm(-1). From these spectra, infrared absorbance and dielectric spectra have been calculated using the Kramers-Kronig inversion technique. The

  10. Examining the Impact of Pre-Induction Social Networking on the Student Transition into Higher Education

    Science.gov (United States)

    Ribchester, Chris; Ross, Kim; Rees, Emma L. E.

    2014-01-01

    This research paper considers how bespoke online social networks have been used to support students' transition into higher education during the weeks immediately prior to formal "on-site" induction. An analysis of online activities showed some differences in the pattern of engagement between two contrasting departments (Geography and…

  11. Starting Online: Exploring the Use of a Social Networking Site to Facilitate Transition into Higher Education

    Science.gov (United States)

    Knight, John; Rochon, Rebecca

    2012-01-01

    It has been widely recognised that transition into higher education (HE) can be challenging for incoming students. Literature identifies three main areas where students may benefit from support: social, practical and academic. This paper discusses a case study that explores the potential of a social networking environment to provide support in…

  12. Mix proportions and properties of CLSC made from thin film transition liquid crystal display optical waste glass.

    Science.gov (United States)

    Wang, Her-Yung; Chen, Jyun-Sheng

    2010-01-01

    In this study, controlled low-strength concrete (CLSC) is mixed using different water-to-binder (W/B) ratios (1.1, 1.3 and 1.5) and various percentages of sand substituted by waste LCD glass sand (0%, 10%, 20% and 30%). The properties of the fresh concrete, including compressive strength, electrical resistivity, ultrasonic pulse velocity, permeability ratio and shrinking of the CLSC, are examined. Results show that increases in amount of waste glass added result in better slump and slump flow, longer initial setting time and smaller unit weight. Compressive strength decreases with increasing W/B ratio and greater amounts of waste glass added. Both electrical resistivity and ultrasonic pulse velocity increase with increases in amount of waste glass and decreases in W/B ratio. On the contrary, the permeability ratio increases with increases in W/B ratio, but decreases with greater amounts of waste glass added. CLSC specimens cured for different durations show little changes in length with shrinkage below 0.025%. Our findings reveal that CLSC mixed using waste LCD glass in place of sand can meet design requirements. Recycling of waste LCD glass not only offers an economical substitute for aggregates, but also an ecological alternative for waste management. 2009 Elsevier Ltd. All rights reserved.

  13. Characteristics of martensitic and strain-glass transitions of the Fe-substituted TiNi shape memory alloys probed by transport and thermal measurements.

    Science.gov (United States)

    Ramachandran, Balakrishnan; Chang, Pei-Chi; Kuo, Yung-Kang; Chien, Chen; Wu, Shyi-Kaan

    2017-11-27

    The electrical resistivity, Seebeck coefficient, thermal conductivity, and specific heat of Ti50Ni50-x Fe x (x = 2.0-10.0 at.%) shape memory alloys (SMAs) were measured to investigate the influence of point defects (Fe) on the martensitic transformation characteristics. Our results show that the Ti50Ni48Fe2 and Ti50Ni47Fe3 SMAs have a two-step martensitic transformation (B2 → R and R → B19'), while the Ti50Ni46Fe4, Ti50Ni44.5Fe5.5, and Ti50Ni44Fe6 SMAs display a one-step martensitic transition (B2 → R). However, the compounds Ti50Ni42Fe8 and Ti50Ni40Fe10 show strain glass features (frozen strain-ordered state). Importantly, the induced point defects significantly alter the martensitic transformation characteristics, namely transition temperature and width of thermal hysteresis during the transition. This can be explained by the stabilization of austenite B2 phase upon Fe substitution, which ultimately leads to the decrease in enthalpy that associated to the martensitic transition. To determine the boundary composition that separates the R-phase and strain glass systems in this series of SMAs, a Ni-rich specimen Ti49Ni45Fe6 was fabricated. Remarkably, a slight change in Ti/Ni ratio converts Ti49Ni45Fe6 SMA into a strain glass system. Overall, the evolution of phase transformation in the Fe-substituted TiNi SMAs is presumably caused by the changes in local lattice structure via the induced local strain fields by Fe point defects.

  14. Ashkin-Teller model and diverse opinion phase transitions on multiplex networks.

    Science.gov (United States)

    Jang, S; Lee, J S; Hwang, S; Kahng, B

    2015-08-01

    Multiplex networks (MNs) have become a platform of recent research in network sciences because networks in many real-world systems interact and function together. One of the main scientific issues in MNs is how the interdependence changes the emerging patterns or phase transitions. Until now, studies of such an issue have concentrated on cluster-breakdown phenomena, aiming to understand the resilience of the system under random failures of edges. These studies have revealed that various phase transition (PT) types emerge in MNs. However, such studies are rather limited to percolation-related problems, i.e., the limit q→1 of the q-state Potts model. Thus, a systematic study of opinion formation in social networks with the effect of interdependence between different social communities, which may be seen as the study of the emerging pattern of the Ising model on MNs, is needed. Here we study a well-known spin model called the Ashkin-Teller (AT) model in scale-free networks. The AT model can be regarded as a model for interacting systems between two species of Ising spins placed on respective layers in double-layer networks. Our study shows that, depending on the interlayer coupling strength and a network topology, unconventional PT patterns can also emerge in interaction-based phenomena: continuous, discontinuous, successive, and mixed-order PTs and a continuous PT not satisfying the scaling relation. The origins of such rich PT patterns are elucidated in the framework of Landau-Ginzburg theory.

  15. Systemic risk and hierarchical transitions of financial networks

    Science.gov (United States)

    Nobi, Ashadun; Lee, Jae Woo

    2017-06-01

    In this paper, the change in topological hierarchy, which is measured by the minimum spanning tree constructed from the cross-correlations between the stock indices from the S & P 500 for 1998-2012 in a one year moving time window, was used to analyze a financial crisis. The hierarchy increased in all minor crises in the observation time window except for the sharp crisis of 2007-2008 when the global financial crisis occurred. The sudden increase in hierarchy just before the global financial crisis can be used for the early detection of an upcoming crisis. Clearly, the higher the hierarchy, the higher the threats to financial stability. The scaling relations were developed to observe the changes in hierarchy with the network topology. These scaling relations can also identify and quantify the financial crisis periods, and appear to contain the predictive power of an upcoming crisis.

  16. Iron phosphate glasses: Bulk properties and atomic scale structure

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Kitheri; Stennett, Martin C.; Hyatt, Neil C.; Asuvathraman, R.; Dube, Charu L.; Gandy, Amy S.; Govindan Kutty, K. V.; Jolley, Kenny; Vasudeva Rao, P. R.; Smith, Roger

    2017-10-01

    Bulk properties such as glass transition temperature, density and thermal expansion of iron phosphate glass compositions, with replacement of Cs by Ba, are investigated as a surrogate for the transmutation of 137Cs to 137Ba, relevant to the immobilisation of Cs in glass. These studies are required to establish the appropriate incorporation rate of 137Cs in iron phosphate glass. Density and glass transition temperature increases with the addition of BaO indicating the shrinkage and reticulation of the iron phosphate glass network. The average thermal expansion coefficient reduces from 19.8 × 10-6 K-1 to 13.4 × 10-6 K-1, when 25 wt. % of Cs2O was replaced by 25 wt. % of BaO in caesium loaded iron phosphate glass. In addition to the above bulk properties, the role of Ba as a network modifier in the structure of iron phosphate glass is examined using various spectroscopic techniques. The FeII content and average coordination number of iron in the glass network was estimated using Mössbauer spectroscopy. The FeII content in the un-doped iron phosphate glass and barium doped iron phosphate glasses was 20, 21 and 22 ± 1% respectively and the average Fe coordination varied from 5.3 ± 0.2 to 5.7 ± 0.2 with increasing Ba content. The atomic scale structure was further probed by Fe K-edge X-ray absorption spectroscopy. The average coordination number provided by extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge structure was in good agreement with that given by the Mössbauer data.

  17. Physical, thermal, infrared and optical properties of Nd3+ doped lithium-lead-germanate glasses

    Science.gov (United States)

    Veeranna Gowda, V. C.

    2015-01-01

    The structure-property relationships of neodymium doped lithium-lead-germanate glasses were investigated. The density was found to increase with the increase of Nd2O3 concentration and its variation is explained in terms of its molecular mass, structural transformation and packing density. Addition of modifier oxide to lead-germanate glass suggests a decreased free space within the glass matrix, resulting in the formation of stiff network. The increase in glass transition temperature specifies strengthening of glass by forming bridging oxygens. The optical properties of glass were measured employing UV-visible spectroscopy. The refractive index values varied nonlinearly with Nd2O3 concentration and were speculated to depend on the electronic polarizability of oxide glasses. The frequencies of the infrared absorption bands were affected marginally and the absorption peaks revealed that the glass matrix consists of [GeO4/2], [GeO6/2] and [PbO4/2] structural units.

  18. Extraordinary variability and sharp transitions in a maximally frustrated dynamic network

    Science.gov (United States)

    Liu, Wenjia; Schmittmann, Beate; Zia, R. K. P.

    2013-03-01

    Most previous studies of complex networks have focused on single, static networks. However, in the real world, networks are dynamic and interconnected. Inspired by the presence of extroverts and introverts in the general population, we investigate a highly simplified model of a social network, involving two types of nodes: one preferring the highest degree possible, and one preferring no connections whatsoever. There are only two control parameters in the model: the number of ``introvert'' and ``extrovert'' nodes, NI and NE. Our key findings are as follows: As a function of NI and NE, the system exhibits a highly unusual transition, displaying extraordinary fluctuations (as in 2nd order transitions) and discontinuous jumps (characteristic of 1st order transitions). Most remarkably, the system can be described by an Ising-like Hamiltonian with long-range multi-spin interactions and some of its properties can be obtained analytically. This is in stark contrast with other dynamic network models which rely almost exclusively on simulations. NSF-DMR-1005417/1244666 and and ICTAS Virginia Tech

  19. Physical, thermal and structural properties of Calcium Borotellurite glass system

    Energy Technology Data Exchange (ETDEWEB)

    Paz, E.C. [CCSST – UFMA, Imperatriz, MA (Brazil); IFMA, Açailândia, MA (Brazil); Dias, J.D.M. [CCSST – UFMA, Imperatriz, MA (Brazil); Melo, G.H.A. [CCSST – UFMA, Imperatriz, MA (Brazil); IFMA, Imperatriz, MA (Brazil); Lodi, T.A. [CCSST – UFMA, Imperatriz, MA (Brazil); Carvalho, J.O. [CCSST – UFMA, Imperatriz, MA (Brazil); IFTO, Araguaína, TO (Brazil); Façanha Filho, P.F.; Barboza, M.J.; Pedrochi, F. [CCSST – UFMA, Imperatriz, MA (Brazil); Steimacher, A., E-mail: steimacher@hotmail.com [CCSST – UFMA, Imperatriz, MA (Brazil)

    2016-08-01

    In this work the glass forming ability in Calcium Borotellurite (CBTx) glass system was studied. Six glass samples were prepared by melt-quenching technique and the obtained samples are transparent, lightly yellowish, with no visible crystallites. The structural studies were carried out by using XRD, FTIR, Raman Spectra, density measurements, and the thermal analysis by using DTA and specific heat. The results are discussed in terms of tellurium oxide content and their changes in structural and thermal properties of glass samples. The addition of TeO{sub 2} increased the density and thermal stability values and decreased glass transition temperature (Tg). Raman and FTIR spectroscopies indicated that the network structure of CBTx glasses is formed by BO{sub 3}, BO{sub 4}, TeO{sub 3}, TeO{sub 3+1} and TeO{sub 4} units. CBTx system showed good glass formation ability and good thermal stability, which make CBTx glasses suitable for manufacturing process and a candidate for rare-earth doping for several optical applications. - Highlights: • Glass forming ability on Calcium Borotellurite system was studied. • The glass structure was investigated by XRD, Raman and FTIR. • The glass network structure of the CBTx glasses is formed by BO{sub 3}, BO{sub 4}, TeO{sub 3}, TeO{sub 3+1} and TeO{sub 4} units. • The density and thermal stability of the CBTx glass decreases with TeO{sub 2} while the Cp and the Tg decreases. • The obtained CBTx glasses are suitable for manufacturing process and rare-earth doping for several optical applications.

  20. The relationship of dynamical heterogeneity to the Adam-Gibbs and random first-order transition theories of glass formation.

    Science.gov (United States)

    Starr, Francis W; Douglas, Jack F; Sastry, Srikanth

    2013-03-28

    We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times for the high- and low-mobility particles naturally explains the well-known decoupling of diffusion and structural relaxation time scales. Despite the inherent difference of dynamics between high- and low-mobility particles, we find a high degree of similarity in the geometrical structure of these particle clusters. In particular, we show that the fractal dimensions of these clusters are consistent with those of swollen branched polymers or branched polymers with screened excluded-volume interactions, corresponding to lattice animals and percolation clusters, respectively. In contrast, the fractal dimension of the strings crosses over from that of self-avoiding walks for small strings, to simple random walks for longer, more strongly interacting, strings, corresponding to flexible polymers with screened excluded-volume interactions. We examine the appropriateness of identifying the size scales of either mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the "mosaic" length of the RFOT model relaxes the conventional assumption that the "entropic droplets" are compact. We also confirm the

  1. Experimental and computer simulation determination of the structural changes occurring through the liquid-glass transition in Cu-Zr alloys

    Science.gov (United States)

    Mendelev, M. I.; Kramer, M. J.; Ott, R. T.; Sordelet, D. J.; Besser, M. F.; Kreyssig, A.; Goldman, A. I.; Wessels, V.; Sahu, K. K.; Kelton, K. F.; Hyers, R. W.; Canepari, S.; Rogers, J. R.

    2010-10-01

    Molecular dynamics (MD) simulations were performed of the structural changes occurring through the liquid-glass transition in Cu-Zr alloys. The total scattering functions (TSF), and their associated primary diffuse scattering peak positions (K p), heights (K h) and full-widths at half maximum (K FWHM) were used as metrics to compare the simulations to high-energy X-ray scattering data. The residuals of difference between the model and experimental TSFs are ∼0.03 for the liquids and about 0.07 for the glasses. Over the compositional range studied, Zr1- x Cu x (0.1 ≤ x ≤ 0.9), K p, K h and K FWHM show a strong dependence on composition and temperature. The simulation and experimental data correlate well between each other. MD simulation revealed that the Cu-Zr bonds undergo the largest changes during cooling of the liquid, whereas the Cu-Cu bonds change the least. Changes in the partial-pair correlations are more readily seen in the second and third shells. The Voronoi polyhedra (VP) in glasses are dominated by only a few select types that are compositionally dependent. The relative concentrations of the dominant VPs rapidly change in their relative proportion in the deeply undercooled liquid. The experimentally determined region of best glass formability, x Cu ∼ 65%, shows the largest temperature dependent changes for the deeply undercooled liquid in the MD simulation. This region also exhibits very strong temperature dependence for the diffusivity and the total energy of the system. These data point to a strong topological change in the best glass-forming alloys and a concurrent change in the VP chemistry in the deeply undercooled liquid.

  2. Investigation of luminescence and laser transition of Dy3+ in Li2O-Gd2O3-Bi2O3-B2O3 glasses

    Science.gov (United States)

    Zaman, F.; Kaewkhao, J.; Srisittipokakun, N.; Wantana, N.; Kim, H. J.; Rooh, G.

    2016-05-01

    The aim of this study is to develop Li2O-Gd2O3-Bi2O3-B2O3 glass doped with different concentration of Dy3+ ions by melt quenching technique for different applications in photonics and laser devices. From the experimental oscillator strength (fexp) of the absorption spectra the JO intensity parameters (Ω λ = 2, 4, 6) have been calculated, and by using these JO intensity parameters various radiative parameters were calculated. By using JO theory the radiative transition probability (AR), radiative lifetime (τR) and branching ratio (βR) for Dy3+ ion have been found. A decrease in lifetimes of the prepared glass by increasing concentration of Dy3+ is because of the energy transfer through cross relaxation and resonant energy transfer channels in the present glass matrix. Using experimental and calculated lifetimes, the quantum efficiency (η) and non-radiative relaxation rates (WNR) of 4F9/2 excited state have been calculated. From emission spectra, effective bandwidths (Δλeff) and emission stimulated emission cross section σ (λp) were found for 4F9/2 → 6HJ (J = 15/2, 13/2, 11/2 and 9/2). Chromaticity results revealed that the CCT values of the LGBiBDy glass samples are in between to those of day light and commercial white light LED sources. Further investigations are under way for the optimization of dopant concentration in the Li2O-Gd2O3-Bi2O3-B2O3 glass.

  3. Thermo-physical and structural studies of sodium zinc borovanadate glasses in the region of high concentration of modifier oxides

    Energy Technology Data Exchange (ETDEWEB)

    Chethana, B.K. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India); Reddy, C. Narayana [Maharani' s Science College for Women, Bangalore 560 001 (India); Rao, K.J., E-mail: kalyajrao@yahoo.co.in [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India)

    2012-07-15

    Highlights: ► Highly modified sodium zinc borovanadate glasses. ► Structural model for borovanadate glasses. ► Network forming tendency of ZnO in borovanadate glasses. ► Fragility can be limited to NBO concentration in borovanadate glasses. -- Abstract: This paper reports investigation of Na{sub 2}O and ZnO modified borovanadate glasses in the highly modified regime of compositions. These glasses have been prepared by microwave route. Ultraviolet (UV) and visible, infrared (IR), Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) and Electron Paramagnetic Resonance (EPR) spectroscopies have been used to characterize the speciation in the glasses. Together with the variation of properties such as molar volume and glass transition temperatures, spectroscopic data indicate that at high levels of modification, ZnO tends to behave like network former. It is proposed that the observed variation of all the properties can be reasonably well understood with a structural model. The model considers that the modification and speciation in glasses are strongly determined by the hierarchy of group electronegativities. Further, it is proposed that the width of the transitions of glasses obtained under same condition reflects the fragility of the glasses. An empirical expression has been suggested to quantify fragility on the basis of width of the transition regions.

  4. Comprehensive study of electronic polarizability and band gap of B2O3-Bi2O3-ZnO-SiO2 glass network

    Science.gov (United States)

    Mustafa, Iskandar Shahrim; Razali, Nur Ain Nabilah; Azman, Nurul Zahirah Noor; Yahaya, Nor Zakiah; Zaini, Muhammad Zulhafiz Mohamad; Rusli, Nur Lina; Nizamani, Muhammad Bakhsh; Kamari, Halimah Mohamed

    Quaternary glasses were successfully fabricated using melt quenching technique based on the chemical compound composition (x)Bi2O3-(0.5‑x) ZnO-(0.2)B2O3-(0.3)SiO2, where (x=0.1, 0.2, 0.3, 0.4, 0.45) mole. The sources of SiO2 was produced from rice husk ash (RHA) at 99.36% of SiO2. The Urbach energy was increased from 0.16eV to the 0.29eV as the mole of Bi2O3 increased in the glass structure. The indirect energy band gap is indicated in decrement pattern with 3.15eV towards 2.51eV. The results of Urbach energy and band gap energy that were obtained are due to the increment of Bi3+ ion in the glass network. The refractive indexes for the prepared glasses were evaluated at 2.36 to 2.54 based on the Lorentz-Lorentz formulation which correlated to the energy band gap. The calculated of molar polarizability, electronic polarizability and optical basicity exemplify fine complement to the Bi2O3 addition in the glass network. The glass sample was indicated in amorphous state.

  5. Phase transitions and self-organized criticality in networks of stochastic spiking neurons

    Science.gov (United States)

    Brochini, Ludmila; de Andrade Costa, Ariadne; Abadi, Miguel; Roque, Antônio C.; Stolfi, Jorge; Kinouchi, Osame

    2016-11-01

    Phase transitions and critical behavior are crucial issues both in theoretical and experimental neuroscience. We report analytic and computational results about phase transitions and self-organized criticality (SOC) in networks with general stochastic neurons. The stochastic neuron has a firing probability given by a smooth monotonic function Φ(V) of the membrane potential V, rather than a sharp firing threshold. We find that such networks can operate in several dynamic regimes (phases) depending on the average synaptic weight and the shape of the firing function Φ. In particular, we encounter both continuous and discontinuous phase transitions to absorbing states. At the continuous transition critical boundary, neuronal avalanches occur whose distributions of size and duration are given by power laws, as observed in biological neural networks. We also propose and test a new mechanism to produce SOC: the use of dynamic neuronal gains - a form of short-term plasticity probably located at the axon initial segment (AIS) - instead of depressing synapses at the dendrites (as previously studied in the literature). The new self-organization mechanism produces a slightly supercritical state, that we called SOSC, in accord to some intuitions of Alan Turing.

  6. UP-DOWN cortical dynamics reflect state transitions in a bistable network

    Science.gov (United States)

    Roxin, Alex; Barthó, Peter; Luczak, Artur

    2017-01-01

    In the idling brain, neuronal circuits transition between periods of sustained firing (UP state) and quiescence (DOWN state), a pattern the mechanisms of which remain unclear. Here we analyzed spontaneous cortical population activity from anesthetized rats and found that UP and DOWN durations were highly variable and that population rates showed no significant decay during UP periods. We built a network rate model with excitatory (E) and inhibitory (I) populations exhibiting a novel bistable regime between a quiescent and an inhibition-stabilized state of arbitrarily low rate. Fluctuations triggered state transitions, while adaptation in E cells paradoxically caused a marginal decay of E-rate but a marked decay of I-rate in UP periods, a prediction that we validated experimentally. A spiking network implementation further predicted that DOWN-to-UP transitions must be caused by synchronous high-amplitude events. Our findings provide evidence of bistable cortical networks that exhibit non-rhythmic state transitions when the brain rests. PMID:28826485

  7. Long-Term Stability of New Co-Amorphous Drug Binary Systems: Study of Glass Transitions as a Function of Composition and Shelf Time

    Directory of Open Access Journals (Sweden)

    Luz María Martínez

    2016-12-01

    Full Text Available The amorphous state is of particular interest in the pharmaceutical industry due to the higher solubility that amorphous active pharmaceutical ingredients show compared to their respective crystalline forms. Due to their thermodynamic instability, drugs in the amorphous state tend to recrystallize; in order to avoid crystallization, it has been a common strategy to add a second component to hinder the crystalline state and form a thermally stable co-amorphous system, that is to say, an amorphous binary system which retains its amorphous structure. The second component can be a small molecule excipient (such as a sugar or an aminoacid or a second drug, with the advantage that a second active pharmaceutical ingredient could be used for complementary or combined therapeutic purposes. In most cases, the compositions studied are limited to 1:1, 2:1 and 1:2 molar ratios, leaving a gap of information about phase transitions and stability on the amorphous state in a wider range of compositions. In the present work, a study of novel co–amorphous formulations in which the selection of the active pharmaceutical ingredients was made according to the therapeutic effect is presented. Resistance against crystallization and behavior of glass transition temperature ( T g were studied through calorimetric measurements as a function of composition and shelf time. It was found that binary formulations with T g temperatures higher than those of pure components presented long-term thermal stability. In addition, significant increments of T g values, of as much as 15 ∘ C, were detected as a result of glass relaxation at room temperature during storage time; this behavior of glass transition has not been previously reported for co-amorphous drugs. Based on these results, it can be concluded that monitoring behavior of T g and relaxation processes during the first weeks of storage leads to a more objective evaluation of the thermomechanical stability of an amorphous

  8. Long-Term Stability of New Co-Amorphous Drug Binary Systems: Study of Glass Transitions as a Function of Composition and Shelf Time.

    Science.gov (United States)

    Martínez, Luz María; Videa, Marcelo; Sosa, Nahida González; Ramírez, José Héctor; Castro, Samuel

    2016-12-14

    The amorphous state is of particular interest in the pharmaceutical industry due to the higher solubility that amorphous active pharmaceutical ingredients show compared to their respective crystalline forms. Due to their thermodynamic instability, drugs in the amorphous state tend to recrystallize; in order to avoid crystallization, it has been a common strategy to add a second component to hinder the crystalline state and form a thermally stable co-amorphous system, that is to say, an amorphous binary system which retains its amorphous structure. The second component can be a small molecule excipient (such as a sugar or an aminoacid) or a second drug, with the advantage that a second active pharmaceutical ingredient could be used for complementary or combined therapeutic purposes. In most cases, the compositions studied are limited to 1:1, 2:1 and 1:2 molar ratios, leaving a gap of information about phase transitions and stability on the amorphous state in a wider range of compositions. In the present work, a study of novel co-amorphous formulations in which the selection of the active pharmaceutical ingredients was made according to the therapeutic effect is presented. Resistance against crystallization and behavior of glass transition temperature ( T g were studied through calorimetric measurements as a function of composition and shelf time. It was found that binary formulations with T g temperatures higher than those of pure components presented long-term thermal stability. In addition, significant increments of T g values, of as much as 15 ∘ C, were detected as a result of glass relaxation at room temperature during storage time; this behavior of glass transition has not been previously reported for co-amorphous drugs. Based on these results, it can be concluded that monitoring behavior of T g and relaxation processes during the first weeks of storage leads to a more objective evaluation of the thermomechanical stability of an amorphous formulation.

  9. Simulation-Based Dynamic Passenger Flow Assignment Modelling for a Schedule-Based Transit Network

    Directory of Open Access Journals (Sweden)

    Xiangming Yao

    2017-01-01

    Full Text Available The online operation management and the offline policy evaluation in complex transit networks require an effective dynamic traffic assignment (DTA method that can capture the temporal-spatial nature of traffic flows. The objective of this work is to propose a simulation-based dynamic passenger assignment framework and models for such applications in the context of schedule-based rail transit systems. In the simulation framework, travellers are regarded as individual agents who are able to obtain complete information on the current traffic conditions. A combined route selection model integrated with pretrip route selection and entrip route switch is established for achieving the dynamic network flow equilibrium status. The train agent is operated strictly with the timetable and its capacity limitation is considered. A continuous time-driven simulator based on the proposed framework and models is developed, whose performance is illustrated through a large-scale network of Beijing subway. The results indicate that more than 0.8 million individual passengers and thousands of trains can be simulated simultaneously at a speed ten times faster than real time. This study provides an efficient approach to analyze the dynamic demand-supply relationship for large schedule-based transit networks.

  10. Inferring Transition Rates of Networks from Populations in Continuous-Time Markov Processes.

    Science.gov (United States)

    Dixit, Purushottam D; Jain, Abhinav; Stock, Gerhard; Dill, Ken A

    2015-11-10

    We are interested inferring rate processes on networks. In particular, given a network's topology, the stationary populations on its nodes, and a few global dynamical observables, can we infer all the transition rates between nodes? We draw inferences using the principle of maximum caliber (maximum path entropy). We have previously derived results for discrete-time Markov processes. Here, we treat continuous-time processes, such as dynamics among metastable states of proteins. The present work leads to a particularly important analytical result: namely, that when the network is constrained only by a mean jump rate, the rate matrix is given by a square-root dependence of the rate, kab ∝ (πb/πa)(1/2), on πa and πb, the stationary-state populations at nodes a and b. This leads to a fast way to estimate all of the microscopic rates in the system. As an illustration, we show that the method accurately predicts the nonequilibrium transition rates in an in silico gene expression network and transition probabilities among the metastable states of a small peptide at equilibrium. We note also that the method makes sensible predictions for so-called extra-thermodynamic relationships, such as those of Bronsted, Hammond, and others.

  11. Switch-like Transitions Insulate Network Motifs to Modularize Biological Networks.

    Science.gov (United States)

    Atay, Oguzhan; Doncic, Andreas; Skotheim, Jan M

    2016-08-01

    Cellular decisions are made by complex networks that are difficult to analyze. Although it is common to analyze smaller sub-networks known as network motifs, it is unclear whether this is valid, because these motifs are embedded in complex larger networks. Here, we address the general question of modularity by examining the S. cerevisiae pheromone response. We demonstrate that the feedforward motif controlling the cell-cycle inhibitor Far1 is insulated from cell-cycle dynamics by the positive feedback switch that drives reentry to the cell cycle. Before cells switch on positive feedback, the feedforward motif model predicts the behavior of the larger network. Conversely, after the switch, the feedforward motif is dismantled and has no discernable effect on the cell cycle. When insulation is broken, the feedforward motif no longer predicts network behavior. This work illustrates how, despite the interconnectivity of networks, the activity of motifs can be insulated by switches that generate well-defined cellular states. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Dramatic reduction of the effect of nanoconfinement on the glass transition of polymer films via addition of small-molecule diluent.

    Science.gov (United States)

    Ellison, Christopher J; Ruszkowski, Robert L; Fredin, Nathaniel J; Torkelson, John M

    2004-03-05

    The effect of nanoconfinement on the glass transition temperature T(g) in thin polymer films is studied as a function of added small-molecule diluent or plasticizer. The decrease [increase] in T(g) found in nanoconfined, neat polystyrene [poly(2-vinyl pyridine)] is suppressed by added diluent, with 13-20 nm thick polystyrene films exhibiting bulk T(g) upon addition of 9 wt % pyrene or 4 wt % dioctylphthalate [corrected]. This is explained by a connection between the size scale of the cooperative dynamics associated with T(g), which decreases with added diluent, and the size scale of the nanoconfinement effect.

  13. Composition-Structure-Property Relationships in Boroaluminosilicate Glasses

    DEFF Research Database (Denmark)

    Zheng, Qiuju; Potuzak, M.; Mauro, J.C.

    2012-01-01

    The complicated structural speciation in boroaluminosilicate glasses leads to a mixed network former effect yielding nonlinear variation in many macroscopic properties as a function of chemical composition. Here we study the composition–structure–property relationships in a series of sodium...... boroaluminosilicate glasses from peralkaline to peraluminous compositions by substituting Al2O3 for SiO2. Our results reveal a pronounced change in all the measured physical properties (density, elastic moduli, hardness, glass transition temperature, and liquid fragility) around [Al2O3]–[Na2O]=0. The structural...

  14. From biological neural networks to thinking machines: Transitioning biological organizational principles to computer technology

    Science.gov (United States)

    Ross, Muriel D.

    1991-01-01

    The three-dimensional organization of the vestibular macula is under study by computer assisted reconstruction and simulation methods as a model for more complex neural systems. One goal of this research is to transition knowledge of biological neural network architecture and functioning to computer technology, to contribute to the development of thinking computers. Maculas are organized as weighted neural networks for parallel distributed processing of information. The network is characterized by non-linearity of its terminal/receptive fields. Wiring appears to develop through constrained randomness. A further property is the presence of two main circuits, highly channeled and distributed modifying, that are connected through feedforward-feedback collaterals and biasing subcircuit. Computer simulations demonstrate that differences in geometry of the feedback (afferent) collaterals affects the timing and the magnitude of voltage changes delivered to the spike initiation zone. Feedforward (efferent) collaterals act as voltage followers and likely inhibit neurons of the distributed modifying circuit. These results illustrate the importance of feedforward-feedback loops, of timing, and of inhibition in refining neural network output. They also suggest that it is the distributed modifying network that is most involved in adaptation, memory, and learning. Tests of macular adaptation, through hyper- and microgravitational studies, support this hypothesis since synapses in the distributed modifying circuit, but not the channeled circuit, are altered. Transitioning knowledge of biological systems to computer technology, however, remains problematical.

  15. Quantifying Complexity in Quantum Phase Transitions via Mutual Information Complex Networks.

    Science.gov (United States)

    Valdez, Marc Andrew; Jaschke, Daniel; Vargas, David L; Carr, Lincoln D

    2017-12-01

    We quantify the emergent complexity of quantum states near quantum critical points on regular 1D lattices, via complex network measures based on quantum mutual information as the adjacency matrix, in direct analogy to quantifying the complexity of electroencephalogram or functional magnetic resonance imaging measurements of the brain. Using matrix product state methods, we show that network density, clustering, disparity, and Pearson's correlation obtain the critical point for both quantum Ising and Bose-Hubbard models to a high degree of accuracy in finite-size scaling for three classes of quantum phase transitions, Z_{2}, mean field superfluid to Mott insulator, and a Berzinskii-Kosterlitz-Thouless crossover.

  16. Kinetic Transition Networks for the Thomson Problem and Smale's Seventh Problem

    Science.gov (United States)

    Mehta, Dhagash; Chen, Jianxu; Chen, Danny Z.; Kusumaatmaja, Halim; Wales, David J.

    2016-07-01

    The Thomson problem, arrangement of identical charges on the surface of a sphere, has found many applications in physics, chemistry and biology. Here, we show that the energy landscape of the Thomson problem for N particles with N =132 , 135, 138, 141, 144, 147, and 150 is single funneled, characteristic of a structure-seeking organization where the global minimum is easily accessible. Algorithmically, constructing starting points close to the global minimum of such a potential with spherical constraints is one of Smale's 18 unsolved problems in mathematics for the 21st century because it is important in the solution of univariate and bivariate random polynomial equations. By analyzing the kinetic transition networks, we show that a randomly chosen minimum is, in fact, always "close" to the global minimum in terms of the number of transition states that separate them, a characteristic of small world networks.

  17. Structural phase transition in a growing network model with tunable member intimacy

    Science.gov (United States)

    Kim, Kibum; Jo, Woo Seong; Kim, Beom Jun

    2017-05-01

    Users of online communities become more intimate in time by writing posts and exchanging comments to each other. Although a certain level of intimacy among a group of members can be beneficial for the activity of the whole community, too strong intimacy among existing members can make newcomers feel alienated, driving them to leave the community. In this letter, we introduce a growing network model in which we systematically study the effect of member intimacy on the formation of connected component of the network. We introduce a parameter called clinginess and control how the member intimacy affects the communication activity. We observe that cumulative number of users who leave the community exhibits a transition-like behavior, similarly to the discontinuous transition in statistical mechanics models. Implication of our result in constructing a sustainable online community is also discussed.

  18. Special Feature: Liquids and Structural Glasses Special Feature: An active biopolymer network controlled by molecular motors

    Science.gov (United States)

    Koenderink, Gijsje H.; Dogic, Zvonimir; Nakamura, Fumihiko; Bendix, Poul M.; MacKintosh, Frederick C.; Hartwig, John H.; Stossel, Thomas P.; Weitz, David A.

    2009-09-01

    We describe an active polymer network in which processive molecular motors control network elasticity. This system consists of actin filaments cross-linked by filamin A (FLNa) and contracted by bipolar filaments of muscle myosin II. The myosin motors stiffen the network by more than two orders of magnitude by pulling on actin filaments anchored in the network by FLNa cross-links, thereby generating internal stress. The stiffening response closely mimics the effects of external stress applied by mechanical shear. Both internal and external stresses can drive the network into a highly nonlinear, stiffened regime. The active stress reaches values that are equivalent to an external stress of 14 Pa, consistent with a 1-pN force per myosin head. This active network mimics many mechanical properties of cells and suggests that adherent cells exert mechanical control by operating in a nonlinear regime where cell stiffness is sensitive to changes in motor activity. This design principle may be applicable to engineering novel biologically inspired, active materials that adjust their own stiffness by internal catalytic control.

  19. Thermodynamic evidence for cluster ordering in Cu46Zr42Al7Y5 ribbons during glass transition

    DEFF Research Database (Denmark)

    Zheng, H.J.; Lv, Y.M.; Sun, Q.J.

    2016-01-01

    This work investigated the response of Cu46Zr42Al7Y5 glass ribbons to both dynamic and static heating using differential scanning calorimeter (DSC). The DSC curve manifests three exothermic responses to dynamic heating, among which the first and the third one are the signatures of the normal sub-...

  20. Moisture sorption isotherms and glass transition temperature of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) roots at 25°C.

    Science.gov (United States)

    Cervenka, L; Kubínová, J; Juszczak, L; Witczak, M

    2012-02-01

    Sorption isotherms of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) root samples were obtained at 25 °C. Elecampe exhibited hysteresis loop in the range of 0.35-0.90 a(w) , whereas burdock roots showed significant differences between adsorption and desorption isotherms from 0.65 to 0.80 a(w) . Blahovec-Yanniotis was considered to give the best fit over the whole range of a(w) tested. Various parameters describing the properties of sorbed water derived from GAB, Henderson and Blahovec-Yanniotis models have been discussed. Differential scanning calorimetric method was used to measure the glass transition temperature (T (g)) of root samples in relation to water activity. The safe moisture content was determined in 12.01 and 14.96 g/100 g d. b. for burdock and elecampe root samples at 25 °C, respectively. Combining the T (g) line with sorption isotherm in one plot, it was found that the glass transition temperature concept overestimated the temperature stability for both root samples.

  1. Analysis of water sorption isotherms of amorphous food materials by solution thermodynamics with relevance to glass transition: evaluation of plasticizing effect of water by the thermodynamic parameters.

    Science.gov (United States)

    Shimazaki, Eriko; Tashiro, Akiko; Kumagai, Hitomi; Kumagai, Hitoshi

    2017-04-01

    Relation between the thermodynamic parameters obtained from water sorption isotherms and the degree of reduction in the glass transition temperature (T g ), accompanied by water sorption, was quantitatively studied. Two well-known glassy food materials namely, wheat gluten and maltodextrin were used as samples. The difference between the chemical potential of water in a solution and that of pure water ([Formula: see text]), the difference between the chemical potential of solid in a solution and that of a pure solid ([Formula: see text]), and the change in the integral Gibbs free energy ([Formula: see text]) were obtained by analyzing the water sorption isotherms using solution thermodynamics. The parameter [Formula: see text] correlated well with ΔT g (≡T g  - T g0 ; where T g0 is the glass transition temperature of dry material), which had been taken to be an index of plasticizing effect. This indicates that plasticizing effect of water on foods can be evaluated through the parameter [Formula: see text].

  2. Allosteric transitions of supramolecular systems explored by network models: application to chaperonin GroEL.

    Directory of Open Access Journals (Sweden)

    Zheng Yang

    2009-04-01

    Full Text Available Identification of pathways involved in the structural transitions of biomolecular systems is often complicated by the transient nature of the conformations visited across energy barriers and the multiplicity of paths accessible in the multidimensional energy landscape. This task becomes even more challenging in exploring molecular systems on the order of megadaltons. Coarse-grained models that lend themselves to analytical solutions appear to be the only possible means of approaching such cases. Motivated by the utility of elastic network models for describing the collective dynamics of biomolecular systems and by the growing theoretical and experimental evidence in support of the intrinsic accessibility of functional substates, we introduce a new method, adaptive anisotropic network model (aANM, for exploring functional transitions. Application to bacterial chaperonin GroEL and comparisons with experimental data, results from action minimization algorithm, and previous simulations support the utility of aANM as a computationally efficient, yet physically plausible, tool for unraveling potential transition pathways sampled by large complexes/assemblies. An important outcome is the assessment of the critical inter-residue interactions formed/broken near the transition state(s, most of which involve conserved residues.

  3. Retrieving infinite numbers of patterns in a spin-glass model of immune networks

    Science.gov (United States)

    Agliari, E.; Annibale, A.; Barra, A.; Coolen, A. C. C.; Tantari, D.

    2017-01-01

    The similarity between neural and (adaptive) immune networks has been known for decades, but so far we did not understand the mechanism that allows the immune system, unlike associative neural networks, to recall and execute a large number of memorized defense strategies in parallel. The explanation turns out to lie in the network topology. Neurons interact typically with a large number of other neurons, whereas interactions among lymphocytes in immune networks are very specific, and described by graphs with finite connectivity. In this paper we use replica techniques to solve a statistical mechanical immune network model with “coordinator branches” (T-cells) and “effector branches” (B-cells), and show how the finite connectivity enables the coordinators to manage an extensive number of effectors simultaneously, even above the percolation threshold (where clonal cross-talk is not negligible). A consequence of its underlying topological sparsity is that the adaptive immune system exhibits only weak ergodicity breaking, so that also spontaneous switch-like effects as bi-stabilities are present: the latter may play a significant role in the maintenance of immune homeostasis.

  4. A fully tetrahedral and highly corner-sharing network model of ZnCl2 glass and its comparison to SiO2 glass

    Science.gov (United States)

    Swansbury, Laura A.; Mountjoy, Gavin

    2017-07-01

    Zinc chloride, ZnCl2, is intermediate between a strong and a fragile glass former. During computational simulations, it is therefore important to account for ion polarizability. This, together with the lack of suitable interatomic potential parameters, is the likely cause for the lack of modeling studies on ZnCl2 glass which contain a high degree of ZnCl4 tetrahedral units. Through using accurate interatomic potential parameters and applying the adiabatic core-shell model, the first fully tetrahedral model of ZnCl2 glass was obtained. The Cl-Zn-Cl bond angle of 109° reproduced the ideal tetrahedral bond angle, and the calculated total neutron and x-ray structure factors closely replicated experimental findings. While 86% of the ZnCl4 tetrahedral units were corner-sharing, 14% were found to be edge-sharing. This led to two distinct contributions in both the Zn-Cl-Zn bond angle distribution and in the Zn⋯Zn nearest neighbour peaks being seen. These are not apparent in studies based on neutron diffraction. By comparing the intermediate glass former ZnCl2 to the strong glass former SiO2, marked differences in ring statistics became apparent. The Zn-Cl-Zn bond angle of around 110° enabled 3-membered rings to form in significant proportions. In contrast, 3-membered rings were only present in SiO2 glass as defects. By calculating the ZnCl2 and SiO2 partial structure factors, strong similarities became visible after scaling according to nearest neighbour distances. Although it was apparent that the main contributions to the first sharp diffraction peak (FSDP) came from cation-anion correlations, the relative scaling of the FSDP positions in ZnCl2 and SiO2 glass was not understood.

  5. Investigations on spectroscopic properties of Er(3+)-doped Li-Zn fluoroborate glass.

    Science.gov (United States)

    Thomas, Sunil; Sajna, M S; George, Rani; Rasool, Sk Nayab; Joseph, Cyriac; Unnikrishnan, N V

    2015-09-05

    Er(3+)-doped Li-Zn fluoroborate glass was synthesized via melt quenching technique. Optical properties of the glass were investigated by UV-Vis-NIR absorption and emission spectra. To evaluate the nature of Er(3+)-ligand bond in the glass network, nephelauxetic ratios and bonding parameter were calculated. Judd-Ofelt analysis and hence the radiative properties of the present glass system were evaluated for ascertaining the suitability of the glass for laser applications and compared those with the emission spectra. Absorption cross-sections have been calculated from the absorption spectrum and stimulated emission cross-sections were estimated using McCumber theory for (4)I13/2↔(4)I15/2 transitions. The results of the present glass were compared with those obtained for some other Er(3+)-doped glass systems. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Effect of composition and temperature on the second harmonic generation in silver phosphate glasses

    Science.gov (United States)

    Konidakis, I.; Psilodimitrakopoulos, S.; Kosma, K.; Lemonis, A.; Stratakis, E.

    2018-01-01

    We herein employ nonlinear laser imaging microscopy to explicitly study the dynamics of second harmonic generation (SHG) in silver iodide phosphate glasses. While glasses of this family have gained extensive scientific attention over the years due to their superior conducting properties, considerably less attention has been paid to their unique nonlinear optical characteristics. In the present study, firstly, it is demonstrated that SHG signal intensity is enhanced upon increasing silver content due to the random formation of silver microstructures within the glass network. Secondly, the SHG temperature dynamics were explored near the glass transition temperature (Tg) regime, where significant glass relaxation phenomena occur. It is found that heating towards the Tg improves the SHG efficiency, whereas above Tg, the capacity of glasses to generate second harmonic radiation is drastically suppressed. The novel findings of this work are considered important in terms of the potential employment of these glasses for the realization of advanced photonic applications like optical-switches and wavelength conversion devices.

  7. Simulation and evaluation of urban rail transit network based on multi-agent approach

    Directory of Open Access Journals (Sweden)

    Xiangming Yao

    2013-03-01

    Full Text Available Purpose: Urban rail transit is a complex and dynamic system, which is difficult to be described in a global mathematical model for its scale and interaction. In order to analyze the spatial and temporal characteristics of passenger flow distribution and evaluate the effectiveness of transportation strategies, a new and comprehensive method depicted such dynamic system should be given. This study therefore aims at using simulation approach to solve this problem for subway network. Design/methodology/approach: In this thesis a simulation model based on multi-agent approach has been proposed, which is a well suited method to design complex systems. The model includes the specificities of passengers’ travelling behaviors and takes into account of interactions between travelers and trains. Findings: Research limitations/implications: We developed an urban rail transit simulation tool for verification of the validity and accuracy of this model, using real passenger flow data of Beijing subway network to take a case study, results show that our simulation tool can be used to analyze the characteristic of passenger flow distribution and evaluate operation strategies well. Practical implications: The main implications of this work are to provide decision support for traffic management, making train operation plan and dispatching measures in emergency. Originality/value: A new and comprehensive method to analyze and evaluate subway network is presented, accuracy and computational efficiency of the model has been confirmed and meet with the actual needs for large-scale network.

  8. Prediction of Damage Factor in end Milling of Glass Fibre Reinforced Plastic Composites Using Artificial Neural Network

    Science.gov (United States)

    Erkan, Ömer; Işık, Birhan; Çiçek, Adem; Kara, Fuat

    2013-08-01

    Glass fibre reinforced plastic (GFRP) composites are an economic alternative to engineering materials because of their superior properties. Some damages on the surface occur due to their complex cutting mechanics in cutting process. Minimisation of the damages is fairly important in terms of product quality. In this study, a GFRP composite material was milled to experimentally minimise the damages on the machined surfaces, using two, three and four flute end mills at different combinations of cutting parameters. Experimental results showed that the damage factor increased with increasing cutting speed and feed rate, on the other hand, it was found that the damage factor decreased with increasing depth of cut and number of the flutes. In addition, analysis of variance (ANOVA) results clearly revealed that the feed rate was the most influential parameter affecting the damage factor in end milling of GFRP composites. Also, in present study, Artificial Neural Network (ANN) models with five learning algorithms were used in predicting the damage factor to reduce number of expensive and time-consuming experiments. The highest performance was obtained by 4-10-1 network structure with LM learning algorithm. ANN was notably successful in predicting the damage factor due to higher R2 and lower RMSE and MEP.

  9. Oxidation and diffusion process in the ferrous iron-bearing glass fibres near glass temperature

    DEFF Research Database (Denmark)

    Yue, Yuanzheng; Korsgaard, Martin; Kirkegaard, Lise

    2004-01-01

    The Fe2+ oxidation and the network modifier diffusion in the Fe2+-bearing glass fibers are studied using differential scanning calorimetry (DSC), thermogravimetry (TG), and secondary neutral mass spectrometry (SNMS). The results show two couplings: 1) between the Fe2+ oxidation and the network...... modifier diffusion; 2) between the oxidation process and the glass transition. Based on these couplings, a phenomenological equation is proposed, which describes both kinetics and dynamics of the oxidation process of the Fe2+-bearing glass fibers. The equation can be used to predict the degree of oxidation...... of the Fe2+-bearing fibers with an average diameter of 3.5 m by knowing the heat-treatment conditions and vice versa....

  10. Luminescence properties of B{sub 2}O{sub 3}–GeO{sub 2}–Gd{sub 2}O{sub 3} scintillating glass doped with rare-earth and transition-metal ions

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xin-Yuan, E-mail: sxy5306@126.com [Department of Physics, Jinggangshan University, Ji’an 343009 (China); Jiang, Da-Guo; Wang, Wen-Feng; Cao, Chun-Yan; Li, Yu-Nong; Zhen, Guo-Tai [Department of Physics, Jinggangshan University, Ji’an 343009 (China); Wang, Hong; Yang, Xin-Xin; Chen, Hao-Hong; Zhang, Zhi-Jun [Key Laboratory of Transparent Opto-functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhao, Jing-Tai, E-mail: jtzhao@mail.sic.ac.cn [Key Laboratory of Transparent Opto-functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2013-07-11

    Novel B{sub 2}O{sub 3}–GeO{sub 2}–Gd{sub 2}O{sub 3} ternary scintillating glasses doped with 1 mol% rare-earth and transition-metal activators were synthesized by melt-quenching method. Their transmittance, photoluminescence (PL) and X-ray excited luminescence (XEL) spectra were investigated. The results suggest that a high content of Gd{sub 2}O{sub 3} is of significance for designing dense glass with density of 6.0 g/cm{sup 3}. And energy transfer from Gd{sup 3+} to the incorporated activators can be realized in the borogermanate glasses. The emission position and decay time can be efficiently tuned by incorporating various kinds of activators. All results imply the developed borogermanate scintillating glass is potential for scintillating fields. -- Highlights: • Glass-forming region of B{sub 2}O{sub 3}–GeO{sub 2}–Gd{sub 2}O{sub 3} ternary system are determined. • Radioluminescence response from transition-metal doped B{sub 2}O{sub 3}–GeO{sub 2}–Gd{sub 2}O{sub 3} glasses. • Radioluminescence response from rare-earth doped B{sub 2}O{sub 3}–GeO{sub 2}–Gd{sub 2}O{sub 3} glasses. • Emission peak position and decay time can be tuneable by incorporating various activators.

  11. Structural investigation on silver phosphate glasses embedded with nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kabi, S. [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Ghosh, A., E-mail: sspag@iacs.res.in [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Nanocrystalline phases are present in silver phosphate glassy matrix embedded with CdI{sub 2}. Black-Right-Pointing-Pointer The size of the nanocrystallites depends on the phosphate network. Black-Right-Pointing-Pointer The presence of different nanocrystalline phases does not affect the basic glass network. Black-Right-Pointing-Pointer The glass transition temperature increases with increase of CdI{sub 2} content. - Abstract: Structural investigations of CdI{sub 2} doped silver phosphate glass-nanocomposites in the system xCdI{sub 2}-(1 - x)(yAg{sub 2}O-(1 - y)P{sub 2}O{sub 5}) are presented in this paper. Although, X-ray diffraction patterns show amorphous nature of the compositions, electron microscopic studies show several nanocrystalline phases such as CdI{sub 2}, {beta}-AgI, AgPO{sub 3} and Ag{sub 4}P{sub 2}O{sub 7} dispersed within the glass matrix. The presence of CdI{sub 2} nanoparticles in cluster form is dominant for the compositions in the limit of the glass forming domain. The particle size in polyphosphate compositions is higher than that of metaphosphate or ultraphosphate compositions. FTIR spectra of these compositions have been investigated. It has been observed that the presence of different nanocrystalline phases does not affect the basic glass network. Differential scanning calorimetric results show that the incorporation of CdI{sub 2} within the glassy matrix increases the glass transition temperature. It is observed that the structural characteristics of the CdI{sub 2} doped silver phosphate glasses are quite different from that of other divalent metal iodide doped glasses.

  12. Electronic phase transitions

    CERN Document Server

    Kopaev, YuV

    1992-01-01

    Electronic Phase Transitions deals with topics, which are presently at the forefront of scientific research in modern solid-state theory. Anderson localization, which has fundamental implications in many areas of solid-state physics as well as spin glasses, with its influence on quite different research activities such as neural networks, are two examples that are reviewed in this book. The ab initio statistical mechanics of structural phase transitions is another prime example, where the interplay and connection of two unrelated disciplines of solid-state theory - first principle ele

  13. Short glass fiber-reinforced composite with a semi-interpenetrating polymer network matrix for temporary crowns and bridges.

    Science.gov (United States)

    Garoushi, Sufyan K; Vallittu, Pekka K; Lassila, Lippo V J

    2008-01-01

    The purpose of this study was to investigate the reinforcement effect of short E-glass fiber fillers on some mechanical properties of temporary crown and bridge (TCB) composite resin with a semi-interpenetrating polymer network (semi-IPN). Experimental temporary fiber reinforced (TFC) composite resin was prepared by mixing 15 wt% of short E-glass fibers (3 mm in length) with a 35 wt% of semi-IPN-resin (dual or chemical cure) with 50 wt% of silane treated particulate silica fillers using a high speed mixing device. Temporary crowns (n=6) and test specimens (2 x 2 x 25 mm3) (n=6) were made from the experimental TFC and conventional TCB composite (control, Protemp Garant, 3M-ESPE, St. Paul, MN, USA). A three-point bending test was done according to ISO standard 10477, and a compression loading test was carried out using a steel ball (Ø 3.0 mm) with a speed of 1.0 mm/min until fracture occurred. The degree of monomer conversion (DC%) of both composites was determined by Fourier transfer infrared (FTIR) spectrometry. The analysis of variance (ANOVA) revealed both dual and chemical cure experimental TFC composite resins had statistically significant (p<0.05) higher flexural strengths (117 and 99 MPa, respectively) and compressive load-bearing capacity (730 and 623 N, respectively) compared to the control TCB composite resin (72 MPa, 549 N). The use of short fiber fillers with semi-IPN polymer matrix yielded an improved mechanical performance compared to a conventional TCB composite resin.

  14. Coordination chemistry of iron in glasses contributing to remote-sensed spectra of the moon

    Science.gov (United States)

    Dyar, M. D.; Burns, R. G.

    1982-01-01

    Ferric iron and tetrahedrally coordinated Fe(2+) ions are identified using Moessbauer and electronic absorption spectroscopic measurements of synthetic glasses equilibrated at P(O2) less than 10 to the -11 atm, simulating the Luna 24 brown glass and Apollo 15 green glass compositions. The presence of 10-20% ferric iron in these low Ti glasses is a result of the absence of Ti(3+) ions. In the brown glass absorption spectra, tetrahedral Fe(3+) and Fe(2+) ions induce an extension of the oxygen-metal charge transfer band into the visible region further than in the green glass containing predominantly octahedral Fe(2+) and Fe(3+) ions. Whereas the glass one-micron band originates from crystal field transitions in octahedral Fe(2+), the glass two-micron band is now positively correlated with tetrahedral Fe(2+) rather than with Fe(2+) ions in pyroxene M2-like sites in the glass structure. The tetrahedral Fe(2+) do not, however, substitute for Si(4+) in glass network-forming sites, instead occurring as network modifiers in larger tetrahedral interstices. The effect of temperature is to induce a pronounced red-shift of the oxygen-iron charge transfer absorption edge, especially for the brown glass, and to intensify significantly the tetrahedral Fe(2+) crystal field two micron band.

  15. A replica exchange transition interface sampling method with multiple interface sets for investigating networks of rare events

    NARCIS (Netherlands)

    Swenson, D.W.H.; Bolhuis, P.G.

    2014-01-01

    The multiple state transition interface sampling (TIS) framework in principle allows the simulation of a large network of complex rare event transitions, but in practice suffers from convergence problems. To improve convergence, we combine multiple state TIS [J. Rogal and P. G. Bolhuis, J. Chem.

  16. Nanoscale confinement and interfacial effects on the dynamics and glass transition/crystallinity of thin adsorbed films on silica nanoparticles

    Science.gov (United States)

    Madathingal, Rajesh Raman

    the silica aggregates. For nanocomposites the interphase region becomes more important as the surface/volume ratio of the nanoparticles increases. Polymers have chain dimensions (characterized by the radius of gyration, Rg) similar to the nanoparticles (Rnanoparticle) themselves, so that chain conformation, mobility and crystallinity can be affected by Rg/Rnanoparticle. Here, both the glass transition temperature (Tg) and degree of crystallinity (Xc) of polyethylene oxide (PEO) on individual SiO 2 nanoparticles of nominal 15, 50 and 100 nm diameter (2 RSiO2 ) , in which Rg (PEO) was greater, equal to or less than RSiO2 was investigated. Plateau adsorption of PEO on SiO2 nanoparticles (PEO-SiO2) increased in the order PEO-SiO 2 (100 nm) > PEO-SiO2 (50 nm) > PEO-SiO2 (15 nm). At plateau adsorption after melting and solidification, the samples were completely amorphous. The Tg of the adsorbed PEO increased in the order PEO-SiO 2 (100 nm) > PEO-SiO2 (50 nm) > PEO-SiO2 (15 nm); since the Tgs were above 25°C in all cases, the PEO behaved more like a brittle solid than an elastomer. For comparable amounts of PEO that were adsorbed from solution but not melted, the melt endotherm increased in the order PEO-SiO2 (15 nm) > PEO-SiO2 (50 nm) > PEO-SiO 2 (100 nm). These trends were interpreted as due to an increase in loop/tail lengths and thus flexibility, with a concomitant ability to crystallize, as Rg (PEO)/RSiO2 decreased and which was the result of less hydrogen bond formation between the oxygens of PEO and the silanols (SiOH) of the SiO 2 as the nanoparticle size decreased. This in turn was attributed to the energetically unfavorable conformations necessary for the PEO chains to adopt in order to hydrogen bond with silanols on the smaller nanoparticles. The degradation behavior of amorphous PMMA and semicrystalline PEO on silica (SiO2) nanoparticles as a function of silanol density and nanoparticle size was investigated by derivative thermogravimetric analysis (DTGA) for

  17. Efficient reconstruction of biological networks via transitive reduction on general purpose graphics processors.

    Science.gov (United States)

    Bošnački, Dragan; Odenbrett, Maximilian R; Wijs, Anton; Ligtenberg, Willem; Hilbers, Peter

    2012-10-30

    Techniques for reconstruction of biological networks which are based on perturbation experiments often predict direct interactions between nodes that do not exist. Transitive reduction removes such relations if they can be explained by an indirect path of influences. The existing algorithms for transitive reduction are sequential and might suffer from too long run times for large networks. They also exhibit the anomaly that some existing direct interactions are also removed. We develop efficient scalable parallel algorithms for transitive reduction on general purpose graphics processing units for both standard (unweighted) and weighted graphs. Edge weights are regarded as uncertainties of interactions. A direct interaction is removed only if there exists an indirect interaction path between the same nodes which is strictly more certain than the direct one. This is a refinement of the removal condition for the unweighted graphs and avoids to a great extent the erroneous elimination of direct edges. Parallel implementations of these algorithms can achieve speed-ups of two orders of magnitude compared to their sequential counterparts. Our experiments show that: i) taking into account the edge weights improves the reconstruction quality compared to the unweighted case; ii) it is advantageous not to distinguish between positive and negative interactions since this lowers the complexity of the algorithms from NP-complete to polynomial without loss of quality.

  18. Critical space-time networks and geometric phase transitions from frustrated edge antiferromagnetism.

    Science.gov (United States)

    Trugenberger, Carlo A

    2015-12-01

    Recently I proposed a simple dynamical network model for discrete space-time that self-organizes as a graph with Hausdorff dimension d(H)=4. The model has a geometric quantum phase transition with disorder parameter (d(H)-d(s)), where d(s) is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean-field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions.

  19. International Expansion and Transition to the Network Structure of the Multinational Companies and Their Social Consequences

    Directory of Open Access Journals (Sweden)

    Daniela Ettaleb

    2015-01-01

    Full Text Available Economic globalization is associated with growing interconnectedness, interdependence and the integration of businesses into a single economic system, improving the competitiveness of businesses, and places new demands and requirements on firms. Companies that wanted to survive in a new, dynamic and competitive environment had to apply new development strategies, whose main motto was to reduce costs and to create greater flexibility on the global market. Many large companies managed huge cost reductions in the globalized economy through international expansion to the industrial periphery and semi-periphery countries (developing countries and Central and Eastern Europe and through the transition from a pyramidal organizational structure to a network structure. The control centre of companies in a network organization deprives hierarchical and pyramidal corporate structures, rather temporarily joins a network of small suppliers, subcontractors and service providers. In the business environment networks are more flexible and adaptable than firms with a hierarchical structure. They are highly effective because they allow significant reductions in the operating costs of the company. On the other hand, the network structure of relations has a number of social consequences, such as the reduction in the number of employees, the rise in non-standard employment contracts and the abolition of responsibility.

  20. Functional Connectivity of Precipitation Networks in the Brazilian Rainforest-Savanna Transition Zone

    Science.gov (United States)

    Adera, S.; Larsen, L.; Levy, M. C.; Thompson, S. E.

    2016-12-01

    In the Brazilian rainforest-savanna transition zone, vegetation change has the potential to significantly affect precipitation patterns. Deforestation, in particular, can affect precipitation patterns by increasing land surface albedo, increasing aerosol loading to the atmosphere, changing land surface roughness, and reducing transpiration. Understanding land surface-precipitation couplings in this region is important not only for sustaining Amazon and Cerrado ecosystems, but also for cattle ranching and agriculture, hydropower generation, and drinking water management. Simulations suggest complex, scale-dependent interactions between precipitation and land cover. For example, the size and distribution of deforested patches has been found to affect precipitation patterns. We take an empirical approach to ask: (1) what are the dominant spatial and temporal length scales of precipitation coupling in the Brazilian rainforest-savanna transition zone? (2) How do these length scales change over time? (3) How does the connectivity of precipitation change over time? The answers to these questions will help address fundamental questions about the impacts of deforestation on precipitation. We use rain gauge data from 1100 rain gauges intermittently covering the period 1980 - 2013, a period of intensive land cover change in the region. The dominant spatial and temporal length scales of precipitation coupling are resolved using transfer entropy, a metric from information theory. Connectivity of the emergent network of couplings is quantified using network statistics. Analyses using transfer entropy and network statistics reveal the spatial and temporal interdependencies of rainfall events occurring in different parts of the study domain.

  1. Gel-expanded to gel-condensed transition in neurofilament networks revealed by direct force measurements

    Science.gov (United States)

    Beck, Roy; Deek, Joanna; Jones, Jayna B.; Safinya, Cyrus R.

    2010-01-01

    Neurofilaments (NF)-the principal cytoskeletal constituent of myelinated axons in vertebrates-consist of three molecular-weight subunit proteins NF-L (low), NF-M (medium) and NF-H (high), assembled to form mature filaments with protruding unstructured C-terminus side arms. Liquid-crystal gel networks of side-arm-mediated neurofilament assemblies have a key role in the mechanical stability of neuronal processes. Disruptions of the neurofilament network, owing to neurofilament over-accumulation or incorrect side-arm interactions, are a hallmark of motor-neuron diseases including amyotrophic lateral sclerosis. Using synchrotron X-ray scattering, we report on a direct measurement of forces in reconstituted neurofilament gels under osmotic pressure (P). With increasing pressure near physiological salt and average phosphorylation conditions, NF-LMH, comprising the three subunits near in vivo composition, or NF-LH gels, undergo for P>Pc~10kPa, an abrupt non-reversible gel-expanded to gel-condensed transition. The transition indicates side-arm-mediated attractions between neurofilaments consistent with an electrostatic model of interpenetrating chains. In contrast, NF-LM gels remain in a collapsed state for PPc. These findings, which delineate the distinct roles of NF-M and NF-H in regulating neurofilament interactions, shed light on possible mechanisms for disruptions of optimal mechanical network properties.

  2. Hardness and incipient plasticity in silicate glasses

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Smedskjær, Morten Mattrup; Mauro, John C.

    2014-01-01

    The scaling of Vickers hardness (Hv) in oxide glasses with varying network modifier/modifier ratio is manifested as either a positive or negative deviation from linearity with a maximum deviation at the ratio of about 1:1. In an earlier study [J. Kjeldsen et al., J. Non-Cryst. Solids 369,61(2013)......The scaling of Vickers hardness (Hv) in oxide glasses with varying network modifier/modifier ratio is manifested as either a positive or negative deviation from linearity with a maximum deviation at the ratio of about 1:1. In an earlier study [J. Kjeldsen et al., J. Non-Cryst. Solids 369......,61(2013)], we observed a minimum ofHv in CaO/MgO sodium aluminosilicate glasses at CaO/MgO = 1:1 and postulated that this minimum is linked to a maximum in plastic flow. However, the origin of this link has not been experimentally verified. In this work, we attempt to do so by exploring the links among Hv......, volume recovery ratio (VR), and plastic deformation volume (VP) under indentation, glass transition temperature (Tg), Young’s modulus (E), and liquid fragility index (m) in CaO/MgO and CaO/Li2O sodium aluminosilicate glasses. We confirm the negative deviations from linearity and find that the maximum...

  3. Mixed alkali effect in glasses containing MnO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, M. Sudhakara; Rajiv, Asha [Department of Physics, Jain University, Bangalore (India); Veeranna Gowda, V. C. [Department of Physics, GovernmentCollege for Women, Chintamani (India); Chakradhar, R. P. S. [CSIR-National Aerospace Laboratories, Bangalore (India); Reddy, C. Narayana [Department of Physics, Maharani' s Science College for Women (PG centre, Bangalore University) Bangalore (India)

    2013-02-05

    Glass systems of the composition xLi{sub 2}O-(25-x)K{sub 2}O-70(0.4ZnO+0.6P{sub 2}O{sub 5})+5MnO{sub 2} (x = 4,8,12,16 and 20 mol %) have been prepared by melt quenching technique. The thermal and mechanical properties of the glasses have been evaluated as a function of mixed alkali content. Glass transition temperature and Vickers's hardness of the glasses show a pronounced deviation from linearity at 12 mol%Li{sub 2}O. Theoretically estimated elastic moduli of the glasses show small positive deviations from linearity. MAE in these properties has been attributed to the localized changes in the glass network. The absorption spectra of Mn{sup 2+} ions in these glasses showed strong broad absorption band at 514 nm corresponding to the transition {sup 6}A{sub 1g}(S){yields}{sup 4}T{sub 1g}(G), characteristic of manganese ions in octahedral symmetry. The fundamental absorption edge in UV region is used to study the optical transitions and electronic band structure. From UV absorption edge, optical band gap energies have been evaluated. Band gap energies of the glasses have exhibited MAE and shows minimum value for 12 mol%Li{sub 2}O glass.

  4. Modifying glass surfaces via internal diffusion

    DEFF Research Database (Denmark)

    Smedskjaer, M.M.; Yue, Y.Z.; Deubener, J.

    2010-01-01

    The surface chemistry and structure of iron-bearing silicate glasses have been modified by means of heat-treatment around the glass transition temperature under different gaseous media at ambient pressure. When the glasses are heat-treated in atmospheric air, oxidation of Fe2+ to Fe3+ occurs, which...... leads to outward diffusion (OD) of divalent cations (primarily Mg2+), i.e., diffusion from the interior of the glass to the surface, and thereby, to formation of an oxide surface nano-layer. in contrast, when the glasses are heat-treated in H-2/N-2 gas containing 10 vol.% H-2, reduction of Fe3+ to Fe2......- ions in the network and their strong attraction to the modifying ions, whereas the latter is due to the requirement of the charge neutrality. The role of N3- in driving OD is verified by the composition profile of the surface layer of the glass treated in pure N-2 gas. The OD exerts pronounced impacts...

  5. Synchronization transitions induced by the fluctuation of adaptive coupling strength in delayed Newman-Watts neuronal networks.

    Science.gov (United States)

    Wang, Qi; Gong, Yubing; Wu, Yanan

    2015-11-01

    Introducing adaptive coupling in delayed neuronal networks and regulating the dissipative parameter (DP) of adaptive coupling by noise, we study the effect of fluctuations of the changing rate of adaptive coupling on the synchronization of the neuronal networks. It is found that time delay can induce synchronization transitions for intermediate DP values, and the synchronization transitions become strongest when DP is optimal. As the intensity of DP noise is varied, the neurons can also exhibit synchronization transitions, and the phenomenon is delay-dependent and is enhanced for certain time delays. Moreover, the synchronization transitions change with the change of DP and become strongest when DP is optimal. These results show that randomly changing adaptive coupling can considerably change the synchronization of the neuronal networks, and hence could play a crucial role in the information processing and transmission in neural systems. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  6. A Low-Carbon-Based Bilevel Optimization Model for Public Transit Network

    Directory of Open Access Journals (Sweden)

    Xu Sun

    2013-01-01

    Full Text Available To satisfy the demand of low-carbon transportation, this paper studies the optimization of public transit network based on the concept of low carbon. Taking travel time, operation cost, energy consumption, pollutant emission, and traffic efficiency as the optimization objectives, a bilevel model is proposed in order to maximize the benefits of both travelers and operators and minimize the environmental cost. Then the model is solved with the differential evolution (DE algorithm and applied to a real network of Baoji city. The results show that the model can not only ensure the benefits of travelers and operators, but can also reduce pollutant emission and energy consumption caused by the operations of buses, which reflects the concept of low carbon.

  7. Relaxation processes and glass transition of confined polymer melts: A molecular dynamics simulation of 1,4-polybutadiene between graphite walls

    Science.gov (United States)

    Solar, M.; Binder, K.; Paul, W.

    2017-05-01

    Molecular dynamics simulations of a chemically realistic model for 1,4-polybutadiene in a thin film geometry confined by two graphite walls are presented. Previous work on melts in the bulk has shown that the model faithfully reproduces static and dynamic properties of the real material over a wide temperature range. The present work studies how these properties change due to nano-confinement. The focus is on orientational correlations observable in nuclear magnetic resonance experiments and on the local intermediate incoherent neutron scattering function, Fs(qz, z, t), for distances z from the graphite walls in the range of a few nanometers. Temperatures from about 2Tg down to about 1.15Tg, where Tg is the glass transition temperature in the bulk, are studied. It is shown that weakly attractive forces between the wall atoms and the monomers suffice to effectively bind a polymer coil that is near the wall. For a wide regime of temperatures, the Arrhenius-like adsorption/desorption kinetics of the monomers is the slowest process, while very close to Tg the Vogel-Fulcher-Tammann-like α-relaxation takes over. The α-process is modified only for z ≤1.2 nm due to the density changes near the walls, less than expected from studies of coarse-grained (bead-spring-type) models. The weakness of the surface effects on the glass transition in this case is attributed to the interplay of density changes near the wall with the torsional potential. A brief discussion of pertinent experiments is given.

  8. Enhancing glass ionomer cement features by using the HA/YSZ nanocomposite: a feed forward neural network modelling.

    Science.gov (United States)

    Rajabzadeh, Ghadir; Salehi, Sahar; Nemati, Ali; Tavakoli, Razeih; Solati Hashjin, Mehran

    2014-01-01

    Despite brilliant properties of glass ionomer cement (GIC), its weak mechanical property poses an obstacle for its use in medical applications. The present research aims to formulate hydroxyapatite/yttria-stabilized zirconia (HA/YSZ) in the composition of GIC to enhance mechanical properties and to improve fluoride release of GIC. HA/YSZ was synthesized via a sol-gel method and characterized by applying X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photo-emission spectroscopy (XPS) and simultaneous thermal analysis (STA) along with transmission electron microscopy (TEM) methods. The synthesized nanocomposite was mixed with GIC at a fixed composition of 5wt%. The effect of different weight percentages of YSZ:HA on GIC was investigated by measuring the compressive strength, diametral tensile strength, microhardness and fluoride release. The results showed that, after 1 and 7 days of setting, the 20wt% nanohydroxyapatite/80wt% stabilized zirconia cement exhibited higher compressive strength (1857-245MPa), higher diametral tensile strength (11-14MPa) and greater microhardness (104-106MPa) as compared with the pure GIC (65-88MPa in compressive strength, 5-9.5MPa in diametral tensile strength and 70-89MPa in microhardness). The reinforced cement, also, exhibited higher fluoride release compared with pure GIC. The artificial neural network (ANN) was trained for modeling the system. Results obtained by ANN have proved to be completely in accordance with expectations. © 2013 Elsevier Ltd. All rights reserved.

  9. Iso-conversional approach for study of glass transition and crystallization kinetics of ternary glassy Se{sub 98−x}Ag{sub 2}In{sub x} (x = 0, 2, 4, 6) system

    Energy Technology Data Exchange (ETDEWEB)

    Dohare, C.; Mehta, N., E-mail: dr_neeraj_mehta@yahoo.co.in

    2014-02-25

    Highlights: • Novel glasses of Se–Ag–In system are prepared. • The effect of In incorporation on glass transition kinetics is studied. • The effect of In incorporation on crystallization kinetics is studied. • We have found remarkable increase in thermal stability. -- Abstract: The glass transition and crystallization kinetics of Se{sub 98−x}Ag{sub 2}In{sub x} (x = 0, 2, 4, 6) glasses have been studied under non-isothermal condition using differential scanning calorimetry (DSC). Using model free approach [Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Tang and Straink], the activation energy of glass transition, ΔE{sub αg} and crystallization kinetics, ΔE{sub αc} have been plotted as a function of extent of conversion, α. The kinetic parameters such as the activation energy (E), Avrami exponent (n), and rate of crystallization (K) have been determined using Kolmogorov–Johnson–Mehl–Avrami (KJMA) model. Glassy nature of as prepared samples was confirmed by XRD (X-ray diffraction), surface morphology and diffraction pattern by SEM and TEM, respectively.

  10. Spatially resolved distribution function and the medium-range order in metallic liquid and glass

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Xiaowei; Wang, Cai-Zhuang; Hao, Shaogang; Kramer, Matthew; Yao, Yongxin; Mendelev, Mikhail; Napolitano, Ralph; Ho, Kai-Ming

    2011-12-23

    The structural description of disordered systems has been a longstanding challenge in physical science. We propose an atomic cluster alignment method to reveal the development of three-dimensional topological ordering in a metallic liquid as it undercools to form a glass. By analyzing molecular dynamic (MD) simulation trajectories of a Cu{sub 64.5}Zr{sub 35.5} alloy, we show that medium-range order (MRO) develops in the liquid as it approaches the glass transition. Specifically, around Cu sites, we observe 'Bergman triacontahedron' packing (icosahedron, dodecahedron and icosahedron) that extends out to the fourth shell, forming an interpenetrating backbone network in the glass. The discovery of Bergman-type MRO from our order-mining technique provides unique insights into the topological ordering near the glass transition and the relationship between metallic glasses and quasicrystals.

  11. Spatially resolved distribution function and the medium-range order in metallic liquid and glass.

    Science.gov (United States)

    Fang, X W; Wang, C Z; Hao, S G; Kramer, M J; Yao, Y X; Mendelev, M I; Ding, Z J; Napolitano, R E; Ho, K M

    2011-01-01

    The structural description of disordered systems has been a longstanding challenge in physical science. We propose an atomic cluster alignment method to reveal the development of three-dimensional topological ordering in a metallic liquid as it undercools to form a glass. By analyzing molecular dynamic (MD) simulation trajectories of a Cu(64.5)Zr(35.5) alloy, we show that medium-range order (MRO) develops in the liquid as it approaches the glass transition. Specifically, around Cu sites, we observe "Bergman triacontahedron" packing (icosahedron, dodecahedron and icosahedron) that extends out to the fourth shell, forming an interpenetrating backbone network in the glass. The discovery of Bergman-type MRO from our order-mining technique provides unique insights into the topological ordering near the glass transition and the relationship between metallic glasses and quasicrystals.

  12. Evolution of karst conduit networks in transition from pressurised flow to free surface flow

    Science.gov (United States)

    Perne, M.; Covington, M. D.; Gabrovšek, F.

    2014-06-01

    We present a novel modelling approach to study the evolution of conduit networks in soluble rocks. Unlike the models presented so far, the model allows a transition from pressurised (pipe) flow to a free surface (open channel) flow in evolving discrete conduit networks. It calculates flow, solute transport and dissolutional enlargement within each time step and steps through time until a stable flow pattern establishes. The flow in each time step is calculated by calling the EPA Storm Water Management Model (EPA SWMM), which efficiently solves the 1-D Saint Venant equations in a network of conduits. We present several cases with low dip and sub-vertical networks to demonstrate mechanisms of flow pathway selection. In low dip models the inputs were randomly distributed to several junctions. The evolution of pathways progresses upstream: initially pathways linking outlets to the closest inputs evolve fastest because the gradient along these pathways is largest. When a pathway efficiently drains the available recharge, the head drop along the pathway attracts flow from the neighbouring upstream junctions and new connecting pathways evolve. The mechanism progresses from the output boundary inwards until all inputs are connected to the stable flow system. In the pressurised phase, each junction is drained by at least one conduit, but only one conduit remains active in the vadose phase. The selection depends on the initial geometry of a junction, initial distribution of diameters, the evolution in a pressurised regime, and on the dip of the conduits, which plays an important role in vadose entrenchment. In high dip networks, the vadose zone propagates downwards and inwards from the rim of the massif. When a network with randomly distributed initial diameters is supplied with concentrated recharge from the adjacent area, the sink point regresses up upstream along junctions connected to the prominent pathways. Large conductive structures provide deep penetration of high

  13. Constrained dynamics of localized excitations causes a non-equilibrium phase transition in an atomistic model of glass formers.

    Science.gov (United States)

    Speck, Thomas; Chandler, David

    2012-05-14

    Recent progress has demonstrated that trajectory space for both kinetically constrained lattice models and atomistic models can be partitioned into a liquid-like and an inactive basin with a non-equilibrium phase transition separating these behaviors. Recent work has also established that excitations in atomistic models have statistics and dynamics like those in a specific class of kinetically constrained models. But it has not been known whether the non-equilibrium phase transitions occurring in the two classes of models have similar origins. Here, we show that the origin is indeed similar. In particular, we show that the number of excitations identified in an atomistic model serves as the order parameter for the inactive-active phase transition for that model. In this way, we show that the mechanism by which excitations are correlated in an atomistic model - by dynamical facilitation - is the mechanism from which the active-inactive phase transition emerges. We study properties of the inactive phase and show that it is amorphous lacking long-range order. We also discuss the choice of dynamical order parameters.

  14. Artificial Neural Networks-Based Software for Measuring Heat Collection Rate and Heat Loss Coefficient of Water-in-Glass Evacuated Tube Solar Water Heaters.

    Science.gov (United States)

    Liu, Zhijian; Liu, Kejun; Li, Hao; Zhang, Xinyu; Jin, Guangya; Cheng, Kewei

    2015-01-01

    Measurements of heat collection rate and heat loss coefficient are crucial for the evaluation of in service water-in-glass evacuated tube solar water heaters. However, conventional measurement requires expensive detection devices and undergoes a series of complicated procedures. To simplify the measurement and reduce the cost, software based on artificial neural networks for measuring heat collection rate and heat loss coefficient of water-in-glass evacuated tube solar water heaters was developed. Using multilayer feed-forward neural networks with back-propagation algorithm, we developed and tested our program on the basis of 915 measured samples of water-in-glass evacuated tube solar water heaters. This artificial neural networks-based software program automatically obtained accurate heat collection rate and heat loss coefficient using simply "portable test instruments" acquired parameters, including tube length, number of tubes, tube center distance, heat water mass in tank, collector area, angle between tubes and ground and final temperature. Our results show that this software (on both personal computer and Android platforms) is efficient and convenient to predict the heat collection rate and heat loss coefficient due to it slow root mean square errors in prediction. The software now can be downloaded from http://t.cn/RLPKF08.

  15. Towards a metallic glass transition in α-Al2O3: A role of pressure-induced amorphization

    Science.gov (United States)

    Gupta, Sanjeev; Jha, Prafulla

    2013-03-01

    Pressure-induced amporphization has been observed experimentally in many electrically insulating materials, including oxides. In none of the cases, the pressure-induced amorphization has been accompanied by metallic conduction. Alumina is one of the most important ceramics of the modern age and has a large band gap of at ambient conditions. In this talk, we will present the results of the study on the behavior of alumina under increasing pressure using first principles plane wave method within the linear response approach. The crystal structure and associated equilibrium lattice constants for α-Al2O3 were obtained by minimizing the calculated total energies as function of a lattice constant. Further, to calculate the entropy and other allied properties, we have used density functional perturbation theory (DFPT). The calculated results show that Al2O3 might turn to metallic glass at pressure achievable in a laboratory.

  16. Interictal to Ictal Phase Transition in a Small-World Network

    Science.gov (United States)

    Nemzer, Louis; Cravens, Gary; Worth, Robert

    Real-time detection and prediction of seizures in patients with epilepsy is essential for rapid intervention. Here, we perform a full Hodgkin-Huxley calculation using n 50 in silico neurons configured in a small-world network topology to generate simulated EEG signals. The connectivity matrix, constructed using a Watts-Strogatz algorithm, admits randomized or deterministic entries. We find that situations corresponding to interictal (non-seizure) and ictal (seizure) states are separated by a phase transition that can be influenced by congenital channelopathies, anticonvulsant drugs, and connectome plasticity. The interictal phase exhibits scale-free phenomena, as characterized by a power law form of the spectral power density, while the ictal state suffers from pathological synchronization. We compare the results with intracranial EEG data and show how these findings may be used to detect or even predict seizure onset. Along with the balance of excitatory and inhibitory factors, the network topology plays a large role in determining the overall characteristics of brain activity. We have developed a new platform for testing the conditions that contribute to the phase transition between non-seizure and seizure states.

  17. Energiewende’s Lone Warriors: A Hyperlink Network Analysis of the German Energy Transition Discourse

    Directory of Open Access Journals (Sweden)

    Jonas Kaiser

    2016-08-01

    Full Text Available This paper explores the integration of different social fields within the German Energy Transition (Energiewende discourse in the election year 2013 by analysing the hyperlink structures online. Energiewende describes the fundamental transition from non-renewable energy to sustainable sources. This goal is both ambitious and controversial. Numerous stakeholders try to make their voices and interests heard and as such politics has to both disseminate and collect information in order to include all relevant groups from different social fields in the political process. This discourse is also visible online. By analysing the hyperlink structures we are able to see the attention distribution of different actor groups in the network. This study shows that most actors tend to link within their own social field and do not aim for a more integrated public sphere. Especially political actors appear to be lone warriors who neither look left or right and mostly link within their own party and ignore other actors. Whereas social field as the media or public administration are relevant within the network we find that scientific actors are ignored by all fields, except for their own.

  18. Influence of Charge and Network Inhomogeneities on the Swollen-Collapsed Transition in Polyelectrolyte Nanogels

    Science.gov (United States)

    Jha, Prateek; Zwanikken, Jos; Detcheverry, François; de Pablo, Juan; Olvera de La Cruz, Monica

    2012-02-01

    Polyelectrolyte nanogels are sub-microscopic networks of solvent-permeated polyelectrolyte chains that undergo large reversible volume changes for a range of environmental stimuli. This volume phase transition behavior finds use in targeted drug delivery, optical switching in photonic crystals, and many other applications that require controlled tunability. Although the strength of electrostatic interactions have a strong influence on the nanogel response, these interactions are not well captured by the classical mean-field theories of macroscopic gels. We develop a simplified Poisson-Boltzmann model of spherical gels, that highlights the importance of charge inhomogeneities and the associated Coulomb interactions in determining the response of gels. Our analysis reveals that nanometer-sized gels, collapsed gels, and gels in media with low salinity or high dielectric constant, have large regions of excess charge, and show clear deviations from the classical Donnan picture of polyelectrolyte gels. The detailed swelling-collapse behavior is obtained using the theoretically-informed coarse-grained simulations, which includes the effects of network imperfections and thermal fluctuations. The simulations capture the universal features of volume phase transition in nanogels.

  19. On the importance of social network sites in the transitions which characterize ‘emerging adulthood’

    Directory of Open Access Journals (Sweden)

    Gianluca Frozzi

    2011-09-01

    Full Text Available Modern-day economic and socio-cultural developments require people to be ever more specialized and mobile in their educational and professional choices. This is particularly relevant for ‘emerging adults’, that is to say, those who find themselves at that stage of life when their scholastic or university education ends, and they begin to make choices regarding their professional working life. Transitions between different activity systems, and changes of residence which they entail, make ‘emerging adulthood’ a particularly unstable period in which young people continually dissolve, create and recreate relationship networks of varying degrees of importance which are able to support them through these changes. Beginning with empirical evidence and theoretical starting points typical of the psychology of education and development, this contribution proposes a theoretical reflection which attempts to analyze the efficacy of Social Network Sites in facilitating and supporting emerging adults during their education and vocational training and the important transitions which they have to face as they develop.

  20. Spray flow-network flow transition of binary Lennard-Jones particle system

    KAUST Repository

    Inaoka, Hajime

    2010-07-01

    We simulate gas-liquid flows caused by rapid depressurization using a molecular dynamics model. The model consists of two types of Lennard-Jones particles, which we call liquid particles and gas particles. These two types of particles are distinguished by their mass and strength of interaction: a liquid particle has heavier mass and stronger interaction than a gas particle. By simulations with various initial number densities of these particles, we found that there is a transition from a spray flow to a network flow with an increase of the number density of the liquid particles. At the transition point, the size of the liquid droplets follows a power-law distribution, while it follows an exponential distribution when the number density of the liquid particles is lower than the critical value. The comparison between the transition of the model and that of models of percolation is discussed. The change of the average droplet size with the initial number density of the gas particles is also presented. © 2010 Elsevier B.V. All rights reserved.

  1. An Extraordinary Transition in a Minimal Adaptive Network of Introverts and Extroverts

    Science.gov (United States)

    Zia, R. K. P.; Liu, Wenjia; Schmittmann, B.

    We study a minimal adaptive network involving two populations, modeling the behavior of extreme introverts (I) and extroverts (E). When chosen to update, an I simply cuts one of its links at random while an E adds a link to any other yet-to-be-connected individual (node). In the steady state, the active links in the system are obviously only the cross-links between the I's and the E's. With no free parameters other than the numbers of each population (NI, NE), this minimal model displays remarkable properties: Through simulations using O(10)-O(1000) nodes, we find that the typical number of cross-links (X) fluctuates surprisingly close to the minimum or the maximum allowed values, depending on whether NI >NE or otherwise. At the transition point (i.e., NI = NE), the fraction X/(NINE) wanders across a substantial part of the unit interval, much like a pure random walk confined between two walls. Since this system can be mapped to a NINE Ising model with spin flip dynamics, we note that such fluctuations are far greater than those in the standard Ising model (at either first or second order transitions). Thus, we refer to the case here as an "extraordinary transition." Thanks to the restoration of detailed balance and the existence of a "Hamiltonian," several qualitative aspects of these remarkable phenomena can be understood analytically

  2. The network of pluripotency, epithelial–mesenchymal transition, and prognosis of breast cancer

    Directory of Open Access Journals (Sweden)

    Voutsadakis IA

    2015-09-01

    Full Text Available Ioannis A Voutsadakis1,2 1Division of Medical Oncology, Department of Internal Medicine, Sault Area Hospital, Sault Ste Marie, ON, Canada; 2Division of Clinical Sciences, Northern Ontario School of Medicine, Sudbury, ON, Canada Abstract: Breast cancer is the leading female cancer in terms of prevalence. Progress in molecular biology has brought forward a better understanding of its pathogenesis that has led to better prognostication and treatment. Subtypes of breast cancer have been identified at the genomic level and guide therapeutic decisions based on their biology and the expected benefit from various interventions. Despite this progress, a significant percentage of patients die from their disease and further improvements are needed. The cancer stem cell theory and the epithelial–mesenchymal transition are two comparatively novel concepts that have been introduced in the area of cancer research and are actively investigated. Both processes have their physiologic roots in normal development and common mediators have begun to surface. This review discusses the associations of these networks as a prognostic framework in breast cancer. Keywords: stem cells, epithelial-to-mesenchymal transition, mesenchymal-to-epithelial transition

  3. Martensite-like transition and spin-glass behavior in nanocrystalline Pr0.5Ca0.5MnO3

    Directory of Open Access Journals (Sweden)

    S. Narayana Jammalamadaka

    2011-12-01

    Full Text Available We report on isothermal pulsed (20 ms field magnetization, temperature dependent AC – susceptibility, and the static low magnetic field measurements carried out on 10 nm sized Pr0.5Ca0.5MnO3 nanoparticles (PCMO10. The saturation field for the magnetization of PCMO10 (∼ 250 kOe is found to be reduced in comparison with that of bulk PCMO (∼300 kOe. With increasing temperature, the critical magnetic field required to ‘melt’ the residual charge-ordered phase decays exponentially while the field transition range broadens, which is indicative of a Martensite-like transition. The AC - susceptibility data indicate the presence of a frequency-dependent freezing temperature, satisfying the conventional Vogel-Fulcher and power laws, pointing to the existence of a spin-glass-like disordered magnetic phase. The present results lead to a better understanding of manganite physics and might prove helpful for practical applications.

  4. Interacting opinion and disease dynamics in multiplex networks: Discontinuous phase transition and nonmonotonic consensus times

    Science.gov (United States)

    Velásquez-Rojas, Fátima; Vazquez, Federico

    2017-05-01

    Opinion formation and disease spreading are among the most studied dynamical processes on complex networks. In real societies, it is expected that these two processes depend on and affect each other. However, little is known about the effects of opinion dynamics over disease dynamics and vice versa, since most studies treat them separately. In this work we study the dynamics of the voter model for opinion formation intertwined with that of the contact process for disease spreading, in a population of agents that interact via two types of connections, social and contact. These two interacting dynamics take place on two layers of networks, coupled through a fraction q of links present in both networks. The probability that an agent updates its state depends on both the opinion and disease states of the interacting partner. We find that the opinion dynamics has striking consequences on the statistical properties of disease spreading. The most important is that the smooth (continuous) transition from a healthy to an endemic phase observed in the contact process, as the infection probability increases beyond a threshold, becomes abrupt (discontinuous) in the two-layer system. Therefore, disregarding the effects of social dynamics on epidemics propagation may lead to a misestimation of the real magnitude of the spreading. Also, an endemic-healthy discontinuous transition is found when the coupling q overcomes a threshold value. Furthermore, we show that the disease dynamics delays the opinion consensus, leading to a consensus time that varies nonmonotonically with q in a large range of the model's parameters. A mean-field approach reveals that the coupled dynamics of opinions and disease can be approximately described by the dynamics of the voter model decoupled from that of the contact process, with effective probabilities of opinion and disease transmission.

  5. Characterization of structural relaxation in inorganic glasses using length dilatometry

    Science.gov (United States)

    Koontz, Erick

    The processes that govern how a glass relaxes towards its thermodynamic quasi-equilibrium state are major factors in understanding glass behavior near the glass transition region, as characterized by the glass transition temperature (Tg). Intrinsic glass properties such as specific volume, enthalpy, entropy, density, etc. are used to map the behavior of the glass network below in and near the transition region. The question of whether a true thermodynamic second order phase transition takes place in the glass transition region is another pending question. Linking viscosity behavior to entropy, or viewing the glass configuration as an energy landscape are just a couple of the most prevalent methods used for attempting to understand the glass transition. The structural relaxation behavior of inorganic glasses is important for more than scientific reasons, many commercial glass processing operations including glass melting and certain forms of optical fabrication include significant time spent in the glass transition region. For this reason knowledge of structural relaxation processes can, at a minimum, provide information for annealing duration of melt-quenched glasses. The development of a predictive model for annealing time prescription has the potential to save glass manufacturers significant time and money as well as increasing volume throughput. In optical hot forming processes such as precision glass molding, molded optical components can significantly change in shape upon cooling through the glass transition. This change in shape is not scientifically predictable as of yet though manufacturers typically use empirical rules developed in house. The classification of glass behavior in the glass transition region would allow molds to be accurately designed and save money for the producers. The work discussed in this dissertation is comprised of the development of a dilatometric measurement and characterization method of structural relaxation. The measurement and

  6. Transition from intelligence cycle to intelligence process: the network-centric intelligence in narrow seas

    Science.gov (United States)

    Büker, Engin

    2015-05-01

    The defence technologies which have been developing and changing rapidly, today make it difficult to be able to foresee the next environment and spectrum of warfare. When said change and development is looked in specific to the naval operations, it can be said that the possible battlefield and scenarios to be developed in the near and middle terms (5-20 years) are more clarified with compare to other force components. Network Centric Naval Warfare Concept that was developed for the floating, diving and flying fleet platforms which serves away from its own mainland for miles, will keep its significance in the future. Accordingly, Network Centric Intelligence structure completely integrating with the command and control systems will have relatively more importance. This study will firstly try to figure out the transition from the traditional intelligence cycle that is still used in conventional war to Network Centric Intelligence Production Process. In the last part, the use of this new approach on the base of UAV that is alternative to satellite based command control and data transfer systems in the joint operations in narrow seas will be examined, a model suggestion for the use of operative and strategic UAVs which are assured within the scope of the NATO AGS2 for this aim will be brought.

  7. Shadows of the susceptible-infectious-susceptible immortality transition in small networks

    Science.gov (United States)

    Holme, Petter

    2015-07-01

    Much of the research on the behavior of the SIS model on networks has concerned the infinite size limit; in particular the phase transition between a state where outbreaks can reach a finite fraction of the population, and a state where only a finite number would be infected. For finite networks, there is also a dynamic transition—the immortality transition—when the per-contact transmission probability λ reaches 1. If λ <1 , the probability that an outbreak will survive by an observation time t tends to zero as t →∞ ; if λ =1 , this probability is 1. We show that treating λ =1 as a critical point predicts the λ dependence of the survival probability also for more moderate λ values. The exponent, however, depends on the underlying network. This fact could, by measuring how a vertex's deletion changes the exponent, be used to evaluate the role of a vertex in the outbreak. Our work also confirms an extremely clear separation between the early die-off (from the outbreak failing to take hold in the population) and the later extinctions (corresponding to rare stochastic events of several consecutive transmission events failing to occur).

  8. Structure and energetics of hydrogen-bonded networks of methanol on close packed transition metal surfaces

    Science.gov (United States)

    Murphy, Colin J.; Carrasco, Javier; Lawton, Timothy J.; Liriano, Melissa L.; Baber, Ashleigh E.; Lewis, Emily A.; Michaelides, Angelos; Sykes, E. Charles H.

    2014-07-01

    Methanol is a versatile chemical feedstock, fuel source, and energy storage material. Many reactions involving methanol are catalyzed by transition metal surfaces, on which hydrogen-bonded methanol overlayers form. As with water, the structure of these overlayers is expected to depend on a delicate balance of hydrogen bonding and adsorbate-substrate bonding. In contrast to water, however, relatively little is known about the structures methanol overlayers form and how these vary from one substrate to another. To address this issue, herein we analyze the hydrogen bonded networks that methanol forms as a function of coverage on three catalytically important surfaces, Au(111), Cu(111), and Pt(111), using a combination of scanning tunneling microscopy and density functional theory. We investigate the effect of intermolecular interactions, surface coverage, and adsorption energies on molecular assembly and compare the results to more widely studied water networks on the same surfaces. Two main factors are shown to direct the structure of methanol on the surfaces studied: the surface coverage and the competition between the methanol-methanol and methanol-surface interactions. Additionally, we report a new chiral form of buckled hexamer formed by surface bound methanol that maximizes the interactions between methanol monomers by sacrificing interactions with the surface. These results serve as a direct comparison of interaction strength, assembly, and chirality of methanol networks on Au(111), Cu(111), and Pt(111) which are catalytically relevant for methanol oxidation, steam reforming, and direct methanol fuel cells.

  9. Differentially correlated genes in co-expression networks control phenotype transitions.

    Science.gov (United States)

    Thomas, Lina D; Vyshenska, Dariia; Shulzhenko, Natalia; Yambartsev, Anatoly; Morgun, Andrey

    2016-01-01

    Co-expression networks are a tool widely used for analysis of "Big Data" in biology that can range from transcriptomes to proteomes, metabolomes and more recently even microbiomes. Several methods were proposed to answer biological questions interrogating these networks. Differential co-expression analysis is a recent approach that measures how gene interactions change when a biological system transitions from one state to another. Although the importance of differentially co-expressed genes to identify dysregulated pathways has been noted, their role in gene regulation is not well studied. Herein we investigated differentially co-expressed genes in a relatively simple mono-causal process (B lymphocyte deficiency) and in a complex multi-causal system (cervical cancer). Co-expression networks of B cell deficiency (Control and BcKO) were reconstructed using Pearson correlation coefficient for two mus musculus datasets: B10.A strain (12 normal, 12 BcKO) and BALB/c strain (10 normal, 10 BcKO). Co-expression networks of cervical cancer (normal and cancer) were reconstructed using local partial correlation method for five datasets (total of 64 normal, 148 cancer). Differentially correlated pairs were identified along with the location of their genes in BcKO and in cancer networks. Minimum Shortest Path and Bi-partite Betweenness Centrality where statistically evaluated for differentially co-expressed genes in corresponding networks.    Results: We show that in B cell deficiency the differentially co-expressed genes are highly enriched with immunoglobulin genes (causal genes). In cancer we found that differentially co-expressed genes act as "bottlenecks" rather than causal drivers with most flows that come from the key driver genes to the peripheral genes passing through differentially co-expressed genes. Using in vitro knockdown experiments for two out of 14 differentially co-expressed genes found in cervical cancer (FGFR2 and CACYBP), we showed that they play

  10. Characterization of voids formed during liquid impregnation of nonwoven multifilament glass networks as related to composite processing

    Science.gov (United States)

    Mahale, Anant D.; Prudhomme, Robert K.; Rebenfeld, Ludwig

    1993-01-01

    A technique based on matching the refractive index of an invading liquid to that of a fiber mat was used to study entrapment of air ('voids') that occurs during forced in-plane radial flow into nonwoven multifilament glass networks. The usefulness of this technique is demonstrated in quantifying and mapping the air pockets. Experiments with a series of fluids with surface tensions varying from 28 x 10(exp -3) to 36 x 10(exp -3) N/m, viscosities from 45 x 10(exp -3) to 290 x 10(exp -3) Pa.s, and inlet flow rates from 0.15 x 10(exp -6) to 0.75 x 10(exp -6) m(exp 3)/s, showed that void content is a function of the capillary number characterizing the flow process. A critical value of capillary number, Ca = 2.5 x 10(exp -3), identifies a zone below which void content increases exponentially with decreasing capillary number. Above this critical value, negligible entrapment of voids is observed. Similar experiments carried out on surface treated nonwoven mats spanning a range of equilibrium contact angles from 20 deg to 78 deg showed that there is a critical contact angle above which negligible entrapment is observed. Below this value, there is no apparent effect of contact angle on the void fraction - capillary number relationship described earlier. Studies on the effect of filament wettability, and fluid velocity and viscosity on the size of the entrapment (voids) were also carried out. These indicate that larger sized entrapments which envelop more than one pore are favored by a low capillary number in comparison to smaller, pore level bubbles. Experiments were carried out on deformed mats - imposing high permeability spots at regular intervals on a background of low permeability. The effect of these spatial fluctuations in heterogeneity of the mat on entrapment is currently being studied.

  11. Non-equilibrium phenomena in confined soft matter irreversible adsorption, physical aging and glass transition at the nanoscale

    CERN Document Server

    2015-01-01

    This book presents cutting-edge experimental and computational results and provides comprehensive coverage on the impact of non-equilibrium structure and dynamics on the properties of soft matter confined to the nanoscale. The book is organized into three main sections: ·         Equilibration and physical aging: by treating non-equilibrium phenomena with the formal methodology of statistical physics in bulk, the analysis of the kinetics of equilibration sheds new light on the physical origin of the non-equilibrium character of thin polymer films. Both the impact of sample preparation and that of interfacial interactions are analyzed using a large set of experiments. A historical overview of the investigation of the non-equilibrium character of thin polymer films is also presented. Furthermore, the discussion focuses on how interfaces and geometrical confinement perturb the pathways and kinetics of equilibrations of soft glasses (a process of tremendous technological interest). ·         Irr...

  12. Elastic properties of Li+ doped lead zinc borate glasses

    Science.gov (United States)

    Rajaramakrishna, R.; Lakshmikantha, R.; Anavekar, R. V.

    2014-04-01

    Glasses in the system 0.25PbO-(0.25-x) ZnO-0.5B2O3-xLi2O have been prepared by the melt quenching technique. Elastic properties, DSC studies have been employed to study the role of Li2O in the present glass system. Elastic properties and Debye temperature have been determined using pulsed echo ultrasonic interferometer operating at 10MHz. Sound velocities Vl, Vt and elastic moduli decrease up to 5 mol% and then gradually increase with increase in Li2O concentration. Debye temperature and the glass transition temperature decreases with increase in Li2O. Densities remains almost constant up to 15 mol% Li2O concentration and increases monotonically while the molar volume decreases with the increase of Li2O concentration. The results are discussed in view of the borate structural network and dual role of Zn and Pb in these glasses.

  13. Clustered marginalization of minorities during social transitions induced by co-evolution of behaviour and network structure.

    Science.gov (United States)

    Schleussner, Carl-Friedrich; Donges, Jonathan F; Engemann, Denis A; Levermann, Anders

    2016-08-11

    Large-scale transitions in societies are associated with both individual behavioural change and restructuring of the social network. These two factors have often been considered independently, yet recent advances in social network research challenge this view. Here we show that common features of societal marginalization and clustering emerge naturally during transitions in a co-evolutionary adaptive network model. This is achieved by explicitly considering the interplay between individual interaction and a dynamic network structure in behavioural selection. We exemplify this mechanism by simulating how smoking behaviour and the network structure get reconfigured by changing social norms. Our results are consistent with empirical findings: The prevalence of smoking was reduced, remaining smokers were preferentially connected among each other and formed increasingly marginalized clusters. We propose that self-amplifying feedbacks between individual behaviour and dynamic restructuring of the network are main drivers of the transition. This generative mechanism for co-evolution of individual behaviour and social network structure may apply to a wide range of examples beyond smoking.

  14. Clustered marginalization of minorities during social transitions induced by co-evolution of behaviour and network structure

    Science.gov (United States)

    Schleussner, Carl-Friedrich; Donges, Jonathan F.; Engemann, Denis A.; Levermann, Anders

    2016-08-01

    Large-scale transitions in societies are associated with both individual behavioural change and restructuring of the social network. These two factors have often been considered independently, yet recent advances in social network research challenge this view. Here we show that common features of societal marginalization and clustering emerge naturally during transitions in a co-evolutionary adaptive network model. This is achieved by explicitly considering the interplay between individual interaction and a dynamic network structure in behavioural selection. We exemplify this mechanism by simulating how smoking behaviour and the network structure get reconfigured by changing social norms. Our results are consistent with empirical findings: The prevalence of smoking was reduced, remaining smokers were preferentially connected among each other and formed increasingly marginalized clusters. We propose that self-amplifying feedbacks between individual behaviour and dynamic restructuring of the network are main drivers of the transition. This generative mechanism for co-evolution of individual behaviour and social network structure may apply to a wide range of examples beyond smoking.

  15. A possible scenario for the fragile-to-strong dynamic crossover predicted by the extended mode-coupling theory for glass transition.

    Science.gov (United States)

    Chong, S-H; Chen, S-H; Mallamace, F

    2009-12-16

    It is argued that the extended mode-coupling theory for glass transition predicts a dynamic crossover in the α-relaxation time and in the self-diffusion constant as a general implication of the structure of its equations of motion. This crossover occurs near the critical temperature T(c) of the idealized version of the theory, and is caused by the change in the dynamics from the one determined by the cage effect to that dominated by hopping processes. When combined with a model for the hopping kernel deduced from the dynamical theory for diffusion-jump processes, the dynamic crossover can be identified as the fragile-to-strong crossover (FSC) in which the α-relaxation time and the self-diffusion constant cross over from a non-Arrhenius to an Arrhenius behavior. Since the present theory does not resort to the existence of the so-called Widom line, to which the FSC in confined water has been attributed, it provides a possible explanation of the FSC observed in a variety of glass-forming systems in which the existence of the Widom line is unlikely. In addition, the present theory predicts that the Stokes-Einstein relation (SER) breaks down in different ways on the fragile and strong sides of the FSC, in agreement with the experimental observation in confined water. It is also demonstrated that the violation of the SER in both the fragile and strong regions can be fitted reasonably well by a single fractional relation with an empirical exponent of 0.85.

  16. Impulsive synchronization of Markovian jumping randomly coupled neural networks with partly unknown transition probabilities via multiple integral approach.

    Science.gov (United States)

    Chandrasekar, A; Rakkiyappan, R; Cao, Jinde

    2015-10-01

    This paper studies the impulsive synchronization of Markovian jumping randomly coupled neural networks with partly unknown transition probabilities via multiple integral approach. The array of neural networks are coupled in a random fashion which is governed by Bernoulli random variable. The aim of this paper is to obtain the synchronization criteria, which is suitable for both exactly known and partly unknown transition probabilities such that the coupled neural network is synchronized with mixed time-delay. The considered impulsive effects can be synchronized at partly unknown transition probabilities. Besides, a multiple integral approach is also proposed to strengthen the Markovian jumping randomly coupled neural networks with partly unknown transition probabilities. By making use of Kronecker product and some useful integral inequalities, a novel Lyapunov-Krasovskii functional was designed for handling the coupled neural network with mixed delay and then impulsive synchronization criteria are solvable in a set of linear matrix inequalities. Finally, numerical examples are presented to illustrate the effectiveness and advantages of the theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Effects of Thermal and Pressure Histories on the Chemical Strengthening of Sodium Aluminosilicate Glass

    Directory of Open Access Journals (Sweden)

    Mouritz N. Svenson

    2016-03-01

    Full Text Available Glasses can be chemically strengthened through the ion exchange process, wherein smaller ions in the glass (e.g., Na+ are replaced by larger ions from a salt bath (e.g., K+. This develops a compressive stress (CS on the glass surface, which, in turn, improves the damage resistance of the glass. The magnitude and depth of the generated CS depends on the thermal and pressure histories of the glass prior to ion exchange. In this study, we investigate the ion exchange-related properties (mutual diffusivity, CS, and hardness of a sodium aluminosilicate glass, which has been densified through annealing below the initial fictive temperature of the glass or through pressure-quenching from the glass transition temperature at 1 GPa prior to ion exchange. We show that the rate of alkali interdiffusivity depends only on the density of the glass, rather than on the applied densification method. However, we also demonstrate that for a given density, the increase in CS and increase in hardness induced by ion exchange strongly depends on the densification method. Specifically, at constant density, the CS and hardness values achieved through thermal annealing are larger than those achieved through pressure-quenching. These results are discussed in relation to the structural changes in the environment of the network-modifier and the overall network densification.

  18. Edge enhanced growth induced shape transition in the formation of GaN nanowall network

    Science.gov (United States)

    Nayak, Sanjay; Kumar, Rajendra; Shivaprasad, S. M.

    2018-01-01

    We address the mechanism of early stages of growth and shape transition of the unique nanowall network (NwN) of GaN by experimentally monitoring its morphological evolution and complementing it by first-principles calculations. Using atomic force and scanning electron microscopy, we observe the formation of oval shaped islands at very early stages of the growth which later transformed into tetrahedron shaped (3 faced pyramid) islands. These tetrahedron shaped islands further grow anisotropically along their edges of the (20 2 ¯ 1) facets to form the wall-like structure as the growth proceeds. The mechanism of this crystal growth is discussed in light of surface free energies of the different surfaces, adsorption energy, and diffusion barrier of Ga ad-atoms on the (20 2 ¯ 1) facets. By first-principles calculations, we find that the diffusion barrier of ad-atoms reduces with decreasing width of facets and is responsible for the anisotropic growth leading to the formation of NwN. This study suggests that formation of NwN is an archetype example of structure dependent attachment kinetic instability induced shape transition in thin film growth.

  19. Groundwater transit time distribution and transfer of nitrates from soils to river network

    Science.gov (United States)

    Michalczyk, Tomasz; Bar-Michalczyk, Dominika; Duliński, Marek; Kania, Jarosław; Malina, Grzegorz; Różański, Kazimierz; Szklarczyk, Tadeusz; Wachniew, Przemysław; Witczak, Stanisław; Zięba, Damian; Żurek, Anna

    2016-04-01

    Measures undertaken to reduce nitrate loadings of agricultural origin to surface waters have to take into account delays associated with pollution transport between the root zone and groundwater abstraction wells or natural discharge zones. Parts of an important fissured-carbonate aquifer (Major Groundwater Basin No. 326) located in southern Poland are polluted, with concentrations of nitrates significantly exceeding the European Union limit of 50 mg/L. The polluted groundwater discharges to the streams of the Kocinka river catchment affecting their water quality. The MODFLOW and MT3DMS codes were used to model flow and transport of contaminants in the aquifer. Transport of conservative solutes was performed in a transient mode, with the steady-state flow field calibrated using present-day distribution of hydraulic heads and discharges of streams draining the aquifer. Time series of tritium data available for 21 production wells and springs, some of them extending over the period of 30 years, were used for calibration of flow and transport model resulting in significant changes in the original conceptual framework of this groundwater system. The regional-scale numerical model of flow and transport allowed for identification of the gaining stream reaches and for estimation of groundwater contributions to streamflow. Observations of in stable isotope composition and stream water chemistry confirmed the results of the numerical model for these particular stream reaches. The numerical model provided also the transit time distribution of groundwater flow through the saturated zone with an average value of 8 years and dominant transit times in the range from 3 to 20 years. Transit times of water through the unsaturated zone are in the range from less than 5 to 25 years with an average value of 10 years. Because of these delays, the results of measures aimed at reducing nitrate loads to the river network will be visible only within the relevant timescales.

  20. Probing Magnetism in 2D Molecular Networks after in Situ Metalation by Transition Metal Atoms.

    Science.gov (United States)

    Schouteden, K; Ivanova, Ts; Li, Z; Iancu, V; Janssens, E; Van Haesendonck, C

    2015-03-19

    Metalated molecules are the ideal building blocks for the bottom-up fabrication of, e.g., two-dimensional arrays of magnetic particles for spintronics applications. Compared to chemical synthesis, metalation after network formation by an atom beam can yield a higher degree of control and flexibility and allows for mixing of different types of magnetic atoms. We report on successful metalation of tetrapyridyl-porphyrins (TPyP) by Co and Cr atoms, as demonstrated by scanning tunneling microscopy experiments. For the metalation, large periodic networks formed by the TPyP molecules on a Ag(111) substrate are exposed in situ to an atom beam. Voltage-induced dehydrogenation experiments support the conclusion that the porphyrin macrocycle of the TPyP molecule incorporates one transition metal atom. The newly synthesized Co-TPyP and Cr-TPyP complexes exhibit striking differences in their electronic behavior, leading to a magnetic character for Cr-TPyP only as evidenced by Kondo resonance measurements.

  1. Phase Transition for the Maki-Thompson Rumour Model on a Small-World Network

    Science.gov (United States)

    Agliari, Elena; Pachon, Angelica; Rodriguez, Pablo M.; Tavani, Flavia

    2017-11-01

    We consider the Maki-Thompson model for the stochastic propagation of a rumour within a population. In this model the population is made up of "spreaders", "ignorants" and "stiflers"; any spreader attempts to pass the rumour to the other individuals via pair-wise interactions and in case the other individual is an ignorant, it becomes a spreader, while in the other two cases the initiating spreader turns into a stifler. In a finite population the process will eventually reach an equilibrium situation where individuals are either stiflers or ignorants. We extend the original hypothesis of homogenously mixed population by allowing for a small-world network embedding the model, in such a way that interactions occur only between nearest-neighbours. This structure is realized starting from a k-regular ring and by inserting, in the average, c additional links in such a way that k and c are tuneable parameters for the population architecture. We prove that this system exhibits a transition between regimes of localization (where the final number of stiflers is at most logarithmic in the population size) and propagation (where the final number of stiflers grows algebraically with the population size) at a finite value of the network parameter c. A quantitative estimate for the critical value of c is obtained via extensive numerical simulations.

  2. Social networks, social participation and self-perceived health among older people in transitional Kosovo.

    Science.gov (United States)

    Jerliu, Naim; Burazeri, Genc; Toçi, Ervin; Kempen, Gertrudis I J M; Jongen, Wesley; Ramadani, Naser; Brand, Helmut

    2014-04-01

    A number of studies proved that social networks and social participation have beneficial health effects in western countries. However, the evidence from southeast European region is scant. We aimed to assess the extent of social networks and social participation and their relationship with self-perceived health status among older people in post-war Kosovo. A nationwide cross-sectional study was conducted in Kosovo in 2011 including a representative sample of 1890 individuals aged ≥65 years (949 men, mean age 73 ± 6 years; 941 women, mean age 74 ± 7 years; response rate: 83%). Social networks were assessed by means of number of friends and family members that participants had contacts with, whereas social participation by involvement in social groupings/organizations. Information on self-perceived health status and demographic and socioeconomic characteristics was also collected. Overall, 93% of study participants reported that they had at least weekly contacts with more than one family member, and 97% reported daily contacts with their respective friends. Conversely, only 14% of participants reported engagement with social groupings. Generally, individuals who had contacts with friends and/or engaged with social organizations reported a better health status. Our findings point to strong family ties in this patriarchal society. Conversely, levels of social participation were considerably lower in Kosovo compared with the western European countries. The low participation levels in social groupings and their putative deleterious health effects should raise the awareness of policymakers to improve the conditions and increase the degree of social participation among older people in transitional Kosovo.

  3. Polymer combination increased both physical stability and oral absorption of solid dispersions containing a low glass transition temperature drug: physicochemical characterization and in vivo study.

    Science.gov (United States)

    Sakurai, Atsushi; Sakai, Toshiro; Sako, Kazuhiro; Maitani, Yoshie

    2012-01-01

    The purpose of this study was establishing a solid dispersion formulation containing a low glass transition temperature (T(g)) and poorly water-soluble drug. Drug/polymer blends with differing physicochemical stabilities and oral absorption were prepared from copolyvidone (PVP-VA), polyvinylpyrrolidone (PVP) or hydroxypropylmethylcellulose (HPMC) by a hot melt extrusion. HPMC drastically increased the drug oral absorption property, while PVP-VA or PVP stabilized solid dispersions during storage by increasing the T(g) in proportion to polymer concentration. Experimental T(g) values corresponded closely with theoretical T(g) values; indeed, the T(g) values of solid dispersion with HPMC did not increase significantly compared to the T(g) value for the drug alone. A solid dispersion formulation incorporating two different polymers-HPMC and either PVP-VA or PVP-maintained increased T(g), physicochemical stability, solubility, and bioavailability of the solid dispresions owing to each polymer. These findings suggested that both oral absorption and physicochemical stability of low-T(g) drug will be improved using less amount of solid dispersion of combined two polymers than polymer alone.

  4. Correlations of norbornenyl crosslinked polyimide resin structures with resin thermo-oxidative stability, resin glass transition temperature and composite initial mechanical properties

    Science.gov (United States)

    Alston, William B.

    1988-01-01

    PMR (polymerization of monomeric reactants) methodology was used to prepare 70 different polyimide oligomeric resins and 30 different unidirectional graphite fiber/polyimide composites. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on resin thermo-oxidative stability and glass transition temperature (Tg) of the cured/postcured resins. A linear correlation of decreasing 316 C resin weight loss/surface area versus (1) decreasing aliphatic content, or (2) increasing benzylic/aliphatic content stoichiometry ratio over a wide range of resin compositions was observed. An almost linear correlation of Tg versus molecular distance between the crosslinks was also observed. An attempt was made to correlate Tg with initial composite mechanical properties (flexural strength and interlaminar shear strength). However, the scatter in mechanical strength data prevented obtaining a clear correlation. Instead, only a range of composite mechanical properties was obtained at 25, 288, and 316 C. Perhaps more importantly, what did become apparent during the correlation study was (1) the PMR methodology could be used to prepare composites from resins containing a wide variety of monomer modifications, (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins formulated exhibited satisfactory processing flow, and (3) that PMR resins exhibited predictable rates of 316 C weight loss/surface area based on their benzylic/aliphatic stoichiometery ratio.

  5. Temperature-, pH- and CO2-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid Copolymers with High Glass Transition Temperatures

    Directory of Open Access Journals (Sweden)

    Yeong-Tarng Shieh

    2016-12-01

    Full Text Available A series of poly(N-isopropylacrylamide-co-acrylic acid (PNIPAAm-co-PAA random copolymers were synthesized through free radical copolymerization in MeOH. The incorporation of the acrylic acid units into PNIPAAm tended to enhance the glass transition temperature (Tg, due to strong intermolecular hydrogen bonding between the amide groups of PNIPAAm and the carboxyl groups of PAA, as observed using 1H nuclear magnetic resonance (NMR and Fourier transform infrared (FTIR spectroscopic analyses. The lower critical solution temperature (LCST increased upon increasing the pH of the aqueous solution containing PNIPAAm-co-PAA because the COOH groups of the PAA segment dissociated into COO− groups, enhancing the solubility of the copolymer. In addition, high-pressure differential scanning calorimetry revealed that the LCSTs of all the aqueous solutions of the copolymers decreased upon increasing the pressure of CO2, suggesting that CO2 molecules had displaced H2O molecules around the polar CONH and COOH groups in PNIPAAm-co-PAA, thereby promoting the hydrophobicity of the copolymers in the aqueous solution. In addition, the values of Tg of a film sample increased upon treatment with supercritical CO2, implying that intermolecular interactions in the copolymer had been enhanced after such treatment.

  6. Medium decoupling of dynamics at temperatures ~100 K above glass-transition temperature: a case study with (acetamide + lithium bromide/nitrate) melts.

    Science.gov (United States)

    Guchhait, Biswajit; Daschakraborty, Snehasis; Biswas, Ranjit

    2012-05-07

    Time-resolved fluorescence Stokes shift and anisotropy measurements using a solvation probe in [0.78CH(3)CONH(2) + 0.22{f LiBr + (1-f) LiNO(3)}] melts reveal a strong decoupling of medium dynamics from viscosity. Interestingly, this decoupling has been found to occur at temperatures ∼50-100 K above the glass transition temperatures of the above melt at various anion concentrations (f(LiBr)). The decoupling is reflected via the following fractional viscosity dependence (η) of the measured average solvation and rotation times ( and , respectively): ∝ (η∕T)(p) (x being solvation or rotation), with p covering the range, 0.20 than for , indicating a sort of translation-rotation decoupling. Multiple probes have been used in steady state fluorescence measurements to explore the extent of static heterogeneity. Estimated experimental dynamic Stokes shift for coumarin 153 in these mixtures lies in the range, 1000 < Δν(t)/cm(-1) < 1700, and is in semi-quantitative agreement with predictions from our semi-molecular theory. The participation of the fluctuating density modes at various length-scales to the observed solvation times has also been investigated.

  7. Solid-state stability of spray-dried insulin powder for inhalation: chemical kinetics and structural relaxation modeling of Exubera above and below the glass transition temperature.

    Science.gov (United States)

    Sadrzadeh, Negar; Miller, Danforth P; Lechuga-Ballesteros, David; Harper, Nancy J; Stevenson, Cynthia L; Bennett, David B

    2010-09-01

    The effect of temperature on the chemical stability of an amorphous spray-dried insulin powder formulation (Exubera) was evaluated in the solid state at constant moisture content. The chemical stability of the powder was assessed using reversed-phase high-performance liquid chromatography (RP-HPLC) and high-performance-size exclusion chromatography (HP-SEC). The major degradants in spray-dried insulin produced during heat stressing were identified as A21-desamidoinsulin (A21) and high molecular weight protein (HMWP). As expected, the rates of formation of A21 and HMWP were observed to increase with temperature. A stretched-time kinetic model (degradation rate is proportional to the square root of time) was applied to the degradant profiles above and below the glass transition temperature (T(g)) and apparent reaction rate constants were determined. Below T(g), isothermal enthalpy of relaxation measurements were used to assess the effect of temperature on molecular mobility. The formation of A21 and HMWP was found to follow an Arrhenius temperature dependence above and below the T(g). Comparison of reaction rate constants to those estimated from structural relaxation experiments suggests that the reaction pathways to form A21 and HMWP below the T(g) may be coupled with the molecular motions involved in structural relaxation.

  8. Measurement of glass transition temperature, residual heat of reaction and mixing ratio of epoxy resins using near infrared spectroscopy: a preliminary study

    DEFF Research Database (Denmark)

    Houmøller, Lars Plejdrup; Laursen, Peter Clemen

    2003-01-01

    As a measure of the degree of curing of epoxy resins, the glass transition temperature, Tg, and the residual heat of reaction, DeltaHr, are often used. In this study, near infrared spectroscopy and multivariate calibration (partial least squares regression (PLSR)) have been used to monitor the two...... variables, using differential scanning calorimetry (DSC) as the reference method. The epoxy under study was a commercial system consisting of the resin, trimethylolpropanetriglycidylether, and the hardener, 3-aminomethyl-3,5,5,-trimethylcyclohexylamine. Using samples cured under different conditions......, calibrations resulted in root mean square errors of cross-validation (RMSECV) of 18 J/g for DeltaHr (range for Hr: 6.1-231.3 J/g) and 7.2ºC for Tg (range for Tg: 41.5-98.8ºC). Also, a PLSR model for mixing ratio of hardener and resin was obtained, resulting in a RMSECV of 0.0040 (range for mixing ratio: 0.180-0.380)...

  9. Response of complex networks to compression: Ca, La, and Y aluminoborosilicate glasses formed from liquids at 1 to 3 GPa pressures

    Energy Technology Data Exchange (ETDEWEB)

    Bista, Saurav, E-mail: sbista@stanford.edu; Stebbins, Jonathan F. [Department of Geological Sciences, Stanford University, Stanford, California 94305 (United States); Morin, Elizabeth I. [Department of Chemistry, Stanford University, Stanford, California 94305 (United States)

    2016-01-28

    Aluminoborosilicate glasses containing relatively high field strength modifiers (Ca, La, and Y) have been compressed at pressures up to 3 GPa and near the glass transition temperature (T{sub g}) and quenched to room temperature at high pressure followed by decompression. Structural changes were quantified with high-resolution {sup 27}Al and {sup 11}B MAS nuclear magnetic resonance at 14.1–18.8 T. The changes with pressure in Al and B coordinations in the recovered samples are quite large with more than 50% decreases in tetrahedral aluminum ({sup IV}Al) and 200%-300% increases in tetrahedral boron ({sup IV}B). Glasses with higher field strength modifiers (La and Y) contain more high coordinated aluminum ({sup V,V} {sup I}Al) at all pressures studied. More high coordinated boron also correlates with higher field strength modifier if all three compositions are compared on an isothermal basis. Although lowering fictive temperature and increasing pressure both increase Al and B coordinations, our study shows that the actual mechanisms for structural changes are most probably different for temperature and pressure effects. Using a rough thermodynamic model to extrapolate to higher pressures, it appears that a simple non-bridging oxygen (NBO) consumption mechanism is not sufficient to convert all the aluminum to octahedral and boron to tetrahedral coordination, suggesting other mechanisms for structural changes could occur at high pressure as NBO becomes depleted.

  10. Local and global synchronization transitions induced by time delays in small-world neuronal networks with chemical synapses.

    Science.gov (United States)

    Yu, Haitao; Wang, Jiang; Du, Jiwei; Deng, Bin; Wei, Xile

    2015-02-01

    Effects of time delay on the local and global synchronization in small-world neuronal networks with chemical synapses are investigated in this paper. Numerical results show that, for both excitatory and inhibitory coupling types, the information transmission delay can always induce synchronization transitions of spiking neurons in small-world networks. In particular, regions of in-phase and out-of-phase synchronization of connected neurons emerge intermittently as the synaptic delay increases. For excitatory coupling, all transitions to spiking synchronization occur approximately at integer multiples of the firing period of individual neurons; while for inhibitory coupling, these transitions appear at the odd multiples of the half of the firing period of neurons. More importantly, the local synchronization transition is more profound than the global synchronization transition, depending on the type of coupling synapse. For excitatory synapses, the local in-phase synchronization observed for some values of the delay also occur at a global scale; while for inhibitory ones, this synchronization, observed at the local scale, disappears at a global scale. Furthermore, the small-world structure can also affect the phase synchronization of neuronal networks. It is demonstrated that increasing the rewiring probability can always improve the global synchronization of neuronal activity, but has little effect on the local synchronization of neighboring neurons.

  11. Eu3+ doped 1La2O3:2WO3:1B2O3 glass and glass-ceramic

    Science.gov (United States)

    Aleksandrov, L.; Iordanova, R.; Dimitriev, Y.; Georgiev, N.; Komatsu, T.

    2014-06-01

    In WO3-La2O3-B2O3 system, glasses were obtained in the region between 20 and 30 mol% La2O3. A liquid-phase separation region was observed near the WO3-B2O3 side. A glass with nominal composition 50WO3:25L2O3:25B2O3 doped with Eu2O3 was synthesized by melt quenching method. The obtained glass was characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), UV-vis, infrared spectroscopy (IR) and photoluminescence spectroscopy (PL). According to the DTA data, Eu3+ ions decrease the glass transition temperature from 621 °C to 574 °C and crystallization temperature from 690 °C to 677 °C. Structural model for the glass network was suggested on the base of IR and UV-vis spectral investigations. It was established that WO4 and WO6 structural units (620-960 cm-1) and BO3 and BO4 polyhedra (1050-1380 cm-1) build up the glass network. During vitrification partial transformation of WO4 to WO6 and BO3 to BO4 was proved. The quenched glass is transparent in the visible region and exhibits typical absorption bands of Eu3+ ions due to the 4f transitions 5D0 → 7Fj (j = 0-4). A glass-ceramic consisting of LaBWO6:Eu3+ nanocrystals with enhanced photoluminescence emissions is synthesized. The intensity of emission increases drastically in the glass-crystalline sample compared with the glass and polycrystalline sample.

  12. Book Review - V Pogoretskyy, Freedom of Transit and Access to Gas Pipeline Networks Under WTO Law (Cambridge University Press, 2017)

    NARCIS (Netherlands)

    Marhold, Anna

    2017-01-01

    In Freedom of Transit and Access to Pipeline Networks under WTO Law, the author appropriately introduces the topic by stating that energy is featuring increasingly prominently as a topic in international trade law. Indeed, while being a dormant issue in the World Trade Organization (“WTO” forum for

  13. Embedding an institution-wide capacity building opportunity around transition pedagogy: First Year Teaching and Learning Network Coordinators

    Directory of Open Access Journals (Sweden)

    Jennifer Clark

    2015-03-01

    Full Text Available A First Year Teaching and Learning Network was established in a regional university with a strong focus on distance education for a very diverse student cohort.  The purpose of the Network, which consisted of a Coordinator in each of nine schools, was to support staff teaching students transitioning into tertiary education. The paper explores the theoretical bases of the structure, its current method of operation, its impact so far, and future plans. The development of the Network illustrates how a university can consciously embed opportunities for staff to take ownership of transition pedagogy and thus encourage widespread capacity building amongst their peers. The experiences of the Network in its first two years provide a case study of how institutional support for the Scholarship of Teaching and Learning, in particular scholarship around capacity building, can be used as a mechanism to promote both staff and student engagement with transition pedagogy resulting in a shift from a second generation approach towards a third generation approach to transition.

  14. Quantitative analysis of the network structure that underlines the transitioning in mechanical responses of pea protein gels

    NARCIS (Netherlands)

    Munialo, C.D.; Linden, van der E.; Ako, K.; Jongh, de H.H.J.

    2015-01-01

    The objective of this study was to analyze quantitatively the network structure that underlines the transitioning in the mechanical responses of heat-induced pea protein gels. To achieve this, gels were prepared from pea proteins at varying pHs from 3.0 to 4.2 at a fixed 100 mg/mL protein

  15. Relaxation of Anisotropic Glasses

    DEFF Research Database (Denmark)

    Deubener, Joachim; Martin, Birgit; Wondraczek, Lothar

    2004-01-01

    Anisotropic glasses are obtained from uniaxial compressing and pulling of glass forming liquids above the transition temperature range. To freeze-in, at least partly the structural state of the flowing melt, cylindrical samples were subjected to a controlled cooling process under constant load...... differential scanning calorimetry (DSC) and dilatometry. The energy release and expansion-shrinkage behaviour of the glasses are investigated as a function of the applied deformation stress. Structural origins of the frozen-in birefringence induced by viscous flow are discussed and correlation between...

  16. Oxynitride glasses: a review

    Directory of Open Access Journals (Sweden)

    Àngel R. Garcia

    2016-11-01

    Full Text Available Oxynitride glasses are special types of silicates or silicoaluminates which have been the object of many studies over the last forty years. They can be prepared by means of various complex methods, leading to variable levels of nitrogen incorporation, though in all cases giving limited transparency in the visible range. More recently, a new family of oxynitride glasses incorporating fluorine has been investigated. This paper outlines the effect of composition, in particular nitrogen and fluorine content, on properties such as glass transition temperature, hardness, Young's modulus, compactness and molar volume.

  17. Oxynitride glasses: a review

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, A.R.; Clausell, C.; Barba, A.

    2016-07-01

    Oxynitride glasses are special types of silicates or silicoaluminates which have been the object of many studies over the last forty years. They can be prepared by means of various complex methods, leading to variable levels of nitrogen incorporation, though in all cases giving limited transparency in the visible range. More recently, a new family of oxynitride glasses incorporating fluorine has been investigated. This paper outlines the effect of composition, in particular nitrogen and fluorine content, on properties such as glass transition temperature, hardness, Young's modulus, compactness and molar volume. (Author)

  18. A novel Bi-doped borosilicate glass as sealant for sodium sulfur battery. Part 1: Thermophysical characteristics and structure

    Science.gov (United States)

    Song, Shufeng; Wen, Zhaoyin; Zhang, Qunxi; Liu, Yu

    A novel Bi-doped borosilicate glass has been developed as sealant for sodium sulfur battery. The thermophysical characteristics like thermal expansion coefficient, glass transition and softening temperatures, viscosities and densities of the Bi-doped and undoped glasses are systematically studied. It is found that the thermal expansion match between the Bi-doped glasses and alpha-alumina/beta-alumina is satisfactory. The Bi-doped glass has a viscosity around 10 5 Pa s in 800-850 °C range, which is suitable to allow a good bonding with the sealed parts. The FTIR analysis indicates that the substitution of Bi 2O 3 for SiO 2 makes the glass network less rigid. Bi 2O 3 builds the glass network as [BiO 6] unit. [BO 4] unit enters the glass network and induces the overlapped vibrations of [BO 4] unit and [SiO 4] tetrahedron. The Bi-doped glass sealant exhibits superior chemical compatibility with alpha-alumina and beta-alumina.

  19. SILICATE GLASSES

    African Journals Online (AJOL)

    AH -- ICp(glass).dt (1) with Cp(glass) being calculated as a linear combination of the C,-functions of the different oxides composing the glass. For validity of this relation, ideal behaviour of the glass components is assumed and the partial heat capacities of the oxides are considered independent of composition in the studied ...

  20. Glass sealing

    Energy Technology Data Exchange (ETDEWEB)

    Brow, R.K.; Kovacic, L.; Chambers, R.S. [Sandia National Labs., Albuquerque, NM (United States)

    1996-04-01

    Hernetic glass sealing technologies developed for weapons component applications can be utilized for the design and manufacture of fuel cells. Design and processing of of a seal are optimized through an integrated approach based on glass composition research, finite element analysis, and sealing process definition. Glass sealing procedures are selected to accommodate the limits imposed by glass composition and predicted calculations.

  1. RADIATION EFFECTS IN PHYSICAL AGING OF BINARY As-S AND As-Se GLASSES

    Energy Technology Data Exchange (ETDEWEB)

    Golovchak, Roman; Shpotyuk, O.; Kozdras, A.; Riley, Brian J.; Sundaram, S. K.; McCloy, John S.

    2011-01-24

    Radiation-induced physical aging effects are studied in binary AsxS100-x and AsxSe100-x (30 ≤ x ≤ 42) glasses by conventional differential scanning calorimetry (DSC) method. It is shown that γ-irradiation (Co60 source, ~ 3 MGy dose) of glassy AsxS100-x caused a measurable increase in glass transition temperature and endothermic peak area in the vicinity of glass transition region, which was associated with acceleration of structural relaxation processes in these materials. In contrast to sulfide glasses, the samples of As-Se family did not exhibit any significant changes in DSC curves after γ-irradiation. The observed difference in radiation-induced physical aging between sulfides and selenides was explained by more effective destruction-polymerization transformations and possible metastable defects formation in S-based glassy network.

  2. Structural properties of Ge-S amorphous networks in relationship with rigidity transitions: An ab initio molecular dynamics study

    Science.gov (United States)

    Chakraborty, S.; Boolchand, P.; Micoulaut, M.

    2017-09-01

    We investigate the amorphous GexS100 -x (with 10 ≤x ≤40 ) system from ab initio simulations. Results show a very good agreement with experimental findings from diffraction and the topology of the obtained structural models is further analyzed and compared with the selenide analog. Differences emerge, however, from a detailed molecular dynamics analysis showing that the ring statistics and the homopolar defects do not evolve similarly. The findings are also connected to rigidity theory, which provides a topological approach to decoding the physics of network glasses, and the effects of composition and temperature are analyzed.

  3. Designing Optical Properties in Infrared Glass

    Science.gov (United States)

    Gleason, Benn

    Chalcogenide glasses (ChGs) are well-known for their attractive optical properties, such as high refractive index and transparency in across infrared wavelengths. ChGs also possess the ability to compositionally tune properties such as the refractive index, the thermo-optic coefficient, and other non-optical properties. Chalcogenide glasses with compositionally tailored physical and optical properties will provide optical designers with new materials necessary to create novel infrared imaging systems requiring new or expanded functionality. This dissertation has evaluated the relationship between glass composition, the resulting atomic structure, and resulting optical and thermo-optical properties, with specific focus on the infrared refractive index and the thermo-optic coefficient (dn/dT). To create these linkages, a series of GeAsSe glasses with increasing Ge content were fabricated across three tielines, and evaluated for their chemical and physical attributes. A novel infrared refractometer was constructed to provide supplemental refractive index and dn/dT data. Findings in this dissertation showed a correlation between the Ge content of the glass composition and several non-optical properties. Namely, as the Ge content increases, the glass transition temperature and Vickers Hardness increase, while the coefficient of thermal expansion decreases. These physical changes are due to the cross-linking of the glassy network by the 4-coordinated Ge additions. In contrast, optical property data showed a strong dependence on the appearance and/or disappearance of specific atomic structures within the glassy network as the glass composition changes. Overall, this study aimed to answer key questions that have not been systematically studied within multi-component chalcogenide glasses. These questions include: (1) How will compositional variations for the sake of optical tunability affect the physical properties which dictate a materials' response to manufacturing

  4. USA National Phenology Network's volunteer-contributed observations yield predictive models of phenological transitions.

    Science.gov (United States)

    Crimmins, Theresa M; Crimmins, Michael A; Gerst, Katharine L; Rosemartin, Alyssa H; Weltzin, Jake F

    2017-01-01

    In support of science and society, the USA National Phenology Network (USA-NPN) maintains a rapidly growing, continental-scale, species-rich dataset of plant and animal phenology observations that with over 10 million records is the largest such database in the United States. The aim of this study was to explore the potential that exists in the broad and rich volunteer-collected dataset maintained by the USA-NPN for constructing models predicting the timing of phenological transition across species' ranges within the continental United States. Contributed voluntarily by professional and citizen scientists, these opportunistically collected observations are characterized by spatial clustering, inconsistent spatial and temporal sampling, and short temporal depth (2009-present). Whether data exhibiting such limitations can be used to develop predictive models appropriate for use across large geographic regions has not yet been explored. We constructed predictive models for phenophases that are the most abundant in the database and also relevant to management applications for all species with available data, regardless of plant growth habit, location, geographic extent, or temporal depth of the observations. We implemented a very basic model formulation-thermal time models with a fixed start date. Sufficient data were available to construct 107 individual species × phenophase models. Remarkably, given the limited temporal depth of this dataset and the simple modeling approach used, fifteen of these models (14%) met our criteria for model fit and error. The majority of these models represented the "breaking leaf buds" and "leaves" phenophases and represented shrub or tree growth forms. Accumulated growing degree day (GDD) thresholds that emerged ranged from 454 GDDs (Amelanchier canadensis-breaking leaf buds) to 1,300 GDDs (Prunus serotina-open flowers). Such candidate thermal time thresholds can be used to produce real-time and short-term forecast maps of the timing

  5. New Erbium Doped Antimony Glasses for Laser and Glass ...

    African Journals Online (AJOL)

    Because of the special spectroscopic properties of the rare earth ions, rare earth doped glasses are widely used in bulk and fiber lasers or amplifiers. The modelling of lasers and searching for new laser transitions require a precise knowledge of the spectroscopic properties of rare earth ions in different host glasses.

  6. On the degelation of networks - Case of the radiochemical degradation of methyl methacrylate - ethylene glycol dimethacrylate copolymers

    Science.gov (United States)

    Richaud, Emmanuel; Gilormini, Pierre; Verdu, Jacques

    2016-05-01

    Methyl methacrylate networks were synthetized and submitted to radiochemical degradation. Ageing was monitored by means of sol-gel analysis and glass transition temperature measurements. Networks were shown to undergo exclusively chain scission process leading to the degelation of network. The critical conversion degree corresponding to degelation (loss of all elastically active chains) is discussed regarding a statistical theory.

  7. On the degelation of networks – Case of the radiochemical degradation of methyl methacrylate – ethylene glycol dimethacrylate copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Richaud, Emmanuel; Gilormini, Pierre; Verdu, Jacques [Arts et Métiers ParisTech, CNRS, PIMM UMR 8006, 151 bd de l’Hôpital, 75013 Paris (France)

    2016-05-18

    Methyl methacrylate networks were synthetized and submitted to radiochemical degradation. Ageing was monitored by means of sol-gel analysis and glass transition temperature measurements. Networks were shown to undergo exclusively chain scission process leading to the degelation of network. The critical conversion degree corresponding to degelation (loss of all elastically active chains) is discussed regarding a statistical theory.

  8. Effect of ZnO on the Thermal Properties of Tellurite Glass

    Directory of Open Access Journals (Sweden)

    H. A. A. Sidek

    2013-01-01

    Full Text Available Systematic series of binary zinc tellurite glasses in the form (ZnOx(TeO2 (where x=0 to 0.4 with an interval of 0.05 mole fraction have been successfully prepared via conventional melt cast-quenching technique. Their density was determined by Archimedes method with acetone as buoyant liquid. The thermal expansion coefficient of each zinc tellurite glasses was measured using L75D1250 dilatometer, while their glass transition temperature (Tg was determined by the SETARAM Labsys DTA/6 differential thermogravimetric analysis at a heating rate of 20 K min−1. The acoustic Debye temperature and the softening temperature (Ts were estimated based on the longitudinal (VL and shear ultrasonic (Vs wave velocities propagated in each glass sample. For ultrasonic velocity measurement of the glass sample, MATEC MBS 8000 Ultrasonic Data Acquisition System was used. All measurements were taken at 10 MHz frequency and at room temperature. All the thermal properties of such binary tellurite glasses were measured as a function of ZnO composition. The composition dependence was discussed in terms of ZnO modifiers that were expected to change the thermal properties of tellurite glasses. Experimental results show their density, and the thermal expansion coefficient increases as more ZnO content is added to the tellurite glass network, while their glass transition, Debye temperature, and the softening temperature decrease due to a change in the coordination number (CN of the network forming atoms and the destruction of the network structure brought about by the formation of some nonbridging oxygen (NBO atoms.

  9. An internet-based communication network for information transfer during patient transitions from skilled nursing facility to the emergency department.

    Science.gov (United States)

    Hustey, Fredric M; Palmer, Robert M

    2010-06-01

    To determine whether the implementation of an Internet-based communication system improves the amount of essential information conveyed between a skilled nursing facility (SNF) and the emergency department (ED) during patient care transitions. Interventional; before and after. ED of an urban teaching hospital with approximately 55,000 visits per year and a 55-bed subacute free-standing rehabilitation facility (the SNF). All patients transferred from the SNF to the ED over 16 months. An Internet-based communication network with SNF-ED transfer form for communication during patient care transitions. Nine elements of patient information assessed before and after intervention through chart review. changes in efficiency of information transfer and staff satisfaction. Two hundred thirty-four of 237 preintervention and all 276 postintervention care transitions were reviewed. The Internet communication network was used in 78 (26%) of all care transitions, peaking at 40% by the end of the study. There was more critical patient information (1.85 vs 4.29 of 9 elements; Pcommunication was higher among ED physicians after the intervention. The use of an Internet-based system increased the amount of information communicated during SNF-ED care transitions and significantly reduced the number of pages in which this information was contained.

  10. Forecasting Method for Urban Rail Transit Ridership at Station Level Using Back Propagation Neural Network

    Directory of Open Access Journals (Sweden)

    Junfang Li

    2016-01-01

    Full Text Available Direct forecasting method for Urban Rail Transit (URT ridership at the station level is not able to reflect nonlinear relationship between ridership and its predictors. Also, population is inappropriately expressed in this method since it is not uniformly distributed by area. In this paper, a new variable, population per distance band, is considered and a back propagation neural network (BPNN model which can reflect nonlinear relationship between ridership and its predictors is proposed to forecast ridership. Key predictors are obtained through partial correlation analysis. The performance of the proposed model is compared with three other benchmark models, which are linear model with population per distance band, BPNN model with total population, and linear model with total population, using four measures of effectiveness (MOEs, maximum relative error (MRE, smallest relative error (SRE, average relative error (ARE, and mean square root of relative error (MSRRE. Also, another model for contribution rate of population per distance band to ridership is formulated based on the BPNN model with nonpopulation variables fixed. Case studies with Japanese data show that BPNN model with population per distance band outperforms other three models and the contribution rate of population within special distance band to ridership calculated through the contribution rate model is 70%~92.9% close to actual statistical value. The result confirms the effectiveness of models proposed in this paper.

  11. Pressure-induced phase transitions in silicon studied by neural network-based metadynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Behler, Joerg [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland); Lehrstuhl fuer Theoretische Chemie, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); Martonak, Roman [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland); Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynska dolina F2, 84248 Bratislava (Slovakia); Donadio, Davide [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland); Department of Chemistry, UC Davis, One Shields Ave., Davis, CA 95616 (United States); Parrinello, Michele [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland)

    2008-12-15

    We present a combination of the metadynamics method for the investigation of pressure-induced phase transitions in solids with a neural network representation of high-dimensional density-functional theory (DFT) potential-energy surfaces. In a recent illustration of the method for the complex high-pressure phase diagram of silicon[Behler et al., Phys. Rev. Lett. 100, 185501 (2008)] we have shown that the full sequence of phases can be reconstructed by a series of subsequent simulations. In the present paper we give a detailed account of the underlying methodology and discuss the scope and limitations of the approach, which promises to be a valuable tool for the investigation of a variety of inorganic materials. The method is several orders of magnitude faster than a direct coupling of metadynamics with electronic structure calculations, while the accuracy is essentially maintained, thus providing access to extended simulations of large systems. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. The effects of formulation and moisture on the stability of a freeze-dried monoclonal antibody-vinca conjugate: a test of the WLF glass transition theory.

    Science.gov (United States)

    Roy, M L; Pikal, M J; Rickard, E C; Maloney, A M

    1992-01-01

    Deacetylvinblastine (DAVLB) hydrazide, a cytotoxic vinca alkaloid, has been linked to the monoclonal antibody, KS1/4, via aldehyde residues of the oxidized carbohydrate groups on the antibody. The resulting KS1/4-DAVLB hydrazide conjugate is unstable in solution with both the acyl hydrazone linkage and the vinca moiety being subject to significant degradation, even at 5 degrees C. This necessitated the development of a freeze-dried formulation of the antibody-drug conjugate. Formulation factors considered were pH, ionic strength, buffer, excipient types, and excipient ratios. A formulation with equal weight ratios of mannitol, glycine, and conjugate in a low ionic strength phosphate buffer at near neutral pH was selected. Stability was studied at various moisture levels (1.4%, 3.0%, and 4.7%) and temperatures (5 degrees C, 25 degrees C, and 40 degrees C). Degradation was measured by size exclusion HPLC (aggregate formation) and by reverse phase HPLC (hydrolysis of hydrazone linkage and vinca decomposition). Differential scanning calorimetry (DSC) indicated that all samples were above their glass transition temperatures, Tg, when stored at 40 degrees C. When stored at 25 degrees C, only the highest moisture sample was initially above its Tg. However, due to crystallization of the excipients during storage and the resulting decrease in Tg, samples stored at 25 degrees C were also above their Tg during much of the storage period. The degradation rate, R, increased sharply with increasing temperature and with increasing moisture level. Degradation kinetics obeyed the Williams-Landel-Ferry relationship, R/Rg = exp[k(T-Tg)], where Rg is the degradation rate at Tg. For all three moisture levels and all three degradation pathways, k = 0.143.

  13. Medium decoupling of dynamics at temperatures ˜100 K above glass-transition temperature: A case study with (acetamide + lithium bromide/nitrate) melts

    Science.gov (United States)

    Guchhait, Biswajit; Daschakraborty, Snehasis; Biswas, Ranjit

    2012-05-01

    Time-resolved fluorescence Stokes shift and anisotropy measurements using a solvation probe in [0.78CH3CONH2 + 0.22{f LiBr + (1-f) LiNO3}] melts reveal a strong decoupling of medium dynamics from viscosity. Interestingly, this decoupling has been found to occur at temperatures ˜50-100 K above the glass transition temperatures of the above melt at various anion concentrations (fLiBr). The decoupling is reflected via the following fractional viscosity dependence (η) of the measured average solvation and rotation times (⟨τs⟩ and ⟨τr⟩, respectively): ⟨τx⟩ ∝ (η/T)p (x being solvation or rotation), with p covering the range, 0.20 < p < 0.70. Although this is very similar to what is known for deeply supercooled liquids, it is very surprising because of the temperature range at which the above decoupling occurs for these molten mixtures. The kinship to the supercooled liquids is further exhibited via p which is always larger for ⟨τr⟩ than for ⟨τs⟩, indicating a sort of translation-rotation decoupling. Multiple probes have been used in steady state fluorescence measurements to explore the extent of static heterogeneity. Estimated experimental dynamic Stokes shift for coumarin 153 in these mixtures lies in the range, 1000 < Δνt/cm-1 < 1700, and is in semi-quantitative agreement with predictions from our semi-molecular theory. The participation of the fluctuating density modes at various length-scales to the observed solvation times has also been investigated.

  14. Perubahan suhu transisi kaca dan massa resin akrilik heat cured akibat kelembaban dan lama penyimpanan (Changes in glass transition temperature and heat cured acrylic resin mass due to moisture and storage time

    Directory of Open Access Journals (Sweden)

    Sherman Salim

    2014-09-01

    Full Text Available Background: Acrylic resins, especially poly methyl methacrylate (PMMA was introduced in 1937. Acrylic resin has favorable properties, among others, aesthetic, color and texture similar to that of the gingival aesthetic in the mouth, relatively low water absorption and dimensional changes. However, some studies suggest that the duration of storage of acrylic resin will affect the changes in the glass transition temperature and the mass of acrylic resin. Purpose: The objective of this research was to study the effect of humidity and storage time led to changes in the glass transition temperature and the mass of the acrylic resin. Methods: The research method is experimental laboratory. Acrylic resin specimens are kept in conditions of humidity of 90%, 70%, 40% and 30% for 24 hours, one week, one month and two months. In this study used three methods of curing, namely conventional JIs, 24-hour curing at 70 °C and using the microwave. Results: Low humidity causes changes in the glass transition temperature and the mass of acrylic resin. Longer storage of acrylic resins in low humidity, can affect change greater than the glass transition temperature and the mass of acrylic resin. Conclusion: It can be concluded that the humidity and longer storage of acrylic resins can affect the glass transition temperature and a change in mass.Latar belakang: Resin akrilik terutama poli metil metakrilat (PMMA telah diperkenalkan pada tahun 1937. Resin akrilik memiliki sifat yang menguntungkan antara lain estetis, warna dan tekstur mirip dengan gingiva sehingga estetik di dalam mulut baik, daya serap air relatif rendah dan perubahan dimensi kecil. Akan tetapi, dari beberapa penelitian menyatakan bahwa lamanya waktu penyimpanan resin akrilik akan berpengaruh pada perubahan suhu transisi kaca dan massa resin akrilik. Tujuan: Tujuan dari penelitian ini adalah untuk mempelajari pengaruh kelembaban dan waktu penyimpanan yang menyebabkan perubahan suhu transisi kaca dan

  15. Fluctuation relations between hierarchical kinetically equivalent networks with Arrhenius-type transitions and their roles in systems and structural biology

    Science.gov (United States)

    Deng, De-Ming; Lu, Yi-Ta; Chang, Cheng-Hung

    2017-06-01

    The legality of using simple kinetic schemes to determine the stochastic properties of a complex system depends on whether the fluctuations generated from hierarchical equivalent schemes are consistent with one another. To analyze this consistency, we perform lumping processes on the stochastic differential equations and the generalized fluctuation-dissipation theorem and apply them to networks with the frequently encountered Arrhenius-type transition rates. The explicit Langevin force derived from those networks enables us to calculate the state fluctuations caused by the intrinsic and extrinsic noises on the free energy surface and deduce their relations between kinetically equivalent networks. In addition to its applicability to wide classes of network related systems, such as those in structural and systems biology, the result sheds light on the fluctuation relations for general physical variables in Keizer's canonical theory.

  16. OPTIMIZING PEDESTRIAN-FRIENDLY WALKING PATH FOR THE FIRST AND LAST MILE TRANSIT JOURNEY BY USING THE ANALYTICAL NETWORK PROCESS (ANP DECISION MODEL AND GIS NETWORK ANALYSIS

    Directory of Open Access Journals (Sweden)

    N. Naharudin

    2017-10-01

    Full Text Available Every transit trip begins and ends with pedestrian travel. People need to walk to access the transit services. However, their choice to walk depends on many factors including the connectivity, level of comfort and safety. These factors can influence the pleasantness of riding the transit itself, especially during the first/last mile (FLM journey. This had triggered few studies attempting to measure the pedestrian-friendliness a walking environment can offer. There were studies that implement the pedestrian experience on walking to assess the pedestrian-friendliness of a walking environment. There were also studies that use spatial analysis to measure it based on the path connectivity and accessibility to public facilities and amenities. Though both are good, but the perception-based studies and spatial analysis can be combined to derive more holistic results. This paper proposes a framework for selecting a pedestrian-friendly path for the FLM transit journey by using the two techniques (perception-based and spatial analysis. First, the degree of importance for the factors influencing a good walking environment will be aggregated by using Analytical Network Process (ANP decision rules based on people’s preferences on those factors. The weight will then be used as attributes in the GIS network analysis. Next, the network analysis will be performed to find a pedestrian-friendly walking route based on the priorities aggregated by ANP. It will choose routes passing through the preferred attributes accordingly. The final output is a map showing pedestrian-friendly walking path for the FLM transit journey.

  17. Optimizing Pedestrian-Friendly Walking Path for the First and Last Mile Transit Journey by Using the Analytical Network Process (anp) Decision Model and GIS Network Analysis

    Science.gov (United States)

    Naharudin, N.; Ahamad, M. S. S.; Sadullah, A. F. M.

    2017-10-01

    Every transit trip begins and ends with pedestrian travel. People need to walk to access the transit services. However, their choice to walk depends on many factors including the connectivity, level of comfort and safety. These factors can influence the pleasantness of riding the transit itself, especially during the first/last mile (FLM) journey. This had triggered few studies attempting to measure the pedestrian-friendliness a walking environment can offer. There were studies that implement the pedestrian experience on walking to assess the pedestrian-friendliness of a walking environment. There were also studies that use spatial analysis to measure it based on the path connectivity and accessibility to public facilities and amenities. Though both are good, but the perception-based studies and spatial analysis can be combined to derive more holistic results. This paper proposes a framework for selecting a pedestrian-friendly path for the FLM transit journey by using the two techniques (perception-based and spatial analysis). First, the degree of importance for the factors influencing a good walking environment will be aggregated by using Analytical Network Process (ANP) decision rules based on people's preferences on those factors. The weight will then be used as attributes in the GIS network analysis. Next, the network analysis will be performed to find a pedestrian-friendly walking route based on the priorities aggregated by ANP. It will choose routes passing through the preferred attributes accordingly. The final output is a map showing pedestrian-friendly walking path for the FLM transit journey.

  18. Hybrid Evolutionary Metaheuristics for Concurrent Multi-Objective Design of Urban Road and Public Transit Networks

    NARCIS (Netherlands)

    Miandoabchi, Elnaz; Farahani, Reza Zanjirani; Dullaert, Wout; Szeto, W. Y.

    This paper addresses a bi-modal multi-objective discrete urban road network design problem with automobile and bus flow interaction. The problem considers the concurrent urban road and bus network design in which the authorities play a major role in designing bus network topology. The road network

  19. Fluoride-containing bioactive glasses: Glass design, structure, bioactivity, cellular interactions, and recent developments

    Energy Technology Data Exchange (ETDEWEB)

    Shah, Furqan A., E-mail: furqan.ali.shah@biomaterials.gu.se

    2016-01-01

    Bioactive glasses (BGs) are known to bond to both hard and soft tissues. Upon exposure to an aqueous environment, BG undergoes ion exchange, hydrolysis, selective dissolution and precipitation of an apatite layer on their surface, which elicits an interfacial biological response resulting in bioactive fixation, inhibiting further dissolution of the glass, and preventing complete resorption of the material. Fluorine is considered one of the most effective in-vivo bone anabolic factors. In low concentrations, fluoride ions (F{sup −}) increase bone mass and mineral density, improve the resistance of the apatite structure to acid attack, and have well documented antibacterial properties. F{sup −} ions may be incorporated into the glass in the form of calcium fluoride (CaF{sub 2}) either by part-substitution of network modifier oxides, or by maintaining the ratios of the other constituents relatively constant. Fluoride-containing bioactive glasses (FBGs) enhance and control osteoblast proliferation, differentiation and mineralisation. And with their ability to release fluoride locally, FBGs make interesting candidates for various clinical applications, dentinal tubule occlusion in the treatment of dentin hypersensitivity. This paper reviews the chemistry of FBGs and the influence of F{sup −} incorporation on the thermal properties, bioactivity, and cytotoxicity; and novel glass compositions for improved mechanical properties, processing, and bioactive potential. - Highlights: • Fluoride ions form charged CaF{sup +} species rather than Si–F bonds. • Fluoride incorporation lowers glass transition and crystallisation temperatures. • Oxynitride and oxyfluoronitride glasses with superior mechanical properties • Mixed-alkali and alkali-free compositions with better processing characteristics.

  20. Making Glass

    OpenAIRE

    Parker, K.; Moore, S.

    2012-01-01

    Journal article comproses: critical reflection, 'Making Glass', HD film with monologue, followed by 'Glass', HD film, stop-motion microscopic and macro photographs In this practice-led exploration of modalities of écriture féminine, I map the shifting subjectivities generated by Glass, a stop-motion animation that performs femininity through close examination and play with glass fragments found among the briny debris of an urban beach. University of Winchester

  1. Phase Transition with the Berezinskii-Kosterlitz-Thouless Singularity in the Ising Model on a Growing Network

    Science.gov (United States)

    Bauer, M.; Coulomb, S.; Dorogovtsev, S. N.

    2005-05-01

    We consider the ferromagnetic Ising model on a highly inhomogeneous network created by a growth process. We find that the phase transition in this system is characterized by the Berezinskii-Kosterlitz-Thouless singularity, although critical fluctuations are absent and the mean-field description is exact. Below this infinite order transition, the magnetization behaves as exp((-const/√(Tc-T)). We show that the critical point separates the phase with the power-law distribution of the linear response to a local field and the phase where this distribution rapidly decreases. We suggest that this phase transition occurs in a wide range of cooperative models with a strong infinite-range inhomogeneity.

  2. STUDY OF FLUORIDE GLASSES DEVITRIFICATION-BASED ...

    African Journals Online (AJOL)

    4 mars 2013 ... ABSTRACT. The kinetics of devitrification of fluoride glasses stabilized by magnesium fluoride when heated for some time between the glass transition and melting temperatures. The crystallization kinetics of AlF3-YF3-PbF2-CdF2-MgF2 glass prepared by melting the halide powders were studied by.

  3. Some recent developments in spin glasses

    Indian Academy of Sciences (India)

    I give some experimental and theoretical background to spin glasses, and then discuss the nature of the phase transition in spin glasses with vector spins. Results of Monte Carlo simulations of the Heisenberg spin glass model in three dimensions are presented. A finite-size scaling analysis of the correlation length of the ...

  4. Some recent developments in spin glasses

    Indian Academy of Sciences (India)

    Abstract. I give some experimental and theoretical background to spin glasses, and then discuss the nature of the phase transition in spin glasses with vector spins. Results of Monte Carlo simulations of the Heisenberg spin glass model in three dimensions are presented. A finite-size scaling analysis of the correlation length ...

  5. Comparative empirical analysis of flow-weighted transit route networks in R-space and evolution modeling

    Science.gov (United States)

    Huang, Ailing; Zang, Guangzhi; He, Zhengbing; Guan, Wei

    2017-05-01

    Urban public transit system is a typical mixed complex network with dynamic flow, and its evolution should be a process coupling topological structure with flow dynamics, which has received little attention. This paper presents the R-space to make a comparative empirical analysis on Beijing’s flow-weighted transit route network (TRN) and we found that both the Beijing’s TRNs in the year of 2011 and 2015 exhibit the scale-free properties. As such, we propose an evolution model driven by flow to simulate the development of TRNs with consideration of the passengers’ dynamical behaviors triggered by topological change. The model simulates that the evolution of TRN is an iterative process. At each time step, a certain number of new routes are generated driven by travel demands, which leads to dynamical evolution of new routes’ flow and triggers perturbation in nearby routes that will further impact the next round of opening new routes. We present the theoretical analysis based on the mean-field theory, as well as the numerical simulation for this model. The results obtained agree well with our empirical analysis results, which indicate that our model can simulate the TRN evolution with scale-free properties for distributions of node’s strength and degree. The purpose of this paper is to illustrate the global evolutional mechanism of transit network that will be used to exploit planning and design strategies for real TRNs.

  6. NEW ERBIUM DOPED ANTIMONY GLASSES FOR LASER AND GLASS AMPLIFICATION

    Directory of Open Access Journals (Sweden)

    B. Tioua

    2015-07-01

    Full Text Available Because of the special spectroscopic properties of the rare earth ions, rare earth doped glasses are widely used in bulk and fiber lasers or amplifiers. The modelling of lasers and searching for new laser transitions require a precise knowledge of the spectroscopic properties of rare earth ions in different host glasses. In this poster will offer new doped erbium glasses synthesized in silicate crucibles were obtained in the combination Sb2O3-WO3-Na2O. Several properties are measured and correlated with glass compositions. The absorption spectral studies have been performed for erbium doped glasses. The intensities of various absorption bands of the doped glasses are measured and the Judd-Ofelt parameters have been computed. From the theory of Judd-Ofelt, various radiative properties, such as transition probability, branching ratio and radiative life time for various emission levels of these doped glasses have been determined and reported. These results confirm the ability of antimony glasses for glass amplification.

  7. Super ionic conductive glass

    Science.gov (United States)

    Susman, S.; Volin, K.J.

    Described is an ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A/sub 1 + x/D/sub 2-x/3/Si/sub x/P/sub 3 - x/O/sub 12 - 2x/3/, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  8. Sampling, storage, and analysis of C2-C7 non-methane hydrocarbons from the US National Oceanic and Atmospheric Administration Cooperative Air Sampling Network glass flasks.

    Science.gov (United States)

    Pollmann, Jan; Helmig, Detlev; Hueber, Jacques; Plass-Dülmer, Christian; Tans, Pieter

    2008-04-25

    An analytical technique was developed to analyze light non-methane hydrocarbons (NMHC), including ethane, propane, iso-butane, n-butane, iso-pentane, n-pentane, n-hexane, isoprene, benzene and toluene from whole air samples collected in 2.5l-glass flasks used by the National Oceanic and Atmospheric Administration, Earth System Research Laboratory, Global Monitoring Division (NOAA ESRL GMD, Boulder, CO, USA) Cooperative Air Sampling Network. This method relies on utilizing the remaining air in these flasks (which is at below-ambient pressure at this stage) after the completion of all routine greenhouse gas measurements from these samples. NMHC in sample aliquots extracted from the flasks were preconcentrated with a custom-made, cryogen-free inlet system and analyzed by gas chromatography (GC) with flame ionization detection (FID). C2-C7 NMHC, depending on their ambient air mixing ratios, could be measured with accuracy and repeatability errors of generally storage (<10 pptv yr(-1)) of samples in these glass flasks. Results from flask NMHC analyses were compared to in-situ NMHC measurements at the Global Atmospheric Watch station in Hohenpeissenberg, Germany. This 9-months side-by-side comparison showed good agreement between both methods. More than 94% of all data comparisons for C2-C5 alkanes, isoprene, benzene and toluene fell within the combined accuracy and precision objectives of the World Meteorological Organization Global Atmosphere Watch (WMO-GAW) for NMHC measurements.

  9. Do Local Food Networks Foster Socio-Ecological Transitions towards Food Sovereignty? Learning from Real Place Experiences

    Directory of Open Access Journals (Sweden)

    Juliana Lutz

    2013-11-01

    Full Text Available Drawing on transition theory, we conceptualize local food networks as innovations that initially function and develop in local niches within a given food regime. As niche-innovations local food networks induce socio-ecological changes on the local level and they have the potential to foster wider transformations of the dominant food regime. Many local food networks adopt the concept of food sovereignty as a kind of “leitmotif”. At the core of this concept lies the question of how to create an agro-food system that, (i allows for democratic participation and civic engagement in food production, and (ii sets up new relationships that avoid social inequity and the exploitation of both humans and nature. In this paper we shed light on how the Austrian local food network “SpeiseLokal” addresses the challenge of operationalizing the concept of food sovereignty. The case study captures the strategies which local food networks embark on and depicts the difficulties they encounter. The paper aims to identify critical points of intersection that either strengthen or constrain local food networks from becoming established, operating, and up-scaling in the ways they wish; that is, in accordance with the principles and aims of food sovereignty, while avoiding a later assimilation into the dominant food regime.

  10. Compositional modification of Se-Ge-Sb chalcogenide glasses by addition of arsenic element

    Science.gov (United States)

    Ghayebloo, M.; Tavoosi, M.; Rezvani, M.

    2017-06-01

    The modification of structural, thermal and optical properties of Se-Ge-Sb glasses by addition of arsenic element was the goal of this study. In this regards, six different glasses of Se60Ge40-xSb5Asx (0 ≤ x ≤ 15) were prepared by conventional melt quenching technique in quartz ampoule. The produced samples were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), UV-Vis-NIR spectrophotometer, Fourier transform infrared (FTIR) and Raman spectroscopy. The fundamental absorption edge for of the glasses was analyzed in terms of the theory proposed by Davis and Mott. Based on the obtained results, the glass transition temperature, optical energy gap and Urbach energy of prepared glasses in this alloying system were in the range of 325-380 °C, 1.43-1.64 eV and 0.03-0.3547 eV, respectively. The as prepared glasses show anomalous behavior at 5-7.5 mole% of arsenic for the glass transition temperature, transmittance, absorption edge, optical energy gap and Urbach energy. Based on the Raman spectra, the structural analysis indicates that, increasing the network connectivity upon increasing the arsenic content up to 7.5 mole% is the main reason of anomalous behavior in Se60Ge40-xSb5Asx (0 ≤ x ≤ 15) system.

  11. Motif-role-fingerprints: the building-blocks of motifs, clustering-coefficients and transitivities in directed networks.

    Directory of Open Access Journals (Sweden)

    Mark D McDonnell

    Full Text Available Complex networks are frequently characterized by metrics for which particular subgraphs are counted. One statistic from this category, which we refer to as motif-role fingerprints, differs from global subgraph counts in that the number of subgraphs in which each node participates is counted. As with global subgraph counts, it can be important to distinguish between motif-role fingerprints that are 'structural' (induced subgraphs and 'functional' (partial subgraphs. Here we show mathematically that a vector of all functional motif-role fingerprints can readily be obtained from an arbitrary directed adjacency matrix, and then converted to structural motif-role fingerprints by multiplying that vector by a specific invertible conversion matrix. This result demonstrates that a unique structural motif-role fingerprint exists for any given functional motif-role fingerprint. We demonstrate a similar result for the cases of functional and structural motif-fingerprints without node roles, and global subgraph counts that form the basis of standard motif analysis. We also explicitly highlight that motif-role fingerprints are elemental to several popular metrics for quantifying the subgraph structure of directed complex networks, including motif distributions, directed clustering coefficient, and transitivity. The relationships between each of these metrics and motif-role fingerprints also suggest new subtypes of directed clustering coefficients and transitivities. Our results have potential utility in analyzing directed synaptic networks constructed from neuronal connectome data, such as in terms of centrality. Other potential applications include anomaly detection in networks, identification of similar networks and identification of similar nodes within networks. Matlab code for calculating all stated metrics following calculation of functional motif-role fingerprints is provided as S1 Matlab File.

  12. Reflections on the role of energy network companies in the energy transition

    NARCIS (Netherlands)

    Steenhuisen, B.M.; De Bruijne, M.L.C.

    2015-01-01

    Background Energy network companies are commonly attributed the public task to help society in becoming greener in the domain of energy. This extra public task has high costs and comes with high uncertainties. It may also compete with existing public tasks of network companies. When network

  13. Spectroscopic and optical properties of Nd{sup 3+} doped fluorine containing alkali and alkaline earth zinc-aluminophosphate optical glasses

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasa Rao, A., E-mail: drsrallam@yahoo.co.i [Department of Physics, K.L. University, Green Fields, Vaddeswaram, 522 502 Guntur (Dt.), A.P. (India); Rupa Venkateswara Rao, B.; Prasad, M.V.V.K.S.; Shanmukha Kumar, J.V. [Department of Physics, K.L. University, Green Fields, Vaddeswaram, 522 502 Guntur (Dt.), A.P. (India); Jayasimhadri, M. [Department of Physics, Changwon National University, 9 Sarimdong, Changwon, Kyongnam 641 773 (Korea, Republic of); Rao, J.L. [Department of Physics, Sri Venkateswara University, Tirupati 517 502, A.P. (India); Chakradhar, R.P.S. [Glass Technology Laboratory, Central Glass and Ceramic Research Institute (CSIR), Kolkata 700 032 (India)

    2009-11-01

    Nd{sup 3+} doped fluorine containing zinc-aluminophosphate glasses have been prepared with alkali and alkaline earth content to understand the effect of network modifiers on radiative process. The physical and optical properties of these glasses have been evaluated. The Judd-Ofelt model for the intensity analysis of induced electric dipole transitions has been applied to the measured oscillator strengths of the absorption bands to determine the three phenomenological intensity parameters OMEGA{sub 2}, OMEGA{sub 4} and OMEGA{sub 6} for each glass. Using these parameters, transition probability (A), total transition probability (A{sub T}), branching ratios (beta{sub R}) radiative life times (tau{sub R}) and integrated cross-section (sigma{sub a}) for the stimulated emission have been theoretically calculated for certain excited Nd{sup 3+} fluorescent levels. From the obtained results the conclusion is made about the possibility of using these glasses as laser material.

  14. Foaming Glass Using High Pressure Sintering

    DEFF Research Database (Denmark)

    Østergaard, Martin Bonderup; Petersen, Rasmus Rosenlund; König, Jakob

    Foam glass is a high added value product which contributes to waste recycling and energy efficiency through heat insulation. The foaming can be initiated by a chemical or physical process. Chemical foaming with aid of a foaming agent is the dominant industrial process. Physical foaming has two...... variations. One way is by saturation of glass melts with gas. The other involves sintering of powdered glass under a high gas pressure resulting in glass pellets with high pressure bubbles entrapped. Reheating the glass pellets above the glass transition temperature under ambient pressure allows the bubbles...

  15. Structural relaxation in annealed hyperquenched basaltic glasses

    DEFF Research Database (Denmark)

    Guo, Xiaoju; Mauro, John C.; Potuzak, M.

    2012-01-01

    The enthalpy relaxation behavior of hyperquenched (HQ) and annealed hyperquenched (AHQ) basaltic glass is investigated through calorimetric measurements. The results reveal a common onset temperature of the glass transition for all the HQ and AHQ glasses under study, indicating that the primary...... relaxation is activated at the same temperature regardless of the initial departure from equilibrium. The analysis of secondary relaxation at different annealing temperatures provides insights into the enthalpy recovery of HQ glasses....

  16. Relaxation Pathways in Metallic Glasses

    Science.gov (United States)

    Gallino, Isabella; Busch, Ralf

    2017-11-01

    At temperatures below the glass transition temperature, physical properties of metallic glasses, such as density, viscosity, electrical resistivity or enthalpy, slowly evolve with time. This is the process of physical aging that occurs among all types of glasses and leads to structural changes at the microscopic level. Even though the relaxation pathways are ruled by thermodynamics as the glass attempts to re-attain thermodynamic equilibrium, they are steered by sluggish kinetics at the microscopic level. Understanding the structural and dynamic pathways of the relaxing glassy state is still one of the grand challenges in materials physics. We review some of the recent experimental advances made in understanding the nature of the relaxation phenomenon in metallic glasses and its implications to the macroscopic and microscopic properties changes of the relaxing glass.

  17. Compositional dependence of structural transition pressures in amorphous phases with mantle-related compositions

    Science.gov (United States)

    Shim, Sang-Heon; Catalli, Krystle

    2009-06-01

    Properties of silicate melts are key to understanding the evolution of the mantles of the Earth and terrestrial planets. Although remarkable progress has been made in first-principle calculations for melts in recent years, structural measurements of silicate melts at in situ high P-T remain one of the most challenging tasks. The study of glasses, kinetically frozen melts, at high pressure can provide valuable insights into related melts in the mantle. We report Raman scattering of MgSiO 3 glass revealing a structural transition at 19-38 GPa, which is associated with increases in the Si sbnd O coordination number, and another transition at 65-70 GPa. However, in CaSiO 3 and Mg 2SiO 4 glasses, the former transition occurs at higher pressures by 5-10 GPa and the latter transition is not observed to our maximum pressure (80 GPa), indicating that a less polymerized Si sbnd O network increases the transition pressures. Our results suggest that the pressure for the structural transitions in these glasses is influenced strongly by the concentration of network former cations and the ionic size of the network modifiers. This observation may have important implications for compositional differentiation in the early magma ocean and the present-day mantle.

  18. Adolescent Mothers in a Transitional Living Facility: An Exploratory Study of Support Networks and Attachment Patterns

    Science.gov (United States)

    Schwartz, Ann E.; McRoy, Ruth G.; Downs, A. Chris

    2004-01-01

    Most of the research literature on attachment and adolescent transitions has addressed youth in family settings. This article explores these issues with a sample of 25 pregnant and parenting teens living in a transitional shelter. Using case records and interview data as well as results of standardized measures of depression, self-esteem, child…

  19. Study of nanostructural behavior and transport properties of BaTiO{sub 3} doped vanadate glasses and glass-ceramics dispersed with ferroelectric nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Al-Assiri, M.S., E-mail: msassiri@kku.edu.s [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); El-Desoky, M.M., E-mail: mmdesoky@gmail.co [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); Department of Physics, Faculty of Education, Suez Canal University, Al-Arish (Egypt); Al-Hajry, A.; Al-Shahrani, A.; Al-Mogeeth, A.M. [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); Bahgat, A.A., E-mail: alaabahgat@yahoo.co [Department of Physics, Faculty of Science, King Khaled University, P.O. Box 9004, Abha (Saudi Arabia); Department of Physics, Faculty of Science, Al-Azhar University, Nasr City 11884, Cairo (Egypt)

    2009-05-01

    Nanostructural behavior and electrical properties of BaTiO{sub 3}-(100-x)V{sub 2}O{sub 5} glasses (where x=35, 40, 45 and 50 mol%) and their corresponding nanocrystalline glass-ceramics were studied. Scanning electron microscopy (SEM) of quenched glasses, confirm the amorphous nature of the glasses present. Also, the overall features of X-ray diffraction (XRD) confirm the amorphous nature of the present glasses. Transmission electron micrograph (TEM) and XRD of the corresponding heat treated sample indicate nanocrystals with a particle size of 20-35 nm. It was found that density (d) increases gradually with the increase of the BaTiO{sub 3} content in the nanocrystalline glass-ceramics. It is observed that the conductivity of the nanocrystalline glass-ceramics is higher than that of the corresponding glassy phase. The high conductivity of these nanocrystalline glass-ceramics is considered to be due to the presence of nanocrystals with a particle size of 20-35 nm. This is attributed to the formation of extensive and dense network of electronic conduction paths which are situated between V{sub 2}O{sub 5} nanocrystals and on their surface. The electrical conductivity of this system can be fitted with Mott's model of nearest neighbor hopping at high temperature. From the best fits, reasonable values of various small polaron hopping (SPH) parameters are obtained. From dielectric permittivity of the as-cast glass samples, no ferroelectric behavior can be observed. Also, the dielectric permittivity (epsilon) values of these glasses are found to be very high compared to familiar vanadium containing glasses. By annealing the glass system around 450 deg. C for 1 h in air, nanocrystalline BaTiO{sub 3} phase precipitates and the corresponding nanocrystalline glass-ceramics showed average broad peak around 352 K in the dielectric permittivity (epsilon). It is interesting to note that pure nanocrystalline BaTiO{sub 3} phase with average particle size less than 100 nm also

  20. FROM CENTRALITY TO INTERMEDIACY IN THE GLOBAL TRANSPORT NETWORK? UKRAINE’S TRIALS AND TRIBULATIONS AS A POTENTIAL TRANSIT COUNTRY

    Directory of Open Access Journals (Sweden)

    Kateryna Grushevska

    2016-09-01

    Full Text Available Ukraine currently is in a very complex economic and political situation, which in itself represents a pivotal point for its further recovery and evolution. Nevertheless, the rise of economic centres in Eastern and Central Europe creates opportunities for Ukraine to develop short sea shipping services (via the Black Sea and water and land-based hub-feeder networks to and from these areas. This paper provides an academic study of the potential of Ukraine in taking up a role in emerging distribution systems in East and Central Europe facilitating the cargo transportation from regions such as Central Asia, Caucasus and even more distant overseas areas. Based on the concepts of intermediacy and centrality as introduced by Fleming and Hayuth (1994 the role of Ukraine in the global and regional transport networks will be analysed in order to assess to what extent particular regions in Ukraine can serve as important gateways to Europe. An extensive review and synthesis of the published studies during the last 20 years on Ukraine’s transit flows and transit function will be presented. The obtained results will be contraposed to the results obtained from about 20 interviews conducted with transport business representatives in Ukraine and abroad. Based on the outcome of bottlenecks and deficiencies in Ukraine’s transport system, the optimal road map for Ukraine’s integration into the European transport network will be defined.

  1. Crystallization study of Te–Bi–Se glasses

    Indian Academy of Sciences (India)

    For a memory/switching material, the thermal stability and ease of glass formation are of crucial importance. The glass transition temperature, , increases slightly with the variation of Bi content. From the heating rate dependence of , the activation energy for glass transition () has been evaluated. The results are ...

  2. A Comprehensive Mapping of High-Level Men’s Volleyball Gameplay through Social Network Analysis: Analysing Serve, Side-Out, Side-Out Transition and Transition

    Directory of Open Access Journals (Sweden)

    Manuel Loureiro

    2017-09-01

    Full Text Available A deeper understanding of the factors behind performance and their interactions is essential to promote better training practices. Notwithstanding, the focus often relies on the outcomes of players’ actions (e.g., efficacy rates, whereas the nature and variations of particular classes of actions remain largely unexplored. Our purpose was to conduct a systemic analysis of categorical game variables and their interactions using Social Network Analysis. Game actions were counted as nodes and their interactions as edges. Eigenvector centrality values were calculated for each node. Eight matches of the Men’s World Cup 2015 were analysed, composing a total of 27 sets (1,209 rallies. Four game complexes were considered: Complex 0 (Serve, Complex I (Side-out, Complex II (Side-out transition and Complex III (Transition. Results showed that teams frequently play in-system when in Complex I (i.e. under ideal conditions, but present reduced variation with regard to attack zones and tempos, whereas in Complex II teams most often play out-of-system. Based on these findings, it was concluded that practicing with non-ideal conditions is paramount for good performance in Complex II. Furthermore, most literature combines Complex II and Complex III as a single unit (counter-attack; however, our results reinforce the notion that these two game complexes differ and should be analysed separately.

  3. The Transition from Alliance Networks to Multilateral Alliances in the Global Airline Industry

    Directory of Open Access Journals (Sweden)

    Sergio G. Lazzarini

    2008-01-01

    Full Text Available This study examines conditions in which alliance networks (informal webs of bilateral entanglements between firms may or may not evolve into multilateral alliances (broad, formal multiple-firm arrangements. I offer a theory to explain the formation of multilateral alliances based on both the resource profile and the structure of existing interfirm networks, and provide an initial test of that theory in the context of the global airline industry. Using data from 75 global airlines and their alliances, I propose a methodology to retrieve samples of alliance networks and then use regression analysis to assess how the resource profile and the structure of these networks influence their formalization into multilateral alliances. I find that multilateral alliances are more likely to emerge when alliance networks exhibit high resource diversity and network structure characterized by moderate density and high centralization. Apparently, while highly sparse networks reduce actors’ awareness of their potential joint collaboration, highly dense or embedded networks substitute for the need for formal controls accompanying multilateral agreements. The effect of centralization suggests that the formation of multilateral alliances tends to be triggered by leading actors directly connected to other network members.

  4. Recycle Glass in Foam Glass Production

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    The foam glass industry turn recycle glass into heat insulating building materials. The foaming process is relative insensitive to impurities in the recycle glass. It is therefore considered to play an important role in future glass recycling. We show and discuss trends of use of recycled glasses...... in foam glass industry and the supply sources and capacity of recycle glass....

  5. Recycle Glass in Foam Glass Production

    OpenAIRE

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    2014-01-01

    The foam glass industry turn recycle glass into heat insulating building materials. The foaming process is relative insensitive to impurities in the recycle glass. It is therefore considered to play an important role in future glass recycling. We show and discuss trends of use of recycled glasses in foam glass industry and the supply sources and capacity of recycle glass.

  6. Natural analogues of nuclear waste glass corrosion.

    Energy Technology Data Exchange (ETDEWEB)

    Abrajano, T.A. Jr.; Ebert, W.L.; Luo, J.S.

    1999-01-06

    This report reviews and summarizes studies performed to characterize the products and processes involved in the corrosion of natural glasses. Studies are also reviewed and evaluated on how well the corrosion of natural glasses in natural environments serves as an analogue for the corrosion of high-level radioactive waste glasses in an engineered geologic disposal system. A wide range of natural and experimental corrosion studies has been performed on three major groups of natural glasses: tektite, obsidian, and basalt. Studies of the corrosion of natural glass attempt to characterize both the nature of alteration products and the reaction kinetics. Information available on natural glass was then compared to corresponding information on the corrosion of nuclear waste glasses, specifically to resolve two key questions: (1) whether one or more natural glasses behave similarly to nuclear waste glasses in laboratory tests, and (2) how these similarities can be used to support projections of the long-term corrosion of nuclear waste glasses. The corrosion behavior of basaltic glasses was most similar to that of nuclear waste glasses, but the corrosion of tektite and obsidian glasses involves certain processes that also occur during the corrosion of nuclear waste glasses. The reactions and processes that control basalt glass dissolution are similar to those that are important in nuclear waste glass dissolution. The key reaction of the overall corrosion mechanism is network hydrolysis, which eventually breaks down the glass network structure that remains after the initial ion-exchange and diffusion processes. This review also highlights some unresolved issues related to the application of an analogue approach to predicting long-term behavior of nuclear waste glass corrosion, such as discrepancies between experimental and field-based estimates of kinetic parameters for basaltic glasses.

  7. Cosmos & Glass

    DEFF Research Database (Denmark)

    Beim, Anne

    1996-01-01

    The article unfolds the architectural visions of glass by Bruno Taut. It refers to inspirations by Paul Sheerbart and litterature and the Crystal Chain, also it analyses the tectonic univers that can be found in the glass pavillion for the Werkbund exposition in Cologne.......The article unfolds the architectural visions of glass by Bruno Taut. It refers to inspirations by Paul Sheerbart and litterature and the Crystal Chain, also it analyses the tectonic univers that can be found in the glass pavillion for the Werkbund exposition in Cologne....

  8. Impact of cationic diffusion on properties of iron-bearing glass fibres

    DEFF Research Database (Denmark)

    Smedskjaer, Morten M.; Yue, Yuanzheng; Deubener, Joachim

    2010-01-01

    A silica-rich surface layer of Fe3+-containing aluminosilicate glass fibres is created by means of an inward diffusion process of divalent network modifying cations. The latter is caused by the reduction of Fe3+ to Fe2+ when the fibres undergo a heat treatment at temperatures around the glass...... transition temperature (Tg) in a reducing H2/N2 atmosphere. The thickness of the surface layer can be adjusted by varying the temperature or the duration of the heat treatment. The reduction process has a significant impact on the glass transition and crystallization behaviour, high temperature stability...... (HTS), and chemical durability of the fibres. The reduction deteriorates the HTS of the fibres in argon due to the decrease of Tg and increase of the crystallization temperatures. However, the crystallization behaviour and HTS in air are not affected by the reduction. This is because a re-oxidation...

  9. Glass-Fiber Networks as an Orbit for Ions: Fabrication of Excellent Antistatic PP/GF Composites with Extremely Low Organic Salt Loadings.

    Science.gov (United States)

    Gu, Senlin; Zhu, Leon; Mercier, Claude; Li, Yongjin

    2017-05-31

    Polypropylene (PP)/glass fiber (GF) composites showing excellent antistatic performance were prepared by a simple melt process blending PP with GF and a small amount of organic salts (OSs). Two types of OSs, tribuyl(octyl)phosphonium bis(trifloromethanesulfonyl)imide (TBOP-TFSI) and lithium bis(trifloromethanesulfonyl)imide (Li-TFSI), with equivalent anions were used as antistatic agents for the composites. It was found that the GF and OSs exhibited significant synergistic effects on the antistatic performance as well as the mechanical properties of the composites. On the one hand, the incorporation of GF significantly enhanced the electric conductivity of the composites at a constant OS loading. On the other hand, the two types of OSs improved the interfacial adhesion between the GF and the PP matrix, which led to an enhancement of the mechanical properties. This study showed that OSs had specific interactions with GFs and were absorbed exclusively on the GF surface. The GF network in the PP matrix provided perfect orbits for the movement of ions, inducing the excellent antistatic performance exhibited by the PP/GF composites at an OS loading of as low as 0.25 wt % when the GF formed a network in the PP matrix.

  10. Are the dynamics of silicate glasses and glass-forming liquids embedded in their elastic properties?

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Mauro, John C.

    According to the elastic theory of the glass transition, the dynamics of glasses and glass-forming liquids are controlled by the evolution of shear modulus. In particular, the elastic shoving model expresses dynamics in terms of an activation energy required to shove aside the surrounding atoms, ...

  11. From birth through transition to maturation : The evolution of technology-based alliance networks

    NARCIS (Netherlands)

    Gilsing, Victor; Cloodt, M.; Roijakkers, N.

    2016-01-01

    This article considers the evolution of interfirm networks within a context of technological change. More specifically, it studies the evolution of structural and positional embeddedness in a network of technology-based alliances when it moves from an early period of invention creation to a

  12. Transition from isotropic to digitated growth modulates network formation in Physarum polycephalum

    Science.gov (United States)

    Vogel, David; Gautrais, Jacques; Perna, Andrea; Sumpter, David J. T.; Deneubourg, Jean-Louis; Dussutour, Audrey

    2017-01-01

    Some organisms, including fungi, ants, and slime molds, explore their environment and forage by forming interconnected networks. The plasmodium of the slime mold Physarum polycephalum is a large unicellular amoeboid organism that grows a tubular spatial network through which nutrients, body mass, and chemical signals are transported. Individual plasmodia are capable of sophisticated behaviours such as optimizing their network connectivity and dynamics using only decentralized information processing. In this study, we used a population of plasmodia that interconnect through time to analyse the dynamical interactions between growth of individual plasmodia and global network formation. Our results showed how initial conditions, such as the distance between plasmodia, their size, or the presence and quality of food, affect the emerging network connectivity.

  13. Magnetic transitions and spin-glass reentrance in two-dimensional [MnII(TCNE)(NCMe)2]X (X = PF6,AsF6,SbF6) molecular magnets

    Science.gov (United States)

    Olson, C. S.; Heth, C. L.; Alema, F. L.; Lapidus, S. H.; Stephens, P. W.; Pokhodnya, K. I.

    2013-06-01

    The structural, spectroscopic and magnetic properties of the two-dimensional (2D) molecule-based magnets of [MnII(TCNE)(NCMe)2]X (X = PF6, AsF6, SbF6; TCNE = tetracyanoethylene, NCMe = acetonitrile) composition are reported. It is shown that the alteration of the interlayer distance by increasing the anion size has little effect on the critical magnetic ordering temperature, Tc, suggesting that it depends predominantly on the intra-plane magnetic exchange. The observed field-induced irreversibility in static magnetization, a slow decay of isothermal remanence below Tc, and the dynamic susceptibility data are in accord with a re-entrant spin-glass nature of the ground state of all materials. In contrast to the isostructural Fe-based magnets, in which strong magnetocrystalline anisotropy facilitates the finite temperature magnetic ordering with the magnetization easy axis perpendicular to the μ4-TCNE•- plane, in the studied Mn-based magnets the easy axis is canted away from the normal direction, due to a small magnetocrystalline anisotropy. The two magnetic transitions observed on cooling are assigned to the ferrimagnetic long-range ordering of the normal magnetization component followed by the re-entrant spin-glass type transition resulting from a random freezing of the in-plane magnetization component.

  14. Effects of the embedding kinetics on the surface nano-morphology of nano-grained Au and Ag films on PS and PMMA layers annealed above the glass transition temperature

    Science.gov (United States)

    Ruffino, F.; Torrisi, V.; Marletta, G.; Grimaldi, M. G.

    2012-06-01

    The morphology evolution of nano-grained Ag and Au films deposited on polystyrene (PS) and poly(methyl methacrylate) (PMMA) polymeric layers were studied, using the atomic force microscopy technique, when annealed above the polymers glass transition temperature. The main effects on the morphology changes were identified with those concerning the embedding kinetics of the Ag and Au nanoparticles in the PS or PMMA layers. The embedding process of the nanoparticles follows as a consequence of the long-range mobility of the polymeric chains above the glass transition temperature. In particular, the dependence of the nanoparticles mean height and surface density on the annealing time at various temperatures was quantified. The analyses of these behaviors allowed us: (1) to distinguish the overall embedding process in a first stage in which a thin wetting layer of the polymer coats the nanoparticles followed by a true embedding process of the nanoparticles into the polymer layer; (2) to evaluate the characteristic coating time for the Ag and Au nanoparticles in the PS and PMMA in the first stage; (3) to evaluate the characteristic embedding velocity for the Ag and Au nanoparticles in the PS and PMMA in the second stage; (4) to derive the activation energies for the embedding process of the Ag and Au nanoparticles in PS and PMMA; (5) to identify the embedding statistics of the Ag and Au nanoparticles in PS and PMMA with a "failure" Weibull statistics.

  15. Dynamics and robustness of the cardiac progenitor cell induced pluripotent stem cell network during cell phenotypes transition.

    Science.gov (United States)

    Yao, Yuangen; Ma, Chengzhang; Deng, Haiyou; Liu, Quan; Cao, Wei; Gui, Rong; Feng, Tianquan; Yi, Ming

    2017-02-01

    Robustness is a fundamental characteristic of biological systems since all living systems need to adapt to internal or external perturbations, unpredictable environments, stochastic events and unreliable components, and so on. A long-term challenge in systems biology is to reveal the origin of robustness underlying molecular regulator network. In this study, a simple Boolean model is used to investigate the global dynamic properties and robustness of cardiac progenitor cell (CPC) induced pluripotent stem cell network that governs reprogramming and directed differentiation process. It is demonstrated that two major attractors correspond to source and target cell phenotypes, respectively, and two dominating attracting trajectories characterise the biological pathways between two major cell phenotypes. In particular, the experimentally observed transition between different cell phenotypes can be reproduced and explained theoretically. Furthermore, the robustness of major attractors and trajectories is largely maintained with respect to small perturbations to the network. Taken together, the CPC-induced pluripotent stem cell network is extremely robustly designed for their functions.

  16. A gene regulatory network model for floral transition of the shoot apex in maize and its dynamic modeling.

    Science.gov (United States)

    Dong, Zhanshan; Danilevskaya, Olga; Abadie, Tabare; Messina, Carlos; Coles, Nathan; Cooper, Mark

    2012-01-01

    The transition from the vegetative to reproductive development is a critical event in the plant life cycle. The accurate prediction of flowering time in elite germplasm is important for decisions in maize breeding programs and best agronomic practices. The understanding of the genetic control of flowering time in maize has significantly advanced in the past decade. Through comparative genomics, mutant analysis, genetic analysis and QTL cloning, and transgenic approaches, more than 30 flowering time candidate genes in maize have been revealed and the relationships among these genes have been partially uncovered. Based on the knowledge of the flowering time candidate genes, a conceptual gene regulatory network model for the genetic control of flowering time in maize is proposed. To demonstrate the potential of the proposed gene regulatory network model, a first attempt was made to develop a dynamic gene network model to predict flowering time of maize genotypes varying for specific genes. The dynamic gene network model is composed of four genes and was built on the basis of gene expression dynamics of the two late flowering id1 and dlf1 mutants, the early flowering landrace Gaspe Flint and the temperate inbred B73. The model was evaluated against the phenotypic data of the id1 dlf1 double mutant and the ZMM4 overexpressed transgenic lines. The model provides a working example that leverages knowledge from model organisms for the utilization of maize genomic information to predict a whole plant trait phenotype, flowering time, of maize genotypes.

  17. Glass Glimpsed

    DEFF Research Database (Denmark)

    Lock, Charles

    2015-01-01

    Glass in poetry as it reflects the viewer and as its power of reflection are both reduced and enhanced by technology.......Glass in poetry as it reflects the viewer and as its power of reflection are both reduced and enhanced by technology....

  18. Spectroscopic properties and luminescence behaviour of europium doped lithium borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Anjaiah, J., E-mail: anjaiah.juluru@gmail.com [Department of Physics, The University of Dodoma, Tanzania, East Africa (Tanzania, United Republic of); Department of Physics, Geethanjali College of Engineering and Technology, Keesara, RR Dist., Hyderabad 501 301 (India); Laxmikanth, C. [Department of Physics, The University of Dodoma, Tanzania, East Africa (Tanzania, United Republic of); Veeraiah, N. [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar, Guntur 522 510, AP. (India)

    2014-12-01

    Li{sub 2}O–MO–B{sub 2}O{sub 3} (MO=ZnO, CaO and CdO) glasses doped with europium are prepared by using the melt quenching technique to study their absorption and luminescence properties to understand their lasing potentialities. The XRD pattern of the glasses confirmed the amorphous nature and the IR spectra reveal the presence of BO{sub 3} and BO{sub 4} units in the glass network. Judd–Ofelt intensity parameters Ω{sub λ} (λ=2, 4, 6) are evaluated from the intensities of various absorption bands of optical absorption spectra. The J–O parameters have been used to calculate transition probabilities (A), lifetime (τ{sub R}), branching ratios (β{sub R}) and stimulated emission cross-section (σ{sub P}) for the {sup 5}D{sub 0}→{sup 7}F{sub J} (J=1–4) transitions of the Eu{sup 3+} ions. The decay from the {sup 5}D{sub 0} level of Eu{sup 3+} ions in these glasses has been measured and analysed. Branching ratios and stimulated emission cross-sections measured for all these glasses show that the {sup 5}D{sub 0}→{sup 7}F{sub 1} transition under investigation has the potential for laser applications. The high stimulated emission cross-section and branching ratios from the present glasses suggests their potential for infra red lasers. The study of the thermoluminescence is also carried out and the data suggests that the CdBEu glass is suitable for thermoluminescence emission output among the three Eu{sup 3+} doped glasses.

  19. Spin glasses

    CERN Document Server

    Bovier, Anton

    2007-01-01

    Spin glass theory is going through a stunning period of progress while finding exciting new applications in areas beyond theoretical physics, in particular in combinatorics and computer science. This collection of state-of-the-art review papers written by leading experts in the field covers the topic from a wide variety of angles. The topics covered are mean field spin glasses, including a pedagogical account of Talagrand's proof of the Parisi solution, short range spin glasses, emphasizing the open problem of the relevance of the mean-field theory for lattice models, and the dynamics of spin glasses, in particular the problem of ageing in mean field models. The book will serve as a concise introduction to the state of the art of spin glass theory, usefull to both graduate students and young researchers, as well as to anyone curious to know what is going on in this exciting area of mathematical physics.

  20. Modification of epoxy-reinforced glass-cloth composites with a perfluorinated alkyl ether elastomer

    Science.gov (United States)

    Rosser, R. W.; Chen, T. S.; Taylor, M.

    1984-01-01

    A perfluorinated alkyl ether diacyl fluoride prepolymer (molecular weight about 1500) was coreacted with Epon 828 epoxy resin and diamino diphenyl sulfone to obtain an elastomer-toughened, glass-cloth composite. Improvements in flexural toughness, impact resistance, and water resistance, without loss of strength, modulus of elasticity or a lowering of the glass-transition temperature, were realized over those of the unmodified composite. Factors concerning optimization of the process are discussed. Results suggest that a simultaneously interpenetrating polymer network may be formed which gives rise to a measured improvement in composite mechanical properties.