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Sample records for ductile-brittle transition behavior

  1. Ductile-brittle transition behavior of tungsten under shock loading conditions

    SciTech Connect

    Lassila, D.H.; Gray, G.T. III

    1993-02-01

    In an effort to characterize the ductile-brittle transition behavior of warm forged tungsten under shock loading conditions, we have performed shock/soft-recovery experiments at 22 and 4000 C. Results at 22 C indicate that shock (19 GPa) induced strains appear to be accommodated by fracture processes, i.e. there were no indications of shock induced plastic deformation and the test sample was reduced to rubble. At 400 C, the test sample was recovered intact and the shock induced plasticity caused deformation banding and an increase in the dislocation density of the material. For reasons unclear, almost no change in the post shock mechanical behavior was observed, despite the significant changes in the microstructure. The results of these experiments demonstrate the principal of a ductile-brittle transition behavior of tungsten under uniaxial shock loading conditions and indicate that explosively driven deformation of tungsten of this material will result in pulverization due to shock loading.

  2. Ductile-brittle transition behavior of V-4Cr-4Ti irradiated in the dynamic helium charging experiment

    SciTech Connect

    Chung, H.M.; Nowicki, L.J.; Busch, D.E.

    1995-04-01

    The objective of this work is to determine the effect of simultaneous displacement damage and dynamically charged helium on the ductile-brittle transition behavior of V-4Cr-4Ti specimens irradiated to 18-31 dpa at 425-600{degrees}C in the Dynamic Helium Charging Experiment (DHCE).

  3. Linking Nanoscales and Dislocation Shielding to the Ductile-Brittle Transition of Silicon

    NASA Astrophysics Data System (ADS)

    Hintsala, Eric; Teresi, Claire; Gerberich, William W.

    2016-06-01

    The ductile-brittle transition of nano/microscale silicon is explored at low-temperature, high stress conditions. A pathway to eventual mechanism maps describing this ductile-brittle transition behavior using sample size, strain rate, and temperature is outlined. First, a discussion of variables controlling the BDT in silicon is given and discussed in the context of development of eventual modeling that could simultaneously incorporate all their effects. For description of energy dissipation by dislocation nucleation from a crack tip, three critical input parameters are identified: the effective stress, activation volume, and activation energy for dislocation motion. These are discussed individually relating to the controlling variables for the BDT. Lastly, possibilities for measuring these parameters experimentally are also described.

  4. Theory of nonequilibrium segregation in an Fe-Mn-Ni ternary alloy and a ductile-brittle-ductile transition

    SciTech Connect

    Heo, N.H.

    1996-07-01

    In an Fe-8Mn-7Ni ternary alloy, age-hardened by coherently formed face-centered tetragonal MnNi intermetallic compounds within the matrix, a modeling based on a regular solution model is performed to formulate the nonequilibrium grain boundary segregation behaviors of the alloying elements, followed by a ductile-brittle-ductile transition in the alloy. An equation is derived representing the segregation kinetics. It is confirmed from the calculations that the segregation behaviors of the elements are directly controlled by the precipitation reaction in the matrix. The nonequilibrium segregation behaviors are characterized by time-temperature diagrams, which show maximum segregation levels of the elements in an intermediate aging time and temperature range. The calculated results explain theoretically and semiquantitatively the relationship between the nonequilibrium segregation of the elements and the ductile-brittle-ductile transition.

  5. Ductile-brittle-ductile transition and grain boundary segregation of Mn and Ni in an Fe-6Mn-12Ni alloy

    SciTech Connect

    Heo, N.H.

    1996-05-15

    Recently, Heo and Lee reported a ductile-brittle-ductile (DBD) transition in an Fe-8Mn-7Ni ternary alloy, which was caused by manganese segregation to the grain boundaries and its desegregation into the matrix. More recently Heo theoretically analyzed the nonequilibrium segregation behaviors of the elements in the Fe-8Mn-7Ni alloy. The aim of the present study is to investigate whether other Fe-6Mn-12Ni ternary alloy also shows the ductile-brittle-ductile transition, and is additionally to ascertain whether calculated results are consistent with experimental data. The study encompasses experimental procedures and a modeling based on the previous research. A general discussion will show that such an approach allows a comprehensive understanding of the ductile-brittle-ductile transition in the Fe-Mn-Ni ternary alloys.

  6. PREDICTION OF CHARACTERISTIC LENGTH AND FRACTURE TOUGHNESS IN DUCTILE-BRITTLE TRANSITION

    SciTech Connect

    Lam, P

    2008-04-15

    Finite element method was used to analyze the three-point bend experimental data of A533B-1 pressure vessel steel obtained by Sherry, Lidbury, and Beardsmore [1] from -160 to -45 C within the ductile-brittle transition regime. As many researchers have shown, the failure stress ({sigma}{sub f}) of the material could be approximated as a constant. The characteristic length, or the critical distance (r{sub c}) from the crack tip, at which {sigma}{sub f} is reached, is shown to be temperature dependent based on the crack tip stress field calculated by the finite element method. With the J-A{sub 2} two-parameter constraint theory in fracture mechanics, the fracture toughness (J{sub C} or K{sub JC}) can be expressed as a function of the constraint level (A{sub 2}) and the critical distance r{sub c}. This relationship is used to predict the fracture toughness of A533B-1 in the ductile-brittle transition regime with a constant {sigma}{sub f} and a set of temperature-dependent r{sub c}. It can be shown that the prediction agrees well with the test data for wide range of constraint levels from shallow cracks (a/W= 0.075) to deep cracks (a/W= 0.5), where a is the crack length and W is the specimen width.

  7. Neutron irradiation effects on the ductile-brittle transition of ferritic/martensitic steels

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.

    1997-08-01

    Ferritic/martensitic steels such as the conventional 9Cr-1MoVNb (Fe-9Cr-1Mo-0.25V-0.06Nb-0.1C) and 12Cr-1MoVW (Fe-12Cr-1Mo-0.25V-0.5W-0.5Ni-0.2C) steels have been considered potential structural materials for future fusion power plants. The major obstacle to their use is embrittlement caused by neutron irradiation. Observations on this irradiation embrittlement is reviewed. Below 425-450{degrees}C, neutron irradiation hardens the steels. Hardening reduces ductility, but the major effect is an increase in the ductile-brittle transition temperature (DBTT) and a decrease in the upper-shelf energy, as measured by a Charpy impact test. After irradiation, DBTT values can increase to well above room temperature, thus increasing the chances of brittle rather than ductile fracture.

  8. Nonequilibrium grain-boundary segregation and ductile-brittle-ductile transition in Fe-Mn-Ni-Ti age-hardening alloy

    SciTech Connect

    Heo, N.H.

    1996-10-01

    Nonequilibrium segregation kinetics of alloying elements and a ductile-brittle-ductile transition behavior have been investigated in an Fe-8.4Mn-7.4Ni-1.7Ti alloy. The alloy experienced a ductile-brittle-ductile (DBD) transition during isothermal aging. In the brittle region, the alloy showed a decrease in intergranular fracture strength and a subsequent increase with aging time. This is due to the segregation of titanium to the grain boundaries and its desegregation into the matrix. The intergranular fracture strength was higher on the zero tensile elongation finish curve than on the start curve. This is because the grain-boundary segregation level of titanium is relatively lower on the finish curve. The lowest intergranular fracture strength increased with increasing aging temperature, which was attributed to a lower grain-boundary segregation level of titanium at higher temperature. Manganese caused an overall reduction in intergranular fracture strength and, as a result, the delayed occurrence of the zero tensile elongation (ZTE) finish curve in a temperature and long-time plot.

  9. Effects of neutron irradiation and hydrogen on ductile-brittle transition temperatures of V-Cr-Ti alloys*1

    NASA Astrophysics Data System (ADS)

    Loomis, B. A.; Chung, H. M.; Nowicki, L. J.; Smith, D. L.

    1994-09-01

    The effects of neutron irradiation and hydrogen on the ductile-brittle transition temperatures (DBTTs) of unalloyed vanadium and V-Cr-Ti alloys were determined from Charpy-impact tests on {1}/{3} ASTM-standard-size specimens and from impact tests on 3-mm diameter discs. The tests were conducted on specimens containing < 30 appm hydrogen and 600-1200 appm hydrogen and on specimens after neutron irradiation to 28-46 atom displacements per atom at 420, 520, and 600°C. The DBTTs were minimum (< -220°C) for V-(1-5)Ti alloys and for V-4Cr- 4Ti alloy with < 30 appm hydrogen. The effect of 600-1200 appm hydrogen in the specimens was to raise the DBTTs by 60-100°C. The DBTTs were minimum (< -200°C) for V-(3-5)Ti and V-4Cr-4Ti alloys after neutron irradiation.

  10. The ductile-brittle size transition of iron aluminide ligaments in an FeAl/TiC composite

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.

    1998-08-10

    The fracture surfaces of FeAl/TiC composites containing 70 vol% TiC were investigated. Since thin iron aluminide ligaments in the composites fractured in a ductile manner, whereas thicker ones fractured by cleavage, a systematic correlation of the fracture mode to the ligament thickness was performed. The results clearly show that FeAl ligaments thicker than about 1--2 {micro}m fracture by cleavage and those smaller in size fracture predominantly in a ductile manner. The ductile failure mode is attributed to the limited dislocation pile-up distance available for very thin ligaments, which prevents high stresses from building up and eliminates cleavage fracture. It is also shown that the ductile-brittle transition size is controlled by alloying and/or heat treatment. No significant dependence of the fracture toughness on the fracture mode would be found.

  11. A Unified Cohesive Zone Approach to Model Ductile Brittle Transition in Reactor Pressure Vessel Steels

    SciTech Connect

    Pritam Chakraborty; S. Bulent Biner

    2014-08-01

    In this study, a unified cohesive zone model has been proposed to predict, Ductile to Brittle Transition, DBT, in Reactor Pressure Vessel, RPV, steels. A general procedure is described to obtain the Cohesive Zone Model, CZM, parameters for the different temperatures and fracture probabilities. In order to establish the full master-curve, the procedure requires three calibration points with one at the upper-shelf for ductile fracture and two for the fracture probabilities, Pf, of 5% and 95% at the lower-shelf. In the current study, these calibrations were carried out by utilizing the experimental fracture toughness values and flow curves. After the calibration procedure, the simulations of fracture behavior (ranging from completely unstable to stable crack extension behavior) in one inch thick compact tension specimens at different temperatures yielded values that were comparable to the experimental fracture toughness values, indicating the viability of such unified modeling approach.

  12. Application of a J-Q model for fracture in the ductile-brittle transition

    SciTech Connect

    Landes, J.D.

    1997-12-01

    A model to predict cleavage failure of precracked bodies in the transition region for steels was recently proposed by the author. It is based on the concept that the stress-controlled fracture of a weak link triggers the failure of the entire body. The stress that triggers fracture is predicted by a numerical crack-tip stress analysis. The model uses toughness measured at one condition as input to predict toughness at another. For example, toughness measured at one temperature can be used to predict toughness at another temperature, or toughness measured from one geometry can be used to predict toughness for another geometry. In this paper the model is applied to predict transition toughness for some cases where the toughness is known so that the predictions from the model can be evaluated. The results show that the predictions have the same trends as many of the measured transition toughness results. The model is also applied to several component-type geometries to show that it can be used to transfer laboratory results to structural component models.

  13. Effect of Thermal Aging on Ductile-Brittle Transition Temperature of Modified 9Cr-1Mo Steel Evaluated with Reference Temperature Approach Under Dynamic Loading Condition

    NASA Astrophysics Data System (ADS)

    Sathyanarayanan, S.; Basu, Joysurya; Moitra, A.; Sasikala, G.; Singh, V.

    2013-05-01

    The effect of thermal aging on the ductile-brittle transition behavior has been assessed for a modified 9Cr-1Mo steel (P91) using the reference temperature approach under dynamic loading condition ( T {0/dy}). The steel in normalized and tempered (NT) condition and in different levels of subsequent cold work (CW) was subjected to thermal aging at temperatures of 873 K and 923 K (600 °C and 650 °C) for 5000 and 10,000 hours. For the NT and all the cold work conditions of the starting material, a drastic increase in T {0/dy} has been noticed after aging at 923 K (650 °C) for 10,000 h. A moderate increase was observed for the NT steel aged at 873 K (600 °C) for 5000 hours and for the 10 pct CW steel aged at 873 K (600 °C) for 10,000 h. A detailed transmission electron microscope (TEM) study of the embrittled materials aged at 923 K (650 °C)/10,000 hours and 873 K (600 °C)/10,000 hours has indicated presence of hexagonal Laves phase of Fe2(Mo,Nb) type with different size and spatial distributions. The increase in the T {0/dy} is attributed to the embrittling effect of a network of Laves phase precipitates along the grain boundaries.

  14. Positive feedback between strain localization and fluid flow at the ductile-brittle transition leading to Pb-Zn-Fe-Cu-Ag ore deposits in Lavrion (Greece)

    NASA Astrophysics Data System (ADS)

    Scheffer, Christophe; Tarantola, Alexandre; Vanderhaeghe, Olivier

    2016-04-01

    At the crustal scale, the ductile-brittle transition (DBT) might correspond to a physical barrier that separates a deep reservoir of metamorphic and magmatic fluids from a shallow reservoir of surficial fluids. Rock rheology, and thus the location of the DBT, is mainly governed by lithology, temperature and the presence/absence of fluids. Accordingly, the position of the DBT potentially evolves during orogenic evolution owing to thermal evolution and fluid circulation. In turn rocks are transferred across it during burial and exhumation. These processes induce connections between fluid reservoirs which might play a role on ore deposition. In this contribution, we discuss the impact of lithological heterogeneities on deformation, fluid flow and ore deposition based on the example of the Lavrion low-angle top-to-the-SSW detachment accommodating gravitational collapse of the Hellenides orogenic belt in Greece. The Lavrion peninsula, localized along the western boundary of the Attic-Cycladic Metamorphic Core Complex, is characterized by Pb-Zn-Fe-Cu-Ag ore mineralization mainly concentrated along a lithological contact (marble/schists) below and within a detachment shear zone. The mylonitic marble below the detachment shear zone is composed of white layers of pure marble alternating with blue layers containing impurities (SiO2, Al2O3, organic matter…). Development of the mylonitic fabric in competent impure blue marble is associated with its preferred dolomitization related to focused fluid infiltration. This mylonitic marble is cross-cut by several cataclastic horizons preferentially developed within the more competent impure blue marble and newly-crystallized dolomitic horizon. These cataclasites are invaded by fluorite and calcite gangue minerals showing locally Mn, Pb, Zn, Fe oxides and/or hydroxides, sphalerite, Ag-galena, Ag-sulfur and native Ag. Oxygen and carbon stable isotopes performed on marble sections point out decarbonation with magmatic contribution and

  15. Modeling the Ductile Brittle Fracture Transition in Reactor Pressure Vessel Steels using a Cohesive Zone Model based approach

    SciTech Connect

    Pritam Chakraborty; S. Bulent Biner

    2013-10-01

    Fracture properties of Reactor Pressure Vessel (RPV) steels show large variations with changes in temperature and irradiation levels. Brittle behavior is observed at lower temperatures and/or higher irradiation levels whereas ductile mode of failure is predominant at higher temperatures and/or lower irradiation levels. In addition to such temperature and radiation dependent fracture behavior, significant scatter in fracture toughness has also been observed. As a consequence of such variability in fracture behavior, accurate estimates of fracture properties of RPV steels are of utmost importance for safe and reliable operation of reactor pressure vessels. A cohesive zone based approach is being pursued in the present study where an attempt is made to obtain a unified law capturing both stable crack growth (ductile fracture) and unstable failure (cleavage fracture). The parameters of the constitutive model are dependent on both temperature and failure probability. The effect of irradiation has not been considered in the present study. The use of such a cohesive zone based approach would allow the modeling of explicit crack growth at both stable and unstable regimes of fracture. Also it would provide the possibility to incorporate more physical lower length scale models to predict DBT. Such a multi-scale approach would significantly improve the predictive capabilities of the model, which is still largely empirical.

  16. A simplified ductile-brittle transition temperature tester

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1973-01-01

    The construction and operation of a versatile, simplified bend tester is described. The tester is usable at temperatures from - 192 to 650 C in air. Features of the tester include a single test chamber for cryogenic or elevated temperatures, specimen alining support rollers, and either manual or motorized operation.

  17. Ductile, Brittle Failure Characteristics as Determined by the State of the Material and the Imposed State of Stress

    SciTech Connect

    Christensen, R M

    2004-02-05

    A method is developed for determining whether a particular mode of failure is expected to be of ductile type or brittle type depending upon both the state of the material and the particular state of stressing the isotropic material to failure. The state of the material is determined by two specific failure properties and a newly formulated failure theory. The ductile versus brittle criterion then involves the state of the material specification and the mean normal stress part of the imposed stress state. Several examples are given for different stress states and a spectrum of materials types. Closely related to the failure mode types are the orientations of the associated failure surfaces. The resulting failure surface angle predictions are compared with those from the Coulomb-Mohr failure criterion. In uniaxial tension, only the present method correctly predicts the octahedral failure angle at the ductile limit, and also shows a distinct failure mode transition from ductile type to brittle type as the state of the material changes. The explicit D-B criterion and the related failure surface orientation methodology are intended to provide a refinement and generalization of the ductile-brittle transition viewed only as a state property to also include a dependence upon the type of stress state taken to failure.

  18. Transient failure behavior of HT9

    SciTech Connect

    Huang, F.H.

    1994-07-01

    Alloy HT9 has-been chosen as candidate materials for fast and fusion reactor applications because the.material exhibits excellent resistance to void swelling. However, ferritic alloys are known to undergo a ductile-brittle transition as the test temperature is decreased. This inherent problem has limited their applications to reactor component materials subjected to low neutron exposures. Despite the ductile-brittle transition problem, results show that the materials exhibit superior resistance to fracture under very high neutron fluences at irradiation temperatures above 380C. Results also show that the transient behavior for HT9 cladding specimens taken from the fuel column region and cladding taken from outside the fuel column or unirradiated cladding are the same. HT9 cladding maintained its transient strength with irradiation to a fluence of 9 {times} 10{sup 22} n/cm{sup 2} (E > 0.1 MeV).

  19. Review of deformation behavior of tungsten at temperature less than 0.2 absolute melting temperature

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.

    1972-01-01

    The deformation behavior of tungsten at temperatures 0.2 T sub m is reviewed, with primary emphasis on the temperature dependence of the yield stress and the ductile-brittle transition temperature. It appears that a model based on the high Peierls stress of tungsten best accounts for the observed mechanical behavior at low temperatures. Recent research is discussed which suggests an important role of electron concentration and bonding on the mechanical behavior of tungsten. It is concluded that future research on tungsten should include studies to define more clearly the correlation between electron concentration and mechanical behavior of tungsten alloys and other transition metal alloys.

  20. A review of the deformation behavior of tungsten at temperatures less than 0.2 of the melting point /K/

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.

    1974-01-01

    The deformation behavior of tungsten at temperatures below 0.2 times the absolute melting temperature is reviewed with primary emphasis on the temperature dependence of the yield stress and the ductile-brittle transition. It is concluded that a model based on the high Peierls stress of tungsten best accounts for the observed mechanical behavior at low temperatures. Recent research suggests an important role of electron concentration and bonding on the mechanical behavior of tungsten. Future research on tungsten should include studies to define more clearly the correlation between electron concentration and mechanical behavior of alloys of tungsten and other transition metal alloys.

  1. Influence of crack orientation on the ductile-brittle behavior in Fe-3 wt.% Si single crystals

    SciTech Connect

    Spielmannova, Alena Landa, Michal; Machova, Anna; Hausild, Petr; Lejcek, Pavel

    2007-10-15

    In this paper we present experimental results from fracture tests performed at room temperature on bcc iron-silicon single crystals with edge cracks of two different orientations (001)[110] and (- 110)[110]. The cracks were loaded under mode I. The fracture toughness and acoustic emission response were measured, and a fractographic analysis obtained via scanning electron microscopy was carried out. Experimental results confirm the basic predictions pertaining to the influence of crack orientation on crack stability from continuum modeling and molecular dynamic simulations in bcc iron.

  2. Mechanical behavior of tungsten shaped charge liner materials

    SciTech Connect

    Lassila, D.H.

    1993-08-01

    Radiographs of jets produced by shaped charges with tungsten liners have documented both ductile and brittle breakup behavior. The relationships between the varying breakup behavior of tungsten shaped charge jets and metallurgical characteristics and/or mechanical behavior of the liner are not understood. In this paper the mechanical behavior of warm-forged and chemical-vapor-deposition (CVD) tungsten is discussed relative to the typical deformation history of an element of liner material which becomes part of the jet. The analyses suggest the following: (1) tungsten liner material is damaged, or possibly pulverized, during shock loading at the high-explosive detonation front; (2) pulverized material is consolidated in the convergence zone under conditions of high pressure, and (3) variations in observed breakup behavior of tungsten may be related to high temperature embrittlement. The low temperature ductile-brittle transition temperature of tungsten (DBTT) is not believed to be directly related to observed variations in break-up behavior of jets.

  3. Application of fracture toughness scaling models to the ductile-to- brittle transition

    SciTech Connect

    Link, R.E.; Joyce, J.A.

    1996-01-01

    An experimental investigation of fracture toughness in the ductile-brittle transition range was conducted. A large number of ASTM A533, Grade B steel, bend and tension specimens with varying crack lengths were tested throughout the transition region. Cleavage fracture toughness scaling models were utilized to correct the data for the loss of constraint in short crack specimens and tension geometries. The toughness scaling models were effective in reducing the scatter in the data, but tended to over-correct the results for the short crack bend specimens. A proposed ASTM Test Practice for Fracture Toughness in the Transition Range, which employs a master curve concept, was applied to the results. The proposed master curve over predicted the fracture toughness in the mid-transition and a modified master curve was developed that more accurately modeled the transition behavior of the material. Finally, the modified master curve and the fracture toughness scaling models were combined to predict the as-measured fracture toughness of the short crack bend and the tension specimens. It was shown that when the scaling models over correct the data for loss of constraint, they can also lead to non-conservative estimates of the increase in toughness for low constraint geometries.

  4. Microscopic failure behavior of nanoporous Gold

    SciTech Connect

    Biener, J; Hodge, A; Hamza, A

    2005-01-10

    Nanoporous metals have recently attracted considerable interest fueled by potential sensor and actuator applications. One of the key issues in this context is the synthesis of high yield strength materials. Nanoporous Au (np-Au) has been suggested as a candidate due to its monolithic character. The material can be synthesized by dealloying Ag-Au alloys, and exhibits an open sponge-like morphology of interconnecting Au ligaments with a typical pore size distribution on the nanometer length scale. Unfortunately, very little is known about the mechanical properties of np-Au besides a length-scale dependent ductile-brittle transition. A key question in this context is: what causes the macroscopic brittleness of np-Au? Is the normal dislocation-mediated plastic deformation suppressed in nanoscale Au ligaments, or is the brittleness a consequence of the macroscopic morphology? Here, we report on the fracture behavior of nanoporous Au studied by scanning electron microscopy. Specifically, we demonstrate the microscopic ductility of nanometer-sized Au ligaments. The observed fracture behavior seems to be general for nanoporous metals, and can be understood in terms of simple fuse networks.

  5. Multiscaling behavior in transition economies

    NASA Astrophysics Data System (ADS)

    Litvin, Vladimir A.

    2004-12-01

    A comparable statistical analysis for the currency exchange rates of the countries with transition economies has been made. Self-criticality has been demonstrated and studied. Non-linear effect for self-criticality indexes has been demonstrated. All effects are essentially nonlinear and differ from ones in the advanced economies.

  6. Theoretical study of electronic structure, phase transition, elastic, and thermodynamic properties of ReN

    NASA Astrophysics Data System (ADS)

    Lei, Hui-Ru; Zhu, Jun; Hao, Yan-Jun; Zhang, Lin; Yu, Bai-Ru; Chen, Long-Qing; Zou, Yang-Chun

    2015-02-01

    Phase transition of rhenium mononitride (ReN) in NaCl, CsCl, zincblende (ZB), NbO, wurtzite (WZ), NiAs, WC, PtS, Pmn21 and Cmc21 structures have been studied by using the projector augmented wave method. It is found that NbO-type structure is the most stable. This conclusion is consistent with the report of Wang et al., while contrary to the results of Zhao et al., Chen et al., Asvini et al., and Hlynsson et al. The phase transition from NbO-type to NiAs-type occurs at ca. 52.8 GPa, which is also in good agreement with that of Wang et al. The elastic constants of NbO- and NiAs-type ReN under high pressure are calculated and found to be increased with the increasing pressures. At the same time, the ductile-brittle behavior is evaluated by Pugh's criteria. Also, we have predicted the density of states and Vickers hardness for NbO and NiAs types of ReN. Finally, the Debye temperature ΘD, thermal expansion α and heat capacity CV for NbO-type structure at high pressures are also derived through the quasi-harmonic Debye model.

  7. In Situ Observation of Creep and Fatigue Failure Behavior for Plasma-Sprayed Thermal Barrier Coating Systems

    NASA Astrophysics Data System (ADS)

    Takahashi, Satoru; Harada, Yoshio

    In order to investigate crack initiation sites and the crack propagation behavior in connection with the microstructure of thermal barrier coating (TBC) systems under creep and fatigue loadings, the failure behavior was observed in situ for plasma-sprayed TBC systems by optical microscopy, as a first step for elucidating the thermo-mechanical failure mechanism. Two types of TBC systems with differing top-coat (TC) microstructures were prepared by changing the processing conditions. The mechanical failure behavior of TBC system was found to depend strongly on the loading conditions. Under static creep loading, many segmentation cracks in the TC widened with increasing creep strain in the substrate. However, the propagation of these cracks into the bond-coat (BC) and alloy substrate was prevented due to the stress relief induced by plastic flow in the BC layer at elevated temperatures. As a result, the TBC system exhibited typical creep rupture behavior with nucleation and coalescence of microcracks in the alloy substrate interior regardless of the TC microstructure. Under dynamic fatigue loading, on the other hand, many fatigue cracks initiated not only from the tips of segmentation cracks in the TC layer but also from the TC/BC interface. Furthermore, it was found that the fatigue cracks propagated into the BC and alloy substrate even at elevated temperatures above the ductile-brittle transition temperature of the BC; the fatigue failure behavior under dynamic fatigue loading was dependent on the TC microstructure and the properties of the TC/BC interface.

  8. Nonuniversal surface behavior of dynamic phase transitions.

    PubMed

    Riego, Patricia; Berger, Andreas

    2015-06-01

    We have studied the dynamic phase transition (DPT) of the kinetic Ising model in systems with surfaces within the mean-field approximation. Varying the surface exchange coupling strength J(s), the amplitude of the externally applied oscillating field h(0), and its period P, we explore the dynamic behavior of the layer-dependent magnetization and the associated DPTs. The surface phase diagram shows several features that resemble those of the equilibrium case, with an extraordinary bulk transition and a surface transition for high J(s) values, independent from the value of h(0). For low J(s), however, h(0) is found to be a crucial parameter that leads to nonuniversal surface behavior at the ordinary bulk transition point. Specifically, we observed here a bulk-supported surface DPT for high field amplitudes h(0) and correspondingly short critical periods P(c), whereas this surface transition simultaneous to the bulk one is suppressed for slow critical dynamics occurring for low values of h(0). The suppression of the DPT for low h(0) not only occurs for the topmost surface layer, but also affects a significant number of subsurface layers. We find that the key physical quantity that explains this nonuniversal behavior is the time correlation between the dynamic surface and bulk magnetizations at the bulk critical point. This time correlation has to pass a threshold value to trigger a bulk-induced DPT in the surface layers. Otherwise, dynamic phase transitions are absent at the surface in stark contrast to the equilibrium behavior of the corresponding thermodynamic Ising model. Also, we have analyzed the penetration depth of the dynamically ordered phase for the surface DPT that occurs for large J(s) values. Here we find that the penetration depth depends strongly on J(s) and behaves identically to the corresponding equilibrium Ising model. PMID:26172695

  9. Behavior of Zr1%Nb Fuel Cladding under Accident Conditions

    SciTech Connect

    Perez-Fero, E.; Hozer, Z.; Windberg, P.; Nagy, I.; Vimi, A.; Ver, N.; Matus, L.; Kunstar, M.; Novotny, T.; Horvath, M.; Gyori, Cs.

    2007-07-01

    The behavior of the VVER fuel (E110) cladding under accident conditions has been investigated at the AEKI in order to study the role of oxidation and hydrogen uptake on the cladding embrittlement and to understand the phenomena that took place during the Paks-2 cleaning tank incident (2003). The test programme covered small scale tests and large scale tests with electrically heated 7-rod bundles in the CODEX (Core Degradation Experiment) facility. Since a hydrogen rich atmosphere could have been formed in the closed tank, the experiments were carried out in hydrogen-steam mixture. According to the results of the small scale tests, a former correlation for the ductile-brittle transitions of E110 in pure steam remained valid in hydrogen rich steam atmosphere as well. During the large scale tests the main conditions of the incident were reconstructed. The test characterized the high temperature oxidation and embrittlement of zirconium in hydrogen rich steam. The observed cladding failure phenomena and the extent of the damage of the test bundle in the quenching phase were very similar to those of the VVER assemblies in the incident. The simulation of the cleaning tank incident provided detailed information on the most probable scenario of the incident. (authors)

  10. Thermo-mechanical fatigue behavior of the intermetallic gamma-TiAl alloy TNB-V5 with different microstructures

    NASA Astrophysics Data System (ADS)

    Roth, M.; Biermann, H.

    2010-07-01

    The cyclic deformation and fatigue behavior of the γ-TiAl alloy TNB-V5 is studied under thermo-mechanical load for the three technically important microstructures Fully-Lamellar (FL), Near-Gamma (NG) and Duplex (DP), respectively. Thus, thermo-mechanical fatigue (TMF) tests were carried out with different temperature-strain cycles, different temperature ranges from 400°C to 800°C and with two different strain ranges. Cyclic deformation curves, stress-strain hysteresis loops and fatigue lives are presented. The type of microstructure shows a surprisingly small influence on the cyclic deformation and fatigue behavior under TMF conditions. For a general life prediction the damage parameter of Smith, Watson and Topper PSWT is well suitable, if the testing and the application temperature ranges, respectively, include temperatures above the ductile-brittle transition temperature (approx. 750°C). If the maximum temperature is below that temperature, the brittle materials' behavior yields a high scatter of fatigue lives and a low slope of the fatigue life curve and therefore the damage parameter PSWT cannot be applied for the live prediction.

  11. Corrosion behavior of mesoporous transition metal nitrides

    SciTech Connect

    Yang, Minghui; Allen, Amy J.; Nguyen, Minh T.; Ralston, Walter T.; MacLeod, Michelle J.; DiSalvo, Francis J.

    2013-09-15

    Transition metal nitrides (TMN) have many desirable characteristics such as high hardness and good thermal stability under reducing conditions. This work reports an initial survey of the chemical stability of mesoporous TMNs (TM=Nb, V, Cr and Ti) in water at 80 °C at neutral, acidic and alkaline pH. The mesoporous TMNs had specific surface areas of 25–60 m{sup 2}/g with average pore sizes ranging from 10 to 50 nm. The high surface areas of these materials enhance the rate of corrosion per unit mass over that of a bulk material, making detection of corrosion much easier. The products were characterized by Rietveld refinement of powder X-ray diffraction (PXRD) patterns and by scanning electron microscopy (SEM). Several nitrides have corrosion rates that are, within error, not distinguishable from zero (±1 Å/day). Of the nitrides examined, CrN appears to be the most corrosion resistant under acidic conditions. None of the nitrides studied are corrosion resistant under alkaline conditions. - Graphical abstract: Corrosion behavior of mesoporous transition metal nitrides (TM=Nb, V, Cr and Ti) in acidic and alkaline solutions at 80 °C for 2 weeks. Display Omitted - highlights: • Corrosion rates of mesoporous transition metal nitrides in aqueous solution is reported. • The mesoporous TMNs had surface areas of 25–60 m{sup 2}/g. • CrN is the most corrosion resistant under the conditions studied.

  12. Effect of He implantation on fracture behavior and microstructural evolution in F82H

    NASA Astrophysics Data System (ADS)

    Yabuuchi, Kiyohiro; Sato, Kiminori; Nogami, Shuhei; Hasegawa, Akira; Ando, Masami; Tanigawa, Hiroyasu

    2014-12-01

    Reduced-activation ferritic/martensitic steels (RAFMs) are the primary candidate structural materials for fusion reactor blanket components. He bubbles, which formed under 14 MeV neutron irradiation, is considered to cause some mechanical property changes. In a previous study, Hasegawa et al. investigated the fracture behavior using Charpy impact test of He implanted F82H by 50 MeV α-particles with cyclotron accelerator, and the ductile brittle transition temperature (DBTT) was increased and intergranular fracture (IGF) was observed. However, the cause of the IGF was not shown in the previous study. To clarify the cause of the IGF of the He implanted F82H by 50 MeV α-particles with cyclotron accelerator, the microstructure of the He implanted F82H was investigated. After Charpy impact test at 233 K, the brittle fracture surface of the He implanted specimen was observed by SEM and TEM. By SEM observation, grain boundary surface was clearly observed from the bottom of the notch to a depth of about 400 μm. This area correspond to the He implanted region. On the other hand, at unimplanted region, river pattern was observed and transgranular fracture occurred. TEM observation revealed the He bubbles agglomeration at dislocations, lath boundaries, and grain boundaries, and the coarsening of precipitates on grain boundaries. IGF of the He implanted F82H was caused by both He bubbles and coarsening precipitates.

  13. The Timing of School Transitions and Early Adolescent Problem Behavior

    ERIC Educational Resources Information Center

    Lippold, Melissa A.; Powers, Christopher J.; Syvertsen, Amy K.; Feinberg, Mark E.; Greenberg, Mark T.

    2013-01-01

    This longitudinal study investigates whether rural adolescents who transition to a new school in sixth grade have higher levels of risky behavior than adolescents who transition in seventh grade. Our findings indicate that later school transitions had little effect on problem behavior between sixth and ninth grades. Cross-sectional analyses found…

  14. Transitional behavior in hydrodynamically coupled oscillators

    NASA Astrophysics Data System (ADS)

    Box, S.; Debono, L.; Phillips, D. B.; Simpson, S. H.

    2015-02-01

    In this article we consider the complete set of synchronized and phase-locked states available to pairs of hydrodynamically coupled colloidal rotors, consisting of spherical beads driven about circular paths in the same, and in opposing senses. Oscillators such as these have previously been used as coarse grained, minimal models of beating cilia. Two mechanisms are known to be important in establishing synchrony. The first involves perturbation of the driving force, and the second involves deformation of the rotor trajectory. We demonstrate that these mechanisms are of similar strength, in the regime of interest, and interact to determine observed behavior. Combining analysis and simulation with experiments performed using holographic optical tweezers, we show how varying the amplitude of the driving force perturbation leads to a transition from synchronized to phase-locked states. Analogies with biological systems are discussed, as are implications for the design of biomimetic devices.

  15. The Timing of School Transitions and Early Adolescent Problem Behavior

    PubMed Central

    Lippold, Melissa A.; Powers, Christopher J.; Syvertsen, Amy K.; Feinberg, Mark E.; Greenberg, Mark T.

    2013-01-01

    This longitudinal study investigates whether rural adolescents who transition to a new school in sixth grade have higher levels of risky behavior than adolescents who transition in seventh grade. Our findings indicate that later school transitions had little effect on problem behavior between sixth and ninth grades. Cross-sectional analyses found a small number of temporary effects of transition timing on problem behavior: Spending an additional year in elementary school was associated with higher levels of deviant behavior in the Fall of Grade 6 and higher levels of antisocial peer associations in Grade 8. However, transition effects were not consistent across waves and latent growth curve models found no effects of transition timing on the trajectory of problem behavior. We discuss policy implications and compare our findings with other research on transition timing. PMID:24089584

  16. Impact properties and hardening behavior of laser and electron-beam welds of V-4Cr-4Ti

    SciTech Connect

    Chung, H.M.; Strain, R.V.; Tsai, H.C.; Park, J.H.; Smith, D.L.

    1996-10-01

    The authors are conducting a program to develop an optimal laser welding procedure that can be applied to large-scale fusion-reactor structural components to be fabricated from vanadium-base alloys. Results of initial investigation of mechanical properties and hardening behavior of laser and electron-beam (EB) welds of the production-scale heat of V-4Cr-4Ti (500-kg Heat 832665) in as-welded and postwelding heat-treated (PWHT) conditions are presented in this paper. The laser weld was produced in air using a 6-kW continuous CO{sub 2} laser at a welding speed of {approx}45 mm/s. Microhardness of the laser welds was somewhat higher than that of the base metal, which was annealed at a nominal temperature of {approx}1050{degrees}C for 2 h in the factory. In spite of the moderate hardening, ductile-brittle transition temperatures (DBTTs) of the initial laser ({approx}80{degrees}C) and EB ({approx}30{degrees}C) welds were significantly higher than that of the base metal ({approx}{minus}170{degrees}C). However, excellent impact properties, with DBTT < {minus}80{degrees}C and similar to those of the base metal, could be restored in both the laser and EB welds by postwelding annealing at 1000{degrees}C for 1 h in vacuum.

  17. Transitional Probability Analysis of Two Child Behavior Analytic Therapy Cases

    ERIC Educational Resources Information Center

    Xavier, Rodrigo Nunes; Kanter, Jonathan William; Meyer, Sonia Beatriz

    2012-01-01

    This paper aimed to highlight the process of therapist direct contingent responding to shape client behavior in two Child Behavior Analytic Therapy (CBAT) cases using transitional probabilities. The Functional Analytic Psychotherapy Rating Scale (FAPRS) was used to code client behaviors and the Multidimensional System for Coding Behaviors in…

  18. Comparison of fracture behavior for low-swelling ferritic and austenitic alloys irradiated in the Fast Flux Test Facility (FFTF) to 180 DPA

    SciTech Connect

    Huang, F.H.

    1992-02-01

    Fracture toughness testing was conducted to investigate the radiation embrittlement of high-nickel superalloys, modified austenitic steels and ferritic steels. These materials have been experimentally proven to possess excellent resistance to void swelling after high neutron exposures. In addition to swelling resistance, post-irradiation fracture resistance is another important criterion for reactor material selection. By means of fracture mechanics techniques the fracture behavior of those highly irradiated alloys was characterized in terms of irradiation and test conditions. Precipitation-strengthened alloys failed by channel fracture with very low postirradiation ductility. The fracture toughness of titanium-modified austenitic stainless steel D9 deteriorates with increasing fluence to about 100 displacement per atom (dpa), the fluence level at which brittle fracture appears to occur. Ferritic steels such as HT9 are the most promising candidate materials for fast and fusion reactor applications. The upper-shelf fracture toughness of alloy HT9 remained adequate after irradiation to 180 dpa although its ductile- brittle transition temperature (DBTT) shift by low temperature irradiation rendered the material susceptible to brittle fracture at room temperature. Understanding the fracture characteristics under various irradiation and test conditions helps reduce the potential for brittle fracture by permitting appropriate measure to be taken.

  19. Mechanical Properties and Fracture Behavior of Nanoporous Au

    SciTech Connect

    Biener, J; Hodge, A M; Wang, Y M; Hayes, J R; Hamza, A V

    2005-06-16

    Nanoporous metals have recently attracted considerable interest fueled by potential sensor and actuator applications. From a material science point of view, one of the key issues in this context is the synthesis of nanoporous metals with both high tensile and compressive strength. Nanoporous gold (np-Au) has been suggested as a candidate material for this application due to its monolithic character. The material can be synthesized by electrochemically-driven dealloying of Ag-Au alloys, and exhibits an open sponge-like structure of interconnecting ligaments with a typical pore size distribution on the nanometer length scale. However, besides the observation of a ductile-brittle transition very little is known about the mechanical behavior of this material. Here, we present our results regarding the mechanical properties and the fracture behavior of np-Au. Depth-sensing nanoindentation reveals that the yield strength of np-Au is almost one order of magnitude higher than the value predicted by scaling laws developed for macroscopic open-cell foams. The unexpectedly high value of the yield strength indicates the presence of a distinct size effect of the mechanical properties due to the sub-micron dimensions of the ligaments, thus potentially opening a door to a new class of high yield strength--low density materials. The failure mechanism of np-Au under tensile stress was evaluated by microscopic examination of fracture surfaces using scanning electron microscopy. On a macroscopic level, np-Au is a very brittle material. However, microscopically np-Au is very ductile as ligaments strained by as much as 200% can be observed in the vicinity of crack tips. Cell-size effects on the microscopic failure mechanism were studied by annealing experiments whereby increasing the typical pore size/ligament diameter from {approx}100 nm to {approx}1{micro}m.

  20. Adolescents' transitions to behavioral autonomy after German unification.

    PubMed

    Haase, Claudia M; Silbereisen, Rainer K; Reitzle, Matthias

    2008-06-01

    The present study examined the timing of behavioral autonomy transitions in two same-aged cohorts of East German adolescents assessed in 1991 and 1996. An earlier timing of autonomy privileges was associated with higher deviant behavior. A later timing of autonomy privileges and responsibilities was linked to structural constraints, specifically, to parental unemployment. Between 1991 and 1996 significant timing differences were observed for some autonomy transitions in the East, implying an adaptation to Western timetables. Our findings illustrate the plasticity of autonomy transitions under conditions of social change. PMID:17688937

  1. Behavioral Risks during the Transition from High School to College

    ERIC Educational Resources Information Center

    Fromme, Kim; Corbin, William R.; Kruse, Marc I.

    2008-01-01

    The transition from high school to college is an important developmental milestone that holds the potential for personal growth and behavioral change. A cohort of 2,245 students was recruited during the summer before they matriculated into college and completed Internet-based surveys about their participation in a variety of behavioral risks…

  2. Adolescents' Transitions to Behavioral Autonomy after German Unification

    ERIC Educational Resources Information Center

    Haase, Claudia M.; Silbereisen, Rainer K.; Reitzle, Matthias

    2008-01-01

    The present study examined the timing of behavioral autonomy transitions in two same-aged cohorts of East German adolescents assessed in 1991 and 1996. An earlier timing of autonomy privileges was associated with higher deviant behavior. A later timing of autonomy privileges and responsibilities was linked to structural constraints, specifically,…

  3. High Throughput Interrogation of Behavioral Transitions in C. elegans

    NASA Astrophysics Data System (ADS)

    Liu, Mochi; Shaevitz, Joshua; Leifer, Andrew

    We present a high-throughput method to probe transformations from neural activity to behavior in Caenorhabditis elegans to better understand how organisms change behavioral states. We optogenetically deliver white-noise stimuli to target sensory or inter neurons while simultaneously recording the movement of a population of worms. Using all the postural movement data collected, we computationally classify stereotyped behaviors in C. elegans by clustering based on the spectral properties of the instantaneous posture. (Berman et al., 2014) Transitions between these behavioral clusters indicate discrete behavioral changes. To study the neural correlates dictating these transitions, we perform model-driven experiments and employ Linear-Nonlinear-Poisson cascades that take the white-noise stimulus as the input. The parameters of these models are fitted by reverse-correlation from our measurements. The parameterized models of behavioral transitions predict the worm's response to novel stimuli and reveal the internal computations the animal makes before carrying out behavioral decisions. Preliminary results are shown that describe the neural-behavioral transformation between neural activity in mechanosensory neurons and reversal behavior.

  4. Cooperative behavior during ferroelectric transitions in KNO3 powder

    NASA Astrophysics Data System (ADS)

    Westphal, M. J.

    1993-09-01

    Experimental evidence of cooperative behavior during the ferroelectric phase transitions in granular and powder KNO3 at atmospheric pressure is presented. Three different experimental studies were performed in which phase transitions were detected and characterized by heat flow calorimetry: (1) the distribution of SiC powder in granular KNO3 was varied; (2) the volume fraction of SiC in powdered KNO3 was varied; and (3) pure KNO3 powder was thermally cycled. All three studies provided evidence of cooperative behavior between the KNO3 particles during the III-II phase transition. The cooperative behavior reduced the temperature range of phase III stability from ˜97-124 °C to that characteristic of bulk material (˜110-124 °C). Separate KNO3 particles behaved as individual ferroelectric domains, with each particle making the phase transition independently near the expected Curie temperature. Particles of KNO3 in intimate physical contact tended to behave cooperatively as a single large ferroelectric domain leading to sharper phase transitions more characteristic of single crystals. The degree of cooperative behavior was dependent upon the extent to which the individual particles were in physical contact. The absence of the III-II phase transition in KNO3 powder that has been reported in the literature can be understood from the results obtained using SiC powder to separate KNO3 particles during heat flow calorimetry measurements.

  5. Transition-Marking Behaviors of Adolescent Males at First Intercourse.

    ERIC Educational Resources Information Center

    McLean, Ann L.; Flanigan, Beverly J.

    1993-01-01

    Examined male transition-marking behaviors from adolescence into adulthood at first intercourse. Findings from 80 adolescent males revealed that alcohol use at first intercourse was unrelated to use of contraceptives at that time but was inversely related to whether first intercourse was planned. Planning was positively related to contraceptive…

  6. Phase Transition Behavior in a Neutral Evolution Model

    NASA Astrophysics Data System (ADS)

    King, Dawn; Scott, Adam; Maric, Nevena; Bahar, Sonya

    2014-03-01

    The complexity of interactions among individuals and between individuals and the environment make agent based modeling ideal for studying emergent speciation. This is a dynamically complex problem that can be characterized via the critical behavior of a continuous phase transition. Concomitant with the main tenets of natural selection, we allow organisms to reproduce, mutate, and die within a neutral phenotype space. Previous work has shown phase transition behavior in an assortative mating model with variable fitness landscapes as the maximum mutation size (μ) was varied (Dees and Bahar, 2010). Similarly, this behavior was recently presented in the work of Scott et al. (2013), even on a completely neutral landscape, for bacterial-like fission as well as for assortative mating. Here we present another neutral model to investigate the `critical' phase transition behavior of three mating types - assortative, bacterial, and random - in a phenotype space as a function of the percentage of random death. Results show two types of phase transitions occurring for the parameters of the population size and the number of clusters (an analogue of species), indicating different evolutionary dynamics for system survival and clustering. This research was supported by funding from: University of Missouri Research Board and James S. McDonnell Foundation.

  7. The Effect of Impingement on Transitional Behavior in Underexpanded Jets

    NASA Technical Reports Server (NTRS)

    Inman, Jennifer A.; Danehy, Paul M.; Nowak, Robert J.; Alderfer, David W.

    2009-01-01

    An investigation into the development of flow unsteadiness in impinging axisymmetric underexpanded jets has been conducted at NASA Langley Research Center. The study has examined the effect of an impingement target placed at various distances and angles on transitional behavior of such jets. Two nozzles, with exit Mach numbers of 1.0 and 2.6, were used in this investigation. Planar laser-induced fluorescence of nitric oxide (NO PLIF) has been used to identify flow unsteadiness and to image transitional and turbulent flow features. Measurements of the location of the onset of various degrees of unsteady flow behavior have been made using these PLIF images. Both qualitative and quantitative comparisons are presented to demonstrate the observed effects of impingement and flow parameters on the process of the transition to turbulence. The presence of the impingement target was found to significantly shorten the distance to transition to turbulence by up to a factor of approximately three, with closer targets resulting in slightly shorter distance to transition and turbulence. The location at which the flow first exhibits unsteadiness was found to have a strong dependence on the presence and location of key flow structures. This paper presents quantitative results on transition criteria for free and impinging jets.

  8. Coordination of behavioral hierarchies during environmental transitions in Caenorhabditis elegans

    PubMed Central

    Vidal-Gadea, Andrés G.; Davis, Scott; Becker, Lindsay; Pierce-Shimomura, Jonathan T.

    2012-01-01

    For animals inhabiting multiple environments, the ability to select appropriate behaviors is crucial as their adaptability is often context dependent. Caenorhabditis elegans uses distinct gaits to move on land and in water. Gait transitions can potentially coordinate behaviors associated with distinct environments. We investigated whether land and water differentially affect the behavioral repertoire of C. elegans. Swimming worms interrupted foraging, feeding, egg-laying and defecation. Exogenous dopamine induced bouts of these land-associated behaviors in water. Our finding that worms do not drink fluid while immersed may explain why higher drug doses are required in water than on land to elicit the same effects. C. elegans is a valid model to study behavioral hierarchies and how environmental pressures alter their balance. PMID:23525841

  9. Influence of TiN Inclusions on the Cleavage Fracture Behavior of Low-Carbon Microalloyed Steels

    NASA Astrophysics Data System (ADS)

    Yan, W.; Shan, Y. Y.; Yang, K.

    2007-06-01

    Toughness is a major concern for low-carbon microalloyed steels. In this work, the impact fracture behavior of two low-carbon Ti-V microalloyed steels was investigated in order to better understand the role of TiN inclusions in the toughness of the steels. The steels had similar chemical compositions and were manufactured by the same rolling process. However, there was an obvious difference in the ductile brittle transition temperature (DBTT) in the Charpy V-notch (CVN) impact tests of the two steels; one (steel 1) possessing a DBTT below -20 °C, while the DBTT of the other (steel 2) was above 15 °C. Scanning electron microscopy (SEM) fractography revealed that there were TiN inclusions at the cleavage fracture initiation sites on the fracture surfaces of steel 2 at both low and room temperatures. It is shown that the TiN inclusions had nucleated on Al2O3 particles and that they had pre-existing interior flaws. A high density of TiN inclusions was found in steel 2, but there was a much lower density in steel 1. Analysis indicates that these inclusions were responsible for the shift of DBTT to a higher temperature in steel 2. A mechanism is proposed for understanding the effect of the size and density of TiN inclusions on the fracture behavior, and the cleavage fracture initiation process is analyzed in terms of the distribution and development of stresses ahead of the notch tip during fracture at both low and room temperatures.

  10. Social Transitions Cause Rapid Behavioral and Neuroendocrine Changes

    PubMed Central

    Maruska, Karen P.

    2015-01-01

    In species that form dominance hierarchies, there are often opportunities for low-ranking individuals to challenge high-ranking ones, resulting in a rise or fall in social rank. How does an animal rapidly detect, process, and then respond to these social transitions? This article explores and summarizes how these social transitions can rapidly (within 24 h) impact an individual’s behavior, physiology, and brain, using the African cichlid fish, Astatotilapia burtoni, as a model. Male A. burtoni form hierarchies in which a few brightly-colored dominant males defend territories and spawn with females, while the remaining males are subordinate, more drab-colored, do not hold a territory, and have minimal opportunities for reproduction. These social phenotypes are plastic and reversible, meaning that individual males may switch between dominant and subordinate status multiple times within a lifetime. When the social environment is manipulated to create males that either ascend (subordinate to dominant) or descend (dominant to subordinate) in rank, there are rapid changes in behavior, circulating hormones, and levels of gene expression in the brain that reflect the direction of transition. For example, within minutes, males ascending in status show bright coloration, a distinct eye-bar, increased dominance behaviors, activation of brain nuclei in the social behavior network, and higher levels of sex steroids in the plasma. Ascending males also show rapid changes in levels of neuropeptide and steroid receptors in the brain, as well as in the pituitary and testes. To further examine hormone–behavior relationships in this species during rapid social ascent, the present study also measured levels of testosterone, 11-ketotestosterone, estradiol, progestins, and cortisol in the plasma during the first week of social ascent and tested for correlations with behavior. Plasma levels of all steroids were rapidly increased at 30 min after social ascent, but were not correlated

  11. Social Transitions Cause Rapid Behavioral and Neuroendocrine Changes.

    PubMed

    Maruska, Karen P

    2015-08-01

    In species that form dominance hierarchies, there are often opportunities for low-ranking individuals to challenge high-ranking ones, resulting in a rise or fall in social rank. How does an animal rapidly detect, process, and then respond to these social transitions? This article explores and summarizes how these social transitions can rapidly (within 24 h) impact an individual's behavior, physiology, and brain, using the African cichlid fish, Astatotilapia burtoni, as a model. Male A. burtoni form hierarchies in which a few brightly-colored dominant males defend territories and spawn with females, while the remaining males are subordinate, more drab-colored, do not hold a territory, and have minimal opportunities for reproduction. These social phenotypes are plastic and reversible, meaning that individual males may switch between dominant and subordinate status multiple times within a lifetime. When the social environment is manipulated to create males that either ascend (subordinate to dominant) or descend (dominant to subordinate) in rank, there are rapid changes in behavior, circulating hormones, and levels of gene expression in the brain that reflect the direction of transition. For example, within minutes, males ascending in status show bright coloration, a distinct eye-bar, increased dominance behaviors, activation of brain nuclei in the social behavior network, and higher levels of sex steroids in the plasma. Ascending males also show rapid changes in levels of neuropeptide and steroid receptors in the brain, as well as in the pituitary and testes. To further examine hormone-behavior relationships in this species during rapid social ascent, the present study also measured levels of testosterone, 11-ketotestosterone, estradiol, progestins, and cortisol in the plasma during the first week of social ascent and tested for correlations with behavior. Plasma levels of all steroids were rapidly increased at 30 min after social ascent, but were not correlated with

  12. Phase transition-like behavior of the magnetosphere during substorms

    NASA Astrophysics Data System (ADS)

    Sitnov, M. I.; Sharma, A. S.; Papadopoulos, K.; Vassiliadis, D.; Valdivia, J. A.; Klimas, A. J.; Baker, D. N.

    2000-06-01

    The behavior of substorms as sudden transitions of the magnetosphere is studied using the Bargatze et al. [1985] data set of the solar wind induced electric field vBs and the auroral electrojet index AL. The data set is divided into three subsets representing different levels of activity, and they are studied using the singular spectrum analysis. The points representing the evolution of the magnetosphere in the subspace of the eigenvectors corresponding to the three largest eigenvalues can be approximated by two-dimensional manifolds with a relative deviation of 10-20%. For the first two subsets corresponding to small and medium activity levels the manifolds have a pleated structure typical of the cusp catastrophe. The dynamics of the magnetosphere near these pleated structures resembles the hysteresis phenomenon typical of first-order phase transitions. The reconstructed manifold is similar to the ``temperature-pressure-density'' diagrams of equilibrium phase transitions. The singular spectra of vBs, AL, and combined data have the power law dependence typical of second-order phase transitions and self-organized criticality. The magnetosphere thus exhibits the signatures of both self-organization and self-organized criticality. It is concluded that the magnetospheric substorm is neither a pure catastrophe of the low-dimensional system nor a random set of avalanches of different scales described by the simple sandpile models. The substorms behave like nonequilibrium phase transitions, with features of both first- and second-order phase transitions.

  13. Transition between different search patterns in human online search behavior

    NASA Astrophysics Data System (ADS)

    Wang, Xiangwen; Pleimling, Michel

    2015-03-01

    We investigate the human online search behavior by analyzing data sets from different search engines. Based on the comparison of the results from several click-through data-sets collected in different years, we observe a transition of the search pattern from a Lévy-flight-like behavior to a Brownian-motion-type behavior as the search engine algorithms improve. This result is consistent with findings in animal foraging processes. A more detailed analysis shows that the human search patterns are more complex than simple Lévy flights or Brownian motions. Notable differences between the behaviors of different individuals can be observed in many quantities. This work is in part supported by the US National Science Foundation through Grant DMR-1205309.

  14. Intergenerational transmission of reproductive behavior during the demographic transition.

    PubMed

    Jennings, Julia A; Sullivan, Allison R; Hacker, J David

    2012-01-01

    New evidence from the Utah Population Database (UPDP) reveals that at the onset of the fertility transition, reproductive behavior was transmitted across generations - between women and their mothers, as well as between women and their husbands' family of origin. Age at marriage, age at last birth, and the number of children ever born are positively correlated in the data, most strongly among first-born daughters and among cohorts born later in the fertility transition. Intergenerational ties, including the presence of mothers and mothers-in-law, influenced the hazard of progressing to a next birth. The findings suggest that the practice of parity-dependent marital fertility control and inter-birth spacing behavior derived, in part, from the previous generation and that the potential for mothers and mothers-in-law to help in the rearing of children encouraged higher marital fertility. PMID:22530253

  15. Transition to organized behavior on suspensions of concentrated bacteria

    NASA Astrophysics Data System (ADS)

    Ganguly, Sujoy; Cisneros, Luis; Kessler, John; Goldstein, Raymond

    2008-11-01

    Concentrated populations of the swimming bacterium Bacillus subtilis develop a collective phase, the Zooming BioNematic, that exhibits large-scale coherence analogous to the molecular alignment of nematic liquid crystals. Bacterial suspensions were prepared in order to experimentally measure the transition to organized behavior as a function of the cell number concentration. PIV analysis was used to obtain cell velocities and define an order parameter in order to characterize the dynamics of the system.

  16. Apparent Transition Behavior of Widely-Used Turbulence Models

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.

    2007-01-01

    The Spalart-Allmaras and the Menter SST k-omega turbulence models are shown to have the undesirable characteristic that, for fully turbulent computations, a transition region can occur whose extent varies with grid density. Extremely fine two-dimensional grids over the front portion of an airfoil are used to demonstrate the effect. As the grid density is increased, the laminar region near the nose becomes larger. In the Spalart-Allmaras model this behavior is due to convergence to a laminar-behavior fixed point that occurs in practice when freestream turbulence is below some threshold. It is the result of a feature purposefully added to the original model in conjunction with a special trip function. This degenerate fixed point can also cause non-uniqueness regarding where transition initiates on a given grid. Consistent fully turbulent results can easily be achieved by either using a higher freestream turbulence level or by making a simple change to one of the model constants. Two-equation k-omega models, including the SST model, exhibit strong sensitivity to numerical resolution near the area where turbulence initiates. Thus, inconsistent apparent transition behavior with grid refinement in this case does not appear to stem from the presence of a degenerate fixed point. Rather, it is a fundamental property of the k-omega model itself, and is not easily remedied.

  17. Apparent Transition Behavior of Widely-Used Turbulence Models

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.

    2006-01-01

    The Spalart-Allmaras and the Menter SST kappa-omega turbulence models are shown to have the undesirable characteristic that, for fully turbulent computations, a transition region can occur whose extent varies with grid density. Extremely fine two-dimensional grids over the front portion of an airfoil are used to demonstrate the effect. As the grid density is increased, the laminar region near the nose becomes larger. In the Spalart-Allmaras model this behavior is due to convergence to a laminar-behavior fixed point that occurs in practice when freestream turbulence is below some threshold. It is the result of a feature purposefully added to the original model in conjunction with a special trip function. This degenerate fixed point can also cause nonuniqueness regarding where transition initiates on a given grid. Consistent fully turbulent results can easily be achieved by either using a higher freestream turbulence level or by making a simple change to one of the model constants. Two-equation kappa-omega models, including the SST model, exhibit strong sensitivity to numerical resolution near the area where turbulence initiates. Thus, inconsistent apparent transition behavior with grid refinement in this case does not appear to stem from the presence of a degenerate fixed point. Rather, it is a fundamental property of the kappa-omega model itself, and is not easily remedied.

  18. From desires to behavior: Moderating factors in a fertility transition

    PubMed Central

    Hayford, Sarah R.; Agadjanian, Victor

    2013-01-01

    BACKGROUND Extensive research in both developed and developing countries has shown that preferences and intentions for future childbearing predict behavior. However, very little of this research has examined high-fertility contexts in sub-Saharan Africa. In particular, the factors that increase or decrease correspondence between fertility desires and behavior in these settings are not well understood. OBJECTIVE This article documents the degree to which the desire to stop childbearing predicts fertility behavior over the short term among married women in rural southern Mozambique, a context where fertility transition is still in the early stages. Analyses test the moderating powers of individual, household, and community characteristics. METHODS Analyses use data from a longitudinal survey of married women of reproductive age (N=1678) carried out in 2006 and 2009 in rural areas of southern Mozambique. Logistic regression models are estimated to predict childbearing between 2006 and 2009 based on desires to stop childbearing and characteristics measured in 2006. RESULTS As expected, the desire to stop childbearing is strongly predictive of fertility behavior. Household wealth, local adult AIDS mortality, and being married to an unsuccessful labor migrant are associated with higher correspondence between reported desire to stop childbearing and fertility behavior. CONCLUSIONS Both factors related to the ability to carry out desires to stop childbearing and factors related to the strength and consistency of these desires moderate the association between desires and behaviors. Future research should expand measurement of fertility preferences to incorporate their strength and consistency as well as direction. PMID:23626485

  19. Behavioral transitions and weight change patterns within the PREMIER trial.

    PubMed

    Bartfield, Jessica K; Stevens, Victor J; Jerome, Gerald J; Batch, Bryan C; Kennedy, Betty M; Vollmer, William M; Harsha, David; Appel, Lawrence J; Desmond, Renee; Ard, Jamy D

    2011-08-01

    Little is known about the transition in behaviors from short-term weight loss to maintenance of weight loss. We wanted to determine how short-term and long-term weight loss and patterns of weight change were associated with intervention behavioral targets. This analysis includes overweight/obese participants in active treatment (n = 507) from the previously published PREMIER trial, an 18-month, multicomponent lifestyle intervention for blood pressure reduction, including 33 intervention sessions and recommendations to self-monitor food intake and physical activity daily. Associations between behaviors (attendance, recorded days/week of physical activity, food records/week) and weight loss of ≥5% at 6 and 18 months were examined using logistic regression. We characterized the sample using 5 weight change categories (weight gained, weight stable, weight loss then relapse, late weight loss, and weight loss then maintenance) and analyzed adherence to the behaviors for each category, comparing means with ANOVA. Participants lost an average of 5.3 ± 5.6 kg at 6 months and 4.0 ± 6.7 kg (4.96% of body weight) by 18 months. Higher levels of attendance, food record completion, and recorded days/week of physical activity were associated with increasing odds of achieving 5% weight loss. All weight change groups had declines in the behaviors over time; however, compared to the other four groups, the weight loss/maintenance group (n = 154) had statistically less significant decline in number of food records/week (48%), recorded days/week of physical activity (41.7%), and intervention sessions attended (12.8%) through 18 months. Behaviors associated with short-term weight loss continue to be associated with long-term weight loss, albeit at lower frequencies. Minimizing the decline in these behaviors may be important in achieving long-term weight loss. PMID:21455122

  20. Model for the elastic behavior near intermartensitic transitions

    NASA Astrophysics Data System (ADS)

    Dai, Liyang; Cullen, James; Wuttig, Manfred

    2005-05-01

    Transitions between different martensitic states have been observed in Ni0.50Mn0.284Ga0.216 using elastic constant measurements. In this paper, we develop a model to explain the reentrant behavior based on a Landau expansion of the free energy in strain space. Here, we assume that the coefficient of the third-order term as well as the second-order term has significant temperature dependence. This assumption results in a C' versus temperature in good agreement with observation. The model and possible modifications to it are discussed and compared to the elastic constant data.

  1. Human behavioral regularity, fractional Brownian motion, and exotic phase transition

    NASA Astrophysics Data System (ADS)

    Li, Xiaohui; Yang, Guang; An, Kenan; Huang, Jiping

    2016-08-01

    The mix of competition and cooperation (C&C) is ubiquitous in human society, which, however, remains poorly explored due to the lack of a fundamental method. Here, by developing a Janus game for treating C&C between two sides (suppliers and consumers), we show, for the first time, experimental and simulation evidences for human behavioral regularity. This property is proved to be characterized by fractional Brownian motion associated with an exotic transition between periodic and nonperiodic phases. Furthermore, the periodic phase echoes with business cycles, which are well-known in reality but still far from being well understood. Our results imply that the Janus game could be a fundamental method for studying C&C among humans in society, and it provides guidance for predicting human behavioral activity from the perspective of fractional Brownian motion.

  2. Transition from supercapacitor to battery behavior in electrochemical energy storage

    SciTech Connect

    Conway, B.E. . Dept. of Chemistry)

    1991-06-01

    In this paper the storage of electrochemical energy in battery, supercapacitor, and double-layer capacitor devices is considered. A comparison of the mechanisms and performance of such systems enables their essential features to be recognized and distinguished, and the conditions for transition between supercapacitor and battery behavior to be characterized. Supercapacitor systems based on two-dimensional underpotential deposition reactions are highly reversible and their behavior arises from the pseudocapaccitance associated with potential-dependence of two-dimensional coverage of electroactive adatoms on an electrode substrate surface. Such capacitance can be 10-100 times the double-layer capacitance of the same electrode area. An essential fundamental difference from battery behavior arises because, in such systems, the chemical and associated electrode potentials are a continuous function of degree of charge, unlike the thermodynamic behavior of single-phase battery reactants. Quai-two-dimensional systems, such as hyperextended hydrous RuP{sub 2}, also exhibit large pseudocapacitance which, in this case, is associated with a sequence of redox redox processes that are highly reversible.

  3. Chaos-order transition in foraging behavior of ants.

    PubMed

    Li, Lixiang; Peng, Haipeng; Kurths, Jürgen; Yang, Yixian; Schellnhuber, Hans Joachim

    2014-06-10

    The study of the foraging behavior of group animals (especially ants) is of practical ecological importance, but it also contributes to the development of widely applicable optimization problem-solving techniques. Biologists have discovered that single ants exhibit low-dimensional deterministic-chaotic activities. However, the influences of the nest, ants' physical abilities, and ants' knowledge (or experience) on foraging behavior have received relatively little attention in studies of the collective behavior of ants. This paper provides new insights into basic mechanisms of effective foraging for social insects or group animals that have a home. We propose that the whole foraging process of ants is controlled by three successive strategies: hunting, homing, and path building. A mathematical model is developed to study this complex scheme. We show that the transition from chaotic to periodic regimes observed in our model results from an optimization scheme for group animals with a home. According to our investigation, the behavior of such insects is not represented by random but rather deterministic walks (as generated by deterministic dynamical systems, e.g., by maps) in a random environment: the animals use their intelligence and experience to guide them. The more knowledge an ant has, the higher its foraging efficiency is. When young insects join the collective to forage with old and middle-aged ants, it benefits the whole colony in the long run. The resulting strategy can even be optimal. PMID:24912159

  4. Artificial emotion triggered stochastic behavior transitions with motivational gain effects for multi-objective robot tasks

    NASA Astrophysics Data System (ADS)

    Dağlarli, Evren; Temeltaş, Hakan

    2007-04-01

    This paper presents artificial emotional system based autonomous robot control architecture. Hidden Markov model developed as mathematical background for stochastic emotional and behavior transitions. Motivation module of architecture considered as behavioral gain effect generator for achieving multi-objective robot tasks. According to emotional and behavioral state transition probabilities, artificial emotions determine sequences of behaviors. Also motivational gain effects of proposed architecture can be observed on the executing behaviors during simulation.

  5. Magnetic Behavior of 3d Transition Metals in Silicon Carbide

    NASA Astrophysics Data System (ADS)

    Miao, Maosheng; Lambrecht, Walter R. L.

    2002-03-01

    The magnetic properties of cubic silicon carbide (SiC) doped by first row transition metals (TM) are studied within the local spin density functional approach using the linearized muffin-tin orbital method in the atomic sphere approximation. It is found that the couplings between the TM d orbitals and the dangling bond states are stronger for the Si site doping, which gives a larger e-t2 splitting. The stronger coupling also delocalizes the t2 states and hence reduces the spin polarization. As a result the TMs tend to have a low spin configuration at the Si site and a high spin one at the C site. On the other hand, the strong couplings lower the formation energy at the Si site and TMs prefer to dope the Si site in both the Si-rich and C-rich limits. For Si site doping, Cr and Mn exhibit the most pronounced magnetic behavior with Cr favoring ferromagnetic and Mn antiferromagnetic nearest neighbor coupling.

  6. Metamorphic core complexes: Expression of crustal extension by ductile-brittle shearing of the geologic column

    NASA Technical Reports Server (NTRS)

    Davis, G. H.

    1985-01-01

    Metamorphic core complexes and detachment fault terranes in the American Southwest are products of stretching of continental crust in the Tertiary. The physical and geometric properties of the structures, fault rocks, and contact relationships that developed as a consequence of the extension are especially well displayed in southeastern Arizona. The structures and fault rocks, as a system, reflect a ductile-through-brittle continuum of deformation, with individual structures and faults rocks showing remarkably coordinated strain and displacement patterns. Careful mapping and analysis of the structural system has led to the realization that strain and displacement were partitioned across a host of structures, through a spectrum of scales, in rocks of progressively changing rheology. By integrating observations made in different parts of the extensional system, especially at different inferred depth levels, it has been possible to construct a descriptive/kinematic model of the progressive deformation that achieved continental crustal extension in general, and the development of metamorphic core complexes in particular.

  7. Quiescent and flow-induced transitional behavior of hydroxypropylcellulose solutions

    NASA Astrophysics Data System (ADS)

    Grizzuti, Nino; Maffettone, Pier Luca

    2003-03-01

    The flow-induced transition of liquid crystalline polymers (LCPs) is studied by rheological techniques. Aqueous solutions of hydroxypropylcellulose (HPC) in water are adopted as a model LCP system. Nonisothermal oscillatory tests are first used to quantitatively determine the "rheological" phase diagram of the HPC/water system under quiescent conditions. The phase diagram compares well with those obtained by other, more conventional techniques. Superposition of oscillatory and steady shear flow is then used to describe the nonisothermal flow-induced transition. In this case, it is shown that a critical shear stress must be reached to effectively induce the isotropic/mesophase transition. Stress-loop experiments are also used to identify the isothermal flow-induced transition, and to provide information on the transition kinetics.

  8. Quantum Phase Transitional Behavior in the Extended Casten Triangle of the Interacting Boson Model

    NASA Astrophysics Data System (ADS)

    Pan, Feng; Wang, Tao; Huo, Y.-S.; Draayer, J. P.

    Quantum phase transitional patterns in the whole parameter space of the consistent-Q Hamiltonian in the Interacting Boson Model are studied based on an implemented Fortran code for numerical computation of the matrix elements in the SU(3) Draayer-Akiyama basis. Results with respect to both ground and some excited states of the model Hamiltonian are discussed. Quantum phase transitional behavior under a variety of parameter situations is shown. It is found that transitional behavior of excited states is more complicated. Pt isotopes are taken as examples in illustrating the prolate-oblate shape phase transition.

  9. Examining Behavioral Risk and Academic Performance for Students Transitioning from Elementary to Middle School

    ERIC Educational Resources Information Center

    Lane, Kathleen Lynne; Oakes, Wendy Peia; Carter, Erik W.; Messenger, Mallory

    2015-01-01

    We studied the transition from elementary to middle school for 74 fifth-grade students. Specifically, we examined how behavioral risk evident in the elementary years, as measured by the "Student Risk Screening Scale" (SRSS), impacts students transitioning from elementary to middle school. First, we examined how student risk status shifts…

  10. Stakeholders' Voices: Defining Needs of Students with Emotional and Behavioral Disorders Transitioning between School Settings

    ERIC Educational Resources Information Center

    Buchanan, Rohanna; Nese, Rhonda N. T.; Clark, Miriam

    2016-01-01

    Students with emotional and behavioral disorders (EBD) too often do not receive adequate services or care in their school settings, particularly during transitions in educational placements. In addition, school support teams often struggle with creating transition plans that honor the needs of students with input from key stakeholders responsible…

  11. Phase Transition Behavior of Novel Soybean Oil-based Thermosensitive Polymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The thermal phase transition behavior of novel soybean oil-based polymers, i.e., hydrolyzed polymers of (epoxidized) soybean oil, was studied. The phase transition temperatures (cloud points) were determined from the inflection points of the light transmittance vs. temperature curves. The effect o...

  12. Study of physiological and behavioral response to transitions between rotating and nonrotating environments

    NASA Technical Reports Server (NTRS)

    Brady, J. F.

    1972-01-01

    Future manned space missions may require transition between artificial gravity and weightlessness environments. The frequency and rate of such transition will influence the psychophysiological responses of man. Abrupt transfers are examined between such rotating and nonrotating environments to determine the physiological and behavioral responses of man. Five subjects were tested using rates of rotation up to 5 rpm.

  13. Promising Practices for Effective Transition for Students with Emotional and Behavioral Disorders

    ERIC Educational Resources Information Center

    Katsiyannis, Antonis; Zhang, Dalun; Mackiewicz, Sara Moore

    2012-01-01

    Students with Emotional and Behavioral Disorders (E/BD) have been consistently experiencing dismal outcomes. The purpose of this chapter is to provide a brief overview of outcomes for this population, examine school-based instructional and behavioral strategies, and discuss transition related practices intended to improve present and future…

  14. Affiliation with Antisocial Peers, Susceptibility to Peer Influence, and Antisocial Behavior during the Transition to Adulthood

    ERIC Educational Resources Information Center

    Monahan, Kathryn C.; Steinberg, Laurence; Cauffman, Elizabeth

    2009-01-01

    Developmental theories suggest that affiliation with deviant peers and susceptibility to peer influence are important contributors to adolescent delinquency, but it is unclear how these variables impact antisocial behavior during the transition to adulthood, a period when most delinquent individuals decline in antisocial behavior. Using data from…

  15. Feeding Behaviors of Transition Dairy Cows Fed Glycerol as a Replacement for Corn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Feed sorting is a natural behavior of dairy cows that can result in inconsistencies in nutritive value of a TMR. The objective of this study was to determine the effects of replacing high moisture corn with glycerol on feed sorting and feeding behavior of transition dairy cows. Twenty-six Holstein ...

  16. Critical behavior at a dynamic vortex insulator-to-metal transition.

    PubMed

    Poccia, Nicola; Baturina, Tatyana I; Coneri, Francesco; Molenaar, Cor G; Wang, X Renshaw; Bianconi, Ginestra; Brinkman, Alexander; Hilgenkamp, Hans; Golubov, Alexander A; Vinokur, Valerii M

    2015-09-11

    An array of superconducting islands placed on a normal metal film offers a tunable realization of nanopatterned superconductivity. This system enables investigation of the nature of competing vortex states and phase transitions between them. A square array creates the eggcrate potential in which magnetic field-induced vortices are frozen into a vortex insulator. We observed a vortex insulator-vortex metal transition driven by the applied electric current and determined critical exponents that coincided with those for thermodynamic liquid-gas transition. Our findings offer a comprehensive description of dynamic critical behavior and establish a deep connection between equilibrium and nonequilibrium phase transitions. PMID:26359398

  17. Critical behavior at a dynamic vortex insulator-to-metal transition

    NASA Astrophysics Data System (ADS)

    Poccia, Nicola; Baturina, Tatyana I.; Coneri, Francesco; Molenaar, Cor G.; Wang, X. Renshaw; Bianconi, Ginestra; Brinkman, Alexander; Hilgenkamp, Hans; Golubov, Alexander A.; Vinokur, Valerii M.

    2015-09-01

    An array of superconducting islands placed on a normal metal film offers a tunable realization of nanopatterned superconductivity. This system enables investigation of the nature of competing vortex states and phase transitions between them. A square array creates the eggcrate potential in which magnetic field-induced vortices are frozen into a vortex insulator. We observed a vortex insulator-vortex metal transition driven by the applied electric current and determined critical exponents that coincided with those for thermodynamic liquid-gas transition. Our findings offer a comprehensive description of dynamic critical behavior and establish a deep connection between equilibrium and nonequilibrium phase transitions.

  18. Identification of nonmonotonic behaviors and stick-slip transition in liquid crystal polymers

    NASA Astrophysics Data System (ADS)

    Pujolle-Robic, Caroline; Noirez, Laurence

    2003-12-01

    The recent identification of shear-induced phases in the isotropic melts of liquid crystal polymers shows that these materials are expected to display original nonlinear behaviors. We have investigated the flow behavior of a nematic sidechain polymer above its isotropic-nematic transition temperature. Nonlinear rheology and birefringence measurements indicate the appearance, above a critical shear rate, of the shear-induced isotropic-nematic phase transition. The rheological behavior of this induced phase is characterized by undamped time-periodic shear stress oscillations. These sustained oscillations are interpreted in terms of a stick-slip mechanism alternating high-friction static state and low-friction kinetic state.

  19. Asymptotic behavior of linearized pipe flow and implications for transition

    NASA Astrophysics Data System (ADS)

    Meseguer, Alvaro; Trefethen, Lloyd N.

    2000-11-01

    A solenoidal Petrov-Galerkin MATLAB spectral code is described for high-accuracy computation of linearized dynamics for Hagen-Poiseuille flow in an infinite circular pipe. Systematic studies are presented of the dependence of eigenvalues, transient growth factors, and other quantities on the discretization parameters, the axial and azimuthal wave numbers, and the Reynolds number Re for Re ranging from 10^2 to the idealized (physically unrealizable) value 10^7. Implications for transition to turbulence are considered in the light of the recent theoretical results of S. J. Chapman. Our computations are in agreement with Chapman's predicted threshold amplitude for transition of order Re-3/2 as Re --> ∞.

  20. Syndromes or Flexibility: Behavior during a Life History Transition of a Coral Reef Fish

    PubMed Central

    White, James R.; McCormick, Mark I.; Meekan, Mark G.

    2013-01-01

    The theory of behavioral syndromes focuses on quantifying variation in behavior within and among individual organisms and attempts to account for the maintenance of differences in behavior that occur in a consistent manner among individuals. Behavioral syndromes have potentially important ecological consequences (e.g. survivorship tradeoffs) and can be shaped by population dynamics through selective mortality. Here, we search for any evidence for consistency of behavior across situations in juveniles of a common damselfish, Pomacentrus amboinensis (Pomacentridae) at the transition between larval habitats in the plankton and juvenile habitats on the reef. Naïve fish leaving the pelagic phase to settle on reefs were caught by light traps and their behaviors observed using similar methods across three different situations (small aquaria, large aquaria, field setting); all of which represent low risk and well-sheltered environments. Seven behavioral traits were compared within and among individuals across situations to determine if consistent behavioral syndromes existed. No consistency was found in any single or combination of behavioral traits for individuals across all situations. We suggest that high behavioral flexibility is likely beneficial for newly-settled fish at this ontogenetic transition and it is possible that consistent behavioral syndromes are unlikely to emerge in juveniles until environmental experience is gained or certain combinations of behaviors are favored by selective mortality. PMID:24386358

  1. Affect and sexual behavior in the transition to university.

    PubMed

    Dalton, Andrea L; Galambos, Nancy L

    2009-10-01

    This research applied a lifespan developmental framework to the study of sexual behavior among late adolescents by examining monthly covariations of penetrative and oral sex with positive and negative affect across the first year of university. Participants were 177 Canadian students who completed baseline questionnaires, followed by six monthly, web-based questionnaires assessing sexual behaviors and affect. Multilevel analyses revealed an average positive relation between oral sex and positive affect. Of six variables, five predicted individual differences in covariation between sex and affect: psychosocial maturity (immature and semi-mature status), attitudes toward sex, prior sexual experience, and living situation. During months when participants reported sexual behavior, psychosocially mature students reported more positive affect than did less mature students; students with more permissive attitudes reported more positive affect than did students with less permissive attitudes; students with no penetrative sexual experience reported more positive affect than students who had penetrative sexual experience; and living away from parents was associated with less negative affect. Implications for further study of sexual behavior from a developmental perspective are discussed. PMID:18814022

  2. Separate and Combined Effects of Visual Schedules and Extinction Plus Differential Reinforcement on Problem Behavior Occasioned by Transitions

    ERIC Educational Resources Information Center

    Waters, Melissa B.; Lerman, Dorothea C.; Hovanetz, Alyson N.

    2009-01-01

    The separate and combined effects of visual schedules and extinction plus differential reinforcement of other behavior (DRO) were evaluated to decrease transition-related problem behavior of 2 children diagnosed with autism. Visual schedules alone were ineffective in reducing problem behavior when transitioning from preferred to nonpreferred…

  3. Clinical ketosis and standing behavior in transition cows.

    PubMed

    Itle, A J; Huzzey, J M; Weary, D M; von Keyserlingk, M A G

    2015-01-01

    Ketosis is a common disease in dairy cattle, especially in the days after calving, and it is often undiagnosed. The objective of this study was to compare the standing behavior of dairy cows with and without ketosis during the days around calving to determine if changes in this behavior could be useful in the early identification of sick cows. Serum β-hydroxybutyrate (BHBA) was measured in 184 cows on a commercial dairy farm twice weekly from 2 to 21d after calving. Standing behavior was measured from 7d before calving to 21d after calving using data loggers. Retrospectively, 15 cows with clinical ketosis (3 consecutive BHBA samples >1.2mmol/L and at least one sample of BHBA >2.9mmol/L) were matched with 15 nonketotic cows (BHBA <1.2mmol/L). Five periods were defined for the statistical analyses: wk -1 (d -7 to -1), d 0 (day of calving), wk +1 (d 1 to 7), wk +2 (d 8 to 14), and wk +3 (d 15 to 21). The first signs of clinical ketosis occurred 4.5±2.1d after calving. Total daily standing time was longer for clinically ketotic cows compared with nonketotic cows during wk -1 (14.3±0.6 vs. 12.0±0.7h/d) and on d 0 (17.2±0.9 vs. 12.7±0.9h/d) but did not differ during the other periods. Clinically ketotic cows exhibited fewer standing bouts compared with nonketotic cows on d 0 only (14.6±1.9 vs. 20.9±1.8bouts/d). Average standing bout duration was also longer for clinically ketotic cows on d 0 compared with nonketotic cows [71.3min/bout (CI: 59.3 to 85.5) vs. 35.8min/bout (CI: 29.8 to 42.9)] but was not different during the other periods. Differences in standing behavior in the week before and on the day of calving may be useful for the early detection of clinical ketosis in dairy cows. PMID:25465623

  4. Complex Transition to Cooperative Behavior in a Structured Population Model

    PubMed Central

    Miranda, Luciano; de Souza, Adauto J. F.; Ferreira, Fernando F.; Campos, Paulo R. A.

    2012-01-01

    Cooperation plays an important role in the evolution of species and human societies. The understanding of the emergence and persistence of cooperation in those systems is a fascinating and fundamental question. Many mechanisms were extensively studied and proposed as supporting cooperation. The current work addresses the role of migration for the maintenance of cooperation in structured populations. This problem is investigated in an evolutionary perspective through the prisoner's dilemma game paradigm. It is found that migration and structure play an essential role in the evolution of the cooperative behavior. The possible outcomes of the model are extinction of the entire population, dominance of the cooperative strategy and coexistence between cooperators and defectors. The coexistence phase is obtained in the range of large migration rates. It is also verified the existence of a critical level of structuring beyond that cooperation is always likely. In resume, we conclude that the increase in the number of demes as well as in the migration rate favor the fixation of the cooperative behavior. PMID:22761736

  5. Oscillatory Behavior in the Transport Properties of Transition Metal Superlattices

    NASA Astrophysics Data System (ADS)

    Kim, Sihong

    Oscillations in the low temperature electrical resistivity, as a function of the individual layer thickness and/or superlattice period, have been recently observed in Co/Ni superlattices. This was believed to be a superlattice effect because the oscillations disappeared with decreasing number of bilayers. In this thesis, systematic studies have been made to understand the origin of this unusual behavior in the electrical transport of Co/Ni superlattices. First, Co/Ni was investigated extensively because Co and Ni have very similar material properties. They are both ferromagnetic, have fcc lattices in thin film form, and have almost identical electronic band structure. Superlattice films were grown by molecular beam epitaxy (MBE) and these structure was characterized by reflection high energy electron diffraction (RHEED), low energy electron diffraction (LEED), Auger electron spectroscopy (AES), and X-ray diffraction (XRD). The measured residual resistivity, usually caused by impurity atoms, lattice defects, interfaces, or grain boundaries, is very small in Co/Ni superlattice films. Due to this small background resistivity, unusual intrinsic resistivity oscillations have been clearly observed in these films. The oscillation amplitude does not change with temperature. However, a small amount of random fluctuation in the superlattice period, artificially introduced during film growth, significantly increases the oscillation amplitude. The resistivity at a minimum rm( rho_{min}) and maximum rm(rho_{max}) of oscillations was also measured as a function of film thickness in order to study the evolution of this effect. rho_{min} increases monotonically with decreasing thickness due to surface scattering, which is well described by the quantum size effect theory. However, rho_{max} becomes nonmonotonic by proper choice of superlattice period, indicating the presence of an additional scattering mechanism associated with the superlattice structure. Similar resistivity

  6. School-to-Life Transition: Perceptions of Youth in Behavior Intervention Programs

    ERIC Educational Resources Information Center

    Flower, Andrea; McKenna, John William; Haring, Christa D.; Pazey, Barbara

    2015-01-01

    Seven high school students with emotional disturbance were interviewed regarding their perceptions of their school experiences in preparation for transition. Students received support services from a behavior intervention program but spent the majority of the school day in general education classes. Interview data were collectively coded and…

  7. Improving the Transition-to-Adulthood Outcomes of Youths with Emotional and Behavioral Disabilities

    ERIC Educational Resources Information Center

    Kang, Mun Ju; Petr, Christopher G.; Morningstar, Mary

    2012-01-01

    Poor transition outcomes for youths with emotional and behavioral disabilities beg for the development of effective intervention models. After reviewing the limited empirical support for seven current intervention models, a critique is conducted that can serve as the foundation for modifying current practices toward building successful…

  8. Transitioning from Elementary School to Middle School: The Ecology of Black Males' Behavior

    ERIC Educational Resources Information Center

    Mundy, Alma Christienne

    2014-01-01

    The purpose of this mixed method study is to explain the ecology Black males experience as they transition from elementary school to middle school in terms of behavior. The Black male graduation rate is well below 50% nationally (Orfield, Losen, Wald, & Swanson, 2004; Schott Foundation for Public Education, 2010). Graduating from high school…

  9. Women in Cultural Transition: Suicidal Behavior in South African Indian Women.

    ERIC Educational Resources Information Center

    Wassenaar, Douglas R.; van der Veen, Marchiene B. W.; Pillay, Anthony L.

    1998-01-01

    The relationship between suicidal behavior and gender, and between gender, culture, and cultural transition for Indians in South Africa is studied. Data on suicide rates are presented. Social change, tension between Indian culture and westernization, traditional power relations, and gender are considered. Three case studies are related to…

  10. Gender-Role Attitudes and Behavior across the Transition to Parenthood

    ERIC Educational Resources Information Center

    Katz-Wise, Sabra L.; Priess, Heather A.; Hyde, Janet S.

    2010-01-01

    On the basis of social structural theory and identity theory, the current study examined changes in gender-role attitudes and behavior across the first-time transition to parenthood and following the birth of a second child for experienced mothers and fathers. Data were analyzed from the ongoing longitudinal Wisconsin Study of Families and Work.…

  11. Transition Tips for Educators Working with Students with Emotional and Behavioral Disabilities

    ERIC Educational Resources Information Center

    Cheney, Douglas

    2012-01-01

    Students with emotional and behavioral disabilities (EBD) have had difficulties in achieving educational, vocational, and community outcomes that would lead to personal success and satisfaction. Some of these outcomes relate to how special education transition programs integrate effective approaches to support success with these students. In this…

  12. Externalizing and Internalizing Behavior Problems, Peer Affiliations, and Bullying Involvement across the Transition to Middle School

    ERIC Educational Resources Information Center

    Farmer, Thomas W.; Irvin, Matthew J.; Motoca, Luci M.; Leung, Man-Chi; Hutchins, Bryan C.; Brooks, Debbie S.; Hall, Cristin M.

    2015-01-01

    Continuity and change in children's involvement in bullying was examined across the transition to middle school in relation to externalizing and internalizing behavior problems in fifth grade and peer affiliations in fifth and sixth grades. The sample consisted of 533 students (223 boys, 310 girls) with 72% European American, 25% African…

  13. The Effects of a High-Probability Request Sequencing Technique in Enhancing Transition Behaviors

    ERIC Educational Resources Information Center

    Banda, Devender R.; Kubina, Richard M., Jr.

    2006-01-01

    In this study, an autism support teacher used a high-probability request sequencing technique to help a middle-school student with autism engage in three transition behaviors. High probability request sequencing refers to a procedure in which 2 to 3 preferred questions, highly associated with compliance, are rapidly given before presenting a low…

  14. Phase Transition Behavior of Novel Soybean Oil-based Thermosensitive Polymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The thermal phase transition behavior of novel soybean oil-based polymers was studied. The effect of polymer concentration on the cloud points was investigated. The light transmittance increased sharply with increasing temperature suggesting dissociation of polymer aggregates. The cloud points we...

  15. Sexual Risk Behavior Associated with Transition to Injection Among Young Non-injecting Heroin Users

    PubMed Central

    Mackesy-Amiti, Mary Ellen; Boodram, Basmattee; Williams, Chyvette; Ouellet, Lawrence J.; Broz, Dita

    2012-01-01

    The aim of this study was to investigate the effects of transitioning from non-injection heroin use to injection drug use on sexual risk behavior. Non-injecting heroin users age 16–30 were enrolled from 2002 to 2005, and were re-interviewed at six-month intervals for up to three years; 561 participants completed at least one follow-up interview. The majority of participants were non-Hispanic (NH) Black (54%), 23% were Hispanic, and 21% were NH white. During follow-up, 154 participants (27.5%) transitioned to injecting drugs. Logistic regression analyses were conducted using generalized estimating equations (GEE) to estimate the effect of transition to injection drug use on changes in sexual risk behavior during follow-up. Transition to injection drug use during follow-up was associated with increased likelihood of sexual risk behavior, especially for men. Harm reduction efforts that focus on preventing initiation or return to injection among non-injecting drug users may also ameliorate HIV sexual risk behaviors. PMID:23065126

  16. Visualization of local phase transition behaviors in ultrathin VO2/TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Sohn, Ahrum; Kanki, Terou; Tanaka, Hidekazu; Kim, Dong-Wook

    VO2 undergoes the first order phase transition and two electronic phases can coexist near the critical temperature. We investigated evolution of the surface work function maps of epitaxial VO2/TiO2 thin films (thickness: 15, 30, and 45 nm) using Kelvin probe force microscopy (KPFM) measurements in the temperature range of 285-330 K. Fully strained thin films were almost free of grain boundaries and thicker films had dislocations caused by strain relaxation. The sample's work function decreases, while spanning the metal-insulator transition (MIT). The work function maps clearly revealed coexistence of the two distinct phase domains. The surface area fraction of the insulating phase near the dislocations was higher than that in other regions. Thicker films have complicated domain patterns; hence, the three-dimensional percolation model properly described the MIT behaviors. In contrast, the two-dimensional percolation model well explained the transition behaviors of uniformly strained thinner films.

  17. Grain size dependent phase transition and superparaelectric behavior of ferroelectric BST

    NASA Astrophysics Data System (ADS)

    Mondal, R. A.; Murty, B. S.; Murthy, V. R. K.

    2015-03-01

    In this article, we investigate the grain size dependent phase transition and polarization behavior of ferroelectric Ba0.9Sr0.1TiO3 (BST). Starting with nanocrystalline powders (crystalline size≈22 nm), various grain sizes were obtained in nano-submicron domain (202-745 nm) by regulating the sintering temperatures (Tsin) in the range of 1050-1300 °C. All samples were found to possess diffuse phase transition characteristics with frequency independent broad dielectric maxima near transition temperature due to the lattice strain contribution. Dielectric stiffness showed tarnished step-like anomalous behavior in the paraelectric state for Tsin≥1200 °C due to the existence of polar (superparaelectric) nano-regions generated by local polarization by off-centered Ti4+ ions exhibiting an exceptionally rare delicate polarization hysteresis loop.

  18. Phase transition and critical behavior of d=3 chiral fermion models with left-right asymmetry

    SciTech Connect

    Gies, Holger; Janssen, Lukas; Rechenberger, Stefan; Scherer, Michael M.

    2010-01-15

    We investigate the critical behavior of three-dimensional relativistic fermion models with a U(N{sub L}){sub L} x U(1){sub R} chiral symmetry reminiscent of the Higgs-Yukawa sector of the standard model of particle physics. We classify all possible four-fermion interaction terms and the corresponding discrete symmetries. For sufficiently strong correlations in a scalar parity-conserving channel, the system can undergo a second-order phase transition to a chiral-symmetry broken phase, which is a 3d analog of the electroweak phase transition. We determine the critical behavior of this phase transition in terms of the critical exponent {nu} and the fermion and scalar anomalous dimensions for N{sub L{>=}}1. Our models define new universality classes that can serve as prototypes for studies of strongly correlated chiral fermions.

  19. Structure and phase transition behavior of strontium modified barium zirconium titanate

    SciTech Connect

    Badapanda, T.; Sarangi, S.; Behera, B.; Saha, S.; Sinha, T. P.

    2015-06-24

    Pervoskite ceramics with composition Ba{sub 1-x}Sr{sub x}Zr{sub 0.05}Ti{sub 0.95}O{sub 3} (x= 0.1, 0.2, 0.3, 0.4 and 0.5) have been prepared by high energy ball milling. X-ray diffraction (XRD) patterns confirm that the all the compositions are in single phase. The composition shows tetragonal symmetry upto x=0.3 and with further increase in Sr content the structure changes to cubic. The temperature dependent dielectric behavior shows three phase transition in the parent material which merges with increase in Sr content. The transition temperature and dielectric constant decreases with increase in Sr concentration. The phase transition becomes more diffused with increment in doping concentration. The ferroelectric behavior of the ceramics is studied by the hysteresis loop.

  20. Transitions between dynamical behaviors of oscillator networks induced by diversity of nodes and edges

    NASA Astrophysics Data System (ADS)

    Werner, Sebastian; Lehnertz, Klaus

    2015-07-01

    We study the impact of dynamical and structural heterogeneity on the collective dynamics of large small-world networks of pulse-coupled integrate-and-fire oscillators endowed with refractory periods and time delay. Depending on the choice of homogeneous control parameters (here, refractoriness and coupling strength), these networks exhibit a large spectrum of dynamical behaviors, including asynchronous, partially synchronous, and fully synchronous states. Networks exhibit transitions between these dynamical behaviors upon introducing heterogeneity. We show that the probability for a network to exhibit a certain dynamical behavior (network susceptibility) is affected differently by dynamical and structural heterogeneity and depends on the respective homogeneous dynamics.

  1. Transitions between dynamical behaviors of oscillator networks induced by diversity of nodes and edges.

    PubMed

    Werner, Sebastian; Lehnertz, Klaus

    2015-07-01

    We study the impact of dynamical and structural heterogeneity on the collective dynamics of large small-world networks of pulse-coupled integrate-and-fire oscillators endowed with refractory periods and time delay. Depending on the choice of homogeneous control parameters (here, refractoriness and coupling strength), these networks exhibit a large spectrum of dynamical behaviors, including asynchronous, partially synchronous, and fully synchronous states. Networks exhibit transitions between these dynamical behaviors upon introducing heterogeneity. We show that the probability for a network to exhibit a certain dynamical behavior (network susceptibility) is affected differently by dynamical and structural heterogeneity and depends on the respective homogeneous dynamics. PMID:26232952

  2. Mechanical properties of electron-beam-melted molybdenum and dilute molybdenum-rhenium alloys

    NASA Technical Reports Server (NTRS)

    Klopp, W. D.; Witzke, W. R.

    1972-01-01

    A study of molybdenum and three dilute molybdenum-rhenium alloys was undertaken to determine the effects of rhenium on the low temperature ductility and other mechanical properties of molybdenum. Alloys containing 3.9, 5.9, and 7.7 atomic percent rhenium exhibited lower ductile-brittle transition temperatures than did the unalloyed molybdenum. The maximum improvement in the annealed condition was observed for molybdenum - 7.7 rhenium, which had a ductile-brittle transition temperature approximately 200 C (360 F) lower than that for unalloyed molybdenum. Rhenium additions also increased the low and high temperature tensile strengths and the high temperature creep strength of molybdenum. The mechanical behavior of dilute molybdenum-rhenium alloys is similar to that observed for dilute tungsten-rhenium alloys.

  3. Nonlinear light behaviors near phase transition in non-parity-time-symmetric complex waveguides.

    PubMed

    Nixon, Sean; Yang, Jianke

    2016-06-15

    Many classes of non-parity-time (PT)-symmetric waveguides with arbitrary gain and loss distributions still possess all-real linear spectrum or exhibit phase transition. In this Letter, nonlinear light behaviors in these complex waveguides are probed analytically near a phase transition. Using multi-scale perturbation methods, a nonlinear ordinary differential equation (ODE) is derived for the light's amplitude evolution. This ODE predicts that a single class of these non-PT-symmetric waveguides supports soliton families and amplitude-oscillating solutions both above and below linear phase transition, in close analogy with PT-symmetric systems. For the other classes of waveguides, the light's intensity always amplifies under the effect of nonlinearity, even if the waveguide is below the linear phase transition. These analytical predictions are confirmed by direct computations of the full system. PMID:27304279

  4. On the behavior of Bronsted-Evans-Polanyi Relations for Transition Metal Oxides

    SciTech Connect

    Vojvodic, Aleksandra

    2011-08-22

    Versatile Broensted-Evans-Polanyi (BEP) relations are found from density functional theory for a wide range of transition metal oxides including rutiles and perovskites. For oxides, the relation depends on the type of oxide, the active site and the dissociating molecule. The slope of the BEP relation is strongly coupled to the adsorbate geometry in the transition state. If it is final state-like the dissociative chemisorption energy can be considered as a descriptor for the dissociation. If it is initial state-like, on the other hand, the dissociative chemisorption energy is not suitable as descriptor for the dissociation. Dissociation of molecules with strong intramolecular bonds belong to the former and molecules with weak intramolecular bonds to the latter group. We show, for the prototype system La-perovskites, that there is a 'cyclic' behavior in the transition state characteristics upon change of the active transition metal of the oxide.

  5. On the behavior of Brønsted-Evans-Polanyi relations for transition metal oxides.

    PubMed

    Vojvodic, A; Calle-Vallejo, F; Guo, W; Wang, S; Toftelund, A; Studt, F; Martínez, J I; Shen, J; Man, I C; Rossmeisl, J; Bligaard, T; Noørskov, J K; Abild-Pedersen, F

    2011-06-28

    Versatile Brønsted-Evans-Polanyi (BEP) relations are found from density functional theory for a wide range of transition metal oxides including rutiles and perovskites. For oxides, the relation depends on the type of oxide, the active site, and the dissociating molecule. The slope of the BEP relation is strongly coupled to the adsorbate geometry in the transition state. If it is final state-like the dissociative chemisorption energy can be considered as a descriptor for the dissociation. If it is initial state-like, on the other hand, the dissociative chemisorption energy is not suitable as descriptor for the dissociation. Dissociation of molecules with strong intramolecular bonds belong to the former and molecules with weak intramolecular bonds to the latter group. We show, for the prototype system La-perovskites, that there is a "cyclic" behavior in the transition state characteristics upon change of the active transition metal of the oxide. PMID:21721645

  6. Nonlinear light behaviors near phase transition in non-parity-time-symmetric complex waveguides

    NASA Astrophysics Data System (ADS)

    Nixon, Sean; Yang, Jianke

    2016-06-01

    Many classes of non-parity-time (PT) symmetric waveguides with arbitrary gain and loss distributions still possess all-real linear spectrum or exhibit phase transition. In this article, nonlinear light behaviors in these complex waveguides are probed analytically near a phase transition. Using multi-scale perturbation methods, a nonlinear ordinary differential equation (ODE) is derived for the light's amplitude evolution. This ODE predicts that the first class of these non-PT-symmetric waveguides support continuous families of solitons and robust amplitude-oscillating solutions both above and below phase transition, in close analogy with PT-symmetric systems. For the other classes of waveguides, the light's intensity always amplifies under the effect of nonlinearity even if the waveguide is below phase transition. These analytical predictions are confirmed by direct computations of the full system.

  7. Investigation of the atypical glass transition and recrystallization behavior of amorphous prazosin salts.

    PubMed

    Kumar, Lokesh; Popat, Dharmesh; Bansal, Arvind K

    2011-01-01

    This manuscript studied the effect of counterion on the glass transition and recrystallization behavior of amorphous salts of prazosin. Three amorphous salts of prazosin, namely, prazosin hydrochloride, prazosin mesylate and prazosin tosylate were prepared by spray drying, and characterized by optical-polarized microscopy, differential scanning calorimetry and powder X-ray diffraction. Modulated differential scanning calorimetry was used to determine the glass transition and recrystallization temperature of amorphous salts. Glass transition of amorphous salts followed the order: prazosin mesylate > prazosin tosylate ~ prazosin hydrochloride. Amorphous prazosin mesylate and prazosin tosylate showed glass transition, followed by recrystallization. In contrast, amorphous prazosin hydrochloride showed glass transition and recrystallization simultaneously. Density Functional Theory, however, suggested the expected order of glass transition as prazosin hydrochloride > prazosin mesylate > prazosin tosylate. The counterintuitive observation of amorphous prazosin hydrochloride having lower glass transition was explained in terms of its lower activation energy (206.1 kJ/mol) for molecular mobility at Tg, compared to that for amorphous prazosin mesylate (448.5 kJ/mol) and prazosin tosylate (490.7 kJ/mol), and was further correlated to a difference in hydrogen bonding strength of the amorphous and the corresponding recrystallized salts. This study has implications in selection of an optimal amorphous salt form for pharmaceutical development. PMID:24310595

  8. Stability and Change in Prosocial and Antisocial Behavior across the Transition to School: Teacher and Peer Perspectives

    ERIC Educational Resources Information Center

    Eivers, Areana R.; Brendgen, Mara; Borge, Anne I. H.

    2010-01-01

    Research Findings: The transition to school is a major developmental milestone, and behavior tendencies already evident at the point of school entry can impact upon a child's subsequent social and academic adjustment. The current study aimed to investigate stability and change in the social behavior of girls and boys across the transition from day…

  9. Phase transition-like behavior of magnetospheric substorms: Global MHD simulation results

    NASA Astrophysics Data System (ADS)

    Shao, X.; Sitnov, M. I.; Sharma, S. A.; Papadopoulos, K.; Goodrich, C. C.; Guzdar, P. N.; Milikh, G. M.; Wiltberger, M. J.; Lyon, J. G.

    2003-01-01

    Using nonlinear dynamical techniques, we statistically investigate whether the simulated substorms from global magnetohydrodynamic (MHD) models have a combination of global and multiscale features, revealed in substorm dynamics by [2000] and featured the phase transition-like behavior. We simulate seven intervals of total duration of 280 hours from the data set used in the above works [, 1985]. We analyze the input-output (vBs-pseudo AL index) system obtained from the global MHD model and compare the results to those inferred from the original set (vBs-observed AL index). The analysis of the coupled vBs-pseudo AL index system shows the first-order phase transition map, which is consistent with the map obtained for the vBs-observed AL index system. Although the comparison between observations and global MHD simulations for individual events may vary, the overall global transition pattern during the substorm cycle revealed by singular spectrum analysis (SSA) is statistically consistent between simulations and observations. The coupled vBs-pseudo AL index system also shows multiscale behavior (scale-invariant power law dependence) in SSA power spectrum. Besides, we find the critical exponent of the nonequilibrium transitions in the magnetosphere, which reflects the multiscale aspect of the substorm activity, different from power law frequency of autonomous systems. The exponent relates input and output parameters of the magnetosphere. We also discuss the limitations of the global MHD model in reproducing the multiscale behavior when compared to the real system.

  10. Behavioral transition from attack to parenting in male mice: a crucial role of the vomeronasal system.

    PubMed

    Tachikawa, Kashiko S; Yoshihara, Yoshihiro; Kuroda, Kumi O

    2013-03-20

    Sexually naive male mice show robust aggressive behavior toward pups. However, the proportion of male mice exhibiting pup-directed aggression declines after cohabitation with a pregnant female for 2 weeks after mating. Subsequently, on becoming fathers, they show parental behavior toward pups, similar to maternal behavior by mothers. To elucidate the neural mechanisms underlying this behavioral transition, we examined brain regions differentially activated in sexually naive males and fathers after exposure to pups, using c-Fos expression as a neuronal activation marker. We found that, after pup exposure, subsets of neurons along the vomeronasal neural pathway-including the vomeronasal sensory neurons, the accessory olfactory bulb, the posterior medial amygdala, the medioposterior division of the bed nucleus of stria terminalis, and the anterior hypothalamic area-were more strongly activated in sexually naive males than in fathers. Notably, c-Fos induction was not observed in the vomeronasal sensory neurons of fathers after pup exposure. Surgical ablation of the vomeronasal organ in sexually naive males resulted in the abrogation of pup-directed aggression and simultaneous induction of parental behavior. These results suggest that chemical cues evoking pup-directed aggression are received by the vomeronasal sensory neurons and activate the vomeronasal neural pathway in sexually naive male mice but not in fathers. Thus, the downregulation of pup pheromone-induced activation of the vomeronasal system might be important for the behavioral transition from attack to parenting in male mice. PMID:23516278

  11. Coparenting Moderates the Association between Firstborn Children's Temperament and Problem Behavior across the Transition to Siblinghood

    PubMed Central

    Kolak, Amy M.; Volling, Brenda L.

    2013-01-01

    The contribution of individual (i.e., negative reactivity) and environmental (i.e., coparenting) characteristics in predicting firstborns’ adjustment after a sibling's birth were examined. Mothers, fathers, and firstborn children from 241 families participated in a family freeplay to assess coparenting interactions before the birth of the second child and parents completed questionnaires on children's temperamental characteristics and behavior problems. Children's externalizing problems significantly increased from pre- to post-birth. Children, on average, did not display more internalizing problems following the infant sibling's birth; however, children high in negative reactivity were more sensitive to undermining coparenting behavior and displayed greater internalizing behaviors across the transition to siblinghood. Negatively reactive children also displayed increases in externalizing behavior across the transition to siblinghood when parents showed high levels of undermining coparenting and low levels of supportive coparenting. Supportive coparenting appeared to be a protective factor in the face of this transition for negatively reactive children in families where parents engaged in high levels of undermining coparenting. Findings suggest that both individual and environmental factors play an important role in firstborns’ adjustment to an infant sibling's birth. Parents of temperamentally sensitive children may benefit from participating in workshops geared towards improving coparenting partnerships prior to the birth of the second child. PMID:23750518

  12. Transitions.

    ERIC Educational Resources Information Center

    Nathanson, Jeanne H., Ed.

    1993-01-01

    This theme issue on transitions for individuals with disabilities contains nine papers discussing transition programs and issues. "Transition Issues for the 1990s," by Michael J. Ward and William D. Halloran, discusses self-determination, school responsibility for transition, continued educational engagement of at-risk students, and service…

  13. Phase transitions in the multi-cellular regulatory behavior of pancreatic islet excitability.

    PubMed

    Hraha, Thomas H; Westacott, Matthew J; Pozzoli, Marina; Notary, Aleena M; McClatchey, P Mason; Benninger, Richard K P

    2014-09-01

    The pancreatic islets of Langerhans are multicellular micro-organs integral to maintaining glucose homeostasis through secretion of the hormone insulin. β-cells within the islet exist as a highly coupled electrical network which coordinates electrical activity and insulin release at high glucose, but leads to global suppression at basal glucose. Despite its importance, how network dynamics generate this emergent binary on/off behavior remains to be elucidated. Previous work has suggested that a small threshold of quiescent cells is able to suppress the entire network. By modeling the islet as a Boolean network, we predicted a phase-transition between globally active and inactive states would emerge near this threshold number of cells, indicative of critical behavior. This was tested using islets with an inducible-expression mutation which renders defined numbers of cells electrically inactive, together with pharmacological modulation of electrical activity. This was combined with real-time imaging of intracellular free-calcium activity [Ca2+]i and measurement of physiological parameters in mice. As the number of inexcitable cells was increased beyond ∼15%, a phase-transition in islet activity occurred, switching from globally active wild-type behavior to global quiescence. This phase-transition was also seen in insulin secretion and blood glucose, indicating physiological impact. This behavior was reproduced in a multicellular dynamical model suggesting critical behavior in the islet may obey general properties of coupled heterogeneous networks. This study represents the first detailed explanation for how the islet facilitates inhibitory activity in spite of a heterogeneous cell population, as well as the role this plays in diabetes and its reversal. We further explain how islets utilize this critical behavior to leverage cellular heterogeneity and coordinate a robust insulin response with high dynamic range. These findings also give new insight into emergent

  14. Phase transition-like behavior in a low-pass filter

    NASA Astrophysics Data System (ADS)

    Krivine, H.; Lesne, A.

    2003-01-01

    We discuss an iterative electric circuit for which the limits of infinite number of elements and zero dissipation in each element do not commute. The circuit is taken from the Feynman lectures, where it was argued on physical considerations that an infinite circuit made only of inductances and capacitances would behave as a dissipative system with nonvanishing resistance below a threshold frequency. The understanding of this behavior requires that the two limits be taken in the appropriate order. This simple example illustrates that caution in multiple limiting procedures is necessary to obtain the correct physical behavior. A close analogy with the standard ferromagnetic transition of the Ising model is drawn.

  15. Phase transition of dynamical herd behaviors for Yen Dollar exchange rates

    NASA Astrophysics Data System (ADS)

    Yoon, Seong-Min; Choi, J. S.; Kim, Y.; Kim, Kyungsik

    2006-01-01

    We study the herd behavior and the phase transition for the yen-dollar exchange rate in the Japanese financial market. It is obtained that the probability distribution of returns satisfies the power-law behavior P(R)≃R with scaling exponents β=3.11, 2.81, and 2.29 at time intervals τ=1min, 30min, and 1 h. The crash region in which the probability density increases with the increasing return appears, when the herding parameter h satisfies h⩾2.33 for the case of τ<30min. We especially obtain that no crash occurs τ>30min and that the probability distribution of price returns occurs in the phase transition at τ=30min.

  16. O the Transition from - to Three-Dimensional Behavior in Adsorbed Films

    NASA Astrophysics Data System (ADS)

    Day, Peter Kenneth

    1993-01-01

    Argon and krypton films adsorbed on graphite foam have been studied in detail using vapor pressure and high resolution, heat capacity measurements. Heat capacity features near the bulk triple point temperature, previously associated with the surface melting of the uniform film, are shown to be due to the melting of bulk material condensed in pores in the substrate. The melting curve of the capillary condensate agrees with the prediction of a modified Clausius -Claperon equation. The second and third layers in argon and the second layer in krypton have a triple point at which two-dimensional solid, liquid, and gas phases coexist atop a solid lower layer. Commensurate-incommensurate transitions are found in the first two layers of argon and in the second layer of krypton, so that monolayer argon melts from a registered phase, but the second layers of both systems melt from incommensurate bilayer phases. The melting of the second and third layers in both systems are likely to be first order, but the data are not conclusive. At coverages starting with 3{1over 2} layers, heat capacity features that are due to reentrant layering-transitions are seen in both systems, confirming the result of recent ellipsometry studies. Further heat capacity peaks suggest phase transitions that join the newly observed reentrant layering-transitions with the well studied layering-transitions at low temperature. These heat capacity peaks may be related to the recently proposed preroughening transition. A mean field theory is developed that reproduced the reentrant layering behavior for ratios of nearest and next nearest neighbor interaction energies greater than a critical value. The mean field theory gives an explanation for the appearance of reentrant layering -transitions at different film thicknesses depending on the substrate-adsorbate interaction parameter. Multilayer phase diagrams are drawn from the data that suggest a crossover from two-dimensional behavior in the second layer to

  17. Transitional behavior between self-Kerr and cross-Kerr effects by two photons

    SciTech Connect

    Koshino, Kazuki

    2007-06-15

    The transitional behavior of the two-photon Kerr effect between the self-Kerr and cross-Kerr cases is investigated. To this end, we have developed a semiclassical method for evaluating the two-photon Kerr effect that is applicable to any two-photon input state. It is revealed that the maximum Kerr effect is obtained when the second photon is input with a delay time that corresponds to the absorption time of the first photon by the optical material.

  18. Critical behavior near the Mott transition in the half-filled asymmetric Hubbard model

    NASA Astrophysics Data System (ADS)

    Hoang, Anh-Tuan; Le, Duc-Anh

    2016-03-01

    We study the half-filled asymmetric Hubbard model within the two-site dynamical mean field theory. At zero temperature, explicit expressions of the critical interaction Uc for the Mott transition and the local self-energy are analytically derived. Critical behavior of the quasiparticle weights and the double occupancy are obtained analytically as functions of the on-site interaction U and the hopping asymmetry r. Our results are in good agreement with the ones obtained by much more sophisticated theory.

  19. Transitions Into Food Insecurity Associated With Behavioral Problems And Worse Overall Health Among Children.

    PubMed

    Kimbro, Rachel Tolbert; Denney, Justin T

    2015-11-01

    Children living in food-insecure households face myriad challenges to their well-being. The Great Recession of December 2007-June 2009 increased food insecurity to the highest levels ever measured in the United States. Using nationally representative data from the period 2010-12 for 6,300 children in the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11, with household incomes below 300 percent of the federal poverty level and a dynamic measure of food insecurity transitions, we assessed the impact of transitions into and out of household food insecurity on the academic achievement, behavioral problems, and health status of young children. We found negligible impacts of food insecurity transitions on academic achievement in first grade. However, we found consistent negative impacts of the transitions on teachers' reports of children's externalizing behaviors, self-control, and interpersonal skills and on parents' reports of children's overall health status. Taken together, our findings underline the importance of food security for children's healthy development. PMID:26526254

  20. The transition from primary to secondary school as stressful life event provoking risky drinking behaviors.

    PubMed

    Junge, Claudia; Krienke, Ute J; Böhme, Karin; Prüß, Franz; Sander, Aleksandra; Niemann, Jörg; Langosch, Jens M

    2016-01-01

    This study is based on a drug prevention project for children in the German-Polish border region known as "Pomerania." The aim of this project was to minimize risk behaviors while developing social skills as protective factors through project-specific training interventions. The present study especially investigates the development of social skills and risk behaviors at German and Polish primary schools in the critical transitional period from primary to secondary school. Data on German 4th graders and Polish 6th graders were collected by means of a longitudinal and control group design through 3rd-party assessment from teachers. The data on social skills was collected through the use of standardized assessment instruments. The study established that social skills could indeed be increased through training and that risk behaviors decreased in both of the treatment groups. The control group showed altogether an increase in risk behavior and a decrease in coping skills. In the Polish treatment group, even risk behaviors which had been detected previously decreased. The German control group showed an increase in risk behaviors and a decrease in coping skills. In the case of the younger German pupils, the effectiveness of the interventions was exhibited indirectly. Despite variations in age and cultural differences, the effects of training were noticeable in children from both countries. The intervention program offered the children adequate assistance in order to successfully cope with this stressful life event. It promoted the development of social skills while minimizing risk behaviors. PMID:26745346

  1. Transitions.

    ERIC Educational Resources Information Center

    Field, David; And Others

    1992-01-01

    Includes four articles: "Career Aspirations" (Field); "Making the Transition to a New Curriculum" (Baker, Householder); "How about a 'Work to School' Transition?" (Glasberg); and "Technological Improvisation: Bringing CNC to Woodworking" (Charles, McDuffie). (SK)

  2. A quaternary lead based perovskite structured materials with diffuse phase transition behavior

    SciTech Connect

    Puli, Venkata Sreenivas; Martinez, R.; Kumar, Ashok; Scott, J.F.; Cavendish Laboratory, Dept. Physics, University of Cambridge, Cambridge CB0 3HE ; Katiyar, Ram S.

    2011-12-15

    Graphical abstract: (a) Curie-Weiss plot for the inverse of the relative dielectric permittivity and (b) log (1/{epsilon} - 1/{epsilon}{sub m}) as function of log (T - T{sub m}) for ceramics at 1 kHz. Highlights: Black-Right-Pointing-Pointer Retaining phase pure structure with quaternary complex stoichiometric compositions. Black-Right-Pointing-Pointer P-E loops with good saturation polarization (P{sub s} {approx} 30.7 {mu}C/cm{sup 2}). Black-Right-Pointing-Pointer Diffused relaxor phase transition behavior with {gamma} estimated is {approx}1.65. -- Abstract: A lead based quaternary compound composed of 0.25(PbZr{sub 0.52}Ti{sub 0.48}O{sub 3}) + 0.25(PbFe{sub 0.5}Ta{sub 0.5}O{sub 3}) + 0.25 (PbF{sub 0.67}W{sub 0.33}O{sub 3}) + 0.25(PbFe{sub 0.5}Nb{sub 0.5}O{sub 3}) - (PZT-PFT-PFW-PFN) was synthesized by conventional solid-state reaction techniques. It showed moderate high dielectric constant, low dielectric loss, and two diffuse phase transitions, one below the room temperature {approx}261 K and other above {approx}410 K. X-ray diffraction (XRD) patterns revealed a tetragonal crystal structure at room temperature where as scanning electron micrograph (SEM) indicates inhomogeneous surface with an average grain size of 500 nm-3 {mu}m. Well saturated ferroelectric hysteresis loops with good saturation polarization (spontaneous polarization, P{sub s} {approx} 30.68 {mu}C/cm{sup 2}) were observed. Temperature-dependent ac conductivity displayed low conductivity with kink in spectra near the phase transition. In continuing search for developing new ferroelectric materials, in the present study we report stoichiometric compositions of complex perovskite ceramic materials: (PZT-PFT-PFW-PFN) with diffuse phase transition behavior. The crystal structure, dielectric properties, and ferroelectric properties were characterized by XRD, SEM, dielectric spectroscopy, and polarization. 1/{epsilon} versus (T) plots revealed diffuse relaxor phase transition (DPT) behavior. The

  3. Transition.

    ERIC Educational Resources Information Center

    Thompson, Sandy, Ed.; And Others

    1990-01-01

    This "feature issue" focuses on transition from school to adult life for persons with disabilities. Included are "success stories," brief program descriptions, and a list of resources. Individual articles include the following titles and authors: "Transition: An Energizing Concept" (Paul Bates); "Transition Issues for the 1990s" (William Halloran…

  4. Crossover behavior of the thermal conductance and Kramers' transition rate theory

    NASA Astrophysics Data System (ADS)

    Sahu, Subin; Velizhanin, Kirill; Chien, Chih-Chun; Dubi, Yonatan; Zwolak, Michael

    2015-03-01

    Heat transport plays opposing roles in nanotechnology, hindering the miniaturization of electronics on one hand and forming the core of novel heattronic devices on the other. Moreover, heat transport in one-dimensional nanostructures has become a central tool in studying the onset of Fourier's law of heat conduction, a yet unresolved puzzle in theoretical physics. We study the paradigmatic setting of heat transport in one-dimensional systems, a lattice coupled to two heat baths held at different temperatures. Using both numerical and analytical tools, we demonstrate that the heat conductance displays a crossover behavior as the coupling to the thermal reservoirs is tuned. We provide evidence that this behavior is universal by examining harmonic, anharmonic, and disordered systems, and discuss the origin of this effect using an analogy with Kramers' transition state theory for chemical reaction rates. This crossover behavior has important implications in the analysis of numerical results, and suggests a novel way to tune the conductance in nanoscale devices.

  5. Delinquent Behavior, the Transition to Adulthood, and the Likelihood of Military Enlistment

    PubMed Central

    Teachman, Jay; Tedrow, Lucky

    2014-01-01

    Using data taken from the 1997 National Longitudinal Survey of Youth we examine the relationship between delinquency and enlistment in the military. We argue that delinquent behavior is positively related to enlistment because military service is an attractive alternative for delinquents to mark their transition to adulthood and their desistance from delinquent behavior. We also argue, however, that this relationship is not linear, with higher levels of delinquent behavior actually acting to reduce the likelihood of enlistment. We further suggest that the relationship between delinquency and enlistment is similar for men and women. We test and find support for our hypotheses using data taken from the 1997 National Longitudinal Survey of Youth. PMID:24576626

  6. Affiliation With Antisocial Peers, Susceptibility to Peer Influence, and Antisocial Behavior During the Transition to Adulthood

    PubMed Central

    Monahan, Kathryn C.; Steinberg, Laurence; Cauffman, Elizabeth

    2010-01-01

    Developmental theories suggest that affiliation with deviant peers and susceptibility to peer influence are important contributors to adolescent delinquency, but it is unclear how these variables impact antisocial behavior during the transition to adulthood, a period when most delinquent individuals decline in antisocial behavior. Using data from a longitudinal study of 1,354 antisocial youth, the present study examined how individual variation in exposure to deviant peers and resistance to peer influence affect antisocial behavior from middle adolescence into young adulthood (ages 14 to 22 years). Whereas we find evidence that antisocial individuals choose to affiliate with deviant peers, and that affiliating with deviant peers is associated with an individual’s own delinquency, these complementary processes of selection and socialization operate in different developmental periods. In middle adolescence, both selection and socialization serve to make peers similar in antisocial behavior, but from ages 16 to 20 years, only socialization appears to be important. After age 20, the impact of peers on antisocial behavior disappears as individuals become increasingly resistant to peer influence, suggesting that the process of desistance from antisocial behavior may be tied to normative changes in peer relations that occur as individuals mature socially and emotionally. PMID:19899911

  7. Phase Transition-like Behavior of Magnetospheric Substorms: Global MHD Simulation Results

    NASA Astrophysics Data System (ADS)

    Shao, X.; Sitnov, M.; Sharma, A. S.; Papadopoulos, K.; Guzdar, P. N.; Goodrich, C. C.; Milikh, G. M.; Wiltberger, M. J.; Lyon, J. G.

    2001-12-01

    Because of their relevance to massive global energy loading and unloading, lots of observations and studies have been made for magnetic substorm events. Using nonlinear dynamical techniques, we investigate whether the simulated substorms from global MHD models have the non-equilibrium phase transition-like features revealed by \\markcite{Sitnov et al. [2000]}. We simulated 6 intervals of total duration of 240 hours from the same data set used in Sitnov et al. [2000]. We analyzed the input-output (vBs--pseudo-AL index) system obtained from the global MHD model and compared the results to those in \\markcite{Sitnov et al. [2000, 2001]}. The analysis of the coupled vBs--pseudo-AL index system shows the first-order phase transition map, which is consistent with the map obtained for the vBs--observed-AL index system from Sitnov et al. [2000]. The explanation lies in the cusp catastrophe model proposed by Lewis [1991]. Although, the comparison between observation and individual global MHD simulations may vary, the overall global transition pattern during the substorm cycle revealed by Singular Spectrum Analysis (SSA) is consistent between simulations and observations. This is an important validation of the global MHD simulations of the magnetosphere. The coupled vBs--pseudo-AL index system shows multi-scale behavior (scale-invarianet power-law dependence) in singular power spectrum. We found critical exponents of the non-equilibrium transitions in the magnetosphere, which reflect the multi-scale aspect of the substorm activity, different from power-law frequency of autonomous systems. The exponents relate input and output parameters of the magnetosphere and distinguish the second order phase transition model from the self-organized criticality model. We also discuss the limitations of the global MHD model in reproducing the multi-scale behavior when compared to the real system.

  8. Phase Transition like Behavior of Magnetospheric Substorms: Global and Multiscale Features from MHD Simulations

    NASA Astrophysics Data System (ADS)

    Shao, X.; Sitnov, M. I.; Sharma, A. S.; Papadopoulos, K.; Goodrich, C. C.; Guzdar, P. N.; Milikh, G. M.; Wiltberger, M. J.; Lyon, J. G.

    2002-05-01

    Studies of the magnetosphere during substorms based on the observational data of the solar wind and the geomagnetic indices have shown clear features of phase transition-like behavior [Sitnov et al., 2000]. The global MHD simulations of the events in the Bargatze et al. [1985] database are used to study the non-equilibrium phase transition-like features of substorms. We simulated 7 intervals of total duration of 280 hours from the same data set used in Sitnov et al. [2000]. From the simulations the AL index is computed from the maximum of the westward Hall current and is referred to as the pseudo-AL index. We analyzed the input-output (vBs-pseudo-AL index) system obtained from the global MHD model and compare the results to those in Sitnov et al. [2000, 2001]. The analysis of the coupled vBs-pseudo-AL index system shows the first-order phase transition characterizing global beahavior, similar to the case of vBs-observed-AL index [Sitnov et al., 2000]. Although, the comparison between observations and global MHD simulations for individual events may vary, the overall global transition pattern during the substorm cycle revealed by singular spectrum snalysis is statistically consistent between simulations and observations. The coupled vBs-pseudo-AL index system shows multi-scale behavior (scale-invariant power-law dependence) in singular power spectrum. We find critical exponents of the non-equilibrium transitions in the magnetosphere, which reflect the multi-scale aspect of the substorm activity, different from power-law frequency of autonomous systems. The exponents relate input and output parameters of the magnetosphere.

  9. Behavior of supercooled aqueous solutions stemming from hidden liquid-liquid transition in water

    NASA Astrophysics Data System (ADS)

    Biddle, John W.; Holten, Vincent; Anisimov, Mikhail A.

    2014-08-01

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid-liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid-liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H2O-NaCl and H2O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid-liquid transition. We elucidate the non-conserved nature of the order parameter (extent of "reaction" between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.

  10. Behavior of supercooled aqueous solutions stemming from hidden liquid–liquid transition in water

    SciTech Connect

    Biddle, John W.; Holten, Vincent; Anisimov, Mikhail A.

    2014-08-21

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid–liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid–liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H{sub 2}O-NaCl and H{sub 2}O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid–liquid transition. We elucidate the non-conserved nature of the order parameter (extent of “reaction” between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.

  11. Tailoring surface phase transition and magnetic behaviors in BiFeO3 via doping engineering.

    PubMed

    Yan, Feng; Xing, Guozhong; Wang, Rongming; Li, Lin

    2015-01-01

    The charge-spin interactions in multiferroic materials (e.g., BiFeO3) have attracted enormous attention due to their high potential for next generation information electronics. However, the weak and deficient manipulation of charge-spin coupling notoriously limits their commercial applications. To tailor the spontaneous charge and the spin orientation synergistically in BiFeO3 (BFO), in this report, the 3d element of Mn doping engineering is employed and unveils the variation of surface phase transition and magnetic behaviors by introducing chemical strain. The spontaneous ferroelectric response and the corresponding domain structures, magnetic behaviors and spin dynamics in Mn-doped BFO ceramics have been investigated systematically. Both the surface phase transition and magnetization were enhanced in BFO via Mn doping. The interaction between the spontaneous polarization charge and magnetic spin reorientation in Mn-doped BFO are discussed in detail. Moreover, our extensive electron paramagnetic resonance (EPR) results demonstrate that the 3d dopant plays a paramount role in the surface phase transition, which provides an alternative route to tune the charge-spin interactions in multiferroic materials. PMID:25774619

  12. Tailoring surface phase transition and magnetic behaviors in BiFeO3 via doping engineering

    PubMed Central

    Yan, Feng; Xing, Guozhong; Wang, Rongming; Li, Lin

    2015-01-01

    The charge-spin interactions in multiferroic materials (e.g., BiFeO3) have attracted enormous attention due to their high potential for next generation information electronics. However, the weak and deficient manipulation of charge-spin coupling notoriously limits their commercial applications. To tailor the spontaneous charge and the spin orientation synergistically in BiFeO3 (BFO), in this report, the 3d element of Mn doping engineering is employed and unveils the variation of surface phase transition and magnetic behaviors by introducing chemical strain. The spontaneous ferroelectric response and the corresponding domain structures, magnetic behaviors and spin dynamics in Mn-doped BFO ceramics have been investigated systematically. Both the surface phase transition and magnetization were enhanced in BFO via Mn doping. The interaction between the spontaneous polarization charge and magnetic spin reorientation in Mn-doped BFO are discussed in detail. Moreover, our extensive electron paramagnetic resonance (EPR) results demonstrate that the 3d dopant plays a paramount role in the surface phase transition, which provides an alternative route to tune the charge-spin interactions in multiferroic materials. PMID:25774619

  13. Behavior of supercooled aqueous solutions stemming from hidden liquid-liquid transition in water.

    PubMed

    Biddle, John W; Holten, Vincent; Anisimov, Mikhail A

    2014-08-21

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid-liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid-liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H2O-NaCl and H2O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid-liquid transition. We elucidate the non-conserved nature of the order parameter (extent of "reaction" between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases. PMID:25149798

  14. Non-Gaussian behavior in jamming / unjamming transition in dense granular materials

    NASA Astrophysics Data System (ADS)

    Atman, A. P. F.; Kolb, E.; Combe, G.; Paiva, H. A.; Martins, G. H. B.

    2013-06-01

    Experiments of penetration of a cylindrical intruder inside a bidimensional dense and disordered granular media were reported recently showing the jamming / unjamming transition. In the present work, we perform molecular dynamics simulations with the same geometry in order to assess both kinematic and static features of jamming / unjamming transition. We study the statistics of the particles velocities at the neighborhood of the intruder to evince that both experiments and simulations present the same qualitative behavior. We observe that the probability density functions (PDF) of velocities deviate from Gaussian depending on the packing fraction of the granular assembly. In order to quantify these deviations we consider a q-Gaussian (Tsallis) function to fit the PDF's. The q-value can be an indication of the presence of long range correlations along the system. We compare the fitted PDF's obtained with those obtained using the stretched exponential, and sketch some conclusions concerning the nature of the correlations along a granular confined flow.

  15. Universal behavior of crystalline membranes: Crumpling transition and Poisson ratio of the flat phase.

    PubMed

    Cuerno, R; Gallardo Caballero, R; Gordillo-Guerrero, A; Monroy, P; Ruiz-Lorenzo, J J

    2016-02-01

    We revisit the universal behavior of crystalline membranes at and below the crumpling transition, which pertains to the mechanical properties of important soft and hard matter materials, such as the cytoskeleton of red blood cells or graphene. Specifically, we perform large-scale Monte Carlo simulations of a triangulated two-dimensional phantom network which is freely fluctuating in three-dimensional space. We obtain a continuous crumpling transition characterized by critical exponents which we estimate accurately through the use of finite-size techniques. By controlling the scaling corrections, we additionally compute with high accuracy the asymptotic value of the Poisson ratio in the flat phase, thus characterizing the auxetic properties of this class of systems. We obtain agreement with the value which is universally expected for polymerized membranes with a fixed connectivity. PMID:26986292

  16. Theory of the anomalous critical behavior for the smectic-A -hexatic transition

    NASA Astrophysics Data System (ADS)

    Kats, E. I.; Lebedev, V. V.; Muratov, A. R.

    2016-06-01

    We propose a theoretical explanation for the long-standing problem of the anomalous critical behavior of the heat capacity near the smectic-A -hexatic phase transition. Experiments find a large specific heat critical exponent α =0.5 -0.7 , which is inconsistent with a small negative value α ≈-0.01 expected for the three-dimensional X Y universality class. We show that most of the observed features can be explained by treating simultaneously fluctuations of the hexatic orientational and translational (positional) order parameters. Assuming that the translational correlation length ξt r is much larger than the hexatic correlation length ξh, we calculate the temperature dependence of the heat capacity in the critical region near the smectic-A -hexatic phase transition. Our results are in quantitative agreement with the calorimetric experimental data.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Phase transitions, {theta} behavior, and instantons in QCD and its holographic model

    SciTech Connect

    Parnachev, Andrei; Zhitnitsky, Ariel R.

    2008-12-15

    In the holographic model of QCD, {theta} dependence sharply changes at the point of confinement-deconfinement phase transition. In large N QCD such a change in {theta} behavior can be related to the breakdown of the instanton expansion at some critical temperature T{sub c}. Associating this temperature with confinement-deconfinement phase transition leads to the description of the latter in terms of dissociation of instantons into the fractionally charged instanton quarks. To elucidate this picture, we introduce the nonvanishing chiral condensate in the deconfining phase and assume a specific Lagrangian for the {eta}{sup '} field in the confining phase. In the resulting picture the high-temperature phase of the theory consists of the dilute gas of instantons, while the low-temperature phase is described in terms of freely moving fractional instanton quarks.

  19. Theory of the anomalous critical behavior for the smectic-A-hexatic transition.

    PubMed

    Kats, E I; Lebedev, V V; Muratov, A R

    2016-06-01

    We propose a theoretical explanation for the long-standing problem of the anomalous critical behavior of the heat capacity near the smectic-A-hexatic phase transition. Experiments find a large specific heat critical exponent α=0.5-0.7, which is inconsistent with a small negative value α≈-0.01 expected for the three-dimensional XY universality class. We show that most of the observed features can be explained by treating simultaneously fluctuations of the hexatic orientational and translational (positional) order parameters. Assuming that the translational correlation length ξ_{tr} is much larger than the hexatic correlation length ξ_{h}, we calculate the temperature dependence of the heat capacity in the critical region near the smectic-A-hexatic phase transition. Our results are in quantitative agreement with the calorimetric experimental data. PMID:27415334

  20. Experimental study of transition metal ion doping on TiO2 with photocatalytic behavior.

    PubMed

    Siddhapara, K S; Shah, D V

    2014-08-01

    In this research, we have studied the doping behaviors of three transition metal ion dopants on the crystal phase, particle sizes, XRD patterns, EDAX spectra, and photoreactivity of TiO2 nanoparticles. Test metal ion concentrations ranged from 1% to 4 at.%, we report the growth of [Fe, Co and Mn]xTiO2 nanocrystals prepared by Sol-Gel technique, followed by freeze-drying treatment at -30 °C temperature for 12 hrs. The obtained Gel was thermally treated at different temperature like 200 °C, 400 °C, 600 °C, 800 °C. Thermal gravimetric analysis (TGA) shows that dopant concentration affects thermal decomposition. The photoreactivities of transition metal ion-doped TiO2 nanoparticles under UV irradiation were quantified by the degradation of formaldehyde. PMID:25936115

  1. Flagella-induced transitions in the collective behavior of confined microswimmers

    NASA Astrophysics Data System (ADS)

    Cheng Hou Tsang, Alan; Kanso, Eva

    2014-08-01

    Bacteria are usually studied in free-swimming planktonic state or in sessile biofilm state. However, little is known about intermediate states where variability in the environmental conditions and/or energy supply to the flagellar propulsive system alter flagellar activity. In this Rapid Communication, we propose an idealized physical model to investigate the effects of flagellar activity on the hydrodynamic interactions among a population of microswimmers. We show that decreasing flagellar activity induces a hydrodynamically triggered transition in confined microswimmers from turbulentlike swimming to aggregation and clustering. These results suggest that the interplay between flagellar activity and hydrodynamic interactions provides a physical mechanism for coordinating collective behaviors in confined bacteria, with potentially profound implications on processes such as molecular diffusion and transport of oxygen and nutrients that mediate transitions in the bacteria physiological state.

  2. Solubility Behavior and Phase Stability of Transition Metal Oxides in Alkaline Hydrothermal Environments

    SciTech Connect

    S.E. Ziemniak

    2000-05-18

    The solubility behavior of transition metal oxides in high temperature water is interpreted by recognizing three types of chemical reaction equilibria: metal oxide hydration/dehydration, metal oxide dissolution and metal ion hydroxocomplex formation. The equilibria are quantified using thermodynamic concepts and the thermochemical properties of the metal oxides/ions representative of the most common constituents of construction metal alloys, i.e., element shaving atomic numbers between Z = 22 (Ti) and Z = 30 (Zn), are summarized on the basis of metal oxide solubility studies conducted in the laboratory. Particular attention is devoted to the uncharged metal ion hydrocomplex, M{sup Z}(OH){sub Z}(aq), since its thermochemical properties define minimum solubilities of the metal oxide at a given temperature. Experimentally-extracted values of standard partial molal entropy (S{sup 0}) for the transition metal ion neutral hydroxocomplex are shown to be influenced by ligand field stabilization energies and complex symmetry.

  3. Universal behavior of crystalline membranes: Crumpling transition and Poisson ratio of the flat phase

    NASA Astrophysics Data System (ADS)

    Cuerno, R.; Gallardo Caballero, R.; Gordillo-Guerrero, A.; Monroy, P.; Ruiz-Lorenzo, J. J.

    2016-02-01

    We revisit the universal behavior of crystalline membranes at and below the crumpling transition, which pertains to the mechanical properties of important soft and hard matter materials, such as the cytoskeleton of red blood cells or graphene. Specifically, we perform large-scale Monte Carlo simulations of a triangulated two-dimensional phantom network which is freely fluctuating in three-dimensional space. We obtain a continuous crumpling transition characterized by critical exponents which we estimate accurately through the use of finite-size techniques. By controlling the scaling corrections, we additionally compute with high accuracy the asymptotic value of the Poisson ratio in the flat phase, thus characterizing the auxetic properties of this class of systems. We obtain agreement with the value which is universally expected for polymerized membranes with a fixed connectivity.

  4. Asymptotic behavior of apparent generalized oscillator strengths for optically forbidden transitions in rare-gas atoms

    SciTech Connect

    Suzuki, T. Y.; Suzuki, H.; Ohtani, S.; Takayanagi, T.; Okada, K.

    2007-03-15

    Apparent generalized oscillator strengths (apparent GOS's) have been measured for three types of optically forbidden transitions in rare-gas atoms as functions of the squared momentum transfer K{sup 2} at small K{sup 2} range ({<=}0.4 a.u.). The apparent GOS's were deduced from the differential cross sections for excitation, which were measured by means of the electron energy-loss spectroscopy. Electron impact energies were 100, 300, and 500 eV, and the scattering angles were from 0.8 degree sign to 10 degree sign . In the case where the first Born approximation does not hold, the apparent GOS as a function of K{sup 2} (the apparent GOS function) shows characteristic dependence on the electron collision energy according to the character of the transition. In the present observation, for the np{sup 6} {sup 1}S{sub 0}{yields}np{sup 5}(n+1)p{sup '}[1/2]{sub 0} transitions, the specific behavior has been observed in the apparent GOS functions characteristic of that for the {sup 1}S{sub 0}{yields}{sup 1}S{sub 0} type transition, in which the term symbols of the initial and the final states do not change. For the np{sup 6} {sup 1}S{sub 0}{yields}np{sup 5}(n+1)p[5/2]{sub 2,3}; [3/2]{sub 1,2} transitions, a certain new type of deviations from the first Born approximation, which is interpreted to be characteristic of the {sup 1}S{sub 0}{yields}{sup 1}D{sub 2} type transition, have been observed in the apparent GOS functions with some modifications depending on respective atomic species. For the 5p{sup 6} {sup 1}S{sub 0}{yields}5p{sup 5}5d [7/2]{sub 3}; [5/2]{sub 3} transitions in Xe, it is observed that the apparent GOS curves have no impact energy dependence for impact energies from 100 eV to 500 eV, which suggests that the first Born approximation is valid for such low impact energies and the curves agree with the Bethe-GOS. It is found that the GOS's varies in proportional to K{sup 4} at small K{sup 2} region ({<=}0.1 a.u.), which suggests that the octupole moment is

  5. Exact coupling threshold for structural transition reveals diversified behaviors in interconnected networks

    NASA Astrophysics Data System (ADS)

    Darabi Sahneh, Faryad; Scoglio, Caterina; Van Mieghem, Piet

    2015-10-01

    An interconnected network features a structural transition between two regimes [F. Radicchi and A. Arenas, Nat. Phys. 9, 717 (2013), 10.1038/nphys2761]: one where the network components are structurally distinguishable and one where the interconnected network functions as a whole. Our exact solution for the coupling threshold uncovers network topologies with unexpected behaviors. Specifically, we show conditions that superdiffusion, introduced by Gómez et al. [Phys. Rev. Lett. 110, 028701 (2013), 10.1103/PhysRevLett.110.028701], can occur despite the network components functioning distinctly. Moreover, we find that components of certain interconnected network topologies are indistinguishable despite very weak coupling between them.

  6. Behavioral needs of the transition cow and considerations for special needs facility design.

    PubMed

    Cook, Nigel B; Nordlund, Kenneth V

    2004-11-01

    Improved building designs come from a better understanding of the behavioral needs of the dairy cow. The costs to provide for these needs in the facility must be offset by improved milk production, health, and longevity. Research is still required to more fully understand the health implications of many building design considerations and their impact on disease. Perhaps the most important end result of an improved environment for the transition cow, however, is an improvement in animal well-being. Better buildings that accommodate the behavioral needs of cows present "win-win" situations where dairy cattle thrive and work is more enjoyable. This results in an improved image for the industry, greater consumer confidence in the quality and safety of the final food product, and a prosperous dairy industry. PMID:15471622

  7. The Role of Goals and Alcohol Behavior during the Transition out of College

    PubMed Central

    Radomski, Sharon A.; Read, Jennifer P.; Bowker, Julie C.

    2015-01-01

    Personal goals are desired outcomes that guide behavior (Palfai et al., 2011), and are typically oriented around age-appropriate developmental tasks (e.g., college graduation, employment). Goals and their pursuit take on much salience during senior year of college as individuals prepare for the transition into adult roles. This also is a time during which naturalistic changes in alcohol consumption are occurring. These changes may impact the relationship between age-related goals and their attainment, thus compromising the likelihood of a successful transition out of college. The present study examined whether and how changes in drinking over senior year moderate the association between achievement goals and related developmental task attainment as students move toward transitioning out of college. Alcohol-involved college seniors (N=437; 62.5% female) were assessed via web survey in September of their senior year and again one year later (T4). Results of multinomial logistic regression revealed that greater Achievement Goals were predictive of college graduation (versus remaining a continuing undergraduate), but only for those whose drinking decreased during senior year. Among those graduated by T4 (n=307), Achievement Goals predicted pursuing graduate education (versus being unemployed), but only for students whose drinking increased during senior year. Thus, Achievement Goals are important predictors of goal attainment as students prepare to transition out of college, and these goals can interact with drinking in complex ways during this time. Findings suggest that interventions aimed at bolstering personal goals and reducing drinking during senior year may increase the likelihood of successful transitions out of the college environment. PMID:25642583

  8. Effects of Multiple Maternal Relationship Transitions on Offspring Antisocial Behavior in Childhood and Adolescence: A Cousin-Comparison Analysis

    ERIC Educational Resources Information Center

    Goodnight, Jackson A.; D'Onofrio, Brian M.; Cherlin, Andrew J.; Emery, Robert E.; Van Hulle, Carol A.; Lahey, Benjamin B.

    2013-01-01

    Previous studies of the association between multiple parental relationship transitions (i.e., when a parent begins or terminates an intimate relationship involving cohabitation) and offspring antisocial behavior have varied in their efforts to rule out confounding influences, such as parental antisocial behavior and low income. They also have been…

  9. Interactions between Maternal Parenting and Children's Early Disruptive Behavior: Bidirectional Associations across the Transition from Preschool to School Entry

    ERIC Educational Resources Information Center

    Combs-Ronto, Lindsey A.; Olson, Sheryl L.; Lunkenheimer, Erika S.; Sameroff, Arnold J.

    2009-01-01

    This study was a prospective 2-year longitudinal investigation of associations between negative maternal parenting and disruptive child behavior across the preschool to school transition. Our main goals were to 1) determine the direction of association between early maternal negativity and child disruptive behaviors across this important…

  10. Maternal Work Behavior under Welfare Reform: How Does the Transition from Welfare to Work Affect Child Development? JCPR Working Paper.

    ERIC Educational Resources Information Center

    Dunifon, Rachel; Kalil, Ariel; Danziger, Sandra K.

    Using data from a longitudinal sample of former and current welfare recipients in Michigan spanning 1997 through 1999, the Womens Employment Study, this analysis examined how transitions from welfare to work affect parenting behavior and child behavior problems. Researchers used a fixed-effects regression design to control for all time-invariant…

  11. Physical activity status of academic professors during their early career transition: an application of the theory of planned behavior.

    PubMed

    Kirk, Megan A; Rhodes, Ryan E

    2012-01-01

    Life-transitions (e.g. parenthood) have been linked to physical inactivity, yet the topic requires further exploration. In this study, we evaluated changes in the physical activity (PA) of adults during their early career transition using retrospective analysis and the theory of planned behavior. Recruitment from January to March 2010 yielded a random sample of 267 assistant professors, ages 25-44, employed within the last five years. Repeated measures analysis of variance (RM ANOVA) concluded that PA declined across the transition (d = 0.36-0.43) and was further attenuated by marriage, work hours, and parenthood status. Discriminant function analysis (DFA) identified specific behavioral and control correlates about PA enjoyment, limited time, inconsistent schedule, work demands, and job pressures to distinguish between those who remained active from those who did not across the transition. PA interventions administered prior to career transitions may be needed to prevent physical inactivity. PMID:22348598

  12. Syntax of Phase Transition Peptide Polymers with LCST and UCST Behavior

    NASA Astrophysics Data System (ADS)

    Garcia Quiroz, Felipe

    "Smart" polymers that sense stimuli in aqueous environments and that respond with a pronounced change in their solvation are of great utility in biotechnology and medicine. Currently, however, only few peptide polymers are known to display this behavior. Here, we uncover the syntax -- defined as the arrangement of amino acids (letters) into repeat units (words) that have a functional behavior of interest -- of a novel and extensive family of genetically encoded "smart" peptide polymers, termed syntactomers, that dictates their ability to undergo a soluble to insoluble phase transition at temperatures above a lower critical solution temperature (LCST) or below an upper critical solution temperature (UCST). We show that this syntax ranges from phase transition polymers composed of simple repeats of a few amino acids to polymers whose syntax resembles the complex sequence of peptide drugs and protein domains that exhibit dual levels of function, as seen by their stimulus responsiveness and biological activity. This seamless fusion of materials and protein design embodied by syntactomers promises, we hope, a new generation of designer polymers with multiple levels of embedded functionality that should lead to new functional materials of broad interest

  13. Optimal control-based bayesian detection of clinical and behavioral state transitions.

    PubMed

    Santaniello, Sabato; Sherman, David L; Thakor, Nitish V; Eskandar, Emad N; Sarma, Sridevi V

    2012-09-01

    Accurately detecting hidden clinical or behavioral states from sequential measurements is an emerging topic in neuroscience and medicine, which may dramatically impact neural prosthetics, brain-computer interface and drug delivery. For example, early detection of an epileptic seizure from sequential electroencephalographic (EEG) measurements would allow timely administration of anticonvulsant drugs or neurostimulation, thus reducing physical impairment and risks of overtreatment. We develop a Bayesian paradigm for state transition detection that combines optimal control and Markov processes. We define a hidden Markov model of the state evolution and develop a detection policy that minimizes a loss function of both probability of false positives and accuracy (i.e., lag between estimated and actual transition time). Our strategy automatically adapts to each newly acquired measurement based on the state evolution model and the relative loss for false positives and accuracy, thus resulting in a time varying threshold policy. The paradigm was used in two applications: 1) detection of movement onset (behavioral state) from subthalamic single unit recordings in Parkinson's disease patients performing a motor task; 2) early detection of an approaching seizure (clinical state) from multichannel intracranial EEG recordings in rodents treated with pentylenetetrazol chemoconvulsant. Our paradigm performs significantly better than chance and improves over widely used detection algorithms. PMID:22893447

  14. Evaluation of transitional behavior of wetness/drought regimes in the Poyang Lake Basin, China

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Sun, Peng; Singh, Vijay P.; Li, Jianfeng; Tu, Xinjun

    2015-08-01

    Transitional behavior of wetness/dryness regimes is investigated using the standardized precipitation/runoff indices (SPI-SRI) and the Markov chain model, and wetness/drought conditions are predicted. Results indicate that (1) the wetness/drought hazards have large negative impacts during initial conditions in the Xiuhe River Basin and manifest their negative impacts during the development condition of the wetness/droughts in the Fuhe and Xiuhe River Basins; in the Ganjiang and Raohe River Basins, however, droughts have their greatest impacts during the lasting time intervals, (2) the occurrence of meteorological or hydrological droughts/floods individually is subject to very low probability, implying close relations between meteorological and hydrological conditions within the Poyang Lake Basin, and (3) an abrupt shift between hydrometeorological wetness and dryness events is identified, specifically in northwest and northeast parts of the Poyang Lake Basin, which could be due to intensifying precipitation regimes in these regions under the influence of increasing temperature. The prediction of droughts indicates that the transitional probability from the second condition to the hydrological drought is the lowest and the transitional probability from the first (or third) condition to the fourth condition is the largest. Results of this study will be of value for developing measures for mitigation of droughts in a changing environment.

  15. Dimensional phase transition from 1D behavior to a 3D Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Pelster, Axel; Morath, Denis; Straßel, Dominik; Eggert, Sebastian

    The emergence of new properties from low-dimensional building blocks is a universal theme in different areas in physics. The investigation of transitions between isolated and coupled low-dimensional systems promises to reveal new phenomena and exotic phases. Interacting 1D bosons, which are coupled in a two-dimensional array, are maybe the most fundamental example of a system which illustrates the concept of a dimensional phase transition. However, recent experiments using ultracold gases have shown a surprising discrepancy between theory and experiment and it is far from obvious if the power laws from the underlying 1D theory can predict the transition temperature and order parameter correctly for all interaction strengths. Using a combination of large-scale Quantum Monte-Carlo simulations and chain mean-field calculations, we show that the behavior of the ordering temperature as a function of inter-chain coupling strength does not follow a universal powerlaw, but also depends strongly on the filling

  16. Anharmonic behavior and structural phase transition in Yb{sub 2}O{sub 3}

    SciTech Connect

    Pandey, Sugandha Dogra; Samanta, K.; Singh, Jasveer; Sharma, Nita Dilawar Bandyopadhyay, A. K.

    2013-12-15

    The investigation of structural phase transition and anharmonic behavior of Yb{sub 2}O{sub 3} has been carried out by high-pressure and temperature dependent Raman scattering studies respectively. In situ Raman studies under high pressure were carried out in a diamond anvil cell at room temperature which indicate a structural transition from cubic to hexagonal phase at and above 20.6 GPa. In the decompression cycle, Yb{sub 2}O{sub 3} retained its high pressure phase. We have observed a Stark line in the Raman spectra at 337.5 cm{sup −1} which arises from the electronic transition between {sup 2}F{sub 5/2} and {sup 2}F{sub 7/2} multiplates of Yb{sup 3+} (4f{sup 13}) levels. These were followed by temperature dependent Raman studies in the range of 80–440 K, which show an unusual mode hardening with increasing temperature. The hardening of the most dominant mode (T{sub g} + A{sub g}) was analyzed in light of the theory of anharmonic phonon-phonon interaction and thermal expansion of the lattice. Using the mode Grüneisen parameter obtained from high pressure Raman measurements; we have calculated total anharmonicity of the T{sub g} + A{sub g} mode from the temperature dependent Raman data.

  17. Anxiety-related behavioral responses of pentylenetetrazole-treated zebrafish larvae to light-dark transitions.

    PubMed

    Peng, Xiaolan; Lin, Jia; Zhu, Yingdong; Liu, Xiuyun; Zhang, Yinglan; Ji, Yongxia; Yang, Xue; Zhang, Yan; Guo, Ning; Li, Qiang

    2016-06-01

    Pentylenetetrazole (PTZ), γ-aminobutyrate (GABA) antagonist, is a convulsant drug, known to induce anxiety and seizures in zebrafish. Changes in the mobility of zebrafish under light-dark transitions reflect anxiety level, serving as a useful behavioral readout. The effects of PTZ treatment have yet to be assayed in this manner. Zebrafish larvae (AB strain) at both 5dpf (days post-fertilization) and 7dpf were treated with different concentrations of PTZ. General locomotor activity and thigmotaxis were analyzed under continuous illumination (normal conditions) or alternating light-dark cycles (stressful conditions). Zebrafish larvae of 5dpf and 7dpf exhibited different sensitivities to PTZ. Anxiety level, measured in terms of response to illumination transitions under the influence of PTZ, demonstrated contrasting tendencies. Dark-light transitions dramatically increased the locomotor activity of zebrafish larvae receiving 8mM PTZ which was indicative of anxiety. This study suggests that PTZ increases the susceptibility by activating the neuron, which perhaps makes light change easier to influence the anxiety level of larvae. We provide useful evidence for putative anti-anxiety drug screening. PMID:27019459

  18. Lasing behaviors upon phase transition in solution-processed perovskite thin films

    NASA Astrophysics Data System (ADS)

    Kao, Tsung Sheng; Chou, Yu-Hsun; Chou, Chun-Hsien; Chen, Fang-Chung; Lu, Tien-Chang

    2014-12-01

    In this paper, the temperature dependent lasing characteristics of solution-processed organic-inorganic halide perovskite CH3NH3PbI3 films have been demonstrated. The lasing temperature can be sustained up to a near room temperature at 260 K. Via the temperature dependent photoluminescence (PL) measurements, an emerged phase-transition band can be observed, ascribing to the crystalline structures changed from the orthorhombic to tetragonal phase states in the perovskites as a function of a gradual increase in the ambient temperature. The optical characteristics of the PL emission peaks and the anomalous shifts of the peak intensities are highly correspondent with the phase states in perovskites at different temperatures, showing a low-threshold lasing behavior at the phase transition. The laser cavities may be formed under multiple random scattering provided by the polycrystalline grain boundary and/or phase separation upon the phase transition. Since the threshold gain is potentially high in the random cavities, the large material gain exhibited by the solution-processed perovskite would be very promising in making practical laser devices.

  19. Work hours, weight status, and weight-related behaviors: a study of metro transit workers

    PubMed Central

    2010-01-01

    Background Associations between hours worked per week and Body Mass Index (BMI), food intake, physical activity, and perceptions of eating healthy at work were examined in a sample of transit workers. Methods Survey data were collected from 1086 transit workers. Participants reported hours worked per week, food choices, leisure-time physical activity and perceptions of the work environment with regard to healthy eating. Height and weight were measured for each participant. Multivariate linear and logistic regressions were conducted to examine associations between work hours and behavioral variables. Associations were examined in the full sample and stratified by gender. Results Transit workers working in the highest work hour categories had higher BMI and poorer dietary habits, with results differing by gender. Working 50 or more hours per week was associated with higher BMI among men but not women. Additionally, working 50 or more hours per week was significantly associated with higher frequency of accessing cold beverage, cold food, and snack vending machines among men. Working 40 or more hours per week was associated with higher frequency of accessing cold food vending machines among women. Reported frequency of fruit and vegetable intake was highest among women working 50 or more hours per week. Intake of sweets, sugar sweetened beverages, and fast food did not vary with work hours in men or women. Physical activity and perception of ease of eating healthy at work were not associated with work hours in men or women. Conclusions Long work hours were associated with more frequent use of garage vending machines and higher BMI in transit workers, with associations found primarily among men. Long work hours may increase dependence upon food availability at the worksite, which highlights the importance of availability of healthy food choices. PMID:21172014

  20. Locomotor behavior across an environmental transition in the ropefish, Erpetoichthys calabaricus.

    PubMed

    Pace, Cinnamon M; Gibb, Alice C

    2011-02-15

    Many amphibious organisms undergo repeated aquatic to terrestrial transitions during their lifetime; limbless, elongate organisms that make such transitions must rely on axial-based locomotion in both habitats. How is the same anatomical structure employed to produce an effective behavior across such disparate habitats? Here, we examine an elongate amphibious fish, the ropefish (Erpetoichthys calabaricus), and ask: (1) how do locomotor movements change during the transition between aquatic and terrestrial environments and (2) do distantly related amphibious fishes demonstrate similar modes of terrestrial locomotion? Ropefish were examined moving in four experimental treatments (in which the water level was to lowered mimic the transition between environments) that varied from fully aquatic to fully terrestrial. Kinematic parameters (lateral excursion, wavelength, amplitude and frequency) were calculated for points along the midline of the body and compared across treatments. Terrestrial locomotion in the ropefish is characterized by long, slow, large-amplitude undulations down the length of the body; in contrast, aquatic locomotion is characterized by short-wavelength, small-amplitude, high-frequency undulations that gradually increase in an anterior to posterior direction. Experimental treatments with intermediate water levels were more similar to aquatic locomotion in that they demonstrated an anterior to posterior pattern of increasing lateral excursion and wave amplitude, but were more similar to terrestrial locomotion with regard to wavelength, which did not change in an anterior to posterior direction. Finally, the ropefish and another elongate amphibious fish, the eel, consistently exhibit movements characterized by 'path following' when moving on land, which suggests that elongate fishes exhibit functional convergence during terrestrial locomotion. PMID:21270300

  1. Synchronization transition of a coupled system composed of neurons with coexisting behaviors near a Hopf bifurcation

    NASA Astrophysics Data System (ADS)

    Jia, Bing

    2014-05-01

    The coexistence of a resting condition and period-1 firing near a subcritical Hopf bifurcation point, lying between the monostable resting condition and period-1 firing, is often observed in neurons of the central nervous systems. Near such a bifurcation point in the Morris—Lecar (ML) model, the attraction domain of the resting condition decreases while that of the coexisting period-1 firing increases as the bifurcation parameter value increases. With the increase of the coupling strength, and parameter and initial value dependent synchronization transition processes from non-synchronization to compete synchronization are simulated in two coupled ML neurons with coexisting behaviors: one neuron chosen as the resting condition and the other the coexisting period-1 firing. The complete synchronization is either a resting condition or period-1 firing dependent on the initial values of period-1 firing when the bifurcation parameter value is small or middle and is period-1 firing when the parameter value is large. As the bifurcation parameter value increases, the probability of the initial values of a period-1 firing neuron that lead to complete synchronization of period-1 firing increases, while that leading to complete synchronization of the resting condition decreases. It shows that the attraction domain of a coexisting behavior is larger, the probability of initial values leading to complete synchronization of this behavior is higher. The bifurcations of the coupled system are investigated and discussed. The results reveal the complex dynamics of synchronization behaviors of the coupled system composed of neurons with the coexisting resting condition and period-1 firing, and are helpful to further identify the dynamics of the spatiotemporal behaviors of the central nervous system.

  2. Yeast product supplementation modulated feeding behavior and metabolism in transition dairy cows.

    PubMed

    Yuan, K; Liang, T; Muckey, M B; Mendonça, L G D; Hulbert, L E; Elrod, C C; Bradford, B J

    2015-01-01

    Yeast supplementation has been shown to increase feed intake and production in some studies with early lactation dairy cows, but the mechanisms underlying such an effect remain unknown. The objective of this study was to assess the effects of supplementing a yeast product derived from Saccharomyces cerevisiae on production, feeding behavior, and metabolism in cows during the transition to lactation. Forty multiparous Holstein cows were blocked by expected calving date and randomly assigned within block to 1 of 4 treatments (n=10) from 21 d before expected calving to 42 d postpartum. Rations were top-dressed with a yeast culture plus enzymatically hydrolyzed yeast (YC-EHY; Celmanax, Vi-COR Inc., Mason City, IA) at the rate of 0, 30, 60, or 90g/d throughout the experiment. Dry matter and water intake, feeding behavior, and milk production were monitored. Plasma samples collected on -21, -7, 1, 4, 7, 14, 21, and 35 d relative to calving were analyzed for glucose, β-hydroxybutyrate, and nonesterified fatty acids. Data were analyzed using mixed models with repeated measures over time. Pre- or postpartum dry matter intake and water intake did not differ among treatments. Quadratic dose effects were observed for prepartum feeding behavior, reflecting decreased meal size, meal length, and intermeal interval, and increased meal frequency for cows received 30 and 60g/d of YC-EHY. Postpartum feeding behavior was unaffected by treatments. Milk yields were not affected (45.3, 42.6, 47.8, and 46.7kg/d for 0, 30, 60, and 90g/d, respectively) by treatments. Tendencies for increased percentages of milk fat, protein, and lactose were detected for cows receiving YC-EHY. Supplementing YC-EHY increased plasma β-hydroxybutyrate and tended to decrease (quadratic dose effect) glucose but did not affect nonesterified fatty acids. Yeast product supplementation during the transition period did not affect milk production and dry matter intake but modulated feeding behavior and metabolism

  3. Social marketing as a tool to improve behavioral health services for underserved populations in transition countries.

    PubMed

    Szydlowski, Steven J; Chattopadhyay, Satya P; Babela, Robert

    2005-01-01

    Human development efforts continue to change the world and improve quality of life for humans. Without the struggle and drive to contemplate new ideas to improve society, the global community would be in a constant state of oppression. Although cultures and norms change as international boundaries are crossed, the universal goal is to improve standards of living to include behavioral health services for underserved populations. In recent times, pioneers and community groups have used social marketing as an instrument to change public perceptions and behaviors within societies. These efforts have transformed nations in the acceptance and understanding of community health and rehabilitation, education, service, and human rights. This article examines the justification for utilization of the concepts and tools of social marketing to bring about proactive behavior modification among segments of underserved populations. A section of this article provides an overview of the basics of social marketing for the benefit of makers of health policy in transition countries. Finally, the case of 2 underserved population segments in the Republic of Slovakia, a new member of the European Union (former socialist block member), is examined for possible implementation. PMID:15825815

  4. Addiction: From Context-Induced Hedonia to Appetite, Based on Transition of Micro-behaviors in Morphine Abstinent Tree Shrews

    PubMed Central

    Duan, Ying; Shen, Fang; Gu, Tingting; Sui, Nan

    2016-01-01

    Drug addiction is viewed as a maladaptive memory induced by contextual cues even in the abstinent state. However, the variations of hedonia and appetite induced by the context during the abstinence have been neglected. To distinguish the representative behaviors between hedonia and appetite, micro-behaviors in abstinent animal such as psycho-activity and drug seeking behaviors were observed in morphine conditioned place preference (CPP). To confirm the different effects of reward between drug and natural reward, a palatable food CPP paradigm was compared in current work. After a 10-day training in CPP with morphine or food, the preference was tested on day 1, 14, 28, and the changes of micro-behaviors were analyzed further. Our data showed that tree shrews treated with morphine performed more jumps on day 1 and more visits to saline paired side on day 28, which indicated a featured behavioral transition from psycho-activity to seeking behavior during drug abstinence. Meanwhile, food-conditioned animals only displayed obvious seeking behaviors in the three tests. The results suggest that the variations of micro-behaviors could imply such a transition from hedonic response to appetitive behaviors during morphine abstinence, which provided a potential behavioral basis for further neural mechanism studies. PMID:27375516

  5. Addiction: From Context-Induced Hedonia to Appetite, Based on Transition of Micro-behaviors in Morphine Abstinent Tree Shrews.

    PubMed

    Duan, Ying; Shen, Fang; Gu, Tingting; Sui, Nan

    2016-01-01

    Drug addiction is viewed as a maladaptive memory induced by contextual cues even in the abstinent state. However, the variations of hedonia and appetite induced by the context during the abstinence have been neglected. To distinguish the representative behaviors between hedonia and appetite, micro-behaviors in abstinent animal such as psycho-activity and drug seeking behaviors were observed in morphine conditioned place preference (CPP). To confirm the different effects of reward between drug and natural reward, a palatable food CPP paradigm was compared in current work. After a 10-day training in CPP with morphine or food, the preference was tested on day 1, 14, 28, and the changes of micro-behaviors were analyzed further. Our data showed that tree shrews treated with morphine performed more jumps on day 1 and more visits to saline paired side on day 28, which indicated a featured behavioral transition from psycho-activity to seeking behavior during drug abstinence. Meanwhile, food-conditioned animals only displayed obvious seeking behaviors in the three tests. The results suggest that the variations of micro-behaviors could imply such a transition from hedonic response to appetitive behaviors during morphine abstinence, which provided a potential behavioral basis for further neural mechanism studies. PMID:27375516

  6. Functional analysis of maladaptive behaviors: Rule as a transitive conditioned motivating operation.

    PubMed

    Belfiore, Phillip J; Kitchen, Thomas; Lee, David L

    2016-01-01

    The purpose of this study was to examine the role of a staff-delivered rule on the occurrence of challenging behavior (stereotypic touching) of an adult with severe intellectual disabilities. Four experimental functional analysis conditions were developed: (a) attention, (b) rule+attention, (c) rule only, and (d) control. Results showed that the percentage of intervals in which stereotypic touching responses (STR) occurred was greater within the experimental condition where a rule statement was embedded with contingent attention. Results are discussed in light of the plasticity of functional analysis technology to allow for stimulus variation within the typical social attention condition, and the suggestion that the rule statement, in this study, may function as a Transitive Conditioned Establishing Operation (CEO-T), asserting that the provision of attention is more valued in the presence of the stated rule. PMID:26692455

  7. Transitions in effective scaling behavior of accelerometric time series across sleep and wake

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, Patrick; Kantelhardt, Jan W.; Zinkhan, Melanie; Schumann, Aicko Y.; Penzel, Thomas; Fietze, Ingo; Pillmann, Frank; Stang, Andreas

    2013-09-01

    We study the effective scaling behavior of high-resolution accelerometric time series recorded at the wrists and hips of 100 subjects during sleep and wake. Using spectral analysis and detrended fluctuation analysis we find long-term correlated fluctuations with a spectral exponent \\beta \\approx 1.0 (1/f noise). On short time scales, β is larger during wake (\\approx 1.4 ) and smaller during sleep (\\approx 0.6 ). In addition, characteristic peaks at 0.2-0.3 Hz (due to respiration) and 4-10 Hz (probably due to physiological tremor) are observed in periods of weak activity. Because of these peaks, spectral analysis is superior in characterizing effective scaling during sleep, while detrending analysis performs well during wake. Our findings can be exploited to detect sleep-wake transitions.

  8. Critical behavior of absorbing phase transitions for models in the Manna class with natural initial states.

    PubMed

    Lee, Sang Bub

    2014-06-01

    The critical behavior of absorbing phase transitions for two typical models in the Manna universality class, the conserved Manna model and the conserved lattice gas model, both on a square lattice, was investigated using the natural initial states. Various critical exponents were estimated using the static and dynamic simulations. The exponents characterizing dynamics of active particles differ considerably from the known exponents obtained using the random initial states, whereas those associated with the steady-state quantities remain the same. The critical exponents for both models were consistent with errors of less than 1% and satisfied the known scaling relations; thus, the known violation of scaling relations for models with a conserved field was resolved using the natural initial states. The results differed by 7%∼12% from the directed percolation values. PMID:25019750

  9. Behavioral risk factors for obesity during health transition in Vanuatu, South Pacific

    PubMed Central

    Dancause, Kelsey Needham; Vilar, Miguel; Wilson, Michelle; Soloway, Laura E; DeHuff, Christa; Chan, Chim; Tarivonda, Len; Regenvanu, Ralph; Kaneko, Akira; Lum, J Koji; Garruto, Ralph M

    2012-01-01

    The South Pacific archipelago of Vanuatu, like many developing countries, is currently experiencing a shift in disease burdens from infectious to chronic diseases with economic development. A rapid increase in obesity prevalence represents one component of this “health transition.” We sought to identify behaviors associated with measures of obesity in Vanuatu. We surveyed 534 adults from three islands varying in level of economic development. We measured height; weight; waist and hip circumferences; triceps, subscapular and suprailiac skinfolds; and percent body fat (%BF) by bioelectrical impedance. We assessed diet through 24-hour dietary recall and physical activity patterns using a survey. We calculated prevalence of obesity and central obesity based on multiple indicators (body mass index, %BF, waist circumference, and waist-to-height ratio), and analyzed differences among islands and associations with behavioral patterns. Obesity prevalence was lowest among rural and highest among suburban participants. Prevalence of central obesity was particularly high among women (up to 73.9%), even in rural areas (ranging from 14.7% to 41.2% depending on the measure used). Heavier reliance on animal protein and incorporation of Western foods in the diet – specifically, tinned fish and instant noodles – was significantly associated with increased obesity risk. Even in rural areas where diets and lifestyles remain largely traditional, modest incorporation of Western foods in the diet can contribute to increased risk of obesity. Early prevention efforts are thus particularly important during health transition. Where public health resources are limited, education about dietary change could be the best target for prevention. PMID:23505203

  10. Iron Damage and Spalling Behavior below and above Shock Induced {alpha} <==> {epsilon} Phase Transition

    SciTech Connect

    Voltz, Christophe; Buy, Francois; Roy, Gilles

    2006-07-28

    The study of dynamic damage and fracture of iron has been undertaken below and above phase transition by series of time resolved experiments using both light gas launcher and powder gun. Shock wave tests were conducted by symmetrical impacts of high purity iron. To reveal the material behavior we have done shock experiments where the target is covered with a window in order to limit release amplitude and to avoid specimen fragmentation. Metallurgical analysis of soft recovered samples yields information about damage and fracture processes related to thermo-mechanical loading paths. Tests conducted without window allow studying effects of both phase change and release transition. Optical and SEM characterizations lead us to observe several modes of damage: brittle, ductile diffuse with void growth and heavily localized smooth one. These figures are related with: rarefaction shock waves or interfaces between transformed and not transformed iron. Simulations are performed with the 1D to compare experimental data with numerical results. We explain post-mortem observations by the complex shock wave structure interactions: P1 and P2 shock fronts associated with some corresponding shock release during unloading stages.

  11. Effect of vision angle on the phase transition in flocking behavior of animal groups

    NASA Astrophysics Data System (ADS)

    Nguyen, P. The; Lee, Sang-Hee; Ngo, V. Thanh

    2015-09-01

    The nature of the phase transition in a system of self-propelling particles has been extensively studied during the past few decades. A theoretical model was proposed by [T. Vicsek et al. Phys. Rev. Lett. 75, 1226 (1995), 10.1103/PhysRevLett.75.1226] with a simple rule for updating the direction of motion of each particle. Based on the model of Vicsek et al., in this paper, we consider a group of animals as particles moving freely in a two-dimensional space. Due to the fact that the viewable area of animals depends on the species, we consider the motion of each individual within an angle φ =ϕ /2 (ϕ is called the angle of view) of a circle centered at its position of radius R . We obtained a phase diagram in the space (φ ,ηc ) with ηc being the critical noise. We show that the phase transition exists only in the case of a wide view's angle φ ≥0.5 π . The flocking of animals is a universal behavior of the species of prey but not the one of the predator. Our simulation results are in good agreement with experimental observation [C. Beccoa et al., Physica A 367, 487 (2006), 10.1016/j.physa.2005.11.041].

  12. Effect of vision angle on the phase transition in flocking behavior of animal groups.

    PubMed

    Nguyen, P The; Lee, Sang-Hee; Ngo, V Thanh

    2015-09-01

    The nature of the phase transition in a system of self-propelling particles has been extensively studied during the past few decades. A theoretical model was proposed by [T. Vicsek et al. Phys. Rev. Lett. 75, 1226 (1995)PRLTAO0031-900710.1103/PhysRevLett.75.1226] with a simple rule for updating the direction of motion of each particle. Based on the model of Vicsek et al., in this paper, we consider a group of animals as particles moving freely in a two-dimensional space. Due to the fact that the viewable area of animals depends on the species, we consider the motion of each individual within an angle φ=ϕ/2 (ϕ is called the angle of view) of a circle centered at its position of radius R. We obtained a phase diagram in the space (φ,η_{c}) with η_{c} being the critical noise. We show that the phase transition exists only in the case of a wide view's angle φ≥0.5π. The flocking of animals is a universal behavior of the species of prey but not the one of the predator. Our simulation results are in good agreement with experimental observation [C. Beccoa et al., Physica A 367, 487 (2006)PHYADX0378-437110.1016/j.physa.2005.11.041]. PMID:26465507

  13. Polarization and resistive switching behavior of ferroelectric tunnel junctions with transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Li, Tao; Lipatov, Alexey; Sharma, Pankaj; Lee, Hyungwoo; Eom, Chang-Beom; Sinitskii, Alexander; Gruverman, Alexei; Alexei Gruverman Team; Alexander Sinitskii Team; Chang-Beom Eom Team

    Transition metal dichalcogenides (TMDs) are emerging 2-dimensional (2D) materials of the MX2 type, where M is a transition metal atom (Mo, W, Ti, Sn, Zr, etc.) and X is a chalcogen atom (S, Se, or Te.). Comparing to graphene, TMDs have a sizable band gap and can be metal, half-metal, semiconductor or superconductor. Their band structures can be tuned by external bias voltage, mechanical force, or light illumination. Their rich physical properties make TMDs potential candidates for a variety of applications in nanoelectronics and optoelectronics. Ferroelectric tunnel junctions (FTJs) are actively studied as a next-generation of non-volatile memory elements. An FTJ comprises a ferroelectric tunnel barrier sandwiched between two electrodes. In this work, we investigate the resistive switching behavior of MoS2/BaTiO3-based FTJs. The ON/OFF ratio can be modulated via electric or mechanical control of the switched polarization fraction opening a possibility of tunable electroresistance effect. Effect of optical illumination on the polarization reversal dynamics has been observed and analyzed based on the polarization-induced modulation of the MoS2 layered electronic properties.

  14. Influences of behavior and academic problems at school entry on marijuana use transitions during adolescence in an African American sample

    PubMed Central

    Reboussin, Beth A.; Ialongo, Nicholas S.; Green, Kerry M.

    2014-01-01

    Background: The aim of this study was to examine how patterns of academic and behavior problems in first grade relate to longitudinal transitions in marijuana use from middle school through entry into high school among African Americans. Methods: Latent class and latent transition analyses were conducted on a community sample of 458 low-income, urban-dwelling African-Americans. Results: Two behavior problem classes emerged at school entry; externalizing and attention/concentration. Academic problems co-occurred with both problem behavior classes although more strongly with attention/concentration. Youth in the attention/ concentration problem class were more likely to transition from no marijuana involvement to use and problems beginning in 7th grade and to use and problems given the opportunity to use marijuana early in high school compared to youth with no problems. Youth in the externalizing behavior problem class were significantly more likely to transition from no involvement to having a marijuana opportunity during the transition to high school compared to youth in the attention/concentration problems class. Conclusions: These findings highlight the importance of developing prevention programs and providing school services that address the co-occurrence of academic and behavior problems, as well as their subtype specific risks for marijuana involvement, particularly for low-income minority youth who may be entering school less ready than their non-minority peers. These findings also provide evidence for a need to continue to deliver interventions in middle and high school focused on factors that may protect youth during these critical transition periods when they may be especially vulnerable to opportunities to use marijuana based on their academic and behavioral risk profile. PMID:25305658

  15. The timing of entry into adult roles and changes in trajectories of problem behaviors during the transition to adulthood.

    PubMed

    Martin, Monica J; Blozis, Shelley A; Boeninger, Daria K; Masarik, April S; Conger, Rand D

    2014-11-01

    This study of a cohort of 451 adolescents examined associations between trajectories of problem behaviors and the timing of entry into work, marriage, and parenthood. We used data from 12 assessments across adolescence, through emerging adulthood and into young adulthood. We employed 2-phase mixed-effects models to estimate growth in substance use and antisocial behavior across adolescence, deceleration in the period that follows, and the change point that marks the transition between the 2 phases. We then examined the degree to which the timing of entry into a specific adult role was associated with change in problem behaviors and the change point between the 2 phases. We hypothesized that earlier entries into adult roles would be associated with earlier transitions to the decline in problem behaviors generally observed during adulthood but that later entries would be associated with more quickly declining rates of problem behaviors during adulthood. As proposed, earlier entries into marriage and parenthood predicted earlier transitions to declining trajectories in both substance use and antisocial behavior during adulthood. The findings also indicated that delayed marriage and parenthood were associated with more quickly decreasing rates of change in substance use, but not antisocial behavior, during adulthood. Thus, the results are consistent with the idea that substance use decreases earlier but not as quickly during adulthood for those with earlier entries into marriage and parenthood. However, the timing of entry into work did not predict trajectory changes. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:25243329

  16. Shear Flow Induced Transition from Liquid-Crystalline to Polymer Behavior in Side-Chain Liquid Crystal Polymers

    NASA Astrophysics Data System (ADS)

    Noirez, L.; Lapp, A.

    1997-01-01

    We determine the structure and conformation of side-chain liquid-crystalline polymers subjected to shear flow in the vicinity of the smectic phase by neutron scattering on the velocity gradient plane. Below the nematic-smectic transition we observe a typical liquid-crystal behavior; the smectic layers slide, leading to a main-chain elongation parallel to the velocity direction. In contrast, a shear applied above the transition induces a tilted main-chain conformation which is typical for polymer behavior.

  17. Temporal behavior of unresolved transition array emission in water window soft x-ray spectral region from multiply charged ions

    NASA Astrophysics Data System (ADS)

    Dinh, Thanh-Hung; Suzuki, Yuhei; Arai, Goki; Li, Bowen; Dunne, Padraig; O'Sullivan, Gerry; Fujioka, Shinsuke; Hasegawa, Noboru; Kawachi, Tetsuya; Nishikino, Masaharu; Higashiguchi, Takeshi

    2015-09-01

    We have characterized the spectral structure and the temporal history of the laser-produced high-Z multi-charged ion plasmas for the efficient water window soft x-ray sources. Strong unresolved transition array emission was observed due to 4d-4f and 4f-5g transitions from Au, Pb, and Bi plasmas in the 280-700 eV photon energy region. The temporal behavior of the emission was essentially similar of that of the laser pulse with a slight delay between different transitions. These results provide feedback for accurate modeling of the atomic processes with the radiative hydrodynamic simulations.

  18. Temporal behavior of unresolved transition array emission in water window soft x-ray spectral region from multiply charged ions

    SciTech Connect

    Dinh, Thanh-Hung Suzuki, Yuhei; Arai, Goki; Higashiguchi, Takeshi; Li, Bowen; Dunne, Padraig; O'Sullivan, Gerry; Fujioka, Shinsuke; Hasegawa, Noboru; Kawachi, Tetsuya; Nishikino, Masaharu

    2015-09-21

    We have characterized the spectral structure and the temporal history of the laser-produced high-Z multi-charged ion plasmas for the efficient water window soft x-ray sources. Strong unresolved transition array emission was observed due to 4d–4f and 4f–5g transitions from Au, Pb, and Bi plasmas in the 280–700 eV photon energy region. The temporal behavior of the emission was essentially similar of that of the laser pulse with a slight delay between different transitions. These results provide feedback for accurate modeling of the atomic processes with the radiative hydrodynamic simulations.

  19. Visualizing phase transition behavior of dilute stimuli responsive polymer solutions via Mueller matrix polarimetry.

    PubMed

    Narayanan, Amal; Chandel, Shubham; Ghosh, Nirmalya; De, Priyadarsi

    2015-09-15

    Probing volume phase transition behavior of superdiluted polymer solutions both micro- and macroscopically still persists as an outstanding challenge. In this regard, we have explored 4 × 4 spectral Mueller matrix measurement and its inverse analysis for excavating the microarchitectural facts about stimuli responsiveness of "smart" polymers. Phase separation behavior of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and pH responsive poly(N,N-(dimethylamino)ethyl methacrylate) (PDMAEMA) and their copolymers were analyzed in terms of Mueller matrix derived polarization parameters, namely, depolarization (Δ), diattenuation (d), and linear retardance (δ). The Δ, d, and δ parameters provided useful information on both macro- and microstructural alterations during the phase separation. Additionally, the two step action ((i) breakage of polymer-water hydrogen bonding and (ii) polymer-polymer aggregation) at the molecular microenvironment during the cloud point generation was successfully probed via these parameters. It is demonstrated that, in comparison to the present techniques available for assessing the hydrophobic-hydrophilic switch over of simple stimuli-responsive polymers, Mueller matrix polarimetry offers an important advantage requiring a few hundred times dilute polymer solution (0.01 mg/mL, 1.1-1.4 μM) at a low-volume format. PMID:26287499

  20. Adolescents in transition: school and family characteristics in the development of violent behaviors entering high school.

    PubMed

    Frey, Ariel; Ruchkin, Vladislav; Martin, Andrés; Schwab-Stone, Mary

    2009-03-01

    Adolescents are vulnerable to becoming involved in problematic behaviors, disengaging academically, and dropping out of school. This study was designed to evaluate the protective role of self-perceived school attachment and family involvement on the development of these negative behaviors during adolescence. The Social and Health Assessment (SAHA) survey was conducted among 652 predominantly minority, inner-city adolescents during their transition from middle to high school in order to examine school attachment, perceived teacher support, parental control, and exposure to community violence as predictors of engagement in violent activities, development of aggressive beliefs, perception of school climate, and academic motivation one year later. Family and school factors appeared to be differentially associated with the negative outcomes. School attachment was associated with lower levels of violent delinquency and aggressive beliefs, as well as with academic motivation. Perceived teacher support was associated with positive perceptions of school climate and with academic motivation. Parental control was associated with lower levels of violent activity and with higher levels of academic motivation. Violence exposure was related to violent delinquency and negative perception of school climate. School attachment, teacher support, parental control, and violence exposure must all be incorporated into school reform efforts intended to break the inner city cycle of violence. PMID:18574687

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

    PubMed

    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. PMID:24186540

  2. PARTNERSHIP TRANSITIONS AND ANTISOCIAL BEHAVIOR IN YOUNG ADULTHOOD: A WITHIN-PERSON, MULTI-COHORT ANALYSIS*

    PubMed Central

    Siennick, Sonja E.; Staff, Jeremy; Osgood, D. Wayne; Schulenberg, John E.; Bachman, Jerald G.; VanEseltine, Matthew

    2014-01-01

    Objectives This study examines the effects of young adult transitions into marriage and cohabitation on criminal offending and substance use, and whether those effects changed since the 1970s as marriage rates declined and cohabitation rates rose dramatically. It also examines whether any beneficial effects of cohabitation depend on marriage intentions. Methods Using multi-cohort national panel data from Monitoring the Future (N = 15,875), the authors estimated fixed effects models relating within-person changes in marriage and cohabitation to changes in criminal offending and substance use. Results Marriage predicts lower levels of criminal offending and substance use, but the effects of cohabitation are limited to substance use outcomes and to engaged cohabiters. There are no cohort differences in the associations of marriage and cohabitation with criminal offending, and no consistent cohort differences in their associations with substance use. There is little evidence of differences in effects by gender or parenthood. Conclusions Young adults are increasingly likely to enter romantic partnership statuses that do not appear as effective in reducing antisocial behavior. Although cohabitation itself does not reduce antisocial behavior, engagement might. Future research should examine the mechanisms behind these effects, and why non-marital partnerships reduce substance use and not crime. PMID:25484453

  3. Multivariate weighted recurrence network inference for uncovering oil-water transitional flow behavior in a vertical pipe

    NASA Astrophysics Data System (ADS)

    Gao, Zhong-Ke; Yang, Yu-Xuan; Cai, Qing; Zhang, Shan-Shan; Jin, Ning-De

    2016-06-01

    Exploring the dynamical behaviors of high water cut and low velocity oil-water flows remains a contemporary and challenging problem of significant importance. This challenge stimulates us to design a high-speed cycle motivation conductance sensor to capture spatial local flow information. We systematically carry out experiments and acquire the multi-channel measurements from different oil-water flow patterns. Then we develop a novel multivariate weighted recurrence network for uncovering the flow behaviors from multi-channel measurements. In particular, we exploit graph energy and weighted clustering coefficient in combination with multivariate time-frequency analysis to characterize the derived complex networks. The results indicate that the network measures are very sensitive to the flow transitions and allow uncovering local dynamical behaviors associated with water cut and flow velocity. These properties render our method particularly useful for quantitatively characterizing dynamical behaviors governing the transition and evolution of different oil-water flow patterns.

  4. Trajectories of prosocial behaviors conducive to civic outcomes during the transition to adulthood: the predictive role of family dynamics.

    PubMed

    Kanacri, Bernadette P Luengo; Pastorelli, Concetta; Zuffianò, Antonio; Eisenberg, Nancy; Ceravolo, Rosalba; Caprara, Gian Vittorio

    2014-12-01

    The current study explored the prediction of civic engagement by diverse trajectories of prosocial behaviors as well family dynamics (i.e., filial self-efficacy and relational parent-child support) across four times of assessment (from age 16-17 to age 22-23) during the transition to adulthood. Three different trajectories of prosocial behaviors were identified for 686 Italian youths: high-increasing (18%), medium-stable (48%), and low-stable (34%). An increasing pattern of change in prosocial behaviors was predicted by filial self-efficacy at age 16-17, which in turn mediated longitudinal relations to civic engagement and civic values at age 22-23. Results highlighted that during the transition to adulthood youths' beliefs about their ability to negotiate with their parents without losing autonomy and relatedness are relevant in promoting prosocial behaviors and civic involvement, especially in the context of Mediterranean countries. PMID:25150589

  5. Multivariate weighted recurrence network inference for uncovering oil-water transitional flow behavior in a vertical pipe.

    PubMed

    Gao, Zhong-Ke; Yang, Yu-Xuan; Cai, Qing; Zhang, Shan-Shan; Jin, Ning-De

    2016-06-01

    Exploring the dynamical behaviors of high water cut and low velocity oil-water flows remains a contemporary and challenging problem of significant importance. This challenge stimulates us to design a high-speed cycle motivation conductance sensor to capture spatial local flow information. We systematically carry out experiments and acquire the multi-channel measurements from different oil-water flow patterns. Then we develop a novel multivariate weighted recurrence network for uncovering the flow behaviors from multi-channel measurements. In particular, we exploit graph energy and weighted clustering coefficient in combination with multivariate time-frequency analysis to characterize the derived complex networks. The results indicate that the network measures are very sensitive to the flow transitions and allow uncovering local dynamical behaviors associated with water cut and flow velocity. These properties render our method particularly useful for quantitatively characterizing dynamical behaviors governing the transition and evolution of different oil-water flow patterns. PMID:27368782

  6. Mechanisms of phase transitions in sodium clusters: From molecular to bulk behavior

    NASA Astrophysics Data System (ADS)

    Calvo, F.; Spiegelmann, F.

    2000-02-01

    The thermodynamics of sodium clusters is investigated by means of a classical empirical potential and a simple quantal tight-binding model. Neutral and singly charged clusters of sizes ranging from 8 to 147 atoms are considered. A very particular attention is paid to the optimization and sampling problems. We determine the lowest-energy structures (global minima) with the "basin-hopping" technique, and the finite-temperature simulations are improved by using the "q-jumping" method and put together with the multiple histogram method. The clusters geometries may be very different on the model used, but also on the ionic charge, up to the size of about 40 atoms. The thermodynamical analysis is performed near the solid-liquid transition by calculating the complete calorific curves (heat capacities) as well as some microscopic parameters to probe the dynamics on the energy landscapes, including the spectra of isomers found by periodic quenching, isomerization indexes and the Lindemann parameter δ. Up to the largest sizes, we find that the heat capacity generally displays several features within the two models, although structural differences in the lowest-energy isomers usually induce different calorific curves. These premelting phenomena are characteristic of isomerizations taking place in a limited part of the configuration space. The thermodynamics appears to be directly related to the lowest-energy structure, and melting by steps is favored by the presence of defects on its surface. We estimate the melting temperatures Tmelt(n) and latent heats of melting L(n), and we observe two very different behaviors of their variations with the size n. Below about 75 atoms, both Tmelt and L exhibit strong non-monotonic variations typical of geometric size effects. This "microscopic" behavior is caused by the dominating premelting effects, and is replaced by a more "macroscopic" behavior for sizes larger than about 93 atoms. The premelting phenomena become there less important

  7. Phase transition and critical behavior of spin-orbital coupled spinel ZnV2O4

    NASA Astrophysics Data System (ADS)

    Li, Wang; Rong-juan, Wang; Yuan-yuan, Zhu; Zhi-hong, Lu; Rui, Xiong; Yong, Liu; Jing, Shi

    2016-01-01

    We present the temperature-dependent susceptibility and specific heat measurement of spinel ZnV2O4. The structural transition with orbital ordering and the antiferromagnetic transition with spin ordering were observed at 50 K and 37 K, respectively. By analysis of the hysteresis behavior between the specific heat curves obtained in warming and cooling processes, the structural transition was confirmed to be the first-order transition, while the antiferromagnetic transition was found to be of the second-order type. At the structural transition, the latent heat and entropy change were calculated from the excess specific heat, and the derivative of pressure with respect to temperature was obtained using the Clausius-Clapayron equation. At the magnetic transition, the width of the critical fluctuation region was obtained to be about 0.5 K by comparing with Gaussian fluctuations. In the critical region, the critical behavior was analyzed by using renormalization-group theory. The critical amplitude ratio A+/A- = 1.46, which deviates from the 3D Heisenburg model; while the critical exponent α is -0.011, which is close to the 3D XY model. We proposed that these abnormal critical behaviors can be attributed to strong spin-orbital coupling accompanied with the antiferromagnetic transition. Moreover, in the low temperature range (2-5 K), the Fermi energy, the density of states near the Fermi surface, and the low limit of Debye temperature were estimated to be 2.42 eV, 2.48 eV-1, and 240 K, respectively. Project supported by the National Basic Research Program of China (Grant No. 2012CB821404), the National Natural Science Foundation of China (Grant Nos. 51172166 and 61106005), the National Science Fund for Talent Training in Basic Science, China (Grant No. J1210061), and the Doctoral Fund of Ministry of Education of China (Grant No. 20110141110007).

  8. Ageneral approach to first order phase transitions and the anomalous behavior of coexisting phases in the magnetic case.

    SciTech Connect

    Gama, S.; de Campos, A.; Coelho, A. A.; Alves, C. S.; Ren, Y.; Garcia, F.; Brown, D. E.; da Silva, L. M.; Magnus, A.; Carvalho, G.; Gandra, G. C.; dos Santos, A. O.; Cardoso, L. P.; von Ranke, P. J.; X-Ray Science Division; Univ. Federal de Sao Paulo; Unv. Estadual de Champinas; Univ. Estadual de Maringa Lab. Nacional de Luz Sincrotron; Northern Univ.; Univ. de Estado do Rio de Janerio

    2009-01-01

    First order phase transitions for materials with exotic properties are usually believed to happen at fixed values of the intensive parameters (such as pressure, temperature, etc.) characterizing their properties. It is also considered that the extensive properties of the phases (such as entropy, volume, etc.) have discontinuities at the transition point, but that for each phase the intensive parameters remain constant during the transition. These features are a hallmark for systems described by two thermodynamic degrees of freedom. In this work it is shown that first order phase transitions must be understood in the broader framework of thermodynamic systems described by three or more degrees of freedom. This means that the transitions occur along intervals of the intensive parameters, that the properties of the phases coexisting during the transition may show peculiar behaviors characteristic of each system, and that a generalized Clausius-Clapeyron equation must be obeyed. These features for the magnetic case are confirmed, and it is shown that experimental calorimetric data agree well with the magnetic Clausius-Clapeyron equation for MnAs. An estimate for the point in the temperature-field plane where the first order magnetic transition turns to a second order one is obtained (the critical parameters) for MnAs and Gd{sub 5}Ge{sub 2}Si{sub 2} compounds. Anomalous behavior of the volumes of the coexisting phases during the magnetic first order transition is measured, and it is shown that the anomalies for the individual phases are hidden in the behavior of the global properties as the volume.

  9. Indoor-Outdoor Space; the Transitional Areas and Their Effect on Human Behavior. Exchange Bibliography No. 517.

    ERIC Educational Resources Information Center

    Bartholomew, Robert

    This brief bibliography lists publications about the transitional areas between buildings or leading into or out of buildings. These spaces are usually public spaces, at least in urban areas, that perform functions influencing human behavior, including visual separation or connection, territorial definition, and control of traffic and climatic…

  10. Predicting Transition and Adjustment to College: Biomedical and Behavioral Science Aspirants' and Minority Students' First Year of College

    ERIC Educational Resources Information Center

    Hurtado, Sylvia; Han, June C.; Saenz, Victor B.; Espinosa, Lorelle L.; Cabrera, Nolan L.; Cerna, Oscar S.

    2007-01-01

    The purpose of this study is to explore key factors that impact the college transition of aspiring underrepresented minority students in the biomedical and behavioral sciences, in comparison with White, Asian students and non-science minority students. We examined successful management of the academic environment and sense of belonging during the…

  11. Family Intervention Effects on Co-Occurring Early Childhood Behavioral and Emotional Problems: A Latent Transition Analysis Approach

    ERIC Educational Resources Information Center

    Connell, Arin; Bullock, Bernadette Marie; Dishion, Thomas J.; Shaw, Daniel; Wilson, Melvin; Gardner, Frances

    2008-01-01

    This study used latent transition analysis (LTA) to examine changes in early emotional and behavioral problems in children age 2 to 4 years resulting from participation in a family-centered intervention. A sample of 731 economically disadvantaged families was recruited from among participants in a national food supplement and nutrition program.…

  12. Short communication: Association of lying behavior and subclinical ketosis in transition dairy cows.

    PubMed

    Kaufman, E I; LeBlanc, S J; McBride, B W; Duffield, T F; DeVries, T J

    2016-09-01

    The objective of this study was to characterize the association of lying behavior and subclinical ketosis (SCK) in transition dairy cows. A total of 339 dairy cows (107 primiparous and 232 multiparous) on 4 commercial dairy farms were monitored for lying behavior and SCK from 14d before calving until 28 d after calving. Lying time, frequency of lying bouts, and average lying bout length were measured using automated data loggers 24h/d. Cows were tested for SCK 1×/wk by taking a blood sample and analyzing for β-hydroxybutyrate; cows with β-hydroxybutyrate ≥1.2mmol/L postpartum were considered to have SCK. Cases of retained placenta, metritis, milk fever, or mastitis during the study period were recorded and cows were categorized into 1 of 4 groups: healthy (HLT) cows had no SCK or any other health problem (n=139); cows treated for at least 1 health issue other than SCK (n=50); SCK (HYK) cows with no other health problems during transition (n=97); or subclinically ketotic plus (HYK+) cows that had SCK and 1 or more other health problems (n=53). Daily lying time was summarized by week and comparisons were made between HLT, HYK, and HYK+, respectively. We found no difference among health categories in lying time, bout frequency, or bout length fromwk -2 towk +4 relative to calving for first-lactation cows. Differences in lying time for multiparous cows were seen inwk +1, when HYK+ cows spent 92±24.0 min/d more time lying down than HLT cows, and duringwk +3 and +4 when HYK cows spent 44±16.7 and 41±18.9 min/d, respectively, more time lying down than HLT cows. Increased odds of HYK+ were found to be associated with higher parity, longer dry period, and greater stall stocking density inwk -1 and longer lying time duringwk +1. When comparing HYK to HLT cows, the same variables were associated with odds of SCK; however, lying time was not retained in the final model. These results suggest that monitoring lying time may contribute to identifying multiparous cows

  13. Effects of monensin on metabolic parameters, feeding behavior, and productivity of transition dairy cows.

    PubMed

    Mullins, C R; Mamedova, L K; Brouk, M J; Moore, C E; Green, H B; Perfield, K L; Smith, J F; Harner, J P; Bradford, B J

    2012-03-01

    The effects of monensin on transition cow metabolism may be dependent on modulation of feeding behavior, rumen pH, and expression of key metabolic genes. Multiparous Holstein cows were used to determine the effects of monensin (400mg/cow daily) on these variables. Cows were randomly assigned, based on calving date, to control or monensin treatments (n = 16 per treatment) 21 d before their expected calving date, and cows remained on treatments through 21 d postpartum. Feeding behavior and water intake data were collected daily. Liver biopsies were conducted after assessing BCS and BW on d -21, -7, 1, 7, and 21 relative to calving for analysis of triglyceride (TG) content as well as mRNA abundance of cytosolic phosphoenolpyruvate carboxykinase, carnitine palmitoyltransferase 1a, and apolipoprotein B. Blood samples were collected 21, 7, and 4 d before expected calving and 1 (day of calving), 4, 7, 14, and 21 d postpartum for nonesterified fatty acid, β-hydroxybutyrate, glucose, insulin, and haptoglobin analyses. Ruminal pH was collected every 5 min on d 1 through 6 postpartum via a wireless indwelling probe. On d 7 postpartum, a caffeine clearance test was performed to assess liver function. Data were analyzed using mixed models with repeated measures over time. Monensin decreased mean plasma β-hydroxybutyrate (734 vs. 616 ± 41 μM) and peak concentrations (1,076 vs. 777 ± 70 μM on d 4 postpartum). Monensin also decreased time between meals prepartum (143 vs. 126 ± 5.0 min) and postpartum (88.8 vs. 81.4 ± 2.9 min), which was likely related to a smaller ruminal pH standard deviation in the first day after cows changed to a lactation ration (0.31 vs. 0.26 ± 0.015). Monensin also increased liver mRNA abundance of carnitine palmitoyltransferase 1a (0.10 vs. 0.15 ± 0.002 arbitrary units), which corresponded to a slower rate of liver TG accumulation from d -7 to +7 (412 vs. 128 ± 83 mg of TG/g of protein over this time period). No significant effects of monensin

  14. Transitions in body and behavior: a meta-analytic study on the relationship between pubertal development and adolescent sexual behavior.

    PubMed

    Baams, Laura; Dubas, Judith Semon; Overbeek, Geertjan; van Aken, Marcel A G

    2015-06-01

    The present meta-analysis studies the relations of pubertal timing and status with sexual behavior and sexual risk behavior among youth aged 10.5-22.4 years. We included biological sex, age, and ethnicity as potential moderators. Four databases were searched for studies (published between 1980 and 2012) on the relation between pubertal timing or status and sexual behavior. The outcomes were (1) sexual intercourse; (2) combined sexual behavior; and (3) risky sexual behavior. Earlier pubertal timing or more advanced pubertal status was related to earlier and more sexual behavior, and earlier pubertal timing was related to more risky sexual behavior. Further, the links between (1) pubertal status and combined sexual behavior and (2) pubertal timing and sexual intercourse status, combined sexual behavior, and risky sexual behavior were stronger for girls than boys. Most links between pubertal status, timing, and sexual behavior and sexual risk behavior were stronger for younger adolescents. Moderation by ethnicity did not yield consistent results. There was significant variation in results among studies that was not fully explained by differences in biological sex, age, and ethnicity. Future research is needed to identify moderators that explain the variation in effects and to design sexual health interventions for young adolescents. PMID:25636818

  15. Micro/nano composited tungsten material and its high thermal loading behavior

    NASA Astrophysics Data System (ADS)

    Fan, Jinglian; Han, Yong; Li, Pengfei; Sun, Zhiyu; Zhou, Qiang

    2014-12-01

    Tungsten (W) is considered as promising candidate material for plasma facing components (PFCs) in future fusion reactors attributing to its many excellent properties. Current commercial pure tungsten material in accordance with the ITER specification can well fulfil the performance requirements, however, it has defects such as coarse grains, high ductile-brittle transition temperature (DBTT) and relatively low recrystallization temperature compared with its using temperature, which cannot meet the harsh wall loading requirement of future fusion reactor. Grain refinement has been reported to be effective in improving the thermophysical and mechanical properties of W. In this work, rare earth oxide (Y2O3/La2O3) and carbides (TiC/ZrC) were used as dispersion phases to refine W grains, and micro/nano composite technology with a process of 'sol gel - heterogeneous precipitation - spray drying - hydrogen reduction - ordinary consolidation sintering' was invented to introduce these second-phase particles uniformly dispersed into W grains and grain-boundaries. Via this technology, fine-grain W materials with near-full density and relatively high mechanical properties compared with traditional pure W material were manufactured. Preliminary transient high-heat flux tests were performed to evaluate the thermal response under plasma disruption conditions, and the results show that the W materials prepared by micro/nano composite technology can endure high-heat flux of 200 MW/m2 (5 ms).

  16. Do specific transitional patterns of antisocial behavior during adolescence increase risk for problems in young adulthood?

    PubMed

    Cook, Emily C; Pflieger, Jacqueline C; Connell, Arin M; Connell, Christian M

    2015-01-01

    Latent transition analysis was used to identify patterns and trajectories of antisocial behavior (ASB) and their association with young adult outcomes in a nationally representative sample of adolescents (N = 5,422; 53.9% female). Participants were on average 13.96 years of age (SD = 1.06) at wave 1 of the study. Latent class analysis identified four classes of ASB including a non-ASB class, an aggressive class, a petty theft class, and a serious ASB class. In general, youth who were classified as serious stable ASB were the most at risk for problematic functioning in young adulthood. Youth who escalated to more serious patterns of ASB or reduced involvement also were at greater risk of negative outcomes in young adulthood compared to stable non-ASB youth, although they generally fared better than youth involved in stable patterns of more serious ASB. Gender differences indicated that involvement in ASB was a greater risk factor for alcohol use among boys and a greater risk factor for depression among girls in young adulthood. Results are discussed in terms of the predictive validity of classes of ASB to functioning in young adulthood and the implications of this research for prevention efforts. PMID:24893667

  17. Do Specific Transitional Patterns of Antisocial Behavior during Adolescence Increase Risk for Problems in Young Adulthood?

    PubMed Central

    Cook, Emily C.; Pflieger, Jacqueline C.; Connell, Arin M.; Connell, Christian M.

    2014-01-01

    Latent transition analysis was used to identify patterns and trajectories of antisocial behavior (ASB) and their association with young adult outcomes in a nationally representative sample of adolescents (N = 5,422; 53.9% female). Participants were on average 13.96 years of age (SD= 1.06) at wave 1 of the study. Latent class analysis identified four classes of ASB including a non-ASB class, an aggressive class, a petty theft class, and a serious ASB class. In general, youth who were classified as serious stable ASB were the most at risk for problematic functioning in young adulthood. Youth who escalated to more serious patterns of ASB or reduced involvement also were at greater risk of negative outcomes in young adulthood compared to stable non-ASB youth, although they generally fared better than youth involved in stable patterns of more serious ASB. Gender differences indicated that involvement in ASB was a greater risk factor for alcohol use among boys and a greater risk factor for depression among girls in young adulthood. Results are discussed in terms of the predictive validity of classes of ASB to functioning in young adulthood and the implications of this research for prevention efforts. PMID:24893667

  18. Anomalous ion-channeling behavior across the superconducting transition in high-T(sub c) materials

    NASA Astrophysics Data System (ADS)

    Rehn, L. E.; Sharma, R. P.; Baldo, P. M.; Liu, J. Z.

    1989-07-01

    Axial channeling scans with minimum RBS yields of less than or = 2 percent were obtained for 1.5 MeV He-4 ions incident along the c-axis in YBa2Cu3O(7-delta) and ErBa2Cu3O(7-delta) single crystals. Large variations in the FWHM of the (001) channeling dip were observed for temperatures between 30 and 300 K. An abrupt, (approx.) 8 percent increase was measured as the temperature was lowered through the superconducting transition T(sub c); the rela tive increase across T(sub c) in the width of the axial dip was even larger for angles of incidence less than the critical angle. A simple analytical procedure for polyatomic materials yields isotropic, average thermal vibrational amplitudes that agree well with considerably less precise neutron powder diffraction results on sintered samples. The individual contribution to the angular channeling dip from the row of Er and Ba atoms parallel to the c-axis can be isolated in the RBS scans of the Er compound. This separation reveals normal (Debye-type) behavior for atoms in the Er-Ba row, demonstrating that the anomalous changes are due solely to atomic displacements in the Cu-O row. Finally, x ray studies using specimens with different O stoichiometries reveal that the anomalous change in the FWHM shifts in temperature in direct proportion to the change in T(sub c).

  19. Transition to superdiffusive behavior in intracellular actin-based transport mediated by molecular motors

    NASA Astrophysics Data System (ADS)

    Bruno, L.; Levi, V.; Brunstein, M.; Despósito, M. A.

    2009-07-01

    Intracellular transport of large cargoes, such as organelles, vesicles, or large proteins, is a complex dynamical process that involves the interplay of adenosine triphosphate-consuming molecular motors, cytoskeleton filaments, and the viscoelastic cytoplasm. In this work we investigate the motion of pigment organelles (melanosomes) driven by myosin-V motors in Xenopus laevis melanocytes using a high-spatio-temporal resolution tracking technique. By analyzing the obtained trajectories, we show that the melanosomes mean-square displacement undergoes a transition from a subdiffusive to a superdiffusive behavior. A stochastic theoretical model, which explicitly considers the collective action of the molecular motors, is introduced to generalize the interpretation of our data. Starting from a generalized Langevin equation, we derive an analytical expression for the mean square displacement, which also takes into account the experimental noise. By fitting theoretical expressions to experimental data we were able to discriminate the exponents that characterize the passive and active contributions to the dynamics and to estimate the “global” motor forces correctly. Then, our model gives a quantitative description of active transport in living cells with a reduced number of parameters.

  20. Behavior of the low-frequency conductivity of silver iodide nanocomposites in the superionic phase transition region

    NASA Astrophysics Data System (ADS)

    Vergent'ev, T. Yu.; Koroleva, E. Yu.; Kurdyukov, D. A.; Naberezhnov, A. A.; Filimonov, A. V.

    2013-01-01

    The behavior of the specific conductivity of composites based on silver iodide embedded in porous glasses with an average pore diameter of 7 ± 1 nm and in artificial opals with a pore diameter of 40-100 nm has been investigated in the temperature range from 300 to 500 K. It has been shown that a decrease in the characteristic pore size does not lead to a change in the order of the phase transition and that the temperature of the transition to the superionic state of silver iodide in a porous glass and in an opal upon heating is close to the phase transition temperature T c in the bulk material (˜420 K). Upon cooling, the phase transition temperature T c significantly decreases, and the phase transition becomes diffuse. With a decrease in the pore size, the region of the temperature hysteresis of the phase transition increases. The dc conductivities of the composites have been estimated from the impedance diagrams. The temperature dependence of the dc conductivity of both composites has a thermally activated nature, and the slope of the curve σ(1/ T) changes near the phase transition, which indicates a change in the activation energy. The activation energies in the low-temperature and high-temperature phases have been estimated at ˜450-470 and ˜100 meV, respectively. The equivalent electrical circuit describing the charge transfer processes in the studied samples has been proposed.

  1. Transport behavior across the field-driven superconductor-insulator transition in amorphous indium oxide films

    NASA Astrophysics Data System (ADS)

    Kim, Min-Soo

    Superconductor-insulator transition (SIT) in two-dimensional (2D) thin films is a beautiful realization of a zero temperature quantum phase transition (QPT) and has been explored both theoretically and experimentally over the last two decades. In addition to the several intrinsic ways (such as thickness) of tuning the transition, external magnetic field has been used to tune from one ground state to another in various condensed matter systems. Amorphous indium oxide thin films, with their unique capability of tuning the disorder level in the system easily, have been proven to be an excellent model system to study the transport mechanisms near and across the SIT in 2D. In this thesis, magnetic field-driven SIT in 2D films of amorphous InO x is studied. The goal of this work is to understand the microscopic transport mechanisms responsible for driving the SIT when the magnetic field direction is continually varied from being perpendicular to the sample plane to parallel. Applying a perpendicular magnetic field resulting in a clear field-driven SIT and a magneto-resistance peak on the insulating side in InO x films have been previously understood in a bosonic picture put forward by M. P. A. Fisher and coworkers. However, this boson-vortex duality picture is expected to give rise to markedly different transport characteristics when the magnetic field is applied parallel to the sample plane. Features found in the parallel-field transport data however can also be explained by the bosonic picture, thereby questioning the applicability of the hitherto successful models to the physics of SIT. An isotropic magnetic field value, where the sample has the exact same resistance irrespective of the angle between the sample plane and magnetic field direction, is found. This isotropic point lies at field values above the critical field (Bc) of the SIT (in both perpendicular and parallel configurations) and above the magnetoresistance peak. The isotropic point is very weakly

  2. Facilitating Transitions between and within Academic Tasks: An Application of Behavioral Momentum

    ERIC Educational Resources Information Center

    Lee, David L.

    2006-01-01

    Transitions are critical times for both teachers and students. Efficient between-task and within-task transitions can greatly improve academic learning time. The purpose of this article was to review one intervention, high-probability (high-p) task sequences, as a method to promote more effective transitions. High-p sequences involve presenting a…

  3. Implications of Weak-Link Behavior on the Performance of Mo/Au Bilayer Transition-Edge Sensors

    NASA Technical Reports Server (NTRS)

    Smith, Stephen J.

    2011-01-01

    Understanding the physical properties of the superconducting-to-normal transition is fundamental for optimizing the design and performance of transition-edge sensors (TESs). Recent critical current measurements of Mol Au bilayer test structures show that they act as weak superconducting links, exhibiting oscillatory, Fraunhofer-like behavior with applied magnetic field. In this paper we investigate the implications of this behavior for TES X-ray detectors, under operational bias conditions. These devices include normal metal features used for absorber attachment and unexplained noise suppression, which result in modifications to the previously reported critical current behavior. We present measurements of the logarithmic resistance sensitivity with temperature, a, and current, b, as a function of applied magnetic field and bias point within the resistive transition. Results show that these important device parameters exhibit similar oscillatory behavior with applied magnetic field, which in turn affects the signal responsivity and noise, and hence the energy resolution. These results show the significance of the critical current in determining the performance of TESs and hold promise to improve future.

  4. Behavioral and Physiological Changes during Benthic-Pelagic Transition in the Harmful Alga, Heterosigma akashiwo: Potential for Rapid Bloom Formation

    PubMed Central

    Tobin, Elizabeth D.; Grünbaum, Daniel; Patterson, Johnathan; Cattolico, Rose Ann

    2013-01-01

    Many species of harmful algae transition between a motile, vegetative stage in the water column and a non-motile, resting stage in the sediments. Physiological and behavioral traits expressed during benthic-pelagic transition potentially regulate the timing, location and persistence of blooms. The roles of key physiological and behavioral traits involved in resting cell emergence and bloom formation were examined in two geographically distinct strains of the harmful alga, Heterosigma akashiwo. Physiological measures of cell viability, division and population growth, and cell fatty acid content were made using flow cytometry and gas chromatography – mass spectrometry techniques as cells transitioned between the benthic resting stage and the vegetative pelagic stage. Video-based tracking was used to quantify cell-level swimming behaviors. Data show increased temperature and light triggered rapid emergence from the resting stage and initiated cell swimming. Algal strains varied in important physiological and behavioral traits, including survivorship during life-stage transitions, population growth rates and swimming velocities. Collectively, these traits function as “population growth strategies” that can influence bloom formation. Many resting cells regained the up-swimming capacity necessary to cross an environmentally relevant halocline and the ability to aggregate in near-surface waters within hours after vegetative growth supporting conditions were restored. Using a heuristic model, we illustrate how strain-specific population growth strategies can govern the timescales over which H. akashiwo blooms form. Our findings highlight the need for identification and quantification of strain-specific physiological and behavioral traits to improve mechanistic understanding of bloom formation and successful bloom prediction. PMID:24124586

  5. Idiopathic REM sleep behavior disorder in the transition to degenerative disease.

    PubMed

    Postuma, Ronald B; Gagnon, Jean-Francois; Vendette, Melanie; Montplaisir, Jacques Y

    2009-11-15

    Idiopathic REM sleep behavior disorder (RBD) predicts Parkinson's disease (PD) and dementia. However, the nature of the disease that emerges from RBD has not been fully characterized. Since 2004, we have been conducting a prospective study of idiopathic RBD patients, providing an opportunity to directly observe patients as they transitioned to a defined neurodegenerative syndrome. Patients with idiopathic RBD underwent an extensive annual evaluation of motor function, olfaction, color vision, autonomic function, cognition and psychiatric symptoms. Neurodegenerative disease was defined according to standard criteria. We compared these measures in patients who had developed PD to those with dementia, all within the first year of developing disease. Of 67 patients, 6 developed PD and eleven developed dementia. Except for cognitive functioning, all tests of olfaction, color vision, autonomic function, depression, and quantitative measures of motor speed were similar in patients with PD and dementia. Of dementia patients, seven met criteria for probable Lewy body dementia (LBD) and four for Alzheimer's disease (or, possible LBD). In all probable LBD cases, the diagnosis was made because of parkinsonism, with no patient experiencing hallucinations or fluctuations. Patients with "Alzheimer's disease" seemed to have LBD, as they demonstrated typical LBD cognitive profiles on neuropsychological testing and were indistinguishable from LBD patients in ancillary measures. Therefore, among RBD patients with new-onset LBD, hallucinations or fluctuations are absent, suggesting that RBD is a reliable early sign of LBD. The indistinguishability of dementia and PD in all ancillary measures suggests a single unitary "RBD-then-neurodegeneration" process, the clinical presentation of which depends upon selective neuronal vulnerability. PMID:19768814

  6. Transition and protective agency of early childhood learning behaviors as portents of later school attendance and adjustment.

    PubMed

    McDermott, Paul A; Rikoon, Samuel H; Fantuzzo, John W

    2016-02-01

    This article reports on the study of differential change trajectories for early childhood learning behaviors as they relate to future classroom adjustment and school attendance. A large sample (N=2152) of Head Start children was followed through prekindergarten, kindergarten, and 1st grade. Classroom learning behaviors were assessed twice each year by teachers who observed gradual declines in Competence Motivation and Attentional Persistence as children transitioned through schooling. Cross-classified multilevel growth models revealed distinct transitional pathways for future adjustment versus maladjustment and sporadic versus chronic absenteeism. Generalized multilevel logistic modeling and receiver operating characteristic curve analyses showed that teachers' earliest assessments were substantially predictive of eventual good classroom adjustment and school attendance, with increasing accuracy for prediction of future sociobehavioral adjustment as time progressed. PMID:26790703

  7. Effect of heat treatment and irradiation temperature on impact behavior of irradiated reduced-activation ferritic steels

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.

    1998-03-01

    Charpy tests were conducted on eight normalized-and-tempered reduced-activation ferritic steels irradiated in two different normalized conditions. Irradiation was conducted in the Fast Flux Test Facility at 393 C to {approx}14 dpa on steels with 2.25, 5, 9, and 12% Cr (0.1% C) with varying amounts of W, V, and Ta. The different normalization treatments involved changing the cooling rate after austenitization. The faster cooling rate produced 100% bainite in the 2.25 Cr steels, compared to duplex structures of bainite and polygonal ferrite for the slower cooling rate. For both cooling rates, martensite formed in the 5 and 9% Cr steels, and martensite with {approx}25% {delta}-ferrite formed in the 12% Cr steel. Irradiation caused an increase in the ductile-brittle transition temperature (DBTT) and a decrease in the upper-shelf energy. The difference in microstructure in the low-chromium steels due to the different heat treatments had little effect on properties. For the high-chromium martensitic steels, only the 5 Cr steel was affected by heat treatment. When the results at 393 C were compared with previous results at 365 C, all but a 5 Cr and a 9 Cr steel showed the expected decrease in the shift in DBTT with increasing temperature.

  8. Subtask 12G3: Fracture properties of V-4Cr-4Ti irradiated in the dynamic helium charging experiment

    SciTech Connect

    Chung, H.M.; Nowicki, L.J.; Busch, D.E.; Smith, D.L.

    1995-03-01

    The objective of this work is to determine the effect of simultaneous displacement damage and dynamically charged helium on the ductile-brittle transition behavior of V-4Cr-4Ti specimens irradiated to 18-31 dpa at 425-600{degrees}C in the Dynamic Helium Charging Experiment (DHCE). One property of vanadium-base alloys that is not well understood in terms of their potential use as fusion reactor structural materials is the effect of simultaneous generation of helium and neutron damage under conditions relevant to fusion reactor operation. In the present DHCE, helium was produced uniformly in the specimen at linear rates ranging from {approx}0.4 to 4.2 appm helium/dpa by the decay of tritium during irradiation to 18-31 dpa at 425-600{degrees}C in Li-filled DHCE capsules in the Fast Flux Test Facility. Ductile-brittle transition behavior of V-4Cr-4Ti, recently identified as the most promising vanadium-base alloy for fusion reactor use, was determined from multiple-bending tests (at -196{degrees}C to 50{degrees}C) and quantitative SEM fractography on TEM disks (0.3-mm thick) and broken tensile specimens (1.0-mm thick). No brittle behavior was observed at temperatures >-150{degrees}C, and predominantly brittle-cleavage fracture morphologies were observed only at -196{degrees}C in some specimens irradiated to 31 dpa at 425{degrees}C during DHCE. Ductile-brittle transition temperatures (DBTTs) were -200{degrees}C to -175{degrees}C for both types of specimens. In strong contrast to tritium-trick experiments in which dense coalescence of helium bubbles is produced on grain boundaries in the absence of displacement damage, no intergranular fracture was observed in the bend-tested specimens irradiated in the DHCE. 24 refs., 3 figs., 2 tabs.

  9. Personality, Freshmen Proactive Social Behavior, and College Transition: Predictors beyond Academic Strategies

    ERIC Educational Resources Information Center

    Wang, Yi; Cullen, Kristin L.; Yao, Xiang; Li, Yixuan

    2013-01-01

    When transitioning to college freshmen must behave proactively in order to strive for success in their collegiate careers and their future life. Past research has mainly focused on the academic strategies of freshmen when investigating the predictors of successful college transition and has paid little attention to students' social strategies. The…

  10. Dissipative Landau-Zener transitions of a qubit: Bath-specific and universal behavior

    SciTech Connect

    Saito, Keiji; Wubs, Martijn; Kohler, Sigmund; Haenggi, Peter; Kayanuma, Yosuke

    2007-06-01

    We study Landau-Zener transitions in a qubit coupled to a bath at zero temperature. A general formula that is applicable to models with a nondegenerate ground state is derived. We calculate exact transition probabilities for a qubit coupled to either a bosonic or a spin bath. The nature of the baths and the qubit-bath coupling is reflected in the transition probabilities. For diagonal coupling, when the bath causes energy fluctuations of the diabatic qubit states but no transitions between them, the transition probability coincides with the standard Landau-Zener probability of an isolated qubit. This result is universal as it does not depend on the specific type of bath. For pure off-diagonal coupling, by contrast, the tunneling probability is sensitive to the coupling strength. We discuss the relevance of our results for experiments on molecular nanomagnets, in circuit QED, and for the fast-pulse readout of superconducting phase qubits.

  11. Theoretical study on the alloying behavior of γ-uranium metal: γ-uranium alloy with 3d transition metals

    NASA Astrophysics Data System (ADS)

    Kurihara, Masayoshi; Hirata, Masaru; Sekine, Rika; Onoe, Jun; Nakamatsu, Hirohide

    2004-03-01

    We have investigated the alloying behavior of γ-uranium with 3d transition metals (TMs) using the relativistic discrete-variational Dirac-Fock-Slater (DV-DFS) method. The d-orbital energy (Md) as an alloying parameter well reproduces the alloying behavior of γ-uranium metal with TMs: (1) in the case of a large Md value (Ti, V, Cr), the solubility of these TM elements in γ-uranium becomes large; (2) in the case of a middle Md value (Mn, Fe, Co), the tendency to form a uranium intermetallic compound with these elements becomes stronger; (3) in the case of a small Md value (Cu), the alloying element is insoluble in γ-uranium. The alloying behavior of γ-uranium with TMs is also discussed in terms of other parameters such as electronegativity and metallic radius.

  12. Critical behavior in the inverse to forward energy transition in two-dimensional magnetohydrodynamic flow.

    PubMed

    Seshasayanan, Kannabiran; Alexakis, Alexandros

    2016-01-01

    We investigate the critical transition from an inverse cascade of energy to a forward energy cascade in a two-dimensional magnetohydrodynamic flow as the ratio of magnetic to mechanical forcing amplitude is varied. It is found that the critical transition is the result of two competing processes. The first process is due to hydrodynamic interactions and cascades the energy to the large scales. The second process couples small-scale magnetic fields to large-scale flows, transferring the energy back to the small scales via a nonlocal mechanism. At marginality the two cascades are both present and cancel each other. The phase space diagram of the transition is sketched. PMID:26871152

  13. Heat-treatment effect on impact properties of reduced-activation steels*1

    NASA Astrophysics Data System (ADS)

    Klueh, R. L.; Maziasz, P. J.; Alexander, D. J.

    1991-03-01

    The effect of heat treatment on the impact behavior of eight experimental heats of reduced-activation ferritic steels was investigated. Steels with 2 {1}/{4}, 5, 9, and 12 wt% Cr and containing tungsten, vanadium, and tantalum were examined. Impact properties of steels with 2 {1}/{4} wt% Cr depended on microstructure, which was affected by cooling rate after austenitization. By heat-treating the 2 {1}/{4} wt% Cr steels to change the microstructure from a bainitic structure containing ferrite to one without ferrite, the ductile-brittle transition temperatures were reduced substantially. The cooling rate had essentially no effect on the high-chromium martensitic steels.

  14. Magnetic Behavior of Nanostructured Mn0.23TaS2 Near Ferromagnetic Transition

    NASA Astrophysics Data System (ADS)

    Cooling, Corey; Shand, Paul; Boyle, K. R.; Kidd, Tim; Strauss, Laura

    2013-03-01

    We have investigated the ferromagnetic transition for tantalum disulfide intercalated with 23% manganese. The material was grown in the form of nanotube/nanowire structures with diameters ranging from 30nm to several hundred nanometers. These nanotube structures give the material a high anisotropy. The material was studied through Curie-Weiss analysis, dc magnetization, and ac susceptibility measurements. The ferromagnetic transition for Mn0.23TaS2 occurs around 85K and varies with the applied dc magnetic field. The ferromagnetic transition is characterized by a peak in the ac susceptibility. Analysis of the susceptibility peaks revealed atypically high critical exponent values when compared to other disordered ferromagnetic systems. The large exponents may be due to the existence of two transitions in close proximity. The first transition (at a higher temperature) is to a ferromagnetic state; the second is to a disordered magnetic state. Arrott-Noakes plotting provided further justification of a multicritical transition. Further work includes taking measurements on a bulk crystalline sample of similar concentration and comparing its properties to those of the nanostructured sample. C. Cooling was supported by NSF Grant No. DMR-1206530.

  15. Mechanical behaviors and phase transition of Ho{sub 2}O{sub 3} nanocrystals under high pressure

    SciTech Connect

    Yan, Xiaozhi; Ren, Xiangting; He, Duanwei E-mail: yangwg@hpstar.ac.cn; Chen, Bin; Yang, Wenge E-mail: yangwg@hpstar.ac.cn

    2014-07-21

    Mechanical properties and phase transition often show quite large crystal size dependent behavior, especially at nanoscale under high pressure. Here, we have investigated Ho{sub 2}O{sub 3} nanocrystals with in-situ x-ray diffraction and Raman spectroscopy under high pressure up to 33.5 GPa. When compared to the structural transition routine cubic -> monoclinic -> hexagonal phase in bulk Ho{sub 2}O{sub 3} under high pressure, the nano-sized Ho{sub 2}O{sub 3} shows a much higher onset transition pressure from cubic to monoclinic structure and followed by a pressure-induced-amorphization under compression. The detailed analysis on the Q (Q = 2π/d) dependent bulk moduli reveals the nanosized Ho{sub 2}O{sub 3} particles consist of a clear higher compressible shell and a less compressible core. Insight into these phenomena shed lights on micro-mechanism studies of the mechanical behavior and phase evolution for nanomaterials under high pressure, in general.

  16. Widespread and persistent invasions of terrestrial habitats coincident with larval feeding behavior transitions during snail-killing fly evolution (Diptera: Sciomyzidae)

    PubMed Central

    2012-01-01

    Background Transitions in habitats and feeding behaviors were fundamental to the diversification of life on Earth. There is ongoing debate regarding the typical directionality of transitions between aquatic and terrestrial habitats and the mechanisms responsible for the preponderance of terrestrial to aquatic transitions. Snail-killing flies (Diptera: Sciomyzidae) represent an excellent model system to study such transitions because their larvae display a range of feeding behaviors, being predators, parasitoids or saprophages of a variety of mollusks in freshwater, shoreline and dry terrestrial habitats. The remarkable genus Tetanocera (Tetanocerini) occupies five larval feeding groups and all of the habitat types mentioned above. This study has four principal objectives: (i) construct a robust estimate of phylogeny for Tetanocera and Tetanocerini, (ii) estimate the evolutionary transitions in larval feeding behaviors and habitats, (iii) test the monophyly of feeding groups and (iv) identify mechanisms underlying sciomyzid habitat and feeding behavior evolution. Results Bayesian inference and maximum likelihood analyses of molecular data provided strong support that the Sciomyzini, Tetanocerini and Tetanocera are monophyletic. However, the monophyly of many behavioral groupings was rejected via phylogenetic constraint analyses. We determined that (i) the ancestral sciomyzid lineage was terrestrial, (ii) there was a single terrestrial to aquatic habitat transition early in the evolution of the Tetanocerini and (iii) there were at least 10 independent aquatic to terrestrial habitat transitions and at least 15 feeding behavior transitions during tetanocerine phylogenesis. The ancestor of Tetanocera was aquatic with five lineages making independent transitions to terrestrial habitats and seven making independent transitions in feeding behaviors. Conclusions The preponderance of aquatic to terrestrial transitions in sciomyzids goes against the trend generally observed

  17. A Conserved Behavioral State Barrier Impedes Transitions between Anesthetic-Induced Unconsciousness and Wakefulness: Evidence for Neural Inertia

    PubMed Central

    Friedman, Eliot B.; Sun, Yi; Moore, Jason T.; Hung, Hsiao-Tung; Meng, Qing Cheng; Perera, Priyan; Joiner, William J.; Thomas, Steven A.; Eckenhoff, Roderic G.; Sehgal, Amita; Kelz, Max B.

    2010-01-01

    One major unanswered question in neuroscience is how the brain transitions between conscious and unconscious states. General anesthetics offer a controllable means to study these transitions. Induction of anesthesia is commonly attributed to drug-induced global modulation of neuronal function, while emergence from anesthesia has been thought to occur passively, paralleling elimination of the anesthetic from its sites in the central nervous system (CNS). If this were true, then CNS anesthetic concentrations on induction and emergence would be indistinguishable. By generating anesthetic dose-response data in both insects and mammals, we demonstrate that the forward and reverse paths through which anesthetic-induced unconsciousness arises and dissipates are not identical. Instead they exhibit hysteresis that is not fully explained by pharmacokinetics as previously thought. Single gene mutations that affect sleep-wake states are shown to collapse or widen anesthetic hysteresis without obvious confounding effects on volatile anesthetic uptake, distribution, or metabolism. We propose a fundamental and biologically conserved concept of neural inertia, a tendency of the CNS to resist behavioral state transitions between conscious and unconscious states. We demonstrate that such a barrier separates wakeful and anesthetized states for multiple anesthetics in both flies and mice, and argue that it contributes to the hysteresis observed when the brain transitions between conscious and unconscious states. PMID:20689589

  18. Head-up transition behavior of pilots with and without head-up display in simulated low-visibility approaches

    NASA Technical Reports Server (NTRS)

    Haines, R. F.; Fischer, E.; Price, T. A.

    1980-01-01

    To quantify head-up transition behavior with and without a flightpath type head-up display, eight rated B-727 pilots each flew 31 manual and coupled approaches in a simulator with B-727 dynamics and collimated model board external scene. Data were also obtained on the roll played by the head-up display in the coupled-to-manual transition. Various wind shears, low visibilities, and ceilings were tested along with unexpected misalignment between the runway and head-up display symbology. The symbolic format used was a conformal scene. Every pilot except one stayed head-up, flying with the display after descending below the ceiling. Without the display and as altitude decreased, the number of lookups from the instrument panel decreased and the duration of each one increased. No large differences in mean number or duration of transitions up or down were found during the head-up display runs comparing the no-misalignment with the lateral instrument landing system offset misalignment runs. The head-up display led to fewer transitions after the pilot made a decision to land or execute a missed approach. Without the display, pilots generally waited until they had descended below the ceiling to look outside the first time, but with it several pilots looked down at their panel at relatively high altitudes (if they looked down at all). Manual takeover of control was rapid and smooth both with and without the display which permitted smoother engine power changes.

  19. Anomalous Structural Transition and Electrical Transport Behaviors in Compressed Zn2SnO4: Effect of Interface

    PubMed Central

    Zhang, Haiwa; Ke, Feng; Li, Yan; Wang, Li; Liu, Cailong; Zeng, Yi; Yao, Mingguang; Han, Yonghao; Ma, Yanzhang; Gao, Chunxiao

    2015-01-01

    The interface effect is one of the most important factors that strongly affect the structural transformations and the properties of nano-/submicro-crystals under pressure. However, characterization of the granular boundary changes in materials is always challenging. Here, using tetrakaidecahedral Zn2SnO4 microcrystals as an example, we employed alternating current impedance, X-ray diffraction methods and transmission electron microscopy to elucidate the effect of the interface on the structure and electrical transport behavior of the Zn2SnO4 material under pressure. We clearly show that grain refinement of the initial microcrystals into nanocrystals (approximately 5 nm) occurs at above 12.5 GPa and is characterized by an anomalous resistance variation without a structural phase transition. A new phase transition pathway from the cubic to hexagonal structure occurs at approximately 29.8 GPa in Zn2SnO4. The unexpected grain refinement may explain the new structural transition in Zn2SnO4, which is different from the previous theoretical prediction. Our results provide new insights into the link between the structural transition, interface changes and electrical transport properties of Zn2SnO4. PMID:26399167

  20. Acculturation and Sexual Risk Behaviors among Latina Adolescents Transitioning to Young Adulthood

    ERIC Educational Resources Information Center

    Lee, Jieha; Hahm, Hyeouk Chris

    2010-01-01

    Latinas in the United States are at a disproportionate risk for STDs and sexual risk behaviors. Among Latinas, acculturation has been found to be one of the most important predictors of these behaviors. Therefore, this study examined the longitudinal association between Latina adolescents' level of acculturation and multiple sexual risk outcomes,…

  1. Adolescents in Transition: School and Family Characteristics in the Development of Violent Behaviors Entering High School

    ERIC Educational Resources Information Center

    Frey, Ariel; Ruchkin, Vladislav; Martin, Andres; Schwab-Stone; Mary

    2009-01-01

    Adolescents are vulnerable to becoming involved in problematic behaviors, disengaging academically, and dropping out of school. This study was designed to evaluate the protective role of self-perceived school attachment and family involvement on the development of these negative behaviors during adolescence. The Social and Health Assessment (SAHA)…

  2. Electronic and magnetic behaviors of graphene with 5d series transition metal atom substitutions: A first-principles study

    NASA Astrophysics Data System (ADS)

    Sun, Minglei; Tang, Wencheng; Ren, Qingqiang; Zhao, Yiming; Wang, Sake; Yu, Jin; Du, Yanhui; Hao, Yitong

    2016-06-01

    The electronic structures and magnetic behaviors of graphene with 5d series transition metal atom substitutions are investigated by performing first-principles calculations. All the impurities are tightly bonded to single vacancy in a graphene sheet. The substitutions of La and Ta lead to Fermi level shifting to valence and conduction band, respectively. Both the two substitutions result in metallic properties. Moreover, the Hf, Os and Pt-substituted systems exhibit semiconductor properties, while the Re and Ir-substituted ones exhibit robust half-metallic properties. Interestingly, W-substituted system shows dilute magnetic semiconductor property. On the other hand, the substitution of Ta, W, Re and Ir induce 0.86 μB, 2 μB, 1 μB and 0.99 μB magnetic moment, respectively. Our studies demonstrate that the 5d series transition metal substituted graphene have potential applications in nanoelectronics, spintronics and magnetic storage devices.

  3. Pressure-Induced Tricritical Behavior of the SmA-Cho Transition in COC

    NASA Astrophysics Data System (ADS)

    Shichijyo, Shiro; Okamoto, Toshiyuki; Takemura, Tetuo

    1982-09-01

    The tricritical nature of the smectic-A-cholesteric (SmA-Cho) transition in cholesteryl oleyl carbonate (COC) was investigated by several methods. Differential thermal analysis (DTA) and volume measurement showed the existence of a tricritical point at 3.1± 0.1× 103 kg/cm2 and 74°C, where the first-order transition converted to the second-order one. The dynamic properties were studied by ultrasonic measurement, and the differences in the transition processes were observed with a polarized microscope. Spherulites were observed in the smectic-A phase above the tricritical point. The structure of the spherulites and the morphology effects are discussed.

  4. Experimental Study of Transitional Flow Behavior in a Simulated Low Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Sohn, Ki Hyeon; DeWitt, Kenneth J.

    2007-01-01

    A detailed investigation of the flow physics occurring on the suction side of a simulated Low Pressure Turbine (LPT) blade was performed. A contoured upper wall was designed to simulate the pressure distribution of an actual LPT airfoil onto a flat lower plate. The experiments were carried out for the Reynolds numbers of 35,000, 70,000, 100,000, and 250,000 with four levels of freestream turbulence ranging from 1 to 4 percent. For the three lower Reynolds numbers, the boundary layer on the flat plate was separated and formed a bubble. The size of laminar separation bubble was measured to be inversely proportional to the freestream turbulence levels and Reynolds numbers. However, no separation was observed for the Re = 250,000 case. The transition on a separated flow was found to proceed through the formation of turbulent spots in the free shear layer as evidenced in the intermittency profiles for Re = 35,000, 70,000, and 100,000. Spectral data show no evidence of Kelvin-Helmholtz of Tollmien-Schlichting instability waves in the free shear layer over a separation bubble (bypass transition). However, the flow visualization revealed the large vortex structures just outside of the bubble and their development to turbulent flow for Re = 50,000, which is similar to that in the free shear layer (separated-flow transition). Therefore, it is fair to say that the bypass and separated-flow transition modes coexist in the transition flows over the separation bubble of certain conditions. Transition onset and end locations and length determined from intermittency profiles decreased as Reynolds number and freestream turbulence levels increase.

  5. Experimental Study of Transitional Flow Behavior in a Simulated Low Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Sohn, Ki Hyeon; DeWitt, Kenneth J.

    1998-01-01

    A detailed investigation of the flow physics occurring on the suction side of a simulated Low Pressure Turbine (LPT) blade was performed. A contoured upper wall was designed to simulate the pressure distribution of an actual LPT airfoil onto a flat lower plate. The experiments were carried out for the Reynolds numbers of 35,000, 70,000, 100,000 and 250,000 with four levels of freestream turbulence ranging from 1% to 4%. For the three lower Reynolds numbers, the boundary layer on the flat plate was separated and formed a bubble. The size of laminar separation bubble was measured to be inversely proportional to the freestream turbulence levels and Reynolds numbers. However, no separation was observed for the Re = 250,000 case. The transition on a separated flow was found to proceed through the formation of turbulent spots in the free shear layer as evidenced in the intermittency profiles for Re = 35,000, 70,000 and 100,000. Spectral data show no evidence of Kelvin-Helmholtz or Tollmien-Schlichting instability waves in the free shear layer over a separation bubble (bypass transition). However, the flow visualization revealed the large vortex structures just outside of the bubble and their development to turbulent flow for Re = 50,000, which is similar to that in the free shear layer (separated-flow transition). Therefore, it is fair to say that the bypass and separated-flow transition modes coexist in the transitional flows over the separation bubble for certain conditions. Transition onset and end locations and length determined from intermittency profiles decrease as Reynolds number and freestream turbulence levels increase.

  6. Recurring features of mid-Miocene transitional geomagnetic field behavior: Observations from NE Nevada and SE Oregon

    NASA Astrophysics Data System (ADS)

    Bogue, S. W.; Glen, J. M. G.

    2014-12-01

    Paleomagnetic results from a 150m thick stack of 15.2 my old lava flows in the Sheep Creek Range (north central Nevada; 40.7N, 243.2E) show that distinctive aspects of the reversing geomagnetic field can recur after 1.5 million years. The Sheep Creek lavas preserve a partial record of what is likely the C5Br-C5Bn geomagnetic reversal. That event occurred 1.5 million years and five polarity switches after reversal (C5Cr-C5Cn) recorded in great detail at Steens Mountain in SE Oregon. During both transitions, the VGP made repeat visits to low latitude positions in South America and near Africa although in different order. This behavior implies a control that varies over a timescale much longer that associated with flow in the outer core (~60 yrs), presumably lateral variations in lower mantle temperature or topography on the core-mantle boundary. Furthermore, the field in both reversals moved from clearly transitional to normal-polarity-like (i.e., down and north) directions before "rebounding" to intermediate directions. It has been suggested recently (Valet et al., Nature 2012) that this kind of behavior (i.e., directional change in the form of precursor- main polarity switch-rebound) may be a systematic aspect of transitional field behavior, a suggestion reinforced by these new observations. The distinctive, two component magnetization of a particular lava flow in the Sheep Creek section has been interpreted by Bogue and Glen (GRL, 2010) as evidence of directional change (~1 deg/week) orders of magnitude faster than normal secular variation. If the field was strong at the end of the directional change, then a large change in the local geomagnetic field vector is implied by the directional data for any initial field strength. Preliminary paleointensity experiments aimed at resolving this aspect of the record are in progress.

  7. Music as Transitional Object and Practice: Children's Spontaneous Musical Behaviors in the Subway

    ERIC Educational Resources Information Center

    Custodero, Lori A.; Calì, Claudia; Diaz-Donoso, Adriana

    2016-01-01

    This study looks at children's music making in a public setting designed for society writ large. Although known to most children in the city, the subway presents a unique environment, both structurally predictable yet sonically dynamic; it is in continuous transition. Adopting Winnicott's psychoanalytical perspective, we make a case for viewing…

  8. Multiscaling behavior of transition economies before and after 1998 Russian financial crisis

    NASA Astrophysics Data System (ADS)

    Litvin, Vladimir A.

    2004-12-01

    The influence of the1998 Russian financial crisis on the statistical properties of currencies in transition economies has been studied. Essential changes before and after crisis were discovered. All effects are essentially nonlinear and differ from the ones in advanced economies.

  9. Molecular Motion in Polymers: Mechanical Behavior of Polymers Near the Glass-Rubber Transition Temperature.

    ERIC Educational Resources Information Center

    Sperling, L. H.

    1982-01-01

    The temperature at which the onset of coordinated segmental motion begins is called the glass-rubber transition temperature (Tg). Natural rubber at room temperature is a good example of a material above its Tg. Describes an experiment examining the response of a typical polymer to temperature variations above and below Tg. (Author/JN)

  10. Transition of Youth and Young Adults with Emotional or Behavioral Difficulties: An Evidence-Supported Handbook

    ERIC Educational Resources Information Center

    Clark, Hewitt B., Ed.; Unruh, Deanne K., Ed.

    2009-01-01

    This comprehensive professional handbook will help transition specialists, general and special educators, school psychologists, and administrators support youth and young adults in setting goals and achieving positive outcomes across employment, education, and community settings. Through up-to-date research and in-depth analyses of five successful…

  11. Compromise, Well-Being, and Action Behaviors in Young Adults in Career Transition

    ERIC Educational Resources Information Center

    Creed, Peter A.; Blume, Kellie

    2013-01-01

    The authors surveyed 186 first-year university students and assessed their level of career compromise associated with making the transition to university. Compromise was operationalized as the discrepancy between the job characteristics of ideal and expected occupations. The authors also assessed career well-being (satisfaction, distress), action…

  12. REPEATED ACQUISITION OF RESPONSE SEQUENCES: THE ANALYSIS OF BEHAVIOR IN TRANSITION

    EPA Science Inventory

    Repeated acquisition (RA) procedures are behavioral preparations in which subjects are required to learn new response sequences with each experimental session. uch procedures avoid problems inherent in non-RA learning procedures. or example, with traditional paradigms, as the sub...

  13. Epithelial-mesenchymal transition, the tumor microenvironment, and metastatic behavior of epithelial malignancies

    PubMed Central

    Talbot, Lindsay J; Bhattacharya, Syamal D; Kuo, Paul C

    2012-01-01

    Objective The mechanisms of cancer metastasis have been intensely studied recently and may provide vital therapeutic targets for metastasis prevention. We sought to review the contribution of epithelial-mesenchymal transition and the tumor microenvironment to cancer metastasis. Summary Background Data Epithelial-mesenchymal transition is the process by which epithelial cells lose cell-cell junctions and baso-apical polarity and acquire plasticity, mobility, invasive capacity, stemlike characteristics, and resistance to apoptosis. This cell biology program is active in embryology, wound healing, and pathologically in cancer metastasis, and along with the mechanical and cellular components of the tumor microenvironment, provides critical impetus for epithelial malignancies to acquire metastatic capability. Methods A literature review was performed using PubMed for “epithelial-mesenchymal transition”, “tumor microenvironment”, “TGF-β and cancer”, “Wnt and epithelial-mesenchymal transition”, “Notch and epithelial-mesenchymal transition”, “Hedgehog and epithelial-mesenchymal transition” and “hypoxia and metastasis”. Relevant primary studies and review articles were assessed. Results Major signaling pathways involved in epithelial-mesenchymal transition include TGF-β, Wnt, Notch, Hedgehog, and others. These pathways converge on several transcription factors, including zinc finger proteins Snail and Slug, Twist, ZEB 1/2, and Smads. These factors interact with one another and others to provide crosstalk between the relevant signaling pathways. MicroRNA suppression and epigenetic changes also influence the changes involved in epithelial-mesenchymal transition. Cellular and mechanical components of the tumor microenvironment are also critical in determining metastatic potential. Conclusions While the mechanisms promoting metastasis are extremely wide ranging and still under intense investigation, the epithelial-mesenchymal transition program and

  14. The transient behavior of scaling in the atmosphere: stratiform/convective transition and applications to sub-grid scale statistics

    NASA Astrophysics Data System (ADS)

    Nogueira, M.; Barros, A. P.

    2014-12-01

    Multifractal behavior holds to a remarkable approximation over wide ranges of spatial scales in orographic rainfall and cloud fields. The scaling exponents characterizing this behavior are shown to be fundamentally transient with nonlinear dependencies on the particular atmospheric state and terrain forcing. In particular, a robust transition is found in the scaling parameters between non-convective (stable) and convective (unstable) regimes, with clear physical correspondence to the transition from stratiform to organized convective orographic precipitation. These results can explain two often reported scaling regimes for atmospheric wind, temperature and water observations. On the one hand, spectral slopes around 2-2.3 arise under non-convective or very weak convective conditions when the spatial patterns are dominated by large-scale gradients and landform. On the other hand, under convective conditions the scaling exponents generally fluctuate around 5/3, in agreement with the Kolmogorov turbulent regime accounting for the intermittency correction. High-resolution numerical weather prediction (NWP) models are able to reproduce the ubiquitous scaling behavior of observed atmospheric fields down to their effective resolution length-scale, below which the variability is misrepresented by the model. The effective resolution is shown to be a transient property dependent on the particular simulated conditions and NWP formulation, implying that a blunt decrease in grid spacing without adjusting numerical techniques may not lead to the improvements desired.Finally, the application of transient spatial scaling behavior for stochastic downscaling and sub-grid scale parameterization of cloud and rainfall fields is investigated. The proposed fractal methods are able to rapidly generate large ensembles of high-resolution statistically robust fields from the coarse resolution information alone, which can provide significant improvements for stochastic hydrological prediction

  15. Child Effortful Control as a Mediator of Parenting Practices on Externalizing Behavior: Evidence for a Sex-Differentiated Pathway across the Transition from Preschool to School

    ERIC Educational Resources Information Center

    Chang, Hyein; Olson, Sheryl L.; Sameroff, Arnold J.; Sexton, Holly R.

    2011-01-01

    An explanatory model for children's development of disruptive behavior across the transition from preschool to school was tested. It was hypothesized that child effortful control would mediate the effects of parenting on children's externalizing behavior and that child sex would moderate these relations. Participants were 241 children (123 boys)…

  16. Some behavioral aspects of energy descent: how a biophysical psychology might help people transition through the lean times ahead

    PubMed Central

    De Young, Raymond

    2014-01-01

    We may soon face biophysical limits to perpetual growth. Energy supplies may tighten and then begin a long slow descent while defensive expenditures rise to address problems caused by past resource consumption. The outcome may be significant changes in daily routines at the individual and community level. It is difficult to know when this scenario might begin to unfold but it clearly would constitute a new behavioral context, one that the behavioral sciences least attends to. Even if one posits a less dramatic scenario, people may still need to make many urgent and perhaps unsettling transitions. And while a robust response would be needed, it is not at all clear what should be the details of that response. Since it is likely that no single response will fix things everywhere, for all people or for all time, it would be useful to conduct many social experiments. Indeed, a culture of small experiments should be fostered which, at the individual and small group level, can be described as behavioral entrepreneurship. This may have begun, hidden in plain sight, but more social experiments are needed. To be of help, it may be useful to both package behavioral insights in a way that is practitioner-oriented and grounded in biophysical trends and to propose a few key questions that need attention. This paper begins the process of developing a biophysical psychology, incomplete as it is at this early stage. PMID:25404926

  17. Stimulant-induced adaptations in neostriatal matrix and striosome systems: transiting from instrumental responding to habitual behavior in drug addiction.

    PubMed

    Canales, Juan J

    2005-03-01

    Converging evidence indicates that repeated exposure to motor stimulants such as cocaine and amphetamine produces marked alterations in network responsiveness of striatal neurons to subsequent challenge with the same stimulant drug. Such alterations, which correlate with persistent patterns of repetitive behavior, associate with distinct compartmental changes in the neostriatum. Striatal matrix system neurons undergo "silencing" following repeated drug challenges, allowing striosome system neurons to exhibit preferential activation. Matrix neurons are innervated by sensory and motor areas of neocortex and are activated in the course of on-going, adaptive behavior. Inactivation of matrix neurons by chronic stimulant exposure may therefore constrain sensorimotor and cognitive processing. In turn, the striosomes are anatomically connected through re-entrant loops with limbic prefrontal and allocortical structures, such as anterior cingulate cortex, orbital frontal cortex, and basolateral amygdala, all of which play a part in stimulant-induced reinforcement and relapse to drug-taking. Moreover, functional evidence links striosome system neurons, which are responsible for providing inhibitory regulatory feedback to midbrain dopamine neurons, with reinforcement-based processes. In considering such evidence, we postulate that recurrent matrix inactivation and recruitment of striosome-based pathways by chronic stimulant exposure represent neural end-points of the transit from action-outcome associative behavior to conditioned habitual responding. Within this theoretical framework, habitual behavior can be elicited by both interoceptive cues and exteroceptive conditioned stimuli to promote the automatic execution of learned responses. PMID:15721792

  18. Some behavioral aspects of energy descent: how a biophysical psychology might help people transition through the lean times ahead.

    PubMed

    De Young, Raymond

    2014-01-01

    We may soon face biophysical limits to perpetual growth. Energy supplies may tighten and then begin a long slow descent while defensive expenditures rise to address problems caused by past resource consumption. The outcome may be significant changes in daily routines at the individual and community level. It is difficult to know when this scenario might begin to unfold but it clearly would constitute a new behavioral context, one that the behavioral sciences least attends to. Even if one posits a less dramatic scenario, people may still need to make many urgent and perhaps unsettling transitions. And while a robust response would be needed, it is not at all clear what should be the details of that response. Since it is likely that no single response will fix things everywhere, for all people or for all time, it would be useful to conduct many social experiments. Indeed, a culture of small experiments should be fostered which, at the individual and small group level, can be described as behavioral entrepreneurship. This may have begun, hidden in plain sight, but more social experiments are needed. To be of help, it may be useful to both package behavioral insights in a way that is practitioner-oriented and grounded in biophysical trends and to propose a few key questions that need attention. This paper begins the process of developing a biophysical psychology, incomplete as it is at this early stage. PMID:25404926

  19. Adaptive and phase transition behavior in performance of discrete multi-articular actions by degenerate neurobiological systems.

    PubMed

    Rein, Robert; Davids, Keith; Button, Chris

    2010-03-01

    The identification of attractors is one of the key tasks in studies of neurobiological coordination from a dynamical systems perspective, with a considerable body of literature resulting from this task. However, with regards to typical movement models investigated, the overwhelming majority of actions studied previously belong to the class of continuous, rhythmical movements. In contrast, very few studies have investigated coordination of discrete movements, particularly multi-articular discrete movements. In the present study, we investigated phase transition behavior in a basketball throwing task where participants were instructed to shoot at the basket from different distances. Adopting the ubiquitous scaling paradigm, throwing distance was manipulated as a candidate control parameter. Using a cluster analysis approach, clear phase transitions between different movement patterns were observed in performance of only two of eight participants. The remaining participants used a single movement pattern and varied it according to throwing distance, thereby exhibiting hysteresis effects. Results suggested that, in movement models involving many biomechanical degrees of freedom in degenerate systems, greater movement variation across individuals is available for exploitation. This observation stands in contrast to movement variation typically observed in studies using more constrained bi-manual movement models. This degenerate system behavior provides new insights and poses fresh challenges to the dynamical systems theoretical approach, requiring further research beyond conventional movement models. PMID:19851763

  20. Optical birefringence and its critical behavior in the vicinity of nematic-smectic A phase transition in a binary mixture

    NASA Astrophysics Data System (ADS)

    Sarkar, Sudipta Kumar; Barman, Purna Chandra; Das, Malay Kumar

    2014-08-01

    Optical birefringence (Δn) measurements as a function of temperature have been performed for binary mixtures of octyloxy cyanobiphenyl (8OCB) and octyl cyanobiphenyl (8CB) liquid crystals by means of a high resolution temperature scanning technique. The temperature dependence of the birefringence (Δn) was determined from the transmitted intensity data for wavelengths λ=532 nm. Using a fitting procedure consistent with the mean field theory and the first order nature of nematic-isotropic (N-I) phase transition, the order parameter critical exponent β has been determined. The critical behavior of the nematic-smectic A (N-SmA) phase transition has been investigated from the high resolution birefringence data and the nature of this transition in the mixtures has been assessed. From the evolution of the critical exponent α, it has been possible to predict the limiting value of the McMillan ratio for the tricritical point (TCP) as well as the 3D-XY universality class.

  1. Half-Metallic Behavior in Doped Sr2CrOsO6 Double Perovskite with High Transition Temperature.

    PubMed

    Samanta, Kartik; Sanyal, Prabuddha; Saha-Dasgupta, Tanusri

    2015-01-01

    Half-metallic magnets with metallic behavior in one spin channel and insulating in the other, have attracted considerable attention due to their potential application possibility. The spin-dependent nature of the carrier scattering due to half-metallic nature of these materials, allows for the resistance to be strongly influenced by the low magnetic field. However, the operating temperatures of such known materials are generally low, opening up the need for half-metallic magnets with high transition temperatures. The double perovskites having general formula A2BB'O6 with alternating ordered arrangement of two transition metal sites, B and B' offer an attractive possibility in this respect. Here, we consider the case of Sr2CrOsO6, which is a ferrimagnetic insulator with transition temperature (Tc) of 725 K, highest ever known in the oxide family, and show that moderate amount of La and Na doping at Sr site can drive the compound half-metallic with high Tc. PMID:26446395

  2. Anomalous structural behavior in the metamagnetic transition of FeRh thin films from a local viewpoint

    NASA Astrophysics Data System (ADS)

    Wakisaka, Yuki; Uemura, Yohei; Yokoyama, Toshihiko; Asakura, Hiroyuki; Morimoto, Hiroyuki; Tabuchi, Masao; Ohshima, Daiki; Kato, Takeshi; Iwata, Satoshi

    2015-11-01

    The metamagnetic transition in FeRh thin films has been investigated via temperature-dependent x-ray-absorption fine-structure spectroscopy in order to gain correlations between magnetization and local electronic and geometric structures. According to the Fe and Rh K -edge x-ray-absorption near-edge structure (XANES), strong hybridization between Fe and Rh was revealed to exist. This Fe-Rh hybridization was observed to decrease during the phase transition from the antiferromagnetic (AFM) to ferromagnetic (FM) phases from the systematic change in the Fe K -edge XANES. In addition, only the Debye-Waller factor of the Fe-Fe pair in the AFM phase was observed to be considerably enhanced when compared with that in the FM phase, which was ascribed to local structural fluctuation inherent in the AFM phase. By considering the different features of the exchange interactions in Fe-Rh and Fe-Fe, this anomalous behavior is interpreted as being consistent with the recent theoretical study proposing the local fluctuations of spin and structure. Therefore, we consider that the local spin and Fe-Fe distance fluctuations play an important role in driving the metamagnetic transition, whereas the Fe-Rh hybridization correlates with the static stability of each magnetic phase.

  3. Anomalous critical behavior in the polymer collapse transition of three-dimensional lattice trails.

    PubMed

    Bedini, Andrea; Owczarek, Aleksander L; Prellberg, Thomas

    2012-07-01

    Trails (bond-avoiding walks) provide an alternative lattice model of polymers to self-avoiding walks, and adding self-interaction at multiply visited sites gives a model of polymer collapse. Recently a two-dimensional model (triangular lattice) where doubly and triply visited sites are given different weights was shown to display a rich phase diagram with first- and second-order collapse separated by a multicritical point. A kinetic growth process of trails (KGTs) was conjectured to map precisely to this multicritical point. Two types of low-temperature phases, a globule phase and a maximally dense phase, were encountered. Here we investigate the collapse properties of a similar extended model of interacting lattice trails on the simple cubic lattice with separate weights for doubly and triply visited sites. Again we find first- and second-order collapse transitions dependent on the relative sizes of the doubly and triply visited energies. However, we find no evidence of a low-temperature maximally dense phase with only the globular phase in existence. Intriguingly, when the ratio of the energies is precisely that which separates the first-order from the second-order regions anomalous finite-size scaling appears. At the finite-size location of the rounded transition clear evidence exists for a first-order transition that persists in the thermodynamic limit. This location moves as the length increases, with its limit apparently at the point that maps to a KGT. However, if one fixes the temperature to sit at exactly this KGT point, then only a critical point can be deduced from the data. The resolution of this apparent contradiction lies in the breaking of crossover scaling and the difference in the shift and transition width (crossover) exponents. PMID:23005384

  4. Relative permittivity behavior and temperature changes in linoleic acid during the phase transition

    NASA Astrophysics Data System (ADS)

    Kościesza, R.; Siegoczyński, R. M.; Rostocki, A. J.; Tefelski, D. B.; Kos, A.; Ejchart, W.

    2008-07-01

    In our earlier works several fatty liquids (edible oils and unsaturated fatty acids) which exhibit existence of a new phase induced by high pressure were presented. Conclusion of those experiments is that C=C bonds existence in these liquids plays a dominant role in a new phase occurrence. Relative permittivity in pure acids investigated till now seems to behave in specific way. That is why we decided to investigate linoleic acid (C18H32O2) under high pressure. In our experiment such quantities as: electric capacity, pressure and temperature were recorded. The experimental setup gives us also a possibility to conduct optical investigations. We observed a transmitted and scattered beams of close infrared light (λ = 800nm) in directions 0° and 90° towards the incident beam. Due to the rapid grow of temperature and the rapid change of transmitted and scattered beams we may say that observed phenomenon is a first order phase transition and a proof for the significant change of liquid structure. This paper contains time dependencies of permittivity, temperature, transmitted and scattered light intensity and also permittivity vs. pressure changes during the phase transition in linoleic acid and first of all measured data analysis which lets us explain the transition reasons.

  5. Transition dynamics and magic-number-like behavior of frictional granular clusters

    NASA Astrophysics Data System (ADS)

    Tordesillas, Antoinette; Walker, David M.; Froyland, Gary; Zhang, Jie; Behringer, Robert P.

    2012-07-01

    Force chains, the primary load-bearing structures in dense granular materials, rearrange in response to applied stresses and strains. These self-organized grain columns rely on contacts from weakly stressed grains for lateral support to maintain and find new stable states. However, the dynamics associated with the regulation of the topology of contacts and strong versus weak forces through such contacts remains unclear. This study of local self-organization of frictional particles in a deforming dense granular material exploits a transition matrix to quantify preferred conformations and the most likely conformational transitions. It reveals that favored cluster conformations reside in distinct stability states, reminiscent of “magic numbers” for molecular clusters. To support axial loads, force chains typically reside in more stable states of the stability landscape, preferring stabilizing trusslike, three-cycle contact triangular topologies with neighboring grains. The most likely conformational transitions during force chain failure by buckling correspond to rearrangements among, or loss of, contacts which break the three-cycle topology.

  6. Resistive transition, polaron dynamics and scaling behavior in Fe doped SrTiO3

    NASA Astrophysics Data System (ADS)

    Ghosh, Arijit; Masud, Md. G.; Sannigrahi, Jhuma; Chaudhuri, B. K.

    2013-04-01

    Temperature dependent electrical transport (ac and dc) and dielectric measurements have been performed with SrFexTi(1-x)O3 (0≤x≤1.0) samples prepared by ceramic route. Metal-insulator like transition observed depending on doping concentration. High dc resistivity of the present system is due to localization of polaronic charge carriers and the dc resistivity data, above respective TMI, fit well with Mott's variable range hopping, Arrhenius conduction mechanism, while a power law nature is followed below TMI. The charge transport mechanism is also revealed from the scaled ac conductivity and dielectric modulus spectrum. The MI transition is considered to be associated with polaron dissociation occurring little below polaron ordering (PO) temperature, TPO. The samples also indicate a cross-over from universal dielectric response (UDR) (f<105 Hz) to second universality (SU) (f>105 Hz). This cross over as well as MI like transition temperature shift towards the lower temperature regime with increasing x.

  7. Atypical behavior in the electron capture induced dissociation of biologically relevant transition metal ion complexes of the peptide hormone oxytocin

    NASA Astrophysics Data System (ADS)

    Kleinnijenhuis, Anne J.; Mihalca, Romulus; Heeren, Ron M. A.; Heck, Albert J. R.

    2006-07-01

    Doubly protonated ions of the disulfide bond containing nonapeptide hormone oxytocin and oxytocin complexes with different transition metal ions, that have biological relevance under physiological conditions, were subjected to electron capture dissociation (ECD) to probe their structural features in the gas phase. Although, all the ECD spectra were strikingly different, typical ECD behavior was observed for complexes of the nonapeptide hormone oxytocin with Ni2+, Co2+ and Zn2+, i.e., abundant c/z' and a'/y backbone cleavages and ECD characteristic S-S and S-C bond cleavages were observed. We propose that, although in the oxytocin-transition metal ion complexes the metal ions serve as the main initial capture site, the captured electron is transferred to other sites in the complex to form a hydrogen radical, which drives the subsequent typical ECD fragmentations. The complex of oxytocin with Cu2+ displayed noticeably different ECD behavior. The fragment ions were similar to fragment ions typically observed with low-energy collision induced dissociation (CID). We propose that the electrons captured by the oxytocin-Cu2+ complex might be favorably involved in reducing the Cu2+ metal ion to Cu+. Subsequent energy redistribution would explain the observed low-energy CID-type fragmentations. Electron capture resulted also in quite different specific cleavage sites for the complexes of oxytocin with Ni2+, Co2+ and Zn2+. This is an indication for structural differences in these complexes possibly linked to their significantly different biological effects on oxytocin-receptor binding, and suggests that ECD may be used to study subtle structural differences in transition metal ion-peptide complexes.

  8. Socio-demographic, behavioral, and health correlates of nutrition transition dietary indicators in San Juan, Puerto Rico

    PubMed Central

    Colón-Ramos, Uriyoán; Pérez-Cardona, Cynthia M.; Monge-Rojas, Rafael

    2014-01-01

    Objective To identify socio-demographic, behavioral, and health-related correlates of food preferences in Puerto Rico that will help determine Caribbean-region populations vulnerable to nutrition transition. Methods Data from a cross-sectional study of a representative sample of 858 adults residing in the San Juan Metropolitan Area of Puerto Rico were analyzed. Multivariable ordinal logistic regressions were used to model the frequency of consumption of 1) fruits and vegetables, 2) tubers/starchy root vegetables, 3) fried foods, and 4) Western-style fast foods as a function of socio-demographic, behavioral, and health-related characteristics. Results Higher frequency of consumption of fruits and vegetables was associated with being physically active and older and having a medium to high level of education, whereas intake of tubers was associated with being older, having a low income, not using government insurance, and having elevated levels of triglycerides. Frequency of consumption of fast food was associated with younger age, higher income, 12–15 years of formal education, and a higher body mass index (BMI), whereas frequency of consumption of fried food was associated with being younger and male, not being a smoker, and having elevated levels of fasting blood glucose. Conclusions The results indicate a nutrition transition in Puerto Rico with health consequences for the Caribbean region. The characteristics of this nutrition transition seem to be determined by income, education, and age, but may also be dictated by access to various food groups. These results set the stage for needed investigation of environmental and individual-level factors that could shape patterns in food consumption. PMID:24553760

  9. Factors Associated with Transitional Shifts in College Students' Physical Activity Behavior

    ERIC Educational Resources Information Center

    Levy, Susan S.; Cardinal, Bradley J.

    2006-01-01

    The Transtheoretical Model (Prochaska & Marcus, 1994) has been widely used as a framework for understanding exercise behavior change. The purpose of this study was to clarify equivocal research findings reported for model predictions when examining stage movement over time rather than static stages and to provide some evidence of the construct…

  10. Developmental Transitions in Youth Behavioral Opposition and Maternal Beliefs in Social Ecological Context

    ERIC Educational Resources Information Center

    Ehrensaft, Miriam K.; Cohen, Patricia; Chen, Henian; Berenson, Kathy

    2007-01-01

    We investigated age-based changes in mothers' complaints about offspring behavioral opposition, and offspring reports of opposition in a prospective longitudinal design (N = 821). Maternal complaints declined from pre-adolescence to early adulthood, but more slowly in low socioeconomic status (SES) and single-parent families. Mothers complained…