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Sample records for ductile-brittle transition behavior

  1. 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).

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    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.

  3. Determination of the ductile-brittle transition temperature from the microplastic-strain rate

    NASA Astrophysics Data System (ADS)

    Andreev, A. K.; Solntsev, Yu. P.

    2008-04-01

    The possibility of the determination of the tendency of cast and deformed steels to brittle fracture using the temperature dependence of the small-plastic-strain rate is studied. The temperature corresponding to the maximum in this curve is found to indicate an abrupt decrease in the steel plasticity, which makes it possible to interpret it as the ductile-brittle transition temperature depending only on the structure of a material.

  4. Effects of helium on ductile-brittle transition behavior of reduced-activation ferritic steels after high-concentration helium implantation at high temperature

    NASA Astrophysics Data System (ADS)

    Hasegawa, A.; Ejiri, M.; Nogami, S.; Ishiga, M.; Kasada, R.; Kimura, A.; Abe, K.; Jitsukawa, S.

    2009-04-01

    The effects of He on the fracture behavior of reduced-activation ferritic/martensitic steels, including oxide dispersion-strengthened (ODS) steels and F82H, was determined by characterizing the microstructural evolution in and fracture behavior of these steels after He implantation up to 1000 appm at around 550 °C. He implantation was carried out by a cyclotron with a beam of 50 MeV α-particles. In the case of F82H, the ductile-to-brittle transition temperature (DBTT) increase induced by He implantation was about 70 °C and the grain boundary fracture surface was only observed in the He-implanted area of all the ruptured specimens in brittle manner. By contrast, no DBTT shift or fracture mode change was observed in He-implanted 9Cr-ODS and 14Cr-ODS steels. Microstructural characterization suggested that the difference in the bubble formation behavior of F82H and ODS steels might be attributed to the grain boundary rupture of He-implanted F82H.

  5. Metallurgical control of the ductile-brittle transition in high-strength structural steels

    SciTech Connect

    Morris, J.W. Jr. |

    1999-08-01

    The models that have been successfully used to control the ductile-brittle transition in high strength structural steels are qualitative in nature, and address the microstructural control of the mechanisms of brittle fracture. The basic idea is incorporated in the Yoffee diagram, which dates from the 1920`s and attributes the ductile-brittle transition to the competition between deformation and fracture; the more difficult brittle fracture becomes, the lower the temperature at which ductile processes dominate. There are two important brittle fracture modes: intergranular separation and transgranular cleavage. The intergranular mode is usually due to chemical contamination, and is addressed by eliminating or gettering the contaminating species. There are also examples of brittle fracture that is due to inherent grain boundary weakness. In this case the failure mode is overcome by adding beneficial species (glue) to the grain boundary. Transgranular cleavage is made more difficult by refining the effective grain size. In high strength steel this is done by refining the prior austenite grain size, by interspersing islands of metastable austenite that transform martensitically under plastic strain, or by disrupting the crystallographic alignment of ferrite grains or martensite laths. The latter mechanism offers intriguing possibilities for future steels with exceptional toughness.

  6. 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.

  7. Acoustic emissions accompanying the compressive ductile-brittle transition in highly- crystalline lavas.

    NASA Astrophysics Data System (ADS)

    Lavallee, Y.; Meredith, P.; Hess, K.; Cordonnier, B.; Dingwell, D. B.

    2007-12-01

    Understanding of the ductile-brittle transition in dome lavas may well contain the key to an adequate description of dome growth and stability. To elucidate this transition in dome lavas, a series of experiments were performed to characterize microcracking during compressive deformation of crystal-rich lavas. Multiphase lavas behave as visco-elastic fluids with a strain-rate dependence of viscosity across the ductile-brittle field. In order to map out the onset of brittle failure across the transition, we have deformed large volume samples (80 mm long by 40 mm diameter) in a high-load, high-temperature uniaxial press equipped with acoustic emission (AE) monitoring sensors. Our apparatus has been calibrated using an NBS717a standard glass. The absence of cracking and associated AE during deformation of this standard, which behaves as a homogeneous viscous melt under our experimental conditions, allows us to calibrate and filter out extraneous background noise. Samples from each of the five volcanoes chosen for this study (Colima, Unzen, Bezimianny, Krakatau, and Tungurahua) were deformed at two temperatures (940 and 980°C) and at stresses from 1 to 50 MPa. At low stresses (1-10 MPa), only a few AE events were detected and the AE rate decreased with increasing strain. Occasional high-energy events were recorded, and attributed to cracking of single crystals. Increasing the stress to 20-30 MPa resulted in an increased AE rate that stayed essentially constant with increasing strain. Occasional high-energy events persisted. At 40 and 50 MPa, the AE rate was higher still, and increased with increasing strain (overwhelming the few high energy events that continued to occur). Preliminary evaluation of the seismic b-value shows a decreasing trend from >3.0 at low stress to <1.5 at high stress, suggesting a shift from distributed small-scale cracking to more localized larger-scale cracking as stress is increased. These results will be discussed in terms of the deformation

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

    SciTech Connect

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

    1997-06-01

    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 will be 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. In addition to irradiation hardening, neutrons from the fusion reaction will produce large amounts of helium in the steels used to construct fusion power plant components. Tests to simulate the fusion environment indicate that helium can also affect the toughness. Steels are being developed for fusion applications that have a low DBTT prior to irradiation and then show only a small shift after irradiation. A martensitic 9Cr-2WVTa (nominally Fe-9Cr-2W-0.25V-0.07Ta-0.1C) steel had a much lower DBTT than the conventional 9Cr-1MoVNb steel prior to neutron irradiation and showed a much smaller increase in DBTT after irradiation. 27 refs., 5 figs., 1 tab.

  9. Fracturing during ductile-brittle transition and development of flow banding in the Takanoobane Rhyolite lava of Aso volcano, Japan

    NASA Astrophysics Data System (ADS)

    Furukawa, K.; Uno, K.

    2014-12-01

    Flow banding, which is characterized by deformation of highly vesicular part, is ubiquitously observed in rhyolite lavas. To explore the origin of the highly vesicular part, we examined Takanoobane rhyolite lava (TR lava) in Aso caldera, Japan, which effused at 51+/-5 ka (Matsumoto et al., 1991). The highly vesicular parts characterized by ductile deformation are well developed in the central crystalline layer, at which the parts tend to be flattened with an increasing of distance from the source. The part develops into flow bands. The highly vesicular parts are also recognized around fractures that developed perpendicular to the flow direction, and adjacent to phenocrysts. The highly vesicular part is composed of cavities with mainly <100 μm in diameter. Microscopic observation and the SEM image show that the cavities have ragged walls characterized by the protrusion of groundmass crystals and phenocrysts. Smith et al. (2001) described such cavities in detail using three silicic lavas in Japan, and proposed that the cavities were formed by failure of the magma by flow during ductile-brittle transition. The authors described the fracturing mechanism as cavitation, and considered that groundmass adjacent to phenocryst also appears to act as a site of strong cavitation because of the steep strain gradient between deforming matrix and non-deforming phenocrysts. The similarity of the textures means that the highly vesicular part in TR lava was also formed by cavitation during ductile-brittle transition. The part would be deformed and flattened with progression of lava deformation. We analyzed the anisotropy of magnetic susceptibility (AMS) to estimate the deformation style of TR lava. The results show that the highly vesicular part was deformed by pure shear strain. We established the following model for the development of flow banding. In TR lava, the highly vesicular parts were formed by failure of the magma during ductile-brittle transition during and/or after lava

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

    SciTech Connect

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

    1993-08-01

    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 dpa at 420, 520, and 600C. The DBTTs were minimum (< {minus}220{degree}C) for V-(105)Ti alloys under for V-4-Cr-4Ti alloy with <30 appm hydrogen. The effect of 600-1200 appm hydrogen in the specimens was to raise the DBTTs by 100--150{degree}C. The DBTTs were minimum (< {minus}220{degree}C) for V-(1-5)Ti alloys and V-4-Cr-4Ti alloys after neutron irradiation.

  11. 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.

  12. 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.

  13. Specimen size effects on ductile?brittle transition temperature in Charpy impact testing

    NASA Astrophysics Data System (ADS)

    Kurishita, H.; Yamamoto, T.; Narui, M.; Suwarno, H.; Yoshitake, T.; Yano, Y.; Yamazaki, M.; Matsui, H.

    2004-08-01

    One key issue for small specimen test techniques is to clarify specimen size effects on test results. In consideration of size effects on determining the ductile-to-brittle transition temperature (DBTT) in Charpy impact testing, a method to evaluate the plastic constraint loss for differently sized Charpy V-notch (CVN) specimens is proposed and applied to a ferritic-martensitic steel, 2WFK, developed by JNC. In the method, a constraint factor, α, that is an index of the plastic constraint is defined as α=σ ∗/σ y∗. Here, σ ∗ is the critical cleavage fracture stress which is a material constant and σ y∗ is the uniaxial yield stress at the DBTT at the strain rate generated in the Charpy impact test. The procedures for evaluating each of σ ∗ and σ y∗ are described and a result of σ ∗ and σ y∗, thus the value of α, is presented for different types of miniaturized and full-sized CVN specimens of 2WFK.

  14. Determination of the gaseous hydrogen ductile-brittle transition in copper-nickel alloys

    NASA Technical Reports Server (NTRS)

    Parr, R. A.; Johnston, M. H.; Davis, J. H.; Oh, T. K.

    1985-01-01

    A series of copper-nickel alloys were fabricated, notched tensile specimens machined for each alloy, and the specimens tested in 34.5 MPa hydrogen and in air. A notched tensile ratio was determined for each alloy and the hydrogen environment embrittlement (HEE) determined for the alloys of 47.7 weight percent nickel to 73.5 weight percent nickel. Stacking fault probability and stacking fault energies were determined for each alloy using the x ray diffraction line shift and line profiles technique. Hydrogen environment embrittlement was determined to be influenced by stacking fault energies; however, the correlation is believed to be indirect and only partially responsible for the HEE behavior of these alloys.

  15. 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

  16. 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.

  17. 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.

  18. Microstructural Features Controlling Ductile-to-Brittle Transition Behavior in High-Strength, Martensitic Steel Weld Metals

    DTIC Science & Technology

    1990-10-01

    Development Report Microstructural Features Controlling Ductile-to- Brittle Transition Behavior in High-Strength, Martensitic Steel Weld Metals C 0by...Martensitic Steel Weld Metals PERSONAL AUTHOR(S) .J. DeLoach, Jr. .TYPE OF REPORT 13b TIME COVERED 114 DATE OF REPORT (Year, Month, Day) 1S PAGE COUNT I...if necessary and identify by block number) FIELD GROUP SUB-GROUP High strength steel , Ductile-brittle transition Martensitic Mechanical proper ties

  19. 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.

  20. 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.

  1. 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.

  2. Further study on the mechanism of the ductile-to-brittle fracture transition in C-Mn base and weld steel

    SciTech Connect

    Wang, G.Z.; Chen, J.H.; Li, Z.H.

    1997-08-01

    In the present study, the crack opening displacement (COD) tests of specimens of C-Mn base and weld steel were carried out in the ductile-brittle transition temperature region. The majority of the specimens were fractured and others were unloaded prior to fracture after ductile fracture initiated and extended. The cavities and cleavage microcracks located in the vicinities of tips of fibrous cracks of the unloaded specimens were observed in detail. The finite element method (FEM) calculations of the stress and strain distribution ahead of the tip of an extending fibrous crack were completed. The mechanism of the ductile-to-brittle fracture transition was further investigated. It was revealed that in the ductile-brittle transition temperature region, the ductile fracture process was independent of temperature. The ductile-to-brittle fracture transition was triggered by initiating a catastrophic extension of a cleavage crack ahead of the fibrous crack tip, which occurred in a condition satisfying a combined criterion composed of three items, i.e., {var_epsilon}{sub p} {ge} {var_epsilon}{sub pc} for initiating a crack nucleus; {sigma}{sub m}/{bar {sigma}} {ge} {Tc} for preventing the crack nucleus from blunting; and {sigma}{sub yy} {ge} {sigma}{sub f} for propagating the crack nucleus. For a specimen in which a fibrous crack occurred and propagated, the critical event for initiating a brittle cleavage fracture was the propagation of a ferrite grain-sized crack into neighboring grains. With extension of a fibrous crack, the behavior of the ductile-to-brittle fracture transition could be analyzed by the effect of the size of an active zone on the initiation of the brittle cleavage fracture.

  3. Fracture behavior of warm forged and CVD tungsten

    SciTech Connect

    Lassila, D.H.; Connor, A.

    1991-02-14

    The fracture behavior of warm forged and chemical vapor deposition (CVD) tungsten was studied. Three-point bend tests were used to determine ductile-brittle transition temperatures (DBTT) of the materials using a strain based criterion for the DBTT which was arrived at by analysis of computer code modelling results of the three-point bend test. The DBTT's of the warm forged materials were found to be considerably lower than those of the CVD materials. Scanning electron microscopy (SEM), scanning Auger electron spectroscopy (SAES) and X-ray photoelectron spectroscopy (XPS) were performed to characterize the fracture morphologies and fracture surface compositions of the materials. All fracture surfaces were found to be comprised entirely of tungsten with significant and varying amounts of oxygen and carbon segregation. A large portion of the fracture surfaces of the warm forged materials is intergranular, although this is not always directly evident from SEM observations. The fracture surfaces of the CVD materials were clearly 100% intergranular. Results of the study suggest that the fracture paths of the different materials were related to the DBTTs. 22 refs., 8 figs., 2 tabs.

  4. 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)

  5. Nonuniversal surface behavior of dynamic phase transitions

    NASA Astrophysics Data System (ADS)

    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 Js, the amplitude of the externally applied oscillating field h0, 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 Js values, independent from the value of h0. For low Js, however, h0 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 h0 and correspondingly short critical periods Pc, whereas this surface transition simultaneous to the bulk one is suppressed for slow critical dynamics occurring for low values of h0. The suppression of the DPT for low h0 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 Js values. Here we find that the penetration depth depends strongly on Js and behaves identically to the corresponding equilibrium Ising model.

  6. First-principles calculations for transition phase, mechanical and thermodynamic properties of ZnS under extreme condition

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Liu, Daijun; Ji, Junyi; Chen, Jianjun; Yu, Yang; Wu, Ruoxi

    2017-02-01

    The structural and mechanical properties of ZnS in both B3 and B1 phases have been investigated by the generalized gradient approximation (GGA) within the plane-wave pseudopotential density functional theory (DFT). The obtained lattice parameters and bulk modulus of ZnS for both B3 and B1 structures are well in line with the available theoretical and experimental results. Using the enthalpy-pressure data, we have predicted that the phase transition pressure of ZnS from B3 to B1 is 17.26 GPa, which is in good agreement with previous experimental values. The hydrostatic pressure-dependent elastic properties of the two structures, such as bulk modulus, shear modulus and Young’s modulus, are discussed. Then, the mechanical characteristics of ZnS, including ductile/brittle behavior and elastic anisotropy of the two cubic single-crystal structures, are investigated in details. Furthermore, the thermodynamic properties of ZnS under extreme condition are explored by quasi-harmonic Debye modeling. The calculated results show that the ductility and elastic anisotropy increase with pressure clearly except the ductility of B1. Besides, the temperature and pressure dependencies of the heat capacity and the Debye temperature are obtained and analyzed in the wide ranges.

  7. Multiferroic behavior at a spin state transition

    NASA Astrophysics Data System (ADS)

    Zapf, Vivien; Chikara, Shalinee; Singleton, John; Lin, Shizeng; Batista, Cristian; Scott, Brian; Smythe, Nathan

    Traditionally, multiferroic behavior is studied in materials with coexisting long-range orders, such as ferromagnetism and ferroelectricity. Here we present multiferroic behavior at a spin-state transition (SST). SSTs, for example, the S = 1 to S = 2 transition in Mn3+ can become cooperative magneto-structural phase transitions due to structural coupling between ions. SSTs are accompanied by change in the orbital occupation and hence, strongly coupled to the lattice and charge degrees of freedom. They are a dominant functionality in metal-organic materials, persisting up to room temperature in some compounds. We demonstrate that a magnetic SST can induce ferroelectricity. We study a Mn-based metal-organic system in which a three-fold degenerate dynamic Jahn-Teller effect at high temperatures vanishes when the temperature is lowered, and the system drops into a lower spin state. Application of a magnetic field restores the high spin Jahn-Teller-active state and allows the Jahn Teller distortions to order cooperatively, creating a dielectric constant change and a net electric polarization. We use high magnetic fields at the NHMFL to study the magnetic and electric behavior of this system across a significant fraction of its T-H phase space, and compare to theoretical modeling.

  8. Thermomechanical Fatigue Behavior of the Intermetallic γ-TiAl Alloy TNB-V5 with Different Microstructures

    NASA Astrophysics Data System (ADS)

    Roth, Marcel; Biermann, Horst

    2010-03-01

    The cyclic deformation and fatigue behavior of the γ-TiAl alloy TNB-V5 is evaluated under thermomechanical load for three different microstructures. For this purpose, strain-controlled thermomechanical fatigue (TMF) tests were carried out with different temperature-strain cycles, different temperature ranges from 400 °C to 800 °C (673 K to 1073 K), and with two different strain ranges to set a fatigue-life relation. Cyclic deformation curves, stress-strain hysteresis loops, and fatigue lives of the tests are presented. The microstructures near-gamma (NG) and duplex (DP) show comparable fatigue lives under all test parameters. The microstructure fully-lamellar (FL) offers longer fatigue lives at the same loading conditions. For a general life prediction, the damage parameter of Smith, Watson, and Topper, P SWT vs fatigue life, is well suitable, if the testing and the application temperature ranges, respectively, include temperatures above the ductile-brittle transition (approximately 750 °C). In the completely brittle material behavior regime the quality of the lifetime prediction is unacceptable. The damage parameter P HL by Haibach and Lehrke shows a comparable correlation to the fatigue life as P SWT. The results are discussed with microstructural investigations.

  9. 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.

  10. Impact behavior of 9-Cr and 12-Cr ferritic steels after low-temperature irradiation

    SciTech Connect

    Klueh, R.L.; Vitek, J.M.; Corwin, W.R.; Alexander, D.J.

    1987-01-01

    Miniature Charpy impact specimens of 9Cr-1MoVNb and 12Cr-1MoVW steels and these steels with 1 and 2% Ni were irradiated in the High-Flux Isotope Reactor (HFIR) at 50/sup 0/C to displacement damage levels of up to 9 dpa. Nickel was added to study the effect of transmutation helium. Irradiation caused an increase in the ductile-brittle transition temperature (DBTT). The 9Cr-1MoVNb steels, with and without nickel, showed a larger shift than the 12Cr-1MoVW steels, with and without nickel. The results indicated that helium also increased the DBTT. The same steels were previously irradiated at higher temperatures. From the present and past tests, the effect of irradiation temperature on the DBTT behavior can be evaluated. For the 9Cr-1MoVNb steel, there is a continuous decrease in the magnitude of the DBTT increase up to an irradiation temperature of about 400/sup 0/C, after which the shift drops rapidly to zero at about 450/sup 0/C. The DBTT of the 12Cr-1MoVW steel shows a maximum increase at an irradiation temperature of about 400/sup 0/C and less of an increase at either higher or lower irradiation temperatures.

  11. Dynamic fracture behavior of Ti-6Al-4V alloy with various stabilities of [beta] phase

    SciTech Connect

    Akmoulin, I.A.; Niinomi, M.; Kobayashi, T. . Dept. of Production Systems Engineering)

    1994-08-01

    The effect of stability of the body-centered cubic (bcc) [beta] phase on the dynamic fracture behavior of Ti-6Al-4V alloy at room temperature and 77 K has been studied. The presence of a highly unstable [beta] phase in the quenched alloy leads to a decrease in both the dynamic fracture toughness and the crack propagation energy, and this decrease becomes more pronounced when test temperature is reduced to 77 K. Somewhat improved fracture characteristics were obtained by applying anneal procedure to receive a fully stable [beta] phase. The highest fracture toughness as well as the greatest crack propagation resistance were observed in the air-cooled grade, where the lattice parameter of the bcc phase was intermediate between those pertaining to quenched and annealed Ti-6Al-4V alloys. The effect is attributed to the vanadium content in the [beta] phase, which is sufficiently high to suppress deformation-induced transformation. On the other hand, the V content should be low enough to retard ductile-brittle transition, typical for the bcc metals at cryogenic temperatures. As a result, marked toughening can be achieved, so that the lowest application temperature of high-strength titanium alloys containing the bcc phase can be decreased significantly.

  12. 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.

  13. 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.

  14. Dynamic fracture behavior of Ti-6Al-4V alloy with various stabilities of βphase

    NASA Astrophysics Data System (ADS)

    Akmoulin, I. A.; Niinomi, M.; Kobayashi, T.

    1994-08-01

    The effect of stability of the body-centered cubic (bcc) β phase on the dynamic fracture behavior of Ti-6Al-4V alloy at room temperature and 77 K has been studied. The presence of a highly unstable β phase in the quenched alloy leads to a decrease in both the dynamic fracture toughness and the crack propagation energy, and this decrease bccomes more pronounced when test temperature is reduced to 77 K. Somewhat improved fracture characteristics were obtained by applying anneal procedure to receive a fully stable β phase. The highest fracture toughness as well as the greatest crack propagation resistance were observed in the air-cooled grade, where the lattice parameter of the bcc phase was intermediate between those pertaining to quenched and annealed Ti-6Al-4V alloys. The effect is attributed to the vanadium content in the β phase, which is sufficiently high to suppress deformation-induced transformation. On the other hand, the V content should be low enough to retard ductile-brittle transition, typical for the bcc metals at cryogenic temperatures. As a result, marked toughening can be achieved, so that the lowest application temperature of high-strength titanium alloys containing the bcc phase can be decreased significantly.

  15. 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…

  16. Comparison of fracture behavior for low-swelling ferritic and austenitic alloys irradiated in the Fast Flux Test Facility (FFTF) to 180 DPA. Revision 1

    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.

  17. 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.

  18. Microstructural, textural and thermal evolution of an exhumed strike-slip fault and insights into localization and rheological transition

    NASA Astrophysics Data System (ADS)

    Cao, Shuyun; Neubauer, Franz; Liu, Junlai; Bernroider, Manfred; Genser, Johann

    2016-04-01

    The presence of deep exhumed crustal rocks with a dominant but contrasting mineralogy results in shear concentration in the rheological weakest layer, which exhibits contrasting patterns of fabrics and thermal conditions during their formation. We tested a combination of methodologies including microstructural and textural investigations, geochronology and geothermometry on deformed rocks from exhumed strike-slip fault, Ailao Shan-Red River, SE, Asian. Results indicate that the exhumed deep crustal rocks since late Oligocene (ca. 28 Ma) to Pliocene (ca. 4 Ma) typically involve dynamic microstructural, textural and thermal evolution processes, which typically record a progressive deformation and syn-kinematic reactions from ductile to semi-ductile and brittle behavior during exhumation. This transformation also resulted in dramatic strength reduction that promoted strain localization along the strike-slip and transtensional faults. Detailed analysis has revealed the co-existence of microfabrics ranging from high-temperatures (granulite facies conditions) to overprinting low-temperatures (lower greenschist facies conditions). The high-temperature microstructures and textures are in part or entirely altered by subsequent, overprinting low-temperature shearing. In quartz-rich rocks, quartz was deformed in the dislocation creep regime and records transition of microfabrics and slip systems during decreasing temperature, which lasted until retrogression related to final exhumation. As a result, grain-size reduction associated by fluids circulating within the strike-slip fault zone at brittle-ductile transition leads to rock softening, which resulted in strain localization, weak rock rheology and the overall hot thermal structure of the crust. Decompression occurred during shearing and as a result of tectonic exhumation. All these results demonstrate that the ductile to ductile-brittle transition involves a combination of different deformation mechanisms, rheological

  19. Tensile and impact behavior of the reduced-activation steels OPTIFER and F82H mod

    NASA Astrophysics Data System (ADS)

    Schäfer, L.

    2000-12-01

    Tensile and charpy impact tests were carried out on some OPTIFER steel grades and F82H mod. The steels show little difference in tensile properties, but pronounced differences in charpy impact properties. Combinations of low ductile-brittle transition temperature (DBTT) and high yield strength are favored for OPTIFER-IV. After aging at 600°C and higher, F82H mod steel embrittles due to precipitation of Laves phase (Cr, Fe)2W, whereas OPTIFER-IV is resistant to aging.

  20. 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,…

  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. Advance Notice for Transition-Related Problem Behavior: Practice Guidelines.

    PubMed

    Brewer, Adam T; Strickland-Cohen, Kathleen; Dotson, Wesley; Williams, D Courtney

    2014-10-01

    Transitions between daily activities can occasion or elicit problem behavior in individuals with intellectual and developmental disabilities (IDD). Providing advance notice to signal an upcoming transition is a common practice in early and special education settings (e.g., Riffel 2010; Sandall et al. 2005). While the literature contains many demonstrations of the efficacy of various advance notice procedures, other studies have shown negative results. Practitioners are faced with the challenge of deciding whether advance notice is a viable treatment option for transition-related problem behavior in light of these contradictory findings. To assist the practitioner in this decision-making process, we provide a brief review of the advance notice literature, concentrating on the studies reporting that advance notice is ineffective at reducing transition-related problems. The goal is to provide practitioners with a better understanding of the environmental conditions under which advance notice is likely to be ineffective at decreasing problem behavior as well as the conditions under which it can be effective at reducing transition-related problem behavior. Discriminating these conditions may yield a useful set of practice guidelines for deciding when advance notice is a viable treatment option for decreasing transition-related problem behavior.

  3. 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.

  4. Improving Coalition Performance by Exploiting Phase Transition Behavior

    DTIC Science & Technology

    2004-09-01

    CODE 13. ABSTRACT (Maximum 200 Words) This document describes research into the effects of phase transitions and related phenomena on the design...implications of these thresholds for "anytime", "good enough soon enough" behavior are discussed. Second, the effects of solution-clustering behavior on...20 Figure 4.4: Example of effects , in oPARIS, of learning simple CNF clauses versus learning of cardinality constraints

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. Intergenerational Transmission of Reproductive Behavior during the Demographic Transition

    PubMed Central

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

    2012-01-01

    New evidence from the Utah Population Database (UPDB) 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

  11. Power law behavior of the zigzag transition in Yukawa clusters

    SciTech Connect

    Sheridan, T. E.; Magyar, Andrew L.

    2010-11-15

    We provide direct experimental evidence that the width of a Yukawa cluster exhibits power law behavior during the one-dimensional (1D) to two-dimensional (2D) zigzag transition. Configurations of small dusty (complex) plasma clusters confined in a biharmonic potential well are characterized as the well anisotropy is varied. When the anisotropy is large the particles are in a 1D straight-line configuration. As the anisotropy is decreased the cluster undergoes a zigzag transition to a 2D configuration. The measured dependence of cluster width on anisotropy follows a power law. A second transition from the zigzag to an elliptical configuration is also observed. The results are in very good agreement with a model of identical particles interacting through a Yukawa potential.

  12. 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.

  13. 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.

  14. TRANSITION FROM KINETIC TO MHD BEHAVIOR IN A COLLISIONLESS PLASMA

    SciTech Connect

    Parashar, Tulasi N.; Matthaeus, William H.; Shay, Michael A.; Wan, Minping

    2015-10-01

    The study of kinetic effects in heliospheric plasmas requires representation of dynamics at sub-proton scales, but in most cases the system is driven by magnetohydrodynamic (MHD) activity at larger scales. The latter requirement challenges available computational resources, which raises the question of how large such a system must be to exhibit MHD traits at large scales while kinetic behavior is accurately represented at small scales. Here we study this implied transition from kinetic to MHD-like behavior using particle-in-cell (PIC) simulations, initialized using an Orszag–Tang Vortex. The PIC code treats protons, as well as electrons, kinetically, and we address the question of interest by examining several different indicators of MHD-like behavior.

  15. Transition from Kinetic to MHD Behavior in a Collisionless Plasma

    NASA Astrophysics Data System (ADS)

    Parashar, Tulasi N.; Matthaeus, William H.; Shay, Michael A.; Wan, Minping

    2015-10-01

    The study of kinetic effects in heliospheric plasmas requires representation of dynamics at sub-proton scales, but in most cases the system is driven by magnetohydrodynamic (MHD) activity at larger scales. The latter requirement challenges available computational resources, which raises the question of how large such a system must be to exhibit MHD traits at large scales while kinetic behavior is accurately represented at small scales. Here we study this implied transition from kinetic to MHD-like behavior using particle-in-cell (PIC) simulations, initialized using an Orszag-Tang Vortex. The PIC code treats protons, as well as electrons, kinetically, and we address the question of interest by examining several different indicators of MHD-like behavior.

  16. Irradiation effects on impact behavior of 12Cr-1MoVW and 2 1/4Cr-1Mo steels

    SciTech Connect

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

    1990-01-01

    Charpy impact tests were conducted on 12CR-1MoVW steel after irradiation in the Fast Flux Test Facility (FFTF) and the Oak Ridge Research Reactor (OOR). One-half-size and one-third-size Charpy specimens were irradiated in FFTF at 365{degree}C. After irradiating half-size-specimens to {approximately}10 and 17 dpa, a shift in ductile-brittle-transition temperature (DBTT) of 160{degree}C was observed for both fluences, indicating a saturation in the shift. A shift DBTT of 151{degree}C was observed for the third-size specimens after irradiation to 10 dpa. Third-size specimens of 12Cr--1MoVW steel irradiated {approximately}7 dpa in the ORR at 330 and 400{degree}C developed shifts in DBTT of 200 and 120{degree}C, respectively, somewhat above and below the shifts observed after irradiation at 365{degree}C in FFTF. This correspondence of results in the mixed-spectrum ORR and the fast-spectrum FFTF is in marked contrast to large differences observed between specimens irradiated in the mixed-spectrum High Flux Isotope Reactor and the fast spectrum Experimental Breeder Reactor. The first data on the effect of fast reactor irradiation on the impact behavior 2{1/4} CR--1Mo steel were obtained. Third-size specimens were irradiated in FFTF to {approximately}10 dpa at 365{degree}C. An increase in DBTT of 170{degree}C was observed, similar of the shift observed for 12Cr--1MoVW steel following comparable irradiation. The reduction in the upper-shelf energy for the 2{1/4} Cr--1Mo steel was less than that observed for 12Cr--1MoVW steel. Because of the low DBTT of unirradiated 2{1/4} Cr--1Mo steel, the DBTT after irradiation remained below that for 12Cr--1MoVW steel.

  17. 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

  18. Experimental observation of transition behavior on a flat plate

    NASA Technical Reports Server (NTRS)

    Nagamatsu, H. T.

    1985-01-01

    In studying transition behavior a shock tube and tunnel were used to produce high temperatures, and thin-film platinum heat gauges were used to measure local heat flux as well as to detect the transition of the laminar boundary layer over a flat plate and a cone. Initial investigations were conducted in the hypersonic shock tunnel to obtain high-temperature information for the development of an ICBM nose cone. Shock Mach numbers as large as 50 with a temperature of 15,000 K after the incident wave were produced in the driven tube. Shock tubes are used to investigate the heat transfer over various surfaces to 2500 K for the development of future gas turbines.

  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.

  20. Phase transitions in tumor growth: III vascular and metastasis behavior

    NASA Astrophysics Data System (ADS)

    Llanos-Pérez, J. A.; Betancourt-Mar, J. A.; Cocho, G.; Mansilla, R.; Nieto-Villar, José Manuel

    2016-11-01

    We propose a mechanism for avascular, vascular and metastasis tumor growth based on a chemical network model. Vascular growth and metastasis, appear as a hard phase transition type, as "first order", through a supercritical Andronov-Hopf bifurcation, emergence of limit cycle and then through a cascade of bifurcations type saddle-foci Shilnikov's bifurcation. Finally, the thermodynamics framework developed shows that the entropy production rate, as a Lyapunov function, indicates the directional character and stability of the dynamical behavior of tumor growth according to this model.

  1. Emergent heavy fermion behavior at the Wigner-Mott transition.

    PubMed

    Merino, Jaime; Ralko, Arnaud; Fratini, Simone

    2013-09-20

    We study charge ordering driven by Coulomb interactions on triangular lattices relevant to the Wigner-Mott transition in two dimensions. Dynamical mean-field theory reveals the pinball liquid phase, a charge ordered metallic phase containing quasilocalized (pins) coexisting with itinerant (balls) electrons. Based on an effective periodic Anderson model for this phase, we find an antiferromagnetic Kondo coupling between pins and balls and strong quasiparticle renormalization. Non-Fermi liquid behavior can occur in such charge ordered systems due to the spin-flip scattering of itinerant electrons off the pins in analogy with heavy fermion compounds.

  2. 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.

  3. Hypnagogic behavior disorder: complex motor behaviors during wake-sleep transitions in 2 young children.

    PubMed

    Pareja, Juan A; Cuadrado, María Luz; García-Morales, Irene; Gil-Nagel, Antonio; Franch, Oriol

    2008-08-01

    A nondescribed behavioral disorder was observed during wake-sleep transitions in 2 young children. Two boys had episodes of abnormal behavior in hypnagogic-and occasionally hypnopompic-periods for 1 year from the time they were 1 year and several months old. The episodes consisted of irregular body movements, which could be either gentle or violent but never made the children get out of bed. They lasted from a few seconds to 2 hours and were associated with poor reactivity and amnesia of the events. Electroencephalography (EEG) recordings showed wake-state features, with brief bursts of hypnagogic hypersynchrony, and did not display seizure activity. A distinctive behavior disorder occurring during wake-sleep transitions with a wake EEG pattern has been identified in very early childhood. The clinical profile does not fit any of the known parasomnias and might belong to a new category of parasomnia.

  4. 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.

  5. Deformation Behavior across the Zircon-Scheelite Phase Transition

    NASA Astrophysics Data System (ADS)

    Yue, Binbin; Hong, Fang; Merkel, Sébastien; Tan, Dayong; Yan, Jinyuan; Chen, Bin; Mao, Ho-Kwang

    2016-09-01

    The pressure effects on plastic deformation and phase transformation mechanisms of materials are of great importance to both Earth science and technological applications. Zircon-type materials are abundant in both nature and the industrial field; however, there is still no in situ study of their deformation behavior. Here, by employing radial x-ray diffraction in a diamond anvil cell, we investigate the dislocation-induced texture evolution of zircon-type gadolinium vanadate (GdVO4 ) in situ under pressure and across its phase transitions to its high-pressure polymorphs. Zircon-type GdVO4 develops a (001) compression texture associated with dominant slip along ⟨100 ⟩{001 } starting from 5 GPa. This (001) texture transforms into a (110) texture during the zircon-scheelite phase transition. Our observation demonstrates a martensitic mechanism for the zircon-scheelite transformation. This work will help us understand the local deformation history in the upper mantle and transition zone and provides fundamental guidance on material design and processing for zircon-type materials.

  6. Collective Behavior of Interacting Particles: Radius-Dependent Phase Transition

    NASA Astrophysics Data System (ADS)

    Tarras, I.; Moussa, N.; Mazroui, M.; Boughaleb, Y.; Hajjaji, A.

    2013-02-01

    The aim of this paper is to study and discuss the effect of three zones (repulsion zone, orientation zone and attraction zone) on the phase transition in 2D-collective moving particles. Our main motivation is to better understand the complex behavior of non-equilibrium multi-agent system by extending the earlier and original model proposed by Viscek et al. [T. Viscek et al., Phys. Rev. Lett.75 (1995) 1226] for one zone. The analysis is performed over different situations by using a numerical simulation method. It is found that the radius R2 of orientation zone plays an important role in the system. In effect, by varying the parameter R2 a phase transition can be achieved from disordered moving of individuals to a group to highly aligned collective motion. The results also show that, the critical value of R2 at which the transition emerges depends strongly on the size of the repulsion zone but not on the size of attraction one.

  7. Deformation Behavior across the Zircon-Scheelite Phase Transition.

    PubMed

    Yue, Binbin; Hong, Fang; Merkel, Sébastien; Tan, Dayong; Yan, Jinyuan; Chen, Bin; Mao, Ho-Kwang

    2016-09-23

    The pressure effects on plastic deformation and phase transformation mechanisms of materials are of great importance to both Earth science and technological applications. Zircon-type materials are abundant in both nature and the industrial field; however, there is still no in situ study of their deformation behavior. Here, by employing radial x-ray diffraction in a diamond anvil cell, we investigate the dislocation-induced texture evolution of zircon-type gadolinium vanadate (GdVO_{4}) in situ under pressure and across its phase transitions to its high-pressure polymorphs. Zircon-type GdVO_{4} develops a (001) compression texture associated with dominant slip along ⟨100⟩{001} starting from 5 GPa. This (001) texture transforms into a (110) texture during the zircon-scheelite phase transition. Our observation demonstrates a martensitic mechanism for the zircon-scheelite transformation. This work will help us understand the local deformation history in the upper mantle and transition zone and provides fundamental guidance on material design and processing for zircon-type materials.

  8. 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.

  9. Cancrinite: Crystal Structure, Phase Transitions, and Dehydration Behavior with Temperature

    SciTech Connect

    Hassan,I.; Antao, S.; Parise, J.

    2006-01-01

    The structural behavior of a cancrinite, Na{sub 5.96}Ca{sub 1.52}[Al{sub 6}Si{sub 6}O{sub 24}](CO{sub 3}){sub 1.57}{center_dot}1.75H{sub 2}O, was determined by using in situ synchrotron X-ray powder diffraction data [{lambda} = 0.91806(5) {angstrom}] at room pressure and from 25 to 982 {sup o}C. The sample was heated at a rate of about 9.5 {sup o}C/min, and X-ray traces were collected at about 15 {sup o}C intervals. The satellite reflections in cancrinite were lost at about 504 {sup o}C, where a phase transition occurs. All the unit-cell parameters for cancrinite also show a discontinuity at 504 {sup o}C. Initially, the [Ca{center_dot}CO{sub 3}] clusters and their vacancies are ordered in the channels, and this ordering is destroyed on heating to give rise to the phase transition. Cancrinite loses water continuously until about 625 {sup o}C; thereafter an anhydrous cancrinite phase exists. From 25 to 952 {sup o}C, a minimal amount of CO{sub 2} is lost from the structure. Over this temperature range, the average bridging angle, which is an indication of the degree of rotation of the tetrahedra, increases from 143.7(4) to 147.7(5){sup o}. Rotations of the tetrahedra are caused by expansion of the Na1-O2 bond lengths.

  10. Aggression, academic behaviors, and popularity perceptions among boys of color during the transition to middle school.

    PubMed

    Xie, Hongling; Dawes, Molly; Wurster, Tabitha J; Shi, Bing

    2013-01-01

    The transition to middle school often presents behavioral and academic challenges to youths. Boys of color (i.e., African American and Hispanic in this study) may be especially vulnerable. In this study, peer nominations of aggressive and academic behaviors as well as youths' perceptions of how these behaviors were related to popularity in peer networks were obtained from the spring semester of fifth grade through the spring semester of seventh grade, with the transition occurring as the students entered the sixth grade. The sample included 188 boys (71 Caucasian, 90 African American, and 27 Hispanic) from an urban school district in the northeastern United States. Trajectory analyses showed that African American boys scored lower in studentship and higher in rule-breaking and aggressive (both physical and social) behaviors prior to the transition, and such differences among ethnic groups were largely maintained during the transition. Hispanic boys displayed decreases in their studentship during the transition. African American boys' perception of how studentship affects popularity was more positive than other boys prior to the transition, but it decreased during the transition. African American boys also endorsed rule breaking and physical and social aggression more positively for popularity prior to the transition, whereas Caucasian and Hispanic boys' endorsement increased during the transition and eventually caught up with those of African American boys in seventh grade. A positive within-individual association was found between youths' popularity perception and their behavior for studentship, rule breaking, and physical aggression, which did not differ by ethnicity.

  11. 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.

  12. Critical behavior in the hydrogen insulator-metal transition

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Mao, H. K.

    1990-01-01

    The vibrational Raman spectrum of solid hydrogen has been measured from 77 to 295 K in the vicinity of the recently observed insulator-metal transition and low-temperature phase transition at 150 gigapascals. The measurements provide evidence for a critical point in the pressure-temperature phase boundary of the low-temperature transition. The result suggests that below the critical temperature the insulator-metal transition changes from continuous to discontinuous, consistent with the general criteria originally proposed by Mott (1949) for metallization by band-gap closure. The effect of temperature on hydrogen metallization closely resembles that of the lower-pressure insulator-metal transitions in doped V2O3 alloys.

  13. A generalized methodology for obtaining quantitative charpy data from test specimens of nonstandard dimensions

    SciTech Connect

    Manahan, M.P. ); Charles, C. , Inc., Washington, DC )

    1990-05-01

    Miniaturized specimen technology enables mechanical behavior determination using a minimum volume of material. A method for obtaining the ductile-brittle transition temperature (DBTT) of ferritic steels was developed using a miniaturized notch test (MNT). Comparisons between conventional and miniaturized specimen DBTTs show that the MNT specimens are capable of delivering a 41-J transition temperature shift with the same accuracy as that obtained using conventional specimens. The work reported was performed on an American Society for Testing Materials A508 steel.

  14. 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…

  15. 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…

  16. Modeling the nonlinear PMMA behavior near glass transition temperature: application to its thermoforming

    NASA Astrophysics Data System (ADS)

    Gilormini, P.; Chevalier, L.; Régnier, G.

    2011-01-01

    Using suitable constitutive equations, numerical simulation allows predicting the properties of transparencies that are thermoformed near their glass transition temperature. Such equations are presented, which describe the nonlinear viscoelastic behavior of poly(methyl methacrylate) at large deformations near glass transition. The simulation of the thermoforming of a transparency at constant and uniform temperature is performed and compared with experimental results.

  17. The Transition to Kindergarten: Predicting Socio-Behavioral Outcomes for Children with and without Disabilities

    ERIC Educational Resources Information Center

    Welchons, Leah Wildenger; McIntyre, Laura Lee

    2017-01-01

    The transition to kindergarten is regarded as a critical early childhood developmental milestone with important implications for later school outcomes. Little prior research has focused on predictors of socio-behavioral kindergarten outcomes using longitudinal research designs. Further, few studies have examined kindergarten transition using…

  18. 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.

  19. Parents, peers, and sexual values influence sexual behavior during the transition to college.

    PubMed

    Wetherill, Reagan R; Neal, Dan J; Fromme, Kim

    2010-06-01

    Several decades of research have identified the contributions of psychosocial influences on adolescent and young adult sexual behavior; however, few studies have examined parental and peer influence and sexual values during the transition from high school to college. The current study tested the influence of sexual values and perceived awareness and caring (PAC), or beliefs about how much parents and peers know and care about students' behavior, on sexual behavior during this transitional period. Using data from a longitudinal study, generalized estimating equations and the generalized linear model were used to examine the associations among sexual values, parental and peer PAC, and sexual behavior, both cross-sectionally and longitudinally. Participants (N = 1,847; 61% female) completed web-based surveys the summer before college matriculation and at the end of the first semester in college. Results indicated that individuals with high levels of both parental and peer PAC engaged in less frequent sexual behaviors and that PAC moderated the effect of sexual values on sexual behaviors. Furthermore, both PAC variables decreased during the transition from high school to college, and high school sexual values, parental PAC, and their interaction predicted the number of sexual partners during the first semester of college. Only sexual values and high school unsafe sexual behaviors predicted unsafe sexual behavior in college. Findings suggest that complex associations exist among perceived awareness and caring, sexual values, and sexual behaviors, and that the transition from high school to college may be an ideal time for safer-sex interventions.

  20. Thermodynamic behavior near a metal-insulator transition

    NASA Technical Reports Server (NTRS)

    Paalanen, M. A.; Graebner, J. E.; Bhatt, R. N.; Sachdev, S.

    1988-01-01

    Measurements of the low-temperature specific heat of phosphorus-doped silicon for densities near the metal-insulator transition show an enhancement over the conduction-band itinerant-electron value. The enhancement increases toward lower temperatures but is less than that found for the spin susceptibility. The data are compared with various theoretical models; the large ratio of the spin susceptibility to specific heat indicates the presence of localized spin excitations in the metallic phase as the metal-insulator transition is approached.

  1. 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…

  2. 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 ...

  3. 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 --> ∞.

  4. A medical profession in transition: exploring naturopathic physician blogging behaviors.

    PubMed

    Walden, Justin

    2013-01-01

    Naturopathic medicine is a holistic healing approach involving natural remedies, wellness, and disease prevention. A literature review shows the discipline is attempting to overcome several professional obstacles and expand into new areas. Amid this transition, the naturopathic community--like other groups--has adopted Web 2.0 technologies such as blogs. This article features interviews with one naturopathic medical student and 17 naturopathic physicians and reviews of interviewee blogs to understand this group's communication activities. Findings suggest blogs are venues for projecting both individual and group credibility to stakeholders. I conclude that blogs serve a "represent all of us" group function and are new examples of gray or alternative health literature.

  5. Effects of an Interdependent Group Contingency on the Transition Behavior of Middle School Students With Emotional and Behavioral Disorders.

    PubMed

    Hawkins, Renee O; Haydon, Todd; McCoy, Dacia; Howard, Andrea

    2017-04-06

    An ABAB design was used to evaluate the effectiveness of an interdependent group contingency with randomized components to improve the transition behavior of middle school students identified with emotional and behavioral disorders (EBDs) served in an alternative educational setting. The intervention was implemented by one teacher with three classes of students, and the dependent variable was the percentage of students ready to begin class at the appropriate time. Data revealed significant improvements in student behavior, providing support for implementation of group contingencies for students with EBDs in alternative educational settings and an example of feasible procedures and data collection methods. (PsycINFO Database Record

  6. 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…

  7. 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.

  8. Aging effects on the mechanical properties of alumina-forming austenitic stainless steels

    SciTech Connect

    Bei, Hongbin; Yamamoto, Yukinori; Brady, Michael P; Santella, Michael L

    2010-01-01

    Isothermal aging and tensile evaluation were conducted for recently developed alumina-forming austenitic stainless steels (AFAs). Microstructural observation reveals that NiAl-type B2 and Fe{sub 2}(Mo,Nb)-type Laves phase precipitates form as dominant second phases in the austenitic matrix during aging at 750 C. At room temperature these precipitates increase the strength but decrease the ductility of the AFA alloys. However, when tested at 750 C, the AFA alloys did not show strong precipitation hardening by these phases, moreover, the elongation to fracture was not affected by aging. Fracture surface and cross-sectional microstructure analysis after tensile testing suggests that the difference of mechanical behaviors between room temperature and 750 C results from the ductile-brittle transition of the B2 precipitates. At room temperature, B2 precipitates are strong but brittle, whereas they become weak but ductile above the ductile-brittle transition temperature (DBTT).

  9. Scaling behavior of sleep-wake transitions across species

    NASA Astrophysics Data System (ADS)

    Lo, Chung-Chuan; Chou, Thomas; Ivanov, Plamen Ch.; Penzel, Thomas; Mochizuki, Takatoshi; Scammell, Thomas; Saper, Clifford B.; Stanley, H. Eugene

    2003-03-01

    Uncovering the mechanisms controlling sleep is a fascinating scientific challenge. It can be viewed as transitions of states of a very complex system, the brain. We study the time dynamics of short awakenings during sleep for three species: humans, rats and mice. We find, for all three species, that wake durations follow a power-law distribution, and sleep durations follow exponential distributions. Surprisingly, all three species have the same power-law exponent for the distribution of wake durations, but the exponential time scale of the distributions of sleep durations varies across species. We suggest that the dynamics of short awakenings are related to species-independent fluctuations of the system, while the dynamics of sleep is related to system-dependent mechanisms which change with species.

  10. 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

  11. Modeling and Simulating Passenger Behavior for a Station Closure in a Rail Transit Network.

    PubMed

    Yin, Haodong; Han, Baoming; Li, Dewei; Wu, Jianjun; Sun, Huijun

    2016-01-01

    A station closure is an abnormal operational situation in which the entrances or exits of a rail transit station have to be closed for some time due to an unexpected incident. A novel approach is developed to estimate the impacts of the alternative station closure scenarios on both passenger behavioral choices at the individual level and passenger demand at the disaggregate level in a rail transit network. Therefore, the contributions of this study are two-fold: (1) A basic passenger behavior optimization model is mathematically constructed based on 0-1 integer programming to describe passengers' responses to alternative origin station closure scenarios and destination station closure scenarios; this model also considers the availability of multi-mode transportation and the uncertain duration of the station closure; (2) An integrated solution algorithm based on the passenger simulation is developed to solve the proposed model and to estimate the effects of a station closure on passenger demand in a rail transit network. Furthermore, 13 groups of numerical experiments based on the Beijing rail transit network are performed as case studies with 2,074,267 records of smart card data. The comparisons of the model outputs and the manual survey show that the accuracy of our proposed behavior optimization model is approximately 80%. The results also show that our model can be used to capture the passenger behavior and to quantitatively estimate the effects of alternative closure scenarios on passenger flow demand for the rail transit network. Moreover, the closure duration and its overestimation greatly influence the individual behavioral choices of the affected passengers and the passenger demand. Furthermore, if the rail transit operator can more accurately estimate the closure duration (namely, as g approaches 1), the impact of the closure can be somewhat mitigated.

  12. Modeling and Simulating Passenger Behavior for a Station Closure in a Rail Transit Network

    PubMed Central

    Yin, Haodong; Han, Baoming; Li, Dewei; Wu, Jianjun; Sun, Huijun

    2016-01-01

    A station closure is an abnormal operational situation in which the entrances or exits of a rail transit station have to be closed for some time due to an unexpected incident. A novel approach is developed to estimate the impacts of the alternative station closure scenarios on both passenger behavioral choices at the individual level and passenger demand at the disaggregate level in a rail transit network. Therefore, the contributions of this study are two-fold: (1) A basic passenger behavior optimization model is mathematically constructed based on 0–1 integer programming to describe passengers’ responses to alternative origin station closure scenarios and destination station closure scenarios; this model also considers the availability of multi-mode transportation and the uncertain duration of the station closure; (2) An integrated solution algorithm based on the passenger simulation is developed to solve the proposed model and to estimate the effects of a station closure on passenger demand in a rail transit network. Furthermore, 13 groups of numerical experiments based on the Beijing rail transit network are performed as case studies with 2,074,267 records of smart card data. The comparisons of the model outputs and the manual survey show that the accuracy of our proposed behavior optimization model is approximately 80%. The results also show that our model can be used to capture the passenger behavior and to quantitatively estimate the effects of alternative closure scenarios on passenger flow demand for the rail transit network. Moreover, the closure duration and its overestimation greatly influence the individual behavioral choices of the affected passengers and the passenger demand. Furthermore, if the rail transit operator can more accurately estimate the closure duration (namely, as g approaches 1), the impact of the closure can be somewhat mitigated. PMID:27935963

  13. Separate and combined effects of visual schedules and extinction plus differential reinforcement on problem behavior occasioned by transitions.

    PubMed

    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 activities. Problem behavior decreased for both participants when extinction and DRO were introduced, regardless of whether visual schedules were also used.

  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. The Impact of Serial Transitions on Behavioral and Psychological Problems among Children in Child Protection Services

    ERIC Educational Resources Information Center

    Saint-Jacques, Marie-Christine; Cloutier, Richard; Pauze, Robert; Simard, Marie; Gagne, Marie-Helene; Poulin, Amelie

    2006-01-01

    This study focuses on the impacts of serial transitions on externalized and internalized behavior disorders, anxiety, and depression among children in child protection services. The research was carried out with a sample of 741 children. The findings demonstrate that the number of times a family is blended is a stronger predictive factor for…

  16. 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.…

  17. 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 American,…

  18. 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…

  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. 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.

  1. 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.

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

    PubMed

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

    2011-08-25

    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.

  3. Magnetic collapse and the behavior of transition metal oxides at high pressure

    NASA Astrophysics Data System (ADS)

    Leonov, I.; Pourovskii, L.; Georges, A.; Abrikosov, I. A.

    2016-10-01

    We report a detail theoretical study of the electronic structure and phase stability of transition metal oxides MnO, FeO, CoO, and NiO in their paramagnetic cubic B 1 structure by employing dynamical mean-field theory of correlated electrons combined with ab initio band-structure methods. Our calculations reveal that under pressure these materials exhibit a Mott insulator-metal transition (IMT) which is accompanied by a simultaneous collapse of local magnetic moments and lattice volume, implying a complex interplay between chemical bonding and electronic correlations. Moreover, our results for the transition pressure show a monotonous decrease from ˜145 to 40 GPa, upon moving from MnO to CoO. In contrast to that, in NiO, magnetic collapse is found to occur at a remarkably higher pressure of ˜429 GPa. We provide a unified picture of such a behavior and suggest that it is primarily a localized to itinerant moment behavior transition at the IMT that gives rise to magnetic collapse in transition metal oxides.

  4. Guest-Dependent Spin-Transition Behavior of Porous Coordination Polymers.

    PubMed

    Ohtani, Ryo; Hayami, Shinya

    2017-02-16

    The host-guest composites of Hofmann-type iron(II) spin-transition (ST) porous coordination polymers incorporating guest molecules show guest-dependent ST behavior in accordance with the respective guest species, which may be a gas, solvent, halogen, or organic molecule. The guest also works as a chemical stimulant to switch the spin state of the host between high and low spin at room temperature. In this review, we discuss guest properties including size, shape, flexibility, chemical properties, and pore loading content, which impact the spin states of the host framework and the ST behavior exhibited by the host-guest composites.

  5. 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.

  6. Behavior of quasinormal modes and high dimension RN-AdS black hole phase transition

    NASA Astrophysics Data System (ADS)

    Chabab, M.; Moumni, H. El; Iraoui, S.; Masmar, K.

    2016-12-01

    In this work we use the quasinormal frequencies of a massless scalar perturbation to probe the phase transition of the high dimension charged AdS black hole. The signature of the critical behavior of this black hole solution is detected in the isobaric as well as in isothermal process. This paper is a natural generalization of Liu et al. (JHEP 1409:179, 2014) to higher dimensional spacetime. More precisely our study shows a clear signal for any dimension d in the isobaric process. As to the isothermal case, we find that this signature can be affected by other parameters like the pressure and the horizon radius. We conclude that the quasinormal modes can be an efficient tool to investigate the first-order phase transition, but fail to disclose the signature of the second-order phase transition.

  7. 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.

  8. The Influence of Family and Teacher Factors on Early Disruptive School Behaviors: A Latent Profile Transition Analysis

    ERIC Educational Resources Information Center

    Racz, Sarah J.; O'Brennan, Lindsey M.; Bradshaw, Catherine P.; Leaf, Philip J.

    2016-01-01

    The kindergarten year plays an important role in establishing children's academic, social, and behavioral adjustment. Early identification of children who experience difficulties with the kindergarten transition is crucial to prevent continued behavioral and emotional problems. Family and school predictors of these early behavioral patterns can…

  9. Sexual motivations and engagement in sexual behavior during the transition to college.

    PubMed

    Patrick, Megan E; Lee, Christine M

    2010-06-01

    Motivations for and against sex are salient predictors of engaging in or abstaining from sex in cross-sectional studies. Participants (N = 637, 41.4% male) provided data on their motivations for and against sex and lifetime sexual behavior prior to entering college and six months into the first year in college. Longitudinal data were used to examine differences on motivations for and against sex reported the summer before college entrance for students who continued to abstain (Nevers, 44.7%), transitioned to sexual behavior in the following months (Transitioners, 11.0%), and who were previously sexually active (Actives, 44.3%). Multivariate analysis of variance analyses indicated that Transitioners evidenced mean-level differences in motivations surrounding sex (greater intimacy and enhancement motives for sex, lower values motives against sex) prior to their behavioral initiation compared to Nevers. In addition, Transitioners reported greater changes in motivations from pre-college to the six-month follow-up, including increased enhancement motivations for sex and decreased values and not ready motivations against sex. Men reported more important motivations for sex and less important motivations against sex than women, with an interaction showing that sexually experienced women reported more important intimacy motivations and sexually inexperienced men reported more important coping motivations for sex. Identifying salient motivations associated with imminent changes in sexual behavior may support the development of sexual health promotion programs that seek to reach sexually inexperienced individuals at important times of transition.

  10. Fast and slow transitions in frontal ensemble activity during flexible sensorimotor behavior

    PubMed Central

    Siniscalchi, Michael J.; Phoumthipphavong, Victoria; Ali, Farhan; Lozano, Marc; Kwan, Alex C.

    2016-01-01

    The ability to shift between repetitive and goal-directed actions is a hallmark of cognitive control. Previous studies have reported that adaptive shifts in behavior are accompanied by changes of neural activity in frontal cortex. However, neural and behavioral adaptations can occur at multiple time scales, and their relationship remains poorly defined. Here, we developed a novel adaptive sensorimotor decision-making task for head-fixed mice, requiring them to shift flexibly between multiple auditory-motor mappings. Two-photon calcium imaging of secondary motor cortex (M2) revealed different ensemble activity states for each mapping. Notably, when adapting to a conditional mapping, transitions in ensemble activity were abrupt and occurred before the recovery of behavioral performance. By contrast, gradual and delayed transitions accompanied shifts towards repetitive responding. These results demonstrate distinct ensemble signatures associated with the start versus end of sensory-guided behavior, and suggest that M2 leads in engaging goal-directed response strategies that require sensorimotor associations. PMID:27399844

  11. 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

  12. Critical behavior of the transport coefficients at the plateau-insulator transition in IQHE

    NASA Astrophysics Data System (ADS)

    Song, Juntao; Prodan, Emil

    2013-03-01

    Using the non-commutative Kubo formula for disordered lattice systems, we mapped the conductivity tensor σ (EF , T) as function of Fermi level EF and temperature T for the disordered Hofstadter model. Convergence and accuracy tests indicate that the simulations can be used to investigate the critical behavior near the plateau-insulator transition. Our analysis provides the first quantitative theoretical confirmation of the well established experimental facts about the critical behavior: 1) The semicircle law for the components of the conductivity tensor; 2) The existence of the quantized Hall insulator state characterized by zero direct and Hall conductivities, but with Hall resistivity quantized at h /e2 ; 3) Single scaling behavior with exponents that are consistent with previous studies. This work was supported by the U.S. NSF grants DMS-1066045 and DMR-1056168.

  13. Critical behaviors and phase transitions of black holes in higher order gravities and extended phase spaces

    NASA Astrophysics Data System (ADS)

    Sherkatghanad, Zeinab; Mirza, Behrouz; Mirzaiyan, Zahra; Mansoori, Seyed Ali Hosseini

    We consider the critical behaviors and phase transitions of Gauss-Bonnet-Born-Infeld-AdS black holes (GB-BI-AdS) for d = 5, 6 and the extended phase space. We assume the cosmological constant, Λ, the coupling coefficient α, and the BI parameter β to be thermodynamic pressures of the system. Having made these assumptions, the critical behaviors are then studied in the two canonical and grand canonical ensembles. We find “reentrant and triple point phase transitions” (RPT-TP) and “multiple reentrant phase transitions” (multiple RPT) with increasing pressure of the system for specific values of the coupling coefficient α in the canonical ensemble. Also, we observe a reentrant phase transition (RPT) of GB-BI-AdS black holes in the grand canonical ensemble and for d = 6. These calculations are then expanded to the critical behavior of Born-Infeld-AdS (BI-AdS) black holes in the third-order of Lovelock gravity and in the grand canonical ensemble to find a van der Waals (vdW) behavior for d = 7 and a RPT for d = 8 for specific values of potential ϕ in the grand canonical ensemble. Furthermore, we obtain a similar behavior for the limit of β →∞, i.e. charged-AdS black holes in the third-order of the Lovelock gravity. Thus, it is shown that the critical behaviors of these black holes are independent of the parameter β in the grand canonical ensemble.

  14. 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…

  15. Estimating Transitional Probabilities with Cross-Sectional Data to Assess Smoking Behavior Progression: A Validation Analysis

    PubMed Central

    Chen, Xinguang; Lin, Feng

    2013-01-01

    Background and objective New analytical tools are needed to advance tobacco research, tobacco control planning and tobacco use prevention practice. In this study, we validated a method to extract information from cross-sectional survey for quantifying population dynamics of adolescent smoking behavior progression. Methods With a 3-stage 7-path model, probabilities of smoking behavior progression were estimated employing the Probabilistic Discrete Event System (PDES) method and the cross-sectional data from 1997-2006 National Survey on Drug Use and Health (NSDUH). Validity of the PDES method was assessed using data from the National Longitudinal Survey of Youth 1997 and trends in smoking transition covering the period during which funding for tobacco control was cut substantively in 2003 in the United States. Results Probabilities for all seven smoking progression paths were successfully estimated with the PDES method and the NSDUH data. The absolute difference in the estimated probabilities between the two approaches varied from 0.002 to 0.076 (p>0.05 for all) and were highly correlated with each other (R2=0.998, p<0.01). Changes in the estimated transitional probabilities across the 1997-2006 reflected the 2003 funding cut for tobacco control. Conclusions The PDES method has validity in quantifying population dynamics of smoking behavior progression with cross-sectional survey data. The estimated transitional probabilities add new evidence supporting more advanced tobacco research, tobacco control planning and tobacco use prevention practice. This method can be easily extended to study other health risk behaviors. PMID:25279247

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

  19. 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.

  20. Critical behavior of ultrasonic attenuation near interaction-driven metal-insulator transitions

    NASA Astrophysics Data System (ADS)

    Dobrosavljević, V.; Kirkpatrick, T. R.; Chen, Changfeng; Belitz, D.

    1991-09-01

    We consider the critical behavior of the ultrasonic attenuation (UA) near interaction-driven metal-insulator transitions. To first order in the disorder no localization corrections are found. Using a field-theoretical nonlinear σ-model representation, and performing a renormalization-group analysis, we show that the absence of first-order corrections follows from the presence of two scaling parts for the UA. The critical exponents for the UA are shown to be sensitive to both the symmetry class and the interaction range, in contrast to the behavior of the conductivity. We have examined the cases of strong magnetic fields and of magnetic impurities where the critical exponents prove to be universal for Coulomb interactions, but are found to be nonuniversal for short-ranged interactions. The UA was further examined near the pseudomagnetic transition that occurs in the absence of magnetic perturbations. In that case, the UA critical exponents were found to vanish, indicating that the UA stays uncritical at this transition.

  1. 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

  2. Elevated temperature stress strain behavior of beryllium powder product

    SciTech Connect

    Abeln, S.P.; Field, R.; Mataya, M.C.

    1995-09-01

    Several grades of beryllium powder product were tested under isothermal conditions in compression over a temperature range of room temperature to 1000 C and a strain rate range from 0.001 s{sup {minus}1} to 1 s{sup {minus}1}. Samples were compressed to a total strain of 1 (64% reduction in height). It is shown that all the grades are strain rate sensitive and that strain rate sensitivity increases with temperature. Yield points were exhibited by some grades up to a temperature of 500 C, and appeared to be primarily dependent on prior thermal history which determined the availability of mobile dislocations. Serrated flow in the form of stress drops was seen in all the materials tested and was most pronounced at 500 C. The appearance and magnitude of the stress drops were dependent on accumulated strain, strain rate, sample orientation, and composition. The flow stress and shape of the flow curves differed significantly from grade to grade due to variations in alloy content, the size and distribution of BeO particles, aging precipitates, and grain size. The ductile-brittle transition temperature (DBTT) was determined for each grade of material and shown to be dependent on composition and thermal treatment. Structure/property relationships are discussed using processing history, microscopy (light and transmission), and property data.

  3. Magnetostructural transition behavior in Fe-doped Heusler Mn-Ni-In ribbon materials

    NASA Astrophysics Data System (ADS)

    Li, Hongwei; Fang, Yue; Feng, Shutong; Zhai, Qijie; Luo, Zhiping; Zheng, Hongxing

    2016-11-01

    In the present work, we investigated magnetostructural transition behavior in Mn-rich Heusler Mn50-xFexNi41In9 (x=0, 1, 2, 3 at%) ribbon materials. Microstructural observations showed that substituting Mn with Fe in Mn50Ni41In9 led to striking grain refinement from ∼50 μm to 5-10 μm, and formation of a secondary phase when Fe content was increased up to 2 at%. Differential scanning calorimetric and thermomagnetic measurements indicated that a paramagnetic→ferromagnetic transition in austenite occurred first, followed with a weak-magnetic martensitic transition upon cooling for the Mn50-xFexNi41In9 (x=0, 1, 2). In case of Mn47Fe3Ni41In9, the martensitic transformation happened between paramagnetic austenite and weak-magnetic martensite, without the presence of the magnetic transition in austenite. The effective refrigeration capacity of Mn49Fe1Ni41In9 reached 137.1 J kg-1 under a magnetic field change of 30 kOe.

  4. Gender-role attitudes and behavior across the transition to parenthood.

    PubMed

    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. Gender-role attitudes, work and family identity salience, and division of household labor were measured for 205 first-time and 198 experienced mothers and fathers across 4 time points from 5 months pregnant to 12 months postpartum. Multilevel latent growth curve analysis was used to analyze the data. In general, parents became more traditional in their gender-role attitudes and behavior following the birth of a child, women changed more than men, and first-time parents changed more than experienced parents. Findings suggest that changes in gender-role attitudes and behavior following the birth of a child may be attributed to both the process of transitioning to parenthood for the first time and that of negotiating the demands of having a new baby in the family. (PsycINFO Database Record (c) 2009 APA, all rights reserved).

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

    PubMed Central

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

    2012-01-01

    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 limited in the representativeness of their samples. Thus, it remains unclear to what degree parents’ multiple relationship transitions have independent effects on children’s antisocial behavior. Analyses were conducted using data on 8,652 6–9-year-old, 6,911 10–13-year-old, and 6,495 14-17-year-old offspring of a nationally representative sample of U.S. women. Cousin-comparisons were used in combination with statistical covariates to evaluate the associations between maternal relationship transitions and offspring antisocial behavior in childhood and adolescence. Cousin-comparisons suggested that associations between maternal relationship transitions and antisocial behavior in childhood and early adolescence are largely explained by confounding factors. In contrast, the associations between maternal relationship transitions and offspring delinquency in late adolescence were robust to measured and unmeasured confounds. The present findings suggest that interventions aimed at reducing exposure to parental relationship transitions or addressing the psychosocial consequences of exposure to parental relationship transitions could reduce risk for offspring delinquency in late adolescence. PMID:22829173

  6. Effects of multiple maternal relationship transitions on offspring antisocial behavior in childhood and adolescence: a cousin-comparison analysis.

    PubMed

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

    2013-02-01

    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 limited in the representativeness of their samples. Thus, it remains unclear to what degree parents' multiple relationship transitions have independent effects on children's antisocial behavior. Analyses were conducted using data on 8,652 6-9-year-old, 6,911 10-13-year-old, and 6,495 14-17-year-old offspring of a nationally representative sample of U.S. women. Cousin-comparisons were used in combination with statistical covariates to evaluate the associations between maternal relationship transitions and offspring antisocial behavior in childhood and adolescence. Cousin-comparisons suggested that associations between maternal relationship transitions and antisocial behavior in childhood and early adolescence are largely explained by confounding factors. In contrast, the associations between maternal relationship transitions and offspring delinquency in late adolescence were robust to measured and unmeasured confounds. The present findings suggest that interventions aimed at reducing exposure to parental relationship transitions or addressing the psychosocial consequences of exposure to parental relationship transitions could reduce risk for offspring delinquency in late adolescence.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. The role of goals and alcohol behavior during the transition out of college.

    PubMed

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

    2015-03-01

    Personal goals are desired outcomes that guide behavior (Palfai, Ralston, & Wright, 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 1 year later (T4). Results of multinomial logistic regression revealed that greater achievement goals were predictive of college graduation (vs. 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 (vs. 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.

  15. Vagal neural crest cell migratory behavior: a transition between the cranial and trunk crest.

    PubMed

    Kuo, Bryan R; Erickson, Carol A

    2011-09-01

    Migration and differentiation of cranial neural crest cells are largely controlled by environmental cues, whereas pathfinding at the trunk level is dictated by cell-autonomous molecular changes owing to early specification of the premigratory crest. Here, we investigated the migration and patterning of vagal neural crest cells. We show that (1) vagal neural crest cells exhibit some developmental bias, and (2) they take separate pathways to the heart and to the gut. Together these observations suggest that prior specification dictates initial pathway choice. However, when we challenged the vagal neural crest cells with different migratory environments, we observed that the behavior of the anterior vagal neural crest cells (somite-level 1-3) exhibit considerable migratory plasticity, whereas the posterior vagal neural crest cells (somite-level 5-7) are more restricted in their behavior. We conclude that the vagal neural crest is a transitional population that has evolved between the head and the trunk.

  16. The Influence of Periodically Non-Stationary Afflux on Transition Behavior of Compressor Grids

    NASA Astrophysics Data System (ADS)

    Teusch, Reinhold

    2001-01-01

    The primary goal of this study is to obtain a deeper look into the physical occurrences within the shovel border layer. The author accomplishes this effort through a detailed examination of non-stationary flow behavior of compressor shovels with Controlled Diffusion Airfoil (CDA)-profiling under the influence of after-running depressions of current salient shovel rows. In addition to the checking of the precision of stationary and non-stationary calculatory processes, criteria are defined for the layout of modern compression shovels under the rubrick of rotor/stator interaction. An overview of the literature is then given regarding both the basic principles of non-stationary transition behavior under the influence of after-running depressions as well as the most up-to-date scholarship on the problematics of the field discussed.

  17. 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…

  18. The Influence of Role Status on Risky Sexual Behavior among African Americans during the Transition to Adulthood

    ERIC Educational Resources Information Center

    Kogan, Steven M.; Brody, Gene H.; Gibbons, Frederick X.; Murry, Velma McBride; Cutrona, Carolyn E.; Simons, Ronald L.; Wingood, Gina; DiClemente, Ralph

    2008-01-01

    Little research has examined the links between role status changes during the transition to adulthood and sexual behaviors that place African Americans at risk for sexually transmitted infections. Moreover, the mediating processes that explain these links, or protective factors that may buffer young adults from risky sexual behavior, are unknown.…

  19. 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…

  20. 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.

  1. 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

  2. Influence of plasticizer content on the transition of electromechanical behavior of PVC gel actuator.

    PubMed

    Ali, Mohammad; Ueki, Takamitsu; Tsurumi, Daijiro; Hirai, Toshihiro

    2011-06-21

    The actuation performance of plasticized poly(vinyl chloride) (PVC) gel actuators in an electric field depends on their chemical composition and electrical and mechanical properties. The influence of plasticizer (dibutyl adipate) content on electromechanical behavior of PVC gels was investigated by impedance spectroscopy and space charge measurement. By plasticizing the PVC, the dielectric constant and space charge density of PVC gel were drastically increased at 1:2 w/w ratio of PVC to plasticizer. To apply the results obtained from the impedance spectroscopy and space charge measurement, electrostatic adhesive forces generated between the PVC gel and the anode were measured. The electrostatic adhesive force at the anode was also dramatically increased at the same plasticizer content. All of the results indicated a transition of electromechanical behavior of PVC gel in the electric field, which was considered to originate from the orientation of polarized plasticizer molecules and dipole rotation of PVC chains. By using the electrostatic adhesive force of PVC gel derived from the electromechanical transition, a new electroactive actuator can be developed for novel applications.

  3. Flow transition behavior between the film flow and rivulet flow on an inclined wall

    NASA Astrophysics Data System (ADS)

    Iso, Yoshiyuki; Chen, Xi

    2010-11-01

    Gas-liquid two-phase flows on the wall like liquid film flows, which are the so-called wetted wall flows, are observed in many industrial processes such as absorption, desorption, distillation and others. For the optimum design of packed columns widely used in those kind of processes, the accurate predictions of the wetted wall flow behavior in packing elements are important, especially in order to enhance the mass transfer between the gas and liquid and to prevent flooding and channeling of the liquid flow. The present study focused on the effects of the change of liquid flow rate and the wall surface texture treatments on the characteristics of wetted wall flows which have the drastic flow transition between the film flow and rivulet flow. In this paper, gas-liquid two-phase flow simulation by using the volume of fluid (VOF) model is applied into wetted wall flows. Firstly, present results showed that the hysteresis of the flow transition between the film flow and rivulet flow arose against the increasing or decreasing stages of the liquid flow rate. It was supposed that this transition phenomenon depends on the history of flow pattern as the change of curvature of interphase surface which leads to the surface tension. Secondary, the present simulations showed that surface texture treatments added on the wall can improve the prevention of liquid channeling and can increase the wetted area.

  4. 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

    2016-11-01

    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.

  5. 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.

  6. Phase transitions and multicritical behavior in the Ising model with dipolar interactions.

    PubMed

    Bab, M A; Horowitz, C M; Rubio Puzzo, M L; Saracco, G P

    2016-10-01

    In this work, the phase diagram of the ferromagnetic Ising model with dipole interactions is revisited with the aim of determining the nature of the phase transition between stripe-ordered phases with width n (h_{n}) and tetragonal liquid (TL) phases. Extensive Monte Carlo simulations are performed in order to study the short-time dynamic behavior of the observables for selected values of the ratio between the ferromagnetic exchange and dipolar constants δ. The obtained results indicate that the h_{1}-TL phase transition line is continuous up to δ=1.2585, while for the h_{2}-TL line a weak first-order character is found in the interval 1.2585≤δ≤1.36 and becomes continuous for 1.37≤δ≤1.9. This result suggests the existence of a tricritical point close to δ=1.37. When it is appropriate, the complete set of critical exponents is obtained, and in all the studied cases they depend on δ but do not belong to the Ising universality class. Furthermore, short-time dynamic studies reveal that at the point where the mentioned lines meet the h_{1}-h_{2} line, i.e., at δ=1.2585, the critical phase corresponding to the h_{1}-TL transition coexists with the h_{2} phase.

  7. 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.

  8. Interlocking Feedback Loops Govern the Dynamic Behavior of the Floral Transition in Arabidopsis[W][OA

    PubMed Central

    Jaeger, Katja E.; Pullen, Nick; Lamzin, Sergey; Morris, Richard J.; Wigge, Philip A.

    2013-01-01

    During flowering, primordia on the flanks of the shoot apical meristem are specified to form flowers instead of leaves. Like many plants, Arabidopsis thaliana integrates environmental and endogenous signals to control the timing of reproduction. To study the underlying regulatory logic of the floral transition, we used a combination of modeling and experiments to define a core gene regulatory network. We show that FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1) act through FD and FD PARALOG to regulate the transition. The major floral meristem identity gene LEAFY (LFY) directly activates FD, creating a positive feedback loop. This network predicts flowering behavior for different genotypes and displays key properties of the floral transition, such as signal integration and irreversibility. Furthermore, modeling suggests that the control of TFL1 is important to flexibly counterbalance incoming FT signals, allowing a pool of undifferentiated cells to be maintained despite strong differentiation signals in nearby cells. This regulatory system requires TFL1 expression to rise in proportion to the strength of the floral inductive signal. In this network, low initial levels of LFY or TFL1 expression are sufficient to tip the system into either a stable flowering or vegetative state upon floral induction. PMID:23543784

  9. The Nonequilibrium Phase and Glass Transition Behavior of β-Lactoglobulin

    PubMed Central

    Parker, Roger; Noel, Timothy R.; Brownsey, Geoffrey J.; Laos, Katrin; Ring, Stephen G.

    2005-01-01

    Concentrated solutions of bovine β-lactoglobulin were studied using osmotic stress and rheological techniques. At pH 6.0 and 8.0, the osmotic pressure was largely independent of NaCl concentration and could be described by a hard sphere equation of state. At pH 5.1, close to the isoelectric point, the osmotic pressure was lower at the lower NaCl concentrations (0 mM, 100 mM) and was fitted by an adhesive hard sphere model. Liquid-liquid phase separation was observed at pH 5.1 at ionic strengths of 13 mM and below. Comparison of the liquid-liquid and literature solid-liquid coexistence curves showed these solutions to be supersaturated and the phase separation to be nonequilibrium in nature. In steady shear, the zero shear viscosity of concentrated solutions at pH 5.1 was observed at shear rates above 50 s−1. With increasing concentration, the solution viscosity showed a progressive increase, a behavior interpreted as the approach to a colloidlike glass transition at ∼60% w/w. In oscillatory shear experiments, the storage modulus crossed the loss modulus at concentrations of 54% w/w, an indication of the approaching glass transition. Comparison of the viscous behavior with predictions from the Krieger-Dougherty equation indicates the hydrodynamic size of the protein decreases with increasing concentration, resulting in a slower approach to the glass transition than a hard sphere system. PMID:15923230

  10. 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.

  11. Universal behavior of the osmotically compressed cell and its analogy to the colloidal glass transition.

    PubMed

    Zhou, E H; Trepat, X; Park, C Y; Lenormand, G; Oliver, M N; Mijailovich, S M; Hardin, C; Weitz, D A; Butler, J P; Fredberg, J J

    2009-06-30

    Mechanical robustness of the cell under different modes of stress and deformation is essential to its survival and function. Under tension, mechanical rigidity is provided by the cytoskeletal network; with increasing stress, this network stiffens, providing increased resistance to deformation. However, a cell must also resist compression, which will inevitably occur whenever cell volume is decreased during such biologically important processes as anhydrobiosis and apoptosis. Under compression, individual filaments can buckle, thereby reducing the stiffness and weakening the cytoskeletal network. However, the intracellular space is crowded with macromolecules and organelles that can resist compression. A simple picture describing their behavior is that of colloidal particles; colloids exhibit a sharp increase in viscosity with increasing volume fraction, ultimately undergoing a glass transition and becoming a solid. We investigate the consequences of these 2 competing effects and show that as a cell is compressed by hyperosmotic stress it becomes progressively more rigid. Although this stiffening behavior depends somewhat on cell type, starting conditions, molecular motors, and cytoskeletal contributions, its dependence on solid volume fraction is exponential in every instance. This universal behavior suggests that compression-induced weakening of the network is overwhelmed by crowding-induced stiffening of the cytoplasm. We also show that compression dramatically slows intracellular relaxation processes. The increase in stiffness, combined with the slowing of relaxation processes, is reminiscent of a glass transition of colloidal suspensions, but only when comprised of deformable particles. Our work provides a means to probe the physical nature of the cytoplasm under compression, and leads to results that are universal across cell type.

  12. Modeling the glass transition of amorphous networks for shape-memory behavior

    NASA Astrophysics Data System (ADS)

    Xiao, Rui; Choi, Jinwoo; Lakhera, Nishant; Yakacki, Christopher M.; Frick, Carl P.; Nguyen, Thao D.

    2013-07-01

    In this paper, a thermomechanical constitutive model was developed for the time-dependent behaviors of the glass transition of amorphous networks. The model used multiple discrete relaxation processes to describe the distribution of relaxation times for stress relaxation, structural relaxation, and stress-activated viscous flow. A non-equilibrium thermodynamic framework based on the fictive temperature was introduced to demonstrate the thermodynamic consistency of the constitutive theory. Experimental and theoretical methods were developed to determine the parameters describing the distribution of stress and structural relaxation times and the dependence of the relaxation times on temperature, structure, and driving stress. The model was applied to study the effects of deformation temperatures and physical aging on the shape-memory behavior of amorphous networks. The model was able to reproduce important features of the partially constrained recovery response observed in experiments. Specifically, the model demonstrated a strain-recovery overshoot for cases programmed below Tg and subjected to a constant mechanical load. This phenomenon was not observed for materials programmed above Tg. Physical aging, in which the material was annealed for an extended period of time below Tg, shifted the activation of strain recovery to higher temperatures and increased significantly the initial recovery rate. For fixed-strain recovery, the model showed a larger overshoot in the stress response for cases programmed below Tg, which was consistent with previous experimental observations. Altogether, this work demonstrates how an understanding of the time-dependent behaviors of the glass transition can be used to tailor the temperature and deformation history of the shape-memory programming process to achieve more complex shape recovery pathways, faster recovery responses, and larger activation stresses.

  13. Observation of the Quantum Anomalous Hall Insulator to Anderson Insulator Quantum Phase Transition and its Scaling Behavior

    NASA Astrophysics Data System (ADS)

    Chang, Cui-Zu; Zhao, Weiwei; Li, Jian; Jain, J. K.; Liu, Chaoxing; Moodera, Jagadeesh S.; Chan, Moses H. W.

    2016-09-01

    Fundamental insight into the nature of the quantum phase transition from a superconductor to an insulator in two dimensions, or from one plateau to the next or to an insulator in the quantum Hall effect, has been revealed through the study of its scaling behavior. Here, we report on the experimental observation of a quantum phase transition from a quantum-anomalous-Hall insulator to an Anderson insulator in a magnetic topological insulator by tuning the chemical potential. Our experiment demonstrates the existence of scaling behavior from which we extract the critical exponent for this quantum phase transition. We expect that our work will motivate much further investigation of many properties of quantum phase transition in this new context.

  14. Transitions in latent classes of sexual risk behavior among young injection drug users following HIV prevention intervention.

    PubMed

    Mackesy-Amiti, Mary Ellen; Ouellet, Lawrence J; Finnegan, Lorna; Hagan, Holly; Golub, Elizabeth; Latka, Mary; Wagner, Karla; Garfein, Richard S

    2014-03-01

    We analyzed data from a large randomized HIV/HCV prevention intervention trial with young injection drug users (IDUs). Using categorical latent variable analysis, we identified distinct classes of sexual behavior for men and women. We conducted a latent transition analysis to test the effect of the intervention on transitions from higher to lower risk classes. Men who were in a high-risk class at baseline who received the intervention were 86 % more likely to be in a low-risk class at follow-up compared to those in the control group (p = 0.025). High-risk intervention participants were significantly more likely to transition to the class characterized by unprotected sex with a main partner only, while low-risk intervention participants were significantly less likely to transition to that class. No intervention effect was detected on the sexual risk behavior of women, or of men who at baseline were having unprotected sex with a main partner only.

  15. 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

  16. 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.

  17. Transition from unsteady to steady jet behavior in pulsing explosive eruptions

    NASA Astrophysics Data System (ADS)

    Reisner, J.; Valentine, G. A.

    2006-12-01

    Field studies of deposits (Paricutin, Lathrop Wells) associated with scoria cone volcanoes and observations of recent eruptions (e.g., Etna 2001) show that explosive basaltic eruptions can have significant sustained columns that produce fallout deposits that blanket hundreds of square kilometers. Such eruptions also typically have phases characterized by discrete explosions (commonly referred to as "Strombolian," after the type location for such activity), but tephra dispersal mainly occurs during periods of sustained eruption columns (so-called "violent Strombolian"). Transitions between Strombolian and violent Strombolian behavior depend, among many other factors, upon the frequency of explosions. Valentine et al. (2005, Geology, v. 33, 629-632) hypothesized that if explosion frequency increases to a value that is similar to or greater than the characteristic roll-over frequency of large eddies as the eruptive mixture exits the vent, then flow pulses will be swamped and mixed by turbulence such that the flow will effectively behave as a steady eruption column. We present results of numerical experiments that allow quantification of the explosion frequency below which each explosion maintains its separate integrity, and above which the "signal" of each explosion is mixed within one or two vent radii downstream from the vent, therefore producing an effectively steady jet (in the sense of the mean flow). Between these two end-members is a regime of behavior where the explosion pulses do not blend together until some height in the jet that is related to the downstream growth of eddy length scales. In such cases, an effectively steady jet is still obtained, but at some distance above the vent. This transitional regime is one way to define the boundary between true Strombolian and violent Strombolian eruptive behaviors, and in turn can help define the role of bubble dynamics in the rising magma column on eruptive behavior. If it is agreed that the term "Strombolian

  18. Particular behavior of the adenine and guanine ring-breathing modes upon the DNA conformational transitions.

    PubMed

    Ghomi, M; Letellier, R; Taillandier, E

    1988-06-01

    Harmonic dynamics calculations performed on the deoxyguanosine (dG) and deoxyadenosine (dA) residues, based on a reliable force field, show that the breathing motions of both guanine and adenine residues are involved in two different vibration modes (750-500 cm-1 spectral region). The calculated results reveal a strong coupling of these modes with the sugar pucker motions. This effect has been verified for the dG residue by the Raman spectra of polyd(G-C). As far as the dA residue is concerned, the particular behavior of the adenine residue breathing mode predicted by these calculations, has been confirmed by Raman spectra of polyd(A-T) undergoing a B----Z conformational transition.

  19. Reproductive behavior during the pre-transitional period: evidence from rural Bologna.

    PubMed

    Rettaroli, Rosella; Scalone, Francesco

    2012-01-01

    A longitudinal, micro-level study of the effect of socioeconomic transformations on fertility mechanisms in the rural hinterland of Bologna between 1818 and 1900 (the beginning of the demographic transition) demonstrates that the premature death of a last-born child reduces the interval between two consecutive childbirths. Thus does it confirm the importance of breast-feeding in determining birth spacing. Women living in complex sharecropping households experienced a significantly higher risk of childbirth than did women in families headed by daily wage earners. In addition, the reproductive behavior of sharecroppers seemed to be substantially invariant to short-term ºuctuations in prices, whereas the laborers' group experienced a negative price effect. Both descriptive and multivariate analyses indicate a slight and gradual decrease in fertility levels during the period in question.

  20. 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.

  1. Effect of degree of branching on the thermoresponsive phase transition behaviors of hyperbranched multiarm copolymers: comparison of systems with LCST transition based on coil-to-globule transition or hydrophilic-hydrophobic balance.

    PubMed

    Cheng, Haixing; Xie, Shaoai; Zhou, Yongfeng; Huang, Wei; Yan, Deyue; Yang, Jintian; Ji, Bing

    2010-05-20

    This work reports for the first time the influence of degree of branching (DB) on the thermoresponsive phase transition behaviors of hyperbranched multiarm copolymers. Two series of PEHO-star-PEOs (series A) and PEHO-star-PDMAEMAs (series B) with the hydrophobic DB-variable PEHO core and different kinds of linear arms (PEO arms or PDMAEMA arms) were synthesized. It was found these two series demonstrate thermoresponsive phase transitions with the lower critical solution temperature (LCST). The studies on the LCST transition mechanism indicate that series A belongs to the thermoresponsive polymer system with LCST transition based on hydrophilic-hydrophobic balance, while series B belongs to the thermoresponsive polymer system with LCST transition based on coil-to-globule transition. Correspondingly, there is a big difference in the DB dependence of LCST transition between series A and series B. For series A, the LCST phase transition is highly dependent on the DB of the PEHO core in copolymers. For series B, the LCST phase transition is independent of the DB but dependent on solution pH. Such results may extend the knowledge on the structure-activity relationship of thermoresponsive highly branched polymers.

  2. Behavior of transition state regulator AbrB in batch cultures of Bacillus thuringiensis.

    PubMed

    Lozano Goné, Astrid Magdalena; Dinorín Téllez Girón, Jabel; Jiménez Montejo, Fabiola Eloisa; Hidalgo-Lara, María Eugenia; López Y López, Víctor Eric

    2014-11-01

    The transition state regulator AbrB is involved in the regulation of various cellular functions such as exponential growth, transition state and sporulation onset, due to its ability to activate, suppress or prevent the inappropriate expression of various genes in Bacillus subtilis. In order to understand combined behavior in batch cultures of AbrB in Bacillus thuringiensis, we cloned and expressed the abrB gene of B. thuringiensis in Escherichia coli. The deduced sequence of abrB gene coded for a protein consisting of 94 amino acids with ~10.5 kDa protein that shares 100 and 85 % identity with those from Bacillus cereus and Bacillus subtilis. The recombinant AbrB protein was used as antigen for the production of rabbit polyclonal antibodies anti-AbrB. Two media cultures with carbon: nitrogen ratios of 7.0, but varying access to nutrients were tested in batch cultures. In the case of both media, AbrB accumulation occurred from the beginning of the process and was maximal during early exponential growth. Thereafter, the level of AbrB decreased when there were no nutrient limitations and coincided with a decreased value in specific growth rate, although growth continued exponentially. Nonetheless, sporulation onset was determined 3 h and 4 h later, in media with highly metabolizable nutrients clean medium and Farrera medium, respectively. Hence, the maximal level of AbrB accumulation in batch cultures of B. thuringiensis is not influenced by limiting nutrients; however, nutrient availability affects the required time lapse for transition state regulator accumulation.

  3. Tunable electronic behavior in 3d transition metal doped 2H-WSe2

    NASA Astrophysics Data System (ADS)

    Liu, Shuai; Huang, Songlei; Li, Hongping; Zhang, Quan; Li, Changsheng; Liu, Xiaojuan; Meng, Jian; Tian, Yi

    2017-03-01

    Structural and electronic properties of 3d transition metal Sc, Ti, Cr and Mn incorporated 2H-WSe2 have been systematically investigated by first-principles calculations based on density functional theory. The calculated formation energies reveal that all the doped systems are thermodynamically more favorable under Se-rich condition than W-rich condition. The geometry structures almost hold that of the pristine 2H-WSe2 albeit with slight lattice distortion. More importantly, the electronic properties have been significantly tuned by the dopants, i.e., metal and semimetal behavior has been found in Sc, Ti and Mn-doped 2H-WSe2, respectively, semiconducting nature with narrowed band gap is expected in Cr-doped case, just as that of the pristine 2H-WSe2. In particular, magnetic character is realized by incorporation of Mn impurity with a total magnetic moment of 0.96 μB. Our results suggest chemical doping is an effective way to precisely tailor the electronic structure of layered transition metal dichalcogenide 2H-WSe2 for target technological applications.

  4. Ferromagnetic domain behavior and phase transition in bilayer manganites investigated at the nanoscale

    DOE PAGES

    Phatak, C.; Petford-Long, A. K.; Zheng, H.; ...

    2015-12-14

    Understanding the underlying mechanism and phenomenology of colossal magnetoresistance in manganites has largely focused on atomic and nanoscale physics such as double exchange, phase separation, and charge order. Here in this article, we consider a more macroscopic view of manganite materials physics, reporting on the ferromagnetic domain behavior in a bilayer manganite sample with a nominal composition of La2-2xSr1+2xMn2O7 with x = 0:38, studied using in-situ Lorentz transmission electron microscopy. The role of magnetocrystalline anisotropy on the structure of domain walls was elucidated. On cooling, magnetic domain contrast was seen to appear first at the Curie temperature within the amore » - b plane. With further reduction in temperature, the change in area fraction of magnetic domains was used to estimate the critical exponent describing the ferromagntic phase transition. Lastly, the ferromagnetic phase transition was accompanied by a distinctive nanoscale granular contrast close to the Curie temperature, which we infer to be related to the presence of ferromagnetic nanoclusters in a paramagnetic matrix, which has not yet been reported in bilayer manganites.« less

  5. Ferromagnetic domain behavior and phase transition in bilayer manganites investigated at the nanoscale

    SciTech Connect

    Phatak, C.; Petford-Long, A. K.; Zheng, H.; Mitchell, J. F.; Rosenkranz, S.; Norman, M. R.

    2015-12-14

    Understanding the underlying mechanism and phenomenology of colossal magnetoresistance in manganites has largely focused on atomic and nanoscale physics such as double exchange, phase separation, and charge order. Here in this article, we consider a more macroscopic view of manganite materials physics, reporting on the ferromagnetic domain behavior in a bilayer manganite sample with a nominal composition of La2-2xSr1+2xMn2O7 with x = 0:38, studied using in-situ Lorentz transmission electron microscopy. The role of magnetocrystalline anisotropy on the structure of domain walls was elucidated. On cooling, magnetic domain contrast was seen to appear first at the Curie temperature within the a - b plane. With further reduction in temperature, the change in area fraction of magnetic domains was used to estimate the critical exponent describing the ferromagntic phase transition. Lastly, the ferromagnetic phase transition was accompanied by a distinctive nanoscale granular contrast close to the Curie temperature, which we infer to be related to the presence of ferromagnetic nanoclusters in a paramagnetic matrix, which has not yet been reported in bilayer manganites.

  6. 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

  7. 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).

  8. Universality and critical behavior of the dynamical Mott transition in a system with long-range interactions

    PubMed Central

    Rademaker, Louk; Vinokur, Valerii M.; Galda, Alexey

    2017-01-01

    We study numerically the voltage-induced breakdown of a Mott insulating phase in a system of charged classical particles with long-range interactions. At half-filling on a square lattice this system exhibits Mott localization in the form of a checkerboard pattern. We find universal scaling behavior of the current at the dynamic Mott insulator-metal transition and calculate scaling exponents corresponding to the transition. Our results are in agreement, up to a difference in universality class, with recent experimental evidence of a dynamic Mott transition in a system of interacting superconducting vortices. PMID:28300065

  9. 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.

  10. 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

  11. Discharge Synchrony during the Transition of Behavioral Goal Representations Encoded by Discharge Rates of Prefrontal Neurons

    PubMed Central

    Mushiake, Hajime; Saito, Naohiro; Aihara, Kazuyuki; Yano, Masafumi; Tanji, Jun

    2008-01-01

    To investigate the temporal relationship between synchrony in the discharge of neuron pairs and modulation of the discharge rate, we recorded the neuronal activity of the lateral prefrontal cortex of monkeys performing a behavioral task that required them to plan an immediate goal of action to attain a final goal. Information about the final goal was retrieved via visual instruction signals, whereas information about the immediate goal was generated internally. The synchrony of neuron pair discharges was analyzed separately from changes in the firing rate of individual neurons during a preparatory period. We focused on neuron pairs that exhibited a representation of the final goal followed by a representation of the immediate goal at a later stage. We found that changes in synchrony and discharge rates appeared to be complementary at different phases of the behavioral task. Synchrony was maximized during a specific phase in the preparatory period corresponding to a transitional stage when the neuronal activity representing the final goal was replaced with that representing the immediate goal. We hypothesize that the transient increase in discharge synchrony is an indication of a process that facilitates dynamic changes in the prefrontal neural circuits in order to undergo profound state changes. PMID:18252744

  12. 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.

  13. 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.

  14. 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

  15. Nonstationary Stochastic Dynamics Underlie Spontaneous Transitions between Active and Inactive Behavioral States

    PubMed Central

    Jun, James J.; Longtin, André

    2017-01-01

    Abstract The neural basis of spontaneous movement generation is a fascinating open question. Long-term monitoring of fish, swimming freely in a constant sensory environment, has revealed a sequence of behavioral states that alternate randomly and spontaneously between periods of activity and inactivity. We show that key dynamical features of this sequence are captured by a 1-D diffusion process evolving in a nonlinear double well energy landscape, in which a slow variable modulates the relative depth of the wells. This combination of stochasticity, nonlinearity, and nonstationary forcing correctly captures the vastly different timescales of fluctuations observed in the data (∼1 to ∼1000 s), and yields long-tailed residence time distributions (RTDs) also consistent with the data. In fact, our model provides a simple mechanism for the emergence of long-tailed distributions in spontaneous animal behavior. We interpret the stochastic variable of this dynamical model as a decision-like variable that, upon reaching a threshold, triggers the transition between states. Our main finding is thus the identification of a threshold crossing process as the mechanism governing spontaneous movement initiation and termination, and to infer the presence of underlying nonstationary agents. Another important outcome of our work is a dimensionality reduction scheme that allows similar segments of data to be grouped together. This is done by first extracting geometrical features in the dataset and then applying principal component analysis over the feature space. Our study is novel in its ability to model nonstationary behavioral data over a wide range of timescales. PMID:28374017

  16. 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.

  17. 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).

  18. Influences of structural mismatch on morphology, phase transition temperature, segmental dynamics and color-transition behaviors of polydiacetylene vesicles.

    PubMed

    Pattanatornchai, Thanutpon; Charoenthai, Nipaphat; Traiphol, Rakchart

    2014-10-15

    In this contribution, we report a systematic study of polydiacetylene (PDA) vesicles fabricated by mixing two types of monomers, 10,12-tricosadiynoic acid (TCDA) and 10,12-pentacosadiynoic acid (PCDA). These diacetylene (DA) monomers constitute the same head group but different alkyl chain length, which in turn causes structural mismatch within the PDA layers. The PCDA:TCDA ratios are 100, 75, 50, 25 and 0mol%. Morphologies and properties of these PDA vesicles are explored by utilizing laser light scattering, transmission electron microscopy, differential scanning calorimetry, temperature-dependent nuclear magnetic resonance spectroscopy (NMR) and spin-lattice relaxation time (T1) measurements. An increase in DA mole ratio to 50mol% leads to significant increase in particle size. The mixed PDA vesicles also exhibit irregular shape with rather rough surface. The mismatch of alkyl side chain causes the drop of phase transition temperature. For the system of mixed poly(PCDA50:TCDA50), its transition temperature is lower than those of the pure PDAs. The NMR line shape analysis detects an abrupt change of proton signal adjacent to the PDA head group during the blue/red color-transition process. The T1 measurements also reveal different local environments of PDA alkyl side chains in the blue and red phases. The mismatch of PDA side chains causes significant drop of the color-transition temperature.

  19. 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…

  20. 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…

  1. 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.…

  2. Origin of exotic ferromagnetic behavior in exfoliated layered transition metal dichalcogenides MoS2 and WS2.

    PubMed

    Luxa, Jan; Jankovský, Ondřej; Sedmidubský, David; Medlín, Rostislav; Maryško, Miroslav; Pumera, Martin; Sofer, Zdeněk

    2016-01-28

    Bulk layered transition metal dichalcogenides (TMDs) show diamagnetic properties. When exfoliated, the materials' band gap increases and changes from an indirect band gap to a direct one. During the exfoliation, the TMDs may undergo a phase transition from 2H to 1T polymorph, which is likely electronically driven and accompanied by a metal-insulator transition. A significantly higher efficiency of the exfoliation was observed using sodium naphthalenide compared to butyllithium. Moreover we demonstrate that the exfoliation has a dramatic influence on the magnetic properties of two TMDs, MoS2 and WS2. These materials become partly ferromagnetic upon exfoliation, which is a highly unexpected behavior. Exotic ferromagnetism is generally observed on samples with a high degree of exfoliation, which indicates the association of this effect with defects formed on the edges of dichalcogenide sheets. Such an exotic ferromagnetic behavior, if properly understood and brought under material engineering control, shall open the door to new applications of these materials.

  3. Feeding behaviors of transition dairy cows fed glycerol as a replacement for corn.

    PubMed

    Carvalho, E R; Schmelz-Roberts, N S; White, H M; Wilcox, C S; Eicher, S D; Donkin, S S

    2012-12-01

    Feed sorting is a natural behavior of dairy cows that can result in inconsistencies in the nutritive value of a total mixed ration (TMR). The objective of this study was to determine the effects of replacing high-moisture corn with glycerol on feed sorting and the feed intake pattern of transition dairy cows. Multiparous Holstein cows (n=26) were paired by expected calving date, housed in individual tie stalls, and fed diets containing either glycerol or high-moisture corn once daily from d -28 to +56 relative to calving. Glycerol was included at 11.5 and 10.8% of the ration dry matter for the pre- and postpartum diets, respectively. The feed consumption pattern was determined by measuring TMR disappearance during the intervals from 0 to 4 h, 4 to 8 h, 8 to 12 h, and 12 to 24 h relative to feed delivery. Feed sorting was determined on d -16, -9, 9, 16, and 51 relative to calving at 4, 8, 12 and 24 h after feeding. The TMR particle size profile was determined at feed delivery and at 4, 8, 12, and 24 after feed delivery by using the Penn State Particle Separator (Nasco, Fort Atkinson, WI) to yield long (>19 mm), medium (<19 mm, >8 mm), short (<8 mm, >1.18 mm), and fine (<1.18 mm) particles. Overall feed intake did not differ between diets and was 14.7±0.4 and 20.2±0.5 kg/d for the pre- and postpartum intervals, respectively. During the prepartum period, glycerol decreased the amount of feed consumed during the first 4h after feed delivery (7.22 vs. 5.59±0.35 kg; control vs. glycerol, respectively) but increased feed consumed from 12 through 24 h after feed delivery (2.22 vs. 3.82±0.35 kg; control vs. glycerol, respectively). Similar effects on the feed consumption pattern were observed after calving. During the prepartum period, cows fed the control diet sorted against long particles, whereas cows fed glycerol did not sort against long particles (77.2 vs. 101.5±3.50% of expected intake for control vs. glycerol; significant treatment effect). The data indicate

  4. Environmental, behavioral, and psychological predictors of transit ridership: Evidence from a community intervention.

    PubMed

    Brown, Barbara B; Werner, Carol M; Smith, Ken R; Tribby, Calvin P; Miller, Harvey J; Jensen, Wyatt A; Tharp, Doug

    2016-06-01

    Understanding who takes advantage of new transit (public transportation) interventions is important for personal and environmental health. We examine transit ridership for residents living near a new light rail construction as part of "complete street," pedestrian-friendly improvements. Adult residents (n=536) completed surveys and wore accelerometer and GPS units that tracked ridership before and after new transit service started. Transit riders were more physically active. Those from environments rated as more walkable were likely to be continuing transit riders. Place attachment, but not perceived physical incivilities on the path to transit, was associated with those who continued to ride or became new riders of transit. This effect was mediated through pro-city attitudes, which emphasize how the new service makes residents eager to explore areas around transit. Thus, place attachment, along with physical and health conditions, may be important predictors and promoters of transit use.

  5. Simple models for heterogeneous catalysis: Phase transition-like behavior in nonequilibrium systems

    NASA Astrophysics Data System (ADS)

    Meakin, Paul; Scalapino, Douglas J.

    1987-07-01

    A simple model for heterogeneous catalysis, recently introduced by Ziff, Gulari, and Barshad (ZGB), has been explored using computer simulation. This is a nonequilibrium model which exhibits phase transition-like behavior. The only parameter in this model (Y) sets the ratio with which two reactive species (A and B2) are fed to the surface (lattice). On the square lattice, ZGB found a range of values of this parameter for which steady states with nonzero A and B concentrations occur. Outside of this range, the surface becomes completely covered with A or B sites. The range of Y values corresponding to steady state with nonzero A and B concentrations is bounded by two ``critical'' values Y1 and Y2. For values of Y close to but above Y1 we have obtained approximate values for the exponents which describe the dependence of the steady-state densities of A and B sites on (Y-Y1). These exponents both seem to have the same value independent of lattice details. We have extended the work of ZGB to the hexagonal lattice, one-dimensional lattice, and narrow strips. The results obtained for the hexagonal lattice are qualitatively similar to those obtained for the square lattice. For the 1D lattice and strips with a width of 2 lattice units, steady states with nonzero A and B site concentrations are not found. For widths of 3 or more lattice units, such steady states are found and the range of the relative probability parameter over which this behavior occurs grows steadily with increasing strip width. We have also obtained new results for the more simple C+D product reaction. Here C and D occupy single lattice sites and react immediately if they are nearest neighbors.

  6. 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.

  7. 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.

  8. Choice behavior in transition: development of preference for the higher probability of reinforcement.

    PubMed Central

    Bailey, J T; Mazur, J E

    1990-01-01

    Ten acquisition curves were obtained from each of 4 pigeons in a two-choice discrete-trial procedure. In each of these 10 conditions, the two response keys initially had equal probabilities of reinforcement, and subjects' choice responses were about equally divided between the two keys. Then the reinforcement probabilities were changed so that one key had a higher probability of reinforcement (the left key in half of the conditions and the right key in the other half), and in nearly every case the subjects developed a preference for this key. The rate of acquisition of preference for this key was faster when the ratio of the two reinforcement probabilities was higher. For instance, acquisition of preference was faster in conditions with reinforcement probabilities of .12 and .02 than in conditions with reinforcement probabilities of .40 and .30, even though the pairs of probabilities differed by .10 in both cases. These results were used to evaluate the predictions of some theories of transitional behavior in choice situations. A trial-by-trial analysis of individual responses and reinforcers suggested that reinforcement had both short-term and long-term effects on choice. The short-term effect was an increased probability of returning to the same key on the one or two trials following a reinforcer. The long-term effect was a gradual increase in the proportion of responses on the key with the higher probability of reinforcement, an increase that usually continued for several hundred trials. PMID:2341823

  9. Distributional behavior of diffusion coefficients obtained by single trajectories in annealed transit time model

    NASA Astrophysics Data System (ADS)

    Akimoto, Takuma; Yamamoto, Eiji

    2016-12-01

    Local diffusion coefficients in disordered systems such as spin glass systems and living cells are highly heterogeneous and may change over time. Such a time-dependent and spatially heterogeneous environment results in irreproducibility of single-particle-tracking measurements. Irreproducibility of time-averaged observables has been theoretically studied in the context of weak ergodicity breaking in stochastic processes. Here, we provide rigorous descriptions of equilibrium and non-equilibrium diffusion processes for the annealed transit time model, which is a heterogeneous diffusion model in living cells. We give analytical solutions for the mean square displacement (MSD) and the relative standard deviation of the time-averaged MSD for equilibrium and non-equilibrium situations. We find that the time-averaged MSD grows linearly with time and that the time-averaged diffusion coefficients are intrinsically random (irreproducible) even in the long-time measurements in non-equilibrium situations. Furthermore, the distribution of the time-averaged diffusion coefficients converges to a universal distribution in the sense that it does not depend on initial conditions. Our findings pave the way for a theoretical understanding of distributional behavior of the time-averaged diffusion coefficients in disordered systems.

  10. 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.

  11. 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…

  12. Self-Determination Perceptions and Behaviors of Diverse Students with LD During the Transition Planning Process

    ERIC Educational Resources Information Center

    Trainor, Audrey A.

    2005-01-01

    Transition models include components of student self-determination during transition planning meetings. Researchers acknowledge that cultural identity may influence both transition decisions and self-determination strategies. Yet the appropriateness of these approaches for culturally and linguistically diverse students with learning disabilities…

  13. 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.

  14. Observed Spectral Invariant Behavior of Zenith Radiance in the Transition Zone Between Cloud-Free and Cloudy Regions

    NASA Technical Reports Server (NTRS)

    Marshak, A.; Knyazikhin, Y.; Chiu, C.; Wiscombe, W.

    2010-01-01

    The Atmospheric Radiation Measurement Program's (ARM) new Shortwave Spectrometer (SWS) looks straight up and measures zenith radiance at 418 wavelengths between 350 and 2200 nm. Because of its 1-sec sampling resolution, the SWS provides a unique capability to study the transition zone between cloudy and clear sky areas. A surprising spectral invariant behavior is found between ratios of zenith radiance spectra during the transition from cloudy to cloud-free atmosphere. This behavior suggests that the spectral signature of the transition zone is a linear mixture between the two extremes (definitely cloudy and definitely clear). The weighting function of the linear mixture is found to be a wavelength-independent characteristic of the transition zone. It is shown that the transition zone spectrum is fully determined by this function and zenith radiance spectra of clear and cloudy regions. This new finding may help us to better understand and quantify such physical phenomena as humidification of aerosols in the relatively moist cloud environment and evaporation and activation of cloud droplets.

  15. 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.

  16. 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.

  17. Impact tests of the tungsten coated stainless steels prepared by using magnetron sputtering with ion beam mixing or electron beam alloying treatment

    NASA Astrophysics Data System (ADS)

    Zou, Yu; Zhan, Chang-Yong; Yang, Bin; Wu, Jian-Chun

    2013-05-01

    Tungsten films were deposited on stainless steel (SS) with ion beam mixing (IBM) or electron beam alloying (EBA) treatment. The ductile-brittle transition behaviors of the specimens were investigated by means of instrumented Charpy impact test at a series of temperature, and SEM was used to observe the morphology of the cross section. Impact tests show that different treatment methods with W films do not have much influence on crack initiation, while EBA treatment with W films can more effectively prevent crack propagation, namely improve the impact toughness of SS than using IBM treatment. The reason that caused this difference was discussed.

  18. Transition behavior of the discrete nonlinear Schrödinger equation.

    PubMed

    Rumpf, Benno

    2008-03-01

    Many nonlinear lattice systems exhibit high-amplitude localized structures, or discrete breathers. Such structures emerge in the discrete nonlinear Schrödinger equation when the energy is above a critical threshold. This paper studies the statistical mechanics at the transition and constructs the probability distribution in the regime where breathers emerge. The entropy as a function of the energy is nonanalytic at the transition. The entropy is independent of the energy in the regime of breathers above the transition.

  19. 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.

  20. Phase Behavior of Diblock Copolymer–Homopolymer Ternary Blends: Congruent First-Order Lamellar–Disorder Transition

    SciTech Connect

    Hickey, Robert J.; Gillard, Timothy M.; Irwin, Matthew T.; Morse, David C.; Lodge, Timothy P.; Bates, Frank S.

    2016-10-13

    We have established the existence of a line of congruent first-order lamellar-to-disorder (LAM–DIS) transitions when appropriate amounts of poly(cyclohexylethylene) (C) and poly(ethylene) (E) homopolymers are mixed with a corresponding compositionally symmetric CE diblock copolymer. The line of congruent transitions, or the congruent isopleth, terminates at the bicontinuous microemulsion (BμE) channel, and its trajectory appears to be influenced by the critical composition of the C/E binary homopolymer blend. Blends satisfying congruency undergo a direct LAM–DIS transition without passing through a two-phase region. We present complementary optical transmission, small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical spectroscopy (DMS) results that establish the phase behavior at constant copolymer volume fraction and varying C/E homopolymer volume ratios. Adjacent to the congruent composition at constant copolymer volume fraction, the lamellar and disordered phases are separated by two-phase coexistence windows, which converge, along with the line of congruent transitions, at an overall composition in the phase prism coincident with the BμE channel. Hexagonal and cubic (double gyroid) phases occur at higher diblock copolymer concentrations for asymmetric amounts of C and E homopolymers. These results establish a quantitative method for identifying the detailed phase behavior of ternary diblock copolymer–homopolymer blends, especially in the vicinity of the BμE.

  1. Family intervention effects on co-occurring early childhood behavioral and emotional problems: a latent transition analysis approach.

    PubMed

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

    2008-11-01

    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. Families with toddlers between age 2 and 3 were randomized either to the Family Check-Up (FCU) or to a nonintervention control group. The FCU's linked interventions were tailored to each family's needs. Assessments occurred at age 2, 3, and 4. The FCU followed age 2 and age 3 assessments. Latent class analyses were conducted on mother reports of behavior and emotional problems from age 2 to 4 to study transitions among the following four groups: (a) externalizing only, (b) internalizing only, (c) comorbid internalizing and externalizing, and (d) normative. LTA results revealed that participation in the FCU increased the likelihood of transitioning from either the comorbid or the internalizing class into the normative class by age 4. These results suggest family interventions in early childhood can potentially disrupt the early emergence of both emotional and behavioral problems.

  2. 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…

  3. 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.

  4. Origin of exotic ferromagnetic behavior in exfoliated layered transition metal dichalcogenides MoS2 and WS2

    NASA Astrophysics Data System (ADS)

    Luxa, Jan; Jankovský, Ondřej; Sedmidubský, David; Medlín, Rostislav; Maryško, Miroslav; Pumera, Martin; Sofer, Zdeněk

    2016-01-01

    Bulk layered transition metal dichalcogenides (TMDs) show diamagnetic properties. When exfoliated, the materials' band gap increases and changes from an indirect band gap to a direct one. During the exfoliation, the TMDs may undergo a phase transition from 2H to 1T polymorph, which is likely electronically driven and accompanied by a metal-insulator transition. A significantly higher efficiency of the exfoliation was observed using sodium naphthalenide compared to butyllithium. Moreover we demonstrate that the exfoliation has a dramatic influence on the magnetic properties of two TMDs, MoS2 and WS2. These materials become partly ferromagnetic upon exfoliation, which is a highly unexpected behavior. Exotic ferromagnetism is generally observed on samples with a high degree of exfoliation, which indicates the association of this effect with defects formed on the edges of dichalcogenide sheets. Such an exotic ferromagnetic behavior, if properly understood and brought under material engineering control, shall open the door to new applications of these materials.Bulk layered transition metal dichalcogenides (TMDs) show diamagnetic properties. When exfoliated, the materials' band gap increases and changes from an indirect band gap to a direct one. During the exfoliation, the TMDs may undergo a phase transition from 2H to 1T polymorph, which is likely electronically driven and accompanied by a metal-insulator transition. A significantly higher efficiency of the exfoliation was observed using sodium naphthalenide compared to butyllithium. Moreover we demonstrate that the exfoliation has a dramatic influence on the magnetic properties of two TMDs, MoS2 and WS2. These materials become partly ferromagnetic upon exfoliation, which is a highly unexpected behavior. Exotic ferromagnetism is generally observed on samples with a high degree of exfoliation, which indicates the association of this effect with defects formed on the edges of dichalcogenide sheets. Such an exotic

  5. Job Performance of Transition-Age Youth with Emotional and Behavioral Disorders.

    ERIC Educational Resources Information Center

    Carter, Erik W.; Wehby, Joseph H.

    2003-01-01

    A study examined the job performance of 47 adolescents with emotional and behavioral disorders. Significant discrepancies were found between supervisors' ratings of the importance of work behaviors and their ratings of adolescents' performance of the same behaviors. Adolescents' self-evaluations were significantly more favorable than the ratings…

  6. The Relationships between Mental Health Symptoms and Gambling Behavior in the Transition from Adolescence to Emerging Adulthood.

    PubMed

    Sagoe, Dominic; Pallesen, Ståle; Hanss, Daniel; Leino, Tony; Molde, Helge; Mentzoni, Rune A; Torsheim, Torbjørn

    2017-01-01

    There is a paucity of longitudinal investigations of gambling behavior in the transition from adolescence to emerging adulthood. We conducted a longitudinal investigation of the associations and patterns of change between mental health symptoms and gambling behavior. A representative sample of Norwegians completed questionnaires containing demographic, mental health, and gambling measures at age 17 (N = 2055), and at ages 18 (N = 1334) and 19 (N = 1277). Using latent class analysis, three classes of gambling behavior were identified: consistent non-gambling (71.1%), consistent non-risk gambling (23.8%), and risky-and-problem gambling (5.1%). Being male, showing higher physical and verbal aggression and having more symptoms of depression were associated with greater odds of belonging to the risky-and-problem gambling class at age 17. Overall, the risky-and-problem gambling class had the highest physical and verbal aggression, anxiety, and depression at 19 years. Our findings elucidate the reciprocal relationship between mental health and gambling behavior in the transition from adolescence to emerging adulthood, and the importance of recognizing these factors in designing targeted interventions.

  7. The Relationships between Mental Health Symptoms and Gambling Behavior in the Transition from Adolescence to Emerging Adulthood

    PubMed Central

    Sagoe, Dominic; Pallesen, Ståle; Hanss, Daniel; Leino, Tony; Molde, Helge; Mentzoni, Rune A.; Torsheim, Torbjørn

    2017-01-01

    There is a paucity of longitudinal investigations of gambling behavior in the transition from adolescence to emerging adulthood. We conducted a longitudinal investigation of the associations and patterns of change between mental health symptoms and gambling behavior. A representative sample of Norwegians completed questionnaires containing demographic, mental health, and gambling measures at age 17 (N = 2055), and at ages 18 (N = 1334) and 19 (N = 1277). Using latent class analysis, three classes of gambling behavior were identified: consistent non-gambling (71.1%), consistent non-risk gambling (23.8%), and risky-and-problem gambling (5.1%). Being male, showing higher physical and verbal aggression and having more symptoms of depression were associated with greater odds of belonging to the risky-and-problem gambling class at age 17. Overall, the risky-and-problem gambling class had the highest physical and verbal aggression, anxiety, and depression at 19 years. Our findings elucidate the reciprocal relationship between mental health and gambling behavior in the transition from adolescence to emerging adulthood, and the importance of recognizing these factors in designing targeted interventions.

  8. 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.

  9. Structures, Phase Transitions and Tricritical Behavior of the Hybrid Perovskite Methyl Ammonium Lead Iodide

    PubMed Central

    Whitfield, P. S.; Herron, N.; Guise, W. E.; Page, K.; Cheng, Y. Q.; Milas, I.; Crawford, M. K.

    2016-01-01

    We have examined the crystal structures and structural phase transitions of the deuterated, partially deuterated and hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI3) using time-of-flight neutron and synchrotron X-ray powder diffraction. Near 330 K the high temperature cubic phases transformed to a body-centered tetragonal phase. The variation of the order parameter Q for this transition scaled with temperature T as Q ∼ (Tc−T)β, where Tc is the critical temperature and the exponent β was close to ¼, as predicted for a tricritical phase transition. However, we also observed coexistence of the cubic and tetragonal phases over a range of temperature in all cases, demonstrating that the phase transition was in fact first-order, although still very close to tricritical. Upon cooling further, all the tetragonal phases transformed into a low temperature orthorhombic phase around 160 K, again via a first-order phase transition. Based upon these results, we discuss the impact of the structural phase transitions upon photovoltaic performance of MAPbI3 based solar cells. PMID:27767049

  10. Structures, Phase Transitions and Tricritical Behavior of the Hybrid Perovskite Methyl Ammonium Lead Iodide

    SciTech Connect

    Whitfield, P. S.; Herron, N.; Guise, W. E.; Page, K.; Cheng, Y. Q.; Milas, I.; Crawford, M. K.

    2016-10-21

    Here, we examine the crystal structures and structural phase transitions of the deuterated, partially deuterated and hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI3) using time-of-flight neutron and synchrotron X-ray powder diffraction. Near 330 K the high temperature cubic phases transformed to a body-centered tetragonal phase. The variation of the order parameter Q for this transition scaled with temperature T as Q (Tc-T) , where Tc is the critical temperature and the exponent was close to , as predicted for a tricritical phase transition. We also observed coexistence of the cubic and tetragonal phases over a range of temperature in all cases, demonstrating that the phase transition was in fact first-order, although still very close to tricritical. Upon cooling further, all the tetragonal phases transformed into a low temperature orthorhombic phase around 160 K, again via a first-order phase transition. Finally, based upon these results, we discuss the impact of the structural phase transitions upon photovoltaic performance of MAPbI3 based solar cells.

  11. Structures, Phase Transitions and Tricritical Behavior of the Hybrid Perovskite Methyl Ammonium Lead Iodide

    NASA Astrophysics Data System (ADS)

    Whitfield, P. S.; Herron, N.; Guise, W. E.; Page, K.; Cheng, Y. Q.; Milas, I.; Crawford, M. K.

    2016-10-01

    We have examined the crystal structures and structural phase transitions of the deuterated, partially deuterated and hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI3) using time-of-flight neutron and synchrotron X-ray powder diffraction. Near 330 K the high temperature cubic phases transformed to a body-centered tetragonal phase. The variation of the order parameter Q for this transition scaled with temperature T as Q ˜ (Tc-T)β, where Tc is the critical temperature and the exponent β was close to ¼, as predicted for a tricritical phase transition. However, we also observed coexistence of the cubic and tetragonal phases over a range of temperature in all cases, demonstrating that the phase transition was in fact first-order, although still very close to tricritical. Upon cooling further, all the tetragonal phases transformed into a low temperature orthorhombic phase around 160 K, again via a first-order phase transition. Based upon these results, we discuss the impact of the structural phase transitions upon photovoltaic performance of MAPbI3 based solar cells.

  12. Ferroelectric Transition and Curie—Weiss Behavior in Some Filled Tungsten Bronze Ceramics

    NASA Astrophysics Data System (ADS)

    Zhu, Xiao-Li; Chen, Xiang-Ming

    2014-01-01

    Ferroelectric transitions in filled tungsten bronze ceramics Sr4R2Ti4Nb6O30, Sr5RTi3Nb7O30 (R=La, Nb, Sm & Eu) and Ba4Nd2Ti4Nb6O30 are investigated with differential scanning calorimetry (DSC) and the Curie—Weiss law fitting to the dielectric constant. The magnitude of the Curie-Weiss constant C ~ 105 suggests displacement-type ferroelectric transition in the present compounds. The large ΔT difference between dielectric maximum temperature Tm and Curie—Weiss temperature T0) values indicate the difficult formation of ferroelectric domains or polar nanoregions in the present compounds and also the characteristics of the first order ferroelectric transition. Three categories are suggested for the ferroelectric transition in the above tungsten bronzes. The ferroelectric transition exhibits large thermal hysteresis. According to the DSC results, gradual recovery of the endothermic peak occurs after aging at temperature below the Curie point, indicating the gradual stability of the ferroelectric phase after cooling from the high-temperature para-electric phase. The relationship between the Curie—Weiss law fitting parameters and the nature of the ferroelectric transition is modified for the filled tungsten bronzes.

  13. Structures, Phase Transitions and Tricritical Behavior of the Hybrid Perovskite Methyl Ammonium Lead Iodide

    DOE PAGES

    Whitfield, P. S.; Herron, N.; Guise, W. E.; ...

    2016-10-21

    Here, we examine the crystal structures and structural phase transitions of the deuterated, partially deuterated and hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI3) using time-of-flight neutron and synchrotron X-ray powder diffraction. Near 330 K the high temperature cubic phases transformed to a body-centered tetragonal phase. The variation of the order parameter Q for this transition scaled with temperature T as Q (Tc-T) , where Tc is the critical temperature and the exponent was close to , as predicted for a tricritical phase transition. We also observed coexistence of the cubic and tetragonal phases over a range of temperaturemore » in all cases, demonstrating that the phase transition was in fact first-order, although still very close to tricritical. Upon cooling further, all the tetragonal phases transformed into a low temperature orthorhombic phase around 160 K, again via a first-order phase transition. Finally, based upon these results, we discuss the impact of the structural phase transitions upon photovoltaic performance of MAPbI3 based solar cells.« less

  14. The effect of pressure on the phase transition behavior of tridecane, pentadecane, and heptadecane: A Fourier transform infrared spectroscopy study

    NASA Astrophysics Data System (ADS)

    Yamashita, Motoi; Hirao, Atsushi; Kato, Minoru

    2011-04-01

    The effect of pressure on the phase transition behavior of tridecane (C13), pentadecane (C15), and heptadecane (C17) has been investigated up to 489, 220, and 387 MPa, respectively, using Fourier transform infrared spectroscopy at 25 °C. The transition between the high pressure ordered (HPO) and high pressure rotator (HPR) phases has been observed in the pressure ranges of 270-220, 106-95, and 152-181 MPa for C13, C15, and C17, respectively, and the transition between the HPR and liquid phases was observed in the pressure ranges of 171-112, 73-47, and 43-70 MPa for C13, C15, and C17, respectively. The P1+P3 band of the methylene rocking mode exhibits factor group splitting caused by intermolecular vibrational coupling. This was observed in both the HPO and HPR phases, while the P1+P3 band did not split in the liquid phase. The separation of the peaks in the P1+P3 band changed discontinuously at the HPO-HPR and HPR-liquid phase transitions, even though the separation is known to change continuously in the transition from the liquid to the high temperature rotator (HTR) phase. In the HPR phase, the ratio of the intensities of the higher and lower frequency components in the P1+P3 doublet is roughly unity independent of pressure, while it is known to be much less than unity in the HTR phase. The separation of the P1+P3 doublet in the HPR phase is found to be larger for longer alkanes. From the intensity ratio, a large proportion of alkane molecules is believed to participate in intermolecular vibrational coupling and possess herringbone-type short-range positional order in the HPR phase. Conversely, in the HTR phase only small proportion of alkane molecules participate in intermolecular vibrational coupling. From the pressure dependence of the separation of the doublet, intermolecular vibrational coupling and herringbone-type short-range positional order is considered to change discontinuously at the HPR-liquid phase transition, while they are reported to change

  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. Birefringence in the vicinity of the smectic-A to smectic-C phase transition: Crossover from X Y critical to tricritical behavior

    NASA Astrophysics Data System (ADS)

    Das, Malay Kumar; Chakraborty, Susanta; Dabrowski, Roman; Czerwiński, Michał

    2017-01-01

    High-resolution birefringence (Δ n ) measurements are carried out to probe the critical behavior at the smectic-A -smectic-C (Sm-A -Sm-C ) phase transition in a binary system. The critical behavior of this transition is explored with the aid of a differential quotient extracted from the Δ n values. The results obtained reveal that the Sm-A -Sm-C and nematic-smectic-A (N -Sm-A ) transitions exhibit nonuniversal behaviors with effective exponents lying between the tricritical and three-dimensional X Y values and follow two distinctly different curves with decreasing width of the Sm-A and N phases, respectively. The origin of such critical behavior is a unique feature for the respective phase transitions.

  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. Parental involvement protects against self-medication behaviors during the high school transition.

    PubMed

    Gottfredson, Nisha C; Hussong, Andrea M

    2011-12-01

    We examined how drinking patterns change as adolescents transition to high school, particularly as a function of parental involvement. Stress associated with the transition to high school may deplete psychological resources for coping with negative daily emotions in an environment when opportunities to drink are more common. A cohort of elevated-risk middle school students completed daily negative affect (sadness, worry, anger, and stress) and alcohol use assessments before and after the transition to high school, resulting in a measurement burst design. Adolescents who reported less parental involvement were at higher risk for drinking on any given day. After (but not before) the transition to high school, daily within-person fluctuations of sadness predicted an increased probability of same-day alcohol use for adolescents who reported that their parents were minimally involved in their lives. The other negative affect indicators were not predictive of use. Our results suggest that the transition to high school may represent an important intervention leverage point, particularly for adolescents who lack adequate parental support to help them cope with day-to-day changes in sadness.

  1. Integer quantum Hall effect in a triangular-lattice: Disorder effect and scaling behavior of the insulator-plateau transition

    NASA Astrophysics Data System (ADS)

    Yu, H. L.; Jiang, C.; Zhai, Z. Y.

    2017-01-01

    We investigate numerically the integer quantum Hall effect in a three-band triangular-lattice model. The three bands own the Chern number C=2,-1,-1, respectively. The lowest topological flat band carrying Chern number C=2, which leads to the Hall plateau σH = 2 (e2 / h) . This Hall plateau is sensitive to the disorder scattering and is rapidly destroyed by the weak disorder. Further increasing the strength of disorder, the gap of density of states always disappears before the vanishing of the corresponding Hall plateau. The scaling behavior of quantum phase transition between an insulator and a quantum Hall plateau is studied. We find that the insulator-plateau transition becomes sharper with increasing the size of system. Due to the different of edge states, the critical energy Ec1 gradually shifts to the center of Hall plateau while Ec2 is unaffected with increasing the disorder strength.

  2. The Kindergarten Transition: Behavioral Trajectories in the First Formal Year of School

    ERIC Educational Resources Information Center

    Welsh, Megan E.; Miller, Faith G.; Kooken, Janice; Chafouleas, Sandra M.; McCoach, D. Betsy

    2016-01-01

    During the first year of school, student success hinges on learning not only new academic skills, but also behavioral expectations and developing self-regulation skills in the classroom. The purpose of this study was to investigate development in behavioral regulation during the kindergarten year. The authors used multilevel models to explore the…

  3. 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)…

  4. Assessing the Transition-Related Social Behavior of Seriously Emotionally Disturbed Adolescents.

    ERIC Educational Resources Information Center

    Bullis, Michael

    1990-01-01

    The newsletter describes two projects of the Teaching Research Infant and Child Center (Oregon) which are developing assessment systems for use with severely emotionally disturbed (SED) adolescents. The first project focuses on job-related social behavior while the second project addresses social behavior in community settings. An introductory…

  5. 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,…

  6. 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.

  7. 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.

  8. 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.

  9. Crossover behavior in the phase transition of the Bose-Einstein condensation in a microwave-driven magnon gas

    SciTech Connect

    Rezende, Sergio M.

    2009-09-01

    A magnon gas in a film of yttrium iron garnet driven by microwave radiation exhibits Bose-Einstein condensation (BEC) when the driving power exceeds a critical value. We show that the nature and the critical exponents of the BEC transition change dramatically if the BEC magnons are significantly coupled to the zone-center magnons. The theoretical results explain the diverse behavior of the order parameter inferred from the experimental data for the light scattering and the microwave emission from the BEC observed with coherent and incoherent microwave pumping.

  10. 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…

  11. Lipid insertion domain unfolding regulates protein orientational transition behavior in a lipid bilayer.

    PubMed

    Cheng, Kwan Hon; Qiu, Liming; Cheng, Sara Y; Vaughn, Mark W

    2015-11-01

    We have used coarse-grained (CG) and united atom (UA) molecular dynamics simulations to explore the mechanisms of protein orientational transition of a model peptide (Aβ42) in a phosphatidylcholine/cholesterol (PC/CHO) lipid bilayer. We started with an inserted state of Aβ42 containing a folded (I) or unfolded (II) K28-A42 lipid insertion domain (LID), which was stabilized by the K28-snorkeling and A42-anchoring to the PC polar groups in the lipid bilayer. After a UA-to-CG transformation and a 1000ns-CG simulation for enhancing the sampling of protein orientations, we discovered two transitions: I-to-"deep inserted" state with disrupted K28-snorkeling and II-to-"deep surface" state with disrupted A42-anchoring. The new states remained stable after a CG-to-UA transformation and a 200ns-UA simulation relaxation. Significant changes in the cholesterol-binding domain of Aβ42 and protein-induced membrane disruptions were evident after the transitions. We propose that the conformation of the LID regulates protein orientational transitions in the lipid membrane.

  12. 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…

  13. 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…

  14. 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)

  15. Scaling Behavior of Factorial Moments of the Multiplicity Difference and Phase Transition Qgp to Hadrons

    NASA Astrophysics Data System (ADS)

    Babichev, L. F.; Khmialeuski, A. N.

    2011-10-01

    The multiplicity difference correlators between two well-separated bins in high energy heavy-ion collisions are studied using Monte-Carlo simulations. Numerical value of the universal scaling exponents γ is calculated and compared whit results obtained within the framework of Ginzburg-Landau theory. Simulations of phase transitions using Monte Carlo generators are discussed.

  16. Pretransitional behavior above the nematic-isotropic phase transition of an auxetic trimer liquid crystal.

    PubMed

    Kang, D; Mahajan, M P; Zhang, S; Petschek, R G; Rosenblatt, C; He, C; Liu, P; Griffin, A C

    1999-10-01

    Static light scattering and electric field-induced Kerr measurements were performed above the nematic-isotropic phase transition of a terminal-lateral-lateral-terminal negative Poisson ratio trimer. For both measurements the inverse susceptibility was observed to be nearly linear with temperature, a result inconsistent with our previously reported Kerr data [Phys. Rev. E 58, 2041 (1998)].

  17. Stick-slip and creep behavior in lubricated granular material: Insights into the brittle-ductile transition

    NASA Astrophysics Data System (ADS)

    Reber, Jacqueline E.; Hayman, Nicholas W.; Lavier, Luc L.

    2014-05-01

    Crustal deformation can occur via stick-slip events, viscous creep, or strain transients at variable rates. Here we explore such strain transients with physical experiments comprising a quasi-two-dimensional shear zone with elastic, acrylic discs and interstitial viscous silicone. Experiments of solely elastic discs produce stick-slip events and an overall (constant volume) strengthening. The addition of the viscous silicone enhances localization but does not greatly change the overall pattern of strengthening. It does, however, damp the stick-slip events, leading to transient, creep-like behavior that approaches the behavior of a Maxwell body. There is no gradual transition from frictional to viscous deformation with increasing amounts of silicone, suggesting that the mixed rheology is in effect as soon as an interstitial fluid is present. Our experiments support the hypothesis that a possible cause for strain transients in nature is an interstitial viscous phase in shear zones.

  18. Meaning made of stress among veterans transitioning to college: examining unique associations with suicide risk and life-threatening behavior.

    PubMed

    Holland, Jason M; Malott, Jesse; Currier, Joseph M

    2014-04-01

    Meaning made of stress has been shown to be a unique predictor of mental and physical health. In this study, we examined the unique associations between two facets of meaning made of stress (comprehensibility and footing in the world) and suicide risk and life-threatening behavior among military veterans who have transitioned to college were examined, controlling for demographic factors, religiousness, combat-related physical injury, combat exposure, depressive symptoms, and posttraumatic stress symptoms. Findings suggest that comprehensibility (having “made sense” of a stressor) is uniquely associated with lower suicide risk and a lower likelihood of driving under the influence of drugs or alcohol and engaging in self-mutilating behaviors.

  19. New Jersey Children's Behavioral Healthcare System: cross service delivery planning for transitional population of youth (ages 16 and 18+ years).

    PubMed

    McGill, Kenneth; McGill, Scott A

    2011-08-01

    The continued need for improvement within a 'system of care' is essential as the need for mental health services by those 'youth' within the child welfare system continually grows. This article outlines the statewide reform of New Jersey's Children's Behavioral Healthcare System, which began in 2000, as well as including the recommendations of the University of South Florida as part of their 'Final Report: Independent Assessment of New Jersey's Child Behavioral Health Services' on continued changes within the system of care. Successful outcomes have resulted from this welfare reform initiative, which include most notably the significant caseload decrease of the Division of Youth and Family Services (DYFS) and the creation of a new cabinet entity, the Department of Children and Families (DCF). This article specifically outlines systemic recommendations to best serve the target population of 'transitional' youth between the ages of 16 to 18+ years utilizing interagency cooperation based upon 'theory of change' and Total Clinical Outcomes Management (TCOM) strategies.

  20. 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

  1. 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)…

  2. 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.

  3. 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

  4. Upper-nose temper phenomena and transition behavior of fracture toughness of 2. 25Cr-1Mo pressure vessel steel

    SciTech Connect

    Holzmann, M.; Man, J.; Vlach, B. . Academy of Sciences)

    1993-12-15

    A non-reversible upper-nose temper embrittlement (UNTE) which is characterized by transcrystalline cleavage could occur in low alloy steels when tempered or post-weld heat treated at temperatures ranging between 600 C to A[sub c1] for longer-time period. The deterioration of mechanical properties, in particular toughness, associated with this process, is a very relevant problem for fabricators of large components in petrochemical and power industry. One must be very careful when evaluating the embrittlement of the structure itself, using results of the Charpy test. The authors of the present work have reported in a recent paper that the cleavage fracture stress [sigma][sub CF], due to structural changes during temper treatment, has fallen steadily from the very beginning of tempering and a model has been suggested, explaining the transition behavior in the Charpy test. Even though the Charpy tests provide valuable information regarding impact toughness properties, the fracture toughness is a more exact material characteristic defining the fracture resistance properties. Therefore, the fracture toughness temperature curves, measured for a variety of tempered conditions, aim to reveal to what extent UNTE phenomena can influence the level and transition behavior of this material characteristic. Some representative results are given in the present paper.

  5. Vortex phase transition and anisotropy behavior of optimized (Li1-x Fe x OH)FeSe single crystals

    NASA Astrophysics Data System (ADS)

    Yi, Xiaolei; Wang, Chunlei; Tang, Qingbin; Peng, Tao; Qiu, Yang; Xu, Junqi; Sun, Haibin; Luo, Yongsong; Yu, Benhai

    2016-10-01

    (Li1-x Fe x OH)FeSe single crystals have been successfully synthesized by a hydrothermal ion-exchange technique. We have carried out systematic research on the influence of the concentration of selenourea (c m) on the superconducting properties of (Li1-x Fe x OH)FeSe single crystals. The optimized specimens possess an onset superconducting transition temperature T c of up to 42 K obtained at c m = 0.8 mol l-1, and the corresponding residual resistivity ratio (RRR = ρ (300 K)/ρ (T c)) is estimated to be 11. The vortex liquid-to-glass phase transition has been discussed based on the collective pinning model. The large distance between the H g and H c2 lines, as well as the much narrower region of the pinned vortex-liquid phase, indicate a weak vortex-pinning ability in (Li1-x Fe x OH)FeSe single crystals. The big out-plane anisotropy behavior versus temperature has been explored according to the anisotropic Ginzburg-Landau theory, and the anisotropy factor Γ displays linear behavior towards temperature similar to that of SmFeAsO1-x F x superconductors.

  6. Learning by looking: Infants' social looking behavior across the transition from crawling to walking.

    PubMed

    Clearfield, Melissa W; Osborne, Christine N; Mullen, Molly

    2008-08-01

    This study investigated how infants gather information about their environment through looking and how that changes with increases in motor skills. In Experiment 1, 9.5- and 14-month-olds participated in a 10-min free play session with both a stranger and ambiguous toys present. There was a significant developmental progression from passive to active social engagement, as evidenced by younger infants watching others communicate more and older infants making more bids for social interaction. Experiment 2 examined longitudinally the impact of age and walking onset on this progression. The transition to independent walking marked significant changes in how often infants watched others communicate and made active bids for social interaction. Results suggest that infants transition from passive observers as crawlers to active participants in their social environment with the onset of walking.

  7. Two-wave behavior under various conditions of transition area from cancellous bone to cortical bone.

    PubMed

    Nagatani, Yoshiki; Mizuno, Katsunori; Matsukawa, Mami

    2014-07-01

    The two-wave phenomenon, the wave separation of a single ultrasonic pulse in cancellous bone, is expected to be a useful tool for the diagnosis of osteoporosis. However, because actual bone has a complicated structure, precise studies on the effect of transition conditions between cortical and cancellous parts are required. This study investigated how the transition condition influenced the two-wave generation using three-dimensional X-ray CT images of an equine radius and a three-dimensional simulation technique. As a result, any changes in the boundary between cortical part and trabecular part, which gives the actual complex structure of bone, did not eliminate the generation of either the primary wave or the secondary wave at least in the condition of clear trabecular alignment. The results led us to the possibility of using the two-wave phenomenon in a diagnostic system for osteoporosis in cases of a complex boundary.

  8. Pressure behavior of phonons and phase transition effects in Hg2I2 model virtual ferroelastics

    NASA Astrophysics Data System (ADS)

    Markov, Yu. F.; Mirovitskii, V. Yu.; Roginskii, E. M.

    2014-11-01

    The Raman spectra of virtual ferroelastic Hg2I2 crystals have been studied in a broad range of hydrostatic pressures. Linear pressure dependences of phonon frequencies are obtained at P < P c, which exhibit jumps and breaks at the phase transition point ( P c = 9 kbar). Grüneisen parameters of the Hg2I2 crystals are determined. The spectra of a ferroelastic phase ( P > P c) in various polarizations exhibit the excitation of new lines from the X point of the Brillouin zone, including transverse (TA) and longitudinal (LA) acoustic phonons. Based on analysis of the experimental and theoretical results, the Raman spectra of ferroelastic Hg2I2 crystals are interpreted and a model of the phase transition in these crystals is proposed.

  9. First-order transition and tricritical behavior of the transverse crystal field spin-1 Ising model

    NASA Astrophysics Data System (ADS)

    Costabile, Emanuel; Viana, J. Roberto; de Sousa, J. Ricardo; de Arruda, Alberto S.

    2015-06-01

    The phase diagram of the spin-1 Ising model in the presence of a transverse crystal-field anisotropy (Dx) is studied within the framework of an effective-field theory with correlation. The effect of the coordination number (z) on the phase diagram in the T -Dx plane is investigated. We observe only second-order transitions for coordination number z < 7, while that for z ≥ 7 we have first- and second-order transitions, with the presence of two tricritical points. The lower tricritical temperature (Tt) decreases monotonically with the increasing value of z, and in the limit of z → ∞ we found Tt = 0, corresponding to the mean-field solution [Ricardo de Sousa and Branco, Phys. Rev. E 77 (2008) 012104] with a single tricritical point in the phase diagram.

  10. Phase behavior of polydisperse spheres: simulation strategies and an application to the freezing transition.

    PubMed

    Wilding, Nigel B; Sollich, Peter

    2010-12-14

    The statistical mechanics of phase transitions in dense systems of polydisperse particles presents distinctive challenges to computer simulation and analytical theory alike. The core difficulty, namely, dealing correctly with particle size fractionation between coexisting phases, is set out in the context of a critique of previous simulation work on such systems. Specialized Monte Carlo simulation techniques and moment free energy method calculations, capable of treating fractionation exactly, are then described and deployed to study the fluid-solid transition of an assembly of repulsive spherical particles described by a top-hat "parent" distribution of particle sizes. The cloud curve delineating the solid-fluid coexistence region is mapped as a function of the degree of polydispersity δ, and the properties of the incipient "shadow" phases are presented. The coexistence region is found to shift to higher densities as δ increases, but does not exhibit the sharp narrowing predicted by many theories and some simulations.

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

    PubMed

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

    2015-10-08

    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.

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

    PubMed Central

    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

  13. Critical behavior of the three-dimensional Ising model with anisotropic bond randomness at the ferromagnetic-paramagnetic transition line.

    PubMed

    Papakonstantinou, T; Malakis, A

    2013-01-01

    We study the ±J three-dimensional (3D) Ising model with a spatially uniaxial anisotropic bond randomness on the simple cubic lattice. The ±J random exchange is applied on the xy planes, whereas, in the z direction, only a ferromagnetic exchange is used. After sketching the phase diagram and comparing it with the corresponding isotropic case, the system is studied at the ferromagnetic-paramagnetic transition line using parallel tempering and a convenient concentration of antiferromagnetic bonds (p(z)=0;p(xy)=0.176). The numerical data clearly point out a second-order ferromagnetic-paramagnetic phase transition belonging in the same universality class with the 3D random Ising model. The smooth finite-size behavior of the effective exponents, describing the peaks of the logarithmic derivatives of the order parameter, provides an accurate estimate of the critical exponent 1/ν=1.463(3), and a collapse analysis of magnetization data gives an estimate of β/ν=0.516(7). These results are in agreement with previous papers and, in particular, with those of the isotropic ±J three-dimensional Ising model at the ferromagnetic-paramagnetic transition line, indicating the irrelevance of the introduced anisotropy.

  14. Critical behavior of the three-dimensional Ising model with anisotropic bond randomness at the ferromagnetic-paramagnetic transition line

    NASA Astrophysics Data System (ADS)

    Papakonstantinou, T.; Malakis, A.

    2013-01-01

    We study the ±J three-dimensional (3D) Ising model with a spatially uniaxial anisotropic bond randomness on the simple cubic lattice. The ±J random exchange is applied on the xy planes, whereas, in the z direction, only a ferromagnetic exchange is used. After sketching the phase diagram and comparing it with the corresponding isotropic case, the system is studied at the ferromagnetic-paramagnetic transition line using parallel tempering and a convenient concentration of antiferromagnetic bonds (pz=0;pxy=0.176). The numerical data clearly point out a second-order ferromagnetic-paramagnetic phase transition belonging in the same universality class with the 3D random Ising model. The smooth finite-size behavior of the effective exponents, describing the peaks of the logarithmic derivatives of the order parameter, provides an accurate estimate of the critical exponent 1/ν=1.463(3), and a collapse analysis of magnetization data gives an estimate of β/ν=0.516(7). These results are in agreement with previous papers and, in particular, with those of the isotropic ±J three-dimensional Ising model at the ferromagnetic-paramagnetic transition line, indicating the irrelevance of the introduced anisotropy.

  15. 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.

  16. Eye Gaze Behavior at Turn Transition: How Aphasic Patients Process Speakers' Turns during Video Observation.

    PubMed

    Preisig, Basil C; Eggenberger, Noëmi; Zito, Giuseppe; Vanbellingen, Tim; Schumacher, Rahel; Hopfner, Simone; Gutbrod, Klemens; Nyffeler, Thomas; Cazzoli, Dario; Annoni, Jean-Marie; Bohlhalter, Stephan; Müri, René M

    2016-10-01

    The human turn-taking system regulates the smooth and precise exchange of speaking turns during face-to-face interaction. Recent studies investigated the processing of ongoing turns during conversation by measuring the eye movements of noninvolved observers. The findings suggest that humans shift their gaze in anticipation to the next speaker before the start of the next turn. Moreover, there is evidence that the ability to timely detect turn transitions mainly relies on the lexico-syntactic content provided by the conversation. Consequently, patients with aphasia, who often experience deficits in both semantic and syntactic processing, might encounter difficulties to detect and timely shift their gaze at turn transitions. To test this assumption, we presented video vignettes of natural conversations to aphasic patients and healthy controls, while their eye movements were measured. The frequency and latency of event-related gaze shifts, with respect to the end of the current turn in the videos, were compared between the two groups. Our results suggest that, compared with healthy controls, aphasic patients have a reduced probability to shift their gaze at turn transitions but do not show significantly increased gaze shift latencies. In healthy controls, but not in aphasic patients, the probability to shift the gaze at turn transition was increased when the video content of the current turn had a higher lexico-syntactic complexity. Furthermore, the results from voxel-based lesion symptom mapping indicate that the association between lexico-syntactic complexity and gaze shift latency in aphasic patients is predicted by brain lesions located in the posterior branch of the left arcuate fasciculus. Higher lexico-syntactic processing demands seem to lead to a reduced gaze shift probability in aphasic patients. This finding may represent missed opportunities for patients to place their contributions during everyday conversation.

  17. Influence of moisture, particle size and pulse flour composition on phase transition behavior of rice flour.

    PubMed

    Nithya, D J; Saravanan, M; Mohan, R Jagan; Alagusundaram, K

    2015-04-01

    Study on the phase transition characteristics is an important parameter in extrusion processing. The influence of Moisture Content (MC), particle size and level of cereal-pulse blend on the glass transition (Tg) and melt (Tm) temperatures of a ready to eat cereal-pulse formulation was determined. All samples were moisture conditioned in a 9 to 27 % with 3 % interval. Tg and Tm were measured by phase transition analyser (PTA). A substantial decrease in Tg and Tm was observed as moisture content level increased from 9 to 27 %. However Tg and Tm values could not be clearly defined below 9 % moisture content and above 27 % moisture content. The Tg and Tm values of the cereal-pulse formulation were found to be increased with increasing pulse composition (5 to 30 % with 5 % interval). Increase in particle size (150, 180, 212, 300, 425 and 500 μ) exhibited significant increase effect on Tg while less significant effect on Tm. This may be due to crystalline regions which play a role in cross linking amorphous regions of the polymeric network and thus suppress the mobility of amorphous regions. The observed differences in Tg and Tm induced by the moisture content, concentration of Bengal gram and particle size will be useful in simulation and optimization of barrel temperature set during extrusion processing.

  18. 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

  19. 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.

  20. Behavioral changes in autistic individuals as a result of wearing ambient transitional prism lenses.

    PubMed

    Kaplan, M; Edelson, S M; Seip, J A

    1998-01-01

    A double-blind crossover design was used to assess the efficacy of wearing ambient lenses to reduce the behavioral symptoms of autism. Eighteen autistic individuals, ranging in age from 7 to 18 years, participated in the study. Behavior, attention, and orientation were evaluated at 1 1/2 months, 2 months, 3 months, and 4 months. Compared to the placebo condition, the results showed a decrease in behavior problems at the 1 1/2 and 2 month assessment periods and a slight loss of these benefits at the 3 and 4 month assessment periods. These findings support the prediction that ambient lenses, worn without engaging in visual-motor exercises, have positive effects on autistic individuals.

  1. Do Teachers' Behavioral Expectations Effect the Transition from a Psychiatric Program to Community Schools?

    ERIC Educational Resources Information Center

    McLeer, S.; And Others

    Moving children from a psychiatric treatment facility to community schools presents significant challenges for children, teachers, and families. This study examined the potential conflicts between the expectations of receiving teachers and the behaviors of elementary school students (N=17) using the Assessments for Integration into Mainstream…

  2. 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…

  3. 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…

  4. Thermal behavior of long wavelength absorption transitions in Spirulina platensis photosystem I trimers.

    PubMed Central

    Cometta, A; Zucchelli, G; Karapetyan, N V; Engelmann, E; Garlaschi, F M; Jennings, R C

    2000-01-01

    In photosystem I trimers of Spirulina platensis a major long wavelength transition is irreversibly bleached by illumination with high-intensity white light. The photobleaching hole, identified by both absorption and circular dichroism spectroscopies, is interpreted as the inhomogeneously broadened Q(y) transition of a chlorophyll form that absorbs maximally near 709 nm at room temperature. Analysis of the mean square deviation of the photobleaching hole between 80 and 300 K, in the linear electron-phonon frame, indicates that the optical reorganization energy is 52 cm(-1), four times greater than that for the bulk, short-wavelength-absorbing chlorophylls, and the inhomogenous site distribution bandwidth is close to 150 cm(-1). The room temperature bandwidth, close to 18.5 nm, is dominated by thermal (homogeneous) broadening. Photobleaching induces correlated circular dichroism changes, of opposite sign, at 709 and 670 nm, which suggests that the long wavelength transition may be a low energy excitonic band, in agreement with its high reorganization energy. Clear identification of the 709-nm spectral form was used in developing a Gaussian description of the long wavelength absorption tail by analyzing the changing band shape during photobleaching using a global decomposition procedure. Additional absorption states near 720, 733, and 743 nm were thus identified. The lowest energy state at 743 nm is present in substoichiometric levels at room temperature and its presence was confirmed by fluorescence spectroscopy. This state displays an unusual increase in intensity upon lowering the temperature, which is successfully described by assuming the presence of low-lying, thermally populated states. PMID:11106627

  5. Mechanical behavior and brittle-ductile transition of high-chromium martensitic steel

    NASA Astrophysics Data System (ADS)

    Odnobokova, M. V.; Kipelova, A. Yu.; Belyakov, A. N.; Kaibyshev, R. O.

    2016-04-01

    The article presents data on the static tensile tests and dynamic impact-toughness tests of a highchromium martensitic 10Kh9V1M1FBR steel (0.12 wt % C, 9.8 wt % Cr, 0.93 wt % W, 1.01 wt % Mo, 0.2 wt % V, 0.05 wt % Nb, 0.05 wt % N, 0.003 wt % B, 0.36 wt % Mn, 0.2 wt % Ni, 0.06 wt % Si, 0.01 wt % P, 0.008 wt % S, 0.02 wt % Cu, 0.1 wt % Co, 0.015 wt % Al, and the remainder is Fe) in the temperature range from 20 to-196°C. In the case of static loading, a reduction in the temperature leads to an increase in the strength characteristics; upon a drop in the temperature from 20 to-100°C, the plasticity also increases. This is connected with the fact that the ductile fracture remains the basic mechanism down to cryogenic temperatures. The brittle-ductile transition related to the transition from ductile intragranular fracture to quasibrittle one is observed at-45°C. The steel exhibits high impact toughness to the temperature of-60°C ( KCV -60 = 95 J/cm2), at which the fraction of the ductile component in fracture is equal to 20%. At 80°C, the impact toughness decreases down to critical values (30 J/cm2), which correlates with the decrease in the fraction of the ductile component on the fracture surface down to 1%. The further decrease in the impact toughness down to 10 J/cm2 at-196°C is related to the transition from intragranular to intergranular brittle fracture.

  6. Novel Electronic Behavior Driving NdNiO3 Metal-Insulator Transition

    NASA Astrophysics Data System (ADS)

    Upton, M. H.; Choi, Yongseong; Park, Hyowon; Liu, Jian; Meyers, D.; Chakhalian, J.; Middey, S.; Kim, Jong-Woo; Ryan, Philip J.

    2015-07-01

    We present evidence that the metal-insulator transition (MIT) in a tensile-strained NdNiO3 (NNO) film is facilitated by a redistribution of electronic density and that it neither requires Ni charge disproportionation nor a symmetry change [U. Staub et al., Phys. Rev. Lett. 88, 126402 (2002); R. Jaramillo et al., Nat. Phys. 10, 304 (2014)]. Given that epitaxial tensile strain in thin NNO films induces preferential occupancy of the eg dx2-y2 orbital we propose that the larger transfer integral of this orbital state with the O 2 p orbital state mediates a redistribution of electronic density from the Ni atom. A decrease in the Ni dx2-y2 orbital occupation is directly observed by resonant inelastic x-ray scattering below the MIT temperature. Furthermore, an increase in the Nd charge occupancy is measured by x-ray absorption at the Nd L3 edge. Both spin-orbit coupling and crystal field effects combine to break the degeneracy of the Nd 5 d states, shifting the energy of the Nd eg dx2-y2 orbit towards the Fermi level, allowing the A site to become an active acceptor during the MIT. This work identifies the relocation of electrons from the Ni 3 d to the Nd 5 d orbitals across the MIT. We propose that the insulating gap opens between the Ni 3 d and O 2 p states, resulting from Ni 3 d electron localization. The transition seems to be neither a purely Mott-Hubbard transition nor a simple charge transfer.

  7. Phase transition behavior and electrical properties of lead-free (Ba1-xCax)(Zr0.1Ti0.9)O3 piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Tian, Ye; Chao, Xiaolian; Wei, Lingling; Liang, Pengfei; Yang, Zupei

    2013-05-01

    Lead-free (Ba1-xCax)(Zr0.1Ti0.9)O3(BCZT) ceramics were synthesized by conventional solid-state sintering process. The Ca ion substitutions on phase transition behavior, microstructure, ferroelectric and piezoelectric properties of BCZT ceramics were systemically investigated. The diffuse phase transition (DPT) behavior was suppressed, while the orthorhombic → tetragonal (O→T) and rhombohedral → orthorhombic (R→O) phase transitions were observed when the Ca content is at x = 0.05. Further increasing the Ca content, the DPT behavior gradually enhanced, and both the O→T and R→O phase transitions gradually evolved into R→T phase transition when the Ca content increases up to 0.15 at 25 °C. This behavior was related with phase structure and morphology, which significantly impacted the ferroelectric and piezoelectric properties near the R→T phase boundary. As a result, the sample with Ca contents of 0.15 shows the outstanding piezoelectric properties (with d33 = 572 pC/N, kp = 57%, Qm = 125, ɛr = 4821, and tan δ = 0.015) while negligible change for the ferroelectric properties. The abnormal ferroelectric behavior and potential factor contributing to large piezoelectric response also were discussed.

  8. Transitions in Wetting Behavior Between Liquid Ag-CuO Alloys and Al2O3Substrates

    SciTech Connect

    Friant, Jared R.; Meier, Alan; Darsell, Jens T.; Weil, K. Scott; Rohrer, G.

    2012-02-24

    Reactive air brazing (RAB) is a method for joining ceramics with applications in high temperature technologies such as gas separation and solid oxide fuel cell (SOFC) components. An understanding of wetting behavior is critical for optimization of the brazing process. In the current study, the wetting behavior of Ag-CuO on Al2O3 was evaluated. Based on in-situ contact angle measurements, three regions of wetting behavior were identified in the composition range of 0 to 40 mol% CuO. The first transition, a 20° decrease between 2 mol% CuO and 4 mol% CuO, was attributed to the liquid composition miscibility gap, and the second, a 10° decrease between 10 mol% CuO and 20 mol% CuO, was hypothesized to be dominated by the formation of a reaction product. Small, discontinuous reaction regions were identified via electron probe microanalysis (EPMA) but could not be verified with X-ray photoelectron spectroscopy analysis (XPS).

  9. Local, cell-nonautonomous feedback regulation of myosin dynamics patterns transitions in cell behavior: a role for tension and geometry?

    PubMed Central

    Saravanan, Surat; Meghana, C.; Narasimha, Maithreyi

    2013-01-01

    How robust patterns of tissue dynamics emerge from heterogeneities, stochasticities, and asynchronies in cell behavior is an outstanding question in morphogenesis. A clear understanding of this requires examining the influence of the behavior of single cells on tissue patterning. Here we develop single-cell manipulation strategies to uncover the origin of patterned cell behavior in the amnioserosa during Drosophila dorsal closure. We show that the formation and dissolution of contractile, medial actomyosin networks previously shown to underlie pulsed apical constrictions in the amnioserosa are apparently asynchronous in adjacent cells. We demonstrate for the first time that mechanical stresses and Rho1 GTPase control myosin dynamics qualitatively and quantitatively, in amplitude and direction, both cell autonomously and nonautonomously. We then demonstrate that interfering with myosin-dependent contractility in single cells also influences pulsed constrictions cell nonautonomously. Our results suggest that signals and stresses can feedback regulate the amplitude and spatial propagation of pulsed constrictions through their influence on tension and geometry. We establish the relevance of these findings to native closure by showing that cell delamination represents a locally patterned and collective transition from pulsed to unpulsed constriction that also relies on the nonautonomous feedback control of myosin dynamics. PMID:23741052

  10. Critical behavior of the order-disorder phase transition in β -brass investigated by x-ray scattering

    NASA Astrophysics Data System (ADS)

    Madsen, A.; Als-Nielsen, J.; Hallmann, J.; Roth, T.; Lu, W.

    2016-07-01

    β -brass exhibits an archetypical example of an order-disorder transition with a critical behavior that was previously investigated by neutron scattering. The data were well described by the three-dimensional (3d) Ising model but the relatively crude experimental resolution prevented an in-depth examination of the single-length scaling hypothesis, a cornerstone in the theory of critical phenomena. With the development of synchrotron x-ray experiments, high-resolution data could be recorded and surprisingly it was found that the single-length scaling did not hold in most critical systems, possibly due to strain originating from surface defects and/or impurities. In this paper we demonstrate single-length critical behavior using high-resolution x-ray scattering in β -brass. The investigations confirm that β -brass behaves like a 3d Ising system over a wide range of length scales comprising correlated clusters of millions of atoms. To vary the surface sensitivity, experiments have been performed both in Bragg reflection and Laue transmission geometries but without any substantial differences observed in the scaling and critical behavior.

  11. DAF-16/FOXO regulates homeostasis of essential sleep-like behavior during larval transitions in C. elegans.

    PubMed

    Driver, Robert J; Lamb, Annesia L; Wyner, Abraham J; Raizen, David M

    2013-03-18

    Sleep homeostasis, which refers to the maintenance of sleep amount or depth following sleep deprivation, indicates that sleep and sleep-like states serve fundamental functions that cannot be bypassed [1]. Homeostasis of sleep-like behavior is observed during C. elegans lethargus, a 2-3 hr behavioral quiescent period that occurs during larval state transitions [2]. Here, we report a role for DAF-16/FOXO, a transcription factor that is active under conditions of stress [3], in the response to deprivation of lethargus quiescence. Forced locomotion during lethargus results in nuclear translocation of DAF-16. The formation of dauer larvae, a developmental state promoted by daf-16, is increased in response to quiescence deprivation. daf-16 mutants show an impaired homeostatic response to deprivation of lethargus quiescence and are hypersensitive to the lethal effects of forced locomotion during lethargus. DAF-16 expression in muscle cells, but not in neurons, is sufficient to restore a homeostatic response to deprivation of quiescence, pointing to a role for muscle in sleep homeostasis. These findings are relevant to clinical observations of altered metabolic signaling in response to sleep deprivation and suggest that these signaling pathways may act in nonneuronal tissue to regulate sleep behaviors.

  12. The cognitive roles of behavioral variability: idiosyncratic acts as the foundation of identity and as transitional, preparatory, and confirmatory phases.

    PubMed

    Eilam, David

    2015-02-01

    Behavior in obsessive compulsive disorder (OCD), in habitual daily tasks, and in sport and cultural rituals is deconstructed into elemental acts and categorized into common acts, performed by all individuals completing a similar task, and idiosyncratic acts, not performed by all individuals. Never skipped, common acts establish the pragmatic part of motor tasks. Repetitive performance of a few common acts renders rituals a rigid form, whereby common acts may serve as memes for cultural transmission. While idiosyncratic acts are not pragmatically necessary for task completion, they fulfill important cognitive roles. They form a long preparatory phase in tasks that involve high stakes, and a long confirmatory phase in OCD rituals. Idiosyncratic acts also form transitional phases between motor tasks, and are involved in establishing identity and preserving the flexibility necessary for adapting to varying circumstances. Behavioral variability, as manifested in idiosyncrasy, thus does not seem to be a noise or by-product of motor activity, but an essential cognitive component that has been preserved in the evolution of behavioral patterns, similar to the genetic variability in biology.

  13. Heterogeneous ice nucleation: Exploring the transition from stochastic to singular freezing behavior

    NASA Astrophysics Data System (ADS)

    Stratmann, F.; Niedermeier, D.; Hartmann, S.; Shaw, R. A.; Clauss, T.; Wex, H.

    2011-12-01

    Heterogeneous ice nucleation directly influences cloud physical processes, precipitation formation, global radiation balances, and therefore Earth's climate (Cantrell and Heymsfield, 2005 and references therein). It is important to understand the heterogeneous freezing process at a fundamental level in order to describe this process in a physically-based way that will behave robustly in weather and climate models. There is longstanding debate as to whether heterogeneous ice nucleation is a stochastic process (e.g., Carte, 1956) or whether it exhibits singular behaviour (e.g., Langham and Mason, 1958). Fundamentally, the stochastic ice nucleation behavior implies ice nucleation being time dependent, while singular behavior is characterized by ice nucleation taking place on specific particle surface sites at a certain temperature and being time independent (Vali and Stansbury, 1966). We addressed this issue using both experimental and theoretical methods. Experiments focused on immersion freezing of Arizona Test Dust (ATD) were carried out using the Leipzig Aerosol Cloud Interaction Simulator (LACIS), a seven meter long laminar flow diffusion chamber. Both, temperature and time dependencies of ATD-particle induced immersion freezing were investigated. It was found, that ATD-particle induced immersion freezing took place over a wide temperature range and exhibited no detectable time dependence within the range investigated. The theoretical investigations were carried out using a Classical Nucleation Theory (CNT) based, i.e., purely stochastic, numerical model. This idealized model treats statistically similar particles as being covered with surface sites (patches of finite area) characterized by different nucleation barriers, but with each surface site following the stochastic nature of ice embryo formation. The model provides a phenomenological explanation for seemingly contradictory experimental results obtained in the past. Based on CNT alone, a population of

  14. Coupled effects of substrate adhesion and intermolecular forces on polymer thin film glass-transition behavior.

    PubMed

    Xia, Wenjie; Keten, Sinan

    2013-10-15

    Intermolecular noncovalent forces between polymer chains influence the mobility and glass-transition temperature (Tg), where weaker interchain interactions, all else being the same, typically results in lower bulk polymer Tg. Using molecular dynamics simulations, here we show that this relation can become invalid for supported ultrathin films when the substrate-polymer interaction is extremely strong and the polymer-polymer interactions are much weaker. This contrasting trend is found to be due to a more pronounced substrate-induced appreciation of the film Tg for polymers with weaker intermolecular interactions and low bulk Tg. We show that optimizing this coupling between substrate adhesion and bulk Tg maximizes thin film Tg, paving the way for tuning film properties through interface nanoengineering.

  15. Heterogeneous ice nucleation: exploring the transition from stochastic to singular freezing behavior

    NASA Astrophysics Data System (ADS)

    Niedermeier, D.; Shaw, R. A.; Hartmann, S.; Wex, H.; Clauss, T.; Voigtländer, J.; Stratmann, F.

    2011-08-01

    Heterogeneous ice nucleation, a primary pathway for ice formation in the atmosphere, has been described alternately as being stochastic, in direct analogy with homogeneous nucleation, or singular, with ice nuclei initiating freezing at deterministic temperatures. We present an idealized, conceptual model to explore the transition between stochastic and singular ice nucleation. This "soccer ball" model treats particles as being covered with surface sites (patches of finite area) characterized by different nucleation barriers, but with each surface site following the stochastic nature of ice embryo formation. The model provides a phenomenological explanation for seemingly contradictory experimental results obtained in our research groups. Even with ice nucleation treated fundamentally as a stochastic process this process can be masked by the heterogeneity of surface properties, as might be typical for realistic atmospheric particle populations. Full evaluation of the model findings will require experiments with well characterized ice nucleating particles and the ability to vary both temperature and waiting time for freezing.

  16. Effect of Tantalum on Ferroelectric Phase Transition Behavior of SrBi4Ti4O15 Sintered Discs

    NASA Astrophysics Data System (ADS)

    Madhavi, K.; Kumar, G. S.; Prasad, G.

    Tantalum modified strontium bismuth titanate ceramic discs with general formula SrBi4Ti(4-5x)Ta4xO15 with x = 0, 0.1, 0.2 and 0.3 have been prepared through solid state reaction method. The samples are poled and dielectric constant, loss and AC conductivity measurements are done in the temperature region (30-600°C). Ta5+ doping brought out interesting changes in dielectric phase transition behavior of the samples. Dielectric loss and conductivity measurements indicate the presence of charged defects. The results indicate changes in the distortion of the lattice. The distortion is calculated from the changes in the Curie temperature. AC conductivity results are understood in terms of the unoccupied sites and oxygen vacancies that are present in the samples.

  17. Structure-mediated transition in the behavior of elastic and inelastic properties of beach tree bio-carbon

    NASA Astrophysics Data System (ADS)

    Kardashev, B. K.; Orlova, T. S.; Smirnov, B. I.; Gutierrez, A.; Ramirez-Rico, J.

    2013-09-01

    Microstructural characteristics and amplitude dependences of the Young modulus E and of internal friction (logarithmic decrement δ) of bio-carbon matrices prepared from beech tree wood at different carbonization temperatures T carb ranging from 600 to 1600°C have been studied. The dependences E( T carb) and δ( T carb) thus obtained revealed two linear regions of increase of the Young modulus and of decrease of the decrement with increasing carbonization temperature, namely, Δ E ˜ AΔ T carb and Δδ ˜ BΔ T carb, with A ≈ 13.4 MPa/K and B ≈ -2.2 × 10-6 K-1 for T carb < 1000°C and A ≈ 2.5 MPa/K and B ≈ -3.0 × 10-7 K-1 for T carb > 1000°C. The transition observed in the behavior of E( T carb) and δ( T carb) at T carb = 900-1000°C can be assigned to a change of sample microstructure, more specifically, a change in the ratio of the fractions of the amorphous matrix and of the nanocrystalline phase. For T carb < 1000°C, the elastic properties are governed primarily by the amorphous matrix, whereas for T carb > 1000°C the nanocrystalline phase plays the dominant part. The structurally induced transition in the behavior of the elastic and microplastic characteristics at a temperature close to 1000°C correlates with the variation of the physical properties, such as electrical conductivity, thermal conductivity, and thermopower, reported in the literature.

  18. Spin-glass phase transition and behavior of nonlinear susceptibility in the Sherrington-Kirkpatrick model with random fields

    NASA Astrophysics Data System (ADS)

    Morais, C. V.; Zimmer, F. M.; Lazo, M. J.; Magalhães, S. G.; Nobre, F. D.

    2016-06-01

    The behavior of the nonlinear susceptibility χ3 and its relation to the spin-glass transition temperature Tf in the presence of random fields are investigated. To accomplish this task, the Sherrington-Kirkpatrick model is studied through the replica formalism, within a one-step replica-symmetry-breaking procedure. In addition, the dependence of the Almeida-Thouless eigenvalue λAT (replicon) on the random fields is analyzed. Particularly, in the absence of random fields, the temperature Tf can be traced by a divergence in the spin-glass susceptibility χSG, which presents a term inversely proportional to the replicon λAT. As a result of a relation between χSG and χ3, the latter also presents a divergence at Tf, which comes as a direct consequence of λAT=0 at Tf. However, our results show that, in the presence of random fields, χ3 presents a rounded maximum at a temperature T* which does not coincide with the spin-glass transition temperature Tf (i.e., T*>Tf for a given applied random field). Thus, the maximum value of χ3 at T* reflects the effects of the random fields in the paramagnetic phase instead of the nontrivial ergodicity breaking associated with the spin-glass phase transition. It is also shown that χ3 still maintains a dependence on the replicon λAT, although in a more complicated way as compared with the case without random fields. These results are discussed in view of recent observations in the LiHoxY1 -xF4 compound.

  19. Effect of specimen size on ductile to brittle transition behavior of martensitic 9Cr steels after various heat treatments

    NASA Astrophysics Data System (ADS)

    Abe, Fujio; Kayano, Hideo

    1996-09-01

    The effect of specimen size on the ductile to brittle transition behavior has been investigated using the full-size and 1/3-size Charpy V-notch specimens of martensitic 9Cr-WVTa steels after quenching, tempering and subsequent prolonged aging treatments. The upper shelf energy (USE) and ductile to brittle transition temperature (DBTT) were widely changed by the heat treatments; the USE varied from 90 to 292 J, and the DBTT from 188 to 325 K. The nominal volume ( Bb) {3}/{2}, where B is the specimen thickness and b the ligament size, was effective as a normalization factor for the USE only in the large USE region above 210 and 8.5 J for the full-size and 1/3-size specimens, respectively. A new normalization factor depending on the USE level was proposed. Although the relationship between the DBTT for the full-size and 1/3-size specimens was different from steel to steel, the shift in DBTT caused by the heat treatments was described by Δ DBTT{1}/{3}- size = (1.2 ± 0.1) ΔDBTT full-size for all the steels examined.

  20. Effects of cold work and phosphorous on the ductile to brittle transition behavior of F82H steels

    NASA Astrophysics Data System (ADS)

    Kim, Byung Jun; Kasada, Ryuta; Kimura, Akihiko; Tanigawa, Hiroyasu

    2011-10-01

    The effects of cold work and phosphorous on ductile to brittle transition behavior were investigated in order to evaluate the effects of hardening and intergranular degradation on the ductile to brittle transition temperature (DBTT) of F82H steel. Yield strength and ultimate tensile strength are increased by increasing the level of cold work. Phosphorous additions resulted in a small increase in the strength of F82H. The DBTT after cold work is shifted to high temperature and upper shelf energy (USE) is decreased. The shift of DBTT and the reduction of USE increase with the cold work level. F82H as-received and cold worked steel fractured in a cleavage mode at temperatures of lower shelf energy (LSE) region. The DBTT is shifted to higher temperatures with increasing phosphorus additions accompanied by the reduction of the USE. Although the hardening is small, a significant embrittlement was observed in the steels added with phosphorus, which was accompanied by intergranular cracking at temperatures in LSE region.

  1. Structural Phase Transition Effect on Resistive Switching Behavior of MoS2 -Polyvinylpyrrolidone Nanocomposites Films for Flexible Memory Devices.

    PubMed

    Zhang, Peng; Gao, Cunxu; Xu, Benhua; Qi, Lin; Jiang, Changjun; Gao, Meizhen; Xue, Desheng

    2016-04-01

    The 2H phase and 1T phase coexisting in the same molybdenum disulfide (MoS2 ) nanosheets can influence the electronic properties of the materials. The 1T phase of MoS2 is introduced into the 2H-MoS2 nanosheets by two-step hydrothermal synthetic methods. Two types of nonvolatile memory effects, namely write-once read-many times memory and rewritable memory effect, are observed in the flexible memory devices with the configuration of Al/1T@2H-MoS2 -polyvinylpyrrolidone (PVP)/indium tin oxide (ITO)/polyethylene terephthalate (PET) and Al/2H-MoS2 -PVP/ITO/PET, respectively. It is observed that structural phase transition in MoS2 nanosheets plays an important role on the resistive switching behaviors of the MoS2 -based device. It is hoped that our results can offer a general route for the preparation of various promising nanocomposites based on 2D nanosheets of layered transition metal dichalcogenides for fabricating the high performance and flexible nonvolatile memory devices through regulating the phase structure in the 2D nanosheets.

  2. Hidden non-Fermi liquid behavior caused by magnetic phase transition in Ni-doped Ba-122 pnictides

    PubMed Central

    Lee, Seokbae; Choi, Ki-Young; Jung, Eilho; Rho, Seulki; Shin, Soohyeon; Park, Tuson; Hwang, Jungseek

    2015-01-01

    We studied two BaFe2−xNixAs2 (Ni-doped Ba-122) single crystals at two different doping levels (underdoped and optimally doped) using an optical spectroscopic technique. The underdoped sample shows a magnetic phase transition around 80 K. We analyze the data with a Drude-Lorentz model with two Drude components (D1 and D2). It is known that the narrow D1 component originates from electron carriers in the electron-pockets and the broad D2 mode is from hole carriers in the hole-pockets. While the plasma frequencies of both Drude components and the static scattering rate of the broad D2 component show negligible temperature dependencies, the static scattering rate of the D1 mode shows strong temperature dependence for the both samples. We observed a hidden quasi-linear temperature dependence in the scattering rate of the D1 mode above and below the magnetic transition temperature while in the optimally doped sample the scattering rate shows a more quadratic temperature dependence. The hidden non-Fermi liquid behavior in the underdoped sample seems to be related to the magnetic phase of the material. PMID:26184412

  3. Weathering the Great Recession: Psychological and Behavioral Trajectories in the Transition from School to Work*

    PubMed Central

    Vuolo, Mike; Staff, Jeremy; Mortimer, Jeylan T.

    2011-01-01

    Studies of career development highlight the importance of finding a good “fit” between individual values, needs, and abilities and the experiences and rewards to be found in particular occupations. Rapid economic change and labor market turbulence make career choice and development life-long processes. Still, early careers are particularly unstable, as young workers move from “survival jobs” to “career jobs” in their quest for a good person-job fit. Little is known, however, about the psychological orientations and behaviors in the post-adolescent period that foster longer-term success in the world of work. The maintenance of high aspirations, crystallization of career goals, and intensive job search may be particularly important. Using multilevel latent class analysis applied to longitudinal data obtained from 1,010 youth surveyed by the ongoing Youth Development Study (YDS), this article examines the interrelations of psychological orientations and behaviors indicative of agentic striving from age 18 to 31. In addition, we assess how these trajectories influence adaptation to declining labor market conditions during the severe economic recession that began in 2007. We find that those who maintain high aspiration and certainty over career goals are better insulated against unemployment between 2007 and 2009 (age 33 to 35), even when educational and self-identified career attainments, adolescent achievement orientations, and social background variables indicative of advantage are controlled. They also have higher hourly wages in 2009. PMID:22059449

  4. Effect of hockey-stick-shaped molecules on the critical behavior at the nematic to isotropic and smectic-A to nematic phase transitions in octylcyanobiphenyl

    NASA Astrophysics Data System (ADS)

    Chakraborty, Anish; Chakraborty, Susanta; Das, Malay Kumar

    2015-03-01

    In the field of soft matter research, the characteristic behavior of both nematic-isotropic (N -I ) and smectic-A nematic (Sm -A N ) phase transitions has gained considerable attention due to their several attractive features. In this work, a high-resolution measurement of optical birefringence (Δ n ) has been performed to probe the critical behavior at the N -I and Sm -A N phase transitions in a binary system comprising the rodlike octylcyanobiphenyl and a laterally methyl substituted hockey-stick-shaped mesogen, 4-(3-n -decyloxy-2-methyl-phenyliminomethyl)phenyl 4-n -dodecyloxycinnamate. For the investigated mixtures, the critical exponent β related to the limiting behavior of the nematic order parameter close to the N -I phase transition has come out to be in good conformity with the tricritical hypothesis. Moreover, the yielded effective critical exponents (α', β', γ') characterizing the critical fluctuation near the Sm -A N phase transition have appeared to be nonuniversal in nature. With increasing hockey-stick-shaped dopant concentration, the Sm -A N phase transition demonstrates a strong tendency to be driven towards a first-order nature. Such a behavior has been accounted for by considering a modification of the effective intermolecular interactions and hence the related coupling between the nematic and smectic order parameters, caused by the introduction of the angular mesogenic molecules.

  5. Head-up transition behavior of pilots during simulated low-visibility approaches

    NASA Technical Reports Server (NTRS)

    Haines, R. F.

    1980-01-01

    Each of 13 commercial pilots from four airlines flew a total of 108 manual flight director approaches in a moving base simulation of a medium-sized turbojet (95,000 lb gross weight) which had a day and night Redifon external scene. Three levels of runway visual range (RVR) (1,600; 2,400; and greater than 8,000 ft), three wind-shear profiles, nine ceiling heights, and continuous and intermittent visibility after initial breakout were tested. The results indicated that: (1) mean decision time ranged from 2 to 4.6 sec for ceilings under 380 ft across the three RVR conditions; (2) mean vertical distance traveled during the visual-cue assessment period was a relatively constant proportion below the existing ceiling; (3) a significant three way interaction in mean decision time between wind shear, day-night, and ceiling RVR variables occurred; (4) mean number of head-up transitions to VFR conditions after breakout ranged from 4.6 to 13.4 and increased as a function of ceiling and severity of wind shear; the typical duration of fixation out the window was 1.5 sec; and (5) subjective pilot ratings of controllability and precision of control as well as amount of skill, attention, or effort required to make the landing were influenced significantly by the wind shear, night conditions, and low breakout ceiling conditions.

  6. Extensive Intestinal Resection Triggers Behavioral Adaptation, Intestinal Remodeling and Microbiota Transition in Short Bowel Syndrome

    PubMed Central

    Mayeur, Camille; Gillard, Laura; Le Beyec, Johanne; Bado, André; Joly, Francisca; Thomas, Muriel

    2016-01-01

    Extensive resection of small bowel often leads to short bowel syndrome (SBS). SBS patients develop clinical mal-absorption and dehydration relative to the reduction of absorptive area, acceleration of gastrointestinal transit time and modifications of the gastrointestinal intra-luminal environment. As a consequence of severe mal-absorption, patients require parenteral nutrition (PN). In adults, the overall adaptation following intestinal resection includes spontaneous and complex compensatory processes such as hyperphagia, mucosal remodeling of the remaining part of the intestine and major modifications of the microbiota. SBS patients, with colon in continuity, harbor a specific fecal microbiota that we called “lactobiota” because it is enriched in the Lactobacillus/Leuconostoc group and depleted in anaerobic micro-organisms (especially Clostridium and Bacteroides). In some patients, the lactobiota-driven fermentative activities lead to an accumulation of fecal d/l-lactates and an increased risk of d-encephalopathy. Better knowledge of clinical parameters and lactobiota characteristics has made it possible to stratify patients and define group at risk for d-encephalopathy crises. PMID:27681910

  7. Internal structure and phase transition behavior of stimuli-responsive microgels in PEG melts.

    PubMed

    Schneider, Florian; Balaceanu, Andreea; Di, Zhenyu; Melnichenko, Yuri B; Allgaier, Jürgen; Pich, Andrij; Schneider, Gerald J; Richter, Dieter

    2017-02-20

    In this work we investigated the behaviour of stimuli-responsive poly(N-vinylcaprolactam) (PVCL) microgels in poly(ethylene glycol) (PEGs) with a linear architecture. We performed small-angle neutron scattering (SANS) experiments at two different microgel concentrations and various temperatures. The results were compared with those on PVCL microgels in water. PVCL in PEG (molecular weight MW = 2 kg mol(-1)) exhibits a volume phase transition temperature (VPTT) at a temperature between 160 and 180 °C. The diameter of the swollen microgel is only slightly smaller than in water. Furthermore, with increasing molecular weight of the surrounding polymer matrices fewer chains penetrate the microgel particles. In agreement with that, we identify a decreasing diameter with increasing molecular weight. In the short chain polymers up to MW = 3 kg mol(-1), PVCL is well dispersed in the matrices with only minor signatures of agglomeration. For the well dispersed systems, we find unperturbed chain conformation of the PEG. Our results clearly show that the miscibility of PVCL and PEG disappears in a molecular weight range of 3 to 10 kg mol(-1).

  8. Ligational behavior of Schiff bases towards transition metal ion and metalation effect on their antibacterial activity

    NASA Astrophysics Data System (ADS)

    Devi, Jai; Batra, Nisha; Malhotra, Rajesh

    2012-11-01

    New Schiff bases pyrazine-2-carboxylicacid (phenyl-pyridin-2-yl-methylene)-hydrazide (Hpch-bp) HL1 and pyrazine-2-carboxylicacid (pyridin-2-ylmethylene)-hydrazide (Hpch-pc) HL2 derived from condensation of pyrazine carboxylic hydrazide (Hpch) with 2-benzoyl pyridine (bp) or pyridine 2-carbaldehyde (pc) and their transition metal complexes of type ML(1-2)2 have been synthesized, where M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). Characterization of ligands and their metal complexes was carried out by elemental analysis, conductimetric studies, magnetic susceptibility, spectroscopic techniques (IR, UV-VIS, NMR, ESR, Mass) and thermogravimetric analysis. The physico-chemical studies revealed octahedral geometry or distorted octahedral geometry around metal ion. These azomethine Schiff base ligands acted as tridentate ? coordinating through carbonyl, azomethine and pyridine nitrogen present in the ligand. The thermodynamic and thermal properties of the complexes have been investigated and it was observed on the basis of these studies that thermal stability of complexes follows the order Mn < Zn < Cu < Co < Ni. The ligands and their complexes were tested for in vitro antibacterial activity at different concentrations against bacteria viz. Gram positive Bacillus subtilis, Micrococcus luteus and Gram negative Pseudomonas aeruginosa, Pseudomonas mendocina. A marked enhancement in biocidal activity of the ligands under similar experimental conditions was observed as a consequence of coordination with metal ions. The trend of growth inhibition in the complexes was found to be in the order: Cu > Mn > Ni > Co > Zn.

  9. Behavioral/Systems/Cognitive Cortical Processing of Dynamic Sound Envelope Transitions

    PubMed Central

    Zhou, Yi; Wang, Xiaoqin

    2012-01-01

    Slow envelope fluctuations in the range of 2-20Hz provide important segmental cues for processing communication sounds. For a successful segmentation, a neural processor must capture envelope features associated with the rise and fall of signal energy, a process that is often challenged by the interference of background noise. This study investigated the neural representations of slowly varying envelopes in quiet and in background noise in the primary auditory cortex (A1) of awake marmoset monkeys. We characterized envelope features based on the local average and rate of change of sound level in envelope waveforms and identified envelope features to which neurons were selective by reverse correlation. Our results showed that envelope feature selectivity of A1 neurons was correlated with the degree of non-monotonicity in their static rate-level functions. Non-monotonic neurons exhibited greater feature selectivity than monotonic neurons in quiet and in background noise. The diverse envelope feature selectivity decreased spike-timing correlation among A1 neurons in response to the same envelope waveforms. As a result, the variability, but not the average, of the ensemble responses of A1 neurons represented more faithfully the dynamic transitions in low-frequency sound envelopes both in quiet and in background noise. PMID:21148013

  10. Geometrically disordered network models, quenched quantum gravity, and critical behavior at quantum Hall plateau transitions

    NASA Astrophysics Data System (ADS)

    Gruzberg, I. A.; Klümper, A.; Nuding, W.; Sedrakyan, A.

    2017-03-01

    Recent results for the critical exponent of the localization length at the integer quantum Hall transition differ considerably between experimental (νexp≈2.38 ) and numerical (νCC≈2.6 ) values obtained in simulations of the Chalker-Coddington (CC) network model. The difference is at least partially due to effects of the electron-electron interaction present in experiments. Here, we propose a mechanism that changes the value of ν even within the single-particle picture. We revisit the arguments leading to the CC model and consider more general networks with structural disorder. Numerical simulations of the new model lead to the value ν ≈2.37 . We argue that in a continuum limit the structurally disordered model maps to free Dirac fermions coupled to various random potentials (similar to the CC model) but also to quenched two-dimensional quantum gravity. This explains the possible reason for the considerable difference between critical exponents for the CC model and the structurally disordered model. We extend our results to network models in other symmetry classes.

  11. Partially satisfied to fully satisfied transitions in co-evolving inverse voter model and possible scaling behavior

    NASA Astrophysics Data System (ADS)

    Choi, C. W.; Xu, C.; Hui, P. M.

    2015-12-01

    Understanding co-evolving networks characterized by the mutual influence of agents' actions and network structure remains a challenge. We study a co-evolving inverse voter model in which agents adapt to achieve a preferred environment with more opposite-opinion neighbors by rewiring their connections and switching opinion. Numerical studies reveal a transition from a dynamic partially satisfied phase to a frozen fully satisfied phase as the rewiring probability is varied. A simple mean field theory is shown to capture the behavior only qualitatively. An improved mean field theory carrying a longer spatial correlation gives better results. Motivated by numerical results in networks of different degrees and mean field results, we propose a scaling variable that combines the rewiring probability and mean degree in a special form. The scaling variable is shown to work well in analyzing data corresponding to different networks and different rewiring probabilities. An application is to predict the results for networks of different degrees based solely on results obtained from networks of one degree. Studying scaling behavior provides an alternative path for understanding co-evolving agent-based dynamical systems, especially in light of the trade-off between complexity of a theory and its accuracy.

  12. Unusual magnetic hysteresis and the weakened transition behavior induced by Sn substitution in Mn{sub 3}SbN

    SciTech Connect

    Sun, Ying; Guo, Yanfeng; Li, Jun; Wang, Xia; Tsujimoto, Yoshihiro; Wang, Cong; Feng, Hai L.; Sathish, Clastin I.; Yamaura, Kazunari; Matsushita, Yoshitaka

    2014-01-28

    Substitution of Sb with Sn was achieved in ferrimagnetic antiperovskite Mn{sub 3}SbN. The experimental results indicate that with an increase in Sn concentration, the magnetization continuously decreases and the crystal structure of Mn{sub 3}Sb{sub 1-x}Sn{sub x}N changes from tetragonal to cubic phase at around x of 0.8. In the doping series, step-like anomaly in the isothermal magnetization was found and this behavior was highlighted at x = 0.4. The anomaly could be attributed to the magnetic frustration, resulting from competition between the multiple spin configurations in the antiperovskite lattice. Meantime, H{sub c} of 18 kOe was observed at x = 0.3, which is probably the highest among those of manganese antiperovskite materials reported so far. With increasing Sn content, the abrupt change of resistivity and the sharp peak of heat capacity in Mn{sub 3}SbN were gradually weakened. The crystal structure refinements indicate the weakened change at the magnetic transition is close related to the change of c/a ratio variation from tetragonal to cubic with Sn content. The results derived from this study indicate that the behavior of Mn{sub 3}Sb{sub 1-x}Sn{sub x}N could potentially enhance its scientific and technical applications, such as spin torque transfer and hard magnets.

  13. Increasing on-task behavior in every student in a second-grade classroom during transitions: validating the Color Wheel system.

    PubMed

    Fudge, Daniel L; Skinner, Christopher H; Williams, Jacqueline L; Cowden, Dan; Clark, Janice; Bliss, Stacy L

    2008-10-01

    A single-case (B-C-B-C) experimental design was used to evaluate the effects of the Color Wheel classroom management system (CWS) on on-task (OT) behavior in an intact, general-education, 2nd-grade classroom during transitions. The CWS included three sets of rules, posted cues to indicate the rules students are expected to be following at that time, and transition procedures for altering activities and rules. Class-wide data analysis showed large, immediate, and sustained increases in OT behavior when the CWS was applied, with OT behavior returning to baseline levels when typical classroom management (TCM) procedures were reinstated. Each student's average phase data also showed increases in OT behavior when the CWS was applied and re-applied, and showed reductions when the CWS was withdrawn. Discussion focuses on evaluating the internal, external, and contextual validity of class-wide remediation and prevention procedures.

  14. Ligational behavior of Schiff bases towards transition metal ion and metalation effect on their antibacterial activity.

    PubMed

    Devi, Jai; Batra, Nisha; Malhotra, Rajesh

    2012-11-01

    New Schiff bases pyrazine-2-carboxylicacid (phenyl-pyridin-2-yl-methylene)-hydrazide (Hpch-bp) HL(1) and pyrazine-2-carboxylicacid (pyridin-2-ylmethylene)-hydrazide (Hpch-pc) HL(2) derived from condensation of pyrazine carboxylic hydrazide (Hpch) with 2-benzoyl pyridine (bp) or pyridine 2-carbaldehyde (pc) and their transition metal complexes of type ML((1-2)2) have been synthesized, where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). Characterization of ligands and their metal complexes was carried out by elemental analysis, conductimetric studies, magnetic susceptibility, spectroscopic techniques (IR, UV-VIS, NMR, ESR, Mass) and thermogravimetric analysis. The physico-chemical studies revealed octahedral geometry or distorted octahedral geometry around metal ion. These azomethine Schiff base ligands acted as tridentate coordinating through carbonyl, azomethine and pyridine nitrogen present in the ligand. The thermodynamic and thermal properties of the complexes have been investigated and it was observed on the basis of these studies that thermal stability of complexes follows the order MnMn>Ni>Co>Zn.

  15. Crossover behavior of the thermal conductance and Kramers’ transition rate theory

    DOE PAGES

    Velizhanin, Kirill A.; Sahu, Subin; Chien, Chih -Chun; ...

    2015-12-04

    Kramers’ theory frames chemical reaction rates in solution as reactants overcoming a barrier in the presence of friction and noise. For weak coupling to the solution, the reaction rate is limited by the rate at which the solution can restore equilibrium after a subset of reactants have surmounted the barrier to become products. For strong coupling, there are always sufficiently energetic reactants. However, the solution returns many of the intermediate states back to the reactants before the product fully forms. Here, we demonstrate that the thermal conductance displays an analogous physical response to the friction and noise that drive themore » heat current through a material or structure. A crossover behavior emerges where the thermal reservoirs dominate the conductance at the extremes and only in the intermediate region are the intrinsic properties of the lattice manifest. Finally, not only does this shed new light on Kramers’ classic turnover problem, this result is significant for the design of devices for thermal management and other applications, as well as the proper simulation of transport at the nanoscale.« less

  16. Crossover behavior of the thermal conductance and Kramers’ transition rate theory

    PubMed Central

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

    2015-01-01

    Kramers’ theory frames chemical reaction rates in solution as reactants overcoming a barrier in the presence of friction and noise. For weak coupling to the solution, the reaction rate is limited by the rate at which the solution can restore equilibrium after a subset of reactants have surmounted the barrier to become products. For strong coupling, there are always sufficiently energetic reactants. However, the solution returns many of the intermediate states back to the reactants before the product fully forms. Here, we demonstrate that the thermal conductance displays an analogous physical response to the friction and noise that drive the heat current through a material or structure. A crossover behavior emerges where the thermal reservoirs dominate the conductance at the extremes and only in the intermediate region are the intrinsic properties of the lattice manifest. Not only does this shed new light on Kramers’ classic turnover problem, this result is significant for the design of devices for thermal management and other applications, as well as the proper simulation of transport at the nanoscale. PMID:26634333

  17. Influence of both cation and alginate nature on the rheological behavior of transition metal alginate gels.

    PubMed

    Agulhon, Pierre; Robitzer, Mike; Habas, Jean-Pierre; Quignard, Françoise

    2014-11-04

    The rheological properties of several ionotropic alginate hydrogels were investigated according to the nature of the divalent cation (Mn(2+), Co(2+), Cu(2+)) and the guluronic fraction of the alginate (HG and LG for "high G-content" and "low G-content"). Six hydrogels (Mn-LG, Mn-HG, Co-LG, Co-HG, Cu-LG and Cu-HG) were synthesized and studied by spectromechanical analyses. On one hand, Cu-HG, Cu-LG and Co-HG behaved as viscoelastic solids: the elastic contribution was higher than the dissipative component in all the frequency range studied (G'>G"). No flow zone (G">G') was detected even at very low values of the shearing frequency. On the other, Mn-HG, Mn-LG and Co-LG presented a spectromechanical behavior that resembled that observed classically for entangled polymers. Indeed, at high frequency, these latter materials could be compared to a viscoelastic solid but at low frequency, the flow zone was described and the viscous character became prevalent with finite relaxation time. Very good correlations with the microscopic structurations of the network were evidenced (rubbery vs. flow zone and fibrillar vs. complex morphology respectively).

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

    PubMed

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

    2015-12-04

    Kramers' theory frames chemical reaction rates in solution as reactants overcoming a barrier in the presence of friction and noise. For weak coupling to the solution, the reaction rate is limited by the rate at which the solution can restore equilibrium after a subset of reactants have surmounted the barrier to become products. For strong coupling, there are always sufficiently energetic reactants. However, the solution returns many of the intermediate states back to the reactants before the product fully forms. Here, we demonstrate that the thermal conductance displays an analogous physical response to the friction and noise that drive the heat current through a material or structure. A crossover behavior emerges where the thermal reservoirs dominate the conductance at the extremes and only in the intermediate region are the intrinsic properties of the lattice manifest. Not only does this shed new light on Kramers' classic turnover problem, this result is significant for the design of devices for thermal management and other applications, as well as the proper simulation of transport at the nanoscale.

  19. Crossover behavior of the thermal conductance and Kramers’ transition rate theory

    SciTech Connect

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

    2015-12-04

    Kramers’ theory frames chemical reaction rates in solution as reactants overcoming a barrier in the presence of friction and noise. For weak coupling to the solution, the reaction rate is limited by the rate at which the solution can restore equilibrium after a subset of reactants have surmounted the barrier to become products. For strong coupling, there are always sufficiently energetic reactants. However, the solution returns many of the intermediate states back to the reactants before the product fully forms. Here, we demonstrate that the thermal conductance displays an analogous physical response to the friction and noise that drive the heat current through a material or structure. A crossover behavior emerges where the thermal reservoirs dominate the conductance at the extremes and only in the intermediate region are the intrinsic properties of the lattice manifest. Finally, not only does this shed new light on Kramers’ classic turnover problem, this result is significant for the design of devices for thermal management and other applications, as well as the proper simulation of transport at the nanoscale.

  20. Crossover behavior of the thermal conductance and Kramers’ transition rate theory

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Kramers’ theory frames chemical reaction rates in solution as reactants overcoming a barrier in the presence of friction and noise. For weak coupling to the solution, the reaction rate is limited by the rate at which the solution can restore equilibrium after a subset of reactants have surmounted the barrier to become products. For strong coupling, there are always sufficiently energetic reactants. However, the solution returns many of the intermediate states back to the reactants before the product fully forms. Here, we demonstrate that the thermal conductance displays an analogous physical response to the friction and noise that drive the heat current through a material or structure. A crossover behavior emerges where the thermal reservoirs dominate the conductance at the extremes and only in the intermediate region are the intrinsic properties of the lattice manifest. Not only does this shed new light on Kramers’ classic turnover problem, this result is significant for the design of devices for thermal management and other applications, as well as the proper simulation of transport at the nanoscale.

  1. Transition of Temporal Scaling Behavior in Percolation Assisted Shear-branching Structure during Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Ren, Jingli; Chen, Cun; Wang, Gang; Liaw, Peter K.

    2017-03-01

    This paper explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10‑2 s‑1 the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at the intermediate temperature. Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10‑2 s‑1.

  2. Transition of Temporal Scaling Behavior in Percolation Assisted Shear-branching Structure during Plastic Deformation

    PubMed Central

    Ren, Jingli; Chen, Cun; Wang, Gang; Liaw, Peter K.

    2017-01-01

    This paper explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10−2 s−1; the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at the intermediate temperature. Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10−2 s−1. PMID:28327562

  3. Atomic-Resolution Visualization of Distinctive Chemical Mixing Behavior of Ni, Co and Mn with Li in Layered Lithium Transition-Metal Oxide Cathode Materials

    SciTech Connect

    Yan, Pengfei; Zheng, Jianming; Lv, Dongping; Wei, Yi; Zheng, Jiaxin; Wang, Zhiguo; Kuppan, Saravanan; Yu, Jianguo; Luo, Langli; Edwards, Danny J.; Olszta, Matthew J.; Amine, Khalil; Liu, Jun; Xiao, Jie; Pan, Feng; Chen, Guoying; Zhang, Jiguang; Wang, Chong M.

    2015-07-06

    Capacity and voltage fading of layer structured cathode based on lithium transition metal oxide is closely related to the lattice position and migration behavior of the transition metal ions. However, it is scarcely clear about the behavior of each of these transition metal ions. We report direct atomic resolution visualization of interatomic layer mixing of transition metal (Ni, Co, Mn) and lithium ions in layer structured oxide cathodes for lithium ion batteries. Using chemical imaging with aberration corrected scanning transmission electron microscope (STEM) and DFT calculations, we discovered that in the layered cathodes, Mn and Co tend to reside almost exclusively at the lattice site of transition metal (TM) layer in the structure or little interlayer mixing with Li. In contrast, Ni shows high degree of interlayer mixing with Li. The fraction of Ni ions reside in the Li layer followed a near linear dependence on total Ni concentration before reaching saturation. The observed distinctively different behavior of Ni with respect to Co and Mn provides new insights on both capacity and voltage fade in this class of cathode materials based on lithium and TM oxides, therefore providing scientific basis for selective tailoring of oxide cathode materials for enhanced performance.

  4. Structure, phase transition, and controllable thermal expansion behaviors of Sc(2-x)Fe(x)Mo₃O₁₂.

    PubMed

    Wu, Meimei; Liu, Xinzhi; Chen, Dongfeng; Huang, Qingzhen; Wu, Hui; Liu, Yuntao

    2014-09-02

    The crystal structures, phase transition, and thermal expansion behaviors of solid solutions of Sc(2-x)Fe(x)Mo3O12 (0 ≤ x ≤ 2) have been examined using X-ray diffraction (XRD), neutron powder diffraction (NPD), and differential scanning calorimetry (DSC). At room temperature, samples crystallize in a single orthorhombic structure for the compositions of x < 0.6 and monoclinic for x ≥ 0.6, respectively. DSC results indicate that the phase transition temperature from monoclinic to orthorhombic structure is enhanced by increasing the Fe(3+) content. High-temperature XRD and NPD results show that Sc(1.3)Fe(0.7)Mo3O12 exhibits near zero thermal expansion, and the volumetric coefficients of thermal expansion derived from XRD and NPD are 0.28 × 10(-6) °C(-1) (250-800 °C) and 0.65 × 10(-6) °C(-1) (227-427 °C), respectively. NPD results of Sc2Mo3O12 (x = 0) and Sc(1.3)Fe(0.7)Mo3O12 (x = 0.7) indicate that Fe substitution for Sc induces reduction of the mean Sc(Fe)-Mo nonbond distance and the different thermal variations of Sc(Fe)-O5-Mo2 and Sc(Fe)-O3-Mo2 bond angles. The correlation between the displacements of oxygen atoms and the variation of unit cell parameters was investigated in detail for Sc2Mo3O12.

  5. Do testosterone declines during the transition to marriage and fatherhood relate to men's sexual behavior? Evidence from the Philippines.

    PubMed

    Gettler, Lee T; McDade, Thomas W; Agustin, Sonny S; Feranil, Alan B; Kuzawa, Christopher W

    2013-11-01

    Testosterone (T) is thought to help facilitate trade-offs between mating and parenting in humans. Across diverse cultural settings married men and fathers have lower T than other men and couples' sexual activity often declines during the first years of marriage and after having children. It is unknown whether these behavioral and hormonal changes are related. Here we use longitudinal data from a large study in the Philippines (n=433) to test this model. We show that among unmarried non-fathers at baseline (n=153; age: 21.5 ± 0.3 years) who became newly married new fathers by follow-up (4.5 years later), those who experienced less pronounced longitudinal declines in T reported more frequent intercourse with their partners at follow-up (p<0.01) compared to men with larger declines in T. Controlling for duration of marriage, findings were similar for men transitioning from unmarried to married (without children) (p<0.05). Men who remained unmarried and childless throughout the study period did not show similar T-sexual activity outcomes. Among newly married new fathers, subjects who had frequent intercourse both before and after the transition to married fatherhood had more modest declines in T compared to peers who had less frequent sex (p<0.001). Our findings are generally consistent with theoretical expectations and cross-species empirical observations regarding the role of T in male life history trade-offs, particularly in species with bi-parental care, and add to evidence that T and sexual activity have bidirectional relationships in human males.

  6. Polyphase ductile/brittle deformation along a major tectonic boundary in an ophiolitic nappe, Alpine Corsica: Insights on subduction zone intermediate-depth asperities

    NASA Astrophysics Data System (ADS)

    Magott, Rémi; Fabbri, Olivier; Fournier, Marc

    2017-01-01

    In an ophiolitic nappe of Alpine Corsica, a major fault zone superimposes metagabbro over serpentinite and peridotite. Ductile and brittle deformation structures are observed in the fault damage zones. In the metagabbro damage zone, early deformation culminates in blueschist or eclogite facies conditions and consists of west-verging mylonitization alternating with pseudotachylyte-forming faulting with undetermined vergence. This early deformation is likely coeval with west-verging seismic (pseudotachylyte-forming) reverse faulting in the footwall peridotite or with aseismic distributed cataclastic deformation of footwall serpentinite. These early events (aseismic mylonitization or distributed cataclasis and seismic faulting) are interpreted as reverse faulting/shear in an east-dipping subducting oceanic lithosphere in Cretaceous to Eocene times. Late deformation events consist of ductile shear and seismic faulting having occurred under retrograde greenschist conditions. Kinematics of the ductile shear is top-to-the-east. These events are interpreted as the result of syn-to post-collision extension of Alpine Corsica in Eocene to Miocene times. The heterogeneous distribution of pseudotachylyte veins along the fault zone (abundant at peridotite-metagabbro interfaces, rare or absent at serpentinite-metagabbro interfaces) is interpreted as the consequence of contrasted frictional properties of the rocks in contact. High-friction peridotite-metagabbro contacts could correspond to asperities whereas low-friction serpentinite-metagabbro contacts could correspond to creeping zones.

  7. Visual analysis of ductility/brittleness of welding fracture points on charpy test specimens using graphical blocks on field programmable gate arrays

    NASA Astrophysics Data System (ADS)

    Tickle, Andrew J.; Camargo-Rodriguez, Anyela; Smith, Jeremy S.

    2008-09-01

    The charpy impact is a technique used to evaluate the toughness of an engineering material that determines the amount of energy absorbed by it during fracture. Initially, measurements were estimated manually and later replaced by a PC version. This study reports the development of the Field Programmable Gate Array (FPGA) portable version. The FPGA based version allows easy analysis of samples without the need of sending them to a lab for analysis. The process, presented here, as the original, is based on measuring the percent of crystal in the test sample after impact, to determine if the material is ductile or brittle. The FPGA version, adapted under the MATLAB Simulink environment, shows a graphical block representation of the charpy impact PC version. An important asset of the FPGA version is its portability, it has to be easily modified and downloaded onto a device to estimate the percent of brittle fracture of the broken Charpy surface. The beauty of the DSP Builder programme is that it allows the model to be compiled to various types of optimised code for any Altera FPGA device. To provide a firm basis for scientific comparison to the new FPGA system, images already analysed via the PC based Java system were also used for testing and comparison purposes. The FPGA system converts the image into an 8 bit grayscale image and analyses it in a 5x5 sampling window. This produces texture features that can be used in a comparison system, similar to the Support Vector Machine (SVM) used in the original. The output is a signal that states the material being tested is brittle or not via an output of '1' for brittle and a '0' for ductile. A detailed pixel by pixel analysis of the various output images is then investigated to state the percentage difference between the PC and FPGA based systems.

  8. Mechanical Behavior of Collagen-Fibrin Co-Gels Reflects Transition From Series to Parallel Interactions With Increasing Collagen Content

    PubMed Central

    Lai, Victor K.; Lake, Spencer P.; Frey, Christina R.; Tranquillo, Robert T.; Barocas, Victor H.

    2013-01-01

    Fibrin and collagen, biopolymers occurring naturally in the body, are commonly-used biomaterials as scaffolds for tissue engineering. How collagen and fibrin interact to confer macroscopic mechanical properties in collagen-fibrin composite systems remains poorly understood. In this study, we formulated collagen-fibrin co-gels at different collagen-to-fibrin ratios to observe changes in overall mechanical behavior and microstructure. A modeling framework of a two-network system was developed by modifying our micro-scale model, considering two forms of interaction between the networks: (a) two interpenetrating but non-interacting networks (“parallel”), and (b) a single network consisting of randomly alternating collagen and fibrin fibrils (“series”). Mechanical testing of our gels show that collagen-fibrin co-gels exhibit intermediate properties (UTS, strain at failure, tangent modulus) compared to those of pure collagen and fibrin. Comparison with model predictions show that the parallel and series model cases provide upper and lower bounds respectively for the experimental data, suggesting that a combination of such interactions exist between collagen and fibrin in co-gels. A transition from the series model to the parallel model occurs with increasing collagen content, with the series model best describing predominantly fibrin co-gels, and the parallel model best describing predominantly collagen co-gels. PMID:22482659

  9. Universal behavior of the γ⁎γ→(π0,η,η′) transition form factors

    PubMed Central

    Melikhov, Dmitri; Stech, Berthold

    2012-01-01

    The photon transition form factors of π, η and η′ are discussed in view of recent measurements. It is shown that the exact axial anomaly sum rule allows a precise comparison of all three form factors at high-Q2 independent of the different structures and distribution amplitudes of the participating pseudoscalar mesons. We conclude: (i) The πγ form factor reported by Belle is in excellent agreement with the nonstrange I=0 component of the η and η′ form factors obtained from the BaBar measurements. (ii) Within errors, the πγ form factor from Belle is compatible with the asymptotic pQCD behavior, similar to the η and η′ form factors from BaBar. Still, the best fits to the data sets of πγ, ηγ, and η′γ form factors favor a universal small logarithmic rise Q2FPγ(Q2)∼log(Q2). PMID:23226917

  10. Improvement of Sintering, Thermal Behavior, and Electrical Properties of Calcium- and Transition Metal-Doped Yttrium Chromite

    SciTech Connect

    Yoon, Kyung J.; Cramer, Carolyn N.; Stevenson, Jeffry W.; Marina, Olga A.

    2010-06-21

    The A-site calcium doped yttrium chromite was additionally doped with various transition metals on the B-site to improve the sintering, thermal behavior and electrical properties of these ceramics for future use as an interconnect material in high temperature solid oxide fuel cells (SOFC). With 10 % addition of Co, Cu, Ni, Fe, and Mn, the single phase orthorhombic perovskite structure remained stable over a wide range of oxygen partial pressures, as confirmed by X-ray diffraction. The substitution of Cu for chromium remarkably improved the sinterability and allowed full densification in air by sintering at 1400 degrees C. The substitution of Co and Ni significantly improved the electrical conductivity of yttrium chromites in both oxidizing and reducing environments. This was explained by the increase of charge carrier density with nickel and cobalt doping, as confirmed by Seebeck measurements. With 10% of nickel dopant, the electrical conductivity of Y0.8Ca0.2CrO3±δ increased from 12 to 38 S/cm in air and from 2 to 15 S/cm in reducing atmosphere at 950 degrees C. Mn doping had a negative effect on the sintering and electrical conductivity.

  11. Effect of the polymer chain length of poly(N-isopropylacrylamide) on the temperature-responsive phase transition behavior of its conjugates with [60]fullerene.

    PubMed

    Uchida, Katsumi; Tamura, Atsushi; Yajima, Hirofumi

    2010-03-01

    In order to develop biomedical materials with specific functionalities, thermoresponsive conjugates [poly(N-isopropylacrylamide)-C(60) (PIPAAm-C(60)) ]of [60]fullerene (C(60)) and PIPAAm with two different polymer chain lengths (4 and 20 kDa) were synthesized by atom transfer radical polymerization. The effects of the polymer chain length on the temperature-responsive phase transition behavior of the synthetic PIPAAm-C(60) conjugates were probed by means of various physicochemical techniques. The coexistence of unimers and molecular assemblies of PIPAAm-C(60) was observed by gel permeation chromatography and dynamic light scattering studies in two PIPAAm-C(60) aqueous solutions below their lower critical solution temperatures (LCSTs). Additionally, below their LCSTs, differences in PIPAAm chain length gave rise to changes in the composition of the unimers and molecular assemblies. In response to temperature, the absorbance of the PIPAAm-C(60) aqueous solution changed according to a two-step behavior profile. Increasing temperature during the primary stage, where a change in the absorbance of the PIPAAm-C(60) aqueous solution took place, did not change the transition temperature, regardless of the solution concentration of PIPAAm-C(60). This absorbance change was associated with the phase transition of the molecular assemblies of PIPAAm-C(60). However, at the second stage, the transition temperature shifted to a higher value with the decrease in the concentration of PIPAAm-C(60), in the same manner as free PIPAAm chains. The second change was associated with the phase transition of the unimeric PIPAAm-C(60). Differences in PIPAAm chain length gave rise to the change in the phase transition behavior of PIPAAm-C(60) aqueous solution. Therefore, the chain length of PIPAAm was found to be a predominant factor involved in the solution characteristics of PIPAAm-C(60). Consequently, the PIPAAm-C(60) is expected to be an intelligent biomaterial possessing heat

  12. Effects of surface wettability and roughness of microchannel on flow behaviors of thermo-responsive microspheres therein during the phase transition.

    PubMed

    Zhou, Ming-Yu; Xie, Rui; Yu, Ya-Lan; Chen, Gang; Ju, Xiao-Jie; Yang, Lihua; Liang, Bin; Chu, Liang-Yin

    2009-08-01

    The flow characteristics of monodisperse thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) microspheres during the phase transition in microchannels with different surface wettabilities and roughnesses are investigated systematically. Glass microchannels are modified by hydroxylation treatment to achieve hydrophilic surface, by self-assembly of chlorotrimethylsilane to realize hydrophobic surface, and by coating with silica nanoparticles to generate rough surface. The phase transition of PNIPAM microspheres in microchannels is induced by local heating. The results show that the surface wettability and roughness of microchannel significantly affect the flow behaviors of PNIPAM microspheres during the phase transition. It is much easier for the PNIPAM microspheres in microchannel with hydrophobic surface to stop right after the phase transition than those in microchannel with hydrophilic surface, and it is also much easier for the PNIPAM microspheres in microchannel with rough surface to stop right after the phase transition than those in microchannel with smooth surface. These results indicate that hydrophobic and rough surface properties of the microchannel can enhance the site-specific targeting of PNIPAM microspheres caused by the phase transition. The results in this study provide valuable information for the application of thermo-responsive drug carriers in site-specific targeting therapy.

  13. Transition from the Lactational Amenorrhea Method to other modern family planning methods in rural Bangladesh: barrier analysis and implications for behavior change communication program intervention design.

    PubMed

    Kouyaté, Robin Anthony; Ahmed, Salahuddin; Haver, Jaime; McKaig, Catharine; Akter, Nargis; Nash-Mercado, Angela; Baqui, Abdullah

    2015-06-01

    The timely transition from Lactational Amenorrhea Method (LAM)(2) to another modern family planning method contributes to healthy spacing of pregnancies by increasing the adoption of family planning during the first year postpartum. Yet, literature suggests challenges in completing a timely LAM transition. To guide program implementation in Bangladesh, this study identified factors influencing women's transition decisions. Eighty postpartum women, comprising 40 who transitioned from LAM(3) and 40 who did not,(4) participated. Half of each group participated in in-depth interviews to explore the decision-making process. All participants responded to a "Barrier Analysis" questionnaire to identify differences in eight behavioral determinants. More than half of transitioners switched to another modern method before or within the same month that LAM ended. Of the 18 transitioners who delayed,(5) 15 waited for menses to return. For non-transitioners, key barriers included waiting for menses to return, misconceptions on return to fertility, and perceived lack of familial support. The LAM transition can help women prevent unintended pregnancy during the first year postpartum. Increased emphasis on counseling women about the risk of pregnancy, and misconceptions about personal fertility patterns are critical for facilitating the transition. Strategies should also include interventions that train health workers and improve social support.

  14. 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.

    PubMed

    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) and their parents and teachers. Three dimensions of parenting, warm responsiveness, induction, and corporal punishment, were assessed via maternal report when children were 3 years old. Child effortful control at age 3 was measured using laboratory tasks and a mother-report questionnaire. Mothers and teachers contributed ratings of child externalizing behavior at age 6. Results showed that the hypothesized model fit the data well and that the pattern of associations between constructs differed for boys and girls. For boys, parental warm responsiveness and corporal punishment had significant indirect effects on children's externalizing behavior three years later, mediated by child effortful control. Such relations were not observed for girls. These findings support a sex-differentiated pathway to externalizing behavior across the transition from preschool to school.

  15. Thermal glass transition beyond the Vogel-Fulcher-Tammann behavior for glass forming diglycidylether of bisphenol A.

    PubMed

    Krüger, J K; Britz, T; Baller, J; Possart, W; Neurohr, H

    2002-12-31

    For the low molecular weight fragile liquid diglycidyl ether of bisphenol A we report, based on Brillouin and dielectric spectroscopy, on a thermal glass transition where the relaxation time of the alpha process does not go to infinity. Instead, the structural alpha relaxation disappears spontaneously at the transition point. That discontinuity in relaxation time coincides with a kink in the longitudinal hypersonic velocity and determines unambiguously the transition from the liquid to the glassy state.

  16. Critical behavior of the number of minima of a random landscape at the glass transition point and the Tracy-Widom distribution.

    PubMed

    Fyodorov, Yan V; Nadal, Celine

    2012-10-19

    We exploit a relation between the mean number N(m) of minima of random Gaussian surfaces and extreme eigenvalues of random matrices to understand the critical behavior of N(m) in the simplest glasslike transition occuring in a toy model of a single particle in an N-dimensional random environment, with N>1. Varying the control parameter μ through the critical value μ(c) we analyze in detail how N(m)(μ) drops from being exponentially large in the glassy phase to N(m)(μ)~1 on the other side of the transition. We also extract a subleading behavior of N(m)(μ) in both glassy and simple phases. The width δμ/μ(c) of the critical region is found to scale as N(-1/3) and inside that region N(m)(μ) converges to a limiting shape expressed in terms of the Tracy-Widom distribution.

  17. Local magnetic behavior across the first order phase transition in La(Fe0.9Co0.015Si0.085)13 magneto caloric compound

    NASA Astrophysics Data System (ADS)

    Bennati, C.; Laviano, F.; Durin, G.; Olivetti, E. S.; Basso, V.; Ghigo, G.; Kuepferling, M.

    2016-02-01

    We visualize, with a magneto optical imaging technique with indicator film, the local magnetic response of the compound La(Fe0.9Co0.015Si0.085)13 during its first order magneto structural transition. The technique allowed us by comparing the stray fields of the main magneto caloric phase and of secondary phases present in the sample to obtain the magnetic behavior of each phase above and below the Curie temperature with respect to the surrounds. Computing the change in the total magnetic flux, when the sample crosses the Curie point, both in cooling and heating, we are able to correlate the average thermal hysteresis of the transition with the local magnetic properties at single sites and analyze the influence of defects on the transition dynamics.

  18. Increasing On-Task Behavior in Every Student in a Second-Grade Classroom during Transitions: Validating the Color Wheel System

    ERIC Educational Resources Information Center

    Fudge, Daniel L.; Skinner, Christopher H.; Williams, Jacqueline L.; Cowden, Dan; Clark, Janice; Bliss, Stacy L.

    2008-01-01

    A single-case (B-C-B-C) experimental design was used to evaluate the effects of the Color Wheel classroom management system (CWS) on on-task (OT) behavior in an intact, general-education, 2nd-grade classroom during transitions. The CWS included three sets of rules, posted cues to indicate the rules students are expected to be following at that…

  19. Improving Transition Behaviors in Students with Autism Spectrum Disorders: A Comprehensive Evaluation of Interventions in Educational Settings

    ERIC Educational Resources Information Center

    Lequia, Jenna; Wilkerson, Kimber L.; Kim, Sunyoung; Lyons, Gregory L.

    2015-01-01

    Students with autism spectrum disorders (ASD) often exhibit rigidity, which can lead to difficulties with transitions. Such difficulties can explain why students with ASD are placed in more restrictive educational environments. This review offers a quantitative synthesis of effects of interventions aimed to improve transitions of students with ASD…

  20. Transition behavior of asymmetric polystyrene-b-poly(2-vinylpyridine) films: A stable hexagonally modulated layer structure

    SciTech Connect

    Park, Sungmin; Koo, Kyosung; Kim, Kyunginn; Ahn, Hyungju; Lee, Byeongdu; Park, Cheolmin; Ryu, Du Yeol

    2015-03-09

    The phase transitions in the films of an asymmetric polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) were investigated by grazing incidence small-angle X-ray scattering (GISAXS) and transmission electron microscopy (TEM). Compared with the sequential transitions in the bulk, hexagonally perforated layer (HPL) – gyroid (GYR) – disorder (DIS) upon heating, the transitions in film geometry were dramatically changed with decreasing thickness due to the growing preferential interactions from substrate, resulting in a thickness-dependent transition diagram including four different morphologies of hexagonally modulated layer (HML), coexisting (HML and GYR), GYR, and DIS. Particularly in the films ≤10Lo, where Lo is d-spacing at 150 °C, a stable HML structure was identified even above the order-to-disorder transition (ODT) temperature of the bulk, which was attributed to the suppressed compositional fluctuations by the enhanced substrate interactions.

  1. Phase transition behaviors of the supported DPPC bilayer investigated by sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM).

    PubMed

    Wu, Heng-Liang; Tong, Yujin; Peng, Qiling; Li, Na; Ye, Shen

    2016-01-21

    The phase transition behaviors of a supported bilayer of dipalmitoylphosphatidyl-choline (DPPC) have been systematically evaluated by in situ sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). By using an asymmetric bilayer composed of per-deuterated and per-protonated monolayers, i.e., DPPC-d75/DPPC and a symmetric bilayer of DPPC/DPPC, we were able to probe the molecular structural changes during the phase transition process of the lipid bilayer by SFG spectroscopy. It was found that the DPPC bilayer is sequentially melted from the top (adjacent to the solution) to bottom leaflet (adjacent to the substrate) over a wide temperature range. The conformational ordering of the supported bilayer does not decrease (even slightly increases) during the phase transition process. The conformational defects in the bilayer can be removed after the complete melting process. The phase transition enthalpy for the bottom leaflet was found to be approximately three times greater than that for the top leaflet, indicating a strong interaction of the lipids with the substrate. The present SFG and AFM observations revealed similar temperature dependent profiles. Based on these results, the temperature-induced structural changes in the supported lipid bilayer during its phase transition process are discussed in comparison with previous studies.

  2. The effect of various metallurgical parameters on the flow and fracture behavior of polycrystalline NiAl near the brittle-to-ductile transition

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.

    1994-01-01

    An investigation of the effect of various metallurgical parameters such as interfaces, allowing additions, test temperature, and strain rate on the flow and fracture behavior of polycrystalline NiAl is summarized. From this study, a more complete understanding of the deformation and fracture behavior of polycrystalline NiAl near the brittle-to-ductile transition temperature has been developed. A mechanism for the BDTT is proposed that is based on the operation of localized dislocation climb processes that operate within the vicinity of the grain boundaries and provide the additional deformation mechanisms necessary for grain-to-grain compatibility during plastic deformation. Finally, methods for improving the low temperature mechanical behavior of NiAl were considered and reviewed within the context of the present knowledge of NiAl-based materials and the operative deformation and fracture mechanisms determined in this study. Special emphasis was placed on the use of second phases for improving low temperature properties.

  3. Proximal Influences on the Trajectory of Suicidal Behaviors and Suicide during the Transition from Adolescence to Young Adulthood.

    PubMed

    Sood, Aradhana Bela; Linker, Julie

    2017-04-01

    Youth transitioning to adulthood have unique developmental tasks that make them vulnerable to suicide. Brain development, life stressors, and psychological adjustments during the transition contribute to a high rate of suicidal gestures. To reduce the incidence of self-harm in this age group, a public health approach that identifies and reduces risk factors and enhances protective factors should be used. Institutions and employment arenas should consider structural supports to facilitate this transition of youth into adulthood, with a particular focus on youth with self-harm thoughts, and should provide education about suicide, evidence-based resources, and intervention programs to encourage help seeking.

  4. Gambling behavior and problem gambling reflecting social transition and traumatic childhood events among Greenland Inuit: a cross-sectional study in a large indigenous population undergoing rapid change.

    PubMed

    Larsen, Christina Viskum Lytken; Curtis, Tine; Bjerregaard, Peter

    2013-12-01

    An increase in social pathologies is a key feature in indigenous populations undergoing transition. The Greenland Inuit are a large indigenous population constituting a majority in their own country, which makes it possible to investigate differences within the population. This led us to study gambling behavior and problem gambling among Greenland Inuit in relation to the ongoing social transition and traumatic events during childhood. A large representative cross-sectional study was conducted among Greenland Inuit (n = 2,189). Data was collected among adults (18+) in 9 towns and 13 villages in Greenland from 2005 to 2010. Problem gambling, gambling behavior and traumatic childhood events were measured through a self-administered questionnaire. The lie/bet screen was used to identify past year and lifetime problem gambling. Social transition was measured as place of residence and a combination of residence, education and occupation. The lifetime prevalence of problem gambling was 16 % among men and 10 % among women (p < 0.0001); and higher in towns (19 %) compared to the capital of Nuuk (11 %) and in villages (12 %) (men only, p = 0.020). Lifetime problem gambling was associated with social transition (p = 0.023), alcohol problems in childhood home (p = 0.001/p = 0.002) and sexual abuse in childhood (women only, p = 0.030). A comparably high prevalence of lifetime problem gambling among Greenland Inuit adds problem gambling to the list of social pathologies in Greenland. A significant association between lifetime problem gambling, social transition and traumatic childhood events suggests people caught between tradition and modern ways of life are more vulnerable to gambling problems.

  5. Behaviorism

    ERIC Educational Resources Information Center

    Moore, J.

    2011-01-01

    Early forms of psychology assumed that mental life was the appropriate subject matter for psychology, and introspection was an appropriate method to engage that subject matter. In 1913, John B. Watson proposed an alternative: classical S-R behaviorism. According to Watson, behavior was a subject matter in its own right, to be studied by the…

  6. Effects of deformation-induced martensite and grain size on ductile-to-brittle transition behavior of austenitic 18Cr-10Mn-N stainless steels

    NASA Astrophysics Data System (ADS)

    Hwang, Byoungchul; Lee, Tae-Ho; Kim, Sung-Joon

    2010-12-01

    Effects of deformation-induced martensite and grain size on ductile-to-brittle transition behavior of austenitic 18Cr-10Mn-(0.3˜0.6)N stainless steels with different alloying elements were investigated by means of Charpy impact tests and microstructural analyses. The steels all exhibited ductile-to-brittle transition behavior due to unusual brittle fracture at low temperatures despite having a face-centered cubic structure. The ductileto-brittle transition temperature (DBTT) obtained from Chapry impact tests did not coincide with that predicted by an empirical equation depending on N content in austenitic Cr-Mn-N stainless steels. Furthermore, a decrease of grain size was not effective in terms of lowering DBTT. Electron back-scattered diffraction and transmission electron microscopy analyses of the cross-sectional area of the fracture surface showed that some austenites with lower stability could be transformed to α'-martensite by localized plastic deformation near the fracture surface. Based on these results, it was suggested that when austenitic 18Cr-10Mn-N stainless steels have limited Ni, Mo, and N content, the deterioration of austenite stability promotes the formation of deformation-induced martensite and thus increases DBTT by substantially decreasing low-temperature toughness.

  7. Toughness of 12%Cr ferritic/martensitic steel welds produced by non-arc welding processes

    SciTech Connect

    Ginn, B.J.; Gooch, T.G.

    1998-08-01

    Low carbon 12%Cr steels can offer reduced life cycle costs in many applications. The present work examined the behavior of commercial steels of varying composition when subject to low heat input welding by the electron beam (EB) process and to a forge cycle by linear friction welding (LFW). Charpy impact testing was carried out on the high temperature heat-affected zone (HAZ)/fusion boundary or weld interface, with metallographic examination. With EB welding, the ductile-brittle transition temperature (DBTT) was below 0 C (32 F) only for steel of low ferrite factor giving a fully martensitic weld area. Higher ferrite factor alloys showed predominantly ferritic transformed microstructures and a transition well above room temperature. Grain coarsening was found even with low EB process power, the peak grain size increasing with both heat input and steel ferrite factor. Use of LFW gave a fine weld area structure and DBTTs around 0 C even in high ferrite factor (FF) material.

  8. Kinetics and microscopic processes of long-term fracture in polyethylene-piping materials. Annual report, February 1, 1989-February 1, 1990

    SciTech Connect

    Brown, N.; Lu, X.

    1990-05-10

    Contents: notchology--the effect of the notching method on the slow crack growth failure in tough polyethylene; the effect of molecular weight on the fatigue behavior of high density polyethylene; the transition from ductile to slow crack growth failure in a copolymer of polyethylene; the ductile-brittle transition in a polyethylene copolymer; a unification of ductile failure and slow crack growth in an ethylene-octene copolymer; the dependence of butyl branch density on slow crack growth in polyethylene-kinetics; slow crack growth under fatigue and constant stress for ethylene-hexene resins with different density of branches; correlation of the fatigue test and the constant load slow crack growth test; relationship between slow crack growth and morphological change in ethylene-hexene copolymers; morphological changes on annealing in hdpe and mdpe and their effect on slow crack growth; ranking of pe gas pipe resins in air and igepal; brittle fracture of pe at low temperature; butt fusion welding.

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

    PubMed

    Dereymaker, Aswin; Van Den Mooter, Guy

    2015-05-01

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

  10. Testing the Effects of Classroom Supports on Children's Social and Behavioral Skills at Key Transition Points Using Latent Growth Modeling

    ERIC Educational Resources Information Center

    Bub, Kristen L.

    2009-01-01

    Social and behavioral problems can interfere with a child's acquisition of age-appropriate skills, which may lead to antisocial behavior in adolescence and adulthood. Thus, determining how best to support positive skills during early childhood is critical. Using data from the first three phases of the NICHD Study of Early Child Care and Youth…

  11. Spin-polarized transport and magnetization reversal behavior of transition metal and half-metallic chromium dioxide thin films and multilayers

    NASA Astrophysics Data System (ADS)

    Anguelouch, Alexandre

    In recent years the interest in the properties of sub-micron ferromagnetic systems has been growing due to both their fundamental significance and practical applications in the fields of magnetic random access memory and magnetic sensing. In the thesis we have studied the magnetization reversal and spin-dependent transport behavior in transition-metal ferromagnets and half-metallic chromium dioxide films and heterostructures. In the case of transition-metal ferromagnets we have investigated the contribution that thermal fluctuations make toward the reversal process of sub-micron patterned elements. We establish that the fluctuations are significant and as a result, that the switching is a stochastic process. Our conclusion is that the Neel-Arrhenius theory of thermally activated magnetic transitions adequately describes the observed behavior. Further, we have demonstrated that domain structure can have a drastic effect on critical "astroid" curves of transition metal micron- and sub-micron-size ferromagnetic films. For these studies, we used magnetic tunnel junctions (MTJs) as a tool for characterization, and we believe that this technique provides a useful method for investigation of the magnetic properties of patterned media. Half-metals are a class of ferromagnets with 100% spin polarization. These materials show great promise for use in magnetoelectronic applications, such as MTJ-based memory and as magnetic sensors. We have perfected a fabrication technique for obtaining single-crystal epitaxial CrO2 films with nearly complete spin polarization. We have analyzed the thickness dependence of electron transport and magnetic properties of CrO2, and have established that the magnetic, transport and structural properties in these films are closely interrelated. We also report the results of our attempts to fabricate CrO2-based MTJs.

  12. Irradiation effects on precipitation and its impact on the mechanical properties of reduced-activation ferritic/martensitic steels

    NASA Astrophysics Data System (ADS)

    Tanigawa, H.; Sakasegawa, H.; Hashimoto, N.; Klueh, R. L.; Ando, M.; Sokolov, M. A.

    2007-08-01

    It was previously reported that reduced-activation ferritic/martensitic steels (RAFs) showed a variety of changes in ductile-brittle transition temperature (DBTT) and yield stress after irradiation at 573 K up to 5 dpa. The precipitation behavior of the irradiated steels was examined and the presence of irradiation induced precipitation which works as if it was forced to reach the thermal equilibrium state at irradiation temperature 573 K. In this study, transmission electron microscopy was performed on extraction replica specimens to analyze the size distribution of precipitates. It turned out that the hardening level multiplied by the square root of the average block size showed a linear dependence on the extracted precipitate weight. This dependence suggests that the difference in irradiation hardening between RAFs was caused by different precipitation behavior on block, packet and prior austenitic grain boundaries during irradiation. The simple Hall-Petch law could be applicable for interpreting this dependence.

  13. High-temperature strength stability of three forms of chemically vapor deposited tungsten

    NASA Technical Reports Server (NTRS)

    Bryant, W. A.

    1974-01-01

    Three types of CVD tungsten (fluoride-produced, chloride-produced, and a layered composite of the two-termed duplex) were evaluated to determine their high-temperature strength and microstructural stability following 5000-hr exposure to temperatures of 1540 and 1700 C. At the highest temperatures investigated (1540 and 1700 C), the tensile strengths of the two basic materials were essentially equal. At lower temperatures, chloride tungsten possessed lower yield strength but higher ultimate strength than fluoride tungsten while the behavior of the duplex material was generally intermediate. Apparent anomalies in high-temperature elongation behavior are explained on the basis of grain boundary cavity formation and recrystallization. The grain size of fluoride tungsten changed only slightly following 5000-h treatment at 1700 C. In contrast, chloride tungsten possessed both poor resistance to grain growth and an accompanying relatively high ductile-brittle transition temperature.

  14. The developmental impact of two first grade preventive interventions on aggressive/disruptive behavior in childhood and adolescence: an application of latent transition growth mixture modeling.

    PubMed

    Petras, Hanno; Masyn, Katherine; Ialongo, Nick

    2011-09-01

    We examine the impact of two universal preventive interventions in first grade on the growth of aggressive/disruptive behavior in grades 1-3 and 6-12 through the application of a latent transition growth mixture model (LT-GMM). Both the classroom-centered and family-centered interventions were designed to reduce the risk for later conduct problems by enhancing the child behavior management practices of teachers and parents, respectively. We first modeled growth trajectories in each of the two time periods with separate GMMs. We then associated latent trajectory classes of aggressive/disruptive behavior across the two time periods using a transition model for the corresponding latent class variables. Subsequently, we tested whether the interventions had direct effects on trajectory class membership in grades 1-3 and 6-12. For males, both the classroom-centered and family-centered interventions had significant direct effects on trajectory class membership in grades 6-12, whereas only the classroom-centered intervention had a significant effect on class membership in grades 1-3. Significant direct effects for females were confined to grades 1-3 for the classroom-centered intervention. Further analyses revealed that both the classroom-centered and family-centered intervention males were significantly more likely than control males to transition from the high trajectory class in grades 1-3 to a low class in grades 6-12. Effects for females in classroom-centered interventions went in the hypothesized direction but did not reach significance.

  15. Sex or candy? Neuroendocrine regulation of the seasonal transition from courtship to feeding behavior in male red-sided garter snakes (Thamnophis sirtalis parietalis).

    PubMed

    Lutterschmidt, Deborah I; Maine, Ashley R

    2014-06-01

    This article is part of a Special Issue "Energy Balance". Seasonal modulation of glucocorticoids plays an important role in supporting critical life-history events, and probably facilitates transitions between different life-history stages. In a well-studied population of red-sided garter snakes (Thamnophis sirtalis parietalis), glucocorticoids are elevated during the mating season, but males dispersing to summer feeding grounds have significantly lower baseline glucocorticoids than courting males at the den. We tested the hypothesis that decreased plasma glucocorticoids mediate the behavioral switch between reproduction and foraging in this species. Using a two-choice Y-maze paradigm, we demonstrate that males treated with the glucocorticoid synthesis inhibitor metyrapone (1 and 3mg implants) prefer feeding cues (worm trail) over reproductive cues (female pheromone trail) significantly earlier than control-treated snakes. The metyrapone-induced changes in appetitive feeding behavior were independent of changes in plasma androgens and body mass loss. Metyrapone-treated males continued to court females at levels similar to those of control-treated snakes, suggesting that appetitive reproductive and ingestive behaviors are not mutually exclusive during this life-history transition. Consistent with this hypothesis, metyrapone treatment did not alter the number of arginine vasotocin-immunoreactive cells in any brain region, while it significantly increased neuropeptide Y-immunoreactive cell number in both the cortex and nucleus sphericus (homologues of the mammalian hippocampus and amygdala, respectively). Our results suggest that male red-sided garter snakes have the potential to maximize reproductive opportunities by continuing to court females they encounter even as they disperse from the den in search of food. Taken together, these data have important implications for understanding the neuroecology of seasonal life-history transitions.

  16. Scaling behavior of the magnetic-field-tuned superconductor-insulator transition in two-dimensional Josephson-junction arrays

    SciTech Connect

    Chen, C.D.; Delsing, P.; Haviland, D.B.; Harada, Y.; Claeson, T.

    1995-06-01

    We have studied the superconductor-insulator (SI) phase transition for two-dimensional (2D) arrays of small Josephson junctions in a weak magnetic field. The data were analyzed within the context of the theory of the magnetic-field-tuned SI transition in 2D superconductors. We show resistance scaling curves over several orders of magnitude for the 2D arrays. The critical exponent {ital z}{sub {ital B}} is determined to be 1.05, in good agreement with the theory. Moreover, the transverse (Hall) resistance at the critical field is found to be very small in comparison to the longitudinal resistance.

  17. Physical Activity in the Transition to University: The Role of Past Behavior and Concurrent Self-Regulatory Efficacy

    ERIC Educational Resources Information Center

    Crozier, Alyson J.; Gierc, Madelaine S. H.; Locke, Sean R.; Brawley, Lawrence R.

    2015-01-01

    Objective: Two studies were conducted to examine the relationship between past physical activity, concurrent self-regulatory efficacy (CSRE), and current physical activity during the transition to university. Participants: Study 1 included 110 first-year undergraduate students recruited during October/November of 2012. Study 2 involved 86…

  18. Helping Students Make the Transition into High School: The Effect of Ninth Grade Academies on Students' Academic and Behavioral Outcomes

    ERIC Educational Resources Information Center

    Somers, Marie-Andrée; Garcia, Ivonne

    2016-01-01

    Ninth Grade Academies (NGAs)--also called Freshman Academies--have attracted national attention as a particularly intensive and promising approach for supporting a successful transition for high school freshmen. An NGA is a self-contained learning community for ninth-graders that operates as a school within a school. NGAs have four core structural…

  19. Sexual Communication, Sexual Goals, and Students' Transition to College: Implications for Sexual Assault, Decision-Making, and Risky Behaviors

    ERIC Educational Resources Information Center

    Lindgren, Kristen P.; Schacht, Rebecca L.; Pantalone, David W.; Blayney, Jessica A.; George, William H.

    2009-01-01

    A qualitative study was conducted to understand college students' experiences and perceptions of sexual communication and sexual goals, and how they were affected by the transition from high school to college. Participants were heterosexual college students (N = 29). Single-sex focus groups were conducted and analyzed for themes. Major themes…

  20. School Performance and Genetic and Environmental Variance in Antisocial Behavior at the Transition from Adolescence to Adulthood

    PubMed Central

    Johnson, Wendy; McGue, Matthew K.; Iacono, William G.

    2009-01-01

    Antisocial behavior increases in adolescence, particularly among those who perform poorly in school. As adolescents move into adulthood, both educational attainment and the extent to which antisocial behavior continues have implications for their abilities to take on constructive social roles. We used a population-representative longitudinal twin study to explore how links between genetic and environmental influences at ages 17 and 24 may be implicated in the developmental processes involved. At age 17, expression of both genetic and nonshared environmental vulnerabilities unique to antisocial behavior was greater among those with low GPA than among those with higher GPA. This suggested that maintenance of high GPA buffered the impact of both genetic and environmental influences encouraging antisocial behavior. When GPA was high, both genetic and environmental influences involved in both traits encouraged good school performance and restrained antisocial behavior. At age 24, however, correlated family environmental influences drove the association between educational attainment and antisocial behavior. Antisocial characteristics involving school performance and educational attainment that transcend generations may slot individuals into social categories that restrict opportunities and reinforce antisocial characteristics. PMID:19586174

  1. Decoupling the Lattice Distortion and Charge Doping Effects on the Phase Transition Behavior of VO2 by Titanium (Ti(4+)) Doping.

    PubMed

    Wu, Yanfei; Fan, Lele; Liu, Qinghua; Chen, Shi; Huang, Weifeng; Chen, Feihu; Liao, Guangming; Zou, Chongwen; Wu, Ziyu

    2015-05-07

    The mechanism for regulating the critical temperature (TC) of metal-insulator transition (MIT) in ions-doped VO2 systems is still a matter of debate, in particular, the unclear roles of lattice distortion and charge doping effects. To rule out the charge doping effect on the regulation of TC, we investigated Ti(4+)-doped VO2 (Ti(x)V(1-x)O2) system. It was observed that the TC of Ti(x)V(1-x)O2 samples first slightly decreased and then increased with increasing Ti concentration. X-ray absorption fine structure (XAFS) spectroscopy was used to explore the electronic states and local lattice structures around both Ti and V atoms in Ti(x)V(1-x)O2 samples. Our results revealed the local structure evolution from the initial anatase to the rutile-like structure around the Ti dopants. Furthermore, the host monoclinic VO2 lattice, specifically, the VO6 octahedra would be subtly distorted by Ti doping. The distortion of VO6 octahedra and the variation of TC showed almost the similar trend, confirming the direct effect of local structural perturbations on the phase transition behavior. By comparing other ion-doping systems, we point out that the charge doping is more effective than the lattice distortion in modulating the MIT behavior of VO2 materials.

  2. Dynamic phase transition properties and hysteretic behavior of a ferrimagnetic core-shell nanoparticle in the presence of a time dependent magnetic field

    NASA Astrophysics Data System (ADS)

    Yüksel, Yusuf; Vatansever, Erol; Polat, Hamza

    2012-10-01

    We have presented dynamic phase transition features and stationary-state behavior of a ferrimagnetic small nanoparticle system with a core-shell structure. By means of detailed Monte Carlo simulations, a complete picture of the phase diagrams and magnetization profiles has been presented and the conditions for the occurrence of a compensation point Tcomp in the system have been investigated. According to Néel nomenclature, the magnetization curves of the particle have been found to obey P-type, N-type and Q-type classification schemes under certain conditions. Much effort has been devoted to investigating the hysteretic response of the particle, and we observed the existence of triple hysteresis loop behavior, which originates from the existence of a weak ferromagnetic core coupling Jc/Jsh, as well as a strong antiferromagnetic interface exchange interaction Jint/Jsh. Most of the calculations have been performed for a particle in the presence of oscillating fields of very high frequencies and high amplitudes in comparison with exchange interactions, which resembles a magnetic system under the influence of ultrafast switching fields. Particular attention has also been paid to the influence of the particle size on the thermal and magnetic properties, as well as magnetic features such as coercivity, remanence and the compensation temperature of the particle. We have found that, in the presence of ultrafast switching fields, the particle may exhibit a dynamic phase transition from paramagnetic to a dynamically ordered phase with increasing ferromagnetic shell thickness.

  3. Decoupling the Lattice Distortion and Charge Doping Effects on the Phase Transition Behavior of VO2 by Titanium (Ti4+) Doping

    PubMed Central

    Wu, Yanfei; Fan, Lele; Liu, Qinghua; Chen, Shi; Huang, Weifeng; Chen, Feihu; Liao, Guangming; Zou, Chongwen; Wu, Ziyu

    2015-01-01

    The mechanism for regulating the critical temperature (TC) of metal-insulator transition (MIT) in ions-doped VO2 systems is still a matter of debate, in particular, the unclear roles of lattice distortion and charge doping effects. To rule out the charge doping effect on the regulation of TC, we investigated Ti4+-doped VO2 (TixV1-xO2) system. It was observed that the TC of TixV1-xO2 samples first slightly decreased and then increased with increasing Ti concentration. X-ray absorption fine structure (XAFS) spectroscopy was used to explore the electronic states and local lattice structures around both Ti and V atoms in TixV1-xO2 samples. Our results revealed the local structure evolution from the initial anatase to the rutile-like structure around the Ti dopants. Furthermore, the host monoclinic VO2 lattice, specifically, the VO6 octahedra would be subtly distorted by Ti doping. The distortion of VO6 octahedra and the variation of TC showed almost the similar trend, confirming the direct effect of local structural perturbations on the phase transition behavior. By comparing other ion-doping systems, we point out that the charge doping is more effective than the lattice distortion in modulating the MIT behavior of VO2 materials. PMID:25950809

  4. Comparison of protein and energy supplementation to mineral supplementation on feeding behavior of grazing cattle during the rainy to the dry season transition.

    PubMed

    Brandão, Rita Kelly Couto; de Carvalho, Gleidson Giordano Pinto; Silva, Robério Rodrigues; Dias, Daniel Lucas Santos; Mendes, Fabrício Bacelar Lima; Lins, Túlio Otávio Jardim D'Almeida; Filho, George Abreu; de Souza, Sinvaldo Oliveira; Barroso, Daniele Soares; de Almeida Rufino, Luana Marta; Tosto, Manuela Silva Libânio

    2016-01-01

    The aim of this study was to evaluate the effects of protein-energy or mineral supplementation on the ingestive behavior of dairy steers on pasture in the post-weaning phase during the rainy to dry season transition. Twenty-two ½ Holstein-Zebu dairy steers with an average initial body weight of 234 ± 16 kg were distributed into a completely randomized design into two groups: protein-energy supplementation and mineral supplementation offered ad libitum. The steers receiving protein-energy supplementation showed higher (P < 0.05) intake of dry matter (DM) and neutral detergent fiber (NDF) than those fed diets composed of mineral salt only. In addition, the animals that received protein-energy supplementation had longer period in grazing and spent on average more time per period eating at the trough (P < 0.05), however no significant differences were observed in the time per period in rumination and time per period in idle (P > 0.05). The supply of protein-energy supplement does not change the feeding behavior, except for an increase in the time spent feeding at the trough. The intake of protein-energy supplement improved the of DM and NDF feed efficiencies in grazing cattle during the rainy to the dry season transition.

  5. On the abnormal "forced hydration" behavior of P(MEA-co-OEGA) aqueous solutions during phase transition from infrared spectroscopic insights.

    PubMed

    Hou, Lei; Wu, Peiyi

    2016-06-21

    Turbidity, DLS and FTIR measurements in combination with the perturbation correlation moving window (PCMW) technique and 2D correlation spectroscopy (2Dcos) analysis have been utilized to investigate the LCST-type transition of a oligo ethylene glycol acrylate-based copolymer (POEGA) in aqueous solutions in this work. As demonstrated in turbidity and DLS curves, the macroscopic phase separation was sharp and slightly concentration dependent. Moreover, individual chemical groups along polymer chains also display abrupt changes in temperature-variable IR spectra. However, according to conventional IR analysis, the C-H groups present obvious dehydration, whereas C[double bond, length as m-dash]O and C-O-C groups exhibit anomalous "forced hydration" during the steep phase transition. From these analyses together with the PCMW and 2Dcos results, it has been confirmed that the hydrophobic interaction among polymer chains drove the chain collapse and dominated the phase transition. In addition, the unexpected enhanced hydration behavior of C[double bond, length as m-dash]O and C-O-C groups was induced by forced hydrogen bonding between polar groups along polymer chains and entrapped water molecules in the aggregates, which originated from the special chemical structure of POEGA.

  6. Renormalization-group study of a superconducting phase transition: Asymptotic behavior of higher expansion orders and results of three-loop calculations

    NASA Astrophysics Data System (ADS)

    Kalagov, G. A.; Kompaniets, M. V.; Nalimov, M. Yu.

    2014-11-01

    We use quantum-field renormalization group methods to study the phase transition in an equilibrium system of nonrelativistic Fermi particles with the "density-density" interaction in the formalism of temperature Green's functions. We especially attend to the case of particles with spins greater than 1/2 or fermionic fields with additional indices for some reason. In the vicinity of the phase transition point, we reduce this model to a ϕ 4 -type theory with a matrix complex skew-symmetric field. We define a family of instantons of this model and investigate the asymptotic behavior of quantum field expansions in this model. We calculate the β-functions of the renormalization group equation through the third order in the ( 4 ∈)-scheme. In the physical space dimensions D = 2, 3, we resum solutions of the renormalization group equation on trajectories of invariant charges. Our results confirm the previously proposed suggestion that in the system under consideration, there is a first-order phase transition into a superconducting state that occurs at a higher temperature than the classical theory predicts.

  7. Quantum phase transition, universality, and scaling behaviors in the spin-1/2 Heisenberg model with ferromagnetic and antiferromagnetic competing interactions on a honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Zhen; Xi, Bin; Chen, Xi; Li, Wei; Wang, Zheng-Chuan; Su, Gang

    2016-06-01

    The quantum phase transition, scaling behaviors, and thermodynamics in the spin-1/2 quantum Heisenberg model with antiferromagnetic coupling J >0 in the armchair direction and ferromagnetic interaction J'<0 in the zigzag direction on a honeycomb lattice are systematically studied using the continuous-time quantum Monte Carlo method. By calculating the Binder ratio Q2 and spin stiffness ρ in two directions for various coupling ratios α =J'/J under different lattice sizes, we found that a quantum phase transition from the dimerized phase to the stripe phase occurs at the quantum critical point αc=-0.93 . Through the finite-size scaling analysis on Q2, ρx, and ρy, we determined the critical exponent related to the correlation length ν to be 0.7212(8), implying that this transition falls into a classical Heisenberg O(3) universality. A zero magnetization plateau is observed in the dimerized phase, whose width decreases with increasing α . A phase diagram in the coupling ratio α -magnetic field h plane is obtained, where four phases, including dimerized, stripe, canted stripe, and polarized, are identified. It is also unveiled that the temperature dependence of the specific heat C (T ) for different α 's intersects precisely at one point, similar to that of liquid 3He under different pressures and several magnetic compounds under various magnetic fields. The scaling behaviors of Q2, ρ , and C (T ) are carefully analyzed. The susceptibility is compared with the experimental data to give the magnetic parameters of both compounds.

  8. Quantum phase transition, universality, and scaling behaviors in the spin-1/2 Heisenberg model with ferromagnetic and antiferromagnetic competing interactions on a honeycomb lattice.

    PubMed

    Huang, Yi-Zhen; Xi, Bin; Chen, Xi; Li, Wei; Wang, Zheng-Chuan; Su, Gang

    2016-06-01

    The quantum phase transition, scaling behaviors, and thermodynamics in the spin-1/2 quantum Heisenberg model with antiferromagnetic coupling J>0 in the armchair direction and ferromagnetic interaction J^{'}<0 in the zigzag direction on a honeycomb lattice are systematically studied using the continuous-time quantum Monte Carlo method. By calculating the Binder ratio Q_{2} and spin stiffness ρ in two directions for various coupling ratios α=J^{'}/J under different lattice sizes, we found that a quantum phase transition from the dimerized phase to the stripe phase occurs at the quantum critical point α_{c}=-0.93. Through the finite-size scaling analysis on Q_{2}, ρ_{x}, and ρ_{y}, we determined the critical exponent related to the correlation length ν to be 0.7212(8), implying that this transition falls into a classical Heisenberg O(3) universality. A zero magnetization plateau is observed in the dimerized phase, whose width decreases with increasing α. A phase diagram in the coupling ratio α-magnetic field h plane is obtained, where four phases, including dimerized, stripe, canted stripe, and polarized, are identified. It is also unveiled that the temperature dependence of the specific heat C(T) for different α's intersects precisely at one point, similar to that of liquid ^{3}He under different pressures and several magnetic compounds under various magnetic fields. The scaling behaviors of Q_{2}, ρ, and C(T) are carefully analyzed. The susceptibility is compared with the experimental data to give the magnetic parameters of both compounds.

  9. Interplay between order-parameter and system parameter dynamics: considerations on perceptual-cognitive-behavioral mode-mode transitions exhibiting positive and negative hysteresis and on response times.

    PubMed

    Frank, T D; Profeta, V L S; Harrison, H S

    2015-06-01

    A mathematical model is presented for the emergence of perceptual-cognitive-behavioral modes in psychophysical experiments in which participants are confronted with two alternatives. The model is based on the theory of self-organization and, in particular, the order parameter concept such that the emergence of a mode is conceptualized as an instability leading to the emergence of an appropriately defined order parameter. The order parameter model is merged with a second model that describes adaptation in terms of a system parameter dynamics. It is shown that the two-component model predicts hysteretic mode-mode transitions when control parameters are increased or decreased beyond critical values. The two-component model can account for both positive and negative hysteresis effects due to the interaction between order parameter and system parameter dynamics. Moreover, the model-based analysis reveals that response time curves look rather flat when response times are relatively decoupled from the mode-mode transition phenomenon. In general, response time curves exhibit a peaked close to the mode-mode transition point. In this context, the possibility is discussed that such peaked response time curves belong to the class of critical phenomena of self-organizing systems. In order to illustrate the relevance of peaked response time curves for future research and research reported in the past, results from a perceptual judgment experiment are reported, in which participants judged their ability to stand on a tilted slope for various angles of inclination. Response time curves were found that exhibited a peak around the mode-mode-transition points between "yes" and "no" responses.

  10. Health Status during College Students' Transition to Adulthood: Health Behaviors, Negative Experiences, and the Mediating Effects of Personal Development

    ERIC Educational Resources Information Center

    Kenzig, Melissa

    2013-01-01

    University attendance includes various activities and experiences that can have a unique impact on psychosocial development and adult health behaviors, and can influence life course outcomes such as short- and long-term health and quality of life. College attendance and health are cyclical and reinforcing factors. Healthier students do better…

  11. The Timing of Entry into Adult Roles and Changes in Trajectories of Problem Behaviors during the Transition to Adulthood

    ERIC Educational Resources Information Center

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

    2014-01-01

    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…

  12. Youth Characteristics Associated with Behavioral and Mental Health Problems during the Transition to Residential Treatment Centers: The Odyssey Project Population

    ERIC Educational Resources Information Center

    Baker, Amy J. L.; Archer, Marc; Curtis, Patrick

    2007-01-01

    This study aimed to determine what youth characteristics were associated with emotional and behavioral problems exhibited within the first three months of placement in residential treatment centers (RTCs) in a sample of youth from 20 agencies in 13 states. Two primary research questions were addressed: 1) What characteristics were associated with…

  13. School Behavior and Disciplinary Experiences of Youth With Disabilities. Facts From The National Longitudinal Transition Study-2 (NLTS2)

    ERIC Educational Resources Information Center

    Gonzalez, Patricia

    2006-01-01

    Problem behavior at school "interferes with the educational process and places a burden on teachers" (U.S. Department of Education 2002, p. III-17). Disciplinary problems have long been linked to negative outcomes for students with disabilities, such as course failure and dropping out of school (Wagner et al. 1991). Parents, administrators,…

  14. Do Adolescents with Emotional and Behavioral Disturbances Attending Schools for Special Education Have Lower Expectations Regarding the Transition to Adulthood?

    ERIC Educational Resources Information Center

    Margraf, Hannah; Pinquart, Martin

    2016-01-01

    Individuals with emotional and behavioral disturbances (EBD) and those attending special schools tend to have poorer adult outcomes than adolescents without EBD and peers from regular schools. Using a four-group comparison (students with or without EBD from special schools and students with or without EBD from regular schools), the present study…

  15. Anisotropic mechanical properties of the MA956 ODS steel characterized by the small punch testing technique

    NASA Astrophysics Data System (ADS)

    Turba, K.; Hurst, R. C.; Hähner, P.

    2012-09-01

    The small punch testing technique was used to assess both creep and fracture properties of the MA956 oxide dispersion strengthened ferritic steel. The anisotropy in mechanical properties was addressed, as well as the alloy's susceptibility to thermal embrittlement. Strong anisotropy was found in the material's creep resistance at 725 °C for longer rupture times. Anisotropic behavior was also observed for the ductile-brittle transition temperature (DBTT). The origin of the anisotropy can be related to the strongly directional microstructure which enables a large amount of intergranular cracking during straining at both high and low temperatures. The DBTT of the alloy is very high, and can be further increased by at least 200 °C after 1000 h of ageing at 475 °C, due to the formation of the Cr-rich α' phase. The particularly high susceptibility of the MA956 to thermal embrittlement is mainly a consequence of its high chromium content.

  16. Influence of restraint and thermal exposure on welds in T-111 and ASTAR-811C

    NASA Technical Reports Server (NTRS)

    Gold, R. E.; Lessmann, G. G.

    1971-01-01

    The notched-tensile, tensile, and bend properties of GTA welds in T-111 and ASTAR-811C sheet were determined following a wide range of thermal exposures in order to define changes in ductility and mechanical property behavior due to weld aging response. No notch sensitivity or unusual tensile response was noted for any of the conditions evaluated. An aging response was noted for the bend ductile-brittle transition temperature determinations on both T-111 and ASTAR-811C welds. A tentative explanation for the observed response of each alloy is presented. In addition, the interrelationship of mechanical and chemical factors leading to underbead cracking in T-111 was investigated. The problem was shown to be amenable primarily to chemical solutions, such as alloy compositional changes. This was demonstrated by the improved performance of ASTAR-811C over T-111 in plate weld studies. Only modest success was achieved using procedural techniques as a means of eliminating underbead cracking.

  17. Magnetostructural coupling behavior at the ferromagnetic transition in double-perovskite S r2FeMo O6

    NASA Astrophysics Data System (ADS)

    Yang, Dexin; Harrison, Richard J.; Schiemer, Jason A.; Lampronti, Giulio I.; Liu, Xueyin; Zhang, Fenghua; Ding, Hao; Liu, Yan'gai; Carpenter, Michael A.

    2016-01-01

    The ordered double-perovskite S r2FeMo O6 (SFMO) possesses remarkable room-temperature low-field colossal magnetoresistivity and transport properties which are related, at least in part, to combined structural and magnetic instabilities that are responsible for a cubic-tetragonal phase transition near 420 K. A formal strain analysis combined with measurements of elastic properties from resonant ultrasound spectroscopy reveal a system with weak biquadratic coupling between two order parameters belonging to Γ4+ and m Γ4+ of parent space group F m 3 ¯m . The observed softening of the shear modulus by ˜50% is due to the classical effects of strain/order parameter coupling at an improper ferroelastic (Γ4+) transition which is second order in character, while the ferromagnetic order parameter (m Γ4+ ) couples only with volume strain. The influence of a third order parameter, for ordering of Fe and Mo on crystallographic B sites, is to change the strength of coupling between the Γ4+ order parameter and the tetragonal shear strain due to the influence of changes in local strain heterogeneity at a unit cell scale. High anelastic loss below the transition point reveals the presence of mobile ferroelastic twin walls which become pinned by oxygen vacancies in a temperature interval near 340 K. The twin walls must be both ferroelastic and ferromagnetic, but due to the weak coupling between the magnetic and structural order parameters it should be possible to pull them apart with a weak magnetic field. These insights into the role of strain coupling and relaxational effects in a system with only weak coupling between three order parameters allow rationalization and prediction of how static and dynamic properties of the material might be tuned in thin film form by choice of strain contrast with a substrate.

  18. Transition from in library use of resources to outside library use: the impact of the Internet on information seeking behavior of medical students and faculty.

    PubMed

    Tao, Donghua; Demiris, George; Graves, Rebecca S; Sievert, MaryEllen

    2003-01-01

    Advances in information technology have introduced both new capabilities and interesting challenges in accessing medical literature. More and more information resources exist in electronic format, such as online databases, journals, books, etc. instead of the traditional print format. In late 1998, there were thirty-five journal titles available online; in 2001, the number rose to over 4,000.1 Desk-top access to online resources is changing library use patterns, which challenges libraries to adjust to this transformed information access environment. Studies of the impact of the internet on information seeking behavior of users in medical environments could provide very valuable information for medical libraries seeking to adapt to this rapid and great evolution. This study aims to explore the impact of the Internet on information seeking behavior of medical students and faculty and their medical library use, to address the possible reasons for this change of information seeking behavior, and to identify the measures essential to the transition from traditional in-library use of resources to remote access. This study is conducted in two phases.

  19. Phase transition behavior of hydrogen bonded liquid crystal (6BA)2-(BPy) x as studied by 2H NMR

    NASA Astrophysics Data System (ADS)

    Mizuno, M.; Tabota, K.; Oigawa, T.; Miyatou, T.; Kumagai, Y.; Ohashi, R.; Ida, T.

    2016-12-01

    The thermal properties and the orientational order of hydrogen-bonded liquid crystals (6BA)2-(BPy)0.4 and (6BA)2-(BPy)0.3 (6BA: 4- n-hexylbenzoicacid, BPy: 4,4'-bipyridine) were investigated by DSC and 2H NMR. On cooling, isotropic liquid - liquid crystal phase transition temperatures were T C= 409 and 405 K for (6BA)2-(BPy)0.4 and (6BA)2-(BPy)0.3, respectively. Thermal anomalies in the liquid crystal phase were observed at T LC1= 402 and T LC2= 375 K for (6BA)2-(BPy)0.4 and at T LC1= 398 and T LC2= 375 K for (6BA)2-(BPy)0.3. For (6BA)2-(BPy)0.4, only the smectic component was created above T LC1. In addition, the nematic component was created below T LC1. The nematic component gradually changed to the smectic component with decreasing temperature and only the smectic component was observed below T LC2. For (6BA)2-(BPy)0.3, only the nematic component was created above T LC2. The phase transition from the nematic phase to the smectic phase took place at around T LC2.

  20. Tribology of Si/SiO2 in humid air: transition from severe chemical wear to wearless behavior at nanoscale.

    PubMed

    Chen, Lei; He, Hongtu; Wang, Xiaodong; Kim, Seong H; Qian, Linmao

    2015-01-13

    Wear at sliding interfaces of silicon is a main cause for material loss in nanomanufacturing and device failure in microelectromechanical system (MEMS) applications. However, a comprehensive understanding of the nanoscale wear mechanisms of silicon in ambient conditions is still lacking. Here, we report the chemical wear of single crystalline silicon, a material used for micro/nanoscale devices, in humid air under the contact pressure lower than the material hardness. A transmission electron microscopy (TEM) analysis of the wear track confirmed that the wear of silicon in humid conditions originates from surface reactions without significant subsurface damages such as plastic deformation or fracture. When rubbed with a SiO2 ball, the single crystalline silicon surface exhibited transitions from severe wear in intermediate humidity to nearly wearless states at two opposite extremes: (a) low humidity and high sliding speed conditions and (b) high humidity and low speed conditions. These transitions suggested that at the sliding interfaces of Si/SiO2 at least two different tribochemical reactions play important roles. One would be the formation of a strong "hydrogen bonding bridge" between hydroxyl groups of two sliding interfaces and the other the removal of hydroxyl groups from the SiO2 surface. The experimental data indicated that the dominance of each reaction varies with the ambient humidity and sliding speed.

  1. Antiferromagnetic spin chain behavior and a transition to 3D magnetic order in Cu(D,L-alanine)2: Roles of H-bonds

    NASA Astrophysics Data System (ADS)

    Calvo, Rafael; Sartoris, Rosana P.; Calvo, Hernán L.; Chagas, Edson F.; Rapp, Raul E.

    2016-05-01

    We study the spin chain behavior, a transition to 3D magnetic order and the magnitudes of the exchange interactions for the metal-amino acid complex Cu(D,L-alanine)2•H2O, a model compound to investigate exchange couplings supported by chemical paths characteristic of biomolecules. Thermal and magnetic data were obtained as a function of temperature (T) and magnetic field (B0). The magnetic contribution to the specific heat, measured between 0.48 and 30 K, displays above 1.8 K a 1D spin-chain behavior that can be fitted with an intrachain antiferromagnetic (AFM) exchange coupling constant 2J0=(-2.12±0.08) cm-1 (defined as ℋex(i,i+1) = -2J0SiṡSi+1), between neighbor coppers at 4.49 Å along chains connected by non-covalent and H-bonds. We also observe a narrow specific heat peak at 0.89 K indicating a phase transition to a 3D magnetically ordered phase. Magnetization curves at fixed T = 2, 4 and 7 K with B0 between 0 and 9 T, and at T between 2 and 300 K with several fixed values of B0 were globally fitted by an intrachain AFM exchange coupling constant 2J0=(-2.27±0.02) cm-1 and g = 2.091±0.005. Interchain interactions J1 between coppers in neighbor chains connected through long chemical paths with total length of 9.51 Å cannot be estimated from magnetization curves. However, observation of the phase transition in the specific heat data allows estimating the range 0.1≤|2J1|≤0.4 cm-1, covering the predictions of various approximations. We analyze the magnitudes of 2J0 and 2J1 in terms of the structure of the corresponding chemical paths. The main contribution in supporting the intrachain interaction is assigned to H-bonds while the interchain interactions are supported by paths containing H-bonds and carboxylate bridges, with the role of the H-bonds being predominant. We compare the obtained intrachain coupling with studies of compounds showing similar behavior and discuss the validity of the approximations allowing to calculate the interchain

  2. Grain boundary chemistry and heat treatment effects on the ductile-to-brittle transition behavior of vanadium alloys

    SciTech Connect

    Kurtz, R.J.; Hamilton, M.L.; Li, H.

    1998-03-01

    One-third scale Charpy impact specimens of V-4Cr-4Ti were given the same heat treatments applied to equivalent specimens of V-5Cr-5Ti. Auger specimens of V-4Cr-4Ti were also heat treated with the Charpy specimens to enable grain boundary chemistry measurements. The microstructural, microchemical and Charpy impact response of V-4Cr-4Ti displayed trends similar to those observed for V-5Cr-5Ti. The results show that grain size plays an important role in determining the ductile-to-brittle transition temperature (DBTT) of these materials and that a threshold level of grain boundary segregant appears to be required to cause grain boundary embrittlement and intergranular fracture.

  3. Structure, dielectric tunability, thermal stability and diffuse phase transition behavior of lead free BZT-BCT ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Sreenivas Puli, Venkata; Pradhan, Dhiren K.; Pérez, W.; Katiyar, R. S.

    2013-03-01

    This paper reports the development of a lead free {Ba(Zr0.2Ti0.8)O3}(1-x){(Ba0.7Ca0.3)TiO3}x - x=0.10, 0.15 and 0.20 - BZT-BCT ceramic solid solution system prepared using a solid-state reaction technique. The evolution of the Raman spectra with temperature was used to study the variation of the basic phase transition of BaTiO3 in these compositions. The phase transition temperature on heating was found to decrease to 310 K, 300 K, and 300 K, respectively, with increasing Ca content on BCT end and decreasing Zr content on BZT end of lead free pseudobinary ferroelectric BZT-BCT system. Tetragonal and rhombohedral phase coexistence is observed at room temperature from X-ray diffraction (XRD) spectra. Rhombohedral phase is identified between the 83 K and 273 K from temperature dependent Raman studies. Raman results are in excellent agreement with those obtained from temperature dependent dielectric measurements. Bulk ceramic BZT-BCT materials have shown interesting temperature dependent dielectric properties and as well as higher values of room temperature dielectric constant ˜7800, 8400, 5200, dielectric tunability ˜82%, figure of merit (FOM) ˜93.71 % with low dielectric loss (tan δ) ˜0.015 to 0.024 and good thermal stability at high sintering temperature (1600 °C); they might be one of the strong candidates for dielectric tunable capacitor applications in an environmentally protective atmosphere.

  4. Impact of Liquid-Vapor to Liquid-Liquid-Vapor Phase Transitions on Asphaltene-Rich Nanoaggregate Behavior in Athabasca Vacuum Residue + Pentane Mixtures

    SciTech Connect

    Long, Bingwen; Chodakowski, Martin; Shaw, John M.

    2013-06-05

    The bulk phase behavior of heavy oil + alkane mixtures and the behavior of the asphaltenes that they contain are topics of importance for the design and optimization of processes for petroleum production, transport, and refining and for performing routine saturates, aromatics, resins, and asphaltenes (SARA) analyses. In prior studies, partial phase diagrams and phase behavior models for Athabasca vacuum residue (AVR) comprising 32 wt % pentane asphaltenes + n-alkanes were reported. For mixtures with pentane, observed phase behaviors included single-phase liquid as well as liquid–liquid, liquid–liquid–vapor, and liquid–liquid–liquid–vapor regions. Dispersed solids were detected under some conditions as well but not quantified. In this work, small-angle X-ray scattering (SAXS) is used to study nanostructured materials in liquid phases present in AVR + n-pentane mixtures from 50 to 170 °C at mixture bubble pressure. The investigation focuses on the impact of the transition from a single AVR-rich liquid to co-existing pentane-rich and AVR-rich liquids on the nanostructure and the nanostructures most resistant to aggregation as the pentane composition axis is approached. Background scattering subtraction was performed using global mixture composition. The robustness of this assumption with respect to values obtained for coefficients appearing in a two level Beaucage unified equation fit is demonstrated. The nanostructured material is shown to arise at two length scales from 1 to 100 wt % AVR. Smaller nanostructures possess mean radii less than 50 Å, while the larger nanostructures possess mean radii greater than 250 Å. The addition of pentane to the AVR causes an increasingly large fraction of the large and small nanostructures to grow in size. Only nanostructures resistant to aggregation remain in the pentane-rich phase as the 0 wt % AVR axis is approached. Step changes in aggregation identified from changes in average radius of gyration, scattering

  5. Phase transitions and electrical behavior of lead-free (K0.50Na0.50)NbO3 thin film

    NASA Astrophysics Data System (ADS)

    Wu, Jiagang; Wang, John

    2009-09-01

    Lead-free (K0.50Na0.50)NbO3 (KNN) thin films with a high degree of (100) preferred orientation were deposited on the SrRuO3-buffered SrTiO3(100) substrate by off-axis radio frequency magnetron sputtering. They possess lower phase transition temperatures (To-t˜120 °C and Tc˜310 °C), as compared to those of KNN bulk ceramic (To-t˜190 °C and Tc˜400 °C). They also demonstrate enhanced ferroelectric behavior (e.g., 2Pr=24.1 μc/cm2) and fatigue endurance, together with a lower dielectric loss (tan δ ˜0.017) and a lower leakage current, as compared to the bulk ceramic counterpart. Oxygen vacancies are shown to be involved in the conduction of the KNN thin film.

  6. Kaempferol, a phytoestrogen, suppressed triclosan-induced epithelial-mesenchymal transition and metastatic-related behaviors of MCF-7 breast cancer cells.

    PubMed

    Lee, Geum-A; Choi, Kyung-Chul; Hwang, Kyung-A

    2017-01-01

    As a phytoestrogen, kaempferol is known to play a chemopreventive role inhibiting carcinogenesis and cancer progression. In this study, the influences of triclosan, an anti-bacterial agent recently known for an endocrine disrupting chemical (EDC), and kaempferol on breast cancer progression were examined by measuring their effects on epithelial-mesenchymal transition (EMT) and metastatic-related behaviors of MCF-7 breast cancer cells. Morphological changes of MCF-7 cells were observed, and a wound-healing assay was performed after the treatment of triclosan and kaempferol. The effects of triclosan and kaempferol on protein expression of EMT-related markers such as E-cadherin, N-cadherin, Snail, and Slug and metastasis-related markers such as cathepsin B, D, MMP-2 and -9 were investigated by Western blot assay. In microscopic observations, triclosan (10(-6)M) or E2 (10(-9)M) induced transition to mesenchymal phenotype of MCF-7 cells compared with the control. Co-treatment of ICI 182,780 (10(-8)M), an ER antagonist, or kaempferol (25μM) with E2 or triclosan restored the cellular morphology to an epithelial phenotype. In a wound-healing scratch and a transwell migration assay, triclosan enhanced migration and invasion of MCF-7 cells, but co-treatment of kaempferol or ICI 182,780 reduced the migration and invasion ability of MCF-7 cells to the control level. In addition, kaempferol effectively suppressed E2 or triclosan-induced protein expressions of EMT and metastasis promoting markers. Taken together, triclosan may be a distinct xenoestrogenic EDC to promote EMT, migration, and invasion of MCF-7 breast cancer cells through ER. On the other hand, kaempferol can be an alternative chemopreventive agent to effectively suppress the metastatic behavior of breast cancer induced by an endogenous estrogen as well as exogenous xenoestrogenic compounds including triclosan.

  7. Anomalous magnetic behavior in the transition metal ions doped Cu{sub 2}O flower-like nanostructures

    SciTech Connect

    Ahmed, Asar; Gajbhiye, Namdeo S.

    2011-01-15

    Cuprous oxide (Cu{sub 2}O) flower-like nanostructures doped with various metal ions i.e. Fe, Co, Ni and Mn have been synthesized by an organic phase solution method. The powder X-ray diffraction study clearly reveals them as single phase simple cubic cuprite lattice. Study of their magnetic properties have shown that these doped samples are ferromagnetic in nature; however, no such property was observed for the undoped Cu{sub 2}O sample. The magnitude of the ferromagnetic behavior was found to be dependent on the dopant metal ions amount, which increased consistently with its increase. As total magnetic moment contribution of the doped metal ions calculated was insignificant, it is believed to have originated from the induced magnetic moments at cation deficiency sites in the material, created possibly due to the disturbance of the crystal lattice by the dopant ions. The existence of the defects has been supported by photoluminescence spectra of the doped samples. -- Graphical abstract: Room temperature ferromagnetic behavior was observed in the Cu{sub 2}O nanoflowers doped with Fe, Co, Ni and Mn ions. Cation deficiencies formed due to dopant ions were possibly responsible for ferromagnetism. Display Omitted

  8. The influence of transition metal oxides type M+/M++ on the vanadium-tellurite glasses electrical behavior

    NASA Astrophysics Data System (ADS)

    di Prátula, Pablo E.; Terny, Soledad; Cardillo, Evangelina C.; Frechero, Marisa A.

    2015-11-01

    In this work, the electrical behavior and structural features of the system xCu2O (1 - x) (0.5V2O5·0.5MoO3) 2TeO2 compared to xAg2O (1 - x) (0.5V2O5·0.5MoO3) 2TeO2 (which was already studied) are explored. The main goal is to determine whether the electronic configuration of Cu+ and Ag+ ions is the key to understand the interactions of these ions with vanadium ions in the glassy matrix studied and to establish the nature of the particular electrical conductivity response. It is shown that despite the fact that both ions (Cu+ and Ag+) have similar electronic configurations but different sizes they have similar electrical behaviors contrary to what is commonly accepted (i.e. silver modified glasses are completely ionic systems, while copper modified glasses are purely electronic -polaronic- semiconductors). It is expected that both behave as mixed electrical conductors, neither pure polaronic nor pure ionic. It has been found that the minimum observed in the isotherm of conductivity can be explained by the structural features of this glassy matrix and not by a change in its mechanism of conduction.

  9. Critical behavior in one dimension: Unconventional pairing, phase separation, BEC-BCS crossover, and magnetic Lifshitz transition

    NASA Astrophysics Data System (ADS)

    Ptok, Andrzej; Cichy, Agnieszka; Rodríguez, Karen; Kapcia, Konrad Jerzy

    2017-03-01

    We study the superconducting properties of population-imbalanced ultracold Fermi mixtures in one-dimensional optical lattices that can be effectively described by the spin-imbalanced attractive Hubbard model in the presence of a Zeeman magnetic field. We use the mean-field theory approach to obtain the ground-state phase diagrams including some unconventional superconducting phases such as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, and the η phase (an extremal case of the FFLO phase), both for the case of a fixed chemical potential and for a fixed number of particles. It allows us to determine optimal regimes for the FFLO phase as well as η -pairing stability. We also investigate the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs (BEC) with increasing attraction, at T =0 . Finally, the obtained results show that in spite of the occurrence of the Lifshitz transition induced by an external magnetic field, the superconducting state can still exist in the system, at higher magnetic field values.

  10. Influence of compression on water sorption, glass transition, and enthalpy relaxation behavior of freeze-dried amorphous sugar matrices.

    PubMed

    Imamura, Koreyoshi; Kagotani, Ryo; Nomura, Mayo; Tanaka, Kazuhiro; Kinugawa, Kohshi; Nakanishi, Kazuhiro

    2011-04-15

    An amorphous matrix comprised of sugar molecules are frequently used in the pharmaceutical industry. The compression of the amorphous sugar matrix improves the handling. Herein, the influence of compression on the water sorption of an amorphous sugar matrix was investigated. Amorphous sugar samples were prepared by freeze-drying, using several types of sugars, and compressed at 0-443 MPa. The compressed amorphous sugar samples as well as uncompressed samples were rehumidified at given RHs, and the equilibrium water content and glass transition temperature (T(g)) were then measured. Compression resulted in a decrease in the equilibrium water content of the matrix, the magnitude of which was more significant for smaller sized sugars. Diffusivity of water vapor in the sample was also decreased to one-hundredth by the compression. The T(g) value for a given RH remained unchanged, irrespective of the compression. Accordingly, the decrease in T(g) with increasing water content increased as the result of compression. The structural relaxation of the amorphous sugar matrices were also examined and found to be accelerated to the level of a non-porous amorphous sugar matrix as the result of the compression. The findings indicate that pores contained in freeze-dried sugar samples interfere with the propagation of structural relaxation.

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

    PubMed

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

    2014-12-10

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

  12. Transition from distributional to ergodic behavior in an inhomogeneous diffusion process: Method revealing an unknown surface diffusivity.

    PubMed

    Akimoto, Takuma; Seki, Kazuhiko

    2015-08-01

    Diffusion of molecules in cells plays an important role in providing a biological reaction on the surface by finding a target on the membrane surface. The water retardation (slow diffusion) near the target assists the searching molecules to recognize the target. Here, we consider effects of the surface diffusivity on the effective diffusivity, where diffusion on the surface is slower than that in bulk. We show that the ensemble-averaged mean-square displacements increase linearly with time when the desorption rate from the surface is finite, which is valid even when the diffusion on the surface is anomalous (subdiffusion). Moreover, this slow diffusion on the surface affects the fluctuations of the time-averaged mean-square displacements (TAMSDs). We find that fluctuations of the TAMSDs remain large when the measurement time is smaller than a characteristic time, and decays according to an increase of the measurement time for a relatively large measurement time. Therefore, we find a transition from nonergodic (distributional) to ergodic diffusivity in a target search process. Moreover, this fluctuation analysis provides a method to estimate an unknown surface diffusivity.

  13. The behavior of the electron density and temperatue at Millstone Hill during the equinox transition study September 1984

    NASA Technical Reports Server (NTRS)

    Richards, P. G.; Torr, D. G.; Buonsanto, M. J.; Miller, K. L.

    1989-01-01

    The ionospheric electron density and temperature variations is simulated during the equinox transition study in September 1984 and the results are compared with measurements made at Millstone Hill. The agreement between the modeled and measured electron density and temperature for the quiet day (18 September) is very good but there are large differences on the day of the storm (19 September). On the storm day, the measured electron density decreases by a factor of 1.7 over the previous day, while the model density actually increases slightly. The model failure is attributed to an inadequate increase in the ratio of atomic oxygen to molecular neutral densities in the MSIS neutral atmosphere model, for this particular storm. A factor of 3 to 5 increase in the molecular to atomic oxygen density ratio at 300 km is needed to explain the observed decrease in electron density. The effect of vibrationally excited N sub 2 on the electron density were studied and found to be small.

  14. Water sorption, glass transition, and protein-stabilizing behavior of an amorphous sucrose matrix combined with various materials.

    PubMed

    Imamura, Koreyoshi; Yokoyama, Toru; Fukushima, Atsushi; Kinuhata, Mitsunori; Nakanishi, Kazuhiro

    2010-11-01

    The effects of various additives on the physical properties of an amorphous sugar matrix were compared. Amorphous, sugar-additive mixtures were prepared by freeze-drying and then rehumidified at given RHs. Sucrose and eighteen types of substances were used as the sugar and the additive, respectively, and water sorption, glass-to-rubber transition, and protein stabilization during freeze-drying for the various sucrose-additive mixtures were examined. The additives were categorized into two groups according to their effects on T(g) and water sorption. Presence of polysaccharides, cyclodextrins, and polymers (large-sized additives) resulted in a decrease in equilibrium water content from the ideal value calculated from individual water contents for sucrose and additive, and in contrast, low MW substances containing ionizable groups (small-ionized additives) resulted in an increase. The increase in T(g) by the addition of large-sized additives was significant at the additive contents >50 wt.% whereas the T(g) was markedly increased in the lower additive content by the addition of small-ionized additives. The addition of small-ionized additives enhanced the decrease in T(g) with increasing water content. The protein stabilizing effect was decreased with increasing additive content in the cases of the both groups of the additives.

  15. Impacts of first-order phase transition and phase coexistence on the universal behavior of inverse magnetocaloric effect

    NASA Astrophysics Data System (ADS)

    Biswas, Anis; Bingham, N. S.; Phan, T. L.; Dan, N. H.; Yu, S. C.; Phan, M. H.; Srikanth, H.

    2014-05-01

    A systematic study of the inverse magnetocaloric effect (IMCE) in Ni50Mn35.8Sn14.2 and Pr0.5Sr0.5MnO3 has been performed to understand the impacts of first-order phase transition (FOPT) and phase coexistence on the universality of the temperature-dependent magnetic entropy change, ΔSM(T). We show that for Ni50Mn35.8Sn14.2—a system exhibiting IMCE associated with FOPT—it is possible to construct a universal master curve to describe ΔSM(T) in different applied fields without rescaling a temperature axis. However, the universality of IMCE does not hold for Pr0.5Sr0.5MnO3—a system with coexisting ferromagnetic and antiferromagnetic phases. The proposed universal curve provides a simple method for extrapolating ΔSM in a wide range of fields and temperatures, thus giving useful guidance to the design of magnetocaloric materials for active magnetic refrigeration technology.

  16. Notch4 Signaling Induces a Mesenchymal–Epithelial–like Transition in Melanoma Cells to Suppress Malignant Behaviors

    PubMed Central

    Rad, Ehsan Bonyadi; Hammerlindl, Heinz; Wels, Christian; Popper, Ulrich; Menon, Dinoop Ravindran; Breiteneder, Heimo; Kitzwoegerer, Melitta; Hafner, Christine; Herlyn, Meenhard; Bergler, Helmut; Schaider, Helmut

    2016-01-01

    The effects of Notch signaling are context-dependent and both oncogenic and tumor-suppressive functions have been described. Notch signaling in melanoma is considered oncogenic, but clinical trials testing Notch inhibition in this malignancy have not proved successful. Here, we report that expression of the constitutively active intracellular domain of Notch4 (N4ICD) in melanoma cells triggered a switch from a mesenchymal-like parental phenotype to an epithelial-like phenotype. The epithelial-like morphology was accompanied by strongly reduced invasive, migratory, and proliferative properties concomitant with the downregulation of epithelial–mesenchymal transition markers Snail2 (SNAI2), Twist1, vimentin (VIM), and MMP2 and the reexpression of E-cadherin (CDH1). The N4ICD-induced phenotypic switch also resulted in significantly reduced tumor growth in vivo. Immunohistochemical analysis of primary human melanomas and cutaneous metastases revealed a significant correlation between Notch4 and E-cadherin expression. Mechanistically, we demonstrate that N4ICD induced the expression of the transcription factors Hey1 and Hey2, which bound directly to the promoter regions of Snail2 and Twist1 and repressed gene transcription, as determined by EMSA and luciferase assays. Taken together, our findings indicate a role for Notch4 as a tumor suppressor in melanoma, uncovering a potential explanation for the poor clinical efficacy of Notch inhibitors observed in this setting. PMID:26801977

  17. The role of ethnicity, sexual attitudes, and sexual behavior in sexual revictimization during the transition to emerging adulthood.

    PubMed

    Rinehart, Jenny K; Yeater, Elizabeth A; Musci, Rashelle J; Letourneau, Elizabeth J; Lenberg, Kathryn L

    2014-01-01

    An experience of child sexual abuse (CSA) substantially increases women's risk of adult sexual assault (ASA), but the mechanisms underlying this relationship are unclear. Previous research often has not examined the full range of ASA experiences or included the influence of ethnicity, sexual behavior, and sexual attitudes on CSA and severity of ASA. The current study utilized path analysis to explore the relationships among ethnicity, sexual attitudes, number of lifetime sexual partners, CSA, and severity of ASA in emerging adult women. Results indicated a significant relationship between CSA and more severe ASA that was partially explained by having more lifetime sexual partners. Additionally, European American women, relative to Hispanic women, reported more severe victimization, which was fully explained by more positive attitudes toward casual sex and having more lifetime sexual partners. These results have implications in the design and implementation of universal and selective prevention programs aimed at reducing ASA and revictimization among emerging adult women.

  18. An "unreasonable effectiveness" of Hilbert transform for the transition phase behavior in an Aharonov-Bohm two-path interferometer

    NASA Astrophysics Data System (ADS)

    Englman, R.

    2016-08-01

    The recent phase shift data of Takada et al. (Phys. Rev. Lett. 113 (2014) 126601) for a two level system are reconstructed from their current intensity curves by the method of Hilbert transform, for which the underlying Physics is the principle of causality. An introductory algebraic model illustrates pedagogically the working of the method and leads to newly derived relationships involving phenomenological parameters, in particular for the sign of the phase slope between the resonance peaks. While the parametrization of the experimental current intensity data in terms of a few model parameters shows only a qualitative agreement for the phase shift, due to the strong impact of small, detailed variations in the experimental intensity curve on the phase behavior, the numerical Hilbert transform yields a satisfactory reproduction of the phase.

  19. Temperature and time behavior of the parameters of the domain structure of triglycine sulfate crystals near the phase transition

    NASA Astrophysics Data System (ADS)

    Drozhdin, S. N.; Golitsyna, O. M.

    2012-05-01

    This paper reports on the results of the investigation into the temperature and time behavior of the parameters of the domain structure in nominally pure and doped (α-alanine, chromium, phosphorus) triglycine sulfate crystals, which has been revealed by piezoresponse force microscopy during observation of the domain structure. The relaxation time dependences on the total perimeter of the domain walls, the velocity of lateral domain-wall motion, and the coefficient of static unipolarity have been obtained using computer image processing of the domain structure of the crystals under investigation. The temperature dependences of these parameters near the Curie temperature have been found. A comparison with the data available in the literature has been made, as well as with the results of our measurements of the permittivity for the same samples and under the same temperature-time conditions.

  20. Examining the phase transition behavior of amphiphilic lipids in solution using statistical temperature molecular dynamics and replica-exchange Wang-Landau methods.

    PubMed

    Gai, Lili; Vogel, Thomas; Maerzke, Katie A; Iacovella, Christopher R; Landau, David P; Cummings, Peter T; McCabe, Clare

    2013-08-07

    Two different techniques - replica-exchange Wang-Landau (REWL) and statistical temperature molecular dynamics (STMD) - were applied to systematically study the phase transition behavior of self-assembling lipids as a function of temperature using an off-lattice lipid model. Both methods allow the direct calculation of the density of states with improved efficiency compared to the original Wang-Landau method. A 3-segment model of amphiphilic lipids solvated in water has been studied with varied particle interaction energies (ε) and lipid concentrations. The phase behavior of the lipid molecules with respect to bilayer formation has been characterized through the calculation of the heat capacity as a function of temperature, in addition to various order parameters and general visual inspection. The simulations conducted by both methods can go to very low temperatures with the whole system exhibiting well-ordered structures. With optimized parameters, several bilayer phases are observed within the temperature range studied, including gel phase bilayers with frozen water, mixed water (i.e., frozen and liquid water), and liquid water, and a more fluid bilayer with liquid water. The results obtained from both methods, STMD and REWL, are consistently in excellent agreement with each other, thereby validating both the methods and the results.

  1. Examining the phase transition behavior of amphiphilic lipids in solution using statistical temperature molecular dynamics and replica-exchange Wang-Landau methods

    NASA Astrophysics Data System (ADS)

    Gai, Lili; Vogel, Thomas; Maerzke, Katie A.; Iacovella, Christopher R.; Landau, David P.; Cummings, Peter T.; McCabe, Clare

    2013-08-01

    Two different techniques - replica-exchange Wang-Landau (REWL) and statistical temperature molecular dynamics (STMD) - were applied to systematically study the phase transition behavior of self-assembling lipids as a function of temperature using an off-lattice lipid model. Both methods allow the direct calculation of the density of states with improved efficiency compared to the original Wang-Landau method. A 3-segment model of amphiphilic lipids solvated in water has been studied with varied particle interaction energies (ɛ) and lipid concentrations. The phase behavior of the lipid molecules with respect to bilayer formation has been characterized through the calculation of the heat capacity as a function of temperature, in addition to various order parameters and general visual inspection. The simulations conducted by both methods can go to very low temperatures with the whole system exhibiting well-ordered structures. With optimized parameters, several bilayer phases are observed within the temperature range studied, including gel phase bilayers with frozen water, mixed water (i.e., frozen and liquid water), and liquid water, and a more fluid bilayer with liquid water. The results obtained from both methods, STMD and REWL, are consistently in excellent agreement with each other, thereby validating both the methods and the results.

  2. Parent Training to Reduce Problem Behaviors over the Transition to High School: Tests of Indirect Effects through Improved Emotion Regulation Skills

    PubMed Central

    Mason, W. Alex; January, Stacy-Ann A.; Fleming, Charles B.; Thompson, Ronald W.; Parra, Gilbert R.; Haggerty, Kevin P.; Snyder, James J.

    2016-01-01

    Adolescent problem behaviors are costly for individuals and society. Promoting the self-regulatory functioning of youth may help prevent the development of such behaviors. Parent-training and family intervention programs have been shown to improve child and adolescent self-regulation. This study helps fill gaps in knowledge by testing for indirect effects of the Common Sense Parenting® (CSP) program on reduced substance use, conduct problems, and school suspensions through previously identified short-term improvements in parents’ reports of their children’s emotion regulation skills. Over two cohorts, 321 low income families of 8th graders were enrolled and randomly assigned to either the standard CSP program, an adapted CSP Plus program, or a minimal-contact control condition. Pretest, posttest, 1-year follow-up, and 2-year follow-up survey assessments were completed by parents and students with 94% retention. Intent-to-treat multivariate path analyses were conducted. Neither intervention had statistically significant total effects on the three targeted adolescent outcomes. CSP, but not CSP Plus, had statistically significant indirect effects on reduced substance use and school suspensions at the 1-year follow-up as well as conduct problems and school suspensions at the 2-year follow-up through increased child emotion regulation skills at posttest. Findings provide some support for emotion regulation as one pathway through which the intervention was associated, indirectly, with reduced substance use, conduct problems, and school suspensions among at-risk students over the high school transition. PMID:26778871

  3. Parent Training to Reduce Problem Behaviors over the Transition to High School: Tests of Indirect Effects through Improved Emotion Regulation Skills.

    PubMed

    Mason, W Alex; January, Stacy-Ann A; Fleming, Charles B; Thompson, Ronald W; Parra, Gilbert R; Haggerty, Kevin P; Snyder, James J

    2016-02-01

    Adolescent problem behaviors are costly for individuals and society. Promoting the self-regulatory functioning of youth may help prevent the development of such behaviors. Parent-training and family intervention programs have been shown to improve child and adolescent self-regulation. This study helps fill gaps in knowledge by testing for indirect effects of the Common Sense Parenting(®) (CSP) program on reduced substance use, conduct problems, and school suspensions through previously identified short-term improvements in parents' reports of their children's emotion regulation skills. Over two cohorts, 321 low income families of 8(th) graders were enrolled and randomly assigned to either the standard CSP program, an adapted CSP Plus program, or a minimal-contact control condition. Pretest, posttest, 1-year follow-up, and 2-year follow-up survey assessments were completed by parents and students with 94% retention. Intent-to-treat multivariate path analyses were conducted. Neither intervention had statistically significant total effects on the three targeted adolescent outcomes. CSP, but not CSP Plus, had statistically significant indirect effects on reduced substance use and school suspensions at the 1-year follow-up as well as conduct problems and school suspensions at the 2-year follow-up through increased child emotion regulation skills at posttest. Findings provide some support for emotion regulation as one pathway through which the intervention was associated, indirectly, with reduced substance use, conduct problems, and school suspensions among at-risk students over the high school transition.

  4. Puzzling calcite-III dimorphism: crystallography, high-pressure behavior, and pathway of single-crystal transitions

    NASA Astrophysics Data System (ADS)

    Pippinger, T.; Miletich, R.; Merlini, M.; Lotti, P.; Schouwink, P.; Yagi, T.; Crichton, W. A.; Hanfland, M.

    2015-01-01

    High-pressure phase transformations between the polymorphic forms I, II, III, and IIIb of CaCO3 were investigated by analytical in situ high-pressure high-temperature experiments on oriented single-crystal samples. All experiments at non-ambient conditions were carried out by means of Raman scattering, X-ray, and synchrotron diffraction techniques using diamond-anvil cells in the pressure range up to 6.5 GPa. The composite-gasket resistive heating technique was applied for all high-pressure investigations at temperatures up to 550 K. High-pressure Raman spectra reveal distinguishable characteristic spectral differences located in the wave number range of external modes with the occurrence of band splitting and shoulders due to subtle symmetry changes. Constraints from in situ observations suggest a stability field of CaCO3-IIIb at relatively low temperatures adjacent to the calcite-II field. Isothermal compression of calcite provides the sequence from I to II, IIIb, and finally, III, with all transformations showing volume discontinuities. Re-transformation at decreasing pressure from III oversteps the stability field of IIIb and demonstrates the pathway of pressure changes to determine the transition sequence. Clausius-Clapeyron slopes of the phase boundary lines were determined as: Δ P/Δ T = -2.79 ± 0.28 × 10-3 GPa K-1 (I-II); +1.87 ± 0.31 × 10-3 GPa K-1 (II/III); +4.01 ± 0.5 × 10-3 GPa K-1 (II/IIIb); -33.9 ± 0.4 × 10-3 GPa K-1 (IIIb/III). The triple point between phases II, IIIb, and III was determined by intersection and is located at 2.01(7) GPa/338(5) K. The pathway of transition from I over II to IIIb can be interpreted by displacement with small shear involved (by 2.9° on I/II and by 8.2° on II/IIIb). The former triad of calcite-I corresponds to the [20-1] direction in the P21/ c unit cell of phase II and to [101] in the pseudomonoclinic C setting of phase IIIb. Crystal structure investigations of triclinic CaCO3-III at non-ambient pressure

  5. Features and regularities in behavior of thermoelectric properties of rare-earth, transition, and other metals under high pressure up to 20 GPa

    SciTech Connect

    Morozova, Natalia V.; Shchennikov, Vladimir V.; Ovsyannikov, Sergey V. E-mail: sergey2503@gmail.com

    2015-12-14

    We report results of systematic investigations of the thermoelectric properties of a number of rare-earth metals, transition metals, and other metals under high pressure up to 20 GPa at room temperature. We studied an effect of applied pressure on the Seebeck effect of scandium (Sc), yttrium (Y), lanthanum (La), europium (Eu), ytterbium (Yb), iron (Fe), manganese (Mn), chromium (Cr), gold (Au), tin (Sn), and CeNi alloy. We found that the high-pressure behavior of the thermopower of three rare-earth metals, namely, Sc, Y, and La, follows a general trend that has been established earlier in lanthanides, and addressed to a s → d electron transfer. Europium and ytterbium, on the contrary, showed a peculiar high-pressure behavior of the thermopower with peaks at near 0.7–1 GPa for Eu and 1.7–2.5 GPa for Yb. Chromium, manganese, and tin demonstrated a gradual and pronounced lowering of the absolute value of the thermopower with pressure. Above 9–11 GPa, the Seebeck coefficients of Mn and Sn were inverted, from n- to p-type for Mn and from p- to n-type for Sn. The Seebeck effect in iron was rather high as ∼16 μV/K and weakly varied with pressure up to ∼11 GPa. Above ∼11 GPa, it started to drop dramatically with pressure to highest pressure achieved 18 GPa. Upon decompression cycle the thermopower of iron returned to the original high values but demonstrated a wide hysteresis loop. We related this behavior in iron to the known bcc (α-Fe) → hcp (ε-Fe) phase transition, and proposed that the thermoelectricity of the α-Fe phase is mainly contributed by the spin Seebeck effect, likewise, the thermoelectricity of the ε-Fe phase—by the conventional diffusion thermopower. We compare the pressure dependencies of the thermopower for different groups of metals and figure out some general trends in the thermoelectricity of metals under applied stress.

  6. The dynamic behavior of thin-film ionic transition metal complex-based light-emitting electrochemical cells

    SciTech Connect

    Meier, Sebastian B. E-mail: wiebke.sarfert@siemens.com; Hartmann, David; Sarfert, Wiebke E-mail: wiebke.sarfert@siemens.com; Winnacker, Albrecht

    2014-09-14

    Light-emitting electrochemical cells (LECs) have received increasing attention during recent years due to their simple architecture, based on solely air-stabile materials, and ease of manufacture in ambient atmosphere, using solution-based technologies. The LEC's active layer offers semiconducting, luminescent as well as ionic functionality resulting in device physical processes fundamentally different as compared with organic light-emitting diodes. During operation, electrical double layers (EDLs) form at the electrode interfaces as a consequence of ion accumulation and electrochemical doping sets in leading to the in situ development of a light-emitting p-i-n junction. In this paper, we comment on the use of impedance spectroscopy in combination with complex nonlinear squares fitting to derive key information about the latter events in thin-film ionic transition metal complex-based light-emitting electrochemical cells based on the model compound bis-2-phenylpyridine 6-phenyl-2,2´-bipyridine iridium(III) hexafluoridophosphate ([Ir(ppy)₂(pbpy)][PF₆]). At operating voltages below the bandgap potential of the ionic complex used, we obtain the dielectric constant of the active layer, the conductivity of mobile ions, the transference numbers of electrons and ions, and the thickness of the EDLs, whereas the transient thickness of the p-i-n junction is determined at voltages above the bandgap potential. Most importantly, we find that charge transport is dominated by the ions when carrier injection from the electrodes is prohibited, that ion movement is limited by the presence of transverse internal interfaces and that the width of the intrinsic region constitutes almost 60% of the total active layer thickness in steady state at a low operating voltage.

  7. THE HIGHLY DYNAMIC BEHAVIOR OF THE INNERMOST DUST AND GAS IN THE TRANSITION DISK VARIABLE LRLL 31

    SciTech Connect

    Flaherty, K. M.; Rieke, G.; Muzerolle, J.; Gutermuth, R.; Balog, Z.; Herbst, W.; Megeath, S. T.; Kun, M.

    2011-05-10

    We describe extensive synoptic multi-wavelength observations of the transition disk LRLL 31 in the young cluster IC 348. We combined 4 epochs of IRS spectra, 9 epochs of MIPS photometry, 7 epochs of cold-mission IRAC photometry, and 36 epochs of warm-mission IRAC photometry along with multi-epoch near-infrared spectra, optical spectra, and polarimetry to explore the nature of the rapid variability of this object. We find that the inner disk, as traced by the 2-5 {mu}m excess, stays at the dust sublimation radius while the strength of the excess changes by a factor of eight on weekly timescales, and the 3.6 and 4.5 {mu}m photometry show a drop of 0.35 mag in 1 week followed by a slow 0.5 mag increase over the next 3 weeks. The accretion rate, as measured by Pa{beta} and Br{gamma} emission lines, varies by a factor of five with evidence for a correlation between the accretion rate and the infrared excess. While the gas and dust in the inner disk are fluctuating, the central star stays relatively static. Our observations allow us to put constraints on the physical mechanism responsible for the variability. The variable accretion, and wind, are unlikely to be causes of the variability, but are both effects of the same physical process that disturbs the disk. The lack of periodicity in our infrared monitoring indicates that it is unlikely that there is a companion within {approx}0.4 AU that is perturbing the disk. The most likely explanation is either a companion beyond {approx}0.4 AU or a dynamic interface between the stellar magnetic field and the disk leading to a variable scale height and/or warping of the inner disk.

  8. Preliminary evaluation of a “formulation-driven cognitive behavioral guided self-help (fCBT-GSH)” for crisis and transitional case management clients

    PubMed Central

    Naeem, Farooq; Johal, Rupinder K; Mckenna, Claire; Calancie, Olivia; Munshi, Tariq; Hassan, Tariq; Nasar, Amina; Ayub, Muhammad

    2017-01-01

    Background Cognitive behavioral therapy (CBT) is found to be effective for common mental disorders and has been delivered in self-help and guided self-help formats. Crisis and transitional case management (TCM) services play a vital role in managing clients in acute mental health crises. It is, therefore, an appropriate setting to try CBT in guided self-help format. Methods This was a preliminary evaluation of a formulation-driven cognitive behavioral guided self-help. Thirty-six (36) consenting participants with a diagnosis of nonpsychotic illness, attending crisis and the TCM services in Kingston, Canada, were recruited in this study. They were randomly assigned to the guided self-help plus treatment as usual (TAU) (treatment group) or to TAU alone (control group). The intervention was delivered over 8–12 weeks. Assessments were completed at baseline and 3 months after baseline. The primary outcome was a reduction in general psychopathology, and this was done using Clinical Outcomes in Routine Evaluation – Outcome Measure. The secondary outcomes included a reduction in depression, measured using the Hospital Anxiety and Depression Scale, and reduction in disability, measured using the World Health Organization Disability Assessment Schedule 2.0. Findings Participants in the treatment group showed statistically significant improvement in overall psychopathology (P<0.005), anxiety and depression (P<0.005), and disability (P<0.005) at the end of the trial compared with TAU group. Conclusion A formulation-driven cognitive behavioral guided self-help was feasible for the crisis and TCM clients and can be effective in improving mental health, when compared with TAU. This is the first report of a trial of guided self-help for clients attending crisis and TCM services. PMID:28331328

  9. Short communication: Effect of canola meal use as a protein source in a starter mixture on feeding behavior and performance of calves during the weaning transition.

    PubMed

    Hadam, D; Kański, J; Burakowska, K; Penner, G B; Kowalski, Z M; Górka, P

    2016-02-01

    The aim of this study was to determine the effect of canola meal use as a protein source in a starter mixture (SM) on feeding behavior and performance of calves during weaning transition. A total of 36 female Holstein calves of a mean age 14.9±1.6 d and body weight 40.1±4.2 kg (mean ± SD) were allocated to 1 of 3 treatments differing in the main source of protein for the SM (12 calves per treatment): (1) soybean meal (TSBM); (2) soybean meal and canola meal (TSBM/TCM); and (3) canola meal (TCM). The SM was offered for ad libitum consumption beginning on the first day of the study, whereas milk replacer (MR) was fed in amounts equal to 900 g (as fed) per day from d 1 to 35 and 450 g/d from d 36 to 42 of the study. Calves were completely weaned on d 43 of the study (57.9±1.6 d of age; mean ± SD), and their performance was monitored for an additional 2 wk. Calf body weight was recorded weekly, and MR and SM intake and fecal fluidity were recorded daily. Feeding behavior of calves during weaning transition, including frequency (no./d), time (min/d), and rate (g/min) of eating the SM as well as frequency and time of drinking water, was monitored on 6 calves per treatment for 2 consecutive days before MR step-down (d 34-35), at MR step-down (d 41-42), and after weaning (d 48-49 of study). Starter mixture intake tended to be higher for TSBM calves as compared with TSBM/TCM calves from d 1 to 35 of the study but was not different between TSBM and TCM calves and was not different between treatments in the whole study period. Calves from TCM treatment had reduced average daily gain (ADG) and feed efficiency (g of ADG/kg of dry matter intake) and a higher fecal score in the period from d 1 to 35 of the study and had lower feed efficiency and tended to have lower ADG in the whole study period as compared with TSBM calves. Average daily gain and feed efficiency did not differ between TSBM and TSBM/TCM calves. Frequency of eating the SM and drinking water as well as time

  10. Coping with Transitions.

    ERIC Educational Resources Information Center

    Bendersky, Nora; And Others

    1984-01-01

    Describes a workshop for nine South American students at the Hebrew University of Jerusalem. The two-day session focussed on exploring coping behaviors that could help students adjust to transitions. (JAC)

  11. Kinking in polymer composites and wood, and, Crack growth in mismatched welds

    NASA Astrophysics Data System (ADS)

    Moran, Peter Malcolm

    This thesis is written in two parts; the first deals with compressive kinking in uniaxial carbon fiber PEEK composites and wood, and the second concerns ductile/brittle fracture in mismatched welds. The parts are dealt with separately below. Kinking. This is the first time that kink band formation and propagation has been video taped. The pictures reveal that kinking in ductile matrix fiber composites occurs in three distinct stages; incipient kinking, transient kinking and steady-state band broadening. Based on these observations a new kinematic model for kinking is proposed. Unlike previous models the present model is able to explain how angled kink bands are formed without violating compatibility or volume preserving constraints. Theoretical predictions for kink band orientation and compression strength under steady-state band broadening are made. Further experiments were conducted that verified the predictions. The steady-state band broadening stress is a very useful design parameter. It is a material parameter and forms a lower bound to the peak stress. Therefore it may be used in the same way as plastic limit loads are used for metals. It is also useful in determining the damage tolerance of a specimen. Mismatched welds. In the ductile/brittle transition regime, the fracture resistance of steel weldments is controlled by the competition between ductile tearing and cleavage fracture. Under typical conditions, a crack in a weld initiates and grows by ductile tearing but, ultimately, failure occurs by catastrophic cleavage fracture. In this study ductile tearing is modeled using Gurson cell elements embedded in an elastic-plastic body. Cleavage fracture is based on a weakest link mechanism in conjunction with brittle microcrack statistics. This model is applied to compute the behavior of undermatched and overmatched welds. The fracture resistance and onset of cleavage fracture are calculated for different crack lengths, specimen geometries and weld widths.

  12. Influence of the micro- and nanoscale local mechanical properties of the interfacial transition zone on impact behavior of concrete made with different aggregates

    SciTech Connect

    Erdem, Savas Dawson, Andrew Robert; Thom, Nicholas Howard

    2012-02-15

    The influence of the microscale local mechanical properties of the interfacial transition zone (ITZ) on macro-level mechanical response and impact behavior is studied for concretes made with copper slag and gravel aggregates. 3D nanotech vertical scanning interferometry, scanning electron microscopy coupled with energy dispersive X-ray micro-analysis, digital image analysis, and 3D X-ray computed tomography were used to characterize the microstructures and the ITZs. It was deduced that a stronger and denser ITZ in the copper slag specimen would reduce its vulnerability to stiffness loss and contribute to its elastic and more ductile response under impact loading. The analysis also indicated that a significant degeneration in the pore structure of the gravel specimen associated with a relatively weaker and non-homogeneous ITZ occurred under impact. Finally, it was also concluded that increased roughness of ITZ may contribute to the load-carrying capacity of concrete under impact by improving contact point interactions and energy dissipation.

  13. Multi-structured temporal behavior of neutral copper transitions in laser-produced plasma in the presence of variable transverse static magnetic field

    SciTech Connect

    Singh, Khwairakpam Shantakumar; Sharma, Ashwini Kumar

    2016-01-15

    We report on the effect of variable magnetic field on temporal behavior of neutral copper (Cu I) transitions in laser-produced copper plasma at atmospheric pressure using optical emission spectroscopy. In the presence of magnetic field, the intensity of copper atomic lines at 510.5, 515.3, and 521.8 nm gets enhanced due to increase in electron-impact excitation rate. The enhancement factor of the neutral lines is different due to different electron-impact excitation rates. We observed that the Cu I profile consists of two components recorded in the absence of magnetic field and at 0.1 T. At magnetic field of 0.3 T, the appearance of third slow component at delayed time, i.e., 122, 130, and 140 ns for Cu I (521.8, 515.3, and 510.5 nm) is also observed. We demonstrate that the generation of slow component is related to electron-impact excitation of Cu I atom rather than backflow particles and instabilities at atmospheric pressure. The instabilities generated during the plasma deceleration by magnetic field can be reduced in the presence of air at atmospheric pressure which will be applicable to enhance the sensitivity of laser-induced breakdown spectroscopy. The fast component is least affected by the magnetic field due to longer magnetic diffusion time.

  14. Real-time tracking the Li+-ion transition behavior and dynamics in solid Poly(vinyl alcohol)/LiClO4 electrolytes

    PubMed Central

    Bao, Lixia; Zou, Xin; Luo, Xin; Pu, Yanlei; Wang, Jiliang; Lei, Jingxin

    2017-01-01

    To delicately track the Li-ion transport in SPEs under an external electric field (EF) is a big challenge, considering the limitation of most spectroscopic methods to monitor the real-time conformational changes and track the dynamic process. Herein, real-time Li-ion transition behavior and transport dynamics in typical poly(vinyl alcohol)/LiClO4 electrolytes under an external EF have been studied by combining time-resolved Fourier transform infrared (FTIR) with two-dimensional correlation FTIR spectroscopy. Results show that no migration of Li-ions has been detected when the time scale of the EF loading is at nanosecond (less than 200 ns). However, for the first time, Li-ions have been found to significantly transfer along the EF direction as the time scale enhances to microsecond order of magnitude and the migration period is less than 10 microseconds. The Li+ migration in the SPEs under an EF is a complicated process including quasi-periodic dissociation and coordination effects between Li-ion carriers and polymeric chains. PMID:28378837

  15. Transition operators in acoustic-wave diffraction theory. I - General theory. II - Short-wavelength behavior, dominant singularities of Zk0 and Zk0 exp -1

    NASA Technical Reports Server (NTRS)

    Hahne, G. E.

    1991-01-01

    A formal theory of the scattering of time-harmonic acoustic scalar waves from impenetrable, immobile obstacles is established. The time-independent formal scattering theory of nonrelativistic quantum mechanics, in particular the theory of the complete Green's function and the transition (T) operator, provides the model. The quantum-mechanical approach is modified to allow the treatment of acoustic-wave scattering with imposed boundary conditions of impedance type on the surface (delta-Omega) of an impenetrable obstacle. With k0 as the free-space wavenumber of the signal, a simplified expression is obtained for the k0-dependent T operator for a general case of homogeneous impedance boundary conditions for the acoustic wave on delta-Omega. All the nonelementary operators entering the expression for the T operator are formally simple rational algebraic functions of a certain invertible linear radiation impedance operator which maps any sufficiently well-behaved complex-valued function on delta-Omega into another such function on delta-Omega. In the subsequent study, the short-wavelength and the long-wavelength behavior of the radiation impedance operator and its inverse (the 'radiation admittance' operator) as two-point kernels on a smooth delta-Omega are studied for pairs of points that are close together.

  16. Real-time tracking the Li(+)-ion transition behavior and dynamics in solid Poly(vinyl alcohol)/LiClO4 electrolytes.

    PubMed

    Bao, Lixia; Zou, Xin; Luo, Xin; Pu, Yanlei; Wang, Jiliang; Lei, Jingxin

    2017-04-05

    To delicately track the Li-ion transport in SPEs under an external electric field (EF) is a big challenge, considering the limitation of most spectroscopic methods to monitor the real-time conformational changes and track the dynamic process. Herein, real-time Li-ion transition behavior and transport dynamics in typical poly(vinyl alcohol)/LiClO4 electrolytes under an external EF have been studied by combining time-resolved Fourier transform infrared (FTIR) with two-dimensional correlation FTIR spectroscopy. Results show that no migration of Li-ions has been detected when the time scale of the EF loading is at nanosecond (less than 200 ns). However, for the first time, Li-ions have been found to significantly transfer along the EF direction as the time scale enhances to microsecond order of magnitude and the migration period is less than 10 microseconds. The Li(+) migration in the SPEs under an EF is a complicated process including quasi-periodic dissociation and coordination effects between Li-ion carriers and polymeric chains.

  17. Hybrid percolation transition in complex networks

    NASA Astrophysics Data System (ADS)

    Kahng, Byungnam

    Percolation has been one of the most applied statistical models. Percolation transition is one of the most robust continuous transitions known thus far. However, recent extensive researches reveal that it exhibits diverse types of phase transitions such as discontinuous and hybrid phase transitions. Here hybrid phase transition means the phase transition exhibiting natures of both continuous and discontinuous phase transitions simultaneously. Examples include k-core percolation, cascading failures in interdependent networks, synchronization, etc. Thus far, it is not manifest if the critical behavior of hybrid percolation transitions conforms to the conventional scaling laws of second-order phase transition. Here, we investigate the critical behaviors of hybrid percolation transitions in the cascading failure model in inter-dependent networks and the restricted Erdos-Renyi model. We find that the critical behaviors of the hybrid percolation transitions contain some features that cannot be described by the conventional theory of second-order percolation transitions.

  18. Hysteretic behavior of Fe(phen){sub 2}(NCS){sub 2} spin-transition microparticles vs. the environment: A huge reversible component resolved by first order reversal curves

    SciTech Connect

    Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian; Laisney, Jérôme; Boillot, Marie-Laure

    2014-01-20

    We discuss the influence of the embedding matrix on the thermal hysteretic behavior of spin transition microparticles of Fe(phen){sub 2}(NCS){sub 2} by using a series of experimental first order reversal curves (FORCs). The shape of FORCs supports the hypothesis considering additional interactions between the spin-transition microparticles and the embedding matrix, which compares to a negative pressure on the particles. A mean-field approach based on negative variable external pressures, together with a cut off/switch on of particles-matrix interactions accounts for the experimental features.

  19. Structural phase transition causing anomalous photoluminescence behavior in perovskite (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}

    SciTech Connect

    Yangui, A.; Pillet, S.; Mlayah, A.; Lusson, A.; Bouchez, G.; Boukheddaden, K. E-mail: kbo@physique.uvsq.fr; Triki, S.; Abid, Y. E-mail: kbo@physique.uvsq.fr

    2015-12-14

    Optical and structural properties of the organic-inorganic hybrid perovskite-type (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}] (abbreviated as C{sub 6}PbI{sub 4}) were investigated using optical absorption, photoluminescence (PL), and x-ray diffraction measurements. Room temperature, optical absorption measurements, performed on spin-coated films of C{sub 6}PbI{sub 4}, revealed two absorption bands at 2.44 and 3.21 eV. Upon 325 nm (3.815 eV) laser irradiation, strong green PL emission peaks were observed at 2.41 eV (P1) and 2.24 eV (P2) and assigned to free and localized excitons, respectively. The exciton binding energy was estimated at 356 meV. At low temperature, two additional emission bands were detected at 2.366 eV (P3) and a large band (LB) at 1.97 eV. The former appeared only below 40 K and the latter emerged below 130 K. The thermal dependence of the PL spectra revealed an abnormal behavior accompanied by singularities in the peak positions and intensities at 40 and 130 K. X-ray diffraction studies performed on powder and single crystals as a function of temperature evidenced significant changes of the interlayer spacing at 50 K and ∼138 K. Around 138 K, a commensurate to incommensurate structural phase transition occurred on cooling. It involves a symmetry breaking leading to a distortion of the PbI{sub 6} octahedron. The resulting incommensurate spatial modulation of the Pb–I distances (and Pb–I–Pb angles) causes a spatial modulation of the band gap, which is at the origin of the emergence of the LB below ∼130 K and the anomalous behavior of the position of P1 below 130 K. The change of the interlayer spacing in the 40-50 K range may in turn be related to the significant decrease of the intensity of P2 and the maximum emission of the LB. These results underline the intricate character of the structural and the PL properties of the hybrid perovskites; understanding such properties should benefit to the design of optoelectronic devices with

  20. Structural phase transition causing anomalous photoluminescence behavior in perovskite (C6H11NH3)2[PbI4].

    PubMed

    Yangui, A; Pillet, S; Mlayah, A; Lusson, A; Bouchez, G; Triki, S; Abid, Y; Boukheddaden, K

    2015-12-14

    Optical and structural properties of the organic-inorganic hybrid perovskite-type (C6H11NH3)2[PbI4] (abbreviated as C6PbI4) were investigated using optical absorption, photoluminescence (PL), and x-ray diffraction measurements. Room temperature, optical absorption measurements, performed on spin-coated films of C6PbI4, revealed two absorption bands at 2.44 and 3.21 eV. Upon 325 nm (3.815 eV) laser irradiation, strong green PL emission peaks were observed at 2.41 eV (P1) and 2.24 eV (P2) and assigned to free and localized excitons, respectively. The exciton binding energy was estimated at 356 meV. At low temperature, two additional emission bands were detected at 2.366 eV (P3) and a large band (LB) at 1.97 eV. The former appeared only below 40 K and the latter emerged below 130 K. The thermal dependence of the PL spectra revealed an abnormal behavior accompanied by singularities in the peak positions and intensities at 40 and 130 K. X-ray diffraction studies performed on powder and single crystals as a function of temperature evidenced significant changes of the interlayer spacing at 50 K and ∼138 K. Around 138 K, a commensurate to incommensurate structural phase transition occurred on cooling. It involves a symmetry breaking leading to a distortion of the PbI6 octahedron. The resulting incommensurate spatial modulation of the Pb-I distances (and Pb-I-Pb angles) causes a spatial modulation of the band gap, which is at the origin of the emergence of the LB below ∼130 K and the anomalous behavior of the position of P1 below 130 K. The change of the interlayer spacing in the 40-50 K range may in turn be related to the significant decrease of the intensity of P2 and the maximum emission of the LB. These results underline the intricate character of the structural and the PL properties of the hybrid perovskites; understanding such properties should benefit to the design of optoelectronic devices with targeted properties.

  1. K/Ar Dating of Fine Grained Sediments Near Prydz Bay, Antarctica: East Antarctic Ice Sheet Behavior During the Middle-Miocene Climate Transition

    NASA Astrophysics Data System (ADS)

    Duchesne, A. E.; Pierce, E. L.; Williams, T.; Hemming, S. R.; Johnson, D. L.; May, T.; Gombiner, J.; Torfstein, A.

    2012-12-01

    ¶ The Middle Miocene Climate Transition (MMCT) (~14 Ma) represents a time of major East Antarctic Ice-Sheet (EAIS) expansion, with research suggesting major global sea level fall on the order of ~60 meters (John et al., 2011, EPSL). Ocean Drilling Program (ODP) core data from Site 1165B near Prydz Bay shows an influx of cobbles deposited ~13.8-13.5 Ma, representing a sudden burst of ice-rafted detritus (IRD) during the MMCT. Based on 40Ar/39Ar dating of hornblendes and/or biotite grains, 5 of 6 dated pebbles from a companion study show Wilkes Land origins, indicating transport from over 1500 kilometers away. However, samples throughout this time interval have an anomalously low abundance of sand, thus we seek to understand the sedimentary processes that led to the deposition of these isolated dropstones in a fine matrix through provenance studies of the core's terrigenous fine fraction. Geochemical provenance studies of the terrigenous fraction of marine sediments can aid in identifying past dynamic EAIS behavior; the few outcrops available on the continent provide specific rock characterizations and age constraints from which cored marine sediments can then be matched to using established radiogenic isotope techniques. Here we apply the K/Ar dating method as a provenance tool for identifying the source area(s) of fine-grained terrigenous sediments (<63 μm) deposited during the MMCT. ¶ After source area characterization, we find that the fine-grained sediments from the mid-Miocene show a mixture of both local Prydz Bay sourcing (~400 Ma signature) and Wilkes Land provenance (~900 Ma signature). While locally-derived Prydz Bay sediments are likely to have been delivered via meltwater from ice and deposited as hemipelagic sediments (with some possible bottom current modification, as this is a drift site), sediments sourced from Wilkes Land required transport via large icebergs. Future work will involve further provenance determination on both the fine

  2. Behavior of the Meat-Borne Bacterium Lactobacillus sakei during Its Transit through the Gastrointestinal Tracts of Axenic and Conventional Mice ▿ †

    PubMed Central

    Chiaramonte, Fabrizio; Blugeon, Sébastien; Chaillou, Stéphane; Langella, Philippe; Zagorec, Monique

    2009-01-01

    A Lactobacillus sakei strain named FLEC01 was isolated from human feces and characterized genotypically. Comparison of the genetic features of this strain with those of both the meat-borne L. sakei strain 23K and another human isolate, LTH5590, showed that they belong to different but closely related clusters. The three L. sakei strains did not persist and only transited through the gastrointestinal tracts (GITs) of conventional C3H/HeN mice. In contrast, they all colonized the GITs of axenic mice and rapidly reached a population of 109 CFU/g of feces, which remained stable until day 51. Five days after mice were fed, a first subpopulation, characterized by small colonies, appeared and reached 50% of the total L. sakei population in mice. Fifteen to 21 days after feeding, a second subpopulation, characterized by rough colonies, appeared. It coexisted with the two other populations until day 51, and its cell shapes were also affected, suggesting a dysfunction of the cell division or cell wall. No clear difference between the behaviors of the meat-borne strain and the two human isolates in both conventional and axenic mice was observed, suggesting that L. sakei is a food-borne bacterium rather than a commensal one and that its presence in human feces originates from diet. Previous observations of Escherichia coli strains suggest that the mouse GIT environment could induce mutations to increase their survival and colonization capacities. Here, we observed similar mutations concerning a food-grade gram-positive bacterium for the first time. PMID:19447958

  3. Transition Planning

    ERIC Educational Resources Information Center

    Statfeld, Jenna L.

    2011-01-01

    Post-school transition is the movement of a child with disabilities from school to activities that occur after the completion of school. This paper provides information about: (1) post-school transition; (2) transition plan; (3) transition services; (4) transition planning; (5) vocational rehabilitation services; (6) services that are available…

  4. Neutron Irradiation Effects on the Mechanical Properties of HY-80 Steel

    DTIC Science & Technology

    1986-12-01

    properties of HY-80 steel to 750*F for the indicated irradiation conditions (Ref. [15]) ..................... 52 Figure 26 DBTT changes of HY-80 steels as...to-brittle transition temperature ( DBTT ) and generally it is in the range of -50 to +20 degress Celsius for unirradiated mild steels , [2]. In the...ductility has on the ductile-brittle transition temperature ( DBTT ). For steels irradiated at less than 450-F, a relatively consistent increase in nil

  5. A translational evaluation of transitions.

    PubMed

    Jessel, Joshua; Hanley, Gregory P; Ghaemmaghami, Mahshid

    2016-06-01

    Transitions with nonhuman animals are typically framed as inescapable changes in signaled reinforcement schedules that result in a pause in responding unique to switches from rich to lean schedules. Pausing is considered to be a function of the aversive qualities of the contrasting reinforcement schedules. Transitions are typically framed in applied research as physical changes in location that evoke problem behavior maintained by the escape of an aversive event or resumption of a preferred event. We attempted to extend the basic framing of transitions to behaviors and contexts of social significance and evaluate a novel treatment for the problem of dawdling by 3 boys who had been diagnosed with autism spectrum disorder during rich-to-lean transitions. Dawdling during physical transitions was most readily observed when transitioning to lean contexts in Experiment 1. We then shortened transition duration in Experiment 2 by programming unsignaled and probabilistic rich reinforcement in the upcoming context.

  6. Contrasting Behavior of the Z Bonds in X-Z···Y Weak Interactions: Z = Main Group Elements Versus the Transition Metals.

    PubMed

    Joy, Jyothish; Jemmis, Eluvathingal D

    2017-02-06

    In contrast to the increasing family of weak intermolecular interactions in main-group compounds (X-Z···Y, Z = main-group elements), an analysis of the Cambridge Structural Database indicates that electron-saturated (18-electron) transition-metal complexes show reluctance toward weak M bond formation (X-M···Y, M = transition metal). In particular, weak M bonds involving electron-saturated (18-electron) complexes of transition metals with partially filled d-orbitals are not found. We propose that the nature of valence electron density distribution in transition-metal complexes is the primary reason for this reluctance. A survey of the interaction of selected electron-saturated transition-metal complexes with electron-rich molecules (Y) demonstrates the following: shielding the possible σ-hole on the metal center by the core electron density in 3d series, and enhanced electronegativity and relativistic effects in 4d and 5d series, hinders the formation of the M bond. A balance in all the destabilizing effects has been found in the 4d series due to its moderate polarizability and primogenic repulsion from inner core d-electrons. A changeover in the donor-acceptor nature of the metal center toward different types of incoming molecules is also unveiled here. The present study confirms the possibility of M bond as a new supramolecular force in designing the crystal structures of electron-saturated transition-metal complexes by invoking extreme ligand conditions.

  7. C/SiC Gradient Oxidation Protective Coating on Graphite by Modified Reactive Melt Infiltration Method: Effects of Processing Parameters on Transition Interface Thickness and High-Temperature Anti-oxidation Behavior

    NASA Astrophysics Data System (ADS)

    Abdollahi, Alireza; Ehsani, Naser

    2017-01-01

    In this research, it was found that the C/SiC transition interface thickness increases without a significant decrease in toughness by modifying the reactive melt infiltration method through the addition of SiC nanoparticles. Also, the effect of the infiltration temperature on the transition interface thickness, isothermal oxidation behavior, and thermal shock resistance of the C/SiC graded coating were investigated. Coatings were characterized by X-ray diffraction, electron probe microanalysis, and scanning electron microscopy with energy-dispersive spectroscopy. Microstructural observations showed that with an increase in the heat treatment temperature, a higher amount of β-SiC (as a product of the infiltration process) is produced, which results in lower surface continuity in the coatings produced at a lower temperature. Moreover, the transition interface thickness increased with a decreasing infiltration temperature. The addition of SiC nanoparticles increased the transition interface thickness and oxidation resistance. After isothermal oxidation at 1773 K (1500 °C) for 10 hours, samples containing 7 wt pct SiC nanoparticles heat treated at 1773 K and 1873 K (1500 °C and 1600 °C) showed 13.3 and 5.03 pct weight loss, respectively.

  8. Experimental investigation of the unusual behavior of local heat transfer coefficient in the transition region of a circular tube with a bell-mouth entrance

    SciTech Connect

    Tam, L.M.; Ghajar, A.J.

    1996-12-31

    The local heat transfer characteristics for ethylene glycol water mixtures flowing in a horizontal circular straight tube with a bell-mouth inlet have been determined experimentally over a flow Reynolds number range of 1,500 to 27,000. A wall-boundary heating condition of uniform heat flux was imposed. The variation of local heat transfer coefficient with length in the transition and turbulent flow regimes is very unusual. For the bell-mouth inlet, the boundary layer along the tube wall is at first laminar and then changes through a transition region to the turbulent condition causing a dip in the Nu-x/D curve. The length of the dip in the transition region is much longer than that in the turbulent region. For the experiments the length of the dip in the transition region varied from x/D = 100 to 175 in comparison to an x/D < 25 for the turbulent region. The presence of the dip in the transition region causes a significant influence on both the local and the average heat transfer coefficients. This is particularly important for heat transfer calculations in short tubes with a bell-mouth inlet.

  9. The Impact of Multiple Types of Child Maltreatment on Subsequent Risk Behaviors among Women during the Transition from Adolescence to Young Adulthood

    ERIC Educational Resources Information Center

    Hahm, Hyeouk Chris; Lee, Yoona; Ozonoff, Al; Van Wert, Michael J.

    2010-01-01

    The purpose of this study was to investigate how different types of child maltreatment, independently and collectively, impact a wide range of risk behaviors that fall into three domains: sexual risk behaviors, delinquency, and suicidality. Cumulative classification and Expanded Hierarchical Type (EHT) classification approaches were used to…

  10. A Variety of Phase‐Transition Behaviors in a Niccolite Series of [NH3(CH2)4NH3][M(HCOO)3]2

    PubMed Central

    Shang, Ran; Chen, Sa; Hu, Ke‐Li; Wang, Bing‐Wu

    2016-01-01

    Abstract A niccolite series of [bnH2 2+][M(HCOO)3]2 (bnH2 2+=1,4‐butyldiammonium) shows four kinds of metal‐dependent phase transitions, from high temperature para‐electric phases to low‐temperature ferro‐, antiferro‐, glass‐like, and para‐electric phases. The conformational flexibility of bnH2 2+ and the different size, mass, and bonding character of the metal ion lead to various disorder‐order transitions of bnH2 2+ in the lattice and relevant framework modulations, thus different phase transitions and dielectric responses. The magnetic members display a coexistence or combination of electric and magnetic orderings in the low‐temperature region. PMID:26892832

  11. Crystal structure and phase transition behavior in (K1-xNax)NbO3-based lead-free piezoelectric ceramic over a wide range of temperatures

    NASA Astrophysics Data System (ADS)

    Yamada, H.; Matsuoka, T.; Kozuka, H.; Yamazaki, M.; Ohbayashi, K.; Ida, T.

    2016-12-01

    The phase transition temperature in a (K, Na)NbO3 (KNN) phase of a KNN-based composite lead-free piezoelectric ceramic with a KTiNbO5 system ((K1-xNax)0.86Ca0.04Li0.02Nb0.85O3-δ-K0.85Ti0.85Nb1.15O5-BaZrO3-Co3O4-Fe2O3-ZnO) is lower than that in an undoped KNN ceramic by approximately 200 °C. We have studied the structural changes around the phase transition by using synchrotron powder X-ray diffraction and transmission electron microscopy. The crystal system of the main KNN phase is assigned to tetragonal as a stable structure at room temperature and does not change to orthorhombic on lowering the temperature all at once. The crystal structure changes from tetragonal to orthorhombic through the successive transition state. The curve of the phase transition temperature from x = 0.33 to 0.75 has a V shape and reaches its lowest value of approximately 0 °C in the vicinity of x = 0.56. From selected-area electron diffraction patterns of the KNN phase, weak superlattice spots owing to the tilt-ordered NbO6 octahedra are observed for x ≥ 0.56. This tilt-ordered NbO6 octahedral phase is formed at the nanometer-scale (nanodomains) in the tetragonal and orthorhombic KNN matrices, regardless of the phase transition. The minimum x to generate the nanodomains is substantially equal to the Na fraction at which the starting temperature of the successive phase transition shifts to the lowest.

  12. Work transitions.

    PubMed

    Fouad, Nadya A; Bynner, John

    2008-01-01

    Individuals make choices in, and adjust to, a world of work that is often a moving target. Because work is so central to human functioning, and transitions in and out of work can have major mental health repercussions, the authors argue that applied psychologists in health services need to understand those transitions. This article focuses on the different types of transition throughout a person's working life and the resources needed at different stages to ensure the success of these transitions. The authors start by examining the roles of capability and adaptability in supporting and facilitating adjustment to work transitions and their relation to identity development. They then examine the role of social and institutional contexts in shaping work transitions and their outcomes. The authors focus on voluntary versus involuntary transitions and then broaden the lens in discussing the policy implications of research on work transitions.

  13. Families in Transition .

    ERIC Educational Resources Information Center

    Bundy, Michael L., Ed.; Gumaer, James, Ed.

    1984-01-01

    Focuses on disrupted families and the role of the school counselor in helping children adjust. Describes characteristics of healthy families, and discusses the transition to the blended family, effects of divorce groups on children's classroom behavior, counseling children in stepfamilies, single-parent families, and parenting strengths of single…

  14. Relationship between mechanical and magnetic properties in cold rolled low carbon steel

    NASA Astrophysics Data System (ADS)

    Takahashi, S.; Kobayashi, S.; Kikuchi, H.; Kamada, Y.

    2006-12-01

    Structure-sensitive properties of minor hysteresis loops have been compared with Vickers hardness and ductile-brittle transition temperature (DBTT) obtained by Charpy impact test for cold rolled low carbon steel. Minor loops were measured with increasing magnetic field amplitude, step by step, and were analyzed in connection with the rolling reduction. We found that minor-loop coefficients deduced from relations between minor-loop parameters increase with increasing rolling reduction and have a simple relationship with both mechanical properties, Vickers hardness, and DBTT. We also found that these coefficients have a linear relation with coercive force obtained by the major loop. The present analysis method using minor loops is highly effective for nondestructive evaluation of ductile-brittle transition, in terms of the high sensitivity to lattice defects as well as low measurement field.

  15. The Effects of Project APPLE (Autistic Preadolescent Proactive Learning Environments) on Academic, Behavioral, and Transitional Needs of Students with Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Cayce, Robin M.

    2012-01-01

    This study addressed the effects of Project APPLE, an intervention created by the researcher and supported by the Guide to Project APPLE, a handbook which provided research-based teaching strategies, modificaitons to the learning environment, and transitional supports for students with ASD, and the teachers with whom their care and education is…

  16. Individual Differences in Growth in Executive Function across the Transition to School Predict Externalizing and Internalizing Behaviors and Self-Perceived Academic Success at 6 Years of Age

    ERIC Educational Resources Information Center

    Hughes, Claire; Ensor, Rosie

    2011-01-01

    Building on an existing latent variable analysis of executive function (EF) in children (N=191, 57% boys and 43% girls) making the transition to school (Hughes et al. (2010), "Developmental Neuropsychology", vol. 35, pp. 20-36), the current study both documented average developmental improvements from 4 to 6 years of age and examined individual…

  17. Tough Polymer Alloys via Chemically Controlled Morphology

    DTIC Science & Technology

    2007-11-02

    involved the use of polyamides , polyesters and polycarbonates as one component in the blend. The other component was a reactive elastomer , an ABS...material, a core-shell impact modifier, or polypropylene. The end group configuration of the polyamide was shown to be an important consideration in...producing super-tough polyamide blends with low ductile-brittle transition temperatures are described. Cavitation of the rubber phase was shown to be an important part of the toughening mechanism in certain cases.

  18. Fusion silicide coatings for tantalum alloys.

    NASA Technical Reports Server (NTRS)

    Warnock, R. V.; Stetson, A. R.

    1972-01-01

    Calculation of the performance of fusion silicide coatings under simulated atmospheric reentry conditions to a maximum temperature of 1810 K (2800 F). Both recently developed and commercially available coatings are included. Data are presented on oxidation rate with and without intentional defecting, the influence of the coatings on the ductile-brittle bend transition temperature, and the mechanical properties. Coatings appear capable of affording protection for at least 100 simulated cycles to 2600 F and 63 cycles to 2800 F.

  19. Mechanical properties of electron-beam-melted molybdenum and dilute Mo-Re alloys.

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    Study of Mo-Re alloys aimed at examining the effects of small rhenium additions on the low-temperature ductility of molybdenum and determining the mechanical properties of dilute Mo-Re alloys. The results obtained indicate that high-purity Mo-Re alloys have ductile-brittle transition temperatures considerably lower than those for unalloyed molybdenum and that rhenium promotes normal solid-solution strengthening in molybdenum at elevated temperatures.

  20. Magnetic transition behavior of perovskite manganites Nd0.5Sr0.3Ca0.2MnO3 polycrystalline

    NASA Astrophysics Data System (ADS)

    Ru, Xing; Su-Lei, Wan; Wen-Qing, Wang; Lin, Zheng; Xiang, Jin; Min, Zhou; Yi, Lu; Jian-Jun, Zhao

    2016-04-01

    A polycrystalline sample Nd0.5Sr0.3Ca0.2MnO3 is prepared by the conventional solid state reaction method. The structure and magnetic properties are investigated with x-ray diffraction (XRD) patterns, a superconducting quantum interference device (SQUID), and electron spin resonance (ESR). The sample is in single phase with the space group Pbnm symmetry. With the decrease of temperature, Nd0.5Sr0.3Ca0.2MnO3 undergoes three magnetic transitions: ferromagnetic transition at T C ≈ 210 K, charge-ordering at T CO ≈ 175 K, and antiferromagnetic transition at T N = 155 K. In addition, the activation energy E a ≈ 52.78 meV can be extracted by curve fitting. Project supported by the National Natural Science Foundation of China (Grant Nos. 11164019, 51562032, and 61565013), the Inner Mongolia Natural Science Foundation, China (Grant Nos. 2015MS0109, NJZZ11166, and NJZY12202), and the Science and Technology in Baotou Production-Study-Research Cooperation Projects, China (Grant No. 2014X1014-01).

  1. Composition-dependent behavior of Co(d7) optical transitions in Cd1-x Cox Ga2S4 mixed crystals

    NASA Astrophysics Data System (ADS)

    Kim, Young-San; Park, Hyun; Hyun, Seung-Cheol; Jin, Moon-Seog; Park, Gye-Choon; Kim, Chang-Dae; Jang, Kiwan; Choi, In-Hwan; Kim, Wha-Tek

    2006-09-01

    The optical transitions due to the cobalt transition metal impurity centers with composition x in Cd1-k Cox Ga2S4 mixed crystals were investigated by optical absorption spectroscopy. The optical absorption spectra showed three crystal-field transitions between the ground state 4A2(4F) and the excited states 4T2(4F), 4T1(4F), and 4T1(4P) of substitutional Co2+ ions that were similar for all the investigated compositions. The crystal-field parameter (Dq ) and the Racah parameter (B ) obtained from the observed absorption bands showed a composition dependence such that the Dq parameter increases; on the other hand, the B parameter decreases with increasing composition x, which implies that the Racah parameter (B ) depends strongly on the host crystal. Also, the total splitting between the highest and the lowest states of the 4T1(4P) state split due to spin-orbit coupling showed a composition dependence varying from 1576 cm-1 to 1232 cm-1 with increasing x . The spin-orbit coupling parameter γ varied from 394 cm-1 to 308 cm-1 with composition x .

  2. Pressure-induced structural phase transition and elastic properties of rare earth Pr chalcogenides and pnictides

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Shriya, Swarna; Varshney, Meenu; Khenata, R.

    2015-01-01

    Pressure-induced structural aspects and elastic properties of NaCl-type (B1) to CsCl-type (B2) structure in praseodymium chalcogenides and pnictides are presented. Ground-state properties are numerically computed by considering long-range Coulomb interactions, Hafemeister and Flygare type short-range overlap repulsion, and van der Waals interaction in the interionic potential. From the elastic constants, Poisson's ratio ν, the ratio RG/B of G (shear modulus) over B (bulk modulus), anisotropy parameter, shear and Young's moduli, Lamé's constant, Kleinman parameter, elastic wave velocity and thermodynamical property such as Debye temperature are calculated. Poisson's ratio ν and the ratio RG/B indicate that PrX and PrY are brittle in B1 phase and ductile in B2 phase. To our knowledge, this is the first quantitative theoretical prediction of the ductile (brittle) nature of praseodymium chalcogenides and pnictides and still awaits experimental confirmation.

  3. Indentation plasticity and fracture in silicon

    NASA Technical Reports Server (NTRS)

    Rybicki, George C.; Pirouz, P.

    1988-01-01

    Measurements of the ductile-brittle transition temperature of heavily doped silicon were carried out using indentation techniques. Diamond pyramid hardness tests were performed on the (100) face of heavily doped N-type and P-type and intrinsic silicon single crystals. Tests were performed over the range 200 C to 850 C and loads of 100 to 500 g were used. Samples were subsequently etched to reveal dislocation rosettes produced by indentation. Intrinsic silicon underwent a ductile-brittle transition at 660 C, P-type at 645 C and N-type at 625 C. Hardness values varied from 1.1 GPa at 700 C to 11.7 GPa at 200 C. Significant effects of hardness on doping were present only at the highest temperatures. Lower loads generally produced higher hardness but load did not affect the Ductile-Brittle Transition Temperature (DBTT). Fracture toughness values ranged from 0.9 MPa m(1/2) at 200 C to 2.75 MPa m(1/2) near the DBTT. Doping did not affect the fracture toughness of silicon. P-type doping increased the size of dislocation rosettes observed after indentation, but N-type did not, in contradiction of the expected results. Results are discussed in terms of the effect of doping on the dislocation mobility in silicon.

  4. Course Selection Theory and College Transition Seminars: An Adaptation of College Choice Models to Explain First-Year Students' Course Enrollment Behavior

    ERIC Educational Resources Information Center

    Graff, Curt Gerard

    2011-01-01

    This dissertation examines the course-enrollment behavior of first-year students at a public Midwestern university. Using the student choice construct, modern college choice theory, and the constructs of habitus, human capital, financial capital, social capital, cultural capital, along with background variables such as gender and locus of control,…

  5. Diverse types of percolation transitions

    NASA Astrophysics Data System (ADS)

    Lee, Deokjae; Cho, Y. S.; Kahng, B.

    2016-12-01

    Percolation has long served as a model for diverse phenomena and systems. The percolation transition, that is, the formation of a giant cluster on a macroscopic scale, is known as one of the most robust continuous transitions. Recently, however, many abrupt percolation transitions have been observed in complex systems. To illustrate such phenomena, considerable effort has been made to introduce models and construct theoretical frameworks for explosive, discontinuous, and hybrid percolation transitions. Experimental results have also been reported. In this review article, we describe such percolation models, their critical behaviors and universal features, and real-world phenomena.

  6. Notch toughness in hot-rolled low carbon steel wire rod

    SciTech Connect

    Baarman, M.H.

    1999-12-01

    Charpy V-notch toughness has been investigated in four hot-rolled, low carbon steels with different grain sizes and carbon contents between 0.019 and 0.057%. The raw material was wire rod designed for drawing and possible subsequent cold heading operations and manufactured from continuous cast billets. In this study, the influence of microstructure, mechanical properties, and alloying elements on the ductile-brittle transition behavior has been assessed. A particular emphasis has been given to the influence of boron with contents up to 0.0097%. As a result, transition temperatures between {minus}29 and +50 C explicated by the material properties have been obtained. The examination also shows that the transition temperature raises with circa 0.5 C for each added ppm boron most likely as a consequence of an enlargement of the ferrite grain size and the reduction of yield and tensile strength. The highest upper shelf energy and lowest transition temperature can be observed in a steel without boron additions and with maximum contents of carbon, silicon, and manganese.

  7. Deformed transition-state theory: Deviation from Arrhenius behavior and application to bimolecular hydrogen transfer reaction rates in the tunneling regime.

    PubMed

    Carvalho-Silva, Valter H; Aquilanti, Vincenzo; de Oliveira, Heibbe C B; Mundim, Kleber C

    2017-01-30

    A formulation is presented for the application of tools from quantum chemistry and transition-state theory to phenomenologically cover cases where reaction rates deviate from Arrhenius law at low temperatures. A parameter d is introduced to describe the deviation for the systems from reaching the thermodynamic limit and is identified as the linearizing coefficient in the dependence of the inverse activation energy with inverse temperature. Its physical meaning is given and when deviation can be ascribed to quantum mechanical tunneling its value is calculated explicitly. Here, a new derivation is given of the previously established relationship of the parameter d with features of the barrier in the potential energy surface. The proposed variant of transition state theory permits comparison with experiments and tests against alternative formulations. Prescriptions are provided and implemented to three hydrogen transfer reactions: CH4  + OH → CH3  + H2 O, CH3 Cl + OH → CH2 Cl + H2 O and H2  + CN → H + HCN, widely investigated both experimentally and theoretically. © 2016 Wiley Periodicals, Inc.

  8. Detection of impurity diamagnetic susceptibility and its behavior in n-Ge:As in the region of the insulator–metal phase transition

    SciTech Connect

    Veinger, A. I. Zabrodskii, A. G.; Makarova, T. L.; Tisnek, T. V.; Goloshchapov, S. I.; Semenikhin, P. V.

    2015-10-15

    The method of superconducting quantum interference device (SQUID) magnetometry is used to measure and study low-temperature (T ≤ 100K) susceptibility in a series of samples of heavily doped Ge:As samples on the insulator side of the insulator–metal phase transition. Subtracting the known values of the magnetic susceptibility of the lattice from the measurement results, the values of the impurity magnetic susceptibility of the system are obtained. Using the method of electron spin resonance, the paramagnetic component of the impurity susceptibility is determined. Subtraction of the paramagnetic component from the total impurity susceptibility is used to obtain, for the first time, the values of the impurity diamagnetic susceptibility (∼5 × 10{sup –8} cm{sup 3}/g). The obtained result is consistent with estimates obtained for the localization radius of an electron at an As donor. Lowering the temperature to T ≤ 4 K leads to an increase in the diamagnetic susceptibility, which is consistent with the observed increase in the paramagnetic susceptibility. The observed effect is accounted for by the transition of impurity electrons from the singlet state to the triplet one.

  9. Water-soluble thermoresponsive α-helical polypeptide with an upper critical solution temperature: synthesis, characterization, and thermoresponsive phase transition behaviors.

    PubMed

    Deng, Yong; Xu, Yanzhi; Wang, Xi; Yuan, Qiulin; Ling, Ying; Tang, Haoyu

    2015-03-01

    Water-soluble polypeptides bearing 1-alkylimidazolium (methyl or n-butyl) and various counter-anions (i.e., Cl(-), I(-) or BF4 (-)) are prepared by ring-opening polymerization of γ-4-chloromethylbenzyl-l-glutamate-based N-carboxyanhydride (3), post-polymerization of poly(γ-4-chloromethylbenzyl-l-glutamate) (4), and ion-exchange reaction. Circular dichroism (CD) analysis reveals that the resulting polypeptides adopt an α-helical conformation in water with a fractional helicity in the range of 30%-56% at 20 °C and exhibit good conformational stability against temperature variations. The polypeptides exhibit lower critical solution temperature (LCST)-type or upper critical solution temperature (UCST)-type transitions in organic solvents or in water. The UCST-type transition temperature (Tpt ) in water is independent on the molecular weight, yet it decreases upon addition of NaCl and increases upon addition of NaI or NaBF4, suggesting a mainly electrostatic interaction mechanism.

  10. Nuclear shape phase transition within a conjunction of γ-rigid and γ-stable collective behaviors in deformation-dependent mass formalism

    NASA Astrophysics Data System (ADS)

    Chabab, M.; El Batoul, A.; Lahbas, A.; Oulne, M.

    2016-12-01

    In this paper, we present a theoretical study of a conjunction of γ-rigid and γ-stable collective motions in critical point symmetries of the phase transitions from spherical to deformed shapes of nuclei using an exactly separable version of the Bohr Hamiltonian with a deformation-dependent mass term. The deformation-dependent mass is applied simultaneously to γ-rigid and γ-stable parts of this famous collective Hamiltonian. Moreover, the β part of the problem is described by means of Davidson potential, while the γ-angular part corresponding to axially symmetric shapes is treated by a harmonic oscillator potential. The energy eigenvalues and normalized eigenfunctions of the problem are obtained in compact forms by making use of the asymptotic iteration method. The combined effect of the deformation-dependent mass and rigidity as well as harmonic oscillator stiffness parameters on the energy spectrum and wave functions is duly investigated. Also, the electric quadrupole transition ratios and energy spectrum of some γ-stable and prolate nuclei are calculated and compared with the experimental data as well as with other theoretical models.

  11. Transitional Care

    ERIC Educational Resources Information Center

    Naylor, Mary; Keating, Stacen A.

    2008-01-01

    Transitional care encompasses a broad range of services and environments designed to promote the safe and timely passage of patients between levels of health care and across care settings. High-quality transitional care is especially important for older adults with multiple chronic conditions and complex therapeutic regimens, as well as for their…

  12. Universal behavior of chalcogenides of rare-earth metals in the transition to a state with intermediate valence at high pressures

    SciTech Connect

    Tsiok, O. B.; Khvostantsev, L. G.; Brazhkin, V. V.

    2015-06-15

    Precision measurements of resistivity, thermopower, and volume are performed for TmS, TmSe, and TmTe under a hydrostatic pressure up to 8 GPa. Comparison of the transport properties and volume of TmTe and SmTe in the valence transition region demonstrates a complete analogy up to quantitative coincidence. It is shown that the thermopower of all thulium and samarium chalcogenides in the lattice collapse region and in subsequent rearrangement of the electron spectrum in a wide range of pressures follow a universal dependence corresponding the passage of the Fermi level through the peak of the density of states (DOS). The results are considered in the context of ideas about the exciton nature of the intermediate valence in chalcogenides of rare-earth metals.

  13. Tetradihydrobenzoquinonate and tetrachloranilate Zr(IV) complexes: single-crystal-to-single-crystal phase transition and open-framework behavior for K4Zr(DBQ)4.

    PubMed

    Imaz, Inhar; Mouchaham, Georges; Roques, Nans; Brandès, Stéphane; Sutter, Jean-Pascal

    2013-10-07

    The molecular complexes K4[Zr(DBQ)4] and K4[Zr(CA)4], where DBQ(2-) and CA(2-) stand respectively for deprotonated dihydroxybenzoquinone and chloranilic acid, are reported. The anionic metal complexes consist of Zr(IV) surrounded by four O,O-chelating ligands. Besides the preparation and crystal structures for the two complexes, we show that in the solid state the DBQ complex forms a 3-D open framework (with 22% accessible volume) that undergoes a crystal-to-crystal phase transition to a compact structure upon guest molecule release. This process is reversible. In the presence of H2O, CO2, and other small molecules, the framework opens and accommodates guest molecules. CO2 adsorption isotherms show that the framework breathing occurs only when a slight gas pressure is applied. Crystal structures for both the hydrated and guest free phases of K4[Zr(DBQ)4] have been investigated.

  14. The effect of the annealing temperature on the transition from conductor to semiconductor behavior in zinc tin oxide deposited atomic layer deposition

    SciTech Connect

    Ahn, Byung Du; Choi, Dong-won Choi, Changhwan; Park, Jin-Seong

    2014-09-01

    We investigated the electrical properties of zinc tin oxide (ZTO) films deposited via atomic layer deposition and compared them to ZnO and SnO{sub 2} films as a function of the annealing temperature. The ZTO and ZnO, except for SnO{sub 2}, films exhibited an electrical transition from a metal to semiconductor characteristics when annealed above 300 °C. The X-ray photoelectron spectroscopy analyses indicate that the relative area of the oxygen vacancy-related peak decreased from 58% to 41% when annealing at temperatures above 400 °C. Thin film transistors incorporating ZTO active layers demonstrated a mobility of 13.2 cm{sup 2}/V s and a negative bias instability of −0.2 V.

  15. Quantum interface unbinding transitions

    NASA Astrophysics Data System (ADS)

    Jakubczyk, P.

    2012-08-01

    We consider interfacial phenomena accompanying bulk quantum phase transitions in the presence of surface fields. On general grounds we argue that the surface contribution to the system free energy involves a line of singularities characteristic of an interfacial phase transition, occurring below the bulk transition temperature Tc down to T=0. This implies the occurrence of an interfacial quantum critical regime extending into finite temperatures and located within the portion of the phase diagram where the bulk is ordered. Even in situations where the bulk order sets in discontinuously at T=0, the system's behavior at the boundary may be controlled by a divergent length scale if the tricritical temperature is sufficiently low. Relying on an effective interfacial model we compute the surface phase diagram in bulk spatial dimensionality d⩾2 and extract the values of the exponents describing the interfacial singularities in d⩾3.

  16. Partnership Transitions and Maternal Parenting

    PubMed Central

    Beck, Audrey N.; Cooper, Carey E.; McLanahan, Sara; Brooks-Gunn, Jeanne

    2011-01-01

    We use data from the Fragile Families and Child Wellbeing Study (N = 1,975) to examine the association between mothers’ partnership changes and parenting behavior during the first five years of their children’s lives. We compare coresidential with dating transitions, and recent with more distal transitions. We also examine interactions between transitions and race/ethnicity, maternal education and family structure at birth. Findings indicate that both coresidential and dating transitions were associated with higher levels of maternal stress and harsh parenting; recent transitions had stronger associations than distal transitions. Maternal education significantly moderates these associations, with less educated mothers responding more negatively to instability in terms of maternal stress, and more educated mothers responding more negatively in terms of literacy activities. PMID:21423848

  17. Transition metals

    PubMed Central

    Rodrigo-Moreno, Ana; Poschenrieder, Charlotte; Shabala, Sergey

    2013-01-01

    Transition metals such as Iron (Fe) and Copper (Cu) are essential for plant cell development. At the same time, due their capability to generate hydroxyl radicals they can be potentially toxic to plant metabolism. Recent works on hydroxyl-radical activation of ion transporters suggest that hydroxyl radicals generated by transition metals could play an important role in plant growth and adaptation to imbalanced environments. In this mini-review, the relation between transition metals uptake and utilization and oxidative stress-activated ion transport in plant cells is analyzed, and a new model depicting both apoplastic and cytosolic mode of ROS signaling to plasma membrane transporters is suggested. PMID:23333964

  18. Transitional Changes in Energy Intake, Skeletal Muscle Content and Nutritional Behavior in College Students During Course-Work Based Nutrition Education

    PubMed Central

    2013-01-01

    The purpose of this study was to investigate whether elective course work based nutrition education in university can change students' body composition and eating habits associated with obesity and its related health risk in first-year college students. A total of 38 students agreed and participated in the study. Participants received a series of lecture about obesity, weight management, and concepts of nutrition and food choices for 13 weeks. The students' BMI and body composition, including body fat and muscle contents, were measured. A 24-hour diet recall for two days was performed for food intake analysis, and the questionnaires for dietary behaviors were collected at the beginning and the end of the study. Paired t-test and χ2-test were used for statistical analysis. Data showed that most of the anthropometric parameters including body weight were not significantly changed at the end of the coursework. Interestingly, skeletal muscle contents in both obese (BMI ≥ 23) and lean (18.5 ≤ BMI ≤ 22.9) subjects were significantly increased. Total energy intake was decreased in total subjects after the study. Also, general nutrition behavior of the subjects including enough hydration and utilization of nutrition knowledge were significantly improved during the study period. The total number of responses to doing aerobic exercise was slightly increased after the study, but the average frequency of exercise in each individual was not changed. These results suggest that class-work based nutrition education on a regular basis could be a time and cost effective method for improving body composition and nutritional behavior in general college students. PMID:23908979

  19. Transitional changes in energy intake, skeletal muscle content and nutritional behavior in college students during course-work based nutrition education.

    PubMed

    Bu, So-Young

    2013-07-01

    The purpose of this study was to investigate whether elective course work based nutrition education in university can change students' body composition and eating habits associated with obesity and its related health risk in first-year college students. A total of 38 students agreed and participated in the study. Participants received a series of lecture about obesity, weight management, and concepts of nutrition and food choices for 13 weeks. The students' BMI and body composition, including body fat and muscle contents, were measured. A 24-hour diet recall for two days was performed for food intake analysis, and the questionnaires for dietary behaviors were collected at the beginning and the end of the study. Paired t-test and χ(2)-test were used for statistical analysis. Data showed that most of the anthropometric parameters including body weight were not significantly changed at the end of the coursework. Interestingly, skeletal muscle contents in both obese (BMI ≥ 23) and lean (18.5 ≤ BMI ≤ 22.9) subjects were significantly increased. Total energy intake was decreased in total subjects after the study. Also, general nutrition behavior of the subjects including enough hydration and utilization of nutrition knowledge were significantly improved during the study period. The total number of responses to doing aerobic exercise was slightly increased after the study, but the average frequency of exercise in each individual was not changed. These results suggest that class-work based nutrition education on a regular basis could be a time and cost effective method for improving body composition and nutritional behavior in general college students.

  20. Spin-orbit contribution to the Hall coefficient approaching the metal-insulator transition: An explanation for the critical behavior of Ge:Sb

    NASA Astrophysics Data System (ADS)

    Castner, T. G.

    1990-09-01

    It is demonstrated that the band spin-orbit contribution to the Hall conductivity σyx can qualitatively explain the critical behavior of the Hall coefficient RH for Ge:Sb reported by Field and Rosenbaum. The spin-orbit contribution to σyx for n-type Ge has been experimentally determined by Chazalviel and leads to an R-1H versus (n/nc-1) dependence that is consistent with the Ge:Sb data. This result demonstrates a significant extraordinary contribution to RH for some very weakly paramagnetic metal-insulator systems when closely approaching the critical density nc.

  1. Critical behavior of La0.7Ca0.3Mn1-xNixO3 manganites exhibiting the crossover of first- and second-order phase transitions

    NASA Astrophysics Data System (ADS)

    Phan, The-Long; Tran, Q. T.; Thanh, P. Q.; Yen, P. D. H.; Thanh, T. D.; Yu, S. C.

    2014-04-01

    We used Banerjee's criteria, modified Arrott plots, and the scaling hypothesis to analyze magnetic-field dependences of magnetization near the ferromagnetic-paramagnetic (FM-PM) phase-transition temperature (TC) of perovskite-type manganites La0.7Ca0.3Mn1-xNixO3 (x=0.09, 0.12 and 0.15). In the FM region, experimental results for the critical exponent β (=0.171 and 0.262 for x=0.09 and 0.12, respectively) reveal two first samples exhibiting tricriticality associated with the crossover of first- and second-order phase transitions. Increasing Ni-doping content leads to the shift of the β value (=0.320 for x=0.15) towards that expected for the 3D Ising model (β=0.325). This is due to the fact that the substitution of Ni ions into the Mn site changes structural parameters and dilutes the FM phase, which act as fluctuations and influence the FM-interaction strength of double-exchange Mn3+-Mn4+ pairs, and the phase-transition type. For the critical exponent γ (=0.976-0.990), the stability in its value demonstrates the PM behavior above TC of the samples. Particularly, around TC of La0.7Ca0.3Mn1-xNixO3 compounds, magnetic-field dependences of the maximum magnetic-entropy change can be described by a power law of |ΔSmax|∝Hn, where values n=0.55-0.77 are quite far from those (n=0.33-0.48) calculated from the theoretical relation n=1+(β-1)/(β+γ). This difference is related to the use of the mean-field theory for the samples exhibiting the magnetic inhomogeneity.

  2. Comparison of Structural Relaxation Behavior in As-Cast and Pre-Annealed Zr-Based Bulk Metallic Glasses Just below Glass Transition

    DOE PAGES

    Haruyama, Osami; Yoshikawa, Kazuyoshi; Yamazaki, Yoshikatsu; ...

    2015-04-25

    In this paper, the α-relaxation of pre-annealed Zr55Cu30Ni5Al10 bulk metallic glasses (BMGs) was compared with that of as-cast Zr-based BMGs including Zr55Cu30Ni5Al10. The α-relaxation was investigated by volume relaxation. The relaxation behavior was well described by a stretched exponential relaxation function, Φ (t) ≈ exp [ - (t/τ α )β α ], with the isothermal relaxation time, τα, and the Kohlrausch exponent, βα. The βα exhibited the strong temperature dependence for the pre-annealed BMG, while the weak temperature dependence was visualized for the as-cast BMG similar to the dynamic relaxation. The τα’s were modified by Moynihan and Narayanaswamy-Tool-Moynihan methods thatmore » reduce the difference in the thermal history of sample. Finally, as a result, the relaxation kinetics in the glass resembled that of a liquid deduced from the behavior of viscosity in the supercooled liquid.« less

  3. Comparison of Structural Relaxation Behavior in As-Cast and Pre-Annealed Zr-Based Bulk Metallic Glasses Just below Glass Transition

    SciTech Connect

    Haruyama, Osami; Yoshikawa, Kazuyoshi; Yamazaki, Yoshikatsu; Yokoyama, Yoshihiko; Egami, Takeshi

    2015-04-25

    In this paper, the α-relaxation of pre-annealed Zr55Cu30Ni5Al10 bulk metallic glasses (BMGs) was compared with that of as-cast Zr-based BMGs including Zr55Cu30Ni5Al10. The α-relaxation was investigated by volume relaxation. The relaxation behavior was well described by a stretched exponential relaxation function, Φ (t) ≈ exp [ - (t/τ α )β α ], with the isothermal relaxation time, τα, and the Kohlrausch exponent, βα. The βα exhibited the strong temperature dependence for the pre-annealed BMG, while the weak temperature dependence was visualized for the as-cast BMG similar to the dynamic relaxation. The τα’s were modified by Moynihan and Narayanaswamy-Tool-Moynihan methods that reduce the difference in the thermal history of sample. Finally, as a result, the relaxation kinetics in the glass resembled that of a liquid deduced from the behavior of viscosity in the supercooled liquid.

  4. Influence of the thermodynamic parameters on the temper embrittlement of SA508 Gr.4N Ni-Cr-Mo low alloy steel with variation of Ni, Cr and Mn contents

    NASA Astrophysics Data System (ADS)

    Park, Sang-Gyu; Lee, Ki-Hyoung; Min, Ki-Deuk; Kim, Min-Chul; Lee, Bong-Sang

    2012-07-01

    It is well known that SA508 Gr.4N low alloy steel offers improved fracture toughness and strength compared to commercial low alloy steels such as SA508 Gr.3 Mn-Mo-Ni low alloy steel. In this study, the effects of Cr, Mn, and Ni on temper embrittlement in SA508 Gr.4N low alloy steel were evaluated from the viewpoint of thermodynamic parameters such as P diffusivity and C activity. The changes of the ductile-brittle transition temperatures before and after aging were correlated with varying alloying element content, and the diffusivity of P and the activity of C were calculated and correlated with the transition behaviors. The addition of Ni, Cr, and Mn reduce the resistance to temper embrittlement, showing increased Transition-Temperature Shift (TTS) and an increased fraction of intergranular fracture. Although the diffusivity of P is changed by the addition of alloying elements, it does not considerably affect the temper embrittlement. The Mn and Cr content in the matrix significantly reduce the C activity, with showing an inversely proportional relationship to TTS. The change of susceptibility to temper embrittlement caused by Cr and Mn addition could be explained by the variation of C activity. Unlike Cr and Mn, Ni has little effect on the temper embrittlement and C activity.

  5. Nanoencapsulation of a water soluble drug in biocompatible polyesters. Effect of polyesters melting point and glass transition temperature on drug release behavior.

    PubMed

    Karavelidis, Vassilios; Giliopoulos, Dimitrios; Karavas, Evangelos; Bikiaris, Dimitrios

    2010-12-23

    Five polyesters based on 1,3-propanediol or ethylene glycol and an aliphatic dicarboxylic acid were used for the preparation of Ropinirole HCl-loaded nanoparticles. The advantage of the present study is that the used polyesters - as well as poly(lactic acid) (PLA) - have similar degree of crystallinity but different melting points, varying from 46.7 to 166.4°C. Based on polymer toxicity on HUVEC, the biocompatibility of these aliphatic polyesters was found comparable to that of PLA and thus the studied polyesters could be used as drug carriers. Drug encapsulation in polyesters was performed via emulsification/solvent evaporation method. Particle size of drug-loaded nanoparticles was between 140 and 190 nm, as measured by light scattering. Drug loading content for all the polyesters varies between 10 and 16% and their entrapment efficiency is relatively high (32-48%). WAXD patterns of nanoparticles show that Ropinirole HCl lies in amorphous state within polymer matrices. Drug release diagrams reveal that the higher percentage of Ropinirole HCl is released during the first 6h after its insertion in the dissolution medium. Fast release rates of the drug are attributed to high hydrophilicity of Ropinirole HCl. Melting point (T(m)) and glass transition temperature (T(g)) of the host polymer matrices seem to be important parameters, since higher drug release rates are observed in polyesters with low T(m) and T(g).

  6. Applicability of scaling behavior and power laws in the analysis of the magnetocaloric effect in second-order phase transition materials

    NASA Astrophysics Data System (ADS)

    Romero-Muñiz, Carlos; Tamura, Ryo; Tanaka, Shu; Franco, Victorino

    2016-10-01

    In recent years, universal scaling has gained renewed attention in the study of magnetocaloric materials. It has been applied to a wide variety of pure elements and compounds, ranging from rare-earth-based materials to transition metal alloys, from bulk crystalline samples to nanoparticles. It is therefore necessary to quantify the limits within which the scaling laws would remain applicable for magnetocaloric research. For this purpose, a threefold approach has been followed: (a) the magnetocaloric responses of a set of materials with Curie temperatures ranging from 46 to 336 K have been modeled with a mean-field Brillouin model, (b) experimental data for Gd has been analyzed, and (c) a 3D-Ising model—which is beyond the mean-field approximation—has been studied. In this way, we can demonstrate that the conclusions extracted in this work are model-independent. It is found that universal scaling remains applicable up to applied fields, which provide a magnetic energy to the system up to 8% of the thermal energy at the Curie temperature. In this range, the predicted deviations from scaling laws remain below the experimental error margin of carefully performed experiments. Therefore, for materials whose Curie temperature is close to room temperature, scaling laws at the Curie temperature would be applicable for the magnetic field range available at conventional magnetism laboratories (˜10 T), well above the fields which are usually available for magnetocaloric devices.

  7. Critical behavior and magnetic entropy change at magnetic phase transitions in Ni50Mn35In14Si1 ferromagnetic shape memory alloy

    NASA Astrophysics Data System (ADS)

    Das, R.; Alagarsamy, P.; Srinivasan, A.

    2014-12-01

    We have investigated critical behaviour and magnetocaloric effect in polycrystalline Ni50Mn35In14Si1 alloy near the second-order ferromagnetic phase transitions (SOPT) at austenite Curie temperature (TC,A) and at martensite Curie temperature (TC,M) by determining the critical exponents, β, γ and δ corresponding to the temperature dependence of spontaneous magnetization, initial susceptibility and isothermal magnetization, respectively. The field dependence of the maximum value of the magnetic entropy change (Δ SM) at the two TC's was estimated using the Maxwell relation as well as from the values of the critical exponents. Values of Δ SM obtained by these two methods at both the SOPT are in remarkable agreement with each other. The critical exponents have been determined by analysing isothermal magnetization data using two different methods, viz., the modified Arrott plot method and the Widom scaling relation. The scaling plots depicted on linear as well as logarithmic scales confirm the reliability of the values of critical exponents obtained. The values of the critical exponents of polycrystalline Ni50Mn35In14Si1 alloy at both the TC's are close to those predicted by mean-field theory confirming the presence of long-range magnetic ordering in the investigated alloy.

  8. Diffused phase transition and relaxor behavior in Pb(Fe2/3W1/3)O3 thin films

    NASA Astrophysics Data System (ADS)

    Kumar, Ashok; Murari, N. M.; Katiyar, R. S.

    2007-04-01

    The authors have synthesized Pb(Fe2/3W1/3)O3 thin films on Pt /Ti/SiO2/Si(100) substrates utilizing chemical solution deposition method. The dielectric relaxation was studied as a function of temperature (100-300K) and frequency (100Hz-1MHz). A broad range of dielectric maxima was found, which shifted towards higher temperature with increase in frequency. The relaxation indication coefficient (γ) and broadening parameter (Δ) were estimated from a linear fit of the modified Curie-Weiss law and were found to be 2.00 and 50K, respectively; indicating strong relaxor behavior. A remarkably good fit to Vogel-Fulcher relationship further supports the relaxor nature of the films. The slim hysteresis loop at low temperature is indicative of ferroelectricity due to the growth of nanopolar regions.

  9. Critical Behavior of Thermal Expansion and Magnetostriction in the Vicinity of the First order transition at the Curie Point of Gd5(SixGe1-x)4

    SciTech Connect

    Han, Mangui

    2004-01-01

    Thermal expansion (TE) and magnetostriction (MS) measurements have been conducted for Gd5(SixGe1-x)4 with a series of x values to study its critical behavior in the vicinity of transition temperatures. It was found that the Curie temperature of Gd5(SixGe1-x)4 for x 0 ~ 0.5 is dependent on magnetic field, direction of change of temperature (Tc on cooling was lower than Tc on heating), purity of Gd starting material, compositions, material preparation methods, and also can be triggered by the external magnetic field with a different dT/dB rate for different x values. For Gd5(Si1.95Ge2.05), Gd5(Si2Ge2), Gd5(Si2.09Ge1.91), it was also found that the transition is a first order magneto-structural transition, which means the magnetic transition and crystalline structure transition occur simultaneously, and completely reversible. Temperature hysteresis and phase coexistence have been found to confirm that it is a first order transformation. While for Gd5(Si0.15Ge3.85), it is partially reversible at some temperature range between the antiferromagnetic and the ferromagnetic state. For Gd5(Si2.3Ge1.7) and Gd5(Si3Ge1), it was a second order transformation between the paramagnetic and ferromagnetic state, because no ΔT have been found. Giant magnetostriction was only found on Gd5(Si1.95Ge2.05), Gd5(Si2Ge2), Gd5(Si2.09Ge1.91) in their vicinity of first order transformation. MFM images have also been taken on polycrystal sample Gd5(Si2.09Ge1.91) to investigate the transformation process. The results also indicates that the Curie temperature was lower and the thermally

  10. Effect of low temperature vacuum annealing on microstructural, optical, electronic, electrical, nanomechanical properties and phase transition behavior of sputtered vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Porwal, Deeksha; Esther, A. Carmel Mary; Dey, Arjun; Gupta, A. K.; Raghavendra Kumar, D.; Bera, Parthasarathi; Barshilia, Harish C.; Bhattacharya, Manjima; Mukhopadhyay, Anoop Kumar; Khan, Kallol; Sharma, Anand Kumar

    2016-10-01

    Vanadium oxide thin films were deposited on quartz substrate by pulsed RF magnetron sputtering technique at 400-600 W and subsequently annealed at 100 °C in vacuum (1.5 × 10-5 mbar). Phase analysis, surface morphology and topology of the films e.g., both as-deposited and annealed were investigated by x-ray diffraction, field emission scanning electron microscopy and atomic force microscopy techniques. X-ray photoelectron spectroscopy (XPS) was employed to understand the elemental oxidation of the films. Transmittance of the films was evaluated by UV-vis-NIR spectrophotometer in the wavelength range of 200-1600 nm. Sheet resistance of the films was measured by two-probe method both for as-deposited and annealed conditions. XPS study showed the existence of V5+ and V4+ species. Metal to insulator transition temperature of the as-deposited film decreased from 339 °C to 326 °C after annealing as evaluated by differential scanning calorimetric technique. A significant change in transmittance was observed in particular at near infrared region due to alteration of surface roughness and grain size of the film after annealing. Sheet resistance values of the annealed films decreased as compared to the as-deposited films due to the lower in oxidation state of vanadium which led to increase in carrier density. Combined nanoindentation and finite element modeling were applied to evaluate nanohardness (H), Young’s modulus (E), von Mises stress and strain distribution. Both H and E were improved after annealing due to increase in crystallinity of the film.

  11. A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca)

    SciTech Connect

    Tan, Xiaoyan; Fabbris, Gilberto; Haskel, Daniel; Yaroslavtsev, Alexander A.; Cao, H.; Thompson, Corey M.; Kovnir, Kirill; Menushenkov, Alexey P.; Chernikov, Roman V.; Garlea, V. Ovidiu; Shatruk, Michael

    2016-03-02

    We demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo(2)As(2) (A = Eu and Ca) has a general consequence of causing these antiferromagnetic materials to become ferromagnets. In all cases, the mixed valence triggered at the electropositive A site results in the increase of the Co 3d density of states at the Fermi level. Remarkably, the dramatic alteration of magnetic behavior results from the very minor (<0.15 eleetron) change in the population of the 3d orbitals. The mixed valence state of En observed in the high-pressure (HP) form of EuCo2As2 exhibits a remarkable stability, achieving the average oxidation state of +2.25 at 12.6 GPa. In the case of CaCo2As2, substituting even 10% of Eu or La into the Ca site causes ferromagnetic ordering of Co moments. Similar to HP-EuCo2As2, the itinerant 3d ferromagnetism emerges from electronic doping into the Co layer because of chemical compression of Eu sites in Ca0.9Eu0.1Co1.91As2 or direct electron doping in Ca0.85La0.15Co1.89As2. The results reported herein demonstrate the general possibility of amplifying minor localized electronic effects to achieve major changes in material's properties via involvement of strongly correlated electrons.

  12. A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca).

    PubMed

    Tan, Xiaoyan; Fabbris, Gilberto; Haskel, Daniel; Yaroslavtsev, Alexander A; Cao, Huibo; Thompson, Corey M; Kovnir, Kirill; Menushenkov, Alexey P; Chernikov, Roman V; Garlea, V Ovidiu; Shatruk, Michael

    2016-03-02

    We demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo2As2 (A = Eu and Ca) has a general consequence of causing these antiferromagnetic materials to become ferromagnets. In all cases, the mixed valence triggered at the electropositive A site results in the increase of the Co 3d density of states at the Fermi level. Remarkably, the dramatic alteration of magnetic behavior results from the very minor (<0.15 electron) change in the population of the 3d orbitals. The mixed valence state of Eu observed in the high-pressure (HP) form of EuCo2As2 exhibits a remarkable stability, achieving the average oxidation state of +2.25 at 12.6 GPa. In the case of CaCo2As2, substituting even 10% of Eu or La into the Ca site causes ferromagnetic ordering of Co moments. Similar to HP-EuCo2As2, the itinerant 3d ferromagnetism emerges from electronic doping into the Co layer because of chemical compression of Eu sites in Ca0.9Eu0.1Co1.91As2 or direct electron doping in Ca0.85La0.15Co1.89As2. The results reported herein demonstrate the general possibility of amplifying minor localized electronic effects to achieve major changes in material's properties via involvement of strongly correlated electrons.

  13. A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca)

    DOE PAGES

    Tan, Xiaoyan; Fabbris, Gilberto; Haskel, Daniel; ...

    2016-02-03

    In this paper, we demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo2As2 (A = Eu and Ca) has a general consequence of causing these antiferromagnetic materials to become ferromagnets. In all cases, the mixed valence triggered at the electropositive A site results in the increase of the Co 3d density of states at the Fermi level. Remarkably, the dramatic alteration of magnetic behavior results from the very minor (<0.15 electron) change in the population of the 3d orbitals. The mixed valence state of Eu observed in the high-pressure (HP) form of EuCo2As2 exhibits amore » remarkable stability, achieving the average oxidation state of +2.25 at 12.6 GPa. In the case of CaCo2As2, substituting even 10% of Eu or La into the Ca site causes ferromagnetic ordering of Co moments. Similar to HP-EuCo2As2, the itinerant 3d ferromagnetism emerges from electronic doping into the Co layer because of chemical compression of Eu sites in Ca0.9Eu0.1Co1.91As2 or direct electron doping in Ca0.85La0.15Co1.89As2. Finally, the results reported herein demonstrate the general possibility of amplifying minor localized electronic effects to achieve major changes in material’s properties via involvement of strongly correlated electrons.« less

  14. Assessing transitional phenomena with the transitional object memory probe.

    PubMed

    Fowler, C; Hilsenroth, M J; Handler, L

    1998-01-01

    Winnicott's concept of transitional relatedness has captured the interest of psychoanalysts because it provides an understanding of the dialectical process occurring between inner and outer reality, and by extension, between analyst and analysand. Clinical observations related to transitional phenomena have led the authors to develop a projective early memory probe that assesses transitional phenomena. The transitional object early memory probe was tested both for its empirical validity and for its clinical utility in psychodynamic psychotherapy. Construct validity was assessed by comparing memory scores to the Rorschach Transitional Object Scale, as well as to therapist ratings of patient behaviors. Results demonstrated moderate correlations between early memory scores and Rorschach scale scores. Equally important was the finding that early memory scores were significantly correlated with therapist ratings of key behavioral patterns in therapy. A case vignette highlights the clinical application of the transitional object probe in assessing the capacity for transitional relatedness. In this case, the data gleaned from the patient's memories provided the therapist with a sharper focus on their role in the patient's growing capacity for more vital and creative contact with reality.

  15. Behavior of dissolved manganese and other trace elements across the oxic/euxinic transition of a meromictic lake, Fayetteville Green Lake, New York, USA

    NASA Astrophysics Data System (ADS)

    Havig, J. R.; McCormick, M.; Bachan, A.; Kump, L. R.

    2014-12-01

    High-depth-resolution sampling of stratified water bodies is often problematic, due to scale and/or accessibility (e.g. the Black Sea or remote lakes). In contrast, Fayetteville Green Lake (FGL), N.Y. is an easily accessible, 53 m deep meromictic system with an oxic upper mixolimnion (dissolved oxygen ~ 350 µM) and a euxinic lower monimolimnion (total sulfide ~1 mM). The accessibility and stability of FGL provides a unique opportunity for high-resolution sampling of a permanently stratified water column, allowing better characterization of the changes in concentration of biologically important trace elements within the framework of major element geochemistry. High-resolution (0.2 - 0.5m) sampling of FGL at various times of year reveals concentration shifts between the oxic and euxinic zone. For Mn, Fe, and Co, dissolved (< 0.2 µm) concentrations are lower in the oxic zone (~ 10 nM, 20 nM, and 1.5 nM, respectively), and higher in the euxinic zone (~ 6000 nM, 200 nM, and 8 nM). Ni and V exhibit little to no difference between the oxic and euxinic zones (~ 90 and 20 nM, respectively), and Zn shows a small decrease with depth (from ~1600 to 1300 nM). Of the elements analyzed, Mo is the only one that exhibits a large decrease from the oxic to euxinic zones (from ~ 180 to 10 nM). The 4-m chemocline between the oxic and euxinic zones over which dramatic changes in trace element concentration occur in FGL is where peak concentrations for several elements are found, including Fe (3.2 μM), Zn (3.1 μM), Co (86 nM), and V (72 nM). The largest peak is observed for Mn, with a peak concentration of 61 μM, and a transition zone that extends well into the overlying mixolimnion and mirrors the decline in oxygen concentration. Manganese concentration peaks in chemoclines have been observed in a variety of stratified systems that exhibit a gap between the decrease in dissolved oxygen and the increase in sulfide concentration, presumably the result of limited vertical mixing and

  16. Presidential Transitions

    DTIC Science & Technology

    2006-06-09

    Podesta for the Heads of Executive Departments and Agencies, “Presidential Transition Guidance,” Nov. 13, 2000. 89 U.S. General Services Administration...2000, presidential election, White House Chief of Staff John Podesta issued a November 13, 2000, memorandum to executive branch agencies stating that

  17. Tessellations & Transitions.

    ERIC Educational Resources Information Center

    Cassidy, Joan

    1998-01-01

    Describes two sixth-grade lessons on the work of M. C. Escher: (1) the first lesson instructs students on tessellations, or tiles that interlock in a repeated pattern; (2) the second lesson explores Escher's drawings of transitions from two- to three-dimensional space. (DSK)

  18. Isothermal fatigue of an aluminide-coated single-crystal superalloy: Part I

    NASA Astrophysics Data System (ADS)

    Totemeier, T. C.; King, J. E.

    1996-02-01

    The isothermal fatigue behavior of a high-activity aluminide-coated single-crystal superalloy was studied in air at test temperatures of 600 °, 800 °, and 1000 °. Tests were performed using cylindrical specimens under strain control at ≈0.25 Hz; total strain ranges from 0.5 to 1.6 pct were investigated. At 600 °, crack initiation occurred at brittle coating cracks, which led to a significant reduction in fatigue life compared to the uncoated alloy. Fatigue cracks grew from the brittle coating cracks initially in a stage II manner with a subsequent transition to crystallographic stage I fatigue. At 800 ° and 1000 °, the coating failed quickly by a fatigue process due to the drastic reduction in strength above 750 °, the ductile-brittle transition temperature. These cracks were arrested or slowed by oxidation at the coating-substrate interface and only led to a detriment in life relative to the uncoated material for total strain ranges of 1.2 pct and above 800 °. The presence of the coating was beneficial at 800 ° for total strain ranges less than 1.2 pct. No effect of the coating was observed at 1000 °. Crack growth in the substrate at 800 ° was similar to 600 °; at 1000 °, greater plasticity and oxidation were observed and cracks grew exclusively in a stage II manner.

  19. Isothermal fatigue of an aluminide-coated single-crystal superalloy. Part 1

    SciTech Connect

    Totemeier, T.C.; King, J.E.

    1996-02-01

    The isothermal fatigue behavior of a high-activity aluminide-coated single-crystal superalloy was studied in air at test temperatures of 600 C, 800 C, and 1,000 C. Tests were performed using cylindrical specimens under strain control at {approximately}0.25 Hz; total strain ranges from 0.5 to 1.6% were investigated. At 600 C, crack initiation occurred at brittle coating cracks, which led to a significant reduction in fatigue life compared to the uncoated alloy. Fatigue cracks grew from the brittle coating cracks initially in a stage 2 manner with a subsequent transition to crystallographic stage 1 fatigue. At 800 C and 1,000 C, the coating failed quickly by a fatigue process due to the drastic reduction in strength above 750 C, the ductile-brittle transition temperature. These cracks were arrested or slowed by oxidation at the coating-substrate interface and only led to a detriment in life relative to the uncoated material for total strain ranges of 1.2% and above 800 C. The presence of the coating was beneficial at 800 C for total strain ranges less than 1.2%. No effect of the coating was observed at 1,000 C. Crack growth in the substrate at 800 C was similar to 600 C; at 1,000 C, greater plasticity and oxidation were observed and cracks grew exclusively in a stage 2 manner.

  20. Miniaturized Charpy test for reactor pressure vessel embrittlement characterization

    SciTech Connect

    Manahan, M.P. Sr.

    1999-10-01

    Modifications were made to a conventional Charpy machine to accommodate the miniaturized Charpy V-Notch (MCVN) specimens which were fabricated from an archived reactor pressure vessel (RPV) steel. Over 100 dynamic MCVN tests were performed and compared to the results from conventional Charpy V-Notch (CVN) tests to demonstrate the efficacy of the miniature specimen test. The optimized sidegrooved MCVN specimens exhibit transitional fracture behavior over essentially the same temperature range as the CVN specimens which indicates that the stress fields in the MCVN specimens reasonably simulate those of the CVN specimens and this fact has been observed in finite element calculations. This result demonstrates a significant breakthrough since it is now possible to measure the ductile-brittle transition temperature (DBTT) using miniature specimens with only small correction factors, and for some materials as in the present study, without the need for any correction factor at all. This development simplifies data interpretation and will facilitate future regulatory acceptance. The non-sidegrooved specimens yield energy-temperature data which is significantly shifted downward in temperature (non-conservative) as a result of the loss of constraint which accompanies size reduction.

  1. Detection of irradiation embrittlement of low-alloy steel for nuclear reactor pressure vessels using a probe type eddy current sensor

    SciTech Connect

    Maeda, Noriyoshi; Yamaguchi, Atsunori; Sugibayashi, Takuya; Kohno, Katsumi

    1999-10-01

    This report describes the results of studies made for the purpose of detecting the irradiation embrittlement of low-alloy steel used for nuclear reactor pressure vessels. For the method of using eddy current to detect material degradation, the device and the sensor employed are light in weight and compact in size, allowing testing without contact. In this study the frequency of input current to the excitation coil is changed in steps of 1 kHz. The output signal is processed by phase detection method, and displayed on a complex plane. It depicts a trajectory as the frequency is changed. To extract features of the trajectories, averaged radius and averaged phase angle are defined and plotted as function of neutron fluence or ductile-brittle transition temperature. Experiment shows that the averaged phase angle and transition temperature decrease as the neutron fluence is increased. Behavior of the averaged phase angle is interpreted employing magnetic permeability and electric conductivity of the test specimens. It becomes clear that electric conductivity decreases as the neutron fluence is increased.

  2. Impact resistance and fractography in ultra high molecular weight polyethylenes.

    PubMed

    Puértolas, J A; Pascual, F J; Martínez-Morlanes, M J

    2014-02-01

    Highly crosslinked ultra high molecular weight polyethylenes (UHMWPE) stabilized by a remelting process or by the addition of an antioxidant are highly wear resistant and chemically stable. However, these polyethylenes currently used in total joint replacements suffer a loss of mechanical properties, especially in terms of fracture toughness. In this study we analyze the impact behavior of different polyethylenes using an instrumented double notch Izod test. The materials studied are three resins: GUR1050, GUR1020 with 0.1wt% of vitamin E, and MG003 with 0.1wt% of vitamin E. These resins were gamma irradiated at 90kGy, and pre and post-irradiation remelting processes were applied to GUR1050 for two different time periods. Microstructural data were determined by means of differential scanning calorimetry and transmission electron microscopy. Fractography carried out on the impact fracture surfaces and images obtained by scanning electron microscopy after etching indicated the existence of a fringe structure formed by consecutive ductile-brittle and brittle-ductile transitions, which is related to the appearance of discontinuities in the load-deflection curves. A correlation has been made of the macroscopic impact strength results and the molecular chain and microstructural characteristics of these aforementioned materials, with a view to designing future resins with improved impact resistance. The use of UHMWPE resins with low molecular weight or the application of a remelting treatment could contribute to obtain a better impact strength behavior.

  3. Some Scenarios for Transition on Turbomachinery Blading

    NASA Technical Reports Server (NTRS)

    Gostelow, J. P.

    2007-01-01

    Measurements on transition under different levels of adverse pressure gradient and free-stream turbulence level are described. This extensive series of investigations, which was predicated on intermittency measurement techniques, has resulted in correlations for transition length and turbulent spot formation rate. These correlations rae intended to be used in conjunction with boundary layer prediction methods and examples are given of such predictions. More effective predictions of the transition region, especially under conditions of variable pressure gradient, are dependent on a more comprehensive understanding of transition and spot behavior. It is expected that this will result in improved transition modeling.

  4. Eliminating Transitions

    ERIC Educational Resources Information Center

    Gallick, Barb; Lee, Lisa

    2010-01-01

    Adults often find themselves transitioning from one activity to another in a short time span. Most of the time, they do not feel they have a lot of control over their schedules, but wish that they could carve out extended time to relax and focus on one project. Picture a group of children in the block area who have spent 15 or 20 minutes building…

  5. Phase transitions in disordered systems

    NASA Astrophysics Data System (ADS)

    Hrahsheh, Fawaz Y.

    Disorder can have a wide variety of consequences for the physics of phase transitions. Some transitions remain unchanged in the presence of disorder while others are completely destroyed. In this thesis we study the effects of disorder on several classical and quantum phase transitions in condensed matter systems. After a brief introduction, we study the ferromagnetic phase transition in a randomly layered Heisenberg magnet using large-scale Monte-Carlo simulations. Our results provide numerical evidence for the exotic infinite-randomness scenario. We study classical and quantum smeared phase transitions in substitutional alloys A1-xBx. Our results show that the disorder completely destroys the phase transition with a pronounced tail of the ordered phase developing for all compositions x < 1. In addition, we find that short-ranged disorder correlations can have a dramatic effect on the transition. Moreover, we show an experimental realization of the composition-tuned ferromagnetic-to-paramagnetic quantum phase transition in Sr1-xCa xRuO3. We investigate the effects of disorder on first-order quantum phase transitions on the example of the N-color quantum Ashkin-Teller model. By means of a strong disorder renormalization group, we demonstrate that disorder rounds the first-order transition to a continuous one for both weak and strong coupling between the colors. Finally, we investigate the superfluid-insulator quantum phase transition of one-dimensional bosons with off-diagonal disorder by means of large-scale Monte-Carlo simulations. Beyond a critical disorder strength, we find nonuniversal, disorder dependent critical behavior.

  6. Critical behavior near the ferromagnetic-paramagnetic phase transition temperature of Pr0.67Ba0.33Mn1-xFexO3 (x=0 and 0.05) manganite

    NASA Astrophysics Data System (ADS)

    Baazaoui, Mohamed; Hcini, Sobhi; Boudard, Michel; Zemni, Sadok; Oumezzine, Mohamed

    2016-03-01

    Critical behavior of Pr0.67Ba0.33Mn1-xFexO3 (x=0 and 0.05) perovskite-manganites is studied around their Curie temperatures (TC). Results reveal that the two samples undergo a second-order phase transition. The estimated critical exponents obtained for x=0 sample are close to the tricritical mean-field model (β=0.246±0.002, γ=1.030±0.018 and δ=5.069 at TC=201 K). Whereas for x=0.05 sample, these exponents are close to the mean-field model (β=0.501±0.026, γ=1.007±0.002 and δ=2.920 at TC=128 K). These critical exponents fulfill the Widom scaling relation δ=1+γ/β, implying the reliability of our values. Based on the critical exponents, the magnetization-field-temperature (M-H-T) data around TC collapses into two curves obeying the single scaling equation M (H , ε) =| ε | β f± (H/|ε|β+γ) with ε=(T-TC)/TC is the reduced temperature.

  7. Phase transition in a super superspin glass

    NASA Astrophysics Data System (ADS)

    Mathieu, R.; De Toro, J. A.; Salazar, D.; Lee, S. S.; Cheong, J. L.; Nordblad, P.

    2013-06-01

    We here confirm the occurrence of spin glass phase transition and extract estimates of associated critical exponents of a highly monodisperse and densely compacted system of bare maghemite nanoparticles. This system has earlier been found to behave like an archetypal spin glass, with, e.g., a sharp transition from paramagnetic to non-equilibrium behavior, suggesting that this system undergoes a spin glass phase transition at a relatively high temperature, Tg ∼ 140 K.

  8. Transitional behavior of quantum Gaussian memory channels

    NASA Astrophysics Data System (ADS)

    Lupo, C.; Mancini, S.

    2010-05-01

    We address the question of optimality of entangled input states in quantum Gaussian memory channels. For a class of such channels, which can be traced back to the memoryless setting, we state a criterion which relates the optimality of entangled inputs to the symmetry properties of the channels’ action. Several examples of channel models belonging to this class are discussed.

  9. Microstructure property analysis of HFIR-irradiated reduced-activation ferritic/martensitic steels

    NASA Astrophysics Data System (ADS)

    Tanigawa, H.; Hashimoto, N.; Sakasegawa, H.; Klueh, R. L.; Sokolov, M. A.; Shiba, K.; Jitsukawa, S.; Kohyama, A.

    2004-08-01

    The effects of irradiation on the Charpy impact properties of reduced-activation ferritic/martensitic steels were investigated on a microstructural basis. It was previously reported that the ductile-brittle transition temperature (DBTT) of F82H-IEA and its heat treatment variant increased by about 130 K after irradiation at 573 K up to 5 dpa. Moreover, the shifts in ORNL9Cr-2WVTa and JLF-1 steels were much smaller, and the differences could not be interpreted as an effect of irradiation hardening. The precipitation behavior of the irradiated steels was examined by weight analysis and X-ray diffraction analysis on extraction residues, and SEM/EDS analysis was performed on extraction replica samples and fracture surfaces. These analyses suggested that the difference in the extent of DBTT shift could be explained by (1) smaller irradiation hardening at low test temperatures caused by irradiation-induced lath structure recovery (in JLF-1), and (2) the fracture stress increase caused by the irradiation-induced over-solution of Ta (in ORNL9Cr-2WVTa).

  10. Embrittlement of CrMo steels after low fluence irradiation in HFIR

    NASA Astrophysics Data System (ADS)

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

    1995-02-01

    Subsize Charpy impact specimens of 9Cr1MoVNb (modified 9Cr1Mo) and 12Cr1MoVW (Sandvik HT9) steels and 12Cr1MoVW with 2% Ni (12Cr1MoVW2Ni) were irradiated in the High Flux Isotope Reactor (HFIR) at 300 and 400°C to damage levels up to 2.5 dpa. The objective was to study the effect of the simultaneous formation of displacement damage and transmutation helium on impact toughness. Displacement damage was produced by fast neutrons, and helium was formed by the reaction of 58Ni with thermal neutrons in the mixed-neutron spectrum of HFIR. Despite the low fluence relative to previous irradiations of these steels, significant increases in the ductile-brittle transition temperature (DBTT) occurred. The 12Cr1MoVW2Ni steel irradiated at 400°C had the largest increase in DBTT and displayed indications of intergranular fracture. A mechanism is proposed to explain how helium can affect the fracture behavior of this latter steel in the present tests, and how it affected all three steels in previous experiments, where the steels were irradiated to higher fluences.

  11. Pressure induced stiffening, thermal softening of bulk modulus and brittle nature of mercury chalcogenides

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Shriya, Swarna; Sapkale, Raju; Varshney, Meenu; Ameri, M.

    2015-07-01

    The pressure and temperature dependent elastic properties of mercury chalcogenides (HgX; X = S, Se and Te) with pressure induced structural transition from ZnS-type (B3) to NaCl-type (B1) structure have been analyzed within the framework of a model interionic interaction potential with long-range Coulomb and charge transfer interactions, short-range overlap repulsion and van der Waals (vdW) interactions as well as zero point energy effects. Emphasis is on the evaluation of the Bulk modulus with pressure and temperature dependency to yield the Poisson's ratio ν, the Pugh ratio ϕ, anisotropy parameter, Shear and Young's modulus, Lamé's constant, Klein man parameter, elastic wave velocity and Debye temperature. The Poisson's ratio behavior infers that HgX are brittle in nature. To our knowledge this is the first quantitative theoretical prediction of the pressure dependence of elastic and thermodynamical properties explicitly the ductile (brittle) nature of HgX and still awaits experimental confirmations.

  12. Tensile and charpy impact properties of irradiated reduced-activation ferritic steels

    SciTech Connect

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

    1996-10-01

    Tensile tests were conducted on eight reduced-activation Cr-W steels after irradiation to 15-17 and 26-29 dpa, and Charpy impact tests were conducted on the steels irradiated to 26-29 dpa. Irradiation was in the Fast Flux Test Facility at 365{degrees}C on steels containing 2.25-12% Cr, varying amounts of W, V, and Ta, and 0.1%C. Previously, tensile specimens were irradiated to 6-8 dpa and Charpy specimens to 6-8, 15-17, and 20-24 dpa. Tensile and Charpy specimens were also thermally aged to 20000 h at 365{degrees}C. Thermal aging had little effect on the tensile behavior or the ductile-brittle transition temperature (DBTT), but several steels showed a slight increase in the upper-shelf energy (USE). After {approx}7 dpa, the strength of the steels increased and then remained relatively unchanged through 26-29 dpa (i.e., the strength saturated with fluence). Post-irradiation Charpy impact tests after 26-29 dpa showed that the loss of impact toughness, as measured by an increase in DBTT and a decrease in the USE, remained relatively unchanged from the values after 20-24 dpa, which had been relatively unchanged from the earlier irradiations. As before, the two 9Cr steels were the most irradiation resistant.

  13. Embrittlement of Cr-Mo steels after low fluence irradiation in HFIR

    SciTech Connect

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

    1995-04-01

    The goal of this work is the determination of the possible effect of the simultaneous formation of helium and displacement damage during irradiation on the Charpy impact behavior. Subsize Charpy impact specimens of 9Cr-1MoVNb (modified 9Cr-1Mo) and 12Cr-1MoVW (Sandvik HT9) steels and 12Cr-1MoVW with 2%Ni (12Cr-1MOVW-2Ni) were irradiated in the High Flux Isotope Reactor (HFIR) at 300 and 400{degree}C to damage levels up to 2.5 dpa. The objective was to study the effect of the simultaneous formation of displacement damage and transmutation helium on impact toghness. Despite the low fluence relative to previous irradiations of these steels, significant increases in the ductile-brittle transition temperature (DBTT) occurred. The 12Cr-1MoVW-2Ni steel irradiated at 400{degree}C had the largest increase in DBTT and displayed indications of intergranular fracture. A mechanism is proposed to explain how helium can affect the fracture behaviour of this latter steel in the present tests, and how it affected all three steels in previous experiments, where the steels were irradiated to higher fluences.

  14. Irradiation dose and temperature dependence of fracture toughness in high dose HT9 steel from the fuel duct of FFTF

    SciTech Connect

    Byun, Thak Sang; Toloczko, M; Maloy, S

    2013-01-01

    Static fracture toughness tests have been performed for high dose HT9 steel using miniature disk compact tension (DCT) specimens to expand the knowledge base for fast reactor core materials. The HT9 steel DCT specimens were from the ACO-3 duct of the Fast Flux Test Facility (FFTF), which achieved high doses in the range of 3 148 dpa at 378 504oC. The static fracture resistance (J-R) tests have been performed in a servohydraulic testing machine in vacuum at selected temperatures including room temperature, 200 C, and each irradiation temperature. Brittle fracture with a low toughness less than 50 MPa m occurred in room temperature tests when irradiation temperature was below 400 C, while ductile fracture with stable crack growth was observed in all tests at higher irradiation temperatures. No fracture toughness less than 100 MPa m was measured when the irradiation temperature was above 430 C. It was shown that the influence of irradiation temperature was dominant in fracture toughness while the irradiation dose has only limited influence over the dose range 3 148 dpa. A post upper-shelf behavior was observed for the non-irradiated and high temperature (>430 C) irradiation cases, which indicates that the ductile-brittle transition temperatures (DBTTs) in those conditions are lower than room temperature. A comparison with the collection of existing data confirmed the dominance of irradiation temperature in the fracture toughness of HT9 steels.

  15. Mode Transition of Trichel pulses

    NASA Astrophysics Data System (ADS)

    Kexin, Zhang; Yongjun, Piao; Miao, Tang; Jingfeng, Tang; Liqiu, Wei; Chaohai, Zhang

    2015-11-01

    The trichel pulse is a typical kind of negative corona current observed in electronegative gases. In this work, stochastic behavior of the trichel pulse has been investigated. The experiment is performed in a negative corona reactor consisting of a stainless steel pin and a stainless steel powered by a dc high voltage source. The characteristic parameters distributions of corona current pulses, including the amplitude, rise time, half-wave time, and repetition frequency, are analyzed statistically. The results show there is a mode transition during the period of voltage increasing. This transition process happens in a certain voltage region, and change of pulse amplitude is the main difference between the two modes.

  16. A liquid-liquid transition can exist in monatomic transition metals with a positive melting slope

    PubMed Central

    Lee, Byeongchan; Lee, Geun Woo

    2016-01-01

    Liquid-liquid transitions under high pressure are found in many elemental materials, but the transitions are known to be associated with either sp-valent materials or f-valent rare-earth elements, in which the maximum or a negative slope in the melting line is readily suggestive of the transition. Here we find a liquid-liquid transition with a positive melting slope in transition metal Ti from structural, electronic, and thermodynamic studies using ab-initio molecular dynamics calculations, showing diffusion anomaly, but no density anomaly. The origin of the transition in liquid Ti is a pressure-induced increase of local structures containing very short bonds with directionality in electronic configurations. This behavior appears to be characteristic of the early transition metals. In contrast, the late transition metal liquid Ni does not show the L-L transition with pressure. This result suggests that the possibility of the L-L transition decreases from early to late transition metals as electronic structures of late transition metals barely have a Jahn-Teller effect and bond directionality. Our results generalize that a phase transition in disordered materials is found with any valence band regardless of the sign of the melting slope, but related to the symmetry of electronic structures of constituent elements. PMID:27762334

  17. A liquid-liquid transition can exist in monatomic transition metals with a positive melting slope

    NASA Astrophysics Data System (ADS)

    Lee, Byeongchan; Lee, Geun Woo

    2016-10-01

    Liquid-liquid transitions under high pressure are found in many elemental materials, but the transitions are known to be associated with either sp-valent materials or f-valent rare-earth elements, in which the maximum or a negative slope in the melting line is readily suggestive of the transition. Here we find a liquid-liquid transition with a positive melting slope in transition metal Ti from structural, electronic, and thermodynamic studies using ab-initio molecular dynamics calculations, showing diffusion anomaly, but no density anomaly. The origin of the transition in liquid Ti is a pressure-induced increase of local structures containing very short bonds with directionality in electronic configurations. This behavior appears to be characteristic of the early transition metals. In contrast, the late transition metal liquid Ni does not show the L-L transition with pressure. This result suggests that the possibility of the L-L transition decreases from early to late transition metals as electronic structures of late transition metals barely have a Jahn-Teller effect and bond directionality. Our results generalize that a phase transition in disordered materials is found with any valence band regardless of the sign of the melting slope, but related to the symmetry of electronic structures of constituent elements.

  18. Adolescents Transitioning to High School.

    PubMed

    Williams, Susan G; Langhinrichsen-Rohling, Jennifer; Wornell, Cory; Finnegan, Heather

    2017-01-01

    Adolescents transitioning to high school may be at greater risk of depression and suicide if they are victims of bullying behavior. This study explored sex differences in bullying victimization (physical, verbal/social, and cyberbullying) and the impact on depressive symptoms and suicidal behaviors in ninth-grade students ( N = 233). Females reported significantly more verbal/social and cyberbullying than male students. There were no significant sex differences in physical bullying; male students who reported physical bullying victimization were more likely to experience depressive symptoms. Verbal/social bullying predicted depressive symptoms in males and females. Females who reported being victims of cyberbullying were more likely to report depressive symptoms, suicide ideation, and suicide attempts. Eighteen students reported suicide attempts, and each also experienced verbal/social bullying. School nurses are positioned to reach out to transitioning students, screen for mental health issues, provide a safe place to talk about bullying experiences, and promote positive mental health.

  19. Dynamic fracture toughness of irradiated A533 Grade B Class 1 pressure vessel steel

    SciTech Connect

    Murty, K.L.; Bamford, W.H.; Shogun, R.P.

    1984-03-01

    The effect of neutron radiation on the fracture characteristics of an A533 Grade B Class 1 pressure vessel steel was investigated using standard and instrumented precracked Charpy impact tests. Use of the instrumented impact test with precracked specimens has allowed fracture toughness values to be determined from the Charpy test. Neutron exposure resulted in minute decreases in the upper-shelf Charpy energy and fracture toughness, and an increase in the ductile brittle transition temperature (DBTT). The Charpy transition temperature shifted about 29 K while the fracture toughness shift was about 20 K. The temperature variation of the dynamic yield strength exhibited dips at DBTT for both unirradiated archive and irradiated materials.

  20. Nucleon Resonance Transition Form factors

    SciTech Connect

    Burkert, Volker D.; Mokeev, Viktor I.; Aznauryan, Inna G.

    2016-08-01

    We discuss recent results from CLAS on electromagnetic resonance transition amplitudes and their dependence on the distance scale (Q2). From the comparison of these results with most advanced theoretical calculations within QCD-based approaches there is clear evidence that meson-baryon contributions are present and important at large distances, i.e. small Q2, and that quark core contributions dominate the short distance behavior.

  1. Topological Lifshitz transitions

    NASA Astrophysics Data System (ADS)

    Volovik, G. E.

    2017-01-01

    Different types of Lifshitz transitions are governed by topology in momentum space. They involve the topological transitions with the change of topology of Fermi surfaces, Weyl and Dirac points, nodal lines, and also the transitions between the fully gapped states.

  2. Transitions: A Personal Perspective.

    ERIC Educational Resources Information Center

    Wood, Ann Stace

    1995-01-01

    Distinguishes between unchosen transitions (children maturing and leaving, parents aging, companies downsizing) and chosen ones (moving, divorce, marriage, career changes). Describes the steps one goes through: uneasiness, renewed energy, complaining, exploration, partial transition, and the completed transition. (JOW)

  3. Electromechanical transition in quantum dots

    NASA Astrophysics Data System (ADS)

    Micchi, G.; Avriller, R.; Pistolesi, F.

    2016-09-01

    The strong coupling between electronic transport in a single-level quantum dot and a capacitively coupled nanomechanical oscillator may lead to a transition towards a mechanically bistable and blocked-current state. Its observation is at reach in carbon-nanotube state-of-art experiments. In a recent publication [Phys. Rev. Lett. 115, 206802 (2015), 10.1103/PhysRevLett.115.206802] we have shown that this transition is characterized by pronounced signatures on the oscillator mechanical properties: the susceptibility, the displacement fluctuation spectrum, and the ring-down time. These properties are extracted from transport measurements, however the relation between the mechanical quantities and the electronic signal is not always straightforward. Moreover the dependence of the same quantities on temperature, bias or gate voltage, and external dissipation has not been studied. The purpose of this paper is to fill this gap and provide a detailed description of the transition. Specifically we find (i) the relation between the current-noise and the displacement spectrum; (ii) the peculiar behavior of the gate-voltage dependence of these spectra at the transition; (iii) the robustness of the transition towards the effect of external fluctuations and dissipation.

  4. Transition Path Theory

    NASA Astrophysics Data System (ADS)

    vanden-Eijnden, E.

    The dynamical behavior of many systems arising in physics, chemistry, biology, etc. is dominated by rare but important transition events between long lived states. For over 70 years, transition state theory (TST) has provided the main theoretical framework for the description of these events [17,33,34]. Yet, while TST and evolutions thereof based on the reactive flux formalism [1, 5] (see also [30,31]) give an accurate estimate of the transition rate of a reaction, at least in principle, the theory tells very little in terms of the mechanism of this reaction. Recent advances, such as transition path sampling (TPS) of Bolhuis, Chandler, Dellago, and Geissler [3, 7] or the action method of Elber [15, 16], may seem to go beyond TST in that respect: these techniques allow indeed to sample the ensemble of reactive trajectories, i.e. the trajectories by which the reaction occurs. And yet, the reactive trajectories may again be rather uninformative about the mechanism of the reaction. This may sound paradoxical at first: what more than actual reactive trajectories could one need to understand a reaction? The problem, however, is that the reactive trajectories by themselves give only a very indirect information about the statistical properties of these trajectories. This is similar to why statistical mechanics is not simply a footnote in books about classical mechanics. What is the probability density that a trajectory be at a given location in state-space conditional on it being reactive? What is the probability current of these reactive trajectories? What is their rate of appearance? These are the questions of interest and they are not easy to answer directly from the ensemble of reactive trajectories. The right framework to tackle these questions also goes beyond standard equilibrium statistical mechanics because of the nontrivial bias that the very definition of the reactive trajectories imply - they must be involved in a reaction. The aim of this chapter is to

  5. Safe Transitions from Hospital to Home

    DTIC Science & Technology

    2011-01-26

    Management 49 Home Health 40 Social Work 36 Behavioral Health 16 Hospice 16 Specialist 12 Care Planning/Coordination 2011 MHS Conference 19 Patient...reduce unplanned readmissions  Readmissions are sometimes preventable - Nationwide, between 9% and 48% of readmitted patients receive substandard care ...during or following the index hospitalization (Archives Internal Medicine 2000) 2011 MHS Conference 6 Transitions " Care transitions is a team sport

  6. Connecting the vulcanization transition to percolation.

    PubMed

    Peng, W; Goldbart, P M; McKane, A J

    2001-09-01

    The vulcanization transition is addressed via a minimal replica-field-theoretic model. The appropriate long-wavelength behavior of the two- and three-point vertex functions is considered diagrammatically, to all orders in perturbation theory, and identified with the corresponding quantities in the Houghton-Reeve-Wallace field-theoretic approach to the percolation critical phenomenon. Hence, it is shown that percolation theory correctly captures the critical phenomenology of the vulcanization transition associated with the liquid and critical states.

  7. CONTROLLING BEHAVIOR CHANGERS' BEHAVIOR.

    ERIC Educational Resources Information Center

    MARKLE, DAVID G.

    AN EMERGING METHODOLOGY OF PROGRAMING AVOIDS SOME OF THE UNFORTUNATE EFFECTS ON PROGRAMER BEHAVIOR PRODUCED BY INTERPRETATIONS OF TWO EARLIER METHODOLOGIES. WHILE SKINNERIAN PROGRAMING OFTEN HAS LED TO TRIVIAL PROGRAMS THROUGH PROBLEMS OF APPLICATION OF THE CRITERIA OF SPECIFIED BEHAVIORAL OBJECTIVES AND LOW ERROR RATES, CROWDERIAN PROGRAMING HAS…

  8. The Quantum Hall Liquid to Insulator Transitions.

    NASA Astrophysics Data System (ADS)

    Shahar, Dan

    Among the stable phases known to exist in a two dimensional electronic system (2DES), the metallic phase is conspicuously missing. Nonetheless, metallic behavior characterized by finite conductivity as the temperature Tto 0, can be observed at local, isolated points. These are the critical points of quantum phase transitions separating the various stable phases. Although these phase transitions occur at T = 0 and are completely governed by quantum mechanical rules, the theoretical understanding of them is mainly in a critical phenomena framework, that is largely analogous to that used to describe traditional, thermodynamic, phase transitions. The purpose of this dissertation is to report on the identification and characterization of a new family of quantum transitions, between the quantum Hall effect and an insulating phase. In these transitions, the system is driven between a quantum Hall liquid and an insulating phase by changing the externally applied magnetic field (B), or the electronic density, n. We conducted a comprehensive, systematic experiment that virtually encompasses the full range of sample quality available to date. In all, 70 samples were prepared and studied, many at very low T ( >20 mK) and high B (<15.5 T). We studied systematically the transport near the transitions both, in the Ohmic, and non-Ohmic, high current, regimes. For each transition studied a clear, temperature independent, transition B field that separates the QHE liquid state and the insulating phase can be unambiguously determined. We find that despite the large disparity in the properties of our samples, the transport behavior near the transition points is virtually indistinguishable from sample to sample. In particular, the resistivity value at the transition point is found to be universal, and close to the quantum unit of resistance, h/e^2. Also, the behavior of the systems upon approaching the transitions obeys scaling rules with the same critical exponents for all the

  9. Tips for Transition

    ERIC Educational Resources Information Center

    Kellems, Ryan, Comp.; Morningstar, Mary E., Comp.

    2009-01-01

    The Tips for Transition contains 134 Transition Tips submitted from all over the country by practitioners. The purpose of the Tips was to identify grassroots transition practices being used by practitioners. Tips are categorized into the following domains: (1) Transition Planning; (2) Student Involvement; (3) Family Involvement; (4) Curriculum and…

  10. Critical Behaviors in Contagion Dynamics

    NASA Astrophysics Data System (ADS)

    Böttcher, L.; Nagler, J.; Herrmann, H. J.

    2017-02-01

    We study the critical behavior of a general contagion model where nodes are either active (e.g., with opinion A , or functioning) or inactive (e.g., with opinion B , or damaged). The transitions between these two states are determined by (i) spontaneous transitions independent of the neighborhood, (ii) transitions induced by neighboring nodes, and (iii) spontaneous reverse transitions. The resulting dynamics is extremely rich including limit cycles and random phase switching. We derive a unifying mean-field theory. Specifically, we analytically show that the critical behavior of systems whose dynamics is governed by processes (i)-(iii) can only exhibit three distinct regimes: (a) uncorrelated spontaneous transition dynamics, (b) contact process dynamics, and (c) cusp catastrophes. This ends a long-standing debate on the universality classes of complex contagion dynamics in mean field and substantially deepens its mathematical understanding.

  11. Magnetocaloric effect and critical behavior in Pr0.5Sr0.5MnO3: an analysis of the validity of the Maxwell relation and the nature of the phase transitions.

    PubMed

    Caballero-Flores, R; Bingham, N S; Phan, M H; Torija, M A; Leighton, C; Franco, V; Conde, A; Phan, T L; Yu, S C; Srikanth, H

    2014-07-16

    The Maxwell relation, the Clausius-Clapeyron equation, and a non-iterative method to obtain the critical exponents have been used to characterize the magnetocaloric effect (MCE) and the nature of the phase transitions in Pr0.5Sr0.5MnO3, which undergoes a second-order paramagnetic to ferromagnetic (PM-FM) transition at TC ~ 247 K, and a first-order ferromagnetic to antiferromagnetic (FM-AFM) transition at TN ~ 165 K. We find that around the second-order PM-FM transition, the MCE (as represented by the magnetic entropy change, ΔSM) can be precisely determined from magnetization measurements using the Maxwell relation. However, around the first-order FM-AFM transition, values of ΔSM calculated with the Maxwell relation deviate significantly from those calculated by the Clausius-Clapeyron equation at the magnetic field and temperature ranges where a conversion between the AFM and FM phases occurs. A detailed analysis of the critical exponents of the second-order PM-FM transition allows us to correlate the short-range type magnetic interactions with the MCE. Using the Arrott-Noakes equation of state with the appropriate values of the critical exponents, the field- and temperature-dependent magnetization [Formula: see text] curves, and hence the [Formula: see text] curves, have been simulated and compared with experimental data. A good agreement between the experimental and simulated data has been found in the vicinity of the Curie temperature TC, but a noticeable discrepancy is present for [Formula: see text]. This discrepancy arises mainly from the coexistence of AFM and FM phases and the presence of ferromagnetic clusters in the AFM matrix.

  12. Mechanical Model of Globular Transition in Polymers

    SciTech Connect

    Tricard, Simon; Shepherd, Robert F.; Stan, Claudiu A.; Snyder, Phillip W.; Cademartiri, Rebecca; Zhu, Danny; Aranson, Igor S.; Shakhnovich, Eugene I.; Whitesides, George M.

    2014-07-30

    In complex, multicomponent systems, polymers often undergo phase transitions between distinct conformations. This paper reports a millimeter-scale granular model of coil-to-globule transitions: one “polymer” chain—a cylinders-on-a-string “pearl necklace”—and many spheres, all shaken on a horizontal surface. It is possible to describe the behavior of this granular system by using formalisms generally used in statistical physics of polymers. Two sets of experiments allowed the observation of first- and second- order coil-to-globule transitions. The model shows that the competition between long- and short range interactions leads to a first-order transition. Well-designed granular system represents another kind of approach to the study of polymer phase transitions and might inspire future designs of polymer-like mesoscale systems.

  13. Investigation of Material Problems for High Temperature, High Power Space Energy-Conversion Systems

    DTIC Science & Technology

    1985-01-01

    Nasser, North Holland Publishing, Amsterdam). 2.117 I-W. Chen and A. Argon: Creep Cavitation in 304 Stainless Steel , Acta Metallurgica 29, 1321, 1981...eyepieces). Picture size a 24 x 36mm. * Macrohardness : Rockwell type macromet hardness tester. Loads: 60, 100, 150 Kgs. Scales: a) B Scale, 1/16" Steel ...1700 cals/mole for Mo and 200 cals/mole for steel . Fig. 4.36 shows the effect of powder purity on ductile-brittle transition temperature of tungsten and

  14. Effect of heat treatment on the impact properties of a 12Cr-1Mo-V-W steel

    SciTech Connect

    Chin, B.A.; Wilcox, R.C.

    1983-11-11

    This paper describes the effects of austenitization and tempering treatments on the strength and impact properties of a 12Cr-1Mo-V-W steel. Data are reported for austenitization temperatures covering the range 900 to 1250/sup 0/C and tempering treatments of 600 to 800/sup 0/C. A 50/sup 0/C improvement in the ductile brittle transition temperature is achieved through heat treatment. This is found to result from elimination of delta ferrite and associated carbides at the delta ferrite-matrix interface. 17 figures.

  15. Low-temperature softening in body-centered cubic alloys

    NASA Technical Reports Server (NTRS)

    Pink, E.; Arsenault, R. J.

    1979-01-01

    In the low-temperature range, bcc alloys exhibit a lower stress-temperature dependence than the pure base metals. This effect often leads to a phenomenon that is called 'alloy softening': at low temperatures, the yield stress of an alloy may be lower than that of the base metal. Various theories are reviewed; the most promising are based either on extrinsic or intrinsic models of low-temperature deformation. Some other aspects of alloy softening are discussed, among them the effects on the ductile-brittle transition temperature.

  16. Effect of cerium on temper embrittlement of P-doped Mn structural steels

    SciTech Connect

    Zhexi, Yuan; Shenhua, Song; Faulkner, R.G.; Tingdong, Xu

    1994-01-01

    The effect of cerium on temper embrittlement of P-doped Mn structural steels has been investigated by measurements of the ductile-brittle transition temperature and observations by AES, SIMS and SEM of the fracture surfaces of isothermally embrittled steels. It is shown that P can bring about the temper embrittlement of Mn structural steels; cerium may reduce the temper embrittlement of the steels and the segregation of cerium to grain boundaries may play an important part in reducing the temper embrittlement of the steels.

  17. Evaluation of molybdenum and its alloys. [Reactor core heat pipes

    SciTech Connect

    Lundberg, L.B.

    1981-01-01

    The choice of pure molybdenum as the prime candidate material for space reactor core heat pipes is critically examined. Pure molybdenum's high ductile-brittle transition temperature appears to be its major disadvantage. The candidate materials examined in detail for this application include low carbon arc-cast molybdenum, TZM-molybdenum alloy, and molybdenum-rhenium alloys. Published engineering properties are collected and compared, and it appears that Mo-Re alloys with 10 to 15% rhenium offer the best combination. Hardware is presently being made from electron beam melted Mo-13Re to test this conclusion.

  18. Distribution of properties in nuclear reactor vessel shells in the unirradiated state

    NASA Astrophysics Data System (ADS)

    Skundin, M. A.; Chernobaeva, A. A.; Zhurko, D. A.; Krasikov, E. A.; Medvedev, K. I.

    2013-04-01

    The distributions of the chemical composition, the strength characteristics, and critical ductile-brittle transition temperature T cr are studied in the axial, radial, and tangential directions of the material of a test ring cut from a standard forging used for a VVER-1000 reactor vessel shell. The values of T cr of specimens cut from the test ring are shown to be well below those of the internal volume of the shell, which can explain the substantial scatter of the results obtained on reference specimens cut from the base metal.

  19. Analysis of a link of embrittlement mechanisms and neutron flux effect as applied to reactor pressure vessel materials of WWER

    NASA Astrophysics Data System (ADS)

    Margolin, B. Z.; Yurchenko, E. V.; Morozov, A. M.; Pirogova, N. E.; Brumovsky, M.

    2013-03-01

    The effect of neutron flux on embrittlement of WWER RPV materials is analyzed for cases when different radiation defects prevail. Data bases on the ductile-brittle transition temperature shifts obtained in the surveillance specimens programs and the research programs are used. The material embrittlement mechanisms for which the flux effect is practically absent and for which the flux effect is remarkable are determined. For case when the phosphorus segregation mechanism dominates the theoretical justification of the absence of the flux effect is performed on the basis of the theory of radiation-enhanced diffusion.

  20. The Use of Video Modeling via a Video iPod and a System of Least Prompts to Improve Transitional Behaviors for Students with Autism Spectrum Disorders in the General Education Classroom

    ERIC Educational Resources Information Center

    Cihak, David; Fahrenkrog, Cynthia; Ayres, Kevin M.; Smith, Catherine

    2010-01-01

    This study evaluated the efficacy of video modeling delivered via a handheld device (video iPod) and the use of the system of least prompts to assist elementary-age students with transitioning between locations and activities within the school. Four students with autism learned to manipulate a handheld device to watch video models. An ABAB…