Science.gov

Sample records for lexbig property behavior

  1. Effective property of tooth enamel: monoclinic behavior.

    PubMed

    Lu, Cunyou; Nakamura, Toshio; Korach, Chad S

    2012-05-11

    Human tooth enamel possesses a unique morphology characterized by a repeated cell arrangement, which is composed of varying orientations of hydroxyapatite crystals. In the past, various investigators have reported diverse mechanical properties based on isotropic or orthotropic mechanical models in their experimental and numerical studies. However, these models are insufficient to capture the accurate microstructural effects on the enamel mechanical response. In this paper, a monoclinic anisotropic model, which offers correct descriptions of enamel deformation behaviors, is introduced. The model takes into account the 3D orientation changes of the hydroxyapatite crystals and their spatial elastic property variations. The proposed approach is based on a unit-cell and periodic boundary conditions, and it utilizes the collective deformation characteristics of many rods to determine 13 independent material constants required for the monoclinic model. These constants are necessary to utilize the effective property model to study various mechanical conditions such as abrasion, erosion, wear and fracture of whole tooth enamel. PMID:22405497

  2. Properties and Transport Behavior among 12 Different Environmental Escherichia coli

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Escherichia coli is a commonly used indicator organism for detecting the presence of fecal-borne pathogenic microorganisms in water supplies. The importance of E. coli as an indicator organism has led to numerous studies looking at cell properties and transport behavior of this microorganism. In man...

  3. Psychometric Properties of the Brief Autism Mealtime Behaviors Inventory

    ERIC Educational Resources Information Center

    DeMand, Alexandra; Johnson, Cynthia; Foldes, Emily

    2015-01-01

    The purpose of this study was to explore the psychometric properties of the Brief Autism Mealtime Behaviors Inventory (BAMBI). In a sample of 273 well-characterized children with ASD, we explored the factor structure of the BAMBI, determined the internal consistency of a newly derived factor structure and provide an empirically derived cut-off for…

  4. Topographical and Functional Properties of Precursors to Severe Problem Behavior

    ERIC Educational Resources Information Center

    Fahmie, Tara A.; Iwata, Brian A.

    2011-01-01

    A literature search identified 17 articles reporting data on 34 subjects who engaged in precursors to severe problem behavior, which we examined to identify topographical and functional characteristics. Unintelligible vocalization was the most common precursor to aggression (27%) and property destruction (29%), whereas self- or nondirected…

  5. Deformation behavior and mechanical properties of amyloid protein nanowires.

    PubMed

    Solar, Max; Buehler, Markus J

    2013-03-01

    Amyloid fibrils are most often associated with their pathological role in diseases like Alzheimer's disease and Parkinson's disease, but they are now increasingly being considered for uses in functional engineering materials. They are among the stiffest protein fibers known but they are also rather brittle, and it is unclear how this combination of properties affects the behavior of amyloid structures at larger length scales, such as in films, wires or plaques. Using a coarse-grained model for amyloid fibrils, we study the mechanical response of amyloid nanowires and examine fundamental mechanical properties, including mechanisms of deformation and failure under tensile loading. We also explore the effect of varying the breaking strain and adhesion strength of the constituent amyloid fibrils on the properties of the larger structure. We find that deformation in the nanowires is controlled by a combination of fibril sliding and fibril failure and that there exists a transition from brittle to ductile behavior by either increasing the fibril failure strain or decreasing the strength of adhesion between fibrils. Furthermore, our results reveal that the mechanical properties of the nanowires are quite sensitive to changes in the properties of the individual fibrils, and the larger scale structures are found to be more mechanically robust than the constituent fibrils, for all cases considered. More broadly, this work demonstrates the promise of utilizing self-assembled biological building blocks in the development of hierarchical nanomaterials. PMID:23290516

  6. Physicochemical properties and combustion behavior of duckweed during wet torrefaction.

    PubMed

    Zhang, Shuping; Chen, Tao; Li, Wan; Dong, Qing; Xiong, Yuanquan

    2016-10-01

    Wet torrefaction of duckweed was carried out in the temperature range of 130-250°C to evaluate the effects on physicochemical properties and combustion behavior. The physicochemical properties of duckweed samples were investigated by ultimate analysis, proximate analysis, FTIR, XRD and SEM techniques. It was found that wet torrefaction improved the fuel characteristics of duckweed samples resulting from the increase in fixed carbon content, HHVs and the decrease in nitrogen and sulfur content and atomic ratios of O/C and H/C. It can be seen from the results of FTIR, XRD and SEM analyses that the dehydration, decarboxylation, solid-solid conversion, and condensation polymerization reactions were underwent during wet torrefaction. In addition, the results of thermogravimetric analysis (TGA) in air indicated that wet torrefaction resulted in significant changes on combustion behavior and combustion kinetics parameters. Duckweed samples after wet torrefaction behaved more char-like and gave better combustion characteristics than raw sample. PMID:27469097

  7. Structures and Properties of Polymers Important to Their Wear Behavior

    NASA Technical Reports Server (NTRS)

    Tanaka, K.

    1984-01-01

    The wear and transfer of various semicrystalline polymers sliding against smooth steel or glass surfaces were examined. The effects of structures, and properties of polymers on their wear behavior are discussed. It is found that the high wear characteristics of PTFE is due to the easy destruction of the banded structure of PTFE. The size of spherulites and the molecular profile are closely related to the magnitude of wear rates of typical semicrystalline polymers. The effects of these factors on the wear rate on the basis of the destruction or melting of spherulites at the frictional surface are discussed. Although the fatigue theory of wear indicates that some mechanical properties are important to wear behavior, it is shown that the theory does not always explain the experimental result obtained on a smooth surface.

  8. Structure property behavior of polyimide siloxane segmented copolymers

    NASA Technical Reports Server (NTRS)

    Arnold, C. A.; Summers, J. D.; Bott, R. H.; Taylor, L. T.; Ward, T. C.

    1987-01-01

    Procedures were developed for preparing soluble fully imidized polyimide-polydimethyl siloxane segmented copolymers of wide ranging compositions. At low siloxane levels, the materails behave as modified polyimides. At higher concentrations, the materials are analogous to thermoplastic elastomers. Characterization by dynamic mechanical and thermal analysis methods will be reported along with an assesment of the bulk mechanical properties and the surface behavior. The surface behavior is particularly interesting since the materials can be tailored to have siloxane surfaces even at rather low siloxane contents. This influences a number of properties such as the coefficient of friction and, importanly, the degradation of these materials under aggressive oxygen environments (e.g., atomic oxygen, oxygen plasma).

  9. Adsorption-induced magnetic properties and metallic behavior of graphene

    SciTech Connect

    Zhou, Yungang; Zu, Xiaotao T.; Gao, Fei; Lv, H. F.; Xiao, Haiyan J.

    2009-09-21

    Magnetic properties and electronic structures of graphene with Cl, S, and P adsorption have been investigated using ab initio calculations. The adsorption of Cl leads to Fermi level shifting to valence band, which results in metallic graphene. A band gap of 0.6 eV emerges in a S-absorbed graphene, leading to the semiconducting graphene. The unpaired electrons in the absorbed P atom is polarized and thus, exhibits a magnetic moment of 0.86 μB, while no magnetic moment has been observed after Cl and S adsorption. This demonstrates that the magnetic properties and conductive behavior of graphene can be modified via atom adsorption. Specially, P-absorbed graphene may be useful for spintronic applications, such as tunneling magnetoresistance.

  10. Cesium Eluate Evaporation Solubility and Physical Property Behavior

    SciTech Connect

    Pierce, R.A.

    2003-06-12

    The baseline flowsheet for low activity waste (LAW) in the Hanford River Protection Project (RPP) Waste Treatment Plant (WTP) includes pretreatment of supernatant by removing cesium using ion exchange. When the ion exchange column is loaded, the cesium will be eluted with a 0.5M nitric acid (HNO3) solution to allow the column to be conditioned for re-use. The cesium eluate solution will then be concentrated in a vacuum evaporator to minimize storage volume and recycle HNO3. To prevent the formation of solids during storage of the evaporator bottoms, criteria have been set for limiting the concentration of the evaporator product to 80 percent of saturation at 25 degrees C. A fundamental element of predicting evaporator product solubility is to collect data that can be used to estimate key operating parameters. The data must be able to predict evaporator behavior for a range of eluate concentrations that are evaporated to the point of precipitation. Parameters that were selected for modeling include solubility, density, viscosity, thermal conductivity, and heat capacity. Of central importance is identifying the effect of varying feed components on overall solubility. The point of solubility defines the upper limit for eluate evaporation operations and liquid storage. The solubility point also defines those chemical compounds that have the greatest effects on physical properties. Third, solubility behavior identifies intermediate points where physical property data should be measured for the database. Physical property data (density, viscosity, thermal conductivity, and heat capacity) may be an integral part of tracking evaporator operations as they progress toward their end point. Once the data have been collected, statistical design software can develop mathematical equations that estimate solubility and other physical properties.

  11. Structure, properties, and dynamic behavior of Earth's inner core

    NASA Astrophysics Data System (ADS)

    Reaman, Daniel Marcus

    Long-standing debate has persisted regarding the nature of the Earth's inner core, from its age and composition to its structure and dynamic high-pressure, high-temperature behavior. The equation of state of the alloy which comprises the inner core, the material transport properties of inner-core materials and the mechanism responsible for its structure are all required to gain further insight into the current and past state of the Earth's deep interior. Experimental work in the diamond-anvil cell (DAC) coupled with theoretical calculations are reported here to constrain these aspects of the Earth's inner core. Use of the DAC has allowed us to determine an equation of state of a planetary-core representative Fe64Ni36 alloy to 95 GP and ˜ 3000 K. Increasing the Ni content in these experiments relative to the estimated abundance in the inner core (˜5--10%) provides a critical investigation on the effects of increasing Ni content on the equation of state of FeNi alloys, thereby providing insight in to the behavior of these alloys at high pressures and temperatures with applications to other planetary cores. The use of micro-fabricated samples in the DAC is a novel new way of measuring material transport properties under high-pressure and temperature conditions. Using micro-fabricated samples in these experiments, with a controlled geometry of Fe and Ni, has allowed the measurement of interdiffusion coefficients in FeNi alloys and extended the previous pressure range of these experiments by a factor of three. The resulting data has been extrapolated to inner-core conditions to place constraints on material transport properties at those conditions while providing insight into some of the other physical properties of inner-core material, such as the solid-state viscosity. The seismically-anisotropic structure of the inner core remains a point of contention amongst geophysicists. Though many viable hypotheses have been put forth regarding the nature of this structure

  12. Mechanical Properties and Fracture Behavior of Nanoporous Au

    SciTech Connect

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

    2005-06-16

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

  13. Charcoal's physical properties are key to understanding its environmental behavior

    NASA Astrophysics Data System (ADS)

    Masiello, Caroline; Brewer, Catherine; Dugan, Brandon; Liu, Zuolin; Gonnermann, Helge; Zygourakis, Kyriacos; Davies, Christian; Panzacchi, Pietro; Gao, Xiaodong; Pyle, Lacey

    2014-05-01

    Charcoal is a highly porous, low density material whose physical properties play a key role in its soil behavior and its environmental fate. In considering biochar, some of its most sought-after environmental effects are a result of its physical characteristics, not its chemical or biological properties. For example, the ability of biochar to retain soil water is widely attributed to its porosity. However, charcoal physical properties are so poorly understood that they are sometimes not characterized at all in the current literature. Here we outline a suite of basic physical properties of charcoal and the likely environmental effects of their variations, with a focus on the interactions between charcoal and water. The most basic physical property of charcoal, its particle size, likely plays a role in its ability to alter the rate of drainage in soils. Particle morphology is also relevant, affecting how particles of soil and char can pack together. Bulk densities of charcoal and soil mixtures can be used to generate a simple estimate of the efficiency of char-soil packing. Charcoal density is an additionally important property and can be measured in a number of ways. Density almost certainly controls the tendency of chars to sink or float, and to erode or remain on the land surface. However, charcoal density can vary by almost a factor of 10 depending on the measurement technique used. We discuss two simple techniques available for measuring char density and the value of information provided by each approach. Finally, we report a simple, fast technique to measure total char porosity, including all pores from nanometers to 10s of micrometers in size. Porosity is at least one of the key controls on the ability of biochar to improve plant-available water, and techniques to measure it have previously been limited to the smallest fraction of pores (N2 sorption) or have required expensive, hazardous procedures (Hg porosimetry). We show that char porosity varies primarily

  14. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

    SciTech Connect

    López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Guirado-López, R. A.; Gámez-Corrales, R.

    2014-11-07

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH–MWCNT). Our MWCNTs have average diameters of ∼2 nm, lengths of approximately 100–300 nm, and a hydroxyl surface coverage θ∼0.1. When deposited on the air/water interface the OH–MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO–LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH–MWCNTs might have promising applications.

  15. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

    NASA Astrophysics Data System (ADS)

    López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Gámez-Corrales, R.; Guirado-López, R. A.

    2014-11-01

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH-MWCNT). Our MWCNTs have average diameters of ˜2 nm, lengths of approximately 100-300 nm, and a hydroxyl surface coverage θ˜0.1. When deposited on the air/water interface the OH-MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO-LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH-MWCNTs might have promising applications.

  16. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes.

    PubMed

    López-Oyama, A B; Silva-Molina, R A; Ruíz-García, J; Gámez-Corrales, R; Guirado-López, R A

    2014-11-01

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH-MWCNT). Our MWCNTs have average diameters of ~2 nm, lengths of approximately 100-300 nm, and a hydroxyl surface coverage θ~0.1. When deposited on the air/water interface the OH-MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO-LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH-MWCNTs might have promising applications. PMID:25381534

  17. Mechanical behavior and elastic properties of prestrained columnar ice

    NASA Astrophysics Data System (ADS)

    Snyder, Scott Aaron

    Experiments on columnar-grained ice at --10 °C reveal changes to its mechanical behavior and elastic properties due to compressive prestrain. Laboratory-grown (152-mm cube) specimens of freshwater and saline ice were prestrained under uniaxial across-column compression (to levels from epsilon p = 0.003 to epsilonp = 0.20, at constant strain rates in the ductile regime) and then reloaded, again under uniaxial across-column compression (at rates from 1x10--6 s--1 to 3 x 10--2s--1). Prestrain caused solid-state recrystallization as well as damage in the form of non-propagating microcracks. These microstructural changes were quantified by analysis of thin sections. Elastic properties in across-column directions, both parallel (x1) and perpendicular ( x2) to the initial loading direction, were obtained from P-wave and S-wave ultrasonic velocities. As a result (and depending on the level) of the prestrain imparted in both materials, Young's modulus E was reduced by as much as 30%; the ductile-to-brittle (D--B) transition strain rate epsilon D/B was increased up to a factor of 3 to 10; and the ductile behavior with respect to loading along a direction within the horizontal ( x1-x2) plane of the parent ice sheet changed from isotropic to anisotropic. As the prestrain rate approached the nominal D--B transition rate of initially undamaged material, the magnitudes of prestrain effects on elastic compliance increased. The shift in the D--B transition, on the other hand, was less sensitive to the prestrain rate. The results are interpreted within the framework of a recent model that predicts the transition strain rate based on the micromechanical boundary between creep and fracture processes. Prestrain primarily affected certain parameters in the model, specifically the power-law creep coefficient B (more so than the creep exponent n), Young's modulus E and, by extension, the fracture toughness KIc. The physical implications of these effects are discussed.

  18. Synthetic melanin films: Assembling mechanisms, scaling behavior, and structural properties

    NASA Astrophysics Data System (ADS)

    Lorite, Gabriela S.; Coluci, Vitor R.; da Silva, Maria Ivonete N.; Dezidério, Shirlei N.; Graeff, Carlos Frederico O.; Galva~O, Douglas S.; Cotta, Mônica A.

    2006-06-01

    In this work we report on the surface characterization of melanin thin films prepared using both water-based and organic solvent-based melanin syntheses. Atomic force microscopy (AFM) analysis of these films suggests that the organic solvent synthesis provides relatively planar basic melanin structures; these basic structures generate surface steps with height in the range of 2-3 nm and small tendency to form larger aggregates. The scaling properties obtained from the AFM data were used to infer the assembling mechanisms of these thin films which depend on the solvent used for melanin synthesis. The behavior observed in organic solvent-based melanin suggests a diffusion-limited aggregation process. Thus films with good adhesion to the substrate and smoother morphologies than water-prepared melanin films are obtained. Electronic structure calculations using a conductorlike screening model were also performed in order to elucidate the microscopic processes of thin film formation. Our results suggest that the agglomerates observed in hydrated samples originate from reaction with water at specific locations on the surface most likely defects on the planar structure.

  19. Correlating attachment behavior with cell properties for eight Porcine Escherichia coli Isolates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study we investigate how growth stage and depositional environment affect variability of cell properties and transport behavior of eight porcine E. coli isolates. We compared the surface properties and transport behavior for cells harvested at two different growth stages (exponential and sta...

  20. Correlating Transport Behavior with Cell Properties for Eight Porcine Escherichia coli Isolates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study we investigate how growth stage and depositional environment affect variability of cell properties and transport behavior of eight porcine E. coli isolates. We compared the surface properties and transport behavior for cells harvested at two different growth stages (exponential and sta...

  1. Correlation Between Domain Behavior and Magnetic Properties of Materials

    SciTech Connect

    Jeffrey Scott Leib

    2003-05-31

    Correlation between length scales in the field of magnetism has long been a topic of intensive study. The long-term desire is simple: to determine one theory that completely describes the magnetic behavior of matter from an individual atomic particle all the way up to large masses of material. One key piece to this puzzle is connecting the behavior of a material's domains on the nanometer scale with the magnetic properties of an entire large sample or device on the centimeter scale. In the first case study involving the FeSiAl thin films, contrast and spacing of domain patterns are clearly related to microstructure and stress. Case study 2 most clearly demonstrates localized, incoherent domain wall motion switching with field applied along an easy axis for a square hysteresis loop. In case study 3, axis-specific images of the complex Gd-Si-Ge material clearly show the influence of uniaxial anisotropy. Case study 4, the only study with the sole intent of creating domain structures for imaging, also demonstrated in fairly simple terms the effects of increasing stress on domain patterns. In case study 5, it was proven that the width of magnetoresistance loops could be quantitatively predicted using only MFM. When all of the case studies are considered together, a dominating factor seems to be that of anisotropy, both magneticrostaylline and stress induced. Any quantitative bulk measurements heavily reliant on K coefficients, such as the saturation fields for the FeSiAl films, H{sub c} in cases 1, 3, and 5, and the uniaxial character of the Gd{sub 5}(Si{sub 2}Ge{sub 2}), transferred to and from the domain scale quite well. In-situ measurements of domain rotation and switching, could also be strongly correlated with bulk magnetic properties, including coercivity, M{sub s}, and hysteresis loop shape. In most cases, the qualitative nature of the domain structures, when properly considered, matched quite well to what might have been expected from theory and calculation

  2. Ergodic properties and thermodynamic behavior of elementary reversible cellular automata. I. Basic properties

    SciTech Connect

    Takesue, Shinji )

    1989-08-01

    This is the first part of a series devoted to the study of thermodynamic behavior of large dynamical systems with the use of a family of full-discrete and conservative models named elementary reversible cellular automata (ERCAs). In this paper, basic properties such as conservation laws and phase space structure are investigated in preparation for the later studies. ERCAs are a family of one-dimensional reversible cellular automata having two Boolean variables on each site. Reflection and Boolean conjugation symmetries divide them into 88 equivalence classes. For each rule, additive conserved quantities written in a certain form are regarded as a kind of energy, if they exist. By the aid of the discreteness of the variables, every ERCA satisfies the Liouville theorem or the preservation of phase space volume. Thus, if an energy exists in the above sense, statistical mechanics of the model can formally be constructed. If a locally defined quantity is conserved, however, it prevents the realization of statistical mechanics. The existence of such a quantity is examined for each class and a number of rules which have at least one energy but no local conservation laws are selected as hopeful candidates for the realization of thermodynamic behavior. In addition, the phase space structure of ERCAs is analyzed by enumerating cycles exactly in the phase space for systems of comparatively small sizes. As a result, it is revealed that a finite ERCA is not ergodic, that is, a large number of orbits coexist on an energy surface. It is argued that this fact does not necessarily mean the failure of thermodynamic behavior on the basis of an analogy with the ergodic nature of infinite systems.

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

    NASA Astrophysics Data System (ADS)

    Kim, Sihong

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

  4. BEHAVIORAL EVALUATION OF THE IRRITATING PROPERTIES OF OZONE

    EPA Science Inventory

    The sensory irritant properties of ozone have been considered to be responsible for symptoms that occur in humans after exposure. This assumption has not been studied explicitly. One way to assess the aversive properties of airborne irritants is to give the exposed individual an ...

  5. Exploration of Psychometric Properties of the Developmental Behavior Checklist.

    ERIC Educational Resources Information Center

    Hastings, Richard P.; Brown, Tony; Mount, Rebecca H.; Cormack, K. F. Magnus

    2001-01-01

    This study performed a factor analysis of the Developmental Behavior Checklist (DBC) with 531 children and adolescents with mental retardation. The DBC is intended to assess psychopathology in youth with mental retardation. Findings indicated substantial overlap with the factor analyses of the scale's developers and high levels of internal…

  6. Measurement Properties of Indirect Assessment Methods for Functional Behavioral Assessment: A Review of Research

    ERIC Educational Resources Information Center

    Floyd, Randy G.; Phaneuf, Robin L.; Wilczynski, Susan M.

    2005-01-01

    Indirect assessment instruments used during functional behavioral assessment, such as rating scales, interviews, and self-report instruments, represent the least intrusive techniques for acquiring information about the function of problem behavior. This article provides criteria for examining the measurement properties of these instruments…

  7. Psychometric Properties of the Disability Assessment Schedule (DAS) for Behavior Problems: An Independent Investigation

    ERIC Educational Resources Information Center

    Tsakanikos, Elias; Underwood, Lisa; Sturmey, Peter; Bouras, Nick; McCarthy, Jane

    2011-01-01

    The present study employed the Disability Assessment Schedule (DAS) to assess problem behaviors in a large sample of adults with ID (N = 568) and evaluate the psychometric properties of this instrument. Although the DAS problem behaviors were found to be internally consistent (Cronbach's [alpha] = 0.87), item analysis revealed one weak item…

  8. Violence-Related Behaviors on School Property among Mississippi Public High School Students, 1993-2003

    ERIC Educational Resources Information Center

    Zhang, Lei; Johnson, William D.

    2005-01-01

    Researchers examined trends and compared subgroup differences in violence-related behaviors on school property among Mississippi public high school students from 1993 to 2003. Findings are based on data from the Mississippi Youth Risk Behavior Surveillance System (YRBSS), a representative sample (N = 9,058) of Mississippi high school students.…

  9. Surfactant-free alternative fuel: Phase behavior and diffusion properties.

    PubMed

    Kayali, Ibrahim; Jyothi, Chemboli K; Qamhieh, Khawla; Olsson, Ulf

    2016-02-01

    Phase behavior of the three components, 1-propanol, water and oil is studied at 10, 25, and 40°C. Biodiesel, limonene and diesel are used as oil phases. NMR self-diffusion measurements are performed to investigate the microstructure of the one-phase regions. Tie lines in the two-phase regions are determined both by proton NMR analysis and compared with theoretical calculations. NMR self-diffusion results for the different components in these systems do not show any sign of confinement or obstructions, demonstrating these mixtures to be structureless solutions. A good agreement between the experimental and calculated phase behavior is obtained. The determined tie lines in the two-phase regions show higher affinity of 1-propanol to water than to oil. PMID:26520824

  10. Metal matrix composite micromechanics: In-situ behavior influence on composite properties

    NASA Technical Reports Server (NTRS)

    Murthy, P. L. N.; Hopkins, D. A.; Chamis, C. C.

    1989-01-01

    Recent efforts in computational mechanics methods for simulating the nonlinear behavior of metal matrix composites have culminated in the implementation of the Metal Matrix Composite Analyzer (METCAN) computer code. In METCAN material nonlinearity is treated at the constituent (fiber, matrix, and interphase) level where the current material model describes a time-temperature-stress dependency of the constituent properties in a material behavior space. The composite properties are synthesized from the constituent instantaneous properties by virtue of composite micromechanics and macromechanics models. The behavior of metal matrix composites depends on fabrication process variables, in situ fiber and matrix properties, bonding between the fiber and matrix, and/or the properties of an interphase between the fiber and matrix. Specifically, the influence of in situ matrix strength and the interphase degradation on the unidirectional composite stress-strain behavior is examined. These types of studies provide insight into micromechanical behavior that may be helpful in resolving discrepancies between experimentally observed composite behavior and predicted response.

  11. Effect of suspension property on granule morphology and compaction behavior

    SciTech Connect

    Hae-Weon Lee, Guesup Song, In-Sik Suk

    1995-12-31

    Granule morphology is an important factor during dry pressing, since it has great influences on die flowability, compaction ratio, and resulting green microstructure. Granule morphology and packing structure of ultrafine Si{sub 3}N{sub 4} particles in the granule were optimized during spray drying by adjusting the suspension structure. The particle packing structure of spray-dried granule was investigated with suspension structure. The effects of granule morphology and its particle packing structure on compaction and resultant sintering behavior were evaluated.

  12. Ion plated gold films: Properties, tribological behavior and performance

    NASA Technical Reports Server (NTRS)

    Spalvins, Talivaldis

    1987-01-01

    The glow discharge energizing favorably modifies and controls the coating/substrate adherence and the nucleation and growth sequence of ion plated gold films. As a result the adherence, coherence, internal stresses, and morphology of the films are significantly improved. Gold ion plated films because of their graded coating/substrate interface and fine uniform densely packed microstructure not only improve the tribological properties but also induce a surface strengthening effect which improves the mechanical properties such as yield, tensile, and fatigue strength. Consequently significant improvements in the tribological performance of ion plated gold films as compared to vapor deposited gold films are shown in terms of decreased friction/wear and prolonged endurance life.

  13. Material Properties of Hagfish Skin, with Insights into Knotting Behaviors.

    PubMed

    Clark, Andrew J; Crawford, Callie H; King, Brooke D; Demas, Andrew M; Uyeno, Theodore A

    2016-06-01

    Hagfishes (Myxinidae) often integrate whole-body knotting movements with jawless biting motions when reducing large marine carcasses to ingestible items. Adaptations for these behaviors include complex arrangements of axial muscles and flexible, elongate bodies without vertebrae. Between the axial muscles and the hagfish skin is a large, blood-filled subcutaneous sinus devoid of the intricate, myoseptal tendon networks characteristic of the taut skins of other fishes. We propose that the loose-fitting skin of the hagfish facilitates the formation and manipulation of body knots, even if it is of little functional significance to steady swimming. Hagfish skin is a relatively thick, anisotropic, multilayered composite material comprising a superficial, thin, and slimy epidermis, a middle dermal layer densely packed with fibrous tissues, and a deep subdermal layer comprised of adipose tissue. Hagfish skin is stiffer when pulled longitudinally than circumferentially. Stress-strain data from uniaxial tensile tests show that hagfish skins are comparable in tensile strength and stiffness to the taut skins of elongate fishes that do not engage in knotting behaviors (e.g., sea lamprey and penpoint gunnel). Sheath-core-constructed ropes, which serve as more accurate models for hagfish bodies, demonstrate that loose skin (extra sheathing) enhances flexibility of the body (rope). Along with a loose-fitting skin, the morphologies of hagfish skin parallel those of moray eels, which are also known for generating and manipulating figure-eight-style body knots when struggling with prey. PMID:27365419

  14. Interfacial properties and mechanical behavior of titanium aluminides

    SciTech Connect

    Yoo, M.H.; Fu, C.L.

    1998-01-01

    The role of various interfaces in deformation and fracture behavior of two phase TiAl-Ti{sub 3}Al alloys is analyzed on the basis of the specific interfacial and surface energies determined from ab initio calculations. The propensity of twinning observed in these alloys is consistent with the low true twin boundary energy. The strong plastic anisotropy reported in TiAl polysynthetically twinned (PST) crystals is attributed partly to the localized slip along lamellar interfaces, thus lowering the yield stress for soft orientations. Interfacial fracture energies are estimated to be the highest for the {alpha}{sub 2}/{gamma} lamellar boundary and the lowest for the 120 {degree} rotational {gamma}/{gamma} boundary. The fracture mode mixity plays an important role in the crack-tip plasticity by ordinary slip and true twinning, leading to translamellar and interfacial fracture.

  15. Photophysical properties and photobiological behavior of amodiaquine, primaquine and chloroquine.

    PubMed

    Viola, Giampietro; Salvador, Alessia; Cecconet, Laura; Basso, Giuseppe; Vedaldi, Daniela; Dall'Acqua, Francesco; Aloisi, Gian Gaetano; Amelia, Matteo; Barbafina, Arianna; Latterini, Loredana; Elisei, Fausto

    2007-01-01

    This article describes the results of a coupled photophysical and photobiological study aimed at understanding the phototoxicity mechanism of the antimalarial drugs amodiaquine (AQ), primaquine (PQ) and chloroquine (CQ). Photophysical experiments were carried out in aqueous solutions by steady-state and time-resolved spectrometric techniques to obtain information on the different decay pathways of the excited states of the drugs and on the transient species formed upon laser irradiation. The results showed that all three drugs possess very low fluorescence quantum yields (10(-2)-10(-4)). Laser flash photolysis experiments proved the occurrence of photoionization processes leading to the formation of a radical cation in all three systems. In the case of AQ the lowest triplet state was also detected. Together with the photophysical properties the photobiological properties of the antimalarial drugs were investigated under UV irradiation, on various biological targets through a series of in vitro assays. Phototoxicity on mouse 3T3 fibroblast and human keratinocyte cell lines NCTC-2544 was detected for PQ and CQ but not for AQ. In particular, PQ- and CQ-induced apoptosis was revealed by the externalization of phosphatidylserine. Furthermore, upon UV irradiation, the drugs caused significant variations of the mitochondrial potential (Deltapsi(mt)) measured by flow cytometry. The photodamages produced by the drugs were also evaluated on proteins, lipids and DNA. The combined approaches were useful in understanding the mechanism of phototoxicity induced by these antimalarial drugs. PMID:18028216

  16. Cesium Eluate Evaporation Solubility and Physical Property Behavior

    SciTech Connect

    Pierce, R.A.

    2003-06-12

    The baseline flowsheet for low activity waste (LAW) in the Hanford River Protection Project (RPP) Waste Treatment Plant (WTP) includes pretreatment of supernatant by removing cesium using ion exchange. When the ion exchange column is loaded, the cesium will be eluted with a 0.5M nitric acid (HNO3) solution to allow the column to be conditioned for re-use. The cesium eluate solution will then be concentrated in a vacuum evaporator to minimize storage volume and recycle HNO3. To prevent the formation of solids during storage of the evaporator bottoms, criteria have been set for limiting the concentration of the evaporator product to 80 percent of saturation at 25 degrees C. Prior work has collected fundamental data for predicting solubility and other physical property measurements. Other ongoing efforts have involved the development of a computer model to predict solubility and physical properties during evaporation. Evaporation experiments were conducted with cesium eluate simulant generated from a pilot scale experiment in the Thermal Fluids Lab (TFL) at the Savannah River Technology Center (SRTC). The data from the experiments will be used to validate the modeling data.

  17. Mechanical properties and failure behavior of unidirectional porous ceramics

    PubMed Central

    Seuba, Jordi; Deville, Sylvain; Guizard, Christian; Stevenson, Adam J.

    2016-01-01

    We show that the honeycomb out-of-plane model derived by Gibson and Ashby can be applied to describe the compressive behavior of unidirectional porous materials. Ice-templating allowed us to process samples with accurate control over pore volume, size, and morphology. These samples allowed us to evaluate the effect of this microstructural variations on the compressive strength in a porosity range of 45–80%. The maximum strength of 286 MPa was achieved in the least porous ice-templated sample (P(%) = 49.9), with the smallest pore size (3 μm). We found that the out-of-plane model only holds when buckling is the dominant failure mode, as should be expected. Furthermore, we controlled total pore volume by adjusting solids loading and sintering temperature. This strategy allows us to independently control macroporosity and densification of walls, and the compressive strength of ice-templated materials is exclusively dependent on total pore volume. PMID:27075397

  18. Mechanical properties and failure behavior of unidirectional porous ceramics

    NASA Astrophysics Data System (ADS)

    Seuba, Jordi; Deville, Sylvain; Guizard, Christian; Stevenson, Adam J.

    2016-04-01

    We show that the honeycomb out-of-plane model derived by Gibson and Ashby can be applied to describe the compressive behavior of unidirectional porous materials. Ice-templating allowed us to process samples with accurate control over pore volume, size, and morphology. These samples allowed us to evaluate the effect of this microstructural variations on the compressive strength in a porosity range of 45–80%. The maximum strength of 286 MPa was achieved in the least porous ice-templated sample (P(%) = 49.9), with the smallest pore size (3 μm). We found that the out-of-plane model only holds when buckling is the dominant failure mode, as should be expected. Furthermore, we controlled total pore volume by adjusting solids loading and sintering temperature. This strategy allows us to independently control macroporosity and densification of walls, and the compressive strength of ice-templated materials is exclusively dependent on total pore volume.

  19. Properties of a Formal Method for Prediction of Emergent Behaviors in Swarm-based Systems

    NASA Technical Reports Server (NTRS)

    Rouff, Christopher; Vanderbilt, Amy; Hinchey, Mike; Truszkowski, Walt; Rash, James

    2004-01-01

    Autonomous intelligent swarms of satellites are being proposed for NASA missions that have complex behaviors and interactions. The emergent properties of swarms make these missions powerful, but at the same time more difficult to design and assure that proper behaviors will emerge. This paper gives the results of research into formal methods techniques for verification and validation of NASA swarm-based missions. Multiple formal methods were evaluated to determine their effectiveness in modeling and assuring the behavior of swarms of spacecraft. The NASA ANTS mission was used as an example of swarm intelligence for which to apply the formal methods. This paper will give the evaluation of these formal methods and give partial specifications of the ANTS mission using four selected methods. We then give an evaluation of the methods and the needed properties of a formal method for effective specification and prediction of emergent behavior in swarm-based systems.

  20. Properties of ferrites important to their friction and wear behavior

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1983-01-01

    Environmental, chemical and crystallographical effects on the fundamental nature on friction and wear of the ferrites in contact with metals, magnetic tapes and themselves are reviewed. The removal of adsorbed films from the surfaces of ferrites results in very strong interfacial adhesion and high friction in ferrite to metal and ferrite to magnetic tape contacts. The metal ferrite bond at the interface is primarily a chemical bond between the metal atoms and the large oxygen anions in the ferrite surface, and the strength of these bonds is related to the oxygen to metal bond strength in the metal oxide. The more active the metal, the higher is the coefficient of friction. Not only under adhesive conditions, but also under abrasive conditions the friction and wear properties of ferrites are related to the crystallographic orientation. With ferrite to ferrite contact the mating of highest atomic density (most closely packed) direction on matched crystallographic planes, that is, 110 directions on /110/planes, results in the lowest coefficient of friction.

  1. Mechanical properties and fracture behavior of single-layer phosphorene at finite temperatures

    NASA Astrophysics Data System (ADS)

    Sha, Zhen-Dong; Pei, Qing-Xiang; Ding, Zhiwei; Jiang, Jin-Wu; Zhang, Yong-Wei

    2015-10-01

    Phosphorene, a new two-dimensional (2D) material beyond graphene, has attracted great attention in recent years due to its superior physical and electrical properties. However, compared to graphene and other 2D materials, phosphorene has a relatively low Young’s modulus and fracture strength, which may limit its applications due to possible structure failures. For the mechanical reliability of future phosphorene-based nanodevices, it is necessary to have a deep understanding of the mechanical properties and fracture behaviors of phosphorene. Previous studies on the mechanical properties of phosphorene were based on first principles calculations at 0 K. In this work, we employ molecular dynamics simulations to explore the mechanical properties and fracture behaviors of phosphorene at finite temperatures. It is found that temperature has a significant effect on the mechanical properties of phosphorene. The fracture strength and strain reduce by more than 65% when the temperature increases from 0 K to 450 K. Moreover, the fracture strength and strain in the zigzag direction is more sensitive to the temperature rise than that in the armchair direction. More interestingly, the failure crack propagates preferably along the groove in the puckered structure when uniaxial tension is applied in the armchair direction. In contrast, when the uniaxial tension is applied in the zigzag direction, multiple cracks are observed with rough fracture surfaces. Our present work provides useful information about the mechanical properties and failure behaviors of phosphorene at finite temperatures.

  2. Psychometric Properties of a Youth Self-Report Measure of Neglectful Behavior by Parents

    ERIC Educational Resources Information Center

    Dubowitz, Howard; Villodas, Miguel T.; Litrownik, Alan J.; Pitts, Steven C.; Hussey, Jon M.; Thompson, Richard; Black, Maureen M.; Runyan, Desmond

    2011-01-01

    Objective: This study aimed to empirically assess psychometric properties of a multi-dimensional youth self-report measure of neglectful behavior by parents. Method: Data were gathered from 593 12-year-old youth participating in the Longitudinal Studies of Child Abuse and Neglect (LONGSCAN) consortium; 272 also had data at age 14. Youth responded…

  3. Argumentation and Students' Conceptual Understanding of Properties and Behaviors of Gases

    ERIC Educational Resources Information Center

    Aydeniz, Mehmet; Pabuccu, Aybuke; Cetin, Pinar Seda; Kaya, Ebru

    2012-01-01

    The purpose of this study was to explore the impact of argumentation-based pedagogy on college students' conceptual understanding of properties and behaviors of gases. The sample consists of 108 students (52 in the control group and 56 in the intervention group) drawn from 2 general chemistry college courses taught by the same instructor. Data…

  4. The Psychometric Properties of the Difficult Behavior Self-Efficacy Scale

    ERIC Educational Resources Information Center

    Oh, Hyun-Kyoung; Kozub, Francis M.

    2010-01-01

    The study was designed to estimate the psychometric properties of Hastings and Brown's (2002a) Difficult Behavior Self-efficacy Scale. Participants were two samples of physical educators teaching in Korea (n = 229) and the United States (U.S.; n = 139). An initial translation of the questionnaire to Korean and pilot study were conducted along with…

  5. Psychometric Properties of a Korean Translation of the "Scales of Independent Behavior--Revised"

    ERIC Educational Resources Information Center

    Cho, Su-Je; Paik, Eunhee; Lee, Byoung-In; Yi, Joonsuk

    2010-01-01

    This study explores the psychometric properties of data drawn from the Korean translation of the full "Scales of Independent Behavior--Revised" (SIB-R). In addition, semantic, content, conceptual, and technical equivalence are examined. The participants include 2,763 typically developing children and 406 children with intellectual disabilities…

  6. Examination of the Psychometric Properties of the Chinese Translated Behavioral Regulation in Exercise Questionnaire-2

    ERIC Educational Resources Information Center

    Chung, Pak Kwong; Liu, Jing Dong

    2012-01-01

    The present study was designed to examine the psychometric properties of the Chinese-translated Behavioral Regulation in Exercise Questionnaire-2 (Markland & Tobin, 2004). A sample of Chinese university students (N =555) was invited to take part in this study. Confirmatory factor analysis was employed to examine the factorial validity, and the…

  7. Structural Properties and Phase Behavior of Crosslinked Networks in Polymer Solutions

    PubMed Central

    Benmouna, Farida; Zemmour, Samira; Benmouna, Mustapha

    2016-01-01

    ABSTRACT Structural properties and phase behavior of crosslinked networks embedded in polymer solutions are theoretically investigated. The partial structure factor of the network is calculated using a matrix formulation of the random phase approximation and the forward scattering limit is correlated with the phase behavior. Swelling and deswelling processes are analyzed in terms of the polymer concentration, the mismatch of solvent quality with respect to polymer and network, the polymers incompatibility and their characteristic sizes. Most studies reported so far in the literature have focussed on the swelling of crosslinked networks and gels in pure solvents but the correlation of the structural properties with the phase behavior in the presence of high molecular weight polymers in solution has not been given sufficient attention. The present work is intended to fill this gap in view of the current efforts to develop novel drug encapsulating and targeted delivery devices. PMID:27134310

  8. Psychometric properties of a Dutch version of the behavior problems inventory-01 (BPI-01).

    PubMed

    Dumont, Eric; Kroes, Diana; Korzilius, Hubert; Didden, Robert; Rojahn, Johannes

    2014-03-01

    There are only a limited number of Dutch validated measurement instruments for measuring behavioral problems in people with a moderate to profound intellectual disability. In this study, the psychometric properties of a Dutch version of the behavior Problems Inventory-01 (BPI-01; Rojahn et al., 2001) have been investigated among 195 people with a moderate to profound intellectual disability who live in a residential facility. The BPI-01 was completed by 42 informants (staff members) of 23 care units. The inter-rater reliability, intra-rater reliability and internal consistency turned out to be good. Factor analysis confirmed two of the three a priori factors and the third factor was a mix of self-injurious (SIB) behavior and stereotypic behavior. The BPI-01 was compared to the Aberrant Behavior Checklist (Aman et al., 1985a) and showed a good convergent validity. This study shows that a Dutch version of the BPI-01 has good psychometric properties for measuring behavior problems in individuals with moderate to profound intellectual disability. PMID:24472503

  9. Computing Legacy Software Behavior to Understand Functionality and Security Properties: An IBM/370 Demonstration

    SciTech Connect

    Linger, Richard C; Pleszkoch, Mark G; Prowell, Stacy J; Sayre, Kirk D; Ankrum, Scott

    2013-01-01

    Organizations maintaining mainframe legacy software can benefit from code modernization and incorporation of security capabilities to address the current threat environment. Oak Ridge National Laboratory is developing the Hyperion system to compute the behavior of software as a means to gain understanding of software functionality and security properties. Computation of functionality is critical to revealing security attributes, which are in fact specialized functional behaviors of software. Oak Ridge is collaborating with MITRE Corporation to conduct a demonstration project to compute behavior of legacy IBM Assembly Language code for a federal agency. The ultimate goal is to understand functionality and security vulnerabilities as a basis for code modernization. This paper reports on the first phase, to define functional semantics for IBM Assembly instructions and conduct behavior computation experiments.

  10. Structure-property relations and modeling of small crack fatigue behavior of various magnesium alloys

    NASA Astrophysics Data System (ADS)

    Bernard, Jairus Daniel

    Lightweight structural components are important to the automotive and aerospace industries so that better fuel economy can be realized. Magnesium alloys in particular are being examined to fulfill this need due to their attractive stiffness- and strength-to-weight ratios when compared to other materials. However, when introducing a material into new roles, one needs to properly characterize its mechanical properties. Fatigue behavior is especially important considering aerospace and automotive component applications. Therefore, quantifying the structure-property relationships and accurately predicting the fatigue behavior for these materials are vital. This study has two purposes. The first is to quantify the structure-property relationships for the fatigue behavior in an AM30 magnesium alloy. The second is to use the microstructural-based MultiStage Fatigue (MSF) model in order to accurately predict the fatigue behavior of three magnesium alloys: AM30, Elektron 21, and AZ61. While some studies have previously quantified the MSF material constants for several magnesium alloys, detailed research into the fatigue regimes, notably the microstructurally small crack (MSC) region, is lacking. Hence, the contribution of this work is the first of its kind to experimentally quantify the fatigue crack incubation and MSC regimes that are used for the MultiStage Fatigue model. Using a multi-faceted experimental approach, these regimes were explored with a replica method that used a dual-stage silicone based compound along with previously published in situ fatigue tests. These observations were used in calibrating the MultiStage Fatigue model.

  11. Physical properties and mechanical behavior of clays with saline pore fluid

    SciTech Connect

    Shimizu, Masayoshi

    1995-12-31

    The sample of which the pore fluid is the sea water was prepared by remolding a powdered clay soil with the natural sea water. Physical and mechanical properties of this sample were compared to those of the sample prepared with distilled water. Results of consistency limits tests, CIU triaxial compression tests and oedometer tests are shown. Effects of the salinity on the effective stress and strain behavior in the states of normal and over consolidation and on the compressibility and consolidation behavior are shown. Discussion is made on the basis of the concept of aggregates of soil grains.

  12. Effects of substrate properties on the hydraulic and thermal behavior of a green roof

    NASA Astrophysics Data System (ADS)

    Sandoval, V. P.; Suarez, F. I.; Victorero, F.; Bonilla, C.; Gironas, J. A.; Vera, S.; Bustamante, W.; Rojas, V.; Pasten, P.

    2014-12-01

    Green roofs are a sustainable urban development solution that incorporates a growing media (also known as substrate) and vegetation into infrastructures to reach additional benefits such as the reduction of: rooftop runoff peak flows, roof surface temperatures, energy utilized for cooling/heating buildings, and the heat island effect. The substrate is a key component of the green roof that allows achieving these benefits. It is an artificial soil that has an improved behavior compared to natural soils, facilitating vegetation growth, water storage and typically with smaller densities to reduce the loads over the structures. Therefore, it is important to study the effects of substrate properties on green roof performance. The objective of this study is to investigate the physical properties of four substrates designed to improve the behavior of a green roof, and to study their impact on the efficiency of a green roof. The substrates that were investigated are: organic soil; crushed bricks; a mixture of mineral soil with perlite; and a mixture of crushed bricks and organic soil. The thermal properties (thermal conductivity, volumetric heat capacity and thermal diffusivity) were measured using a dual needle probe (Decagon Devices, Inc.) at different saturation levels, and the hydraulic properties were measured with a constant head permeameter (hydraulic conductivity) and a pressure plate extractor (water retention curve). This characterization, combined with numerical models, allows understanding the effect of these properties on the hydraulic and thermal behavior of a green roof. Results show that substrates composed by crushed bricks improve the thermal insulation of infrastructures and at the same time, retain more water in their pores. Simulation results also show that the hydraulic and thermal behavior of a green roof strongly depends on the moisture content prior to a rainstorm.

  13. Structural properties and gas sensing behavior of sol-gel grown nanostructured zinc oxide

    NASA Astrophysics Data System (ADS)

    Rajyaguru, Bhargav; Gadani, Keval; Rathod, K. N.; Solanki, Sapana; Kansara, S. B.; Pandya, D. D.; Shah, N. A.; Solanki, P. S.

    2016-05-01

    In this communication, we report the results of the studies on structural properties and gas sensing behavior of nanostructured ZnO grown using acetone precursor based modified sol-gel technique. Final product of ZnO was sintered at different temperatures to vary the crystallite size while their structural properties have been studied using X-ray diffraction (XRD) measurement performed at room temperature. XRD results suggest the single phasic nature of all the samples and crystallite size increases from 11.53 to 20.96nm with increase in sintering temperature. Gas sensing behavior has been studied for acetone gas which indicates that lower sintered samples are more capable to sense the acetone gas and related mechanism has been discussed in the light of crystallite size, crystal boundary density, defect mechanism and possible chemical reaction between gas traces and various oxygen species.

  14. Effect of γ-radiation on dynamic viscoelastic properties and thermal behavior for LDPE

    NASA Astrophysics Data System (ADS)

    Shuzhong, Li; Zhongda, He; Wanxi, Zhang

    1993-07-01

    The effect of γ-radiation on dynamic viscoelastic properties and thermal behavior for low density polyethylene(LDPE)have been investigated. The store energy modulus (E) of the samples increased after radiation. The β and α transition temperature shifted to higher temperature with increasing irradiation dose. The results of thermal analysis show that crystal melting temperature(Tm), enthalpy(ΔHm) and crystal disapperance temperature(Td) for irradiated samples decreases with increasing of dose.

  15. On the role of physiochemical properties on evaporation behavior of DISI biofuel sprays

    NASA Astrophysics Data System (ADS)

    Knorsch, Tobias; Heldmann, Markus; Zigan, Lars; Wensing, Michael; Leipertz, Alfred

    2013-06-01

    Biofuels and alternative fuels are increasingly being blended to conventional gasoline fuel to reduce the overall CO2 emissions. The effect on NOx and soot formation is still unclear as the atomization and evaporation of gasoline with biocomponents differ depending on fuel specific physiochemical properties. This work focuses on describing the biofuel evaporation behavior of gasoline sprays at homogeneous charge (early injection timing) and stratified-charge conditions (late injection timing mode) used in modern direct injection spark ignition engines (DISI). A spray plume of a 6-hole solenoid injector is analyzed in terms of liquid spray propagation, and local droplet sizes studied in an injection chamber. Depending on the operating conditions, different physiochemical properties are found to dominate the atomization and evaporation processes: For low and moderate ambient temperature and pressure, high-boiling point components show a strong influence on the spray droplet size distribution. However, at elevated temperature and pressure, the evaporation behavior changes completely. Due to a high degree of evaporation, the evaporation cooling effect dominates the local droplet sizes. Fuel mixtures owing a larger heat of vaporization show larger droplet sizes—even if these fuels have a lower boiling point. Depending on the local evaporation behavior, the different remaining droplet momentum in the spray controls the air entrainment and the subsequent progress of evaporation and mixing. Overall, it can be stated that the heat of vaporization is a dominating physiochemical property for the droplet evaporation rate at high-level supercharged conditions.

  16. Phase behavior and permeability properties of phospholipid bilayers containing a short-chain phospholipid permeability enhancer.

    PubMed

    Risbo, J; Jørgensen, K; Sperotto, M M; Mouritsen, O G

    1997-10-01

    The thermodynamic phase behavior and trans-bilayer permeability properties of multilamellar phospholipid vesicles containing a short-chain DC10PC phospholipid permeability enhancer have been studied by means of differential scanning calorimetry and fluorescence spectroscopy. The calorimetric scans of DC14PC lipid bilayer vesicles incorporated with high concentrations of DC10PC demonstrate a distinct influence on the lipid bilayer thermodynamics manifested as a pronounced freezing-point depression and a narrow phase coexistence region. Increasing amounts of DC10PC lead to a progressive lowering of the melting enthalpy, implying a mixing behavior of the DC10PC in the bilayer matrix similar to that of a substitutional impurity. The phase behavior of the DC10PC-DC14PC mixture is supported by fluorescence polarization measurements which, furthermore, in the low-temperature gel phase reveal a non-monotonic concentration-dependent influence on the structural bilayer properties; small concentrations of DC10PC induce a disordering of the acyl chains, whereas higher concentrations lead to an ordering. Irreversible fluorescence quench measurements demonstrate a substantial increase in the trans-bilayer permeability over broad temperature and composition ranges. At temperatures corresponding to the peak positions of the heat capacity, a maximum in the trans-bilayer permeability is observed. The influence of DC10PC on the lipid bilayer thermodynamics and the associated permeability properties is discussed in terms of microscopic effects on the lateral lipid organization and heterogeneity of the bilayer. PMID:9370247

  17. Refinement of elastic, poroelastic, and osmotic tissue properties of intervertebral disks to analyze behavior in compression.

    PubMed

    Stokes, Ian A F; Laible, Jeffrey P; Gardner-Morse, Mack G; Costi, John J; Iatridis, James C

    2011-01-01

    Intervertebral disks support compressive forces because of their elastic stiffness as well as the fluid pressures resulting from poroelasticity and the osmotic (swelling) effects. Analytical methods can quantify the relative contributions, but only if correct material properties are used. To identify appropriate tissue properties, an experimental study and finite element analytical simulation of poroelastic and osmotic behavior of intervertebral disks were combined to refine published values of disk and endplate properties to optimize model fit to experimental data. Experimentally, nine human intervertebral disks with adjacent hemi-vertebrae were immersed sequentially in saline baths having concentrations of 0.015, 0.15, and 1.5 M and the loss of compressive force at constant height (force relaxation) was recorded over several hours after equilibration to a 300-N compressive force. Amplitude and time constant terms in exponential force-time curve-fits for experimental and finite element analytical simulations were compared. These experiments and finite element analyses provided data dependent on poroelastic and osmotic properties of the disk tissues. The sensitivities of the model to alterations in tissue material properties were used to obtain refined values of five key material parameters. The relaxation of the force in the three bath concentrations was exponential in form, expressed as mean compressive force loss of 48.7, 55.0, and 140 N, respectively, with time constants of 1.73, 2.78, and 3.40 h. This behavior was analytically well represented by a model having poroelastic and osmotic tissue properties with published tissue properties adjusted by multiplying factors between 0.55 and 2.6. Force relaxation and time constants from the analytical simulations were most sensitive to values of fixed charge density and endplate porosity. PMID:20711754

  18. Behavioral screening measures delivered with a smartphone app: psychometric properties and user preference.

    PubMed

    Bush, Nigel E; Skopp, Nancy; Smolenski, Derek; Crumpton, Rosa; Fairall, Jonathan

    2013-11-01

    The smartphone is an increasingly widespread technological vehicle for general health and psychological health promotion, evaluation, education, and sometimes intervention. However, the psychometric performance of behavioral health screening measures has not been commonly evaluated for the new, small-format, touch-screen medium. Before mobile-based applications for behavioral health screening can be disseminated confidently, the reliability and the validity of measures administered by the smartphone must be evaluated. We compared psychometric properties (i.e., internal consistency and test-retest reliability) of seven behavioral health measures completed on paper, a computer, and an iPhone by 45 army soldiers. The results showed the internal consistencies of the smartphone-delivered measures to be equivalent and very high across all three modalities and the test-retest reliability of the iPhone measures also to be very high. Furthermore, completion of the behavioral screening measures by the iPhone was highly preferred over the other modalities and was reported to be easy and convenient. Our findings help corroborate the use of smartphones and other small mobile devices for behavioral health screening. PMID:24177488

  19. Mechanical Behavior of Agave Americana L. Fibres: Correlation Between Fine Structure and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Msahli, S.; Chaabouni, Y.; Sakli, F.; Drean, J. Y.

    In this study, results of a mechanical behavior study of fibres extracted from the agave Americana L. plant, the most abundant variety in Tunisia, are presented. These results deal with the principal and mechanical characteristics of these fibres which are the elongation at break, the elasticity modulus and the rupture facture. These results permitted to situate these fibres, compared to the other textile fibres, as materials that can be used in technical applications such as reinforcing composites or geotextile. In order to understand the mechanical properties of these fibres, a correlation study between the properties already cited and the fine structure was done. The obtained results showed that the mechanical properties of agave Americana L. fibres are closely related to the individual fibers deformations and to the natural matrix (lignin and gums) that links these elementary fibres.

  20. Role of differential physical properties in emergent behavior of 3D cell co-cultures

    NASA Astrophysics Data System (ADS)

    Kolbman, Dan; Das, Moumita

    2015-03-01

    The biophysics of binary cell populations is of great interest in many biological processes, whether the formation of embryos or the initiation of tumors. During these processes, cells are surrounded by other cell types with different physical properties, often with important consequences. For example, recent experiments on a co-culture of breast cancer cells and healthy breast epithelial cells suggest that the mechanical mismatch between the two cell types may contribute to enhanced migration of the cancer cells. Here we explore how the differential physical properties of different cell types may influence cell-cell interaction, aggregation, and migration. To this end, we study a proof of concept model- a three-dimensional binary system of interacting, active, and deformable particles with different physical properties such as elastic stiffness, contractility, and particle-particle adhesion, using Langevin Dynamics simulations. Our results may provide insights into emergent behavior such as segregation and differential migration in cell co-cultures in three dimensions.

  1. Behavior of grafted polymers on nanofillers and their influence on polymer nanocomposite properties

    NASA Astrophysics Data System (ADS)

    Dukes, Douglas Michael

    Polymer nanocomposites continue to receive wide-spread acclaim for their potential to improve composite materials beyond conventional macroscale fillers. The improvement lies both in the altered properties of the particle itself and in the interaction region surrounding the filler. As the surface area of the filler increases, a greater volume fraction of this interphase region is present in the composite. However, simply minimizing the particle size to maximize surface area introduces additional problems; the larger specific surface area promotes aggregation to reduce the surface energy. Since the composite's properties are largely tied to the morphology, aggregation prevents control over the dispersion state of the filler, and thus the properties. Therefore, disaggregation and morphology control are vital to achieving designable nanocomposites. To accomplish both tasks, this thesis focuses on the behavior of grafted polymer coatings on nanoparticles and their in uence on the macroscopic properties. Grafted chains play an integral role in both morphology control and reinforcement. To investigate the behavior of polymer brushes on nanoparticles, polystyrene was grafted on 15 nm silica particles at varying graft densities and molecular weights. Dynamic light scattering studies in dilute solution were performed to obtain the brush height as a function of both graft density and molecular weight. Three distinct regimes of behavior exist, the "mushroom", the semi-dilute polymer brush (SDPB), and the concentrated polymer brush (CPB) regimes. In the CPB regime, which is an extraordinary configuration of highly-stretched chains on densely grafted surfaces, the brush height h was found to scale as h ∝ N4/5, where N is the degree of polymerization. This result is contrary to the observed scaling of the CPB in flat interface systems, where h ∝ N1. To explore the behavior of grafted chains in the melt, molecular dynamics simulations were performed on grafted nanoparticles

  2. Rheological properties, gelling behavior and texture characteristics of polysaccharide from Enteromorpha prolifera.

    PubMed

    Qiao, Leke; Li, Yinping; Chi, Yongzhou; Ji, Yinglu; Gao, Yan; Hwang, Hueymin; Aker, Winfred G; Wang, Peng

    2016-01-20

    Polysaccharide from Enteromorpha prolifera (PE) which is the most common green algae is gradually becoming an attractive candidate with novel functions by virtue of its unique chemical and physicochemical properties. The infrared spectrum (FT-IR) of PE confirmed that it is a distinctive, sulfated heteropolysaccharide. Dynamic rheology was systematically conducted to investigate the effect of concentration, temperature, pH, and electrolytes on PE. The flow behavior testing verified its pseudoplastic character. A closed hysteresis loop was obtained when the PE concentration reached 10 g/L. For the phase angel (tanδ) was always less than 1, the solid-like behavior of PE is also found at 10-14 g/L PE in the linear viscoelastic region (LVR). Furthermore, study on its potential gelling behavior showed that 16 g/L PE could form a gel and had well textural properties. The unique functional groups and characteristics of PE provided the possibility to apply into food industry. PMID:26572475

  3. Mechanical properties and crystallization behavior of hydroxyapatite/poly(butylenes succinate) composites.

    PubMed

    Guo, Wenmin; Zhang, Yihe; Zhang, Wei

    2013-09-01

    Biodegradable synthetic polymers have attracted much attention nowadays, and more and more researches have been done on biodegradable polymers due to their excellent mechanical properties, biocompatibility, and biodegradability. In this work, hydroxyapatite (HA) particles were melt-mixing with poly (butylenes succinate) (PBS) to prepare the material, which could be used in the biomedical industry. To develop high-performance PBS for cryogenic engineering applications, it is necessary to investigate the cryogenic mechanical properties and crystallization behavior of HA/PBS composites. Cryogenic mechanical behaviors of the composites were studied in terms of tensile and impact strength at the glass transition temperature (-30°C) and compared to their corresponding behaviors at room temperature. With the increase of HA content, the crystallization of HA/PBS composites decreased and crystallization onset temperature shifted to a lower temperature. The diameter of spherulites increased at first and decreased with a further HA content. At the same time, the crystallization rate became slow when the HA content was no more than 15wt% and increased when HA content reached 20wt%. In all, the results we obtained demonstrate that HA/PBS composites reveal a better tensile strength at -30°C in contrast to the strength at room temperature. HA particles with different amount affect the crystallization of PBS in different ways. PMID:23348918

  4. Hydrodynamic behavior and dilute solution properties of Ulva fasciata algae polysaccharide.

    PubMed

    Shao, Ping; Zhu, Yueqiong; Qin, Minpu; Fang, Zhongxiang; Sun, Peilong

    2015-12-10

    Hydrodynamic behavior and dilute solution properties of Ulva fasciata polysaccharides (UFP) were investigated. Experimental results indicated that the variation of hydrodynamic behavior of UFP was affected by the type and concentration of salts. The specific viscosity of UFP in water increased with its increasing concentration. The slopes of the double logarithmic plots in the dilute and semi-dilute solutions were 0.86 and 1.99, respectively. The molecular conformation could be semi-flexible like. Huggins plots of UFP solutions in the presence of salts including Na(+), K(+), Mg(2+) and Ca(2+) showed that the hydrodynamic behavior of the UFP was strongly affected by the types and strength of salt ion. The stiffness parameter of UFP solution was 0.1149, higher than that of other reported polysaccharides, indicating that it could tolerate high salt concentration. Dynamic rheological results suggested that 0.5% UFP solution was a typical characteristic of polymer solution in the dilute region. This work provided some valuable and fundamental information in understanding the physicochemical properties of UFP solution. PMID:26428159

  5. Surface properties and corrosion behavior of Co-Cr alloy fabricated with selective laser melting technique.

    PubMed

    Xin, Xian-zhen; Chen, Jie; Xiang, Nan; Wei, Bin

    2013-01-01

    We sought to study the corrosion behavior and surface properties of a commercial cobalt-chromium (Co-Cr) alloy which was fabricated with selective laser melting (SLM) technique. For this purpose, specimens were fabricated using different techniques, such as SLM system and casting methods. Surface hardness testing, microstructure observation, surface analysis using X-ray photoelectron spectroscopy (XPS) and electrochemical corrosion test were carried out to evaluate the corrosion properties and surface properties of the specimens. We found that microstructure of SLM specimens was more homogeneous than that of cast specimens. The mean surface hardness values of SLM and cast specimens were 458.3 and 384.8, respectively; SLM specimens showed higher values than cast ones in hardness. Both specimens exhibited no differences in their electrochemical corrosion properties in the artificial saliva through potentiodynamic curves and EIS, and no significant difference via XPS. Therefore, we concluded that within the scope of this study, SLM-fabricated restorations revealed good surface properties, such as proper hardness, homogeneous microstructure, and also showed sufficient corrosion resistance which could meet the needs of dental clinics. PMID:23553145

  6. Unravelling merging behaviors and electrostatic properties of CVD-grown monolayer MoS2 domains.

    PubMed

    Hao, Song; Yang, Bingchu; Gao, Yongli

    2016-08-28

    The presence of grain boundaries is inevitable for chemical vapor deposition (CVD)-grown MoS2 domains owing to various merging behaviors, which greatly limits its potential applications in novel electronic and optoelectronic devices. It is therefore of great significance to unravel the merging behaviors of the synthesized polygon shape MoS2 domains. Here we provide systematic investigations of merging behaviors and electrostatic properties of CVD-grown polycrystalline MoS2 crystals by multiple means. Morphological results exhibit various polygon shape features, ascribed to polycrystalline crystals merged with triangle shape MoS2 single crystals. The thickness of triangle and polygon shape MoS2 crystals is identical manifested by Raman intensity and peak position mappings. Three merging behaviors are proposed to illustrate the formation mechanisms of observed various polygon shaped MoS2 crystals. The combined photoemission electron microscopy and kelvin probe force microscopy results reveal that the surface potential of perfect merged crystals is identical, which has an important implication for fabricating MoS2-based devices. PMID:27586938

  7. Flavin Derivatives with Tailored Redox Properties: Synthesis, Characterization, and Electrochemical Behavior.

    PubMed

    Kormányos, Attila; Hossain, Mohammad S; Ghadimkhani, Ghazaleh; Johnson, Joe J; Janáky, Csaba; de Tacconi, Norma R; Foss, Frank W; Paz, Yaron; Rajeshwar, Krishnan

    2016-06-27

    This study establishes structure-property relationships for four synthetic flavin molecules as bioinspired redox mediators in electro- and photocatalysis applications. The studied flavin compounds were disubstituted with polar substituents at the N1 and N3 positions (alloxazine) or at the N3 and N10 positions (isoalloxazines). The electrochemical behavior of one such synthetic flavin analogue was examined in detail in aqueous solutions of varying pH in the range from 1 to 10. Cyclic voltammetry, used in conjunction with hydrodynamic (rotating disk electrode) voltammetry, showed quasi-reversible behavior consistent with freely diffusing molecules and an overall global 2e(-) , 2H(+) proton-coupled electron transfer scheme. UV/Vis spectroelectrochemical data was also employed to study the pH-dependent electrochemical behavior of this derivative. Substituent effects on the redox behavior were compared and contrasted for all the four compounds, and visualized within a scatter plot framework to afford comparison with prior knowledge on mostly natural flavins in aqueous media. Finally, a preliminary assessment of one of the synthetic flavins was performed of its electrocatalytic activity toward dioxygen reduction as a prelude to further (quantitative) studies of both freely diffusing and tethered molecules on various electrode surfaces. PMID:27243969

  8. Iranian Version of Manchester Driving Behavior Questionnaire (MDBQ): Psychometric ‎Properties

    PubMed Central

    Alavi, Seyyed Salman; Mohammadi, Mohammadreza; Soori, Hamid; Mohammadi Kalhori, Soroush; Sepasi, Neda; Khodakarami, Rasoul; Farshchi, Mojtaba; Hasibi, Niloofar; Rostami, Soodabeh; Razi, Hadis; Babareisi, Mohammad

    2016-01-01

    Objective: Since the study of driving behavior is of great importance, we conducted this research to ‎investigate the psychometric properties and the factorial structure of the Manchester Driver ‎Behavior Questionnaire (DBQ) in Iranian drivers.‎ Method: This cross – sectional research was performed on a sample of 800 drivers (of category D and ‎C) aged 23- 75 who were referred to Imam Sajjad Centre for drug Addiction Diagnosis. ‎Manchester Driver Behavior Questionnaire (DBQ), a demographic questionnaire, were ‎conducted to the sample. To analyze data, we used factor analysis, internal consistency ‎‎(Cronbach's’α), split half, and test-retest using SPSS18 Software.‎ Results: As a result of reliability analysis and exploratory factor analysis by principal component and Varimax rotation, we extracted six factors (willful violations, unintentional errors, advertent errors, deliberate mistakes, unintentional violation, and unintentional mistakes, respectively). The factors reliability ranged from 0.65 to 0.75. The test-retest correlations of the DBQ and split- half reliability were 0.56 and 0.77, respectively. Conclusion: The results revealed that the Persian version of the DBQ in category D and C drivers is a ‎valid and reliable tool to assess driving behaviors in Iranian drivers.‎ PMID:27252767

  9. Structure, Thermal Properties, and Combustion Behavior of Plasma Synthesized Nano-Aluminum Powders

    NASA Astrophysics Data System (ADS)

    Pivkina, A.; Ivanov, D.; Frolov, Yu.; Mudretsova, S.; Schoonman, J.

    2006-08-01

    The plasma electro-condensation process was used to synthesize nano-sized aluminum powders. Adding different chemicals modified the physical and chemical properties of these powders. To characterize the nano-sized powders, X-ray diffraction, TEM, BET analyses, and simultaneous TG/DSC analyses were performed. TG/DSC analyses revealed a dramatic degradation of the aluminum oxide layer after storage of the aluminum powder in air for a period of several months. The burning rate of the model solid propellant with nano-sized aluminum was experimentally examined. The combustion behavior of nano-sized aluminum will be presented and will be compared with the combustion behavior of the micron-sized powders.

  10. Effects of lightweight fly ash aggregate properties on the behavior of lightweight concretes.

    PubMed

    Kockal, Niyazi Ugur; Ozturan, Turan

    2010-07-15

    Influence of different lightweight fly ash aggregates on the behavior of concrete mixtures was discussed. The performance characteristics of lightweight concretes (LWCs) and normalweight concrete (NWC) were investigated through compressive strength, modulus of elasticity and splitting tensile strength representing the mechanical behavior; through rapid chloride permeability representing the transport properties and through rapid freezing and thawing cycling representing the durability of concrete. In order to investigate the aggregate-cement paste interfacial transition zone (ITZ), SEM observations were performed. Regression and graphical analysis of the experimental data obtained were also performed. An increase in compressive strength was observed with the increase in oven-dry density. The ratios of splitting tensile strength to compressive strength of lightweight aggregate concretes were found to be similar to that of normalweight concrete. All the 28- and 56-day concrete specimens had a durability factor greater than 85 and 90, respectively, which met the requirement for freezing and thawing durability. PMID:20399557

  11. Development and psychometric properties of the health-risk behavior inventory for Chinese adolescents

    PubMed Central

    2012-01-01

    Background There is a growing body of research investigating adolescent risk behaviors in China, however, a comprehensive measure that evaluates the full spectrum of relevant risk behaviors is lacking. In order to address this important gap, the current study sought to develop and validate a comprehensive tool: the Health-Risk Behavior Inventory for Chinese Adolescents (HBICA). Methods Adolescents, ages 14–19 years (n = 6,633), were recruited from high schools across 10 cities in mainland China. In addition, a clinical sample, which included 326 adolescents meeting DSM-IV criteria for Conduct Disorder, was used to evaluate predictive validity of the HBICA. Psychometric properties including internal consistency (Cronbach’s alpha), test-retest reliability, convergent validity, and predictive validity were analyzed. Results Based upon item analysis and exploratory factor analysis, we retained 33 items, and 5 factors explained 51.75% of the total variance: Suicide and Self-Injurious Behaviors (SS), Aggression and Violence (AV), Rule Breaking (RB), Substance Use (SU), and Unprotected Sex (US). Cronbach’s alphas were good, from 0.77 (RB) to 0.86 (US) for boys, and from 0.74 (SD) to 0.83(SS) for girls. The 8 weeks test–retest reliabilities were moderate, ranged from 0.66 (AV) to 0.76 (SD). External validities was strong, with Barratt Impulsiveness Scale-11 was 0.35 (p < 0.01), and with aggressive behavior and rule-breaking behavior subscales of the Youth Self Report were 0.54 (p < 0.01) and 0.68 (p < 0.01), respectively. Predictive validity analysis also provided enough discriminantity, which can distinguish high risky individual effectively (cohen’ d = 0.79 – 2.96). Conclusions These results provide initial support for the reliability and validity of the Health-Risk Behavior Inventory for Chinese Adolescents (HBICA) as a comprehensive and developmentally appropriate assessment instrument for risk behaviors in Chinese adolescents. PMID

  12. Determination of hydration properties and thermal behavior of Paecilomyces variotii by differential scanning calorimetry.

    PubMed

    Canel, R S; Ludemann, V; De La Osa, O; Wagner, J R

    2013-01-01

    Due to the structure and the composition of Paecilomyces variotii, the mycelia of this fungus could have potential applications as ingredients in wettable foods. For this use, drying could be employed, justifying the study of thermal behavior of P. variotii. The objectives of this work were to perform a study of thermal behavior of P. variotii isolates, to evaluate the hydration properties of these mycelia and to analyze the effect of different technological parameters on the latter properties. Wet cultures exhibited a wide endothermic transition, with mean values of peak temperature of 61 degrees C and denaturation enthalpy of4 J/g dry matter. Initial (50 degrees C) and final (80 degrees C) temperatures of the endothermic transition were used to dry the mycelia. Freeze-drying was also assayed. For all dried mycelia, a decrease in denaturation enthalpy between 40 and 50% was observed for drying at 50 degrees C and freeze-drying, and a drastic decrease of almost 100% for drying at 80 degrees C. According to the hydration properties, wet mycelia exhibited water holding capacity (WHC) value of 45 g water/g dry matter. Significant differences among dried mycelia, resulting WHC values in order: 50 degrees C > freeze-dried > 80 degrees C (p < 0.05) were revealed for each P. variotii strain. Fungi obtained by drying at 50 degrees C and by freeze-drying, showed a rapid water absorption (t(1/2) < 0.1 min). Ionic strength, pH and particle size of dried mycelia influenced the hydration properties. PMID:25507782

  13. Starch behaviors and mechanical properties of starch blend films with different plasticizers.

    PubMed

    Nguyen Vu, Hoang Phuong; Lumdubwong, Namfone

    2016-12-10

    The main objective of the study was to gain insight into structural and mechanical starch behaviors of the plasticized starch blend films. Mechanical properties and starch behaviors of cassava (CS)/and mungbean (MB) (50/50, w/w) starch blend films containing glycerol (Gly) or sorbitol (Sor) at 33% weight content were investigated. It was found that tensile strength TS and %E of the Gly-CSMB films were similar to those of MB films; but%E of all Sor-films was identical. TS of plasticized films increased when AM content and crystallinity increased. When Sor was substituted for Gly, crystallinity of starch films and their TS increased. The CSMB and MB films had somewhat a similar molecular profile and comparable mechanical properties. Therefore, it was proposed the starch molecular profile containing amylopectin with high M¯w, low M¯w of amylose, and the small size of intermediates may impart the high TS and%E of starch films. PMID:27577902

  14. Mechanical Properties and Fracture Behavior of Directionally Solidified NiAl-V Eutectic Composites

    NASA Astrophysics Data System (ADS)

    Milenkovic, Srdjan; Caram, Rubens

    2015-02-01

    Directional solidification of eutectic alloys has been recognized as promising technique for producing in situ composite materials exhibiting balance of properties. Therefore, an in situ NiAl-V eutectic composite has been successfully directionally solidified using Bridgman technique. The mechanical behavior of the composite including fracture resistance, microhardness, and compressive properties at room and elevated temperatures was investigated. Damage evolution and fracture characteristics were also discussed. The obtained results indicate that the NiAl-V eutectic retains high yield strength up to 1073 K (800 °C), above which there is a rapid decrease in strength. Its yield strength is higher than that of binary NiAl and most of the NiAl-based eutectics. The exhibited fracture toughness of 28.5 MPa√m is the highest of all other NiAl-based systems investigated so far. The material exhibited brittle fracture behavior of transgranular type and all observations pointed out that the main fracture micromechanism was cleavage.

  15. Polymerization Behavior and Polymer Properties of Eosin-Mediated Surface Modification Reactions.

    PubMed

    Avens, Heather J; Randle, Thomas James; Bowman, Christopher N

    2008-10-17

    Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eight fold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from 5-fold lower eosin surface densities (2.8 vs. 14 eosins/µm(2)) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities. PMID:19838291

  16. Polymerization Behavior and Polymer Properties of Eosin-Mediated Surface Modification Reactions

    PubMed Central

    Avens, Heather J.; Randle, Thomas James; Bowman, Christopher N.

    2008-01-01

    Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eight fold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from 5-fold lower eosin surface densities (2.8 vs. 14 eosins/µm2) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities. PMID:19838291

  17. Synthesis, Sintering Behavior, Structure, and Electrical Properties of 5YSZ Electrolyte

    NASA Astrophysics Data System (ADS)

    Xia, Jinfeng; Nian, Hongqiang; Liu, Wei; Xu, Haifang; Jiang, Danyu

    2015-09-01

    In some applications, such as automotive oxygen sensors, 5 mol% Y2O3-stabilized zirconia (5YSZ) is generally used because its ionic conductivity and mechanical properties are excellent. In this study, fine 5YSZ powders, which contain only small aggregates with particle sizes in the 40-60 nm range, were prepared by a hydrolysis-hydrothermal method. Powder calcination behavior, ceramic sintering behavior, microstructure, and conductivity were studied. This research proved that the calcination temperature has a great influence on the size and phase composition of the powder. The sintering temperature of the 5YSZ ceramic significantly affected its final grain size and density. The results show that a powder pre-treatment temperature of 1100 °C and a sintering temperature of 1350 °C for 2 h can produce excellent 5YSZ ceramics. The grain size and microstructure of 5YSZ ceramics influence the bulk resistance, grain resistance, and grain boundary resistance; the value of grain resistance decreased and grain boundary resistance increased with increasing grain size and sintering temperature. Considering all aspects of the grain size, conductivity, density, and mechanical properties, the optimal sintering temperature was found to be 1350 °C. The highest value measured for conductivity was about 2.79 × 10-3 S/cm, measured at 700 °C.

  18. Phase behavior, structure, and properties of colloidal microsphere-nanoparticle mixtures

    NASA Astrophysics Data System (ADS)

    Tohver, Valeria

    2001-10-01

    We have studied the phase behavior, structure and properties of binary mixtures of negligibly charged colloidal microspheres and highly repulsive nanoparticles. The interactions between such species were investigated via scanning angle reflectometry, zeta potential measurements, and sedimentation studies. At pH < 3, the nanoparticles are highly charged with an estimated zeta potential of 65 mV and the colloidal microspheres are negligibly charged with a measured zeta potential of roughly 1 mV. Under these conditions, scanning angle reflectometry measurements indicated no nanoparticle adsorption occurs on model silica surfaces (i.e., oxidized silicon wafers). However, zeta potential measurements carried out on dilute microsphere suspensions revealed that these microspheres exhibited an effective charge buildup as a function of nanoparticle volume fraction at pH = 1.5. This behavior which we refer to as nanoparticle haloing can stem solely from their repulsive interactions in solution and has a profound effect on the phase behavior, structure and properties of these binary mixtures. The phase behavior, structure, and properties of binary mixtures of negligibly charged colloidal microspheres were studied for two size ratios of 95 and 197 at pH = 1.5. In the absence of nanoparticle additions, the system spontaneously assembled into a colloidal gel whose strength increased with microsphere volume fraction. Between a lower and upper critical nanoparticle volume fraction, such binary mixtures formed a stable fluid phase due to nanoparticle haloing. In this concentration regime, colloidal microsphere crystals could be assembled under gravity-driven sedimentation. Confocal microscopy revealed that such crystals exhibited a center-to-center microsphere separation distance of 2 amusphere, where amusphere is the microsphere radius. Above the upper critical nanoparticle volume fraction, depletion flocculation induced by the presence of highly charged nanoparticles in solution

  19. 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…

  20. Understanding about How Different Foaming Gases Effect the Interfacial Array Behaviors of Surfactants and the Foam Properties.

    PubMed

    Sun, Yange; Qi, Xiaoqing; Sun, Haoyang; Zhao, Hui; Li, Ying

    2016-08-01

    In this paper, the detailed behaviors of all the molecules, especially the interfacial array behaviors of surfactants and diffusion behaviors of gas molecules, in foam systems with different gases (N2, O2, and CO2) being used as foaming agents were investigated by combining molecular dynamics simulation and experimental approaches for the purpose of interpreting how the molecular behaviors effect the properties of the foam and find out the key factors which fundamentally determine the foam stability. Sodium dodecyl sulfate SDS was used as the foam stabilizer. The foam decay and the drainage process were determined by Foamscan. A texture analyzer (TA) was utilized to measure the stiffness and viscoelasticity of the foam films. The experimental results agreed very well with the simulation results by which how the different gas components affect the interfacial behaviors of surfactant molecules and thereby bring influence on foam properties was described. PMID:27434752

  1. The dielectric behavior of perovskite-related manganese oxides with stretched bonds or multiferroic properties

    NASA Astrophysics Data System (ADS)

    Denyszyn, Jonathan Charles

    This dissertation presents two investigations into the dielectric behavior of non-d0 perovskite-related manganese oxides: the first investigation probes the unique multiferroic properties of the hexagonal-perovskite series RMn1-xGaxO3 (R = Y, Ho) and the second explores the importance of lattice stress and the effect of the metal-cation d n-character on the dielectric properties of the perovskite series SryCa1-yMn1-xBxO3-delta (B = Ti, Zr). In the hexagonal-perovskite series, doping the Mn-site with Ga increased the c lattice constant and diluted the magnetic interactions in the ab plane. The interplay of these two effects perturbed the ferrielectric, antiferromagnetic, and multiferroic interactions. The change in these interactions demonstrated chemical control of the multiferroic interactions in the hexagonal-perovskite system for the first time and highlighted the structural mechanism behind the multiferroic properties. In the second investigation, the relationship between the tensile stress on the (Mn--O) bond and the ionic dielectric constant of SryCa 1-yMnO3-delta proved difficult to quantify because the small band gap and chemical activity of the Mn4+ cation made samples with y ≥ 0.5 too conducting to measure the dielectric relaxations. To explore the ionic contribution to the dielectric behavior by an alternate path, a doping scheme was devised to decrease the sample conductivity of SrMnO 3-delta at the expense of some of the tensile stress on the (Mn--O) bond. Doping the Mn site with larger 4+ cations (Ti and Zr) reduced the dielectric constant; however, the reduction of the dielectric constant cannot be explained by the effect of the tensile stress on the (Mn--O) bond alone.

  2. Mechanical properties and failure behaviors of the interface of hybrid graphene/hexagonal boron nitride sheets

    PubMed Central

    Ding, Ning; Chen, Xiangfeng; Wu, Chi-Man Lawrence

    2016-01-01

    Hybrid graphene/h-BN sheet has been fabricated recently and verified to possess unusual physical properties. During the growth process, defects such as vacancies are unavoidably present at the interface between graphene and h-BN. In the present work, typical vacancy defects, which were located at the interface between graphene and h-BN, were studied by density functional theory. The interface structure, mechanical and electronic properties, and failure behavior of the hybrid graphene/h-BN sheet were investigated and compared. The results showed that the formation energy of the defective graphene/h-BN interface basically increased with increasing inflection angles. However, Young’s modulus for all graphene/h-BN systems studied decreased with the increase in inflection angles. The intrinsic strength of the hybrid graphene/h-BN sheets was affected not only by the inflection angles, but also by the type of interface connection and the type of defects. The energy band structure of the hybrid interface could be tuned by applying mechanical strain to the systems. These results demonstrated that vacancies introduced significant effects on the mechanical and electronic properties of the hybrid graphene/h-BN sheet. PMID:27527371

  3. The Effect of Cerium Oxide Addition on the Properties and Behavior of Y-TZP

    PubMed Central

    Ragurajan, D.; Satgunam, M.; Golieskardi, M.

    2014-01-01

    The effects of CeO2 addition on the sintering behavior and mechanical properties of Y-TZP have been investigated over a wide sintering regime by pressureless sintering. It has been revealed that small additions of CeO2 (0.3–1.0 wt%) to Y-TZP were beneficial in enhancing the mechanical properties and hydrothermal ageing resistance of Y-TZP. Sintered samples were used to evaluate the bulk density, Vickers's hardness, Young's modulus, and fracture toughness of the material. CeO2 doped Y-TZPs were sintered at relatively low temperatures (1250°C and 1350°C) retaining high bulk density (>97% of theoretical density) and high Young's modulus (>200 GPa) without sacrificing tetragonal phase stability. The optimum level of dopant was found to be at 0.5 wt% for sintering between 1250°C and 1450°C using the standard 2 h holding time cycle, with sintered body exhibiting excellent combination of properties when compared to the undoped ceramics. In this experiment, the addition of 0.5 wt% recorded a bulk density reading of 5.9 g/cm3, Vickers hardness value of 13.2 GPa, Young's modulus value of 211 GPa, and fracture toughness of 6.4 MPam1/2, respectively, in a temperature range of 1400–1450°C.

  4. Corrosion behavior and mechanical properties of bioactive sol-gel coatings on titanium implants.

    PubMed

    Catauro, M; Bollino, F; Papale, F; Giovanardi, R; Veronesi, P

    2014-10-01

    Organic-inorganic hybrid coatings based on zirconia and poly (ε-caprolactone) (PCL) were prepared by means of sol-gel dip-coating technique and used to coat titanium grade 4 implants (Ti-4) in order to improve their wear and corrosion resistance. The coating chemical composition has been analysed by ATR-FTIR. The influence of the PCL amount has been investigated on the microstructure, mechanical properties of the coatings and their ability to inhibit the corrosion of titanium. SEM analysis has shown that all coatings have a nanostructured nature and that the films with high PCL content are crack-free. Mechanical properties of the coatings have been studied using scratch and nano-indentation tests. The results have shown that the Young's modulus of the coatings decreases in presence of large amounts of the organic phase, and that PCL content affects also the adhesion of the coatings to the underlying Ti-4 substrate. However, the presence of cracks on the PCL-free coatings affects severely the mechanical response of the samples at high loads. The electrochemical behavior and corrosion resistance of the coated and uncoated substrate has been investigated by polarization tests. The results have shown that both the coatings with or without PCL don't affect significantly the already excellent passivation properties of titanium. PMID:25175226

  5. Mechanical properties and failure behaviors of the interface of hybrid graphene/hexagonal boron nitride sheets.

    PubMed

    Ding, Ning; Chen, Xiangfeng; Wu, Chi-Man Lawrence

    2016-01-01

    Hybrid graphene/h-BN sheet has been fabricated recently and verified to possess unusual physical properties. During the growth process, defects such as vacancies are unavoidably present at the interface between graphene and h-BN. In the present work, typical vacancy defects, which were located at the interface between graphene and h-BN, were studied by density functional theory. The interface structure, mechanical and electronic properties, and failure behavior of the hybrid graphene/h-BN sheet were investigated and compared. The results showed that the formation energy of the defective graphene/h-BN interface basically increased with increasing inflection angles. However, Young's modulus for all graphene/h-BN systems studied decreased with the increase in inflection angles. The intrinsic strength of the hybrid graphene/h-BN sheets was affected not only by the inflection angles, but also by the type of interface connection and the type of defects. The energy band structure of the hybrid interface could be tuned by applying mechanical strain to the systems. These results demonstrated that vacancies introduced significant effects on the mechanical and electronic properties of the hybrid graphene/h-BN sheet. PMID:27527371

  6. In vitro biodegradation behavior, mechanical properties, and cytotoxicity of biodegradable Zn-Mg alloy.

    PubMed

    Gong, Haibo; Wang, Kun; Strich, Randy; Zhou, Jack G

    2015-11-01

    Zinc-Magnesium (Zn-Mg) alloy as a novel biodegradable metal holds great potential in biodegradable implant applications as it is more corrosion resistant than Magnesium (Mg). However, the mechanical properties, biodegradation uniformity, and cytotoxicity of Zn-Mg alloy remained as concerns. In this study, hot extrusion process was applied to Zn-1 wt % Mg (Zn-1Mg) to refine its microstructure. Effects of hot extrusion on biodegradation behavior and mechanical properties of Zn-1Mg were investigated in comparison with Mg rare earth element alloy WE43. Metallurgical analysis revealed significant grain size reduction, and immersion test found that corrosion rates of WE43 and Zn-1Mg were reduced by 35% and 57%, respectively after extrusion. Moreover, hot extrusion resulted in a much more uniform biodegradation in extruded Zn-1Mg alloy and WE43. In vitro cytotoxicity test results indicated that Zn-1Mg alloy was biocompatible. Therefore, hot extruded Zn-1Mg with homogenous microstructure, uniform as well as slow degradation, improved mechanical properties, and good biocompatibility was believed to be an excellent candidate material for load-bearing biodegradable implant application. PMID:25581552

  7. Sintering behavior and mechanical properties of zirconia compacts fabricated by uniaxial press forming

    PubMed Central

    Oh, Gye-Jeong; Yun, Kwi-Dug; Lee, Kwang-Min; Lim, Hyun-Pil

    2010-01-01

    PURPOSE The purpose of this study was to compare the linear sintering behavior of presintered zirconia blocks of various densities. The mechanical properties of the resulting sintered zirconia blocks were then analyzed. MATERIALS AND METHODS Three experimental groups of dental zirconia blocks, with a different presintering density each, were designed in the present study. Kavo Everest® ZS blanks (Kavo, Biberach, Germany) were used as a control group. The experimental group blocks were fabricated from commercial yttria-stabilized tetragonal zirconia powder (KZ-3YF (SD) Type A, KCM. Corporation, Nagoya, Japan). The biaxial flexural strengths, microhardnesses, and microstructures of the sintered blocks were then investigated. The linear sintering shrinkages of blocks were calculated and compared. RESULTS Despite their different presintered densities, the sintered blocks of the control and experimental groups showed similar mechanical properties. However, the sintered block had different linear sintering shrinkage rate depending on the density of the presintered block. As the density of the presintered block increased, the linear sintering shrinkage decreased. In the experimental blocks, the three sectioned pieces of each block showed the different linear shrinkage depending on the area. The tops of the experimental blocks showed the lowest linear sintering shrinkage, whereas the bottoms of the experimental blocks showed the highest linear sintering shrinkage. CONCLUSION Within the limitations of this study, the density difference of the presintered zirconia block did not affect the mechanical properties of the sintered zirconia block, but affected the linear sintering shrinkage of the zirconia block. PMID:21165274

  8. Examination of the Addictive and Behavioral Properties of Fatty Acid-Binding Protein Inhibitor SBFI26.

    PubMed

    Thanos, Panayotis K; Clavin, Brendan H; Hamilton, John; O'Rourke, Joseph R; Maher, Thomas; Koumas, Christopher; Miao, Erick; Lankop, Jessenia; Elhage, Aya; Haj-Dahmane, Samir; Deutsch, Dale; Kaczocha, Martin

    2016-01-01

    The therapeutic properties of cannabinoids have been well demonstrated but are overshadowed by such adverse effects as cognitive and motor dysfunction, as well as their potential for addiction. Recent research on the natural lipid ligands of cannabinoid receptors, also known as endocannabinoids, has shed light on the mechanisms of intracellular transport of the endocannabinoid anandamide by fatty acid-binding proteins (FABPs) and subsequent catabolism by fatty acid amide hydrolase. These findings facilitated the recent development of SBFI26, a pharmacological inhibitor of epidermal- and brain-specific FABP5 and FABP7, which effectively increases anandamide signaling. The goal of this study was to examine this compound for any possible rewarding and addictive properties as well as effects on locomotor activity, working/recognition memory, and propensity for sociability and preference for social novelty (SN) given its recently reported anti-inflammatory and analgesic properties. Male C57BL mice were split into four treatment groups and conditioned with 5.0, 20.0, 40.0 mg/kg SBFI26, or vehicle during a conditioned place preference (CPP) paradigm. Following CPP, mice underwent a battery of behavioral tests [open field, novel object recognition (NOR), social interaction (SI), and SN] paired with acute SBFI26 administration. Results showed that SBFI26 did not produce CPP or conditioned place aversion regardless of dose and did not induce any differences in locomotor and exploratory activity during CPP- or SBFI26-paired open field activity. We also observed no differences between treatment groups in NOR, SI, and SN. In conclusion, as SBFI26 was shown previously by our group to have significant analgesic and anti-inflammatory properties, here we show that it does not pose a risk of dependence or motor and cognitive impairment under the conditions tested. PMID:27092087

  9. Examination of the Addictive and Behavioral Properties of Fatty Acid-Binding Protein Inhibitor SBFI26

    PubMed Central

    Thanos, Panayotis K.; Clavin, Brendan H.; Hamilton, John; O’Rourke, Joseph R.; Maher, Thomas; Koumas, Christopher; Miao, Erick; Lankop, Jessenia; Elhage, Aya; Haj-Dahmane, Samir; Deutsch, Dale; Kaczocha, Martin

    2016-01-01

    The therapeutic properties of cannabinoids have been well demonstrated but are overshadowed by such adverse effects as cognitive and motor dysfunction, as well as their potential for addiction. Recent research on the natural lipid ligands of cannabinoid receptors, also known as endocannabinoids, has shed light on the mechanisms of intracellular transport of the endocannabinoid anandamide by fatty acid-binding proteins (FABPs) and subsequent catabolism by fatty acid amide hydrolase. These findings facilitated the recent development of SBFI26, a pharmacological inhibitor of epidermal- and brain-specific FABP5 and FABP7, which effectively increases anandamide signaling. The goal of this study was to examine this compound for any possible rewarding and addictive properties as well as effects on locomotor activity, working/recognition memory, and propensity for sociability and preference for social novelty (SN) given its recently reported anti-inflammatory and analgesic properties. Male C57BL mice were split into four treatment groups and conditioned with 5.0, 20.0, 40.0 mg/kg SBFI26, or vehicle during a conditioned place preference (CPP) paradigm. Following CPP, mice underwent a battery of behavioral tests [open field, novel object recognition (NOR), social interaction (SI), and SN] paired with acute SBFI26 administration. Results showed that SBFI26 did not produce CPP or conditioned place aversion regardless of dose and did not induce any differences in locomotor and exploratory activity during CPP- or SBFI26-paired open field activity. We also observed no differences between treatment groups in NOR, SI, and SN. In conclusion, as SBFI26 was shown previously by our group to have significant analgesic and anti-inflammatory properties, here we show that it does not pose a risk of dependence or motor and cognitive impairment under the conditions tested. PMID:27092087

  10. Development of methacrylate/silorane hybrid monomer system: Relationship between photopolymerization behavior and dynamic mechanical properties.

    PubMed

    Song, Linyong; Ye, Qiang; Ge, Xueping; Singh, Viraj; Misra, Anil; Laurence, Jennifer S; Berrie, Cindy L; Spencer, Paulette

    2016-07-01

    Resin chemistries for dental composite are evolving as noted by the introduction of silorane-based composites in 2007. This shift in the landscape from methacrylate-based composites has fueled the quest for versatile methacrylate-silorane adhesives. The objective of this study was to evaluate the polymerization behavior and structure/property relationships of methacrylate-silorane hybrid systems. Amine compound ethyl-4-(dimethylamino) benzoate (EDMAB) or silane compound tris(trimethylsilyl) silane (TTMSS) was selected as coinitiators. The mechanical properties of the copolymer were improved significantly at low concentrations (15, 25, or 35 wt %) of silorane when EDMAB was used as coinitiator. The rubbery moduli of these experimental copolymers were increased by up to 260%, compared with that of the control (30.8 ± 1.9 MPa). Visible phase separation appeared in these formulations if the silorane concentrations in the formulations were 50-75 wt %. The use of TTMSS as coinitiator decreased the phase separation, but there was a concomitant decrease in mechanical properties. In the neat methacrylate formulations, the maximum rates of free-radical polymerization with EDMAB or TTMSS were 0.28 or 0.06 s(-1) , respectively. In the neat silorane resin, the maximum rates of cationic ring-opening polymerization with EDMAB or TTMSS were 0.056 or 0.087 s(-1) , respectively. The phase separation phenomenon may be attributed to differences in the rates of free-radical polymerization of methacrylates and cationic ring-opening polymerization of silorane. In the hybrid systems, free-radical polymerization initiated with EDMAB led to higher crosslink density and better mechanical properties under dry/wet conditions. These beneficial effects were, however, associated with an increase in heterogeneity in the network structure. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 841-852, 2016. PMID:25953619

  11. Magnetic property and possible half-metal behavior in Co-doped graphene

    SciTech Connect

    Li, Zhongyao Xie, Wenze; Liu, Xingen; Wu, Yong

    2015-02-28

    The magnetic property and band structures of Co-monolayer doped graphene were examined on the basis of density-functional theory. The magnetic moment of the system is closely related to the interfacial spacing. Magnetic-nonmagnetic transition would be produced by decreasing the layer distance. Although the magnetic moment can also be reduced by increasing the lattice constant, the ground states are magnetic states under tension. Besides, the increase of lattice constant greatly enlarges the direct and indirect gaps of spin-down bands near the Fermi level. With a little increase of the Fermi level or the electron density, half-metal behavior would be expectable in the Co-doped graphene under tension.

  12. Thermal properties and crystallization behavior of thermoplastic starch/poly(ɛ-caprolactone) composites.

    PubMed

    Cai, Jie; Xiong, Zhouyi; Zhou, Man; Tan, Jun; Zeng, Fanbing; Meihuma; Lin, Shun; Xiong, Hanguo

    2014-02-15

    TPS/PCL composites were prepared by PCL melt blending with modified corn starch. The structure, thermal properties, morphology and crystallization behavior of these composites were investigated by FTIR, TGA, SEM, XRD and DSC. FTIR confirmed the existence of the interaction between PCL and TPS, whereas TGA showed that the thermal stability was decreased by the addition of TPS. Meanwhile, SEM showed a weak interfacial adhesion with increasing TPS. According to the Avrami theory, TPS functioned as a nucleating agent to improve the crystallinity rate of PCL. However, the XRD analysis revealed that the crystallinity decreased. At the same time, the ΔE(a) of the composites was higher than those of neat PCL. These changes in values all indicated that mobility constraints existed in the PCL chains with the increasing of TPS, which leaded to a drop in the crystallization ability of PCL. PMID:24507343

  13. Structural, electronic, mechanical, and transport properties of phosphorene nanoribbons: Negative differential resistance behavior

    NASA Astrophysics Data System (ADS)

    Maity, Ajanta; Singh, Akansha; Sen, Prasenjit; Kibey, Aniruddha; Kshirsagar, Anjali; Kanhere, Dilip G.

    2016-08-01

    Structural, electronic, mechanical, and transport properties of two different types of phosphorene nanoribbons are calculated within the density functional theory and nonequilibrium Green's function formalisms. Armchair nanoribbons turn out to be semiconductors at all widths considered. Zigzag nanoribbons are metallic in their layer-terminated structure, but undergo Peierls-like transition at the edges. Armchair nanoribbons have smaller Young's modulus compared to a monolayer, while zigzag nanoribbons have larger Young's modulus. Edge reconstruction further increases the Young's modulus of zigzag nanoribbons. A two-terminal device made of zigzag nanoribbons show negative differential resistance behavior that is robust with respect to edge reconstruction. We have also calculated the I -V characteristics for two nonzero gate voltages. The results show that the zigzag nanoribbons display strong p -type character.

  14. Cell Attachment Behavior on Solid and Fluid Substrates Exhibiting Spatial Patterns of Physical Properties

    PubMed Central

    Oliver, Ann E.; Ngassam, Viviane; Dang, Phuong; Sanii, Babak; Wu, Huawen; Yee, Chanel K.; Yeh, Yin; Parikh, Atul N.

    2009-01-01

    The ability to direct proliferation and growth of living cells using chemically and topologically textured surfaces is finding many niche applications, both in fundamental biophysical investigations of cell-surface attachment as well as in developing design principles for many tissue engineering applications. Here we address cellular adhesion behavior on solid patterns of differing wettability (a static substrate) and fluid patterns of membrane topology (a dynamic substrate). We find striking differences in the cellular adhesion characteristics of lipid mono- and bilayers, despite their essentially identical surface chemical and structural character. These differences point to the importance of subtle variations in the physical properties of the lipid mono- and bilayers (e.g., membrane tension and out-of-plane undulations). Furthermore, we find that introducing phosphatidylserine into the patterned lipidic substrates causes a loss of cell-patterning capability. Implications of this finding for the mechanism by which phosphatidylserine promotes cellular adhesion are discussed. PMID:19453187

  15. Rheological behavior and cryogenic properties of cyanate ester/epoxy insulation material for fusion superconducting magnet

    NASA Astrophysics Data System (ADS)

    Wu, Z. X.; Li, L. F.; Li, J. W.; Huang, C. J.; Tan, R.; Tu, Y. P.

    2014-01-01

    In a Tokamak fusion reactor device like ITER, insulation materials for superconducting magnets are usually fabricated by a vacuum pressure impregnation (VPI) process. Thus these insulation materials must exhibit low viscosity, long working life as well as good radiation resistance. Previous studies have indicated that cyanate ester (CE) blended with epoxy has an excellent resistance against neutron irradiation which is expected to be a candidate insulation material for a fusion magnet. In this work, the rheological behavior of a CE/epoxy (CE/EP) blend containing 40% CE was investigated with non-isothermal and isothermal viscosity experiments. Furthermore, the cryogenic mechanical and electrical properties of the composite were evaluated in terms of interlaminar shear strength and electrical breakdown strength. The results showed that CE/epoxy blend had a very low viscosity and an exceptionally long processing life of about 4 days at 60 °C.

  16. Rheological behavior and cryogenic properties of cyanate ester/epoxy insulation material for fusion superconducting magnet

    SciTech Connect

    Wu, Z. X.; Huang, C. J.; Li, L. F.; Li, J. W.; Tan, R.; Tu, Y. P.

    2014-01-27

    In a Tokamak fusion reactor device like ITER, insulation materials for superconducting magnets are usually fabricated by a vacuum pressure impregnation (VPI) process. Thus these insulation materials must exhibit low viscosity, long working life as well as good radiation resistance. Previous studies have indicated that cyanate ester (CE) blended with epoxy has an excellent resistance against neutron irradiation which is expected to be a candidate insulation material for a fusion magnet. In this work, the rheological behavior of a CE/epoxy (CE/EP) blend containing 40% CE was investigated with non-isothermal and isothermal viscosity experiments. Furthermore, the cryogenic mechanical and electrical properties of the composite were evaluated in terms of interlaminar shear strength and electrical breakdown strength. The results showed that CE/epoxy blend had a very low viscosity and an exceptionally long processing life of about 4 days at 60 °C.

  17. Thixoforming of an ECAPed Aluminum A356 Alloy: Microstructure Evolution, Rheological Behavior, and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Campo, Kaio Niitsu; Zoqui, Eugênio José

    2016-04-01

    Thixoforming depends upon three aspects: (a) solid to liquid transformation; (b) size and morphology of the remaining solid phase in the semisolid state, and (c) the effect of both input factors on rheology of the semisolid slurry. The aluminum A356 alloy presents an ideal solid to liquid transformation, but the solidification process generates coarse aluminum dendrites surrounded by eutectic. In this regard, Equal Channel Angular Pressing (ECAP) has great potential as a method for manufacturing thixotropic raw material due to its grain refining effect. Therefore, the microstructure evolution and rheological behavior in the semisolid state of an ECAPed aluminum A356 alloy were investigated. Samples were heated up to 853 K (580 °C) and held for 0, 30, 60, 90, 210, and 600 seconds at this temperature. The isothermal heat treatment caused the globularization of the solid phase without any significant microstructure coarsening. Compression tests were carried out at the same temperature and holding times using an instrumented mechanical press. Apparent viscosities values close to 250 Pa s were obtained, revealing the exceptional rheological behavior of the produced samples. The thixoformed material also presented good mechanical properties, with high yield and ultimate tensile strength values (YS = 110/122 MPa, UTS = 173/202), and good ductility (E = 6.9/7.5 pct). These results indicate that the production of the A356 alloy via the ECAP process increases its thixoformability.

  18. Effect of filler surface properties on stress relaxation behavior of carbon nanofiber/polyurethane nanocomposites

    NASA Astrophysics Data System (ADS)

    Sedat Gunes, I.; Jimenez, Guillermo; Jana, Sadhan

    2009-03-01

    The effect of carbon nanofiber (CNF) surface properties on tensile stress relaxation behavior of CNF/polyurethane (PU) nanocomposites was analyzed. PU was synthesized from methylene diisocyanate, polypropylene glycol (PPG diol), and butanediol. CNF, oxidized CNF (ox-CNF), and PPG diol grafted CNF (ol-CNF) were selected as fillers. ol-CNF was obtained by grafting PPG diol onto ox-CNF by reacting it with the carboxyl groups present on ox-CNF surface. The atomic ratios of oxygen to carbon present on the filler surfaces were 0.13 and 0.18 on ox-CNF and on ol-CNF as compared to 0.015 on CNF, mostly due to the presence oxygen containing polar groups on the surfaces of the former. The composites were prepared by in-situ polymerization and melt mixing in a chaotic mixer. The stress relaxation behavior of composites was determined at room temperature after inducing a tensile strain of 100%. The presence of fillers augmented the rate of stress relaxation in composites which was highest in the presence of CNF. The results suggested that relatively weak polymer-filler interactions in composites of CNF promoted higher stress relaxation.

  19. Review of outcome measurement instruments in Alzheimer's disease drug trials: psychometric properties of behavior and mood scales.

    PubMed

    Perrault, A; Oremus, M; Demers, L; Vida, S; Wolfson, C

    2000-01-01

    This article reviews the reliability and validity of eight scales for behavior and mood problems that were identified in a comparative analysis of Alzheimer's disease (AD) drug trials. The scales are the Brief Psychiatric Rating Scale, the Alzheimer's Disease Assessment Scale-noncognitive, the Relative's Assessment of Global Symptomatology, the Consortium to Establish a Registry for Alzheimer's Disease-Behavior Rating Scale for Dementia, the Dementia Behavior Disturbance scale, the Neuropsychiatric Inventory, and two scales for depressive symptoms, the Cornell Scale for Depression in Dementia and the Dementia Mood Assessment Scale. This article also examines methodological limitations in the way the published literature has assessed the psychometric properties of these scales. The aim is to help clinicians and potential trial investigators select appropriate measurement instruments with which to assess behavior and mood problems in AD and to assist AD researchers in the evaluation of the psychometric properties of such scales. PMID:11128058

  20. Abnormalities of physics and mechanical properties, behavior of helium and hydrogen in the V-Ti alloys (Overview)

    NASA Astrophysics Data System (ADS)

    Staltsov, M. S.; Chernov, I. I.; Kalin, B. A.; Korchagin, O. N.; Anan'in, V. M.

    2016-04-01

    The paper presents the results of studies of physical and mechanical properties, helium and hydrogen behavior in vanadium-titanium alloys depending on titanium content. In particular, the results of helium swelling research, thermal desorption studies of helium and hydrogen behavior, results of internal friction measurements, measuring amount of hydrogen retained introduced by various methods. It was shown that the addition of titanium to vanadium have nonmonotonic influence on the behavior of implanted helium and hydrogen, as well as on the physical and mechanical and radiation properties known in literature. It is expected that such an abnormal influence of titanium on various properties of vanadium-titanium alloys occurs because of the interaction of vanadium and titanium atoms with atoms of interstitial impurities.

  1. Damage formation, fatigue behavior and strength properties of ZrO2-based ceramics

    NASA Astrophysics Data System (ADS)

    Kozulin, A. A.; Narikovich, A. S.; Kulkov, S. N.; Leitsin, V. N.; Kulkov, S. S.

    2016-08-01

    It is suggested that a non-destructive testing technique using a three-dimensional X-ray tomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO2-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical properties of the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 105 stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material.

  2. Gabra5-gene haplotype block associated with behavioral properties of the full agonist benzodiazepine chlordiazepoxide.

    PubMed

    Clément, Y; Prut, L; Saurini, F; Mineur, Y S; Le Guisquet, A-M; Védrine, S; Andres, C; Vodjdani, G; Belzung, C

    2012-08-01

    The gabra5 gene is associated with pharmacological properties (myorelaxant, amnesic, anxiolytic) of benzodiazepines. It is tightly located (0.5 cM) close to the pink-eyed dilution (p) locus which encodes for fur color on mouse chromosome 7. We tested the putative role of the gabra5 gene in pharmacological properties of the full non specific agonist chlordiazepoxide (CDP), using behavioral and molecular approaches in mutated p/p mice and wild type F2 from crosses between two multiple markers inbred strain ABP/Le and C57BL/6By strain. From our results, using rotarod, light-dark box, elevated maze and radial arm maze tests, we demonstrate that p/p mice are more sensitive than WT to the sensory motor, anxiolytic and amnesic effect of CDP. This is associated with the presence of a haplotypic block on the murine chromosome 7 and with an up regulation of gabra5 mRNAs in hippocampi of p/p F2 mice. PMID:22677273

  3. Mechanical Properties, Corrosion Behavior, and Microstructures of a MIG-Welded 7020 Al Alloy

    NASA Astrophysics Data System (ADS)

    Peng, Xiaoyan; Cao, Xiaowu; Xu, Guofu; Deng, Ying; Tang, Lei; Yin, Zhimin

    2016-03-01

    7020 aluminum alloy plates were welded by metal inert gas welding method, with the ER5183 welding wire containing Zr and ER5356 welding wire without Zr, respectively. The mechanical properties, corrosion behavior, and microstructures of these two welded joints were investigated. The tensile strength and ductilities of the joints are inferior to those of base alloy, and the lowest hardness is obtained in the welded zone, while the heat-affected zones are more sensitive to corrosion than the base metal and welded zones. The base metal shows a deformed subgrains microstructure, and the heat-affected zones still remain in elongated shape, where the soften zones form as a result of η' (MgZn2) coarsening. Two welded zones are mainly characterized by as-cast structure; however, grains are refined and a zone of equiaxed grains forms along the bonding boundary due to the Zr addition into ER5183 Al alloy. Accordingly, the mechanical properties and corrosion resistance in this zone of the joint with ER5183 exhibit better than those of the joint with ER5356.

  4. Synthesis, Thermal Properties, and Thermoresponsive Behaviors of Cyclic Poly(2-(dimethylamino)ethyl Methacrylate)s.

    PubMed

    An, Xiaonan; Tang, Qingquan; Zhu, Wen; Zhang, Ke; Zhao, Youliang

    2016-06-01

    This study aims at physicochemical properties of thermo- and pH/CO2 -responsive cyclic homopolymers. Three examples of cyclic poly(2-(dimethylamino)ethyl methacrylate)s (PDMAs) are synthesized by combining the reversible addition-fragmentation chain transfer process and the Diels-Alder ring-closure reaction. After cyclization, the glass transition temperature significantly increases (ΔTg = 51.8-59.7 °C) due to the different configurational entropy and end groups, and the maximum decomposition temperature to lose the pendent groups is drastically decreased from 309 to 278 °C. Effects of polymerization degree, polymer concentration, additive of NaCl, and pH/CO2 on lower critical solution temperature behaviors of PDMA aqueous solutions are investigated. The cloud points (Tc ) of ring PDMAs are usually higher than their linear precursors, and the ΔTc values obtained under a fixed condition can reach up to 20.7 °C, revealing the crucial role of the topology effect. This study paves the way for unique properties and applications of smart cyclic polymers and their derivatives. PMID:27126247

  5. Effects of heating rate on slow pyrolysis behavior, kinetic parameters and products properties of moso bamboo.

    PubMed

    Chen, Dengyu; Zhou, Jianbin; Zhang, Qisheng

    2014-10-01

    Effects of heating rate on slow pyrolysis behaviors, kinetic parameters, and products properties of moso bamboo were investigated in this study. Pyrolysis experiments were performed up to 700 °C at heating rates of 5, 10, 20, and 30 °C/min using thermogravimetric analysis (TGA) and a lab-scale fixed bed pyrolysis reactor. The results show that the onset and offset temperatures of the main devolatilization stage of thermogravimetry/derivative thermogravimetry (TG/DTG) curves obviously shift toward the high-temperature range, and the activation energy values increase with increasing heating rate. The heating rate has different effects on the pyrolysis products properties, including biochar (element content, proximate analysis, specific surface area, heating value), bio-oil (water content, chemical composition), and non-condensable gas. The solid yields from the fixed bed pyrolysis reactor are noticeably different from those of TGA mainly because the thermal hysteresis of the sample in the fixed bed pyrolysis reactor is more thorough. PMID:25063973

  6. A study on the mechanical properties and deformation behavior of injection molded PMMA-TSP laminated composite

    NASA Astrophysics Data System (ADS)

    Wang, Jaeyoon; Lee, Moon Kyu; Park, Seon-Mi; Hong, Seokmoo; Kim, Naksoo

    2012-03-01

    To evaluate the deformed features of a polymer and touch screen panel laminated material and to secure a reliability of the design method, it is crucial to predict a thermo-mechanical behavior of the polymers. The reliability problems of polymer-TSP laminated module subjected to temperature and humidity changes mainly occur due to features with time-dependent material properties as well as differences in the coefficients of thermal expansion between the polymer and TSP. Therefore, it is necessary to consider the viscous behavior which causes changes in material properties which include temperature-dependent properties along with the time-dependent properties. In this study, a tensile test is conducted to obtain fundamental material properties and a creep test is used to characterize viscous properties of the polymer. Material properties from the tensile and the creep test are verified by the tensile and creep simulations. Also, the finite element analysis is used to simulate the time-dependent behaviors during a high temperature conditions while predicting thermal deformations. Numerical results are compared with experimental results. The result shows that the shape deformations of the polymer-TSP laminated module calculated by the finite element analysis with visco-elastic-plastic material model are in a good agreement with the experiment. Based on analytical results, we predict the thermal deformation of the PMMA-TSP composite plate in consideration of the effect of viscous features and set up the organized numerical analysis procedure using FE analysis.

  7. Development of a microfluidic device for determination of cell osmotic behavior and membrane transport properties.

    PubMed

    Chen, Hsiu-Hung; Purtteman, Jester J P; Heimfeld, Shelly; Folch, Albert; Gao, Dayong

    2007-12-01

    An understanding of cell osmotic behavior and membrane transport properties is indispensable for cryobiology research and development of cell-type-specific, optimal cryopreservation conditions. A microfluidic perfusion system is developed here to measure the kinetic changes of cell volume under various extracellular conditions, in order to determine cell osmotic behavior and membrane transport properties. The system is fabricated using soft lithography and is comprised of microfluidic channels and a perfusion chamber for trapping cells. During experiments, rat basophilic leukemia (RBL-1 line) cells were injected into the inlet of the device, allowed to flow downstream, and were trapped within a perfusion chamber. The fluid continues to flow to the outlet due to suction produced by a Hamilton Syringe. Two sets of experiments have been performed: the cells were perfused by (1) hypertonic solutions with different concentrations of non-permeating solutes and (2) solutions containing a permeating cryoprotective agent (CPA), dimethylsulfoxide (Me(2)SO), plus non-permeating solute (sodium chloride (NaCl)), respectively. From experiment (1), cell osmotically inactive volume (V(b)) and the permeability coefficient of water (L(p)) for RBL cells are determined to be 41% [n=18, correlation coefficient (r(2)) of 0.903] of original/isotonic volume, and 0.32+/-0.05 microm/min/atm (n=8, r(2)>0.963), respectively, for room temperature (22 degrees C). From experiment (2), the permeability coefficient of water (L(p)) and of Me(2)SO (P(s)) for RBL cells are 0.38+/-0.09 microm/min/atm and (0.49+/-0.13) x 10(-3)cm/min (n=5, r(2)>0.86), respectively. We conclude that this device enables us to: (1) readily monitor the changes of extracellular conditions by perfusing single or a group of cells with prepared media; (2) confine cells (or a cell) within a monolayer chamber, which prevents imaging ambiguity, such as cells overlapping or moving out of the focus plane; (3) study individual cell

  8. Assessment of Disruptive Behaviors in Preschoolers: Psychometric Properties of the Disruptive Behavior Disorders Rating Scale and School Situations Questionnaire

    ERIC Educational Resources Information Center

    Pelletier, Julie; Collett, Brent; Gimpel, Gretchen; Crowley, Susan

    2006-01-01

    Disruptive behavior disorders (e.g., attention-deficit/hyperactivity disorder and oppositional defiant disorder) are increasingly being diagnosed in preschool children. However, the assessment and differential diagnosis of these disorders presents several challenges to clinicians. For example, most rating scales used to help diagnose such problems…

  9. Predicting the Operating Behavior of Ceramic Filters from Thermo-Mechanical Ash Properties

    SciTech Connect

    Hemmer, G.; Kasper, G.

    2002-09-19

    Stable operation, in other words the achievement of a succession of uniform filtration cycles of reasonable length is a key issue in high-temperature gas filtration with ceramic media. Its importance has rather grown in recent years, as these media gain in acceptance due to their excellent particle retention capabilities. Ash properties have been known for some time to affect the maximum operating temperature of filters. However, softening and consequently ''stickiness'' of the ash particles generally depend on composition in a complex way. Simple and accurate prediction of critical temperature ranges from ash analysis--and even more so from coal analysis--is still difficult without practical and costly trials. In general, our understanding of what exactly happens during break-down of filtration stability is still rather crude and general. Early work was based on the concept that ash particles begin to soften and sinter near the melting temperatures of low-melting, often alkaline components. This softening coincides with a fairly abrupt increase of stickiness, that can be detected with powder mechanical methods in a Jenicke shear cell as first shown by Pilz (1996) and recently confirmed by others (Kamiya et al. 2001 and 2002, Kanaoka et al. 2001). However, recording {sigma}-{tau}-diagrams is very time consuming and not the only off-line method of analyzing or predicting changes in thermo-mechanical ash behavior. Pilz found that the increase in ash stickiness near melting was accompanied by shrinkage attributed to sintering. Recent work at the University of Karlsruhe has expanded the use of such thermo-analytical methods for predicting filtration behavior (Hemmer 2001). Demonstrating their effectiveness is one objective of this paper. Finally, our intent is to show that ash softening at near melting temperatures is apparently not the only phenomenon causing problems with filtration, although its impact is certainly the ''final catastrophe''. There are other

  10. Flex - rigid behavior of quartzite and its mineralogical, microstructural and textural properties from EBSD

    NASA Astrophysics Data System (ADS)

    Dorabiato Barbosa, Pamela; Ávila, Carlos Fernando; Evangelista Lagoeiro, Leonardo; Pinheiro Sampaio, Ney; Martins Graça, Leonardo

    2016-04-01

    It was investigated the mechanical properties of the quartzite found in the 'Moeda' Formation from the mineral province of the 'Quadrilátero Ferrífero', Brazil. Rocks with variations from flexible (in some portions) to completely rigid are rare and found only in some specific locations in the whole world. It's flexibility has been usually related to the presence of minerals with tabular habit, that act as structural support to the rock and regulates the flexibility. Besides, the intrinsic behavior of this type of rock is marked by their microstructures and the typical preferred crystallographic orientations. In order to characterize the causes of this unique mechanical property, oriented sections of these rocks with different behaviors, flexible and stiff, were prepared and investigated with EBSD. The results showed differences in grain sizes (with grain area as proxy) and grain boundary lengths for quartz grains, the spatial distribution of muscovite, as well as crystallographic fabrics. The boundaries of the quartz grains observed in the stiff sample are linear, while in the flexible sample they're irregular. Quartz grains with sizes smaller than 30 μm2 are 30% larger in the flexible quartzite than those of the rigid counterparts.. This relation reverses for grains with an area greater than 30,000 μm2. Muscovite occurs as isolated grains in the rigid samples while in the flexible ones grains more continuously distributed and interconnected.. When the directions of the samples are plotted in the crystal reference system a contrasting crystallographic texture arises. The X-directions of the sample concentrate in the axes of the quartz. For the rigid samples it is te Y-directions that show preference to align parallel to the poles of the positive rhomb ({01-12} = this is the acute rhomb; rhomb is {01-11]). The rigid quartzite showed a strong <21 ̅1 ̅0> () crystallographic fabric parallel to the macroscopic lineation, whereas for the flexible ones the

  11. Effects of alloying elements on the mechanical properties and corrosion behaviors of 2205 duplex stainless steels

    NASA Astrophysics Data System (ADS)

    Liou, Horng-Yih; Tsai, Wen-Ta; Pan, Yeong-Tsuen; Hsieh, Rong-Iuan

    2001-04-01

    The effects of alloying elements on the microstructure, mechanical properties, and corrosion behaviors of duplex stainless steels (DSSs) have been investigated in this study. Experimental alloys were prepared by varying the concentrations of the constituent elements in DSSs. Hot ductility test, tensile test, charpy impact test, and corrosion test were performed to evaluate the properties of the experimental alloys. The results showed that the extent of edge cracking of DSSs increased with the increasing value of the crack sensitivity index (CSI). The higher the hot ductility index (HDI) was, the better the hot ductility of DSSs achieved. Austenite ( γ) stabilizer generally caused a decrease in the strength and an increase in the charpy impact absorbed energy of the stainless steel. On the contrary, ferrite ( α) former exerted its beneficial effect on the strength but became detrimental to the toughness of DSSs. The presences of sulfur and boron also caused a decrease in the impact energy, but nitrogen and carbon hardly affected the toughness within the concentration range tested in this study. The value of pitting nucleation potential ( E np ) of different nitrogen contents in 3.5 wt.% NaCl solution at room temperature was almost the same, but the value of pitting protection potential ( E pp ) among these alloys was increased with increasing the content of nitrogen. The susceptibility to stress corrosion cracking (SCC) of DSSs was high when tested in boiling 45 wt.% MgCl2 solution. On the other hand, the time to failure of the experimental steels in 40 wt.% CaCl2 solution at 100 °C was longer than that in MgCl2 solution. Nitrogen could affect the SCC behavior of DSSs in CaCl2 solution through the combinative effects by varying the pitting resistance and the slip step dissolution. An optimum nitrogen (N) content of 0.15 wt.% was found where the highest SCC resistance could be obtained. Although γ phase exhibited better resistance to SCC, cracks were found to

  12. Frictional and Poromechanical Properties of Serpentinite: Implications for Deep Fault Slip Behavior

    NASA Astrophysics Data System (ADS)

    Scuderi, M. M.; Carpenter, B. M.; Marone, C.; Saffer, D. M.

    2014-12-01

    Recent observations of deep tremor and low-frequency earthquakes (LFE) have raised fundamental questions about the physics of quasidynamic rupture and the underlying fault zone processes. The presence of serpentinite at P-T conditions characteristic of deep tremor and LFE suggests that it may be an important element in complex fault slip, however, little is known about its hydrological and mechanical properties. Here, we report on experiments designed to investigate the frictional behavior of serpentinite recovered from outcrops (SO1 and SO2) and the SAFOD borehole (G27). XRD analyses reveal the presence of lizardite, kaolinite, talc and hydrotalcite in the SO1; lizardite, clinochlore and magnetite in SO2; and lizardite, quartz and calcite in G27. We powdered samples from intact blocks to a grain size <150 µm and sheared the resulting gouge in a double-direct shear configuration using a true triaxial deformation apparatus. Effective normal stress (σ'n = σn - Pp) was kept constant at values ranging from 2 to 40 MPa. Shear stress was applied via a constant load point displacement rate, and velocity was increased stepwise from 0.1 to 100 μm/s, after which a series of slide-hold-slides (SHS) were performed. We measured permeability normal to the shear direction and recovered samples for microstructural analysis. Mechanical strength varied from m=0.17 for SO1, m=0.33 for SO2 and m=0.53 for G27. Gouges exhibit an overall velocity strengthening behavior, with values approaching velocity neutral at the highest effective normal stress. SHS tests show positive healing rates for S02 and G27; whereas, SO1 samples exhibit zero or negative healing rates. Permeability decreases with increasing σ'n, with SO1 (k = 10-20m2) showing the lowest values. Microstructural observations revealed a well-developed R-Y-P fabric in SO1, which is not observed in SO2 and G27. We posit that the development of different shear fabrics controlled by mineralogy controls frictional and

  13. Coating of carbon nanotube fibers: variation of tensile properties, failure behavior and adhesion strength

    NASA Astrophysics Data System (ADS)

    Mäder, Edith; Liu, Jian-Wen; Hiller, Janett; Lu, Weibang; Li, Qingwen; Zhandarov, Serge; Chou, Tsu-Wei

    2015-07-01

    An experimental study of the tensile properties of CNT fibers and their interphasial behavior in epoxy matrices is reported. One of the most promising applications of CNT fibers is their use as reinforcement in multifunctional composites. For this purpose, an increase of the tensile strength of the CNT fibers in unidirectional composites as well as strong interfacial adhesion strength is desirable. However, the mechanical performance of the CNT fiber composites manufactured so far is comparable to that of commercial fiber composites. The interfacial properties of CNT fiber/polymer composites have rarely been investigated and provided CNT fiber/epoxy interfacial shear strength of 14.4 MPa studied by the microbond test. In order to improve the mechanical performance of the CNT fibers, an epoxy compatible coating with nano-dispersed aqueous based polymeric film formers and low viscous epoxy resin, respectively, was applied. For impregnation of high homogeneity, low molecular weight epoxy film formers and polyurethane film formers were used. The aqueous based epoxy film formers were not crosslinked and able to interdiffuse with the matrix resin after impregnation. Due to good wetting of the individual CNT fibers by the film formers, the degree of activation of the fibers was improved leading to increased tensile strength and Young’s modulus. Cyclic tensile loading and simultaneous determination of electric resistance enabled to characterize the fiber’s durability in terms of elastic recovery and hysteresis. The pull-out tests and SEM study reveal different interfacial failure mechanisms in CNT fiber/epoxy systems for untreated and film former treated fibers, on the one hand, and epoxy resin treated ones, on the other hand. The epoxy resin penetrated between the CNT bundles in the reference or film former coated fiber, forming a relatively thick CNT/epoxy composite layer and thus shifting the fracture zone within the fiber. In contrast to this, shear sliding along

  14. Effect of cargo properties on in situ forming implant behavior determined by noninvasive ultrasound imaging

    PubMed Central

    Solorio, Luis; Olear, Alexander M.; Zhou, Haoyan; Beiswenger, Ashlei C.; Exner, Agata A.

    2012-01-01

    Diagnostic ultrasound has been shown to be an effective method for the noninvasive characterization of in situ forming implant behavior both in vivo and in vitro through the evaluation of the echogenic signal that forms as a consequence of the polymer phase transition from liquid to solid. The kinetics of this phase transition have a direct effect on drug release and can be altered through factors that change the mass transfer events of the solvent and aqueous environment, including properties of the entrapped active agent. This study examined the effect of payload properties on implant phase inversion, swelling, drug release, and polymer degradation. Poly(DL-lactide-co-gylcolide) implants were loaded with either: sodium fluorescein, bovine serum albumin (BSA), doxorubicin (Dox), or 1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI). Fluorescein and Dox were released at near equivalent rates throughout the diffusion phase of release but due to differing drug–matrix interactions, Dox-loaded implants released a lower mass of drug during the degradation phase of release. DiI was not readily released, and due to increased depot hydrophobicity, resulted in significantly lower swelling than the other formulations. The initial echogenicity was higher in Dox-loaded implants than those loaded with fluorescein, but after the initial precipitation, phase inversion and drug release occurred at near equivalent rates for both Dox and fluorescein-loaded implants. Nonlinear mathematical fitting was used to correlate drug release and phase inversion, providing a noninvasive method for evaluating implant release (R2>0.97 for Dox, BSA, and fluorescein; DiI had a correlation coefficient of 0.56). PMID:22712054

  15. Structures and Surface Properties of "Cyclic" Polyoxyethylene Alkyl Ethers: Unusual Behavior of Cyclic Surfactants in Water.

    PubMed

    Hirose, Yuki; Taira, Toshiaki; Sakai, Kenichi; Sakai, Hideki; Endo, Akira; Imura, Tomohiro

    2016-08-23

    The cyclization of amphiphiles has emerged as an attractive strategy for inducing remarkable properties in these materials without changing their chemical composition. In this study, we successfully synthesized three cyclic polyoxyethylene dodecyl ethers (c-POEC12's) with different ring sizes and explored the effects of their topology on their surface and self-assembly properties related to their function, comparing them with those of their linear counterparts (l-POEC12's). The surface activity of the c-POEC12's remained almost constant despite the change in their hydrophobic and hydrophilic balance (HLB) value, while that of the l-POEC12's decreased with an increase in the HLB value as general surfactants. In contrast to the normal micelles seen in the case of the l-POEC12's (3.4-9.7 nm), the cyclization of the POEC12's resulted in the formation of large spherical structures 72.8-256.8 nm in size. It also led to a dramatic decrease of 28 °C in the cloud point temperature. Furthermore, the cyclization of the POEC12's markedly suppressed the rate of protease hydrolysis caused by the surfactants. The initial rate of reduction of a detergent enzyme from Bacillus licheniformis was increased by more than 40% in the case of c-POE600C12 and c-POE1000C12, even though they exhibited surface activities almost equal to or higher than those of their linear counterparts. These results suggest that cyclization induces unusual aqueous behaviors in POEC12, making the surfactant milder with respect to detergent enzymes while ensuring it exhibits increased surface activity. PMID:27462805

  16. Features of microbiological behavior and biocide properties of electrosynthesized polymethylolacrylamide films

    NASA Astrophysics Data System (ADS)

    Kolzunova, Lidia G.

    2016-05-01

    The biocide properties of an electrosynthesized of acrylamide, N,N'-methylene-bis-acrylamide and formaldehyde copolymer films against the Staphylococcus aureus and bacterial association extracted from seawater (marine biological organisms) were investigated. Copolymer films were stable in organic solvents, acids and alkali and insoluble in water, though capable to swelling ability. Besides, the polymer is thermally stable up to 237°C. It was established that the anti-bacterial effect of the films started to be expressed after two days and was maintained from 2 up to 45 days. It was established that the degree of polymer films toxicity depended on the polymer synthesis conditions, pre-treatment method and duration of the biological object exposure to the effect. It was shown that antiseptic properties of the polymer material under study were imparted by formaldehyde both as sorbed by the polymer and as included into the copolymer composition. The toxicological effect of the polymethylolacrylamide films under study on microorganisms can be applied as in medicine (antiseptic materials and implants) as for equipment protection from bio-fouling and bio-corrosion. Microbiological stability and sterilizing effect of electrosynthesized polymethylolacrylamide ultrafiltration membranes enables one not only to prolong the operation time of film membranes, but also to provide partial sterilization of organic solutions to be filtered. It was established that polymer waste can be utilized by means of microbial destruction. It was found that the washed out polymer induced a specific bacteria behavior consisting of a complex of reactions directed to search, capture and consume nutrients.

  17. Extraction of mechanical properties of articular cartilage from osmotic swelling behavior monitored using high frequency ultrasound.

    PubMed

    Wang, Q; Zheng, Y P; Niu, H J; Mak, A F T

    2007-06-01

    Articular cartilage is a biological weight-bearing tissue covering the bony ends of articulating joints. Negatively charged proteoglycan (PG) in articular cartilage is one of the main factors that govern its compressive mechanical behavior and swelling phenomenon. PG is nonuniformly distributed throughout the depth direction, and its amount or distribution may change in the degenerated articular cartilage such as osteoarthritis. In this paper, we used a 50 MHz ultrasound system to study the depth-dependent strain of articular cartilage under the osmotic loading induced by the decrease of the bathing saline concentration. The swelling-induced strains under the osmotic loading were used to determine the layered material properties of articular cartilage based on a triphasic model of the free-swelling. Fourteen cylindrical cartilage-bone samples prepared from fresh normal bovine patellae were tested in situ in this study. A layered triphasic model was proposed to describe the depth distribution of the swelling strain for the cartilage and to determine its aggregate modulus H(a) at two different layers, within which H(a) was assumed to be linearly dependent on the depth. The results showed that H(a) was 3.0+/-3.2, 7.0+/-7.4, 24.5+/-11.1 MPa at the cartilage surface, layer interface, and deep region, respectively. They are significantly different (p<0.01). The layer interface located at 70%+/-20% of the overall thickness from the uncalcified-calcified cartilage interface. Parametric analysis demonstrated that the depth-dependent distribution of the water fraction had a significant effect on the modeling results but not the fixed charge density. This study showed that high-frequency ultrasound measurement together with triphasic modeling is practical for quantifying the layered mechanical properties of articular cartilage nondestructively and has the potential for providing useful information for the detection of the early signs of osteoarthritis. PMID:17536909

  18. Calcein release behavior from liposomal bilayer; influence of physicochemical/mechanical/structural properties of lipids.

    PubMed

    Maherani, Behnoush; Arab-Tehrany, Elmira; Kheirolomoom, Azadeh; Geny, David; Linder, Michel

    2013-11-01

    The design of the drug delivery depends upon different parameters. One of the most noticeable factors in design of the drug delivery is drug-release profile which determines the site of action, the concentration of the drug at the time of administration, the period of time that the drug must remain at a therapeutic concentration. To get a better understanding of drug release, large unilamellar liposomes containing calcein were prepared using 1,2-dioleoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1,2-palmitoyl-sn-glycero-3-phosphocholine, and a mixture of them; calcein was chosen as a model of hydrophilic drug. The calcein permeability across liposomal membrane (with different compositions) was evaluated on the basis of the first-order kinetic by spectrofluorometer. Also, the effects of liposome composition/fluidity as well as the incubation temperature/pH were investigated. Furthermore, we simulated the digestion condition in the gastrointestinal tract in humans, to mimic human gastro-duodenal digestion to monitor calcein release during the course of the digestion process. In vitro digestion model ''pH stat'' was used to systematically examine the influence of pH/enzyme on phospholipid liposomes digestion under simulated gastro-duodenal digestion. The results revealed that calcein permeates across liposomal membrane without membrane disruption. The release rate of calcein from the liposomes depends on the number and fluidity of bilayers and its mechanical/physical properties such as permeability, bending elasticity. Chemo-structural properties of drugs like as partition coefficient (Log P), H-bonding, polar surface area (PSA) are also determinative parameter in release behavior. Finally, stimulated emission depletion (STED) microscopy was used to study calcein translocation through liposomal bilayers. PMID:23871914

  19. Investigation of Swelling Behavior and Mechanical Properties of a pH-Sensitive Superporous Hydrogel Composite

    PubMed Central

    Gupta, N. Vishal; Shivakumar, H.G.

    2012-01-01

    The objective of the present study is to develop and investigate the swelling behavior of pH-sensitive Superporous Hydrogel (SPH) and SPH composite (SPHC). A novel superporous hydrogel containing poly (methacrylic acid-co-acrylamide) was synthesized from methacrylic acid and acrylamide through the aqueous solution polymerization, using N,N-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. SPHCs were made in the same way, except for the using of Ac-Di-Sol as a stabilizer. The synthesized SPH and SPHC were characterized by Fourier-transform infrared spectroscopy, swelling kinetics, porosity, mechanical properties and scanning electron microscopy. The swelling of SPH and SPHC was sensitive towards the pH, ionic strength, and temperature stimuli. The study of the surface morphology of SPH using scanning electron microscopy showed a highly porous structure. SPH polymers showed higher swelling ratio but less mechanical stability compared to SPHC polymers, which showed lower swelling ratio but a higher mechanical stability. With a change in pH from acidic to basic, a considerable increase in swelling was observed. Since the prepared SPH and SPHC swell only in the basic pH, it may be concluded that SPH and SPHC can be used as the pH-sensitive drug delivery system. PMID:24250471

  20. Mechanical properties and corrosion behavior of Mg-Gd-Ca-Zr alloys for medical applications.

    PubMed

    Shi, Ling-Ling; Huang, Yuanding; Yang, Lei; Feyerabend, Frank; Mendis, Chamini; Willumeit, Regine; Ulrich Kainer, Karl; Hort, Norbert

    2015-07-01

    Magnesium alloys are promising candidates for biomedical applications. In this work, influences of composition and heat treatment on the microstructure, the mechanical properties and the corrosion behavior of Mg-Gd-Ca-Zr alloys as potential biomedical implant candidates were investigated. Mg5Gd phase was observed at the grain boundaries of Mg-10Gd-xCa-0.5Zr (x=0, 0.3, 1.2wt%) alloys. Increase in the Ca content led to the formation of additional Mg2Ca phase. The Ca additions increased both the compressive and the tensile yield strengths, but reduced the ductility and the corrosion resistance in cell culture medium. After solution heat treatment, the Mg5Gd particles dissolved in the Mg matrix. The compressive strength decreased, while the corrosion resistance improved in the solution treated alloys. After ageing at 200°C, metastable β' phase formed on prismatic planes and a new type of basal precipitates have been observed, which improved the compressive and tensile ultimate strength, but decreased the ductility. PMID:25837343

  1. Predicting enzyme behavior in nonconventional media: correlating nitrilase function with solvent properties.

    PubMed

    Kaul, Praveen; Banerjee, U C

    2008-07-01

    The insolubility of nitrile substrates in aqueous reaction mixture decreases the enzymatic reaction rate. We studied the interaction of fourteen water miscible organic solvents with immobilized nitrile hydrolyzing biocatalyst. Correlation of nitrilase function with physico-chemical properties of the solvents has allowed us to predict the enzyme behavior in such non-conventional media. Addition of organic solvent up to a critical concentration leads to an enhancement in reaction rate, however, any further increase beyond the critical concentration in the latter leads to the decrease in catalytic efficiency of the enzyme, probably due to protein denaturation. The solvent dielectric constant (epsilon) showed a linear correlation with the critical concentration of the solvent used and the extent of nitrile hydrolysis. Unlike alcohols, the reaction rate in case of aprotic solvents could be linearly correlated to solvent log P. Further, kinetic analysis confirmed that the affinity of the enzyme for its substrate (K (m)) was highly dependent upon the aprotic solvent used. Finally, the prospect of solvent engineering also permitted the control of enzyme enantioselectivity by regulating enantiomer traffic at the active site. PMID:18317826

  2. Effects of H content on the tensile properties and fracture behavior of SA508-III steel

    NASA Astrophysics Data System (ADS)

    Liu, Jia-hua; Wang, Lei; Liu, Yang; Song, Xiu; Luo, Jiong; Yuan, Dan

    2015-08-01

    SA508-III steel was charged with different hydrogen (H) contents using a high-pressure thermal charging method to study the effects of H content on the tensile properties and evaluate the H embrittlement behavior of the steel. The results indicate that the ultimate tensile strength remains nearly unchanged with the addition of H. In contrast, the yielding strength slightly increases, and the elongation significantly decreases with increasing H content, especially at concentrations exceeding 5.6 × 10-6. On the basis of fractographic analysis, it is clear that the addition of H changes the fracture mode from microvoid coalescence to a mixture of river patterns and dimples. Carbides are strong traps for H; thus, the H atoms easily migrate in the form of Cottrell atmosphere toward the carbides following moving dislocations during tensile deformation. In addition, stress-induced H atoms accumulate at the interface between carbides and the matrix after necking under three-dimensional stress, which weakens the interfacial bonding force. Consequently, when the local H concentration reaches a critical value, microcracks occur at the interface, resulting in fracture.

  3. Mechanical Properties of Electroactive Polymer Gels and Their Behavior in DC Electric Fields

    NASA Astrophysics Data System (ADS)

    Yao, Li; Krause, Sonja

    2000-03-01

    We have reported the bending deformation of swollen crosslinked partially sulfonated triblock copolymer poly(styrene-b-ethylene-co-butylene-b-styrene) (S-SEBS) hydrogels in DC electric fields in previous APS meetings(Bull. Am. Phys. Soc., 43 (1), 598, 1998 and 44 (1), 757, 1999). However, very little force was generated from the bending of the S-SEBS gel due to the low modulus of this highly elastic material. For the present study, partially sulfonated crosslinked polystyrene gels (XL-S-PS) were prepared. The gel bending behavior of XL-S-PS gels was studied in four different sulfonated solutions with varied cations including Na^+, Cs^+, (CH_3)_4NH^+ and (Bu)_4NH^+. Comparison of gel bending of S-SEBS and XL-S-PS gels indicated qualitative similarities and quantitative differences. The bending motion of the XL-S-PS gels in electric fields was slower than that of the S-SEBS gels but more force was generated in the XL-S-PS gel system. Nanoparticles were used as fillers in some of the XL-S-PS gels to modify their mechanical properties which will be discussed in the presentation.

  4. Effects of Ce on Inclusions, Microstructure, Mechanical Properties, and Corrosion Behavior of AISI 202 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Cai, Guojun; Li, Changsheng

    2015-10-01

    The sizes and morphologies of nonmetallic inclusions, microhardness, tensile strength, and Charpy impact toughness in AISI 202 stainless steel with different Ce contents were synthetically analyzed by means of SEM, TEM, microhardness tester, and tensile and Charpy impact tests. Effects of Ce addition on the corrosion behavior were investigated in 5 wt.% H2SO4 solution for different periods of time through measuring AC impedance. The EIS measurements indicate that the steels with Ce addition exhibit higher R p values than those without Ce, which illustrates the relative resistance to uniform corrosion is accompanied by an increasing Ce addition. Ce addition to AISI 202 stainless steel improves its uniform corrosion resistance owing to metamorphic inclusions and the improvement of electrode potential in matrix. Upon increasing Ce addition, the indentation morphology of samples transfers from sink-in types to pile-up types, explaining good machinability of steels containing Ce. It is witnessed from the fracture mode that Ce refines the grain size of steels, significantly increasing the strength; in the meantime, its plasticity is improved, thereby solving the contradiction between the strength and the plasticity of steels. It is concluded that AISI 202 stainless steel with 0.016 wt.% Ce addition in the mass fraction has the best mechanical properties and the uniform corrosion resistance.

  5. Tailoring Phase Behavior and Mechanical Properties in Thermoplastic Elastomers through Block Sequence and Macromolecular Architecture

    NASA Astrophysics Data System (ADS)

    Burns, Adam; Register, Richard

    2015-03-01

    Block copolymers exhibit unique properties which depend not only on the identities of the constituent blocks but also the block sequence and macromolecular architecture. Thermoplastic elastomers (TPEs) are a prime example. In TPEs the arrangement of glassy end blocks flanking a long rubbery midblock gives rise to a physically cross-linked, elastic solid. Exchanging the glassy blocks for crystalline blocks can improve the processability and solvent resistance, but adversely affects the mechanical performance. The block sequence crystalline-glassy-rubbery-glassy-crystalline has been developed to combine the advantages of both crystalline and glassy blocks. Careful selection of block lengths produces materials in which the order-disorder transition temperature lies below the melting point of the crystalline block, ensuring that the melt will be homogeneous above the melting point. Access to single-phase melts provides a large reduction in viscosity and elasticity over conventional TPEs, which remain microphase-separated in the melt. Inserting the glassy blocks between the crystalline and rubbery blocks produces a vitreous layer surrounding the crystalline domains, which improves the room-temperature mechanical performance. Incorporating the crystalline-glassy-rubbery motif into the arms of star block copolymers adds another level of control. The star architecture introduces a permanent cross-link at the center of the star without appreciably affecting the phase behavior.

  6. Effects of antibacterial nanostructured composite films on vascular stents: hemodynamic behaviors, microstructural characteristics, and biomechanical properties.

    PubMed

    Cheng, Han-Yi; Hsiao, Wen-Tien; Lin, Li-Hsiang; Hsu, Ya-Ju; Sinrang, Andi Wardihan; Ou, Keng-Liang

    2015-01-01

    The purpose of this research was to investigate stresses resulting from different thicknesses and compositions of hydrogenated Cu-incorporated diamond-like carbon (a-C:H/Cu) films at the interface between vascular stent and the artery using three-dimensional reversed finite element models (FEMs). Blood flow velocity variation in vessels with plaques was examined by angiography, and the a-C:H/Cu films were characterized by transmission electron microscopy to analyze surface morphology. FEMs were constructed using a computer-aided reverse design system, and the effects of antibacterial nanostructured composite films in the stress field were investigated. The maximum stress in the vascular stent occurred at the intersections of net-like structures. Data analysis indicated that the stress decreased by 15% in vascular stents with antibacterial nanostructured composite films compared to the control group, and the stress decreased with increasing film thickness. The present results confirmed that antibacterial nanostructured composite films improve the biomechanical properties of vascular stents and release abnormal stress to prevent restenosis. The results of the present study offer the clinical benefit of inducing superior biomechanical behavior in vascular stents. PMID:24648307

  7. Investigation of Properties and Wear Behavior of HVOF Sprayed TiC-Strengthened Fe Coatings

    NASA Astrophysics Data System (ADS)

    Bobzin, Kirsten; Schlaefer, Thomas; Richardt, Katharina; Warda, Thomas; Reisel, Guido

    2009-12-01

    High-velocity oxyfuel (HVOF) sprayed carbide based coatings (such as Cr3C2/NiCr) are industrially well established for wear protection applications. Due to their high carbide content of typically 75 wt.% and more, they provide very high hardness and excellent wear resistance. Unfortunately, costs for matrix materials such as nickel underlie strong fluctuations and are normally well above the prices for iron. Therefore an alternative concept to conventional carbides is based on TiC-strengthened low-cost Fe-base materials, which are already used for sintering processes. Depending on the carbon content, the Fe-base material can additionally offer a temperable matrix for enhanced wear behavior. The sprayability of TiC-strengthened Fe-powders with a gaseous and a liquid fuel driven HVOF system was investigated in this study. The resulting coatings were analyzed with respect to microstructure, hardness, and phase composition and compared with galvanic hard chrome, NiCrBSi, and Cr3C2/NiCr (80/20) coatings as well as with sintered Fe/TiC reference materials. Furthermore, the Fe/TiC coatings were heat treated to proof the retained temperability of the Fe matrix after thermal spray process. Tribometer tests (pin-on-disk tests) were conducted to determine wear properties.

  8. Dynamic behaviors and transport properties of ethanol molecules in transmembrane cyclic peptide nanotubes.

    PubMed

    Li, Rui; Fan, Jianfen; Li, Hui; Yan, Xiliang; Yu, Yi

    2015-07-01

    Classical molecular dynamics simulations have been performed to investigate the dynamic behaviors and transport properties of ethanol molecules in transmembrane cyclic peptide nanotubes (CPNTs) with various radii, i.e., 8×(WL¯)n=3,4,5/POPE. The results show that ethanol molecules spontaneously fill the octa- and deca-CPNTs, but not the hexa-CPNT. In the octa-CPNT, ethanol molecules are trapped at individual gaps with their carbon skeletons perpendicular to the tube axis and hydroxyl groups towards the tube wall, forming a broken single-file chain. As the channel radius increases, ethanol molecules inside the deca-CPNT tend to form a tubular layer and the hydroxyl groups mainly stretch towards the tube axis. Computations of diffusion coefficients indicate that ethanol molecules in the octa-CPNT nearly lost their diffusion abilities, while those in the deca-CPNT diffuse as 4.5 times as in a (8, 8) carbon nanotube with a similar tube diameter. The osmotic and diffusion permeabilities (pf and pd, respectively) of the octa- and deca-CPNTs transporting ethanol were deduced for the first time. The distributions of the gauche and trans conformers of ethanol molecules in two CPNTs are quite similar, both with approximately 57% gauche conformers. The non-bonded interactions of channel ethanol with a CPNT wall and surrounding ethanol were explored. The potential of mean force elucidates the mechanism underlying the transporting characteristics of channel ethanol in a transmembrane CPNT. PMID:26156492

  9. Dynamic behaviors and transport properties of ethanol molecules in transmembrane cyclic peptide nanotubes

    NASA Astrophysics Data System (ADS)

    Li, Rui; Fan, Jianfen; Li, Hui; Yan, Xiliang; Yu, Yi

    2015-07-01

    Classical molecular dynamics simulations have been performed to investigate the dynamic behaviors and transport properties of ethanol molecules in transmembrane cyclic peptide nanotubes (CPNTs) with various radii, i.e., 8 × ( W L ¯ ) n = 3 , 4 , 5 / POPE . The results show that ethanol molecules spontaneously fill the octa- and deca-CPNTs, but not the hexa-CPNT. In the octa-CPNT, ethanol molecules are trapped at individual gaps with their carbon skeletons perpendicular to the tube axis and hydroxyl groups towards the tube wall, forming a broken single-file chain. As the channel radius increases, ethanol molecules inside the deca-CPNT tend to form a tubular layer and the hydroxyl groups mainly stretch towards the tube axis. Computations of diffusion coefficients indicate that ethanol molecules in the octa-CPNT nearly lost their diffusion abilities, while those in the deca-CPNT diffuse as 4.5 times as in a (8, 8) carbon nanotube with a similar tube diameter. The osmotic and diffusion permeabilities (pf and pd, respectively) of the octa- and deca-CPNTs transporting ethanol were deduced for the first time. The distributions of the gauche and trans conformers of ethanol molecules in two CPNTs are quite similar, both with approximately 57% gauche conformers. The non-bonded interactions of channel ethanol with a CPNT wall and surrounding ethanol were explored. The potential of mean force elucidates the mechanism underlying the transporting characteristics of channel ethanol in a transmembrane CPNT.

  10. Aging behavior and mechanical properties of maraging steels in the presence of submicrocrystalline Laves phase particles

    SciTech Connect

    Mahmoudi, A.; Ghavidel, M.R. Zamanzad; Nedjad, S. Hossein; Heidarzadeh, A.; Ahmadabadi, M. Nili

    2011-10-15

    Cold rolling and annealing of homogenized Fe-Ni-Mn-Mo-Ti-Cr maraging steels resulted in the formation of submicrocrystalline Fe{sub 2}(Mo,Ti) Laves phase particles. Optical and scanning electron microscopy, X-ray diffraction, tensile and hardness tests were used to study the microstructure, aging behavior and mechanical properties of the annealed steels. The annealed microstructures showed age hardenability during subsequent isothermal aging at 753 K. Ultrahigh fracture stress but poor tensile ductility was obtained after substantial age hardening in the specimens with 2% and 4% chromium. Increasing chromium addition up to 6% toughened the aged microstructure at the expense of the fracture stress by increasing the volume fraction of retained austenite. The Laves phase particles acted as crack nucleation sites during tensile deformation. - Highlights: {yields} Laves phases dispersed in a BCC iron matrix by annealing of cold rolled samples. {yields} The samples showed age hardenability during subsequent isothermal aging at 753 K. {yields} Ultrahigh fracture stress but poor ductility was obtained after age hardening. {yields} Increasing chromium addition toughened the aged microstructure. {yields} Laves phase particles acting as crack nucleation sites during tensile deformation.

  11. Inclusion of Regional Poroelastic Material Properties Better Predicts Biomechanical Behavior of Lumbar Discs Subjected to Dynamic Loading

    PubMed Central

    Williams, Jamie R.; Natarajan, Raghu N.; Andersson, Gunnar B.J.

    2009-01-01

    Understanding the relationship between repetitive lifting and the breakdown of disc tissue over several years of exposure is difficult to study in vivo and in vitro. The aim of this investigation was to develop a three-dimensional poroelastic finite element model of a lumbar motion segment that reflects the biological properties and behaviors of in vivo disc tissues including swelling pressure due to the proteoglycans and strain dependent permeability and porosity. It was hypothesized that when modeling the annulus, prescribing tissue specific material properties will not be adequate for studying the in vivo loading and unloading behavior of the disc. Rather, regional variations of these properties, which are known to exist within the annulus, must also be included. Finite element predictions were compared to in vivo measurements published by Tyrrell et al., (Tyrrell et al., 1985) of percent change in total stature for two loading protocols, short-term creep loading and standing recovery and short-term cyclic loading with standing recovery. The model in which the regional variations of material properties in the annulus had been included provided an overall better prediction of the in vivo behavior as compared to the model in which the annulus properties were assumed to be homogenous. This model will now be used to study the relationship between repetitive lifting and disc degeneration. PMID:17156786

  12. Properties of the Driving Behavior Survey Among Individuals with Motor Vehicle Accident-Related Posttraumatic Stress Disorder

    PubMed Central

    Clapp, Joshua D.; Baker, Aaron S.; Litwack, Scott D.; Sloan, Denise M.; Beck, J. Gayle

    2014-01-01

    Data suggest anxious drivers may engage in problematic behaviors that place themselves and others at increased risk of negative traffic events. Three domains of problematic behavior – exaggerated safety/caution, performance deficits, and hostile/aggressive behaviors – previously were identified during development of the Driving Behavior Survey (DBS), a novel measure of anxiety-related behavior. Extending this research, the current study examined the psychometric properties of DBS scores among individuals with posttraumatic stress disorder (PTSD) subsequent to motor vehicle trauma (N = 40). Internal consistencies and 12-week test-retest reliabilities for DBS scales ranged from good to excellent. Comparison of scores to normative student data indicated dose-response relationships for safety/caution and performance deficit subscales, with increased frequency of anxious behavior occurring within the PTSD sample. Associations with standard clinical measures provide additional evidence for anxiety-related driving behavior as a unique marker of functional impairment, distinct from both avoidance and disorder-specific symptoms. PMID:24325891

  13. Properties of the Driving Behavior Survey among individuals with motor vehicle accident-related posttraumatic stress disorder.

    PubMed

    Clapp, Joshua D; Baker, Aaron S; Litwack, Scott D; Sloan, Denise M; Beck, J Gayle

    2014-01-01

    Data suggest anxious drivers may engage in problematic behaviors that place themselves and others at increased risk of negative traffic events. Three domains of problematic behavior--exaggerated safety/caution, performance deficits, and hostile/aggressive behaviors--previously were identified during development of the Driving Behavior Survey (DBS), a novel measure of anxiety-related behavior. Extending this research, the current study examined the psychometric properties of DBS scores among individuals with posttraumatic stress disorder (PTSD) subsequent to motor vehicle trauma (N=40). Internal consistencies and 12-week test-retest reliabilities for DBS scales ranged from good to excellent. Comparison of scores to normative student data indicated dose-response relationships for safety/caution and performance deficit subscales, with increased frequency of anxious behavior occurring within the PTSD sample. Associations with standard clinical measures provide additional evidence for anxiety-related driving behavior as a unique marker of functional impairment, distinct from both avoidance and disorder-specific symptoms. PMID:24325891

  14. Densification behavior, nanocrystallization, and mechanical properties of spark plasma sintered Fe-based bulk amorphous alloys

    NASA Astrophysics Data System (ADS)

    Singh, Ashish Kumar

    Fe-based amorphous alloys are gaining increasing attention due to their exceptional wear and corrosion resistance for potential structural applications. Two major challenges that are hindering the commercialization of these amorphous alloys are difficulty in processing of bulk shapes (diameter > 10 mm) and lack of ductility. Spark plasma sintering (SPS) is evolving as a promising technique for processing bulk shapes of amorphous and nanocrystalline materials. The objective of this work is to investigate densification behavior, nanocrystallization, and mechanical properties of SPS sintered Fe-based amorphous alloys of composition Fe48Cr15Mo14Y2C15B6. SPS processing was performed in three distinct temperature ranges of amorphous alloys: (a) below glass transition temperature (Tg), (b) between Tg and crystallization temperature (Tx), and (c) above Tx. Punch displacement data obtained during SPS sintering was correlated with the SPS processing parameters such as temperature, pressure, and sintering time. Powder rearrangement, plastic deformation below T g, and viscous flow of the material between Tg and Tx were observed as the main densification stages during SPS sintering. Micro-scale temperature distributions at the point of contact and macro-scale temperature distribution throughout the sample during SPS of amorphous alloys were modeled. The bulk amorphous alloys are expected to undergo structural relaxation and nanocrystallization during SPS sintering. X-ray diffraction (XRD), small angle neutron scattering (SANS), and transmission electron microscopy (TEM) was performed to investigate the evolution of nanocrystallites in SPS sintered Fe-based bulk amorphous alloys. The SANS analysis showed significant scattering for the samples sintered in the supercooled region indicating local structural and compositional changes with the profuse nucleation of nano-clusters (~4 nm). Compression tests and microhardness were performed on the samples sintered at different

  15. PROPERTIES AND BEHAVIOR OF 238PU RELEVANT TO DECONTAMINATION OF BUILDING 235-F

    SciTech Connect

    Duncan, A.; Kane, M.

    2009-11-24

    This report was prepared to document the physical, chemical and radiological properties of plutonium oxide materials that were processed in the Plutonium Fuel Form Facility (PuFF) in building 235-F at the Savannah River Plant (now known as the Savannah River Site) in the late 1970s and early 1980s. An understanding of these properties is needed to support current project planning for the safe and effective decontamination and deactivation (D&D) of PuFF. The PuFF mission was production of heat sources to power Radioisotope Thermoelectric Generators (RTGs) used in space craft. The specification for the PuO{sub 2} used to fabricate the heat sources required that the isotopic content of the plutonium be 83 {+-} 1% Pu-238 due to its high decay heat of 0.57 W/g. The high specific activity of Pu-238 (17.1 Ci/g) due to alpha decay makes this material very difficult to manage. The production process produced micron-sized particles which proved difficult to contain during operations, creating personnel contamination concerns and resulting in the expenditure of significant resources to decontaminate spaces after loss of material containment. This report examines high {sup 238}Pu-content material properties relevant to the D&D of PuFF. These relevant properties are those that contribute to the mobility of the material. Physical properties which produce or maintain small particle size work to increase particle mobility. Early workers with {sup 238}PuO{sub 2} felt that, unlike most small particles, Pu-238 oxide particles would not naturally agglomerate to form larger, less mobile particles. It was thought that the heat generated by the particles would prevent water molecules from binding to the particle surface. Particles covered with bound water tend to agglomerate more easily. However, it is now understood that the self-heating effect is not sufficient to prevent adsorption of water on particle surfaces and thus would not prevent agglomeration of particles. Operational

  16. Melting Behavior and Chemical Properties of the Iron-Carbon System

    NASA Astrophysics Data System (ADS)

    Prakapenka, V.; Kantor, I.; Kubo, A.; Kuznetsov, A.; Dera, P.; Rivers, M.; Sutton, S.

    2008-12-01

    One of the most challenging experiments related to the laser heating technique in the diamond anvil cell (DAC) is an unambiguous x-ray based detection of melting by recording high quality diffuse x-ray scattering from molten materials at high pressure. Employing a newly developed, advanced, flat top laser heating system at GSECARS, we were able to perform on-line melting experiments at pressures up to 60 GPa. The capability to maintain the molten sample in the DAC for a relatively long time (at least 60 s) allowed us to collect high quality x-ray scattering data suitable for structure analysis even from low-Z molten materials, such as Si, Ge, Fe, Fe3C, Fe7C3 etc. In this work, we focused on the melting behavior and chemical properties of the iron-carbon system at pressures up to ~170 GPa studied with on-line micro x-ray diffraction in a double sided laser heated DAC at GSECARS (Sector 13, APS). Iron carbides (Fe3C, Fe7C3) were synthesized in- situ in the DAC from various mixtures of Fe and C powders with different atomic ratios. We have found that the chemical reaction between iron and carbon takes place independent of the structure of starting phases of iron (fcc or hcp) and carbon (graphite or diamond). The reaction temperature increased gradually from ~1000 K to ~1700 K as pressure increased from 6 GPa to 155 GPa. The melting temperature of iron carbide was found to be systematically lower than for iron by ~300-400 degrees in the pressure range 20-60 GPa. The experimentally measured structure factor and related pair distribution function of iron carbide melt were analyzed and compared with pure iron data at related pressures. High- pressure, high-temperature stability of iron carbide phases at the relevant Earth's mantle-core conditions and physical/chemical properties of iron-carbon melts provide important constraints on models of the formation of D" layer and interactions at the core mantle boundary. Implications of these results for the composition and

  17. Lysozyme entrapped within reverse hexagonal mesophases: physical properties and structural behavior.

    PubMed

    Mishraki, Tehila; Libster, Dima; Aserin, Abraham; Garti, Nissim

    2010-01-01

    A model protein (lysozyme) was incorporated into monoolein-based reverse hexagonal (H(II)) mesophase and its structure effects were characterized by small angle X-ray scattering, ATR-FTIR spectroscopy, and rheological measurements. Modifications in molecular organization of the H(II) mesophases as well as the conformational stability of lysozyme (LSZ) as a function of pH and denaturating agent (urea) were clarified. Up to 3 wt.% LSZ can be solubilized into the H(II). The vibration FTIR analysis revealed that LSZ interacted with OH groups of glycerol monooleate (GMO) in the outer interface region, resulting in strong hydrogen bonding between the surfactant and its environment. Simultaneously, the decrease in the hydrogen-bonded carbonyl population of GMO was monitored, indicating dehydration of the monoolein carbonyls. These molecular interactions yielded a minor decrease in the lattice parameter of the systems, as detected by small angle X-ray scattering. Furthermore, LSZ was crystallized within the medium of the hexagonal structures in a single crystal form. The alpha-helix conformation of lysozyme was stabilized at high pH conditions, demonstrating greater helical structure content, compared to D(2)O solution. Moreover, the hexagonal phase decreased the unfavorable alpha-->beta transition in lysozyme, thereby increasing the stability of the protein under chemical denaturation. The rheological behavior of the hexagonal structures varied with the incorporation of LSZ, reflected in stronger elastic properties and pronounced solid-like response of the systems. The hydrogen bonding enhancement in the interface region of the structures was most likely responsible for these phenomena. The results of this study provided valuable information on the use of hexagonal systems as a carrier for incorporation and stabilization of proteins for various applications. PMID:19748240

  18. Tensile Properties and Fracture Behavior of Different Carbon Nanotube-Grafted Polyacrylonitrile-Based Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Naito, Kimiyoshi

    2014-11-01

    The tensile properties and fracture behavior of different carbon nanotube (CNT)-grafted polyacrylonitrile-based (T1000GB) single carbon fibers were investigated. Grafting of CNTs was achieved via chemical vapor deposition (CVD). When Fe(C5H5)2 (also applied via CVD) was used as the catalyst, the tensile strength and Weibull modulus of the carbon fibers were improved, possibly due to the growth of dense CNT networks on the carbon fibers, which may have led to a reduction in the number of strength-limiting defects. Separately, at lower concentrations of an Fe(NO3)3·9H2O catalyst in ethanol, which was applied via dipping, the tensile strength of CNT-grafted fibers was nearly identical to that of the as-received fibers, although the Weibull modulus was higher. For higher concentrations of the Fe(NO3)3·9H2O catalyst, however, the tensile strength and the Weibull modulus were lower than those for the as-received material. Although the density of the CNT network increased with the concentration of the Fe(NO3)3·9H2O catalyst in the ethanol solution, heating of the ethanolic Fe(NO3)3·9H2O catalyst solution generated nitric acid (HNO3) due to decomposition, which damaged the fiber surfaces, resulting in an increase in the number of flaws and consequently a reduction in the tensile strength. Therefore, the tensile strength and Weibull modulus of CNT-grafted carbon fibers vary due to the combination of these effects and as a function of the catalyst concentration.

  19. Elastic properties and buckling behavior of single-walled carbon nanotubes functionalized with diethyltoluenediamines using molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Ajori, S.; Rouhi, S.

    2015-01-01

    Carbon nanotube (CNT) modification processes are of great importance for good dispersion of CNTs and load transfer issues in nanocomposites. Among these processes, polymer covalent functionalization is found to be an effective way to alter the mechanical properties and behavior of pristine CNTs. Therefore, the mechanical properties and buckling behavior of diethyltoluenediamines (DETDA) functionalized CNTs are investigated employing molecular dynamics (MD) simulations. The results demonstrate that as the polymer weight percentage increases, Young's modulus and critical buckling load increase almost linearly for both regular and random polymer distributions, whereas critical strain decreases with different trends depending on the type of polymer distribution. Finally, the buckling mode shapes of the presented models are illustrated and it was revealed that there are some differences between the mode shapes of functionalized CNTs and those of pristine CNTs.

  20. Improved prediction of rat cortical bone mechanical behavior using composite beam theory to integrate tissue level properties.

    PubMed

    Kim, Grace; Boskey, Adele L; Baker, Shefford P; van der Meulen, Marjolein C H

    2012-11-15

    Tissue level characteristics of bone can be measured by nanoindentation and microspectroscopy, but are challenging to translate to whole bone mechanical behavior in this hierarchically structured material. The current study calculated weighted section moduli from microCT attenuation values based on tissue level relationships (Z(lin,a) and Z(lin,b)) between mineralization and material properties to predict whole bone mechanical behavior. Z(lin,a) was determined using the equation of the best fit linear regression between indentation modulus from nanoindentation and mineral:matrix ratio from Raman spectroscopy. To better represent the modulus of unmineralized tissue, a second linear regression with the intercept fixed at 0 was used to calculate Z(lin,b). The predictive capability of the weighted section moduli calculated using a tissue level relationship was compared with average tissue level properties and weighted section moduli calculated using an apparent level relationship (Z(exp)) between Young's Modulus and mineralization. A range of bone mineralization was created using vitamin D deficiency in growing rats. After 10 weeks, left femurs were scanned using microCT and tested to failure in 3 point bending. Contralateral limbs were used for co-localized tissue level mechanical properties by nanoindentation and compositional measurements by Raman microspectroscopy. Vitamin D deficiency reduced whole bone stiffness and strength by ∼35% and ∼30%, respectively, but only reduced tissue mineral density by ∼10% compared with Controls. Average tissue level properties did not correlate with whole bone mechanical behavior while Z(lin,a), Z(lin,b), and Z(exp) predicted 54%, 66%, and 80% of the failure moment respectively. This study demonstrated that in a model for varying mineralization, the composite beam model in this paper is an improved method to extrapolate tissue level data to macro-scale mechanical behavior. PMID:23021607

  1. Frictional properties of the active San Andreas Fault at SAFOD: Implications for fault strength and slip behavior

    NASA Astrophysics Data System (ADS)

    Carpenter, B. M.; Saffer, D. M.; Marone, C.

    2015-07-01

    We present results from a comprehensive laboratory study of the frictional strength and constitutive properties for all three active strands of the San Andreas Fault penetrated in the San Andreas Observatory at Depth (SAFOD). The SAFOD borehole penetrated the Southwest Deforming Zone (SDZ), the Central Deforming Zone (CDZ), both of which are actively creeping, and the Northeast Boundary Fault (NBF). Our results include measurements of the frictional properties of cuttings and core samples recovered at depths of ~2.7 km. We find that materials from the two actively creeping faults exhibit low frictional strengths (μ = ~0.1), velocity-strengthening friction behavior, and near-zero or negative rates of frictional healing. Our experimental data set shows that the center of the CDZ is the weakest section of the San Andreas Fault, with μ = ~0.10. Fault weakness is highly localized and likely caused by abundant magnesium-rich clays. In contrast, serpentine from within the SDZ, and wall rock of both the SDZ and CDZ, exhibits velocity-weakening friction behavior and positive healing rates, consistent with nearby repeating microearthquakes. Finally, we document higher friction coefficients (μ > 0.4) and complex rate-dependent behavior for samples recovered across the NBF. In total, our data provide an integrated view of fault behavior for the three active fault strands encountered at SAFOD and offer a consistent explanation for observations of creep and microearthquakes along weak fault zones within a strong crust.

  2. Steady shear flow behavior of sage seed gum affected by various salts and sugars: Time-independent properties.

    PubMed

    Yousefi, Ali R; Eivazlou, Razieh; Razavi, Seyed M A

    2016-10-01

    The rheological properties of food hydrocolloids are remarkably influenced by the quality of solvent/cosolutes in a food system. In this work, the steady shear flow behavior of sage seed gum (SSG, 0.5% w/w) at the presence of different levels of salts (KCl & MgCl2, 0-100mM) and sugars (sucrose, lactose & glucose, 0-6% w/w) was studied. It was found that the rheological properties of SSG were affected by the type of sugars and salts and their concentrations as well. Synergistic interaction was observed between SSG and sugars which enhanced the viscosity of gum solutions, while salts addition diminished the viscosity. SSG solutions exhibited a shear thinning behavior at all conditions tested. Various time-independent rheological models were used to fit the shear stress-shear rate data, although the Herschel-Bulkley (R(2)=0.994-0.999) and Sisko (R(2)=0.995-0.999) models showed the best results to describe the flow behavior of SSG. In the presence of salts, the yield stress (τ0), consistency coefficient (k), and flow behavior index (n) values decreased. The k and τ0 values enhanced and the n value lowered in the presence of sugars. Divalent cations of Mg(2+) and sucrose roughly showed more effect on rheological parameters than others. PMID:27316768

  3. Physical properties and Consolidation behavior of sediments from the N. Japan subduction zone

    NASA Astrophysics Data System (ADS)

    Valdez, R. D., II; Lauer, R. M.; Ikari, M.; Kitajima, H.; Saffer, D. M.

    2013-12-01

    Sediment hydraulic properties, consolidation state, and ambient pore pressure development are key parameters that affect fluid migration, deformation, and the slip behavior and mechanical strength of subduction zone megathrusts. In order to better understand the dynamics and mechanisms of large subduction earthquakes, Integrated Oceanic Drilling Program (IODP) Expedition 343, drilled into the toe of the Japan Trench subduction zone in a region of large shallow slip in the M 9.0 Tohoku earthquake, as part of the Japan Trench Fast Drilling Project (J-FAST). Here, we report on two constant rate of strain (CRS) uniaxial consolidation experiments and two triaxial deformation experiments on bedded claystone and clayey mudstone core samples collected from the frontal prism and subducted sediment section cored at Site C0019, 2.5 km landward of the Japan Trench, from depths of 697.18 and 831.45 mbsf. The goals of our experiments were: (1) to define the hydraulic and acoustic properties of sediments that host the subduction megathrust fault that slipped in the M 9.0 Tohoku earthquake; and (2) to constrain in-situ consolidation state and its implications for in-situ stress. The permeability-porosity trends are similar for the two samples, and both exhibit permeability that decreases systematically with increasing effective stress and decreasing porosity, and which varies log-linearly with porosity. Permeabilities of material from the frontal prism decrease from 5×10-18 m2 at 5 MPa effective stress, to 3.0×10-19 m2 at 70 MPa, and porosities decrease from 51% to 29%, while permeabilities of the subducted sediment sample decrease from 5×10-18 m2 at 5 MPa to 3.6×10-19 m2 at 90 MPa, and porosities decrease from 49% to 36%. In-situ permeabilities for the prism and underthrust sediment samples, estimated using laboratory defined permeability-porosity relationships, are 4.9×10-18 m2 and 3.7×10-18 m2, respectively. Elastic wavespeeds increase systematically with increasing

  4. Interplay of differential cell mechanical properties, motility, and proliferation in emergent collective behavior of cell co-cultures

    NASA Astrophysics Data System (ADS)

    Sutter, Leo; Kolbman, Dan; Wu, Mingming; Ma, Minglin; Das, Moumita

    The biophysics of cell co-cultures, i.e. binary systems of cell populations, is of great interest in many biological processes including formation of embryos, and tumor progression. During these processes, different types of cells with different physical properties are mixed with each other, with important consequences for cell-cell interaction, aggregation, and migration. The role of the differences in their physical properties in their collective behavior remains poorly understood. Furthermore, until recently most theoretical studies of collective cell migration have focused on two dimensional systems. Under physiological conditions, however, cells often have to navigate three dimensional and confined micro-environments. We study a confined, three-dimensional binary system of interacting, active, and deformable particles with different physical properties such as deformability, motility, adhesion, and division rates using Langevin Dynamics simulations. Our findings may provide insights into how the differences in and interplay between cell mechanical properties, division, and motility influence emergent collective behavior such as cell aggregation and segregation experimentally observed in co-cultures of breast cancer cells and healthy breast epithelial cells. This work was partially supported by a Cottrell College Science Award.

  5. Dual Ionic and Photo-Crosslinked Alginate Hydrogels for Micropatterned Spatial Control of Material Properties and Cell Behavior.

    PubMed

    Samorezov, Julia E; Morlock, Colin M; Alsberg, Eben

    2015-07-15

    Biomaterial properties such as mechanics, degradation rate, and cell adhesivity affect cell behaviors including spreading, proliferation, and differentiation. To engineer complex tissues, it is often desirable to achieve precise spatial control over these properties. Here, methacrylated alginate (MA-ALG) was used to create hydrogels comprising a single base material with regions of different types and levels of crosslinking and subsequently different material properties. Ionic and ultraviolet light crosslinking mechanisms were combined to create dual-crosslinked hydrogels with significantly increased stiffness and decreased swelling compared to calcium-crosslinked or UV-crosslinked hydrogels. MC3T3 cells showed significantly enhanced proliferation on the surface of dual-crosslinked hydrogels compared with calcium-crosslinked hydrogels. Photomasks were then used to create patterned hydrogels with precise spatial control over regions that were only calcium-crosslinked versus dual-crosslinked. This spatial variation in crosslinking mechanism permitted local regulation of the hydrogel physical properties and alignment of cells seeded on their surface. Photomasks were also used to create hydrogels with patterned presentation of cell adhesion ligands, leading to spatial control over cell attachment and proliferation. This biomaterial system can be useful for providing patterned, instructive cues to guide cell behavior for engineering complex tissues. PMID:25799217

  6. Fracture Behavior and Properties of Functionally Graded Fiber-Reinforced Concrete

    SciTech Connect

    Roesler, Jeffery; Bordelon, Amanda; Gaedicke, Cristian; Park, Kyoungsoo; Paulino, Glaucio

    2008-02-15

    In concrete pavements, a single concrete mixture design is selected to resist mechanical loading without attempting to adversely affect the concrete pavement shrinkage, ride quality, or noise attenuation. An alternative approach is to design distinct layers within the concrete pavement surface which have specific functions thus achieving higher performance at a lower cost. The objective of this research was to address the structural benefits of functionally graded concrete materials (FGCM) for rigid pavements by testing and modeling the fracture behavior of different combinations of layered plain and synthetic fiber-reinforced concrete materials. Fracture parameters and the post-peak softening behavior were obtained for each FGCM beam configuration by the three point bending beam test. The peak loads and initial fracture energy between the plain, fiber-reinforced, and FGCM signified similar crack initiation. The total fracture energy indicated improvements in fracture behavior of FGCM relative to full-depth plain concrete. The fracture behavior of FGCM depended on the position of the fiber-reinforced layer relative to the starter notch. The fracture parameters of both fiber-reinforced and plain concrete were embedded into a finite element-based cohesive zone model. The model successfully captured the experimental behavior of the FGCMs and predicted the fracture behavior of proposed FGCM configurations and structures. This integrated approach (testing and modeling) demonstrates the viability of FGCM for designing layered concrete pavements system.

  7. Evaluation of seawater exposure on mechanical properties and failure behavior of E-Glass/BMI composite for marine use

    NASA Astrophysics Data System (ADS)

    Zhao, Yian; Wang, Zhiying; Seah, Leong Keey; Chai, Gin Boay

    2015-03-01

    Since composite material is playing an increasingly important role in the marine and offshore drilling industry, it is essential to have a good understanding on degradation of the material in the seawater environment. This study investigates the influence of seawater exposure on the mechanical and failure behavior of E-Glass/BMI composite. The water diffusion behavior in the composite has been studied through immersing the specimens in seawater under different conditions. The diffusion rate accelerates with increase of temperature, and the material shows irreversible damage due to seawater absorption at the temperature of 80°C. It is also found that external stress would significantly increase the water absorption. The water uptake in the specimen at 50°C showed a two stage behavior dominated by Fickian law and polymeric relaxation respectively, and saturation was not achieved in 8 months. After diffusion, the Tg of the material is considerably lowered due to plasticization effect. However the effect was found to be reversible after drying the specimen. Based on the testing results of tensile, flexure and fatigue properties of the composites, it is concluded that seawater exposure especially at elevated temperature leads to significant degradation on mechanical properties of the composite. However, the flexural strength of BMI composite with seawater absorption becomes less susceptible to temperature change. It is also found that the seawater absorption doesn't show significant effect on the stiffness of the material.

  8. Mechanical properties and constitutive behaviors of as-cast 7050 aluminum alloy from room temperature to above the solidus temperature

    NASA Astrophysics Data System (ADS)

    Bai, Qing-ling; Li, Hong-xiang; Du, Qiang; Zhang, Ji-shan; Zhuang, Lin-zhong

    2016-08-01

    The mechanical properties and constitutive behaviors of as-cast AA7050 in both the solid and semi-solid states were determined using the on-cooling and in situ solidification approaches, respectively. The results show that the strength in the solid state tends to increase with decreasing temperature. The strain rate plays an important role in the stress-strain behaviors at higher temperatures, whereas the influence becomes less pronounced and irregular when the temperature is less than 250°C. The experimental data were fitted to the extended Ludwik equation, which is suitable to describe the mechanical behavior of the materials in the as-cast state. In the semi-solid state, both the strength and ductility of the alloy are high near the solidus temperature and decrease drastically with decreasing solid fraction. As the solid fraction is less than 0.97, the maximum strength only slightly decreases, whereas the post-peak ductility begins to increase. The experimental data were fitted to the modified creep law, which is used to describe the mechanical behavior of semi-solid materials, to determine the equivalent parameter f GBWL, i.e., the fraction of grain boundaries covered by liquid phase.

  9. Subtask 12F4: Effects of neutron irradiation on the impact properties and fracture behavior of vanadium-base alloys

    SciTech Connect

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

    1995-03-01

    Up-to-date results on the effects of neutron irradiation on the impact properties and fracture behavior of V, V-Ti, V-Cr-Ti and V-Ti-Si alloys are presented in this paper, with an emphasis on the behavior of the U.S. reference alloys V-4Cr-4Ti containing 500-1000 wppm Si. Database on impact energy and cluctile-brittle transition temperature (DBTT) has been established from Charpy impact tests of one-third-size specimens irradiated at 420{degrees}C-600{degrees}C up to {approx}50 dpa in lithium environment in fast fission reactors. To supplement the Charpy impact tests fracture behavior was also characterized by quantitative SEM fractography on miniature tensile and disk specimens that were irradiated to similar conditions and fractured at -196{degrees}C to 200{degrees}C by multiple bending. For similar irradiation conditions irradiation-induced increase in DBTT was influenced most significantly by Cr content, indicating that irradiation-induced clustering of Cr atoms takes place in high-Cr (Cr {ge} 7 wt.%) alloys. When combined contents of Cr and Ti were {le}10 wt.%, effects of neutron irradiation on impact properties and fracture behavior were negligible. For example, from the Charpy-impact and multiple-bend tests there was no indication of irradiation-induced embrittlement for V-5Ti, V-3Ti-1Si and the U.S. reference alloy V-4Cr-4Ti after irradiation to {approx}34 dpa at 420{degrees}C to 600{degrees}C, and only ductile fracture was observed for temperatures as low as -196{degrees}C. 14 refs., 8 figs., 1 tab.

  10. Psychometric Properties of the Portuguese Version of the Adaptive Behavior Scale

    ERIC Educational Resources Information Center

    Santos, Sofia; Morato, Pedro; Luckasson, Ruth

    2014-01-01

    The adaptive behavior construct has gained prominent attention in human services over the last several years in Portugal, and its measurement has become an integral part of the assessment of populations with intellectual disability. In Portugal, diagnosis remains exclusively based on IQ measures, although some attention recently has been given to…

  11. Spectroscopic Analysis of 10MAG/LDAO Reverse Micelles to Determine Characteristic Properties and Behavioral Extrema

    NASA Astrophysics Data System (ADS)

    Berg, Joshua; Mawson, Cara; Norris, Zach; Nucci, Nathaniel

    Reverse micelles are spontaneously organizing complexes of surfactant that encapsulate a nanoscale pool of water in a bulk non-polar solvent. Reverse micelle (RM) mixtures have a wide range of applications, including biophysical investigation of protein systems. A new RM mixture composed of decyl-1-monoglycerol (10MAG) and lauryldimethylammonium-N-oxide (LDAO) was recently described. This mixture has the potential to prove more widely applicable for use of RMs in applications that involve encapsulation of macromolecules, yet little is known about the phase behavior or size of reverse micelles created by this mixture. Data describing such behaviors for this mixture are presented here. We have used dynamic light scattering (DLS) and fluorescence spectroscopy to investigate the size and partitioning behavior of RMs in varying mixtures of 10MAG, LDAO, water, pentane, and hexanol. These data demonstrate that the 10MAG/LDAO RM mixture exhibits markedly different phase and RM size behavior than that of commonly used RM surfactant mixtures. The implications of these findings for use of the 10MAG/LDAO mix for RM applications will also be addressed. Funding provided by Rowan University.

  12. Diversity of Cell Properties and Transport Behavior Among 12 Enviromental Escherichia Coli Isolates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Escherichia coli is a commonly used indicator organism for detecting the presence of fecal-borne pathogenic microorganisms in water supplies. The importance of E. coli as an indicator organism has led to numerous studies looking at surface characteristics and transport behavior of this important mi...

  13. Dynamic mechanical behavior of human dentin and collagen: Methods and properties

    NASA Astrophysics Data System (ADS)

    Ryou, Heonjune

    Experimental evaluations of human coronal dentin and its collagen fibrils were performed by Dynamic Mechanical Analysis (DMA) using nanoindentation and Atomic Force Microscopy (AFM). The primary objectives were to quantify the changes in mechanical behavior of intertubular and peritubular dentin with age, and to evaluate the nanostructure and mechanical behavior of the collagen fibrils. Specimens of coronal dentin were evaluated by nanoDMA using single indents and in scanning mode via scanning probe microscopy. Collagen fibrils from coronal dentin were evaluated using Pulse-Force Mode (PFM) AFM (Peakforce QNM). Nanoindentation results showed that there were no significant differences in the storage modulus or complex modulus between the two age groups (18-25 versus 54-83 yrs) for either the intertubular or peritubular dentin. However, there were significant differences in the dampening behavior between the young and old tissues, as represented in the loss modulus and tanϕ responses. For both the intertubular and peritubular components, the capacity for dampening was significantly lower in the old group. Scanning based nanoDMA showed that the tubules of old dentin exhibit a gradient in elastic behavior, with decrease in elastic modulus from the cuff to the center of tubules filled with newly deposited mineral. AFM results showed that the stiffness of the old dentin fibrils in the peak and trough regions were greater than the young dentin fibrils. In addition, there were significant differences in the dampening behavior between the young and old dentin fibrils, as represented in the energy dissipation, phase angle and loss modulus responses. For both the peak and trough regions, the dissipative capacity was significantly lower in the old dentin fibrils.

  14. Dependence of mechanical behavior of the murine tail disc on regional material properties: a parametric finite element study.

    PubMed

    Hsieh, Adam H; Wagner, Diane R; Cheng, Louis Y; Lotz, Jeffrey C

    2005-12-01

    In vivo rodent tail models are becoming more widely used for exploring the role of mechanical loading on the initiation and progression of intervertebral disc degeneration. Historically, finite element models (FEMs) have been useful for predicting disc mechanics in humans. However, differences in geometry and tissue properties may limit the predictive utility of these models for rodent discs. Clearly, models that are specific for rodent tail discs and accurately simulate the disc's transient mechanical behavior would serve as important tools for clarifying disc mechanics in these animal models. An FEM was developed based on the structure, geometry, and scale of the mouse tail disc. Importantly, two sources of time-dependent mechanical behavior were incorporated: viscoelasticity of the matrix, and fluid permeation. In addition, a novel strain-dependent swelling pressure was implemented through the introduction of a dilatational stress in nuclear elements. The model was then validated against data from quasi-static tension-compression and compressive creep experiments performed previously using mouse tail discs. Finally, sensitivity analyses were performed in which material parameters of each disc subregion were individually varied. During disc compression, matrix consolidation was observed to occur preferentially at the periphery of the nucleus pulposus. Sensitivity analyses revealed that disc mechanics was greatly influenced by changes in nucleus pulposus material properties, but rather insensitive to variations in any of the endplate properties. Moreover, three key features of the model-nuclear swelling pressure, lamellar collagen viscoelasticity, and interstitial fluid permeation-were found to be critical for accurate simulation of disc mechanics. In particular, collagen viscoelasticity dominated the transient behavior of the disc during the initial 2200 s of creep loading, while fluid permeation governed disc deformation thereafter. The FEM developed in this

  15. Is Substance Use Associated with Perpetration and Victimization of Physically Violent Behavior and Property Offences among Homeless Youth? A Systematic Review of International Studies

    ERIC Educational Resources Information Center

    Heerde, Jessica A.; Hemphill, Sheryl A.

    2015-01-01

    Background: Substance use is a commonly reported problem associated with numerous adverse outcomes among homeless youth. Homelessness is reportedly a covariate to perpetration of, and victimization from, physically violent behavior and property offences. Of particular importance in both the perpetration of, and victimization from these behaviors,…

  16. Study of mechanical properties, microstructures and corrosion behavior of al 7075 t651 alloy with varying strain rate

    NASA Astrophysics Data System (ADS)

    Mukherjee, A.; Ghosh, M.; Mondal, K.; Venkitanarayanan, P.; Moon, A. P.; Varshney, A.

    2015-02-01

    Compression test of Al 7075 T651 was carried out at high strain rates (1138 - 2534 s-1) using Split Hopkinson Pressure Bar and at slow strain rate (10-4s-1) in 100KN Universal Testing machine to understand the improvement in mechanical properties and associated changes in microstructures. Cylindrical specimens of 6 mm height and 6 mm diameter were compressed dynamically. The influence of strain rates on mechanical properties, microstructure evolution and corrosion behavior after immersion test in 3.5% NaCl solution was also investigated. Strain rate, withdrawal stress and yield stress were observed to increase with impact velocity in high strain rate tests, while in slow strain rate tests, n value was observed to increase with increasing total strain. Microstructural observations revealed that after high strain rate test, grains of Al matrix were elongated. It was observed that corrosion resistance decreased with increase in impact velocity.

  17. Effects of Sn addition on the microstructure, mechanical properties and corrosion behavior of Ti–Nb–Sn alloys

    SciTech Connect

    Moraes, Paulo E.L.; Contieri, Rodrigo J.; Lopes, Eder S.N.; Robin, Alain; Caram, Rubens

    2014-10-15

    Ti and Ti alloys are widely used in restorative surgery because of their good biocompatibility, enhanced mechanical behavior and high corrosion resistance in physiological media. The corrosion resistance of Ti-based materials is due to the spontaneous formation of the TiO{sub 2} oxide film on their surface, which exhibits elevated stability in biological fluids. Ti–Nb alloys, depending on the composition and the processing routes to which the alloys are subjected, have high mechanical strength combined with low elastic modulus. The addition of Sn to Ti–Nb alloys allows the phase transformations to be controlled, particularly the precipitation of ω phase. The aim of this study is to discuss the microstructure, mechanical properties and corrosion behavior of cast Ti–Nb alloys to which Sn has been added. Samples were centrifugally cast in a copper mold, and the microstructure was characterized using optical microscopy, scanning electron microscopy and X-ray diffractometry. Mechanical behavior evaluation was performed using Berkovich nanoindentation, Vickers hardness and compression tests. The corrosion behavior was evaluated in Ringer's solution at room temperature using electrochemical techniques. The results obtained suggested that the physical, mechanical and chemical behaviors of the Ti–Nb–Sn alloys are directly dependent on the Sn content. - Graphical abstract: Effects of Sn addition to the Ti–30Nb alloy on the elastic modulus. - Highlights: • Sn addition causes reduction of the ω phase precipitation. • Minimum Vickers hardness and elastic modulus occurred for 6 wt.% Sn content. • Addition of 6 wt.% Sn resulted in maximum ductility and minimum compression strength. • All Ti–30Nb–XSn (X = 0, 2, 4, 6, 8 and 10%) alloys are passive in Ringer's solution. • Highest corrosion resistance was observed for 6 wt.% Sn content.

  18. Behavioral phenotypic properties of a natural occurring rat model of congenital stationary night blindness with Cacna1f mutation.

    PubMed

    An, Jing; Wang, Li; Guo, Qun; Li, Li; Xia, Feng; Zhang, Zuoming

    2012-09-01

    Cacna1f gene mutation could lead to incomplete congenital stationary night blindness (iCSNB) disease. The CSNB-like phenotype rat is a spontaneous rat model caused by Cacna1f gene mutation. The present study explored the phenotypic properties of behavior performance in CSNB rats further. The vision-related behaviors of CSNB rats were assessed with a Morris water maze (MWM), passive avoidance tests, and open-field test. Motor ability was evaluated with a rotarod test and a wire hang test, and mechanical pain and thermalgia were used to evaluate sensory system function. Electroretinograms (ERGs) were recorded to evaluate the function of the retina. The vision-related results showed that longer latencies of escape and reduced probe trial in MWM for CSNB rats. There were more errors in avoidance test; CSNB rats were more active in the open field and presented a different pattern of exploration. The locomotor-related behaviors showed shorter falling latencies in the rotarod test and shorter gripping time in CSNB rats. And mechanical thresholds of pain increased in CSNB rats. The ERGs indicated that both the amplitude and latency of rod and cone systems were impaired in the CSNB rats. In summary, Cacna1f gene mutation changed the performance of various behaviors in the CSNB rat aside from vision-related phenotype. Cacna1f gene might play a role in a wide range of responses in the organism. These results confirm the importance of a comprehensive profile for understanding the behavior phenotype of Cacna1f gene mutation in CSNB rat. PMID:22800190

  19. Mechanical behavior, properties and reliability of tin-modified lead zirconate titanate.

    SciTech Connect

    Watson, Chad Samuel

    2003-08-01

    The influences of temperature and processing conditions (unpoled or poled-depoled) on strength, fracture toughness and the stress-strain behavior of tin-modified lead zirconate titanate (PSZT) were evaluated in four-point bending. PSZT exhibits temperature-dependent non-linear and non-symmetric stress-strain behavior. A consequence of temperature dependent non-linearity is an apparent reduction in the flexural strength of PSZT as temperature increases. At room temperature the average stress in the outer-fiber of bend bars was 84 MPa, whereas, for specimens tested at 120 C the average failure stress was only 64 MPa. The load-carrying capacity, however, does not change with temperature, but the degree of deformation tolerated by PSZT prior to failure increased with temperature.

  20. Predictive Models with Patient Specific Material Properties for the Biomechanical Behavior of Ascending Thoracic Aneurysms.

    PubMed

    Trabelsi, Olfa; Duprey, Ambroise; Favre, Jean-Pierre; Avril, Stéphane

    2016-01-01

    The aim of this study is to identify the patient-specific material properties of ascending thoracic aortic aneurysms (ATAA) using preoperative dynamic gated computed tomography (CT) scans. The identification is based on the simultaneous minimization of two cost functions, which define the difference between model predictions and gated CT measurements of the aneurysm volume at respectively systole and cardiac mid-cycle. The method is applied on five patients who underwent surgical repair of their ATAA at the University Hospital Center of St. Etienne. For these patients, the aneurysms were collected and tested mechanically using an in vitro bench. For the sake of validation, the mechanical properties found using the in vivo approach and the in vitro bench were compared. We eventually performed finite-element stress analyses based on each set of material properties. Rupture risk indexes were estimated and compared, showing promising results of the patient-specific identification method based on gated CT. PMID:26178871

  1. The structural properties of InGaN alloys and the interdependence on the thermoelectric behavior

    NASA Astrophysics Data System (ADS)

    Kucukgok, Bahadir; Wu, Xuewang; Wang, Xiaojia; Liu, Zhiqiang; Ferguson, Ian T.; Lu, Na

    2016-02-01

    The III-Nitrides are promising candidate for high efficiency thermoelectric (TE) materials and devices due to their unique features which includes high thermal stability. A systematic study of the room temperature TE properties of metalorganic chemical vapor deposition grown InxGa1-xN were investigated for x = 0.07 to 0.24. This paper investigated the role of indium composition on the TE properties of InGaN alloys in particular the structural properties for homogenous material that did not show significant phase separation. The highest Seebeck and power factor values of 507 μV K-1 and 21.84 × 10-4 Wm-1K-1 were observed, respectively for In0.07Ga0.93N at room temperature. The highest value of figure-of-merit (ZT) was calculated to be 0.072 for In0.20Ga0.80N alloy at room temperature.

  2. Properties of the Visible Light Phototaxis and UV Avoidance Behaviors in the Larval Zebrafish

    PubMed Central

    Guggiana-Nilo, Drago A.; Engert, Florian

    2016-01-01

    For many organisms, color is an essential source of information from visual scenes. The larval zebrafish has the potential to be a model for the study of this topic, given its tetrachromatic retina and high dependence on vision. In this study we took a step toward understanding how the larval zebrafish might use color sensing. To this end, we used a projector-based paradigm to force a choice of a color stimulus at every turn of the larva. The stimuli used spanned most of the larval spectral range, including activation of its Ultraviolet (UV) cone, which has not been described behaviorally before. We found that zebrafish larvae swim toward visible wavelengths (>400 nm) when choosing between them and darkness, as has been reported with white light. However, when presented with UV light and darkness zebrafish show an intensity dependent avoidance behavior. This UV avoidance does not interact cooperatively with phototaxis toward longer wavelengths, but can compete against it in an intensity dependent manner. Finally, we show that the avoidance behavior depends on the presence of eyes with functional UV cones. These findings open future avenues for studying the neural circuits that underlie color sensing in the larval zebrafish. PMID:27594828

  3. Properties of the Visible Light Phototaxis and UV Avoidance Behaviors in the Larval Zebrafish.

    PubMed

    Guggiana-Nilo, Drago A; Engert, Florian

    2016-01-01

    For many organisms, color is an essential source of information from visual scenes. The larval zebrafish has the potential to be a model for the study of this topic, given its tetrachromatic retina and high dependence on vision. In this study we took a step toward understanding how the larval zebrafish might use color sensing. To this end, we used a projector-based paradigm to force a choice of a color stimulus at every turn of the larva. The stimuli used spanned most of the larval spectral range, including activation of its Ultraviolet (UV) cone, which has not been described behaviorally before. We found that zebrafish larvae swim toward visible wavelengths (>400 nm) when choosing between them and darkness, as has been reported with white light. However, when presented with UV light and darkness zebrafish show an intensity dependent avoidance behavior. This UV avoidance does not interact cooperatively with phototaxis toward longer wavelengths, but can compete against it in an intensity dependent manner. Finally, we show that the avoidance behavior depends on the presence of eyes with functional UV cones. These findings open future avenues for studying the neural circuits that underlie color sensing in the larval zebrafish. PMID:27594828

  4. Ab initio calculations of optical properties of silver clusters: cross-over from molecular to nanoscale behavior

    NASA Astrophysics Data System (ADS)

    Titantah, John T.; Karttunen, Mikko

    2016-05-01

    Electronic and optical properties of silver clusters were calculated using two different ab initio approaches: (1) based on all-electron full-potential linearized-augmented plane-wave method and (2) local basis function pseudopotential approach. Agreement is found between the two methods for small and intermediate sized clusters for which the former method is limited due to its all-electron formulation. The latter, due to non-periodic boundary conditions, is the more natural approach to simulate small clusters. The effect of cluster size is then explored using the local basis function approach. We find that as the cluster size increases, the electronic structure undergoes a transition from molecular behavior to nanoparticle behavior at a cluster size of 140 atoms (diameter ~1.7 nm). Above this cluster size the step-like electronic structure, evident as several features in the imaginary part of the polarizability of all clusters smaller than Ag147, gives way to a dominant plasmon peak localized at wavelengths 350 nm ≤ λ ≤ 600 nm. It is, thus, at this length-scale that the conduction electrons' collective oscillations that are responsible for plasmonic resonances begin to dominate the opto-electronic properties of silver nanoclusters.

  5. Photophysical Properties and Adsorption Behaviors of Novel Tri-Cationic Boron(III) Subporphyrin on Anionic Clay Surface.

    PubMed

    Tsukamoto, Takamasa; Shimada, Tetsuya; Takagi, Shinsuke

    2016-03-23

    Two types of +3-charged subporphyrin derivatives with m- and p-methylpyridinium as the meso-aryl substituents were designed and synthesized. Their photophysical properties with and without anionic saponite clay were investigated. These cationic subporphyrins were suitably designed for adsorption on the saponite nanosheet surface with their photoactivity. Absorption and emission spectra of these subporphyrin-saponite complexes exhibited strong bathochromic shifts due to the flattening of the molecules on the nanosheet. This behavior was observed as drastic visual changes in their luminescence colors. Additionally, aggregation behaviors were not observed in the saponite complexes even at high dye loading levels for both subporphyrins. Moreover, under such condition, their fluorescence properties on the saponite surface were not only maintained but also enhanced without unexpected deactivations despite the dye molecules are densely introduced on the solid surface. These findings are beneficial for applications of the dye-clay complexes to photofunctional materials such as strongly luminescent materials, highly sensitive clay sensors and artificial photosynthesis systems. PMID:26928385

  6. Wetting behavior and nanotribological properties of silicon nanopatterns combined with diamond-like carbon and perfluoropolyether films

    NASA Astrophysics Data System (ADS)

    Pham, D. C.; Na, K.; Piao, S.; Cho, I.-J.; Jhang, K.-Y.; Yoon, E.-S.

    2011-09-01

    A large number of silicon (Si) patterns consisting of nanopillars of varying diameter and pitch have been fabricated and further coated with diamond-like carbon (DLC) and perfluoropolyether (Z-DOL) films. The wetting behavior and nano-adhesion/friction of the patterns are investigated experimentally in relation to the nanostructures and the hydrophobicity of the materials. Measurements of water contact angle illustrate that the patterning-enhanced wettability of the Si flat surface, along with two distinct wettings which are in good agreement with the Wenzel and hemi-wicking states, depended on the value of the pitch-over-diameter ratio. In the case of the coated patterns, three wetting states are observed: the Cassie-Baxter, the Wenzel, and a transition from the Cassie-Baxter into the Wenzel, which varies with regard to the hydrophobic properties of the DLC and Z-DOL. In terms of tribological properties, it is demonstrated that a combination of the nanopatterns and the films is effective in reducing adhesive and frictional forces. In addition, the pitch and diameter of the patterns are found to significantly influence their adhesion/friction behaviors.

  7. Schools, Taxes, and Voter Behavior: An Analysis of School District Property Tax Elections.

    ERIC Educational Resources Information Center

    Alexander, Arthur J.; Bass, Gail V.

    This research is based on more than 1,600 school district property tax elections in California from the mid-1950s to 1972. Population, housing, social, demographic, and economic information by school district was available. This large, comprehensive, and consistent data base permitted investigation of the choices of the electorate with respect to…

  8. Links between mechanical behavior of cancellous bone and its microstructural properties under dynamic loading.

    PubMed

    Prot, M; Saletti, D; Pattofatto, S; Bousson, V; Laporte, S

    2015-02-01

    Previous studies show that in vivo assessment of fracture risk can be achieved by identifying the relationships between microarchitecture description from clinical imaging and mechanical properties. This study demonstrates that results obtained at low strain rates can be extrapolated to loadings with an order of magnitude similar to trauma such as car crashes. Cancellous bovine bone specimens were compressed under dynamic loadings (with and without confinement) and the mechanical response properties were identified, such as Young׳s modulus, ultimate stress, ultimate strain, and ultimate strain energy. Specimens were previously scanned with pQCT, and architectural and structural microstructure properties were identified, such as parameters of geometry, topology, connectivity and anisotropy. The usefulness of micro-architecture description studied was in agreement with statistics laws. Finally, the differences between dynamic confined and non-confined tests were assessed by the bone marrow influence and the cancellous bone response to different boundary conditions. Results indicate that architectural parameters, such as the bone volume fraction (BV/TV), are as strong determinants of mechanical response parameters as ultimate stress at high strain rates (p-value<0.001). This study reveals that cancellous bone response at high strain rates, under different boundary conditions, can be predicted from the architectural parameters, and that these relations with mechanical properties can be used to make fracture risk prediction at a determined magnitude. PMID:25577437

  9. Modified flax fibers reinforced soy-based composites: mechanical properties and water absorption behavior

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Flax fibers are often used in reinforced composites which have exhibited numerous advantages such as high mechanical properties, low density and biodegradability. On the other hand, the hydrophilic nature of flax fiber is a major problem. In this study, we prepare the soybean oil based composites ...

  10. Monoacylglycerol Lipase Inhibitor JZL184 Improves Behavior and Neural Properties in Ts65Dn Mice, a Model of Down Syndrome

    PubMed Central

    Lysenko, Larisa V.; Kim, Jeesun; Henry, Cassandra; Tyrtyshnaia, Anna; Kohnz, Rebecca A.; Madamba, Francisco; Simon, Gabriel M.; Kleschevnikova, Natalia E.; Nomura, Daniel K.; Ezekowitz, R . Alan B.; Kleschevnikov, Alexander M.

    2014-01-01

    Genetic alterations or pharmacological treatments affecting endocannabinoid signaling have profound effects on synaptic and neuronal properties and, under certain conditions, may improve higher brain functions. Down syndrome (DS), a developmental disorder caused by triplication of chromosome 21, is characterized by deficient cognition and inevitable development of the Alzheimer disease (AD) type pathology during aging. Here we used JZL184, a selective inhibitor of monoacylglycerol lipase (MAGL), to examine the effects of chronic MAGL inhibition on the behavioral, biochemical, and synaptic properties of aged Ts65Dn mice, a genetic model of DS. In both Ts65Dn mice and their normosomic (2N) controls, JZL184-treatment increased brain levels of 2-arachidonoylglycerol (2-AG) and decreased levels of its metabolites such as arachidonic acid, prostaglandins PGD2, PGE2, PGFα, and PGJ2. Enhanced spontaneous locomotor activity of Ts65Dn mice was reduced by the JZL184-treatement to the levels observed in 2N animals. Deficient long-term memory was also improved, while short-term and working types of memory were unaffected. Furthermore, reduced hippocampal long-term potentiation (LTP) was increased in the JZL184-treated Ts65Dn mice to the levels observed in 2N mice. Interestingly, changes in synaptic plasticity and behavior were not observed in the JZL184-treated 2N mice suggesting that the treatment specifically attenuated the defects in the trisomic animals. The JZL184-treatment also reduced the levels of Aβ40 and Aβ42, but had no effect on the levels of full length APP and BACE1 in both Ts65Dn and 2N mice. These data show that chronic MAGL inhibition improves the behavior and brain functions in a DS model suggesting that pharmacological targeting of MAGL may be considered as a perspective new approach for improving cognition in DS. PMID:25474204

  11. Emerging collective behavior and local properties of financial dynamics in a public investment game

    NASA Astrophysics Data System (ADS)

    da Silva, Roberto; Bazzan, Ana L. C.; Baraviera, Alexandre T.; Dahmen, Sílvio R.

    2006-11-01

    In this paper we consider a simple model of a society of economic agents, namely a variation of the well known “public investment game”, where each agent can contribute with a discrete quantity, i.e., cooperate to increase the benefits of the group. Interactions take place among nearest neighbors and depend on the motivation level (insider information, economy prospects). The profit is used to update individual motivations. We first explore a deterministic scenario and the existence of fixed points and attractors. We also consider the presence of noise, where profits fluctuate stochastically. In this scenario we analyze the global persistence as a function of time-a measure of the probability that the amount of money of the entire group remains at least equal to its initial value. Our simulations show that this quantity has a power law behavior. We have also performed simulations with a population of heterogeneous agents, including deceivers and conservatives. We show that, although there is no regular pattern regarding the average wealth, robust power laws for persistence do exist and argue that this can be used to characterize the emerging collective behavior. The influence of the motivation updating and the presence of conservatives and deceivers on persistence is also studied. Simulations for the local persistence exploring two different versions of this concept: the probability of a particular agent not going bankrupt (i.e., remaining wealth ⩾0 up to time t) and the probability of a particular agent making more money than he initially had. Different power law behaviors are also observed in these situations.

  12. Microstructural characterization of the chemomechanical behavior of asphalt in terms of aging and fatigue performance properties

    NASA Astrophysics Data System (ADS)

    Allen, Robert Grover

    The study of asphalt chemo-mechanics requires a basic understanding of the physical properties and chemical composition of asphalt and how these properties are linked to changes in performance induced by chemical modifications. This work uniquely implements the framework of chemo-mechanics by investigating two types of chemical modification processes, natural (oxidative aging) and synthetic (chemical doping) as they relate not only to macro-scale properties of asphalt binder but also to the asphalt microstructure and nanorheology. Furthermore, this study demonstrates the application of atomic force microscopy (AFM) imaging and the extraction of nano-scale engineering properties, i.e. elastic modulus, relaxation modulus, and surface energy, as a method to predict performance related to the fatigue characteristics of asphalt binders by modeling intrinsic material flaws present amongst phase interfaces. It was revealed that oxidative aging induces substantial microstructural changes in asphalt, including variations in phase structure, phase properties, and phase distribution. It has also been shown that certain asphalt chemical parameters have a consistent and measureable effect on the asphalt microstructure that is observed with AFM. In fact, particular phases that emerged via chemical doping revealed a surprising correlation between oxidative aging and the saturates chemical parameter of asphalt in terms of how they explicitly impact durability and performance of asphalt. By implementing a crack initiation model---which requires measureable microstructural characteristics as an input parameter---it was found that microstructural flaws (depending on the extremity) can have a more profound impact on asphalt performance than the properties of the material located between the flaws. It was also discovered by comparing the findings to performance data in the Strategic Highway Research Program's (SHRP's) Materials Reference Library (MRL), that the crack initiation model

  13. Controllable fabrication of zinc borate hierarchical nanostructure on brucite surface for enhanced mechanical properties and flame retardant behaviors.

    PubMed

    Wang, Xuesong; Pang, Hongchang; Chen, Wendan; Lin, Yuan; Zong, Lishuai; Ning, Guiling

    2014-05-28

    A novel and efficient halogen-free composite flame retardant (CFR) consisting of a brucite core and a fine zinc borate [Zn6O(OH)(BO3)3] hierarchical nanostructure shell was designed and synthesized via a facile nanoengineering route. It had been demonstrated that this unique hybrid structure possessed a high BET specific surface area (65 m(2)/g) and could significantly enhance the interfacial interaction when mixing with ethylene-vinyl acetate (EVA). This improved the transfer of stress between CFR particles and EVA matrix and increased the viscosity of EVA/EVA blends, which was beneficial for droplet inhibition and char forming. The mechanical properties and flammability behaviors of the EVA/CFR blends had been compared with the EVA/physical mixture (PM, with the given proportion of brucite and Zn6O(OH)(BO3)3). The mechanical properties of EVA/CFR blends, especially the tensile strength (TS), presented a remarkable increase reaching at least a 20% increment. Meanwhile, with the same 45 wt % of fillers, the EVA/CFR formulation could achieve a limiting oxygen index (LOI) value of 33 (37.5 % higher than that of EVA/PM blends) and UL-94 V-0 rating. Moreover, the heat release rate (HRR), peak heat release rate (PHRR), total heat released (THR), smoke production rate (SPR) and mass loss rate (MLR) were considerably reduced, especially PHRR and SPR for EVA/CFR blends were reduced to 32%. According to this study, the design of fine structure might pave the way for the future development of halogen-free flame retardants combining both enhanced mechanical properties and excellent flame retardant behaviors. PMID:24813539

  14. The role of composition and microstructure gradients on weld metal properties and behavior: Progress report, 1 January 1988--31 December 1988

    SciTech Connect

    Matlock, D.K.; Olson, D.L.

    1989-01-01

    The effects of weld metal compositional and microstructural gradients on phase transformation, microstructural stability, and mechanical properties are considered from a fundamental basis in weld metal alloys which are primarily austenitic (e.g., stainless steels). Models which incorporate compositional gradients are developed to predict the resulting weld metal properties and behavior. The mechanical properties of weld metal are modeled based on composite theory in which individual weld metal zones are considered as discrete elements within a composite structure. 17 refs., 28 figs.

  15. An experimental study on arsoles: structural variation, optical and electronic properties, and emission behavior.

    PubMed

    Ishidoshiro, Makoto; Imoto, Hiroaki; Tanaka, Susumu; Naka, Kensuke

    2016-06-01

    We experimentally demonstrated the intrinsic nature of arsoles as promising functional heteroles. A series of 2,5-diarylarsoles are easily and safely prepared through the procedure in which non-volatile arsenic intermediates are employed to overcome the synthetic barrier due to the concern of volatility of the arsenic precursors used in conventional methods. A Pd-catalyzed Suzuki-Miyaura coupling reaction can be applied to the obtained arsoles for fine molecular design, unlikely to phospholes. It was demonstrated that the optical and electronic properties, i.e. emission colors, quantum yields, and energy levels of the frontier orbitals, are similar to those of phospholes, as conventional theoretical studies have predicted. Furthermore, it was found that arsoles showed mechanochromic properties. PMID:27080400

  16. Relaxation behavior and nonlinear properties of thermally stable polymers based on glycidyl derivatives of quercetin

    NASA Astrophysics Data System (ADS)

    Mishurov, Dmytro; Voronkin, Andrii; Roshal, Alexander; Brovko, Oleksandr

    2016-07-01

    Cross-linked polymers on the basis of di-, tri and tetraglycidyl ethers of quercetin (3,3‧,4‧,5,7-pentahydroxyflavone) were synthesized, and then, poled in electrical field of corona discharge. Investigations of structural, thermal and optical parameters of the polymer films were carried out. It was found that the polymers obtained from di- and triglycidyl quercetin ethers had high values of macroscopic quadratic susceptibilities and substantial stability of nonlinear optical (NLO) properties after the poling. Tetraglycidyl ether of quercetin forms the polymer of lower quadratic susceptibility, which demonstrates noticeable relaxation process resulting in decrease of the NLO effect. It is supposed that the difference of the NLO properties is due to peculiarities of physical network of the polymers, namely to the ratio between numbers of hydrogen bonds formed by hydroxyl groups of chromophore fragments and by the ones of interfragmental parts of the polymeric chains.

  17. Oxygen-induced magnetic properties and metallic behavior of a BN sheet

    SciTech Connect

    Zhou, Yungang; Zu, Xiaotao T.; Yang, Ping; Xiao, Hai Yan; Gao, Fei

    2010-11-24

    In this paper, ab initio method has been employed to study the adsorption energies, electronic structures and magnetic properties of a BN sheet functionalized by oxygen (O) atom. The adsorption process is typically exothermic, and some unusual properties can be revealed with different adsorption sites. The energy gap of BN sheet narrows due to the strong hybridization between O and BN electronic states when O locates above a BN bond or a nitrogen atom. Upon the adsorption of O above a B3N3 ring or a boron atom, the electrons of O-adsorbed BN system are polarized, which gives rise to the magnetic moment of 2.0 μB. In this case, Fermi level crosses the valence band, resulting the O-adsorbed BN system to be metallic. Furthermore, potential energy curves analysis shows that the magnetism and matellic of BN system can be modulated by the external temperature and pressure.

  18. Discriminative properties of the reinforcer can be used to attenuate the renewal of extinguished operant behavior.

    PubMed

    Trask, Sydney; Bouton, Mark E

    2016-06-01

    Previous research on the resurgence effect has suggested that reinforcers that are presented during the extinction of an operant behavior can control inhibition of the response. To further test this hypothesis, in three experiments with rat subjects we examined the effectiveness of using reinforcers that were presented during extinction as a means of attenuating or inhibiting the operant renewal effect. In Experiment 1, lever pressing was reinforced in Context A, extinguished in Context B, and then tested in Context A. Renewal of responding that occurred during the final test was attenuated when a distinct reinforcer that had been presented independent of responding during extinction was also presented during the renewal test. Experiment 2 established that this effect depended on the reinforcer being featured as a part of extinction (and thus associated with response inhibition). Experiment 3 then showed that the reinforcers presented during extinction suppressed performance in both the extinction and renewal contexts; the effects of the physical and reinforcer contexts were additive. Together, the results further suggest that reinforcers associated with response inhibition can serve a discriminative role in suppressing behavior and may be an effective stimulus that can attenuate operant relapse. PMID:26400498

  19. Psychometric Properties of the Dietary Salt Reduction Self-Care Behavior Scale.

    PubMed

    Srikan, Pratsani; Phillips, Kenneth D

    2014-06-19

    Valid, reliable, and culturally-specific scales to measure salt reduction self-care behavior in older adults are needed. The purpose of this study was to develop the Dietary Salt Reduction Self-Care Behavior Scale (DSR-SCB) for use in hypertensive older adults with Orem's self-care deficit theory as a base. Exploratory factor analysis, Rasch modeling, and reliability were performed on data from 242 older Thai adults. Nine items loaded on one factor (factor loadings = 0.63 to 0.79) and accounted for 52.28% of the variance (Eigenvalue = 4.71). The Kaiser-Meyer-Olkin method of sampling adequacy was 0.89, and the Bartlett's test showed significance (χ(2) (df =36) = 916.48, p < 0.0001). Infit and outfit mean squares ranged from 0.81 to 1.25, while infit and outfit standardized mean squares were located at ±2. Cronbach's alpha was 0.88. The 9-item DSR-SCB is a short and reliable scale. PMID:24951525

  20. Potential antidepressant properties of cysteamine on hippocampal BDNF levels and behavioral despair in mice.

    PubMed

    Shieh, Chu-Hsin; Hong, Chen-Jee; Huang, Yn-Ho; Tsai, Shih-Jen

    2008-08-01

    Several studies have demonstrated that antidepressants increase central brain-derived neurotrophic factor (BDNF) levels, suggesting that BDNF signaling is important for the therapeutic mechanism of antidepressants. Recent work has found that cysteamine and its related agent, cystamine, are neuroprotective in Huntington's disease mice, and act by enhancing the secretion of central BDNF. In the present study, the potential antidepressant effects of cysteamine were examined by behavioral paradigms and biochemical assay. Male BALB/CByJ mice were given a single dose of normal saline, 10 mg/kg of imipramine or either 50, 100 or 200 mg/kg of cysteamine (i.p.) 30 min before undergoing the forced-swimming test (FST) or the tail suspension test (TST). Other groups of mice treated with the same drugs and doses, without behavioral tests, were sacrificed for hippocampal BDNF measurements. We found that, compared with the control group, the cysteamine 200-mg/kg group showed a significant reduction in immobility time in the FST (P<0.01) and TST (P<0.01), and showed lower activity in the open field test (P<0.01). A significant increase in hippocampal BDNF levels was found in the cysteamine 200-mg/kg group (P<0.05). Our findings suggested that cysteamine may possess an antidepressant-like effect, which may be mediated by increasing central BDNF levels. PMID:18582526

  1. Magnetocaloric properties and critical behavior of high relative cooling power FeNiB nanoparticles

    NASA Astrophysics Data System (ADS)

    Chaudhary, V.; Maheswar Repaka, D. V.; Chaturvedi, A.; Sridhar, I.; Ramanujan, R. V.

    2014-10-01

    Low cost magnetocaloric nanomaterials have attracted considerable attention for energy efficient applications. We report a very high relative cooling power (RCP) in a study of the magnetocaloric effect in quenched FeNiB nanoparticles. RCP increases from 89.8 to 640 J kg-1 for a field change of 1 and 5 T, respectively, these values are the largest for rare earth free iron based magnetocaloric nanomaterials. To investigate the magnetocaloric behavior around the Curie temperature (TC), the critical behavior of these quenched nanoparticles was studied. Detailed analysis of the magnetic phase transition using the modified Arrott plot, Kouvel-Fisher method, and critical isotherm plots yields critical exponents of β = 0.364, γ = 1.319, δ = 4.623, and α = -0.055, which are close to the theoretical exponents obtained from the 3D-Heisenberg model. Our results indicate that these FeNiB nanoparticles are potential candidates for magnetocaloric fluid based heat pumps and low grade waste heat recovery.

  2. Electrospinning, mechanical properties, and cell behavior study of chitosan/PVA nanofibers.

    PubMed

    Koosha, Mojtaba; Mirzadeh, Hamid

    2015-09-01

    Electrospinning process has been widely used to produce nanofibers from polymer blends. Poly(vinyl alcohol) (PVA) and chitosan (CS) have numerous biomedical applications such as wound healing and tissue engineering. Nanofibers of CS/PVA have been prepared by many works, however, a complete physicochemical and mechanical characterization as well as cell behavior has not been reported. In this study, PVA and CS/PVA blend solutions in acetic acid 70% with different volume ratios (30/70, 50/50, and 70/30) were electrospun in constant electrospinning process parameters. The structure and morphology of nanofibrous mats were characterized by SEM, FTIR, and XRD methods. The best nanofibrous mat was achieved from the CS/PVA 30/70 blend solution regarding the electrospinning throughput. The dynamic mechanical thermal analysis (DMTA) of PVA and CS/PVA 30/70 nanofibrous mats were measured which were not considered in the previous studies. DMTA results in accordance to the DSC analysis approved the partial compatibility between the two polymers, while a single glass transition temperature was not observed for the blend. The tensile strength of PVA and CS/PVA nanofibers were also reported. Results of cell behavior study indicated that the heat stabilized nanofibrous mat CS/PVA 30/70 was able to support the attachment and proliferation of the fibroblast cells. PMID:25727934

  3. Analysis of Cooperative Behavior in Multiple Kinesins Motor Protein Transport by Varying Structural and Chemical Properties

    PubMed Central

    Uppulury, Karthik; Efremov, Artem K.; Driver, Jonathan W.; Jamison, D. Kenneth

    2012-01-01

    Intracellular transport is a fundamental biological process during which cellular materials are driven by enzymatic molecules called motor proteins. Recent optical trapping experiments and theoretical analysis have uncovered many features of cargo transport by multiple kinesin motor protein molecules under applied loads. These studies suggest that kinesins cooperate negatively under typical transport conditions, although some productive cooperation could be achieved under higher applied loads. However, the microscopic origins of this complex behavior are still not well understood. Using a discrete-state stochastic approach we analyze factors that affect the cooperativity among kinesin motors during cargo transport. Kinesin cooperation is shown to be largely unaffected by the structural and mechanical parameters of a multiple motor complex connected to a cargo, but much more sensitive to biochemical parameters affecting motor-filament affinities. While such behavior suggests the net negative cooperative responses of kinesins will persist across a relatively wide range of cargo types, it is also shown that the rates with which cargo velocities relax in time upon force perturbations are influenced by structural factors that affect the free energies of and load distributions within a multiple kinesin complex. The implications of these later results on transport phenomena where loads change temporally, as in the case of bidirectional transport, are discussed. PMID:24489614

  4. Magnetocaloric properties and critical behavior of high relative cooling power FeNiB nanoparticles

    SciTech Connect

    Chaudhary, V.; Maheswar Repaka, D. V.; Chaturvedi, A.; Ramanujan, R. V.; Sridhar, I.

    2014-10-28

    Low cost magnetocaloric nanomaterials have attracted considerable attention for energy efficient applications. We report a very high relative cooling power (RCP) in a study of the magnetocaloric effect in quenched FeNiB nanoparticles. RCP increases from 89.8 to 640 J kg{sup −1} for a field change of 1 and 5 T, respectively, these values are the largest for rare earth free iron based magnetocaloric nanomaterials. To investigate the magnetocaloric behavior around the Curie temperature (T{sub C}), the critical behavior of these quenched nanoparticles was studied. Detailed analysis of the magnetic phase transition using the modified Arrott plot, Kouvel-Fisher method, and critical isotherm plots yields critical exponents of β = 0.364, γ = 1.319, δ = 4.623, and α = −0.055, which are close to the theoretical exponents obtained from the 3D-Heisenberg model. Our results indicate that these FeNiB nanoparticles are potential candidates for magnetocaloric fluid based heat pumps and low grade waste heat recovery.

  5. Evaluating the effects of local floodplain management policies on property owner behavior

    NASA Astrophysics Data System (ADS)

    Bollens, Scott A.; Kaiser, Edward J.; Burby, Raymond J.

    1988-05-01

    Floodplain management programs have been adopted by more than 85% of local governments in the nation with designated flood hazard areas. Yet, there has been little evaluation of the influence of floodplain policies on private sector decisions. This article examines the degree to which riverine floodplain management affects purchase and mitigation decisions made by owners of developed floodplain property in ten selected cities in the United States. We find that the stringency of such policies does not lessen floodplain property buying because of the overriding importance of site amenity factors. Indeed, flood protection measures incorporated into development projects appear to add to the attractiveness of floodplain location by increasing the perceived safety from the hazard. Property owner responses to the flood hazard after occupancy involve political action more often than individual on-site mitigation. Floodplain programs only minimally encourage on-site mitigation by the owner because most owners have not experienced a flood and many are unaware of the flood threat. It is suggested that floodplain programs will be more effective in meeting their objectives if they are directed at intervention points earlier in the land conversion process.

  6. Tailoring the magnetic properties and magnetorheological behavior of spinel nanocrystalline cobalt ferrite by varying annealing temperature.

    PubMed

    Sedlacik, Michal; Pavlinek, Vladimir; Peer, Petra; Filip, Petr

    2014-05-14

    Magnetic nanoparticles of spinel nanocrystalline cobalt ferrite were synthesized via the sol-gel method and subsequent annealing. The influence of the annealing temperature on the structure, magnetic properties, and magnetorheological effect was investigated. The finite crystallite size of the particles, determined by X-ray diffraction and the particle size observed via transmission electron microscopy, increased with the annealing temperature. The magnetic properties observed via a vibrating sample magnetometer showed that an increase in the annealing temperature leads to the increase in the magnetization saturation and, in contrast, a decrease in the coercivity. The effect of annealing on the magnetic properties of ferrite particles has been explained by the recrystallization process at high temperatures. This resulted in grain size growth and a decrease in an imposed stress relating to defects in the crystal lattice structure of the nanoparticles. The magnetorheological characteristics of suspensions of ferrite particles in silicone oil were measured using a rotational rheometer equipped with a magnetic field generator in both steady shear and small-strain oscillatory regimes. The magnetorheological performance expressed as a relative increase in the magnetoviscosity appeared to be significantly higher for suspensions of particles annealed at 1000 °C. PMID:24668306

  7. Behavior of optical properties of coagulated blood sample at 633 nm wavelength

    NASA Astrophysics Data System (ADS)

    Morales Cruzado, Beatriz; Vázquez y Montiel, Sergio; Delgado Atencio, José Alberto

    2011-03-01

    Determination of tissue optical parameters is fundamental for application of light in either diagnostics or therapeutical procedures. However, in samples of biological tissue in vitro, the optical properties are modified by cellular death or cellular agglomeration that can not be avoided. This phenomena change the propagation of light within the biological sample. Optical properties of human blood tissue were investigated in vitro at 633 nm using an optical setup that includes a double integrating sphere system. We measure the diffuse transmittance and diffuse reflectance of the blood sample and compare these physical properties with those obtained by Monte Carlo Multi-Layered (MCML). The extraction of the optical parameters: absorption coefficient μa, scattering coefficient μs and anisotropic factor g from the measurements were carried out using a Genetic Algorithm, in which the search procedure is based in the evolution of a population due to selection of the best individual, evaluated by a function that compares the diffuse transmittance and diffuse reflectance of those individuals with the experimental ones. The algorithm converges rapidly to the best individual, extracting the optical parameters of the sample. We compare our results with those obtained by using other retrieve procedures. We found that the scattering coefficient and the anisotropic factor change dramatically due to the formation of clusters.

  8. The aging behavior of types 308 and 308CRE stainless steels and its effect on mechanical properties

    SciTech Connect

    Vitek, J.M.; David, S.A.

    1987-01-01

    Aging of 308 and 308CRE SS was studied at 475 to 850/sup 0/C for aging times up to 10,000 hours. Above 550/sup 0/C, aging of 308 steel resulted in precipitation of carbides and the transformation of ferrite to sigma phase or the formation of sigma phase in initially ferrite-free material. The elevated-temperature aging of 308CRE steel resulted in the precipitation of titanium-rich carbides, nitrides, and sulfides, and the transformation of ferrite to sigma phase. The distribution of precipitates was affected by the initial condition of the materials. The elevated-temperature creep properties, and in particular the improved properties of 308CRE, were related to the precipitate distribution. Below 550/sup 0/C, aging of welded type 308 steel, precipitation of G-phase within the ferrite was observed, as well as the decomposition of ferrite into alpha and alpha prime. With the help of a novel mechanical properties microprobe, which was capable of determining the hardness of the minor constituent ferrite phase, the hardness behavior as a function of aging could be related to the microstructures. These results are interpreted in terms of the potential susceptibility of these alloys to 475/sup 0/C embrittlement.

  9. Analysis of the genetic behavior of some starch properties in indica rice ( Oryza sativa L.): thermal properties, gel texture, swelling volume.

    PubMed

    Bao, J. S.; Sun, M.; Corke, H.

    2002-02-01

    Starch comprises about 90% of milled rice, so that the eating and cooking quality of rice is mainly affected by the starch properties. In the present paper, we analyzed the genetical behavior of gelatinization temperature tested by differential scanning calorimetry (DSC), gel texture, and the swelling volume (SV) of indica rice with an incomplete cross of 4x8 parents. A genetic model which can dissect the effects of triploid seed, the cytoplasm, and the maternal plant on the endosperm traits was used. The results indicated that peak temperature (T(p)), conclusion temperature (T(c)) and enthalpy (DeltaH) were controlled by three types of genetic effects: seed direct (endosperm) effects, cytoplasmic effects and maternal effects. No cytoplasmic effects for the onset temperature (T(o)), hardness and SV, and no maternal effects for cohesiveness were found. The additive variances ( V (A)+ V (Am)) were larger than the dominance variances ( V (D)+ V (Dm)) for all the traits except for T(c), which suggested that selection could be applied for the starch properties in early generations. The total narrow-sense heritability for each parameter was over 60%, indicating that selection advances were predictable in the early generations for these traits. PMID:12582713

  10. Oxidation behavior and mechanical properties of laminated Hf-Ta coatings

    NASA Astrophysics Data System (ADS)

    Chen, Yung-I.; Huang, Yu-Ren; Chang, Li-Chun

    2015-11-01

    This study explores the internal oxidation of laminated Hf-Ta coatings with a cyclically gradient chemical concentration distribution along the growth direction. The oxidation behavior was examined by annealing the coatings at 400-600 °C in a 15 ppm O2-N2 atmosphere for 30 min. The variations in crystalline structure, nanohardness, chemical states, and chemical composition profiles in depth after various annealing conditions were investigated. The results indicate that all the Hf-Ta coatings maintain a laminated structure after annealing at 400-600 °C. Internal oxidation conducts during 500 and 600 °C annealing, but part of the outmost layers exhibits complex oxides after annealing at 600 °C. The nanohardness of annealed Hf-Ta coatings related to the formation of HfO2, Hf6Ta2O17, and amorphous Ta-oxide were studied.

  11. An uncommon redox behavior sheds light on the cellular antioxidant properties of ergothioneine.

    PubMed

    Servillo, Luigi; Castaldo, Domenico; Casale, Rosario; D'Onofrio, Nunzia; Giovane, Alfonso; Cautela, Domenico; Balestrieri, Maria Luisa

    2015-02-01

    Ergothioneine (ESH), an aromatic thiol occurring in the human diet and which accumulates in particular cells, is believed to act as an antioxidant. However, its redox mechanism remains unclear and it does not seem to provide any advantage compared to other antioxidants, such as alkylthiols, which are better reducing agents and generally present in cells at higher levels. Here, we investigated by ESI-MS the products of ESH oxidation produced by neutrophils during oxidative burst and, to further elucidate ESH redox behavior, we also analyzed the oxidation products of the reaction of ESH with hypochlorite in cell-free solutions. Indeed, neutrophils are the main source of hypochlorite in humans. Furthermore, we also tested other biologically relevant oxidants, such as peroxynitrite and hydrogen peroxide. Our results indicate that treatment of human neutrophils with phorbol 12-myristate 13-acetate in the presence of ESH leads to a remarkable production of the sulfonated form (ESO3H), a compound never described before, and hercynine (EH), the desulfurated form of ESH. Similar results were obtained when ESH was subjected to cell-free oxidation in the presence of hypochlorite, as well as hydrogen peroxide or peroxynitrite. Furthermore, when the disulfide of ESH was reacted with those oxidants, we found that it was also oxidized, with production of EH and ESO3H, whose amount was dependent on the oxidant strength. These data reveal a unique ESH redox behavior, entirely different from that of alkylthiols, and suggest a mechanism, so far overlooked, through which ESH performs its antioxidant action in cells. PMID:25483556

  12. Effect of Coal Properties and Operation Conditions on Flow Behavior of Coal Slag in Entrained Flow Gasifiers: A Brief Review

    SciTech Connect

    Wang,Ping; Massoudi, Mehrdad

    2011-01-01

    Integrated gasification combined cycle (IGCC) is a potentially promising clean technology with an inherent advantage of low emissions, since the process removes contaminants before combustion instead of from flue gas after combustion, as in a conventional coal steam plant. In addition, IGCC has potential for cost-effective carbon dioxide capture. Availability and high capital costs are the main challenges to making IGCC technology more competitive and fully commercial. Experiences from demonstrated IGCC plants show that, in the gasification system, low availability is largely due to slag buildup in the gasifier and fouling in the syngas cooler downstream of the gasification system. In the entrained flow gasifiers used in IGCC plants, the majority of mineral matter transforms to liquid slag on the wall of the gasifier and flows out the bottom. However, a small fraction of the mineral matter (as fly ash) is entrained with the raw syngas out of the gasifier to downstream processing. This molten/sticky fly ash could cause fouling of the syngas cooler. Therefore, it is preferable to minimize the quantity of fly ash and maximize slag. In addition, the hot raw syngas is cooled to convert any entrained molten fly slag to hardened solid fly ash prior to entering the syngas cooler. To improve gasification availability through better design and operation of the gasification process, better understanding of slag behavior and characteristics of the slagging process are needed. Slagging behavior is affected by char/ash properties, gas compositions in the gasifier, the gasifier wall structure, fluid dynamics, and plant operating conditions (mainly temperature and oxygen/carbon ratio). The viscosity of the slag is used to characterize the behavior of the slag flow and is the dominating factor to determine the probability that ash particles will stick. Slag viscosity strongly depends on the temperature and chemical composition of the slag. Because coal has varying ash content and

  13. Mechanical properties and in vitro behavior of nanofiber-hydrogel composites for tissue engineering applications

    NASA Astrophysics Data System (ADS)

    Kai, Dan; Prabhakaran, Molamma P.; Stahl, Benjamin; Eblenkamp, Markus; Wintermantel, Erich; Ramakrishna, Seeram

    2012-03-01

    Hydrogel-based biomaterial systems have great potential for tissue reconstruction by serving as temporary scaffolds and cell delivery vehicles for tissue engineering (TE). Hydrogels have poor mechanical properties and their rapid degradation limits the development and application of hydrogels in TE. In this study, nanofiber reinforced composite hydrogels were fabricated by incorporating electrospun poly(ɛ-caprolactone) (PCL)/gelatin ‘blend’ or ‘coaxial’ nanofibers into gelatin hydrogels. The morphological, mechanical, swelling and biodegradation properties of the nanocomposite hydrogels were evaluated and the results indicated that the moduli and compressive strengths of the nanofiber reinforced hydrogels were remarkably higher than those of pure gelatin hydrogels. By increasing the amount of incorporated nanofibers into the hydrogel, the Young’s modulus of the composite hydrogels increased from 3.29 ± 1.02 kPa to 20.30 ± 1.79 kPa, while the strain at break decreased from 66.0 ± 1.1% to 52.0 ± 3.0%. Compared to composite hydrogels with coaxial nanofibers, those with blend nanofibers showed higher compressive strength and strain at break, but with lower modulus and energy dissipation properties. Biocompatibility evaluations of the nanofiber reinforced hydrogels were carried out using bone marrow mesenchymal stem cells (BM-MSCs) by cell proliferation assay and immunostaining analysis. The nanocomposite hydrogel with 25 mg ml-1 PCL/gelatin ‘blend’ nanofibers (PGB25) was found to enhance cell proliferation, indicating that the ‘nanocomposite hydrogels’ might provide the necessary mechanical support and could be promising cell delivery systems for tissue regeneration.

  14. Mechanical properties and in vitro behavior of nanofiber-hydrogel composites for tissue engineering applications.

    PubMed

    Kai, Dan; Prabhakaran, Molamma P; Stahl, Benjamin; Eblenkamp, Markus; Wintermantel, Erich; Ramakrishna, Seeram

    2012-03-01

    Hydrogel-based biomaterial systems have great potential for tissue reconstruction by serving as temporary scaffolds and cell delivery vehicles for tissue engineering (TE). Hydrogels have poor mechanical properties and their rapid degradation limits the development and application of hydrogels in TE. In this study, nanofiber reinforced composite hydrogels were fabricated by incorporating electrospun poly(ε-caprolactone) (PCL)/gelatin 'blend' or 'coaxial' nanofibers into gelatin hydrogels. The morphological, mechanical, swelling and biodegradation properties of the nanocomposite hydrogels were evaluated and the results indicated that the moduli and compressive strengths of the nanofiber reinforced hydrogels were remarkably higher than those of pure gelatin hydrogels. By increasing the amount of incorporated nanofibers into the hydrogel, the Young's modulus of the composite hydrogels increased from 3.29 ± 1.02 kPa to 20.30 ± 1.79 kPa, while the strain at break decreased from 66.0 ± 1.1% to 52.0 ± 3.0%. Compared to composite hydrogels with coaxial nanofibers, those with blend nanofibers showed higher compressive strength and strain at break, but with lower modulus and energy dissipation properties. Biocompatibility evaluations of the nanofiber reinforced hydrogels were carried out using bone marrow mesenchymal stem cells (BM-MSCs) by cell proliferation assay and immunostaining analysis. The nanocomposite hydrogel with 25 mg ml(-1) PCL/gelatin 'blend' nanofibers (PGB25) was found to enhance cell proliferation, indicating that the 'nanocomposite hydrogels' might provide the necessary mechanical support and could be promising cell delivery systems for tissue regeneration. PMID:22322583

  15. Tensile Properties and Swelling Behavior of Sealing Rubber Materials Exposed to High-Pressure Hydrogen Gas

    NASA Astrophysics Data System (ADS)

    Yamabe, Junichiro; Nishimura, Shin

    Rubber O-rings exposed to high-pressure hydrogen gas swell, and the volume increase induced by swelling influences tensile properties of the O-rings. Samples of nonfilled (NF), carbon black-filled (CB), and silica-filled (SC) sulfur-vulcanized acrylonitrile-butadiene rubber were exposed to hydrogen at 30 °C and pressures of up to 100 MPa, and the effect of hydrogen exposure on the volume increase, hydrogen content, and tensile properties was investigated. The residual hydrogen content, measured 35 minutes after decompression, increased with increasing hydrogen pressure in the range 0.7-100 MPa for all three samples. In contrast, the volumes of NF, CB, and SC barely changed at pressures below 10 MPa, whereas they increased at pressures above 10 MPa. This nonlinear volume increase is probably related to the free volume of the rubber structure. The volume increase of the CB and SC samples was smaller than that of the NF samples, possibly because of the superior tensile properties of CB and SC. As the volumes of the NF, CB, and SC samples increased, their tensile elastic moduli decreased as a result of a decrease in crosslink density and elongation by volume increase. Although the true fracture stress of NF was barely dependent on the volume of the specimen, those of CB and SC clearly decreased as the volume increased. The decrease in the true fracture stress of CB and SC was related to the volume increase by swelling, showing that the boundary structure between the filler and the rubber matrix was changed by the volume increase.

  16. Different behavioral effect dose–response profiles in mice exposed to two-carbon chlorinated hydrocarbons: Influence of structural and physical properties

    SciTech Connect

    Umezu, Toyoshi Shibata, Yasuyuki

    2014-09-01

    The present study aimed to clarify whether dose–response profiles of acute behavioral effects of 1,2-dichloroethane (DCE), 1,1,1-trichloroethane (TCE), trichloroethylene (TRIC), and tetrachloroethylene (PERC) differ. A test battery involving 6 behavioral endpoints was applied to evaluate the effects of DCE, TCE, TRIC, and PERC in male ICR strain mice under the same experimental conditions. The behavioral effect dose–response profiles of these compounds differed. Regression analysis was used to evaluate the relationship between the dose–response profiles and structural and physical properties of the compounds. Dose–response profile differences correlated significantly with differences in specific structural and physical properties. These results suggest that differences in specific structural and physical properties of DCE, TCE, TRIC, and PERC are responsible for differences in behavioral effects that lead to a variety of dose–response profiles. - Highlights: • We examine effects of 4 chlorinated hydrocarbons on 6 behavioral endpoints in mice. • The behavioral effect dose–response profiles for the 4 compounds are different. • We utilize regression analysis to clarify probable causes of the different profiles. • The compound's physicochemical properties probably produce the different profiles.

  17. Fundamentals of poly(lactic acid) microstructure, crystallization behavior, and properties

    NASA Astrophysics Data System (ADS)

    Kang, Shuhui

    Poly(lactic acid) is an environmentally-benign biodegradable and sustainable thermoplastic material, which has found broad applications as food packaging films and as non-woven fibers. The crystallization and deformation mechanisms of the polymer are largely determined by the distribution of conformation and configuration. Knowledge of these mechanisms is needed to understand the mechanical and thermal properties on which processing conditions mainly depend. In conjunction with laser light scattering, Raman spectroscopy and normal coordinate analysis are used in this thesis to elucidate these properties. Vibrational spectroscopic theory, Flory's rotational isomeric state (RIS) theory, Gaussian chain statistics and statistical mechanics are used to relate experimental data to molecular chain structure. A refined RIS model is proposed, chain rigidity recalculated and chain statistics discussed. A Raman spectroscopic characterization method for crystalline and amorphous phase orientation has been developed. A shrinkage model is also proposed to interpret the dimensional stability for fibers and uni- or biaxially stretched films. A study of stereocomplexation formed by poly(l-lactic acid) and poly(d-lactic acid) is also presented.

  18. Atomic-scale simulations of material behaviors and tribology properties for BCC metal film

    NASA Astrophysics Data System (ADS)

    H, D. Aristizabal; P, A. Parra; P, López; E, Restrepo-Parra

    2016-01-01

    This work has two main purposes: (i) introducing the basic concepts of molecular dynamics analysis to material scientists and engineers, and (ii) providing a better understanding of instrumented indentation measurements, presenting an example of nanoindentation and scratch test simulations. To reach these purposes, three-dimensional molecular dynamics (MD) simulations of nanoindentation and scratch test technique were carried out for generic thin films that present BCC crystalline structures. Structures were oriented in the plane (100) and placed on FCC diamond substrates. A pair wise potential was employed to simulate the interaction between atoms of each layer and a repulsive radial potential was used to represent a spherical tip indenting the sample. Mechanical properties of this generic material were obtained by varying the indentation depth and dissociation energy. The load-unload curves and coefficient of friction were found for each test; on the other hand, dissociation energy was varied showing a better mechanical response for films that present grater dissociation energy. Structural change evolution was observed presenting vacancies and slips as the depth was varied. Project supported by la DirecciónNacional de Investigación of the Universidad Nacional de Colombia, “the Theoretical Study of Physical Properties of Hard Materials for Technological Applications” (Grant No. 20101007903).

  19. Synthesis, physical properties and self-assembly behavior of azole-fused pyrene derivatives

    NASA Astrophysics Data System (ADS)

    Xiao, Jinchong; Xiao, Xuyu; Zhao, Yanlei; Wu, Bo; Liu, Zhenying; Zhang, Xuemin; Wang, Sujuan; Zhao, Xiaohui; Liu, Lei; Jiang, Li

    2013-05-01

    A novel selenadiazole-fused pyrene derivative PySe was successfully synthesized and characterized. Its single structure is almost planar and adopts a sandwich-herringbone packing model. The self-assembly behaviors based on compound PySe and its analogue thiadiazole-fused pyrene derivative PyS were studied in detail and the as-formed nanostructures were fully characterized by means of UV-vis absorption, emission spectra, X-ray diffraction, field emission SEM and TEM. We attribute the bathochromic shift absorption and emission spectra of PyS and PySe in aqueous solution to the formation of J-type aggregation. In addition, our investigation demonstrated that the shape and size of the as-prepared nanostructures could be tuned by different chalcogen analogues and the volume ratio of water to organic solvent.A novel selenadiazole-fused pyrene derivative PySe was successfully synthesized and characterized. Its single structure is almost planar and adopts a sandwich-herringbone packing model. The self-assembly behaviors based on compound PySe and its analogue thiadiazole-fused pyrene derivative PyS were studied in detail and the as-formed nanostructures were fully characterized by means of UV-vis absorption, emission spectra, X-ray diffraction, field emission SEM and TEM. We attribute the bathochromic shift absorption and emission spectra of PyS and PySe in aqueous solution to the formation of J-type aggregation. In addition, our investigation demonstrated that the shape and size of the as-prepared nanostructures could be tuned by different chalcogen analogues and the volume ratio of water to organic solvent. Electronic supplementary information (ESI) available: TGA analysis, spectra characterization data for compound 1, 2, 3 and X-ray crystallographic data for compound PySe (2, CIF). CCDC 917821. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3nr00523b

  20. Predicting fatigue properties of cast aluminum by characterizing small-crack propagation behavior

    NASA Astrophysics Data System (ADS)

    Caton, Michael John

    2001-07-01

    The increased use of cast aluminum in structural components requires a deeper understanding of the mechanisms controlling fatigue properties in order to enable improved predictive capabilities. Of particular interest is the ability to model the influence of processing variables on the fatigue performance of alloys used in automotive applications such as engine blocks and cylinder heads. This thesis describes the results of a study conducted on cast W319 aluminum, a commercial Al-Si-Cu alloy used in automotive engine components, and presents a model that effectively predicts fatigue properties in this alloy as a function of material condition. The very high cycle fatigue regime (˜109 cycles) was examined using ultrasonic testing equipment (20 kHz) and distinct endurance limits were observed. The initiation and propagation of small fatigue cracks (˜5 mum to 2 mm) were monitored by a standard replication technique. It was observed that cracks initiate almost exclusively from microshrinkage pores and that the initiation life is negligible even at stresses below the endurance limit. The endurance limits result from the arrest of small cracks. Small crack growth rates were determined for a variety of material conditions where the influence of solidification time, heat treatment, and grain refinement were investigated. In addition, the influences of applied stress amplitude, stress ratio, and loading frequency on small crack growth were examined. A significant small crack effect was identified in this alloy and standard correlating parameters such as DeltaK and DeltaJ do not adequately characterize small crack growth. A correlating parameter written as [(epsilonmax sigmaa/sigma yield)s a] is proposed and shown to effectively characterize small crack growth for a wide range of stresses and a wide range of solidification conditions. In this parameter, epsilonmax is the total strain corresponding to the maximum applied stress, sigmaa is the stress amplitude, sigma yield is

  1. Effect of laser shot peening without coating on the surface properties and corrosion behavior of 316L steel

    NASA Astrophysics Data System (ADS)

    Kalainathan, S.; Sathyajith, S.; Swaroop, S.

    2012-12-01

    This paper discusses the results of laser peening without coating on low carbon austenitic stainless steel 316L. Unlike typical experiments on laser peening without coating (LPwC) performed with frequency doubled (green) laser and underwater irradiation, the present study reports LPwC with infrared radiation using thin layer of water as confinement medium. The dependence of laser pulse density on properties such as surface roughness, surface residual stress, microhardness, and corrosion behavior of LPwC specimen were investigated. The magnitude of surface compressive residual stress on laser peened specimen showed appreciable improvement compared to unpeened base material. Microhardness of the specimen improved by 30-40% after LPwC. However, the potentiodynamic polarization study indicated that though there is an enhancement of corrosion potential (Ecorr), the corrosion current density (Icorr) increased with increase in laser pulse density.

  2. Biomechanics of chiasmal compression: Sensitivity of the mechanical behaviors of nerve fibers to variations in material property and geometry

    NASA Astrophysics Data System (ADS)

    Wang, Xiaofei; Neely, Andrew J.; McIlwaine, Gawn G.; Lueck, Christian J.

    2016-05-01

    The mechanism of bitemporal hemianopia is still unclear. Previous research suggested that the nerve fiber packing pattern may contribute to the selective damage of nasal (crossed) nerve fibers. Numerical models were built using finite element modeling to study the biomechanics of optic nerve fibers. The sensitivity of the mechanical behaviors of the nerve fibers to variations of five parameters in the nerve fiber model were investigated using design of experiments (DOE). Results show that the crossing angle is a very significant factor that affects a wide range of responses of the model. The strain difference between the crossed and the uncrossed nerve fibers may account for the phenomenon of bitemporal hemianopia. This work also highlights the need for more accurate material properties of the tissues in the model and an improved understanding of the microstructure of the optic chiasm.

  3. Effects of lignite properties on the hydroliquefaction behavior of representative Turkish lignites

    SciTech Connect

    Oener, M.; Bolat, E.; Dincer, S. )

    1992-01-01

    This paper reports on the conversion and yield data obtained for hydroliquefaction of 11 different Turkish lignites in tetralin, anthracene, and creosote oils with or without catalyst at 440{degrees}C and 80 bar that were correlated with the lignite properties obtained from proximate, ultimate, and petrographic analyses. The intercorrelation of experimental results and analytical data was evaluated by both simple linear regression and stepwise multiple linear regression analyses. Simple linear correlations between conversion and yield data with individual lignite parameters are unsatisfactory. An approach utilizing a stepwise multiple linear regression analysis lead to a number of linear equations relating oil yields to ash, sulfur, volatile matter, elemental carbon, maceral, and xylene extract contents of the lignites.

  4. Synthesis of New Styrylquinoline Cellular Dyes, Fluorescent Properties, Cellular Localization and Cytotoxic Behavior

    PubMed Central

    Dulski, Mateusz; Mrozek-Wilczkiewicz, Anna; Cieslik, Wioleta; Spaczyńska, Ewelina; Bartczak, Piotr; Ratuszna, Alicja; Polanski, Jaroslaw; Musiol, Robert

    2015-01-01

    New styrylquinoline derivatives with their photophysical constants are described. The synthesis was achieved via Sonogashira coupling using the newly developed heterogeneous nano-Pd/Cu catalyst system, which provides an efficient synthesis of high purity products. The compounds were tested in preliminary fluorescent microscopy studies to in order to identify their preferable cellular localization, which appeared to be in the lipid cellular organelles. The spectroscopic properties of the compounds were measured and theoretical TD-DFT calculations were performed. A biological analysis of the quinolines that were tested consisted of cytotoxicity assays against normal human fibroblasts and colon adenocarcinoma cells. All of the compounds that were studied appeared to be safe and indifferent to cells in a high concentration range. The presented results suggest that the quinoline compounds that were investigated in this study may be valuable structures for development as fluorescent dyes that could have biological applications. PMID:26114446

  5. Structural Properties and Resistance-Switching Behavior of Thermally Grown NiO Thin Films

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Wook; Jung, Ranju; Park, Bae Ho; Li, Xiang-Shu; Park, Chanwoo; Shin, Seongmo; Kim, Dong-Chirl; Lee, Chang Won; Seo, Sunae

    2008-03-01

    We investigated the structural and electrical properties of polycrystalline NiO thin films on Pt electrodes formed by thermal oxidation. A Ni-Pt alloy phase was found at the interface, which could be explained by the oxidation kinetics and reactions of Ni, NiO, and Pt. An increase in the oxidation temperature decreased the volume of the alloy layer and improved the crystalline quality of the NiO thin films. Pt/NiO/Pt structures were fabricated, and they showed reversible resistance switching from a high-resistance state (HRS) to a low-resistance state (LRS) and vice versa during unipolar current-voltage measurements. The oxidation temperature affected (did not affect) the HRS (LRS) resistance of the Pt/NiO/Pt structures. This indicated that the transport characteristics of HRS and LRS should be different.

  6. Ab initio studies of atomic properties and experimental behavior of element 119 and its lighter homologs.

    PubMed

    Borschevsky, A; Pershina, V; Eliav, E; Kaldor, U

    2013-03-28

    Static dipole polarizabilities of element 119 and its singly charged cation are calculated, along with those of its lighter homologs, Cs and Fr. Relativity is treated within the 4-component Dirac-Coulomb formalism and electron correlation is included by the single reference coupled cluster approach with single, double, and perturbative triple excitations (CCSD(T)). Very good agreement with available experimental values is obtained for Cs, lending credence to the predictions for Fr and element 119. The atomic properties in group-1 are largely determined by the valence ns orbital, which experiences relativistic stabilization and contraction in the heavier elements. As a result, element 119 is predicted to have a relatively low polarizability (169.7 a.u.), comparable to that of Na. The adsorption enthalpy of element 119 on Teflon, which is important for possible future experimental studies of this element, is estimated as 17.6 kJ/mol, the lowest among the atoms considered here. PMID:23556718

  7. Ab initio studies of atomic properties and experimental behavior of element 119 and its lighter homologs

    NASA Astrophysics Data System (ADS)

    Borschevsky, A.; Pershina, V.; Eliav, E.; Kaldor, U.

    2013-03-01

    Static dipole polarizabilities of element 119 and its singly charged cation are calculated, along with those of its lighter homologs, Cs and Fr. Relativity is treated within the 4-component Dirac-Coulomb formalism and electron correlation is included by the single reference coupled cluster approach with single, double, and perturbative triple excitations (CCSD(T)). Very good agreement with available experimental values is obtained for Cs, lending credence to the predictions for Fr and element 119. The atomic properties in group-1 are largely determined by the valence ns orbital, which experiences relativistic stabilization and contraction in the heavier elements. As a result, element 119 is predicted to have a relatively low polarizability (169.7 a.u.), comparable to that of Na. The adsorption enthalpy of element 119 on Teflon, which is important for possible future experimental studies of this element, is estimated as 17.6 kJ/mol, the lowest among the atoms considered here.

  8. Residual stress, mechanical behavior and electrical properties of Cu/Nb thin-film multilayers

    SciTech Connect

    Griffin, A.J. Jr.; Hundley, M.F.; Jervis, T.R.; Kung, H.H.; Scarborough, W.K.; Walter, K.C.; Nastasi, M.; Embury, J.D.

    1995-09-01

    Effect of compositional wavelength (modulation) on residual stress, electrical resistivities and mechanical properties of Cu/Nb thin-film multilayers sputtered onto single-crystal Si substrates, was evaluated. Electrical resistivities were measured down to 4 K using a standard 4-point probe. Differential specimen curvature was used to determine residual stress, and a microprobe was used to obtain hardness and elastic modulus. Profilometry, ion-beam analysis and TEM were used. Hardness of the Cu-Nb multilayers increased with decreasing compositional wavelength so that the layered structures had hardness values in excess of either constituent and the hardness predicted by the rule of mixtures. A peak in net residual compressive stress of the multilayers was observed at a compositional wavelength of 100 nm. No resistivity plateau was observed within the composition wavelength range studied.

  9. Interactions between Surfactants in Solution and Electrospun Protein Fibers: Effects on Release Behavior and Fiber Properties.

    PubMed

    Stephansen, Karen; García-Díaz, María; Jessen, Flemming; Chronakis, Ioannis S; Nielsen, Hanne M

    2016-03-01

    Intermolecular interaction phenomena occurring between endogenous compounds, such as proteins and bile salts, and electrospun compounds are so far unreported, despite the exposure of fibers to such biorelevant compounds when applied for biomedical purposes, e.g., tissue engineering, wound healing, and drug delivery. In the present study, we present a systematic investigation of how surfactants and proteins, as physiologically relevant components, interact with insulin-loaded fish sarcoplasmic protein (FSP) electrospun fibers (FSP-Ins fibers) in solution and thereby affect fiber properties such as accessible surface hydrophilicity, physical stability, and release characteristics of an encapsulated drug. Interactions between insulin-loaded protein fibers and five anionic surfactants (sodium taurocholate, sodium taurodeoxycholate, sodium glycocholate, sodium glycodeoxycholate, and sodium dodecyl sulfate), a cationic surfactant (benzalkonium chloride), and a neutral surfactant (Triton X-100) were studied. The anionic surfactants increased the insulin release in a concentration-dependent manner, whereas the neutral surfactant had no significant effect on the release. Interestingly, only minute amounts of insulin were released from the fibers when benzalkonium chloride was present. The FSP-Ins fibers appeared dense after incubation with this cationic surfactant, whereas high fiber porosity was observed after incubation with anionic or neutral surfactants. Contact angle measurements and staining with the hydrophobic dye 8-anilino-1-naphthalenesulfonic acid indicated that the FSP-Ins fibers were hydrophobic, and showed that the fiber surface properties were affected differently by the surfactants. Bovine serum albumin also affected insulin release in vitro, indicating that also proteins may affect the fiber performance in an in vivo setting. PMID:26389817

  10. Pentaglyme-K salt binary mixtures: phase behavior, solvate structures, and physicochemical properties.

    PubMed

    Mandai, Toshihiko; Tsuzuki, Seiji; Ueno, Kazuhide; Dokko, Kaoru; Watanabe, Masayoshi

    2015-01-28

    We prepared a series of binary mixtures composed of certain K salts (KX) and pentaglyme (G5) with different salt concentrations and anionic species ([X](-): [(CF3SO2)2N](-) = [TFSA](-), [CF3SO3](-) = [TfO](-), [C4F9SO3](-) = [NfO](-), PF6(-), SCN(-)), and characterized them with respect to their phase diagrams, solvate structures, and physicochemical properties. Their phase diagrams and thermal stability strongly implied the formation of equimolar complexes. Single-crystal X-ray crystallography was performed on certain equimolar complexes, which revealed that G5 molecules coordinate to K(+) cations in a characteristic manner, like 18-crown-6 ether in the crystalline state, irrespective of the paired anions. The solvate structures in the molten state were elucidated by a combination of temperature-dependent Raman spectroscopy and X-ray crystallography. A drastic spectral variation was observed in the [K(G5)1][TfO] Raman spectra, indicating that solvate structures in the crystalline state break apart upon melting. The solvate stability of [K(G5)1]X is closely related to the ion-ion interaction of the parent salts. A stable solvate forms when the ion-dipole interaction between K(+) and G5 overwhelms the ion-ion interaction between K(+) and X(-). Furthermore, the physicochemical properties of certain equimolar mixtures were evaluated. A Walden plot clearly reflects the ionic nature of the molten equimolar complexes. Judging from the structural characteristics and dissociativity, we classified [K(G5)1]X into two groups, good and poor solvate ionic liquids. PMID:25501925

  11. Adsorption behavior and adhesive properties of biopolyelectrolyte multilayers formed from cationic and anionic starch.

    PubMed

    Johansson, Erik; Lundström, Lisa; Norgren, Magnus; Wågberg, Lars

    2009-07-13

    Cationic starch (D.S. 0.065) and anionic starch (D.S. 0.037) were used to form biopolyelectrolyte multilayers. The influence of the solution concentration of NaCl on the adsorption of starch onto silicon oxide substrates and on the formation of multilayers was investigated using stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D). The wet adhesive properties of the starch multilayers were examined by measuring pull-off forces with the AFM colloidal probe technique. It was shown that polyelectrolyte multilayers (PEM) can be successfully constructed from cationic starch and anionic starch at electrolyte concentrations of 1 mM NaCl and 10 mM NaCl. The water content of the PEMs was approximately 80% at both electrolyte concentrations. However, the thickness of the PEMs formed at 10 mM NaCl was approximately twice the thickness formed at 1 mM NaCl. The viscoelastic properties of the starch PEMs, modeled as Voigt elements, were dependent on the polyelectrolyte that was adsorbed in the outermost layer. The PEMs appeared to be more rigid when capped by anionic starch than when capped by cationic starch. The wet adhesive pull-off forces increased with layer number and were also dependent on the polyelectrolyte adsorbed in the outermost layer. Thus, starch PEM treatment has a large potential for increasing the adhesive interaction between solid substrates to levels higher than can be reached by a single layer of cationic starch. PMID:21197962

  12. Characterizing the Peano fluidic muscle and the effects of its geometry properties on its behavior

    NASA Astrophysics Data System (ADS)

    Veale, Allan Joshua; Xie, Sheng Quan; Anderson, Iain Alexander

    2016-06-01

    In this work, we explore the basic static and dynamic behavior of a hydraulically actuated Peano muscle and how its geometry affects key static and dynamic performance metrics. The Peano muscle, or pouch motor is a fluid powered artificial muscle. Similar to McKibben pneumatic artificial muscles (PAMs), it has the ability to generate the high forces of biological muscles with the low threshold pressure of pleated PAMs, but in a slim, easily distributed form. We found that Peano muscles have similar characteristics to other PAMs, but produce lower free-strains. A test rig capable of measuring high-speed flow rates with a Venturi tube revealed that their efficiency peaks at about 40% during highly dynamic movements. Peano muscles with more tubes and of a greater size do not move faster. Also, their muscle tubes should have an aspect ratio of at least 1:3 and channel width greater than 20% to maximize performance. These findings suggest that finite element modeling be used to optimize more complex Peano muscle geometries.

  13. High Temperature Tensile Properties and Fatigue Behavior of a Melt-Infiltrated SiC/SiC Composite

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Calomino, Anthony M.; Brewer, David N.; Kiraly, Louis J. (Technical Monitor)

    2002-01-01

    High temperature fatigue behavior of a woven, SiC/SiC ceramic matrix composite (CMC) was investigated in air at two temperatures. The reinforcement for the CMC consisted of 5HS Sylramic(Trademark) fabric with a [0deg/90deg]4s lay-up. The SiC matrix material was infiltrated into the fiber-preform with a slurry-cast, melt-infiltration process. Tensile and fatigue test specimens were machined from the CMC plates. Initially tensile tests were conducted to obtain the average values of tensile properties at 1038 and 1204 C. Subsequently, low-cycle fatigue (LCF) tests with zero and two-hour hold-times at the maximum stress were conducted at the same two temperatures. Fatigue life data generated in the LCF tests were used to determine the geometric mean fatigue lives. In this paper, the tensile behavior and the fatigue durability of the CMC determined under different loading conditions are documented. In addition, reductions observed in the cyclic lives of the composite due to the two hour hold-time at maximum tensile stress are discussed.

  14. Characterization of Tensile Properties, Limiting Strains, and Deep Drawing Behavior of AA5754-H22 Sheet at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Panicker, Sudhy S.; Singh, Har Govind; Panda, Sushanta Kumar; Dashwood, Richard

    2015-11-01

    Automotive industries are very much interested in characterization of formability improvement of aluminum alloys at elevated temperatures before designing tools, heating systems, and processing sequences for fabrication of auto-body panels by warm forming technology. In this study, tensile tests of AA5754-H22 aluminum alloy were carried out at five different temperatures and three different strain rates to investigate the deformation behavior correlating with Cowper-Symonds constitutive equation. Laboratory scale warm forming facilities were designed and fabricated to perform limiting dome height and deep drawing tests to evaluate forming limit strains and drawability of sheet metal at different tool temperatures. The forming limit strain and dome height improved significantly when both the die and punch were heated to 200 °C. Remarkable improvement in deep drawn cup depth was observed when die and punch temperatures were maintained at 200 and 30 °C, respectively, producing a non-isothermal temperature gradient of approximately 93 °C across the blank from flange to center. The forming behavior at different isothermal and non-isothermal conditions were predicted successfully using a thermo-mechanical FE model incorporating temperature-dependent properties in Barlat-89 yield criterion coupled with Cowper-Symonds hardening model, and the thinning/failure location in deformed cups were validated implementing the experimental limiting strains as damage model.

  15. Influence of original microstructure on the transformation behavior and mechanical properties of ultra-high-strength TRIP-aided steel

    NASA Astrophysics Data System (ADS)

    Yin, Hong-xiang; Zhao, Ai-min; Zhao, Zheng-zhi; Li, Xiao; Li, Shuang-jiao; Hu, Han-jiang; Xia, Wei-guang

    2015-03-01

    The transformation behavior and tensile properties of an ultra-high-strength transformation-induced plasticity (TRIP) steel (0.2C-2.0Si-1.8Mn) were investigated by different heat treatments for automobile applications. The results show that F-TRIP steel, a traditional TRIP steel containing as-cold-rolled ferrite and pearlite as the original microstructure, consists of equiaxed grains of intercritical ferrite surrounded by discrete particles of M/RA and B. In contrast, M-TRIP steel, a modified TRIP-aided steel with martensite as the original microstructure, containing full martensite as the original microstructure is comprised of lath-shaped grains of ferrite separated by lath-shaped martensite/retained austenite and bainite. Most of the austenite in F-TRIP steel is granular, while the austenite in M-TRIP steel is lath-shaped. The volume fraction of the retained austenite as well as its carbon content is lower in F-TRIP steel than in M-TRIP steel, and austenite grains in M-TRIP steel are much finer than those in F-TRIP steel. Therefore, M-TRIP steel was concluded to have a higher austenite stability, resulting in a lower transformation rate and consequently contributing to a higher elongation compared to F-TRIP steel. Work hardening behavior is also discussed for both types of steel.

  16. Effect of food preservatives on the hydration properties and taste behavior of amino acids: a volumetric and viscometric approach.

    PubMed

    Banipal, Tarlok S; Kaur, Navalpreet; Kaur, Amanpreet; Gupta, Mehak; Banipal, Parampaul K

    2015-08-15

    Thermodynamic and transport properties of aqueous solutions are very useful in the elucidation of solute-solvent and solute-solute interactions, which help to understand the hydration and taste behavior of solutes. The densities and viscosities of L-glycine, β-alanine and L-leucine have been determined in water and in aqueous solutions of sodium propionate (NaP) and calcium propionate (CaP) at temperatures 298.15 and 308.15K. From these data, apparent molar volumes (V2,ϕ), viscosity B-coefficients and corresponding transfer parameters (ΔtrV2,ϕo and ΔtrB) have been calculated. The dB/dT values suggest that L-glycine and β-alanine act as structure-breaker, while L-leucine acts as structure-maker both in water and in aqueous solutions of NaP and CaP. The decrease in hydration number and change in taste behavior have also been observed with increasing concentration of the cosolute. PMID:25794759

  17. Flexible polyelectrolyte chain in a strong electrolyte solution: Insight into equilibrium properties and force-extension behavior from mesoscale simulation.

    PubMed

    Malekzadeh Moghani, Mahdy; Khomami, Bamin

    2016-01-14

    Macromolecules with ionizable groups are ubiquitous in biological and synthetic systems. Due to the complex interaction between chain and electrostatic decorrelation lengths, both equilibrium properties and micro-mechanical response of dilute solutions of polyelectrolytes (PEs) are more complex than their neutral counterparts. In this work, the bead-rod micromechanical description of a chain is used to perform hi-fidelity Brownian dynamics simulation of dilute PE solutions to ascertain the self-similar equilibrium behavior of PE chains with various linear charge densities, scaling of the Kuhn step length (lE) with salt concentration cs and the force-extension behavior of the PE chain. In accord with earlier theoretical predictions, our results indicate that for a chain with n Kuhn segments, lE ∼ cs (-0.5) as linear charge density approaches 1/n. Moreover, the constant force ensemble simulation results accurately predict the initial non-linear force-extension region of PE chain recently measured via single chain experiments. Finally, inspired by Cohen's extraction of Warner's force law from the inverse Langevin force law, a novel numerical scheme is developed to extract a new elastic force law for real chains from our discrete set of force-extension data similar to Padè expansion, which accurately depicts the initial non-linear region where the total Kuhn length is less than the thermal screening length. PMID:26772586

  18. Flexible polyelectrolyte chain in a strong electrolyte solution: Insight into equilibrium properties and force-extension behavior from mesoscale simulation

    NASA Astrophysics Data System (ADS)

    Malekzadeh Moghani, Mahdy; Khomami, Bamin

    2016-01-01

    Macromolecules with ionizable groups are ubiquitous in biological and synthetic systems. Due to the complex interaction between chain and electrostatic decorrelation lengths, both equilibrium properties and micro-mechanical response of dilute solutions of polyelectrolytes (PEs) are more complex than their neutral counterparts. In this work, the bead-rod micromechanical description of a chain is used to perform hi-fidelity Brownian dynamics simulation of dilute PE solutions to ascertain the self-similar equilibrium behavior of PE chains with various linear charge densities, scaling of the Kuhn step length (lE) with salt concentration cs and the force-extension behavior of the PE chain. In accord with earlier theoretical predictions, our results indicate that for a chain with n Kuhn segments, lE ˜ cs-0.5 as linear charge density approaches 1/n. Moreover, the constant force ensemble simulation results accurately predict the initial non-linear force-extension region of PE chain recently measured via single chain experiments. Finally, inspired by Cohen's extraction of Warner's force law from the inverse Langevin force law, a novel numerical scheme is developed to extract a new elastic force law for real chains from our discrete set of force-extension data similar to Padè expansion, which accurately depicts the initial non-linear region where the total Kuhn length is less than the thermal screening length.

  19. Influence of composition on precipitation behavior and stress rupture properties in INCONEL RTM740 series superalloys

    NASA Astrophysics Data System (ADS)

    Casias, Andrea M.

    Increasing demands for energy efficiency and reduction in CO2 emissions have led to the development of advanced ultra-supercritical (AUSC) boilers. These boilers operate at temperatures of 760 °C and pressures of 35 MPa, providing efficiencies close to 50 pct. However, austenitic stainless steels typically used in boiler applications do not have sufficient creep or oxidation resistance. For this reason, nickel (Ni)-based superalloys, such as IN740, have been identified as potential materials for AUSC boiler tube components. However, IN740 is susceptible to heat-affected-zone liquation cracking in the base metal of heavy section weldments. To improve weldability, IN740H was developed. However, IN740H has lower stress rupture ductility compared to IN740. For this reason, two IN740H modifications have been produced by lowering carbon content and increasing boron content. In this study, IN740, IN740H, and the two modified IN740H alloys (modified 1 and 2) were produced with equiaxed grain sizes of 90 ìm (alloys IN740, IN740H, and IN740H modified 1 alloys) and 112 µm (IN740H modified 2 alloy). An aging study was performed at 800 °C on all alloys for 1, 3, 10, and 30 hours to assess precipitation behavior. Stress rupture tests were performed at 760 °C with the goal of attaining stress levels that would yield rupture at 1000 hours. The percent reduction in area was measured after failure as a measure of creep ductility. Light optical, scanning electron, and transmission electron microscopy were used in conjunction with X-ray diffraction to examine precipitation behavior of annealed, aged, and stress rupture tested samples. The amount and type of precipitation that occurred during aging prior to stress rupture testing or in-situ during stress rupture testing influenced damage development, stress rupture life, and ductility. In terms of stress rupture life, IN740H modified 2 performed the best followed by IN740H modified 1 and IN740, which performed similarly, and IN740

  20. Behavior and Properties of Mature Lytic Granules at the Immunological Synapse of Human Cytotoxic T Lymphocytes

    PubMed Central

    Ming, Min; Schirra, Claudia; Becherer, Ute; Stevens, David R.; Rettig, Jens

    2015-01-01

    Killing of virally infected cells or tumor cells by cytotoxic T lymphocytes requires targeting of lytic granules to the junction between the CTL and its target. We used whole-cell patch clamp to measure the cell capacitance at fixed intracellular [Ca2+] to study fusion of lytic granules in human CTLs. Expression of a fluorescently labeled human granzyme B construct allowed identification of lytic granule fusion using total internal reflection fluorescence microscopy. In this way capacitance steps due to lytic granule fusion were identified. Our goal was to determine the size of fusing lytic granules and to describe their behavior at the plasma membrane. On average, 5.02 ± 3.09 (mean ± s.d.) lytic granules were released per CTL. The amplitude of lytic granule fusion events was ~ 3.3 fF consistent with a diameter of about 325 nm. Fusion latency was biphasic with time constants of 15.9 and 106 seconds. The dwell time of fusing lytic granules was exponentially distributed with a mean dwell time of 28.5 seconds. Fusion ended in spite of the continued presence of granules at the immune synapse. The mobility of fusing granules at the membrane was indistinguishable from that of lytic granules which failed to fuse. While dwelling at the plasma membrane lytic granules exhibit mobility consistent with docking interspersed with short periods of greater mobility. The failure of lytic granules to fuse when visible in TIRF at the membrane may indicate that a membrane-confined reaction is rate limiting. PMID:26296096

  1. Crystallization behavior and magnetic properties in High Fe content FeBCSiCu alloy system

    NASA Astrophysics Data System (ADS)

    Fan, X. D.; Shen, B. L.

    2015-07-01

    High Fe content FeBCSiCu nanocrystalline alloys are prepared by annealing melt-spun amorphous ribbons with aim at increasing saturation magnetic flux density. Microstructures identified by XRD and TEM reveal that Cu addition inhibits the surface crystallization of Fe86B7C7 alloy and improve its glass-forming ability. Activation energy of crystallization calculated by Kissinger's equation indicates that both Cu and Si addition promotes the precipitation of α-Fe phase and improves the thermal stability. VSM and DC B-H loop tracer measurements show that the Fe85.5B7C6Si1Cu0.5 nanocrystalline alloy exhibits high saturation magnetic flux density of 1.8 T and low coercivity of 10 A/m, respectively. AC properties measured by AC B-H analyzer show this alloy exhibits low core loss of 0.35 W/kg at 1 T at 50 Hz. Low material cost and convenient productivity make the Fe85.5B7C6Si1Cu0.5 nanocrystalline alloy an economical application in industry.

  2. Vectran Fiber Time-Dependent Behavior and Additional Static Loading Properties

    NASA Technical Reports Server (NTRS)

    Fette, Russell B.; Sovinski, Marjorie F.

    2004-01-01

    Vectran HS appears from literature and testing to date to be an ideal upgrade from Kevlar braided cords for many long-term, static-loading applications such as tie-downs on solar arrays. Vectran is a liquid crystalline polymer and exhibits excellent tensile properties. The material has been touted as a zero creep product. Testing discussed in this report does not support this statement, though the creep is on the order of four times slower than with similar Kevlar 49 products. Previous work with Kevlar and new analysis of Vectran testing has led to a simple predictive model for Vectran at ambient conditions. The mean coefficient of thermal expansion (negative in this case) is similar to Kevlar 49, but is not linear. A positive transition in the curve occurs near 100 C. Out-gassing tests show that the material performs well within parameters for most space flight applications. Vectran also offers increased abrasion resistance, minimal moisture regain, and similar UV degradation. The effects of material construction appear to have a dramatic effect in stress relaxation for braided Vectran. To achieve the improved relaxation rate, upgrades must also examine alternate construction or preconditioning methods. This report recommends Vectran HS as a greatly improved replacement material for applications where time-dependent relaxation is a major factor.

  3. Colloidal properties and behaviors of 3 nm primary particles of detonation nanodiamonds in aqueous media.

    PubMed

    Mchedlov-Petrossyan, N O; Kamneva, N N; Marynin, A I; Kryshtal, A P; Ōsawa, E

    2015-06-28

    This study was aimed to reveal the principal colloidal properties of the aqueous dispersion of extremely small primary single-crystalline diamond particles in water. Together with the non-diamond layer, the size of the colloidal species is 2.8 ± 0.6 nm as found via DLS of the initial 5.00 wt/vol% hydrosol. Anionic dyes are readily adsorbed on the colloidal species. This is in line with the positive zeta-potential. The critical coagulation concentrations of the 0.19 wt/vol% nanodiamond hydrosol were determined with a set of inorganic electrolytes and anionic surfactants. The data are in line with the Schulze-Hardy rule for "positive" sols. The fulfillment of the lyotropic (Hofmeister) series was also observed for single-charged anions. The abnormal influence of alkali gives evidence of the acidic nature of the positive charge of the nanodiamond species. Application of acid-base indicators allows estimating the value of the interfacial electrical potential of the nanodiamond particles. Upon dilution from 5.00% to 0.01%, the colloidal system under study exhibits unusual changes. The average size increases ca. ten-fold as determined by DLS. The TEM images support this observation. At the same time, the viscosity drops. This phenomenon was explained in terms of the so-called periodic colloidal structures (colloidal crystals) in concentrated solutions. PMID:26035732

  4. A phosphorescent copper(I) complex: Synthesis, characterization, photophysical property, and oxygen-sensing behavior

    NASA Astrophysics Data System (ADS)

    Wen, Caihong; Tao, Guoquan; Xu, Xinhua; Feng, Xiaoqing; Luo, Rongcheng

    2011-09-01

    In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(Phen-Np)(POP)]BF 4, where Phen-Np and POP stand for 2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline and bis(2-(diphenylphosphanyl)phenyl) ether, respectively. [Cu(Phen-Np)(POP)]BF 4 renders a yellow phosphorescence peaking at 545 nm, with a long excited state lifetime of 4.69 μs. Density functional calculation reveals that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. We electrospun composite nanofibers of [Cu(Phen-Np)(POP)]BF 4 and polystyrene (PS), hoping to explore the possibility of using the composite nanofibers as an oxygen sensing material. The finally obtained samples with average diameter of ˜300 nm exhibit a maximum sensitivity of 7.2 towards molecular oxygen with short response time of 7 s due to the large surface-area-to-volume ratio of nanofibrous membranes. No photobleaching is detected in these samples.

  5. Improved Mechanical Properties and Sustained Release Behavior of Cationic Cellulose Nanocrystals Reinforeced Cationic Cellulose Injectable Hydrogels.

    PubMed

    You, Jun; Cao, Jinfeng; Zhao, Yanteng; Zhang, Lina; Zhou, Jinping; Chen, Yun

    2016-09-12

    Polysaccharide-based injectable hydrogels have several advantages in the context of biomedical use. However, the main obstruction associated with the utilization of these hydrogels in clinical application is their poor mechanical properties. Herein, we describe in situ gelling of nanocomposite hydrogels based on quaternized cellulose (QC) and rigid rod-like cationic cellulose nanocrystals (CCNCs), which can overcome this challenge. In all cases, gelation immediately occurred with an increase of temperature, and the CCNCs were evenly distributed throughout the hydrogels. The nanocomposite hydrogels exhibited increasing orders-of-magnitude in the mechanical strength, high extension in degradation and the sustained release time, because of the strong interaction between CCNCs and QC chains mediated by the cross-linking agent (β-glycerophosphate, β-GP). The results of the in vitro toxicity and in vivo biocompatibility tests revealed that the hydrogels did not show obvious cytotoxicity and inflammatory reaction to cells and tissue. Moreover, DOX-encapsulated hydrogels were injected beside the tumors of mice bearing liver cancer xenografts to assess the potential utility as localized and sustained drug delivery depot systems for anticancer therapy. The results suggested that the QC/CCNC/β-GP nanocomposite hydrogels had great potential for application in subcutaneous and sustained delivery of anticancer drug to increase therapeutic efficacy and improve patient compliance. PMID:27519472

  6. Phase Behavioral and Structural Properties of an Efficient Solvent-Free Model of Lipid Bilayers

    NASA Astrophysics Data System (ADS)

    Revalee, Joel; Laradji, Mohamed

    2007-03-01

    High-power computers facilitate the study of lipid bilayer membranes. Any computer model used to simulate such membranes must account for their spontaneous self- assembly due to hydrophobic interactions between lipid tails and water. This is usually done by simulating lipid molecules in explicit solvent. In such simulations most of the system is occupied by the solvent. It is therefore computationally desirable for equilibrium studies of lipid membranes to develop a model that leads to self-assembly of lipids without explicit solvent. We designed such a model, and show that its use leads to faster simulations than what can be achieved with current solvent-free models. This model utilizes soft interactions to account for hydrophobic effects (instead of the Lennard-Jones potential). Investigation of the lipids' diffusion coefficient, single-lipid orientational order parameter and internal energy as functions of temperature reveal a structural phase diagram in the membrane from a gel-like hexatic phase to a fluid phase. The characterization of membrane elastic properties from this model will also be presented.

  7. Differences in gasification behaviors and related properties between entrained gasifier fly ash and coal char

    SciTech Connect

    Jing Gu; Shiyong Wu; Youqing Wu; Ye Li; Jinsheng Gao

    2008-11-15

    In the study, two fly ash samples from Texaco gasifiers were compared to coal char and the physical and chemical properties and reactivity of samples were investigated by scanning electron microscopy (SEM), SEM-energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), N{sub 2} and CO{sub 2} adsorption method, and isothermal thermogravimetric analysis. The main results were obtained. The carbon content of gasified fly ashes exhibited 31-37%, which was less than the carbon content of 58-59% in the feed coal. The fly ashes exhibited higher Brunauer-Emmett-Teller (BET) surface area, richer meso- and micropores, more disordered carbon crystalline structure, and better CO{sub 2} gasification reactivity than coal char. Ashes in fly ashes occurred to agglomerate into larger spherical grains, while those in coal char do not agglomerate. The minerals in fly ashes, especial alkali and alkaline-earth metals, had a catalytic effect on gasification reactivity of fly ash carbon. In the low-temperature range, the gasification process of fly ashes is mainly in chemical control, while in the high-temperature range, it is mainly in gas diffusion control, which was similar to coal char. In addition, the carbon in fly ashes was partially gasified and activated by water vapor and exhibited higher BET surface area and better gasification activity. Consequently, the fact that these carbons in fly ashes from entrained flow gasifiers are reclaimed and reused will be considered to be feasible. 15 refs., 7 figs., 5 tabs.

  8. The cleavage and surface properties of wet and dry ground spodumene and their flotation behavior

    NASA Astrophysics Data System (ADS)

    Zhu, Guangli; Wang, Yuhua; Liu, Xiaowen; Yu, Fushun; Lu, Dongfang

    2015-12-01

    The flotability of wet and dry ground spodumene was found different when sodium oleate was used as a collector, and the flotation recovery of wet ground spodumene was higher than that of dry ground spodumene. It is well known that the flotability of minerals is closely related with their crystal structures and surface properties, therefore morphology and structure examinations on wet and dry ground spodumene were performed by SEM and XRD. It was confirmed that wet ground spodumene had smoother surface and more exposed {1 1 0} and {1 0 0} planes, while more exposed {0 1 0} planes were found on dry ground spodumene surface. The specific surface areas of wet and dry ground spodumene in size fraction of -105 + 38 μm were determined to be 0.252 m2/g and 0.382 m2/g, respectively. However, the maximum adsorption densities of sodium oleate on wet and dry ground spodumene were 21.5 × 10-6 mol/m2 and 12.5 × 10-6 mol/m2, respectively. The densities of surface Alsbnd O broken bonds were calculated to be 6.376 × 1018, 4.351 × 1018 and 14.057 × 1018/m2 for {1 1 0}, {0 1 0} and {1 0 0}, respectively. The result indicated that {1 0 0} and {1 1 0} planes were more favorable for the adsorption of oleic acid ion than {0 1 0} plane.

  9. Effects of chitosan coating on physical properties and pharmacokinetic behavior of mitoxantrone liposomes.

    PubMed

    Zhuang, Jie; Ping, Qineng; Song, Yunmei; Qi, Jianping; Cui, Zheng

    2010-01-01

    The objective of this work was to evaluate the physical properties and in vivo circulation of chitosan (CH)-coated liposomes of mitoxantrone (MTO). Changes in particle size and zeta potential confirmed the existence of a coating layer on the surface of liposomes. The in vitro release of adsorbed CH from the liposomes was significantly slower than CH solution, indicating the stable interaction between CH and liposomes. The physical stability of the CH-coated liposomes was evaluated by measuring the change in particle size before and after freeze-drying and rehydration. The smallest change was observed when saturated adsorption of CH occurred (0.3%). The sustained release in vitro of MTO from CH-coated liposomes confirmed the increased stability of liposomes. Systemic circulation of CH-coated MTO liposomes was examined. The 0.3% CH-coated liposomes showed the longest circulation time. It could be concluded that the prolonged retention time of the liposomes was closely related with CH coating and its stability effect. PMID:20957162

  10. Quality properties and adsorption behavior of freeze-dried beef meat from the Biceps femoris and Semimembranosus muscles.

    PubMed

    Aykın, Elif; Erbaş, Mustafa

    2016-11-01

    The aim of this research was to determine the quality properties and adsorption behavior of freeze-dried beef meat from the Biceps femoris and Semimembranosus muscles. Most quality properties of both muscles were similar apart from total fat content. Freeze-dried meat pieces were kept in ten different equilibrium levels of relative humidity (2.0-97.3%) at 5, 15, 25 and 30°C. The experimental data were evaluated using BET (Brunauer-Emmett-Teller) and GAB (Guggenheim, Anderson and deBoer) models. The equilibrium moisture contents of freeze-dried Biceps femoris were lower than those of Semimembranosus at all water activities and temperature. The constants m0 and C of BET and GAB equations were determined to be between 6.27 and 8.07g/100g dry matter and 9.32-13.73, respectively. Constant k was about 0.90 at all temperatures, and the GAB equation exhibited a better fit to the experimental data of both muscles as a result of all %E values being approximately equal to 10%. PMID:27379930

  11. Effect of nano-SiC on the sintering behavior and properties of calcined carbon derived from mesocarbon microbeads

    NASA Astrophysics Data System (ADS)

    Xia, Hongyan; Wang, Jiping; Liu, Guiwu; Shi, Zhongqi; Qiao, Guanjun

    2010-08-01

    Calcined carbon materials derived from mesocarbon microbeads (MCMBs) with or without pre-oxidative treatment were prepared and the effect of doped nano-SiC powder on the sintering behavior and properties was investigated. The results showed that the sintering shrinkage and density increment of the samples doped with 5 wt.% nano-SiC were higher than those with 3 wt.% and 10 wt.%, due to the amount of defects and extent of graphitization controlled by the content of nano-SiC. Physical and mechanical properties improved remarkably after doping a certain amount of nano-SiC. The highest bending strength of 122 MPa and lowest electric resistivity of 28 μΩ m were obtained when doping 5 wt.% nano-SiC in green MCMBs. Ball-milling contributed to reduction of particle sizes of MCMBs/nano-SiC mixtures and hence reduced or eliminated the gaps between particles in the calcined materials. The catalytic effect of nano-SiC can promote particle rearrangement and structure improvement during the sintering.

  12. Structure, mechanical property and corrosion behaviors of (HA+β-TCP)/Mg-5Sn composite with interpenetrating networks.

    PubMed

    Wang, X; Li, J T; Xie, M Y; Qu, L J; Zhang, P; Li, X L

    2015-11-01

    In this paper, a novel (Hydroxyapatite+β-tricalcium phosphate)/Mg-5Sn ((HA+β-TCP)/Mg-5Sn) composite with interpenetrating networks was fabricated by infiltrating Mg-5Sn alloy into porous HA+β-TCP using suction casting technique. The structure, mechanical property and corrosion behaviors of the composite have been evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical testing, electrochemical and immersion test. It is shown that the molten Mg-5Sn alloy has infiltrated not only into the pores but also into the struts of the HA+β-TCP scaffold to forming a compact composite. The microstructure observation also shows that the Mg alloy contacts to the HA+β-TCP closely, and no reaction layer can be found between Mg-5Sn alloy and scaffold. The ultimate compressive strength of the composite is as high as 176MPa, which is about four fifths of the strength of the Mg-5Sn bulk alloy. The electrochemical and immersion tests indicate that the corrosion resistance of the composite is better than that of the Mg-5Sn bulk alloy. The corrosion products on the composite surface are mainly Mg(OH)2, Ca3(PO4)2 and HA. Appropriate mechanical and corrosion properties of the (HA+β-TCP)/Mg-5Sn composite indicate its possibility for new bone tissue implant materials. PMID:26249605

  13. The diastereomers of mannosylerythritol lipids have different interfacial properties and aqueous phase behavior, reflecting the erythritol configuration.

    PubMed

    Fukuoka, Tokuma; Yanagihara, Takashi; Imura, Tomohiro; Morita, Tomotake; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

    2012-04-01

    Mannosylerythritol lipids (MELs) produced by yeasts are one of the most promising glycolipid biosurfactants. There are two MEL diastereomers, in which the configurations of the erythritol moieties are opposite. The 4-O-β-D-mannopyranosyl-(2S,3R)-erythritol (S-form) or 4-O-β-D-mannopyranosyl-(2R,3S)-erythritol (R-form) is the hydrophilic domain. In this study, we prepared S- and R-form MEL homologs with similar fatty acyl groups, and compared their interfacial properties. Among the four diastereomers (S-MEL-B and -D/R-MEL-B and -D), R-form MELs showed a higher critical aggregation concentration and hydrophilicity compared to the corresponding S-form. R-form MELs also efficiently formed relatively large vesicles compared to S-form. Moreover, we estimated the binary phase diagram of the MEL-water system and compared the aqueous phase behavior among the four diastereomers. The present MELs self-assembled into a lamellar (L(α)) structure at all concentration ranges. Meanwhile, the one-phase L(α) region of R-form MELs was wider than those of S-form MELs. R-form MELs may maintain more water between the polar layers in accordance with an extension of the interlayer spacing. These results suggest that the differences in MEL carbohydrate configurations significantly affect interfacial properties, self-assembly, and hydrate ability. PMID:22341919

  14. Microstructure, mechanical properties, corrosion behavior and hemolysis of as-extruded biodegradable Mg-Sn-Zn alloy

    NASA Astrophysics Data System (ADS)

    Hou, L.; Li, Z.; Pan, Y.; Du, L.; Li, X.; Zheng, Y.; Li, L.

    2016-04-01

    As biodegradable biomaterials, magnesium alloys have favorable physical, chemical and mechanical properties, as well as good biocompatibility, and are expected to totally biodegrade in the body environment. The microstructure, mechanical properties, corrosion behaviors and hemolysis of biodegradable Mg-Sn-Zn alloy were investigated under three extrusion ratios in the present work. It is revealed that the as-extruded microstructure is obviously refined with smaller grains compared with the as-cast structure while some twins form simultaneously. The tensile strengths of the as-extruded alloys fabricated with the higher extrusion ratio is 249MPa, and elongations is 16.3% respectively. Besides, the corrosion rate of as-extruded magnesium alloys increases with the increasing extrusion ratio. The hemolysis test result shows that the hemolysis rate of biodegradable magnesium alloys fabricated with the higher extrusion ratio is 4.8%, when hemolysis rate lower than 5% has been demonstrated safe according to ISO 10993-4. In conclusion, the as-extruded biodegradable Mg-Sn-Zn alloy shows great potential as a novel medical implant material.

  15. Preparation and properties of graphene oxide-regenerated cellulose/polyvinyl alcohol hydrogel with pH-sensitive behavior.

    PubMed

    Rui-Hong, Xie; Peng-Gang, Ren; Jian, Hui; Fang, Ren; Lian-Zhen, Ren; Zhen-Feng, Sun

    2016-03-15

    In this study, graphene oxide reinforced regenerated cellulose/polyvinyl alcohol (GO-RCE/PVA) ternary hydrogels were successfully prepared via a repeated freezing and thawing method in NaOH/urea aqueous solution. The effect of GO content on the mechanical properties, swelling behavior, water content of composite hydrogels was investigated. It was found that the mechanical properties of GO-RCE/PVA ternary hydrogels were largely enhanced relative to RCE/PVA hydrogels. With the addition of 1.0wt% GO, the tensile strength was increased by 40.4% from 0.52MPa to 0.73MPa, accompanied by the increase of the elongation at break (from 103% to 238%). Meanwhile, GO-RCE/PVA ternary hydrogels performed the excellent pH-sensitivity, and the higher pH leaded to higher swelling ratio. With 0.8wt% GO loading, the swelling ratio of GO-RCE/PVA ternary hydrogel was improved from 150% (pH=2) to 310% (pH=14). In addition, a slight increase in the water content of the ternary hydrogel was achieved with increasing concentrations of GO. It is believed that this novel ternary hydrogels is a promising material in the application of biomedical engineering and intelligent devices. PMID:26794756

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

    SciTech Connect

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

    1996-10-01

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

  17. Effect of compressed CO2 on the properties of AOT reverse micelles studied by spectroscopy and phase behavior

    NASA Astrophysics Data System (ADS)

    Liu, Dongxia; Zhang, Jianling; Han, Buxing; Fan, Jiufeng; Mu, Tiancheng; Liu, Zhimin; Wu, Weize; Chen, Jing

    2003-09-01

    Combination of reverse micellar solutions and supercritical or compressed carbon dioxide (CO2) is a new and interesting topic. This work conducted the first study on the effect of compressed CO2 on the micro-properties (e.g., micropolarity, ionic strength, pH) of the sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles in isooctane by phase behavior measurement, Fourier transform infrared and UV-vis spectroscopic techniques. The results show that CO2 can dissolve in both the organic-continuous phase and the water cores of the reverse micelles. The properties of the reverse micelles can be tuned continuously by changing the pressure of CO2 because the solubility of CO2 in the solution and in the water cores depends on the pressure. CO2 in the water cores can be ionized to produce HCO3-1 and H+. The micropolarity and ionic strength of the water cores increase with the pressure of CO2. Accordingly, the pH is reduced as the pressure and water-to-surfactant molar ratio (w0) are increased.

  18. Soil and biosolid nano- and macro-colloid properties and contaminant transport behavior

    NASA Astrophysics Data System (ADS)

    Ghezzi, Jessique L.

    Despite indications that they are potential contaminant transport systems and threats to groundwater quality, very little effort has been invested in comparing contaminant transport behavior of natural environmental nanocolloids and their corresponding macrocolloid fractions in the presence of As, Se, Pb, and Cu contaminants. This study involved physico-chemical, mineralogical, stability and contaminant-transport characterizations of nano- (< 100 nm) and macro-colloids (100-2000 nm) fractionated from three Kentucky soils and one biosolid waste. Particle size was investigated with SEM/TEM and dynamic light scattering. Surface reactivity was estimated using CEC and zeta potential. Mineralogical composition was determined by XRD, FTIR, and thermogravimetric analyses. Sorption isotherms assessed affinities for Cu2+, Pb2+, AsO3-, and SeO4 -2 contaminants, while settling kinetics experiments of suspensions at 0, 2 and 10 mg/L contaminants determined stability and transportability potential. Undisturbed 18x30 cm KY Ashton Loam soil monoliths were also used for transport experiments, involving infusion of 50 mg L-1 colloid suspensions spiked with 2 mg L-1 mixed contaminant loads in unsaturated, steady state, unit gradient downward percolation experiments. Overall, nanocolloids exhibited greater stability over corresponding macrocolloids in the presence and absence of contaminants following specific mineralogy trends. Physicochemical characterizations indicated that extensive organic carbon surface coatings and higher Al/Fe:Si ratios may have induced higher stability in the nanocolloid fractions, in spite of some hindrance by nano-aggregation phenomena. In the transport experiments, nanocolloids eluted significantly higher concentrations of colloids, total, and colloid-bound metals than corresponding macrocolloids. Contaminant elutions varied by colloid type, mineralogy and contaminant, with the following sequences: soil-colloids>bio-colloids, smectitic

  19. Acoustic method of investigating the material properties and humidity sensing behavior of polymer coated piezoelectric substrates

    NASA Astrophysics Data System (ADS)

    Caliendo, Cinzia

    2006-09-01

    The relative humidity (RH) sensing behavior of a polymeric film was investigated by means of polymer coated surface acoustic wave (SAW) delay lines implemented on single crystal piezoelectric substrates, such as quartz and LiNbO3, and on thin piezoelectric polycrystalline films, such as ZnO and AlN, on Si and GaAs. The same SAW delay line configuration was implemented on each substrate and the obtained devices' operating frequency was in the range of 105-156MHz, depending on the type of the substrate, on its crystallographic orientation, and on the SAW propagation direction. The surface of each SAW device was covered by the same type RH sensitive film of the same thickness and the RH sensitivity of each polymer coated substrate, i.e., the SAW relative phase velocity shift per RH unit changes, was investigated in the 0%—80% RH range. The perturbational approach was used to relate the SAW sensor velocity response to the RH induced changes in the physical parameters of the sensitive polymer film: the incremental change in the mass density and shear modulus of the polymer film per unit RH change were estimated. The shift of the bare SAW delay lines operating frequency induced by the presence of the polymer film, at RH =0% and at T =-10°C, allowed the experimental estimation of the mass sensitivity values of each substrate. These values were in good accordance with those reported in the literature and with those theoretically evaluated by exact numerical calculation. The shift of the bare SAW delay lines propagation loss induced by the polymer coating of the device surface, at RH =0% and at ambient temperature, allowed the experimental estimation of the elastic sensitivity of each substrate. These values were found in good accordance with those available from the literature. The temperature coefficient of delay and the electromechanical coupling coefficient of the bare substrates were also estimated. The membrane sensitivity to ethanol, methanol and isopropylic

  20. Thermal aging effects on the microstructure, oxidation behavior, and mechanical properties of as-cast nickel aluminide alloys

    NASA Astrophysics Data System (ADS)

    Lee, Dongyun

    The thermal aging effects on the microstructure, oxidation behavior at 900° and 1100°C, and mechanical properties of IC221M (Ni3Al based intermetallic alloy, ASTM A1002-99) were investigated. The microstructure consists of dendritic arms of the gamma (nickel solid solution) phase containing cube-shape gamma' (Ni3Al precipitates. The interdendritic regions are mostly gamma' (Ni3Al with up to 8 vol.% gamma + Ni5Zr eutectic constituents. Thermal aging effects on the microstructures and how microsegregation affects the oxidation behavior were examined. Four primary changes in the microstructures were observed: (1) there is considerable homogenization of the cast microstructures with aging, (2) the volume fraction of gamma' increases with aging time and temperature, (3) the gamma' phase coarsens, and (4) the volume fraction of the gamma + Ni5Zr eutectic constituents decreases. During the initial stages of oxidation at 900°C, surface oxides form along the microsegregation patterns, revealing the cast microstructures. The first oxide to form is mostly NiO with small amounts of Cr2O 3, ZrO2, NiCr2O4, and theta-Al 2O3. Initial oxidation occurs primarily in the interdendritic regions due to microsegregation of alloying elements during casting. With further aging, the predominant surface oxides become NiO and NiAl2O 4 spinel, with a continuous film of alpha-Al2O3 forming immediately beneath them. Although these oxides are constrained to the near surface region, other oxides penetrate to greater depths, facilitated by oxidation of the gamma + Ni5Zr eutectic constituents. These oxides appear in the microstructure as long, thin spikes of ZrO2 surrounded by a sheath of Al2O3. They can penetrate to depths greater than 10 times that of the continuous surface oxide. The oxidation behavior at 1100°C is similar to that at 900°C, but the oxidation kinetics are faster, NiO dominates at all aging periods, and the surface oxides do not adhere to the matrix meaning that a protective

  1. Mechanical properties and platelet adhesion behavior of diamond-like carbon films synthesized by pulsed vacuum arc plasma deposition

    NASA Astrophysics Data System (ADS)

    Leng, Y. X.; Chen, J. Y.; Yang, P.; Sun, H.; Wan, G. J.; Huang, N.

    2003-05-01

    Diamond-like carbon (DLC) is an attractive biomedical material due to its high inertness and excellent mechanical properties. In this study, DLC films were fabricated on Ti6Al4V and Si(1 0 0) substrates at room temperature by pulsed vacuum arc plasma deposition. By changing the argon flow from 0 to 13 sccm during deposition, the effects of argon flow on the characteristics of the DLC films were systematically examined to correlate to the blood compatibility. The microstructure and mechanical properties of the films were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) surface analysis, a nano-indenter and pin-on-disk tribometer. The blood compatibility of the films was evaluated using in vitro platelet adhesion investigation, and the quantity and morphology of the adherent platelets was investigated employing optical microscopy and scanning electron microscopy. The Raman spectroscopy results showed a decreasing sp 3 fraction (an increasing trend in ID/ IG ratio) with increasing argon flow from 0 to 13 sccm. The sp 3:sp 2 ratio of the films was evaluated from the deconvoluted XPS spectra. We found that the sp 3 fraction decreased as the argon flow was increased from 0 to 13 sccm, which is consistent with the results of the Raman spectra. The mechanical properties results confirmed the decreasing sp 3 content with increasing argon flow. The Raman D-band to G-band intensity ratio increased and the platelet adhesion behavior became better with higher flow. This implies that the blood compatibility of the DLC films is influenced by the sp 3:sp 2 ratio. DLC films deposited on titanium alloys have high wear resistance, low friction and good adhesion.

  2. Phase behavior, rheological property, and transmutation of vesicles in fluorocarbon and hydrocarbon surfactant mixtures.

    PubMed

    Yuan, Zaiwu; Qin, Menghua; Chen, Xiushan; Liu, Changcheng; Li, Hongguang; Hao, Jingcheng

    2012-06-26

    We present a detailed study of a salt-free cationic/anionic (catanionic) surfactant system where a strongly alkaline cationic surfactant (tetradecyltrimethylammonium hydroxide, TTAOH) was mixed with a single-chain fluorocarbon acid (nonadecafluorodecanoic acid, NFDA) and a hyperbranched hydrocarbon acid [di-(2-ethylhexyl)phosphoric acid, DEHPA] in water. Typically the concentration of TTAOH is fixed while the total concentration and mixing molar ratio of NFDA and DEHPA is varied. In the absence of DEHPA and at a TTAOH concentration of 80 mmol·L(-1), an isotropic L(1) phase, an L(1)/L(α) two-phase region, and a single L(α) phase were observed successively with increasing mixing molar ratio of NFDA to TTAOH (n(NFDA)/n(TTAOH)). In the NFDA-rich region (n(NFDA)/n(TTAOH) > 1), a small amount of excess NFDA can be solubilized into the L(α) phase while a large excess of NFDA eventually leads to phase separation. When NFDA is replaced gradually by DEHPA, the mixed system of TTAOH/NFDA/DEHPA/H(2)O follows the same phase sequence as that of the TTAOH/NFDA/H(2)O system and the phase boundaries remain almost unchanged. However, the viscoelasticity of the samples in the single L(α) phase region becomes higher at the same total surfactant concentration as characterized by rheological measurements. Cryo-transmission electron microscopic (cryo-TEM) observations revealed a microstructural evolution from unilamellar vesicles to multilamellar ones and finally to gaint onions. The size of the vesicle and number of lamella can be controlled by adjusting the molar ratio of NFDA to DEHPA. The dynamic properties of the vesicular solutions have also been investigated. It is found that the yield stress and the storage modulus are time-dependent after a static mixing process between the two different types of vesicle solutions, indicating the occurrence of a dynamic fusion between the two types of vesicles. The microenvironmental changes induced by aggregate transitions were probed by

  3. Thermal Properties, Thermal Shock, and Thermal Cycling Behavior of Lanthanum Zirconate-Based Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Guo, Xingye; Lu, Zhe; Jung, Yeon-Gil; Li, Li; Knapp, James; Zhang, Jing

    2016-06-01

    Lanthanum zirconate (La2Zr2O7) coatings are newly proposed thermal barrier coating (TBC) systems which exhibit lower thermal conductivity and potentially higher thermal stability compared to other traditional thermal barrier systems. In this work, La2Zr2O7 and 8 wt pct yttria stabilized zirconia (8YSZ) single-layer and double-layer TBC systems were deposited using the air plasma spray technique. Thermal properties of the coatings were measured. Furnace heat treatment and jet engine thermal shock tests were implemented to evaluate coating performance during thermal cycling. The measured average thermal conductivity of porous La2Zr2O7 coating ranged from 0.59 to 0.68 W/m/K in the temperature range of 297 K to 1172 K (24 °C to 899 °C), which was approximately 25 pct lower than that of porous 8YSZ (0.84 to 0.87 W/m/K) in the same temperature range. The coefficients of thermal expansion values of La2Zr2O7 were approximately 9 to 10 × 10-6/K from 400 K to 1600 K (127 °C to 1327 °C), which were about 10 pct lower than those of porous 8YSZ. The double-layer coating system consisting of the porous 8YSZ and La2Zr2O7 layers had better thermal shock resistance and thermal cycling performance than those of single-layer La2Zr2O7 coating and double-layer coating with dense 8YSZ and La2Zr2O7 coatings. This study suggests that porous 8YSZ coating can be employed as a buffer layer in La2Zr2O7-based TBC systems to improve the overall coating durability during service.

  4. Thermal Properties, Thermal Shock, and Thermal Cycling Behavior of Lanthanum Zirconate-Based Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Guo, Xingye; Lu, Zhe; Jung, Yeon-Gil; Li, Li; Knapp, James; Zhang, Jing

    2016-03-01

    Lanthanum zirconate (La2Zr2O7) coatings are newly proposed thermal barrier coating (TBC) systems which exhibit lower thermal conductivity and potentially higher thermal stability compared to other traditional thermal barrier systems. In this work, La2Zr2O7 and 8 wt pct yttria stabilized zirconia (8YSZ) single-layer and double-layer TBC systems were deposited using the air plasma spray technique. Thermal properties of the coatings were measured. Furnace heat treatment and jet engine thermal shock tests were implemented to evaluate coating performance during thermal cycling. The measured average thermal conductivity of porous La2Zr2O7 coating ranged from 0.59 to 0.68 W/m/K in the temperature range of 297 K to 1172 K (24 °C to 899 °C), which was approximately 25 pct lower than that of porous 8YSZ (0.84 to 0.87 W/m/K) in the same temperature range. The coefficients of thermal expansion values of La2Zr2O7 were approximately 9 to 10 × 10-6/K from 400 K to 1600 K (127 °C to 1327 °C), which were about 10 pct lower than those of porous 8YSZ. The double-layer coating system consisting of the porous 8YSZ and La2Zr2O7 layers had better thermal shock resistance and thermal cycling performance than those of single-layer La2Zr2O7 coating and double-layer coating with dense 8YSZ and La2Zr2O7 coatings. This study suggests that porous 8YSZ coating can be employed as a buffer layer in La2Zr2O7-based TBC systems to improve the overall coating durability during service.

  5. Rock magnetic properties related to thermal treatment of siderite: Behavior and interpretation

    NASA Astrophysics Data System (ADS)

    Pan, Yongxin; Zhu, Rixiang; Banerjee, Subir K.; Gill, J.; Williams, Q.

    2000-01-01

    Detailed analyses of rock magnetic experiments were conducted on the oxidation products of high-purity natural crystalline siderite that were thermally treated in air atmosphere. Susceptibilities increase sharply between 400° and 530°C indicative of some new ferrimagnetic mineral phase generation. Both a drop (between 540° and 590°C) on the heating cycle and a dramatic increase (from 590°C to 520°C) on the cooling cycle occurred and are well consistent with the characteristic of magnetite. A distinct Hopkinson-type susceptibility peak indicates that hematite is the terminal product if siderite is heated to 700°C over and over. It has been revealed in detail that the original inverse magnetic susceptibility fabric contributed by the crystalline anisotropy of siderite in siderite-bearing specimens is changed to a normal magnetic fabric during incremental heating over 410°-490°C. This is a result of dominant contributions from the distribution anisotropy of newly transformed ferromagnetic minerals. A strong chemical-viscous remanent magnetization could be produced during siderite oxidation in an external field. Rock magnetic experimental results show that magnetite, maghemite, and hematite are the transformation products of high-temperature oxidation of siderite in air. Maghemite was not completely inverted to hematite even at temperature as high as 690°C during incremental thermal treatments. The mineral transformation processes were confirmed by conventional optical microscopic observation, X-ray diffractometry and Mössbauer spectroscopic analyses. These results indicate that the rock magnetic methods used here are reliable and highly sensitive in detecting very small magnetic phase changes in rocks. We conclude that these temperaturedependent variations of magnetic properties can be used as criteria for identification of siderite in rocks and sediments. Furthermore, it is clear that great care should be exercised in thermal demagnetization of siderite

  6. Properties, Solution State Behavior, and Crystal Structures of Chelates of DOTMA

    PubMed Central

    Aime, Silvio; Botta, Mauro; Garda, Zoltán; Kucera, Benjamin E.; Tircso, Gyula; Young, Victor G.; Woods, Mark

    2011-01-01

    The chemistry of polyamino carboxylates and their use as ligands for Ln3+ ions is of considerable interest from the point of view of the development of new imaging agents. Of particular interest is the chemistry of the macrocyclic ligand 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and its derivatives. Herein we report that the tetramethylated DOTA derivative, DOTMA, possess several properties that, from an imaging agent development point of view, are more advantageous than those of the parent DOTA. In particular, the Ln3+ chelates of DOTMA exhibit a marked preference for the monocapped twisted square antiprismatic coordination isomer which imparts more rapid water exchange kinetics on the chelates; τM298 was determined to be 85 ns for GdDOTMA. Differential analysis of the 17O R2ρ temperature profiles of both GdDOTA and GdDOTMA afforded the τM298 values for the square (SAP) and twisted square antiprismatic (TSAP) isomers of each chelate that were almost identical: 365 ns (SAP) and 52 ns (TSAP). The origin of this accelerated water exchange in the TSAP isomer appears to be the slightly longer Gd–OH2 bond distance (2.50 Å) that is observed in the crystal structure of GdDOTMA which crystallizes in the P2 space group as a TSAP isomer. The Ln3+ chelates of DOTMA also exhibit high thermodynamic stabilities ranging from log KML = 20.5 for CeDOTMA, 23.5 for EuDOTMA and YbDOTMA comparable to, but a shade lower than, those of DOTA. PMID:21819052

  7. Physical and chemical modifications of surface properties lead to alterations in osteoblast behavior

    NASA Astrophysics Data System (ADS)

    Dorst, Kathryn Elizabeth

    Proper formation of the bone extracellular matrix (ECM), or osteoid, depends on the surface properties of pre-existing tissue and the aqueous chemical environment. Both of these factors greatly influence osteoblast migration, cytoskeletal organization, and calcium nodule production, important aspects when considering the biocompatibility of bone implants. By perturbing the physical and/or chemical micro-environment, it may be possible to elucidate effects on cellular function. To examine these factors, murine pre-osteoblasts (MC3T3-E1 subclones 4 and 24) were seeded on polydimethylsiloxane (PDMS) substrates containing "wide" micro-patterned ridges (20 mum width, 30 mum pitch, & 2 mum height), "narrow" micro-patterned ridges (2 mum width, 10 mum pitch, 2 mum height), no patterns (flat PDMS), and standard tissue culture (TC) polystyrene as a control. Zinc concentration was adjusted to mimic deficient (0.23 muM), serum-level (3.6 muM), and zinc-rich (50 muM) conditions. It was found that cells exhibited distinct anisotropic migration in serum-level zinc and zinc-deficient media on the wide PDMS patterns, however this was disrupted under zinc-rich conditions. Production of differentiation effectors, activated metalloproteinase-2 (MMP-2) and transforming growth factor - beta 1 (TGF-beta1), was increased with the addition of exogenous zinc. Early stage differentiation, via alkaline phosphatase, was modified by zinc levels on patterned polydimethylsiloxane (PDMS) surfaces, but not on flat PDMS or tissue culture polystyrene (TC). Late stage differentiation, visualized through calcium phosphate nodules, was markedly different at various zinc levels when the cells were cultured on TC substrates. This susceptibility to zinc content can lead to differences in bone mineral production on certain substrates if osteoblasts are not able to maintain and remodel bone effectively, a process vital to successful biomaterial integration.

  8. Spectroscopic properties and luminescence behavior of Nd3+ doped zinc alumino bismuth borate glasses

    NASA Astrophysics Data System (ADS)

    Mahamuda, Sk.; Swapna, K.; Srinivasa Rao, A.; Jayasimhadri, M.; Sasikala, T.; Pavani, K.; Rama Moorthy, L.

    2013-09-01

    Zinc Alumino Bismuth Borate (ZnAlBiB) glasses doped with different concentrations of neodymium are prepared by using the melt quenching technique to study their physical, absorption and luminescence properties to understand the lasing potentialities of these glasses. From the absorption spectra various spectroscopic parameters and Judd-Ofelt (JO) parameters are evaluated. These JO parameters are used to calculate the transition probability (A), radiative lifetime (τR), and branching ratios (βR) for most of the fluorescent levels of Nd3+. The emission spectra recorded for these glasses gives three prominent transitions 4F3/2→4I9/2, 4F3/2→4I11/2 and 4F3/2→4I13/2 for which effective band widths (ΔλP) and stimulated emission cross-sections (σse) are evaluated. Branching ratios and stimulated emission cross-sections measured for all these glasses show that the 4F3/2→4I11/2 transition under investigation has the potential for laser applications. The intensity of Nd3+ emission spectra increases with increasing concentrations of Nd3+ up to 1 mol% and beyond 1 mol% the concentration quenching is observed. The high stimulated emission cross-section and branching ratios from the present glasses suggests their potential for infrared lasers. From the absorption and emission spectral studies it was found that, 1 mol% of Nd3+ ion concentration is optimum for Zinc Alumino Bismuth Borate glasses to generate a strong laser emission at 1060 nm.

  9. Property.

    ERIC Educational Resources Information Center

    Goldblatt, Steven M.

    In this chapter on decisions made by federal and state courts during 1983 concerning school property it is noted that no new trends emerged during the year. Among the topics addressed are the extent of school board authority over property use and other property matters; the attachment and detachment of land from school district holdings; school…

  10. Property.

    ERIC Educational Resources Information Center

    Piele, Philip K.

    Several court cases involving acquisition, use, and disposal of property by institutions of higher education are briefly summarized in this chapter. Cases discussed touch on such topics as municipal annexation of university property; repurchase of properties temporarily allocated to faculty members; implications of zoning laws and zoning board…

  11. Viscoelastic properties and adsorption behaviors of two kinds of pyridine insoluble fractions of coal extracts with different aggregated states

    SciTech Connect

    Hengfu Shui; Zhicai Wang

    2007-09-15

    Two kinds of pyridine insoluble fractions (PI) of coal extracts with different solubilities in N-methyl-2-pyrrolidinone (NMP) were characterized in this paper. PI-0 was obtained by the pyridine fractionation of Upper Freeport coal extracts with a CS{sub 2}/NMP mixed solvent (1:1 by volume), and its solubility in NMP is 53 wt %. While PI-1, which was obtained by the removal of NMP and tetrabutylammonium acetate (TBAA) from a PI-0 solution in NMP containing TBAA, was almost completely soluble in NMP. Solid-state {sup 13}CNMR spectra indicated that the two PIs have the same chemical structure. The viscoelastic properties and methanol adsorption behaviors of the two PIs were measured. The dynamic viscoelasticities of the two PIs are similar, and the elastic modulus (G') of PI-1 is lower before the softening temperature than that of PI-0, suggesting that the macromolecular network of PI-1 is looser compared to that of PI-0. The methanol sorption behaviors of PI-0 and PI-1 are also similar, and lines curve-fitted with the Langmuir-Henry equation were in agreement with the experimental data, suggesting that the bulk structure of the two PIs is similar. The methanol sorption for PI-1 is larger than that for PI-0. The constants of the Langmuir-Henry equation obtained by successive fitting for the two PIs indicated that the microporosity of PI-1 is larger than that of PI-0. The results obtained here suggested that the dissociation of molecular interactions is responsible for the high solubility of PI-1. 20 refs., 7 figs., 3 tabs.

  12. Mechanical Properties and Electrochemical Corrosion Behavior of Al/Sn-9Zn- xAg/Cu Joints

    NASA Astrophysics Data System (ADS)

    Huang, M. L.; Huang, Y. Z.; Ma, H. T.; Zhao, J.

    2011-03-01

    The effect of Ag content on the wetting behavior of Sn-9Zn- xAg on aluminum and copper substrates during soldering, as well as the mechanical properties and electrochemical corrosion behavior of Al/Sn-9Zn- xAg/Cu solder joints, were investigated in the present work. Tiny Zn and coarsened dendritic AgZn3 regions were distributed in the Sn matrix in the bulk Sn-9Zn- xAg solders, and the amount of Zn decreased while that of AgZn3 increased with increasing Ag content. The wettability of Sn-9Zn-1.5Ag solder on Cu substrate was better than those of the other Sn-9Zn- xAg solders but worse than that of Sn-9Zn solder. The wettability of Sn-9Zn-1.5Ag on the Al substrate was also better than those of the other Sn-9Zn- xAg solders, and even better than that of Sn-9Zn solder. The Al/Sn-9Zn/Cu joint had the highest shear strength, and the shear strength of the Al/Sn-9Zn- xAg/Cu ( x = 0 wt.% to 3 wt.%) joints gradually decreased with increasing Ag content. The corrosion resistance of the Sn-9Zn- xAg solders in Al/Sn-9Zn- xAg/Cu joints in 5% NaCl solution was improved compared with that of Sn-9Zn. The corrosion potential of Sn-9Zn- xAg solders continuously increased with increasing Ag content from 0 wt.% to 2 wt.% but then decreased for Sn-9Zn-3Ag. The addition of Ag resulted in the formation of the AgZn3 phase and in a reduction of the amount of the eutectic Zn phase in the solder matrix; therefore, the corrosion resistance of the Al/Sn-9Zn- xAg/Cu joints was improved.

  13. Burst Firing in a Motion-Sensitive Neural Pathway Correlates with Expansion Properties of Looming Objects that Evoke Avoidance Behaviors

    PubMed Central

    McMillan, Glyn A.; Gray, John R.

    2015-01-01

    The locust visual system contains a well-defined motion-sensitive pathway that transfers visual input to motor centers involved in predator evasion and collision avoidance. One interneuron in this pathway, the descending contralateral movement detector (DCMD), is typically described as using rate coding; edge expansion of approaching objects causes an increased rate of neuronal firing that peaks after a certain retinal threshold angle is exceeded. However, evidence of intrinsic DCMD bursting properties combined with observable oscillations in mean firing rates and tight clustering of spikes in raw traces, suggest that bursting may be important for motion detection. Sensory neuron bursting provides important timing information about dynamic stimuli in many model systems, yet no studies have rigorously investigated if bursting occurs in the locust DCMD during object approach. We presented repetitions of 30 looming stimuli known to generate behavioral responses to each of 20 locusts in order to identify and quantify putative bursting activity in the DCMD. Overall, we found a bimodal distribution of inter-spike intervals (ISI) with peaks of more frequent and shorter ISIs occurring from 1–8 ms and longer less frequent ISIs occurring from 40–50 ms. Subsequent analysis identified bursts and isolated single spikes from the responses. Bursting frequency increased in the latter phase of an approach and peaked at the time of collision, while isolated spiking was predominant during the beginning of stimulus approach. We also found that the majority of inter-burst intervals (IBIs) occurred at 40–50 ms (or 20–25 bursts/s). Bursting also occurred across varied stimulus parameters and suggests that burst timing may be a key component of looming detection. Our findings suggest that the DCMD uses two modes of coding to transmit information about looming stimuli and that these modes change dynamically with a changing stimulus at a behaviorally-relevant time. PMID:26696845

  14. Influence of the local anesthetic tetracaine on the phase behavior and the thermodynamic properties of phospholipid bilayers.

    PubMed Central

    Böttner, M; Winter, R

    1993-01-01

    We investigated the influence of the local anesthetic tetracaine on the thermodynamic properties and the temperature- and pressure-dependent phase behavior of the model biomembrane 1,2-dimyristoyl-sn-glycero-3-phosphocholine by using volumetric measurements at temperatures ranging from 0 degrees to 40 degrees C and at pressures from ambient up to 1000 bar. The pVT measurements were complemented by temperature-dependent differential scanning calorimetric measurements. Information about the influence of different concentrations of the local anesthetic on the thermodynamic changes accompanying the lipid phase transitions, and on the thermal expansion coefficient, the isothermal compressibility, and the volume fluctuations of the lipids in their different phases, could be obtained from these experiments. The incorporation of tetracaine leads to an overall disordering of the membrane, as can be inferred from the depression of the main transition temperature and the reduction of the volume change at the main lipid phase transition. The expansion coefficient alpha p and the isothermal compressibility chi T of the lipid bilayer are enhanced by the addition of tetracaine and strongly enhanced values of alpha p and chi T, and the lipid volume fluctuations are found in the direct neighborhood of the main phase transition region. As tetracaine can be viewed as a model system for amphiphilic molecules, these results also provide insight into the general understanding of the physicochemical action of amphiphilic molecules on membranes. The experimental results are compared with recent theoretical predictions for the phase behavior of anesthetic-lipid systems, and the biological relevance of this study is discussed. PMID:8298033

  15. Mechanical Properties and Corrosion Behavior of CeO2 and SiC Incorporated Al5083 Alloy Surface Composites

    NASA Astrophysics Data System (ADS)

    Amra, M.; Ranjbar, Khalil; Dehmolaei, R.

    2015-08-01

    In this investigation, nano-sized cerium oxide (CeO2) and silicon carbide (SiC) particles were stirred and mixed into the surface of an Al5083 alloy rolled plate using friction stir processing (FSP) to form a surface nano-composite layer. For this purpose, various volume ratios of the reinforcements either separately or in the combined form were packed into a pre-machined groove on the surface of the plate. Microstructural features, mechanical properties, and corrosion behavior of the resultant surface composites were determined. Microstructural analysis, optical microscopy and scanning electron microscopy, showed that reinforcement particles were fairly dispersed inside the stir zone and grain refinement was gained. Compared with the base alloy, all of the FSP composites showed higher hardness and tensile strength values with the maximum being obtained for the composite containing 100% SiC particles, i.e., Al5083/SiC. The corrosion behavior of the samples was studied by conducting potentiodynamic polarization tests and assessed in terms of corrosion potential, pitting potential, and passivation range. The result shows a significant increase in corrosion resistance of the base alloy; i.e., the longest passivation range when CeO2 alone was incorporated into the surface by acting as cathodic inhibitors. Composites reinforced with SiC particles exhibited lower pitting resistance due to the formation of microgalvanic couples between cathodic SiC particles and anodic aluminum matrix. The study was aimed to fabricate metal matrix surface composites with improved hardness, tensile strength, and corrosion resistance by the incorporation of CeO2 and SiC reinforcement particles into the surface of Al5083 base alloy. Optimum mechanical properties and corrosion resistance were obtained for the FSP composite Al5083/(75%CeO2 + 25%SiC). In this particular FSP composite, hardness and tensile strength were increased by 30, and 14%, respectively, and passivation range was increased

  16. Statistical Properties of Sleep-Wake Behavior in the Rat and Their Relation to Circadian and Ultradian Phases

    PubMed Central

    Stephenson, Richard; Famina, Svetlana; Caron, Aimee M.; Lim, Joonbum

    2013-01-01

    circadian timescales. Citation: Stephenson R; Famina S; Caron AM; Lim J. Statistical properties of sleep-wake behavior in the rat and their relation to circadian and ultradian phases. SLEEP 2013;36(9):1377-1390. PMID:23997372

  17. Electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys for biomedical applications.

    PubMed

    Lu, Jinwen; Zhao, Yongqing; Niu, Hongzhi; Zhang, Yusheng; Du, Yuzhou; Zhang, Wei; Huo, Wangtu

    2016-05-01

    The present study is to investigate the microstructural characteristics, electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys with Fe addition for biomedical application, and Ti-6Al-4V alloy with two-phase (α+β) microstructure is also studied as a comparison. Microstructural characterization reveals that the phase and crystal structure are sensitive to the Fe content. Ti-6Al alloy displays feather-like hexagonal α phase, and Ti-6Al-1Fe exhibits coarse lath structure of hexagonal α phase and a small amount of β phase. Ti-6Al-2Fe and Ti-6Al-4Fe alloys are dominated by elongated, equiaxed α phase and retained β phase, but the size of α phase particle in Ti-6Al-4Fe alloy is much smaller than that in Ti-6Al-2Fe alloy. The corrosion resistance of these alloys is determined in SBF solution at 37 °C. It is found that the alloys spontaneously form a passive oxide film on their surface after immersion for 500 s, and then they are stable for polarizations up to 0 VSCE. In comparison with Ti-6Al and Ti-6Al-4V alloys, Ti-6Al-xFe alloys exhibit better corrosion resistance with lower anodic current densities, larger polarization resistances and higher open-circuit potentials. The passive layers show stable characteristics, and the wide frequency ranges displaying capacitive characteristics occur for high iron contents. Elasticity experiments are performed to evaluate the elasticity property at room temperature. Ti-6Al-4Fe alloy has the lowest Young's modulus (112 GPa) and exhibits the highest strength/modulus ratios as large as 8.6, which is similar to that of c.p. Ti (8.5). These characteristics of Ti-6Al-xFe alloys form the basis of a great potential to be used as biomedical implantation materials. PMID:26952395

  18. Effects of WC phase contents on the microstructure, mechanical properties and tribological behaviors of WC/a-C superlattice coatings

    NASA Astrophysics Data System (ADS)

    Pu, Jibin; He, Dongqing; Wang, Liping

    2015-12-01

    Nanocomposite WC/a-C coatings with variable contents of tungsten carbide (WC1-x) and amorphous carbon (a-C) were successfully fabricated using a magnetron sputtering process. The microstructure, mechanical properties and tribological behaviors of the as-fabricated coatings were investigated and compared. The results showed that the "superlattice coating" feature of an alternating multilayer structure with a-C and WC1-x nanocrystallites layers on the nanoscale was formed. These multilayer superlattice structures led to diminished residual stress and improved the strength of the adhesion to the substrate. The WC/a-C coating with W 5.43 at.% exhibited low friction coefficients of 0.05 at 25 °C and 0.28 at 200 °C. This significant improvement in the tribological performances of the WC/a-C coating was mainly attributed to the superior "superlattice" microstructure and the formation of a continuously compacted tribofilms, which was rich in graphitized carbon at 25 °C and dominated by the friction triggered WO3 at 200 °C. Moreover, the WC/a-C coating with W 5.43 at.% achieved optimal anti-wear properties at 25 °C due to the synergistic combination of the enhancement effects of the WC1-x nanoparticles and the partition effect from the transfer film that restricted direct contact of the steel ball with the coating and thus prevented further intense wear. The accelerated wear of the WC/a-C coating with the increase of the WC phase content at 200 °C might be due to the combination of oxidation wear and abrasive wear that originated from the WC1-x phase.

  19. Mechanical properties of the cuticles of three cockroach species that differ in their wind-evoked escape behavior

    PubMed Central

    Clark, Andrew J.

    2014-01-01

    The structural and material properties of insect cuticle remain largely unexplored, even though they comprise the majority (approximately 80%) of animals. Insect cuticle serves many functions, including protection against predatory attacks, which is especially beneficial to species failing to employ effective running escape responses. Despite recent advances in our understanding of insect escape behaviors and the biomechanics of insect cuticle, there are limited studies on the protective qualities of cuticle to extreme mechanical stresses and strains imposed by predatory attacks, and how these qualities vary between species employing different escape responses. Blattarians (cockroaches) provide an appropriate model system for such studies. Wind-evoked running escape responses are strong in Periplaneta americana, weak in Blaberus craniifer and absent in Gromphodorhina portentosa, putting the latter two species at greater risk of being struck by a predator. We hypothesized that the exoskeletons in these two larger species could provide more protection from predatory strikes relative to the exoskeleton of P. americana. We quantified the protective qualities of the exoskeletons by measuring the puncture resistance, tensile strength, strain energy storage, and peak strain in fresh samples of thoracic and abdominal cuticles from these three species. We found a continuum in puncture resistance, tensile strength, and strain energy storage between the three species, which were greatest in G. portentosa, moderate in B. craniifer, and smallest in P. americana. Histological measurements of total cuticle thickness followed this same pattern. However, peak strain followed a different trend between species. The comparisons in the material properties drawn between the cuticles of G. portentosa, B. craniifer, and P. americana demonstrate parallels between cuticular biomechanics and predator running escape responses. PMID:25101230

  20. Effects of Al(3+) doping on the structure and properties of goethite and its adsorption behavior towards phosphate.

    PubMed

    Li, Wei; Wang, Longjun; Liu, Fan; Liang, Xiaoliang; Feng, Xionghan; Tan, Wenfeng; Zheng, Lirong; Yin, Hui

    2016-07-01

    Al substitution in goethite is common in soils, and has strong influence on the structure and physicochemical properties of goethite. In this research, a series of Al-doped goethites were synthesized, and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The adsorption behavior of these samples towards PO4(3-) was also investigated. Characterization results demonstrated that increasing Al content in goethite led to a reduction in crystallinity, increase in specific surface area (SSA), and morphology change from needle-like to granular. Rietveld structure refinement revealed that the lattice parameter a remained almost constant and b slightly decreased, but c was significantly reduced, and the calculated crystal density increased. EXAFS analysis demonstrated that the Fe(Al)-O distance in the structure of the doped goethites was almost the same, but the Fe-Fe(Al) distance decreased with increasing Al content. Surface analysis showed that, with increasing Al content, the content of OH groups on the mineral surface increased. The adsorption of phosphate per unit mass of Al-doped goethite increased, while adsorption per unit area decreased owing to the decrease of the relative proportion of (110) facets in the total surface area of the minerals. The results of this research facilitate better understanding of the effect of Al substitution on the structure and properties of goethite and the cycling of phosphate in the environment. PMID:27372115

  1. Transcription factors FOXA1 and FOXA2 maintain dopaminergic neuronal properties and control feeding behavior in adult mice.

    PubMed

    Pristerà, Alessandro; Lin, Wei; Kaufmann, Anna-Kristin; Brimblecombe, Katherine R; Threlfell, Sarah; Dodson, Paul D; Magill, Peter J; Fernandes, Cathy; Cragg, Stephanie J; Ang, Siew-Lan

    2015-09-01

    Midbrain dopaminergic (mDA) neurons are implicated in cognitive functions, neuropsychiatric disorders, and pathological conditions; hence understanding genes regulating their homeostasis has medical relevance. Transcription factors FOXA1 and FOXA2 (FOXA1/2) are key determinants of mDA neuronal identity during development, but their roles in adult mDA neurons are unknown. We used a conditional knockout strategy to specifically ablate FOXA1/2 in mDA neurons of adult mice. We show that deletion of Foxa1/2 results in down-regulation of tyrosine hydroxylase, the rate-limiting enzyme of dopamine (DA) biosynthesis, specifically in dopaminergic neurons of the substantia nigra pars compacta (SNc). In addition, DA synthesis and striatal DA transmission were reduced after Foxa1/2 deletion. Furthermore, the burst-firing activity characteristic of SNc mDA neurons was drastically reduced in the absence of FOXA1/2. These molecular and functional alterations lead to a severe feeding deficit in adult Foxa1/2 mutant mice, independently of motor control, which could be rescued by L-DOPA treatment. FOXA1/2 therefore control the maintenance of molecular and physiological properties of SNc mDA neurons and impact on feeding behavior in adult mice. PMID:26283356

  2. Single-Molecule-Magnet Behavior and Fluorescence Properties of 8-Hydroxyquinolinate Derivative-Based Rare-Earth Complexes.

    PubMed

    Gao, Hong-Ling; Jiang, Li; Wang, Wen-Min; Wang, Shi-Yu; Zhang, Hong-Xia; Cui, Jian-Zhong

    2016-09-01

    Five tetranuclear rare-earth complexes, [RE4(dbm)4L6(μ3-OH)2] [HL = 5- (4-fluorobenzylidene)-8-hydroxylquinoline; dbm = 1,3-diphenyl-1,3-propanedione; RE = Y (1), Eu (2), Tb (3), Dy (4), Lu (5)], have been synthesized and completely characterized. The X-ray structural analyses show that each [RE4] complex is of typical butterfly or rhombus topology. Each RE(III) center exists in an eight-coordinated square-antiprism environment. Magnetic studies reveal that complex 4 displays single-molecule-magnet behavior below 10 K under a zero direct-current field, with an effective anisotropy barrier (ΔE/kB = 56 K). The fluorescence properties of complexes 1-5 were also investigated. Complexes 2-4 showed their characteristic peaks for the corresponding RE(III) center, while complexes 1 and 5 showed the same emission peaks with the ligand when they were excited at the same wavelength. PMID:27560459

  3. Effects of water molecules on tribological behavior and property measurements in nano-indentation processes - a numerical analysis

    PubMed Central

    2013-01-01

    Nano/micro-manufacturing under wet condition is an important consideration for various tool-based processes such as indentation, scratching, and machining. The existence of liquids adds complexity to the system, changes the tool/work interfacial condition, and affects material behaviors. For indentation, it may also affect material property measurements. However, little effort has been made to study this challenging issue at nano- or atomistic scale. In this study, we tackle this challenge by investigating nano-indentation processes submerged in water using the molecular dynamics (MD) simulation approach. Compared with dry indentation in which no water molecules are present, the existence of water molecules causes the increase of indentation force in initial penetration, but the decrease of indentation force in full penetration. It also reduces the sticking phenomenon between the work and tool atoms during indenter retraction, such that the indentation geometry can be better retained. Meanwhile, nano-indentation under wet condition exhibits the indentation size effect, while dry nano-indentation exhibits the reverse indentation size effect. The existence of water leads to higher computed hardness values at low indentation loads and a smaller value of Young's modulus. In addition, the friction along the tool/work interface is significantly reduced under wet indentation. PMID:24044504

  4. New Li-ion Battery Evaluation Research Based on Thermal Property and Heat Generation Behavior of Battery

    NASA Astrophysics Data System (ADS)

    Lv, Zhe; Guo, Xun; Qiu, Xin-ping

    2012-12-01

    We do a new Li-ion battery evaluation research on the effects of cell resistance and polarization on the energy loss in batteries based on thermal property and heat generation behavior of battery. Series of 18650 cells with different capacities and electrode materials are evaluated by measuring input and output energy which change with charge-discharge time and current. Based on the results of these tests, we build a model of energy loss in cells' charge-discharge process, which include Joule heat and polarization heat impact factors. It was reported that Joule heat was caused by cell resistance, which included DC-resistance and reaction resistance, and reaction resistance could not be easily obtained through routine test method. Using this new method, we can get the total resistance R and the polarization parameter η. The relationship between R, η, and temperature is also investigated in order to build a general model for series of different Li-ion batteries, and the research can be used in the performance evaluation, state of charge prediction and the measuring of consistency of the batteries.

  5. Examining the effects of wall numbers on buckling behavior and mechanical properties of multiwalled carbon nanotubes via molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Y.; Wang, C. M.; Tan, V. B. C.

    2008-03-01

    Molecular dynamics simulations are performed on multiwalled carbon nanotubes (MWCNTs) under axial compression to investigate the effects of the number of walls and their van der Waals (vdW) interaction on the buckling behaviors and mechanical properties (Young's modulus and Poisson's ratio). The Brenner second-generation reactive empirical bond order and Lennard-Jones 12-6 potential have been adopted to describe the short-range bonding and long-range vdW atomic interaction within the carbon nanotubes, respectively. In the presence of vdW interaction, the buckling strain and Young's modulus of MWCNTs increase as the number of tubes is increased while keeping the outermost tube diameter constant, whereas Poisson's ratio was observed to decrease. On the other hand, when the MWCNTs are formed by progressively adding outer tubes while keeping the innermost tube diameter constant, Young's modulus and buckling strain were observed to decrease, whereas Poisson's ratio increases. The buckling load increases with increasing the number of walls due to the larger cross-sectional areas. Individual tubes of MWCNTs with a relatively large difference between the diameters of the inner and outer tubes buckle one at a time as opposed to simultaneously for MWCNTs with a relatively small difference in diameters.

  6. Structure, mechanical properties, corrosion behavior and cytotoxicity of biodegradable Mg-X (X=Sn, Ga, In) alloys.

    PubMed

    Kubásek, J; Vojtěch, D; Lipov, J; Ruml, T

    2013-05-01

    As-cast Mg-Sn, Mg-Ga and Mg-In alloys containing 1-7 wt.% of alloying elements were studied in this work. Structural and chemical analysis of the alloys was performed by using light and scanning electron microscopy, energy dispersive spectrometry, x-ray diffraction, x-ray photoelectron spectroscopy and glow discharge spectrometry. Mechanical properties were determined by Vickers hardness measurements and tensile testing. Corrosion behavior in a simulated physiological solution (9 g/l NaCl) was studied by immersion tests and potentiodynamic measurements. The cytotoxicity effect of the alloys on human osteosarcoma cells (U-2 OS) was determined by an indirect contact assay. Structural investigation revealed the dendritic morphology of the as-cast alloys with the presence of secondary eutectic phases in the Mg-Sn and Mg-Ga alloys. All the alloying elements showed hardening and strengthening effects on magnesium. This effect was the most pronounced in the case of Ga. All the alloying elements at low concentrations of approximately 1 wt.% were also shown to positively affect the corrosion resistance of Mg. But at higher concentrations of Ga and Sn the corrosion resistance worsened due to galvanic effects of secondary phases. Cytotoxicity tests indicated that Ga had the lowest toxicity, followed by Sn. The most severe toxicity was observed in the case of In. PMID:23498278

  7. Place Cell Networks in Pre-weanling Rats Show Associative Memory Properties from the Onset of Exploratory Behavior.

    PubMed

    Muessig, L; Hauser, J; Wills, T J; Cacucci, F

    2016-08-01

    Place cells are hippocampal pyramidal cells that are active when an animal visits a restricted area of the environment, and collectively their activity constitutes a neural representation of space. Place cell populations in the adult rat hippocampus display fundamental properties consistent with an associative memory network: the ability to 1) generate new and distinct spatial firing patterns when encountering novel spatial contexts or changes in sensory input ("remapping") and 2) reinstate previously stored firing patterns when encountering a familiar context, including on the basis of an incomplete/degraded set of sensory cues ("pattern completion"). To date, it is unknown when these spatial memory responses emerge during brain development. Here, we show that, from the age of first exploration (postnatal day 16) onwards, place cell populations already exhibit these key features: they generate new representations upon exposure to a novel context and can reactivate familiar representations on the basis of an incomplete set of sensory cues. These results demonstrate that, as early as exploratory behaviors emerge, and despite the absence of an adult-like grid cell network, the developing hippocampus processes incoming sensory information as an associative memory network. PMID:27282394

  8. Microstructure, texture evolution, mechanical properties and corrosion behavior of ECAP processed ZK60 magnesium alloy for biodegradable applications.

    PubMed

    Mostaed, Ehsan; Hashempour, Mazdak; Fabrizi, Alberto; Dellasega, David; Bestetti, Massimiliano; Bonollo, Franco; Vedani, Maurizio

    2014-09-01

    Ultra-fine grained ZK60 Mg alloy was obtained by multi-pass equal-channel angular pressing at different temperatures of 250°C, 200°C and 150°C. Microstructural observations showed a significant grain refinement after ECAP, leading to an equiaxed and ultrafine grain (UFG) structure with average size of 600nm. The original extrusion fiber texture with planes oriented parallel to extrusion direction was gradually undermined during ECAP process and eventually it was substituted by a newly stronger texture component with considerably higher intensity, coinciding with ECAP shear plane. A combination of texture modification and grain refinement in UFG samples led to a marked reduction in mechanical asymmetric behavior compared to the as-received alloy, as well as adequate mechanical properties with about 100% improvement in elongation to failure while keeping relatively high tensile strength. Open circuit potential, potentiodynamic and weight loss measurements in a phosphate buffer solution electrolyte revealed an improved corrosion resistance of UFG alloy compared to the extruded one, stemming from a shift of corrosion regime from localized pitting in the as-received sample to a more uniform corrosion mode with reduced localized attack in ECAP processed alloy. Compression tests on immersed samples showed that the rate of loss of mechanical integrity in the UFG sample was lower than that in the as-received sample. PMID:24971801

  9. Place Cell Networks in Pre-weanling Rats Show Associative Memory Properties from the Onset of Exploratory Behavior

    PubMed Central

    Muessig, L.; Hauser, J.; Wills, T. J.; Cacucci, F.

    2016-01-01

    Place cells are hippocampal pyramidal cells that are active when an animal visits a restricted area of the environment, and collectively their activity constitutes a neural representation of space. Place cell populations in the adult rat hippocampus display fundamental properties consistent with an associative memory network: the ability to 1) generate new and distinct spatial firing patterns when encountering novel spatial contexts or changes in sensory input (“remapping”) and 2) reinstate previously stored firing patterns when encountering a familiar context, including on the basis of an incomplete/degraded set of sensory cues (“pattern completion”). To date, it is unknown when these spatial memory responses emerge during brain development. Here, we show that, from the age of first exploration (postnatal day 16) onwards, place cell populations already exhibit these key features: they generate new representations upon exposure to a novel context and can reactivate familiar representations on the basis of an incomplete set of sensory cues. These results demonstrate that, as early as exploratory behaviors emerge, and despite the absence of an adult-like grid cell network, the developing hippocampus processes incoming sensory information as an associative memory network. PMID:27282394

  10. Dynamic Mechanical Properties, Crystallization Behavior and Morphology of Nanoscale Tin Fluorophosphate Glass/Polyamide 66 Hybrid Materials.

    PubMed

    Liu, Huiwen; Yang, Jing; Yu, Honglin; Zou, Xiaoxuan; Jing, Bo; Dai, Wenli

    2016-04-01

    The dynamic mechanical properties, crystallization behavior and morphology of nanoscale Tg tin fluorophosphate glass (TFP glass)/polyamide 66 (PA66) hybrid materials were investigated by XRD, DSC and SEM. The experimental results showed that the Tg of TFP/PA66 hybrid decreased and the third relaxation in the highly filled hybrid appeared due to the interaction between the TFP glass and amide groups of PA66. The storage modulus of the hybrid materials increased with increase in the content of TFP at low temperatures but had little effect at high temperatures. This result was attributed to the stiffness depression of the TFP glass when the temperature rose above its Tg and the similar elasticity of the two phases because of the interaction between the components. The degree of crystallinity and a, y crystal content of PA66 both decreased due to the interaction between the two phases. In addition, the phase defect, the size distribution and the compatibility of TFP in the PA66 matrix were discussed by SEM, the results showed that the TFP appeared aggregation partly, but had the favorable compatibility in the PA66 matrix. PMID:27451779

  11. Thermal decomposition behaviors and kinetic properties of 1,8-naphthalic anhydride loaded dense nano-silica hybrids

    NASA Astrophysics Data System (ADS)

    Wang, Jinpeng; Sun, Jihong; Wang, Feng; Ren, Bo

    2013-06-01

    A certain amount of (3-aminopropyl)triethoxysilane (APTES) and various capacity of 1,8-naphthalic anhydride (NA) were employed to modify and then graft onto the surface of the dense nano-silica spheres (DNSS) via a post-grafting method, and thereby, a novel luminescent density nano-silica hybrid materials have been successfully synthesized. Meanwhile, the structures and properties of obtained hybrid DNSS were characterized by XRD, TEM, N2 sorption, FT-IR, and TG analysis. Furthermore, the thermal stability of before and after modification were demonstrated by using both Kissinger methods and Ozawa-Flynn-Wall methods. Particularly, the thermal decomposition behaviors of amino-modified groups and NA-grafted organic molecules were emphasized based on the TG and DTG analysis and then the related mechanism was put forward according to Coats and Redfern methods. Finally, as a comparison, the obtained results and the proposed decomposition mechanism of hybrid DNSS with non-pores were discussed with that of mesopores silicas in details.

  12. Property.

    ERIC Educational Resources Information Center

    Piele, Philip K.; Johnson, Margaret M.

    This chapter deals with 1981 cases involving disputes over property. Cases involving the detachment and attachment of land continue to dominate the property chapter with 11 cases reported, the same number summarized in last year's chapter. One case involving school board referenda raised the interesting question of whether or not a state could…

  13. Property.

    ERIC Educational Resources Information Center

    Bickel, Robert D.; Zeller, Trisha A.

    A number of cases related to property issues involving institutions of higher education are examined in this chapter. Cases discussed touch on such topics as funding for property and equipment acquisition; opposition to building construction or demolition; zoning issues; building construction and equipment contracts; and lease agreements. Current…

  14. Property.

    ERIC Educational Resources Information Center

    Goldblatt, Steven M.; Piele, Philip K.

    This chapter reviews 1982 cases related to school property. Cases involving citizen efforts to overturn school board decisions to close schools dominate the property chapter, and courts continue to uphold school board authority to close schools, transfer students, and sell or lease the buildings. Ten cases involving detachment and attachment of…

  15. Property.

    ERIC Educational Resources Information Center

    Piele, Philip K.

    Chapter 7 of a book on school law, this chapter deals with 1979 cases involving disputes over property. Cases involving taxpayer attempts to prevent the construction of school buildings dominate this year's property chapter, as they did last year's. Yet, paradoxically, there is also a significant increase in cases in which taxpayers tried to…

  16. Influence of Post-Weld Annealing on Transformation Behavior and Mechanical Properties of Laser-Welded NiTi Alloy Wires

    NASA Astrophysics Data System (ADS)

    Yan, Xiaojun; Ge, Yuli

    2014-10-01

    The influence of annealing on the transformation behavior, mechanical, and functional properties of laser-welded NiTi wires was investigated. The results show that Ti3Ni4 precipitates occur after post-weld annealing and coarsen with increasing annealing temperature. The as-welded specimen exhibits one-step B2 → B19' transformation, while the annealed ones show two-step B2 → R → B19' transformation. Annealing at 400 °C for 1 h can improve the tensile strength and superelasticity of the welded joints. However, these properties decrease when annealing at 500 °C for 1 h. The change of mechanical and functional properties after annealing is attributed to the different size of Ti3Ni4 precipitates. Annealing to produce smaller coherent precipitates (10 nm) improves the mechanical and functional properties of the welded joints. As the Ti3Ni4 precipitates coarsen, the mechanical and functional properties decrease.

  17. Comparison of Elevated Temperature Tensile Properties and Fatigue Behavior of Two Variants of a Woven SiC/SiC Composite

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Brewer, David N.; Sreeramesh, Kalluri

    2005-01-01

    Tensile properties (elastic modulus, proportional limit strength, in-plane tensile strength, and strain at failure) of two variants of a woven SiC/SiC composite, manufactured during two separate time periods (9/99 and 1/01), were determined at 1038 and 1204 C by conducting tensile tests on specimens machined from plates. Continuous cycling fatigue tests (R = 0.05) and 20 cpm) were also conducted at the same two temperatures on specimens from both composites. In this study, average tensile properties, 95% confidence intervals associated with the tensile properties, and geometric mean fatigue lives of both composite materials are compared. The observed similarities and differences in the tensile properties are highlighted and an attempt is made to understand the relationship, if any, between the tensile properties and the fatigue behaviors of the two woven composites.

  18. Effect of stoichiometry on the dielectric properties and soft mode behavior of strained epitaxial SrTiO3 thin films on DyScO3 substrates

    SciTech Connect

    Lee, Che-Hui; Skoromets, Volodymyr; Biegalski, Michael D; Lei, Shiming; Haislmaier, Ryan; Uecker, Reinhard; Bernhagen, Margitta; Xi, Xiaoxing; Gopalan, Venkatraman; Marti, Xavier; Kamba, Stanislav; Kuzel, Petr; Schlom, Darrell

    2013-01-01

    The effect of stoichiometry on the dielectric properties and soft mode behavior of strained epitaxial Sr1-xTiO3 films grown on DyScO3 substrates is reported. Direct comparisons between nominally stoichiometric and non-stoichiometric films have been performed through measurements of lattice parameters, temperature-dependent permittivities, second harmonic generation, and terahertz dielectric spectra. The nominally stoichiometric film shows dispersion-free low-frequency permittivity with a 23 sharp maximum and pronounced soft mode behavior. Our results suggest that strained perfectlystoichiometric SrTiO3 films should not show relaxor behavior and that relaxor behavior emergesfrom defect dipoles that arise from non-stoichiometry in the highly polarizable strained SrTiO3 matrix

  19. Influence of chemical extraction on rheological behavior, viscoelastic properties and functional characteristics of natural heteropolysaccharide/protein polymer from Durio zibethinus seed.

    PubMed

    Amid, Bahareh Tabatabaee; Mirhosseini, Hamed

    2012-01-01

    In recent years, the demand for a natural plant-based polymer with potential functions from plant sources has increased considerably. The main objective of the current study was to study the effect of chemical extraction conditions on the rheological and functional properties of the heteropolysaccharide/protein biopolymer from durian (Durio zibethinus) seed. The efficiency of different extraction conditions was determined by assessing the extraction yield, protein content, solubility, rheological properties and viscoelastic behavior of the natural polymer from durian seed. The present study revealed that the soaking process had a more significant (p < 0.05) effect than the decolorizing process on the rheological and functional properties of the natural polymer. The considerable changes in the rheological and functional properties of the natural polymer could be due to the significant (p < 0.05) effect of the chemical extraction variables on the protein fraction present in the molecular structure of the natural polymer from durian seed. The natural polymer from durian seed had a more elastic (or gel like) behavior compared to the viscous (liquid like) behavior at low frequency. The present study revealed that the natural heteropolysaccharide/protein polymer from durian seed had a relatively low solubility ranging from 9.1% to 36.0%. This might be due to the presence of impurities, insoluble matter and large particles present in the chemical structure of the natural polymer from durian seed. PMID:23203099

  20. Influence of Chemical Extraction on Rheological Behavior, Viscoelastic Properties and Functional Characteristics of Natural Heteropolysaccharide/Protein Polymer from Durio zibethinus Seed

    PubMed Central

    Amid, Bahareh Tabatabaee; Mirhosseini, Hamed

    2012-01-01

    In recent years, the demand for a natural plant-based polymer with potential functions from plant sources has increased considerably. The main objective of the current study was to study the effect of chemical extraction conditions on the rheological and functional properties of the heteropolysaccharide/protein biopolymer from durian (Durio zibethinus) seed. The efficiency of different extraction conditions was determined by assessing the extraction yield, protein content, solubility, rheological properties and viscoelastic behavior of the natural polymer from durian seed. The present study revealed that the soaking process had a more significant (p < 0.05) effect than the decolorizing process on the rheological and functional properties of the natural polymer. The considerable changes in the rheological and functional properties of the natural polymer could be due to the significant (p < 0.05) effect of the chemical extraction variables on the protein fraction present in the molecular structure of the natural polymer from durian seed. The natural polymer from durian seed had a more elastic (or gel like) behavior compared to the viscous (liquid like) behavior at low frequency. The present study revealed that the natural heteropolysaccharide/protein polymer from durian seed had a relatively low solubility ranging from 9.1% to 36.0%. This might be due to the presence of impurities, insoluble matter and large particles present in the chemical structure of the natural polymer from durian seed. PMID:23203099

  1. Studies of fatty acid composition, physicochemical and thermal properties, and crystallization behavior of mango kernel fats from various Thai varieties.

    PubMed

    Sonwai, Sopark; Ponprachanuvut, Punnee

    2014-01-01

    Mango kernel fat (MKF) has received attention in recent years due to the resemblance between its characteristics and those of cocoa butter (CB). In this work, fatty acid (FA) composition, physicochemical and thermal properties and crystallization behavior of MKFs obtained from four varieties of Thai mangoes: Keaw-Morakot (KM), Keaw-Sawoey (KS), Nam-Dokmai (ND) and Aok-Rong (AR), were characterized. The fat content of the mango kernels was 6.40, 5.78, 5.73 and 7.74% (dry basis) for KM, KS, ND and AR, respectively. The analysis of FA composition revealed that all four cultivars had oleic and stearic acids as the main FA components with ND and AR exhibiting highest and lowest stearic acid content, respectively. ND had the highest slip melting point and solid fat content (SFC) followed by KS, KM and AR. All fat samples exhibited high SFC at 20℃ and below. They melted slowly as the temperature increased and became complete liquids as the temperature approached 35°C. During static isothermal crystallization at 20°C, ND displayed the highest Avrami rate constant k followed by KS, KM and AR, indicating that the crystallization was fastest for ND and slowest for AR. The Avrami exponent n of all samples ranged from 0.89 to 1.73. The x-ray diffraction analysis showed that all MKFs crystallized into a mixture of pseudo-β', β', sub-β and β structures with β' being the predominant polymorph. Finally, the crystals of the kernel fats from all mango varieties exhibited spherulitic morphology. PMID:24919475

  2. Property.

    ERIC Educational Resources Information Center

    Piele, Philip K.

    Reflecting widespread unhappiness with the growing tax burdens in this country, the most active area of litigation reported in the property chapter this year involves various attempts by taxpayers to prevent the construction or remodeling of public school facilities. While some taxpayers fought to keep schools from being built, others in New York…

  3. Trends in the Prevalence of Behaviors That Contribute to Violence on School Property. National YRBS: 1991-2011

    ERIC Educational Resources Information Center

    Centers for Disease Control and Prevention, 2011

    2011-01-01

    The national Youth Risk Behavior Survey (YRBS) monitors priority health risk behaviors that contribute to the leading causes of death, disability, and social problems among youth and adults in the United States. The national YRBS is conducted every two years during the spring semester and provides data representative of 9th through 12th grade…

  4. Preliminary Psychometric Properties of an Observation System to Assess Teachers' Use of Effective Behavior Support Strategies in Preschool Classrooms

    ERIC Educational Resources Information Center

    Vujnovic, Rebecca K.; Fabiano, Gregory A.; Waschbusch, Daniel A.; Pelham, William E.; Greiner, Andrew; Gera, Shradha; Linke, Stuart; Gormley, Matt; Buck, Melina

    2014-01-01

    Challenging behaviors are one of the most common concerns of early educators, and preschool teachers continue to report feeling unprepared to meet the needs of children displaying challenging behaviors. Overall, traditional standardized classroom assessments have evaluated global classroom quality, but they may not capture the reciprocal and…

  5. Psychometric properties of questionnaires measuring associations between behavioral factors and diabetes care for youth with type 2 diabetes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Because of the recency of the large numbers of youth diagnosed with type 2 diabetes (T2D), measures of adherence behavior and family response to diabetes have not been developed or tested. The objective of this study is to identify whether questionnaires on personal and family behaviors regarding th...

  6. Structure, Properties, and In Vitro Behavior of Heat-Treated Calcium Sulfate Scaffolds Fabricated by 3D Printing.

    PubMed

    Asadi-Eydivand, Mitra; Solati-Hashjin, Mehran; Shafiei, Seyedeh Sara; Mohammadi, Sepideh; Hafezi, Masoud; Abu Osman, Noor Azuan

    2016-01-01

    The ability of inkjet-based 3D printing (3DP) to fabricate biocompatible ceramics has made it one of the most favorable techniques to generate bone tissue engineering (BTE) scaffolds. Calcium sulfates exhibit various beneficial characteristics, and they can be used as a promising biomaterial in BTE. However, low mechanical performance caused by the brittle character of ceramic materials is the main weakness of 3DP calcium sulfate scaffolds. Moreover, the presence of certain organic matters in the starting powder and binder solution causes products to have high toxicity levels. A post-processing treatment is usually employed to improve the physical, chemical, and biological behaviors of the printed scaffolds. In this study, the effects of heat treatment on the structural, mechanical, and physical characteristics of 3DP calcium sulfate prototypes were investigated. Different microscopy and spectroscopy methods were employed to characterize the printed prototypes. The in vitro cytotoxicity of the specimens was also evaluated before and after heat treatment. Results showed that the as-printed scaffolds and specimens heat treated at 300°C exhibited severe toxicity in vitro but had almost adequate strength. By contrast, the specimens heat treated in the 500°C-1000°C temperature range, although non-toxic, had insufficient mechanical strength, which was mainly attributed to the exit of the organic binder before 500°C and the absence of sufficient densification below 1000°C. The sintering process was accelerated at temperatures higher than 1000°C, resulting in higher compressive strength and less cytotoxicity. An anhydrous form of calcium sulfate was the only crystalline phase existing in the samples heated at 500°C-1150°C. The formation of calcium oxide caused by partial decomposition of calcium sulfate was observed in the specimens heat treated at temperatures higher than 1200°C. Although considerable improvements in cell viability of heat-treated scaffolds were

  7. Structure, Properties, and In Vitro Behavior of Heat-Treated Calcium Sulfate Scaffolds Fabricated by 3D Printing

    PubMed Central

    Asadi-Eydivand, Mitra; Solati-Hashjin, Mehran; Shafiei, Seyedeh Sara; Mohammadi, Sepideh; Hafezi, Masoud; Abu Osman, Noor Azuan

    2016-01-01

    The ability of inkjet-based 3D printing (3DP) to fabricate biocompatible ceramics has made it one of the most favorable techniques to generate bone tissue engineering (BTE) scaffolds. Calcium sulfates exhibit various beneficial characteristics, and they can be used as a promising biomaterial in BTE. However, low mechanical performance caused by the brittle character of ceramic materials is the main weakness of 3DP calcium sulfate scaffolds. Moreover, the presence of certain organic matters in the starting powder and binder solution causes products to have high toxicity levels. A post-processing treatment is usually employed to improve the physical, chemical, and biological behaviors of the printed scaffolds. In this study, the effects of heat treatment on the structural, mechanical, and physical characteristics of 3DP calcium sulfate prototypes were investigated. Different microscopy and spectroscopy methods were employed to characterize the printed prototypes. The in vitro cytotoxicity of the specimens was also evaluated before and after heat treatment. Results showed that the as-printed scaffolds and specimens heat treated at 300°C exhibited severe toxicity in vitro but had almost adequate strength. By contrast, the specimens heat treated in the 500°C–1000°C temperature range, although non-toxic, had insufficient mechanical strength, which was mainly attributed to the exit of the organic binder before 500°C and the absence of sufficient densification below 1000°C. The sintering process was accelerated at temperatures higher than 1000°C, resulting in higher compressive strength and less cytotoxicity. An anhydrous form of calcium sulfate was the only crystalline phase existing in the samples heated at 500°C–1150°C. The formation of calcium oxide caused by partial decomposition of calcium sulfate was observed in the specimens heat treated at temperatures higher than 1200°C. Although considerable improvements in cell viability of heat-treated scaffolds

  8. Psychometric properties of the French translation of the Behavioral Activation for Depression Scale-Short Form (BADS-SF) in non-clinical adults.

    PubMed

    Wagener, Aurélie; Van der Linden, Martial; Blairy, Sylvie

    2015-01-01

    A decrease in the level of engagement in activities ("behavioral activation") is usually observed in major depressive disorder. Because behavioral treatments of depression aim to counteract that mechanism, assessing changes in behavioral activation during treatment is of great interest. Therefore, Manos et al. (2011) developed a scale that assesses these changes, which was called the Behavioral Activation for Depression Scale-Short Form (BADS-SF). The aim of this study is to present a French version of this scale and to discuss its psychometric properties. The BADS-SF was translated into French, and 504 non-clinical adults completed an online survey that was composed of that scale and convergent measures. Exploratory and confirmatory factor analyses were performed in two independent samples, and a two-factor solution was recommended, which references two functions of the engagement in activities (i.e., "activation" and "avoidance"). The results showed high levels of internal consistency and satisfying scores in terms of skewness and kurtosis. Moreover, relationships with measures of depression and behavioral systems indicated a good convergent validity. Therefore, the French BADS-SF can be seen as a reliable and valid instrument. PMID:25458479

  9. DIRAC: A new version of computer algebra tools for studying the properties and behavior of hydrogen-like ions

    NASA Astrophysics Data System (ADS)

    McConnell, Sean; Fritzsche, Stephan; Surzhykov, Andrey

    2010-03-01

    During recent years, the DIRAC package has proved to be an efficient tool for studying the structural properties and dynamic behavior of hydrogen-like ions. Originally designed as a set of MAPLE procedures, this package provides interactive access to the wave and Green's functions in the non-relativistic and relativistic frameworks and supports analytical evaluation of a large number of radial integrals that are required for the construction of transition amplitudes and interaction cross sections. We provide here a new version of the DIRAC program which is developed within the framework of MATHEMATICA (version 6.0). This new version aims to cater to a wider community of researchers that use the MATHEMATICA platform and to take advantage of the generally faster processing times therein. Moreover, the addition of new procedures, a more convenient and detailed help system, as well as source code revisions to overcome identified shortcomings should ensure expanded use of the new DIRAC program over its predecessor. New version program summaryProgram title: DIRAC Catalogue identifier: ADUQ_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUQ_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC license, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 45 073 No. of bytes in distributed program, including test data, etc.: 285 828 Distribution format: tar.gz Programming language: Mathematica 6.0 or higher Computer: All computers with a license for the computer algebra package Mathematica (version 6.0 or higher) Operating system: Mathematica is O/S independent Classification: 2.1 Catalogue identifier of previous version: ADUQ_v1_0 Journal reference of previous version: Comput. Phys. Comm. 165 (2005) 139 Does the new version supersede the previous version?: Yes Nature of problem: Since the early days of quantum mechanics, the

  10. Testing Students with Special Educational Needs in Large-Scale Assessments – Psychometric Properties of Test Scores and Associations with Test Taking Behavior

    PubMed Central

    Pohl, Steffi; Südkamp, Anna; Hardt, Katinka; Carstensen, Claus H.; Weinert, Sabine

    2016-01-01

    Assessing competencies of students with special educational needs in learning (SEN-L) poses a challenge for large-scale assessments (LSAs). For students with SEN-L, the available competence tests may fail to yield test scores of high psychometric quality, which are—at the same time—measurement invariant to test scores of general education students. We investigated whether we can identify a subgroup of students with SEN-L, for which measurement invariant competence measures of adequate psychometric quality may be obtained with tests available in LSAs. We furthermore investigated whether differences in test-taking behavior may explain dissatisfying psychometric properties and measurement non-invariance of test scores within LSAs. We relied on person fit indices and mixture distribution models to identify students with SEN-L for whom test scores with satisfactory psychometric properties and measurement invariance may be obtained. We also captured differences in test-taking behavior related to guessing and missing responses. As a result we identified a subgroup of students with SEN-L for whom competence scores of adequate psychometric quality that are measurement invariant to those of general education students were obtained. Concerning test taking behavior, there was a small number of students who unsystematically picked response options. Removing these students from the sample slightly improved item fit. Furthermore, two different patterns of missing responses were identified that explain to some extent problems in the assessments of students with SEN-L. PMID:26941665

  11. Testing Students with Special Educational Needs in Large-Scale Assessments - Psychometric Properties of Test Scores and Associations with Test Taking Behavior.

    PubMed

    Pohl, Steffi; Südkamp, Anna; Hardt, Katinka; Carstensen, Claus H; Weinert, Sabine

    2016-01-01

    Assessing competencies of students with special educational needs in learning (SEN-L) poses a challenge for large-scale assessments (LSAs). For students with SEN-L, the available competence tests may fail to yield test scores of high psychometric quality, which are-at the same time-measurement invariant to test scores of general education students. We investigated whether we can identify a subgroup of students with SEN-L, for which measurement invariant competence measures of adequate psychometric quality may be obtained with tests available in LSAs. We furthermore investigated whether differences in test-taking behavior may explain dissatisfying psychometric properties and measurement non-invariance of test scores within LSAs. We relied on person fit indices and mixture distribution models to identify students with SEN-L for whom test scores with satisfactory psychometric properties and measurement invariance may be obtained. We also captured differences in test-taking behavior related to guessing and missing responses. As a result we identified a subgroup of students with SEN-L for whom competence scores of adequate psychometric quality that are measurement invariant to those of general education students were obtained. Concerning test taking behavior, there was a small number of students who unsystematically picked response options. Removing these students from the sample slightly improved item fit. Furthermore, two different patterns of missing responses were identified that explain to some extent problems in the assessments of students with SEN-L. PMID:26941665

  12. Traumatic Brain Injury in Young Rats Leads to Progressive Behavioral Deficits Coincident with Altered Tissue Properties in Adulthood

    PubMed Central

    Ajao, David O.; Pop, Viorela; Kamper, Joel E.; Adami, Arash; Rudobeck, Emil; Huang, Lei; Vlkolinsky, Roman; Hartman, Richard E.; Ashwal, Stephen; Obenaus, André

    2012-01-01

    Abstract Traumatic brain injury (TBI) affects many infants and children, and results in enduring motor and cognitive impairments with accompanying changes in white matter tracts, yet few experimental studies in rodent juvenile models of TBI (jTBI) have examined the timeline and nature of these deficits, histologically and functionally. We used a single controlled cortical impact (CCI) injury to the parietal cortex of rats at post-natal day (P) 17 to evaluate behavioral alterations, injury volume, and morphological and molecular changes in gray and white matter, with accompanying measures of electrophysiological function. At 60 days post-injury (dpi), we found that jTBI animals displayed behavioral deficits in foot-fault and rotarod tests, along with a left turn bias throughout their early developmental stages and into adulthood. In addition, anxiety-like behaviors on the zero maze emerged in jTBI animals at 60 dpi. The final lesion constituted only ∼3% of brain volume, and morphological tissue changes were evaluated using MRI, as well as immunohistochemistry for neuronal nuclei (NeuN), myelin basic protein (MBP), neurofilament-200 (NF200), and oligodendrocytes (CNPase). White matter morphological changes were associated with a global increase in MBP immunostaining and reduced compound action potential amplitudes at 60 dpi. These results suggest that brain injury early in life can induce long-term white matter dysfunction, occurring in parallel with the delayed development and persistence of behavioral deficits, thus modeling clinical and longitudinal TBI observations. PMID:22697253

  13. Traumatic brain injury in young rats leads to progressive behavioral deficits coincident with altered tissue properties in adulthood.

    PubMed

    Ajao, David O; Pop, Viorela; Kamper, Joel E; Adami, Arash; Rudobeck, Emil; Huang, Lei; Vlkolinsky, Roman; Hartman, Richard E; Ashwal, Stephen; Obenaus, André; Badaut, Jérôme

    2012-07-20

    Traumatic brain injury (TBI) affects many infants and children, and results in enduring motor and cognitive impairments with accompanying changes in white matter tracts, yet few experimental studies in rodent juvenile models of TBI (jTBI) have examined the timeline and nature of these deficits, histologically and functionally. We used a single controlled cortical impact (CCI) injury to the parietal cortex of rats at post-natal day (P) 17 to evaluate behavioral alterations, injury volume, and morphological and molecular changes in gray and white matter, with accompanying measures of electrophysiological function. At 60 days post-injury (dpi), we found that jTBI animals displayed behavioral deficits in foot-fault and rotarod tests, along with a left turn bias throughout their early developmental stages and into adulthood. In addition, anxiety-like behaviors on the zero maze emerged in jTBI animals at 60 dpi. The final lesion constituted only ∼3% of brain volume, and morphological tissue changes were evaluated using MRI, as well as immunohistochemistry for neuronal nuclei (NeuN), myelin basic protein (MBP), neurofilament-200 (NF200), and oligodendrocytes (CNPase). White matter morphological changes were associated with a global increase in MBP immunostaining and reduced compound action potential amplitudes at 60 dpi. These results suggest that brain injury early in life can induce long-term white matter dysfunction, occurring in parallel with the delayed development and persistence of behavioral deficits, thus modeling clinical and longitudinal TBI observations. PMID:22697253

  14. Validating the Children's Behavior Questionnaire in Dutch Children: Psychometric Properties and a Cross-Cultural Comparison of Factor Structures

    ERIC Educational Resources Information Center

    Sleddens, Ester F. C.; Kremers, Stef P. J.; Candel, Math J. J. M.; De Vries, Nanne N. K.; Thijs, Carel

    2011-01-01

    In this article, we examined the factorial validity of the Dutch translation of the Children's Behavior Questionnaire (CBQ) and the Very Short Form scores. In addition, we conducted cross-cultural comparisons of temperament structure. In total, 353 parents of 6- to 8-year-olds completed the instrument. The original higher order factor structure of…

  15. The Children’s Behavior Questionnaire very short scale: Psychometric properties and development of a one-item temperament scale

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Little research has been conducted on the psychometrics of the very short scale (36 items) of the Children’s Behavior Questionnaire, and no one-item temperament scale has been tested for use in applied work. In this study, 237 United States caregivers completed a survey to define their child’s behav...

  16. Mechanical Properties and Fracture Behaviors of the As-Extruded Mg-5Al-3Ca Alloys Containing Yttrium at Elevated Temperature.

    PubMed

    Son, Hyeon-Taek; Kim, Yong-Ho; Kim, Taek-Soo; Lee, Seong-Hee

    2016-02-01

    Effects of yttrium (Y) addition on mechanical properties and fracture behaviors of the as-extruded Mg-Al-Ca based alloys at elevated temperature were investigated by a tensile test. After hot extrusion, the average grain size was refined by Y addition and eutectic phases were broken down into fine particles. Y addition to Mg-5Al-3Ca based alloy resulted in the improvement of strength and ductility at elevated temperature due to fine grain and suppression of grain growth by formation of thermally stable Al2Y intermetallic compound. PMID:27433675

  17. Decomposition of 1,2-dichloroethane over CeO2 modified USY zeolite catalysts: effect of acidity and redox property on the catalytic behavior.

    PubMed

    Huang, Qinqin; Xue, Xiaomin; Zhou, Renxian

    2010-11-15

    CeO(2) modified ultrastable Y zeolite (CeO(2)-USY) catalysts were prepared and were used as the catalysts for the decomposition of 1,2-dichloroethane (DCE). The catalytic behavior of these catalysts was evaluated by micro-reaction and temperature-programmed surface reaction (TPSR) technique. The results reveal that CeO(2)-USY catalysts exhibit good catalytic activity for DCE decomposition and high selectivity to the formation of CO(2) and HCl. Both acidity and redox property play important roles in the DCE decomposition, and the synergy between CeO(2) species and USY zeolite shows an enhancement in the catalytic activity for DCE decomposition. CeO(2)-USY (1:8) with high dispersion of CeO(2) species and a much more suitable combination of acidity and redox property exhibits the best catalytic activity. PMID:20709452

  18. Investigation into the phenomena affecting the retention behavior of basic analytes in chaotropic chromatography: Joint effects of the most relevant chromatographic factors and analytes' molecular properties.

    PubMed

    Čolović, Jelena; Kalinić, Marko; Vemić, Ana; Erić, Slavica; Malenović, Anđelija

    2015-12-18

    The aim of this study was to systematically investigate the phenomena affecting the retention behavior of structurally diverse basic drugs in ion-interaction chromatographic systems with chaotropic additives. To this end, the influence of three factors was studied: pH value of the aqueous phase, concentration of sodium hexafluorophosphate, and content of acetonitrile in the mobile phase. Mobile phase pH was found to affect the thermodynamic equilibria in the studied system beyond its effects on the analytes' ionization state. Specifically, increasing pH from 2 to 4 led to longer retention times, even with analytes which remain completely protonated. An explanation for this phenomenon was sought by studying the adsorption behavior of acetonitrile and chaotropic additive onto stationary phase. It was shown that the magnitude of the developed surface potential, which significantly affects retention - increases with pH, and that this can be attributed to the larger surface excess of acetonitrile. To study how analytes' structural properties influence their retention, quantitative structure-retention modeling was performed next. A support vector machine regression model was developed, relating mobile phase constituents and structural descriptors with retention data. While the ETA_EtaP_B_RC and XlogP can be considered as molecular descriptors which describe factors affecting retention in any RP-HPLC system, TDB9p and RDF45p are molecular descriptors which account for spatial arrangement of polarizable atoms and they can clearly relate to analytes' behavior on the stationary phase surface, where the electrostatic potential develops. Complementarity of analytes' structure with that of the electric double layer can be seen as a key factor influencing their retention behavior. Structural diversity of analytes and good predictive capabilities over a range of experimental conditions make the established model a useful tool in predicting retention behavior in the studied

  19. Swallow-tailed alkyl and linear alkoxy-substituted dibenzocoronene tetracarboxdiimide derivatives: synthesis, photophysical properties, and thermotropic behaviors.

    PubMed

    Yang, Tengzhou; Pu, Jialing; Zhang, Jun; Wang, Wenguang

    2013-05-17

    A series of dibenzocoronene tetracarboxdiimide derivatives decorated with alkyl swallow-tail and alkoxy moieties were synthesized, and their structures were characterized. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an effective oxidant was first used in the benzannulation of perylene diimides with the almost quantitative yield. The thermotropic behavior was investigated using differential scanning calorimetry (DSC) and polarization optical microscopy (POM). The introduction of alkyl swallow-tail and alkoxy substituents facilitates thermotropic liquid crystalline behavior. The branching site of alkyl swallow-tail units at the α position and the longer alkoxy chains played a similar role in lowering the mesophase transition as well as isotropization transition temperatures. The UV-vis absorption spectra of all compounds appeared as absorption in 425-600 nm region, and POM images of certain compounds exhibited characteristic columnar hexagonal (Col(h)) packing and readily self-assembled into a homeotropic alignment toward the substrate. PMID:23600443

  20. Studies on tensile properties and fracture behavior of Al-6Si-0.5Mg (-Cu or/and Ni) alloys at various strain rates

    NASA Astrophysics Data System (ADS)

    Hossain, A.; Gulshan, F.; Kurny, A. S. W.

    2016-07-01

    The aim of this paper is to evaluate the effects of various strain rates on the tensile properties of Al-6Si-0.5Mg cast alloys with Cu or/and Ni additions and to establish data on the stress-strain behavior of the alloys with applications in automotive engineering. Experimental alloys of the following composition were prepared by melt processing technique. Both microstructure and the mechanical properties were investigated. The uniaxial tension test was carried out at strain rates ranging from 10-4s-1 to 10-2s-1. Tensile strengths were found to increase with ageing temperature and the maximum being attained at peak age condition (1hr at 225°C). The additions of Cu or/and Ni resulted in an increase in tensile strength and 2wt% Cu content alloy (Al-6Si-0.5Mg-2Cu) showed maximum strength. Evaluation of tensile properties at three strain rates (10-4, 10-3 and 10-2s-1) showed that strain rates affected the tensile properties significantly. At higher strain rates the strength was better but ductility was poor.

  1. Mechanical properties and drug release behavior of PCL/zein coated 45S5 bioactive glass scaffolds for bone tissue engineering application

    PubMed Central

    Fereshteh, Zeinab; Nooeaid, Patcharakamon; Fathi, Mohammadhossein; Bagri, Akbar; Boccaccini, Aldo R.

    2015-01-01

    This article presents data related to the research article entitled “The effect of coating type on mechanical properties and controlled drug release of PCL/zein coated 45S5 bioactive glass scaffolds for bone tissue engineering” [1]. We provide data on mechanical properties, in vitro bioactivity and drug release of bioactive glass (BG) scaffolds coated by poly (ε-caprolactone) (PCL) and zein used as a controlled release device for tetracycline hydrochloride (TCH). By coating the BG scaffolds with PCL or PCL/zein blend the mechanical properties of the scaffolds were substantially improved, i.e., the compressive strength increased from 0.004±0.001 MPa (uncoated BG scaffolds) to 0.15±0.02 MPa (PCL/zein coated BG scaffolds). A dense bone-like apatite layer formed on the surface of PCL/zein coated scaffolds immersed for 14 days in simulated body fluid (SBF). The data describe control of drug release and in vitro degradation behavior of coating by engineering the concentration of zein. Thus, the developed scaffolds exhibit attractive properties for application in bone tissue engineering research. PMID:26966716

  2. Aggregation behavior of sodium lauryl ether sulfate with a positively bicharged organic salt and effects of the mixture on fluorescent properties of conjugated polyelectrolytes.

    PubMed

    Tang, Yongqiang; Liu, Zhang; Zhu, Linyi; Han, Yuchun; Wang, Yilin

    2015-02-24

    The aggregation behavior of anionic single-chain surfactant sodium lauryl ether sulfate containing three ether groups (SLE3S) with positively bicharged organic salt 1,2-bis(2-benzylammoniumethoxy)ethane dichloride (BEO) has been investigated in aqueous solution, and the effects of the BEO/SLE3S aggregate transitions on the fluorescent properties of anionic conjugated polyelectrolyte MPS-PPV with a larger molecular weight and cationic conjugated oligoelectrolyte DAB have been evaluated. Without BEO, SLE3S does not affect the fluorescent properties of MPS-PPV and only affects the fluorescent properties of DAB at a higher SLE3S concentration. With the addition of BEO, SLE3S and BEO form gemini-like surfactant (SLE3S)2-BEO. When the BEO/SLE3S molar ratio is fixed at 0.25, with increasing the BEO/SLE3S concentration, the BEO/SLE3S mixture forms large, loosely arranged aggregates and then transforms to closely packed spherical aggregates and finally to long thread-like micelles. The photoluminescence (PL) intensity of MPS-PPV varies with the morphologies of the BEO/SLE3S aggregates, while the PL intensity of DAB is almost independent of the aggregate morphologies. The results demonstrate that gemini-like surfactants formed through intermolecular interactions can effectively adjust the fluorescent properties of conjugated polyelectrolytes. PMID:25641198

  3. Behavioral and molecular neuroepigenetic alterations in prenatally stressed mice: relevance for the study of chromatin remodeling properties of antipsychotic drugs.

    PubMed

    Dong, E; Tueting, P; Matrisciano, F; Grayson, D R; Guidotti, A

    2016-01-01

    We have recently reported that mice born from dams stressed during pregnancy (PRS mice), in adulthood, have behavioral deficits reminiscent of behaviors observed in schizophrenia (SZ) and bipolar (BP) disorder patients. Furthermore, we have shown that the frontal cortex (FC) and hippocampus of adult PRS mice, like that of postmortem chronic SZ patients, are characterized by increases in DNA-methyltransferase 1 (DNMT1), ten-eleven methylcytosine dioxygenase 1 (TET1) and exhibit an enrichment of 5-methylcytosine (5MC) and 5-hydroxymethylcytosine (5HMC) at neocortical GABAergic and glutamatergic gene promoters. Here, we show that the behavioral deficits and the increased 5MC and 5HMC at glutamic acid decarboxylase 67 (Gad1), reelin (Reln) and brain-derived neurotrophic factor (Bdnf) promoters and the reduced expression of the messenger RNAs (mRNAs) and proteins corresponding to these genes in FC of adult PRS mice is reversed by treatment with clozapine (5 mg kg(-1) twice a day for 5 days) but not by haloperidol (1 mg kg(-1) twice a day for 5 days). Interestingly, clozapine had no effect on either the behavior, promoter methylation or the expression of these mRNAs and proteins when administered to offspring of nonstressed pregnant mice. Clozapine, but not haloperidol, reduced the elevated levels of DNMT1 and TET1, as well as the elevated levels of DNMT1 binding to Gad1, Reln and Bdnf promoters in PRS mice suggesting that clozapine, unlike haloperidol, may limit DNA methylation by interfering with DNA methylation dynamics. We conclude that the PRS mouse model may be useful preclinically in screening for the potential efficacy of antipsychotic drugs acting on altered epigenetic mechanisms. Furthermore, PRS mice may be invaluable for understanding the etiopathogenesis of SZ and BP disorder and for predicting treatment responses at early stages of the illness allowing for early detection and remedial intervention. PMID:26756904

  4. Magnetic order and heavy fermion behavior in CePd{sub 1+x}Al{sub 6-x}: Synthesis, structure, and physical properties

    SciTech Connect

    Tobash, Paul H.; Ronning, Filip; Thompson, J.D.; Bobev, Svilen; Bauer, Eric D.

    2010-03-15

    The physical properties including magnetic susceptibility, specific heat, and electrical resistivity of single crystals are reported for the compound CePd{sub 1+x}Al{sub 6-x} (x=0.5) which crystallizes in the tetragonal SrAu{sub 2}Ga{sub 5}-type structure (space group P4/mmm). The compound was grown from an excess of molten Al flux from the respective elements and the crystal structure was established from single-crystal X-ray diffraction. Anomalies in the low temperature specific heat C{sub p}(T) and electrical resistivity rho(T) show that the compound undergoes ferromagnetic order at T{sub C}=2.8 K. In the ordered state, CePd{sub 1.5}Al{sub 5.5} displays heavy fermion behavior with a Sommerfeld coefficient of ca. 500 mJ/mol-K{sup 2}. - Graphical abstract: The compound CePd{sub 1+x}Al{sub 6-x} (x=0.5) has been synthesized and structurally characterized by single-crystal X-ray diffraction. The measured physical properties of temperature and field dependent magnetic susceptibility, specific heat, and electrical resistivity suggests that the compound undergoes ferromagnetic order at ca. 2.8 K and further exhibits relatively heavy fermion behavior with a Sommerfeld coefficient of 500 mJ/mol-K2.

  5. Role of glass structure in defining the chemical dissolution behavior, bioactivity and antioxidant properties of zinc and strontium co-doped alkali-free phosphosilicate glasses.

    PubMed

    Kapoor, Saurabh; Goel, Ashutosh; Tilocca, Antonio; Dhuna, Vikram; Bhatia, Gaurav; Dhuna, Kshitija; Ferreira, José M F

    2014-07-01

    We investigated the structure-property relationships in a series of alkali-free phosphosilicate glass compositions co-doped with Zn(2+) and Sr(2+). The emphasis was laid on understanding the structural role of Sr(2+) and Zn(2+) co-doping on the chemical dissolution behavior of glasses and its impact on their in vitro bioactivity. The structure of glasses was studied using molecular dynamics simulations in combination with solid state nuclear magnetic resonance spectroscopy. The relevant structural properties are then linked to the observed degradation behavior, in vitro bioactivity, osteoblast proliferation and oxidative stress levels. The apatite-forming ability of glasses has been investigated by X-ray diffraction, infrared spectroscopy and scanning electron microscopy-energy-dispersive spectroscopy after immersion of glass powders/bulk in simulated body fluid (SBF) for time durations varying between 1h and 14 days, while their chemical degradation has been studied in Tris-HCl in accordance with ISO 10993-14. All the glasses exhibit hydroxyapatite formation on their surface within 1-3h of their immersion in SBF. The cellular responses were observed in vitro on bulk glass samples using human osteosarcoma MG63 cell line. The dose-dependent cytoprotective effect of glasses with respect to the concentration of zinc and strontium released from the glasses is also discussed. PMID:24709542

  6. Enhanced mechanical properties and in vitro corrosion behavior of amorphous and devitrified Ti40Zr10Cu38Pd12 metallic glass.

    PubMed

    Fornell, J; Van Steenberge, N; Varea, A; Rossinyol, E; Pellicer, E; Suriñach, S; Baró, M D; Sort, J

    2011-11-01

    The effects of annealing treatments on the microstructure, elastic/mechanical properties, wear resistance and corrosion behavior of rod-shaped Ti40Zr10Cu38Pd12 bulk glassy alloys, synthesized by copper mold casting, are investigated. Formation of ultrafine crystals embedded in an amorphous matrix is observed for intermediate annealing temperatures, whereas a fully crystalline microstructure develops after heating to sufficiently high temperatures. The glassy alloy exhibits large hardness, relatively low Young's modulus, good wear resistance and excellent corrosion behavior. Nanoindentation measurements reveal that the sample annealed in the supercooled liquid region exhibits a hardness value of 9.4 GPa, which is 20% larger than in the completely amorphous state and much larger than the hardness of commercial Ti-6Al-4V alloy. The Young's modulus of the as-cast alloy (around 100 GPa, as determined from acoustic measurements) increases only slightly during partial devitrification. Finally, the anticorrosion performance of the Ti40Zr10Cu38Pd12 alloy in Hank's solution has been shown to ameliorate as crystallization proceeds and is roughly as good as in the commercial Ti-6Al-4V alloy. The outstanding mechanical and corrosion properties of the Ti40Zr10Cu38Pd12 alloy, both in amorphous and crystalline states, are appealing for its use in biomedical applications. PMID:22098871

  7. Effect of blending and emulsification on thermal behavior, solid fat content, and microstructure properties of palm oil-based margarine fats.

    PubMed

    Saadi, S; Ariffin, A A; Ghazali, H M; Miskandar, M S; Abdulkarim, S M; Boo, H C

    2011-01-01

    The ability of palm oil (PO) to crystallize as beta prime polymorph has made it an attractive option for the production of margarine fat (MF). Palm stearin (PS) expresses similar crystallization behavior and is considered one of the best substitutes of hydrogenated oils due to its capability to impart the required level of plasticity and body to the finished product. Normally, PS is blended with PO to reduce the melting point at body temperature (37 °C). Lipid phase, formulated by PO and PS in different ratios were subjected to an emulsification process and the following analyses were done: triacylglycerols, solid fat content (SFC), and thermal behavior. In addition, the microstructure properties, including size and number of crystals, were determined for experimental MFs (EMFs) and commercial MFs (CMFs). Results showed that blending and emulsification at PS levels over 40 wt% significantly changed the physicochemical and microstructure properties of EMF as compared to CMF, resulting in a desirable dipalmitoyl-oleoyl-glycerol content of less than 36.1%. SFC at 37 °C, crystal size, crystal number, crystallization, and melting enthalpies (ΔH) were 15%, 5.37 μm, 1425 crystal/μm(2), 17.25 J/g, and 57.69J/g, respectively. All data reported indicate that the formation of granular crystals in MFs was dominated by high-melting triacylglycerol namely dipalmitoyl-oleoyl-glycerol, while the small dose of monoacylglycerol that is used as emulsifier slowed crystallization rate. Practical Application: Most of the past studies were focused on thermal behavior of edible oils and some blends of oils and fats. The crystallization of oils and fats are well documented but there is scarce information concerning some mechanism related to crystallization and emulsification. Therefore, this study will help to gather information on the behavior of emulsifier on crystallization regime; also the dominating TAG responsible for primary granular crystal formations, as well as to determine

  8. Drawing dependent structures, mechanical properties and cyclization behaviors of polyacrylonitrile and polyacrylonitrile/carbon nanotube composite fibers prepared by plasticized spinning.

    PubMed

    Li, Xiang; Qin, Aiwen; Zhao, Xinzhen; Liu, Dapeng; Wang, Haiye; He, Chunju

    2015-09-14

    Drawing to change the structural properties and cyclization behaviors of the polyacrylonitrile (PAN) chains in crystalline and amorphous regions is carried out on PAN and PAN/carbon nanotube (CNT) composite fibers. Various characterization methods including Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and thermal gravimetric analysis are used to monitor the structural evolution and cyclization behaviors of the fibers. With an increase of the draw ratio during the plasticized spinning process, the structural parameters of the fibers, i.e. crystallinity and planar zigzag conformation, are decreased at first, and then increased, which are associated with the heat exchange rate and the oriented-crystallization rate. A possible mechanism for plasticized spinning is proposed to explain the changing trends of crystallinity and planar zigzag conformation. PAN and PAN/CNT fibers exhibit various cyclization behaviors induced by drawing, e.g., the initiation temperature for the cyclization (Ti) of PAN fibers is increased with increasing draw ratio, while Ti of PAN/CNT fibers is decreased. Drawing also facilitates cyclization and lowers the percentage of β-amino nitrile for PAN/CNT fibers during the stabilization. PMID:26235219

  9. Effect of micro shot peening on the mechanical properties and corrosion behavior of two microstructure Ti-6Al-4V alloy

    NASA Astrophysics Data System (ADS)

    Ahmed, Aymen A.; Mhaede, Mansour; Wollmann, Manfred; Wagner, Lothar

    2016-02-01

    Titanium alloys continue to be used extensively for the fabrication of surgical implants due to their excellent mechanical, physical and biological performance. The surface modification is the main technique to maintain a relatively good mechanical properties and biocompatibility. In this study, a surface modification through micro shot peening (SP) using different ceramic shot (850, 450 and 125-250 μm) at 0.22 mmA have been done on two microstructures Ti-6Al-4V alloy. The effect of this treatment on the corrosion behavior, surface roughness, microhardness profiles, and residual stresses were investigated. In addition, the corrosion behavior of the ultra-fine grain of Ti-6Al-4V materials produced by rotary swaging (RS) deformation has been investigated and compared with the duplex (DU) and globular (GL) microstructures. The corrosion behavior was studied using potentiodynamic polarization and electro impedance spectroscopy techniques. The electrochemical tests were performed in Ringer's solution at 37 °C. The results show that shot peening resulted in near-surface maximum hardness and residual stresses values. Increasing the shot size led to a lower surface roughness and an improved corrosion resistance. However, SP reduces the corrosion resistance compared with the untreated materials. The globular microstructure shows high corrosion rate compared with the duplex and nanostructured materials.

  10. Effects of high-energy electro-pulsing treatment on microstructure, mechanical properties and corrosion behavior of Ti-6Al-4V alloy.

    PubMed

    Ye, Xiaoxin; Wang, Lingsheng; Tse, Zion T H; Tang, Guoyi; Song, Guolin

    2015-04-01

    The effect of electro-pulsing treatment (EPT) on the microstructure, mechanical properties and corrosion behavior of cold-rolled Ti-6Al-4V alloy strips was investigated in this paper. It was found that the elongation to failure of materials obtains a noticeable enhancement with increased EPT processing time while slightly sacrificing strength. Fine recrystallized grains and the relative highest elongation to failure (32.5%) appear in the 11second-EPT samples. Grain coarsening and decreased ductility were brought in with longer EPT duration time. Fracture surface analysis shows that transition from intergranular brittle facture to transgranular dimple fracture takes place with an increase in processing time of EPT. Meanwhile, corrosion behavior of titanium alloys is greatly improved with increased EPT processing time, which is presented by polarization test and surface observation with the beneficial effect of forming a protective anatase-TiO2 film on the surface of alloys. The rapid recrystallization behavior and oxide formation of the titanium alloy strip under EPTs are attributed to the enhancement of nucleation rate, atomic diffusion and oxygen migration resulting from the coupling of the thermal and athermal effects. PMID:25687017

  11. Influence of the sputtering flow regime on the structural properties and magnetic behavior of Fe-Ga thin films (Ga ˜ 30 at.%)

    NASA Astrophysics Data System (ADS)

    Muñoz-Noval, A.; Ordóñez-Fontes, A.; Ranchal, R.

    2016-06-01

    In this paper we analyze the structure of Fe-Ga layers with a Ga content of ˜30 at.% deposited by the sputtering technique under two different regimes. We also studied the correlation between the structure and magnetic behavior of the samples. Keeping the Ar pressure fixed, we modified the flow regime from ballistic to diffusive by increasing the distance between the target and the substrate. X-ray diffraction measurements have shown a lower structural quality when growing in the diffusive flow. We investigated the impact of the growth regime by means of x-ray absorption fine structure (XAFS) measurements and obtained signs of its influence on the local atomic order. Full multiple scattering and finite difference calculations based on XAFS measurements point to a more relevant presence of a disordered A 2 phase and of orthorhombic Ga clusters on the Fe-Ga alloy deposited under a diffusive regime; however, in the ballistic sample, a higher presence of D 03/B 2 phases is evidenced. Structural characteristics, from local to long range, seem to determine the magnetic behavior of the layers. Whereas a clear in-plane magnetic anisotropy is observed in the film deposited under ballistic flow, the diffusive sample is magnetically isotropic. Therefore, our experimental results provide evidence of a correlation between flow regime and structural properties and its impact on the magnetic behavior of a rather unexplored compositional region of Fe-Ga compounds.

  12. Mechanical properties and in vivo behavior of a biodegradable synthetic polymer microfiber - extracellular matrix hydrogel biohybrid scaffold

    PubMed Central

    Hong, Yi; Huber, Alexander; Takanari, Keisuke; Amoroso, Nicholas J.; Hashizume, Ryotaro; Badylak, Stephen F.; Wagner, William R.

    2011-01-01

    A biohybrid composite consisting of extracellular matrix (ECM) gel from porcine dermal tissue and biodegradable elastomeric fibers was generated and evaluated for soft tissue applications. ECM gel possesses attractive biocompatibility and bioactivity with weak mechanical properties and rapid degradation, while electrospun biodegradable poly(ester urethane)urea (PEUU) has good mechanical properties but limited cellular infiltration and tissue integration. A concurrent gel electrospray/polymer electrospinning method was employed to create ECM gel/PEUU fiber composites with attractive mechanical properties, including high flexibility and strength. Electron microscopy revealed a structure of interconnected fibrous layers embedded in ECM gel. Tensile mechanical properties could be tuned by altering the PEUU/ECM weight ratio. Scaffold tensile strengths for PEUU/ECM ratios of 67/33, 72/28 and 80/20 ranged from 80–187 kPa in the longitudinal axis (parallel to the collecting mandrel axis) and 41–91 kPa in the circumferential axis with 645–938% breaking strains. The 72/28 biohybrid composite and a control scaffold generated from electrospun PEUU alone were implanted into Lewis rats, replacing a full-thickness abdominal wall defect. At 4 wk, no infection or herniation was found at the implant site. Histological staining showed extensive cellular infiltration into the biohybrid scaffold with the newly developed tissue well integrated with the native periphery, while minimal cellular ingress into the electrospun PEUU scaffold was observed. Mechanical testing of explanted constructs showed evidence of substantial remodeling, with composite scaffolds adopting properties more comparable to the native abdominal wall. The described elastic biohybrid material imparts features of ECM gel bioactivity with PEUU strength and handling to provide a promising composite biomaterial for soft tissue repair and replacement. PMID:21303718

  13. Validity and psychometric properties of the measure of psychologically abusive behaviors among young women and women in distressed relationships.

    PubMed

    Follingstad, Diane R; Coker, Ann L; Lee, Eunkyung; Williams, Corrine M; Bush, Heather M; Mendiondo, Marta M

    2015-07-01

    The Measure of Psychologically Abusive Behaviors (MPAB) was developed recently to improve on prior scales. Two nationally solicited samples of women were utilized to further validate the MPAB through the use of a criterion group, factor analysis, and designation of a threshold for accurate classification. MPAB scores were twice as high in the criterion group (M = 38.75 vs. M = 18.85; F = 22.17). Using a cutpoint of 1, the sensitivity and specificity for MPAB were .725 and .628, respectively. Cronbach's alpha was .97 for both samples. These data provide additional evidence for the MPAB as valid and internally consistent. PMID:25926051

  14. Phase behavior and physicochemical properties of sodium octyl sulfate/n-decane/1-hexanol/aqueous AlCl[sub 3] middle-phase microemulsion

    SciTech Connect

    Abe, Masahiko; Yamazaki, Tadao; Ogino, Keizo )

    1992-03-01

    The phase behavior and physicochemical properties of sodium octyl sulfate/n-decane/1-hexanol/aqueous AlCl[sub 3] middle-phase microemulsion have been studied as a function of salinity to develop an experimental investigation for better understanding of the microstructure of a middle-phase microemulsion. The system exhibits a Winsor-type phase transition (Winsor I [leftrightarrow] Winsor III [leftrightarrow] Winsor II) with increasing salinity. Over an appreciable salinity (from 0.50% to 9.2%), the formation of Winsor III, composed of a middle-phase microemulsion in equilibrium with the excess water and oil phases, was observed. It has been observed that as the salinity is increased, the phase volume of the middle-phase microemulsion undergoes a drastic decrease at a specific brine concentration (3.8%). Furthermore, the physicochemical properties such as water content, electrical conductivity, diffusion coefficient, and solubilization of 1-hexanol in the AlCl[sub 3] middle-phase microemulsion all show abrupt changes at this salinity. The drastic change in the phase volume and physicochemical properties at the specific salinity of 3.8% may be attributed to a phase inversion of the AlCl[sub 3] middle-phase microemulsion from oil-rich to water-rich continuous phase with increasing AlCl[sub 3] concentration, which is quite a different behavior from that observed for monovalent and divalent salt systems. Specifically, it may be assumed that a fluctuating structure of bicontinuous type and a liquid crystal structure overcome the droplet structure in the phase equilibrium at a certain salinity during the increase in the trivalent salt concentration. 25 refs., 10 figs.

  15. Effect of counterion on the mesomorphic behavior and optical properties of columnar pyridinium ionic liquid crystals derived from 4-hydroxypyridine

    NASA Astrophysics Data System (ADS)

    Pană, Amalia; Badea, Florentina L.; Iliş, Monica; Staicu, Teodora; Micutz, Marin; Pasuk, Iuliana; Cîrcu, Viorel

    2015-03-01

    A series of 3,4,5-tridodecyloxybenzyl pyridinium salts derived from 4-hydroxypyridine has been designed and prepared. The liquid crystalline properties of these compounds were investigated by polarized optical microscopy, differential scanning calorimetry and powder X-ray diffraction while their thermal stability was studied by thermogravimetric analysis. The N-3,4,5-tridodecyloxybenzyl-4-pyridone intermediate shows a monotropic columnar hexagonal mesophase ranging from 56 °C down to room temperature while the corresponding bromide dodecyl O-alkylated pyridinium salt shows one enantiotropic columnar mesophase and one additional monotropic columnar phase at lower temperatures. Replacing bromide ion (Br-) with other counterions (NO3-, BF4- and PF6-) resulted in mesophase suppression. These luminescent pyridinium salts show weak emission in dichloromethane solutions at room temperature and a pronounced red-shifted emission in solid state. Photoluminescent properties of the pyridinium salts do not depend significantly on the nature of counterion employed.

  16. A study of the kinetics of swelling in cylindrical polystyrene gels: Mechanical behavior and final properties after swelling

    NASA Astrophysics Data System (ADS)

    Hakiki, Abdelkrim; Herz, Jean E.

    1994-11-01

    Mechanical properties of cylindrical polystyrene gels were investigated both by the kinetics of swelling and uniaxial elastic modulus. These gels were prepared by specific chemical reactions using well-defined difunctional and precursor polymers. From the data of the kinetics of swelling we determined the cooperative diffusion coefficient of the gel and the related mesh size. Experimental results were found to be consistent with the theory of Tanaka et al. Elastic moduli were interpreted on the basis of the phantom and affine models.

  17. Studies on the steady shear flow behavior and chemical properties of water-soluble polysaccharide from Ziziphus lotus fruit.

    PubMed

    Adeli, Mostafa; Samavati, Vahid

    2015-01-01

    The extraction of water-soluble polysaccharide from Ziziphus lotus fruit (WPZL) was performed by ultrasonic-assisted extraction method. A Box-Behnken design (BBD) was applied to evaluate the effects of three independent variables (ultrasonic power (X1: 70-100 W), extraction time (X2: 10-30 min), extraction temperature (X3: 55-95 °C), and water to raw material ratio (X4: 5-25)) on the extraction yield of APH. The effect of temperature and concentration on flow behavior of gum solution was studied. WPZL solutions exhibited shear-thinning non-Newtonian flow behavior for concentrations above 0.5% (w/v). The viscosity of fully hydrated gum solutions decreased as temperature increase. The correlation analysis of the mathematical-regression model indicated that quadratic polynomial model could be employed to optimize the extraction of WPZL. The optimal conditions to obtain the highest extraction of WPZL (13.398 ± 0.019%) were as follows: ultrasonic power, 88.77 W; extraction time, 29.96 min, extraction temperature, 77.73 °C and water to raw material ratio 24.44 mL/g. PMID:25195543

  18. An assessment of selected properties of the fluorescent tracer, Tinopal CBS-X related to conservative behavior, and suggested improvements

    NASA Astrophysics Data System (ADS)

    Licha, Tobias; Niedbala, Anne; Bozau, Elke; Geyer, Tobias

    2013-03-01

    SummaryA conservative or well known reactive behavior of water tracers is a prerequisite in the quantitative evaluation of their tracer breakthrough curves. The fluorescent dye, Tinopal CBS-X, is one of the few licensed fluorescent dyes for water tracing with safe use. Its main advantage is its blue fluorescence, which is barely visible to the human eye and thus can be used when coloring water must be avoided. However, scientists have described the recovery of this dye as poor to very poor in field tracer experiments. Hence, this study focuses on examining the interaction of the main water chemistry with Tinopal CBS-X by determining the solubility products of the dye with most common cations. The findings of this investigation reveal that the tracer forms precipitates of very low aqueous solubility with di- and trivalent cations (pKsp 6.4-16.8). As a consequence, Tinopal CBS-X is not a conservative tracer and respective tracer breakthrough curves will exhibit strong tailings at least in part, as result of precipitations formed. The addition of a chemical modifier, EDTA, is suggested to enhance the solubility of Tinopal CBS-X in order to overcome its non-conservative behavior. Equations for estimating the amount of EDTA necessary are provided. In the light of these results, earlier reported tracer breakthrough curves are revisited and re-interpreted.

  19. Supramolecular structure, phase behavior and thermo-rheological properties of a poly (L-lactide-co-ε-caprolactone) statistical copolymer.

    PubMed

    Ugartemendia, Jone M; Muñoz, M E; Santamaria, A; Sarasua, J R

    2015-08-01

    PLAcoCL samples, both unaged, termed PLAcoCLu, and aged over time, PLAcoCLa, were prepared and analyzed to study the phase structure, morphology, and their evolution under non-quiescent conditions. X- ray diffraction, Differential Scanning Calorimetry and Atomic Force Microscopy were complemented with thermo-rheological measurements to reveal that PLAcoCL evolves over time from a single amorphous metastable state to a 3 phase system, made up of two compositionally different amorphous phases and a crystalline phase. The supramolecular arrangements developed during aging lead to a rheological complex behavior in the PLAcoCLa copolymer: Around Tt=131 °C thermo-rheological complexity and a peculiar chain mobility reduction were observed, but at T>Tt the thermo-rheological response of a homogeneous system was recorded. In comparison with the latter, the PLLA/PCL 70:30 physical blend counterpart showed double amorphous phase behavior at all temperatures, supporting the hypothesis that phase separation in the PLAcoCLa copolymer is caused by the crystallization of polylactide segment blocks during aging. PMID:25933171

  20. Modeling the Peano fluidic muscle and the effects of its material properties on its static and dynamic behavior

    NASA Astrophysics Data System (ADS)

    Veale, Allan Joshua; Xie, Sheng Quan; Anderson, Iain Alexander

    2016-06-01

    The promise of wearable assistive robotics cannot be realized without the development of actuators that mimic the behavior and form of biological muscles. Planar fluidic muscles known as Peano muscles or pouch motors have the potential to provide the high force and compliance of McKibben pneumatic artificial muscles with the low threshold pressure of pleated pneumatic artificial muscles. Yet they do so in a soft and slim form that can be discreetly distributed over the human body. This work is an investigation into the empirical modeling of the Peano muscle, the effect of its material on its performance, and its capabilities and limitations. We discovered that the Peano muscle could provide responsive and discreet actuation of soft and rigid bodies requiring strains between 15% and 30%. Ideally, they are made of non-viscoelastic materials with high tensile and low bending stiffnesses. While Sarosi et al’s empirical model accurately captures its static behavior with an root mean square error of 10.2 N, their dynamic model overestimates oscillation frequency and damping. We propose that the Peano muscle be modeled by a parallel ideal contractile unit and viscoelastic element, both in series with another viscoelastic element.

  1. Electron beam irradiated polyamide-6,6 films—II: mechanical and dynamic mechanical properties and water absorption behavior

    NASA Astrophysics Data System (ADS)

    Sengupta, Rajatendu; Tikku, V. K.; Somani, Alok K.; Chaki, Tapan K.; Bhowmick, Anil K.

    2005-04-01

    Electron beam irradiation of poly(iminohexamethylene-iminoadipoyl) (Polyamide-6,6) films was carried out over a range of irradiation doses (20-500 kGy) in air. The mechanical properties were studied and the optimum radiation dose was 200 kGy, where the ultimate tensile stress (UTS), 10% modulus, elongation at break (EB) and toughness showed significant improvement over the unirradiated film. At a dose of 200 kGy, the UTS was improved by 19%, the 10% modulus by ˜9% and the EB by ˜200% over the control. The dynamic mechanical properties of the films were studied in the temperature region 303-473 K to observe the changes in the glass transition temperature ( Tg) and loss tangent (tan δ) with radiation dose. The storage modulus of the film receiving a radiation dose of 200 kGy was higher than the unirradiated film. The water uptake characteristics of the Polyamide-6,6 films were investigated. The water uptake was less for the films that received a radiation dose of 200 and 500 kGy than the unirradiated film. The role of crystallinity, crosslinking and chain scission in affecting the tensile, dynamic mechanical and water absorption properties was discussed.

  2. Behavior of PAH/mineral associations during thermodesorption: impact for the determination of mineral retention properties towards PAHs.

    PubMed

    Biache, Coralie; Lorgeoux, Catherine; Saada, Alain; Faure, Pierre

    2015-05-01

    Polycyclic aromatic hydrocarbons (PAHs) associated with two minerals (silica sand and bentonite) presenting opposite retention properties were analyzed with a thermodesorption (Td)-GC-MS coupling in order to validate this technique as a new and rapid way to evaluate the solid sorption properties. Two analysis modes were used, evolved gas analysis (EGA) and Td with cryo-trap. EGA allowed a real-time monitoring of the compounds desorbed during a temperature program and gave a first screening of the samples while Td gave more precise indications on compound abundances for selected temperature ranges. When associated with silica sand, PAHs were released at relatively low temperatures (<300 °C) close to corresponding boiling point, whereas for the PAH/bentonite mixture, PAHs were desorbed at much higher temperatures; they were also present in much lower abundance and were associated with mono-aromatic compounds. With bentonite, the PAH abundances decreased and the mono-aromatics increased with the increasing PAH molecular weight. These results indicated a clear PAH retention by the bentonite due to polymerization, followed by a thermal cracking at higher temperatures. The Td-GC-MS was proven to efficiently underline differences in retention properties of two minerals, and this study highlights the great potential of this technique to evaluate compound/matrix bond strength and interaction. PMID:25772555

  3. Investigation on the microstructure, mechanical property and corrosion behavior of the selective laser melted CoCrW alloy for dental application.

    PubMed

    Lu, Yanjin; Wu, Songquan; Gan, Yiliang; Li, Junlei; Zhao, Chaoqian; Zhuo, Dongxian; Lin, Jinxin

    2015-04-01

    In this study, an experimental investigation on fabricating Ni-free CoCrW alloys by selective laser melting (SLM) for dental application was conducted in terms of microstructure, hardness, mechanical property, electrochemical behavior, and metal release; and line and island scanning strategy were applied to determine whether these strategies are able to obtain expected CoCrW parts. The XRD revealed that the γ-phase and ε-phase coexisted in the as-SLM CoCrW alloys; The OM and SEM images showed that the microstructure of CoCrW alloys appeared square-like pattern with the fine cellular dendrites at the borders; tensile test suggested that the difference of mechanical properties of line- and island-formed specimens was very small; whilst the outcomes from the electrochemical and metal release tests indicated that the island-formed alloys showed slightly better corrosion resistance than line-formed ones in PBS and Hanks solutions. Considering that the mechanical properties and corrosion resistance of line-formed and island-formed specimens meet the standards of ISO 22674:2006 and EN ISO 10271, CoCrW dental alloys can be successfully fabricated by line and island scanning strategies in the SLM process. PMID:25686979

  4. Effect of Cr on Microstructure, Mechanical Properties, and Wear Behavior of In Situ 20 wt.%Al2O3/Fe-25Al Composites

    NASA Astrophysics Data System (ADS)

    Bai, Yaping; Xing, Jiandong; Guo, Yongchun; Li, Jianping; He, Yuanyuan; Ma, Shengqiang

    2015-02-01

    In order to improve the room temperature ductility and high temperature strength of Fe-25Al alloys, in situ 20 wt.%Al2O3/Fe-25Al composites with 0, 1, 2, 3, 4, and 5 at.% Cr element contents (0-6.70 wt.%) were prepared by mechanical alloying inducing self-propagating reaction with subsequent plasma-activated sintering. Microstructures, room temperature hardness, flexural strength, fracture toughness, and compression property and wear behavior at mid-high temperatures of the sintered samples were tested and analyzed. The results showed that all the composites with Cr element addition had good microstructure with fine grain size and high relative density. The flexural strength and fracture toughness increased first and then decreased with increasing content of Cr. Especially, the composites with 3 at.% Cr had the highest flexural strength, highest fracture toughness, and best compressive properties during 298-1073 K, and the main fracture mechanism changed from brittle fracture at room temperature to plastic deformation and pullout of the second phase at 673 K. With Cr content increasing, the friction coefficients decreased and the wear rates increased because of decreasing hardness. The composites with 3 at.% Cr had excellent wear properties with lower friction coefficient and wear rate.

  5. Adsorption and corrosion inhibition properties of thiocarbanilide on the electrochemical behavior of high carbon steel in dilute acid solutions

    NASA Astrophysics Data System (ADS)

    Loto, Roland Tolulope; Loto, Cleophas Akintoye; Joseph, Olufunmilayo; Olanrewaju, Gabriel

    The inhibition performance of thiocarbanilide on the electrochemical corrosion behavior of high carbon steel in 1 M H2SO4 and HCl acid solutions was studied through weight loss method and potentiodynamic polarization test. Data obtained showed that the organic compound performed effectively in acid solutions at all concentrations with an average thiocarbanilide inhibition efficiency above 70% in H2SO4 acid and 80% in HCl acid from weight loss and potentiodynamic polarization test respectively. Results from corrosion thermodynamic calculations showed that the adsorption of thiocarbanilide onto the steel was through chemisorption mechanism whereby the redox electrochemical process responsible for corrosion and the electrolytic transport of corrosive anions were simultaneously suppressed. Statistical derivations through ANOVA analysis confirm that the influences of both the inhibitor concentration and exposure time on inhibition efficiency values are negligible. Adsorption of the compound was determined to obey the Langmuir and Frumkin isotherm model.

  6. Understanding the NMR properties and conformational behavior of indole vs. azaindole group in protoberberines: NICS and NCS analysis

    NASA Astrophysics Data System (ADS)

    Kadam, Shivaji S.; Toušek, Jaromír; Maier, Lukáš; Pipíška, Matej; Sklenář, Vladimír; Marek, Radek

    2012-11-01

    We report here the preparation and the structural investigation into a series of 8-(indol-1-yl)-7,8-dihydroprotoberberine derivatives derived from berberine, palmatine, and coptisine. Structures of these new compounds were characterized mainly by 2D NMR spectroscopy and the conformational behavior was investigated by using methods of density-functional theory (DFT). PBE0/6-311+G** calculated NMR chemical shifts for selected derivatives correlate excellently with the experimental NMR data and support the structural conclusions drawn from the NMR experiments. An interesting role of the nitrogen atom in position N7' of the indole moiety in 8-(7-azaindol-1-yl)-7,8-dihydroprotoberberines as compared to other 8-indolyl derivatives is investigated in detail. The experimentally observed trends in NMR chemical shifts are rationalized by DFT calculations and analysis based on the nucleus-independent chemical shifts (NICS) and natural localized molecular orbitals (NLMOs).

  7. Antipsychotic, antidepressant, and cognitive-impairment properties of antipsychotics: rat profile and implications for behavioral and psychological symptoms of dementia.

    PubMed

    Kołaczkowski, Marcin; Mierzejewski, Paweł; Bienkowski, Przemyslaw; Wesołowska, Anna; Newman-Tancredi, Adrian

    2014-06-01

    Many dementia patients exhibit behavioral and psychological symptoms (BPSD), including psychosis and depression. Although antipsychotics are frequently prescribed off-label, they can have marked side effects. In addition, comparative preclinical studies of their effects are surprisingly scarce, and strategies for discovery of novel pharmacotherapeutics are lacking. We therefore compared eight antipsychotics in rat behavioral tests of psychosis, antidepressant-like activity, and cognitive impairment as a basis for preclinical evaluation of new drug candidates. The methods used in this study include inhibition of MK-801-induced hyperactivity, forced swim test (FST), passive avoidance (PA), spontaneous locomotor activity, and catalepsy. The drugs exhibited antipsychotic-like activity in the MK-801 test but with diverse profiles in the other models. Risperidone impaired PA performance, but with some dose separation versus its actions in the MK-801 test. In contrast, clozapine, olanzapine, lurasidone, and asenapine showed little or no dose separation in these tests. Aripiprazole did not impair PA performance but was poorly active in the MK-801 test. Diverse effects were also observed in the FST: chlorpromazine was inactive and most other drugs reduced immobility over narrow dose ranges, whereas clozapine reduced immobility over a wider dose range, overlapping with antipsychotic activity. Although the propensity of second-generation antipsychotics to produce catalepsy was lower, they all elicited pronounced sedation. Consistent with clinical data, most currently available second-generation antipsychotics induced cognitive and motor side effects with little separation from therapeutic-like doses. This study provides a uniform in vivo comparative basis on which to evaluate future early-stage drug candidates intended for potential pharmacotherapy of BPSD. PMID:24599316

  8. Softness and non-spherical shape define the phase behavior and the structural properties of lysozyme in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Baumketner, A.; Melnyk, R.; Holovko, M. F.; Cai, W.; Costa, D.; Caccamo, C.

    2016-01-01

    In this study, Boltzmann inversion is applied in conjunction with molecular dynamics simulations to derive inter-molecular potential for protein lysozyme in aqueous solution directly from experimental static structure factor. The potential has a soft repulsion at short distances and an attraction well at intermediate distances that give rise to the liquid-liquid phase separation. Moreover, Gibbs ensemble Monte Carlo simulations demonstrate that a non-spherical description of lysozyme is better suited to correctly reproduce the experimentally observed properties of such a phase separation. Our findings shed new light on the common problem in molecular and cell biology: "How to model proteins in their natural aqueous environments?"

  9. Softness and non-spherical shape define the phase behavior and the structural properties of lysozyme in aqueous solutions.

    PubMed

    Baumketner, A; Melnyk, R; Holovko, M F; Cai, W; Costa, D; Caccamo, C

    2016-01-01

    In this study, Boltzmann inversion is applied in conjunction with molecular dynamics simulations to derive inter-molecular potential for protein lysozyme in aqueous solution directly from experimental static structure factor. The potential has a soft repulsion at short distances and an attraction well at intermediate distances that give rise to the liquid-liquid phase separation. Moreover, Gibbs ensemble Monte Carlo simulations demonstrate that a non-spherical description of lysozyme is better suited to correctly reproduce the experimentally observed properties of such a phase separation. Our findings shed new light on the common problem in molecular and cell biology: "How to model proteins in their natural aqueous environments?" PMID:26747821

  10. A Computational and Experimental Approach Linking Disorder, High-Pressure Behavior, and Mechanical Properties in UiO Frameworks.

    PubMed

    Hobday, Claire L; Marshall, Ross J; Murphie, Colin F; Sotelo, Jorge; Richards, Tom; Allan, David R; Düren, Tina; Coudert, François-Xavier; Forgan, Ross S; Morrison, Carole A; Moggach, Stephen A; Bennett, Thomas D

    2016-02-12

    Whilst many metal-organic frameworks possess the chemical stability needed to be used as functional materials, they often lack the physical strength required for industrial applications. Herein, we have investigated the mechanical properties of two UiO-topology Zr-MOFs, the planar UiO-67 ([Zr6O4(OH)4 (bpdc)6], bpdc: 4,4'-biphenyl dicarboxylate) and UiO-abdc ([Zr6O4(OH)4 (abdc)6], abdc: 4,4'-azobenzene dicarboxylate) by single-crystal nanoindentation, high-pressure X-ray diffraction, density functional theory calculations, and first-principles molecular dynamics. On increasing pressure, both UiO-67 and UiO-abdc were found to be incompressible when filled with methanol molecules within a diamond anvil cell. Stabilization in both cases is attributed to dynamical linker disorder. The diazo-linker of UiO-abdc possesses local site disorder, which, in conjunction with its longer nature, also decreases the capacity of the framework to compress and stabilizes it against direct compression, compared to UiO-67, characterized by a large elastic modulus. The use of non-linear linkers in the synthesis of UiO-MOFs therefore creates MOFs that have more rigid mechanical properties over a larger pressure range. PMID:26797762

  11. Design rules for rational control of polymer glass formation behavior and mechanical properties with small molecular additives

    NASA Astrophysics Data System (ADS)

    Mangalara, Jayachandra Hari; Simmons, David

    Small molecule additives have long been employed to tune polymers' glass formation, mechanical and transport properties. For example, plasticizers are commonly employed to suppress polymer Tg and soften the glassy state, while antiplasticizers, which stiffen the glassy state of a polymer while suppressing its Tg, are employed to enhance protein and tissue preservation in sugar glasses. Recent literature indicates that additives can have a wide range of possible effects, but all of these have not been clearly understood and well appreciated. Here we employ molecular dynamics simulations to establish design rules for the selection of small molecule additives with size, molecular stiffness, and interaction energy chosen to achieve targeted effects on polymer properties. We furthermore find that a given additive's effect on a polymer's Tg can be predicted from its Debye-Waller factor via a function previously found to describe nanoconfinement effects on the glass transition. These results emphasize the potential for a new generation of targeted molecular additives to contribute to more targeted rational design of polymers. We acknowledge the Keck Foundation and the Ohio Supercomputing Center for financial and computational support of this effort, respectively.

  12. Impact of Cross-Tie Properties on the Modal Behavior of Cable Networks on Cable-Stayed Bridges.

    PubMed

    Ahmad, Javaid; Cheng, Shaohong; Ghrib, Faouzi

    2015-01-01

    Dynamic behaviour of cable networks is highly dependent on the installation location, stiffness, and damping of cross-ties. Thus, these are the important design parameters for a cable network. While the effects of the former two on the network response have been investigated to some extent in the past, the impact of cross-tie damping has rarely been addressed. To comprehend our knowledge of mechanics associated with cable networks, in the current study, an analytical model of a cable network will be proposed by taking into account both cross-tie stiffness and damping. In addition, the damping property of main cables in the network will also be considered in the formulation. This would allow exploring not only the effectiveness of a cross-tie design on enhancing the in-plane stiffness of a constituted cable network, but also its energy dissipation capacity. The proposed analytical model will be applied to networks with different configurations. The influence of cross-tie stiffness and damping on the modal response of various types of networks will be investigated by using the corresponding undamped rigid cross-tie network as a reference base. Results will provide valuable information on the selection of cross-tie properties to achieve more effective cable vibration control. PMID:26167539

  13. Impact of Cross-Tie Properties on the Modal Behavior of Cable Networks on Cable-Stayed Bridges

    PubMed Central

    Ahmad, Javaid; Cheng, Shaohong; Ghrib, Faouzi

    2015-01-01

    Dynamic behaviour of cable networks is highly dependent on the installation location, stiffness, and damping of cross-ties. Thus, these are the important design parameters for a cable network. While the effects of the former two on the network response have been investigated to some extent in the past, the impact of cross-tie damping has rarely been addressed. To comprehend our knowledge of mechanics associated with cable networks, in the current study, an analytical model of a cable network will be proposed by taking into account both cross-tie stiffness and damping. In addition, the damping property of main cables in the network will also be considered in the formulation. This would allow exploring not only the effectiveness of a cross-tie design on enhancing the in-plane stiffness of a constituted cable network, but also its energy dissipation capacity. The proposed analytical model will be applied to networks with different configurations. The influence of cross-tie stiffness and damping on the modal response of various types of networks will be investigated by using the corresponding undamped rigid cross-tie network as a reference base. Results will provide valuable information on the selection of cross-tie properties to achieve more effective cable vibration control. PMID:26167539

  14. Effect of silver nanoparticles and cellulose nanocrystals on electrospun poly(lactic) acid mats: morphology, thermal properties and mechanical behavior.

    PubMed

    Cacciotti, Ilaria; Fortunati, Elena; Puglia, Debora; Kenny, Josè Maria; Nanni, Francesca

    2014-03-15

    The fabrication of ternary fibrous mats based on poly(lactic) acid (PLA), cellulose nanocrystals (CNCs, both pristine (p-CNCs) and modified with a commercial surfactant (s-CNCs)) and silver (Ag) nanoparticles by electrospinning is reported. Amounts of 1 and 5 wt.% were selected for Ag and CNCs, respectively. Neat PLA and binary PLA/Ag, PLA/p-CNCs and PLA/s-CNCs were produced as references. The CNCs and Ag influence on the microstructural, thermal and mechanical properties was investigated. The Ag and/or p-CNCs addition did not remarkably affect fiber morphology and average size dimension (between (468 ± 111) and (551 ± 122)nm), whereas the s-CNCs presence led to the deposition of a honeycomb-like network on a underneath layer of randomly oriented fibers. The efficiency of the surfactant use in promoting the CNC dispersion was demonstrated. A slight enhancement (e.g. around 25%, in terms of strength) of the mechanical properties of p-CNCs loaded fibers, particularly for PLA/Ag/p-CNCs, was revealed, whereas mats with s-CNCs showed a decrement (e.g. around 35-45%, in terms of strength), mainly imputable to the delamination between the upper honeycomb-like layer and the lower conventional fibrous mat. PMID:24528696

  15. Structural evolution, sintering behavior and microwave dielectric properties of (1−x)Li{sub 2}TiO{sub 3} + xLiF ceramics

    SciTech Connect

    Ding, Yaomin; Bian, Jianjiang

    2013-08-01

    Graphical abstract: - Highlights: • Structure, sinterability and dielectric properties of LiF-doped Li{sub 2}TiO{sub 3} were studied. • Li{sub 2}TiO{sub 3} can be densitied (TD 98%) at lower sintering temperature by LiF additions. • Excellent microwave dielectric properties could be obtained. - Abstract: Structural evolution, sintering behavior, and microwave dielectric properties of (1−x)Li{sub 2}TiO{sub 3} + xLiF (0.05 ≤ x ≤ 0.70) ceramics have been studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Raman spectra, thermal dilatometry and microwave resonant measurement at the frequency of about 7–11 GHz. The results show that Li{sub 2}TiO{sub 3} can form limited solid solution with LiF (x ≤ 0.4) and LiF second phase appeared when x{sup 3}0.5. The structure of the solid solution transformed from ordered monoclinic phase (β-Li{sub 2}TiO{sub 3} (ss)) to disordered cubic rock salt (α-Li{sub 2}TiO{sub 3} (ss)) when x{sup 3}0.15. The presence of short range ordering was confirmed for the cubic phase. The sinterability was considerably improved by doping with LiF. Densified ceramics with about 95–98% theoretical density could be obtained for the doped compositions after sintering at 900–1150 °C/2 h. An optimized microwave dielectric properties with ε{sub r} of ∼23.6, Q × f of ∼108,000 GHz and τ{sub f} of ∼4.2 ppm/°C could be obtained for the x = 0.1 composition after sintering at 1100 °C/2 h.

  16. Hygroscopicity Behavior, Activation Properties and Chemical Composition of Atmospheric Aerosol at a Background Site in the Megacity Region of Peking

    NASA Astrophysics Data System (ADS)

    Henning, Silvia; Nowak, Andreas; Mildenberger, Katrin; Göbel, Tina; Nekat, Bettina; van Pinxteren, Dominik; Herrmann, Hartmut; Zhao, Chunsheng; Wiedensohler, Alfred; Stratmann, Frank

    2010-05-01

    Large areas of China suffer from heavy air pollution (both gaseous and particulate) caused by strong economic growth in the last two decades. However, knowledge concerning the physical and chemical properties of the resulting aerosol particles populations, and their effects on the optical properties of the atmosphere, is still sparse. In the framework of the investigations presented here, comprehensive measurements concerning aerosol particle hygroscopicity, CCN ability, composition, and optical properties were performed. The investigations are part of the DFG-funded project HaChi (Haze in China) and are conducted in collaboration with the Peking University. A conclusive parameterization of aerosol hygroscopicity and activation data is aimed for, which will then be implemented in a meso-scale model to investigate aerosol-cloud-radiation and precipitation interactions. During two intensive measurements campaigns (March 2009 and July/ August 2009), in-situ aerosol measurements have been performed in an air-conditioned mobile laboratory next to the Wuqing Meteorological Station (39°23'8.53"N, 117°1'25.88"E), which is located between Bejing and Tijanjin and is thereby an ideal background site in a megacity region. The particle number size distribution (TDMPS), the particle optical properties (MAAP and nephelometer) and their hygroscopic properties at high RH (HH-TDMA, LACIS-mobile) were characterized as well as their cloud nucleating properties above supersaturation (DMT-CCNC). 24 h PM1 particle samples were continuously collected over the two campaigns in winter and summer using a DIGITEL high volume sampler (DHA-80). Additionally two 6h size-resolved samples (daytime and night-time) were collected each day applying an 11-stage Berner impactor. The size-selection of HH-TDMA, LACIS and the CCNC was synchronized with the Berner stages. Opening analysis of the winter campaign data showed that the HH-TDMA usually detected a hydrophobic and a hygroscopic mode, i.e., the

  17. Electrochemical properties and lithium ion solvation behavior of sulfone-ester mixed electrolytes for high-voltage rechargeable lithium cells

    NASA Astrophysics Data System (ADS)

    Watanabe, Yuu; Kinoshita, Shin-ichi; Wada, Satoshi; Hoshino, Keiji; Morimoto, Hideyuki; Tobishima, Shin-ichi

    2008-05-01

    Sulfone-ester mixed solvent electrolytes were examined for 5 V-class high-voltage rechargeable lithium cells. As the base-electrolyte, sulfolane (SL)-ethyl acetate (EA) (1:1 mixing volume ratio) containing 1 M LiBF4 solute was investigated. Electrolyte conductivity, electrochemical stability, Li+ ion solvation behavior and cycleability of lithium electrode were evaluated. 13C NMR measurement results suggest that Li+ ions are solvated with both SL and EA. Charge-discharge cycling efficiency of lithium anode in SL-EA electrolytes was poor, being due to its poor tolerance for reduction. To improve lithium charge-discharge cycling efficiency in SL-EA electrolytes, following three trials were carried out: (i) improvement of the cathodic stability of electrolyte solutions by change in polarization through modification of solvent structure; isopropyl methyl sulfone and methyl isobutyrate were investigated as alternative SL and EA, respectively, (ii) suppression of the reaction between lithium and electrolyte solutions by addition of low reactivity surfactants of cycloalkanes (decalin and adamantane) or triethylene glycol derivatives (triglyme, 1,8-bis(tert-butyldimethylsilyloxy)-3,6-dioxaoctane and triethylene glycol di(methanesulfonate)) into SL-EA electrolytes, and (iii) change in surface film by addition of surface film formation agent of vinylene carbonate (VC) into SL-EA electrolytes. These trials made lithium cycling behavior better. Lithium cycling efficiency tended to increase with a decrease in overpotential. VC addition was most effective for improvement of lithium cycling efficiency among these additives. Stable surface film is formed on lithium anode by adding VC and the resistance between anode/electrolyte interfaces showed a constant value with an increase in cycle number. When the electrolyte solutions without VC, the interfacial resistance increased with an increase in cycle number. VC addition to SL-EA was effective not only for Li/LiCoO2 cell with charge

  18. Coagulation behavior and floc properties of compound bioflocculant-polyaluminum chloride dual-coagulants and polymeric aluminum in low temperature surface water treatment.

    PubMed

    Huang, Xin; Sun, Shenglei; Gao, Baoyu; Yue, Qinyan; Wang, Yan; Li, Qian

    2015-04-01

    This study was intended to compare coagulation behavior and floc properties of two dual-coagulants polyaluminum chloride-compound bioflocculant (PAC-CBF) (PAC dose first) and compound bioflocculant-polyaluminum chloride (CBF-PAC) (CBF dose first) with those of PAC alone in low temperature drinking water treatment. Results showed that dual-coagulants could improve DOC removal efficiency from 30% up to 34%. Moreover, CBF contributed to the increase of floc size and growth rate, especially those of PAC-CBF were almost twice bigger than those of PAC. However, dual-coagulants formed looser and weaker flocs with lower breakage factors in which fractal dimension of PAC-CBF flocs was low which indicates a looser floc structure. The floc recovery ability was in the following order: PAC-CBF>PAC alone>CBF-PAC. The flocculation mechanism of PAC was charge neutralization and enmeshment, meanwhile the negatively charged CBF added absorption and bridging effect. PMID:25872730

  19. Development of the novel ferrous-based stainless steel for biomedical applications, part I: high-temperature microstructure, mechanical properties and damping behavior.

    PubMed

    Wu, Ching-Zong; Chen, Shih-Chung; Shih, Yung-Hsun; Hung, Jing-Ming; Lin, Chia-Cheng; Lin, Li-Hsiang; Ou, Keng-Liang

    2011-10-01

    This research investigated the high-temperature microstructure, mechanical properties, and damping behavior of Fe-9 Al-30 Mn-1C-5 Co (wt.%) alloy by means of electron microscopy, experimental model analysis, and hardness and tensile testing. Subsequent microstructural transformation occurred when the alloy under consideration was subjected to heat treatment in the temperature range of 1000-1150 °C: γ → (γ+κ). The κ-phase carbides had an ordered L'1(2)-type structure with lattice parameter a = 0.385 nm. The maximum yield strength (σ(y)), hardness, elongation, and damping coefficient of this alloy are 645 MPa, Hv 292, ~54%, and 178.5 × 10(-4), respectively. These features could be useful in further understanding the relationship between the biocompatibility and the wear and corrosion resistance of the alloy, so as to allow the development of a promising biomedical material. PMID:21783164

  20. Mechanical properties and tribological behavior of fullerene-like hydrogenated carbon films prepared by changing the flow rates of argon gas

    NASA Astrophysics Data System (ADS)

    Guo, Junmeng; Wang, Yongfu; Liang, Hongyu; Liang, Aimin; Zhang, Junyan

    2016-02-01

    Fullerene-like hydrogenated carbon (FL-C:H) films as carbon materials were prepared by direct current plasma enhanced chemical vapor deposition (dc-PECVD) technique. The content of FL nanostructure was confirmed by high-resolution transmission electron microscopy (HRTEM), visible Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The effect of fullerene-like nanostructure on the friction behavior of the films was studied using a reciprocating ball-on-flat tribometer in humid environment. It is concluded that the curved FL nanostructure provide the film excellent mechanical properties and friction performance. Interestingly, combining with the results of Raman analyses of the wear debris, we find that new FL nanostructure form during the friction process. These new FL nanostructure may originate from the rapid annealing and stress relaxation of unstable carbon clusters.

  1. Volcanic aerosol optical properties and phase partitioning behavior after long-range advection characterized by UV-Lidar measurements

    NASA Astrophysics Data System (ADS)

    Miffre, A.; David, G.; Thomas, B.; Rairoux, P.; Fjaeraa, A. M.; Kristiansen, N. I.; Stohl, A.

    2012-03-01

    In this paper, an UV-polarization Lidar is used to study the optical properties of volcanic aerosol in the troposphere. The particles were released by the mid-April 2010 eruption of the Eyjafjallajökull volcano (63.63°N, 19.62°W, Iceland) and passed in the troposphere above Lyon (45.76°N, 4.83°E, France) after advection over 2600 km. The FLEXPART particle dispersion model was applied to simulate the volcanic ash transport from Iceland to South West Europe, at the border of the air traffic closure area. Time-altitude plots of FLEXPART ash concentrations as well as of aerosol backscattering are presented, showing the arrival of volcanic particles in the troposphere above Lyon and their mixing into the planetary boundary layer. The particle UV-backscattering coefficient was typically 4 Mm -1 sr -1 and highly sensitive and accurate particle UV-depolarization measurements were performed, with depolarization ranging from a few to 44%. After few days long-range transport, observed ash particles are still non spherical. The observed variations of the backscattering and depolarization coefficients can be attributed to variations in the volcanic particles content. Ash mass concentrations are then retrieved. Moreover, a partitioning into spherical and non spherical particles is evaluated from number concentration ratios between solid ash particles and spherical hydrated sulfate particles. The microphysical properties of volcanic particles can thus be studied by associating an UV-polarization remote sensing instrument with a numerical volcanic ash dispersion model.

  2. Critical behavior of phase interfaces in porous media: Analysis of scaling properties with the use of noncoherent and coherent light

    SciTech Connect

    Zimnyakov, D. A. Sadovoi, A. V.; Vilenskii, M. A.; Zakharov, P. V.; Myllylae, R.

    2009-02-15

    Image sequences of the surface of disordered layers of porous medium (paper) obtained under noncoherent and coherent illumination during capillary rise of a liquid are analyzed. As a result, principles that govern the critical behavior of the interface between liquid and gaseous phases during its pinning are established. By a cumulant analysis of speckle-modulated images of the surface and by the statistical analysis of binarized difference images of the surface under noncoherent illumination, it is shown that the macroscopic dynamics of the interface at the stage of pinning is mainly controlled by the power law dependence of the appearance rate of local instabilities (avalanches) of the interface on the critical parameter, whereas the growth dynamics of the local instabilities is controlled by the diffusion of a liquid in a layer and weakly depends on the critical parameter. A phenomenological model is proposed for the macroscopic dynamics of the phase interface for interpreting experimental data. The values of critical indices are determined that characterize the samples under test within this model. These values are compared with the results of numerical simulation for discrete models of directed percolation corresponding to the Kardar-Parisi-Zhang equation.

  3. Solution properties and taste behavior of lactose monohydrate in aqueous ascorbic acid solutions at different temperatures: Volumetric and rheological approach.

    PubMed

    Sarkar, Abhijit; Sinha, Biswajit

    2016-11-15

    The densities and viscosities of lactose monohydrate in aqueous ascorbic acid solutions with several molal concentrations m=(0.00-0.08)molkg(-1) of ascorbic acid were determined at T=(298.15-318.15)K and pressure p=101kPa. Using experimental data apparent molar volume (ϕV), standard partial molar volume (ϕV(0)), the slope (SV(∗)), apparent specific volumes (ϕVsp), standard isobaric partial molar expansibility (ϕE(0)) and its temperature dependence [Formula: see text] the viscosity B-coefficient and solvation number (Sn) were determined. Viscosity B-coefficients were further employed to obtain the free energies of activation of viscous flow per mole of the solvents (Δμ1(0≠)) and of the solute (Δμ2(0≠)). Effects of molality, solute structure and temperature and taste behavior were analyzed in terms of solute-solute and solute-solvent interactions; results revealed that the solutions are characterized predominantly by solute-solvent interactions and lactose monohydrate behaves as a long-range structure maker. PMID:27283672

  4. Forecasting the In Vivo Behavior of Radiocontaminants of Unknown Physicochemical Properties Using a Simple In Vitro Test.

    PubMed

    Griffiths, N M; Coudert, S; Moureau, A; Laroche, P; Angulo, J F; Van der Meeren, A

    2016-08-01

    An understanding of the "bioavailability" of disseminated radiocontaminants is a necessary adjunct in order to tailor treatment and to calculate dose. A simple test has been designed to predict the bioavailability of different actinide forms likely to be found after dissemination of radioactive elements by dispersal devices or nuclear reactor incidents. Plutonium (Pu) or Americium (Am) nitrate or MOX (U,PuO2) are immobilized in culture wells using a static gel phase simulating biological compartments (lung, wound, etc.). Gels are incubated in a fluid phase representing physiological media (plasma, sweat, etc.). Transfer of radionuclide from static to fluid phase reflects contaminant bioavailability. After 48 h of incubation in physiological saline, Am transfer from static to fluid phase was greater than for Pu (70% vs. 15% of initial activity). Transfer of Pu or Am was markedly less from the oxide form of the two elements (1% Am and 0.05% Pu transferred). Medium representing intracellular lysosomal fluid (pH 4) increased transfer of Pu and Am, whereas culture medium including serum reduced actinide transfer. Actinide transfer was also reduced by elements of the extracellular matrix present in the static gel phase. Increasing DTPA concentrations (5 to 500 μM) to the fluid phase significantly enhanced transfer of Pu and Am. Although this agarose gel cannot fully represent in vivo complexity, this simple test can be used to investigate and predict the behavior in vivo of radiocontaminants to support medical treatments and medical forensic investigations. PMID:27356051

  5. Corrosion behavior and tensile properties of AISI 316LN stainless steel exposed to flowing sodium at 823 K

    SciTech Connect

    Pillai, S.R.; Barasi, N.S.; Khatak, H.S.; Terrance, A.L.E.; Kale, R.D.; Rajan, M.; Rajan, K.K.

    2000-02-01

    Austenitic stainless steel of the grade AISI 316 LN was exposed to flowing sodium in a loop at 823 K for 6,000 h to examine the corrosion and mass-transfer behavior. The specimens were incorporated in specially designed sample holders in the loop. These were retrieved and examined by various metallurgical techniques. Specimens were also subjected to thermal aging in the same sample holder to aid in separating the consequences of exposure to sodium from those cause by mere thermal effects. Microstructural investigations have revealed that thermal aging caused the precipitation of carbides at the grain boundaries. Exposure to sodium caused the leaching of elements such as chromium and nickel from the specimen. Loss of nickel from the austenite phase promoted the generation of ferrite phase. Microhardness investigation revealed the hardening of the sodium-exposed surface. Analysis using an electron Probe Microanalyzer revealed that the surface of the steel was both carburized and nitrided. Tensile tests indicated that there is no appreciable difference in the yield strength (YS) and ultimate tensile strength (UTS) of the thermally aged and sodium-exposed specimens when compared with the material in the as-received condition. However, the thermally aged and sodium-exposed specimens showed a decrease in the uniform elongation and total elongation at rupture, perhaps due to carburization and nitridation.

  6. Decanuclear Ln10 Wheels and Vertex-Shared Spirocyclic Ln5 Cores: Synthesis, Structure, SMM Behavior, and MCE Properties.

    PubMed

    Das, Sourav; Dey, Atanu; Kundu, Subrata; Biswas, Sourav; Narayanan, Ramakirushnan Suriya; Titos-Padilla, Silvia; Lorusso, Giulia; Evangelisti, Marco; Colacio, Enrique; Chandrasekhar, Vadapalli

    2015-11-16

    The reaction of a Schiff base ligand (LH3) with lanthanide salts, pivalic acid and triethylamine in 1:1:1:3 and 4:5:8:20 stoichiometric ratios results in the formation of decanuclear Ln10 (Ln = Dy (1), Tb (2), and Gd (3)) and pentanuclear Ln5 complexes (Ln = Gd (4), Tb (5), and Dy (6)), respectively. The formation of Ln10 and Ln5 complexes are fully governed by the stoichiometry of the reagents used. Detailed magnetic studies on these complexes (1-6) have been carried out. Complex 1 shows a SMM behavior with an effective energy barrier for the reversal of the magnetization (Ueff) = 16.12(8) K and relaxation time (τo) = 3.3×10(-5) s under 4000 Oe direct current (dc) field. Complex 6 shows the frequency dependent maxima in the out-of-phase signal under zero dc field, without achieving maxima above 2 K. Complexes 3 and 4 show a large magnetocaloric effect with the following characteristic values: -ΔSm = 26.6 J kg(-1) K(-1) at T = 2.2 K for 3 and -ΔSm = 27.1 J kg(-1) K(-1) at T = 2.4 K for 4, both for an applied field change of 7 T. PMID:26420030

  7. Novel 1D coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n}: Synthesis, structure, magnetic properties and thermal behavior

    SciTech Connect

    Fomina, Irina; Dobrokhotova, Zhanna; Aleksandrov, Grygory; Emelina, Anna; Bykov, Mikhail; Bogomyakov, Artem; Puntus, Lada; Novotortsev, Vladimir; Eremenko, Igor

    2012-01-15

    The new 1D coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n} (1), where Piv=OOCBu{sup t-}, was synthesized in high yield (>95%) by the reaction of thulium acetate with pivalic acid in air at 100 Degree-Sign S. According to the X-ray diffraction data, the metal atoms in compound 1 are in an octahedral ligand environment unusual for lanthanides. The magnetic and luminescence properties of polymer 1, it's the solid-phase thermal decomposition in air and under argon, and the thermal behavior in the temperature range of -50 Horizontal-Ellipsis +50 Degree-Sign S were investigated. The vaporization process of complex 1 was studied by the Knudsen effusion method combined with mass-spectrometric analysis of the gas-phase composition in the temperature range of 570-680 K. - Graphical Abstract: Novel 1D coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n} was synthesized and studied by X-ray diffraction. The magnetic, luminescence properties, the thermal behavior and the volatility for the compound {l_brace}Tm(Piv){sub 3{r_brace}n} were investigated. Black-Small-Square Highlights: Black-Right-Pointing-Pointer We synthesized the coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n}. Black-Right-Pointing-Pointer Tm atoms in polymer have the coordination number 6. Black-Right-Pointing-Pointer Polymer exhibits blue-color emission at room temperature. Black-Right-Pointing-Pointer Polymer shows high thermal stability and volatility. Black-Right-Pointing-Pointer Polymer has no phase transitions in the range of -50 Horizontal-Ellipsis +50 Degree-Sign S.

  8. Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy Rene N4. II - Low cycle fatigue behavior

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Gayda, J.; Miner, R. V.

    1986-01-01

    The low cycle fatigue (LCF) properties of a single-crystal nickel-base superalloy Rene N4, have been examined at 760 and 980 C in air. Specimens having crystallographic orientations near the 001, 011, -111, 023, -236, and -145 lines were tested in fully reversed, total-strain-controlled LCF tests at a frequency of 0.1 Hz. At 760 C, this alloy exhibited orientation dependent tension-compression anisotropies of yielding which continued to failure. Also at 760 C, orientations exhibiting predominately single slip exhibited serrated yielding for many cycles. At 980 C, orientation dependencies of yielding behavior were smaller. In spite of the tension-compression anisotropies, cyclic stress range-strain range behavior was not strongly orientation dependent for either test temperature. Fatigue life on a total strain range basis was highly orientation dependent at 760 and 980 C and was related chiefly to elastic modulus, low modulus orientations having longer lives. Stage I crack growth on 111 planes was dominant at 760 C, while Stage II crack growth occurred at 980 C. Crack initiation generally occurred at near-surface micropores, but occasionally at oxidation spikes in the 980 C tests.

  9. Brownian dynamics simulation of orientational behavior, flow-induced structure, and rheological properties of a suspension of oblate spheroid particles under simple shear

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takehiro; Suga, Takanori; Mori, Noriyasu

    2005-08-01

    Brownian dynamics (BD) simulations were carried out for suspensions of oblate spheroid particles interacting via the Gay-Berne (GB) potential. The oblate spheroid particles were applied as a model of disc-like particles and the system of suspension of the particles was considered. Numerically analyzed were both the change in phase with the number density of the particles at equilibrium state and the behavior of the particles in simple shear flows. The system changed from isotropic phase to nematic one with increasing the particle concentration. In the simulation of shear flows, the shear was imposed upon the systems in nematic phase at equilibrium. The systems exhibited various motions of the director depending on the shear rate, e.g. the continuous rotation of director at low shear rates, the wagging at moderate shear rates, and the flow aligning at high shear rates. Temporal change in inner structure of suspensions was also analyzed and collapse of initial particle configurations due to shear was found. Moreover, rheological properties of the suspension were investigated. The numerical simulation predicted the shear-thinning in viscosity, negative first normal stress difference, and positive second normal stress difference, and these results qualitatively agreed with the predictions using a constitutive equation for discotic nematics. The present study proved that the BD simulation using spheroid particles interacting via the GB potential is an effective approach for investigating the flow behavior and flow-induced structure of suspensions of disklike particles at a particulate level.

  10. Brownian dynamics simulation of orientational behavior, flow-induced structure, and rheological properties of a suspension of oblate spheroid particles under simple shear.

    PubMed

    Yamamoto, Takehiro; Suga, Takanori; Mori, Noriyasu

    2005-08-01

    Brownian dynamics (BD) simulations were carried out for suspensions of oblate spheroid particles interacting via the Gay-Berne (GB) potential. The oblate spheroid particles were applied as a model of disc-like particles and the system of suspension of the particles was considered. Numerically analyzed were both the change in phase with the number density of the particles at equilibrium state and the behavior of the particles in simple shear flows. The system changed from isotropic phase to nematic one with increasing the particle concentration. In the simulation of shear flows, the shear was imposed upon the systems in nematic phase at equilibrium. The systems exhibited various motions of the director depending on the shear rate, e.g. the continuous rotation of director at low shear rates, the wagging at moderate shear rates, and the flow aligning at high shear rates. Temporal change in inner structure of suspensions was also analyzed and collapse of initial particle configurations due to shear was found. Moreover, rheological properties of the suspension were investigated. The numerical simulation predicted the shear-thinning in viscosity, negative first normal stress difference, and positive second normal stress difference, and these results qualitatively agreed with the predictions using a constitutive equation for discotic nematics. The present study proved that the BD simulation using spheroid particles interacting via the GB potential is an effective approach for investigating the flow behavior and flow-induced structure of suspensions of disklike particles at a particulate level. PMID:16196575

  11. Optical behavior and structural property of CuAlS₂ and AgAlS₂ wide-bandgap chalcopyrites.

    PubMed

    Ho, Ching-Hwa; Pan, Chia-Chi

    2014-08-01

    Single crystals of CuAlS₂ and AgAlS₂ were grown by chemical vapor transport method using ICl₃ as the transport. The as-grown CuAlS₂ crystals reveal transparent and light-green color. Most of them possess a well-defined (112) surface. The AgAlS₂ crystals essentially show transparent and white color in vacuum. As the AgAlS₂ was put into the atmosphere, the crystal surface gradually darkened and became brownish because of the surface reaction with humidity or hydrogen gas. After a long-term chemical reaction process, the AgAlS₂ will transform into a AgAlO₂ oxide with yellow color. From x-ray diffraction measurements, both CuAlS₂ and AgAlS₂ as-grown crystals show single-phase and isostructural to a chalcopyrite structure. The (112) face is more preferable for the formation of the chalcopyrite crystals. The energies of interband transitions of the CuAlS₂ and AgAlS₂ were determined accurately by thermoreflectance measurements in a wide energy range of 2-6 eV. The valence-band electronic structures of CuAlS₂ and AgAlS₂ have been detailed and characterized using polarized-thermoreflectance measurements in the temperature range between 30 and 300 K. The band-edge transitions belonging to the E(∥) and E(⊥) polarizations have been, respectively, identified. The band edge of AgAlS₂ is near 3.2 eV while that of AgAlS₂ is about 3.5 eV. On the basis of the experimental analyses, optical and sensing behaviors of the chalcopyrite crystals have been realized. PMID:25090358

  12. The effect of tissue-engineered cartilage biomechanical and biochemical properties on its post-implantation mechanical behavior.

    PubMed

    Khoshgoftar, Mehdi; Wilson, Wouter; Ito, Keita; van Donkelaar, Corrinus C

    2013-01-01

    The insufficient load-bearing capacity of today's tissue-engineered (TE) cartilage limits its clinical application. Focus has been on engineering cartilage with enhanced mechanical stiffness by reproducing native biochemical compositions. More recently, depth dependency of the biochemical content and the collagen network architecture has gained interest. However, it is unknown whether the mechanical performance of TE cartilage would benefit more from higher content of biochemical compositions or from achieving an appropriate collagen organization. Furthermore, the relative synthesis rate of collagen and proteoglycans during the TE process may affect implant performance. Such insights would assist tissue engineers to focus on those aspects that are most important. The aim of the present study is therefore to elucidate the relative importance of implant ground substance stiffness, collagen content, and collagen architecture of the implant, as well as the synthesis rate of the biochemical constituents for the post-implantation mechanical behavior of the implant. We approach this by computing the post-implantation mechanical conditions using a composition-based fibril-reinforced poro-viscoelastic swelling model of the medial tibia plateau. Results show that adverse implant composition and ultrastructure may lead to post-implantation excessive mechanical loads, with collagen orientation being the most critical variable. In addition, we predict that a faster synthesis rate of proteoglycans compared to that of collagen during TE culture may result in excessive loads on collagen fibers post-implantation. This indicates that even with similar final contents, constructs may behave differently depending on their development. Considering these aspects may help to engineer TE cartilage implants with improved survival rates. PMID:22389193

  13. Effect of Interfacial Microstructure Evolution on Mechanical Properties and Fracture Behavior of Friction Stir-Welded Al-Cu Joints

    NASA Astrophysics Data System (ADS)

    Xue, P.; Xiao, B. L.; Ma, Z. Y.

    2015-07-01

    The interfacial microstructure evolution of Al-Cu joints during friction stir welding and post-welding annealing and its influence on the tensile strength and the fracture behavior were investigated in detail. An obvious interface including three sub-layers of α-Al, Al2Cu, and Al4Cu9 intermetallic compound (IMC) layers is generated in the as-FSW joint. With the development of annealing process, the α-Al layer disappeared and a new IMC layer of AlCu formed between initial two IMC layers of Al2Cu and Al4Cu9. The growth rate of IMC layers was diffusion controlled before the formation of Kirkendall voids, with activation energy of 117 kJ/mol. When the total thickness of IMC layers was less than the critical value of 2.5 μm, the FSW joints fractured at the heat-affected zone of Al side with a high ultimate tensile strength (UTS) of ~100 MPa. When the thickness of IMC layers exceeded 2.5 μm, the joints fractured at the interface. For relatively thin IMC layer, the joints exhibited a slightly decreased UTS of ~90 MPa and an inter-granular fracture mode with crack propagating mainly between the Al2Cu and AlCu IMC layers. However, when the IMC layer was very thick, crack propagated in the whole IMC layers and the fracture exhibited trans-granular mode with a greatly decreased UTS of 50-60 MPa.

  14. Anisotropy in Mechanical Properties and Fracture Behavior of an Oxide Dispersion Fe20Cr5Al Alloy

    NASA Astrophysics Data System (ADS)

    Chao, J.; Capdevila, C.

    2014-08-01

    Anisotropy of fracture toughness and fracture behavior of Fe20Cr5Al oxide dispersion-strengthened alloy has been investigated by means of compression tests, hardness tests, and wedge splitting test. The results show a small effect of the compression direction on yield strength (YS) and strain hardening. The YS is minimum for longitudinal direction and maximum for the tangential direction. The transverse plastic strain ratio is similar for tangential and longitudinal directions but very different from that in normal direction. Hardness depends on the indentation plane; it is lower for any plane parallel to the L-T plane and of similar magnitude for the other orthogonal planes, i.e., the L-S and T-S planes. Macroscopically, two failure modes have been observed after wedge-splitting tests, those of LS and TS specimens in which fracture deviates along one or two branches normal to the notch plane, and those of LT, TL, SL, and ST specimens in which fracture propagates along the notch plane. Besides LT and TL specimens present delaminations parallel to L-T plane. Both, the fracture surface of branching cracks and that of the delaminations, show an intergranular brittle fracture appearance. It is proposed that the main cause of the delamination and crack branching is the alignment in the mesoscopic scale of the ultrafine grains structure which is enhanced by the <110>-texture of the material and by the presence in the grain boundaries of both yttria dispersoids and impurity contaminations. An elastoplastic finite element analysis was performed to study what stress state is the cause of the branches and delaminations. It is concluded that the normal to the crack branches and/or the shear stress components could determine the crack bifurcation mechanism, whereas the delamination it seems that it is controlled by the magnitude of the stress component normal to the delamination plane.

  15. Structural properties of magnetic nanoparticles determine their heating behavior - an estimation of the in vivo heating potential

    PubMed Central

    2014-01-01

    Magnetically induced heating of magnetic nanoparticles (MNP) in an alternating magnetic field (AMF) is a promising minimally invasive tool for localized tumor treatment by sensitizing or killing tumor cells with the help of thermal stress. Therefore, the selection of MNP exhibiting a sufficient heating capacity (specific absorption rate, SAR) to achieve satisfactory temperatures in vivo is necessary. Up to now, the SAR of MNP is mainly determined using ferrofluidic suspensions and may distinctly differ from the SAR in vivo due to immobilization of MNP in tissues and cells. The aim of our investigations was to study the correlation between the SAR and the degree of MNP immobilization in dependence of their physicochemical features. In this study, the included MNP exhibited varying physicochemical properties and were either made up of single cores or multicores. Whereas the single core MNP exhibited a core size of approximately 15 nm, the multicore MNP consisted of multiple smaller single cores (5 to 15 nm) with 65 to 175 nm diameter in total. Furthermore, different MNP coatings, including dimercaptosuccinic acid (DMSA), polyacrylic acid (PAA), polyethylenglycol (PEG), and starch, wereinvestigated. SAR values were determined after the suspension of MNP in water. MNP immobilization in tissues was simulated with 1% agarose gels and 10% polyvinyl alcohol (PVA) hydrogels. The highest SAR values were observed in ferrofluidic suspensions, whereas a strong reduction of the SAR after the immobilization of MNP with PVA was found. Generally, PVA embedment led to a higher immobilization of MNP compared to immobilization in agarose gels. The investigated single core MNP exhibited higher SAR values than the multicore MNP of the same core size within the used magnetic field parameters. Multicore MNP manufactured via different synthesis routes (fluidMAG-D, fluidMAG/12-D) showed different SAR although they exhibited comparable core and hydrodynamic sizes. Additionally, no

  16. Electric properties and phase transition behavior in lead lanthanum zirconate stannate titanate ceramics with low zirconate content

    NASA Astrophysics Data System (ADS)

    Zeng, Tao; Lou, Qi-Wei; Chen, Xue-Feng; Zhang, Hong-Ling; Dong, Xian-Lin; Wang, Gen-Shui

    2015-11-01

    The phase transitions, dielectric properties, and polarization versus electric field (P-E) hysteresis loops of Pb0.97La0.02(Zr0.42Sn0.58-xTix)O3 (0.13≤ x ≤0.18) (PLZST) bulk ceramics were systematically investigated. This study exhibited a sequence of phase transitions by analyzing the change of the P-E hysteresis loops with increasing temperature. The antiferroelectric (AFE) to ferroelectric (FE) phase boundary of PLZST with the Zr content of 0.42 was found to locate at the Ti content between 0.14 and 0.15. This work is aimed to improve the ternary phase diagram of lanthanum-doped PZST with the Zr content of 0.42 and will be a good reference for seeking high energy storage density in the PLZST system with low-Zr content. Project supported by the National Natural Science Foundation of China (Grant Nos. 51202273, 11204304, and 11304334) and the Science and Technology Commission of Shanghai Municipality, China (Grant No. 14DZ2261000).

  17. Scale effects of nanomechanical properties and deformation behavior of Au nanoparticle and thin film using depth sensing nanoindentation

    PubMed Central

    Maharaj, Dave

    2014-01-01

    Summary Nanoscale research of bulk solid surfaces, thin films and micro- and nano-objects has shown that mechanical properties are enhanced at smaller scales. Experimental studies that directly compare local with global deformation are lacking. In this research, spherical Au nanoparticles, 500 nm in diameter and 100 nm thick Au films were selected. Nanoindentation (local deformation) and compression tests (global deformation) were performed with a nanoindenter using a sharp Berkovich tip and a flat punch, respectively. Data from nanoindentation studies were compared with bulk to study scale effects. Nanoscale hardness of the film was found to be higher than the nanoparticles with both being higher than bulk. Both nanoparticles and film showed increasing hardness for decreasing penetration depth. For the film, creep and strain rate effects were observed. In comparison of nanoindentation and compression tests, more pop-ins during loading were observed during the nanoindentation of nanoparticles. Repeated compression tests of nanoparticles were performed that showed a strain hardening effect and increased pop-ins during subsequent loads. PMID:24991519

  18. Three interesting coordination compounds based on metalloligand and alkaline-earth ions: Syntheses, structures, thermal behaviors and magnetic property

    NASA Astrophysics Data System (ADS)

    Zhou, Qiang; Qian, Jun; Zhang, Chi

    2016-09-01

    Based on metalloligand LCu ([Cu(2,4-pydca)2]2-, 2,4-pydca2- = pyridine-2,4-dicarboxylate) and alkaline-earth ions (Ca2+, Sr2+, and Ba2+), three interesting coordination compounds, [Ca(H2O)7][LCu·H2O]·H2O (1), {Sr[LCu·H2O]·4H2O}n (2), and {Ba[LCu·H2O]·8H2O}n (3), have been synthesized and well-characterized by elemental analysis, infrared spectroscopy, thermogravimetric and single-crystal X-ray diffraction analysis. X-ray crystallographic studies reveal that 1 features a discrete 0D coordination compound, while 2 and 3 exhibit the 2D network and 1D chain structures, respectively. Compound 2 is constructed from {LCu}2 dimers connected with {Sr2} units, which is fabricated by two Sr2+ ions bridged via two μ2-O bridges, while compound 3 is formed by 1D {Ba}n chain linked with metalloligands LCu and exhibits an interesting sandwich like chain structure. It is noted that the coordination numbers of alkaline-earth ions are in positive correlation with their radiuses. Moreover, the magnetic property of compound 2 has been studied.

  19. Scale effects of nanomechanical properties and deformation behavior of Au nanoparticle and thin film using depth sensing nanoindentation.

    PubMed

    Maharaj, Dave; Bhushan, Bharat

    2014-01-01

    Nanoscale research of bulk solid surfaces, thin films and micro- and nano-objects has shown that mechanical properties are enhanced at smaller scales. Experimental studies that directly compare local with global deformation are lacking. In this research, spherical Au nanoparticles, 500 nm in diameter and 100 nm thick Au films were selected. Nanoindentation (local deformation) and compression tests (global deformation) were performed with a nanoindenter using a sharp Berkovich tip and a flat punch, respectively. Data from nanoindentation studies were compared with bulk to study scale effects. Nanoscale hardness of the film was found to be higher than the nanoparticles with both being higher than bulk. Both nanoparticles and film showed increasing hardness for decreasing penetration depth. For the film, creep and strain rate effects were observed. In comparison of nanoindentation and compression tests, more pop-ins during loading were observed during the nanoindentation of nanoparticles. Repeated compression tests of nanoparticles were performed that showed a strain hardening effect and increased pop-ins during subsequent loads. PMID:24991519

  20. Structure−Property Correlations in Hybrid Polymer−Nanoparticle Electrospun Fibers and Plasmonic Control over their Dichroic Behavior

    SciTech Connect

    Sharma, Nikhil; McKeown, Steven J.; Ma, Xin; Pochan, Darrin J.; Cloutier, Sylvain G.

    2010-12-07

    Electrospinning constitutes a simple and versatile approach of fabricating polymer heterostructures composed of nanofibers. A preferred alignment of polymer crystallites stems from complex shear elongational forces and generates a strong intrinsic optical anisotropy in typical electrospun fibers of semicrystalline polymers. While it can prove useful for certain devices, this intrinsic anisotropy can be extremely detrimental for other key applications such as high-performance polymer-based lighting and solar-energy harvesting platforms. We report a dramatic reduction in the intrinsic dichroism of electrospun poly(ethylene oxide) fibers resulting from the incorporation of inorganic nanoparticles in the polymer matrix. This effect is shown to originate from a controllable randomization of the orientational ordering of the crystalline domains in the hybrid nanofibers and not merely from a reduction in crystallinity. This improved understanding of the crystalline structure-optical property correlation then leads to a better control over the intrinsic anisotropy of electrospun fibers using localized surface-plasmon enhancement effects around metallic nanoparticles.

  1. Crystallization behaviors and electric properties of (Pb0.8Ca0.2)TiO3 thin films prepared by a sol-gel route

    NASA Astrophysics Data System (ADS)

    Chi, Q. G.; Zhu, H. F.; Lin, J. Q.; Chen, C. T.; Wang, X.; Chen, Y.; Lei, Q. Q.

    2013-05-01

    The pure tetragonal perovskite (Pb0.8Ca0.2)TiO3 (PCT) thin films deposited on (1 1 1)Pt/Ti/SiO2/Si substrate were successfully achieved by a sol-gel route, and the influence of pyrolysis temperature on crystallization behaviors and electric properties of the PCT films was investigated. It was found that the film pyrolyzed at 450 °C could be crystallized at temperature as low as 450 °C, while the film pyrolyzed at 350 °C is amorphous under the same crystallization temperature. It was also found that the PCT films pyrolyzed at different temperatures could be fully crystallized when the crystallization temperature was raised to 600 °C, and compared to the film pyrolyzed at 350 °C, the film pyrolyzed at 450 °C exhibited higher (1 0 0) orientation and possessed enhanced electric properties (remanent polarization ∼19.5 μC/cm2, piezoelectric constant ∼125 pm/v, pyroelectric coefficient ∼310 μC/m2K).

  2. Effect of cerium on structure modifications of a hybrid sol–gel coating, its mechanical properties and anti-corrosion behavior

    SciTech Connect

    Cambon, Jean-Baptiste; Esteban, Julien; Ansart, Florence; Bonino, Jean-Pierre; Turq, Viviane; Santagneli, S.H.; Santilli, C.V.; Pulcinelli, S.H.

    2012-11-15

    Highlights: ► New sol–gel routes to replace chromates for corrosion protection of aluminum. ► Effect of cerium concentration on the microstructure of xerogel. ► Electrochemical and mechanical performances of hybrid coating with different cerium contents. ► Good correlation between the different results with an optimal cerium content of 0.01 M. -- Abstract: An organic–inorganic hybrid coating was developed to improve the corrosion resistance of the aluminum alloy AA 2024-T3. Organic and inorganic coatings derived from glycidoxypropyl-trimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al(O{sup s}Bu){sub 3}, with different cerium contents, were deposited onto aluminum by dip-coating process. Corrosion resistance and mechanical properties were investigated by electrochemical impedance measurements and nano-indentation respectively. An optimal cerium concentration of 0.01 M was evidenced. To correlate and explain the hybrid coating performances in relation to the cerium content, NMR experiments were performed. It has been shown that when the cerium concentration in the hybrid is higher than 0.01 M there are important modifications in the hybrid structure that account for the mechanical properties and anti-corrosion behavior of the sol–gel coating.

  3. Sintering behavior and dielectric properties of Bi3+-substituted Nd(Zn0.5Ti0.5)O3 microwave ceramics

    NASA Astrophysics Data System (ADS)

    Hu, Mingzhe; Ding, Zhao; Xiong, Gang; Ji, Denghui; Zhang, Kesheng

    2015-12-01

    The sintering behavior and dielectric properties of Bi3+-substituted Nd(Zn0.5Ti0.5)O3 (abbreviated as NZT) microwave ceramics (Nd1-xBix)(Zn0.5Ti0.5)O3 (0 ≤ x ≤ 0.15) (abbreviated as NBZT) are investigated. XRD results reveal the formation of single perovskite solid solutions for x ≤ 0.05 samples. For x > 0.05 samples, pyrochlore phase begins to segregate from the perovskite phase and its volume fraction increases with x. B-site Zn2+/Ti4+ 1:1 long range order (LRO) is detected by Raman Spectroscopy. The degree of LRO varies as a function of sintering conditions and chemical composition. The microwave dielectric properties of the composition are measured. By substituting Bi3+ for Nd3+, the temperature coefficient of resonant frequency (τf) tunes toward zero, however, the microwave quality factor, (Qf) deteriorates. For x = 0.03, τf reaches a minimum value of -18.9ppm/∘C with relative permittivity of ɛr = 48.2 and Qf = 1430GHz, respectively. The effect of Bi-doping on the Qf value is discussed.

  4. Effect of different processings on mechanical property and corrosion behavior in simulated body fluid of Mg-Zn-Y-Nd alloy for cardiovascular stent application

    NASA Astrophysics Data System (ADS)

    Zhu, Shi-Jie; Liu, Qian; Qian, Ya-Feng; Sun, Bin; Wang, Li-Guo; Wu, Jing-Min; Guan, Shao-Kang

    2014-09-01

    The biomagnesium alloys have been considered to be one of the most potential biodegradable metal materials due to its good mechanical compatibility, biological compatibility, biological security and biodegradable characteristics. However, the two major problems of high degradation rates in physiological environment and low mechanical properties prevent the development of biomagnesium alloys. In the present work, the samples of Mg-Zn-Y-Nd alloy were prepared by cyclic extrusion compression (CEC) and equal channel angular pressing (ECAP). The microstructures, mechanical properties of alloy and its corrosion behavior in simulated body fluid (SBF) were evaluated. The results reveal that Mg-Zn-Y-Nd alloy consists of equiaxial fine grain structure with the homogeneous distribution of micrometer size and nano-sized second phase, which was caused by the dynamic recrystallization during the ECAP and CEC. The corrosion resistance of alloy was improved. The tensile and corrosion resistance were improved, especially the processed alloy exhibit uniform corrosion performances and decreased corrosion rate. This will provide theoretical ground for Mg-Zn-Y-Nd alloy as vascular stent application.

  5. High-pressure behavior and thermoelastic properties of niobium studied by in situ x-ray diffraction

    SciTech Connect

    Zou, Yongtao E-mail: yongtaozou6@gmail.com; Li, Baosheng; Qi, Xintong; Wang, Xuebing; Chen, Ting; Li, Xuefei; Welch, David

    2014-07-07

    In situ synchrotron energy dispersive x-ray diffraction (XRD) experiments on Nb have been conducted at pressures up to 6.4 GPa and temperatures up to 1073 K. From the pressure-volume-temperature measurements, thermoelastic parameters were derived for the first time for Nb based on the thermal pressure (ΔP{sub th}) equation of state (EOS), modified high-T Birch-Murnaghan EOS, and Mie-Grüneisen-Debye EOS. With the pressure derivative of the bulk modulus K{sub T}{sup ´} fixed at 4.0, we obtained the ambient isothermal bulk modulus K{sub T0}=174(5) GPa, the temperature derivative of bulk modulus at constant pressure (∂K{sub T}/∂T){sub P}=-0.060(8) GPa K⁻¹ and at constant volume (∂K{sub T}/∂T){sub V}=-0.046(8) GPa K⁻¹, the volumetric thermal expansivity α{sub T}(T)=2.3(3)×10⁻⁵+0.3(2)×10⁻⁸T (K⁻¹), as well as the pressure dependence of thermal expansion (∂α/∂P){sub T}=(₋2.0±0.4)×10⁻⁶ K⁻¹ GPa⁻¹. Fitting the present data to the Mie-Grüneisen-Debye EOS with Debye temperature Θ₀=276.6 K gives γ₀=1.27(8) and K{sub T0}=171(3) GPa at a fixed value of q=3.0. The ambient isothermal bulk modulus and Grüneisen parameter derived from this work are comparable to previously reported values from both experimental and theoretical studies. An in situ high-resolution, angle dispersive XRD study on Nb did not indicate any anomalous behavior related to pressure-induced electronic topological transitions at ~5 GPa as has been reported previously.

  6. Study on mechanical properties and damage behaviors of Kevlar fiber reinforced epoxy composites by digital image correlation technique under optical microscope

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Shao, Wenquan; Ji, Hongwei

    2010-10-01

    Kevlar fiber-reinforced epoxy (KFRE) composites are widely used in the fields of aerospace, weapon, shipping, and civil industry, due to their outstanding capabilities. In this paper, mechanical properties and damage behaviors of KFRE laminate (02/902) were tested and studied under tension condition. To precisely measure the tensile mechanical properties of the material and investigate its micro-scale damage evolution, a micro-image measuring system with in-situ tensile device was designed. The measuring system, by which the in-situ tensile test can be carried out and surface morphology evolution of the tensile specimen can be visually monitored and recorded during the process of loading, includes an ultra-long working distance zoom microscope and a in-situ tensile loading device. In this study, a digital image correlation method (DICM) was used to calculate the deformation of the tensile specimen under different load levels according to the temporal series images captured by an optical microscope and CCD camera. Then, the elastic modulus and Poisson's ratio of the KFRE was obtained accordingly. The damage progresses of the KFRE laminates were analyzed. Experimental results indicated that: (1) the KFRE laminate (02/902) is almost elastic, its failure mode is brittle tensile fracture.(2) Mechanical properties parameters of the material are as follows: elastic modulus is 14- 16GPa, and tensile ultimate stress is 450-480 Mpa respectively. (3) The damage evolution of the material is that cracks appear in epoxy matrix firstly, then, with the increasing of the tensile loading, matrix cracks add up and extend along a 45° angle direction with tensile load. Furthermore, decohesion between matrix and fibers as well as delamination occurs. Eventually, fibers break and the material is damaged.

  7. A metallographic study of porosity and fracture behavior in relation to the tensile properties in 319.2 end chill castings

    SciTech Connect

    Samuel, A.M.; Samuel, F.H.

    1995-09-01

    A metallographic study of the porosity and fracture behavior in unidirectionally solidified end chill castings of 319.2 aluminum alloy (Al-6.2 pct Si-3.8 pct Cu-0.5 pct Fe-0.14 pct Mn-0.06 pct Mg-0.073 pct Ti) was carried out using optical microscopy and scanning electron microscopy (SEM) to determine their relationship with the tensile properties. The parameters varied in the production of these castings were the hydrogen ({approximately}0.1 and {approximately}0.37 mL/100 g Al), modifier (0 and 300 ppm Sr), and grain refiner (0 and 0.03 wt pct Ti) concentrations, as well as the solidification time, which increased with decreasing distance from the end chill bottom of the casting, giving dendrite arm spacings (DASs) ranging from {approximately}15 to {approximately}95 {micro}m. Image analysis and energy dispersive X-ray (EDX) analysis were employed for quantification of porosity/microstructural constituents and fracture surface analysis (phase identification), respectively. The results showed that the local solidification time (viz. DAS) significantly influences the ductility at low hydrogen levels; at higher levels, however, hydrogen has a more pronounced effect (porosity related) on the drop in ductility. Porosity is mainly observed in the form of elongated pores along the grain boundaries, with Sr increasing the porosity volume percent and grain refining increasing the probability for pore branching. The beneficial effect of Sr modification, however, improves the alloy ductility. Fracture of the Si, {beta}-Al{sub 5}FeSi, {alpha}-Al{sub 15}(Fe,Mn){sub 3}Si{sub 2}, and Al{sub 2}Cu phases takes place within the phase particles rather than at the particle/Al matrix interface. Sensitivity of tensile properties to DAS allows for the use of the latter as an indicator of the expected properties of the alloy.

  8. Dendritic Arm Spacing Affecting Mechanical Properties and Wear Behavior of Al-Sn and Al-Si Alloys Directionally Solidified under Unsteady-State Conditions

    NASA Astrophysics Data System (ADS)

    Cruz, Kleber S.; Meza, Elisangela S.; Fernandes, Frederico A. P.; Quaresma, José M. V.; Casteletti, Luiz C.; Garcia, Amauri

    2010-04-01

    Alloys of Al-Sn and Al-Si are widely used in tribological applications such as cylinder liners and journal bearings. Studies of the influence of the as-cast microstructures of these alloys on the final mechanical properties and wear resistance can be very useful for planning solidification conditions in order to permit a desired level of final properties to be achieved. The aim of the present study was to contribute to a better understanding about the relationship between the scale of the dendritic network and the corresponding mechanical properties and wear behavior. The Al-Sn (15 and 20 wt pct Sn) and Al-Si (3 and 5 wt pct Si) alloys were directionally solidified under unsteady-state heat flow conditions in water-cooled molds in order to permit samples with a wide range of dendritic spacings to be obtained. These samples were subjected to tensile and wear tests, and experimental quantitative expressions correlating the ultimate tensile strength (UTS), yield tensile strength, elongation, and wear volume to the primary dendritic arm spacing (DAS) have been determined. The wear resistance was shown to be significantly affected by the scale of primary dendrite arm spacing. For Al-Si alloys, the refinement of the dendritic array improved the wear resistance, while for the Al-Sn alloys, an opposite effect was observed, i.e., the increase in primary dendrite arm spacing improved the wear resistance. The effect of inverse segregation, which is observed for Al-Sn alloys, on the wear resistance is also discussed.

  9. Electrochemical behavior of polypyrrol/AuNP composites deposited by different electrochemical methods: sensing properties towards catechol

    PubMed Central

    García-Hernández, Celia; Medina-Plaza, Cristina; Martín-Pedrosa, Fernando; Blanco, Yolanda; de Saja, José Antonio

    2015-01-01

    Summary Two different methods were used to obtain polypyrrole/AuNP (Ppy/AuNP) composites. One through the electrooxidation of the pyrrole monomer in the presence of colloidal gold nanoparticles, referred to as trapping method (T), and the second one by electrodeposition of both components from one solution containing the monomer and a gold salt, referred to as cogeneration method (C). In both cases, electrodeposition was carried out through galvanostatic and potentiostatic methods and using platinum (Pt) or stainless steel (SS) as substrates. Scanning electron microscopy (SEM) demonstrated that in all cases gold nanoparticles of similar size were uniformly dispersed in the Ppy matrix. The amount of AuNPs incorporated in the Ppy films was higher when electropolymerization was carried out by chronopotentiometry (CP). Besides, cogeneration method allowed for the incorporation of a higher number of AuNPs than trapping. Impedance experiments demonstrated that the insertion of AuNPs increased the conductivity. As an electrochemical sensor, the Ppy/AuNp deposited on platinum exhibited a strong electrocatalytic activity towards the oxidation of catechol. The effect was higher in films obtained by CP than in films obtained by chronoamperometry (CA). The influence of the method used to introduce the AuNPs (trapping or cogeneration) was not so important. The limits of detection (LOD) were in the range from 10−5 to 10−6 mol/L. LODs attained using films deposited on platinum were lower due to a synergy between AuNPs and platinum that facilitates the electron transfer, improving the electrocatalytic properties. Such synergistic effects are not so pronounced on stainless steel, but acceptable LOD are attained with lower price sensors. PMID:26665076

  10. The Behavior of IAPWS-95 from 250 to 300 K and Pressures up to 400 MPa: Evaluation Based on Recently Derived Property Data

    SciTech Connect

    Wagner, Wolfgang Thol, Monika

    2015-12-15

    Over the past several years, considerable scientific and technical interest has been focused on accurate thermodynamic properties of fluid water covering part of the subcooled (metastable) region and the stable liquid from the melting line up to about 300 K and pressures up to several hundred MPa. Between 2000 and 2010, experimental density data were published whose accuracy was not completely clear. The scientific standard equation of state for fluid water, the IAPWS-95 formulation, was developed on the basis of experimental data for thermodynamic properties that were available by 1995. In this work, it is examined how IAPWS-95 behaves with respect to the experimental data published after 1995. This investigation is carried out for temperatures from 250 to 300 K and pressures up to 400 MPa. The starting point is the assessment of the current data situation. This was mainly performed on the basis of data for the density, expansivity, compressibility, and isobaric heat capacity, which were derived in 2015 from very accurate speed-of-sound data. Apart from experimental data and these derived data, property values calculated from the recently published equation of state for this region of Holten et al. (2014) were also used. As a result, the unclear data situation could be clarified, and uncertainty values could be estimated for the investigated properties. In the region described above, detailed comparisons show that IAPWS-95 is able to represent the latest experimental data for the density, expansivity, compressibility, speed of sound, and isobaric heat capacity to within the uncertainties given in the release on IAPWS-95. Since the release does not contain uncertainty estimates for expansivities and compressibilities, the statement relates to the error propagation of the given uncertainty in density. Due to the lack of experimental data for the isobaric heat capacity for pressures above 100 MPa, no uncertainty estimates are given in the release for this pressure

  11. The Behavior of IAPWS-95 from 250 to 300 K and Pressures up to 400 MPa: Evaluation Based on Recently Derived Property Data

    NASA Astrophysics Data System (ADS)

    Wagner, Wolfgang; Thol, Monika

    2015-12-01

    Over the past several years, considerable scientific and technical interest has been focused on accurate thermodynamic properties of fluid water covering part of the subcooled (metastable) region and the stable liquid from the melting line up to about 300 K and pressures up to several hundred MPa. Between 2000 and 2010, experimental density data were published whose accuracy was not completely clear. The scientific standard equation of state for fluid water, the IAPWS-95 formulation, was developed on the basis of experimental data for thermodynamic properties that were available by 1995. In this work, it is examined how IAPWS-95 behaves with respect to the experimental data published after 1995. This investigation is carried out for temperatures from 250 to 300 K and pressures up to 400 MPa. The starting point is the assessment of the current data situation. This was mainly performed on the basis of data for the density, expansivity, compressibility, and isobaric heat capacity, which were derived in 2015 from very accurate speed-of-sound data. Apart from experimental data and these derived data, property values calculated from the recently published equation of state for this region of Holten et al. (2014) were also used. As a result, the unclear data situation could be clarified, and uncertainty values could be estimated for the investigated properties. In the region described above, detailed comparisons show that IAPWS-95 is able to represent the latest experimental data for the density, expansivity, compressibility, speed of sound, and isobaric heat capacity to within the uncertainties given in the release on IAPWS-95. Since the release does not contain uncertainty estimates for expansivities and compressibilities, the statement relates to the error propagation of the given uncertainty in density. Due to the lack of experimental data for the isobaric heat capacity for pressures above 100 MPa, no uncertainty estimates are given in the release for this pressure

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

    NASA Astrophysics Data System (ADS)

    Morozova, Natalia V.; Shchennikov, Vladimir V.; Ovsyannikov, Sergey V.

    2015-12-01

    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 (ɛ-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 ɛ-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.

  13. 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.

  14. Changes in triphasic mechanical properties of proteoglycan-depleted articular cartilage extracted from osmotic swelling behavior monitored using high-frequency ultrasound.

    PubMed

    Wang, Q; Zheng, Y P; Niu, H J

    2010-03-01

    This study aims to obtain osmosis-induced swelling strains of normal and proteoglycan (PG) depleted articular cartilage using an ultrasound system and to investigate the changes in its mechanical properties due to the PG depletion using a layered triphasic model. The swelling strains of 20 cylindrical cartilage-bone samples collected from different bovine patellae were induced by decreasing the concentration of bath saline and monitored by the ultrasound system. The samples were subsequently digested by a trypsin solution for approximately 20 min to deplete proteoglycans, and the swelling behaviors of the digested samples were measured again. The bi-layered triphasic model proposed in our previous study (Wang et al., J Biomech Eng-Trans ASME 2007; 129: 413-422) was used to predict the layered aggregate modulus Ha from the data of depth-dependent swelling strain, fixed charge density and water content. It was found that the region near the bone, for the normal specimens, had a significantly higher aggregate modulus (Ha1 = 20.6 +/- 18.2 MPa) in comparison with the middle zone and the surface layer (Ha2 = 7.8 +/- 14.5 MPa and Ha3 = 3.6 +/- 3.2 MPa, respectively) (p < 0.001). The normalized thickness of the deep layer h1 was 0.68 +/- 0.20. After the trypsin digestion, the parametric values decreased to Ha1 = 13.6 +/- 9.6 MPa, Ha2 = 6.7 +/- 11.5 MPa, Ha3 = 2.7 +/- 3.2 MPa, and h1 = 0.57 +/- 0.28. Other models were also used to analyze data and the results were compared. This study showed that high-frequency ultrasound measurement combined with the triphasic modeling was capable of nondestructively quantifying the alterations in the layered mechanical properties of the proteoglycan-depleted articular cartilage. PMID:20806723

  15. Ground state properties and thermoelectric behavior of Ru2VZ (Z=Si, ge, sn) half-metallic ferromagnetic full-Heusler compounds

    NASA Astrophysics Data System (ADS)

    Yalcin, Battal Gazi

    2016-06-01

    The ground state properties namely structural, mechanical, electronic and magnetic properties and thermoelectric behavior of Ru2VZ (Z=Si, Ge and Sn) half-metallic ferromagnetic full-Heusler compounds are systematically investigated. These compounds are ferromagnetic and crystallize in the Heusler type L21 structure (prototype: Cu2MnAl, Fm-3m 225). This result is confirmed for Ru2VSi and Ru2VSn by experimental work reported by Yin and Nash using high temperature direct reaction calorimetry. The studied materials are half-metallic ferromagnets with a narrow direct band gap in the minority spin channel that amounts to 31 meV, 66 meV and 14 meV for Ru2VSi, Ru2VGe, and Ru2VSn, respectively. The total spin magnetic moment (Mtot) of the considered compounds satisfies a Slater-Pauling type rule for localized magnetic moment systems (Mtot=(NV-24)μB), where NV=25 is the number of valence electrons in the primitive cell. The Curie temperature within the random phase approximation (RPA) is found to be 23 K, 126 K and 447 K for Ru2VSi, Ru2VGe and Ru2VSn, respectively. Semi-classical Boltzmann transport theories have been used to obtain thermoelectric constants, such as Seebeck coefficient (S), electrical (σ/τ) and thermal conductivity (κ/τ), power factor (PF) and the Pauli magnetic susceptibility (χ). ZTMAX values of 0.016 (350 K), 0.033 (380 K) and 0.063 (315 K) are achieved for Ru2VSi, Ru2VGe and Ru2VSn, respectively. It is expected that the obtained results might be a trigger in future experimentally interest in this type of full-Heusler compounds.

  16. Psychometric Properties of the "Aberrant Behavior Checklist," the "Anxiety, Depression and Mood Scale," the "Assessment of Dual Diagnosis" and the "Social Performance Survey Schedule" in Adults with Intellectual Disabilities

    ERIC Educational Resources Information Center

    Rojahn, Johannes; Rowe, Ellen W.; Kasdan, Shana; Moore, Linda; van Ingen, Daniel J.

    2011-01-01

    Progress in clinical research and in empirically supported interventions in the area of psychopathology in intellectual disabilities (ID) depends on high-quality assessment instruments. To this end, psychometric properties of four instruments were examined: the "Aberrant Behavior Checklist" (ABC), the "Assessment of Dual Diagnosis" (ADD), the…

  17. Effect of Chain-Extenders on the Properties and Hydrolytic Degradation Behavior of the Poly(lactide)/Poly(butylene adipate-co-terephthalate) Blends

    PubMed Central

    Dong, Weifu; Zou, Benshu; Yan, Yangyang; Ma, Piming; Chen, Mingqing

    2013-01-01

    Biodegradable poly(lactide)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends were prepared by reactive blending in the presence of chain-extenders. Two chain-extenders with multi-epoxy groups were studied. The effect of chain-extenders on the morphology, mechanical properties, thermal behavior, and hydrolytic degradation of the blends was investigated. The compatibility between the PLA and PBAT was significantly improved by in situ formation of PLA-co-PBAT copolymers in the presence of the chain-extenders, results in an enhanced ductility of the blends, e.g., the elongation at break was increased to 500% without any decrease in the tensile strength. The differential scanning calorimeter (DSC) results reveal that cold crystallization of PLA was enhanced due to heterogeneous nucleation effect of the in situ compatibilized PBAT domains. As known before, PLA is sensitive to hydrolysis and in the presence of PBAT and the chain-extenders, the hydrolytic degradation of the blend was evident. A three-stage hydrolysis mechanism for the system is proposed based on a study of weight loss and molecular weight reduction of the samples and the pH variation of the degradation medium. PMID:24152436

  18. 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.

  19. The influence of Mg on creep properties and fracture behaviors of Mar-M247 superalloy under 1255 K/200 MPa

    SciTech Connect

    Bor, H.Y.; Chao, C.G.; Ma, C.Y.

    2000-05-01

    The effects of Mg microadditions on the high-temperature/low stress (1,255 K/200 MPa) creep properties and fracture behavior of a Mar-M247 supralloy were investigated in this study. The results of quantitative statistical analyses showed that when Mg microadditions up to 50 ppm were made, the MC carbides located at grain boundaries (designated GB MC) were significantly refined and spheroidized and the number of MC carbides decreased. In addition, the M{sub 23}C{sub 6} carbides present on GBs dramatically increased with increasing Mg contents up to 50 ppm, and the creep resistance was enhanced under the test condition of 1,255 K/200 MPa. However, the creep performance of a Mar-M247 superalloy containing 80 ppm Mg deteriorated due to the formation of an extremely large amount of MC carbide and a decrease in the number of M{sub 23}C{sub 6} carbides at GBs. The cracks mainly initiated and propagated along GBs in both the Mg-free and Mg-containing Mar-M247 superalloys under 1,255 K/200 MPa, and the final rupture was caused by intergranular fracture. Under the present creep condition, the optimal Mg microaddition to a Mar-M247 superalloy should be 30 to 50 ppm.

  20. Grain size effect on phase transition behavior and electrical properties of (Bi1/2K1/2)TiO3 piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Hagiwara, Manabu; Fujihara, Shinobu

    2015-10-01

    Dense and phase-pure (Bi1/2K1/2)TiO3 (BKT) ceramics with various grain sizes from 0.18 to 1.01 µm were prepared by conventional sintering of a hydrothermally synthesized fine powder. The decrease in grain size resulted in the reductions in tetragonality, remanent polarization, and the piezoelectric d33 coefficient, whereas the room-temperature dielectric permittivity slightly increased with decreasing grain size. The measurement of the temperature dependence of permittivity revealed that BKT exhibited the spontaneous relaxor-to-normal ferroelectric (R-nFE) phase transition. It was also found that the maximum permittivity was decreased and the R-nFE transition was inhibited by the reduction in grain size. In this paper, on the basis of the observed grain-size-dependent phase transition behaviors, microstructural models are proposed for both coarse- and fine-grained BKT ceramics, and the mechanism underlying the grain size effect on the electrical properties is discussed.

  1. Phase behavior and interfacial properties of a switchable ethoxylated amine surfactant at high temperature and effects on CO2-in-water foams.

    PubMed

    Chen, Yunshen; Elhag, Amro S; Reddy, Prathima P; Chen, Hao; Cui, Leyu; Worthen, Andrew J; Ma, Kun; Quintanilla, Heriberto; Noguera, Jose A; Hirasaki, George J; Nguyen, Quoc P; Biswal, Sibani L; Johnston, Keith P

    2016-05-15

    The interfacial properties for surfactants at the supercritical CO2-water (C-W) interface at temperatures above 80°C have very rarely been reported given limitations in surfactant solubility and chemical stability. These limitations, along with the weak solvent strength of CO2, make it challenging to design surfactants that adsorb at the C-W interface, despite the interest in CO2-in-water (C/W) foams (also referred to as macroemulsions). Herein, we examine the thermodynamic, interfacial and rheological properties of the surfactant C12-14N(EO)2 in systems containing brine and/or supercritical CO2 at elevated temperatures and pressures. Because the surfactant is switchable from the nonionic state to the protonated cationic state as the pH is lowered over a wide range in temperature, it is readily soluble in brine in the cationic state below pH 5.5, even up to 120°C, and also in supercritical CO2 in the nonionic state. As a consequence of the affinity for both phases, the surfactant adsorption at the CO2-water interface was high, with an area of 207Å(2)/molecule. Remarkably, the surfactant lowered the interfacial tension (IFT) down to ∼5mN/m at 120°C and 3400 psia (23MPa), despite the low CO2 density of 0.48g/ml, indicating sufficient solvation of the surfactant tails. The phase behavior and interfacial properties of the surfactant in the cationic form were favorable for the formation and stabilization of bulk C/W foam at high temperature and high salinity. Additionally, in a 1.2 Darcy glass bead pack at 120°C, a very high foam apparent viscosity of 146 cP was observed at low interstitial velocities given the low degree of shear thinning. For a calcium carbonate pack, C/W foam was formed upon addition of Ca(2+) and Mg(2+) in the feed brine to keep the pH below 4, by the common ion effect, in order to sufficiently protonate the surfactant. The ability to form C/W foams at high temperatures is of interest for a variety of applications in chemical synthesis

  2. A Factor Analytic Investigation of the BASC-2 Behavioral and Emotional Screening System Parent Form: Psychometric Properties, Practical Implications, and Future Directions

    ERIC Educational Resources Information Center

    Dowdy, Erin; Chin, Jenna K.; Twyford, Jennifer M.; Dever, Bridget V.

    2011-01-01

    The Behavior Assessment System for Children, Second Edition (BASC-2) Behavioral and Emotional Screening System Parent Form (BESS Parent; Kamphaus & Reynolds, 2007) is a recently developed instrument designed to identify behavioral and emotional risk in students. To describe the underlying factor structure for this instrument, exploratory (EFA) and…

  3. Surface properties and dye loading behavior of Zn{sub 2}SnO{sub 4} nanoparticles hydrothermally synthesized using different mineralizers

    SciTech Connect

    Annamalai, Alagappan; Eo, Yang Dam; Im, Chan; Lee, Man-Jong

    2011-10-15

    We present for the first time the influence of different mineralizers on the isoelectric point (IEP) of zinc stannate (Zn{sub 2}SnO{sub 4}) nanoparticles hydrothermally prepared using three different mineralizers, viz., Na{sub 2}CO{sub 3}, KOH and tert-butyl amine, and the effect of the IEPs on the dye loading behavior of Zn{sub 2}SnO{sub 4} based photoelectrodes in dye sensitized solar cells (DSSCs). To produce highly crystalline, uniform sized Zn{sub 2}SnO{sub 4} nanoparticles, hydrothermal processing parameters, such as reaction temperature, time, and the mineralizers used have been critically adjusted. The structural and morphological features of the as-synthesized Zn{sub 2}SnO{sub 4} nanoparticles have been observed using both scanning and transmission electron microscopy. For the surface state characterization of shape- and size-controlled Zn{sub 2}SnO{sub 4} nanoparticles, the IEPs of Zn{sub 2}SnO{sub 4} surfaces were determined through zeta potential measurements. The IEPs were found to be 5.7, 7.4 and 8.1 for Zn{sub 2}SnO{sub 4} nanoparticles formed using Na{sub 2}CO{sub 3}, KOH and tert-butyl amine, respectively, suggesting that the surface properties of Zn{sub 2}SnO{sub 4} nanoparticles can be manipulated through the choice of the mineralizers used during the hydrothermal reaction. The amount of N719 dye loading on the surfaces of Zn{sub 2}SnO{sub 4} electrodes having different IEPs was also evaluated. It was revealed that the higher the IEP, the higher the dye loading amount, which means that the IEP mainly affects the dye loading at the dye-metal oxide interface. - Highlights: {yields} The effect of various mineralizers on the isoelectric point of Zn{sub 2}SnO{sub 4} was discussed. {yields} The IEP of Zn{sub 2}SnO{sub 4} can be modified by the choice of mineralizer. {yields} Change in IEP affects the surface properties and the morphology of Zn{sub 2}SnO{sub 4} particles. {yields} Modified surface affects the N719 dye loading behaviour of the Zn{sub 2

  4. Electrochemical growth behavior, surface properties, and enhanced in vivo bone response of TiO2 nanotubes on microstructured surfaces of blasted, screw-shaped titanium implants

    PubMed Central

    Sul, Young-Taeg

    2010-01-01

    TiO2 nanotubes are fabricated on TiO2 grit-blasted, screw-shaped rough titanium (ASTM grade 4) implants (3.75 × 7 mm) using potentiostatic anodization at 20 V in 1 M H3PO4 + 0.4 wt.% HF. The growth behavior and surface properties of the nanotubes are investigated as a function of the reaction time. The results show that vertically aligned nanotubes of ≈700 nm in length, with highly ordered structures of ≈40 nm spacing and ≈15 nm wall thickness may be grown independent of reaction time. The geometrical properties of nanotubes increase with reaction time (mean pore size, pore size distribution [PSD], and porosity ≈90 nm, ≈40–127 nm and 45%, respectively for 30 minutes; ≈107 nm, ≈63–140 nm and 56% for one hour; ≈108 nm, ≈58–150 nm and 60% for three hours). It is found that the fluorinated chemistry of the nanotubes of F-TiO2, TiOF2, and F-Ti-O with F ion incorporation of ≈5 at.%, and their amorphous structure is the same regardless of the reaction time, while the average roughness (Sa) gradually decreases and the developed surface area (Sdr) slightly increases with reaction time. The results of studies on animals show that, despite their low roughness values, after six weeks the fluorinated TiO2 nanotube implants in rabbit femurs demonstrate significantly increased osseointegration strengths (41 vs 29 Ncm; P = 0.008) and new bone formation (57.5% vs 65.5%; P = 0.008) (n = 8), and reveal more frequently direct bone/cell contact at the bone–implant interface by high-resolution scanning electron microscope observations as compared with the blasted, moderately rough implants that have hitherto been widely used for clinically favorable performance. The results of the animal studies constitute significant evidence that the presence of the nanotubes and the resulting fluorinated surface chemistry determine the nature of the bone responses to the implants. The present in vivo results point to potential applications of the TiO2 nanotubes in the

  5. Metallic behavior in low-dimensional honeycomb SiB crystals: A first-principles prediction of atomic structure and electronic properties

    NASA Astrophysics Data System (ADS)

    Hansson, Anders; de Brito Mota, F.; Rivelino, Roberto

    2012-11-01

    We present a detailed analysis of the atomic and electronic structure of a two-dimensional monolayer of boron and silicon elements within periodic density functional theory. The proposed h-SiB sheet is a structural analog of hexagonal boron nitride (h-BN) and exhibits a good structural stability, compared to the structure of silicene. The calculated cohesive energy of an infinite sheet of h-SiB is of 4.71 eV/atom, whereas the corresponding value for silicene is 4.09 eV/atom. However, h-SiB sheets are not able to be stacked into a three-dimensional graphitelike structure, leading to a new hexagonal phase. On the other hand, h-SiB is predicted to roll up into single-walled silicon boron nanotubes (SWSiBNTs) of which we examine the electronic properties of some zigzag and armchair tubes. The strain energy of the SWSiBNTs are four to five times lower than the strain energy of the corresponding carbon nanotubes. In contrast to more polar honeycomb monolayers, the h-SiB sheet is not semiconducting or semimetallic. It has a delocalized charge density like graphene, but the π band and the two highest occupied σ bands are only partly filled. This results in a high density of states around the Fermi level and a metallic behavior of the h-SiB sheet. Interestingly, all the low-dimensional h-SiB-based structures, including the smallest to the largest stable tubes studied here, are predicted to form metallic systems.

  6. Influence of lamination direction on fracture behavior and mechanical properties of TiNi SMA wire-embedded CFRP smart composites

    NASA Astrophysics Data System (ADS)

    Jang, Byung-Koog; Koo, Ja-Ho; Toyama, Nobuyuki; Akimune, Yoshio; Kishi, Teruo

    2001-08-01

    TiNi/CFRP composites were fabricated by hot-pressing in the temperature range of 130-180 degree(s)C, by controlling the applied pressure. The TiNi wires were embedded as an 1mm interval into the center of CFRP layers and CFRP host materials were stacked as 0, 30, 60 and 90 degrees configuration on tensile direction, respectively. The stress-strain curve and tensile strength of composites strongly depends on stacking direction of carbon fibers. The tensile strength of TiNi/CFRP composites with stacking direction of 0 and 90 degrees configuration are about 1.2GPa and 50MPa, respectively. The microstructural properties of TiNi/CFRP composites were observed by SEM. Pore and/or voids were found to congregate near the embedded TiNi wire and they increased in proportion to stacking direction of carbon fibers. Larger pores and interfacial crack were also observed at interface between TiNi wires and epoxy resin. Furthermore, the fracture behavior was studied by an AE technique during tensile test, to analyze the fracture process. The effects of surface treatment of TiNi wire by acid etching to improve the interfacial bonding strength between TiNi wire and epoxy matrix are also investigated. The average interfacial bonding strength of the TiNi wire embedded in CFRP matrix was evaluated by pull out test. It was confirmed that surface treatment of TiNi wire by acid etching improved the interfacial bonding strength. Acid etching by HF+HNO3 mixed solution significantly increased the interfacial bonding strength. The damage recovery effect of SMA in specimen was successfully confirmed by heating above 70 degree(s)C.

  7. Low-Temperature Sintering Behavior and Dielectric Properties of Li2O-Nb2O5-TiO2 Ceramics with Li-B-Si-O Glass

    NASA Astrophysics Data System (ADS)

    Li, Enzhu; Zhang, Peng; Mi, Yuean; Wang, Jing; Yuan, Ying; Zhou, Xiaohua

    2015-11-01

    This paper reports an investigation of the low-temperature sintering behaviors, microstructures, and microwave dielectric properties of Li1.0Nb0.6Ti0.5O3 (LNT) ceramics fired with addition of different amounts of Li2O-B2O3-SiO2 (LBS) glass. The results suggest that addition of LBS glass can effectively reduce the sintering temperature of LNT ceramic from 1100°C to 900°C without detriment of its microwave dielectric properties. However, addition of excess LBS glass leads to rapid grain growth and therefore decreases the density and microwave dielectric properties of the LNT ceramic. Optimized specimens with 1.0 wt.% LBS glass sintered at 900°C possessed excellent microwave dielectric properties of ɛ r ≈ 66.17, Q × f ≈ 5170 GHz ( f = 4.32 GHz), and τ f ≈ 19.2 ppm/°C.

  8. New 1-D and 3-D thiocyanatocadmates modified by various amine molecules and Cl(-)/CH3COO(-) ions: synthesis, structural characterization, thermal behavior and photoluminescence properties.

    PubMed

    Guo, Bing; Zhang, Xiao; Wang, Yan-Ning; Huang, Jing-Jing; Yu, Jie-Hui; Xu, Ji-Qing

    2015-03-21

    Under ambient conditions, reactions of CdCl2/Cd(CH3COO)2, SCN(-) and various organic amine molecules in strongly acidic solutions afforded the five new thiocyanatocadmates [H2(abpy)][CdCl2(SCN)2] (abpy = azobispyridine) 1, [H(apy)][Cd(SCN)3] (apy = 4-aminopyridine) 2, [H(ba)]2[CdCl2(SCN)2] (ba = tert-butylamine) 3, [H2(tmen)][Cd3Cl6(SCN)2] (tmen = N,N,N',N'-tetramethylethylenediamine) 4, and [H(dba)]2[Cd2(CH3COO)2(SCN)4] (dba = dibutylamine) 5. In compound 2 only, the CH3COO(-) ions in Cd(CH3COO)2 were completely displaced by SCN(-), producing a chained thiocyanatocadmate [Cd(SCN)3](-). In the other four compounds, the Cl(-) or CH3COO(-) ions appeared in the final inorganic anion frameworks. In compound 1, the Cl(-) ions doubly bridge the Cd(2+) centers, forming a one-dimensional (1-D) infinite chain, and the SCN(-) group exists in a terminal form, whereas in compound 3, the reverse situation is observed. Due to a trans-mode arrangement for two terminal Cl(-) or SCN(-) ions around each Cd(2+) center, the inorganic anion chains in compounds 1 and 3 both show a linear shape. In compound 4, Cd(2+) and Cl(-) first aggregate to form a 1-D endless chain with a composition of Cd3Cl6, which can be described as a linear arrangement of the open double cubanes. SCN(-) serves as the second connector, propagating the Cd3Cl6 chain into a three-dimensional (3-D) network with the occluded H2(tmen)(2+) cations. In compound 5, the SCN(-) groups doubly bridge the Cd(2+) centers, forming a 1-D zigzag-shape chain. The formation of the zigzag chain likely derives from chelation of the CH3COO(-) group to the Cd(2+) center. The thermal behavior and the photoluminescence properties of the title compounds were also investigated. PMID:25669175

  9. Influencing Behavior.

    ERIC Educational Resources Information Center

    Howk, Cherie

    1992-01-01

    Teacher interpretations of student behavior frequently provide the data to analyze problem behaviors. There is no absolute way to determine whether behaviors are appropriate or inappropriate. Effective teacher intervention involves reducing the old behavior and introducing new activities to reinforce appropriate behavior. The article suggests…

  10. Behavior dynamics: One perspective

    PubMed Central

    Marr, M. Jackson

    1992-01-01

    Behavior dynamics is a field devoted to analytic descriptions of behavior change. A principal source of both models and methods for these descriptions is found in physics. This approach is an extension of a long conceptual association between behavior analysis and physics. A theme common to both is the role of molar versus molecular events in description and prediction. Similarities and differences in how these events are treated are discussed. Two examples are presented that illustrate possible correspondence between mechanical and behavioral systems. The first demonstrates the use of a mechanical model to describe the molar properties of behavior under changing reinforcement conditions. The second, dealing with some features of concurrent schedules, focuses on the possible utility of nonlinear dynamical systems to the description of both molar and molecular behavioral events as the outcome of a deterministic, but chaotic, process. PMID:16812655

  11. Structure-Property Relationships in CO2-philic (Co)polymers: Phase Behavior, Self-Assembly, and Stabilization of Water/CO2 Emulsions.

    PubMed

    Girard, Etienne; Tassaing, Thierry; Marty, Jean-Daniel; Destarac, Mathias

    2016-04-13

    This Review provides comprehensive guidelines for the design of CO2-philic copolymers through an exhaustive and precise coverage of factors governing the solubility of different classes of polymers. Starting from computational calculations describing the interactions of CO2 with various functionalities, we describe the phase behavior in sc-CO2 of the main families of polymers reported in literature. The self-assembly of amphiphilic copolymers of controlled architecture in supercritical carbon dioxide and their use as stabilizers for water/carbon dioxide emulsions then are covered. The relationships between the structure of such materials and their behavior in solutions and at interfaces are systematically underlined throughout these sections. PMID:27014998

  12. Psychometric Properties of the Lithuanian Adlerian Parental Assessment of Child Behavior Scale (LAPACBS) in Parents of 6- to 12-Year-Olds

    ERIC Educational Resources Information Center

    Kern, Roy M.; Jonyniene, Jolita

    2012-01-01

    The structure-related validity and internal consistency reliability of the translated version of the Adlerian Parental Assessment of the Child Behavior Scale (APACBS) which would be referred to as the Lithuanian APACBS (LAPACBS) was the focus of the research study. A factor analysis was performed using a sample of 246 Lithuanian parents. It…

  13. Precise Modulation of the Breathing Behavior and Pore Surface in Zr-MOFs by Reversible Post-Synthetic Variable-Spacer Installation to Fine-Tune the Expansion Magnitude and Sorption Properties.

    PubMed

    Chen, Cheng-Xia; Wei, Zhangwen; Jiang, Ji-Jun; Fan, Yan-Zhong; Zheng, Shao-Ping; Cao, Chen-Chen; Li, Yu-Hao; Fenske, Dieter; Su, Cheng-Yong

    2016-08-16

    To combine flexibility and modifiability towards a more controllable complexity of MOFs, a post-synthetic variable-spacer installation (PVSI) strategy is used to implement kinetic installation/ uninstallation of secondary ligands into/from a robust yet flexible proto-Zr-MOF. This PVSI process features precise positioning of spacers with different length, size, number, and functionality, enabling accurate fixation of successive breathing stages and fine-tuning of pore surface. It shows unprecedented synthetic tailorability to create complicated MOFs in a predictable way for property modification, for example, CO2 and R22 adsorption/separation, thermal/chemical stability, and extended breathing behavior. PMID:27405047

  14. Metallic behavior and negative differential resistance properties of (InAs){sub n} (n = 2 − 4) molecule cluster junctions via a combined non–equilibrium Green's function and density functional theory study

    SciTech Connect

    Wang, Qi; Li, Rong; Xu, Yuanlan; Zhang, Jianbing; Miao, Xiangshui; Zhang, Daoli

    2014-06-21

    In this present work, the geometric structures and electronic transport properties of (InAs){sub n} (n = 2, 3, 4) molecule cluster junctions are comparatively investigated using NEGF combined with DFT. Results indicate that all (InAs){sub n} molecule cluster junctions present metallic behavior at the low applied biases ([−2V, 2V]), while NDR appears at a certain high bias range. Our calculation shows that the current of (InAs){sub 4} molecule cluster–based junction is almost the largest at any bias. The mechanisms of the current–voltage characteristics of all the three molecule cluster junctions are proposed.

  15. Arrestant property of recently manipulated soil on Macrotermes michaelseni as determined through visual tracking and automatic labeling of individual termite behaviors.

    PubMed

    Petersen, Kirstin; Bardunias, Paul; Napp, Nils; Werfel, Justin; Nagpal, Radhika; Turner, Scott

    2015-07-01

    The construction of termite nests has been suggested to be organized by a stigmergic process that makes use of putative cement pheromone found in saliva and recently manipulated soil ("nest material"), hypothesized to specifically induce material deposition by workers. Herein, we tracked 100 individuals placed in arenas filled with a substrate of half nest material, half clean soil, and used automatic labeling software to identify behavioral states. Our findings suggest that nest material acts to arrest termites; termites prefer to spend time on nest material when compared against clean soil. Residency time was significantly greater, and all construction behaviors occurred significantly more often on nest material. The arrestant function of nest material must be accounted for in experiments that seek semiochemical cues for the organization of labor. Future research will focus on the manner in which termites combine olfaction with tactile cues as well as other organizing factors during construction. PMID:25865171

  16. A comparison study on the densification behavior and mechanical properties of gelcast vs conventionally formed B{sub 4}C sintered conventionally and by microwaves

    SciTech Connect

    Menchhofer, P.A.; Kiggans, J.O.; Morrow, M.S.; Schechter, D.E.

    1996-06-01

    The utilization of microwave energy for reaching high temperatures necessary to densify B{sub 4}C powder is compared with conventional means of sintering by evaluating the mechanical properties after densification. Microwave energy has been shown to be an effective means for achieving high sintered densities, even though temperatures of {approximately} 2,250 C are required. In this study, green preforms of B{sub 4}C specimens were sintered by both conventional and microwave heating. This study also utilized an advanced forming method called ``Gelcasting`` developed at ORNL. Gelcasting is a fluid forming process whereby high solids suspensions of powders containing dissolved monomers are cast into a mold, then polymerized or ``gelled`` in situ. This investigation compares microstructures and mechanical properties of both Gelcast B{sub 4}C and ``conventionally`` die-pressed B{sub 4}C. The microstructures and final mechanical properties of B{sub 4}C specimens are discussed.

  17. Making behavioral technology transferable

    PubMed Central

    Pennypacker, H. S.; Hench, Larry L.

    1997-01-01

    The paucity of transferred behavioral technologies is traced to the absence of strategies for developing technology that is transferable, as distinct from strategies for conducting research, whether basic or applied. In the field of engineering, the results of basic research are transformed to candidate technologies that meet standardized criteria with respect to three properties: quantification, repetition, and verification. The technology of vitrification and storage of nuclear waste is used to illustrate the application of these criteria. Examples from behavior analysis are provided, together with suggestions regarding changes in practice that will accelerate the development and application of behavioral technologies. PMID:22478284

  18. Ferroelectric properties and fatigue behavior of heteroepitaxial PbZr1-xTixO3 thin film fabricated by hydrothermal epitaxy below Curie temperature

    NASA Astrophysics Data System (ADS)

    Ahn, W. S.; Jung, W. W.; Choi, S. K.

    2006-01-01

    A heteroepitaxial PbZr1-xTixO3 (PZT) thin film was fabricated by means of hydrothermal epitaxy at 210 °C below Curie temperature without undergoing the paraelectric to ferroelectric phase transition. From transmission electron microscope and piezoresponse force microscope observations, it was confirmed that the fabricated PZT thin films had only a -c monodomain without an a domain in the as-synthesized state. The polarization-electric-field hysteresis curve and the fatigue behavior of the heteroepitaxial PZT capacitor with a Pt top and n-type semiconductor bottom electrode was observed. The remanent polarization 2Pr of the PZT capacitor was about 63 μC/cm2. This value was much lower compared to that of the PbTiO3 capacitor, which was also fabricated by means of hydrothermal epitaxy at 160 °C below Curie temperature. It was suggested that a lower polarization of the PZT capacitor was due to the nonswitchable interfacial layer grown in the initial growth stage. However, this layer did not exert an influence on the fatigue behavior of the PZT capacitor: the PZT capacitor with an ordinary Pt top electrode and a Nb-doped SrTiO3 semiconductor bottom electrode revealed fatigue-free behavior in up to 1011 switching cycles.

  19. Youth Risk Behavior Surveillance: United States, 2001.

    ERIC Educational Resources Information Center

    Grunbaum, Jo Anne; Kann, Laura; Kinchen, Steven A.; Williams, Barbara; Ross, James G.; Lowry, Richard; Kolbe, Lloyd

    2002-01-01

    Examined national Youth Risk Behavior Survey data and state and local surveys of high school students to investigate behaviors contributing to unintentional injuries, violence, substance use, age at initiation of risk behaviors, substance abuse on school property, sexual behaviors contributing to pregnancy and sexually transmitted diseases,…

  20. Property in Nonhuman Primates

    ERIC Educational Resources Information Center

    Brosnan, Sarah F.

    2011-01-01

    Property is rare in most nonhuman primates, most likely because their lifestyles are not conducive to it. Nonetheless, just because these species do not frequently maintain property does not mean that they lack the propensity to do so. Primates show respect for possession, as well as behaviors related to property, such as irrational decision…

  1. Structures, electrical properties, and leakage current behaviors of un-doped and Mn-doped lead-free ferroelectric K{sub 0.5}Na{sub 0.5}NbO{sub 3} films

    SciTech Connect

    Wang, Lingyan E-mail: wren@mail.xjtu.edu.cn; Ren, Wei E-mail: wren@mail.xjtu.edu.cn; Shi, Peng; Wu, Xiaoqing

    2014-01-21

    Lead-free ferroelectric un-doped and doped K{sub 0.5}Na{sub 0.5}NbO{sub 3} (KNN) films with different amounts of manganese (Mn) were prepared by a chemical solution deposition method. The thicknesses of all films are about 1.6 μm. Their phase, microstructure, leakage current behavior, and electrical properties were investigated. With increasing the amounts of Mn, the crystallinity became worse. Fortunately, the electrical properties were improved due to the decreased leakage current density after Mn-doping. The study on leakage behaviors shows that the dominant conduction mechanism at low electric field in the un-doped KNN film is ohmic mode and that at high electric field is space-charge-limited and Pool-Frenkel emission. After Mn doping, the dominant conduction mechanism at high electric field of KNN films changed single space-charge-limited. However, the introduction of higher amount of Mn into the KNN film would lead to a changed conduction mechanism from space-charge-limited to ohmic mode. Consequently, there exists an optimal amount of Mn doping of 2.0 mol. %. The 2.0 mol. % Mn doped KNN film shows the lowest leakage current density and the best electrical properties. With the secondary ion mass spectroscopies and x-ray photoelectron spectroscopy analyses, the homogeneous distribution in the KNN films and entrance of Mn element in the lattice of KNN perovskite structure were also confirmed.

  2. Influence of CuO addition to BaSm{sub 2}Ti{sub 4}O{sub 12} microwave ceramics on sintering behavior and dielectric properties

    SciTech Connect

    Zuo Mingwen; Li Wei . E-mail: liwei@mail.sic.ac.cn; Shi Jianlin; Zeng Qun

    2006-06-15

    Microwave dielectric ceramics of tungsten-bronze-type BaSm{sub 2}Ti{sub 4}O{sub 12} were prepared by doping CuO (up to 2 wt.%) as the liquid-phase sintering aid. The effects of CuO additive on the densification, micro structure and dielectric properties were investigated. Due to the liquid-phase effect, the sintering temperature of BaSm{sub 2}Ti{sub 4}O{sub 12} ceramics with 1 wt.% CuO addition can be effectively reduced to 1160 deg. C, about 200 deg. C lower than that of pure BaSm{sub 2}Ti{sub 4}O{sub 12} ceramics, while good microwave dielectric properties of {epsilon} {sub r} = 75.8, Q*f = 4914.6 GHz and {tau} {sub f} = -7.65 ppm/deg. C were still achieved.

  3. Research on sintering behavior and microwave dielectric property of (Mg0.95Ca0.05)TiO3 ceramics for cross coupling filter

    NASA Astrophysics Data System (ADS)

    Luo, Chunya; Ma, Zhichao; Hu, Laisheng; Hu, Mingzhe; Huang, Xiaomin

    2015-12-01

    The microwave dielectric properties of 0.95%MgTiO3-0.05%CaTiO3 (abbreviated as 95MCT hereafter) ceramics have been studied for application in dielectric cross coupling filters. ZnO and Nb2O5 were selected as liquid sintering aids to lower the sintering temperature and enhance the Qf value of 95MCT and simultaneously we varied the mole ratio of ZnO : Nb2O5 to tune the microwave dielectric properties of 95MCT. When the ZnO : Nb2O5 mole ratio was 1.5 and the co-doping content was 0.25 wt.%, the optimal sintering temperature of 95MCT ceramic could be lowered from 1400∘C to 1320∘C and the Qf value could be improved by about 7.7%. The optimal microwave dielectric properties obtained under this condition were Qf = 72730 GHz (6.8 GHz), ɛr = 20.29 and τf = -6.84ppm/∘C, which demonstrated great potential usage in ceramic industry. High values of Qf ceramic were used to design the dielectric cross coupling filter. The dielectric filter measured at 2.35 GHz exhibited a 6.7% bandwidth (insert loss > -3 dB) of center frequency.

  4. Research of electrosurgical unit with novel antiadhesion composite thin film for tumor ablation: Microstructural characteristics, thermal conduction properties, and biological behaviors.

    PubMed

    Shen, Yun-Dun; Lin, Li-Hsiang; Chiang, Hsi-Jen; Ou, Keng-Liang; Cheng, Han-Yi

    2016-01-01

    The objective of this study was to use surface functionalization to evaluate the antiadhesion property and thermal injury effects on the liver when using a novel electrosurgical unit with nanostructured-doped diamond-like carbon (DLC-Cu) thin films for tumor ablations. The physical and chemical properties of DLC-Cu thin films were characterized by contact angle goniometer, scanning electron microscope, and transmission electron microscope. Three-dimensional (3D) hepatic models were reconstructed using magnetic resonance imaging to simulate a clinical electrosurgical operation. The results indicated a significant increase of the contact angle on the nanostructured DLC-Cu thin films, and the antiadhesion properties were also observed in an animal model. Furthermore, the surgical temperature in the DLC-Cu electrosurgical unit was found to be significantly lower than the untreated unit when analyzed using 3D models and thermal images. In addition, DLC-Cu electrodes caused a relatively small injury area and lateral thermal effect. The results indicated that the nanostructured DLC-Cu thin film coating reduced excessive thermal injury and tissue adherence effect in the liver. PMID:25647366

  5. Bathroom Behaviors

    MedlinePlus

    ... Listen Español Text Size Email Print Share Bathroom Behaviors Page Content Article Body My son is very ... and your support will ease him into correct behavior. Last Updated 11/21/2015 Source Guide to ...

  6. Behavioral Economics

    PubMed Central

    Reed, Derek D.; Niileksela, Christopher R.; Kaplan, Brent A.

    2013-01-01

    In recent years, behavioral economics has gained much attention in psychology and public policy. Despite increased interest and continued basic experimental studies, the application of behavioral economics to therapeutic settings remains relatively sparse. Using examples from both basic and applied studies, we provide an overview of the principles comprising behavioral economic perspectives and discuss implications for behavior analysts in practice. A call for further translational research is provided. PMID:25729506

  7. High dielectric permittivity and improved mechanical and thermal properties of poly(vinylidene fluoride) composites with low carbon nanotube content: effect of composite processing on phase behavior and dielectric properties.

    PubMed

    Kumar, G Sudheer; Vishnupriya, D; Chary, K Suresh; Patro, T Umasankar

    2016-09-23

    The composite processing technique and nanofiller concentration and its functionalization significantly alter the properties of polymer nanocomposites. To realize this, multi-walled carbon nanotubes (CNT) were dispersed in a poly(vinylidene fluoride) (PVDF) matrix at carefully selected CNT concentrations by two illustrious methods, such as solution-cast and melt-mixing. Notwithstanding the processing method, CNTs induced predominantly the γ-phase in PVDF, instead of the commonly obtained β-phase upon nanofiller incorporation, and imparted significant improvements in dielectric properties. Acid-treatment of CNT improved its dispersion and interfacial adhesion significantly with PVDF, and induced a higher γ-phase content and better dielectric properties in PVDF as compared to pristine CNT. Further, the γ-phase content was found to be higher in solution-cast composites than that in melt-mixed counterparts, most likely due to solvent-induced crystallization in a controlled environment and slow solvent evaporation in the former case. However, interestingly, the melt-mixed composites showed a significantly higher dielectric constant at the onset of the CNT networked-structure as compared to the solution-cast composites. This suggests the possible role of CNT breakage during melt-mixing, which might lead to higher space-charge polarization at the polymer-CNT interface, and in turn an increased number of pseudo-microcapacitors in these composites than the solution-cast counterparts. Notably, PVDF with 0.13 vol% (volume fraction, f c  = 0.0013) of acid-treated CNTs, prepared by melt-mixing, displayed the relative permittivity of ∼217 and capacitance of ∼5430 pF, loss tangent of ∼0.4 at 1 kHz and an unprecedented figure of merit of ∼10(5). We suggest a simple hypothesis for the γ-phase formation and evolution of the high dielectric constant in these composites. Further, the high-dielectric composite film showed marked improvements in mechanical and thermal

  8. High dielectric permittivity and improved mechanical and thermal properties of poly(vinylidene fluoride) composites with low carbon nanotube content: effect of composite processing on phase behavior and dielectric properties

    NASA Astrophysics Data System (ADS)

    Sudheer Kumar, G.; Vishnupriya, D.; Chary, K. Suresh; Umasankar Patro, T.

    2016-09-01

    The composite processing technique and nanofiller concentration and its functionalization significantly alter the properties of polymer nanocomposites. To realize this, multi-walled carbon nanotubes (CNT) were dispersed in a poly(vinylidene fluoride) (PVDF) matrix at carefully selected CNT concentrations by two illustrious methods, such as solution-cast and melt-mixing. Notwithstanding the processing method, CNTs induced predominantly the γ-phase in PVDF, instead of the commonly obtained β-phase upon nanofiller incorporation, and imparted significant improvements in dielectric properties. Acid-treatment of CNT improved its dispersion and interfacial adhesion significantly with PVDF, and induced a higher γ-phase content and better dielectric properties in PVDF as compared to pristine CNT. Further, the γ-phase content was found to be higher in solution-cast composites than that in melt-mixed counterparts, most likely due to solvent-induced crystallization in a controlled environment and slow solvent evaporation in the former case. However, interestingly, the melt-mixed composites showed a significantly higher dielectric constant at the onset of the CNT networked-structure as compared to the solution-cast composites. This suggests the possible role of CNT breakage during melt-mixing, which might lead to higher space-charge polarization at the polymer–CNT interface, and in turn an increased number of pseudo-microcapacitors in these composites than the solution-cast counterparts. Notably, PVDF with 0.13 vol% (volume fraction, f c = 0.0013) of acid-treated CNTs, prepared by melt-mixing, displayed the relative permittivity of ∼217 and capacitance of ∼5430 pF, loss tangent of ∼0.4 at 1 kHz and an unprecedented figure of merit of ∼105. We suggest a simple hypothesis for the γ-phase formation and evolution of the high dielectric constant in these composites. Further, the high-dielectric composite film showed marked improvements in mechanical and thermal

  9. Behaviorism Evolves.

    ERIC Educational Resources Information Center

    Cook, Donald A.

    1993-01-01

    Reviews basic ideas presented in this special issue on the evolution of behaviorism. Topics addressed include stimulus and response; research with animals; applications to education and training; human motivation; theory through computer programs; experimental analysis of behavior; behaviorism moving into other disciplines; cognitive…

  10. Classroom Behavior

    ERIC Educational Resources Information Center

    Segal, Carmit

    2008-01-01

    This paper investigates the determinants and malleability of noncognitive skills. Using data on boys from the National Education Longitudinal Survey, I focus on youth behavior in the classroom as a measure of noncognitive skills. I find that student behavior during adolescence is persistent. The variation in behavior can be attributed to…

  11. Behavioral Medicine.

    ERIC Educational Resources Information Center

    Garfield, Sol L., Ed.

    1982-01-01

    Contains 18 articles discussing the uses of behavioral medicine in such areas as obesity, smoking, hypertension, and headache. Reviews include discussions of behavioral medicine and insomnia, chronic pain, asthma, peripheral vascular disease, and coronary-prone behavior. Newly emerging topics include gastrointestinal disorders, arthritis,…

  12. Antecedent influences on behavior disorders.

    PubMed Central

    Smith, R G; Iwata, B A

    1997-01-01

    The influence of antecedent events on behavior disorders has been relatively understudied by applied behavior analysts. This lack of research may be due to a focus on consequences as determinants of behavior and a historical disagreement on a conceptual framework for describing and interpreting antecedent variables. We suggest that antecedent influences can be described using terms derived from basic behavioral principles and that their functional properties can be adequately interpreted as discriminative and establishing operations. A set of studies on assessment and treatment of behavior disorders was selected for review based on their relevance to the topic of antecedent events. These studies were categorized as focusing on assessment of antecedent events, antecedent treatments for behavior disorders maintained by either positive or negative reinforcement, and special cases of antecedent events in behavior disorders. Some directions for future research on antecedent influences in the analysis and treatment of behavior disorders are discussed. PMID:9210312

  13. Crack-Healing Behavior and Bending Strength Properties of SiC Ceramics Based on the Type of Additive SiO2 Employed

    NASA Astrophysics Data System (ADS)

    Nam, Ki Woo; Kim, Jong Soon; Park, Seung Won

    Silicon carbide (SiC) exhibits good strength at high temperatures and resistance to radioactivity. However, it has poor fracture toughness. The ability to heal cracks represents a very desirable means of overcoming this weakness. This study focuses on the crack-healing behavior and bending strength of SiC ceramics to which sintering additives have been added. Optimized crack-healing condition was found to be 1hr at an atmospheric level of 1100 °C. The maximum crack size that can be healed at the optimized condition was a semi-elliptical surface crack of 450 µm in diameter. Si oxide was revealed to be the principle material involved in crack-healing.

  14. Effects of plasma surface modification on interfacial behaviors and mechanical properties of carbon nanotube-Al{sub 2}O{sub 3} nanocomposites

    SciTech Connect

    Guo Yan; Cho, Hoonsung; Shi Donglu; Lian Jie; Song Yi; Abot, Jandro; Poudel, Bed; Ren Zhifeng; Wang Lumin; Ewing, Rodney C.

    2007-12-24

    The effects of plasma surface modification on interfacial behaviors in carbon nanotube (CNT) reinforced alumina (Al{sub 2}O{sub 3}) nanocomposites were studied. A unique plasma polymerization method was used to modify the surfaces of CNTs and Al{sub 2}O{sub 3} nanoparticles. The CNT-Al{sub 2}O{sub 3} nanocomposites were processed by both ambient pressure and hot-press sintering. The electron microscopy results showed ultrathin polymer coating on the surfaces of CNTs and Al{sub 2}O{sub 3} nanoparticles. A distinctive stress-strain curve difference related to the structural interfaces and plasma coating was observed from the nanocomposites. The mechanical performance and thermal stability of CNT-Al{sub 2}O{sub 3} nanocomposites were found to be significantly enhanced by the plasma-polymerized coating.

  15. Structural and magnetic properties and evidence of spin-glass behavior induced by Fe-doping in perovskite manganites B-site

    SciTech Connect

    Tlili, M.T.; Bejar, M.; Dhahri, E.; Sajieddine, M.; Valente, M.A.; Hlil, E.K.

    2011-02-15

    AMn{sub 1-x}Fe{sub x}O{sub 3} (A = La{sub 0.75}Ca{sub 0.08}Sr{sub 0.17} and x = 0-0.23) compounds, sintered at 700 deg. C, were characterized by X-ray diffraction (XRD) at room temperature. Rietveld refinement has shown that samples can be indexed in the orthorhombic (Pnma) structure for low Fe-content (x {<=} 0.046) and rhombohedral (R-3c) structure for high Fe-content (x {>=} 0.115). The transmission Moessbauer spectra have revealed the same isomer shift {delta} value assigned to Fe{sup 3+} ion for all compounds. The magnetization behavior and the Curie temperature T{sub C} have shown a large dependence on the fractional composition x. In fact, the M(T) curves have revealed the presence of a long-range ferromagnetic state below T{sub C} for compounds with x {<=} 0.115, and a spin-glass state (SGS) at low temperature for high Fe-content (x {>=} 0.177). Research Highlights: {yields} La{sub 0.75}Ca{sub 0.08}Sr{sub 0.17}Mn{sub 1-x}Fe{sub x}O{sub 3} compounds undergo a transition ortho-rhombo at x=0.046. {yields} On the rhombohedral phase, the magnetization is governed by the DE interaction {yields} The magnetization undergoes a strong decrease at high x-values (x{>=}0.115). {yields} Compounds show a strong AFM interaction with a spin-glass state at high Fe-content {yields} Hysteresis loops, M(H) confirm this behavior.

  16. Cortical Neuron Response Properties Are Related to Lesion Extent and Behavioral Recovery after Sensory Loss from Spinal Cord Injury in Monkeys

    PubMed Central

    Reed, Jamie L.; Gharbawie, Omar A.; Burish, Mark J.; Kaas, Jon H.

    2014-01-01

    Lesions of the dorsal columns at a mid-cervical level render the hand representation of the contralateral primary somatosensory cortex (area 3b) unresponsive. Over weeks of recovery, most of this cortex becomes responsive to touch on the hand. Determining functional properties of neurons within the hand representation is critical to understanding the neural basis of this adaptive plasticity. Here, we recorded neural activity across the hand representation of area 3b with a 100-electrode array and compared results from owl monkeys and squirrel monkeys 5–10 weeks after lesions with controls. Even after extensive lesions, performance on reach-to-grasp tasks returned to prelesion levels, and hand touches activated territories mainly within expected cortical locations. However, some digit representations were abnormal, such that receptive fields of presumably reactivated neurons were larger and more often involved discontinuous parts of the hand compared with controls. Hand stimulation evoked similar neuronal firing rates in lesion and control monkeys. By assessing the same monkeys with multiple measures, we determined that properties of neurons in area 3b were highly correlated with both the lesion severity and the impairment of hand use. We propose that the reactivation of neurons with near-normal response properties and the recovery of near-normal somatotopy likely supported the recovery of hand use. Given the near-completeness of the more extensive dorsal column lesions we studied, we suggest that alternate spinal afferents, in addition to the few spared primary axon afferents in the dorsal columns, likely have a major role in the reactivation pattern and return of function. PMID:24647955

  17. Sintering behavior of Cr in different atmospheres and its effect on the microstructure and properties of copper-based composite materials

    NASA Astrophysics Data System (ADS)

    Wang, Ye; Yan, Qing-zhi; Zhang, Fei-fei; Ge, Chang-chun; Zhang, Xiao-lu; Zhao, Hai-qin

    2013-12-01

    Copper matrix composites consisting of chromium (Cr) or ferrochrome (Cr-Fe) as strengthening elements and molybdenum disulfide as a lubricant had been sintered in nitrogen and hydrogen atmosphere, respectively. Their morphology and energy-dispersive X-ray spectrometry (EDS) analysis showed that serious interaction occurred between MoS2 and Cr (or Cr-Fe) particles when the samples were sintered in hydrogen atmosphere. Chromium sulfide compound (Cr x S y ) was formed as a reaction product, which decreased the density and strength of the composites remarkably. This interaction was inhibited when the samples were sintered in nitrogen atmosphere; thus, the mechanical properties of the composites were improved.

  18. Thermophysical properties

    SciTech Connect

    Kayser, R.F.

    1992-10-01

    Numerous fluids have been identified as promising alternative refrigerants, but much of the information needed to predict their behavior as pure fluids and as components in mixtures does not exist. In particular, reliable thermophysical properties data and models are needed to predict the performance of the new refrigerants in heating and cooling equipment, and to design and optimize equipment to be reliable and energy efficient. Objective of this project is to provide highly accurate, selected thermophysical properties data for Refrigerants 32, 123, 124, and 125, and to use these data to fit simple and complex equations of state and detailed transport property models. The new data will fill gaps in the existing data sets and resolve the problems and uncertainties that exist in and between the data sets. This report describes the progress made during the third quarter of this fifteen-month project, which was initiated in late January, 1992.

  19. Thermophysical properties

    SciTech Connect

    Kayser, R.F.

    1993-01-01

    Numerous fluids have been identified as promising alternative refrigerants, but much of the information needed to predict their behavior as pure fluids and as components in mixtures does not exist. In particular, reliable thermophysical properties data and models are needed to predict the performance of the new refrigerants in heating and cooling equipment and to design and optimize equipment to be reliable and energy efficient. The objective of this project is to provide highly accurate, selected thermophysical properties data for Refrigerants 32, 123, 124, and 125, and to use these data to fit simple and complex equations of state and detailed transport property models. The new data will fill gaps in the existing data sets and resolve the problems and uncertainties that exist in and between the data sets. This report describes the progress made during the fourth quarter of this fifteen-month project, which was initiated in late January, 1992.

  20. The influence of starch oxidization and aluminate coupling agent on interfacial interaction, rheological behavior, mechanical and thermal properties of poly(propylene carbonate)/starch blends

    NASA Astrophysics Data System (ADS)

    Jiang, Guo; Zhang, Shui-Dong; Huang, Han-Xiong; The Key Laboratory of Polymer Processing Engineering of the Ministry of Education Team

    Poly(propylene carbonate) (PPC) is a kind of new biodegradable polymer that is synthesized by copolymerization of propylene oxide and carbon dioxide. In this work, PPC end-capped with maleic anhydride (PPCMA)/thermoplastic starch (TPS), PPCMA/thermoplastic oxidized starch (TPOS) and PPCMA/AL-TPOS (TPOS modified by aluminate coupling agent) blends were prepared by melt blending to improve its thermal and mechanical properties. FTIR results showed that there existed hydrogen-bonding interaction between PPCMA and starch. SEM observation revealed that the compatibility between PPCMA and TPOS was improved by the oxidation of starch. The enhanced interfacial interactions between PPCMA and TPOS led to a better performance of PPC blends such as storage modulus (G'), loss modulus (G''), complex viscosity (η*), tensile strength and thermal properties. Furthermore, the modification of TPOS by aluminate coupling agent (AL) facilitated the dispersion of oxidized starch in PPC matrix, and resulted in increasing the tensile strength and thermal stability. National Natural Science Foundation of China, National Science Fund of Guangdong Province.

  1. Rat calvaria osteoblast behavior and antibacterial properties of O(2) and N(2) plasma-implanted biodegradable poly(butylene succinate).

    PubMed

    Wang, Huaiyu; Ji, Junhui; Zhang, Wei; Wang, Wei; Zhang, Yihe; Wu, Zhengwei; Zhang, Yumei; Chu, Paul K

    2010-01-01

    Poly(butylene succinate), a novel biodegradable aliphatic polyester with excellent processability and mechanical properties, was modified by O(2) or N(2) plasma immersion ion implantation (PIII). X-ray photoelectron spectroscopy and contact angle measurements were carried out to reveal the surface characteristics of the treated and control specimens. The in vitro effects of the materials on seeded osteoblasts were detected by cell viability assay, alkaline phosphatase activity test, and real-time polymerase chain reaction analysis. Plate counting was performed to investigate the antibacterial properties. Our results show that both PIII treatments significantly improve the hydrophilicity of PBSu, and CO and nitrogen groups (CNH and CNH(2)) can be detected on the PBSu after O(2) and N(2) PIII, respectively. The modified samples exhibit similar compatibility to osteoblasts, which is better than that of the control, but O(2) PIII and N(2) PIII produce different effects according to the osteogenic gene expressions of seeded osteoblasts on the materials. Moreover, the N(2) plasma-modified PBSu exhibits anti-infection effects against Staphylococcus aureus and Escherichia coli but no such effects can be achieved after O(2) PIII. PMID:19631768

  2. Theoretical survey on M@C80 (M = Ca, Sr, and Ba): Behavior of different alkaline earth metal impacting the chemical stability and electronic properties

    NASA Astrophysics Data System (ADS)

    Cui, Jin-Bo; Guo, Yi-Jun; Li, Qiao-Zhi; Zhao, Pei; Zhao, Xiang

    2016-08-01

    Structures of mono-metallofullerenes M@C80 (M = Ca, Sr, and Ba) that separated in early experiment are determined owning the C2v(31920)-C80 cage. The change rule of properties for M@C80 (M = Ca, Sr, and Ba) influenced by different inner metal are discussed. As the trapped metal changes from calcium to barium, performance of thermodynamic stabilities for M@C2v(31920)-C80, M@C2v(31922)-C80, and M@D5h(31923)-C80 are significantly different. Orbital analysis suggests that the lowest unoccupied molecular orbitals (LUMOs) of Ca@C2v(31920)-C80 and Ca@D5h(31923)-C80 are mostly located on the trapped metal, whereas reduction reactions of Ca@C2v(31920)-C80 and Ca@D5h(31923)-C80 occur on the fullerene cage. Natural electron configuration analyses demonstrates that the decentralized electron back-donation of Ba@C2v(31920)-C80 would take responsible for the instability of itself. Electronic properties such as electron affinities and ionization potentials are significantly affected by encapsulated metal are also found. Computational UV-visible-NIR spectra for M@C2v(31920)-C80 (M = Ca, Sr, Ba) are in perfect accord with the spectra obtained experimentally.

  3. An investigation on the effect of surface morphology and crystalline texture on corrosion behavior, structural and magnetic properties of electrodeposited nanocrystalline nickel films

    NASA Astrophysics Data System (ADS)

    Nasirpouri, F.; Sanaeian, M. R.; Samardak, A. S.; Sukovatitsina, E. V.; Ognev, A. V.; Chebotkevich, L. A.; Hosseini, M.-G.; Abdolmaleki, M.

    2014-02-01

    In this work, nanocrystalline nickel films with different surface morphologies were electrodeposited from Watts bath using direct (DC), pulsed (PC), and pulsed reverse (PRC) current techniques. The effect of electrodeposition conditions on the evolution of microstructure, cathodic efficiency, crystallographic micro-texture, micro-hardness, magnetic and corrosion properties of nickel films were investigated. Ni films electrodeposited by PC method revealed the highest cathodic efficiency due to minimum amount of hydrogen evolution. All films electrodeposited by PC and PRC methods making the films nanocrystalline (NC) exhibited greater hardness values and smaller crystallite size compared to those deposited by DC method. A preferential crystallographic orientation or texture was found in Ni films depending upon the electrodeposition pulse shape, as the microstructure is polycrystalline in the DC electrodeposited films, while exhibits <1 1 1> and <1 0 0> crystallographic growth directions for PC and PRC methods, respectively. Magnetic properties of the nanocrystalline Ni films indicate the existence of strong magnetocrystalline anisotropy depending on the microstructure of the films. Corrosion evaluation results showed that the PC electrodeposited NC-Ni films are more corrosion resistive in 2 mol/l NaOH solution, compared to those electrodeposited by PRC and DC methods. In contrast, in 0.5 mol/l H2SO4 solution, corrosion resistance of the films is in descending order from PC to PRC and DC.

  4. Interseismic deformation along the Mexican Subduction Zone: GPS-constrained coupling, and relationships with seismic and aseismic fault behavior, long term deformation and fault properties

    NASA Astrophysics Data System (ADS)

    Rousset, B.; Graham, S. E.; Cubas, N.; Radiguet, M.; Lasserre, C.; Socquet, A.; Campillo, M.; Walpersdorf, A.; Cotte, N.; DeMets, C.

    2013-12-01

    Recent observations have shown that a large diversity of mechanisms accommodates the deformation on subduction zones interfaces, especially with the discovery of slow slip events. Our study aims at comparing Oaxaca and Guerrero areas in the Mexican subduction zone. In these two areas, slow slip events have been discovered in the vicinity of seismic gaps, as well as tremor activity. We derive a regional, interseismic coupling map based on continuous GPS. It reveals lateral variations of coupling at shallow depth (0-25 km, offshore), with two well coupled zones (coupling > 0.7) alternating with two low coupled zones (coupling < 0.3). Below the continent, the entire zone is highly coupled (>0.7 as well), with a down dip, northern limit between coupled and uncoupled areas that is laterally homogeneous, at a distance of 170 km from the trench. Coupling spatial variations are first analyzed with respect to the spatial extension of Slow Slip Events, Tremors and Earthquakes. The analysis of the long-term morphology (bathymetry, topography, sedimentation, gravity) also highlights longitudinal variations, consistent in overall with the GPS-derived coupling variations. This suggests that these coupling variations are, to the first order, persistent over geological time scales (10^6 yr), and representative of fault plane properties that influence the building of the morphology. A mechanical analysis based on the critical tapper theory aims at reconciling geodetic observations and long term observations by determining lateral variations of frictional properties on critical areas of the subduction interface.

  5. Heat shrinkable behavior, physico-mechanical and structure properties of electron beam cross-linked blends of high-density polyethylene with acrylonitrile-butadiene rubber

    NASA Astrophysics Data System (ADS)

    Reinholds, Ingars; Kalkis, Valdis; Merijs-Meri, Remo; Zicans, Janis; Grigalovica, Agnese

    2016-03-01

    In this study, heat-shrinkable composites of electron beam irradiated high-density polyethylene (HDPE) composites with acrylonitrile-butadiene rubber (NBR) were investigated. HDPE/NBR blends at a ratio of components 100/0, 90/10, 80/20, 50/50 and 20/80 wt% were prepared using a two-roll mill. The compression molded films were irradiated high-energy (5 MeV) accelerated electrons up to irradiation absorbed doses of 100-300 kGy. The effect of electron beam induced cross-linking was evaluated by the changes of mechanical properties, gel content and by the differences of thermal properties, detected by differential scanning calorimetry. The thermo-shrinkage forces were determined as the kinetics of thermorelaxation and the residual shrinkage stresses of previously oriented (stretched up to 100% at above melting temperature of HDPE and followed by cooling to room temperature) specimens of irradiated HDPE/NBR blends under isometric heating-cooling mode. The compatibility between the both components was enhanced due to the formation of cross-linked sites at amorphous interphase. The results showed increase of mechanical stiffness of composites with increase of irradiation dose. The values of gel fraction compared to thermorelaxation stresses increased with the growth of irradiation dose level, as a result of formation cross-linked sites in amorphous PP/NBR interphase.

  6. Electrochemical corrosion behavior, microstructure and magnetic properties of sintered Nd-Fe-B permanent magnet doped by CuZn5 powders

    NASA Astrophysics Data System (ADS)

    Liu, W. Q.; Wang, Z.; Sun, C.; Yue, M.; Liu, Y. Q.; Zhang, D. T.; Zhang, J. X.

    2014-05-01

    Nd-Fe-B permanent magnets with a small amount of CuZn5 powders doping were prepared by conventional sintered method. The effects of CuZn5 contents on magnetic properties and microstructure, electrochemical corrosion resistance of sintered Nd-Fe-B magnets were systematically studied. The results show that the magnetic properties of magnets do not have a significant variation by CuZn5 powders doping; the coercivity of magnets rises gradually, while the remanence of the magnets decreases a little with increasing of the CuZn5 amount. The CuZn5 doped magnets have more positive corrosion potential, Ecorr, and much lower corrosion current density, icorr, than the magnets without CuZn5 doping, indicating CuZn5 doping could improve the corrosion resistance. Both Zn and Cu enrich mainly into the Nd-rich phase, fully improve the wettability between the Nd-rich phase and the Nd2Fe14B phase, and repair the defects of the main phase, so the coercivity of magnets doped with CuZn5 powders rises. Such microstructure modification effectively restrains the aggressive inter-granular corrosion. As a result, the CuZn5 doped magnet possesses excellent corrosion resistance in NaCl electrolyte.

  7. Making Behavioral Activation More Behavioral

    ERIC Educational Resources Information Center

    Kanter, Jonathan W.; Manos, Rachel C.; Busch, Andrew M.; Rusch, Laura C.

    2008-01-01

    Behavioral Activation, an efficacious treatment for depression, presents a behavioral theory of depression--emphasizing the need for clients to contact positive reinforcement--and a set of therapeutic techniques--emphasizing provision of instructions rather than therapeutic provision of reinforcement. An integration of Behavioral Activation with…

  8. Neuroscientific Measures of Covert Behavior

    ERIC Educational Resources Information Center

    Ortu, Daniele

    2012-01-01

    In radical behaviorism, the difference between overt and covert responses does not depend on properties of the behavior but on the sensitivity of the measurement tools employed by the experimenter. Current neuroscientific research utilizes technologies that allow measurement of variables that are undetected by the tools typically used by behavior…

  9. Structure, sintering behavior, and microwave dielectric properties of (1 − x) CaWO{sub 4}–xYLiF{sub 4} (0.02 ≤ x ≤ 0.10) ceramics

    SciTech Connect

    Bian, Jian Jiang Ding, Yao Min

    2015-07-15

    Highlights: • Structure, sinterability, and dielectric properties of CaWO{sub 4}–YLiF{sub 4} were studied. • CaWO{sub 4} can be densified (TD 97%) at 750 °C/2 h by YLiF{sub 4} doping. • Excellent microwave dielectric properties could be obtained. - Abstract: Structures and sintering behaviors of (1 − x) CaWO{sub 4}–xYLiF{sub 4} (0.02 ≤ x ≤ 0.10) ceramic have been investigated by X-ray powder diffraction (XRD), dilatometry, scanning electron microscopy (SEM) in this work. The microwave dielectric properties were measured with a network analyzer at the frequency of about 8–15 GHz. Limited solid solution could be formed within the compositional range of x < 0.1. The sintering temperature of CaWO{sub 4} could successfully be reduced to ∼750 °C/2 h by doping with small amount of YLiF{sub 4}. An optimized microwave dielectric properties with ϵ{sub r} = 10.5, Q × f = 73 000 GHz and τ{sub f} = −37.7 ppm/°C could be obtained after sintered at the 750 °C for 2 h for x = 0.04 compositions. XRD and back scattering SEM analysis indicated that the (1 − x) CaWO{sub 4}–xYLiF{sub 4} (x = 0.04) ceramic could be chemically compatible with Ag after sintering at 750 °C/2 h.

  10. Francis Bacon's behavioral psychology.

    PubMed

    MacDonald, Paul S

    2007-01-01

    Francis Bacon offers two accounts of the nature and function of the human mind: one is a medical-physical account of the composition and operation of spirits specific to human beings, the other is a behavioral account of the character and activities of individual persons. The medical-physical account is a run-of-the-mill version of the late Renaissance model of elemental constituents and humoral temperaments. The other, less well-known, behavioral account represents an unusual position in early modern philosophy. This theory espouses a form of behavioral psychology according to which (a) supposed mental properties are "hidden forms" best described in dispositional terms, (b) the true character of an individual can be discovered in his observable behavior, and (c) an "informed" understanding of these properties permits the prediction and control of human behavior. Both of Bacon's theories of human nature fall under his general notion of systematic science: his medical-physical theory of vital spirits is theoretical natural philosophy and his behavioral theory of disposition and expression is operative natural philosophy. Because natural philosophy as a whole is "the inquiry of causes and the production of effects," knowledge of human nature falls under the same two-part definition. It is an inquisition of forms that pertains to the patterns of minute motions in the vital spirits and the production of effects that pertains both to the way these hidden motions produce behavioral effects and to the way in which a skillful agent is able to produce desired effects in other persons' behavior. PMID:17623872

  11. Towards Behavioral Reflexion Models

    NASA Technical Reports Server (NTRS)

    Ackermann, Christopher; Lindvall, Mikael; Cleaveland, Rance

    2009-01-01

    Software architecture has become essential in the struggle to manage today s increasingly large and complex systems. Software architecture views are created to capture important system characteristics on an abstract and, thus, comprehensible level. As the system is implemented and later maintained, it often deviates from the original design specification. Such deviations can have implication for the quality of the system, such as reliability, security, and maintainability. Software architecture compliance checking approaches, such as the reflexion model technique, have been proposed to address this issue by comparing the implementation to a model of the systems architecture design. However, architecture compliance checking approaches focus solely on structural characteristics and ignore behavioral conformance. This is especially an issue in Systems-of- Systems. Systems-of-Systems (SoS) are decompositions of large systems, into smaller systems for the sake of flexibility. Deviations of the implementation to its behavioral design often reduce the reliability of the entire SoS. An approach is needed that supports the reasoning about behavioral conformance on architecture level. In order to address this issue, we have developed an approach for comparing the implementation of a SoS to an architecture model of its behavioral design. The approach follows the idea of reflexion models and adopts it to support the compliance checking of behaviors. In this paper, we focus on sequencing properties as they play an important role in many SoS. Sequencing deviations potentially have a severe impact on the SoS correctness and qualities. The desired behavioral specification is defined in UML sequence diagram notation and behaviors are extracted from the SoS implementation. The behaviors are then mapped to the model of the desired behavior and the two are compared. Finally, a reflexion model is constructed that shows the deviations between behavioral design and implementation. This

  12. Behavioral effects of microwaves

    SciTech Connect

    Stern, S.

    1980-01-01

    Microwaves can produce sensations of warmth and sound in humans. In other species, they also can serve as cues, they may be avoided, and they can disrupt ongoing behavior. These actions appear to be due to heat produced by energy absorption. The rate of absorption depends on the microwave parameters and the electrical and geometric properties of the subject. We therefore, cannot predict the human response to microwaves based on data from other animals without appropriate scaling considerations. At low levels of exposure, microwaves can produce changes in behavior without large, or even measureable, changes in body temperature. Thermoregulatory behavior may respond to those low levels of heat, and thereby affect other behavior occurring concurrently. There are no data that demonstrate that behavioral effects of microwaves depend on any mechanism other than reactions to heat. Our interpretation of whether a reported behavioral effect indicates that microwaves may be hazardous depends on our having a complete description of the experiment and on our criteria of behavioral toxicity.

  13. Influence of U doping on the growth behavior, electronic structure and magnetic properties of Pdn (n = 1-12) clusters: a first principles study

    NASA Astrophysics Data System (ADS)

    Chattaraj, Debabrata; Parida, Suresh Chandra; Dash, Smruti; Majumder, Chiranjib

    2014-10-01

    The influence of U doping on the structural, electronic and magnetic properties of Pdn clusters was investigated using the spin-polarized DFT including the spin-orbit coupling term. The results reveal significant alterations in the geometry of the Pdn clusters in presence of U. Unlike Pdn, where 3D structure onsets at n = 4, for UPdn-1 cluster, it is at n = 6. The energetics of Pdn and UPdn-1 clusters suggests that the incorporation of U in Pdn clusters not only improves the stability but also quenches the unusual magnetic moment of Pdn clusters. These features have been explained by the strong f-d orbitals interactions. Supplementary material in the form of one pdf file available from the Journal web page at http://http//dx.doi.org/10.1140/epjd/e2014-50080-0

  14. Impact of seed layer on post-annealing behavior of transport and magnetic properties of Co/Pt multilayer-based bottom-pinned perpendicular magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Chatterjee, Jyotirmoy; Tahmasebi, Taiebeh; Swerts, Johan; Sankar Kar, Gouri; De Boeck, Jo

    2015-06-01

    The magnetic and transport properties of Co/Pt multilayer-based bottom-pinned perpendicular magnetic tunnel junctions (pMTJs) on Ru, Hf, and Ru/Hf seed layers (SLs) were investigated after annealing at different temperatures. The perpendicular synthetic antiferromagnetic (pSAF) layer on the Ru SL was found to be thermally robust (after annealing at 400 °C for 30 min). A high tunnel magnetoresistance (TMR) ratio of 100% was achieved at a low resistance-area product (5.5 Ω·µm2) and was stable up to 350 °C. For the stack on Ru SL, TMR degradation after annealing was caused by the degradation of the pMTJ (CoFeB/MgO/CoFeB), while in the Hf and Ru/Hf SL, both the pMTJ and pSAF were affected.

  15. Structure, Mechanical Properties, and Fracture Behavior of a Fe-Cr-V Alloy Doped with Nitrogen by High-Temperature Gas-Phase Nitriding

    NASA Astrophysics Data System (ADS)

    Nikulin, Sergey A.; Khatkevich, Vladimir M.; Rogachev, Stanislav O.; Denisenko, Kristina S.

    2015-12-01

    The microstructure, phase composition, and room-temperature mechanical properties of the corrosion-resistant Fe-20pctCr-5pctV alloy doped with nitrogen by high-temperature gas-phase nitriding under different conditions have been investigated. The nitriding of the Fe-20pctCr-5pctV alloy at T = 1223 K to 1373 K (950 °C to 1100 °C) and subsequent annealing at T = 973 K (700 °C) lead to the precipitation of large vanadium nitride and disperse chromium nitride particles in the ferrite matrix. Such a treatment increases the strength of the Fe-20pctCr-5pctV alloy at room temperature by 1.6 times, while maintaining the adequate relative elongation. The alloy in the initial state and after nitriding is highly resistant to corrosion.

  16. Adhesion property and high-temperature oxidation behavior of Cr-coated Zircaloy-4 cladding tube prepared by 3D laser coating

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Gil; Kim, Il-Hyun; Jung, Yang-Il; Park, Dong-Jun; Park, Jeong-Yong; Koo, Yang-Hyun

    2015-10-01

    A 3D laser coating technology using Cr powder was developed for Zr-based alloys considering parameters such as: the laser beam power, inert gas flow, cooling of Zr-based alloys, and Cr powder control. This technology was then applied to Zr cladding tube samples to study the effect of Cr coating on the high-temperature oxidation of Zr-based alloys in a steam environment of 1200 °C for 2000s. It was revealed that the oxide layer thickness formed on the Cr-coated tube surface was about 25-times lower than that formed on a Zircaloy-4 tube surface. In addition, both the ring compression and the tensile tests were performed to evaluate the adhesion properties of the Cr-coated sample. Although some cracks were formed on the Cr-coated layer, the Cr-coated layer had not peeled off after the two tests.

  17. Properties of V1 neurons tuned to conjunctions of visual features: application of the V1 saliency hypothesis to visual search behavior.

    PubMed

    Zhaoping, Li; Zhe, Li

    2012-01-01

    From a computational theory of V1, we formulate an optimization problem to investigate neural properties in the primary visual cortex (V1) from human reaction times (RTs) in visual search. The theory is the V1 saliency hypothesis that the bottom-up saliency of any visual location is represented by the highest V1 response to it relative to the background responses. The neural properties probed are those associated with the less known V1 neurons tuned simultaneously or conjunctively in two feature dimensions. The visual search is to find a target bar unique in color (C), orientation (O), motion direction (M), or redundantly in combinations of these features (e.g., CO, MO, or CM) among uniform background bars. A feature singleton target is salient because its evoked V1 response largely escapes the iso-feature suppression on responses to the background bars. The responses of the conjunctively tuned cells are manifested in the shortening of the RT for a redundant feature target (e.g., a CO target) from that predicted by a race between the RTs for the two corresponding single feature targets (e.g., C and O targets). Our investigation enables the following testable predictions. Contextual suppression on the response of a CO-tuned or MO-tuned conjunctive cell is weaker when the contextual inputs differ from the direct inputs in both feature dimensions, rather than just one. Additionally, CO-tuned cells and MO-tuned cells are often more active than the single feature tuned cells in response to the redundant feature targets, and this occurs more frequently for the MO-tuned cells such that the MO-tuned cells are no less likely than either the M-tuned or O-tuned neurons to be the most responsive neuron to dictate saliency for an MO target. PMID:22719829

  18. P(AAm-co-MAA) semi-IPN hybrid hydrogels in the presence of PANI and MWNTs-COOH: improved swelling behavior and mechanical properties.

    PubMed

    Liu, Zhanqing; Luo, Yanling; Zhang, Kaipu

    2008-01-01

    A highly pH-sensitive hybrid hydrogel with semi-interpenetrating networks (semi-IPN)composed of co-polymer networks of acrylamide-methacrylic acid (P(AAm-co-MAA)) and polyaniline (PANI)/carboxyl-functionalized multi-walled carbon nanotubes (MWNTs-COOH) was designed and synthesized by a cross-linking co-polymerization route in the presence of N,N-methylene bisacrylamide (BIS) and ammonium persulfate (APS). The structural and morphological characterization and mechanical properties of the gels were investigated using a Equinx55 FT-IR spectrometer, an environmental scanning electron microscope and a dynamical viscoelasticity analyzer, respectively. Swelling capability of the hybrid hydrogels was examined under the conditions of various pH buffer solutions (1.35, 6.95 and 12.86) at a temperature of 27 degrees C. P(AAm-co-MAA) co-polymer hydrogels were discussed as a control sample at the same time. The experimental results indicated that the prepared P(AAm-co-MAA) co-polymer hydrogels showed a high equilibrium swelling ratio in distilled water, pH-responsive characteristics and excellent strain recoverability. After having incorporated the polyelectrolyte PANI and MWNTs-COOH into the above-mentioned network, the P(AAm-co-MAA)/PANI/MWNTs-COOH semi-IPN hybrid hydrogels obtained possessed an even higher sensitivity to pH environments, good swelling reversibility, higher ultimate compressive strength and good strain recoverable ability. Swelling experimentations in buffer solutions of different pH revealed that the semi-IPN hybrid hydrogels possessed higher tensile strengths at a lower pH than at a higher pH value. All the excellent properties may primarily be attributed to the formation and weakening or disappearance of a repulsive force based on hydrogen bonds, as well as appearance of attractive forces of pole-pole interactions between PANI chains at different pH values. PMID:18973726

  19. Relaxor Behavior and Dielectric Properties of Bi(Zn2/3Nb1/3)O3-Modified BaTiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Xiuli; Chen, Jie; Huang, Guisheng; Ma, Dandan; Fang, Lang; Zhou, Huanfu

    2015-12-01

    (1 - x)BaTiO3- xBi(Zn2/3Nb1/3)O3 [(1 - x)BT- xBZN, 0 ≤ x ≤ 0.2] ceramics were prepared via a conventional solid-state reaction method. X-ray diffraction (XRD) patterns and Raman spectra analysis show that the ceramics are tetragonal phase when x ≤ 0.02, and transform to pseudocubic phase as x ≥ 0.06. The temperature and frequency dependences of relative permittivity indicate a gradual crossover from a classic ferroelectric to relaxor ferroelectric. The dielectric relaxor behavior follows a modified Curie-Weiss law. The degree of the phase transition diffuseness ( γ) and the deviation from the Curie-Weiss law (Δ T_{{d}} ) increase to the maximum at x = 0.08, and subsequently decrease with further increasing x values, which associated with the appearance of polar nanoregions on account of the formation of random fields included local electric fields and elastic fields. Nevertheless, the random fields may decrease by reason of the interaction between the local electric fields and elastic fields.

  20. Emulsifying properties and oil/water (O/W) interface adsorption behavior of heated soy proteins: effects of heating concentration, homogenizer rotating speed, and salt addition level.

    PubMed

    Cui, Zhumei; Chen, Yeming; Kong, Xiangzhen; Zhang, Caimeng; Hua, Yufei

    2014-02-19

    The adsorption of heat-denatured soy proteins at the oil/water (O/W) interface during emulsification was studied. Protein samples were prepared by heating protein solutions at concentrations of 1-5% (w/v) and were then diluted to 0.3% (w/v). The results showed that soy proteins that had been heated at higher concentrations generated smaller droplet size of emulsion. Increase in homogenizer rotating speed resulted in higher protein adsorption percentages and lower surface loads at the O/W interface. Surface loads for both unheated and heated soy proteins were linearly correlated with the unadsorbed proteins' equilibrium concentration at various rotating speeds. With the rise in NaCl addition level, protein adsorption percentage and surface loads of emulsions increased, whereas lower droplet sizes were obtained at the ionic strength of 0.1 M. The aggregates and non-aggregates displayed different adsorption behaviors when rotating speed or NaCl concentration was varied. PMID:24460091

  1. Improving the degradation behavior and in vitro biological property of nano-hydroxyapatite surface- grafted with the assist of citric acid.

    PubMed

    Jiang, Liuyun; Jiang, Lixin; Xiong, Chengdong; Su, Shengpei

    2016-10-01

    To obtain ideal nano-hydroxyapatite(n-HA) filler for poly(lactide-co-glycolide) (PLGA), a new surface-grafting with the assist of citric acid for nano-hydroxyapatite (n-HA) was designed, and the effect of n-HA surface-grafted with or without citric acid on in vitro degradation behavior and cells viability was studied by the experiments of soaking in simulated body fluid (SBF) and incubating with human osteoblast-like cells (MG-63). The change of pH value, tensile strength reduction, the surface deposits, cells attachment and proliferation of samples during the soaking and incubation were investigated by means of pH meter, electromechanical universal tester, scanning electron microscope (SEM) coupled with energy-dispersive spectro-scopy (EDS), fluorescence microscope and MTT method. The results showed that the introduction of citric acid not only delayed the strength reduction during the degradation by inhibiting the detachment of n-HA from PLGA, but also endowed it better cell attachment and proliferation, suggesting that the n-HA surface-grafted with the assist of citric acid was an important bioactive ceramic fillers for PLGA used as bone materials. PMID:27343845

  2. Supramolecular Assembly of Molecular Rare-Earth-3,5-Dichlorobenzoic Acid-2,2':6',2″-Terpyridine Materials: Structural Systematics, Luminescence Properties, and Magnetic Behavior.

    PubMed

    Carter, Korey P; Thomas, Kara E; Pope, Simon J A; Holmberg, Rebecca J; Butcher, Ray J; Murugesu, Muralee; Cahill, Christopher L

    2016-07-18

    The syntheses and crystal structures of 16 new rare-earth (RE = La(3+)-Y(3+))-3,5-dichlorobenzoic acid-terpyridine molecular materials characterized via single-crystal and powder X-ray diffraction are reported. These 16 complexes consist of four unique structure types ranging from molecular dimers (La(3+) and Ce(3+)) to tetramers (Pr(3+)-Y(3+)) as one moves across the RE(3+) series. This structural evolution is accompanied by subsequent changes in modes of supramolecular assembly (halogen bonding, halogen-π, halogen-halogen, and π-π interactions). Solid-state visible and near-infrared lifetime measurements were performed on complexes 6 (Sm(3+)), 7 (Eu(3+)), 9 (Tb(3+)), 10 (Dy(3+)), 11 (Ho(3+)), 12 (Er(3+)), and 14 (Yb(3+)), and characteristic emission was observed for all complexes except 11. Lifetime data for 11, 12, and 14 suggest sensitization by the terpy antenna does occur in near-infrared systems, although not as efficiently as in the visible region. Additionally, direct current magnetic susceptibility measurements were taken for complexes 10 (Dy(3+)) and 12 (Er(3+)) and showed dominant ferromagnetic behavior. PMID:27347607

  3. The evaluation of physical properties and in vitro cell behavior of PHB/PCL/sol-gel derived silica hybrid scaffolds and PHB/PCL/fumed silica composite scaffolds.

    PubMed

    Ding, Yaping; Yao, Qingqing; Li, Wei; Schubert, Dirk W; Boccaccini, Aldo R; Roether, Judith A

    2015-12-01

    PHB/PCL/sol-gel derived silica hybrid scaffolds (P5S1S) and PHB/PCL/fumed silica composite scaffolds (P5S1N) with a 5:1 organic/inorganic ratio were fabricated through a combination of electrospinning and sol-gel methods and dispersion electrospinning, respectively. In contrast to the silica nanoparticle aggregates appearing on the fiber surface of P5S1N, smooth and uniform fibers were obtained for P5S1S. The fiber diameter distribution, tensile strength, thermal gravimetric analysis (TGA), and cellular behavior of both types of scaffolds were characterized and studied. The tensile strength results and TGA indicated that the interfacial interaction between the organic and the inorganic phase was enhanced in P5S1S over the nanocomposite scaffolds, and cells exhibited significantly higher alkaline phosphate activity (ALP) for P5S1S, which makes P5S1S hybrid scaffolds candidate materials for bone tissue engineering applications. PMID:26364089

  4. Drosophila mutants of the autism candidate gene neurobeachin (rugose) exhibit neuro-developmental disorders, aberrant synaptic properties, altered locomotion, impaired adult social behavior and activity patterns

    PubMed Central

    Wise, Alexandra; Tenezaca, Luis; Fernandez, Robert W.; Schatoff, Emma; Flores, Julian; Ueda, Atsushi; Zhong, Xiaotian; Wu, Chun-Fang; Simon, Anne F.; Venkatesh, Tadmiri

    2016-01-01

    Autism spectrum disorder (ASD) is a neurodevelopmental disorder in humans characterized by complex behavioral deficits, including intellectual disability, impaired social interactions and hyperactivity. ASD exhibits a strong genetic component with underlying multi-gene interactions. Candidate gene studies have shown that the neurobeachin gene is disrupted in human patients with idiopathic autism (Castermans et al., 2003). The gene for neurobeachin (NBEA) spans the common fragile site FRA 13A and encodes a signal scaffold protein (Savelyeva et al., 2006). In mice, NBEA has been shown to be involved in the trafficking and function of a specific subset of synaptic vesicles. (Medrihan et al., 2009; Savelyeva, Sagulenko, Schmitt, & Schwab, 2006). rugose (rg) is the Drosophila homologue of the mammalian and human neurobeachin. Our previous genetic and molecular analyses have shown that rg encodes an A kinase anchor protein (DAKAP 550), which interacts with components of the EGFR and Notch mediated signaling pathways, facilitating cross-talk between these and other pathways (Shamloula et al., 2002). We now present functional data from studies on the larval neuromuscular junction that reveal abnormal synaptic architecture and physiology. In addition, adult rg loss-of-function mutants exhibit defective social interactions, impaired habituation, aberrant locomotion and hyperactivity. These results demonstrate that Drosophila neurobeachin (rugose) mutants exhibit phenotypic characteristics reminiscent of human ASD and thus could serve as a genetic model for studying autism spectrum disorders. PMID:26100104

  5. Controlled synthesis, asymmetrical transport behavior and luminescence properties of lanthanide doped ZnO mushroom-like 3D hierarchical structures.

    PubMed

    Yue, Dan; Lu, Wei; Jin, Lin; Li, Chunyang; Luo, Wen; Wang, Mengnan; Wang, Zhenling; Hao, Jianhua

    2014-11-21

    Lanthanide doped ZnO mushroom-like 3D hierarchical structures have been fabricated by polyol-mediated method and characterized by various microstructural and optical techniques. The results indicate that the as-prepared ZnO:Ln(3+) (Ln = Tb, Eu) samples have a hexagonal phase structure and possess a mushroom-like 3D hierarchical morphology. The length of the whole mushroom from stipe bottom to pileus top is about 1.0 μm, and the diameters of pileus and stipe are about 0.8 μm and 0.4 μm, respectively. It is found that the flow of N2 is the key parameter for the formation of the novel ZnO structure and the addition of (NH4)2HPO4 has a prominent effect on the phase structure and the growth of mushroom-like morphology. The potential mechanism of forming this morphology is proposed. The pileus of the formed mushroom is assembled by several radial ZnO:Ln(3+) nanorods, whereas the stipe is composed of over layered ZnO:Ln(3+) nanosheets. Moreover, asymmetrical I-V characteristic curves of ZnO:Ln(3+) mushrooms indicate that the texture composition of the 3D hierarchical morphology might lead to the asymmetrical transport behavior of electrical conductivity. Lanthanide doped ZnO samples can exhibit red or green emission under the excitation of UV light. PMID:25293373

  6. Advances and challenges in analytical characterization of biotechnology products: mass spectrometry-based approaches to study properties and behavior of protein therapeutics

    PubMed Central

    Kaltashov, Igor A.; Bobst, Cedric E.; Abzalimov, Rinat R.; Wang, Guanbo; Baykal, Burcu; Wang, Shunhai

    2011-01-01

    Biopharmaceuticals are a unique class of medicines due to their extreme structural complexity. The structure of these therapeutic proteins is critically important for their efficacy and safety, and the ability to characterize it at various levels (from sequence to conformation) is critical not only at the quality control stage, but also throughout the discovery and design stages. Biological mass spectrometry (MS) offers a variety of approaches to study structure and behavior of complex protein drugs and has already become a default tool for characterizing the covalent structure of protein therapeutics, including sequence and post-translational modifications. Recently, MS-based methods have also begun enjoying a dramatic growth in popularity as a means to provide information on higher order structure and dynamics of biotechnology products. In particular, hydrogen/deuterium exchange MS and charge state distribution analysis of protein ions in electrospray ionization (ESI)MS offer a convenient way to assess the integrity of protein conformation. Native ESI MS also allows the interactions of protein drugs with their therapeutic targets and other physiological partners to be monitored using simple model systems. MS-based methods are also applied to study pharmacokinetics of biopharmaceutical products, where they begin to rival traditional immunoassays. MS already provides valuable support to all stages of development of biopharmaceuticals, from discovery to post-approval monitoring, and its impact on the field of biopharmaceutical analysis will undoubtedly continue to grow. PMID:21619926

  7. Synthesis, crystal structure, high-temperature behavior and magnetic properties of CoBiO(AsO4), a Co analogue of paganoite

    NASA Astrophysics Data System (ADS)

    Aliev, Almaz; Kozin, Michael S.; Colmont, Marie; Siidra, Oleg I.; Krivovichev, Sergey V.; Mentré, Olivier

    2015-09-01

    Single crystals and powder samples of Co analogue of paganoite CoBiO(AsO4) have been obtained by high-temperature solid-state reactions. Crystal structure [triclinic, , a = 5.2380(3), b = 6.8286(4), c = 7.6150(4) Å, α = 111.631(2), β = 108.376(2), γ = 108.388(2)°, V = 209.55(2) Å3] has been refined to R 1 = 0.018 on the basis of 1524 unique observed reflections. CoBiO(AsO4) is isotypic to paganoite, NiBiO(AsO4). The crystal structure can be described as based upon [OCoBi]3+ chains of edge-sharing (OBi2Co2) tetrahedra linked via (AsO4) groups. Differential thermal analysis reveals no phase decomposition till 850 °C, when the compound starts to melt. A small endothermic peak is observed near 330 °C. Thermal expansion has been studied by high-temperature powder X-ray diffraction. Thermal expansion coefficients ( α a = 10.1 × 10-6, α b = 12.6 × 10-6, α c = 10.5 × 10-6 K-1) indicate a relatively isotropic behavior with the less intense expansion direction parallel to the direction of the chains of oxocentered tetrahedra. Magnetic susceptibility of CoBiO(AsO4) reveals the presence of an antiferromagnetic ordering at T N = 15.4 K.

  8. Microstructures, Mechanical Properties, and Strain Hardening Behavior of an Ultrahigh Strength Dual Phase Steel Developed by Intercritical Annealing of Cold-Rolled Ferrite/Martensite

    NASA Astrophysics Data System (ADS)

    Mazaheri, Y.; Kermanpur, A.; Najafizadeh, A.

    2015-07-01

    A dual phase (DP) steel was produced by a new process utilizing an uncommon cold-rolling and subsequent intercritical annealing of a martensite-ferrite duplex starting structure. Ultrafine grained DP steels with an average grain size of about 2 μm and chain-networked martensite islands were achieved by short intercritical annealing of the 80 pct cold-rolled duplex microstructure. The strength of the low carbon steel with the new DP microstructure was reached about 1300 MPa (140 pct higher than that of the as-received state, e.g., 540 MPa), without loss of ductility. Tensile testing revealed good strength-elongation balance for the new DP steels (UTS × UE ≈ 11,000 to 15,000 MPa pct) in comparison with the previous works and commercially used high strength DP steels. Two strain hardening stages with comparable exponents were observed in the Holloman analysis of all DP steels. The variations of hardness, strength, elongation, and strain hardening behavior of the specimens with thermomechanical parameters were correlated to microstructural features.

  9. Study of mechanical properties and high temperature oxidation behavior of a novel cold-spray Ni-20Cr coating on boiler steels

    NASA Astrophysics Data System (ADS)

    Kaur, Narinder; Kumar, Manoj; Sharma, Sanjeev K.; Kim, Deuk Young; Kumar, S.; Chavan, N. M.; Joshi, S. V.; Singh, Narinder; Singh, Harpreet

    2015-02-01

    In the current investigation, high temperature oxidation behavior of a novel cold-spray Ni-20Cr nanostructured coating was studied. The nanocrystalline Ni-20Cr powder was synthesized by the investigators using ball milling, which was deposited on T22 and SA 516 steels by cold spraying. The crystallite size based upon Scherrer's formula for the developed coatings was found to be in nano-range for both the substrates. The accelerated oxidation testing was performed in a laboratory tube furnace at a temperature 900 °C under thermal cyclic conditions. Each cycle comprised heating for one hour at 900 °C followed by cooling for 20 min in ambient air. The kinetics of oxidation was established using weight change measurements for the bare and the coated steels. The oxidation products were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and X-ray mapping techniques. It was found from the results that the coating was successful in reducing the weight gain of SA213-T22 and SA 516-Grade 70 steel by 71% and 94%, respectively. This may be attributed to relatively denser structure, lower porosity and lower oxide content of the coating. Moreover, the developed nano-structured Ni-20Cr powder coating was found to perform better than its counterpart micron-sized Ni-20Cr powder coating, in terms of offering higher oxidation resistance and hardness.

  10. Energy-storage properties and high-temperature dielectric relaxation behaviors of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Zhang, T. F.; Tang, X. G.; Liu, Q. X.; Jiang, Y. P.; Huang, X. X.; Zhou, Q. F.

    2016-03-01

    (1  -  x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (x  =  0, 5, and 10 mol%) ceramics were prepared using a conventional mixed oxide solid state reaction method. The low-temperature relaxor behavior of (1  -  x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 ceramics were examined in the temperature range from 120 to 523 K. A broad dielectric maximum that shifted to higher temperatures with increasing frequency, signified the relaxor-type behavior of these ceramics. The value of the relaxation parameter γ  =  1.61-1.94 estimated from the linear fit of the modified Curie-Weiss law indicated the relaxor nature. High-temperature dielectric relaxation phenomena were found in the temperature region 600-850 K. Energy-storage properties were also analyzed, and the energy-storage density calculated from hysteresis loops reached about 0.47 J cm-3 at room temperature.

  11. Functions of Maladaptive Behavior in Intellectual and Developmental Disabilities: Behavior Categories and Topographies

    ERIC Educational Resources Information Center

    Rojahn, Johannes; Zaja, Rebecca H.; Turygin, Nicole; Moore, Linda; van Ingen, Daniel J.

    2012-01-01

    Research has shown that different maladaptive behavior categories may be maintained by different contingencies. We examined whether behavior categories or behavior topographies determine functional properties. The "Questions about Behavioral Function" with its five subscales ("Attention", "Escape", "Nonsocial", "Physical", and "Tangible") was…

  12. Behavior modification.

    PubMed

    Pelham, W E; Fabiano, G A

    2000-07-01

    Attention deficit/hyperactivity disorder (ADHD) is a chronic and substantially impairing disorder. This means that treatment must also be chronic and substantial. Behavior Modification, and in many cases, the combination of behavior modification and stimulant medication, is a valid, useful treatment for reducing the pervasive impairment experienced by children with ADHD. Based on the research evidence reviewed, behavior modification should be the first line of treatment for children with ADHD. PMID:10944662

  13. Controlled synthesis, asymmetrical transport behavior and luminescence properties of lanthanide doped ZnO mushroom-like 3D hierarchical structures

    NASA Astrophysics Data System (ADS)

    Yue, Dan; Lu, Wei; Jin, Lin; Li, Chunyang; Luo, Wen; Wang, Mengnan; Wang, Zhenling; Hao, Jianhua

    2014-10-01

    Lanthanide doped ZnO mushroom-like 3D hierarchical structures have been fabricated by polyol-mediated method and characterized by various microstructural and optical techniques. The results indicate that the as-prepared ZnO:Ln3+ (Ln = Tb, Eu) samples have a hexagonal phase structure and possess a mushroom-like 3D hierarchical morphology. The length of the whole mushroom from stipe bottom to pileus top is about 1.0 μm, and the diameters of pileus and stipe are about 0.8 μm and 0.4 μm, respectively. It is found that the flow of N2 is the key parameter for the formation of the novel ZnO structure and the addition of (NH4)2HPO4 has a prominent effect on the phase structure and the growth of mushroom-like morphology. The potential mechanism of forming this morphology is proposed. The pileus of the formed mushroom is assembled by several radial ZnO:Ln3+ nanorods, whereas the stipe is composed of over layered ZnO:Ln3+ nanosheets. Moreover, asymmetrical I-V characteristic curves of ZnO:Ln3+ mushrooms indicate that the texture composition of the 3D hierarchical morphology might lead to the asymmetrical transport behavior of electrical conductivity. Lanthanide doped ZnO samples can exhibit red or green emission under the excitation of UV light.Lanthanide doped ZnO mushroom-like 3D hierarchical structures have been fabricated by polyol-mediated method and characterized by various microstructural and optical techniques. The results indicate that the as-prepared ZnO:Ln3+ (Ln = Tb, Eu) samples have a hexagonal phase structure and possess a mushroom-like 3D hierarchical morphology. The length of the whole mushroom from stipe bottom to pileus top is about 1.0 μm, and the diameters of pileus and stipe are about 0.8 μm and 0.4 μm, respectively. It is found that the flow of N2 is the key parameter for the formation of the novel ZnO structure and the addition of (NH4)2HPO4 has a prominent effect on the phase structure and the growth of mushroom-like morphology. The potential

  14. Immobilized Multifunctional Polymersomes on Solid Surfaces: Infrared Light-Induced Selective Photochemical Reactions, pH Responsive Behavior, and Probing Mechanical Properties under Liquid Phase.

    PubMed

    Iyisan, Banu; Janke, Andreas; Reichenbach, Philipp; Eng, Lukas M; Appelhans, Dietmar; Voit, Brigitte

    2016-06-22

    Fixing polymersomes onto surfaces is in high demand not only for the characterization with advanced microscopy techniques but also for designing specific compartments in microsystem devices in the scope of nanobiotechnology. For this purpose, this study reports the immobilization of multifunctional, responsive, and photo-cross-linked polymersomes on solid substrates by utilizing strong adamantane-β-cyclodextrin host-guest interactions. To reduce nonspecific binding and retain better spherical shape, the level of attractive forces acting on the immobilized polymersomes was tuned through poly(ethylene glycol) passivation as well as decreased β-cyclodextrin content on the corresponding substrates. One significant feature of this system is the pH responsivity of the polymersomes which has been demonstrated by swelling of the immobilized vesicles at acidic condition through in situ AFM measurements. Also, light responsivity has been provided by introducing nitroveratryloxycarbonyl (NVOC) protected amine molecules as photocleavable groups to the polymersome surface before immobilization. The subsequent low-energy femtosecond pulsed laser irradiation resulted in the cleavage of NVOC groups on immobilized polymersomes which in turn led to free amino groups as an additional functionality. The freed amines were further conjugated with a fluorescent dye having an activated ester that illustrates the concept of bio/chemo recognition for a potential binding of biological compounds. In addition to the responsive nature, the mechanical stability of the analyzed polymersomes was supported by computing Young's modulus and bending modulus of the membrane through force curves obtained by atomic force microscopy measurements. Overall, polymersomes with a robust and pH-swellable membrane combined with effective light responsive behavior are promising tools to design smart and stable compartments on surfaces for the development of microsystem devices such as chemo/biosensors. PMID

  15. Implicit Partitioned Cardiovascular Fluid-Structure Interaction of the Heart Cycle Using Non-newtonian Fluid Properties and Orthotropic Material Behavior.

    PubMed

    Muehlhausen, M-P; Janoske, U; Oertel, H

    2015-03-01

    Although image-based methods like MRI are well-developed, numerical simulation can help to understand human heart function. This function results from a complex interplay of biochemistry, structural mechanics, and blood flow. The complexity of the entire system often causes one of the three parts to be neglected, which limits the truth to reality of the reduced model. This paper focuses on the interaction of myocardial stress distribution and ventricular blood flow during diastole and systole in comparison to a simulation of the same patient-specific geometry with a given wall movement (Spiegel, Strömungsmechanischer Beitrag zur Planung von Herzoperationen, 2009). The orthotropic constitutive law proposed by Holzapfel et al. (Philos. Trans. R. Soc. Lond. Ser. A, 367:3445-3475, 2009) was implemented in a finite element package to model the passive behavior of the myocardium. Then, this law was modified for contraction. Via the ALE method, the structural model was coupled to a flow model which incorporates blood rheology and the circulatory system (Oertel, Prandtl-Essentials of Fluid Mechanics, 3rd edn, Springer Science + Business Media, 2010; Oertel et al., Modelling the Human Cardiac Fluid Mechanics, 3rd edn, Universitätsverlag Karlsruhe, 2009). Comparison reveals a good quantitative and qualitative agreement with respect to fluid flow. The motion of the myocardium is consistent with physiological observations. The calculated stresses and the distribution are within the physiological range and appear to be reasonable. The coupled model presented contains many features essential to cardiac function. It is possible to calculate wall stresses as well as the characteristic ventricular fluid flow. Based on the simulations we derive two characteristics to assess the health state quantitatively including solid and fluid mechanical aspects. PMID:26577098

  16. Correlations of Different Surface Tests: Tire Behavior Math Model for the High Speed Civil Transport (HSCT) and Michelin Tire Properties Tests for Boeing 777

    NASA Technical Reports Server (NTRS)

    Roman, Ivan

    1995-01-01

    In the surfaces correlation study, several different volumetric and drainage measurement techniques for classifying surface texture were evaluated as part of a major study to develop and improve methods for predicting tire friction performance on all types of pavement. The objective of the evaluation was to seek relationships between the different techniques, and to relate those results to surface frictional characteristics. We needed to know how each of the tests could be related to each other. Another of my assigned projects was to make a tire behavior math model for the High Speed Civil Transport (HSCT) using the same methods used for the space shuttle a few years ago. A provided third order equation with two variables was used. This model will also be used for studies with the Boeing 777. Only a few changes will be necessary to adapt it for this other aircraft, which is the newest offered by Boeing. In my final project I was involved with testing the tires for this new aircraft using the Aircraft Landing Dynamics Facility (ALDF) test carriage within the carriage house at LaRC. A 50 inch diameter radial tire manufactured by Michelin Aircraft Tire Corporation had to be tested to double overload of 114,000 pounds. The rated load of each tire is 57,000 pounds, but Boeing required tests assuming failure of a companion tire that could have cost Michelin approximately $12 million to build a facility to provide the required test capability. Here at LaRC, only minimum modifications to the facility were required to perform this specific test.

  17. Microstructure, Mechanical Properties, and Two-Body Abrasive Wear Behavior of Cold-Sprayed 20 vol.% Cubic BN-NiCrAl Nanocomposite Coating

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-Tao; Yang, Er-Juan; Shang, Fu-Lin; Yang, Guan-Jun; Li, Chen-Xin; Li, Chang-Jiu

    2014-10-01

    20 vol.% cubic boron nitride (cBN) dispersoid reinforced NiCrAl matrix nanocomposite coating was prepared by cold spray using mechanically alloyed nanostructured composite powders. The as-sprayed nanocomposite coating was annealed at a temperature of 750 °C to enhance the inter-particle bonding. Microstructure of spray powders and coatings was characterized. Vickers microhardness of the coatings was measured. Two-body abrasive wear behavior of the coatings was examined on a pin-on-disk test. It was found that, in mechanically alloyed composite powders, nano-sized and submicro-sized cBN particles are uniformly distributed in nanocrystalline NiCrAl matrix. Dense coating was deposited by cold spray at a gas temperature of 650 °C with the same phases and grain size as those of the starting powder. Vickers hardness test yielded a hardness of 1063 HV for the as-sprayed 20 vol.% cBN-NiCrAl coating. After annealed at 750 °C for 5 h, unbonded inter-particle boundaries were partially healed and evident grain growth of nanocrystalline NiCrAl was avoided. Wear resistance of the as-sprayed 20 vol.% cBN-NiCrAl nanocomposite coating was comparable to the HVOF-sprayed WC-12Co coating. Annealing of the nanocomposite coating resulted in the improvement of wear resistance by a factor of ~33% owing to the enhanced inter-particle bonding. Main material removal mechanisms during the abrasive wear are also discussed.

  18. Mechanical properties and in vitro cellular behavior of zinc-containing nano-bioactive glass doped biphasic calcium phosphate bone substitutes.

    PubMed

    Badr-Mohammadi, Mohammad-Reza; Hesaraki, Saeed; Zamanian, Ali

    2014-01-01

    In the present study, different amounts (0.5-5 wt%) of a sol gel-derived zinc-containing nano-bioactive glass (NBG-Zn) powder were added to biphasic calcium phosphate (BCP). The mixtures were sintered at 1,100-1,300 °C and physical characteristics, mechanical properties, phase composition and morphology of them were studied. The samples were also soaked in human blood plasma for 15 days to evaluate variations in their surface morphologies. Rat calvarium-derived osteoblastic cells were seeded on tops of various samples and cell adhesion, proliferation, and alkaline phosphatase activity were evaluated at different culturing periods. The maximum bending strength (62 MPa) was obtained for BCP containing 0.5 wt% NBG-Zn at temperature 1,200 °C. This value was approximately 80% higher than that of pure BCP. The bending strength failed when both sintering temperature and amount of added NBG-Zn increased. At 1,100 °C, NBG-Zn additive did not change the phase composition of BCP. At temperatures 1,200 and 1,300 °C, both alpha-tricalcium calcium phosphate (α-TCP) and beta-tricalcium phosphate (β-TCP and) phases were detected. However, adding higher amount of NBG-Zn to BCP resulted in elevation of β-TCP at 1,200 °C and progression of α-TCP at 1,300 °C. Based on the microscopic observations, adding 0.5 wt% NBG-Zn to BCP led to disappearance of grain boundaries, reduction of micropores and formation of a monolithic microstructure. No calcium phosphate precipitation was observed on sample surfaces after soaking in blood plasma, but some pores were produced by phase dissolution. The size and volume of these pores were directly proportional to NBG-Zn content. Based on the cell studies, both BCP and NBG-Zn-added BCP samples supported attachment and proliferation of osteoblasts, but higher alkaline phosphatase enzyme was synthesized within the cells cultured on NBG-Zn-added BCP. Overall, biphasic calcium phosphate materials with improved mechanical and biological properties

  19. Investigations on the electronic, structural, magnetic properties related to shape-memory behavior in Ti{sub 2}CoX (X=Al, Ga, In)

    SciTech Connect

    Wei, Xiao-Ping; Chu, Yan-Dong; Sun, Xiao-Wei; E, Yan; Deng, Jian-Bo; Xing, Yong-Zhong

    2015-02-15

    Highlights: • The analysis of phase stability trend is studied for Ti{sub 2}CoX(X = Al, Ga, In). • Ti{sub 2}CoGa is more suitable as shape memory alloy. • Total magnetic moments disappear with a increase of c/a ratio for all systems. • Density of states at the Fermi level are also shown. - Abstract: Using the full-potential local orbital minimum-basis method, we have performed a systematic investigations on the electronic, structural, and magnetic properties related to shape memory applications for Ti{sub 2}CoX (X=Al, Ga, In) alloys. Our results confirm that these alloys are half-metallic ferromagnets with total magnetic moment of 2μ{sub B} per formula unit in austenite phase, and undergo a martensitic transformation at low temperatures. The relative stabilities of the martensitic phases differ considerably between Ti{sub 2}CoX (X=Al, Ga, In). Details of the electronic structures suggest that the differences in hybridizations between the magnetic components are responsible for trends of phase. Quantitative estimates for the energetics and the magnetizations indicate that Ti{sub 2}CoGa is a promising candidate for shape memory applications.

  20. Effect of composition and corrosion properties of the metallic matrix on the erosion-corrosion behavior of HVOF sprayed WC-coatings

    SciTech Connect

    Rogne, T.; Solem, T.; Berget, J.

    1998-12-31

    In corrosive media the wear resistance of ceramic-metallic coatings is dependent on the corrosion resistance of the metal matrix. Other factors that will affect the coating deterioration are the corrosivity of the medium and any galvanic interaction from the surrounding material. This paper presents results from a study where different types of WC(Co/Cr/Mo/Ni) powders have been sprayed by HVOF, Diamond Jet 2600 Hybrid equipment. The properties of the sprayed coatings have been verified by metallographic studies and by erosion-corrosion testing both under corrosive and non-corrosive conditions. The results clearly demonstrate the importance of having a metal matrix at least as corrosion resistance as the surrounding materials. When wear exposed components in pipe systems, pumps or valves are coated with a WC type coating, the corrosion resistance of the metal matrix should be compatible to the material of the rest of the system. This is especially important when the surrounding materials are corrosion resistant alloys as stainless steels, where the coatings otherwise will act as an anode. This work is relevant for field production equipment in the oil and gas industry.

  1. Evaluation of the optoelectronic properties and corrosion behavior of Al2O3-doped ZnO films prepared by dc pulsed magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Zubizarreta, C.; Berasategui, E. G.; Bayón, R.; Escobar Galindo, R.; Barros, R.; Gaspar, D.; Nunes, D.; Calmeiro, T.; Martins, R.; Fortunato, E.; Barriga, J.

    2014-12-01

    The main requirements for transparent conducting oxide (TCO) films acting as electrodes are a high transmission rate in the visible spectral region and low resistivity. However, in many cases, tolerance to temperature and humidity exposure is also an important requirement to be fulfilled by the TCOs to assure proper operation and durability. Besides improving current encapsulation methods, the corrosion resistance of the developed TCOs must also be enhanced to warrant the performance of optoelectronic devices. In this paper the performance of aluminum-doped zinc oxide (AZO) films deposited by pulsed dc magnetron sputtering has been studied. Structure, optical transmittance/reflectance, electrical properties (resistivity, carrier concentration and mobility) and corrosion resistance of the developed coatings have been analyzed as a function of the doping of the target and the coating thickness. Films grown from a 2.0 wt% Al2O3 target with a thickness of approximately 1 µm showed a very low resistivity of 6.54  ×  10-4 Ωcm and a high optical transmittance in the visible range of 84%. Corrosion studies of the developed samples have shown very low corrosion currents (nanoamperes), very high corrosion resistances (in the order of 107 Ω) and very high electrochemical stability, indicating no tendency for electrochemical corrosion degradation.

  2. Microwave dielectric properties and sintering behavior of nano-scaled ({alpha} + {theta})-Al{sub 2}O{sub 3} ceramics

    SciTech Connect

    Huang, C.-L. Wang, J.-J.; Yen, F.-S.; Huang, C.-Y.

    2008-06-03

    The dielectric properties at microwave frequencies and the microstructures of nano ({alpha} + {theta})-Al{sub 2}O{sub 3} ceramics were investigated. Using the high-purity nano ({alpha} + {theta})-Al{sub 2}O{sub 3} powders can effectively increase the value of the quality factor and lower the sintering temperature of the ceramic samples. Grain growth can be limited with {theta}-phase Al{sub 2}O{sub 3} addition and high-density alumina ceramics can be obtained with smaller grain size comparing to pure {alpha}-Al{sub 2}O{sub 3}. Relative density of sintered samples can be as high as 99.49% at 1400 deg. C for 8 h. The unloaded quality factors Q x f are strongly dependent on the sintering time. Further improvement of the Q x f value can be achieved by extending the sintering time to 8 h. A dielectric constant ({epsilon}{sub r}) of 10, a high Q x f value of 634,000 GHz (measured at 14 GHz) and a temperature coefficient of resonant frequency ({tau}{sub f}) of -39.88 ppm/deg. C were obtained for specimen sintered at 1400 deg. C for 8 h. Sintered ceramic samples were also characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM)

  3. Sensing properties of multiwalled carbon nanotubes grown in MW plasma torch: electronic and electrochemical behavior, gas sensing, field emission, IR absorption.

    PubMed

    Majzlíková, Petra; Sedláček, Jiří; Prášek, Jan; Pekárek, Jan; Svatoš, Vojtěch; Bannov, Alexander G; Jašek, Ondřej; Synek, Petr; Eliáš, Marek; Zajíčková, Lenka; Hubálek, Jaromír

    2015-01-01

    Vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with an average diameter below 80 nm and a thickness of the uniform VA-MWCNT layer of about 16 µm were grown in microwave plasma torch and tested for selected functional properties. IR absorption important for a construction of bolometers was studied by Fourier transform infrared spectroscopy. Basic electrochemical characterization was performed by cyclic voltammetry. Comparing the obtained results with the standard or MWCNT‑modified screen-printed electrodes, the prepared VA-MWCNT electrodes indicated their high potential for the construction of electrochemical sensors. Resistive CNT gas sensor revealed a good sensitivity to ammonia taking into account room temperature operation. Field emission detected from CNTs was suitable for the pressure sensing application based on the measurement of emission current in the diode structure with bending diaphragm. The advantages of microwave plasma torch growth of CNTs, i.e., fast processing and versatility of the process, can be therefore fully exploited for the integration of surface-bound grown CNTs into various sensing structures. PMID:25629702

  4. Sensing Properties of Multiwalled Carbon Nanotubes Grown in MW Plasma Torch: Electronic and Electrochemical Behavior, Gas Sensing, Field Emission, IR Absorption

    PubMed Central

    Majzlíková, Petra; Sedláček, Jiří; Prášek, Jan; Pekárek, Jan; Svatoš, Vojtěch; Bannov, Alexander G.; Jašek, Ondřej; Synek, Petr; Eliáš, Marek; Zajíčková, Lenka; Hubálek, Jaromír

    2015-01-01

    Vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with an average diameter below 80 nm and a thickness of the uniform VA-MWCNT layer of about 16 μm were grown in microwave plasma torch and tested for selected functional properties. IR absorption important for a construction of bolometers was studied by Fourier transform infrared spectroscopy. Basic electrochemical characterization was performed by cyclic voltammetry. Comparing the obtained results with the standard or MWCNT‐modified screen-printed electrodes, the prepared VA-MWCNT electrodes indicated their high potential for the construction of electrochemical sensors. Resistive CNT gas sensor revealed a good sensitivity to ammonia taking into account room temperature operation. Field emission detected from CNTs was suitable for the pressure sensing application based on the measurement of emission current in the diode structure with bending diaphragm. The advantages of microwave plasma torch growth of CNTs, i.e., fast processing and versatility of the process, can be therefore fully exploited for the integration of surface-bound grown CNTs into various sensing structures. PMID:25629702

  5. Structure and optical properties of polycrystalline NiO films and its resistive switching behavior in Au/NiO/Pt structures

    NASA Astrophysics Data System (ADS)

    Lai, J. C.; Wang, X. C.; Mi, W. B.; Ding, Y. H.; Yang, B. H.

    2015-12-01

    Structure and optical of polycrystalline NiO films fabricated by reactive sputtering and its resistive switching properties in Au/NiO/Pt structures are investigated. The size of surface uniform pyramid-like islands and average surface roughness increase with the increase of NiO film thickness (t). The NiO films grow with the preferred (111) orientation at 400 °C, but both (100) and (110)-oriented grains exist in the films fabricated at room temperature. Raman results reveal that the crystallinity of the films fabricated at 400 °C becomes good by comparing with that at room temperature. The optical band gap monotonically decreases from 4.44 eV at t=22 nm to 3.55 eV at t=800 nm. The resistance of the Au/NiO/Pt/Ti/glass structures could be switched between two stable states including low and high resistance states. The bipolar endurance performance of the resistive switching remains nondegradable after 200 cycles. The resistive switching can be ascribed to the carrier trapping and detrapping induced by the electric field, which can change the thickness of the depletion layer at Au/NiO interface.

  6. Incoherence-coherence crossover and low-temperature Fermi-liquid-like behavior in AFe2As2 (A  =  K, Rb, Cs): evidence from electrical transport properties.

    PubMed

    Xiang, Z J; Wang, N Z; Wang, A F; Zhao, D; Sun, Z L; Luo, X G; Wu, T; Chen, X H

    2016-10-26

    We study the normal-state transport properties of AFe2As2 (A  =  K, Rb and Cs) single crystals using Hall coefficient, resistivity and magnetoresistance (MR) measurements. In all three materials, the Hall coefficient R H shows a strong temperature dependence, which is typical for multi-band systems. In particular, R H develops an upturn below a characteristic temperature [Formula: see text], which is in agreement with the incoherence-coherence crossover reported in recent nuclear magnetic resonance studies. A Fermi-liquid-like state, characterized by T (2) behavior of the resistivity and a positive orbital MR obeying Kohler's rule, emerges below T FL  ∼0.4 [Formula: see text]. The superconducting transition temperature T c experiences a simultaneous suppression with [Formula: see text] and T FL as the alkali ion's radius increases from A  =  K to A  =  Cs, suggesting that the unconventional superconductivity in the AFe2As2 series is related to the strength of the electronic coherence. A phase diagram, similar to that in the heavy fermion Kondo lattice system, is obtained. Based on all the experimental evidence, we argue that the physical properties of this family of heavily hole-doped Fe-based superconductors are controlled by the hybridization between itinerant carriers and localized orbitals, and the Kondo scenario could be effective in such a case. PMID:27589485

  7. Behavior Matters

    PubMed Central

    Fisher, Edwin B.; Fitzgibbon, Marian L.; Glasgow, Russell E.; Haire-Joshu, Debra; Hayman, Laura L.; Kaplan, Robert M.; Nanney, Marilyn S.; Ockene, Judith K.

    2011-01-01

    Behavior has a broad and central role in health. Behavioral interventions can be effectively used to prevent disease, improve management of existing disease, increase quality of life, and reduce healthcare costs. A summary is presented of evidence for these conclusions in cardiovascular disease/diabetes, cancer, and HIV/AIDS as well as with key risk factors: tobacco use, poor diet, physical inactivity, and excessive alcohol consumption. For each, documentation is made of (1) moderation of genetic and other fundamental biological influences by behaviors and social–environmental factors, (2) impacts of behaviors on health, (3) success of behavioral interventions in prevention, (4) disease management, (5) and quality of life, and (6) improvements in the health of populations through behavioral health promotion programs. Evidence indicates the cost effectiveness and value of behavioral interventions, especially relative to other common health services, as well as the value they add in terms of quality of life. Pertinent to clinicians and their patients as well as to health policy and population health, the benefits of behavioral interventions extend beyond impacts on a particular disease or risk factor. Rather, they include broad effects and benefits on prevention, disease management, and well-being across the life span. Among priorities for dissemination research, the application of behavioral approaches is challenged by diverse barriers, including socioeconomic barriers linked to health disparities. However, behavioral approaches including those emphasizing community and social influences appear to be useful in addressing such challenges. In sum, behavioral approaches should have a central place in prevention and health care of the 21st century. PMID:21496745

  8. Comparing the Psychometric Properties of the Checklist of Nonverbal Pain Behaviors (CNPI) and the Pain Assessment in Advanced Dementia (PAIN-AD) Instruments

    PubMed Central

    Ersek, Mary; Herr, Keela; Neradilek, Moni Blazej; Buck, Harleah G.; Black, Brianne

    2010-01-01

    Objective To examine and compare the psychometric properties of two common observational pain assessment tools used in persons with dementia. Design In a cross-sectional descriptive study nursing home (NH) residents were videotaped at rest and during a structured movement procedure. Following one training session and one practice session, two trained graduate nursing research assistants independently scored the tapes using the two pain observation tools. Setting Fourteen nursing homes in Western Washington State participating in a randomized controlled trial of an intervention to enhance pain assessment and management. Participants Sixty participants with moderate to severe pain were identified by nursing staff or chosen based on the pain items from the most recent Minimum Data Set assessment. Measures Checklist of Nonverbal Pain Indicators (CNPI) and the Pain Assessment in Advanced Dementia (PAINAD), demographic and pain-related data (Minimum Data Set), nursing assistant reports of participants’ usual pain intensity, Pittsburgh Agitation Scale (PAS). Results Internal consistency for both tools was good except for the CNPI at rest for one rater. Inter-rater reliability for pain presence was fair (K = 0.25 for CNPI with movement; K = 0.31 for PAINAD at rest) to moderate (K = 0.43 for CNPI at rest; K = 0.54 for PAINAD with movement). There were significant differences in mean CNPI and PAINAD scores at rest and during movement, providing support for construct validity. However, both tools demonstrated marked floor effects, particularly when participants were at rest, Conclusions Despite earlier studies supporting the reliability and validity of the CNPI and the PAINAD, findings from the current study indicate that these measures warrant further study with clinical users, should be used cautiously both in research and clinical settings and only as part of a comprehensive approach to pain assessment. PMID:20088854

  9. Oxidation Behavior and Electrical Properties of NiO- and Cr2O3- Forming Alloys for Solid Oxide Fuel Cell Interconnects.

    SciTech Connect

    Brady, Michael P; Pint, Bruce A; Lu, Z G; Zhu, Jiahong; Milliken, C; kreidler, E; Miller, Leslie S; Armstrong, Timothy R.; Walker, Larry R

    2006-01-01

    The goal of this paper was to determine if NiO-forming alloys are a viable alternative to Cr{sub 2}O{sub 3}-forming alloys for solid-oxide fuel-cell (SOFC) metallic interconnects. The oxide-scale growth kinetics and electrical properties of a series of Li- and Y{sub 2}O{sub 3}-alloyed, NiO-forming Ni-base alloys and La-, Mn-, and Ti-alloyed Fe-18Cr-9W and Fe-25Cr base ferritic Cr{sub 2}O{sub 3}-forming alloys were evaluated. The addition of Y{sub 2}O{sub 3} and Li reduced the NiO scale growth rate and increased its electrical conductivity. The area-specific-resistance (ASR) values were comparable to those of the best (lowest ASR) ferritic alloys examined. Oxidation of the ferritic alloys at 800 C in air and air+10% H{sub 2}O (water vapor) indicated that Mn additions resulted in faster oxidation kinetics/thicker oxide scales, but also lower oxide scale ASRs. Relative in-cell performance in model SOFC stacks operated at 850 C indicated a 60-80% reduction in ASR by Ni+Y{sub 2}O{sub 3}, Ni+Y{sub 2}O{sub 3}, Li, and Fe-25Cr+La,Mn,Ti interconnects over those made from a baseline, commercial Cr{sub 2}O{sub 3}-forming alloy. Collectively, these results indicate that NiO-forming alloys show potential for use as metallic interconnects.

  10. [ASRS v.1.1., a tool for attention-deficit/hyperactivity disorder screening in adults treated for addictive behaviors: psychometric properties and estimated prevalence].

    PubMed

    Pedrero Pérez, Eduardo J; Puerta García, Carmen

    2007-01-01

    ASRS v.1.1. is a self-applied brief instrument for the screening of individuals presenting symptoms of attention-deficit/hyperactivity disorder (ADHD), and proposed by the WHO. The purpose of the present work was to test the instrument and examine the results of its application to a sample of 280 individuals in treatment for substance-related disorders (cross-sectional descriptive study). We administered simultaneously in the initial phases of treatment the ASRS v.1.1. (short form) and the MCMI-II to the full sample and the Wender Utah Rating Scale (WURS), ADHD-Rating Scale-IV and ASRS v.1.1. (complete form) to various sub-samples. Diagnostic interviews were also carried out and the psychometric properties and factorial structure of ASRS v.1.1. were explored. Good convergent validity, sensitivity, specificity and diagnostic capability were obtained for the six-item version of ASRS v.1.1., even though 4 out of 6 items did not discriminate between Axis I and II disorders assessed through the MCMI-II and diagnostic interviews. According to DSM-IV-TR criteria the estimated prevalence of ADHD in the sample of addicts was 8.2%. ASRS v.1.1. is criticized as a specific instrument for ADHD detection, since most of its items appear to measure a non-specific dimension of compulsiveness/impulsiveness, common to Axis-I and Axis-II disorders. Other criticisms made in the discussion concern the lack of specificity of DSM criteria and the confusion they generate among the concepts of symptom, sign and trait (including the impact on study results), the general use of the A criterion but the omission of the B, C, D and E criteria of the DSM category, differences in samples (with regard to both severity and selection criteria), and the artifactual increases in prevalence found in many studies. PMID:18173102

  11. Behavioral economics

    PubMed Central

    Hursh, Steven R.

    1984-01-01

    Economics, like behavioral psychology, is a science of behavior, albeit highly organized human behavior. The value of economic concepts for behavioral psychology rests on (1) their empirical validity when tested in the laboratory with individual subjects and (2) their uniqueness when compared to established behavioral concepts. Several fundamental concepts are introduced and illustrated by reference to experimental data: open and closed economies, elastic and inelastic demand, and substitution versus complementarity. Changes in absolute response rate are analyzed in relation to elasticity and intensity of demand. The economic concepts of substitution and complementarity are related to traditional behavioral studies of choice and to the matching relation. The economic approach has many implications for the future of behavioral research and theory. In general, economic concepts are grounded on a dynamic view of reinforcement. The closed-economy methodology extends the generality of behavioral principles to situations in which response rate and obtained rate of reinforcement are interdependent. Analysis of results in terms of elasticity and intensity of demand promises to provide a more direct method for characterizing the effects of “motivational” variables. Future studies of choice should arrange heterogeneous reinforcers with varying elasticities, use closed economies, and modulate scarcity or income. The economic analysis can be extended to the study of performances that involve subtle discriminations or skilled movements that vary in accuracy or quality as opposed to rate or quantity, and thus permit examination of time/accuracy trade-offs. PMID:16812401

  12. Dynamics of human innovative behaviors

    NASA Astrophysics Data System (ADS)

    Lin, Ying-Ting; Han, Xiao-Pu; Wang, Bing-Hong

    2014-01-01

    How to promote the innovative activities is an important problem for modern society. In this paper, combining the evolutionary games with information spreading, we propose a lattice model to investigate dynamics of human innovative behaviors based on benefit-driven assumption. Simulations show several properties in agreement with peoples’ daily cognition on innovative behaviors, such as slow diffusion of innovative behaviors, gathering of innovative strategy on “innovative centers”, and quasi-localized dynamics. Furthermore, our model also emerges rich non-Poisson properties in the temporal-spatial patterns of the innovative status, including the scaling law in the interval time of innovation releases and the bimodal distributions on the spreading range of innovations, which would be universal in human innovative behaviors. Our model provides a basic framework on the study of the issues relevant to the evolution of human innovative behaviors and the promotion measurement of innovative activities.

  13. Making behavioral activation more behavioral.

    PubMed

    Kanter, Jonathan W; Manos, Rachel C; Busch, Andrew M; Rusch, Laura C

    2008-11-01

    Behavioral Activation, an efficacious treatment for depression, presents a behavioral theory of depression--emphasizing the need for clients to contact positive reinforcement--and a set of therapeutic techniques--emphasizing provision of instructions rather than therapeutic provision of reinforcement. An integration of Behavioral Activation with another behavioral treatment, Functional Analytic Psychotherapy, addresses this mismatch. Functional Analytic Psychotherapy provides a process for the therapeutic provision of immediate and natural reinforcement. This article presents this integration and offers theoretical and practical therapist guidelines on its application. Although the integration is largely theoretical, empirical data are presented in its support when available. The article ends with a discussion of future research directions. PMID:18420541

  14. Behavior of the potential antitumor V(IV)O complexes formed by flavonoid ligands. 3. Antioxidant properties and radical production capability.

    PubMed

    Sanna, Daniele; Ugone, Valeria; Fadda, Angela; Micera, Giovanni; Garribba, Eugenio

    2016-08-01

    The radical production capability and the antioxidant properties of some V(IV)O complexes formed by flavonoid ligands were examined. In particular, the bis-chelated species of quercetin (que), [VO(que)2](2-), and morin (mor), [VO(mor)2], were evaluated for their capability to reduce the stable radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) and produce the hydroxyl radical (•)OH by Fenton-like reactions, where the reducing agent is V(IV)O(2+). The results were compared with those displayed by other V(IV)O complexes, such as [VO(H2O)5](2+), [VO(acac)2] (acac=acetylacetonate) and [VO(cat)2](2-) (cat=catecholate). The capability of the V(IV)O flavonoids complexes to reduce DPPH is much larger than that of the V(IV)O species formed by non-antioxidant ligands and it is due mainly to the flavonoid molecule. Through the 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trapping assay of the hydroxyl radical it was possible to demonstrate that in acidic solution V(IV)O(2+) has an effectiveness in producing (•)OH radicals comparable to that of Fe(2+). When V(IV)O complexes of flavonoids were taken into account, the amount of hydroxyl radicals produced in Fenton-like reactions depends on the specific structure of the ligand and on their capability to reduce H2O2 to give (•)OH. Both the formation of reactive oxygen species (ROS) under physiological conditions by V(IV)O complexes of flavonoid ligands and their radical scavenging capability can be put in relationship with their antitumor effectiveness and it could be possible to modulate these actions by changing the features of the flavonoid coordinated to the V(IV)O(2+) ion, such as the entity, nature and position of the substituents and the number of phenolic groups. PMID:27184413

  15. Behavior change

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This brief entry presents the mediating-moderating variable model as a conceptual framework for understanding behavior change in regard to physical activity/exercise and adiposity. The ideas are applied to real world situations....

  16. Discrimination theory of rule-governed behavior

    PubMed Central

    Cerutti, Daniel T.

    1989-01-01

    In rule-governed behavior, previously established elementary discriminations are combined in complex instructions and thus result in complex behavior. Discriminative combining and recombining of responses produce behavior with characteristics differing from those of behavior that is established through the effects of its direct consequences. For example, responding in instructed discrimination may be occasioned by discriminative stimuli that are temporally and situationally removed from the circumstances under which the discrimination is instructed. The present account illustrates properties of rule-governed behavior with examples from research in instructional control and imitation learning. Units of instructed behavior, circumstances controlling compliance with instructions, and rule-governed problem solving are considered. PMID:16812579

  17. Behavioral economics and behavioral momentum

    PubMed Central

    Nevin, John A.

    1995-01-01

    Some relations between elasticity of demand and the conditions of reinforcement are reanalyzed in terms of resistance to change, in ways suggested by the metaphor of behavioral momentum; some relations between resistance to change and the conditions of reinforcement are reanalyzed in terms of elasticity of demand, in ways suggested by behavioral economics. In addition, some data on labor supply in relation to variable-ratio schedules and alternative reinforcement are reanalyzed in terms of resistance to change and compared with steady-state resistance data for performance on multiple and concurrent interval schedules. The results of these studies can be summarized by two functions based on the behavioral momentum approach, relating relative behavioral mass to relative reinforcement per response or per unit time. The former is a relation between relative unit price and relative behavioral mass, suggesting the possibility of convergent measurement of a theoretical construct common to both approaches. However, the momentum and economic approaches differ fundamentally on whether it is preferable to construe discriminated operant behavior as selected and strengthened by its consequences or as part of a behavior–consequence bundle that maximizes utility. PMID:16812775

  18. Disregulated Alcohol-Related Behavior among College Drinkers: Associations with Protective Behaviors, Personality, and Drinking Motives

    ERIC Educational Resources Information Center

    Isaak, Matthew I.; Perkins, David R.; Labatut, Tiffany R.

    2011-01-01

    Objective: This study investigated the psychometric properties of the Disregulated Alcohol-Related Behaviors Inventory (DARBI), a measure of harmful alcohol-related behavior, and the relationship between protective behavior use and scores on the DARBI and several other measures. Participants: Participants were 281 undergraduate volunteers (60%…

  19. Informed Consent for Intrusive Behavioral Treatments: Behavioral Treatment and Review System.

    ERIC Educational Resources Information Center

    Irvin, Larry K.; Singer, George S.

    Informed consent is required from a child's parent or guardian before use of some types of behavior modification for severe behavior problems, such as tantrums, self-abuse, aggression, stealing, destruction of property, etc. Behavior modification procedures that produce physical or psychological discomfort or pain require informed consent because…

  20. Behavior Modification

    ERIC Educational Resources Information Center

    Boardman, Randolph M.

    2010-01-01

    In a perfect world, students would never talk back to school staff and never argue or fight with each other. They would complete all their assigned tasks, and disciplinary actions never would be needed. Unfortunately, people don't live in a perfect world. Student behavior is a daily concern. Teachers continue to refer students to the office as a…

  1. Behavior Therapy

    MedlinePlus

    ... and consequences. Give your child a specified reward (positive reinforcement) every time she shows the desired behavior. Give your child a consequence (unwanted result or punishment) consistently when she has ... in a positive way. Most experts recommend using both medication and ...

  2. Property Differencing for Incremental Checking

    NASA Technical Reports Server (NTRS)

    Yang, Guowei; Khurshid, Sarfraz; Person, Suzette; Rungta, Neha

    2014-01-01

    This paper introduces iProperty, a novel approach that facilitates incremental checking of programs based on a property di erencing technique. Speci cally, iProperty aims to reduce the cost of checking properties as they are initially developed and as they co-evolve with the program. The key novelty of iProperty is to compute the di erences between the new and old versions of expected properties to reduce the number and size of the properties that need to be checked during the initial development of the properties. Furthermore, property di erencing is used in synergy with program behavior di erencing techniques to optimize common regression scenarios, such as detecting regression errors or checking feature additions for conformance to new expected properties. Experimental results in the context of symbolic execution of Java programs annotated with properties written as assertions show the e ectiveness of iProperty in utilizing change information to enable more ecient checking.

  3. Precursor manic behavior in the assessment and treatment of episodic problem behavior for a woman with a dual diagnosis.

    PubMed

    Allen, Marissa B; Baker, Jonathan C; Nuernberger, Jodi E; Vargo, Kristina K

    2013-01-01

    A functional analysis examined the relation between consequences that maintained episodic problem behavior (aggression, property destruction, and elopement) in the presence and absence of manic behaviors (MB). Results suggested that the presence of MB was correlated with the sensitivity of problem behavior to attention as a reinforcer during a functional analysis and that problem behaviors were maintained by attention. Noncontingent reinforcement was subsequently implemented and demonstrated to be effective in reducing problem behavior during the presence of manic behaviors. PMID:24114233

  4. Mathematics as verbal behavior.

    PubMed

    Marr, M Jackson

    2015-04-01

    "Behavior which is effective only through the mediation of other persons has so many distinguishing dynamic and topographical properties that a special treatment is justified and indeed demanded" (Skinner, 1957, p. 2). Skinner's demand for a special treatment of verbal behavior can be extended within that field to domains such as music, poetry, drama, and the topic of this paper: mathematics. For centuries, mathematics has been of special concern to philosophers who have continually argued to the present day about what some deem its "special nature." Two interrelated principal questions have been: (1) Are the subjects of mathematical interest pre-existing in some transcendental realm and thus are "discovered" as one might discover a new planet; and (2) Why is mathematics so effective in the practices of science and engineering even though originally such mathematics was "pure" with applications neither contemplated or even desired? I argue that considering the actual practice of mathematics in its history and in the context of acquired verbal behavior one can address at least some of its apparent mysteries. To this end, I discuss some of the structural and functional features of mathematics including verbal operants, rule-and contingency-modulated behavior, relational frames, the shaping of abstraction, and the development of intuition. How is it possible to understand Nature by properly talking about it? Essentially, it is because nature taught us how to talk. PMID:25595115

  5. OPEC behavior

    NASA Astrophysics Data System (ADS)

    Yang, Bo

    This thesis aims to contribute to a further understanding of the real dynamics of OPEC production behavior and its impacts on the world oil market. A literature review in this area shows that the existing studies on OPEC still have some major deficiencies in theoretical interpretation and empirical estimation technique. After a brief background review in chapter 1, chapter 2 tests Griffin's market-sharing cartel model on the post-Griffin time horizon with a simultaneous system of equations, and an innovative hypothesis of OPEC's behavior (Saudi Arabia in particular) is then proposed based on the estimation results. Chapter 3 first provides a conceptual analysis of OPEC behavior under the framework of non-cooperative collusion with imperfect information. An empirical model is then constructed and estimated. The results of the empirical studies in this thesis strongly support the hypothesis that OPEC has operated as a market-sharing cartel since the early 1980s. In addition, the results also provide some support of the theory of non-cooperative collusion under imperfect information. OPEC members collude under normal circumstances and behave competitively at times in response to imperfect market signals of cartel compliance and some internal attributes. Periodic joint competition conduct plays an important role in sustaining the collusion in the long run. Saudi Arabia acts as the leader of the cartel, accommodating intermediate unfavorable market development and punishing others with a tit-for-tat strategy in extreme circumstances.

  6. Genes and human behavior: the emerging paradigm.

    PubMed

    Drew, A P

    1997-03-01

    The physical properties of human beings and other organisms as well as their social behavioral traits are manifestations of both genetic inheritance and environment. Recent behavioral research has indicated that certain characteristics or behaviors--such as schizophrenia, divorce, and homosexuality--are highly heritable and are not governed exclusively by social environment. A balanced view of human behavior includes the effects of social learning as well as of genetically determined behavior. A new paradigm promotes enhanced understanding and acceptance of human diversity, be it cultural, racial, or sexual, and has the potential to unite scientists and theologians by creating common grounds of understanding. PMID:15719495

  7. Bi2Sr2CaCu2O8 + x round wires with Ag/Al oxide dispersion strengthened sheaths: microstructure-properties relationships, enhanced mechanical behavior and reduced Cu depletion

    NASA Astrophysics Data System (ADS)

    Kajbafvala, Amir; Nachtrab, William; Wong, Terence; Schwartz, Justin

    2014-09-01

    Ag/Al alloys with various Al content (0.50 wt%, 0.75 wt%, 1.00 wt%, and 1.25 wt%) are made by powder metallurgy and used as the outer sheath material for Bi2Sr2CaCu2O8 + x (Bi2212)/Ag/AgAl multifilamentary round wires (RW). Bi2212/Ag/AgAl RW microstructural, mechanical and electrical properties are studied in various conditions, including as-drawn, after internal oxidation, and after partial melt processing (PMP). The results are compared with the behavior of a Bi2212/Ag/Ag0.20Mg wire of the same geometry. The grains in as-drawn Ag/Al alloys are found to be ˜25% smaller than those in the corresponding Ag/0.20 wt%Mg, but after PMP, the Ag/Al and Ag/0.20 wt%Mg grain sizes are comparable. Tensile tests show that Bi2212/Ag/AgAl green wires have yield strength (YS) of ˜115 MPa, nearly 65% higher than that of Bi2212/Ag/Ag0.20Mg. After PMP, the Bi2212/Ag/AgAl YS is about 35% greater than that of Bi2212/Ag/Ag0.20Mg. Furthermore, Bi2212/Ag/AgAl wires exhibit higher ultimate tensile strength and modulus and twice the elongation-to-failure. Atomic resolution high-angle annular dark-field scanning transmission electron microscopy, high resolution transmission electron microscopy and energy dispersive spectroscopy demonstrate the formation of nanosize MgO and Al2O3 precipitates via internal oxidation. Large spherical MgO precipitates are observed on the Ag grain boundaries of Ag/0.20 wt%Mg alloy, whereas the Al2O3 precipitates are distributed homogenously in the dispersion-strengthened (DS) Ag/Al alloy. Furthermore, it is found that less Cu diffused from the Bi2212 filaments in the Bi2212/Ag/Ag0.75Al wire during PMP than from the filaments in the Bi2212/Ag/Ag0.20Mg wire. These results show that DS Ag/Al alloy is a strong candidate for improved Bi2212 wire.

  8. Behavioral dimensions of food security.

    PubMed

    Timmer, C Peter

    2012-07-31

    The empirical regularities of behavioral economics, especially loss aversion, time inconsistency, other-regarding preferences, herd behavior, and framing of decisions, present significant challenges to traditional approaches to food security. The formation of price expectations, hoarding behavior, and welfare losses from highly unstable food prices all depends on these behavioral regularities. At least when they are driven by speculative bubbles, market prices for food staples (and especially for rice, the staple food of over 2 billion people) often lose their efficiency properties and the normative implications assigned by trade theory. Theoretical objections to government efforts to stabilize food prices, thus, have reduced saliency, although operational, financing, and implementation problems remain important, even critical. The experience of many Asian governments in stabilizing their rice prices over the past half century is drawn on in this paper to illuminate both the political mandates stemming from behavioral responses of citizens and operational problems facing efforts to stabilize food prices. Despite the theoretical problems with free markets, the institutional role of markets in economic development remains. All policy instruments must operate compatibly with prices in markets. During policy design, especially for policies designed to alter market prices, incentive structures need to be compatible with respect to both government capacity (bureaucratic and budgetary) and empirical behavior on the part of market participants who will respond to planned policy changes. A new theoretical underpinning to political economy analysis is needed that incorporates this behavioral perspective, with psychology, sociology, and anthropology all likely to make significant contributions. PMID:20855628

  9. Behavioral dimensions of food security

    PubMed Central

    Timmer, C. Peter

    2012-01-01

    The empirical regularities of behavioral economics, especially loss aversion, time inconsistency, other-regarding preferences, herd behavior, and framing of decisions, present significant challenges to traditional approaches to food security. The formation of price expectations, hoarding behavior, and welfare losses from highly unstable food prices all depends on these behavioral regularities. At least when they are driven by speculative bubbles, market prices for food staples (and especially for rice, the staple food of over 2 billion people) often lose their efficiency properties and the normative implications assigned by trade theory. Theoretical objections to government efforts to stabilize food prices, thus, have reduced saliency, although operational, financing, and implementation problems remain important, even critical. The experience of many Asian governments in stabilizing their rice prices over the past half century is drawn on in this paper to illuminate both the political mandates stemming from behavioral responses of citizens and operational problems facing efforts to stabilize food prices. Despite the theoretical problems with free markets, the institutional role of markets in economic development remains. All policy instruments must operate compatibly with prices in markets. During policy design, especially for policies designed to alter market prices, incentive structures need to be compatible with respect to both government capacity (bureaucratic and budgetary) and empirical behavior on the part of market participants who will respond to planned policy changes. A new theoretical underpinning to political economy analysis is needed that incorporates this behavioral perspective, with psychology, sociology, and anthropology all likely to make significant contributions. PMID:20855628

  10. The role of composition and microstructure gradients on weld metal properties and behavior: Progress report for the period of June 1, 1987 to December 31, 1987. [Fe-Al-Cr-Mn-Ni weld metals

    SciTech Connect

    Matlock, D.K.; Olson, D.L.

    1988-01-01

    The effects of weld metal compositional and microstructural gradients on phase transformations, microstructural stability, and mechanical properties are considered from a fundamental basis in weld metal alloys which are primarily austenitic (e.g., stainless steels). Models which incorporate compositional gradients are developed to predict the resulting weld metal properties. The mechanical properties of weld metals are modeled based on composite theory in which individual weld metal zones are considered as discrete elements within a composite structure. 23 figs.

  11. Some verbal behavior about verbal behavior

    PubMed Central

    Salzinger, Kurt

    2003-01-01

    Beginning with behavior analysts' tendency to characterize verbal behavior as “mere” verbal behavior, the author reviews his own attempt to employ it to influence both his staff and policies of our government. He then describes its role in psychopathology, its effect on speakers in healing themselves and on engendering creativity. The paper ends by calling to our attention the role of verbal behavior in the construction of behavior analysis. PMID:22478393

  12. Properties of ceramic candle filters

    SciTech Connect

    Pontius, D.H.; Starrett, H.S.

    1994-10-01

    The objectives of this program have been: (1) the post-test evaluation of candle filters, (2) to measure the material properties of current filter materials, destructively and non-destructively, and to relate these properties and behaviors to in-service performance, (3) to develop an understanding of the material requirements for hot gas filter elements, (4) to develop material property goals for filter materials, and (5) to establish test matrices and a protocol to evaluate candidate filter materials.

  13. Autistic behavior, behavior analysis, and the gene.

    PubMed

    Malott, Richard W

    2004-01-01

    This article addresses the meaning of autism, the etiology of autistic behavior and values, the nature-nurture debate, contingencies vs. genes, and resistance to a behavioral analysis of autism. PMID:22477285

  14. The behavioral economics of violence.

    PubMed

    Rachlin, Howard

    2004-12-01

    From the viewpoint of teleological behaviorism the first question to ask in attempting to understand any behavior, including violent behavior, is: What are its contingencies of reward and punishment? Or, to put the question in economic terms: What are the short-term and long-term costs and benefits that such behavior entails? Let us therefore consider the costs and benefits of youth violence. Among the short-term costs of violent behavior are the physical effort of the act, the possibility of immediate physical retaliation, immediate social disapproval, and the opportunity cost of other social acts that the violent behavior takes the place of (you can't be affectionate and violent at the same time, for instance). Among the immediate benefits of violent behavior are the intrinsic satisfaction of the violent act itself and any extrinsic benefit; if A violently appropriates B's new sneakers then obtaining the sneakers reinforces A's violence. These immediate benefits may well outweigh the costs in many contexts. Among the long-term costs of violent behavior are delayed retaliation, possible social disapproval and loss of social support, rejection from a social group, job loss, and health risks associated with a violent lifestyle. Among the long-term benefits are long-term intimidation of others (your neighbor is less likely to build a fence on your property if you have a reputation for violence), and a possibly exciting lifestyle. These long-term benefits may well be outweighed by the long-term costs. Opposition of long-term net costs to short-term net benefits, where it exists, creates a personal self-control trap: Overall satisfaction may decrease monotonically with rate of the target behavior but, regardless of its rate, the immediate satisfaction of doing it is always higher than that of not doing it. In the case of violent behavior, this trap is exacerbated by the fact that as a person's violence increases, net immediate reinforcement also increases (due to

  15. Dielectric properties and glassy behavior study of 70(Na0.5Bi0.5) TiO3-30SrTiO3 lead-free ceramic

    NASA Astrophysics Data System (ADS)

    Praharaj, S.; Rout, D.; Kar, B. B.; Subramanian, V.

    2016-05-01

    This paper reports the dielectric and glassy behavior of 70(Na0.5Bi0.5) TiO3-30SrTiO3 (NBT-30ST) lead-free perovskite relaxor. The temperature dependent dielectric data indicates that the material undergoes a diffuse phase transition at Tm (temperature corresponding to maximum dielectric constant) with diffuseness coefficient γ˜2. The material also shows frequency dispersion around Tm with a high ΔTm (Tm,1MHz - Tm, 0.1kHz) value of ˜42. The above parameters manifest strong relaxor behavior of NBT-30ST. Moreover, the results are analyzed by employing empirical models such as V-F law, Power law to explore the glassy behavior associated with the system. The frequency dependent Tm analysis revealed greater interactions between the polar nano regions (PNRs). For further information on PNRs, the dielectric behavior at much higher and lower temperature than Tm has also been analyzed.

  16. Positive Behavior Support and Applied Behavior Analysis

    ERIC Educational Resources Information Center

    Johnston, J. M.; Foxx, R. M.; Jacobson, J. W.; Green, G.; Mulick, J. A.

    2006-01-01

    This article reviews the origins and characteristics of the positive behavior support (PBS) movement and examines those features in the context of the field of applied behavior analysis (ABA). We raise a number of concerns about PBS as an approach to delivery of behavioral services and its impact on how ABA is viewed by those in human services. We…

  17. Steps in Behavior Modividation.

    ERIC Educational Resources Information Center

    Straughan, James H.; And Others

    James H. Straughan lists five steps for modifying target behavior and four steps for working with teachers using behavior modification. Grant Martin and Harold Kunzelmann then outline an instructional program for pinpointing and recording classroom behaviors. (JD)

  18. Stages and Behaviors

    MedlinePlus

    ... Stage Caregiving Middle-Stage Caregiving Late-Stage Caregiving Behaviors Aggression & Anger Anxiety & Agitation Depression Hallucinations Memory Loss & ... Legal Documents alz.org » Caregiver Center » Stages and Behaviors Text size: A A A Stages / Behaviors As ...

  19. Intellectual Property.

    ERIC Educational Resources Information Center

    Swinson, John V.

    2000-01-01

    Intellectual property is a term that covers a number of different rights. Considers issues such as what are the basic forms of intellectual property; who owns the intellectual property created by a teacher; who owns intellectual property created by students; and use of downloaded materials from the internet. (Author/LM)

  20. Behavioral Health & Performance

    NASA Video Gallery

    Summary of the Behavioral Health and Performance Operations Group’s work including an overview of astronaut selection, behavioral health services provided to astronauts, the psychological aspects o...